Gas sparging methods

Gallart, M., Tomas, X., et al. (2004). Relationship between foam parameters obtained by the gas-sparging method and sensory evaluation of sparkling wines. J. Sci. FoodAgric. 84(2), 127-133. 

The methods reported in the literature and used to quantify the foaming properties of sparkling wines can be classified into methods based on measuring the kinetics of CO2 discharging, gas sparging methods and image analysis methods. 

Gallart, M., Lopez-Tamames, E., Buxaderas, S. (1997). Foam measurements in wines compara-sion of parameters obtained by gas sparging method. J. Agric. Food Chem., 45, 4687 690. 

Gas-liquid mass transfer in fermentors is discussed in detail in Section 12.4. In dealing with in gas-sparged stirred tanks, it is more rational to separate and a, because both are affected by different factors. It is possible to measure a by using either a light scattering technique [9] or a chemical method [4]. Ihe average bubble size can be estimated by Equation 7.26 from measured values of a and the gas holdup e. Correlations for have been obtained in this way [10, 11], but in order to use them it is necessary that a and d are known. 

Cell-protecting additives, such as Pluronic F-68, are commonly included as a media component to reduce cell damage in gas-sparged, agitated cultures. Despite the value of Pluronic F-68 in protecting cells, there is a potential problem in that Pluronic may have some cytosolic effects it may reduce the yield of the producer cell line in culture and there is a possibility of complexation or co-purification with a cell product. The replacement of Pluronic with fatty acids, as well as being positive for the half-lives and production of cultured cell lines, provides an alternative method to protect producer cells in agitated cultures (Butler et al., 1999). 

Nomnicrobial processes for destruction of cyanide wastes have been extensively investigated and are well known. Parga et al. (2003) have reported several oxidation methods for treating cyanide solutions. Such methods include (1) destruction of cyanide by oxidation with chlorine dioxide in a gas-sparged hydrocyclone reactor, (2) destruction by ozone in a stirred batch reactor, and... 

The most applied technique for generating foam is by a simple dispersion technique (mechanical shaking or whipping). This method is unsatisfactory since it is difficult to accurately control the amount of air incorporated. The most convenient method is to pass a flow of gas (sparging) through an oriflce with a well-deflned radius To-... 

An added problem is that excessive gas sparging may cause cell damage particularly in cultures with a large surface to volume ratio. This problem may be offset by the use of chemical protectants such as the polymer, Pluronic F-68, or by alternative methods of introducing oxygen into the culture. The alternative methods may include gas sparging in a media reservoir not in contact with the cells... 

Callaghan and Neustadter [31] have made a study of the foam stabilities of air-crude oil and natural gas-crude oil systems using a variety of light crude oils of viscosities 14 mPa s. This study, at ambient temperature using a sparging method, concerned so-called dead oils from which natural gas had been separated. It also involved a comparison of the foam behavior with critical film rupture thicknesses, bulk phase, and surface shear viscosities together with dilatational surface properties. 

In other cases, the method of removal depends upon the nature of the product, e.g. gases may be (1) vented from the reactor, possibly via a slight reduction In pressure (2) displaced from the electrolyte via inert gas sparging (3) segregated via a solid polymer electrolyte (section 5.2) or recirculated via a gas-liquid separator. Liquid products may be (1) separated by flotation or settlement if they are immiscible and have a markedly different density to the electrolyte or (2) emulsified by mixing, then swept out of the reactor. Solid products can be separated via (I) flotation or settlement (2) fluidization or tangential shear to remove them from the reactor (3) solvent extraction or incorporation into a mercury phase, e.g. amalgamation of metals. 

First the gas entry method can be decided. With a vessel, the gas is preferably sparged in through a dip pipe discharging (preferably via a sparge... 

Ozone can be analyzed by titrimetry, direct and colorimetric spectrometry, amperometry, oxidation—reduction potential (ORP), chemiluminescence, calorimetry, thermal conductivity, and isothermal pressure change on decomposition. The last three methods ate not frequently employed. Proper measurement of ozone in water requites an awareness of its reactivity, instabiUty, volatility, and the potential effect of interfering substances. To eliminate interferences, ozone sometimes is sparged out of solution by using an inert gas for analysis in the gas phase or on reabsorption in a clean solution. Historically, the most common analytical procedure has been the iodometric method in which gaseous ozone is absorbed by aqueous KI. 

Ozone in the gas phase can be deterrnined by direct uv spectrometry at 254 nm via its strong absorption. The accuracy of this method depends on the molar absorptivity, which is known to 1% interference by CO, hydrocarbons, NO, or H2O vapor is not significant. The method also can be employed to measure ozone in aqueous solution, but is subject to interference from turbidity as well as dissolved inorganics and organics. To eliminate interferences, ozone sometimes is sparged into the gas phase for measurement. 

Measurements Using Liquid-Phase Reactions. Liquid-phase reactions, and the oxidation of sodium sulfite to sodium sulfate in particular, are sometimes used to determine kiAi. As for the transient method, the system is batch with respect to the liquid phase. Pure oxygen is sparged into the vessel. A pseudo-steady-state results. There is no gas outlet, and the inlet flow rate is adjusted so that the vessel pressure remains constant. Under these circumstances, the inlet flow rate equals the mass transfer rate. Equations (11.5) and (11.12) are combined to give a particularly simple result ... 

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