Biomedical Engineering Reference
In-Depth Information
17.4.
Hydrazine has been studied extensively for use in monopropellant thrusters for space
flights of long duration. Thrusters are used for altitude control of communication
satellites. Here the decomposition of hydrazine over a packed bed of alumina-
supported iridium catalyst is of interest (Smith O.I. and Solomon W.C.
Ind. Eng. Chem.
Fund
. 21: 374, 1982). In a proposed study, a 2% hydrazine in 98% heliummixture is to be
passed over a packed bed of cylindrical particles 2 mm in diameter and 5 mm in length
at a gas-phase superficial velocity of 5 m/s and a temperature of 700 K. The kinematic
viscosity of helium at this temperature is 4.0
10
4
m
2
/s. The hydrazine
decomposition reaction is believed to be external mass transfer-limited under these
conditions. If the packed bed is 0.05 m in length, what conversion can be expected? The
bed porosity is 28% and the diffusivity of hydrazine in helium is 6.9
10
5
m
2
/s at
298 K. Assume isothermal operation.
17.5. (a)
Weetall H.H. and Havewala N.B. (
Biotechnol. Bioeng. Symp
. No. 3, Wiley, New York,
pp. 241
e
266, 1972) report the following data (
Table P17.5-1
) for the production of
dextrose from com starch using both soluble and immobilized (azo-glass beads)
glucoamylase in a fully agitated CSTR system.
TABLE P17.5-1
Product concentration, g-dextrose/L
Time, min
Soluble
Immobilized
0
12
18.4
15
40
135
30
76.5
200
45
94.3
236
60
120
260
75
135.5
258
90
151.2
262
105
150.4
266
120
155.7
278
135
160.1
300
150
164.9
310
165
170
306
225
316
415
320
1.
Soluble data:
T
¼
60
C, [
S
]
0
¼
168 g-starch/L, [E]
0
¼
11,600 units,
¼
volume
1000 mL.
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