Magnesium bisulphite recovery from waste gas - contg. magnesium oxide dust, by multistage washing with magnesium sulphite suspension (OE150376)

The recovery of the S and Mg in the form of technically pure Mg(HSO3)2 from the waste gases bearing MgO dust from a liquor combustion plant in a multistage washing process, in which the waste gas is washed with MgSO3 suspension in >=1 stage, comprises producing a water-insol. MgSO3 cpd. in a suspension at least in a second washing stage and sepg. from the suspension, then passing the suspension freed from coarse MgSO3 into a clarifier, in which the water-soluble impurities are drained from the water-insol. constituents and the remaining fine grained suspension is recycled to the second washing stage, whilst the coarse MgSO3 is passed to the first stage in the form of a suspension and converted to Mg(HSO3)2 by the SO2-rich waste gas stream. The prodt. is obtd. in very pure form.