Dual product pressure swing adsorption and membrane operations
AssigneePraxair Technology, Inc.
InventorsDale A. Lagree, David R. Thompson
Life of this patent
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Abstract
The waste gas of PSA-air separation operations is passed to a membrane system for enhanced recovery of a second product. By capturing the portion found to contain a high concentration of either nitrogen or oxygen in the waste stream, the efficiency of the overall separation is enhanced.
Claims20
In a pressure swing adsorption process for the recovery of either oxygen or nitrogen as a high purity product in an adsorption system having at least one adsorbent bed containing adsorbent material capable of selectively adsorbing either oxygen or nitrogen as the more readily adsorbable component of feed air, said process comprising, on a cyclic basis in each bed, an adsorption/desorption/repressurization sequence in which product gas is recovered from the system and a waste stream is separately discharged therefrom, the improvement comprising:
- (a) separating a portion of the waste stream from a net waste portion thereof, the separated portion having a non-product component purity higher than the average purity level of said component in the waste stream, said purity level being at least equal to a minimum acceptable level desired for said non-product component;
- (b) passing said separated portion of the waste stream to a membrane system capable of selectively recovering either nitrogen or oxygen present as a non-product component of the separated portion of the waste stream from impurities present therein;
- (c) discharging the net waste portion of the waste stream;
- (d) discharging said impurities form the membrane system;
- and
- (e) recovering the non-product component of the separated portion of the waste stream as a high purity second product, whereby the recovery of high purity oxygen and nitrogen streams enhances the efficiency of the overall air separation process.
In a pressure swing adsorption system for the recovery of either oxygen or nitrogen product in an adsorption system having at least one adsorbent bed containing adsorbent material capable of selectively adsorbing either oxygen or nitrogen as the more readily adsorbable component of feed air, said system being adapted for operation of a processing sequence comprising adsorption, desorption and repressurization in which product gas is recovered from the system and a waste stream is separately discharged from said system, the improvement comprising:
- (a) a permeable membrane system capable of selectively recovering either nitrogen or oxygen present as a principal component of said waste stream from impurities present therein;
- (b) control means for separating a portion of the waste stream from a net waste portion thereof, the separated portion having a non-product component purity higher than the average purity level of said component in the waste stream, said purity level being at least equal to a minimum acceptable level established for the non-product component;
- (c) conduit means for passing the separated portion of the waste stream to said membrane system;
- (d) conduit means for discharging the net waste portion of the waste stream;
- (e) conduit means for discharging the impurities form the membrane system;
- and
- (f) conduit means for separately recovering the principal component of the waste stream from the membrane system, whereby the recovery of high purity oxygen and nitrogen streams enhances the efficiency of the overall air separation operation.
Dependencies are inferred from the claim text.