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290 Chapter 6

L/D = 8.5 / (1.625) = 5.23. Because L/D is greater than 5.0, size a horizon-
tal separator. We could stop here, however, because five is not a precise number
and 5.23 is close to 5.0.
Now, size a horizontal separator using the procedure outlined in Table 6.12
and the equations listed in Table 6.11.
Select a mist eliminator. From Equation 6.11.3, k = 0.35 ffs (0.0107 m/s).
v
From Equation 6.11.2, the maximum vapor velocity,
( 31.15-1.372 Y /2
v v = 1.25 (0.35) I ————————— I = 2.038 fl/s (0.621 m/s)
I 1.372 )

From Equation 6.11.1,

2
2
A = 200.7 / 60 (0.5) (2.038) = 3.283 ft (0.0283 m )
From Equation 6.11.4, the separator diameter,
1/2
D = [ (4 / 3.142) (3.283) ] = 2.044 ft (0.623 m)
From Figure 6.5, the minimum vapor-phase height is 2.75 ft (0.838 m). Because
the liquid level is at the middle of the separator, the minimum D = 5.5 ft (1.68 m).
From Equation 6.11.,

2
2
2
A = (3.142 / 4) (5.5) = 23.76 ft (2.21 m )
Now, from Equation 6.11.5 for a separator that is half filled with liquid,
5.0 gal/min 8.75 min 1
— =0.4923 ft (0.150m)
7.481 gal/ft 3 1 0.5 (23.76) ft 2

which, clearly, is not satisfactory.
The L/D ratio should be in the range of 3.0 < L/D < 5.0. If we select 3.2,
then,
L = 3.2 (5.5) = 17.60 ft (5.36 m)

Round off the length to 17.75 ft (5.41 m). This separator is larger than the vertical
separator.
Let us try to reduce the size of the horizontal separator. If we move the mist
eliminator to outside of the separator shell, as shown in Figure 6.3.1, the diameter

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