The potential of deterministic global optimization in hierarchical process design is discussed and its application is demonstrated for conceptual design with two examples arising from hydroformylation with tunable solvents (Schafer et al., 2012 [32]). In the first example, deterministic global optimization is utilized to evaluate flowsheet options for the separation of a binary mixture in a process comprising distillation and melt crystallization units. In the second example, the standard countercurrent design of multistage melt crystallization is compared to more general configurations described by a superstructure. Parameter studies based on globally optimal solutions are carried out for the second example. For each example, we provide a model formulation that can be solved with standard software within reasonable time. (C) 2015 Elsevier B.V. All rights reserved.