Cubic plus association equation

Kontogeorgis, G. M., M. L. Michelsen, G. K. Folas, S. Derawi, N. von Solms, and E. H. Stenby. 2006a. Ten years with the applications of cubic-plus-association EOS to pure organic compounds and self-associating system (cubic-plus-association) equation of state. Part 1. Pure compounds and self-associating systems. Industrial and Engineering Chemistry Research. 45, 4855. 

In the thermodynamic model presented here, the Cubic-Plus-Association equation of state combined is used to model the fluid phases. The hydrate phase is modelled by the solid solution theory of van der Waals and Platteeuw. Good agreement between the model predictions and experimental data is observed, demonstrating the reliability and robustness of the developed model. The CPA EoS is shown to be a very successful model for multi-phase multi-component mixtures containing hydrocarbons, glycols and water. 

The cubic plus association equation of state, discussed in Chapter 4, is a combination of the Soave-Redlich-Kwong equation with first-order perturbation theory for associating fluids that is essentially the same as in the SAFT equation, and is given by Michelsen and Hendricks. The cubic plus association equation of state has been reviewed in refs 188, 189 and 190. Because of the association term, similar to that used for SAFT, the equation is no longer cubic. The cubic plus association equation of state is as follows ... 

Combining rules given by eqs 5.200 and 5.201 have been used with the cubic plus association equation. Wolbach and Sandler provided ah initio justification for eq 5.200. For (methanol-1-water) Koh et al also validated the use of either eq 5.198 or 5.200. For (vapour- -liquid), (liquid-I-liquid) and (solid-I-liquid) equilibria ref 189 lists the eombining rules preferred for 18 cross-associating mixtures. 

Derawi et a/. " found eqs 5.197 and 5.199 were preferred for the optimal representation of the phase boundaries for (methanol + water), (ethane-1,2-diol -l-waer), (2-hydroxyethoxy)ethan-2-ol - -water and (2-[2-(2-hydroxyethoxy) ethoxyjethanol + water) ref. 201 defines the acronyms for the combining rules used in the literature. The phase boundaries of (water -I- ethanol + CO2) were considered in the context of the cubic plus association equation by Perakis et with combining rules given by eqs 5.198 and eqs 5.199 where the expression for included an additional interaction parameter ly as a multiplying factor (1 /y) the parameters kij and ly are adjusted to reproduee the... 

The cubic plus association equation has been applied to oil reservoir hydrocarbons with the ubiquitous water using the combining rule given by eq 5.200. The phase equilibria of (water- -CO2) is important for carbon sequestration in geological formations and requires methods to predict the phase boundaries and solubility. Pappa et al estimated the phase boundaries... 

For mixtures of hydrocarbons and alcohols, often involved in hydrate inhibition, the cubic plus association equation of state has been used to estimate the (vapour + liquid) and (liquid-b Uquid) equilibria. In both cases no combining rules are needed for the association parameters and for (alcohol + hydrocarbon). 

Ma J, Li J, Fan D, Peng C, Liu H, Hu Y (2011) Modeling pVT properties and vapor-liquid equilibrium of ionic liquids using cubic-plus-association equation of state. Chin J Chem Eng 19 1009-1016... 

To conclude, predictive cubic EoS (PPR78, PR2SRK, PSRK, VTPR, UMR-PR) make a perfect job to simulate the phase behaviour of crude oils, gas condensate and natural gases. For processes in which water and/or glycol are present (e.g. transportation processes), it is advised to use more complex EoS like the CPA (Cubic-Plus-Association) by (Derawi et al., 2003) or equation deriving from the SAFE (Statistical Associating Fluid Theory) which are however non predictive (many parameters have to be fitted on experimental data). 

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