Effects of riser geometry on gas–solid flow characteristics in circulating fluidized beds--颗粒学报PARTICUOLOGY

Tu, Q., & Wang, H. (2020). Effects of riser geometry on gas–solid flow characteristics in circulating fluidized beds. Particuology, 49, 205-217. https://doi.org/10.1016/j.partic.2019.05.002

Effects of riser geometry on gas–solid flow characteristics in circulating fluidized beds

Qiuya Tu ^a *, Haigang Wang ^{a b}

a Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 10090, China
b University of Chinese Academy of Sciences, Beijing 100049, China

10.1016/j.partic.2019.05.002

Volume 49, April 2020, Pages 205-217

Received 2 January 2019, Revised 29 March 2019, Accepted 6 May 2019, Available online 17 July 2019, Version of Record 26 February 2020.

E-mail: tuqiuya@iet.cn

Highlights

• Circular, square, and rectangular risers were studied at two different bed heights.

• A single bubble appeared in circular and square risers.

• Double bubbles existed in the rectangular riser.

• A single-core annulus structure appeared in circular and square risers.

• A double-core annulus structure emerged on the long side of the rectangular riser.

Abstract

The performance of a circulating fluidized bed strongly depends on its parameter settings, including that of riser geometry. In this study, a laboratory-scale circulating fluidized bed with three different riser geometries (circular, square, and rectangular) that had the same cross-sectional area and height was operated under two static bed heights (20, and 35 cm). Electrical capacitance tomography was combined with differential pressure transducers and an optical-fiber probe to measure the solids’ volume fraction, differential pressure fluctuations, and radial particle concentration variations. Computational particle fluid dynamics simulations were also performed. The results showed that single bubbles appeared in the bottom region of the circular and square risers and double bubbles in the bottom region of the rectangular riser. The autocorrelation of capacitance signals was periodic for the circular and square risers and non-periodic for the rectangular riser. The radial particle concentration profiles showed a single-core annulus structure in the circular and square risers, but a double-core annulus structure along the long side and single-core annulus structure along the short side in the rectangular riser. Shannon entropy analysis showed that fluidization was less disordered and most predictable for the rectangular riser.

Graphical abstract

Keywords

Circulating fluidized bed; Riser geometry; Static bed height; Bubble shape; Electrical capacitance tomography; Computational particle fluid dynamics

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