Mimicking layer inversion in solid-liquid fluidized beds in narrow tubes

TL;DR

This study explores the dynamics of solid particles during layer inversion in binary solid-liquid fluidized beds within narrow tubes, using experimental tracking and CFD-DEM simulations to understand particle movement and inversion timing.

Contribution

It combines experimental high-speed imaging with numerical CFD-DEM modeling to analyze layer inversion mechanisms in narrow tube fluidized beds, a novel approach for this phenomenon.

Findings

Measured particle displacement during inversion

Determined characteristic inversion time

Validated CFD-DEM simulation results

Abstract

This paper investigates experimentally and numerically the dynamics of solid particles during the layer inversion of binary solid-liquid fluidized beds in narrow tubes. Layer inversion can happen in solid classifiers and biological reactors, where different solid particles coexist and segregation by diameter and density occurs. The fluidized beds were formed in a 25.4 mm-ID pipe and consisted of alumina and aluminum beads with diameters of 6 and 4.8 mm, respectively. We placed initially the lighter particles on the bottom in order to force an inversion of layers, mimicking the layer inversion mechanism. In the experiments, we filmed the bed with a high-speed camera and tracked individual beads along images, while in numerical simulations we computed the bed evolution with a CFD-DEM (computational fluid dynamics - discrete element method) code. We found the distances traveled by individual particles during the inversion and the characteristic time for layer inversion.