CL 351 Homework # 8
Due date: 7 November 2005
1.
In the production of styrene from toluene and
hydrogen, it is required to recover most of the benzene from a saturated liquid
stream containing 5 mol% benzene, 20 mol% toluene, 5 mol% ethylbenzene, 20 mol%
styrene, 15 mol% diethylbenzene, 5 mol% triethylbenzene and 30 mol%
diphenyl. Design a distillation column
to recover 98% of benzene in the distillate and 99.9% toluene in the bottoms
stream. Use Fenske-Underwood-Gilliland
met
lnP = A –
B/(T-C) with P in Pa and T in K.
Component |
A |
B |
C |
Benzene |
20.793 |
2788 |
52.4 |
Toluene |
20.893 |
3096 |
53.7 |
Ethylbenzene |
20.893 |
3279 |
60 |
Styrene |
20.893 |
3328 |
63.7 |
Diethylbenzene |
20.993 |
3657 |
71.2 |
Triethylbenzene |
21.093 |
4000 |
81 |
Diphenyl |
21.593 |
4602 |
70.4 |
1.
A batch still is loaded with 100 kmol of a liquid
containing a binary mixture of 50 mol% benzene in toluene. As a function of time, make plots of a) still
temperature, b) instantaneous vapour composition, c) still composition and d)
average total distillate composition.
Assume a constant boilup rate of 10 kmol/hr and a constant relative
volatility of 2.41 at a pressure of 101.13 kPa.
T-x-y data for benzene-toluene system at 1 atm is given below
x |
0.1 |
0.2 |
0.3 |
0.4 |
0.5 |
0.6 |
0.7 |
0.8 |
0.9 |
0.95 |
y |
0.21 |
0.37 |
0.51 |
0.61 |
0.71 |
0.79 |
0.86 |
0.91 |
0.96 |
0.98 |
T, oC |
105.3 |
101.5 |
98 |
95.1 |
92.3 |
89.7 |
87.3 |
85 |
82.7 |
81.4 |
2.
Consider separation of 200 kmol/hr mixture of 55
mol% n-hexane and 45 mol% p-xylene in a distillation column operating with a
reflux ratio of 1.0. The mixture contains
equal amounts of vapour and liquid, that is, it is a partially vapourized
feed. The distillate and bottoms
purities are 95% hexane and 97% p-xylene.
Boiling points of hexane and p-xylene are 68.7oC and 138.3 oC
and, their densities are 659 kg/m3 and 861 kg/m3. Find the diameter of the top and bottom
sections of the distillation column if the sections are operated at 60%
flooding. If the diameters are
different, what do you recommend? Redo
the calculations for a saturated liquid feed.