| The industrial boilers are important equipments in the industrial field.The combustion process is the key link for industrial boilers in operation.The control quality is closely related to the operating efficiency of the boiler and pollution in combustion process.Hence,the control technology study of combustion process is one of the concerns of thermal power and control technology.The boiler combustion process is complex.The traditional control method can not relize contol for those complex obiects.The deveolpment of intelligent control technology provides an effective way to improve the quality of boiler combustion control.In this thesis,the furnace combustion unit in the industrial boiler control system is regarded as research object,and the varying offset control method is proposed to solve the problems of oxygen-excess and oxygen-deficient combustion for the double closed-loop cascade proportional control in the existing furnace combustion system.The above method increases the boiler combustion efficiency,and thus decreases the pollution from the boiler combustion.Firstly,this thesis briefly introduces the basic process flow and the excess air coefficient characteristic;then,builds the mathematical model of research object based on its basic principle.Secondly,analyzes the principle of single,double and varying bi-double crossing limit combustion control mode,then through the Simulink toolbox,simulates those control models and compares the control effect,and discusses the range of offset parameters(offset function,positive and negative offset of fuel and air)about the varying-offset double cross limiting control,then obtains the sub-optimal offset parameters.Thirdly,uses the intelligent genetic algorithm(GA)to search the suitable offset parameters,and applies the optimized parameters in the varying-offset cross-limiting combustion control system,to achieve the control target of furnace combustion.Finally,uses the Semi-physical simulation platform(SMPT-1000)to testify the control effects by varying bi-double crossing limitcombustion control method.The result shows that,improved control technology can not only increase the thermal efficiency,reduce the heat loss in combustion process,but also ensure the stability of export steam and remain the excess air coefficient in best combustion range with the load varying.Then the problems of peroxy and hypoxia combustion can be solved in the combustion process.Simulation and semi-physical simulation results show that,the combustion control technology optimized by GA improves the thermal utilization efficiency of fuels and reduces the pollutant and harmful gas from the boiler combustion.This techonolgy provides practical value for increasing the economic efficiency of industrial boilers and achieving energy-saving emission. |
