(205a) Process Design and Intensification of Dividing Wall Column for an Industrial Methyl Methacrylate Separation Process | AIChE

(205a) Process Design and Intensification of Dividing Wall Column for an Industrial Methyl Methacrylate Separation Process


Tian, Y. - Presenter, Texas A&M University
Meduri, V., Texas A&M University
Vedant, S., Texas A&M University
Pistikopoulos, E., Texas A&M Energy Institute, Texas A&M University
In pursuit of more energy efficient distillation technologies, dividing wall column (DWC) designs have received increasing attention from the chemical industry for multi-component separation [1,2]. Comparing to conventional distillation sequences, DWC features a compact and intensified design structure with less investment costs by integrating the whole process into a single shell column. Significant energy savings (approximately 30%) have also been reported due to reduced re-mixing effects occurring in the column and thus higher thermodynamic efficiency [3]. One DWC application of industrial importance is for purification of the reaction product mixture from preparation of methyl methacrylate, which also contains methanol, water, and oligomers of methyl methacrylate [4,5]. A patented design alternative for this heterogeneous azeotropic separation problem consists of a dividing wall column integrated with a decanter, showing 7.6% higher product recovery rate than a conventional two-column design flowsheet given the same energy consumption rate [4].

In this work, we revisit this industrial methyl methacrylate separation process based on our recently proposed framework for design, synthesis, and operational analysis of process intensification systems [6]. Specifically, a phenomena-based synthesis representation is developed using the Generalized Modular Representation Framework (GMF) to capture DWC systems with fundamental chemical building blocks (i.e., mass/heat exchange module and pure heat exchange module) [7-9]. To describe the non-ideal vapor-liquid-liquid behavior, rigorous thermodynamic models (e.g. UNQUAC) is explicitly incorporated in the synthesis model. The base case DWC design presented in [4] is then simulated with a pre-fixed building block structure to validate the accuracy and efficiency of GMF for this specific case study. Thereafter, a superstructure optimization model is formulated to systematically generate the optimal and intensified process alternative(s) for improved cost performance without any pre-postulation of plausible process unit or flowsheets. The resulting phenomenological process alternatives are translated to unit operation-based flowsheet for rigorous design and simulation using Aspen Plus. Given the inherent highly nonlinear dynamics with multiple steady-states in DWC systems, explicit/multi-parametric model predictive controllers designed via the PAROC framework [9] are applied to the above derived DWC-based flowsheets to ensure feasible operation under disturbance and uncertainty. Two alternative case studies are also presented for comparison of design strategies as well as optimality of the process solutions: (i) unit operation-based optimization of the base case design, and (ii) unit operation-based optimization of the conventional two-column flowsheet design with heat integration.


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