Generalized pyrolysis model for combustible solids

This paper presents a generalized pyrolysis model that can be used to simulate the gasification of a variety of combustible solids encountered in fires. The model, Gpyro, can be applied to noncharring polymers, charring solids, intumescent coatings, and smolder in porous media. Temperature, species, and pressure distributions inside a thermally stimulated solid are determined by solving conservation equations for the gaseous and condensed phases. Diffusion of species from the ambient into the solid is calculated with a convective–diffusive solver, providing the capability to calculate the flux and composition of volatiles escaping from the solid. To aid in determining the required material properties, Gpyro is coupled to a genetic algorithm that can be used to estimate the model input parameters from bench-scale fire tests or thermogravimetric (TG) analysis. Model calculations are compared to experimental data for the thermo-oxidative decomposition of a noncharring solid (PMMA), thermal pyrolysis of a charring solid (white pine), gasification and swelling of an intumescent coating, and smolder in polyurethane foam. Agreement between model calculations and experimental data is favorable, especially when one considers the complexity of the problems simulated.