JP2781985B2 - Air liquefaction separation method and apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air liquefaction separation method and an apparatus therefor, and more particularly to a method for collecting high-purity nitrogen having a low content of low boiling components such as hydrogen, helium, and neon. And its device.

[Conventional technology]

High-purity nitrogen widely used in the semiconductor industry and the like is required to be as pure as possible. For example, it is desired that the content of hydrogen be 1 ppm or less. for that reason,
First, the present applicant has developed an air liquefaction separation method capable of obtaining high-purity nitrogen having a low content of low-boiling components such as hydrogen (see JP-A-60-142183 and JP-A-60-142184). .

The above-mentioned air liquefaction separation method includes providing many rectification stages of a rectification column, or arranging an auxiliary rectification column in addition to the main rectification column, in addition to the main rectification, low boiling components contained in nitrogen. The nitrogen is rectified to remove the low boiling point components contained in the nitrogen, and the low boiling components are separated and discharged.

[Problems to be solved by the invention]

However, with the development of the semiconductor industry in recent years, nitrogen with less impurities has been required, and a slight increase in the amount of the low-boiling component due to a slight change in the raw air component has also become a problem.

Therefore, an object of the present invention is to provide an air liquefaction separation method and apparatus capable of further reducing the content of low boiling components in high purity nitrogen product to 0.1 ppm or less.

[Means for solving the problem]

In order to achieve the above object, a first configuration of the air liquefaction separation method of the present invention is to perform air liquefaction separation in which raw air is compressed, purified, cooled, and then introduced into a double rectification column to perform liquefaction rectification. In the method, feed air introduced into the double rectification column,
It is introduced above an auxiliary rectification shelf provided at the lower part of the lower tower of the double rectification tower, and a heating source is provided below the auxiliary rectification shelf to vaporize liquefied air to be separated at the lower part of the lower tower to raise gas. And liquefied air at the lower part of the lower tower is led out, and at least a part of the liquefied air is introduced into the middle part of the upper tower of the double rectification column. After performing gas-liquid separation or auxiliary rectification
The liquefied nitrogen is introduced into an upper tower, and high-purity nitrogen is led out from the upper tower.

Further, the second configuration is an air liquefaction separation method in which raw material air is compressed, purified, cooled, and then introduced into a rectification column to perform liquefaction rectification separation. While deriving nitrogen gas, high-purity nitrogen gas is derived from a stage several stages below the top of the rectification column of the rectification stage attached above the normal number of rectification stages, and at least a part of the nitrogen gas is condensed to the condensation evaporator. It is characterized in that it is introduced, liquefied and derived, and used as a reflux liquid of the rectification column.

Further, a first configuration of the air liquefaction / separation device of the present invention is an air liquefaction / separation device for compressing and purifying raw material air, introducing the compressed air into a double rectification column, and performing liquefaction rectification separation. A path for introducing the cooled raw material air above an auxiliary rectification shelf provided at a lower part of the lower tower of the double rectification tower, means for heating liquefied air at the lower part of the lower tower, and liquefaction of the lower part of the lower tower A path for introducing air into the middle part of the upper column of the double rectification column, means for extracting liquefied nitrogen in the middle part of the lower column to perform gas-liquid separation or auxiliary rectification, and liquefaction after the gas-liquid separation or auxiliary rectification A path for introducing nitrogen into the upper middle part of the upper column is provided, and high-purity liquefied nitrogen is derived from a stage several stages below the rectification column top of a plurality of rectification stages attached to a normal rectification stage. Route to the top of the upper tower or multiple rectifications attached to the normal rectification stage The high purity nitrogen gas is led out from a stage several stages below the top of the lower column, at least a part of which is introduced into the main condensing evaporator, liquefied and led out. The other is provided with a path for introducing the gas into the upper part of the upper tower, and a path for drawing out high-purity nitrogen gas from the upper part of the upper part of the tower. A path for introducing above the auxiliary rectification shelf provided in the lower part of the double rectification tower, means for heating the liquefied air at the lower part of the lower tower, and double rectification of the liquefied air at the lower part of the lower tower A path for introducing the liquid nitrogen in the middle part of the lower tower to perform gas-liquid separation or auxiliary rectification by introducing liquefied nitrogen in the middle part of the lower tower, and transferring the liquefied nitrogen after the gas-liquid separation or auxiliary rectification to the upper tower. A path for introduction to the upper part of the middle stage, and an upper part of the lower tower or a condensing evaporator A path for deriving high-purity liquefied nitrogen from the upper tower, introducing a nitrogen gas containing a large amount of low-boiling component gas from the upper tower, and a plurality of paths provided in a normal rectification stage. A path for leading high-purity nitrogen gas from a stage several stages below the top of the rectification stage and below the top of the rectification stage is provided.

(Operation)

According to the first configuration of the method of the present invention, a low-boiling component in the raw air introduced into the lower column can be separated in the rectification stage below the raw air introduction section, and is introduced into the upper column. Low boiling components in liquefied air can be reduced,
Since the low boiling components in liquefied nitrogen can be reduced, the low boiling components in the upper tower can be reduced together with the reduction of the low boiling components in the liquefied air, and the low boiling components in the collected nitrogen can be significantly reduced. it can.

Further, according to the second configuration of the method of the present invention, the low-boiling components concentrated at the top of the rectification column are discharged, and the high-purity nitrogen gas having a low content of low-boiling components is reduced from the rectification stage several stages below the top of the column. Can be derived. In addition, by condensing a part of the high-purity nitrogen gas to form a reflux liquid, the amount of low-boiling components introduced into the rectification column can be reduced.

〔Example〕

Hereinafter, the present invention will be described in more detail based on embodiments shown in the drawings.

First, FIG. 1 shows a first embodiment of the present invention, in which a plurality of rectification stages attached below a normal main rectification shelf are arranged in a lower column lower portion 2c of a double rectification column 1. The reboiler 4 is disposed below the auxiliary rectification shelf 3.

The raw material air GA is compressed and purified by a normal pretreatment device, and then introduced into the main heat exchanger 5 and cooled. Most of the raw material air AX is taken out of the main heat exchanger 5 after being cooled to the vicinity of the liquefaction point, and is piped to the lower column of the lower tower.
It is introduced above the auxiliary rectification shelf 3 of 2c. Further, a part AY of the raw material air cooled to the intermediate temperature in the main heat exchanger 5 is discharged from the intermediate part of the main heat exchanger 5 and then re-boiled.
And heats the oxygen-enriched liquefied air (hereinafter referred to as liquefied air) LA, which will be described later, and cools itself, and is introduced above the auxiliary rectification shelf 3 like most of the raw material air AX. .

In the lower tower 2, a rectification operation is performed at a pressure of about 5 kg / cm ² G, whereby nitrogen gas GN is separated from the lower tower upper part 2a, and the liquefied air LA is separated from the lower tower lower part 2c. This liquefied air LA
A part of the raw air supplied to the reboiler 4 is heated and vaporized by a part AY, and becomes a rising gas in the lower tower 2. The ascending gas comes in gas-liquid contact with the liquefied raw material air and the liquefied air (reflux liquid) rectified and flowing down in the main rectification shelf above the lower tower in the auxiliary rectification shelf 3, and has a low boiling point in the liquid. The components rise to the upper part of the lower tower 2 while being rectified in the respective rectification racks while being vaporized.

In addition, liquefied air LA derived from pipe 2 from lower tower lower part 2c
Is the operating pressure of the upper tower 9 by the pressure reducing valve 8, for example, 0.5 kg / cm ² G
After the pressure has been reduced to, the mixture is introduced into the upper central part 9c.

Next, a part of the impure liquefied nitrogen MN flowing down the middle part 2b of the lower column as the reflux liquid 2 was led out by the pipe 10, and the flow rate and the pressure were adjusted by the pressure reducing valve 11, and the pressure was reduced to almost the operating pressure of the upper tower 9. Later, it is introduced into the gas-liquid separator 12. The impurity liquefied nitrogen MN that has been decompressed and introduced into the gas-liquid separator 12 is partially vaporized and separated into a gas phase part Xa and a liquid phase part Ya. By this gas-liquid separation, most of the low-boiling components in the impure liquefied nitrogen MN are vaporized and concentrated in the upper gas phase Xa.
From the top through the exhaust valve 13.

The discharge valve 13 functions to adjust the amount of the gas phase portion Xa to be discharged and to control the amount of vaporized impurity liquefied nitrogen MN by maintaining the inside of the gas-liquid separator 12 at an appropriate pressure. Accordingly, while controlling the opening degree of the discharge valve 13 to adjust the amount of the gas phase portion Xa discharged from the gas-liquid separator 12, the gas-liquid separator 12
It is possible to control the vaporization amount of the impure liquefied nitrogen MN by adjusting the internal pressure, that is, the degree of pressure reduction.

The impure liquefied nitrogen MN, whose low-boiling components have been reduced by such gas-liquid separation, is led out from the bottom of the gas-liquid separator 12 and introduced into the upper part 9b in the upper tower.

Further, the nitrogen gas GN separated into the lower tower upper part 2a is:
A portion is collected as product nitrogen gas and the like via a pipe 14, and the remainder is introduced into a condensing evaporator 15 arranged in the upper tower lower part 9d, and is condensed and liquefied by performing heat exchange with liquefied oxygen LO described later. It becomes liquefied nitrogen LN and is led out of the pipe 16. This liquefied nitrogen
Most of the LN is returned to the upper part 2a of the lower tower and becomes a reflux liquid of the lower tower 2, and a part of the liquid is reduced to the pressure of the upper tower 9 by the pressure reducing valve 18 via the pipe 17 and is returned to the auxiliary rectification tower 19. Introduced as a liquid.

A part of the high-purity nitrogen gas PN of the upper tower upper part 9a is introduced as a rising gas in the lower part of the auxiliary rectification tower 19, and rectification is performed by the high-purity nitrogen gas PN and the liquefied nitrogen LN. I,
The low-boiling components in the liquefied nitrogen LN are concentrated at the top of the auxiliary rectification column 19. The gas phase portion Xb containing a large amount of low-boiling components concentrated at the top of the auxiliary rectification column 19 is led out through the discharge valve 20.
This discharge valve 20 is a discharge valve attached to the gas-liquid separator 12.
As in the case of 13, the amount of the gas phase part Xb to be discharged is adjusted, and the liquefied nitrogen LN
It has the function of controlling the amount of vaporization. Therefore, the gas phase part discharged from the auxiliary rectification tower 19 by controlling the opening of the discharge valve 20 is controlled.
While adjusting the amount of Xb, the pressure in the auxiliary rectification column 19,
That is, it is possible to control the vaporization amount of the liquefied nitrogen LN by adjusting the degree of pressure reduction.

The liquefied nitrogen Yb whose low boiling components have been reduced by such auxiliary rectification is led out from the bottom of the auxiliary rectification column 19 and introduced into the upper column upper portion 9a.

As described above, the liquefied air LA whose low-boiling components have been reduced by the auxiliary rectification in the auxiliary rectifying shelf 3 of the lower tower lower part 2c, the impure liquefied nitrogen Ya whose low-boiling components have been reduced by the gas-liquid separation in the gas-liquid separator 12, The liquefied gas such as liquefied nitrogen Yb whose low-boiling components have been reduced by the auxiliary rectification in the auxiliary rectification column 19 is introduced into each of the upper column 9 at a predetermined position as a reflux liquid, rectified in the upper column 9 and rectified in the lower column 9d. Of liquid nitrogen LO and high-purity nitrogen gas PN in the upper part 9a.

The liquefied oxygen LO in the upper tower lower part 9d exchanges heat with the above-mentioned nitrogen gas GN in the condensing evaporator 15, evaporates and evaporates to the ascending gas in the upper tower 9, and a part of it is led out as oxygen gas GO. . Impurity nitrogen gas WN is led out from upper part 9b in the upper tower, and high-purity nitrogen gas PN is led out from upper part 9a in the upper tower. As described above, since the high-purity nitrogen gas PN is obtained by rectifying the liquefied gas after separating the low-boiling components, a high-purity nitrogen gas PN containing almost no low-boiling components such as hydrogen is obtained. Can be

In this way, by removing the low boiling components in each liquefied gas introduced from the lower tower 2 and introduced into the upper tower 9 in advance, the low boiling components in the liquefied gas introduced into the upper tower 9 can be significantly reduced. Can be reduced. Therefore, low boiling components in the high-purity nitrogen gas PN obtained by rectifying these liquefied gases can be significantly reduced.

The following table shows the results of computer simulations for confirming the effect of reducing the low-boiling components in the high-purity nitrogen gas PN in the above examples. At the time of calculation, the concentration of hydrogen gas was measured as a representative of low-boiling gas, and the amount of hydrogen in the raw air GA was set to 100 ppm in order to clarify the reduction effect. As shown in FIG. 1, the measurement points of the flow rate of each gas or liquid [Nm ³ / h] and the hydrogen concentration [ppm] are as shown in FIG. Liquefied air LA, C introduced into the middle part 9c of the column, impure liquefied nitrogen MN derived from the middle part 2b of the lower tower, D: gas phase part Xa, E discharged from the top of the gas-liquid separator 12, E: upper part 9b in the upper part of the tower Liquid phase part Ya, F: liquefied nitrogen LN derived from lower tower upper part 2a, G: gas phase part Xb discharged from the top of auxiliary rectification tower 19, H: introduced into upper tower upper part 9a Liquefied nitrogen Yb, I: High-purity nitrogen gas PN collected from the upper tower upper part 9a, J: Impure nitrogen gas WN derived from the upper tower upper part 9b.

As is clear from the table, low-boiling components were removed at three points between the lower tower 2 and the path from the lower tower 2 to the upper tower 9 so that even when 10 ppm of hydrogen was contained in the raw material air, , The hydrogen content in the product high-purity nitrogen gas PN is 0.
It can be less than 02ppm.

FIG. 2 shows a modification of the first embodiment, in which high-purity nitrogen gas PN collected from an upper tower 9 is replaced by a compressor in place of the reboiler 4 provided in the lower tower lower part 2c shown in FIG. twenty one
And then blown into a rising gas.
Other configurations can be the same as those of the embodiment shown in FIG. 1, and their illustration and detailed description are omitted.

Thus, even if the high-purity nitrogen gas PN is used as the ascending gas, the low-boiling components in the liquefied air LA can be reduced by rectification in the auxiliary rectification shelf 3.

Therefore, similarly to the above-described embodiment, the low-boiling components in the liquefied air LA introduced into the upper tower 9 can be reduced, so that the amount of the low-boiling components in the high-purity nitrogen gas PN rectified and collected in the upper tower 9 can be reduced. Can be reduced.

The gas blown into the lower tower lower part 2c is not limited to the high-purity nitrogen gas PN. For example, various gases may be used as long as they have a low content of low-boiling components such as oxygen gas and exhaust gas derived from the upper tower 9. Can be used.

As shown in the above two embodiments, by providing the auxiliary rectification shelf 3 in the lower tower lower part 2c and rectifying, the low boiling point component in the liquefied air LA derived from the lower tower lower part 2c can be reduced. Further, low-boiling components are reduced by performing gas-liquid separation or auxiliary rectification of impure liquefied nitrogen MN in the lower tower middle part 2b and liquefied nitrogen LN in the lower tower upper part 2a, and then introduced into the upper tower 9 to obtain products. The amount of low-boiling components in the high-purity nitrogen gas PN to be collected can be significantly reduced.

Next, FIG. 3 shows a second embodiment of the present invention, in which nitrogen gas UN containing a large amount of low-boiling components is led out from a lower column upper portion 2a of the double rectification column 1 by a pipe 22, and the lower column is removed. From the rectification stage 2d, which is several stages below the top of 2, a low-boiling component nitrogen gas GN is led out by a pipe 23 through a pipe 23, a part of which is introduced into a condensing evaporator 15 and liquefied and led out from a pipe 16 to be liquefied. It is configured to obtain nitrogen LN.

In this way, the nitrogen gas GN derived from the rectification stage 2d several stages below the top of the lower column is introduced into the condensation evaporator 15 and the liquefied nitrogen LN
Thus, liquefied nitrogen LN having a small amount of low boiling components can be obtained. Therefore, the liquefied nitrogen LN is directly transferred to the pipe 17 without passing through means for separating low boiling components on the way.
Through the pressure reducing valve 18 to the upper tower upper part 9a.

The other flows of the liquefied air LA and the impure liquefied nitrogen MN, and the raw material air GA and various derived gases are the same as those in the first embodiment. I do.

FIG. 4 shows other low-boiling-point component reducing means in each part of the double rectification column 1 shown in each of the above-mentioned examples. FIG. 4 (a) shows a large content of low-boiling-point components from the top of the lower column. The nitrogen gas UN is led out through a pipe 22, and a part of the nitrogen gas UN is
And the remaining part is condensed and evaporated in the evaporator 15 to obtain the reflux liquid of the lower column 2, and the rectification stage 2d several stages below the top of the lower column
Liquefied nitrogen LN having a low content of low-boiling-point components is derived from the liquefied nitrogen LN, a part of which is collected as product liquefied nitrogen PLN, and the remainder is supplied to the upper column 9 as a reflux liquid. By configuring the lower tower upper part 2a in this way,
Liquefied nitrogen LN having a low boiling point component can be obtained from the lower tower upper part 2a, and product liquefied nitrogen PLN having a low boiling point component can be obtained. In addition, the low boiling point component in the liquefied nitrogen LN introduced as a reflux into the upper tower 9 can be obtained. Can be reduced.

FIG. 4 (b) uses an auxiliary rectification column 26 instead of the gas-liquid separator 12 for reducing low boiling components in the impure liquefied nitrogen MN. That is, while introducing the impure liquefied nitrogen MN derived from the lower column middle portion 2b as the reflux liquid of the auxiliary rectification column 26, an appropriate gas HG, for example, the gas of the upper column 9 or the lower column Rectification is performed by introducing a gas obtained by reducing the pressure of nitrogen gas or the like in the gas 2 as an ascending gas, and the gas phase Xc containing a large amount of low boiling components is discharged from the top of the auxiliary rectification column 26, and the low boiling components are discharged from the bottom. The low-boiling component in the upper column 9 is reduced by deriving the liquid phase portion Yc in which is reduced and introducing the liquid phase portion Yc into the upper column 9 in the same manner as in each of the above embodiments.

FIG. 4 (c) shows the top tower 9e from the top tower 9e.
Derived low boiling point components concentrated to 9e together with nitrogen gas VN,
It is formed so that high-purity nitrogen gas PN having a low low-boiling-point component content is collected from a rectification stage 9f several stages below the upper tower top 9e. By setting the position of the high-purity nitrogen gas PN derived from the upper column upper part 9a to the rectification stage 9f several stages below the upper column top 9e, the low boiling point slightly introduced into the upper column 9 is obtained. Components can be separated, high purity nitrogen gas
Low boiling components in PN can be further reduced.

FIG. 5 shows a single rectification column 30 in which the configuration of the upper portion of the lower column shown in the second embodiment is applied.

The raw material air GA which has been compressed, refined and cooled and introduced into the lower part of the single rectification column 30 is separated into oxygen-enriched liquefied air LA in the lower part 30c and nitrogen gas in the top part 30a by a normal rectification operation. I do. At this time, the low-boiling components contained in the raw material air GA are concentrated in the nitrogen gas at the top 30a by the rectification operation.

Therefore, a large amount of low-boiling components are discharged into the nitrogen gas UN discharged from the tower top 30a through the pipe 31 along with the pipe 31. On the other hand, the high-purity nitrogen gas PN derived from the rectification stage 30b, which is several stages below the tower top 30a, by the pipe 32,
Since low-boiling components are discharged from 30a, it is possible to obtain low-boiling components.

Further, the high-purity nitrogen gas PN thus obtained is introduced into the condensing evaporator 33 and liquefied by heat exchange with liquefied air LA introduced from the lower part of the tower through the pipe 34 and the valve 35 to liquefy. A part of the nitrogen LN is collected as product liquefied nitrogen PLN, and the remainder is returned to the top 30a of the single rectification column 30 to form a reflux liquid having a low content of low boiling components. As a result, a low-boiling component having a small amount is obtained as the reflux liquid in the single rectification column 30, and the amount of the low-boiling component in the column is reduced as compared with the case where the nitrogen gas at the top 30a is liquefied and used as the reflux liquid. The amount of low-boiling components in the high-purity nitrogen gas PN to be reduced and collected can be further reduced. The vaporized liquefied air is discharged from the upper part of the condensing evaporator 33 as an exhaust gas WG.

Next, FIG. 6 shows a third embodiment of the present invention, in which high-purity nitrogen gas PN derived from the upper column upper part 9a of the double rectification column 1 is shown.
Is located at the rectification stage part 9f several stages below the top of the tower. By forming the upper tower upper part 9a in this way, even if the amount of low boiling components in the liquefied nitrogen LN liquefied and introduced in the condensing evaporator 15 from the lower tower upper part 2a is large, the rectification of the upper tower top High-purity nitrogen gas PN with a small amount of low-boiling components can be obtained by rectifying and separating low-boiling components in the stage, and the low-boiling components separated at this time can be discharged together with nitrogen gas VN from the top of the column .

Also, as shown in FIG. 7, in this embodiment, the same auxiliary rectification column 26 as shown in FIG. 4 (b) is used as a means for separating low-boiling components in the impure liquefied nitrogen MN. Is possible. Such an auxiliary rectification column 26 is superior in the ability to separate low-boiling components as compared with the gas-liquid separator 12, but is expensive to manufacture, so that the auxiliary rectification column 26 is appropriately adjusted according to the desired composition of the high-purity nitrogen gas PN. Can be used.

The number of stages of the auxiliary rectification shelf 3 provided at the lower portion 2c of the lower column or the number of rectification stages for separating low-boiling components provided at the upper portion of the column is appropriately set depending on the amount of liquid, liquid composition, and the like. ,
Normal rectification operation can be performed sufficiently, and the number of stages and the introduction position of each gas or liquid can be set so that a gas or liquid of a predetermined composition can be obtained from each part of the tower. By doing so, it is possible to obtain a high-purity nitrogen gas having a desired purity by performing a rectification operation. Further, the means for reducing the low-boiling components in liquefied nitrogen and impure liquefied nitrogen can be any of gas-liquid separation or auxiliary rectification shown in the above examples, but is appropriately selected depending on the desired purity of high-purity nitrogen gas and the like. can do.

Further, in the description of each of the above embodiments, only the parts necessary for carrying out the method of the present invention are illustrated and described, but the present invention is directed to a double rectification column equipped with ordinary various auxiliary facilities. And other gas products and liquid products can be sampled at the same time. Further, as described above, higher-purity nitrogen gas can also be obtained by variously combining conventionally used means for reducing low-boiling components.

Further, a source gas for collecting neon or the like by collecting a released gas containing a low-boiling component as a main component may be used.

〔The invention's effect〕

As described above, the present invention introduces the raw material air into the rectification stage several stages higher than the lower column lower part, and provides a heating source at the lower part or blows a gas having a low content of low boiling components. Since auxiliary rectification is performed, the amount of low-boiling components in the liquefied air derived from the lower column and introduced into the upper column can be reduced, and the amount of low-boiling components in high-purity nitrogen gas collected as a product can be reduced. Can be reduced. further,
Low-boiling components in liquefied nitrogen or nitrogen gas can be reduced by gas-liquid separation of liquefied nitrogen derived from the lower tower, or by auxiliary rectification using an auxiliary rectification column or auxiliary rectification shelf. The low-boiling components introduced into the upper column accompanying the liquefied nitrogen can also be reduced.

In addition, by discharging a gas containing a large amount of low-boiling components from the top of the column, and by extracting nitrogen gas from a rectification stage part several stages below the top of the column, it is possible to obtain nitrogen gas having a low-boiling-point component, By liquefying this to form a reflux liquid, the amount of low-boiling components in the column can be reduced and high-purity nitrogen gas can be obtained.

As a result, even when the content of the low-boiling components in the raw material air fluctuates and increases greatly, the amount of the low-boiling components in the high-purity nitrogen gas can be easily suppressed to a reference value or less, and furthermore, Also, the collection rate of high-purity nitrogen gas can be improved, and the amount of high-purity nitrogen collected in an air liquefaction and separation apparatus of the same scale can be greatly increased.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a first embodiment in which the present invention is applied to a double rectification column, FIG. 2 is a system diagram showing a modification of the first embodiment, and FIG. System diagram, FIG. 4 is a system diagram of a main part showing another embodiment of low boiling point component reducing means in a double rectification column, FIG. 5 is a system diagram showing an example applied to a single rectification column, FIG. Is a system diagram showing a third embodiment applied to a double rectification column, and FIG. 7 is a system diagram of a main part showing another embodiment of a means for reducing low boiling components in the third embodiment. 1 Double tower, 2 lower tower, 2a Upper tower, 2b
... middle part of lower tower, 2c ... lower part of lower tower, 2d ... rectification stage attached above normal rectification shelf of lower tower, 3 ... auxiliary rectification shelf, 4 ... reboiler, 9 ... Upper tower, 9a: Upper part of upper tower, 9b: Upper part of upper tower, 9c: Middle part of upper tower, 12: Gas-liquid separator, 19, 26 ... Auxiliary rectification tower, 30 ... Single rectification tower ,
A to J: Measurement points of flow rate and hydrogen concentration, GA: Raw material air, LA: Liquefied air, LN: Liquefied nitrogen, MN: Impure liquefied nitrogen, PN: High-purity nitrogen gas

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F25J 3/00-3/04

Claims (9)

(57) [Claims] In the air liquefaction separation method for compressing, purifying and cooling raw air, and then introducing the compressed air into a double rectification column to perform liquefied rectification separation, the raw air introduced into the double rectification column is mixed with the mixed air. It is introduced above the auxiliary rectification shelf provided at the lower part of the lower tower of the rectification tower, and a heating source is provided below the auxiliary rectification shelf to vaporize liquefied air separated at the lower part of the lower tower to generate ascending gas. At the same time, liquefied air at the lower part of the lower tower is led out, at least a part of the liquefied air is introduced into the middle part of the upper tower of the double rectification tower, and liquefied nitrogen at the upper part and / or the middle part of the lower tower is led out from the lower tower. After performing gas-liquid separation or auxiliary rectification, and introducing the liquefied nitrogen into an upper tower, and extracting high-purity nitrogen from the upper part of the upper tower. 2. The auxiliary rectification shelf is a plurality of rectification stages attached to a normal rectification stage, and is located below a raw material air introduction section of a lower tower. Claim 1
The air liquefaction separation method described. 3. The air liquefaction separation method according to claim 1, wherein a gas having a lower content of gas components having a lower boiling point than nitrogen is blown into the lower portion of the lower tower in place of the heating source at the lower portion of the lower column. 4. An air liquefaction separation method in which raw air is compressed, purified and cooled, and then introduced into a rectification column to perform liquefaction rectification, wherein nitrogen gas having a high content of low boiling components is contained from the top of the rectification column. And high-purity nitrogen gas is derived from a stage several stages below the top of the rectification column, at least a part of which is introduced into a condensation evaporator to be liquefied and derived. An air liquefaction separation method characterized by the following. 5. The air liquefaction / separation method according to claim 4, wherein several stages below the top of the rectification column are provided several stages above a normal rectification stage. 6. The air liquefaction separation method according to claim 4, wherein the rectification column is a lower column of a double rectification column. 7. An air liquefaction / separation apparatus for compressing, purifying and cooling raw air, and then introducing the purified air into a double rectification column to perform liquefaction rectification, wherein the purified and cooled raw air is mixed with the lower column of the double rectification column. A path for introducing above the auxiliary rectification shelf provided at the lower part of the lower tower, means for heating liquefied air at the lower part of the lower tower, and liquefied air at the lower part of the lower tower in the middle part of the upper tower of the double rectification tower. A path for introducing, means for conducting liquid-liquid separation or auxiliary rectification by extracting liquefied nitrogen in the lower column middle part, and a path for introducing liquefied nitrogen after gas-liquid separation or auxiliary rectification to the upper middle part of the upper column And further, a route or a normal route for deriving high-purity liquefied nitrogen from a stage several stages below the top of the rectification column of a plurality of rectification stages attached to the normal rectification stage and introducing it to the upper part of the upper column Higher than a few columns below the top of the lower column of the multiple rectification stages attached to the rectification stage And at least part of the nitrogen gas is introduced into the main condensing evaporator and liquefied and derived, and divided into two, one is provided to the lower tower top, and the other is provided to the upper tower upper part, An air liquefaction / separation apparatus comprising a path for leading high-purity nitrogen gas from the upper part of the upper tower. 8. An air liquefaction / separation apparatus for compressing, purifying and cooling raw air and then introducing it into a double rectification column to perform liquefied rectification separation, wherein the purified and cooled raw air is mixed with the lower column of the double rectification column. A path for introducing above the auxiliary rectification shelf provided at the lower part of the lower tower, means for heating liquefied air at the lower part of the lower tower, and liquefied air at the lower part of the lower tower in the middle part of the upper tower of the double rectification tower. A path for introducing, means for conducting liquid-liquid separation or auxiliary rectification by extracting liquefied nitrogen in the lower column middle part, and a path for introducing liquefied nitrogen after gas-liquid separation or auxiliary rectification to the upper middle part of the upper column And a path for leading high purity liquefied nitrogen from the upper part of the lower column or the condensing evaporator and introducing it to the upper part of the upper part, and a path for discharging nitrogen gas containing a large amount of low boiling component gas from the upper part of the upper part, The top of several rectification stages attached to a normal rectification stage Cryogenic air separation apparatus characterized by comprising a path for deriving the high-purity nitrogen gas from the several stages of a stage from the top. 9. The air liquefaction / separation apparatus according to claim 7, wherein several rectification stages of the lower tower and the upper tower are provided above a normal rectification stage. .