Heat pump assisted sorption carbon capture with steam condenser heat recovery in a decarbonised coal-fired power plant

Abstract

More than 50% energy input of coal-fired power plant is lost in the condensation of steam turbine in a temperature range of 30–35 ℃. Carbon capture technology has a negative influence on power generation efficiency of coal-fired power plant. Thus, it is essential to find an efficient method for waste heat recovery and increase the overall energy efficiency in coal-fired power plant with carbon capture. A novel integrated system including absorption heat pump and adsorption carbon capture based on coal-fired power plant is then presented. Waste heat from steam condenser is recovered by absorption heat pumps driven by steam extracted from low pressure steam turbine. The output hot medium from the absorption heat pumps is further heated to desorption temperature for the regeneration process of adsorbents by the extracted steam. The results show that heat penalty increases with the increase of the desorption temperature, and the heat recovery amount has an opposite trend. Compared with the conventional coal-fired power plant, thermal efficiency of the integrated system increases by 0.854%. The efficiency decrease of the compression work accounts for over a half of the total efficiency decrease due to the compression and the capture process. External heat recovery is applied in flue gas and the multi-compression process, and the thermal efficiency increase can be improved to 1.453% when compared with 0.725% of the system without external heat recovery. It proves that absorption heat pump could play a significant role in the energy saving of adsorption carbon capture system.