The design of a structurally controllable separation system becomes extremely important for ensuring product quality and process operability. In this paper, a shortcut disturbance model is developed to characterize the propagation of various types of disturbances through a ternary separation system. The model is linear and has an excellent predictability. In applications, it requires much less information than a process simulator does. This greatly facilitates the analysis of possibly a large number of process alternatives in the early stages of process design. A practical example demonstrates the effectiveness of the model application.