Alumina and silica produced by chlorination of power-plant fly ash treatment.

A process of chlorination of fly ash is described here 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 1 473 K were calculated: chlorination with chlorine gas; chlorination with chlorine gas in the presence of coal; 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 (alpha-Al2O3) and silica with both high yield and purity.
A process of chlorination of fly ash is described here 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 1 473 K were calculated: chlorination with chlorine gas; chlorination with chlorine gas in the presence of coal; 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 (alpha-Al2O3) and silica with both high yield and purity.