Research And Engineering Application Of Low Grade Energy Heating Technology For Large Coal-fired Unit

This thesis aims at the efficient use of the low grade waste heat power of steam turbine and reduce the loss of cold source to improve the energy efficiency of cogeneration unit.First of all,this thesis puts forward the energy saving method by the way of reducing the average temperature of heat source based on the energy analysis theory of heating process.According to this theoretical scheme,a heating system with low grade energy depth and cascade utilization is designed.Secondly,the low grade energy depth cascade heating system is formed by using 4 units of Shanxi Gujiao Xingneng thermal power plant as a case set.According to the local environment of the case set,the boundary condition of heating is determined.Then the single unit is modeled by the system simulation software Ebsilon,and then the single unit is connected in series,so as to realize the integration model of the system.Through simulation,the variable working condition calculation of the system is realized.The performance curves of the unit and the whole system are drawn to study the performance of the system deeply,as well as the adaptability of the system.Finally,the operation scheme of the heating system is designed and optimized based on the two thermal economic indicators:the average standard coal consumption rate and energy efficiency.Matlab programming is used to implement the optimization function,and the program is verified by using the actual heat network running data.In this thesis,the performance analysis and optimization research are carried out for the low grade energy depth cascade heating system.The thermal economy,energy consumption rate and heating capacity of the system in heating are calculated,and the influencing factors are analyzed and discussed preliminarily.The results show that the low grade energy depth cascade heating system has a good energy saving effect.It can improve the thermal economy of the heating system,reduce the average heat source temperature and effectively utilize the waste heat of the exhaust steam.It can also realize the principle of "temperature counterpart and cascade utilization" and the energy quality matching principle.The optimization results of the operation scheme of the system show that different heating operation schemes have significant influence on the thermal economy of the system.It is necessary to optimize the design of the system operation scheme according to the actual heating conditions.Therefore,the low grade energy depth cascade utilization technology is a high efficiency heating technology with the prospect of engineering application.