**2. Methodology**

The utilized simultaneous cost optimization model is mainly based on a superstructure MINLP formulation and a hybrid genetic algorithm developed by Luo et al. [20] to solve the problem resulting from this formulation. A common HEN optimization problem statement is described by a set of *Nh* hot process streams, *Nc* cold process streams, their respective heat capacity flow rates . *W* and heat transfer coefficients *h*. The supply and target temperatures ( *T* and *Tout*) of the process streams are given as well as the hot utility *HU* and cold utility streams *CU* with their respective temperature levels. Furthermore, the cost parameters should be known to perform a cost optimization.
