Mathematical model of smoldering combustion in a carbonaceous porous medium - Part 1 - Development of pyrolysis and combustion models for a cylindrical geometry

In Part 1 of this two-part paper on the development of pyrolysis and combustion models for a carbonaceous porous medium, the methodology for elucidating the smoldering mechanism in a carbonaceous parous medium is described. The smoldering process was segregated into two major reaction zones - a pyrolysis zone and a combustion zone. Two independent models for a cylindrical geometry were developed: a steady-state two-dimensional model for the pyrolysis zone resulting in char formation, and a steady-state two-dimensional model for the combustion zone, i.e., char oxidation. The interface temperature between the two zones is defined as the temperature at which the pyrolysis is complete or the residual char ignites, which can be determined experimentally. In order to analyze the mechanism of smoldering combustion, the heat flux required for the smoldering to proceed in the pyrolysis zone (Q(req)) and the heat flux (Q(sup)) fed from the combustion zone into the pyrolysis zone were obtained from the models developed for any linear burn rate (LBR). Like temperature, these heat fluxes must be balanced at the interface between the two zones. The LBR corresponding to the intersect of Q(req) and Q(sup) can be used to determine the LBR, temperature and density profiles of the smoldering combustion of a cylindrical geometry.