Aeration, fermentators mass transfer

Calculate mass transfer coefficient in a 60 m3 fermenter with a gas and liquid interfacial area of a = 0.3 m2-m 3, given pbroth = 1200kg m-3. The small reactor has working volume of 0.18m3, 1 vvm aeration rate. Oxygen transfer rate (OTR) is 0.25kmol in 3 h 3. There are two sets of impellers, and flat-blade turbine types of impeller were used, HL= 1.2/),. Find the exact specifications of a large fermenter. 

An aerated stirred-tank fermenter equipped with a standard Rushton turbine of the following dimensions contains a liquid with density p = 1010kgm and viscosity n = 9.8 X 10 Pa s. The tank diameter D is 0.90 m, liquid depth Hl = 0.90 m, impeller diameter d = 0.30 m. The oxygen diffusivity in the liquid Dl is 2.10 X 10 5 cm- s T Estimate the stirrer power required and the volumetric mass transfer coefficient of oxygen (use Equation 7.36b), when air is supplied from the tank bottom at a rate of 0.60 m min at a rotational stirrer speed of 120 rpm, that is 2.0 s T... 

Fermentation media may exhibit a highly viscous non-Newtonian flow behavior (1,2) resulting in low aeration efficiencies (3). For studying the volumetric mass transfer coefficients (kj a) under such conditions solutions of sodium carboxymethylcellulose (CMC) are often used as model media. In bubble columns such investiga-... 

In many mass transfer operations the effect of gas phase residence time distribution is neglected. In fermentations and in wastewater aeration systems, a 15% consumption of the oxygen from the inlet air is on the high side. This translates to going from 21% oxygen to 18% at the outlet. If the air is backmixed, the gas phase composition in equilibrium with the liquid would be based on 18% oxygen. If a simple plug flow assumption is made instead, the composition only rises to 19.5%. This is a minor effect. 

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