|How the SeQual ATF System Works
The SeQual ATF system, shown in the illustration at the left,
incorporates a unique method to concentrate oxygen. The
system uses a new twist along with a proven technology called
Pressure Swing Adsorption, or PSA (see bottom of page).
SeQual's 12-bed system uses a small geared motor to slowly turn
a maintenance-free rotary distribution valve. This self-cleaning
valve, built into each ATF unit, directs the flow of compressed air
to one set of four molecular sieve beds at a time. Simultaneously,
another four beds are purged to atmosphere through the valve.
The final four beds are interconnected through the valve to
equalize pressure as they transition between adsorbing and
desorbing. This eliminates both electronic cycling controls and
The ATF's continuously rotating distribution valve is simpler and
inherently more reliable than those used in conventional
concentrators. The rotary valve turns at only two revolutions per
minute causing negligible wear. The valve's flat pressure -
balanced graphite rotor mates with a silicon carbide stator plate
and testing has shown that it will have an almost indefinite life
since the valve faces continuously lap themselves together.
The design of this 12-bed system greatly reduces the pressure
variations in the system. One advantage of this is reduced noise
level. The ATF is more easily silenced because this design
breaks the larger pulsing sounds of conventional two-bed purging
into many smaller impulses.
In addition, the low amplitude inlet pressure variations reduce the noise generated by the air compressor itself and also
reduce wear on compressor components, particularly the intake and exhaust flapper valves, increasing system
The lightweight ATF is simple and compact, eliminating nearly 100 pneumatic and electrical connections found in a
conventional concentrator. Compared with a conventional two-bed concentrator, the ATF is capable of delivering higher
purity oxygen at greater flow rates using an equivalent compressor with similar quantities of molecular sieve in each
Pressure swing adsorption (PSA) is commonly used to separate oxygen from air
with the use of molecular sieves. A characteristic of these sieves, made from
crystalline Zeolite, is to selectively adsorb the individual gases in air. Air is forced
under pressure into one end of a sieve bed, or column, and as the air flows through
the sieve the different component gases are adsorbed and stratified (as shown to
the right) in an order dependant on each gases' natural characteristics. This
separating of the component gases allows the oxygen to be drawn off at a high
Once the full bed length is saturated, it must be regenerated by purging the other
adsorbed gases. This desorbing is accomplished by lowering the pressure in the
bed and allowing some of the concentrated gas product to back-flush the unit. This
adsorption and desorption process is completely reversible and can be repeated
indefinitely without the bed becoming clogged or worn out.
One inherent feature of this process is that moisture in the air is also separated in
the sieve so the concentrated oxygen that is produced is dry.
(Pressure Swing Adsorption)