REGENERABLE ZINC TITANATE SORBENTS FOR HOT-GAS DESULFURIZATION PROCESS

Abstract

Hot-Gas Desulfurization (HGD) is the main process for hydrogen sulphide removal from gases at high temperature.Higher efficiency and lower cost are achived by using zinc oxide based sorbents as they can effectively reduce the H 2 S content in gases to ppm levels and can be regenerated for multicycle operation.Zinc titanate sorbents, a mixedmetal oxide prepared by combining ZnO and TiO 2 at high temperature, is currently one of the leading sorbents for HGD process.In desulphurizing process, titanium oxide prevent ZnO reduction to volatile metallic zinc.Depending on the ZnO:TiO 2 molar ratio and the preparation and calcination conditions, several phases of zinc titanate (Zn 2 TiO 4 , ZnTiO 3 or Zn 2 Ti 3 O 8 ) can be formed.By calcination at 700-720 0 C for 4 hours of mixed oxides with ZnO:TiO 2 molar ratio 2:1, only Zn 2 TiO 4 are formed with 90-95% efficiency.For mixtures with excess of TiO 2 (ZnO:TiO 2 molar ratio 1:1 and 2:3) on similary conditions, Zn 2 TiO 4 and Zn 2 Ti 3 O 8 in different molar ratio are formed.Regeneration of sulphuretted zinc titanate sorbents is strongly influenced by the temperature, a complete regeneration with high rate of the oxidation reaction being possible at 600-700 0 C temperature range.The titanium oxide excess from ZnO:TiO 2 ≤ 2:1 molar ratio titanates, prevent sorbent sintering or attrition and zinc sulphate formation, allowing a multiple desulphurizing-regeneration cycles.