Development of quantitative techniques to characterise mineral matter transformations in a pulverised coal fired boiler

Slagging costs the global utility industry several billion dollars annually in reduced power generation and equipment maintenance. The efficiency of removing the slag deposits by sootblowing is affected by the growth, shedding and thermal resistance of the deposit. The purpose of this paper is to describe the development of techniques that can be used to quantitatively measure slagging. These techniques were developed at the 350 MW opposed-fired boilers of Collide 'B' Power Station, Biloela, QLD, Australia. Characterisation of the mineral matter transformations was determined by isokinetically sampling pulverised coal (PC) from the pulverised fuel (PF) pipes; measuring the temperature profile in the boundary layer of the furnace; retrieving quenched particulate ash from the thermal boundary layer; and collecting deposits formed on disposable air-cooled mild steel slagging probes inserted in the furnace port. The differences in deposit growth and strength might be correlated with fundamental variations in the mineral matter composition and distribution in the pulverised coal. Preliminary analyses of molten regions of deposits have revealed the primary phase field of iron cordierite (2FeO.2AlO.5SiO), with melting points ranging from 1088 to 1208 °C, to be responsible for slag formation at the Collide boiler