Establishment And Application Of EPR1750MW Nuclear Power Unit Thermal Economic Analysis Model

With the economic development,China's energy consumption will continue to grow.While the increase in environmental pollution,once again lead to the whole of society to coal-led energy structure of the reflection.The safety of nuclear power development has become an irresistible trend.Under such circumstances,it is of great significance to improve the thermal economy of the nuclear power plant,reduce the cost of power generation,and ensure the safe operation of the unit.In this paper,by comparing the thermodynamic system of nuclear power unit with that of conventional thermal power unit,combining with the characteristics of the secondary circuit thermal system of PWR nuclear power plant,taking the domestic EPR1750 MW nuclear power unit as an example to establish a general mathematical model,which is easy to use matrix analysis method to analyze thermal economy of nuclear power unit.On this basis,an energy efficiency analysis model of multi-element perturbed thermodynamic system is established,and the mapping rules,structural characteristics and rules of usage of the model are explained.Finally,the sensitivity modulus of multi-parameter disturbance to unit energy efficiency are calculated.The main contents and conclusions of this paper are as follows:Firstly,we analyze the characteristics of PWR EPR1750 MW nuclear power unit thermal system,and establish the unified physical model of thermal economic analysis of nuclear power unit.The accuracy of the model is further proved by comparing the conventional heat balance method to the calculation of extraction coefficients at all levels.On the basis of the unified physical model,the circulating heat absorption equation,the steam turbine internal work equation and the thermodynamic system steam-water distribution equation of the original system are decomposed into the equations of the control units at all levels and transformed into matrix equations.Finally we can obtain the mathematical model of thermal economic analysis.Then we deal with the energy efficiency matrix by equation differential calculus,We can obtain the parameters affecting the energy efficiency of the unit,making the unit energy-saving targeted.Secondly,We analyze the thermal economy of nuclear power plant by multi-parameter perturbation.The multivariate parametric perturbation includes the wide-area parameters and the local parameters.Among them,the wide-area parameters mainly include the main steam pressure,the main steam temperature,reheat steam temperature.The local parameters mainly include the parameters of the heater and the parameters of the auxiliary steam-water.We can calculate the influence of multi-parameter perturbation on the energy efficiency of the unit.Furthermore the relative intensity coefficient of each disturbance to energy efficiency is obtained,which represents the degree of influence on the unit energy efficiency changing for every 1% variation of the parameter perturbation.By calculating and analyzing,we can draw the following conclusions:a)For wide-area parameter perturbation,under rated operating conditions,the relative sensitivity of the main steam pressure is 0.028561,the relative sensitivity of the main steam temperature is 0.10288,and the relative sensitivity of reheat steam temperature is 0.064933.At the same time,the staff should pay special attention to the main steam pressure and reheat temperature changes when in low load and pay attention to the main steam temperature changes in the high load.In a certain range,if the main steam pressure,the main steam temperature,reheat steam temperature increases,the unit energy efficiency will improve.b)For the local parameter disturbance,when the heater pressure drop and the upper difference increases,the energy efficiency of the unit will reduce.At the same time the extraction steam pressure loss of 1,3,4 number heater is relatively high sensitivity,so we should pay special attention to 1,3,4 number of heater extraction steam pressure loss changes.The upper difference of 1,4 number heater is relatively high sensitivity,so we need pay special attention to the 1,4 heater.Therefore,during the maintenance and overhaul of the unit we pay attention to changes in the number of heaters 1,3,4,in order to effectively improve the operating efficiency of the unit.c)The relative sensitivity of wide-area parameter disturbance is 100 ~ 1000 times greater than that of local disturbance.Therefore,in the unit maintenance operation,we should give priority to control the working fluid temperature,to reduce the working fluid temperature disturbance on the unit energy efficiency adverse effectsThirdly,The energy efficiency analysis of the EPR1750 MW nuclear power plant has proved the usability of the model and pointed out the key factors affecting the energy efficiency of the unit,which provides a theoretical support for unit operation supervision and improves unit thermal economy.