WO1997000227A1 - Process for producing high-purity chemicals - Google Patents

Abstract

A process for producing high-purity chemicals, such as high-purity sulfuric acid or high-purity ammonia water, suitable for use in semiconductor manufacture. High-purity sulfuric acid is produced via the absorption step wherein water is brought into contact with gaseous sulfuric anhydride, the stripping step where sulfurous acid gas is separated and removed, and the transporting step conducted through a liquid pumping system wherein the liquid-containing section is made from non-metallic material. High-purity ammonia water is produced via the absorption step wherein ammonia gas is absorbed in water and the step of cooling ammonia water and recirculating the same to the absorption step by utilizing the liquid pumping system wherein the liquid-contacting section is made from non-metallic material. The liquid pumping system is composed of a tank for reserving high-purity chemicals, a transfer tank, supply and discharge pipings, a piping for supplying gases to the transfer tank, and a piping for discharging gases from the transfer tank. This process provides high-purity sulfuric acid and ammonia water freed extremely from impurities such as metals and sulfurous acid gas.

Description

 9 Saito Itoda »High Purity Chemical Manufacturing Method Technical Field

The present invention relates to a method for producing high-purity chemicals (such as high-purity sulfuric acid and high-purity ammonia water) that can be suitably used in a semiconductor production process. More specifically, the present invention relates to a high-purity sulfuric acid from which a metal component as an impurity and sulfur dioxide gas (sulfur dioxide S 0 ₂ ) are highly removed, and a high-purity ammonia water having an extremely low concentration of a metal component as an impurity. And a method for producing the same. Background art

 In the semiconductor manufacturing process, inorganic chemicals such as acids and alcohols, and organic solvents such as alcohols and ketones are used in wafers (including those in the process of being processed into devices). The same is used for etching, cleaning, peeling, etc. Large-scale integrated circuit to be manufactured by such a semiconductor manufacturing process

As (LSI) becomes denser and more highly integrated, various types of contamination (contamination) are affecting the yield, quality, and reliability of semiconductor products. Therefore, it has been required that the chemicals to be used in the semiconductor manufacturing process themselves have few impurities and have as high a purity as possible.

 Normally, a semiconductor manufacturing process includes many elemental technologies (oxidation, film growth, etching, etc.). However, in order to connect these elemental technologies, a cleaning operation, that is, processing by each elemental technology is performed. It is indispensable to remove various contaminants generated by physical and chemical means. Therefore, in the semiconductor manufacturing process,

“Washing” is the most basic and essential technology.

As a cleaning liquid component for silicon wafers in semiconductor processes, for example, Sulfuric acid may be used for the purpose of peeling off or removing contaminated organic substances and contaminated metals by oxidation and the like. However, if a metal component as an impurity is present in the sulfuric acid, there is a possibility that the electrical characteristics of the silicon wafer may be reduced or the device performance obtained may be disadvantageously reduced. In addition, in the case where sulfurous acid gas as an impurity is present in such sulfuric acid, the same disadvantages as described above may occur. Therefore, sulfuric acid used in a semiconductor manufacturing process is required to have a low metal concentration and a low sulfur dioxide gas concentration. However, there has not yet been found a method for producing high-purity sulfuric acid that satisfies such requirements and can be carried out efficiently from an industrial viewpoint.

 —On the other hand, in the semiconductor manufacturing process, ammonia water may be used as a component of a wafer cleaning liquid for the purpose of removing organic substances and / or heavy metals. Ammonia water used for such applications is required to be highly clean and pure, as in the case of sulfuric acid described above. In particular, the presence of metals such as iron, aluminum, sodium, calcium, and magnesium in the ammonia water may significantly reduce the reliability of the obtained semiconductor. As mentioned above, the required level of reliability of semiconductors has been further enhanced in recent years, and for that purpose, high-purity ammonia water in which the concentration of each metal component is controlled to a lower level is required. .

 However, the ammonia water obtained by the conventional method has not always been satisfactory from the viewpoint of the high required level described above.

 An object of the present invention is to provide a method for producing high-purity sulfuric acid from which metal components and sulfurous acid gas as impurities are highly removed.

Another object of the present invention is to provide a method for producing high-purity aqueous ammonia having an extremely low concentration of metal as an impurity. Disclosure of the invention

 As a result of intensive studies, the inventor of the present invention has found that, after the generation of a chemical by gas absorption, the transportation or transfer of the chemical using a liquid pumping system in which the wetted part (a part in contact with the liquid; wetted part) is made of a nonmetallic material. Circulation was found to be extremely effective in achieving the above objectives.

 The method for producing high-purity sulfuric acid of the present invention is based on the above findings. More specifically, the method comprises contacting water with gaseous sulfuric anhydride which may contain sulfurous acid gas as an impurity, Absorbing water into water to produce sulfuric acid;

 Stripping the sulfuric acid with air to separate and remove sulfurous acid gas in the sulfuric acid;

 Transporting at least a portion of the sulfuric acid by a liquid pumping system in which a liquid contact part is made of a nonmetallic material;

 And a liquid storage system for storing the sulfuric acid, a transfer tank for transferring the sulfuric acid, a supply pipe for supplying sulfuric acid to the transfer tank, and the transfer tank. A discharge pipe for discharging sulfuric acid, a gas supply pipe for supplying gas to the transfer tank, and a gas discharge pipe for discharging gas from the transfer tank. .

 According to the present invention, further, an absorption step of generating ammonia water by absorbing ammonia gas into water;

 Cooling the ammonia water generated in the absorption step and then circulating the ammonia water to the absorption step again, the method including a step of performing the circulation by a liquid pumping system in which a liquid contact part is made of a nonmetallic material;

And a transfer tank for transferring the ammonia water, a supply pipe for supplying the ammonia water to the transfer tank, and a discharge pipe for discharging the ammonia water from the transfer tank. A gas supply pipe for supplying gas to the transfer tank; and a gas discharge for discharging gas from the transfer tank. The present invention provides a method for producing high-purity aqueous ammonia, comprising a pipe. The most significant feature of the present invention having the above-described configuration is that the liquid pumping system in which the liquid contact portion is made of a nonmetallic material transports or circulates the chemical generated by gas absorption. That is, according to the research of the present inventor, it was difficult to control the metal concentration in a high-purity chemical solution (sulfuric acid, ammonia water, etc.) to a sufficiently low level in the conventional method because of the problem of centrifugal pumps and the like. It has been found that it is based on transporting or circulating the high-purity chemical solution using an element having a liquid contact drive unit (rotating part, sliding part, etc.).

 More specifically, according to the study of the present inventors, in the conventional high-purity chemical liquid manufacturing system, the liquid is rotated from a liquid contact rotating part (or a liquid contact sliding part) such as a bearing constituting the pump into the chemical liquid. It was found that the metal was eluted, increasing the metal concentration in the high-purity chemical. As a result of further research based on such findings, the present inventors have found that using a liquid pumping system in which the liquid contact part is made of a nonmetallic material makes it possible to elute metal into a highly pure chemical solution. It has been found that it is possible to carry out sufficient transportation or circulation while controlling extremely effectively. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a block diagram of a block diagram showing a schematic configuration of an example of an apparatus for producing high-purity sulfuric acid for carrying out the production method of the present invention.

 FIG. 2 is a block diagram of a block diagram showing a schematic configuration of another example of a high-purity sulfuric acid production apparatus for carrying out the production method of the present invention.

 FIG. 3 is a block diagram flow chart showing a schematic configuration of a high-purity sulfuric acid production apparatus used in Example 1 described later.

FIG. 4 is a block-type flow diagram showing a schematic configuration of an example of an apparatus for producing high-purity aqueous ammonia for carrying out the production method of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, the present invention will be described in detail with reference to the drawings as necessary.

 (Production method of high purity sulfuric acid)

 FIG. 1 is a flow chart showing an example of a high-purity sulfuric acid production apparatus for performing the production method of the present invention. In FIG. 1, reference numerals are: 1: sulfuric anhydride, 2: water, 3: high-purity sulfuric acid, 4: air, 5: vent, 6: absorption tower, 7: sulfuric acid, 8: cooler, 9: storage Evening, 10: stripping tower, 11: sulfuric acid supply pipe, 12: transfer sunset inlet valve, 13: gas supply pipe, 14: gas inlet valve, 15: gas discharge pipe, 16: gas outlet valve, 17: transfer Tank, 18: transfer tank outlet valve, 19: sulfuric acid discharge pipe.

 Referring to FIG. 1, in such an embodiment, high-purity sulfuric acid (3) is produced from gaseous sulfuric anhydride (1), which may contain sulfurous acid gas as an impurity, and water (2). . This manufacturing method includes the following steps (a) to (c).

(a) Absorption step: In the absorption tower (6), water (2) is brought into contact with gaseous sulfuric anhydride (SO ₃ ) (1) to absorb gaseous sulfuric anhydride into water, thereby reducing Obtaining sulfuric acid (7) which may optionally contain sulfurous acid gas;

 (b) Transporting step: A step of transporting and supplying at least a portion of the above-mentioned sulfuric acid to the following stripping step, wherein the sulfuric acid supplied from the absorption tower is transferred to a transfer tank (17) in which the liquid contact part is a nonmetallic material. ), Liquid pressure feed including sulfuric acid supply piping to the transfer tank (11), sulfuric acid discharge piping from the transfer tank (19), gas supply piping to the transfer tank (13), and gas discharge piping from the transfer tank (1.5) Transporting sulfuric acid by the system;

 (c) Stripping process: In a stripping tower (10), sulfuric acid supplied from the transportation process is stripped with air (4) to separate and remove sulfurous acid gas in sulfuric acid from sulfuric acid, thereby achieving high purity. A step of obtaining sulfuric acid (3).

(Absorption process) In the absorption step of the present invention, water (2) and gaseous sulfuric anhydride are added in the absorption tower (6).

This is a step of obtaining sulfuric acid (7), which may contain sulfurous acid gas as an impurity, by bringing gaseous sulfuric anhydride into water by contacting with (1).

The above raw material serving as gaseous sulfur trioxide (S0 ₃₎ is not particularly limited, for ease of impurity-removal, the content of sulfur dioxide (S0 ₂₎ is less than 100 wt ppm (more 10 ppm by weight The following is preferred. As such sulfuric anhydride, a commercially available sulfuric anhydride can be used, and the commercially available sulfuric anhydride usually contains sulfur dioxide gas at about 10 to 100 ppm by weight.

Water (2) used as a raw material with sulfuric anhydride (S0 ₃₎ described above is preferably-called ultra-pure water. Ultrapure water that can be suitably used in the present invention has a specific resistance of 18 18Ω · cm or more, a number of fine particles of 10 / ml or less, and a chlorine concentration Ορρπκ of 10 colonies / ml or less. For details of such pure water, reference can be made, for example, to Takashi Banbo, “Silicon LSI and Chemistry,” p. 101 (1993), Dainippon Tosho.

 As the absorption tower (6) for bringing sulfuric anhydride and water into contact with each other, a conventional one such as a packed tower can be used. The absorption tower is preferably filled with packing such as Raschig rings.

 In this absorption step, for example, gaseous sulfuric anhydride is supplied from the lower part of the absorption tower (packed tower), ultrapure water is supplied from the upper part of the absorption tower, and both are brought into contact in the absorption tower. Good. Here, air may be supplied from the lower part of the absorption tower for the purpose of removing sulfurous acid gas. The absorption tower in this step may also be supplied with sulfuric acid recycled from a transportation step described later, and combined with the ultrapure water, and then contacted with gaseous sulfuric anhydride.

 (Transportation process) '

The transporting step of the present invention is a step of transporting and supplying at least a part of the sulfuric acid obtained in the absorption step to the following stripping step. In this transportation process The transfer of sulfuric acid supplied from the absorption tower to the transfer tank (17), the sulfuric acid supply pipe to the transfer tank (11), the sulfuric acid discharge pipe from the transfer tank (19), It is preferable that sulfuric acid be transported by a liquid pumping system including a gas supply pipe (13) to the transfer tank and a gas discharge pipe (15) from the transfer tank. (Liquid pumping system)

 In the liquid pumping system according to the present invention, the transfer by the pressure of the liquid is basically performed by the same mechanism as that of the biston flow. That is, the gas pushes the liquid out of the tank.

 More specifically, the principle of pumping in the present invention is based on Bernoulli's theorem (for details of the theorem, see, for example, Isao Okada, “Chemical Engineering”, pp. 54-59 (1987) Tokyo Denki University Press) When the pressure energy (p) of the gas exceeds the sum of the potential energy (Z) and the friction loss (f) of the liquid, the liquid moves (motion). To start.

 Stationary state: P. (Pressure) = Z (potential energy) + f (friction loss)

 Moving state: (pressure) = Z (potential energy) + f (friction loss) + V (motion)

(However, P ₁ > P ₀ )

The liquid pressure feeding system that can be suitably used in the present invention includes: a transfer tank (17) whose liquid contact portion is made of a non-metallic material; a sulfuric acid supply pipe (11) to the transfer tank; This system includes a gas supply pipe to the transfer tank (13) and a gas discharge pipe from the transfer tank (15). Non-metallic materials that make up the liquid contacting part of the transfer tank include fluoroplastics such as polytetrafluoroethylene (Teflon) (for example, tetrafluoroethylene-perfluorovinyl ether copolymer (PFA), Tetrafluoroethylene (PTFE) or the like can be suitably used. The gas used in the liquid pumping system is not particularly limited as long as it is a clean gas, but a clean gas such as air or nitrogen is preferable. Here, "clean gas" refers to a gas from which fine particles have been removed. The gas in the pumping system is, from a safety point of view, It is preferably a gas filtered through a 0.05 to 0.2111 filter, and the pressure of the gas is 1.0 to 2.0 kg / cm ² G (G: gauge pressure; a value obtained by subtracting the atmospheric pressure. Yes, it is preferable to be about 0 kg / cm ² G = lkg / cm ² ). The temperature of the sulfuric acid at the outlet of the cooler installed upstream of the storage tank (9) is preferably 60 to 180 ° C from the viewpoint of stripping. The temperature is 60. If it is less than C, the effect of stripping sulfurous acid gas in sulfuric acid may be insufficient. On the other hand, if the temperature exceeds 18 CTC, elution of metal into sulfuric acid may be accelerated.

 In the present invention, the above-described liquid pumping system is used in the following method.

'Is preferred. That is, the sulfuric acid in the storage tank (9) is supplied by gravity to the transfer tank (17) through the sulfuric acid supply pipe (11). At this time, transfer tank outlet # (18) is closed and sulfuric acid is stored in the transfer tank. Next, the transfer tank inlet valve (12) is closed, the transfer tank outlet valve (18) is opened, and gas is supplied to the transfer tank from the gas supply pipe (13) to the transfer tank. Sulfuric acid is pumped out of the transfer tank. At this time, keep the gas outlet valve (16) closed. When the transfer of sulfuric acid in the transfer tank is completed, close the gas inlet valve (14), open the gas outlet valve (16), and supply the sulfuric acid in the storage tank (9) to the transfer tank (17) again. Enter the cycle. In this way, sulfuric acid is transported by the liquid pumping system.

 As shown in FIG. 1, it is preferable that two or more of the above-mentioned liquid pumping systems are arranged in parallel with the flow of sulfuric acid. In the aspect in which the liquid pumping systems are installed in parallel in this way, by shifting the time cycle of each liquid pumping system and operating, a more continuous transport or circulation of sulfuric acid becomes possible. The above operation (such as sequential control of opening and closing of the valve) of the liquid pressure feeding system described above can be automatically performed by using a known automatic control system.

In the embodiment shown in FIG. 1, at least a part of the sulfuric acid is striped in this step. The remaining sulfuric acid is recycled to the absorption process.

 (Striping process)

 In the stripping step of the present invention, in the stripping tower (10), sulfuric acid supplied from the transportation step (by operating the liquid pumping system) may be stripped with air (4) to remove the sulfuric acid. In this step, high-purity sulfuric acid (3) is obtained by separating and removing certain sulfurous acid gas from sulfuric acid.

 As the stripping tower, the same one as the absorption tower described in the absorption step can be used. In this step, for example, it is possible to adopt a method in which sulfuric acid to be stripped is supplied from the upper part of the stripping tower, air is supplied from the lower part of the stripping tower, and both are brought into contact in the stripping tower. . (Other aspects)

 In the present invention, as a modification of the above-described embodiment of FIG. 1, the stripping step and the transporting step may be as follows as shown in FIG.

 Stripping process: In a stripping tower (10), sulfuric acid (7) supplied from the absorption process is stripped with air (4) to separate and remove sulfurous acid gas that may be contained in sulfuric acid from sulfuric acid. Obtaining high-purity sulfuric acid (3);

 Transporting step: A step of branching and collecting at least a part of the sulfuric acid supplied from the above-mentioned stripping step as product sulfuric acid. The sulfuric acid supplied from the absorption tower is cooled (after being cooled by the cooler (8)) and stored in the storage tank ( 9), the sulfuric acid in the storage tank is further transferred to the transfer tank (17), the sulfuric acid supply pipe to the transfer tank (11), and the sulfuric acid discharge pipe from the transfer tank (19). ), The process of transporting sulfuric acid by a liquid pressure feeding system including a gas supply pipe (13) to the transfer tank and a gas discharge pipe (15) from the transfer tank.

 The configuration in FIG. 2 other than the above is the same as that described in FIG.

(High purity sulfuric acid) The high-purity sulfuric acid obtained by the above-described production method of the present invention can have a metal content of 10 wt% or less and a sulfurous acid gas concentration of 1 wtppm or less. Such high-purity sulfuric acid can be optimally used as a cleaning solution for silicon wafers and the like in a semiconductor manufacturing process.

 (Production method of high-purity ammonia water)

 FIG. 4 is a flowchart showing an example of a high-purity ammonia water producing apparatus for carrying out the producing method of the present invention. In FIG. 4, reference numerals 21: ammonia gas, 22: water, 23: ammonia water, 24: absorber, 25: cooler, 26

: Transfer tank, 27: ammonia water supply pipe, 28: ammonia water discharge pipe, 29: gas supply pipe, 30: gas discharge pipe, '31: transfer tank inlet valve, 32: transfer tank outlet valve, 33: gas inlet Valve, 34: gas outlet valve.

 Referring to FIG. 4, in such an embodiment, ammonia gas (21) is

(22) to produce high-purity aqueous ammonia (23). This manufacturing method includes the following steps (A) and (B).

 (A) absorption step: in the absorption device (24), a step of generating ammonia water by absorbing ammonia gas into water;

 (B) Circulation step: a step in which the ammonia water obtained in the above-mentioned absorption step is led to a cooler (25) to be cooled, and then circulated again to the absorption step, and the liquid contact part is a non-metallic material Transfer tank (26), Ammonia water supply pipe to transfer tank (27), Ammonia water discharge pipe from transfer tank (28), Gas supply pipe to transfer tank

A process of circulating ammonia water by a liquid pumping system including (29) and a gas discharge pipe (30) from the transfer tank.

 (Ammonia gas)

It is preferable to remove minute impurities in the ammonia gas as a raw material using a high-precision filter (pore size: 0.05 / m or less) before absorbing it into water. The other raw material water is ultrapure water as described above (specific resistance is 18ΜΩ · cm Above) are preferably used.

 (Absorption process)

 The absorption step is a step of obtaining ammonia water by absorbing ammonia gas into water in an absorption device. As the absorber, any of an absorption tower and an absorption tank can be used. Here, the absorption tower is a tower-type absorption device filled with packing material, and the absorption tank is a tank-type absorption device having a blow-out portion of ammonia gas in a lower part. As the absorption step, a known step generally used in the production of aqueous ammonia can be used.

 In the above absorption step, the ammonia gas is absorbed by water to produce ammonia water. At this time, a considerable amount of heat of absorption is generated due to the absorption of the ammonia gas, and the temperature of the ammonia water rises. Therefore, in order to increase the concentration of the aqueous ammonia, it is preferable to provide a circulation step of recirculating the aqueous ammonia to the absorption step while cooling the aqueous ammonia.

 (Circulation process)

 In the circulation step of the present invention, the ammonia water obtained in the absorption step is guided to a cooler (25) to be cooled, and then circulated again to the absorption step, wherein the liquid contact part is a nonmetallic material Transfer tank (26), ammonia water supply pipe to transfer tank (27), ammonia water discharge pipe from transfer tank (28), gas supply pipe to transfer tank (29) and transfer tank In this step, the ammonia water is circulated by the liquid pumping system including the gas discharge pipe (30).

 As the above-described cooler, a cooler including a known heat exchanger or the like can be used without particular limitation.

 (Liquid pumping system)

The liquid pumping system in the embodiment of FIG. 4 includes a transfer tank (26) in which the liquid contact portion is made of a non-metallic material, an ammonia water supply pipe (27) to the transfer tank, and an ammonia water discharge pipe (2) from the transfer tank. 8), gas supply piping to the transfer tank (29) and transfer · This system includes a gas discharge pipe (30) from the feed tank. As the nonmetallic material forming the liquid contact part of the transfer tank, a fluorine resin such as polytetrafluoroethylene (Teflon) can be exemplified as in the case of the above-mentioned sulfuric acid production.

As the gas used in the liquid pumping system, a clean gas such as air or nitrogen is preferable as in the case of the above-mentioned sulfuric acid production. The pressure of the gas is preferably about 1.0 to 1.9 kgZcm ² .

 A preferred method of using the above liquid pumping system is as follows.

 That is, the ammonia water generated by the absorption device (24) is supplied to the transfer tank (26) by gravity through the ammonia water supply pipe (27). At this time, the transfer tank outlet valve (32) is closed and ammonia water is stored in the transfer tank. Next, the transfer tank inlet valve (31) is closed, the transfer tank outlet valve (32) is opened, and gas is supplied to the transfer tank from the gas supply pipe (29) to the transfer tank. The ammonia water inside is pumped out from the transfer tank. At this time, keep the gas outlet valve (34) closed. When the transfer of the ammonia water in the transfer tank is completed, close the gas inlet valve (33), open the gas outlet valve (34), and supply the ammonia water in the absorber (24) to the transfer tank (26) again. Enter the cycle to do. In this way, circulation of the ammonia water is performed.

 As shown in FIG. 4, it is preferable that two or more of the above-mentioned liquid pumping systems are arranged in parallel with the flow of ammonia water. In such an embodiment, a more continuous circulation of the ammonia water is made possible by operating the liquid pumping system and the time cycle of each unit at a different time.

 The above operation of the liquid pumping system can be automatically performed by using a known automatic control system. ―

<Example> ''

 Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1 Referring to FIG. 3, 200 kg of 89% by weight sulfuric acid was injected into a Teflon tank (capacity: 200 L). The sulfuric acid, ultrapure water: to (resistivity 18ΜΩ · cm or more), which has been prepared by absorbing gaseous sulfur trioxide (S0 _3), as non neat S0 ₂ (the sulfur dioxide) l Oppm and metal impurities as shown in Table 1 below.

 The above impurity analysis was performed by the ICP-MS method. More specifically, after the sample solution to be treated is divided into fine mist by a nebulizer, a metal element in the sample solution is ionized using an inductively coupled plasma (ICP), and the ionized element is ionized. Was separated by mass using the mass spectrometer described above, and the types and amounts of metal elements in the sample solution were determined.

 The sulfuric acid in the tank 9 was heated to a liquid temperature of 80 using the liquid pumping system shown in FIG. C, liquid circulation was performed at an average flow rate of 8 L / hr for 24 hours.

The liquid pumping system used here consists of a storage tank 9 (capacity: 20 L) made of Teflon, the liquid contact part of which is a non-metallic material, a sulfuric acid supply pipe 11 to the transfer tank 17, and a sulfuric acid discharge pipe from the transfer tank 17. 19, a gas supply pipe 13 to the transfer tank 17, and a gas discharge pipe 15 from the transfer tank. The components of the liquid pumping system were made of stainless steel, but their wetted parts were all coated with Teflon-lining (thickness: about 3 mm). Clean air with a pressure of 2.0 kg / cm ² G was used as the gas for the liquid pumping system.

 For the high-purity sulfuric acid obtained as described above, the same metal content analysis as before the circulation was performed. The results obtained are shown in Table 1 below.

Comparative Example 1

200 kg of 89% by weight sulfuric acid as in Example 1 except that a commercially available Teflon centrifugal pump was used instead of the liquid pumping system used in Example 1 (Figure 3) and the average flow rate was 8 L / hr. For 24 hours. The results obtained are shown in Table 1 below. 7/00227 1629

<Table 1> Before circulation

 Metal content in sulfuric acid (ppt) <Example 1> <Comparative example 1> Aluminum 10 12 1100

 2 3 1200

 Magnesium 5 5 112

 14 15 2175

Example 2

Using the apparatus shown in Fig. 4, high-purity ammonia water was produced. An absorption tank with a capacity of 1 Om ³ is used as the absorption device (24), a tank with a content of 0.02 m ³ is used as the transfer tank (26), and a pressure of 1.9 kg / cm ² of clean air was used.

1 Om ³ ultrapure water (specific resistance: 18ΜΩ · cm or more) was charged into the absorption tank, and ammonia gas was supplied to the absorption tank at a rate of 30 kg / hr to generate ammonia water. The ammonia water thus produced was circulated for 24 hours at a liquid temperature of 25 ° C. and an average flow rate of 200 L / min under the conditions described above to obtain 29% by weight of high-purity ammonia water. .

 The content of gold in the aqueous ammonia was measured by the same ICP-MS method as in Example 1. As a result, constant values of 5 wt% of iron, 5 wt% of aluminum, and 1 wt% of calcium were obtained.

Comparative Example 2

Except that a commercially available centrifugal pump was used instead of the liquid pumping system used in Example 2. Produced ammonia water in the same manner as in Example 2.

 The metal content in the ammonia water thus obtained was 13 weight parts per weight of iron, 3 weight parts per million of aluminum, and 5 weight parts per billion of calcium. Industrial applicability

 As described above, according to the present invention, an absorption step in which water is brought into contact with gaseous sulfuric anhydride which may contain a sulfurous acid gas as an impurity, and the sulfuric anhydride is absorbed in water to generate sulfuric acid. When ;

 Stripping the sulfuric acid with air to separate and remove the sulfurous acid gas in the sulfuric acid;

 Transporting at least a portion of the sulfuric acid by a liquid pumping system in which a liquid contact part is made of a nonmetallic material;

 And a liquid storage system for storing the sulfuric acid, a transfer tank for transferring the sulfuric acid, a supply pipe for supplying sulfuric acid to the transfer tank, and the transfer tank. A method for producing high-purity sulfuric acid, comprising: a discharge pipe for discharging sulfuric acid; a gas supply pipe for supplying gas to the transfer tank; and a gas discharge pipe for discharging gas from the transfer tank. Provided.

 According to the present invention, further, an absorption step of generating ammonia water by absorbing ammonia gas into water;

 Cooling the ammonia water generated in the absorption step and then circulating the ammonia water to the absorption step again, the method including a step of performing the circulation by a liquid pumping system in which a liquid contact part is made of a nonmetallic material;

And a transfer tank for transferring the ammonia water, a supply pipe for supplying the ammonia water to the transfer tank, and a discharge pipe for discharging the ammonia water from the transfer tank. A gas supply pipe for supplying gas to the transfer tank; and a gas discharge for discharging gas from the transfer tank. The present invention provides a method for producing high-purity aqueous ammonia, comprising a pipe. According to the above-described production method of the present invention, it is a high-purity sulfuric acid from which a metal component as an impurity and a sulfurous acid gas have been highly removed, or a high-purity ammonia water from which a metal component as an impurity has been highly removed, Sulfuric acid or high-purity ammonia water that can be optimally used in a semiconductor manufacturing process can be manufactured.

Claims

»3 ή 1. contacting water with gaseous sulfuric anhydride which may contain sulfurous acid gas as an impurity, and absorbing the sulfuric anhydride into water to form sulfuric acid; and stripping the sulfuric acid with air. Stripping to separate and remove sulfurous acid gas in the sulfuric acid;  Transporting at least a portion of the sulfuric acid by a liquid pumping system in which a liquid contact part is made of a nonmetallic material;  And a liquid storage system for storing the sulfuric acid, a transfer tank for transferring the sulfuric acid, a supply pipe for supplying sulfuric acid to the transfer tank, and the transfer tank. High-purity sulfuric acid, comprising: a discharge pipe for discharging sulfuric acid; a gas supply pipe for supplying gas to the transfer tank; and a gas discharge pipe for discharging gas from the transfer tank. Manufacturing method.  2. The production method according to claim 1, wherein the absorption step, the transportation step, and the stripping step are performed in this order; and, in the transportation step, at least a portion of the sulfuric acid generated in the absorption step is supplied to the stripping step.  3. The method according to claim 1, wherein the absorption step, the stripping step, and the transporting step are performed in this order; and in the transporting step, at least a part of the sulfuric acid stripped in the stripping step is branched and collected as product sulfuric acid. Production method.  4. The production method according to claim 1, wherein two or more liquid pumping systems arranged in parallel to the sulfuric acid flow are used.  5. The method according to claim 1, wherein air or nitrogen is used as a gas in the liquid pumping system.  6. an absorption step of generating ammonia water by absorbing ammonia gas into water; After cooling the ammonia water generated in the absorption step, it is circulated again to the absorption step Performing the circulation by a liquid pumping system in which the liquid contact part is made of a non-metallic material;  And a transfer tank for transferring the ammonia water, a supply pipe for supplying the ammonia water to the transfer tank, and a discharge pipe for discharging the ammonia water from the transfer tank. A gas supply pipe for supplying gas to the transfer tank; and a gas discharge pipe for discharging gas from the transfer tank.  7. The production method according to claim 6, wherein two or more liquid pumping systems arranged in parallel with the flow of the ammonia water are used.  8. The method according to claim 6, wherein air or nitrogen is used as the gas in the liquid pumping system.