Numerical investigation on the gas and temperature evolutions during the spontaneous combustion of coal in a large-scale furnace

Abstract

To understand the development of coal oxidation reaction, the process of coal spontaneous combustion in a large-scale furnace was numerically simulated by employing finite element method and further validated through experiments. The evolutions of oxygen volume fraction and temperature distributions in the furnace were obtained. Furthermore, the influences of air supply volume and the thermal boundary temperature on carbon monoxide productions and maximum temperature changes were investigated. It was found that the released gaseous products and oxygen consumptions of the coal-oxygen reaction increased slowly before 60 °C, and rapidly after exceeding 100 °C. The low oxygen volume fraction region was generated away from the air inlet and moved towards the air inlet. The movement of high-temperature spots in the furnace could be divided into heat storage stage, thermal stability stage and rapid oxygen consumption stage. With the acceleration of coal-oxygen reaction, the region of high-temperature spot first moved away from the air inlet, and then migrated towards the air inlet. In addition, the higher volume of air supply and thermal boundary temperature could promote coal-oxygen reactions and cause thermal runaway when the critical values were reached. This study is helpful for the prevention of the coal spontaneous combustion.