Effects of Moisture on the Ignition and Combustion Characteristics of Lignite Particles: Modeling and Experimental Study

The influence of the moisture content on the ignition and combustion characteristics of lignite single particles was studied using an ignition model of single coal particles with moisture and experimental investigations in a visual drop tube furnace under the temperature of 1300 K. The moisture content and the lignite particle size were varied within the ranges of 0-20% and 75-250 mu m, respectively. The images of the combustion process illustrated that higher moisture content caused a significant ignition delay. The probability of homogeneous ignition was greatest when the particle size was 125-150 mu m and the moisture content was 5%. An ignition model was employed to explain the mechanism of the influence of moisture content on the ignition and combustion characteristics, which embedded the chemical percolation devolatilization model to increase the accuracy of predictions. The predicted results show that there was an overlap in the release of moisture and volatile matter from the lignite particle during the combustion at a high heating rate. The devolatilization rate increases with the increase of moisture, which explains the increase in the probability of homogeneous ignition and fragmentation. Both particle size and moisture content have two-sided effects on the ignition mode, which causes the complexity and irregularity of the ignition mode of particles with moisture.