Characterizing a two-stage downdraft biomass gasifier using a representative particle model

Gasification is a thermochemical process that converts biomass into energy, and syngas is the principal product of gasification; however, gasification additionally produces tar that harmed human health, the environment, and syngas-fueled equipment. Tar content in syngas compositions can be decreased by adding a secondary air inlet. To model the same, the representative particle model (RPM) is used herein. Two proposed models characterize the gasifier, dividing it into two quasi-reactors (first model) and assuming the air inlets as one intake (second model). Independent variables represent the initial conditions of the mixed convection region and equivalence ratios (ER). Results of the first model could simulate gasification phenomena, such as temperature distribution, particle composition, the change in syngas composition to ER, and tar content, whereas the second model could simulate the phenomenon as a syngas composition with a standard deviation of 8.51. Addition of temperature-dependent air inlet density in gas species mass balance was suitable for modelling the gasifier. Research found that CO and H₂ contents increased in syngas, whereas CO₂, CH₄, and H₂O contents decreased as ER increased. Research concludes that the first model must be further evaluated to investigate syngas compositions more accurately.