An Oxygen Balancing Approach To Determine The Extent Of Fire In An Underground Coal Mine

Abstract

Coal can easily be oxidized and has a prominent selfheating capacity. In underground coal mine, coal has a tendency to combust spontaneously under sufficient oxygen through ventilation. Uncontrolled spontaneous combustion of coal in an underground coal mine is a very serious problem. Spontaneous combustion of coal is one of the major hazard in any underground coal mining operations. If not detected early and managed properly, it can seriously affect the safety of workers and productivity. Thus, fire in underground coal mines need to be detected at an early stage so that effective measures can be taken before the fire assumes a very advanced stage. But detection of spontaneous heating or oxidation to know the status of heating is not a simple task. Gaseous products of spontaneous combustion, such as carbon monoxide, ethylene and hydrogen, are commonly used in coal mines as indicators to reflect the state of the spontaneous combustion. However, use of machineries, gases released from strata and other sources inside the mine also emits carbon dioxide, carbon monoxide and other gases when gets intermixed with the gases emitted from spontaneous combustion makes it difficult to assess the extent of fire in the mine. However, combustion of coal is not possible without its oxidation. Underground mines are ventilated by regulated supply of air containing oxygen causing oxidation, which is an exothermic reaction. When the heat released due to oxidation is not dissipated, temperature of coal goes on increasing, and thereby further increasing the rate of oxidation, till it reaches the ignition temperature of coal and cause spontaneous combustion. This study is an attempt to develop an approach to detect the extent of fire in underground mine is developed based on the amount of oxygen consumption or rate of oxidation. Other conventional approaches based on the presence of different gaseous products of combustion like CO, CO2 have the limitations of their sources other than spontaneous combustion or the different gas ratios based on these gases may indicate the stage of heating but the size of fire or in other words, quantity of coal involved in the process of oxidation cannot be estimated or assessed. The proposed approach of determining the extent of fire based on oxygen consumption is more appropriate and helpful in fire emergency planning and reducing the risk due to mine fire hazards.