The feasibility and performance of using producer gas as a gasifying medium

The gasification process in a 20-kW downdraft gasifier is investigated using Computational Fluid Dynamics. The research aims to examine the feasibility of air and producer gas co-injectionas a gasifying medium on the performance of the whole process. To this end, the effect of varying the injected amount of the producer gas on producer gas composition, emissions, H2 production, producer gas yield and higher heating value (HHV), the gasification, and carbon conversion efficiencies are reported. The results reveal promising findings for boosting the producer hydrogen amounts, and the corresponding heating values, with lower CO2 levels. The ratio of the injected producer gas (within the gasifying medium) to the total required amount of air for gasification is defined by z (eqn. (10)), and it is found that optimum z values are around (0.25–0.5). For the same working conditions of moisture content (MC), feedstock, and equivalence ratio (ER), the gasifying medium of z= (0.25–0.5) has higher HHV, gasification, and carbon conversion efficiencies than air gasification up to 33%, 31%, and 19% respectively. Additionally, for the same optimum range of z, it is found that the producer gas yield, and H2 production are higher than air gasification by 10%, and 34% respectively, with a reduction in CO2 by 18%. Consequently, the research presents a significant potential for higher yield, rich H2, and CO2-free syngas production, while demonstrating a promising novelty and technique that is applicable to any sort of the gasification units’ type and capacity. •A 20-kW 2D Computational Fluid Dynamics (CFD) model for downdraft biomass gasifier is built.•The research aims to examine the feasibility of recycling the producer gas as a gasifying medium for the first time.•The results reveal promising findings for boosting the syngas yield, H2 production, and higher HHV, with lower CO2 levels.•The technique is applicable to any sort of the gasification units' type and capacity.