Page 254 - Petroleum and Gas Field Processing

Examination of the table shows that the retention time
constraint governs the design up to a diameter of 96 in.; then,
the settling constraint governs. Suitable selections would be 84
in. 22 ft, or 96 in. 17 ft.
2. Horizontal Recatangular Cross-Section Skimmer. Using Eq. (12)
(settling constraint),

ð70Þð8000Þð1:1Þ
WL ¼
2
0:2ð200Þ
2
¼ 77 ft ðE3Þ
Using the retention time constraint, Eq. (14)
2 3
W L ¼ð0:008Þð8000Þð10Þ¼ 640 ft ðE4Þ

L(ft) L(ft)
W(ft) H w ¼ 0.5 W Settling [Eq. (E3)] Retention [Eq. (E4)]
5 2.5 15.40 26.6
6 3.0 12.83 17.28
7 3.5 11.00 13.06

Again, the retention time constraint governs the design of the
skimmer. The suitable selections are skimmers that are 6 ft wide
by 18 ft long, and 7 ft wide by 14 ft long. The height of the water
in the skimmer is limited to one-half of the width.
3. Vertical Cylindrical Skimmer. The settling constraint [Eq. (16)]
provides the minimum diameter for the skimmer:

2 ð6691Þð8000Þð1:1Þ
D ¼ 2 ¼ 7360
0:2ð200Þ

D min ¼ 85:79 in:

Because the diameter is greater than 48 in., the settling equation
should be multiplied by a factor that is greater than 1 to account
for turbulence and short-circuiting. Using a factor of 1.5 gives

D min ¼ 105 in:

Copyright 2003 by Marcel Dekker, Inc. All Rights Reserved.