Investigation on on-off characteristic of 80 MW pulverized coal industrial water boiler

The burner is usually considered to be the core equipment of pulverized coal boiler, and gradually become a priority in the research of on-off process of boiler. A kind of reversed-jet swirl burner is widely used in the medium-mini pulverized coal boiler to satisfy a wide operating load and a frequent on-off process due to its better stable combustion characteristic. In this paper, the 80 MW pulverized coal boiler, which adopts the reversed-jet swirl burner with double cone pre-combustion chamber, was investigated. On the basic of the measured data of operating load, feed frequency, the flue gas average temperature in furnace and the selective catalytic reduction (SCR) system, the star-up with different initial conditions and normal shut-down process was analyzed. The results show that the pulverized coal burner had a rapid on-off ability. The start-up process was divided into stages of load rapidly increase and slowly increase based on the changes in feed frequency. In the load rapid increase stage, the rising rate of operating load could reach over 3.0%/min. The 3.6%/min and 3.11%/min could be achieved on the rising rate of operating load for the cooling and heating star-up (CS and HS) case of furnace respectively, where cooling and heating mean the low and high temperature of return water condition. During the star-up process, the rising rate of operating load was limited by the mismatch of burning rate of pulverized coal and heating transfer rate of furnace. It indicated that the heating transfer rate lagged behind the burning rate. And the burning rate of pulverized coal was limited by the frequency of storage-type pulverized coal feed system. In the HS case, when the operating loads reached at a rated design value, the lag behind of heating transfer rate was reflected in 13.31 MW operating load increasing. The flue gas temperature in the upper, middle and lower parts of furnace for the HS case is higher than that for the CS case, but the rising rate of flue gas temperature is lower than that for the CS case. And it can enter the temperature region early to make SCR reaction. During the shutdown process, with the help of rapid cut-off of the feed system, the reducing rate of operating load was divided into rapid and slow stages with reducing rates of 9.69%/min and 1.09%/min respectively. The flue gas temperature in the furnace and SCR system decreased rapidly, the shutdown process was rapidly reached.