A new approach of CO2 separation by applying rapid expansion of supercritical CO2 rich natural gas

The previous methods for CO₂ separation from CO₂ rich natural gas led to expensive production costs. This work was implemented to overcome the problems utilizing a new approach economically. The cooling and rapid expansion processes were integrated for the CO₂ separation from CO₂ rich natural gas on the supercritical condition. The experimental apparatus was newly constructed to perform the experiments, and the results were simulated using a various equation of state. The result reveals that the inlet temperature of supercritical expansion diminished the outlet temperature and the gas condensed easily. The simulation indicated that the 70% CO₂ in natural gas was condensed easier than 45% CO₂. We found that the outlet temperature of −42 °C and the vapor fraction of 0.69 was attained at the CO₂ composition of 70%. Besides, the pressure drop change influences the vapor fraction at various CO₂ compositions. The vapor fraction under supercritical diminished significantly compared with the non-supercritical condition. The expansion coefficient determined utilizing the equation of state escalates by the enhancement of expansion inlet temperature based on CO₂ composition in natural gas. The acid gas equation of state was the perfect equation to estimate the expansion coefficient with the absolute average error of 4.83%. This work suggests that the CO₂ separation from CO₂ rich natural gas with the cooling and rapid expansion method promotes the new approach to overcome the disadvantages of previous methods.