A plant for the production of low purity oxygen, in which a low pressure stream of incoming air is cooled against outgoing gas streams and fed into a high pressure fractionating column, and a high pressure stream of incoming air is cooled against outgoing gas streams, partially condensed against boiling liquid oxygen product in a product vaporizer, and separated into gas and liquid streams, the liquid stream being sub-cooled and expanded into a low pressure fractionating column while a major part of the gas stream is re-heated and expanded to provide plant refrigeration. Crude liquid oxygen from the bottom of the high pressure column is cooled against waste outgoing nitrogen from the low pressure column and then admitted to the low pressure column after first being used to liquefy some of the nitrogen from the high pressure column in an external reboiler/condenser. Liquid oxygen product from the low pressure column is pumped to a higher pressure before being passed through the sub-cooler and the product vaporizer. The remainder of the high pressure column nitrogen is liquefied in a second external reboiler/condenser by the separated high pressure liquid feed on its way to the low pressure column. The liquefied high pressure column nitrogen is used as reflux for the two columns, that for the low pressure column being cooled against outgoing waste nitrogen. The expander exhaust is likewise cooled against outgoing waste nitrogen before admission to the low pressure column.
An improved air separation process wherein a stream which is warmed to provide temperature control for a reversing heat exchanger and is expanded to generate plant refrigeration is desuperheated before being introduced to a low pressure distillation column. The process is particularly useful when argon is a desired product of the air separation.
A method and equipment are disclosed herein which liquefy and separate air through the use of a multiple rectifying tower system comprising a high pressure tower and a low pressure tower. The rectifying regions of the high pressure tower and the low pressure tower are divided into an equal number (at least two) of segments and gases at the tops of the respective segments of the high pressure tower are permitted to exchange heat with circulating liquids or liquid oxygen at the bottoms of the respective segments of the low pressure tower and to evaporate the circulating liquids or the liquid oxygen. The gases are then condensed to provide a circulating liquid for the low pressure tower.
A cryogenic rectification method for producing a product stream from a gaseous mixture having higher and lower volatility components and heavy impurities. In accordance with the method, the mixture is separated by a cryogenic rectification process employing one or more columns having plates, trays or packing for intimately contacting ascending vapor and descending liquid streams within the column. The mixture to be separated after having been compressed is combined with the recycle stream to produce a combined stream which is purified in a prepurification unit that is designed to remove the heavy contaminants. The combined steam is divided into major and minor streams. The major stream is then cooled and separated into liquid and vapor phases. Heavy impurities concentrate in the liquid phase taken as the recycle stream, which is then pumped to a high enough pressure for vaporization of the impurities. The resulting vapor is then reduced in pressure and combined with the incoming gaseous mixture. The concentration of heavy impurities in the vapor phase is reduced to a sufficient extent such that a product stream concentrated in the lower volatility component will have a reduction in its heavy impurity concentration. The product stream is pumped to pressure and vaporized against a portion of mixture using a boosted pressure subsidiary stream made up of a minor portion of the gaseous mixture.
A cryogenic rectification system wherein liquid oxygen from a cryogenic air separation plant is pressurized and then vaporized in a high pressure liquefier producing product high pressure oxygen gas and generating liquid nitrogen for enhanced liquid product production.
The present invention is an improvement to a standard nitrogen generator. The improvement is two-fold; first, the addition of one or more distillation stages above the reboiler, which stages effectively transform the reboiler/condenser into a partial low pressure column and allow further separation (rectification) of the nitrogen generator bottoms liquid into two streams. Second, the recycle of the overhead stream (at a composition close to that of air) from the top of the low pressure column to the main air compressor. Additionally, at least a portion of the oxygen-enriched stream that exits the low pressure column below the bottom tray is expanded to provide refrigeration for the cycle.
