Impact of the crystallite parameters and coal ranks on oxidation and combustion properties of Carboniferous coals and Jurassic coals

Abstract

Coal fires have become a global issue that poses the immense threat to energy resources, environment, the economy, and human health. Given that the chemical structure substantially affects the propensity and behavior of coal fire, two raw Xinjiang Jurassic coals (collected from Piliqing and Yuxing collieries, PLQ and YX) and two Shanxi Carboniferous coals (collected from Dongqu and Fenghuangshan collieries, DQ and FHS) were selected to explore the impact of crystallite parameters and coal ranks on the oxidation and combustion properties of Carboniferous and Jurassic coals. X-ray diffraction (XRD) was used to determine the partial ordering and crystal parameters, crossing-point temperature (CPT) was used to evaluate the spontaneous combustion tendency, and temperature-programmed system (TPS) was used to estimate the coal spontaneous combustion tendency and forecast the coal self-ignition property. The experimental data and the existing literature were used to compare and discuss the variations. Results show that Jurassic coals were characterized by higher volatiles, moisture and oxygen, lower coal ranks, and degree of order than the Carboniferous coals. The values of CPT are PLQ < YX < DQ < FHS, thereby showing the same variation trend as the coal ranks and interlayer spacing (d002). The CPT value has good positive linear with random reflectance of vitrinite (Ro) and a perfectly negative linear with interlayer spacing (d002), indicating that the coal ranks and interlayer spacing (d002) have a significant impact on the combustion properties. The oxygen consumption also is impacted by coal ranks and interlayer spacing (d002). The concentration of index gases tends to increase exponentially with an increase in coal temperature. The Jurassic coals easily and rapidly produce the index gases.