A method for producing organic low-carbon fuel for blast furnace ironmaking

Abstract

A method for producing an organic low-carbon fuel for blast furnace ironmaking comprises: subjecting a biomass raw material to hydrothermal carbonization to remove harmful alkali metal elements from the biomass raw material to obtain biomass hydrothermal char; mixing the biomass hydrothermal char with waste plastics and subjecting the mixture to low-temperature pyrolysis and carbonization to obtain a low-carbon fuel with high fixed carbon and calorific value; adding the low-carbon fuel and a blast furnace flux to a coal mill for pulverization, and then injecting the fuel into the tuyere vortex zone through an injection system for combustion, thereby providing heat and a reducing agent for blast furnace smelting. The low-carbon fuel used for blast furnace injection according to the present invention can fully meet the requirements of blast furnace smelting, reduce CO2 emissions from ironmaking production, and simultaneously address pollution generated by waste plastics. Furthermore, the fuel ratio of blast furnace injection is increased, and the coke ratio is reduced, thereby providing broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallurgy, relates to a blast furnace low-carbon ironmaking production technology, and in particular to a method for producing an organic low-carbon fuel for blast furnace ironmaking. Background Art

[0002] Blast furnace ironmaking is the core process in traditional steelmaking, accounting for over 70% of the total energy consumption and CO2 emissions of the entire steel production process. Reducing energy consumption and CO2 emissions from blast furnace ironmaking is crucial for the steel industry. Biomass raw materials are green and renewable, offering significant environmental and low-carbon advantages over traditional fossil fuels like coal. Appropriate application of biomass in blast furnace ironmaking can effectively reduce CO2 emissions from the steel production process.

[0003] China remains a major producer and user of plastic products. With growing environmental awareness, the harmless disposal of waste plastics has become a focus of public attention. Traditional methods for waste plastic disposal include recycling, incineration for power generation, and landfill. Using waste plastics in blast furnace ironmaking not only reduces CO2 emissions by replacing pulverized coal with hydrogen-rich waste plastics, but also allows for harmless and resourceful waste disposal, offering new insights into the development of low-carbon steel mills in cities.

[0004] The primary fossil fuels consumed in blast furnace ironmaking are coke and pulverized coal injection (PFI). Comparing the primary roles of coke and PFI in blast furnaces reveals that biomass and waste plastics offer a more feasible alternative to pulverized coal injection. Key factors limiting the use of biomass and waste plastics in blast furnace injection include high levels of harmful elements, difficulty in pulverizing, and low calorific value. Implementing biomass and waste plastics in blast furnace injection is crucial for reducing CO2 emissions from ironmaking. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for producing organic low-carbon fuel for blast furnace ironmaking, which prepares biomass and waste plastics into high-quality low-carbon fuel for blast furnace injection, replaces coal powder for blast furnace injection, and effectively reduces the consumption of fossil fuels in blast furnace ironmaking production.

[0006] In order to achieve the above objectives, the technical solutions adopted in this disclosure are:

[0007] A method for producing an organic low-carbon fuel for blast furnace ironmaking comprises the following process steps:

[0008] S1. The biomass raw material is coarsely crushed and then hydrothermally carbonized. After carbonization, solid-liquid separation is performed to obtain biomass hydrothermal carbon;

[0009] S2. The obtained biomass hydrothermal charcoal is subjected to low-temperature pyrolysis and carbonization with waste plastics to obtain a low-carbon fuel with high fixed carbon and calorific value;

[0010] S3: The prepared low-carbon fuel is mixed with a blast furnace flux and then added to a coal mill for pulverization to obtain a modified low-carbon fuel powder with a high ash melting point and excellent combustion performance;

[0011] S4. The prepared modified low-carbon fuel powder is injected into the tuyere cyclotron zone through the injection system for combustion to provide heat and reducing agent for blast furnace smelting.

[0012] Furthermore, the mass proportion of the S2 biomass hydrothermal charcoal is 30% to 100%, the low-temperature pyrolysis carbonization temperature is 500-700°C, and the fixed carbon content of the obtained low-carbon fuel is greater than 75%, the calorific value is greater than 28MJ / kg, and the Hardgrove grindability index is greater than 70%.

[0013] Furthermore, the S3 blast furnace flux is one or a mixture of limestone, dolomite, and forsterite, the mass ratio of the blast furnace flux is 1%-5%, and the ash softening temperature of the modified low-carbon fuel powder is greater than 1250°C.

[0014] Furthermore, the proportion of the S4 modified low-carbon fuel powder with a particle size less than 0.074 mm is greater than 60%, the blast furnace hot air temperature is greater than 1200°C, the blast oxygen enrichment rate is greater than 3%, and the combustion rate of the blast furnace injected modified low-carbon fuel powder in the tuyere swirl zone is greater than 75%.

[0015] The beneficial effects of the present invention are as follows: low-carbon fuels obtained from biomass and waste plastics using the method of the present invention can partially or completely replace coal powder for application in blast furnace ironmaking production, which can effectively reduce the consumption of injected coal in the blast furnace ironmaking production process and reduce CO2 emissions in the steel production process; applying biomass and waste plastics to blast furnace ironmaking production solves the pollution caused by waste plastics, and can also increase the blast furnace coal injection ratio and reduce the coke ratio; reducing the content of harmful elements in biomass raw materials, which can improve the economic and technical indicators of blast furnace smelting and realize low-carbon and high-efficiency production of blast furnaces; high-quality low-carbon fuels are prepared by coupling hydrothermal carbonization and pyrolysis carbonization technology, and their metallurgical properties are further improved through the crushing process and the modification effect of blast furnace flux, thereby realizing safe, efficient and low-carbon production in blast furnaces. DETAILED DESCRIPTION

[0016] The technical solutions of various embodiments of the present invention will be further described below.

[0017] A method for producing organic low-carbon fuel for blast furnace ironmaking, comprising the following steps:

[0018] S1. The biomass raw material is coarsely crushed and then hydrothermally carbonized. After carbonization, solid-liquid separation is performed to obtain biomass hydrothermal carbon;

[0019] S2. The biomass hydrothermal charcoal prepared in step S1 is subjected to low-temperature pyrolysis and carbonization with waste plastics to obtain a low-carbon fuel with high fixed carbon and calorific value;

[0020] S3. The low-carbon fuel obtained in step S2 is mixed with a blast furnace flux and added to a coal mill for pulverization to obtain a modified low-carbon fuel powder having a high ash melting point and excellent combustion properties;

[0021] S4. The modified low-carbon fuel powder obtained in step S3 is injected into the tuyere cyclotron zone through the injection system for combustion to provide heat and reducing agent for blast furnace smelting.

[0022] The S1 hydrothermal carbonization treatment mainly removes harmful alkali metal elements in the biomass raw materials, and prepares biomass hydrothermal carbon with a potassium content of less than 0.3%.

[0023] The mass proportion of the S2 biomass hydrothermal charcoal is 30%~100%, the low-temperature pyrolysis carbonization temperature is 500~700℃, and the fixed carbon content of the obtained low-carbon fuel is greater than 75%, the calorific value is greater than 28MJ / kg, and the Hardgrove grindability index is greater than 70%.

[0024] The S3 blast furnace flux is one or a mixture of limestone, dolomite, and forsterite, with a mass ratio of 1%-5% and an ash softening temperature of the modified low-carbon fuel powder greater than 1250°C.

[0025] The proportion of the S4 modified low-carbon fuel powder with a particle size less than 0.074 mm is greater than 60%, the blast furnace hot air temperature is greater than 1200°C, the blast oxygen enrichment rate is greater than 3%, and the combustion rate of the blast furnace injected modified low-carbon fuel powder in the tuyere vortex zone is greater than 75%. Example 1

[0026] A method for producing organic low-carbon fuel for blast furnace ironmaking, using corn stalks and waste plastic bottles as raw materials, comprises the following steps:

[0027] Corn stalks were coarsely shredded to a length of less than 10 cm and then loaded into a high-pressure reactor. Reaction water was added to maintain a liquid-to-solid ratio of 3:1. The reactor was sealed and heated, and the hydrothermal carbonization temperature within the reactor was raised to 210°C by controlling the heating power. After 30 minutes of heat preservation, heating was stopped and the pressure relief valve was opened. After pressure relief, the carbonized liquid was discharged and extruded for dehydration to obtain biomass hydrothermal carbon cakes. The alkali metal content of the hydrothermal carbon cakes was 0.13%. The biomass hydrothermal carbon cakes and waste plastics were then loaded into a low-temperature pyrolysis rotary kiln for pyrolysis and carbonization. The mass ratio of biomass hydrothermal carbon was 50%. The pyrolysis temperature of the low-temperature pyrolysis rotary kiln was controlled at 550°C for 40 minutes. After completion of pyrolysis and carbonization, the fuel was discharged through the discharge port and cooled to produce low-carbon fuel. The low-carbon fuel had a fixed carbon content of 79.5%, an ash content of 3.8%, a calorific value of 28.9 MJ / kg, and a Hastelloy Grindability Index of 81%. 96% low-carbon fuel was mixed with 4% limestone powder and fed into a medium-speed mill for pulverization. The resulting modified low-carbon fuel powder had a particle size of less than 0.074 mm, accounting for 82% of the total. The ash softening temperature of the modified low-carbon fuel powder was 1260°C. The modified low-carbon fuel powder was used together with pulverized coal in blast furnace smelting. The injection rate of the modified low-carbon fuel powder was 31kg / tHM, the hot air temperature was 1210°C, and the blast oxygen enrichment rate was 3.6%. The combustion rate of the modified low-carbon fuel powder injected into the blast furnace in the tuyere vortex zone was 78.3%. The economic and technical indicators of blast furnace smelting were good. Compared with traditional all-pulverized coal-injection blast furnaces, CO2 emissions were reduced by 73.5kg / tHM per ton of iron. Example 2

[0028] A method for producing organic low-carbon fuel for blast furnace ironmaking, using waste wood and waste plastic water pipes as raw materials, includes the following steps:

[0029] Waste wood is crushed to particles less than 5 cm in size and then loaded into a high-pressure reactor. Reaction water is added to maintain a liquid-to-solid ratio of 2.5:1. The reactor is sealed and heated. The hydrothermal carbonization temperature within the reactor is raised to 200°C by controlling the heating power. After holding for 30 minutes, heating is stopped and the pressure relief valve is opened. After pressure relief, the carbonized liquid is discharged and extruded for dehydration to produce biomass hydrothermal carbon cakes. The alkali metal content of the hydrothermal carbon cakes is 0.05%. The biomass hydrothermal carbon cakes and waste plastic water pipes are then loaded into a low-temperature pyrolysis rotary kiln for pyrolysis and carbonization. The mass ratio of biomass hydrothermal carbon is 60%. The pyrolysis temperature of the low-temperature pyrolysis rotary kiln is controlled at 650°C for 30 minutes. After completion of pyrolysis and carbonization, the fuel is discharged through a discharge port and cooled to produce low-carbon fuel. The low-carbon fuel has a fixed carbon content of 81.5%, an ash content of 1.7%, a calorific value of 30.2 MJ / kg, and a Hastelloy Grindability Index of 85%. 97% low-carbon fuel was mixed with 3% limestone powder and fed into a medium-speed mill for pulverization. The resulting modified low-carbon fuel powder had a particle size of less than 0.074 mm, accounting for 76% of the total. The ash softening temperature of the modified low-carbon fuel powder was 1320°C. The modified low-carbon fuel powder was used together with pulverized coal in blast furnace smelting. The injection rate of the modified low-carbon fuel powder was 31kg / tHM, the hot air temperature was 1210°C, and the blast oxygen enrichment rate was 3.6%. The combustion rate of the modified low-carbon fuel powder injected into the blast furnace in the tuyere vortex zone was 77.6%. The economic and technical indicators of blast furnace smelting were good. Compared with traditional all-pulverized coal-injection blast furnaces, CO2 emissions were reduced by 80.6kg / tHM per ton of iron.

[0030] Because waste wood has lower ash and alkali metal content than corn straw, the resulting hydrothermal biomass char has an even lower alkali metal content, reaching the level of ultra-low alkalinity coal, completely avoiding the negative impact of high alkali metal content in biomass feedstock on blast furnace smelting. Waste plastic water pipes are primarily composed of PVC. Raising the pyrolysis and carbonization temperature effectively removes chlorine from PVC, preventing excessive chlorine in the resulting low-carbon fuel, which could negatively impact blast furnace smelting. The low-carbon fuel produced in Example 2 has lower ash content, higher fixed carbon content, and higher calorific value. When used as blast furnace injection fuel, it can replace more pulverized coal, resulting in even greater CO2 reduction. Example 3

[0031] A method for producing organic low-carbon fuel for blast furnace ironmaking, using waste wood and waste plastic bottles as raw materials, includes the following steps:

[0032] Waste wood is crushed to particles less than 5 cm in size and then loaded into a high-pressure reactor. Reaction water is added to maintain a liquid-to-solid ratio of 2.5:1. The reactor is sealed and heated. The hydrothermal carbonization temperature within the reactor is raised to 200°C by controlling the heating power. After holding for 30 minutes, heating is stopped and the pressure relief valve is opened. After pressure relief, the carbonized liquid is discharged and extruded for dehydration to produce biomass hydrothermal carbon cakes. The alkali metal content of the hydrothermal carbon cakes is 0.05%. The biomass hydrothermal carbon cakes and waste plastic bottles are then combined in a low-temperature pyrolysis rotary kiln for pyrolysis and carbonization. The mass ratio of biomass hydrothermal carbon is 50%. The pyrolysis temperature of the low-temperature pyrolysis rotary kiln is controlled at 510°C for 40 minutes. After completion of pyrolysis and carbonization, the fuel is discharged through a discharge port and cooled to produce low-carbon fuel. The low-carbon fuel has a fixed carbon content of 76.3.5%, an ash content of 1.4%, a calorific value of 28.3 MJ / kg, and a Hastelloy Grindability Index of 87%. 97% low-carbon fuel was mixed with 3% dolomite powder and fed into a medium-speed mill for pulverization. The resulting modified low-carbon fuel powder had a particle size of less than 0.074 mm, accounting for 79% of the total. The ash softening temperature of the modified low-carbon fuel powder was 1310°C. The modified low-carbon fuel powder was used together with pulverized coal in blast furnace smelting. The injection rate of the modified low-carbon fuel powder was 31kg / tHM, the hot air temperature was 1210°C, the blast oxygen enrichment rate was 3.6%, and the combustion rate of the modified low-carbon fuel powder injected into the blast furnace in the tuyere vortex zone was 82.6%. The blast furnace smelting had good economic and technical indicators. Compared with traditional all-pulverized coal-injected blast furnaces, CO2 emissions were reduced by 77.5kg / tHM per ton of iron.

[0033] Waste wood hydrochar and waste plastic bottles can be fully carbonized at relatively low pyrolysis carbonization temperatures, achieving a low-carbon fuel grindability of 87%. Under the same pulverizing conditions, a finer particle size of modified low-carbon fuel powder can be obtained. Dolomite has a superior catalytic effect compared to limestone, improving the combustibility of low-carbon fuel. Its superior combustion reactivity and finer particle size allow the modified low-carbon fuel powder to have a higher combustion rate when injected into a blast furnace, helping to reduce the amount of unburned coal in the blast furnace. This plays a significant role in further increasing the coal injection ratio, reducing the coke ratio, and improving the economic and technical indicators of blast furnace production. Example 4

[0034] A method for producing organic low-carbon fuel for blast furnace ironmaking, using corn stalks and waste plastic bottles as raw materials, comprises the following steps:

[0035] Corn stalks were coarsely shredded to a length of less than 10 cm and then loaded into a high-pressure reactor. Reaction water was added to maintain a liquid-to-solid ratio of 3:1. The reactor was sealed and heated, and the hydrothermal carbonization temperature within the reactor was raised to 210°C by controlling the heating power. After 30 minutes of heat preservation, heating was stopped and the pressure relief valve was opened. After pressure relief, the carbonized liquid was discharged and extruded for dehydration to obtain biomass hydrothermal carbon cakes. The alkali metal content of the hydrothermal carbon cakes was 0.13%. The biomass hydrothermal carbon cakes and waste plastics were then loaded into a low-temperature pyrolysis rotary kiln for pyrolysis and carbonization. The mass ratio of biomass hydrothermal carbon was 50%. The pyrolysis temperature of the low-temperature pyrolysis rotary kiln was controlled at 550°C for 40 minutes. After completion of pyrolysis and carbonization, the fuel was discharged through the discharge port and cooled to produce low-carbon fuel. The low-carbon fuel had a fixed carbon content of 79.5%, an ash content of 3.8%, a calorific value of 28.9 MJ / kg, and a Hastelloy Grindability Index of 81%. 96% low-carbon fuel was mixed with 4% limestone powder and fed into a medium-speed mill for pulverization. The resulting modified low-carbon fuel powder had a particle size of less than 0.074mm, accounting for 82% of the total. The ash softening temperature of the modified low-carbon fuel powder was 1350°C. The modified low-carbon fuel powder was used together with pulverized coal in blast furnace smelting. The injection rate of the modified low-carbon fuel powder was 50kg / tHM, the hot air temperature was 1250°C, and the blast oxygen enrichment rate was 4.5%. The combustion rate of the modified low-carbon fuel powder injected into the blast furnace in the tuyere vortex zone was 82.1%. The blast furnace smelting had good economic and technical indicators. Compared with traditional all-pulverized coal-injection blast furnaces, the CO2 emissions per ton of iron were reduced by 112.5kg / tHM.

[0036] Blast furnace injection parameters are also important factors affecting the effectiveness of injecting modified low-carbon fuels. By increasing the hot blast temperature and blast oxygen enrichment rate, the combustion rate of the injected fuel in the tuyere vortex zone can be improved, further increasing the injection volume of low-carbon fuel. This also increases the combustion rate of the injected fuel in the tuyere vortex zone, reducing the amount of unburned coal in the blast furnace, thereby achieving the goal of reducing the blast furnace pressure difference and increasing blast furnace output. At the same time, by injecting more modified low-carbon fuel instead of injected coal, CO2 emissions from blast furnace smelting can be further reduced, with good economic, environmental, and social benefits.

Claims

1. A method for producing organic low-carbon fuel for blast furnace ironmaking, characterized in that The following steps are involved: S1. The biomass raw material is coarsely crushed and then hydrothermally carbonized. After carbonization, solid-liquid separation is performed to obtain biomass hydrothermal charcoal; the biomass raw material includes a mixture of one or more agricultural straw, waste wood, and waste plastics; S2. subjecting the prepared biomass hydrochar to low-temperature pyrolysis carbonization with waste plastics, with the biomass hydrochar accounting for 30% to 100% by mass and the low-temperature pyrolysis carbonization temperature being 500°C to 700°C, to obtain a low-carbon fuel having a fixed carbon content greater than 75%, a calorific value greater than 28 MJ / kg, and a Hardgrove grindability index greater than 70%, thereby obtaining a low-carbon fuel with high fixed carbon content and calorific value; S3: The prepared low-carbon fuel is mixed with a blast furnace flux and then added to a coal mill for pulverization to obtain a modified low-carbon fuel powder with a high ash melting point and excellent combustion performance; S4. The prepared modified low-carbon fuel powder is injected into the tuyere vortex zone through the injection system for combustion to provide heat and reducing agent for blast furnace smelting. The proportion of the modified low-carbon fuel powder with a particle size less than 0.074 mm is greater than 60%, the blast furnace hot air temperature is greater than 1200°C, the blast oxygen enrichment rate is greater than 3%, and the combustion rate of the modified low-carbon fuel powder injected into the blast furnace in the tuyere vortex zone is greater than 75%.

2. The method for producing an organic low-carbon fuel for blast furnace ironmaking according to claim 1, characterized in that: In S3, the blast furnace flux is one or a mixture of limestone, dolomite, and forsterite, the mass ratio of the blast furnace flux is 1% to 5%, and the ash softening temperature of the modified low-carbon fuel powder is greater than 1250°C.