Defoaming Using Rotary Devices

Deshpande and Barigou [14] have tabulated a useful summary of the many published empirical studies of defoaming using various rotary devices. In Appendix 7.1, Table 7.A1, we produce an updated version of that table where later studies are included and an error in a citation is rectified. Whether performance has been studied in either bubble colunms or stirred vessels is indicated. Most of the reported studies are at laboratory scale, concerned with controlling the foam of dilute aqueous surfactant solutions in sparged vessels of <0.5 m diameter. Only two reported studies concern pilot scale with practical systems—Kraft (paper) mill effluent [15] and recombinant Bacillus fermentation [16]. 

For applications where chemical antifoam use is unacceptable, the text examines mechanical means of defoaming, such as the use of rotary devices and ultrasound. 

In conclusion, it should be stated that the present primitive level of understanding of rotary and ultrasonic defoaming may prevent design of significantly improved devices and realization of the true potential of these methods. Finally, we note that the use of fixed porous packed beds of appropriate wettability may have potential in either replacing or supplementing such devices in certain circumstances where the presence of antifoams is unacceptable. 

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