Page 131 - Applied Process Design For Chemical And Petrochemical Plants Volume II

120 Applied Process Design for Chemical and Petrochemical Plants

3. Calculate tray efficiency for C3H4. From Figure 858 at n = 18 trays theoretical, and Ai =
Using O'Connell's correlation: 0.001235 read EA, except that in this low region some
values cannot be read accurately. When Ai is consider-
(solvent) at 104°F = 2.3 cp
ably less than 1.0, use EA = Ai (very little light material
sp. gr. = 1.0 recovered), and when Ai is quite a bit larger than 1 .O ,
Mol. wt. solvent = 180 use Eai = 1 .O (heavy material mostly recovered).
K = 0.07 Mols component absorbed/hr = (VN + 1) (Y(N + 1)i) Ei
= (890) (0.562) (0.001235)
Sp. Gr. solvent - - (1.0) (62.3) = 4.94 = 0.617
HP =
(Kc H ) (M. W.solvent) (0.07) (180) Mols component absorbed/mol lean oil = X, = 0.0617/64.8
34
= 0.00933
_=_= 4'9 2.13
HP
p 2.3 Mols of component in off gas out top of absorber:
= 500.0 - 0.617 = 499.383 mols/hr
Efficiency = 46.5% (From Figure 8-29)
Use: 45% Mols component in, out top of absorber/mol inlet
Actual number trays in column = 40 rich gas
Theoretical trays based on 45% efficiency = (40) (.45)
= 18
4. Using Ei = 96.5% for CgH4, read Ai from Figure 8-58.
Atn=18 0.001235 = 0.562 - Y1
A.= =Ai = 1.04 0.562
Ai = L0/J!A7~ + 1
Vv + 1 = 890 mols/hr Yli = 0.5614
Lo = (1.04) (0.07) (890) = 64.8 mols/hr 6. Correcting values and recalculating
Lo/Vy + 1 = 64.8/890.0 = 0.0728
.
5.
.. . -. . Inlet L,(l+ZXiR)
Component Y(N + 1)i Mols/Hr VN + 1 Ki Eai
Eai
H2 0.562 500.0 0.00144 0.00144
H2 0.562 500.0 0.001235 0.00 1235 CH4 0.0235 20.9 0.001513 0.001513
CH4 0.0235 20.9 0.00130 0.00 130 C2H2 0.1478 131.5 0.01048 0.01048
C2H2 0.1478 131.5 0.009 0.009 co 0.258 230.0 0.00689 0.00689
co 0.258 230.0 0.00592 0.00592 CsH4 0.00393 3.5 1.21 0.98
C3H4 0.00393 3.5 1.04 0.965 C4H2 0.00462 4.1 9.43 1 .oo
c4H2 0.00462 4.1 8.1 1 .ooo
0.99985 890.0
Mols/Hr Off Gas
Component Absorbed Xx Mols/Hr Yli
Mols/Hr Mols/Hr
Component Absorbed Xx Off Gas Yli (04 H2 0.72 0.0111 499.28 0.561
CH4 0.031'7 0.000488 20.869 0.0232
H2 0.617 0.00953 "499.383 0.561 C2H2 1.38 0.0213 130.12 0.1463
CH4 0.0272 0.00042 20.8728 0.02348 co 1.383 0.0244 228.415 0.257
C2H2 1.185 0.0183 130.315 0.14647 CsH4 3.43 0.0529 0.07 0.00008
co 1.36 0.021 228.64 0.2565 C4H2 4.1 0.0633 0 0
CsH4 3.37 0.052 0.13 0.00014 11.246 0.1734 878.754 0.9775
4.1 0.0633 0 0
'4% 10.659 0.1645
- .... - ..
*These are subtraction differences and do not infer that the results are Typical calculations, using hydrogen:
this accurate.
Ai= Lo (l+Z%iR)=- 0'0728 (1 + 0.1645) = 0.00144
Typical calculations: for hydrogen VN+I (Ki 1 59.0
Ai = 0.0728/59.0 = 0.001235
Mols component absorbed/hr = (0.00144) (500) = 0.72