Metallgesellschaft Aktiengesellschaft

Stadtwerke Munster Gmbh

Norbert Olhms

Hugo Grimm

Karl-Heinz Dorr

Heinz Neumann

In flue gases or other humid exhaust gases which are relatively cold and contain SO.sub.2, NO.sub.2 and other gaseous pollutants, the SO.sub.2 content is oxidized to SO.sub.3 and the NO content is reduced by a catalytic treatment, the SO.sub.3 content is condensed as sulfuric acid and other gaseous pollutants are removed by being scrubbed with aqueous liquids at low temperatures. In order to heat up the flue gas to the temperature required for the catalysis, the flue gas is heated up in a first heating-up stage by an indirect heat exchange with the catalytically treated gas before the catalytic treatment, the heated-up gas is heated up further in a second heating-up stage to the temperature required for the catalytic treatment, the catalytically treated gas which has been cooled in the first heating-up stage is cooled further in an indirect heat exchanger below the dew point temperature of sulfuric acid and is subsequently fed to an SO.sub.3 condenser. The remaining sulfuric acid vapor is absorbed by sprayed dilute sulfuric acid to form a dilute sulfuric acid having a predetermined concentration, the gas leaving the SO.sub.3 condenser is scrubbed in a scrubber with a sprayed aqueous liquid and is thus cooled to 40.degree. to 60.degree. C. and the purified gas is reheated to the required chimney inlet temperature.

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Munich, Georgia

Norbert Olhms