Robinson and Wilke

In this work, the dynamic method is used to measure kLa values. The mathematical model is exactly similar to that used by Robinson and Wilke (15). However, due to the low gas hold-up employed in this work, negligible error results from neglecting gas dynamics (Dunn and Einsele, 17). A detailed description of... 

The work of Robinson and Wilke [469] was probably the first one which quantitatively investigated the effect of salts on gassing of liquids. The ionic strength was established as an influence quantity, which was calculated as follows I = 0.5 52 2 Wi [g-ion/1] all ions have therefore to be taken into consideration, (zj is the charge number of an ion i and m is its molality.)... 

The effect of dissolved salts was clarified by Robinson and Wilke [32], who showed that adding any electrolyte to water inhibited bubble coalescence and that the agitation exponent in the equation for k a gradually increased from 0.4-0.9 as the ionic strength changed from 0 to 0.40. Since surfactants can also affect the bubble size, it is difficult to predict a or k a for multi-component solutions. 

Dhanuka and Stepanek [24] measured volumetric and area-based mass transfer coefficients and interfacial areas in a three-phase fluidized bed using the technique suggested by Robinson and Wilke [25]. The chemical system used was 1.01 M sodium carbonate-sodium bicarbonate solution with a buffer ratio of one, containing 0.01 M sodium hypochlorite to enhance the reaction rateo Pure CO2 and CO2 with N2 as the gas phase and three sizes (1.98, 4.08, and 5086mm) of glass ballotini as the solid phase were used. Their... 

In the present study, the technique suggested by Robinson and Wilke [25] was used. Experiments were performed by simultaneous chemical absorption of CO2 in NaOH solution and physical desorption of dissolved oxygen from the liquid phase. Therefore, physical desorption and chemical absorption rates were measured under truly identical physico-chemical and hydrodynamic conditions,... 

Chemical methods can also be used to measure kta. Robinson and Wilke (1974) describe an ingenious method to obtain kLa and a simultaneously, by desorption of oxygen (rate oc kLa) and reaction-enhanced absorption of carbon dioxide (regime 111 see Chapter 11) into potassium hydroxide solution (rate a a). 

Light transmittance methods for interfacial area have been widely employed in gas-liquid systems. Sridhar and Potter (1978) describe one of the more successful versions. The techniques are described in more detail in the liquid-liquid section. Chemical methods can be used to measure interfacial area, as described above (Section 4-7.5 Robinson and Wilke, 1974). Sampling methods are not suitable since it is impossible to withdraw a sample isokinetically. Generally, the results from chemical and physical methods do not agree. Chemical methods tend to have a bias toward the smaller bubbles of the distribution, whereas these may be missed by physical methods. 

Robinson W., Wilke C.R., Simultaneous Measurement of Inteifacial Area and Mass Transfer Coefficients for a Well-Mixed Gas Dispersion in Aqueous Electrolyte Solutions, AIChE J. 20 (1974) 3,... 

C.W. Robinson, C.R. Wilke, Simultaneous measurement of interfacial area and mass transfer coefficients for a well-mixed gas dispersion in aqueous electrolyte solutions, AIChE J. 20 (1974) 285-294. 

The technique of simultaneous absorption with fast pseudo-mth-order reaction and physical absorption or desorption concurrently, used by Wilke and Robinson (R14), Linek (L15), and Beenacker and Van Swaaij (Bll), is certainly a promising effort to understand the whole complex problem of transport in gas-liquid reactors, since it provides simultaneous measurement oik fi and a. But still it may leave some doubt as to a value of/cL, which can be changed by the occurrence of chemical reaction. As discussed by Prasher (P13), it will be even more promising to conduct such simultaneous experiments in a regime where both hydrodynamics and reaction have comparable effects. 

Robinson C.W., Wilke C.R., Oxygen Absorption in Stirred Tanks A Comda-tion for Ionic Strength Effects, Biotechn. and Bioengng. 15 (1973), p. 755-782... 

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