Prediction of ash-deposition characteristics in co-combustion conditions with CCSEM

Abstract

In pulverized coal-fired boilers, coal-ash deposition on heat transfer surfaces can cause operational problems. It is important to predict ash-deposition characteristics based on the ash composition of the raw coal in advance. However, general prediction methods do not always agree with actual ash deposition under co-combustions. In this study, we investigated the relationship between the mineral particles in raw coal samples analyzed with CCSEM and the ash-deposition characteristics in an actual boiler collected with the newly designed sampling system. The main conclusions drawn were as follows: (1) iron components were condensed in the early-stage ash deposition of the secondary superheater-tube area, and the amount of iron components affected the ash-adhesion properties; and (2), these ash-adhesion properties had a positive correlation with the new index based on included minerals, which were iron oxide, iron-aluminum silicate, iron silicate, and pyrite; (3) this index was able to predict ash-deposition characteristics with high accuracy.