Agitation and Aeration – Section 2

1. When the height of an aerated bioreactor is increased, it will increase the oxygen transfer rate by

A. increasing the partial pressure of oxygen at the base of the reactor
B. decreasing the saturation concentration of oxygen in the reactor
C. decreasing the gas-holdup
D. all of the above

Correct Answer: A. increasing the partial pressure of oxygen at the base of the reactor

2. Which of the following is correct for the off-center impellers?

A. Off-centre impellers can be used with any size reactor
B. Off-centre impellers should only be used with reactors with volumes less than 10 m3
C. The impeller should never be placed in an off-center position
D. Off-centre impellers can be used when the volume is greater than 10 m3

Correct Answer: B. Off-centre impellers should only be used with reactors with volumes less than 10 m3

3. The power required by an impeller in a gas sparged system compare to the power required by impeller operating at the same speed in a gas-free liquid is usually

A. lesser
B. higher
C. same
D. may be lesser or higher depending upon the geometry

Correct Answer: A. lesser

4. Which of the following stirrer requires the least amount of energy for same yield?

A. Mig
B. Intermig
C. Turbine
D. Disc

Correct Answer: B. Intermig

5. A reactor has a total volume of 50,000 liters. If it has a headspace volume of 10,000 liters, then the volume of liquid in the reactor will be

A. 10,000 l
B. 20,000 l
C. 30,000 l
D. 40,000 l

Correct Answer: D. 40,000 l

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