Biomass charcoal ball for converter heat supplement and preparation method and use method thereof

Abstract

The application discloses a kind of biomass charcoal ball for converter heat supplement and its preparation method and use method, the raw material composition and weight percentage of the biomass charcoal ball are as follows: biomass charcoal powder 50-70%; hazardous waste flame retardant material 4-12%; iron-based material powder 13-30%; the rest is binder and balling agent;The biomass charcoal ball can greenly and environmentally protect the converter molten steel to supplement heat, improve the amount of converter scrap steel, improve the converter scrap steel ratio, reduce carbon dioxide emissions;Its use method is simple, can be added into the furnace from high-position bin before converter blowing early.

Description

Technical Field

[0001] This invention belongs to the field of green steelmaking technology, specifically relating to a biomass char ball for converter reheating, its preparation method, and its application method. Background Technology

[0002] Forestry biomass is abundant, accounting for 90% of the Earth's fixed energy. Biochar is a carbonaceous product mainly obtained from plants through high-temperature pyrolysis or redox reactions. Biochar is characterized by high carbon content, low ash content, low volatile matter, and high calorific value. It is primarily formed by plants absorbing carbon dioxide from the environment and converting it into carbon. The use of biochar can effectively utilize biomass resources, reduce dependence on fossil fuels, and decrease carbon dioxide emissions, making it an excellent alternative to fossil fuels. Due to its porous structure with pore sizes ranging from a few micrometers to tens of micrometers, biochar has a specific surface area tens or even hundreds of times larger than other fossil carbon products such as coal and coke, and a low ash content. This allows oxygen to come into more complete contact with the biochar during combustion, promoting the combustion reaction and resulting in a relatively fast combustion rate.

[0003] Since biochar is usually made from biomass materials such as plant fibers, most of the moisture and volatile substances in the raw materials are removed during the carbonization process, while the fiber structure is retained, forming a porous structure. These pores lead to a decrease in the density of biochar.

[0004] Biochar has advantages such as high carbon content, low ash content, and high calorific value. If biomass resources can be effectively utilized, it can become a green supplementary heating material for converter steelmaking. However, due to the porous structure, large specific surface area, fast combustion speed, and low density of biochar, if it is directly crushed and added to the converter through the furnace opening, it will burn rapidly or float on the slag surface and oxidize quickly, and the heat generated cannot enter the molten steel. Therefore, existing technologies use methods to increase the weight of biochar so that it can penetrate the slag layer after being added through the furnace opening.

[0005] For example, Chinese patent CN113005260A discloses a converter composite heating agent and its preparation method. Specifically, it discloses that the raw materials for the converter composite heating agent include a heat-replenishing agent, a regulator, a catalyst, a weight-gaining agent, a heat-enhancing agent, and a binder. The mass percentages of each component are: heat-replenishing agent 50-60%, regulator 10-15%, catalyst 1-3%, weight-gaining agent 10-20%, heat-enhancing agent 5-10%, and binder 2-4%. The heat-replenishing agent is composed of at least two of the following: waste graphite electrode powder, biochar powder, and semi-coke powder. The particle size of the waste graphite electrode powder, biochar powder, and semi-coke powder is ≤0.150mm. The regulator is composed of active lime powder and lightly calcined dolomite powder in a mass ratio of 2:1, with both active lime powder and lightly calcined dolomite powder having a particle size ≤0.150mm; the catalyst is composed of pyrolusite powder with a particle size ≤0.150mm; the weighting agent is steel granules with a particle size ≤5mm and a TFe mass percentage content ≥85%; the heat-increasing agent is composed of crystalline silicon cutting grade III sand with a particle size ≤0.150mm and secondary aluminum ash with a particle size ≤1mm, wherein the mass ratio of crystalline silicon cutting grade III sand and secondary aluminum ash is 4:1 to 9:1; the binder is one or a combination of phenolic resin and coal tar.

[0006] The graphite, semi-coke, and coke powder mentioned in the aforementioned patents are all fossil fuels. Their addition increases carbon dioxide emissions. The silicon oxidation in ferrosilicon powder releases heat to generate SiO2, requiring the addition of lime to balance the alkalinity. Lime production emits a large amount of carbon dioxide, further increasing carbon emissions. Furthermore, the patents fail to consider the characteristics of biomass char, such as its large pore structure, large specific surface area, and fast combustion speed. They do not provide targeted measures or methods to reduce the combustion rate of biomass char in the converter, ensuring that the heat released from biomass char oxidation is fully absorbed into the molten steel. Summary of the Invention

[0007] To solve the above-mentioned technical problems, the present invention provides a biomass char ball for converter reheating, its preparation method and usage method. The biomass char ball can reheat molten steel in a green and environmentally friendly way, increase the amount of scrap steel used in the converter, increase the scrap steel ratio in the converter, and reduce carbon dioxide emissions. Its usage method is simple, and it can be added into the furnace from the high-level silo in the early stage of converter blowing.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A biomass charcoal ball for converter reheating, wherein the raw material composition and weight percentage of the biomass charcoal ball are as follows:

[0010] Biochar powder 50-70%;

[0011] 4-12% of hazardous waste flame retardant materials;

[0012] Iron-based material powder 13-30%;

[0013] The remainder consists of binders and balling agents.

[0014] The biochar powder has a particle size ≤2mm; the carbon content in the biochar powder is 50-80%.

[0015] The hazardous waste flame retardant material is any one or more of high alumina powder and magnesia sand; the particle size of the hazardous waste flame retardant material is 300-400 mesh.

[0016] In the aforementioned hazardous waste flame retardant material, the weight percentage of any one or both of Al2O3 and MgO is 30-70%.

[0017] The iron-based material powder is any one or more of iron ore powder, iron powder, and steel balls for shot blasting; the particle size of the iron-based material powder is ≤3mm.

[0018] The iron-based material powder contains 60-95% iron by weight.

[0019] The particle size of the biomass charcoal balls used for converter reheating is 10-50 mm; the carbon content in the biomass charcoal balls used for converter reheating is 35-55%.

[0020] The binder is an inorganic or organic binder, such as any one or more of dextrin, water glass, and synthetic resin.

[0021] The pelleting agent is an inorganic or organic pelleting agent, such as any one or more of starch and bentonite.

[0022] The present invention also provides a method for preparing biomass char balls for converter reheating. The preparation method includes the following steps: mixing and stirring the raw materials in the formula amount for 30-60 minutes, adding water at a solid-liquid ratio of 100:(2-10), continuing to stir to form a semi-dry material, and then pelletizing, sieving, curing, and drying to prepare biomass char balls for converter reheating.

[0023] The present invention also provides a method for using the biomass char balls for converter reheating, wherein the biomass char balls for converter reheating are added into the furnace from the high-level silo in the early stage of converter blowing.

[0024] The amount of biomass char balls added for converter reheating is 1.5 to 8.5 kg / t of molten steel, preferably 6.0 to 8.5 kg / t of molten steel. The more biomass char balls added, the more carbon dioxide emissions are reduced.

[0025] Furthermore, when charging the converter with molten iron and scrap steel, add 10 kg more scrap steel per ton of molten steel and reduce the amount of molten iron per ton of molten steel accordingly. Also, add 2-15 kg of biomass char balls per ton of molten steel for reheating during the blowing process.

[0026] Due to its porous structure, low bulk density, light weight, large specific surface area, and fast combustion speed, biochar cannot be directly added to the converter to reheat molten steel. This invention addresses this by mixing biochar powder with high-melting-point hazardous waste flame-retardant iron-based material powder and then pelletizing it, thereby increasing the density of the biochar powder and the specific gravity of the biochar pellets. During the converter blowing process, the biochar pellets are added to the converter from the high-level silo. After addition, the biochar pellets can penetrate the slag layer and slowly oxidize and burn during contact with the molten steel. The released heat can be transferred to the molten steel to raise its temperature. Biochar is formed by plants absorbing carbon dioxide and converting it into carbon. Utilizing biochar to increase the temperature of the molten steel in the converter pool and increasing the amount of scrap steel used can reduce carbon dioxide emissions.

[0027] The mechanism of use of biomass charcoal balls for converter reheating provided by this invention is as follows:

[0028] In the early stages of converter blowing, biomass char balls are added from the silo. Because the biomass char balls are heavier than converter slag, they penetrate the slag layer and distribute between the molten steel and slag. The biomass char powder evenly distributed within the balls reacts with oxygen at high temperatures to produce carbon monoxide and carbon dioxide, releasing heat that enters the molten steel. Based on the characteristics of solid-liquid phase reactions, the active oxygen in the molten steel first reacts with the biomass char powder on the surface of the char balls in a carbon-oxygen reaction. The high-melting-point flame retardant material left after the surface biomass char powder dissolves into the steel slag, exposing the inner biomass char powder to the molten steel. The inner biomass char powder continues to react with the active oxygen in the molten steel in a carbon-oxygen reaction, and the high-melting-point flame retardant material left after the reaction continues to dissolve into the steel slag until the entire biomass char ball has reacted and dissolved, producing carbon monoxide and carbon dioxide at high temperatures, releasing heat that enters the molten steel. Through the exothermic oxidation reaction of carbon and oxygen in layers of biomass charcoal balls, heat is transferred into the molten steel during the converter blowing process, replenishing and raising the temperature of the molten steel. During the life cycle of the plant absorbing carbon dioxide and the biomass charcoal balls reacting with oxygen to release heat, carbon dioxide emissions are not increased. At the same time, the amount of scrap steel used in the converter blowing process can be increased, the amount of molten iron charged can be reduced, and carbon dioxide emissions are reduced.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. This invention reduces the combustion rate of biomass charcoal by crushing it and incorporating hazardous waste flame-retardant materials. The SiO2 and Al2O3 components in the hazardous waste flame-retardant materials can also lower the melting point of the converter slag, thus better promoting the steel-slag reaction during the converter blowing process. Furthermore, iron-based material powder is added to increase the weight of the charcoal, which is then extruded into pellets. The iron-based material powder acts as aggregate during the extrusion process, improving the strength of the biomass charcoal pellets, reducing the breakage rate during use, and providing environmentally friendly reheating for the converter molten steel. This also increases the amount of scrap steel used in the converter, improves the scrap steel ratio, and reduces carbon dioxide emissions.

[0031] 2. The biomass charcoal balls for converter reheating provided by the present invention can be added into the furnace from the high-level silo in the early stage of converter blowing.

[0032] 3. The raw materials used in this invention are all industrial waste, which are inexpensive and realize the recycling of industrial waste. Detailed Implementation

[0033] This invention provides biomass charcoal balls for converter reheating, wherein the raw material composition and weight percentage of the biomass charcoal balls are as follows:

[0034] Biochar powder 50-70%;

[0035] 4-12% of hazardous waste flame retardant materials;

[0036] Iron-based material powder 13-30%;

[0037] The remainder consists of binders and balling agents.

[0038] The biochar powder has a particle size ≤2mm; the carbon content in the biochar powder is 50-80%.

[0039] The hazardous waste flame retardant material is any one or more of high alumina powder and magnesia sand; the particle size of the hazardous waste flame retardant material is 300-400 mesh.

[0040] In the aforementioned hazardous waste flame retardant material, the weight percentage of any one or both of Al2O3 and MgO is 30-70%.

[0041] The iron-based material powder is any one or more of iron ore powder, iron powder, and steel balls for shot blasting; the particle size of the iron-based material powder is ≤3mm.

[0042] The iron-based material powder contains 60-95% iron by weight.

[0043] The binder is an inorganic or organic binder, such as one or more of dextrin, water glass, and synthetic resin.

[0044] The pelleting agent is an inorganic or organic pelleting agent, such as any one or more of starch and bentonite.

[0045] The preparation method of the biomass charcoal balls for converter reheating includes the following steps: mixing and stirring the raw materials in the formula amount for 30-60 minutes, adding water according to the solid-liquid ratio of 100:(2-10), continuing to stir to form a semi-dry material, and then preparing biomass charcoal balls for converter reheating through pelletizing, sieving, curing and drying.

[0046] The biomass charcoal balls used for converter reheating are added into the furnace from the high-level silo during the early stage of converter blowing.

[0047] The amount of biomass char balls added for converter reheating is 1.5 to 8.5 kg / t of molten steel, preferably 6.0 to 8.5 kg / t of molten steel.

[0048] Furthermore, when charging the converter with molten iron and scrap steel, an additional 10 kg of scrap steel per ton of molten steel is charged, while the amount of molten iron per ton of molten steel is reduced by 10 kg. During the blowing process, 2-15 kg of biomass charcoal balls per ton of molten steel are added for supplemental heating. The invention will now be described in detail with reference to specific embodiments.

[0049] Unless otherwise specified, all contents in this invention are weight percentages.

[0050] Example 1

[0051] A biomass charcoal ball for converter reheating, wherein the raw material composition and weight percentage of the biomass charcoal ball are as follows:

[0052] Biochar powder 70%;

[0053] 8% of hazardous waste flame retardant materials;

[0054] 13% iron-based material powder;

[0055] 5% dextrin;

[0056] Starch 4%.

[0057] Among them, the particle size of biomass charcoal powder is ≤2mm, and the carbon content in biomass charcoal powder is 50%; the particle size of hazardous waste flame retardant material is 300 mesh, the hazardous waste flame retardant material is high alumina powder, and the weight percentage of Al2O3 in high alumina powder is 33%; the particle size of iron-based material powder is ≤3mm, the iron-based material powder is iron powder, and the weight percentage of Fe in iron powder is 95%.

[0058] The preparation method of the biomass charcoal balls for converter reheating is as follows: mix and stir the raw materials according to the formula for 45 minutes, add water according to the solid-liquid ratio of 100:3, continue stirring to form a semi-dry material, and then pelletize, screen, cure and dry to prepare biomass charcoal balls for converter reheating with a particle size of 20mm and a C content of 32%.

[0059] Taking the production of Q235 in a 120-ton converter at a certain factory as an example, the biomass charcoal balls prepared in this embodiment for converter reheating are used as the raw material for converter reheating. Details are as follows:

[0060] (1) When charging the converter with molten iron and scrap steel, on the basis of achieving heat balance, an additional 10 kg of scrap steel per ton of molten steel is charged, correspondingly reducing the amount of molten iron per ton of molten steel by 10 kg. During the blowing process, 2-10 kg of biomass char balls are added for supplemental heating. 10 kg of molten iron contains 0.43 kg of carbon, which generates 1.58 kg of carbon dioxide during the blowing process. The carbon dioxide emissions per ton of molten steel can be reduced by 1.58 kg in the converter process. 10 kg of molten iron generates 11.8 kg of carbon dioxide during the reduction of iron ore into molten iron, resulting in a total reduction of 13.38 kg of carbon dioxide.

[0061] (2) After the converter starts blowing, slag-forming material is added from the high-level silo to form slag;

[0062] (3) After the slag is formed in the early stage of the converter, biomass char balls are added from the high-level silo.

[0063] (4) As the oxygen lance continues to blow oxygen, the biomass carbon balls oxidize and release heat, thus replenishing the heat of the molten steel.

[0064] Table 1. Reduction of hot metal charge and carbon dioxide emissions during converter blowing process using biomass char balls

[0065]

[0066] Example 2

[0067] A biomass charcoal ball for converter reheating, wherein the raw material composition and weight percentage of the biomass charcoal ball are as follows:

[0068] Biochar powder 55%;

[0069] 10% of hazardous waste flame retardant materials;

[0070] Iron-based material powder 24%;

[0071] 3% water glass;

[0072] 8% bentonite.

[0073] Among them, the particle size of biomass charcoal powder is ≤2mm, and the carbon content in biomass charcoal powder is 80%; the particle size of hazardous waste flame retardant material is 400 mesh, the hazardous waste flame retardant material is magnesia, and the weight percentage of MgO in magnesia is 40%; the particle size of iron-based material powder is ≤3mm, the iron-based material powder is iron powder, and the weight percentage of Fe in iron powder is 73%.

[0074] The preparation method of the biomass char balls used for converter reheating is the same as in Example 1.

[0075] The biomass char balls for converter reheating prepared in this embodiment have a particle size of 30 mm and a carbon content of 40%.

[0076] Taking the production of Q235 in a 120-ton converter at a certain factory as an example, the biomass charcoal balls prepared in this embodiment for converter reheating are used as the raw material for converter reheating. Details are as follows:

[0077] (1) When the converter is charged with molten iron and scrap steel, on the basis of meeting the heat balance, an additional 10 kg of scrap steel / ton of molten steel is charged, and the corresponding amount of molten iron / ton of molten steel is reduced. During the blowing process, 3-12 kg / ton of molten steel is added to supplement the heat with biomass char balls.

[0078] (2) After the converter starts blowing, slag-forming material is added from the high-level silo to form slag;

[0079] (3) After the slag is formed in the early stage of the converter, biomass char balls are added from the high-level silo.

[0080] (4) As the oxygen lance continues to blow oxygen, the biomass carbon balls oxidize and release heat, thus replenishing the heat of the molten steel.

[0081] Table 2. Reduction of hot metal charge and carbon dioxide emissions during converter blowing process using biomass char balls.

[0082]

[0083] Example 3

[0084] A biomass charcoal ball for converter reheating, wherein the raw material composition and weight percentage of the biomass charcoal ball are as follows:

[0085] Biochar powder 60%;

[0086] 12% of hazardous waste flame retardant materials;

[0087] Iron-based material powder 19%;

[0088] 3% dextrin;

[0089] 6% bentonite.

[0090] Among them, the particle size of biomass charcoal powder is ≤2mm, and the carbon content in biomass charcoal powder is 68%; the particle size of hazardous waste flame retardant material is -400 mesh, and the hazardous waste flame retardant material is composed of high alumina powder and magnesia in a mass ratio of 1:1. The weight percentage of Al2O3 in high alumina powder is 34%, and the weight percentage of MgO in magnesia is 43%; the particle size of iron-based material powder is ≤3mm, and the iron-based material powder is shot blasting steel balls, and the weight percentage of iron in shot blasting steel balls is 82%.

[0091] The preparation method of the biomass char balls used for converter reheating is the same as in Example 1.

[0092] The biomass char balls for converter reheating prepared in this embodiment have a particle size of 50 mm and a carbon content of 41%.

[0093] Taking the production of Q235 in a 120-ton converter at a certain factory as an example, the biomass charcoal balls prepared in this embodiment for converter reheating are used as the raw material for converter reheating. Details are as follows:

[0094] (1) When charging the converter with molten iron and scrap steel, on the basis of meeting the heat balance, add 10 kg more scrap steel per ton of molten steel and correspondingly reduce the charging of molten iron per ton of molten steel. During the blowing process, add 3-12 kg of biomass char balls per ton of molten steel for heat supplementation. (2) After the converter starts blowing, add slag-forming material from the high-level silo to form slag.

[0095] (3) After the slag is formed in the early stage of the converter, biomass char balls are added from the high-level silo.

[0096] (4) As the oxygen lance continues to blow oxygen, the biomass carbon balls oxidize and release heat, thus replenishing the heat of the molten steel.

[0097] Table 3. Reduction of hot metal charge and carbon dioxide emissions during converter blowing process using biomass char balls

[0098]

[0099] Comparative Example 1

[0100] In Example 1, all the hazardous waste flame retardant materials in the raw materials were replaced with an equal weight of biomass charcoal powder, and everything else was the same as in Example 1.

[0101] Comparative Example 2

[0102] In Example 1, all the iron-based material powder in the raw materials was replaced with an equal weight of biochar powder, and everything else was the same as in Example 1.

[0103] Comparative Examples 1 and 2 could not be compressed into balls. Without the addition of hazardous waste flame retardant, the balls would fall apart during the compression process. Without the addition of iron powder, the balls had no strength after compression and would break easily when squeezed by hand.

[0104] As can be seen from the above, the biomass char balls provided by this invention can reheat molten steel in a green and environmentally friendly manner, increasing the amount of scrap steel used in the converter, increasing the scrap steel ratio in the converter, and reducing carbon dioxide emissions; moreover, the breakage rate of the biomass char balls during use is below 0.01%. The above detailed description of a biomass char ball for converter reheating, its preparation method, and its usage method, with reference to the embodiments, is illustrative rather than limiting. Several embodiments can be listed according to the defined scope. Therefore, changes and modifications without departing from the overall concept of this invention should be within the protection scope of this invention.

Claims

1. A type of biomass charcoal ball for converter reheating, characterized in that, The raw material composition and weight percentage of the biomass charcoal balls are as follows: Biochar powder 50-70%; 4-12% of hazardous waste flame retardant materials; Iron-based material powder 13-30%; The remainder consists of binders and pelletizing agents; The hazardous waste flame retardant material is any one or more of high-alumina powder and magnesia.

2. The biomass charcoal balls for converter reheating according to claim 1, characterized in that, The biochar powder has a particle size ≤2mm; the carbon content in the biochar powder is 50-80%.

3. The biomass charcoal balls for converter reheating according to claim 1, characterized in that, The particle size of the hazardous waste flame retardant material is 300-400 mesh.

4. The biomass charcoal balls for converter reheating according to claim 1, characterized in that, In the aforementioned hazardous waste flame retardant material, the weight percentage of any one or both of Al2O3 and MgO is 30-70%.

5. The biomass charcoal balls for converter reheating according to claim 1, characterized in that, The iron-based material powder is any one or more of iron ore powder, iron powder, and steel balls for shot blasting; the particle size of the iron-based material powder is ≤3mm.

6. The biomass charcoal balls for converter reheating according to claim 1, characterized in that, The iron-based material powder contains 60-95% iron by weight.

7. The biomass charcoal balls for converter reheating according to claim 1, characterized in that, The particle size of the biomass charcoal balls used for converter reheating is 10-50 mm; the carbon content in the biomass charcoal balls used for converter reheating is 35-55%.

8. The method for preparing biomass charcoal balls for converter reheating as described in any one of claims 1-7, characterized in that, The preparation method includes the following steps: mixing and stirring the raw materials in the formula amount for 30-60 minutes, adding water according to a solid-liquid ratio of 100:(2-10), continuing to stir to form a semi-dry material, and then preparing biomass char balls for converter reheating through pelletizing, sieving, curing, and drying.

9. The method of using biomass charcoal balls for converter reheating as described in any one of claims 1-7, characterized in that, The biomass charcoal balls used for converter reheating are added into the furnace from the high-level silo during the early stage of converter blowing.

10. The method of using biomass charcoal balls for converter reheating according to claim 9, characterized in that, The amount of biomass char balls added for converter reheating is 1.5~8.5 kg / t of molten steel.

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