Experimental measurement of gas diffusivity in bitumen: Results for carbondioxide

A new technique is developed to measure the diffusivity of gas in bitumen a s a function of composition. Results are presented for a carbon dioxide-bit umen system, which is of considerable industrial relevance. The technique e mploys transient pressure data obtained from a nonintrusive pressure decay experiment at constant temperature and volume. The underlying theory is pre sented along with a computational algorithm to calculate diffusivity. Using experimental pressure decay data in the range 25-90 degrees C at 4 MPa, th e diffusivity of carbon dioxide in bitumen is calculated. The results are c ompared with the limited data available in the literature. The approach is straightforward and can be easily applied to other nonvolatile liquid syste ms.