Fire Ladder Study to Assess Spontaneous Combustion Propensity of Indian Coal

Spontaneous combustion of Indian coals was investigated using sponcomb rig at University of Nottingham, UK to assess their susceptibility. In present study authors used eleven coal samples collected from the Jharia coalfield (JCF), India covering both fiery and non-fiery coal seams. Both thermal as well as gas profiles from sponcomb rig were studied critically to develop a fire ladder facilitating assessment of spontaneous combustion propensity of coal. The product of combustion gases (CO, CO2, CH4 and H2) emitted from sponcomb rig within the temperature range between ambient and 300 °C of these coal samples were studied. It has been observed that in this study temperature of coal samples reached to 550 °C. The signature of gases released from heating reveal that the CO releases in low temperature range i.e. 60–120 °C whereas H2 in temperature range 80–140 °C. The emission of CO2 initiates within the temperature range from 180 to 240 °C whereas CH4 releases at higher temperature range i.e. 360–480 °C. The oxygen concentration of the product of combustion gases reduces as the CO2 levels increase. The initial product of combustion gas i.e. CO followed by H2 indicates spontaneous combustion of coal in laboratory condition for Jharia coalfield. The temperatures at which CO and H2 release in the level of 50 ppm (i.e. TCO50, TH250) and modified crossing point temperature of coal (CPTCT) determined from sponcomb rig categorises the coal as per their propensity to spontaneous combustion. The results of these methods have been compared with other standard method i.e. crossing point temperature method, which is widely adopted in India to verify the suitability of this method.