Research On The Control Of Coal Feedforward And Combustion Optimization Of Supercritical Units

At present,energy and environmental problems become increasingly prominent,the supercritical units are increasingly becoming the developmental trend of thermal power plant due to the characteristics of high efficiency and low energy consumption.The combustion control system of the supercritical units is an important part of the whole control system.At present,most coal-fired power plants have wide sources of coal and large calorific value deviation,which seriously affect the control of the combustion system.The control level further affects the safety and economy of the whole unit.Therefore,it is necessary to study a kind of coal self-adaptive control strategy which is suitable for supercritical units,to improve the safety and economy of unit operation and to optimize the control system of supercritical units.This paper design the adaptive coal feed-forward correction to work coefficient of coal as a starting point,by means of the combination forecast model ideas to establish a prediction model of coal into the furnace,the optimal fixed weight coefficient by 1 hour before the work of coal coefficient of a preliminary forecast for the current work of coal coefficient,through the grid instruction further regulation in the coal,the coefficient of boiling coal power coal and coal into the furnace coal forecast,to improve the accuracy of the coal into the furnace.Boiler combustion system is a typical complex industry control system,is a strong coupling,nonlinear,big inertia,change disturbance in fierce multivariable input and output of the system,air volume,ventilation rate,which send to the parameters,such as coal to fluctuations will have an effect on the combustion system,influence the safe operation of boiler.Classic PID control is difficult to the requirements of both dynamic and static index,difficult to satisfactory control effect and cause the control quality is not high,raw material consumption is too large,the more serious threaten to the production equipment and the safety of the operator.Is inheriting traditional thoughts of the PID that "to eliminate the deviation based on the deviation" and combining the immunity Control technology at the core of the thought "with the proper wave process to guide" of the object,on the basis of designing the Intelligent trajectory guidance controller(Intelligent Track behind the Control,ITGC),and its application to the coal quantity in the feedback Control system.By means of the concept of coal quality correction coefficient,the control scheme of combustion system is established.The main steam pressure is an important parameter to characterize the energy supply and demand of the supercritical unit.At present,most of the fuel coal in coal-fired power plants fluctuate greatly,causing the main steam pressure fluctuating frequently,which seriously affects the safe operation of the unit.Based on the feedforward control system of fuel quantity,this paper applies ITGC control algorithm to the boiler combustion system and further optimizes the combustion system.In the whole adjustment process,the control loop of coal and furnace exhaust loop,drum wind and lead wind loop shall be coordinated and output in accordance with different set algorithms to realize the stable operation of the combustion control system of the boiler.Adopt the method of node pressure once-through boiler dynamic mathematical model can be divided into three node pressure,pressure on each node list the conservation of mass and energy conservation equation,and then to simplify,dimensionless equation,finally will get the supercritical unit 3 series pressure node can fuel-steam pressure model of the system.Based on the design data of a 660 MW supercritical unit,the parameters of the supercritical unit fuel-steam pressure system are calculated in 100% THA,75%THA and 50% THA.