Continuous Counter-current Process Research Articles

Scaling the electrophoretic separation of rapeseed proteins and oleosomes

Gentle extraction of ingredients from raw materials is essential for high-quality food ingredients and can lead to reducing the use of water, chemicals, and energy in the extraction. For example, a simple aqueous extraction can yield a mixture of oil, in the form of a natural oil-in-water oleosome emulsion, and proteins. The oleosomes and proteins can then be further separated in a next step. We explored a continuous counter-current electrophoretic process that separates oleosomes and proteins based on their electrophoretic mobility by balancing an electric field with an opposing solvent flow. The separation is accomplished through the retention of the component with the higher electrophoretic mobility, the oleosomes, and the passage of the proteins, having lower mobility. The fluxes of oleosomes and proteins from rapeseed, after aqueous extraction, were analyzed as a function of the electric field (0–75 Vcm−1) and 1.2 ± 0.1 mLmin-1 solvent flow rate. At 50 Vcm−1, the permeation flux of proteins was 10-fold higher than that of oleosomes, as shown by the selectivity increasing to 9.84 from 1.90 at 25 Vcm−1. The difference in their flux promises to become more pronounced under an increasing treatment duration, but two main technical limitations, electrolysis-based pH alteration and membrane fouling, restrict further separation. We expect the listed challenges can be mitigated with the addition of electrode rinse chambers and the use of larger pore size membranes.

Online optimization of dynamic binding capacity and productivity by model predictive control

In preparative and industrial chromatography, the current viewpoint is that the dynamic binding capacity governs the process economy, and increased dynamic binding capacity and column utilization are achieved at the expense of productivity. The dynamic binding capacity in chromatography increases with residence time until it reaches a plateau, whereas productivity has an optimum. Therefore, the loading step of a chromatographic process is a balancing act between productivity, column utilization, and buffer consumption. This work presents an online optimization approach for capture chromatography that employs a residence time gradient during the loading step to improve the traditional trade-off between productivity and resin utilization. The approach uses the extended Kalman filter as a soft sensor for product concentration in the system and a model predictive controller to accomplish online optimization using the pore diffusion model as a simple mechanistic model. When a soft sensor for the product is placed before and after the column, the model predictive controller can forecast the optimal condition to maximize productivity and resin utilization. The controller can also account for varying feed concentrations. This study examined the robustness as the feed concentration varied within a range of 50%. The online optimization was demonstrated with two model systems: purification of a monoclonal antibody by protein A affinity and lysozyme by cation-exchange chromatography. Using the presented optimization strategy with a controller saves up to 43% of the buffer and increases the productivity together with resin utilization in a similar range as a multi-column continuous counter-current loading process.

Semicontinuous Lixiviation Process for Compound Extraction from Cannabis sativa grown in Colombia

The extraction of compounds present in Cannabis sativa biomass from Colombian crops was studied using a semi-continuous lixiviation process. To this effect, three extraction stages were implemented, in which successive transfers were carried out at fixed times, seeking to emulate a continuous countercurrent process. In this way, the intention is to provide the Colombian agroindustry with an extraction method that is efficient and requires a lower initial investment than other techniques such as supercritical fluid extraction. Absolute ethanol was used as solvent, and constant temperature and stirring speed were applied. The obtained results indicate that, once the process is stabilized, extracted mass percentages (with respect to the total mass on a dry basis) of 10,5% at 40 °C and 9,5% at 19 °C are achieved, which are competitive compared to the 11,07% achieved through Soxhlet extraction. Besides, the proposed process is clearly a better alternative than a single-stage extraction method, through which it was possible to extract 5% of the mass. Five cannabinoids were identified in the obtained extract, and, with the proposed process, it was possible to extract 66% of cannabidiol present in the original biomass.

Simulating Continuous Counter-Current Leaching Process for Indirect Mineral Carbonation Under Microwave Irradiation

Mineral carbonation is a promising avenue to realize a deep reduction in carbon dioxide emissions. Though many methods were studied to improve the leaching ratio of mineral leached by ammonium salt, little attention has been received to the problem that the calcium leaching ratio increases while its concentration drops rapidly with the liquid-solid ratio increasing. The continuous counter-current leaching for mineral carbonation process under microwave irradiation is proposed in this study, and the results show that the simulating continuous counter-current leaching process in this article not only is beneficial to improve the leaching ratio and concentration of calcium ions in solution at the same time, but also increases the relative purity of calcium in leached solution. And the produced calcium carbonate products meet the requirements of industrial precipitation of calcium carbonate.

Non-aqueous solvent extraction of indium from an ethylene glycol feed solution by the ionic liquid Cyphos IL 101: speciation study and continuous counter-current process in mixer-settlers.

A solvometallurgical process for the separation of indium(iii) and zinc(ii) from ethylene glycol solutions using the ionic liquid extractants Cyphos IL 101 and Aliquat 336 in an aromatic diluent has been investigated. The speciation of indium(iii) in the two immiscible organic phases was investigated by Raman spectroscopy, infrared spectroscopy, EXAFS and 115In NMR spectroscopy. At low LiCl concentrations in ethylene glycol, the bridging (InCl3)2(EG)3 or mononuclear (InCl3)(EG)2 complex is proposed. At higher lithium chloride concentrations, the first coordination sphere changes to two oxygen atoms from one bidentate ethylene glycol ligand and four chloride anions ([In(EG)Cl4]−). In the less polar phase, indium(iii) is present as a tetrahedral [InCl4]− complex independent of the LiCl concentration. After the number of theoretical stages had been determined using a McCabe–Thiele diagram for extraction by Cyphos IL 101, the extraction and scrubbing processes were performed in lab-scale mixer–settlers to test the feasibility of working in continuous mode. Indium(iii) was extracted quantitatively in four stages, with 19% co-extraction of zinc(ii). The co-extracted zinc(ii) was scrubbed selectively in six stages using an indium(iii) scrub solution. Indium(iii) was recovered from the loaded less polar organic phase as indium(iii) hydroxide (98.5%) by precipitation stripping with an aqueous NaOH solution.

Optimization of the Supercritical Carbon Dioxide Separation of Bergapten from Bergamot Essential Oil.

The possibility of following traditional cold-press extraction with the post process continuous separation of bergapten from bergamot essential oil was investigated. A fractionation tower was used in an experiment in which cold-pressed bergamot oil was extracted in a continuous countercurrent process by supercritical carbon dioxide under different conditions. Bergapten is fairly soluble in CO2 in its supercritical phase, in particular at a density of 277.90 kg⋅m-3, corresponding to a pressure of 8 MPa and temperature of 40°C. Under these conditions, an extract with 0.198% bergapten was obtained, a figure slightly below the percentage of bergapten contained in cold-pressed oil (0.21%). However, at densities below 200 kg⋅m-3, the amount of bergapten in the extracted oil was negligible. Of all tested conditions for separation, the best was found to be at a pressure of 8 MPa and temperature of 70°C, conditions under which bergapten was not detected. The results of the experiment showed that bergapten, and the non-volatile fraction in general, was extracted only in small quantities and was not extracted at all with at a CO2 pressure of 8 MPa.

Supercritical carbon dioxide separation of fish oil ethyl esters by means of a continuous countercurrent process with an internal reflux

The continuous countercurrent fractionation of fish oil ethyl esters using supercritical carbon dioxide is studied, modelling a process with internal reflux generated by a thermal gradient at the top stage. A methodology for process design is proposed and applied to determine the relationships between the temperature at the top stage (T1), the number of theoretical stages (N), and the solvent to feed ratio (S/F), with the aim of providing a quantitative comparison with the external reflux process. The internal reflux process is viable and, for stated process specifications (mass fraction and recovery of C20+C22 ethyl esters of 95%), provides comparable or better results than the external reflux process. For example, operating at 13.3MPa and 50°C, and keeping T1 in the range (66–70)°C, the specifications are attained with N and S/F in the range 16–30 and 88–120, respectively.

Development and demonstration of innovative partitioning processes (i-SANEX and 1-cycle SANEX) for actinide partitioning

Two full continuous countercurrent processes for the recovery of trivalent actinides (An(III)) from a simulated PUREX raffinate solution (HAR) were developed and demonstrated using miniature laboratory-scale centrifugal contactors: the innovative SANEX and the 1-cycle SANEX processes. The innovative SANEX process was successfully demonstrated in a 16 + 16 stage flow sheet. In the first 16 stages, Am(III), Cm(III), and Ln(III) were quantitatively co-extracted from the HAR by a TODGA-based extractant. The decontamination factors (DFs) for the major non-lanthanide fission products were >103. The loaded extractant was then subjected to two stripping steps using the second 16 stages of the flow sheet. The first stripping step concerned the selective stripping of Am(III) + Cm(III) at fairly high acidity (0.35 ML−1 HNO3) with the new hydrophilic N-chelating selective ligand SO3-Ph-BTP. High An(III) recoveries >99.8% were achieved with high decontamination factors toward the trivalent lanthanides. In the second step, the residual stripping of Ln(III) from loaded organic phase was carried out quantitatively using 0.5 ML−1 citric acid solution at pH 3. However, Ru proved to be the only exception and remained to a large extent (12.8%) in the spent extractant. A more challenging route also studied at our laboratories is the 1-cycle SANEX process, i.e. direct An(III) separation from HAR using an extractant mixture of CyMe4BTBP and TODGA in 1-octanol/TPH diluent. A demonstration process was also successfully implemented using a 16 + 16 stage flow sheet on the above-mentioned laboratory-scale centrifugal contactor rig. It was demonstrated that a selective extraction and high recovery of >99.8% of Am(III) and >99.4% Cm(III) was achieved with low contamination of fission products. Both new processes are major contributions to the field of partitioning and important steps forward toward the industrial implementation of MA partitioning.

Extraction of Copper and Cobalt from Nickel Chloride Solution with N<sub>235</sub>

Copper and cobalt were extracted from nickel chloride solution with N235. The various parameters considered in this work were N235concentration, reaction time, phase ratio (O/A) and pH value. The optimum conditions are determined that concentration of N235 in organic phase is 40% (volume fraction), the phase ratio (O/A) is 1:2, pH value is 2~4, chloride concentration is 5.76 mol/L and the reaction time is 4 min. Under the optimized operating conditions, cobalt and copper extracted effectively and the extraction rates at the single stage reached 90% and 97%, respectively. After five stage continuous counter-current process, the concentrations of copper, cobalt, iron in the raffinate are less than 0.0008 g/L，0.008 g/L and 0.0025 g/L, respectively, and the recovery of nickel is higher than 92%. The separation effect is steady and satisfied for the electrolysis.

A theoretical study of continuous counter-current chromatography for adsorption isotherms with inflection points

Continuous counter-current chromatographic processes have been increasingly applied in the last years. For chromatographic systems characterized by linear or Langmuir adsorption equilibria, there are nowadays reliable design rules available to decide whether a separation is feasible and which operating parameters should be used. For more complex equilibrium functions, theoretical methods are less developed. More realistic adsorption isotherms are frequently characterized by inflection points in their courses. A flexible model capable to quantify single solute and competitive adsorption isotherms is provided by statistical thermodynamics. In this work, second-order truncations of a statistical model involving inflection points are investigated. The classical scanning technique is used to identify the region of applicable operating parameters. Then an alternative approach is suggested, which verifies the existence and shape of the suitable parameter region by infeasibility certificates. Using the True Moving Bed model, both approaches are compared for different feed concentrations, purity requirements and column efficiencies.

Demonstration of a SANEX Process in Centrifugal Contactors using the CyMe4‐BTBP Molecule on a Genuine Fuel Solution

Efficient recovery of minor actinides from a genuine spent fuel solution has been successfully demonstrated by the CyMe4‐BTBP/DMDOHEMA extractant mixture dissolved in octanol. The continuous countercurrent process, in which actinides(III) were separated from lanthanides(III), was carried out in laboratory centrifugal contactors using an optimized flow‐sheet involving a total of 16 stages. The process was divided into 9 stages for extraction from a 2 M nitric acid feed solution, 3 stages for lanthanide scrubbing, and 4 stages for actinide back‐extraction. Excellent feed decontamination factors for Am (7000) and Cm (1000) were obtained and the recoveries of these elements were higher than 99.9%. More than 99.9% of the lanthanides were directed to the raffinate except Gd for which 0.32% was recovered in the product.

Modelling of the phase behaviour for vegetable oils at supercritical conditions

This work describes a generalized procedure for high pressure equilibrium calculations for vegetable oils. The present approach considers any vegetable oil as composed by two key components: oleic acid (OA) and triolein (TO). OA is representing the low molecular weight compounds, those related with acid value and the products of degradation. TO refers the fatty content. The mathematical procedure used commercial ASPEN-plus ® software package to process CO 2–OA–TO equilibrium data according to the classical cubic equations of state (EOS). The theoretical data calculated by the package fit fairly well with the experimental results published for a wide variety of vegetable oils, especially for seed extracts. Equilibrium calculation theoretical results were in good agreement with literature data for acid value and also confirmed than can be used to predict properly continuous countercurrent processes. The model proposed in this work can be useful for preliminary scale-up and economical evaluations avoiding specific equilibrium data determination, with special interest in deacidification processes.

Continuous countercurrent deterpenation of lemon essential oil by means of supercritical carbon dioxide: Experimental data and process modelling

A thermodynamic model based on the Peng–Robinson equation of state was developed in order to perform high-pressure phase equilibria calculations for the system carbon dioxide–lemon essential oil. The multicomponent natural oil was simulated by a mixture of three key components, one for each relevant class of compounds (monoterpenes, monoterpene oxygenated derivatives and sesquiterpenes). Firstly the proposed model was validated on semi-batch experimental data and then it was used to simulate the behaviour of a continuously operated countercurrent column. Experiments on deterpenation process on a packed column, operating as a stripping section, were carried out in the temperature range 50–70 °C and pressure range 8.7–11.2 MPa. The comparison between experimental results and process simulation demonstrated that the proposed model is capable of reliable predictions on the behaviour of the countercurrent continuous deterpenation process. Furthermore, an average height equivalent to a theoretical plate of about 40 cm was estimated, for the stated packing and operating conditions. A case study for the production of 10-fold high quality oil, with strict specifications for the recovery of oxygenated compounds (99%), was investigated by simulations of a continuous countercurrent process with an external reflux. The linkage between the number of theoretical stages, the reflux ratio and the solvent to feed ratio was investigated throughout the above-mentioned pressure and temperature ranges. Operating conditions at higher pressure and temperature proved to be more favourable. As an example, operating a 20 theoretical stage column at 70 °C and 11.2 MPa, it is possible to attain process specifications with a solvent to feed ratio of about 63.

Comparative study of solvent extraction of vanadium from sulphate solutions by primene 81R and alamine 336

A comparative study of the solvent extraction of vanadium in sulphate media using primary amine PRIMENE 81R and tertiary amine ALAMINE 336 dissolved in kerosene has been carried out. pH conditions for both amines, mechanism proposal and extraction isotherms have been determined, yielding best results for primary amine. Equilibrium studies were used to assess the conditions of vanadium recovery in a continuous counter-current process using leaching solutions.

Decrease of HF Concentration in Process Solutions before Extractive Separation of Tantalum(V) from Niobium(V)

To improve separation of tantalum(V) from niobium(V) in their extraction from fluoride solutions, different ways for decreasing the fluoride ion concentration in the aqueous phase were tested. The efficiency of decomposition of rare-metal concentrate in continuous countercurrent process with several equilibrium decomposition stages was studied.

A new technique for quick production of ammonium paratungstate (APT) crystals by a liquid membrane

The alkaline feed of crude sodium tungstate obtained from the caustic fusion of black tungsten ore was neutralized to a pH value near 9 to eliminate Si as routine, then the resulting feed was directly used as the external aqueous phase without eliminating P, As and Mo. Through a single stage batch liquid membrane process at room temperature for 5 min under optimum operation conditions obtained by an orthogonal test, APT directly crystallizes in the internal aqueous phase with 99.87% yield and the quality attained was the first grade of a national standard; meanwhile the pH value of the effluents was lowered to 6–7 in itself suitable for direct discharge and without W (VI) lost out of the raffinate. Finally, a continuous counter-current process of a single stage for a pilot plant was proposed.

Continuous Isotope Separation in Systems with Solid Phase. I. Gas-Phase Separation of Isotopes of the Light Elements

Abstract A continuous countercurrent process for separation of isotopes of the light elements in gas-solid systems is reported. To separate hydrogen isotopes a hydrideforming palladium adsorbent and a zeolite 13A were used as a solid phase. The molecular sieve was also used to separate oxygen, nitrogen, and argon isotopes. The simulated moving-bed technique (SMB) was employed to organize a countercurrency between gas and solid phases without actual movement of the latter phase. Details of the experimental SMB unit operating in the gas phase are presented, and the results of the separation tests are discussed. A multichannel disk rotary valve was used to switch the flows. It is shown that the process takes advantage of a continuous operation and possesses very high separation efficiency with HETP values comparable to those for the equivalent conventional chromatographic process. It appears that the process proposed is ideally suited for processing tritium-containing streams to produce commodity-grade triti...

Mathematical simulation and calculation of the continuous countercurrent process of ion-exchange extraction of strontium from strongly mineralized solutions

The program “Countercurrent” is developed for the simulation of a continuous ionexchange extraction of strontium from strongly mineralized NaCl and CaCl2 solutions using a KB-4 carboxylic cation-exchanger in the countercurrent columns. The program allows one to calculate the conditions of Ca and Sr separation depending on the mode of operation at the sorption and regeneration stages, the residual Sr content on the overloaded sorbent, and the Sr separation on incompletely regenerated KB-4. It also makes it possible to find the optimal separation conditions. The program “Countercurrent” can be also used to simulate other ion-exchange processes.

Dynamics of continuous countercurrent mass-transfer processes—IV. Multicomponent waves and asymmetric dynamics

This paper complements the approximate dynamic model of multicomponent countercurrent mass-transfer processes presented in Part III based on an adaptation of the equilibrium coherence theory for fixed-bed sorption to countercurrent operation. The numerical technique presented in Part II has been extended to multicomponent systems. Resulting from the numerical solution, the nonlinear wave behavior under nonequilibrium conditions has verified that the coherence theory provides good predictions of dynamic response patterns. In addition, a cause-and-effect analysis has been performed on “asymmetric dynamics” in multicomponent systems, and has shown that such a phenomenon is a natural consequence of nonlinear wave behavior. An effective simple control strategy has been proposed to combat such an unfavorable phenomenon.

Dynamics of continuous countercurrent mass-transfer processes—III. Multicomponent systems

In earlier papers, a differential model has been presented for the dynamics of countercurrent mass-transfer processes in single-component systems. This paper extends the approximations developed in Part II to multicomponent systems by adapting an equilibrium theory for fixed beds based on coherence of concentration waves to countercurrent processes. The analysis focuses on the propagation of disturbance waves on nonuniform steady-state backgrounds and takes into account the critical column-end effect observable only under nonequilibrium conditions. This simplified approach provides a better understanding of physical phenomena and a handy tool for quick predictions of dynamic response patterns, the knowledge of which is useful for upgrading the control and design of countercurrent columns.