Process for removal of ammonia, hydrogen sulfide and hydrogen cyanide

Abstract

Coke oven gases are washed with an aqueous metallic salt solution of sulfuric acid or sulfurous acid to absorb ammonia, hydrogen sulfide and hydrogen cyanide. The washing solution is then oxidized to recover elementary sulfur. A portion of the oxidized washing fluid is returned for continued washing of gas and a portion of the washing fluid is diverted to a separater where solid compounds which include metal hydroxide and metal cyanide compounds are removed leaving ammonium sulfate solution. The ammonium sulfate solution is heated with combustion air and in a heating agent to produce combustion products including nitrogen, hydrogen and an acid anhydride. The solid compounds from separater are conducted as a aqueous suspension to a reaction vessel wherein, at elevated temperature and pressure, hydrolysis products are formed including free ammonia, metal hydroxide and formate salts. The metal hydroxide is reacted with the acid anhydride in a condensation tower to form reaction products including an aqueous solution of the metal salt which is then conducted together with the formate salt products for further washing of the gas. The ammonia product from the hydrolysis process is returned for washing by the aqueous metallic salt solution and subsequent removal by combustion process.