Concentration-Thermal Swing Adsorption Process for Separation of Bulk Liquid Mixtures

Abstract

A novel concentration-thermal swing adsorption process is described for separation of bulk binary liquid mixtures. The process is designed to produce essentially two pure products with high recoveries of both components. It is particularly suited for separation of azeotropic or close-boiling liquid mixtures which are difficult to separate by distillation. An example of the performance of the new process for separation of an azeotropic water-methyl acetate mixture is given. Experimental binary surface excess equilibrium isotherms, adsorptive mass transfer coefficients, and column dynamics for adsorption of water-methyl acetate mixtures on NaX zeolite are reported.     

Prediction of Vapor‐Liquid Equilibrium inside Capillary Porous Plates

Capillary distillation is a relatively new separation process which uses capillary porous media for the separation of mixtures. It utilizes the solid‐liquid interfacial forces to alter the vapor‐liquid equilibrium (VLE) of mixtures inside the capillary porous plates. Previous studies have shown that capillary porous plates could significantly alter the VLE of binary mixtures. It was shown that the main factors affecting the alteration of VLE of binary mixtures are the polarization of the liquids and the porous plates as well as the polarization difference between the mixture components. In this study, the VLE data for the mixtures inside capillary porous plates have been predicted using the Wilson model and the theory of Abu Al‐Rub and Datta on VLE inside capillary porous media. The validity of the developed model has been assessed by comparing predicted VLE results of some binary mixtures inside capillary porous plates with experimental VLE data. The comparison showed that the model developed could predict the VLE of the studied systems accurately.     

Propane/Propylene Separation by Simulated Moving Bed II. Measurement and Prediction of Binary Adsorption Equilibria of Propane,Propylene, Isobutane,and 1-Butene on 13X Zeolite

Abstract

The design of a simulated moving bed (SMB) process relies on valid thermodynamic predictions of multicomponent adsorption built up from accurate binary adsorption equilibrium data. Experimental adsorption equilibria of binary mixtures constituted by propane, propylene, isobutane and 1-butene on 13X zeolite were determined using breakthrough experiments at 373 K and 150 kPa. In addition, these binary adsorption experiments allow to confirm the choice of isobutane as an interesting desorbent for the separation of propane-propylene by SMB, since it has an intermediate selectivity between the two species to separate. Various prediction models are available in the literature but only a few of them have both physical and thermodynamical consistency. The ideal adsorbed solution theory (IAST), the thermodynamically consistent extended Toth model (TCET), and the physically-consistent extended Toth isotherm (PCET) were used to predict binary adsorption equilibria from pure component adsorption isotherms parameters. The PCET model was found suitable for representing the adsorption equilibrium of the different hydrocarbon mixtures with a reasonably good accuracy.     

Effects of Ultrasonic Waves on Vapor-Liquid Equilibrium of an Azeotropic Mixture

Abstract

Azeotropic and extractive distillation techniques used to separate azeotropic mixtures are among the most challenging separation processes in the chemical industry. In this work, an innovative distillation technique which employed ultrasonic waves was proposed to intensify the conventional multi-column azeotropic distillation method into a single-column alternative. The effects of ultrasonic intensity on the vapor-liquid equilibrium (VLE) of methyl-tert-butyl-ether (MTBE)-methanol was investigated at 50, 100, 200, and 250 W/A·cm² and at a fixed frequency of 40 kHz. Studies were also done to examine the effects of ultrasonic frequency on the VLE data at 25 and 68 kHz frequencies. It was found that ultrasonic waves at 50 W/A·cm² intensity and 25 kHz frequency gave the highest relative volatility (α) at 2.654 and completely eliminated the MTBE-methanol azeotrope, thereby allowing highly pure MTBE to be recovered in just a single distillation column. The results revealed that ultrasonic waves had the potential to favorably manipulate α, and hence, the VLE of an azeotropic mixture.     

ON THE COMPOSITION-DEPENDENT INTERACTION PARAMETERS IN EQUATIONS OF STATE

Composition-dependent interaction parameters have been applied to the calculation of vapor-liquid equilibria (VLE) in mixtures containing components of different chemical nature. Binary VLE have been correlated and ternary VLE have been predicted from binary data using five different mixing rules. Binary data can be accurately correlated for systems with moderate deviations from ideality using mixing rules with two binary parameters. For very strongly nonideal mixtures three binary parameters are needed. For the prediction of ternary VLE from binary information only the mixing rules of Panagiotopoulos and Reid (1986) and Schwartzentruber et al. (1987) are reliable. For most systems the quality of predicting ternary data is comparable to the quality of correlating binary data. Significant deviations are noted only for strongly nonideal systems close to phase separation. In these cases it is recommended to use models incorporating association in an explicit form. KEYWORDS Equations of state Mixing rules Multicomponent Vapor-liquid equilibria.     

A Calorimetric Method for the Determination of Binary Phase Compositions at High Temperatures and Pressures

Abstract

The design and operation of supercritical separation equipment are dependent upon an accurate knowledge of phase equilibria among the components involved in the processes. Using high-pressure, high-temperature flow calorimeters, we have developed a method for determining phase splitting in binary mixtures from heat-of-mixing data taken in the region of the mixture critical locus. The flow calorimetric procedure for determining heats of mixing, phase equilibria, and the critical locus curve is described. The advantages and simplicity of using flow calorimetry to determine these data are discussed. Phase behavior of several binary CO₂-hydrocarbon systems is presented.     

A Study of the Separation Efficiency in the Concentric-Tube Countercurrent Separation Process under Generalized Linear Applied Fields and with Recycles at Both Ends

Abstract

The mathematical model for the separation of binary mixtures has been extended to a concentric-tube continuous-contact countercurrent column under generalized linear external fields and with recycles at both ends. An analytical solution is obtained by use of the orthogonal expansion method. Numerical results for separation in a thermal diffusion column are also illustrated.     

A modification of Wong-Sandler mixing rule for the prediction of vapor-liquid equilibria in binary asymmetric systems

Systems consisting of light components and heavy hydrocarbons are highly asymmetric and industrially important. Design and control of facilities for separation and purification of such mixtures require vapor-liquid equilibrium data. Coupling of the cubic equation of state (EOS) with excess Gibbs energy models (EOS/G ^ex models) failed to represent the vapor-liquid equilibria (VLE) of such systems accurately. The main purpose of this work is to present a modification of Wong-Sandler mixing rule with using the composition dependent binary interaction parameter. Vaporliquid equilibria for 30 binary systems are calculated using the SRK equation of state with proposed model and Wong-Sandler mixing rule. Calculated pressures and mole fractions of vapor phase are compared with experimental data. The average absolute percentage deviation indicates that error involved in the application of modified Wong-Sandler model is less than Wong-Sandler model in most cases.     

Extractive Distillation of p-Cresol/2,6-Xylenol Mixtures in the Presence of Alkanolamines

Abstract

The separation of p-cresol/2,6-xylenol mixtures has been investigated by extractive distillation in the presence of alkanolamines. The interaction parameters of liquid phase models, such as Wilson, NRTL, and UNIQUAC, have been estimated from binary vapor-liquid equilibrium data. The predicted relative volatility values for the p-cresol/2,6-xylenol mixtures in the presence of the alkanolamines were compared with experimental data.     

Separation of a Two-Component Particulate Material Mixture by a Vibro-Impacting Separator

Abstract

The vibro-impacting separator, the so-called Paddy table, is widely used for the separation of the components of binary mixtures of particulate materials. This paper presents an improved mathematical model of vibro-impacting separation and experimental results aimed at the further investigation of vibro-impacting motion, the adequacy of the model, and the improvement of the efficiency of vibro-impacting separation, with special attention to friction between the particles and the operational element of the separator. It is concluded that friction decreases the instability of the periodic symmetric motion of the particles and that the model adequately represents the physical system in the range of the operational variables tested. Also, it is found that the formulas obtained are suitable for design purposes and that friction decreases the separation efficiency. In conclusion, we believe that vibro-impacting separation is a promising candidate for many fields of industry.     

Preferential Adsorption and Selective Permeation of Alcohol/Hydrocarbon Mixtures in Reverse Osmosis

Abstract

In binary mixtures of alcohols and hydrocarbons there are two types of reverse osmosis performances. These are selective permeation of the alcohol and selective permeation of the hydrocarbon. Liquid chromatography results have been used to predict the selective permeation of reverse osmosis membranes where the membranes may be difficult to fabricate as well as to determine performance limits in terms of separation. These results are of interest for the production of oxygenated fuel blending agents where specifications require the removal of unreacted methanol for further processing and distillation is not viable.     

乙腈+水+离子液体等压汽液平衡测定与计算

采用改进的Ellis平衡蒸馏仪测定了乙腈+水+1-乙基-3-甲基咪唑磷酸二乙酯盐([EMIM][DEP])、乙腈+水+{1-乙基-3-甲基咪唑醋酸盐([EMIM][OAC])+[EMIM][DEP]}常压(101.3 kPa)等压汽液平衡(VLE)数据。实验结果表明，备选离子液体可促进水+乙腈混合物的分离并消除其共沸点。借助NRTL模型成功关联了含离子液体的三元和四元VLE实验数据，获得了乙腈-[EMIM][DEP]、水-[EMIM][DEP]和[EMIM][OAC]-[EMIM][DEP]二元交互作用参数。应用COSMO-SAC预测了实验VLE，结果令人满意。量化计算表明可与水形成强相互作用的离子液体更易促进乙腈与水的分离。     

LIQUID-LIQUID EQUILIBRIA OF ORGANIC COMPOUNDS: MEASUREMENT,CORRELATION AND PREDICTION†

The knowledge of phase equilibria is an important step in the development of extraction processes. This knowledge is usually gained from experiments. However, this procedure is expensive when a suitable solvent has to be found for a specific separation. Therefore methods for predicting phase equilibria are needed. While formerly these methods were largely based on empirical assumptions, the use of the concept of local compositions by Wilson⁶ offers a semi-empirical approach.

There is one disadvantage of this approach: the parameters of models like UNIQUAC or NRTL have to be fitted to different types of data, to liquid-liquid equilibria (LLE) for the immiscible pairs of components and to vapour-liquid equilibria (VLE) or other data for the miscible pairs in a system with mutual solubility.

To demonstrate the problem we performed measurements in the binary systems: n-octane/aniline and methylcylohexane/aniline. of both liquid-liquid equilibrium and vapour-liquid equilibrium: for the second type of measurements ebulliomeiry was used. The prediction of LLE has been improved with two new concepts. One is based on the well-known UNIFAC method. The use of the Lyngby-Dorlmund data bank made it possible to determine a new parameter table merely based on LLE data.

The second method is based on common UNIQUAC parameters which have been determined with the data base.     

Production of Motor Fuel Grade Alcohol by Concentration Swing Adsorption

Abstract

A new cyclic process concept called “concentration swing adsorption” for separation of bulk binary liquid mixtures is described. The process carries out the primary separation by selective liquid-phase adsorption of one of the components of the feed mixture on an adsorbent. The adsorbed component is then desorbed by a desorbent liquid which is equally or more strongly adsorbed than the slectively adsorbed component of the feed mixture. The desorbent liquid is removed from the adsorbent by displacing it with the less strongly adsorbed component of the feed mixture so that the adsorbent can be resused. The process also includes a complementary step where the adsorbent is rinsed with the more strongly adsorbed component of the feed mixture so that two essentially pure products are produced from the feed mixture with high recoveries of both components. At least one simple distillation is also required by the process which separates the desorbent liquid from the less strongly adsorbed component of the feed mixture. The process can be used to separate liquid mixtures with close boiling components or azeotropic mixtures which require energy intensive distillation. A very efficient separation can be achieved in these cases by spending only a fraction of the distillation energy. An example of such an application, viz., separation of a bulk ethanol–water mixture for motor fuel grade alcohol production, is described. A local equilibrium model of the process is used to evaluate the performance of the process for that separation using an activated carbon as the adsorbent and acetone as the desorbent liquid. Experimentally measured equilibrium adsorption characteristics for ethanol–water, acetone–water, and acetone–ethanol binary liquid mixtures on the carbon as well as adsorption column dynamics for the steps of the process are reported.     

Vapor–liquid equilibria of hydrogen chloride,phosgene, benzene,chlorobenzene, ortho‐dichlorobenzene,and toluene by molecular simulation

Vapor–liquid equilibria (VLE) of nine binary mixtures containing hydrogen chloride or phosgene in the solvents benzene, chlorobenzene, ortho‐dichlorobenzene, and toluene as well as the mixture hydrogen chloride + phosgene are predicted by molecular modeling and simulation. The underlying force fields for the pure substances are developed on the basis of quantum chemical information on molecular geometry and electrostatics. These are individually optimized to experimental pure fluid data on the vapor pressure and saturated liquid density, where the deviations are typically less than 5 and 0.5 %, respectively. The unlike dispersive interaction is optimized for seven of the nine studied binaries. Previously unpublished experimental binary VLE data, measured by BASF in the vicinity of ambient temperature, are predominantly used for these fits. VLE data, including dew point composition, saturated densities and enthalpy of vaporization, are predicted for a wide range of temperatures and compositions. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Hydrostatic Levitation of Particles in Electric and Magnetic Fields

Abstract

Nonhomogeneous magnetic and electric fields generate levitational forces in magnetic and dielectric liquids whereby particles are separated according to their specific gravity and magnetic and electric properties, respectively. The corresponding systems are called magnetohydrostatic separation and wet dielectric separation. These forces depend on the field intensity and gradient, and on properties of the liquid and the particles to be levitated. This paper deals with the potential application of electric fields as compared with that of the magnetic field. It is shown that unless special measures are taken, the electric field is inferior to such an extent that its application is not promising. In this context the influences of particle size and shape in both methods are discussed.     

Distillation of Ethanol-Water Solutions in the Presence of Potassium Acetate

Abstract

Complete separation of ethanol-water mixtures through salt addition has been demonstrated in a continuously operated single sieve-plate-column including salt recycling. The effect of salt concentration as well as reflux ratio on the separation are outlined based on experimental data. The results clearly indicate that distillation in the presence of salts is an economical alternative to more conventional processes.     

Thermodynamic data for separation of ternary mixture (1,2-propanediol + 1,3-butanediol + 1,4-butanediol) by distillation

Thermodynamic behaviors of ternary system (1,2-propanediol (1,2-PG)?+?1,3-butanediol (1,3-BD)?+?1,4-butanediol (1,4-BD)) were studied in this paper. Vapor–liquid equilibria (VLE) data of systems (1,2-PG?+?1,3-BD), (1,2-PG?+?1,4-BD), (1,3-BD?+?1,4-BD), and (1,2-PG?+?1,3-BD?+?1,4-BD) were measured at 101.3?kPa. The binary interactive parameters were obtained by regressed the binary VLE data with different models. The results have shown that the Wilson model, the NRTL model and the UNIQUAC model are suitable to describe the ternary system, but the UNIFAC model is not appropriate; the residue curve map of the ternary system was obtained on the basis of the binary interactive parameters. Finally, the design and optimization of the two-column sequence distillation process were completed for separation of the ternary system. Under the optimized conditions, product amounts of 1,2-PG, 1,3-BD, and 1,4-BD can be up to 0.98, 0.90, and 0.98, respectively, after separation.     

Applicability of the Perturbed Hard Chain Equation of State for Simulation of Distillation Processes in the Oleochemical Industry. Part II: Purification of Glycerol

Abstract

Glycerol is a major by-product in the oleochemical industry with extensive end-use markets. Synthetic and natural glycerine fractions are currently purified using steam distillation at subatmospheric pressures. Due to the increasing interest of the pharmaceutical industry in ultrapure glycerol, supercritical fluid extraction followed by appropriate fractionation steps are also employed. It would therefore be convenient to utilize a single thermodynamic model that is capable of predicting all thermodynamic properties needed, and that also covers the whole pressure range which is currently applied in both industries. Different equations of state and activity coefficient models were scanned, and the perturbed hard chain equation of state (PHC-EOS) provided better results than those obtained using activity coefficient models. Pure component parameters were computed using vapor pressure data for glycerol. The fitted parameters were incorporated in the PHC-EOS and resulted in good reproduction of binary vapor—liquid equilibria. Calculations of multicomponent mixtures were performed using these binary parameters. A flow-sheeting program was utilized to simulate a steam distillation process consisting of two integrated columns, operated at subatmospheric pressures, for the purification of different glycerine feedstocks. The simulated flow rate, concentration, and temperature profiles were compared with some operating data obtained from a major oleochemical plant. Analysis of this comparison revealed that the PHC-EOS is very well suited for simulating different distillation processes for the purification of crude glycerine feedstocks.     

Some Liquid Thermal Diffusion Separations in a Continuous Thermogravitational Column

Abstract

The separation of three binary mixtures on n-heptane-1,1,2,2-tetrachloroethylene, n-propanol-1,1,2,2-tetrachloroethylene, and n-heptane-methylcyclohexane was studied in a continuously operated thermogravitational column. The effects of feed rate, the ratio of top and bottom product rates, and temperature difference on separation were determined. The separations were found to be dependent on the feed rate with the maximum separation occurring at flow rates approaching zero. Over the range studied, the effect of top to bottom product flow rate ratio was found to be negligible. Temperature difference appeared to influence separation when finite flow rates were used.