Simplified overall rate expression for shrinking-core bituminous char combustion

Abstract

A simplified expression for the char combustion rate in a fluidized bed is elaborated based on the shrinking-core model. A general mass balance equation for the carbon as well as a particle mass distribution in the bed has been obtained for a particle or outer diameter D and core diameter D c . Experiments were carried out to investigate the validity of the shrinking-core model for a bituminous coal at different coal particle sizes. This type of coal was found to burn according to the shrinking-core model provided the particles are large enough ( D>3 mm), though the core diameter of the burnt particles does not tend to be zero even after long burning times in the bed. The applicability of the shrinking-core model was found to increase with diameter. Higher bed temperatures also appear to increase the model's validity for the range of interest for fluidized bed combustion.