Field and laboratory simulation study of hot spots in stockpiled bituminous coal

Large coal piles (50-150 000 tons) undergo weathering processes during long-term storage in open air. Chemisorption of atmospheric oxygen, formation of surface oxides, and partial oxidative decomposition of the coal macromolecule matrix result in the release of organic and inorganic gases [e.g., methane (CH₄), ethylene (C₂H₄), ethane (C ₂H₆), carbon dioxide (CO₂), carbon monoxide (CO), and hydrogen (H₂)]. Some of these processes are exothermic, and when the rate of heat dissipation in the pile is lower than that of its formation, a significant increase in the temperature can be measured. These places are termed "hot spots", which, in extreme cases, can result in fire eruptions. The maximal temperature measured in the hot spots was 330 °C. Monitoring of hot spots at the Israel Electric Company (IEC) bituminous coal storage sites has been conducted. A unique monitoring unit that can penetrate up to 8 m into the coal pile to sample gases and also measure the temperature was used.