CRYSTALLIZATION OF METHANE HYDRATES FROM AN EMULSION IN A FLOWLOOP: EXPERIMENTS IN A GAS-LIQUID-LIQUIDSYSTEM WITH A GAS-LIFT
Trung-Kien PHAM a,c , Ana CAMEIRAO a,* , Jean-Michel HERRI a , Philippe GLENAT b
a Gas Hydrate Dynamics Centre, Ecole Nationale Supérieure des Mines de Saint-Etienne, 158 Cours Fauriel, Saint-Etienne 42023, France b TOTAL S.A., CSTJF, Avenue Larribau, Pau Cédex 64018, France
Arunabha Kundu, Eric Dumont, Anne-Marie Duquenne and Henri Delmas* Laboratoire de Génie Chimique de Toulouse, CNRS UMR 55-03, Parc d’Activités de Basso Cambo, 5 rue Paulin Talabot, 31100 Toulouse, France
Experimental results of mass transfer in air-water system with a dispersed immiscible organic liquid in a bubble column 0.076 m in diameter for seven different organic liquids at various hold-up are presented. Experiments are carried out at gas superficial velocity in the range 0.0052-0.026 m/s at 293 K. The volumetric mass transfer coefficient, k L a is determined by dynamic gas absorption technique. Overall gas hold-up is also measured. Slight addition of n-decane, dodecane and n-heptane in air-water medium significantly enhances mass transfer from the gas phase, to the continuous aqueous phase whereas toluene, anisole and 2-ethyl- 1-hexanol retard mass transfer.
valve V1. When the reading in oxygen sensor (8) (Orbisphere, indicating instrument: model 3660 and oxygen sensor: model 31120A) is zero, then the supply of the nitrogen is stopped by closing simultaneously valve V6 and valve V1. Then the volume above the liquid column and all the other volumes occupied by gas are renewed with atmospheric air without disturbing the liquid column by opening valves V5 and V7 and closing valve V9. After confirming from the reading of the oxygen sensor, that the volume occupied by gas is totally filled with air, the compressor is stopped, valves V5 and V7 are closed, and valve V9 is opened. Then the finite volume of air is sparged through the liquid column by means of the compressor. Different superficial gas velocities can be selected. Decrease in oxygen concentration in air is monitored as a function of time through the recorder (9) (connected to the oxygen electrode) and the data is transferred to the computer (10) for further analysis. The overall gas hold-up is calculated from the variation of position of the free surface in the aerated and non-aerated column. Before doing experiment for each organic liquid, the column is thoroughly cleaned.
A potential advance for lipopeptides recovery from fermentation broth is the application of the low-cost liquid membrane process. This separation technique, based on solvent extraction, is called pertraction and operates in three-liquid-phase systems. Pertraction process is a combination of extraction and stripping operations performed simultaneously in one stage . The main advantages of pertraction towards classical liquid-liquid extraction are the use of smaller quantities of organic solvent due to continuous regeneration of the solvent, as well as the possibility to recover the target species even in cases of low distribution coefficients . Pertraction allows producing of valuable products of high quality at reduced costs, because of possibility to use as liquid membranes less powerful but more selective, less toxic and less expensive solvents than in the case of conventional solvent extraction. The interest of liquid membrane process for recovery of fermentation products have grown rapidly. Liquid membrane technique was successfully applied for recovery of some bioactive substances from fermentation broths [10, 11], but there are no data on lipopeptides recovery by using pertraction processes.
Institut Langevin, CNRS, ESPCI ParisTech and Universit´ e Paris Diderot, UMR 7587, 1 rue Jussieu, 75238 Paris Cedex 05, France
Levitating a liquid over a vapor film was limited to droplets. Here we show that on curved substrates a larger quantity of fluid can be suspended. This opens a new possibility for exploring new free liquid surface phenomena without any contact with a solid. In one of the simplest possible situation, a large fluid torus is levitated over a circular trough. A poloidal flow inside the ring generates a wave on its inner side, making it polygonal. This wave is described by a solitonic model which balances surface tension and a pressure depletion due to the distortion of the poloidal flow.
Special care should be taken from the beginning to ensure exchanger form factor gives an optimal balance between pressure drop and exchanger effectiveness. The ex- treme uncertainty and unconventional nature of testing for this project due to Covid19 led to a somewhat ad hoc approach which resulted in further challenges down the line. The LAMEE design was based on a total surface area requirement and the perception that risk of leakage would be reduced if fewer plates were used. In hindsight, a design with more layers (15-25) and larger face area would have significantly reduced pres- sure drop in the LAMEE and allowed greater mass flow. This would have not only improved system electrical COP, but also relieved some of the challenges encountered in collecting reliable data associated with low flow rates.
The use of miniaturized processes is promising according to two main frameworks: (i) process intensiﬁcation ( Stankiewicz and Moulijn, 2000 ; Commenge et al., 2005 ) with an improvement of safety due to conﬁnement and small amount of chemicals ( Burns and Ramshaw, 2001 ; De Mello and Wooton, 2002 ) and (ii) microdevices designed as labs on chips for data acquisition at laboratory scale such as kinetic data ( Sarrazin, 2006 ; Tsoligkas et al., 2007 ), physico-chemical properties ( Guillot et al., 2006 ) or biological mechanisms information ( Stanley et al., 2012 ) for a better sizing and control of pilot and industrial plants. For both applications it is important to understand the physical and chemical mechanisms at microscale. To carry out liquid–liquid process, mass transfer coefﬁcients estimation is required to obtain reliable process designs and/or data acquisitions for kinetic laws identiﬁcation. Few works focused on experimental mass transfer http://dx.doi.org/10.1016/j.ces.2013.11.009
Observations in three-dimensional foam samples do not allow us to study thoroughly the stability criterion in dy- namical events. A simpler experimental configuration is studied, with only two bubbles. As presented in Fig. 3 , two soap films are deposited at the ends of two vertical cylindrical tubes (outside diameter between 1 to 10 mm), facing each other and held at a distance controlled with a micrometer screw. Connections of the tubes to a syringe pump allow us to inject air and thus to inflate two bubbles of controlled radius R measured by videoscopy before bubbles come into contact. After contact, the two bubbles are joined by a thin liquid film surrounded by a circular PB, as described in Fig. 3 . The quantity of liquid in this ring is related to the radius of curvature r of the PB and to the radius of separating contact film, R c : V 2R c r 2 , where
Identification of the contacting mechanisms between the gas and liquid phases is a real challenge for the development of GLL reactions. In multiphase reactors, not only the reacting components must be efficiently mixed, but the conditions in the reactor must also allow the different components in the different phases to be able to come into contact and react. Depending on the physical and chemical properties of the system, the reaction then will take place either at the surface of a gas bubble (G/L interface), at the surface of a liquid drop (L/L interface) or within the continuous liquid bulk. If the selected reactor type or the steps used to put the gas and liquid into contact are not well adapted to the reaction mechanism, there will be a low yield of product caused by ineffective interphase contact within the reaction process. Furthermore, it may also result in the failure to obtain the desired product of the chemical reaction. In GLL reactions, the means in which the gas and liquid phases are contacted is strongly determined by the technological characteristics of the reactor, and therefore, a good understanding of the contacting mechanisms and mass transfer between phases is needed before designing or choosing a chemical reactor. Whilst there are a number of studies in the literature dealing with the demonstration and performance of GLL reactions, none of these identify in which phase the chemical reaction takes place, nor the limiting steps that control it. In addition, the available studies do not evaluate if the reactor type and phase contacting method are well adapted to the reaction being performed, or not. Indeed, identification of the limiting steps of a chemical process and designing the reactor and operating conditions –such that the limitations can be minimized or even suppressed– is the basis of process intensification.
The commercial XRF spectrometer used to analyse both aqueous and organic phases after extraction is a SPECTRO XEPOS (AMETEK) model. It is commercially equipped with an energy dispersive X-ray analyser (ED-XRF) that used the energy loss of the X photon in a silicon material to determine the spectrum by a suitable signal processing. Secondary targets reduce background noise compared to the output signal from the tube and improve fluorescence detection. Liquid samples were placed in 6 mm diameter cups, the bases of which consisted of a 4 μm thick prolene film. The XRF spectrometer was used to analyse a series of eleven cups in sequence, using a rotating carousel that positions the sample to be measured above the inverted optical part. A volume of 100 μL for each of the samples was placed in the micro-cups of analysis for a duration of 40 minutes. The X-ray tube generator was set at 40 kV and an intensity of 0.160 mA. The Zirconium secondary target was monitored between 15 and 17 keV to visualize the fluorescence of all lanthanides and iron: between 4 keV and 10 keV.
requirements of liquid-liquid extraction devices: from 50 µm to 3 mm.
• When the number of droplets is limited (fewer than 30 droplets with a mean diameter of 1 mm), the shadow density is less than 10% and the Royer  criterion is met. The paths of droplets with polydisperse diameters can then be reconstructed by successive acquisitions.
of nano ﬂuids,[ 10 ] the temperature pro ﬁles in micro-reactors,[ 11 ] the monitoring of exo- thermic reaction stability [ 12 ] and the measurement of the temperature of small amounts of liquid in micro- ﬂuidic chips.[ 13 ] Moreover, in the ﬁeld of micro-ﬂuidics, many react- ing chemical ﬂows are carried out for thermochemical analysis. The ﬁrst theoretical and numerical studies of chemical reactions [ 14,15 ] were performed in straight channels within continuous ﬂow systems. In this conﬁguration, at the inlet of the channel, a simple interdiffusional mixing zone is established; the length of this zone is mainly handled by the inner diameter of the channel, as well as by the diffusion coef ﬁcient. Some tech- niques have also been developed to quantify the heat released by a chemical reaction. Wang et al. [ 16 ] measured the temperature in miniaturised systems using detached sensors to estimate the reaction enthalpy. Other studies have shown the possibility to carry out a well-adapted calorimetry analysis of the experimental micro- ﬂuidics condi- tions.[ 17,18 ] Some infrared thermography studies have been carried out under co ﬂow conditions, where the diffusion limitation due to species mixing is thoroughly demon- strated.[ 19,20 ] Then, to overcome the problem of diffusion limitations and to intensify reactant mixing, the ﬂow analyses were performed using droplets. Based on this new hydrodynamic con ﬁguration, many studies were dedicated to the characterisation of physical behaviour.[ 21–23 ] Today, a wide range of physical and chemical phenomena are studied based on the droplet con ﬁguration. The main advantage of such biphasic ﬂows (i.e. droplets) is a consideration of the droplet as an independent reactor. In this case, homogenous mixing can be achieved faster by implementing chaotic advection,[ 24 ] as well as by establishing hydrodynamic recirculation inside the droplet.[ 25 ] Some numerical studies concerning the thermal effects of heat transport in a droplet-laden ﬂow [ 26 ] have also been studied. Moreover, many experimental and theoretical works concerning the thermal effects and thermal characterisation of segmented liquid gas ﬂows have been presented.[ 27–29 ] Most of these studies concern the cooling systems of minia- turised electronic devices, which are used to improve micro-heat exchangers.
Table 1 provides some examples of mean droplet size correla- tion including their range of applications depending on the chem- ical parameters (viscosity, densities, and interfacial tension), equipment parameters (porosity, pore diameter, pipe diameter, stirrer dimension. . .) and the operating conditions (flow rate, shear rate, pulsation. . .). Their limitations are underlined. Balances between hydrodynamic conditions and physico-chemical parame- ters are different from batch in continuous processes because breakage, coalescence phenomenon and interface stabilization act on different time scales. It is important to understand the mechanisms which display the droplet size in this type of contin- uous liquid–liquid contactors. These different contactors can thus be used to generate droplets and be associated with different Nomenclature
High dispersed phase concentration
a b s t r a c t
The aim of this paper is to investigate the influence of physico-chemical parameters on liquid–liquid dispersion at high dispersed phase concentration in Sulzer SMV TM mixer. Four different oil-in-water systems involving two different surfactants are used in order to evaluate the effect of interfacial tension, densities and viscosities ratio on mean droplets size diameters. Moreover the influence of the dispersed phase concentration on the pressure drop as well as on the droplet size distribution is investigated. Two different droplets size distribution analysis techniques are used in order to compare the resulting Sauter mean diameters. The comparison between residence time in the mixer and surfactants adsorption kinetics leads to take into account the evolution of the interfacial tension between both phases at short times. Finally experimental results are correlated as a function of dimensionless Reynolds and Weber numbers.
Also physically-based models using the conservation of gas and liquid fluxes have been developed (Fernandes et al., 1983; Lin´e, 1983; Nydal, 1991; Brauner and Ullmann, 2004). In these models the aeration of the liquid slug is obtained by modeling the en- trained gas flux at the rear of the Taylor bubble. A complete description of different regions of the flow and of the gas entrainment flux are needed in these models. The conservation of gas and liquid fluxes permits to close the model and to obtain pre- dictions for the mean void fraction. In this study we want to develop and test such a physically based model for the prediction of liquid slug aeration and mean void fraction in vertically oriented upward intermittent flow. Improved models will be developed for describing the flow in the liquid slug and for the entrained gas flux, and experimen- tal data will be used to check the validity of our models. The conceptual approach of Brauner and Ullmann (2004) based on an equilibrium of surface energy flux will be applied to model the gas entrainment flux at the rear of the Taylor bubble. Two mechanisms of gas entrainment will be considered: the turbulent ’jet’ present at the rear of the Taylor bubble (Brauner and Ullmann, 2004), and the work done by the pressure jump at the rear of the Taylor bubble.
hydrogen bond network with a consequent increase of molecular mobility; in contrast, compression of a “normal” liquid leads to a progressive loss of mobility as the molecules are brought closer to each other  . The pressure dependence of translational and rotational diffusion coef- ficients of bulk water has been reported in Refs. [6 –9] . Results are expressed as the pressure dependence of the ratio R ðPÞ ¼ XðPÞ=XðP atm Þ, where X stands for the measured transport property. Water behaves as a normal liquid (i.e., R decreases with pressure) at temperatures above the melting point, while the anomalous behavior (i.e., R increases with pressure) is present already at 273 K and gets strongly enhanced when water is supercooled to 243 K, where R ðP ¼ 1 kbarÞ is between 1.6 and 2. The pressure effect on translational diffusion is smaller than that on rotational diffusion and exhibits a maximum located at about 1.5–2.0 kbar for translation and about 2.5–3.0 kbar for rotation. Unfortunately, due to homogeneous nuclea- tion, experiments on bulk water at temperatures below 243 K are impossible; however, given the divergence of the inverse diffusion coefficient at T s , the anomalous pressure effect is expected to increase on lowering the temperature towards T s . The qualitative explanation of these effects
Neutron imaging is a viable method for capturing quasi two-dimensional convective and diffusive processes in solutions containing Gd 3+ ions. A pre-existing con- centration of paramagnetic fluid in some region can be redistributed within a miscible liquid by the magnetic field gradient force, which counteracts density-difference driven convection. Furthermore, double-diffusive convec- tion in the system of magnetic Gd(NO 3 ) 3 and nonmag-