Role of H₂O in oxidative regeneration of ZnS formed from high-temperature desulfurization ZnO sorbent

To develop an easily regenerable zinc oxide high-temperature desulfurization sorbent, the role of H₂O in the course of oxidative regeneration of zinc sulfide in the presence of O₂ were studied using ZnO without support material as a sorbent. Oxidative regeneration of ZnS in the presence of water vapor was examined using TPR technique and H₂¹⁸O. From this study, the following results were obtained: ZnS was converted to SO₂ and H₂ by H₂O in the absence of O₂ at high temperature (> ca. 600 °C); in the first step in the oxidative regeneration, ZnS predominantly reacted with H₂O more than O₂; the SO₂ formed from ZnS contained oxygen from H₂O. From the experimental results, it was found that the oxidative regeneration of ZnS in the presence of H₂O and O₂ can be expressed by the following two equations: ZnS + 3H₂O ⇆ ZnO + SO₂ + 3H₂; 3H₂ + 3/2 O₂ → 3H₂O. In the absence of H₂O or in the case of very low value of H₂O/O₂ concentration ratio, the following reaction also occurred: ZnS + 3/2 O₂ → ZnO + SO₂.