*3.1. HEN Retrofit Design Proposals for Single Operating Point—Generation of Superstructure*

In a first step, retrofit design measures are derived using single-period and well-proven retrofit design methodologies. Additionally, "experience-based" design proposals may be considered, which can be based on, e.g., already known operability issues. By means of this, the designer is actively involved in the design process, which can be beneficial in industrial applications. The derived design changes are collected in a superstructure, which eventually represents all design proposals that are considered.
