CFD modelling of spatiotemporal evolution of detailed tar species in a downdraft gasifier

The rising demand for renewable energy around the world has sparked interest in biomass gasification. However, the technology greatly suffers because of tar species produced during the gasification process, which limits direct use of the produced gas. To address this issue, the paper presents a novel piece of work that focuses on the formation and evolution of tar species consisting of benzene, naphthalene, toluene, and phenol. A two-dimensional numerical model for a downdraft biomass gasifier is developed with a total of 20 thermochemical kinetic reactions to investigate the formation of tar species in the gasifier with the effect of residence time. The model's predictions are validated with the experimental and kinetic data and found to be in good agreement. Besides, the model's ability to simulate the producer gas production from a downdraft gasifier is examined. Reaction rates for volatiles decomposition, combustion, and gasification reactions under different working conditions are investigated. Overall, benzene has the highest concentration of the selected tar species, followed by naphthalene, and with relatively modest amounts of phenol and toluene