Behavior of ion-exchanged Ca in coal during pyrolysis and CO_2 gasification was experimentally simulated using a mineral-matter-free coal sample. The sample was prepared from Loy Yang brown coal by a sequence of alkali-hydrolysis solubilization, solvent extraction, Ca-ion exchange and solvent removal. Upon heating the sample in N_2 atmosphere up to 1673K, the ion-exchanged Ca formed into particles of CaO or CaS with sizes of 10-20nm. CaO held at 1673K probably converted into Ca due to carbothermal reduction in char and Ca was volatilized to an extent of about 75% leaving the rest as CaS. On the other hand, the extent of Ca volatilization was negligible in CO_2 even after nearly complete char gasification. During CO_2 gasification, ion-exchanged Ca was mainly converted into composite or mixed oxide particles together with Si and Al which initially resided in the sample in organic forms.
