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WO2025194206A1 - Réduction directe de minerai métallifère - Google Patents

Réduction directe de minerai métallifère

Info

Publication number
WO2025194206A1
WO2025194206A1 PCT/AU2025/050238 AU2025050238W WO2025194206A1 WO 2025194206 A1 WO2025194206 A1 WO 2025194206A1 AU 2025050238 W AU2025050238 W AU 2025050238W WO 2025194206 A1 WO2025194206 A1 WO 2025194206A1
Authority
WO
WIPO (PCT)
Prior art keywords
microwave energy
zone
microwave
furnace
conveyor
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/AU2025/050238
Other languages
English (en)
Inventor
Christopher Dodds
Andrew Batchelor
Jose Rodrigues
Samuel Kingman
Gabriela Duran JIMENEZ
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Technological Resources Pty Ltd
Original Assignee
Technological Resources Pty Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from AU2024900749A external-priority patent/AU2024900749A0/en
Application filed by Technological Resources Pty Ltd filed Critical Technological Resources Pty Ltd
Publication of WO2025194206A1 publication Critical patent/WO2025194206A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
    • F27B9/06—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity heated without contact between combustion gases and charge; electrically heated
    • F27B9/062—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity heated without contact between combustion gases and charge; electrically heated electrically heated
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/76—Prevention of microwave leakage, e.g. door sealings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65G—TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS
    • B65G17/00—Conveyors having an endless traction element, e.g. a chain, transmitting movement to a continuous or substantially-continuous load-carrying surface or to a series of individual load-carriers; Endless-chain conveyors in which the chains form the load-carrying surface
    • B65G17/06—Conveyors having an endless traction element, e.g. a chain, transmitting movement to a continuous or substantially-continuous load-carrying surface or to a series of individual load-carriers; Endless-chain conveyors in which the chains form the load-carrying surface having a load-carrying surface formed by a series of interconnected, e.g. longitudinal, links, plates, or platforms
    • B65G17/065—Conveyors having an endless traction element, e.g. a chain, transmitting movement to a continuous or substantially-continuous load-carrying surface or to a series of individual load-carriers; Endless-chain conveyors in which the chains form the load-carrying surface having a load-carrying surface formed by a series of interconnected, e.g. longitudinal, links, plates, or platforms the load carrying surface being formed by plates or platforms attached to a single traction element
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65G—TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS
    • B65G17/00—Conveyors having an endless traction element, e.g. a chain, transmitting movement to a continuous or substantially-continuous load-carrying surface or to a series of individual load-carriers; Endless-chain conveyors in which the chains form the load-carrying surface
    • B65G17/06—Conveyors having an endless traction element, e.g. a chain, transmitting movement to a continuous or substantially-continuous load-carrying surface or to a series of individual load-carriers; Endless-chain conveyors in which the chains form the load-carrying surface having a load-carrying surface formed by a series of interconnected, e.g. longitudinal, links, plates, or platforms
    • B65G17/067—Conveyors having an endless traction element, e.g. a chain, transmitting movement to a continuous or substantially-continuous load-carrying surface or to a series of individual load-carriers; Endless-chain conveyors in which the chains form the load-carrying surface having a load-carrying surface formed by a series of interconnected, e.g. longitudinal, links, plates, or platforms the load carrying surface being formed by plates or platforms attached to more than one traction element
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65G—TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS
    • B65G17/00—Conveyors having an endless traction element, e.g. a chain, transmitting movement to a continuous or substantially-continuous load-carrying surface or to a series of individual load-carriers; Endless-chain conveyors in which the chains form the load-carrying surface
    • B65G17/30—Details; Auxiliary devices
    • B65G17/32—Individual load-carriers
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B13/00—Making spongy iron or liquid steel, by direct processes
    • C21B13/004—Making spongy iron or liquid steel, by direct processes in a continuous way by reduction from ores
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B13/00—Making spongy iron or liquid steel, by direct processes
    • C21B13/12—Making spongy iron or liquid steel, by direct processes in electric furnaces
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B4/00—Electrothermal treatment of ores or metallurgical products for obtaining metals or alloys
    • C22B4/08—Apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D11/00—Arrangement of elements for electric heating in or on furnaces
    • F27D11/12—Arrangement of elements for electric heating in or on furnaces with electromagnetic fields acting directly on the material being heated
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/6408—Supports or covers specially adapted for use in microwave heating apparatus
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/78—Arrangements for continuous movement of material
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B4/00—Electrothermal treatment of ores or metallurgical products for obtaining metals or alloys
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D99/00—Subject matter not provided for in other groups of this subclass
    • F27D99/0001—Heating elements or systems
    • F27D99/0006—Electric heating elements or system
    • F27D2099/0028—Microwave heating
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27M—INDEXING SCHEME RELATING TO ASPECTS OF THE CHARGES OR FURNACES, KILNS, OVENS OR RETORTS
    • F27M2001/00—Composition, conformation or state of the charge
    • F27M2001/02—Charges containing ferrous elements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27M—INDEXING SCHEME RELATING TO ASPECTS OF THE CHARGES OR FURNACES, KILNS, OVENS OR RETORTS
    • F27M2003/00—Type of treatment of the charge
    • F27M2003/16—Treatment involving a chemical reaction
    • F27M2003/165—Reduction
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/70—Feed lines
    • H05B6/707—Feed lines using waveguides

Definitions

  • the present invention also relates to an endless conveyor that is suitable for use in a furnace, such as a linear hearth furnace, that includes a means for supplying microwave energy to heat a microwave absorbent material, with the conveyor being configured to form a barrier to loss of microwave energy from gaps in the conveyor.
  • Such direct reduced iron for example while hot, may be subsequently melted in a furnace to create hot metal, then cast as pig iron or refined further to steel in a metallurgical furnace.
  • microwave absorbent material is understood herein to mean a solid substance that can absorb microwave energy (typically producing heat), comprising completely or in part a mined material that has been formed by a geological process.
  • microwave absorbent material may be a blend of mined materials or combinations of mined and non-mined material(s), may be in a loose or bound form, and/or may have already undergone some solid-state chemical or thermal process. It is not necessary that the microwave absorbent material be particularly absorbent to microwave energy on entry to the furnace, only that it readily absorbs microwave energy at the time of application of microwave energy, and such absorbency is created by bringing such material to predetermined temperatures.
  • Iron ore and biomass are examples of microwave absorbent materials.
  • Naturally occurring spodumene is another example of a microwave absorbent material.
  • direct reduced iron is understood herein to mean solid iron produced from the direct reduction of iron ore to iron by a reducing agent at temperatures below the bulk melting temperature of the iron.
  • direct reduced iron (DRI) is understood to have at least 85% metallisation.
  • SAF submerged arc furnace
  • ESF electric smelting furnace
  • Biomass can take many forms and avoiding competition with food production is key for biomass selection. Examples of biomass that might meet the selection criteria include elephant grass, sugar cane bagasse, forestry by-products, excess straw, azolla and seaweed/macroalgae. Such biomass availability varies considerably from one geographic location to another - and will most likely be a significant factor in determining the size and location of future biomass-based iron plants given the volume of material required and the economic challenges in transporting such material long distances.
  • EMC Electromagnetic compatibility
  • the invention is the result of work to develop an apparatus for the invention described in International application PCT/AU2021/051398 (WO2022/109663).
  • the invention provides an apparatus for heating a microwave absorbent material that comprises a furnace, such as a linear hearth furnace, the furnace comprising: a micro wave energy zone, a means for supplying microwave energy to the microwave energy zone, and an endless conveyor for transporting the material through the microwave energy zone and being configured to form a part of a barrier to loss of microwave energy from the zone.
  • a furnace such as a linear hearth furnace
  • the furnace comprising: a micro wave energy zone, a means for supplying microwave energy to the microwave energy zone, and an endless conveyor for transporting the material through the microwave energy zone and being configured to form a part of a barrier to loss of microwave energy from the zone.
  • the invention also provides an apparatus for continuously producing direct reduced metal material (DRM) from a metalliferous ore and a carbon rich solid reductant, such as biomass, the apparatus comprising a furnace, such as a linear hearth furnace, the furnace comprising: a micro wave energy zone, a means for supplying microwave energy to the microwave energy zone and heating the ore and the reductant and reducing the ore to DRM in the zone, and an endless conveyor for transporting the ore and the reductant through the microwave energy zone and being configured to form a part of a barrier to loss of microwave energy from the zone.
  • DRM direct reduced metal material
  • the invention also provides an apparatus for continuously producing direct reduced iron (DRI) from iron ore and biomass comprising a furnace, such as a linear hearth furnace, the furnace comprising: a micro wave energy zone, a means for supplying microwave energy to the microwave energy zone and heating the ore and biomass and reducing the ore to DRI, and an endless conveyor for transporting the ore and biomass through the microwave energy zone and being configured to form a part of a barrier to loss of microwave energy from the zone.
  • a furnace such as a linear hearth furnace
  • the furnace comprising: a micro wave energy zone, a means for supplying microwave energy to the microwave energy zone and heating the ore and biomass and reducing the ore to DRI, and an endless conveyor for transporting the ore and biomass through the microwave energy zone and being configured to form a part of a barrier to loss of microwave energy from the zone.
  • endless conveyor is understood herein to mean a type of conveyor has a base for carrying material that moves in a continuous loop.
  • microwave energy barrier is understood herein to mean a structure that is capable of reducing the amount of microwave energy escaping the furnace by a factor of at least 100 (20 dB), typically a factor of at least 1000 (30 dB), and more typically a factor of at least 10,000 (40 dB). If the barrier was the only barrier to microwave energy being emitted from the furnace, then for personnel safety reasons alone the furnace would need to be designed to be capable of ensuring that leakage at 50 mm or more from the furnace does not exceed 5 milliwatt (5 mW) of energy per cm 2 .
  • the conveyor may comprise a plurality of metal sections that are not transparent to microwaves extending transverse to a direction of travel of the conveyor and coupled together with a gap between adjacent metal sections.
  • the metal sections may be coupled together so that adjacent metal sections can change orientation relative to each other when the conveyor moves in a curved path.
  • the invention also provides an apparatus for heating a microwave absorbent material, the apparatus comprising a furnace, the furnace comprising: a micro wave energy zone, a means for supplying microwave energy to the microwave energy zone and heating a microwave absorbent material in the zone, and an endless conveyor for carrying a microwave absorbent material through the furnace, the conveyor comprising a base comprising a plurality of metal sections extending transverse to a direction of travel through the furnace and defining a base for carrying the microwave absorbent material and being coupled together so that there is a gap between adjacent metal sections so that adjacent metal sections can change orientation relative to each other when the conveyor moves in a curved path, and with the conveyor being configured to form a part of a microwave energy barrier to loss of microwave energy from the microwave energy zone.
  • Each gap may extend across the width of the metal sections.
  • Each gap may extend through a thickness of the metal sections.
  • each gap defines a tortuous pathway.
  • the tortuous pathway may comprise one or more than one change of direction.
  • the one or more than one change of direction may comprise one or more than one bend in the pathway.
  • the microwave energy barrier is an important part of the furnace for health and safety reasons, electromagnetic compatibility (EMC), and for process reliability reasons.
  • the metal sections of the conveyor are not transparent to microwaves and therefore are a part of the microwave energy barrier.
  • each gap defines or comprises a choking structure that restricts microwave leakage through the gap and forms a part of a microwave energy barrier.
  • each gap could define a pathway for microwaves to travel from the microwave energy zone and escape the microwave energy zone.
  • the gap is designed to be a minimum physical distance, preventing arcing. Due to the need for physical separation, energy leakage through this opening can occur.
  • choking structure is understood herein to mean a structure that restricts microwave leakage.
  • the choking structure may be configured to absorb and therefore attenuate rather than reflect microwaves into the microwave energy zone.
  • the gap may be at least partially filled with an absorbent material.
  • Carbon foam is an example of an absorbent material.
  • the feed material for the furnace may be very absorbent.
  • the choking structure may be configured to reflect microwaves into the microwave energy zone.
  • each gap may define or comprise a choking structure as a result of the design of the gap.
  • the design selection may take into account dimensions and changes of direction of a pathway defined by the gap, noting that the wavelength and intensity of the microwaves will have an impact on dimensions and changes of direction.
  • the design selection is not solely governed by what is necessary to allow adjacent metal sections to change orientation relative to each other when the conveyor moves in a curved path.
  • the choking structure may comprise the one or more than one change of direction of the pathway.
  • the choking structure may comprise a deadend in the pathway.
  • deadend is understood herein to mean in general terms a reflective structure formed for example by a closed groove.
  • the deadend may extend from a bend in the pathway.
  • the deadend may be a branch of a main part of the pathway.
  • the deadend may be configured to reflect microwaves into the microwave energy zone.
  • the choking structure may be a quarter wave choking structure that is a result of a number of design features of each gap.
  • the pathway comprises a deadend.
  • the deadend may extend from a bend in the pathway and is in the form of a channel extending across the width of each metal section (which may also be described as a closed groove). In effect, the deadend is a branch from a part of the pathway.
  • the quarter wave choking structure relies on a property of impedance transformation of a transmission line, in which the impedance transforms to its inverse every quarter wavelength from its termination.
  • the quarter wave choking structure may comprise an entry section from the microwave energy zone, a deadend (closed groove) extending from the entry section, and an exit section.
  • the deadend section may terminate in a physical short circuit (high microwave reflection) and have a length equal to or approximate to a quarter of the wavelength of an operational microwave frequency (wavelength slightly different than free space). This presents a point of very high impedance at a deadend entry.
  • the length from the deadend entry to an entry gap at a top surface of the metal sections is equal to or approximates a quarter wavelength of the operational microwave frequency, making its impedance very low, forming a virtual electrical connection (i.e. virtual short circuit, high microwave reflection).
  • the length of the exit section also equals or approximates a quarter wavelength of the operational microwave frequency and ensures a low impedance on the entry gap and, therefore, a high microwave reflection.
  • the choking structure is selected to reduce the amount of microwave energy escaping the furnace by a factor of at least 30 dB, typically by a factor of at least 40 db.
  • the choking structure may be configured so that there is very little loss of energy via absorption in deadend.
  • the deadend may comprise a channel extending across the width of the metal sections.
  • the pathway may comprise a filler element for preventing dust penetrating the pathway.
  • the pathway may comprise a filler element for maintaining a desired geometry of the pathway.
  • the filler element is at least substantially transparent to microwaves.
  • the filler be transparent to microwaves.
  • a part of one metal section may overlap at least a part of a successive metal section when the conveyor is travelling through the microwave energy zone, and there is a vertical space between the overlapping sections, with the space forming an initial part of the gap, and with the initial part extending from the microwave energy chamber.
  • the metal sections do not overlap, and there is a space between one metal section and a successive metal section when the conveyor is travelling through the microwave energy zone, with the space forming an initial part of the gap, and with the initial part extending downwardly, typically vertically, from the microwave energy chamber.
  • Each metal section may comprise a leading edge element and a trailing edge element extending transverse to the travel direction of the conveyor, with each gap being between the leading edge element of one metal section and the trailing edge element of the successive metal section.
  • Each leading edge element and the trailing edge element may have a width, a thickness, and an upper surface that faces the microwave energy zone when the conveyor is travelling through the micro wave energy zone.
  • Each gap may extend across the width of each leading edge element and each trailing edge element.
  • Each gap may extend through the thickness of each leading edge element and each successive trailing edge element.
  • the metal sections may be in the form of pans.
  • the pans may comprise a flat base.
  • Each pan may comprise end edges, for example in the form of flanges, that extend upwardly from opposite sides of the base of the pan.
  • the apparatus may include pans having side edges comprising flanges that have the same gap structure as the base of the pans (for the purposes of forming part of the microwave energy barrier).
  • the microwave energy barrier is an important part of the furnace for health and safety reasons, electromagnetic compatibility (EMC), and for process reliability reasons.
  • EMC electromagnetic compatibility
  • the choking structure of the conveyor is one part of the microwave energy barrier.
  • the microwave energy barrier may also comprise a microwave choking structure at a feed inlet of the microwave energy zone.
  • the microwave energy barrier may also comprise a microwave choking structure at a discharge outlet of the micro wave energy zone.
  • the furnace may comprise walls that define opposite sides of the microwave energy zone.
  • the side walls may be fixed walls in relation to the conveyor when the conveyor is moving through the furnace.
  • the side walls and the conveyor may be positioned so that these is a gap between each side wall and the conveyor to allow movement of the conveyor without contacting the side walls.
  • Each gap may define a potential pathway for microwaves to travel from the microwave energy zone and escape the microwave energy zone.
  • the chamber includes a choking structure to minimise microwave leakage through the gaps that forms a part of the microwave energy barrier.
  • the microwave energy barrier may comprise choking structures for the gap between each side wall and the side flanges.
  • the base of the conveyor may be formed from any suitable material.
  • Aluminium which terms includes aluminium alloys
  • aluminium alloys is a preferred material from the perspective of being a conductor and substantially not absorbing microwaves.
  • one limitation of aluminium is being able to withstand furnace temperatures for production of DRE Stainless steel is another option. It is not the best material from the perspective of being a conductor and not absorbing microwaves, but it is able to withstand furnace temperatures for production of DRI.
  • Other materials include, by way of example, Inconel and other high temperature metal alloys and ceramic materials.
  • the base of the conveyor may further comprise a layer (such as a coating) of a material on an upper surface of the metal sections.
  • the layer may be metallic to minimise surfaces losses.
  • the layer may be transparent to microwave energy.
  • the layer may be configured to lift material off the metal sections.
  • the metalliferous ores may be an iron ore.
  • the invention also provides an endless conveyor for carrying a material through a furnace for heating microwave absorbent material in the material with microwave energy, the conveyor comprising a base for carrying the material, the base comprising a plurality of metal sections extending transverse to a direction of travel through the furnace, and being coupled together so that there is a gap between adjacent metal sections with the gap being configured to form a part of a microwave energy barrier to loss of microwave energy from a microwave energy zone of the furnace.
  • Each gap may extend across the width of the metal sections.
  • each gap is a tortuous pathway.
  • the pathway may comprise one or more than one change of direction.
  • the choking structure may be configured to reflect microwaves into the microwave energy zone.
  • the design selection may take into account dimensions and changes of direction of the pathway defined by the gap, noting that the wavelength and intensity of the microwaves will have an impact on dimensions and changes of direction.
  • the design selection is not solely governed by what is necessary to allow adjacent metal sections to change orientation relative to each other when the conveyor moves in the curved path.
  • the choking structure may comprise the one or more than one change of direction of the pathway.
  • the deadend may be a branch of a main part of the pathway.
  • Figure 1 is (a) a schematic diagram of one embodiment of a linear hearth furnace of an apparatus for producing direct reduced iron (DRI) from briquettes of a composite of iron ore fragments and biomass in accordance with the invention, (b) a temperature profile along the length of a furnace of the apparatus for an embodiment of a method for producing direct reduced iron (DRI) from briquettes of a composite of iron ore fragments and biomass in accordance the invention, and (c) a plot of off-gas volumetric flow rate of gases produced along the length of the furnace during the course of the method;
  • DRI direct reduced iron
  • Figure 2 is a computer rendered image of a microwave energy zone of the furnace shown in Figure 1 with sections of the furnace removed to show an embodiment of the conveyor of the apparatus within the microwave energy zone, with the conveyor being one embodiment of a conveyor in accordance with the invention;
  • Figure 3 is a computer rendered image similar to that shown in Figure 2, viewed from one end of the microwave energy zone;
  • Figure 5 is a side view of an enlargement of a part of Figure 4 that includes additional details of how successive metal sections of the embodiment of the conveyor are interlinked together;
  • Figure 7 is a simplified diagram that shows the interlinked end elements of successive metal sections of another embodiment of a conveyor (typically travelling from left to right as shown) in accordance with the invention
  • Figure 8 is a simplified diagram that shows the interlinked end elements of successive metal sections of another embodiment of a conveyor (typically travelling from left to right as shown) in accordance with the invention.
  • Figure 9 is a simplified diagram that shows the interlinked end elements of successive metal sections of another, but not the only other, embodiment of a conveyor (typically travelling from left to right as shown) in accordance with the invention. DESCRIPTION OF EMBODIMENTS
  • Figure l is a schematic diagram of an embodiment of a linear hearth furnace of an apparatus for producing direct reduced iron (DRI) of the present invention taken as a longitudinal section through the furnace.
  • DRI direct reduced iron
  • the furnace shown in Figure 1 is part of an apparatus that is configured for continuously producing direct reduced iron (“DRI”) from microwave absorbent material in the form of iron ore and biomass, typically at least initially in the form of briquettes of a composite of iron ore fragments and biomass.
  • DRI direct reduced iron
  • the linear hearth furnace includes an endless conveyor that, in use, transports iron ore and biomass through a furnace having an inlet for iron ore and biomass and an outlet for DRI and between the inlet and outlet a feed zone, a preheat zone, a microwave energy zone (for heating material with microwave energy) and a discharge zone, and a transition zone between the preheat zone and the microwave energy zone.
  • the transition zone includes a compacting device for compacting preheated material, typically by reducing the height of preheated material, as it passes thereunder, so that it presents a more homogenised as described herein bed of material as a result of compaction which is better suited to processing in the microwave energy zone.
  • the linear hearth furnace generally identified by the numeral 3, includes an elongate chamber defined by a refractory-lined base wall 82, opposed side walls 84 (see Figures 2 and 3), and a hood 86 that has the following zones along its length: a feed zone 10 that includes an inlet to the chamber and is configured to receive a feed material in the form of briquettes (not shown) of iron ore and biomass, i.e. briquette material, a preheat zone 20 for heating material, i.e.
  • iron ore and biomass in the briquettes and reducing iron ore and releasing volatiles in biomass and producing a preheated material, with the volatiles being combusted in the preheat zone, a microwave energy zone 30 for heating the preheated material further and reducing iron ore and forming DRI; a transition zone 25 between the preheat zone 20 and the microwave energy zone 30, with the transition zone 25 including a passageway 275 for gas flow from the microwave energy zone 30 to the preheat zone 20 and a compacting device 251 for compacting the preheated material; a discharge zone 40 for DRI that includes an outlet of the chamber.
  • the furnace 3 also comprises an endless conveyor 50 having a metallic material base (described further below) that, in use, moves in a continuous loop through the chamber from the inlet to the outlet and transports material that is at least initially in the form of briquettes on the base through the chamber from the inlet and discharges DRI from the outlet and then returns to the inlet to be re-loaded with additional briquettes.
  • a metallic material base described further below
  • the furnace 3 also comprises an assembly (not shown) for supporting and moving the conveyor 50 through the chamber.
  • the assembly may be any suitable assembly.
  • the furnace 3 also comprises a flue gas outlet 70 in the preheat zone 20 for discharging gases produced in the furnace by heating and/or combustion within the furnace.
  • the furnace 3 also comprises a means for supplying microwave energy to the microwave energy zone that heats iron ore and biomass and reduces ore to DRI.
  • the feed zone 10 includes a feed chute 12 and is configured to continuously feed briquettes into the feed zone 10 via the inlet to form a relatively uniform bed of briquettes on the moving conveyor 50 in the feed zone 10 of the chamber, while restricting outflow of furnace gases via the inlet.
  • relatively uniform bed of briquettes is understood herein to mean a relatively uniform layer of briquettes covering the base of the conveyor 50 and typically having a consistent ‘bed’ thickness, at least lengthwise, i.e., in the direction of briquette travel within the furnace. This does not however mean that individual briquettes have to be stacked in anything more than a random way on the base, noting that in some embodiments this may be desirable.
  • the discharge zone 40 is configured to continuously discharge DRI from the discharge zone 40 via the outlet, while restricting the inflow of oxygen-containing gases into the microwave energy zone 30 of the chamber from outside the chamber.
  • the discharge zone 40 includes an enclosed discharge chute 42 that has a downwardly directed opening that has a flow control valve 44 that can be selectively operated to allow DRI to flow through the opening.
  • the preheat zone 20 has a plurality of air or oxygen-enriched air fed burners 22 for generating heat by burning combustible gases in a top space of the preheat zone 20.
  • the burners 22 are spaced along the length of the preheat zone 20. The optimal spacing can be readily determined by a skilled person for any given operating conditions, such as the amount and type of biomass and the amount and type of iron ore and the required metallisation.
  • the combustible gases generated in the furnace include combustible gases originating within the furnace.
  • the combustible gases include: volatiles in biomass in material moving through the preheat zone 20; and combustible reduction gases, such as CO, generated by reduction of iron ore in material in: (i) the preheat zone 20; and
  • the microwave energy zone 30 is an anoxic environment. Heat is provided by microwaves. Microwaves heat iron ore and biomass and reduce ore to DRI.
  • Figure 1(b) illustrates the typical operating temperatures along the length of the furnace, varying from room temperature at the inlet end to 1100°C at the DRI discharge outlet end.
  • the means for supplying microwave energy to the microwave energy zone comprises a source of microwave energy (not shown) and pipework that transfers microwave to the microwave energy zone.
  • the pipework includes a plurality of microwave energy input units 32 (waveguides 64 and horns 66) in a top space of the microwave energy zone.
  • the microwave energy may have any suitable microwave frequency and vary by country, but the current industrial frequencies of around 2450MHz, 915MHz, 443MHz and 330 MHz are of most interest.
  • the horns 66 form an interface 80 (see the horizontal dotted line in Figure 1) that separates the microwave energy zone 30 into an upper sub zone 56 and a lower sub zone 58.
  • the horns 66 are pyramidal horns, more particularly sectoral horns 66 in the embodiment shown in Figure 1.
  • the horns 66 are arranged in rows (see Figure 1(b)) having microwave outlets 70 for microwave energy.
  • the microwave outlets 70 are rectangular in transverse section.
  • the rows extend across a width of a section of the microwave energy zone 30 and along a length of the section above a top surface of the conveyor 50 and, in use above a top surface of material carried on the conveyor 50.
  • the section may be any suitable length and any suitable width.
  • the horns 66 are not in contact with each other at the microwave outlets 70 of the horns 66 and there are gaps 76 between the horns 66 at this location (see Figure 3).
  • the interface 80 as shown as a horizontal dotted line in Figure 1, is a sharp transition between the upper sub zone 56 and the lower sub zone 58. It is noted that the invention is not confined to a sharp transition.
  • the horns 66 are defined by side walls 72, 74 that are typically formed from metal sheet material.
  • the horns 66 are rectangular in transverse section and are formed with only one pair of opposing side walls 72 being flared and diverging with distance from the waveguides 64 and the other pair of opposing side walls 74 being parallel to each other which, in use, produces a fan-shaped beam, which is narrow in the plane of the flared side walls, but wide in the plane of the narrow side walls.
  • the flaring may be in the E-plane (electric field) or H-plane (magnetic field) direction to form a rectangular opening at its output end.
  • the horns 66 in each row are placed above the conveyor 50 so that the shorter sides of the rectangular microwave outlets 70 (with the shorter sides being the side walls 74) are parallel to the direction of moment of the conveyor 50 within the microwave energy zone 30.
  • the horns 66 are arranged and configured so that the cumulative effect of the field patterns of the horns is to maximise the homogeneity of treatment of the material on the conveyor 50.
  • the transition zone 25 includes a passageway 275 for gas flow from the microwave energy zone 30 to the preheat zone 20 and a compacting device 251 for compacting the preheated material.
  • the compacting device 251 is in the form of a driven roller.
  • the compacting device 251 is provided to break-up and compact material on the conveyor 50 as it moves through the transition zone 25 from the preheat zone 20 to the microwave energy zone 30 so that it presents a more homogenised and uniform height bed of material which is better suited to processing with microwave energy in the microwave energy zone 30.
  • the compacting device 251 does this by applying a downward force onto material and thereby breaking and compacting by reducing the height of material passing through the gap between the compacting device 251 and the conveyor 50. It is noted that there may be a combination of surface and profile and range of densities in the bed. Typically, the bed is a high density packed bed.
  • a suspended refractory wall 253 sits in front of the compacting device 251.
  • a gap between a lower end of the wall and the conveyor 50 defines a passage for material to pass therethrough prior to being compacted by the compacting device 251. It also forms a barrier over which upper end reduction gases generated in the microwave energy zone 30 that enter the upper sub zone 56 can pass from the microwave energy zone 30 to the preheat zone 20.
  • reduction gases generated in the microwave energy zone 30 flow into the preheat zone 20 counter-current to the direction of movement of briquettes on the conveyor 50 through the furnace from the inlet to the outlet.
  • the counter-current flow of reduction gases from the microwave energy zone 30 into the preheat zone 20 is caused by a higher gas pressure in the microwave energy zone 30 compared to gas pressure in the preheat zone 20.
  • the volume of reduction gases generated in the microwave energy zone 30 is illustrated by the plot of off-gas volumetric flow rate shown in Figure 1(c). The Figure shows a peak in gas produced in the microwave energy zone 30.
  • the counter-current flow of reduction gases from the microwave energy zone 30 to the preheat zone 20 transfers combustible gases, such as CO, that are generated in reactions that reduce iron ore in the microwave energy zone 30 to the preheat zone 20.
  • combustible gases in the gas flow from the microwave energy zone 30 are combusted by the plurality of air or oxygen-enriched air fed burners 22 spaced along the length of the preheat zone 20.
  • the temperature profile shown in Figure 1 is an example of a suitable temperature profile along the length of the furnace.
  • the conveyor 50 transports material that is initially in the form of briquettes (not shown) of iron ore and biomass that are on the base successively and continuously through the zones 10, 20, 25, 30, 40 in a sequential manner and eventually circles back in its endless pathway so that each portion of the refractory or metallic base material of the conveyor 50 eventually presents itself at the feed zone 10 to be loaded with more briquettes.
  • the refractory or metallic base material has residual heat from the chamber when the conveyor 50 returns to the feed zone 10.
  • reduction and other gases generated in the chamber are discharged as a flue gas via the flue gas outlet 70 in the preheat zone 20.
  • the briquettes may be manufactured by any suitable method.
  • measured amounts of iron ore fines and biomass and water (which may be at least partially present as moisture in the biomass) and optionally flux is charged into a suitable size mixing drum (not shown) and the drum rotated to form a homogeneous mixture. Thereafter, the mixture may be transferred to a suitable briquette-making apparatus (not shown) and cold-formed into briquettes.
  • the briquettes are roughly 20 cm 3 in volume and contain 30-40% biomass (e.g., elephant grass at 20% moisture).
  • a small amount of flux material such as limestone
  • the physical structure of the DRI at the end of the process is not critical. The physical structure may be friable and break easily or it could resemble a robust 3D “chocolate bar”.
  • the design of the conveyor 50 is an important factor in minimising microwave energy loss from the furnace.
  • microwave energy zone 30 microwave energy zone
  • fixed side walls in relation to the moving conveyor
  • Figures 2 and 3 are images of a part of the microwave energy zone 30 of the linear hearth furnace shown in Figure 1 with sections of the furnace removed to show an embodiment of the conveyor of the furnace within the microwave energy zone, with the conveyor being one embodiment of a conveyor in accordance with the invention.
  • Figure 4 is an enlargement of a vertical cross-section through a part of the furnace shown in Figures 2 and 3.
  • Figure 5 is a side view of an enlargement of a part of Figure 4 that includes additional details not shown in Figure 4.
  • Figure 6 is a microwave energy (E-field) pattern for the part of the furnace shown in Figure 4.
  • Figures 2 and 3 show the conveyor 50 passing through the microwave energy zone 30.
  • the conveyor 50 passes under a section of the hood 86 and between the side walls 84 of the chamber.
  • the Figures also show a series of vertical waveguides 64 extending through openings in the hood 86.
  • the waveguides are connected to horns 66, as shown in Figure 1.
  • Two such horns 66 are shown in Figure 3, with a further three horns 66 in the background of the Figure.
  • One such horn 66 is shown in Figure 6.
  • the conveyor 50 is configured to form a part of a microwave energy barrier to loss of micro wave energy from the micro wave energy zone 30.
  • the base of the conveyor 50 comprises a plurality of metal sections 88 extending transverse to a direction of travel of the conveyor 50 through the furnace 3. Typically, the metal sections 88 are perpendicular to the travel direction.
  • the metal sections 88 are not transparent to microwaves and therefore are a part of the microwave energy barrier.
  • Such conveyors can be used for the transport of any material where microwave energy provides at least part of the of the energy for heating the material in a furnace 3, and the furnace is configured to have a microwave energy zone 30.
  • the metal sections 88 are coupled together so that there is a gap, generally identified by the numeral 90, between adjacent metal sections 88.
  • the metal sections 88 are in the form of pans that have a flat base 100 and flanges 102 that extend upwardly and outwardly from opposite ends of the base 100.
  • the side walls 84 of the chamber are inboard of the flanges 102. There is a gap 110 between each side wall 84 and the flanges 102 on that side of the conveyor 50 to allow the conveyor 50 to move relative to the side walls 84 without contacting the side walls.
  • the gaps 110 define potential pathways for microwaves to travel from the microwave energy zone 30 and escape the zone 30.
  • the chamber includes a choking structure 112 to minimise microwave leakage through the gaps 110.
  • the choking structure 112 comprises a tortuous pathway that is configured to reflect microwaves back through the gaps 110 into the microwave energy zone 30.
  • each metal section 88 comprises a leading edge element, generally identified by the numeral 92, and a trailing edge element, generally identified by the numeral 94, extending transverse to the travel direction of the conveyor 50 through the microwave energy zone 30.
  • Each gap 90 is between the leading and trailing edges elements 92, 94 and extends across the width and through a thickness of the metal sections 88.
  • each metal section 88 rotates relative to successive and preceding metal sections 88 as the metal sections move around the curved path, shown for example on the right side of Figure 2, without the metal sections 88 contacting each other and interfering with movement in the curved path.
  • each gap 90 is a potential pathway for microwaves to travel from the microwave energy zone 30 and escape the zone 30.
  • each gap 90 defines or comprises a choking structure.
  • the choking structure in this embodiment returns microwaves by reflecting microwaves into the micro wave energy zone.
  • the choking structure is configured to absorb microwaves and therefore attenuates rather than reflects microwaves.
  • the choking structure is a quarter wave choking structure.
  • each gap 90 is formed as a tortuous pathway, with multiple bends and changes in direction, with the lengths of some sections of the pathway being formed to be one quarter of the wavelength(s) of the micro waves.
  • the pathway includes a deadend 68.
  • the deadend 68 extends from a bend in the pathway and is in the form of a channel extending across the width of each metal section 88 (which may also be described as a closed groove).
  • the deadend 68 is a branch from a part of the pathway.
  • the deadend 68 is formed to be one quarter of the wavelength(s) of the microwaves.
  • the choking structure is configured so that there is no more than 0.04% loss of energy from the deadend.
  • the choking structure relies on a property of impedance transformation of a transmission line, in which the impedance transforms to its inverse every quarter wavelength from its termination.
  • the choking structure comprises an entry section (C) - (B), a deadend (closed groove) section (B) - (A), and an exit section (B) - (D).
  • the deadend section (B) - (A) terminates in a physical short circuit (A) (high microwave reflection, of a length equal or close to a quarter of the wavelength of an operational microwave frequency - wavelength slightly different than free space). This presents a point of very high impedance at the deadend entry (B).
  • the distance from this point to an entry gap (C) at a top surface of the metal sections is equal to or also approximates a quarter wavelength of the operational microwave frequency, making its impedance very low, forming a virtual electrical connection (i.e.
  • the microwave energy (E-field) pattern shown in Figure 6 was generated with a sample 104 (that reflects material that has passed through the transition zone) supported by the conveyor 50 in the microwave energy zone 30 (microwave energy zone) and microwaves being supplied to the microwave energy zone 30 via microwave energy input units 32 (waveguides 64 and horns 66), with one horn 66 shown in the Figure.
  • the legend on the right side of the Figure indicates the microwave energy (E-field) strength in different sections of the furnace shown in the Figure. It is evident from the Figure that there is a high E-field in an early part of the deadend 68 and in a part of the pathway of the gap 90 that leads into the deadend 68. It is also evident from the Figure that there are substantially no microwaves in the last part 98 of the pathway. It follows that the Figure indicates that substantially no microwaves escaping the zone 30.
  • the gap 90 is a less tortuous pathway than the gap 90 in the embodiment shown in Figures 2-6 and does not include a deadend.
  • the pathway is formed as a quarter wave choking structure that comprises two changes of direction that reduce loss of microwaves from the microwave energy zone 30 by reflecting microwaves into the micro wave energy zone 30.
  • the embodiment shown in Figure 8 comprises:
  • the filler element 106 is at least substantially transparent to microwaves.
  • the embodiment shown in Figure 9 comprises:
  • the gap 90 and the deadend 108 form a quarter wave choking structure.
  • the above-described furnace including the embodiments of the conveyor 50 with the choking structures shown in the Figures, is an effective apparatus for heating a material using micro wave energy as a source of energy.
  • Many modifications may be made to the embodiments described in relation to the Figures without departing from the spirit and scope of the invention.
  • the invention is not confined to such structures and extends to any suitable choking structures in the gap that can reflect microwaves that would otherwise pass through the gap into the microwave energy zone 30.
  • the invention extends to embodiments not shown in the drawings in which the choking structures 90 of the gaps are configured to absorb rather than reflect microwaves.
  • microwave absorbent materials in the form of iron ore and biomass
  • the invention also extends to other microwave absorbent materials such as naturally occurring spodumene.

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Abstract

L'invention concerne un appareil de chauffage d'un matériau absorbant les micro-ondes comprenant un four 3 qui a une zone d'énergie micro-ondes 30 et un transporteur sans fin 50 pour transporter le matériau à travers la zone d'énergie micro-ondes 30 de telle sorte que le matériau sur le transporteur peut être exposé à de l'énergie micro-ondes. Le transporteur forme une partie d'une barrière d'énergie micro-ondes qui empêche la perte d'énergie micro-onde à partir de la zone d'énergie micro-ondes. Le transporteur comprend une base pour transporter un matériau. La base comprend une pluralité de sections métalliques 88 s'étendant transversalement à une direction de déplacement à travers le four qui sont couplées ensemble avec un espace 90 entre des sections métalliques adjacentes de telle sorte que des sections métalliques adjacentes peuvent changer d'orientation l'une par rapport à l'autre lorsque le transporteur se déplace dans un trajet incurvé. L'espace définit ou comprend une structure d'étranglement 112 qui limite une fuite de micro-ondes à travers l'espace.
PCT/AU2025/050238 2024-03-20 2025-03-14 Réduction directe de minerai métallifère Pending WO2025194206A1 (fr)

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AU2024900749A AU2024900749A0 (en) 2024-03-20 Metalliferous ore direct reduction

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WO2025194206A1 true WO2025194206A1 (fr) 2025-09-25

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63172828A (ja) * 1987-01-12 1988-07-16 Toshiba Corp 高周波加熱装置
EP2385146B1 (fr) * 2009-01-31 2017-04-05 Tokyo University of the Arts Four de fusion vertical à micro-ondes
EP3260559A1 (fr) * 2015-02-09 2017-12-27 Innceinnmat, S.L. Procédé sélectif d'extraction de minéraux de minerais bruts et appareil pour la mise en oeuvre du procédé
JP2022037435A (ja) * 2020-08-25 2022-03-09 三菱電機株式会社 加熱調理器
WO2023173159A1 (fr) * 2022-03-12 2023-09-21 Technological Resources Pty. Limited Fer à réduction directe à base de biomasse
GB2617858A (en) * 2022-04-22 2023-10-25 Anglo American Technical & Sustainability Services Ltd System and method for treating mined material

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63172828A (ja) * 1987-01-12 1988-07-16 Toshiba Corp 高周波加熱装置
EP2385146B1 (fr) * 2009-01-31 2017-04-05 Tokyo University of the Arts Four de fusion vertical à micro-ondes
EP3260559A1 (fr) * 2015-02-09 2017-12-27 Innceinnmat, S.L. Procédé sélectif d'extraction de minéraux de minerais bruts et appareil pour la mise en oeuvre du procédé
JP2022037435A (ja) * 2020-08-25 2022-03-09 三菱電機株式会社 加熱調理器
WO2023173159A1 (fr) * 2022-03-12 2023-09-21 Technological Resources Pty. Limited Fer à réduction directe à base de biomasse
GB2617858A (en) * 2022-04-22 2023-10-25 Anglo American Technical & Sustainability Services Ltd System and method for treating mined material

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