Experimental analysis of thermal conductivity of different ranks of coal

Coal spontaneous combustion is a serious threat in safe production of coal, which could result in a coal fire, causing waste of resources and serious injuries and fatalities.Heat transfer between coal and rock is one of the key factors causing coal spontaneous combustion.Thus, research on heat transfer between coal and rock is essential to reduce coal spontaneous combustion.The thermal conductivity of coal is a major parameter for determining the thermal ability of coal.In this study, we analyze the thermal conductivity of different ranks of coal and investigate the effect of temperature and moisture content on thermal conductivity.Five coal samples of different ranks,namely coking coal, long flame coal, lignite, anthracite, and non-stick coal,were tested respectively under different ambient temperatures and moisture contents.Meanwhile, the thermal conductivity of these five coal samples was measured by the LFA457 laser thermal conductivity meter.In addition, the Pearson correlation coefficient methodwas applied to explore the effect of different coal compositions on thermal conductivity.The results indicate that the thermal conductivity of coal samples is negatively correlated with thecoal rank.In another word, lower thermal conductivity is associated with higher coal rank.When temperature is -50～10 ℃, the thermal conductivity of coal increases swiftly with the increase of temperature.When temperature is 10～50 ℃, the thermal conductivity of coal increases slowly and then tends to be stable.A lower degree of coal maturity indicates a greater effect of moisture content on thermal conductivity.It is also found that ash has the most significant influence on thermal conductivity of coal, then followed by fixed carbon, volatile matter,and moisture.This experimental study provides an understanding of influence factors and variation laws of thermal conductivity of different ranks of coal, and further provides a theoretical basis for the prevention and control of coal fire disasters.