A method for using biomass fuel for blast furnace injection

Abstract

The present invention discloses a method for injecting biomass fuel into a blast furnace, wherein the mixed fuel obtained by replacing part of the fossil fuel with biomass shaped fuel that has not been carbonized at high temperature is injected into the blast furnace from the tuyere of the blast furnace through an injection device to complete combustion and smelting reactions. The method of the present invention can reduce the use of fossil fuels, reduce carbon emissions and SO2 pollution without affecting smelting indicators. The implementation process does not require the introduction of carbonization equipment, eliminates the grinding and powder transportation process of pipeline fuel transportation, explosion-proof safety, and environmental protection links, saves a lot of investment and operating costs, has high safety and reliability, high economic utilization value, and can achieve economic and green smelting.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, and specifically relates to a method for using biomass fuel for blast furnace injection. Background Technology

[0002] Blast furnace injection is a technical measure in ironmaking where fuels (natural gas, coke oven gas, heavy oil, pulverized coal, etc.) are injected into the blast furnace. It is an important coke-saving measure in the steel industry. It can significantly reduce the coke ratio, promote smooth charge movement, and has a noticeable effect on increasing output and improving pig iron quality.

[0003] Currently, anthracite is the primary fuel used for blast furnace injection. Its characteristics include low volatile matter content, making it less prone to explosion during pulverization, conveying, and injection. However, its disadvantages include low combustibility and combustion efficiency, requiring grinding to a particle size of less than 0.074 mm. Later, to improve combustibility and efficiency, some high-volatile bituminous coal was added to the anthracite. However, this resulted in poor safety, as fine bituminous coal with high volatile matter content is highly explosive. Furthermore, the pulverization, conveying, and injection systems are extremely complex, involving high investment, low efficiency, high failure rates, poor safety, and high processing costs, thus becoming a limiting factor for many blast furnaces to further increase the coal ratio.

[0004] The massive depletion of fossil resources has exacerbated the already acute tension between resource reserves and steel production capacity. Reducing the enormous pressure this highly polluting and energy-intensive industry places on the environment and resources is imperative. Against this backdrop, seeking a clean and renewable alternative has become an inevitable trend.

[0005] Biomass fuel, the most widely available plant fuel in nature, is converted from CO2 and H2O through photosynthesis. Biomass fuel typically has 10-30% fixed carbon, 60-80% volatile matter, less than 5% ash, and a calorific value of around 3900-4800 kcal / kg, only 50-60% of that of anthracite. It also has extremely low sulfur and phosphorus content; after high-temperature carbonization, its calorific value can reach 7000-8000 kcal / kg, making it a viable alternative or partial substitute for metallurgical fossil fuels. The main characteristic of biomass fuel is its high volatile matter content (50-80%). When injected into a blast furnace, it rapidly decomposes into various combustible gases, resulting in fast combustion and high efficiency, making it an ideal fuel for blast furnace injection. However, the combustion mechanism of volatile matter gases is completely different from that of anthracite carbon. Volatile matter combustion is a gas-gas one-phase reaction, while anthracite carbon combustion is a gas-solid two-phase reaction, with a much lower combustion rate and efficiency. Biomass fuel, as a renewable resource, has abundant reserves in my country, equivalent to 5 billion tons of standard coal. Replacing some fossil fuels can reduce carbon emissions, conserve energy, reduce emissions, and promote environmental protection, making it one of the future directions for energy development, with significant and far-reaching implications.

[0006] Methods for using biomass fuel for blast furnace injection have been reported. For example, CN110218826B discloses a method for injecting biomass hydrothermal char into a blast furnace, including S1) preparing biomass hydrothermal char by hydrothermal carbonization of biomass; S2) crushing and pulverizing the mixture of biomass hydrothermal char and coal, and mixing them uniformly; S3) injecting the mixture after crushing and mixing in S2) into the blast furnace uniformly through the pulverized coal injection conveying and distribution system of the ironmaking plant via the coal lance, direct injection pipe and tuyeres; S4) setting the combustion rate of the injected fuel in front of the tuyeres to be greater than 60%, the theoretical combustion temperature of the tuyeres to be between 2000-2350℃, and the gas flow index in the furnace belly to be less than 70 m³ / min, to ensure normal production of blast furnace ironmaking. CN108003959A discloses a method for replacing pulverized coal injection in blast furnaces using biomass carbonization. The method involves extruding dried biomass raw materials such as straw into briquettes, then carbonizing these briquettes at 300–1000℃ in a carbonization furnace to obtain carbon powder. This carbon powder, mixed with pulverized coal, is injected into the blast furnace, significantly reducing the coal ratio and flux usage, thus improving production efficiency. It also fully utilizes the latent heat of flue gas, reducing exhaust emissions. Waste gas from the combustion chamber is filtered through a microporous ceramic tube before being released into the air. Biomass resources, as well as the sensible heat of the flue gas, and the oxygen and carbon monoxide in the flue gas, are utilized in ironmaking production. Furthermore, biomass resources can also be used to replace pulverized coal or coke powder used in iron ore sintering machines. CN102666880A discloses a method for utilizing biomass in a blast furnace. In this method, biomass is dry distilled to produce biomass coke with a Hardgrove Grindability Index (HGI) of 45 or higher; a mixture of the biomass coke and coal is micronized to generate pulverized material; and the pulverized material is blown into the blast furnace as an auxiliary reducing material from the tuyeres.

[0007] The above are just representative technologies. It can be seen that existing methods for using biomass in blast furnace injection all involve replacing a portion of the pulverized coal with carbonized biomass before injection. However, high-temperature carbonization is equivalent to building a coking plant, complicating the factory process and procedures, and potentially increasing processing costs compared to coke, thus rendering biomass fuel substitution uneconomical. On the other hand, biomass has a high fiber content, leading to high power consumption, low efficiency, and high costs during mechanical crushing. Furthermore, the high fiber aspect ratio in biomass powder results in poor gas-solid transport performance, easily clogging pipes and distributors during transport, making it difficult to utilize existing ironmaking plant equipment for pulverization, transport, and injection into the blast furnace. Summary of the Invention

[0008] To address the aforementioned problems, this invention provides a method for using biomass fuel in blast furnace injection. This method has low equipment requirements, does not affect smelting indicators, reduces carbon emissions and SO2 pollution, has high economic value, and can achieve economical and green smelting.

[0009] This invention provides a method for using biomass fuel for blast furnace injection. The method involves replacing part of the fossil fuel with biomass briquettes that have not been carbonized at high temperatures to obtain a mixed fuel, which is then injected into the blast furnace from the tuyeres through an injection device to complete the combustion and smelting reaction.

[0010] The amount of biomass briquettes that replaces fossil fuels, measured by calorific value, is 10-50% of the calorific value of the previous fossil fuels.

[0011] The biomass briquettes are pellet fuels with a particle size distribution of 1 to 5 mm;

[0012] The biomass briquettes have a particle size distribution of 1-3 mm, 3-4 mm, and 4-5 mm in a weight ratio of 0-60:20-30:10-20.

[0013] The moisture content of the biomass briquettes is less than 3% wt.

[0014] As a specific embodiment of the present invention, the raw materials for the uncarbonized biomass briquette fuel are selected from one or more of the following: waste crop straw, sawdust, waste wood, branches, hay, fruit shells, fruit pits, rice husks, bagasse, and rice bran.

[0015] As a specific embodiment of the present invention, the fossil fuel is anthracite, or a mixture of anthracite and bituminous coal.

[0016] In a specific embodiment of the present invention, the fossil fuel is pulverized coal or granular coal.

[0017] In a specific embodiment of the present invention, the pulverized coal injection equipment includes a transport component and a pulverized coal injection component; the transport component is a bucket elevator or a bucket belt conveyor; the pulverized coal injection component includes a hopper, the bottom of which is provided with two conical discharge ports, each of which is sequentially connected along the discharge direction to a discharge pipe, a guide pipe, a hopper, a pulverized coal injection hopper, a rotary feeder, and a pulverized coal injection gun; the inlet of the guide pipe and the outlet of the hopper are both provided with dome valves; the side wall of the pulverized coal injection hopper is provided with a fluidizing pressurization device, and the pulverized coal injection hopper is also provided with a weighing sensor; the rotary feeder is driven by a variable frequency motor; the output end of the pulverized coal injection gun is connected to the tuyeres of the blast furnace; the output end of the transport component is connected to the inlet of the hopper.

[0018] As a specific embodiment of the present invention, the pulverized coal injection gun includes an inner tube and an outer tube that are nested together. The diameter of the inner tube is matched with the particle size of the mixed fuel, and the outer tube is connected to a compressed air pipe through a high-pressure valve.

[0019] Biomass fuel refers to fuel produced by burning biomass materials, primarily agricultural and forestry waste, and is distinguished from fossil fuels. This invention describes uncarbonized biomass pellet fuel, which refers to pellet-shaped, directly usable fuel made from biomass raw materials, including but not limited to waste crop straw, sawdust, waste wood, branches, hay, fruit shells, fruit pits, rice husks, bagasse, and rice husks, through processes such as crushing, mixing, extrusion, binding (with the addition of a small amount of binder), and drying. It can be obtained commercially or homemade. A very small amount of binder can be added during the molding process; this can be organic binders such as modified lignin, syrup, starch or lignosulfonates, asphalt, etc., or inorganic binders such as water glass, lime, cement, and steelmaking sludge. During the molding process, due to the exothermic reaction of extrusion molding or heating as required by the process, the temperature can reach over 100°C, making the binder's role more prominent. After cooling, the powder can be solidified together.

[0020] In this invention, the particle size range of the uncarbonized biomass briquettes is controlled within 1–5 mm, particularly with a weight ratio of 0–60:20–30:10–20 for particle sizes of 1–3 mm, 3–4 mm, and 4–5 mm. This ensures complete combustion of the biomass fuel at the vent, providing sufficient calorific value. Particle sizes below this range, such as those containing a large amount of <200 mesh (0.074 mm), pose a risk of explosion within the fuel storage silo and injection system due to the high volatile content of the biomass fuel. This necessitates additional explosion-proof safety facilities and devices, increasing costs and complicating the process. Particle sizes larger than this range are difficult to burn completely in a short time.

[0021] The biomass briquettes in this invention only replace a portion of fossil fuels. The weight of the injected fuel is calculated based on the calorific value of both fuels for ease of control and operation. The overall principle of substitution is heat balance, meaning the total calorific value of the injected fuel remains unchanged or substantially unchanged before and after substitution with biomass briquettes. When used for blast furnace injection, the two fuels can be pre-mixed, transported, and filled into the silo for injection in a mixed state. Alternatively, the two fuels can be transported and filled into different hoppers, and then mixed and injected at the blast furnace tuyeres.

[0022] This invention injects uncarbonized biomass briquettes directly into the vent, allowing them to decompose and burn in a short time. The heat is then directly used to smelt and melt slag, significantly improving combustion efficiency and utilization.

[0023] The injection equipment of the present invention can also be newly built or renovated near an existing blast furnace, as shown in the example below. Figure 1 The design shown can also be redesigned, depending on the actual situation, without specific limitations. According to... Figure 1The bucket elevator, a mature and readily available mechanical and electrical combination device with chain-type loading hoppers, is used for the large-angle, high-slope transfer of powder and granular materials. It can be flexibly assembled according to needs. Its advantages include a small footprint, low investment, and quick returns. It is specifically designed for the transfer of bulk materials with high difficulty, steep slopes, and large angles, and can even transport materials vertically from low to high angles. It can also perform multi-level transfers with "Z"-shaped bends. Assembly is very flexible. The key component is the chain-type hopper, used for material loading and transfer. Alternatively, the invention can transfer biomass fuel to the silo without a bucket elevator, using a large-angle bucket belt conveyor. The structure is similar to a bucket elevator, but the belt is made of rubber, while bucket elevators are generally made of steel. Another option is to build a separate belt conveyor system to transport biomass fuel to the fuel silo, suitable for new blast furnaces or pulverized coal injection equipment, but this increases investment and complicates the process.

[0024] The beneficial effects of this invention are as follows:

[0025] The present invention provides a method for blast furnace injection of biomass fuel. A mixed fuel obtained by replacing part of fossil fuel with uncarbonized biomass briquettes is injected into the blast furnace through the tuyeres using an injection device. The high-volatile biomass briquettes rapidly decompose and burn under the high-temperature, high-wind, and oxygen-rich conditions of the tuyeres' swirl zone, with the heat directly used to melt the slag. This improves the combustion efficiency and utilization rate of the biomass fuel. This method reduces fossil fuel use, carbon emissions, and SO2 pollution without affecting smelting parameters. The implementation process does not require carbonization equipment, eliminates the need for grinding and conveying fuel via pipelines, and avoids explosion-proof safety and environmental protection measures, saving significant investment and operating costs. It offers high safety and reliability, high economic value, and enables economical and green smelting, possessing significant and far-reaching implications. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the spraying equipment in Example 1;

[0027] In the diagram: 1-Booth; 2-Discharge pipe; 3-Guide pipe; 4-Tank; 5-Pulverized water tank; 6-Rotary feeder; 7-Pulverized coal gun; 8-Dome valve; 9-Weighing sensor; 10-Fluidized pressurization device; 11-Blast furnace; 12-Bucket elevator. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] 1. Preparation of biomass briquettes

[0031] Collect waste crop straw, sawdust, waste wood, branches, hay, fruit shells, fruit pits, rice husks, sugarcane bagasse, and rice husks. Following conventional biomass briquette fuel preparation methods, the above raw materials are crushed, mixed, extruded, bound with water glass, and dried to form granules with a particle size distribution of 1-3mm, 3-4mm, and 4-5mm particles in a weight ratio of 60:20:20, and a moisture content of less than 3% wt.

[0032] 2. Preparation of the jet blasting equipment

[0033] like Figure 1 As shown, the pulverized coal injection equipment includes a bucket elevator 12, the output end of which is located above the silo 1. The silo 1 is used to store fuel. The bottom of the silo 1 is provided with two conical discharge ports. Each conical discharge port is connected in sequence along the discharge direction to a discharge pipe 2, a guide pipe 3, a tank 4, a pulverized coal injection tank 5, a rotary feeder 6, and a pulverized coal injection gun 7. The inlet of the guide pipe 3 and the outlet of the tank 4 are both provided with dome valves 8. The side wall of the pulverized coal injection tank 5 is provided with a fluidizing and pressurizing device 10 so that the fuel entering the pulverized coal injection tank is sprayed out in a continuous injection manner. The pulverized coal injection tank 5 is also provided with a weighing sensor 9. The rotary feeder 6 is driven by a variable frequency motor. The pulverized coal injection gun 7 includes an inner tube and an outer tube that are nested together. The inner tube is used for fuel to pass through, and its diameter is matched with the particle size of the mixed fuel. The outer tube is connected to a compressed air pipe through a high-pressure valve to provide the conveying power medium. The output end of the pulverized coal injection gun 7 is connected to the tuyeres of the blast furnace 11.

[0034] 3. Methods for using biomass fuel in blast furnace injection

[0035] The uncarbonized biomass briquettes obtained in step 1 are used to replace a portion of the anthracite granules. The replacement amount of the biomass briquettes, measured by calorific value, is 10% of the calorific value of the original anthracite granules. The resulting mixed fuel is transported from a lower location to a higher location via a bucket elevator. It then passes sequentially through a discharge pipe, a guide pipe, and a feed hopper to the injection tank. The injection tank continuously injects fuel under pressure. Feeding is achieved through a volumetric rotary feeder driven by a variable frequency motor beneath the injection tank. The motor speed is adjusted to ensure a continuously controllable rate of injection into the blast furnace via a pulverized coal injection gun. The actual discharge rate is controlled by a speed-adjustable motor with a maximum speed ratio of 5:1, and the weight-based discharge accuracy is ±2%.

[0036] Example 2

[0037] 1. Preparation of biomass briquettes

[0038] Commercially available granular, uncarbonized biomass briquettes with a moisture content of less than 3% wt and a particle size distribution of 3-4 mm and 4-5 mm in a weight ratio of 30:10 (raw materials include crop straw, fruit husks, and rice husks).

[0039] 2. Preparation of the jet blasting equipment

[0040] like Figure 1 As shown, the pulverized coal injection equipment includes a bucket elevator 12, the output end of which is located above the silo 1. The silo 1 is used to store fuel. The bottom of the silo 1 is provided with two conical discharge ports. Each conical discharge port is connected in sequence along the discharge direction to a discharge pipe 2, a guide pipe 3, a tank 4, a pulverized coal injection tank 5, a rotary feeder 6, and a pulverized coal injection gun 7. The inlet of the guide pipe 3 and the outlet of the tank 4 are both provided with dome valves 8. The side wall of the pulverized coal injection tank 5 is provided with a fluidizing and pressurizing device 10 so that the fuel entering the pulverized coal injection tank is sprayed out in a continuous injection manner. The pulverized coal injection tank 5 is also provided with a weighing sensor 9. The rotary feeder 6 is driven by a variable frequency motor. The pulverized coal injection gun 7 includes an inner tube and an outer tube that are nested together. The inner tube is used for fuel to pass through, and its diameter is matched with the particle size of the mixed fuel. The outer tube is connected to a compressed air pipe through a high-pressure valve to provide the conveying power medium. The output end of the pulverized coal injection gun 7 is connected to the tuyeres of the blast furnace 11.

[0041] 3. Methods for using biomass fuel in blast furnace injection

[0042] The uncarbonized biomass briquettes obtained in step 1 are used to replace a portion of the anthracite pellets. The replacement amount of the biomass briquettes, measured by calorific value, is 50% of the calorific value of the original anthracite pellets. The resulting mixed fuel is transported from a lower location to a higher location via a bucket elevator. It then passes sequentially through a discharge pipe, a guide pipe, and a feed hopper to the injection tank. The injection tank continuously injects fuel under pressure, fed by a volumetric rotary feeder driven by a variable frequency motor beneath the injection tank. The motor speed is adjusted to ensure a continuously controllable rate of injection into the blast furnace via a pulverized coal injection gun. The actual discharge rate is controlled by a speed-adjustable motor with a maximum speed ratio of 5:1, and the discharge accuracy by weight is ±2%.

[0043] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A method for using biomass fuel for blast furnace injection, characterized in that: The method comprises the following steps: using biomass briquette fuel that has not been carbonized at high temperature to replace part of the fossil fuel to obtain a mixed fuel, and injecting the mixed fuel into the blast furnace from the tuyere of the blast furnace through an injection device to complete the combustion and smelting reaction; The replacement amount of the biomass briquette fuel is calculated based on calorific value, which is 10-50% of the calorific value of the fossil fuel previously replaced; The biomass briquette fuel is a granular fuel with a particle size distribution of 1 to 5 mm; The particle size distribution of the biomass briquette fuel is 1-3mm particle size, 3-4mm particle size, 4-5mm particle size, and the weight ratio is 0-60:20-30:10-20; The moisture content of the biomass briquette fuel is less than 3%wt; The raw materials of the biomass briquette fuel that has not been carbonized at high temperature are selected from a mixture of one or more of waste crop straw, sawdust, waste wood, branches, hay, fruit shells, fruit cores, rice husks, bagasse, and rice bran.

2. The method for using biomass fuel for blast furnace injection according to claim 1, characterized in that: The fossil fuel is anthracite, or a mixture of anthracite and bituminous coal.

3. The method for using biomass fuel for blast furnace injection according to claim 1, characterized in that: The fossil fuel is pulverized coal or granular coal.

4. The method for using biomass fuel for blast furnace injection according to claim 1, characterized in that: The injection equipment includes a transport component and an injection component; the transport component is a bucket elevator or a bucket belt conveyor; the injection component includes a silo, and two conical discharge ports are provided at the bottom of the silo, and each of the conical discharge ports is sequentially connected with a discharge pipe, a guide pipe, a material tank, a blowing tank, a rotary feeder and a coal injection gun along the discharge direction; the inlet of the guide pipe and the outlet of the material tank are both provided with a dome valve; a fluidizing pressurizing device is provided on the side wall of the blowing tank, and a weighing sensor is also provided on the blowing tank; the rotary feeder is driven by a variable frequency motor; the output end of the coal injection gun is connected to the tuyere of the blast furnace; the output end of the transport component is connected to the inlet of the silo.

5. The method for using biomass fuel for blast furnace injection according to claim 4, characterized in that: The coal injection gun comprises an inner tube and an outer tube which are mutually sleeved, the caliber of the inner tube matches the particle size of the mixed fuel, and the outer tube is connected to a compressed air pipe through a high-pressure valve.

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