JPH0744943Y2 - Air separation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an air separation device capable of obtaining high-purity nitrogen containing no carbon monoxide.

[Conventional technology]

The structure and operation of the conventional air separation device will be described with reference to FIG. In addition, here, an example of a so-called external cold utilization type air separation device that utilizes the cold of LNG is taken as an example.

The raw material air filtered by the raw material air filter 1 is pressurized by the raw material compressor 2 to a pressure (for example, 5 Kg / cm ² g) necessary for performing the adsorption operation in the adsorption device 3 and the moisture content in the adsorption device 3 is increased. After the unnecessary components such as carbon dioxide are removed, the cold box C is entered. 4 is a precooler.

The adsorption device 3 is composed of two adsorption towers 3a and 3b, which are switched by a switching valve (not shown) so that adsorption and regeneration are alternately repeated at regular time intervals.

The cold box C comprises a main heat exchanger 5, a rectification column 6, a circulating nitrogen heat exchanger 10, and a flash bottle (pressure reducer) 11.

Further, the rectification column 6 has a raw material air pressure (for example, 5 Kg / cm ² g).
And a lower pressure (for example, 0.
Low pressure column 8 operated at ^{2 to} 0.5 Kg / cm ² g) and both columns
It consists of a heat exchanger (main evaporator) 9 for exchanging heat between 7 and 8.

The raw material air discharged from the adsorption device 3 is cooled to near the boiling point by the main heat exchanger 5, and then enters the high pressure column 7 of the rectification column 6,
While rising in the column, the nitrogen concentration gradually increases due to contact with refluxing liquid nitrogen, and nitrogen gas having a low oxygen content is obtained at the top.

This nitrogen gas is introduced into the heat exchanger 9 where it is condensed by heat exchange with liquid oxygen to become liquid nitrogen, part of which is at the top of the low pressure column as the low pressure column reflux liquid, and part of which is the high pressure column reflux liquid. Is supplied to the top of the high-pressure column, and the rest is withdrawn as liquid nitrogen in the liquid nitrogen tank 12.

The high-pressure column reflux liquid contacts with air to increase the oxygen concentration as it descends in the high-pressure column 7, and is withdrawn from the column bottom as liquid air containing 35 to 40% of oxygen. Is supplied to.

This liquid air increases the oxygen concentration while descending in the low pressure column 8, liquid oxygen is extracted from the bottom of the column to the liquid oxygen tank 13, and nitrogen gas having a low oxygen content is extracted from the top of the column. Further, nitrogen gas having a high oxygen content is extracted from the upper part of the low pressure column, heated by the main heat exchanger 5, and then supplied to the adsorption device 3 as an adsorption column regeneration gas.

The low-pressure nitrogen gas discharged from the top of the low-pressure column is partly heated by the main heat exchanger 5 and the rest by the circulating nitrogen heat exchanger 10, then passed through the circulating nitrogen precooler 14 and the circulating nitrogen compressor 15. Pressurized. This pressurized nitrogen gas is LN
G Cooled in the heat exchanger 16 and liquefied, circulating nitrogen heat exchanger 10
Enter the low temperature section.

The liquid nitrogen discharged from the heat exchanger 10 is decompressed to the pressure of the high-pressure column 7 by the flash bottle 11, part of which is gasified and returns to the circulating nitrogen compressor 15 via the heat exchanger 10, and the rest is the top of the high-pressure column. As a reflux liquid. 15a is a circulating nitrogen compressor 1
The low-pressure stage compressor 5 and the high-pressure stage compressor 15b. Also,
Reference numeral 17 is a refrigerant pump, and 18 is an LNG warmer.

By the way, recently, the demand for high-purity nitrogen that does not contain carbon monoxide for semiconductor production is increasing, and accordingly, the production of high-purity nitrogen by an air separation device is required.

However, since the boiling points of nitrogen and carbon monoxide are close to each other, it is possible to separate them only by the rectification operation in the rectification column.

Therefore, conventionally, as shown in FIG.
A reaction device 19 using a noble metal catalyst such as platinum is provided, and the reaction device 19 causes carbon monoxide in the raw material air to react with oxygen to form carbon dioxide, which is then adsorbed and removed by the adsorption device 3. There is. In FIG. 4, 20 is a heater for heating the raw material air before entering the reaction apparatus 19, 21 is a refrigerator for cooling the raw material air discharged from the reaction apparatus 19, and 22 is air from the air cooled by the refrigerator 21. It is a drain separator that removes water.

[Problems to be solved by the device]

However, according to this conventional means, the whole amount of the raw material air is processed in the reaction device 19, so that the amount of gas to be processed in the reaction device 19 becomes extremely large.

For example, if feed air throughput of large devices 30,000 ³ / h, even though the demand for high-purity nitrogen is small and approximately 100~2,000Nm ³ / h, handles all the feed air This is a great waste, and the large amount of expensive precious metal catalyst used makes it extremely uneconomical, which has been a serious problem especially in large air separation devices.

Note that this problem is not limited to the air separation device using the external cold, and similarly occurs in the air separation device in which the raw air is adiabatically expanded by the expansion turbine to generate cold.

Therefore, the present invention provides an air separation device that can significantly reduce the amount of gas to be processed in the reactor to obtain the same high-purity nitrogen as the conventional one, and thereby reduce the amount of precious metal catalyst used. To do.

[Means for Solving the Problems]

The present invention provides an air separation apparatus comprising a rectification column comprising a high pressure column for separating raw air into liquid air and nitrogen gas, and a low pressure column for separating liquid air into liquid oxygen and nitrogen gas. The high-pressure column of the rectification column is vertically divided into an upper part and a lower part, and a nitrogen gas line is provided to take out all the low-purity nitrogen gas containing oxygen and carbon monoxide produced in the lower part. In the line, a reaction device for reacting carbon monoxide and oxygen in the low-purity nitrogen gas to produce carbon dioxide, and an adsorption device for adsorbing and removing the carbon dioxide produced in this reaction device to produce high-purity nitrogen gas And the nitrogen gas line outlet side is connected to the upper stage of the high-pressure column.

[Action]

According to the above configuration, since the low-purity nitrogen gas generated in the high-pressure column (lower part) of the rectification column is taken out to the nitrogen gas line and processed in the reactor, the throughput of this reactor is lower than that of the conventional device. Can be greatly reduced. Therefore, the amount of expensive noble metal catalyst to be used in the reactor can be greatly reduced.

Further, since high-pressure nitrogen gas is taken out from the high-pressure column of the rectification column for processing, it is not necessary to pressurize the nitrogen gas to a pressure necessary for performing the adsorption operation in the adsorption device. That is,
There is no need to provide a separate pressurizing means as in the case of taking out low-pressure nitrogen gas from the low-pressure column.

Further, in order to liquefy by treating all the nitrogen gas generated in the lower part of the high pressure column of the rectification column with the reactor and returning it to the upper part of the high pressure column, take out only a part of the nitrogen gas generated in the high pressure column. Compared with the case of processing, the amount of processing is large and high-purity nitrogen gas can be manufactured efficiently.

In addition, the nitrogen gas after the reaction treatment is used as another rectification column (sub-rectification column).
Compared with the case of rectifying and liquefying by putting in, the equipment is simple and the cost is low.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS.

In the following embodiments, an air separation device using an external cold is used as an example of application in accordance with the above-mentioned conventional description. In the following embodiments, the same parts as those of the conventional device shown in FIGS. 3 and 4 are designated by the same reference numerals,
The duplicate description will be omitted.

First Example (See FIG. 1) The high-pressure column 7 of the rectification column 6 is vertically divided into a lower stage 7a and an upper stage 7b, and the inlet side of the nitrogen gas line 23 is in the lower stage 7a of the high-pressure column 7. The outlet side is connected to each of the upper steps 7b.

This nitrogen gas line 23 is led out of the cold box C through the main heat exchanger 5, and in the nitrogen gas line 23 led out of the cold box C, a heater 24 for heating is sequentially provided from the inlet side of the line. A reaction device 25 having a noble metal catalyst such as platinum, a refrigerator 26, and a sub-adsorption device 27 for removing and adsorbing carbon dioxide are provided.

The sub-adsorption device 27 is an adsorption device 3 for raw material air (hereinafter,
Like the main adsorption device (to distinguish it from the sub-adsorption device 27), it comprises two adsorption towers 27a and 27b, which are switched by a switching valve (not shown) so as to repeat adsorption and regeneration at regular time intervals.

Note that, as in the main adsorption device 3, the nitrogen gas taken out from the upper part of the low-pressure column 8 in the rectification column 6 is used for regeneration of the adsorption column of the secondary adsorption device 27.

In this configuration, the low-purity nitrogen gas containing oxygen and carbon monoxide, which has been taken into the nitrogen gas line 23 from the high pressure column lower stage portion 7a of the rectification column 6, is sent to the reactor 25 via the heater 24,
Here, carbon monoxide in the nitrogen gas and oxygen react to form carbon dioxide.

This carbon dioxide is adsorbed and removed by the secondary adsorption device 27, and the high-purity nitrogen gas (containing a small amount of oxygen) after this carbon dioxide is removed.
Is returned to the upper stage section 7b of the high-pressure column.

This high-purity nitrogen gas is subjected to rectification in the upper stage section 7b of the high-pressure column and then sent to the low-pressure column 8 to be liquefied and become high-purity liquid nitrogen.

A part of this high-purity liquid nitrogen is sent to the upper part of the low-pressure column for reflux, and the rest is taken out to the high-purity liquid nitrogen tank 31.

In this air separation device, the low-purity nitrogen gas taken out from the lower part 7a of the high-pressure column of the rectification column 6 as described above, that is, the gas to be treated is narrowed down and treated in the reaction device 25. As described above, the amount of processing gas in the reaction device 25 is much smaller than that in the reaction device 19 of the conventional device which treats the entire amount of the raw material air.

Therefore, the amount of the noble metal catalyst to be used in the reaction device 25 can be greatly reduced.

For example, in an air separator with a raw air consumption of 50,000 Nm ³ / h, high-purity nitrogen gas that does not contain carbon monoxide is 50%.
When 0 Nm ³ / h is required, the amount of noble metal catalyst required in the reactor 19 was 10 m ³ in the conventional device, whereas the amount of noble metal catalyst required in the reactor 25 was 100 minutes in the present device. One
0.1m ³ is enough.

Second Embodiment (see FIG. 2) Only differences from the first embodiment will be described.

In the first embodiment, a nitrogen gas line is provided separately from the main adsorption device 3.
While the auxiliary suction device 27 dedicated to 23 is provided, the dual suction device 28 is used in the second embodiment.

That is, the combined adsorption device 28 comprises three adsorption towers 28a, 28b, 28c.
By connecting them to the raw material air line, the nitrogen gas line 23, and the regeneration line alternately at regular time intervals,
It is configured to repeat the adsorption action for the raw material air, the adsorption action for the low-purity nitrogen gas, and the regeneration. 29.30 is a switching valve for switching these adsorption towers 28a, 28b, 28c.

With this configuration, the adsorption equipment becomes simpler and the equipment cost can be reduced as compared with the case where the separate adsorbing devices 3 and 27 for the raw material air and the nitrogen gas are used as in the first embodiment.

By the way, it is advantageous to take out high-purity nitrogen in the form of liquid nitrogen as in each of the above embodiments in terms of transportation and the like, but it may be taken out in the form of nitrogen gas.

On the other hand, the present invention can be applied not only to the external cold utilization type air separation device exemplified in the above embodiment but also to the type air separation device of which the expansion turbine produces cold.

[Effect of device]

As described above, according to the present invention, the high-pressure column of the rectification column is divided into a lower section and an upper section, and all the low-purity nitrogen gas produced in the lower section is taken out, treated with a reactor, and then treated in the upper section. Since it is configured to be returned to the unit, the treatment amount in the reaction device can be greatly reduced as compared with the conventional device that treats the entire amount of raw material air. Therefore, the amount of expensive noble metal catalyst to be used in the reactor can be greatly reduced, and the cost can be very low.

Further, since high-pressure nitrogen gas is taken out from the high-pressure column of the rectification column as the low-purity nitrogen gas to be treated in the reactor, it is necessary to pressurize the nitrogen gas to a pressure necessary for performing the adsorption operation in the adsorption device. There is no. That is, there is no need to provide a separate pressurizing means as in the case of taking out nitrogen gas from the low pressure column. Therefore, the equipment is simple and the equipment cost is low.

Further, in order to liquefy by treating all the nitrogen gas generated in the lower part of the high pressure column of the rectification column with the reactor and returning it to the upper part of the high pressure column, take out only a part of the nitrogen gas generated in the high pressure column. Compared with the case of processing, the amount of processing is large and high-purity nitrogen gas can be manufactured efficiently.

In addition, the nitrogen gas after the reaction treatment is used as another rectification column (sub-rectification column).
Compared with the case of rectifying and liquefying by putting in, the equipment is simple and the cost is low.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart showing a first embodiment of the present invention, and FIG. 2 is a flow chart showing the second embodiment of the present invention, which is applied to an air separation device using an external cold. 3 and 4 are flow sheets showing a conventional device. 6 rectification tower, 7 rectification tower high pressure tower, 7a ...... lower part of the high pressure tower, 7b ...... upper part, 8 ...... low pressure tower, 23 ...... nitrogen gas line, 25 ...... Reactor, 27 ... Adsorption device.

Claims (1)

[Scope of utility model registration request] 1. An air separation apparatus comprising a rectification column comprising a high-pressure column for separating raw air into liquid air and nitrogen gas, and a low-pressure column for separating the liquid air into liquid oxygen and nitrogen gas. The high-pressure column of the rectification column is vertically partitioned into an upper part and a lower part, and a nitrogen gas line is provided for taking out all low-purity nitrogen gas containing oxygen and carbon monoxide produced in the lower part. In the gas line, a reactor for reacting carbon monoxide and oxygen in the low-purity nitrogen gas into carbon dioxide, and an adsorption for removing the carbon dioxide produced in this reactor to obtain high-purity nitrogen gas An air separation device, wherein the device is provided, and the outlet side of the nitrogen gas line is connected to the upper stage part of the high-pressure column.