Research On Peak Regulation Performance And Load Distribution Of High Back-pressure Combined Heat And Power Units

The high back-pressure cogeneration unit can recover the waste heat from the exhaust steam of the steam turbine,increase the heating capacity of the unit and realize the cascade utilization of energy.It is an efficient energy conversion and utilization way of primary fuel energy,and plays an important role in clean heating in northern China.At present,the structure of power system has changed,and the contradiction between heat and electricity in heating period is prominent.But due to the "heat-led" operation mode of the high back-pressure heating unit,its electrical load and heat load are interrelated,leading to limited peak regulation capacity.It is urgent to conduct in-depth research on the electric and heating load characteristics of high back-pressure cogeneration units,analyze the operation characteristics of high back-pressure heating units during winter while engaged in peak shaving of power system.On these basis,the corresponding operation strategies are formulated for the purposes of energy saving,emission reduction and peak regulation capacity improvement of heating units,so as for realizing the safe and stable energy supply and efficient operation of units.In this thesis,the operation strategy of high back-pressure cogeneration unit in different periods is studied.Firstly,the different heating way of the cogeneration units are introduced.Based on the second law of thermodynamics,the energy consumption analysis model,the variable condition calculation model and load distribution model of the high back pressure cogeneration unit are established respectively.Taking a 600MW subcritical unit as a case,the thermal system model of high back-pressure heating unit is built through Ebsilon simulation software.A modified model of the exhaust steam enthalpy value was established by using the fitting method.Combined with the thermodynamic system model and the modified model of the exhaust steam enthalpy value,the load characteristic range of the cogeneration unit was given to provide the load adjustment range for the subsequent analysis of variable working conditions.According to the boundary conditions of district heating network in the case study,the variation law of heating energy consumption of units under different heat load distribution is analyzed,and the operation strategy of cascade heating system in heating season is given.Analyze the performance of heating units under different back-pressures under different working conditions,obtain the best operating back pressure of heating units with high back pressure under different ambient temperatures,and ensure the lowest corresponding heating energy consumption.The variation law of coal consumption of cogeneration units under different power loads of heating system was summarized.Taking the minimum total fuel consumption as the optimization objective,the variation of coal consumption rate with load of each unit was analyzed.Optimal distribution of electrical load between two units was carried out according to the law of equal slight increase rate.According to the change of total electrical load demand,the operation strategy of two units was given to minimize the total fuel consumption.The performance of peak regulation in heating season of cogeneration system is analyzed.The results show that it is necessary to sacrifice economy while increasing the capacity of peak shaving.When the units deeply engage in peak regulation shaving of power system,the optimal operating back-pressure of the high back-pressure units and the optimal operating strategy of the cogeneration heating system are given,so as to provide theoretical guidance for the peak regulation of the high back-pressure heating units.