Fluid mechanics of crossflow magnetically stabilized fluidized beds

Abstract

From the analogy of laminar flow through a circular pipe, a simple model describing the fluid mechanics of a crossflow magnetically stabilized fluidized bed (MSB) in an inclined channel was developed. Predictions from the model compared favorably with experimental data for the bed top surface and solids velocity profiles. It was found that the flow of MSB sollds can be described as a non-Newtonian fluid, where standard rheological models such as power law or Blngham plastic apply. The effective viscosity of an MSB was found to decrease with increasing channel shear rate. Thus, a magnetically stabilized bed of solids appears as a "shear thinning fluid". High yield stresses are the controlling mechanism at low bed flow rates, while a truly vlscous flow exists once the bed solids establish steady-state flow. The decrease in bed fluidity with Increasing magnetic field was confirmed and further quantified.

Magnetic Field Assisted Fluidization - A Unified Approach Part 7. Mass Transfer: Chemical reactors, basic studies and practical implementations thereof

“…and Colaloglou, 1984a) without any deviation from the plug flow behaviour with high solids flow gradient (as it was reported by Cheremisinoff et al, 1985). and Colaloglou, 1984a) without any deviation from the plug flow behaviour with high solids flow gradient (as it was reported by Cheremisinoff et al, 1985).…”

“…It is an original Exxon's innovation (Siegel, 1984) and its mechanics (Siegel, 1988;Siegell and Colaloglou, 1984a, b;Siegell et al, 1985a,b;) was extensively reviewed in Part 4 (Hristov, 2004). The solids flow exhibits a Bingham velocity profile (Fig.S.llc) and rheology (Siegell and Colaloglou, 1984b;Cheremisinoff et al, 1985). The fields used with these devices are axial and created by a solenoid.…”

“…The separation efficiency in term of 'transfer units" (see Fig.3.1e) is higher than that of a conventional packed bed and HETP increases as the gas velocity is increased (Siegell et al, 1986a, b). After: Cheremisinoff et al (1985); Siegel! (Siegel et al, 1985a) The basic assumptions (Siegel et al (1985a) of the crossflow MSB chromatography are (see Fig.3.13): i) Steady-state, and ii) Uniformly: temperature, pressure, bed porosity, particle size, interparticle porosity, gas phase velocity and solids phase velocity.…”

Mathematical analysis of crossflow magnetically stabilized fluidized-bed chromatography

“…Nearly uniform solids flow profiles for crossflow MSB's have been reported previously (Siegell and Couláloglou, 1984). However, conditions under which a Significant solids flow gradient may exist have been studied (Cheremisinoff et al, 1985). With large deviations from the plug flow behavior, the separation efficiency of the unit could be greatly impaired.…”