The implication of mineral coalescence behaviour on ash formation and ash deposition during pulverised coal combustion

In modelling the fate of minerals of pulverised coal in coal-fired boilers, ash formation is a primary step that decides ash particle size distribution and composition. Frequently, two extreme schemes have been used regarding mineral coalescence behaviour within individual char particles, i.e. no coalescence and full coalescence. However, their implications on ash deposition and thermal performance have not been investigated. In the present paper, the implications of coalescence of included minerals on ash character and subsequent ash deposition are demonstrated by means of an ash formation model and an ash deposition model. The simulated results in a cylindrical furnace for an Australian bituminous coal indicate that ash deposition and thermal performance are significantly influenced by the coalescence behaviour of included minerals.