Detailed Insight into Microscopic Phenomena Using 3D-Tomography Data to Develop a Better Model for Dead-End Filtration

Executive Summary

validate the results.

investigated particle and filter cake properties. Laboratory tests of the integral parameters

the local contact angle within the cake structure could be demonstrated on many of the

suspension, the wetting behavior could be precisely adjusted. The influence of changes in

with the mother liquor. By changing the ethanol content of the otherwise aqueous

Al2O3 (alumina) and CaSiO3 (wollastonite) particles were filtered at different combinations

Varying the wettability served as a parameter study. For this purpose hydrophobic coated

along the wetting line of the hydraulic isolated liquid areas within the pore space.

analysis of wet filter cakes allowed the measurement of the local contact angle distribution

coordination number, pore-to-pore relationships and the tortuosity of the filter cake. An

Detailed analysis of the tomographic data provided pore size distributions, the particle

filter cakes were determined and compared with results of standard measurement methods.

step, simple parameters such as total porosity or particle size distribution of the scanned

Commercially available software as well as specially developed code was used. In a first

sharpened and segmented by means of image processing before further analysis.

cake structure followed. The image data sets of the tomography were denoised, smoothed,

and measured in the µCT. After the measurement, a morphological analysis of the filter

The proof of comparability was followed by analyses of filter cake built in the in situ cell

the laboratory (Laboratory VDI Nutsch) and in the downscaled in situ Nutsch filter.

situ experiment to the larger scale. The proof was provided by validation experiments in

by preliminary investigations, which proved the transferability of the results from the in

during and after the process. The direct measurements in the µCT (in situ) were preceded

in µCT in order to examine the filtration process and the filter cakes built up without change

For this purpose, it was necessary to downscale a standard pressure Nutsch for direct use

filter cake, i.e. to obtain spatially resolved data instead of integral parameters.

The main objective was to obtain local information from the inside of the

the process-relevant structural effects of the filter cakes can be investigated nondestructively.

cake structure and other relevant filtration properties. Using X-ray computed tomography,

The aim of this project was to investigate the influence of particle properties on the filter

parameters such as the filtration resistance.

of the filter cake, such as its pore size distribution and tortuosity, and associated process

particles affect the structure of the filter cake. Associated with them are resulting properties

belonging fluid and particles. Size, shape, wetting behavior and other properties of the

Filtration properties are strongly dependent on the properties of the suspension, the