Continuous Liquid Phase Research Articles

Phase inversion phenomena in vertical three-phase flow: Experimental study on the influence of fluids viscosity, duct geometry and gas flow rate

Improper sizing of pipelines and production tubings in the petroleum industry is often caused by lack of understanding of three-phase flow, which is characterized by gas flowing together with an immiscible water-oil mixture. There is the presence of a continuous liquid phase and a liquid dispersed phase, as observed in liquid-liquid flows, i.e., one can observe either a dispersion or emulsion of oil in water (o/w) or dispersion or emulsion of water in oil (w/o). The transition from o/w to w/o, or the other way around, is defined as phase-inversion. This phenomenon is characterized by a sharp increase in the pressure gradient, leading to significant pressure loss in the oil production system. The goal is to investigate the effects of oil viscosity, channel geometry (circular pipe or annular duct) and superficial gas velocity on the phenomenon of phase inversion in vertical liquid-liquid-gas flows, using oil with three different viscosities (ranging from 70 mPa s to 280 mPa s), tap water and compressed air as working fluids. The experiments were carried out in three different geometries: (i) glass pipe of 50 mm i.d., (ii) glass pipe of 95 mm i.d. and (iii) concentric annular duct with 95 mm of hydraulic diameter (glass outer pipe and PVC internal pipe). The experiments were performed under equivalent Reynolds number to evaluate the geometry effect. New data as total pressure gradient and volumetric fractions were obtained for all geometries. The results suggest that the extrapolation of results obtained in circular pipes with low viscosity oil and low gas flow rates to annular-duct flow with viscous oils and high gas flow rates can lead to significant errors.

A note on using VOF method for polymer bead manufacturing

The production of mono-dispersed spherical and non-spherical polymer beads and capsules using micro-fluidics requires precise control of dispersed phase which are distributed in a continuous phase. The prediction of two phase or three phase flow patterns in the mini/micro channels finds its application in production process of such spherical polymers. In the present work a numerical model based flow analysis is done for creation of the spherical/non spherical dispersed air bubbles in a continuous liquid phase. The results are validated with experiments done in a similar liquid–gas flow experiments carried out in a glass mini channel of size 2.05 mm. The flow regime is recorded with a high speed camera. The volume of fluid model in ANSYS Fluent software is used to predict the flow pattern details numerically. The model can be effectively used for predicting the size behavior in such spherical/non-spherical polymer bead production.

Analysis, design and synthesis of water-based magnetorheological fluid for CMMRF process

A computational fluid dynamics (CFD) simulation has been performed to study the instability behaviour of water-based magnetorheological fluid (MR fluid) which is being used as a polishing medium of the chemo-mechanical magnetorheological finishing (CMMRF) process. This article deals with the flow behaviour of the dispersed solid phase in a continuous liquid phase due to the gravity-assisted flow, which results in sedimentation of the MR fluid with time. In the present work, the causes of the fluid sedimentation have been identified through the CFD simulation. The sedimentation effect is minimized by nano-coating on iron particles using hydrocarbon chains through chemical reaction which is studied and analysed by using ab initio molecular dynamics simulation through density functional theory (DFT). The phenomenon observed through the simulation work is experimentally validated. The experimental results show that the MR fluid with nano-coating yields better stability against sedimentation.

Graphene Oxide as An Efficient Photocatalyst For Photocatalytic Reduction of CO2 Into Solar Fuel

Photocatalytic reduction of CO2 into solar fuel such as methane and methanol, is an attractive approach to simultaneously solve the energy crisis and global warming problem. Herein, comparative photocatalytic activity of graphene oxide nanosheets have been investigated for photocatalytic reduction of CO2 into methane and methanol in continuous gas and liquid phase photoreactor system. The graphene oxide sheets were prepared according to Tour's method. The chemical composition and optical properties was evaluated through XPS and UV-vis spectroscopy. Graphene oxide nanosheets exhibited maximum amount of 224.87 I¼mol/g.h methanol and 14.8 I¼mol/g.h methane in liquid and gas phase system, respectively. Higher yield of methanol in liquid phase compared to methane in gaseous system can be attributed to dispersion of graphene oxide sheets in water. Hence, graphene oxide nanosheets are efficient photocatalyst for CO2 reduction into methanol. Nevertheless, further research is essential to improve the photostability of graphene oxide sheets for real application of photocatalytic CO2 reduction. © Universiti Malaysia Pahang, Malaysia.

Mode Transition of Droplet Formation in a Semi-3D Flow-Focusing Microfluidic Droplet System.

Uniform droplets have significant potential in many biological applications due to their higher surface area to volume ratio. This paper proposed a semi-three-dimensional (sime-3D) flow-focusing microfluidic system, which was fabricated using the multi-layer soft lithography method. Based on the semi-3D structure, we focus on droplets formation modes and droplet uniformity at different bulk concentration of surfactant. The relationships between droplets uniformity, droplets breakup processes (jetting mode, dripping mode and tip-streaming mode) and surfactant concentration was investigated. It was found that three droplet generation modes occur through adjusting the pressure ratio in two inlet channels and the concentration of surfactant in continuous phase liquid. The jetting mode would transform to the dripping mode or the tip-streaming mode as the pressure ratio in different surfactant concentrations increased. Furthermore, the uniformity of droplets could be improved through the transition of jetting to dripping mode. We assumed that the uniformity declined through the transition of jetting to tip-streaming, and explored the specific transitions from jetting to dripping mode and tip-streaming mode. Dripping mode leads to high droplet uniformity, and generation frequency decreases with increasing pressure ratio. Tip-streaming mode is considered as an extreme state of jetting mode, leading to higher formation frequency and smaller droplet size at low uniformity.

Investigating bubble dynamics in a bubble column containing shear thinning liquid using a dual-tip probe

Bubble dynamics was characterized experimentally in non-Newtonian shear thinning fluids with different viscosities by a dual-tip resistivity probe. The experiments were carried out in a 9 cm diameter column while the superficial gas velocity varied between 0.5 and 7 cm/s. Air, injected through a diffuser, was the dispersed phase and various solutions of carboxy-methyl cellulose were used as the continuous liquid phase. An algorithm was developed to detect each individual contact of bubbles with the probe needles. It was shown that increasing the viscosity produces larger bubbles which make the homogeneous flow regime instable at liquid viscosities greater than 7 cP. It was found that the axial profiles of bubble chord length and velocity are affected by both shear thinning behavior of the solutions and the viscosity of the solution. The shear thinning behavior causes a descending trend of axial distribution of bubble rise velocity. Moreover, gas holdup reaches a maximum in the middle of the column in solutions studied. The probability distribution of bubble chord length was well fitted by a log-normal distribution. However, the bubble rise velocity distribution is Gaussian in the homogeneous regime at low gas flow rates. Correlations are given for evaluating bubble chord length and bubble rise velocity.

The Effect of Catalyst in the Process of Nano-Silica Particle Formation as a Hydrophobic Material

<p>Nano Silica is known as a hydrophobic material used to coat the material that further modifies the surface properties of the material. In this study the process of making nano silica material is using sol-gel method. The sol gel process is defined as the process of forming an inorganic compound through chemical reaction in solution at a low temperature wherein the process a phase changes from the colloidal suspension (sol) to a continuous liquid phase (gel). The types of catalyst were studied. The result was then applied to cotton, polyamide and silk fabrics. Acid catalyst showed the greatest moisture reduction based on Moisture Content and Moisture Regain evaluation in cotton and polyamide fabrics, whereas base catalysts showed a significantly less moisture reduction on the three fabrics. The use of these types of catalyst will also affect the value of the tensile strength of each fiber. Tensile test results showed that the use of acid catalysts decreased the maximum tensile strength in cotton fabrics by 88.57%, compared to polyamide and silk fabrics and the use of base catalyst showed less significant decreased on tensile strength for all fabrics.</p>

Research progress of bicontinuous interfacially jammed emulsion gel (Bijel)

In 2005, a bicontinuous arrangement of domains was explored by large-scale computer simulations. In a binary liquid host, the behaviors of neutrally wetting particles were simulated following an instantaneous quench into the demixed region. As the two mutually immiscible liquids phase separate, particles can be swept up by the freshly created interface and jam together as the domains coarsen, forming a particle-stabilized interface between two continuous liquid phases. This type of material is known as “bicontinuous interfacially jammed emulsion gel” (Bijel), and has been demonstrated experimentally using water-lutidine mixture in 2007. It is believed that Bijels have rich potential applications in diverse areas including healthcare, food, energy and reaction engineering due to their unique structural, mechanical and transport properties.As a new class of soft materials, Bijels have received great attention in recent years, and have been developed by using different liquids and non-spherical particles. However, a wide gap remains between the experimental systems and the industrial applications. This short review will critically assess current progress of Bijels and relevant studies including the attempts and challenges to use them in industry; the creation of Bijels by direct mixing at room temperature will be highlighted specifically.Chapter 1 presents the theoretical background. For binary-liquid systems containing dispersed colloidal particles, arrested composites can be created via the stabilization of convoluted fluid-fluid interfaces. Based on this, different morphologies of Pickering emulsions would be obtained. Chapter 2 first focuses on some complex emulsions, including Janus droplets and multiple emulsions, and then induces the bi-continuous structures. Such structures were originally formed through spinodal decomposition, which catches the phase demixing of an initially single-phase liquid mixture containing a colloidal suspension, and normally needs to control the temperature carefully. In Chapter 3, the mechanism of spinodal decomposition is presented. Chapter 4 shows some recent research progress of Bijels, including the studies with different liquid systems, nonspherical particles and some chemical property measurements. This chapter also summarizes the challenges in using Bijels in industry. In Chapter 5, a new method of creating Bijels by direct mixing at room temperature is demonstrated. This method simply needs high viscosity liquids, nanoparticles and a surfactant; it not only bridges the gap between conventional Bijel production (see Chapter 3) and that of particle stabilized bicontinuous structures using bulk polymers, but also bypasses the careful particle modification and phase separation steps for conventional Bijels. In Chapter 6 some conclusions are drawn and a general outlook is also provided.

Sensitive determination of psychotropic drugs in urine samples using continuous liquid-phase microextraction with an extraction solvent lighter than water

A novel extraction vessel was employed, for the first time, in continuous liquid-phase microextraction (CLPME) with an extraction solvent lighter than water for the extraction of psychotropic drugs from urine samples.

Investigation of the combined effect of air pockets and air bubbles on fluid transients

AbstractThis paper presents numerical and experimental investigations of the combined effect on pressure transients of air pockets and homogenous water–air bubble mixtures. An air pocket can accumulate at a high point of a pipeline along the control section located at the transition between pipes with sub- and supercritical slope, forcing open channel flow conditions underneath the pocket that ends in a hydraulic jump at the downward sloping pipe. The turbulence action at the jump generates small air bubbles that are entrained and transported along the pipe producing a two-component bubbly flow within the continuous liquid phase. A numerical model is developed, combining the explicit–implicit scheme proposed by McGuire and Morris and the method of characteristics for solving the quasi-linear hyperbolic partial differential equations for transient two-phase flow expressed in conservation form. To verify the proposed model, an experimental apparatus made of PVC was used to carry out hydraulic transient experiments. Tests were conducted in a tank–pipe–valve system and a valve with a pneumatic actuator at the downstream end generated transients. Numerical results at the test section pipe compares favorably with experimental data. The results show that pressure transients are significantly reduced with increasing air-pocket volumes and bubbly flow air content.

A Side-Stream Catalysis/Membrane Filtration System for the Continuous Liquid-Phase Hydrogenation of Phenol over Pd@CN to Produce Cyclohexanone

A catalysis/membrane filtration system combining a catalytic reaction and a separation process can realize the in situ separation of ultrafine catalysts from the reaction mixture and make the production continuous. In this study, a side-stream catalysis/membrane filtration system was developed for the first time for the continuous liquid-phase hydrogenation of phenol over Pd@CN to produce cyclohexanone. The operating parameters including the reaction and filtration conditions were optimized by balancing their influences on the catalytic and separation properties. It was found that the properties of the side-stream catalysis/membrane filtration system depended strongly on the operating conditions. Continuous phenol hydrogenation over Pd@CN was performed under the optimized operating conditions. A stable operation of 30 h was achieved with both a phenol conversion and a cyclohexanone selectivity of greater than 85%, and the ceramic membrane showed excellent stability. This study is a contribution to the dev...

Computational fluid dynamics (CFD) analysis of airlift bioreactor: effect of draft tube configurations on hydrodynamics, cell suspension, and shear rate.

The biomass productivity of microalgae cells mainly depends on the hydrodynamics of airlift bioreactor (ABR). Thus, the hydrodynamics of concentric tube ABR was initially studied using two-phase three-dimensional CFD simulations with the Eulerian-Lagrangian approach. The performance of ABR (17 L) was examined for different configurations of the draft tube using various drag models such as Grace, Ishii-Zuber, and Schiller-Naumann. The gas holdups in the riser and the downcomer were well predicted using E-L approach. This work was further extended to study the dispersion of microalgae cells in the ABR using three-phase CFD simulations. In this model (combined E-E and E-L), the solid phase (microalgae cells) was dispersed into the continuous liquid phase (water), while the gas phase (air bubbles) was modeled as a particle transport fluid. The effect of non-drag forces such as virtual mass and lift forces was also considered. Flow regimes were explained on the basis of the relative gas holdup distribution in the riser and the downcomer. The microalgae cells were found in suspension for the superficial gas velocities of 0.02-0.04ms-1 experiencing an average shear of 23.52-44.56s-1 which is far below the critical limit of cell damage.

Rheological studies of functional polyurethane composite with solid additives

The rheological dynamic characteristics of the functional polyurethane foam composite with solid additives (calcium iodate particles, aluminum flakes) were experimentally measured using an oscillatory rotational rheometer ARES-G2. Our previous studies demonstrated that the presence of the gas bubbles alters the rheology of the continuous liquid phase. The experimental tests results show that the apparent viscosity (the shear stress applied to a fluid divided by the shear rate) of the two-phase mixture increases with the concentration of the aluminum additive and decreases with the temperature rise. The rheological measurements showed that the functional foam exhibits a strong time-dependent and thixotropic (shear thinning) behavior. The rheological behavior of this composite can be described with the power law–generalized non-Newtonian fluid model. The apparent viscosity of the polyurethane increases with both the testing time (exponentially) and the solid content (polynomial) in the mixture. The measured rheological characteristics of the polyurethane-based functional foam will be helpful for material designers and developers.

Characterizing fluid dynamics in a bubble column aimed for the determination of reactive mass transfer

Bubble column reactors are multiphase reactors that are used in many process engineering applications. In these reactors a gas phase comes into contact with a fluid phase to initiate or support reactions. The transport process from the gas to the liquid phase is often the limiting factor. Characterizing this process is therefore essential for the optimization of multiphase reactors. For a better understanding of the transfer mechanisms and subsequent chemical reactions, a laboratory-scale bubble column reactor was investigated. First, to characterize the flow field in the reactor, two different methods have been applied. The shadowgraphy technique is used for the characterisation of the bubbles (bubble diameter, velocity, shape or position) for various process conditions. This technique is based on particle recognition with backlight illumination, combined with particle tracking velocimetry (PTV). The bubble trajectories in the column can also be obtained in this manner. Secondly, the liquid phase flow has been analysed by particle image velocimetry (PIV). The combination of both methods, delivering relevant information concerning disperse (bubbles) and continuous (liquid) phases, leads to a complete fluid dynamical characterization of the reactor, which is the pre-condition for the analysis of mass transfer between both phases.

Capillary Foams: Formation Stages and Effects of System Parameters

Foams are concentrated dispersions of gas bubbles in a continuous liquid phase. They are ubiquitous in nature and familiar from beer, frothed milk, and bubble baths; moreover, they play important roles in industrial applications ranging from petrochemicals to pharmaceuticals, food, and cosmetics. Recently, we reported the discovery of “capillary foams”, a new class of stable foams obtained by frothing a suspension of colloidal particles in the presence of a small amount of oil. In this study, we explored in more detail the formation stages of capillary foams and found that particle networks are formed first, which then entrap the gas bubbles (in this case, air bubbles). We further investigated the influence of particle concentration and wettability on the formation of capillary foams. As the fraction of particles is increased, the foam volume first increases and then reaches a plateau value. Finally, capillary foams were prepared at different oil fractions, using oils with different interfacial properties...

A proposal of a hydrodynamic model to low Reynolds numbers in a liquid-solid inverse fluidized bed reactor

Campos-Diaz, K. E., & Alvarez-Cruz, J. L. (May-June, 2017). A proposal of a hydrodynamic model to low Reynolds numbers in a liquid-solid inverse fluidized bed reactor. Water Technology and Sciences (in Spanish), 8(3), 143-150. This paper examines the fundamental characteristics of an inverse liquid- solid inverse fluidized bed reactor. In this reactor, many experiments were performed using three sizes of polypropylene spherical solids, lighter than water, with different diameters (4.00, 4.16 and 4.18 mm) and of densities ranging from 808 to 867 kg/m3 , these were fluidized by continuous liquid phase flow. Various bed heights were obtained at different flowrates from 0.95 to 9.5 (L min-1). A predictive model is developed for the hydrodynamic behavior, such as height and solid holdups (bed porosity), this model was derived from the balance of forces acting on a single particle and the set of particles found in the fluidized bed; uses process parameters, such as reactor dimensions, particle properties, and liquid flowrates as input variables, this model also includes the inertial drag coefficient which allow extended a non-spherical particles. This model has several advantages when compared with previously reported. Among them, advantages such as standard deviation values ≤0.9% between experimental and calculated bed porosity, the bed porosity can be expressed in terms of the Reynolds and Archimedes numbers and this model estimate bed porosity in a range of Reynolds number from 5.5 to 200 which has not been studied in an inverse fluidized bed reactors.

Study on the applicability of dynamic light scattering (DLS) to microemulsions including supercritical carbon dioxide-swollen micelles

The applicability of dynamic light scattering (DLS) for the characterization of the size of supercritical carbon dioxide (sc-CO2)-swollen micelles in a polyester polyol-based multicomponent microemulsion with nonionic surfactant has been thoroughly proved for the first time in this work. Systematic experiments confirming that a hydrodynamic mode is observable in either a homodyne or a heterodyne detection scheme as well as the evaluation of the influence of the laser power applied to the slightly colored microemulsion have ensured an accurate implementation of this technique for a technically relevant system. The correlation times associated with the translational diffusion coefficient of the swollen micelles in a continuous liquid phase were measured for temperatures from (298.15 to 338.15)K at pressures of (90 and 100)bar. While there was no significant effect of pressure, it was found that the translational diffusion coefficient increases with increasing temperature as expected. We postulate this is primarily related to the effect of decreasing viscosity of the continuous phase. An estimation of the hydrodynamic diameter of the sc-CO2-swollen micelles is in good agreement with values for similar systems reported in the literature. For the derivation of absolute sizes for corresponding systems, also dynamic viscosity and refractive index data will be determined simultaneously in a currently developed closed experimental loop.

Isobaric Vapor–Liquid Equilibria for Two Binary Systems {Propylene Glycol Methyl Ether Acetate + Methanol} and {Propylene Glycol Methyl Ether Acetate + N,N-Dimethylformamide} at p = 30.0, 50.0, and 70.0 kPa

The isobaric vapor–liquid equilibria (VLE) data for two binary systems of propylene glycol methyl ether acetate (PMA) + N,N-dimethylformamide (DMF) and propylene glycol methyl ether acetate (PMA) + methanol (MeOH) at 30.0, 50.0, and 70.0 kPa were measured by utilizing a modified Rose–Williams still type apparatus which could be able to quickly form the dual cycle of continuous vapor and liquid phase in this work. On the basis of Herington area test and Van Ness point test, the thermodynamic consistency of the experiment data was verified. Meanwhile, VLE data that we obtained were correlated with nonrandom two-liquid (NRTL) and Margules activity coefficient models. The results demonstrated that the calculated values were in good conformity with the experimental data in this study. In addition, azeotropic behavior was observed in the binary system of PMA and DMF at reduced pressures.

Continuous Synthesis of γ-Valerolactone in a Trickle-Bed Reactor over Supported Nickel Catalysts

Various Ni-based catalysts were tested in the continuous liquid phase hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) in a trickle-bed reactor using water as solvent with the aim to develop an economic and environmentally friendly way for the GVL synthesis. For this purpose, various synthesis methods were used to prepare Ni-based catalysts, which were first screened in batch reactors. Characterization by X-ray diffraction, temperature-programmed reduction, electron microscopy, hydrogen chemisorption, and X-ray absorption spectroscopy showed that slow precipitation using urea resulted in a good Ni dispersion. The dispersion also improved at lower Ni loading, and smaller Ni particles mostly showed an enhanced catalytic performance for the synthesis of GVL. 5 wt % Ni/Al2O3 prepared by wet impregnation showed the highest specific activity for the hydrogenation of LA to GVL (90% LA conversion and 75% GVL yield) featuring an average Ni particle size of 6 nm. Some deactivation of the catalysts was ...

Continuous Liquid-Phase Hydrogenation of 1,4-Butynediol to High-Purity 1,4-Butanediol over Particulate Raney Nickel Catalyst in a Fixed Bed Reactor

The work describes the results on the hydrogenation of the 2-butyne-1,4-diol (BYD) to 1,4-butanediol (BAD) over both slurry and particulate Raney nickel catalysts (Ra Ni) in batch and in a fixed bed reactor system. The detailed study on the kinetics of the reaction obtained in batch conditions revealed the existence of four stages in the overall hydrogenation network. In the first region, A, the starting BYD produces exclusively cis-2-butene-1,4-diol (cis-BED) and to a lesser degree the respective 4-hydroxybutanal (γ-HALD). In the second region, B, the cis-BED takes part in three parallel reactions of hydrogenation to BAD, isomerization to trans-2-butene-1,4-diol (trans-BED), and the formation of additional γ-HALD. In the third region, C, the trans-BED is mostly engaged in further hydrogenation to BAD, and surprisingly, starts producing the main byproduct, n-butanol (BOL). In the last kinetic region, D, the accumulated 4-hydroxybutanal is slowly hydrogenated to BAD. A completely different reaction profile...