Modelling oxygen-limited and self-sustained smoldering propagation: Underground coal fires driven by thermal buoyancy

摘要

Modelling oxygen-limited and self-sustained smoldering propagation is of significance for prevention of fire hazards and optimization of applied systems. However, two issues remain unsolved in the conven-tional models: (a) adjustment of TG-scale kinetic parameters applied to bed-scale propagation, and (b) decoupling oxidative reaction and oxygen transport in multi-scale porous media. In this work, an analytic expression of oxidative reaction rates limited by oxygen transport is derived from the conservation equa-tions of oxygen species transport in gas and solid. Then, both oxidative reaction rates controlled by the kinetic reaction (Arrhenius equation) and oxygen transport (analytic expression) are integrated into the conservation equations of mass, energy, and oxygen species transport. In this model, five-step reaction scheme is considered and their kinetic parameters obtained from TG experiments are employed with-out any adjustment. Along with the Darcy air flow driven by thermal buoyancy, this model is applied to predict oxygen-limited and self-sustained smoldering propagation of underground coal fires. The pro-posed model is compared with laboratory experiments and the conventional model. Results show that the proposed model well predicts the oxygen-limited and self-sustained smoldering propagations of un-derground bituminous and anthracite coal fires. The predictability of the proposed model is better than the conventional model in spite of great effort to modify kinetic parameters best fitting with experimen-tal data. It is validated that the proposed model addresses the two puzzled issues in the conventional model with respect to buoyancy-driven, oxygen-limited, and self-sustained smoldering propagation of underground coal fires. This work may help to improve models of self-sustained propagation of other smoldering fires and applied smoldering systems.(c) 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.