An experimental study on monitoring and early warning of spontaneous coal combustion fires using CPM

At present, the conventional indicator gas has a blank temperature interval in the monitoring of coal spontaneous combustion fire area, and the monitoring accuracy is easy to be interfered by wind flow, which leads to the inaccurate grasp of the situation of the fire area. To solve this problem, the characteristics of condensable particulate matter (CPM) released into the air during spontaneous combustion and heating are analyzed in this paper through a particle collection system. The results showed that the CPM captured by the system gradually increased when the coal temperature rose above 250℃, and the diameter was above 1um. After 300℃, the release of CPM increased significantly, which was more than 10 times that below 300℃. Test analysis showed that these CPMs were mainly phenols and polycyclic aromatic hydrocarbons, which accounted for 22 % and 37 % respectively after 300℃. CPM mainly comes from the pyrolysis stage and the early stage of combustion of coal. Aliphatic macromolecules and polycyclic aromatic compounds generated by pyrolysis are the precursors of CPM. Due to the limitation of oxygen diffusion, these compounds are released into the air due to insufficient oxidation and eventually form CPM. It is worth noting that the release amount and composition of CPM have a good correspondence with coal temperature. The research results can fill the temperature gap of monitoring fire situation by conventional gas, and help to improve the accuracy of monitoring, which is of great significance for the protection of coal resources and safe production. [Display omitted] •The characteristics of condensable particles released by coal in the high temperature stage of spontaneous combustion are tested.•The correlation between particulate matter and coal molecular chemical structure during spontaneous combustion evolution is analyzed.•Using the research method of air pollutants, it is revealed that there is a good correspondence between coal temperature and particulate matter.•The research results can make up for the gaps and deficiencies of the existing coal fire monitoring methods.