THREE-STAGE HEAT EXCHANGER FOR COOLING FLUE GASES WITH MINIMAL CORROSION OF EXCHANGER; INTERMEDIATE COOLING BY FLUID INJECTION INTO GASES

摘要

The present invention relates to a heat-exchanger assembly for heating comfort air or process gas with the aid of consumed comfort air or used process gas in a heat-exchanger assembly which comprises at least three process stages. In the first stage (7), the temperature of the air or gas is lowered on the primary side down to the dew point temperature of the air or gas, primarily to precipitate acid. In the second stage (4, 12), the air or gas is cooled rapidly with water or cold air, and in the third stage (3) the temperature is further lowered, in the absence of corrosion attack on the heat transfer surfaces or surrounding parts. This is achieved by introducing water into the second stage or by introducing into the second stage air of low temperature and therewith of low moisture content. This air ''dries'' the air or gas arriving from stage one and prevents condensation from forming on the surfaces in stage three.