Permeability estimation in filter cake based on X-ray microtomography and Lattice Boltzmann method

Abstract

The separation of particulate solids from liquids by filtration constitutes an important stage in many industrial processes. For the study of flows in filter cake, the microstructure and permeability are of critical importance and can influence the efficiency of the fluid flow and mass transfer. In this study, filtration tests are carried out with quartz particles of different size distribution and shapes. Base on this, we combined the X-ray microtomography (XMT) and Lattice Boltzmann Method (LBM) simulation as a comprehensive approach to further analyzed and discussed the influence of particle property on microstructural detail and fluid transport of filter cake. In addition, the permeability of filter cake was predicted by two mathematical models and compared with the numerical and experimental data. From this analysis, it is found that if the particle properties could be specified for a filtration, the target properties would be for the particles to have as large a size as possible, be as near to spherical as possible. LBM is capable of describing the details of flow transport which occurs in filter cake and calculating its permeability. The fluid flux in filter cake strongly depends on flow main channels which is more related to the width of channels than the numbers of channels. Combined with CT test, we observe that improving pore connectivity and pore size is more effective than increasing porosity and number of pores for improving the cake permeability, and decreasing the pore tortuosity can also increase the flow velocity. Both the Kozeny-Carman model and the fractal model are questionable and not appropriate for determining cake permeability.