The success of technical processes with suspensions is strongly dependent on the particle properties. The increasing demand for narrow particle size distributions and known physical and/or electrochemical properties, especially for fine particles < 10 µm is leading to new processes which can provide such dispersed particles. [1]. Existing separation processes like hydrocyclones, centrifugal applications or crossflow fractionation face the challenge of achieving the desired particle size without a high energy and/or time consumption.

In this contribution, a cross-sectional fractionation technique is being presented, which is a promising method for the highly specific separation of micro and submicron suspensions. A discontinuous operation was developed from Altmann and Ripperger [2] and was further elaborated by Loesch et al. [3, 4]. The method not only allows fractionation with regard to the particle size, but also the charge of the individual particles, therefore a multidimensional particle separation. The fractionation process is based on a crossflow of a particle carrying fluid (feed) and particle-free water (filtrate) (cf. Figure 1). Both flow parallel, upwards against the gravitational field through a separationmodule. The actual fractionation takes place at the separationmedia, located between the two main channels...

For laminar flow conditions, the mainly acting hydrodynamic forces can be divided into two characteristic forces, the drag force F_D and the lift force F_L. The drag force acts along the flow direction, the lift force orthogonally to it. Based on the size-dependent hydrodynamic forces bigger particles are transported into the core flow. To separate the smaller particles in the wall-near boundary layer, which are less influenced by this effect, a separation medium with pores bigger than the particle size is adjusted. A very small differential pressure between the two channels allows a suction of a small volume of the suspension flow into the filtrate channel, containing only small particles. The sedimentation also occurs, but is not directly involved in the fractionation process. By adding a superimposed electrical field, which is acting orthogonally to the main flow, the particles are subjected to an additionally electrophoretic force F_E. The magnitude and direction of this force is determined by the particle properties, in particular the electrophoretic mobility and is competing to the hydrodynamic force.

In this present work the investigation of the hydrodynamic fractionation and the particle deflection in the electric field is carried out.....