METHOD FOR DIRECTLY PREPARING A SULPHATE OR SULPHATES FROM EXHAUST GASES CONTAINING SO2 GAS

摘要

1409593 Sulphur dioxide from gases OSAKA KOHAI CO Ltd 16 March 1973 [18 March 1972] 12734/73 Heading C1A SO 2 is removed from O 2 -containing waste gases and Ca or Mg sulphate prepared by contacting the gases in an alkaline region with an aqueous liquor containing a Ca- and/or Mg-containing compound and a Mn (II) salt in an amount sufficient to form MnO 2 with dissolved O 2 thereby forming a sulphite, contacting the resultant liquor in an acidic region with further waste gases to oxidize the sulphite to sulphate with the aid of O 2 in the waste gases. The Ca or Mg compound may be CaCO 3 , Ca(OH) 2 , Mg(OH) 2 , MgCO 3 and/or dolomite. The Mn (II) salt may be MnCl 2 or MnSO 4 in an amount of at least 0À00077 mol/l. Waste gases containing O 2 and 0À15% by vol. SO 2 may be scrubbed countercurrently by a slurry of Ca(OH) 2 and MnCl 2 sprayed via 10 into the alkaline region of tower 3. The CaSO 3 -containing liquor formed passes into the acidic tank 2 where the liquor is mixed with the incoming SO 2 and O 2 -containing waste gas which oxidizes the sulphite into sulphate. The acidic liquor is then passed to separator 6 to remove the solid CaSO 4 , the mother liquor then being recycled via make-up tank 7 to spray heads 10. MgSO 4 may be removed from the acidic liquor by neutralizing with Mg(OH) 2 , scrubbing with SO 2 gases and then cooling the resulting liquor.