CN-121974588-A - Process for treating overhaul slag by utilizing high Wen Mohai mixing ratio of calcium carbonate and sodium carbonate

Abstract

The invention discloses a process for treating overhaul slag by high Wen Mohai. Crushing aluminum electrolysis overhaul slag, mixing the crushed aluminum electrolysis overhaul slag with sodium carbonate and calcium carbonate, reacting the sodium carbonate with the overhaul slag at a high temperature to convert fluorine-containing compounds into soluble fluorides, and simultaneously mixing the calcium carbonate at the high temperature to convert the soluble fluorides into CaF 2 to achieve the effect of curing fluorine. The invention can effectively solve the problem of safe disposal of dangerous waste residues generated by electrolytic aluminum, so that the dangerous waste residues meet the environmental protection requirement, and further the purpose of comprehensive and harmless treatment of the waste residues generated by electrolytic aluminum overhaul is realized.

Inventors

• SUN ZE
• YANG XIAOBO
• HAN QIMING
• WANG GUANGLE
• XU YANXIA
• ZHANG HAITAO

Assignees

• 青海民族大学
• 华东理工大学
• 青海省新型建材工贸有限责任公司

Dates

Publication Date

20260505

Application Date

20251128

Claims (10)

1. 1. A process for treating overhaul slag by utilizing high Wen Mohai mixing height of calcium carbonate and sodium carbonate is characterized by comprising the following steps: a) Pretreatment, namely crushing and screening the overhaul slag, and then carrying out magnetic separation to remove ferromagnetic substances in the overhaul slag; b) Mixing, namely mixing the overhaul slag pretreated in the step a) with calcium carbonate and sodium carbonate according to the mass ratio of 100 (10-30) to 5-20 to obtain a mixed material; c) High temperature calcining, namely placing the mixed material obtained in the step b) into a high temperature furnace, and calcining in two stages under the air atmosphere; The first stage of calcination, namely, raising the temperature from room temperature to 800-950 ℃ at a temperature raising rate of 5-15 ℃ per minute; The second stage of calcination, namely continuously heating to 1100-1300 ℃ at the temperature rising rate of 5-15 ℃ per minute; d) And (3) post-treatment, namely cooling and crushing the calcined product in the step c) to obtain a harmless solid product.
2. 2. The process for treating overhaul slag by utilizing the mixed height Wen Mohai of calcium carbonate and sodium carbonate according to claim 1, wherein in the first-stage calcination, the temperature is raised to 800-950 ℃ from room temperature, and then the temperature is kept for 30-90 minutes; in the second stage calcination, after the temperature is raised to 1100-1300 ℃, the temperature is kept for 60-120 minutes.
3. 3. The process for treating overhaul slag by utilizing the high Wen Mohai percent of mixing calcium carbonate and sodium carbonate according to claim 2, wherein the calcining temperature in the first stage is 850-900 ℃, the heat preservation time is 50-70 minutes, the calcining temperature in the second stage is 1150-1250 ℃, and the heat preservation time is 80-100 minutes.
4. 4. The process for treating overhaul slag by utilizing the high Wen Mohai% mixing ratio of calcium carbonate and sodium carbonate according to claim 2, wherein the temperature rising rate of the first stage calcination is 5-10 ℃ per min, and the temperature rising rate of the second stage calcination is 5-10 ℃ per min.
5. 5. The process for treating overhaul slag by utilizing the high Wen Mohai percent of calcium carbonate and sodium carbonate mixture as claimed in claim 1, wherein the crushing in the step a) adopts a jaw crusher and a hammer crusher for combined crushing; The screening adopts a vibrating screen.
6. 6. The process for treating overhaul slag by utilizing the high Wen Mohai percent of calcium carbonate and sodium carbonate mixture as claimed in claim 1 is characterized in that the particles with the particle size smaller than 5mm are obtained after screening in the step a), and the magnetic separation in the step a) is performed by utilizing a magnetic separator.
7. 7. The process for treating overhaul slag by using the high Wen Mohai% mixing ratio of calcium carbonate and sodium carbonate according to claim 1, wherein in the step d), the cooling mode is furnace-following cooling or natural cooling in air.
8. 8. The process for treating overhaul slag by utilizing the high Wen Mohai percent of calcium carbonate and sodium carbonate mixture as claimed in claim 1, wherein the overhaul slag is aluminum electrolysis bath overhaul slag produced in the aluminum electrolysis industry and comprises aluminum oxide, fluoride, cyanide, carbide, sodium salt and a small amount of heavy metal.
9. 9. The process for treating overhaul slag by using high Wen Mohai% mixing ratio of calcium carbonate and sodium carbonate according to claim 1, wherein in the step d), the leaching concentration of fluorine in the obtained harmless solid product is lower than 100mg/L.
10. 10. The process for treating overhaul slag by using the high Wen Mohai% mixing ratio of calcium carbonate and sodium carbonate according to claim 1, wherein in the step d), the obtained harmless solid product can be used as a cement admixture, a concrete admixture or a road subgrade material after being crushed.

Description

Process for treating overhaul slag by utilizing high Wen Mohai mixing ratio of calcium carbonate and sodium carbonate Technical Field The invention relates to the technical field of environmental protection and solid waste treatment, in particular to a harmless treatment and recycling process of overhaul slag generated in the electrolytic aluminum industry, and especially relates to a method for stabilizing pollutants in overhaul slag by using calcium carbonate and sodium carbonate as a composite curing agent and through high-temperature calcination. Background The overhaul slag is solid waste generated when the aluminium electrolysis cell is operated for years and the lining materials (such as cathode carbon blocks, refractory bricks, insulating bricks and the like) are corroded and damaged by molten electrolyte and metal aluminium, so that the aluminium electrolysis cell has to be subjected to overhaul. The main components of the electrolyte comprise aluminum oxide (Al 2O3), cryolite (Na 3AlF6), fluoride such as sodium fluoride and calcium fluoride, cyanide (such as NaCN, na 4Fe(CN)6, etc.), aluminum carbide (Al 4C3) and a small amount of heavy metal (such as lead, cadmium, arsenic, etc.) generated in the electrolytic process. The major repair slag is listed by the country as hazardous waste (HW 48), the hazard of which is mainly expressed in: 1. the water-soluble fluoride has high content, and can release high-concentration fluoride ions (F -) when being leached by water or rainwater, pollute soil and underground water and endanger animal and plant health and human health. 2. Contains highly toxic cyanide, which is a highly toxic substance and constitutes a serious threat to the environment and the ecosystem. 3. Heavy metal leaching risk that under acidic conditions, heavy metals in the slag may be leached out, causing heavy metal pollution. At present, the treatment method of the overhaul slag mainly comprises the following steps: The landfill method is to simply landfill the overhaul slag or landfill after solidification. The method occupies a large amount of land, has long-term environmental leakage risk, does not fundamentally eliminate pollution, belongs to a passive treatment mode, and is gradually eliminated. And the hydraulic flushing method is to flush out soluble fluoride and cyanide in the overhaul slag by using water and then treat the flushing liquid. The method can remove part of soluble salts, but can generate a large amount of wastewater with high salt, high fluorine and high cyanide, has high treatment difficulty and high cost, and can not treat insoluble fluoride and solidified heavy metal. High temperature incineration/melting process-melting the overhaul slag at high temperature (typically > 1300 ℃) to decompose organics (including cyanide), fluoride goes into flue gas or forms stable minerals, heavy metals solidify in the slag. The method has the advantages of thorough treatment effect, extremely high energy consumption, severe equipment requirements, huge operation cost, complex flue gas treatment system and easy secondary pollution. The chemical stabilization method is to add curing agents such as cement, lime, fly ash and the like, and fix pollutants through physical wrapping and chemical reaction. The method has low cost but poor long-term stability, and under complex natural environment (such as acid rain), the fixed fluoride and heavy metal can be leached again, and the risk of 'timing bomb' exists. Therefore, the development of a new process for harmless treatment of the overhaul slag, which has the advantages of high treatment efficiency, low operation cost, environmental friendliness and capability of realizing resource utilization, is an urgent need for sustainable development of the current aluminum industry. Disclosure of Invention Therefore, the invention aims to solve the technical problem of overcoming the defects of the prior art and providing a process for treating overhaul slag by utilizing the high Wen Mohai mixing ratio of calcium carbonate and sodium carbonate. The process aims to efficiently and thoroughly remove cyanide in the overhaul slag with lower cost and energy consumption, convert soluble fluoride into a stable and low-solubility mineral phase, and simultaneously solidify heavy metal, so as to finally obtain a stable product capable of being recycled. The technical scheme of the invention is that the process for treating overhaul slag by utilizing the high Wen Mohai mixing ratio of calcium carbonate and sodium carbonate comprises the following steps: a) Pretreatment, namely crushing and screening the overhaul slag, and then carrying out magnetic separation to remove ferromagnetic substances in the overhaul slag; b) Mixing, namely mixing the overhaul slag pretreated in the step a) with calcium carbonate and sodium carbonate according to the mass ratio of 100 (10-30) to 5-20 to obtain a mixed material; c) High temperature calcining, namely placing the mixe