A method and system for coupling biomass solid waste power generation and preparation of a biomass char blowing agent for steelmaking

Abstract

The application provides a method and system for coupling biomass solid waste power generation and preparing a biomass charcoal foaming agent for steelmaking, and relates to the field of solid waste treatment. The method comprises the following steps: a part of biomass solid waste is subjected to gasification through a gasification furnace to obtain gasification carbon and biomass gas, and another part of biomass solid waste is subjected to carbonization through a carbonization furnace; the carbonization comprises a low-temperature pyrolysis stage, a high-temperature pyrolysis stage and a slow cooling stage in sequence; the total amount of pyrolysis gas generated by the carbonization furnace is less than or equal to 15-25 Nm 3 / h, and the carbonization is ended to obtain pyrolysis carbon; and the gasification carbon and the pyrolysis carbon are compounded to obtain a biomass charcoal foaming agent for steelmaking. The method provided by the application realizes deep utilization of biomass solid waste by utilizing the obtained gas for power generation while preparing a biomass charcoal product suitable for an electric furnace steelmaking foaming agent.

Description

Technical Field

[0001] This application relates to the field of solid waste treatment, and in particular to a method and system for coupling biomass solid waste power generation with the preparation of biomass char foaming agent for steelmaking. Background Technology

[0002] Biomass solid waste has the characteristics of large stock and renewability, but the disposal of biomass solid waste is subject to problems such as high cost, the need to improve the value of the products obtained, and the general market prospects.

[0003] Biochar, as an ideal foaming agent and alternative carbon source in electric arc furnace (EAF) steelmaking, offers significant advantages in reducing carbon emissions. However, current biochar production faces a dual challenge: on the one hand, pyrolysis processes targeting biochar have low biomass feedstock conversion rates, requiring approximately 3 tons of feedstock to produce 1 ton of biochar, resulting in high costs and hindering its industrial application in EAF steelmaking; on the other hand, while biochar is produced as a byproduct in gasification processes targeting biomass fuel gas, its yield is relatively low, making it difficult to meet the large-scale demand for biochar in EAF steelmaking.

[0004] Therefore, the key to realizing the industrial-scale application of biochar in the field of electric arc furnace steelmaking lies in solving the problems of price and output of biochar produced from biomass solid waste, and obtaining biochar that can effectively reduce the power consumption in the electric arc furnace steelmaking process, reduce the biochar consumption per ton of steel, and significantly shorten the smelting time. Summary of the Invention

[0005] The purpose of this application is to provide a method and system for coupling biomass solid waste power generation and preparing biomass char foaming agent for steelmaking, so as to solve the above-mentioned problems.

[0006] To achieve the above objectives, this application adopts the following technical solution:

[0007] A method for coupling biomass solid waste power generation and preparing biochar foaming agent for steelmaking includes:

[0008] A portion of the biomass solid waste is gasified in a gasifier to obtain gasified char and biomass gas, while another portion of the biomass solid waste is carbonized in a carbonization furnace; the carbonization includes a low-temperature pyrolysis stage, a high-temperature pyrolysis stage, and a slow cooling stage performed sequentially.

[0009] During the low-temperature pyrolysis stage, a portion of the biomass gas is input into the combustion chamber of the carbonization furnace as a carbonization heat source, and the excess biomass gas is purified and sent to the generator set for power generation; all the pyrolysis gas generated by the carbonization furnace is recycled back to the combustion chamber of the carbonization furnace as a carbonization heat source; the pyrolysis temperature of the low-temperature pyrolysis stage is 300-400℃.

[0010] After the low-temperature pyrolysis stage is completed, the amount of biomass gas input into the carbonization furnace is increased so that the pyrolysis temperature rises to 600-700℃; when the pyrolysis gas can maintain the pyrolysis temperature at 600-700℃, all the biomass gas is sent to the generator set for power generation.

[0011] When the pyrolysis temperature is higher than 700°C, the high-temperature pyrolysis stage is completed. The pyrolysis gas of a specific volume flow rate is purified and sent to the generator set for power generation, so that the pyrolysis temperature gradually decreases. When the total amount of pyrolysis gas produced by the carbonization furnace is less than or equal to the specific volume flow rate, the supply of pyrolysis gas to the generator set is stopped.

[0012] The total amount of pyrolysis gas produced by the carbonization furnace is less than or equal to 15-25 Nm³. 3 When the carbonization time is / h, pyrolytic carbon is obtained at the end of the carbonization process;

[0013] The gasified char and the pyrolysis char are compounded to obtain a biomass char foaming agent for steelmaking.

[0014] Preferably, when the biomass solid waste is straw and the amount used is less than 1 ton, the specific volumetric flow rate is 55-70 Nm³. 3 / h, and for every additional ton of dosage, the specific volumetric flow rate increases by 30-40 Nm. 3 / h.

[0015] Preferably, when the biomass solid waste is wood-based and the amount used is less than 1 ton, the specific volumetric flow rate is 40-50 Nm³. 3 / h, and for every additional ton of dosage, the specific volumetric flow rate increases by 20-30 Nm. 3 / h.

[0016] Preferably, when the biomass solid waste is fruit shells and the amount used is less than 1 ton, the specific volumetric flow rate is 25-40 Nm³. 3 / h, and for every additional ton of dosage, the specific volumetric flow rate increases by 5-15 Nm³. 3 / h.

[0017] If the actual pyrolysis gas flow rate input to the generator set is lower than a specific flow rate range, the carbonization furnace temperature will be too high, resulting in a decrease in pyrolysis char production and inefficient utilization of the pyrolysis gas heat, thus increasing the cost of the composite biochar product. If the actual pyrolysis gas flow rate input to the generator set is higher than a specific flow rate range, the carbonization furnace temperature will be too low, leading to incomplete carbonization of the pyrolysis char, a significant increase in reactivity, and a decrease in carbon yield of the composite biochar product during electric arc furnace steelmaking.

[0018] Therefore, it is particularly important to clearly understand the relationship between the types of biomass feedstocks, their corresponding specific volumetric flow rates, usage amounts, the acquisition of pyrolysis char, and the quality of pyrolysis char production with the amount added during the steelmaking process and the carbon recovery rate.

[0019] Preferably, the fixed carbon content of the gasified char after removing moisture is not less than 80%.

[0020] Preferably, the fixed carbon content of the pyrolytic char after removing moisture is not less than 70%.

[0021] Preferably, the biomass char foaming agent for steelmaking includes a composite biomass char foaming agent for top feeding, a composite biomass char foaming agent for furnace wall and / or furnace door spray gun injection, and a composite biomass char foaming agent for slag internal injection.

[0022] In the composite biochar foaming agent for top feeding, the content of gasified carbon is 30-40 wt%, the total volatile matter content is not higher than 10 wt%, and the particle size of the composite foaming agent is 10-150 mm.

[0023] In the composite biomass char foaming agent used for spraying the furnace wall and / or furnace door, the content of gasified char is 20-30 wt%, the total volatile matter content is not higher than 15 wt%, and the particle size of the composite foaming agent is not greater than 3 mm.

[0024] In the composite biochar foaming agent for internal injection of slag, the content of gasified carbon is 10-20 wt%, the total volatile matter content is not higher than 20 wt%, and the particle size of the composite foaming agent is not greater than 5 mm.

[0025] Preferably, the moisture content of the biochar foaming agent for steelmaking is not higher than 3 wt%.

[0026] Preferably, the raw materials of the biomass char foaming agent for steelmaking also include a binder, and the amount of binder added is 0.5%-5% of the total mass of the gasified char and the pyrolytic char.

[0027] Preferably, the particle size of the biomass solid waste is 50-150 mm, and the moisture content is not higher than 15 wt%.

[0028] This application also provides a system for coupling biomass solid waste power generation and preparing biomass char foaming agent for steelmaking, comprising:

[0029] A gasifier is used to process biomass solid waste and produce gasified char and biomass gas.

[0030] A carbonization furnace is used to process biomass solid waste and produce pyrolysis char and pyrolysis gas.

[0031] A pyrolysis gas recovery device is used to recover pyrolysis gas from the carbonization furnace;

[0032] A gas purification device is used to purify the biomass gas and the pyrolysis gas from the pyrolysis gas recovery device;

[0033] A generator set for generating electricity using the biomass gas and the pyrolysis gas;

[0034] The gasifier is connected to the carbonization furnace and the gas purification device. The gas outlet of the carbonization furnace is connected to the inlet of the pyrolysis gas recovery device. The gas outlet of the pyrolysis gas recovery device is connected to the carbonization furnace and the gas purification device. The gas outlet of the gas purification device is connected to the generator set.

[0035] Preferably, the carbonization furnace is an intermittent carbonization furnace, and the capacity of a single intermittent carbonization furnace is not less than 4 cubic meters.

[0036] Compared with the prior art, the beneficial effects of this application include:

[0037] This application provides a method and system for coupling biomass solid waste power generation and preparing biochar foaming agents for steelmaking. Using biomass solid waste as raw material, the process involves heat treatment in a gasifier and a carbonization furnace to obtain gasified char and pyrolysis char, which are then compounded to obtain a biochar product suitable for electric arc furnace steelmaking foaming agents. This process uses pyrolysis gas and biomass gas as heat sources for the carbonization furnace, while excess pyrolysis gas and biomass gas are incorporated into a gas purification device before being delivered to the generator set. This enhances the utilization value of pyrolysis gas and biomass gas and achieves efficient and low-carbon biochar production. Furthermore, this method relies on existing biomass power plant facilities, requiring only the addition of a pyrolysis system and a pretreatment system, resulting in low equipment investment and significantly reducing biochar production costs. In addition, the biochar product prepared by this method has a higher fixed carbon content compared to traditional pyrolysis biochar, effectively reducing energy consumption during electric arc furnace steelmaking, lowering biochar consumption per ton of steel, and significantly shortening smelting time. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0039] Figure 1 This is a schematic diagram of a system for coupling biomass solid waste power generation and preparing biomass char foaming agent for steelmaking, as provided in the embodiment. Detailed Implementation

[0040] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0041] Example 1

[0042] like Figure 1 As shown, this embodiment provides a system for coupling biomass solid waste power generation and preparing biomass char foaming agent for steelmaking, specifically including: a gasifier, a carbonization furnace, a pyrolysis gas recovery device, a gas purification device, and a generator set;

[0043] The gasifier is used to process biomass solid waste and produce gasified char and biomass gas. The carbonization furnace is used to process biomass solid waste and produce pyrolysis char and pyrolysis gas. The pyrolysis gas recovery device is used to recover the pyrolysis gas from the carbonization furnace. The gas purification device is used to purify the biomass gas and the pyrolysis gas from the pyrolysis gas recovery device. The generator set is used to generate electricity using biomass gas and pyrolysis gas.

[0044] The gas outlet of the gasifier is connected to the carbonization furnace and the gas purification device. The gas outlet of the carbonization furnace is connected to the inlet of the pyrolysis gas recovery device. The gas outlet of the pyrolysis gas recovery device is connected to the carbonization furnace and the gas purification device. The gas outlet of the gas purification device is connected to the generator set.

[0045] In one optional implementation, the carbonization furnace is an intermittent carbonization furnace, and the capacity of a single intermittent carbonization furnace is not less than 4 cubic meters.

[0046] In other alternative implementations, multiple carbonization furnaces and gasification furnaces may be installed.

[0047] Example 2

[0048] This embodiment provides a method for coupling biomass solid waste power generation and preparing biomass char foaming agent for steelmaking.

[0049] The biomass solid waste in the gasifier is peach wood, and the carbonization furnace contains corn stalks; both have a particle size of 150mm and a moisture content of 5wt%, using the system provided in Example 1 (wherein there are two carbonization furnaces, each with a capacity of 5m³). 3 Each unit can carbonize 1 ton of biomass feedstock per cycle.

[0050] Peach wood is gasified in a gasifier to produce charcoal and biomass gas, while corn stalks are carbonized in a carbonization furnace. The carbonization process includes the following steps:

[0051] Low-temperature pyrolysis stage: In the initial stage, since no pyrolysis gas is generated in the carbonization furnace, biomass gas generated in the gasifier is used as a heat source to maintain the pyrolysis temperature of the carbonization furnace at 350 degrees Celsius for low-temperature carbonization, thereby reducing the porosity of the biochar product and increasing the biochar product yield. As pyrolysis proceeds, because the pyrolysis gas generated in this stage has a low calorific value, it is all circulated to the combustion chamber of the carbonization furnace to provide a heat source for pyrolysis. At the same time, the input of biomass gas is reduced to ensure the stability of the pyrolysis temperature. Once the pyrolysis gas can sustain the carbonization furnace temperature independently, the high-temperature pyrolysis stage begins.

[0052] High-temperature pyrolysis stage: Increase the biomass gas flow rate to ensure the carbonization furnace temperature reaches 600℃ within 8 minutes, thereby improving the graphitization degree of the biochar product, which helps reduce its reactivity and thus lowers the burn-off rate when using biochar products in electric arc furnace steelmaking. Once the pyrolysis gas can sustain the carbonization furnace temperature independently, the biomass gas input is shut off, and the entire carbonization heat source is provided by the pyrolysis gas.

[0053] Slow cooling stage: When the temperature of the carbonization furnace exceeds 700℃, part of the pyrolysis gas is released at a volumetric flow rate of 60 Nm³. 3 The pipeline leading to the gas purification device uses the residual pyrolysis gas as a heat source in the carbonization furnace. As the pyrolysis process proceeds, the pyrolysis gas flow rate gradually decreases, and the carbonization furnace slowly cools down until the total generated pyrolysis gas flow rate is less than the aforementioned specific volumetric flow rate. At this point, the input of pyrolysis gas to the gasification system is stopped. The process continues until the total generated pyrolysis gas volumetric flow rate is less than 20 Nm³. 3 At that time, the pyrolysis process ends.

[0054] The fixed carbon content of the gasified char after removing moisture was 85%, and the fixed carbon content of the pyrolytic char after removing moisture was 74%.

[0055] The biochar composite foaming agent prepared by this system has a mixing mass ratio of gasified carbon to pyrolysis carbon of 3:7, a total volatile matter content of 7 wt%, and a particle size of 120 mm. It is used as a foaming agent in the smelting process of 100t electric arc furnace scrap steel + 20% molten iron, and the feeding method is top feeding.

[0056] The production cost of biochar prepared using this method is 800 yuan lower than that of biochar prepared by traditional pyrolysis, and the biochar yield is three times higher than that of biochar prepared by traditional gasification power generation. In addition, compared with biochar prepared by traditional pyrolysis process, the amount of biochar used in electric arc furnace steelmaking can be reduced by 5 kg / ton of steel.

[0057] Example 3

[0058] This embodiment provides a method for coupling biomass solid waste power generation and preparing biomass char foaming agent for steelmaking.

[0059] The biomass solid waste in the gasifier is coconut shells, and the carbonization furnace contains a mixture of rice straw and corn straw, both with a particle size of 70mm and a moisture content of 10wt%. The system provided in Example 1 is used (where there is one carbonization furnace with a single unit capacity of 15m³). 3 Each unit can carbonize 3 tons of biomass raw materials in a single operation.

[0060] Coconut shells are gasified in a gasifier to produce charcoal and biomass gas. A mixture of rice straw and corn straw is carbonized in a carbonization furnace. The carbonization process includes the following steps:

[0061] Low-temperature pyrolysis stage: In the initial stage, since no pyrolysis gas is generated in the carbonization furnace, biomass gas generated in the gasifier is used as a heat source to maintain the pyrolysis temperature of the carbonization furnace at 400 degrees Celsius for low-temperature carbonization, thereby reducing the porosity of the biochar product and increasing the biochar product yield. As pyrolysis progresses, because the pyrolysis gas generated in this stage has a low calorific value, it is all circulated to the combustion chamber of the carbonization furnace to provide a heat source for pyrolysis. At the same time, the input of biomass gas is reduced to ensure the stability of the pyrolysis temperature. Once the pyrolysis gas can sustain the carbonization furnace temperature independently, the high-temperature pyrolysis stage begins.

[0062] High-temperature pyrolysis stage: Increase the biomass gas flow rate to ensure the carbonization furnace temperature reaches 700℃ within 10 minutes, thereby increasing the graphitization degree of the biochar product, which helps reduce its reactivity and thus lowers the burn-off rate when using biochar products in electric arc furnace steelmaking. Once the pyrolysis gas can sustain the carbonization furnace temperature independently, the biomass gas input is shut off, and the entire carbonization heat source is provided by the pyrolysis gas.

[0063] Slow cooling stage: When the temperature of the carbonization furnace exceeds 700℃, part of the pyrolysis gas is released at a volumetric flow rate of 130 Nm³. 3 The pipeline leading to the gas purification device uses the residual pyrolysis gas as a heat source in the carbonization furnace. As the pyrolysis process proceeds, the pyrolysis gas flow rate gradually decreases, and the carbonization furnace slowly cools down until the total generated pyrolysis gas flow rate is less than the aforementioned specific volumetric flow rate. At this point, the input of pyrolysis gas to the gasification system is stopped. The process continues until the total generated pyrolysis gas volumetric flow rate is less than 15 Nm³. 3 At that time, the pyrolysis process ends.

[0064] The fixed carbon content of the gasified char after removing moisture was 89%, and the fixed carbon content of the pyrolytic char after removing moisture was 76%.

[0065] The biochar composite foaming agent prepared by this system has a mixing mass ratio of gasified carbon to pyrolysis carbon of 1:4, a total volatile matter content of 12 wt%, and a particle size of 2 mm. It is used as a foaming agent in the 80t electric arc furnace all-scrap steel smelting process, and the feeding method is carbon lance blowing through the furnace wall.

[0066] The production cost of biochar prepared using this method is 600 yuan lower than that of biochar prepared by traditional pyrolysis, and the biochar yield is three times higher than that of biochar prepared by traditional gasification power generation. In addition, the amount of biochar used in electric arc furnace steelmaking can be reduced by 3 kg / ton of steel compared to biochar prepared by traditional pyrolysis processes.

[0067] Example 4

[0068] This embodiment provides a method for coupling biomass solid waste power generation and preparing biomass char foaming agent for steelmaking.

[0069] The biomass solid waste in the gasifier is corn stalks, and the carbonization furnace is peach wood; both have a particle size of 80mm and a moisture content of 5wt%, using the system provided in Example 1 (where there are 3 carbonization furnaces, each with a capacity of 12m³). 3 Each unit can carbonize 3 tons of biomass raw materials in a single operation.

[0070] Peach wood is gasified in a gasifier to produce charcoal and biomass gas, while corn stalks are carbonized in a carbonization furnace. The carbonization process includes the following steps:

[0071] Low-temperature pyrolysis stage: In the initial stage, since no pyrolysis gas is generated in the carbonization furnace, biomass gas generated in the gasifier is used as a heat source to maintain the pyrolysis temperature of the carbonization furnace at 300 degrees Celsius for low-temperature carbonization, thereby reducing the porosity of the biochar product and increasing the biochar product yield. As pyrolysis progresses, because the pyrolysis gas generated in this stage has a low calorific value, it is all circulated to the combustion chamber of the carbonization furnace to provide a heat source for pyrolysis. At the same time, the input of biomass gas is reduced to ensure the stability of the pyrolysis temperature. Once the pyrolysis gas can sustain the carbonization furnace temperature independently, the high-temperature pyrolysis stage begins.

[0072] High-temperature pyrolysis stage: Increase the biomass gas flow rate to ensure the carbonization furnace temperature reaches 600℃ within 5 minutes, thereby improving the graphitization degree of the biochar product, which helps reduce its reactivity and thus lowers the burn-off rate when using biochar products in electric arc furnace steelmaking. Once the pyrolysis gas can sustain the carbonization furnace temperature independently, the biomass gas input is shut off, and the entire carbonization heat source is provided by the pyrolysis gas.

[0073] Slow cooling stage: When the temperature of the carbonization furnace exceeds 700℃, part of the pyrolysis gas is released at a volumetric flow rate of 100 Nm³. 3 The pipeline leading to the gas purification device uses the residual pyrolysis gas as a heat source in the carbonization furnace. As the pyrolysis process proceeds, the pyrolysis gas flow rate gradually decreases, and the carbonization furnace slowly cools down until the total generated pyrolysis gas flow rate is less than the aforementioned specific volumetric flow rate. At this point, the input of pyrolysis gas to the gasification system is stopped, and the total generated pyrolysis gas volumetric flow rate is less than 25 Nm³. 3 At that time, the pyrolysis process ends.

[0074] The fixed carbon content of the obtained gasified char after removing moisture was 82%, and the fixed carbon content of the obtained pyrolytic char after removing moisture was 78%.

[0075] The biochar composite foaming agent prepared by this system has a mixing mass ratio of gasified carbon to pyrolysis carbon of 1:9, a total volatile matter content of 15wt%, and a particle size of 5mm. It is used as a foaming agent in the smelting process of scrap steel + 30% direct reduced iron in a 120t electric arc furnace, and the feeding method is internal injection into the slag.

[0076] The production cost of biochar prepared using this method is 650 yuan lower than that of biochar prepared by traditional pyrolysis, and the biochar yield is four times higher than that of biochar prepared by traditional gasification power generation. In addition, compared with biochar prepared by traditional pyrolysis process, the amount of biochar used in electric arc furnace steelmaking can be reduced by 4 kg / ton of steel.

[0077] Comparative Example 1

[0078] If the gasifier in Example 2 is used for gasification and power generation alone, the biomass solid waste in the gasifier is peach wood with a particle size of 150mm and a moisture content of 5wt%. The peach wood biochar that can be produced per hour is 0.35t, which is 1 / 3 of the composite biochar production in Example 2. This gasified char is applied as a foaming agent in the 100t electric arc furnace scrap steel + 20% molten iron smelting process by top feeding. The particle size is 120mm, and the biochar usage per ton of steel is 20.5kg / ton of steel. Compared with the biochar usage in electric arc furnace steelmaking in Example 2, it can only be reduced by 0.5kg / ton of steel. However, due to the lower output, the preparation cost of composite biochar in Example 2 is increased by 500 yuan.

[0079] Comparative Example 2

[0080] If two carbonization furnaces from Example 2 are used for individual carbonization, the biomass solid waste in the carbonization furnace is corn stalks with a particle size of 150mm and a moisture content of 5wt%. The amount of corn stalk biochar that can be produced per hour is 0.7t, and the preparation cost per ton of biochar is 2000 yuan, which is 800 yuan higher than the preparation cost of composite biochar in Example 2. This pyrolysis char is applied as a foaming agent in the 100t electric arc furnace scrap steel + 20% molten iron smelting process by top feeding. The particle size is 120mm, and the amount of biochar used per ton of steel is 26kg / ton of steel, which is 5kg / ton of steel higher than the amount of biochar used in electric arc furnace steelmaking in Example 2.

[0081] The method and system provided in this application produce biochar that can be used as a foaming agent in electric arc furnace steelmaking with various charge structures, including 50-200t of all scrap steel, scrap steel + molten iron, and scrap steel + direct reduced iron. The production cost of the biochar is reduced by 500-1000 yuan compared to traditional pyrolysis-based biochar production, and the biochar yield is increased by 3-6 times compared to traditional gasification power generation. Furthermore, the amount of biochar used in electric arc furnace steelmaking is reduced by 3-5 kg / ton of steel.

[0082] This application couples a biomass pyrolysis system with biomass gasification power generation, significantly reducing the production cost of biochar by increasing the utilization value of pyrolysis gas and reducing equipment investment. Furthermore, by mixing the biochar produced from the pyrolysis and gasification systems in a specific ratio, two highly efficient foaming agents for electric arc furnace steelmaking are prepared. These foaming agents can stably and efficiently generate foamed slag during the smelting process, effectively reducing energy consumption and significantly improving smelting efficiency.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method of cogeneration of biomass solid waste and preparation of a biomass char blowing agent for steelmaking, characterized by, The method comprises the following steps: a part of the biomass solid waste is gasified by a gasifier to obtain gasification carbon and biomass gas, and another part of the biomass solid waste is carbonized by a carbonization furnace; the carbonization comprises sequentially performing a low-temperature pyrolysis stage, a high-temperature pyrolysis stage and a slow cooling stage; when the low-temperature pyrolysis stage is performed, part of the biomass gas is input into a combustion chamber of the carbonization furnace as a carbonization heat source, and the excess biomass gas is purified and sent to a generator set for power generation; the pyrolysis gas generated by the carbonization furnace is all recycled back to the combustion chamber of the carbonization furnace as a carbonization heat source; the pyrolysis temperature of the low-temperature pyrolysis stage is 300-400 ℃; after the low-temperature pyrolysis stage is completed, the amount of the biomass gas input into the carbonization furnace is increased, so that the pyrolysis temperature is increased to 600-700 ℃; when the pyrolysis gas can maintain the pyrolysis temperature at 600-700 ℃, the biomass gas is all sent to the generator set for power generation; when the pyrolysis temperature is higher than 700 ℃, the high-temperature pyrolysis stage is completed, a specific volume flow rate of the pyrolysis gas is purified and sent to the generator set for power generation, so that the pyrolysis temperature is gradually reduced; when the total amount of the pyrolysis gas generated by the carbonization furnace is less than or equal to the specific volume flow rate, the pyrolysis gas is stopped from being sent to the generator set; The total amount of pyrolysis gas generated by the carbonization furnace is less than or equal to 25 Nm 3 When the carbonization is completed, pyrolysis carbon is obtained; the gasification carbon and the pyrolysis carbon are compounded to obtain a biomass carbon foaming agent for steelmaking.

2. The method of claim 1, wherein the biomass solid waste is coupled to generate power and to produce a biomass char blowing agent for steelmaking. when the biomass solid waste is straw and the amount is less than 1 ton, the specific volume flow is 55-70 Nm 3 / h, and the specific volume flow increases by 30-40 Nm 3 / h per ton of increase in the amount. when the biomass solid waste is wood-based and the amount is less than 1 ton, the specific volumetric flow rate is 40-50 Nm 3 / h, and for each additional ton, the specific volumetric flow rate increases by 20-30 Nm 3 / h; when the biomass solid waste is shell type and the amount is less than 1 ton, the specific volume flow is 25-40 Nm 3 / h, and the specific volume flow increases by 5-15 Nm 3 / h for each ton of increase in the amount.

3. The method of claim 1, wherein the biomass solid waste is coupled to generate power and to produce a biomass char blowing agent for steelmaking. The fixed carbon content of the gasification carbon after removing moisture is not less than 80%.

4. The method of claim 1, wherein the biomass solid waste power generation and the preparation of the biomass char blowing agent for steelmaking are coupled. The fixed carbon content of the pyrolysis carbon after removing moisture is not less than 70%.

5. The method of claim 1, wherein the biomass solid waste power generation and the preparation of the biomass char blowing agent for steelmaking are coupled. The biomass carbon foaming agent for steelmaking comprises a composite biomass carbon foaming agent for top charging, a composite biomass carbon foaming agent for a furnace wall and / or a furnace door lance spraying and a composite biomass carbon foaming agent for slag internal spraying; In the composite biomass carbon foaming agent for top charging, the content of the gasification carbon is 30-40 wt%, the total content of volatile matter is not higher than 10 wt%, and the particle size of the composite foaming agent is 10-150 mm; In the composite biomass carbon foaming agent for the furnace wall and / or the furnace door lance spraying, the content of the gasification carbon is 20-30 wt%, the total content of volatile matter is not higher than 15 wt%, and the particle size of the composite foaming agent is not greater than 3 mm; In the composite biomass carbon foaming agent for slag internal spraying, the content of the gasification carbon is 10-20 wt%, the total content of volatile matter is not higher than 20 wt%, and the particle size of the composite foaming agent is not greater than 5 mm.

6. The method of claim 1, wherein the biomass solid waste power generation and the preparation of the biomass char blowing agent for steelmaking are coupled. The moisture content of the biomass carbon foaming agent for steelmaking is not higher than 3 wt%.

7. The method of claim 1, wherein the biomass solid waste is coupled to generate power and to produce a biomass char blowing agent for steelmaking. The raw material of the biomass carbon foaming agent for steelmaking further comprises a binder, and the addition amount of the binder is 0.5%-5% of the total mass of the gasification carbon and the pyrolysis carbon.

8. The method of cogeneration of biomass solid waste and preparation of biomass char blowing agent for steelmaking according to any one of claims 1 to 7, characterized in that, The particle size of the biomass solid waste is 50-150 mm, and the moisture content is not higher than 15 wt%.

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