KR102084294B1 - Method and apparatus for producing high purity nitric oxide for semiconductor using the nitric acid production process - Google Patents

Abstract

The present invention relates to a high-purity nitrogen monoxide production method and apparatus for manufacturing semiconductor, the high-purity nitrogen monoxide production method according to the present invention (a) is produced in the nitric acid production process for producing nitric acid by oxidizing ammonia, low-purity nitrogen monoxide (B) separating and purifying the mixed gas by using a boiling point difference, and (c) adsorbing and purifying the separated and purified mixed gas by using an adsorbent.

Description

Method and apparatus for producing high purity nitric oxide for semiconductors using nitric acid production process {Method and apparatus for producing high purity nitric oxide for semiconductor using the nitric acid production process}

The present invention relates to a method and apparatus for producing high purity nitrogen monoxide for semiconductors, and more particularly, to continuously produce high purity nitrogen monoxide from a mixed gas containing low purity nitrogen monoxide, which is a mass produced in a commercial nitric acid manufacturing process. A method and apparatus are disclosed.

As the semiconductor device is highly integrated, the thickness of an insulating film such as an oxide film that forms and insulates a film on the semiconductor device is gradually becoming thin. However, when impurities penetrate into the thin insulating film, the electrical characteristics of the semiconductor device are degraded.

In order to overcome this problem, a method of forming a nitride film by depositing nitrogen (N) ions on an insulating film such as an oxide film has been developed and used in recent years. Such a nitride film can prevent impurity intrusion such as a hot carrier effect caused during driving of the device and boron by subsequent heat treatment.

A method of forming such a nitride film includes an oxidation method using gases such as ammonia (NH ₃ ), nitrogen monoxide (NO), and nitrous oxide (N ₂ O).

Although nitrous oxide (N ₂ O), which is easy to handle and excellent in oxidizing properties, is widely used in these gases, nitrous oxide is photodecomposed by a lamp in a separate chamber before being introduced into a semiconductor manufacturing process chamber. Since nitrogen monoxide (NO) and nitrogen (N) are recombined and energy loss increases as shown in Formula 1, nitrogen (N) generated by photolysis of nitrogen monoxide is gradually used.

[Formula 1]

N ₂ O + hv → NO + 1/2 N ₂ → N ₂ O + NO + N ₂

Where h is Planck's constant and v is the frequency of photons

In addition, nitrogen monoxide generates oxygen (O ₂ ) reactive radicals having a large amount of oxidation reactivity as shown in [Formula 2] in a chamber of a high temperature semiconductor manufacturing process for forming an oxide film, and easily reacts with a main reaction material necessary for forming an oxide film. It is a material that can contribute greatly to the yield and productivity of the oxide film forming semiconductor process.

[Formula 2]

4NO → N ₂ O ₃ + N ₂ O

N ₂ O ₃ → N ₂ + 3 / 2O ₂

N ₂ O → N ₂ + 1/2 O ₂

Nitrogen monoxide requires high purity in the semiconductor manufacturing process to prevent recombination after decomposition and to prevent defects in the semiconductor wafer due to impurities.

Such a method for producing high purity nitrogen monoxide for semiconductors is disclosed in the following patent document. According to this, sodium nitrite (NaNO ₂ ) and sulfuric acid (H ₂ SO ₄ ) is added to the reactor and stirred and mixed with a stirrer to generate nitrogen monoxide, wherein the reaction is as shown in [Formula 3] below.

[Formula 3]

3NaNO ₂ + H ₂ SO ₄ → Na ₂ SO ₄ + NaNO ₃ + 2NO + H ₂ O

However, such a conventional method for producing nitrogen monoxide is an overinvestment method to be applied as a small amount of production method, and a large cost investment and production cost are required for mass production, and thus the supply price is high. Semiconductor manufacturers have a limited problem in expanding production applications of the semiconductor oxide film process due to the expensive high-purity nitrogen monoxide using this conventional manufacturing method.

Therefore, there is an urgent need for a method for solving the problems of the conventional method for producing nitrogen monoxide.

KR 10-1257794 B1

The present invention is to solve the above problems of the prior art, an aspect of the present invention is to continuously produce high-purity nitrogen monoxide using a large amount of industrial low-purity nitrogen monoxide produced as a reactant for nitric acid production in the nitric acid production process. To provide a method and an apparatus for applying the same.

In addition, another aspect of the present invention is to separate and purify the mixed gas containing low-purity nitrogen monoxide produced in the nitric acid production process using a boiling point difference, and to perform the adsorption process again using an adsorbent, thereby performing a continuous purification process of two steps Through this, to provide a method and apparatus for producing high purity nitrogen monoxide of 99.999% or more applicable to semiconductor manufacturing.

The high purity nitrogen monoxide production method according to the present invention comprises the steps of: (a) oxidizing ammonia to produce nitric acid to produce nitric acid, and supplying a mixed gas containing low purity nitrogen monoxide; (b) separating and purifying the mixed gas by using a boiling point difference; And (c) adsorbing and purifying the mixed gas separated and purified using an adsorbent. It includes.

In addition, in the high-purity nitrogen monoxide production method according to the present invention, between the step (a) and the step (b), the step of cooling the mixed gas, gas-liquid separation, cooling and condensation purification; further includes.

In addition, in the method for producing high purity nitrogen monoxide according to the present invention, the step (b) may include: removing a high boiling point impurity having a higher boiling point than the nitrogen monoxide from the mixed gas using a first distillation column; And removing a low boiling point impurity having a lower boiling point than the nitrogen monoxide from the mixed gas from which the high boiling point impurity is removed using a second distillation column.

In addition, in the high-purity nitrogen monoxide production method according to the present invention, between the step (b) and the step (c), the step of compressing, cooling, and condensation purification of the mixed gas from which the low boiling point impurities are removed; It further includes.

In addition, in the high-purity nitrogen monoxide production method according to the present invention, the step (c), but using the pair of adsorption tower, each adsorbent is disposed therein, alternately, adsorb the impurities in any one of the first adsorption tower Purification and regeneration by heating the adsorbent in another second adsorption tower.

In addition, in the high-purity nitrogen monoxide production method according to the present invention, after the step (c), the step of cooling and storing the adsorbed and purified mixed gas; further includes.

On the other hand, the high purity nitrogen monoxide production apparatus according to the present invention is produced in the nitric acid production process for producing nitric acid by oxidizing ammonia, supply unit for supplying a mixed gas containing low purity nitrogen monoxide; A distillation unit including at least one distillation column including a reboiler, a column, and a cooler, and purifying the mixed gas using a boiling point difference; And at least one adsorption tower having an adsorbent disposed therein, the adsorption unit configured to adsorb and purify the mixed gas purified by the distillation unit.

In addition, in the high-purity nitrogen monoxide production apparatus according to the present invention, the distillation unit, the distillation column is disposed in a pair, the first distillation column of any of which is supplied with the mixed gas from the supply unit than the nitrogen monoxide The high boiling point impurities having a relatively high boiling point are removed, and the second distillation column, which is another one, is supplied with the mixed gas purified from the first distillation column to remove the low boiling point impurities having a lower boiling point than the nitrogen monoxide.

In addition, in the high-purity nitrogen monoxide production apparatus according to the present invention, the adsorption unit, a pair of the adsorption tower is disposed separately, further comprising a heating unit for heating each of the adsorption tower; alternately, a pair of the The first adsorption tower, which is one of the adsorption towers, adsorbs and purifies the mixed gas, and the other, the second adsorption tower, regenerates the adsorbent.

In addition, a high-purity nitrogen monoxide production apparatus according to the present invention, the first cooling chiller (chiller) for cooling the mixed gas supplied from the supply unit, condensing impurities; And a gas-liquid separator that separates the condensed liquid impurity and the gaseous mixed gas and supplies the gaseous mixed gas to the first distillation column.

In addition, high purity nitrogen monoxide production apparatus according to the present invention, a compressor for receiving and compressing the mixed gas from the distillation unit; And a second cooling chiller (chiller) receiving and cooling the mixed gas compressed from the compressor to condense and remove impurities and supplying the mixed gas to the adsorption unit.

In addition, the high-purity nitrogen monoxide production apparatus according to the present invention, receiving the mixed gas from the adsorption unit, the cooling tank for cooling and storing at a predetermined temperature; further includes.

In addition, the high-purity nitrogen monoxide production apparatus according to the present invention, the cooling tank, the tank unit having a receiving space therein to store the mixed gas; An injection tube for injecting the mixed gas into the accommodation space; A cooling jacket having a hollow in which the first refrigerant flows and surrounding the outer surface of the tank part; And a cooling tube formed in a spiral tube shape and having a second refrigerant flowing therein and disposed in the accommodation space.

The features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings.

Prior to this, the terms or words used in the present specification and claims should not be interpreted in the ordinary and dictionary sense, and the inventors may appropriately define the concept of terms in order to best explain their own invention. It should be interpreted as meanings and concepts corresponding to the technical idea of the present invention based on the principle that the present invention.

According to the present invention, by purifying a large amount of low-purity nitrogen monoxide produced in the commercial manufacturing process of industrial nitric acid can continuously produce a large amount of high-purity nitrogen monoxide for semiconductor, reducing the investment cost of the reaction process equipment required in the prior art can do.

In addition, by separating and purifying the mixed gas generated after the ammonia oxidation reaction in the nitric acid production process to produce nitrogen monoxide having a purity of 99.98% or more, and through the adsorption process to produce a high purity nitrogen monoxide of 99.999% or more, the purification process is simple This can reduce the production cost.

Furthermore, the reduction of the manufacturing cost of high purity nitrogen monoxide according to the present invention may lead to an increase in production efficiency and application in the semiconductor oxide film manufacturing process.

1 and 2 is a flow chart of a high purity nitrogen monoxide production method according to an embodiment of the present invention.
Figure 3 is a flow chart of a high purity nitric oxide production method according to another embodiment of the present invention.
Figure 4 is a schematic view showing a high purity nitrogen monoxide production apparatus according to the present invention.
5 is a cross-sectional view schematically showing a cross section of the cooling tank shown in FIG.

The objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments associated with the accompanying drawings. In the present specification, in adding reference numerals to the components of each drawing, it should be noted that the same components as possible, even if displayed on different drawings have the same number as possible. In the following description, detailed descriptions of related well-known techniques that may unnecessarily obscure the subject matter of the present invention will be omitted.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 and 2 is a flow chart of a high purity nitrogen monoxide production method according to an embodiment of the present invention.

As shown in Figure 1, the high-purity nitrogen monoxide production method according to the present invention (a) is produced in the nitric acid production process for producing nitric acid by oxidizing ammonia, supplying a mixed gas containing low-purity nitrogen monoxide ( S100), (b) separating and purifying the mixed gas using the boiling point difference (S200), and (c) using the adsorbent, and adsorbing and purifying the separated and purified mixed gas (S300).

The present invention relates to a method for producing high purity nitrogen monoxide. Nitrogen monoxide is used to form an oxide film on a semiconductor device in a semiconductor manufacturing process, and high purity is required to prevent recombination after decomposition and semiconductor wafer defects due to impurities. Conventionally, high purity nitric oxide for semiconductors was prepared by stirring sodium nitrite (NaNO ₂ ) and sulfuric acid (H ₂ SO ₄ ), but this is a small amount of production method, which requires a lot of investment and production cost in mass production. There is a problem in the application of the expanded production of the semiconductor oxide film process, as a solution to the high purity nitrogen monoxide production method according to the present invention was devised.

Specifically, the high purity nitrogen monoxide production method according to the present invention includes a mixed gas supply step (S100), a separation purification step (S200), and an adsorption purification step (S300).

First, in the mixed gas supply step (S100) to separate the nitrogen monoxide generated in the commercial nitric acid manufacturing process, it is supplied to the separation and purification step (S200) to be described later.

In general, the commercial manufacturing process of industrial nitric acid is based on the Ostwald process, which can be divided into three main process steps:

Ⅰ: Ammonia Oxidation Step

4NH ₃ (g) + 5O ₂ (g) → 4NO (g) + 6H ₂ O (g)

II: Nitric Oxide Oxidation and Nitrogen Dioxide Dimerization Step

2NO (g) + O ₂ (g) → 2NO ₂ (g)

2NO ₂ (g) → N ₂ O ₄ (g)

III: Dinitrogen tetraoxide absorption step

3N ₂ O ₄ (g) + 2H ₂ O (l) → 4HNO ₃ (aq) + 2NO (g)

According to this, nitrogen monoxide is produced by high temperature oxidation of ammonia under a noble metal catalyst, where the nitrogen monoxide is converted into nitrogen dioxide dimers such as dinitrogen tetraoxide through an oxidation process, and dinitrogen tetraoxide reacts with water to produce nitric acid. do. At this time, the produced nitric acid has a concentration of 50 to 69% by weight, it is produced as a concentrated nitric acid of 90 to 98% by weight through an additional concentration process if necessary.

In the present invention, using a part of the flow of nitrogen monoxide generated by ammonia high temperature oxidation in the industrial nitric acid manufacturing process, to produce a high-purity nitrogen monoxide through a separation purification step (S200), adsorption purification step (S300) and the like to be described later. Bar, the mixed gas supply step (S100) may be performed in connection with the nitric acid production process. On the other hand, in the mixed gas supply step (S100), nitrogen monoxide is supplied in the form of a mixed gas mixed with other impurities with low purity. That is, nitrogen monoxide is mixed with impurities in the mixed gas generated after the ammonia oxidation process in the nitric acid production process or after the nitric acid production, and the mixed gas is supplied. Such mixed gas contains, in addition to air, nitrogen monoxide, nitrous oxide, nitrogen dioxide, moisture, unreacted ammonia, and the like. Among them, a large amount of water and nitrous oxide are contained, which is not suitable for use of low-purity nitrogen monoxide directly for semiconductors.

On the other hand, in order to receive the mixed gas from the nitric acid manufacturing process, and to supply it, a portion of the mixed gas generated in the nitric acid manufacturing process is stored and used separately, or a separate supply pipe to a piping facility through which the mixed gas flows in the nitric acid manufacturing process, And a valve or the like may be used to directly separate a portion of the mixed gas flow in the nitric acid manufacturing process.

As described above, the present invention uses a low-purity nitrogen monoxide produced in large quantities for the purpose of nitric acid production in the industrial nitric acid manufacturing process, rather than producing a low-purity nitrogen monoxide through a separate process, interworking with the nitric acid manufacturing process It is possible to produce high purity nitrogen monoxide continuously and in large quantities.

When the mixed gas is separated and supplied in the nitric acid manufacturing process, a separation and purification step (S200) is performed. Since the components constituting the mixed gas have different boiling points, in the separation and purification step S200, impurities other than nitrogen monoxide may be removed using difference in boiling points of the respective components. At this time, the main impurities removed are water, nitrous oxide, nitrogen dioxide, unreacted ammonia, nitrogen, oxygen and the like. Such separation purification can be carried out using at least one distillation column. The distillation column includes a reboiler, a column, and a cooler, and its structure and function correspond to general knowledge in the art to which the present invention pertains, and description thereof will be omitted.

On the other hand, in one example, the separation and purification step (S200) may be carried out a two-step separation and purification process using a pair of distillation column. Specifically, the high boiling point impurities are removed in one of the pairs of distillation columns, and the low boiling point impurities are continuously removed in the other second distillation column. The boiling point of nitrogen monoxide is about -151.8 占 폚. Relatively, nitrogen dioxide, unreacted ammonia, water, and the like, including nitrous oxide having a boiling point of approximately -88.8 占 폚, have a higher boiling point than nitrogen monoxide. Components having a higher boiling point than nitrogen monoxide are called high boiling impurities. On the other hand, components having a lower boiling point than nitrogen monoxide, such as nitrogen (boiling point: about -198.5 ℃), oxygen (boiling point: about -183 ℃), etc. of the components of the mixed gas are low-boiling impurities.

Separation and purification in the first distillation column proceeds for the purpose of removing high-boiling impurities, using liquid nitrogen to maintain the upper cooler temperature at -85 ~ -95 ℃, the lower reboiler temperature -60 ~- Maintain at 50 ℃, the operating pressure is maintained at 3 to 5 atm. Under these operating conditions, according to the low temperature distillation method, a high boiling point impurity is condensed under the first distillation column to be discharged and removed through a pipe in the liquid phase, and a mixed gas containing nitrogen monoxide is discharged above the first distillation column. Here, the discharged mixed gas is introduced into the second distillation column.

In the second distillation column, the upper cooler temperature is maintained at -150 to -140 ° C by using liquid nitrogen, and the lower reboiler temperature is maintained at -90 to -80 ° C, respectively. The exhaust gas is removed, and a mixed gas containing nitrogen monoxide is collected through the lower portion of the second distillation column.

Here, since the operating conditions of the distillation column are not necessarily limited to the above, the scope of the present invention is not limited by the operating conditions.

While the two-stage separation and purification process proceeds, the purity of nitrogen monoxide in the mixed gas is gradually increased, but it is not possible to secure high purity nitrogen monoxide over 99.995% required for use in semiconductor manufacturing. Thus, the adsorption purification step (S300) is performed on the mixed gas collected through the lower part of the second distillation column.

Adsorption purification step (S300) is a process for purifying the separated and purified mixed gas using an adsorbent. At this time, the adsorbent to be used is determined according to the impurities to be adsorbed and purified, for example formed of at least one selected from the group consisting of Molecular Sieve, activated carbon, silica gel, activated alumina gel, and low temperature regenerated gel. Can be. Preferably, a liquid curive having pores capable of adsorbing impurities without absorbing nitrogen monoxide is suitable. Such an adsorbent may be disposed in an adsorption tower, and the adsorption purification process may be performed using at least one adsorption tower.

In the present invention, the adsorption purification process and the regeneration process may be performed simultaneously. Here, the regeneration process is to regenerate the adsorbent reacted with the impurities, it may be made by heating the adsorbent to a predetermined temperature. Specifically, a pair of adsorption towers each having an adsorbent are used, while one of the first adsorption towers is used to adsorb and purify impurities, and the other is a second adsorption tower. Here, the adsorption purification process and the regeneration process alternately proceed between the first adsorption tower and the second adsorption tower. Meanwhile, in order to heat the adsorbent, a heating unit such as an electric heater is installed in the adsorption tower, and the temperature of the adsorption tower in which the adsorption purification process is performed may be maintained at room temperature.

Through such a purification process, it is possible to manufacture nitrogen monoxide for high purity semiconductors of 99.999% or more.

Overall, according to the high-purity nitrogen monoxide production method according to the present invention, by purifying a large amount of low-purity nitrogen monoxide produced in the commercial production process of industrial nitric acid to continuously manufacture a large amount of high-purity nitrogen monoxide for semiconductor, during the nitric acid manufacturing process After separating and purifying the mixed gas generated after the ammonia oxidation reaction, it is possible to simply manufacture the high purity nitrogen monoxide more than 99.999% through the adsorption process, thereby reducing the investment cost and production cost of the reaction process equipment required in the prior art. . Through this, it is expected to increase production efficiency and increase application in the semiconductor oxide film manufacturing process.

Figure 3 is a flow chart of a high purity nitric oxide production method according to another embodiment of the present invention.

Referring to Figure 3, the present invention may further include a cooling condensation purification step (S150) between the mixed gas supply step (S100) and the separation and purification step (S200).

Cooling condensation purification step (S150) is a process performed before the separation purification step (S200) for the hot mixed gas supplied from the nitric acid production process. In the cooling condensation purification step (S150), first, the mixed gas of high temperature is cooled to condense some of impurities in the mixed gas. Here, the cooling of the mixed gas may use a cooling chiller (chiller) for a heat exchanger, and at this time, the temperature of the cooling chiller may be maintained at -20 ~ -10 ℃. However, the temperature of the cooling chiller is not necessarily limited thereto. Impurities that condense in this process are mainly water and nitrogen monoxide.

When some of the impurities are condensed into the liquid phase, the liquid impurities are removed by gas-liquid separation, and the remaining mixed gas is introduced into the separation and purification step (S200). Here, gas-liquid separation can use the gas-liquid separator generally used.

On the other hand, the high purity nitrogen monoxide production method according to the present invention may further comprise a cooling condensation purification step (S250) between the separation purification step (S200) and the adsorption purification step (S300).

In the cooling condensation purification step (S250), the mixed gas from which the low boiling point impurities have been removed is compressed and cooled to further remove condensed residual impurities in the mixed gas. Here, the compression of the mixed gas using a compressor or the like, the cooling using a cooling chiller, etc., wherein the temperature of the cooling chiller is maintained in the range of -20 ~ 10 ℃, preferably -15 ~ 0 ℃.

In addition, the present invention may further include a cold storage step (S400) after the adsorption purification step (S300).

In the cold storage step (S400), the mixed gas that has undergone the adsorption and purification process is cooled and stored at a predetermined temperature. To this end, a cooling tank is used, the temperature of which is maintained at -20 to 0 ° C., and the internal pressure can be maintained at 300 to 700 psi. Under these conditions, impurities, such as water, in the mixed gas stored in the cooling tank are condensed and separated under the cooling tank. Thus, nitrogen monoxide having higher purity can be obtained through the upper portion of the cooling tank.

Hereinafter, an apparatus capable of performing the above-described high purity nitrogen monoxide production method will be described. Duplicate contents will be omitted or simply described. However, since the apparatus described below is an example of a device to which the high purity nitrogen monoxide production method according to the present invention can be applied, the high purity nitrogen monoxide production method according to the present invention is necessarily executed only by the device, or the scope of rights by the device is limited. It is not limited.

Figure 4 is a schematic view showing a high purity nitrogen monoxide production apparatus according to the present invention.

As shown in Figure 4, the high-purity nitrogen monoxide production apparatus according to the present invention is produced in the nitric acid production process for producing nitric acid by oxidizing ammonia, the supply unit for supplying a mixed gas (1) containing low-purity nitrogen monoxide ( 10) distillation unit 20 including at least one distillation column 21, 23 including reboilers 21a, 23a, columns, and coolers 21c, 23c, and using a boiling point difference to purify the mixed gas. And at least one adsorption tower (31, 33) having an adsorbent disposed therein, and an adsorption unit (30) for adsorbing and purifying the mixed gas purified by the distillation unit (20).

Specifically, the high purity nitrogen monoxide production apparatus according to the present invention includes a supply unit 10, a distillation unit 20, and the adsorption unit 30.

The supply unit 10 supplies the mixed gas 1 containing low purity nitrogen monoxide to the distillation unit 20. At this time, the mixed gas (1) is produced in the nitric acid production process for producing nitric acid by oxidizing ammonia. Accordingly, the supply unit 10 is configured to separately store a portion of the mixed gas 1 generated from the nitric acid manufacturing process, or continuously separate a portion of the mixed gas 1 flow in real time. For example, the supply unit 10 may be formed of a supply pipe, a valve, and the like, which are separately installed in a piping facility through which the mixed gas 1 flows in the nitric acid manufacturing process. In addition, a pressure gauge is additionally installed to adjust the pressure of the mixed gas 1 guided to the supply pipe, or the supply pipe is connected to a plurality of branch pipes to prevent the pressure of the mixed gas 1 in the nitric acid manufacturing process from dropping rapidly. It may be configured.

The distillation unit 20 includes at least one distillation column 21 and 23 to purify the mixed gas supplied from the supply unit 10. The distillation towers 21 and 23 are columns formed between the reboilers 21a and 23a disposed at the bottom, the coolers 21c and 23c disposed at the top, and the reboilers 21a and 23a and the coolers 21c and 23c. It includes, the distillation column (21, 23) is a conventional technique, so description thereof will be omitted.

As an embodiment, the distillation column is a pair, and the first distillation tower 21, which is one of them, receives the mixed gas from the supply unit 10 to remove the high boiling point impurities 3, and the second distillation tower ( 23 may be supplied with the purified mixed gas from the first distillation column 21 to remove the low boiling point impurities 4. Here, the high boiling point impurity 3 is an impurity such as nitrous oxide, nitrogen dioxide, unreacted ammonia, water, etc., which has a relatively high boiling point compared to nitrogen monoxide, and the low boiling point impurity 4 is an impurity such as nitrogen or oxygen, which has a relatively low boiling point. Means.

Here, the first distillation column 21 may be maintained in the cooler 21c temperature of -85 ~ -95 ℃, the reboiler 21a temperature of -60 ~ -50 ℃, the operating pressure of 3 to 5 atm In this case, the high boiling point impurity 3 is condensed and discharged through a pipe connected to the lower part of the first distillation tower 21 in the liquid phase, and the purified mixed gas is along the pipe connected to the upper part of the first distillation tower 21. Inflow).

The second distillation column 23 maintains the temperature of the upper cooler 23c at -150 to -140 ° C and the temperature of the lower reboiler 23a at -90 to -80 ° C, respectively. 2 is removed and discharged through a pipe connected to the upper part of the distillation tower 23, and the purified mixed gas is transferred to the adsorption part 30 through a pipe under the second distillation tower 23.

The adsorption unit 30 includes adsorption towers 31 and 33 to purify the mixed gas purified by the distillation unit 20. Here, at least one adsorption tower (31, 33) is arranged, each of the adsorbent is disposed. The adsorbent may be formed of any one or more selected from the group consisting of Molecular Sieve, activated carbon, silica gel, activated alumina gel, and low temperature regenerated gel. Preferably, the liquid curive is suitable. When the adsorbent reacts with the impurities to adsorb the impurities, high purity nitrogen monoxide may be obtained through the adsorption part 30.

As an embodiment of the adsorption unit 30, a pair of adsorption towers 31 and 33 may be separated and the heating units 35 and 37 may be formed in the adsorption towers 31 and 33. The heating sections 35 and 37 may use, for example, an electric heater as a means capable of heating the adsorbent. Therefore, while adsorbing and purifying impurities in the first adsorption tower 31, which is one of the pairs of adsorption towers 31 and 33, the second adsorption tower 33, which is the other, can heat the adsorbent to regenerate the adsorbent. Since the adsorption purification process and the regeneration process are alternately performed between the first adsorption tower 31 and the second adsorption tower 33, the adsorption purification process and the regeneration process may be performed simultaneously.

Meanwhile, before the mixed gas is supplied to the distillation unit 20, a first cooling chiller 40 and a gas-liquid separator 50 may be further included to condense and remove impurities.

The first cooling chiller 40 receives a high temperature mixed gas from the supply unit 10 and cools the mixed gas. Here, the temperature of the first cooling chiller 40 is maintained at -20 to -10 deg. C, so that a part of the impurities 2, such as moisture and nitrogen monoxide in the mixed gas, are condensed. The mixed gas containing the liquid condensed impurities 2 is delivered to the gas-liquid separator 50 through a pipe.

The gas-liquid separator 50 separates the liquid impurities 2 from the mixed gas and the remaining mixed gas. At this time, the liquid impurities 2 are separated and discharged through a pipe connected to the lower part of the gas-liquid separator 50, and the mixed gas is supplied to the distillation unit 20 through a pipe connected to the upper part of the gas-liquid separator 50. Here, the mixed gas supplied to the distillation unit 20 is transferred to the temporary storage buffer tank (B) through the transfer pump (P), and pressurized to 3 to 10 atm or less so that the upper side mixed gas is distillation unit (20) ) May be introduced into the first distillation column 21.

In addition, the high purity nitrogen monoxide production apparatus according to the present invention may further include a compressor 70, and a second cooling chiller (80).

The compressor 70 receives the mixed gas from the distillation unit 20 and compresses the mixed gas before the purified mixed gas flows into the adsorption unit 30. At this time, when the distillation unit 20 is formed of the first distillation tower 21 and the second distillation tower 23, the mixed gas is supplied through the lower pipe of the second distillation tower 23.

The mixed gas compressed by the compressor 70 is introduced into the second cooling chiller 80, the temperature of the second cooling chiller 80 is maintained at -20 ~ 10 ℃, preferably -15 ~ 0 ℃, Cool the introduced mixed gas. Accordingly, the mixed gas is supplied to the adsorption unit 30 along the pipe while the residual impurities in the mixed gas purified by the distillation unit 20 are removed.

In addition, the high purity nitrogen monoxide production apparatus according to the present invention may further include a cooling tank (60).

The cooling tank 60 receives the purified mixed gas from the adsorption part 30 and cools it to a predetermined temperature and stores it. At this time, the temperature in the cooling tank 60 is maintained at -20 ~ 0 ℃, the internal pressure may be maintained at 300 ~ 700 psi. Under these conditions, impurities such as moisture in the mixed gas stored in the cooling tank 60 are condensed and separated under the cooling tank 60. Therefore, nitrogen monoxide having higher purity can be obtained through the upper portion of the cooling tank 60.

Hereinafter, a specific structure of the cooling tank 60 will be described.

5 is a cross-sectional view schematically showing a cross section of the cooling tank shown in FIG.

Referring to FIG. 5, the cooling tank 60 according to the present invention may include a tank part 61, an injection tube 63, a cooling jacket 65, and a cooling tube 67.

The tank unit 61 is a container having an accommodation space therein, and is formed so that a mixed gas is injected and stored in the accommodation space. Here, the internal pressure may be maintained at 300 ~ 700 psi. However, the internal pressure is not necessarily limited thereto.

The injection tube 63 injects the purified mixed gas transferred from the adsorption unit 30 into the accommodation space of the tank unit 61.

The cooling jacket 65 is formed to surround the outer surface of the tank 61, and has a hollow therein, and the first coolant R1 is received or flows in the hollow to cool the tank 61. The cooling jacket 65 is formed with a first refrigerant inlet tube through which the first refrigerant R1 is injected and a first refrigerant discharge tube through which the first refrigerant R1 is discharged from the hollow, thereby forming the first refrigerant R1. The mixed gas can be cooled to a predetermined temperature while continuously circulating.

The cooling tube 67 is disposed in the accommodation space of the tank 61 to cool the mixed gas. The cooling tube 67 cools the mixed gas using the second refrigerant R2 flowing therein. Specifically, the cooling tube 67 is formed in the form of a spiral tube, and the contact surface with the mixed gas is extended to efficiently cool the mixed gas. have. On the other hand, the second refrigerant injection pipe 66 for supplying the second refrigerant (R2) to one end of the cooling tube 67, the second refrigerant discharge pipe for discharging the second refrigerant (R2) to the other end of the cooling tube 67 68 may be connected to each other so that the second refrigerant R2 may be circulated.

Here, the first refrigerant (R1) and the second refrigerant (R2) may be used in the freon-based refrigerants R22, R407C, etc., not necessarily limited to this may be used all known refrigerants that can be used in the air conditioning refrigeration field, In this case, the first refrigerant R1 and the second refrigerant R2 may use the same or different refrigerants. The temperature of the cooling tank 60 may be maintained at −20˜0 ° C. by the first and second refrigerants R1 and R2.

When the mixed gas is cooled and stored in the cooling tank 60 formed as described above, impurities 5 such as moisture in the mixed gas are condensed to the lower portion of the tank 61 accommodating space, and the high purity nitrogen monoxide is the upper portion of the accommodating space. As it is separated, the impurities 5 are discharged through the impurity discharge pipe 64 connected to the lower part of the receiving space, and nitrogen monoxide of high purity may be obtained through the nitrogen monoxide discharge pipe 62 connected to the upper part of the receiving space.

Hereinafter, the present invention will be described in more detail with reference to specific examples and evaluation examples.

Example 1 Cold Condensation Purification and Separation Purification

First, the hot mixed gas discharged through the ammonia oxidizer in the actual commercial nitric acid manufacturing process was supplied at a flow rate of 1 to 10 L / min and cooled using a cooling chiller for a heat exchanger. Here, the temperature of the cooling chiller was kept at -20 to -10 ° C. At this time, some of the substances such as moisture, nitrogen dioxide, etc. in the mixed gas is condensed, and separated into a liquid phase and a gas phase using a gas-liquid separator. The liquid components condensed in the lower part of the gas-liquid separator were mainly water and nitrogen dioxide.

Next, the mixed gas was transferred to a temporary storage buffer tank through a pipe connected to the upper part of the gas-liquid separator, pressurized to 3 to 10 atm or less, and the mixed gas was introduced into the first distillation column. The upper cooler temperature of the first distillation column was maintained at -85 ~ -95 ℃ using liquid nitrogen, the lower reboiler temperature was operated to be -60 ~ -50 ℃, the operating pressure in the distillation column was 3 ~ 5 atm Maintained. Accordingly, the break point is relatively high in the lower part of the first distillation column, and thus easily liquefied water, nitrogen dioxide, ammonia, nitrous oxide, and the like are separated from the upper part of the first distillation column by nitrogen distillation.

The liquid substances condensed at the bottom were removed through the liquid pipe, and the mixed gas from which the primary impurities were removed was introduced into the second distillation column through the pipe installed on the upper part of the first distillation column. In the second distillation column, the upper cooler temperature was maintained at -150 ~ -140 ℃ using liquid nitrogen, the lower reboiler temperature is -90 ~ -80 ℃, collecting only the high-purity nitrogen monoxide through the bottom of the distillation column, Gaseous impurities (such as nitrogen and unreacted oxygen) were discharged through the top of the distillation column.

Example 2: Cold Condensation Purification, Adsorption Purification, and Cold Storage

The mixed gas separated and purified in Example 1 was supplied to the compressor through the bottom pipe of the second distillation column, and was compressed and introduced into the cooling chiller. Here, the temperature of the cooling chiller was kept at -15 to 0 ° C.

Next, the mixed gas which passed through the cooling chiller was introduce | transduced into the 1st adsorption tower and the 2nd adsorption tower. At this time, one of the adsorption tower was carried out by the adsorption purification step, while the other adsorption tower was carried out alternately. Here, the adsorber disposed in each of the adsorption towers was made using Molecure 3A. In the adsorption and purification process, the temperature of the adsorption tower was maintained at room temperature.

Finally, the mixed gas after the adsorption and purification process was maintained in a temperature range of -20 to 0 ° C. and injected into a cooling tank having an internal pressure of 300 to 700 psi.

Evaluation Example 1 Analysis of Mixed Gas Components Inflowed from a Nitric Acid Production Process

In Example 1, the mixed gas supplied from the nitric acid manufacturing process was analyzed using FT-IR and GC. The mixed gas to be analyzed is a mixed gas discharged from the ammonia oxidizer of the nitric acid manufacturing process. As a result, nitrogen monoxide was 9.3 Vol%, nitrous oxide was 15.3 Vol%, nitrogen dioxide was 7.2 Vol% and moisture was 68.2 Vol%. Through this, it can be seen that the mixed gas contains a large amount of water and nitrous oxide, and nitrogen monoxide is low enough to be unsuitable for use in semiconductors.

Evaluation Example 2 Analysis of Composition Ratio of Substances Discharged from the Distillation Column of Example 1

The composition ratio (%) of the material discharged from the first distillation column and the second distillation column of Example 1 was analyzed, and the results are shown in the following [Table 1].

Substance First distillation column Second distillation column Top bottom Top bottom NO 38.7 0.6 0.03 99.98 N ₂ 0 <0.001 59.2 <0.001 0.02 NO ₂ <0.001 22.1 <0.001 <0.001 H ₂ 0 <0.001 19.9 - <0.001 NH ₃ - 1.2 - - N ₂ 39.6 <0.001 76.2 - O ₂ 21.7 <0.001 23.5 -

As shown in Table 1, after passing through the second distillation column, nitrogen monoxide was able to obtain a purity of 99.98% or more at the bottom of the distillation column. However, since high purity of 99.995% or more is required to be used for semiconductor manufacturing, it is necessary to additionally perform the purification process of Example 2.

Evaluation Example 3: Impurity Analysis in the Cooling Tank of Example 2

After performing Example 2, the components of impurities located in the upper and lower portions of the cooling tank were analyzed. The results are shown in Table 2 below.

analysis
location Impurities (ppm) H ₂ O NO ₂ N ₂ O H ₂ O ₂ N ₂ CH ₄ CO ₂ CO Top 0.258 2.426 0.188 <0.1 <0.1 4.125 <0.1 <0.1 <0.1 bottom 0.287 2.365 0.196 <0.1 <0.1 4.037 <0.1 <0.1 <0.1

Through the results in Table 2, it can be seen that according to the present invention, more than 99.999% of nitrogen monoxide for high purity semiconductors can be produced.

Although the present invention has been described in detail through specific examples, it is intended to describe the present invention in detail, and the present invention is not limited thereto, and should be understood by those skilled in the art within the technical spirit of the present invention. It is obvious that modifications and improvements are possible.

All simple modifications and variations of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be apparent from the appended claims.

1: mixed gas 10: supply part
20: distillation unit 21: first distillation column
23: second distillation column 30: adsorption unit
31: first adsorption tower 33: second adsorption tower
35, 37: heating part 40: first cooling chiller
50: gas-liquid separator 60: cooling tank
61: tank 63: injection tube
65: cooling jacket 67: cooling tube
70: compressor 80: second cooling chiller

Claims (13)

(a) supplying a mixed gas produced in a conventional nitric acid manufacturing process for oxidizing ammonia to produce nitric acid and containing low purity nitrogen monoxide;
(b) separating and purifying the mixed gas by using a boiling point difference; And
(c) adsorbing and purifying the mixed gas separated and purified using an adsorbent;
In the step (a), a portion of the mixed gas generated in the nitric acid production process is separately stored and supplied, or a supply pipe is installed in a piping facility of the nitric acid production process through which the mixed gas flows to separately supply a portion of the mixed gas. ,
Between the step (a) and the step (b), the step of cooling the mixed gas supplied from the nitric acid production process, gas-liquid separation, the first cooling condensation purification;
Compressing and cooling the separated and purified mixed gas between the step (b) and the step (c) and cooling the second cooling condensation step; And
After the step (c), the step of cooling and storing the adsorbed and purified mixed gas at a temperature range of -20 to 0 ° C. and a pressure range of 300 to 700 psi using a cooling tank to condense and separate the moisture in the mixed gas. Including more,
The cooling tank,
A tank unit having an accommodation space therein to store the mixed gas;
An injection tube for injecting the mixed gas into the accommodation space;
A cooling jacket having a hollow in which the first refrigerant flows and surrounding the outer surface of the tank part;
A cooling tube formed in the form of a spiral tube and having a second refrigerant flowing therein and disposed in the accommodation space to cool the mixed gas while contacting the injected mixed gas;
An impurity discharge tube communicating with an inner lower portion of the accommodation space to discharge the separated water; And
And a nitrogen monoxide discharge tube communicating with the inner portion of the accommodation space and discharging the nitrogen monoxide with high purity.
delete The method according to claim 1,
Step (b),
Removing high boiling point impurities having a higher boiling point than the nitrogen monoxide from the mixed gas by using a first distillation column; And
Removing low-boiling impurities having a lower boiling point than nitrogen monoxide from the mixed gas from which the high-boiling impurities are removed using a second distillation column;
High purity nitrogen monoxide production method comprising a.
delete The method according to claim 1,
In step (c),
Production of high-purity nitrogen monoxide using a pair of adsorption towers disposed therein, and alternately adsorbing and purifying impurities in one of the first adsorption towers, and heating and regenerating the adsorbents in another second adsorption tower. Way.
delete A supply unit which is produced in a conventional nitric acid manufacturing process for oxidizing ammonia to produce nitric acid, and supplies a mixed gas containing low purity nitrogen monoxide;
A distillation unit including at least one distillation column including a reboiler, a column, and a cooler, and purifying the mixed gas using a boiling point difference; And
And an adsorption unit including at least one adsorption tower having an adsorbent disposed therein and adsorbing and purifying the mixed gas purified by the distillation unit.
The supply unit separates and supplies a portion of the mixed gas generated in the nitric acid manufacturing process, or installs a supply pipe in a piping facility of the nitric acid manufacturing process in which the mixed gas flows, and separately supplies a portion of the mixed gas.
A first cooling chiller (chiller) for cooling the mixed gas supplied from the supply part to condense impurities;
A gas-liquid separator that separates the condensed liquid impurities and supplies the mixed gas to the distillation column;
A compressor that receives the mixed gas from the distillation unit and compresses the mixed gas;
A second cooling chiller (chiller) that receives the compressed compressed gas from the compressor and cools it, condenses and removes impurities, and supplies the mixed gas to the adsorption unit; And
Receiving the mixed gas from the adsorption unit, by cooling and storing the mixed gas at a temperature range of -20 ~ 0 ℃ and 300 ~ 700 psi, a cooling tank for condensing and separating the moisture in the mixed gas;
The cooling tank,
A tank unit having a receiving space therein to store the mixed gas;
An injection tube for injecting the mixed gas into the accommodation space;
A cooling jacket having a hollow in which the first refrigerant flows and surrounding the outer surface of the tank part;
A cooling tube formed in the form of a spiral tube and having a second refrigerant flowing therein and disposed in the accommodation space to cool the mixed gas while contacting the injected mixed gas;
An impurity discharge tube communicating with an inner lower portion of the accommodation space to discharge the separated water; And
And a nitrogen monoxide discharge pipe communicating with the inner upper portion of the accommodation space and discharging the nitrogen monoxide with high purity.
The method according to claim 7,
The distillation unit,
The distillation column is disposed in a pair, and the first distillation column, which is one of them, receives the mixed gas from the supply unit to remove high boiling point impurities having a relatively higher boiling point than the nitrogen monoxide, and the second distillation column is another. The high purity nitrogen monoxide production apparatus for removing the low boiling point impurities having a relatively low boiling point than the nitrogen monoxide by receiving the mixed gas purified from the first distillation column.
The method according to claim 7,
The adsorption unit,
A pair of the adsorption tower is disposed separately,
A heating unit for heating each of the adsorption towers;
Including more,
Alternately, a high-purity nitrogen monoxide production apparatus in which a first adsorption tower, which is one of the pair of adsorption towers, adsorbs and purifies the mixed gas, and a second adsorption tower, which is the other, heat-regenerates the adsorbent.
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