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Rapid Pressure Swing Adsorption Process for Production of Oxygen-Enriched Air

IP.com Disclosure Number: IPCOM000019345D
Publication Date: 2003-Sep-11
Document File: 5 page(s) / 652K

Publishing Venue

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Abstract

Low to medium purity oxygen-enriched air containing 23-50 mole% oxygen has many applications in the chemical, metallurgical and environmental industries. These include enhanced combustion in burners, furnaces and cupolas, controlled oxidation in chemical and biochemical reactors, sewage treatment, aquaculture, etc.

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Rapid Pressure Swing Adsorption Process

for Production of Oxygen-Enriched Air

         Low to medium purity oxygen-enriched air containing 23-50 mole% oxygen has many applications in the chemical, metallurgical and environmental industries. These include enhanced combustion in burners, furnaces and cupolas, controlled oxidation in chemical and biochemical reactors, sewage treatment, aquaculture, etc.

         A novel rapid pressure swing adsorption (RPSA) process to directly produce 23-50 mole% O2 enriched product gas from ambient air was disclosed in U.S. Patent 5,071,449. The process uses a single adsorber vessel which contains one or more pairs of shallow adsorbent layers separated by perforated metal plates. Each layer consists of a sublayer of a desiccant at the feed air end for removal of water from the ambient air and a sublayer of a zeolite for selective adsorption of nitrogen from the dry air. Each layer is cyclically subjected to sequential steps of (a) simultaneous pressurization-adsorption and (b) simultaneous depressurization-purge with O2 enriched gas. Figure 1 is a schematic diagram of the process using a two layer adsorber. Compressed air is fed to one layer of the adsorbent which undergoes step a of the process and produces an oxygen enriched gas. A part of this gas is withdrawn as product gas and the balance is used to purge the companion layer undergoing step (b) after the purge O2 gas pressure is reduced across the perforated plate. A nitrogen enriched waste gas is also produced by the process.

         A total cycle time of 8-12 seconds is used, of which 4-6 seconds are used for steps (a) and (b). Consequently, the specific oxygen production rate (volume/volume of total adsorbent/time) from the RPSA process is increased by more than an order of magnitude compared to that from a conventional pressure swing or vacuum swing adsorption process for production of O2. This translates to an order of magnitude reduction in the adsorbent inventory. For example, the process can produce more than 250 liters/liter/hour of 50% O2 enriched air using NaX as the adsorbent [1]. The oxygen recovery and specific cyclic production capacity by the RPSA process as functions of feed air pressure and O2 product composition are given by Figure 2.

         The RPSA process removes water from the compressed feed air as well as separates the air into the oxygen enriched product gas. This requires that the feed air be compressed to at least 25 psig so that the pressure swing drying of the compressed air can be carried out efficiently. Thus, a minimum amount of compression energy is necessary to operate the above described RPSA process.

         The purpose of this article is to describe a new embodimen...