Modeling of gas flow and temperature fields in underground coal fires

A two-dimensional model to simulate the flow and temperature fields in unde rground coal fires has been studied. The model is based on the theory of na tural convection in porous media. A numerical solution procedure is used. I ts predictions are compared with the limited field temperature data availab le. It is found from the model predictions that fractures or higher permeab ility are necessary to enhance natural convection. The air penetrates in th e area behind the fire where many fractures of higher permeability occur du e to subsidence. Air flows out from the hot area or cold area in front of t he fire. In a shallow depth fire convection plays an important role, wherea s in a deep fire convection velocities are smaller. Moreover, secondary com bustion of volatiles produced from coal seam in the fracture or crack can m arkedly increase the convection. (C) 2001 Elsevier Science Ltd. All rights reserved.