Experimental Methods for Parameter Estimations

In previous sections, we examined the design parameters for gas-liquid, gas-solid, liquid-liquid, gas-liquid-solid, biological polymerization, and special types of mechanically agitated reactors. In this section we present a brief review on available techniques for the measurement of various mixing and transport parameters for a mechanically agitated vessel. Both physical and chemical techniques are examined. 

The simplest method for determining gas holdup g is the measurement of the heights of the aerated liquid, La, and the nonaerated liquid, L. The average gas holdup eg is then 

This method is not time-consuming, but it is not very accurate (15-20%) when waves or foams exist on top of the dispersion. Reith et al. (1968) and 

Burgess and Calderbank (1973) used a more accurate manometric technique to measure the height of the dispersion. In this technique, the clear liquid height in the dispersion is measured through successive pressure tapping (e.g., with a manometer) on the side of the vessel. The gas holdup is related to the pressure drop as 

An electric technique to measure the gas holdup was implemented by Linek and Mayrhoferova (1969). In this method, the surface elevation of the gas-liquid interface of the nonaerated and aerated liquid in the vessel is detected at certain selected points by means of an electrical probe. The height is determined by the vertical position of the probe at which the sum of contact times equals one-half of the measurement period. The gas holdup is then calculated from the total surface elevation, the cross-section of the reactor, and the liquid volume. The accuracy of the measured value of the total surface elevation is claimed by the authors to be +0.2 mm. 

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Experimental methods for parameter estimation. In order to determine the relative importance of mass transport processes in gas/liquid/solid-reactions, it is recommended to measure the global reaction rate as function of catalyst concentration m (keeping all other operating variables constant). With the assumption of spherical catalyst particles, the specific surface of the catalyst can be calculated as... 

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