Sulphur di:oxide absorption in buffered weak acid soln. - with addn. of heavy metal cpd. to prevent accumulation of thiosulphate and sulphate

摘要

In the absorption of SO2 from gases by scrubbing with an aq. soln. of a weak inorganic or polybasic organinc acid buffered to pH 3-9 at 0-65 degrees C, with regeneration of the soln by expelling the absorbed SO2 at a temp. between 50 degrees C and the b.pt. of the soln., followed by cooling and recirculation, heavy metal cpds. (I) are added to (pt. of) the circulating soln., which form metal sulphides which are stable and scarcely soluble in the acid region. The addn. of (I) causes sepn. of thiosulphate and/or interrupts the chain reaction of conversion of thiosulphate to sulphate, so that the increase in the thiosulphate content and thus the sudden multiplication of the sulphate content is suppressed.