Recovery of ammonia and sulphur dioxide from sulphuric acid containing ammonium sulphate or bisulphate

摘要

Ammonia and sulphur dioxide are recovered from aqueous sulphuric acid containing ammonium sulphate or bisulphate by heating the solution to 400 DEG -600 DEG C. in a reducing atmosphere. The solution used may be a by-product of the reaction of sulphuric acid with a cyanohydrin, e.g. acetone or ethylene cyanohydrin, to form acrylic or methacrylic acid derivatives and contains at least 50% by weight of free sulphuric acid, while the ammonia provides 5-15% of the weight of the solution. The solution is introduced in a finely dispersed form produced by spraying into the reducing atmosphere, which may comprise the combustion products of a gas or oil burner and may contain not more than 3%, preferably 2%, of free oxygen. The solution may be first combined with the combustion products of a gas or oil burner and then sprayed on to or passed through a bed of a heated solid material, e.g. coke, fire brick, aluminium oxide, or ceramic, at 450 DEG -520 DEG C. The solution may contain organic impurities, e.g. acetone disulphonic acid, which are capable of providing the reducing atmosphere. The sulphur dioxide may be oxidized back to sulphur trioxide.