Optimization of synthesis gas production in the biomass chemical looping gasification process operating under auto-thermal conditions

Abstract Biomass Chemical Looping Gasification (BCLG) is a promising route to obtain N2 free high purity syngas. In this work, heat and mass balances were solved to determine the auto-thermal operation conditions that maximize the syngas yield in a BCLG system. A Fe-based oxygen carrier and pine wood as fuel were considered for the simulation. Two methods to control the transference of oxygen between the air reactor (AR) and fuel reactor (FR) were analysed. Syngas yield was higher controlling the oxygen fed to the AR by the air flow (OCM-1) than controlling the oxygen supplied to the FR by the oxygen carrier circulation flow (OCM-2). The influence of different operating parameters, such as oxygen carrier transport capacity, preheating of gases fed to the system, steam/biomass ratio, fuel reactor temperature, was also analysed. It is noteworthy that working with OCM-2 it is necessary to optimize the amount of active phase in synthetic oxygen carriers or to dilute the natural oxygen carriers (ores, wastes) with an inert material to maintain realistic temperature difference values between reactors. Therefore, it is recommended to operate with the OCM-1 as it has the advantages of a more flexible operation and the possibility of obtaining pure N2.