Investigation of Spontaneous Combustion of Coal in Underground Coal Mining

Abstract

The risk of spontaneous combustion of coal is highly serious especially for underground coal mines. Coals react with oxygen immediately after producing in coal mines and they are subject to spontaneous combustion. This reaction is an exothermic reaction and coals give heat to the surrounding air. If the heat is not removed from the surrounding air, spontaneous combustion occurs and then flaming fire starts. In addition, in underground coal mine besides exothermic reactions, hazardous, explosive and flammable gases are released to the surrounding air. This situation causes interruptions in production, economical losses and environmental problems. In order to avoid these problems, coal production at the longwall should be stopped and the contact of the coal with air should be prevented. In this study, the temperatures changes throughout the longwall in the spontaneous combustion condition were measured by a temperature sensor placed inside the longwall. In addition, while the temperature recording was carried out for inner part of the longwall, the temperature of the exhaust air and concentration of some mine gases (CO, CH4, O2 and CO2) were also measured. Graham’s ratio was calculated and used to determine of spontaneous combustion with the concentration of those mine gases. The temperatures of the longwall were increased in time and the coal production of longwall was stopped. After eliminating the air contact of coal, the temperature recording was continued. The temperature changing for the inner part of the longwall were observed continuously.