The progressive ash formation and deposition dynamics in a 25 kW coal combustor

摘要

The ash deposition process in practical boilers is dependent upon the coal property and the combustion condition, which complicates the prediction and precaution of the problem. In this paper we investigate the progressive ash formation and deposition behaviors in a 25 kW self-sustained pulverized coal combustor for three types of coal samples. The Si/Al-dominated Hami lignite experiences an increase in the ultrafine PM_(0.2) quantity during the char burning regime, opposite to the sodium-rich ZD lignite, and that trend is attributed to the contribution of refractory elements. As for the deposition characteristics, the deposit formed by HAF-2 bituminous is remarkably strengthened when the temperature goes up to 950-1150°C. Moreover, the deposit morphology shows the presence of coarse mode particle only within the central windward region. The incident velocity distribution reveals that the oblique impaction is an essential factor that hinders the particle sticking on the lateral sides.