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CN-121990537-A - Method for recycling converter steel slag

CN121990537ACN 121990537 ACN121990537 ACN 121990537ACN-121990537-A

Abstract

The invention discloses a method for recycling converter steel slag, which comprises the steps of mixing high-alkalinity steel slag and multi-source solid waste according to the alkalinity of the converter thermal steel slag, so as to obtain solid-solution and layered non-phosphate slag, high-chlorine slag and ferro-phosphorus slag, respectively recycling the non-phosphate slag, the high-chlorine slag and the ferro-phosphorus slag to corresponding working procedures of steel production for digestion, cooling, crushing and acid leaching the low-alkalinity steel slag, returning the obtained ferro-phosphorus slag to sintering for digestion, and respectively recovering iron phosphate and calcium chloride products after micro-electrolysis, oxidation and precipitation treatment of leaching liquid, thereby realizing zero emission of waste water. The invention carries out quality-classifying treatment on the steel slag according to the difference of the alkalinity of the thermal state steel slag of the converter, improves the harmless treatment effect of the steel slag, greatly reduces the outer discharge amount of the steel slag, is environment-friendly and has low treatment cost, realizes the synergistic and efficient treatment of different steel slag, solid waste and waste acid of steel plants through a simple and easy-to-operate process, has less waste gas emission and no waste water emission, and the required raw materials are all solid waste generated in the steel industry, and has low overall treatment cost and environmental friendliness.

Inventors

  • YANG BENTAO
  • YE HENGDAI
  • GAO XU
  • ZHOU XIANGQIU
  • CHEN HONG
  • ZHU GANG
  • LI YONG
  • ZHOU MO
  • Ji Guangheng

Assignees

  • 湖南中冶长天节能环保技术有限公司
  • 中南大学

Dates

Publication Date
20260508
Application Date
20241101

Claims (10)

  1. 1. A method for recycling converter steel slag is characterized by comprising the following steps: 1) The steel slag discharged from the converter is divided into high-alkali thermal state steel slag and low-alkali thermal state steel slag according to the alkalinity of the steel slag; 2) Adding multi-source solid waste into high-alkali thermal steel slag to perform a mixing reaction to obtain a mixed solid solution after the reaction is completed, collecting an upper layer material of the mixed solid solution and recycling the upper layer material as converter furnace charge, collecting a middle layer material of the mixed solid solution and recycling the middle layer material to be mixed with waste acid in the step 3) to perform a leaching reaction, collecting a lower layer material of the mixed solid solution and adding the lower layer material of the mixed solid solution into the high-alkali thermal steel slag to perform the mixing reaction in a recycling way, collecting dust generated in the mixing reaction process and recycling the dust to be mixed with the waste acid in the step 3) to perform the leaching reaction; 3) Cooling and crushing the low-alkali thermal steel slag, mixing the low-alkali thermal steel slag with waste acid, carrying out leaching reaction, carrying out solid-liquid separation after the reaction is completed to obtain iron slag and leaching liquid, recycling the iron slag as a sintering material, and carrying out subsequent treatment on the leaching liquid; 4) Sequentially carrying out iron-carbon micro-electrolysis and oxidation treatment on the leaching solution obtained in the step 3) and then carrying out solid-liquid separation to obtain ferric phosphate and waste liquid; Preferably, in the step 3), the low-alkali thermal steel slag is cooled by air to obtain high-temperature hot gas, the waste heat of the high-temperature hot gas is utilized to obtain intermediate-temperature gas, the intermediate-temperature gas is recycled to the step 4) to be used as dry hot air to obtain low-temperature waste gas, and the low-temperature waste gas is recycled to the step 3) to be used as cooling air of the low-alkali thermal steel slag after being combined with the air.
  2. 2. A process according to claim 1, wherein in step 1), the high-alkali hot steel slag has an alkalinity of more than 1.5, preferably more than 1.8, more preferably more than 2.0, and/or In step 1), the alkalinity of the low alkali thermal state steel slag is not higher than 2.0, preferably not higher than 1.8, more preferably not higher than 1.5.
  3. 3. The method according to claim 1 or 2, wherein in the step 2), the multi-source solid waste is mixed solid waste composed of coal gangue, waste carbon powder, blast furnace bag ash, aluminum ash, sintering ash and converter secondary ash; Preferably, the addition amount of the multi-source solid waste is 5-20% of the total mass of the high-alkali thermal steel slag, preferably 5-18%, and more preferably 7-15%.
  4. 4. The method according to any one of claims 1 to 3, wherein the multi-source solid waste comprises 10 to 40wt% of coal gangue, 5 to 30wt% of waste carbon powder, 5 to 25wt% of blast furnace bag ash, 15 to 40wt% of aluminum ash, 3 to 15wt% of sintering ash, 2 to 15wt% of converter secondary ash, preferably 15 to 30wt% of coal gangue, 10 to 25wt% of waste carbon powder, 10 to 20wt% of blast furnace bag ash, 20 to 35wt% of aluminum ash, 5 to 12wt% of sintering ash, and 5 to 12wt% of converter secondary ash.
  5. 5. The method according to any one of claims 1 to 4, wherein in step 2), the reaction is a stirred reaction for a period of 0.2 to 2 hours, preferably 0.3 to 1.5 hours, more preferably 0.4 to 1 hour.
  6. 6. A process according to claim 1 to 5, wherein in step 2) the upper layer material comprises 60 to 85%, preferably 65 to 80%, more preferably 70 to 75% of the total mass of the mixed solid solution, and/or In the step 2), the middle layer material accounts for 3-25% of the total mass of the mixed solid solution, preferably 5-20%, more preferably 10-15%, and/or In the step 2), 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%.
  7. 7. A process as claimed in claim 1 to 6, wherein in step 2) the phosphorus content of the upper layer is not more than 0.5%, preferably not more than 0.3%, more preferably not more than 0.2%, and/or In step 2), the chlorine content in the middle layer material is not less than 0.3%, preferably not less than 0.5%, more preferably not less than 0.7%; Preferably, in step 2), the lower layer material is circulated for a plurality of times (for example, 3 to 8 times) of mixing reaction and then discharged.
  8. 8. The method according to any one of claims 1 to 7, wherein in step 3), the cooling is to cool the low-alkali thermal steel slag to below 150 ℃, preferably below 120 ℃, more preferably below 100 ℃; preferably, the cooling mode is that compressed air is adopted for countercurrent heat exchange cooling, and the cooling rate is 30-100 ℃, preferably 40-80 ℃, and more preferably 50-70 ℃.
  9. 9. A process according to any one of claims 1 to 8, wherein in step 3) the crushing is carried out by grinding the cooled steel slag to a particle size of less than 2mm, preferably less than 1mm, and/or In the step 3), the pH of the leaching reaction is 1-4.5, preferably 2-4, the duration of the leaching reaction is 0.5-10 h, preferably 1-8 h, and the solid-liquid mass ratio of the leaching reaction is 1:3-30, preferably 1:5-20.
  10. 10. The method according to any one of claims 1 to 9, wherein in step 4), the duration of the iron-carbon micro-electrolysis is not less than 10min, preferably 20 to 60min, and/or In the step 4), the oxidation treatment is carried out for 10-60 min, preferably 15-45 min, after adding hydrogen peroxide, the addition amount is 0.5-2 g/L, preferably 0.8-1.5 g/L, and/or In the step 4), the calcium agent is calcium oxide and/or calcium hydroxide, the addition amount of the calcium agent is 2-12 g/L, preferably 3-8 g/L, and the drying is spray drying.

Description

Method for recycling converter steel slag Technical Field The invention relates to steel slag treatment, in particular to a method for recycling converter steel slag, and belongs to the technical field of steel slag and solid waste comprehensive treatment. Background The steel slag discharge amount in China is huge, the annual newly increased discharge amount exceeds 1 hundred million tons, and at present, the steel slag treatment mainly takes cement building materials as main materials, and the problems of low added value, low utilization rate (only about 40%) and the like exist. With the amendment of GB175-2023 general Portland Cement, it is explicitly stated that by the time of day 1 of 6.2024, steel slag can no longer be used as a mixed material for general Portland cement. Proper treatment of steel slag becomes a serious bottleneck problem of green sustainable development in the steel industry in China. The steel slag is rich in a large amount of iron resources, and the iron oxide reaches 15-25%, but the steel slag contains a large amount of harmful elements (phosphorus) of steel materials, so that the space for recycling the steel slag is limited. If the dephosphorization technology of the steel slag can be developed, the restriction of internal circulation smelting of the steel slag is broken through, the steel slag discharge can be greatly reduced, the production of building materials is not needed, and the source reduction and the resource circulation are realized. Aiming at the steel slag dephosphorization technology, chinese patent CN117778669A discloses a method for gasifying and dephosphorizing converter final slag and recycling dephosphorization slag, wherein a carbonaceous dephosphorization agent is added into the converter slag for gasifying and dephosphorizing, and the dephosphorization slag can be recycled to a sintering process. The method can effectively remove phosphorus and realize the circulation of steel slag, but has the problems of poor dephosphorization effect, poor slag-phosphorus separation effect and the like in practical application. Chinese patent CN110184399a discloses a "steel slag treatment method using two steps of oxidative desulfurization and reductive dephosphorization", wherein dephosphorization adopts gas-based reductive dephosphorization, and uses mixed gas of CO and CO 2 to convert phosphorus into phosphorus gas for removal, and the dephosphorization effect of the method is good and can reach 80%, but the method has high toxicity of phosphorus gas, and risk of personnel poisoning and explosion of mixed gas exists. Chinese patent CN110526745A discloses a method for separating phosphorus from dephosphorized steel slag and preparing phosphate fertilizer, firstly, oxidizing the dephosphorized steel slag in a molten state, cooling, crushing and leaching to obtain low-phosphorus residues and phosphorus-containing leaching solution, wherein the method can effectively remove and recycle phosphorus to a certain extent, but the steel slag amount is large, the produced byproduct waste water amount is too large, and the disposal cost is high. Disclosure of Invention Aiming at the problems of poor dephosphorization effect, large exhaust emission, large wastewater emission and the like in the prior art of steel slag treatment, the invention provides a method for recycling converter steel slag, which is characterized in that high-alkalinity steel slag and multi-source solid waste are mixed and reacted according to the alkalinity of the converter thermal steel slag, so that phosphorus-free slag, high-chlorine slag and ferrophosphorus slag which are in solid solution state and layered with each other can be obtained, and then are respectively recycled to corresponding working procedures of steel production for digestion, the low-alkalinity steel slag is cooled, crushed and acid leached, the obtained iron slag is returned to sintering for digestion, and leaching liquid is respectively recycled to obtain iron phosphate and calcium chloride products after micro-electrolysis, oxidation and precipitation treatment, so that zero emission of wastewater is realized. The invention realizes the high-efficiency treatment of different steel slag through a simple and easy-to-operate process, has less waste gas emission and no waste water emission, and the required raw materials are all solid waste generated in the steel industry, so that the method has low overall treatment cost and is environment-friendly. In order to achieve the technical purpose, the technical scheme adopted by the invention is as follows: A method for recycling converter steel slag, the method comprising: 1) The steel slag discharged from the converter is divided into high-alkali thermal state steel slag and low-alkali thermal state steel slag according to the alkalinity. 2) Adding multi-source solid waste into the high-alkali thermal state steel slag to carry out a mixing reaction, and obtaining a mixed solid solution afte