Gas separation

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The plant illustrated in FIGS.
1 and 2 has a carbon molecular sieve section comprising two adsorbent beds C1 and C2 and a zeolite molecular sieve section comprising two adsorbent beds Z1 and Z2.
A first pump P1 serves the purpose of evacuating the beds of the carbon sieve section at the appropriate stages of their operating cycles and delivering the desorbed components to gas holders G1 and G2 as more fully described below.
A second pump P2 serves the purpose of drawing the feedstock for the zeolite sieve section through its beds Z1 and Z2 at the appropriate stages of their operating cycles and delivering the high purity oxygen product through the outlet line L1.
A third pump P3 serves the purpose of evacuating the beds of the zeolite sieve section and passing the feedstock for the carbon sieve section through its beds C1 and C2 at the appropriate stages of the operating cycles of the beds.
With reference to FIGS.
2 and 3, the operation of the plant is as follows.
Dealing first with the carbon sieve section, valves V1, V3, and V21 open so that pump P3 draws in feed air, which is pretreated in an adsorbent bed B to remove carbon dioxide and moisture, and passes the air through bed C1 of the carbon sieve section where oxygen is preferentially adsorbed.
The unadsorbed gas, largely nitrogen and argon, passes out of the plant to waste via line L2.
After a predetermined time period valve V21 closes and valve V20 opens so that an oxygen rich gas drawn from gas holder G2 passes through bed C1 purging out air from the interstices of the bed and providing more oxygen for adsorption by the carbon sieve.
After another predetermined time period valve V20 closes and V19 opens (as also does valve V16) so that the pump P3 begins to evacuate bed Z2 of the zeolite section and passes the desorbed gas from that bed, which also has an enhanced proportion of oxygen in comparison with the original air feedstock, through bed C1.
Valves V1, V3 and V19 then close, valve V5 opens, and bed C1 goes on to its evacuation (desorption) step