EFFICIENT METHOD OF NEUTRALIZING CYANIDE-CONTAINING GASEOUS WASTES AND WASTE WATER IN A METHOD OF PRODUCING ALKALI METAL CYANIDES Russian patent published in 2020 - IPC C01C3/10 B01D53/14 B01D53/34 

FIELD: chemical industry.

SUBSTANCE: method of producing alkali metal cyanides in form of solid substances involves absorption of hydrogen cyanide from a reaction gas containing hydrogen cyanide, in an aqueous solution of an alkali metal hydroxide to obtain an aqueous solution of an alkali metal cyanide. Further, a first combustion step is carried out, on which gaseous wastes containing cyanide are subjected to sub-stoichiometric combustion at temperature of 1000–1500 °C and ratio between existing oxygen and stoichiometrically required oxygen, making from 0.75 to 1. Obtained reaction mixture is cooled down to 800–950 °C is a method of introducing an aqueous solution. Reaction mixture obtained as a result of cooling is subjected to second stage of combustion by supplying additional oxygen in super stoichiometric conditions at temperature from 700 to not more than 1000 °C and ratio between provided oxygen and stoichiometrically required oxygen, making from not less than 1 to 2.5. Then, crystallisation is carried out by adding an alkali metal cyanide solution to an evaporative crystallizer which is heated while providing pressure below atmospheric pressure, and condensation of cyanide-containing vapors to form a cyanide-containing steam condensate. Thereafter, the cyanide-containing steam condensate is recycled as the aqueous solution to the stage of cooling the reaction mixture.

EFFECT: invention increases environmental friendliness of producing alkali metal cyanides by reducing formation of gaseous wastes and waste water.

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