Mathematical modeling and experimental validation of ash deposition in a pulverized-coal boiler

• Published in: Applied thermal engineering Vol. 110; pp. 720 - 729
• Main Authors: Zheng, Shu, Zeng, Xiongwei, Qi, Chaobo, Zhou, Huaichun
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 05.01.2017
• Subjects: Ash deposition; Direct simulation Monte Carlo; Dynamic mathematical model; Ash deposition; Direct simulation Monte Carlo; Dynamic mathematical model
• ISSN: 1359-4311
• DOI: 10.1016/j.applthermaleng.2016.08.221

•A dynamic model of ash deposit formation was developed by DSMC method.•The deposit thickness of the inner layer is less than that of the outer layer.•The ash deposit thickness increases by 47.52% with the load increases by 20%.•Results are consistent with the morphology of ash deposit determined by SEM/EDS. A dynamic mathematical model of the fly ash transport and sticking in a pulverized-coal boiler was developed by a direct simulation Monte Carlo (DSMC) method. In this paper, the critical velocity model was used to calculate ash sticking rate during the initial deposition stage and the viscosity model was used to describe the outer layer deposition. The dynamic process of ash deposition was simulated and the distributions of adhesion particle size were obtained. The simulation results show that the ash deposit thickness increases by 47.52% with the load increases by 20% and the Alkaline Earth Metal (AAEM)-rich enhanced deposits of bulk ash particles are apparently stickier than the other ash particles. The experiments were carried out at two different loads and the morphology of ash deposit samples was analyzed by SEM/EDS. The propotion of particle size in 2μm were most in the deposition inner layer. The mean deposit thickness calculated by the DSMC method agreed with the measured value and the maximum relative error was 5.23%. A parametric study quantified the influence of changed operational conditions and ash material properties on the deposit formation process.