Numerical and experimental investigation of the compaction of suspended elastic-plastic microparticles in a centrifugal force field

Centrifuges are widely used in processes of particle technology to separate different phases based on density. During centrifugation, the sedimented particles can undergo plastic deformation, forming a compressible cake. However, the mechanisms governing cake compressibility, particularly the nonlinear distribution of porosity and stress induced by plastic deformation, remain insufficiently understood. In this study, the compaction behaviour of elastic-plastic microparticles during centrifugation was investigated through experiments and simulations using Computational Fluid Dynamics coupled with Discrete Element Method (CFD-DEM). Spherical paraffin particles with low-temperature-dependent mechanical properties have been produced to vary plastic deformation by changing their yield pressure via temperature in the centrifuge. Ethanol-based suspensions of these particles were centrifuged at varying rotational speeds and temperatures using an analytical photocentrifuge to investigate the interplay between particle mechanics and applied centrifugal forces. The resulting sediments were analysed via micro-computed tomography (μCT) to assess the porosity distribution within the compacted cake. To model particle bed formation, CFD-DEM simulations were performed using a multiphase solver incorporating liquid, gas and particle phases, along with centrifugal, Euler and Coriolis forces. An elastic-plastic contact model was employed in the DEM, with parameters such as Young's modulus and yield pressure obtained via single particle compression tests with a nanoindenter. Both experimental and simulation results demonstrated that increasing rotational speed and thus centrifugal force enhances sediment compaction, primarily driven by particle plastic deformation and significantly influenced by the radial pressure distribution, resulting in a nonlinear porosity profile within the particle bed. • Plastic deformation significantly enhances the compaction of particulate cake formed during centrifugation of suspensions. • The deformation behaviour of paraffin particles is strongly influenced by their temperature-dependent mechanical properties. • Multiphase CFD-DEM simulations incorporating an elastic-plastic contact model accurately capture sedimentation dynamics, cake compaction, particle deformation, size-dependent effects, and the spatial distribution of porosity and contact forces under centrifugal fields. • The resolved stress distributions within the compacted sediment reveal the influence of the radial pressure gradients.