Polymeric
hollow fiber membranes are designed with a thin, permeable wall that
separates gases based on their relative permeability rates. Every membrane
supplier has a unique polymer and proprietary construction and surface
treatments to optimize the productivity (total flow of product gas per
area of membrane), or recovery (product gas relative to the feed air
consumed).
Process
control is simple, with the nitrogen purity governed primarily by the
velocity of the air down the bore of the bore, or conversely, the time
allowed for permeation of the fast gases vs. the slow gases. Therefore,
backpressure control regulates both the flow rate and the ultimate
nitrogen purity from a fixed number of membranes. The higher the desired N2
purity, the smaller the flow rate. Also affecting performance is
feed air pressure (more pressure+ increased flow), and feed air
temperature (higher temperature yields more flow but a reduced recoveries.
