(430d) Optimal Design and Analysis of Membrane-Based Reactive Separations

Membrane-based separation techniques have shown promises to be used in chemical industries due to their lower energy consumption, steady-state operation, simple design and modularity. They also offer higher selectivity for the separation of valuable components from dilute mixtures [1,2]. A membrane reactor, which is an intensified equipment that combines separation and reaction phenomena into a single unit operation, can offer a significant improvement in size, energy efficiency, and overall process performance and cost [3]. Limited studies have been performed for the synthesis and optimization of membrane reactors [4,5]. Nonetheless, a generic optimization-based study of a membrane-based reactive-system can increase adoption of these technologies by showing their benefits. Additionally, it can guide experimental work on synthesis of candidate membrane materials. To this end, this work develops a comprehensive platform for the design, analysis, synthesis and optimization of membrane-based reactive separation systems using the building block representation of chemical processes developed in our group [6,7]. In this representation, building blocks are positioned within a two-dimensional grid which can be used to represent several physical and chemical phenomena [8,9]. For instance, a plug flow reactor can be represented by multiple catalyst-carrying blocks positioned in series. Additionally, when the blocks adjacent to the reactor blocks are separated by a membrane material, a membrane reactor is represented. The generic model formulation of membrane-based reaction separation system is a mixed-integer nonlinear program (MINLP) that can be solved for different objective functions including maximizing yield, maximizing single-pass conversion; and minimizing energy consumption, reactor size; and minimizing hazards related to high operating temperatures and pressures. For example, when applied to a syngas-to-methanol process, we have obtained a membrane reactor configuration that has more than 30% increase in methanol yield compared to that of commercially used methanol reactors [10]. We have also observed that, for the same methanol yield, the energy consumption is reduced by 30%, the amount of catalyst and the reactor size are reduced by 48%, reactor pressure can be reduced from 77 bar to 55 bar, and the maximum temperature within the reactor is reduced from 541 K to 507 K. All these lead to significant savings in energy, associated CO₂ emissions and cost while improving the safety. The proposed framework is also generic in a sense that it can be applied for numerous process configurations and pathways that utilize membrane-based reactive separation for many different process applications.

References:

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[7] Li, J., Demirel, S.E. and Hasan, M.M.F., 2018. Process synthesis using block superstructure with automated flowsheet generation and optimization. AIChE Journal, 64(8), pp.3082-3100.

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[10] Samimi, F., Rahimpour, M.R. and Shariati, A., 2017. Development of an efficient methanol production process for direct CO2 hydrogenation over a Cu/ZnO/Al2O3 catalyst. Catalysts, 7(11), p.332.