Page 312 - Chemical process engineering design and economics

Separator Design 291

,1,

Figure 6.3.1 A horizontal gas-liquid separator with an external mist elimi-
nator.

will be reduced. From the calculation of separator diameter given above, D =2.044
ft (24.53 in, 0.623 m). Because D < 30 in (0.762 m), we can use pipe. From the
chemical engineering hand book [66], select a 30 in (0.762 m) Schedule ST pipe,
which has an inside diameter of 29.25 in (2.438 ft, 0.743 m), an inside cross-
2
2
sectional area of 4.666 ft (0.4335 m ), and a wall thickness of 0.375 in (9.53
mm). The allowable pressure for carbon steel at 200 °F (93.3 °C) is 266 psig (18.3
barg), which is above the design pressure of 50 psig (3.45 barg).
5.0 gal/min 8.75 min 1
L = ——————— ————— ——————— = 2.507 ft (0.764m)
7.481 gal/ft 3 1 0.5 (4.707) ft 2

Round off the length to 2.5 ft (0.762 m).
Check the L/D ratio.

L/D = 2.5 72.438 = 1.03

which is not within the limits of 3.0 < L/D < 5.0.

If we select L/D = 3.2,

L = 3.2 (2.448) = 6.541 ft (1.994 m)

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