Thermodynamic Investigation of Carbon Deposition and Sulfur Evolution in Chemical Looping Combustion with Syngas

Abstract

Chemical looping combustion (CLC) with syngas, a synthesized gas mixture of CO, H2, CO2, H2O(g), N2, and H2S, was investigated using thermodynamic simulation, with focus on carbon deposition and sulfur evolution in CLC. Five metal oxides, such as NiO, CuO, Fe2O3, Mn3O4, and CoO, were selected as oxygen carriers for CLC application. Different influencing factors on the formation of carbon deposits were investigated, including pressure, fuel reactor (FR) temperature, oxygen excess number Φ (denoting the availability of lattice oxygen in the oxygen carrier to the fuel), and fuel gas composition. Higher temperature and larger oxygen excess number Φ inhibited the formation of carbon deposits while the pressurized condition caused the opposite. The increase of H2O(g) and CO2 fraction in syngas reduced carbon deposition while, in contrast, a larger H2S occurrence in syngas led to more carbon deposits to be formed. A sensitivity analysis to the different factors revealed that carbon deposition was mainly determin...