References of "Toye, Dominique"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailInvestigating the effects of hydrodynamics and mixing on mass transfer through the free-surface in stirred tank bioreactors
de Lamotte, Anne ULg; Delafosse, Angélique ULg; Calvo, Sébastien ULg et al

in Chemical Engineering Science (2017), 172

In stirred-tank bioreactors, flow structures of various length and time scales are implied in scalar transport phenomena, such as gas species transfer through the liquid free-surface and their ... [more ▼]

In stirred-tank bioreactors, flow structures of various length and time scales are implied in scalar transport phenomena, such as gas species transfer through the liquid free-surface and their homogenization in the bulk. A proper understanding of the underlying mechanisms, i.e. hydrodynamics, mixing and mass transfer, and of their interactions is required to design and develop reliable and efficient production-scale bioprocesses. The objective of the present work is to experimentally investigate the coupling between gas-liquid mass transfer of oxygen with mixing efficiency and circulation patterns inside an arbitrarily chosen stirred-tank configuration aerated through the liquid free-surface, a baffled 20 L-vessel agitated by two Rushton turbines. Based on global parameter values, the most appropriate rotating speed, N = 300 rpm, is selected in order to further study local hydrodynamic quantities using Particle Image Velocimetry (PIV), as well as mixing and mass transfer dynamics using Planar Laser-Induced Fluorescence (PLIF). The results obtained with these local experimental methods are analyzed in detail. Their averages are first successfully compared to global data. Statistical analysis of their spatial distributions show that large-scale flow patterns significantly influence mass transfer through the free-surface of the stirred tank. Even if global measurements show that global characteristic times for mixing and mass transfer differ by two orders of magnitude, local experimental characterization shows persistent vertical gradients of dissolved gas concentrations. So the dissolved gas concentration is not as perfectly uniform as one might expect. [less ▲]

Detailed reference viewed: 24 (7 ULg)
Full Text
Peer Reviewed
See detailRecent Evolutions and Trends in the Use of Computer Aided Chemical Engineering for Educational Purposes at the University of Liège
Léonard, Grégoire ULg; Belboom, Sandra ULg; Toye, Dominique ULg et al

in Computer Aided Chemical Engineering (2017)

The present paper addresses the evolution and perspectives in the teaching of CAPE methods in the Department of Chemical Engineering at the University of Liège. The transition that happened in the 90ies ... [more ▼]

The present paper addresses the evolution and perspectives in the teaching of CAPE methods in the Department of Chemical Engineering at the University of Liège. The transition that happened in the 90ies with the arrival of commercial software is highlighted, as the learning outcomes evolved from the ability of building programs to solve chemical engineering problems towards the ability to use complex commercial software and to understand their limitations. Moreover, CAPE methods were extended to non-dedicated CAPE courses, which is illustrated here by the goals and challenges of their use in courses like “Reactor Engineering” and “Life Cycle Analysis”. It was observed that students sometimes assume that CAPE softwares provide straightforward and trustworthy solutions without the need of understanding their mathematical bases and assumptions. Thus, solutions to make students aware of these limitations are proposed, including the creation of an integrated project focussing on complex multi-disciplinary issues, evidencing the need for critical input from the operator. [less ▲]

Detailed reference viewed: 18 (1 ULg)
Full Text
See detailSTUDY ON THE STRUCTURAL EVOLUTION OF SEWAGE SLUDGE DURING CONVECTIVE DRYING
Li, Jie; Fraikin, Laurent ULg; Salmon, Thierry ULg et al

Poster (2017, June 19)

The structure of the sludge sample continues changing during drying as a result of the shrinkage phenomenon. Then the exchange area becomes smaller and the drying rate decreases. The sludge collected in a ... [more ▼]

The structure of the sludge sample continues changing during drying as a result of the shrinkage phenomenon. Then the exchange area becomes smaller and the drying rate decreases. The sludge collected in a wastewater treatment plant (Grosses Battes WWTP, Belgium) was chosen for both lab-scale experiment and pilot-scale experiment. X-ray macrotomography (resolution: 0.36 mm per pixel) and X-ray microtomography (resolution: 41 μm per pixel) were used to explore the structure evolution of the sludge bed and the single extrudate respectively. 2D cross-sections of the sludge bed and the single extrudate were acquired, which supply a convenient way to investigate the evolution of the structure. The results show that the structure of both the sludge bed and the single extrudate distinctly changes during the drying process. [less ▲]

Detailed reference viewed: 10 (0 ULg)
Full Text
See detailX-ray tomography : a tool for revealing local distribution of liquid in structured packed columns
Toye, Dominique ULg

Conference (2017, May)

Presentation of the x-ray tomography setup and of the experimental results relative to the fluid distribution and to the flow morphology in a column packed with high performance packing (Mellapak 752Y ... [more ▼]

Presentation of the x-ray tomography setup and of the experimental results relative to the fluid distribution and to the flow morphology in a column packed with high performance packing (Mellapak 752Y). The influence of liquid flowrate and of liquid viscosity is addressed. Results are used to get information required to model the mass-transfer performance in the column. [less ▲]

Detailed reference viewed: 30 (4 ULg)
Full Text
Peer Reviewed
See detailInfluence of sawdust addition on drying of wastewater sludges: Comparison of structural characteristics
Li, Jie; Plougonven, Erwan ULg; Fraikin, Laurent ULg et al

in Drying Technology (2017), 35(8), 925-932

Detailed reference viewed: 29 (6 ULg)
Peer Reviewed
See detailIntegrated Project with Focus on Energy Transition and Circular Economy for Developing Engineering Students' Soft Skills
Léonard, Grégoire ULg; Pfennig, Andreas ULg; Toye, Dominique ULg et al

Poster (2016, September 05)

The present work reports the experience of an integrated project developed at the University of Liege for master students in chemical engineering. The goals are to promote the acquisition of soft skills ... [more ▼]

The present work reports the experience of an integrated project developed at the University of Liege for master students in chemical engineering. The goals are to promote the acquisition of soft skills and to consolidate technical knowledge by integrating and linking chemical engineering disciplines usually taught separately. A case study was selected to address some of the challenges related to energy transition: students had to design the energy system of a remote island and make it as energy independent and CO2-neutral as possible by 2030. The course of action during the academic year, the assessment of soft skills, and the tools offered to ease the mentoring and encourage the acquisition of soft skills are described. Not all implemented techniques performed equally well, and this project finally appeared to be a challenge for the teaching team as well. 1 Introduction and background Over the last few years, University authorities, industrial partners as well as national and international experts that evaluated the education quality of our Department (AEQES, CTI) strongly suggested that opportunities should be offered to students to increase their soft skills as part of their curriculum. Moreover, many developments in chemical engineering are related to energy transition and circular economy, which are both transdisciplinary to conventional lectures. In this paper, we present methods and mentoring tools developed to teach students technical and soft skills for multi-disciplinary topics. 2 Description of the integrated project Objectives and constraints were defined at the onset of the project for both technical and soft skills. The technical objective was to propose an energy system that would make Reunion Island as energy independent and CO2-neutral as possible by 2030. This idea originated in the challenge set by the Eurecha 2015 student contest[1], for which students had to design facilities for a sheikhdom: electricity, water recycling, production of fertilizers… In our case, Reunion Island (~850 000 inhabitants) was considered as a case study as it is remote, has large biomass resources and high potential for renewable energies. Besides the objectives mentioned above and in order to force students to look at chemical engineering processes, the treatment of wastewater was imposed as well as the use of a synthetic liquid fuel as energy carrier. The targeted soft skills included working in large groups of minimum 4 students, efficient communication of results in English - both written and oral -, ability to integrate knowledge from various disciplines, development of critical mind and demonstration of independent and creative thinking. 3 Course of actions A team of 8 professors and senior scientists mentored the project and contributed to its assessment. The 10-ECTS project was divided in two parts. In the fall semester, students made global energy balances to design the energy system that would fulfill the objectives. As a result, a Sankey diagram of the energy flows on Reunion Island by 2030 was produced to allow for an overview of the available Island’s resources and needs, as well as of processes that can make the link between resources and needs. In the spring semester, two processes identified in the first part, namely the synthesis of bio-ethanol and bio-methanol, were modelled in more details using commercial software. Different tools were used to encourage student initiatives and work: • The use of a shared on-line portfolio for students to gather their documents improved their internal communication, but this remained a marginal channel for communication with teachers • In the fall semester, students orally presented progress reports every two weeks. After a feedback to students, the teaching team met to discuss the achievements and set the objectives for the next two weeks. This was very positive for the communication inside the teaching team. However, presentations every fortnight implied a work overload for students that had to constantly focus on preparing the presentations. • From the beginning, students were strongly encouraged to reach out to field experts whose contacts were provided. However, they preferred to rely mostly on Internet as their main source of information and reached out only rarely for help and usually very late. • In the fall semester, students had to designate new team leaders in turn every fortnight. This was abandoned as it prevented the establishment of clear structures in the group, reducing its efficiency. • In the spring semester, work tables allowed students to work directly with the teacher specialized in their task. This was appreciated by students and teachers, and it needs to be further encouraged. • Help in the group organization and interactions was provided by the PSGO (psychology of groups and organizations). This also included videoscopy, i.e. filming the students during their presentations and analyzing the records with them. This help was appreciated by students. The assessment was based on technical results for 60%, and soft skills for 40%. The evaluation of technical skills was done partly by all teachers equally and partly by teachers whose expertise was the closest to the technical sub-tasks. For soft skills, efficient communication, creativity in the work and results and links with conventional lectures were assessed. Critical thinking was evaluated through the relevance of qualitative and quantitative results and discussions. Group work was assessed by the teachers as well as by students through mutual evaluation. 4 Conclusions and perspectives The integrated project gave students a first opportunity to improve their soft skills along with their technical knowledge. It also improved their communication skills and their fluency in English. The teaching team proposed different mentoring techniques to encourage efficient work, with varying results. Finally, as the assessment ignored soft skills improvements, it may be modified by evaluating soft skills all year long so both the final result and the observed improvements contribute to the grade. Reference Eurecha, The European Committee for the Use of Computers in Chemical Engineering Education, 2015. Announcement for student contest problem competition 2015. http://bari.upc.es/eurecha/. [less ▲]

Detailed reference viewed: 60 (8 ULg)
Full Text
Peer Reviewed
See detailDPSC colonization of functionalized 3D textiles
Ortiz, Marine; Rosales-Ibáñez, R; Pozos-Guillén, A. et al

in Journal of Biomedical Materials Research, Part B : Applied Biomaterials (2016), 10.1002/jbm.b.33609

Detailed reference viewed: 104 (38 ULg)
Full Text
Peer Reviewed
See detailLarge-Eddy Simulations of microcarrier exposure to potentially damaging eddies inside mini-bioreactors
Collignon, Marie-Laure ULg; Delafosse, Angélique; Calvo, Sébastien ULg et al

in Biochemical Engineering Journal (2016)

Mechanically stirred vessels equipped with rotating impellers generate heterogeneous transitional or turbulent flows. However, some cells as animal or human mesenchymal stem cells (hMSC) adhered on ... [more ▼]

Mechanically stirred vessels equipped with rotating impellers generate heterogeneous transitional or turbulent flows. However, some cells as animal or human mesenchymal stem cells (hMSC) adhered on microcarriers, are reputed sensitive to hydromechanical stresses arising from stirring. Many publications, especially using Computational Fluid Dynamics, characterize spatial fields of velocity and turbulence inside bioreactors but the exposure frequency to these stresses is never taken into account in the case of animal cell culture bioreactor description. To fill this gap, this study used both CFD Reynolds-Averaged and Large-Eddy Simulations to characterize the hydrodynamics inside 250 mL mini-bioreactors, which is a relevant volume for hMSC cultures. Five impeller geometries were studied. From the velocity and turbulence fields calculated, an energy dissipation/circulation function, related to both frequency and intensity of potentially damaging hydrodynamic events for the cells, was determined for various operating conditions. Based on the simulation results, the marine propeller operating in up-pumping mode seems to be the most adapted condition, since it exhibits a low frequency of exposure to an acceptable intensity of the turbulent dissipation rate. From a general point of view, the new methodology proposed should be used in the future to screen the most adapted bioreactor geometry to biological constraints. [less ▲]

Detailed reference viewed: 76 (17 ULg)
Full Text
Peer Reviewed
See detailPositive Operations on Wastewater Sludge Drying: Comparison of Back-Mixing and Sawdust Addition
Li, Jie; Plougonven, Erwan ULg; Fraikin, Laurent ULg et al

in Energy & Fuels (2016), 30(4), 3014-3019

Detailed reference viewed: 31 (4 ULg)
Peer Reviewed
See detailConvective drying behavior of sawdust-sludge mixtures in a fixed bed
Li, Jie; Fraikin, Laurent ULg; Salmon, Thierry ULg et al

in Drying Technology (2016), 34(4), 395-402

Detailed reference viewed: 36 (9 ULg)
Full Text
Peer Reviewed
See detailInfluence of process operating conditions on solvent thermal and oxidative degradation in post-combustion CO2 capture
Léonard, Grégoire ULg; Crosset, Cyril; Toye, Dominique ULg et al

in Computers & Chemical Engineering (2015), 83

The CO2 post-combustion capture with amine solvents is modeled as a complex system interconnecting process energy consumption and solvent degradation and emission. Based on own experimental data ... [more ▼]

The CO2 post-combustion capture with amine solvents is modeled as a complex system interconnecting process energy consumption and solvent degradation and emission. Based on own experimental data, monoethanolamine degradation is included into a CO2 capture process model. The influence of operating conditions on solvent loss is validated with pilot plant data from literature. Predicted solvent consumption rates are in better agreement with plant data than any previous work, and pathways are discussed to further refine the model. Oxidative degradation in the absorber is the largest cause of solvent loss while thermal degradation does not appear as a major concern. Using a single model, the process exergy requirement decreases by 10.8% and the solvent loss by 11.1% compared to our base case. As a result, this model provides a practical tool to simultaneously minimize the process energy requirement and the solvent consumption in post-combustion CO2 capture plants with amine solvents. [less ▲]

Detailed reference viewed: 118 (21 ULg)
Full Text
Peer Reviewed
See detailFungal biofilm reactor improves the quality of a fusion protein GLA::GFP produced by Aspergillus oryzae
Zune, Quentin ULg; Delepierre, Anissa ULg; Bauwens, Julien ULg et al

Poster (2015, October)

Fungal biofilm is known to promote the excretion of secondary metabolites, in accordance with solid-state related physiological mechanisms. In this work, the potentialities of fungal biofilm will be ... [more ▼]

Fungal biofilm is known to promote the excretion of secondary metabolites, in accordance with solid-state related physiological mechanisms. In this work, the potentialities of fungal biofilm will be investigated in the context of the production of a Gla::GFP fusion protein by Aspergillus oryzae. Since the production of this protein is under the control of the promoter glaB, specifically induced in solid-state fermentation, biofilm mode of culture is expected to enhance the global productivity. However, we found that the glaB promoter is also activated in submerged bioreactor and the fusion protein production is higher in this mode of culture. This result is related to the high shear stress leading to biomass autolysis and leakage of intracellular fusion protein into the extracellular medium. Moreover, 2D-gel electrophoresis highlights preservation of the fusion protein integrity produced in biofilm conditions whereas proteolysis strongly affects fusion protein recovery in the submerged cultures performed at high stirring rate. Fungal biofilm reactor design was then further investigated and the scale-up potentialities were evaluated. Indeed, the specific design investigated in this work involves the use of metal structured packing exhibiting a high specific area and that can be easily expanded to large-scale bioprocessing conditions. [less ▲]

Detailed reference viewed: 102 (24 ULg)
Full Text
Peer Reviewed
See detailEuler–Lagrange approach to model heterogeneities in stirred tank bioreactors – Comparison to experimental flow characterization and particle tracking
Delafosse, Angélique ULg; Calvo, Sébastien ULg; Collignon, Marie-Laure ULg et al

in Chemical Engineering Science (2015), 134

The aim of this work is the validation of an Euler–Lagrange modeling approach coupling a CFD-based compartment model (Eulerian approach) and a stochastic model based on a Continuous-Time Markov Chain ... [more ▼]

The aim of this work is the validation of an Euler–Lagrange modeling approach coupling a CFD-based compartment model (Eulerian approach) and a stochastic model based on a Continuous-Time Markov Chain (Lagrangian approach). The turbulent flow structure and the mixing process in a bioreactor stirred by an axial Mixel TT impeller is characterized by PIV and tracer experiments. Comparison between experimental and numerical data shows that the CFD-based compartment model is able to reproduce accurately the spatial heterogeneities inside the bioreactor. The trajectory of a small tracer particle which perfectly follows the fluid flow is measured by optical trajectography. It is then simulated by a stochastic model which is either based on an homogeneous or on an inhomogeneous Continuous Time Markov Chain (CTMC). Comparison of residence and circulation time distributions in three zones defined inside the bioreactor shows that the inhomogeneous CTMC model predicts with an excellent accuracy the particle trajectories inside the bioreactor. The modeling approach proposed here could be an useful tool to design scale-down bioreactors in order to reproduce at lab-scale the stress levels encountered in large-scale production bioreactors and to characterize and compare different bioreactor configurations. [less ▲]

Detailed reference viewed: 67 (29 ULg)
Full Text
Peer Reviewed
See detailSurface aeration in baffled stirred tanks: hydrodynamics, mixing and mass transfer characteristics
de Lamotte, Anne ULg; Delafosse, Angélique ULg; Calvo, Sébastien ULg et al

Poster (2015, September)

Biotechnological and chemical processes often need a supply of gas for acceptable product formation. In some applications - where either gas requirements/reactor volumes are relatively low, or bubbles are ... [more ▼]

Biotechnological and chemical processes often need a supply of gas for acceptable product formation. In some applications - where either gas requirements/reactor volumes are relatively low, or bubbles are undesirable - aeration through the liquid free-surface is enough to meet the demand. In case of sparged stirred tanks, aeration through the liquid free-surface is a factor to be determined when scaling-up /down processes. Gas-liquid transfer is strongly influenced by the hydrodynamic conditions. Two phenomena, occurring at different scales, can be coupled in order to explain mass transfer : (i) circulation (macroscale) and (ii) mixing/homogenization (microscale). Mixing/homogenization takes into consideration the small eddies responsible for the rippled liquid free-surface and for the concentration gradients surrounding it. Circulation determines the fluid path across the reactor as well as its contribution of the surface aeration and leads to periodic and local deformation of the liquid free-surface. Circulation also accounts for the design of the reactor, where the scaling problems are focused. The objective of this work is to develop an experimental approach able to fully (global and local quantities) characterize a chosen agitation configuration in terms of hydrodynamics, mixing and transfer, in order to assess the capability of computational methods to predict gas-liquid mass transfer due to aeration through the liquid free-surface. [less ▲]

Detailed reference viewed: 92 (16 ULg)
Full Text
Peer Reviewed
See detailMultiscale structure characterization of sawdust-waste water sludge extrudates dried in a pilot-scale fixed bed
Li, Jie ULg; Plougonven, Erwan ULg; Fraikin, Laurent ULg et al

in Biomass and Bioenergy (2015), 81(0), 98-107

Abstract Convective drying of waste water sludge and sawdust-sludge mixtures in a pilot-scale fixed bed was studied. Drying was performed in a cross-flow convective dryer using 500 g of wet material ... [more ▼]

Abstract Convective drying of waste water sludge and sawdust-sludge mixtures in a pilot-scale fixed bed was studied. Drying was performed in a cross-flow convective dryer using 500 g of wet material extruded through a disk with circular dies 12 mm in diameter. The structure of the bed mainly shows volume shrinkage and crack formation during drying. Several characterization techniques were used over a wide range of scales from nm up to mm. The overall bed structure was imaged with X-ray macrotomography, at a resolution of 0.36 mm per pixel. Single extrudates were scanned with X-ray microtomography, at a resolution of 41 μm per pixel. Pore structure of the dried samples were characterized by mercury porosimetry (7.5 nm < dp < 150 μm). Results show significant structural changes on all scales with increasing amounts of sawdust: shrinkage decreases, crack formation increases, and the pores become larger. This confirms the benefits of sawdust addition for sludge drying applications. [less ▲]

Detailed reference viewed: 29 (10 ULg)
Peer Reviewed
See detailHydrodynamics, mixing and mass transfer in baffled stirred tanks
de Lamotte, Anne ULg; Delafosse, Angélique ULg; Calvo, Sébastien ULg et al

in Proceedings of the 15th European Conference on Mixing (2015, June)

The present work presents CFD simulations of hydrodynamics, mixing and mass transfer in a surface-aerated baffled stirred tank. The modelling of the multiphase flow is realized via an Euler-Euler approach ... [more ▼]

The present work presents CFD simulations of hydrodynamics, mixing and mass transfer in a surface-aerated baffled stirred tank. The modelling of the multiphase flow is realized via an Euler-Euler approach. Three closure models are tested for the resolution of the RANS equations. When fully-developed flow field is reached, gas-liquid transfer is implemented with a local mass transfer coefficient estimated by the eddy cell model, and the temporal evolution of dissolved gas concentration is predicted.Hydrodynamic and mixing quantities as well as mass transfer parameters for the different turbulence models are compared with experimental data available for the same geometrical and operating features. A critical analysis of the prediction results allow to assess the models capabilities and to highlight the possible critical issues of the simulations. [less ▲]

Detailed reference viewed: 118 (25 ULg)