EP4545655A1 - Method for producing steel in a plant composite - Google Patents

Abstract

The invention relates to a method for steel production in a plant network (1), wherein the plant network (1) comprises:
- a direct reduction reactor (2) or a blast furnace,
- if necessary, an electric oven (3)
- a converter (4),
- a gas pipeline system (5, 5', 5"),
- if necessary, a processing unit (6), and
- a chemical plant (7).

The converter process is planned to involve the addition of organically coated steel scrap. Synthesis gas is produced from the converter gas or a portion of the converter gas and preferably enriched with _H2 . In the chemical plant, methanol _CH3OH is produced from the synthesis gas or the enriched synthesis gas. This can be further processed, for example, in a paint factory (8), into an organic coating material.

Description

The invention relates to a process for steel production in a plant network.

In the context of efforts to reduce _CO2 emissions associated with steel production, the approach of reusing carbon is receiving increasing attention.

This applies both to conventional steel production using the blast furnace route and to variants used in the context of the so-called green transformation, such as a direct reduction electric steel route.

In a frequently used method of conventional steel production, consisting of pig iron production in a blast furnace followed by conditioning of the pig iron in the converter steelworks to produce crude steel, oxygen is blown onto liquid pig iron in the converter to remove disruptive impurities such as carbon, silicon, sulfur and phosphorus. In this process, additives for slag formation, such as lime, and alloying agents are usually added to the converter. A converter gas is produced in the converter which contains, for example, between 50 and 100 vol.% CO, 10 to 20 vol.% _N2 , approx. 15 vol.% CO2 and 2 vol.% _H2 . In the conventional blast furnace route with a downstream converter steelworks, it is common practice to use the converter gas for energy purposes.

With the expected increased use of direct reduction and subsequent smelting for steel production, efforts to improve the efficiency of such a production route for steel production are gaining importance.

Against this background, the object of the invention is to provide an improved coordination of the process steps of a steel production process.

The invention is solved by a method having the features of claim 1. The invention is also solved by a method having the features of claim 16.

A process for steel production in a plant network is planned.

According to the invention, the plant network comprises a converter for refining a provided iron melt into crude steel in a converter process. The provided iron melt preferably originates from a blast furnace or a direct reduction reactor, or both a blast furnace and a direct reduction reactor. In the converter, the conditioning of a provided iron melt into the intermediate product crude steel, which is to be considered the end product within the scope of this application. The process according to the invention thus has the advantage, among other things, of being carried out in a plant network that, with the converter, has a known and often already existing unit. The effort required to provide a plant network is thereby reduced.

The plant also has a gas pipeline system connected to the converter, which is used to carry converter gas that is released in the converter during the converter process.

Coupled with the gas pipeline system, the plant network includes a chemical plant, which is supplied with converter gas from the converter process via the stationary gas pipeline system.

According to the invention, it is now provided that upstream of the chemical plant or in the chemical plant, on the basis of the converter gas or a portion of the converter gas, a Synthesis gas is produced. In a preferred embodiment, the synthesis gas is subsequently enriched with _H2 using a mixing device coupled to the gas line system or alternatively in a mixing unit within the chemical plant, so that the synthesis gas subsequently contains the components carbon monoxide and/or carbon dioxide as well as hydrogen in the intended ratio.

According to the invention, following the production of the synthesis gas or the production of the synthesis gas with subsequent enrichment with H ₂ in the chemical plant, the subsequent product methanol CH ₃ OH is produced from the synthesis gas or with the enriched synthesis gas.

With this procedure, converter gases containing a high proportion of CO can be reused in an effort to prevent the escape of CO compounds into the atmosphere as best as possible. Within the scope of the present invention, it is provided for this purpose to produce a synthesis gas which is provided as a starting mixture by processing, i.e. at least purifying, the converter gas. This synthesis gas is then particularly preferably enriched with _H2 as an enriched synthesis gas with the specified mixing ratio, often approximately in the ratio of one CO molecule to 2 _H2 molecules, and serves as a starting material for the production of methanol. The chemical plant used for the production of methanol _CH3OH is, due to its coupling with the gas pipeline system, part of the plant network used according to the invention. The procedure according to the invention and its developments can therefore achieve the use of gases arising during steel production, namely the converter gases, for the efficient production of the extremely important chemical raw material methanol.

Methanol can be produced in the chemical plant using the CO, CO ₂ and H ₂ fractions obtained from the converter gas, based on the reactions CO + 2 H ₂ → CH ₃ OH and CO ₂ + 3 H ₂ → CH ₃ OH + H ₂ O. Depending on the molecule number ratio of CO molecules to CO ₂ molecules, the optional addition of H ₂ molecules can be provided, for example with regard to the stoichiometric optimization for the two reactions mentioned above.

According to the invention, the converter process takes place with the addition of organically coated steel scrap. The addition of steel scrap to the converter process has several advantages. Firstly, the addition of steel scrap can be used to cool the converter if necessary, thus enabling the temperature in the converter to be regulated within certain limits. Furthermore, the addition of steel scrap to the converter process ensures that a starting material is added for the production of the steel which, in terms of its chemical composition, is already close to the target composition, so that oxidation processes, in particular those leading to _CO2 , are reduced in their extent relative to the tonnage. Furthermore, the addition of steel scrap makes it possible to regulate the atomic composition of the melt within certain limits.

For example, a paint may be provided as an organic coating; in this case, the organically coated steel scrap is painted steel scrap.

The organic coating can be, for example, a film made of PP or PET.

The measure to introduce organically coated steel scrap into the converter process is based on the knowledge that at the temperatures prevailing in the converter, the pyrolytic combustion of the organic coating is to be expected, whereby the resulting gases, which contain a high proportion of CO and CO ₂ , is largely unproblematic due to the further use of the converter gas as a starting material for a synthesis gas - as the developers of the present development have recognized. Due to the chemical composition of the base materials of conventional organic coatings, for example conventional paints, it is to be expected that the addition of organically coated steel scrap will result in an increase in the CO content in the converter gas within a range. It has been shown that the reaction of the organic coating, due to the polymer base typically present in the organic coating, takes place during combustion in a converter process of the known type predominantly to form CO and not CO _2. The introduction of organically coated steel scrap into the converter processes has the effect of significantly simplifying the use of such steel scrap in a circular process, since the chemical or mechanical removal of the coating, for example by means of paint stripping, which would otherwise be necessary, is not currently known on a large industrial scale or is not economical. This means that the organic coating present on steel scrap can be reused as a chemical base material via the converter gas and the planned further processing into synthesis gas with the subsequent production of methanol. This represents a step toward an improved circular economy. In contrast to the previously known energy utilization, the material utilization of carbon present on steel scrap as a component of the coating has now been achieved.

It is particularly preferred that the carbon content of the organic coating contained in the steel scrap, for example paint, is at least 30 atomic%.

For example, it may be provided that at any time during the converter process a proportion of more than 10 wt.% of the melt, preferably more than 20 wt.% of the melt, particularly preferably more than 30 wt.% of the melt, comes from molten steel scrap.

In a preferred development, the plant combination comprises a blast furnace for reducing and melting iron ore to form an iron melt, which is used as the iron melt to be provided according to the invention.

In a preferred further development, the plant network includes, among other things, a direct reduction reactor for the direct reduction of iron ore to sponge iron.

The direct reduction reactor is a facility in which a solid-state reaction takes place, removing oxygen from the iron ore. The reducing agents used for this process include coal or natural gas, or, more recently and expectedly increasingly in the future, atomic or molecular hydrogen. The reaction takes place at a temperature below the melting point of the iron ore, so its external form remains largely unchanged. This fact gives rise to the commonly used term "sponge iron" for the product of the processes taking place in the direct reduction reactor.

The direct reduction reactor can, for example, be designed as a shaft furnace with a reduction zone through which the iron ore flows in the opposite direction to the direction of the reducing gas. Direct reduction reactors as such are well known in practice.

Iron ore is fed into the direct reduction reactor and reduced to sponge iron in the direct reduction reactor under the action of a reducing agent.

Steel production based on the direct reduction of iron ore is receiving considerable attention in the effort to reduce _CO2 emissions as comprehensively as possible. In one possible embodiment, the production of sponge iron in a direct reduction reactor is followed by melting in an electric melting furnace. If necessary, a further treatment of the melt follows, in which it is freed from oxygen-affine components by blowing in oxygen. This step can be carried out, for example, in a converter steelworks of a known type, as is known in particular from steel production using the blast furnace route. According to the invention, such a converter process is carried out as explained above.

The iron ore preferably passes through the direct reduction reactor in continuous operation. During the passage through the direct reduction reactor, the iron ore is reduced to sponge iron using a reducing gas, in particular molecular hydrogen and/or natural gas. The process control and the process parameters, such as the residence time of the iron ore in the direct reduction reactor and the flow rate of reducing gas, result in the iron ore being converted to sponge iron with a degree of metallization that is usually more than 80 percent, preferably more than 90 percent, and particularly preferably more than 95 percent, at the point where the sponge iron exits the direct reduction plant.

In such a preferred development, the system combination also has an electric furnace, which is used for Melting the sponge iron to form an iron melt, which is refined in the converter as the iron melt to be provided according to the invention.

When using an electric furnace, the heat for melting the sponge iron is generated electrically. Any type of electrically powered electric furnace is suitable.

An electric furnace, also known as an electric heating system for melting metal or heating liquid metal, can be an electric arc furnace (EAF), where arcs are formed between the electrode and the metal. Possible designs include an alternating current electric arc furnace (EAFac), a direct current electric arc furnace (EAFdc), and a ladle furnace (LF).

A preferred option is the use of an electric furnace operating with arc resistance heating. Such an electric furnace operates on the principle of forming arcs between the electrode and the charge and heating the charge or slag, particularly by means of the Joule effect. Melting furnaces with arc resistance heating can, for example, be designed as submerged electric arc furnaces (SAF), in which the electrode is immersed in the charge or slag, as alternating current submerged arc furnaces (SAFac), or as direct current submerged arc furnaces (SAFdc). Other designs are furnaces in which the electrode ends just above the slag. In this type of furnace, the slag is not shielded by the charge, at least in the area of the electrode. The slag is therefore open at the top, and the brush-shaped arc ( brush arc ) visible from above. This furnace type is called an open slag bath furnace (OBSF).

In a further development of the method according to the invention, the electric furnace is particularly preferably designed as a submerged electric arc furnace ( SAF).

Alternatively, in a further development of the method according to the invention, the electric furnace is particularly preferably designed as an open slag bath furnace (OBSF).

The sponge iron produced in the direct reduction reactor is then transported to the electric furnace and melted into an iron melt. In some embodiments of the process, additives are added to the electric furnace, particularly one or more of hard coal, natural gas, or steel scrap.

The molten iron produced in the electric furnace is then conditioned into crude steel in the converter. For this purpose, for example, a tapping is carried out from the electric furnace at discrete intervals, the extracted material is transported to the converter, fed into it, and treated there in a converter process, preferably in a converter process familiar from the blast furnace route in the manner described above, in particular by means of oxygen injection.

In the described further development, in which the plant combination comprises the direct reduction reactor and the electric furnace, the knowledge is used that in the novel intended production of steel by means of a route consisting of a direct reduction reactor with a downstream electric furnace and subsequent implementation of a converter process in a known manner or based on the known manner, it has surprisingly turned out to be necessary that an iron melt in liquefied form is used for the converter process which has a sufficiently high level of carbon for the intended converter processes.

This results in the realization that the addition of additives, in particular those containing carbon, to the electric furnace takes place at least to an extent that converter processes become possible which usually occur with the emission of CO and CO _2. This in turn results in the fact that even in steel production based on the production and further use of sponge iron by means of direct reduction, at least in the described development with a downstream combination of electric furnace and converter, converter gas compositions are surprisingly obtained which in particular have a high proportion of carbon monoxide. Typical compositions of the converter gas in this case are, for example, between 50 and 100 vol.% CO, preferably between 60 and 70 vol.% CO, 10 to 20 vol.% N ₂ , approx. 15 vol.% CO ₂ and 2 to 5 vol.% H ₂ . Obtaining a converter process in the observed manner with correspondingly high proportions of CO and CO ₂ was not intuitively expected due to the aim of reducing CO emissions and the continuous use of direct reduction with the reducing gas H ₂ .

In a preferred development of the process, it is provided that the direct reduction is carried out with hydrogen in the direct reduction reactor, wherein a particle number fraction of the hydrogen atoms used for direct reduction of at least 0.9, preferably of at least 0.95, are present as H ₂ molecules. Particularly preferably, the direct reduction is carried out exclusively with molecular hydrogen. The use of the highest possible proportion of H ₂ for the direct reduction has the advantage that - unlike, for example, in the Use of natural gas is the case - the formation of _CO2 during direct reduction is minimized or completely avoided in accordance with the proportion of molecular hydrogen in the direct reduction, which is desirable in the context of the efforts to minimize _CO2 emissions against the background of the desired approximation to climate neutrality of the process.

Particularly preferred is direct reduction exclusively with molecular hydrogen produced from water electrolysis. This process variant has the advantage that _CO2 emissions are reduced or even completely avoided not only during direct reduction but also during the production of the molecular hydrogen used for this purpose.

It is particularly preferred that the sponge iron be melted with the addition of carbon carriers to the electric furnace. The addition of carbon carriers to the electric furnace has the effect of maintaining the temperature in the furnace, and the carbon content of the resulting melt can be adjusted by adjusting the amount of carbon carriers.

It is particularly preferred that the electric furnace be a melting furnace with arc resistance heating. A melting furnace with arc resistance heating has the advantage that, due to its typically non-flat design, it naturally counteracts undesirable nitrogen ingress into the molten iron. The resulting melts therefore offer excellent conditions for producing steels with a comparatively low nitrogen content in subsequent process steps. This has a beneficial effect on many steel properties and is therefore often desirable.

Particularly preferably, the addition of carbon carriers, in particular hard coal and/or natural gas, to the electric furnace is adjusted in such a way that a C content of between 2.0 wt.% and 4.5 wt.% is achieved in the melt.

The converter used is preferably an LD converter, i.e., a converter of the so-called Linz-Donauwitz design. The use of an LD converter has the particular advantage that it is already present in many plant networks along the blast furnace route, so that the provision of a modified plant network for such a steelmaking process within the plant network can be achieved with reduced effort. Consequently, the advantageous use of converter gases in a chemical plant is also possible for steel production starting from direct reduction.

Particularly preferably, the target value of the CO content in the converter gas can be set to a value of at least 60 vol.%.

In one embodiment, it can be provided that, in the plant network for carrying out the reduction of iron ore, only the described direct reduction is operated in the direct reduction reactor, optionally in further direct reduction reactors, so that the crude steel is produced exclusively from sponge iron produced by direct reduction and without the additional involvement of a blast furnace process. In other words, it can be provided that the process is carried out exclusively on the basis of direct reduction of iron ore to sponge iron in a direct reduction reactor, i.e., in other words, that no other unit for iron ore reduction is operated in the plant network other than one or more direct reduction reactors, in particular no blast furnace.

Particularly preferably, a proportion of at least 80 vol.% of the converter gas is fed into the chemical plant in order to achieve the material utilization of the highest possible proportion of the converter gas.

A further idea of the invention provides that methanol produced by a method according to the invention or one of its developments is used to produce an organic coating material, for example a paint, whereby an improvement in the circular economy is advantageously achieved.

A further concept of the invention provides a method for recycling carbon. This involves treating an iron melt in a converter process. This can be done, for example, in one of the ways described above.

Organically coated steel scrap is added to the molten iron and melted there. In the converter process, the molten iron and the molten steel scrap are refined into crude steel, and a carbon-containing converter gas is produced as a byproduct.

The carbon-containing converter gas is withdrawn, and the withdrawn carbon-containing converter gas, or a portion of this withdrawn carbon-containing converter gas, is converted into a synthesis gas upstream of a chemical plant or within a chemical plant, wherein the synthesis gas is preferably also enriched with hydrogen. This can be done, for example, in the manner described above.

In the chemical plant, methanol is produced with the synthesis gas or the enriched synthesis gas, whereby the methanol is fed into the production of an organic coating material, for example a paint, on a carbon basis, whereby the produced coating material is applied as an organic coating on a steel and At the end of its life, it is returned to the converter process as organically coated steel scrap. The organic coating is burned by pyrolysis in the converter process, and the carbon contained in the organic coating thus further enriches the converter gas with carbon.

A further aspect of the invention provides a process for carbon recycling. This process comprises steel production in accordance with the invention or in a further development of the invention.

Methanol is produced according to the invention using synthesis gas produced according to the invention or the enriched synthesis gas, wherein the methanol is then fed to the production of an organic coating, for example a paint production, on a carbon basis, wherein the produced organic coating is applied to a steel and at the end of its life is returned to the converter process as organically coated steel scrap.

It has been shown that the organic coating is burned by pyrolysis in the converter process, whereby the carbon contained in the organic coating further enriches the converter gas with carbon.

The development is explained below using a drawing that shows an example of implementation.

It shows
Fig. 1 : a highly simplified block diagram illustrating a steel production process in a plant network that includes a direct reduction reactor to provide molten iron.

Steel is produced in a plant complex 1, which includes a direct reduction reactor 2, an electric furnace 3 and a converter 4. In the direct reduction reactor, iron ore is converted into exposed to a reducing atmosphere, for example consisting of methane _CH4 (in particular as natural gas) or of _H2 or of a mixture of _H2 and methane, whereby sponge iron is produced, which is then removed and fed into the electric furnace 3. With the aim of increasingly changing steel production towards climate neutrality of the process, it is particularly preferred to provide as high a proportion of the reducing atmosphere as _H2 . In the electric furnace 3, the sponge iron is melted to form an iron melt. The iron melt is then fed to the converter 4 in order to produce crude steel in a converter process. For this purpose, unwanted impurities, in particular carbon, silicon and phosphorus, are removed by blowing oxygen onto the iron melt. In order to achieve slag formation and to be able to prepare a targeted alloy composition, lime is added as a slag former and alloying agent. Furthermore, it can be provided that steel scrap is fed into the converter process, in particular the addition of organically coated steel scrap, for example painted steel scrap. At the top of the converter, a converter gas is withdrawn and introduced into a gas line system 5.

The gas pipeline system leads the converter gas, which is released in the converter during the converter process, into a processing unit 6, in which, by cleaning the remaining gas and adding H ₂ , a synthesis gas enriched with H ₂ is produced, which, after being passed on via a further section 5' of the gas pipeline system, is intended for use in a chemical plant 7.

After feeding the enriched synthesis gas into the chemical plant 7, the starting product is the downstream product methanol CH ₃ OH is produced there. This methanol can then be used for further processing into chemical products, for example, further processed in several steps into an organic coating material, for example finally in a paint factory 8, in order to be further processed into reusable paints. For example, the methanol can be further processed into aromatics or olefins, for example using known methanol-to-olefins (MTO) and methanol-to-aromatics (MTA) processes, or for example into one or more of ethene, propene, butene, benzene, toluene, o-, m-, p-xylene, which are then further processed into polyesters, melamine resins, polyurethanes, acrylates and/or epoxides and can be used as basic components of coating materials. In particular, ethene, propene and, to a lesser extent, butene can be produced using the MTO process. In particular, benzene, toluene, and xylene can be produced using the MTA process. These compounds are therefore products of the MTO and MTA processes, respectively.

There is therefore a possibility of combining steel production, in particular according to the principle of direct reduction, with a circular economy with a high proportion of material reuse of organic coatings, such as industrial paints, which are fed into the system during the process in the form of organically coated steel scrap, for example painted steel scrap, at the location of converter 4.

Claims (16)

Process for steel production in a plant network, the plant network comprising: - a converter for refining a provided iron melt into crude steel in a converter process, - a gas pipeline system connected to the converter for conveying converter gas released in the converter during the converter process, - a chemical plant connected to the gas pipeline system to supply the chemical plant with the converter gas carried in the gas pipeline system,
characterized by that the converter process is carried out with the addition of organically coated steel scrap, that a synthesis gas is produced from the converter gas or a portion of the converter gas before or in the chemical plant and is preferably enriched with H ₂ , and that methanol CH ₃ OH is produced in the chemical plant using the synthesis gas or the enriched synthesis gas. Method according to claim 1, characterized in that the plant complex comprises: a blast furnace for reducing and melting iron ore to an iron melt. Method according to claim 1, characterized in that the system network comprises: - a direct reduction reactor for the direct reduction of iron ore to sponge iron, - an electric furnace for melting the sponge iron into molten iron. Process according to claim 3, characterized in that in the direct reduction reactor the direct reduction is carried out with hydrogen, wherein a particle number fraction of the hydrogen atoms used in the direct reduction for the direct reduction of at least 0.9, preferably of at least 0.95, are present as H ₂ molecules. Process according to one of claims 3 or 4, characterized in that the direct reduction is carried out exclusively with molecular hydrogen. Process according to one of claims 3 to 5, characterized in that the direct reduction is carried out exclusively with molecular hydrogen produced from water electrolysis. Method according to one of claims 3 to 6, characterized in that the melting of the sponge iron takes place with the addition of carbon carriers in the electric furnace. Method according to one of claims 3 to 7, characterized in that the electric furnace is a melting furnace with arc resistance heating. Process according to one of claims 3 to 8, characterized in that by adding carbon carriers to the electric furnace, a C content in the melt is adjusted between 2.0 wt.% and 4.5 wt.%. Method according to one of claims 3 to 9, characterized in that in the plant network for the reduction of iron ore, only the direct reduction reactor and optionally further direct reduction reactors are operated, so that the iron melt is produced exclusively from sponge iron produced by direct reduction and without additional involvement of a blast furnace process. Method according to one of the preceding claims, characterized in that the converter is an LD converter. Method according to one of the preceding claims, characterized in that the organic coating of the organically coated steel scrap contains a carbon content of at least 30 atomic%. Method according to one of the preceding claims, characterized in that a target value of the CO content of the converter gas is at least 60 vol.%. Process according to one of the preceding claims, characterized in that a proportion of at least 80 vol.% of the converter gas is fed into the chemical plant. Process for producing a precursor of an organic coating, for example a lacquer, characterized characterized in that methanol produced by a process according to one of the preceding claims is provided as starting product. Carbon recycling processes, where an iron melt is treated in a converter process, wherein organically coated steel scrap is added to the molten iron and melted therein, and in the converter process the molten iron and the molten steel scrap are refined into crude steel and a carbon-containing converter gas is produced, wherein the carbon-containing converter gas is withdrawn and the withdrawn carbon-containing converter gas or a part of this withdrawn carbon-containing converter gas is converted into a synthesis gas upstream of a chemical plant or in a chemical plant, preferably the synthesis gas is enriched with hydrogen, where methanol is produced in the chemical plant using the synthesis gas or the enriched synthesis gas, wherein the methanol is fed to the production of an organic coating material, for example a paint, based on carbon, whereby the produced coating material is applied as an organic coating on a steel and at the end of its life is returned to the converter process as organically coated steel scrap, The organic coating is burned by pyrolysis in the converter process and the carbon contained in the organic coating thus additionally enriches the converter gas with carbon.

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