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Item type:Publication, Access status: with files , Rapid multi-criteria screening of energy-integrated distillation processes for nonideal mixturesSeveral thousand distillation columns are industrially employed for various separations, accounting for a substantial share of the industrial energy demand. In order to reduce their energy requirements various means for energy integration, such as direct heat integration, multi-effect distillation, thermal coupling, or vapor recompression can be applied. Considering these options and combinations of these, several hundred possible process configurations can be designed even for separations into three product streams, while the choice for a best option depends strongly on the specific separation task and system properties. In order to enable a reliable case-specific evaluation, which avoids simplified heuristics or simplified thermodynamics, this article presents a computationally efficient, algorithmic framework for a multi-criteria evaluation of more than 750 energy-integrated distillation sequences for multicomponent separations in three product streams. The framework employs thermodynamically sound pinch-based shortcut models that do not rely on constant relative volatility and constant molar overflow assumptions, making it applicable to nonideal and azeotropic mixtures. Based on the minimum energy duties and the respective flowsheet information, classical estimation methods for equipment sizes, operating costs, and capital investment, are employed. Several case studies demonstrate the framework's applicability to azeotropic systems, its computational efficiency benefits that enable performing sensitivity analyses for varied process, thermodynamic, and economic scenarios.Publicationtype: Journal Article73 48 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Beyond dividing wall columns: Improved process intensification through liquid-only transfer and heat integrationMany chemical companies aim to achieve climate neutrality by 2050, requiring raw material changes and significant reductions in process energy. Since distillation accounts for a large share of energy use, it is a key target for process improvements. One promising approach is thermal coupling between columns, which is already industrially implemented, especially in dividing wall columns. However, such configurations often suffer from limited operational flexibility due to the fixed vapor split between parallel sections, which is largely fixed during design and difficult to adjust during operation. This limitation can be overcome by replacing each bidirectional vapor-and-liquid connection with a liquid-only transfer side stream. This concept allows each column to operate at an individual pressure and enables new options for heat integration. The present study introduces a structured approach for assessing and optimizing such systems with one or two liquid-only transfer side streams, particularly when combined with direct heat integration. Promising configurations are first identified through an efficient shortcut screening and can further be optimized using superstructure optimization. A case study on separating benzene, toluene, and para-xylene demonstrates that liquid-only transfer configurations with direct heat integration can significantly reduce energy and costs, and in many cases outperform conventional thermally coupled systems.Publicationtype: Journal Article53 65 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Refrigerant selection and cycle design for industrial heat pump applications exemplified for distillation processesMechanical compression heat pumps are indispensable to facilitate the transition from thermally driven processes to renewable energy by electrification, upgrading low-temperature waste heat to recycle it at a higher temperature level. However, the implementation of such heat pumps up to date encounters limitations, due to equipment limitations and a lack of tools for the design of process concepts for the application of high-temperature heat pumps. The optimal design of heat pumps relies heavily on the selection of an appropriate refrigerant, as the thermodynamic properties significantly affect the heat pump cycle design and performance. While existing methods are capable of identifying thermodynamically beneficial refrigerants, they do not directly account for practical constraints such as limitations on the compressor discharge temperature, compression ratio, and vacuum operation. The current study proposes a fast-screening approach for arbitrary heat pump applications, considering a large set of established refrigerants. The method automatically assesses the performance of the refrigerants for a specified set of heat sink and source, adjusting the heat pump design with an optional internal heat exchanger in case of necessary superheating prior to compression. The approach is illustrated for the evaluation of heat pump-assisted distillation processes.Publicationtype: Journal Article101 34 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Pimp my distillation sequence - shortcut-based screening of intensified configurationsDistillation processes account for a substantial share of the industrial energy demand. Yet, these energy requirements can be reduced by a variety of energy integration methods, including various forms of direct heat integration, multi-effect distillation, thermal coupling and vapor recompression. Consequently, these intensification methods should be evaluated quantitatively in comparison to each other for individual separation tasks, instead of benchmarking single options with conventional sequences or relying on simplified heuristics. In order to overcome the computational burden of a broad assessment of a large number of process alternatives, a computationally-efficient framework for the energetic and economic evaluation of such energy integrated distillation processes is presented, which builds on thermodynamically-sound shortcut models that do not rely on constant relative volatility and constant molar overflow assumptions.Publicationtype: Journal Article33 19 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Electrified distillation – optimized design of closed cycle heat pumps with refrigerant selection and flash-enhanced mechanical vapor recompressionImproving the energy efficiency of distillation processes is crucial for reducing the high energy demand and environmental impact of the chemical industry. Compression heat pumps play a significant role in this transformation as they are able to upgrade and recover heat rejected at low temperatures, reducing the need for external heat sources and simultaneously enable process electrification. Mechanical vapor recompression is the most prominent heat pump concept in distillation but limited by its reliance on process streams, which can lead to high external heat demand, or even inapplicability of the concept due to thermal instability or mechanical compressor limitations. Closed cycle heat pumps are less explored, since they require an extra heat exchanger and increased temperature lift compared to mechanical vapor recompression. However, they can overcome some of the limitations by allowing for unrestricted selection of the most attractive refrigerant, which may outplay the structural disadvantages. The current study presents a novel design approach for rapid heat pump evaluation, applicable to any subcritical refrigerant solely based on temperature levels and duties. A two-step approach enables the identification of the best-performing refrigerant from a set of suitable candidates for a given distillation process, considering practical constraints such as the need for superheating to avoid condensation, as well as limits for the compressor discharge temperature and compression ratios. The most promising refrigerant and heat pump configuration is further evaluated by a techno-economical optimization based on a superstructure model for which the performance is compared with a novel mechanical vapor recompression design utilizing a vapor recycle and internal preheating. The optimization results not only showcase fully electrified distillation for all heat pump-assisted processes but also highlight that closed cycle heat pumps with proper refrigerant selection can provide significant energy and cost savings while clarifying the respective advantages and limitations of competing concepts.Publicationtype: Journal Article72 69 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Optimization-based process synthesis by phenomena-based building blocks and an MINLP framework featuring structural screeningAn existing approach for optimization-based process synthesis with abstracted phenomena-based building blocks (PBB) is extended by implementing it into a novel MINLP framework with structural screening. Consistency across the multilayer MINLP framework is guaranteed by creating a MathML/XML data model and subsequently exporting the code to the different program parts. The novel framework focuses both on fidelity by implementing thermodynamically sound models and on generality by employing a state-space superstructure that spans a large search space. In order to retain tractability, we insert a structural screening layer which pre-screens based on binary decision variables of the superstructure by graph- and rule-based analyses, penalizing non-physical instances without solution of the underlying MINLP. The MINLP framework is successfully applied on two challenging synthesis tasks to determine the separation of the feed streams of benzene and toluene, as well as of n-pentane, n-hexane, and n-heptane utilizing superstructures with two, respectively four PBB.Publicationtype: Journal Article27 85 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Optimal retrofit of simple distillation sequences to thermally coupled side-stream configurationsRetrofitting existing plant equipment to a more energy efficient setup is a promising and sustainable way to cut down on the energy demand and consequently the operating costs of a chemical processing plant. While this opportunity is attractive in terms of low capital expenditure and construction time, it is also highly challenging for the design engineers. Degrees of freedom in grassroot design transform into constraints in the retrofit project and finding an optimal design within the constraints of the existing equipment, requires a sophisticated model-based approach. In this work, such an approach is presented for the retrofit of distillation column sequences to thermally coupled side-stream configurations. Based on this approach, an easy evaluation of retrofit opportunities in terms of investment and operating costs is facilitated. The potential of this retrofit is illustrated in the current contribution by means of a case study, which compares the retrofit option to a fully thermally coupled dividing wall column grassroot design. While the dividing wall column generally allows for higher energy savings, the investment in the retrofit is significantly smaller, which yields a considerably quicker amortization.Publicationtype: Conference Paper54 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Process intensification by integration of distillation and vapor permeation or pervaporation - an academic and industrial perspectiveSince membrane separations, such as vapor permeation (VP) or pervaporation (PV), are not limited by vapor-liquid equilibrium, their coupling with distillation can exert a synergistic effect, overcome the thermodynamic limits of distillation, and improve energy efficiency, especially suitable for the separation of azeotropic mixtures that otherwise requires special distillation processes. Therefore, there is an increasing number of such studies, and it is of great significance to comprehensively explore the process integration of distillation with VP or PV. This review first introduces the mechanism model of membrane separation and membrane materials, then comprehensively summarizes the academic research in terms of hybrid configurations of distillation with VP or PV in the following aspects: separation of azeotropic or close-boiling mixtures, promoting reactions by selectively removing a product, and energy savings, providing guidelines for subsequent application and future research. Finally, this review gives typical industrial cases of distillation and membrane-coupled separation processes and highlights some deficiencies of current research in this area.Publicationtype: Journal ArticleScopus© Citations 11 104 765 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Analyse des Potentials thermisch gekoppelter Rektifikationskolonnen ohne Dampfaustausch(2021-11); ; Publicationtype: Conference Presentation75 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Curse and Blessing-The Role of Water in the Homogeneously Ru-Catalyzed Epoxidation of Technical Grade Methyl Oleate(2021-08-30); ; ; ; A homogeneous Ru-catalyst was investigated toward its potential recycling in methyl oleate epoxidation under mild conditions using hydrogen peroxide as a green oxidant. The literature-known catalyst complex, in situ formed from ruthenium acetylacetonate and dipicolinic acid, offers excellent selectivity toward epoxidation of technical grade (91.5%) methyl oleate. The resulting product methyl 9,10-epoxy stearate exhibits versatile applications. It is used industrially as a biobased epoxide for plasticizers and lubricants, or it can be further processed into polyurethanes. In this work, we first report a concept for homogeneous catalyst recycling, including extraction of the epoxide into an organic phase. Particular emphasis was on the effect of water, as it would accumulate due to recycling of the aqueous catalyst phase and replenishment of hydrogen peroxide prior to each recycling run. Consequently, mass transfer limitations needed to be addressed. By a combined extraction-distillation technique, we report the first sufficient homogeneous catalyst recycling strategy for Ru-catalyzed epoxidation of methyl oleate. Removal of water and separation of epoxide allowed for a ∑TON of 1243 after seven recycling runs with 97% selectivity toward epoxide and a TTON of 1384 after 13 runs, respectively, while catalyst leaching into the product phase was negligibly small. Moreover, pervaporation using a poly(vinyl alcohol) membrane was investigated as a promising technique for both removal of water and retention of the catalyst showing very promising results.Publicationtype: Journal Article68