A comparison of gasification phenomena among raw biomass, torrefied biomass and coal in an entrained-flow reactor

Gasification of torrefied biomass is a promising technique for producing synthesis gas (syngas) of higher quality than has previously been available. In this study, in order to evaluate the potential of the technique, gasification processes for three different materials, which include raw bamboo, torrefied bamboo (at 280°C for 1h), and high-volatile bituminous coal in an entrained-flow gasifier using O₂ as the gasification agent, are studied numerically and compared to each other. The obtained results suggest that in all cases, the carbon conversions of the three fuels are higher than 90%. However, the cold gasification efficiency for raw bamboo is low, mainly due to the relatively lower calorific value of the material. In the case of the torrefied bamboo fuel, the gasification performance is enhanced significantly and is quite similar to the coal gasification under the same conditions. It appears that the optimum oxygen-to-fuel mass flow ratios for the gasification of raw bamboo, torrefied bamboo, and coal are 0.9, 0.7, and 0.7, and their equivalence ratios are 0.692, 0.434, and 0.357, respectively. Under optimum conditions with respect to the equivalence ratio, the cold gas efficiency of torrefied bamboo is improved by 88%, as compared to raw bamboo.