Research On Optimization Control Technology Of Combustion System Of Coal-fired Boiler In Power Station

This paper focuses on the optimization control for improving the matching degree of wind and powder in the combustion system of power station boilers,and further improving the efficiency of boiler and reducing the amount of nitrogen oxide.The matching degree of wind and powder in the combustion process of boilers directly affects the economical operation of the generating units and environmental protection.Meanwhile,the above process has the characteristics of nonlinearity and strong coupling.Therefore,how to improve the matching degree of wind and powder in the combustion process has been a long-standing problem in the research of thermal engineering of power station.In this paper,the main factors that restrict the internal wind-powder matching and operational flexibility improvement of the boiler combustion system are explored.Some main constraints of the combustion process are divided into two aspects: the milling side and the furnace side.Then,in order to further analyze the variation characteristics of relevant operating parameters,a simulation model of the combustion system was constructed.The simulation model mainly includes three parts: the milling system,the furnace combustion channel and the auxiliary simulation system.It can reflect the variation characteristics of the internal parameters of the combustion system when the load command changes,which lays a foundation for the subsequent optimization control research.One of the main reasons for the poor matching effect of wind and powder in the furnace during combustion is that the control performance of the amount of powder into the furnace is poor due to the difficulty in accurately grasping the dynamic characteristics of the pulverizing system.On the one hand,the pulverizing system has large pure delay,on the other hand,it is greatly affected by the primary wind flow.Therefore,an improved Smith lag estimator is adopted in this paper to compensate the pure delay of the pulverizing process effectively.Additionally,on the basis of analyzing the influence characteristics of the primary wind on the powder yield,this paper explores the methods of improving the response characteristics of the pulverizing system through the primary wind feedforward,and provides two feedforward control ideas that can improve the response ability of the pulverizing system.At present,the research on the modelling,simulation and optimal control of combustion process inside the furnace mainly focuses on the black-box intelligent optimization algorithms but pays little attention to the internal mechanism of combustion process.Based on the analysis of the main factors affecting NOx generation and boiler efficiency in combustion process,the corresponding simulation calculation model is constructed,and a comprehensive evaluation index which can consider the economical operation of combustion process and environmental protection simultaneously is proposed in this paper.Based on the proposed comprehensive evaluation index,this paper also provides an online optimization method to realize the optimal trade-off of boiler efficiency and NOx generation.In the simulation experiment,this method can effectively deal with the contradiction between economy and environmental protection during the operation of combustion system,and thus realize the comprehensive optimization of combustion process.