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Carvalho P.J.,University of Aveiro | Pereira L.M.C.,University of Aveiro | Goncalves N.P.F.,University of Aveiro | Queimada A.J.,INFOCHEM | Coutinho J.A.P.,University of Aveiro
Fluid Phase Equilibria | Year: 2015

A new high pressure cell was developed to measure the high pressure phase behavior of gas+aqueous salt solutions and validated through the measurement, and comparison against literature data, of two systems, the H2O+CO2 and H2O+CO2+NaCl, at temperatures up to 363K and pressures up to 13MPa. As previously reported by others, a salting out effect on the carbon dioxide solubility in water by NaCl is observed, decreasing its solubility as the salt concentration increases. Electrolyte versions of the cubic-plus-association and the RKSA-Infochem equations of state were used to estimate the H2O+CO2 and H2O+CO2+NaCl phase behavior, with both EoS providing a good representation of the experimental data. © 2014 Elsevier B.V.

Pedrosa N.,Infochem | Szczepanski R.,Infochem | Zhang X.,Infochem
Fluid Phase Equilibria | Year: 2013

The challenges of modelling phase behaviour for flow assurance applications involve not only gas, oil and aqueous phases but also encompass a variety of solid phases including hydrates, waxes and asphaltenes. We describe an integrated approach to the modelling process that is based on an industry-standard equation of state with a number of well-established modifications. The same underlying petroleum fluid characterisation procedure is used to generate compositional models that can describe all the fluid and solid phases for flow assurance applications. The particular characteristics of aqueous phases, electrolytes, dissolved wax and asphaltenes are handled by a series of add-on models that extend the basic equation of state. Each solid phase has its own dedicated model that is based on clear physical principles.We present examples of complex phase behaviour calculations involving multiple phases including hydrates, waxes and asphaltenes and show how the different solids interact.Although a sound description of the phase behaviour is fundamental for flow assurance, modelling the fate of precipitated solids is also important. We briefly describe our wax deposition model and demonstrate how the thermodynamic model impacts on deposition calculations. © 2013 Elsevier B.V.

Sousa J.M.M.V.,Polytechnic Institute of Coimbra | Sousa J.M.M.V.,University of Coimbra | Granjo J.F.O.,University of Coimbra | Queimada A.J.,Infochem | And 3 more authors.
Journal of Chemical Thermodynamics | Year: 2014

In this work, experimental values of gas solubility of hydrofluorocarbons (CHF3, CH2F2 and CH3F) in three room-temperature ionic liquids (RTILs) were determined within the temperature range 288 K to 308 K and at atmospheric pressure. The RTILs used were trihexyltetradecylphosphonium chloride ([P6,6,6,14][Cl]), tributyl(methyl)phosphonium methylsulfate ([P4,4,4,1][C 1SO4]), and tributyl(ethyl)phosphonium diethylphosphate ([P4,4,4,2][(C2)2PO4]). The data gathered have been modelled using two approaches: the Cubic plus Association equation of state (CPA EoS) and the regular-solution theory (RST). The experimental measurements were then discussed critically and the modelling results compared. © 2014 Elsevier Ltd. All rights reserved.

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