STABILITY OF ZINC-OXIDE HIGH-TEMPERATURE DESULFURIZATION SORBENTS FOR REDUCTION

Zinc oxide was examined as a high-temperature desulfurization sorbent. At high temperature (>ca. 600-degrees-C), the zinc oxide sorbent is reduced to metallic zinc with reductive gas in a coal derived gas, and then the metallic zinc evaporates. This reduction and vaporization was not completely prevented by the additions of ZrO2, TiO2, and Al2O3 to the zinc oxide. There duction and vaporization tendencies of zinc oxide were studied by the temperature-programmed reduction (TPR) method using thermobalance, under different conditions which simulated practical desulfurization of hot coal-derived gases. From these results, the stability of zinc oxide for reduction followed by vaporization could be expressed by an experimental equation using concentrations of H-2, CO, H2O, and CO2 in coal-derived gases and temperature as functions. From the measurements of TPR profiles and reactivities of the zinc oxide sorbents containing the additives, it is suggested that stabilization of zinc oxide by additives without a decrease of the reactivity of zinc oxide is a very difficult problem.