JP3573933B2 - UV oxidation equipment - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a total organic carbon measurement system (sometimes referred to as a “TOC meter”) for measuring total organic carbon (TOC) in water, typically representing the degree of water pollution, or organic particulates or colloids in water. The present invention relates to an improvement in an ultraviolet oxidizing apparatus used in an ion exchange TOC removal system or the like for completely removing organic molecules in a state and irradiating an organic substance in water with ultraviolet rays to oxidize the organic substance.
[0002]
[Prior art]
Water used for cleaning semiconductors, manufacturing medical chemicals and injection solutions, chemical analysis, etc., substantially contains impurities, for example, fine particles, various ions, microorganisms such as bacteria, and dissolved substances such as organic compounds. Is not essential. A system for producing such pure water generally uses a combination of various filtration means including a reverse osmosis method, a distillation method, an ion exchange method, an adsorption method, a vacuum degassing method, an ultraviolet oxidation method, and an ultrafiltration method. In particular, for example, in the semiconductor manufacturing field, the circuit interval is becoming narrower as the degree of integration of the LSI is increased, so that it is necessary to further purify the semiconductor cleaning water in order to prevent a circuit short circuit. Particulates, bacteria and organic matter must be removed as much as possible.
[0003]
As one of the methods for expressing the cleanliness of pure water, there is a total organic carbon (TOC) value (expressed in μg / l or ppb), which indicates the degree of contamination by the amount of carbon in organic matter in water. For reference, a semiconductor cleaning application may require a TOC value of 0.20 μg / l or less.
[0004]
As a means for measuring the TOC value of pure water, a TOC meter of an ultraviolet (UV) oxidation method is widely used. In such a TOC meter, after measuring the conductivity of the sample water flowing in the measurement line with a first conductivity sensor, the sample water is introduced into an ultraviolet irradiation unit, and the sample water is irradiated with ultraviolet rays. Irradiation converts organic carbon in the sample water into organic acids. Thereafter, the conductivity of the sample water is measured by the second conductivity sensor, and the TOC value of the sample water is calculated from the known data based on the difference representing the change in the conductivity obtained by the first and second conductivity sensors. Ask.
[0005]
Also, the raw water supplied to the semiconductor cleaning pure water production system or the recovered and used pure water from the semiconductor cleaning process unit may include a considerably high TOC value, and particularly, the recovered pure water from the semiconductor cleaning process unit. In some cases, the organic solvent used in the semiconductor cleaning process section may be mixed, and in this case, the TOC amount of the used pure water becomes about 500 ppb or more. In order to reduce the high TOC value in raw water or used pure water containing a TOC amount exceeding a predetermined level, usually, such water is introduced into an ultraviolet irradiation section and irradiated with ultraviolet light to convert organic substances in the water into organic acids. And then removed from the water with an ion exchange device, so that pure water with a low TOC value is obtained.
[0006]
[Problems to be solved by the invention]
One type of a conventional UV oxidation apparatus used in a TOC meter, an ion exchange TOC removal system, and the like is provided so as to be wound around a cylindrical ultraviolet irradiation lamp in order to increase the efficiency of organic matter oxidation by ultraviolet light. It has a helical tube made of a transparent material, typically quartz, capable of transmitting ultraviolet light from the lamp. However, in the conventional ultraviolet oxidation apparatus, a considerably long irradiation time, for example, about 10 minutes is required to completely oxidize the organic matter in the sample water by the ultraviolet light, and thus the measurement time for the TOC meter becomes long. In TOC removal systems, removal efficiency has been limited.
[0007]
By the way, it is known that titanium oxide has a function of promoting the oxidative decomposition of organic substances dissolved in water as a photocatalyst. This is based on the principle that titanium oxide generates OH radicals by interaction with received light, and the OH radicals effectively and quickly oxidize organic substances. Titanium oxide has been demonstrated to be chemically stable, substantially harmless to the environment, and has no potential toxicity among photocatalytic materials.
[0008]
Also in the field of TOC measurement, there is a conventional technique in which a pair of titanium oxide-coated electrodes is arranged and used in an ultraviolet irradiation chamber in order to monitor the oxidation state of organic substances in sample water.
[0009]
However, in the configuration of the related art, since the contact area between the sample water and the titanium oxide-coated electrode is limited, it cannot be said that the oxidation of the organic matter in the water is sufficiently promoted.
[0010]
Accordingly, an object of the present invention is to provide an improved ultraviolet oxidation apparatus utilizing a photocatalyst, which is used in a TOC meter, a TOC removal system, and the like and promotes the oxidation of organic substances in a liquid by titanium oxide in view of the problems of the prior art. Is to do.
[0011]
[Means for completing the task]
The gist of the present invention is to provide a spiral quartz tube provided around a cylindrical ultraviolet irradiation lamp, and a titanium oxide-coated hollow glass bead which is disposed immediately below the ultraviolet irradiation lamp and is suspended. A hollow container provided with a hollow portion and made at least in part of a transparent material, wherein the container has an inlet for introducing a liquid into the hollow portion for ultraviolet irradiation and water from the hollow portion for discharging water after the ultraviolet irradiation. Characterized in that the transparent part of the container is arranged toward the ultraviolet irradiation lamp so as to transmit the ultraviolet light from the ultraviolet irradiation lamp leaking through the quartz tube into the hollow part. In the device .
[0014]
A feature of the present invention is that it can be retrofitted to existing UV oxidizers, and thus the UV oxidizer of the present invention comprises a spiral quartz tube provided around a cylindrical UV irradiation lamp, and a UV irradiation lamp. And a hollow container provided with a hollow portion for receiving titanium oxide-coated hollow glass beads in a floating state and at least partially made of a transparent material. The container has an inlet for introducing a liquid into the hollow portion for ultraviolet irradiation and an outlet for sending water after the ultraviolet irradiation from the hollow portion, and the transparent portion of the container is irradiated with ultraviolet light leaking through a quartz tube. It is arranged toward the ultraviolet irradiation lamp so as to transmit ultraviolet light from the lamp into the hollow portion.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Referring particularly to FIG. 1 of the drawings, there is shown a UV oxidizer generally designated by the numeral 10 as a first embodiment of the present invention. The ultraviolet oxidizing apparatus 10 includes an elongated transparent spiral quartz tube 14 as a liquid passage means provided around a cylindrical ultraviolet irradiation lamp 12. FIG. 2 is a partially cutaway view showing one turn of the exit end of the spiral tube 14 made of quartz of FIG. 1 in an enlarged manner, and is a view best showing the features of the present invention as described later.
[0016]
In the illustrated first embodiment, the ultraviolet oxidizing apparatus 10 is provided, for example, in connection with a sample water measurement line incorporated in a pure water production system for semiconductors, and measures ultraviolet rays (UV) for measuring the TOC value of raw water or pure water. 1) The quartz tube 14 is of a known type as a whole and constitutes a part of an oxidation type TOC meter (not shown). The quartz tube 14 extends between an inlet end 16, an outlet end 18 and an inlet end and an outlet end. And a helical passage or hollow portion 20 through which the sample water passes. The ultraviolet irradiation lamp 12 irradiates sample water flowing through the spiral tube 14 from the inlet end 16 to the outlet end 18 with ultraviolet light through the transparent quartz wall, thereby completely oxidizing organic substances in the water. Functions to form organic acids.
In the known TOC meter, the inlet end 16 of the quartz tube is connected to a first sensor (not shown) for measuring the conductivity of the sample water before irradiation with ultraviolet light collected in the sample water measurement line, and the outlet end 18 thereof. Is connected to a second sensor (also not shown) that measures the conductivity of the sample water in a state where the organic matter has been completely oxidized by receiving the ultraviolet light. The TOC meter is connected to the first and second sensors, detects a difference between the measured conductivity values obtained by the first and second sensors, and determines the TOC value of the sample water based on the difference. Means are further provided.
[0017]
As clearly shown in FIG. 2, the helical passage 20 of the quartz tube 14 is preferably a multiplicity of hollow glass coated with titanium oxide over its entire surface, preferably from its inlet end 16 to its outlet end 18. The beads 22 are accommodated. As generally known as a type of photocatalyst, the titanium oxide film applied to such hollow glass beads generates OH radicals in water that promote the oxidation of organic matter in water by interaction with irradiated ultraviolet light. Help to make. By filling titanium oxide in the form of beads in a quartz tube in a floating state, the effective surface area is larger than that of titanium oxide coated in two electrodes, for example, and a larger amount of OH radicals is generated. It will be appreciated that better photocatalysis will thus be obtained.
[0018]
FIG. 3 is a cross-sectional view taken along line II of an arbitrary part of the spiral tube turn shown in FIG. 2, and FIGS. 3A, 3B, and 3C are diagrams during operation of the ultraviolet oxidation apparatus. FIG. 2 is a view exemplarily showing how a titanium oxide-coated hollow glass bead 22 is located in a passage or a hollow portion 20 constituted by a quartz tube wall. The beads 22 are not positioned so as to block the passage cross section, but allow sufficient water to pass between the quartz tube wall and the ultraviolet light from the ultraviolet irradiation lamp without being obstructed so much as shown in the drawing. It must be of a size and shape that allows sufficient irradiation of the entire water. As an example, when the inner diameter of the passage of the quartz tube 14 is about 3 to 4 mm, the particle diameter of the titanium oxide-coated hollow glass beads is about 1.5 to 2 mm. According to the experimental results, it is desirable that about 2 to 3 beads are randomly placed in an arbitrary passage section of the quartz tube.
[0019]
Referring again to FIG. 2, at the outlet end 18 of the quartz tube, there is provided a withdrawal preventing means 24 for preventing the titanium oxide-coated hollow glass beads from coming out of the quartz tube with the flow of the liquid. Have been. In the illustrated embodiment, the withdrawal preventing means is, for example, a thin stainless wire that is rolled and pushed into the internal passage of the quartz tube to serve as a screen or a filter. After insertion, the wire mesh screen 24 is pressed and held against the quartz tube wall by its springback action. Those skilled in the art will recognize various alternatives to such wire mesh screens. In essence, any filter or screen means is used that allows water to pass but does not allow the helical tube 14 to escape with the beads entrained. The screen means can be fixed to the quartz tube wall using any conventional fixing means. Preferably, such withdrawal prevention means 24 is also located at the inlet end 16 of the helical tube (not shown).
[0020]
FIG. 4 is a perspective view showing an ultraviolet oxidizing apparatus 30 as another embodiment of the present invention, and FIG. 5 is a view taken along line 5-5 of the ultraviolet oxidizing apparatus 30 of FIG. It is sectional drawing. The ultraviolet oxidizing apparatus of this embodiment is typically incorporated in series with a TOC removal system provided in a pure water production system for semiconductors, for example, to feed raw water or a liquid to be treated flowing through an inlet end. The organic carbon in the liquid is changed to an organic acid state by irradiating ultraviolet rays, and thereafter, is sent out from the outlet end for the next processing. The organic acid-containing water after the ultraviolet irradiation is then transferred to an ion-exchange resin device, which removes organic acids in the water by ion-exchange action to reduce the total amount of organic carbon in the water and further purify the water. High water.
[0021]
The ultraviolet oxidizing device 30 has a liquid passage means 32 in the form of a channel-shaped hollow container disposed longitudinally below and near the ultraviolet irradiation lamp 12. The container 32 is made of a rectangular body 34 having a groove in cross section open toward the ultraviolet irradiation lamp 12, and a transparent material, preferably quartz, fixedly attached to the top edge thereof by any fixing means such as a clamp frame 36. It has a plate-like closure 38 made of glass, and a container hollow portion or inner chamber 40 constituted by the main body 34 and the closure 38. Opposite ends of the container body 34 are provided with an inlet tubular member 42 for receiving water into the chamber 40 and an outlet tubular member 44 for sending water that has been completely oxidized from the chamber 40 by ultraviolet irradiation from the chamber 40. Is provided.
[0022]
As can be seen in FIG. 5, the hollow or internal passage 40 of the container 32 filled with the flowing water contains a large number of titanium oxide-coated hollow glass beads 22 in a floating state. The inner part of the end of the container body 34 to which the outlet tubular member is attached may be provided with a bead removal preventing means made of a filter. If placed below or at the bottom of the container, the beads will be floating and will not fall out of the container 32 without such a draw-out preventing means. The mounting location of the inlet tubular member may be the same.
[0023]
As in the case of the liquid passage means 14 of the first embodiment, the container 32 as the liquid passage means of the second embodiment also transmits ultraviolet light from an ultraviolet irradiation lamp through the quartz glass plate 38 and Should be dimensioned so that they can be sufficiently irradiated through the suspended titanium oxide-coated hollow glass beads 22 to the water present thereunder. Therefore, even if the depth of the chamber 40 is increased to accommodate more beads, the ultraviolet rays hardly reach the water portion at the bottom of the chamber, and the oxidation of organic substances contained therein is not promoted. As an example, it is desirable that the relationship of L = 2 to 3d be satisfied, where L is the lateral upper opening dimension of the container in which the quartz glass plate 38 is placed, and d is the outer diameter of the ultraviolet irradiation lamp 12. Was found experimentally. When using titanium oxide-coated hollow glass beads having a particle size of about 1.5 to 2 mm, the depth of the hollow portion of the container is about 3 to 4 mm. According to the experimental results, in this case as well, it is desirable that about 2 to 3 beads float in a vertically overlapping manner in water in the hollow portion of the container. Preferably, the distance between the upper surface of the quartz glass plate 38 and the outer peripheral portion of the ultraviolet irradiation lamp 12 is about 1 to 3 mm. In order to prevent the ultraviolet rays from the ultraviolet irradiation lamp from reacting with oxygen existing in the gap to generate ozone and thereby reduce the ultraviolet irradiation amount, at least the ultraviolet irradiation lamp and the container 32 are connected to each other. The space between them is preferably sealed by, for example, a cover, and the sealed space is filled with nitrogen gas.
[0024]
FIG. 6 shows a conventional ultraviolet oxidation apparatus comprising a helical elongated quartz tube 14 provided around an ultraviolet irradiation lamp 12 and a titanium oxide bead as a liquid passage means according to a second embodiment of the present invention. The configuration example in which the storage container 32 is retrofitted is shown. The container 32 is disposed in the longitudinal direction immediately below the ultraviolet irradiation lamp 12 provided with the spiral tube 14, and is disposed with its quartz glass plate 38 facing upward. As shown, the inlet 42 of the container 32 may be connected to a source of raw or pure water, and the outlet 44 may be connected to the inlet end 16 of the spiral quartz tube 14. During the operation of the ultraviolet oxidizing apparatus, the water passing through the container 32 receives the ultraviolet irradiation from the ultraviolet irradiation lamp leaked through the quartz tube 14 through the quartz glass plate 38 and receives the titanium oxide coated hollow. The photocatalysis of the glass beads 22 promotes the oxidation of the contained organic matter.
[0025]
FIG. 7 shows a measurement of the change in conductivity of water with respect to ultraviolet irradiation time using water containing benzoxine, which is relatively difficult to oxidize by ultraviolet light, using the photocatalyst-based ultraviolet oxidation apparatus of the present invention shown in FIG. The result is shown by a solid line. On the other hand, the results obtained using the conventional ultraviolet oxidation apparatus under the same conditions are indicated by broken lines.
[0026]
When the benzoxin-containing water is irradiated with ultraviolet light, the conductivity curve rises and peaks as the benzoxin changes to an organic acid, and then falls to a substantially constant value. As is well known to those skilled in the art, the point at which the conductivity takes a constant value can be considered as a complete oxidation point (hereinafter, referred to as "point F"). As can be seen with reference to such a graph, the UV irradiation time at point F of the conductivity curve for the device of the present invention, shown by the solid line, is about 3 minutes, which is required to completely oxidize benzoxin in water. You can think of it as time. On the other hand, in the case of the conventional machine shown by the dotted line, the ultraviolet irradiation time at the point F is about 6 minutes. Therefore, by using the titanium oxide-coated hollow glass beads according to the concept of the present invention, even organic substances which are relatively hard to oxidize can be completely oxidized in about half the oxidation time as compared with the conventional method. Thus, in the TOC meter embodying the present invention, the TOC measurement time can be reduced to about 1/2, and in the TOC removal system of the present invention, the TOC removal efficiency is doubled.
[0027]
[Brief description of the drawings]
FIG. 1 is a perspective view of an ultraviolet oxidizing apparatus comprising a helical elongated quartz tube provided around a cylindrical ultraviolet irradiation lamp similarly to the conventional configuration.
FIG. 2 is an enlarged partial cutaway view showing one turn at the outlet end of the quartz spiral tube of FIG. 1, and is a view best showing the features of the present invention.
FIG. 3 is a cross-sectional view taken along line II of an arbitrary portion of the spiral tube turn shown in FIG. 2, and FIGS. 3A, 3B, and 3C are diagrams during operation of the ultraviolet oxidation apparatus. FIG. 4 is a view exemplarily showing how the titanium oxide-coated hollow glass beads 22 are located in a passage or a hollow portion formed of a quartz tube wall.
FIG. 4 is a perspective view showing an ultraviolet oxidizing apparatus as another embodiment of the present invention, in which a container for accommodating hollow glass beads coated with titanium oxide and allowing water to pass therethrough is disposed under an ultraviolet irradiation lamp. FIG.
5 is a cross-sectional view of the ultraviolet oxidizing apparatus of FIG. 4 taken along line 5-5.
FIG. 6 is a perspective view showing an example in which features of the present invention are retrofitted to a conventional ultraviolet oxidation apparatus.
FIG. 7 shows a comparative experiment result of the present invention and a conventional configuration in which organic substances in water are irradiated with ultraviolet rays to be in an organic acid state, the vertical axis is plotted with the electric conductivity, and the horizontal axis is plotted with ultraviolet (UV) irradiation time. FIG.
[Explanation of symbols]
10, 30 UV oxidation device 12 UV irradiation lamp 14 Helical quartz tube 16, 42 Inlet end 18, 44 Outlet end 20, 40 Hollow portion 22 Titanium oxide-coated hollow glass beads 24 Wire mesh screen 32 Titanium oxide-coated hollow glass beads container 38 Quartz glass plate

Claims (1)

A spiral quartz tube provided around the cylindrical ultraviolet irradiation lamp, and a hollow portion which is disposed immediately below the ultraviolet irradiation lamp and accommodates the titanium oxide-coated hollow glass beads in a floating state, and A hollow container partially made of a transparent material, the container has an inlet for introducing a liquid into the hollow portion for ultraviolet irradiation, and an outlet for sending water after the ultraviolet irradiation from the hollow portion, An ultraviolet oxidation apparatus, wherein the transparent portion of the container is arranged toward the ultraviolet irradiation lamp so as to transmit the ultraviolet light from the ultraviolet irradiation lamp leaking through the quartz tube into the hollow portion.

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