(586f) A Process Intensification Synthesis Framework for the Design of Divided Wall Columns

Novel separation concepts based on process intensification (PI) principles have received burgeoning interest from the chemical industry to address the dual challenge of energy efficiency and environmental sustainability [1,2]. As one of the commercialized PI technologies, divided wall column (DWC) features a fully thermally coupled and single-shell distillation column for the separation of multi-component mixtures. The task-integrated design scheme, with improved thermodynamic efficiency, can lead to approximately 30% savings in capital expenditure, space, and energy [3]. For the computer-aided design of divided wall columns, extensive efforts have been made leveraging process synthesis and superstructure optimization to systematically generate optimal DWC configurations and simultaneously evaluate their performance metrics with other distillation alternatives (e.g., distillation sequences, thermally coupled distillation) [4-6]. Recent advances in process intensification synthesis [7-9], in which phenomenological building blocks are used to intensify the chemical systems towards ultimate performance limits, further opens up the opportunity to innovate the multi-component separation process from process fundamental perspective and to exploit the potential by divided wall columns.

In this work, we present a process intensification synthesis approach for the design of divided wall columns based on recent extensions of the Generalized Modular Representation Framework [10-11]. A superstructure-based representation leveraging modular phenomenological building blocks is utilized to intensify the fundamental chemical performance (e.g., mass transfer, heat transfer) and to systematically generate novel process structures without pre-postulation of equipment design (including but not limited to divided wall columns). To accurately describe the possible liquid-vapor and liquid-liquid phase behaviors of the multi-component mixture, rigorous thermodynamic models (e.g., UNIQUAC) are explicitly incorporated in the synthesis model. The synthesis problem is formulated as a single mixed-integer nonlinear optimization problem. The applicability and versatility of the proposed framework will be showcased via an industrial case study on methyl methacrylate purification by Dow Global Technologies [12]. Two new divided wall column designs are obtained, both of which can achieve equipment size reduction and substantial energy savings (Design 1: 18%, Design 2: 37%) compared to the original patent design. A two-column design is also generated which provides promising energy savings while needs to overcome the process bottleneck on product purity by incorporating membrane-assisted separation.

Reference

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