Stable mechanism of 29 MW high speed pulverized coal burner

The pulverized coal industrial boiler is widely used in municipal heating and industrial parks because of its quick firing and loading. In order to improve its economic performance and reduce the fuel cost，it is necessary to im⁃ prove the fuel adaptability of pulverized coal industrial boiler. High⁃speed pulverized coal burner is the key equipment of pulverized coal industrial boiler. The stable burning mechanism of 29 MW high⁃speed pulverized coal burner is in⁃ vestigated in this study. Firstly，the ignition heat formula of power plant boiler burner is modified and the pulver⁃ ized coal industrial boiler ignition heat formula is obtained. The ignition heat under seven kinds of loadings is calculated. Secondly，a numerical simulation is used to analyze the variation of the recirculation zone under six working condi⁃ tions and the mixing coefficient is used to analyze the mixing of primary and secondary air at the boundary of the recir⁃ culation zone at working condition f. Finally，the combustion characteristic of 40 t/h steam boiler using mixed coal and Shenfu bituminous coal equipped with high⁃speed pulverized coal burner is analyzed. The research results show that the ignition heat of primary air pulverized coal in high⁃speed pulverized coal burner increases with the load. When the load increases from 35% to 100%，the ignition heat of Shenfu bituminous coal and mixed coal are 450-850 kW and 650-1 300 kW respectively. The size of the recirculation area of the high⁃speed pulverized coal burner has little change with the load. The tension of stable combustion in the burner under high load is greater than that under the low load. The recirculation area is close to the cap of the primary air duct when the load is 55% and 75%. At the working condition f，the boundary mixing coefficient of the recirculation zone gradually increases from negative value to positive value with the increase of L / d. This indicates that the high temperature flue gas can en⁃ ter the recirculation zone in time to heat the primary air flow，the flue can go out and mix with the second air at the end of the recirculation zone. At the same time，it forms a stagnation zone and generate orderly flame. Industrial tests show that the burner could fire smoothly under low loads when the mixed coal is used and it will be unstable when the secondary air volume exceeds 20 000 Nm3 / h. This is because the orderly flame at the stagnation area in the burner is gradually blown out by cold air and the steady combustion cycle in the burner is broken.