Coupled Drying and Devolatilization of Low Rank Coals in Fluidized Beds: An Experimental and Theoretical Study
A model is proposed for the coupled drying and devolatilization of large particles of low rank coals in fluidized beds. The model is based on the individual models developed and tested experimentally for drying and for devolatilization (using predried coal) and reported earlier. The temperature profile in the dry shell generated by the movement of a receding drying front (constituting a moving boundary problem) is assumed to characterize the rate of devolatilization during the first stage of the coupled phenomena when drying and devolatilization occur simultaneously. The temperature profile at the end of drying is used as an initial condition for solving analytically the transient heat conduction equation (with a convective boundary condition) for characterizing the remaining possible devolatilization after the drying is completed.
An empirical correlation is proposed for the estimation of the total time required for the coupled drying and devolatilization process.
The model predictions are compared with experimental data collected for Mississippi lignite in a three inch fluidized bed.
KeywordsCoal Particle Biot Number Convective Boundary Condition Transient Heat Conduction Equation Devolatilization Process
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