GB1411330A - Process for desulphurisation of waste gas - Google Patents

Abstract

1411330 Desulphurization of waste gas; sulphur TSUKISHIMA KIKAI CO Ltd 19 Sept 1973 43928/73 Heading C1A Waste gas containing an oxide of sulphur is desulphurized by (i) contact with an aqueous alkaline alkali metal containing solution to produce a desulphurized gas and a sulphur containing aqueous solution, (ii) pyrolysing the sulphur containing aqueous solution from (i) under reducing conditions to form an H 2 S containing gas stream having entrained alkali metal solids, (iii) separating the entrained solids from the gas stream, (iv) cooling the separated gas to form an aqueous condensate and a H 2 S containing residual gas, (v) mixing the solids from (ii) with the condensate from (iv) to form an aqueous alkali-metal containing solution, (vi) oxidizing any sulphides in the aqueous solution from (v), (vii) recycling at least a portion of the oxidized solution from (vi) to (i), and (viii) oxidizing the H 2 S containing residual gas from (iv) to recover elemental sulphur. Step (viii) may comprise (a) contacting the gas from step (iv) which contains residual H 2 S with an alkaline aqueous alkali-metal containing solution containing a catalyst for H 2 S oxidation to absorb H 2 S and obtain a sulphur-containing solution, (b) contacting the aqueous solution from (a) with oxygen to form elemental sulphur, (c) separating the elemental sulphur from the catalyst-containing solution, (d) adding a portion of the alkali-metal containing aqueous solution from step (vi) to the catalyst containing solution from (b), (e) recycling a portion of the catalyst-containing solution after treatment as in (c) and (d) to step (a), and (f) recycling a portion of the catalyst-containing aqueous solution from (c) to pyrolysis step (ii) for pyrolysis together with the aqueous solution from step (i). The preferred aqueous absorbing solution used in step (i) is aqueous sodium carbonate.