| dc.description.abstract | The growing concern about climate change and related greenhouse gas emissions is leading to the promotion of research into the use of environmentally friendly renewable energy. Biomass gasification and subsequent biofuels synthesis is a promising alternative to fossil fuels and can contribute to a solution to the energy crisis. However, this process also generates a great variety of contaminants that have severe detrimental effects on downstream applications and therefore must be removed. Among these pollutants, sulfur species are particularly harmful to catalysts.
The state-of-the art technology for sulfur removal is high-temperature gas cleaning with regenerable solid sorbents, as it is an energy-efficient and low-cost process. Manganese-based sorbents are considered a promising alternative as they possess high thermal stability and less sensitivity than other materials to the presence of steam.
This report is focused on using pelletized shaped manganese-based sorbents for the removal of H2S, based in a chemical looping process. The developed sorbents are egg-shell pellets where different contents of active phases (manganese oxides) are loaded on the external layer (100-200 𝜇𝑚) of the alumina supports.
The evaluation of the capacity and stability of the sorbents in the removal of H2S is carried out using 10 reduction-sorption-regeneration cycles at 600ºC under dry and steam conditions. High sorption capacities are obtained and a good stability is observed even in the presence of steam.
Besides the development of the sorbents, the effect of the different syngas components is also studied with the help of a thermochemical software, FactSage 7.2. The overall results indicate that the presence of steam for the removal of H2S is a challenging issue as it hinders the sulfidation reaction physically and thermodynamically. The presence of H2, CO and CO2 also have an important effect through the water-gas shift reaction and the reduction of the manganese oxide phases of the sorbent. | |