Perforated Rotating Disc Contactor Research Articles

Experimental modeling of mean drop size and dispersed phase holdup in rotating disc contactors, using RSM

In this study, the behavior of hydrodynamic parameters was investigated in agitated columns including Asymmetric rotating disc contactor (ARDC), Perforated rotating disc contactor (PRDC), Oldshue–Rushton column (ORC), and Kuhni. The effects of various parameters, including rotor speed (rpm), dispersed and continuous phase velocities, interfacial parameters, and type of RDCs on the dispersed phase holdup and Sauter mean drop diameter were studied. The response surface methodology (RSM) based on the central composite design (CCD) approach was applied for the experimental modeling of three standard systems including toluene-water, butyl acetate-water, and butanol-water. Results showed that the enhancement of rotor speed and dispersed and continuous phase velocities would enhance the dispersed phase holdup. PRDC showed the least enhancement of dispersed phase holdup compared to the other three columns. Our investigation demonstrated that Sauter mean droplet diameter decreased with the rotor speed increase, and this declining trend is more appreciable in ORC and Kuhni columns. Additionally, by increasing dispersed phase velocity in the four columns, the droplet size in the ORC column is larger than the columns. However, by increasing continuous phase velocity, subtle changes in droplet size was observed. Based on the experimental data, new correlations have been presented to predict Sauter mean drop diameter and dispersed phase holdup for agitated columns by analysis of variance (ANOVA). The coefficient of determination (R2) was obtained to be 0.9612 and 0.9495 for Sauter mean drop diameter and dispersed phase holdup, respectively, indicating a good correlation between the predicted and observed values of the models.

Response surface methodology study of dispersed phase holdup and mean droplet size in a perforated rotating disc contactors (PRDC)

ABSTRACT This research aims to optimize the influential hydrodynamic parameters in liquid-liquid extraction columns for three different systems of butanol–water, n-butylacetate–water, and toluene–water recommended by the European Federation of Chemical Engineering. The operating conditions of rotor speed, continuous phase, and dispersed phase velocities and two responses of the dispersed phase holdup of dispersed phase and Sauter mean drop diameter are considered to examine their interaction effects in a perforated rotating disc contactor (PRDC) pilot plant by response surface methodology (RSM). A desirable consistency between the predicted and experimental data was observed due to an R2 value higher than 0.99. The maximum dispersed phase holdup and minimum Sauter mean drop diameter (d32 ) were obtained at 0.117 and 0.599 mm, respectively. The results pointed out that the rotor speed is the most substantial variable in the studied responses.

Utilizing RSM for experimental modeling of mass transfer coefficients in a perforated rotating disc contactor (PRDC)

This study aims to examine and optimize the solvent extraction process of two different liquid-liquid systems, including toluene–acetone-water and n-butylacetate–acetone-water, in a perforated rotating disc contactor (PRDC) pilot plant according to response surface methodology (RSM). The interaction effects of four influential parameters of dispersed phase velocity, and continuous phase velocity, rotor speed, and system type (interfacial tension) are investigated. Three responses of dispersed phase hold-up, Sauter mean drop diameter (d32), and volumetric overall mass transfer coefficient (Kod.a) are correlated based on the central composite design (CCD) method. Satisfactory consistency between the predicted and empirical data based on the correlation coefficient (R2) values of higher than 0.99 for all responses. From investigating the interaction effects of parameters, the increase in the Kod.a and d32 responses was detected in both systems when the rotation speed and dispersed phase velocity are enhanced, respectively. The optimized values of Kod.a, hold-up, and d32 responses were obtained 12.257, 0.118, and 1.114, respectively, for the n-butylacetate system at 305 rpm, 10 m/s, and 9.75 m/s as rotation speed, continuous, and dispersed phase velocities, respectively.

Performance of continuous countercurrent extractor on the fractionation of Citrus bergamia essential oil using ethanol/water mixtures as solvents

Bergamot model mixture and crude bergamot essential oil (CBEO) were fractionated in a perforated rotating disc contactor (PRDC) using as solvents ethanol with 30% (Et30) and 40% (Et40) water, in mass. The apparatus performance was evaluated by experimental extraction indices, essential oil (EO) folding and estimative of mass transfer coefficients. The effects of the solvent to feed mass flow ratio (S/F), disc rotation speed (DRS), feed composition, and water content in the solvent over the process performance were thus appraised. Furthermore, the fractionation of model mixtures was simulated by Aspen Plus software. It was experimentally verified that higher S/F improved the extraction indices and mass transfer, whereas solvent Et40 and higher DRS also contributed for that results. Solvent Et40 extracted lower amount of components from the EO, but the Folds were similar to the ones achieved using solvent Et30. The simulation followed the same tendency. For the model mixture, a 1.54-fold EO was obtained, while for the CBEO a 1.4-fold EO was reached. Overall, solvent Et40, S/F close to 2, and low DRS exhibited the best results for the fractionation of CBEO in PRDC.

Extraction of oxygenated compounds from crude citrus latifolia peel oil using ethanol/water mixtures as solvents: Phase equilibrium and continuous equipment operation

Abstract Citrus latifolia (acid lime) essential oil, an important commodity in the international market, was fractionated by solvent extraction. New liquid–liquid equilibrium (LLE) data for systems composed of crude acid lime essential oil (CALEO), ethanol, and water at T = (298.2 ± 0.1) K were acquired for different water contents in the solvent and mass ratios between the solvent and CALEO (S/EO). The performance of the NRTL parameters available in the literature was evaluated by comparing the predicted LLE phases compositions with the experimental data. Higher water content in the solvent led to lower migration of the components from the raffinate to the extract phase but increased the solvent selectivity for oxygenated compounds. Low S/EO also decreased the migration of the components. The predicted composition exhibited satisfactory results, with global deviations in mass fraction up to 0.02. The CALEO was also fractionated in a perforated rotating disc contactor, using ethanol/water mixtures as solvents. The process performance was evaluated by experimental and simulated extraction indices. As in the LLE, additional water in the solvent and lower solvent to feed mass flow ratio (S/F) led to less extraction of the components, but higher experimental Folds were achieved (6-fold using ethanol 40 and 8-fold using 50% w/w water). Finally, greater water content in the solvent was also related to higher experimental values of density, viscosity and surface tension, especially for the extract phases, contributing for better operational conditions.

Use of axial dispersion model for determination of Sherwood number and mass transfer coefficients in a perforated rotating disc contactor

The mass transfer process in a perforated rotating disk contactor (PRDC) using a toluene–acetone–water system was investigated. The volumetric overall mass transfer coefficients are calculated in a PRDC column. Both mass transfer directions are considered in experiments. The influences of operating variables containing agitation rate, dispersed and continuous phase flow rates and mass transfer in the extraction column are studied. According to obtained results, mass transfer is significantly dependent on agitation rate, while the dispersed and continuous phase flow rates have a minor effect on mass transfer in the extraction column. Furthermore, a novel empirical correlation is developed for prediction of overall continuous phase Sherwood number based on dispersed phase holdup, Reynolds number and mass transfer direction. There has been great agreement between experimental data and predicted values using a proposed correlation for all operating conditions.

Fractionation of citrus essential oil by liquid–liquid extraction using a perforated rotating disc contactor

Abstract Citrus essential oils are important raw materials used in the formulation of many products, including soft and alcoholic drinks, flavoring agents, cosmetics, perfumes and toiletries. With the aim of improving the quality and, consequently, the price of the product, the separation of terpenic hydrocarbons and oxygenated compounds is required. The fractionation of essential oils may be achieved using diverse techniques, including liquid–liquid extraction using the appropriate solvents. This study was aimed at the fractionation of citrus essential oil model systems, composed of limonene and linalool mixtures, and crude orange essential oil (COEO) using continuous equipment known as a perforated rotating disc contactor (PRDC), in which mixtures of ethanol and water were used as the solvent. The effect of some variables, including disc rotation speed (DRS), linalool content in the feed (%LF), water content in the solvent (w 4, S ) and the ratio between the solvent and the feed mass flows (S/F), on process performance, using model mixtures, was studied. The fractionation process using the PRDC achieved concentration of linalool in the extract, on a solvent-free basis, 7-fold using a hydroalcoholic solvent with a water content of 30% by mass, and close to 10-fold using a solvent with 40% water by mass. With respect to the fractionation of COEO, the extraction indices reported here were in accordance with those determined for model systems, being obtained a concentration of oxygenated compounds of 10-fold using solvent with 30% of water and 15-fold using solvent with 40% of water.

Deacidification of palm oil by solvent extraction

Abstract The present work reports the influence of some process variables on the losses/transfer of fatty compounds during the deacidification of palm oil by liquid–liquid extraction. The response surface methodology (RSM) was used to analyze the effect of the mass ratio of oil to solvent and the water content in the solvent, aiming to minimize the losses of neutral oil and maximize the transfer of free fatty acids plus carotenoids preservation. By using appropriate conditions observed in RSM analysis (mass ratio of oil to solvent equal to 0.74 and water content around 6 mass%), the deacidification of palm oil by continuous liquid–liquid extraction was performed in a perforated rotating disc contactor (PRDC). The experimental results indicate that it is possible to obtain refined palm oil with a free acidity lower than 0.1 mass% by continuous liquid–liquid extraction.

Mass transfer coefficients in a perforated rotating disc contactor (PRDC)

The volumetric overall mass transfer coefficients were investigated in a pilot scale perforated rotating disc contactor (PRDC) of 113mm internal diameter, using axial diffusion model for two different liquid–liquid systems. The effects of operating parameters including the disc rotational speed and dispersed and continuous phase velocities on the mass transfer performance are investigated. The previous models for dispersed phase overall mass transfer coefficient were reviewed and compared with the experimental data. The results show that the previous correlations do not have enough accuracy for prediction of mass transfer performance in this extractor. Effective diffusivity is applied instead of molecular diffusivity in Gröber equation and enhancement factor is predicted from experimental data as a function of holdup of the dispersed phase, Reynolds number and Eötvös number. Good agreement between prediction and experiments was found for all operating conditions that were investigated.

A study of drop size distribution and mean drop size in a perforated rotating disc contactor (PRDC)

Drop size distribution and Sauter mean drop diameters have been measured in a 113mm diameter perforated rotating disc contactor for three different liquid–liquid systems. The effects of operating variables including rotor speed and dispersed and continuous phase velocities are investigated. The results show that drop size is strongly dependent on the rotor speed and interfacial tension, but only slightly dependent on the phase velocities. Drop size distributions are appropriately described using normal and log-normal probability density function, and empirical correlations are derived to predict the parameters of the distribution curve as a function of operating conditions and physical properties of the systems. An empirical correlation is also proposed for prediction of the Sauter mean drop diameter in terms of properties of the liquid–liquid systems and operating variables. Good agreement between the prediction and experiments is found for all investigated operating conditions.

Hold-up and flooding characteristics in a perforated rotating disc contactor (PRDC)

Dispersed phase hold-up and flooding behavior were investigated in a pilot plant scale perforated rotating disc contactor (PRDC) using three different liquid–liquid systems.

Aqueous two-phase system for citrinin extraction from fermentation broth

Aqueous two-phase systems (ATPSs) were investigated for effective extraction of citrinin from Penicillium citrinum fermentation broth. The citrinin partitioning behaviour in each ATPS (polyethylene glycol–phosphate salts) was evaluated in terms of the following parameters: polyethylene glycol (PEG) molecular weight, pH and tie line length. The target molecule (citrinin) presented high affinity to the PEG rich phase in most of the experiments. The best recovery yield (98.4%) was obtained using PEG 4000 (20%w/w)/phosphate salt (16.7%w/w), pH 3.4 at room temperature (28–30°C), but the best citrinin partitioning (36.41) was observed at pH 5.7 using the same ATPS. Continuous citrinin extraction studies were performed using the fermentation broth and this ATPS in a perforated rotating disc contactor (PRDC). Recovery up to 98.44% supports the possible use of this system on a laboratory scale.

Continuous extraction of α-toxin from a fermented broth of Clostridium perfringens Type A in perforated rotating disc contactor using aqueous two-phase PEG–phosphate system

A 2 3–1 factorial experimental design was used to evaluate the performance of a perforated rotating disc contactor to extract α-toxin from the fermented broth of Clostridium perfringens Type A by aqueous two-phase system of polyethylene glycol–phosphate salts. The influence of three independent variables, specifically the dispersed phase flowrate, the continuous phase flowrate and the disc rotational speed, was investigated on the hold up, the mass transfer coefficient, the separation efficiency and the purification factor, taken as the response variables. The optimum dispersed phase flowrate was 3.0 mL/min for all these responses. Besides, maximum values of hold up (0.80), separation efficiency (0.10) and purification factor (2.4) were obtained at this flowrate using the lowest disc rotational speed (35 rpm), while the optimum mass transfer coefficient (0.165 h −1) was achieved at the highest agitation level (140 rpm). The results of this study demonstrated that the dispersed phase flowrate strongly influenced the performance of PRDC, in that both the mass transfer coefficient and hold up increased with this parameter.

Studies of efficiency in a perforated rotating disc contactor using a polymer-polymer aqueous two-phase systems

The mass transfer process in a perforated rotating disc contactor (PRDC) using a polymer-polymer aqueous two-phase system was investigated. The results show that the efficiency did not show a regular trend with the increase of the dispersed phase velocity and increased with the rotation velocity. The separation efficiency was higher for three rotating discs than for four discs. The increase in tie-line length decreased the efficiency. The separation efficiency reached high values, about 96% under conditions studied in this work.

Recovery of ascorbic oxidoreductase from crude extract with an aqueous two-phase system in a perforated rotating disc contactor

A continuous perforated rotating disc contactor was used to extract the enzyme ascorbic oxidoreductase (E.C.1.10.3.3) from crude extract of Curcubita maxima with an aqueous two-phase system of poly (ethylene glycol) and phosphate salts. The effect of dispersed phase velocity on either protein mass transfer coefficients or separation efficiency at 1, 2 and 3 mL/min was studied. An increase of the mass transfer coefficients was observed with the dispersed phase velocity, while the separation efficiency showed a small decrease with the increase of this parameter. The experimental results obtained during continuous extraction showed that the ascorbic oxidoreductase activity was partitioned preferentially into the salt-rich phase in all conditions studied. The best recovery of enzyme activity was 236%, with a purification factor of 34 in flow rates of 1 mL/min for dispersed phase.

Performance of a perforated rotating disc contactor in the continuous extraction of a protein using the PEG–cashew-nut tree gum aqueous two-phase system

The characterisation of bovine serum albumin (BSA) mass transfer mechanisms in a perforated rotating disc contactor (PRDC) using an aqueous two-phase system (ATPS) composed of poly(ethylene glycol) (PEG) and a polysaccharide, the cashew-nut tree gum, was described. The PEG-rich phase was used as the dispersed phase and protein transfer took place from the dispersed to the continuous phase. Studies of the effect of dispersed phase velocity, system composition and disc rotation speed on either protein mass transfer coefficients or column hold-up showed that the dispersed phase hold-up and the volumetric mass transfer coefficient increased with increasing the dispersed phase velocity and disc rotation speed.

Integration of production and aqueous two-phase systems extraction of extracellular Fusarium solani pisi cutinase fusion proteins

Genetic engineering was integrated with the production and purification of Fusarium solani pisi cutinases, in order to obtain the highest amount of enzyme activity units, after purification. An aqueous two-phase system (ATPS) of polyethylene glycol 3350, dipotassium phosphate and whole broth was used for the extraction of three extracellular cutinases expressed in Saccharomyces cerevisiae. The production/extraction process was evaluated regarding cutinases secretion in the medium, partition behaviour and extraction yields in the ATPS. The proteins studied were cutinase wild type and two fusion proteins of cutinase with the tryptophane-proline (WP) fusion tags, namely (WP) 2 and (WP) 4. The (WP) 4 fusion protein enabled a 300-fold increase of the cutinase partition coefficient when comparing to the wild type. However, the secretion of the fusion proteins was lower than of the wild type cutinase secretion. A batch extraction strategy was compared with a continuous extraction in a perforated rotating disc contactor (PRDC). The batch and continuous systems were loaded with as much as 60% (w/w) whole cultivation broth. The continuous extraction strategy provided a 2.5 higher separation capacity than the batch extraction strategy. Considering the integrated process, the cutinase-(WP) 2 proved to lead to the highest product activity, enabling five and six times more product activity than the wild type and the (WP) 4 fusion proteins, respectively.

Hydrodynamics and mass transfer in aqueous two-phase protein extraction using a continuous perforated rotating disc contactor

A continuous perforated rotating disc contactor was used to extract bovine serum albumin (BSA) with aqueous two-phase systems based on polyethylene glycol (PEG) and phosphate salts. The dispersed phase holdup and mass transfer coefficient were determined. It was found that the dispersed phase holdup increased with increasing PEG phase velocity. The overall mass transfer coefficient for BSA was independent of the PEG phase velocity.

Dispersed Phase Hold-Up in a Perforated Rotating Disc Contactor (PRDC) Using Aqueous Two-Phase Systems.

Dispersed phase hold-up and characteristic velocity in a perforated rotating disc contactor were studied using an aqueous two-phase system composed by polyethylene glycol 6000 and dibasic potassium phosphate. The geometrical and operational variables were flow free area of discs, rotating speed and volume flow ratio. Flow free area of discs showed small influence on the hold-up values. It was also observed the increase of the hold-up on the rotating speeds and phase flow ratios.

Continuous extraction of a recombinant cutinase from Escherichia coli disrupted cells with reversed micelles using a perforated rotating disc contactor

This work reports on the continuous extraction of a recombinant cutinase with reversed micelles using a perforated rotating disc contactor. Intracellular cutinase was directly extracted at 20°C with 100 mM AOT in isooctane from complex biological media of Escherichia coli disrupted cells. The optimal conditions for the direct extraction of the enzyme from media containing cell debris led to an extraction yield of 54.4%.