A numerical study of solid fuel combustion in a moving bed

• Main Author: Ko, Daekwun
• Other Authors: Kanury, A. Murty
• Language: en_US
• Published: 2012
• Subjects: Coal > Combustion > Mathematical models; Coal-fired furnaces > Mathematical models
• Online Access: http://hdl.handle.net/1957/35623

Coal continues to be burned by direct combustion in packed or moving bed in small size domestic furnaces, medium size industrial furnaces, as well as small power stations. Recent stringent restrictions on exhaust emissions call for a better understanding of the process of combustion of coal in beds. The present study is a prelude to developing methods of analysis to obtain this improved understanding. A one-dimensional steady-state computational model for combustion of a bed of solid fuel particles with a counterflowing oxidant gas has been developed. Air, with or without preheating, is supplied at the bottom of the bed. Spherical solid fuel particles (composed of carbon and ash) are supplied at the top of the bed. Upon sufficient heating in their downward descent, the carbon in particles reacts with oxygen of the flowing gas. The governing equations of conservation of mass, energy, and species are integrated numerically to obtain the solid supply rate whose carbon content can be completely consumed by a given gas supply rate. The distributions of solid and gas temperatures, of concentrations of various gas species, of carbon content in solid, and of velocity and density of gas mixture are also calculated along the bed length. The dependence of these distributions on the solid and gas supply rates, the air supply temperature, the size of solid fuel particle, and the initial carbon content in solid is also investigated. The calculated distributions are compared with the available measurements from literature to find reasonable agreement. More gas supply is needed for complete combustion at higher solid supply rate. At a given gas supply rate, more solid fuel particles can be consumed at higher gas supply temperature, for larger particle size, and for lower initial carbon content in solid. The temperature of the bed becomes higher for higher solid supply rate, higher gas supply temperature, larger solid particle diameter, or lower initial carbon content in solid. These reasonable results lead one to encourage extension of the model presented here to more complex problems involving combustion of coals in beds including the effects of drying and pyrolysis. === Graduation date: 1994