References of "Heyen, Georges"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailOptimization of experimental procedure and statistical data treatment for kinetics of ethylene hydrogenation on a copper-magnesia catalyst
Pirard, Sophie ULg; Heinrichs, Benoît ULg; Heyen, Georges ULg et al

in Chemical Engineering Journal (2008), 138(1-3), 367-378

This study is an example of practical application of kinetic data treatment for simultaneous model discrimination and parameter estimation. The study is applied to the hydrogenation of ethylene on a ... [more ▼]

This study is an example of practical application of kinetic data treatment for simultaneous model discrimination and parameter estimation. The study is applied to the hydrogenation of ethylene on a copper-magnesia catalyst and brings a deepened analysis about the experimental strategy by comparing several alternative strategies using a priori and sequential experimental designs. The best model corresponds to a Langmuir-Hinshelwood mechanism with non-competing adsorption of hydrogen and ethylene and where the rate-determining step is either the addition of molecularly adsorbed hydrogen or the addition of the second atom of hydrogen adsorbed dissociatively. Furthermore, the important question of knowing in practice how many designs and how many measurements per design are actually necessary to determine accurate kinetic and physico-chemical parameters, is addressed. A data correction procedure is also presented that takes catalyst deactivation into account. (C) 2007 Elsevier B.V. All rights reserved. [less ▲]

Detailed reference viewed: 33 (7 ULg)
Full Text
Peer Reviewed
See detailRow by row simulation of heat recovery steam generators : comparing different types of initialization as well as the LMTD and ε-NTU simulation method
Dumont, Marie-Noëlle ULg; Heyen, Georges ULg

Conference (2007, May)

We developed a model which makes it possible to simulate a boiler rows by row. This model as well uses the European approach of log mean temperature difference as the American approach of effectiveness ... [more ▼]

We developed a model which makes it possible to simulate a boiler rows by row. This model as well uses the European approach of log mean temperature difference as the American approach of effectiveness-number of transfer unit. These approaches are compared in term of results and speed of calculation. We also present the difficulties encountered and some means of circumventing them. Some cases of superheater are treated in order to illustrate our matter. [less ▲]

Detailed reference viewed: 25 (11 ULg)
Full Text
Peer Reviewed
See detailCarbon nanotubes synthesis by CCVD process : kinetic study on a Fe-Co/Al2O3 catalyst
Pirard, Sophie; Douven, Sigrid ULg; Bossuot, Christophe et al

in Carbon (2007), 45(6), 1167-1175

A kinetic study was performed to describe the initial specific rate of multi-walled carbon nanotube synthesis by catalytic chemical vapor deposition (CCVD) on a bimetallic cobalt-iron catalyst at high ... [more ▼]

A kinetic study was performed to describe the initial specific rate of multi-walled carbon nanotube synthesis by catalytic chemical vapor deposition (CCVD) on a bimetallic cobalt-iron catalyst at high temperature using ethylene decomposition to solid carbon and gaseous hydrogen. The study uses a mass spectrometer that allows reaction rate to be inferred from the exhaust gas composition measurements. The aim is to obtain a better understanding of the elementary steps involved in the production of carbon nanotubes so as to derive phenomenological kinetic models in agreement with experimental data. The best models assume the elimination of the first hydrogen atom from adsorbed ethylene as rate determining step and involve a hydrogen adsorption weak enough to be neglected. It was proved that hydrogen partial pressure has no influence on initial reaction rate of carbon nanotube synthesis with the catalyst used for this study. Activation energy and ethylene adsorption enthalpy were found to be equal to around 130 and - 130 kJ mol(-1), respectively. (C) 2007 Elsevier Ltd. All rights reserved. [less ▲]

Detailed reference viewed: 96 (2 ULg)
Full Text
Peer Reviewed
See detailProcess monitoring using a combination of data driven techniques and model based data validation
Duchesne, Arnaud; Heyen, Georges ULg; Mack, Philippe et al

in Revista de Chimie (2007), 58(4), 423-426

Process monitoring is made difficult when measurements are subjected to errors, since pertinent information is hidden in the measurement noise. To address this issue, one can use model based data ... [more ▼]

Process monitoring is made difficult when measurements are subjected to errors, since pertinent information is hidden in the measurement noise. To address this issue, one can use model based data validation, or rely on statistical techniques to analyze large historical data sets (data mining). An industrial case study is presented here, where a model based approach (data validation) is compared to data driven techniques. [less ▲]

Detailed reference viewed: 68 (7 ULg)
Full Text
Peer Reviewed
See detailA kinetic study of multi-walled carbon nanotube synthesis by catalytic chemical vapor deposition using a Fe-Co/Al2O3 catalyst
Pirard, Sophie ULg; Douven, Sigrid ULg; Bossuot, Christophe et al

in Carbon (2007), 45(6), 1167-1175

A kinetic study was performed to describe the initial specific rate of multi-walled carbon nanotube synthesis by catalytic chemical vapor deposition (CCVD) on a bimetallic cobalt-iron catalyst at high ... [more ▼]

A kinetic study was performed to describe the initial specific rate of multi-walled carbon nanotube synthesis by catalytic chemical vapor deposition (CCVD) on a bimetallic cobalt-iron catalyst at high temperature using ethylene decomposition to solid carbon and gaseous hydrogen. The study uses a mass spectrometer that allows reaction rate to be inferred from the exhaust gas composition measurements. The aim is to obtain a better understanding of the elementary steps involved in the production of carbon nanotubes so as to derive phenomenological kinetic models in agreement with experimental data. The best models assume the elimination of the first hydrogen atom from adsorbed ethylene as rate determining step and involve a hydrogen adsorption weak enough to be neglected. It was proved that hydrogen partial pressure has no influence on initial reaction rate of carbon nanotube synthesis with the catalyst used for this study. Activation energy and ethylene adsorption enthalpy were found to be equal to around 130 and - 130 kJ mol(-1), respectively. (C) 2007 Elsevier Ltd. All rights reserved. [less ▲]

Detailed reference viewed: 91 (2 ULg)
Peer Reviewed
See detailAnalysis of Minimal In-Flight Oxygen Collection Cycle for Two Stage Launchers
Bizzarri, Didier; Heyen, Georges ULg; Hendrick, Patrick et al

in 14th AIAA/AHI International Space Planes and Hypersonic Systems and Technologies Conference (2006, November)

Detailed reference viewed: 26 (2 ULg)
Full Text
Peer Reviewed
See detailComparaison de techniques de validation dynamique de données
Heyen, Georges ULg; Gerkens, Carine ULg; Mateus, Miguel et al

(2006, October)

Detailed reference viewed: 39 (7 ULg)
Peer Reviewed
See detailPROPULSION AND VEHICLE INTEGRATION FOR REUSABLE LAUNCHER USING IN-FLIGHT OXYGEN COLLECTION
Bizzarri, Didier; Hendrick, Patrick; Heyen, Georges ULg et al

in EUROPEAN CONFERENCE FOR AEROSPACE SCIENCES (EUCASS) (2005, July)

The use of in-flight Oxygen Collection has shown to significantly improve space launcher performance. The conceptual approach followed by the Royal Military Academy of Brussels (RMA) has tried to widen ... [more ▼]

The use of in-flight Oxygen Collection has shown to significantly improve space launcher performance. The conceptual approach followed by the Royal Military Academy of Brussels (RMA) has tried to widen the available design margins in order to reduce the required technological leap and limit the economical risk associated with such a development. The aim of the ESA-funded theoretical and experimental study on an air separation device is to demonstrate the possibility of performing efficient air distillation in a compact rotating column. An integration of the vehicle, propulsion system and separation unit designs is presented aiming to optimise the overall vehicle performance while keeping technological difficulty and system complexity at a reasonable level. Reference vehicles are presented in their specific mission profiles with an emphasis on TSTO’s. Different layouts of the internal energy and mass flowsheets have been studied and were compared in order to make best use of the refrigeration capacity of the hydrogen fuel running though the propulsion system during the first phase of the flight considering the separator as a classical distillation column. This analysis provides the requirements in terms of heat exchange capacity, compression ratios and number of so-called transfer units needed in the separator. Here, the system is intentionally kept simple, to limit complexity, but the analysis is thorough and accurate, including, for example, the effect of the presence of argon. Results for a supersonic carrier are presented. An analysis of the separation unit to reach those requirements has been performed. That includes internals, practical building with estimates of pressure drop, separation performance and flow limitation. The sizing of the separator bed is provided for a carrier plane showing that such on-board separator is indeed practical. [less ▲]

Detailed reference viewed: 21 (2 ULg)
Peer Reviewed
See detailExperimental Study Of An In-Flight Air Separation Device
Bizzarri, Didier; Hendrick, Patrick; Heyen, Georges ULg et al

in AIAA/CIRA 13th International Space Planes and Hypersonics Systems and Technologies Conference (2005, May)

Intending to provide in-flight Oxygen Collection capability to new launchers, a subscale model of a centrifugally enhanced air distillation unit is under development. The vehicle we foresee for this ... [more ▼]

Intending to provide in-flight Oxygen Collection capability to new launchers, a subscale model of a centrifugally enhanced air distillation unit is under development. The vehicle we foresee for this application is described elsewhere, the present paper concentrating only on the technological and experimental aspects. While the test setup has already been shown to be able to provide the adequate cooling power, the rig is still under construction. The experimental and technical aspects include choices and main trade-offs that had to be made during the design process. Of particular interest are the stainless steel all welded heat exchangers allowing for deep cooling and liquefaction of air from the main compressor and dryers. Specifically, developed hardware is described in details. On the test rig side, design of the rotating cryogenic separator is explained, including mechanical aspects, heat management and sealing. The whole system has modes of operation allowing, among other parameters, to explore various air compositions and mass flows rates on the gaseous and liquid sides. Perspectives are given for the testing of the separator. [less ▲]

Detailed reference viewed: 109 (3 ULg)
Peer Reviewed
See detailIntegration of vehicle, propulsion system and separation unit designs for a launcher using in-flight oxygen collection
Bizzarri, Didier; Hendrick, Patrick; Heyen, Georges ULg et al

in AIAA/CIRA 13th International Space Planes and Hypersonics Systems and Technologies Conference (2005, May)

The use of in-flight Oxygen Collection has shown to significantly improve space launcher performance. The conceptual approach followed by the Royal Military Academy of Brussels (RMA) has tried to widen ... [more ▼]

The use of in-flight Oxygen Collection has shown to significantly improve space launcher performance. The conceptual approach followed by the Royal Military Academy of Brussels (RMA) has tried to widen the available design margins in order to reduce the required technological leap and limit the economical risk associated with such a development. The aim of the ESA-funded theoretical and experimental study on an air separation device is to demonstrate the possibility of performing efficient air distillation in a compact rotating column. An integration of the vehicle, propulsion system and separation unit designs is presented aiming to optimise the overall vehicle performance while keeping technological difficulty and system complexity at a reasonable level. Reference vehicles are presented in their specific mission profiles with an emphasis on TSTO’s. Different layouts of the internal energy and mass flowsheets are compared, in order to make best use of the refrigeration capacity of the hydrogen fuel running though the propulsion system during the first phase of the flight considering the separator as a classical distillation column. This analysis provides the requirements in terms of heat exchange capacity, compression ratios and number of so-called transfer units needed in the separator. Here, the system is intentionally kept simple, to limit complexity, but the analysis is thorough and accurate, including, for example, the effect of the presence of argon. An analysis of the separation unit to reach those requirements is proposed. That includes internals, practical building with estimates of pressure drop, separation performance and flow limitation. Analysis of size reduction of the distillation unit from usual 1-g column to the high-g unit is provided as well as the scale up methodology of laboratory results. First experimental results obtained with our centrifugally enhanced distillation separation system are presented and perspectives for a larger on-board operational unit proposed. [less ▲]

Detailed reference viewed: 30 (2 ULg)
Full Text
Peer Reviewed
See detailSensor network design using genetic algorithm
Gerkens, Carine ULg; Heyen, Georges ULg

(2004, September)

Detailed reference viewed: 39 (9 ULg)
Full Text
Peer Reviewed
See detailMathematical modelling and design of an advanced once-through heat recovery steam generator
Dumont, Marie-Noëlle ULg; Heyen, Georges ULg

in Computers & Chemical Engineering (2004), 28(5), 651-660

The once-through heat recovery steam generator (HRSG) design is ideally matched to very high temperature and pressure, well into the supercritical range. Moreover this type of boiler is structurally ... [more ▼]

The once-through heat recovery steam generator (HRSG) design is ideally matched to very high temperature and pressure, well into the supercritical range. Moreover this type of boiler is structurally simpler than a conventional one, since no drum is required. In a conventional design, each tube plays a well-defined role: water preheating, vaporisation, superheating. Empirical equations are available to predict the average beat transfer coefficient for each region. For once-through applications, this is no more the case and mathematical models have to be adapted to account for the disappearance of the conventional economiser, boiler and superheater. General equations have to be used for each tube of the boiler, and the actual heat transfer condition in each tube has to be identified. The mathematical complexity as well as the number of equations is increased. A thermodynamic model has been selected and implemented to suit very high pressure (up to 240 bar), sub- and supercritical steam properties. Model use is illustrated by two case studies: a 180 bar once-through boiler (OTB) and a conventional boiler superheater and reheater. (C) 2004 Elsevier Ltd. All rights reserved. [less ▲]

Detailed reference viewed: 86 (15 ULg)
Full Text
Peer Reviewed
See detailHow CAPE tools can contribute to process sustainability
Kalitventzeff, Boris ULg; Heyen, Georges ULg; Closon, Hervé et al

in Journal of Cleaner Production (2004), 12(2), 117-124

The concern of the EFCE for sustainability. Four recent case studies to illustrate how CAPE tools contribute to process sustainability: (1) ultimate plant operation at Wacker-Chemie (DE), (2) development ... [more ▼]

The concern of the EFCE for sustainability. Four recent case studies to illustrate how CAPE tools contribute to process sustainability: (1) ultimate plant operation at Wacker-Chemie (DE), (2) development of a new sulphuric acid plant with Air Liquide (FR), (3) plant retrofit for CO2 abatement at Kemira (BE), (4) insertion of a new plant in an existing Solvay industrial site (Asia). (C) 2003 Published by Elsevier Ltd. [less ▲]

Detailed reference viewed: 132 (10 ULg)
Full Text
Peer Reviewed
See detailData reconciliation and sampling protocol design, case of a paper deinking process
Brown, David; Marechal, François; Heyen, Georges ULg et al

in Paperi Ja Puu-Paper and Timber (2004), 86(8), 565-570

An equation solver data reconciliation software has been used to build a validated model of a waste paper deinking mill, by combining control room measurements and process design specifications. An ... [more ▼]

An equation solver data reconciliation software has been used to build a validated model of a waste paper deinking mill, by combining control room measurements and process design specifications. An optimal sampling protocol to validate the model by using only control room measurements has been determined by identifying, with genetic algorithm programming, the additional sampling points and corresponding sensors required to compensate for the lack of redundant measurements. [less ▲]

Detailed reference viewed: 87 (15 ULg)
Full Text
Peer Reviewed
See detailMathematical modelling and design of an advanced once-through heat recovery steam generator
Dumont, Marie-Noëlle ULg; Heyen, Georges ULg

in Computer Aided Chemical Engineering (2003), 14

The once-through heat recovery steam generator design is ideally matched to very high temperature and pressure, well into the supercritical range. Moreover this type of previous termboilernext term is ... [more ▼]

The once-through heat recovery steam generator design is ideally matched to very high temperature and pressure, well into the supercritical range. Moreover this type of previous termboilernext term is structurally simpler than a conventional one, since no drum is required. A specific mathematical model has been developed. Thermodynamic model has been implemented to suit very high pressure (up to 240 bar), sub- and supercritical steam properties. We illustrate the model use with a 180 bar once-through previous termboilernext term (OTB). [less ▲]

Detailed reference viewed: 18 (8 ULg)
Full Text
Peer Reviewed
See detailComputer-Aided Design of Redundant Sensor Networks
Heyen, Georges ULg; Dumont, Marie-Noëlle ULg; Kalitventzeff, Boris ULg

Poster (2002, May)

A systematic method to design sensor networks able to identify key process parameters with a required precision at a minimal cost is presented. The procedure is based on a linearised model, derived ... [more ▼]

A systematic method to design sensor networks able to identify key process parameters with a required precision at a minimal cost is presented. The procedure is based on a linearised model, derived automatically from a rigorous non-linear data reconciliation model. A genetic algorithm is used to select the sensor types and locations. [less ▲]

Detailed reference viewed: 22 (7 ULg)
Full Text
Peer Reviewed
See detailPlant monitoring and fault detection - Synergy between data reconciliation and principal component analysis
Amand, Thierry; Heyen, Georges ULg; Kalitventzeff, Boris ULg

in Computers & Chemical Engineering (2001), 25(4-6), 501-507

Data reconciliation and principal component analysis are tno recognised statistical methods used for plant monitoring and fault detection. We propose to combine them for increased efficiency. Data ... [more ▼]

Data reconciliation and principal component analysis are tno recognised statistical methods used for plant monitoring and fault detection. We propose to combine them for increased efficiency. Data reconciliation is used in the first step of the determination of the projection matrix for principal component analysis (eigenvectors). principal component analysis can then be applied to raw process data for monitoring purpose. The combined use of these techniques aims at a better efficiency in fault detection. It relies mainly in a lower number of components to monitor. The method is applied to a modelled ammonia synthesis loop. (C) 2001 Elsevier Science Ltd. All rights reserved. [less ▲]

Detailed reference viewed: 20 (3 ULg)