Flash calculations for continuous or semicontinuous mixtures by use of an equation of state

Abstract

This work describes two procedures for performing flash calculations using continuous thermodynamics. The first procedure, called the mejthod of moments, provides only an approximation because it does not strictly satisfy all material balances; however, In some cases this approximation can be very good. A second procedure, called the quadrature method, uses efficient Gaussian integration; it does not use an algebraic form for the distribution function but provides exact solutions to the flash problem at selected values of the distribution variable. Both procedures are Illustrated with realistic examples, including fluid mixtures where a selected component (e.g., C02) is considered as a discrete component while all others are considered as continuous components; this Is the semicontinuous case. Calculations are also given for fluid mixtures containing several homologous series (or ensembles) as found, for example, in pefroleum mixtures where the ensembles may be paraffinic, naphthenic, and aromatic hydrocarbons. Calculated results using the quadrature method are compared to experimental data for phase equilibria in a natural-gas mixture. Agreement Is very good for compositions of coexisting phases and for liquid yield during retrograde condensation.

Phase equilibria in polydisperse and associating copolymer solutions: Poly(ethene-co-(meth)acrylic acid)–monomer mixtures

“…The concept is similar to the one used by Cotterman and Prausnitz in their studies into the so-called continuous thermodynamics [25].…”

Nematic-isotropic phase behaviours of polydisperse polymer/liquid crystal systems: Applicability of continuous thermodynamics

“…Furthermore, we modify χ to take into account both polymer concentration and temperature and employ a continuous thermodynamics [16][17][18] characterized by a continuous molar mass distribution. We also quantitatively investigate the nematic-isotropic phase transition behaviors of polydisperse polystyrene (PS)/nematic liquid crystal systems and compare our proposed model with experimental results.…”

Liquid-liquid equilibria for solutions of polydisperse polymers. Continuous thermodynamics for the close-packed lattice model

“…During the last 10 years, Ratzsch, Kehlen and coworkers [13,14,15], and Cottennan and Prausnitz [16,17] developed a functional approach, where chemical potentials are defined using functiori~ : a1s to incorporate the molar-mass distribution or the chain-length distribution of a polymer · solute. The functional fonn of partial derivatives and higher-order variations of ftmctionals are also defined to derive thennodynamic relations for chemical potentials, spinodals and critical points.…”