JPS6259523A - Apparatus for producing ammonia water - Google Patents

Abstract

PURPOSE:To produce ammonia water having low impurity content, by evaporating liquid ammonia in an evaporator while leaving a part of the liquid or solid impurities in unevaporated state and filtering the solid or liquid particulate impurities entrained to the evaporated ammonia gas with a filter. CONSTITUTION:The apparatus is composed of an evaporator to evaporate liquid ammonia, a filter to filtrate the evaporated ammonia, an ammonia absorption column for dissolving and absorbing ammonia gas in ultra-pure water and having a circulation line to circulate the bottom fluid to the column top and a storage tank to store ammonia water discharged from the absorption tank. The absorption column is furnished with a sensor for detecting the concentration of the ammonia water, an automatic change-over device to discharge the ammonia water in the absorption column to the storage tank when the detected concentration reaches a prescribed level and a by-pass line branched from the circulation line. The ammonia water in the circulation line is poured directly to the bottom part of the absorption column through the by-pass line and the bottom ammonia water is agitated and uniformized by this action.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ammonia water production apparatus for inexpensively producing ammonia water at a constant concentration with few impurities from liquefied ammonia.

``Conventional technology'' For example, when manufacturing integrated circuits on Noricon wafers at a conductor factory to create so-called 0-deep circuits, impurities are strictly removed to maintain the quality. Measures have been taken to regulate the wafers, and the detergent used to clean the wafers must have a high purity level of 113%.In particular, the presence of hard particles must be Since this degrades the properties of semiconductors, its purity is checked by optical inspection using the Tyndall phenomenon.

Ammonia water is used as such a cleaning agent, but
Conventionally, this ammonia water has been used by transporting commercially available ammonia water sealed in a can into a factory, filtering it through a filter, and storing it in a tank.

[Problems to be Solved by the Invention] However, the purity of the commercially available ammonia water as described above is not high enough to meet the purpose, and furthermore,
It may absorb dust left in the container during transportation or tank transfer, or it may come in contact with the air and absorb the dust, and it may also react with carbon dioxide in the air (7), producing ammonium carbonate. This may further reduce the purity.

In addition, ammonia water can be filtered with a fine 1.r
It is not easy to remove impurities, and it is very difficult to obtain ammonia water with low impurities using this method.

[Means for Solving the Problems-1] In order to solve the above-mentioned problems, the present invention provides an evaporator that raises the temperature of liquefied ammonia to vaporize it, and filters the vaporized ammonia gas to remove impurities. an ammonia absorption tower that dissolves ammonia gas in ultrapure water and drains it to the absorption port, and a circulation line that returns the fluid at the bottom to the top of the tower; The ammonia absorption tower is equipped with a storage tank for storing ammonia water, and the ammonia absorption tower is equipped with a sensor that detects the ammonia concentration in the ammonia water. An automatic switching device that discharges water to the storage tank, and a bypass line that is branched from the circulation line and that pours the ammonia water in the circulation line directly into the bottom of the ammonia absorption tower to stir and homogenize the ammonia water at the bottom. I have set it up so I can use it myself.

[Function] According to such an ammonia water production apparatus, fine solid or liquid impurities contained in ammonia gas are filtered and removed by a fine filter. This purified ammonia gas is dissolved and absorbed in ultrapure water that is refluxed through a circulation line in an ammonia absorption tower.

The ammonia water here is stored at the bottom of the ammonia absorption tower, and is stirred by water injection from the bypass line to equalize the temperature and the ammonia concentration. This prevents the automatic switching device from malfunctioning due to the sensor erroneously detecting the concentration.

:Example] An embodiment of the present invention will be described below with reference to FIG.

Liquefied ammonia, which is the raw material, is stored in the raw material tank l.
Passed through control valve 2 to evaporator 3.

This evaporator 3 consists of a meandering pipe 3b installed in a temperature raising tank 3a containing hot water or steam, and is designed to efficiently evaporate liquefied ammonia.

In the pipe 3c on the discharge side of the evaporator 3, fine particles of tetrafluoroethylene polymer (particle size 0.1 to
A well-known gas filter 4 filled with 0.2 μm) is attached.

Further, in the piping 3c in front of the gas filter 4, there is provided a pressure regulating device 5 that detects the pressure of the piping 3c 17 and opens and closes the control valve 2 based on the detected pressure.

A pipe 4a on the discharge side of the gas filter 4 is conveyed to an ammonia absorption tower 7 via a control valve 6. This ammonia absorption tower 7 has an upper small diameter portion 7a and a lower large diameter portion 7b.
The small diameter portion 7a is filled with a gas-liquid contact layer 8 filled with a porous material (Raschig ring, Terraret, etc.).
is formed.

A pressure regulator 9 is provided above the gas-liquid contact layer 8 to open and close the control valve 6 by detecting the pressure at the top of the column.

A circulation line 10 is provided between the bottom of the large diameter portion 7b and the top of the small diameter portion 7a (J), through which water is circulated by a pump P. In this circulation line 10, a cooler II is installed after the pump P. The system is designed to cool ammonia water whose temperature has risen due to the heat of dissolution of ammonia, making the absorption of ammonia more efficient.

The above-mentioned cooler 1 is a conventional type in which piping is installed inside the cooling water tank, and the cooling water flow q is set to a value such that there is no temperature rise in the ammonia 1 absorption tower 7 (set to 1).

”-6 The circulation line 10 includes a main line 10a connected to the top of the ammonia absorption tower 7 after the cooler 11,
It is directly introduced into the large diameter portion 7h and branched into a bypass line 1ott. The end of the bypass line 101 which is introduced into the large diameter portion 7b is configured to have a large effect of stirring the fluid in this portion.

Further, this ammonia absorption tower 7 is provided with a supply line 12 for supplying new ultrapure water.

l-, the ring line IO is branched after the pump P, and a υ outlet line 15 is provided which is connected to the storage tank 14 via the filter 13. After the branching point of the lever, the circulation line IO and discharge line 15 are equipped with solenoid valves 16 and 17 for opening and closing, respectively, and on the other hand, before the pump P of the circulation line 10, A conductivity meter (sensor) 18 is provided to detect the conductivity of the internal fluid, and when this detected value reaches a predetermined value (the concentration of ammonia water reaches a required value), the solenoid valve 16 of the circulation line 1O is closed, the solenoid valve 17 of the discharge line 15 is opened, and the ammonia water is automatically discharged into the storage tank 14. .

In addition, there is a relationship between the conductivity of ammonia water and the ammonia concentration as shown in Figure 2, and when the concentration exceeds 5 wt%, there is an almost linear correlation on a one-to-one basis, so this conductivity is measured. This allows the ammonia concentration to be detected.

The filter 13 is provided to remove relatively large pieces of dirt that have suddenly been mixed in.

Further, the storage tank 14 is sealed, and the inside is filled with pipe 2.
0 is filled with inert gas such as high-purity nitrogen gas to prevent contamination with dust and reactions with carbon dioxide in the air.

The piping and equipment A that constitute the above-mentioned manufacturing equipment are made of highly corrosion-resistant stainless steel (SUS304), and the gaskets and filters for maintaining airtightness are made of tetrafluoroethylene polymer.

Further, since the pressure regulator 5.9 controls the line pressure so that it does not greatly exceed normal pressure, the withstand pressure of the line is not set particularly high.

In this manufacturing equipment, not only the discharge of the product from the absorption tower 7, but also the supply of ammonia gas to the absorption tower 7, the temperature control of the temperature raising tank 3a of the evaporator 3, etc. are automated, and batch processing is sequentially performed automatically. It is supposed to be carried out in

Next, let's explain the operation of the ammonia water production apparatus configured as described above.

The amount of impurities in the raw liquefied ammonia produced in this production apparatus is not particularly restricted, and commercially available products can be used. Note that pure liquefied ammonia has a boiling point of 133° C. and a heat of vaporization of 327 cal/g.

As shown in FIG. 2, the electrical conductivity reaches its maximum when the ammonia concentration is around 5 wt%, so the ammonia water subjected to surface treatment is left in the absorption tower 7 so that the initial value of the ammonia concentration does not fall below that value. Then fill it with ultrapure water from the supply line 12.

The liquefied ammonia in the sealed raw material tank 1 is sent by its own gas pressure to the evaporator 3 via the control valve 2, where it is vaporized, and then sent to the gas filter 4.

At this time, liquid or solid impurities contained in the liquefied ammonia are filtered out by the gas filter 4.

The ammonia gas that has passed through the gas filter 4 is guided to the ammonia absorption tower 7, where it is dissolved and absorbed in ultrapure water or aqueous ammonia. At this time, the ammonia gas efficiently contacts and reacts in the gas-liquid contact layer 8 with ultrapure water or ammonia water which is ejected from the column head through the circulation line 10 and the main line 10a.

This ammonia water rises in temperature due to the heat of dissolution of ammonia gas. For example, if 28i% ammonia gas is dissolved in ultrapure water at 0°C and no cooling is performed, the temperature of ammonia water is calculated to be 150%. It can even reach temperatures above °C. As shown in Fig. 3, the equilibrium vapor pressure of ammonia water will increase significantly as the temperature rises, so in order to prevent the ammonia dissolution reaction from proceeding, ammonia gas must be sent into the ammonia absorption tower 7. The partial pressure must be increased, and
The pressure resistance of the ammonia absorption tower 7 and the piping must be set higher accordingly. To prevent such a temperature upper limit
In this case, the ammonia water is cooled by the cooler 11 installed in the circulation line 10, and a part of the ammonia water is cooled by the cooler 11 installed in the circulation line 10.
is led to the top of the tower again, and a part of it is routed to the bypass line lOb.
It is injected into the large-diameter portion 7b of the absorption tower 7 through.

The water injected from the bypass line IOb is transferred to the large diameter section 7.
By lowering the concentration of ammonia water in step b and stirring it, the concentration was uniformly adjusted to 1. In addition to efficiently absorbing ammonia, the conductivity meter 18 of the automatic switching device 19
This allows for accurate operation.

In addition, a flow rate adjustment valve is provided in this bypass line lOb,
On the other hand, a temperature discharge or a pressure gauge is provided inside the ammonia absorption tower 7, and the flow of the bypass line IOb is increased or decreased depending on the detected temperature or pressure to control the ammonia absorption reaction, and the pressure is adjusted to : You may choose not to exceed.

The pressure regulator 9 at the top of the absorption tower 7 closes the control valve 6 when the pressure in this area exceeds a predetermined value, thereby regulating the inflow of ammonia gas.

The pressure inside the ammonia absorption tower 7 is kept low by dissolving the ammonia scum, but as the dissolution reaction progresses,
If the temperature rises by -1- because the cooling cannot keep up, the vapor pressure of the ammonia water will also increase and the efficiency of dissolution will drop, so for example, set the pressure adjustment device 9's set pressure horn to 0,
The progress of the reaction is controlled by reducing the pressure at the top to 5 kg/am2.

The rate of such ammonia gas absorption reaction decreases as the ammonia concentration in ammonia water increases5, but
As a result, the gas pressure in the pipes 3c and 4a increases, and when it reaches a predetermined value, the control valve 2 is closed by a signal from the pressure regulator 5, thereby controlling the supply of ammonia gas.

When the concentration of ammonia water, which was gradually concentrated in the process described in 1-, reaches a predetermined value, the conductivity meter will measure the predetermined value (
When the ammonia concentration is 28wt%, the conductivity is 380μ
rJ/cm), the automatic switching device [9:) solenoid valve I6 is closed, the solenoid valve 17 leading to the discharge line 15 is opened, and the ammonia water is conveyed through the filter 13 to the storage tank ■4. be done.

When the impurities in the ammonia water produced in this process were analyzed, it was found that A1.11. Ca, Cu, Fe, Mg.

χ4n, Na, Pb,! According to such an ammonia water production apparatus in which all of En and Zn are 0.0 ippm or less, the internal liquid is circulated in the ammonia absorption tower 7, and a cooler 11 is provided in the circulation line 10. The heat of dissolution of ammonia gas is absorbed, and the ammonia gas is efficiently absorbed without increasing the pressure inside the ammonia absorption tower 7.

Then, the bypass line 10b stirs the water stored at the bottom of the ammonia absorption tower 7, making the temperature and ammonia concentration uniform, so that, for example, only the upper part of the stored water becomes hot water, which inhibits the absorption of ammonia. , the inner wall of the ammonia absorption tower 7 is damaged
<trl, NJ? -4y'/+IQh<Uneven ammonia water level is detected and the automatic switching device does not malfunction.

In the ammonia absorption tower 7, absorption of ammonia gas is performed batchwise (batch type) to stably generate ammonia water, and the concentration of ammonia water is detected and its discharge is automated and dried. In addition to keeping the concentration of the ammonia water generated constant, batch processing is performed automatically in sequence, reducing labor and making the work more efficient.

[Effects of the Invention] As detailed above, the present invention includes an evaporator that raises the temperature of liquefied ammonia and vaporizes it, a filter that filters the vaporized ammonia gas and removes impurities, and a column that removes the bottom fluid. The ammonia absorption tower is equipped with an ammonia absorption tower having a circulation line at the top for dissolving and absorbing the ammonia gas in ultrapure water, and a storage tank for storing ammonia water discharged from the ammonia absorption tower. A sensor that detects the ammonia concentration in ammonia water,
When the detection value of this sensor reaches a predetermined value, the ammonia water in the ammonia absorption tower is discharged to the flood storage tank 2. An automatic switching device is installed, and the above-mentioned circulation pipe 1 A bypass radiator is installed and configured, which is branched off from the circulation line and pours the ammonia in the circulation line directly into the bottom of the ammonia absorption tower to stir and homogenize the water in the bottom of the ammonia absorption tower. 1. The purified ammonia gas is efficiently absorbed into ultrapure water while controlling the reaction at a uniform temperature and pressure f) in an ammonia absorption tower. Therefore, by using commercially available liquefied ammonia as a raw material, it is possible to produce ammonia water at a low cost, without any impurities, and at a constant concentration.In addition, the durability Vr of equipment such as ammonia absorption towers and piping can be improved. Since there is no need to increase
It's true.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the configuration of an ammonia production apparatus according to an embodiment of the present invention, Fig. 2 is a graph showing the relationship between the concentration of ammonia and the conductivity of ammonia water, and Fig. 3 is a graph showing the relationship between the ammonia concentration and the conductivity of ammonia water at various temperatures. It is a graph showing the relationship between concentration and ≦equilibrium vapor pressure. 3... Evaporator, 4... Gas filter, 7...
...Ammonia absorption tower, IO...Circulation line,
10b... Bypass line, 14... Storage tank, 18... Conductivity meter (sensor), 19 - Automatic switching device.

Claims (1)

[Claims] It has an evaporator that raises the temperature of liquefied ammonia and vaporizes it, a filter that filters the vaporized ammonia gas and removes impurities, and a circulation line that refluxes the fluid at the bottom to the top of the tower to make the ammonia gas ultrapure. The ammonia absorption tower is equipped with an ammonia absorption tower that dissolves and absorbs water, and a storage tank that stores the ammonia water discharged from the ammonia absorption tower. an automatic switching device that discharges the ammonia water in the ammonia absorption tower to the storage tank when the detected value reaches a predetermined value; An apparatus for producing ammonia water, characterized in that it is provided with a bypass line that pours the ammonia water into the bottom of the bottle and stirs the ammonia water at the bottom to make it uniform.