KR0168707B1 - Air separation method and apparatus for producing nitrogen - Google Patents

Abstract

An air separation method and apparatus for the production of nitrogen is provided, which partially vaporizes and phase-separates the oxygen enriched liquid produced as the bottom of a distillation column. The vapor phase is expanded so that the liquid phase is depressurized and then introduced into the upper condenser to provide cooling while condensing reflux to the distillation column. On the one hand, some of the oxygen rich liquid can be sufficiently vaporized and then expanded to provide cooling. In such a case, another portion of the oxygen rich liquid can be used to condense reflux to the distillation column. A portion of the air to be separated is liquefied against the oxygen rich liquid to be vaporized and then introduced into the bottom of the distillation column to produce the level of production and purity obtained when all the oxygen rich liquid stream is used for condensation of reflux to the tower. Keep it.

Description

Air separation method and apparatus for the production of nitrogen

1 is a schematic illustration of an air separation device operated according to the method and apparatus of the present invention.

FIG. 2 illustrates another embodiment of FIG. 1, wherein components and streams that perform the same function are referred to in FIG.

The present invention relates to a process for separating air by low temperature rectification processes using distillation columns to produce nitrogen products. More specifically, the present invention provides a top coupled to the distillation column using another portion of the oxygen enriched liquid after vaporizing and then expanding to provide cooling and expansion of a portion of the oxygen rich liquid produced as a column bottom in the distillation column. It relates to such a method and apparatus for condensing nitrogen vapor in a condenser. Even more particularly, the present invention relates to such a method and apparatus for vaporizing a portion of an oxygen rich liquid by a portion of the inlet air and further condensate streams having less oxygen than the air recovered from the distillation column under certain conditions. will be. A portion of the inlet air and additional condensate streams are liquefied by it and introduced into the distillation column as additional reflux streams to maintain nitrogen production rates and / or concentrations at prior art levels.

Nitrogen is produced by cold rectification of air in an air separation plant. Often such plants use a single distillation column and are known in the art as nitrogen generators. After the air is filtered, compressed and purified, the temperature suitable for rectifying the air is cooled. This temperature is typically at or near the dew point of the air. The air is then introduced into a distillation column having a liquid-vapor contact element that can be assembled or formed by random trays and / or packings. In the distillation column, the rising vapor phase of the air is in contact with the downward liquid phase. As a result of the contact, the liquid phase is more concentrated with oxygen to produce an oxygen-rich liquid column bottom, and the rising vapor phase is more concentrated with nitrogen to produce a nitrogen-filled vapor column.

In order to reflux the distillation column, an upper condenser is provided for partially condensing the nitrogen vapor column. The condensate is sent back to the distillation column as reflux. Typically, an oxygen rich liquid stream consisting of the bottoms is recovered, expanded to low temperature and introduced as coolant for the upper condenser. The product is recovered as steam from the upper region of the distillation column.

In any type of air separation plant, there is a continuous heat leak into the plant and there is an enthalpy difference between the air feed and the product stream at the warm end of the plant. Such heat dissipation requires cooling the air separation plant. If the nitrogen product is maintained at the distillation column pressure, cooling is generally supplied from the outside of the distillation column cover. The work expansion obtained from the vaporized oxygen enriched liquid (all of which is vaporized in the upper condenser or by expanding the air to a distillation column pressure at higher pressure) is a common method of supplying cooling.

There is also a “liquid support plant” that adds liquid nitrogen from the external source to the distillation tower to provide the necessary cooling.

As discussed, the present invention relates to an air separation technique that cools in a manner that reduces energy costs in the production of nitrogen products. This is accomplished by using air separation energy more efficiently and generating energy (previously excess) that can be used for cooling.

The present invention provides an air separation process for producing a nitrogen product. According to this method, air is separated by a low temperature rectification process using a distillation column to produce an oxygen rich liquid column bottoms and a nitrogen enriched vapor column top. A top condenser is provided to condense at least a portion of the nitrogen-rich vapor column and reflux the distillation column.

In one embodiment, the low temperature rectification process comprises partially vaporizing an oxygen rich liquid stream consisting of an oxygen rich liquid column bottoms. After the vaporization the oxygen rich liquid stream is separated into liquid and vapor phases and the expansion of the liquid phase stream consisting of the liquid phase results in a temperature difference between the liquid phase stream and the nitrogen rich vapor column. The liquid phase stream is introduced as a coolant stream into the upper condenser to transfer heat from at least a portion of the nitrogen rich vapor to the coolant stream to condense at least a portion of the nitrogen rich vapor column. The vapor phase stream consisting of the vapor phase is worked up to expand to produce a refrigerant stream that is used to at least partially cool the cold rectification process. The resulting stream is recovered from the remainder of the nitrogen enriched vapor column product not used as reflux in the distillation column to produce a nitrogen product.

In another aspect of the invention, the low temperature rectification process comprises dividing an oxygen rich liquid stream consisting of oxygen rich liquid column bottoms into first and second partial streams. The first partial stream is expanded to produce a temperature difference between the first partial stream and the nitrogen-rich vapor column. The first partial stream is introduced into the upper condenser as a coolant stream to transfer heat from at least a portion of the nitrogen rich vapor to the coolant stream to condense at least a portion of the nitrogen rich vapor column. The second partial stream is vaporized and then partially warmed. The second partial stream is worked up to expand to produce a refrigerant stream that is used to at least partially cool the cold rectification process. The product stream is recovered from the remainder of the distillation column which is not used as reflux in the distillation column to produce nitrogen product.

The present invention also provides an air separation apparatus for producing the nitrogen product. According to the device, a filter is provided for the filtration of air and a compressor is connected to the filter for the compression of the air. A post-cooler is provided to remove the heat of compression from the air and a pre-purification unit is provided for the purification of the air. The main heat exchange means cools the air to a temperature suitable for rectifying the air and the distillation column is arranged to rectify the air into an oxygen rich liquid column bottom and a nitrogen enriched vapor column. A top condenser is connected to the distillation column to condense at least a portion of the nitrogen-rich steam column for reflux to the distillation column.

According to a further aspect the present invention provides a vaporization means for connecting vaporization means to the distillation column to partially vaporize an oxygen rich liquid stream consisting of an oxygen rich liquid column bottom and for separating the oxygen rich liquid stream into a liquid phase and a vapor phase. Connect the phase separator to the means. The phase separator is connected to an upper condenser to transfer heat from at least a portion of the nitrogen enriched vapor to a coolant stream consisting of a liquid phase stream consisting of a liquid phase. As a result, at least a portion of the nitrogen-rich vapor column is condensed and the coolant stream is vaporized to form a vaporized coolant stream therefrom. A pressure reducing valve is inserted between the phase separator and the upper condenser to expand the liquid phase stream, thereby producing a coolant stream and generating a temperature difference between the coolant stream and the nitrogen rich vapor column. A phase separator is also connected to the main heat exchange means to partially warm up the vapor phase stream consisting of the vapor phase. An expansion means is connected to the main heat exchange means in order to expand and expand the vapor phase stream to produce a coolant stream. The main heat exchange means communicates with the expansion means to sufficiently warm the refrigerant stream in the main heat exchange means. Extracting means for extracting a product stream consisting of the remainder of the nitrogen-rich steam column (part not used as reflux in the distillation column) to produce a nitrogen product, the main heat exchange means being connected to the product stream extraction means The product stream is sufficiently warmed in the main heat exchange means.

According to a still further aspect of the invention, a top condenser is connected to the distillation column to transfer heat from at least a portion of the nitrogen rich vapors to a coolant stream consisting of a first partial stream of oxygen rich liquid column bottoms. This condenses at least a portion of the nitrogen enriched vapor column and vaporizes the coolant stream to produce a vaporized coolant stream. A pressure reducing valve is inserted between the distillation tower and the upper condenser to expand the first partial stream thereby producing a coolant stream and generating a temperature difference between the coolant stream and the nitrogen rich vapor column. Vaporization means are also connected to the distillation column to vaporize a second partial stream consisting of an oxygen rich liquid column bottoms. The vaporization means is also connected to the main heat exchange means to partially warm the second partial stream. An expansion means is connected to the primary heat exchange means to expand and perform the second partial stream to produce a refrigerant stream. The main heat exchange means communicates with the expansion means to sufficiently warm the refrigerant stream in the main heat exchange means. An extraction means is provided for extracting the product stream consisting of the remainder of the nitrogen-rich steam column top (part not used as reflux in the distillation column) to produce nitrogen product. The main heat exchange means is also connected to the product stream extraction means to sufficiently warm the product stream in the main heat exchange means.

The function of the present invention is to produce nitrogen products using greater driving force than necessary for the distillation of air. In the present invention, the oxygen rich liquid acts as a coolant for condensing reflux to the distillation column and supplies at least a portion of the cooling requirement of the plant independent of the typical cooling process mentioned above.

Since not all of the oxygen rich liquid is used for the reflux condensation role, there is potentially an insufficient supply of reflux generated by the upper condenser. To compensate for this reduced reflux occurrence, medium reflux can be supplied at very low levels by liquid air, and optionally liquid reflux and another reflux stream having less oxygen than air. Thus, in yet another aspect, the present invention indirectly heat exchanges a portion of the air that will separate the oxygen-rich liquid stream or portion thereof, preferably with another vapor stream recovered from a distillation column having less oxygen content than the air. Thereby partially or completely vaporizing and thereby liquefying a portion of the air to be separated and optionally another vapor stream. Subsequently, a portion of the air to be separated, and preferably another liquefied vapor stream recovered from the distillation column, is introduced into the distillation column as an intermediate reflux stream to produce the product stream, the entire oxygen rich liquid stream being subjected to at least a portion of the nitrogen rich vapor column. Maintain at the level obtained when condensing. Prior to partial vaporization of the oxygen-rich liquid stream, or complete vaporization of a portion of the oxygen-rich liquid stream, the oxygen-rich liquid is expanded to a portion of the air and preferably with the vapor stream recovered from the distillation column, if present. It creates a temperature difference for indirect heat exchange.

For FIG. 1, a single tower nitrogen generator 10 is illustrated. Inlet air stream 12 is filtered by filter 14 to remove dust indenters and the like. The air stream 12 is filtered and then compressed by the compressor 16, after which the heat of compression is removed by a conventional after-cooler 18. Heavy trace components of water, carbon dioxide, and air, for example hydrocarbons, are removed by the pre-purification unit 20 connected to the after-cooler 18. The preliminary purification unit 20 may comprise a plurality of adsorbent stages operating out of phase for regeneration.

The filtered and purified air stream 12 is then introduced into the main heat exchanger 22. The air to be separated is introduced into the main heat exchanger 22 and then cooled sufficiently to a temperature suitable for rectifying the air. In this regard, the term “cooling sufficiently” as used herein and in the claims means cooling to the temperature at which rectification is performed. As used herein and in the claims, the term “enoughly warmed” means to warm to the temperature of the warm end of the main heat exchanger 22. The term “partially warmed” means to warm to a temperature higher than the rectification temperature but below the temperature of the warm end of the main heat exchanger 22.

After the air stream 12 is sufficiently cooled in the main heat exchanger 22, it is divided into first and second substreams 24 and 26, respectively. For this purpose, the joint formed by the T-section of the pipe, hammer, etc. is connected to the main heat exchanger. The first substream 24 constitutes the majority of the air to be separated, which may be the liquid-vapor contact elements 32, 34 and 36 (these may be trays and / or assembled packings, random packings, etc.). Is introduced into a single distillation column 30 provided. Distillation column (30) is rectified into an oxygen-rich liquid column bottom collected in the base region (38) of the distillation column (30) and a nitrogen-rich vapor column collected in the upper region (40) of the distillation column (30). . An upper condenser 42 is connected to the distillation column 30 to condense at least a portion of the nitrogen-rich steam column top collected in the upper region 40 of the distillation column 30. At the end of this, a portion of the nitrogen vapor stream 44 is extracted from the upper region 40 of the distillation column 30 and introduced into the upper condenser 42. Nitrogen vapor stream 44 is partially condensed by coolant stream 46, which in turn is vaporized to produce vaporized coolant stream 47. After condensation, the nitrogen vapor stream 44 is recovered as reflux stream 48 and sent to the upper region 40 of the distillation column 30.

An oxygen rich liquid stream 50 consisting of an oxygen rich liquid column bottom is extracted from the base region 38 of the distillation column 30. Oxygen-rich liquid stream 50 is then preferably subcooled in subcooler unit 52 to minimize the formation of steam upon subsequent valve expansion. Thereafter, the oxygen rich liquid stream 50 is passed through a pressure reducing valve 55 (hereinafter described in more detail) and then partially vaporized in the vaporizer 54 and then introduced into the phase separator 56 to introduce an oxygen rich liquid stream. Separate 50 into liquid and vapor phase.

A liquid phase stream 58 consisting of a liquid phase is extracted from the phase separator 56 and then passed through a pressure reducing valve 60 to sufficiently enhance the temperature of the liquid phase stream 58 which can act as a coolant for the upper condenser 42. Thus, the liquid phase stream 58 after passing the pressure reducing valve 60 is diverted to the coolant stream 46 discussed above.

A phase separator 56 is also connected to the main heat exchanger 22 to partially warm the vapor phase stream 62 consisting of the vapor phase in the main heat exchanger 22. The vaporized stream 62 after it has been partially warmed is expanded in a turboexpander 64 or other expansion device connected to the main heat exchanger 22.

In the illustrated embodiment, the refrigerant stream 66 is also partially warmed, as in the subcooler unit 52, to warm the vaporized coolant stream 47 and the product stream. As illustrated, the vaporized coolant stream 47 is sufficiently warmed in the subcooler unit 52 and then in the main heat exchanger 22 to generate a nitrogen wastestring designated WN W. A portion of the warmed vaporized coolant stream 47 can be fed to the preliminary purification unit 20 for regeneration of the stage. The main heat exchanger 22 communicates with the turboexpander 64 and consequently warms the refrigerant stream 66 in the main heat exchanger 22 and releases it as a closed string, denoted WN 2. A product stream 68 is produced, consisting of the nitrogen-rich steam column top collected in the upper region 40 of the distillation column 30. Product stream 68 constitutes the remainder of the nitrogen-rich steam column that was not used to produce reflux to distillation column 30. After partial warming in the sub cooling unit 52, the product stream 68 is sufficiently warmed in the main heat exchanger 22 and discharged as a product stream represented by PN. For the partial warming of the above mentioned stream, as already mentioned, the oxygen rich liquid stream 50 is secondaryly cooled.

In the single tower nitrogen generator 10, the oxygen rich liquid stream 50 is partially vaporized in the vaporizer 54, so that only a portion of the oxygen rich liquid stream 50 is used as coolant in the upper condenser 42. As a result, condensation of the columnar product provides less reflux in the single tower nitrogen generator 10 than in the prior art nitrogen generator. If no other reflux is added (the process contemplated by the present invention), the nitrogen generator of the present invention has a lower production rate and / or produces lower purity nitrogen than prior art designs. However, the present invention also contemplates a process embodiment in which such reduced reflux is supplemented by providing an intermediate reflux stream into the bottom of the distillation column 30 where additional liquid reflux is particularly needed.

This intermediate reflux allows the single tower nitrogen generator 10 to have the same production speed and purity as would be expected in a similar prior art plant design. At the end of the above, the second substream 26 is liquefied in the vaporizer 54. In order to generate a temperature difference between the secondary cooled oxygen rich liquid stream 50 and the second secondary stream 26, a pressure reducing valve 55 is applied to reduce the pressure and temperature of the oxygen rich liquid stream 50. The pressure reduction of the oxygen rich liquid stream 50 is below the pressure of the distillation column 30, but still a sufficient pressure is applied to the oxygen rich liquid stream 50 so that the vapor stream 62 derived from the stream can serve as a refrigerant. Create At a lower distillation column pressure, for example a pressure of 8 bai, the vapor stream 72 extracted from the distillation column 30 at approximately the same point as the point where the second stream 26 is introduced into the distillation column 30 after liquefaction. Liquefaction produces additional reflux to distillation column 30. Vapor stream 72 is then liquefied in vaporizer 54 and introduced as a further reflux above the point of introduction of the liquefied second substream 26. As is apparent, the pressure reducing valve 55 also generates a temperature difference between the oxygen rich liquid stream 50 and the vapor stream 72.

Possible modifications to the apparatus 10 include operating the distillation column 30 at high pressure. In such cases, an expander may also be coupled to the coolant stream 46. This increases the overall plant cooling and thus the amount of liquid produced. In addition, such a turboexpander may also be used to drive a recycle compressor to recycle some of the oxygen rich liquid contained in the coolant stream 46 back into the distillation column 30 to further increase production. As can also be seen, partial vaporization of the oxygen rich liquid stream 50 is not limited to the embodiment illustrating partial vaporization performed by liquefying a portion of the incoming air. For example, in suitable low pressure distillation column applications, a stream from the distillation column, which does not have the correct composition of liquid air, may be used in place of liquefied air.

With respect to FIG. 2, another embodiment of a single tower nitrogen generator 10 is illustrated. In the nitrogen generator 10, the oxygen rich stream 50 is subcooled in the sub cooler unit 52 and then split into first and second partial streams 50a and 50b. The first partial stream 50a is expanded at the first pressure reducing valve 60 to produce a coolant stream 46. Subsequently, the second partial stream 50b is expanded by the pressure reducing valve 55 and then sufficiently vaporized in the vaporizer 54. The sufficiently vaporized stream 63 is then partially warmed in the main heat exchanger 22 and expanded in the turboexpander 64.

Example 1

The following is a charted calculated example of a possible process of a single tower nitrogen generator 10 (illustrated in FIG. 1) according to the present invention. In this embodiment, the distillation column 30 uses a low pressure drop assembled packing and is estimated to have about 100 theoretical stages. The second partial stream 26 is liquefied and then applied to the distillation column in about six theoretical stages from the base. Stream 72 is withdrawn from the distillation column in about six theoretical stages from the base and condensed and then sent from the base of the distillation column 30 to about 16 theoretical stages.

In this embodiment, "L" refers to the liquid state and "V" refers to the vapor state. The purity of the top product, the recovery of nitrogen as a fraction of the air feed, and the addition and recovery points are sensitive to the physical properties of the database used to perform the calculation. The inherent loss of preliminary purification unit operation was included in stream 12. As will be appreciated by those skilled in the art, the subcooler 52 may be at a low point relative to the waste reservoir of the distillation column 30.

Thus, in a prior art design that produces gaseous nitrogen products of the same amount, fraction recovery from air, purity and pressure as the turboexpander cools by expanding the air into the distillation column, stream 12 is typically about 3.94. You can compress it immediately. In the present invention, the air will be compressed to only about 3.45 bar.

Example 2

The following is a charted calculated example of a possible process of a single tower nitrogen generator 10 (illustrated in FIG. 2) according to the present invention. In this embodiment, the distillation column 30 uses a low pressure drop assembled packing and is estimated to have about 100 theoretical stages. The second partial stream 26 is liquefied and then applied to the distillation column in about six theoretical stages from the base. Stream 72 is withdrawn from the distillation column in about six theoretical stages from the base and condensed and then sent from the base of the distillation column 30 to about 16 theoretical stages.

While the present invention has been described with reference to preferred embodiments, it will be understood by those skilled in the art that many modifications, additions, and omissions may be made without departing from the spirit and scope of the invention.

Claims (14)

A distillation tower for producing an oxygen-rich liquid column bottoms and a nitrogen-rich vapor column, and separating the air by a low temperature rectification process using a top condenser to condense at least a portion of the nitrogen-rich vapor column to reflux the column. An air separation method for the production of a nitrogen product, said low temperature rectification process comprising the steps of: partially vaporizing an oxygen rich liquid stream comprised of said oxygen rich liquid column bottoms; Separating the oxygen rich liquid stream into a liquid and vapor phase; Expanding the liquid phase stream consisting of the liquid phase to generate a temperature difference between the liquid phase stream and the nitrogen rich vapor column, and introducing the liquid phase stream into the upper condenser as a coolant stream to heat the coolant stream from at least a portion of the nitrogen rich vapor. Conveying and condensing at least a portion of said nitrogen-rich vapor column by said; Performing work to expand the vapor phase stream comprised of the vapor phase to produce a refrigerant stream used to at least partially cool the cold rectification process; And extracting a product stream from the remainder of the nitrogen-rich vapor column that is not used as the reflux in the distillation column to produce the nitrogen product. The method of claim 1, wherein the oxygen-rich liquid stream is partially vaporized by indirect heat exchange with a portion of the air to be separated to liquefy the portion of the air to be separated; Introducing the portion of the air to be separated into the distillation column as intermediate reflux to maintain the production of the product stream at the level obtained when the entire oxygen rich liquid stream is used to condense at least a portion of the nitrogen rich vapor column; Before the partial vaporization of the oxygen rich liquid stream, the oxygen rich liquid stream is expanded to generate a temperature difference for the indirect heat exchange between the portion of the air and the oxygen rich liquid stream. The method of claim 2, further comprising: recovering a vapor stream from the distillation column; Condensing the vapor stream by further indirect heat exchange between the vapor stream and the oxygen rich stream; And introducing the vapor stream back into the distillation column above the intermediate reflux as further reflux. Separating the air by a low temperature rectification process using a distillation tower to produce an oxygen rich liquid column bottoms and a nitrogen rich vapor column, and an upper condenser to condense at least a portion of the nitrogen rich vapor column to reflux the column. A method of air separation for the production of nitrogen products, the method comprising the steps of: separating the oxygen rich liquid stream consisting of the oxygen rich liquid column bottoms into first and second partial streams; Expanding the first partial stream to produce a temperature difference between the first partial stream and the nitrogenous vapor tower top and introducing the first partial stream into the upper condenser as a coolant stream to provide the coolant from at least a portion of the nitrogenous vapor. Transferring heat to the stream and thereby condensing at least a portion of said nitrogen-rich vapor column; Vaporizing the second partial stream; Performing work to expand the second partial stream to produce a refrigerant stream that is used to at least partially cool the cold rectification process; And extracting a product stream from the remainder of the nitrogen-rich vapor column that is not used as the reflux in the distillation column to produce the nitrogen product. The method of claim 4, wherein the second partial stream is vaporized by indirect heat exchange with the portion of air to be separated to liquefy the portion of the air to be separated; Introducing the portion of the air to be separated into the distillation column as intermediate reflux to produce the product stream such that a flow rate equivalent to both the first and second partial streams is used to condense at least a portion of the nitrogen-rich vapor column. Maintained at the level obtained; Prior to said vaporizing said second partial stream, expanding said second partial stream to produce a temperature difference for said indirect heat exchange between said portion of said air and said second partial stream. The method of claim 5, further comprising: recovering a vapor stream from the distillation column; Condensing the vapor stream by further indirect heat exchange between the vapor stream and the second partial stream; And introducing the vapor stream back into the distillation column above the intermediate reflux as further reflux. 4. The method of claim 3, wherein the oxygen rich liquid stream is subcooled in a subcooling unit prior to partial vaporization; Vaporizing the coolant stream by the heat transfer to the coolant stream to produce a vaporized coolant stream; Dividing the air to be separated into first and second substreams; Introducing the first substream into the distillation column; Forming the portion of the air to be separated by the second substream; Subcooling the oxygen enriched stream through additional heat exchange with the refrigerant stream, the product stream and the vaporized coolant stream in a subcooling unit; The refrigerant, vaporized coolant and product stream are partially warmed in the subcooling unit and then sufficiently warmed. A filter for filtering air; A compressor coupled to the filter for compressing the air; A post-cooler for removing compressed heat from the air; A pre-purification unit for purifying the air; Main heat exchange means for cooling the air to a temperature suitable for its rectification; A distillation column arranged to rectify the air into an oxygen rich liquid column bottoms and a nitrogen rich vapor column top; An upper condenser connected to the distillation column for condensing at least a portion of the nitrogen-rich vapor column material to reflux the distillation column; Vaporization means for partially vaporizing an oxygen rich liquid stream consisting of said oxygen rich liquid column bottoms; A phase separator connected to the vaporization means to separate the oxygen rich liquid stream into liquid and vapor phase, wherein the phase separator transfers heat from at least a portion of the nitrogen rich vapor to a coolant stream consisting of the liquid phase stream consisting of the liquid phase. Connected to the top condenser to condense at least a portion of the nitrogen enriched vapor column and vaporize the coolant stream to produce a vaporized coolant stream; A pressure reducing valve inserted between the phase separator and the upper condenser to expand the liquid phase stream to produce the coolant stream and to generate a temperature difference between the coolant stream and the nitrogen enriched vapor column, wherein the phase separator is also provided with the vapor Connected to said main heat exchange means to partially warm up a vapor phase stream consisting of beds); Expansion means connected to said main heat exchange means to perform expansion of said vapor phase stream to produce a refrigerant stream, wherein said main heat exchange means communicates with said expansion means to bring said refrigerant stream into said main heat exchange means. Warm completely in); And means for extracting a product stream consisting of the remainder of said nitrogen-rich steam column not used as said reflux in said distillation column to produce said nitrogen product, wherein said main heat exchange means exchanges said product stream for said main heat exchange. Connected to said product stream extraction means to allow sufficient warming in the means). 9. The method of claim 8, wherein said vaporization means is connected to said main heat exchange means, and said vaporizing means is adapted to partially vaporize said oxygen rich liquid stream and to liquefy said portion of said air to be separated. Means for indirect heat exchange between said portion of air, and a first arranged to expand said oxygen rich liquid stream to produce a temperature difference for said indirect heat exchange between said portion of air and said oxygen rich liquid stream Has a pressure reducing valve; The pressure reducing valve is inserted between the phase separator and the upper condenser constituting the second pressure reducing valve; Wherein said vaporization means introduces said portion of said air to be separated into said distillation column as intermediate reflux to produce the production of said fire stream when said total oxygen rich liquid stream is used to condense at least a portion of said nitrogen rich vapor column. A device connected to said distillation column to maintain at a level. The vaporization means of claim 9, wherein the vaporization means also has means for further indirect heat exchange between the vapor stream and the oxygen rich liquid stream to condense the vapor stream and the vapor stream from the distillation column into the vaporization means. A device connected to the distillation column for flowing back and then back to the distillation tower above the intermediate reflux as further reflux. A filter for filtering air; A compressor coupled to the filter for compressing the air; A post-cooler for removing compressed heat from the air; A pre-purification unit for purifying the air; Main heat exchange means for cooling the air to a temperature suitable for its rectification; A distillation column arranged to rectify the air into an oxygen-rich liquid column bottoms and a nitrogen-rich vapor column; A top connected to the distillation tower for condensing at least a portion of the nitrogen-rich vapor column to reflux the distillation tower, while vaporizing a coolant stream comprising the first partial stream consisting of the oxygen-rich liquid column bottoms to produce a vaporized coolant stream. Condenser; A pressure reducing valve connected to said upper condenser to expand said first partial stream to produce said coolant stream and to generate a temperature difference between said coolant stream and said nitrogen-rich vapor column; Vaporization means for vaporizing a second partial stream consisting of said oxygen enriched liquid bottoms, wherein said vaporization means is connected to said main heat exchange means to partially warm said second partial stream; Expansion means connected to the main heat exchange means to perform the operation to expand the second partial stream to produce a refrigerant stream, wherein the main heat exchange means is adapted to completely warm the refrigerant stream in the main heat exchange means. In communication with said expansion means); And means for extracting a product stream consisting of the remainder of said nitrogen-rich steam column not used as said reflux in said distillation column to produce said nitrogen product, wherein said main heat exchange means exchanges said product stream for said main heat exchange. Connected to said product stream extraction means to warm up completely in the means). 12. The method of claim 11, wherein the vaporization means is connected to the main heat exchange means and the vaporization of the second partial stream and the air to be separated to vaporize the second partial stream and liquefy a portion of the air to be separated Means for indirect heat exchange between portions, and a first pressure reducing valve arranged to expand the second partial stream to generate a temperature difference for the indirect heat exchange between the portion of the air and the second partial stream; Have; The pressure reducing valve is inserted between the sub-cooling unit and the upper condenser constituting the second pressure reducing valve; The vaporization means introduces the portion of the air to be separated into the distillation column as intermediate reflux to produce the product stream such that a flow rate equivalent to both the first and second partial streams is at least a portion of the nitrogen-rich vapor column. An apparatus connected to said distillation column to maintain at the level obtained when used for condensation. The vaporization means of claim 12, wherein the vaporization means also has means for further indirect heat exchange between the vapor stream and the second partial stream to condense the vapor stream and the vapor stream from the distillation column into the vaporization means. A device connected to the distillation column for flowing back and then back to the distillation tower above the intermediate reflux as further reflux. 9. The apparatus of claim 8, further comprising: a subcooling unit inserted between the distillation tower and the upper condenser to subcool the oxygen rich liquid stream; And a junction connected to the main heat exchange means to divide the air to be separated into first and second substreams, wherein the junction is connected to the distillation column such that the first substream flows into the distillation column and the separation Said portion of air is connected to vaporization means such that said portion of air is formed by said second substream; said main heat exchange means arranged to sufficiently warm said refrigerant, vaporized coolant and said product stream, and said refrigerant, vaporized coolant And connected to the subcooling unit such that the product stream is partially warmed in the subcooling unit and then sufficiently warmed therein.