Improved Prediction of Water Properties and Phase Equilibria with a Modified Cubic Plus Association Equation of State

Abstract

One of the major challenges of an equation of state lies in the description of water and aqueous systems. Its abundance and unique properties turn water into one of the most important molecules in the industry. However, because of these peculiar characteristics, its modeling is far more complex than for any other common solvent. In this work, a modified cubic plus association (CPA) model, which includes the correct description of the pure component critical temperature and critical pressure, is expanded to water and its systems. A brief analysis of the predicted water purity properties is conducted, comparing those to a previous version of the model. Results for a group of binary systems, including liquid−liquid equilibria with alkanes and alcohols, highlighting their minima in aqueous solubility, and gas solubility in water/water solubility in gas, are also presented. Finally, ternary and multicomponent systems of water + hydrocarbons and water + polar compound + hydrocarbons are also modeled and discussed.

Heat Capacities of Fluids: The Performance of Various Equations of State

“…Palma et al − proposed a modified CPA EoS to calculate the C v , C p , C v res , and C p res of alcohols and water at saturation. In their works, the original α function (one parameter) was replaced by a 5-parameter function, and two different kinds of ( T -independent and T -dependent) volume shifts were added to the EoS.…”

“…The energy parameter and covolume were obtained by solving the corresponding equations at the critical points in order to improve the accuracy of the critical properties. Generally, their modified CPA shows satisfactory performance for heat capacities and their residual properties, and the only exception is for the C p of glycerol with an AAD of 15%. , The T -independent volume shift used in the modified CPA has no influence on heat capacity calculations, while the C v of several alcohols can be better described with a T -dependent volume shift.…”

“…Compared with the original CPA EoS, the modified CPA proposed by Palma et al gives much higher accuracy for the C p for water, while the AAD of ρ sat,l increases as the data of this property are not included in the fitting procedure. 19 In Table 3 are also presented and compared the saturated properties of water obtained from the original CPA and PC-SAFT at reduced temperatures up to 0.96. 31 Both EoS can accurately reproduce the VLE data.…”

“…Palma et al − modified the CPA EoS with a five-parameter function in the attractive term (the so-called α function) and a volume shift, and they analyzed its performance for the estimation of saturated C v , C p , and residual C p ( C p res ) for water and alcohols. Then, they compared their results with the original CPA.…”

High-pressure experimental vapour-liquid-liquid equilibrium measurements and modelling for natural gas processing: Equipment validation, and the system CH4+nC6H14+H2O

“…Given that nC6+H2O exhibits the complex binary interactions, the model predictions might be improved by the implementation of Mathias-Copeman[48] (MC) parameters. Palma et al[49] achieved excellent results for water-alkane LLE by fitting new MC parameters whilst applying specific restrictions in the parameterization. Polishuk et al[50] have highlighted the effect of kij on LLE prediction and phase behaviour classification in their development of a global phase diagram method.…”