Study on specific properties of thermally altered coal and its utilization suggestions

Coal will still occupy the dominant position in energy consumption structure of China for a long time. The deep development and mining of coal will inevitably encounter more igneous intrusions and thermally altered coal affected by them.Comparing with plutonic metamorphosed coal, thermally altered coal is more likely to bring risks of gas outburst and spontaneous combustion, and it will probably bring a series of safety problems during the development and mining processes of coal. On the other hand, due to the special nature of thermally altered coal and existing technological conditions, the value of thermallyaltered coal is limited. Therefore, summarizing the special properties and exploring the potential application of thermallyaltered coal are not only helpful to the deep mining of coal, but also beneficial to the utilization of thermallyaltered coal. Thermally altered coal is distributed worldwide, and relevant reports are made by many coal mining countries. Since thermally altered coal was firstly reported in the mid 1800s, a lot of researches about the coal petrology, geochemistry, mineralogy, etc. have been done. Basing on these literatures, this review summarized specific properties of thermally altered coal from the aspects of coal petrology, minerals, elements, maturity, potential of hydrogen generation, isotope, optical properties, porosity, macromolecular structure, etc., and discussed the factors affected thermally altered coal.According to the specific properties of thermally altered coal, especially the chemical structure, a possible future development of thermally altered coal was also proposed in this work, i.e., thermally altered coal may be a potential feedstock for preparing carbon materials.The abundant pore structure of thermally altered coal, coupled with the good seal of igneous intrusion and proper geological conditions, will probably make thermally altered coals to be good coal bed methane reservoirs.