Page 120 - Applied Process Design For Chemical And Petrochemical Plants Volume II

Distillation 109

16. Mols of component in outlet gas/mol inlet rich gas
Solve for Y1i 100 - (% recovery) (total mols in)
100

(c) Mols component absorbed = inlet - outlet
If th.e X1 in equilibrium with Y1 is desired: 3. Calculate: E~ for specified component (specified in
1.)
(8- 197)
mols component in - mols component out
Eai =
17. Improved values can be obtained by recalculation mols component in
from Step 11 if there is too great a difference between = specified fraction recovery
the ‘‘E mols absorbed from trial no. 1 and trial no. 2.
4. Minimum (L/V) for specified component:
First Trial

Inlet Mols/Hr A=- L
Component Y(N + 1)i In Ki VKi
m a m a a Assuming equilibrium at bottom, L71= 1. Ignoring
a a a a e ZX gives slightly conservative value,
a a e m a
1 .oo Z@

Fraction
Absorbed, Mols Mol/=
Component Ei Absorbed & Off Gas 5. Operating &,/VN + do
= (specified unit) (Lo& + l)min
a a a a m a
a a a a a a 6. Operating
--
e a a a m a
Za X* X.
=(&lo (+) (8-199)
For second trial, see Step 11.
18. A graphical stepwise procedure offered by Sherwood
[62] also summarized by Reference 18. Y and X are 7. Theoretical plates at operating (LJVN + 1): solve for
plotted and handled stepwise as in distillation. The N.
equilibrium line equation is for any single component:
(8 - 200)
(8 - 198)

For a complete denuded inlet solvent at the top ZX
= 0, using K at top column conditions. The slope of
the operating line = L,/Vx + 1 = mols lean oil enter- 8. Actual trays at operating (L,/VN + 1):
ing/mols wet gas entering.
No = N/Eo
Qbsorption-Determine Number Trays For Specified E, values may be calculated from Figure 8-29 or
Product Absorption assumed at 20 to 50% as an estimating value for
hydrocarbon oil and vapors, pressures atmospheric
1. For fixed tower temperature, pressure, gas feed rate, to 800 psig, and temperatures of 40°F to 130°F (see
specified or assumed operating (Lo/Vx+l) times Table 8-1 1).
minimum value, specified component recovery out 9. Lean oil rate:
of inlet gas.
2. Calculate: Lo = (Ai) (Ki) (VN + 110, mols/hr (8-201)
(a) Mols component in inlet gas/hr
(b) Mols in outlet gas 10. For other components: E,i is estimated by