Biomass-based iron production using smelting reduction vessel

Abstract

A process and apparatus for producing molten iron from iron ore and biomass using at least one hearth furnace and a smelting reduction vessel (SRV) is disclosed. The process and apparatus produce molten iron using a hearth furnace to initiate reduction of iron ore and complete reduction of ore in a smelter reduction vessel where fuel gas generated in the smelter reduction vessel is combusted to supply heat in the hearth furnace.

Description

Technical Field

[0001] This invention relates to a process and equipment for producing molten iron from iron ore and biomass.

[0002] In particular, although not exclusively related to, a process and apparatus for producing molten iron from iron ore and biomass using a hearth furnace, to initiate and complete the reduction of the iron ore in a smelting reduction vessel, wherein fuel gases generated in the smelting reduction vessel are burned to provide heat in the hearth furnace.

[0003] The term "hearth furnace" describes a furnace comprising a longitudinally (either linear or circular) generally horizontally extending heating chamber and a base extending along the length of the chamber from the inlet end to the outlet end, the base carrying material through the chamber for rapid heat treatment within the chamber.

[0004] The term "molten iron" refers to liquid iron containing at least 2% dissolved carbon by weight.

[0005] The term "smelt reduction vessel" (often abbreviated as "SRV" and also described as "direct reduction vessel") refers to, for example, in HIsmelt TM and HIsarna TM The process (1-12) (hereinafter collectively referred to as the "HISRV-based approach") uses a direct smelting furnace of the type that is either blown air or blown oxygen. It does not contain any type of electric heating element, but instead obtains the necessary process heat from the partial combustion of carbon and pool-derived CO / H2 by injecting oxygen-containing gas into the upper region of the vessel. Commercial examples of this type of furnace are operating in China (Molong in Shandong Province and Jianlong CISP in Inner Mongolia). background

[0006] Historically, steelmaking has been a carbon-intensive process, with most of the carbon used ultimately being oxidized into CO2 and released into the atmosphere. As countries worldwide seek to reduce overall atmospheric CO2, steel manufacturers face pressure to find ways to produce steel without causing net greenhouse gas emissions. In particular, there is pressure to avoid using coal and natural gas, often collectively referred to as "fossil fuels," which are non-renewable and contribute to increased atmospheric greenhouse gas concentrations.

[0007] Most of the world's iron is produced via the blast furnace route, a technology that existed before the Industrial Revolution. Even with technological advancements, blast furnaces currently require approximately 700-900 kg of metallurgical coal to produce one ton of iron and emit high levels of CO2, about 1.8-2.0 t CO2 per ton of hot metal. The use of fossil fuels, particularly the demand for coal (in the form of coke), is the fundamental feedstock for blast furnace operation, and it is not possible to simply use hydrogen from it as a complete substitute.

[0008] An alternative method in blast furnaces is to produce direct reduced iron (DRI) by directly reducing solid iron ore with carbon monoxide and hydrogen derived from natural gas (or coal). This reduction occurs at a temperature below the bulk melting temperature of the solid. For the purposes of this art description, "direct reduced iron" (DRI) is understood to have a metallization rate of at least 85%, where the metallization rate refers to the degree to which iron oxides are converted into metallic iron during the reduction of the iron oxides, expressed as a percentage of the mass of metallic iron divided by the mass of total iron.

[0009] While such facilities (outside India) are fewer in number compared to blast furnaces, numerous processes exist for direct reduction of iron ore. In India, coal-based rotary kilns are used to produce DRI, also known as sponge iron (accounting for nearly 20% of world DRI production). Elsewhere, they tend to be gas-based shaft furnace processes (accounting for nearly 80% of world DRI production). Gas-based direct reduction units are typically part of integrated small steel mills located near electric arc furnace (EAF) steelmaking facilities, but some DRI originates from dedicated direct reduction units (often based on Midrex furnaces). TM or HYL TMThe process involves transporting the raw materials (DRI) to remote steel mills. Because DRI is typically melted in an electric arc furnace along with scrap steel, which is used as other feedstock, to directly produce steel (typically with far less than 0.8% carbon by weight), there are stringent requirements on the levels of impurities in DRI, such as gangue and phosphorus, which are expensive and difficult to remove in EAF. Therefore, the iron ore used to produce DRI is usually crushed and ground to micron-sized particles to remove gangue minerals. Such fine powder is difficult to handle (both in terms of transport and handling), so it is then agglomerated using water and / or binders to produce “green” pellets of similar size. These “green” pellets, after drying, are then fed into a furnace where they are sintered into hardened granules (a process known as hardening), which are then ultimately fed as feedstock to direct reduction units (or sometimes as high-quality iron ore feedstock to blast furnaces to help dilute gangue from the lumpy or sintered iron ore used in blast furnaces). The "green" pellets that form the granules have a typical compressive strength of about 10 N when wet and 50 N when dry. As granules (after hardening), they have a compressive strength of about 2000 N.

[0010] A futuristic alternative to all of the above methods is to use hydrogen to produce DRI from iron ore (in the form of hardened pellet feed), which is then smelted in an EAF to produce steel. To make this route carbon neutral, renewable (green) energy needs to be converted into hydrogen (especially during periods of low wind / solar costs), followed by the use of hydrogen to produce DRI. This route has strong support in Europe and the potential to become an important part of a global solution (13). However, there are limitations: 1. The required electricity is high (estimated at 3500 kWh / t-4500 kWh / t up to the liquid steel stage), and the cost of green electricity needs to be low (or alternatively, a high carbon tax) in order to become more cost-effective than coal-based and natural gas-based processes.

[0011] 2. The hydrogen consumption demand for DRI production may be stable, while hydrogen production itself may be cyclical, consistent with the availability of intermittent renewable energy sources such as wind and solar power. This necessitates buffering methods to balance supply and demand. The storage and supply of large quantities of hydrogen presents a significant technical challenge. Underground salt caverns and depleted natural gas reservoirs appear to show good potential. However, not all geographic locations are suitable for this type of hydrogen storage. Furthermore, suitable storage locations may not be close to existing EAF steel mills and / or integrated steelmaking facilities' DRI facilities, leading to supply challenges.

[0012] 3. Only low-gangue ore types (or ore types that can be easily upgraded to remove gangue) can be used with the DRI / EAF combination. EAF will severely penalize high-gangue ore types, making them essentially uncompetitive. This means that most ores currently used in blast furnaces may become uneconomical for such a process route.

[0013] It is known that sustainable biomass can be a complementary part of this solution, serving as an alternative to fossil fuels. When used, the combustion of either fossil fuels or biomass releases CO2. However, when fast-growing plants are the source of biomass, they are primarily a carbon-neutral energy source (because roughly the same amount of CO2 is absorbed as the plant regenerates through photosynthesis).

[0014] To date, the only commercial ironmaking process that directly uses biomass is the small-scale blast furnace with charcoal (primarily located in Brazil). This option has certain limitations associated with charcoal production. Previous attempts to insert biomass into processes originally designed for coal (such as conventional blast furnaces and coke ovens) have been negligible at best, typically relying on a pre-carbonization step of the biomass and generally quite disappointing in terms of overall CO2 impact. This is largely because the properties of biomass are vastly different from those of coal. For successful use of biomass, it is necessary to redesign the process around the fundamental properties of biomass.

[0015] Biomass can take many forms, and avoiding competition with food production is key to biomass selection. Examples of biomass that may meet the selection criteria include elephant grass, bagasse, forestry byproducts, surplus rice straw, azolla, and seaweed / macrophyte. Such biomass availability varies significantly from one geographic location to another. Considering the volume of material required and the economic challenges of transporting such materials over long distances, this will most likely be a crucial factor determining the scale and location of future biomass-based iron plants.

[0016] Biomass such as wood chips has been shown in laboratory-scale studies (14) to reduce iron ore to solid iron by mixing it with iron ore and placing it in a furnace that heats the ore to over 800°C in a controlled atmosphere to prevent re-oxidation of the reduced material. While mixing contributes to the efficiency of the reduction process, it can present challenges on an industrial scale as a continuous process, where the gas flow generated by convection heating as part of the reduction process carries away fine carbon particles, leading to significant challenges in gas processing / coke recycling, or significant carbon waste due to the need to clean up exhaust gases from the process before being released into the atmosphere.

[0017] Another example is disclosed in AU 2007227635 B2(5) (described from laboratory-stage experiments). This patent discloses the use of briquettes (e.g., in the shape of bonded spherical balls) produced by mixing iron ore concentrate containing magnetite (Fe3O4), sawdust that has passed through a 4.75 mm sieve, a small amount of flour, and lightly wetting (to achieve agglomeration). Such a compound is dried at 105°C during processing (to provide strength and rigidity). The compound is then placed in a furnace (which is electrically heated) at a temperature exceeding 1375°C for the reduction of the iron ore. The patent discloses that fine iron ore particles should preferably be used, and although particles “up to 0.25 inches in diameter” (i.e., the maximum size of typical fine iron ore particles is 6.35 mm) or larger can be used, “the processing time would be unnecessarily long, and the particles would not contribute to their formation as a coherent mass.”

[0018] The application of electromagnetic energy to produce DRI during iron ore reduction has also been considered. Electromagnetic energy, such as microwave (MW) and radio frequency (RF) energy, can be used either simply as heating energy or as a means to increase the reaction rate or provide additional heating at critical moments in the reaction process. One of the first known laboratory attempts by the applicant is described in U.S. Patent 4,906,290, in which briquettes containing a mixture of fine iron ore powder, coal, and quicklime are subjected to microwaves until they glow red, and then rapidly placed in a crucible where they are smelted to produce molten iron containing 3.8% carbon. While the microwave products from the microwaves appear not to have been examined, it is highly likely that DRI was produced.

[0019] Therefore, numerous laboratory-scale studies have shown that iron ore tested by mixing it with biomass and heating the mixture in a small furnace can produce DRI in a manner that appears (on the surface) slightly better than what was expected from first principles. While the reasons may be unclear, the results represent a technological "sweetspot." The technological challenge remains how to achieve this efficiently on a large scale.

[0020] There are many possible methods. One of these methods (described in international application PCT / AU2021 / 051398) involves briquetting the ore and biomass, then preheating the material to approximately 600°C–900°C using a linear or rotary hearth furnace to remove volatile components. Under these conditions, the ore pre-reduction rate is expected to reach approximately 10%–70%. This is followed by a microwave treatment stage, in which the briquettes are heated to approximately 1000°C–1100°C and further reduced (using residual biochar), with a reduction rate typically around 90%–95%, and in some cases up to almost complete metallization. This DRI can then be supplied to an electric melting furnace or induction furnace, where it is melted to produce pig iron.

[0021] The applicant subsequently conducted further development work on the method described above to better establish how to implement it on a large scale in an efficient manner. In doing so, the applicant discovered an alternative method in which the process does not rely on heating using any type of electrical or electromagnetic energy. Instead, heating is provided via a partial combustion reaction in a melting reduction vessel.

[0022] The above description should not be regarded as an endorsement of common knowledge in Australia or other regions. Overview of publicly available content

[0023] The applicant has conducted research and development work on the following: an effective and efficient method for producing molten pig iron from iron ore using biomass (as a source of reducing agent and as a heating source for iron ore).

[0024] Heating using electromagnetic energy in the form of microwaves is a core requirement of the applicant's main research and development path ("EM energy approach").

[0025] The applicant has considered an alternative research and development pathway that includes a molten pool-based melting reduction vessel (“SRV”) of the type used in the HI SRV-based pathway.

[0026] The applicant's initial view was that the HI SRV-based approach would (i) require its fuel to be predominantly in the form of coal, and (ii) generate exhaust gases that would be unsuitable for use in the ore-biomass preheating step. Given that the applicant has developed the HIsmelt technology and possesses considerable knowledge related to this and related technologies, this initial view was prudent.

[0027] This invention is based on the applicant's understanding that if the HISRV-based pathway includes the following, then the HISRV-based method is an effective and efficient alternative to the iron ore to EM energy pathway for producing molten iron: (i) Intentionally using more, typically substantially more, biomass in briquettes (or other suitable composite forms of iron ore and biomass) than proposed for the EM energy pathway, in order to avoid the necessity of using coal in the smelting reduction vessel, and (ii) Use industrial-grade (pure) oxygen as an oxidant in the smelting reduction vessel to provide exhaust gas suitable (in terms of calorific value and flame temperature) for countercurrent return to the iron ore-biomass preheating stage.

[0028] In the context of iron ore and biomass, the term "complex" is understood herein to mean any combination of iron ore and biomass physically bonded together, such as briquetting. For example, iron ore and biomass can be physically bonded together by a compaction process with or without binders and with or without fluxes.

[0029] The term “industrially produced oxygen,” also known as “industrial grade oxygen,” is understood in this document to mean oxygen with a purity level of 95% or higher, such as when produced by an air separation unit (ASU).

[0030] The term “heating value,” often referred to as “calorific value,” is understood in this article to mean the amount of heat released during combustion.

[0031] While compound furnaces are desirable for increasing contact between the reducing agent (released from biomass) and the ore, the applicant further recognizes that using furnaces other than hearth furnaces to preheat the ore, at least for the compound, presents several limitations. For example, rotary kilns are generally unsuitable because the compound can break up as it rotates through the furnace, potentially leading to excessive dust generation. Similarly, shaft furnaces are generally unsuitable because the compound typically cannot withstand the weight of the load in a shaft furnace.

[0032] In a broad sense, the present invention provides a process and apparatus for producing molten iron from iron ore and biomass using a hearth furnace, to initiate and complete the reduction of the iron ore in a smelting reduction vessel, wherein fuel gases generated in the smelting reduction vessel are burned to supply heat in the hearth furnace.

[0033] In a broad sense, the present invention provides a process for producing molten iron from iron ore and biomass using at least one hearth furnace and a smelting reduction vessel (SRV), the process comprising: (a) A compound containing 40%-55% biomass (based on dry weight) of iron ore and biomass is supplied to a hearth furnace and the compound is heated and combustible gases released from the biomass in the compound are burned and the iron ore in the compound is partially reduced, and a heated and partially reduced iron ore product is produced and discharged from the hearth furnace, wherein the product has a temperature in the range of 550°C-950°C and is pre-reduced to between 20% and 70% mainly by radiant heat from burners in the upper region of the hearth furnace. (b) The partially reduced iron ore product (typically hot) is supplied to the molten pool in the smelting reduction vessel via a solid injection gun, and the iron ore in the product is melted and reduced to molten iron. (c) Supplying industrially produced oxygen to the top of the smelting reduction vessel and partially combusting the waste gases produced by the reaction of materials in the molten pool, and discharging partially combusted and hot waste gases from the smelting reduction vessel, wherein the degree of afterburning (as defined herein) is between 50% and 75%; and (d) Cool and purify at least a portion of the partially combusted and hot exhaust gas discharged from the smelting reduction vessel and use it as fuel gas in the hearth furnace.

[0034] the term: (a) In the context of “biomass,” “based on dry weight” is generally understood to mean “dry” under constant, selected environmental conditions. While the procedure for determination may vary depending on the biomass chosen, for consistency of determinations, refer to ASTM E1757-19. Standard Practice for Preparation of Biomass for Compositional Analysis ";and (b) In accordance with the standard dictionary meaning of the term, “mainly” in the context of “radiative heat” is understood in this paper to mean “most”.

[0035] The hot exhaust gas discharged from the furnace can be further burned (incinerated) in the boiler to remove residual CO, and then used to generate steam when hot, and then to generate electricity.

[0036] Optionally, after the steam used for power generation is raised, the hot exhaust gas can be cooled, dusted, and then treated in a CO2 removal system such as an amine scrubber, and the resulting captured CO2 can be sent to a geological storage facility.

[0037] For the purpose of controlling carbon in metals, a small amount of coal or biochar can be co-supplied to the smelting reduction vessel so that it constitutes no more than 10% of the total carbon input to the SRV on an annual average basis, typically no more than 5%.

[0038] A certain amount of natural gas or other combustible fuel can be supplied to the product discharge end of the hearth furnace to supplement the combustible gas released from biomass when providing radiant heat, wherein the total amount of such fuel does not exceed 3 GJ / ton of molten iron, typically not exceeding 2 GJ / ton of molten iron.

[0039] Step (b) may include supplying the partially reduced iron ore product into a molten pool at a temperature above 300°C, typically above 400°C, and more typically 500°C via a solid injection gun.

[0040] Step (c) may include according to HIsmelt TM and HIsarna TM The operating principle of the process for smelting and reducing iron ore is as described in references (1-12), and the contents of these references are incorporated herein by cross-reference.

[0041] The furnace can be a linear furnace, a rotary furnace, or any other suitable furnace.

[0042] The compound initially supplied to the furnace can be of any suitable size.

[0043] By way of examples, the complex can have a size of less than 25 cm. 3 And greater than 2 cm 3 Their volume. Typically, they can be 3 cm. 3 -20 cm 3 The volume.

[0044] By way of example, as a compact, the compound can have a major size of 1 cm-10 cm, typically 2 cm-6 cm, and more typically 2 cm-4 cm.

[0045] By way of further example, such a block can typically be a cuboid, i.e., a box shape, with six sides and all angles between the sides being right angles. By way of example, a block can also be a "pillow-shaped" block.

[0046] Although not limited to this, briquettes can be formed by the close contact of iron ore fragments and biomass through compaction.

[0047] An implementation of a process based on the HI SRV path typically includes the following steps: 1. Ore and biomass (optionally together with fluxing materials) are formed into briquettes or other suitable composite forms, wherein the amounts of ore and biomass are selected based on factors including having sufficient biomass to generate enough energy for the process. One consideration is selecting an amount of biomass capable of generating sufficient energy to produce the heat for the hearth furnace and smelting reduction vessel used in the process, and for reducing the iron ore in the hearth furnace and smelting reduction vessel. Typically, when biomass is the sole energy source in the process, the amount of biomass is 40%–55% (based on dry ore + dry biomass) in briquettes or other suitable composite forms. In all these calculations, the relevant properties of the ore and biomass are taken into account.

[0048] 2. The briquettes or other suitable compound forms are supplied to a hearth furnace, where they are preheated to an average temperature of approximately 550°C–950°C and pre-reduced to approximately 20%–70% (this percentage relates to the extent to which oxygen is removed from the ore from the assumed starting point of Fe₂O₃). The term “average” temperature is understood herein to account for possible temperature variations within the compound, and thus a temperature of, for example, 600°C assumes that the temperature on the surface of the compound may be higher than the temperature inside the compound. Typically, the hearth furnace operating conditions are selected such that when the briquettes or other compound forms are discharged from the hearth furnace, the biomass in these forms has been completely devolatileized and is in the form of char or other graphitic materials.

[0049] 3. The concentration from the smelting reduction vessel is approximately 2.5 MJ / Nm. 3 -4.0 MJ / Nm 3 Clean exhaust gas with a calorific value (based on LHV) is delivered to a burner in the top space of the hearth furnace, where it is burned with air (which may be preheated and / or partially oxygen-rich), thereby transferring radiant heat to the briquettes for preheating and pre-reduction in the hearth furnace.

[0050] 4. Bed gas from briquettes (or from other compound forms) is an additional fuel source for these combustion reactions, and the hearth furnace top space burner system operates in an oxygen-deficient manner (meaning that O2 is only present in the direct plume region of each burner).

[0051] 5. The briquettes or other compound forms are removed from the hearth furnace at an average temperature of 550°C–950°C and typically supplied to the melting reduction vessel while still hot, typically at a temperature above 300°C, via a solids injection lance. Appropriate hot solids handling equipment is used to manage the transfer and conditioning of this hot, partially reduced material into the melting reduction vessel. It should be noted that the briquettes or other compound forms may have already been broken to some extent during their movement through the hearth furnace. It should also be noted that in some cases, it may be necessary to break the briquettes or other compound forms to make them suitable for injection into the melting reduction vessel via a solids injection lance.

[0052] 6. As described herein, industrial-grade oxygen is used as an oxidant in the headspace of the smelting reduction vessel, in accordance with HISmelt-based... TM The known principle of the path generates heat. Hot metal and slag are discharged from the smelting reduction vessel in the normal manner.

[0053] 7. The exhaust gas from the melting reduction vessel is cooled from about 1500°C to about 600°C in a membrane wall exhaust hood or any other suitable option, and the heat from this cooling step is used to generate saturated vapor.

[0054] 8. Subsequently, the exhaust gas from the smelting reduction vessel is subjected to wet scrubbing and cleaning to achieve a calorific value of approximately 2.5 MJ / Nm³. 3 -4.0 MJ / Nm 3 (LHV-based) fuel gas. This fuel gas is used as described in step 3 above.

[0055] 9. After the exhaust gas from the smelting reduction vessel (along with gases from the briquetting bed or other composite form beds) is burned in the hearth furnace to provide the necessary process heat, the exhaust gas from the hearth furnace is sent to an afterburner to burn off residual CO by adding additional air. The exhaust gas leaving the hearth furnace typically has an afterburning rate of 85%–98% (defined as [CO2+H2O] / [CO+CO2+H2+H2O], expressed as a percentage in mole fraction).

[0056] 10. Hot flue gas from the afterburner (typically containing 1%–8% free oxygen) is used for steam boosting and power generation in power plants. The goal of power generation is energy self-sufficiency, so that little or no net electricity is imported from elsewhere.

[0057] 11. Optionally (depending on local conditions), flue gas from a power plant can be sent to a CO2 removal system, where it is scrubbed to remove CO2 (e.g., using an amine scrubber). The captured CO2 can then be piped to a CO2 capture and storage (CCS) resource, such as a deep brine layer. Additional (input) electricity is required for CO2 capture and storage under these conditions.

[0058] If electric heating is used in the process (e.g., a combination of microwave and electric melting), approximately 30%–40% biomass is typically used in briquettes (based on dry ore and biomass, excluding any fluxing materials). This provides sufficient carbon for producing hot metal containing 2%–4% dissolved carbon. If the electric heating elements are removed and a melting reduction vessel is used instead, the biomass in briquettes or other suitable compound form needs to be increased to approximately 40%–55% (based on dry ore + dry biomass). At this level, sufficient carbon is available for the SRV. A small amount of coal (or biochar) supplied to the SRV can still be used for furnace process control purposes, but this will account for no more than approximately 10% of the total SRV fuel input (based on LHV) on an annual average basis.

[0059] If the CCS option described above (in step 10) is used, the vast majority of the sequestered CO2 will be biomass-derived. The net effect is the removal of CO2 from the atmosphere via biomass as an intermediate, with the final CO2 sequestered in suitable underground geological structures. This achieves essentially the same function as CCS's Direct Air Capture (DAC), while avoiding its associated high costs, and simultaneously producing molten pig iron from iron ore.

[0060] The present invention also provides an apparatus for producing molten iron from iron ore and biomass, the apparatus comprising: (a) At least one preheater, such as a hearth furnace, comprising a compound feed inlet and a product outlet, means for conveying more than one compound along a path from the inlet to the outlet, a top space above the path, and more than one burner in the upper region of the top space, said hearth furnace being configured to produce a heated and partially reduced iron ore product from the compound, said product having a temperature in the range of 550°C to 950°C and being pre-reduced to between 20% and 70% primarily by radiant heat from the burners; and (b) A smelting reduction vessel for containing a molten pool and for melting and reducing heated and partially reduced iron ore products from a hearth furnace, and for generating molten iron products and exhaust gases; and (c) A connection between the hearth furnace and the smelting reduction vessel, which is used to transfer at least a portion of the exhaust gas from the smelting reduction vessel to the burner of the hearth furnace for use as fuel gas for the burner.

[0061] The furnace can be a linear furnace, a rotary furnace, or any other suitable furnace.

[0062] The device for conveying the compound along the path can be a conveyor or any other suitable option for supporting and conveying the compound.

[0063] The melting reduction vessel can be based on HIsmelt as described in references (1-12). TM and HIsarna TM The melting and reduction vessel of the process, and the public information of these references is incorporated herein by cross-reference.

[0064] For example, a smelting reduction vessel may include a furnace, upwardly extending sidewalls, a top including a vent hood, at least one solid injection lance and at least one gas injection lance, and separate outlets for discharging molten iron and molten slag, respectively.

[0065] The connection between the furnace and the smelting reduction vessel can be any suitable connection.

[0066] Typically, the connection includes a pipe connecting the burner of the hearth furnace and the smelting reduction vessel for transferring exhaust gas from the smelting reduction vessel to the burner of the hearth furnace.

[0067] Typically, the connection includes a unit such as a vapor membrane hood for cooling exhaust gases from the smelting reduction vessel from about 1500°C to about 600°C.

[0068] Typically, the connection includes units for washing and cleaning exhaust gases, such as wet scrubbers.

[0069] The complex can be any suitable size.

[0070] The complex can be any suitable shape.

[0071] Iron ore and biomass composites can be in briquette form.

[0072] Briquetting can be formed by the close contact of iron ore fragments and biomass through compaction.

[0073] The term "briquettes," as initially supplied to preheaters such as hearth furnaces, is understood herein as a broad term referring to a composite of iron ore fragments and biomass formed by the compaction of the iron ore fragments and biomass into close contact, or alternatively by mixing and binding the iron ore and biomass together, for example, during agglomeration. Those skilled in the art generally describe the latter (especially when in spherical form) as pellets. While "raw" pellets are considered to present some inherent challenges, particularly since they typically require careful drying first (thus avoiding any sudden steam escape), and any binder used cannot be one that undergoes significant transient volatilization during heating—both of which could lead to structural failure of the pellets; pellets are not excluded as feed material according to this method, however the term briquettes excludes indurated pellets, as such pellets essentially achieve their increased compressive strength by oxidizing iron ore fragments back to a higher oxidation state at a certain temperature and by sintering to create at least some cross-bonding between such fragments. Therefore, they cannot contain biomass (at least not in an uncarbonized form, i.e., any residual carbon residue can only exist as a result of oxidation without providing enough time to reach equilibrium).

[0074] It will be understood that the composition, size, shape, and / or integrity of briquettes will change as they are processed through a hearth furnace and eventually leave. Briquettes may lose their structural integrity and not resemble the form of feed briquettes.

[0075] The use of the term "briquette" when describing material passing through a hearth furnace is not intended to limit itself to the material initially supplied to the furnace, but is used merely for descriptive convenience.

[0076] The term "fragment" is understood herein to mean any suitable size of iron ore lump (e.g., passing through a suitable sieve with a spacing of 6.35 mm or less), and as used herein, some skilled in the art may understand that the term "fragment" is better described as "granular" and / or "fine-grained." It is intended that such terms be used synonymously. Iron ore can be any suitable type of iron ore, such as magnetite, hematite, and / or goethite. However, this does not exclude other iron-rich ores from which iron can be extracted, such as laterite, titanomagnetite, and vanadium-bearing magnetite, as the more common forms of iron ore from which iron is traditionally extracted are not locally available.

[0077] The term "biomass" is understood herein to mean living or recently living organic matter. Specific biomass products used in the compounding of iron ore fragments and biomass include, by way of example, forestry products and their byproducts (in the form of wood chips, sawdust, and residues from wood chips and sawdust), agricultural products and their byproducts (such as sorghum, hay, rice straw, and bagasse), agricultural residues (such as almond shells and nut shells), specially cultivated energy crops such as giant silvergrass (Miscanthus giganteus) and switchgrass, macroalgae and microalgae produced in aquatic environments, and recycled urban timber and paper waste.

[0078] The present invention also provides a hot metal product manufactured by the method described above.

[0079] The present invention also provides a hot metal product manufactured in the apparatus described above. Brief description of the attached diagram

[0080] The invention is further described by way of example with reference to the accompanying drawings, in which: Figure 1 This is a schematic diagram of one embodiment of a process and apparatus according to the invention for producing molten iron from briquettes of iron ore fragments and biomass without CO2 capture and storage (CCS); and Figure 2 This is a schematic diagram of another embodiment (although not the only other embodiment) of the process and apparatus according to the invention for producing molten iron from briquettes of iron ore fragments and biomass complexes, with CO2 capture and storage (CCS). Description of the implementation plan

[0081] Figure 1 and Figure 2 This includes considerable process information regarding the embodiments of the invention shown in these figures. The process information in the figures comes from a process model accessible to the applicant. The embodiments of the invention shown in these figures are technically feasible implementations based on that model.

[0082] refer to Figure 1 Iron ore-biomass composite briquettes 1 (or any other suitable composite of ore and biomass) are formed in a cold briquetting apparatus 31 by mixing 50% (wet) biomass 33, 45.6% (wet) iron ore 35, 2.4% (wet) dolomite 37, and 2.0% (wet) limestone 39 together to form a mixture and compacting the mixture into briquettes. Based on the mass of dry ore plus dry biomass in the mixture, the resulting briquettes 1 have a biomass content of 48.5%.

[0083] The briquette 1 is fed into a linear furnace 2 comprising a main chamber 71 and moved from the feed end 41 through the furnace 2 to the discharge end 45 on a ring conveyor 43. It is heated to an average temperature of 806°C and pre-reduced by 34.3% within 24 minutes to produce a product with 34.3% pre-reduction (corresponding to a metallization rate of 10.2%, as previously defined), 22.41% C, and trace amounts of P and S. This product is discharged from the discharge end as thermal solid-state DRI product 3. The carbon content in thermal solid-state DRI product 3 is 22.4%.

[0084] It should be noted that when the briquette 1 moves through the linear furnace 2, some cracking may occur in the briquette 1, and therefore the briquette 1 may not have the same shape as at the feed end 41.

[0085] In this embodiment, three identical linear hearth furnaces (LHF) (not shown) are used in parallel, and the hot solid DRI product 3 from each LHF is combined into a single stream for further downstream processing.

[0086] It should be noted that any suitable number of LHFs can be used. It should also be noted that the technician will understand what is needed to combine multiple streams.

[0087] The hot solids DRI product 3 is supplied to the hot solids processing system, identified by line 47 in the figure, and from there enters HIsmelt via the solids injection nozzle 49 of the container. TM Smelting Reduction Vessel (SRV) 4.

[0088] The thermal solids handling system 47 can be any suitable system for transporting thermal materials. The thermal solids DRI product 3 is transported via a carrier gas 55 supplied to the line 47.

[0089] Only two solid injection nozzles 49 are shown in the figure. It can be readily understood that the SRV 4 may have multiple additional solid injection nozzles 49 positioned around the sidewalls of the SRV 4.

[0090] SRV 4 is as described in References 1-12, and the contents of these references are incorporated by cross-reference.

[0091] Additional feed into SRV 4 via solid injection nozzle 49 consists of small amounts of (i) anthracite 5 and (ii) calcined lime 6. These feeds 5 and 6 are combined and conveyed via line 51 to supply line 47 via N2 carrier gas. The resulting mixed SRV feed in line 47 contains 23.6% C. According to the standard description of the HI SRV-based path as described in References 1-12, the solids injected via line 47 generate a jet in the SRV.

[0092] It should be noted that in this embodiment, biomass is the sole heat source in the linear hearth furnace 2 and the SRV 4. Specifically, in this embodiment (though not necessarily in all embodiments), there is no electrically based heating system involving electrodes or any type of electromagnetic radiation (such as microwaves). Other embodiments of the invention may include electrically based heating systems.

[0093] For example, industrially produced oxygen 7 with a purity level of 95% or higher, generated by an air separation unit (ASU) (not shown), is injected into the top space of the SRV for the purpose of generating heat.

[0094] CO and char from the pool are partially combusted in SRV 4, producing approximately 65% ​​post-combustion SRV exhaust gas (meaning that approximately 65% ​​of the CO has been converted into CO2). The SRV exhaust gas is discharged via duct 57 extending from the exhaust hood 59 of SRV 4.

[0095] The main molten product stream from SRV 4 is hot metal 8 discharged via the overflow weir 61 of SRV 4. Following the conventional HI SRV-based pathway, hot metal 8 is expected to have 4.0% C and low concentrations of impurities (particularly silicon, manganese, and phosphorus). It can be cast into pigs for transport as chill feed to EAF-based steel mills, or used as hot metal and directly processed into steel in a co-located downstream steelmaking furnace.

[0096] Another molten product stream from SRV 4 is molten slag 9, which is periodically discharged from SRV 4 via pipeline 63. This material is similar to blast furnace slag in terms of availability in cement manufacturing or other applications typically associated with such slag.

[0097] The hot SRV exhaust gas is first cooled from about 1500°C to about 600°C in a vapor membrane hood 65, and then wet-washed and cleaned in unit 67 to produce a calorific value of about 3.15 MJ / Nm³. 3 The fuel gas 11 (based on LHV) is split into three equal streams and sent to three LHF 2 (only one is shown in the figure), where it is burned in a set of top space burners 69 in chamber 71 of LHF 2.

[0098] The LHF 2 shown in the figure has 16 burners 69 spaced apart along its length. It can be readily understood that the LHF 2 can have any suitable number of burners 69. In each LHF 2, air is fed via a heat exchanger 12 to generate preheated air 13 at a temperature of 400°C. The preheated air 13 is also added to the LHF burners 69 to generate heat for the preheating stage in the LHF.

[0099] The LHF 2 top space temperature is maintained at approximately 1200°C–1400°C, and heat is transferred to the briquetting bed primarily via radiation generation to minimize briquetting carbon oxidation and dust generation.

[0100] The rightmost burner 69 (closest to the unit's heat exhaust end 45, and identified by the number 16 in the diagram) receives an additional 2000 Nm of heat. 3 / h natural gas 14, to provide the necessary heat at the starting point of the combustion gas pipeline.

[0101] The hot exhaust gas is generated along the length of the chamber of LHF 2 and moves to the left side of LHF 2, as shown in the figure.

[0102] At the exhaust end of LHF 2 (shown on the left in the diagram), the exhaust gas has an afterburning rate of approximately 94%, meaning that most of the CO has been burned into CO2, but a small amount of residual CO remains. This exhaust gas is supplied via line 75 to afterburner 15, where additional preheated air is added and complete combustion is achieved. From here, the fully combusted exhaust gas is conveyed to boiler 16 via heat exchanger 12 in line 77.

[0103] If the hot metal from SRV 4 is directly processed into steel in the BOF workshop, there is an opportunity to capture and use the BOF gas in boiler 16 as supplemental fuel (along with a very small amount of natural gas for ignition flame maintenance). Heat is extracted from the hot flue gas in boiler 16, and in this example, 132 MW of electricity is generated. This electrical power is well sufficient to power the entire facility, including the air separation unit that supplies oxygen to SRV 4.

[0104] The flue gas from boiler 16 is dusted in bag filter 79. From there, the clean flue gas 17 is discharged into the atmosphere.

[0105] exist Figure 2 The second embodiment shown is relative to the above regarding Figure 1 The only significant difference described is the capture of CO2 from the boiler flue gas flow for containment (CCS).

[0106] refer to Figure 2 , from Figure 1The warm gas 20 of LHF 2 shown in the diagram and the hot-burning BOF gas / air 21 are combusted and provide heat to the steam loop, typically identified by numeral 81. Boiler flue gas from loop 81 is conveyed via line 83 to a bag filter 85 at 220°C. Details of the flue gas are shown in box 23 in the figure. The flue gas passes through the bag filter 85 and is then pressurized to 0.2 bar gauge pressure in fan 24. It is then conveyed via gas cooler 25 to amine scrubber 26, where most of the CO2 is transferred from the gas to the amine-containing scrubbing liquid. The absorbed CO2 is released back into the gas phase in stripper 27, from where it is conveyed to cleaning and compression equipment 28 for delivery to suitable CO2 sequestration resources.

[0107] Stripping tower 27 requires a significant amount of low-grade heat to evaporate the absorbed CO2. This heat is transferred from the main steam loop to reboiler 29. The main loop effectively uses the amine reboiler 29 as a condenser at 5 bar absolute pressure, but this sacrifices steam cycle efficiency and generates only 82.7 MW of electricity (compared to 132 MW in Example 1). Therefore, the entire plant requires an input of approximately 96 MW of electricity (to offset the 302 t / h of CO2 sent to the CCS).

[0108] Without departing from the spirit and scope of the invention, the above description of... Figure 1 and Figure 2 The described implementation scheme has undergone many modifications.

[0109] Through examples, although the above is about Figure 1 and Figure 2 The described embodiments are very specific in terms of the values ​​of temperature and other parameters in the various flowcharts of the accompanying drawings, as demonstrated by the details in the drawings, but the invention is not limited to these specific operational data.

[0110] Similarly, the present invention is not limited to specific information regarding the linear hearth furnace 2 and the smelting reduction vessel 4, as well as other equipment shown in the figure.

[0111] The embodiments described are two or more possible operating examples of the process and apparatus of the present invention. Those skilled in the art will understand variations of these embodiments within the scope of the present invention. References

[0112] 1. PCT / AU99 / 00884 (WO2000 / 22176) “A process and apparatus for producing metals and metal alloys”, priority, October 14, 1988 2. U.S. Patent 6,989,042, “Direct Smelting Process and Apparatus”, Priority, April 17, 2000 3. U.S. Patent 8,221,675, “Smelt-reduction vessel and Cooler Therefor”, priority dated May 18, 2006. 4. U.S. Patent 9,175,907, “Direct Smelting Process and Apparatus”, priority, February 9, 2010. 5. Australian Patent 2011301784 (WO2012 / 034184) “Direct Smelting Process”, priority, September 15, 2011 6. U.S. Patent 9,359,656, “Direct Smelting Process”, Priority: February 9, 2012 7. PCT / AU2012 / 000293 (WO2012 / 126055) “Direct Smelting Process for HighSulphur Feed”, Priority, March 21, 2012 8. PCT / AU2012 / 001486 (WO2013 / 082658) “Starting a Smelting Process”, Priority, December 6, 2011 9. PCT / AU2012 / 001481 (WO2013 / 082653) “Starting a Smelting Process”, Priority, December 6, 2011 10. PCT / AU2012 / 001487 (WO2013 / 082659) “Starting a Smelting Process”, priority, December 6, 2011 11. PCT / AU2014 / 001098 (WO2015 / 081376) “Smelting Process and Apparatus”, Priority, December 4, 2014 12. PCT / AU2014 / 001146 (WO2015 / 089563) “Smelting Process and Apparatus”, Priority, December 19, 2014 13. Vogl, V et al., Assessment of hydrogen direct reduction for fossil-free steelmaking, Journal of Cleaner production 203 (218) 736-745 14. Strezov, V, Iron ore reduction using sawdust: experimental analysis and kinetic modelling, renewable Energy 31(12) 1892-1905, October 2006

Claims

1. A process for producing molten iron from iron ore and biomass using at least one hearth furnace and a smelting reduction vessel (SRV), the process comprising: (a) A compound comprising 40%-55% biomass (based on dry weight) of iron ore and biomass is supplied to a hearth furnace and the compound is heated, combustible gases released from the biomass in the compound are burned, and the iron ore in the compound is partially reduced, and a heated and partially reduced iron ore product is produced and discharged from the hearth furnace, wherein the product has a temperature in the range of 550°C-950°C and is pre-reduced to between 20% and 70% primarily by radiant heat from burners in the upper region of the hearth furnace. (b) The partially reduced iron ore product is supplied to the molten pool in the smelting reduction vessel through a solid injection gun, and the iron ore in the product is melted and reduced to molten iron; (c) Supplying industrially produced oxygen to the top of the smelting reduction vessel and partially combusting the waste gases produced by the reaction of the materials in the molten pool, and discharging the partially combusted and hot waste gases from the smelting reduction vessel, wherein the degree of afterburning is between 50% and 75%; and (d) Cooling and purifying the partially combusted and hot exhaust gas discharged from the smelting reduction vessel and using it as fuel gas in the hearth furnace.

2. The process according to claim 1, wherein the hot exhaust gas discharged from the furnace is further burned (incinerated) in the boiler to remove residual CO, and then used to generate steam when hot, and thereby generate electricity.

3. The process according to claim 1 or 2, wherein optionally after the steam for power generation is raised, the hot gas is cooled and dusted, then processed in a CO2 removal system such as an amine scrubber, and the resulting captured CO2 is sent to a geological storage facility.

4. The process according to claim 1, wherein for the purpose of controlling metallic carbon, a small amount of coal or biochar is co-supplied to the SRV such that it constitutes no more than 10% of the total carbon input of the SRV on an annual average basis.

5. The process according to claim 1, wherein a certain amount of natural gas or other combustible fuel is supplied to the product discharge end of the hearth furnace to supplement the combustible gas released from biomass when radiant heat is provided, wherein the total amount of such fuel does not exceed 3 GJ / ton of molten pig iron.

6. The process according to claim 1, wherein the composite of iron ore and biomass is in the form of briquettes.

7. The process according to claim 6, wherein the briquettes are formed by the iron ore fragments and biomass coming into close contact through compaction.

8. The process according to any one of the preceding claims, wherein the partially reduced iron ore product is injected into a molten pool through the solid injection gun at a temperature above 300°C.

9. The process according to claim 8, wherein the injection temperature is higher than 500°C.

10. An apparatus for producing molten iron from iron ore and biomass, comprising: (a) At least one hearth furnace comprising a compound feed inlet and a product outlet, means for conveying more than one compound along a path from the inlet to the outlet, a top space above the path, and more than one burner in the upper region of the top space, the hearth furnace being configured to produce a heated and partially reduced iron ore product from the compound, wherein the product has a temperature in the range of 550°C to 950°C and is pre-reduced to between 20% and 70% primarily by radiant heat from the burner. (b) A smelting reduction vessel for containing a molten pool and for melting and reducing the heated and partially reduced iron ore product from the hearth furnace, and for producing molten iron product and exhaust gas; and (c) A connection between the hearth furnace and the smelting reduction vessel, which is used to transfer at least a portion of the exhaust gas from the smelting reduction vessel to the burner of the hearth furnace for use as fuel gas for the burner.

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