TWO-STEP MEMBRANE GAS SEPARATION PROCESS WITH MEMBRANES HAVING DIFFERENT SELECTIVITIES

摘要

A gas separation process for treating a gas stream containing vapors of condensable components. The process includes two membrane separation steps, the second step using membranes of lower selectivity than the first step. Advantageously, the first membrane separation step may be carried out outside the pressure-ratio-limited region and the second membrane separation step may be carried out within the pressure-ratio-limited region. The second residue stream is a desired product of the process, and the process is particularly useful for applications where the target concentration of component A in this product is low, such as below 1-2 vol%.