Correlation of pressure drop and holdup in a packed distillation column

Author

Nello Del Gobbo, New Jersey Institute of Technology

Document Type

Thesis

Date of Award

6-30-1960

Degree Name

Master of Science in Chemical Engineering - (M.S.)

Department

Chemical Engineering

First Advisor

George C. Keeffe

Second Advisor

C. L. Mantell

Third Advisor

Saul I. Kreps

Abstract

Reed and Fenske have proposed a relationship that correlates the variables of packing dimensions, operating conditions, and fluid properties involved in countercurrent flow through packed distillation columns. Pressure drop and holdup data, obtained by atmosphere is distillation in columns packed with wire helices, was applied to the correlation by Reed and Fenske with good results. At reduced pressures limited data indicated the possibility of variations in the correlation as a function of the molecular weight of the material distilled.

Cummins investigated the effect of reduced pressure and holdup in distillation for several liquids using protruded packing. An attempt to correlate the data proved ineffective, and Cummins proposed a modification of the Reed-Fenske relationship based on liquid viscosity that appeared to result in an improved correlation of his data.

To determine the validity of the Reed-Fenske correlation, pressure drop and dynamic holdup were obtained for seven organic solvents under conditions of atmospheric and vacuum distillation. A 1 inch diameter column, packed with 56 inches of protruded stainless steel packing, was used for this study. Single phase flow of vapor, distillation at total reflux, and operation at constant liquid loadings with variable vapor rates, were investigated.

This investigation has shown that the observed variations in pressure drop as a function of molecular weight and operating head pressure in distillation can be correlated by applying the appropriate form of the Reed-Fenske relationship. Over the pressure range of 250 mm Hg. absolute to atmospheric pressure, a new correlation of single phase (vapor) flow through dry packing was obtained as follows:

ρgΔPf₀³/μ_gS³ = 1.45 (G/μS)^1.8

Extensive flow data, obtained over the pressure range of 250 mm Hg. absolute to atmospheric pressure, for countercurrent two phase flow as in distillation at total reflux or at constant liquid loadings with variable vapor rates was correlated for the first time by the following equation:

ρgΔ(f_o-H)³ /μ²_gS³ = 1.7(G/μ_g S)^1.71

When holdup data is lacking, an estimate of the pressure drop in two phase countercurrent flow for the pressure range of 250 mm Hg. absolute to atmospheric pressure can be made from the following equation:

ρgΔP/μ²_g = 3.0 x 10^-5(G/μ_g)^1.71

Modification of the Reed-Fenske relationship by substitution of liquid viscosity for vapor viscosity, as suggested by Cummins, did not result in an improved correlation of the test data.

Recommended Citation

Del Gobbo, Nello, "Correlation of pressure drop and holdup in a packed distillation column" (1960). Theses. 2950.
https://digitalcommons.njit.edu/theses/2950