Assessment of Spontaneous Heating Susceptibility of Coals Using Wet Oxidation Potential Difference Technique

Abstract

The main reason behind the spontaneous heating of coal is auto-oxidation. The after effect of spontaneous heating is a major setback in the production of coal.The spontaneous heating depends on many intrinsic factors such as, Ash content, moisture content, volatile matter content and fixed carbon. Apart from all the above mentioned parameters, wet oxidation potential difference method can also be correlated so as to predict its spontaneity for heat. The spontaneous heating susceptibility varies over a large span, thus the experiments become an important tool in predicting the vulnerability to spontaneous heating of a coal sample. In this project, the wet oxidation potential difference experiment was conducted for 20 different coal samples from different mines across India. The coal samples were collected by channel sampling and then they were prepared according to the Indian Standards. The calorific value of all the samples was measured using the Bomb Calorimeter and proximate analysis was also conducted so as to obtain the different parameters about the coal samples such as calorific value, ash, moisture, volatile matter, fixed carbon content. Correlation study was carried out to assess the spontaneous heating susceptibility of coal. In India, generally crossing point method is used for assessment of spontaneous heating susceptibility of coal. However, this method has certain draw backs.The results are dependent upon packing density, rate of heating and oxygen flow rate etc, and sometimes the results are not reproducible. Moreover it takes more than three hours to complete the experiment. Compared to CPT, the wet oxidation experiments only takes about 40 minutes for completion and the results are reproducible. From the correlation analysis, it was found that WOPD indicated a fair measurement of spontaneous heating susceptibility as it showed high correlation with the intrinsic properties such as moisture and volatile matter.