US Patent 7438746 Off-gas feed method and target gas purification system

The invention provides an off-gas feeding method that supplies the off-gas discharged from a plurality of adsorption towers (A, B, C) to an off-gas consumption unit (1), when performing a pressure swing adsorption process of repeating a cycle including a plurality of steps, to enrich and separate the target gas out of a gas mixture in the adsorption towers (A, B, C) loaded with an adsorbent. The method allows at least one of the plurality of adsorption towers (A, B, C) to discharge the off-gas, in all the steps included in the cycle, so as to continue to supply the off-gas to the off-gas consumption unit (1) without interruption.