JPH0412391B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an air liquefaction separation method and apparatus for extracting high purity nitrogen with a low content of low boiling point components such as hydrogen.

[Conventional technology]

As a method and apparatus for producing nitrogen industrially, a so-called air liquefaction separation method is used, in which air is used as a raw material, liquefied, and its components are separated by rectification based on the difference in their boiling points. Therefore, conventional methods for carrying out this rectification will be explained for an apparatus using a single type rectifying column and an apparatus using a double type rectifying column.

Figure 1 shows an example of a single-type rectification column, in which compressed and refined feed air from which dust, carbon dioxide, and moisture have been removed is passed through route 1.
is introduced into the lower part of the single-type rectification column 2, and is rectified by the reflux liquid flowing down the rectification plate 3 from the upper part of the single-type rectification column 2, and nitrogen gas is introduced into the upper part of the single-type rectification column 2. However, oxygen-rich liquefied air is also purified at the bottom. Of this, the nitrogen gas is led out as a product nitrogen gas through a route 4, and a part of it passes through a route 5 and enters the condenser evaporator 6 that is sectioned directly above the single rectification column 2. The liquid is liquefied by heat exchange with liquefied air introduced from the bottom part 2 through route 7, and becomes a reflux liquid from the upper part of single rectification column 2 through route 8.

Fig. 2 shows an example of a double rectification column, in which feed air introduced into the lower column 10 from route 9 in substantially the same way as the single rectification column 2 is rectified between it and the reflux liquid, and nitrogen is added to the upper part of the lower column 10. The gas is produced at the bottom of the lower column 10 to form liquefied air. Nitrogen gas in the upper part of the lower column 10 enters the condensing evaporator 12 through a path 11, exchanges heat with liquefied oxygen, becomes liquefied nitrogen, and passes through a path 13 into the lower column 10.
It is returned to the upper part as a reflux liquid, and a part of it passes through the path 14 and is introduced into the top of the upper column 15 to become a reflux liquid. Then, a part of the oxygen gas vaporized in the condenser evaporator 12 is rectified with the liquefied air reflux liquid introduced from the path 16, becoming a gas with a high nitrogen concentration, and further becomes the liquefied nitrogen reflux liquid. The nitrogen gas is rectified between the nitrogen gas and the nitrogen gas, which is then led out from the top of the upper column 15 through a path 17. Further, oxygen gas is led out from the lower part of the upper column 15 through a path 18.

Note that 3a and 3b are rectifier plates.

[Problem to be solved by the invention]

However, the product nitrogen gas produced in this way contains concentrated low-boiling components such as hydrogen that were contained in trace amounts in the raw air. That is,
Product nitrogen gas generally contains 2 to 10 ppm of hydrogen,
Contains 8-20ppm helium and 40-100ppm neon. Even if these components are present in minute amounts, they have a significant effect on products in fields such as the semiconductor industry that require ultra-high purity nitrogen, and improvements have been required.

The present invention has been made in view of the above points, and an object of the present invention is to provide a method and apparatus for efficiently, simply and inexpensively reducing and removing low-boiling components such as hydrogen in product nitrogen.

[Means to solve the problem]

In order to achieve the above object, the method of the present invention includes an air liquefaction separation method for collecting high purity nitrogen.
A portion of the nitrogen gas containing a high content of low boiling point components such as hydrogen is drawn out from the top of the rectification column while adjusting its amount,
The remainder is drawn out from the top of the rectification column, condensed in a condensing evaporator, and introduced into the top of the rectification column as a reflux liquid, and hydrogen, etc. High-purity liquefied nitrogen with a low content of low-boiling point components can be derived, or this high-purity liquefied nitrogen can be expanded and depressurized through an expansion valve, then introduced into a condensing evaporator and vaporized to produce low-boiling point components such as hydrogen. It is characterized by producing high-purity nitrogen gas with a low content.

Another method of the present invention is an air liquefaction separation method for collecting high-purity nitrogen, in which a portion of the nitrogen gas containing a large content of low-boiling components such as hydrogen is removed from the top of the lower part of the double rectification column. The remaining amount is extracted from the top of the rectification column and condensed in a condensing evaporator.
At the same time, high-purity liquefied nitrogen with a low content of low-boiling components such as hydrogen is drawn out from the rectification stage several stages below the top of the lower column, and is introduced into the top of the rectification column as a reflux liquid. It is characterized in that it is introduced as a reflux liquid into the upper column after expansion and pressure reduction through the upper column, and high-purity nitrogen gas with a low content of low-boiling components such as hydrogen is led out from the top of the upper column.

The device of the present invention is an air liquefaction separation device that liquefies raw air and collects high-purity nitrogen by rectifying it in a rectification column. There is a route in which a part of the nitrogen gas is led out via a regulating means, a route in which the remaining part is led out and introduced into a condensing evaporator and introduced into the top of the rectification column, and a route in which a part of the remaining part is led out and introduced into a condensing evaporator to the top of the rectification column. It is characterized by providing a path for delivering high-purity liquefied nitrogen with a low content of low-boiling point components such as hydrogen from the distillation stage.

Further, the apparatus of the present invention is characterized in that the number of rectification stages is increased by several stages, and the rectification column is a lower column of a single-type rectification column or a double-type rectification column.

〔Example〕

Hereinafter, the present invention will be explained in more detail based on embodiments shown in the drawings. In the following description, the same elements as those of the conventional example shown in FIGS. 1 and 2 are given the same reference numerals, and detailed description thereof will be omitted.

First, FIG. 3 shows the main part of an air liquefaction separation apparatus using a single rectification column. In addition to the rectifying plate 3, the single rectifying column 2 used in this apparatus is provided with several rectifying plates 19a above it, and at the top thereof, nitrogen containing a large amount of low boiling point components such as hydrogen is placed. A path 4 for deriving the gas is provided, and a rectification stage several stages below the top, that is, directly below the rectification plate 19a, contains the highest purity gas which has a low oxygen content and low boiling point components such as hydrogen. A path 25 is provided to lead out liquefied nitrogen.

In the case of this single type rectification column 2, a portion of the nitrogen gas containing a high content of low boiling point components such as hydrogen is passed from the top of the single type rectification column 2 through the control valve 24 in the path 4 to control the degree of concentration of low boiling point components. At the same time, the remaining nitrogen gas is introduced into the condenser evaporator 6 via route 5, and is converted into liquefied nitrogen through heat exchange with the liquefied air introduced via route 7. It is returned to the top of the distillation column 2 as a reflux liquid, and rectified to remove low boiling point components between it and the rising nitrogen gas by flowing down the rectification plate 19a. Then, high-purity liquefied nitrogen with a low content of low-boiling components such as hydrogen is led out from directly below the rectification plate 19a through a path 25, and after being expanded and depressurized through an expansion valve 27 in a path 26,
High purity nitrogen gas, which is introduced into the condensing evaporator 6 and has a low content of low boiling point components such as vaporized hydrogen, is led out through a path 28. Note that the high-purity liquefied nitrogen in the route 25 can also be directly led out from the route 29. It goes without saying that the amount of nitrogen gas led out from the route 4 is adjusted by the control valve 24 so that the content of low boiling point components such as hydrogen contained in the liquefied nitrogen led out from the route 25 is 1 ppm or less. .

FIG. 4 shows the main parts of an air liquefaction separation device using a double rectification column. In addition to the rectifying plate 3a of the lower column 10, the double rectifying column used in this apparatus is provided with several stages of rectifying plates 19b above the lower column 10, and at the top of the lower column 10, low boiling point components such as hydrogen are A path 30 for deriving a portion of nitrogen gas with a high content, a path 11 for introducing a portion of the nitrogen gas into the condensing evaporator 12, and liquefied nitrogen liquefied by exchanging heat with liquefied oxygen in the condensing evaporator 12. A route 13 that returns the liquid to the top of the lower column 10 as a reflux liquid, a route 32 that leads out high-purity liquefied nitrogen with a low content of low-boiling components such as hydrogen from directly below the rectification plate 19b, and a route 13 that branches off from the route 32. , a path 33 for introducing the high-purity liquefied nitrogen into the condensing evaporator 12 after expanding and lowering the pressure through the expansion valve 34;
A path 35 for leading out high-purity nitrogen gas is provided.

In the case of this double rectification column, a part of the nitrogen gas containing a high content of low-boiling point components such as hydrogen is passed from the top of the lower column 10 by controlling the degree of concentration of the low-boiling point components with the control valve 31 of the path 30. While controlling the flow rate, the remaining nitrogen gas is introduced into the condensing evaporator 12 via the path 11, and is converted into liquefied nitrogen through heat exchange with liquefied oxygen, and returned to the top of the lower column 10 as a reflux liquid through the path 13. By lowering the rectification plate 19b, rectification is performed to remove low-boiling components with nitrogen gas. Then, high-purity liquefied nitrogen with a low content of low boiling point components such as hydrogen is led out from directly below the rectifying plate 19b via a path 32, and is introduced into the expansion valve 3 of a path 33.
After expansion and depressurization through the nitrogen gas pipe 4, the nitrogen gas is introduced into the condensing evaporator 12, where it is vaporized, and high-purity nitrogen gas with a low content of low-boiling components such as hydrogen is led out through the path 35. Note that the high-purity liquefied nitrogen in the route 32 can also be directly led out from the route 36. In addition, high-purity liquefied nitrogen from route 32 is passed through route 14' and expansion valve 20' to upper column 1.
5 as a reflux liquid, and high-purity nitrogen gas with a low content of low-boiling components such as hydrogen can also be led out from the top of the upper column 15 via route 17'. In the above case, the amount of nitrogen gas led out from the path 30 is controlled by the control valve 3 so that the amount of low boiling point components such as hydrogen in the liquefied nitrogen led out from the path 32 is 1 ppm or less.
Needless to say, it can be derived by adjusting 1.

〔Effect of the invention〕

As explained below, in an air liquefaction separation method for collecting high-purity nitrogen, the present invention extracts a portion of nitrogen gas containing a large amount of low-boiling components such as hydrogen from the top of a rectification column while controlling the amount. The remainder is discharged from the top of the rectification column, condensed in a condensing evaporator, and introduced into the top of the rectification column as a reflux liquid, and hydrogen, etc. High-purity liquefied nitrogen with a low content of low-boiling point components is derived, or the high-purity liquefied nitrogen obtained in this way is expanded through an expansion valve and introduced into a condensing evaporator after being expanded to high pressure, where it is vaporized to produce hydrogen, etc. Since high-purity nitrogen gas with a low content of low-boiling components is derived, high-purity nitrogen can be produced efficiently, simply, and at low cost.

In addition, a part of the nitrogen gas containing a high content of low boiling point components such as hydrogen is drawn out from the top of the lower part of the double rectification column while adjusting its amount, and the remaining part is drawn out from the top of the rectification column and then sent to the condenser evaporator. It is condensed, drawn out, and introduced as a reflux liquid to the top of the rectification column, and high-purity liquefied nitrogen with a low content of low-boiling components such as hydrogen is drawn out from a rectification stage several stages below the top of the lower column. After expansion and depressurization, the reflux liquid is introduced into the upper column through the expansion valve, and high-purity nitrogen gas with a low content of low-boiling components such as hydrogen is extracted from the top of the upper column. High purity nitrogen can be produced easily and inexpensively.

Furthermore, in an air liquefaction separation device that liquefies raw air and collects high-purity nitrogen by rectifying it in a rectification column, nitrogen gas with a high content of low-boiling components such as hydrogen is collected from the top of the rectification column. A route in which the remaining part is drawn out through a regulating means, a route in which the remaining part is drawn out and introduced into a condensing evaporator and then introduced into the top of the rectification column, and a route in which hydrogen, etc. By using this device, the amount of high-purity nitrogen gas discharged outside the system can be minimized, making it efficient and simple. Moreover, high purity nitrogen gas can be produced at low cost.

Note that this means of increasing the number of rectification stages can be particularly suitably employed in new plants.

[Brief explanation of drawings]

Figures 1 and 2 show the main parts of a conventional air liquefaction separation device. Figure 1 is a system diagram of a single type rectification column, Figure 2 is a system diagram of a double type rectification column, and Figure 3 is a system diagram of a double type rectification column. Figures 3 and 4 respectively show the main parts of an air liquefaction separation device to which the present invention is applied. This is a diagram of the applied system. 2...Single rectification column, 6...Condensing evaporator, 10...
... lower column, 12 ... condensing evaporator, 15 ... upper column, 19a, 19b ... rectification plate, 20', 27,
34...expansion valve, 24, 31...control valve.

Claims (1)

[Scope of Claims] 1. In an air liquefaction separation method for collecting high-purity nitrogen, a portion of nitrogen gas containing a high content of low-boiling components such as hydrogen is drawn out from the top of a rectification column while adjusting its amount, The remainder is drawn out from the top of the rectification column, condensed in a condensing evaporator, and introduced into the top of the rectification column as a reflux liquid, and hydrogen, etc. An air liquefaction separation method characterized by deriving high purity liquefied nitrogen with a low content of low boiling point components. 2. In the air liquefaction separation method for collecting high-purity nitrogen, a portion of the nitrogen gas containing a high content of low-boiling components such as hydrogen is drawn out from the top of the rectification column while adjusting the amount, and the remainder is transferred to the top of the rectification column. After being extracted from the rectifying column, it is condensed in a condensing evaporator, and introduced as a reflux liquid to the top of the rectification column, and the content of low boiling point components such as hydrogen is The method is characterized in that high-purity liquefied nitrogen with a low content of hydrogen is derived, and after being expanded and depressurized via an expansion valve, it is introduced into a condensing evaporator and vaporized to derive high-purity nitrogen gas with a low content of low-boiling point components such as hydrogen. Air liquefaction separation method. 3 In the air liquefaction separation method for collecting high-purity nitrogen, a part of the nitrogen gas containing a high content of low-boiling components such as hydrogen is drawn out from the top of the lower part of the double rectification column while adjusting the amount, and the remainder is purified. After being drawn out from the top of the distillation column, it is condensed in a condensing evaporator, drawn out and introduced into the top of the rectification column as a reflux liquid, and low-boiling components such as hydrogen are removed from the rectification stage several stages below the top of the lower column. High-purity liquefied nitrogen with a low content is extracted, expanded and depressurized through an expansion valve, and then introduced as a reflux liquid into the upper column. From the top of the upper column, high-purity nitrogen gas with a low content of low-boiling components such as hydrogen is produced. An air liquefaction separation method characterized by deriving. 4. In an air liquefaction separation device that liquefies raw air and collects high-purity nitrogen by rectification separation using a rectification column, a portion of the nitrogen gas containing a high content of low-boiling components such as hydrogen is extracted from the top of the rectification column. There is a route in which the remainder is introduced through a regulating means, a route in which the remainder is introduced into a condensing evaporator and then introduced into the top of the rectification column, and a route in which hydrogen, etc. An air liquefaction separation device characterized by providing a path for deriving high purity liquefied nitrogen with a low content of low boiling point components. 5. The air liquefaction separation apparatus according to claim 4, wherein the rectification column is provided with several rectification stages. 6. The air liquefaction separation apparatus according to claim 4, wherein the rectification column is a single type rectification column. 7. The air liquefaction separation apparatus according to claim 4, wherein the rectification column is a lower column of a double rectification column.