abstract
In this work, the measurement of diffusion coefficients in supercritical carbon dioxide and their modelling by different approaches were accomplished. In the experimental part, the chromatographic impulse response method (CIR) was employed, using a capillary column with an internal coating of poliethylene glycol. The measurements were carried out at various temperatures and constant pressure (197 bar). The curve fitting method was applied for the determination of the diffusivity values. In the modeling part, the experimental diffusion coefficients were compared with those computed by various models from the literature: the hydrodynamic equations of Tyn-Calus, Reddy-Doraiswamy, and Lusis-Ratcliff; the freevolume equation of Dymond-Hildebrand-Batschinski; and one correlation based on the Schmidt number. A new hydrodynamic equation was also developed based on the Lusis-Ratcliff model. It was tested with an extensive database containing 161 systems and 4393 datapoints, and gave rise to relative deviations (AARD) of 9.97% for all solutes except n-alkanes, and 6.42% for n-alkanes. The original model provided 27.22% of error. Finally, the modified correlation based on the Schmidt number reduced the global error by half (from 8.54% to 4.20%).
subject category
MESTRADO INTEGRADO EM ENGENHARIA QUÍMICA
authors
Ricardo Manuel Grade Gonçalves
our authors
supervisors
Carlos Manuel Silva; Francisco Avelino Silva Freitas
Groups