Experimental Study on Chemical Looping Co-gasification of Alfalfa and Polyethylene with Iron Ore as the Oxygen Carrier for High H₂/CO Production

Abstract

Biomass and plastic waste gasification has been demonstrated as a promising technology for developing a long-term waste management system that reduces emissions and enhances energy recovery. Chemical looping co-gasification of alfalfa (AL) and polyethylene (PE) with Fe2O3 as oxygen carrier (OC) was studied in a fixed-bed reactor. The effects of temperature, steam/alfalfa mass ratio (S/AL), OC/alfalfa mass ratio (OC/AL), and PE/alfalfa mixing ratio (PE/AL) were investigated. The results revealed that at a gasification temperature of 950 °C, the optimum product distribution was achieved with a S/AL ratio of 1, an OC/AL ratio of 0.5, and PE/AL mixing ratios of 50 and 75%. The presence of PE in the feedstock led to higher production of synthetic gas, particularly the hydrogen yield, as the H2/CO ratio increased to more than 2 to match the demand of Fischer–Tropsch synthesis. At a mixing ratio of 50%, the lower heating value and the H2/CO ratio achieved their maximum values of 14.05 (MJ/Nm3) and 2.50, respectively. This research clarified that the combined gasification of biomass with plastic constitutes an ideal approach for high-quality synthesis gas production as well as environmental preservation and materials recycling.