Semipermeable membrane gas separation system

Claim 1

In a process for separating a more readily diffusing component from a gaseous mixture containing said readily diffusing component and at least one less readily diffusing component, by diffusion through a semipermeable membrane having an upstream barrier side and a downstream side, the improvement which comprises admixing to the gaseous mixture to be separated on the upstream barrier side about 5 to 25% of a gaseous component having a substantially higher rate of diffusion than said more readily diffusing component and diffusing resultant admixture, whereby the admixed gaseous component passes through the semipermeable membrane thereby lowering partial pressure of the more readily diffusing component on said passage side whereby the rate of diffission of the more readily diffused component is increased compared to a process wherein no admixture is conducted, wherein the gaseous mixture consists essentially of methane and carbon dioxide and the gaseous component admixed prior to diffusion is steam.