DEVELOPMENT OF A SAWDUST FIRED FLUIDIZED BED REACTOR FOR SYNTHETIC GAS PRODUCTION

Abstract

In this project, locally available materials such as mild steel and clay were used to develop a fluidized bed gasifier suitable for sawdust gasification. This can be a valuable source of energy for domestic and cottage industry use. Sawdust was first processed by converting it to pellets. Tests were carried out on the pellets using a bomb calorimeter using the ASTM-E771 standard. An air distributor plate is placed at the end of a plenum connected to radially spaced tuyeres. The reactor was designed using standard gasifier design charts and model equations from previous research works. Experimental tests showed that the pellets have a heating value of 16.36 MJ of energy per kg and a higher percentage of volatile matter of 57.62% (ASTM-E872) and a lower percentage of fixed carbon than the initial sawdust sample. A bubbling fluidized bed gasifier was developed with 5 tuyeres and an operational velocity of 1.77 m/s. On experimental and performance tests, the pellets were loaded into the reactor and then fired. Air was forced into the plenum, after which the air distributor plate help provide evenly distributed jets of air in the bed resulting in complete and incomplete combustion. The heat produced leads to pyrolysis and eventually gasification of the sawdust pellets at reactor temperatures of 600⁰C, 650⁰C and 700⁰C. The produced synthesis gas composed of methane 63.4%, Ammonia 1.09%, Carbon monoxide 0.63%, Hydrogen sulphide 0.84% and carbon dioxide 34.04%. The gas was ignited showing it was combustible. This gas provides a source of alternative energy from waste biomass that could be used in homes, cottage industries and eventually adapted to various other applications.