Three-bed nonimmobilized rapid pressure-swing adsorber

A method of distilling liquid oxygen from ambient air using an apparatus, comprising:

• drawing ambient air containing oxygen and nitrogen into said apparatus through an air inlet port;
• compressing said ambient air into a stream of compressed air;
• adsorbing impurities in said filtered airstream with a pressure-swing adsorber having a first molecular sieve bed, a second molecular sieve bed, and a third molecular sieve bed;
• cooling a portion of said airstream from said pressure-swing adsorber to a temperature at which a substantial portion of said airstream condenses;
• separating nitrogen from oxygen in said cooled portion of said airstream;
• collecting said separated oxygen;
• and
• alternating the molecular sieve bed which adsorbs said filtered air after a process interval during which the sieve bed which last adsorbed said filtered air is decompressed for a first portion of said process interval and purged for a second portion of said process interval, and during which the sieve bed which was decompressed in the preceding process interval is purged for an initial portion of said process interval and pressurized for a later portion of said process interval, and the sieve bed which was pressurized during the preceding interval adsorbs impurities from said filtered air.

A rapid pressure-swing adsorber apparatus for use in an oxygen/nitrogen separation system having a cryogenic distillation system comprising:

• a feed gas supply conduit;
• an exhaust conduit;
• an adsorption process output conduit leading to the cryogenic distillation system;
• a waste gas conduit leading from the cryogenic distillation system;
• three parallel beds of nonimmobilized molecular sieve-type adsorbent material, said beds each including first and second ends, a purge inlet line located in said first end connected to said waste gas conduit, a purge outlet line located in said second end and connected to said exhaust conduit, a feed gas inlet line located in said first end and connected to said feed gas supply conduit, and an adsorption process output line located in said second end connected to said adsorption process output conduit;
• a first pressure-regulated valve positioned in each said purge inlet line for preventing flow from the corresponding adsorber bed and permitting flow upon a predetermined threshold pressure differential between said adsorber bed and said waste gas conduit;
• a second pressure-regulated valve positioned in each said adsorption process output line for preventing flow to the corresponding adsorber bed and permitting flow upon a predetermined threshold pressure differential between said adsorber bed and said adsorption process output conduit;
• a purge valve positioned in each said purge output line selectably operable to alternately permit and prevent flow from the corresponding adsorber bed to said exhaust conduit;
• a feed gas valve positioned in each said feed gas inlet line selectably operable to alternately permit and prevent flow to the corresponding adsorber bed from said feed gas supply line;
• a three-way valve positioned in each said feed gas inlet line, said 3-way valve comprising a first leg connected to the corresponding bed, an output leg connected to said exhaust conduit and an input leg connected to said feed gas supply line, said three-way valve adapted to allow only a limited flow through either of said input and output legs;
• and
• a microprocessor for controlling the operational states of said purge valves and said three-way valves.

A method of purifying a feed gas using at least three parallel nonimmobilized molecular sieve-type pressure-swing adsorber beds, each bed connected to a feed gas inlet conduit and an exhaust conduit on a first end, and a process output conduit and a purge gas conduit on a second end, said method including the steps of:

• flowing feed gas from said inlet conduit through a first one of said beds at a first pressure from said first end to said second end and to said output conduit, while simultaneously flowing purge gas from said purge gas conduit through said second and third beds at a second pressure lower than said first pressure from said second end to said first end and to said exhaust conduit;
• determining a shut-off time for terminating feed gas flow through said first bed;
• preventing purge flow through said second bed prior to said shut-off time;
• raising the pressure within said second bed to said first pressure;
• flowing feed gas from said inlet conduit through said second bed at said first pressure from said first end to said second end and to said output conduit prior to said shut-off time;
• terminating feed gas flow through said first bed at said shut-off time;
• lowering the pressure within said first bed to said second pressure;
• and
• continuing flowing feed gas from said inlet conduit through said second bed at a first pressure from said first end to said second end and to said output conduit, while simultaneously flowing purge gas from said purge gas conduit through said first and third beds at a second pressure lower than said first pressure from said second end to said first end and to said exhaust conduit.