A COMPUTER PROGRAM FOR THE CORRELATION

OF BINARY VAPOR-LIQUID EQUILIBRIA DATA

Jacob H. Lashover

Tulane University, New Orleans, Louisiana

January 2, 2015

Abstract: This FORTRAN program was used to correlate the binary

vapor-liquid equilibria (VLE) systems which were used to build the

representations of the multicomponent systems for calculations in Monte

Carlo Marching. The Redlich-Kister (R-K) activity coefficient model

was chosen for this work although other models such as Wilson,

Margules, van Laar, etc. could also be used when non-electrolytic

systems at low to moderate pressures are considered.

The Taylor series was used as a linearization and convergence

technique to solve the simultaneous, non-linear equations which are

encountered when binary VLE data are fitted using a least-squares

criterion. Pressure-liquid composition, vapor composition-liquid

composition, and temperature-liquid composition data, optionally

weighted with the Gilmont method, were correlated using the 3rd order

R-K equations to relate activity coefficients to liquid composition.

Computer output consists essentially of equilibrium composition curves

and the B and C constant for each binary pair which are used as inputs to

calculate VLE for multicomponent systems.

Future work will show the replacement of this program with

one using Monte Carlo Marching and programmed in QB64.

Derivatives of the R-K equations will not be required thus facilitating

the addition of the Wilson, van Laar, Margules and other activity

coefficient models. The original work was first published at the

November, 1962 meeting of the American Chemical Society in

Gatlinburg, Tennessee where Dr. Edward Teller presented some of his

work in the same group of papers. The author was privileged to be

selected to participate in a panel discussion which included Dr. Teller.

All of the distillation columns for Union Carbide’s Sevin©

process were designed using VLE correlations from this program.

Pressure-liquid composition data were obtained from the equilibrium

pressures of cylinders, in a constant temperature bath, into which the

components were injected by weight to avoid exposure to personnel.

Keywords: Vapor-liquid equilibrium, Taylor series, convergence,

simultaneous non-linear equations, multicomponent systems