Production of Multi-Channel-Capillary Membranes

Development and assembly of units for the production of multi-channel-capillary membranes for improved separation and cost reduction

Membrane processes are beside distillation and extraction one of the most used separation techniques. They can be used e.g. for the hemodialysis, for purification of pharmaceutical products and for desalination.

The aim of the present project is the development of spinnerets for the production of multi-channel-capillary membranes. The spinning nozzle molds a polymer solution into the desired capillary membrane in a so called phase inversion process. Therefore, it is necessary that the polymer solution hardens on the boundary layer with the so called non-solvent (e.g. water). A diffusion of the non-solvent into the pores occurs. The outer face of the membrane will be hardened by its insertion with an external coagulation bath. In general, capillary membranes with one channel and an outer diameter of one to two millimeters are thin walled and not stable against mechanical forces. In contrast to capillary membranes, multi-channel capillary membranes with up to seven channels per membrane (i.e. mult channel-capillary-membranes) are more stable and show an increased performance in separation properties accompanied by reduced costs.

Commercially available multi-channel-capillary membranes are made of ceramics (e.g. alumina oxide). On the one hand, they are highly resistant against chemicals, but on the other hand they are very expensive and sensitive to sudden temperature changes.

By producing and employing the spinneret it should be possible to apply the phase inversion process and its advantages, like the variety of materials, on membranes. Through the combination of phase inversion processes and multi channel techniques selective, chemically inert membranes with high performance should be achievable. Furthermore, new membranes with reduced production and operation costs can be expected.

The project gives the pupils a deeper understanding of applied research and development in the field of process engineering. They are involved in the assembly of the spinnerets and feed systems as well as in the characterization of the specified conditions like chemical resistance, transportation of liquids with high viscosity etc.

This project has been completed.