ABSTRACT
In the present study, the performance of a CaMn0.775Ti0.125Mg0.1O2.9-δ perovskite used as an oxygen carrier to burn sour gas with different H2S concentrations (up to 3000 vppm) in a continuous 500 Wth 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 CaSO4. The reactivity with CH4 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 (SO2 and H2S) 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.
