200 Best MCQs on Agitation and aeration- biochemical engineering

Q49). 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:

a).1.3 m
b).3.3 m
c).5.3 m
d).7.3 m

Correct Answer:
1.3 m
Explaination:

Q50). In the bubble boundary layer, oxygen concentration can be determined by measuring

a).the steady state oxygen concentration in a mixed aerated reactor before inoculation
b).the steady state oxygen concentration in a mixed aerated reactor after inoculation
c).the steady state oxygen concentration in the boundary layer using a micro-probe
d).volume of oxygen supplied

Correct Answer:
the steady state oxygen concentration in a mixed aerated reactor before inoculation
Explaination:

Q51). Impeller damage can be minimized by

a).using specially designed axial flow impellers
b).using radial flow impellers
c).using Intermig impellers
d).all of the above

Correct Answer:
using specially designed axial flow impellers
Explaination:

Q52). To increase the oxygen transfer rate in a shake flask culture system, which of the following (s) is/are followed?

a).Liquid volume in the flask is reduced
b).Stirrer speed is increased
c).Baffled flasks are used
d).All of the above

Correct Answer:
All of the above
Explaination:

Q53). What is/are the major difference(s) between disc and turbine type stirrer?

a).Blades in disc type are projected out beyond the edge of disc while blades are curved one in turbine type
b).Turbine type requires 50 % less air than disc type for the same yield and energy consumption
c).Both (a) and (b)
d).Number of blades in the stirrer

Correct Answer:
Both (a) and (b)
Explaination:

Q54). In the design of a paddle agitator, the ratio of paddle diameter to tank diameter is normally taken as

a).0.1
b).0.8
c).0.25
d).0.5

Correct Answer:
0.8
Explaination:

Q55). The oxygen absorption rate can be determined by

a).sodium sulfite oxidation method
b).dynamic gassing out technique
c).direct measurement
d).all of these

Correct Answer:
all of these
Explaination:

Q56). Industrial paddle agitators turn at the speed of

a).20 and 150 rpm
b).150 and 300 rpm
c).400 and 800 rpm
d).1150 rpm

Correct Answer:
20 and 150 rpm
Explaination: