Although frequently used in chemical industry detailed models of downstream processes have rarely been applied to the downstream processes of biological or pharmaceutical products. A typical downstream process for the purification of biological products comprises six general purification steps: cell removal, concentration, capture, purification, polishing and filling. Each purification step can consist of different unit operations like chromatography, filtration or membrane adsorbers. In order to increase the understanding of the complete downstream process dynamic, detailed models for the different unit operations such as ultrafiltration, chromatography and membrane adsorbers have been implemented into the commercial simulation environment Aspen Custom Modeler™. Based on these models a complete, generic downstream process model has been developed in which each unit operation can be replaced easily by another one. Despite of model complexity the process model proves robust numerical convergence properties and offers valuable model flexibility. This process model is used to compare and optimize different process setups by altering the unit operations and their design parameters with respect to productivities and yields without the need of elaborate experiments.