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DB Series Nitrogen Generator DB5-20 Model
3. General Operation
Pressure Swing Adsorption (PSA) technology uses 2 vessels (or 2 sets of vessels) each filled with a
bed of carbon molecular sieve (CMS). One bed is “online” and generating nitrogen from the process
air, while the other bed is “offline” being regenerated. The sets of vessels and corresponding process
valves will switch back and forth between generating and regenerating to produce a constant supply
of high quality, high purity nitrogen gas.
Reference the graphical schematic below.
Generating: Clean, dry compressed air, which contains nitrogen, oxygen, argon, and other trace
gases, flows into the ‘Air In.’ With inlet valve (PV 101) and outlet valve (PV 107) open, the compressed
air flows into the online adsorption vessel (AV 101) and across the carbon molecular sieve (CMS).
Oxygen and other trace gases are adsorbed by the CMS, allowing nitrogen to flow through to the
nitrogen buffer tank (NST 101). Lastly, the nitrogen gas flows from the buffer tank and back through
the generator where it is filtered, through a final sterile air filter, and pressure regulated before going
to the application.
Regenerating: Inlet valve (PV 102) and outlet valve (PV 108) open are closed, the exhaust valve
(PV 104) is open, and the offline adsorption vessel(s) (AV 102) regenerate. In order to regenerate, the
offline bed is exhausted to atmospheric pressure. This releases the oxygen (and other trace gas) mol-
ecules from the CMS.
Equalization: Prior to changeover, the adsorption vessels must equalize in pressure. All inlet valves
(PV 101 and PV 102), outlet valves (PV 102 and PV 108) and exhaust valves (PV 103 and PV 104)
close. Equalization valves (PV 105 and PV 106) open and the adsorption vessels (AV 101 and
AV 102) equalize in pressure. This minimizes the exhausting of the gas in the online vessel (AV 101)
during changeover and pre-pressurizes the CMS in the offline vessel (AV 102) so that it can adsorb
oxygen more efficiently straight away. During equalization no nitrogen is being generated. The nitro-
gen buffer tank (NST 101) is sized to ensure a continuous supply of nitrogen is provided to application
at design flow, purity and pressure.
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