Method for improving whiteness of sodium thiocyanate in coking desulfurization waste liquid

Abstract

The invention relates to a method for improving whiteness of sodium thiocyanate in coking desulfurization waste liquid. The method sequentially comprises the following steps: (1) pretreatment; (2) decolorization; (3) mixed salt concentration; (4) extraction, separation and decolorization; (5) refined salt concentration and crystallization; (6) refined salt washing and centrifugation. A sodium thiocyanate product with the whiteness of more than 80 is obtained after centrifugation. The extraction method provided by the invention is simple, the operation is convenient, and sodium thiosulfate and sodium sulfate in desulfurization and decyanation waste liquid produced in the PDS desulfurization production process of a coking plant are effectively separated, so that the high-purity sodium thiocyanate separation product is extracted; the extracted sodium thiocyanate has high whiteness and can meet the requirements as a pesticide or an active pharmaceutical ingredient; the emission of wastewater and the environmental pollution of the coking plant are reduced, the chemical raw material with high purity and high added value is simultaneously recovered, and the economic benefits of an enterprise are increased.

Description

technical field [0001] The invention relates to the technical field of utilizing coke oven gas desulfurization waste liquid, in particular to a method for improving the whiteness of sodium thiocyanate in coking desulfurization waste liquid. Background technique [0002] At present, some domestic coking plants adopt PDS wet desulfurization and decyanation process. The process has the advantages of high desulfurization and decyanation efficiency, small investment in equipment, and simple operation. However, this method does not match the corresponding waste liquid treatment technology. The waste liquid produced by PDS wet sodium desulfurization and decyanation process mainly contains sodium thiocyanate, sodium thiosulfate and sodium sulfate. Among them, sodium thiocyanate accounts for 18.5% to 24.5%, sodium sulfate accounts for 7.0% to 11.5%, and sodium thiosulfate only accounts for 0.5% to 1.5%, and the content is relatively small. [0003] At present, waste liquid treatme...

AI Technical Summary

Problems solved by technology

Because coking desulfurization waste liquid contains colored components such as sulfur, tar, catalyst (containing various non-ferrous metal ions or organic macromolecules) and phenol, the sodium thiocyanate extracted from it is yellow or black, that is, the whiteness is very low and cannot Meet the requirements of sodium thiocyanate as a pesticide or pharmaceutical raw material

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