Process for separation of gases with reduced maintenance costs

A method for separating gases from a crude gas stream comprising at least two components, wherein in an apparatus comprising a feed stream separation stage, a retentate separation stage and a permeate separation stage, each stage being a membrane separation stage with gas separation membranes,

• a) a feed stream is separated in the feed stream separation stage into a first permeate stream and a first retentate stream,
• b) the first retentate stream is separated in the retentate separation stage into a second permeate stream and a second retentate stream,
• c) the first permeate stream is separated in the permeate separation stage into a third retentate stream and a third permeate stream,
• d) the second retentate stream is removed as a first product,
• e) the third permeate stream is removed as a second product, and
• f)the second permeate stream and the third retentate stream are combined with the crude gas stream to give the feed stream,
• and wherein
• i) the combined gas volume of the second permeate stream and the third retentate stream is from 60 to 100% of the volume of the crude gas stream,
• ii) the total capacity of the gas separation membranes in the retentate separation stage is higher than the total capacity of the gas separation membranes in the feed stream separation stage, the total capacity being measured for nitrogen Grade 4.8 under standard conditions as defined in the description, and
• iii) the quotient of the pressure ratio over the permeate separation stage to the pressure ratio over the feed stream separation stage is in a range of from 0.5 to 8.