Page 112 - Applied Process Design For Chemical And Petrochemical Plants Volume II

Distillation 101

Table 8-8
Henry's Law Constants and Optimum Stripping Factors for Selected Organic Compounds for Use With Tray Towers
@ 25°C (77°F)
~~~-~
Henry's Law L = 30 L = 300 L = 3,000
Chemicals constant XN/% % gPm gPm @m
.~
1,1,2,2-tetrachloroethane 24.02 4.75 1.7 1.65 1.35
0.05 2.3 2.1 1.6
1,1,2-trichIoroethane 47.0 4.75 1.98 1.98 1.56
0.05 3.10 3.00 2.18
1,2dichloroethane 61.2 4.75 2.09 2.14 1.67
0.05 3.34 3.31 2.40
propylene dichloride 156.8 4.75 3.1 3.3 2.5
0.05 5.1 5.5 4.0
methylene chloride 177.4 4.75 2.96 3.38 2.57
0.05 5.38 5.84 4.1
chloroform 188.5 4.75 3.15 3.6 2.72
0.05 5.8 6.3 4.37
l,l,l-trichloroethane 273.56 4.75 4.1 4.6 3.2
0.05 7.1 7.2 5.5
1,2-dichloroethene 295.8 4.75 3.7 4.7 3.4
0.05 7.59 8.6 5.84
1, l-dichloroethane 303.0 4.75 3.81 4.84 3.5
0.05 7.8 8.9 6.0
hexachloroethane 547.7 4.75 6.3 7.3 5.1
0.05 10.5 14.5 8.4
hexachlorobutadiene 572.7 4.75 6.5 7.8 5.3
0.05 11.0 15.2 9.1
trichloroethylene 65 1 .O 4.75 6.6 8.3 5.8
0.05 13.9 16.9 10.9
1, ldichloroethene 834.03 4.75 7.2 10.5 6.9
0.05 12.0 19.2 12.0
perchloroethane 1,596.0 4.75 9.8 13.3 11.8
0.05 16.1 36.1 22.4
carbon tetrachloride 1,679.1'7 4.75 9.2 11.7 12.1
0.05 13.4 33.0 21.0
_- -~ ~ .-
Used by permksion, Chem. 15%. Li, K Y. and Hsiao, K J., V. 98, No. 7 (1991), p. 114; all rights reserved.

For PDC: '7. Determine the tower diameter based on the flows of
(6) above. See Chapter 9, this volume for packed
Vmin = L/K= (300 gpm) (8.33) (359)/(18) (156.8) tower design.
= 317.8 scf/min
4. Use the larger air rate as control required, which is
the 317.8 scf/minute required for PDC, to calculate Troubleshooting, Predictive Maintenance and Controls
the optimum flowrate. for Distillation Columns
5. Vopt = (3.9) (317.8) = 1,239.4 scf/min
Troubleshooting currently is much more sophisticated
Sopt = K/ (L/Vopt)
due to the technical tools available for investigating and
Vopt = Sopt (Vmin) analyzing performance than several years ago. The
gamma radiation scanning technique of several distilla-
6. Therefore, the operating conditions would be:
tion specialist companies [la& 1821 provides one type of
L = 300 gpm data gathering that can significantly aid in determining
\I = 1,239 scf/min (minimum, may want to consider actu- whether a column is having liquid/vapor flow and or dis-
ally using 10-15% more for some assurance that the tribution problems. Figure 8-56 is one case study of a prob-
required condi~ons will be met. lem column. This system provides an accurate density pro-