GB710830A - A process for the preparation of cyano compounds from the waste liquors of fermentation indutsries - Google Patents

Abstract

Cyano compounds are recovered from waste liquors of fermentation industries by burning the concentrated waste liquor, e.g. 50 to 60 per cent. dry solids content, with a limited amount of air so that all or the greater part of the potassium sulphate in the liquor is reduced to potassium sulphide as in Specification 647,866, thereby simultaneously converting the nitrogen compounds to cyano compounds which are recovered from the ash obtained. Recovering may be by fractional crystallization but preferably the ash, dissolved in water, is treated as in Specification 647,866 by treatment with carbon dioxide to yield a gaseous mixture of hydrogen cyanide and hydrogen sulphide which are separately recovered. The potassium sulphate is converted to the carbonate. The hydrogen cyanide may be separated from the hydrogen sulphide by washing followed by fractional distillation and optional conversion with caustic soda to alkali metal cyanide or the hydrogen cyanide may be reacted with iron salts or oxides which are then treated with lime to form calcium ferrocyanide. The latter may be converted to potassium ferrocyanide with potassium chloride and carbonate.