Method for hot-state cyclic treatment of steel slag

Abstract

The invention discloses a steel slag hot-state circulation treatment method, which is characterized in that based on the characteristics of steel slag and steel mill solid waste, a new thought of combining the steel slag with specific solid waste for coordinated treatment so as to realize steel slag dephosphorization and solid waste absorption is provided, and reaction products obtained by the synergistic treatment of the steel slag and the solid waste have different melting points and are easy to separate; accumulation and enrichment of harmful elements in the solid waste are greatly avoided; the low-cost enrichment of phosphorus in the steel slag is realized, the discharge capacity of the steel slag can be greatly reduced, and particularly, the obtained phosphorus-free slag has higher heat and can be circularly used for converter smelting, so that the energy is saved. Compared with an existing reduction gasification dephosphorization technology, the dephosphorization effect is better, the waste gas emission amount is small, no waste water is discharged, in addition, the technology is more concise, the stability is higher, and the input cost is lower.

Description

Technical Field

[0001] This invention relates to the treatment of steel slag, specifically to a method for hot recycling of steel slag, belonging to the field of integrated treatment technology for steel slag and solid waste. Background Technology

[0002] my country has a massive steel slag discharge, with annual increases exceeding 100 million tons. Currently, steel slag disposal mainly focuses on cement production, which suffers from low added value and low utilization rate (only about 40%). With the revision of GB175-2023 "General Portland Cement," it is clearly stipulated that from June 1, 2024, steel slag will no longer be allowed as a blending material in general Portland cement. The proper disposal of steel slag has become a major bottleneck for the green and sustainable development of my country's steel industry.

[0003] Steel slag is rich in iron resources, with iron oxides accounting for 15-25%. However, it also contains a large amount of phosphorus, a harmful element in steel materials, which limits its internal recycling potential. If steel slag dephosphorization technology can be developed to overcome the constraints of internal steel slag recycling, steel slag emissions can be greatly reduced, eliminating the need for building material production and achieving source reduction and resource recycling.

[0004] Regarding steel slag dephosphorization technology, Chinese patent CN117778669A discloses "A Method for Gasification Dephosphorization of Converter Final Slag and Recycling of Dephosphorized Slag." This method involves adding a carbonaceous dephosphorizing agent to the converter slag for gasification dephosphorization, and the dephosphorized slag can be recycled back to the sintering process. This method can effectively remove phosphorus and achieve steel slag recycling; however, it suffers from poor dephosphorization effect and inadequate slag-phosphorus separation in practical applications. Chinese patent CN110184399A discloses "A Steel Slag Treatment Method Using a Two-Step Oxidative Desulfurization and Reduction Dephosphorization Process," in which dephosphorization employs gas-based reduction dephosphorization, utilizing a mixture of CO and CO2 to convert phosphorus into phosphorus gas for removal. This method has a good dephosphorization effect, reaching 80%; however, the phosphorus gas produced is highly toxic, posing a risk of personnel poisoning and explosion of the mixed gas. Chinese patent CN110526745A discloses "A method for separating phosphorus from dephosphorized steel slag and preparing phosphate fertilizer". The method first oxidizes the dephosphorized steel slag in a molten state, then cools it and crushes and leaches it to obtain low-phosphorus residue and phosphorus-containing leachate. This method can achieve effective removal and recovery of phosphorus to a certain extent, but the amount of steel slag is large, the amount of by-product wastewater generated is too large, and the disposal cost is high. Summary of the Invention

[0005] To address the problems of poor dephosphorization, large emissions of waste gas, and large amounts of wastewater in existing steel slag treatment technologies, this invention provides a method for hot recycling of steel slag. By mixing and reacting hot steel slag with multi-source solid waste, phosphorus-free slag, high-chlorine slag, and phosphorus-iron slag in a solid solution state and layered with each other can be obtained. These can then be recycled to the corresponding processes in steel production for disposal. This method is simple, easy to operate, produces little waste gas and no wastewater, and uses solid waste generated in the steel industry as raw materials. The overall treatment cost is low, achieving the goal of treating waste with waste.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: A method for hot recycling of steel slag, the method comprising: 1) Add multi-source solid waste to the hot steel slag discharged from the converter for reaction, and a mixed solid solution is obtained after the reaction is completed.

[0007] 2) Collect the upper layer of the mixed solid solution and recycle it as converter charge; collect the middle layer of the mixed solid solution and recycle it as sintering material; collect the lower layer of the mixed solid solution and add it to the hot steel slag for recycling step 1).

[0008] Preferably, in step 1), the multi-source solid waste is a mixed solid waste composed of coal gangue, waste carbon powder, blast furnace bag ash, aluminum ash, sintering ash, and converter secondary ash.

[0009] Preferably, the multi-source solid waste includes: 10-40 wt% coal gangue, 5-30 wt% waste carbon powder, 5-25 wt% blast furnace bag filter ash, 15-40 wt% aluminum ash, 3-15 wt% sintering ash, and 2-15 wt% converter secondary ash. More preferably, the multi-source solid waste includes: 15-30 wt% coal gangue, 10-25 wt% waste carbon powder, 10-20 wt% blast furnace bag filter ash, 20-35 wt% aluminum ash, 5-12 wt% sintering ash, and 5-12 wt% converter secondary ash (all are mass fraction percentages).

[0010] Preferably, the amount of multi-source solid waste added is 5-20% of the total mass of hot steel slag, more preferably 5-18%, and even more preferably 7-15%.

[0011] Preferably, the temperature of the hot steel slag is 1400~1700℃, more preferably 1450~1650℃, and even more preferably 1500~1600℃.

[0012] Preferably, in step 1), the reaction is a stirred reaction, and the stirring time is 0.2-2 hours, preferably 0.3-1.5 hours, and more preferably 0.4-1 hours. Preferably, in step 2), the upper layer material accounts for 60-85% of the total mass of the mixed solid solution, preferably 65-80%, and more preferably 70-75%.

[0013] Preferably, the phosphorus content in the upper layer material is no more than 0.5%, more preferably no more than 0.3%, and even more preferably no more than 0.2%.

[0014] Preferably, in step 2), the intermediate layer material accounts for 3-25% of the total mass of the mixed solid solution, more preferably 5-20%, and even more preferably 10-15%.

[0015] Preferably, the chlorine content in the intermediate layer material is not less than 0.3% by mass, more preferably not less than 0.5%, and even more preferably not less than 0.7%.

[0016] Preferably, in step 3), the lower layer material accounts for 1 to 20% of the total mass of the mixed solid solution, more preferably 3 to 18%, and even more preferably 5 to 15%.

[0017] As a preferred option, the lower layer material is recycled in step 1) multiple times (e.g., 3 to 8 times) before being discharged.

[0018] Preferably, in step 1), the generated gas is filtered (preferably by negative pressure filtration) using a ceramic membrane before being discharged. The filtered dust is returned to the sintering feed.

[0019] In this invention, steel slag typically contains about 2-5% phosphorus, and direct recycling of it would adversely affect the converter. Since phosphorus in steel slag mainly exists as a Ca3(PO4)2 solid solution, reducing it to elemental phosphorus or phosphorus gas is a prerequisite for its removal. However, considering that converting all the phosphorus into phosphorus gas would require a large amount of forced draft and generate a large amount of toxic phosphorus gas, posing a safety hazard, this invention, based on the characteristics of steel slag and solid waste generated by steel plants and other processes, reforms each solid waste and mixes it with hot steel slag. This results in the formation of phosphorus-free slag, high-chloride slag, and phosphorus-iron slag with significantly different and easily separable components from the steel slag and multi-source solid waste. These three slag phases can be disposed of separately within the steel production process, thereby achieving low-cost disposal of steel slag and multi-source solid waste.

[0020] In this invention, reformed multi-source solid waste is mixed with hot steel slag. The reducing agents in the multi-source solid waste (such as the carbonaceous matter contained in coal gangue, waste carbon powder, and blast furnace bag ash) are used to convert most of the phosphorus in the steel slag into elemental phosphorus and a small amount of phosphorus gas at low cost. The main reaction process involved is Ca3(PO4)2(s) + 5C(s) = 3CaO(s) + P2(g) + 5CO(g). Simultaneously, the obtained elemental phosphorus undergoes an alloying reaction with the iron inherent in the hot converter steel slag and the iron in the multi-source solid waste (such as blast furnace bag ash, sintering ash, and converter secondary ash) under high-temperature conditions, transforming it into a stable phosphorus-iron phase. Furthermore, it should be noted that if carbon or biomass is simply used to reduce the phosphorus in the steel slag, the reduction process is endothermic, which can cause the steel slag to solidify during the reaction. In this invention, the multi-source solid waste also contains a considerable amount of Zn and Al (generally from aluminum ash and secondary ash from converters). The exothermic effect of the combustion of elemental Zn and Al in the solid waste can be used to achieve self-heating of the entire steel slag treatment, thereby avoiding the low-temperature solidification of phosphorus in the steel slag due to the endothermic reduction.

[0021] In this invention, after steel slag is mixed and reacted with multi-source solid waste, it will stratify according to its melting point and density. The upper layer is mainly CaO-SiO2-MgO-Al2O3 slag (i.e., phosphorus-free slag), generally accounting for more than 60% of the total slag. This part of the slag can be directly used as a slagging agent in the next converter, realizing the recycling of steel slag. The middle layer is mainly a eutectic mixture containing chlorine and fluorine (i.e., high-chlorine slag), generally accounting for about 3-25% of the total slag. It originates from the fluorine and chloride salts carried in the added solid waste, which react with calcium, iron, etc. during the dephosphorization of the steel slag. The lower layer is mainly ferrophosphorus (i.e., ferrophosphorus slag), generally accounting for about 1-20% of the total slag. When the phosphorus content is not high, it can be used for the recycling reaction of the steel slag in the next converter. Since the three slag phases have significantly different densities, a slag skimmer can be used to separate the reacted steel slag. In other words, based on the different melting points of the three slag phases, this invention achieves the recycling and consumption of steel slag on the one hand, and the enrichment and separation of phosphorus in steel slag on the other hand, and further achieves the selective separation and open-circuit disposal of harmful elements in solid waste.

[0022] In this invention, the dephosphorization of converter steel slag generally needs to be controlled at a high basicity (generally requiring an basicity greater than 1.5 (preferably greater than 2). When the initial basicity of the steel slag is low, the basicity can be increased by adding calcium oxide or magnesium oxide, with basicity R = CaO / SiO2). Comprehensive treatment of multi-source solid waste and hot steel slag can also increase the basicity of the steel slag. After the basicity is increased, the steel slag is more suitable for subsequent recycling after reduction dephosphorization.

[0023] In this invention, the process flow is roughly as follows: 1) A certain amount of multi-source solid waste (a mixture composed of coal gangue, carbon powder, blast furnace bag ash, aluminum ash, sintering ash, converter secondary ash, etc. in different proportions) is added to the high-temperature hot steel slag discharged from the converter, and the mixture is stirred thoroughly to react and obtain a layered mixed solid solution; 2) The gas generated during the reaction is collected in a centralized manner, and is generally intercepted by a ceramic membrane before being discharged. The dust obtained after the ceramic membrane interception is used for subsequent storage; 3) After the reaction in step 1), the slag pot is tilted at a certain angle to facilitate the two-stage slag removal treatment of the mixed solid solution in the slag pot: the upper slag of the first stage generally accounts for about 60-85% of the solid solution, which is phosphorus-free slag and can be directly returned to the next converter for recycling; the middle slag of the second stage generally accounts for about 3-25% of the solid solution, which is high-chloride slag and can be directly returned to sintering for recycling. 4) The remaining lower layer slag after step 3) is used to mix and react with the slag of the next furnace. Generally, after 3 to 8 cycles, it can be discharged.

[0024] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1. Based on the characteristics of steel slag and steel plant solid waste, this invention proposes a new approach to combine steel slag with specific solid waste for synergistic treatment, thereby achieving synergistic dephosphorization and solid waste disposal of steel slag. Compared with the existing reduction gasification dephosphorization, it has better dephosphorization effect, smaller waste gas emissions and no wastewater discharge. In addition, the process is simpler, more stable and has lower input cost.

[0025] 2: The reaction products obtained from the co-processing of steel slag and solid waste of this invention have different melting points and are easy to separate, which greatly avoids the accumulation and enrichment of harmful elements in solid waste; it realizes the low-cost enrichment of phosphorus in steel slag and can significantly reduce the amount of steel slag discharged. In particular, the phosphorus-free slag obtained has high heat and can be recycled for converter smelting, thereby saving energy. Attached Figure Description

[0026] Figure 1 This is a process flow diagram of the method described in this invention. Detailed Implementation

[0027] The technical solution of the present invention will be illustrated below with examples. The scope of protection sought by the present invention includes, but is not limited to, the following embodiments. Example 1

[0028] Multi-source solid waste is obtained by mixing 20 parts coal gangue, 20 parts waste carbon powder, 15 parts blast furnace bag ash, 25 parts aluminum ash, 10 parts sintering ash, and 10 parts converter secondary ash evenly according to the mass ratio.

[0029] 1000 kg of hot steel slag (approximately 1600℃, phosphorus content approximately 3.2%) discharged from the converter was placed in a slag pot along with 150 kg of multi-source solid waste. The mixture was then stirred and reacted for 0.5 h, resulting in a mixed solid solution. The gases generated during the reaction were intercepted by a ceramic membrane before being discharged. The dust collected after the ceramic membrane was removed was returned to the sintering batch for use.

[0030] The slag pot is tilted, and approximately 76% of the slag material from the upper layer of the mixed solid solution is collected as phosphorus-free slag (phosphorus content approximately 0.18%, dephosphorization rate approximately 94.38%) and recycled as converter feed. Approximately 10% of the slag material from the middle layer of the mixed solid solution is collected as high-chlorine slag (chlorine content approximately 0.82%) and recycled as sintering feed. The remaining lower layer of the mixed solid solution is collected as ferrophosphate slag and added to hot steel slag for recycling and reaction with multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (approximately 161 kg) is discharged for disposal. Example 2

[0031] Multi-source solid waste is obtained by mixing 30 parts coal gangue, 10 parts waste carbon powder, 15 parts blast furnace bag ash, 25 parts aluminum ash, 10 parts sintering ash, and 10 parts converter secondary ash evenly according to the mass ratio.

[0032] 1000 kg of hot steel slag (approximately 1630°C, phosphorus content approximately 2.9%) discharged from the converter was placed in a slag pot along with 150 kg of multi-source solid waste. The mixture was then stirred and reacted for 0.5 h, resulting in a mixed solid solution. The gases generated during the reaction were intercepted using a ceramic membrane before being discharged. The dust collected after the ceramic membrane was used for sintering and batching.

[0033] The slag pot is tilted, and approximately 72% of the slag material from the upper layer of the mixed solid solution is collected as phosphorus-free slag (phosphorus content approximately 0.21%, dephosphorization rate approximately 92.76%) and recycled as converter feed. Approximately 19% of the slag material from the middle layer of the mixed solid solution is collected as high-chlorine slag (chlorine content approximately 0.61%) and recycled as sintering feed. The remaining lower layer of the mixed solid solution is collected as ferrophosphate slag and added to hot steel slag for recycling and reaction with multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (approximately 104 kg) is discharged for disposal. Example 3

[0034] Multi-source solid waste is obtained by mixing 20 parts coal gangue, 25 parts waste carbon powder, 10 parts blast furnace bag ash, 25 parts aluminum ash, 10 parts sintering ash, and 10 parts converter secondary ash evenly according to the mass ratio.

[0035] 1000 kg of hot steel slag (approximately 1610°C, phosphorus content approximately 3.3%) discharged from the converter was placed in a slag pot along with 150 kg of multi-source solid waste. The mixture was then stirred and reacted for 0.5 h, resulting in a mixed solid solution. The gases generated during the reaction were intercepted using a ceramic membrane before being discharged. The dust collected after the ceramic membrane was removed was returned to the sintering batching process.

[0036] The slag pot is tilted, and approximately 74% of the slag material from the upper layer of the mixed solid solution is collected as phosphorus-free slag (phosphorus content approximately 0.28%, dephosphorization rate approximately 91.52%) and recycled as converter feed. Approximately 16% of the slag material from the middle layer of the mixed solid solution is collected as high-chlorine slag (chlorine content approximately 0.54%) and recycled as sintering feed. The remaining lower layer of the mixed solid solution is collected as ferrophosphate slag and added to hot steel slag for recycling and reaction with multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (approximately 115 kg) is discharged for disposal. Example 4

[0037] Mix 20 parts coal gangue, 20 parts waste carbon powder, 10 parts blast furnace bag ash, 30 parts aluminum ash, 10 parts sintering ash, and 10 parts converter secondary ash evenly according to the mass ratio to obtain multi-source solid waste.

[0038] 1000 kg of hot steel slag (approximately 1620°C, phosphorus content approximately 3.0%) discharged from the converter was placed in a slag pot along with 150 kg of multi-source solid waste. The mixture was then stirred and reacted for 0.5 h, resulting in a mixed solid solution. The gases generated during the reaction were intercepted using a ceramic membrane before being discharged. The dust collected after the ceramic membrane was used for sintering and batching.

[0039] The slag pot is tilted, and approximately 74% of the slag material from the upper layer of the mixed solid solution is collected as phosphorus-free slag (phosphorus content approximately 0.19%, dephosphorization rate approximately 93.67%) and recycled as converter feed. Approximately 12% of the slag material from the middle layer of the mixed solid solution is collected as high-chlorine slag (chlorine content approximately 0.51%) and recycled as sintering feed. The remaining lower layer of the mixed solid solution is collected as ferrophosphate slag and added to hot steel slag for recycling and reaction with multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (approximately 161 kg) is discharged for disposal. Example 5

[0040] Multi-source solid waste is obtained by mixing 20 parts coal gangue, 20 parts waste carbon powder, 15 parts blast furnace bag ash, 30 parts aluminum ash, 5 parts sintering ash, and 10 parts converter secondary ash evenly according to the mass ratio.

[0041] 1000 kg of hot steel slag (approximately 1615°C, phosphorus content approximately 3.4%) discharged from the converter was placed in a slag pot along with 150 kg of multi-source solid waste. The mixture was then stirred and reacted for 0.5 h, resulting in a mixed solid solution. The gases generated during the reaction were intercepted using a ceramic membrane before being discharged. The dust collected after the ceramic membrane was used for sintering and batching.

[0042] The slag pot is tilted, and the top 76% of the slag material in the mixed solid solution is collected as phosphorus-free slag (phosphorus content approximately 0.16%, dephosphorization rate approximately 95.29%) and recycled as converter feed. The middle 6% of the slag material in the mixed solid solution is collected as high-chlorine slag (chlorine content approximately 0.44%) and recycled as sintering feed. The remaining bottom layer of the mixed solid solution is collected as ferrophosphate slag and added to hot steel slag for recycling and reaction with multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (approximately 197 kg) is discharged for disposal. Example 6

[0043] Multi-source solid waste is obtained by mixing 25 parts coal gangue, 20 parts waste carbon powder, 15 parts blast furnace bag ash, 25 parts aluminum ash, 5 parts sintering ash, and 10 parts converter secondary ash evenly according to the mass ratio.

[0044] 1000 kg of hot steel slag (approximately 1630°C, phosphorus content approximately 2.8%) discharged from the converter was placed in a slag pot along with 150 kg of multi-source solid waste. The mixture was then stirred and reacted for 0.5 h, resulting in a mixed solid solution. The gases generated during the reaction were intercepted using a ceramic membrane before being discharged. The dust collected after the ceramic membrane was used for sintering and batching.

[0045] The slag pot is tilted, and the top 79% of the slag material in the mixed solid solution is collected as phosphorus-free slag (phosphorus content approximately 0.26%, dephosphorization rate approximately 90.71%) and recycled as converter feed. The middle 4% of the slag material in the mixed solid solution is collected as high-chlorine slag (chlorine content approximately 0.47%) and recycled as sintering feed. The remaining bottom layer of the mixed solid solution is collected as ferrophosphate slag and added to hot steel slag for recycling and reaction with multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (approximately 186 kg) is discharged for disposal. Example 7

[0046] Multi-source solid waste is obtained by mixing 20 parts coal gangue, 25 parts waste carbon powder, 15 parts blast furnace bag ash, 25 parts aluminum ash, 10 parts sintering ash, and 5 parts converter secondary ash evenly according to the mass ratio.

[0047] 1000 kg of hot steel slag (approximately 1620°C, phosphorus content approximately 3.2%) discharged from the converter was placed in a slag pot along with 150 kg of multi-source solid waste. The mixture was then stirred and reacted for 0.5 h, resulting in a mixed solid solution. The gases generated during the reaction were intercepted using a ceramic membrane before being discharged. The dust collected after the ceramic membrane was removed was returned to the sintering batching process.

[0048] The slag pot is tilted, and approximately 77% of the slag material from the upper layer of the mixed solid solution is collected as phosphorus-free slag (phosphorus content approximately 0.19%, dephosphorization rate approximately 94.06%) and recycled as converter feed. Approximately 9% of the slag material from the middle layer of the mixed solid solution is collected as high-chlorine slag (chlorine content approximately 0.73%) and recycled as sintering feed. The remaining lower layer of the mixed solid solution is collected as ferrophosphate slag and added to hot steel slag for recycling and reaction with multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (approximately 161 kg) is discharged for disposal. Example 8

[0049] Multi-source solid waste is obtained by mixing 20 parts coal gangue, 25 parts waste carbon powder, 15 parts blast furnace bag ash, 20 parts aluminum ash, 10 parts sintering ash, and 10 parts converter secondary ash evenly according to the mass ratio.

[0050] 1000 kg of hot steel slag (approximately 1625°C, phosphorus content approximately 3.1%) discharged from the converter was placed in a slag pot along with 150 kg of multi-source solid waste. The mixture was then stirred and reacted for 0.5 h, resulting in a mixed solid solution. The gases generated during the reaction were intercepted using a ceramic membrane before being discharged. The dust collected after the ceramic membrane was used for sintering and batching.

[0051] The slag pot is tilted, and approximately 79% of the slag material from the upper layer of the mixed solid solution is collected as phosphorus-free slag (phosphorus content approximately 0.20%, dephosphorization rate approximately 93.55%) and recycled as converter feed. Approximately 11% of the slag material from the middle layer of the mixed solid solution is collected as high-chlorine slag (chlorine content approximately 0.50%) and recycled as sintering feed. The remaining lower layer of the mixed solid solution is collected as ferrophosphate slag and added to hot steel slag for recycling and reaction with multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (approximately 115 kg) is discharged for disposal. Example 9

[0052] Multi-source solid waste is obtained by mixing 20 parts coal gangue, 15 parts waste carbon powder, 20 parts blast furnace bag ash, 25 parts aluminum ash, 10 parts sintering ash, and 10 parts converter secondary ash evenly according to the mass ratio.

[0053] 1000 kg of hot steel slag (approximately 1610°C, phosphorus content approximately 2.9%) discharged from the converter was placed in a slag pot along with 150 kg of multi-source solid waste. The mixture was then stirred and reacted for 0.5 h, resulting in a mixed solid solution. The gases generated during the reaction were intercepted using a ceramic membrane before being discharged. The dust collected after the ceramic membrane was used for sintering and batching.

[0054] The slag pot is tilted, and approximately 75% of the slag material from the upper layer of the mixed solid solution is collected as phosphorus-free slag (phosphorus content approximately 0.22%, dephosphorization rate approximately 92.41%) and recycled as converter feed. Approximately 12% of the slag material from the middle layer of the mixed solid solution is collected as high-chlorine slag (chlorine content approximately 0.75%) and recycled as sintering feed. The remaining lower layer of the mixed solid solution is collected as ferrophosphate slag and added to hot steel slag for recycling and reaction with multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (approximately 150 kg) is discharged for disposal. Example 10

[0055] Multi-source solid waste is obtained by uniformly mixing 10 parts coal gangue, 23 parts waste carbon powder, 17 parts blast furnace bag ash, 28 parts aluminum ash, 11 parts sintering ash, and 11 parts converter secondary ash according to the mass ratio.

[0056] 1000 kg of hot steel slag (approximately 1600℃, phosphorus content approximately 3.2%) discharged from the converter was placed in a slag pot along with 150 kg of multi-source solid waste. The mixture was then stirred and reacted for 0.5 h, resulting in a mixed solid solution. The gases generated during the reaction were intercepted by a ceramic membrane before being discharged. The dust collected after the ceramic membrane was removed was returned to the sintering batch for use.

[0057] The slag pot is tilted, and approximately 70% of the slag material from the upper layer of the mixed solid solution is collected as phosphorus-free slag (phosphorus content approximately 0.32%, dephosphorization rate approximately 90.00%) and recycled as converter feed. Approximately 18% of the slag material from the middle layer of the mixed solid solution is collected as high-chlorine slag (chlorine content approximately 0.46%) and recycled as sintering feed. The remaining lower layer of the mixed solid solution is collected as ferrophosphate slag and added to hot steel slag for recycling and reaction with multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (approximately 138 kg) is discharged for disposal. Example 11

[0058] Multi-source solid waste is obtained by uniformly mixing 24 parts coal gangue, 5 parts waste carbon powder, 18 parts blast furnace bag ash, 29 parts aluminum ash, 12 parts sintering ash, and 12 parts converter secondary ash according to the mass ratio.

[0059] 1000 kg of hot steel slag (approximately 1600℃, phosphorus content approximately 3.2%) discharged from the converter was placed in a slag pot along with 150 kg of multi-source solid waste. The mixture was then stirred and reacted for 0.5 h, resulting in a mixed solid solution. The gases generated during the reaction were intercepted by a ceramic membrane before being discharged. The dust collected after the ceramic membrane was removed was returned to the sintering batch for use.

[0060] The slag pot is tilted, and approximately 68% of the slag material from the upper layer of the mixed solid solution is collected as phosphorus-free slag (phosphorus content approximately 0.34%, dephosphorization rate approximately 89.38%) and recycled as converter feed. Approximately 20% of the slag material from the middle layer of the mixed solid solution is collected as high-chlorine slag (chlorine content approximately 0.43%) and recycled as sintering feed. The remaining lower layer of the mixed solid solution is collected as ferrophosphate slag and added to hot steel slag for recycling and reaction with multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (approximately 138 kg) is discharged for disposal. Example 12

[0061] Multi-source solid waste is obtained by uniformly mixing 22.5 parts of coal gangue, 22.5 parts of waste carbon powder, 5 parts of blast furnace bag ash, 28 parts of aluminum ash, 11 parts of sintering ash, and 11 parts of converter secondary ash according to the mass ratio.

[0062] 1000 kg of hot steel slag (approximately 1600℃, phosphorus content approximately 3.2%) discharged from the converter was placed in a slag pot along with 150 kg of multi-source solid waste. The mixture was then stirred and reacted for 0.5 h, resulting in a mixed solid solution. The gases generated during the reaction were intercepted by a ceramic membrane before being discharged. The dust collected after the ceramic membrane was removed was returned to the sintering batch for use.

[0063] The slag pot is tilted, and approximately 67% of the slag material from the upper layer of the mixed solid solution is collected as phosphorus-free slag (phosphorus content approximately 0.28%, dephosphorization rate approximately 91.25%) and recycled as converter feed. Approximately 15% of the slag material from the middle layer of the mixed solid solution is collected as high-chlorine slag (chlorine content approximately 0.43%) and recycled as sintering feed. The remaining lower layer of the mixed solid solution is collected as ferrophosphate slag and added to hot steel slag for recycling and reaction with multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (approximately 207 kg) is discharged for disposal. Example 13

[0064] Multi-source solid waste is obtained by mixing 23 parts coal gangue, 23 parts waste carbon powder, 17 parts blast furnace bag ash, 15 parts aluminum ash, 11 parts sintering ash, and 11 parts converter secondary ash evenly according to the mass ratio.

[0065] 1000 kg of hot steel slag (approximately 1600℃, phosphorus content approximately 3.2%) discharged from the converter was placed in a slag pot along with 150 kg of multi-source solid waste. The mixture was then stirred and reacted for 0.5 h, resulting in a mixed solid solution. The gases generated during the reaction were intercepted by a ceramic membrane before being discharged. The dust collected after the ceramic membrane was removed was returned to the sintering batch for use.

[0066] The slag pot is tilted, and approximately 71% of the slag material from the upper layer of the mixed solid solution is collected as phosphorus-free slag (phosphorus content approximately 0.42%, dephosphorization rate approximately 86.88%) and recycled as converter feed. Approximately 13% of the slag material from the middle layer of the mixed solid solution is collected as high-chlorine slag (chlorine content approximately 0.49%) and recycled as sintering feed. The remaining lower layer of the mixed solid solution is collected as ferrophosphate slag and added to hot steel slag for recycling and reaction with multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (approximately 184 kg) is discharged for disposal. Example 14

[0067] Multi-source solid waste is obtained by mixing 21.5 parts coal gangue, 21.5 parts waste carbon powder, 16 parts blast furnace bag ash, 27 parts aluminum ash, 3 parts sintering ash, and 11 parts converter secondary ash evenly according to the mass ratio.

[0068] 1000 kg of hot steel slag (approximately 1600℃, phosphorus content approximately 3.2%) discharged from the converter was placed in a slag pot along with 150 kg of multi-source solid waste. The mixture was then stirred and reacted for 0.5 h, resulting in a mixed solid solution. The gases generated during the reaction were intercepted by a ceramic membrane before being discharged. The dust collected after the ceramic membrane was removed was returned to the sintering batch for use.

[0069] The slag pot is tilted, and approximately 69% of the slag material from the upper layer of the mixed solid solution is collected as phosphorus-free slag (phosphorus content approximately 0.31%, dephosphorization rate approximately 90.31%) and recycled as converter feed. Approximately 10% of the slag material from the middle layer of the mixed solid solution is collected as high-chlorine slag (chlorine content approximately 0.45%) and recycled as sintering feed. The remaining lower layer of the mixed solid solution is collected as ferrophosphate slag and added to hot steel slag for recycling and reaction with multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (approximately 242 kg) is discharged for disposal. Example 15

[0070] Multi-source solid waste is obtained by mixing 22 parts coal gangue, 22 parts waste carbon powder, 16 parts blast furnace bag ash, 27 parts aluminum ash, 11 parts sintering ash, and 2 parts converter secondary ash evenly according to the mass ratio.

[0071] 1000 kg of hot steel slag (approximately 1600℃, phosphorus content approximately 3.2%) discharged from the converter was placed in a slag pot along with 150 kg of multi-source solid waste. The mixture was then stirred and reacted for 0.5 h, resulting in a mixed solid solution. The gases generated during the reaction were intercepted by a ceramic membrane before being discharged. The dust collected after the ceramic membrane was removed was returned to the sintering batch for use.

[0072] The slag pot is tilted, and approximately 70% of the slag material from the upper layer of the mixed solid solution is collected as phosphorus-free slag (phosphorus content approximately 0.34%, dephosphorization rate approximately 89.38%) and recycled as converter feed. Approximately 16% of the slag material from the middle layer of the mixed solid solution is collected as high-chlorine slag (chlorine content approximately 0.43%) and recycled as sintering feed. The remaining lower layer of the mixed solid solution is collected as ferrophosphate slag and added to hot steel slag for recycling and reaction with multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (approximately 161 kg) is discharged for disposal. Example 16

[0073] Example 1 was repeated, except the amount of multi-source solid waste was adjusted to 50 kg. After the reaction was completed, the slag pot was tilted, and approximately 65% ​​of the slag material from the upper layer of the mixed solid solution was collected as phosphorus-free slag (phosphorus content approximately 1.2%, dephosphorization rate approximately 61.29%) and recycled as converter feed. Approximately 9% of the slag material from the middle layer of the mixed solid solution was collected as high-chlorine slag (chlorine content approximately 1.02%) and recycled as sintering feed. The remaining lower layer of the mixed solid solution was collected as ferrophosphate slag and added to hot steel slag for recycling and reaction with the multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (approximately 273 kg) was discharged for disposal. Example 17

[0074] Example 1 was repeated, except that the hot steel slag was cooled to 1400°C before adding multi-source solid waste for reaction. After the reaction was completed, the slag pot was tilted, and about 60% of the slag material in the upper layer of the mixed solid solution was collected as phosphorus-free slag (phosphorus content about 1.1%, dephosphorization rate about 62.07%) and recycled as converter feed. About 10% of the slag material in the middle layer of the mixed solid solution was collected as high-chlorine slag (chlorine content about 0.76%) and recycled as sintering feed. The remaining lower layer of the mixed solid solution was collected as ferrophosphate slag and added to the hot steel slag for recycling and reaction with multi-source solid waste. After repeating the above steps 4 times, the resulting ferrophosphate slag (about 345 kg) was discharged for disposal.

[0075] Comparative Example 1 Example 1 was repeated, except that all the multi-source solid waste was replaced with coal gangue. After the reaction was completed, the slag pot was tilted, and about 75% of the slag material in the upper layer of the mixed solid solution was collected as phosphorus-free slag (phosphorus content about 1.46%, dephosphorization rate about 51.33%) and recycled as converter feed. About 2% of the slag material in the middle layer of the mixed solid solution was collected as high-chlorine slag (chlorine content about 0.91%) and recycled as sintering feed. The remaining lower layer of the mixed solid solution was collected as ferrophosphate slag and added to hot steel slag for recycling and reaction with the multi-source solid waste. After the above steps were repeated 4 times, the resulting ferrophosphate slag (about 265 kg) was discharged for disposal.

[0076] Comparative Example 2 Example 1 was repeated, except that all the multi-source solid waste was replaced with carbon powder. After the reaction was completed, the slag pot was tilted, and about 79% of the slag material on the top layer of the mixed solid solution was collected as phosphorus-free slag (phosphorus content of about 1.53%, dephosphorization rate of about 47.24%) and recycled as converter feed. Almost no high-chlorine slag was generated. The remaining mixed solid solution material was collected as ferrophosphate slag and added to the hot steel slag for recycling and reaction with the multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (about 242 kg) was discharged for disposal.

[0077] Comparative Example 3 Example 1 was repeated, except that all the multi-source solid waste was replaced with blast furnace bag ash. After the reaction was completed, the slag pot was tilted, and about 50% of the slag material in the upper layer of the mixed solid solution was collected as phosphorus-free slag (phosphorus content about 1.34%, dephosphorization rate about 58.13%) and recycled as converter feed. About 5% of the slag material in the middle layer of the mixed solid solution was collected as high-chlorine slag (chlorine content about 0.60%) and recycled as sintering feed. The remaining lower layer of the mixed solid solution was collected as ferrophosphate slag and added to the hot steel slag for recycling and reaction with the multi-source solid waste. After the above steps were repeated 4 times, the resulting ferrophosphate slag (about 518 kg) was discharged for disposal.

[0078] Comparative Example 4 Example 1 was repeated, except that all the multi-source solid waste was replaced with aluminum ash. After the reaction was completed, the slag pot was tilted, and about 80% of the slag material from the upper layer of the mixed solid solution was collected as phosphorus-free slag (phosphorus content about 0.42%, dephosphorization rate about 85.52%) and recycled as converter feed. About 2% of the slag material from the middle layer of the mixed solid solution was collected as high-chlorine slag (chlorine content about 0.51%) and recycled as sintering feed. The remaining lower layer of the mixed solid solution was collected as ferrophosphate slag and added to the hot steel slag for recycling and reaction with the multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (about 227 kg) was discharged for disposal.

[0079] Comparative Example 5 Example 1 was repeated, except that all the multi-source solid waste was replaced with sintering ash. After the reaction was completed, the slag pot was tilted, and the top 45% of the slag material of the mixed solid solution was collected as phosphorus-free slag (phosphorus content approximately 2.12%, dephosphorization rate approximately 32.26%) and recycled as converter feed. The middle 20% of the slag material of the mixed solid solution was collected as high-chlorine slag (chlorine content approximately 1.03%) and recycled as sintering feed. The remaining bottom layer of the mixed solid solution was collected as ferrophosphate slag and added to the hot steel slag for recycling and reaction with the multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (approximately 403 kg) was discharged for disposal.

[0080] Comparative Example 6 Example 1 was repeated, except that all the multi-source solid waste was replaced with converter secondary ash. After the reaction was completed, the slag pot was tilted, and about 50% of the slag material from the upper layer of the mixed solid solution was collected as phosphorus-free slag (phosphorus content about 1.94%, dephosphorization rate about 32.14%) and recycled as converter feed. About 1% of the slag material from the middle layer of the mixed solid solution was collected as high-chlorine slag (chlorine content about 1.05%) and recycled as sintering feed. The remaining lower layer of the mixed solid solution was collected as ferrophosphate slag and added to the hot steel slag for recycling and reaction with the multi-source solid waste. After repeating the above steps four times, the resulting ferrophosphate slag (about 564 kg) was discharged for disposal.

Claims

1. A method for hot recycling of steel slag, characterized in that: The method includes: 1) Add multi-source solid waste to the hot steel slag discharged from the converter and react to obtain a mixed solid solution after the reaction is completed; 2) Collect the upper layer of the mixed solid solution and recycle it as converter charge; collect the middle layer of the mixed solid solution and recycle it as sintering material; collect the lower layer of the mixed solid solution and add it to the hot steel slag for recycling step 1).

2. The method according to claim 1, characterized in that: In step 1), the multi-source solid waste is a mixed solid waste composed of coal gangue, waste carbon powder, blast furnace bag ash, aluminum ash, sintering ash, and converter secondary ash.

3. The method according to claim 1 or 2, characterized in that: The multi-source solid waste includes: 10-40 wt% coal gangue, 5-30 wt% waste carbon powder, 5-25 wt% blast furnace bag ash, 15-40 wt% aluminum ash, 3-15 wt% sintering ash, and 2-15 wt% converter secondary ash, preferably 15-30 wt% coal gangue, 10-25 wt% waste carbon powder, 10-20 wt% blast furnace bag ash, 20-35 wt% aluminum ash, 5-12 wt% sintering ash, and 5-12 wt% converter secondary ash.

4. The method according to any one of claims 1-3, characterized in that: The amount of multi-source solid waste added is 5-20% of the total mass of hot steel slag, preferably 5-18%, and more preferably 7-15%.

5. The method according to any one of claims 1-4, characterized in that: The temperature of the hot steel slag is 1400~1700℃, preferably 1450~1650℃, and more preferably 1500~1600℃.

6. The method according to any one of claims 1-5, characterized in that: In step 1), the reaction is a stirring reaction, and the stirring reaction time is 0.2~2h, preferably 0.3~1.5h, and more preferably 0.4~1h.

7. The method according to any one of claims 1-6, characterized in that: In step 2), the upper layer material accounts for 60-85% of the total mass of the mixed solid solution, preferably 65-80%, and more preferably 70-75%. Preferably, the phosphorus content in the upper layer material is no more than 0.5%, more preferably no more than 0.3%, and even more preferably no more than 0.2%.

8. The method according to any one of claims 1-7, characterized in that: In step 2), the intermediate layer material accounts for 3-25% of the total mass of the mixed solid solution, preferably 5-20%, and more preferably 10-15%. Preferably, the chlorine content in the intermediate layer material is not less than 0.3% by mass, more preferably not less than 0.5%, and even more preferably not less than 0.7%.

9. The method according to any one of claims 1-8, characterized in that: In step 3), the lower layer material accounts for 1-20% of the total mass of the mixed solid solution, preferably 3-18%, and more preferably 5-15%. As a preferred option, the lower layer material is recycled in step 1) multiple times (e.g., 3 to 8 times) before being discharged.

10. The method according to any one of claims 1-9, characterized in that: In step 1), during the reaction process, the generated gas is filtered using a ceramic membrane (preferably a negative pressure filter) and then discharged; the filtered dust is returned to the sintering feed.

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