Preparation process and evaluation method of carburizer using superfine carbon powder as raw material

Abstract

The application provides a preparation process and evaluation method of a recarburant taking superfine carbon powder as a raw material, step 1: according to target recarburant components, different carbon content, sulfur content and nitrogen content, and superfine carbon powder with a particle size of more than 200 meshes are dosed and uniformly mixed; step 2: a composite bonding system composed of 1% inorganic binder and 1% organic binder is mixed with the superfine carbon powder to granulate, and graphite recarburant is obtained through extrusion and drying; step 3: the graphite recarburant is subjected to forming property evaluation and high-temperature thermal stability evaluation. The application realizes high-value recycling of the superfine carbon powder, reduces the production cost of the recarburant, and the prepared recarburant has the advantages of high carbon absorption rate, good high-temperature stability and environmental protection without pollution.

Description

Technical Field

[0001] This invention relates to the field of carbon raiser preparation technology, specifically to a carbon raiser preparation process and evaluation method using ultrafine carbon powder as raw material. Background Technology

[0002] Carbon raisers are indispensable auxiliary materials in the iron and steel smelting and casting industries. Their core function is to compensate for the carbon loss during smelting, precisely adjust the carbon content in molten steel, and optimize the microstructure and mechanical properties of metallic materials. They directly affect casting quality, steel strength, and processing performance, holding an irreplaceable position in fields such as ductile iron and alloy steel production. With the rapid development of high-end equipment manufacturing and precision casting industries, the performance requirements for carbon raisers are constantly increasing. Ultrafine carbon powder, due to its advantages of large specific surface area, high carbon activity, fast melting speed, and high carbon absorption rate, has gradually become the core raw material for high-performance carbon raisers. Its application can effectively improve the graphitization effect of molten iron, reduce defects such as porosity and cracks in castings, and meet the production needs of high-end castings.

[0003] Currently, the sources of ultrafine carbon powder raw materials used in the industrial preparation of carbon raisers are relatively limited. Traditional raw materials mainly rely on natural graphite, petroleum coke, and pitch coke, which are processed through ultrafine grinding. These raw materials are non-renewable resources with limited reserves, and the costs of mining, purification, and ultrafine grinding are high. Long-term large-scale use will significantly increase the production costs of enterprises and is not conducive to the green and sustainable development of the industry. At the same time, with the rapid iteration of industries such as new energy, electronics, and chemicals, a large amount of waste containing high-purity carbon has been generated. In addition to waste lithium-ion battery anode powder, this includes waste graphite electrode powder, carbon fiber processing waste, coal-based needle coke tailings, and carbon black deep processing residues. After processing, these wastes can yield ultrafine carbon powder with a high fixed carbon content, reaching over 90%, providing a good foundation for use as raw materials for carbon raisers.

[0004] However, the current state of resource utilization of the aforementioned carbon-containing wastes is far from optimistic. On the one hand, if these wastes are discarded directly, it not only results in a serious waste of valuable carbon resources, but the trace impurities they contain also pollute the soil, water bodies, and atmosphere, causing environmental governance challenges. On the other hand, existing recycling technologies mostly involve simple crushing and screening, followed by the use of these wastes as low-value fillers in fields such as construction and rubber. This results in low resource utilization rates and fails to achieve high-value recovery of carbon resources, contradicting the resource recycling requirements under the current "dual carbon" goals. Furthermore, even if these wastes are processed into ultrafine carbon powder, their extremely small particle size, large specific surface area, and high surface energy make them prone to agglomeration. Additionally, the surface characteristics of ultrafine carbon powder from different sources vary significantly, making it significantly more difficult to form as a carbon additive than conventional carbon powder.

[0005] Granulation is a crucial step in the production of ultrafine toner-based recarburizers. The selection and compatibility of the binder directly determine the recarburizer's molding effect, particle strength, high-temperature stability, and performance. It is key to solving the problems of ultrafine toner agglomeration and molding difficulties. Currently, the binders used in industrial recarburizer granulation are relatively limited, mainly consisting of single inorganic or single organic binders. Both types of single binders have significant performance defects, making it difficult to meet the high-performance, environmentally friendly, and low-cost production requirements of ultrafine toner-based recarburizers. Specific problems are as follows.

[0006] The core issues with pure inorganic binders lie in their bonding performance and molding effect. While these binders offer advantages such as good environmental friendliness, low cost, and minimal generation of harmful gases at high temperatures, their bonding strength is generally insufficient. They cannot effectively overcome the agglomeration phenomenon caused by the large specific surface area and high surface energy of ultrafine carbon powder, making it difficult to firmly bond the dispersed ultrafine carbon powder particles into a molded shape. The molded recarburizer particles have extremely low strength and are prone to breakage and pulverization during transportation, storage, and addition to molten iron. This not only fails to ensure the uniform addition of the recarburizer but may also increase carbon loss due to powder dispersion. At the same time, some inorganic binders undergo crystal transformation under high-temperature smelting environments, further reducing the overall particle integrity and resulting in a high high-temperature pulverization rate, severely affecting the stability of the recarburizing effect and failing to meet the requirements of large-scale industrial applications.

[0007] Pure organic binders suffer from prominent problems such as poor high-temperature stability, insufficient environmental friendliness, or high cost. They can be specifically divided into three categories: First, asphalt-based binders, although they have strong adhesion and can achieve the initial molding of ultrafine carbon powder, are prone to decomposition during high-temperature smelting, producing harmful gases such as benzo[a]pyrene, which pollute the environment and do not meet the current requirements for green and low-carbon industrial development. Moreover, they are prone to carbonization and volatilization at high temperatures, leading to a decrease in the strength of the carbon-reinforcing agent particles and an increase in carbon loss. Second, resin-based binders have good molding effects and can effectively solve the problem of ultrafine carbon powder agglomeration, but their production costs are high, and they are prone to carbonization and volatilization at high temperatures, which also causes carbon loss and affects carbon-reinforcing efficiency. Third, natural organic binders such as sodium carboxymethyl cellulose and starch are widely available, low in cost, and have good environmental friendliness, but their high-temperature stability is extremely poor. They will decompose and burn rapidly at smelting temperatures, making it impossible to ensure that the carbon-reinforcing agent particles do not break during transportation and addition to molten iron. The integrity of the particles is difficult to maintain, which in turn affects the stability of the carbon-reinforcing effect and cannot meet the production needs of high-end castings. In addition, single binders also have the problem of poor compatibility. Neither pure inorganic nor pure organic binders can take into account the differences in surface characteristics of ultrafine toners from different sources. It is difficult to achieve a synergistic improvement in adhesion, molding effect and high-temperature stability, which further limits the high-value utilization of ultrafine toners prepared from various carbon-containing wastes.

[0008] Compared with various single binders, organic-inorganic composite binders effectively make up for many of the shortcomings of single binders, showing significant advantages and becoming the core direction for solving the problem of ultrafine carbon powder molding and preparing high-performance carbon additives. Its core advantages are mainly reflected in two key aspects: First, the high-temperature pulverization rate is low. Through the synergistic effect of organic and inorganic components, the composite binder retains the high-temperature stability of the inorganic binder while effectively solving the problem of ultrafine carbon powder agglomeration by leveraging the strong adhesive force of the organic binder. The resulting carbon raiser particles have high strength and good integrity, and are not easily decomposed or broken in the high-temperature smelting environment. The high-temperature pulverization rate is greatly reduced, ensuring that the carbon raiser particles enter the molten iron intact and reducing carbon loss. Second, the carbon raising effect is good. The composite binder has stronger adaptability and can adjust the ratio of organic and inorganic components according to the surface characteristics of ultrafine carbon powder from different sources to optimize the bonding effect. This ensures that the ultrafine carbon powder is evenly dispersed and firmly formed, and its advantages of high carbon activity and high melting speed are fully utilized. This can effectively improve the carbon absorption rate, accurately compensate for carbon burn-off during the smelting process, optimize the microstructure and mechanical properties of metal materials, reduce defects such as porosity and cracks in castings, and meet the production needs of high-end castings. Meanwhile, composite adhesives can also balance environmental protection and low cost. By rationally selecting components, they can achieve zero harmful gas emissions and controllable raw material costs, which aligns with the industry's green and sustainable development.

[0009] Patent application CN116254388A discloses a graphite granule carbon raiser and its preparation method. High-purity graphite powder is added to a mixing device, along with a starch binder, and mixed thoroughly. The mixed material is then conveyed by a conveyor belt to a granulator for granulation. The granulated particles are then conveyed by a conveyor belt to a dryer for drying and shaping. The dried and shaped graphite particles are then conveyed by a conveyor belt to a cooling zone for cooling. After cooling, quality inspection is performed, and qualified particles are packaged. However, this patent cannot completely solve the existing technical problems, nor can it meet the needs of this invention. Summary of the Invention

[0010] In view of the deficiencies in the prior art, the purpose of this invention is to provide a process and evaluation method for preparing a carbon raiser using ultrafine carbon powder as raw material.

[0011] The process and evaluation method for preparing a carbon raiser using ultrafine carbon powder as raw material, provided by the present invention, include: Step 1: According to the requirements of fixed carbon, sulfur and nitrogen content of the target carbon additive, mix the waste battery negative electrode graphite, dust removal powder and natural graphite and other ultrafine carbon powder with a mesh size of 200 or above. Step 2: Mix the ultrafine carbon powder with a composite binder system consisting of 1% calcium-based bentonite and 1% starch to obtain a graphite carbonizer; Step 3: Evaluate the molding performance and high-temperature thermal stability of the graphite carburizer.

[0012] Preferably, the calcium-based bentonite contains ≥70% montmorillonite.

[0013] Preferably, the mixing and granulation process is as follows: A preset amount of deionized water was added to the ultrafine carbon powder and composite binder system, and after mixing in a mixer for 30 minutes, a uniform raw material to be granulated was obtained. The mixed material is fed into an extrusion granulator, and the granulation pressure is adjusted to 8~12 MPa and the granulation temperature is 25~40 ℃. The material is then extruded into particles with a particle size of 2~15 mm to obtain graphite carburizing agent.

[0014] Preferably, after obtaining the graphite recarburizer, the graphite recarburizer is sent to a drying oven and dried at a low temperature of 80~100 ℃ for 2~3 h, and then the temperature is raised to 120~150 ℃ for 1~2 h, until the moisture content of the particles is ≤0.5%, and dried particles are obtained.

[0015] Preferably, the amount of deionized water added is 5% to 15% of the total mass of ultrafine carbon powder and calcium-based bentonite.

[0016] Preferably, the rotational speed of the extrusion granulator is 60~100 r / min; the die diameter of the extrusion granulator is 2~15 mm.

[0017] Preferably, the molding performance evaluation includes: random sampling After extrusion granulation, the wet granules are dried and cured. The qualified granules with a particle size of 2-15mm, no surface cracks, and no looseness are weighed. The molding rate is calculated using the following expression:

[0018] in, The molding rate is expressed as %; The mass of a qualified carbon raiser is expressed in grams. The mass of randomly selected carbon raiser is expressed in grams.

[0019] Preferably, the high-temperature stability evaluation includes: random sampling Qualified carbon raiser granules were placed in a high-temperature furnace and heated at 950℃ for 30 minutes. After cooling to room temperature, the granules were sieved through a 2 mm standard sieve, and the mass of the powder passing through the sieve was weighed. The high-temperature pulverization rate is calculated using the following expression:

[0020] in, High-temperature pulverization rate, in percentages (%) This refers to the mass of the powder, expressed in grams. The initial mass of the carbon raiser is measured in grams.

[0021] The carbon raiser is in the form of spherical or columnar particles with a particle size of 2–15 mm and a bulk density of 1.2–1.5 g / cm³. 3 Radial mechanical strength ≥75 N, no breakage when dropped from a height of 1.5 m; fixed carbon content ≥92%, sulfur content ≤0.3%, nitrogen content ≤1500 ppm, ash content ≤5%, moisture content ≤0.5%.

[0022] Preferably, the carbon absorption rate of the carbon raiser during the iron and steel smelting process is determined by the following method: The carbon raiser is added to the molten iron at 1500℃ for 10 min, the carbon content of the molten iron before and after carbonization is measured, and the carbon absorption rate is calculated as follows:

[0023] in, Carbon absorption rate, in percentages (%) The carbon content of the molten iron after carbonization is expressed in % (%). The carbon content of molten iron before carbon addition is expressed in % (%). This refers to the amount of carbon raiser added, expressed in kg. The carbon content of the carbon raiser is fixed, in units of %.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention uses ultrafine carbon-containing waste such as graphite from waste battery negative electrodes and dust removal powder as raw materials. Through processes such as batching, mixing, granulation, and drying, it transforms them into high-performance carbon additives, avoiding the waste of carbon resources and environmental pollution, significantly reducing the production cost of carbon additives, and meeting the requirements of green and sustainable development. (2) The present invention uses an organic-inorganic composite bonding system composed of 1% calcium-based bentonite and 1% starch. By utilizing the high temperature stability of inorganic binder and the strong bonding force of organic binder, the problem of large specific surface area and easy pulverization at high temperature of ultrafine carbon powder is overcome, so that the granulation molding rate can reach more than 90%, the particles are uniform, the surface is free from cracks and looseness, and the molding performance is excellent. (3) Through the optimized ratio of composite binder and drying and curing process, the high-temperature pulverization rate of the carbon raiser prepared by the present invention is ≤5% under the condition of holding at 950℃ for 30min. The particles remain intact in the high-temperature smelting environment, avoiding problems such as low carbon absorption rate, unstable carbon raising and smoke caused by pulverization, thus ensuring the stability and environmental protection of the smelting process. (4) The carbon refining agent of the present invention has a fixed carbon content of ≥92%, sulfur content ≤0.3%, nitrogen content ≤1500ppm, ash content ≤5%, and carbon absorption rate ≥90%. The carbon refining agent has good melting and dispersibility under smelting conditions such as electric furnace and LF furnace, and the carbon composition is precisely controlled, which can meet the stringent requirements of high-end automotive steel, pipeline steel, bearing steel and other steel performance requirements. (5) This invention does not require complex equipment and adopts conventional steps of batching, mixing, extrusion granulation, drying and curing. It uses room temperature kneading and low temperature drying, resulting in low energy consumption. The raw materials are waste products, and the binder is inexpensive. The overall production cost is significantly lower than that of traditional carbon raisers, making it suitable for large-scale industrial production. (6) This invention specifically proposes indicators such as molding rate, particle strength, high temperature pulverization rate, fixed carbon content, sulfur content, nitrogen content, and carbon absorption rate, as well as their calculation formulas and measurement methods, which provide an objective and quantifiable basis for the performance evaluation of carbon additive products and help ensure product quality stability. Attached Figure Description

[0025] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 Flowchart for granulation of carbon raiser. Detailed Implementation

[0026] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0027] Example 1 like Figure 1 This invention provides a process and evaluation method for preparing a carbon raiser using ultrafine carbon powder as raw material, comprising: Ultrafine carbon powder batching and mixing steps: By accurately batching and mixing the obtained solid waste such as waste battery negative electrode graphite and dust removal powder, carbon raiser raw materials with target carbon, sulfur and nitrogen content are obtained. Binder Granulation Steps: In actual steelmaking applications, using only inorganic binders to prepare recarburizers has certain application drawbacks. The active components in inorganic binders readily react with oxides such as SiO2, CaO, and Al2O3 present in the molten steel at high temperatures, forming a composite slag system with a low melting point and stable structure. This slag phase rapidly encapsulates the carbon particles inside the recarburizer, forming a barrier layer that severely hinders the diffusion, dissolution, and release of carbon into the molten steel, thus significantly reducing the actual recarburizing efficiency of the recarburizer and affecting the recarburizing effect and composition control precision of the molten steel. In contrast, using a composite binder system combining organic and inorganic binders can synergistically leverage the advantages of both types of binders. This not only ensures the forming effect and high-temperature strength of the recarburizer particles but also effectively increases the impact penetration depth of the recarburizer when added to the molten steel, allowing it to quickly penetrate the slag layer on the surface of the molten steel and disperse evenly inside, reducing carbon powder floating and burning loss and slag encapsulation, thereby significantly improving the utilization rate of the recarburizer and the overall recarburizing effect. Among various organic-inorganic composite binder formulations, the graphite carburizer prepared using a composite binder system consisting of 1% calcium-based bentonite and 1% starch exhibits the best thermal strength performance. The calcium-based bentonite has a montmorillonite content of ≥70%, and its bonding strength is 2 to 3 times that of ordinary clay.

[0028] For the carbon raisers prepared by the above process, a specific evaluation index system was established to comprehensively evaluate the molding performance, high-temperature stability, and performance of the carbon raisers. The specific evaluation indexes and methods are as follows: I. Evaluation Indicators and Methods for Molding Performance The core indicators for evaluating the granulation effect of ultrafine toner include particle formation rate, particle strength, and particle uniformity. The specific evaluation methods are as follows: 1. Pellet forming rate: randomly sampled After extrusion granulation, the wet granules are dried and cured. The mass of qualified granules with a particle size of 2-15 mm, no surface cracks, and no loose particles is then weighed. Molding rate The calculation formula is as shown in formula (1); Evaluation criteria: a molding rate ≥ 90% indicates that the granulation effect is good and the problem of granulation difficulty is solved; a molding rate < 90% indicates that the granulation process needs to be optimized.

[0029] (1) in, The molding rate is expressed as %; The mass of a qualified carbon raiser is expressed in grams. The mass of randomly selected carbon raiser is expressed in grams.

[0030] 2. Particle strength: Using a particle strength tester, in accordance with GB / T 44750-2024 standard, 10 qualified particles were randomly selected, and the compressive strength of each individual particle was measured. The average value was taken as the particle strength.

[0031] II. High-Temperature Thermal Stability Evaluation Indicators and Methods The evaluation of the anti-pulverization performance of carbon raisers under high-temperature environments is based on key indicators including high-temperature pulverization rate and high-temperature strength retention rate. The specific evaluation methods are as follows: High-temperature pulverization rate: random sampling Qualified carbon raiser granules were placed in a high-temperature furnace and heated at 950℃ for 30 minutes. After cooling to room temperature, the granules were sieved through a 2 mm standard sieve, and the mass of the powder passing through the sieve was weighed. The formula for calculating the high-temperature pulverization rate is as shown in formula (2). Evaluation criteria: High-temperature pulverization rate ≤ 5% indicates that the carbon raiser has good high-temperature anti-pulverization performance and solves the problem of easy pulverization at high temperature; High-temperature pulverization rate > 5% indicates that the high-temperature stability of the carbon raiser is insufficient and the graphitization process or the amount of modified additives needs to be adjusted.

[0032] (2) in, High-temperature pulverization rate, in percentages (%) This refers to the mass of the powder, expressed in grams. The initial mass of the carbon raiser is measured in grams.

[0033] The high-temperature pulverization rate of recarburizers is a key indicator for evaluating their high-temperature resistance to pulverization and an important basis for assessing their ability to function stably in the high-temperature environment of steelmaking. Controlling and reducing the high-temperature pulverization rate of recarburizers is of irreplaceable importance for ensuring the stability of the smelting process, improving steel quality, reducing production costs, and achieving environmentally friendly and safe production. Under the high-temperature conditions of steelmaking, if the recarburizer particles are severely pulverized, a series of chain-like negative effects will occur: First, the ultrafine carbon powder formed by pulverization is easily carried away by the high-speed airflow in the furnace, which not only significantly reduces the actual utilization rate of the recarburizer and causes direct waste of raw materials, but also makes it difficult to accurately control the carbon content of molten steel, resulting in compositional fluctuations. This forces repeated adjustments to the composition during the smelting process, prolonging the smelting cycle and affecting the production rhythm and continuity. At the same time, a large amount of dust can also clog key equipment such as dust removal pipes and tuyeres on the furnace top, causing problems such as abnormal furnace pressure, molten steel splashing, and furnace wall nodules. In severe cases, it can even lead to unplanned furnace shutdowns, posing a direct threat to production safety and efficiency. Secondly, the fine particles produced by pulverization are difficult to sink effectively into the molten steel, tending to burn on the surface or be blown away by airflow. This prevents uniform carbonization and easily leads to uneven carbon distribution within the steel, causing component segregation and affecting the subsequent rolling performance of the steel. Simultaneously, the ash and impurities released during pulverization increase the content of non-metallic inclusions in the steel, reducing its purity and weakening its strength, toughness, and fatigue resistance, making it difficult to meet the stringent performance requirements of high-end automotive steel, pipeline steel, and bearing steel. Furthermore, the reduced raw material utilization and extended smelting cycle caused by high-temperature pulverization directly increase the carbonization cost and energy consumption per ton of steel, reducing the production efficiency of converters or electric furnaces. Problems such as furnace nodules and equipment blockages also increase the cost of subsequent equipment maintenance and repair, further compressing the company's profit margins. From an environmental and safety perspective, the fugitive dust generated by high-temperature pulverization significantly increases the dust concentration in the workshop, affecting not only the occupational health of workers but also greatly increasing the processing load on the dust removal system, potentially exceeding environmental emission limits and posing compliance risks. Simultaneously, ultrafine carbon powder can easily form explosive mixtures near the high-temperature furnace opening, posing a dust explosion hazard and threatening safe production at the smelting site. Therefore, by optimizing the bonding system and improving the preparation process, controlling the high-temperature pulverization rate of the carbon raiser to ≤5% can reduce pulverization during the smelting process, achieving efficient, uniform, and controllable carbon raising. This not only stabilizes the smelting process and improves steel quality but also effectively reduces production costs, environmental pressure, and safety risks, serving as a crucial guarantee for the stable industrial application of carbon raiser products.

[0034] III. Performance Evaluation Indicators and Methods The evaluation of the actual performance of carbon raisers in steel smelting and casting is based on key indicators including fixed carbon content, sulfur content, nitrogen content, and carbon absorption rate. The specific evaluation methods are as follows: 1. Fixed carbon content: The fixed carbon content in the carbon raiser is determined by the combustion weight method according to GB / T 15057.1-2018 standard; Evaluation standard: Fixed carbon content ≥90%, meeting the requirements for use in steel smelting and casting.

[0035] 2. Sulfur content: The sulfur content in the carbon raiser is determined by infrared absorption method according to GB / T 15057.4-2018 standard; evaluation standard: sulfur content ≤0.1%, to avoid defects such as porosity and inclusions during smelting.

[0036] 3. Nitrogen content: The nitrogen content in the carbon raiser is determined by the formaldehyde method according to YB / T 6261-2024 standard; evaluation standard: nitrogen content ≤0.3%, to prevent nitrogen from affecting the mechanical properties of the casting.

[0037] 4. Carbon absorption rate: Under the conditions of 1550℃ and 10 min, the carbon re-carbonizing agent is added to the molten iron, and the carbon content of the molten iron before and after carbonization is measured to calculate the carbon absorption rate; the calculation formula is as shown in formula (3); evaluation standard: carbon absorption rate ≥90% indicates that the carbon re-carbonizing agent has excellent effect.

[0038] (3) in, Carbon absorption rate, in percentages (%) The carbon content of the molten iron after carbonization is expressed in % (%). The carbon content of molten iron before carbon addition is expressed in % (%). This refers to the amount of carbon raiser added, expressed in kg. C The carbon content of the carbon raiser is fixed, in units of %.

[0039] Example 2 This invention provides a method for granulating a carbon raiser using ultrafine carbon powder as raw material and an organic / inorganic composite binder as binder, comprising: Step 1, Ingredients: The obtained waste battery negative electrode graphite, graphite slag, dust removal powder, petroleum coke powder and other ultrafine high carbon micro powders are mixed according to the requirements of the target carbon refining agent fixed carbon, sulfur content and nitrogen content to obtain the raw materials for carbon refining agent preparation. Step 2, mixing: Add graphite micro powder, several parts of composite binder, and an appropriate amount of deionized water to a mixer and mix for more than 30 minutes to obtain a uniform mixture; Step 3, extrusion granulation: The mixture obtained in step 2 is fed into an extrusion granulator, the granulation pressure is adjusted to 8~12MPa and the granulation temperature is 25~40℃, and the mixture is extruded into particles with a particle size of 2~15mm to obtain the carbon raiser; Step 4, drying and curing: The carbon raiser is sent into a drying oven and dried at a low temperature of 80~100℃ for 2~3 hours, then the temperature is raised to 120~150℃ for 1~2 hours, until the moisture content of the particles is ≤0.5%, and dried particles are obtained.

[0040] The mixture of waste battery graphite slag, negative electrode powder, and dust removal powder has a fixed carbon content of ≥93%.

[0041] The amount of deionized water added is 18-25% of the total mass of graphite powder and calcium-based bentonite.

[0042] The extrusion granulator has a rotation speed of 60~100 r / min; the die diameter of the extrusion granulator is 2~15 mm, and the forming rate is ≥90%.

[0043] The present invention also provides a carbon raiser prepared by the above granulation method, wherein the carbon raiser is spherical or columnar particles with a particle size of 2-15 mm and a bulk density of 1.2-1.5 g / cm³. 3 Radial mechanical strength ≥75 N, no breakage when dropped from a height of 1.5 m; fixed carbon content ≥92%, sulfur content ≤0.3%, nitrogen content ≤1500 ppm, ash content ≤5%, moisture content ≤0.5%.

[0044] The carbon-adding agent has a carbon absorption rate of ≥90% in the steelmaking process and can be used to supplement carbon elements in electric arc furnace steelmaking, converter steelmaking or casting production.

[0045] Example 3 This invention provides a high-carbon, low-sulfur carbon raiser for application in an electric arc furnace refining furnace, as detailed below: The measured values ​​of the main physicochemical properties of the carbon raiser are: w(C) ≥ 93.4%, w(S) ≤ 0.001%, w(H2O) ≤ 0.2%, and w(ash content) ≤ 1.8%. In the electric arc furnace refining process, carbon adjustment was performed on SWBPH1 and SWBPH13 steel grades. The carbon raiser was added according to the target carbon content, stirred evenly, and then tapped. The carbon content of the molten steel was tested, and the yield was calculated. Experimental results: Carbon yield for heat number 1 was 90%, for heat number 2 it was 90%, and for heat number 3 it was 91%.

[0046] In this embodiment, the carbon raiser has a high carbon content, extremely low sulfur and impurities, good melting and dispersibility, and a stable carbon yield of 90%~91%. The carbon composition of the molten steel is precisely controlled, meeting the requirements of the electric furnace refining process.

[0047] Example 4 This invention provides a modified binder carbonizer, which is applied in a 120 t LF furnace, as detailed below: The technical specifications of the carbon raiser are: w(C)≥92%, w(S)≤0.3%, volatile matter + ash content≤8.0%, w(H2O)≤0.50%, and particle size 1~5mm≥90%.

[0048] First round of testing: A carbon raiser was added to the LF furnace, with a total dosage of 185 kg. The carbon raiser did not melt well, and the average carbon yield of the three furnaces was 65.7%, which did not meet the requirements.

[0049] Second round of testing: Adjusting the binder system, S1 and S2 type recarburizing agents were prepared, with a total trial quantity of 795 kg. Using Q235B steel as the test subject, the agents were added during the carbon conditioning stage of the LF furnace, and samples were taken for testing after stirring for 3 minutes. S1 type recarburizing agent: 6 heats were tested, with a total addition of 335 kg of recarburizing agent. The carbon recovery rate was 80.4%~95.0%, with an average of 88.3%, and good melting performance. S2 type recarburizing agent: 4 heats were tested, with a total addition of 275 kg of recarburizing agent. The carbon recovery rate was 60.6%~90.2%, with an average of 78.7%, and moderate melting performance. Under the same operating conditions, the average carbon recovery rate of existing recarburizing agents is 89.5%, and the carbon recovery rate of S1 type is comparable to existing products.

[0050] This embodiment significantly improves the melting and carbon absorption efficiency of the recarburizer through binder modification. The S1 type recarburizer has a stable carbon yield and uniform composition control in the LF furnace, and can be used for carbon adjustment in the refining of low carbon steel.

[0051] Those skilled in the art will understand that, in addition to implementing the system, apparatus, and their modules provided by this invention in purely computer-readable program code, the same program can be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system, apparatus, and their modules provided by this invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; alternatively, modules for implementing various functions can be considered both software programs implementing the method and structures within the hardware component.

[0052] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A process and evaluation method for preparing a carbon raiser using ultrafine carbon powder as raw material, characterized in that, include: Step 1: According to the requirements of fixed carbon, sulfur and nitrogen content of the target carbon additive, mix the ultrafine carbon powder of 200 mesh or above, including graphite of waste battery negative electrode, dust removal powder and natural graphite. Step 2: Mix the ultrafine carbon powder with a composite binder system consisting of 1% calcium-based bentonite and 1% starch to obtain a graphite carbonizer; Step 3: Evaluate the molding performance and high-temperature thermal stability of the graphite carburizer.

2. The preparation process and evaluation method of the carbon raiser using ultrafine carbon powder as raw material according to claim 1, characterized in that, The montmorillonite content in the calcium-based bentonite is ≥70%.

3. The preparation process and evaluation method of the carbon raiser using ultrafine carbon powder as raw material according to claim 1, characterized in that, The process of mixed granulation is as follows: A predetermined amount of deionized water was added to the ultrafine carbon powder and composite binder system, and the mixture was stirred for 30 minutes to obtain a uniform raw material. The mixed material is fed into an extrusion granulator, and the granulation pressure is adjusted to 8~12 MPa and the granulation temperature is 25~40 ℃. The material is then extruded into particles with a particle size of 2~15 mm to obtain graphite carburizing agent.

4. The preparation process and evaluation method of the carbon raiser using ultrafine carbon powder as raw material according to claim 1, characterized in that, After obtaining the graphite recarburizer, the graphite recarburizer is sent to a drying oven and dried at a low temperature of 80~100 ℃ for 2~3 h, and then the temperature is raised to 120~150 ℃ for 1~2 h, until the moisture content of the particles is ≤0.5%, and the dried particles are obtained.

5. The preparation process and evaluation method of the carbon raiser using ultrafine carbon powder as raw material according to claim 1, characterized in that, The amount of deionized water added is 5% to 15% of the total mass of ultrafine carbon powder and calcium-based bentonite.

6. The preparation process and evaluation method of the carbon raiser using ultrafine carbon powder as raw material according to claim 1, characterized in that, The extrusion granulator has a rotation speed of 60~100 r / min; the die diameter of the extrusion granulator is 2~15 mm.

7. The preparation process and evaluation method of the carbon raiser using ultrafine carbon powder as raw material according to claim 1, characterized in that, The molding performance evaluation includes: random sampling After extrusion granulation, the wet granules are dried and cured. The mass of qualified granules with a particle size of 2-15 mm, no surface cracks, and no looseness is then measured. The molding rate is calculated using the following expression: in, The molding rate is expressed as %; The mass of a qualified carbon raiser is expressed in grams. The mass of randomly selected carbon raiser is expressed in grams.

8. The preparation process and evaluation method of the carbon raiser using ultrafine carbon powder as raw material according to claim 1, characterized in that, The high-temperature stability evaluation includes: random sampling Qualified carbon raiser granules were placed in a high-temperature furnace and heated at 950℃ for 30 minutes. After cooling to room temperature, the granules were sieved through a 2 mm standard sieve, and the mass of the powder passing through the sieve was weighed. The high-temperature pulverization rate is calculated using the following expression: in, High-temperature pulverization rate, in percentages (%) This refers to the mass of the powder, expressed in grams. The initial mass of the carbon raiser is measured in grams.

9. The preparation process and evaluation method of the carbon raiser using ultrafine carbon powder as raw material according to claim 1, characterized in that, The carbon raiser is in the form of spherical or columnar particles with a particle size of 2–15 mm and a bulk density of 1.2–1.5 g / cm³. 3 Radial mechanical strength ≥75 N, no breakage when dropped from a height of 1.5 m; fixed carbon content ≥92%, sulfur content ≤0.3%, nitrogen content ≤1500 ppm, ash content ≤5%, moisture content ≤0.5%.

10. The preparation process and evaluation method of the carbon raiser using ultrafine carbon powder as raw material according to claim 1, characterized in that, The carbon absorption rate of the carbon raiser in the iron and steel smelting process is determined as follows: The carbon raiser is added to the molten iron at 1500℃ for 10 min, and the carbon content of the molten iron before and after carbonization is measured. The carbon absorption rate is calculated using the following expression: in, Carbon absorption rate, in percentages (%) The carbon content of the molten iron after carbonization is expressed in % (%). The carbon content of molten iron before carbon addition is expressed in % (%). This refers to the amount of carbon raiser added, expressed in kg. The carbon content of the carbon raiser is fixed, in units of %.

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