Cold-state total recovery and reutilization method for aluminum-calcium refining slag

Abstract

The invention discloses a cold-state total recovery and reutilization method for aluminum-calcium refining slag, and belongs to the technical field of ferrous metallurgy solid waste reutilization. The classical aluminum-calcium refining slag generated in the reduction desulfurization process such as LF refining and converter rear top slag modification has the characteristics of low phosphorus capacity, high alkalinity, low melting point and certain sulfur capacity, and the cold-state total recovery, reprocessing and reutilization in a converter steelmaking system of the aluminum-calcium refining slag can be realized by the method disclosed by the invention; the recycled aluminum-calcium refining slag raw blocks and recycled aluminum-calcium refining slag powder particle composite pressing ball byproducts can be applied to metallurgical links such as converter oxidation dephosphorization slagging, silicon deoxidation steel top slag modification and LF stirring decarbonization fluxing, so that cold-state full recycling of the aluminum-calcium refining slag is realized in a real sense; the method has positive significance in the aspects of reducing environmental pollution, improving the quality of steel slag hot braising byproducts, reducing the steelmaking cost and the like.

Description

Technical Field

[0001] The invention relates to a method for cold full recovery and reuse of aluminum-calcium refining slag, belonging to the technical field of recycling solid waste from iron and steel metallurgy. Background Art

[0002] The classic aluminum-calcium refining slag produced by the reduction desulfurization process such as LF refining and converter top slag modification is generated by the interaction or reaction of various slag-making materials in the high-temperature process. The various components have fully reacted in the refining process to form a large number of low-melting complex phases, which have the characteristics of low phosphorus content, high basicity, low melting point and certain sulfur content and recyclable value. At present, most of the domestic processes adopt the process of pouring the excess of the ladle into the next ladle and then entering the LF refining to recycle the hot slag online, and the influence of the number of recycling and the amount of recycling on the refining effect must be balanced, so only part of its recycling value is exerted. In addition, many steel companies are restricted by many factors and cannot carry out online hot recycling and discard, resulting in a large amount of waste of this type of white slag. In addition, many steel mills and research institutions in the industry have conducted sufficient theoretical research and demonstration on its cold recycling, but due to the limitations of process and tooling design, there are very few cases where the system is applied to actual production and forms an industrial chain. In recent years, in response to the national call for carbon peak and carbon neutrality, energy conservation and emission reduction are urgent, and all walks of life are working closely together. Under the current situation, it is of great significance to step up research efforts and promote the cold full recycling and reuse of this type of aluminum-calcium refining slag. Summary of the invention

[0003] The present invention aims to provide a method for the full cold recovery and reuse of aluminum-calcium refining slag, which can realize scientific full-industry chain recovery and mass production integrating hot initial crushing of aluminum-calcium refining slag, sealed slow cooling in a stewing tank, cold crushing and screening, and reprocessing for metallurgical reuse in the steelmaking system, so as to maximize its reusable value, reduce steelmaking costs, and make positive contributions to energy conservation and emission reduction.

[0004] The treatment object of the present invention is: aluminum-calcium refining slag produced by reduction desulfurization processes such as LF refining and converter top slag modification. The aluminum-calcium refining slag has the characteristics of low phosphorus content, high basicity, low melting point and certain sulfur content. The method can realize the cold full recovery, reprocessing and reuse of the aluminum-calcium refining slag in the converter steelmaking system. The recovered aluminum-calcium refining slag block and the recovered aluminum-calcium refining slag powder composite briquetting by-product can be used in metallurgical links such as converter oxidation dephosphorization slag making, silicon deoxidation steel top slag modification, LF stirring decarburization fluxing, etc., realizing the real cold full recovery and reuse of aluminum-calcium refining slag, which has positive significance in reducing environmental pollution, improving the quality of steel slag by-products, and reducing steelmaking costs.

[0005] The present invention provides a method for fully recovering and reusing aluminum-calcium refining slag in cold state, comprising the following steps: S1. The aluminum-calcium refining slag produced in the reduction and desulfurization process such as LF refining and converter top slag reforming is poured into the slag tank after continuous casting and steel pouring; S2, the slag pot is transported to the outer slag bay which is sheltered from wind and dry; S3, turning over the hot red slag in the slag tank at the outer slag span, and then using an oil hammer or a raking machine to perform preliminary crushing; S4. The crushed hot red slag is quickly loaded into the hot stewing tank of the hot stewing line by a forklift and sealed; S5, a hot stewing tank filled with red crushed aluminum-calcium refining slag is slowly cooled to room temperature in an outer slag span away from wind; S6, the hot stewing tank is transported to the aluminum-calcium refining slag screening and crushing line for further processing; S7. The crushed cold aluminum-calcium refining slag is preliminarily screened and magnetically separated in a cold slag crushing line, and the large slag is crushed and then screened to obtain three intermediate by-products: 5mm-40mm blocky aluminum-calcium slag, aluminum-calcium refining slag powder particles below 5mm, and residual steel; S8. The aluminum-calcium refining slag powder with a size of less than 5 mm produced by the screening and crushing line is transported to the cold solidification ball production line by belt or tank truck; S9. In the cold solid pressing ball production line, aluminum-calcium refining slag powder and particles with a size of less than 5 mm are mixed with other materials to produce multifunctional cold solid pressing balls such as high-efficiency composite decarburization slag-making agent for ladle, silicon deoxidation steel top slag modifier, and converter high-efficiency dephosphorization slag agent; S10. The various types of briquetting by-products produced are returned to the converter or ladle refining process and used in metallurgical processes such as slag making and dephosphorization in the converter, melting and slag adjustment in the steelmaking process, and ladle stirring and decarburization.

[0006] The specific process details of the above method are described as follows: In step S1, the aluminum-calcium refined slag is solid waste slag generated in the production process of all-aluminum killed steel with a finished product [Si] ≤ 0.10%, and its typical chemical components are generally as follows by weight percentage: CaO: 50% to 60%, Al2O3: 20% to 35%, SiO2 ≤ 18%, MgO: 5% to 8%, (FeO + MnO) ≤ 1.5%.

[0007] In step S2, the environment of the site for hot slag turning and crushing of the dried external slag protected from wind must meet the following conditions: water vapor volume content <1%, temperature > 20°C, and no natural wind around.

[0008] In the steps S3 and S4, the hot red slag in the slag pot is turned over and crushed initially, and then put into the hot stew pot for sealing and slow cooling. The operation must be carried out under the condition that the red slag temperature is ≥700°C to prevent: C3S (tricalcium silicate) precipitated in the white slag from causing volume expansion during the unreasonable cooling process due to the transformation of β-C2S to γ-C2S lattice, resulting in severe explosion and powdering; the gaps between the red slag after crushing can offset the slow volume expansion during the slow cooling process; thereby obtaining blocky aluminum-calcium slag with a particle size of more than 5 mm accounting for more than 85%.

[0009] In step S4, the red slag is sealed after the initial crushing in the following manner: the bottom of the hot stewing tank is paved with 20 mm to 30 mm dry white slag, and after the red slag is loaded, the top is evenly covered with ≥ 20 mm dry white slag, and the top of the slag tank is finally sealed with a tank cover. The hot stewing tank is a cast iron or cast steel container with a wall thickness of more than 8 mm, and can be sealed with a cover.

[0010] In step S5, slow cooling generally takes 36 hours to 72 hours, and the room temperature is an ambient temperature of 20° C. to 40° C. that can be touched by hand when the wall temperature of the hot stew pot is detected by a manual handheld thermometer.

[0011] In the steps S6 and S7, the aluminum-calcium refining slag screening and crushing line is a special cold slag crushing processing production line, which can realize the functions of aluminum-calcium refining slag screening, residual steel magnetic separation, re-crushing to target particle size products and re-screening. The entire aluminum-calcium refining slag screening and crushing line ultimately produces three intermediate by-products: 5mm-40mm blocky aluminum-calcium slag, aluminum-calcium refining slag powder particles below 5mm, and residual steel. The recycled residual steel can be directly recycled as scrap steel.

[0012] Specifically, the aluminum-calcium refining slag screening and crushing line includes a vibrating feeder, a coarse jaw crusher, a fine jaw crushing and screening machine, a fine material bin, a rod mill screening machine, a coarse material belt conveyor and a fine material belt conveyor connected in sequence: the aluminum-calcium refining slag after initial screening enters the vibrating feeder, enters the coarse jaw crusher along the first belt conveyor, and is crushed for the first time to obtain a coarsely crushed aluminum-calcium slag with a uniform particle size of less than 15 cm; the coarsely crushed aluminum-calcium slag enters the fine jaw crushing and screening machine along the second belt conveyor, and is crushed for the second time and screened to obtain 5mm-40mm blocky aluminum-calcium The slag by-products that are screened over and the aluminum-calcium refining slag powder particles that are less than 5 mm are screened under. After being crushed, the aluminum-calcium refining slag powder particles that are less than 5 mm enter the next process along the third belt conveyor. In this process, after iron removal by the hanging magnetic roller, the magnetic small-grade scrap steel and the aluminum-calcium refining slag powder particles that are less than 5 mm are respectively sent to the waste belt conveyor and the fine material bin. The materials in the fine material bin enter the rod mill screening machine along the fourth belt conveyor. After further grinding and screening, the aluminum-calcium slag powder is sent to the coarse material belt conveyor or the fine material belt conveyor along the fifth belt conveyor to produce aluminum-calcium refining slag powder particles with different mesh requirements.

[0013] Furthermore, a 15cm grid screen is installed in the vibrating feeder to preliminarily screen out large pieces of residual steel larger than 15cm and the aluminum-calcium slag on the screen. The on-screen material is transported by a forklift to a nearby external processing site, where the large pieces of residual steel are magnetically separated and recovered by a magnetic disk crane. The large pieces of aluminum-calcium slag after selection are returned to the coarse material bin by a forklift.

[0014] Furthermore, a coarse aluminum-calcium slag bin is provided under the grid screen in the vibrating feeder to collect the screened material below 15 cm and the large aluminum-calcium slag above 15 cm selected from an external site.

[0015] Furthermore, the ends of the coarse material belt conveyor and the fine material belt conveyor are equipped with hanging magnetic rollers to remove iron and select scrap steel of smaller particle size and aluminum-calcium refining slag powder particles with different mesh requirements.

[0016] In the steps S8 and S9, the cold solid pressed ball production line can realize the production of multifunctional cold solid pressed balls according to the formula of aluminum calcium refined slag powder with different mesh sizes below 5mm and other raw and auxiliary materials, such as silicon deoxidized steel top slag modifier, converter high-efficiency dephosphorization slag agent, ladle high-efficiency composite decarburization slag agent, etc. After the cold solid pressed balls are dried, the cold strength of the drum must reach more than 10kN and the particle size must reach 5mm to 40mm to meet the requirements of multiple transfers and the addition of high-level silos in the steelmaking system.

[0017] Specifically, the cold-setting ball pressing production line includes a feed bin (multiple), a mixing mixer, a mixing bin, a ball press and a mesh belt dryer connected in sequence, and materials are transported between the various devices by conveyors; first, the material enters the mixing mixer from the feed bin along the raw material conveyor, is mixed with other materials in proportion, and enters the mixing bin after stirring, and then enters the ball press along the mixing and ball pressing return conveyor. After ball pressing, the material is sent to the mesh belt dryer by the raw ball conveyor for drying and other operations.

[0018] Furthermore, the present invention provides a high-efficiency composite decarburization slag-making agent for ladle, which is prepared by using the aluminum-calcium refined slag powder of less than 5 mm produced by the above-mentioned cold slag crushing line as raw materials and other raw materials. The raw material ratio is: based on the aluminum-calcium refined slag powder of less than 5 mm produced by the above-mentioned cold slag crushing line, 0%~20% iron oxide scale, 1%~2% raw dolomite powder raw slag material, 0.5%~1.5% inorganic binder aluminate cement, 5%~7% organic binder corn starch, 0%~10% water are added respectively for weight batching, mixing, ball pressing, drying, and producing 5mm~40mm high oxidation low melting point composite slag-making agent. The main chemical components of the high-efficiency composite decarburization slag-making agent are: CaO: 35%~50%, Al2O3: 15%~30%, SiO2≤10%, MgO: 5%~15%, FeO≥5%, and the single ball compressive strength is ≥10kN. It is used to add to the ladle stirring and decarburization metallurgical process to quickly increase the top slag oxidizability and the thickness of the covering layer, and play a metallurgical role in improving the stirring decarburization efficiency and covering the molten steel to reduce secondary oxidation losses. Furthermore, in the process of preparing the slag-making agent, the particle size of the aluminum-calcium refining slag powder can be controlled by selecting the mesh number of the production line screening machine to facilitate the regulation of the adhesion of the cold-solidified pellets and the strength after drying. The preferred particle size is 80μm to 150μm. Furthermore, the drying method and drying temperature of the product (raw ball) obtained after ball pressing can be controlled as needed to meet the balance and drying requirements of the production process. It is preferably dried or dried at a temperature of 30℃ to 190℃ for 24h to 96h.

[0019] Furthermore, the present invention provides a silicon-deoxidized steel top slag modifier, which is a 5mm-40mm blocky aluminum-calcium slag produced by the above-mentioned cold slag crushing line and a powdered aluminum-calcium refining slag produced by the cold solidification briquetting production line. The main chemical composition of the silicon-deoxidized steel top slag modifier is consistent with that of the aluminum-calcium refining slag, which is: CaO: 50%-60%, Al2O3: 20%-35%, SiO2≤18%, MgO: 5%-8%, (FeO+MnO)≤1.5%. It is used to return to the steelmaking system as a silicon-deoxidized steel tapping slag washing and modifier, which can play a metallurgical role such as diluting the top slag to absorb silicon oxide inclusions and reduce phosphorus return, and further modifying the top slag with melting lime. Furthermore, the aluminum-calcium refining slag powder and raw slag balls produced by the cold solidification ball production line are as follows: 2% to 5% of mineral powder binder is added to the aluminum-calcium refining slag powder and particles below 5 mm produced by the above-mentioned cold slag crushing line, and the mixture is weighed, mixed, ball-pressed and dried to produce 5mm to 40mm aluminum-calcium raw slag balls, and the compressive strength of a single ball is ≥10kN.

[0020] Furthermore, the present invention provides a converter high-efficiency dephosphorization slag agent, in which 0% to 10% converter dry dust fine ash, 0% to 10% sintering dust ash, 15% to 40% alumina red mud and 2% to 5% mineral powder binder are added to the aluminum-calcium refining slag powder below 5 mm produced by the cold slag crushing line as a basis, and then weighed, mixed, pressed into balls and dried to produce a 5mm to 40mm converter high-efficiency dephosphorization slag agent. The main chemical components of the converter high-efficiency dephosphorization slag agent are: CaO: 20% to 40%, Al2O3: 8% to 15%, SiO2≤10%, MgO: 5% to 8%, Na2O: 1.5% to 4.0%, Fe2O3≥40%, and the single ball compressive strength is ≥10kN. The converter high-efficiency dephosphorization slag-forming agent is used to return to the converter smelting process. It can play a metallurgical role such as quickly melting lime during the dephosphorization period to improve the early dephosphorization efficiency, replacing part of the calcium slag-forming agent to reduce the converter steelmaking cost, etc.

[0021] The percentages described in the present invention are all weight percentages.

[0022] Beneficial effects of the present invention: (1) The present invention provides a method for cold-state recovery and reuse of aluminum-calcium refining slag, which can achieve the goal of obtaining more than 85% of blocky aluminum-calcium raw slag larger than 5 mm through preliminary crushing and slow cooling of the aluminum-calcium refining slag in the red state, and the cold slag crushing and cold solid ball production line produces cold solid balls and residual steel that can be reused in the converter steelmaking system, realizing the cold processing and recycling of aluminum-calcium refining slag on a dedicated line, completely solving the problem that only part of its beneficial elements can be recycled through hot recycling and that some enterprises cannot recycle in the hot state, and realizing nearly 100% cold-state recovery and reuse of aluminum-calcium refining slag in the true sense.

[0023] (2) The present invention provides a method for cold recovery and reuse of aluminum-calcium refining slag, which produces 5mm-40mm block aluminum-calcium slag, slag briquette and multifunctional composite cold briquette produced by cold slag crushing and cold solid briquetting production line. The output of aluminum-calcium refining slag block and slag briquette can reach more than 85%, which has the characteristics of low cost, high efficiency, and universal applicability of operation and production methods. The corresponding by-products can be used for metallurgical links such as silicon deoxidized steel slag washing and top slag modification in the steelmaking system, efficient slag desulfurization in the converter smelting process, and ladle stirring composite decarburization and slag making, replacing other auxiliary materials such as electric melting flux, converter iron-containing material and slag desulfurization agent, ladle decarburization agent, etc. to achieve the same metallurgical effect, reduce the cost of auxiliary materials such as lime, and achieve near-zero emission of solid waste slag, and simultaneously reduce the adverse effect of free calcium on the quality of steel slag by-products after the high-basicity aluminum-calcium refining slag and converter slag are mixed and hot-stewed. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a process flow chart of the cold state full recovery and reuse method of aluminum-calcium refining slag of the present invention; Figure 2 This is a schematic diagram of the screening and crushing line of aluminum-calcium refining slag of the present invention; Figure 3 This is a schematic diagram of the aluminum-calcium refined slag cold solid pressed ball production line of the present invention; In the figure: 1 is a coarse material bin, 2 is a grid screen, 3 is a vibrating feeder, 4 is a first belt conveyor, 5 is a coarse jaw crusher, 6 is a second belt conveyor, 7 is a fine jaw crusher and screening machine, 8 is a third belt conveyor, 9 is a hanging magnetic roller, 10 is a waste belt conveyor, 11 is a fine material bin, 12 is a fourth belt conveyor, 13 is a rod mill screening machine, 14 is a fifth belt conveyor, 15 is a coarse material belt conveyor, 16 is a second hanging magnetic roller, 17 is a fine material belt conveyor; 18 is a feed bin, 19 is a raw material conveyor, 20 is a mixer, 21 is a mixing bin, 22 is a mixing and ball pressing return conveyor, 23 is a ball pressing machine, 24 is a raw ball conveyor, 25 is a mesh belt dryer, and 26 is a finished ball conveyor. DETAILED DESCRIPTION

[0025] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making other innovations are within the scope of protection of the present invention.

[0026] The present invention provides a method for cold full recovery and reuse of aluminum-calcium refining slag, comprising the following steps: S1. The aluminum-calcium refining slag produced in the reduction and desulfurization process such as LF refining and converter top slag reforming is poured into the slag tank after continuous casting and steel pouring; S2, the slag pot is transported to the outer slag bay which is sheltered from wind and dry; S3, turning over the hot red slag in the slag tank at the outer slag span, and then using an oil hammer or a raking machine to perform preliminary crushing; S4. The crushed hot red slag is quickly loaded into the hot stewing tank of the hot stewing line by a forklift and sealed; S5, a hot stewing tank filled with red crushed aluminum-calcium refining slag is slowly cooled to room temperature in an outer slag span away from wind; S6, the hot stew tank is transported to the aluminum-calcium refining slag screening and crushing line for further processing. The production line layout diagram is as attached Figure 2As shown; Specifically, the aluminum-calcium refining slag screening and crushing line includes a vibrating feeder 3, a coarse jaw crusher 5, a fine jaw crushing and screening machine 7, a fine material bin 11, a rod mill screening machine 13, a coarse material belt conveyor 15 and a fine material belt conveyor 17 connected in sequence: the aluminum-calcium refining slag after initial screening enters the vibrating feeder 1, enters the coarse jaw crusher 5 along the first belt conveyor 4, and is crushed for the first time to obtain coarsely crushed aluminum-calcium slag with a particle size of less than 15 cm, and the coarsely crushed aluminum-calcium slag enters the fine jaw crushing and screening machine 7 along the second belt conveyor 6, and is crushed for the second time and screened to obtain 5mm-40mm blocky aluminum-calcium ore The slag by-products on the screen and the aluminum-calcium refining slag powder below 5 mm are crushed and enter the next process along the third belt conveyor 8. In this process, the magnetic small-grained scrap steel and the aluminum-calcium refining slag powder below 5 mm are removed by the magnetic hanging roller 9, and then sent to the waste belt conveyor 10 and the fine material bin 11 respectively. The material in the fine material bin 11 enters the rod mill screening machine 13 along the fourth belt conveyor 12. After further grinding and screening, the aluminum-calcium slag powder is sent to the coarse material belt conveyor 15 or the fine material belt conveyor 17 along the fifth belt conveyor 14 to produce aluminum-calcium refining slag powder with different mesh requirements.

[0027] Furthermore, a 15 cm grid screen 2 is provided in the vibrating feeder 3 to preliminarily screen out large pieces of residual steel larger than 15 cm and the aluminum-calcium slag on the screen. The on-screen material is transported by a forklift to a nearby external processing site, and the large pieces of residual steel are magnetically separated and recovered by a magnetic disk crane. The large pieces of aluminum-calcium slag after selection are returned to the coarse material bin 1 by a forklift.

[0028] Furthermore, a coarse aluminum-calcium slag bin is provided under the grid screen in the vibrating feeder 3 to collect the undersize of the grid screen below 15 cm and the large aluminum-calcium slag above 15 cm selected from an external site.

[0029] Furthermore, the ends of the coarse material belt conveyor and the fine material belt conveyor are equipped with hanging magnetic rollers to remove iron and select scrap steel of smaller particle size and aluminum-calcium refining slag powder particles with different mesh requirements.

[0030] S7. The crushed cold aluminum-calcium refining slag is preliminarily screened and magnetically separated in a cold slag crushing line, and the large slag is crushed and then screened to obtain three intermediate by-products: 5mm-40mm blocky aluminum-calcium slag, aluminum-calcium refining slag powder particles below 5mm, and residual steel; S8. The aluminum-calcium refining slag powder with a size of less than 5 mm produced by the screening and crushing line is transported to the cold solidification ball production line by belt or tank truck. The production line layout diagram is as follows Figure 3As shown; specifically, the cold solidification ball pressing production line includes a feeding bin 18, a mixing mixer 20, a mixing bin 21, a ball pressing machine 23 and a mesh belt dryer 25 which are connected in sequence, and materials are transported between the above-mentioned devices by conveyors; first, the material enters the mixing mixer 20 from the feeding bin 18 along the raw material conveyor 19, is mixed with other materials in proportion, and enters the mixing bin 21 after stirring, and then enters the ball pressing machine 23 along the mixing and ball pressing return conveyor 22, and after ball pressing, is sent to the mesh belt dryer 25 by the raw ball conveyor 24 for drying and other operations.

[0031] S9. In the cold solid pressed ball production line, aluminum-calcium refined slag powder and particles below 5mm are mixed with other materials according to the process to produce multifunctional cold solid pressed balls such as high-efficiency composite decarburization slag-making agent for ladle, silicon deoxidation steel top slag modifier, high-efficiency dephosphorization slag agent for converter, etc. After the cold solid pressed balls are dried, the cold strength of the drum must reach more than 10kN and the particle size must reach 5mm~40mm to meet the needs of multiple transfers and the addition of high-level silos to the steelmaking system.

[0032] S10. The various types of briquetting by-products produced are returned to the converter or ladle refining process and used in metallurgical processes such as slag making and dephosphorization in the converter, melting and slag adjustment in the steelmaking process, and ladle stirring and decarburization.

[0033] The 5mm-40mm blocky aluminum calcium slag and slag briquette produced by the above production line can be directly used in steelmaking production to replace other materials with the same function, which is efficient and low-cost. The aluminum calcium refined slag powder less than 5mm produced by the above production line and the dried iron oxide scale recycled from steelmaking or rolling mills are used as raw materials, mixed with inorganic binder aluminate cement and organic binder corn starch and other auxiliary materials, and a high-efficiency composite decarbonization slag-making agent is prepared by cold solidification briquetting. The selected aluminum calcium refined slag powder less than 5mm needs to be tested and identified in advance to ensure that the sulfur content is ≤0.5%. The selected iron oxide scale needs to be dried in advance to ensure that the moisture content is ≤1%. The main components of the selected inorganic binder aluminate cement are CaO and Al2O3 components, and SiO2≤10% to prevent the alkalinity of the composite decarbonization slag-making agent from being unfavorable. At the same time, it does not contain other harmful elements that are unfavorable to molten steel, and has a certain high-temperature plastic effect. The main component of the organic binder corn starch is a hydrocarbon-based inorganic substance. The deoxidation in the steelmaking environment produces a gas that does not pollute the molten steel. Other auxiliary materials are raw slag materials such as raw dolomite powder. The main carbonate components of the raw slag materials decompose in the steelmaking environment and have a certain slag adjustment and foaming effect. The prepared high-efficiency composite decarburization slag-making agent has a strength of about 10kN after drying. When added in an appropriate amount during the ladle stirring and decarburization period, it can quickly melt and cover the molten steel within 1 minute, providing sufficient oxygen potential driving force required for decarburization stirring, and reducing the oxidation and burning caused by the exposure of the molten steel. The low-melting-point aluminum-calcium slag and raw slag materials can continuously melt lime and foam the top slag in the subsequent reduction period to facilitate rapid slag formation or arc burial, strengthen the reduction slag desulfurization and other metallurgical purposes; improve the slag formation rate and decarburization speed, and reduce the use of lime, fluxing agent and foaming agent.

[0034] According to one aspect of the present invention, the present invention provides the following technical solution: a method for fully recovering and reusing aluminum-calcium refining slag in cold state to prepare a high-efficiency composite decarbonization slag-making agent comprises the following steps: S1. The 5mm-40mm aluminum calcium slag and residual steel obtained by the above steps S1-S7 can be directly used in steelmaking production to replace other materials with the same function. The remaining aluminum calcium refined slag powder particles below 5mm can be used as one of the raw materials for preparing high-efficiency composite decarburization slag-making agents in cold solid pressed balls; S2. The aluminum-calcium refining slag powder with a size of less than 5 mm produced by the screening and crushing line is transported to the cold solidification ball production line by belt or tank truck; S3. In the cold solidification ball production line, aluminum-calcium refined slag powder particles with a diameter of less than 5 mm enter the feed bin. At the same time, other feed bins prepare iron oxide scale and raw dolomite powder, aluminate cement, and corn starch; S4. Place aluminum-calcium refined slag powder of less than 5 mm in the mixing bin; S5. Put iron oxide and raw dolomite powder in the mixing bin and mix well; S6. Place aluminate cement binder in the mixing bin and mix well; S7. Add corn starch binder and water into the mixing bin and mix well; S8. Use a crawler-type ball press to make green balls with a size of 20mm to 40mm; S9. Dry the raw balls to obtain a highly efficient composite decarbonization slag-making agent.

[0035] In step S1 of preparing a high-efficiency composite decarburizing slag-making agent, the aluminum-calcium refining slag powder particles below 5 mm can be controlled by the mesh selection of the production line screening machine to facilitate the regulation of the cold-solidified pellet adhesion and the strength after drying, for example, it can be 80μm to 150μm, and the specific aluminum-calcium refining slag powder particle size is such as but not limited to any one of 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm or a combined grading range. The red state initial crushing and the raw slag before hot stewing and slow cooling must be tested and identified in advance to ensure that the sulfur content in the aluminum-calcium refining slag powder particles is ≤0.5%, so as to reduce the adverse effects of initial sulfur on the reduction desulfurization period. According to the needs, the proportion of 5mm-40mm block slag or aluminum-calcium refined slag powder and granular slag briquette production can be controlled to more than 85% of the total by-product production of the entire production line. In steelmaking production, it can directly replace electric melting or sintering aluminum-calcium refined slag, converter slag quick dissolving agent and other materials for equivalent use. The technical scheme of the present invention will not be further explained in this regard. The 5mm-40mm block aluminum-calcium slag produced according to the technical scheme of the present invention will gradually become powder due to moisture absorption when stored under natural conditions for 48 to 72 hours; therefore, the production and sales connection between the processes should be well done to accelerate digestion and reduce inventory, or the silo should be equipped with a drying device to avoid moisture absorption and powderization to ensure its normal use; In step S2 of preparing a high-efficiency composite decarbonization slag-making agent, the method of transporting the aluminum-calcium refining slag powder to the briquetting production line is not limited to transporting by belt or tank truck; In the steps S3-S4 of preparing the high-efficiency composite decarbonization slag-forming agent, the material bin used for preparing the high-efficiency composite decarbonization slag-forming agent by cold solid pressing balls must be dedicated to the material and must be cleared before replacing it with other materials or changing the product; In step S5 of preparing a high-efficiency composite decarburization slag-forming agent, the mass ratios of iron oxide added to the aluminum-calcium refining slag powder are 0%, 10%, and 20% of the aluminum-calcium refining slag powder, respectively, and the mass ratios of raw dolomite powder added are 1%, 1.5%, and 2% of the aluminum-calcium refining slag powder, respectively. Specifically, the mass ratio of iron oxide added to the aluminum-calcium refining slag powder is, for example, but not limited to, any one of 0%, 10%, and 20% or a range between any two of them; the mass ratio of raw dolomite powder added to the aluminum-calcium refining slag powder is, for example, but not limited to, any one of 1%, 1.5%, and 2% or a range between any two of them. By comparison, it was found that compared with not adding iron oxide, adding a certain proportion of iron oxide has a better effect on the ladle stirring and decarburization of low-carbon and high-oxygen molten steel; In step S6 of preparing a high-efficiency composite decarbonization slag-making agent, the mass ratio of aluminate cement binder added to the aluminum-calcium refining slag powder is 0.5%, 1.0%, and 1.5% of the aluminum-calcium refining slag powder. Specifically, the mass ratio of aluminate cement binder added to the aluminum-calcium refining slag powder is taken as an example but not limited to any one of 0.5%, 1.0%, and 1.5%, or the range between any two. Comparison shows that the strength of the cold-solidified pellets with the addition of aluminate cement binder is more likely to meet the requirements of smelting use, and at the same time, the mass ratio needs to be appropriately changed according to the adjustment of the top slag component of the steel type to be produced; In step S7 of preparing a high-efficiency composite decarbonization slag-forming agent, the mass ratio of corn starch binder added to the aluminum-calcium refining slag powder is 5% to 7% of the aluminum-calcium refining slag powder, and the mass ratio of water added is 8% to 9% of the aluminum-calcium refining slag powder. Specifically, the mass ratio of corn starch binder added to the aluminum-calcium refining slag powder is, for example, but not limited to, any one of 5%, 6%, 7% or the range between any two of them; the mass ratio of water added to the aluminum-calcium refining slag powder is, for example, but not limited to, any one of 8%, 8.5%, 9% or the range between any two of them. Adding water and corn starch can make the mixture better balled and form green balls with a certain strength at low temperatures; In step S8 of preparing a high-efficiency composite decarbonization slag-making agent, the size of the green balls can be adjusted according to the needs of the ball pressing equipment capacity, slag-making speed, and smoothness of adding the silo, for example, it can be 5mm to 40mm. Specifically, the size of the green balls is, for example, but not limited to, any one of 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, or the range between any two; In step S9 of preparing a high-efficiency composite decarbonization slag-making agent, the drying method and drying temperature of the green balls can be controlled as needed to meet the production process balance and drying requirements, for example, the green balls can be air-dried or dried at a temperature of 30°C to 190°C for 24h to 96h. Specifically, the drying temperature is, for example but not limited to, any one of 30°C, 50°C, 70°C, 90°C, 110°C, 130°C, 150°C, 170°C, 190°C or any two thereof; the drying or drying time is, for example but not limited to, any one of 24h, 32h, 40h, 48h, 56h, 64h, 72h, 80h, 88h, 96h or any two thereof.

[0036] The high-efficiency composite decarburization slag-making agent for steel ladles prepared by the above method can be added to the ladle stirring decarburization metallurgical link to rapidly increase the top slag oxidizability and the thickness of the covering layer, so as to improve the stirring decarburization efficiency and cover the molten steel to reduce the secondary oxidation loss. The rich low-melting-point aluminum-calcium slag and raw slag-making material can continuously melt lime and foam the top slag in the subsequent reduction period to quickly form slag or bury the arc, and strengthen the metallurgical purposes such as reduction slag desulfurization.

[0037] The technical solution of the present invention is further described below in conjunction with specific embodiments. Example 1

[0038] A method for fully recovering and reusing aluminum-calcium refining slag in cold state comprises the following steps: S1. Control the mesh size to obtain 120μm aluminum-calcium refining slag powder as one of the raw materials for preparing efficient composite decarburization slag-making agent by cold solid pressing ball; S2. The 120μm aluminum-calcium refining slag powder produced by the screening and crushing line is transported to the cold solidification ball production line by tank truck; S3. In the cold solidification ball production line, 120μm aluminum calcium refined slag powder enters the feed bin. At the same time, other feed bins prepare raw dolomite powder, aluminate cement, and corn starch; S4. Place 120 μm aluminum-calcium refined slag powder in the mixing bin; S5. Add 1% raw dolomite powder into the mixing bin and mix well; S5. Add 1% aluminate cement and mix well; S6. Add 6% corn starch binder and 8% water and mix well; S7. Use a crawler-type ball press to make green balls with a size of 20 mm; S8. Dry the raw balls at 120℃ for 24h to obtain a high-efficiency composite decarbonization slag-making agent. Example 2

[0039] A method for fully recovering and reusing aluminum-calcium refining slag in cold state comprises the following steps: S1. Control the mesh size to obtain 90 μm aluminum-calcium refining slag powder as one of the raw materials for preparing efficient composite decarburization slag-making agent in cold solid pressed balls; S2. The 90μm aluminum-calcium refining slag powder produced by the screening and crushing line is transported to the cold solidification ball production line by tank truck; S3. In the cold solidification ball production line, 90μm aluminum calcium refined slag powder enters the feed bin. At the same time, other feed bins prepare iron oxide, raw dolomite powder, aluminate cement, and corn starch; S4. Place 90 μm aluminum-calcium refined slag powder in the mixing bin; S5. Add 10% iron oxide and 1.5% raw dolomite powder into the mixing bin and mix well; S5. Add 1% aluminate cement and mix well; S6. Add 6.5% corn starch binder and 8.5% water and mix well; S7. Use a crawler-type ball press to make green balls with a size of 20 mm; S8. Dry the raw balls at 120℃ for 32h to obtain a high-efficiency composite decarbonization slag-making agent. Example 3

[0040] A method for fully recovering and reusing aluminum-calcium refining slag in cold state comprises the following steps: S1. Control the mesh size to obtain 90 μm aluminum-calcium refining slag powder as one of the raw materials for preparing efficient composite decarburization slag-making agent in cold solid pressed balls; S2. The 90μm aluminum-calcium refining slag powder produced by the screening and crushing line is transported to the cold solidification ball production line by tank truck; S3. In the cold solidification ball production line, 90μm aluminum calcium refined slag powder enters the feed bin. At the same time, other feed bins prepare iron oxide scale, raw dolomite, aluminate cement, and corn starch; S4. Place 90 μm aluminum-calcium refined slag powder in the mixing bin; S5. Add 20% iron oxide and 1.5% raw dolomite powder into the mixing bin and mix well; S5. Add 1.5% aluminate cement and mix well; S6. Add 7% corn starch binder and 9% water and mix well; S7. Use a crawler-type ball press to make green balls with a size of 20 mm; S8. Dry the raw balls at 120℃ for 32h to obtain a high-efficiency composite decarbonization slag-making agent.

[0041] Embodiment 4-6 Further application of the high-efficiency composite decarbonization slagging agent prepared in the above embodiments 1 to 3: A converter low-carbon steel smelting process, the smelting steel is high-performance low-carbon SPHC, and the smelting path is: molten iron → converter deep decarburization and phosphorus control → non-deoxidation alloying steel tapping → post-furnace ladle stirring oxidation period decarburization → LF temperature rise compensation and reduction period desulfurization. Examples 4 to 6 respectively add the cold solid pressed balls prepared in Examples 1 to 3 as high-efficiency composite decarburization slag-making agents to the ladle for stirring decarburization, and the addition amount is 5kg / t steel. The decarburization amount, stirring time, process temperature drop, reduction period lime and flux consumption and other data obtained by ladle refining in Examples 4 to 6 are shown in Table 1.

[0042] Comparative Example 0 A converter low-carbon steel smelting process, the smelting steel is high-performance low-carbon SPHC, and the smelting path is: molten iron → converter deep decarburization and phosphorus control → non-deoxidation alloying steel tapping → post-furnace ladle stirring oxidation period decarburization → LF temperature rise compensation and reduction period desulfurization. Comparative Example 0 does not use the cold solid pressed balls of Examples 1-3 as a high-efficiency composite decarburization slag-making agent to add to the ladle for stirring decarburization. The decarburization amount, stirring time, process temperature drop, reduction period lime and flux consumption and other data obtained by ladle refining in Comparative Example 0 are shown in Table 1.

[0043] Table 1 Ladle stirring decarburization effect and slag consumption of Examples 4-6 and Comparative Example 0

[0044] As can be seen from Table 1, the high-efficiency composite decarburization slag-making agent prepared in the embodiment of the present invention can increase the decarburization rate during the ladle stirring decarburization period and reduce oxidation burning and temperature loss. At the same time, the slagging and fluxing lime have good effects, which can increase the arc submergence and heating rate during the LF reduction desulfurization period and reduce the loss of flux such as lime and pre-melted slag, thereby realizing the solid waste resource recycling and reuse of aluminum-calcium refining slag.

[0045] The specific implementation methods of other cold-state recycled materials of aluminum-calcium refining slag involved in the embodiments of the present invention, such as silicon-deoxidized steel top slag modifier and converter high-efficiency dephosphorization slag agent, will not be described in detail. The technical solution of the present invention and the above three but not limited to the three corresponding reprocessing and recycling slag products and metallurgical uses can digest the solid waste of aluminum-calcium refining slag through reasonable matching and balanced use, and finally degrade it into low-basicity, high-phosphorus and sulfur content and other worthless materials with almost no reuse value, thus achieving near-zero discharge of solid waste of aluminum-calcium refining slag in the true sense.

[0046] The above is a preferred embodiment of the present invention, and does not limit the protection scope of the present invention. All industrial production practices that directly / indirectly carry out similar cold full recovery and re-treatment of aluminum-calcium refining slag using the contents of the present invention under the conception of the technical solution of the present invention are included in the protection scope of the present invention.

Claims

1. A method for fully recovering and reusing aluminum-calcium refining slag in cold state, characterized in that The steps include: S1. The aluminum-calcium refining slag produced in the LF refining and converter rear top slag reforming reduction desulfurization process is poured into the slag tank after the continuous casting and steel pouring is completed; S2, the slag pot is transported to the outer slag bay which is sheltered from wind and dry; S3, turning over the hot red slag in the slag tank at the outer slag span, and then using an oil hammer or a raking machine to perform preliminary crushing; S4. The crushed hot red slag is quickly loaded into the hot stewing tank of the hot stewing line by a forklift and sealed; S5, a hot stewing tank filled with red crushed aluminum-calcium refining slag is slowly cooled to room temperature in an outer slag span away from wind; S6, the hot stewing tank is transported to the aluminum-calcium refining slag screening and crushing line for further processing; S7. The crushed cold aluminum-calcium refining slag is preliminarily screened and magnetically separated in a cold slag crushing line, and the large slag is jaw-broken and then screened to obtain three intermediate by-products: 5mm-40mm blocky aluminum-calcium slag, aluminum-calcium refining slag powder particles below 5mm, and residual steel; S8. The aluminum-calcium refining slag powder with a diameter less than 5 mm produced by the screening and crushing line is transported to the cold solidification ball production line by belt or tank truck; S9. In the cold solid pressed ball production line, aluminum calcium refining slag powder and other materials with a size of less than 5 mm are used to produce multifunctional cold solid pressed balls according to the process, including high-efficiency composite decarburization slag-making agent for ladle, silicon deoxidation steel top slag modifier, and high-efficiency dephosphorization slag agent for converter; S10. The various briquetting by-products produced are returned to the converter or ladle refining process and used for slag making and dephosphorization in the converter, melting and slag adjustment in the steelmaking process, and ladle stirring and decarburization.

2. The method for cold full recovery and reuse of aluminum-calcium refining slag according to claim 1, characterized in that: In step S1, the aluminum-calcium refining slag is a solid waste slag generated in the production process of all-aluminum killed steel with a finished product [Si] ≤ 0.10%, and its chemical components are as follows by weight percentage: CaO: 50% to 60%, Al2O3: 20% to 35%, SiO2 ≤ 18%, MgO: 5% to 8%, (FeO + MnO) ≤ 1.5%.

3. The method for cold full recovery and reuse of aluminum-calcium refining slag according to claim 1, characterized in that: In step S2, the wind-proof and dry external slag is turned over and crushed in a hot slag crushing site, and the environment thereof needs to meet the following conditions: water vapor volume content <1%, temperature > 20°C, and no natural wind around; In the steps S3 and S4, the hot red slag in the slag pot is turned over and preliminarily crushed, and then put into the hot stew pot for sealed slow cooling. This operation must be carried out under the condition that the red slag temperature is ≥700°C, so as to obtain blocky aluminum-calcium slag with a particle size of more than 5mm accounting for more than 85%; in the step S5, the slow cooling needs to be carried out for 36h to 72h.

4. The method for cold full recovery and reuse of aluminum-calcium refining slag according to claim 3, characterized in that: In the step S4, the sealing method of the red slag after the initial crushing is: the bottom of the hot stewing tank is paved with 20mm to 30mm dry white slag, and after the red slag is loaded, the top is evenly covered with ≥20mm dry white slag, and the top of the slag tank is finally sealed with a tank cover; the hot stewing tank is a cast iron or cast steel container with a wall thickness of more than 8mm.

5. The method for cold full recovery and reuse of aluminum-calcium refining slag according to claim 1, characterized in that: In the steps S6 and S7, the aluminum-calcium refining slag screening and crushing line can realize the screening of aluminum-calcium refining slag, residual steel magnetic separation, re-crushing to target particle size products and re-screening functions; the aluminum-calcium refining slag screening and crushing line includes a vibrating feeder, a coarse jaw crusher, a fine jaw crushing and screening machine, a fine material bin, a rod mill screening machine, a coarse material belt conveyor and a fine material belt conveyor connected in sequence: the aluminum-calcium refining slag after the initial screening enters the vibrating feeder, enters the coarse jaw crusher along the first belt conveyor, and is crushed for the first time to obtain coarsely crushed aluminum-calcium slag with a particle size of less than 15 cm, and the coarsely crushed aluminum-calcium slag enters the fine jaw crushing and screening machine along the second belt conveyor, The second crushing and screening are carried out to obtain 5mm-40mm blocky aluminum-calcium slag by-product overscreen and 5mm aluminum-calcium refining slag powder underscreen. After crushing, the aluminum-calcium refining slag powder below 5mm enters the next process along the third belt conveyor. In this process, after iron removal by the hanging magnetic roller, the magnetic small-grained scrap steel and the aluminum-calcium refining slag powder below 5mm are respectively sent to the waste belt conveyor and the fine material bin. The material in the fine material bin enters the rod mill screening machine along the fourth belt conveyor. The aluminum-calcium slag powder after grinding and screening by the rod mill screening machine is sent to the coarse material belt conveyor or the fine material belt conveyor along the fifth belt conveyor to produce aluminum-calcium refining slag powder with different mesh requirements.

6. The method for cold full recovery and reuse of aluminum-calcium refining slag according to claim 1, characterized in that: In the steps S8 and S9, the cold solid pressed ball production line can realize the production of multifunctional cold solid pressed balls with aluminum-calcium refined slag powder particles of different mesh sizes below 5 mm and other raw and auxiliary materials according to the formula. The cold drum cold strength of the cold solid pressed balls after drying must reach more than 10kN and the particle size must reach 5mm to 40mm; The cold-setting ball pressing production line includes a feeding bin, a mixing mixer, a mixing bin, a ball pressing machine and a mesh belt dryer which are connected in sequence. First, the material enters the mixing mixer from the feeding bin along the raw material conveyor, is mixed with other materials in proportion, and enters the mixing bin after mixing and stirring, and then enters the ball pressing machine along the mixing and ball pressing return conveyor. After ball pressing, the material is sent to the mesh belt dryer by the raw ball conveyor for drying operation.

7. The method for cold full recovery and reuse of aluminum-calcium refining slag according to claim 1, characterized in that: A high-efficiency composite decarburization slag-making agent for a steel ladle is prepared with aluminum-calcium refining slag powder particles below 5 mm as raw materials, and the raw material ratio is as follows: taking the aluminum-calcium refining slag powder particles below 5 mm produced by the above-mentioned cold slag crushing line as a benchmark, 0%-20% iron oxide scale, 1%-2% raw dolomite powder raw slag material, 0.5%-1.5% inorganic binder aluminate cement, 5%-7% organic binder corn starch, and 0%-10% water are added respectively for weight batching, mixing, ball pressing, and drying to produce a 5mm-40mm high-oxidizability low-melting-point composite slag-making agent; the main chemical components of the high-efficiency composite decarburization slag-making agent are: CaO: 35%-50%, Al2O3: 15%-30%, SiO2≤10%, MgO: 5%-15%, FeO≥5%, and the single ball compressive strength is ≥10kN.

8. The method for cold recovery and reuse of aluminum-calcium refining slag according to claim 7, characterized in that: In the process of preparing the slag-forming agent, the particle size of the aluminum-calcium refined slag powder is 80μm to 150μm; the drying method and drying temperature of the product obtained by ball pressing are: airing or drying at a temperature of 30℃ to 190℃ for 24h to 96h.

9. The method for cold full recovery and reuse of aluminum-calcium refining slag according to claim 1, characterized in that: The silicon-deoxidized steel top slag modifier is prepared with 5mm-40mm blocky aluminum-calcium slag produced by a cold slag crushing line and aluminum-calcium refined slag powder and slag balls produced by a cold solid briquetting production line as raw materials; the aluminum-calcium refined slag powder and slag balls produced by the cold solid briquetting production line are prepared by adding 2%-5% of a mineral powder binder based on the aluminum-calcium refined slag powder and particles below 5mm produced by the above-mentioned cold slag crushing line, mixing, briquetting, and drying to produce 5mm-40mm aluminum-calcium slag balls with a single ball compressive strength of ≥10kN.

10. The method for cold full recovery and reuse of aluminum-calcium refining slag according to claim 1, characterized in that: A high-efficiency dephosphorization slag agent for converter is prepared with aluminum-calcium refining slag powder with a size of less than 5 mm produced by a cold slag crushing line as raw material, and the raw material ratio is as follows: taking the aluminum-calcium refining slag powder with a size of less than 5 mm produced by the above-mentioned cold slag crushing line as a benchmark, 0% to 10% of converter dry dust removal fine ash, 0% to 10% of sintering dust removal ash, 15% to 40% of alumina plant red mud and 2% to 5% of mineral powder binder are added to the slag powder for weight batching, mixing, ball pressing and drying to produce a 5mm to 40mm high-efficiency dephosphorization slag agent for converter; the chemical composition of the high-efficiency dephosphorization slag agent for converter is: CaO: 20% to 40%, Al2O3: 8% to 15%, SiO2≤10%, MgO: 5% to 8%, Na2O: 1.5% to 4.0%, Fe2O3≥40%, and the single ball compressive strength is ≥10kN.

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