Abstract: A gas production system that can supply liquefied gas obtained by rectifying source gas as product gas continuously with high heat efficiency without using a machine that has a risk of contamination like a pump. A gas production system includes a single pressure device having a single pressurized container to which liquefied gas extracted from a rectification unit is supplied, a pressure line for extracting and vaporizing a part of the liquefied gas in the pressurized container and returning the part of the liquefied gas to the pressurized container, and a second heat exchange unit that is disposed in the pressure line, and a liquefied gas storage unit that stores liquefied gas which is led out from the pressurized container.

Abstract: A process is provided for separating syngas fuel into a CO-rich stream for feeding to oxyfuel combustor means of CO2 turbine means and a H2-rich stream for feeding to air-fuel gas turbine means for generating power provides opportunity to realize operating and equipment advantages.

Abstract: A process is provided for separating syngas fuel into a CO-rich stream for feeding to oxyfuel combustor means of CO2 turbine means and a H2-rich stream for feeding to air-fuel gas turbine means for generating power provides opportunity to realize operating and equipment advantages.

Abstract: The invention relates to a method and device for obtaining compressed oxygen and compressed nitrogen by the low-temperature separation of air in a distillation column system for nitrogen-oxygen separation, said distillation column system having at least one high-pressure column (8) and one low-pressure column (460), wherein the low-pressure column (460) is in a heat-exchanging connection with the high-pressure column (8) by means of a main condenser (461) designed as a condenser-evaporator. Feed air is compressed in an air compressor (2). The compressed feed air (6, 734, 802, 840) is cooled down in a main heat exchanger (20) and at least partially introduced into the high-pressure column (8). An oxygen-enriched liquid (462, 465) is removed from the high-pressure column (8) and fed to the low-pressure column (460) at a first intermediate position (464, 467, 906).

Abstract: A system and method for air separation using a supplemental refrigeration cycle is provided. A portion of the refrigeration required by the air separation plant to produce a liquid product stream is supplied via a supplemental refrigeration circuit configured to direct a cooled refrigerant produced by the turboexpander through the main heat exchanger of the air separation plant. The refrigeration capacity is controlled by removing or adding a portion of the refrigerant in the supplemental refrigeration circuit to adjust the inlet pressure while maintaining a substantially constant volumetric flow rate and substantially constant pressure ratio across the compressor. Removing the refrigerant from the supplemental refrigeration circuit decreases the refrigeration imparted by the supplemental refrigeration circuit and thus decreases the production of the liquid product stream.

Abstract: The present invention relates to a method and apparatus for producing a pressurized product stream product by cryogenic rectification. A main heat exchanger, used in the cryogenic rectification, warms a pumped product stream composed of oxygen-rich or nitrogen-rich liquid and thereby produces the pressurized product stream. Layers of the main heat exchanger are designed such that a reduction in the heat transfer area provided within the main heat exchanger for warming the pumped product stream occurs at a location at which the temperature of the pumped product stream exceeds either the critical or a dew point temperature of such stream. The reduction in heat transfer area leaves regions of the layers able to heat or cool another stream that is used in connection with the cryogenic rectification. Such other stream can be a refrigerant stream that allows the introduction of additional refrigeration to increase production of liquid products.

Abstract: A hybrid system which utilizes high purity oxygen from a local pipeline, which is blended with low purity oxygen from an on-site or local cryogenic distillation system, thus resulting in a blend of intermediate quality which satisfies the needs of the customer. In order to offset the operating and energy costs associated with this fairly low profit margin intermediate purity oxygen, high purity nitrogen at high pressure is simultaneously exported to the local pipeline, thereby acting as a credit to the overall system.

Abstract: Method and arrangement for adjusting nitrogen and oxygen concentrations within regions of an aircraft. The method includes separating nitrogen from ambient air onboard an aircraft thereby establishing a high-concentration nitrogen supply and then dispensing high-concentration nitrogen from the supply to a fire-susceptible, non-habitable region of the aircraft where the high-concentration nitrogen is reservoired thereby decreasing the capability for the atmosphere therein to support combustion. Oxygen is also separated from the ambient air thereby establishing a high-concentration oxygen supply that is dispensed to an occupant cabin of the aircraft thereby increasing the level of oxygen concentration within the cabin to a level greater than the naturally occurring concentration of oxygen at the experienced internal cabin pressure.

Abstract: A method and to an apparatus for producing oxygen by separating air using cryogenic distillation is presented.

Abstract: The present invention relates to a method and apparatus for producing a pressurized product stream product by cryogenic rectification. A main heat exchanger, used in the cryogenic rectification, warms a pumped product stream composed of oxygen-rich or nitrogen-rich liquid and thereby produces the pressurized product stream. Layers of the main heat exchanger are designed such that a reduction in the heat transfer area provided within the main heat exchanger for warming the pumped product stream occurs at a location at which the temperature of the pumped product stream exceeds either the critical or a dew point temperature of such stream. The reduction in heat transfer area leaves regions of the layers able to heat or cool another stream that is used in connection with the cryogenic rectification. Such other stream can be a refrigerant stream that allows the introduction of additional refrigeration to increase production of liquid products.

Abstract: A method and apparatus of producing high purity oxygen in connection with low purity liquid oxygen produced by a plurality of cryogenic air separation plants. The low purity liquid oxygen from the air separation plants is introduced into a distillation column of an auxiliary cryogenic rectification plant that is reboiled by nitrogen also produced by such the air separation plants. Nitrogen is separated from the low purity liquid oxygen to produce high purity liquid oxygen from residual liquid located in a bottom region of the distillation column that can be taken as a product. Optionally, an argon column can be connected to the distillation column to produce a liquid argon product stream.

Abstract: The present invention includes a method for converting renewable energy source electricity and a hydrocarbon feedstock into a liquid fuel by providing a source of renewable electrical energy in communication with a synthesis gas generation unit and an air separation unit. Oxygen from the air separation unit and a hydrocarbon feedstock is provided to the synthesis gas generation unit, thereby causing partial oxidation reactions in the synthesis gas generation unit in a process that converts the hydrocarbon feedstock into synthesis gas. The synthesis gas is then converted into a liquid fuel.

Abstract: A distillation apparatus and method in which first and second compressed streams are formed from a compressed feed stream, for example, compressed air. The first compressed stream is fully cooled within a main heat exchanger so that it is substantially condensed. The second compressed stream is partly cooled within the main heat exchanger and then introduced into a turboexpander at a temperature such that the turboexpander exhaust stream is superheated. Part of the first compressed stream is mixed with the exhaust stream to produce a combined stream that is no more than 10° C. above saturation temperature at the pressure of the exhaust stream. The combined stream is introduced into a distillation column unit to produce one or more products that are enriched in components of the feed to be separated. In such manner the turboexpansion can occur at a higher temperature and with increased refrigerating effect.

Abstract: A process for carrying out cryogenic air separation wherein liquid oxygen is pressurized and vaporized against condensing feed air to produce oxygen gas product wherein excess plant refrigeration is generated such that the aggregate warm end temperature difference of the process exceeds the minimum internal temperature difference of the primary heat exchanger by at least 2 K.

Abstract: Methods and apparatus for treating a liquid bath of oxygen. A liquid bath of at least 70 mol % of oxygen is located at the base of a cryogenic distillation column. The bath is continuously boiled by an aluminum reboiler. A portion of the liquid bath is purged to prevent a build up of inflammable impurities in the bath. A portion of the purge is sent to a second reboiler, which is less inflammable than the first reboiler. Oxygen boiled by the second reboiler is sent back to the column, and a portion of the oxygen rich liquid bath treated by the second reboiler is also purged. The invention also relates to an apparatus of carrying out this method.

Abstract: A cryogenic air separation process is set forth wherein, in order to provide the refrigeration necessary when at least a portion of the oxygen product is desired as liquid oxygen, LNG-derived refrigeration is used to liquefy a nitrogen stream in the process. A key to the present invention is that, instead of feeding the liquefied nitrogen to the distillation column, the liquefied nitrogen is heat exchanged against the air feed to the distillation column system.

Abstract: A process and apparatus for highly efficient production of industrial gases by the cryogenic distillation of air, wherein a feed stream of compressed air, is supercharged to high pressure, cooled, and mixed with various recycle streams of supercharged air, to regulate the expander turbine operating temperature. The need for pre-cooling equipment downstream of the supercharger, which is widely employed in industry to manage the temperature of the incoming compressed air stream, is eliminated.

Abstract: Air is separated in a single fractionation column (116) to produce a top nitrogen gaseous fraction (142) and a bottom liquid fraction (120) containing less than (80) mole percent of oxygen. A liquid nitrogen product (136) is also produced. The necessary refrigeration is created by expansion with the performance of external work of firstly a stream of compressed air in an expansion turbine (114) and of secondly a stream of vaporised bottom fraction in an expansion turbine (128). At least part of the feed to the column (116) comes from the turbine (114). The outlet pressure of the turbine (114) is essentially the gaseous nitrogen product pressure. A double fractionation column may be used instead of the single fractionation column (116).

Abstract: In a process for separation of air by cryogenic distillation integrated with an associated process, air is separated in a separation unit (1), fluid is sent from the separation unit to an associated process, steam (3) is derived from the associated process, at least part of the steam is used in the separation unit and at least one fluid stream (11) is sent from the air separation unit to the atmosphere, at least when the steam is used in the air separation unit.

Abstract: The invention concerns a method for generating energy, which consists in conveying to an air separation apparatus (5) air from a compressor (1) coupled to an expansion machine (3). A nitrogen-enriched gaseous flow (11) containing between 3 and 18% of oxygen is conveyed to a combustion chamber (19) with a combustible flow (17) and the combustion gases (33) are expanded in the expansion machine. Optionally air from an auxiliary compressor (21) can be conveyed to the combustion chamber.

Abstract: The invention relates to a process and apparatus for producing nitrogen by low-temperature fractionation of air in a rectification system which has a high-pressure column (4) and a low-pressure column (5). Feed air (1, 3) is introduced into the high-pressure column (4). An oxygen-containing liquid fraction (11) is removed from the high-pressure column (4) and fed into the low-pressure column (5). Gaseous nitrogen (18) is extracted from the low-pressure column (5) above a mass transfer section (25), which has at least one theoretical or practical plate, and is at least partially condensed in a top condenser (17) by indirect heat exchange with a refrigerant (13). High-purity nitrogen is removed from the low-pressure column below the mass transfer section (25), and is obtained as a nitrogen product (26, 27, 30). The process and apparatus have a refrigeration-supply system, in which a refrigeration fluid (31) flows.

Abstract: Xenon and/or krypton are recovered from oxygen containing gas, typically derived from liquid oxygen bottoms in a cryogenic air separation plant, by selective adsorption on a Li and Ag exchange zeolite containing 5 to 40% Ag exchange capacity on an equivalents basis, with periodic thermal regeneration of the adsorbent.

Abstract: Systems and methods are disclosed for the power efficient production of high-pressure gaseous oxygen product. In a preferred embodiment, a liquid oxygen stream is pumped to a low to medium pressure and warmed within a first heat exchanger such as a brazed aluminum plate fin heat exchanger. The liquid oxygen stream is then pumped to a further pressure and then vaporized in a second heat exchanger to produce a high-pressure gaseous oxygen stream. In an embodiment, a high-pressure air stream may be utilized in the second heat exchanger for vaporizing the oxygen stream and cooling the air stream. The air stream may be utilized as a feed for the cryogenic air unit. A portion of the air stream at a medium pressure may be utilized in the first heat exchanger. A portion of the air stream may also be expanded to recover energy.

Abstract: The invention concerns a method for generating energy, which consists in conveying to an air separation apparatus (5) air from a compressor (1) coupled to an expansion machine (3). A nitrogen-enriched gaseous flow (11) containing between 3 and 18% of oxygen is conveyed to a combustion chamber (19) with a combustible flow (17) and the combustion gases (33) are expanded in the expansion machine. Optionally air from an auxiliary compressor (21) can be conveyed to the combustion chamber.

Abstract: A system for producing high and ultra high purity nitrogen comprising a first column for the production of nitrogen and a second column having a top condenser wherein boil off from the second column top condenser is turboexpanded to generate refrigeration for the system.

Abstract: A system for producing high purity nitrogen comprising a higher pressure first column having a top condenser and a lower pressure second column wherein boil off from the first column top condenser is turboexpanded to generate refrigeration for the system.

Abstract: In a single column distillation system for obtaining gaseous and liquid nitrogen with a variable proportions of liquid product by low-temperature separation from air, a first portion (12, 13) of nitrogen-rich fraction (5, 7, 8) is fed downstream of circulation compressor (9) to the liquefaction chamber of a condenser-evaporator (14) associated with the single column and condensed under a pressure higher than the operating pressure of the single column (4). A liquid oxygen-enriched fraction (228, 231) from the distillation column system is at least partially evaporated in the evaporation chamber of condenser-evaporator (14). A portion (18) of nitrogen-rich liquid (15, 16) from condenser-evaporator (14) is drawn off at least at times as liquid product. A second oxygen-enriched gas (221, 521) is removed from one of columns (546) of the distillation system and/or from the evaporation chamber of condenser-evaporator (14), machine expanded(23), and heated in main heat exchanger (2).

Abstract: For obtaining gaseous nitrogen by low-temperature separation from air, a distillation column system has a single column (4). Compressed air (1) is cooled in a main heat exchanger (2) and fed (3) to single column (4). A nitrogen-rich fraction (5, 7, 8) is drawn off from the distillation column system and compressed at least in part in a circulation compressor (9, 1063). A first part (12, 13) of nitrogen-rich fraction (5, 7, 8) is fed downstream from circulation compressor (9) to the liquefaction chamber of a condenser-evaporator (14) and is condensed under a pressure higher than the operating pressure of single column (4), so to form nitrogen-rich liquid (15, 16). A liquid oxygen-enriched fraction (231) from the distillation column system is at least partially evaporated in the evaporation chamber of condenser-evaporator (14). A first oxygen-enriched gas (234, 533) formed in the evaporation chamber of condenser-evaporator (14), is introduced into single column (4).

Abstract: A cryogenic rectification system comprising three columns wherein high purity oxygen is produced in the third column which is fed from at least one of the first and second columns, which do not share a common condenser/reboiler, and reboiled using feed air or first column top vapor.

Abstract: A combined main air/O2 enriched product compressor for use with an air separation unit that produces O2 enriched product is provided that includes a prime mover that drives a bull gear. The bull gear drives at least two pinion gears, and the pinion gears drive several compression stages where at least one compression stage compresses feed air for the air separation unit and at least one compressor stage compresses O2 enriched product from the air separation unit. The combined main air/O2 enriched product compressor satisfies all air separation unit feed air requirements and at least some compression for the oxygen product from the air separation unit. A method is also provided.

Abstract: A cryogenic air separation system particularly useful for producing elevated pressure product wherein additional reflux is generated by a heat pump circuit operating between the upper portion and an intermediate location of the lower pressure column of a double column.

Abstract: A cryogenic air separation system, which may be used to produce ultra high purity nitrogen or ultra high purity oxygen, wherein kettle liquid is vaporized in two steps using a split kettle top condenser and vapor from the first step compressed and then recycled to the cryogenic rectification column.

Abstract: A process is provided for the production of intermediate pressure oxygen. Intermediate pressure is defined as a pressure range between about 15 psia and about 27 psia, and preferably between about 17 psia and about 23 psia. The process uses a double column cryogenic air separation system for the production of oxygen from air which includes a higher pressure column and a lower pressure column, wherein a nitrogen-enriched fraction from the higher pressure column is condensed by indirect heat exchange in a reboiler-condenser that provides at least a fraction of the boilup at the bottom of the lower pressure column. Oxygen is withdrawn from the lower pressure column as a liquid and vaporized. One portion of air is feed air to the higher pressure column and a another portion of air is at least partially condensed by indirect heat exchange with the vaporizing oxygen. The latter portion of air is at least partially condensed at a pressure less than the pressure of the feed air to the higher pressure column.

Abstract: A combined system comprising an integrated gasifier combined cycle power generation system, an air separation unit which provides oxygen to a partial oxidation gasification unit gasifier and an inventory section which stores liquid oxygen or liquid air until it is needed.

Abstract: There are included a fractionating tower for liquefying and separating the compressed air cooled by heat exchangers to an ultralow temperature, a liquid oxygen takeout path for guiding the liquid oxygen in the above-mentioned fractionating tower to the above-mentioned heat exchangers to gasify so as to become a gasified oxygen, and a product oxygen gas takeout path which extends from the front end of the above-mentioned liquid oxygen takeout path and increases the temperature of the above-mentioned gasified oxygen so as to obtain a product oxygen gas, the above-mentioned liquid oxygen takeout path being provided with an oxygen gas pressurizing pump, and the above-mentioned product oxygen gas takeout path on the side upstream the above-mentioned heat exchangers being provided with an expansion turbine.

Abstract: A double rectification column air separation method and apparatus in which a stream of oxygen-enriched liquid air from a higher pressure rectification column is at least partially vaporized in indirect heat exchange with a stream of purified, compressed, gaseous air. The stream of purified, compressed air is condensed and a stream of the resulting vapor after having been warmed is expanded in a turbine with the performance of external work. After expansion, the resulting vapor is introduced into the lower pressure rectification column and a stream of the resulting condensed air is introduced into the higher pressure column at an intermediate mass exchange level thereof.

Abstract: There is provided a unit capable of simultaneously producing nitrogen of ra high purity and oxygen of ultra high purity from air as a feed material. Feed air is introduced into to the bottom 15 of a first rectification column 6. Liquid nitrogen of ultra high purity is recovered from between the upper rectifying part 12 and middle rectifying part 13, and liquid air free of high boiling point components is recovered from between the middle rectifying part 13 and lower rectifying part 14. Oxygen-rich liquid air collected in the bottom 15 is reduced in pressure by an expansion valve 31, and then introduced into a nitrogen condenser 8 as a refrigerant. After a portion of said liquid air is reduced in pressure by an expansion valve 33, it is introduced into the second rectification column 7, where low boiling point components are separated from the top part 21 and liquid oxygen of ultra high purity is recovered from the bottom 23.

Abstract: The present invention relates to an elevated pressure air separation cryogenic process wherein feed air is compressed, treated to remove water and carbon dioxide, cooled to cryogenic temperature in a main heat exchanger having a cold end and a warm end and fed to a distillation column system having at least two (2) distillation columns for separation into at least a nitrogen-enriched product, an oxygen-enriched product and a gaseous waste stream characterized in that at least a portion of said waste stream is (isentropically) expanded to produce work and work produced by the expansion is used to provide at least a portion of the work required to compress a process stream other than the gaseous waste stream at a temperature warmer than the temperature of the cold end of said main heat exchanger. The alternative process streams to be compressed can be: at least a portion of the feed air, at least a portion of the oxygen-enriched product or at least a portion of the nitrogen-enriched product.

Abstract: The present invention relates to a process for the cryogenic distillation of air in a distillation column system that contains at least one distillation column wherein the boil-up at the bottom of the distillation column producing the oxygen product is provided by condensing a stream whose nitrogen concentration is equal to or greater than that in the feed air stream. The process of the present invention comprises the steps of: (a) generating work energy which is at least ten percent (10%) of the overall refrigeration demand of the distillation column system; (b) work expanding a process stream to produce additional work energy such that the total work generated along with step (a) exceeds the total refrigeration demand of the cryogenic plant; and (c) using the work which is generated in excess of the refrigeration need of the distillation column system to cold compress a process stream at a temperature lower than the ambient temperature.

Abstract: In the method and device, nitrogen is obtained by two-stage rectification of air in a double column. Double column contains a high-pressure column and a medium-pressure column that are in a heat-exchange relationship with each other. Entering air is compressed, purified, cooled in a main heat exchanger against separation products, and fed to rectification. At least one nitrogen product fraction is taken from high-pressure column. A nitrogen gas fraction from double column is heated, expanded, and brought into indirect heat exchange with an oxygen-enriched liquid from the lower region of medium-pressure column. In this way, the nitrogen gas fraction is at least partially condensed and the oxygen-enriched liquid is at least partially evaporated. The condensate formed in the indirect heat exchange is at least partially fed to medium-pressure column.

Abstract: The present invention relates to a process for the cryogenic distillation of air in a distillation column system that contains at least one distillation column wherein the boil-up at the bottom of the distillation column producing the oxygen product is provided by condensing a stream whose nitrogen concentration is equal to or greater than that in the feed air stream, which comprises the steps of: (a) generating work energy which is at least ten percent (10%) of the overall refrigeration demand of the distillation column system by at least one of the following two methods: (1) work expanding a first process stream with nitrogen content equal to or greater than that in the feed air and then condensing at least a portion of the expanded stream by latent heat exchange with at least one of the two liquids: (i) a liquid at an intermediate height in the distillation column producing oxygen product and (ii) one of the liquid feeds to this distillation column having an oxygen concentration equal to or preferably grea

Abstract: A method and apparatus for separating air to produce an oxygen product in which air is separated within a double column arrangement. In the double column arrangement part of the air to be separated reboils a lower pressure column and is then introduced into the higher pressure column for separation. Another part of the air is partially cooled and then expanded with the performance of work and then introduced into the lower pressure column to supply part of the refrigeration requirements. The remaining part of the refrigeration requirements is supplied by partially vaporizing a crude liquid oxygen stream within a head condenser used to produce reflux for the higher and lower pressure columns. The partially vaporized stream is then phase separated into liquid and vapor phases. The liquid phase is introduced into the lower pressure column and the vapor stream after having been partially warmed is turboexpanded to provide the remaining refrigeration requirements of the plant.

Abstract: An apparatus and method for separating nitrogen within a single column nitrogen generator in which refrigeration is added by waste expansion. Part of the incoming air stream after having been partially cooled is turbo-expanded to increase the refrigeration supplied, thereby to allow the removal of the liquid nitrogen product.

Abstract: The present invention relates to a process for the cryogenic distillation of air in a distillation column system having at least one distillation column operating at a higher pressure and one distillation column operating at a lower pressure, wherein feed air is cooled and fed to the higher pressure column, wherein the boil-up at the bottom of the lower pressure column producing the oxygen product is provided by condensing a stream having a nitrogen concentration equal to or greater than that of the feed air stream and wherein at least two expanders are employed to provide refrigeration to the distillation column system, wherein the first expander is operated at an inlet temperature near ambient or above ambient temperature and the second expander is operated at an inlet temperature colder than ambient, characterized in that at least one of the two expanders employs at least one of the following steps: (a) work expanding a portion of the feed air; (b) work expanding a process stream with a nitrogen content eq

Abstract: In a process for the cryogenic distillation of air in a distillation column system that contains at least one distillation column wherein the boil-up at the bottom of the distillation column producing the oxygen product is provided by condensing a stream whose nitrogen concentration is equal to or greater than that in the feed air stream, which comprises the steps of: (a) generating work energy which is in excess of the overall refrigeration demand of the distillation column system by at least one of the following three methods: (1) work expanding a first process stream with nitrogen content equal to or greater than that in the feed air and then condensing at least a portion of the expanded stream by latent heat exchange with at least one of the two liquids: (i) a liquid at an intermediate height in the distillation column producing oxygen product and (ii) one of the liquid feeds to this distillation column having an oxygen concentration equal to or preferably greater than the concentration of oxygen in the f

Abstract: A method and apparatus for producing nitrogen within a nitrogen generator in which coolant streams composed of column bottoms and liquid having a nitrogen content greater than column bottoms are withdrawn from the column and then used to condense tower overhead for reflux purposes. The liquid composed of the oxygen-rich liquid after vaporization is expanded in a turboexpander with a performance of work. The other coolant stream is recompressed, cooled and then used to produce boil-up in the bottom of the column in order to produce the liquid vapor ratio in the bottom of the column.

Abstract: A dual column cryogenic rectification system for producing high purity nitrogen at elevated pressure wherein top vapor from a first column is processed in an intermediate heat exchanger of a second column and oxygen-rich vapor from the second column is turboexpanded to generate refrigeration for the separation.

Abstract: A cryogenic rectification system for producing high pressure oxygen wherein a portion of the feed air is condensed by indirect heat exchange with pressurized liquid oxygen and then passed, preferably after subcooling, into the lower pressure column of a double column system.

Abstract: A high purity nitrogen generator unit which is excellent in the energy efficiency and the recovery of high purity nitrogen gas, is provided. In a rectification column 1, feed air is separated to oxygen-rich liquid air and nitrogen gas. The oxygen-rich liquid air in its bottom is reduced in pressure by a first expansion valve 21 and sent to a composition regulation column 3. The nitrogen gas in its top is condensed in a nitrogen condenser 2, the resulting liquid nitrogen is returned as a reflux liquid to the rectification column 1 and non-condensed gas is released. After oxygen-rich waste gas in the lower part of the composition regulation column 3 is reduced in pressure by an expansion turbine 6, it is released by way of a first heat exchanger 4. Mixed gas in the top of the composition regulation column 3 is introduced for re-circulation into a first compressor 5.

Abstract: A unit capable of simultaneously producing nitrogen of ultra high purity and liquid oxygen of ultra high purity, is provided. The inside of the first rectification column 6 is demarcated to an upper rectifying part 12, and upper-stage middle rectifying part 13, a lower-stage middle rectifying part 14 and a lower rectifying part 15. To the upper part 11 above the upper rectifying part 12 is connected a nitrogen condenser 8. A second rectification column 7 is demarcated to an upper rectifying part 22 and a lower rectifying part 23, and has a reboiler 25 provided under its lower rectifying part 22. Ultra high purity liquid nitrogen is recovered from between the upper rectifying part 12 and upper-stage middle rectifying part 13 of the first rectification column 6, and ultra high purity liquid oxygen is recovered from below the lower rectifying part 23 of the second rectification column 7.