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Home Biochemical Engineering Agitation and Aeration Comments

  • Question
  • Industrial paddle agitators turn at the speed of


  • Options
  • A. 20 and 150 rpm
  • B. 150 and 300 rpm
  • C. 400 and 800 rpm
  • D. 1150 rpm

  • Correct Answer
  • 20 and 150 rpm 


  • Agitation and Aeration problems


    Search Results


    • 1. To increase the oxygen transfer rate in a shake flask culture system, which of the following (s) is/are followed?

    • Options
    • A. Liquid volume in the flask is reduced
    • B. Stirrer speed is increased
    • C. Baffled flasks are used
    • D. All of the above
    • Discuss
    • 2. The Intermig impeller is

    • Options
    • A. an axial flow impeller which can be used for the culture of aerobic organisms
    • B. directed upwards rather than towards the base of the reactor
    • C. a fork shaped extensions to the impeller facilitate bubble break up
    • D. All of the above
    • Discuss
    • 3. Which of the following is not classified as an axial flow impeller?

    • Options
    • A. A propeller
    • B. A marine impeller
    • C. A Rushton turbine
    • D. A hydrofoil impeller
    • Discuss
    • 4. The oxygen absorption rate can be determined by

    • Options
    • A. sodium sulfite oxidation method
    • B. dynamic gassing out technique
    • C. direct measurement
    • D. all of these
    • Discuss
    • 5. The power required by an impeller in a gas sparged system compare to the power required by impeller operating at same speed in a gas free liquid is usually

    • Options
    • A. lesser
    • B. higher
    • C. same
    • D. may be lesser or higher depending upon the geometry
    • Discuss
    • 6. Detergent like substances produced by microorganisms during a fermentation will lead to

    • Options
    • A. decrease the surface tension of the liquid
    • B. accumulate at the gas liquid interface
    • C. decrease the rate of bubble coalescence
    • D. all of the above
    • Discuss
    • 7. Which of the following stirrer requires least amount of energy for same yield?

    • Options
    • A. Mig
    • B. Intermig
    • C. Turbine
    • D. Disc
    • Discuss
    • 8. Pure oxygen, if used instead of air will increase oxygen transfer rates because

    • Options
    • A. the saturation concentration of oxygen is higher
    • B. the bubble size is smaller
    • C. the oxygen transfer coefficient is larger
    • D. the partial pressure of oxygen in the gas phase is lower
    • Discuss
    • 9. A cylindrical reactor fitted with Rushton Turbine has a liquid volume of 100,000 litres. It has an aspect ratio (the ratio of the channel height to the width) of 2:1. The diameter of the impeller should be approximately:

    • Options
    • A. 1.3 m
    • B. 3.3 m
    • C. 5.3 m
    • D. 7.3 m
    • Discuss
    • 10. Which of the following is correct for the off-centre impellers?

    • Options
    • 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-centre position
    • D. Off-centre impellers can be used when volume is greater than 10 m3
    • Discuss


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