Abstract: In order to obtain the requisite chimney temperature of cleaned gas discharged from a desulfurizing installation, and in order to avoid problems resulting at temperatures below the dew point of sulfuric acid in heat exchangers made of steel, the invention provides the following measures: the heat exchange between the crude gas stream and the cleaned gas stream is made in a first stage including conventional heat exchangers made of steel. An additional stage of heat exchangers between the crude and cleaned gas streams is constructed of corrosion-resistant and adhesion inhibiting plastic material and operating in a lower temperature range. Transfer conduits of corrosion-resistant material connect the lower temperature heat exchangers to forcibly transfer a heat carrying fluid.

Abstract: An air cooled surface consenser has a plurality of heat-exchange tubes extending transversely of the direction of air flow and each provided with heat-exchange fins. The interior of each tube is completely unobstructed and the tubes are of oval or elliptical cross section having a major interior dimension normal to their elongation which has a ratio of at least 6:1 with reference to a minor interior dimension which extends normal to the major dimension and the direction of elongation.