Absorption of hydrogen sulphide from waste contg. carbon di:sulphide from viscose prodn. - in sodium hydroxide soln. contg. silicone oil or paraffin or alcohol

Spray columns are used as absorber and NaOH soln. as absorbent, with recovery of Na2S and/or NaHs soln., 0.0001-0.004 wt.%, w.r.t. the NaOH soln., of silicone oils and/or paraffins and/or alcohols are added to the absorption system. ADVANTAGE - Absorption effect is high, and there is negligible residual content (0.3%) of H2S, even with a high initial concn. (2000-3000 mg/cubic m). High quality solns. of Na2S and/or NaHS, with only small amts. of Na2S2O3, are obtd. In an example, 150 kg/h of H2S was led with a waste air stream of 50,000 cubic m/h into an absorber fed with 1500 1/h or NaOH (200 g/l of NaOH and 40 g/l of hemicellulose), giving conversion to a soln. contg. 120 g/l of Na2S and 40 g/l of NaHS. The amt. of Na2S2O3 formed was 28.5 g/l. During 24 h, 2 x 100 ml of polyalkylene glycol was added discontinuously, when the formation of Na2S2O3 fell to 7.5 g/l. The content of residual H2S was 0.3-0.1 wt.%, compared with an initial value of 1 wt.