Biomedical Engineering Reference
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It is desired to double the capacity of the existing plant by processing twice the feed of
reactant A while maintaining the same fractional conversion of A to B in the reactor.
How much larger a reactor, in terms of catalyst weight, would be required if all other
operating variables are held constant? Describe the effects of the flow rate, tempera-
ture, and particle size at conversion.
17.8. You are working for company A and you join a research group working on
immobilized enzymes. Harry, the head of the lab, claims that immobilization improves
the stability of the enzyme. His proof is that the enzyme has a half-life of 10 days in free
solution but under identical conditions of temperature, pH, and medium composition,
the measured half-life of a packed column is 30 days. The enzyme is immobilized in
a porous sphere of 5 mm in diameter. Is Harry's reasoning right? Do you agree with
him and Why?
17.9. A decomposition reaction is carried out on a solid catalyst
A
B
/
over two different pellet sizes. The pellets were contained in a differential reactor that
has sufficient turbulence such that the external mass transfer effects are negligible. We
know that the adsorption coverage of A on the catalyst site is minimal and thus
K A / N
. The reaction on the catalyst surface is thus virtually first order. The results
of two experimental runs made under identical conditions are as shown in Table
P17.9-1 . Estimate the Thiele modulus and effectiveness factor for each pellet. How
small should the pellets be made to virtually eliminate all internal diffusion effects
on the overall reaction kinetics?
TABLE P17.9-1
Measured rate,
mol-A/(g-cat$s)
Pellet size, mm
Run 1
2.00
3.80
Run 2
0.200
20.0
17.10. A decomposition reaction is carried out on a solid catalyst
A
/
B
รพ
C
over two different pellet sizes. The pellets were contained in a differential reactor that
has sufficient turbulence such that the external mass transfer effects are negligible.
We know that the adsorption coverage of A on the catalyst site is very strong and
thus K A /
0. The reaction on the catalyst surface is thus virtually zeroth order. The
results of two experimental runs made under identical conditions are as shown in
Table P17.10-1 . Estimate the Thiele modulus and effectiveness factor for each pellet.
How small should the pellets be made to virtually eliminate all internal diffusion
effects on the overall reaction kinetics?
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