Design and optimization of alternative processes for the separation of the CO2-C2H6 azeotrope to enhance product quality

Abstract

CO2-EOR (Enhanced Oil Recovery) technology has both economic and environmental benefits, while simultaneously leads to higher CO2 content in associated natural gas. Due to existence of CO2-C2H6 azeotrope, the recovery rate of C2H6 is low and the product purity cannot meet specifications during the cryogenic distillation process of light hydrocarbons recovery from associated natural gas. For breaking CO2-C2H6 azeotrope and dual recovery of CO2 and C2H6, four types of extractive cryogenic distillation processes are designed through Aspen Hysys7.2 commercial process simulator and optimized by sensitivity analysis. Total annual cost is the only valid indicator to be used to find the optimum alternative extraction distillation process. Simulation results of optimal extraction distillation process -3 showed that the purity of CO2 and C2H6 is higher than 95% and 96% respectively, and the recovery rate of CO2 and C2H6 respectively reaches up to 92.6% and 97.5%. The conclusion shows that the extractive cryogenic distillation processes are effective and efficient.