Page 322 - Process Equipment and Plant Design Principles and Practices by Subhabrata Ray Gargi Das

324 Chapter 11 Distillation

The system factor SF for horizontal and vertical vessels (with mist eliminator) is given in
Table 11.9 against values of the separation factor s.

1=2
V L (11.36)
s ¼ðm L = m V Þðr =r Þ
Table 11.9 Separation factor at 85% flooding velocity (with mist eliminator).
System factor SF(m/sec)
s For vertical drum, SF v For horizontal drum, SF h

0.006 0.0762 0.0953
0.008 0.0914 0.1142
0.01 0.1006 0.1258
0.02 0.1219 0.1524
0.04 0.1341 0.1676
0.06 0.1341 0.1676
0.08 0.1310 0.1638
0.1 0.1280 0.1600
0.2 0.1128 0.1410
0.4 0.0884 0.1105
0.6 0.0671 0.0839
0.8 0.0549 0.0686
1.0 0.0488 0.0610
2 0.0228 0.0285
4 0.0101 0.0126
6 0.0055 0.0069

A higher value of the system factor SF allows a higher allowable maximum vapour velocity and
leads to lower cross section. Since higher disengagement height (h disengaging ) would reduce entrain-
ment and allow higher SF to be used, a second approach to sizing is based on Table 11.10 that tabulates
(maximum) allowable SF against values of h disengaging .

Table 11.10 SF values based on disengaging height (h disengaging ) with mist eliminator.
h disengaging 75 100 125 150 175 200 225 250 275 300 325 350
(mm)
Allowable 0.12 0.15 0.19 0.22 0.25 0.29 0.32 0.35 0.38 0.40 0.42 0.43
SF value