Smoldering Combustion In Porous Media Kinetic Models For Numerical Simulations

Abstract

Enhanced technologies for power generation using unconventional fuels - oil shale and its semicoke, oil sands, extra-heavy oil and biomass from municipal solid waste and from sewage sludge - have in common thermochemical processes composed of complex chemical reactions. This work deals with the formulation and optimization of the chemical mechanism typically involved in oil shale pyrolysis and oil shale and its semi-coke combustion. Inverse problems (using the Levenberg-Marquardt algorithm) were employed to minimize the error between estimated values and the thermogravimetric data for kinetic pathways of 3-steps for oil shale pyrolysis, and 4-steps and 3-steps proposed for oil shale and its semi-coke respectively. The kinetic parameters such as reaction order, pre-exponential factor, activation energy and stoichiometric coefficients that affect drying, pyrolysis, oxidation and decarbonation reactions were estimated with success. Also, statistic and residual errors were evaluated, resulting in a reasonable value for all estimations. In addition, the kinetic mechanism proposed and estimated for semi-coke combustion was applied in a code in porous media. A parametric study between temperature profile and air velocity, and temperature profile and fixed carbon concentration was made. This study shows that the temperature profile is extremely influenced by these parameters confirming that the front propagation was controlled by O2 supply.