Retention of Arsenic and Selenium during Hot Gas Desulfurization Using Metal Oxide Sorbents

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The present work explores the possibility of capturing toxic elements other than sulfur in coal gasification flue gases using metal oxide mixtures. Arsenic and selenium compounds were the elements selected for study because they are toxic species which are present in coal gasification flue gases in different amounts, depending on temperature. Among the regenerable sorbents already developed for hot gas cleaning systems in Integrated Gasification Combined Cycles, metal oxide mixtures based on iron, titanium, or zinc oxides (zinc ferrites and zinc titanates) were tested for arsenic and selenium retention. These sorbents have previously been proved to possess good characteristics for H 2 S(g) retention. The study was carried out in a laboratory scale reactor, using the sorbent in a fixed bed, at 550 °C. Good retention capacities (56 mg g - 1 ) were obtained in these conditions for selenium in a metal oxide mixture containing zinc titanate. A metal oxide mixture containing zinc ferrite proved to be an appropriate sorbent for both elements, retention capacities being 21 mg g - 1 for arsenic and 55 mg g - 1 for selenium. The results obtained indicate that arsenic and selenium compounds can be retained together with sulfur compounds in these sorbents and be desorbed in the sorbent regeneration processes.