Andreas Pfennig

University of Liège | ulg · Department of Chemical Engineering

Both carbon dioxide uptake and albedo of the land surface affect global climate. However, climate change mitigation by increasing carbon uptake can cause a warming trade-off by decreasing albedo, with most research focusing on afforestation and its interaction with snow. Here, we present carbon uptake and albedo observations from 176 globally distr...

Phosphorus (P) is an indispensable nutrient for agriculture. Recovery and recycling of phosphorus from waste streams is necessary to ensure a circular P economy and reduce dependence on disproportionately distributed mineral P resources. In this study, a new process called 'PULSE' is presented for the recovery of P from sewage sludge, which can han...

The potential for phosphorus (P) recovery from various sources in Southern Vietnam has been assessed in this study. Five types of waste were studied, namely sediment from catfish pond, manure from cattle and pig farming, and also sludge from domestic and rubber-latex processing wastewater-treatment plants. The study identifies P-reserve and assesse...

de Computational‐Fluid‐Dynamics (CFD)‐Simulationen in Kombination mit Tropfenpopulationsbilanzen führen zu einem praxisgerechten Standard, um auf Basis verfügbarer Prozessdaten den Strömungsverlauf – und damit die Verweilzeitverteilung – in liegenden Abscheidern beliebiger Größe zu berechnen. Durch Implementierung des Tropfenverhaltens wird auch di...

Zusammenfassung Als fairer Beitrag Deutschlands zur Einhaltung der globalen 1,5-Grad-Grenze werden 16 Orientierungspunkte für eine klimaverträgliche Energieversorgung vorgestellt. Es wird davon ausgegangen, dass hierfür die deutschen energiebedingten CO2-Emissio-nen in etwa 15 Jahren weitgehend auf Null sinken müssen. Energieeinsparung hilft, den...

Rare-earth metals, such as La(III), Nd(III), Eu(III), or Y(III), which are recycled from electronic waste in urban miningUrban mining, can be separated and purified utilizing reactive extractionReactive extraction. Process developmentProcess development and equipment design then aim to determine the optimal reactive extractant, diluent, any additio...

GERMAN SUMMARY (English Summary further below): Die Zeit drängt. Ohne schnell wirksame Gegenmaßnahmen werden Erderhitzung und Biodiversitätsverlust Ausmaße annehmen, welche die Lebensweise von Menschen nicht abschätzbaren Risiken aussetzen. Obwohl die Herausforderungen weiten Teilen der Bevölkerung bewusst sind, werden dringend nötige Entscheidung...

https://de.scientists4future.org/s4f-empfiehlt-repraesentative-klima-buergerinnenversammlung-2021/

Berlin, October 2, 2020 | Scientists for Future (S4F) confirm that the demands of Fridays for Future (FFF) on EU politics are factually necessary and scientifically justified. According to IPCC calculations , the EU27 will have a residual budget for emissions of 20 Gt CO from 2021 to limit global warming to a maximum of 1.5 degrees. An 80% reductio...

Dies ist ein Kapitel der 12. Auflage des VDI-Wärmeatlas.

Bis in die 1980er drehte sich alles um Entwicklungshilfe. Als die Menschheit die 6-Milliarden-Marke in den 1990ern knackte, war das Thema die Bevölkerungsexplosion. Heute ist alles Klimawandel. Aber: Die Weltbevölkerung wächst rasant weiter und mehr als jeder zehnte Mensch hungert. Die Probleme von damals sind also noch lange nicht gelöst. Schlimme...

In the so‐called Branntwein AG chemical‐engineering bachelor students first produce wine from a chosen type of fruit, which is then distilled twice to arrive at schnapps as the final product. Before performing the process, the required steps are designed based on an adequate mathematical representation. Besides these engineering skills, soft skills...

A coalescence model in the context of the ReDrop concept (Representative Drops) is proposed to design technical equipment for separating liquid‐liquid dispersions in settlers or extraction columns. A fundamental study of drop interactions has been performed to obtain the complete picture of coalescence. The model proposed accounts for collision fre...

To obtain a consistent view of sustainable future development, scenarios based on global balances have been derived. The world population may grow significantly faster than generally expected by many studies with up to 11.6 billion people in 2050. The climate goal of 1.5 °C can realistically not be reached any more and it is shown why it has been s...

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Background Extraction is the method of choice for separating sensitive products. For example, it has been applied in aromatics and rare‐earth metal separation. Recently, biotechnological processes enter the field of bulk chemicals and might benefit from process intensification by in‐situ extraction of inhibiting products, however in the presence of...

We can create a happy and sustainable future, if we see our world as a interconnected system and act accordingly. --- How will we survive as humanity for the next hundred years? What do the upcoming challenges such as climate change, energy transition and global hunger mean for us individually? In order to develop a positive perspective for our f...

Molecular-dynamics simulations of liquid water show deterministic chaos, i.e. an intentionally introduced molecular position shift of an individual molecule increases exponentially by a factor of 10 in 0.23 ps. This is a Lyaponov instability. As soon as it reaches molecular scale, the direction of the resulting shift in molecular motions is unpredi...

Discrete modeling is a concept to establish thermodynamics on Shannon entropy expressed by variables that characterize discrete states of individual molecules in terms of their interacting neighbors in a mixture. To apply this method to condensed-phase lattice fluids, this paper further develops an approach proposed by Vinograd which features discr...

Experiments of single-drop sedimentation and mass transfer on a laboratory scale for the extraction of acetone from a water + acetone mixture by means of the ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate (HMIMPF6) were performed at a temperature of 298.2 K and ambient pressure. Study of the system equilibrium conditions in a previous...

Extraction is a downstream-process option in bio-based processes. Since the knowledge of phase-separation behavior is essential for designing efficient separation processes, this study investigates the settling and coalescence behavior of bio-based extraction systems using a standard lab-scale settling cell. The influence of different buffer media...

Background The production of polymers constitutes the major mass flow in chemical industry. The foreseeable future change from fossil to renewable resources leads to the demand for more production routes based on biotechnological conversions. These routes preferably require biocompatible components and possess certain limitations in temperature an...

In this paper a precedently developed surrogate optimization algorithm for fossil fuels, which originally allowed simultaneous fitting of the True Boiling Point (TBP) curve, the liquid density at 15°C and the cetane number, is refined towards its application to biodiesel and its mixtures with fossil diesel. For this purpose, the algorithm is extend...

Product isolation from aqueous-organic reaction mixtures that contain high concentrations of whole cells constitutes a challenging task in bioprocessing. Stirring of the biphasic reaction media leads to the formation of solvent droplets coated by surface active components and an emulsion forms. We used an early focus on phase separation to simplify...

Design of an extraction apparatus is significantly influenced by the coalescence behavior of a given material system. At the same time, quantifying coalescence of a system in an extraction column is tedious, as pilot-plant experiments have to be performed. These tests have to be carried out for each system individually, as coalescence is strongly i...

No abstract is available for this article.

No abstract is available for this article.

Discrete modeling is a novel approach that uses the concept of Shannon entropy to develop thermodynamic models that can describe fluid-phase behavior. While previous papers have focused on reviewing its theoretical background and application to the ideal-gas model as one limiting case for fluid phases, this paper addresses its application to lattic...

No abstract is available for this article.

The design of extraction columns based on information from lab experiments and appropriate simulation tools allows reduction of time and costs compared to conventional design methods using pilot-plant experiments. For this purpose, the behavior of drops and drop swarms is investigated in lab-scale experiments in order to create mathematical models...

The correct representation of a fuel, in terms of its physical and chemical properties and its combustion kinetics poses, a challenge to modern engine development when state-of-the-art simulation technology is used. In this context, a promising approach is the use of surrogates that emulate the properties of real fuels, where the surrogates are mad...

Thermodynamic modeling using the concept of Shannon entropy is a promising approach, especially in the field of describing fluid-phase behavior. This paper introduces the method of discrete modeling, using the ideal-gas model as an illustrative example, and derives a general equation of state. Discrete modeling is based on discrete states of indivi...

Thermodynamic modeling of extensive systems usually implicitly assumes the additivity of entropy. Furthermore, if this modeling is based on the concept of Shannon entropy, additivity of the latter function must also be guaranteed. In this case, the constituents of a thermodynamic system are treated as subsystems of a compound system, and the Shanno...

Fast and efficient procedures are increasingly important in process development since the time frame between development and market entry is reduced. The evaluation of alternatives is time consuming, but especially important to assure the choice of the optimal process. A simple and fast method to speed up process development while considering numer...

Liquid-liquid dispersions which are occurring in the petrochemical and chemical industry are commonly separated in gravity settlers. To improve the settler design, phase separation of the dispersions was studied. The parameters having the greatest effect on the phase separation under gravity are drop size, drop-size distribution, as well as driving...

Carbon dioxide can be used in various ways as a cheap C1 source. However, the utilization of CO2 requires energy or energy-rich reagents, which leads to further emissions, and therefore, diminishes the CO2 -saving potential. Therefore, life cycle assessment (LCA) is required for each process that uses CO2 to provide valid data for CO2 savings. Carb...

The vast majority of today's chemical products are based on crude oil. An attractive and sustainable alternative feedstock is biomass. Since crude oil and biomass differ in various properties, new synthesis pathways and processes have to be developed. In order to prioritize limited resources for research and development (R & D), their economic pote...

About 80% of the chemical products are still based on crude oil. Bio-based materials will increasingly gain importance. As the fraction of oxygen is normally higher in biomass than in crude oil as well as in the derived conventional products, this implies a need to develop new synthesis pathways. Depending on the types of new synthesis pathways, th...

In order to use the potential of drop-population balance simulations for the design of Kuhni pilot-plant columns, a quantitative understanding of the effect of compartment geometry on drop residence-time distribution is necessary since this is crucial for the accuracy of the simulation. This work presents an experimental method based on single-drop...

Crude oil is the most important raw material for the chemical industry. Due to the continually rising price of crude oil, alternative carbon sources are becoming increasingly important. Biomass is basically the only available renewable carbon source. Because the chemical composition of biomass differs from fossil raw materials, the raw-material cha...

A new expression for the excess Gibbs energy based on molecular orientations is derived. In this expression, the effect of molecular orientation on a molecular interaction is explicitly taken into account. In this way the three-dimensional structure of molecules can be accounted for and effects like multiple contact points or steric hindrance can b...

Population-balances are a powerful method to predict the population behavior of drops in chemical-engineering equipment such as solvent extraction columns. In such columns a complex interaction of different phenomena, namely drop sedimentation, mass transfer, drop breakage and coalescence as well as axial dispersion occurs. In this article the conc...

Investigations of mass transfer behavior with the standard test system of the European Federation of Chemical Engineering (EFCE) for the reactive extraction zinc + D2EHPA (di(2-ethylhexyl) phosphoric acid) were carried out. Experiments were performed with single droplets in a mass transfer cell on lab-scale. In the experiments, contact time for the...

Die Dimensionierung von Extraktionskolonnen erfolgt in der Regel auf Basis von experimentellen Untersuchungen im Labor und Auslegungsversuchen im Technikum. Eine neue, alternative Auslegungsmethode basiert auf Einzeltropfenuntersuchungen zum Stoffaustausch und zur Sedimentation im Labormaßstab, aus denen die erforderlichen Modellparameter zur Simul...

Reactive extraction is not only used to refine noble metals or to enrich nuclear fuels but also to separate components of low concentration from a liquid phase. Due to superimposed reaction this is more efficient than by conventional solvent extraction. Compared to solvent extraction, the interactions in reactive extraction are more complex due to...

Durch die Auslegung von Extraktionskolonnen basierend auf Experimenten im Labormaßstab und Simulationen lassen sich Zeit und Kosten sparen, da die heute üblichen, teuren Technikumsexperimente entfallen. Das Verhalten einzelner Tropfen bzw. Tropfenschwärme wird im Labormaßstab untersucht. Systemspezifische Parameter geeigneter Modelle werden an die...

A standard segment is used to determine the structural parameters r and q of the UNIQUAC combinatorial-entropy term. Generally, it is assumed that the choice of the standard segment and the influence of the absolute value of q are negligible. The standard segment area, however, does not cancel out in the model equation and, therefore, is a model pa...

ReDrop is a simulation tool which can predict the behaviour of pulsed extraction columns on pilot-plant scale. Because it follows a certain number of drops during their entire lifetime in an extraction column, it can be seen as a Monte-Carlo solution of drop-population balances. ReDrop is based on single-drop models which have system-specific param...

In the present paper freely sedimenting n-butanol droplets in water are simulated by means of computational fluid dynamics. The finite-element and the extended finite-element methods were implemented and evaluated. The level-set function is used for capturing the interface movement. The three-dimensional nonstationary simulations included the stage...

The sedimentation characteristics of the reactive standard test system zinc + D2EHPA are investigated in this work. Experiments with single droplets rising in a stagnant continuous phase have been carried out. The concentration of D2EHPA, zinc, and sulfuric acid as well as the diameter of the droplets are varied. The velocity of droplets is observe...

Thermische Verfahrenstechnik an der RWTH Aachen. Nicole Ko-priwa ist Diplom-Ingenieurin und wissenschaftliche Mitarbeiterin an diesem Lehrstuhl, zu dessen wissenschaftlichem Personal auch M. Sc. Sara Fayyaz sowie M. Sc. José Ayesteran gehören. Stu-denten des Lehrstuhls, die an der im Vorspann genannten Vorle-sung mitgewirkt haben, sind: und Till We...

The behavior of separation columns can be simulated by molecular simulation, where the influence of all relevant elements of a separation stage is taken into account. In order to decrease the computational time the column is divided in separation stages, where the simulation of each stage is carried out on an individual computer and the number of s...

The usual approach to design extraction columns is mostly based on pilot-plant experiments. These experiments are time- and material-consuming. Therefore an alternative method is to simulate the behaviour of technical equipment. This can be achieved by solving the drop-population balances. In this case the mathematical complexity of solving the pop...

In order to experimentally estimate the rate-determining steps and the kinetic parameters of interfacial reaction models, e.g. for the design of reactive-extraction equipment, the Nitsch cell and its variants are broadly used. In the present study, an optimized Nitsch cell was designed with the help of a kinetic model from the literature to improve...

EinleitungErarbeitung der AufgabenstellungApparate für die Flüssig-Flüssig-Extraktion Kolonnen Kolonnen ohne EnergiezufuhrKolonnen mit EnergiezufuhrMixer-SettlerExtraktionsmaschinenEmpfehlungen für die Anwendung der verschiedenen ExtraktorbauartenEinschränkung der Bauarten für typische ExtraktionsaufgabenVersuche und Modellierung von Extraktoren im...

The rigorous optimization of the geometry of a glass cell with computational fluid dynamics (CFD) is performed. The cell will be used for non-invasive nuclear magnetic resonance (NMR) measurements on a single droplet levitated in a counter current of liquid in a conical tube. The objective function of the optimization describes the stability of the...

Reaktivextraktion verbindet Reaktion und Extraktion in einem Prozessschritt und ist damit ein Ansatz zur Prozessintensivierung. Zur Modellierung des reaktiven Stofftransports in Kolonnen ist es notwendig, die kinetischen Parameter der chemischen Reaktion zu bestimmen. Bisher ist eine Vielzahl von Laborexperimenten dafür notwendig. Optimale Versuchs...