Combined membrane-pressure swing adsorption method for recovery of helium

A method for obtaining helium from a helium-containing process gas, said method comprising:

• a) feeding a helium-containing process gas having a pressure of less than 15 bar to a compression,
• b) feeding the process gas that leaves the compression to a prepurifying unit in which troublesome components are removed;
• c) guiding the process gas from the troublesome components have been removed to a first membrane separation stage having a first membrane which is more readily permeable for helium than for at least one further component present in the process gas;
• d) guiding a first retentate stream that has not passed through the first membrane to a second membrane separation stage having a second membrane which is more readily permeable for helium than for at least one further component present in the process gas;
• e) separating helium from a first helium-containing permeate stream that has passed through the first membrane by means of pressure swing adsorption to produce a helium-containing product stream;
• and
• f) recycling a second helium-containing permeate stream that has passed through the second membrane to the first membrane separation stage, and recycling a purge gas from the pressure swing adsorption to the first membrane separation stage.