Experimental investigation of erosion effect on microstructure and oxidation characteristics of long-flame coal

Abstract

To study the effect of erosion on coal microstructure and its oxidation characteristics, eroded coals were prepared by eroding coal samples in an acidic aqueous solution for 30 days, 90 days and 180 days, respectively. The microcrystalline structure, pore structure and active groups distribution of coal samples were studied using X-ray diffractometer, low-temperature N2 adsorption and infrared spectra. Temperature-programmed experiment was used to analyze the oxidation characteristics of raw coal and eroded coals. The results reflected that the number of aromatic layers and coalification degree of eroded coal are reduced compared with raw coal. The average pore diameter increases, which promotes oxygen transportation in coal pores. Under the erosion effects, the content of active groups such as hydroxyl (–OH), methylene (–CH2), and methyl (–CH3) in coal increases. Eroded coals, especially the coal eroded for 180-day demonstrate more oxygen consumption and CO production than raw coal during the oxidation process, and their apparent activation energies decrease. Besides, the enhancement mechanism of eroded coal's oxidation activity is expounded from the aspects of the increase of active sites and the improvement of pore structure. In brief, erosion effect increases the spontaneous combustion tendency of coal.