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Item type:Publication, Access status: without files , Sustainable distillation processesDistillation is one of the oldest separation technologies and still the most widely applied fluid separation process in the chemical industry. The outstanding role of distillation columns builds on the fact that it is the only unit operation capable of high capacities and high purities for multiple product streams. The flexibility and robustness further favour the use of distillation columns, which are also considered as one of the most mature separation technologies. Yet, distillation is of limited use for processing thermally sensitive streams and it is assumed to be the most energy-intensive among all separation processes. Consequently, it is of major interest to improve or replace distillation processes, in order to reduce energy consumption and improve process sustainability. The current chapter provides an overview of the different means for improving the sustainability of individual distillation columns and distillation processes for multi-product separations, as well as close boiling and azeotropic mixtures.Publicationtype: Book Part43 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Model Discrimination for Multicomponent Distillation – A Geometrical Approach for Total Reflux(2020-07-01); ; ; ; While rate-based models are available in commercial flowsheet simulation tools, packed distillation columns are still mostly designed based on the equilibrium stage model in combination with HETP values. In order to discriminate between both types of models in a simple way, this article proposes an algorithmic test, based on a geometric criterion for total reflux operation. Substantial differences are illustrated especially for wide-boiling mixtures, while component-specific mass transfer rates either increase or reduce the deviation. The derived results are validated by dedicated experiments.Publicationtype: Journal Article55 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Efficient optimization-based design of energy-integrated azeotropic distillation processes(2020-02-02); ; ; The separation of azeotropic mixtures is frequently performed by extractive or heteroazeotropic distillation processes. The design of these processes requires careful selection of a suitable solvent and is specifically challenging since feasibility and optimality of the processes require consideration of the closed loop design including solvent recovery. Consideration of energy integration further complicates the design task and is usually conducted as post-evaluation step. The current publication proposes an efficient optimization-based design approach, which allows for the direct evaluation of several energy-integrated process concepts, while significantly reducing manual effort and computational time through a polylithic modeling and solution approach. The developed approach allows for a simultaneous evaluation of solvent selection and energy integration and is illustrated for different case studies, including the evaluation extractive and heteroazeotropic distillation for the dehydration of ethanol, as well as the evaluation of multiple solvent candidates for the extractive distillation of acetone and methanol.Publicationtype: Journal Article42 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Optimization-based design of dividing wall columns with extended and multiple dividing walls for three- and four-product separations(2019-12); ; While dividing wall columns can be considered an established technology and success story of distillation process intensification, the application of the technology is still limited in relation to the vast number of existing distillation columns. This can at least to some extent be traced back to potential controllability issues and the complexity of the process design. While the first issue is especially related to internal vapor splits, which require an accurate design and consideration of column hydrodynamics, the latter issue becomes more severe with an increasing number of products and column sections, for which the number of degrees of freedom and design alternatives increase exponentially. While modified design concepts for dividing wall columns that allow for an external control of vapor splits have been proposed, similar to four-product dividing wall columns, there is still a lack of computationally efficient tools for the design and optimization of these energy-efficient thermally coupled distillation processes. The current article presents an optimization-based approach for the design of such complex and integrated distillation processes, enabling a case-specific economic assessment and benchmarking. The application is demonstrated for different case studies, including the separation of an azeotropic quaternary system in a multi-dividing wall column.Publicationtype: Journal Article67 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Efficient optimization-based design of energy-integrated distillation processes(2019-10-04); While providing only low thermodynamic efficiency, distillation is still the default option for the separation of liquid mixtures in the chemical industry. Fortunately, various concepts for energy integration have been proposed to improve the energy efficiency. Yet, the selection of the cost-optimal process among the potential alternatives is tedious, as the performance of the different options has to be evaluated for each specific separation. Thus, efficient means for rigorous design are required, that allow for a comparison of the competing alternatives. For this purpose, a computationally efficient method for a rigorous optimization-based design of various energy-integrated distillation sequences is proposed in the current article and demonstrated for 16 different process variants for the separation of a multicomponent mixture into three product streams. The application to three case studies, including the separation of ideal, non-ideal and azeotropic mixtures, demonstrates its computational efficiency and effectiveness in identifying economically attractive energy-integrated distillation processes.Publicationtype: Journal Article39 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Optimization of extractive distillation – integrated solvent selection and energy integrationThe separation of azeotropic mixtures is of particular importance for bio-based processes in the chemical industry. Extractive and heteroazeotropic distillation are oftentimes the favored solution for medium to large scale processes due to their proven robustness and the economics of scale. The feasibility as well as economic efficiency of these processes depends strongly on the selection of a suitable mass separating agent (MSA). Furthermore, energy integration can increase the energy and economic efficiency of these thermal processes. Since, MSA selection, process design and energy integration are usually performed as consecutive steps in process design, potential synergies are easily missed, resulting in sub-optimal choices. In order to determine an optimal process design, including solvent selection and energy integration, an efficient optimization-based approach for the design of extractive distillation processes is proposed. The application of the method is illustrated for the separation of the azeotropic mixture of acetone and methanol. The results highlight that the optimal MSA choice under consideration of energy integration differs from the selection without energy integration.Publicationtype: Conference Paper50 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Choosing the right model for distillation processes in packed columns: Theory and experimentsPacked distillation columns are usually designed on the basis of a sequential approach, in which first the Equilibrium Stage (EQ) model is used to quantify the separation effort before the required packing height is determined by HETP values. This approach is often sufficient for process design and proper sizing of the column. However, in certain cases the combination of the EQ model and HETP values results in an inappropriate column design. The design accuracy can be improved using a rate-based (RB) approach. Unfortunately, there is no reliable heuristic available to decide which modeling approach should be chosen. Therefore, the current study investigates the need for rate-based modeling in distillation processes by systematically evaluating the differences between EQ and RB composition trajectories. A criterion based on the Euclidean distance is proposed to evaluate the differences between the EQ and RB trajectories. Then, by means of a selectivity analysis basic criteria for model discrimination are derived and validated experimentally. Generally, for wide boiling mixtures the differences between the EQ and RB trajectories are the most distinct. The differences in the trajectories can be further increased or decreased by component specific mass transfer.Publicationtype: Journal Article211 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , A Systematic Approach towards Synthesis and Design of Pervaporation-Assisted Separation Processes(2017-11); ; While membrane processes like pervaporation are considered as key technology towards more sustainable separation processes, they are rarely considered in conceptual design. In order to enable an identification of promising applications, the current article proposes a systematic approach that covers the synthesis of pervaporation-assisted process variants and promotes the use of optimization-based methods for process analysis. It seeks to minimize and guide necessary experiments and includes competitive reference processes as well as further means for process intensification in the evaluation.Publicationtype: Journal Article32 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Efficient optimization-based design of energy-intensified azeotropic distillation processesThe separation of azeotropic mixtures is a difficult task in the downstream processing of many industrial processes. Although potentially less energy intensive separation techniques are available, the separation by extractive or heteroazeotropic distillation is often the method of choice, particularly for large scale processes. By application of different concepts for energy-intensification such as heat integration, the use of heat pumps or concepts of thermal coupling the separation efficiency of these thermal separation processes can be improved. However, the comparison of these different variants and the identification of the most energy or economicly beneficial option for a specific separation is an elaborate task. Therefore, an existing approach for the design of energy-intensified distillation processes has been extended to the design of extractive and heteroazeotropic distillation. The method utilizes a superstructure model based on the MESH equations including non-ideal thermodynamics. All considered process variants are evaluated by means of an automated procedure requiring nothing more than the definition of feed and product specifications as well as the thermodynamic model. The method is demonstrated for the dehydration of ethanol with the help of additional mass separating agents. While the investigated case study shows only small saving potential by the considered means of energy-intensification, it demonstrates the computational efficiency of the proposed design approach. Moreover, the method can easily be adapted for other separation tasks, requiring only minor changes.Publicationtype: Conference Paper30 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Conceptual Design of Highly Integrated Processes – Optimization of Dividing Wall Columns(2017-05); Process intensification provides a whole toolbox of innovative solutions for improved energy efficiency of chemical processes. However, evaluation of this potential is hampered by the unavailability of suitable models and design tools. Integrated processes like dividing wall columns either have to be mapped by available unit operation models or tailored equation-based models have to be developed. The current article reviews available methods for conceptual design and optimization of dividing wall columns and provides a detailed comparison of two representative optimization approaches.Publicationtype: Review Article22