Process gas treating apparatus

Abstract

An apparatus for condensing water vapor and vaporized solvent from process exhaust gas, such as from an industrial solvent drying oven process is described. The apparatus includes two parallel condenser assemblies which are alternately shifted between condensing and defrost modes. One of the assemblies is shifted into the condensing mode while the other is in the defrost mode and the other is shifted into the condensing mode while the one is in the defrost mode. When in the condensing mode, water vapor is condensed from the process exhaust gas in a water condenser such as a counterflow heat exchanger and solvent vapor is condensed therefrom by a solvent condenser such as a refrigeration coil positioned within a cold zone of the assembly. When in the defrost mode, a recirculating defrost loop is provided through which gas is circulated and heated for defrost purposes. Following defrosting, the defrosted condenser assembly is pre-cooled prior to shifting from the defrost mode back to the condensing mode. Valves are provided for shifting the condensing assemblies between the condensing and defrost modes and are positioned outside of the cold zone to minimize the effect of cold temperature on them.