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Partic. vol. 56 pp. 207-214 (June 2021)
doi: 10.1016/j.partic.2020.10.009

Experimental study of the solid circulation rate in a pressurized circulating fluidized bed

Jinding Hu, Daoyin Liu*, Heng Li, Cai Liang, Xiaoping Chen

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dyliu@seu.edu.cn

Highlights

    • Gas–solid flow studied in a pressurized circulating fluidized bed up to 0.6 MPa. • Solid circulation was obtained for different pressures and average particle sizes. • The gas–solid slip velocity rapidly decreased with increasing pressure. • The flow regimes and nondimensional gas–solid slip velocity were analyzed. • An empirical equation was obtained for the relationship between the solid circulation rate and operating parameters.

Abstract

The solid circulation rate is essential for design of pressurized circulating fluidized beds (PCFBs). With increasing pressure from atmospheric pressure to a few bars, the gas density linearly increases with the pressure, which affects the gas–solid flow characteristics. In this work, experiments were performed at room temperature in a cold PCFB apparatus with a riser of 3.3 m in height and 0.05 m in diameter. The solid circulation rate was studied from 20 to 80 kg/(m2·s) under various conditions with increasing pressure from 0.1 to 0.6 MPa and fluidizing gas velocity from around 1.5 to 8.0 m/s for different Geldart B group particles. Most of the conditions were in the flow regimes of core-annulus flow (CAF) only and CAF with a turbulent fluidized bed at the bottom. The trend of the apparent slip factor with the dimensionless slip velocity was similar at different pressures and for different average particle sizes, and it converged to an exponential function. An empirical equation was obtained by fitting the solid circulation rate with the operating parameters (particle transport velocity, particle volume fraction, Archimedes number, and Froude number), which is helpful for design and operation of PCFBs.

Graphical abstract

Keywords

Pressurized; Circulating fluidized bed; Solid circulation rate; Particle volume fraction; Gas–solid slip velocity