Removal of gaseous alkali metal compounds from hot flue gas by solid sorbents

Active bauxite, silicon dioxide, diatomaceous earth and ash have been found suitable for alkali removal from hot flue gas in a coal conversion system. The effect of temperature on the alkali adsorption/reaction using these sorbents was surveyed in the experiments in which a thermogravimetric analyzer was utilized under a simulated flue gas condition. Equilibrium calculations were also carried out to determine the mechanism of reaction. The results reveal that although all these sorbents are available for the alkali removal, the active bauxite and silicon dioxide are more effective, and the calculations suggest that a higher temperature can take more advantage to the alkali removal.