The influences of moisture on particle ignition behavior of Chinese and Indonesian lignite coals in hot air flow

The effect of moisture content on ignition and combustion behavior of Chinese (HL) and Indonesian (YN) lignite were investigated. Particles with a size range of 75-105 μm with different moisture contents were injected in a bench-scale, electrically heated transparent reactor and the combustion of individual particles was observed with a high-resolution high-speed camera. Direct ignition observations indicated that most of the HL lignite particles underwent extensive fragmentation during ignition. Fragmentation was attributed to the explosive diffusion of volatiles and water vapor to the particle surface as a result of fast heating rate. Fragmentation reduced the particle size and increased the possibility of heterogeneous ignition of individual fragments. YN lignite particles on the other hand, underwent one-mode whole particle ignition upon heating. Higher moisture content caused a significant ignition delay in both lignite samples. 10% and 20% moisture in lignite samples resulted in around 83 and 160 ms delay in ignition for both coals. Higher intensity of fragmentation of HL particles during combustion compared to YN lignite resulted in shorter total particle combustion time at higher moisture contents. The findings of this study advanced the knowledge of the effects of moisture on ignition and combustion of low-rank coals.