JP7514604B2 - Regenerant supply device and ultrapure water production device - Google Patents

Description

The present invention relates to a regenerant supply device and an ultrapure water production device.

In the manufacturing process of semiconductor devices and liquid crystal devices, ultrapure water, from which impurities have been highly removed, is used as a cleaning liquid for cleaning electronic components such as semiconductor wafers and glass substrates. Ultrapure water is generally produced by sequentially treating raw water (river water, groundwater, industrial water, etc.) in a pretreatment system, a primary pure water system, and a secondary pure water system (subsystem). It is known that metal components dissolve from the piping and pumps used in such ultrapure water production equipment, which causes deterioration of the water quality of the ultrapure water. In particular, in recent years, with the high integration and miniaturization of semiconductor devices, ultrapure water with a metal concentration at the pg/L level is required, and it is necessary to reduce the amount of metal components dissolved as much as possible. In response to this, several measures have been proposed to minimize the effects of metal component dissolution (see, for example, Patent Documents 1 and 2).

JP 2004-154713 A JP 2011-224489 A

Some of the primary pure water systems and subsystems mentioned above are equipped with ion exchange resin towers filled with ion exchange resin, and some are further equipped with a regenerant supply device that supplies a regenerant to the ion exchange resin tower to regenerate the ion exchange resin. In such regenerant supply devices, the tank that stores the regenerant and the inner surface of the pipes that transport the regenerant are generally lined with rubber to prevent the elution of metal components by the regenerant, such as acids and alkalis. However, even with this, the quality of the ultrapure water can still be affected by the elution of metal components, and the cause of this is currently not clearly understood.

The object of the present invention is to provide a regenerant supply device and an ultrapure water production device that minimize the effects of leaching of metal components.

In order to achieve the above-mentioned object, the regenerant supply device of the present invention is for supplying a regenerant consisting of an acid that regenerates a cation exchange resin to an ion exchange resin tower filled with a cation exchange resin inside in an ultrapure water production apparatus, and comprises a tank that is installed outdoors and has a rubber lining on its inner surface for storing the regenerant, piping that connects the tank to the ion exchange resin tower and has a rubber lining on its inner surface , and a temperature control mechanism that controls the temperature of the regenerant supplied from the tank to the ion exchange resin tower through the piping, and the temperature control mechanism has a heat-insulating material made of urethane foam that insulates the inside of the tank from the heat of the outside air and suppresses the temperature rise of the regenerant inside the tank.

The ultrapure water production apparatus of the present invention also includes an ion exchange resin tower filled with a cation exchange resin, and the regenerant supply device described above.

With this type of regenerant supply device and ultrapure water production system, the temperature of the regenerant can be controlled to prevent the leaching of metal components from tanks and piping, which can occur when the regenerant becomes too hot.

As described above, according to the present invention, the effects of leaching of metal components can be minimized.

1 is a schematic configuration diagram of an ultrapure water production system according to a first embodiment of the present invention. 1 is a graph showing the results of measuring the change in the amount of metal components eluted from the lining material when the temperature of the regenerant is changed. FIG. 6 is a schematic configuration diagram of a tank in a regenerant supplying device according to a second embodiment of the present invention. FIG. 11 is a schematic configuration diagram of an ultrapure water production system according to a third embodiment of the present invention.

The following describes an embodiment of the present invention with reference to the drawings. In this specification, the regenerant supplying device of the present invention is described using an example in which it is used to regenerate ion exchange resin (cation exchange resin) in an ultrapure water production system, but it can also be suitably used as a cleaning liquid supplying device that supplies cleaning liquid (acid) in the manufacturing process of semiconductor devices and liquid crystal devices.

First Embodiment
FIG. 1 is a schematic diagram of an ultrapure water production system according to a first embodiment of the present invention.

The ultrapure water production system 1 produces ultrapure water by sequentially treating the water to be treated, and has an ion exchange resin tower 2 filled with a cation exchange resin inside. The ion exchange resin tower 2 constitutes the primary pure water system or secondary pure water system (subsystem) of the ultrapure water production system 1, and has the function of mainly removing metal ions (e.g. calcium ions) from the water to be treated. Note that other devices that constitute the primary pure water system or subsystem (such as various membrane filtration devices, ultraviolet oxidation devices, and electrical deionization water production devices) are not shown here.

Furthermore, the ultrapure water production system 1 has a regenerant supplying device 3 that supplies an acid (e.g., hydrochloric acid or sulfuric acid) to the ion exchange resin tower 2 as a regenerant for regenerating the cation exchange resin when the ion exchange group of the cation exchange resin is saturated and the processing performance of the ion exchange resin tower 2 is reduced. The regenerant supplying device 3 is installed outdoors and has a tank 10 that stores the regenerant and a pipe 20 that connects the tank 10 to the ion exchange resin tower 2. The tank 10 is made of a lightweight, high-strength, and corrosion-resistant material, such as fiber-reinforced plastic (FRP), and its inner surface is lined with an acid-resistant material. The pipe 20 is made of, for example, polyvinyl chloride, and its inner surface is lined with an acid-resistant material, similar to the tank 10. Examples of the lining material used here include natural hard rubber and butyl rubber.

However, especially in the summer when the influence of the outside air temperature and direct sunlight is large, the outer surface of the tank 10 installed outdoors may become hot, and the regenerant inside the tank 10 may also become hot. In addition, the regenerant is retained inside the piping 20, but since the amount of the regenerant is smaller than that inside the tank 10, it is more susceptible to the influence of the outside air temperature and direct sunlight and may become hotter. In this embodiment, in order to block such heat from the outside air and appropriately manage the internal temperatures of the tank 10 and the piping 20, the tank 10 and the piping 20 are provided with heat shielding materials 13, 23, respectively. Specifically, the tank 10 has a double-wall structure consisting of an inner wall 11 and an outer wall 12, and a heat shielding material 13 is arranged in the gap between the inner wall 11 and the outer wall 12. In addition, the piping 20 also has a double-pipe structure consisting of an inner pipe 21 and an outer pipe 22, and a heat shielding material 23 is provided in the gap between the inner pipe 21 and the outer pipe 22. It is preferable to use urethane foam as the material for the heat shields 13 and 23 because it is acid-resistant. In addition, urethane foam is lightweight and easy to process, and is also preferable because it can be easily installed by simply filling the gap and curing it.

The installation of such heat shields 13, 23 is based on the knowledge that if the temperature of the regenerant rises due to improper temperature management, the amount of metal components leaching from the lining applied to the inner surface of the tank 10 and the piping 20 will increase. The experimental results that led to this knowledge are explained below.

The inventors measured the change in the amount of metal components eluted from the lining material when the temperature of the regenerant was changed. Specifically, a small plastic bottle (polyethylene bottle) was prepared, the lining material and 1N hydrochloric acid were sealed inside, and these were stored for 20 hours each at room temperature (23°C) and high temperature (60°C), and the concentrations of various metals contained in the hydrochloric acid removed were then measured. Natural hard rubber was used as the lining material, and the metal concentrations were measured using an inductively coupled plasma optical emission analyzer.

Figure 2 is a graph showing the measurement results of various metal concentrations, showing the ratio of various metal concentrations at high temperatures when the concentration of each metal at room temperature is taken as 100%. As is clear from this graph, it was confirmed that the metal concentration at high temperatures was higher than at room temperature for all metals measured. This shows that as the temperature of the hydrochloric acid in contact with the lining material increases, the amount of metal components eluted from the lining material increases.

From this perspective, in this embodiment, as described above, heat shields 13, 23 are provided to thermally insulate the inside of tank 10 and piping 20 from the outside. Heat shields 13, 23 function as a temperature control mechanism that controls the temperature of the regenerant supplied from tank 10 through piping 20 to ion exchange resin tower 2, and can appropriately control the temperature of the regenerant so that it does not become excessively hot. This makes it possible to suppress the elution of metal components from the lining applied to the inner surface of tank 10 and piping 20, which may occur when the regenerant becomes hot, and to reduce the metal concentration in the ultrapure water produced by ultrapure water production apparatus 1 as much as possible.

In this embodiment, heat shielding materials 13, 23 are placed in the gaps in the double wall structure of the tank 10 and the gaps in the double pipe structure of the piping 20, respectively, but the method of installing the heat shielding materials is not limited to this. For example, the heat shielding materials can be placed so as to cover the outer periphery of the tank, or so as to cover the outer periphery of the piping. This makes it possible to install the heat shielding materials in existing tanks and piping, and makes it possible to additionally implement temperature management of the regenerant even in existing regenerant supply devices. Note that, as described above, it is preferable to use urethane foam as the heat shielding material, as it is easy to install in such existing regenerant supply devices.

In the illustrated example, the heat shielding material 23 is installed on the portion of the piping 20 that is exposed to the outdoors, but the heat shielding material 23 may be installed over the entire range of the piping 20. For example, if the ion exchange resin tower 2 is installed outdoors and the piping 20 is also installed outdoors, it is preferable that the heat shielding material 23 is installed over the entire range of the piping 20.

Second Embodiment
3 is a schematic diagram of a tank in a regenerant supplying device according to a second embodiment of the present invention. This embodiment is a modification of the first embodiment, in which the configuration of the tank in the regenerant supplying device is changed. Therefore, only the configuration of the tank in this embodiment will be described below.

In this embodiment, an air circulation means 30 is provided to circulate air between the inner wall 11 and the outer wall 12 of the tank 10 as a temperature control mechanism for controlling the temperature of the regenerant inside the tank 10. The air circulation means 30 has an air inlet 31 provided at the bottom of the tank 10, an air outlet 32 provided at the top of the tank 10, and a baffle plate 33 provided in the hollow portion S between the inner wall 11 and the outer wall 12, forming a spiral passage that connects the air inlet 31 and the air outlet 32.

With this type of air circulation means 30, even if the air in the hollow section S becomes hot due to the outside air temperature or direct sunlight, the air can be moved to the top of the tank 10 and discharged to the outside, making it possible to appropriately manage the temperature of the regenerant in the tank 10. Note that air may be forcibly introduced into the hollow section S by installing a blower or the like in the air inlet 31 or air outlet 32, but since this requires a separate power source, when forcibly introducing air, it is preferable to introduce conditioned air from the building in which the ion exchange resin tower 2 is installed, for example, using a duct or the like.

A water-cooled system could be used to control the temperature of the regenerant, but this would require the installation of piping within the hollow section S of the tank 10, which could lead to increased costs and weight for the tank 10, and would also require measures to prevent water leakage due to deterioration over time. In addition, not only would a pump be required to circulate the cooling water, but the tank 10 used in this embodiment is very large, with a capacity of over 10,000 L, so a large amount of cooling water would also be required. From this perspective, it is preferable to control the temperature of the regenerant inside the tank 10 by circulating air within the hollow section S, as in this embodiment.

Third Embodiment
4 is a schematic diagram of an ultrapure water production system according to a third embodiment of the present invention. This embodiment is an embodiment that can be additionally applied to the first and second embodiments, and therefore, although explanation is omitted, the heat shield material of the first embodiment and the air circulation means of the second embodiment may be provided in the regenerant supply device of this embodiment.

The regenerant supply device 3 of this embodiment has a heat exchanger 41, a temperature sensor 42, and a drain valve (drainage means) 43 as a temperature control mechanism for the regenerant. The heat exchanger 41 is installed in the building in which the ion exchange resin tower 2 is installed in the piping 20, specifically, near the boundary between the building and the outdoors, and has the function of cooling the regenerant. The temperature sensor 42 is installed downstream of the heat exchanger 41 in the piping 20 and has the function of detecting the temperature of the regenerant flowing in the piping 20. The drain valve 43 is installed further downstream than the temperature sensor 42 and has the function of discharging the regenerant flowing in the piping 20 to the outside based on the detection result of the temperature sensor 42. Specifically, the drain valve 43 discharges the regenerant to the outside (for example, an acid neutralization tank, etc.) when the temperature of the regenerant is equal to or higher than a predetermined temperature, and supplies the regenerant directly to the ion exchange resin tower 2 when the temperature of the regenerant is lower than the predetermined temperature.

In the ultrapure water production system 1, similar linings are applied to the liquid-contacting surfaces of other components other than the tank 10 and the piping 20, and such linings may also cause an increase in the amount of metal components eluted due to contact with the high-temperature regenerant (acid). In contrast, in this embodiment, the above-mentioned configuration makes it possible to prevent the high-temperature regenerant from coming into contact with the linings applied to components other than the tank 10 and the piping 20, i.e., to reduce the amount of metal components eluted from such components as much as possible. As a result, it becomes possible to reduce the metal concentration in the ultrapure water produced by the ultrapure water production system 1 as much as possible.

It is preferable to use groundwater as the cooling medium for the heat exchanger 41, but since there is a possibility that the heat exchanger 41 may become clogged due to the precipitation of hardness components and silica contained in the groundwater, it is also possible to use circulating water from the manufacturing process of semiconductor devices or liquid crystal devices, for example.

REFERENCE SIGNS LIST 1 Ultrapure water production apparatus 2 Ion exchange resin tower 3 Regenerant supply device 10 Tank 11 Inner wall 12 Outer wall 13 Heat shielding material 20 Pipe 21 Inner pipe 22 Outer pipe 23 Heat shielding material 30 Air circulation means 31 Air inlet 32 Air outlet 33 Straightening plate 41 Heat exchanger 42 Temperature sensor 43 Drain valve S Hollow portion

Claims (8)

A regenerant supplying device for supplying a regenerant comprising an acid for regenerating a cation exchange resin to an ion exchange resin tower filled with the cation exchange resin,
a tank installed outdoors, with an inner surface lined with rubber, for storing the regenerant;
a pipe connecting the tank and the ion exchange resin tower, the pipe having an inner surface lined with rubber ;
a temperature control mechanism for controlling the temperature of the regenerant supplied from the tank through the piping to the ion exchange resin tower,
the temperature control mechanism is a heat shield that insulates the inside of the tank from heat of the outside air and suppresses a rise in temperature of the regenerant inside the tank, the heat shield being made of urethane foam;
A regenerant supply device for ultrapure water production equipment . The tank has a double-wall structure consisting of an inner wall and an outer wall,
The regenerant supply apparatus of claim 1 , wherein the heat shield is disposed between the inner wall and the outer wall. The regenerant supply device according to claim 1, wherein the heat shield is arranged to cover the outer periphery of the tank. The regenerant supply device according to any one of claims 1 to 3, wherein the temperature control mechanism has a separate heat shielding material made of urethane foam that insulates the inside of the piping from heat from the outside air and suppresses a rise in temperature of the regenerant inside the piping. At least a portion of the piping that is placed outdoors has a double pipe structure consisting of an inner pipe and an outer pipe,
The regenerant supply apparatus of claim 4 , wherein the additional heat shield is disposed between the inner tube and the outer tube. The regenerant supply device according to claim 4, wherein the separate heat insulating material is arranged to cover the outer periphery of the portion of the piping that is arranged externally. The regenerant supply device according to any one of claims 1 to 6, wherein the temperature control mechanism comprises a heat exchanger provided in the piping for cooling the regenerant, a temperature sensor provided in the piping downstream of the heat exchanger for detecting the temperature of the regenerant flowing in the piping, and a drainage means for discharging the regenerant flowing in the piping to the outside based on the detection result of the temperature sensor. 8. An ultrapure water producing apparatus comprising: an ion exchange resin tower filled with a cation exchange resin; and a regenerant supplying device according to any one of claims 1 to 7, which supplies a regenerant comprising an acid that regenerates the cation exchange resin to the ion exchange resin tower.

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