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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 Article72 44 - 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 Article51 60 - 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 30 - 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 Article28 18 - 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 Article66 61 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Electrifying distillation − Optimization-based evaluation of internally heat-integrated distillation columnsImproving the energy efficiency of distillation processes is essential for reducing the chemical industry's substantial energy demand and environmental footprint. The use of mechanical heat pumps with compressors is an important asset in this transformation process, as it not only enables the recovery of heat rejected at low temperature, reducing external energy requirements, but also facilitates the electrification of chemical processes and distillation in specific. The necessary temperature lift dictates the required compression rate for the compressor and is therefore of considerable importance for the applicability of mechanical heat pumps. By operating the rectifying and stripping sections of a column at different pressures and enabling heat exchange between the respective sections, temperature lift and compression ratio can be reduced for the so-called Internally Heat-Integrated Distillation Columns compared to mechanical vapor recompression. In order to enable a quick problem specific evaluation of the possible benefits of this concept we propose two novel superstructure models for optimal design, that allow for heat exchange between stages at the same height or arbitrary stages in the rectifying and stripping section, provided a minimum temperature difference is maintained. The respective optimization problems are solved as a series of successively relaxed mixed-integer nonlinear programming problems in GAMS. An automatic stepwise initialization and optimization strategy provides a computationally efficient approach for the determination of optimized designs.Publicationtype: Journal Article38 47 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Umfassendes Screening intensivierter Destillationsprozesse(2024-03-06); Um eine deutliche Reduktion der Treibhausgasemissionen in der chemischen Industrie zu erzielen, können insbesondere Destillationsprozesse, die für einen erheblichen Teil des industriellen Energiebedarfs verantwortlich sind, intensiviert werden. Hierzu können verschiedene Formen direkter Wärmeintegration, Multi-Effekt-Destillation und thermischer Kopplung, z.B. in Form von Trennwandkolonnen, genutzt werden. Durch eine strukturelle Erweiterung können thermische Kopplungen auch durch reinen Flüssigtransfer erzielt werden, indem der entsprechende Wärmeübertrager für eine verlängerte Kolonnensektion erhalten bleibt. Neben dem Energiesparpotential der thermischen Kopplung kann durch eine Druckvariation eine zusätzliche direkte Wärmeintegration erzielt werden, wodurch abhängig von dem spezifischen Gemisch und der Feedzusammensetzung eine weitere Senkung des Energieverbrauchs um bis zu über 30 % ermöglicht wird [1]. Um für eine Trennaufgabe die beste Konfiguration zu bestimmen, sollten sämtliche Prozesskonfigurationen im Vergleich zueinander bewertet werden, wobei zusätzlich zu den benannten Alternativen die Elektrifizierung mittels Wärmepumpen zu evaluieren ist. Um die Vielzahl konkurrierender Prozessvarianten effizient unter unterschiedlichen Randbedingungen zu evaluieren, wird in der aktuellen Arbeit ein erweitertes Shortcut-Screening [2] vorgestellt, das über 200 Prozessalternativen für die destillative Trennung eines Ausgangsgemisches in drei Produkte evaluiert. Das vorgestellte Shortcut-Screening-Tool ermittelt alle relevanten Massen- und Energieströme für optimierte Betriebsparameter, berücksichtigt Temperaturniveaus in der Integration und hinsichtlich einer wirtschaftliche Bewertung und ermöglicht eine schnelle Orientierung um die aussichtsreichsten Alternativen für eine detaillierte Betrachtung zu identifizieren. Anhand eines Fallbeispiels wird veranschaulicht, wie das Potenzial und die Sensitivität einzelner Konfigurationen für unterschiedliche Rahmenbedingungen bewertet und die vielversprechendsten Alternativen identifiziert werden. [1] M. Skiborowski 2020, Comp. Aid. Chem. Eng., 48, 991-996 [2] M. Skiborowski, 2018, Chemical Engineering Transactions, 69, 199–204.Publicationtype: Conference Presentation60 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Can simple side stream configurations compete with fully thermally coupled dividing wall columns?It is well known that thermal coupling of distillation columns can substantially decrease the energy requirements of distillation processes, which is confirmed by several hundred industrial implementations of dividing wall columns. However, the respective vapor splits have to be properly designed and require consistent hydrodynamics in the adjacent column sections. These limitations can be overcome by transformation of the thermal coupling to a side stream configuration, which adds a degree of freedom for operation of the process and allows the columns to be operated at different pressures. The current study investigates energy requirements and operating costs of single side stream configurations thermodynamically equivalent to side-rectifier and side-stripper columns in comparison to fully thermally coupled dividing wall columns and heat-integrated configurations. While side-stream configurations provide an interesting retrofit option and are competitive to fully-coupled dividing wall columns for certain ranges of feed compositions, they can outperform them significantly exploiting additional heat integration.Publicationtype: Conference Paper214 278 - 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 Presentation74