Process for treating calcium sulphate from flue gas desulphurisation units

摘要

In a process for treating calcium sulphate from flue gas desulphurisation units which are operated on a lime base, the calcium sulphate withdrawn in the form of the dihydrate from the flue gas desulphurisation unit is reacted with an aqueous solution of ammonia, ammonium carbonate or ammonium bicarbonate or a mixture thereof and with carbonic acid. The reaction products calcium carbonate and ammonium sulphate are separated from each other. The ammonium sulphate is withdrawn from the unit, while the calcium carbonate is directly returned to the flue gas desulphurisation unit. The ammonia, ammonium carbonate or ammonium bicarbonate required for treating the calcium sulphate is obtained at least in part from the gas purification of a coking plant.