Gasification of Pelletized Woody Biomass Using a Downdraft Reactor and Impact of Material Bridging

Abstract

Biomass gasification shows a great potential to displace fossil fuels. In this study, the gasification of pelletized hard wood using a 10 kW downdraft gasifier is investigated. The variations of pressure and temperature parameters during the gasification process with air as a reagent medium were controlled. The gasifier started in continuous mode to burn the wood pellet feedstock. The results from the continuous mode indicate average temperatures of 838 and 754°C for combustion and reduction zones inside the gasifier, respectively, which shows a low temperature gasification process. Moreover, the pressure in the combustion zone varied on average from −1.30 to −1.64 kPa, while the pressure on top of the main reactor showed average variation of less than 0.07 kPa. The pressure drop is assumed to be caused by bridging of the feedstock, which results in a large part of the feedstock to not flow and be burnt inside the reactor. The shape of feedstock is theorized to be the major reason for the feedstock to bridge, with air leaks in the reactor resulting from sealing challenges intensifying the problem.