Magnetic field assisted fluidization: A modified Richardson–Zaki equation--颗粒学报PARTICUOLOGY

Valverde, J. M., & Castellanos, A. (2007). Magnetic field assisted fluidization: A modified Richardson–Zaki equation. China Particuology, 5(1), 61–70. https://doi.org/10.1016/j.cpart.2007.01.001

Magnetic field assisted fluidization: A modified Richardson–Zaki equation

Jose Manuel Valverde ^a *, Antonio Castellanos ^a

a Faculty of Physics, Universidad de Sevilla Avenida Reina Mercedes s/n, 41012 Sevilla, Spain

10.1016/j.cpart.2007.01.001

Volume 5, Issues 1–2, February–April 2007, Pages 61-70

Received 16 June 2006, Accepted 6 January 2007, Available online 6 June 2007.

E-mail: jmillan@us.es

Highlights

Abstract

Magnetic particles can be uniformly fluidized by coupling the gas flow with an externally imposed magnetic field. Interparticle forces generated by the magnetic field cause aggregation of the particles in chain-like structures preferentially oriented along the magnetic field lines. In the present paper, we study the implications of the formation of these special types of aggregates on the empirical Richardson–Zaki (RZ) equation, originally proposed to describe the expansion of fluidized beds of non-aggregated particles. We have addressed two important issues, namely the flow regime, which is a function of the size of the aggregates, and the effect of shape and orientation of the chain-like aggregates with respect to gas flow on fluid drag. We propose a modified RZ equation (MRZE) in which the velocity scale, given by the terminal settling velocity of the individual aggregates, and the RZ exponent are predetermined as a function of the chain length. The chain length depends on the ratio of the magnetic energy to gravitational energy, and is estimated from the magnetic field intensity, and particle magnetization, size and density. Predictions of the MRZE are successfully compared with published results in the literature on the expansion of magnetic particles in the presence of externally applied magnetic fields.

Graphical abstract

Keywords

Fluidization; Geldart B; Magnetic particles; Aggregation; Richardson–Zaki equation

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