GB419788A - Recovery of elemental sulphur - Google Patents

Abstract

<PICT:0419788/III/1> In the recovery of sulphur from gases containing sulphur dioxide by reduction with hot carbonaceous material, the sulphur dioxide is removed from the gases by a solvent, e.g. triethanolamine, aniline, pyridine or, preferably, a mixture of ammonium sulphite and ammonium bisulphite, the sulphur dioxide being recovered and the solvent regenerated by heat, and the dioxide reduced. The products of reduction are purified by passage through or over molten sulphur, preferably at 350 to 400 DEG C., after which the gases are rapidly cooled to a temperature above the melting point of sulphur but not exceeding 150 DEG C., the form of condenser being that described in Specification 419,787. As shown, gases containing sulphur dioxide, e.g. smelter or converter gases, all fed in at the base of an absorption tower 1 down which is passed a solution of the absorbing agent from a tank 2, the solution containing at 25 DEG C. 100 to 200 grammes per litre of ammonium sulphite and 700 to 800 of ammonium bisulphite. From the tower 1, the solution is pumped through a heat exchanger 4 to the top of a tower 5 where it is steam heated to boiling, the hot regenerated liquid returning through the heat exchanger 4 to the tank 2 and the sulphur dioxide passing through a dryer 15 to a gasometer 9 or direct to a heat exchanger 10 and thence, after admixture with air, to the base of the reduction furnace 11, to the top of which carbonaceous matter is fed. To remove impurities from the solvent solution, a portion of the liquid is diverted from the base of the tower 5 to a tank 7 where it is treated with sulphuric acid, the sulphur dioxide evolved being returned to the tower 5. From the tank 7 the liquid passes to a tank 8 for treatment with lime, the resultant ammonia being returned to the base of the tower 1. The reaction products from the furnace 11 pass through the heat exchanger 10 to a tower 12 where they are washed with molten sulphur to remove impurities and then passed to a condenser 13 of the kind referred to above.