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

Data From Exercise 41

Performance data for a distillation tower separating a 50/50 by weight percent mixture of methanol and water are as follows:

Feed rate = 45,438 lb/h; feed condition = bubble-point liquid at feed-tray pressure;

Wt% methanol in distillate ¼ 95.04; Wt% methanol in bottoms = 1.00;
Reflux ratio = 0.947; reflux condition ¼ 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 inches;
Weir length = 42.5 inches; hole area = 10%; hole size = 3 / 16 inch;
Weir height = 2 inches; tray spacing =24 inches;
Viscosity of feed = 0.34 cP; Surface tension of distillate = 20 dyne/cm;
Surface tension of bottoms = 58 dyne/cm;
Temperature of top tray = 154F; temperature of bottom tray  207^οF
Vapor–liquid equilibrium data at column pressure in mole fraction of methanol are

Based on the above data: 

(a) Determine the overall tray efficiency assuming the reboiler is equivalent to 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.

Transcribed Image Text:

Atmospheric- pressure column Oxygen product Air feed 4 to 5 atm column Throttle valve FREEWAY www Figure 7.45 Data for Exercise 7.40. Nitrogen product Reflux condenser- boiler Liquid oxygen Liquid nitrogen