CN-121990698-A - Method for comprehensively treating solid waste and acid waste water of steel slag collaborative steel mill

CN121990698ACN 121990698 ACN121990698 ACN 121990698ACN-121990698-A

Abstract

The invention discloses a method for comprehensively disposing solid waste and acid waste water of a steel mill by utilizing steel slag, which is characterized in that the method is used for carrying out quality-dividing treatment on the thermal-state steel slag of a converter according to the alkalinity difference of the steel slag and respectively coupling the solid waste and the acid waste water of the steel mill to carry out comprehensive treatment, so that the method has the advantages of realizing low-cost treatment of the steel slag, other solid waste of the steel mill and the acid waste water, simultaneously substantially avoiding the discharge of three wastes, greatly reducing the discharge of the steel slag, realizing the recycling treatment of the solid waste of the waste water, simultaneously realizing the obvious full recycling of the steel slag, along with low overall operation cost, simple operation, convenient flow treatment, environmental friendliness and the like.

Inventors

YANG BENTAO
LI YONG
CHEN HONG
ZHOU XIANGQIU
LIU CHANGQI
CHEN YAO
LUO RUI

Assignees

湖南中冶长天节能环保技术有限公司

Dates

Publication Date: 20260508
Application Date: 20241101

Claims (10)

1. A method for comprehensively disposing solid waste and acid waste water of a steel slag collaborative steel plant 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) Sequentially cooling, crushing and magnetically separating the low-alkali thermal-state steel slag to obtain magnetic iron and phosphorus-containing slag, mixing the phosphorus-containing slag with waste acid for leaching reaction, carrying out solid-liquid separation after the reaction is finished 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) Mixing the leaching solution obtained in the step 3) with wet desulphurization wastewater to obtain mixed waste liquid, adding a weight removing agent and an oxidizing agent into the mixed waste liquid to perform weight removal and oxidation treatment, and performing solid-liquid separation after the treatment to obtain waste residue and waste liquid; 5) Adding a calcium agent into the waste liquid obtained in the step 4) to perform primary alkali adjustment precipitation treatment, performing solid-liquid separation to obtain struvite precipitation and high-calcium solution, continuously adding the calcium agent into the high-calcium solution to perform secondary alkali adjustment precipitation treatment, performing solid-liquid separation to obtain calcium phosphate slag and high-salt filtrate, recycling the calcium phosphate slag to the step 3), mixing the calcium phosphate slag with waste acid to perform leaching reaction, and performing recycling treatment on the high-salt filtrate to obtain calcium salt.
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. 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. The method according to any one of claims 1 to 3, wherein in the step 2), 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; Preferably, in step 2), the reaction is a stirred reaction, and the duration of the stirred reaction is 0.2 to 2 hours, preferably 0.3 to 1.5 hours, more preferably 0.4 to 1 hour.
5. A process according to claim 1 to 4, 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%.
6. A process as claimed in claim 1 to 5, 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 0.1%, 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 recycled for a plurality of (preferably 3 to 8) mixing reactions and discharged.
7. The method according to any one of claims 1 to 6, 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, in the step 3), the cooling mode is that compressed air is adopted for countercurrent heat exchange cooling, and the cooling rate is 30-100 ℃, preferably 40-80 ℃, more preferably 50-70 ℃; preferably, in the step 3), the compressed air cools the low-alkali thermal steel slag to obtain high-temperature hot gas, the high-temperature hot gas is subjected to waste heat utilization to obtain low-temperature gas, and the low-temperature gas is recycled to the step 3) and used as cooling air of the low-alkali thermal steel slag.
8. A process according to any one of claims 1 to 7, 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.
9. The method according to any one of claims 1 to 8, wherein in step 4), the mixing volume ratio of the leachate to the wet desulfurization waste water is 1 to 5:1, preferably 1.5 to 4:1, and/or In the step 4), the weight removing agent is sodium sulfide or a weight capturing agent, the adding amount of the weight removing agent is 0.05-2 g/L, preferably 0.1-1 g/L, and/or In the step 4), the addition amount of the hydrogen peroxide oxidized into hydrogen peroxide is 0.05-0.8 g/L, preferably 0.1-0.5 g/L.
10. The method according to any one of claims 1 to 9, wherein in step 5), the calcium agent is calcium oxide and/or calcium hydroxide; Preferably, the addition amount of the calcium agent is such that the pH of the waste liquid is 8-9.5, preferably 8.5-9, during the primary alkali adjustment precipitation treatment, and the addition amount of the calcium agent is such that the pH of the high-calcium solution is 9.5-11, preferably 10-10.5, during the secondary alkali adjustment precipitation treatment.

Description

Method for comprehensively treating solid waste and acid waste water of steel slag collaborative steel mill Technical Field The invention relates to treatment of solid waste and waste water in a steel mill, in particular to a method for comprehensively treating the solid waste and acid waste water in the steel mill by utilizing steel slag, belonging to the technical field of comprehensive treatment of the steel slag, the solid waste and the waste acid. 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. Meanwhile, steel plants contain a large amount of waste acid and waste water, such as cold rolling acid-containing waste water and sintering wet desulfurization waste water, the direct treatment cost is high, and as in Chinese patent CN110436671A, a zero emission treatment method and system for sintering wet desulfurization waste water, the ammonia nitrogen and magnesium ions are contained in the wet desulfurization waste water, phosphoric acid is added into the solution, so that the ammonia nitrogen is converted into magnesium ammonium phosphate to precipitate, and the ammonia nitrogen is removed. However, the method has the advantages of more expensive phosphate radical, finer sediment, more coagulant aid and a larger sedimentation tank. Disclosure of Invention Aiming at the problems of poor dephosphorization effect, large exhaust emission, high disposal cost caused by large exhaust emission and the like in the prior art when steel slag, solid waste, acid waste and the like of a steel mill are treated separately, the invention provides a method for comprehensively disposing the solid waste and the acid waste of the steel mill by the steel slag in cooperation with the steel slag, and the method for comprehensively disposing the solid waste and the acid waste of the steel mill by the coupling of different alkalinity of the hot steel slag of a converter. In order to achieve the technical purpose, the technical scheme adopted by the invention is as follows: a method for comprehensively disposing steel slag and solid waste and acid waste water of a steel plant comprises the following steps: 1) The steel slag discharged from the converter is divi