Insight into the biomass pyrolysis volatiles reaction with an iron-based oxygen carrier in a two-stage fixed-bed reactor

Abstract

The reaction between biomass pyrolysis volatiles and oxygen carrier (OC) is a non-negligible issue in the chemical looping combustion or chemical looping reforming of pyrolysis gas. This study systematically investigated the reaction characteristic of biomass pyrolysis volatiles with iron-based oxygen carriers, aiming to produce hydrogen by chemical looping reforming of pyrolysis gas. This work also examined the evolution of three-phase product distribution (carbon deposition, tar, and gas), which was generated through the reaction between biomass pyrolysis volatiles and an iron-based oxygen carrier. The results indicate that increasing the amount of oxygen carrier and temperature facilitated the tar conversion into more gas and less deposited carbon. The low valent state of Fe promotes tar cracking, decreasing tar content while increasing carbon deposition. Moreover, an increase in OC usage formed more naphthalene in tar, which gets much more pronounced with the low valent state of iron oxides. The consumption of CO in the biomass volatile matter (VM) reforming reaction is significant, and the carbon in tar is mainly transformed into CO2. The tar conversion with biomass VM produces less carbon deposition and higher gas yield than coal VM due to large amounts of light tar. The concentration of reducing gas is sufficient to reduce Fe2O3 to FeO, which is essential for the chemical looping hydrogen generation.