Pulsed Plate Column Research Articles

Experimental investigation, modelling, and order of magnitude analysis of oxygen mass transfer in pulsed plate column with α‐Fe2O3 nanofluid

AbstractVolumetric oxygen mass transfer coefficient (kLa) is an important parameter in the design of various reactors and bioreactors. In the present work, the influence of α‐Fe2O3 nanofluid on the enhancement of kLa is studied in a pulsed plate column (PPC). An enhancement factor of greater than one showed that the nanofluid is favourable in enhancing the mass transfer rate. The effect of pulsing velocity on kLa is observed to fall under two regimes: the dispersion regime and emulsion regime. The kLa enhancement factor is found to be higher in TiO2 nanofluid than in α‐Fe2O3 nanofluid, indicating that the type of nanofluid influences the enhancement factor. The order of magnitude analysis showed that localized convection triggered by the Brownian motion of nanoparticles is the phenomenon responsible for kLa enhancement. A dimensionless multiple regression analysis (MRA) model was developed to predict kLa in the nanoparticle loading range of 0.003–0.019 (v/v%), relating the Sherwood number with oscillating Reynolds number (1200 ≤ Reo ≤ 20,000), gas flow Reynolds number (0.135 ≤ Reg ≤0.370), Schmidt number (1300 ≤ Sc ≤2700), and Brownian Reynolds number (2.81 × 10−4 ≤ ReB ≤5 × 10−4). The pseudo‐homogeneous model could accurately predict the enhancement until critical loading conditions.

TiO2 nanofluid for oxygen mass transfer intensification in pulsed plate column

Oxygen mass transfer coefficient (kLa) is a key parameter in biochemical, photochemical, or other reactors. Pulsed plate column (PPC) has a potential application as a gas-liquid contactor. In the present work, TiO2 nanofluid mediated oxygen mass transfer intensification in PPC is studied. The pulsing velocity (A × f) and nanoparticle loading in volume percent (Φ) have an interacting effect on kLa. The effect of Φ on kLa, showed a dual regime of an increase in kLa with an increase in Φ up to a critical loading (Φ CL ) and decrease in kLa on further increase in Φ. The effect of (A × f) on kLa showed three regimes. Φ CL & kLa were found to decrease as the nanoparticle's size increased. Dimensionless correlations based on multiple regression analysis and ANN models were developed to predict the kLa values in PPC with TiO2 nanofluids.

Efficient biosorption of Pb(II) on Pteris vittata L. from aqueous solution using pulsed plate column technique

ABSTRACT Biosorption is an alternative method of remediation that is devoid of the limitations associated with physiochemical techniques. This paper investigates the ability of the pteridophyte, Pteris vittata L., proven to have heavy metal hyper-accumulation capacity in living forms, to adsorb Pb(II) from an aqueous system in its powdered and pelletized form. At best-operating conditions, P. vittata L. pinnae powder exhibited Pb(II) biosorption capacity of 125 mg/g. Bench-scale Pulsed Plate column studies using pelletized biosorbent demonstrated continuous Pb(II) removal efficiency of 99.93%. With no commercial value and application, untreated P. vittata is a potential resource that will contribute to biosorption technology.

Prediction of Concentration Profiles in an L‐Shaped Pulsed Extraction Column

AbstractThe L‐shaped extraction pulsed plate column is believed to be able to perform under operating conditions between those of the vertical and the horizontal pulsed plate columns. It has an extraction efficiency similar to the vertical pulsed plate column. Here, the mass transfer performance of this novel column type was investigated and the application of three different models, i.e., the plug flow, the axial dispersion, and the back flow models, was evaluated to predict the solute concentration profile along the column length. The water‐acetone‐n‐butyl acetate and the water‐acetone‐toluene systems were used. The influence of the operational parameters on the height of the mass transfer unit and the back flow coefficients was evaluated using the back flow model. New correlations were proposed to predict the height of the mass transfer unit along with the back flow coefficients in each phase, which were in satisfactory agreement with the experimental data.

Study of holdup and slip velocity in an L-shaped pulsed sieve-plate extraction column

High-end applications require a very tall vertical extraction column in some cases which deteriorates protection against radiation and cannot be employed for indoor applications. On the other hand, horizontal extraction columns offer higher efficiency and pretension, but lower maximum throughput. In order to address this issue, the L-shaped pulsed extraction column is a new type of extractors which were recently introduced for such applications with area constraints. The objective of this study is to evaluate the effects of operating parameters and physical properties on the variation of holdup and slip velocity in this type of extractors for three liquid systems including toluene–water, butyl acetate–water and n butanol–water without and under mass transfer condition. A comprehensive investigation on the determination of predictive ability of available correlations for the holdup and slip velocity in pulsed plate columns has been conducted. Finally, new correlations are proposed for prediction of these parameters regarding operational conditions and physical properties.

Bioleaching of copper from electronic waste using Acinetobacter sp. Cr B2 in a pulsed plate column operated in batch and sequential batch mode

The amount of metal content present in electronic waste (e-waste) such as printed circuit boards (PCBs) exceeds that present in rich minerals thus allowing the use of PCBs as artificial ores. The copper content in PCBs is 10–30 mass %, which is the highest among all the metallic elements. The recovery of copper from e-waste serves dual fold benefit of conservation of metal resources and overcoming environmental hazard due to e-waste accumulation. In the currently reported study, a pulsed plate bioreactor in which the inter-plate spaces were packed with e-waste material was effectively employed for bioleaching of copper from e-waste using Acinetobacter sp. Cr B2. Various factors such as inoculum size, e-waste loading, frequency and amplitude of pulsation that significantly affected the bioleaching efficiency were studied. Inoculum size of 9% (v/v), frequency of 0.2s−1, amplitude of 6.5cm and total e-waste loading of 40g with 10g/stage were found to provide maximum bioleaching of Cu. Around 23% of Cu bioleaching was achieved under these conditions by batch mode of operation. Increasing the number of sequential cycles of operation in sequential batch mode further improved the bioleaching efficiency, by overcoming the maximum copper solubility and growth limitations of the single batch operation. With five cycles of sequential batch operation around 63% leaching of Cu could be achieved. The bioleaching was found to be mediated both by the action of extracellular enzymes and metabolites. The study demonstrated the potential application of pulsed plate bioreactor for larger scale application of copper bioleaching from PCBs.

Experimental investigation concerning the effect of mass transfer direction on mean drop size and holdup in a horizontal pulsed plate extraction column

A schematic diagram of the horizontal pulsed plate column has been used.

Mixing and solid‐liquid mass transfer characteristics in a three phase pulsed plate column with packed bed of solids in interplate spaces—a novel aerobic immobilized cell bioreactor

AbstractBACKGROUND: The pulsed plate column (PPC) with packed bed of solids in the interplate spaces finds use as a three phase aerobic bioreactor and is a potential heterogeneous catalytic reactor. Good knowledge of the extent of mixing in the liquid phase and solid‐liquid mass transfer coefficient are essential for modeling, design and optimization of these columns. The present work aims at the study of liquid phase mixing and solid–liquid mass transfer characteristics in a three phase PPC.RESULTS: Residence time distribution studies were performed. Dispersion number was found to increase with increase in liquid superficial velocities, frequency of pulsation, amplitude of pulsation and the vibrational velocities. Increase in frequency and amplitude of pulsation, and hence increase in vibrational velocity, resulted in increase of the solid–liquid mass transfer coefficient.CONCLUSIONS: The mixing behaviour in this contactor approximated a mixed flow behaviour. The three phase PPC was found to outperform many other kinds of three phase contactors in terms of solid liquid mass transfer characteristics. Empirical correlations developed can be used for the determination of solid–liquid mass transfer coefficients for three phase PPC and hence can facilitate the design, scale‐up and modeling of these columns, when used as chemical or biochemical reactors. Copyright © 2011 Society of Chemical Industry

Oxygen Mass Transfer Coefficients in a Three-Phase Pulsed Plate Bioreactor

Volumetric oxygen mass transfer coefficient is a decisive parameter for the selection of any contactor as an aerobic bioreactor. A pulsed plate column with fixed bed of solids in interplate spaces is a recent innovation in the field of immobilized cell bioreactors. Volumetric oxygen mass transfer coefficients are determined in a three-phase pulsed plate column involving air and water phases and with a fixed bed of glass particles, which can serve as a surface for cell immobilization packed in the interplate spaces. The volumetric mass transfer coefficients obtained in this column range from 0.067 to 0.1495 s-1 in the range of air superficial velocities from 0.011 to 0.047m/s and vibrational velocities from 0.825 to 6cm/s. Volumetric oxygen mass transfer coefficient has increased with the increase in superficial air velocity and vibrational velocity. Empirical correlation relating kLa with these variables was developed. The volumetric oxygen mass transfer coefficient values in the three-phase pulsed plate column are found to be similar or higher than the literature reported values for conventional two-phase pulsed plate columns. The values of volumetric oxygen mass transfer coefficients in the three-phase pulsed plate column are of higher order of magnitude than the literature reported values of volumetric oxygen mass transfer coefficient for many other three-phase gas-liquid-solid reactors. The pulsed plate column with fixed bed of solids is proven to have all the potential to be used as an aerobic bioreactor with immobilized cells due to its better gas-liquid mass transfer characteristics.

Combined effect of plate pulsation parameters and phenol concentrations on the phenol removal efficiency of a pulsed plate bioreactor with immobilized cells

Continuous aerobic biodegradation of phenol in synthetic wastewater with phenol at different concentrations (200, 300, 500, 800 and 900 ppm) was carried out in a pulsed plate column, which is used as a bioreactor with immobilised cells of Nocardia hydrocarbonoxydans (NCIM 2386) at a dilution rate of 0.4094 h(-1) and amplitude of 4.7 cm at various frequencies of pulsation (0, 0.25, 0.5, 0.75 and 1 s(-1)). The effect of frequency of pulsation on the steady state performance of the bioreactor for phenol biodegradation at different influent concentrations was studied. Percentage degradations were observed to be a combined effect of volumetric phenol loading, reactor residence time, mass transfer limitations and phenol inhibition effect. At 500 ppm influent phenol concentration the effect of frequencies of pulsation on the steady state percentage degradation at different amplitudes was studied. The percentage degradation increased with increase in frequency and almost 100% degradation was achieved at 0.75 s(-1), 0.5 s(-1) or 0.25 s(-1), with 3.3, 4.7 or 6.0 cm amplitudes respectively and hence the vibrational velocity (amplitude*frequency) was found to influence the steady state performance of the reactor. It was found that optimum vibrational velocities need to be fixed for maximum removal efficiency of the bioreactor depending on the influent phenol concentration.

Dependence of Holdup on Height in a Pulsed Plate Column Based on Binary Liquid‐Liquid Equilibrium Data

AbstractHoldup has been measured at various frequencies, amplitudes, continuous and dispersed phase flow rates for binary systems in a pulsed plate column capable of providing samples at various heights. The binary systems have been so selected as to cover a wide spectrum of interfacial tensions. Dispersed phase holdup was found to increase with height in a logarithmic fashion at conditions away from the flooding point and to become almost invariant with height near flooding conditions. The interfacial tension of the binary system has a large effect on the dispersed phase holdup. In systems having low interfacial tension, a small increase in any of the parameters can increase the holdup significantly and lead to flooding. In systems having high interfacial tension, on the other hand, variations in system parameters do not affect system performance significantly.

Back Mixing and Optimization of Pulsed Plate Column Employing the Central Composite Rotatable Design

Back Mixing and Optimization of Pulsed Plate Column Employing the Central Composite Rotatable Design

Dispersed phase holdup and drop size distribution in pulsed plate columns

AbstractDispersed phase holdup was measured in a pulsed plate column for the kerosene‐water system under binary conditions and under solute transfer from dispersed to continuous and continuous to dispersed phases. The experimental data were satisfactorily modelled through a recirculation regime model.The drop size distribution, measured by a photographic technique, exhibited a multinodal character at low agitation rates and high dispersed phase flow rate. Sauter mean drop diameter was found to depend on the agitation rate, the dispersed phase flow rate, the mass transfer direction and the plate free area. Correlations for d32 and the interfacial area were presented using Kolmogoroff's isotropic turbulence model.

THE DYNAMICS OF PULSED PLATE EXTRACTION COLUMNS PART 2 DROPLET SIZE STUDIES IN THE ABSENCE OF MASS TRANSFER

ABSTRACT Published droplet size data for the system 30X TBP/OK - 2M aqueous nitric acid have been re-evaluated and compared with new measurements for the system 2 OX TBP/OK - 3M aqueous nitric acid. Correlations are presented for the Sauter mean and the dispersed phase holdup. At frequencies in excess of 1.5 Hz, pulsed plate columns tend to operate in the continuous dispersion regime and dvs increases linearly with holduo provided that the column internals ara not wetted by the dispersed phase, so that dvs = dovs + mx In this expression, m is a constant for a given system and is a measure of the rate of increase of droplet size with holdup. The term do vs+ mx is the characteristic droplet size, i.e. the limiting value of dvsat substantially zero holdup and is a function of the system properties and the pulse frequency and amplitude. In the case of the 20% TBP/OK system, it was found that equation (2) only described the variation of droplet size with holdup provided that the additional requirement (2fA) >4 × 10−2ms−1was met.This is thought to reflect the tendency for the sieve plates to promote droplet coalescence when (2fA) < 4 × 10−2ms−1. At pulse frequencies less than 1.5 Hz, mixer- settler type operation is apparent and is accompanied by considerable droplet coalescence during each pulse cycle. In this situation, the mean droplet size becomes larger and independent of holdup so that dvs becomes synonymous with do vsand, for a given system, depends only upon the pulse frequency and amplitude. These results are discussed in the context of the wetting characteristics of the column internals.There is evidence that the latter plays a major part in droplet recombination processes, and gross coalescence induced by wetting can be more significant than simple interdroplet coalescence. Until the wetting characteristics of column internals can be taken into account quantitatively, the present results should be considered specific to the equipment and extraction systems employed.

Measurement and modelling of droplet coalescence and breakage in a pulsed‐plate extraction column

AbstractDroplet coalescence and breakage rats in a pulsed‐plate extraction column have been measured using the colorimetric method of Hamilton and Pratt (1980). The results were interpreted in terms of rate constants, defined appropriately for the mixer‐settler and emulsion regions of operation respectively, using a discrete population balance model. It is shown that the resulting values of these constants can be used to predict accurately the steady‐state droplet‐size distribution and apparent coalescence rate. Computations for a typical extraction system indicated that the effect of polydispersivity on performance is surprisingly small for the pulsed plate column.

Effect of column diameter on backmixing in pulsed plate columns

Effect of column diameter on backmixing in pulsed plate columns

Axial dispersion in a pulsed plate column

AbstractA technique involving the indicator colour change in an acidbase reaction has been used to measure axial dispersion coefficients in a 15 cm diameter pulsed column. Data have been obtained mainly for single phase (aqueous) flow with two different types of plate at two different spacings. With coarsely perforated plates, the dispersion coefficient is proportional to (amplitude)2 times frequency, but semicircular unperforated baffle plates show a dependence on amplitude times frequency. These results are critically compared with published data, and two types of flow regime for axial dispersion are indicated.

Studies on the Pulsed Plate Column

Variations of the concentration of the continuous phase in the pulsed plate column were measured in the experiments on the extraction of acetic acid from methylisobutyl ketone by means of water.In this column, the longitudinal mixing was very intensive. The variation of the concentration was approximated on the assumption that the backmixing diffusivity was constant throughout the column.Capacity coefficient eliminated from the effect of the longitudinal mixing and the backmixing diffusivity were calculated in the present work.It was concluded that the decrease of extraction efficiency in the lower range of operating condition was caused by the longitudinal mixing.

Developments in Horizontal Pulsed Contactors for Liquid-Liquid Extraction Processes

An air-pulsed horizontal mixer-settler is described along with a horizontal pulsed-plate column which uses a single air pulse line regardless of the number of stages. Experimental setups and methods of operation are described and mass transfer data are given and discussed. It is concluded that the air- pulsed mixersettler and the horizontal pulse column perform comparably with conventional equipment. Air-pulsing gives an advantage in corrosive and radioactive processing. The horizontal pulse column offers advantages over other horizontal contactors in ease of construction, maintenance, and stability of operation, and cascades are more compact, saving on shielding costs, (T.R.H.)