Bubble enhancement

The combination of SVE with air sparging technology. Air sparging involves the injection of air into the saturated zone of contaminated groundwater. The air bubbles enhance the... 

This river stretch would be treated with the large-eddy model without bubble enhancement. 

From the data reported above, it is clear that the semi-continuous system is much more efficient than the batch one. If the main cause of microbial death is the CO2 concentration in the liquid phase, in the flux process high gas concentrations are reached faster, as the bubbling enhances and favours the mass transport of CO2 from the gas- to the liquid phase. In the semi-continuous process, a total sterilization is obtained with an operating pressure of 74 bar and an exposure time of 10 minutes, while in a batch process, 60 minutes are needed with an operating pressure of 200 bars. Tables 9.10-4 and 9.10-5 give results for other experiments run with the semi-continuous system. 

Clearly, this mechanism is more complex than ordinary boiling mechanisms, and any theoretical formulation of devolatilization must take into account this complexity. An initial attempt to formulate semiquantitative elements of this mechanism was made by Albalak et al. (41). They proposed that once a nucleus of a macrobubble is created and the bubble begins to grow, the stretched inner surface of the bubble enhances the rate of nucleation just beneath the soft surface, thus generating new blisters, as shown schematically in Fig. 8.20. 

FIGURE 8.35 Bubbling enhanced flux for filtration of dextran solution. (Adapted from Cui, Z.F., Experimental investigation on enhancement of crossflow ultrafiltration with air sparging, in Aterson, R.P. (Ed.), Effective Membrane Processes-New Perspective, Mechanical Engineering Publications, London, 1993, 237-245.)... 

For bubbling-enhanced tubular membrane filtration, Cui et al. [77] have attributed the main mechanisms to... 

Katz et al. [127] and Nakajima and Shiozawa [128], for example, found that coefficients on the upper finned tubes in a bundle are higher than coefficients on the lower tubes as a result of bubble-enhanced circulation. Similar results are reported by Arai et al. [129] for a bundle of Thermoexcel-E tubes. It is quite probable that with certain types of enhanced tubes it is sufficient to use the special tubes only in the lower rows since the bubble-enhanced circulation in the upper rows is so high that enhanced tubes are not effective there. 

D. B. R. Kenning and Y. S. Kao, Convective Heat Transfer to Water Containing Bubbles Enhancement Not Dependent on Thermocapillarity, Int. J. Heat Mass Transfer (15) 1709-1718,1972. 

The meaning of estimates of the diffusion layer thickness at higher wind speeds is less clear. Under more dynamic conditions, capillary and larger waves extend the interface, bubbles enhance gas transfer and turbulence renews the interface. Thus, any estimate of diffusion layer thickness based on measurements of gas transfer rates must be considered only a nominal or effective thickness. In this regard, Broecker and Peng [3] estimate a global average thickness of the diffusion layer of about 40 pm based on rates of invasion of natural radiocarbon C02. 

In a gas flotation unit, air is bubbled through oily water to capture oil particles which then rise with the bubble to form a scum at the surface of the flotation unit. The scum can be removed by rotating paddles. Chemicals are often added to destabilise the inlet stream and enhance performance. 

The phenomenon of acoustic cavitation results in an enormous concentration of energy. If one considers the energy density in an acoustic field that produces cavitation and that in the coUapsed cavitation bubble, there is an amplification factor of over eleven orders of magnitude. The enormous local temperatures and pressures so created result in phenomena such as sonochemistry and sonoluminescence and provide a unique means for fundamental studies of chemistry and physics under extreme conditions. A diverse set of apphcations of ultrasound to enhancing chemical reactivity has been explored, with important apphcations in mixed-phase synthesis, materials chemistry, and biomedical uses. 

Interaction of Solids With Flotation Reagents. For flotation to occur with the aid of reagents, such compounds must adsorb at the sohd—hquid interface unless the soHd to be floated is naturally hydrophobic. In this latter case only depression can be attempted by the use of additional ions or depressants that hinder bubble—particle adhesion. Frothers (typically long-chain alcohols) and/or modifying agents such as hydrocarbon oils can, however, be used to enhance the collection of naturally hydrophobic soflds such as M0S2, talc, or plastics. 

Other imaging techniques such as magnetic resonance and ultrasound have opened up avenues of tremendous potential for contrast medium enhancement (123). Ultrasound contrast media developments have centered around encapsulated air micro-bubbles. Magnetic resonance contrast agents iavolve metal—ligand complexes and have evolved from ionic to nonionic species, much as radiopaques have. 

Bourbon Distillation. The basic distiUation system for the production of bourbon and other straight whiskeys consists of a beer stiU and a beer heater, thumper, or doubler (Fig. 4). The whiskey stiU consists of between 14 and 21 stripping trays. The upper portion of the stiU is fitted with either a bubble cap section or a section packed with copper rings to enhance the removal of unwanted flavors and ethyl carbamate precursors. The reduction of carbamate precursors requites strict adherence to a cleaning protocol with a 5% caustic solution as often as twice a week. 

The overall benefits of this high efficiency combustor over a conventional bubbling- or turbulent-bed regenerator are enhanced and controlled carbon-bum kinetics (carbon on regenerated catalyst at less than 0.05 wt %) ease of start-up and routiae operabiUty uniform radial carbon and temperature profiles limited afterbum ia the upper regenerator section and uniform cyclone temperatures and reduced catalyst iaventory and air-blower horsepower. By 1990, this design was well estabUshed. More than 30 units are ia commercial operation. 

Another modification is the use of microbubble column flotation (13). In this process, smaller bubbles are generated to enhance the recovery of micrometer-sized particles. A countercurrent flow of feed slurry is also used to further enhance the bubble—particle attachment. The process is capable of produciug ultraclean coals containing less than 0.8% ash. 

Both high bulk and surface shear viscosity delay film thinning and stretching deformations that precede bubble bursting. The development of ordered stmctures in the surface region can also have a stabilizing effect. Liquid crystalline phases in foam films enhance stabiUty (18). In water-surfactant-fatty alcohol systems the alcohol components may serve as a foam stabilizer or a foam breaker depending on concentration (18). 

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