Effect of particle system on slag formation and shedding characteristics of high alkali metal coal in full-scale circulating fluidized bed boiler based on Nano-CT

In the combustion process of Zhundong coal, many factors had obvious influence on slagging process. In this paper, the influence of particle system on slag formation and shedding process was evaluated. Two slags were sampled at two CFBBs super heaters which temperatures were similar and the ash particles size and concentration were different. The collected slags were separated, and the inner layer was analyzed by XRF, XRD, and Nano-CT. The results suggested that the area ratio of particles smaller than 2 μm to the region area was above 80% in each region, indicating that the inner layer was dominated by fine particles. Furthermore, the proportion of particles decreased in each region of two slags with the increase of particle size. The influence of particle system on the slag formation and shedding process was proposed. The accumulation of small particles was the cause of slag formation, while large particles had great influence on slag shedding. The presence of large particles increased the porosity and reduced the contact area between particles, the binding force between the particles was weaker than that between particles and tubes. Therefore, the fracture location of two slags was different, which made the internal surface presented different appearances.