Recovering waste heat from flue gas of combined heat and power plants for district heating in China

Currently, the flue gas heat recovery rate is very low in China. But flue gas can contain a large amount of waste heat according to the heat balance of the boiler. In the meantime, flue gas heat loss also dominates different kinds of heat losses for a boiler. Therefore, it is necessary to reduce the flue gas temperature and recover sensible and latent heat for district heating purpose. This paper discusses the application mode of a flue gas scrubber for a combined heat and power (CHP) plant, calculate the flue gas recovery rate using absorption heat pumps and analyse the feasibility for a real case study in China. The results show that the maximum heat recovery rate is about 8% if the flue gas can be cooled down to 30°C, and the payback time for the flue gas scrubber is around 5 years.