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Item type:Publication, Access status: without files , Structured packing design with minimized pressure drop for thermal separation columns by CFD-based shape optimizationDistillation still is the most widely applied thermal separation process in the chemical industry, but high energy demand goes along with it. Electrification and minimizing industrial column's energy demand are essential from an economic and ecological perspective. A lever to minimize energy demand and thermal stress on specialty chemicals is the development of novel structured packings with minimized pressure drop. These can now be realized by additive manufacturing. To fully exploit this potential, mathematical optimization techniques need to be applied. For the first time, a highly efficient computational fluid dynamics (CFD)-based adjoint shape optimization method is applied in structured packing design with minimized pressure drop. The design approach, embedded in a holistic development method, is presented. Selected results of a shape optimization study of a Rombopak basic element reveal a 13.7% reduction in pressure drop at constant specific surface area. The design method contributes to the development of next generation structured packings.Publicationtype: Journal Article21 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Axial dispersion modelling of the residence time distribution in a millistructured plate reactor(Elsevier, 2025-07-01); ; ; ; Micro- and millistructured reactors offer significant advantages compared to conventional batch reactors in terms of heat and mass transfer as well as process safety. Especially in case of fast and exothermic reactions, the space-time-yield of batch reactors is often limited by poor heat transfer and slow mixing. The use of millistructured reactors, such as the ART plate reactor PR37 of Ehrfeld Mikrotechnik, can overcome heat and mass transfer limitations and significantly extend applicable process windows, while providing sufficient capacity for industrial applications. Previous investigations showed that the reactor offers high heat transfer coefficients as well as short micromixing times at moderates Reynolds numbers. In order to further characterize the performance of the reactor and the possible operating window, the current work provides a thorough study of the residence time distribution on the basis of pulse experiments and a model-based evaluation of the deviation from ideal plug flow on the basis of the axial dispersion model. The results demonstrate that the reactor closely resembles the ideal plug flow even for Reynolds numbers of just about Re ≈ 100. Due to its meandering, periodically diverging/converging process channels, the formation of secondary flow is promoted resulting in an increased cross-mixing and thus a considerably reduced axial dispersion compared straight channels. For further analysis, as well as model-based assessment and design of the reactor, a correlation for the axial dispersion coefficient is derived which is applicable for a wide process window.Publicationtype: Journal Article69 29 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Investigation of micromixing in the ART plate reactor PR37 using the acetal cleavage method and different mixing modelsThe mixing time can strongly affect the yield of a desired product if side reactions occur. Mixing is therefore of great practical importance. Millireactors enable comparatively high flow rates at moderate pressure drops and are thus well suited for production purposes. In this work, the mixing performance of the millistructured reactor ART PR37 is investigated using the Bourne method. Four plate types with similar meandering, converging/diverging process channels, but different hydraulic diameters have been studied over a wide range of Reynolds numbers. Mixing times have been calculated using two different mixing models, the IEM model and a recently introduced modified incorporation model. Mixing times were found to be less than 0.1 second for Reynolds numbers exceeding 150. For higher Reynolds numbers, mixing times in the range of 0.02 to 0.03 s are achievable without prohibitively high pressure drops. The ART PR37 is therefore a promising option for mixing-sensitive reactions.Publicationtype: Journal Article106 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Novel additively manufacturable structured packings developed by innovative design methods(2022-09); Publicationtype: Conference Poster not in Proceedings63 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Designing novel structured rackings by topology optimization and additive manufacturingAdditive manufacturing (AM) reveals a completely new freedom in design and development of structured packings for thermal separation columns. This potential might lead to the next generation of high-performance packings, but it can only be fully used if novel design methods are developed. One of these innovative design methods is presented in this contribution. A topology optimization approach based on the coupling of a stochastic optimization algorithm and computational fluid dynamics (CFD) simulations is applied to generatively design structured packings. By its application, novel structured packing shapes may be found. Binary elements, which are either defined as packing material or as empty elements, are considered as design variables in a defined design space. A multi-objective genetic algorithm with tailored process- and manufacturing- related constraints is used to identify the best packing material distribution within the column shell, revealing minimized pressure drop and maximized surface area. In this paper, the optimization tool and CFD model are presented before selected results of an exemplary topology optimization study are given. The objective of this study is the development of a packing element for a lab scale distillation column. The promising results prove the viability of the design method, showing that it is possible to generatively design structured packings algorithm-based and without any well-defined initial packing geometries as starting point.Publicationtype: Conference Paper127 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Demonstration of applied linear model predictive control for an enzymatic reactive dividing wall columnThe synergistic integration of different processing steps in multifunctional units offers huge potential for bioprocess intensification. Especially reactive separation technologies have been widely applied in chemical processes, with reactive distillation being termed the front-runner of industrial process intensification. The concept can be transferred to bioprocesses in terms of enzymatic reactive distillation, which can further be intensified through thermal coupling with a subsequent distillation column into an enzymatic reactive dividing wall column. While such a highly integrated process offers considerable potential for operational and investment cost savings, it also faces operational challenges and limitations caused by the strong degree of integration and the temperature sensitivity of the biocatalyst, that need to be addressed by a sophisticated process control system. The current study demonstrates the applicability and efficiency of a linear model predictive control approach for the enzymatic reactive dividing wall column in a pilot plant application. The transesterification of butanol and hexyl acetate to hexanol and butyl acetate, catalyzed by the enzyme CalB (Novozym 435), serves as a model reaction. The control performance is illustrated for a setpoint adjustment and a feed disturbance, for which a comparative evaluation with an established PI-control approach is conducted.Publicationtype: Journal Article111 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Evaluation of process integration for the intensification of a biotechnological process(2021-10); ; ; ; Process intensification is a well-known and established method to improve ecological and economic efficiency of large-scale chemical processes. Process intensification in form of integrating an in-situ product or intermediate removal can also improve processes. In this study the effects of integrating an intermediate separation in form of an extraction centrifuge and a product separation in form of a pre-purification into a multi-enzyme cascade as well as the potential for further process integration in form of a reactive extraction centrifuge are analyzed for a biotechnological process. In order to evaluate the application of process integration, different process configurations are compared regarding to the efficiency using a model-based approach. Although the highly integrated process leads to lower space-time yields in some cases, an operating window can be identified in which the space-time yield is significantly higher compared to a sequential process. In order to distinguish both cases and thus choose a suitable operating point simulative studies are required. Moreover, a potential for further integration can be identified for the reference process studied in this work.Publicationtype: Journal Article97 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , An innovative approach for fatty acid reduction to fatty aldehydesThe increasing demand for fatty aldehydes as natural flavoring agents nowadays grapples with current production processes requiring harsh reaction conditions and hazardous chemicals. Our research group proved the concept of an innovative, sustainable process based on renewable plant oils for fatty aldehyde production: fatty acids reduction via zerovalent iron. In this study, we present for the first time extensive supporting data characterizing the metal particles used as co-reactants and the core step of the reaction, with varying process parameters. Furthermore, process improvement is demonstrated in that addition of fatty ester-obtained alcohol regenerates metal particles, thereby increasing process yield and selectivity as well as avoiding resource waste. Hexanoic acid reduction to hexanal in the presence of iron particles was used as a reference reaction system, generating a 40% hexanoic acid conversion using Fe 36 µm-particles. To increase overall process sustainability, we explored the possibility of an in toto exploitation of the starting materials (esters) through an a posteriori reduction of the oxidized iron, exemplarily with the alcohol hexanol. The hexanoic acid conversion rate was thereby increased to 83%, while a 44-fold increase in hexanal yield was observed.Publicationtype: Journal ArticleScopus© Citations 5 101 313 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Multi-enzyme cascade reaction in a miniplant two-phase-system: model validation and mathematical optimization(Wiley, 2021-01-11); ; ; ; Biotechnological application of multiple enzymes in different phases for target compounds synthesis poses a significant challenge for industrial process development. At the same time, a growing demand for natural flavors and fragrances opens up possibilities for novel biotechnological processes to replace current chemical synthesis routes, with additional advantages such as avoiding harsh reaction conditions and toxic chemicals, and less by-products in the system. Within complex biotechnological processes, the key for unfolding their industrial application potential in bioprocess engineering lies in their mathematical modeling. In this contribution, a multi-enzyme cascade reaction in a two-phase system implemented in a miniplant-scale reactor setup is mathematically modeled for the example of the flavoring agent cinnamyl cinnamate. Using our validated model and a mathematical optimization tool based on a genetic algorithm, optimization runs are performed to demonstrate the potential of computer-aided process development for complex biotechnological processes.Publicationtype: Journal ArticleScopus© Citations 11 157 342 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Energy saving potential of reactive dividing wall columns with azeotropic reaction systems(2020-12-14); The reactive dividing wall column (RDWC) is a highly integrated process that enables savings in investment and operational costs. Nevertheless, the high grade of integration leads to an extremely complex process behavior, complicating the prediction of the advantageousness of RDWC for a given task during process design. So far, many applications have been proposed in literature for RDWC, but little general knowledge on the influence of reaction system properties on the RDWC has been published. Latter studies are limited to ideal reaction system properties. This article investigates the influence of non-ideal reaction system properties, focusing on azeotropic phase equilibrium. A comprehensive process understanding of how the non-ideal separation properties affect the energy saving potential of RDWC is developed. The results are combined in short heuristics, which allow the process engineer a quick and easy evaluation of the energy saving potential of RDWC for the investigated reaction systems during process synthesis.Publicationtype: Journal Article146