Self-ignition risk classification for coal dust layers of three coal types on a hot surface

Pulverised coal in industrial sites and their dust can experience spontaneous combustion and self-heating, increasing the risk of fire and dust explosion. The main objective of the present study was to resolve thermal combustibility (as reflected by comprehensive combustibility index [S-n] and kinetic properties) for three types of coal (S1-BN, S2-CY, and S3-JM) through thermal analysis. The Sn values of the samples indicated a degradation in the quality of comprehensive combustibility. Apparent activation energies (E-a) at the initial stage of spontaneous coal combustion (130-300 degrees C) were decided through Achar and Coats-Redfern methods. Moreover, thermal susceptibility (minimum auto-ignition temperature [MAIT] and thermodynamic parameters) was evaluated using the hot plate method. The MAIT values for the three coal dust layers were 210, 220, and 300 degrees C. The results exhibited that heat conduction was the dominant heat transfer mode that originated the temperature distribution within the coal dust layer under the subcritical conditions for ignition; while it converted chemical reaction controlled-mode after thermal runaway. Furthermore, the results based on an improved risk matrix approach showed the S1-BN and S2-CY samples had a high self-ignition risk, whereas the S3-JM sample had a moderate ignition risk. (C) 2020 Elsevier Ltd. All rights reserved.