Publication in Journal: Applied Soft Computing (18 October 2021)

Comparison of data selection methods for modeling chemical processes with artificial neural networks

Fabian Zapf, Thomas Wallek

Instance selection aims at selecting model training data in a way that the performance of the trained models is maximized. In the context of modeling chemical processes by artificial neural networks, it can serve as an essential preprocessing step since measurement data of such processes are commonly highly clustered and thus far away from being ideally normally distributed. In this paper, four filter methods from literature and a newly proposed method for data selection are tested and combined with a convex hull data selection algorithm, which results in ten different selection approaches. These approaches are applied to five selected datasets by training feed-forward artificial neural networks with the produced split datasets. The final mean model deviation is used to quantify the algorithms’ performance and their standard deviation to provide information about their reproducibility. It is found that the convex hull extended algorithms self-organizing maps based stratified sampling with a proportional allocation rule and the newly proposed self-information-based subset selection perform best for real-world chemical engineering data.

Applied Soft Computing, Volume 113, Part B, December 2021, 107938

Keynote am ersten Wissenschaftstag der TU Graz (29 September 2021)

Wissenschaft gestaltet Zukunft. Am jährlichen interdisziplinären Wissenschaftstag TU Graz – Science for Future zeigen Forschende der TU Graz, wie sie über alle Disziplinen hinweg den gesellschaftlichen Herausforderungen mit innovativen Technologien begegnen und unsere Zukunft mitgestalten.

Viktor Hacker, Mobilität & Produktion: Volle Energie für den Klimaschutz

Programm 2021: Klima und Energie

9:30 Begrüßung und Eröffnung des Wissenschaftstages der TU Graz

Horst Bischof, Vizerektor für Forschung der TU Graz

Harald Kainz, Rektor der TU Graz

Grußworte Karin Schaupp, Vorsitzende des Universitätsrates der TU Graz

Grußworte Peter Piffl-Percevic, in Vertretung des Bürgermeisters der Stadt Graz

Grußworte Barbara Eibinger-Miedl, Landesrätin für Wissenschaft und Forschung

9:45 Keynotes

Gast-Keynote Claudia KEMFERT:

Corona und Klimaneutralität: Wege aus der Krise

TU Graz Keynote Martin WILKENING:
Designstrategien für neue Materialien zur Energiespeicherung

TU Graz Keynote Viktor HACKER:

Mobilität & Produktion: Volle Energie für den Klimaschutz

12:00 Mittagspause

13:00 Themensessions

16:30 Posterpräsentationen

17:00 Podiumsdiskussion "Science for Future? Kann die Wissenschaft das Klima retten?"

Preisverleihung "TU Graz SciPix - Forschung im Fokus", Forschungsfoto-Wettbewerb der TU Graz

Ab 18:00 Abendessen und Networking

Moderation: Marlene Nowotny (Ö1 Wissenschaftsredaktion)

Final report of the successful fuel cell and hydrogen summer school (26 September 2021)

The Summer School on Polymer Electrolyte Fuel Cells and Hydrogen was successfully organised and held for the thirteenth time (Final Report).

Die Sommerakademie über Polymerelektrolytbrennstoffzellen und Wasserstoff wurde zum dreizehnten Mal erfolgreich organisiert und durchgeführt (Abschlussbericht)

Study abroad and mobility programs (25 September 2021)

Study Abroad Video by Dr. Barbara Lorber, Faculty of Technical Chemistry, Chemical and Process Engineering, Biotechnology.

Article in Chemie Ingenieur Technik (2 September 2021)

Reactive Distillation for Solvent Regeneration after Biphasic Carboxylic Acid Esterification

Andreas Toth, Matthäus Siebenhofer, Susanne Lux

Emulsion-enhanced biphasic esterification has proven to be applicable for carboxylic acid recovery from dilute aqueous process streams. The carboxylic acid is esterified with 1-octanol in an emulsified regime with 4-dodecylbenzenesulfonic acid (4-DBSA) or Ni(DBSA)2 as catalyst. After phase separation, the laden solvent phase must be regenerated. This study presents a regeneration concept based on reactive distillation with transesterification of the octyl ester-laden solvent with methanol. The regenerated solvent is reused in the extraction step.

Chemie Ingenieur Technik (2021) 93,10, 1493-1501

Publication in Holzforschung (30 August 2021)

Investigation of acid hydrolysis for carbohydrate analysis in kraft black liquor

Maitz, Silvia and Kienberger, Marlene

Black liquor (BL) from the kraft process is considered a promising feedstock for several biorefinery scenarios. Besides lignin and carboxylic acids, this liquor also contains hemicelluloses and their degradation products. A simple and reliable detection of those is of importance for further processing of the liquor. The present paper presents a thorough investigation of quantitative analysis of carbohydrates, by performing acid hydrolysis experiments with a concentrated BL sample of 44% total dry solids. The hydrolysates were then analysed for the four monosaccharides arabinose, xylose, galactose and glucose, by high performance ion chromatography (HPIC) with pulsed amperometric detection. The amount of sulphuric acid needed for complete hydrolysis of the carbohydrates was determined in the range of 3.5–5 mol kg−1 of BL. A lower acid concentration led to insufficient liberation of galactose and glucose, while higher acid concentrations led to degradation of arabinose and xylose. The carbohydrate degradation was also investigated over time for different dilutions and hydrolysis temperatures. These experiments confirmed that the hexoses require considerably harsher conditions for complete liberation compared to xylose and arabinose. The use of internal recovery standards (RSs) was tested; the highest recoveries were obtained by direct spiking of the samples with the RS prior to hydrolysis.

Holzforschung, vol. , no. , 2021, pp. 000010151520210047

Publication in Computers & Chemical Engineering (30 August 2021)

Gray-box surrogate models for flash, distillation and compression units of chemical processes

Fabian Zapf, Thomas Wallek

Surrogate models of chemical processes can substitute rigorous models that are computationally expensive or of limited stability by simplified and typically solely data-driven models. In this work, gray-box surrogate models of classical process engineering unit operations comprising flash, distillation and compression units are developed to provide accurate models that allow for fast and stable predictions in view of later optimization of coupled models. The gray-box surrogates are first tested as individual models and then applied to model the cracked-gas compression of an ethylene plant, including a recycle stream. The process streams are hydrocarbon mixtures containing 50 components, which typically leads to significant convergence issues with rigorous approaches. A concluding comparison of the proposed surrogate models’ accuracies proves their robustness and computational efficiency and highlights the advantages of the proposed modeling methodology that complements and extends simple but physically meaningful white-box models with black-box models from the field of machine learning.

Computers & Chemical Engineering, Volume 155, 107510


Publication in Fuel (27 August, 2021)

The influence of hydrogen sulfide contaminations on hydrogen production in chemical looping processes

Bernd Stoppacher, Sebastian Bock, Karin Malli, Michael Lammer, Viktor Hacker

Chemical looping with iron-based oxygen carriers enables the production of hydrogen from various fossil and biogenic primary energy sources. In applications with real producer gases, such as biogas or gasified biomass, hydrogen sulfide represents one of the most challenging contaminants. The impact of H2S on the reactivity of a Fe2O3/Al2O3 oxygen carrier material in chemical looping hydrogen production was investigated in the present work. Possible deactivation mechanisms of sulfur are discussed in detail on the basis of thermodynamic data. An experimental study in a fixed-bed reactor system gave experimental evidence on the fate of sulfur in chemical looping hydrogen systems. A profound interpretation was achieved through the fulfillment of the overall sulfur mass balance within a mean deviation of 3.7%. Quantitative investigations showed that hydrogen consumption in the reduction phase decreased by 12% at 100 ppm H2S in the feed gas.

Figure 1: Temperature profile (black), concentration for H2S (red) and SO2 (blue) of a redox cycle with reduction (grey background), steam oxidation (yellow) and air oxidation (blue background).

Fuel 307 (2022) 121677

Zukunftsfonds Steiermark: Approved projects in the 13th call for proposals (23 August, 2021)

Zukunftsfonds Steiermark: Approved projects in the 13th call for proposals of the Future Fund of the Styrian Provincial Government and the City of Graz (Climate Protection Fund). Short presentations of the projects in the video (FC-Core 08:16 min).

Article in Chemie Ingenieur Technik (26 July, 2021)

Modeling of Single Droplet Mass Transfer of Acetic Acid with Triisooctylamine-Based Solvent

Georg Rudelstorfer, Matthäus Siebenhofer and Annika Grafschafter

The design of mass transfer systems based on data on the mass transfer of single droplets is still a major challenge, although it has been intensively discussed for decades. Modelling extraction with chemical reaction causes additional difficulties. Single droplet mass transfer of acetic acid from an aqueous carrier into a triisooctylamine-based solvent modified with the Lewis acid modifier isodecanol and the diluent Shellsol T was studied with the result that mass transfer of acetic acid into triisooctylamine-based solvent droplets is limited by diffusion of the loaded solvent from the interface into the droplet bulk phase.

Chemie Ingenieur Technik

2021 First Prize of the ‘Forum Technik und Gesellschaft’ for Dissertations

2021 First Prize of the ‘Forum Technik und Gesellschaft’ for Dissertations

For his research achievements in the development of a new sustainable process for hydrogen production at CEET, Dr Sebastian Bock was selected from 70 submissions and received the sponsorship award for special social relevance from the Forum Technik und Gesellschaft.

The transformation to a sustainable, decarbonised energy system is more topical than ever in social, scientific and political terms. The application-oriented provision of renewable energies is essential for their efficient use. In Austria in particular, there is enormous potential for the use of sustainable bioenergy.

In Sebastian Bock's dissertation, a concept for decentralised hydrogen production developed and patented at TU Graz was transferred to an industrial process. The innovative chemical looping process for hydrogen production was developed specifically for the requirements of small and medium-sized plants. The demonstration on an industrially relevant scale took place in what is currently the world's largest 10 kW fixed-bed test plant in Graz.

The added social value of the work lies in particular in the transfer of a scientific concept into an industrial process for hydrogen supply. Such decentralised concepts increase energy self-sufficiency and the added value of rural areas. In the medium and long term, local anchoring also increases awareness of sustainable mobility and the acceptance of hydrogen technologies.

Hauptpreis 2021 des Forums Technik und Gesellschaft für Dissertationen

Für seine Forschungsleistungen zur Entwicklung eines neuen nachhaltigen Verfahrens zur Wasserstofferzeugung am CEET wurde Dr. Sebastian Bock aus 70 Einreichungen ausgewählt und erhielt den Förderpreis für besondere gesellschaftliche Relevanz vom Forum Technik und Gesellschaft.

Die Transformation zu einem nachhaltigen, dekarbonisierten Energiesystem ist in gesellschaftlicher, wissenschaftlicher und politischer Hinsicht aktueller denn je. Die anwendungsorientierte Bereitstellung von erneuerbaren Energien ist essentiell für deren effiziente Nutzung. Gerade in Österreich gibt es ein enormes Potenzial für die Nutzung nachhaltiger Bioenergie.

In der Dissertation von Sebastian Bock wurde ein an der TU Graz entwickeltes und patentiertes Konzept zur dezentralen Wasserstofferzeugung in einen industriellen Prozess überführt. Das innovative Chemical-Looping-Verfahren zur Wasserstofferzeugung wurde speziell für die Anforderungen von kleinen und mittleren Anlagen entwickelt. Die Demonstration im industriell relevanten Maßstab erfolgte in der derzeit weltweit größten 10-kW-Festbettversuchsanlage in Graz.

Der gesellschaftliche Mehrwert der Arbeit liegt insbesondere in der Überführung eines wissenschaftlichen Konzepts in ein industrielles Verfahren zur Wasserstoffversorgung. Solche dezentralen Konzepte erhöhen die Energieautarkie und die Wertschöpfung des ländlichen Raums. Mittel- und langfristig erhöht die lokale Verankerung auch das Bewusstsein für nachhaltige Mobilität und die Akzeptanz von Wasserstofftechnologien.

Foto: ©alumniTUGraz 1887/Clemens Nestroy.

Publication in Energies (20 July, 2021)

Identifiability Analysis of Degradation Model Parameters from Transient CO2 Release in Low-Temperature PEM Fuel Cell under Various AST Protocols

Andraž Kravos, Ambrož Kregar, Kurt Mayer, Viktor Hacker and Tomaž Katrašnik

The detrimental effects of the catalyst degradation on the overall envisaged lifetime of low-temperature proton-exchange membrane fuel cells (LT-PEMFCs) represent a significant challenge towards further lowering platinum loadings and simultaneously achieving a long cycle life. The elaborated physically based modeling of the degradation processes is thus an invaluable step in elucidating causal interaction between fuel cell design, its operating conditions, and degradation phenomena. This analysis enables optimal reduction of the set of calibration parameters, which results in the speed up of both the calibration process and the general simulation time while retaining the full extrapolation capabilities of the framework.

Energies 2021, 14(14), 4380

Article in Fuel Cells (July 14, 2021)

Cold Start Behavior and Freeze Characteristics of a Polymer Electrolyte Membrane Fuel Cell

Kocher, K., Kolar, S., Ladreiter, W. & Hacker, V.

Vehicle applications require efficient cold start capability and durability of polymer electrolyte membrane fuel cells. In this study, we propose different self-cold-start strategies including flushing the PEMFC at shutdown and using galvanostatic operation at start-up. The cold-start properties from -5 °C of a single cell are investigated experimentally in situ at laboratory scale. The amount of cumulative charge transfer density, corresponding to the amount of product water, is used as an index to quantify the cold start capability.

Gas purging prior to freezing facilitates cold start of the PEMFC, although the improvement is relatively small compared to other methods, such as gradually increasing the current during start-up. Microscopic examinations of the membrane electrode assembly (MEA) after a cold start failure are be carried out to determine the material degradation due to ice formation.

Fuel Cells, Wiley, online early view, article FUCE1748

FWF Research project on hydrogen production approved (July 01, 2021)

In the FWF Decision Board meeting no. 84 of 21. June 2021, another research project was approved for CEET!

Advanced ceramic supported oxygen carriers – ACCEPTOR

Chemical Looping is one of the most promising technologies for CO2 sequestration. The Reformer Steam Iron Cycle, first published in 2003, is based on a fixed-bed chemical looping scheme with the scope of hydrogen production from locally available renewable resources. This allows the production of pre-pressurized (100 bar), high purity (99.999%) hydrogen for fuel cells in decentralized systems. The key constraint to its widespread use is the low material stability, which is particularly essential in fixed-bed reactors. The main challenge is the maintenance of the chemical and structural integrity of the oxygen carrier over several thousand reduction and oxidation cycles, as it is impossible to replace the material during ongoing operation in fixed beds.

Fortschrittliche keramische Sauerstoffträgermaterialien - ACCEPTOR

Chemical Looping ist eine der vielversprechendsten Technologien zur CO2-Sequestrierung. Der Reformer-Eisen-Dampf-Prozess, der erstmals 2003 veröffentlicht wurde, basiert auf einem Festbett-Chemical-Looping-Schema mit der Möglichkeit der Wasserstoffproduktion aus lokal verfügbaren erneuerbaren Ressourcen. Dies ermöglicht die Produktion von komprimierten (100 bar), hochreinem (99,999%) Wasserstoff für Brennstoffzellen in dezentralen Systemen. Die größte Herausforderung ist die Aufrechterhaltung der chemischen und strukturellen Integrität des Sauerstoffträgers über mehrere tausend Reduktions- und Oxidationszyklen, da ein Austausch des Materials im laufenden Betrieb in Festbetten nicht möglich ist.

Publication in Energies (June 20, 2021)

Combining baffles and secondary porous layers for performance enhancement of proton exchange membrane fuel cells

Mihanović, L., Penga, Ž., Xing, L. & Hacker, V.

A numerical study compares the currently most common flow field configurations, porous, biporous, porous with baffles, fine mesh Toyota 3D and traditional rectangular flow field. Operation at high current densities is considered to clarify the effects of the flow field designs on overall heat transfer and liquid water removal. A comprehensive, multiphase, non-isothermal 3D fluid dynamics model is developed based on current heat and mass transfer sub-models, including the full formulation of the Forchheimer inertia effect and the permeability ratio of the biporous layers. The conclusions of this work aids in the development of compact and high-performance proton exchange membrane fuel cell stacks

Energies 2021, 14(12), 3675;

Publication in Applied Energy Materials (June 17, 2021)

Novel Bimetallic Pd−X (X = Ni, Co) Nanoparticles Assembled on N‑Doped Reduced Graphene Oxide as an Anode Catalyst for Highly Efficient Direct Sodium Borohydride−Hydrogen Peroxide Fuel Cells

Hosseini, G., Daneshvariesfahlan, V., Wolf, S. & Hacker, V.

Bimetallic Pd-X (X = Ni, Co) nanoparticles on nitrogen-doped reduced graphene oxide (N-rGO) are prepared by a solid-state thermal technique followed by polyol reduction to be used as anode electrocatalysts for direct sodium borohydride-hydrogen peroxide fuel cells. The physical characterisation of the synthesised materials is investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. Finally, a direct sodium borohydride-hydrogen peroxide fuel cell with Pt/C as cathode and Pd-X (X = Ni, Co)/N-rGO as anode is constructed and operated with a power density of 353.84 and 275.35 mW cm-2 at 60 °C.

ACS Appl. Energy Mater. 2021, 4, 6, 6025–6039

Publication in Chemical Engineering and Processing – Process Intensification (June 16, 2021)

Interfacial Mass Transfer in Quaternary Liquid-Liquid Systems

Nagl, R., Zeiner, T., & Zimmermann, P.

Interfacial properties such as interfacial mass transfer are essential for the design and optimization of industrial separation processes. In this work we investigate the interfacial behavior of the two quaternary systems water + toluene + ethanol + acetone and water + toluene + ethanol + tetrahydrofuran and the relation between interfacial enrichment and mass transfer. The Concentration Gradient Theory (CGT) is combined with the Koningsveld-Kleintjens (KK) model to calculate interfacial tension and interfacial concentration profiles. By expanding a recent study of ternary systems with ethanol, acetone or tetrahydrofuran as transferring components we demonstrate that interfacial mass transfer in quaternary systems can be modeled with CGT + KK in good accordance to experimental data by adjusting a single additional binary mobility coefficient. Moreover, the present study indicates a hint on a link between interfacial enrichment and interfacial mass transfer.

Chemical Engineering and Processing - Process Intensification., 2021, Article number 108501.

BioBASE innovation platform established (May 27, 2021)

The Institute of Chemical Engineering and Environmental Technology is a partner of BioBASE, the new innovation platform for bioeconomy and circular economy. With the support of BioBASE, new national and transnational as well as cross-sectoral cooperations between and within industry and science are being established. BioBASE focuses on the entire value chain of the bioeconomy and circular economy. The intensive use of fossil and mineral resources contributes to progressive climate change; a reversal in the energy and production system is therefore necessary. BioBASE is launching an innovation platform to promote biobased products and the recycling of products in a wide range of application areas. The Biorefinery working group at the ICVT is concerned with the isolation of valuable materials from biobased process flows by means of the application, adaptation and new development of thermal separation processes.

Right from the start, BioBASE has been embedded in a strong network of around 60 partner organisations and institutions, including some major Austrian companies as well as specialist representatives from the chemical, pulp and paper, wood, food and stone and ceramics industries. From the scientific side, BioBASE is supported by the most important universities and research institutions in this field. In addition, state governments of the federal states and location agencies or clusters are also part of the BioBASE network.



Das Institut für Chemische Verfahrenstechnik und Umwelttechnik ist Partner von BioBASE, der neuen Innovationsplattform für Bioökonomie und Kreislaufwirtschaft. Mit Unterstützung von BioBASE werden neue nationale und transnationale sowie auch branchenübergreifende Kooperationen zwischen und innerhalb Wirtschaft und Wissenschaft etabliert. BioBASE betrachtet mit ihren Schwerpunkten die gesamte Wertschöpfungskette der Bioökonomie & Kreislaufwirtschaft. Der intensive Einsatz fossiler und mineralischer Ressourcen trägt zum fortschreitenden Klimawandel bei, eine Umkehr im Energie- und Produktionssystem ist daher notwendig. BioBASE startet eine Innovationsplattform zur Forcierung biobasierter Produkte sowie der Kreislaufführung von Produkten in den unterschiedlichsten Anwendungsbereichen. Die AG Biorefinery am ICVT beschäftig sich dabei mit der Isolierung von Wertstoffen aus biobasierten Prozessströme mittels Anwendung, Adaptierung und Neuentwicklung von Thermischen Trennverfahren.

BioBASE ist schon vom Start weg in ein starkes Netzwerk von rund 60 Partnerorganisationen und -institutionen eingebettet, darunter einige wesentliche österreichische Unternehmen sowie Fachvertretungen aus der chemischen-, der Papier- und Zellstoff-, der Holz-, der Lebensmittel- und der Stein- und keramischen Industrie. Von wissenschaftlicher Seite wird BioBASE von den wichtigsten Universitäten und Forschungseinrichtungen aus diesem Bereich unterstützt. Darüber hinaus sind Landesregierungen der Bundesländer und Standortagenturen bzw. Cluster ebenfalls Teil des BioBASE-Netzwerks.

Erasmus and traineeship at CEET (May 21, 2021)

Erasmus+ traineeship student Mark Kozamernik shares his experience about life in Graz and work at the Institute of Chemical Engineering and Environmental Technology (CEET) at TU Graz during the Covid pandemic (TU Graz blog English).

Erasmus+-Praktikant Mark Kozamernik berichtet über das Leben in Graz und die Arbeit am Institut für Chemische Verfahrenstechnik und Umwelttechnik (CEET) an der TU Graz während der COVID-Pandemie (TU Graz blog German).

Publication in Processes (May 3 , 2021)

Systematic Review on Isolation Processes for Technical Lignin

Marlene Kienberger, Silvia Maitz, Thomas Pichler and Paul Demmelmayer

Technologies for the isolation of lignin from pulping process streams are reviewed in this article. Based on published data, the WestVaco process, the LignoBoost process, the LigoForce SystemTM and the SLRP process are reviewed and discussed for the isolation of lignin from Kraft black liquor. The three new processes that have now joined the WestVaco process are compared from the perspective of product quality. Further, isolation processes of lignosulfonates from spent sulfite liquor are reviewed. The limitation for this review is that data are only available from lab scale and pilot scale experiments and not from industrial processes. Key output of this paper is a technology summary of the state of the art processes for technical lignins, showing the pros and cons of each process.

Processes, 2021, Volume 9, Issue 5, 804

Announcement of the Special Issue on Fuel Cells (November 2, 2020)

Development of Advanced Models for Analysis and Simulation of
Fuel Cells

The guest editors Prof. Katrašnik and Prof. Hacker invite you to submit articles for a special issue of Energies on “Development of Advanced Models for Analysis and Simulation of Fuel Cells”. To address the requirements on shorter product development cycles and reduced development costs, while boosting power density, efficiency, service life and safety, it is necessary to rely on advanced simulation models in the development process of fuel cells, their components, and fuel-cell-based systems. Simulation models are also indispensable for the analysis of fuel cells and for precise online monitoring.

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