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Gas Volume Fraction Hold-up

Either local gas volume fraction or the vessel average fraction (gas hold-up) may be measured. Where the amount of surface motion in the gas-liquid system is not excessive, an estimate of the vessel average gas hold-up may be made by visual observation of the level change (possibly aided by video analysis). [Pg.196]

A more reliable technique, and one that can be used where there are larger surface fluctuations, is to use an ultrasonic radar probe (Machon et al., 1991). Such probes are commercially available, from, for example, Endress and Hauser. The probe is mounted above a representative part of the fluctuating surface and measures the distance to the surface. Care must be taken in the calibration (especially if any foam is present) to ensure that the true surface is detected and that an adequate range of fill levels is covered. Some foams will not be penetrated by the ultrasonic beam. Calibration with a moving liquid surface is recommended. [Pg.196]

A cruder but effective method for overall gas hold-up in batch vessels is the spillover technique. The vessel is filled to the overflow before gassing then the gas displaces its own volume of liquid, which is collected and measured. [Pg.196]

Local gas fraction is measured using conductivity probes or optical probes. These conductivity probes typically measure the conductivity across two parallel plates about 10 mm square and 10 mm apart. The optical probes are the same as those used in sohd-liquid work. Both types require careful calibration with the liquid under study. [Pg.196]

Among the steady-state methods, the hydrogen peroxide-catalase method of Hickman (1988a) is the most commonly used. It can be used at any scale with aqueous systems at pH around 7, but not with ionic solutes such as NaCl, KCl, or K2SO4 (sometimes used to render the liquid noncoalescing). Air is the usual gas feed, and the liquid contains the enzyme catalase in excess. Hydrogen [Pg.196]


See other pages where Gas Volume Fraction Hold-up is mentioned: [Pg.264]    [Pg.196]   


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