Dissolution of a Carbon Dioxide Bubble in a Vertical Pipe

2007 ◽  
Author(s):  
Satoru Abe ◽  
Hideaki Okawa ◽  
Shigeo Hosokawa ◽  
Akio Tomiyama
Keyword(s):  
Carbon Dioxide ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Relative Velocity ◽  
Bubble Diameter ◽  
Bulk Liquid ◽  
Vertical Pipe ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Millipore Water

Dissolution of single carbon dioxide (CO2) bubbles in a vertical pipe of 25 mm in diameter are measured to examine the effects of the ratio λ of sphere–volume equivalent bubble diameter d to pipe diameter D, liquid Reynolds number ReL and surfactants on mass transfer. The bubble diameter d and Reynolds number ReL are varied from 5.0 to 26 mm (λ = 0.20 − 1.0) and from 0 to 3100, respectively. Millipore water, tap water and water contaminated with Triton X–100 are used for the liquid phase. Mass transfer coefficients kL are evaluated from changes in d. The kL decreases with increasing λ for bubbles in stagnant millipore water because of the decrease in bubble rising velocity due to the wall effect. Measured Sherwood numbers Sh do not depend on ReL because a turbulent fluctuation velocity in bulk liquid flow is much smaller than a relative velocity between a bubble and liquid. The mass transfer correlation for a bubble in a stagnant liquid proposed by Johnson et al. is applicable to a bubble in pipe flow, provided that a correct relative velocity between a bubble and liquid is substituted in the correlation. Due to the retardation of capillary wave, mass transfer coefficients for bubbles in contaminated water becomes smaller than those in millipore and tap waters.

Mass Transfer From a Bubble in a Vertical Pipe

2011 ◽  
Author(s):  
Shogo Hosoda ◽  
Ryosuke Sakata ◽  
Kosuke Hayashi ◽  
Akio Tomiyama
Keyword(s):  
Carbon Dioxide ◽  
Mass Transfer ◽  
Bubble Diameter ◽  
Vertical Pipe ◽  
Oblate Spheroidal ◽  
Wide Range ◽  
Bubble Sizes ◽  
Small Bubbles ◽  
Taylor Bubbles

Mass transfer from single carbon dioxide bubbles in a vertical pipe is measured using a stereoscopic image processing method to develop a mass transfer correlation applicable to a wide range of bubble and pipe diameters. The pipe diameters are 12.5, 18.2 and 25.0 mm and the bubble diameter ranges from 5 to 26 mm. The ratio, λ, of bubble diameter to pipe diameter is therefore varied from 0.2 to 1.8, which covers various bubble shapes such as spherical, oblate spheroidal, wobbling, cap, and Taylor bubbles. Measured Sherwood numbers, Sh, strongly depend on bubble shape, i.e., Sh of Taylor bubbles clearly differs from those of spheroidal and wobbling bubbles. Hence two Sherwood number correlations, which are functions of the Peclet number and the diameter ratio λ, are deduced from the experimental data: one is for small bubbles (λ < 0.6) and the other for Taylor bubbles (λ > 0.6). The applicability of the proposed correlations for the prediction of bubble dissolution process is examined through comparisons between measured and predicted long-term bubble dissolution processes. The predictions are carried out by taking into account the presence of all the gas components in the system of concern, i.e. nitrogen, oxygen and carbon dioxide. As a result, good agreements for the dissolution processes for various bubble sizes and pipe diameters are obtained. It is also demonstrated that it is possible to evaluate an equilibrium bubble diameter and instantaneous volume concentration of carbon dioxide in a bubble using a simple model based on a conservation of gas components.

Experimental Investigation of Enhanced Absorption of Carbon Dioxide in Diethanolamine in a Microreactor

2013 ◽  
Author(s):  
Harish Ganapathy ◽  
Amir Shooshtari ◽  
Serguei Dessiatoun ◽  
Mohamed Alshehhi ◽  
Michael M. Ohadi
Keyword(s):  
Carbon Dioxide ◽  
Mass Transfer ◽  
Natural Gas ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Absorption Efficiency ◽  
Optimum Operating ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Liquid Absorption

Natural gas in its originally extracted form comprises carbon dioxide and hydrogen sulfide as small, but non-negligible fractions of its dominant component, methane. Natural gas in the above form is typically subjected to a sweetening process that removes these acid gases. Microscale technologies have the potential to substantially enhance mass transport phenomena on account of their inherently high surface area to volume ratio. The present work reports the mass transfer characteristics during gas-liquid absorption in a microreactor. The absorption of CO2 mixed with N2 into aqueous diethanolamine was investigated in a single straight channel having a hydraulic diameter of 762 micrometer and circular cross-sectional geometry. The performance of the reactor was characterized with respect to the absorption efficiency and mass transfer coefficient. Close to 100% absorption efficiency was obtained under optimum operating conditions. Shorter channel lengths were observed to yield enhanced values of mass transfer coefficient on account of the improved utilization of the liquid reactants’ absorption capacity for a given reactor volume. In comparison to the 0.5 m long channel, the mass transfer coefficients with the 0.3 m and 0.1 m channels were higher on an average by 35.2% and 210%, respectively. Parametric studies investigating the effects of phase superficial velocity, liquid and gas phase concentration were performed. The mass transfer coefficients achieved using the present minichannel reactor were 1–3 orders of magnitude higher than that reported using conventional gas-liquid absorption systems.

scholarly journals Extraction of Clove and Vetiver Oils with Supercritical Carbon Dioxide: Modeling and Simulation

2007 ◽  
Vol 1 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Julian Martínez ◽  
Paulo T.V. Rosa ◽  
M. Angela A. Meireles
Keyword(s):  
Carbon Dioxide ◽  
Mass Transfer ◽  
Large Scale ◽  
Raw Material ◽  
Feed Ratio ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Extraction Curve ◽  
Kinetics Of

The kinetics of supercritical fluid extraction (SFE) of clove and vetiver oils using carbon dioxide as solvent was studied, in order to establish an efficient method to predict extraction curves on large scale. The mass transfer model of Sovová was used to adjust the experimental SFE data, which were obtained at 100 bar and 35 °C for clove and 200 bar and 40 °C for vetiver, using extraction columns of different geometry and solvent flow rates. Some other process parameters, such as bed density and porosity, solvent to feed ratio and solvent velocity were kept constant from one experiment to another, in order to verify if the mass transfer coefficients adjusted by the model varied. The results show that the model of Sovová was able to predict an overall extraction curve for clove from data obtained with twenty times less raw material, since the mass transfer coefficients remained the same and the predicted curves were similar to the observed ones. For vetiver, the simulation was not as effective, probably due to the effects of transport properties on the process.

Interface Tracking Simulation of Mass Transfer From a Dissolving Bubble

2011 ◽  
Author(s):  
Kosuke Hayashi ◽  
Akio Tomiyama
Keyword(s):  
Carbon Dioxide ◽  
Mass Transfer ◽  
Volume Change ◽  
Empirical Models ◽  
Interface Tracking ◽  
Vertical Pipe ◽  
Transfer Coefficients ◽  
Species Concentration ◽  
Tracking Method ◽  
Benchmark Tests

An interface tracking method for predicting bubble dissolution process is proposed. A non-diffusive scheme for advecting species concentrations is adopted to accurately compute the volume change due to mass transfer. The applicability of the proposed method is examined through several benchmark tests, i.e. mass transfer from a static bubble and that from free rising bubbles. Predicted species concentration distributions and mass transfer coefficients agree well with theoretical and empirical models. Dissolution of single carbon dioxide bubbles in a vertical pipe filled with water is also simulated. The bubbles consist only of carbon dioxide, and nitrogen and oxygen are initially dissolved in water. The volume change due to dissolution of carbon dioxide from the bubbles and evaporation of nitrogen and oxygen from water are well predicted.

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