Process optimization-based adsorbent selection for ethane recovery from residue gas

The design and optimization of a pressure/vacuum swing adsorption process for the separation of ethane (C2) from residue gas (2.4 mol% ethane and the rest being methane) is presented. To achieve this, experimental measurements, modeling and optimization tools are developed to characterize the adsorbents, define the cycle configuration, and find the optimal operating conditions for the process. Adsorbents from two different families, namely, titano-silicate (Na-ETS-10) and activated carbons are chosen. Experimental high-pressure isotherms were measured and described using a dual-site Langmuir model. A rigorous one-dimensional model is developed to simulate the adsorption process. Two different pressure/vacuum swing adsorption (PVSA) cycle configurations are proposed and assessed based on C2 purity and recovery. The effect of feed temperature is studied and is shown to have a high impact on the separation. Finally, a multi-objective optimization study is performed to identify the material that offers the best trade-off between the two objective functions: C2 purity; and recovery. Among the adsorbents examined, Na-ETS-10 is found to provide the best performance with a possibility of obtaining ≈76% purity at a recovery of 68%.