Theoretical Flammability Diagram for Analyzing Mine Gases

Out of the thermal balance method, a method of presenting mine fire data is proposed in this work. By grouping fuels into a pseudo fuel, grouping nitrogen and oxygen into a pseudo air, and using carbon dioxide as the diluent, a diluted flammability diagram is reconstructed for this oxygen-modified environment. The flammability envelop is controlled by oxygen availability, while the operation point is controlled by fuel/diluent availability. The relative position between the envelop and the operation point shows the flammable state of this mixture. Coward’s explosive triangle is also applied using the limiting oxygen concentration derived from the diagram. Both are most useful in guiding the suppression operation for an underground coal mine fire.