The volumetric and thermodynamic functions correlated by Pitzer and co-workers analytically represented with improved accuracy by a modified BWR equation of state. The representation provides a smooth transition between the original tables of Pitzer et al. and more recent extensions to lower temperatures. It is in a form particularly convenient for computer use.

A generalized thermodynamic correlation based on three‐parameter corresponding states

A new correlation of second virial coefficients of both polar and nonpolar systems is presented. It uses the Pitzer-Curl correlation for nonpolar compounds, but in a modified form. The second virial coefficient of nonhydrogen bonding compounds (ketones, acetaldehyde, acetonitrile, ethers) and weakly hydrogen bonding compounds (phenol) is fitted satisfactorily with only one additional parameter per compound, which is shown to be a strong function of the reduced dipole moment. Two parameters are needed for hydrogen bonding compounds (alcohols, water), but for alcohols, one parameter has been kept constant and the other expressed as a function of the reduced dipole moment. The extension of the correlation to mixtures is satisfactory, direct, and involves only one coefficient per binary.

An empirical correlation of second virial coefficients

We propose an extension of the law of corresponding states that can be applied to systems—such as colloidal suspensions—that have widely different ranges of attractive interactions. We argue that the “reduced” second virial coefficient is a convenient parameter to quantify the effective range of attraction. Knowledge of the pair-potential alone allows one to estimate the relative location of the liquid–vapor and solid–fluid coexistence curves.

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Extended corresponding-states behavior for particles with variable range attractions

Physical property data for many of the key components used in the simulation for the ethanol from lignocellulose process are not available in the standard ASPEN PLUS property databases. Indeed, many of the properties necessary to successfully simulate this process are not available anywhere. In addition, inputting the available properties into each simulation is awkward and tedious, and mistakes can be easily introduced when a long list of physical property equation parameters is entered. Therefore, one must evaluate the literature, estimate properties where necessary, and determine a set of consistent physical properties for all components of interest. The components must then be entered into an in-house NREL ASPEN PLUS database so they can be called on without being retyped into each specific simulation. The first phase of this work is complete. A complete set of properties for the currently identifiable important compounds in the ethanol process is attached. With this as the starting base the authors can continue to search for and evaluate new properties or have properties measured in the laboratory and update the central database.

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Charles M. Huggins

Papers

The Volumetric and Thermodynamic Properties of Fluids. II. Compressibility Factor, Vapor Pressure and Entropy of Vaporization1