Method for extraction of high purity sodium thiocyanate from desulfurization waste liquid or desulfurization liquid mixed salt

Abstract

The invention discloses a method for extraction of high purity sodium thiocyanate from a desulfurization waste liquid or a desulfurization liquid mixed salt. The method comprises the steps of: 1) subjecting the desulfurization waste liquid to preliminary evaporation, conducting cooling to lower than certain temperature when reaching certain concentration, then taking alcohol as a solvent, and injecting the alcohol thereinto, and keeping the temperature above 48DEG C in the process; 2) then performing cooling to less than 48DEG C so as to make sodium thiosulfate therein and free water generate sodium thiosulfate of crystal water and make the generated product precipitate in the alcohol solution, and then separating the sodium thiosulfate from a small amount of impurities by filtration; and 3) concentrating the alcohol solution, cooling and recovering the evaporated alcohol, returning the product to the system to undergo recycling, and carrying out evaporation, concentration and crystallization, thus obtaining the high purity sodium thiocyanate. The method provided by the invention has the advantages of low production energy consumption, short process, simple operation, good product quality, and obvious economic benefits.

Description

technical field [0001] The invention relates to an extraction method, in particular to a method for extracting high-purity sodium thiocyanate from desulfurization waste liquid or mixed salt obtained from desulfurization liquid. Background technique [0002] In the coke production process, a large amount of gas will be produced, and the gas contains a certain amount of hydrogen sulfide and hydrogen cyanide. In order to avoid pollution to the atmosphere, the coke oven gas must be desulfurized and decyanidated. A large amount of desulfurization waste liquid will be generated during the treatment process. The components of desulfurization waste liquid are: sodium thiocyanate, sodium thiosulfate, water and a small amount of impurities such as sodium sulfate and sulfur. [0003] At present, the total amount of desulfurization waste liquid discharged by domestic coking enterprises is about 1 million tons, most of which are discharged directly without treatment, or mixed with cokin...

AI Technical Summary

Problems solved by technology

[0007] However, no matter which method the sodium thiocyanate product extracted is low in content and poor in quality, the sodium thiocyanate product produced by this type of method has a small market capacity, a low price, and meager profits, so that most enterprises do not Actively invest funds to treat desulfurization waste liquid, which is the root cause of inability to eliminate environmental pollution

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