Design, manufacture, and performance evaluation of waste heat recovery unit in a gasification plant

Abstract

Johansson biomass gasification system is a standalone power generation system as it utilizes the syngas produced from the downdraft gasifier in an internal combustion gas engine for power generation. The syngas exiting the gasifier and entering the cyclone dissipates heat on the body of the cyclone due to the high temperature at which it exit. In addition this same syngas undergoes some cooling process at the gas scrubber before reaching the gas engine. As the gas engine drives the synchronous generator for power generation, some of the un-combusted gases exit through the exhaust pipe at high temperatures. All these add-up as waste heat within the gasification system, hence there is a significant opportunity for waste heat recovery in Johansson biomass gasification system. Syngas cleanup prior to its utilization in downstream application is a necessity due to the presence of contaminants such as carbon particles. The cleanup of syngas depends on the composition of syngas, further application requirement and economic consideration. Hence the choice and the design of a syngas cleaning process should be influenced by economic and energetic cost. Cold gas cleanup which is usually carried out at low temperature is considered as a conventional approach in syngas cleanup due to proven reliability and efficient removal of contaminants. However, cold gas cleanup result in significant loss of heat in the form of waste heat.