TGA/DSC study to characterise and classify coal seams conforming to susceptibility towards spontaneous combustion

Thermogravimetric analysis/differential scanning calorimeter (TGA/DSC) technique along with basic coal characteristics study is carried out for eighty coal samples of Indian coalfields, to determine spontaneous combustion propensity behaviour of coal. TGA study of coal samples indicates that there is an increase in the mass of coal samples in the temperature range 150–350 ℃, which may be due to oxygen adsorption and absorption. The correlation and principal component analysis states that the component of proximate analysis (M_ad, VM_d, FR, and VR) have an acceptable correlation with the TGA experiments results i.e., T_gsh and T_gign. Multiple fixed nonlinear regression analysis shows that thermogravimetry (TG) experiment results T_gign may be the best index to categorise/classify the coal as per their susceptibility towards spontaneous combustion. The authors proposed four groups of classification as per their propensity towards spontaneous combustion depending upon the moisture (M_ad), volatile matter (VM_d), and TG ignition temperature from differential thermogravimetric (DTG) curve (T_gign) using hierarchal clustering analysis. The coal samples of different seams from Indian coalfield may be classified into four different clusters, viz. very highly/extremely susceptible (T_gign < 260 ℃), highly susceptible (260 ℃ ≤ T_gign < 290 ℃), moderately susceptible (290 ℃ ≤ T_gign ≤ 320 ℃), and poorly susceptible (T_gign > 320 ℃). The field observations and TGA/DSC experiment results with the following statistical analysis substantiate a similar assessment.