Countercurrent Extraction Column Research Articles

Hybrid process for separation of morpholine−water mixture: A rigorous design with experimental confirmation based on LLE and VLE data

The separation of morpholine from the aqueous effluent stream is carried out using an efficient hybrid extraction-distillation (HED) system using commercially viable solvents 2-ethyl hexanol and toluene, which makes heteroazeotrope with water. This paper investigated the tie-line, mutual solubility and VLE measurements, and thermodynamic modeling. On comparing the two solvents, 2-ethyl hexanol emerged as an appropriate extractant. The experimental tie-line data regressed by the NRTL model and a deviation of 0.8 indicates a good correlation between experimental and predicted data. Further, the process is designed, simulated, and optimization is performed by minimizing total annual cost (TAC) as the objective function. At extract/solvent to feed ratio S/F of 0.78 mol fraction, number of stages, NT of 28, 99.8% morpholine recovered in the extract phase with TAC of $23.3×104/y. Subsequently, the extract phase is fed to the heteroazeotropic distillation column to remove moisture followed by the final recovery column. Finally, a laboratory-scale experiment was conducted to verify the separation performance in the downscaled (3.5×50 cm) counter-current extraction column.

Process Development on the High-Yielding Reactive Extraction of Xylose with Boronic Acids

Previous studies have identified the reactive extraction of xylose from water to an organic phase by means of esterification with boronic acid (BA) on a laboratory scale as a promising step for producing furfural from lignocellulosic biomass. In this study, the extraction is investigated further, to lay out the foundations needed for development to an industrial process, and prove that it works with a real feedstock. Various parameters, such as temperature, interfacial area, and choice of solvent and BA, were evaluated. Experiments were carried out with both pure xylose and acid hydrolysate of bagasse. Our findings show that xylose can be extracted from acid hydrolysate with a high single-pass yield of 85 mol % and low losses of BA of 0.25% when using naphthalene BA at 90 °C. Furthermore, an extraction isotherm was constructed for the naphthalene BA-DowTherm A system, showing a high extraction yield of 85% per pass at various concentrations. This allowed for the preliminary design of a countercurrent extraction column, which needs 3 trays to recover 90% of the sugars from an acid bagasse hydrolysate at a solvent-to-feed ratio (S/F) of 1:1.

Extraction of methylcyclohexane−toluene mixture using imidazolium ionic liquids

Separation of aromatics from non-aromatic hydrocarbons was exemplified assuming the liquid-phase extraction process for methylcyclohexane−toluene model mixture separation using the newly tested 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMim][NTf2]) ionic liquid (IL). For this process a separation unit was proposed consisting of separation part represented by a counter-current extraction column and regeneration part including a vacuum evaporator and a vacuum distillation column. Separation of feed composed of 10 mole% of toluene in methylcyclohexane was considered in the designed separation unit. Designed separation efficiency of the unit was based on the following specifications: minimum methylcyclohexane and toluene content in the product streams of 99.5 mole% and the purity of regenerated extraction solvent recycled to the extraction column above 99 mole%.Mathematical model of a counter-current extractor was compiled and its operation was simulated in the Matlab environment. In extractor simulations, proprietary phase equilibrium data were employed. Ternary liquid–liquid equilibrium (LLE) of the methylcyclohexane−toluene−[EMim][NTf2] system was estimated experimentally, from which the model parameters of the original NRTL equation were evauated and used for the ternary phase equilibrium description.Aspen Plus was used to design a separation unit for the title hydrocarbons mixture separation, including the extraction solvent regeneration. Simulation of the proposed separation unit operation was focused not only on its separation efficiency but also on the evaluation of the unit energetic requirements.Results of the unit design calculations (parameters of individual equipment, heat duties) obtained for the tested ionic liquid [EMim][NTf2] were confronted with the simulation results obtained for two ILs recommended in the literature for the non-aromatic–aromatic hydrocarbon mixture separation, namely 1‑butyl‑3-methylimidazolium tetracyanoborate [BMim][TCB] and 1-hexyl-3-methylimidazolium tetracyanoborate [HMim][TCB]. Based on the energetic analysis, the heat integration of the suggested separation unit was carried out for ionic liquid [HMim][TCB], which appeared to be the most efficient extraction solvent among those tested in this study, The heat integration resulted in about 71% reduction of the heat demand of the proposed separation unit.

Health-Promoting Properties of Borage Seed Oil Fractionated by Supercritical Carbon Dioxide Extraction.

Borage (Borago officinalis L.) seed oil is an important source of γ–linolenic acid, which is normally used as a treatment against different pathologies. Since the fractionation of this interesting seed oil has many environmental, economic and biological benefits, two borage fractionation techniques after extraction with CO2 under supercritical conditions have been studied: precipitation in two cyclone separators and countercurrent extraction column. Both techniques have successfully collected free fatty acids in one fraction: (i) two separators set up in series obtained the highest concentration of free fatty acids in separator 2 at 90 bar/40 °C; (ii) when countercurrent extraction column was used, the acidity index of the raffinate stream was independent from the operating conditions (2.6 ± 0.5%). Furthermore, the composition of the fatty acids, as well as their antioxidant and cytotoxic activities, were determined. The profile of the fatty acids obtained by either of these two methods remained unaltered, so that the crude oil exhibited improved antioxidant and cytotoxic properties. All the extracts obtained in the two cyclone separators at the same pressure/temperature conditions displayed high tumouricidal activity against HL 60 promyelocytic leukaemia cells, even if the extracts at 50% concentration from separator 2 presented a lower inhibitory activity (IC50). The extracts from separator 2 at 90 bar/40 °C exhibited the highest anti-proliferative activity at low doses (IC50 of 0.3 μL/mL for the trypan blue exclusion test). To reach the lethal dose—IC50—with the product obtained through countercurrent column fractionation, a concentration of 2 μL/mL of crude borage oil raffinate was required.

Modelling and simulation of supercritical CO2 extraction of bioactive compounds from vegetable oil waste

Deodorizer distillates are waste by-product from vegetable oil industries. It has excellent potential as a source of bioactive compounds. Therefore, the aim of this study was to model the thermodynamic phase equilibrium and optimize the supercritical CO2 extraction processes for concentrating valuable minor components from rapeseed oil deodorizer distillates (RODD). The extraction was done in a countercurrent extraction column at pressure (35−40 MPa), temperature (313 K) and solvent to feed mass ratio (S/F) of 5. The raw material employed was initially saponified. Investigating the extraction process, representing phase equilibria behavior of the multicomponent oil-type material/CO2 mixture and prediction the steady-state efficiency of the extractor was done by using the Stryjek–Vera Peng–Robinson equation of state as a thermodynamic model for the experimental bubble pressures and vapor compositions. The extraction of β-sitosterol and vitamin E in the saponified RODD at predicted conditions showed a recovery of 76 wt% with a purity of 60 wt% and a recovery of 85 wt% with a purity of 75 wt% respectively. Furthermore, the use of a modified sample increased the phytosterol and tocopherol efficiency and purity. The absolute average relative deviation between the theoretical and experimental was within the range of 1–12%, which is considered as a good agreement. The coupling of thermodynamic modeling with experimental work offered an efficient and rapid tool for analyzing the viability of the supercritical extraction.

Salting-Out Assisted Liquid-Liquid Extraction (SALLE) for the separation of morpholine from aqueous stream: Phase equilibrium, optimization and modeling

In the present study, enhanced liquid-liquid extraction i.e., salting-out assisted liquid-liquid extraction (SALLE) was explored for the separation of morpholine from the aqueous stream. The salting out capacities of two kosmotropes K2CO3 and KCl with solvents (1-decanol and toluene) was investigated within its solubility limit. A Taguchi optimization technique was investigated to obtain the optimum combination of parameters employing a mixed array design (23×22). The results demonstrated that the salting-out effect of K2CO3 in combination with 1-decanol was more pronounced than KCl and thereby the tie-line data was generated for this quaternary system comprising water + morpholine + K2CO3 + 1-decanol at various temperatures (293.15–313.15 K). As the CO32− anion shows the more negative value of Gibb's free energy of hydration, ΔGhyd than Cl− revealed the better salting-out ability of CO32− ion. In other terms, the B-coefficients of the constituent anions (CO32− and Cl−) have been discussed further, which is related to the salt kosmotropicity, revealed the interactions between water molecules and electrolyte ions and their effect on the water lattice around the solute particles. Also, the critical concentration of K2CO3 required to form two phases is reduced with a rise in temperature. Further, the process parameters influencing the extraction efficiency, such as tie-line length, (TLL) of the quaternary system was also evaluated and data fitted to the Eisen-Joffe model to perform the consistency test in respect of the overall concentration of salt to water in each phase. The Eisen-Joffe salt parameter, Ks which signifies the reliability of the tie-line data, was obtained in the range of 1.71–5.93 and the tie-line data was also accurately predicted by the NRTL activity coefficient model. The applicability of the SALLE was finally investigated in the continuous counter-current extraction column indicating the SALLE to show good performance on the separation efficiency of morpholine.

Reactive Zinc Extraction with D2EHPA in a Kühni Miniplant Column

AbstractReactive extraction of Zn2+ with di‐(2‐ethylhexyl) phosphoric acid (D2EHPA) was examined in a multistage countercurrent extraction column of type Kühni. Hydrodynamics and mass transfer for the reactive European Federation of Chemical Engineering (EFCE) test system were comprehensively experimentally investigated in a DN32 Kühni miniplant column. The experiments demonstrate that the column hydrodynamics and mass transfer performance markedly depend on throughputs, phase ratio, energy input as well as on the component concentrations. Using a simple equilibrium stage model, it was found that two to four stages per meter can be reached in the miniplant extractor. The system physical properties (density, viscosity, interfacial tension) of the reactive test system change rapidly due to mass transfer, which is considered by appropriate correlations.

Fractionation of hops-extract–ethanol solutions using dense CO2 with a counter-current extraction column

Hops-extract–ethanol solutions were contacted counter-currently with dense CO2 in a 0.22 m column at temperatures of (313.2–353.2) K, pressures of (5.0–12.0) MPa, at solute-free solvent-to-feed (S/F) mass ratios of 3.8 and 8.6 for fractionating flavor and bitter compounds. Flavor-purity ratio (Pf) defined as flavor-compound mass over identified-compound mass was about 1.0 at 313.2 K, 6 MPa at S/F = 8.6. At these conditions, flavor-recovery ratio (Rf) defined as flavor-compound mass over feed flavor-compound mass was less than 0.03. At 353.2 K, 12.0 MPa at S/F = 8.6, maximum column productivity (Pf = 0.76, Rf = 0.69) was obtained. Conditions giving maximum purity and highest selectivity (Pf = 0.99, Rf = 0.27) were 333.2 K, 8.0 MPa at S/F = 8.6. In fractionation of feed solutions containing ethanol, column performance is dominated by ethanol distribution that is conveniently manipulated with conditions of the CO2.

Continuous counter-current centrifugal extraction column with high throughput using a spiral inner cylinder

This article presents a continuous counter-current extraction column with a high throughput that relies on a modified Taylor–Couette vortex flow in a centrifugal force field. The extraction column consists of a top settler, bottom settler, stationary outer cylinder connecting the two settlers, and rotating inner cylinder with a spiral guide channel. The organic and aqueous phases flow continuously and counter-currently through the annulus between the outer and inner cylinders. The high-speed inner cylinder breaks up the organic phase into small droplets in the continuous aqueous phase, and three flow patterns, i.e., a disordered droplet flow, banded droplet flow, and full droplet flow, can be formed at different rotating speeds. The spiral rotating inner cylinder was proved to facilitate the formation of the banded droplet flow, which enhances the mass transfer and increases the operating flexibility. A high back-extraction efficiency of approximately 95.6% was achieved using a spiral rotating inner cylinder of 25 cm in contact height with a rotating speed of 800 rpm, even at a high total throughput of up to 7.3 L h−1 cm−2.

Design of the Hydrocarbon Recovery Section from the Extract Stream of the Aromatic Separation from Reformer and Pyrolysis Gasolines Using a Binary Mixture of [4empy][Tf2N] + [emim][DCA] Ionic Liquids

Reformer and pyrolysis gasolines are the main benzene, toluene, ethylbenzene, and xylenes (BTEX) sources. In our previous works, the aromatic extraction from reformer and pyrolysis gasoline models formed by three n-alkanes, benzene, toluene, and xylenes were studied using a binary mixture of ionic liquids (ILs). The results showed that the {[4empy][Tf2N] + [emim][DCA]} IL mixture with [4empy][Tf2N] mole fraction of 0.3 required a comparable countercurrent extraction column to that of the Sulfolane process, and extracted BTEX had quite a higher purity using the IL mixture in the three gasoline models analyzed. Here, we have studied the hydrocarbon recovery from the extract stream obtained in these works. For that purpose, the vapor–liquid equilibria (VLE) data involving the extracted hydrocarbons and the IL mixed solvent have been determined by the headspace–gas chromatography (HS–GC) technique for several temperatures. Afterward, the simulation of two new process configurations based on adiabatic flash di...

Slope curve method for the analysis of separations in extraction columns of infinite height

A new method for the conceptual design of counter-current extraction columns, the slope curve method (SCM), is presented. It is a graphical method based on the equilibrium stage model and developed here for ternary mixtures. The well-known stage-to-stage construction in the ternary phase diagram is replaced by a concise representation in the so-called slope diagram. In that diagram, the slope curve represents the tie lines and operating lines represent material balances. Infinite column height is assumed so that for given feed and solvent composition, the only remaining degree of freedom is the solvent-to-feed ratio. Varying that parameter, all feasible solutions are obtained in the slope diagram. The corresponding product compositions can be reconstructed. Using the method, it is readily shown that internal pinches only occur for certain classes of mixtures, which can be readily identified based on an analysis of the shape of the slope curve. As the SCM yields a complete survey of all feasible solutions it is particularly suited for feasibility studies in conceptual design as well as for obtaining general insights in extractive separations.

Incorrect Ternary Liquid–liquid Equilibria Description Versus Extractor Design Simulation

The presented study focuses on the separation of aromatics from aliphatic hydrocarbons by liquid-phase extraction using ionic liquids. The aim of this study was to show the impact of incorrect description of liquid–liquid equilibria of the separated system on the extractor design parameters.Extraction is usually applied for the separation or concentration of dilute solutions with the aim to achieve minimum concentration of the separated component in the final raffinate. Therefore, correct description of the liquid–liquid (L-L) equilibrium in this concentration region is very important for the industrial practice. For thermodynamic description of a ternary L-L equilibrium, excess Gibbs energy dependencies on the mixture composition are applied. Model parameters of the mentioned equations can be evaluated from different experimental equilibrium data. The most commonly used experimental data are ternary tie lines.Parameters of the GE equations evaluated from experimental tie lines usually provide good or evenexcellent description of the given ternary L-L area. Extrapolation of the L-L data beyond this region, however, can sometimes lead to incorrect L-L equilibrium description. This problem is shown on the real ternary system heptane – toluene – 3-methyl-N-butylpyridinium tetracyanoborate ([3-mebupy][B(CN)4)]). This study proves serious discrepancies in the extractor design parameters using the NRTL equation parameters evaluated from experimental ternary equilibrium data. Depending on the initial guess, the mathematical model of a continuous counter-current extraction column offered at least three different values of the extraction solvent consumption for the preset purity of the final raffinate and of the number of theoretical stages.

Removal of Refractive Sulfur and Aromatic Compounds from Straight-Run, Fluidized Catalytic Cracking, and Coker Gas Oil Using N-Methyl-2-pyrrolidone in Batch and Packed-Bed Extractors

In the present study, removal of sulfur and aromatic compounds from straight-run gas oil (SRGO), light cycle oil (LCO), coker gas oil (CGO), and their mixture, termed as mixed gas oil (MGO), was studied using N-methyl-2-pyrrolidone (NMP) solvent in a single-stage batch extractor and continuous countercurrent packed-bed extraction column. The effect of the extraction temperature (TE), solvent/feed ratio (S/F), and antisolvent concentration (Wc) on the degree of sulfur removal (Dsr), yield of extracted gas oil (Y%), and performance factor (Pf,α), which combines both Dsr and yield, was studied in a single-stage batch extractor. After optimization of the operating conditions for SRGO, LCO, and CGO in a single-stage batch extractor, studies on MGO were carried out in both a single-stage batch extractor and continuous countercurrent packed bed at estimated optimized values of TE, S/F, and Wc. Issues related to the loss of valuable hydrocarbons with extract and value addition to extract hydrocarbon have been add...

Dearomatization of pyrolysis gasolines from mild and severe cracking by liquid–liquid extraction using a binary mixture of [4empy][Tf2N] and [emim][DCA] ionic liquids

In Europe and Japan, benzene, toluene, and xylenes (BTX) are usually obtained by liquid–liquid extraction from pyrolysis gasolines using organic solvents such as sulfolane. In the last few years, ionic liquids (ILs) have been studied as potential substitutes of conventional solvents in the extraction of BTX from alkanes. In this paper, we have studied the dearomatization of pyrolysis gasolines obtained by mild and severe cracking using the binary IL mixture composed of the 1-ethyl-4-methylpyridinium bis(trifluoromethylsulfonyl)imide ([4empy][Tf2N]) and the 1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA]) and also employing sulfolane to compare the performance of both extraction solvents. To choose the most appropriate conditions of temperature and solvent to feed ratio to perform the extraction of BTX from pyrolysis gasolines, several extractive properties have been estimated from the experimental results employing the IL mixture and sulfolane. Simulations of countercurrent extraction columns in the dearomatization of both pyrolysis gasolines have also been made using the Kremser equation. The dearomatization of pyrolysis gasolines by the {[4empy][Tf2N]+[emim][DCA]} IL mixture would require a higher number of equilibrium stages in the extractor than that employing sulfolane. By contrast, the purity of extracted aromatics would be substantially greater using the IL-based solvent, simplifying the subsequent purification of the BTX.

Separation of BTEX from a naphtha feed to ethylene crackers using a binary mixture of [4empy][Tf2N] and [emim][DCA] ionic liquids

The separation of BTEX from petroleum streams with aromatic contents between 20 and 65wt.% is usually made by liquid–liquid extraction. Nevertheless, there are no technologies currently available to perform the separation of aromatics from streams with an aromatic content lower than 20wt.%. In this work, we have studied the separation of BTEX from a naphtha feed to ethylene crackers with a total aromatic content equal to 10wt.%. Aromatics are not converted to olefins in ethylene crackers and their presence increases operating costs and the size of furnaces. Because of this, the separation of BTEX from this stream has been studied using the binary IL mixture formed by the 1-ethyl-4-methylpyridinium bis(trifluoromethylsulfonyl)imide ([4empy][Tf2N]) and the 1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA]), since this IL mixture previously showed adequate extractive properties in the BTEX extraction from reformer gasoline. The separation of BTEX from the naphtha has also been studied using sulfolane, the most used solvent in aromatic extraction at industrial scale. The influence of temperature and solvent to feed ratio on several extractive properties has been carried out from the experimental results employing both extraction solvents. The Kremser equation has been used to simulate the countercurrent extraction columns in the separation of BTEX from the naphtha, studying the effect of the number of equilibrium stages in the extraction yield of BTEX and in the purity of the aromatics obtained.

Biodiesel production in a counter-current reactive extraction column: Modelling, parametric identification and optimisation

Reactive extraction is a potential alternative for biodiesel production, in which reaction and glycerol separation are simultaneous, increasing conversion, yield and process productivity. This paper presents a stepwise reaction–separation model for a counter-current reactive extraction column, used in homogeneous-base-catalyzed palm oil methanolysis, and the models’ parameters are identified from the results of a set of experimental tests. In addition, multi-criteria optimisation of the process conditions was performed using an evolutionary algorithm. The optimum conditions provide for palm oil conversion of 97.7%, a yield to FAME of 99.5% and a process productivity of 1.4m3 FAMEh−1m−3 in a single reaction step. Finally, a comparison of the process productivity with co-current and batch processes was made. As the counter-current reactive extraction process does not require the intermediate separation stages required in co-current and batch processes, its productivity is 1.5 and 6.9 times higher than those processes, respectively.

Development of a miniature Taylor-Couette extractor column for nuclear solvent extraction

Miniature annular centrifugal contactors are nearly perfect for shielded hot-cell applications during flowsheet evaluation but these contactors require complex maintenance of electrical drive-motors during radioactive experiments. To reduce the number of electrical drives in the shielded cell, an indigenous design of miniature Taylor Couette (TC) mixing based countercurrent differential extraction column has been developed. In this paper, results of mass transfer experiments for an indigenously developed TC column with 30% TBP/aqueous nitric acid solutions are reported. The developed device worked perfectly in counter–current differential mode and demonstrated equivalence to multiple-extraction stages while working with a single electrical drive. The developed TC unit demonstrated operation with a reduced efficiency without flooding even in absence of rotor rotation. This observation is a vital step towards designing of robust contactors, which do not flood during temporary power failure or failure of drive mechanism.

Modeling of a two-phase countercurrent pulsed sieve plate extraction column—A hybrid CFD and radiotracer RTD analysis approach

A Computational Fluid Dynamics (CFD) based model of a two-phase countercurrent pulsed sieve plate extraction column has been developed. Euler–Euler multiphase flow model and standard k– ɛ turbulence model for multiphase flow were used. Sieve plates in the column were modeled using the porous media formulation. The coefficients of porous media were evaluated using radiotracer RTD analysis data. A pulse generation model was developed and incorporated to simulate the effect of pulses in the system. The developed simulation approach has been proved successful and it provided the possibility of modeling the subject system with lesser computational resources. The models used for CFD simulation of the system were suitable and simulation results were found 72.17% of the radiotracer experiment.

Presenting an Empirical Correlation for Maximum Sauter Mean Diameter in a Spray Extraction Column

Based on the importance of drops' behavior in liquid-liquid extraction, the maximum sauter mean drop diameter has been investigated and correlated in a counter-current spray extraction column with two chemical systems. Spargers were set of nozzles in all experiments. Studying the effects of several parameters on drops size, some correlations were estimated by the last available version of software “Eviews”. Finally, the best empirical correlation was selected based on lowest error and highest conformity with the experimental data. It’s notable that, in this paper, the maximum sauter mean drop diameter was investigated and correlated for first time in a spray extraction column. Comparing final selected correlation with experimental data, it’s observed that the correlation mentioned above has an error about 4.22% with empirical data that shows the good accuracy of this correlation.

Design and Cost Evaluation of a Separation Process for a Multicomponent Mixture Using Dense CO2

Simulations done on the separation of a multicomponent mixture exiting an enzymatic reactor using dense CO2 as solvent are presented. The enzymatic reaction was carried out in the liquid phase although the CO2 was introduced in supercritical state (80 bar and 40 °C). The purpose was to obtain α-methylbenzyl acetate, a fruity and floral aroma used in the food and cosmetic industries, from the corresponding alcohol and acetic anhydride. The separation of the effluent, consisting of five components (two products, the nonconverted reactants, and the solvent) was done in a series of countercurrent extraction columns where, again, CO2 was used as solvent. It was introduced at relatively low pressure (20 bar) since higher values lead to solubilization of all the components. The influence of the S/F ratio, the feed inlet position, the column dimensions and the use of reflux was analyzed for the separation of the main product with a model available from literature. The diameter of the column was estimated to avoid flooding. Then, the flow sheet of the integrated reaction−separation process with CO2 recycling was presented and discussed. Using an pressure−enthalpy diagram, the energy costs were deduced. The fixed costs were also guessed from previous experience. Using both items, the economical evaluation of the process was performed for a 5-d operation corresponding to the annual production of the aroma. The analysis showed that the process could be feasible after a fine optimization of the enzyme lifetime and reaction efficiency since the downstream separation was inexpensive. In order to make the process effectively profitable, applications would have to be found for the rest of the year (e.g., on the synthesis of other esters).