Neighborhood Relationships of Widely Distributed and Irregularly Shaped Particles in Partially Dewatered Filter Cakes

Abstract

A more thorough understanding of the properties of bulk material structures in solid–liquid separation processes is essential to understand better and optimize industrially established processes, such as cake filtration, whose process outcome is mainly dependent on the properties of the bulk material structure. Here, changes of bulk properties like porosity and permeability can originate from local variations in particle size, especially for non-spherical particles. In this study, we mix self-similar fractions of crushed, irregularly shaped Al2O3 particles (20 to 90 µm and 55 to 300 µm) to bimodal distributions. These mixtures vary in volume fraction of fines (0, 20, 30, 40, 50, 60 and 100 vol.%). The self-similarity of both systems serves the improved parameter correlation in the case of multimodal distributed particle systems. We use nondestructive 3D X-ray microscopy to capture the filter cake microstructure directly after mechanical dewatering, whereby we give particular attention to packing structure and particle–particle relationships (porosity, coordination number, particle size and corresponding hydraulic isolated liquid areas). Our results reveal widely varying distributions of local porosity and particle contact points. An average coordination number (here 5.84 to 6.04) is no longer a sufficient measure to describe the significant bulk porosity variation (in our case, 40 and 49%). Therefore, the explanation of the correlation is provided on a discrete particle level. While individual particles < 90 µm had only two or three contacts, others > 100 µm took up to 25. Due to this higher local coordination number, the liquid load of corresponding particles (liquid volume/particle volume) after mechanical dewatering increases from 0.48 to 1.47.

Experimental Method Development for the Formation of Filter Cakes with Inhomogeneous Cake Geometry

“…1). Sie wird u. a. durch die Kuchenbildung bestimmt 13, 14 und ist ein wichtiger Parameter zur Charakterisierung der makroskopischen Struktur von Haufwerken 15. …”

Quantitative Analysis of Separated Impurities inside Filter Cakes with Phantom-Aided X-ray Tomography

“…Kieselguhr (ρ = 2.29 g/cm 3 ), also known as diatomaceous earth, is a siliceous sediment derived from fossilized diatoms. Based on its application as a contrast agent in CT imag-ing [31], barium sulphate (BaSO 4 , ρ = 4.36 g/cm 3 ) is used as a highly attenuating impurity. See Table A1 of Appendix A for details regarding both particle systems.…”

“…In addition to the geometrical magnification, a setup with additional optics, a so-called X-ray microscope (XRM), allows a further increase in resolution by one order of magnitude. Nowadays, XRM systems which can achieve a resolution of a few µm have become a standard tool in the engineering sciences for the characterization of particle systems, for example to support the understanding of separation processes [2,3].…”

Analysis of the Effect of Coordination Number on Permeability of the Three-Dimensional (3D) Rock Model Using the Lattice Boltzmann Method (LBM)

“…The coordination number is a crucial factor that impacts the topology of porous rocks, consequently affecting the rock's permeability value [6]. The distribution of coordination numbers can exhibit variations within porous media, contingent upon factors such as porosity, localized fluctuations in grain size distribution, and rock type [7]. Coordination number estimation can be done using a microscopic approach.…”