Correlation of bubble-cap fractionating-column plate efficiencies

✍ Scribed by Earl D. Oliver; C. C. Watson

• Publisher: American Institute of Chemical Engineers
• Year: 1956
• Tongue: English
• Weight: 995 KB
• Volume: 2
• Category: Article
• ISSN: 0001-1541
• DOI: 10.1002/aic.690020105

✦ Synopsis

Abstract

A method of estimating the true conditions of operation of a bubble‐cap tray is presented. Intermediate between the Murphree and the Lewis methods, which represent the extremes of actual operation, this method involves the use of a correlation to determine the degree of liquid mixing on the tray and the use of new relations between the Murphree vapor efficiency, the Lewis case I efficiency, and the true local efficiency. For the last, partial liquid mixing is taken into account.

Data were obtained on an 18‐in. O.D. three‐tray bubble‐cap tower containing ten 3‐in. bubble caps a tray. Partial liquid mixing was correlated for changes in vapor and liquid rates, pressure, temperature, and weir height for the system ethylene dichloride‐toluene.

Efficiency data on acetone‐water, ethanol‐water, and ethylene dichloride‐toluene showed the following effects: (1) low concentration of lwo boiler usually, but not always, resulted in low true local efficiencies, always with high Murphree efficiencies; (2) vapor velocity effects are more intimately connected with slot velocity than superficial velocity (and hence entrainment); (3) raising the pressure gives higher efficiencies; (4) an increase in liquid depth increases the true local efficiency but may have no effect on the Murphree efficiency.