Biomass direct reduced iron

Abstract

A process for producing direct reduced iron ("DRI") from iron ore and biomass in a single stage fluidized bed includes: injecting (a) iron ore, (b) gaseous oxygen, and (c) a solid reducing agent comprising biomass into a reaction zone of a fluidized bed operating in a temperature range of 750°C - 850°C, and reducing the iron ore and forming DRI in the fluidized bed, and discharging DRI having a metallization of at least 70% from the fluidized bed.

Description

Technical Field

[0001] This invention relates to a process and apparatus for producing direct reduced iron (“DRI”) from iron ore and biomass.

[0002] This invention particularly relates to a process and apparatus for producing DRI in a fluidized bed system. This DRI can be used to manufacture hot metal, cold pig iron, or steel in an electric furnace.

[0003] The term "direct reduced iron" ("DRI") is understood herein to refer to iron produced by the direct reduction of iron ore (in the form of briquettes, lumps, pellets, or fine powders) to iron using a reducing gas at temperatures below the bulk melting temperature of the solid. The degree to which iron oxide within the ore is converted to metallic iron is called "metallisation" and is measured as the percentage of the mass of metallic iron produced by the conversion divided by the mass of all iron.

[0004] The present invention also relates to processes and equipment for producing molten metals (such as cold pig iron or steel) from DRI. background

[0005] Climate change is driving a fundamental reassessment of future options for iron and steel production.

[0006] Blast furnaces currently dominate primary iron production and emit high levels of CO2, approximately 1.8 to 2.0 t CO2 per metric ton of pig iron. These emissions are caused by the use of fossil fuels, particularly the need for coal (in the form of coke) as the basic feedstock for blast furnace operation.

[0007] An alternative method for blast furnaces is the direct reduction of solid iron ore using carbon monoxide and hydrogen derived from natural gas or coal. While such plants are considerably smaller in tonnage, there are a fair number of process versions compared to blast furnaces. Typically, plants for direct reduction of iron (outside India) tend to use gas-based shaft furnaces, where pellets of ore already hardened through a process known as “induration” are reduced, such as those in Midrex. TM and HYL TM Process.

[0008] Non-ball feeding methods (although seemingly limited in commercial success) are those that utilize fluidized bed technologies such as Circofer. TM Finmet TMand Finex TM The advantage of this method is that fine ores can be directly loaded into the process without the need to agglomerate the ore into small pellets (and subsequently consolidate them). To date, the most successful of these processes is probably the Finex process (now offered by Primetals Technologies), developed by Posco of South Korea and Siemens VAI Metal Technology of Austria. The key is a four-stage, bubbling fluidized bed reactor system in which the ore is countercurrently reduced to DRI by reducing gases produced from coal gasification.

[0009] A futuristic alternative to the above is to convert renewable (green) energy into hydrogen (especially when wind / solar costs are low), subsequently produce DRI (using hydrogen), and then smelt it in EAF to produce steel. This route has strong support (especially in Europe) and has the potential to be an important part of a global solution (1). However, it has limitations such as:

[0010] 1. The amount of electricity required is high (3000 kWh / t-4000 kWh / t), and the cost of green power needs to be low (or the carbon tax high) to make it cost-effective.

[0011] 2. Hydrogen consumption at DRIs is likely to be stable, while production may be cyclical (consistent with the availability of low-cost, off-peak renewable energy). This necessitates substantial buffering to balance supply and demand. Large-scale hydrogen storage and supply presents technological challenges. Underground salt caverns and depleted natural gas reservoirs appear to offer good potential. However, not all geographic locations are suitable for this type of hydrogen storage. Furthermore, suitable storage locations may not be close to iron and / or steel facilities, leading to logistical supply challenges.

[0012] 3. Only low-gangue ore types (or those that can be easily upgraded to remove gangue) can be used with the DRI / EAF combination; that is, the iron oxide content must be high and the amount of impurities low. EAF will be unfavorable for high-gangue ores (due to slag make), making them essentially uncompetitive as DRI feed to EAF. This means that many 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.

[0014] When in use, the combustion of fossil fuels or biomass releases CO2. However, when fast-growing plants are the source of biomass, they are primarily carbon-neutral energy sources (because almost the same amount of CO2 is absorbed as the plant regenerates through photosynthesis).

[0015] To date, there is no large-scale commercial ironmaking process that directly uses biomass.

[0016] Previous attempts to incorporate biomass into processes originally designed for coal, such as blast furnaces and coke ovens, have been negligible at best and generally quite disappointing in terms of overall CO2 impact. This is largely because the properties of biomass are significantly different from those of coal. To successfully utilize biomass, it is necessary to redesign processes around its fundamental properties.

[0017] Biomass can take many forms, but avoiding competition with food production is a key issue. Examples of biomass that may meet such criteria include elephant grass, bagasse, wood waste, excess straw, duckweed, and seagrass / macroalgae. The availability of such biomass varies significantly from one geographic location to another and will likely be a significant factor determining the size and location of any future biomass-based ironworks (given the volume of material required and the economic challenges of transporting such materials over long distances).

[0018] Multiple laboratory-scale studies (2) 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 expected by first principles. While the reasons may be unclear, the result serves as a technological "sweet spot." The technological challenge is how to achieve this efficiently on a large scale.

[0019] There are many possible methods.

[0020] An attempt at such a method is described in international application PCT / AU2017 / 051163A in the name of the applicant. It involves briquetting ore and biomass, then using a furnace, such as a linear or rotary hearth furnace (or rotary kiln), to preheat the material to at least 400°C, thereby devolatileitizing the biomass and removing any bound water from the ore. If this preheating reaches about 800°C-900°C, under such conditions, the ore pre-reduction is expected to reach about 40%-70%. This is followed by a microwave treatment stage (in a non-oxidizing atmosphere), where the briquettes are heated to about 1000°C-1100°C and further reduced (using residual biochar), where the reduction is typically about 90%-95%, and in some cases up to almost complete metallization. This DRI can then be fed into an open-arc furnace or induction furnace to produce pig iron.

[0021] This invention is an alternative method for producing DRI.

[0022] The above description should not be regarded as an endorsement of common knowledge in Australia or elsewhere.

[0023] Overview of this disclosure

[0024] This invention is based on the use of a circulating fluidized bed system with biomass feed and completely avoids the ore-biomass briquetting step. Certain types of biomass considered poor candidates for briquetting may be particularly well-suited to this process.

[0025] More specifically, the present invention is based on an inventive modification of the known process “Circofer” as described in references (3) and (4). These documents describe a coal-based method for producing DRI in a circulating fluidized bed (CFB) that uses one or more downward-facing oxygen nozzles to generate heat for the process while allowing the lower region of the bed to maintain reducing conditions suitable for DRI production. This process has been extensively tested using coal as a reducing agent at a pilot plant in Frankfurt am Main, Germany.

[0026] This invention is based on the understanding that, with biomass feed, different operating parameters than those used in the Circofer process can be employed, and these different operating parameters do not depend on the presence of a significant percentage of carbon particles in the bed as required in the Circofer process. This point is further discussed below under the heading "Differences between this invention and the Circofer process".

[0027] In summary, the present invention provides a process for producing direct reduced iron (“DRI”) from iron ore and biomass in a single-stage fluidized bed, the process comprising: injecting (a) iron ore, (b) gaseous oxygen and (c) a solid reducing agent comprising biomass into a reaction zone of a fluidized bed operating in a temperature range of 750°C to 850°C, reducing the iron ore in the fluidized bed to form DRI, and discharging DRI having a metallization rate of at least 70% from the fluidized bed.

[0028] The term "single-stage" is understood herein to mean that a gas and a solid are brought into contact with each other in a fluidized bed in such a way that they are mixed together and remain at (or close to) a single common operating temperature. The exhaust gas and solids are then removed from the fluidized bed, wherein the exhaust gas temperature is at least as high as the solid temperature.

[0029] The present invention also provides a process for producing direct reduced iron (“DRI”) from iron ore and biomass in a fluidized bed as a single-stage operation, the process comprising:

[0030] (a) Iron ore is fed into a fluidized bed having (i) a lower region having a higher volume concentration of DRI relative to the rest of the bed and operating at a temperature of 750°C–850°C, (ii) an intermediate region having a lower concentration of DRI and a higher concentration of carbon relative to the lower region, and (iii) an upper region relatively low in both DRI and carbon.

[0031] (b) A solid reducing agent comprising at least 80% by weight of dried biomass is pneumatically injected into the lower region of the bed (typically, the moisture content of the dried biomass is typically less than about 20%-30% by weight), and

[0032] (c) Injecting oxygen via one or more generally downward-facing nozzles extending into the fluidized bed above the DRI-rich region, and

[0033] Iron ore is reduced in a fluidized bed to form DRI, and the DRI is discharged from the fluidized bed, which typically has a metallization rate of at least 70%.

[0034] The term "dry weight" is understood in this document to refer to the weight of biomass after it has been dried using standard techniques. Many standards may exist for biomass, generally revolving around heating the biomass to 105°C and measuring its weight before and after drying. One such standard is ISO 18134-3:2015. Sometimes, for lignocellulosic biomass, "dry weight" is referred to as "oven-dried tonne" (odt).

[0035] A fluidized bed can be a segmented fluidized bed, which is an operation that creates a concentration gradient of a given solid material in the fluidized bed, where a higher concentration of solid material is at the bottom of the fluidized bed, a medium concentration of solid material is in the middle of the fluidized bed, and a lower concentration of solid material is at the top of the fluidized bed.

[0036] A fluidized bed can be a separated fluidized bed, that is, an operation in which finer, lower-density particles are separated to the top of the fluidized bed and coarser, higher-density particles are separated to the bottom of the fluidized bed.

[0037] The process may include selecting operating conditions such as feed rate, particle size of solid feed material, gas velocity, and fluidized bed size, such that the temperature in the lower region is 800°C-850°C.

[0038] Step (b) may include selecting a solid reducing agent containing at least 85% by weight of dried biomass.

[0039] Step (b) may include selecting a solid reducing agent that comprises at least 90% by weight of dried biomass.

[0040] A fluidized bed can be a circulating fluidized bed.

[0041] A fluidized bed can be a bubbling fluidized bed.

[0042] The process may include injecting iron ore in the form of fine powder.

[0043] The process may include preheating the iron ore before injecting it into the fluidized bed.

[0044] The process may include drying the biomass at a solid temperature below 250°C prior to injection.

[0045] Preferably, feed rate disturbances during biomass injection are avoided. The reasons for this preference are further discussed below under the heading "Differences between the Invention and the Circofer Process".

[0046] By way of example, the process may include controlling the injection of the reducing agent so that the instantaneous deviation of the mass flow rate is less than 15% of the average time-average flow rate measured by the pressure drop of the spray gun, typically less than 10%.

[0047] The process may include injecting a reducing agent in the form of a relatively free-flowing powder, which is suitable for smooth pneumatic injection.

[0048] The oxygen injection step (c) may include injecting oxygen as pure oxygen, as part of air, or as part of oxygen-enriched air.

[0049] The fluidized bed pressure drop (excluding the gas distributor pressure drop) from the top surface of the gas distributor to the inlet of the cyclone separator of the fluidized bed can be at least 220 mbar.

[0050] The process may include injecting biomass such that the resulting plume passes through a fluidized bed with a pressure drop of at least 200 mbar (from the calculated bottom of the biomass injection plume to the cyclone separator inlet).

[0051] The process may include further reduction of the DRI from the fluidized bed in a microwave oven with a non-oxidizing atmosphere.

[0052] The process may include forming a blend of a solid containing a fixed carbon material and DRI from a fluidized bed, and then feeding the blend into a microwave oven to promote further reduction of the DRI.

[0053] The process can also include melting DRI in an electric furnace.

[0054] The present invention also provides an apparatus for producing direct reduced iron (“DRI”) from iron ore and biomass, the apparatus comprising a fluidized bed having a reaction zone and an inlet for injecting (a) iron ore, (b) gaseous oxygen and (c) a solid reducing agent comprising biomass into the reaction zone, the reaction zone being adapted to operate in a temperature range of 750°C to 850°C for reducing iron ore in the fluidized bed and forming DRI.

[0055] A fluidized bed may include a lower region, a middle region, and an upper region. The lower region has a higher volume concentration of DRI relative to the rest of the bed and operates at a temperature of 750°C–850°C. The middle region has a lower concentration of DRI and a higher concentration of carbon relative to the lower region. The upper region is relatively low in both DRI and carbon during use.

[0056] The equipment may include a pneumatic system for injecting a solid reducing agent into the lower region of a fluidized bed, the solid reducing agent comprising, for example, at least 80% by weight of dried biomass.

[0057] The device may include one or more downward-facing nozzles for injecting oxygen into the fluidized bed.

[0058] The equipment may include a gas distribution device for injecting fluidizing gas into the lower region of the fluidized bed.

[0059] The present invention also provides a process and apparatus for producing molten metal (such as cold pig iron or steel) from DRI, wherein the DRI is derived from the process and apparatus for producing DRI described above. Brief description of the attached diagram

[0060] The invention is further described by way of example with reference to the accompanying drawings, in which:

[0061] Figure 1 This is a schematic diagram of one embodiment of a process and apparatus according to the present invention for producing direct reduced iron (“DRI”) from iron ore and biomass, said process and apparatus including a biomass-feed fluidized bed system; and

[0062] Figures 2-4 The illustration is for use in, as shown in the invention. Figure 1 The process flow diagram describes an embodiment of a process and equipment for producing direct reduced iron (“DRI”) from iron ore and biomass in a fluidized bed and then producing hot metals from DRI.

[0063] Description of the implementation plan

[0064] As mentioned above, broadly speaking, the present invention provides a process and apparatus for producing direct reduced iron (“DRI”) from iron ore and biomass, comprising a single-stage fluidized bed operating in a temperature range of 750°C–850°C, typically 800°C–850°C, wherein iron ore, gaseous oxygen and biomass are injected into the reaction zone of the fluidized bed.

[0065] Figure 1 This is a schematic diagram of one embodiment of the fluidized bed process and fluidized bed equipment for DRI production according to the present invention.

[0066] Reference Figure 1 Generally, fluidized bed equipment identified by the number 23 includes a fluidized bed with three zones: (i) a lower zone rich in DRI (Zone A), which has a higher volumetric concentration of DRI in use compared to the rest of the bed and operates at a temperature of 750°C–850°C; (ii) an intermediate zone (Zone B), which has a higher carbon content in use compared to the lower zone; and (iii) a top space (Zone C), which is relatively poor in terms of DRI and carbon in use compared to the other zones.

[0067] A fluidized bed can be either bubbling (lower gas velocity) or circulating (higher gas velocity). It can be any other suitable fluidized bed.

[0068] The fluidized bed includes an outlet 7 for process exhaust gases from the fluidized bed in the upper section of zone C.

[0069] The fluidized bed apparatus 23 also includes a cyclone separator (D) that separates dust from the process exhaust gas from outlet 7 and discharges the cleaned exhaust gas via outlet 6. Cyclone separator D returns a portion of the dust to the fluidized bed, whereby the returned dust is supplied to zone A via inlet 8.

[0070] The fluidized bed includes a suitable gas distribution device 9 for injecting fluidizing gas 4 into the lower section of zone A. By way of example, this gas is typically a mixture of hydrogen and carbon monoxide derived from clean (and reheated) process waste gas discharged from cyclone separator D.

[0071] The fluidized bed includes nozzle 3 (or more nozzles) for injecting oxygen into zone C of the fluidized bed. As shown in the figure, the nozzle has a vertically extending, downward-guided outlet. It should be noted that the injection angle can be any suitable downward-extending angle.

[0072] The fluidized bed includes an inlet (or multiple inlets) for injecting fine iron ore powder into zones A and / or B of the bed. Optionally, the fine iron ore powder is preheated in external devices (e.g., a venturi contacting device and an additional cyclone separator). The maximum size of this feed iron ore powder is typically 3 mm–6 mm. The ore can be pre-dried externally before being allowed to enter the preheating system.

[0073] The fluidized bed includes an inlet (or multiple inlets) for pneumatically injecting a dry, shredded / powdered reducing agent in the form of biomass 2 into the lower region of DRI-rich zone A. Biomass pyrolysis occurs rapidly as the material is heated, resulting in the "soot lubrication" effect described below.

[0074] In the use of fluidized bed equipment 23, fine iron ore powder, biomass and oxygen are injected into the fluidized bed, and the operating conditions are controlled so that zone A of the bed is in a temperature range of 750℃-850℃, typically 800℃-850℃.

[0075] By way of example, the operating conditions include feed rate, particle size of solid feed material, gas velocity, and fluidized bed size, such that the temperature in the lower region is 750°C-850°C, typically 800°C-850°C.

[0076] Under these conditions, iron ore is reduced to DRI through a combination of reducing gases from biomass, in-bed Boudouard reforming to CO, and reducing gases (mainly CO and H2) from the bottom feed. DRI product 5 is removed from the lower section of Zone A via an outlet.

[0077] The chemical reaction in Zone A is endothermic. To maintain the bed at the desired temperature, heat must be supplied. This comes from oxygen injection via downward-directed nozzles in the lower part of Zone C. The oxygen combusts locally available process gases (CO and H2), and the resulting hot flue gas flows downwards toward Zone A. Heat transfer from this hot gas to the particles in Zones A and B provides the necessary heat transfer to maintain Zone A at the desired temperature.

[0078] The metallization rate of DRI produced in a fluidized bed can be adjusted according to the needs of downstream processing options by appropriately selecting the feed material, feed rate, feed temperature, and temperature in the fluidized bed.

[0079] DRI product 5 can be further reduced in a second fluidized bed (not shown) or a series of continuous fluidized beds (not shown), or it can be directly fed into an electric heating furnace or an electric melting furnace (not shown).

[0080] Figures 2-4 The illustration is for use in the present invention. Figure 1 The process flow diagram of an embodiment of the fluidized bed reactor 23 described herein, which produces direct reduced iron (“DRI”) from iron ore and biomass and then produces hot metal from DRI in an electric heating furnace or electric melting furnace.

[0081] Figures 2-4 The data in the figure comes from the model developed by the applicant.

[0082] Figure 2 The process and equipment shown in the diagram illustrate an implementation scheme using a single-stage circulating fluidized bed (CFB) for the production of 10,000 tons / year of pig iron.

[0083] exist Figure 2 In the fluidized bed equipment 23, regions A, B, C, and D are interconnected, such as... Figure 1 The regions shown only represent regions with different concentrations of solids and gases.

[0084] According to the definition of a single-stage fluidized bed above, gas and solid are considered to be mixed with each other in the fluidized bed device 23.

[0085] Before feeding 225.4 t / h of wet iron ore into the two-stage Venturi preheating system 25, the iron ore is dried in a fluidized bed dryer 21 (separate from and independent of the fluidized bed unit 23), where it is heated to 832°C. This preheated material is then fed via inlet 2 into the system. Figure 1 The main circulating fluidized bed (“CFB”) described.

[0086] Miscanthus (elephant grass) biomass is chopped, dried in dryer 31, and fed into the bottom of the CFB via inlet 2. The biomass received as is (166.5 t / h) has a moisture content of 20%, while the injected biomass has a moisture content of 10%.

[0087] Fluidized gas 4 (229 kNm) 3 / h, at 800°C) is fed into the bottom of the CFB via gas distribution device 9 (see Figure 1 ).

[0088] Oxygen (41.1 kNm) 3 / h) is injected into the intermediate section via the downward-facing oxygen nozzle 3, as shown.

[0089] Under the above conditions, the iron ore powder, biomass, and oxygen injected into the CFB lead to... Figure 1 The formation of zones A, B, C, and D is described, with zone A located in the temperature range of 750℃-850℃, typically 800℃-850℃.

[0090] The top gas discharged from the fluidized bed via outlet 7 passes through a two-stage ore preheating Venturi preheating system 25 and is transferred as stream 27 to scrubber assembly 29, where it is scrubbed to remove (i) water and (ii) carbon dioxide before 80% of the top gas is reheated and returned to the CFB as fluidized gas.

[0091] The product DRI with a 70% metallization rate (152.1 t / h) is removed from the CFB via outlet 5 and conveyed in pipeline 53 to open-arc electric furnace 33. It is melted in the furnace (with the addition of 14.7 t / h of coke shavings 35 and 11.6 t / h of calcined lime 37) to produce 126.9 t / h of pig iron 39 and 28.2 t / h of slag 41.

[0092] Sludge and effluent from the CFB loop are combusted in a separate fluidized bed boiler 45 to generate power (157.6 MWe). Additional (untreated or simply shredded) biomass is also fed into boiler 45 (100 t / h) to generate sufficient power to keep the overall process power-neutral (no significant demand on input power). A small amount of limestone may be added to fluidized bed boiler 45 to capture sulfur as CaSO4.

[0093] Figure 3 The implementation plan for the process and equipment in the project is as follows: Figure 2 The implementation scheme differs in that the DRI from the CFB is first passed to a low-speed bubbling fluidized bed system 47, where the DRI is further reduced to a metallization rate of 92.5%. From here, the DRI is passed to... Figure 2 The described open-arc electric melting furnace 33.

[0094] Figure 4 The implementation plan for the process and equipment in the project is as follows: Figure 2 The difference in the implementation scheme is that the DRI from CFB is fed into the relevant... Figure 2 The described open-arc electric furnace 33 is previously processed in a microwave oven 49. Coke dust 51 is added to the DRI as it enters the microwave oven 49 to provide a reducing agent.

[0095] Differences between this invention and the CIRCOFER process

[0096] As mentioned above, this invention is an inventive modification of the known process “Circofer” as described in references (3) and (4). It should be noted that reference to these references does not imply an admission that the disclosures in the references are part of common general knowledge in Australia or elsewhere.

[0097] The key differences between the Circofer process and the process of this invention are as follows:

[0098] 1. This process is based on the use of biomass rather than coal.

[0099] 2. This process operates at temperatures outside the operating temperature range of the Circofer process.

[0100] In the Circofer process, the core reactor operates with the following fluidized bed: (i) a lower region rich in sandy / particulate DRI, (ii) a middle region richer in carbon, and (iii) an upper region, i.e., a top space that is depleted in phase (mainly gas with carbon dust and a very small amount of iron-rich dust).

[0101] The key to operating the Circofer process is the injection of coal at the bottom of the bed, maintained at approximately 900°C–950°C. At this location, the fluidized particles (primarily) consist of granular / sandy DRI. Without the coal injection at the bottom of the bed, such particles would rapidly become viscous and form agglomerates, and the process would then cease. However, the coal particles are pneumatically injected into this region and rapidly heated, releasing the products of coal pyrolysis (volatiles, soot, reducing gases). It is believed that these volatile materials readily crack on the surface of the thermally fluidized DRI particles, coating them with a soot-like substance that provides a barrier interface preventing the agglomeration of large quantities of DRI particles. This, along with the significant separation of DRI particles from each other by carbon particles, is why the Circofer process can operate at approximately 950°C with metallized granular DRI particles without adhesion.

[0102] In contrast, other fluidized bed reduction processes such as Finmet utilize granular metallized particles in a fluidized bed (without coal injection). TM Or Finex TM The process is limited to a maximum temperature of approximately 750°C-800°C to avoid adhesion.

[0103] The coal-based Circofer process cannot operate effectively at temperatures far below approximately 950°C. The main reason is that the Boudouard reaction (CO₂ + C → CO) must be activated in the main bed. This reaction becomes active at approximately 900-950°C, and if the process is too cold, the in-bed reforming of CO₂ to CO becomes too slow, and the DRI metallization rate decreases.

[0104] In the Circofer process, oxygen is injected at a high height in the reaction vessel (far above the bottom DRI-rich zone) in one or more downward-facing jets. The amount of oxygen is regulated to provide the necessary process heat. If mispositioned (too low), this oxygen jet can easily burn the DRI, causing accretion and halting the process. Sufficient distance (in a hydrodynamic sense) is needed for the main combustion process gases (CO and H2) plus carbon, where the resulting hot gas, depleted of oxygen, flows downward into the DRI-rich zone described above (for heat transfer). Inevitably, some finer DRI particles will be present in the oxygen flame—these particles are burned into FeO and (as very hot droplets) projected downward back into the DRI-rich mainstream bed. Upon contact with larger DRI particles, they melt, solidify, and subsequently remetallize. The result is a controlled agglomeration process in which fine iron ore particles are transformed into granular (sandy) DRI agglomerates with very low iron unit loss to dust.

[0105] The conventional thinking is that the Circofer process requires maintaining 10%-30% char (as char particles) in the main bed to help physically separate DRI particles at (typically) 950°C and prevent adhesion. If the injected coal produces fine char that rapidly decomposes into fine powder and is blown out of the system, this would lead to excessive coal consumption and reduced productivity. It is for this reason that the conventional thinking effectively discourages the use of biomass—according to this logic, biomass will not produce the desired char particles, and therefore a Circofer process using biomass will not work.

[0106] As mentioned above, the present invention is based on the understanding that biomass feed can be operated with different operating parameters than the Circofer process, and these different operating parameters do not depend on the presence of a significant percentage of carbon particles in the bed.

[0107] The applicant has recognized that, for the Circofer process, dependence on the presence of a significant percentage of carbon particles in the bed is unnecessary for the present invention for the following reasons:

[0108] 1. The Boudouard reaction in biomass is active at temperatures approximately 100°C lower than that in coal. This means the bed can operate at approximately 800°C–850°C and still produce sufficient in-bed CO2 reforming to produce CO.

[0109] 2. Using a main bed at 800℃-850℃, DRI particles will be inherently less sticky than they are in a normal Circofer system.

[0110] 3. By injecting biomass at the bottom and ensuring minimal feed rate deviation in time, pyrolysis and soot lubrication to coat particles (and prevent adhesion) can be promoted by making the DRI-rich portion of the bed deeper than the DRI-rich portion in the Circofer process, which would otherwise be otherwise. In the Circofer process, the bottom bed residence time (measured by dividing the vertical height of the lower dense bed by the apparent gas velocity) is typically about 1 second. For the process of this invention, this residence time will be about 1.5 to 2 times that time (about 1.5 to 2.0 seconds of residence time on the same basis). In practice, this means that the lower bed is physically about 1.5 to 2 times deeper, and the pressure drop is correspondingly higher.

[0111] The pyrolysis of coal and biomass differs. Given the higher moisture content of biomass, a longer bed residence time is typically required to achieve the necessary pyrolysis (and bed lubrication). This is why deeper, DRI-rich beds (and higher fluidized bed pressure drops) are usually necessary.

[0112] To maximize the lubrication effect of the soot, it is also preferable to avoid feed rate disturbances during biomass injection in the context of this invention. The soot coating on DRI pellets is a transient phenomenon, where surface carbon is exhausted (via the Boudouard reaction) as part of iron ore reduction. DRI pellets require a continuous replenishment of fresh surface soot / carbon coatings to avoid a more readily adherent "bare iron" surface. The transient nature of these coatings means that any interruption in the biomass feed can lead to "bare iron" within a very short time, and the process will be compromised. Therefore, a stable, uninterrupted biomass feed is preferred.

[0113] In any device / process according to the present invention, the key factors to be considered in order to minimize disturbances in the injected feed rate are feeder mechanics: (feeder type, nozzle arrangement, conveying conditions, biomass feed particle size measurement and moisture content).

[0114] Typically, industrial-scale injection systems are not designed to be perfectly smooth because (i) this is usually more expensive, and (ii) the processes discussed are generally able to tolerate some degree of variability without significant consequences. However, in this case, tolerance is low, and extra care will be taken in this regard.

[0115] Many modifications can be made to the implementation scheme described above without departing from the spirit and scope of the invention.

[0116] Through examples, although in terms of Figure 1The fluidized bed in the described embodiment is a separated fluidized bed, but the invention is not limited thereto and extends to any suitable type of fluidized bed.

[0117] By way of other examples, the present invention is not limited to Figures 2-4 The embodiments of the process and equipment for producing direct reduced iron (“DRI”) according to the present invention are shown in the figure.

[0118] Through another example, although about Figures 2-4 The described implementation scheme uses Miscanthus plants (elephant grass) as biomass processing, but the invention is not limited to this and extends to the use of any suitable biomass.

[0119] Through another example, although about Figures 2-4 The described implementation scheme uses a temperature of 800°C and 229 kNm 3 Fluidized bed operation at a flow rate of / h, but the invention is not limited thereto and extends to any suitable flow rate and temperature of the fluidizing gas.

[0120] Through another example, although about Figures 2-4 The described implementation scheme uses 41.1 kNm 3 The invention is not limited to oxygen injection operations per hour, but extends to any suitable flow rate.

[0121] References

[0122] 1. Vogl, V et al., Assessment of hydrogen direct reduction for fossil-free steelmaking, Journal of Cleaner production 203 (218) 736-745

[0123] 2. Strezov, V, Iron ore reduction using sawdust: experimental analysis and kinetic modeling, renewable Energy 31(12) 1892-1905, October 2006

[0124] 3. A Orth, H Eichberger, D Philp, and R Dry, U.S. Patent Application US2008 / 0210055A1, September 4, 2008

[0125] 4. A Orth, H Eichberger, D Philp and R Dry, WIPO International Publication No. WO2005 / 116280 A1.

Claims

1. A process for producing direct reduced iron (DRI) from iron ore and biomass in a single-stage fluidized bed, comprising injecting (a) iron ore, (b) gaseous oxygen and (c) a solid reducing agent comprising biomass into a reaction zone of a fluidized bed operating in a temperature range of 750°C-850°C, reducing the iron ore in the fluidized bed to form DRI, and discharging DRI having a metallization rate of at least 70% from the fluidized bed, the process characterized in that: (a) The fluidized bed is operated such that (i) the lower region of the fluidized bed has a higher volumetric concentration of DRI and an operating temperature of 750°C–850°C relative to the rest of the bed, (ii) the middle region of the fluidized bed has a lower concentration of DRI and a higher concentration of carbon relative to the lower region, and (iii) the upper region of the fluidized bed is relatively depleted in both DRI and carbon. (b) The solid reducing agent is pneumatically injected into the lower region of the bed, wherein the solid reducing agent comprises at least 80% by weight of dried biomass, and (c) Injecting oxygen via one or more downward-facing nozzles extending into the fluidized bed above the lower region.

2. The process according to claim 1, wherein the fluidized bed is a circulating fluidized bed.

3. The process according to claim 1, wherein the fluidized bed is a bubbling fluidized bed.

4. The process according to any one of the preceding claims includes injecting iron ore in the form of fine powder.

5. The process according to any one of claims 1-3, comprising preheating the iron ore before injecting it into the fluidized bed.

6. The process according to claim 4, comprising preheating the iron ore before injecting it into the fluidized bed.

7. The process according to any one of claims 1-3 and 6, comprising drying the biomass at a solid temperature below 250°C prior to injection.

8. The process according to claim 4, comprising drying the biomass at a solid temperature below 250°C prior to injection.

9. The process according to claim 5, comprising drying the biomass at a solid temperature below 250°C prior to injection.

10. The process according to any one of claims 1-3, 6 and 8-9, comprising controlling the injection of the reducing agent such that the instantaneous deviation of the mass flow rate is less than 15% of the average time-average flow rate measured by the pressure drop across the spray gun.

11. The process of claim 4, further comprising controlling the injection of the reducing agent such that the instantaneous deviation of the mass flow rate is less than 15% of the average time-average flow rate measured by pressure drop across the spray gun.

12. The process of claim 5, further comprising controlling the injection of the reducing agent such that the instantaneous deviation of the mass flow rate is less than 15% of the average time-average flow rate measured by pressure drop across the spray gun.

13. The process of claim 7, further comprising controlling the injection of the reducing agent such that the instantaneous deviation of the mass flow rate is less than 15% of the average time-average flow rate measured by pressure drop across the spray gun.

14. The process according to any one of claims 1-3, 6, 8-9 and 11-13, comprising injecting the reducing agent in the form of a relatively free-flowing powder, the relatively free-flowing powder being adapted for smooth pneumatic injection.

15. The process of claim 4, comprising injecting the reducing agent in the form of a relatively free-flowing powder, the relatively free-flowing powder being suitable for smooth pneumatic injection.

16. The process of claim 5, comprising injecting the reducing agent in the form of a relatively free-flowing powder, the relatively free-flowing powder being suitable for smooth pneumatic injection.

17. The process of claim 7, comprising injecting the reducing agent in the form of a relatively free-flowing powder, the relatively free-flowing powder being suitable for smooth pneumatic injection.

18. The process of claim 10, comprising injecting the reducing agent in the form of a relatively free-flowing powder, the relatively free-flowing powder being adapted for smooth pneumatic injection.

19. The process according to any one of claims 1-3, 6, 8-9, 11-13 and 15-18, wherein the pressure drop from the top surface of the gas distributor of the fluidized bed to the inlet of the waste gas cyclone separator of the fluidized bed is at least 220 mbar after excluding the pressure drop of the gas distributor.

20. The process of claim 4, wherein the pressure drop from the top surface of the gas distributor of the fluidized bed to the inlet of the waste gas cyclone separator of the fluidized bed is at least 220 mbar after excluding the pressure drop of the gas distributor.

21. The process according to claim 5, wherein the pressure drop from the top surface of the gas distributor of the fluidized bed to the inlet of the waste gas cyclone separator of the fluidized bed is at least 220 mbar after excluding the pressure drop of the gas distributor.

22. The process of claim 7, wherein the pressure drop from the top surface of the gas distributor of the fluidized bed to the inlet of the waste gas cyclone separator of the fluidized bed is at least 220 mbar after excluding the pressure drop of the gas distributor.

23. The process of claim 10, wherein the pressure drop from the top surface of the gas distributor of the fluidized bed to the inlet of the waste gas cyclone separator of the fluidized bed is at least 220 mbar after excluding the pressure drop of the gas distributor.

24. The process of claim 14, wherein the pressure drop from the top surface of the gas distributor of the fluidized bed to the inlet of the waste gas cyclone separator of the fluidized bed is at least 220 mbar after excluding the pressure drop of the gas distributor.

25. The process according to any one of claims 1-3, 6, 8-9, 11-13, 15-18 and 20-24, comprising injecting biomass such that the resulting plume passes through the fluidized bed from the calculated bottom of the biomass injection plume to the inlet of the exhaust gas cyclone separator with a pressure drop of at least 200 mbar.

26. The process of claim 4, comprising injecting biomass such that the resulting plume passes through the fluidized bed from the calculated bottom of the biomass injection plume to the inlet of the exhaust gas cyclone separator with a pressure drop of at least 200 mbar.

27. The process of claim 5, comprising injecting biomass such that the resulting plume passes through the fluidized bed from the calculated bottom of the biomass injection plume to the inlet of the exhaust gas cyclone separator with a pressure drop of at least 200 mbar.

28. The process of claim 7, comprising injecting biomass such that the resulting plume passes through the fluidized bed from the calculated bottom of the biomass injection plume to the inlet of the exhaust gas cyclone separator with a pressure drop of at least 200 mbar.

29. The process of claim 10, comprising injecting biomass such that the resulting plume passes through the fluidized bed from the calculated bottom of the biomass injection plume to the inlet of the exhaust gas cyclone separator with a pressure drop of at least 200 mbar.

30. The process of claim 14, comprising injecting biomass such that the resulting plume passes through the fluidized bed from the calculated bottom of the biomass injection plume to the inlet of the exhaust gas cyclone separator with a pressure drop of at least 200 mbar.

31. The process of claim 19, comprising injecting biomass such that the resulting plume passes through the fluidized bed from the calculated bottom of the biomass injection plume to the inlet of the exhaust gas cyclone separator with a pressure drop of at least 200 mbar.

32. The process according to any one of claims 1-3, 6, 8-9, 11-13, 15-18, 20-24 and 26-31, comprising further reducing the DRI from the fluidized bed in a microwave oven with a non-oxidizing atmosphere.

33. The process of claim 4, further reducing the DRI from the fluidized bed in a microwave oven with a non-oxidizing atmosphere.

34. The process of claim 5, further reducing the DRI from the fluidized bed in a microwave oven with a non-oxidizing atmosphere.

35. The process of claim 7, further reducing the DRI from the fluidized bed in a microwave oven with a non-oxidizing atmosphere.

36. The process of claim 10, further reducing the DRI from the fluidized bed in a microwave oven with a non-oxidizing atmosphere.

37. The process of claim 14, further reducing the DRI from the fluidized bed in a microwave oven with a non-oxidizing atmosphere.

38. The process of claim 19, further reducing the DRI from the fluidized bed in a microwave oven with a non-oxidizing atmosphere.

39. The process of claim 25, further reducing the DRI from the fluidized bed in a microwave oven with a non-oxidizing atmosphere.

40. The process of claim 32, comprising forming a blend of a solid comprising a fixed carbon material and DRI from the fluidized bed, and then feeding the blend into the microwave oven to promote further reduction of the DRI.

41. The process according to any one of claims 33-39, comprising forming a blend of a solid comprising a fixed carbon material and DRI from the fluidized bed, and then feeding the blend into the microwave oven to promote further reduction of the DRI.

42. The process according to any one of claims 1-3, 6, 8-9, 11-13, 15-18, 20-24, 26-31 and 33-40 further includes melting DRI in an electric furnace.

43. The process according to claim 4 further includes melting DRI in an electric furnace.

44. The process according to claim 5 further includes melting DRI in an electric furnace.

45. The process according to claim 7 further includes melting DRI in an electric furnace.

46. ​​The process according to claim 10 further includes melting DRI in an electric furnace.

47. The process according to claim 14 further includes melting DRI in an electric furnace.

48. The process according to claim 19 further includes melting DRI in an electric furnace.

49. The process according to claim 25 further includes melting DRI in an electric furnace.

50. The process of claim 32 further includes melting DRI in an electric furnace.

51. The process according to claim 41 further includes melting DRI in an electric furnace.

52. An apparatus for a process for producing direct reduced iron (DRI) from iron ore and biomass according to claim 1, comprising a fluidized bed apparatus including a fluidized bed having The reaction zone includes a lower region, a middle region, and an upper region suitable for operation at temperatures of 750°C to 850°C. A gas distribution device for injecting fluidizing gas into the lower region; An inlet, the inlet being used for (a) iron ore, (b) gaseous oxygen and (c) a solid reducing agent containing biomass; A pneumatic system for injecting the solid reducing agent into the lower region, the solid reducing agent comprising at least 80% by weight of dry biomass; as well as One or more downward-facing nozzles for injecting gaseous oxygen into the reaction zone.

53. The apparatus of claim 52, wherein at least one inlet for iron ore is located at a position higher than that of at least one inlet for a solid reducing agent containing biomass in the reaction zone.

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