Study On Energy Saving Of Power Plant Thermodynamic System Based On The Second Law Of Thermodynamics

In this paper, a 1000 MW Double Reheat Power Unit and a 1000 MW Ultra Supercritical Unit which is widely under commission and operation in China are taken as the recearch objects. And we take the exergy analysis and specific consumption analysis theory as analysis methods,these two analysis methods are based on The Second Law of Thermodynamics. After a theoretic analysis of the application of analysis method in the power plant thermodynamic system,the whole thermal system is divided into several parts according to the structure characteristic of unit and the transitive relation of refrigerant and energy exchange relationship. And then, the exergy analysis model and the specific consumption model for boilers system, steam turbines system, condenser system, heat regenerative system, pipeline system and their likes are established.On this basis, those analysis models are applied to calculate exergy loss and exergy efficiency of each unit equipments and the whole system.Then, the distribution of its specific consumption in the 1000 MW double reheat power unit and a 1000 MW Ultra Supercritical Unit are calculated.And analyze the reasons of each losses of exergy to work out some effective measures to save energy and provide evidence for optimization of thermodynamic system in both structural optimization and Parameter Optimization.In addition, based on the the matrix equation of exergy loss in regenerative system, quantitative calculation of influence of the the exergy loss of regenerative system which caused by parameters disturbance is made with the theory of differential.At last, considering the thermal parameters and structure characteristic of the 1000 MW double reheat power unit, a new optimal allocation scheme of feedwater pump is given.In this scheme the pressure boost of feedwater is completed by two feedwater pumps instead of one feedwater pump which is used commonly,and take a optimal selection of steam sources used for driving steam turbine which provide power for the feedwater pumps. The results showed that with the optimal selection of steam sources for the feedwater pumps,it can obviously decrease the coal consumption without considering the influence of the small steam turbine efficiency which caused by the changing of steam parameters used for driving steam turbine which provide power for the feedwater pumps.