Page 89 - Applied Process Design For Chemical And Petrochemical Plants Volume II

78 Applied Process Design for Chemical and Petrochemical Plants

The feed is a boiling point liquid from statement of problem: toms bubble point could be determined, and from this an
approximation could have been made of the pinch tem-
q= 1.0 perature. Because these cannot be calculated, one must
use trial-anderror to get correct pinch temperature.
Ls = L + qF
Because the 1.017 is reasonably close to 1.0, continue
Basis: 1 mol feed: calculations composition of rectifying pinch:

Ls = 0.674 + (1) (1) = 1.674
(min)

Compo- DXDinr/
nents (K1- Lr/Vr) Revised Mol Fraction
2=h 0.333 0.333/1.017 = 0.328
3=1 0.580 0.3’2
Vs = 1.332 4=L 0.104 0.102
1.017 1.002
= . -_ Ls - 674 1.255
Vs 1.332
Determine temperature of stripping section pinch:
Determine temperature of rectifying section pinch.

Compo- DxDi - b@ .L &-L, DxDi/V, Compo- Ks@ L/V,- Bxgi/VS
---___--- ai& Vr Vr Ki - (Lrflr) -- Ls/Vs 130°F q ~ K B K B (L,/Vs)-aiK~
nents BXB~ Bxpi/V,
~
DXD~ Vr
nentS
118°F ~i
1
0.169 1
h 0.01072 0.00805 0.50 0.53 0.024 0.333 0.10
1 0.428 0.321 1.06 1.0 1.06 0.506 0.554 0.580 1 =H 0.10 1.332=0.0752 0.25 0.308 0.947 0.0794
L 0.225 2.0 2.12 1.614 0.104 2 = h 0.214 0.1605
- 3=1 0.0214 0.0160 1.00 1.23 0.028 0.640
Note: 0.225/1.332 = 0.169 L - 1.017 0.9714
&=UiKg
B - reference
Exact KB must lie between 1.23 and 1.24. Because there
is a difference involved in calculation, the result is very
Assume temperature at rectifying pinch., If the compo- sensitive to small changes in K.
nents were known, then the overhead dew point and bot-

Figure 8-48. Colburn minimum reflux factors,
above (C,,) and below (C,,,) feed point. Used by
permission, Colburn, A. P. The American Institute
(-1- II=p for c. of Chemical Engineers, Trans. her. lnst. Chem.
oc bq-lb for C, Engr. V. 37 (1 941), p. 805, all fights reserved.