Process simulator-based optimization of biorefinery downstream processes under the Generalized Disjunctive Programming framework

7 Downstream processing of biofuels and bio-based chemicals represents a challenging problem for 8 process synthesis and optimization, due to the intrinsic nonideal thermodynamics of the liquid 9 mixtures derived from the (bio)chemical conversion of biomass. In this work, we propose a new 10 interface between the process simulator SimSci PRO/II and the optimization environment of GAMS 11 for the structural and parameter optimization of this type of flowsheets with rigorous and detailed 12 models. The optimization problem is formulated within the Generalized Disjunctive Programming 13 framework and the solution of the reformulated MINLP problem is approached with a decomposition 14 strategy based on the Outer Approximation algorithm, where NLP subproblems are solved with the 15 BzzMath derivative free optimizer, and MILP master problems are solved with CPLEX/GAMS. 16 Several validation examples are proposed spanning from the economic optimization of two different 17 distillation columns, the dewatering task of diluted bio-mixtures, up to the distillation sequencing 18 with simultaneous mixed-integer design of each distillation column for a quaternary mixture in the 19 presence of azeotropes. 20 21