Modeling & Simulation of Pyrolysis: Effect of Convective Heat Transfer & Orders of Reactions

Pyrolysis is a process by which a biomass feedstock is thermally degraded in the absence of air/oxygen. It is used for the production of solid (charcoal), liquid (tar and other organics) and gaseous products. In the present study, a mathematical model to describe the pyrolysis of a single solid particle of biomass is used to study the effect of convective heat transfer coefficient and orders of reactions. Pyrolysis rate has been simulated by a scheme consisting of two parallel primary reactions and a third reaction for secondary interactions between volatile and gaseous products and the char. Finite difference method using pure implicit scheme is used for solving heat transfer equation and Runge-Kutta 4 order method for chemical kinetics equations. The model equation is solved for cylindrical pellets, spheres and slab geometries of equivalent radius ranging from 0.00025 m to 0.013 m, and temperature ranging from 303 K to 1000 K, and the results are presented here. The work carried out in the present study is important and useful for optimal design of the biomass gasifiers, reactors, etc. It is very useful in the design of industrial pyrolysis units also.