Numerical investigation of the back-mixing and non-uniform characteristics in the three-dimensional full-loop circulating fluidized bed combustor with six parallel cyclones

• Main Authors: Yang, Shiliang, Wang, Shuai, Luo, Kun, Fan, Jianren, Chew, Jia Wei
• Other Authors: School of Chemical and Biomedical Engineering
• Format: Article
• Language: English
• Published: 2021
• Subjects: Engineering::Bioengineering; Circulating Fluidized Bed; Two-phase Flow
• Online Access: https://hdl.handle.net/10356/150283
• Institution: Nanyang Technological University

The design and operation of circulating fluidized bed (CFB), which offers excellent heat and mass transfer, remain challenging because of the lack of a comprehensive understanding. CFD-DEM is used here for the high-fidelity simulation of the three-dimensional full-loop CFB with six parallel cyclones. Detailed information on the particle-scale information (i.e., solid dispersion, particle rotational speed, fluid and collision forces, mass distribution, and backing-mixing intensity) throughout the CFB are presented for the first time. Interesting results include: (i) the solid dispersion behavior is significantly different among the three directions; (ii) the solid loading in the middle cyclone on one side of the riser is twice that of the two adjacent ones, and this non-uniform distribution underscores the need for full-loop simulation for the CFB with multiple cyclones; (iii) the solid dispersion coefficients in all three directions, fluid force, collision force and particle rotational speed are similar among the six cyclones and correspondingly the standpipes; and (iv) approximately 50% and 48% of the total material are distributed respectively in the riser and standpipes. The results obtained provide valuable insights regarding the mass loading, particle-scale characteristics and non-uniform distribution of the solid phase throughout the entire CFB.