Mass and thermal analysis of burning wood spheres

Abstract

The thermal and mass characteristics of single wood spheres burning in hot air flows were experimentally investigated. The combustion characteristics of interest are the pyrolysis temperature, the ignition temperature, and change of fuel properties and burning rate during combustion. The wood spheres were ignited by hot air flowing around the spheres at different flow rates. The burning process was interrupted with water quenching at different stages of combustion. Samples of mid-burning wood spheres were inspected by X-ray and dissection to investigate the interior conditions of the wood sphere. The materials at different locations inside the sphere were analyzed for chemical composition distributions. The experiments provide extensive data allowing the analysis of wood sphere burning rates and thermochemical characteristics during different stages of combustion. A correlation for estimating wood sphere burning rates during flaming combustion was proposed. The wood pyrolysis temperatures were heating-rate dependent. Material composition analysis showed that the atomic ratios of H and O of the internal material of burning wood spheres, irrespective of location, were essentially within a close range during either pyrolysis or flaming combustion.