GB1331561A - Treatment of gases - Google Patents

Abstract

1331561 SO 2 removal from gaseous effluents BRITISH GAS CORP 29 Feb 1972 6552/71 Heading C1A SO 2 is removed from an effluent gas stream by passing a major portion of the stream together with H 2 over a first catalyst bed thereby producing a gas stream containing H 2 S, and then passing this stream together with air and the remaining minor portion of the effluent stream over a second catalyst bed thereby converting the SO 2 and some of the H 2 S and into elemental S, condensing the S formed and then passing the resulting H 2 S stream to an H 2 S stripping stage. The first and second catalyst beds may be a catalyst of NiO-MoO 3 , CoO 3 -MoO 3 , uraniathoria, urania-MoO 3 or mixtures thereof on a support. The preferred catalysts are NiO (1-5%)-MoO 3 (3-10%); CoO (1-4%)- MoO 3 (11-16%); MoO 3 (1-20%)-urania (2-15%); the percentages being calc. as the wt. of the metal based on the total wt. of the catalyst. The supports may be active Al 2 O 3 , bauxite, corundum, silica, kaolin, powdered brick, and/or alkaline earth metal oxide. The temp. of the catalyst beds is preferably 300- 350‹ C. The H 2 S stripping step may be carried out by passing the gas stream over ZnO or washing the gas with a soln. of sodium vanadate and the disodium salt of anthraquinone disuiphonic acid. The SO 2 effluent containing, e.g. 10-15% SO 2 , may be that obtained by removal of the S content of fuel oils by means of heating the oil in a fluidized bed of active CaO granules, CaS being formed and the S then removed as SO 2 from the CaS by heating in a second fluidized bed supplied with air, the CaO then being recycled to the first bed. The major stream may contain 75% of the total effluent gas. The remaining 25% is preferably contacted with the H 2 S stream from the first catlyst bed and air in a water condenser prior to being reheated and passed through the second catalyst bed.