Other Correlations for kLa

For kLa with non-Newtonian (excluding viscoelastic) fluids, Equation 7.45 [23], which is based on data with water and aqueous solutions of sucrose and carbox-ymethylcellulose (CMC) in a 15 cm column, may be useful. Note that kLa in this equation is defined per unit volume of dear liquid, without aeration. 

For kLa in bubble columns for non-Newtonian (including viscoelastic) fluids, see Section 12.4.1. 

The correlations for kLa as discussed above are for homogeneous liquids. Bubbling gas-liquid reactors are sometimes used for suspensions, and bioreactors of this type must often handle suspensions of microorganisms, cells, or immobilized 

In general, the gas holdups and kLa for suspensions in bubbling gas-liquid reactors decrease substantially with increasing concentrations of solid particles, possibly because the coalescence of bubbles is promoted by presence of particles, which in turn results in a larger bubble size and hence a smaller gas-liquid interfacial area. Various empirical correlations have been proposed for the kLa and gas holdup in slurry bubble columns. Equation 7.46 [24], which is dimensionless and based on data for suspensions with four bubble columns, 10-30 cm in diameter, over a range of particle concentrations from 0 to 200 kg m 3 and particle diameter of 50-200 pm, can be used to predict the ratio r of the ordinary kLo values in bubble columns. This can, in turn, be predicted for example by Equation 7.41, to the kLa values with suspensions. 

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