For the conditions of Exercise 7.41, a laboratory Oldershaw column measures an average Murphree vapor-point efficiency of 65%. Estimate EMV and Eo.

In Exercise 7.41

The following performance data have been obtained for a distillation tower separating a 50/50 by weight percent mixture of methanol and water:

Feed rate = 45,438 lb/h. Feed condition = bubble-point liquid at feed-tray pressure, Wt% methanol in distillate 95.04. and Wt% methanol in bottoms =1.00

Reflux ratio = 0.947; Reflux condition = saturated liquid

Boilup ratio = 1.138; Pressure in reflux drum = 14.7 psia

Type condenser = total; Type reboiler = partial

Condenser pressure drop = 0.0 psi; Tower pressure drop = 0.8 psi

Trays above feed tray = 5; Trays below feed tray = 6

Total trays = 12; Tray diameter = 6 ft

Type tray = single-pass sieve tray; Flow path length = 50.5 in.

Weir length 42,5 in.; Hole area = 10%; Hole size = 3/16 in.

Weir height = 2 in.; Tray spacing = 24 in.

Viscosity of feed = 0,34 cP

Surface tension of distillate = 20 dyne/cm; Surface tension of bottoms = 58 dyne/cm Temperature of top tray = 154°F; Temperature of bottom tray = 207oF Vapor-liquid equilibrium data at column pressure in mole fraction of methanol are

Based on the above data:

(a) Determine the overall tray efficiency from the data, assuming that the reboiler is the equivalent of a theoretical stage.

(b) Estimate the overall tray efficiency from the Drickamer- Bradford correlation.

(c) Estimate the overall tray efficiency from the O'Connell correlation, accounting for length of flow path.

(d) Estimate the Murphree vapor tray efficiency by the method of Chan and Fair.

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