COMPARATIVE ENERGY AND EXERGY ANALYSIS OF A POWER PLANT WITH SUPER-CRITICAL AND SUB-CRITICAL

Abstract

The aim of this study that how to effect live steam parameters reheat and feed water preheater numbers on efficiencies of energy and exergy at coal-fired power plants. Moreover, two desuperheaters and a regenerative turbine are added USCPP (Case 3) to approach best results. Soma Power Plant (Case 1) consists of one reheat stage, two HPRHs and four LPRHs with one DEA. It is operated sub-critic and coal is used for a fuel. Live steam conditions of Soma Power Plant set at 13,92 MPa and 540 degrees C, and the reheat steam is reheated to 540 degrees C. Supercritical Power Plant (Case 2) consists of the same main components of Case 1. However, steam parameters of Case 2 are increased to 262.5 Bar and 600 degrees C to determine impact of the steam parameters on power plant efficiencies. USCPP which consists of two reheat stages, four HPRHs, six LPRHs with one DEA is designed to generate live steam under nominal conditions of 30 Bar and 600 degrees C. Besides, reheat steam are heated to 620 degrees C. Simulations have been carried out Ebsilon Professional software and pressure drops at preheaters and reheats are also considered. Some assumptions are made in the analysis. The thermal and exergy efficiencies of USCPP increase by 9.241 and 8.06 percentage points compared with Soma power plant, respectively. The results of this study that live steam parameters which are increased from sub-critical values to super-critical values have enormous influence on energy and exergy efficiencies. Secondly, adding second reheat stage has positive impact to improve power plant efficiencies. Finally, augmenting feed water preheater number, adding two desuperheater and one regenerative turbine increase power plant efficiencies. However, optimum numbers of feed water preheaters are determined considering economic parameters.