Thermodynamic Performance Analysis of a New CHP System With Absorption Heat Pump in a Direct Air Cooling Power Plant

Abstract

A new waste heat recovery scheme based on absorption heat pumps (AHP) applied in CHP (Combined Heat and Power) system was proposed to decrease heating energy consumption of existing CHP systems by recovering waste heat of exhausted steam from a steam turbine of coal-fired direct air cooling units. Based on the establishment of thermodynamic analysis model, through adopting the design parameters of the 135 MW direct air-cooled power plants in China, the performances, especially the exergy losses of the unit as well as its subsystems mainly including six parts at different heating modes were obtained at one specific load. Compared with conventional heating mode, when the thermoelectric ratio is 100%, the power output increases around 3.81 MW, coal consumption rate decreases 11.69 g/(kW·h) and total exergy loss decreases 6.892 MW under 100% THA load, while the energy and exergy efficiencies of the integrated system increase 1.29 % and 1.25 %, respectively. Additionally, the change laws of total exergy loss, energy and exergy efficiency of integrated system at different loads also were studied. The results provide not only theory basis and scientific support for the design of the coal-fired power plants with absorption heat pump recovering waste heat, but also a new scheme of energy saving and optimization for the units.