Thermo-economic analyses of the waste heat and water recovery system from flue gas by heat pump integrated with different heat utilization ways in coal-fired power plant

Abstract

To recover the waste heat and water simultaneously from flue gas after wet desulphurization, a novel method by adding a flash evaporation device and heat pump system was proposed. The thermal-economic theoretical models for systems integrated with three different heat utilization ways were established based on the method of equivalent enthalpy drop. A typical 300 MW coal-fired power plant was selected as a case to compare the thermo-economic performance. Results show that when the flue gas temperature decreased from 50°C to 30°C, the amounts of recovered waste heat and water could be up to 65.2MW and 81.4t/h, respectively. At the same heat output of 11.3 MW from heat pump, the heat utilization way of pre-heating air exhibited the best energy-saving performance with the net efficiency of power plant increasing to 42.46% from 42.3%.