A method for fully recovering and reusing aluminum-calcium refining slag in cold state

Abstract

The present invention discloses a method for cold-state full recovery and reuse of aluminum-calcium refining slag, which belongs to the technical field of solid waste reuse in iron and steel metallurgy. The classic aluminum-calcium refining slag produced by reduction desulfurization processes such as LF refining and converter top slag modification has the characteristics of low phosphorus content, high alkalinity, low melting point and certain sulfur content. The method of the present invention can realize cold-state 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 pelletizing by-product can be applied to metallurgical links such as converter oxidation dephosphorization slag making, silicon deoxidation steel top slag modification, LF stirring decarburization and fluxing, realizing true cold-state full recovery and reuse of aluminum-calcium refining slag, which has positive significance in reducing environmental pollution, improving the quality of steel slag hot stewing by-products, and reducing steelmaking costs.

Description

Technical Field

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

[0002] Classic aluminum-calcium refining slag, produced during reductive desulfurization processes such as LF refining and converter top slag reforming, is formed by the interaction or reaction of various slag-forming materials at high temperatures. During the refining process, the various components undergo thorough reactions, forming a large number of complex phases with low melting points. These phases possess properties such as low phosphorus content, high basicity, low melting point, and a certain sulfur content, making them highly recyclable. Currently, most domestic processes utilize online recycling of hot slag by pouring the remaining slag from the ladle into the next ladle before re-entering LF refining. This process also requires balancing the impact of the number of recycling cycles and the amount of recycling used on refining results, thus only partially realizing its recycling value. Furthermore, many steel companies are unable to implement online hot recycling due to various constraints, resulting in the disposal of this white slag, resulting in significant waste. Furthermore, numerous steel mills and research institutions within the industry have conducted extensive theoretical research and demonstration on its cold-state recycling potential. However, due to limitations in process and tooling design, few cases have been successfully implemented in production and established an industry chain. Summary of the Invention

[0003] The present invention aims to provide a method for the complete cold recovery and reuse of aluminum-calcium refining slag, which can realize scientific full-industry chain recycling 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 present invention targets at treating the 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 present 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 true 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 cold-state full recovery and reuse of aluminum-calcium refining slag, comprising the following steps:

[0006] S1, the aluminum-calcium refining slag produced in the reduction and desulfurization process such as LF refining and converter top slag reforming, after the continuous casting and pouring of steel, the remaining ladle is poured into the slag pot;

[0007] S2. The slag pot is transported to the outer slag bay where it is sheltered from wind and dry;

[0008] S3. Turn over the hot red slag in the slag pot at the outer slag span, and then use an oil hammer or a ramming machine to perform preliminary crushing;

[0009] S4. The crushed hot red slag is quickly loaded into the hot stewing tank of the hot stewing line by a forklift and sealed;

[0010] S5, the hot stew pot filled with red crushed aluminum-calcium refined slag is slowly cooled to room temperature in an outer slag span away from wind;

[0011] S6. The hot stewing tank is transported to the aluminum-calcium refining slag screening and crushing line for further processing;

[0012] S7. The crushed cold aluminum-calcium refining slag is initially screened and magnetically separated in a cold slag crushing line, and the large slag is jaw-broken and then screened again to obtain three intermediate by-products: 5mm-40mm lump aluminum-calcium slag, aluminum-calcium refining slag powder and particles less than 5mm, and residual steel;

[0013] 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 pellet production line by belt or tank truck;

[0014] S9. In the cold solid pellet production line, aluminum-calcium refining slag powder with a particle size of less than 5mm is mixed with other materials to produce multifunctional cold solid pellets such as high-efficiency composite decarburization slag-making agent for ladle, silicon deoxidation steel top slag modifier, and high-efficiency dephosphorization slag agent for converter;

[0015] S10. The various 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, fluxing and slag modification in the steel tapping process, and ladle stirring and decarburization.

[0016] The specific process details of the above method are described as follows:

[0017] 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 typical chemical components are generally as follows by weight: CaO: 50% to 60%, Al2O3: 20% to 35%, SiO2 ≤ 18%, MgO: 5% to 8%, (FeO + MnO) ≤ 1.5%.

[0018] In step S2, the environment of the hot slag turning and crushing site for the dry and windproof outer slag should meet the following conditions: water vapor volume content <1%, temperature > 20°C, and no natural wind around.

[0019] In the steps S3 and S4, the hot red slag in the slag pot is turned over and preliminarily crushed, and then placed in a hot stew pot for sealed slow cooling. This must be done at a red slag temperature of ≥700°C to prevent: C3S (tricalcium silicate) precipitated in the white slag from undergoing a β-C2S to γ-C2S lattice transformation during an unreasonable cooling process, resulting in volume expansion and severe explosion and pulverization; the gaps between the red slag after crushing can offset the slow volume expansion during the slow cooling process; thereby obtaining a blocky aluminum-calcium slag with a particle size of more than 5 mm accounting for more than 85%.

[0020] In step S4, after the initial crushing, the red slag is sealed by paving the bottom of the hot stew pot with 20 mm to 30 mm of dry white slag. After the red slag is added, the top is evenly covered with 20 mm or more of dry white slag. Finally, the top of the slag pot is sealed with a lid. The hot stew pot is a cast iron or cast steel container with a wall thickness of 8 mm or more and can be sealed with a lid.

[0021] In step S5, slow cooling generally takes 36 hours to 72 hours, and the room temperature is the ambient temperature of 20° C. to 40° C., which is touchable when the wall temperature of the hot stew pot is detected by a handheld thermometer.

[0022] In steps S6 and S7, the aluminum-calcium refining slag screening and crushing line is a dedicated cold slag crushing production line that can perform functions such as aluminum-calcium refining slag screening, residual steel magnetic separation, re-crushing to the target particle size product, and re-screening. The entire aluminum-calcium refining slag screening and crushing line ultimately produces three intermediate by-products: 5mm-40mm lump aluminum-calcium slag, aluminum-calcium refining slag powder and particles less than 5mm, and residual steel. The recovered residual steel can be directly recycled as scrap steel.

[0023] 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 the initial screening enters the vibrating feeder, enters the coarse jaw crusher along the first belt conveyor, and undergoes the first crushing to obtain the coarse crushed aluminum-calcium slag with a uniform particle size of less than 15 cm. The coarse crushed aluminum-calcium slag enters the fine jaw crushing and screening machine along the second belt conveyor, and undergoes the second crushing and screening to obtain 5mm to 40mm block aluminum-calcium The raw slag by-product oversize and the aluminum-calcium refining slag powder below 5mm are crushed and then sent to the next process along the third belt conveyor. In this process, the magnetic small-sized scrap steel and the aluminum-calcium refining slag powder below 5mm are removed by the hanging magnetic roller and then sent to the waste belt conveyor and fine material bin respectively. The material in the fine material bin is sent to 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 with different mesh requirements.

[0024] 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.

[0025] Furthermore, a coarse aluminum-calcium slag bin is provided under the screen in the vibrating feeder to collect the undersize of the screen below 15 cm and the large aluminum-calcium slag above 15 cm selected from an external site.

[0026] 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 size requirements.

[0027] In steps S8 and S9, the cold pelletizing line can produce multifunctional cold pellets using aluminum-calcium refining slag powders of various mesh sizes below 5 mm and other raw materials according to a formula, such as a silicon-deoxidized steel top slag modifier, a high-efficiency converter dephosphorization slag agent, and a high-efficiency composite decarburization slag agent for ladle steel. After drying, the cold pellets must achieve a cold drum strength of at least 10 kN and a particle size of 5 mm to 40 mm to meet the requirements of multiple transfers and addition to the high-level silo of the steelmaking system.

[0028] Specifically, the cold-setting pelletizing production line includes a feed bin (multiple), a mixing mixer, a mixing silo, a pelletizing machine and a mesh belt dryer connected in sequence, and materials are transported between each device through a conveyor; 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 silo after stirring, and then enters the pelletizing machine along the mixing and pelletizing return conveyor, and after pelletizing, is sent to the mesh belt dryer by the raw ball conveyor for drying and other operations.

[0029] Furthermore, the present invention provides a high-efficiency composite decarburizing slag-making agent for ladle steel. This agent is prepared using the aluminum-calcium refining slag powder (less than 5 mm) produced by the cold slag crushing line as a raw material and other raw materials. The raw material ratio is as follows: 0%-20% iron oxide scale, 1%-2% raw dolomite powder, 0.5%-1.5% inorganic binder aluminate cement, 5%-7% organic binder corn starch, and 0%-10% water are added to the aluminum-calcium refining slag powder (less than 5 mm) produced by the cold slag crushing line. The ingredients are then weighed, mixed, pressed into balls, and dried to produce a 5mm-40mm, highly oxidizable, low-melting-point composite slag-making agent. The main chemical components of this high-efficiency composite decarburizing slag-making agent are: CaO: 35%-50%, Al2O3: 15%-30%, SiO2≤10%, MgO: 5%-15%, FeO≥5%, and a single-ball compressive strength of 10 kN or higher. It is added to the ladle stirring and decarburization metallurgical process to rapidly increase the oxidizability of the top slag and the thickness of the coating, thereby improving the stirring and decarburization efficiency and covering the molten steel to reduce secondary oxidation losses. Furthermore, during the slagging agent preparation process, the particle size of the aluminum-calcium refining slag can be controlled by selecting the mesh size of the production line screening machine to facilitate the adjustment of the cohesiveness of the cold-set pellets and the strength after drying. The preferred particle size is 80μm to 150μm. Furthermore, the drying method and temperature of the resulting pellets (green pellets) can be controlled as needed to meet the production process balance and drying requirements. Preferably, they are air-dried or dried at a temperature of 30°C to 190°C for 24 to 96 hours.

[0030] Furthermore, the present invention provides a silicon-deoxidized steel top slag modifier, which is made by briquetting the 5mm-40mm alumina-calcium slag produced by the cold slag crushing line and the alumina-calcium refining slag powder and granular slag produced by the cold solidification briquetting line. The main chemical composition of the silicon-deoxidized steel top slag modifier is consistent with that of the alumina-calcium refining slag: CaO: 50%-60%, Al2O3: 20%-35%, SiO2 ≤18%, MgO: 5%-8%, (FeO + MnO) ≤1.5%. It is returned to the steelmaking system as a top slag washing and modifier for silicon-deoxidized steel tapping slag. It can dilute the top slag, absorb silica inclusions, reduce phosphorus reversion, and further improve the top slag by fluxing lime. Furthermore, the aluminum-calcium refining slag powder and raw slag pellets produced by the cold solidification pelletizing production line are as follows: 2% to 5% of mineral powder binder is added to the aluminum-calcium refining slag powder and raw slag pellets with a diameter of less than 5 mm produced by the above-mentioned cold slag crushing line, and the mixture is weighed, mixed, pelletized, and dried to produce 5mm to 40mm aluminum-calcium raw slag pellets with a single ball compressive strength of ≥10kN.

[0031] Furthermore, the present invention provides a high-efficiency converter dephosphorization slag agent. To the aluminum-calcium refining slag powder less than 5 mm produced by the cold slag crushing line, 0% to 10% converter dry dust fine ash, 0% to 10% sintering dust ash, 15% to 40% alumina plant red mud, and 2% to 5% mineral powder binder are added. The mixture is then weighted, mixed, pelletized, and dried to produce a 5 mm to 40 mm high-efficiency converter dephosphorization slag agent. The main chemical components of the high-efficiency converter 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 a single-ball compressive strength ≥ 10 kN. 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.

[0032] The percentages described in the present invention are all percentages by weight.

[0033] Beneficial effects of the present invention:

[0034] (1) The present invention provides a method for the cold recovery and reuse of aluminum-calcium refining slag, which can achieve the goal of obtaining more than 85% of aluminum-calcium lumps larger than 5 mm from the aluminum-calcium refining slag through preliminary crushing and slow cooling in the red state. The cold slag crushing and cold solid pellet production line produces cold solid pellets 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, and completely solving the problem that hot recycling can only recycle part of its beneficial elements and that some enterprises cannot recycle in hot state, thus realizing the true meaning of nearly 100% cold recovery and reuse of aluminum-calcium refining slag.

[0035] (2) The present invention provides a method for the cold recovery and reuse of aluminum-calcium refining slag. The 5mm to 40mm block aluminum-calcium slag, slag pellets and multifunctional composite cold-solidified pellets produced by the cold slag crushing and cold solidification pellet production line can account for more than 85% of the total output of aluminum-calcium refining slag blocks and slag pellets. The method has the characteristics of low cost, high efficiency, and universal applicability of operation and production methods. The corresponding by-products can be used in 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. It can replace other auxiliary materials such as electric melting flux, converter iron-containing material and slag-reducing agent, and ladle decarburization agent to achieve the same metallurgical effect, reduce the cost of auxiliary materials such as lime, and achieve near-zero emission of solid waste slag. It also reduces the adverse effect of free calcium on the quality of steel slag by-products after the mixed hot stewing treatment of high-alkalinity aluminum-calcium refining slag and converter slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] 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;

[0037] Figure 2 This is a schematic diagram of the screening and crushing line for aluminum-calcium refining slag of the present invention;

[0038] Figure 3 This is a schematic diagram of the aluminum-calcium refined slag cold solidification ball production line of the present invention;

[0039] In the figure: 1 is a coarse material bin, 2 is a grid screen, 3 is a vibrating feeder, 4 is the 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 the 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 feeding bin, 19 is a raw material conveyor, 20 is a mixing 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

[0040] The following will be described clearly and completely with reference to the technical solutions in the embodiments. It is obvious that the embodiments described are only part of the embodiments of the present invention, not all of them. 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.

[0041] The present invention provides a method for cold-state full recovery and reuse of aluminum-calcium refining slag, comprising the following steps:

[0042] S1, the aluminum-calcium refining slag produced in the reduction and desulfurization process such as LF refining and converter top slag reforming, after the continuous casting and pouring of steel, the remaining ladle is poured into the slag pot;

[0043] S2. The slag pot is transported to the outer slag bay where it is sheltered from wind and dry;

[0044] S3. Turn over the hot red slag in the slag pot at the outer slag span, and then use an oil hammer or a ramming machine to perform preliminary crushing;

[0045] S4. The crushed hot red slag is quickly loaded into the hot stewing tank of the hot stewing line by a forklift and sealed;

[0046] S5, the hot stew pot filled with red crushed aluminum-calcium refined slag is slowly cooled to room temperature in an outer slag span away from wind;

[0047] 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 shown in the 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 the initial screening enters the vibrating feeder 1, enters the coarse jaw crusher 5 along the first belt conveyor 4, and undergoes the first crushing to obtain coarsely crushed aluminum-calcium slag with a particle size of less than 15 cm. The coarsely crushed aluminum-calcium slag enters the fine jaw crushing and screening machine 7 along the second belt conveyor 6, and undergoes the second crushing and screening to obtain 5mm-40mm blocky aluminum-calcium raw materials. The slag by-product oversize 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-sized scrap steel and the aluminum-calcium refining slag powder below 5 mm are removed by the hanging magnetic 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 along the fifth belt conveyor 14 to the coarse material belt conveyor 15 or the fine material belt conveyor 17 to produce aluminum-calcium refining slag powder with different mesh requirements.

[0048] Furthermore, a 15 cm grid screen 2 is provided in the vibrating feeder 3 to preliminarily screen out large pieces of residual steel and aluminum-calcium slag oversize that are larger than 15 cm. The oversize materials are 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 1 by a forklift.

[0049] 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.

[0050] 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 size requirements.

[0051] S7. The crushed cold aluminum-calcium refining slag is initially screened and magnetically separated in a cold slag crushing line, and the large slag is jaw-broken and then screened again to obtain three intermediate by-products: 5mm-40mm lump aluminum-calcium slag, aluminum-calcium refining slag powder and particles less than 5mm, and residual steel;

[0052] S8, the aluminum-calcium refining slag powder with a particle size of less than 5mm 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-setting ball pressing production line includes a feeding bin 18, a mixing mixer 20, a mixing bin 21, a ball press 23 and a mesh belt dryer 25 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 press 23 along the mixing and ball pressing return conveyor 22. After ball pressing, it is sent to the mesh belt dryer 25 by the raw ball conveyor 24 for drying and other operations.

[0053] S9. In the cold solid pressed ball production line, aluminum-calcium refined slag powder 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 addition to the high-level silo of the steelmaking system.

[0054] S10. The various 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, fluxing and slag modification in the steel tapping process, and ladle stirring and decarburization.

[0055] The 5mm-40mm lumpy alumina-calcium slag and slag briquettes produced by the above-mentioned production line can be directly used in steelmaking, replacing other materials with equivalent functions, offering high efficiency and low cost. Using alumina-calcium refined slag powder and particles smaller than 5mm produced by the above-mentioned production line and dried iron scale recovered from steelmaking or rolling mills as raw materials, mixed with inorganic binder aluminate cement and organic binder corn starch, along with other auxiliary materials, a high-efficiency composite decarburization slag-forming agent is prepared through cold-consolidation briquetting. The selected alumina-calcium refined slag powder and particles smaller than 5mm must be pre-tested to ensure a sulfur content of ≤0.5%. The selected iron scale must be pre-dried to ensure a moisture content of ≤1%. The selected inorganic binder aluminate cement primarily consists of CaO and Al2O3, with a SiO2 content of ≤10% to prevent negative effects on the alkalinity of the composite decarburization slag-forming agent. It also contains no other harmful elements that could harm molten steel and exhibits a certain degree of high-temperature plasticity. The organic binder, corn starch, is primarily composed of hydrocarbon-based inorganic compounds. During deoxidation in the steelmaking environment, it produces gases that do not contaminate the molten steel. Other auxiliary materials used include raw slag materials such as raw dolomite powder, whose primary carbonate components decompose under the steelmaking environment, providing a slag-conditioning and foaming effect. The resulting high-efficiency composite decarburizing slag-forming agent exhibits a strength of approximately 10 kN after drying. When added in appropriate amounts during the ladle stirring and decarburization phase, it rapidly melts and covers the molten steel within 1 minute, providing sufficient oxygen potential driving force for decarburization stirring while minimizing oxidation and burning caused by exposed molten steel. The low-melting-point calcium-aluminate slag and raw slag materials continuously flux lime and foam the top slag during the subsequent reduction phase, facilitating rapid slagging or arc submergence, enhancing metallurgical goals such as reduction slag desulfurization. This improves slagging and decarburization rates while also reducing the use of lime, fluxing agents, and foaming agents.

[0056] 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 slagging agent, comprising the following steps:

[0057] S1. The 5mm-40mm lumpy calcium aluminum slag and residual steel obtained in steps S1-S7 above can be directly used in steelmaking to replace other materials with the same function. The remaining calcium aluminum refined slag powder particles under 5mm can be used as one of the raw materials for the preparation of high-efficiency composite decarburization slag-making agents in cold-pressed pellets;

[0058] S2. The aluminum-calcium refining slag powder with a particle size of less than 5 mm produced by the screening and crushing line is transported to the cold solidification pelletizing production line by belt or tank truck;

[0059] S3. In the cold-pressed pelletizing line, aluminum-calcium refined slag powder with a particle size of less than 5mm enters the feed bin. Meanwhile, other feed bins prepare iron scale, raw dolomite powder, aluminate cement, and corn starch.

[0060] S4. Place aluminum-calcium refining slag powder less than 5mm in the mixing bin;

[0061] S5. Add iron oxide and raw dolomite powder into the mixing bin and mix well;

[0062] S6. Add aluminate cement binder into the mixing bin and mix well;

[0063] S7. Add corn starch binder and water to the mixing bin and mix well;

[0064] S8. Use a crawler-type briquetting machine to produce green balls with a size of 20mm to 40mm;

[0065] S9. Dry the green balls to obtain a high-efficiency composite decarbonization slagging agent.

[0066] In step S1 of preparing a high-efficiency composite decarbonization slagging agent, the aluminum-calcium refining slag powder particles of less than 5 mm can be controlled by selecting the mesh size of the production line screening machine to facilitate the regulation of the adhesion of the cold-solidified pellets and the strength after drying. For example, the particle size can be 80 μm to 150 μm. The specific particle size of the aluminum-calcium refining slag powder particles is, but not limited to, any one of 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, and 150 μm, or a combination of the grading ranges. The raw slag must be tested and analyzed in advance before the initial crushing of the red state and the hot stewing and slow cooling to ensure that the sulfur content in the aluminum-calcium refining slag powder is ≤0.5% to reduce the adverse effects of the initial sulfur on the reduction desulfurization period. According to the needs, the proportion of 5mm to 40mm block slag or aluminum-calcium refined slag powder and granular slag briquette production below 5mm can be controlled to more than 85% of the total output of by-products 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 solution of the present invention will not be further explained in this regard. The 5mm to 40mm block aluminum-calcium raw slag produced according to the technical solution 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 a drying device should be added to the silo to avoid moisture absorption and powderization to ensure its normal use;

[0067] In step S2 of preparing a high-efficiency composite decarbonization slagging agent, the method of transporting the aluminum-calcium refining slag powder to the briquetting production line is not limited to conveying by belt or tank truck;

[0068] In steps S3-S4 of preparing a high-efficiency composite decarbonization slag-forming agent, the silo used for preparing the high-efficiency composite decarbonization slag-forming agent by cold solidification and pressing must be dedicated to the material and must be cleared before replacing it with other materials or changing the product;

[0069] 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 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, high-oxygen molten steel;

[0070] In step S6 of preparing a high-efficiency composite decarbonization slag-forming agent, the mass ratio of the aluminate cement binder added to the calcium-aluminate refining slag powder is 0.5%, 1.0%, and 1.5% of the calcium-aluminate refining slag powder. Specifically, the mass ratio of the aluminate cement binder added to the calcium-aluminate refining slag powder is, for example, but not limited to, any one of 0.5%, 1.0%, and 1.5%, or a range between any two of them. Comparison revealed that the strength of the cold-solidified pellets containing the aluminate cement binder more easily meets the requirements for smelting use. At the same time, the mass ratio needs to be appropriately adjusted based on the top slag composition of the steel being produced.

[0071] 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;

[0072] In step S8 of preparing a high-efficiency composite decarbonization slagging agent, the size of the green balls can be adjusted according to the needs of the ball pressing equipment capacity, slagging speed, and smoothness of adding materials to the hopper, and can be, for example, 5 mm to 40 mm. Specifically, the size of the green balls is, for example, but not limited to, any one of 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, and 40 mm, or a range between any two thereof;

[0073] In step S9 of preparing a high-efficiency composite decarbonization slagging 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 aired or dried at a temperature of 30°C to 190°C for 24 hours to 96 hours. 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, and 190°C, or a range between any two thereof; the airing or drying time is, for example but not limited to, any one of 24 hours, 32 hours, 40 hours, 48 ​​hours, 56 hours, 64 hours, 72 hours, 80 hours, 88 hours, and 96 hours, or a range between any two thereof.

[0074] The high-efficiency composite decarburization and slagging agent prepared by the above method can be added to the ladle stirring and decarburization metallurgical process to rapidly increase the oxidizability of the top slag and the thickness of the cover layer, thereby improving stirring and decarburization efficiency and covering the molten steel to reduce secondary oxidation losses. The low-melting-point alumina-calcium slag and raw slag-making material can continuously flux lime and foam the top slag during the subsequent reduction phase, facilitating rapid slagging or arc submergence, and enhancing reduction slagging and desulfurization, among other metallurgical purposes.

[0075] The technical solution of the present invention is further described below with reference to specific embodiments. Example 1

[0076] A method for fully recovering and reusing aluminum-calcium refining slag in a cold state comprises the following steps:

[0077] S1. Control the mesh size to obtain 120μm aluminum-calcium refining slag powder as one of the raw materials for preparing efficient composite decarbonization slag-making agent by cold solid pressing ball;

[0078] S2. The 120μm aluminum-calcium refining slag powder produced by the screening and crushing line is transported by tank truck to the cold solidification pelletizing production line;

[0079] S3. In the cold-pressed pelletizing line, 120μm aluminum-calcium refined slag powder enters the feed silo. Meanwhile, other feed silos prepare raw dolomite powder, aluminate cement, and corn starch.

[0080] S4. Place 120μm aluminum-calcium refined slag powder in the mixing bin;

[0081] S5. Add 1% raw dolomite powder into the mixing bin and mix well;

[0082] S5. Add 1% aluminate cement and mix well;

[0083] S6. Add 6% corn starch binder and 8% water and mix well;

[0084] S7. Use a crawler-type briquetting machine to produce green balls with a size of 20 mm;

[0085] S8. Dry the green balls at 120℃ for 24h to obtain a high-efficiency composite decarbonization slagging agent. Example 2

[0086] A method for fully recovering and reusing aluminum-calcium refining slag in a cold state comprises the following steps:

[0087] S1. Control the mesh size to obtain 90μm aluminum-calcium refining slag powder as one of the raw materials for preparing efficient composite decarbonization slag-making agent by cold solid pressing ball;

[0088] S2. The 90μm aluminum-calcium refined slag powder produced by the screening and crushing line is transported by tank truck to the cold solidification and pelletizing production line;

[0089] S3. In the cold-pressed pelletizing line, 90μm aluminum-calcium refined slag powder enters the feed silo. Simultaneously, other feed silos prepare iron oxide scale, raw dolomite powder, aluminate cement, and corn starch.

[0090] S4. Place 90μm aluminum-calcium refining slag powder in the mixing bin;

[0091] S5. Add 10% iron oxide and 1.5% raw dolomite powder into the mixing bin and mix well;

[0092] S5. Add 1% aluminate cement and mix well;

[0093] S6. Add 6.5% corn starch binder and 8.5% water and mix well;

[0094] S7. Use a crawler-type briquetting machine to produce green balls with a size of 20 mm;

[0095] S8. Dry the green balls at 120℃ for 32h to obtain a high-efficiency composite decarbonization slagging agent. Example 3

[0096] A method for fully recovering and reusing aluminum-calcium refining slag in a cold state comprises the following steps:

[0097] S1. Control the mesh size to obtain 90μm aluminum-calcium refining slag powder as one of the raw materials for preparing efficient composite decarbonization slag-making agent by cold solid pressing ball;

[0098] S2. The 90μm aluminum-calcium refined slag powder produced by the screening and crushing line is transported by tank truck to the cold solidification and pelletizing production line;

[0099] S3. In the cold-pressed pelletizing line, 90μm aluminum-calcium refined slag powder enters the feed bin. Simultaneously, other feed bins prepare iron scale, raw dolomite, aluminate cement, and corn starch.

[0100] S4. Place 90μm aluminum-calcium refining slag powder in the mixing bin;

[0101] S5. Add 20% iron oxide and 1.5% raw dolomite powder into the mixing bin and mix well;

[0102] S5. Add 1.5% aluminate cement and mix well;

[0103] S6. Add 7% corn starch binder and 9% water and mix well;

[0104] S7. Use a crawler-type briquetting machine to produce green balls with a size of 20 mm;

[0105] S8. Dry the green balls at 120℃ for 32h to obtain a high-efficiency composite decarbonization slagging agent.

[0106] Examples 4-6

[0107] Further application of the high-efficiency composite decarbonization slagging agent prepared in Examples 1 to 3 above:

[0108] A converter low-carbon steel smelting process is described, wherein the steel grade to be smelted is high-performance low-carbon SPHC. The smelting path is: molten iron → deep decarburization and phosphorus control in the converter → alloying and tapping without deoxidation → decarburization during the oxidation period with ladle stirring at the rear end of the furnace → LF temperature rise compensation and desulfurization during the reduction period. In Examples 4-6, the cold-pressed pellets prepared in Examples 1-3 were added to the ladle as a high-efficiency composite decarburization and slagging agent for stirring and decarburization at a rate of 5 kg / t of steel. The decarburization amount, stirring time, process temperature drop, and lime and flux consumption during the reduction period obtained in Examples 4-6 are shown in Table 1.

[0109] Comparative Example 0

[0110] A converter low-carbon steel smelting process is disclosed, wherein the steel grade to be smelted is high-performance low-carbon SPHC. The smelting path is: molten iron → deep decarburization and phosphorus control in the converter → alloying and tapping without deoxidation → decarburization during the ladle stirring oxidation period after the furnace → LF temperature rise compensation and desulfurization during the reduction period. Comparative Example 0 does not utilize the cold-pressed pellets described in Examples 1-3 as a high-efficiency composite decarburization and slagging agent for stirring and decarburization in the ladle. Data obtained from ladle refining in Comparative Example 0, including decarburization, stirring time, process temperature drop, and lime and flux consumption during the reduction period, are shown in Table 1.

[0111] Table 1 Ladle stirring decarburization effect and slag consumption of Examples 4-6 and Comparative Example 0

[0112]

[0113] As shown in Table 1, the high-efficiency composite decarburization and slagging agent prepared in accordance with the present invention can increase the decarburization rate during the ladle stirring decarburization phase and reduce oxidation burns and temperature losses. Furthermore, it has excellent slagging and fluxing lime effects, increasing the arc submersion and heating rates during the LF reduction desulfurization phase and reducing flux losses such as lime and pre-melted slag, thereby enabling the recycling of solid waste resources from aluminum-calcium refining slag.

[0114] The specific implementation methods of other cold-state recycled materials of the aluminum-calcium refining slag involved in the embodiments of the present invention, such as the silicon deoxidized steel top slag modifier and the 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, corresponding recycled slag products and metallurgical uses can be reasonably matched and balanced to digest the solid waste of aluminum-calcium refining slag, and ultimately degrade it into worthless materials with low alkalinity, high phosphorus and sulfur content, which have almost no reusable value, thereby achieving near-zero solid waste emissions of aluminum-calcium refining slag in the true sense.

[0115] The above is a preferred embodiment of the present invention, and does not limit the scope of protection of the present invention. Any industrial production practice that directly / indirectly performs similar cold-state full recovery and re-treatment of aluminum-calcium refining slag using the contents of the present invention's specification under the conception of the technical solution of the present invention is included in the scope of protection of the present invention.

Claims

1. A method for the complete recovery and reuse of cold aluminum-calcium refining slag, characterized in that The steps include: S1. Aluminum-calcium refining slag produced during LF refining and converter top slag reforming and reduction desulfurization, after continuous casting and pouring, is poured into the slag pot with the remaining ladle. Aluminum-calcium refining slag is a solid waste slag produced during the production of finished aluminum-killed steel with [Si] ≤ 0.10%, and its chemical composition by weight percentage is: CaO: 50% to 60%, Al2O3: 20% to 35%, SiO2 ≤ 18%, MgO: 5% to 8%, FeO + MnO: ≤ 1.5%; S2. The slag pot is transported to the outer slag bay where it is sheltered from wind and dry; S3. Turn over the hot red slag in the slag pot at the outer slag span, and then use an oil hammer or a ramming 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, the hot stew pot filled with red crushed aluminum-calcium refined 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 initially screened and magnetically separated in a cold slag crushing line, and the large slag is jaw-broken and then screened again to obtain three intermediate by-products: 5mm-40mm lump aluminum-calcium slag, aluminum-calcium refining slag powder and particles less than 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 pellet production line by belt or tank truck; S9. In the cold solid pellet production line, aluminum-calcium refining slag powder with a particle size of less than 5mm is mixed with other materials to produce multifunctional cold solid pellets, 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 for slag making and dephosphorization in the converter, fluxing and slag modification in the tapping process, and ladle stirring and decarburization. In the step S9, A high-efficiency composite decarburization slag-making agent for a ladle is prepared using aluminum-calcium refining slag powder with a diameter of less than 5 mm as raw material. The specific steps are as follows: using the aluminum-calcium refining slag powder with a diameter of less than 5 mm produced by the cold slag crushing line as a basis, adding 0% to 20% of iron oxide scale, 1% to 2% of raw dolomite powder raw slag material, 0.5% to 1.5% of inorganic binder aluminate cement, 5% to 7% of organic binder corn starch, and 0% to 10% of water, respectively, and performing weight batching, mixing, pelletizing, and drying to produce a high-efficiency composite decarburization slag-making agent for a ladle with a diameter of 5 mm to 40 mm and a high oxidation and low melting point; A silicon-deoxidized steel top slag modifier is prepared using 5mm-40mm lumpy aluminum-calcium slag produced by a cold slag crushing line and aluminum-calcium refined slag powder and granules produced by a cold solid briquetting production line as raw materials. The specific steps of briquetting the aluminum-calcium refined slag powder and granules produced by the cold solid briquetting production line are as follows: adding 2%-5% of a mineral powder binder to the aluminum-calcium refined slag powder and granules with a diameter less than 5mm produced by the cold slag crushing line, mixing, briquetting, and drying, to produce aluminum-calcium refined slag powder and granules with a diameter of 5mm-40mm, with a single slag compressive strength of ≥10kN. An efficient dephosphorization slag agent for a converter is prepared using the aluminum-calcium refining slag powder with a size of less than 5 mm produced by a cold slag crushing line as raw material. The specific steps are: using 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 basis, adding 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 to the slag powder, and then weighing the ingredients, mixing, pelletizing and drying to produce a 5mm to 40mm efficient dephosphorization slag agent for a converter.

2. The method for cold-state full recovery and reuse of aluminum-calcium refining slag according to claim 1, characterized in that: In step S2, the dry and windproof outer slag is turned over and crushed in a hot slag crushing site, and the environment must 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.

3. The method for cold-state full recovery and reuse of aluminum-calcium refining slag according to claim 2, characterized in that: In the step S4, the red slag is sealed after the initial crushing as follows: 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 8mm or more.

4. The method for cold-state 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 is used to screen the aluminum-calcium refining slag, separate the residual steel magnetically, crush it again to the target particle size product and screen it again; 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; the coarsely crushed aluminum-calcium slag enters the fine jaw crushing and screening machine along the second belt conveyor, and is then The second crushing and screening are carried out to obtain 5mm~40mm blocky aluminum-calcium slag by-product oversize and 5mm aluminum-calcium refined slag powder undersize. After crushing, the aluminum-calcium refined slag powder undersize 5mm enters the next process along the third belt conveyor. In this process, after iron removal by the hanging magnetic roller, the magnetic small-sized scrap steel and the aluminum-calcium refined slag powder undersize 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 along the fifth belt conveyor to the coarse material belt conveyor or the fine material belt conveyor to produce aluminum-calcium refined slag powder with different mesh requirements.

5. The method for cold-state full recovery and reuse of aluminum-calcium refining slag according to claim 1, characterized in that: In steps S8 and S9, the cold solid pressed ball production line is used to produce multifunctional cold solid pressed balls with aluminum-calcium refined slag powder particles of different mesh sizes below 5 mm and other raw materials according to the formula. After the cold solid pressed balls are dried, the cold drum strength must reach more than 10 kN and the particle size must reach 5 mm to 40 mm. The cold-setting pelletizing production line includes a feed bin, a mixing mixer, a mixing bin, a pelletizing machine and a mesh belt dryer connected in sequence; 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 pelletizing machine along the mixing and pelletizing return conveyor. After pelletizing, the material is sent to the mesh belt dryer by the raw ball conveyor for drying.

6. The method for cold-state full recovery and reuse of aluminum-calcium refining slag according to claim 1, characterized in that: The main chemical components of the high-efficiency composite decarbonization slagging agent are: CaO: 35%~50%, Al2O3: 15%~30%, SiO2≤10%, MgO: 5%~15%, FeO≥5%, and the single ball compressive strength is ≥10kN.

7. The method for cold-state full recovery and reuse of aluminum-calcium refining slag according to claim 6, characterized in that: During the preparation of the slag-forming agent, the particle size of the aluminum-calcium refined slag powder is 80μm to 150μm; the drying method of the product obtained by pelletizing is: airing or drying at a temperature of 30℃ to 190℃ for 24h to 96h.

8. The method for cold-state full recovery and reuse of aluminum-calcium refining slag according to claim 1, characterized in that: The chemical composition of the converter high-efficiency dephosphorization slag agent is: CaO: 20%~40%, Al2O3: 8%~15%, SiO2≤10%, MgO: 5%~8%, Na2O: 1.5%~4.0%, Fe2O3≥40%, and the single ball compressive strength is ≥10kN.

Images