Intermediate temperature electrochemical Claus process for sulphur recovery

Abstract

Abstract This investigation addresses an electrochemical Claus cell incorporating perovskite solid electrolytes and potentially H 2 S tolerant metal sulphide anode electrocatalysts for promoting H 2 S oxidation to sulphur and water. Cells possessed the general configuration: H 2 S, AB 2 S 4 (or WS 2 ) |doped ABO 3 | La 0.9 Sr 0.1 CoO 3 , O 2 , where AB 2 S 4 corresponded to NiFe 2 S 4 and CuCo 2 S 4 and ABO 3 to the perovskite solid electrolytes BaTh 0.9 Gd 0.1 O 3 and BaCe 0.9 Gd 0.1 O 3 . These latter components were selected from reasoning that has shown correlation between activation energy E a for ionic conduction and perovskite solid-state lattice parameters. For oxygen-anion or proton-conducting solid electrolytes water, as an electrochemical reaction product, would be formed in anode and cathode compartments respectively. The predominant oxidizable electroactive species present in the anode compartment was suggested to be hydrogen originating from the initial thermal dissociation of H 2 S(H 2 S ⇌ H 2 + 1 2 S 2 ) at operating temperatures. The empirical trend for exchange current densities ( i 0 ) suggests relative activities for promoting the subject reaction in the cell anode compartment to be NiFe 2 S 4 > WS 2 > CuCo 2 S 4 . To avoid condensation of sulphur on anode electrocatalysts, cells should be operated at above 700°C.