JP3095237B2 - Ultra high purity nitrogen production equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for producing ultra-high purity nitrogen.

[Conventional technology]

Conventional production equipment for high-purity nitrogen, for example, high-purity nitrogen gas, compresses raw air with a compressor, cools it through a heat exchanger and sends it into a rectification column, where the raw air is cryogenically liquefied and separated. To produce nitrogen gas, which is refined with a purifier. This type of nitrogen gas production equipment uses an expansion turbine driven by oxygen-rich exhaust gas by-produced in the rectification tower to cool compressed air passing through the heat exchanger, and utilizes the cold generated there. doing. Since the expansion turbine is a high-speed rotating device (several tens of thousands of revolutions / minute), it is difficult to quickly follow a load fluctuation such as an increase in demand for product nitrogen gas. Therefore, the increase in the amount of cold generated is delayed in response to a large increase in the demand for the product nitrogen gas, and during that time, there is a major problem that impure nitrogen gas is produced. Further, as described above, since the expansion turbine rotates at high speed, high precision is required in terms of the mechanical structure, which is expensive, and has the disadvantage that specially trained personnel are required. That is, since the expansion turbine is a high-speed device, the above-described problems occur, and there has been a strong demand for removing the expansion turbine.

For this reason, the present inventors have developed an apparatus that removes the expansion turbine, replaces it with liquid nitrogen and supplies it to the rectification tower in a cold state, and liquefies and separates the air to produce nitrogen gas. We have filed an application (Japanese Patent Application No. 59-146332) and received a public notice (Japanese Patent Application No. 61-46747). This device (hereinafter referred to as the “proposed device”) was directly installed on the premises of a semiconductor manufacturing plant or the like, manufactured at a liquid nitrogen manufacturing plant (having a large cryogenic separator), and transported by tank lorry. Things are stored in storage tanks and used as cold. This apparatus can produce, by weight, 10 high-purity product nitrogen gases per cold liquid nitrogen transported by lorry. In addition, since the obtained product has high purity, a conventional purifier is not required.
In addition, the operation following the load fluctuation can be promptly dealt with by controlling the supply amount of the liquid nitrogen, so that the product purity at the time of the load fluctuation does not decrease.

[Problems to be solved by the invention]

However, in the electronics industry, semiconductor manufacturing technology has been dramatically advanced, and nitrogen gas of extremely high purity is required as a nitrogen gas used for the technology. For example, in the above proposed apparatus, the impurity O ₂ can be suppressed to about 0.05 ppm, and the impurity such as CO ₂ and CH ₄ can be suppressed to about 0.01 ppm. However, H ₂ and He cannot be suppressed, and about 0.2 ppm remains. However, the existence of such H ₂ , He, especially H ₂ , has a great adverse effect on semiconductor manufacturing today, when semiconductor manufacturing technology has advanced dramatically.

The present invention has been made in view of such circumstances,
An object of the present invention is to provide a production apparatus capable of producing not only O ₂ , CO ₂ , and CH ₄ but also ultra-high-purity nitrogen having extremely small amounts of impurities such as H ₂ and He.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a heat exchanger for cooling raw air to an ultra-low temperature, and a first heat exchanger for liquefying a part of the compressed air cooled to an ultra-low temperature, storing the compressed air at the bottom and extracting nitrogen gas from the top. Rectifier, a condenser built-in type decompressor provided above the first rectifier, and the liquid air stored at the bottom of the first rectifier as cold for cooling the condenser. A liquid empty pipe leading to the condensing device, a first discharging pipe for discharging the vaporized gas generated in the decomposing device to the outside, and a part of the nitrogen gas generated in the first rectifying column, A first reflux liquid pipe for guiding into the vessel, a second reflux liquid pipe for returning the liquid nitrogen generated in the condenser to the first rectification column as a reflux liquid, and a cooling liquid for cooling liquid from outside the apparatus. And a tank for receiving and storing the supply of the cold liquid in the tank for generating cold heat. A supply pipe to supply the above-mentioned decompressor as cold for condenser cooling in place of the cold generated by the expander, and a low-boiling-point impure component gas separated in the process of liquefaction of nitrogen gas in the above-mentioned condenser and taken out. Discharge pipe, a second rectification column for vaporizing low-boiling impurities due to a difference in boiling point and separating and removing the low-impure components from liquid nitrogen, and a second rectification of the liquid nitrogen in the first rectification column. An introduction pipe for introducing into the column, a second discharge pipe for discharging the vaporized low-boiling impurity components from inside the second rectification column, and a liquid from which the low-boiling impurity components have been removed in the second rectification column A product liquid nitrogen take-out pipe for taking out nitrogen as a product, a product nitrogen gas take-out pipe for vaporizing a portion of liquid nitrogen from which low-boiling impurities have been removed in the second rectification column and taking out the product nitrogen gas, Branch from liquid nitrogen extraction pipe A first aspect is an ultrahigh-purity nitrogen production apparatus provided with a branch pipe extending to a condenser and passing through the condenser and then extending to the second rectification column. A second aspect is an ultra-high-purity nitrogen production apparatus having the same configuration as that of the apparatus of the first aspect except that the apparatus is supplied to the first aspect.

[Action]

In the apparatus of the present invention, the raw material air is cooled to a very low temperature by the heat exchanger, and in that state, it enters the bottom of the first rectification column and a part thereof is liquefied and accumulated as liquid air. The liquid air is sent to the condenser and used for cooling the condenser in the condenser. This condensator or rectification column is simultaneously supplied with cold such as liquid nitrogen and the like, which is produced by another cryogenic separation device and transported by a tank lorry and stored in the tank of the device, thereby performing a condenser cooling operation. . The condenser has a first
Nitrogen gas collected in the upper part of the first rectification column is introduced by the rectification operation of the rectification column, and is liquefied by the cold cooling operation. Then, the liquefied component is returned as a reflux liquid into the first rectification column. The returned liquid nitrogen (including the liquid nitrogen generated in the rectification column) is sent to the second rectification column,
Therefore, low-boiling impurities such as hydrogen and helium having a boiling point lower than that of nitrogen are removed by vaporization to obtain an ultra-high-purity product. Further, according to the proposed apparatus, it was difficult to remove He and the like having a boiling point lower than that of nitrogen. However, the apparatus of the present invention removes the He by a discharge pipe extending from the second rectification column and the condenser. it, and a portion of the liquid nitrogen taken out of the product liquid nitrogen takeout pipe from returning to the second rectification column to the gas by a condenser, very high purity, for example, O ₂ is 0.001 ppm, CO is 0.01 ppm, 0.002 ppm of CO ₂ and CH ₄
0.0005 ppm, H ₂ comes to ultra-high purity nitrogen can be obtained that less 0.005 ppm.

 Next, examples will be described.

〔Example〕

FIG. 1 shows an embodiment of the present invention. In the figure, 1 is an air compressor, 2 is a drain separator, 3 is a CFC cooler, and 4 is a set of two adsorption towers. The inside of the adsorption tower 4 is filled with a molecular sieve, and adsorbs and removes H ₂ O and CO ₂ in the air compressed by the air compressor.
Reference numeral 5 denotes a compressed air supply pipe for sending compressed air from which H ₂ O and CO ₂ have been adsorbed and removed. Reference numeral 6 denotes a main heat exchanger to which compressed air from which H ₂ O and CO ₂ have been adsorbed and removed by the adsorption tower 4 is sent. Reference numeral 7 denotes a compressed air delivery pipe through which compressed air cooled to an extremely low temperature by the main heat exchanger 6 is sent. Reference numeral 8 denotes a first rectification column, into which compressed air cooled to an extremely low temperature by the main heat exchanger 6 is sent to the bottom. In the first rectification column 8, part of the compressed air is liquefied and stored at the bottom as liquid air 9, and nitrogen is stored at the top in a gaseous state. The nitrogen gas stored in the upper portion is rectified in a process of ascending and passing through a number of rectification racks (not shown) in the first rectification column 8 to become high-purity products. Reference numeral 10 denotes a first decomposer provided on the upper part of the first rectification column 8, and a first reflux liquid pipe 12 from the upper part of the first rectification column 8 to the upper part of the internal condenser 11. Is extending. Nitrogen gas at the upper part of the rectification column 8 is introduced into the condenser 11 through the first reflux liquid pipe 12 and liquefied. Reference numeral 13 denotes a second reflux liquid pipe, which introduces the liquid nitrogen liquefied and generated in the condenser 11 as a reflux liquid into a reflux liquid reservoir 14 above the first rectification column 8. Reference numeral 13a denotes a first discharge pipe for releasing gaseous components such as H ₂ and He in the nitrogen gas introduced into the condenser 11 which are lower in boiling point than nitrogen. To the outside and release H ₂ and He to the outside. Numeral 15 denotes a liquid empty pipe, which cools the condenser 11 and introduces liquid air 9 at the bottom of the rectification column into the first condensing unit 10 as refrigeration for liquefying nitrogen gas passing therethrough. Reference numeral 16 denotes a liquid nitrogen tank for storing liquid nitrogen to be cooled, which stores liquid nitrogen manufactured by another cryogenic separation device and carried by a tank lorry or the like. For convenience of illustration, the tank 16 is illustrated at the top of the drawing, but the tank 16 is installed on the ground. Reference numeral 17 denotes a supply pipe extending from the liquid nitrogen tank 16 to the first decomposer 10, and cools the condenser 11 by the cold heat of the liquid nitrogen. First
The liquid nitrogen and the liquid air supplied from the bottom of the rectification column 8 exist in a mixed state in the separator 10. Reference numeral 18 denotes a discharge pipe extending from the upper part of the first condenser 10 through the main heat exchanger 6, and performs a cooling action in the first condenser 10 and is itself vaporized, which is a liquid air and a liquid. The mixed gas of nitrogen is discharged to the outside as exhaust gas through the main heat exchanger 6. 18a is extend to and evaporator 18b a waste pipe to passing connexion outside, the mixed liquid collects in the bottom-most portion of the first partial condenser 10 (CH ₄ or the like is mixed is concentrated by repetition of condensation) It is gasified and released. A branch pipe 5a branched from the compressed air supply pipe 5 extends to the evaporator 18b, and a part of the compressed air is supplied to the evaporator 18b.
Cool by exchanging heat. 19 is a second rectification column. 20
Is an introduction pipe extending from the liquid nitrogen reservoir 20a at the top of the first rectification column 8 to the second rectification column 19, and the liquid nitrogen (reflux liquid + rectification column) collected at the top of the first rectification column 8 (Liquid nitrogen produced by the rectification of the above) is introduced into the second rectification column 19. The second rectification column 19 vaporizes and removes impurities such as H ₂ and He having a lower boiling point than nitrogen from the liquid nitrogen fed through the introduction pipe 20. Reference numeral 21 denotes a second discharge pipe extending from the upper part of the second rectification column 19, and sends a low-boiling impure component such as He vaporized to the condenser 21a to liquefy nitrogen gas entrained in the low-boiling impure component. 21b transfers the liquefied nitrogen to the second rectification column 19
Is a return pipe. Reference numeral 21g denotes a pipe extending from the upper part of the condenser 21a through the main heat exchanger 6, and discharges the low-boiling-point impure components to the normal temperature by heat exchange to the outside. 21c is a second decompressor incorporating the condenser 21a.
1c includes a pipe 21e extending from the center of the first rectification column 8.
Thereby, liquid nitrogen (impurities are not sufficiently removed) in the liquid reservoir at the center of the first rectification column 8 is supplied. This liquid nitrogen is used for cooling the condenser 21a. Reference numeral 21f denotes a waste nitrogen pipe for discharging waste liquid nitrogen vaporized by heat exchange in the condenser 21a to the outside via the main heat exchanger 6. In the second rectification column 19, liquid nitrogen that has been purified from ultra-high purity by removing low boiling impurities such as H ₂ and He is stored at the bottom thereof. Product liquid nitrogen extraction pipe for extracting ultra-high purity product liquid nitrogen from the bottom of the second rectification column 19
The pipe 24 extends, and the ultra-high purity liquid nitrogen is supplied to the demand by the pipe 24. Reference numeral 25 denotes a branch pipe branched from the pipe 24. The branch pipe extends from the bottom to the top of the condenser 11 and extends to the second rectification column 19, where the condenser 11 is cooled by the cold heat of the product liquid nitrogen. Liquid nitrogen vaporized in the second rectification column 19
It works to return to below the middle stage. Reference numeral 26 denotes a product nitrogen gas extraction pipe extending from the middle stage of the second rectification column 19 through the main heat exchanger 6, and formed at the bottom of the second rectification column 19 by vaporization of the stored liquid nitrogen. Nitrogen gas and the above condenser
The nitrogen gas generated in step 11 is supplied to demand as ultra-high purity product nitrogen gas at room temperature. In the figure, LIC is a liquid level gauge paired with a valve, which controls the opening or opening / closing of the valve according to the liquid level at the mounting location and constantly controls the liquid level at the mounting location. The dashed line indicates a vacuum cool box, and the inside of the box is vacuum-cooled.

In this configuration, the raw air is compressed by the air compressor 1, the moisture is removed by the drain cooler 2, and further cooled by the Freon cooler 3.
And H ₂ O and CO ₂ are adsorbed and removed. Then, it is sent to the main heat exchanger 6, cooled to an extremely low temperature, and introduced into the bottom of the first rectification column 8 in a gas-liquid mixed state. The raw material air is further cooled and vaporized at the bottom of the first rectification column 8, and a part of the air is collected as liquid air at the bottom of the first rectification column 8. The remainder rises in the first rectification column 8, is rectified in the process, and oxygen is liquefied and separated by the difference in boiling points. As a result, liquid nitrogen containing a large amount of oxygen (a part of which is introduced as waste liquid nitrogen into the waste liquid nitrogen tank 21c through the pipe 21e) accumulates in a substantially central portion of the first rectification column 8, and a high level is formed in the upper part. Pure nitrogen gas accumulates. The liquid air collected at the bottom of the first rectification column 8 is introduced via a pipe 15 into a first decomposer 10 where the condenser 11 is cooled.
Nitrogen gas collected at the upper part of the first rectification column 8 is introduced into the condenser 11, cooled and liquefied by the cold of the liquid air, and formed as a reflux liquid at the upper part of the first rectification column 8. Flow down. Further, the first decomposer 10 includes a liquid nitrogen tank 16
Liquid nitrogen is supplied from the
Cool 11 The liquid air and liquid nitrogen vaporized by cooling the condenser 11 are taken out of the upper part of the first decomposer 10 as a waste gas by a pipe 18 and discharged to the outside after cooling the raw air by the main heat exchanger 6. Is done. Meanwhile, the first
The liquid nitrogen (as well as the reflux liquid, the liquid nitrogen generated by the rectification operation of the first rectification column 8) which flows down as the above-mentioned reflux liquid is supplied to the upper part of the rectification column 8 by a pipe. After passing through 20, it is sent to a second rectification column 19, where low-boiling impurities (helium, H ₂ ) are vaporized and removed. This allows
The liquid nitrogen is ultra-purified and accumulates as a product at the bottom of the second rectification column 19. Part of this ultra-high-purity liquid nitrogen is supplied to demand through a pipe 24, and the rest is branched pipe 25.
Then, the gas is sent to the condenser 11, where it is vaporized and returned to the second rectification column 19 as ultra-high purity product nitrogen gas. This ultrahigh-purity product nitrogen gas is sent to the main heat exchanger 6 via the take-out pipe 26, where it exchanges heat with the raw material air, and is itself brought to room temperature and used for demand. The low-boiling-point impure component gas such as He vaporized and removed in the second rectification column 19 is sent to the condenser 21a, where the waste liquid nitrogen introduced from the central portion of the first rectification column 8 is removed. After being cooled and liquefied and removed from the nitrogen gas, the nitrogen gas is introduced into the pipe 21g and discharged to the outside through the main heat exchanger 6.

In addition, when the whole apparatus is enlarged and the amount of low-boiling-point impure component gases such as He is increased, the above-mentioned He or the like can be used as a product. In the above description, the liquid nitrogen is stored in the liquid nitrogen tank 16 and supplied to the first decomposer 10, but instead, liquid air is stored and stored in the first
Or a liquefied natural gas such as liquefied propane may be stored and sent.

This device does not introduce cold such as liquid nitrogen into the rectification column, so even if impurities are mixed during the cold,
It has the advantage that it does not mix into the product nitrogen.

FIG. 2 shows another embodiment. In this embodiment, the liquid nitrogen supply pipe 30 extends from the liquid nitrogen tank 16 to the center of the first rectification column 8 as well. Other parts are the same as in FIG. By doing so, the same operation and effect as described above can be obtained, and since the amount of cold supply to the entire apparatus is increased, the time required for stopping and restarting the apparatus can be significantly reduced. The effect will be obtained. Further, the portion X surrounded by the dashed line in FIG. 1 may be changed as shown in FIG.

〔The invention's effect〕

As described above, the ultrapure nitrogen production apparatus of the present invention
Without using an expansion turbine, instead using a cold storage tank,
The cold in the cold storage tank is defined as the cold in the entire apparatus. Therefore, since the expansion turbine, which is a high-speed rotating device, is not used, the operation personnel of the expansion turbine is not required, and a fine follow-up operation to load fluctuation (change in the amount of product nitrogen taken out) becomes possible. Purity products can be supplied stably. In addition, the apparatus of the present invention includes a second rectification column, into which the liquid nitrogen obtained in the first rectification column is introduced, to remove He having a boiling point lower than that of nitrogen, and to remove the liquid from the condenser. Proposal mentioned at the beginning to remove low boiling He and the like in the extended discharge pipe, and to gasify a part of the liquid nitrogen taken out from the product liquid nitrogen take-out pipe by the condenser and return it to the second rectification column. He and the like that cannot be separated by the apparatus can also be removed, and it becomes possible to produce ultra-high-purity product nitrogen that cannot be obtained by the above-described proposed apparatus.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of one embodiment of the present invention, FIG. 2 is a configuration diagram of another embodiment, and FIG. 3 is an explanatory diagram of a modified example of a portion surrounded by a chain line X in FIG. . 5 ... Compressed air supply pipe, 6 ... Main heat exchanger, 8 ...
1st rectification column, 9 ... liquid air, 10 ... 1st decomposer,
11 ... condenser, 12 ... first reflux liquid pipe, 13 ... second
Reflux liquid pipe, 13a ... first discharge pipe, 15 ... liquid empty pipe, 16 ... liquid nitrogen tank, 17 ... supply pipe,
19 ... second rectification tower, 20 ... introduction pipe, 21 ... second
Discharge pipe, 24 …… Product liquid nitrogen discharge pipe, 26 ……
Product nitrogen gas extraction pipe

Continuation of the front page (56) References JP-A-2-68476 (JP, A) JP-A-60-142184 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F25J 1 / 00-5/00

Claims (2)

(57) [Claims] 1. A heat exchanger for cooling raw air to an extremely low temperature,
A first rectification tower which liquefies a part of the compressed air cooled to an extremely low temperature and accumulates at the bottom to take out nitrogen gas from the top; and a condenser built-in type provided at the top of the first rectification tower A condenser, a liquid empty pipe that guides the stored liquid air at the bottom of the first rectification column to the condenser for cooling the condenser, and discharges vaporized gas generated in the condenser to the outside. A first discharge pipe, a first reflux liquid pipe for guiding a part of the nitrogen gas generated in the first rectification column into the condenser, and a liquid nitrogen reflux in the condenser. In a device comprising a second reflux liquid pipe for returning the liquid as liquid into the first rectification column, and a tank for receiving and storing the cold liquid from outside the device, the cold liquid in the tank is used for generating cold heat. Supply pipe to supply to the above-mentioned decompressor as cold for condenser cooling in place of the cold generated by the expander A discharge pipe for taking out the low-boiling-point impure component gas separated in the process of liquefaction of the nitrogen gas in the condenser, and a discharge pipe for discharging the gas to the outside; A second rectification column, an introduction pipe for introducing liquid nitrogen in the first rectification column to the second rectification column, and a low-boiling impure component vaporized from the second rectification column. A second discharge pipe for discharging, a product liquid nitrogen extraction pipe for extracting liquid nitrogen from which low-boiling impurity components have been removed in the second rectification column as a product,
A product nitrogen gas take-out pipe which vaporizes a part of the liquid nitrogen from which the low boiling point impurities have been removed in the second rectification column and takes out the product nitrogen gas, and a branch from the product liquid nitrogen take-out pipe to the condenser. An ultra-high-purity nitrogen producing apparatus, comprising a branch pipe extending to the second rectification column after passing through the condenser. 2. A heat exchanger for cooling the raw material air to an extremely low temperature.
A first rectification tower which liquefies a part of the compressed air cooled to an extremely low temperature and accumulates at the bottom to take out nitrogen gas from the top; and a condenser built-in type provided at the top of the first rectification tower A condenser, a liquid empty pipe that guides the stored liquid air at the bottom of the first rectification column to the condenser for cooling the condenser, and discharges vaporized gas generated in the condenser to the outside. A first discharge pipe, a first reflux liquid pipe for guiding a part of the nitrogen gas generated in the first rectification column into the condenser, and a liquid nitrogen reflux in the condenser. In a device provided with a second reflux liquid pipe for returning the liquid as liquid into the first rectification column and a tank for receiving and storing liquid nitrogen from outside the device, the liquid nitrogen in the tank is used for generating cold heat. Supply to the first rectification column as cold for cooling the condenser in place of the cold generated by the expander And a discharge pipe for taking out the low-boiling-point impure component gas separated in the liquefaction process of the nitrogen gas in the condenser, and discharging the gas to the outside, and vaporizing the low-boiling-point impure component due to a difference in boiling point to separate from the liquid nitrogen. A second rectification column to be removed, an introduction pipe for introducing liquid nitrogen in the first rectification column to the second rectification column, and a low-boiling point impurity vaporized from the second rectification column A second discharge pipe for discharging the components, a product liquid nitrogen take-out pipe for taking out liquid nitrogen from the second rectification column from which low-boiling impurity components have been removed, and a low-pressure pipe inside the second rectification column. A product nitrogen gas extraction pipe which vaporizes a part of the liquid nitrogen from which the boiling point impurities have been removed and takes it out as product nitrogen gas, and a branch from the product liquid nitrogen extraction pipe, which extends to the condenser, passes through the condenser, and then passes through the condenser. Branch pie extending to rectification tower 2 The claim (1) ultra-high purity nitrogen producing apparatus according provided.