Effect of H2S presence on chemical looping reforming (CLR) of biogas with a firebrick supported NiO oxygen carrier

Biogas containing CH4 and CO2 can be used in CLR for H-2 generation, while the H2S presence may affect oxygen carrier activity and reforming property. In this study, a 2000 ppm H2S was mixed with modelled biogas (CH4/CO2 = 3/2) to explore its effects on the CLR process. Experiments were conducted in a batch fluidized bed using a firebrick supported NiO oxygen carrier. The presence of 2000 ppm H2S decreased the oxygen carrier activity, thus resulting in a significant lower gas yield from the biogas as compared to the cases without H2S. Increase of temperature slightly alleviated the interaction between H2S and the oxygen carrier, hence a slightly higher gas (H-2 and CO) yield was achieved at 950 degrees C than 750 and 850 degrees C. In reforming, H2S was mainly converted to CS2, while COS and SO2 were minors. After several cycles without H2S, the material restored its original activity. Sulfur element and NiS2 crystalline were found in the reduced oxygen carrier according to XRD, XPS, SEM-EDX, HRTEM-EDX and ICP-OES analyses.

Automated summary

This study found that the presence of H2S can decrease the activity of the oxygen carrier and result in a lower gas yield from the biogas, while increasing temperature can alleviate this impact. During reforming, H2S mainly converts to CS2.