Optimization Of Thermal System Parameters Of Double Reheat Unit Based On Energy Level Theory

Double reheat power generation technology is an important method to realize energy saving,emission reduction and sustainable development of the thermal power industry.The thermal system parameters of the double reheat unit have an important influence on its thermal economy,so further research is needed.Due to the existence of wet steam separator and fresh steam circuit in the secondary circuit thermal system of nuclear power plant,it is difficult to adopt general analysis methods for its thermal economy.This paper takes the double reheat unit and the secondary circuit thermal system as the research object,combined with the principles and methods of energy level theory,to carry out research on the optimization of the thermal system parameters of the double reheat unit and the economic evaluation of the secondary circuit thermal system.Aiming at the shortcomings of the current optimization methods for thermal parameters of the conventional power plant regenerative system,the particle swarm optimization is applied to the thermal parameter optimization of the regenerative system.On the basis of the standard particle swarm optimization,its inertia weight factor is improved.The test function example verifies that the improved particle swarm optimization has good solution accuracy and stability,and suitable for the parameter optimization problem of the thermal system of the double reheat unit.An optimization model with extraction steam pressure as the optimized variable and cycle thermal efficiency as the objective function was established for the thermal system of the double reheat unit through derivation,and it was verified by a 660 MW unit with main steam parameters of 31MPa/600 ℃ /620 ℃ /620 ℃ The model is optimized,and the improved particle swarm optimization and genetic algorithm are used for optimization.The optimization results show that the improved particle swarm algorithm has better convergence speed and accuracy.The influence of the feed water temperature,the number of regenerative stages,and the main steam parameters on the cycle thermal efficiency of the unit is analyzed.The results show that when only the distribution of feed water enthalpy rise is optimized,the cycle thermal efficiency of the unit is increased by 0.48% compared with the original design value;when the feed water temperature is also optimized,the cycle thermal efficiency of the unit can be increased by 1.4% compared with the original design value.When other thermal parameters are constant and the number of regenerative stages is increased,the cycle thermal efficiency of the unit will also increase,and the addition of a low-pressure heater will bring higher thermal economic benefits than the addition of a high-pressure heater;only the initial temperature is increased.The thermal efficiency of the cycle has a greater impact on the thermal efficiency of the cycle than simply increasing the initial pressure;the greater the initial temperature of the main steam,the greater the increase in the initial pressure on the thermal efficiency of the cycle.According to the energy level theory of the thermal systems,thermal system in the secondary circuit of a nuclear power plant is regarded as a coupling problem between the thermal system of the primary reheat unit and its internal energy level.Through decoupling analysis,the variation law of the efficiency of the secondary circuit thermal system with the system structure is gradually considered.Without increasing the complexity of the energy saving theory,the quantitative relationship between the efficiency of the secondary circuit thermal system and the structure of the system itself is obtained,and the correctness of the algorithm was finally verified with a 900 MW unit.Results show that in the secondary circuit thermal system of a nuclear power plant,the separator can not only improve the safety of the system,but also significantly improve the thermal economy of the thermal system.