Process Design for Ultrafiltration of Complex Process Streams

Sammanfattning: Considerable effort has been dedicated over the years to model and simulate the ultrafiltration process. Most approaches are theoretical and therefore not applicable to industrial process streams. When treating such solutions, a combination of experiments and simulations is needed. In this thesis, a method has been developed for design and optimization of UF plants. The method uses experiments in combination with calculations performed in a simulation tool. The tool allows the user to predict the performance of a full-scale UF plant without the need for extensive experimental work. With the proposed method, it is possible to simulate the evolution of flux, TMP, cross-flow velocity and concentration along the membrane length and to evaluate the importance of these parameters on the ultrafiltration performance. The versatility of the method has been demonstrated by applying it to solutions with different filtration characteristics. The calculations show that the process parameters can vary considerably along the membrane, having a profound effect on the process, a fact that must be taken into account when designing an ultrafiltration plant. The influence of the different parameters will vary depending on the feed solution characteristics, module configuration and operating conditions. It has been shown that the performance of an ultrafiltration plant may, in some cases, be improved by decreasing the cross-flow velocity, contrary to conventional operational practice. It has also been shown that the frictional pressure drop can have a considerable negative effect on the performance of full-scale modules. Since the frictional pressure drop is more pronounced for viscous fluids, the module design is especially important when treating such fluids.