Abstract: The present invention concerns a cryogenic air separation process which intermittently diverts a portion of the air feed as repressurization gas for a front-end two bed pressure swing adsorption adsorption system which system is used to remove impurities from the air feed. In particular, the present invention is an improvement to said process for at least partially eliminating reductions in the purity of the product streams from the air separation unit caused by the intermittent diversions of the air feed as repressurization gas. The improvement comprises reducing the flow of both the nitrogen-enriched waste stream and the crude liquid oxygen stream from the air separation unit during those intermittent periods when repressurization gas is required in the pressure swing adsorption system.

Abstract: A process for separating mixtures which comprise oxygen, nitrogen, and argon by cryogenic distillation in a distillation system where the system is comprised of a distillation column that produces a nitrogen-enriched stream, an oxygen-enriched stream, and an argon-enriched stream, and a sidearm column which has a sump and receives the argon-enriched stream from the distillation column. During an interruption of flow of the argon-enriched stream into the sidearm column, the liquid inventory in the sidearm column is collected at a point above the sump and recirculated through the sidearm column during re-startup of the sidearm column.

Abstract: A cryogenic air separation system which is subject to periods of significant changes in product demand is controlled during such periods to minimize the impact of transient operation on product purity. A double-column distillation system is utilized in which a nitrogen-rich liquid is withdrawn from the higher-pressure column and introduced into the lower-pressure column as reflux. An inventory of this liquid is maintained in a holdup tank for storage or withdrawal during periods of transient operation. In addition, nitrogen vapor product from the lower-pressure column is recycled to the higher-pressure column, and the nitrogen vapor recycle rate is controlled as a function of the liquid level in the holdup tank. The flow rate of nitrogen-rich liquid withdrawn from the higher-pressure column is controlled as a function of its composition.

Abstract: A cryogenic air separation system which is subject to periods of significant changes in product demand is controlled during such periods to minimize the impact of transient operation on product purity. The feed air is introduced directly into the higher pressure column of a distillation system having at least two columns, and nitrogen-rich and oxygen-rich vapor products are withdrawn from the lower pressure column. The flow rate of the nitrogen-rich vapor product is controlled as a function of the feed air flow rate by a feed air flow controller which controls the suction pressure of the nitrogen product compressor. The set point of the flow controller is manipulated as a function of the composition of the oxygen-enriched vapor product. A nitrogen-rich liquid is withdrawn from the higher-pressure column and introduced into the lower-pressure column as reflux. An inventory of this liquid is maintained in a holdup tank for storage or withdrawal during periods of transient operation.

Abstract: The present invention relates to a thermally regenerable adsorptive process for the purification of a feed air, wherein the feed air is contacted with a solid adsorbent to remove at least water and carbon dioxide, wherein, periodically, the solid adsorbent is thermally regenerated by contacting the solid adsorbent with a regeneration gas stream which is essentially free of at least water and carbon dioxide, wherein the regeneration gas is a nitrogen-enriched stream removed from an elevated pressure air separation unit fed with the purified feed air, characterized in that the removed nitrogen-enriched stream is compressed in a multiple staged compressor and that the regeneration gas is a portion of the nitrogen-enriched stream which is removed from an interstage of the multiple stage compressor and then contacted with the solid adsorbent.