Justus Altmann

Particle deposition and layer formation at the crossflow microfiltration

A microscopic model of the layer formation and the cake growth at the crossflow microfiltration will be introduced. The model considers the hydrodynamic, adhesive and friction forces acting on a single particle during the filtration process. It can be shown that mainly the balance between the lift force and the drag force of the filtrate flow determines the layer formation at the membrane. Particle attachment to the layer is mostly an irreversible process. This is due to the large influence of the adhesive forces. The irreversibility of particle attachment was proved by experiments with monodisperse particles. The introduced model allows the prediction of the instationary crossflow filtration processes. The filtration rate and structure of the formed layer can be calculated. In the case of a filtration at constant transmembrane pressure the model calculation shows a good correspondence to the experimental results.

Crossflow microfiltration – state of the art

Abstract Microfiltration is the oldest membrane process and shows up to now the largest market for technical membranes and membrane modules. In technical applications crossflow microfiltration is an established process for the separation of microparticles, bacteria and emulsion droplet. The following article describes the development and the state of the art. It makes a contribution to understand the mechanisms of crossflow filtration.

Crossflow electrofiltration in pilot scale

In crossflow filtration, a filter cake is formed on the membrane in the course of filtration. This cake acts as an additional resistance and significantly decreases the high initial permeate flow rate and thus the efficiency of the process. As particles in suspensions carry an electric charge, it is possible by means of a suitable superposition of the crossflow filtration with an electric field to prevent or reduce cake formation, and to considerably increase the stationary permeate rate. While this process has been successfully demonstrated in laboratory scale there are no reports about scale-up applications. In this paper filtration results with a pilot scale crossflow electrofiltration plant are reported. The presented investigations comprise the microfiltration of mineral and biological slurries with constant and pulsed fields. It was possible to increase the specific permeate rate markedly compared to the value without field; for a mineral slurry the obtained increase rate was more than 10. An estimation of the specific energy input demonstrates the cost-saving potential of this technique.

A New Method for the Classification of Micron and Submicron Particles

A new technique for the separation and reduction of fine particle fractions in the lower micron and submicron range was introduced. Experiments demonstrated high-grade efficiencies down to cut points of 0.5 μm with a very small quantity of misplaced material.

Dynamische Extinktionsspektroskopie – Eine Chance zur Erweiterung des Messbereiches photometrischer Partikelmesstechniken

Dynamic extinction spectroscopy is based on the simultaneous application of dynamic extinction measurement and optical extinction spectroscopy for online particle size measurement. It covers a range of particle sizes and size distributions from approx. 80 nm to 250 pm. Different applications will underline the potential of this measuring method for online process control.