Abstract Twu, C.H., Coon, J.E. and Cunningham, J.R., 1994. A generalized vapor pressure equation for heavy hydrocarbons. Fluid Phase Equilibria, 96: 19-31. Pitzer's acentric factor is widely used in physical property estimations; one important area is that of generalized vapor pressure correlations. Since Pitzer's acentric factor is defined in terms of the vapor pressure at a reduced temperature equal to 0.7, using this approach to generalize a vapor pressure equation gives excellent accuracy at reduced temperatures between 0.7 and 1.0, but predicts vapor pressures less accurately at lower reduced temperatures. To improve the vapor pressure prediction of hydrocarbons at low reduced temperatures, the definition of the acentric factor is re-examined and a modified acentric factor is proposed. Two sets of generalized vapor pressure equations are presented, with Pitzer's acentric factor and the modified acentric factor, respectively, as the third corresponding states parameter. These two equations are applied from the triple point to the critical point. Both correlations give more accurate vapor pressure predictions than the Lee-Kesler (1975) 2 correlation, especially at low reduced temperatures, with the correlation using the modified acentric factor as the third parameter being the most accurate. Additionally, an internally consistent approach is proposed for estimating the normal boiling point, critical temperature and critical pressure of petroleum fractions using a single low temperature vapor pressure data point. The procedure proposed uses either correlation from this work and gives an accurate estimation of the normal boiling point and acentric factor for heavy petroleum fractions for use in equations of state.
[1]
Robert F. Curl,et al.
Volumetric and Thermodynamic Properties of FluidsEnthalpy, Free Energy, and Entropy
,
1958
.
[2]
J. B. Maxwell,et al.
Derivation and Precision of a New Vapor Pressure Correlation for Petroleum Hydrocarbons
,
1957
.
[3]
Byung-Ik Lee,et al.
A generalized thermodynamic correlation based on three‐parameter corresponding states
,
1975
.
[4]
Kenneth S. Pitzer,et al.
The Volumetric and Thermodynamic Properties of Fluids. I. Theoretical Basis and Virial Coefficients1
,
1955
.
[5]
Chorng H. Twu,et al.
An internally consistent correlation for predicting the critical properties and molecular weights of petroleum and coal-tar liquids
,
1984
.
[6]
Wolfgang Wagner,et al.
New vapour pressure measurements for argon and nitrogen and a new method for establishing rational vapour pressure equations
,
1973
.
[7]
Robert F. Curl,et al.
The Volumetric and Thermodynamic Properties of Fluids. II. Compressibility Factor, Vapor Pressure and Entropy of Vaporization1
,
1955
.
[8]
Prediction of physical properties for non-polar compounds, petroleum and coal liquid fractions
,
1991
.