GB1181703A - A Process for Removing Sulphur Dioxide from Waste Gases - Google Patents

Abstract

1,181,703. Removing SO2 from gases. J. DERKA, R. KLIMECEK and V. VEVERKA. 28 March, 1967 [31 March, 1966], No. 14031/67. Heading C1A. SO2 is removed from waste gases in 2 stages, by contacting the gases (i) with an ammonium sulphite-bisulphite solution, which is regenerated (by boiling off an SO2/steam mixture then crystallizing out (NH4)2SO4) and recycled, and (ii) with the condensate obtained by cooling the SO2/steam mixture, this condensate then being passed to the first stage. The SO2/steam mixture may be precooled (and desorbed of any NH3) by passing it in heat exchange (14) with the loaded solution from the first stage absorber (13) before regeneration, and H2O is then condensed out (at 16) by cooling to 35‹ C. The condensates from heat exchanger (14) and condenser (16) are passed in heat exchange (17) with the SO2/steam mixture before it enters 14 to desorb any SO2, then cooled to 35‹ C. (18) and passed to a receiver (22), to which NH3 is also fed. Water may be added to receiver (22) or drawn off from cooler (18) as necessary. The second stage solution circulates through receiver (22) and second stage absorber (23) where it contacts the gas from absorber (13). The loaded solution from absorber (13) is regenerated (15) by boiling at 105-110‹ C., and cooled to 35‹ C. (19 and 20) to crystallize out (NH4)2SO4 which is centrifuged (21), the liquors being mixed with the solution from 22 and recycled to absorber (13). Some NH3 may also be added to the first stage circuit, and H2SO4 may be introduced, e.g. into regenerator (15) to increase the yield of (NH4)2SO4. This H2SO4 may have been used to dry the product SO2. The numerals refer to Fig. 2 (not shown).