A method and system for gasification co-production of reducing gas and biomass char for smelting

Abstract

The application provides a method and system for smelting by gasification co-production of reducing gas and biomass char, belonging to the field of blast furnace smelting. The method comprises: capturing carbon dioxide from blast furnace gas to obtain carbon dioxide gas and upgraded gas; carrying out gasification reaction of biomass raw material and carbon dioxide gas to obtain crude synthesis gas and biomass char; carrying out tar cracking and reforming of the crude synthesis gas to obtain refined synthesis gas; mixing and heating the refined synthesis gas and the upgraded gas to obtain high-temperature reducing gas; delivering the high-temperature reducing gas to a blast furnace tuyere for hydrogen-rich gas injection; and mixing and pulverizing the biomass char and blast furnace injection coal, and using the mixture for blast furnace injection. The carbon-neutral biomass resources and the carbon dioxide obtained by the carbon capture unit are efficiently converted into high-quality reducing gas, which is used for hydrogen-rich injection of the blast furnace, thereby reducing fuel consumption of the blast furnace smelting system, realizing recycling of carbon dioxide resources, and achieving the effect of reducing carbon dioxide emission.

Description

Technical Field

[0001] This application relates to the field of blast furnace smelting technology, and in particular to a method and system for gasification co-production of reducing gas and biochar for smelting. Background Technology

[0002] The blast furnace-converter long process is the dominant technology in current steel production. Its production process is accompanied by high carbon emission intensity, making it one of the major contributors to carbon emissions in the industrial sector.

[0003] To address the challenges of emission reduction, the steel industry is focusing on exploring key technological pathways, including carbon capture and utilization and hydrogen-rich blast furnace smelting. Among these, capturing carbon dioxide emitted during production and converting it into low-carbon reducing gas suitable for blast furnace smelting is considered a significant emission reduction technology. Biomass, as a zero-carbon renewable energy source, has the potential to react with carbon dioxide to produce syngas, making it possible to convert carbon dioxide into a metallurgical reducing agent. However, effectively coupling biomass utilization and carbon dioxide conversion into the blast furnace smelting system to construct an integrated process that achieves carbon recycling and reduces carbon emissions remains a technical challenge that needs to be addressed. Summary of the Invention

[0004] This application provides a method and system for gasification co-production of reducing gas and biochar for smelting, in order to solve the following technical problem: how to effectively couple biomass utilization and carbon dioxide conversion to the blast furnace smelting system, and construct an integrated process that can realize carbon recycling and reduce carbon emissions.

[0005] In a first aspect, embodiments of this application provide a method for gasification co-production of reducing gas and biochar for smelting, the method comprising: Carbon dioxide is captured from blast furnace gas to obtain carbon dioxide gas and upgraded gas; The biomass feedstock is reacted with the carbon dioxide gas to produce crude syngas and biochar. The crude syngas is subjected to tar cracking and reforming to obtain refined syngas; The refined syngas is mixed with the upgraded coal gas and heated to obtain high-temperature reducing gas; The high-temperature reducing gas is transported to the blast furnace tuyeres for hydrogen-rich gas injection. The biomass char is pulverized and mixed with blast furnace pulverized coal to obtain composite pulverized fuel, which is then used for blast furnace pulverization. The carbon dioxide produced by the blast furnace is captured for recycling.

[0006] Optionally, the biomass raw material includes: biomass pellets, selected from at least one of straw, corn cobs, branches or sawdust.

[0007] Optionally, the gasification reaction is carried out in a moving bed gasification reactor, and the gasification reaction adopts a catalytic gasification method; The vaporizing agent in the vaporization reaction is carbon dioxide and / or oxygen; The gasification reaction includes the following parameters: gasification temperature of 800℃~1000℃, pressure of 0.3MPa~2.0MPa, and gasifying agent consumption of 0.05~0.16.

[0008] Optionally, the tar cracking and reforming is carried out in a fixed-bed cracking reactor, and the tar cracking and reforming adopts a catalytic cracking method; The pyrolysis temperature of the tar cracking reforming is 700℃~850℃, and the pressure is 0.3MPa~2.0MPa; The tar content in the refined syngas is <25 mg / Nm³. 3 .

[0009] Optionally, the heat source for the gasification reaction comes from the combustion of blast furnace gas and / or the upgraded gas; The heat for the tar cracking and reforming comes from the heat carried by the gasification reaction; The gas pipeline between the gasification reaction and the tar cracking and reforming is insulated.

[0010] Optionally, the heating method for the mixture of refined syngas and upgraded coal gas is high-temperature plasma heating, the temperature of the heated mixture is 850℃~1250℃, and the energy medium for heating is green electricity.

[0011] Optionally, in the high-temperature reducing gas, the hydrogen gas fraction is >18%, the carbon monoxide volume fraction is >40%, the carbon dioxide volume fraction is <3%, and the nitrogen gas fraction is <35%.

[0012] Optionally, the mass proportion of biochar in the composite pulverized fuel is no more than 15%.

[0013] In a second aspect, embodiments of this application provide a system for gasification co-production of reducing gas and biochar for smelting, the system being adapted to the method described in any one of the first aspects, the system comprising: A blast furnace unit is used for smelting and producing molten iron, blast furnace slag, and blast furnace gas. A carbon capture unit, connected to the blast furnace unit, is used to capture carbon dioxide from the blast furnace gas and output carbon dioxide gas and upgraded gas. The gasification unit, connected to the carbon capture unit, is used to receive biomass raw materials and carbon dioxide gas and perform a gasification reaction to output crude syngas and biochar. A tar cracking unit, connected to the gasification unit, is used to upgrade the crude syngas and output refined syngas. The gas heating unit, connected to the tar cracking unit and the carbon capture unit, is used to mix and heat the refined syngas and the upgraded coal gas to generate high-temperature reducing gas, which is then sent back to the blast furnace unit for hydrogen-rich injection.

[0014] Optionally, the system further includes a dust removal unit disposed between the tar cracking unit and the gas heating unit; The gasification unit is a moving bed gasification reactor; The tar cracking unit is a fixed-bed cracking reactor; The gas heating unit is a high-temperature plasma heater.

[0015] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a method for gasification co-production of reducing gas and biochar for smelting. By efficiently converting carbon dioxide obtained from carbon capture units into high-quality reducing gas from carbon-neutral biomass resources, the gas is used for hydrogen-rich injection in blast furnaces. This reduces fuel consumption in the blast furnace smelting system, realizes the recycling of carbon dioxide resources, and achieves the effect of reducing carbon dioxide emissions. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic flow diagram of a method for gasification co-production of reducing gas and biochar for smelting, provided for embodiments of this application; Figure 2 This is a schematic diagram of the structure of a system for gasification co-production of reducing gas and biochar for smelting, provided in an embodiment of this application. Figure label: M1 - Blast furnace unit; M2 - Gasification unit; M3 - Tar cracking unit; M4 - Dust removal unit; M5 - Gas heating unit; M6 - Carbon capture unit; F1 - Iron ore; F2 - Coke; F3 - Pulverized coal; F4 - Hot air; F5 - Oxygen enrichment; F6 - Biomass; P1 - Molten iron; P2 - Blast furnace slag; P3 - Blast furnace gas; P4 - Biochar; P5 - Crude syngas; P6 - Decarbonized gas; P7 - Reducing gas. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "including" and "contains" as used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0021] Figure 1 This is a schematic flowchart illustrating a method for gasification co-production of reducing gas and biochar for smelting, provided as an embodiment of this application.

[0022] like Figure 1 As shown in the embodiments of this application, a method for gasification co-production of reducing gas and biochar for smelting is provided, the method comprising: Carbon dioxide is captured from blast furnace gas to obtain carbon dioxide gas and upgraded gas; The biomass feedstock is reacted with the carbon dioxide gas to produce crude syngas and biochar. The crude syngas is subjected to tar cracking and reforming to obtain refined syngas; The refined syngas is mixed with the upgraded coal gas and heated to obtain high-temperature reducing gas; The high-temperature reducing gas is transported to the blast furnace tuyeres for hydrogen-rich gas injection. The biomass char is pulverized and mixed with blast furnace pulverized coal to obtain composite pulverized fuel, which is then used for blast furnace pulverization. The carbon dioxide produced by the blast furnace is captured for recycling.

[0023] The core process logic of the method provided in this application lies in constructing a material and energy cycle with biomass as a carbon-neutral carrier and blast furnace gas carbon dioxide as the reaction medium, and deeply coupling it into the blast furnace smelting system to achieve carbon emission reduction. The functions of each step are as follows: Carbon dioxide capture (blast furnace gas): This step is the starting point of the cycle, separating CO2 from the blast furnace gas. Its functions are twofold: first, to obtain the key gasifying agent (CO2) required for subsequent gasification reactions; and second, to upgrade the blast furnace gas, reducing its CO2 concentration and increasing its calorific value as fuel gas.

[0024] Biomass carbon dioxide gasification: This is the core conversion step for realizing carbon resource utilization. Its function is to utilize the captured CO2 to undergo an endothermic gasification reaction with biomass, converting solid biomass and gaseous CO2 together into crude syngas rich in CO and H2, while simultaneously producing carbon as a byproduct. This step achieves the conversion of zero-carbon biomass and captured CO2 into syngas with reducing value.

[0025] Tar cracking and reforming: This step is a gas purification and upgrading step. Its function is to convert the heavy tar components that are difficult to remove from the crude syngas produced by gasification into smaller molecule syngas (such as CO and H2) through high-temperature catalytic cracking, thereby significantly reducing the tar content, avoiding blockage of subsequent pipelines and equipment, and obtaining refined syngas with stable composition and higher quality.

[0026] Mixing and heating: This step is the final stage in the preparation of reducing gas. Its functions are twofold: first, to mix refined syngas (high reducing power, low nitrogen) with upgraded coal gas (with certain calorific value and reducing power, but high nitrogen content) in a certain proportion to prepare a reducing gas composition and total amount that meets the requirements of blast furnace injection; second, to heat the mixed gas to a high temperature through heating (such as plasma) so that it can provide effective physical heat after being injected into the blast furnace and avoid fluctuations in furnace conditions.

[0027] High-temperature reducing gas injection: This step involves applying the previously prepared low-carbon reducing product to the core process of blast furnace ironmaking. Its function is to inject high-temperature reducing gas from the tuyeres into the blast furnace hearth, partially replacing expensive coke and pulverized coal, providing reducing agents (CO, H2), heat, and activating the hearth. Hydrogen-rich gas can also enhance indirect reduction, theoretically reducing fossil carbon consumption.

[0028] Biomass char production and injection: This step realizes the resource utilization of gasification solid products. Its function is to mix the biomass char produced as a byproduct of gasification with blast furnace pulverized coal to produce composite fuel, replacing part of the fossil coal powder for injection. As a zero-carbon fuel, biomass char can directly reduce the fossil carbon input in the injection process.

[0029] Carbon dioxide recycling and capture: This step constitutes a closed-loop carbon cycle in the entire process. Its function is to capture CO2 again from the newly generated blast furnace gas after the application of reducing gas and biochar. The captured CO2 can be reused in the gasification unit. This creates an internal carbon cycle of "capture-utilization-recapture" within the process, significantly reducing the system's demand for new fossil carbon sources and net carbon emissions into the atmosphere.

[0030] In some embodiments, the biomass feedstock includes: biomass pellets, selected from at least one of straw, corn cobs, branches, or sawdust.

[0031] Biomass raw material selection (straw, corn cobs, etc.): Common agricultural and forestry waste pellets are selected to ensure that the raw materials are widely available, low in cost, and have renewable and carbon-neutral properties, which is the basis for achieving green and low-carbon processes.

[0032] In some embodiments, the gasification reaction is carried out in a moving bed gasification reactor, and the gasification reaction employs a catalytic gasification method; The vaporizing agent in the vaporization reaction is carbon dioxide and / or oxygen; The gasification reaction includes the following parameters: gasification temperature of 800℃~1000℃, pressure of 0.3MPa~2.0MPa, and gasifying agent consumption of 0.05~0.16.

[0033] Reactor and method (moving bed, catalytic gasification): Moving bed facilitates full gas-solid contact and carbon product discharge; catalytic gasification can significantly reduce the reaction activation energy, and its core function is to greatly increase the syngas yield, reduce tar generation and reduce biochar by-products under relatively mild conditions (such as 900℃).

[0034] Gasifying agent (CO2 and / or O2): The main gasifying agent is the captured CO2, whose core function is to consume CO2 and produce CO; the addition of a small amount of O2 can provide some of the heat required for the reaction and maintain the reaction temperature.

[0035] Temperature (800~1000℃), pressure (0.3~2.0MPa), and gasifying agent specific consumption (0.05~0.16): This temperature range is the effective range to ensure the full progress of endothermic reactions such as Boudouard and to obtain syngas with high CO content. Moderate pressurization is beneficial for increasing the reaction rate and making the equipment more compact. Controlling the specific consumption of the gasifying agent optimizes carbon conversion efficiency and avoids excessive CO2 dilution of the syngas. For example, the vaporization temperature can be 800℃, 830℃, 850℃, 880℃, 900℃, 930℃, 960℃, 990℃, etc.; the pressure can be 0.3MPa, 0.5MPa, 0.7MPa, 0.9MPa, 1.2MPa, 1.5MPa, 1.8MPa, 2.0MPa, etc.; and the vaporization agent specific consumption can be 0.05, 0.065, 0.08, 0.095, 0.11, 0.125, 0.14, 0.16, etc.

[0036] In some embodiments, the tar cracking and reforming is carried out in a fixed-bed cracking reactor, and the tar cracking and reforming adopts a catalytic cracking method; The pyrolysis temperature of the tar cracking reforming is 700℃~850℃, and the pressure is 0.3MPa~2.0MPa; The tar content in the refined syngas is <25 mg / Nm³. 3 .

[0037] Reactors and methods (fixed bed, catalytic cracking): Fixed bed has a simple structure and is suitable for catalytic reactions; catalytic cracking is used to directionally break down large tar molecules into small combustible molecules, thus efficiently removing tar.

[0038] Temperature (700~850℃) and pressure (0.3~2.0MPa): This temperature range is sufficient to achieve efficient tar cracking in the presence of a catalyst, while avoiding excessive carbon deposition. The pressure is matched with the front-end gasification pressure to reduce system pressure loss. The cracking temperature for tar cracking and reforming can be 700℃, 725℃, 750℃, 775℃, 800℃, 820℃, 835℃, 850℃, etc.; the pressure can be 0.3MPa, 0.4MPa, 0.6MPa, 0.8MPa, 1.1MPa, 1.4MPa, 1.7MPa, 2.0MPa, etc.

[0039] Tar content (<25mg / Nm 3 The purpose of these strict limits is to ensure that the refined syngas meets the gas cleanliness requirements for subsequent long-distance transportation, heating, and blast furnace injection processes, and to prevent blockage and contamination.

[0040] In some embodiments, the heat source for the gasification reaction comes from the combustion of blast furnace gas and / or the upgraded gas; The heat for the tar cracking and reforming comes from the heat carried by the gasification reaction; The gas pipeline between the gasification reaction and the tar cracking and reforming is insulated.

[0041] Utilizing blast furnace gas or upgraded gas within the system for gasification heating, and using the sensible heat of the gasified gas for pyrolysis heating, maximizes the internal energy utilization efficiency of the system and reduces external energy consumption. Pipeline insulation reduces heat loss during the transport of high-temperature working fluids, maintaining the required reaction temperature.

[0042] In some embodiments, the heating method for the mixture of refined syngas and upgraded coal gas is high-temperature plasma heating, the temperature of the heated mixture is 850℃~1250℃, and the energy medium for heating is green electricity.

[0043] Reducing gas heating parameters (plasma, 850~1250℃, green electricity): High-temperature plasma heating is used to achieve rapid, ultra-high temperature heating of the gas. The temperature range of 850~1250℃ ensures that the reducing gas provides sufficient effective heat after being injected into the blast furnace. The use of green electricity as the energy medium is specified to avoid new carbon emissions from the use of fossil fuel electricity during the heating process, ensuring the low-carbon nature of the entire chain. For example, the temperature of the heated mixed gas can be 850℃, 920℃, 980℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃, etc.

[0044] In some embodiments, the high-temperature reducing gas has a hydrogen gas fraction >18%, a carbon monoxide volume fraction >40%, a carbon dioxide volume fraction <3%, and a nitrogen gas fraction <35%.

[0045] High-temperature reducing gas composition requirements (H2>18%, CO>40%, CO2<3%, N2<35%): This composition specification defines the standard for high-quality reducing gas. High H2 and CO content ensures strong reducing properties; low CO2 content prevents ineffective components from being introduced into the blast furnace; controlling N2 content maximizes the concentration and calorific value of the reducing gas, optimizing the injection effect. For example, the hydrogen volume fraction can be 18.5%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, etc.; the carbon monoxide volume fraction can be 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, etc.; the carbon dioxide volume fraction can be 0.5%, 1.0%, 1.5%, 1.8%, 2.2%, 2.5%, 2.7%, 2.9%, etc.; and the nitrogen volume fraction can be 20%, 23%, 26%, 29%, 31%, 32.5%, 33.5%, 34.5%, etc.

[0046] In some embodiments, the mass proportion of biochar in the composite pulverized fuel is no higher than 15%.

[0047] Biochar blending ratio (≤15%): This ratio limit is based on considerations of blast furnace injection process safety and combustion characteristics. Biochar and pulverized coal have different properties; controlling their blending within a certain ratio ensures the combustion performance, transportation stability, and blast furnace acceptance of the composite fuel, achieving a smooth substitution.

[0048] Figure 2 This is a schematic diagram of a system for gasification co-production of reducing gas and biochar for smelting, provided as an embodiment of this application.

[0049] Based on a general inventive concept, such as Figure 2 As shown in the figure, this application provides a system for gasification co-production of reducing gas and biochar for smelting. The system is adapted to the method described in any one of the above-mentioned methods, and the system includes: Blast furnace unit M1 is used for smelting and producing molten iron P1, blast furnace slag P2 and blast furnace gas P3; Carbon capture unit M6 is connected to the blast furnace unit M1 and is used to capture carbon dioxide from the blast furnace gas P3, and output carbon dioxide gas and upgraded gas. Gasification unit M2 is connected to carbon capture unit M6 and is used to receive biomass F6 raw material and carbon dioxide gas and perform gasification reaction to output crude syngas P5 and biochar F6. The tar cracking unit M3 is connected to the gasification unit M2 and is used to upgrade the crude syngas P5 to output refined syngas. The gas heating unit M5 is connected to the tar cracking unit M3 and the carbon capture unit M6. It is used to mix and heat the refined syngas and the upgraded coal gas to generate high-temperature reducing gas P7, which is then sent back to the blast furnace unit M1 for hydrogen-rich injection.

[0050] In some embodiments, the system further includes a dust removal unit M4 disposed between the tar cracking unit M3 and the gas heating unit M5; The gasification unit M2 is a moving bed gasification reactor; The tar cracking unit M3 is a fixed-bed cracking reactor; The gas heating unit M5 is a high-temperature plasma heater.

[0051] The system and method provided in this application have the following significant advantages: The core advantage of this application lies in the construction of an internal carbon cycle that uses carbon-neutral biomass as a medium to deeply couple blast furnace gas carbon capture, carbon dioxide resource conversion and blast furnace smelting, thereby realizing the systematic substitution of fossil fuels by renewable energy and the closed-loop utilization of carbon dioxide, thus significantly reducing carbon emissions in the long blast furnace-converter process.

[0052] Specifically, its advantages are reflected in two aspects: material flow and energy flow. In terms of material flow, this method separates carbon dioxide from blast furnace gas through a carbon capture unit and directly supplies it as a gasifying agent to the gasification unit for catalytic gasification with biomass feedstock. This design achieves targeted and quantitative resource-based conversion of captured carbon dioxide, transforming it together with carbon from biomass into refined syngas rich in carbon monoxide and hydrogen. This refined syngas is then mixed with upgraded gas produced by carbon capture and heated to form high-temperature reducing gas, which is injected back into the blast furnace, replacing some of the reduction and heating functions of coke and pulverized coal. Simultaneously, the biomass char produced as a byproduct of gasification is pulverized and reused in the blast furnace as part of the composite injection fuel. This series of steps constitutes an internal material cycle from the blast furnace exhaust to the blast furnace input: "carbon dioxide-syngas / biomass char-molten iron," significantly reducing the production unit's dependence on new fossil carbon sources and the system's net carbon emissions.

[0053] In terms of energy flow, this application optimizes energy utilization efficiency through system integration design. The heat required for the gasification reaction comes from the combustion of blast furnace gas or upgraded gas within the system, while the heat required for tar cracking directly utilizes the sensible heat of the high-temperature crude syngas generated by the gasification reaction, and losses are reduced through pipeline insulation. Furthermore, the final heating of the reducing gas employs high-temperature plasma technology powered by green electricity, ensuring the cleanliness of the final injection stage. This energy integration strategy reduces the external energy consumption of the process and maintains the low-carbon attributes of the entire chain.

[0054] In summary, this application, through innovative process coupling and system integration, not only converts carbon dioxide in blast furnace gas into valuable smelting reducing agents and fuels, but also utilizes carbon-neutral biomass to achieve carbon recycling. By working synergistically from the two dimensions of source substitution and process recycling, it provides an effective low-carbon technology path for blast furnace ironmaking, a high-carbon emission process.

[0055] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards / industry standards / the disclosure herein; if there are no corresponding national standards / industry standards / the disclosure herein, they are performed according to generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer.

[0056] Example The specific process flow of the system for smelting production based on biomass carbon dioxide gasification co-production of reducing gas and biochar provided in this embodiment is as follows: Figure 2 As shown: Blast furnace unit M1, through the input of iron ore F1, coke F2, and pulverized coal F3, along with hot blast F4 and oxygen-enriched gas F5, carries out smelting production, producing molten iron P1 and byproducts blast furnace slag P2 and blast furnace gas P3. Blast furnace gas carbon capture unit M6 removes carbon dioxide from the blast furnace gas and introduces it into gasification unit M2. Simultaneously, carbon-neutral biomass F6 is added to the gasification unit for biomass-carbon dioxide catalytic gasification, producing crude syngas P5 and byproduct carbon P4. The biomass carbon is dried, crushed, ground, and screened, and then injected into the blast furnace along with the pulverized coal. Crude syngas P5 enters tar cracking unit M3 for upgrading, and after dust removal unit M4, it enters gas heating unit M5. There, it is mixed with the upgraded syngas P6 obtained from carbon capture unit M6 in a certain proportion and heated to the required temperature before being injected into the blast furnace with hydrogen-rich gas. This application achieves green and low-carbon production in the blast furnace smelting system by injecting low-carbon, hydrogen-rich reducing gas, injecting biomass charcoal, and recycling part of the carbon dioxide.

[0057] Specifically, a certain blast furnace has a volume of 2600m³. 3 Daily iron production is 6735 tons, and blast furnace gas production per ton of iron is 1661 Nm³. 3 The composition of blast furnace gas is shown in Table 1. In this embodiment, hardwood biomass pellets were used, and their industrial analysis and elemental analysis results are shown in Table 2.

[0058] Table 1 Composition of blast furnace gas and decarbonized upgrading gas

[0059] Table 2. Industrial analysis and elemental analysis results of miscellaneous wood biomass pellets from the examples.

[0060] The process utilizes biomass carbon dioxide gasification technology to prepare reducing gas and biochar for blast furnace injection. Relevant gasification experimental schemes and process parameters are shown in Table 3, and the proportions of refined syngas and biochar obtained under different reaction conditions are shown in Table 4. This embodiment uses the gasification process parameters from Case 4 to prepare reducing gas and biochar through biomass carbon dioxide catalytic gasification.

[0061] Table 3 Biomass carbon dioxide gasification process parameters

[0062] Table 4. Biomass carbon dioxide gasification products

[0063] In this embodiment, 2600m 3100 Nm³ of high-temperature reducing gas is injected per ton of iron in the blast furnace. 3 The calculated reducing gas requirement is approximately 28,100 Nm³. 3 / h, this portion of the reducing gas is obtained by mixing the upgraded blast furnace gas after carbon capture (its composition is shown in Table 1) and the refined syngas obtained from the biomass carbon dioxide catalytic gasification according to Case 4. The CO2 obtained from the blast furnace gas capture is directly used for biomass carbon dioxide catalytic gasification. The calculated carbon capture capacity of the blast furnace gas is 10225 Nm³. 3 / h, the amount of upgraded coal gas obtained is approximately 8000 Nm³. 3 / h; the biomass feed rate is approximately 11.4 t / h. The carbon dioxide obtained from carbon capture is pressurized to 0.65 MPa and added to the gasification unit as a gasifying agent (the calculated gasifying agent specific consumption is approximately 0.11). The reaction temperature is 900℃. The resulting crude syngas directly enters the 850℃ tar cracking unit for further reaction. After dust removal, it can produce refined syngas (20100 Nm³) at a temperature of 800℃ and a pressure of 0.55~0.60 MPa. 3 / h, with a byproduct of 0.307t / h of carbon. After mixing the above-mentioned upgraded coal gas and refined syngas, a medium-temperature reducing gas with a temperature of about 550℃ is obtained. The composition of the reducing gas is shown in Table 5.

[0064] Table 5 100 Nm of iron injected per ton 3 Gas composition under reducing conditions

[0065] The 550℃ intermediate-temperature reducing gas is then heated to 1200℃ high-temperature reducing gas using 1800℃ high-temperature plasma powered by green electricity. This high-temperature reducing gas is then used for hydrogen-rich gas injection into the blast furnace tuyeres. Calculations show that the replacement ratio of the 1200℃ high-temperature reducing gas to coke is approximately 0.63 kg / Nm³. 3 The actual carbon reduction is 153 kg / tHM. Biomass char production is 0.307 t / h, and the proportion of pulverized fuel injected is approximately 0.7% of the composite injected fuel, resulting in a carbon reduction of approximately 4 kg / tHM, for a total carbon reduction of 157 kg / tHM. The biomass carbon dioxide gasification unit uses blast furnace gas for heating, with a heating efficiency of 80%, resulting in carbon emissions of approximately 59 kg / tHM. In summary, the overall carbon reduction effect of this embodiment is 98 kg / tHM, demonstrating a significant carbon emission reduction effect.

[0066] It should be noted that the energy medium required for the blast furnace gas carbon capture unit in this embodiment is clean energy such as green electricity, and its carbon emissions are almost zero.

[0067] Furthermore, one or more technical solutions in the embodiments of this application have at least the following technical effects or advantages: In this embodiment, by efficiently converting carbon dioxide obtained from carbon capture units into high-quality reducing gas from carbon-neutral biomass resources into hydrogen-rich gas for use in blast furnace hydrogen injection, the fuel consumption of the blast furnace smelting system is reduced, carbon dioxide resources are recycled, and carbon dioxide emissions are reduced.

[0068] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for gasification co-production of reducing gas and biochar for smelting, characterized in that, The method includes: Carbon dioxide is captured from blast furnace gas to obtain carbon dioxide gas and upgraded gas; The biomass feedstock is reacted with the carbon dioxide gas to produce crude syngas and biochar. The crude syngas is subjected to tar cracking and reforming to obtain refined syngas; The refined syngas is mixed with the upgraded coal gas and heated to obtain high-temperature reducing gas; The high-temperature reducing gas is transported to the blast furnace tuyeres for hydrogen-rich gas injection. The biomass char is pulverized and mixed with blast furnace pulverized coal to obtain composite pulverized fuel, which is then used for blast furnace pulverization. The carbon dioxide produced by the blast furnace is captured for recycling.

2. The method according to claim 1, characterized in that, The biomass raw materials include: biomass pellets, selected from at least one of straw, corn cobs, branches or sawdust.

3. The method according to claim 1, characterized in that, The gasification reaction is carried out in a moving bed gasification reactor, and the gasification reaction adopts a catalytic gasification method. The vaporizing agent in the vaporization reaction is carbon dioxide and / or oxygen; The gasification reaction includes the following parameters: gasification temperature of 800℃~1000℃, pressure of 0.3MPa~2.0MPa, and gasifying agent consumption of 0.05~0.

16.

4. The method according to claim 1, characterized in that, The tar cracking and reforming is carried out in a fixed-bed cracking reactor, and the tar cracking and reforming adopts a catalytic cracking method; The pyrolysis temperature of the tar cracking reforming is 700℃~850℃, and the pressure is 0.3MPa~2.0MPa; The tar content in the refined syngas is <25 mg / Nm³. 3 .

5. The method according to claim 1, characterized in that, The heat source for the gasification reaction comes from the combustion of blast furnace gas and / or upgraded gas; The heat for the tar cracking and reforming comes from the heat carried by the gasification reaction; The gas pipeline between the gasification reaction and the tar cracking and reforming is insulated.

6. The method according to claim 1, characterized in that, The heating method for the mixture of refined syngas and upgraded coal gas is high-temperature plasma heating, and the temperature of the heated mixture is 850℃~1250℃. The energy medium for heating is green electricity.

7. The method according to claim 1, characterized in that, In the high-temperature reducing gas, the hydrogen gas fraction is >18%, the carbon monoxide volume fraction is >40%, the carbon dioxide volume fraction is <3%, and the nitrogen gas fraction is <35%.

8. The method according to claim 1, characterized in that, The mass proportion of biochar in the composite pulverized fuel is no higher than 15%.

9. A system for gasification co-production of reducing gas and biochar for smelting, characterized in that, The system is adapted to the method according to any one of claims 1 to 8, the system comprising: A blast furnace unit is used for smelting and producing molten iron, blast furnace slag, and blast furnace gas. A carbon capture unit, connected to the blast furnace unit, is used to capture carbon dioxide from the blast furnace gas and output carbon dioxide gas and upgraded gas. The gasification unit, connected to the carbon capture unit, is used to receive biomass raw materials and carbon dioxide gas and perform a gasification reaction to output crude syngas and biochar. A tar cracking unit, connected to the gasification unit, is used to upgrade the crude syngas and output refined syngas. The gas heating unit, connected to the tar cracking unit and the carbon capture unit, is used to mix and heat the refined syngas and the upgraded coal gas to generate high-temperature reducing gas, which is then sent back to the blast furnace unit for hydrogen-rich injection.

10. The system according to claim 9, characterized in that, The system also includes a dust removal unit disposed between the tar cracking unit and the gas heating unit; The gasification unit is a moving bed gasification reactor; The tar cracking unit is a fixed-bed cracking reactor; The gas heating unit is a high-temperature plasma heater.

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