Investigation of Ash-Related Problem on Sequential Feeding Method for Coal Co-Combustion in Drop Tube Furnace

In this study, sequential feeding method was conducted due to some coal-fired power plants not being equipped by coal blending facility. Its effect on ash-related problem was investigated using drop tube furnace combustion test and ash particle observation method. AUS coal (low-slagging risk sample) and KT coal (high-slagging risk sample) were used to obtain AK-1 coal and AK-2 coal. AK-1 coal was a coal sample of out-furnace blending method, while AK-2 coal was coal sample of sequential feeding method. AK-1 probe tended to be more similar to AUS coal with only a small spot of ash attached on the probe surface. Meanwhile, AK-2 probe had more ash attached on the probe surface, indicating more severe slagging than AK-1 probe. According to ash morphology, the result indicated that the upper layer of slag tended to be more similar to AUS coal ash, while initial layer of slag of AK-2 coal contained more KT coal ash. Based on ash mineralogy, sodium in AK-2 coal was distributed evenly which was different with AK-1 coal. This result shows that sequential feeding method is not applicable to reduce slagging and fouling risk of KT coal.