Spontaneous heating and fire in coal mines

Spontaneous heating and fire in coal mines is a major problem worldwide and has been a great concern both for the industry and researchers in this field. Majority of fires existing today in different coalfields are mainly due to spontaneous combustion of coal. The auto oxidation of coal ultimately leads to spontaneous combustion which is the major root cause for the disastrous of coal mine in leading and coal producing countries like USA, China, Australia, India and Germany. It is a slow process and the heat evolved is carried away by air. This process of self-heating of coal or other carbonaceous material resulting eventually in its ignition is termed as "spontaneous heating" or "auto oxidation'. Coal can interact with oxygen in the air at ambient temperature liberating heat. If the heat is allowed to accumulate the interaction rate increases and may ultimately lead to tires known as spontaneous tires. The exact mechanism of the reaction of oxygen with coal is not completely understood as the chemical nature of coal is not yet fully established. But most of the workers agree that the reaction of oxygen with coal is a surface phenomenon and proceeds through a loosely bound coal-oxygen-water complex with subsequent steps being breakdown of the complex to simpler molecules such as CO, CO2 and H2O etc. Most popular hypothesis is that the overall reaction proceeds through a chain mechanism with moisture facilitating the formation of free radicals that act as chain carrier. Due to fire in coal mines, hues quantity of noxious gases liberated in the atmosphere which damage the ecological balance of nature. There are various technologies available in different parts of world to prevent and control spontaneous heating. Out of these technologies, chemical inhibitors play a vital role to control and combat tires. The main objective of this paper is to elaborate the causes, mechanism of spontaneous heating and technological advancement mainly development of chemical inhibitors for controlling and combating lire in coal mines. (C) 2013 International Association for Fire Safety Science. Published by Elsevier Ltd. Open access under CC BY-NC-ND license. Selection and peer-review under responsibility of the Asian-Oceania Association of Fire Science and Technology