Biomass Gasification with Oxygen Enriched Air in Packed Bed Gasifier

Abstract

Biomass gasification processes are recently attracting attention to produce renewable gaseous fuels as alternatives of fossil fuels. However, raw woody biomass resources to be able to use for biomass gasification are limited because the biomass containing high moisture may lead to low heating values of the gaseous fuels produced, which are inappropriate for the use in gas engines. Then, the introduction of oxygen-enriched air into the gasification reactor has been proposed in this study, which can reduce heat loss during the gasification due to the sensible heat of nitrogen in the gasified gas and increase concentrations of combustible substances in the syngas. Additionally, high partial pressure of oxygen promotes the gasification reaction rates, improving the carbon conversion efficiency. A downdraft packed bed gasifier, which is known to be suitable for small-scale distributed utilization of biomass resources, was selected for woody biomass gasification experiments in this study. After switching the inlet gas from air to oxygen enriched air, the temperature at the top surface of biomass pellet bed rose sharply. The temperature through the packed bed was also kept high under the oxygen enriched air gasification, compared with the normal air gasification. Moreover, the syngas with more H₂ and CO significantly increased. The thermo-equilibrium calculations were conducted to confirm the gaseous compositions and their difference between the air and oxygen enriched air gasification. As a result, the calculation was almost consistent with the experimental results obtained.