Comparison of low-cost and synthetic oxygen carriers for the Biomass Chemical Looping Gasification process

Abstract

Biomass Chemical Looping Gasification (BCLG) is a novel technology which permits the production of high purity, N2-free renewable syngas. In this work, the behavior of seven oxygen carriers, 4 low-cost (3 ores, and 1 waste) and 3 synthetic materials, was compared during continuous operation in a 1.5 kWth BCLG unit. For that, oxygen-to-fuel ratio (λ) and fuel reactor (FR) temperature were varied in a wide range of operating conditions. High carbon conversion, ηcc (> 95 %) and fuel conversion, Xb, (> 85%) were found for all the oxygen carriers. The same trends in the syngas composition were observed with low-cost and synthetic oxygen carriers when the λ and FR temperature were varied. However, the amount of syngas generated was higher for synthetic oxygen carriers due to their catalytic effect on CH4 conversion. In addition, tar concentration in the generated syngas was lower using synthetic oxygen carriers than with low-cost materials and these concentrations decreased with increasing FR temperature. Finally, lifetime values between 100 h and 900 h were determined for all the oxygen carriers, being the best ilmenite (600 h) among the low-cost materials and Fe10Al (900) among the synthetic ones.