Biomass charcoal ball for electric furnace and preparation method and application thereof

Abstract

The application discloses a biomass charcoal ball for an electric furnace and a preparation method and application thereof, and the biomass charcoal ball for the electric furnace is obtained through proportioning and balling, can replace traditional carbon balls or molten iron carbon, and can be effectively applied in electric furnace smelting, and can reduce electric furnace smelting emission, form good foamed slag, fully absorb combustion chemical energy by a molten steel pool, and reduce the content of iron oxide in furnace slag and the like.

Description

Technical Field

[0001] This invention relates to the field of biochar utilization technology, and more specifically, to a biochar ball for electric furnace, its preparation method, and its application. Background Technology

[0002] Under the dual-carbon background, the steel industry is developing towards a green and low-carbon emission trend. Electric arc furnaces (EAFs), which primarily use scrap steel as raw material, have near-zero carbon emissions when the scrap steel is disposed of as waste. Therefore, the carbon emissions from EAF smelting are significantly lower than those from converters, which use molten iron as the main raw material. However, EAFs require oxygen blowing during the smelting process to provide the necessary chemical energy and ensure good stirring of the molten pool. This necessitates the addition of carbon during the smelting process to utilize the carbon-oxygen reaction to stir the molten pool. Currently, the main methods for adding carbon are using carbon-containing iron raw materials, adding ordinary carbon balls, or injecting carbon powder. This still results in a large amount of CO2 being generated during EAF smelting. To further reduce the carbon emissions from the necessary carbon addition in EAFs, the application of biochar in metallurgy is being considered. Biomass resources are a renewable and clean energy source, mainly including agricultural crops and their waste (corn stalks, rice stalks, and rice husks, etc.), forestry waste (forest growth residues and forest production residues, etc.), animal manure products, and the biodegradable portions of industrial and municipal waste. Biochar is produced by treating biomass at high temperatures under anaerobic conditions (i.e., pyrolysis), during which the oil and gas in the biomass are burned off, resulting in a charcoal-like carbon product. Internationally, biochar is generally considered to be produced by natural plant growth through photosynthesis, which fixes CO2. The CO2 released during its combustion does not increase the Earth's carbon emissions, so the carbon emissions from biochar formation can be considered very low.

[0003] The application of biochar is of great significance for achieving green and low-carbon steelmaking in the steel industry. Biochar can be used as fuel or reducing agent in processes such as blast furnaces, sintering, and pelletizing. It can also be used as a carburizing agent and foaming agent in electric arc furnace steelmaking. Biomass resources have great potential to become an alternative carbon source for electric arc furnace steelmaking. The application of biochar primarily involves the preparation of biochar with coal-like properties. Biochar powder is mainly produced through low-temperature pyrolysis. After preparation, due to its very low density and high nitrogen and phosphorus content in some biochar, its application in metallurgy faces more difficult technical bottlenecks.

[0004] Research and applications of biochar in electric furnaces are mainly in Europe, as follows: Dankwah et al. studied the ability of reducing slag from tire and coke mixtures to oxidize iron, carburize, and desulfurize. Adding tires to coke significantly improved the reduction of iron oxide and increased the carbon content in the reduced metals while slightly reducing the sulfur content. It is feasible to use tires blended with coke as a partial or complete replacement for coke used in electric arc furnace steelmaking as a reducing agent and carbon raiser. In the European DEW steel plant, the use of biochar powder to replace coal had no negative impact on the slag and molten steel composition. However, due to the high reactivity of the biochar powder, it burned directly after being injected into the furnace, preventing it from penetrating into the slag and thus affecting the foaming effect. The European FENO plant also experienced low biochar utilization efficiency when adding briquetted biochar powder into the furnace. The European MH plant's pulverized biochar injection experiment did not achieve a significant foaming effect because the charcoal powder had poor wettability, low density, and high reactivity, causing it to burn directly upon entering the furnace. This resulted in insufficient charcoal powder penetrating into the slag layer, leading to poor slag foaming.

[0005] In summary, existing technologies for biochar application in electric arc furnaces primarily employ either furnace door injection or briquetting methods, enabling biochar use in electric arc furnaces. However, the injection method, using furnace door or wall lances, suffers from low efficiency due to the very low density of biochar, making it difficult to inject it to the bottom of the slag layer. This results in poor biochar utilization efficiency, as the energy released during combustion is difficult to absorb by the molten steel pool, and the foaming slag effect is also poor in electric arc furnaces. Current biochar briquetting technology produces very low-density pellets, leading to similar utilization efficiency issues after addition to the molten pool. Furthermore, biochar application presents safety concerns such as spontaneous combustion, all of which require the development of new technologies to address.

[0006] In view of the above, there is an urgent need to study a new method for the preparation and application of biochar, which can realize the effective application of biochar in electric arc furnace smelting, and can play a role in reducing emissions from electric arc furnace smelting, creating good foam slag, ensuring that the chemical energy of combustion is fully absorbed by the molten steel pool, and reducing the iron oxide content of slag. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a biomass char ball for electric furnaces, its preparation method, and its application. The biomass char ball for electric furnaces is obtained through batching and pelletizing. This biomass char ball can replace traditional carbon balls or carbon in molten iron, achieving effective application in electric furnace smelting. It can reduce emissions from electric furnace smelting, create good foam slag, ensure that the chemical energy of combustion is fully absorbed by the molten steel pool, and reduce the iron oxide content in the slag.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] The first aspect of the present invention provides a biomass charcoal ball for an electric furnace, the composition of which includes fixed carbon, elemental iron and other unavoidable components;

[0010] The fixed carbon content is 30–45 wt%, and the elemental iron content is 25–35 wt%.

[0011] The density of the biomass charcoal balls used in the electric furnace is 1.9–2.3 g / cm³. 3 .

[0012] Preferably, the other unavoidable components include S, P2O5, N, FeOx, SiO2, CaO, and water; wherein the S content is <0.05wt%, the P2O5 content is <0.15wt%, the N content is <0.1%, and the water content is <1wt%.

[0013] Preferably, the compressive strength of a single biomass charcoal ball for an electric furnace is ≥10MPa, and the diameter is 2-5cm.

[0014] Preferably, the drop strength of the biomass charcoal balls for the electric furnace meets the requirement that they will not break after being dropped three times from a height of 2 meters.

[0015] Preferably, the raw materials used in the preparation of biomass charcoal balls for the electric furnace include the following components by mass percentage: 30-40% direct reduced iron powder, 55-65% biochar powder, and 3-6% binder.

[0016] Preferably, the biochar powder is selected from one of wood charcoal powder, bamboo charcoal powder, and coffee grounds charcoal powder; and / or

[0017] The adhesive is made from waste corn flour and sodium silicate, wherein the waste corn flour has a mass percentage content of 50-60% and the sodium silicate has a mass percentage content of 40-50%.

[0018] A second aspect of the present invention provides a method for preparing biomass charcoal balls for electric furnaces as described in the first aspect of the present invention, comprising the following steps:

[0019] S1, Pyrolysis-treated biochar is made into powder to obtain biochar powder;

[0020] S2, the biochar powder obtained in step S1 is mixed and stirred with direct reduced iron powder and binder, water is added and pressed into spheres, then baked at low temperature, and after cooling, biochar balls for electric furnaces are obtained.

[0021] Preferably, in step S1, the particle size of the biochar powder is <0.2 mm.

[0022] Preferably, in step S2:

[0023] The amount of water used is 8-15 wt% of the total amount of biochar powder, direct reduced iron powder, and binder; and / or

[0024] During the low-temperature baking process, the baking temperature is 70-100℃ and the baking time is 3-5 hours.

[0025] Preferably, in step S2, the biomass charcoal balls for the electric furnace are packaged and stored in moisture-proof woven bags.

[0026] A third aspect of the present invention provides the application of biomass charcoal balls for electric furnaces as described in the first aspect of the present invention in the electric furnace smelting process.

[0027] Preferably, biomass char balls for electric furnaces are added in multiple batches after the slag from the electric furnace smelting process has formed and become fluid.

[0028] The total amount of biomass charcoal balls added to the electric furnace is 5-20 kg / t steel, the amount added each time is 1-3 kg / t steel, and the time interval between each addition is 2-3 minutes.

[0029] The beneficial effects of this invention are as follows:

[0030] 1. The biochar used in this invention is mainly wood charcoal powder, bamboo charcoal powder and coffee grounds charcoal powder because these three types of biochar have relatively low phosphorus, sulfur and nitrogen content, their auto-ignition point meets current safety requirements in laboratory testing, and they have a high carbon content, which can play a metallurgical role in electric furnace smelting without polluting the molten steel.

[0031] 2. The adhesive prepared by the present invention using waste corn flour and sodium silicate can meet the strength requirements of biochar balls after low-temperature baking;

[0032] 3. The biomass char balls for electric furnaces prepared by this invention can reduce carbon emissions by 5-30 kg CO2 / t steel and reduce power consumption by more than 20 kWh / t by replacing traditional carbon balls or carbon in molten iron, and control the FeOx content in slag to remain stable below 25%. The biomass char balls for electric furnaces prepared by this invention are particularly suitable for all-scrap steel electric furnace smelting or smelting mode of scrap steel plus direct reduced iron.

[0033] 4. This invention enables the effective application of biochar in electric arc furnace smelting, thereby reducing emissions from electric arc furnace smelting, creating good foam slag, ensuring that the chemical energy from combustion is fully absorbed by the molten steel pool, and reducing the iron oxide content in the slag. Attached Figure Description

[0034] Figure 1 This is a schematic flowchart of the method for preparing biomass charcoal balls for electric furnaces according to the present invention;

[0035] Figure 2This is a sample image of the biomass charcoal balls for electric furnaces according to the present invention. Detailed Implementation

[0036] To better understand the above-mentioned technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0037] This invention provides a biomass charcoal ball for electric furnaces, comprising fixed carbon, elemental iron, and other unavoidable components; the fixed carbon content is 30-45 wt%, the elemental iron content is 25-35 wt%, and the density of the biomass charcoal ball for electric furnaces is 1.9-2.3 g / cm³. 3 .

[0038] Other unavoidable components include S, P2O5, N, FeOx, SiO2, CaO, and water. Among these, S, P2O5, N, and water are all harmful components, requiring S content <0.05wt%, P2O5 content <0.15wt%, N content <0.1wt%, and water content <1wt%. The remaining component is FeO. x The oxides introduced by direct reduction of iron, such as SiO2 and CaO, and the volatiles introduced by biochar.

[0039] The compressive strength of a single biomass charcoal ball for an electric furnace is ≥10MPa, and the diameter is 2-5cm.

[0040] The raw materials used in the preparation of biomass charcoal balls for this electric furnace include the following components by mass percentage: 30-40% direct reduced iron powder, 55-65% biochar powder, and 3-6% binder. The biochar powder is selected from one of wood charcoal powder, bamboo charcoal powder, or coffee grounds charcoal powder; the binder is prepared from waste corn flour and sodium silicate, with the waste corn flour accounting for 50-60% by mass and the sodium silicate accounting for 40-50% by mass.

[0041] The aforementioned biomass charcoal briquettes for electric furnaces are primarily made by pressing direct reduced iron powder and biochar powder into briquettes. This is mainly to increase the density of the biomass charcoal briquettes. Direct reduced iron powder is chosen because it is also a low-carbon emission raw material, and the price of direct reduced iron powder, especially if used as waste material, is low. The mass ratio is set primarily to control density, aiming to maintain the density of the biomass charcoal briquettes at 1.9–2.3 g / cm³. 3 This ensures that the biomass char balls added to the molten pool of the electric furnace can remain suspended within the slag layer. The actual density of the electric furnace slag, as measured, is 2.5–2.7 g / cm³. 3 However, due to foaming during the electric furnace smelting process, the actual density is between 1.9 and 2.3 g / cm³. 3Between these parameters, the density of the biomass charcoal balls used in the electric arc furnace is sufficient to allow them to suspend in the slag. Furthermore, this design does not require direct contact between the biomass charcoal balls and molten steel. This is because the biomass charcoal balls have a high nitrogen and moisture content; direct contact with molten steel could easily increase nitrogen and hydrogen content, which is detrimental to steel composition control. Therefore, this invention ensures, through formula ratio design and related density design, that the biomass charcoal balls used in the electric arc furnace can play an effective metallurgical role without contaminating the molten steel. The biochar powder selected in this invention is mainly wood charcoal powder, bamboo charcoal powder, and coffee grounds powder because these three types of biochar have relatively low phosphorus, sulfur, and nitrogen content, their auto-ignition points meet current safety requirements in laboratory testing, and they have a high fixed carbon content. They can play a metallurgical role in electric arc furnace smelting without contaminating the molten steel. Straw charcoal is not selected due to its low fixed carbon content and high phosphorus content. The compressive strength of a single biomass charcoal ball for electric furnaces is above 10MPa, and the drop strength meets the requirement of not breaking after three consecutive drops from a height of 2 meters. This is mainly because the charcoal balls will not be crushed in large quantities during application, hence the strength requirement.

[0042] Combination Figure 1 As shown, the above-mentioned method for preparing biomass charcoal balls for electric furnaces includes the following steps:

[0043] S1, Pyrolysis-treated biochar is made into powder to obtain biochar powder;

[0044] Biochar is pyrolyzed to remove volatiles, and the pyrolyzed biochar is then powdered to obtain biochar powder with a particle size <0.2mm. Biochar powder can be made from one of the following: wood charcoal powder, bamboo charcoal powder, or coffee grounds charcoal powder.

[0045] S2, the biochar powder obtained in step S1 is mixed and stirred with direct reduced iron powder and binder, water is added and pressed into spheres, then baked at low temperature, and after cooling, biochar balls for electric furnaces are obtained.

[0046] The biochar powder obtained in step S1 is mixed with direct reduced iron powder and a binder. Water (8-15 wt% of the total raw materials, including biochar powder, direct reduced iron powder, and binder) is added and pressed into spheres. These spheres are then baked at 70-100°C for 3-5 hours to increase strength. After cooling, biochar spheres for electric furnaces are obtained. These biochar spheres are stored in moisture-proof woven bags, with each bag containing 500-1000 kg. Storage requires moisture protection and ventilation.

[0047] To ensure the strength of the biomass charcoal balls used in the electric furnace, the binder is made of waste corn flour and sodium silicate, with the waste corn flour accounting for 50-60% by mass and the sodium silicate accounting for 40-50% by mass.

[0048] Direct reduced iron powder can be made from low-grade reduced iron powder produced in vertical shaft furnaces that cannot be directly used in electric furnaces, such as direct reduced iron tailings powder.

[0049] From a preparation process perspective, the key technology lies in the safe preparation of biochar. This invention uses a binder made from waste corn flour and sodium silicate, which meets the strength requirements of the biochar balls after low-temperature baking. The baking temperature of 70-100℃ is selected based on laboratory research results, indicating a suitable temperature for baking without spontaneous combustion. Baking temperatures above 100℃ cannot avoid the risk of spontaneous combustion, while baking temperatures below 70℃ result in too low baking efficiency. After preparation, the biochar balls for electric furnaces are packaged primarily for moisture protection; preventing moisture absorption prevents pulverization and eliminates the possibility of spontaneous combustion.

[0050] This invention also provides an application of biomass char balls for electric furnaces in the electric furnace smelting process. The biomass char balls are transported to a silo, and the total amount of biomass char balls added per ton of steel is 5-20 kg / t. The biomass char balls are added in multiple batches after the slag has formed and become fluid. Each addition is 1-3 kg / t of steel, with an interval of 2-3 minutes between additions. The addition of biomass char balls to the electric furnace creates good foamed slag, and the foamed slag is maintained for 2-3 minutes after each addition, thereby reducing power consumption and slag FeO content. x Content and Effects. Application Results: Biomass charcoal briquettes used in electric furnaces, by replacing traditional charcoal briquettes or molten iron carbon, reduce carbon emissions by 5-30 kg CO. 2 / t steel, reducing power consumption by more than 20kWh / t, and controlling slag FeO x The content remains stable below 25%.

[0051] Biomass char balls for electric arc furnaces should be added after the slag has formed and become fluid. After entering the molten steel slag reaction pool from the high-level silo, the biomass char balls can use their own momentum to penetrate the slag layer and undergo a chemical reaction, releasing CO and CO2 bubbles to drive slag foaming. Due to their density, they can remain suspended deep within the slag, resulting in good foaming slag and more efficient CO2 bubble generation. The generated CO2 bubbles release more chemical energy to heat the molten steel pool. This invention requires adding 1-3 kg / t of steel each time. If the addition is below this lower limit, the slag foaming effect will be poor; if it is above this upper limit, it is prone to large splashing. Multiple additions are possible, from 2 to 8 times, but the total addition should be limited to 5-20 kg / t of steel. Adding too little will have a small effect, while adding too much will affect the production rhythm and prolong the smelting cycle. The 2-3 minute interval between additions is mainly determined based on the measured foaming maintenance time in large-scale production. Of course, if actual production conflicts with the addition of other slag-forming agents, the interval can be extended according to the actual production situation.

[0052] Example 1

[0053] Bamboo charcoal that has undergone pyrolysis is processed into powder to obtain bamboo charcoal powder;

[0054] Direct reduced iron powder, bamboo charcoal powder, and binder from the vertical shaft furnace are mixed and stirred evenly. The particle size of both direct reduced iron powder and bamboo charcoal powder must be less than 0.2 mm. The mass ratio of direct reduced iron powder is 35%, bamboo charcoal powder is 60%, and binder is 5%. The binder is made from waste corn flour and sodium silicate, with waste corn flour accounting for 50% and sodium silicate for 50%. After mixing the above raw materials evenly, 8-15 wt% water is added, and the mixture is formed into blocks and pressed into double-hemispherical pellets. These pellets are then baked at 80℃ for 4 hours, followed by cooling. The resulting biomass charcoal pellets for electric furnaces are as follows: Figure 2 As shown. After preparation, package in 500kg sealed woven bags to prevent moisture absorption during storage.

[0055] The prepared biomass charcoal briquettes for electric furnaces were analyzed and found to contain the following components: fixed carbon: 40%, metallic Fe: 32%, S: 0.04%, P2O5: 0.09%, N: 0.07%, and H2O: 0.04%. The remaining components are oxides introduced by direct reduction of iron, such as FeOx, SiO2, and CaO, and volatiles introduced by the biomass briquettes; their content is not specified. The density was measured to be 2.1 g / cm³. 3 It has a compressive strength of 15MPa and a drop strength requirement of 2 meters three times consecutively without breaking, meeting the requirements for electric furnace applications.

[0056] Electric Furnace Application: The aforementioned biomass charcoal balls for electric furnaces were transported to the high-level silo at the electric furnace plant. Before transportation, the packaging bags were removed, and the silos were sealed to prevent moisture during transport. The biomass charcoal balls were then placed in the high-level silo and applied to a 150-ton all-scrap steel smelting electric furnace. After the slag formed and became fluid, 200 kg of biomass charcoal balls were added in five batches, totaling one ton, with a 2.5-minute interval between each addition. After the addition of the biomass charcoal balls, the arc noise was reduced from over 95 decibels to below 90 decibels, indicating that the biomass charcoal balls were effective in creating foamy slag. After smelting, the steel composition analysis showed no significant increase in nitrogen, sulfur, or phosphorus. The final smelting power consumption of the electric furnace decreased from 360 kWh / t with the conventional addition of ordinary carbon powder to 330 kWh / t, and the slag iron oxide content decreased from 40% to 23%. The reduced slag iron oxide content indicates an increased iron recovery rate during steelmaking. In the electric furnace smelting process, adding the biomass char balls prepared in this embodiment reduces carbon emissions by 10 kg / t compared to the conventional addition of coke powder.

[0057] Example 2

[0058] The pyrolyzed charcoal is made into powder to obtain charcoal powder;

[0059] Direct reduced iron powder, charcoal powder, and binder from the vertical shaft furnace are mixed and stirred evenly. The particle size of both the direct reduced iron powder and charcoal powder must be less than 0.2 mm. The direct reduced iron powder accounts for 30% of the total mass, the charcoal powder 64%, and the binder 6%. The binder is made from waste corn flour and sodium silicate, with waste corn flour accounting for 60% and sodium silicate 40%. After mixing the above raw materials evenly, 8-15 wt% water is added, and the mixture is formed into blocks and pressed into double-hemispherical pellets. These pellets are then baked at 100℃ for 3 hours and subsequently cooled. After preparation, the pellets are sealed in 1000 kg woven bags to prevent moisture absorption during storage.

[0060] The prepared biomass charcoal balls for electric furnaces were analyzed and their composition is as follows: fixed carbon: 45%, metallic Fe: 30%, S: 0.07%, P2O5: 0.09%, N: 0.05%, and H2O: 0.03%, with the remainder being FeO. x The oxides introduced by direct reduced iron (SiO2, CaO, etc.) and the volatiles introduced by biochar balls are not subject to requirements regarding their content; the density is measured to be 1.9 g / cm³. 3 It has a compressive strength of 10MPa and a drop strength requirement of 2 meters three times consecutively without breaking, meeting the requirements for electric furnace applications.

[0061] The aforementioned biomass charcoal balls for electric arc furnaces were transported to the high-level silo at the electric arc furnace plant. Before transport, the packaging bags were removed, and the silos were sealed to prevent moisture during transport. The biomass charcoal balls were then placed in the high-level silo and applied to an electric arc furnace smelting 100 tons of scrap steel with 20% direct reduced iron hot briquettes. After the slag formed and became fluid, 300 kg of biomass charcoal balls were added in five batches, totaling 1.5 tons, with a 3-minute interval between each addition. After the addition of the biomass charcoal balls, the arc noise was reduced from over 95 decibels to below 90 decibels, indicating that the biomass charcoal balls were effective in creating foamy slag. After smelting, the steel composition analysis showed no significant increase in nitrogen, sulfur, or phosphorus. The final power consumption of the electric arc furnace decreased from 380 kWh / t with the conventional addition of ordinary carbon powder to 350 kWh / t, and the iron oxide content in the slag decreased from 45% to 25%. The reduced iron oxide content in the slag indicates an increase in iron recovery during the steelmaking process. In the electric furnace smelting process, adding the biomass char balls prepared in this embodiment reduces carbon emissions by 25 kg / t compared to the conventional addition of coke powder.

[0062] Example 3

[0063] The pyrolysis-treated coffee grounds charcoal is made into powder to obtain coffee grounds charcoal powder;

[0064] Direct reduced iron powder from the vertical shaft furnace, coffee grounds charcoal powder, and binder are mixed and stirred evenly. The particle size of both direct reduced iron powder and coffee grounds charcoal powder must be less than 0.2mm. The proportions of direct reduced iron powder (40%), coffee grounds charcoal powder (55%), and binder (5%) are as follows: binder is made from waste corn flour and sodium silicate, with waste corn flour comprising 60% and sodium silicate 40%. After mixing the above raw materials evenly, 8-15 wt% water is added, and the mixture is formed into blocks and pressed into double-hemispherical pellets. These pellets are then baked at 70℃ for 5 hours and subsequently cooled. After preparation, the pellets are sealed in 1000kg woven bags to prevent moisture absorption during storage.

[0065] The prepared biomass charcoal balls for electric furnaces were analyzed and their composition is as follows: solid C: 30%, metallic Fe: 35%, S: 0.01%, P2O5: 0.02%, N: 0.04%, and H2O: 0.08%, with the remainder being FeO. x The oxides introduced by direct reduction of iron (such as SiO2 and CaO) and the volatiles introduced by coffee grounds are not subject to requirements regarding their content; the density was measured at 2.3 g / cm³. 3 It has a compressive strength of 20MPa and a drop strength that meets the requirement of not breaking after three consecutive drops from a height of 2 meters, which meets the requirements for electric furnace applications.

[0066] The aforementioned biomass charcoal balls for electric arc furnaces were transported to the high-level silo at the electric arc furnace plant. Before transport, the packaging bags were removed, and the silos were sealed to prevent moisture during transport. Once in the high-level silo, the biomass charcoal balls were applied to a 150-ton all-scrap steel smelting electric arc furnace. After the slag formed and became fluid, 150 kg of biomass charcoal balls were added in five batches, totaling 0.75 tons, with a two-minute interval between each addition. After the addition of the biomass charcoal balls, the arc noise was reduced from over 95 decibels to below 88 decibels, indicating that the biomass charcoal balls were effective in creating foamy slag. After smelting, the steel composition analysis showed no significant increase in nitrogen, sulfur, or phosphorus. The final smelting power consumption of the electric arc furnace decreased from 350 kWh / t with the addition of ordinary carbon powder to 350 kWh / t, and the iron oxide content in the slag decreased from 40% to 30%. The reduced iron oxide content in the slag indicates an increase in iron recovery during the steelmaking process. In the electric furnace smelting process, adding the biomass char balls prepared in this embodiment reduces carbon emissions by 8.25 kg / t compared to the conventional addition of coke powder.

[0067] In summary, the biomass char balls prepared by this invention can replace traditional char balls or molten iron with carbon, thereby reducing carbon emissions by 5-30 kg CO2 / t steel, reducing power consumption by more than 20 kWh / t, and controlling the FeOx content in the slag to remain stable below 25%. It is particularly suitable for electric arc furnace smelting of all scrap steel or smelting mode of scrap steel plus direct reduced iron.

[0068] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the essential spirit of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A type of biomass charcoal ball for electric furnaces, characterized in that: The composition of the biomass charcoal balls used in the electric furnace includes fixed carbon, elemental iron, and other unavoidable components; The fixed carbon content is 30-45 wt%, and the elemental iron content is 25-35 wt%. The density of the biomass charcoal balls used in the electric furnace is 1.9~2.3 g / cm³. 3 , Other unavoidable components include S, P2O5, N, FeOx, SiO2, CaO, and water; wherein the S content is <0.05wt%, the P2O5 content is <0.15wt%, the N content is <0.1wt%, and the water content is <1wt%. The compressive strength of a single biomass charcoal ball for an electric furnace is ≥10MPa, and its diameter is 2~5cm. The drop strength of the biomass charcoal balls used in the electric furnace meets the requirement that they will not break after being dropped three times from a height of 2 meters. The raw materials used in the preparation of biomass charcoal balls for the electric furnace include the following components by mass percentage: 30-40% direct reduced iron powder, 55-65% biochar powder, and 3-6% binder. The biochar powder is selected from one of wood charcoal powder, bamboo charcoal powder, and coffee grounds charcoal powder. The adhesive is made from waste corn flour and sodium silicate, wherein the waste corn flour has a mass percentage content of 50-60% and the sodium silicate has a mass percentage content of 40-50%.

2. A method for preparing biomass charcoal balls for electric furnaces as described in claim 1, characterized in that, Includes the following steps: S1, Pyrolysis-treated biochar is made into powder to obtain biochar powder; S2, the biochar powder obtained in step S1 is mixed and stirred with direct reduced iron powder and binder, water is added and pressed into spheres, then baked at low temperature, and after cooling, biochar balls for electric furnaces are obtained.

3. The method for preparing biomass charcoal balls for electric furnaces according to claim 2, characterized in that: In step S1, the particle size of the biochar powder is <0.2mm.

4. The method for preparing biomass charcoal balls for electric furnaces according to claim 2, characterized in that, In step S2: The amount of water used is 8-15 wt% of the total amount of biochar powder, direct reduced iron powder, and binder; and / or During the low-temperature baking process, the baking temperature is 70~100℃ and the baking time is 3~5 hours.

5. The method for preparing biomass charcoal balls for electric furnaces according to claim 2, characterized in that, In step S2, the biomass charcoal balls for the electric furnace are packaged and stored in moisture-proof woven bags.

6. The application of the biomass charcoal briquettes for electric furnaces as described in claim 1 in the electric furnace smelting process.

7. The application according to claim 6, characterized in that, After the slag from the electric furnace smelting process is formed and becomes fluid, biomass char balls for the electric furnace are added in multiple batches. The total amount of biomass charcoal balls added to the electric furnace is 5~20 kg / t steel, the amount added each time is 1~3 kg / t steel, and the time interval between each addition is 2~3 min.

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