Influence of higher equivalence ratio on the biomass oxygen gasification in a pilot scale fixed bed gasifier

Abstract

The characteristics of biomass oxygen gasification with a higher equivalence ratio (0.31–0.40) in a pilot scale (50 kg/h) downdraft fixed bed gasification system were studied using pine wood block and corn stalk briquette as feedstocks. Experiments were carried out to investigate the influence of the higher equivalence ratio on the gasification performance. The gas composition was analyzed by gas chromatography. Upon increasing the equivalence ratio from 0.31 to 0.40, the reaction temperature, gas yield, and carbon conversion efficiency increased, while the lower heating value and tar and dust contents of syngas decreased. The gas yield and carbon conversion efficiency of corn stalk briquette gasification were lower than those of pine wood block gasification by about 3.0% and 5.0% at each equivalence ratio. The higher equivalence ratio strengthened the gasification and improved the gas yield as well as carbon conversion but lowered the lower heating value of the syngas. Too high equivalence ratio (>0.40) would result in excess gasification and more combustible components being burnt out. Too low equivalence ratio (<0.31) would lead to incomplete gasification and more tar residue. The optimal equivalence ratios were 0.37 and 0.33 for corn stalk briquette and pine wood block, respectively. The results of this study will help to improve our understanding of syngas production with low tar and medium heating values by biomass oxygen gasification.