Process of purifying flue gases

摘要

In flue gases or other humid exhaust gases which contain NOx and SO2, the NOx content is reduced and the SO2 content is oxidized to SO3 by a catalytic processing and the SO3 content is subsequently condensed as sulfuric acid. In order to prevent a clogging and deterioration of the catalyst and a contamination of the sulfuric acid the flue gas is subjected before the catalytic processing to a fine dedusting by a scrubbing with hot dilute sulfuric acid. In dependence on the water content of the flue gases the concentration of sulfuric acid in the dilute sulfuric acid and the temperature of the latter are adjusted so that no water will be transferred from the flue gases to the dilute sulfuric acid and no water or only a small amount of water will be transferred from the dilute sulfuric acid to the flue gas.