A method for making high-quality pellets by mixing stainless steel ash with carbon for improving element yield

Abstract

The invention discloses a method for making high-quality balls by mixing stainless steel ash with carbon for improving element yield. The method comprises the following steps: (1) proportioning materials in balls: the digested stainless steel 300 series dust ash, stainless steel iron oxide scale, dry quenching dust ash, organic binder, inorganic binder and water are proportioned in a mass ratio of 70:5:15:2:3:5; (2) preparing materials; (3) adding water and mixing; (4) stuffing materials; (5) initial pressing; (6) final pressing: the balls produced by initial pressing enter the ball conveying belt through the inclined chute at the bottom of the roller ball press to feed the final pressing ball press; the balls after final pressing enter the ball discharging belt through the inclined screen plate at the bottom of the ball press; the crushed and powdered materials are transported to the initial pressing feeding belt through the return material belt under the screen to continue initial pressing, and the cycle is repeated; (7) transportation.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and in particular to a method for making high-quality pellets of stainless steel ash and carbon for improving element yield. Background Art

[0002] The amount of dust generated in the stainless steelmaking process is considerable, among which there is a 300 series dust ash with a typical composition as shown in the following table.

[0003] .

[0004] The dust ash above is extremely fine in particle size and contains high levels of iron oxide and chromium oxide. If it can be reused in the metallurgical process to restore and utilize chromium and iron metals, it will help reduce corporate costs while disposing of solid waste. At present, domestic stainless steel companies mainly adopt the following two modes for the disposal of stainless steel dust ash:

[0005] First, set up a special silo to produce sintered ore together with stainless steel pickling sludge in the sintering batching process to supply the steelmaking process. Most domestic stainless steel companies are independent stainless steel production lines with unified design and one-time construction, which are connected to sintering, ironmaking, steelmaking, and steel rolling. This recycling model can make full use of valuable elements and has relatively significant economic and environmental benefits. However, for enterprises that build iron-making and steel-making blast furnaces one after another and put them into production while they are being built, there are no uniform independent production lines for sintering-iron-steel-rolling. After the blast furnace is tapped, it is cross-supplied to the carbon steelmaking or stainless steelmaking system, and it is impossible to realize that chromium-nickel iron water is exclusively used for stainless steel making. After a part of the iron water is supplied to carbon steel, not only can the chromium and nickel elements in it not be utilized, but the quality risk of carbon steel products is also increased. In this way, it can only reflect environmental benefits, but not economic benefits. The difficulty in using sintering is the dust of fine materials and the difficulty of unloading shed materials.

[0006] Second, build a cold-pressed ball production line in the company's stainless steel plant, cold-press the dust ash and stainless steel acid mud together, and then use it for stainless steel arc furnaces and dephosphorized converters. When used in an electric arc furnace, since nickel-iron blocks and high-carbon ferrochrome are used as metal materials, and coke and carbon powder are added to form a high-carbon molten pool, most of the nickel and iron in the dust can be reduced, and 50-60% of chromium can be reduced. Although the economic efficiency is not as good as that of sintering, it achieves the goal of not leaving the factory, not spreading, and self-circulating solid waste, which is a relatively reasonable method that takes into account both economic and environmental benefits.

[0007] In addition, in order to ensure sufficient heat for the AOD furnace in the post-processing process of the electric arc furnace, it is often necessary to add a portion of coke while using high-carbon nickel iron and chromium iron. When the electric arc furnace is blowing oxygen to burn and generate heat, the carbon content of the molten pool is increased, so that there is sufficient combustion heat agent during the argon oxygen refining of the AOD furnace, and the temperature of the AOD furnace molten pool is increased to improve the effect of decarburization and chromium preservation. Although lump coke has high strength, suitable particle size, and is easy to add through the silo, the price is often more than 2,000 yuan, which is not economical.

[0008] Although the second method of stainless steel dust removal is feasible, due to the characteristics of full powder and high calcium oxide materials that are not easy to form balls, there are also problems such as high ball pressing costs (the high cost is mainly reflected in the high binder ratio and the high binder costs), large powder loading rate, and easy dust. At the same time, relying solely on the molten pool carbon to reduce metal oxides, the reducing atmosphere is insufficient, the reduction kinetic conditions are not ideal, the recovery rate of iron and nickel, especially the recovery rate of chromium, is not high, and there is still a lot of room for improvement. At present, there is no relevant technology application in the field of stainless steel dust removal ash balling in China to solve the above problems. Summary of the invention

[0009] In view of the above technical problems, the present invention provides a method for making high-quality pellets by mixing carbon with stainless steel ash for improving element yield.

[0010] In order to achieve the above object, the technical solution of the present invention is as follows:

[0011] A method for making high-quality pellets by mixing stainless steel ash with carbon for improving element yield comprises the following steps:

[0012] (1) Material ratio in the ball: Digested stainless steel 300 series dust, stainless steel oxide scale, dry quenching dust, organic binder, inorganic binder and water are mixed in a mass ratio of 70:5:15:2:3:5;

[0013] (2) Material preparation: Stainless steel 300 series dust is digested by special equipment and weighed with a weighing hopper, and then fed to a closed feeding belt by electric vibration, and then fed to a mixer; stainless steel oxide scale is fed to a mixer through a closed feeding belt; organic binders and inorganic binders are placed in storage bins respectively, weighed with a weighing hopper, and then fed to a closed feeding belt by electric vibration, and then fed to a mixer; CDQ dust is added to the cone bin by a small loader through a reserved side-opening temporary feeding inlet, and the cone bin is fed to the weighing hopper by electric vibration and then to the closed feeding belt by electric vibration, and then fed to a mixer;

[0014] (3) Add water and mix: The roller of the mixer rotates no less than 100 times to ensure that the material, water and binder are fully dispersed and mixed to eliminate the raw material lumps. While stirring, add water according to the humidity of the material to fully moisten the material;

[0015] (4) Stuffing: The mixed materials are transported to a large cone silo by a belt conveyor. The materials are first taken from the bottom by electric vibration, and the upper materials are ensured to be stuffed for more than 3 hours to promote further dispersion and mixing of the materials, water and binder;

[0016] (5) Initial pressing: The steamed material is fed by the feeding belt conveyor to the roller briquetting machine for the first round of briquetting. A spiral forced feeder is installed on the top of the roller briquetting machine to ensure the filling rate of the ball sockets on the roller surface.

[0017] (6) Final pressing: The balls from the initial pressing enter the ball conveying belt through the inclined chute at the bottom of the roller press to feed the final pressing press. The balls after the final pressing enter the ball discharging belt through the inclined screen plate at the bottom of the press. The crushed and powdered materials are transported to the initial pressing feeding belt through the return belt under the screen to continue the initial pressing, and the cycle continues.

[0018] (7) Transshipment:

[0019] 1) Ball discharge: Multiple groups of ball discharge belts are connected to transport finished balls, and finally piled into a cone-shaped initial ball pile through an adjustable-angle ball discharge belt conveyor. Subsequent balls roll down in sequence with the initial ball pile as a buffer slope to reduce breakage. The balls are discharged while moving to one side on the upward belt, and finally a circular ridge-shaped ball pile is formed. After more than 12 hours of air drying and aging hardening, they are shoveled to a large ball pile for further air drying;

[0020] 2) The pellets in the large pellet pile are taken according to the principle of first-come-first-served, and transported to the ground warehouse through equipment;

[0021] 3) The pellets in the ground bin are fed to the auxiliary material feeding belt through electric vibration and then to the steelmaking feeding platform, and then fed to the high-level silo above the electric arc furnace by the feeding trolley for standby use.

[0022] Among them, in the step (6), based on comprehensive considerations of the heat transfer, mass transfer, ease of balling, ease of demoulding and production efficiency of the pellets, the pellets are elliptical in shape, thick in the middle and thin on both sides, with a length of 40 mm, a width of 25 mm and a thickness of 15 mm.

[0023] Wherein, in the step (3), the mixer is a large wheel-milling mixer.

[0024] Among them, in step (7) 1), in a production line with sufficient space, more sets of belt connections are used to control the distance of the annular ball pile. By raising the belt to create a quarter-circular ring-shaped low beam, the pile is radially stored from the inside to the outside, which can reduce tipping and further reduce the amount of broken materials.

[0025] Among them, in step (7) 2), the pellets are transported to the ground warehouse by equipment, specifically by using a loader to load the pellets onto a well-sealed vehicle with a retractable tarpaulin and transporting them to the stainless steelmaking auxiliary material ground warehouse, and then dumping them after opening the dust removal.

[0026] Among them, in the step (7) 2), the pellets are transported to the underground warehouse by equipment, specifically using a loader to feed the warehouse, and the warehouse electrically vibrates to feed the pellets to a conveyor belt under the warehouse, and the conveyor belt directly delivers the pellets to the underground warehouse of the steelmaking process.

[0027] The beneficial effects of the present invention are:

[0028] 1. Fully consider the physical and chemical properties of the material, deeply master the key points of briquetting technology, and fully consider the process characteristics of the electric arc furnace. With reliable principles, low costs, and convenient operations, the strength of stainless steel dust ash pellets can be improved, the powder and dust in the transportation process can be reduced, and the reduction recovery rate of valuable metal elements in the pellets can be further improved. At the same time, cheap carbon can replace the higher-priced lump coke originally added to the stainless steel electric arc furnace to increase the carbon content of the molten pool, thereby achieving a significant improvement in economic benefits overall.

[0029] 2. With new ideas, meticulous design and operating procedures, efficient utilization of difficult-to-treat solid wastes such as stainless steel dust, iron oxide scale and dry quenching dust has been achieved, which has reduced the environmental pressure on the enterprise, improved the enterprise's efficiency, and is conducive to the healthy and high-quality development of the enterprise.

[0030] 3. After successful application, it can set up a model in the metallurgical industry, have a demonstration effect, and can drive the solid waste utilization of metallurgical enterprises, with economic, social and environmental benefits.

[0031] 4. The present invention can solve the problems of low quality of the original briquetting of stainless steel dust ash, high crushed material, high powder loading rate, easy dust, unsatisfactory reduction kinetic conditions, low chromium-nickel-iron yield, and high cost of heating with coke and carbon. The process fully considers the physical and chemical properties of the material, deeply grasps the key points of briquetting technology, and fully considers the process characteristics of the electric arc furnace. With low investment and relatively simple operation, the strength of the stainless steel dust ash pellets is improved and the powder and dust in the reverse transportation process are reduced. At the same time, the reduction recovery rate of the valuable metal elements in the pellets is improved, and the powdered cheap carbon (dry quenching dust ash) is used to replace the more expensive lump coke. The synergy of agglomeration and metal yield is achieved, and the utilization of dust ash is combined with the utilization of carbon powder, which significantly improves the overall economic benefits. At the same time, by using it according to its characteristics and reasonably matching it, it fully utilizes solid waste resources, reduces the burden of solid waste management of enterprises, and promotes steel enterprises, especially stainless steel enterprises, to reduce costs, increase efficiency and develop high quality.

[0032] 5. The present invention analyzes the characteristics of various materials, reasonably designs the dosage form and proportions, and fully utilizes the characteristics of various materials. The oxides in the dust removal ash are in close contact with the carbon. The elliptical shape of the ball, the appearance of being thick in the middle and thin on both sides, and the size of 40mm in length, 25mm in width and 15mm in thickness take into account the heat transfer and mass transfer effects, improve the reduction kinetic conditions, and provide a main way to increase the reduction rate of metal oxides and the metal recovery rate. At the same time, through the ball pressing method, the reducing agent effect of carbon is utilized, and the powder is converted into a spherical block material that is easy to use, replacing the lump coke required by the process.

[0033] 6. The carbon material of the present invention uses dry quenching coke dust ash which is too fine to be used in the metallurgical process to replace lump coke, which reduces the oxygen potential of the iron molten pool and plays the role of metal oxide reducing agent and reducing atmosphere creator on the surface of pellets and slag surface. The combination of two binders with different properties and different specialties can more reliably maintain the high strength of the pellets.

[0034] 7. The present invention adopts a special ball-making method to ensure the strength of the pellets. In terms of material preparation, each material involved in the ball pressing has a special storage bin and is weighed before being mixed, which ensures the purity of the material and accurate measurement, laying a foundation for improving the quality of the ball pressing and the metallurgical properties. A large-scale wheel-milling mixer is used for mixing for more than 100 turns, and then a large-scale electric vibration feeding cone bin is used to suffocate the material (wake up the material). A double-roll ball press with a forced feeding function and a shallower ball socket is used for initial pressing, which ensures that the material, water and binder are fully dispersed, mixed and moistened, further laying a foundation for improving the quality of the ball pressing and the metallurgical properties. A double-roll ball press with a forced feeding function and a deeper ball socket is used for final pressing, which ensures that the filling rate of the material in the ball socket and the density of the ball are improved, which is another guarantee mechanism for improving the quality of the ball pressing and the metallurgical properties.

[0035] 8. When discharging balls, the present invention adopts multiple groups of ball discharging belts to connect and transport finished balls, and at the end, a cone-shaped initial ball pile is formed by a ball discharging belt machine with adjustable elevation angle, and subsequent balls roll down with the initial ball pile as a slope to reduce breakage; while discharging balls, the upward belt moves to one side to form a circular ridge-type ball pile, which is convenient for initial air drying and shoveling to a large pile for further air drying; for production lines with sufficient space, more groups of belts are connected to control the distance of the circular ball pile, and a quarter-circular ring-shaped low beam is created by the upward belt to radiate from the inside to the outside for storage; the balls of the large ball pile are taken according to the principle of first-come-first-served. The above method reduces the breakage rate of the balls and the amount of powder, and creates conditions for reducing dust during transportation and use and avoiding losses caused by suction by the dust removal system. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0037] A method for making high-quality pellets by mixing stainless steel ash with carbon for improving element yield comprises the following steps:

[0038] (1) Material ratio in the ball: Digested stainless steel 300 series dust, stainless steel oxide scale, dry quenching dust, organic binder, inorganic binder and water are mixed in a mass ratio of 70:5:15:2:3:5;

[0039] (2) Material preparation: Stainless steel 300 series dust is digested by special equipment and weighed with a weighing hopper, and then fed to a closed feeding belt by electric vibration, and then fed to a mixer; stainless steel oxide scale is fed to a mixer through a closed feeding belt; organic binders and inorganic binders are placed in storage bins respectively, weighed with a weighing hopper, and then fed to a closed feeding belt by electric vibration, and then fed to a mixer; CDQ dust is added to the cone bin by a small loader through a reserved side-opening temporary feeding inlet, and the cone bin is fed to the weighing hopper by electric vibration and then to the closed feeding belt by electric vibration, and then fed to a mixer;

[0040] (3) Add water and mix: The roller of the mixer rotates no less than 100 times to ensure that the material, water and binder are fully dispersed and mixed to eliminate the raw material lumps. While stirring, add water according to the humidity of the material to fully moisten the material;

[0041] (4) Stuffing: The mixed materials are transported to a large cone silo by a belt conveyor. The materials are first taken from the bottom by electric vibration, and the upper materials are ensured to be stuffed for more than 3 hours to promote further dispersion and mixing of the materials, water and binder;

[0042] (5) Initial pressing: The steamed material is fed by the feeding belt conveyor to the roller briquetting machine for the first round of briquetting. A spiral forced feeder is installed on the top of the roller briquetting machine to ensure the filling rate of the ball sockets on the roller surface.

[0043] (6) Final pressing: The balls from the initial pressing enter the ball conveying belt through the inclined chute at the bottom of the roller press to feed the final pressing press. The balls after the final pressing enter the ball discharging belt through the inclined screen plate at the bottom of the press. The crushed and powdered materials are transported to the initial pressing feeding belt through the return belt under the screen to continue the initial pressing, and the cycle continues.

[0044] (7) Transshipment:

[0045] 1) Ball discharge: Multiple groups of ball discharge belts are connected to transport finished balls, and finally piled into a cone-shaped initial ball pile through an adjustable-angle ball discharge belt conveyor. Subsequent balls roll down in sequence with the initial ball pile as a buffer slope to reduce breakage. The balls are discharged while moving to one side on the upward belt, and finally a circular ridge-shaped ball pile is formed. After more than 12 hours of air drying and aging hardening, they are shoveled to a large ball pile for further air drying;

[0046] 2) The pellets in the large pellet pile are taken according to the principle of first-come-first-served, and transported to the ground warehouse through equipment;

[0047] 3) The pellets in the ground bin are fed to the auxiliary material feeding belt through electric vibration and then to the steelmaking feeding platform, and then fed to the high-level silo above the electric arc furnace by the feeding trolley for standby use.

[0048] Among them, in the step (6), based on comprehensive considerations of the heat transfer, mass transfer, ease of balling, ease of demoulding and production efficiency of the pellets, the pellets are elliptical in shape, thick in the middle and thin on both sides, with a length of 40 mm, a width of 25 mm and a thickness of 15 mm.

[0049] Wherein, in step (3), the mixer is a large wheel-milling mixer.

[0050] Among them, in step (7) 1), in production lines with sufficient space, more sets of belt connections are used to control the distance of the annular ball pile. By raising the belt to create a quarter-circular ring-shaped low beam, the pile is radially stored from the inside to the outside, which can reduce tipping and further reduce the amount of broken materials.

[0051] Among them, in step (7) 2), the pellets are transported to the ground warehouse by equipment, specifically by using a loader to load them onto a well-sealed vehicle with a retractable tarpaulin and transport them to the stainless steelmaking auxiliary material ground warehouse, and then dumping them after opening the dust removal.

[0052] Among them, in step (7) 2), the pellets are transported to the underground warehouse by equipment, specifically using a loader to feed the warehouse, and the warehouse electrically vibrates to feed the pellets to a conveyor belt under the warehouse, and the conveyor belt directly delivers the pellets to the underground warehouse of the steelmaking process.

[0053] Among them, the function design of each material:

[0054] Stainless steel 300 series dust removal ash: provides valuable elements Cr, Ni, Fe in the form of oxides, and provides a portion of CaO in the form of slaked lime, which can save the amount of lime used in electric arc furnaces, and realizes partial carbonation consolidation through the action of hourly ash and carbon dioxide in the air, which is an auxiliary pellet strength guarantee mechanism;

[0055] Carbon material: CDQ dust ash is selected, which comes from the dust collection system of the CDQ process of the coking plant, and the particle size below 100 mesh accounts for more than 80%. It is used here to replace the original carbon material of the stainless steel arc furnace - lump coke to reduce the oxygen potential of the iron molten pool, and at the same time, it serves as a reducing agent for metal oxides in the dust ash and a reducing atmosphere creator for furnace gas near the pellet surface and slag surface;

[0056] Organic binder is the main mechanism to ensure the strength of pellets. It ensures the higher late strength of pellets through the unique aging hardening characteristics of organic agents. It decomposes after being heated to create a reducing atmosphere.

[0057] Inorganic binder ensures that the newly pressed wet balls have a certain strength, which is convenient for the balls to be transported in a short period of time after pressing. It is an auxiliary mechanism to ensure the strength of the balls.

[0058] Water is a promoter that allows the base material and binder particles to fully contact each other, and an inducer that enables the organic and inorganic binders to play a bonding role.

[0059] The present invention can reduce and improve the principle of metal recovery:

[0060] The basic reaction of reducing chromium oxide in dust ash with solid carbon at a high temperature below 1600℃ in an electric arc furnace is:

[0061] 2 / 3Cr 2 O 3 +2C=4 / 3Cr+2CO (1)∆Gϴ=516890-339.5T The reaction starting temperature is 1250℃;

[0062] 2 / 3Cr 2 O 3 +26 / 9C=4 / 9Cr3C2+2CO(2) ∆Gϴ=478234-347.15T The reaction starting temperature is 1100℃;

[0063] 2 / 3Cr 2 O 3 +18 / 7C=4 / 21Cr7C3+2CO (3)∆Gϴ=482281-343.54TThe reaction start temperature is 1130℃;

[0064] 2 / 3Cr 2 O 3 +54 / 23C=4 / 69Cr23C6+2CO(4)∆Gϴ=494369-341.72TThe reaction starting temperature is 1175℃.

[0065] It can be seen that the reaction temperature of chromium carbide is lower than that of pure chromium, and the reaction starting temperature of carbide with high carbon content is lower than that of carbide with low carbon content, so the formation of carbide with high carbon content is easier to proceed first. Since chromium and carbon have the property of forming stable carbides, the reduction of chromium oxide with carbon reducing agent is Cr 23 C 6 Cr 7 C 3 , and Cr 3 C 2 From the principles of iron and steel metallurgy, we know that Fe 2 O 3 The reduction temperature is about 900℃, so the iron oxide in the dust is higher than Cr 2 O 3 It is preferentially reduced at a lower temperature. It fuses with chromium carbide to form a composite carbide (Cr, Fe). 3 C 2 、(Cr,Fe) 7 C 3 、(Cr,Fe) 23 C 6 The formation of these composite carbides not only reduces the melting point of the alloy formed by iron, chromium and carbon, but also reduces the activity of Cr from the perspective of chemical equilibrium, so that the reduction reaction can proceed at a lower temperature. Therefore, the presence of iron in the dust removal ash is conducive to the reduction of chromium oxide in the dust removal ash.

[0066] When the temperature of the arc furnace molten pool is further increased, the later reduced Cr2O3 decarburizes the already reduced carbides, and the reaction is:

[0067] 14 / 5Cr 3 C 2 +2 / 3Cr 2 O 3 =4 / 3Cr+6 / 5Cr 7 C 3 +2CO(5)∆Gϴ=543609-309.45T The reaction starting temperature is 1490℃

[0068] 2Cr 7 C 3 +2 / 3Cr 2 O 3 =2 / 3Cr 23 C 6 +2CO (6)∆Gϴ=621315-328.13T The reaction starting temperature is 1620℃

[0069] 1 / 3Cr 23 C 6 +2 / 3Cr2 O 3 =9Cr+2CO (7)∆Gϴ=655173-326.67T The reaction starting temperature is 1730℃

[0070] The temperature of chromium oxide decarburization is relatively high. In a stainless steel arc furnace, the temperature can reach above 1600°C before steel is tapped, so the decarburization reaction of formula (5) is mainly carried out, the reaction of formula (6) is rarely carried out, and the reaction of formula (7) is only carried out in the high temperature zone of the arc (accounting for less than 20% of all decarburization reactions). The metallic chromium or chromium carbide generated by the decarburization reaction is called part of the arc furnace molten pool.

[0071] Finally, after arc impact, stirring by blowing carbon powder and re-mixing when tapping steel from the arc furnace, a stainless steel mother liquor with a more uniform composition and temperature containing elements such as chromium, nickel, iron, and carbon is formed and added to the AOD refining furnace for subsequent process treatments such as decarburization, chromium retention, and impurity removal.

[0072] In summary, the initial stage of the reduction of stainless steel dust begins with the reduction of iron oxides. As the temperature rises (above 1200°C), the part of the chromium oxide in contact with the reducing agent begins to slowly reduce to form chromium and iron composite carbides. The chromium carbides generated by the reduction reaction, together with the carbonaceous reducing agent, continue to reduce the residual Cr at a higher temperature (above 1600°C). 2 O 3 Reduction is carried out and carbides are decarburized. Since the main charge in the electric arc furnace is high-carbon nickel-iron blocks with a small amount of high-carbon ferrochrome blocks, there are two types of reduction reactions after the metal material in the furnace melts and a molten pool appears. One is the reduction reaction of the carbon inside the molten pellets (that is, part of the slag phase) to the oxides, and the other is the reduction reaction of the carbon in the molten pool to the oxides in the slag phase (part of the carbon in the molten pool also comes from the dissolution of carbon in the carbon-matched pellets). Since the oxide and carbon particles in the carbon-matched pellets are extremely fine and in close contact, the reduction reaction is mainly controlled by the diffusion of the reduction products, and the transfer of carbon to metal oxides is not the main rate-controlling link in the entire reduction stage. Overall, the reduction kinetic conditions are improved, and the reduction rates of chromium and iron are increased. The formation of CO during the reduction process strengthens the reducing atmosphere above the molten pool and around the pellets, further promoting the increase in the reduction rates of chromium and iron.

[0073] Material use of stainless steel dust removal ash and carbon pellets

[0074] In order to maximize the recovery rate of valuable metals in dust ash carbon balls on the basis of scientific ball making and transportation, the following special feeding process is adopted under reliable theoretical support:

[0075] (1) When the scrap steel and iron blocks in the electric arc furnace are melted by the arc and oxygen lance to form a molten pool, stainless steel dust removal ash and carbon pellets are added.

[0076] (2) Carbon pellets are added in small amounts and multiple times. For a 100-ton electric arc furnace, three batches of 1 ton each are added from the beginning of the molten pool to the complete melting. After the molten pool is completely melted, three batches of 1 ton each are added during the temperature rise stage. No more pellets are added 10 minutes before tapping.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for high-quality pelletizing of stainless steel ash with carbon for improving element yield, characterized in that: The following steps are involved: (1) Material ratio in the ball: Digested stainless steel 300 series dust, stainless steel oxide scale, dry quenching dust, organic binder, inorganic binder and water are mixed in a mass ratio of 70:5:15:2:3:5; (2) Material preparation: Stainless steel 300 series dust is digested by special equipment and weighed with a weighing hopper, and then fed to a closed feeding belt by electric vibration, and then fed to a mixer; stainless steel oxide scale is fed to a mixer through a closed feeding belt; organic binders and inorganic binders are placed in storage bins respectively, weighed with a weighing hopper, and then fed to a closed feeding belt by electric vibration, and then fed to a mixer; CDQ dust is added to the cone bin by a small loader through a reserved side-opening temporary feeding inlet, and the cone bin is fed to the weighing hopper by electric vibration and then to the closed feeding belt by electric vibration, and then fed to a mixer; (3) Add water and mix: The roller of the mixer rotates no less than 100 times to ensure that the material, water and binder are fully dispersed and mixed to eliminate the raw material lumps. While stirring, add water according to the humidity of the material to fully moisten the material; (4) Stuffing: The mixed materials are transported to a large cone silo by a belt conveyor. The materials are first taken from the bottom by electric vibration, and the upper materials are ensured to be stuffed for more than 3 hours to promote further dispersion and mixing of the materials, water and binder; (5) Initial pressing: The steamed material is fed by the feeding belt conveyor to the roller briquetting machine for the first round of briquetting. A spiral forced feeder is installed on the top of the roller briquetting machine to ensure the filling rate of the ball sockets on the roller surface. (6) Final pressing: The balls from the initial pressing enter the ball conveying belt through the inclined chute at the bottom of the roller press to feed the final pressing press. The balls after the final pressing enter the ball discharging belt through the inclined screen plate at the bottom of the press. The crushed and powdered materials are transported to the initial pressing feeding belt through the return belt under the screen to continue the initial pressing, and the cycle continues. (7) Transshipment: 1) Ball discharge: Multiple groups of ball discharge belts are connected to transport finished balls, and finally piled into a cone-shaped initial ball pile through an adjustable-angle ball discharge belt conveyor. Subsequent balls roll down in sequence with the initial ball pile as a buffer slope to reduce breakage. The balls are discharged while moving to one side on the upward belt, and finally a circular ridge-shaped ball pile is formed. After more than 12 hours of air drying and aging hardening, they are shoveled to a large ball pile for further air drying; 2) The pellets in the large pellet pile are taken according to the principle of first-come-first-served, and transported to the underground warehouse through equipment; 3) The pellets in the ground bin are fed to the auxiliary material feeding belt through electric vibration and then to the steelmaking feeding platform, and then fed to the high-level silo above the electric arc furnace by the feeding trolley for standby use.

2. A method for high-quality pelletizing of stainless steel ash with carbon for improving element yield according to claim 1, characterized in that: In the step (6), based on comprehensive considerations of the heat transfer, mass transfer, ease of balling, ease of demoulding and production efficiency of the pellets, the pellets are elliptical in shape, thick in the middle and thin on both sides, with a length of 40 mm, a width of 25 mm and a thickness of 15 mm.

3. The method for high-quality pelletizing of stainless steel ash with carbon for improving element yield according to claim 1, characterized in that: In the step (3), the mixer is a large wheel-mill mixer.

4. A method for high-quality pelletizing of stainless steel ash with carbon for improving element yield according to claim 1, characterized in that: In step (7) 1), in production lines with sufficient space, more sets of belt connections are used to control the distance of the annular ball pile. By raising the belt to create a quarter-circular ring-shaped low beam, the pile is radially stored from the inside to the outside, which can reduce tipping and further reduce the amount of broken materials.

5. The method for high-quality pelletizing of stainless steel ash with carbon for improving element yield according to claim 1, characterized in that: In step (7) 2), the pellets are transported to the warehouse by equipment, specifically by using a loader to load the pellets onto a well-sealed vehicle with a retractable tarpaulin and transporting them to the stainless steelmaking auxiliary material warehouse, and then dumping the pellets after dust removal is turned on.

6. A method for high-quality pelletizing of stainless steel ash with carbon for improving element yield according to claim 1, characterized in that: In step (7) 2), the pellets are transported to the underground warehouse by equipment, specifically by using a loader to feed the warehouse, and the warehouse electrically vibrates and feeds the pellets to a conveyor belt under the warehouse, and the conveyor belt directly delivers the pellets to the underground warehouse of the steelmaking process.