Optimal synthesis of p-xylene separation processes based on crystallization technology

This paper addresses the synthesis and optimization of crystallization processes for pxylene recovery for systems with feed streams of high concentration, a case that arises in hybrid designs where the first step is commonly performed by adsorption. A novel superstructure and its corresponding mixed-integer nonlinear programming (MINLP) model are proposed. The distinct feature of this superstructure is the capability to generate optimum or near optimum flowsheets for a wide range of specifications of p-xylene compositions in the feed stream of the process. In order to cope with the complexity of the MINLP model a two-level decomposition approach, consisting of the solution of an aggregated model and a detailed model, is proposed. The results obtained show good performance of the decomposition strategy, and the optimal flowsheets and p-xylene recoveries are in agreement with results reported in patents. Corresponding author. Tel.: +1 412 268 2230; fax: +1 412 268 7139. E-mail address: [email protected]