Deposition and release behavior of H2S during chemical looping hydrogen production process

Abstract

Chemical looping hydrogen production process is a promising technology for producing low-carbon hydrogen from various fossil and biogenic energy sources. However, the typical contaminant in feedstock, hydrogen sulfide, has a potential influence on the process. Herein, this study investigated the influence of hydrogen sulfide on the chemical looping hydrogen production process. Results show that the presence of hydrogen sulfide in the fuel reduces the reaction performance of the oxygen carrier because sulfur is deposited in the oxygen carrier during the reduction stage to produce iron sulfide species (FeS2, Fe7S8 and FeS). Then the iron sulfide is converted to hydrogen sulfide and sulfur dioxide during the hydrogen production and air oxidation stage, respectively. H2 production temperature is an important factor in controlling the production of hydrogen sulfide, which will not be produced at temperature below 710 °C. In addition, the air oxidation regeneration step ensures that sulfur does not accumulate in the oxygen carrier, thus improving the cycle stability of the oxygen carrier.