Page 27 - Applied Process Design For Chemical And Petrochemical Plants Volume II

16 Applied Process Design for Chemical and Petrochemical Plants

For binary mixtures [147]: where Xi = mols of a component i in vapor plus mols of same
1. Set the temperature and pressure of the flash chamber. component in liquid, divided by total mols of feed
2. Make a material balance on a single component. (both liquid and vapor)
= total mol fraction, regardless of whether compo-
FtXi = Vyi + Ixi (8-21) nent is in liquid or vapor.
3. Knowing F, calculate amount and composition of V FXi=vyi+LXi (8-23H)
and L.
Ft = F + V, = mols of feed plus mols of noncondensable gases xi = yi/&
From Henry’s Law: yi=V+L/& (8-231)

FtXfi = Vtyi + L (yi/Ki) (8 - 22)
Vt = V + V, = mols of vapor formed plus mols non- (8 - 235)
condensed gases

&=&xi 2yi = 1.0
4. Ft = V, + L (8 - 22A)
(8- 23K)
(8-23)

To calculate, V, L, yi’s, and xi’s:
Yi x, (8 - 23A)
1. Assume: V
2. Calculate: L = F - V
3. Calculate: L/V
After calculating V, calculate the xi’s and yi’s:
4. Look up q’s at temperature and total pressure of sys-
tem
Fx,
yiv = - (8 - 23B) 5. Substitute in:
L
1+-
KiV
Then, (8 - 24)
(7)
y. =- (8 - 23C) 6. If an equality is obtained from:
l+- L Vcdc = Vassmed the amount of vapor was satisfactory
KiV as assumed.
Calculate each y; after calculating the yi’s, calculate xi’s
F1(,
(8 - 25)
as follows: V=- -1 L +-+- Fx, Fx, +*.e. -
L
L
L
1+- l+- l+- 1+-
(8-8) K1V K2V K3V KiV
(8-23D) 7. vyi =- Fx; (8 - 23B)
1+- L
KiV
(8- 8)
(8 - 23C)
(8 - 23E)
(8 - 23F)
(8 - 23G) 8. Calculate each yi as in (7) above, then the xi’s are
determined
Yi - Pi
xi Jd