Optimal Design Of Denitration Control System In Thermal Power Plant

With the increase of the total capacity of the thermal generator assembly and the enhancement of the environmental awareness of the domestic people,the emission standard of NOx in China is bound to be further improved.A denitration technology of selective catalytic reduction(SCR)denitration technology is widely used because of its advantages of high denitration efficiency,small secondary pollution and mature technology.However,the traditional control strategy of SCR system can play a certain role,but it can't meet practical demands in terms of rapidity and accuracy.The research on the mathematical model of SCR system and control strategy can provide technical means to realize nitrogen oxide emission standard in power plant,and it has application value in improving the field control effect.In this paper,the SCR flue gas denitration system of a power plant unit is taken as the research object,and correlation analysis of factors influencing denitration efficiency has been done.An multi-dimension ARX model of the SCR denitration system is established by using time-series data and mechanism of the denitration process,and the least square method is used for parameter identification of the model.Lastly,the accuracy of model identification is verified by simulations,and results show that the model fits well and validates its effectiveness.The model can approximately reflect the dynamic properties of denitration system in power plant,and provides a model reference for automatic control of ammonia injection and efficient reduction of NOx emission.In this paper,the model is used to study the control strategy of ammonia injection in the SCR denitration system.The internal model controller is designed to realize denitration control,which is better than the traditional PID control.In order to reduce the influence of uncontrollable input and disturbance,unit load and inlet concentration of NOx,etc.are used to design a feedforward controller.The control system reduces the SCR operation cost while ensuring the discharge up to the standard,accurately controls the ammonia injection quantity on the premise of ensuring the denitration efficiency,avoids the adverse effect of excessive ammonia injection on the safe and stable operation of SCR downstream equipment.And it is verified for cases of variable load and AGC operation,and works well.Finally,the Kingview is used to realize online monitoring,and Data exchange platform is built by using the OPC technology to complete data exchange between the control system and the plant.The control algorithm is programmed by using VC.The control system has been installed on the denitration site,and it needs further verification and debugging.The preliminary verification results show that the control system has good control effect,strong stability and practicability,and it can be used in thermal power plants.