Effect of Air Supply Location and Equivalence Ratio on Thermal Performance of Downdraft Gasifier Fed by Wood Sawdust

Abstract

Many efforts have been performed by researchers worldwide to find out alternative technologies for renewable energy conversion to encounter the shortage of fossil fuel. Biomass gasification, one of many promising energy conversion technologies, has become more attractive in recent years. The present work aims to investigate the effect of air tuyere-grate distance (i.e., 260, 330, and 400 mm) and equivalence ratio (i.e. 0.15, 0.20, and 0.25) on the thermal behaviour of the small-scale downdraft gasifier fed by sawdust. The reactor has an internal diameter of 300 mm and a height of 725 mm (from the grate to the top). The axial temperature profile of the reactor, the volume fraction of carbon monoxide, hydrogen, and methane, the higher heating value of the producer gas, and cold gas efficiency are observed and analysed. The results indicate that the tuyere position above the grate affects the performance of the gasifier. The maximum higher heating value of the producer gas (HHVg) and the maximum cold gas efficiency (CGE) are found at an optimum tuyere-grate distance of 330 mm and an equivalence ratio of 2.0. The maximum values of HHVg and CGE are 2.84 MJ/Nm3 and 66.36%, respectively.