Papers by Christophe Wylock
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Chemical Engineering Science, 2017
The water scrubbing of biogas is an efficient, cheap and environmental friendly process to remove... more The water scrubbing of biogas is an efficient, cheap and environmental friendly process to remove CO 2 from biogas in order to upgrade it into biomethane. This work deals with the modelling and simulations of a scrubber-flash-stripper high pressure water scrubbing process, which is currently the most mature technology. The model and its associated simulation procedure can be used to estimate appropriate device sizes as well as to assess the performance of a given plant. Thanks to this tool, an optimized configuration is computed for a reference case. A sensitivity analysis is also realized in term of scrubbing efficiency and CH 4 slippage. The influence of parameters related to the water recycling as well as the operating parameters is investigated. Moreover, the sensitivity of the model with respect to the solubility and transfer coefficient parameters is analyzed, in order to gain insight on the parameter to focus in the framework of a model calibration by experimental results.
The Canadian Journal of Chemical Engineering, 2016
To understand CO2 absorption into a basic solution saturated porous medium or a Hele-Shaw cell, t... more To understand CO2 absorption into a basic solution saturated porous medium or a Hele-Shaw cell, the effect of the chemical reaction between dissolved CO2 and the basic reactant in the solution on the onset of a buoyancy-driven instability in a gas absorption process is analyzed theoretically. For the infinitely fast reaction, new linear and non-linear stability equations are derived without the quasi-steady state assumption (QSSA) and solved analytically. The present stability analysis without the QSSA shows that the important parameters are the dimensionless densification numbers and the reactant concentration ratio. For the physically unstable system, the chemical reaction can induce a non-monotonic density profile and has an important effect on the onset of instability motion. The effect of the reactant concentration ratio on the stability of the system is strongly dependent on the physical situation. Here, we call the system which is physically stable when there is no chemical reaction as the physically stable system. Even for this physically stable system, the chemical reaction makes the system unstable and induces the gravitational fingering instability motion. Also, it is found that the stability of the physically stable system is relatively insensitive to the non-monotonicity of the density profile.
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The Journal of Physical Chemistry B, 2014
Density variations induced by gas absorption in reactive aqueous solutions often trigger buoyancy... more Density variations induced by gas absorption in reactive aqueous solutions often trigger buoyancy-induced motions, generally in the form of plumes monotonically sinking into the bulk liquid and enhancing the absorption rate. Here, we contrast two types of CO 2-absorbing alkaline solutions, studying their dynamics inside a vertical Hele-Shaw cell by interferometry. While the first one indeed behaves as expected, the second one leads to a quite unusual oscillatory (phase-slipping) dynamics of convective plumes, which moreover does not lead to a significant transfer enhancement. Thanks to a simplified model of momentum and species transport, we show that this particular dynamics is related to a nonmonotonic density stratification, resulting in a stagnant layer close to the interface. Conditions for this to occur are highlighted in terms of the ratios of species' diffusivities and their contribution to density, a classification deemed to be useful for optimizing chemisorption (e.g., for CO 2 capture or sequestration) processes.
Energy Conversion and Management, 2017
Biogas upgrading by water scrubbing followed by biomethane compression is an environmentally beni... more Biogas upgrading by water scrubbing followed by biomethane compression is an environmentally benign process. It may be achieved using various plant configurations characterised by various power requirements with associated effects on biomethane sustainability. Therefore, the current study has been undertaken to systematically investigate the power requirements of a range of water scrubbing options. Two groups of water scrubbing are analysed: (1) high pressure water scrubbing (HPWS) and (2) near-atmospheric pressure water scrubbing (NAPWS). A water scrubbing plant model is constructed, experimentally validated and simulated for seven upgrading plant configurations. Simulation results show that the power requirement of biogas upgrading in HPWS plants is mainly associated with biogas compression while in NAPWS plants a significant power is required for water *Manuscript Click here to view linked References pumping. Biomethane compression to 20 MPa also contributes remarkably. It isobserved that the lowest specific power requirement can be obtained for a NAPWS plant without water regeneration (0.24 kWh/Nm 3 raw biogas) but this plant requires cheap water supply, e.g. outlet water from a sewage treatment plant or river. The second is HPWS without flash (0.29 kWh/Nm 3 raw biogas). All other HPWS with flash and NAPWS with water regeneration plants have specific power requirements between 0.30 and 0.33 kWh/Nm 3 raw biogas. Biogas compression without upgrading requires about 0.29 kWh/Nm 3 raw biogas. The thermodynamic efficiency of biogas upgrading is between 2.2 and 9.8% depending on the plant configuration while biomethane compression efficiency is higher, about 55%. This result implies that the upgrading process has a remarkable potential for improvement whereas compression is very close to its thermodynamic limit. The potential for minimising energy dissipation in the state-of-the-art HPWS upgrading plant with flash by applying a rotary hydraulic pumping device is evaluated at about 0.036 kWh/Nm 3 raw biogas meaning the specific power requirement reduction of 10%.
CO2 absorption in initially quiescent reactive aqueous solution is studied in a Hele-Shaw cell in... more CO2 absorption in initially quiescent reactive aqueous solution is studied in a Hele-Shaw cell in order to quantify the CO2absorption rate. CO2 transfer leads to a density stratification in the liquid phase below the interface and hydrodynamic instabilities appear after acertain time. The instability patterns are observed using a Mach-Zehnder interferometer for two different aqueous solution.
We study contact angle hysteresis by tracking stable and metastable contact angles upon varying t... more We study contact angle hysteresis by tracking stable and metastable contact angles upon varying the volume of a liquid inside a chemically heterogeneous microchannel. We construct a graphical force balance for this system with a straight contact line. Hysteresis is induced by wettability gradients above a finite threshold value. Sufficiently above this threshold, we find good agreement with the reported formulas for the hysteresis force for a diluted system of defects. In particular it is found to be proportional to the defect force squared and the defect concentration.
This work deals with the mathematical modelling of the CO2 absorption in initially quiescent aque... more This work deals with the mathematical modelling of the CO2 absorption in initially quiescent aqueous solutions, coupled with a chemical reaction in the liquid phase, inside a Hele-Shaw cell. Two different aqueous solutions are considered experimentally and it is observed that the absorption, initially driven by the diffusion, leads to the appearance of gravitational instabilities with different dynamics, depending on the considered case. Assuming that these instabilities are triggered by a Rayleigh-Taylor mechanism, a two-dimensional model, coupling the diffusion, the chemical reaction and buoyancy-driven convection, is proposed to simulate the development of such instabilities. It is observed that the simulations reproduce the density variation pattern and that the simulated instability dynamics agree qualitatively with the experimental observation in both cases considered. In addition, the simulation enables to assess the influence of the instabilities on the CO2 absorption rate a...
Introduction: The assessment of forest soil respiration and its isotopic composition is one of th... more Introduction: The assessment of forest soil respiration and its isotopic composition is one of the important issues for the carbon cycling modeling (in the framework of greenhouse gas emission control) because it is often inaccurate. Indeed, the soil respiration is a complex process, depending on the coupling of several phenomena, which is therefore highly sensitive to any disturbance. A measurement campaign has been realized at the permanent forest experimental site of Hartheim (Germany). Two measured parameters are the time evolution of the global CO2 flux leaving the soil FCO2 and the isotopic ratio d [CO2] between the two natural isotopes CO2 and CO2 in this flux, which are used as tracers enabling the monitoring of the production and transport phenomena. In the time evolution of FCO2 and d [CO2], significant intra-hour fluctuations are observed, which cannot be explained by a solely diffusive transport of the CO2 in the soil. It is conjectured that these fluctuations are induce...
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Papers by Christophe Wylock
The results presented during this paper session have been published in the following peer-reviewed article :
C. Wylock, P. Colinet, T. Cartage, B. Haut. " Coupling between mass transfer and chemical reactions during the absorption of CO2 in a NaHCO3-Na2CO3 brine : experimental and theoretical study". International journal of chemical reactor engineering, 6-A4 (2008).
A postprint version can be downloaded on the Institutional Depositery of the Université Libre de Bruxelles :
https://dipot.ulb.ac.be/dspace/bitstream/2013/66164/12/IJCRE-2008-1502_PostPrint.pdf
The results presented during this paper session have been published in the following peer-reviewed article :
C. Wylock, P. Colinet, T. Cartage, B. Haut. "Contribution à l'étude du couplage transfert de matière-réaction chimique lors de l'absorption du CO2 dans une saumure". Récents Progrès en Génie des Procédés 95 (2007), ISBN 2-910239-69-1, Ed. SFGP, Paris, France.
A postprint version can be downloaded on the Institutional Depositery of the Université Libre de Bruxelles :
https://dipot.ulb.ac.be/dspace/bitstream/2013/67411/8/RPGP-2007-95_PostPrint.pdf