Design of a static micro-cell for phase equilibrium measurements: measurements and modelling

Caleb Narasigadu 1
1 CEP/Fontainebleau
CEP - Centre Énergétique et Procédés
Abstract : This study covers the design of a new apparatus that enables reliable vapour pressure and equilibria measurements for multiple liquid and vapour phases of small volumes (a maximum of 18 cm3). These phase equilibria measurements include: vapour-liquid equilibrium (VLE), liquid-liquid equilibrium (LLE) and vapour-liquid-liquid (VLLE). The operating temperature of the apparatus ranges from 253 to 473 K and the operating pressure ranges from absolute vacuum to 1600 kPa. The sampling of the phases is accomplished using a single Rapid-OnLine-Sampler-Injector (ROLSITM). A novel technique is used to achieve sampling for each phase. The technique made use of a metallic rod in an arrangement to compensate for volume changes during sampling. As part of this study, vapour pressure and phase equilibrium data were measured to test the operation of the newly developed apparatus. New experimental vapour pressure and VLE data were also measured for systems of interest to petrochemical companies. The experimental vapour pressure data obtained were regressed using the extended Antoine and Wagner equations. The experimental VLE data measured were regressed with thermodynamic models using the direct and combined methods. For the direct method the Soave-Redlich-Kwong and Peng-Robinson equations of state were used with the temperature dependent function (α) of Mathias and Copeman (1983). For the combined method, the virial equation of state with the second virial coefficient correlation of Tsonopoulos (1974) was used together with one of the following liquid-phase activity coefficient model: TK-Wilson, NRTL and modified UNIQUAC. Thermodynamic consistency testing was also performed for all the VLE experimental data measured where almost all the systems measured showed good thermodynamic consistency for the point test of Van Ness et al. (1973) and direct test of Van Ness (1995).
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Caleb Narasigadu. Design of a static micro-cell for phase equilibrium measurements: measurements and modelling. Chemical and Process Engineering. École Nationale Supérieure des Mines de Paris; University of KwaZulu-Natal - Afrique du Sud, 2011. English. ⟨NNT : 2011ENMP0071⟩. ⟨pastel-00679369⟩

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