BEHAVIOR OF CARBOXYL-BOUND POTASSIUM DURING COMBUSTION OF AN ION-EXCHANGED LIGNITE

The reactions of potassium during combustion of a potassium-ion-exchan ged Beulah lignite have been investigated. Combustion was carried out in a drop-tube furnace and CCSEM and XAFS spectroscopy were used to ch aracterize the coal and ash samples. The reactions of the ion-exchange d potassium were quite similar to those of carboxyl-bound sodium in th e original coal. The principal K-containing ash phases observed were a K-aluminosilicate glass and a K-Ca sulfate. The K-aluminosilicate gla ss composition range was clustered around the composition of kalsilite (KAlSiO4). The K-Ca-sulfate mixture exhibited a composition range fro m K2SO4 to CaSO4, with a mixed (Ca, K-2) SO4 being more abundant than either of the pure sulfate phases.