Oscillatory Baffled Column Research Articles

Enhancement of CO2 removal from flue gas in an oscillatory baffled column using potassium carbonate solution

One of the efficient methods for reducing CO2 emissions from flue gas streams in oil refineries and power plants is the CO2absorption process using alkali solution. Potassium carbonate (K2CO3) solution, as CO2 absorbent, was used in the present study due to its high CO2 absorption capacity. However, K2CO3 has a drawback which is represented by its slow reaction with CO2. To overcome this issue, an oscillatory baffled column (OBC) was utilized as a contactor to maintain a high degree of mixing in the CO2 absorption system and thereby increasing the reaction rate between K2CO3 and CO2 as well as enhancing the mass transfer rate. In this study the effect of different operation conditions of the process namely; inlet flue gas flow rate (15 % (v/v) CO2 balanced with N2) and oscillation conditions on CO2 absorption in a semi-batch OBC were investigated. The experiments were performed with range of modified Reynolds Number of Oscillation (Reo′ = 0⎼1450) and aeration rates (0⎼1 vvm) using K2CO3 (100 g/L, 0.72 M)0.1.8–3.5-fold of enhancement of CO2 absorption rates was achieved by using OBC with respect to that obtained by baffled column (BC) (only baffles without oscillation) and plane bubble column (PBC) (without baffles and oscillation), respectively.The use of K₂CO₃ as a solvent in an oscillating reactor (OBR) to remove CO₂ represents a new method due to the high reactivity of K₂CO₃ with CO₂, forming stable bicarbonate and carbonate compounds. OBR's enhanced mixing capabilities improve mass transfer rates and reaction efficiency, allowing for more effective CO2 capture compared to conventional reactors. This combination leverages the strengths of both the chemical reactivity of K₂CO₃ and the mechanical benefits of OBR, potentially leading to more efficient and scalable CO2 removal processes.

Comparative study of advanced oxidation treatment of tannery effluent in Multi-orifice Oscillatory Baffled Column with sono-catalytic treatment using Titanium Dioxide

<p>Treatment of tannery effluent is a key issue that requires novel research. The presented work is an attempt to carry out advanced oxidation process in a Multi-orifice Oscillatory Baffled Column using ozone as oxidizer and compare the extent of treatment with sono-catalytic treatment with TiO2 as catalyst. Studies have been carried out to understand the effect of treatment time, concentration of effluent and oscillation frequency upon ozonation and the effect of power of ultrasound, time of treatment and catalyst loading for sono-catalytic treatment. For ozonation the COD, BOD and TDS reduction obtained are 88.8%, 84.01%, 90.73% respectively and for sono-TiO2 treatment the reduction of COD, BOD and TDS obtained are 91.2%, 91.5%, 94%. Optimization and analysis of variables is carried out to identify the effective factors for treatment.</p>

Performance evaluation of oscillatory baffle Bunsen reactor in iodine sulfur thermochemical process for hydrogen production

<abstract> <p>Hydrogen is an environmentally attractive transportation fuel that can replace fossil fuels. The iodine-sulfur (I-S) thermo-chemical process involves three reaction steps. The Bunsen reaction is one of the main reaction steps of I-S process and plays an important role in defining overall process efficiency. Different types of reactors are being studied, including the oscillatory baffle Bunsen reactor. The reactor selection is based on process intensification and process integration, i.e., reaction and separation in the single equipment. Simulations are performed for two-dimensional cases by solving incompressible Navier-Stokes equations along with continuity equation, the geometry chosen is of single section in the column and diameter of 50 mm and baffle spacing of 50, 75,100 mm i.e. 1, 1.5 and 2 times the diameter of column and baffle free area 22%. The residence time distribution experiments are carried out in a metallic reactor with NaCl as a tracer operated at different frequencies, amplitudes and flow rates. D/uL is evaluated from experimental curves. The power per unit mass is compared for oscillatory baffled column and stirred tank for a semi-batch process. From the numerical simulations, good eddy interactions are present at higher frequencies and amplitudes and at a baffle spacing of 1.5 times the diameter of the column. Residence time distribution analysis gives a lower dispersion number at medium frequencies and higher amplitudes with constant flow rate. If the flow rates are high, then it is better to operate at higher frequencies and amplitudes to achieve plug flow behavior. Power per unit mass is less for oscillatory baffle column compared to the stirred tank of given configuration. With better mixing performance and less power per unit volume, the oscillatory baffle column is a good alternative to other columns.</p> </abstract>

Numerical Simulation of a Gas–Liquid Oscillatory Baffled Column Focusing on Hydrodynamics and Mass Transfer

Numerical Simulation of a Gas–Liquid Oscillatory Baffled Column Focusing on Hydrodynamics and Mass Transfer

Mixing Time and Scale‐up Investigation of a Moving‐Baffle Oscillatory Baffled Column

AbstractMixing time and scale‐up behavior were investigated for a moving‐baffle oscillatory baffled column (MB‐OBC). Computational fluid dynamics software was used to investigate the effects of the oscillation conditions and changes in the column scale on the dimensionless mixing time. The results indicate that small amplitudes combined with high frequencies are detrimental to the mixing efficiency and that the scale‐up of an MB‐OBC is linearly dependent on the column diameter. This work, in combination with previous studies, proves that the predictability of the hydrodynamic behavior during scale‐up is inherent to oscillatory baffled columns. This trait is desirable for adapting these columns for industrial‐scale applications.

Comparison of mixing performance between stationary-baffle and moving-baffle batch oscillatory baffled columns via numerical modeling

This paper presents a numerical comparison of the mixing performance between two configurations of batch oscillatory baffled column: the stationary-baffle column and the moving-baffle column. Computational fluid dynamic (CFD) software was used to investigate the effect of various oscillation conditions on fluid flow and mixing for both configurations. Population balance modeling was used to validate each column using droplet size distribution data for multiphase flow simulations. Column performance was evaluated in terms of power requirement, axial and radial flow dominance, and mixing time. The results suggest that better convective mixing occurs in stationary-baffle columns due to the increased axial velocity magnitudes produced for this configuration of column with respect to moving-baffle columns operating at the same oscillation frequency and amplitude.

Oscillatory power number, power density model, and effect of restriction size for a moving‐baffle oscillatory baffled column using CFD modelling

AbstractAlthough single‐hole oscillatory columns have been studied since the 1990s, to this day there is an absence of appropriate dimensionless groups to express the hydrodynamic conditions and power requirement for the moving‐baffle oscillatory baffled column (OBC). This paper uses computational fluid dynamic (CFD) software coupled with moving overset meshing to aid in the derivation of the first dimensionless oscillatory power number for OBCs. In terms of the moving‐baffle OBC, this work marks the first time a power density equation has been derived specifically to account for this column's unique hydrodynamic profile. Equations for period‐averaged Reynolds number and period‐averaged Strouhal numbers were developed to better estimate the fluid intensity within these moving‐baffle columns. This work serves as an example of how complex and challenging flow regimes, such as periodically oscillating flow, can be simplified and analyzed to produce appropriate design equations.

Application of Electrical Resistance Tomography in an Oscillatory Baffled Column for Gas-Liquid Two-Phase Flow

Oscillatory baffled column (OBC) has a high potential for industrial application especially contacting gas and liquid phase. However, there are still lacks of research regarding the dynamics of gas-liquid phase specifically on the visualization of internal flow. Electrical Resistance Tomography (ERT) technique has capabilities to visualize mixing process internally without invading the flow. The objective of this study is to investigate the gas-liquid mixing distribution in an OBC by applying tomography technique model ITS P2000 of ERT system. The parameters investigated are phase distribution, gas hold up and power density. The experimental work was carried out in an OBC with a diameter of 145 mm and 720 mm height. The column is consisted of four planes of sixteen stainless steel ERT electrodes. The results of the research have shown that 70 mm of oscillation amplitude and 2 Hz of oscillation frequency give the best result with 73% of gas hold up and 12433.39W/m3.

CFD population balance modeling and dimensionless group analysis of a multiphase oscillatory baffled column (OBC) using moving overset meshes

This paper presents a CFD model and hydrodynamic study of a moving-baffle oscillatory baffled column (moving-baffle OBC). This work marks the first instance that moving overset meshing was used to simulate agitator motion in a fluid system. Population balance results are validated with experimental data for the inverse-suspension of non-reactive aqueous acrylamide in Isopar oil. A comparison of the droplet size distributions produced via various multiphase simulation methods was performed, resulting in a better overall agreement with the experimental literature for simulations applying the volume of fluid (VOF) multiphase method. Hydrodynamic studies reveal patterns of local flow circulations and centermost axial currents in relation to agitator position. Examination of the dimensionless groups traditionally used to describe flow conditions for moving-baffle OBCs reveal a considerable discrepancy between the previously-defined oscillatory Reynolds number and oscillatory Strouhal number with numbers derived from fluid flow within the column. A numerical correction has been presented to illustrate the nonlinear effect of oscillation amplitude on fluid flow through the system and to provide a more realistic estimation of the Reynolds number and Strouhal number for the modeled moving-baffle OBC.

Intensification of ozonation processes in a novel, compact, multi-orifice oscillatory baffled column

A novel approach for the intensification of ozonation of water and wastewater is presented using a highly efficient and compact multi-orifice oscillatory baffled column (MOBC) ozonation contactor. The MOBC uniquely yielded full (i.e. 100%) use of the ozone supplied with a very short (2.25min) liquid contact time under continuous operation and reducing the need of further gas–liquid contacting equipment downstream from the MOBC. The increased performance of the MOBC ozonation reactor was benchmarked against a bubble column (BC) design and resulted in 20% increase on the rate of p-hydroxybenzoic acid (p-HBA) degradation, 75% increase in the rate of mineralisation of p-HBA per mole of ozone consumed, and 4.5–5.0-fold increase in the rate of mineralisation of p-HBA per mole of ozone supplied. This results from the very small size of bubbles (few hundreds of microns) and enhanced gas–liquid mass transfer and hold-up generated in the presence of small fluid pulsations and orifice baffles.

CO2 Dissolution and Design Aspects of a Multiorifice Oscillatory Baffled Column

Dissolution of CO2 in water was studied for a batch vertical multiorifice baffled column (MOBC) with varying orifice diameters (d0) of 6.4–30 mm and baffle open area (α) of 15–42%. Bubble size distributions (BSDs) and the overall volumetric CO2 mass transfer coefficient (KLa) were experimentally evaluated for very low superficial gas velocities, UG of 0.12–0.81 mm s–1, using 5% v/v CO2 in the inlet gas stream at a range of fluid oscillations (f = 0–10 Hz and x0 = 0–10 mm). Remarkably, baffles presenting large do = 30 mm and α = 36%, therefore in the range typically found for single-orifice oscillatory baffled columns, were outperformed with respect to BSD control and CO2 dissolution by the other baffle designs or the same aerated column operating without baffles or fluid oscillations. Flow visualization and bubble tracking experiments also presented in this study established that a small do of 10.5 mm combined with a small value of α = 15% generates sufficient, strong eddy mixing capable of generating and...

Effect of oscillation amplitude on velocity distributions in an oscillatory baffled column (OBC)

This paper presents a numerical study of the effect of oscillation amplitude in oscillatory baffled column (OBC) using computational fluid dynamics. The numerical work was carried out for single phase liquid flow for an unsteady 3-D model using commercial software, Fluent (2006). This work was concentrated on the effect of oscillation amplitude. Three amplitudes of 5, 10 and 15mm with constant frequency of 1Hz are applied. Vortex and cycle average velocities at different points are analyzed. The studies show the maximum velocity for 5mm, 10mm and 15mm in an OBC are 0.11m/s, 0.25m/s and 0.40m/s respectively in the first cycle of oscillation. At a constant frequency, greater oscillation amplitude displaces the liquid to a further distance and builds a larger vortex. Vortex length was 1.5 times bigger when oscillation amplitude changes from 5mm to 10mm and 2 times when the amplitude is triple from 5mm. The detailed validation is presented somewhere else; this research is focused on the effect of oscillation.

Evaluation of rate of cyclopentane hydrate formation in an oscillatory baffled column using laser induced fluorescence and energy balance

We report a novel method using laser induced fluorescence (LIF) for observing cyclopentane hydrate formation in an oscillatory baffled column (OBC). In LIF, a dye fluoresces in a hydrate system when induced by a laser; this highlights the areas in which hydrates are present, allowing the hydrate formation regimes to be identified and rates evaluated. Using temperature measurements of the system, the rates of hydrate formation are also determined by a thermal method. The work shows that there is a high correlation between the LIF and the thermal techniques in obtaining kinetic information on cyclopentane hydrate. The results indicate that there are possibly three mechanisms governing hydrate growth. With the absence of mixing, a film formation is observed. At high mixing intensities uniform droplet dispersion is resulted, where fluid mechanics is the controlling parameter. At low mixing conditions a combination of the two mechanisms co-exists, interfacial mechanics is thought to be the dominant factor. The trends in the rates of hydrate formation are different in each of these regimes.

Flotation in a novel oscillatory baffled column

This paper presents an evaluation of an oscillatory baffled column (OBC) as a novel flotation device. The cell is based on a standard column design but employs a novel agitation mechanism where a series of baffle plates are oscillated sinusoidally through the fluid. This type of agitation has been shown to produce a more evenly distributed shear rate in the cell and allows the effect of agitation on particle–bubble contacting to be decoupled from gas dispersion effects. The column was first characterised in terms of mixing and gas dispersion, before being flotation tested using a quartz-amine system. Results indicated that the OBC was able to improve the flotation rate constant by up to 60% for fine particles (<30 μm) and by between 30% and 40% for coarser particles, relative to a standard flotation column. Interestingly, optimal flotation performance was obtained at power intensities orders of magnitude lower than those found in similar studies in stirred systems. This is believed to arise from the even distribution of shear in the OBC together with the oscillatory motion of the fluid in the cell. This oscillatory motion does not contribute to the average power intensity in the fluid and therefore results in more fluid motion per unit energy than would be obtained in a conventional stirred system. The OBC was therefore able to significantly improve flotation rates at power intensities orders of magnitude lower than those found in conventional cells.

Oscillatory Flow Mixer for Pulp Bleaching

This paper reports the results of an investigation on the use of oscillatory baffled column as a mixer for pulp bleaching. Unbleached hardwood kraft pulp was bleached using hydrogen peroxide. Variables studied were oscillation frequency, oscillation amplitude, and pulp consistency. The mixing process was achieved by oscillating pulp suspension in a periodically baffled column at a certain frequency and amplitude. The mixing quality of pulp bleaching was quantified using mixing index. The results showed that mixing quality improved with oscillation frequency and amplitude, but decreased with pulp consistency. This typical device is very promising as a mixer for pulp bleaching.

Gas Holdup and Gas-Liquid Mass Transfer Investigations in an Oscillatory Flow in a Baffled Column

Gas holdup and gas-liquid mass transfer were investigated in a vertical baffled column. Pure carbon dioxide (C02) was used as the dispersed phase and tap water was used as the continuous phase. Gas holdup and mass transfer rate of C02 were measured under semi-batch condition, while the liquid phase was measured in batch mode. Gas holdup was estimated as the volume fraction of the gas in the two-phase mixture in the column. Mass transfer was expressed in terms of the liquid-side volumetric mass transfer coefficient (kLa). The effects of oscillation frequency, oscillation amplitude and gas flow rate on gas holdup andmass transfer were also determined. The results showed that a significant increase in gas holdup and mass transfer could be achieved in an oscillatory baffled column compared to a bubble column. Gas holdup and mass transfer were correlated as a function of power density and superficial gas velocity. Keywords: gas holdup, mass transfer coefficient, power density, superficial gas velocity

Simulation of oscillatory baffled column: CFD and population balance

In the present work, an attempt has been made to combine population balance and a CFD approach for simulating the flow in oscillatory baffled column (OBC). Three-dimensional Euler–Euler two-fluid simulations are carried out for the experimental data of Oliveira and Ni [2001. Gas hold-up and bubble diameter in a gassed oscillatory baffled column. Chemical Engineering Science 56, 6143–6148]. The experimental data include the average hold-up profile and bubble size distribution in the OBC. All the non-drag forces (turbulent dispersion force, lift force) and the drag force are incorporated in the model. The coalescence and breakage effects of the gas bubbles are modeled according to the coalescence by the random collision driven by turbulence and wake entrainment while for bubble breakage by the impact of turbulent eddies. Predicted liquid velocity and averaged gas hold-up are compared with the experimental data. The profile of the mean bubble diameter in the column and its variation with the superficial gas velocity is studied. Bubble size distribution obtained by the model is compared with the experimental data.

An investigation of the effect of viscosity on mixing in an oscillatory baffled column using digital particle image velocimetry and computational fluid dynamics simulation

Abstract In this paper, we examine the effect of viscosity on the performance of the oscillatory baffled column (OBC) using the digital particle image velocimetry (DPIV) technique and computational fluid dynamics (CFD) codes. A selection of Newtonian (1–210 cP) and shear thinning fluids is investigated. The effects of viscosity on mixing are carefully observed by analysing flow patterns generated by both the DPIV and CFD methods. A ratio of the plane-averaged axial over the radial velocity is defined to quantify such the viscosity effects. For the given geometry the velocity ratio approaches to 2 very quickly at increased oscillatory Reynolds numbers, regardless of the Newtonian and non-Newtonian fluids used. An empirical critical ratio of 3.5 is identified, below which the system mixes sufficiently. This would act as the guide for industrial applications where a viscous fluid is mixed in an aqueous solution in the OBC.

Characterization of a gas‐liquid OBC: Bubble size and gas holdup

AbstractA fundamental experimental study of gas‐liquid contacting in an oscillatory baffled column is presented focusing on the effect of fluid oscillation on gas holdup and bubble size. The results show that beyond a critical level of fluid oscillation the Sauter mean diameter of the dispersion is substantially reduced, while the gas holdup (and, thus, the residence time of the gas phase) increases significantly. The reduction of bubble size was described in terms of bubble breakage, caused by the interaction of the bubbles with eddies. The experimental results were modeled by applying Kolmogoroff's theory of isotropic turbulence. The steep increase in the gas holdup with oscillation was mainly due to bubble entrainment by large vortices, formed by the oscillatory flow in the presence of baffles. A semi‐theoretical expression, based on the forces acting on a bubble, was proposed, and was able to accurately match the experimental trends. The results also show that the gas‐liquid hydrodynamics are mainly governed by the oscillatory operating conditions, and independent of the type of gas sparger. © 2004 American Institute of Chemical Engineers AIChE J, 50: 3019–3033, 2004

Numerical and Experimental Investigations into The Effect of Gap Between Baffle and Wall on Mixing in an Oscillatory Baffled Column

We report our numerical and experimental investigation of the effect on mixing of implementing 0, 2, 4 and 6 mm gaps between the outer edge of baffles and the inner diameter of an Oscillatory Baffled Column (OBC). Large eddy simulation and digital particle image velocimetry techniques have been used to obtain the flow patterns and quantify the flow field and turbulence, such as the velocity ratio, integral length scale and mixing time scale versus the oscillatory Reynolds numbers. It is shown that the global mixing intensity and the turbulence length scale decrease, while the Kolmogorov time scale increases with increasing gap size in the range of experimental conditions tested in this work, which suggests a need for new configuration of OBC with baffle gap for certain applications involving particulates.