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288 Chapter 6

Figure 6.5. This diameter might result in a short separator length if the liquid flow
rate is small. If this occurs it may be necessary to increase the separator length, or
employ other designs for reducing the diameter as given by Sigales [73]. The
equations are listed in Table 6.11, and the calculation procedure for calculating L
and D is given in Table 6.12. As was the case for vertical gas-liquid separators, if
L/D < 3, increase L so that L/D > 3, even if the liquid surge volume is increased.
Similarly, if L/D > 5 increase D so that L/D < 5. Increasing D will reduce the gas
velocity and increase the liquid surge volume, which is in the right direction. The
volume of the dished heads is not included in the design procedure. Example 6.3
illustrates the calculation procedure for sizing horizontal gas-liquid separators.
Table 6.12 Calculation Procedure for Sizing Horizontal Gas-Liquid
Separators__________________________________

1. Select k v from Equation 6.11.3.

2. Calculate the maximum vapor velocity, v v, from Equation 6.11.2.

3. Calculate the cross-sectional area, A, from Equation 6.11.1.

4. Calculate D using Equation 6.11.4. Round off D in 6 in (0.152 m) intervals,
starting at 30 in (0.762 m). If D is less then 30 in (0.762), use standard pipe.

5. Select a liquid phase surge time, t s, from Equation 6.11.6.

6. Calculate the separator length from Equation 6.11.5. Round off L in 3 in
(0.0762 m) intervals (for example, in feet, 5.0, 5.25, 5.5, 5.75 etc.)

7. If L/D < 3.0, then recalculate L so that L/D > 3.0 by setting L/D = 3.2. If L/D >
5.0, then recalculate D so that L/D < 5.0 by setting L/D = 4.8.

Example 6.3 Sizing a Gas-Liquid Separator___________________

Calculate the length and diameter of a gas-liquid separator to separate 200.7
3
3
3
ft /min (5.68 m /min) of vapor from 5.0 gal/min (0.0189 m /min) of a liquid.
Data
3
3
vapor density 1.372 Ib/ft (21.98 kg/m )
3
liquid density 31.15 Ib/ft 3 (499.0 kg/m )
design pressure 50 psig (3.45 barg)
design temperature 200 °F (93.3 °C)
material carbon steel

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