Investigation of mass transfer on single droplets for the reactive extraction of zinc with D2EHPA

Investigations of mass transfer behavior with the standard test system of the European Federation of Chemical Engineering (EFCE) for the reactive extraction zinc + D2EHPA (di(2‐ethylhexyl) phosphoric acid) were carried out. Experiments were performed with single droplets in a mass transfer cell on lab‐scale. In the experiments, contact time for the mass transfer between droplets and continuous phase, concentrations of zinc, D2EHPA and sulfuric acid, diameter of droplets and hole‐diameter of sieve trays were varied. These experimental results show a systematic investigation of single droplet mass transfer behavior for the standard test system of the EFCE for the reactive extraction of zinc with D2EHPA. In the mass transfer model reported here, all transient effects are considered with an instability parameter, which was determined through experiments in a mass transfer cell. The simulation results with obtained instability parameters are in a good agreement with the experimental results. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Sedimentation behavior of droplets for the reactive extraction of zinc with D2EHPA

The sedimentation characteristics of the reactive standard test system zinc + D2EHPA are investigated in this work. Experiments with single droplets rising in a stagnant continuous phase have been carried out. The concentration of D2EHPA, zinc, and sulfuric acid as well as the diameter of the droplets are varied. The velocity of droplets is observed to be transient for several seconds. High mass‐transfer rates increase the velocity of single droplets for the case of reactive extraction whereas for physical systems contrary behavior is observed. Therefore, droplets seem to behave principally different in reactive and physical extraction. This is explained by the interfacially active properties of D2EHPA. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Investigation of the reaction between single aerosol acid droplets and ammonia gas

An experimental technique has been developed for the continuous measurement of the reaction dynamics between single liquid droplets and reactive gases. The technique is based on the suspension of electrically charged droplets in an electrodynamic field where droplet masses are determined from weight-balancing direct-current voltages. From the droplet mass history, the extent of the reaction is determined as a function of time, particle size and ammonia gas partial pressure. Droplet reactions are conducted under continuously mixed fluid-dynamical conditions.

It is found that surface phase reaction, gas phase diffusion and internal particle diffusion sequentially control the reaction dynamics of the particles. At constant external ammonia gas partial pressure, the maximum extent of reaction achieved during the surface phase reaction is insensitive to particle size while the maximum extent of reaction achieved during the gas phase diffusion-controlled process increases with increasing particle size. In fact for sufficiently small particles the gas phase diffusion process is completely inhibited and subsequent internal particle diffusion does not occur. Correspondingly, the final extent of reaction is determined by the duration of the gas phase diffusion-controlled process. Furthermore, increasing the external ammonia gas partial pressure decreases the maximum extent of reaction achieved during the gas phase diffusion-controlled process and consequently the final extent of reaction.     

Evaporation of single droplets of ethanol-fuel oil mixtures

Measurements of droplet evaporation behaviour are reported for mixtures of pure and denatured ethanol with No. 2 fuel oil. A model for the evaporation of droplets of these mixtures is presented which uses continuous thermodynamics to describe the fuel oil fraction. Activity coefficients were used to describe non-ideal phase equilibrium behaviour. Distribution function parameters for the fuel oil were fitted from a continuous thermodynamics simulation of the ASTM distillation test; this simulation was also used to test the accuracy of the phase equilibrium model. The model is shown to give very good agreement with the measurements. Internal boiling of the liquid is seen to take place during evaporation of the alcohol, but is not sufficiently violent to eject mass from the droplet.     

Break-up of droplets in Karr reciprocating plate extraction column

The breaking rate of individual drops was investigated in a Karr type reciprocating plate extraction column. The binary systems used were: water-1,2-dichloroethane, water-toluene and water-n-butanol. The breakage probability and the conditional probability of breaking-up into a given number of daughter droplets, as well as the drop size distribution of daughter droplets, were the measured characteristics. Relations between the breakage probabilities and the breakage frequency were derived.A mathematical model of the frequency of breaking-up into > and more droplets developed was based on the assumption that collisions with turbulent eddies of the Kolmogoroff region of universal equilibrium are responsible for the process. A probabilistic model of daughter drop size distribution was also derived in the form of a β-distribution. The models were compared with experimental results and a good agreement was obtained.     

反应萃取技术的研究现状

化工过程强化包括设备强化和方法强化,反应萃取技术就是方法强化的技术之一。本文综述了反应萃取技术的基本原理及其分类,介绍了它在反应工程方厩的应用和研究进展,并对今后的发展前景进行了展望。与传统方法相比,反应萃取技术作为一种新兴耦合技术能显著提高效率、减少废物排放,是一种高效、节能、清洁、安全、可持续发展的化工新技术。     

Ignition characteristics of liquid hydrocarbon fuels as single droplets

An investigation into the effects of fuel boiling point and chemical type on the autoignition of single droplets of a number of pure hydrocarbons is reported. Ignition delay times were measured using the suspended droplet technique, and a numerical model was developed to extract reaction rate constants for the fuels. The results show that both fuel boiling point and chemical kinetics are important contributors to the ignition delay.     

Calculation of reactive extraction in countercurrent columns

The kinetics of extraction processes with chemical reaction was studied experimentally on the system copper/Acorga PT 5050 and quantified according to meaningful kinetic models. These were coupled with other models describing the behaviour of dispersions in columns in order to permit a computer aided simultation of reactive extraction. Thus, a better prediction of column performance is achieved.     

络合萃取法提取发酵液中丁二酸盐的研究

为提高微生物发酵法生产丁二酸的产品提取收率,研究利用三辛胺/正辛醇体系对发酵液进行络合萃取。比较硫酸和阳离子交换树脂两种前处理发酵液方式对络合萃取丁二酸的影响,以及用氨水反萃制备丁二酸铵。结果表明：通过阳离子交换树脂前处理发酵液,三辛胺/正辛醇体系对丁二酸的萃取率高于硫酸前处理,可达到91.3%;氨水是一种优良反萃剂,萃取剂重复使用5次,平均萃取率为90.4%,平均反萃率为94.9%,且萃取率和反萃率未见明显下降。     

Investigation of liquid–liquid phase equilibria for reactive extraction of lactic acid with organophosphorus solvents

BACKGROUND: Lactic acid is a versatile commodity chemical with a variety of applications. Synthesis of lactic acid either through fermentation of carbohydrates or through chemical synthesis is state of the art. Separation from dilute aqueous solution is complex and accounts for the major part of production costs. Reactive extraction based on reversible adduct formation is a promising alternative for the separation of lactic acid. RESULTS: Extraction was carried out with the organophosphorus solvents tri‐n‐butyl phosphate, tri‐n‐octylphosphine oxide and Cyanex 923. Shellsol T was used as diluent. Partition coefficients increase with increasing extractant content and decreasing temperature. Cyanex 923 has several advantages compared with tri‐n‐butyl phosphate and tri‐n‐octylphosphine oxide with respect to lactic acid distribution and hydrodynamic properties. Liquid‐liquid phase equilibria for lactic acid extraction with Cyanex 923 were modeled. Selectivity of lactic acid extraction with respect to glycolic acid and formic acid was discussed. CONCLUSION: The organophosphorus extractant Cyanex 923 was found to be an appropriate solvent for lactic acid extraction from aqueous solutions. Experimental data and model data based on the Law of Mass Action showed good agreement. Lactic acid extraction from multi‐acid solution showed good selectivity compared with glycolic acid. Lactic acid selectivity is low with respect to formic acid. © 2012 Society of Chemical Industry     

Measurement of the condensational growth of single hygroscopic acid aerosol droplets

The condensational growth of hygroscopic phosphoric acid droplets is quantified using a bihyperboloidal electrodynamic chamber. The droplet mass increase is determined from the direct current voltage required to balance the droplet at the null point of the electrodynamic field. The diameter of the droplet (15–65 μm) is measured using a 35 mm objective in conjunction with a calibrated image splitter. Dew point temperatures are monitored by a condensation type hygrometer and ambient temperatures are measured with a thermistor. Mass and diameter increases are measured over the relative humidity range from 5 to 80%. Comparison of data derived from this study compare favorably with existing data on the water activity of orthophosphoric acid solutions.     

Kinetic study on reactive extraction of phenylalanine enantiomers with BINAP-copper complexes

Enantioselective liquid–liquid extraction has attracted considerable attention for its potential use in large-scale production. Kinetic data are needed for the reliable scale-up of the process. This paper reports the kinetic study of reactive extraction of phenylalanine (Phe) enantiomers with BINAP–copper complex (BINAP–Cu) as a chiral selector. The theory of extraction accompanied by a chemical reaction was applied. The effects of agitation speed, interfacial area, pH value of aqueous phase, initial concentration of Phe enan-tiomers and initial concentration of BINAP–Cu on the specific rate of extraction were investigated. The for-ward rate constants of the reactions in the reactive extraction process are 7.93 × 10?5 m5/2·mol?1/2·s?1 for D-Phe and 1.29 × 10?4 m5/2·mol?1/2·s?1 for L-Phe.     

Transport processes at single droplets in micellar liquid/liquid systems

In many industrial applications, the knowledge of the occurring transport processes in liquid/liquid systems is of great interest to design a multiphase reactor or an extraction column, for instance. All transport processes in liquid/liquid systems are governed by the interface. In some processes surfactants are needed. Surfactants change many interfacial properties which affect the transport processes. In this work, the influence of high surfactant concentrations (micellar systems) on transport processes is regarded. To understand, the occurring reduction of the drop rise velocity and of mass transfer rates experimental investigations of the occurring interfacial phenomena are carried out. Therefore, interfacial tension measurements as well as colloidal probe atomic force measurements of liquid/liquid systems were conducted. It was proved that for high nonionic surfactant concentrations a change of the phase behavior must be taken into consideration to describe transport processes in micellar liquid/liquid systems. © 2014 American Institute of Chemical Engineers AIChE J, 61: 1092–1104, 2015     

Kinetics study on the reactive extraction of homophenylalanine enantiomers with BINAP-copper complex

This paper reports on the kinetics study of the reactive extraction of homophenylalanine (Hph) enantiomers with BINAP (2,2’-Bis(diphenylphosphino)-1,1’-binaphthalene)-copper complex (BINAP-Cu) as the chiral selector. The kinetic model was established based on the theory of interfacial chemical reactive extraction. Simultaneously, the effects of agitation speed, interface area, pH value of the aqueous phase, initial concentration of Hph enantiomers and initial concentration of BINAP-Cu on the specific rate of extraction were investigated. The forward rate constants of the reactions in reactive extraction process were found to be 6.16 × 10^?4 m^2.5mol^?0.5s^?1 for D-Hphe and 7.303 × 10^?4 m^2.5mol^?0.5s^?1 for L-Hphe.     

Equilibrium studies on reactive extraction of lactic acid with an amine extractant

Equilibrium studies on the extraction of lactic acid from aqueous solutions with tri-n-octylamine (TOA) in xylene were made in the temperature range 293–323 K. The formulation of the extracted species in the organic phase and the corresponding equilibrium constants were numerically determined at different temperatures. Also, the apparent thermodynamic functions were calculated. Finally, the effect of a water-insoluble organic acid, di(2-ethylhexyl)phosphoric acid (D2EHPA), on this extraction was investigated. Synergistic and antagonistic effects were observed in the presence of D2EHPA, mainly depending on the concentration ratio of D2EHPA to TOA.     

Terminal and transient drop rise velocity of single toluene droplets in water

The knowledge of the drop rise velocity in dispersed systems is of fundamental importance. Especially, the residence time is needed for calculation of mass transfer rates in extraction columns. This work deals with fluid dynamic measurements of toluene droplets rising in water ranging from 1.0 to 7.0 mm, with the premise of high purity of the used chemicals. The toluene/water‐system is widely used as a test system with high interfacial tension. A semiempirical correlation for pure systems to predict the terminal velocity of single rising/falling droplets based on experimental data is presented. Results show that a distinction between maximum and characteristic mean values of the drop rise velocity is necessary, especially in the diameter range 2.4–3.0 mm where unexpected velocity fluctuations occur. Two distinct terminal rise velocities were observed for 3 mm droplets. Furthermore, comparisons of the Weber‐Reynolds‐correlation and the drag coefficient with correlations from literature show good agreement. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Investigation of ethyl acetate reactive distillation process

In this paper, an extensive study of ethyl acetate synthesis by homogeneously catalyzed reactive distillation is presented. Reactive distillation is a promising operation whereby reaction and separation take place within a single distillation column. The synergistic effect of this combination has the potential to increase conversion, improve selectivity and facilitate separation tasks. The feasibility of ethyl acetate synthesis is examined using the reactive distillation lines diagram. A completely rate-based simulator DESIGNER developed within the framework of a large European research project is used in order to predict concentrations, temperatures and other important process variables. In order to validate theoretical predictions, a set of reactive distillation experiments is performed in a glass tray column with 80 bubble cap trays. The concentrations and temperature profiles computed by DESIGNER agree well with the experimental data.     

Investigation on the simulation of the reactive extrusion of nylon 6

In this article, a novel simulation of the processing conditions of the anionic ring-opening polymerization of nylon 6 in a counterrotating twin-screw extruder by use of a modified Haake Rheometer run at elevated temperatures is described. Experimental results for several combinations of processing parameters are presented. General relations between processing parameters, conversion ratio, and molecular weight of the product are observed. These observations can be used in the eventual scaling up of investigation to an actual twinscrew extruder. © 1995 John Wiley & Sons, Inc.     

Effects of transport and phase equilibrium on fast, nearly irreversible reactive extraction

Integration of reaction and separation can be exploited to drive reversible reactions in the direction of the desired product using multiphase flow contacting. In the case of nearly irreversible, fast reactions, however, the dynamics of the product have little influence on the reactor efficiency in say liquid-liquid reactive extraction. A similar intensification in reaction efficiency to reactive separation can be achieved by exploiting phase equilibrium or asymmetry in mass transfer rates of the reactants. Here, a model for two-layer biphasic flow and homogeneous reaction is proposed for co-current reactive extraction, demonstrating that localization and intensification of reaction occurs in the region between the entrance and crossover. Crossover occurs if the reactant in stoichiometric deficit preferentially populates the reacting phase due to sufficient imbalance in either mass transfer coefficients or phase equilibrium. We develop an infinite Peclet number (convection dominates over bulk diffusion) model that indicates that crossover occurs when