Importance of process conditions in the displacement of protein concentrates from spiral-wound membrane modules

Displacement processes accompany every start-up or shut-down of spiral-wound membrane module plants used for the production of food concentrates. In this process, large amounts of product are usually discarded due to dilution with the displacing fluid. In order to reduce product losses by improved process control, the relationships between the key process conditions and the duration of the displacement of non-Newtonian products from spiral-wound membrane modules need to be known. While previous studies assess the impact of single factors on the duration of the displacement, we reveal that considering one factor at a time is not sufficient for describing the displacement duration because the factors interact. Our conclusions are based on statistical designs of experiments and response surface models. As expected, the models suggest that the flow rate, the spacer dimensions, and the concentrate viscosity affect the displacement duration. Moreover, the models reveal interactions of the mentioned factors. Surprisingly, neither the temperature nor the viscosity of the displacing fluid turned out to have a significant effect on the displacement duration. Finally, the Reynolds number was not identified as a predictor for the displacement duration. The practical relevance of the study is that displacement durations become more predictable allowing improved process control and thus an option for the reduction of product losses during displacement processes.