Characteristics of Membrane Separation:
Membrane units are relatively small
The membrane tubes are made out of porous polymer and are extremely thin. One separator unit contains a bundle of these membranes.
Processes have many membrane separators depending on the flow rate and purity of product needed.
Start up details:
Start-up for a membrane process is fast compared to PSA and cryogenic separation. Steady-state is reached after about 2-3 volumes of air have passed through.
Advantages of Membrane Separation:
Most economical process at low flow rates (up to 40,000 SCFH).
Simplest process in terms of calculators and engineering design.
Least costly for repairs and maintenence.
Lowest tax and insurance.
Requires the least amount of equipment for start-up.
Disadvantages of Membrane Separation:
Nitrogen purity is not good enough for certain process where there must be 1 part per billion purity. For such processes, cryogenic separation must be used.