Gas Dissolution, Release, and Bubble Formation in Flotation Systems

Wang, Lawrence K.; Shammas, Nazih K.; Selke, William A.; Aulenbach, Donald B.

doi:10.1007/978-1-60327-133-2_2

Cited by 23 publications

(18 citation statements)

References 11 publications

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“…The column "Pressure" shows the pressure recorded after which the apparent viscosity no longer changed. As it was expected, the larger the volume of entrained air, the larger the pressure required to achieve full air dissolution in the liquid phase (see Table 1) (Elkey et al, 1994;Wang et al, 2010) and the larger the reduction of the rheological properties (Krieger, 1972). However, the experimental pressure values for which the rheological properties stabilized are higher than the theoretical ones required to achieve full dissolution.…”

Section: Capillary Numbermentioning

confidence: 73%

“…The solubility coefficient of air in water at 1.01 bar (atmospheric pressure) and 20 • C is 1.85%v/v (% volume of gas/volume of water) (Krofta and Wang, 2000). As the solubility coefficient varies linearly with barometric conditions (Wang et al, 2010), 1.84%v/v was used to compensate for the local altitude and calculate the theoretical minimum required pressure (Equation 3) to fully dissolve the air bubbles into the liquid phase of the paste. It should however be noted that in the evaluated cement pastes, the amount of water was sufficient to dissolve all air, a condition which may not be valid for concrete.…”

Section: Materials and Mixture Designmentioning

confidence: 99%

“…Where p is the partial pressure, k is Henry's law constant and C is the concentration of the dissolved gas in solution at equilibrium (Wang et al, 2010). Therefore, as the pressure increases, the capacity of water to carry dissolved air increases proportionally.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of Air Dissolution and Reappearance Under Pressure in Cement Pastes by Means of Rheology

2019

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Concrete pumping is the most used technique to transfer concrete from the mixer truck to the formwork. Numerous studies have been performed on the flow behavior of concrete in pipes, as well as the consequences of pumping on fluid and hardened concrete properties. One of the negative consequences of pumping concrete is a decrease in freeze-thaw resistance. This is caused by a decrease in air content and an increase in air bubble size, due to dissolution and reappearance of air and air bubble coalescence under pressure. This paper investigates the capability of rheology to understand air dissolution and reappearance in cement paste under combined action of pressure and flow. A majority of the air bubbles in the cement pastes show low capillary-numbers, indicating the applied stress is insufficient to overcome the surface tension. Removing air causes a decrease in viscosity (or shear stress), up to a certain threshold pressure sufficient for full dissolution of the air. For mixtures with small air bubbles, the sudden application of pressure causes an immediate decrease in viscosity or shear stress. Mixtures with larger bubbles display a more gradual decrease in viscosity with the application of pressure. At depressurization, the viscosity of the sample is recovered almost instantly, although in some cases the viscosity is not fully recovered. This can be attributed to either an immediate air loss or to a coarsening of the air-void system, resulting in less non-deformable air bubbles in the paste.

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Section: Capillary Numbermentioning

confidence: 73%

Section: Materials and Mixture Designmentioning

confidence: 99%

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Characterization of Air Dissolution and Reappearance Under Pressure in Cement Pastes by Means of Rheology

2019

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“…In this case, it would be expected that the rise time of the bubbles should be shorter than the time required for solidification of the molten weld pool. A simple treatment of the terminal velocity of a rising bubble in a fluid of known viscosity is given by Stoke's equation as [23] V…”

Section: Resultsmentioning

confidence: 99%

Keyhole-induced porosity in laser-arc hybrid welded aluminum

Ola

Doern

2015

Int J Adv Manuf Technol

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Keyhole-induced macro-porosity, which results from the collapse of the keyhole that formed by the reaction forces of metal vapors, is a major problem limiting laser and laser-arc hybrid weldability of age-hardenable aluminum alloys, such as AA2024-T3. The mechanism of porosity suggests that the weld metal solidifies more rapidly than the possible rise velocity of the gas bubbles that formed during keyhole collapse, resulting in severe porosity. The porosity behavior of AA2024-T3 during laser-arc hybrid welding was studied using microscopy and X-ray radiography techniques. Porosity-free welding of the alloy is attainable in the conduction mode welding, whereas porosity increased significantly with increased laser intensity during keyhole mode welding. Porosity was mostly severe when the beam was focused at the surface of the workpiece. The laser beam and the arc decouple from each other with increased laser-wire distance, affecting keyhole depth and porosity. In order to control porosity during laser-arc hybrid welding of aluminum alloys, the role of various welding parameters on the material's response should be balanced with the required weld geometry.

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“…A theoretical maximum based on calculation of the percent methane volume / water volume yields a ratio of 1:9.6, meaning that based on approximate value for a 100 m volume of Mediterranean seawater ascending from 3000 m to surface waters, exsolution of methane would provide a gas volume of approximately 960 m 3 (Yamamoto et al, 1976;Wang et al, 2010). Because vaporization is about 18 kJ/mol (Max & Johnson, 2011), the effects would be felt within the water mass as a whole, and the low-salinity water would be cooled further prior to separation of the more buoyant gas from the water.…”

Section: Discussion and Conceptual Modelmentioning

confidence: 99%

Submarine vortices derived from natural gas hydrate conversion: a mechanism for ocean mixing

Barnard

Max

Gualdesi³

2017

Medit. Mar. Sci.

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We propose that the source water for some abyssal undular vortices cored by cool, low-salinity water identified at depths in excess of 2,500 m in the deepwater region of the Eastern Mediterranean Basin may be related to conversion of natural gas hydrate (NGH) in abyssal marine sediments. The conditions for extensive formation of NGH in the gas hydrate stability zones (GHSZ) of the upper seafloor sediments existed in this region during previous glacial episodes when colder water supported a thicker GHSZ. Seafloor warming during the most recent interglacial caused thinning of the GHSZ at its base and has driven endothermic NGH dissociation that would have released large volumes of low-salinity water and gas that would tend to pond below the base GHSZ. Periodically, trapped low-salinity water and gas would be released into the sea through the overlying sediments. Buoyant low-salinity water masses, supersaturated with gas and locally containing free gas would ascend and introduce a dynamic element into an otherwise generally static environment. As a result of the interaction of the rise of this buoyant plume and Coriolis acceleration the ascending mass would begin to rotate and form a vortex tube in midwater. NGH conversion within the seafloor introduces large coherent masses of low-salinity, lower-temperature water containing a buoyant free gas fraction from near-surface reservoirs into the abyssal depths even where there may only be a weak natural gas petroleum system.

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Gas Dissolution, Release, and Bubble Formation in Flotation Systems

Cited by 23 publications

References 11 publications

Characterization of Air Dissolution and Reappearance Under Pressure in Cement Pastes by Means of Rheology

Characterization of Air Dissolution and Reappearance Under Pressure in Cement Pastes by Means of Rheology

Keyhole-induced porosity in laser-arc hybrid welded aluminum

Submarine vortices derived from natural gas hydrate conversion: a mechanism for ocean mixing

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