Experimental Investigation into the Spontaneous Ignition Behavior of Upgraded Coal Products

Abstract

The propensity for spontaneous ignition of nine coal samples and their upgraded products were experimentally investigated. The basket method was used to study the effects of the variation of mineral matter and volatile content on the spontaneous ignition of coal. The removal of mineral matter by chemical leaching caused the spontaneous ignition temperature (SIT) to decrease, which indicated a higher propensity for ignition. As the mineral matter increased, SIT increased approximately linearly. The results indicated that the SIT of coal char first decreased with a decreasing volatile content and then rapidly increased as the volatile content continued to decline, because of the deepening of the devolatilization. This paper proposes a prediction model based on the oxygen and carbon ratio (O/C) parameter in raw coal, which can be used to predict its SIT.

Investigation of combustion characteristics and kinetics of coal gangue with different feedstock properties by thermogravimetric analysis

“…This may imply that the ignition index may not be the only factor to be concerned, related to ignition temperature. The possible reasons are the effect of ash content on ignition performance because high ash content can affect oxygen diffusion and heat transfer [12]. The higher ash content (70.8-77.0%) in S1, S5 and S7 result in the greater resistance of oxygen diffusion and the higher temperature gradient between the inside and outside of the particle.…”

“…The correlation results also suggest that volatile matter plays an important role in the process of coal gangue combustion. The fast ignition of high volatile content gangue can increase particle temperature and ignite the fixed carbon in advance [12]. Hence, it is deduced that co-combustion of coal gangue with high volatile content materials is helpful for coal gangue combustion.…”

“…The reason for this is that coal gangue contains numerous surface functional groups. These functional groups are very active and may take part more easily in the oxidation process [12]. During the heating process, the activation energy increases.…”

“…High-ash coal gangue combustion behavior is not only influenced by combustible matter but also by mineral matter. This effect is most probably due to the heat absorption of mineral matter [9,11,12]. Moreover, the feedstock properties (combustible matter, mineral matter) of coal gangue are different depending on source, coal rank, and coal mining technique and washing technology.…”

A novel lignite-fired power plant integrated with a vacuum dryer: System design and thermodynamic analysis

“…A very large proportion of the 'noncaloric content' e water, which is sometimes as high as 60%, absorbs a great amount of heat to evaporate during the combustion process, leading to a lower caloric value of lignite than that of the black coal. Moreover, lignite has a susceptibility to spontaneous ignition due to the sensitive volatile content [2,3]. So, it is costly to transport and store lignite.…”