LAUSR

We describe a process of chlorination of fly ash with either chlorine gas or calcium chloride, which successfully decomposes mullite and permits the extraction of a number of industrially useful, acid-soluble compounds. As a guide for determining optimal input molar ratios and temperatures, the Gibbs energies for three groups of reactions of major fly ash components between 973 K and 1473 K were calculated: (1) chlorination with chlorine gas; (2) chlorination with chlorine gas in the presence of coal; (3) chlorination with calcium chloride. Laboratory-scale measurements with fly ash from six coal combustion power plants in Kazakhstan show that chlorination with either calcium chloride or chlorine gas allows efficient extraction of alumina (α-Al2O3) and silica with both high yield and purity.