JP2003183021A - Method and apparatus for continuously purifying ammonia gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for directly and continuously purifying low price crude ammonia gas for industrial applications having a purity of about 99.9% or recovered ammonia gas at a location where the ammonia is to be used into high purity ammonia gas having a purity of 99.999 to 99.9999% or higher that can be used in a semiconductor producing process, and to provide an apparatus therefor. <P>SOLUTION: In a process step A, the crude ammonia gas is introduced into a dehydrating tower (3) under a substantially room temperature filled with a barium oxide-based moisture removing agent to remove by reaction the moisture contained in the gas. In a process step B, the ammonia gas from which moisture is removed in the process step A is introduced into an intermediate reflux part (42) of a distillation column (4), liquefying the ammonia gas and separating low boiling point impurities at an upper condensation/cooling part (41). The liquefied material flows down to a lower storage part (43) to form the substantially high purity ammonia. Small amount of impurities contained in the stored liquid is removed by boiling at a lowest boiling/heating part (44). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously purifying high-purity ammonia gas used in, for example, a semiconductor manufacturing process from industrial ammonia or recovered ammonia (collectively referred to as ammonia gas). And the device.

[0002]

2. Description of the Related Art In the semiconductor device manufacturing industry, a large amount of high-purity ammonia is consumed as a nitrogen source in the manufacturing process of silicon nitride films and light emitting diodes, and the consumption amount is increasing year by year.

Ammonia used in the semiconductor device manufacturing industry is required to have extremely high purity, and a purification method capable of continuously supplying high purity ammonia is desired.

As a method of removing impurities in the ammonia production process, a method of removing impurities by distillation and a method of removing impurities by adsorption using an adsorbent such as synthetic zeolite are known. High-purity ammonia is manufactured by each company's method, but the ammonia purity is generally 99.999% or more in the shipping inspection value, and the content of impurities is about several hundreds of ppb as a large component.

With the recent advances in film-forming technology, when ammonia is used in the manufacture of semiconductors, it is necessary to purify it to a higher degree of purity. Therefore, refining is performed again at the place of actual use to reduce impurities. Is taken.

Further, the high-purity ammonia produced in the ammonia production plant by the above method is generally transported in a liquid state by a lorry, transferred to a tank of a semiconductor device production plant, which is a main user, and used. .

As a method for purifying ammonia to a high purity, a method of contacting ammonia with a getter alloy at a temperature of about 100 ° C. to remove oxygen and water (Japanese Patent Laid-Open No. 4-496).
No. 292413) or a method of removing oxygen, carbon monoxide, and carbon dioxide by contacting with a nickel catalyst at room temperature (Japanese Patent Laid-Open No. 2000-169138).
Further, the present applicant has proposed a method of contacting ammonia at room temperature with barium oxide alone or a mixture mainly containing barium oxide to remove water to 5 ppb or less (JP-A-9-142833). reference).

[0008]

With the progress of higher integration of semiconductors, it is required to stably and continuously supply high-purity ammonia at low cost.

As described above, when the high-purity ammonia produced in the ammonia production plant is used by being fed by a truck, when the tank is filled from the production tank or the tank is filled with nitrogen, the nitrogen is filled. , Impurities such as oxygen and water may be mixed and re-contaminated, and the purity of ammonia may decrease.

In particular, water has a strong affinity with ammonia, and the water adsorbed on the surface of the metal used in the transportation of ammonia or the tank for storage tanks and the supply pipes comes into contact with the ammonia to be desorbed. There is a risk of increasing the water concentration and causing a decrease in purity, and any of these causes a decrease in the manufacturing yield of semiconductor devices.

Further, even when the high purity ammonia can maintain the purity at the time of production without the above-mentioned contamination, it is introduced into a CVD apparatus for a silicon nitride film which requires particularly high purity for the reason described above. It is necessary to carry out purification again immediately before, and to reduce the contamination of impurities to the limit.

As a method for reducing impurities at the place where ammonia is used, there are the above-mentioned proposed purification methods. However, in each of the purification methods, the impurities that can be removed are limited components. There is a limit that methane cannot be removed. Also, the price of semiconductor grade high purity ammonia is 1
It is as expensive as 0 times.

Against this background, the present invention has a purity of 99.999 to 99.9999, which can be used in the semiconductor manufacturing process at a place where ammonia is used as an inexpensive industrial crude ammonia gas or a recovered ammonia gas having a purity of about 99.9%. The object of the present invention is to provide a method for directly and continuously purifying high-purity ammonia having a purity of at least%, and an apparatus therefor.

[0014]

A method for continuously purifying ammonia gas according to the present invention is a method for continuously purifying a crude ammonia gas containing water and low boiling impurities having a boiling point lower than that of ammonia. Performing a step A of introducing crude ammonia gas into a dehydration tower (3) at a substantially room temperature filled with a barium-based moisture remover and reacting and removing moisture contained in the crude ammonia gas, and Condensation cooling section (41), intermediate reflux section (42), lower storage section (43), is divided into the lowest boiling heating section (44), and the upper portion of the ammonia gas discharge section containing impurities (45), A distillation column (4) equipped with a purified liquefied ammonia take-out part (46) is used in the lower part, and the ammonia whose water has been removed by the above step A is provided in the intermediate reflux part (42) of the distillation column (4). Introduce gas to condense and cool upper part
While liquefying the ammonia gas at (41) and separating low-boiling impurities, the liquefied substance is made to flow down to the lower storage section (43) to form substantially high-purity ammonia, which is further contained in the stored liquid. It is characterized in that step B is carried out to remove trace impurities by boiling in the lowermost boiling heating section (44).

The continuous purification apparatus for ammonia gas of the present invention is an apparatus for continuously purifying crude ammonia gas containing water and low boiling impurities having a boiling point lower than that of ammonia. It is divided into a dehydration tower (3) for filling, an upper condensation cooling section (41), an intermediate reflux section (42), a lower storage section (43), and a lowermost boiling heating section (44), and the upper section A discharge column (45) for ammonia gas containing impurities, and a distillation column (4) provided with a discharge section (46) for purified liquefied ammonia at the bottom are provided.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

<Crude Ammonia> The continuous purification method for ammonia gas of the present invention is a method for continuously purifying crude ammonia gas containing water and low boiling impurities having a boiling point lower than that of ammonia.

Examples of the crude ammonia targeted for removing impurities in the present invention include commercially available industrial ammonia having a purity of about 99.9% and recovered ammonia. The water concentration in the crude ammonia is usually 100 ppm or less, preferably 50 ppm or less. Low-boiling impurities having a lower boiling point than ammonia contained in crude ammonia are hydrogen (H
₂ ), oxygen (O ₂ ), nitrogen (N ₂ ), argon (Ar), carbon monoxide (C
O), carbon dioxide (CO ₂ ), methane (CH ₄ ), ethane (C ₂ H ₆ ),
Ethylene (C ₂ H ₄ ), propane (C ₃ H ₈ ), propylene (C ₃ H ₆ ),
Examples include silane (SiH ₄ ), phosphine (PH ₃ ), arsine (AsH ₃ ), and germane (GeH ₄ ). However, of these, the content of impurities from ethane to germane is practically almost undetectable even in crude ammonia.

<Step A> In step A, crude ammonia gas is introduced into a dehydration tower (3) at a substantially room temperature filled with a barium oxide-based water removing agent, and the water contained in the crude ammonia gas is reacted. This is the step of removing.

To introduce the crude ammonia gas into the dehydration tower (3), for example, the crude ammonia container (1) containing the crude ammonia is heated by the heater (2) and taken out as the vapor phase crude ammonia gas. Made by.

Examples of the barium oxide-based water removing agent include barium oxide alone or a mixture mainly containing barium oxide (for example, a mixture of barium oxide and a substance capable of removing water such as calcium oxide). In the latter mixture, the proportion of barium oxide in the mixture is preferably 50 mol% or more.

The shape of the filling composed of the barium oxide-based water removing agent may be any of powder, granules, molded products and the like. In order to suppress the pressure loss when introducing the crude ammonia gas, the molded product is Is preferred. When shaping into granules or molded articles, an excipient and a bulking agent can be added.

The water contained in the crude ammonia gas is removed by charging the barium oxide-based water removing agent into the dehydration tower (3) (columnar column), and then introducing the crude ammonia gas substantially at room temperature. Is done by doing. Moisture is
It reacts with barium oxide to form barium hydroxide, which is fixed in the column. At that time, the water concentration at the column outlet was 5
It is maintained at an extremely low concentration below ppb.

The space velocity (SV) at that time is practically 5
It is preferably set to 00 hr ^-1 or less. This is because the water content can be removed even if the space velocity is increased, but the continuous use time becomes short.

The filling height of the packing in the dehydration tower (3) is
There is no particular limitation, but considering the increase in pressure loss, 20
It is preferable to set it to 00 mm or less.

The number of dehydration towers (3) (the number of columns) may be one, but in consideration of continuous operation, it is preferable to alternately use two towers.

<Step B> Step B is a step of separating and refining the low boiling point impurities remaining in the ammonia gas from which the water has been reacted and removed in the step A, by a distillation operation.

In this step B, the upper condensing cooling section (4
1), an intermediate reflux section (42), a lower storage section (43), and a bottom boiling heating section (44), and an ammonia gas discharge section (45) containing impurities in the upper section and a refinement section in the lower section. A distillation column (4) equipped with an outlet (46) for the liquefied liquefied ammonia is used.

In step B, the ammonia gas from which water has been removed in step A is introduced into the intermediate reflux part (42) of the distillation column (4), and the ammonia gas is fed into the upper condensing cooling part (41). While liquefying and separating low-boiling-point impurities, the liquefied substance is made to flow down to the lower reservoir (43) to form substantially high-purity ammonia, and the trace impurities contained in the stored liquid are heated to the bottom by boiling. Drive out by boiling in part (44). As a result, highly pure ammonia is obtained.

In step B, in order to liquefy the ammonia gas, it is preferable to maintain the upper condensing cooling part (41) in the temperature range of -5 to 10 ° C. When the temperature of the upper condensing cooling part (41) becomes lower than -5 ° C, liquefaction becomes easy, but the temperature of the liquefied ammonia becomes low, and the pressure of the purified high-purity ammonia becomes low. Sometimes it is necessary to boost the pressure again. On the other hand, when the temperature of the upper condensing cooling part (41) becomes higher than 10 ° C., the condensing efficiency deteriorates and the heat exchange area required for condensing increases.

In step B, it is preferable to maintain the bottom boiling heating section (44) in the temperature range of 30 to 50 ° C. When the temperature of the lowermost boiling heating section (44) becomes lower than 30 ° C., the temperature difference from the liquid ammonia becomes small, and the efficiency of expelling dissolved impurities due to boiling decreases. on the other hand,
When the temperature of the bottom boiling heating section (44) becomes higher than 50 ° C, the temperature of liquid ammonia becomes too high, the pressure becomes high, and the pressure difference with the introduced ammonia becomes small. It becomes difficult to obtain the flow rate.

Further, in step B, the discharge flow rate of the ammonia gas containing impurities is preferably set to 0.1 to 10% of the flow rate introduced into the distillation column (4) by volume ratio. When the discharge flow rate is less than 0.1%, the concentration of low boiling point impurities that are non-condensable components increases in the distillation column (4), and the condensation and liquefaction efficiency of ammonia decreases. On the other hand, the discharge flow rate is 10
When it is larger than%, the amount of ammonia that can be taken out as a product becomes small, which is disadvantageous in terms of economical refining.

<Measures for Continuous Purification> In order to obtain highly pure ammonia having a stable purity by continuous purification, it is desirable to take the following measures.

In the above step A, water cannot be regenerated because water is removed by an irreversible reaction. Therefore, it is necessary to replace with a new column before water flows out from the column (dehydration tower (3)).

In the present invention, the concentration of water is measured by sampling the gas at the intermediate position of the packed bed of the column, preferably, for example, at the position of about 1/3 of the upstream side from the gas outlet of the packed bed to measure the water concentration. The water concentration of the high-purity ammonia product in the lower storage part (43) of the distillation column (4) is also measured, and the difference in water concentration between the two is calculated, and the time for changing the packing in the dehydration column (3) is detected. It is preferable.

As a specific example, in the case of crude ammonia of Example 1 described later, the water difference set value is set to, for example, (28 ppm-
(0.01ppm) / 3 of 9.3ppm for control so that the dehydration tower (3) can be replaced after making maximum use of the dehydration capacity of about 1/3 of the downstream side of the sampling pipe installation position for moisture measurement. You can

It should be noted that even when the water concentration of the above column (dehydration tower (3)) alone is used, it is possible to know when the column should be replaced. However, in this method, the time when the water concentration starts to increase becomes the time for replacement, and the packed bed of about 1/3 on the downstream side of the column cannot be effectively used, which is a disadvantage compared to the previous method. Becomes

The water concentration in ammonia, the sampling gas for water concentration monitor in contact with calcium carbide (CaC _2), after the water content in the ammonia was converted to acetylene (C ₂ H _2), a gas chromatograph ( For example, a hydrogen flame ionization gas chromatograph (GC-
FID)). The water concentration can be monitored using a Fourier transform infrared spectrophotometer (FT-IR) (for example, a Fourier transform infrared spectrophotometer (FT-IR) equipped with a gas cell having an optical path length of about 10 m). .
By these methods, the water content of 100 ppb or less can be quantified. And with these analyzers, dehydration tower (3)
Moisture in the gas in the column and the lower storage part (43) of the distillation column (4)
By measuring the water content in the purified ammonia of (1), the time of replacement of the dehydration column (3) column and the quality of the product can be determined at the same time.

When replacing the dehydration column (3) column described above, after replacing oxygen and water remaining in the pipe with an inert gas such as nitrogen gas, it is further purified with purified high-purity ammonia. It is desirable to carry out a pressure equalization operation with high-purity ammonia after purging and purging out the remaining inert gas.

More specifically, before using the dehydration column (3) in the step A, the purified ammonia in the distillation column (4) lower storage part (43) in the step B is added to the dehydration column (3). After introducing and purging impurities in the system, a pressure equalizing operation is performed.

In addition, the dehydration tower (3) is purged with purified ammonia in the lower storage section (43) of the distillation tower (4) in step B, and the exhaust gas after the purging is recovered, and the recovered gas is used in the step. In A, it is desirable to reuse it as a part of the raw material ammonia supplied to the dehydration tower (3).

<Continuous Purification Apparatus> In order to carry out the above-mentioned continuous purification method, the continuous purification apparatus for ammonia gas of the present invention is a dehydration tower for filling a barium oxide-based water removing agent.
(3) is divided into an upper condensation cooling section (41), an intermediate reflux section (42), a lower storage section (43), and a lowermost boiling heating section (44), and the upper part thereof contains ammonia gas containing impurities. A discharge part (45) and a distillation column (4) equipped with a purified liquefied ammonia take-out part (46) are provided at the bottom. The attached devices or members will be described in the examples below.

<Operation> According to the present invention, by the cooperation of the dehydration reaction operation in the step A and the distillation separation operation in the step B, the purified ammonia gas can be obtained by removing both water and low boiling impurities in the crude ammonia. , Continuously and reliably achieved.

Further, since the operation of step A can be carried out substantially at room temperature and the operation of step B can be carried out in the temperature range of -5 to 50 ° C., all treatment steps for purification of ammonia can be carried out. Can be achieved with a reasonably economical low pressure device and at pressures below about 1 MPaG.

[0045]

EXAMPLES The present invention will be further described with reference to examples.

Example 1 FIG. 1 is an explanatory diagram showing an example of a flow and an apparatus for continuously purifying ammonia gas according to the present invention.
In addition, (V) in FIG. 1 is a valve.

As raw crude ammonia, purity 99.9
% Or more industrial ammonia was used. Contained in raw materials
As shown in Table 1 below, impurities include 28 ppm of water.
(H₂O) as well as hydrogen (H₂), Oxygen (O₂), Nitrogen (N₂), Argo
(Ar), carbon monoxide (CO), carbon dioxide (CO₂), Methane (C
H_Four) And other low boiling impurities such as
Rare (ethane (C₂H₆), Ethylene (C₂H_Four),propane
(C₃H₈), Propylene (C ₃H₆), Silane (SiH_Four), Phosphine
(PH₃), Arsine (AsH₃), German (GeH_Four) Is almost inspected
Will not be issued).

This raw material is filled in the crude ammonia container (1). This crude ammonia container (1) is equipped with a heater (2).
The temperature is controlled to 25 ° C by the, and the pressure of ammonia is maintained at about 0.9 MPaG. This raw material was taken out from the gas phase part of the crude ammonia container (1) and adjusted to 10 NL / min by the flow rate controller (F ₁ ), and then the dehydration tower (3)
Will be introduced to.

The dehydration tower (3) consists of two towers (3A) and (3B), and each tower uses a stainless steel column having an inner diameter of 83.1 mm and a height of 800 mm. Each of the towers was packed with barium oxide (Ba
O) 50% by weight, polyethylene 30% by weight, alumina 2
About 3 liters of cylindrical compression molded pellets having a diameter of 4 mm and a length of 3.5 mm having a composition of 0% by weight are filled.

A pipe for measuring the water concentration is provided from a position approximately 1/3 on the upstream side from the gas outlet of the packed bed of the dehydration tower (3), and the dehydration tower (3) on the use side is provided. To the specified flow rate with the flow rate controller (F ₄ )
It is being introduced into.

Ammonia derived from the dehydration tower (3) is
Introduced into the middle reflux section (42) of the distillation column (4), the refrigerator (47)
Is liquefied in the upper condensing cooling part (41) whose temperature is controlled to 0 ° C., and low boiling point impurities are separated. The liquefied ammonia flows down and is stored in the lower storage section (43). A part of the stored liquefied ammonia was heated by the heater (48)
Impurities that have been vaporized and dissolved in the lowermost boiling heating section (44) whose temperature is controlled to 0 ° C. are separated.

The low boiling point impurities separated in the upper condensing boiling section (41) and the lowermost boiling heating section (44) are discharged from the discharge section (45) at the upper part of the distillation column (4) by a flow rate controller (F ₃ ). It is discharged at a flow rate adjusted to 50 Nml / min.

High-purity ammonia from which impurities have been separated is
Passing through the high-purity ammonia extraction section (46) at the bottom of the distillation column (4),
Product Ammonia Evaporator (49) after vaporization, then flow regulator
It is adjusted to 10 NL / min with (F ₂ ) and taken out as high-purity ammonia gas.

The impurities of this high-purity ammonia gas were measured using a hydrogen flame ionization type gas chromatograph (GC-FID) and a photoionization type gas chromatograph (GC-PID).

As a result, as shown in Table 2 below, the water content
(H ₂ O) is removed, as well as hydrogen (H ₂ ), oxygen (O ₂ ), nitrogen (N ₂ ), argon (Ar), carbon monoxide (CO), carbon dioxide (C
O ₂ ) and methane (CH ₄ ) have been removed to extremely low concentrations, and ethane (C ₂ H ₆ ), ethylene (C ₂ H ₄ ), propane (C ₃ H _8), propylene (C ₃ H _6), silane (SiH _4), phosphine (PH _3), arsine
Impurities such as (AsH ₃ ) and germane (GeH ₄ ) having a boiling point lower than that of ammonia were hardly contained in the high-purity ammonia gas.

Example 2 The temperature of the upper condensing cooling section (41) of the distillation column (4) was -5 ° C. and 0
℃, 5 ℃, 10 ℃, the temperature of the bottom boiling heating part (44) 3
The temperature was changed to 0 ° C., 40 ° C., and 50 ° C., and the crude ammonia was purified under the same conditions as in Example 1 except for the temperature condition of the distillation operation.

In the purification under any temperature conditions, the impurities of the obtained high-purity ammonia did not change from the concentrations shown in Table 2, and sufficient purification ability was obtained.

The pressure of the high-purity ammonia obtained by the distillation operation under each temperature condition was at a practically no problem level as shown in Table 3 below.

Example 3 Continuous purification was carried out under the same conditions as in Example 1, and the water concentration in the middle position of the packed bed of the dehydration tower (3) and the lower storage part (4
The water concentration of 3) and the water concentration were alternately measured by the water concentration measuring device (5) and calculated by the calculator (6).

The moisture concentration measuring instrument (5) is a hydrogen flame ionization type gas chromatograph (GC-FI) equipped with an automatic measuring function.
D) was used. The water content was measured by converting it to acetylene (C ₂ H ₂ ) using a calcium carbide (CaC ₂ ) packed column installed immediately before the GC-FID introduction part. The lower limit of quantification is 10 ppb.

At 2280 hours after the start of the purification, the water concentration in the middle position of the packed bed of the dehydration column (3) was found to increase.
The water concentration in the lower storage part (43) of (4) was 310% after the start of purification.
It was less than 10 ppb by 0 hours.

Example 4 A Fourier transform infrared spectrophotometer (FT-IR) equipped with a gas cell having an optical path length of 10 m was used as the moisture concentration measuring instrument (5), except that
It measured on the same conditions as Example 3. Lower limit of quantification is 100pp
b.

At 2300 hours after the start of purification, the water concentration in the middle position of the packed bed of the dehydration column (3) increased, but the distillation column
The water concentration in the lower storage part (43) of (4) was 312 after the start of purification.
It was less than 100 ppb by 0 hours.

Example 5 The dehydration tower (3), which had no dehydration capacity, was replaced with a new tower,
Oxygen and water remaining in the pipe were replaced with nitrogen gas. Then, dehydration tower with purified high-purity ammonia (3)
After purging the inside and replacing the nitrogen remaining in the tower and the pipe, the pressure was equalized with high-purity ammonia. While recovering the ammonia mainly containing nitrogen gas discharged by the purge into the waste ammonia recovery container (7), the booster (8) boosts the pressure to about 1 MPaG and introduces it into the feed ammonia supply pipe for purification. It was

The impurities of high-purity ammonia obtained by the purification did not change from the concentrations shown in Table 2, and sufficient purification ability was obtained.

[0066]

[Table 1]      Impurity H₂    O₂    N₂    Ar CO CO₂    CH_Four    H₂O   Concentration (ppm) 4 21 138 1 0.10 0.52 342 28

[0067]

[Table 2]      Impurity H₂      O₂      N₂      Ar CO CO₂     CH_Four    Concentration (ppm) <0.05 <0.01 <0.01 <0.01 <0.01 0.02 <0.01   Impurity H₂O C₂H₆    C₂H_Four    C₃H₈    C₃H₆    SiH_Four    PH₃    Concentration (ppm) <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01   Impurity AsH₃    GeH_Four   Concentration (ppm) <0.01 <0.01

[0068]

[Table 3]

[0069]

According to the present invention, by the cooperation of the dehydration reaction operation in step A and the distillation separation operation in step B,
It is possible to produce high-purity ammonia having a purity that can be used in the semiconductor manufacturing industry by directly using an inexpensive industrial crude ammonia gas or recovered ammonia gas as a raw material and directly purifying it at a place of use.

Further, since the operation of step A can be carried out substantially at room temperature and the operation of step B can be carried out in the temperature range of -5 to 50 ° C., all treatment steps for purification of ammonia can be carried out. Can be achieved with a reasonably economical low pressure device and at pressures below about 1 MPaG.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a flow and an apparatus when performing continuous purification of ammonia gas according to the present invention.

[Explanation of symbols]

(1) ... crude ammonia container, (2) ... heater, (3), (3A), (3B) ... dehydration tower, (4) ... distillation tower, (41) ... upper condensation cooling section, (42) ... Middle part reflux part, (43) ... lower storage part, (44) ... bottom boiling heating part, (45) ... ammonia gas discharge part (including impurities), (46) ... of (purified) liquefied ammonia Extraction unit, (47) ... Refrigerator, (48) ... Heating machine, (49) ... Product ammonia vaporizer, (5) ... Water concentration measuring instrument, (6) ... Calculator, (7) ... Waste ammonia recovery container , (8)… Booster, (F ₁ ) to (F ₄ )… Flow regulator, (V)… Valve

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Makoto Uchino             2-4-11 Tsubohoncho, Nishi-ku, Osaka City, Osaka Prefecture             Within Taiyo Toyo Oxygen Co., Ltd. (72) Inventor Shinichi Ando             2-4-11 Tsubohoncho, Nishi-ku, Osaka City, Osaka Prefecture             Within Taiyo Toyo Oxygen Co., Ltd. F-term (reference) 4D052 AA02 CE00 GA03 GB00 HA00                       HA02 HA49 HB02

Claims (8)

[Claims] 1. A method for continuously purifying a crude ammonia gas containing water and a low-boiling point impurity having a boiling point lower than that of ammonia, comprising dehydration at substantially room temperature filled with a barium oxide-based water removing agent. Introducing crude ammonia gas into the tower (3) and carrying out step A of reacting and removing water contained in the crude ammonia gas; and an upper condensation cooling section (41), an intermediate reflux section (42), Lower reservoir (4
3), a distillation column which is divided into the lowest boiling heating section (44), and in which the upper section has an exhaust section (45) for ammonia gas containing impurities, and the lower section has an extraction section (46) for purified liquefied ammonia. (Four)
Is used in the intermediate reflux section (42) of the distillation column (4).
By introducing the ammonia gas from which water has been removed by the liquefied ammonia gas in the upper condensing cooling unit (41) and liquefying the ammonia gas and separating low boiling point impurities, the liquefied substance is allowed to flow down to the lower storage unit (43). 1. A continuous purification method of ammonia gas, characterized in that step B is carried out to obtain highly pure ammonia, and further, trace impurities contained in the stored liquid are expelled by boiling in the lowermost boiling heating part (44). 2. In step B, the upper condensing cooling part (41) is
The continuous refining method according to claim 1, wherein the lowermost boiling heating section (44) is maintained in a temperature range of 30 to 50 ° C while being maintained in a temperature range of 5 to 10 ° C. 3. In the step B, the discharge flow rate of the ammonia gas containing impurities is adjusted by the volume ratio of the introduction flow rate of the distillation column (4).
The continuous purification method according to claim 1, wherein the concentration is set to 0.1 to 10%. 4. Low boiling point impurities are hydrogen (H ₂ ), oxygen (O ₂ ), nitrogen (N ₂ ), argon (Ar), carbon monoxide (CO), carbon dioxide (C
O ₂ ), methane (CH ₄ ), ethane (C ₂ H ₆ ), ethylene (C ₂ H ₄ ),
Propane (C ₃ H _8), propylene (C ₃ H _6), silane (SiH _4), phosphine (PH _3), arsine (AsH ₃₎ and germane (GeH ₄₎
The continuous purification method according to claim 1, which comprises at least one impurity selected from the group consisting of: 5. The water concentration in the middle position of the packed bed of the dehydration column (3) in the step A and the water concentration in the lower storage part (43) of the distillation column (4) in the step B are monitored and the water concentration of both is monitored. 2. The continuous purification method according to claim 1, wherein the difference is calculated to detect the time when the packing is replaced in the dehydration tower (3). 6. Before using the dehydration tower (3) in step A, the purified ammonia of the distillation column (4) lower storage part (43) in step B is introduced into the dehydration tower (3). 2. The continuous purification method according to claim 1, wherein the pressure equalizing operation is performed after purging impurities in the system. 7. The distillation column (4) lower storage part (43) in step B
The purified dehydrated ammonia is used to purge the dehydration tower (3), the exhaust gas after the purge is recovered, and the recovered gas is reused as part of the raw material ammonia supplied to the dehydration tower (3) in step A. The continuous purification method according to claim 1, wherein 8. An apparatus for continuously purifying crude ammonia gas containing water and low-boiling impurities having a boiling point lower than that of ammonia, wherein a dehydration tower (3) for filling a barium oxide-based water removing agent is provided.
And the upper condensing cooling section (41), the intermediate reflux section (42), the lower storage section (4
3), a distillation column which is divided into the lowest boiling heating section (44), and has an ammonia gas-containing discharge section (45) in the upper section and a refined liquefied ammonia extraction section (46) in the lower section. (Four)
An apparatus for continuously purifying ammonia gas, comprising: