Publication D: Network model of porous media – Review of old ideas with new methods
https://opara.zih.tu-dresden.de/xmlui/handle/123456789/1945
The paper takes up the old ideas of describing porous media with several tube and network models. The wellknown
models received from literature gave a good concept of dewatering equilibria resulting in capillary
pressure curves and pore size distributions (PoSD). However, numerical methods and measurement techniques
were not sophisticated allowing to evaluate the models appropriately.
In this work, a numerical method based on statistics is introduced to validate the network model of FATT from
1956: The porous filter cake structure is implemented as a matrix, which elements represent the pore size
correlating with the capillary entrance pressure for each pore. The input for the calculations can be any mathematical
approximation of a PoSD, which can be derived from capillary pressure tests or micro computer tomography
(μCT) analysis of the filter cake.
A procedure based on the concept of FATT is presented to generate dewatering equilibria for different applied
pressures. Therefore, the elements of the matrix are checked to be ‘dewatered’ regarding to their size, position,
the applied pressure level and the progress of dewatering. The network model known from literature is improved
by implementing additional conditions for the description of physical phenomena, such as the formation of
residual bridge liquid or hydrodynamic isolated areas.
X-ray microscopy, mercury intrusion tests and laboratory desaturation experiments by using semipermeable
membranes for capillary pressure tests are used to validate the pore size distribution. The different results are
integrated into the matrix model as starting parameters. For the laboratory experiments, the PoSD is calculated
from the measured capillary pressure curve, using the distributed tube model and the YOUNG-LAPLACE-equation
on an equal basis to the established mercury intrusion analysis. However, with the tomography measurements, it
is possible to determine PoSD using different defined geometry elements fitting inside the pore space. The force
balance is evaluated at the pore entrance by using the wetting line of the pore throat. The direct measurement of
the void geometry allows the calculation of the pressure distribution without the LAPLACIAN assumptions.
In this way, the difference between experimental, measured and modelled PoSDs is emphasised to validate the
old (and improved) ideas of network models describing porous media2021-09-23T11:14:24ZX-ray tomography scan of partially dewatered filter cake
https://opara.zih.tu-dresden.de/xmlui/handle/123456789/1966
X-ray tomography scan of partially dewatered filter cake
Löwer, Erik
X-ray tomography image of a partially dewatered filter cake. The initial slurry contains Al2O3 particles suspended in a potassium iodide-glycerol solution. These were separated by cake-forming filtration followed by dewatering. All filtration and dewatering experiments took place in an in situ apparatus within the Zeiss Xradia 510 X-ray microscope. The filter cake is dewatered until the minimum degree of saturation is reached within the pore space. A scan is taken at the equilibrium state before and after dewatering.
see note parameter.png in each measurement file for further measurement and reconstruction parameters
2021-01-01T00:00:00Z