Boiler Stack Gas Heat Recovery

摘要

This report is a detailed study of various heat recovery schemes for Navy shore facilities to use otherwise lost stack heat. The waste heat can be used alternatively to improve the boiler efficiency through feedwater and/or combustion-air preheating, or to lighten the boiler load through process-steam/water heating. The procedure for estimating the energy potential of a given flue-gas stream is explained in detail with sample plots. Based upon economic analysis for available options, three cost effective methods of recovering waste heat were identified; the conventional economizer, the direct-contact heat exchanger, and the indirect-contact condensing heat exchanger with temperature-raising by heat pumps, if appropriate. Important items such as materials, corrosion, maintenance, control, and retrofit are discussed. It is recommended that the entire process of selection and planning be incorporated in Computer Aided Engineering (CAE) software, and the conclusions be verified by testing in an actual retrofit unit.