Optimisation and graphical representation of multi-stage membrane plants

A procedure is given for the design and optimisation of continuous multi-stage membrane plants using the example of whey ultrafiltration. During the design stage, the number of stages, area per stage, diafiltration water ratios and possible pressures can be varied to minimise capital and operating costs. The concept of an optimal or ideal plant was developed to provide a basis for comparison for the designs. To interpret the results, and check the validity of the optimisation results, a variety of graphical representations were developed. Graphical profiles of purity versus total solids, and of protein concentration versus lactose concentration were effective when interpreting design results and a graph of component mass flux helped identify yield losses. These and other graphs provided insight into the designs and often enable sensible improvements to them.