Sulfur Interaction and Regeneration of CaMn 0.775 Ti 0.125 Mg 0.1 O 2.9-δ Perovskite as Oxygen Carrier during Combustion of Sour Gas in a 500 W th Chemical Looping Combustion Unit.

In the present study, the performance of a CaMn 0.775 Ti 0.125 Mg 0.1 O 2.9-δ perovskite used as an oxygen carrier to burn sour gas with different H 2 S concentrations (up to 3000 vppm) in a continuous 500 W th chemical looping combustion (CLC) prototype was investigated. After 29 h of sour gas combustion, the combustion efficiency had dropped by 18% in comparison with the reference test without sulfur addition. The characterization of the used particles of the perovskite confirmed that the presence of sulfur in the fuel gas had a poisonous effect through the formation of undesired compounds, such as CaSO 4 . The reactivity with CH 4 and oxygen uncoupling capacity decreased, which could explain the decrease in the combustion efficiency. Two regeneration processes, one at high temperature (1273 K) and another one at low temperature (773-873 K), were carried out in a batch fluidized bed reactor to remove the amount of sulfur accumulated in the oxygen carrier particles. The detection of appreciable amounts of gaseous sulfur-based compounds (SO 2 and H 2 S) during the experimentation and the postcharacterization results obtained through different techniques such as X-ray diffraction, ultimate analysis, and thermogravimetric analysis confirmed the effectiveness of both processes. Finally, the feasibility of implementation of the regeneration processes in a commercial CLC unit was thoroughly analyzed.