(222c) Simulation of Filter Cake Formation and Filter Washing during Solid-Liquid Separation

Slurry filtration is a critical process in many industrial applications for separating solids from liquids, where a porous filter cake forms on a filter medium (Puderbach et al., 2021). The pressure drop during filtration is influenced by the combined resistances of the filter cake, the filter medium, and the transitional layer created by interactions between the first particle layer and the filter medium. In certain applications, cake washing becomes essential. This step involves replacing the carrier liquid—often contaminated with undesirable chemicals—with a clean liquid, which may be of the same type or a different one, to ensure the desired level of purity. A detailed understanding of the micromechanics of filter cake formation and washing, including particle-fluid, particle-particle, and particle-medium interactions, is essential for accurately describing pore permeability, filter cake growth, and washing dynamics.

This study presents the development and application of a Computational Fluid Dynamics (CFD) model to simulate filter cake formation and washing during solid-liquid separation. The model employs the Eulerian Granular Model in ANSYS Fluent (Fluent, 2006; Kabir and Gamwo, 2018) to solve transient 3D flow equations, capturing the process from the initial stages of cake formation to the complete replacement of the liquid. The simulations are applied to concentrated oil-fine sand slurries filtered through a particle filter with cloth filtering layers adjacent to the liquid outlets.

The results show that gravity significantly influences flow patterns during both cake formation and washing, leading to noticeable changes in density distribution within the filter. The washing process is characterized by the formation of a narrow particle-free zone near the inlet and transient flow patterns that are highly sensitive to the particle-liquid density ratio. These findings underscore the importance of incorporating gravitational effects and density variations to accurately model and predict the dynamics of cake filtration and washing processes.

Keywords: Filter Cake Dynamics, Solid-Liquid Separation, Multiphase Flow Simulation

Literature

Fluent Inc. (2006). FLUENT 6.3 User’s Guide. Lebanon, NH: Fluent Inc.

Kabir, M. A., & Gamwo, I. K. (2018). Multiphase flow in porous media: Cake formation during extreme drilling processes. In M. M. Rashid (Ed.), Application of thermo-fluid processes in energy systems (pp. [specific pages, if available]). Springer. https://doi.org/10.1007/978-981-10-0697-5_11

Puderbach, V., Schmidt, K., & Antonyuk, S. (2021). A coupled CFD-DEM model for resolved simulation of filter cake formation during solid-liquid separation. Processes, 9(5), 826. https://doi.org/10.3390/pr9050826

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC

Release Number LLNL-ABS-20003953