In this study, the process of membrane cleaning by supercritical fluid extraction was investigated. Polypropylene microfiltration membranes, contaminated with oils, were treated in a batch process with a supercritical fluid (SCF). As extractant, pure supercritical carbon dioxide or supercritical carbon dioxide with admixtures of methanol, ethanol and isopropanol were used. Single-stage and multi-stage extraction was carried out and process efficiency was determined. The obtained results showed that addition of organic solvents significantly enhances the cleaning performance, which increases with increase of organic solvent concentration and decreases with increasing temperature. All three solvents showed a comparable effect of efficiency enhancement. The results confirmed that supercritical fluid extraction can be applied for polypropylene membrane cleaning.

The role of capillary pumping on the course of cleaning porous materials containing liquid contaminants using supercritical fluids was investigated numerically. As a specific process to be modelled, cleaning of porous membranes, contaminated with soybean oil, using supercritical carbon dioxide as the cleaning fluid (solvent) was considered. A 3D pore-network model, developed as an extension of a 2D drying model, was used for performing pore scale simulations. The influence of various process parameters, including the coordination number of the pore network, the computational domain size, and the external flow mass transfer resistance, on the strength of the capillary pumping effect was investigated. The capillary pumping effect increases with increasing domain size and decreasing external flow mass transfer resistance. For low coordination numbers of the pore network, the capillary pumping effect is not noticeable at macro scale, while for high coordination numbers, the opposite trend is observed – capillary pumping may influence the process at macro scale. In the investigated system, the coordination number of the pore network seems to be low, as no capillary pumping effects were observed at macro scale during experimental investigation and macro-scale modelling of the membrane cleaning process.

The electrostatic impulse method is an established method for producing microbeads or capsules. Such particles have found application in biomedical engineering and biotechnology. The geometric properties of the droplets – constituting precursors of microbeads and capsules – can be precisely controlled by adjusting the geometry of the nozzle system, the physical properties and the flow rate of the fluids involved, as well as the parameters of the electrostatic impulse. In this work, a method of mathematical modeling of the droplet generation process using the electrostatic impulse method in a single nozzle system is presented. The developed mathematical model is an extension of the standard Volume of Fluid (VOF) model by addition of the effect of the electric field on the fluid flow. The model was implemented into the OpenFOAM toolkit for computational fluid dynamics (CFD). The performed CFD simulation results showed good agreement with experimental data. As a result, the influence of all process parameters on the droplet generation process was studied. The most significant change in droplet generation was caused by changing the electrostatic impulse strength. The presented modeling method can be used for optimization of process design and for studying the mechanisms of droplet generation. It can be extended to describe multi nozzle systems used for one-step microcapsule production.