Final assignment

[E Jervis]

ChE 562: Fermentation Engineering (Winter Term 1998)
Problem Set #4: Unit Operations

1) Bailey & Ollis 9.4

2) Bailey & Ollis 11.2

3) Bailey & Ollis 11.4
Note: eq 1E1.1 is on page 10 of Bailey & Ollis
In part b use eq 11.3 and recall that uh is just the velocity of the
interface of the settling suspension

4) Bailey & Ollis 11.9
Note: tau in the first equation is the “apparent” time constant for the
processes described in part b of the question
b) p(t) decreases because
- loss of key internal biosynthesis enzymes
- consumption of key precursor
- increased cell death / endogenous maintenance

5) To ensure turbulent conditions and minimum mixing time during agitation
with a turbine impeller, the Re must be kept above 10E4.
(a) A stirred laboratory-scale fermentor with a turbine impeller 5 cm in
diameter is operated at 800 rpm. If the density of broth being stirred is
close to that of water, what is the upper limit for the viscosity of the
suspension for adequate mixing
(b) The mixing system is scaled up so the tank and impeller are 15 times the
diameter of the laboratory equipment. The stirrer in the large vessel is
operated so that the stirrer tip speed is the same as that in the laboratory
apparatus. How does the scale-up affect the maximum viscosity allowable for
maintenance of turbulent mixing conditions.