Assessment of spontaneous heating of fresh and oxidized coals

Abstract

Coal oxidation is a natural phenomenon, It may begin in the pit itself or during the operations of extraction, preparation, transportation and storage. A fresh coal is more reactive to oxygen than a weathered coal i.e. it is more liable to spontaneous heating. To see the rate of decrease in the oxidation rate, first coal samples were taken and three samples were prepared from each sample. First sample was same as the sample taken while the second sample was obtained by oxidizing the sample at 200 degree C for 1 day. Third sample was obtained by oxidizing the coal at 200 degree C for 3 day. Then susceptibility of each of these samples were checked by crossing point temperature method, differential thermal analysis and wet oxidation potential method. For the experimentation purpose total of 15 samples were taken. Among these 6 samples were from SECL, 2 samples were from MCL, 2 samples were from CCL, 3 samples were from SCCL. 2 samples were collected from Indonesia to compare it’s characteristics with the Indian coals. The intrinsic property of both the fresh and oxidized coal was determined by proximate analysis. Similarly susceptibility of both fresh and oxidized coal to spontaneous heating was calculated by crossing point temperature and wet oxidation potential.From the experimental results it was found that the volatile matter content of the coal increases as the sample is oxidized while the liability of the coal to spontaneous heating decreases with oxidation. For coals with high fixed carbon content the change in liability of spontaneous heating is significant even after 1 day oxidation. While in case of coals with low fixed carbon content the change in liability of spontaneous heating is not too significant. It is expected that finding of this work will help in deciding whether to adopt any precautionary measures for oxidized coals.