Thermodynamic performance analysis of a novel electricity-heating cogeneration system (EHCS) based on absorption heat pump applied in the coal-fired power plant

摘要

A novel electricity-heating cogeneration system (EHCS) which is equipped with an absorption heat pump (AHP) system to recover waste heat from exhaust steam of the steam turbines in coal-fired thermal power plants is proposed to reduce heating energy consumption and improve the utilization of the fossil fuels in existing CHP (Combined Heat and Power) systems. According to the first and second thermodynamic law, the changes of the performance evaluation indicators are analyzed, and exergy analyses for key components of the system are carried out as well as changes of exergy indexes focusing on 135 MW direct air cooling units before and after modification. Compared with the conventional heating system, the output power increases by about 3.58 MW, gross coal consumption rate and total exergy loss respectively reduces by 11.50 g/kW h and 4.649 MW, while the total thermal and exergy efficiency increases by 1.26% and 1.45% in the EHCS when the heating load is 99,918 kJ at 75% THA condition. Meanwhile, the decrement of total exergy loss and increment of total exergy efficiency increase with the increasing of the heating load. The scheme cannot only bring great economic benefits but also save fossil resources, which has a promising market application potential. (C) 2015 Elsevier Ltd. All rights reserved.