Frame-and-plate filter presses are widely employed in industrial solid–liquid separation due to their high efficiency and modular design. Conventional sizing and design methodologies, however, typically assume uniform suspension distribution across all filter chambers. In industrial operation, this assumption is rarely satisfied, leading to non-uniform filling, heterogeneous cake formation, and an increased risk of overfilling and clogging. To compensate for these effects, conservative safety margins are commonly applied, resulting in suboptimal operation and process efficiency.

This contribution investigates the mechanisms governing non-uniform flow distribution and cake buildup in an industrial-scale filter press, with the aim of developing a deeper understanding of the optimal parameters for filter press operations, and formulating a predictive modeling framework suitable for Digital Twin applications. Quantitative descriptions of compartment-level non-uniformities are lacking in the literature, as direct experimental measurements are invasive and often impractical, while CFD simulations of complete filter presses have traditionally been considered computationally prohibitive.

Building on compartment-scale CFD modeling that allow for a reduced complexity of the internals of each plate, a numerical framework is presented that enables the simultaneous simulation of multiple filter chambers with sufficient local resolution to capture relevant flow phenomena. The approach provides detailed spatial information on pressure losses, flow maldistribution, and chamber-to-chamber interactions under realistic operating conditions, allowing for a systematic analysis of the origins of uneven cake formation.

Finally, a mechanistic model for flow division within the filter press is formulated and validated against the CFD results. The model successfully reproduces the compartment-level flow distribution observed in the CFD simulations over a range of operating conditions, including varying Reynolds numbers, numbers of compartments, and suspension properties. This validation enables the identification and physical interpretation of the key model parameters governing flow maldistribution, providing a rational basis for improved filter press sizing and operation.