WO2025227186A1

WO2025227186A1 - Production of iron and steel

Info

Publication number: WO2025227186A1
Application number: PCT/AU2025/050420
Authority: WO
Inventors: Mark Sceats; Matthew Gill; Thomas Dufty; Timothy Collins; Mathew WALKER; Phillip Hodgson; Andrew OKELY; Matthew Boot-Handford; Yun Xia
Original assignee: Calix Pty Ltd
Current assignee: Calix Pty Ltd
Priority date: 2024-04-29
Filing date: 2025-04-29
Publication date: 2025-11-06
Anticipated expiration: 2026-10-29

Abstract

Disclosed is a process for reducing iron ore. The process comprises: feeding a powder comprising iron ore and a first gas into a first reactor and indirectly heating the first reactor so as to heat the powder and the gas to a temperature at which the iron ore is converted to magnetite; and feeding a resultant powder comprising magnetite and a reducing gas into a second reactor and indirectly heating the second reactor so as to heat the powder comprising magnetite and the reducing gas to a temperature at which the magnetite is reduced to iron, to thereby form a powder comprising iron. Also disclosed is a system for reducing iron ore and vertical reactors for use in reducing iron ore and other pyro-processes.

Description

PRODUCTION OF IRON AND STEEL

PRIORITY

This application claims priority from Australian Provisional Application No. 2024901210, the entire contents of the specification of which is incorporated herein by way of cross-reference.

TECHNICAL FIELD

This disclosure generally relates to the pyro-processing of materials and, more specifically, to processes and systems for the production of iron and steel.

BACKGROUND ART

The iron and steel industry is responsible for about 6-8% of global CO2 emissions, and there is a need for the steel industry to reduce its CO2 emissions to mitigate global warming. The World Steel Association reported that, in 2019, the CO2 emissions intensity was about 1,800 kg of CO2 per tonne of steel and the energy intensity was about 19.84 GJ/tonne for the production of 1.1 billion tonnes of steel. Since 2010, the CO2 emissions intensity has increased from 1,800 to 1,830 and the energy intensity has fallen slightly from 20.13 to 19.84 GJ/tonne. Steel processes generally include ironmaking from iron ore and steelmaking steps, which may be closely integrated for steelmaking directly from iron ore.

It would be appreciated by a person skilled in the art that the prior art of iron and steel is vast and deep, and most of the patents relevant to processes used in these industries have been progressed through iterative improvements of processes adopted well over 30 years ago. The energy intensity of the currently used processes are typically very high, and the high emissions intensity is a consequence of the development of these processes using processed coal for combustion, reduction, electrodes, and for incorporation in carbon steels.

The pathway to producing low emissions intensity iron and steel is primarily based on the use of low-emissions power, and hydrogen gas for the iron reduction process. In particular, many technologies looking at the production of low emissions iron and steel look towards a modification of the current DRI process to use low emissions hydrogen in a process called H-DRI. However, the efficacy and economics of H-DRI processes at commercial scale has yet to be demonstrated.

It may be advantageous to provide an H-DRI process that is able to be scaled-up to commercial scale and which further lowers CO2 emissions and energy consumption. It is to be understood that, if any prior art is referred to herein, such reference does not constitute an admission that the prior art forms a part of the common general knowledge in the art, in Australia or any other country.

SUMMARY

Process for iron ore reduction - ironmaking and steel

Disclosed herein in a first aspect is a process for reducing iron ore. The process of the first aspect may be particularly suitable for reducing low grade iron ore so as to produce a high-grade iron, generally referred to as sponge iron. The process may comprise the continuous flash H-DRI reduction of iron ore powders for ironmaking using an indirectly heated reactor which operates in a regime of dilute downwards flow of particles in a gas, injected initially as hydrogen.

The process can comprise feeding a powder comprising iron ore and a first gas into a first reactor. The first reactor can be indirectly heated so as to heat the powder and the gas to a temperature at which the iron ore, typically hematite, goethite, or siderite is converted to magnetite.

The process can also comprise feeding a resultant powder comprising magnetite and a reducing gas into a second reactor. The second reactor can be indirectly heated so as to heat the powder comprising magnetite and the reducing gas to a temperature at which the magnetite is reduced to iron, to thereby form a powder comprising iron.

The two-stage setup of the process, in which magnetite is formed in the first reactor, can allow for separation of gangue from the product of the first reactor, so that the magnetite that is fed to the second reactor is of a higher grade. In addition, as explained below, the two-stage setup of the process can allow for recycling and reuse of process gases and energy recovery from hot solids where applicable.

In this regard, in some embodiments, an exhaust gas from the second reactor may be passed to the first reactor. Thus, the first gas that is fed to the first reactor may comprise the exhaust gas from the second reactor. Using the exhaust gas from the second reactor as, or as part of, the first feed gas can be advantageous because the exhaust gas is already at an elevated temperature. As a result, the thermal requirements of the first reactor may be reduced (i.e., because the first gas is already preheated). In addition, the exhaust gas from the second reactor may comprise hydrogen and water in concentrations at which further reduction of magnetite in the first reactor tends to be minimised. The exhaust gas from the second reactor can, in this regard, be ‘trimmed’ to be suitable for feeding to the first reactor. In some embodiments, the powder comprising iron ore and/or the powder comprising magnetite may be in the form of a powder with particles size of below about 250 pm diameter. The powder may be ground prior to injection into the respective reactor to achieve the particle sizes of below about 250 pm diameter. Such particles may be referred to as ultra-fines. It is to be understood that the term “ultra-fines” as used herein refers to particles with a 90% volume of less than 250 pm in diameter. An advantage of employing ultra-fines is that the reduction of ultra-fine particles is very fast and is typically complete within a reactor residence time of less than about 60 seconds, typical of a flash pyroprocess in a continuous flow reactor. The fast reaction for ultra-fines may mean that there is no need to employ fluidised bed technology.

In some embodiments, the iron ore in the powder fed to the first reactor may comprise iron in the Fe³⁺ state. For example, the iron ore may comprise hematite, goethite, siderite or other minerals which comprise iron in the Fe³⁺ state. Such minerals are advantageously able to be reduced to magnetite, in which the iron atoms are in the Fe²⁺ state, in the first reactor, with the magnetite leaving the first reactor then able to be cooled and separated, such as magnetically, from a gangue component of the iron ore powder feed.

The separated magnetite (i.e., of a higher grade) may then be fed to the to the second reactor. In this regard, minimising the reduction of magnetite in the first reactor may be advantageous. This is because magnetite (being magnetic) may be more easily separable from a remaining non-magnetic gangue (i.e., the gangue present in the powder comprising iron ore). By maximising the amount of iron present as magnetite, the iron lost to the gangue during magnetic separation may be minimised. Separating the non-magnetic gangue from the magnetite can also increase the purity of the iron produced by the second reactor.

In some embodiments, prior to feeding the magnetite to the second reactor, the magnetite may be agglomerated. Agglomeration may be required to increase the particle size of the magnetite feed to the second reactor (i.e., so that it is of a more optimal size for the second reactor reduction reaction - e.g. to fall under a better flow regime).

In some embodiments, each of the first reactor and the second reactor may be operated in a dilute flow regime. Such a flow regime can optimise reaction kinetics and reactant conversion.

In some embodiments, the first reactor may be indirectly heated so as to maintain a temperature of between 700 °C to 1100 °C within the reactor. For example, the first reactor may be indirectly heated so as to maintain a temperature of between 700 °C to 1050 °C, such as between 700 °C to around 900 °C. Additionally, the second reactor may be indirectly heated so as to maintain a temperature of between 700 °C to 1100 °C within the reactor. For example, the second reactor may be indirectly heated so as to maintain a temperature of between 700 °C to 1050 °C, such as between 700 °C to around 900 °C. This temperature range has been found to be optimal towards the conversion reactions taking place in each reactor. In addition, at high temperatures agglomeration may be reduced, and reactor fouling attributed to the propensity of particles with a high fraction of iron atoms in the elemental Fe° state particles to bind thereto may also be reduced. In this regard, the reactor temperature is typically lower than the temperature at which the iron ore agglomerates. Accordingly, it will be appreciated that the temperature of the first reactor and the second reactor will depend on the material to be heated, i.e., because different ores tend to start to agglomerate at different temperatures.

In some embodiments, the gas input to the first reactor may comprise carbon monoxide, hydrogen, water (i.e., present as steam at the elevated temperatures of the first reactor), methane, or mixtures thereof. In certain variations, the gas input to the first reactor may comprise hydrogen and water. For example, in some embodiments, the gas may comprise hydrogen and water, for example, in a one-to-one stoichiometric ratio. Typically, the reaction conditions of the first reactor, including the reactor temperature and the composition of the gas input to the first reactor, are controlled so as to optimise the formation of magnetite from the input ore that is in the Fe³⁺ state, and to suppress the further reduction of magnetite to iron in the Fe° state. It is noted that the optimal composition of the gas input to the first reactor can be dependent on the reactor temperature. For example, when the gas input comprises carbon monoxide and carbon dioxide, and when the first reactor is operated at a temperature of about 900 °C, it has been found that it can be optimal to maintain a stoichiometric ratio of CO:CC>2 of less than about 2.9: 1. On the other hand, when the first reactor is operated at a temperature of about 1100 °C, it can be optimal to maintain a stoichiometric ratio of CO:CO2 of less than about 1.2:1. In addition, it is thought that, when the atmosphere further comprises a one- to-one stoichiometric ratio of hydrogen to steam, magnetite can optimally be produced from the input iron ore that is in the Fe³⁺ state, and further reduction of magnetite to iron in the Fe° state may be suppressed.

In some embodiments, the reducing gas input to the second reactor may comprise carbon monoxide, hydrogen, water (i.e., present as steam at the elevated temperature of the second reactor), methane, or mixtures thereof. For example, the reducing gas may comprise hydrogen and water in a two-to-one stoichiometric ratio. It is thought that, when the magnetite in the second reactor is heated in an atmosphere comprising a two-to-one stoichiometric ratio of hydrogen to water, optimal reduction of the magnetite to iron can occur. In some of these embodiments, the hydrogen may be completely consumed. In some embodiments, the process may further comprise collecting an exhaust gas from the first reactor. The first gas typically comprises water. Because the exhaust gas is typically at a temperature of between 700 to 1100 °C (i.e., the operating temperature of the first reactor), the water is present as steam. In this regard, the process may comprise condensing the water from the collected exhaust gas. The first gas may also comprise hydrogen. The process may further comprise separating a gas comprising hydrogen from the condensed water. The separated gas comprising hydrogen may be recycled to the second reactor. Thus, the reducing gas fed to the second reactor may comprise the separated gas. This can advantageously reduce the amount of fresh hydrogen required by the process. In some of these embodiments, the hydrogen may be used for reduction reactions within the second reactor only. Accordingly, no oxygen is provided. In such embodiments, no oxygen is required for combustion with hydrogen for heating within the second reactor. Instead, indirect heating is provided. For example, the particles inside the reactor can be indirectly heated by heating the reactor walls, which then provide heat to the particles inside the reactor by thermal radiation (i.e., blackbody radiation from the reactor walls).

In some variations, renewable power may be used to produce any additional hydrogen required for iron reduction using water electrolysis. Accordingly, the condensed water may be used as some or all of the feed to said water electrolysis process.

In some variations, the process may further comprise passing the high-grade powder, i.e., comprising iron, from the second reactor through a hot-briquetted iron plant to produce sponge iron briquettes. Heat may be recovered from the briquetting plant and used, for example, to preheat the powder or hydrogen, as part of the overall process. The cooled sponge iron briquettes may then be sold, e.g., to steelmakers. Thus, the sponge iron briquettes may form one of the products of the process as disclosed herein.

In other variations, the process may instead comprise converting the powder comprising iron into steel. Advantageously, the steel produced by the process as disclosed herein can comprise a low, or zero emissions, or negative emissions steel. In addition, the powder can be converted into a specified steel, i.e., the steel can be made to have a specific composition based on requirements of a customer. Because the processes described herein typically comprise high temperature pyro-processes, there can be energy savings in using hot powder from the second reactor to manufacture steel.

In some of these variations, prior to converting the iron into steel, the powder comprising iron from the second reactor may be mixed with various additives. In the context of this specification, the term ‘additives’ should be understood as comprising any material that is added to support downstream processing operations including melting/smelting and gangue removal operations, purification operations and steelmaking operations. Such additives can comprise, but are not limited to, carburizing agents, fluxing agents, slag modifiers, refractory stabilisers, etc.

In some of these variations in which the powder comprising iron from the second reactor is mixed with additives, the additives can comprise carbon and slag modifiers/refractory stabilisers formed from a mixture of calcium oxide (CaO) and magnesium oxide (MgO). The ratio of these additives (e.g., the ratio of the CaO and MgO) is typically one which slags the iron or steel most advantageously. The additives may alternatively or additionally comprise other additives known in the art of steelmaking. The powder comprising iron may already be at an elevated temperature (i.e., because the second reactor is typically operated at an elevated temperature). The powder and additives may be heated to metallise the materials, so as to create a liquid steel and a separable slag. The powder and additives may be heated before addition using renewable power, or from heat recovered from hot gas and powder streams in the overall process, or from the additive manufacturing process in order to minimise cost of power and emissions. A mixture comprising the iron and additives may thereby be produced.

In some of these embodiments, the calcium oxide and/or magnesium oxide may be produced from limestone, dolomite and/or magnesite by indirectly heating the limestone, dolomite and/or magnesite so as to produce a pure CO2 stream for carbon capture and storage or re-use.

In some embodiments of these variations, the process may comprise briquetting the mixture comprising the iron and the additives and cooling the briquettes. The briquetting process reduces the porosity of the mixture to air and moisture so that reactions of iron or additives are inhibited. In particular, briquetting lowers the reactivity of the iron and/or additives to air and water, thus preventing spontaneous exothermic runaway reactions when exposed to oxygen/air and the splitting of water to produce hydrogen. Notably, briquetting to certain specifications is required for safe shipping of DRI. Briquetting also results in densification of the iron and additives, making shipping more economical on a volume basis. Briquettes comprising the iron and additives may thereby be produced. The briquettes may be sold to end-users such as steelmakers. The briquettes may be of particular use to steelmakers because they already comprise suitable additives. In this regard, the concentration and type of additives added to the powder comprising iron may be selected based on the requirements of the steelmakers, particularly with respect to energy efficiency, including transport. Thus, the briquettes comprising the iron and additives may form another of the products of the process as disclosed herein. However, in further variations, the mixture comprising the iron and the additives may instead be passed to and heated in an electric arc furnace under conditions whereby the iron is converted to steel. In the electric arc furnace, additional additives may be employed (e.g., to trim the steel and produce a steel having a desired composition).

In some of these variations, the process may further comprise passing a portion of exhaust gas from the first reactor to the electric arc furnace.

In some of these variations, when carbon monoxide is present in the reducing gas that is fed into the second reactor, carbon monoxide may therefore be present in the first reactor exhaust gas. Thus, the process may further comprise scrubbing carbon monoxide (when present) from the first reactor exhaust gas, or scrubbing carbon monoxide (when present) from a remaining portion of the first reactor exhaust gas. In either case, the process may also comprise clean-up of the resultant scrubbed exhaust gas.

In some of these variations in which carbon monoxide is present in the reducing gas that is fed into the second reactor, the composition of the reducing gas that is fed into the second reactor may be selected so that the ratio of CO and CO2 in the exhaust gas from the second reactor (i.e., which is used as the reducing gas input to the first reactor) is such that the reduction of Fe2Oi to FesOr (i.e., magnetite) is thermodynamically limited. Additionally, the ratio of CO and CO2 can be selected such that the first reactor also serves as a CO polishing step in which CO present in the first reducing gas is consumed. This can eliminate the need for any additional scrubbing of the first reactor exhaust gas. It is nevertheless noted that incomplete CO consumption may be desirable when the first reactor exhaust gas is to be used for certain applications, such as for methanol production. It is noted that many of the catalysts employed in methanol synthesis processes are prone to poisoning by oxygen. Advantageously, when CO is present in the first reactor exhaust gas, it can react with any oxygen that might also be present in the feed to a methanol production stage (e g., such as oxygen that may be present in in other gas streams that are mixed with the first reactor exhaust gas so as to form the feed gas to the methanol production stage). This can reduce and/or eliminate catalyst poisoning, thereby extending the life of the catalyst. It is further noted that CO can itself be converted to methanol and that, during methanol synthesis, CO2 present may be first converted to CO, before then being converted to methanol. Therefore, any CO present in the first reactor exhaust can itself be converted to methanol in the methanol production stage.

In some embodiments, the process may further comprise a pyrolyser. In the pyrolyser, a waste or biomass may be converted to carbon and a gas comprising hydrogen, steam, carbon monoxide and carbon dioxide (i.e., via the process of pyrolysis). The pyrolyser may be of a sorbent enhanced gasification type (i.e., so as to reduce and/or eliminate carbon dioxide and/or carbon monoxide in the gas produced by the pyrolyser, thereby producing a gas comprising hydrogen). The energy for pyrolysis may be provided in a reactor that uses indirect heating. The sorbent used to capture carbon, as CO or CO2, in the pyrolysis gas stream may be lime (CaO) or dolime (MgO.CaO) made from limestone (CaCOi), or dolomite (MgCOi.CaCC ), respectively. The gas comprising hydrogen may be separated from the carbon. The gas comprising hydrogen may be used as a supplementary reducing gas stream for the first reactor and/or the second reactor. The carbon and ash, may be collected and used as an additive to support downstream melting/smelting gangue removal and steelmaking processes and for producing the mixture comprising the iron and additives.

In some embodiments, such as when the sorbent enhanced gasifier process is used to make carbon, the gasifier output is hydrogen. The hydrogen may be used as or as part of a reducing gas for iron reduction (e.g., as a reducing gas for the processes for reducing iron disclosed in other aspects herein). The used sorbent contains the carbon captured from the gasifier gas stream as CaCCh, which may be processed back to CaO for recycling into the sorbent enhanced gasifier using an indirectly heated calciner, so that the CO2 is released as a pure CO2 stream that can be sequestered or used using the relevant known arts. In these embodiments, renewable power can be used to heat the pyrolyser, so the pyrolysis process to make carbon and hydrogen is chemically emission free, independently of whether or not biomass or waste is used.

In some embodiments, the sorbent may comprise calcium oxide and/or magnesium oxide, and the sorbent may be produced from limestone, dolomite and/or magnesite by indirectly heating the limestone, dolomite and/or magnesite so as to produce a pure CO2 stream for carbon capture and storage or re-use. In this regard, in some embodiments, the process may further comprise a calciner for producing lime (CaO), magnesia (MgO) or dolime (MgO.CaO) from limestone (CaCOs), magnesite (MgCOi) or dolomite (MgCOs.CaCOi) respectively.

In some embodiments, the process may further comprise one or more beneficiation stages in which an iron ore is treated so as to produce the powder comprising iron ore to be fed into the first reactor.

In some embodiments, renewable power may be used for indirectly heating the first reactor, the second reactor, the pyrolyser (when present) and other ancillaries (when present), such as the briquetting stage.

Process for making briquettes for steelmaking Disclosed herein in a second aspect is a process for producing a steel precursor. The process can comprise providing a source of high-grade iron. The process can also comprise mixing the high-grade iron with flux additives such that the high-grade iron forms a homogeneous mixture with the flux additives. The mixing process can be performed at an elevated temperature. The process can further comprise cooling the homogeneous mixture to form the steel precursor (e.g. as a briquette for shipping).

The steel precursor may be particularly suitable for use in steelmaking. For example, the steel precursor may be sold as a product to a steelmaker. The steelmaker can then further process the steel precursor (e.g., in an electric arc furnace), to convert the steel precursor into steel.

Advantageously, with the process of the second aspect, the stage of forming the steel precursor is separate from a process in which the steel precursor is converted into steel. This is in contrast to processes of the prior art in which the high-grade iron, along with various additives, are directly mixed in a furnace (e.g., an electric arc furnace, blast furnace, etc. in which the steel is formed). By separating the two processes, i.e., the forming of the steel precursor and the conversion to steel, the two processes may advantageously be performed at separate times and/or in separate geographical locations. For example, the forming of the steel precursor can be performed in a location where the iron ore is produced and where renewable power is plentiful to produce hydrogen for reduction, and power for heating any indirectly heated reactors, and where limestone or dolomite are available for making low emissions additives, such as fluxing agents, and CO2 sorbents, and biomass or waste are available to make carbon from pyrolysis. The costs and CO2 emissions associated with transporting iron ore, carbon, and additives to a steel processing facility can be minimised. The low emission steel precursor can then be shipped to a second location (e.g., where there is a demand for steel and/or where there is existing infrastructure but where the supply of renewable electricity /hydrogen is limited). The steel precursor can be processed into the steel at the second location, where further additives may be added, as required, to make e.g. low emission steel.

In some embodiments of the second aspect, the source of high-grade iron may comprise a powder comprising high-grade iron. For example, the powder comprising high-grade iron may be produced according to the process as set forth in the first aspect as disclosed herein.

In some embodiments of the second aspect, the various additives may comprise one or more of: magnesium oxide, calcium oxide, carbon, low FeO slag. Alternative or additional additives may be used as required, e.g., to produce a steel precursor with a required composition. Typically, the additives will comprise materials which support downstream processes such as melting/smelting operations and steel making. Suitable additives will be known to those skilled in the relevant art, but can comprise fluxing agents, slag modifiers, refractory stabilisers, etc.

In some embodiments of the second aspect, the elevated temperature may comprise a temperature of between 700 to 1100 °C.

In some embodiments of the second aspect, cooling the homogeneous mixture to form the steel precursor may comprise briquetting the homogeneous mixture.

System for iron ore reduction - ironmakine and steel

Disclosed herein in a third aspect is a system for reducing iron ore. The system of the third aspect may be particularly suitable for converting low grade iron ore into sponge iron.

The system can comprise a first indirectly heated reactor. The first indirectly heated reactor can be configured such that a powder comprising iron ore and a first gas are each able to be fed into the first indirectly heated reactor. Said reactor can be further configured such that the powder and the gas are able to be heated therein to a temperature at which the iron ore is converted to magnetite.

The system can also comprise a second indirectly heated reactor. The second indirectly heated reactor can be configured such that the magnetite and a reducing gas are each able to be fed into the second indirectly heated reactor. Said reactor can be further configured such that the magnetite and reducing gas are able to be heated to a temperature at which the magnetite is reduced, to thereby form a powder comprising iron.

The two-stage setup of the system likewise has the attendant benefits as outlined above for the process of the first aspect.

In some embodiments of the third aspect, the system may further comprise a recycle line that is configured to receive and pass an exhaust gas from the second reactor. The recycle line may be further configured to feed the exhaust gas to the first reactor such that the first gas comprises the exhaust gas. As above, using the exhaust gas from the second reactor as, or as part of, the first gas feed can be advantageous because the exhaust gas is already at an elevated temperature, which can reduce the thermal requirements of the first reactor. In addition, the ratio of hydrogen to water in the first gas may be such that further reduction of magnetite in the first reactor tends to be minimised (i.e., the reaction in the second reactor may be controlled/operated to produce the desired ratio of hydrogen to water in the exhaust gas to be fed to the first reactor). In some embodiments of the third aspect, the system may further comprise a magnetic separator in which the magnetite produced by the first reactor is separated from a gangue. The separated magnetite may then be in a more optimal form (e.g., of a higher grade) to be fed to the second reactor. Separating the non-magnetic gangue from the magnetite may also increase the purity of the iron produced by the second reactor.

In some embodiments of the third aspect, the system may further comprise an agglomeration stage to which the separated magnetite is passed. In the agglomeration stage, the magnetite may be agglomerated, prior to it being fed to the second reactor. Agglomeration may be required to increase the particle size of the magnetite (i.e. to a more optimal size for the reaction of the second reactor).

In some embodiments of the third aspect, the system may further comprise a condenser to which an exhaust gas from the first reactor is passed. When the exhaust gas comprises water, the water is present as steam. Accordingly, in the condenser, the water (when present) is condensed from the exhaust gas from the first reactor. The condenser may comprise a hydrogen separator in which the gas comprising hydrogen is separated from the condensed water.

In some embodiments of the third aspect, the system may further comprise a recycle line that is configured to receive and pass the separated gas comprising hydrogen from the condenser and feed it to the second reactor. In this regard, the reducing gas fed to the second reactor may comprise the separated gas comprising hydrogen. Advantageously, by recycling the hydrogen, the requirement for fresh hydrogen may be reduced.

In some variations of the third aspect, the system may further comprise a briquetting plant. The briquetting plant may be configured to convert the powder comprising iron into briquettes. The briquettes may comprise sponge iron and may be sold as a product.

In some other variations of the third aspect, the system may further comprise one or more processing stages that are configured to convert the powder comprising iron into steel. In some of these other variations, the system may further comprise a mixer in which the powder comprising iron (i.e., as produced by the second reactor) is mixed with additives. A mixture comprising the iron and the additives may thereby be produced. Said mixture may then be converted into steel. As above, the additives can comprise materials which support downstream processes such as melting/smelting operations, purification processes, and steel making. Suitable additives will be known to those skilled in the relevant art, but can comprise fluxing agents, slag modifiers, refractory stabilisers, etc.

In some of these other variations, the system may further comprise a briquetting unit that is configured to convert the mixture into briquettes of iron and flux additives. The briquettes may then be sold as a product. Advantageously, the briquettes may be of particular value to steelmakers because they already comprise the flux additives. This can reduce the complexity of converting the briquettes into steel (e.g., in an electric arc furnace).

In some of these other variations, the system may further comprise an electric arc furnace in which the mixture is heated under conditions by which steel is produced.

In some embodiments of these other variations, the system may further comprise a series of pipes that are configured to receive and pass a portion of the exhaust gas from the first reactor and feed it to the electric arc furnace.

In some embodiments of the third aspect, the system may further comprise a scrubber. The scrubber may be configured to scrub carbon monoxide (when present) from the first reactor exhaust gas. Alternatively or additionally, the scrubber may be configured to scrub the carbon monoxide (when present) from a remaining portion of the first reactor exhaust gas that is not fed to the electric arc furnace. In some of these embodiments, the system may further comprise a condenser that is configured to condense water from the resultant scrubbed exhaust gas.

In some embodiments of the third aspect, the system may further comprise a pyrolyser in which biomass is converted to carbon and a gas comprising hydrogen and carbon monoxide. As above, the pyrolyser may be of a sorbent enhanced gasification type (i.e., so as to reduce and/or eliminate carbon dioxide and/or carbon monoxide in the gas produced by the pyrolyser). In the pyrolyser, the biomass may be converted to carbon and a gas comprising hydrogen and carbon monoxide by pyrolysis.

The system may further comprise a gas separator configured to separate the gas comprising hydrogen and carbon monoxide from the carbon. The separated gas comprising hydrogen and carbon monoxide may be passed, e.g., through a recycle line, from the separator and into to the second reactor, such that the reducing gas fed into the second reactor comprises said separated gas.

In some embodiments of the third aspect, the system may further comprise one or more beneficiation stages. The one or more beneficiation stages may be configured to treat an iron ore so as to produce the powder comprising iron ore to be fed into the first reactor.

In some embodiments of the third aspect, the first reactor and the second reactor may each comprise an externally heated vertical reactor. Each of the externally heated vertical reactors may comprise: a vertically oriented reactor tube; a hopper located adjacent to a top end of the reactor tube and configured to feed the powder comprising iron ore such that said powder falls downwards in the reactor tube; one or more reducing gas feed ports arranged along the reactor tube from a base thereof for feeding a reducing gas into the reactor tube; heating elements positioned vertically adjacent to at least one wall of the reactor tube and configured to provide heat to be conducted through the at least one wall, so as to heat the powder and the gas within the reactor tube to a temperature at which the powder and the gas are able to react; a gas exhaust positioned adjacent to the top end of the reactor tube; and an iron powder output positioned at a base of the reactor tube.

Counter- then co- flow process

Disclosed herein in a fourth aspect is a process for reducing iron ore. The process of the fourth aspect may be particularly suitable for reducing low grade or lower grade iron ore so as to produce a high-grade iron, generally referred to as sponge iron. The process may comprise the continuous flash H-DRI reduction of iron ore powders for ironmaking using an indirectly heated reactor which operates in a regime of dilute flow of particles in a gas, injected initially as hydrogen.

The process of the fourth aspect can comprise feeding a powder comprising iron ore and a reducing gas into a first reactor and indirectly heating the first reactor so as to heat the powder and the gas to a temperature at which the iron ore is partially reduced.

The process of the fourth aspect can also comprise feeding a resultant exhaust gas in which at least some of the partially reduced iron ore is entrained from the first reactor to a second reactor and indirectly heating the second reactor so as to heat the partially reduced iron ore and the exhaust gas to a temperature at which the partially reduced iron ore is further reduced.

In some embodiments of the fourth aspect, in the first reactor, the powder and the reducing gas may flow in a counter-flow arrangement, and in the second reactor, the partially reduced iron ore and the exhaust gas may flow in a co-flow arrangement.

In some embodiments of the fourth aspect, the process may further comprise collecting a remaining partially reduced iron ore from the first reactor and collecting the further reduced iron ore from the second reactor.

In some embodiments of the fourth aspect, the process may further comprise passing a second exhaust gas from the second reactor to a gas-particle separation stage. In the gasparticle separation stage, entrained further reduced iron may be separated from the second exhaust gas. The separated further reduced iron may be combined with the remaining partially reduced iron ore from the first reactor and the further reduced iron ore from the second reactor, thereby forming a sponge iron product. In some embodiments of the fourth aspect, each of the first reactor and the second reactor may be indirectly heated so as to maintain a temperature of between 700 °C to 1100 °C within the respective reactor. For example, each reactor may be indirectly heated so as to maintain a temperature of between 700 °C to 1050 °C, such as between 700 °C to around 900 °C. This temperature range has been found to be optimal towards the conversion reactions taking place in each reactor. In addition, at high temperatures, agglomeration may be reduced and reactor fouling attributed to the propensity of particles with a high fraction of iron atoms in the elemental Fe° state particles to bind thereto may also be reduced. In this regard, each of the reactor temperatures is typically lower than the temperature at which the iron ore agglomerates. Accordingly, it will be appreciated that the temperature of the first reactor and the second reactor will depend on the material to be heated.

In some embodiments of the fourth aspect, the reducing gas may comprise hydrogen. When the reducing gas comprises hydrogen, the second exhaust gas comprises water. The second exhaust gas may further comprise hydrogen. For instance, when an excess of hydrogen is used in the reducing gas fed to the first reactor, such that not all of the hydrogen is consumed in the first reactor and the second reactor.

In some embodiments of the fourth aspect, the process may further comprise collecting the second exhaust gas and condensing water therefrom. A gas comprising hydrogen may then be separated from the condensed water. For example, when an excess of hydrogen is used in the reducing gas. The gas comprising hydrogen may be reused in forming the reducing gas which is fed into the first reactor. In this way, the excess hydrogen is able to be recovered and recycled. However, it is noted that, typically, the composition of the reducing gas will be selected such that all the hydrogen is consumed in the first reactor.

In some embodiments of the fourth aspect, the iron ore in the powder fed to the first reactor may comprise hematite, goethite or siderite in the F^e3+ state. In some of these embodiments, both the partially reduced iron ore and the further reduced iron ore may comprise iron and/or magnetite.

In some embodiments of the fourth aspect, the process may further comprise passing the sponge iron product through a hot-briquetted iron plant to produce iron briquettes. The iron briquettes may be sold as a valuable by-product of the process. Alternatively or additionally, the process may further comprise converting some or all of the sponge iron product into steel. The steel may be sold as a (or another) valuable by-product of the process.

In some embodiments of the fourth aspect, the process may comprise the steelmaking process of the first aspect. Co-flow then counter-flow with separate feeds

Disclosed herein in a fifth aspect is a process for reducing iron ore. The process of the eighth aspect may be suitable for reducing low grade or lower grade iron ore so as to produce a high-grade iron, generally referred to as sponge iron. The process of the eighth aspect may also be suitable for reducing low grade iron ore so as to produce magnetite. The process may comprise the continuous flash H-DRI reduction of iron ore powders for ironmaking using an indirectly heated reactor which operates in a regime of dilute flow of particles in a gas, injected initially as hydrogen.

The process of the fifth aspect can comprise feeding a first powder comprising iron and a first reducing gas into a first reactor such that the first powder and the first reducing gas flow in a co-flow arrangement. The process can also comprise indirectly heating the first reactor so as to heat the first powder and the first reducing gas to a temperature at which the iron is converted to magnetite. As explained below, the iron in the first powder can comprise iron in a number of forms, oxidation states, etc. However, the first powder will comprise at least some iron which is able to be reduced to magnetite.

The process of the fifth aspect can also comprise feeding a second powder comprising iron and a second reducing gas into a second reactor such that the second powder and the second reducing gas flow in a counter-flow arrangement. The process can comprise indirectly heating the second reactor so as to heat the second powder and the second reducing gas to a temperature at which the iron is reduced. A powder comprising reduced iron is thereby formed.

The process of the fifth aspect can further comprise passing a second exhaust gas from the second reactor to the first reactor, such that the first reducing gas comprises the exhaust gas from the second reactor. The second exhaust gas can comprise entrained powders from the second reactor. The entrained powders may be passed along with the second exhaust gas into the first reactor. This is in contradistinction to other processes in which the entrained powders are separated from the exhaust gas and reintroduced into the reactor. By eliminating the need for such a separation stage, the design and construction of the second reactor may be simplified.

In some embodiments of the fifth aspect, the feed to the second reactor may comprise magnetite. When the feed to the second reactor comprises magnetite, the reduced iron may comprise elemental iron. Alternatively, in other embodiments, the feed to the second reactor may instead comprise hematite, goethite and siderite and combinations thereof. In these embodiments, the reduced iron typically comprises magnetite. In some embodiments of the fifth aspect, the feed to the first reactor may comprise hematite, goethite, magnetite, wustite and/or elemental iron.

In some embodiments of the fifth aspect, the feed to the second reactor may further comprise magnesium oxide and/or calcium oxide. For example, the magnesium oxide and/or calcium oxide may be included as anti-sticking agents.

In some embodiments of the fifth aspect, the process may further comprise passing a first exhaust gas in which the powder comprising the magnetite is entrained to a gas-powder separation stage. In the gas-powder separation stage, the powder comprising the magnetite may be separated from the first exhaust gas.

In some embodiments of the fifth aspect, the separated powder comprising the magnetite may be passed to a magnetic separation stage in which the magnetite is magnetically separated from a gangue. The separated magnetite may be fed to the second reactor.

In some embodiments of the fifth aspect, each of the first reactor and the second reactor may be operated in a dilute flow regime.

In some embodiments of the fifth aspect, each of the first reactor and the second reactor may be indirectly heated so as to maintain a temperature of between 700 °C to 1100 °C within the respective reactor. For example, each reactor may be indirectly heated so as to maintain a temperature of between 700 °C to 1050 °C, such as between 700 °C to around 900 °C. As above, at high temperatures, agglomeration may be reduced, and reactor fouling attributed to the propensity of particles with a high fraction of iron atoms in the elemental Fe° state particles to bind thereto may also be reduced.

In some embodiments of the fifth aspect, the second reducing gas may comprise hydrogen. In these embodiments, the first reducing gas may comprise hydrogen and water.

In some embodiments of the fifth aspect, the first exhaust gas may be passed to the second reactor. In this regard, the second reducing gas may comprise the first exhaust gas.

In some embodiments of the fifth aspect, the first exhaust gas may comprise water. In these embodiments, the first exhaust gas may be passed to a condenser in which the water is condensed. When the first exhaust gas further comprises hydrogen, a gas comprising hydrogen may be separated from the condensed water. The gas comprising hydrogen may be recycled to the second reactor.

In some embodiments of the fifth aspect, a portion of the second powder fed to the second reactor may become entrained in the second exhaust gas. For example, as the second exhaust gas passes out of the reactor, a portion of the second powder may become entrained therein. The second exhaust gas, along with the entrained powder, may be passed to the first reactor. The powder feed to the first reactor may further comprise the entrained portion of the second powder.

In some embodiments of the fifth aspect, the process may further comprise passing the powder comprising elemental iron through a hot-briquetted iron plant to produce sponge iron briquettes. Alternatively or additionally, the process may further comprise passing the powder comprising elemental iron through a magnetic separation stage to produce a higher-grade iron powder.

Hydrogen production

Disclosed herein in a sixth aspect is a process for producing hydrogen. The process can be advantageously employed for producing hydrogen for use in reducing iron. The process can also be employed for upgrading a low-grade reduced iron, at the same time as producing hydrogen for use in a subsequent reduction process.

The process of the sixth aspect can comprise feeding a first powder comprising elemental iron and a first gas comprising water vapour into a first reactor such that the first powder and the first gas flow in a co-flow arrangement. The first reactor can be indirectly heated so as to heat the first powder and the first gas to a temperature at which the iron and water are converted to magnetite and hydrogen.

In some embodiments of the sixth aspect, the process may comprise feeding a second powder comprising iron and a second reducing gas into a second reactor such that the second powder and the second reducing gas flow in a counter-flow arrangement. The second reactor may be indirectly heated so as to heat the second powder and the second reducing gas to a temperature at which the iron is reduced. A powder comprising reduced iron may thereby be formed. The second exhaust gas may be passed from the second reactor to the first reactor, such that the first gas comprises the second exhaust gas.

In some embodiments of the sixth aspect, a gas comprising hydrogen is passed from the first to the second reactor, such that the first reducing gas comprises the exhaust gas from the second reactor.

In some embodiments of the sixth aspect, the second powder may comprise magnetite, hematite, goethite, siderite, titanomagnetite, ilmenite, or mixtures thereof. The reduced material may comprise elemental iron. In some embodiments of the sixth aspect, the process may comprise the process as defined by the eighth aspect.

Finishing/polishing reactor

Disclosed herein in a seventh aspect is a process for producing a steel precursor.

The process of the seventh aspect can comprise feeding a gas and a powder comprising iron and one or more carbonates into a reactor such that the powder and the gas flow in a counter-flow arrangement. The reactor can be indirectly heated so as to heat the powder and the gas to a temperature at which the one or more carbonates are decomposed, thereby producing an exhaust gas comprising carbon dioxide. The heated powder may be suitable for use as a feed to a hot briquetting plant. Alternatively or additionally, the heated powder may be suitable for use as a feed in a steelmaking process, such as a smelter or an electric arc furnace.

The process of the seventh aspect can also comprise passing the exhaust gas comprising carbon dioxide to a solid oxide electrolyser in which the carbon dioxide is electrolysed, thereby forming a gas comprising carbon monoxide. The gas fed to the reactor can comprise the gas comprising carbon monoxide.

In this regard, the process of the seventh aspect can be used to both calcine the one or more carbonates, as well as producing a mix of iron and additives suitable for use in a downstream process (such as a hot briquetting stage, a smelter, an electric arc furnace etc.). This is in contradistinction to processes of the prior art in which the one or more carbonates are calcined in a separate vessel. The calcined carbonates (i.e., in the form of oxides) are then mixed with the iron in a separate stage. This is possible because the gas exhaust from the reactor is passed to a solid-state electrolyser, in which the carbon dioxide is converted into carbon monoxide, which can be recycled back to the reactor.

In some embodiments of the seventh aspect, the one or more carbonates may comprise calcium carbonate and/or magnesium carbonate. In these embodiments, the calcium carbonate and/or magnesium carbonate may be decomposed into calcium oxide and/or magnesium oxide - both known and useful slag modifiers/refractory stabilisers.

In some embodiments of the seventh aspect, the gas may further comprise hydrogen. Hydrogen may be present as an inert gas or may be present to facilitate further reduction of iron that is present in the powder comprising iron in an oxidised form. In this regard, in some embodiments, the iron may comprise iron in an oxidised form and the process may further comprise indirectly heating the reactor so as to heat the powder and the gas to a temperature at which the iron is reduced. For example, the reduced iron may comprise elemental iron. The oxidised iron may comprise FeO.

In some embodiments of the seventh aspect, the exhaust gas may further comprise water, as steam. In the solid oxide electrolyser, the water may be electrolysed such that a gas comprising carbon monoxide and hydrogen is formed. The gas fed to the reactor may comprise the gas comprising carbon monoxide and hydrogen.

In some embodiments of the seventh aspect, the process may further comprise indirectly heating the reactor so as to heat the powder and the gas to a temperature at which the iron is carburised. For example, so as to produce iron carbide. Carburised iron can be advantageously used as a feed to a steelmaking process.

In some embodiments of the seventh aspect, the process may further comprise feeding one or more additional additives into the reactor. Feeding the one or more additional additives into the reactor, may reduce and/or eliminate the need for further additives to be added in downstream processes. This can reduce the complexity of operating such downstream processes. The one or more additional additives may comprise any known additives which support downstream processing operations. For example, these additional additives may comprise carburizing agents, fluxing agents, slag modifiers, refractory stabilisers, etc. For example, the additives may comprise magnesium oxide and/or calcium oxide. Advantageously, the process can enable flexibility in terms of the additives employed. In particular, it is thought that, by introducing the additives into the reactor, cheaper additives may be employed. For instance, carbonates may be employed instead of oxides as slag modifiers/refractory stabilisers, because the carbonates may be calcined in the reactor.

In some embodiments of the seventh aspect, the reactor may be operated in a dilute flow regime.

In some embodiments of the seventh aspect, the reactor may be indirectly heated so as to maintain a temperature of between 700 °C to 1050°C therewithin.

In some embodiments of the seventh aspect, the process may further comprise passing the heated powder through a hot-briquetted iron plant to produce sponge iron briquettes. Alternatively or additionally, the process may further comprise converting the heated powder into steel. For example, in a smelter or an electric arc furnace.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described by way of example only, with reference to the accompanying drawings in which Fig- 1 is a process flow diagram, in block form, of an embodiment of a two-stage process for producing sponge iron and/or pig iron from iron ore.

Fig. 2 is a process flow diagram, in block form, of an embodiment of a two-stage process for producing steel from iron ore.

Fig. 3 is a process flow diagram, in block form, of another embodiment of a two-stage process for producing sponge iron or steel comprising a co-flow stage and a counter-flow stage.

Fig. 4 is a process flow diagram, in block form, of another embodiment of a two-stage process for producing sponge iron or steel.

Fig. 5 is a process flow diagram, in block form, of another embodiment of a two-stage process for producing sponge iron or steel in which the feed to the first and the second stages is different.

Fig. 6 is a process flow diagram, in block form, of an embodiment of a polishing reactor for producing sponge iron.

The same reference numerals are used to denote the same features in each diagram.

DETAILED DESCRIPTION

In the following detailed description, reference is made to accompanying drawings which form a part of the detailed description. The illustrative embodiments described in the detailed description, depicted in the drawings and defined in the claims, are not intended to be limiting. Other embodiments may be utilised, and other changes may be made without departing from the spirit or scope of the subject matter presented. It will be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the drawings can be arranged, substituted, combined, separated and designed in a wide variety of different configurations, all of which are contemplated in this disclosure.

Disclosed herein are processes and systems for reducing iron ore. The process comprises: feeding a powder comprising iron ore and a first gas into a first reactor and indirectly heating the first reactor so as to heat the powder and the gas to a temperature at which the iron ore is converted to magnetite; and feeding a resultant powder comprising magnetite and a reducing gas into a second reactor and indirectly heating the second reactor so as to heat the powder comprising magnetite and the reducing gas to a temperature at which the magnetite is reduced to iron, to thereby form a powder comprising iron. The processes and systems employ continuous flash H-DRI reduction of iron ore powders for ironmaking using an indirectly heated reactor which operates in a regime of dilute downwards flow of particles in a gas, injected initially as hydrogen.

In some variations, the reduced iron ore is converted into high grade iron, generally referred to as sponge iron. In this regard, this variation includes the extraction of gangue from the iron ore to upgrade the iron product to sponge iron. The sponge iron can be suitable for transportation to end-users, such as steelmakers who use the sponge iron to make steel. It will be appreciated that sponge iron can be advantageous compared to sponge iron because it generally comprises more iron and less impurities (on a weight basis). For example, the sponge iron can be shipped to steelmakers instead of iron ore. In this regard, the production of sponge iron advantageously adds value to the iron ore, i.e., because the sponge iron provides the iron in an already reduced and higher purity form compared to iron ore and the cost of shipping to steelmakers is reduced.

In other variations, the reduced iron ore is converted into steel as an extension of the process, with the steel transported to end-users. The steelmaking process can be advantageously tailored to meet the required steel specifications; for example, by adding different additives. Both these variations will be described in further detail below with reference to Figs. 1 and 2.

Both variations can advantageously employ indirectly heated vertical reactors of the type described in detail in the applicant’s PCT application no. WO2023064981, the entire contents of the specification of which is incorporated herein by way of cross-reference. WO2023064981 discloses an indirectly heated vertical reactor, suitable for use in the reduction of iron ore, and which can lower CO2 emissions associated with the reduction thereof and the production of steel. As described in detail in WO2023064981, the reactor is particularly advantageous in that it enables the processing of iron ore in the form of a powder, rather than pellets. It is noted that, in pellet-based processes, heat transfer between a pellet and the reducing gas is often limited by the thickness of the pellets. In contrast, heat transfer between a powder and the reducing gas can occur at a faster rate, resulting in faster reaction rates, e.g., because powders have a higher surface area to volume ratio. This can decrease the residence time of the iron ore within the reactor. Moreover, it is noted that the need for a pelletisation step increases the complexity and energy requirements of a process primarily because the pellets require thermal induration to gain the strength required.

In the present disclosure, both variations (i.e., ironmaking and steelmaking), employ two indirectly heated reactors of the type described in WO2023064981 in series. In the first reactor, iron ore, typically in the form of a mixture of hematite, goethite and siderite (all with iron in the Fe3+ state) is converted to magnetite, cooled and beneficiated through magnetic separation. In the second reactor, the magnetite is heated and reduced into iron. The iron product can be used to make hot iron briquettes and cooled for transport, or it can be directly as a hot input for (steelmaking. If beneficiation is not used, the product is sponge iron.

Advantageously, by separating the conversion of input iron ore to magnetite from the reduction of magnetite to iron, the non-magnetic gangue can be separated from the magnetite, i.e., prior to the second reduction stage. This can result in a reduced iron of higher purity as compared to, e.g., to processes of the prior art in which the iron ore is converted to magnetite and reduced to iron in the same reactor. This is because some gangue is difficult to separate from goethite during beneficiation stages. However, because said gangue is non-magnetic, it is more easily separated from the magnetite (which is magnetic), using e.g., magnetic separation. Also, by separating the conversion of the iron ore to magnetite from the reduction of magnetite to iron, various reactor gas recycle configurations can be employed, as explained in more detail hereafter.

In order to efficiently employ the indirectly heated vertical reactors of the type described in detail in WO2023064981, the powder feed to the reactor (i.e., comprising iron ore or magnetite) is typically in the form of an ultra-fine powder with a mean size of below about 200 pm diameter. The advantage of employing ultra-fine powder in the processes and systems disclosed herein is that the conditions of the reactor(s) can be such that the reduction process of the ultra-fine particles is very fast, and is typically complete within a reactor residence time of less than about 60 seconds. Such residences times are typical of a flash pyro-process in a continuous flow reactor. The fast reaction for ultra-fines means there is no need for a fluidised bed technology for iron reduction. In contrast, a dilute flow regime can instead be employed within the reactor.

By contrast, a slow reduction H-DRI process (such as those commonly employed in the prior art) may be carried out using granules of iron ore, of a diameter of about 10 mm or larger, that flow downwards in a slow moving packed-bed in a reactor in a counterflow of injected reducing gas. The slow-moving bed approach is used in conventional DRI and proposed H-DRI processes. Slow-moving beds are subject to disintegration of granules by the large interparticle forces generated by the slow movement. Fines and ultra-fines produced from such disintegration may lead to blockages and inhomogeneous gas flows, that may lower the average degree of metallisation of the product. Sufficiently strong granules must be made by granulation followed by thermal annealing (also called sintering or induration) to generate a high strength required to suppress disintegration. These granulation processes consume significant energy and are responsible for significant residual CO2 emissions, even when hydrogen is later used as a reductant. To achieve near-net zero emissions iron, there is a need for a continuous process that does not require pelletisation and annealing.

It would be apparent to a person skilled in the art that the degree of reaction of a flash reaction with a low particle volume process may offset a slow process with a high particle volume. Hence the flux of iron product, in kg m'² s'¹ may be similar for a flash process of small particles and a slow, moving bed of large particles.

In any gas-particle reactor, a long tail of small ultra-fines may occur from grinding processes, which may be elutriated with the gas during the required gas-particle separation. To compensate, a grinding process, such as a cylindrical grinder, that fuses the tail of small ultra-fines particles by grinding pressure prior to injection into the reactor may be employed. Any elutriated fines may be captured in cyclone separators and be reinjected into the reactor.

The dilute flow regime employed by the indirectly heated vertical reactors of the present disclosure can have sufficiently low solids to gas volume such that an upwards flow of reducing gas does not support the formation of a fluidised bed of particles. As a result, management of discontinuous flows of charging, discharging and other transients of fluidised bed H-DRI reactors are not encountered. Experiments show that the reduction reactions are sufficiently fast for porous ultrafine iron ores that there is no need to impose the restrictions of forming a fluidised bed.

Ironmaking - Fig, 1

Fig. 1 is a process flow diagram, set out in block form, of a process 10 for producing sponge iron from iron ore. In the process 10, the iron ore is reduced to sponge iron. The process 10 is comprised of three main blocks: a H-pyro-beneficiation block 12, an H-DRI block 14, and a hydrolyser block 16. In the H-pyro-beneficiation block 12, iron ore 18 is converted into magnetite 20 in a vertical reactor 30 of the type disclosed in WO2023064981. The magnetite 20 is transported, e.g., conveyed, from the beneficiation block 12 to the H-DRI block 14 in which it is converted into, in the illustrated embodiment, sponge iron 22. In the H-DRI block 14, a second vertical reactor 32 of the type disclosed in WO2023064981 is employed to reduce the magnetite to iron. In the third hydrolyser block 16, a gas 36 comprising hydrogen and water, suitable for use in the H-DRI reactor 32 is produced. The gas 36 can comprise unused hydrogen, i.e., recycled and separated from the exhaust gas from the first reactor 50, as well as recovered water present in the exhaust gas from the first reactor 50. Additional hydrogen can be supplied by an electrolyser in which water, or condensed water, is electrolysed. Each of these blocks is described in more detail below. H-pyro-beneficiation block 12

In the H-pyro-beneficiation block 12, incoming iron ore 18 is converted into magnetite 20. The iron in the iron ore 18 is predominantly in the Fe³⁺ oxidation state. The iron ore 18 typically comprises low-grade iron, e.g., from a mine. The low-grade iron ore 18 can comprise non-magnetic ores such as hematite, goethite or a hematite-goethite mix or other ores such a siderite, or magnetic ores such as such a magnetite. However, typically, the feed to the process 10 is a non-magnetic iron ore. The iron ore may also contain minerals containing chromium, manganese, lithium, and rare-earth that, in metallic form, can be used in steelmaking. That is, as will be appreciated, such low-grade iron ores 18 typically comprise a significant fraction of non-iron-containing minerals, i.e., gangue. In this regard, the iron ore 18 may be subjected to one or more beneficiation stages in which the ore is upgraded. For example, gravitational separation based on density may be used to remove denser gangue material from the iron ore.

In the illustrated embodiment of Fig. 1, the low-grade iron ore 18 is first subjected to a crushing stage 36. In the crushing stage 36, the low-grade iron ore 18 is crushed so as to reduce the particle size thereof. The crushing stage 36 can comprise any crushing technologies known to those in the art, e.g., crusher, mill, etc. The crushed ore is then passed through a size separation stage (not shown) in which gangue 28 is separated from a crushed iron ore 38, e.g., based on a difference in particle size, with the gangue 28 typically having larger diameter particles than the crushed iron ore 38. It will be understood that the crushed iron ore 38 comprises a higher concentration of iron than the low-grade iron ore 18, however the concentration of iron in the crushed iron ore 38 is typically still low, such that the crushed iron ore 38 may still be classified as a low-grade iron ore. The gangue 28 can be collected and disposed of as waste or used as landfill in, e.g., a mine.

The crushed iron ore 38 is transported, e.g., conveyed, to a grinder 40. In the grinder 40, the crushed iron ore 38 is ground so as to produce a powder comprising iron 42. The powder comprising iron 42 typically has a particle size of less than 250 pm, i.e., such that it is suitable to be fed into the first vertical reactor 30. The grinder 40 can comprise a variety of known crushers and/or grinders.

The operation of the vertical reactors, such as the first vertical reactor 30, is described in greater detail in WO2023064981. In the reactor 30, the crushed iron ore 42 is heated in the presence of a gas 44 so as to produce magnetite. In particular, the reactor 30 is typically operated at a temperature of between about 700 to 1100 °C. For example, the first reactor 30 can be operated at a temperature of between 700 °C to 1050 °C, such as between 700 °C to around 900 °C. This temperature range has been found to be optimal towards the conversion of magnetite. In addition, at high temperatures cascading agglomeration may be reduced and reactor fouling may also be reduced. In this regard, the reactor temperature is typically lower than the temperature at which the crushed iron ore 42 agglomerates.

The conversion of goethite in the crushed iron ore 28 to magnetite is a temperature-based reduction reaction, i.e., the decomposition of goethite into magnetite is facilitated by heating the crushed iron ore 42 to within this temperature range in the presence of a reducing gas. In this regard, the gas 44 typically comprises hydrogen, i.e., so as to facilitate the reduction of the goethite to magnetite. However, the gas 44 may alternatively or additionally comprise ammonia. It is noted that the selection of either gas (i.e., hydrogen and/or ammonia) can remove the use of carbon monoxide, methane, and/or syngas as a reducing gas, as the traditional ironmaking processes. As a result, the CO2 emissions of the process as disclosed herein may be greatly reduced (i.e., compared to prior art processes). An advantage of ammonia is that it is more readily shipped as a liquid than hydrogen. However, a disadvantage of ammonia in a flash reduction process is the increase in the gas flow rate as the reaction proceeds, due to the nitrogen produced. With hydrogen as the reductant gas, the iron reduction process generates steam in the exhaust, so that the molar gas flow rate is essentially preserved. Although the embodiments described herein are described with reference to hydrogen as the reducing gas, it is thought that the same principles outlined apply when ammonia is used as the reducing gas. As will be explained in more detail below, the gas 44 typically comprises an exhaust gas from a second reactor 32. By using the exhaust gas 44 from the second reactor 32, heat in the exhaust gas 44 can be recovered (i.e., because the gas provides its thermal energy to the iron 42 in the reactor 30). The gas 44 may be a mixture of hydrogen and water. It will be appreciated that, at the temperatures employed for the first reactor 30 and the second reactor 32, the water is in the form of steam. Because the exhaust gas 44 does not comprise oxygen, oxidation of the iron 42 can be avoided. However, it is noted that, if the concentration of hydrogen in the gas 44 is too high, the magnetite may be caused to be further reduced, e.g., to elemental iron. Hence, the concentration of hydrogen in the gas 44 is controlled.

Typically, the reactor 30 is operated in a dilute flow regime in which there is an excess of reducing gas (hydrogen). An excess of reducing gas can help suppress the reverse reaction. As will be described in further detail below, the excess reducing gas is separated from the powder and recycled, such that most of the reducing gas is ultimately consumed. Steam, a product from the reduction reaction of iron oxides with hydrogen, is separated from remaining hydrogen, generally by condensation of steam to water. This gas cleanup process involves not only the separation of water, but also entrained powder and other gases produced in powder reduction processes, such as sulphur and chorine, to optimise the product quality. Entrained powder is reinjected into the reactor until consumed.

The inventors note that it can be advantageous to minimise the further reduction of magnetite (e.g., to iron) in the reactor 30 because magnetite (being magnetic) may be easily separated from remaining non-magnetic gangue (i.e., by magnetic separation). In this regard, the conditions in the reactor 30 are controlled such that the reduction of magnetite formed therein is minimised and/or altogether suppressed.

The ratio of hydrogen to water in an atmosphere in which iron is heated is known to affect the propensity of the magnetite to further reduce. By further controlling the stoichiometric quantities of hydrogen and water in the gas 44 in the reactor 30, conditions can be maintained under which the reduction of magnetite in the reactor 30 is thermodynamically unfavourable. It is also known that the thermodynamics of the reduction reaction are dependent on temperature, as well as the stoichiometric ratio of hydrogen to water present in the gas 44. It is thought that, at a temperature of between about 700 to 1100 °C (i.e., the typical operating temperatures of the reactor 30), a stoichiometric ratio of hydrogen to water (present in the form of steam at such temperatures) of about 1:1 can minimise the further reduction of magnetite to, e.g., iron. However, it will be appreciated that other stoichiometric ratios and other operating temperatures may be employed. As above, the reactor 30 may alternatively be operated such that some reduction of magnetite occurs in the reactor 30. For example, when magnetic separation of remaining gangue is not required (e.g., where such gangue has been removed prior to feeding to the reactor 30).

In some embodiments, the gas 44 comprises carbon monoxide and carbon dioxide. In such embodiments, the reactor temperature and the ratio of carbon monoxide to carbon dioxide in an atmosphere in which iron is heated can also affect the propensity of magnetite to further reduce. As such, the reaction conditions of the reactor 30, including the reactor temperature and the composition of the gas 44, is typically controlled so as to optimise the formation of magnetite from the input ore and to suppress the further reduction of magnetite to iron in the Fe° state. It is noted that the optimal composition of the gas 44 input to the reactor 30 is dependent on the reactor 30 temperature. For example, when the reactor 30 is operated at a temperature of about 900 °C, it has been found that it can be optimal to maintain a stoichiometric ratio of CO:CO2 of less than about 2.9: 1 in the gas 44. On the other hand, when the reactor 30 is operated at a temperature of about 1100 °C, it can be optimal to maintain a stoichiometric ratio of CO:CO2 of less than about 1.2: 1 in the gas 44. However, it will be appreciated that other stoichiometric ratios and other operating temperatures may be employed. Alternatively, the reactor 30 may be operated such that some reduction of magnetite occurs in the reactor 30. For example, when magnetic separation of remaining gangue is not required (e.g., where such gangue has been removed prior to feeding to the reactor 30).

The first reactor 30 is indirectly heated to raise the temperature of the powder and the reducing gas therewithin to a temperature at which the hematite/goethite in the ore is reduced to magnetite. Typically, the degree of reduction is about 75-85% on an iron basis. In particular, indirect heating is used to heat the powder and the gas to a temperature whereby the required degree of reduction is achieved within the residence time of the powder in the reactor 30. Heat recuperation from the hot output gas and powder streams may be used to minimise the heating for the powder and gas entering the reactor. It is noted that the use of counterflow of powder and gases in each segment can reduce the heat transfer energy demand and shorten the required reactor length. It is also noted that, because hydrogen is used as the reducing gas, the reduction reaction is a small exothermic reaction. This is in contrast to when carbon monoxide and hydrogen are employed (as in traditional processes), wherein the reduction reaction is highly exothermic. It will also be appreciated that the flow of the gas 44 can be further controlled so as to provide a required residence time of the iron 42 within the reactor 30, as well as the required fluid dynamics within the reactor 30. The flow of gas 44 may be either co- or counter- flow to the falling powder flow.

From the reactor 30, a stream 46 comprising the gases (i.e., hydrogen and water to the extent to which they are present in the gas 44) with entrained particles (now comprising iron primarily in the form of magnetite, as well as remaining gangue) is collected and passed to a magnetic separator 48. As well as separating the magnetic magnetite 52 from a non-magnetic gangue 26, the magnetic separator 48 is configured to also separate the gases 50 in which the particles in the stream 46 were entrained. The magnetic separator 48 can comprise any known magnetic separation process (e.g., high grade magnetic separation and/or wet high intensity magnetic separation). In this regard, it will be appreciated that an advantage of reducing the hematite/goethite to magnetite in the reactor 30 is that the magnetic properties of magnetite may be exploited so as to enable separation of the magnetite from gangue. Typically, the magnetite must be cooled sufficiently below the Curie temperature of magnetite to enable efficient magnetic separation. The use of magnetic separation at high temperatures may be used, such as using a roll magnetic separator which does not use permanent magnets.

The non-magnetic gangue 26 is disposed of, e.g., as waste, or for use as landfill (e.g., at a mine site). As will be described in further detail below, the gases 50 are passed to the hydrolyser block 16. Advantageously, by separating the non-magnetic gangue 26 from the magnetite, a final sponge iron product 22 of higher purity may be achieved. This is compared to processes of the prior art in which the goethite is converted to magnetite and reduced to iron in the same reactor.

Alternatively, the stream 46 can be passed through a gas separator prior to the magnetic separator 48, such that entrained particles are separated from the gases (i.e., hydrogen and water to the extent to which they are present in the gas 44) and only the particles present in the stream 46 are passed to the magnetic separator 48. The stream 46 comprising the magnetite can be optionally cooled, such as by flash quenching, prior to the magnetic separator 48 (or prior to the gas separator, when present).

The magnetite 52 is typically in the form of a super-fine powder, with particle sizes of 10 pm or less. It is noted that, when in such small particle sizes, the magnetite 52 is generally too small to be directly used as a feed to the second reactor 32. When the magnetite 52 comprises such small particle sizes, the magnetite 52 is passed to a fusion plant 54. In the fusion plant 54, the magnetite 52 is agglomerated so as to form magnetite with larger particle diameters. In particular, agglomeration is performed so as to form an ultra-fine magnetite powder 20. Typically, the ultra-fine powder comprises particles with diameters of less than about 250 pm, i.e., such that the ultra-fine magnetite powder 20 is suitable to be used as a feed to the second reactor 32. The ultra-fine magnetite powder 20 is transported, e.g., conveyed, from the fusion plant 54 to the second reactor 32 of the H- DRI block 14. Alternatively, for example when the magnetite 52 is already in the form of an ultra-fine powder with particles that are larger than 10 pm in diameter (i.e., as opposed to a super-fine powder), the magnetite 52 can be directly transported to the second reactor 32 and the fusion plant 54 may be by-passed and/or eliminated from the process 10 altogether.

H-DRI block 14

The fine magnetite powder 20 (or the magnetite 52) is fed into a second H-DRI reactor 32. As above, the H-DRI reactor 32 comprises a vertical reactor of the type described and taught in detail in WO2023064981. In the process 10, the reactor 32 is operated so as to cause the magnetite in the powder 20 (or the magnetite 52) to be reduced to iron.

To facilitate reduction of the magnetite to iron, a reducing gas is required. In this regard, a reducing gas 56, in this embodiment in the form of a mixture of hydrogen and water, is fed into the reactor 32, along with the fine magnetite powder 20. The reducing gas 56 and powder 20 are each inputted such that a dilute gas flow regime is established within the reactor 32. The reducing gas 56 may be in co- or counter- flow with the powder 20. The advantages of using a gas comprising hydrogen as the reducing gas will be appreciated from WO2023064981, namely, that the carbon footprint of the process 10 may be minimised. The reducing gas 56 can be pre-heated in a heat-exchanger 60, e.g., using process heat. As above, the advantage of employing ultra-fine particles in a dilute flow regime is that the reduction reaction occurs very quickly, resulting in shorter reactor residence times.

It will be appreciated that the kinetics of the reduction reaction of magnetite in the reactor 32 can be affected by the stoichiometric ratio of hydrogen and water present in the reducing gas 56, as well as the operating temperature of the reactor 32 and the stoichiometric ratio of hydrogen to magnetite. Typically, a stoichiometric excess of hydrogen is employed. In particular, hydrogen is added in an excess within a range of 50- 100%. Typically, the operating conditions of the reactor 32 are controlled such that a degree of metallisation in excess of about 90%, such as an excess of about 95% on an iron basis is achieved. It is thought that, by using an excess of hydrogen, with a stoichiometric ratio of hydrogen to water of about 2:1, and an operating temperature between 700 to 1100 °C, at least about 95% of the magnetite can be reduced to metallic iron in the reactor 32 to iron within the typical reactor residence times of between 10 to 50 s. At the same time, hydrogen present in the gas 56 is converted into water, which adds to the water already present therein.

As with the first reactor 30, the second reactor 32 is indirectly heated to raise the temperature of the powder and the reducing gas to a temperature at which the magnetite is reduced. It is noted that, in this way, the external heating of the reactor 32 (as well as the reactor 30) may be used to primarily control the reactor operation. Heat (for both reactors) may be generated from renewable power to reduce scope three CO2 emissions.

In some embodiments, the first reactor may be indirectly heated so as to maintain a temperature of between 700 °C to 1100 °C within the reactor. Additionally, the second reactor may be indirectly heated so as to maintain a temperature of between 700 °C to 1100 °C within the reactor. This temperature range has been found to be optimal towards the conversion reactions taking place in each reactor. The temperature is sufficiently high that the intermediate wustite form of iron oxide is unstable with respect to iron, and the temperature is sufficiently low that cascading agglomeration of particles may be inhibited.

Exiting the reactor 32 is a gas 44 comprising hydrogen and water, i.e., because not all the hydrogen is consumed in the reactor 32, and an iron powder 58, now primarily comprising iron (i.e., because the magnetite is reduced to iron in the reactor 32). Advantageously, because up to about half of the hydrogen in the gas 56 is converted into water in the reactor 32, the stoichiometric ratio of hydrogen to water in the exhaust gas 44 exiting the reactor 32 is closer to about 1 : 1. As a result, the exhaust gas 44 is suitable for use as the gas in the first reactor 30 (i.e., because at these ratios of hydrogen to water, reduction of the magnetite to iron is not thermodynamically preferred). In this regard, exhaust gas 44 from the reactor 32 is passed to the first reactor 30 for use as a reactor (e.g., carrier) gas therein. It is noted that the exhaust gas 44 can comprise ultra-fine powder, to the extent to which the ultra-fine powder is elutriated from the reactor 32 with the exhaust gas 44. In some embodiments, the exhaust gas 44 with the entrained ultra-fmes is passed to the first reactor 30. Advantageously, this allows the ultra-fmes to be further processed in the first reactor. In some of these embodiments, the exhaust gas 44 (along with the elutriated ultra-fines from the reactor 32) is inputted into the reactor 30 at a lower end thereof. It is thought that this can increase the residence time of the ultra-fmes in the reactor 30 because the downwardly falling input powder to the reactor 30 (i.e., the crushed iron 42) helps to suppress the elutriation of these ultra-fines from the reactor 30. In this regard, it is thought that injecting the ultra-fines into the bottom of the reactor 30 can significantly increase the extent of reduction within the ultra-fmes and reduce elutriation thereof from the reactor 30. In other embodiments, the ultra-fines are separated from the exhaust gas 44. The separated ultra-fmes can then be re-injected into the reactor 32, for example, by combining the ultra-fines with the powder 20 or by combining the ultra-fines with the gas 56. In another variation, the reactor 30 and/or the reactor 32 each comprise one or more hollow tubes located within the reactor body. The tubes are configured to allow the ultra- fmes (either as a powder or with a suitable gas) to be input therethrough. As the ultra- fmes flow within the hollow tubes, the ultra-fines are heated and the iron contained therein is reduced.

Returning to the illustrated embodiment of Fig. 1, the iron powder 58 is passed (e.g., conveyed) to a briquetting unit 62 in which the iron powder 58 is converted into briquettes 64. The operation of the briquetting unit 62 will be understood by those skilled in the art. Converting the iron powder 58 into impervious sponge iron briquettes 64 increases the ease of transportation. For example, when transported as briquettes, the risk of spontaneous combustion of iron ultra-fmes in air during transportation may be reduced and/or eliminated. It will be appreciated that the briquettes 64 comprise sponge iron. Sponge iron may be preferred to sponge iron by end-users (e.g., steelmakers) because it tends to comprise higher iron concentrations.

In the illustrated embodiment of Fig. 1, the briquettes 64 are indirectly cooled in a heat exchanger 60 by a cool gas 36 comprising hydrogen and water. As the briquettes 64 are cooled in the heat exchanger 60, the gas 36 is heated, thereby forming the heated gas 56 which is used as a gas feed to the reactor 32. In this way, heat from the hot briquettes may be recuperated for use elsewhere in the process. Using heat from the briquettes 64 to preheat the gas 56 can reduce the energy requirements of the process 10. The cooled briquettes, now in the form of a sponge iron product 22 and typically at a temperature at or near an ambient temperature, are ready for transportation to an end-user (e g., a steelmaker). It is noted that, if the sponge iron product 22 from the heat exchanger 60 is still at an elevated temperature, the sponge iron product 22 can be allowed to cool to a temperature at or near an ambient temperature prior to transportation.

Hydrolyser block 16

As above, in the third hydrolyser block 16, a gas 36 comprising hydrogen and water, suitable for use in the H-DRI reactor 32 is produced. Exhaust gas 50 from the first reactor 30 is passed to a condenser 66 within the hydrolyser block 16. As above, the exhaust gas 50 typically comprises hydrogen and water. In the condenser 66, water present in the exhaust gas 50 is condensed therefrom. The condensed water 67 can further comprise contaminants, such as particulate matter entrained in the exhaust gas 50 that becomes entrained in the condensed water 67. The entrained particular matter typically contains ultra-fines that are elutriated from the reactor 30, along with the exhaust gas 50. In this regard, the condensed water 67 is passed to a water clean-up 68 in which the contaminants therein are removed as waste 70. The water clean-up 68 can comprise any known methods or processes for removing the contaminants (e.g., filtering, flocculants, etc.). As will be appreciated, the exact methods or processes required will depend on the type and concentration of the contaminants. In some embodiments, prior to or as part of the water clean-up 68, particulate matter entrained in the exhaust gas 50 is separated therefrom. The separated particulate matter can then be recycled and reinjected back into the reactor 30. For example, the separated particulate matter can be injected into the reactor 30 along with the reducing gas 214. This is particularly advantageous when the reducing gas 214 is fed into the reactor 30 at a lower end thereof. This is because it has been found that injecting ultra-fine particles into the lower end of the reactor 30 increases the extent of reduction of the ultra-fine particles and also reduces further elutriation of the ultra-fine particles. However, it will be appreciated that the ultra-fine particles can otherwise be input into the reactor 30 along with the powder 20. The cleaned water 72 is collected for re-use in the process 10. In the illustrated embodiment of the process, the cleaned water 72 is passed to an electrolyser 74. In the electrolyser 74, the water is electrolysed into hydrogen and oxygen. The oxygen can be sold as a by-product. The hydrogen 76 is separated from the oxygen, using technologies well-known in the art. The hydrogen 76 is combined with the hydrogen 78 recovered from the exhaust 50 in the condenser 66. This combined hydrogen stream 36 ultimately forms part of the reducing gas 56 fed to the second reactor 32. In this regard, water (not shown) is typically added to the combined hydrogen stream 36 (i.e., so as to produce a gas 36 comprising hydrogen and water). It will be appreciated that the amount of water added to the combined hydrogen will depend on the stoichiometric hydrogen to water requirements of the second reactor 32. The combined hydrogen stream 36 along with added water represents a cool gas and is therefore passed through the heat exchanger 60, where it indirectly cools the briquettes 64 and is thereby heated, thereby forming the heated gas 56 which is then fed to the reactor 32.

Make-up water 34 is added to the electrolyser 74 as required (e.g., when the amount of hydrogen produced by the cleaned water 72 plus the amount of recovered hydrogen 78 is not sufficient).

Steelmaking - Fig, 2

Fig. 2 is a process flow diagram, set out in block form, of a process 200 for producing steel from iron ore in an integrated process. The steel may be used to produce other steel products.

In the process 200, the iron ore is reduced to iron, which is then used to make steel. The process 200 is comprised of three main blocks: a H-pyro-beneficiation block 202, an H- DRI block 204, and an ancillary block 206. In the H-pyro-beneficiation block 202, iron ore 18 is converted into magnetite 20 in a vertical reactor 30 of the type disclosed in WO2023064981. The magnetite 20 is transported, e.g., conveyed, from the beneficiation bock 12 to the H-DRI block 204 in which it is converted into, in the illustrated embodiment, sponge iron 58. The sponge iron 58 is further converted into steel 208. In the H-DRI block 204, a second vertical reactor 32 of the type disclosed in WO2023064981 is employed to reduce the magnetite to iron. Because both the H-pyro- beneficiation block 202 and the H-DRI block 204 employ high temperature pyroprocesses, there are energy savings in using hot magnetite 20 from the vertical reactor 30 to manufacture the sponge iron 58 in the second reactor 32. The iron is then mixed with additives and heated to melt the materials, thereby creating a liquid steel, which is then processed in, in the illustrated embodiment, an electric arc furnace 220 so as to produce the steel 208 or steel products. Advantageously, the process 200 may produce steel via a zero-process emissions process (i.e., there is no CO2 produced by the main process itself), for example, when renewable sources are used to provide the energy for the process 200. As above, in the context of this specification, the term ‘additives’ should be understood as comprising any material that is added to support downstream processing operations including melting/smelting and gangue removal operations, purification operations and steelmaking operations. Such additives can comprise, but are not limited to, carburizing agents, fluxing agents, slag modifiers, refractory stabilisers, etc.

In the ancillary block 206, a gas 216 comprising hydrogen and water, suitable for use in the H-DRI reactor 32 is produced. The gas 216 can comprise unused hydrogen, i.e., from the exhaust gas 50 from the first reactor 30, as well as recovered water present in the exhaust gas 50 from the first reactor 30. In some embodiments, the gas 216 can further comprise carbon monoxide. Each of these blocks is described in more detail below.

H-pyro beneficiation block 202

The configuration and operation of the H-pyro beneficiation block 202 of Fig. 2 is substantially the same as the configuration and operation of the H-pyro beneficiation block 12 of Fig. 1. As such, the operation of the crushing 36, grinding 40, first reactor 30, and magnetic separator 48 are not described again in detail.

It is noted that, in the illustrated embodiment of block 202 of Fig. 2, the exhaust gas 50 from the first reactor 30 is separated from the stream 46 prior to the magnetic separator 48. However, in an alternative embodiment, the exhaust gas 50 passes with the solid material to the magnetic separator 48, with the exhaust gas 50 then being separated therefrom as part of the magnetic separation stage. Some or all of the exhaust gas 50 is passed to the ancillary block 206, with a remaining portion (if required) being passed to the electric arc furnace 220.

As above, in the reactor 30, the crushed iron ore 42 is heated in the presence of a gas 214 so as to produce magnetite. In particular, the reactor 30 is typically operated at a temperature of between about 700 to 1100 °C, with conversion of goethite to magnetite being a temperature-based reaction.

The gas 214 typically comprises an exhaust gas from the second reactor 32. By using the exhaust gas 214 from the second reactor 32, heat in the exhaust gas 214 can be recovered (i.e., because it provides its thermal energy to the iron 42 in the reactor 30). In the embodiment of the process 200 illustrated in Fig. 2, the exhaust gas 214 is typically a mixture of hydrogen and water, but can also comprise CO2, as well as some CO. Because the exhaust gas 214 does not comprise oxygen, oxidation of the iron 42 can be avoided. However, hydrogen and CO present in the gas 214 reduces goethite in the iron ore 42 to magnetite.

It is noted that the gas 214 can further comprise ultra-fine powder, to the extent to which the ultra-fine powder is elutriated from the reactor 32 with the exhaust gas 214. In some embodiments, the exhaust gas 214 with the entrained ultra-fines is passed directly to the first reactor 30, such that the ultra-fines are further processed in the first reactor. In some of these embodiments, the exhaust gas 214 (along with the elutriated ultra-fines from the reactor 32) is inputted into the reactor 30 at a lower end thereof. It is thought that this can increase the residence time of the ultra-fines in the reactor 30 because the downwardly falling input powder to the reactor 30 (i.e., the crushed iron 42) helps to suppress the elutriation of these ultra-fines from the reactor 30. In this regard, it is thought that injecting the ultra-fines into the bottom of the reactor 30 can significantly increase the extent of reduction within the ultra-fines and reduce elutriation thereof from the reactor 30. In other embodiments, the ultra-fines are separated from the exhaust gas 214. The separated ultra-fines can then be re-injected into the reactor 32, for example, by combining the ultra-fines with the powder 20 or by combining the ultra-fines with the gas 56. In another variation, the reactor 30 and/or the reactor 32 each comprise one or more hollow tubes located within the reactor body. The tubes are configured to allow the ultrafines (either as a powder or with a suitable gas) to be input therethrough. As the ultrafines flow within the hollow tubes, the ultra-fines are heated and the iron contained therein is reduced.

As above, it can be advantageous to minimise the further reduction of magnetite because magnetite may be easily separated from remaining non-magnetic gangue (i.e., by magnetic separation). In this regard, the conditions in the reactor 30 are controlled such that the further reduction of magnetite therein is minimised and/or altogether suppressed. For example, as above, the stoichiometric quantities of hydrogen and water in the gas 214 fed to the reactor 30 and the operating temperature of the reactor 30 can both be controlled so as to reduce the extent to which the magnetite reduces. In this regard, the gas 214 in reactor 30 primarily acts as a carrier gas.

The reactor temperature and the ratio of carbon monoxide to carbon dioxide in an atmosphere in which iron is heated affects the propensity of magnetite to further reduce. As such, the reaction conditions of the reactor 30, including the reactor temperature and the composition of the gas 214, is typically controlled so as to optimise the formation of magnetite from the input ore and to suppress the further reduction of magnetite to iron in the Fe° state. It is noted that the optimal composition of the gas 214 input to the reactor 30 is dependent on the reactor 30 temperature. For example, when the reactor 30 is operated at a temperature of about 900 °C, it has been found that it can be optimal to maintain a stoichiometric ratio of CO:CO2 of less than about 2.9: 1 in the gas 214. On the other hand, when the reactor 30 is operated at a temperature of about 1100 °C, it can be optimal to maintain a stoichiometric ratio of CO:CO2 of less than about 1.2: 1 in the gas 214. However, it will be appreciated that other stoichiometric ratios and other operating temperatures may be employed. Alternatively, the reactor 30 may be operated such that some reduction of magnetite occurs in the reactor 30. For example, when magnetic separation of remaining gangue is not required (e g., where such gangue has been removed prior to feeding to the reactor 30).

H-DRI block 204 The magnetite 52 from the magnetic separator 48 is transported (e.g., conveyed) to the fusion grinder 54 of the H-DRI block 204. It is also noted that, in the process 200 of Fig. 2, the fusion plant 54 is located in the H-DRI block 204. This is because, in the process 200, additional iron in the form of a commercial high-grade iron ore 210 can be combined with the magnetite 52 prior to the fusion plant 54, so as to produce a combined iron stream 212. The commercial high-grade iron ore 210 is typically in the form of a fine powder comprising magnetite. If required, the incoming commercial high-grade iron ore may undergo one or more crushing and/or grinding stages so as to produce the commercial high-grade iron ore 210 that is combined with the magnetite 52. The commercial highgrade iron ore can be added to the process 200 to increase the throughput of iron, e.g., when the flowrate of magnetite 52 is insufficient. Alternatively, the commercial highgrade iron ore 210 may be used instead of the magnetite 52 (e.g., when the magnetic separator 48 is offline). The commercial high-grade iron is typically purchased from an external supplier (e.g., a concentrator).

The combined iron stream 212, i.e., comprising the commercial high-grade iron ore 210 (when used) and the magnetite 52 (from the magnetic separator 48), is transported (e.g., conveyed) to the fusion plant 54. The commercial high-grade iron ore 210 (when used) and the magnetite 52 (from the magnetic separator 52) may be passed through an optional mixing stage in which the two sources of iron are mixed so as to increase the homogeneity of the combined iron stream 212. Alternatively, the two sources of iron can be mixed in the fusion plant 54 (i.e., as part of the agglomeration process). As above, agglomeration is typically required because the particle sizes of iron in the combined iron stream 212 are typically too small for feeding directly to the second reactor 32 (i.e., the particles may have diameters as small as <10 pm).

As above, in the fusion plant 54, the combined iron stream 212 is agglomerated so as to form an ultra-fine iron powder 20. Typically, the fine powder comprises particles with diameters of less than about 250 pm, i.e., such that the ultra-fine magnetite powder 20 is suitable to be used as a feed to the second reactor 32. The ultra-fine magnetite powder 20 is transported (e g., conveyed) from the fusion plant 54 to the second reactor 32 of the H- DRI block 14. Alternatively, for example when the combined iron stream 212 is already in the form of an ultra-fine powder with particles that are larger than 10 pm in diameter (i.e., as opposed to a super-fine powder), the combined iron stream 212 can be directly transported to the second reactor 32 and the fusion plant 54 may be by-passed and/or eliminated altogether.

As above, the ultra-fine magnetite powder 20 is fed into the second H-DRI reactor 32, the second reactor 32 comprising a vertical reactor of the type described and taught in detail in WO2023064981. In the process 200, the reactor 32 is operated so as to cause the magnetite in the powder 20 to be reduced to iron.

To facilitate reduction of the magnetite to iron, a reducing gas is required. In this regard, a reducing gas 216, in this embodiment in the form of a mixture of CO, hydrogen and water, is fed into the reactor 32, along with the fine magnetite powder 20. The advantages of using a gas comprising hydrogen as the reducing gas will be appreciated from WO2023064981, namely, that the carbon footprint of the process 10 may be minimised. By controlling the conditions within the reactor 32 (i.e., temperature, ratio of hydrogen to water in the reducing gas), hydrogen and CO in the reducing gas 216 are both caused to reduce the magnetite to iron, as the magnetite powder 20 falls through the reactor tube, with the hydrogen and CO being converted to water and CO2 respectively.

It can be advantageous to minimise the amount of CO present in the reducing gas 216 (i.e., so as to minimise the amount of CO2 produced). For example, in some embodiments, the composition of the reducing gas 216 that is fed into the reactor 32 is selected so that the ratio of CO and CO2 in the exhaust gas 214 from the second reactor 32 (i.e., which is used as the reducing gas input to the reactor 30) is such that the reduction of Fe2Oi to FesOr (i.e., magnetite) within the reactor 30 is thermodynamically limited. Additionally, the ratio of CO and CO2 is such that the reactor 30 also serves as a CO polishing step in which CO present in the gas 214 is consumed. This can eliminate the need for any additional scrubbing of the first reactor exhaust gas 50. It is nevertheless noted that incomplete CO consumption may be desirable when the first reactor exhaust gas it to be used for certain applications, such as for methanol/ sustainable aviation fuel production.

However, it is noted that CO provides a thermal advantage in that the reduction of iron by CO is exothermic, whereas the reduction to iron by hydrogen is endothermic. In this way, as the CO reduces magnetite, energy is released. This can reduce the amount of heating required to the reactor 32 (i.e., because the energy released through the exothermic reduction of iron by CO provides some of the energy for the endothermic reduction of iron by hydrogen). In addition, a portion of the CO and iron may be converted to cementite, which adds carbon into the iron powder 58. This can reduce the amount of carbon that needs to be added in the hot mixer 218. Nevertheless, when CO is present in the reducing gas 216, the concentration of CO therein is typically minimised. It is noted that the concentration of CO in the reducing gas 216 may be dependent on a number of factors such as: the nature of the feedstock used in the pyrolyser 252 (e.g., its carbon content), how the pyrolyser 252 is operated, etc.

As above, the kinetics of the reduction reaction of magnetite in the reactor 32 can be affected by the stoichiometric ratio of hydrogen and water present in the reducing gas 216, as well as the operating temperature of the reactor 32 and the stoichiometric ratio of hydrogen to magnetite. Typical reaction conditions can comprise: a stoichiometric excess of hydrogen compared to iron; a stoichiometric ratio of hydrogen to water of about 2:1; and an operating temperature between 700 to 1100 °C. Under these reaction conditions, it is thought that at least about 90%, such as about 95% of the magnetite can be reduced in the reactor 32 to iron within the typical reactor residence times of between 10 to 50 s. For example, it is thought that nearly complete reduction of the magnetite may be achieved in the reactor 32. Any remaining magnetite (e.g., magnetite which is not reduced in the reactor 32) forms part of the iron powder 58. At the same time, hydrogen present in the gas 216 is converted into water, which adds to the water already present therein.

When CO is present in the reducing gas 216, it is thought that substantially all the CO is converted to CO2 within the reactor 32, such that the exhaust gas 214 comprises essentially no CO. In this regard, exiting the reactor 32 is a gas 216 comprising hydrogen, water and CO2 (i.e., because not all the hydrogen is consumed in the reactor 32), and an iron powder 58, now primarily comprising iron (i.e., because the magnetite is reduced to iron in the reactor 32, as well as any remaining magnetite that was not reduced to iron). As above, because up to about half of the hydrogen in the reducing gas 216 is converted into water in the reactor 32, the stoichiometric ratio of hydrogen to water in the exhaust gas 214 exiting the reactor 32 is closer to about 1 : 1. As a result, the exhaust gas 214 may be used as the carrier gas in the first reactor 30 (i.e., because at these ratios of hydrogen to water, reduction of the magnetite in the iron 42 is not thermodynamically preferred). In this regard, the exhaust gas 214 from the reactor 32 is passed to the first reactor 30 for use as the carrier gas therein.

In some embodiments, the first reactor may be indirectly heated so as to maintain a temperature of between 700 °C to 900 °C within the reactor. Additionally, the second reactor may be indirectly heated so as to maintain a temperature of between 700 °C to 900 °C within the reactor. This temperature range has been found to be optimal towards the conversion reactions taking place in each reactor. The temperature is sufficiently high that the intermediate wustite form of iron oxide is unstable with respect to iron, and the temperature is sufficiently low that cascading agglomeration of particles may be inhibited.

It is noted that when the degree of metallisation is about 95% or more, the sponge iron may be suitable for use to make steel using electric arc furnace (EAF) processes, including submerged EAFs, without severe impact on the EAF efficiency. A lower metallisation can be accommodated in a blister furnace processes or in an EAF which has a very high consumption of scrap. In some embodiments, such as when the iron ore comprises minerals comprising chromium, manganese, lithium and rare-earth that are used in steelmaking, the sponge iron 58 from the second reactor may be mixed with a solid reductant such as char, silicon, ferrosilicon, aluminium or aluminium dross and reduced in a third reactor (not shown) to produce a ferro-metal used as an additive for special steel making. Such a process may use fusion or briquetting of the powders to bring the solid-state reactants into closer contact than a powder mix to make an H-DRI ferro-alloy as an additive for special steels.

In the illustrated embodiment of Fig. 2, the iron powder 58 is passed to a hot mixer 218. In the hot mixer 218, the iron powder 58 is mixed with one or more additives. The hot mixer 218 typically operates at an elevated temperature such as between about 700 to 1100 °C. Maintaining elevated temperatures during mixing can increase the thermal efficiency of the process 200. This is because the downstream processing units also operate at elevated temperatures. By operating the hot mixer 218 at the elevated temperature, the need to cool down and then reheat the mix may be avoided. It is noted that some energy will be required to maintain the elevated temperature in the hot mixer 218. In the hot mixer 218, the iron powder 58 is mixed with one or more additives so as to form a homogeneous mix 226. Further, in the hot mixer 218, the one or more additives are mixed with the iron powder 58 so as to form a composition that is suitable for processing into a steel 208 in the electric arc furnace 220. Compositions suitable for processing into a steel in electric arc will be understood and appreciated by those skilled in the art. For instance, one or more additives, such as one or more suitable fluxing agents, slagging agents, carburizing agents, slag modifiers, refractory stabilisers, etc. may be added in the hot mixer 218. Suitable additives 222 are known to include magnesium oxide and/or calcium oxide. As will be explained in further detail below, both magnesium oxide and/or calcium oxide can be advantageously provided using the applicant’s own Low Emissions Intensity Lime and Cement (LEILAC) process 228.

Typically, the iron powder 58 does not comprise much carbon, i.e., because the reduction does not rely on the direct combustion of e.g., coke, within the reactor unlike prior art processes. As such, carbon 224 is also added to the hot mixer 218. It will be appreciated that the quantity of carbon 224 added will depend on the composition of carbon required in the steel 208. Other additives that can be added will be known to those skilled in the art. For example, low FeO slag.

Advantageously, the process 200 provides flexibility with regard to the steel 208 in that a wide range of additives may be added, in a desirable order, either to the iron or in the furnace, to produce a wide range of (in some embodiments zero emissions) steel products. In this regard, a differentiating feature of the present process it that it enables a wide range of steels to be produces using innovative additives. For example, the types of additives for steel making may include: a) slagging agents of novel zero emissions magnesium oxide and calcium oxide mix made from a patented calcination process of carbonate minerals such as limestone, dolomite and mixtures thereof formulated to match the basicity of the residual gangue in the spongeiron to remove such gangue from the steelmaking processes, b) low emissions char for the manufacture of carbon steels, where the char may be made from biomass with CO2 capture as described herein, to deliver the low emissions char for carbon steels as required, and hydrogen for use in the H-DRI vertical reactors, so as to minimise the hydrogen demand from electrolysers, c) low emissions metal alloys containing metallised elements such as chromium, manganese, rare-earths, and lithium produced using a process in which three indirectly heated reactors are employed for the subsequent reduction of ores so as to produce low emissions additives for special purpose steels.

In respect of (a), the applicant’s patent PCT/AU2021/051183 provides a reactor suitable for the calcination of magnetite and dolomite in the general field of calcination of carbonate minerals. Such a process may be used to make the low emissions materials with the right basicity and reactivity for slagging. Alternatively, ball milling of iron and iron oxides is known to capture CO2, under pressure from the mill, from waste gas steams to form siderite (FeCCh), which may be heated to produce a clean CO2 stream. Mixtures of CaO, siderite and other iron ore can also be used to capture CO2 in a ball mill, with the CO2 then able to be released by heating the milled material.

In respect of (b), the carbon used to make carbon steels, the carbon may also be made from a process known as Indirect Gasification of Biomass in which the zero-emissions magnesium oxide and calcium oxide described above is heated with the biomass in an indirect heater in which the volatile carbon is released as syngas (H2 + CO). During the process, the CO is converted to H2 by steam through the Sorbent Enhanced Gasification (SEG) process:

The H2 can be used in the iron reduction process to offset that required from electrolysers, the CaCOi is recalcined to CO2 gas for storage and utilisation, and the lime is used for slagging. It is thought that the use of an indirectly heated Sorbent Enhanced Gasification reactor and the regeneration of a pure CO2 stream using an indirect heating process (such as that described in PCT/AU2021/051183) is a novel flowsheet configuration. The indirect heating may be from renewable power, i.e., so that the process is low or zero emissions. The resultant mix 226 comprising the iron ore powder 58 and the various additives 222, 224 is passed to an electric arc furnace 220. The resultant mix 226 may be directly injected as a hot product into the EAF. During mixing, the iron and additives are in close contact, thereby facilitating uniformity in the melt and promoting fast reactions in the EAF. In the electric arc furnace 220, the mix 226 is processed into steel 208. The operation of the electric arc furnace 220 will be known to those skilled in the art. It will also be seen in the flowsheet of Fig. 2 that a portion 53 of the exhaust gas 50 from the first reactor 30 can be used in the electric arc furnace 220 (e.g., for blowing, as required). Additional additives 230 can be added to the electric arc furnace 220 as required. For example, additives such as Si, Mn, Cr, or other elements, may be added so that the resultant steel 208 has the desired composition. Scrap iron can also be added (e.g., when additional iron is required). It will be appreciated that the additives added will be driven by the end-user’s specifications regarding the steel 208. At the same time, a low FeO slag 232 is also produced. The low FeO slag 232 can be collected and re-used (e.g., added to the hot mixer 218 or used as a form of scrap). Alternatively, the low FeO slag 232 may be discarded or sold as a waste stream. It will be appreciated that furnaces other than electric arc furnaces may be employed for processing the mix 226 into steel. For example, a blister furnace or a blister oxidation furnace may instead be used.

It is noted that, by removing gangue 26 from the magnetite 52, the grade of iron powder 58 reporting to the electric arc furnace 220 may ultimately be increased. This can increase the efficiency of the electric arc furnace. It is noted that efficiency losses in electric arc furnaces due to the presence of gangue typically limits the use of such furnaces for low- grade ores. By providing a process in which a low-grade ore can be upgraded, it can become possible to process such low-grade ores with electric arc furnaces. Electric arc furnaces are becoming preferred over other steelmaking processes (e.g., basic oxygen furnaces, blast furnaces, etc.) because electric arc furnaces are not reliant on the combustion of coke for energy.

In the process 200, the hot mixer 218, in which the iron powder 58 is mixed with additives, is a separate processing step to the electric arc furnace 220, in which the mixture 226 (optionally with additives 230) is processed into steel 208 (and slag 232) It is noted that this is in contrast to known processes in which the iron powder is typically added directly to the electric arc furnace, along with the additives and other additives. A benefit of having separate a separate hot mixer stage is that, in some variations of the process 200, the mix 226 is able to be directed/diverted to a briquetting stage (i.e., instead of being directed to the electric arc furnace 220) or a granulating stage. In such variations, in the briquetting stage or the granulating stage, the mix is used to form briquettes or granules comprising the iron powder and additives. Heat can be recovered from the briquettes or granules for use elsewhere within the process 200 (e.g., preheat the reducing gas 216 feed into the second reactor 32).

The briquettes are sold as an end-product to steelmakers. Because the briquettes or granules are advantageously already pre-loaded with the additives (e.g., carbon, magnesium oxide, calcium oxide, etc.) this can reduce the complexity and cost of processing the briquettes or granules into steel (e.g., compared to processing sponge iron or iron briquettes which do not already comprise the additives). Another advantage is that the process 200 can be split into two stages, performed in different geographical locations. In the first stage, the low-grade iron ore 18 is converted into the briquettes or granules comprising the mix 226. This stage can be performed at or near the location where the iron ore is produced (e.g., at a mine) and/or where renewable power is plentiful to produce hydrogen for reduction, and power for heating any indirectly heated reactors. Said location can also be at or near a location where limestone or dolomite are available for making low emissions additives (such as CaO and/or MgO). The briquettes or granules can then be shipped to a second location (e.g., where there is a demand for steel). The briquettes or granules can be processed into the steel at this second location, where further additives may be added, as required. The second location may be one at which there is existing infrastructure for processing the briquettes or granules into steel, but where the supply of renewable electricity /hydrogen is limited.

It is noted that, in some embodiments the low-grade iron ore 18 may already comprise or be dominantly comprise of magnetite to a degree that magnetic separation can be achieved on the ground iron ore ultra-fines 42. In these embodiments, the first reactor 30 may not be required (i.e., because the iron is already in the form of magnetite). Alternatively, in other embodiments, the first reactor 30 may still be employed. This is because the kinetics of reduction of magnetite iron ores is generally lower that hematite/goethite ores. The first reactor may be retained to partially oxidise the iron ore to accelerate the metallisation of the iron in the second reactor.

For either non-magnetic or magnetic iron ores, the energy loss from cooling and heating the powder for gangue separation is minimised using a heat exchange system, including options for a Heat Recovery Steam Regenerator (HRSG) to provide clean water to an electrolyser plant, as an embodiment. There are many options for configurations for this process. In some embodiments, the exhaust gas from the second reactor may be passed to the first reactor without gas clean up. In some embodiments the exhaust gas from the second reactor may be used without gas clean up because the exhaust gas is already at an elevated temperature. It would be understood by a person skilled in the art that such optimisation is difficult to achieve with discontinuous reduction reactors such as fluidised beds.

Ancillary block 206

In the ancillary block 206, the reducing gas 216 comprising hydrogen, water, and, in some embodiments, further comprising CO, is produced. Additives for the hot mixer 218 are also produced.

Some or all of the exhaust gas 50 from the first reactor 30 (i.e., the portion 236 of the exhaust gas that is not passed to the electric arc furnace 220) is passed through a lime cycle clean-up stage 234. In the lime cycle clean-up stage 234, CO2 (i.e., due to the oxidation of CO) and CO (i.e., that is not converted to CO2) present in the exhaust gas 236 are scrubbed using magnesium oxide and/or calcium oxide 238. As the exhaust gas is scrubbed, the calcium oxide reacts with the CO and/or CO2 to form calcium carbonate. A resultant stream 262 comprising magnesium oxide and calcium carbonate is collected for re-use in producing the magnesium oxide and/or calcium oxide 238. The scrubbing can be performed using any means known (e.g., using a fluidised bed reactor). The lime cycle clean-up stage 234 is operated such that substantially all the CO and CO2 is scrubbed from the portion 236 of the exhaust gas. In this regard, exiting the lime cycle clean-up stage 234 is a gas 240 comprising hydrogen and water which is passed to a condenser 242.

Alternatively, the lime cycle clean-up stage 234 can instead be arranged such that the reducing gas 216 is caused to be scrubbed prior to it being fed to the second reactor 32. In such embodiments, a scrubbed reducing gas comprising hydrogen and water (i.e., because the CO is scrubbed therefrom) is passed from the lime cycle clean-up stage to the second reactor 32. It can be advantageous to scrub the reducing gas 216 prior to the second reactor 32 when it is undesirable to pass CO into the second reactor 32. In these embodiments, the exhaust gas 236 need not be scrubbed, i.e., because it does not comprise CO2 (or CO) since the CO is scrubbed prior to the second reactor 32 and is passed directly to the condenser 242.

The scrubbed gas stream 240 (or the exhaust gas 236) is typically at an elevated temperature of between about 700 to 1100 °C (i.e., the temperature at which the first reactor 30 operates). As such, water in the gas 240 (or in the exhaust gas 236) is in the form of water vapour (or superheated steam). In the condenser 242, the gas 240 (or the exhaust gas 236) is cooled so as to cause the water to condense, whilst the hydrogen remains as a gas. The hydrogen gas stream 248 is collected for re-use (e.g., to form the reducing gas 216). The condensed water 244 is also collected for re-use (e.g., for generating hydrogen in the electrolyser 246). In the electrolyser 246, water 256 is electrolysed so as to form hydrogen 258 and oxygen (not shown), with the hydrogen 258 being collected for use in forming the reducing gas 216. The water 256 comprises the condensed water 244 and can comprise additional make-up water 34 (e.g., when additional hydrogen is required). The oxygen can be sold as a by-product.

The process 200 also comprises a pyrolyser 252. In the pyrolyser 252, biomass 250 undergoes pyrolysis to thereby produce syngas and carbon, in the form of bio-char. In this regard, an advantage of the pyrolyser 252 is that it can produce carbon 255 (e.g., for use in the hot mixer 218). It is noted, however, that in other embodiments, the pyrolyser 252 may be omitted. For example, when the carbon for the hot mixer 218 is obtained from a different source or when no carbon is required in downstream processing units.

When the process 200 comprises a pyrolyser 252, the pyrolyser 252 is typically in the form of a sorbent enhanced gasification (SEG) type pyrolyser. The benefit of employing SEG is that most of the carbon dioxide, along with a significant proportion of the carbon monoxide, may be scrubbed from the syngas within the pyrolyser 252, such that the syngas 254 is a hydrogen-enriched syngas 254. It is thought that the SEG may be operated such that nearly all the CO2 and CO are scrubbed from the syngas, such that the gas 254 exiting the pyrolyser 252 primarily comprises hydrogen. In particular, a mixture of magnesium oxide and/or calcium oxide 264 are used to scrub the CO and CO2 from the syngas produced by pyrolysis of the biomass 250, thereby producing a mixture of magnesium oxide and/or calcium carbonate 266. The mixture of magnesium oxide and/or calcium carbonate 266 is collected for re-use in producing the mixture of magnesium oxide and/or calcium oxide 264.

As above, any CO (and/or CO2) remaining in the gas 254, i.e., that was not removed by the SEG, can be removed by a lime cycle clean-up stage, e g., either before the reducing gas 216 enters the second reactor 32 or before the exhaust gas 236 from the first reactor 30 enters the condenser 242.

The gas 254 (i.e., hydrogen-enriched syngas or primarily hydrogen) is combined with the hydrogen 258 from the electrolyser and the hydrogen 248 recovered from the exhaust gas 236. These gases are further combined with water vapour (not shown) to form the reducing gas 216. The volume of the gas 254, the hydrogen 258 from the electrolyser and the water vapour are each adjusted so as to form the reducing gas 216 with a desired composition (i.e., as explained above). The pyrolyser 252 also produces a bio-char 255 (i.e., due to the pyrolysis of the biomass 250). The bio-char 255 is used as an additive in the hot mixer 218, i.e., as the source of carbon for the steel. In one embodiment, the pyrolyser 252 also comprises an indirectly heated reactor of the type described and taught in detail in WO2023064981. Without being bound by theory, it is thought that the pyrolyser 252 operates using the same principle as in other applications of the vertical reactor disclosed in WO2023064981. In particular, the reactor operating conditions such as the gas composition, gas flow, and powder throughput are controlled so as to achieve the required pyrolysis of the biomass.

As referenced above, the magnesium oxide and/or calcium oxide 222, 238, 264, for use in the hot mixer 218, the lime cycle clean-up 234, and the pyrolyser 252 respectively can be advantageously produced using the applicant’s own Low Emissions Intensity Lime and Cement (LEILAC) process 228. The configuration and operation of the LEILAC process 228, including the configuration and operation of a suitable calciner, is described in more detail in the applicant’s granted Australian Patent no. 2017351743, the entire contents of which are incorporated herein by reference.

At a high-level, the feed 260 to the LEILAC process 228 comprises limestone and/or dolomite. It will be appreciated that, when the feed 260 comprises only limestone, the streams 222, 238, 264 will comprise only calcium oxide. On the other hand, when the feed 260 comprises dolomite, either alone or in combination with limestone, the streams 222, 238, 264 will comprise magnesium oxide and calcium oxide.

The limestone and/or dolomite feed 260, as well as the recycle streams comprising magnesium oxide and/or calcium carbonate 262, 266, are calcined using an indirectly heated reactor, to thereby produce the calcium oxide and/or magnesium oxide 222, 238, 264. At the same time, a pure CO2 stream 268 is produced. Advantageously, in the LEILAC process 228, the pure CO2 stream 268 is kept separate from any other process emissions, e.g., exhaust gases.

It is noted that any or all of the CO2 streams process by the process (e g. the pure CO2 stream 268, as well as any CO2 streams from the reactors or the additive making processes (when present), including the slagging agents, biochar and steel mill slag) may be used to make zero emissions methanol or higher hydrocarbons by further reacting the pure CO2 streams with hydrogen. Other known processes can be used to reduce CO2 streams to chars for the uses described above. The intent of such these processes is to limit the requirement for underground sequestration of CO2 streams from steelmaking processes when most of the CO2 has been removed using hydrogen for making H-DRI. Such embodiments may provide a route for zero emissions steelmaking. Alternative Embodiment of Ironmaking and Steelmaking - Fig, 3

Fig. 3 is a process flow diagram, set out in block form, of another embodiment of a process 600 and system for producing reduced iron from iron ore. The reduced iron is typically in the form of sponge iron and may be sold as sponge iron briquettes or converted into steel. Similar to the processes 10, 200 described with reference to Figs. 1 and 2 respectively, the process 600 of Fig. 3 comprises two indirectly heated vertical reactors 602, 604. Each of the vertical reactors 602, 604 comprises an indirectly heated vertical reactor as described in WO2023064981. Unlike the processes 10, 200, the process 600 does not comprise a magnetic separator between the first reactor and the second reactor. In this regard, the process 600 may be employed when a magnetic separator is not required. For example, when the iron ore powder used as feed to the process 600 is already of a high enough grade such that further gangue separation is not required and/or it can be employed when the desired product output is low grade briquettes. Alternatively, as another example, when magnetite is the desired product of the process, the process 600 may be employed. As a further example, the process 600 may be employed when the reduction kinetics are fast enough to facilitate reduction of hematite and/or goethite to elemental iron in a single reactor.

The feed to the process 600 is iron ore (e.g., from a mine site). The iron ore typically undergoes one or more beneficiation stages (not shown) to remove at least some of the gangue therefrom. The one or more beneficiation stages can comprise, for example, crushing, grinding, etc., as described above with reference to Fig. 1. Exiting the one or more beneficiation stages is an upgraded iron ore in the form of an ultra-fine powder 606 that is suitable to be used as a feed to the first reactor 602. The ultra-fine powder 606 is comprised of particles that are predominantly less than 250 pm in diameter. In this regard, the ultra-fine powder 606 is fed to the first reactor 606. As described above and in WO2023064981, the ultra-fine powder 606 is fed into an upper end of the first reactor 602, such that the ultra-fine powder 606 is caused to fall downwardly through the reactor tube 608. At the same time, a reducing gas 610 enters the reactor tube 608 through one or more gas input ports located at a lower end of the reactor tube 610. As a result, the reducing gas 610 is caused to flow upwardly through the reactor tube 608, such that the powder and the gas flow in a counter-current arrangement. The flow of the gas and the powder are controlled so as to cause a dilute flow regime to be established within the reactor tube 608. The flow of the reducing gas 610 can be further controlled so as to provide a required residence time of the powder 606 within the reactor tube 608 (e.g., usually between 10s to 120s, such as between about 40s to 120s), as well as the required fluid dynamics within the reactor tube 608 (i.e., a dilute flow regime).

As above, the reducing gas 610 typically comprises hydrogen. The use of hydrogen is advantageous because the product of the reduction reaction between hydrogen and iron is water (and reduced iron). Thus, the generation of greenhouse gases such as carbon dioxide may be altogether avoided.

The first reactor 602 is indirectly heated by an external heater 612. The external heater 612 surrounds the reactor tube 608 and provides energy in the form of radiative energy. In particular, the external heater 612 heats the walls of the first reactor tube 608, causing the walls to radiate energy into the reactor tube 602. The external heater 612 can be powered through electricity and/or combustion. The external heater 612 is typically controlled so as to maintain a temperature of between about 700 to 1100 °C within the reactor tube 608. As a result, as the reducing gas 610 and powder 606 are heated within the reactor tube 608, iron is caused to be reduced. At the same time, hydrogen present within the reducing gas is converted to water (i.e., because the reduction reaction between hydrogen and iron produces reduced iron and water).

It will be appreciated that the form of the reduced iron will depend on the composition of the powder 606, as well as the operating conditions of the first reactor 602. For example, when the iron is in the form of goethite, the iron may be either partially reduced to magnetite or may be fully reduced, e.g., to elemental iron. As explained above, the composition of the gas 610 can influence the degree to which the iron is reduced because the ratio of hydrogen to water in an atmosphere in which iron is heated is known to affect the propensity of the magnetite to further reduce. In some embodiments, the first reactor 602 may be controlled such that the iron is reduced only to magnetite. This can be advantageous when the powder 606 comprises significant quantities of non-magnetic gangue. This is because, when the iron is in the form of magnetite, the iron is magnetic, allowing separation of the magnetite from non-magnetic gangue (e.g., by magnetic separation). The magnetite can then be further reduced, e.g., in another vertical reactor.

However, in other embodiments, the first reactor 602 is instead controlled such that the iron is directly reduced to elemental iron. This can be advantageous when the resultant elemental iron is of a sufficiently high grade such that it can be used in the production of sponge iron or when it is desired to produce elemental iron in the first instance. It is noted that magnetic separation can additionally or alternatively be performed on elemental iron to upgrade an elemental iron product.

As another example, when the iron is already in the form of magnetite, the first reactor 602 can be controlled to reduce the magnetite to elemental iron.

As above, the first reactor 602 is configured such that the powder 606 falls downwardly through the reactor tube 608 and the reducing gas 610 travels upwards through the reactor tube 608 (i.e., in a counter-flow arrangement). As the reducing gas 610 travels upwards through the reactor tube 608, smaller particles present within the powder become entrained therein and are elutriated with the reducing gas from an upper end 614 of the reactor tube 608. Said reducing gas and entrained powder comprise an exhaust gas 620 of the first reactor 602. The exhaust gas 620 comprises water (i.e., because some of the hydrogen is converted to water due to the reaction between the iron and the hydrogen). The reducing gas 610 typically comprises an excess of hydrogen, such that the exhaust gas 620 further comprises hydrogen.

At the same time, larger particles present within the powder continue falling downwardly through the reactor tube 608. These larger particles exit the reactor tube 608 via a powder outlet 616, located at a lower end of the reactor tube 608. The powder outlet 616 is configured to allow the larger particles to collect at the lower end of the reactor tube 608 and to be transported therefrom (e.g., by a conveyor or screw auger). The powder 618 collected from the powder outlet 616 comprises reduced (or partially reduced) iron, depending on the desired product (as explained above). It is thought that, by using a dilute flow regime and residence times of 10 to 50 s, a reduction of above 90%, such as about 95%, may be achieved in the first reactor 602.

The residence time of the smaller particles of powder that become entrained in the exhaust gas 620 may be less than the residence time of the larger particles of powder that are collected from the powder outlet 616. As a consequence, the degree of the reduction of these entrained particles tends to be less than the degree of reduction of the powder collected from the powder outlet 616. That is, the small particles of powder entrained in the exhaust gas typically comprise a partly reduced iron ore powder. In this regard, the exhaust gas 620 is passed to a second reactor 604 in which the partially reduced iron ore is further reduced. The second reactor 604 comprises a vertically oriented indirectly heated reactor of the type described in WO2023064981. Specifically, as the exhaust gas 620 from the first reactor 602 reaches the upper end 614 of the reactor tube 608, it is directed into a transfer tube 619. The transfer tube 619 fluidly connects the upper end 614 of the reactor tube 608 of the first reactor 602 with an upper end 622 of the reactor tube 624 of the second reactor 604. In this regard, the exhaust gas 620 is caused to flow along the transfer tube 619 and into the upper end 622 of the reactor tube 624. The exhaust gas 620, along with the entrained partially reduced iron ore powder, is caused to flow downwardly through the reactor tube 624. That is, the gas and powder flow in a co-flow arrangement. It is noted that this is in contradistinction to the first reactor 602 in which the reducing gas 610 and powder 606 are caused to flow in a counter-flow arrangement.

The second reactor 604 comprises an external heater 626 located around the reactor tube 624 and configured to indirectly heat the reactor tube 624. Typically, the reactor tube 624 is heated to a temperature of between about 700 °C to about 900 °C (i.e., a temperature at which further reduction of the partially reduced iron is caused to occur). As a result, the downwardly falling gas and powder are heated (i.e., by the external heater 626) to a temperature at which any iron in the powder which is not reduced (i.e., because the powder comprises partially reduced iron ore) is caused to be reduced (i.e., by the reducing gas).

As with the first reactor 602, the operation of the second reactor 604 can be controlled so as to achieve a desired reacted powder product. For example, in some embodiments, the second reactor 604 can be controlled such that the reacted powder product comprises magnetite. In these embodiments, the iron is not completely reduced to elemental iron. Alternatively, in other embodiments, the second reactor 604 can be controlled such that the reacted powder product comprises elemental iron.

The downwardly falling powder in the second reactor 604 tends to comprise small particle sizes. In particular, the average particle size of the powder in the second reactor 604 is smaller than the average particle size of the powder in the first reactor 602. This is because it is the smaller particles from the first reactor 602 that tend to be elutriated into the second reactor 604. The fluid dynamics (e.g., gas velocity) within the second reactor 604 are typically controlled such that most of the particles tend to drop out of the gas flow and fall (e g., due to gravity) into a reacted powder outlet 630 located at a lower end 628 of the reactor. Meanwhile, only a small proportion of the particles will tend to remain entrained within the gas.

In this regard, located at a lower end 628 of the reactor tube 624 is the reacted powder outlet 634 and a gas exhaust 636. Most (if not all) of the reacted powder 630 exits at the reacted powder outlet 634. The reacted powder outlet 634 is configured to allow the powder to collect at the lower end 628 of the reactor tube 624 (i.e., as it drops out of the gas flow) and be transported therefrom (e.g., with a screw auger or conveyer). It is thought that, by using a dilute flow regime and residence times of 10 to 50 s in the second reactor 604, the reacted powder 630 may comprise a product in which at least 90% of the iron has been reduced, such as about 95%. The reduced iron is in the form of, e g., magnetite or elemental iron, depending on the desired end-product.

The second exhaust gas 632 exits the second reactor 604 at a gas exhaust 636. It is noted that, in this regard, the configuration of the second reactor 604 is different than the first reactor 602 and different to most of the vertical reactors described in WO2023064981, wherein the gas exhaust is located at a top of respective reactor (because the respective reactor is operated in a counter-flow arrangement). On the other hand, because the second reactor 604 operates in a co-flow arrangement, both the reacted powder output 634 and the gas exhaust 636 are located at the lower end 628 of the reactor tube 624. The second exhaust gas 632 is typically passed to a gas-particle separator 638. In the gasparticle separator 638, entrained powder is separated from the cleaned second exhaust gas 640, enabling near complete recovery of the powder. The gas-particle separator 638 may be in any form known to those in the art. For example, the gas-particle separator 638 may comprise a bag filter. Entrained powder collected by the bag filter may be periodically removed therefrom (e.g., as the bag filter becomes filled).

The cleaned second exhaust gas 640 comprises water (i.e., due to the reduction reaction between iron and hydrogen within the second reactor 604) and can also comprise hydrogen (e.g., when an excess of hydrogen was used in the reducing gas 610). The cleaned second exhaust gas 640 can be collected for re-use. For example, when the cleaned second exhaust gas 640 comprises water and hydrogen, the water can be condensed therefrom (e g., using a condenser). The condensed water can be re-used as process water or in an electrolyser for generating additional hydrogen (with an oxygen by-product). The hydrogen separated from the water in the condenser can be re-used in the reducing gas.

The powder 618 from the powder outlet 616 of the first reactor 602, the powder 630 from the powder outlet 634 of the second reactor 604, and powder 642 collected from the gasparticle separator 638 are all used as feed to a briquetting stage 644. As above, the combined powder comprises reduced iron in the form of, e.g., magnetite or elemental iron, depending on the desired end-product. In the briquetting stage 644, the combined powder is processed into briquettes 646. The briquettes 646 comprise, e.g., sponge iron or magnetite, depending on the desired end-product.

It will be appreciated that the process 600 differs from the processes 10, 200 in that in the process 600, one reactor 602 operates in a counter-flow arrangement whilst the other reactor 604 operates in a co-flow arrangement. In this regard, it is thought that the process 600 may be advantageously employed when carryover of fines with the exhaust gas 620 from the first reactor 602 is sufficiently low and when the kinetics are sufficiently fast within each reactor 602, 604 for the reduction reaction(s) to occur. As another example, it is thought that the process 600 may be advantageously employed when significant partitioning and elutriation of ultra-fines with the exhaust gas 620 from the first reactor 602 occurs and when the kinetics are sufficiently fast within each reactor 602, 604 for the reduction reaction(s) to occur. Advantageously, this configuration of reactors can enable a higher degree of metallisation and, in some embodiments, complete metallisation, of the iron.

In addition, it is thought that, under these conditions, processing elutriated fines from the first reactor 602 in this manner can have advantages including simplification of the plant, a reduction of the overall tower height, and elimination of equipment (e.g., cyclone, baghouse) at height (i.e., because the elutriated fines of the first reactor 602 do not need to be separated from the gas exhaust and the gas-particle separation equipment in the second reactor 604 is located at a lower end thereof). By processing fines in co-flow, recirculation of powder within the first reactor is eliminated which can reduce the buildup of the powder within the reactor. Furthermore, high temperature dedusting between the reactor stages is eliminated, which can allow for efficient use of heat within the exhaust gas from the first reactor.

Dual Reactor Process for Ironmaking - Fig. 4

Fig. 4 is a process flow diagram, set out in block form, of a further embodiment of a process 800 and system for reducing iron. The reduced iron may be in the form of sponge iron and may be sold as sponge iron briquettes. The process 800 may be used to produce reduced iron when the input the input material is sufficiently high grade and/or the desired product output is low grade briquettes. In these embodiments, the production of reduced iron can be targeted in both reactors. Alternatively, the reduced iron may be in the form of magnetite. When the reduced iron is in the form of magnetite, the reduced iron may be used as a feed to another process in which the iron is further reduced, e.g., to sponge iron. For example, the magnetite can be used as feed to an H-DRI process.

The process 800 comprises two reactors 802, 804. Each of the vertical reactors 802, 804 comprises an indirectly heated vertical reactor as described in WO2023064981. Similar to the process 600, one reactor 804 is operated using a counter-current flow regime, whilst the other reactor 802 is operated using a co-flow regime. Such a process may be advantageously employed when carryover of fines with the exhaust gas from the first reactor is sufficiently low and when the kinetics are sufficiently fast within each reactor for the reduction reaction(s) to occur. It is thought that, under these conditions, processing elutriated fines from the first reactor in this manner can have the attendant advantages outlined above with respect to the process 600. However, unlike the process 600, the same reduction reaction(s) need not be occurring in each of the reactors 802, 804. In particular, and as will be outlined in more detail below, reactor 804 is operated to produce either elemental iron or magnetite, whilst reactor 802 is typically operated to produce magnetite

The feed to the process 800 is low-grade iron ore 801, such as hematite and/or goethite. The low-grade iron ore 801 can be from, for example, a mine. As will be appreciated, such low-grade iron ores 801 typically comprise a significant fraction of non-iron- containing minerals, i.e., gangue, and comprises a wide range of particle sizes. In this regard, the iron ore 801 may be subjected to one or more beneficiation stages in which the ore is upgrade and converted to an ultra-fine powder (with particle sizes of less than 250 pm). For example, gravitational separation based on density may be used to remove denser gangue material from the iron ore. As another example, a milling circuit 806 may be used to reduce the particle size of the material. The milled material can then be passed through a size separation stage (not shown) in which gangue (not shown) is separated from crushed iron ore 808, e.g., based on a difference in particle size, with the gangue typically having larger diameter particles than the crushed iron ore 808. It will be understood that the crushed iron ore 808 comprises a higher concentration of iron than the low-grade iron ore 801, however the concentration of iron in the crushed iron ore 808 is typically still low, such that the crushed iron ore 808 may still be classified as a low- grade iron ore. The gangue can be collected and disposed of as waste or used as landfill in, e.g., a mine.

The crushed iron ore 808 is typically in the form of a powder comprising iron with a particle size of less than 250 pm, i.e., such that it is suitable to be fed into the first vertical reactor 802. The iron ore can be crushed so as to achieve such particle sizes using any known means in the art.

The operation of the vertical reactors, such as the first vertical reactor 802, is described in greater detail in WO2023064981 and above with references to processes 10, 200 and 600. In the reactor 802, the crushed iron ore 808 is heated in the presence of a gas 810 so as to produce magnetite. In particular, the reactor 802 is typically operated at a temperature of between about 700 to 1100 °C. The conversion of goethite in the crushed iron ore 808 to magnetite is a temperature-based reduction reaction, i.e., the decomposition of hematite/goethite into magnetite is facilitated by heating the crushed iron ore 808 to within this temperature range in the presence of a reducing gas. In this regard, the gas 810 typically comprises hydrogen, i.e., so as to facilitate the reduction of the goethite to magnetite. It is noted that the reduction of hematite/goethite is typically exothermic. Therefore, the heating to the reactor 802 can be used to control the reactor temperature, with low overall energy required. Alternatively or additionally, the feed rate of the crushed iron ore 808 can be used to moderate reactor temperature. For example, by increasing the feed rate of the crushed iron ore 808, the temperature within the reactor 802 can be increased.

As will be explained in more detail below, the gas 810 comprises an exhaust gas from a second reactor 804. By using the exhaust gas 810 from the second reactor 804, heat in the exhaust gas 810 can be recovered (i.e., because the gas provides its thermal energy to the iron 808 in the reactor 802). The gas 810 is typically a mixture of hydrogen and water. The gas 810 can also comprise powder that was elutriated from the second reactor 804 along with the gas 810. The elutriated powder can comprise magnetite or partially reduced magnetite. Typically, the reactor 802 is operated in a dilute flow regime, with the concentration of hydrogen in the exhaust gas 810 controlled such that substantially all the hydrogen is consumed in the reactor 802 (i.e., due to the reduction reaction between the hematite/goethite/magnetite and the hydrogen).

Because the first reactor 802 operates in a co-flow regime, both the iron ore 808 and the gas 810 flow downwardly through the reactor. The first reactor 802 is indirectly heated to raise the temperature of the powder and the reducing gas therewithin to a temperature at which the hematite/goethite in the ore is reduced. Typically, the first reactor 802 is operated such that the hematite/goethite is reduced to magnetite. At the same time, powder elutriated with the exhaust gas 810 into the first reactor 802 is reduced, e.g., to magnetite or elemental iron. However, the inventors note that it can be advantageous to minimise the further reduction of magnetite (e.g., to iron) in the reactor 802 because magnetite (being magnetic) may be easily separated from remaining non-magnetic gangue (i.e., by magnetic separation). In this regard, the conditions in the reactor 802 may be controlled such that the reduction of magnetite formed therein is minimised and/or altogether suppressed. However, alternatively, the conditions in the reactor 802 may be controlled so as to promote reduction of magnetite to, e.g., elemental iron.

Exiting a bottom of the reactor 802 is an exhaust gas 812 in which the (now reduced) powder comprising iron is entrained. The exhaust gas 812 typically comprises steam, being a product from the reduction reaction of iron oxides with hydrogen. As above, the exhaust gas 812 typically comprises little to no hydrogen, i.e., because the composition of the exhaust gas 810 and the feed rate into the reactor 802 are controlled such that substantially all the hydrogen is consumed in the reactor 802.

The exhaust gas 812 is passed to a gas-powder separation stage 814 in which the entrained powder 828 is separated from the gas 818. The gas 818, comprising steam, is condensed 820 so as to produce water 822. The water 822 is collected for re-use in the process, e.g., to create hydrogen by electrolysis or as process water. It is noted that by operating the process 800 such that no hydrogen remains in the exhaust gas 812, this gas clean-up process can be simplified, i.e., because the only products are iron powder and water. However, it is noted that, in the event that some hydrogen remains in the exhaust gas 812, during the condensation 820 of steam to water, said hydrogen will remain as a gas (i.e., it will not be condensed). This hydrogen can be collected for re-use in the process or vented to the atmosphere (e.g., if the volume of hydrogen is small).

The powder 828, primarily comprising magnetite, is collected. If the iron content of the powder 828 is sufficiently high (i.e., such that the powder constitutes a high-grade magnetite product), the powder 828 is collected as a magnetite product 830 of the process 800. Alternatively, for example when the iron content of the powder 828 is low, the powder 828 can be passed to a magnetic separator 824. The magnetic separator 824 can comprise any known magnetic separation process (e.g., high gradient magnetic separation and/or wet high intensity magnetic separation). In this regard, it will be appreciated that an advantage of reducing the hematite/goethite to magnetite in the reactor 802 is that the magnetic properties of magnetite may be exploited so as to enable separation of the magnetite from gangue. Typically, the magnetite must be cooled sufficiently below the Curie temperature of magnetite to enable efficient magnetic separation. The use of magnetic separation at high temperatures may be used, such as using a roll magnetic separator which does not use permanent magnets. The non-magnetic gangue (not shown) is disposed of, e.g., as waste, or for use as landfill (e.g., at a mine site). The separated magnetic material comprises a high-grade magnetite 826. It will be appreciated that the magnetite 826 is of a higher grade than the magnetite 828 because of the removal of nonmagnetic gangue therefrom. The magnetite 826 is collected as a magnetite product 830 of the process 800.

It is noted that, unlike the process 10 and 200 in which the magnetite product of the first reactor is almost immediately processed in the second reactor (i.e., so as to form a continuous process), the magnetite product 830 of the first reactor 802 of the process 800 need not be almost immediately processed in the second reactor 804. That is, the magnetite 830 need not be continuously used as a feed to the second reactor 904. For example, the magnetite product 830 can be stored for later use. Alternatively, the magnetite product 830 can be sold as a by-product of the process 800.

Turning now to the second reactor 804, the second reactor 804 comprises a vertical reactor of the type described and taught in detail in WO2023064981. The feed to the second reactor 804 typically comprises magnetite 834. The magnetite 834 can comprise naturally formed magnetite, e.g., in the form of a magnetite concentrate 832. Alternatively, the magnetite 834 can comprise the magnetite product 830 of the first reactor 802. As another alternatively, the magnetite 834 can comprise a blend of both naturally formed magnetite 832 and the magnetite product 830 of the first reactor 802. It is noted that naturally formed magnetite is typically denser than that produced by the first reactor 802. In this regard, the naturally formed magnetite may be referred to as ‘dense magnetite’, whilst the magnetite product 803 may be referred to as ‘porous magnetite’. Advantageously, the process 800 is inherently flexible with regard to the magnetite feed source because it can make use of the magnetite product 830 of the first reactor and/or externally produced magnetite feed sources.

The second reactor 804 comprises an H-DRI reactor, in which iron in the magnetite feed 834 is reduced to elemental iron. That is, the reactor 804 is operated to as to cause magnetite to be reduced to elemental iron. To facilitate reduction of the magnetite to iron, a reducing gas is required. In this regard, a reducing gas 835, in this embodiment in the form of either hydrogen or a mixture of hydrogen and water, is fed into the reactor 804, along with the fine magnetite powder 834. The reducing gas 835 and powder 834 are each inputted such that a dilute gas flow regime is established within the reactor 804 and such that the reducing gas 835 flows upwardly through the reactor 804, whilst the powder 834 falls downwardly therethrough, i.e., in a counter-flow regime. The advantages of using a gas comprising hydrogen as the reducing gas will be appreciated from WO2023064981, namely, that the carbon footprint of the process 800 may be minimised. As above, the advantage of employing ultra-fine particles in a dilute flow regime is that the reduction reaction occurs very quickly, resulting in shorter reactor residence times.

The reducing gas 835 can be pre-heated in a heat-exchanger 844, e.g., using process heat. When the reducing gas 835 is preheated, some or all 842 of the feed gas 840 (e.g., from a hydrogen supply) is passed through the heat-exchanger 844, so as to produce a preheated gas 846 which is used as the reducing gas 835 into the reactor 804. When no preheating is used, the feed gas 840 is passed directly 838 to the reactor 804.

As with the first reactor 802, the second reactor 804 is indirectly heated to raise the temperature of the powder and the reducing gas to a temperature at which the magnetite is reduced to elemental iron. It is noted that, the external heating of the reactor 804 may be used to primarily control the reactor operation. However, the reduction of magnetite to elemental iron tends to be slightly endothermic, meaning the energy requirements of the second reactor 804 tend to be greater than the first reactor 802. Heat (for both the first reactor 802 and the second reactor 804) may be generated from renewable power to reduce scope three CO2 emissions.

In some embodiments, the first reactor may be indirectly heated so as to maintain a temperature of between 700 °C to 900 °C within the reactor. Additionally, the second reactor may be indirectly heated so as to maintain a temperature of between 700 °C to 900 °C within the reactor. This temperature range has been found to be optimal towards the conversion reactions taking place in each reactor. The temperature is sufficiently high that the intermediate wustite form of iron oxide is unstable with respect to iron, and the temperature is sufficiently low that cascading agglomeration of particles may be inhibited. Typically, the operating conditions of the reactor 804 are controlled such that a degree of metallisation in excess of about 90%, such as an excess of about 95% on an iron basis is achieved. At the same time, hydrogen present in the gas 835 is converted into water. It has been found that, depending on the configuration and operation of the reactor 804, the ultra-fine powder 834 can sometimes have a tendency to stick to the interior walls of the reactor 804. It is thought that magnesium oxide and/or calcium oxide can act as an anti-stick coating in the second reactor 804. In this regard, magnesium oxide and/or calcium oxide 815 can be added as an optional feed to the reactor 804. For example, the magnesium oxide and/or calcium oxide 815 can be blended with the magnetite 834 feed prior to being fed into the second reactor 804. Alternatively, the magnesium oxide and/or calcium oxide 815 can be inputted into the second reactor 804 through a different feed input thereto, i.e., such that the magnesium oxide and/or calcium oxide 815 and the magnetite 834 are not mixed prior to being fed into the reactor 804.

Exiting the reactor 804 is a gas 810 comprising hydrogen and water, i.e., because not all the hydrogen is consumed in the reactor 804, and an iron powder 836, now primarily comprising iron (i.e., because the magnetite is reduced to iron in the reactor 804). When magnesium oxide and/or calcium oxide 815 are also fed into the reactor 804, the iron powder 836 further comprises magnesium oxide and/or calcium oxide. The gas 810 further comprises fine powder that becomes entrained within the gas 810 as the gas flows upwardly through the reactor 804 and is elutriated along with the gas 810 from the reactor 804. Unlike the process 10, 200, the elutriated powder is not separated from the gas 810. Rather, the gas 10, along with the elutriated powder is passed to the first reactor 802, in which the gas 810 acts a reducing gas and the elutriated powder is reduced. Advantageously, because the gas 810 still comprises hydrogen, it is suitable for use as the gas in the first reactor 802. Of further advantage is that, by passing the elutriated powder along with the gas to the first reactor, the need for separation equipment (e.g., cyclone, baghouse) at height (i.e., because the gas exits at a top of the reactor 804) is eliminated. By processing fines in co-flow, recirculation of powder within the reactor is eliminated which can reduce the build-up of the powder within the reactor. Furthermore, high temperature dedusting between the reactor stages is eliminated, which can allow for efficient use of heat within the exhaust gas from the first reactor.

The iron powder 836, now primarily comprising elemental iron, and which can further comprise magnesium oxide and/or calcium oxide (i.e., when magnesium oxide and/or calcium oxide 815 is used as a feed to the reactor 804), is collected from the second reactor 804. Depending on the grade of the iron powder 836, the iron powder is either directly briquetted or subjected to further upgrading. In particular, when the iron powder 836 comprises a high-grade iron, the iron powder 836 is passed to a briquetting stage 850. In the briquetting stage 850, the iron powder 836 is formed into sponge iron briquettes 848. The briquettes 848 can then be sold as a by-product of the process 800. Alternatively, the briquettes 848 can be used in the production of steel. It is noted that when magnesium oxide and/or calcium oxide is used as a feed to the reactor 804, the briquettes 848 also comprise magnesium oxide and/or calcium oxide. This can reduce the quantity of additives required in the steelmaking process, i.e., because the magnesium oxide and/or calcium oxide already present in the briquettes act as slagging agents.

When the iron powder 836 comprises a lower-grade iron, the iron powder 836 is instead passed to a dry magnetic separation stage 854. In the dry magnetic separation stage 854, the iron powder 836 is subjected to a dry magnetic separation in which non-magnetic gangue (not shown) is removed from a high-grade iron powder 856. Such a magnetic separation stage 854 is typically employed when the grade of feed into the second reactor 804 is lower than the desired grade of feed. It will be appreciated that this can occur due to, for example, transient process conditions, performance of the first reactor 802 (e.g., when the magnetite product 830 from the first reactor 802 is used as some or all of the feed 834 to the second reactor 804), lower than expected grade of magnetite concentrate 832 (e.g., when the magnetite feed 834 to the second reactor 804 comprises magnetite concentrate 832). It is noted that, when the magnetite feed 834 comprises the magnetite product 830 from the first reactor 802, the magnetic separation stage 824 can be omitted, and the magnetic separation stage 854 may instead be employed. This is because, in some circumstances, the magnetic separation stage 854 (which is performed on the iron powder 836 comprising elemental iron) may provide a more effective and/or a more cost-effective separation compared to the magnetic separation stage 824 (which is performed on the magnetite 828).

The high-grade iron powder 856 (also termed DRI powder because the iron is produced through direct reduction) can be stored 858 and then sold as a by-product of the process 800. Alternatively, the high-grade iron powder 856 can be processed into sponge iron briquettes. As will be explained below, at least some of the high-grade iron powder 856 may be stored and used to generate hydrogen.

Variations and modifications may be made to the process 800 without departing from the spirit or ambit of the disclosure. For example, the operation of both reactors 802, 804 can be controlled so as to produce elemental iron. That is, the product of the reactor 802 can comprise elemental iron. In such variations, the conditions of the reactor 802 are controlled such that the hematite/goethite is reduced to magnetite, which, in turn, is further reduced. The reduced iron from the first reactor 802 and the second reactor 804 can be combined into an iron powder 836.

Dual Reactor Process for Hydrogen Production - Fig. 5

Fig. 5 is a process flow diagram, set out in block form, of a further embodiment of a process 900 and system for reducing iron and in which hydrogen is produced. The reduced iron may be in the form of sponge iron and may be sold as sponge iron briquettes. Alternatively, some or all of the reduced iron may be used for the production of hydrogen. Advantageously, the process 900 utilises DRI (i.e., iron produced through a direct reduction process, such as the processes 10, 200, 600, 800) as a hydrogen storage medium for minimisation of top-up hydrogen. This can allow for continuous operations and production of DRI whilst minimising energy consumption (e.g., during times of high electricity prices or low renewable availability). The process 900 can also provide a way of recirculating and upgrading DRI which is at a lower grade than what is desired.

The process 900 comprises two reactors 902, 904. Each of the vertical reactors 902, 904 comprises an indirectly heated vertical reactor as described in WO2023064981. Similar to the process 800, one reactor 904 is operated using a counter-current flow regime, whilst the other reactor 902 is operated using a co-flow regime. Such a process may be advantageously employed when carryover of fines with the exhaust gas from the first reactor is sufficiently low and when the kinetics are sufficiently fast within each reactor for the reaction(s) to occur. It is thought that, under these conditions, processing elutriated fines from the first reactor in this manner can have the attendant advantages outlined above with respect to the process 600. However, unlike the process 600 or 800, in the process 900, iron is oxidised in the first reactor 902 (i.e., as opposed to being reduced) so as to produce magnetite and hydrogen. Magnetite (or other non-reduced forms of iron) is used as feed to the second reactor 904 in which the iron is reduced, typically to elemental iron.

In this regard, the feed to the first reactor 902 of the process 900 is reduced iron 906. For example, the reduced iron 906 may be from an H-DRI or DRI process in which iron (e.g., in the form of magnetite, hematite, goethite) is directly reduced to (elemental) iron. However, it will be appreciated that the reduced iron 906 can comprise reduced iron from an alternative source. Depending on the form of the reduced iron 906, the reduced iron 906 may be subjected to one or more pretreatment stages (not shown) prior to being used as feed to the first reactor 902. For example, when the reduced iron 906 is in the form of particles with diameters greater than 250 pm, the reduced iron 906 is subjected to a particle size reduction treatment in which the size of the particles is reduced such that the feed to the first reactor 902 is an ultra-fine powder with particle sizes less than 250 pm. Alternatively, when the reduced iron 906 is in the form of a very fine powder with diameters of about 10 pm (i.e., such as might be produced from an H-DRI process in which a heated vertical reactor of the type described in WO2023064981 is used), the reduced iron 906 may be subjected to a fusion process (e.g., such as the fusion plant 54 described with reference to Figs. 1 and 2) in which the particles are agglomerated to form an ultra-fine powder with particle sizes of less than 250 pm. The operation of the vertical reactors, such as the first vertical reactor 902, is described in greater detail in WO2023064981. In the reactor 902, the reduced iron 906 is heated in the presence of a gas 908 so as to produce oxides of iron. Typically, the conditions within the reactor 902 are controlled such that magnetite is the primary product of the reaction. It will be appreciated that the reaction of reduced iron 906 to magnetite is an oxidation reaction, in which the elemental iron (in the reduced iron 906) is oxidised. In particular, the reaction conditions in the reactor 902 are controlled such that the oxidation reaction produces magnetite. This is because, as described below, magnetite is magnetic, allowing for the magnetic separation of the magnetite from gangue. In this regard, the gas 908 comprises water vapour (i.e., steam) which acts to oxidise the iron. That is, the water vapour and reduced iron react according to the following mechanism:

3 Fe + 4 H2O — >■ Fe3O4 + 4 H2

The reactor 902 is typically operated at a temperature of between about 700 to 1100 °C. The temperature is controlled through indirect heating of the reactor 902, noting that the oxidation of iron to magnetite is an endothermic reaction, requiring energy input (e.g., in the form of the heating provided by the indirect heating of the reactor 902).

As will be explained in more detail below, the gas 908 comprises an exhaust gas from the second reactor 904. By using the exhaust gas 908 from the second reactor 904, heat in the exhaust gas 908 can be recovered (i.e., because the gas provides its thermal energy to the reduced iron 906 in the reactor 902). The gas 908 comprises hydrogen and water vapour. Typically, the gas 908 only comprises a stoichiometric amount of water vapour based on the quantity of reduced iron 906 fed to the reactor 902 such that substantially all the water vapour is consumed within the reactor 902. The gas 908 can also comprise powder that was elutriated from the second reactor 904 along with the gas 908. The elutriated powder can comprise hematite, goethite and/or magnetite or partially reduced forms of hematite, goethite and/or magnetite.

Typically, the reactor 902 is operated in a dilute flow regime in which the gas 908 and reduced iron 906 are both caused to fall downwardly through the reactor 902 in a co-flow arrangement. As above, the reactor 902 is indirectly heated to raise the temperature of the reduced iron and the gas therewithin to a temperature at which the reduced iron is oxidised to magnetite. At the same time, powder elutriated with the gas 908 that is in a reduced form is likewise oxidised, i.e., to magnetite. It can be advantageous to minimise the further oxidation of magnetite (e.g., to hematite/goethite) in the reactor 902 because magnetite (being magnetic) may be easily separated from remaining non-magnetic gangue (i.e., by magnetic separation). Exiting the reactor 902 is an exhaust gas 910 comprising hydrogen in which the oxidised iron (still in the form of a powder of fine particles) is entrained. As above, the reactor 902 is controlled such that the exhaust gas 910 primarily comprises hydrogen. That is, the reactor 902 is controlled such that nearly all (if not all) of the water vapour in the gas 908 is consumed through the oxidation of the reduced iron 906. It will be appreciated that this can be achieved by controlling the composition of the gas 908 (i.e., through controlling the operation of the reactor 904) and/or by controlling the feed rate of the reduced iron 906 (i.e., by increasing the feed rate when there is more water vapour present in the gas 908).

The exhaust gas 910 is passed to a gas-powder separation stage 912 in which the entrained powder 914 is separated from the gas 922. The gas 922 substantially comprises hydrogen. In this regard, the gas 922 is suitable for use as a reducing gas in an H-DRI reactor, such as the second reactor 904. It is noted that, if the gas 922 comprises water vapour, the water vapour can be condensed therefrom (i.e., so as to produce water and a hydrogen gas). However, by controlling the reactor 902 such that the gas 922 does not comprise water vapour, the condensation step can be advantageously eliminated. This can simplify the flowsheet of the process 900 compared to, e.g., the processes 10, 200, in which a condensation step is required.

The powder 914, primarily comprising magnetite, is collected. If the iron content of the powder 914 is sufficiently high (i.e., such that the powder constitutes a high-grade magnetite product), the powder 918 is collected as a magnetite product 920 of the process 900. Alternatively, for example when the iron content of the powder 914 is low, the powder 914 can be passed to a magnetic separator 916. The magnetic separator 916 can comprise any known magnetic separation process (e.g., high gradient magnetic separation and/or wet high intensity magnetic separation). Typically, the magnetite must be cooled sufficiently below the Curie temperature of magnetite to enable efficient magnetic separation. The separated magnetic material comprises a high-grade magnetite 917. It will be appreciated that the magnetite 917 is of a higher grade than the magnetite 914 because of the removal of non-magnetic gangue therefrom. The magnetite 917 is collected as a magnetite product 920 of the process 800.

In this regard, it will be appreciated that an advantage of oxidising the reduced iron to magnetite in the reactor 902 is that the magnetic properties of magnetite may be exploited so as to enable separation of the magnetite from gangue, thereby resulting in a higher- grade magnetite. This can be particularly beneficial when the reduced iron 906 is of a lower grade than desired. By using this reduced iron 906 as the feed to the process 900, the grade of the final iron product can be increased. This is because the lower-grade reduced iron, after oxidation to magnetite, can be more easily separated from non- magnetic gangue. The high-grade magnetite produced by the magnetic separator 916 can then be used as feed to an H-DRI process, so as to reduce the magnetite back to elemental iron. The final elemental iron is at a higher-grade than the reduced iron feed 906 (i.e., due to the removal of gangue therefrom). At the same time, the hydrogen produced by the oxidation reaction with water can be used as the reducing gas in such an H-DRI process. In this regard, the magnetite product 920 of the first reactor 902 can be used as feed 928 to the second reactor 904. The magnetite product 920 can be used immediately and continuously as feed 928 to the second reactor 904. Alternatively or additionally, the magnetite product 920 can be stored for later use as a feed 928 to the second reactor 904. As another alternative, the magnetite product 920 can be sold as a by-product of the process 900.

Turning now to the second reactor 904, the second reactor 904 comprises a vertical reactor of the type described and taught in detail in WO2023064981. In the second reactor 904, iron in the feed 925 is reduced to elemental iron. In this regard, the feed 925 to the second reactor 904 comprises one or more of hematite/goethite 926 (e.g., low-grade iron ore concentrate which has undergone one or more beneficiation stages so that it is suitable for use as a feed to the second reactor 904), the magnetite product from the first reactor 928 (also called porous magnetite) and/or magnetite concentrate 930 (also called dense magnetite). That is, the feed 925 can comprise a single feed or the feed 925 can comprise a blend of material from different sources. In this regard, the process 900 is advantageous because it is flexible with regard to the exact feed source of the second reactor 904.

The feed 925 is in the form of an ultra-fine powder with particle sizes of less than 250 pm. As above, the second reactor 904 comprises an H-DRI reactor, in which iron in the feed 925 (i.e., iron present as hematite, goethite, magnetite) is reduced to elemental iron. To facilitate reduction the, e.g., hematite, goethite, magnetite, to iron, a reducing gas is required. In this regard, a reducing gas, in this embodiment in the form of hydrogen, is fed into the reactor 904, along with the feed 925. The reducing gas and feed 925 are each inputted such that a dilute gas flow regime is established within the reactor 904 and such that the reducing gas flows upwardly through the reactor 904, whilst the powder 925 falls downwardly therethrough, i.e., in a counter-flow regime. The advantages of using a gas comprising hydrogen as the reducing gas will be appreciated from WO2023064981, namely, that the carbon footprint of the process 900 may be minimised. As above, the advantage of employing ultra-fine particles in a dilute flow regime is that the reduction reaction occurs very quickly, resulting in shorter reactor residence times, e.g., within about 10 to 50 s.

The reducing gas is comprised of the gas 922 substantially comprising hydrogen from the first reactor 902. That is, the hydrogen produced due to the oxidation of iron in the first reactor 902 can advantageously be used as a reducing gas in the second reactor 904. The second reactor 904 is indirectly heated to raise the temperature of the powder and the reducing gas to a temperature at which the iron in the feed 925 is reduced to elemental iron. It is noted that, the external heating of the reactor 904 may be used to primarily control the reactor operation. Heat (for both the first reactor 902 and the second reactor 904) may be generated from renewable power to reduce scope three CO2 emissions.

In some embodiments, the second reactor may be indirectly heated so as to maintain a temperature of between 700 °C to 900 °C within the reactor. This temperature range has been found to be optimal towards the conversion reactions taking place in each reactor The temperature is sufficiently high that the intermediate wustite form of iron oxide is unstable with respect to iron, and the temperature is sufficiently low that cascading agglomeration of particles may be inhibited. Typically, the operating conditions of the reactor 904 are controlled such that a degree of metallisation in excess of about 90%, such as an excess of about 95% on an iron basis is achieved. At the same time, hydrogen present in the gas 922 is converted into water.

Typically, an excess of hydrogen is employed in the second reactor 902 so as to facilitate the near complete reduction of the iron targeted in the second reactor 902. It is noted that, if the gas 922 does not comprise sufficient hydrogen to ensure a stoichiometric amount of hydrogen is present in the second reactor 902 (i.e., compared to the amount of iron in the feed 925), make-up hydrogen 934 can be used to supplement the gas 922. It will be appreciated that the volume of make-up hydrogen 934 will be dependent on the deficit (i.e., the difference between the hydrogen requirement of the second reactor 904 and the hydrogen in the gas 922).

The make-up hydrogen 934 can be sourced from, for example, an electrolyser 932. The hydrogen 936 produced by the electrolyser 932 can be preheated in a heat-exchanger 938, e.g., using process heat, so as to form a preheated hydrogen stream 940, which is directed into the second reactor 904. Alternatively, the hydrogen 934 can be directly passed into the second reactor 904 (i.e., without preheating).

In instances where the make-up hydrogen 934 requires electricity to be generated (e.g., when an electrolyser 932 is used to produce the hydrogen from water), surges in electricity prices can increase the operating costs of the process 900. In addition, low renewable availability can increase the carbon footprint of the process 900. The inventors note that the process 900 can be particularly advantageously employed in such scenarios. This is because, in the process 900, hydrogen is produced by the first reactor 902 for use in the second reactor 904. This can decrease the amount of make-up hydrogen 934 required. In turn, this can decrease the need for electrolysis, which can decrease the overall electricity requirements of the process 900. Advantageously, the operation of the first reactor 902 can be controlled, based on the hydrogen requirements. For example, when the electricity prices are low, the throughput (and hydrogen output) of the first reactor 902 is decreased, because it is not as expensive to operate the electrolyser 932 and use the electrolyser as the main hydrogen source. However, when the electricity prices are high (e.g., in a price surge), the throughput (and hydrogen output) of the first reactor 904 is increased, thereby reducing the output required by the electrolyser and reducing the costs associated with operating the electrolyser.

In this regard, in the process 900, the reduced iron can be effectively used as a storage medium for hydrogen, enabling hydrogen generation in the first reactor 902 through oxidation of the reduced iron. Hydrogen is then consumed in the second reactor 904, regenerating the reduced (elemental) iron, with at least some of the iron from the second reactor 904 being set aside for later use in the first reactor 902.

It has been found that, depending on the configuration and operation of the reactor 904, the ultra-fine powder 925 can sometimes have a tendency to stick to the interior walls of the reactor 904. As described above with reference to process 800, it is thought that magnesium oxide and/or calcium oxide can act as an anti-stick coating in the second reactor 904. In this regard, magnesium oxide and/or calcium oxide 924 can be added as an optional feed to the reactor 904. For example, the magnesium oxide and/or calcium oxide 924 can be blended with the feed 925 prior to being fed into the second reactor 904. Alternatively, the magnesium oxide and/or calcium oxide 924 can be inputted into the second reactor 904 through a different feed input thereto, i.e., such that the magnesium oxide and/or calcium oxide 924 and the feed 925 are not mixed prior to being fed into the reactor 904.

Exiting the reactor 904 is a gas 908 comprising hydrogen and water, i.e., because not all the hydrogen is consumed in the reactor 904, and an iron powder 942, now primarily comprising iron (i.e., because the magnetite is reduced to iron in the reactor 904). Because the reactor 904 is operated in a counter-flow arrangement, the gas 908 exits at an upper end thereof, whilst the iron powder 942 exits at a lower end thereof. When magnesium oxide and/or calcium oxide 924 are also fed into the reactor 904, the iron powder 942 further comprises magnesium oxide and/or calcium oxide. The gas 908 further comprises fine powder that becomes entrained within the gas 908 as the gas flows upwardly through the reactor 904 and is elutriated along with the gas 908 from the reactor 904. The gas 908, along with the elutriated powder is passed to the first reactor 902, in which water vapour present in the gas 908 acts to oxidise iron present in the form of the reduced iron 906 feed to the reactor 902 and in the elutriated powder. Advantageously, because the gas 908 comprises water vapour (i.e., as steam at the high temperature employed in the reactors 902, 904), it is suitable for use as the gas in the first reactor 902. Of further advantage is that, by passing the elutriated powder along with the gas to the first reactor, the need for separation equipment (e.g., cyclone, baghouse) at height (i.e., because the gas exits at a top of the reactor 904) is eliminated.

The iron powder 942, now primarily comprising elemental iron, and which can further comprise magnesium oxide and/or calcium oxide (i.e., when magnesium oxide and/or calcium oxide 924 is used as a feed to the reactor 904), is collected from the second reactor 904. Depending on the grade of the iron powder 942, the iron powder is either directly briquetted or subjected to further upgrading. In particular, when the iron powder 942 comprises a high-grade iron, the iron powder 942 is passed to a briquetting stage 944. In the briquetting stage 944, the iron powder 942 is formed into sponge iron briquettes 946. The briquettes 946 can then be sold as a by-product of the process 900. Alternatively or additionally, the briquettes 946 can be used in the production of steel. It is noted that when magnesium oxide and/or calcium oxide is used as a feed to the reactor 904, the briquettes 946 also comprise magnesium oxide and/or calcium oxide. This can reduce the quantity of additives required in the steelmaking process, i.e., because the magnesium oxide and/or calcium oxide already present in the briquettes act as slagging agents.

When the iron powder 946 comprises a lower-grade iron, the iron powder 942 is instead passed to a dry magnetic separation stage 945. In the dry magnetic separation stage 945, the iron powder 942 is subjected to a dry magnetic separation in which non-magnetic gangue (not shown) is removed from a high-grade iron powder 948. Such a magnetic separation stage 945 is typically employed when the grade of feed into the second reactor 904 is lower than the desired grade of feed. As above, this can occur due to, for example, transient process conditions, performance of the first reactor, lower than expected grade of feed to the second reactor, etc. It is noted that, when the magnetite product 920 from the first reactor 902 is used as feed to the second reactor 904, the magnetic separation stage 916 can be omitted, and the magnetic separation stage 945 may instead be employed. This is because, in some circumstances, the magnetic separation stage 945 (which is performed on the iron powder 942 comprising elemental iron) may provide a more effective and/or a more cost-effective separation compared to the magnetic separation stage 916 (which is performed on the magnetite 914). Of course, it will be appreciated that both magnetic separation stages 916, 945 may be omitted (e g., where both the magnetite 914 and the iron powder 942 are of sufficiently high grades) or both magnetic separation stages 916, 945 may be included (e.g., where both the magnetite 914 and the iron powder 942 are of a lower grade than desired). The high-grade iron powder 948 can be stored 950 and then sold as a by-product of the process 900. Alternatively, the high-grade iron powder 948 can be processed into sponge iron briquettes. As another alternative, some of the high-grade iron powder 948 may be used as the reduced iron 906 feed to the first reactor 902, i.e., to generate hydrogen for use in the second reactor 904.

Polishing/Finishing Reactor - Fig, 6

Fig. 6 is a process flow diagram, set out in block form, of a further a process 1000 and system which can advantageously employ a vertical reactor of the type described in detail in WO2023064981. In the process 1000, a vertical reactor 1002 is employed as a finishing/polishing reactor. In this regard, the process 1000 can be advantageously employed for a number of uses, such as: to reheat cold DRI (e g., reduced elemental iron from any of the above processes) for hot briquetting; further upgrading the metallisation extent of reduced iron; carburisation of reduced iron through recirculation of carbon monoxide. Additionally, the process 1000 can be employed to calcine a carbonate, such as magnesium carbonate and/or calcium carbonate, at the same time as reheating cold DRI, upgrading the metallisation extent of reduced iron and/or carburisation of reduced iron. In this regard, the process 1000 can be employed to produce a precursor for use in steelmaking. However, as will be appreciated, the process 1000 is not limited to only these applications and can also have other applications.

The feed to the process 1000 is a powder comprising iron 1004. The powder comprises an ultra-fine powder with particle sizes of less than 250 pm. The iron is typically in the form of reduced (elemental) iron. The reduced iron may be the product of a direct reduction process. For example, the reduced iron can comprise reduced iron 858 from the process 800 and/or reduced iron 950 from the process 900. Alternatively or additionally, the reduced iron can comprise reduced iron from any other iron reduction process. The powder comprising iron 1004 can additionally comprise iron in the form of iron oxide, such as FeO. For example, the FeO may be recycled from a slagging process.

The powder comprising iron 1004 is fed to the reactor 1002. Typically, the powder comprising iron 1004 is fed to an upper end of the reactor 1002 such that the powder falls downwards through the reactor. At the same time, a gas 1008 is fed into the bottom of the reactor 1002, such that the gas flows upwardly through the reactor. In this regard, the gas 1008 and the powder 1004 are caused to flow counter-currently within the reactor. The gas 1008 and the powder 1004 are each inputted to the reactor 1002 such that a dilute flow regime is caused to occur therewithin.

It will be appreciated that the composition of the gas 1008, as well as the operating conditions within the reactor 1002 will depend on the application in which the reactor is employed. For example, when the reactor 1002 is used in the reheating of cold reduced iron (e.g., so as to produce a hot reduced iron suitable for use as a feed for hot briquetting), the gas 1008 typically comprises hydrogen. Advantageously, by employing a gas 1008 comprising hydrogen, the reactor 1002 can be operated so as to cause remaining iron oxides to be reduced to elemental iron, thereby upgrading the reduced iron. Similarly, when the reactor 1002 is used for further upgrading of the metallisation extent of the feed, the gas 1008 comprises hydrogen. In this way, the gas 1008 can act as a reducing gas and the conditions within the reactor 1002 are controlled so as to cause any remaining iron oxides to be reduced to elemental iron, thereby upgrading the iron. It is noted that the gas 1008 can further comprise carbon monoxide, which can likewise act as a reducing gas. One advantage of carbon monoxide is that the reduction reaction of iron with carbon monoxide is exothermic, which can reduce energy requirements within the reactor. On the other hand, when the reactor 1002 is used for carburisation of iron, the gas 1008 can further comprise carbon monoxide. The carbon monoxide can provide the carbon for the carburisation, resulting in the production of iron carbide (e.g., FesC).

In-use, the reactor 1002 is indirectly heated to a temperature at which the desired reaction (or the preheating) occurs. Typically, a reactor temperature of between about 700 °C to about 900 °C is targeted. Heat may be generated using renewable sources so as to reduce scope 3 carbon dioxide emissions.

One or more optional materials 1006 can also be used as feed to the reactor 1002, in addition to the powder 1004. These optional materials 1006 may be blended with the powder 1004, with the blend fed to the reactor 1002 as a single input. Alternatively, the optional materials 1006 may be inputted into the reactor 1002 separately to the powder 1004. For example, as explained above with reference to processes 800, 900, magnesium oxide and/or calcium oxide may be added to the reactor 1002 as anti-sticking agents. Additionally, when the reactor 1002 is employed for carburisation, the optional materials 1006 may comprise (or may further comprise) a carbonate, such as magnesium carbonate and/or calcium carbonate. The carbonate provides a source of carbon (or an additional source of carbon when the gas 1008 comprises carbon monoxide), which can react with the iron, so as to produce iron carbide. At the same time, the carbonate is decomposed into an oxide and carbon dioxide. As will be explained in further detail below, the optional materials 1006 may also comprise a carbonate, such as magnesium carbonate and/or calcium carbonate, when concurrent calcination of these carbonates is desired. For example, when it is desired to produce a product that comprises magnesium oxide and/or calcium oxide. It is noted that such a product may be advantageously used as a feed to a smelter or a steelmaking process, because it already comprises the necessary additives (e.g., the magnesium oxide and/or the calcium oxide). In these variations, the reactor 1002 is operated so as to cause the magnesium carbonate and/or calcium carbonate to be decomposed into the respective oxides, with carbon dioxide produced as a by-product.

Exiting the reactor 1002 at the powder outlet is a powder product 1012. It will be appreciated that the composition of the powder product 1012 will depend on the application in which the reactor 1002 is used. For example, when the reactor 1002 is used for preheating reduced iron, the powder product 1012 comprises the preheated reduced iron, which is suitable to be used as a feed 1014 to a hot briquetting process 1016. As another example, when the reactor 1002 is used for upgrading the metallisation extent of the feed, the powder product 1012 comprises an upgraded reduced iron product. The upgraded reduced iron product may be suitable for use as a feed 1014 to a hot briquetting process 1016 (i.e., to produce sponge iron briquettes). Alternatively or additionally, the upgraded reduced iron product may be suitable for use as a feed 1018 to a smelter/EAF 1020 It is noted that the use of the one or more optional materials 1006 in the reactor 1002 may reduce the amount of additional additives required in the smelter/EAF 1020 to support smelting (e.g., fluxing agents, slagging agents, etc ). This is because additives such as calcium oxide and/or magnesium oxide (present either due to the direct addition of calcium oxide and/or magnesium oxide or due to the addition of magnesium carbonate and/or calcium carbonate which each decompose into the oxide form in the reactor) can each act as suitable additives. As a further example, when the reactor 1002 is used for carburisation, the powder product 1012 comprises iron carbide, as well as elemental iron, and can be suitable for further processing into steel.

Exiting the top of the reactor 1002 is an exhaust gas 1010 (i.e., because the gas 1008 is caused to flow upwardly through the reactor 1002). Again, the composition of the exhaust gas 1010 will depend on the application in which the reactor 1002 is employed. For example, when the reactor 1002 is used for preheating reduced iron and/or for upgrading the metallisation extent of the feed, the exhaust gas 1010 can comprise water and/or hydrogen. As above, in these applications, hydrogen is typically present in the gas 1008 because using hydrogen in the gas 1008 can result in further reduction of non-reduced iron in the feed. Reduction of the non-reduced iron causes the formation of water (i.e., because the reduction of iron with hydrogen produces water). Typically, some hydrogen will remain in the gas 1008, because an excess of hydrogen is employed. The gas 1008 may further comprise carbon dioxide, for example, when carbon monoxide is used as a reducing gas as an alternative to or in addition to hydrogen. As another example, when the reactor 1002 is used for carburisation, the gas 1010 typically comprises carbon dioxide. Some hydrogen and/or water may also be present (e.g., if hydrogen is present in the gas 1008 and further reduction of iron occurs within the reactor 1002). As a further example, when magnesium carbonate and/or calcium carbonate are inputted into the reactor (i.e., as the one or more other materials 1006), the exhaust gas 1010 typically comprises carbon dioxide, because the carbonates tend to decompose at the temperatures at which the reactor 1002 is operated. Reactions between the carbonates and the iron can also result in the production of carbon dioxide.

The exhaust gas 1010 can further comprise fine powder that is elutriated from the reactor 1002 along with the exhaust gas 1010. In this regard, the reactor 1002 typically comprises a gas-powder separator (not shown). For example, as described in WO2023064981, the reactor can comprise one or more cyclones and/or bag filter(s) installed at an upper end thereof and arranged such that the exhaust gas 1010 is caused to flow through the cyclone(s)/bag filter(s) before exiting the reactor 1002. The elutriated powder is trapped by the cyclone(s)/bag filter(s) and is reinjected into the reactor 1002.

The exhaust gas 1010, now substantially free of fine powder, is collected for subsequent treatment. It will be appreciated that the treatment processes employed depend on the composition of the exhaust gas 1010. For example, when the exhaust gas comprises water vapour and hydrogen, the water vapour can be condensed from the exhaust gas, so as to produce a gas comprising hydrogen, which gas can be recycled for reuse in the reactor (e.g., as a reducing gas).

As another example, when the exhaust gas 1010 comprises carbon dioxide and/or water, the exhaust gas can be passed through a solid oxide electrolyser 1026. In the solid oxide electrolyser 1026, water is converted into oxygen and hydrogen. At the same time, carbon dioxide is converted into oxygen and carbon monoxide. Exiting an outlet of the solid oxide electrolyser 1026 is a gas comprising oxygen 1028. The gas comprising oxygen 1028 can either be collected and sold, or can be vented into the atmosphere. Exiting at another outlet of the solid oxide electrolyser 1026 is a gas 1030 comprising carbon monoxide and/or hydrogen. The gas 1030 comprising carbon monoxide and/or hydrogen can be collected and reused in the reactor 1002 (e.g., as a reducing gas or for carburisation). Additional hydrogen 1032 (e.g., from electrolysis) and/or syngas 1034 can be added to the gas 1030. For example, additional hydrogen 1032 and/or syngas 1034 can be added to the gas 1030 so as to achieve a required hydrogen and/or carbon monoxide composition in the feed gas 1008 to the reactor 1002. Alternatively, additional carbon monoxide can be supplied to the feed gas 1008 by adding additional carbon dioxide 1022 prior to the solid oxide electrolyser 1026. This is because, as above, in the solid oxide electrolyser 1026, the carbon dioxide is converted to carbon monoxide. The carbon dioxide 1022 can be mixed with the exhaust gas 1010, with the mixed gas 1024 fed to the solid oxide electrolyser 1026. It will be appreciated that the quantity of carbon dioxide 1022 mixed with the exhaust gas 1010 can be adjusted based on a target carbon monoxide concentration in the feed gas 1008. It is noted that, in other processes in which a sponge iron product from a DRI reactor is mixed with magnesium oxide and/or calcium oxide (e.g., in a steelmaking process), the magnesium oxide and/or calcium oxide are typically added to a sponge iron product after the DRI reactor. For example, in the process 200 (see Fig. 2), the magnesium oxide and/or calcium oxide 222 is generated by calcining 228 limestone and/or dolomite 260 (i.e., magnesium carbonate and/or calcium carbonate). The magnesium oxide and/or calcium oxide 222 is mixed with the sponge iron 58 in a hot mixer 218. On the other hand, the process 1000 provides a way of calcining the magnesium carbonate and/or calcium carbonate at the same time as, e.g., preheating the reduced iron, upgrading the reduced iron, carburisation of iron.

It is noted that a key to enabling the concurrent calcination of the magnesium carbonate and/or calcium carbonate is the provision of the solid oxide electrolyser 1026, which is able to regenerate the reducing gas (i.e., the gas 1030 comprising hydrogen and carbon monoxide). In particular, the solid oxide electrolyser enables the regeneration of carbon monoxide from carbon dioxide (i.e., as compared to a normal electrolyser which can regenerate the hydrogen from the water but cannot regenerate the carbon monoxide). This advantageously enables the exhaust gas 1010 to be recycled.

In addition, the need for a hot mixer may be avoided, because the product of the reactor 1002 is a powder 1012 comprising the reduced and/or carburised iron, along with other suitable additives, including calcium oxide and/or magnesium oxide, which act as slagging agents. That is, the additives required for the subsequent smelting/EAF process(es) can already be present in the powder 1012.

It is thought that the one or more other materials 1006 can further comprise other suitable additives. In this way, the inventors note that the process 1000 provides flexibility to the input of additives, because the additives can be added directly into the reactor 1002, in addition to or as an alternative to being added downstream (e.g., in a hot mixer). It is also thought that the process 1000 may also enable lower cost additives to be employed. In this regard, the process 1000 also provides a way of producing a suitable precursor for steelmaking.

Variations and modifications may be made to the parts previously described without departing from the spirit or ambit of the disclosure.

For example, in the above processes, the reducing gas comprises hydrogen and water. However, it will be appreciated that the reducing gas may alternatively or additionally comprise one or more other gases such as carbon monoxide and/or methane. In the claims which follow and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the process, system and reactor as disclosed herein.

Claims

1. A process for reducing iron ore, the process comprising: feeding a powder comprising iron ore and a first reducing gas into a first reactor and indirectly heating the first reactor so as to heat the powder and the gas to a temperature at which the iron ore is converted to magnetite; and feeding a resultant powder comprising magnetite and a second reducing gas into a second reactor and indirectly heating the second reactor so as to heat the powder comprising magnetite and the second reducing gas to a temperature at which the magnetite is reduced to iron, to thereby form a powder comprising iron.

2. A process as claimed in claim 1, wherein an exhaust gas from the second reactor is passed to the first reactor, such that the first reducing gas comprises the exhaust gas from the second reactor.

3. A process as claimed in claim 1 or 2, wherein the iron ore in the powder fed to the first reactor comprises iron in the Fe³⁺ oxidation state such as hematite, goethite and siderite ores.

4. A process as claimed in any one of the preceding claims, wherein the magnetite from the first reactor is magnetically separated from a gangue, with the separated magnetite being fed to the to the second reactor.

5. A process as claimed in claim 4, wherein, prior to feeding the magnetite to the second reactor, the magnetite is agglomerated.

6. A process as claimed in any one of the preceding claims, wherein each of the first reactor and the second reactor is operated in a dilute flow regime.

7. A process as claimed in any one of the preceding claims, wherein each of the first reactor and the second reactor is indirectly heated so as to maintain a temperature of between 700 °C to 1100 °C within the respective reactor.

8. A process as claimed in any one of the preceding claims, wherein the first reducing gas input to the first reactor comprises carbon monoxide, hydrogen, steam, methane, or mixtures thereof.

9. A process as claimed in claim 8, wherein the first reducing gas input to the first reactor comprises hydrogen and steam.

10. A process as claimed in claim 9, wherein the gas comprises hydrogen and steam in a one-to-one stoichiometric ratio.

11. A process as claimed in any one of the preceding claims, wherein the second reducing gas input to the second reactor comprises carbon monoxide, hydrogen, steam, methane, or mixtures thereof.

12. A process as claimed in claim 11, wherein the second reducing gas comprises hydrogen and steam in a two-to-one stoichiometric ratio.

13. A process as claimed in claim 11 or 12, the process further comprising collecting an exhaust gas from the first reactor and condensing water therefrom.

14. A process as claimed in claim 13, wherein a gas comprising hydrogen is separated from the condensed water.

15. A process as claimed in claim 14, wherein the separated gas comprising hydrogen is recycled to the second reactor such that the reducing gas fed to the second reactor comprises the separated gas.

16. A process as claimed in any one of the preceding claims, the process further comprising passing the powder comprising iron through a hot-briquetted iron plant to produce sponge iron briquettes.

17. A process as claimed in any one of claims 1 to 15, comprising converting the powder comprising iron into steel.

18. A process as claimed in claim 17, wherein, prior to converting the iron into steel, the powder comprising iron is mixed with additives, to thereby produce a mixture comprising the iron and the additives.

19. A process as claimed in claim 18, wherein the additives comprise one or more of magnesium oxide, calcium oxide and carbon.

20. A process as claimed in claim 18 or 19, comprising briquetting the mixture to produce briquettes comprising the iron and the additives.

21. A process as claimed in any one of claims 18 to 20, comprising passing to and heating the mixture in an electric arc furnace under conditions whereby the iron is converted to steel.

22. A process as claimed in claim 21, the process further comprising passing a portion of exhaust gas from the first reactor to the electric arc furnace.

23. A process as claimed in claim 21 or 22, comprising scrubbing carbon monoxide (when present) from the first reactor exhaust gas, or scrubbing carbon monoxide (when present) from a remaining portion of the first reactor exhaust gas, and condensing a resultant scrubbed exhaust gas.

24. A process as claimed in any one of claims 17 to 23, the process further comprising a pyrolyser in which biomass or waste is converted to carbon and a gas comprising hydrogen, steam, carbon monoxide and carbon dioxide.

25. A process as claimed in claim 24, wherein the pyrolyser is of a sorbent enhanced gasification type in which carbon monoxide and/or carbon dioxide are removed from the gas comprising hydrogen, steam, carbon monoxide and carbon dioxide, thereby producing a gas comprising hydrogen.

26. A process as claimed in claim 24 or 25, wherein the gas comprising hydrogen is separated from the carbon.

27. A process as claimed in claim 26, wherein the gas comprising gas is used as a supplementary source of reducing gas for the first reactor and/or the second reactor.

28. A process as claimed in claim 26 or 27 when dependent on claim 19, wherein the carbon is collected and used as an additive in producing the mixture comprising the iron and the additives.

29. A process as claimed in any one of claims 19 to 25, the process further comprising a calcination process in which limestone, dolomite and/or magnesite are heated in a calciner comprising an indirectly heated reactor so as to generate the calcium oxide, the magnesium oxide and/or so as to regenerate the sorbent, and to produce a pure CO2 stream.

30. A process as claimed in any one of the preceding claims, wherein, when the first reducing gas and/or the second reducing gas comprise hydrogen, make-up hydrogen is produced by water electrolysis, wherein the water electrolysis is powered by renewable power.

31. A process as claimed in any one of the preceding claims, wherein renewable power is used for providing energy to the first reactor, the second reactor, the pyrolyser (when present), the calciner (when present), and other ancillaries such as the briquetting stage (when present) and the furnace (when present).

32. A process as claimed in any one of the preceding claims, the process further comprising one or more beneficiation stages in which an iron ore is treated so as to produce the powder comprising iron ore to be fed into the first reactor.

33. A process for producing a steel precursor, the process comprising: providing a source of high-grade iron; mixing the high-grade iron with additives at a temperature whereby the high-grade iron forms a homogeneous mixture with the additives; and cooling the homogeneous mixture to form the steel precursor.

34. A process as claimed in claim 33, wherein the source of high-grade iron comprises a powder comprising high-grade iron.

35. A process as claimed in claim 34, wherein the powder comprising highgrade iron is produced according to the process as set forth in any one of claims 1 to 15.

36. A process as claimed in any one of claims 33 to 35, wherein the additives comprise one or more of: magnesium oxide, calcium oxide, and carbon.

37. A process as claimed in any one of claims 33 to 35, wherein the elevated temperature comprises a temperature of between 700 to 1100 °C.

38. A process as claimed in in any one of claims 33 to 35, wherein cooling the homogeneous mixture to form the steel precursor comprises briquetting the homogeneous mixture.

39. A system for reducing iron ore, the system comprising: a first indirectly heated reactor that is configured such that a powder comprising iron ore and a first reducing gas are each able to be fed, and in which the powder and the reducing gas are able to be heated to a temperature at which the iron ore is converted to magnetite; and a second indirectly heated reactor that is configured such that the magnetite and a second reducing gas are each able to be fed, and in which the magnetite and the second reducing gas are able to be heated to a temperature at which the magnetite is reduced, to thereby form a powder comprising iron.

40. A system as claimed in claim 39, the system further comprising a recycle line that is configured to pass an exhaust gas from the second reactor and feed it to the first reactor such that the first reducing gas comprises the exhaust gas.

41. A system as claimed in claim 39 or 40, the system further comprising a magnetic separator in which the magnetite is separated from a gangue, and whereby the separated magnetite is able to be fed to the second reactor.

42. A system as claimed in claim 41, the system further comprising an agglomeration stage to which the magnetite is passed and in which it is agglomerated, prior to it being fed to the second reactor.

43. A system as claimed in any one of claims 39 to 42, the system further comprising a condenser to which an exhaust gas from the first reactor is passed and in which water (when present) is condensed therefrom.

44. A system as claimed in claim 43, wherein the condenser comprises a hydrogen separator in which the gas comprising hydrogen is separated from the water.

45. A system as claimed in claim 43 or 44, the system further comprising a recycle line that is configured to pass the separated gas comprising hydrogen from the condenser and feed it to the second reactor such that the second reducing gas comprises the separated gas comprising hydrogen.

46. A system as claimed in any one of claims 39 to 45, the system further comprising a briquetting unit that is configured to convert the powder comprising iron into briquettes.

47. A system as claimed in any one of claims 39 to 45, the system further comprising one or more processing stages that are configured to convert the powder comprising iron into steel.

48. A system as claimed in claim 47, the system further comprising a mixer in which the powder comprising iron is mixed with additives, to thereby produce a mixture comprising the iron and the additives, with the mixture being converted into steel.

49. A system as claimed in claim 48, the system further comprising a briquetting unit that is configured to convert the mixture into briquettes of iron and flux additives.

50. A system as claimed in claim 48 or 49, the system further comprising an electric arc furnace in which the mixture is heated under conditions by which steel is produced.

51. A system as claimed in claim 50, the system further comprising a series of pipes that are configured to pass a portion of the exhaust gas from the first reactor and feed it to the electric arc furnace.

52. A system as claimed in any one of claims 39 to 51, the system further comprising a scrubber that is configured to scrub carbon monoxide (when present) from the first reactor exhaust gas.

53. A system as claimed in claim 52 when dependent on claim 51, wherein the scrubber is configured to scrub the carbon monoxide (when present) from a remaining portion of the first reactor exhaust gas that is not fed to the electric arc furnace.

54. A system as claimed in claim 52 or 53, the system further comprising a condenser that is configured to condense water from the resultant scrubbed exhaust gas.

55. A system as claimed in any one of claims 47 to 54, the system further comprising a pyrolyser in which biomass is converted to carbon and a gas comprising hydrogen and carbon monoxide.

56. A system as claimed in claim 55, the system further comprising a gas separator configured to separate the gas comprising hydrogen and carbon monoxide from the carbon.

57. A system as claimed in claim 54, the system further comprising a recycle line that is configured to pass the separated gas comprising hydrogen and carbon monoxide from the separator and feed it to the second reactor, such that the second reducing gas fed into the second reactor comprises said separated gas.

58. A system as claimed in any one of claims 39 to 57, the system further comprising one or more beneficiation stages that are configured to treat an iron ore so as to produce the powder comprising iron ore to be fed into the first reactor.

59. A system as claimed in any one of claims 39 to 58, wherein the first reactor and the second reactor each comprise an externally heated vertical reactor, each of the externally heated vertical reactors comprising: a vertically oriented reactor tube; a hopper located adjacent to a top end of the reactor tube and configured to feed the powder comprising iron ore such that said powder falls downwards in the reactor tube; one or more reducing gas feed ports arranged along the reactor tube from a base thereof for feeding a reducing gas into the reactor tube; heating elements positioned vertically adjacent to at least one wall of the reactor tube and configured to provide heat to be conducted through the at least one wall, so as to heat the powder and the gas within the reactor tube to a temperature at which the powder and the gas are able to react; a gas exhaust positioned adjacent to the top end of the reactor tube; and an iron powder output positioned at a base of the reactor tube.

60. A process for reducing iron ore, the process comprising: feeding a powder comprising iron ore and a reducing gas into a first reactor and indirectly heating the first reactor so as to heat the powder and the gas to a temperature at which the iron ore is partially reduced; and feeding a resultant exhaust gas in which at least some of the partially reduced iron ore is entrained from the first reactor to a second reactor and indirectly heating the second reactor so as to heat the partially reduced iron ore and the exhaust gas to a temperature at which the partially reduced iron ore is further reduced.

61. A process as claimed in claim 60, wherein, in the first reactor, the powder and the reducing gas flow in a counter-flow arrangement and, in the second reactor, the partially reduced iron ore and the exhaust gas flow in a co-flow arrangement.

62. A process as claimed in claim 60 or 61, the process further comprising collecting a remaining partially reduced iron ore from the first reactor and collecting the further reduced iron ore from the second reactor.

63. A process as claimed in any one of claims 60 to 62, the process further comprising passing a second exhaust gas from the second reactor to a gas-particle separation stage in which entrained further reduced iron is separated from the second exhaust gas.

64. A process as claimed in claim 63 when dependent on claim 62, the process further comprising combining the separated further reduced iron from the gasparticle separation stage with the remaining partially reduced iron ore from the first reactor and the further reduced iron ore from the second reactor, thereby forming a sponge iron product

65. A process as claimed in any one of claims 60 to 64, wherein each of the first reactor and the second reactor is indirectly heated so as to maintain a temperature of between 700 °C to 1100 °C within the respective reactor.

66. A process as claimed in any one of claims 60 to 65, wherein the reducing gas comprises hydrogen.

67. A process as clamed in claim 66 when dependent from any one of claims 62 to 65, the process further comprising collecting the second exhaust gas and condensing water therefrom.

68. A process as claimed in claim 67, wherein a gas comprising hydrogen is separated from the condensed water.

69. A process as claimed in any one of claims 60 to 68, wherein the iron ore in the powder fed to the first reactor comprises goethite and both the partially reduced iron ore and the further reduced iron ore comprise iron and/or magnetite.

70. A process as claimed in claim 64, or in any one of claims 65 to 69 when dependent on claim 64, further comprising passing the sponge iron product through a hot-briquetted iron plant to produce iron briquettes.

71. A process as claimed in claim 64, or in any one of claims 65 to 69 when dependent on claim 64, further comprising converting the sponge iron product into steel.

72. A process as claimed in claim 71, the process being otherwise as defined in any one of claims 18 to 31.

73. A process for reducing iron ore, the process comprising: feeding a first powder comprising iron and a first reducing gas into a first reactor such that the first powder and the first reducing gas flow in a co-flow arrangement, and indirectly heating the first reactor so as to heat the first powder and the first reducing gas to a temperature at which the iron is converted to magnetite; and feeding a second powder comprising iron and a second reducing gas into a second reactor such that the second powder and the second reducing gas flow in a counter-flow arrangement, and indirectly heating the second reactor so as to heat the second powder and the second reducing gas to a temperature at which the iron is reduced, to thereby form a powder comprising reduced iron, wherein a second exhaust gas from the second reactor is passed to the first reactor, such that the first reducing gas comprises the exhaust gas from the second reactor.

74. A process as claimed in claim 73, wherein the feed to the second reactor comprises magnetite and the reduced iron comprises elemental iron.

75. A process as claimed in claim 73, wherein the feed to the second reactor comprises any mix of hematite, goethite and siderite and the reduced iron comprises magnetite.

76. A process as clamed in any one of claims 73 to 75, wherein the feed to the first reactor comprises any mix of hematite, goethite, siderite, magnetite, wustite and/or elemental iron.

77. A process as claimed in any one of claims 73 to 76, wherein the feed to the second reactor further comprises magnesium oxide and/or calcium oxide.

78. A process as claimed in any one of claims 73 to 77, comprising passing a first exhaust gas in which the powder comprising the magnetite is entrained to a gas-powder separation stage in which the powder comprising the magnetite is separated from the first exhaust gas.

79. A process as claimed in claim 78, wherein the separated powder comprising the magnetite is passed to a magnetic separation stage in which the magnetite is magnetically separated from a gangue.

80. A process as claimed in claim 79, wherein the separated magnetite is fed to the second reactor.

81. A process as claimed in any one of claims 73 to 80, wherein each of the first reactor and the second reactor is operated in a dilute flow regime.

82. A process as claimed in any one of claims 73 to 81, wherein each of the first reactor and the second reactor is indirectly heated so as to maintain a temperature of between 700 °C to 1100 °C within the respective reactor.

83. A process as clamed in any one of claims 73 to 82, wherein the second reducing gas comprises hydrogen and the first reducing gas comprises hydrogen and water.

84. A process as claimed in any one of claims 79 to 83 when dependent on claim 78, wherein the first exhaust gas is passed to the second reactor, such that the second reducing gas comprises the first exhaust gas.

85. A process as claimed in any one of claims 79 to 83, wherein the first exhaust gas comprises water and wherein the first exhaust gas is passed to a condenser in which the water is condensed.

86. A process as claimed in claim 85, wherein the first exhaust gas further comprises hydrogen, and wherein a gas comprising hydrogen is separated from the condensed water and recycled to the second reactor.

87. A process as claimed in any one of claims 73 to 86, wherein a portion of the second powder fed to the second reactor is entrained in the second exhaust gas and is passed to the first reactor therewith, such that the powder feed to the first reactor further comprises the entrained portion of the second powder.

88. A process as claimed in any one of claims 73 to 87, the process further comprising passing the powder comprising elemental iron through a hot-briquetted iron plant to produce sponge iron briquettes.

89. A process as claimed in any one of claims 73 to 88, the process further comprising passing the powder comprising elemental iron through a magnetic separation stage to produce a higher-grade iron powder.

90. A process for producing hydrogen, the process comprising: feeding a first powder comprising elemental iron and a first gas comprising water vapour into a first reactor such that the first powder and the first gas flow in a co-flow arrangement, and indirectly heating the first reactor so as to heat the first powder and the first gas to a temperature at which the iron and water are converted to magnetite and hydrogen.

91. A process as claimed in claim 90, further comprising: feeding a second powder comprising iron and a second reducing gas into a second reactor such that the second powder and the second reducing gas flow in a counter-flow arrangement, and indirectly heating the second reactor so as to heat the second powder and the second reducing gas to a temperature at which the iron is reduced, to thereby form a powder comprising reduced iron; and passing a second exhaust gas from the second reactor to the first reactor, such that the first gas comprises the second exhaust gas.

92. A process as claimed in claim 90 or 91, wherein a gas comprising hydrogen is passed from the first to the second reactor, such that the first reducing gas comprises the exhaust gas from the second reactor.

93. A process as claimed in claim 91 or claim 92 when dependent on claim 90, wherein the second powder comprises any mix of magnetite, hematite, goethite or siderite and the reduced iron comprises elemental iron.

94. A process as claimed in any one of claims 90 to 93, being otherwise as defined in any one of claims 77 to 89.

95. A process for producing a steel precursor, the process comprising: feeding a gas and a powder comprising iron and one or more carbonates into a reactor such that the powder and the gas flow in a counter-flow arrangement, and indirectly heating the reactor so as to heat the powder and the gas to a temperature at which the one or more carbonates are decomposed, thereby producing an exhaust gas comprising carbon dioxide; passing the exhaust gas comprising carbon dioxide to a solid oxide electrolyser in which the carbon dioxide is electrolysed, thereby forming a gas comprising carbon monoxide, and wherein the gas fed to the reactor comprises the gas comprising carbon monoxide.

96. A process as claimed in claim 95, wherein the one or more carbonates comprises calcium carbonate and/or magnesium carbonate.

97. A process as claimed in claim 95 or 96, wherein the gas further comprises hydrogen.

98. A process as claimed in claim 97, wherein the iron comprises iron in an oxidised form and the process further comprises indirectly heating the reactor so as to heat the powder and the gas to a temperature at which the iron is reduced.

99. A process as claimed in claim 98, wherein the reduced iron comprises elemental iron.

100. A process as claimed in claim 98 or 99, wherein the oxidised iron is FeO.

101. A process as claimed in any one of claims 98 to 100, wherein the exhaust gas further comprises water and wherein, in the solid oxide electrolyser, the water is electrolysed such that a gas comprising carbon monoxide and hydrogen is formed, and wherein the gas fed to the reactor comprises the gas comprising carbon monoxide and hydrogen.

102. A process as claimed in any one of claims 99 to 101, wherein the process further comprises indirectly heating the reactor so as to heat the powder and the gas to a temperature at which the iron is carburised.

103. A process as claimed in any one of claims 99 to 102, further comprising feeding one or more additional additives into the reactor.

104. A process as claimed in claim 103, wherein the one or more additional additives comprise magnesium oxide and/or calcium oxide.

105. A process as claimed in any one of claims 98 to 104, wherein the reactor is operated in a dilute flow regime.

106. A process as claimed in any one of claims 98 to 104, wherein the reactor is indirectly heated so as to maintain a temperature of between 700 °C to 1100 °C therewithin.

107. A process as claimed in any one of claims 98 to 104, the process further comprising passing the heated powder through a hot-briquetted iron plant to produce sponge iron briquettes.

108. A process as claimed in any one of claims 98 to 104, the process further comprising converting the heated powder into steel.