Experimental and Numerical Method for Estimating Diffusion Coefficient of the Carbon Dioxide into Light Components

This study addresses the diffusion coefficient of CO 2 into light-hydrocarbons. Experiments were done under nonisothermal and nonisobaric conditions, using dynamic pendant drop volume analysis to measure the change in hydrocarbon drop volume due to CO 2 diffusion, for 25–45 °C and 25–65 bar. A new numerical model was developed, where a spherical drop was used rather than the actual pendant shaped drop, which enabled sensitivity studies. The approach showed 3–6% difference in the surface area of the spherical drop compared to experimental drop. This is translated to less than 6% difference when compared to the published data. Interfacial tension investigations showed a change from a negative (decreasing) to positive (increasing) trend with temperature for pressures 30–60 bar. A suggested explanation was based on the density difference between the drop (CO 2 +hydrocarbon) and the surrounding CO 2 . Further, the observed higher diffusion coefficient of n -hexane compared to n -decane may be attributed to viscosity.