Annular Centrifugal Extractor Research Articles

Mass transfer and hydrodynamic studies in a 100 μm diameter microfluidic channel in a rotated helical configuration

A simple 3D rotated microfluidic mixer design is reported with evaluation of hydrodynamic and mass transfer performance. Proposed device had a minimalistic configuration of 3 turns, rotated in x, y, and z planes. The helical mixer volume was only 3.14 μL due to usage of 100 μm dia micro bore tubing. The proposed device was different from conventional CFI and its variants. The analysis for hydrodynamic performance indicated a massive specific interfacial area, much more than for the 50 mm centrifugal extractor with the same PUREX aqueous-organic pair. Higher volumetric amass transfer coefficients were reported for the proposed device as compared to conventional mixers (impellers and Taylor-Couette mixers). Energy dissipation values were also reported to be much higher than that of a contemporary annular centrifugal extractor. Mixing-time values (tm) were estimated at least two-order lower than residence time values (τ). Proposed design complied all the four directives of the concurrent PI paradigm.

Liquid Hold-up Volume and Phase Ratio (A/O) of HNO3–DtBuCH18C6/n-Octanol System in an Annular Centrifugal Extractor

ABSTRACT The crown ether strontium extraction (CESE) process has been developed for the recovery or removal of Sr from acidic high-level liquid waste (HLLW) in China, where the extractant is 4’,4”(5”)-di-(tert-butyldicyclohexano)-18-crown-6 (DtBuCH18C6) and the diluent is n-octanol. When the CESE process was operated in annular centrifugal extractors (ACEs) for demonstration by cold and hot tests, it was found that the outlet aqueous phases had organic-phase entrainment even though ACEs operated at a low rotor speed. For the successful operation of the CESE process in ACEs, effects of the operating and geometrical parameters on the liquid hold-up volume and phase ratio (aqueous phase/organic phase, A/O) of the HNO3 –DtBuCH18C6/n-octanol system in a ϕ20 ACE were systematically investigated to find the cause of the above-mentioned hydrodynamic performance problem of the CESE process using the liquid-fast-separation method. It is shown that the operating and geometrical parameters have effects on the liquid hold-up volume and phase ratio (A/O). Moreover, the phase ratio (A/O) in the separation zone of the rotor is less than 1.5 under most of the present experimental conditions, which shows organic-phase entrainment may easily occur in the outlet aqueous phase. The cause can be that the density difference of two phases is small, viscosity of the organic phase is large, and interfacial tension of the extraction system is low.

Comparison of the hydraulic characteristics of the 30%TRPO/kerosene―HNO3 and iPr-C[4]C-6/n-octanol―HNO3 systems in an annular centrifugal extractor

The hydraulic characteristics of the 30% TRPO (trialkylphosphine oxide)/kerosene―1.0 M HNO3 and 0.025 M iPr-C [4]C-6 (25,27-bis(isopropoxy) calix [4]-26,28-crown-6)/n-octanol―1.3 M HNO3 systems were systematically investigated in a φ20 ACE (annular centrifugal extractor) to find the cause of the hydraulic performance problem of the CECE (calixcrown ether extraction) process operated in ACEs. The results show that the operating and structure parameters have different influences on the F (A/O) (phase ratio (A/O)) and V (liquid hold-up volume). Moreover, the Vr (V of the rotor) of the 30%TRPO/kerosene―HNO3 and iPr-C [4]C-6/n-octanol―HNO3 systems are almost same, while the Vm (V of the mixing zone) and Vt (total V of the ACE) for the former are slightly higher than those for the latter under the same experimental conditions. Meanwhile, both the Fm (A/O) (F (A/O) of the mixing zone) and Fs(A/O) (F (A/O) of the separating zone) for the 30%TRPO/kerosene―HNO3 system are also higher than those for the iPr-C [4]C-6/n-octanol―HNO3 system under the same experimental conditions. Moreover, the Fs(A/O) of the iPr-C [4]C-6/n-octanol―HNO3 system is less than 1.5 under most of the present experimental conditions, which shows organic phase entrainment may easily occur in the outlet aqueous phase. This may be the cause of the hydraulic performance problem of the CECE process operated in ACEs.

Pilot continuous centrifugal liquid-liquid extraction of extra virgin olive oil biophenols and gram-scale recovery of pure oleocanthal, oleacein, MFOA, MFLA and hydroxytyrosol

This study provides an efficient pilot-scale liquid-liquid extraction process for the recovery of total phenolic fraction (TPF) from extra virgin olive oil (EVOO) and the further purification of the major TPF constituents (oleocanthal, oleacein, monoaldehydic form of oleuropein aglycone, monoaldehydic form of ligstroside aglycone and hydroxytyrosol) using successively centrifugal partition chromatography and reversed phase high performance liquid chromatography. Special attention was paid for the selection of the appropriate raw material, which should be rich in the targeted high-value compounds. For the extraction of the selected EVOOs, a green technique based on liquid-liquid partitioning using the biphasic system n-Hept/EVOO/EtOH/H2O 3:2:3:2 v/v was carried out, first on pioneering laboratory-scale annular centrifugal extractor (ACE) and then on pilot device. 240 L from three different EVOOs (3x80 L of each EVOO) were extracted yielding 285 g of TPF in approximately 2 h. The second step of this procedure was the purification of the target compounds. A preparative centrifugal partition chromatography (CPC) process was firstly applied for the initial TPF fractionation using a step gradient elution-extrusion method with a series of 4 biphasic systems composed of n-Hept/EtOAc/EtOH/H2O in ratios 4:1:3:2, 3:2:3:2, 2:3:3:2 and 1:4:3:2 (v/v/v/v). Preparative reversed phase high performance liquid chromatography (prep-RP-HPLC) was then carried out to polish the target compounds from the enriched CPC fractions resulting in purity higher than 97%. In parallel, the above purification analysis led to the isolation of four minor TPF constituents of which three are new natural products (EDA lactone, (1R, 8E)-1-ethoxy-ligstroside aglycon and (1S, 8E)-1-ethoxy-ligstroside aglycon) and one ((9E, 11E)-13-oxotrideca-9,11-diencoic acid) is described for the first time as EVOO constituent.

Design Modification in the Stationary Bowl of Annular Centrifugal Extractors to Handle Adverse Conditions

The annular centrifugal extractor is one of the robust stage-wise solvent extraction contactors. In a multistage operation, failure of any single stage leads to the stoppage of the entire annular c...

Continuous Interfacial Centrifugal Separation and Recovery of Silver Nanoparticles

AbstractContinuous‐flow separation and recovery of silver nanoparticles (AgNPs) using an annular centrifugal extractor (ACE) is demonstrated. Separation was achieved at the liquid‐liquid interface based on the balance between centrifugal force and the solubility of the capping agent. A mathematical model is presented to understand the mechanism in greater detail. The separation of poly(vinylpyrrolidone) (PVP)‐coated AgNPs in an ACE using a strong immiscible solvent was performed. The material accumulated at the interface was separated periodically without discontinuing the operation. The method is also suitable for separation of large particles or 1D/2D nanostructures even employing a single annular centrifugal extractor. Stable AgNPs were selected for a detailed antimicrobial activity study.

CFD Study of the Effect of Geometrical Shape of Separation Blades on the Rotor Performance of an Annular Centrifugal Extractor (ACE)

CFD Study of the Effect of Geometrical Shape of Separation Blades on the Rotor Performance of an Annular Centrifugal Extractor (ACE)

Hydraulic characteristics of n-octanol/aqueous solution systems in a 25-mm annular centrifugal extractor

ABSTRACTThe hydraulic characteristics of the n-octanol/H2O, n-octanol/1 M HNO3 solution, and kerosene/H2O systems in the 25-mm annular centrifugal extractor (ACE) were investigated to provide guidance for optimizing the operation parameters and heavy phase weir diameter of the 25-mm ACEs used in a production line to extract 137Cs and 90Sr using the calixcrown ether cesium extraction (CECE) and crown ether strontium extraction (CESE) processes, respectively, from high-level liquid waste (HLLW). The effects of the flow ratio (A/O), rotor speed, and heavy phase weir diameter on the hydraulic characteristics of n-octanol/aqueous solution systems in the 25-mm ACE are complex. Moreover, the hydraulic characteristics of n-octanol/aqueous solution systems are very different from those of the kerosene/H2O system in the 25-mm ACE. All results showed when the 25-mm ACEs will be used in the CECE and CESE processes, the heavy phase weir diameter and rotor speed should correspond to ranges of 12.5 to 13.0 mm and 3000 to 3500 r/min, respectively, to meet the requirement the total flow rate of 3 L/h in the production line for the recovery of 137Cs and 90Sr.

High-efficient synergistic extraction of Co(II) and Mn(II) from wastewater via novel microemulsion and annular centrifugal extractor

Environmental pollution by industrial effluents polluted with hazardous heavy metals has great concern. A novel microemulsion system (sodium dodecanoate/pentan-1-ol/heptane/NaCl) was prepared for the treatment of cobalt (Co) and manganese (Mn) wastewater. The effects of the batch extraction conditions were systematically studied and the extraction efficiency of Co(II) and Mn(II) were 98.2% and 97.5% respectively at the optimal conditions. Utilizing the centrifugal reinforcement of the annular centrifugal extractor (ACE), the continuous extraction of cobalt and manganese wastewater by microemulsion could be achieved. Under the optimized operation conditions: the motor speed of 1988 rpm, a flow ratio of 1/5, and a total flow rate of 48 L/h, the maximum extraction efficiency reached up to 99.9% for Co(II) and 99.1% for Mn(II), respectively. The stripping of Co(II) and Mn(II) from the microemulsion phase was also conducted using hydrogen chloride solution, indicating a high stripping efficiency. The investigation of synergistic extraction with microemulsion and ACE proposed an efficient treatment for Co and Mn wastewater.

Rotor Speed and Supply Flow Rate Effects on Flow Behavior in an Annular Centrifugal Extractor

Rotor Speed and Supply Flow Rate Effects on Flow Behavior in an Annular Centrifugal Extractor

An industrial-scale annular centrifugal extractor for the TRPO process

Annular centrifugal extractors (ACEs) offer advantages including excellent hydraulic and mass-transfer performance, small hold-up volume, short residence time, and thus low solvent degradation, high nuclear criticality, easy start-up and shut-down, high compact structure. Therefore, ACEs have attracted increasing interest for future nuclear processing schemes, including the partitioning of high-level liquid waste (HLLW). Laboratory-scale and pilot-scale ACEs have been applied in demonstration tests of the trialkyl phosphine oxide (TRPO) process for HLLW partitioning. In this study, an industrial-scale ACE (260 mm in rotor diameter) with magnetic coupling and a “hanging” rotor structure was developed for the TRPO process. Moreover, a series of hydraulic and mass-transfer tests were carried out in the industrial-scale ACE. The maximum throughput can reach 10 m3/h under suitable operation parameters when kerosene is used as the organic phase, and water is used as the aqueous phase. The influence of the total flowrate, the flow ratio (aqueous/organic, A/O), and the rotor speed on the liquid hold-up volume was determined. The extraction stage efficiency is higher than 98% under test parameters for extraction of Nd3+ and HNO3, using 30% TRPO kerosene as the extractant from an HNO3 solution containing Nd. All results show good performance of the industrial-scale ACE for the TRPO process.

Mass transfer and hydrodynamic studies in a 50 mm diameter centrifugal extractor

Centrifugal extractor is a preferred device for process intensification in solvent extraction. The complexities of high radiation damage to solvent and resultant degradation of solvent performance also necessitate the need for fast contactors like centrifugal extractors in the nuclear fuel recycle operations. In this study, mass transfer performance as well as hydrodynamic characterization was reported for a 50mm diameter annular centrifugal extractor. Mass transfer studies included extraction and stripping experiments with solvent-aqueous pair of 30% Tri-n-butyl phosphate/n-dodecane and aqueous nitric acid solutions for different operating conditions like rotor speed, combined throughput and phase flow ratios. Flooding zone was characterized. Dispersed-phase holdups in annular as well as rotor regions and interfacial area for mass transfer were measured at different operating conditions. Non-ideal effects were studied by conducting residence time distribution analysis using aqueous phase as well as organic phase pulse tracer experiments. Various models like dispersion and tanks-in-series models were applied to experimental data. The contactor in study, was approximated as N number of tanks in series with a finite dead volume.

Liquid–liquid extraction in microchannels and conventional stage-wise extractors: A comparative study

The objective of the study is to compare the performance of microchannels and conventional stage-wise extractors for liquid–liquid extraction by using a standard phase system. Three different microchannels – a T-junction microchannel, a serpentine microchannel and a split-and-recombine microchannel – have been used in the experiments. Conventional extractors are represented by a mixer-settler and an annular centrifugal extractor. The phase system used in the experiments is water (succinic acid) n-butanol system which is one of the standard phase systems recommended by the European Federation of Chemical Engineering. The extractors have been compared on the basis of percentage extraction, overall volumetric mass transfer coefficient and specific extraction rate. When compared on the basis of percentage extraction, performance of the microchannels and the conventional stage-wise extractors is found to be almost similar. Maximum values of overall volumetric mass transfer coefficient and specific extraction rates are found to be more in the microchannels than in the conventional stage-wise extractors. The ratio of maximum overall volumetric mass transfer coefficient in microchannels and conventional stage-wise extractors is found to range from 1 to 8.1. The ratio of maximum specific extraction rate in microchannels and conventional stage-wise extractors is found to range between 2.3 and 9.7.

Effect of Cylinder Rotation on Flow Characteristics of the Annular Region in Annular Centrifugal Extractor

The flow patterns in the annular region of a 50 mm annular centrifugal extractor (ACE) were studied using phase particle image velocimetry (PIV), by which the distributions of radial velocity, axial velocity, vorticity, turbulent kinetic energy (TKE), and micromixing time of a fluid under different rotating Reynolds numbers were investigated. In the center of the annular region, both the radial and axial velocities of the fluid are close to zero, regardless of the rotating Reynolds number changes. The TKE of the fluid along the radial direction is small at center and large on the edge. The results show that the mixing process mainly occurs at the region near the outer cylinder’s sidewall, and the mixing time in this region is less than that in the internal annular region. Besides, the whole mixing efficiency is proportional to the rotational speed when the speed is below a certain level, and then gradually reaches a plateau when the speed is further increased.

Characterisation of submicron size entrainment in the aqueous product stream of a 40 mm diameter centrifugal extractor for 30% tbp/nitric acid biphasic system

Annular centrifugal extractor is a favoured solvent extraction contactor where process flowsheet requires a low hold-up, lower residence times and compact layout. However during operation of annular centrifugal extractor, a small entrainment, generally of the order of few hundred ppm, is always observed. To characterise this small entrainment, hydrodynamic experiments in a no-mass transfer mode were conducted on a 40 mm centrifugal extractor with 30%TBP/dodecane and acidified water. The aqueous product stream was analysed by dynamic light scattering based methods and drop size distribution was experimentally measured. The maximum entrained micro-drop size was typically below 1 μm in most of the cases and in the rest it was well below 10 μm. Thus the original assertion, that small entrainment occurred due to micro-sized drops, was proved right. However due to complex relations of peak locations and relative peak intensities to the physical and operating properties of solvent extraction system, mathematical modelling or correlation of experimental results was not feasible.

Measurement of drop size characteristics in annular centrifugal extractors using phase Doppler particle analyzer (PDPA)

Drop size distributions have been measured in a 39mm annular centrifugal extractor using phase Doppler particle analyzer (PDPA). The power consumption and the interfacial tension have been varied in the range of 10–450kW/m3 and 13–33mN/m, respectively. The two liquid phases have been selected with different density and viscosity ratios. The results have been analyzed using Rosin–Rammler distribution function. A correlation has been developed for the drop size distribution. The same has been compared with the correlations in the literature.

Residence Time Distribution and Flow Patterns in the Single-Phase Annular Region of Annular Centrifugal Extractor

Flow between two concentric cylinders with high-speed rotation of the inner cylinder, also termed as turbulent Taylor−Couette flow, is an integral part of annular centrifugal extractor (ACE). The vortex motion in the annular region causes intense mixing, of the two liquids, and their separation occurs in the inner cylinder under centrifugal action. In the present work, a systematic study of residence time distribution (RTD) in the annular region of ACE has been carried out experimentally as well as using computational fluid dynamics (CFD). The effects of rotational speed (10 ≤ ω ≤ 40, r/s), aspect ratio of annulus (11 ≤ Γ ≤ 48), width of annular gap (1.5 ≤ d ≤ 6.5, mm), and the flow ratio of the immiscible fluids (0.73 ≤ FR ≤ 2.4) have been systematically investigated. Effect of flow ratio, annular gap, and rotational speed has been investigated on the RTD. It was found that the flow in ACE is near to back-mixed behavior because of the presence of counterrotating vortices. The number of vortices depends o...

Flow Visualization and Three-Dimensional CFD Simulation of the Annular Region of an Annular Centrifugal Extractor

The single phase flow patterns in the annular region of an annular centrifugal extractor (ACE) have been studied both experimentally and computationally. Experiments were conducted using particle image velocimetry (PIV) and laser Doppler velocimetry (LDV) to understand the flow patterns and velocity profiles in both the presence and the absence of the net flow through the annulus. The data obtained in these experiments have been used for the validation of the computational fluid dynamics (CFD) simulations. Further, complete energy balance has been established. The CFD simulations were performed over a wide range of operating conditions. In contrast with the Taylor annular region (having no end effects), the ACE was found to exhibit markedly different cell patterns. The number of cells was found to be strongly dependent on the Taylor number. The effect of the internals such as radial baffles in the annulus, as well as vanes on the bottom plate, on the flow patterns has been investigated. From the simulations it was revealed that the flow patterns in ACE were also dependent on the start-up procedure of the equipment.

Computational Flow Modeling and Visualization in the Annular Region of Annular Centrifugal Extractor

Flow between two concentric cylinders, with either or both of them rotating, has potential advantages over the conventional process equipment. This flow, which is also termed Taylor−Couette flow and exhibits a variety of flow regimes, has been studied using computational fluid dynamics (CFD) simulations. The onset of centrifugal instability, the various cell patterns, and the velocity profiles have been predicted and compared with the available experimental data. To extend the base of experimental information, new measurements have been made using laser Doppler velocimetry (LDV) and particle image velocimetry (PIV). For the entire range of experimental data, the Reynolds stress model (RSM) was determined to exhibit good predictive ability for the mean components of velocity and the turbulent kinetic energy. The wavelengths of the vortices in various regimes have also been determined using CFD and were observed to be in good conformity with all the available experimental results. Furthermore, very good agr...