Performance Study of a Woody Downdraft Gasifier: Numerical Investigation and Experimental Validation

Abstract

Biomass gasification is an established and widely utilized renewable energy system. The research work aims to develop and construct a downdraft gasifier to investigate gasifier performance. The gasifier’s performance and cold gas efficiency were calculated for three volumetric airflow rates: 7.16 m³/h, 5.97 m³/h, and 4.78 m³/h. The efficiency was found maximum of 69.6% for an airflow rate of 7.16 m³/h. The oxidation zone and neck region of the gasifier reactor had the maximum recorded temperatures of 845 °C and 823 °C for Swietenia macrophylla (SM) and Mangifera indica (MI), respectively. A two-dimensional computational fluid dynamics (CFD) model for a downdraft gasifier was also developed using ANSYS/FLUENT software. The simulation results provided valuable insights into thermal characteristics and the gasification process taking place inside the gasifier. Taking into account the introduction of wood at a rate of 6.2 kg/h and the flow of air at a rate of 7.16 m³/h, predictions were made about the composition of syngas, and subsequently, validation of the model was conducted with experimental data. The simulation study visually represents the gasification process, illustrating the distribution of velocity and the contours of carbon monoxide, carbon dioxide, and hydrogen within the gasifier.