Mass Transfer Studies in a Novel Perforated Plate Bubble Column

2010 ◽  
Vol 8 (1) ◽  
Author(s):  
S. Dhanasekaran ◽  
T. Karunanithi
Keyword(s):  
Mass Transfer ◽  
Liquid Velocity ◽  
Bubble Column ◽  
Perforated Plate ◽  
Gas Velocity ◽  
Plate Spacing ◽  
Mass Transfer Studies ◽  
Superficial Gas Velocity ◽  
Superficial Liquid Velocity

This investigation reports the experimental and theoretical results carried out to evaluate the volumetric mass transfer coefficient (kLa) in a novel hybrid rotating and reciprocating perforated plate bubble column. Countercurrent condition is performed. kLa is studied by the absorption of oxygen from air into deoxygenated water at room temperature (27 ± 1°C). Effects of agitation level, superficial gas velocity, superficial liquid velocity and plate spacing on kLa were analyzed and found to be significant. With an increase in agitation level at a constant superficial gas and liquid velocities, the breakage process of gas bubbles starts to be more pronounced and intensive oxygen mass transfer occurs. Hence, kLa increases sharply. kLa increases with an increase in superficial gas velocity, due to higher gas holdup and the enhanced breakup of bubbles. Similarly, kLa increases with an increase in superficial liquid velocity and the effect is found to be significant. When plate spacing is decreased (by increasing the number of plates), it is observed that the kLa increases at higher superficial gas velocity and agitation level. Correlation is developed for the determination of kLa and found to concur with experimental results. This correlation can be used for the determination of kLa for this hybrid column with 95% accuracy within the range of variables investigated in this present study.

Bubble Diameter and Effective Interfacial Area in a Novel Hybrid Rotating and Reciprocating Perforated Plate Bubble Column

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Dhanasekaran S ◽  
Karunanithi T
Keyword(s):  
Liquid Velocity ◽  
Bubble Column ◽  
Bubble Diameter ◽  
Perforated Plate ◽  
Interfacial Area ◽  
Gas Velocity ◽  
The Mean ◽  
Superficial Gas Velocity ◽  
Plate Column

This investigation reports on the experimental and theoretical investigation carried out to evaluate the bubble diameter and effective interfacial area in a novel Hybrid Rotating and Reciprocating Perforated Plate Bubble Column. Air-water system is used in this investigation. Countercurrent mode is employed. The effects of agitation level, superficial gas velocity and superficial liquid velocity on the bubble size distribution are studied. The mean bubble diameter is predicted using photographic technique. A simple correlation is developed for the determination of mean bubble diameter. It is found that the mean bubble diameter values for hybrid column are 1.8 to 2.5 times smaller when compared with conventional reciprocating plate column. The interfacial area is calculated based on the experimental results of the gas holdup and bubble diameter. Effects of agitation level, superficial gas velocity, superficial liquid velocity and plate free area on the interfacial area have been investigated. Correlations are developed for the determination of interfacial area for both mixer-settler and emulsion regions. It could be noted that the interfacial area for the hybrid column is 3 to 6 times higher in both mixer-settler region and emulsion region than that of conventional reciprocating plate column which is quite large.

Statistical Analysis of Experimental Variables on Gas Holdup in Novel Bubble Column Using Box-Behnken Design

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
S Dhanasekaran ◽  
T Karunanithi
Keyword(s):  
Liquid Velocity ◽  
Bubble Column ◽  
Perforated Plate ◽  
Water System ◽  
Gas Holdup ◽  
Bubble Columns ◽  
Interactive Effects ◽  
Stirred Tank Reactors ◽  
Plate Spacing ◽  
Superficial Gas Velocity

A novel hybrid rotating and reciprocating perforated plate bubble column is designed indigenously. The novelty lies in combining the effects of stirred tank reactors, bubble columns and reciprocating plate columns using bevel gear arrangement. Box-Behnken experimental design in response surface methodology is chosen to predict the relationship between experimental variables and desired response of gas holdup. Agitation level, superficial gas velocity, superficial liquid velocity, perforation diameter and plate spacing are used as experimental variables. Air-water system is used in this investigation. The linear, square and interactive effects of experimental variables on gas holdup are studied. The F-test and P values were used to identify the experimental variables that significantly impact gas holdup.

scholarly journals The Effect of a Modified Downcomer on the Hydrodynamics in an External Loop Airlift Reactor

2006 ◽  
Author(s):  
Samuel T. Jones ◽  
Theodore J. Heindel
Keyword(s):  
Liquid Velocity ◽  
Bubble Column ◽  
Gas Holdup ◽  
Area Ratio ◽  
Airlift Reactor ◽  
Open Area ◽  
Gas Velocity ◽  
External Loop ◽  
Superficial Gas Velocity ◽  
Superficial Liquid Velocity

Gas holdup and superficial liquid velocity in the downcomer and riser are studied for an external loop airlift reactor with an area ratio of 1:16. Two downcomer configurations are investigated consisting of the downcomer open or closed to the atmosphere. Experiments for these two configurations are carried out over a range of superficial gas velocities from UG = 0.5 to 20 cm/s using three aeration plates with open area ratios of 0.62, 0.99 and 2.22%. These results are compared to a bubble column operated with similar operating conditions. Experimental results show that the gas holdup in the riser does not vary significantly with a change in the downcomer configuration or bubble column operation, while a considerable variation is observed in the downcomer gas holdup. Gas holdup in both the riser and downcomer are found to increase with increasing superficial gas velocity. Test results also show that the maximum gas holdup for the three aerator plates is similar, but the gas holdup trends are different. The superficial liquid velocity is found to vary considerably for the two downcomer configurations. However, for both cases the superficial liquid velocity is a function of the superficial gas velocity and/or the flow condition in the downcomer. These observed variations are independent of the aerator plate open area ratio. When the downcomer vent is open to the atmosphere, the superficial liquid velocity is initially observed to increase with increasing superficial gas velocity until the onset of choking occurs in the downcomer. Increasing the superficial gas velocity beyond the onset of choking increases the effect of choking and decreases the superficial liquid velocity. Once maximum choking is reached, the superficial liquid velocity becomes independent of the superficial gas velocity. When the downcomer vent is closed to the atmosphere, the superficial liquid velocity is initially observed to decrease with increasing superficial gas velocity as choking in the downcomer is immediately present. Once maximum choking occurs, the superficial liquid velocity once again becomes independent of the superficial gas velocity.

Effect of Drag-Reducing Agent on Slug Characteristics in Multiphase Flow in Inclined Pipes

1999 ◽  
Vol 121 (2) ◽  
pp. 86-90 ◽  
Author(s):  
C. Kang ◽  
W. P. Jepson ◽  
M. Gopal
Keyword(s):  
Pressure Drop ◽  
Multiphase Flow ◽  
Liquid Film ◽  
Froude Number ◽  
Liquid Velocity ◽  
Translational Velocity ◽  
Gas Velocity ◽  
Superficial Gas Velocity ◽  
Inclined Pipes ◽  
Superficial Liquid Velocity

The effect of drag-reducing agent (DRA) on multiphase flow in upward and downward inclined pipes has been studied. The effect of DRA on pressure drop and slug characteristics such as slug translational velocity, the height of the liquid film, slug frequency, and Froude number have been determined. Experiments were performed in 10-cm i.d., 18-m long plexiglass pipes at inclinations of 2 and 15 deg for 50 percent oil-50 percent water-gas. The DRA effect was examined for concentrations ranging from 0 to 50 ppm. Studies were done for superficial liquid velocities between 0.5 and 3 m/s and superficial gas velocities between 2 and 10 m/s. The results indicate that the DRA was effective in reducing the pressure drop for both upflow and downflow in inclined pipes. Pressure gradient reduction of up to 92 percent for stratified flow with a concentration of 50 ppm DRA was achieved in ±2 deg downward inclined flow. The effectiveness of DRA for slug flow was 67 percent at a superficial liquid velocity of 0.5 m/s and superficial gas velocity of 2 m/s in 15 deg upward inclined pipes. Slug translational velocity does not change with DRA concentrations. The slug frequency decreases from 68 to 54 slugs/min at superficial liquid velocity of 1 m/s and superficial gas velocity of 4 m/s in 15 deg upward inclined pipes as the concentration of 50 ppm was added. The height of the liquid film decreased with the addition of DRA, which leads to an increase in Froude number.

scholarly journals Effects of Liquid Velocity on Pressure Gradient, Slip and Interfacial Friction Factor in Annular Flow in Horizontal Pipe

2018 ◽  
Vol 3 (8) ◽  
pp. 5
Author(s):  
Uche Osokogwu
Keyword(s):  
Pressure Gradient ◽  
Friction Factor ◽  
Annular Flow ◽  
Liquid Velocity ◽  
Interfacial Friction ◽  
Gas Velocity ◽  
Horizontal Pipe ◽  
Mixture Density ◽  
Superficial Gas Velocity ◽  
Superficial Liquid Velocity

Experimental investigations on annular flow behaviour in two-phase (air/water) flow in horizontal pipe were conducted using 2-inch (0.0504m) with a total length of 28.68m closed loop system. The emphasis from the experiments were on pressure gradient, slip and interfacial friction factor in annular flow. For interfacial friction factor, the entrainment, gas quality, the droplets and slip mixture density values were obtained through the experimental results which were substituted to determine it. In all, effects of liquid velocity were felt, as increase in superficial liquid velocity, increases the interfacial friction factor and pressure gradient in annular flow in horizontal pipes. More so, increase in superficial gas velocity, reduces the interfacial friction factor. Thus, interfacial friction factor decreases with increases in superficial gas velocity, while the pressure gradient increases with increase in superficial liquid velocity. The lower the superficial liquid velocity, the higher the slip but the lower the pressure gradient. Likewise, the lower the superficial liquid velocity, the more ripple waves obtained while the higher the superficial liquid velocity, the more disturbance waves in annular flow in horizontal pipe from the experiments.

CFD-PBM simulation of hydrodynamics of microbubble column with shear-thinning fluid

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Xi Zhang ◽  
Ping Zhu ◽  
Shuaichao Li ◽  
Wenyuan Fan ◽  
Jingyan Lian
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Radial Direction ◽  
Liquid Velocity ◽  
Bubble Column ◽  
Gas Holdup ◽  
Gas Velocity ◽  
Gas Distributor ◽  
Superficial Gas Velocity ◽  
The Right

Abstract A numerical simulation was performed to study the hydrodynamics of micro-bubble swarm in bubble column with polyacrylamide (PAM) aqueous solution by using computational fluid dynamics coupled with population balance models (CFD-PBM). By considering rheological characteristics of fluid, this approach was able to accurately predict the features of bubble swarm, and validated by comparing with the experimental results. The gas holdup, turbulent kinetic energy and liquid velocity of bubble column have been elucidated by considering the influences of superficial gas velocity and gas distributor size respectively. The results show that with the rise of the superficial gas velocity, the gas holdup and its peak width increase significantly. Especially, the curve peak corresponding to high gas velocity tends to drift obviously toward the right side. Except for the occurrence of a smooth holdup peak at the column center under the condition of the moderate distributor size, the gas holdups for the small and large distributor sizes become flat in the radial direction respectively. The distribution of turbulent kinetic energy presents an increasingly asymmetrical feature in the radial direction and also its variation amplitude enhances obviously with the rise of gas velocity. The increase in gas distributor size can enhance markedly turbulent kinetic energy as well as its overall influenced width. At the low and moderate superficial gas velocity, the curves of the liquid velocity in radial direction present the Gaussian distributions, whereas the perfect distribution always is broken in the symmetry for high gas velocity. Both liquid velocities around the bubble column center and the ones near both column walls go up consistently with the gas distributor size, especially near the walls at the large distributor size condition.

Effect of Vibrating Sparger on Mass Transfer, Gas Holdup, and Bubble Size in a Bubble Column Reactor

2013 ◽  
Vol 11 (1) ◽  
pp. 47-56 ◽  
Author(s):  
Laleh Hadavand ◽  
Ali Fadavi
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Vibration Frequency ◽  
Bubble Size ◽  
Bubble Column ◽  
Gas Holdup ◽  
Bubble Column Reactor ◽  
Gas Velocity ◽  
Superficial Gas Velocity

Abstract Bubble size has a key role in gas holdup and mass transfer in bubble column reactors. In order to have small and uniform bubbles, a new structure was designed; the reactor operates in two modes, with vibrating sparger and conventional bubble column in which sparger is fixed. In vibrating mode, the sparger vibrates gently during gas entering. The vibrating sparger performs like a paddle, resulting in a forced recirculation of gas–liquid inside the reactor; moreover, the bubble detachment is accelerated. The superficial gas velocity was between 0.003 and 0.013 ms− 1, and the vibration frequency was changed between 0 and 10.3 Hz. The bubble size was measured at three various positions of the reactor height by photographic method and using MATLAB 7.0.1 software. The mass transfer coefficient was determined by means of the dynamic gassing-out method. The results show that the bubbles were bigger in vibrating mode than those working without vibration. The bubble size decreases with increase in height from sparger. Gas holdup increased with increase in superficial gas velocity and vibration frequency. The effect of vibration increased the gas holdup with an average of 70% for all superficial gas velocities. Volumetric mass transfer coefficient was almost stable as vibration frequency increased.

scholarly journals Gas–liquid mass transfer using advanced optical probe in a mimicked FT slurry bubble column

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Lu Han ◽  
Premkumar Kamalanathan ◽  
Muthanna H. Al-Dahhan
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Bubble Column ◽  
Operating Pressure ◽  
Gas Velocity ◽  
Liquid Phase Mass Transfer ◽  
Solids Loading ◽  
Superficial Gas Velocity ◽  
Reactor Models

AbstractGas-liquid volumetric liquid-phase mass transfer coefficient (kLa) was studied in a slurry bubble column at the conditions mimicking Fischer–Tropsch synthesis. To avoid the hydrodynamic disturbances due to the gas switching, oxygen enriched air dynamic absorption method was used. Influence of reactor models (CSTR, ADM and RCFD) on the volumetric mass transfer coefficient was investigated. Effect of operating pressure, superficial gas velocity and solids loading were investigated. From the reactor models investigated, it is recommended to use ADM model for kLa study. If the CSTR model is used, applicability of the model should be checked. With increase in the superficial gas velocity and operating pressure, volumetric liquid-phase mass transfer coefficient increases, while it decreases with the solids loading corroborating with the literature.

Foam Breakup in CFC/GLCC© System

2018 ◽  
Author(s):  
Ramin Dabirian ◽  
Ardian Nababan ◽  
Ilias Gavrielatos ◽  
Ram S. Mohan ◽  
Ovadia Shoham
Keyword(s):  
Liquid Velocity ◽  
Petroleum Industry ◽  
Life Time ◽  
Production Operation ◽  
Gas Velocity ◽  
Operational Conditions ◽  
Break Up ◽  
Superficial Gas Velocity ◽  
Churn Flow ◽  
Superficial Liquid Velocity

Foaming is a common phenomenon in the petroleum industry. Foams can be desirable for drilling applications, whereby the cutting bits are lubricated, and cuttings are carried up to the surface. However, foam can be undesirable for production operation, which hinders the gas-liquid separation process. Experimental investigation has been conducted on foam break-up in a standalone Churn Flow Coalescer (CFC), a standalone Gas Liquid Cylindrical Cyclone (GLCC©) and a combined CFC/GLCC© system. A 1-inch Foam Characterization Rig (FCR) is utilized. The FCR is equipped with a 3-inch diameter CFC, which is connected in series to a 2-inch diameter GLCC©. A total of 30 experimental runs are conducted for both Gas Mode (GM) and Liquid Mode (LM) operations. A surfactant (SI-403) with concentration of 0.025%, superficial liquid velocities of 0.1 and 0.15 m/s and superficial gas velocities of 0.5, 1, and 1.5 m/s are used in the experiments. The experimental results show that for the GM operation, the foam break-up in combined CFC/GLCC© system is more efficient than that in the standalone GLCC©, for the same flow conditions. Lowering the superficial gas velocity or increasing the superficial liquid velocity produce less stable foam, larger gas bubbles and lower half-life time. The outlet clear liquid flow rate (with no foam) under the LM operation increases with increasing superficial liquid velocity or decreasing superficial gas velocity. The recommended operational conditions for the CFC are at low superficial gas velocities, lower than the transition boundary to churn flow in the CFC.

Impact of Dense Internals on Fluid Dynamic Parameters in Bubble Column

2018 ◽  
Vol 16 (12) ◽  
Author(s):  
Dinesh V. Kalaga ◽  
Vishal Bhusare ◽  
H.J. Pant ◽  
Jyeshtharaj B. Joshi ◽  
Shantanu Roy
Keyword(s):  
Liquid Phase ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Liquid Velocity ◽  
Bubble Column ◽  
Vertical Tube ◽  
Gas Holdup ◽  
Gas Velocity ◽  
Cross Sectional ◽  
Superficial Gas Velocity

Abstract Industrial gas-liquid processes such as oxidation, hydrogenation, Fischer-Trospch synthesis, liquid-phase methanol synthesis, and nuclear fission are exothermic in nature; the reactor of choice for such processes is, therefore, a bubble column equipped with heat exchanging internals. In addition to maintaining the desired process temperature, the heat exchanging vertical tube internals are used to control flow structures and liquid back mixing. The present work reports the experimentally measured gas hold-up, mean liquid velocity and liquid phase turbulent kinetic energy, using the Radioactive Particle Tracking (RPT) technique, in a 120 mm diameter bubble column equipped with dense vertical tube internals covering 23 % of the total cross-sectional area of the column. The effect of superficial gas velocity (44–265 mm/s) on gas hold-up, mean liquid velocity and turbulent kinetic energy is presented and discussed. It has been inferred from the experimental results that the vertical tube internal located at the center of the column plays a vital role in affecting the hydrodynamics when compared to the conventional internal configurations reported in the literature. For the chosen dense internal configuration, the cross-sectional distribution of the gas holdup, mean liquid velocity and turbulent kinetic energy show asymmetry for all the superficial gas velocities investigated. The overall gas holdup and the liquid turbulence increases with an increase in the superficial gas velocity. The strong liquid circulation velocities have been seen upon the insertion of the dense internals.

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