Energy, Equipment and Cost Savings by Using a Membrane Unit in an Amine-Based Absorption Process for CO sub(2) Removal

A hybrid system consisting of a membrane unit and an amine-based process for CO sub(2) removal in the oxidative coupling of methane is investigated experimentally and in simulations. Absorption processes with two different absorbents for removing 90% of CO sub(2) from the feed stream are regarded as benchmarks and compared to the membrane process with respect to potential energy, equipment, and cost reductions. The results show that a membrane unit using polyimide could assist with CO sub(2) capture and lead to a reduction of the consumed energy per kilogram of CO sub(2) by 40% and also reduce the size of the absorption columns. Alternative processes with a two-step membrane cascade to enhance the recovery of product ethylene are also discussed. Ethylene can be directly produced through oxidative coupling of methane instead of cracking process, but a CO sub(2) separation section is necessary in the downstreaming. A hybrid system of membrane unit and chemical absorption process is presented that provides energy and cost savings compared to the commonly used CO sub(2) removal process.