Modeling & Simulation of Pyrolysis: Influence of Particle Size and Temperature

In the present study, a mathematical model to describe the pyrolysis of a single solid particle of biomass is used to study the influence of particle size and temperature in the pyrolysis of biomass. The pyrolysis rate has been simulated by a kinetic scheme involving three reactions (primary and secondary): two parallel reactions and a third 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 2700 K. Some very interesting trends are found, especially with respect to the effect of temperature on final pyrolysis time. The final pyrolysis time first decreases at lower values of temperature and then increases as temperature is further increased, providing an optimum value of temperature at which final pyrolysis time is minimum. This interesting phenomenon, which was not reported by investigators earlier, is well explained by means of the pyrolysis kinetics.