Kinetics of ethane exsolution and dissolution in bitumen

Abstract

Dissolution and exsolution of gases are common in many engineering applications. Dissolution and exsolution occur across a gas-liquid interface when the equilibrium condition is disturbed. This study presents experimentally measured data on the exsolution and dissolution kinetics of ethane and bitumen (a viscous liquid) system across a temperature range of 80–140 °C and pressure differences of 0.69 and 0.35 MPa. Analytical models were adopted to estimate the exsolution and dissolution coefficients from the measured data for the ethane/bitumen system. The diffusivity values for the exsolution and dissolution processes were estimated to range from (2.65–10.48) × 10⁻⁸ m²/s and (0.73–6.18) × 10⁻⁹ m²/s, respectively, at a pressure difference of 0.69 MPa, and from (1.61–8.33) × 10⁻⁸ m²/s and (0.89–10.78) × 10⁻⁹ m²/s, respectively, at a pressure difference of 0.35 MPa. For both pressure differences, the exsolution kinetics were shown to be faster than dissolution in the ethane/bitumen system. This was also confirmed by higher activation energy for the exsolution process calculated using the Arrhenius equation. The results offer valuable insights into the kinetics of gas exsolution and dissolution, with applications in designing and optimizing processes where nonequilibrated gases and liquids are brought into contact.