Process and system for treating waste salt slurry produced in production of sodium chlorate

Abstract

The invention discloses a process and system for treating waste salt slurry produced in production of sodium chlorate. The process comprises the following steps: (1) grinding of the waste salt slurry;(2) oxidation; (3) dissolving of chromium ions; (4) washing; and (5) reduction. The system comprises a grinding machine, an oxidation and dissolution system, a washing system, a reduction system anda wastewater regulating tank. The invention has the following advantages: the chromium ions wrapped in the waste salt slurry are released through grinding and crushing and are then removed from the waste salt slurry through oxidation, dissolution, washing, reduction and other treatment of the waste salt slurry, so the problems of great difficulty in treatment of chromium ions in waste salt slurryand incomplete removal of the chromium ions are overcome; and the chromium content of dechromed filter residues obtained after the treatment is subjected to leaching toxicity testing according to thenational standard (HJ / T299-2007) in China, and results prove that the content of Cr<6+> in leachate is 0 mg / L, the content of total chromium is 2.4mg / l, reaching the environmental protection comprehensive utilization standard (HJ / T301 2007), a reductive detoxification rate is 99.5%, and the chromium content of the treated waste salt slurry is below national standards in China and meets national environmental protection emission standards.

Description

Technical field: [0001] The invention relates to the field of industrial waste treatment, in particular to a treatment process and system for waste salt mud in sodium chlorate production. Background technique: [0002] In the production process of sodium chlorate, in order to catalyze the main reaction, reduce the amount of oxygen generated, control the pH value in the electrolytic cell, and remove the perchlorate ions produced by the electrolytic reaction, sodium dichromate needs to be added to the system; the production per ton Sodium chlorate needs to add about 0.118kg of sodium dichromate. At the same time, in the production process of sodium chlorate, in order to remove calcium ions, magnesium ions and sulfate ions in the raw salt, it is necessary to add sodium hydroxide, sodium carbonate, calcium chloride to the production system, and remove calcium ions, magnesium ions and sulfate ions Ion precipitation; during this process, the chromium ions added in the production ...

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Problems solved by technology

The patent No. CN101209873A "Chromium separation and recovery method containing hexavalent chromium waste residue" uses sodium carbonate or sodium bicarbonate as a mineralizer to increase Cr 6+ The dissolution rate, but the Cr in the waste salt mud 3+ Difficult to dissolve out, causing the total chromium content in the waste salt mud to exceed the standard

Notification number is CN105016387A patent "a kind of processing method of chromium salt mud", adopts adding oxidizing agent, leaching agent etc. to make the Cr in chromium salt mud 3+ Convert to Cr 6+ And dissolve to improve Cr 6+ The dissolution rate of the waste salt mud can improve the removal rate of chromium ions in the waste salt mud; but it has the following problems: 1. The waste salt mud particles are hard and difficult to dissolve, and it does not carry out any treatment on the waste salt mud. 3+ It is difficult to leach, and the treatment of chromium ions is not complete, and the total chromium content in the waste salt mud will still exceed the standard

2. Waste salt mud is produced by adding drugs to remove calcium ions, magnesium ions and sulfate ions in raw salt during the production of sodium chlorate, as well as perchlorate ions produced during electrolysis of sodium chlorate production. The waste salt mud treatment Finally, even if the dechroming solution is crystallized to remove sulfate, there are still a large amount of oxidants, leaching agents, reducing agents and other chemicals in the dechroming solution, as well as a large amount of perchlorate ions. If the liquid is directly returned to the chlorate production system, it will cause the enrichment of perchlorate ions in the sodium chlorate production system, which will seriously cause the system to explode, and there are extremely serious safety hazards; The agent contains more metal ions. Once metal ions such as barium ions enter the sodium chlorate production system, it will cause the anode of the electrolytic cell to fail. Excessive metal ions will increase the load on the sodium chlorate production system and affect the performance of the sodium chlorate production system. normal operation

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