Method for recovering thiocyanate from coke oven gas desulfuration and decyanation wastewater

Abstract

The invention discloses a method for recovering thiocyanate from coke oven gas desulfuration and decyanation wastewater. The method comprises the steps of: adding persulfate or sulfuric acid to polyamine salt wastewater for reacting with ammonium thiosulfate so as to generate ammonium sulfate and ammonium sulfite, and further oxidizing into ammonium sulfate and sulfur, thus the wastewater is changed into a two-component mixed liquid which contains ammonium thiocyanate and ammonium sulfate and is easy to separate by crystallization from a three-component mixed liquid, and high-efficiency separation is realized. The purity of the obtained ammonium thiocyanate crystal can reach 99%.

Description

Technical field

[0001] The invention relates to a method for recovering thiocyanate by using coke oven gas desulfurization and decyanation wastewater, in particular to a method for directly using coke oven gas desulfurization and decyanation wastewater to recover ammonium thiocyanate, ammonium sulfate and sulfur. Background technique

[0002] During the coking process of coal, about 30-35% of the sulfur is converted into hydrogen sulfide and other sulfides, which enter the coal gas together with hydrogen cyanide, forming gaseous impurities. Coke oven gas generally contains 5-8g / m of hydrogen sulfide 3 , Hydrogen cyanide 1-2.5g / m 3 . Hydrogen sulfide and hydrogen cyanide are highly corrosive and toxic, and cause extremely strong corrosion to production equipment and pipelines. They can also cause poisoning and deactivation of synthesis gas chemical reaction catalysts, which seriously affect the yield and quality of the final product.

[0003] For this reason, after the mixed gas is...