Research And Application Of Fine Control Of Boiler Burner Combustion State Under Deep Peaking

Realizing the fine control of boiler burner combustion state under deep peaking is of great significance for the safe and stable operation of boilers.It can not only effectively prevent abnormal combustion behavior under low load,but also improve boiler combustion efficiency,improve fuel utilization,reduce NOx and carbon emissions,and make the boiler operate safely,reliably and stably.The primary air coal ratio and balanced distribution of primary air powder in direct blowing pulverizing system is an important factor affecting the combustion state of the burner.The traditional wind-powder flow rate leveling mainly relies on adjustable shrinkage holes,which cannot be adjusted under thermal conditions,and there is not enough straight pipe section at the mill inlet for uniform mixing of hot and cold air,resulting in inaccurate measurement of the mill inlet air volume,which brings great difficulties to the accurate control of the mill primary air coal ratio.Therefore,under deep peaking conditions,it is crucial to achieve fine control of boiler burner combustion state for low load and stable combustion of boiler.In this paper,we build a fine control system of boiler burner combustion state under deep peak regulation from the control of primary air coal ratio and the leveling control of air flow rate at the outlet of the mill.Firstly,in order to realize stable and reliable air-powder flow rate equalization control,a supporting automatic control algorithm of the mill outlet air-powder flow rate is written based on the air-powder flow rate data measured by non-intrusive electrostatic sensors.Secondly,in order to realize the accurate measurement of mill inlet air flow,a soft measurement method of mill inlet air flow based on electrostatic method is proposed,and the functions of mill inlet air flow,raw coal full water and mill outlet air flow are constructed by establishing the air flow and heat balance model of traditional medium-speed mill.On this basis,the mill inlet air volume and raw coal full water are calculated using the wind-powder flow rate measured by the electrostatic method,and a fine control strategy of mill primary air-coal ratio based on the soft measurement of mill inlet air volume is designed.Finally,the burner combustion state control software was developed based on TwinCAT 3 to realize the automatic control of the whole process of data acquisition,processing,calculation and adjustment,and the boiler burner combustion state fine control system was installed in a power station in China.At the same time,the calculated values of mill inlet air volume and raw coal full water were compared with the data of DCS,which proved the accuracy of the control system and provided strong support for the boiler stable combustion under deep peaking conditions.