JP2736546B2 - 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. Is rectified to remove the low boiling components contained in nitrogen, and the amount is reduced by separating and discharging.

[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.

Accordingly, 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 and 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 a method for air liquefaction separation in which raw air is compressed and purified, cooled, and then introduced into a double rectification column to perform liquefaction separation. In, the liquefied air to be separated at the lower column lower part of the double rectification tower is decompressed and decompressed and then separated into gas and liquid, and the separated gas phase is discharged, and the liquid phase is separated from the upper part of the double rectification column The second configuration is characterized in that it is introduced into the middle column of the column, the impure liquefied nitrogen in the middle column of the lower column of the double rectification column is led out, decompressed, gas-liquid is separated, and the separated gas phase is discharged. In addition, the liquid phase is introduced into the upper middle part of the upper column of the double rectification column, and the third configuration separates the liquid liquefied nitrogen in the upper portion of the lower column of the double rectification column or in the upper portion of the lower column. Derived liquefied nitrogen by condensing nitrogen gas with a condensation evaporator, decompressed and separated gas and liquid Discharging the separated gas phase, and introducing the liquid phase into the upper portion of the upper column of the double rectification column. In any of the first to third configurations, the upper column This is a method characterized in that high-purity nitrogen gas is led out from the upper part of the upper tower which combines the upper part.

Further, a fourth configuration of the method of the present invention is the air liquefaction separation method in which the raw material air is compressed, purified, cooled, and then introduced into a single rectification column to perform liquefaction rectification separation. A condensing evaporator is provided at the bottom, liquefied air distilled out at the bottom is led out, decompressed, gas-liquid is separated, the separated gas phase is discharged, and the liquid phase is separated into the lower middle stage of the single rectification column. And high-purity nitrogen is led out from the upper part.

The air liquefaction / separation apparatus of the present invention is an air liquefaction / separation apparatus which compresses, purifies and cools raw air, introduces the compressed air into a double rectification column, and performs liquefaction rectification. A path for leading the liquefied gas from the lower and / or middle part of the lower tower and / or the upper part of the lower tower, a means for decompressing the derived liquefied gas and gas-liquid separation, and separating the separated liquid phase part into the middle and / or upper part of the upper tower And a path for introducing high-purity nitrogen is provided at the upper part of the upper tower. In particular, the liquefied gas is oxygen-enriched. It is characterized by liquefied air and / or nitrogen-enriched liquefied nitrogen and / or liquefied nitrogen.

(Operation)

The air liquefaction separation method and the air liquefaction separation device having the above first to third constitutions include liquefied air separated at the lower part of the lower column of the double rectification column, impure liquefied nitrogen in the middle part of the lower column, or liquefied nitrogen Alternatively, at least one of the liquefied nitrogen condensed in the condensation evaporator is decompressed and gas-liquid separated, and the separated gas phase is discharged, and the liquid phase is introduced into each predetermined position of the upper column. Low-boiling components such as hydrogen that are separated as a gas phase during gas-liquid separation after decompression can be discharged out of the system, reducing the amount of low-boiling components introduced into the upper column and reducing High-purity nitrogen gas having a low content of low-boiling components can be collected.

Further, in the single rectification column, as shown in the fourth configuration of the above method, a condensing evaporator is provided at the lower part, and the liquefied air distilled out of the condensing evaporator is further decompressed to perform gas-liquid separation. Since it is introduced in the middle stage, similarly to the double rectification column, low boiling components such as hydrogen separated as a gas phase during gas-liquid separation after decompression can be discharged out of the system, and provided for rectification. The amount of low-boiling components in the liquefied air can be reduced, and high-purity nitrogen gas having a low content of low-boiling components can be collected from the top of the column.

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

First, FIG. 1 shows a first embodiment of the present invention, in which a liquefied gas derived from a lower column of a double rectification column and introduced into an upper column,
That is, an example in which the present invention is applied to all of liquefied air, impure liquefied nitrogen, and liquefied nitrogen condensed by a condensation evaporator is shown.

This is because the purging of low-boiling components in the liquefied air and the impure liquefied nitrogen has been conventionally performed by purifying only the low-boiling components in the liquefied nitrogen. Is based on the finding that a higher purity product nitrogen gas can be obtained.

The raw material air GA is compressed and refined by a usual pretreatment device, and cooled to near the liquefaction point.
Of the lower tower 3c. In this lower tower 3,
A rectification operation is performed at a pressure of 5 kg / cm ² G, and nitrogen gas GN is separated in the lower tower upper part 3a, and oxygen-enriched liquefied air (hereinafter, simply referred to as liquefied air) LA is separated in the lower tower lower part 3c. .

First, the liquefied air LA is led out from the lower tower lower part 3c by the pipe 4 and introduced into the gas-liquid separator 5. This gas-liquid separator 5
Is located higher than the lower tower lower part 3c, and the pressure of the liquefied air LA introduced into the gas-liquid separator 5 is increased without using a pressure reducing valve due to the difference in head pressure between the liquefied air LA and the liquefied air LA of the lower tower lower part 3c. To a reduced pressure. The decompression of the liquefied air LA causes the liquefied air
The low-boiling components such as hydrogen, helium, and neon contained in LA are separated into a gaseous phase portion Xa vaporized and a liquid phase portion Ya containing nitrogen, oxygen, argon and the like.

The degree of decompression of the liquefied air LA is selected to be a value necessary and sufficient to vaporize low-boiling components such as hydrogen contained in the liquefied air LA. If the gas cannot be vaporized and the pressure is reduced too much,
And the like provided for rectification in the process are also not preferable because a large amount of them is vaporized. Normally, a pressure reduction of about 0.4 kg / cm ² G is sufficient, but the operating pressure of the lower tower 3 and the upper tower 6 or liquefied air
An appropriate degree of decompression is selected depending on the amount of LA introduced.

Gas phase part rich in low boiling components separated by gas-liquid separator 5
Xa is derived via the discharge valve 7. This discharge valve 7 controls the amount of gas phase part Xa to be discharged, and
It functions to control the amount of vaporized liquefied air LA by keeping the inside at an appropriate pressure. Therefore, while controlling the opening degree of the discharge valve 7 to adjust the amount of the gas phase part Xa discharged from the gas-liquid separator 5, the pressure inside the gas-liquid separator 5, that is, the degree of pressure reduction, is controlled. It is possible to control the amount of vaporization of the air LA.

Further, if the amount of vaporization in the gas-liquid separation is large, the amount of reflux liquid in the upper tower 6 is reduced. Therefore, the amount of vaporization is several percent, preferably 1 to 3%. In order to obtain this amount of vaporization, both pressure reduction at the liquid head and pressure reduction at the valve can be adopted,
The impure liquefied nitrogen MN and liquefied nitrogen LN described later can be started up in front of the supercooler 19 and decompressed by the liquid head, similarly to the liquefied air LA. The degree of the pressure reduction is calculated by a rising height × density and is usually about several meters. However, impure liquefied nitrogen MN,
The liquefied nitrogen LN is supercooled to a considerable extent in the supercooler 19,
In general, the amount of vaporization when the pressure is reduced to a pressure corresponding to the pressure of the upper tower 6 is several percent, and duplication of a pressure reducing valve or the like can be avoided. Also, the liquefied air LA may be passed through the subcooler 19 and then decompressed to an intermediate pressure at which the amount of vaporization becomes several percent, thereby performing gas-liquid separation.

On the other hand, the liquid phase part Ya separated at the lower part of the gas-liquid separator 5 is drawn out from the bottom part, and the pressure is reduced to a pressure corresponding to the operating pressure of the upper tower 6 by the pressure reducing valve 8, for example, 0.5 kg / cm ² G, and the upper part It is introduced into the middle stage 6c of the tower. The lower tower lower portion 3c includes the bottom of the lower tower 3 or a rectification stage one to several stages higher than the bottom.

Next, a part of the impure liquefied nitrogen MN flowing down the lower tower middle stage 3b as a reflux liquid is led out by a pipe 9, and after passing through a subcooler 19 as necessary, the flow rate and pressure are adjusted by a reflux liquid control valve 10. The pressure is adjusted and reduced to approximately the operating pressure of the upper tower 6, for example, 0.5 kg / cm ² G, and then introduced into the gas-liquid separator 11. The impure liquefied nitrogen MN introduced into the gas-liquid separator 11 vaporizes a low-boiling component similarly to the liquefied air LA, and separates into a gas phase part Xb and a liquid phase part Yb. The gas phase portion Xb containing a large amount of low-boiling components is discharged to an exhaust gas path 12 described later, and is separated at a lower portion of the gas-liquid separator 11.
Yb is led out from its bottom and introduced into the middle upper part 6b of the upper tower 6.

Further, the nitrogen gas GN separated in the lower tower upper part 3a is:
The liquid is introduced into the condensing evaporator 14 disposed in the lower part 6d of the upper tower via the pipe 13, and exchanges heat with liquefied oxygen LO, which will be described later, to be condensed and liquefied to become liquefied nitrogen LN. This liquefied nitrogen LN
Most of the liquid is returned to the upper part 3a of the lower tower and becomes a reflux liquid of the lower tower 3, a part of which passes through a pipe 16 and passes through a subcooler 19 as necessary. The pressure is reduced to a pressure and introduced into the gas-liquid separator 18. In the same manner, gas-liquid separation is performed, and the gas phase Xc containing a large amount of low-boiling components is discharged to the exhaust gas path 12, and the liquid phase Yc is separated from the bottom of the gas-liquid separator 18 to the upper column.
Introduced in 6a.

The liquid-phase portions Yb and Yc separated by the gas-liquid separators 11 and 18 are:
The liquid is introduced into the upper tower 6 by the pressure difference of the liquid head. The pressure in the gas-liquid separators 11 and 18 is adjusted by the reflux liquid control valve 10 or the pressure reducing valve 17 so as to be higher than the pressure in the upper tower 6. After the liquid separators 11 and 18 are led out, they can be introduced under reduced pressure by a pressure reducing valve. The liquefied air LA is introduced into the gas-liquid separator 5 after being decompressed by a pressure difference caused by the liquid head, but may be depressurized to a predetermined pressure via a decompression valve.

As described above, the liquid phase parts Ya, Yb, and Yc from which the low-boiling components have been separated by the gas-liquid separators 5, 11, and 18, that is, the liquefied air LA and the liquefied nitrogen LN
The liquefied gas such as is introduced into the predetermined position of the upper tower 6 as a reflux liquid, and is rectified in the upper tower 6 to be separated into liquefied oxygen LO in the lower part 6d and high-purity nitrogen gas PN in the upper part 6a. beneath
The 6d liquefied oxygen LO exchanges heat with the above-mentioned nitrogen gas GN in the condensing evaporator 14, evaporates and evaporates to become ascending gas in the upper tower 6, and a part of the gas is led out as oxygen gas GO.

Then, high-purity nitrogen gas PN is led out from the upper tower upper part 6a, and impure nitrogen gas WN is discharged from the middle upper part 6b in the exhaust gas path 12a.
Is derived. 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 Furthermore, this upper tower 6
If a low-boiling component is separated by providing an auxiliary rectification stage or an auxiliary rectification column similar to that described in the prior art, high-purity nitrogen gas containing no low-boiling component can be obtained.
It is also possible to obtain higher purity nitrogen gas by extracting the position of the high-purity nitrogen gas PN from the rectification stage several stages below the top instead of the top of the top tower.

In this manner, all of the liquefied gas derived from the lower tower 3 and introduced into the upper tower 6 is similarly decompressed and separated into gas and liquid, and the gas containing the low-boiling component that has been vaporized is discharged out of the system. Low boiling components in the liquefied gas introduced into the upper tower 6 can be greatly reduced. Therefore, low boiling components in the high-purity nitrogen gas PN obtained by rectifying these liquefied gases can be significantly reduced.

FIG. 2 shows a second embodiment of the present invention, in which liquefied air derived from the lower tower lower part 3c and introduced into the upper tower middle stage 6c.
LA, upper tower middle section upper part 6b derived from lower tower middle section 3b
The liquefied nitrogen introduced into the upper column 6a is introduced into the upper column 6a while the impure liquefied nitrogen MN introduced into the upper column 6a is introduced into the gas-liquid separators 5 and 11 to separate gas and liquid as in the first embodiment. nitrogen
The position where LN is led out from the lower tower 3 is changed to reduce the low boiling point components. In the following description, the first
Components that are the same as those in the first embodiment shown in the figure are given the same reference numerals, and detailed description thereof will be omitted.

The liquefied nitrogen LN derived from the lower tower 3 is derived from a rectification section 3d several stages below the top of the lower tower. The liquefied nitrogen LN of the rectification stage component 3d is liquefied nitrogen that is obtained by condensing and liquefying the nitrogen gas GN at the top of the lower tower in the condensing evaporator 14 and introducing it as reflux into the lower tower. The low-boiling components contained in the liquefied nitrogen LN are reduced by the low-boiling components being entrained in the ascending gas. Therefore, the liquefied nitrogen LN is supplied to the pressure reducing valve 17 without gas-liquid separation.
The pressure is reduced under a and introduced into the upper column upper part 6a to obtain a reflux liquid having a low boiling point component.

Also in this embodiment, similarly to the above-described embodiment, the upper tower 6
Since the low-boiling components in each liquefied gas introduced into the reactor are reduced, the amount of the low-boiling components in the high-purity nitrogen PN collected from the upper portion 6a can be reduced by rectification and separation in the upper tower 6. . The low-boiling components concentrated at the top of the lower tower can be discharged by providing an appropriate purge nozzle (not shown) at the top of the lower tower or the condensing evaporator 14.

Next, FIG. 3 shows a third embodiment of the present invention, in which the liquefied gas introduced into the upper column 6 is supplied to the liquefied air LA in the lower column 3c.
And liquefied nitrogen LN liquefied by the condensing evaporator 14. In the present embodiment, gas-liquid separation for separating and discharging low-boiling components is applied only to the liquefied air LA. That is, the liquefied air LA derived from the lower column lower part 3c is introduced into the gas-liquid separator 5 in the same manner as in the first embodiment, and the gas phase Xa containing a large amount of vaporized low-boiling components is discharged and separated. Liquid phase
While Ya is decompressed by the pressure reducing valve 8 and introduced into the upper middle stage 6c, the liquefied nitrogen LN is separated without separating low boiling components.
It is introduced into the upper tower upper part 6a as a reflux liquid. Therefore, a low-boiling component is introduced into the upper tower upper part 6a together with the liquefied nitrogen LN.

Therefore, in the present embodiment, the position at which the high-purity nitrogen gas PN is led out from the upper tower 6 is slightly moved downward from the top,
The rectification stage 6e is several stages below the top where the liquefied nitrogen LN containing the low boiling point component is introduced. This rectification stage part 6e
The liquefied air LA having a low boiling point component introduced from the lower column lower part 3c through the gas-liquid separator 5 into the upper column 6 rises while being rectified and rises while the liquefied air LA containing a small amount of low boiling component gas rises, and is introduced into the top of the column. Is in a gas-liquid equilibrium with the reflux liquid (liquefied nitrogen) LD flowing down, and this part of the reflux liquid LD has a small amount of low-boiling components present in the liquid phase itself due to the gas-liquid equilibrium relationship (gas phase About 1/7
0) and several stages of rectification operations from the top of the column
Since the low-boiling components contained in the water are raised to the top of the column accompanying the ascending gas GF, the content of the low-boiling components is very small. Therefore, by collecting high-purity nitrogen gas PN from the rectification stage 6e, high-purity nitrogen gas containing almost no low-boiling components can be obtained.

Then, nitrogen gas containing low boiling point components is
VN is led out, and from the middle upper part 6b, an impurity nitrogen gas WN is led out in the same manner as in the above-mentioned two embodiments. Also, from the lower tower upper part 3a, a part of the nitrogen gas GN containing a lot of low-boiling components is led out to adjust the amount of reflux liquid in the upper tower 6, and if necessary, the nitrogen gas in the upper tower upper part 6a Collected together with VN.

As shown in the above embodiments, the liquefied gas introduced into the upper tower 6, ie, the liquefied air LA in the lower part 3 c of the lower tower, the impure liquefied nitrogen MN in the middle part 3 b of the lower tower, and the liquefied nitrogen LN in the upper part 3 a of the lower tower 3 (condensation evaporator) (Including liquefied nitrogen condensed in the above), the gas-liquid is separated by reducing the pressure, and the separated gas phase is discharged, whereby the amount of the low-boiling components introduced into the upper column 6 can be reduced. In addition, the amount of low-boiling components in the high-purity nitrogen gas PN collected as a product can be reduced.

The following table shows the results of calculations performed by computer simulation to confirm the effect of reducing the low-boiling components in the high-purity nitrogen gas PN in each of the above Examples. In the calculation, the concentration of hydrogen gas was measured as a representative of the low-boiling gas, and the hydrogen amount of the raw air GA was measured at 10 ppm in order to clarify the reduction effect. As shown in FIGS. 1 to 3, the measurement points of the flow rate [Nm ³ / h] and the hydrogen concentration [ppm] of each gas or liquid are as follows: A: raw air GA, B: lower tower lower part 3c. Derived liquefied air LA, C: Gas phase part Xa, D discharged from gas-liquid separator 5, Liquid phase part Ya introduced into upper tower middle stage 6c, E: Impure liquefaction derived from lower tower middle stage 3b Nitrogen MN, F: Gas phase part Xb discharged from the gas-liquid separator 11, G: Liquid phase part Yb introduced into the middle part 6b of the upper column, H: Liquefied nitrogen LN, I derived from the upper part 3a of the lower column : Gas phase Xc, J discharged from gas-liquid separator 18: Liquid phase Yc introduced into upper part 6 a of upper column, K: High purity nitrogen gas PN, L collected from upper part 6, L: Upper part 6 Nitrogen gas WN, M: nitrogen gas VN derived from the upper tower 6.

As shown in the above table, the gas-liquid separator 18
The liquid phase part Yc (measurement point J; liquefied nitrogen) introduced into the liquid phase, despite the gas-liquid separation, still has other liquid phase parts Ya and Yb
Although a larger amount of hydrogen is entrained than (measurement points D and G), if the liquefied nitrogen LN is introduced into the upper column 6 as it is without providing the gas-liquid separator 18, a larger amount of hydrogen Since hydrogen (refer to the measurement point H) is introduced into the upper tower 6, about 18 ppm of hydrogen is mixed in the high-purity nitrogen gas PN (measurement point K) to be collected.

Next, FIG. 4 shows a fourth embodiment of the present invention.
This shows a case where only high-purity nitrogen gas is collected.

The compressed, purified and cooled raw material air GA is stored in the reservoir 20e
And liquefied by a condensing evaporator 21 provided at the lower part of the tower 20, and accumulates in a bottom 20f. The reservoir 2
If several rectification stages 20g are provided in 0e, low-boiling components can be separated here, and the low-boiling components such as hydrogen separated can be led out of the system from the conduit 22. The rectification stage 20g may be provided according to the hydrogen concentration in the raw material air GA and the required concentration of the low boiling component in the product nitrogen.

The liquefied air GL at the bottom 20f is led out from the conduit 23,
After the pressure is reduced through the valve 24, the gas is introduced into the gas-liquid separator 25.
Here, the gas phase part Xd generated by the pressure reduction is discharged out of the system from the conduit 26, and the liquid phase part Yd is discharged from the conduit 27 to the lower part 20d of the single rectification column 20.
Introduce to. The introduction part of the liquid phase part Yd is
It may be directly above 21 or several steps above the rectification stage.
The oxygen-enriched liquefied air LA accumulated in the condensing evaporator 21 enters the condensing evaporator 29 via a conduit 28 and is vaporized and discharged.
The high-purity nitrogen gas PN is led out from the upper part 20a of the column, a part of it is converted into a product, and the remaining part is introduced into the condensing evaporator 29 to be liquefied, and is introduced again as the reflux liquid of the single rectification column 20 from the top 20a. The same process as in a conventional nitrogen production method using a single rectification column is performed. Also in the case of this embodiment, low-boiling components can be purged by the gas-liquid separator 25 and / or the liquid reservoir 20e below the single rectification column 20, and high-purity nitrogen with improved purity can be collected.

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. However, 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. Also, as mentioned above,
Higher purity nitrogen gas can also be obtained by variously combining other means for reducing low boiling components applicable to this type of double rectification column. Further, as a means for separating gas and liquid, it is not necessary to use the gas / liquid separator itself as a device, and if it is possible to vaporize the low boiling point component in the path and separate it from the liquid phase, its form and name It is possible to use without being limited to. Further, the source gas for collecting neon or the like by collecting the released gas containing the separated low-boiling component as a main component may be used.

〔The invention's effect〕

As described above, in the double rectification column, the method and the apparatus of the present invention can be applied to the liquefied air at the lower part of the lower tower, the impure liquefied nitrogen at the lower part of the lower tower, or the liquefied nitrogen at the upper part of the lower tower (liquefaction condensed by the condensation evaporator). When introducing nitrogen (including nitrogen) to a predetermined position in the upper tower, the gas is separated from the lower tower after decompression and decompression, and the separated gas phase is discharged.
Since the liquid phase is introduced into the upper column at a predetermined position, the low-boiling components introduced into the upper column can be reduced, and the amount of low-boiling components in the nitrogen gas collected as a product can be reduced.
Further, in the single rectification column, the liquefied air that distills out at the bottom from the condensing evaporator provided at the lower part of the single rectification column is decompressed and then separated into gas and liquid. And the liquid phase is introduced at a predetermined position in the single rectification column, so that low-boiling components used for rectification can be reduced, and the amount of low-boiling components in nitrogen gas collected as a product can be reduced. Can be.

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.

In addition, since it can be easily configured by simply adding a simple gas-liquid separation means and a valve to a normal double rectification column, the cost of the apparatus is slightly increased and it is possible to cope with existing equipment. .

[Brief description of the drawings]

1 is a system diagram showing a first embodiment of the present invention, FIG. 2 is a system diagram showing a second embodiment, FIG. 3 is a system diagram showing a third embodiment, and FIG. 4 is a fourth embodiment. FIG. 2 Double rectification tower, 3 Lower tower, 3a Upper tower, 3b
…… Lower tower middle, 3c …… Lower tower lower, 5,11,18,25 …… Gas-liquid separator, 6 …… Upper tower, 6a …… Upper tower upper, 6b …… Upper tower middle upper, 6c… … Middle stage of the upper tower, 7 …… Discharge valve, 8,1
7, 17a: Pressure reducing valve, 20: Single rectification column, 21: Condensation evaporator, A to M: Measurement points of flow rate and hydrogen concentration, LA: Liquefied air, LN: Liquefied nitrogen, MN: … Impure liquefied nitrogen, PN… High-purity nitrogen gas, Xa, Xb, Xc, Xd… Vapor phase, Ya, Yb, Yc, Yd…
… Liquid phase

Claims (6)

(57) [Claims] 1. An air liquefaction method for compressing, purifying and cooling raw air, and introducing the compressed air into a double rectification column to perform liquefaction rectification separation. After decompression and decompression, the gas-liquid is separated, the separated gas phase is discharged, and the liquid phase is introduced into the middle stage of the upper column of the double rectification column, and high-purity nitrogen is derived from the upper column. An air liquefaction separation method characterized by the above-mentioned. 2. The air liquefaction separation method of compressing, purifying and cooling the raw material air and then introducing it into a double rectification column to perform liquefaction rectification separation, wherein the impure liquefied nitrogen in the middle stage of the lower column of the double rectification column is removed. After derivation and decompression, the gas-liquid is separated, the separated gas phase is discharged, and the liquid phase is introduced into the upper middle part of the upper column of the double rectification column, and high-purity nitrogen is derived from the upper column upper part. An air liquefaction separation method characterized by the above-mentioned. 3. An air liquefaction method for compressing, purifying and cooling a raw material air and then introducing the compressed air into a double rectification column to perform liquefaction rectification separation, wherein liquefied nitrogen in the upper part of the lower column of the double rectification column or The liquid nitrogen that is condensed by the condensing evaporator from the nitrogen gas to be separated at the upper part of the lower tower is led out, and the gas and liquid are separated after decompression.
An air liquefaction separation method comprising discharging a separated gas phase portion, introducing a liquid phase portion into an upper portion of an upper column of the double rectification column, and extracting high-purity nitrogen from an upper portion of the upper column. 4. An air liquefaction separation method in which raw air is compressed, purified, cooled, and then introduced into a single rectification column to perform liquefaction rectification separation, wherein a condensing evaporator is provided below the single rectification column. The liquefied air that distills out at the bottom is taken out, decompressed, and then separated into gas and liquid.The separated gas phase is discharged, and the liquid phase is introduced into the middle lower part of the single rectification column, and the purity is higher than that of the upper part. An air liquefaction separation method comprising deriving nitrogen. 5. An air liquefaction / separation apparatus for compressing, purifying and cooling raw air, and then introducing the compressed air into a double rectification column to perform liquefaction rectification. A path for leading the liquefied gas from the middle part and / or the upper part of the lower tower, a means for decompressing the derived liquefied gas and performing gas-liquid separation,
A path for introducing the separated liquid phase part into the upper part of the upper tower and / or the upper part of the middle part of the upper tower and / or an upper part of the upper part, and a path for leading out high-purity nitrogen at the upper part of the upper part. Air liquefaction separator. 6. The liquefied gas is oxygen-enriched liquefied air and / or
6. The air liquefaction separation device according to claim 5, wherein the device is nitrogen-enriched liquefied nitrogen and / or liquefied nitrogen.