Weight-optimized portable oxygen concentrator
System for producing an oxygen-rich gas comprising (a) a primary gas mover including a first and a second compressor, wherein the primary gas mover is characterized by a weight W p ; (b) a drive motor adapted to drive the first and second compressors; (c) a rechargeable power supply characterized by a weight, W b ; and (d) a pressure/vacuum swing adsorption unit adapted to separate the pressurized feed air into an oxygen-rich product at a product flow rate F p and an oxygen-depleted waste gas, wherein the adsorption unit comprises a plurality of adsorber beds containing an adsorbent and characterized by a total adsorbent weight W a ; and wherein the combined weight, W t , of the adsorbent, the primary gas mover, and the rechargeable power supply is characterized by the expression 0.75 F p <W t <2.02 F p where F p is in liters per min (at 23° C. and 1 atma pressure), and W a , W p , and W b are in pounds.
1. A method for producing an oxygen-rich product gas comprising
(a) providing a primary gas mover including a first compressor for compressing atmospheric air to provide pressurized feed air and a second compressor adapted to compress an oxygen-depleted waste gas from subatmospheric pressure to atmospheric pressure, a drive motor for driving the first and second compressors, and a rechargeable battery for providing power to the drive motor, wherein the rechargeable power supply is characterized by an operating run time between maximum and minimum working charge;
(b) providing a pressure/vacuum swing adsorption system adapted to separate the pressurized feed air into the oxygen-rich product gas and the oxygen-depleted waste gas, wherein the adsorption system comprises a plurality of adsorber beds containing adsorbent; and
(c) operating each of the adsorber beds in turn through an adsorption cycle including at least the repeating steps of feed/provide product, depressurization, evacuation, and repressurization;
wherein the method is characterized by any of the operating parameters
(1) the rechargeable battery provides between 0.02 and 0.17 KWh of power during the operating run time between maximum and minimum working charge;
(2) the total working capacity of the adsorbent in each adsorber bed during the adsorption cycle is between 1.2×10 −4 and 6.7×10 −4 lbmoles of nitrogen;
(3) the first compressor moves between 1.14×10 −4 and 4.01×10 −4 lbmoles of pressurized feed air during the feed/provide product step; and
(4) the second compressor moves between 3.47×10 −4 and 9.96×10 −4 lbmoles of waste gas during the depressurization and evacuation steps.
2. The method of claim 1 wherein the pressure/vacuum swing adsorption system has four adsorber beds and each of the adsorber beds undergoes in turn a series of adsorption cycle steps which comprise
(A) a feed/make product step wherein the pressurized feed air is introduced into a feed end of the bed while the oxygen-enriched product gas is withdrawn from a product end of the bed;
(B) a feed/make product/provide repressurization step wherein the pressurized feed air is introduced into a feed end of the bed while an oxygen-enriched product gas is withdrawn from a product end of the bed, and wherein a portion of the product gas is used for pressurizing another bed undergoing its final repressurization step;
(C) a depressurization step in which the bed is depressurized by withdrawing gas therefrom, wherein at least a portion of the gas withdrawn therefrom is transferred to another bed undergoing a repressurization step;
(D) a provide purge step in which the bed is further depressurized by withdrawing gas therefrom, wherein at least a portion of the gas withdrawn therefrom is transferred to another bed undergoing a purge step;
(E) an evacuation step in which gas is withdrawn from the feed end of the bed until the bed reaches a minimum subatmospheric bed pressure;
(F) a purge step in which the bed is purged by introducing purge gas into the product end of the bed while continuing to evacuate the bed, wherein the purge gas is provided from another bed undergoing step (D);
(G) a repressurization step in which pressurization gas is introduced into the product end of the bed, wherein the pressurization gas is provided from another bed undergoing step (C); and
(H) a final repressurization step in which product gas from another bed is introduced into the product end of the bed.
3. The method of claim 1 wherein the minimum bed pressure is between 0.25 and 1.0 atma.
4. The method of claim 1 wherein the minimum bed pressure is between 0.45 and 0.8 atma.
5. The method of claim 1 wherein the pressure of the oxygen-enriched product gas is between 1.2 and 1.6 atma.
6. The method of claim 1 wherein the oxygen-enriched product gas is provided at a flow rate in the range of 0.5 to 3.0 liters per mm (defined at 23° C. and 1 atma pressure).
7. A method for producing an oxygen-rich product gas comprising
(a) providing a primary gas mover including a first compressor for compressing atmospheric air to provide pressurized feed air and a second compressor adapted to compress an oxygen-depleted waste gas from subatmospheric pressure to atmospheric pressure, a drive motor for driving the first and second compressors, and a rechargeable battery for providing power to the drive motor, wherein the rechargeable power supply is characterized by an operating run time between maximum and minimum working charge;
(b) providing a pressure/vacuum swing adsorption unit adapted to separate the pressurized feed air into the oxygen-rich product gas and the oxygen-depleted waste gas, wherein the adsorption unit comprises a plurality of adsorber beds containing adsorbent selective for the adsorption of nitrogen from air, and
(c) operating each of the adsorber beds in turn through an adsorption cycle including at least the repeating steps of feed/provide product, depressurization, evacuation, and repressurization;
wherein the minimum pressure in the evacuation step is between 0.35 and 1.00 atma.