Systematic Strategy for Obtaining a Dividing-Wall Column Applied to an Extractive Distillation Process

Abstract

Currently, process intensification using dividing-wall columns (DWCs) is one of the most promising alternatives for reducing the costs of the distillation process. However, for extractive distillation, there are still questions regarding whether the DWC is a more economical option than the conventional sequence (CS). Normally, extractive DWCs are simulated with two thermally coupled columns (TCSs), and their designs are usually obtained by setting the TCSs in different ways that do not necessarily constitute an optimum design. Thus, this work proposes a systematic procedure based on stage equilibrium for obtaining an optimized DWC configuration, in terms of operability and design. A strict comparison between the DWC configuration and the CS (also optimized) was performed, and the best results in terms of the total annual cost (TAC) were obtained for columns with a distinct number of stages in each section of the wall; however, these columns did not outperform the optimized conventional systems.

Review of extractive distillation. Process design, operation, optimization and control

“…Staak and Grützner (2017) published an industrial case study based on a E-DWC developed by Lonza AG. Most literature works simulate E-DWC with equivalent conventional process, but a current challenge remains the development of E-DWC design methods (Cordeiro et al, 2017), Kiss and Ignat (2012) studied E-DWC to concentrate and dehydrate bioethanol in a single step by integrating all units of the conventional sequence, including a pre-concentrator into only one distillation column. The results show that energy savings of 17%, and a similar decrease in capital cost were achieved.…”

Optimal design of extractive dividing-wall column using an efficient equation-oriented approach

“…Optimal design of the EDWC has received considerable attention during the last decade [6][7][8]. Several approaches have been proposed for the optimal design, including sequential sensitivity analysis-based optimisation methods, sequential quadratic programming (SQP) algorithms and genetic algorithms (GA).…”

“…Several approaches have been proposed for the optimal design, including sequential sensitivity analysis-based optimisation methods, sequential quadratic programming (SQP) algorithms and genetic algorithms (GA). The sequential sensitivity analysis-based method conducts a series of process simulations using rigorous equilibrium stage models through changing one or a few design variables at each time while the other design variables are fixed [3,4,6,9]. This method can fail to converge in process simulation of the EDWC due to the entrainer recycle, complex configuration of the EDWC and strong nonideality of the mixture system.…”

“…It often requires a large number of simulations to generate a best design. Although some heuristics are introduced to improve computational efficiency [6], they can identify a feasible design solution without guaranty of the solution optimality [10].…”

Proportional-Integral Control and Model Predictive Control of Extractive Dividing-Wall Column Based on Temperature Differences

“…Extractive distillation (ED) is the predominant technology for the separation of liquid mixtures with azeotrope and/or low relative volatility in the chemical and pharmaceutical industries, which cannot be realized by the conventional distillation. , An additional entrainer (also known as solvent) is added to alter the relative volatility of liquid mixtures in ED, and two pure components can then be obtained at the top of two columns together with entrainer at the bottom of the second column . However, the thermal efficiency of ED based on conventional two-column sequence is low at 5–20%. , Various approaches have been developed to intensify and improve the ED process, e.g., extractive dividing-wall column (EDWC), − ED with varying pressure, and heat-integrated ED. − …”