WO2002024587A1

WO2002024587A1 - Quartz glass for short wave length ultraviolet ray, discharge lamp using the same, container therefor and ultraviolet irradiation apparatus

Info

Publication number: WO2002024587A1
Application number: PCT/JP2001/008197
Authority: WO
Inventors: Koji Nakano
Original assignee: Photoscience Japan Corporation
Priority date: 2000-09-21
Filing date: 2001-09-20
Publication date: 2002-03-28
Also published as: JP2002097036A

Abstract

A quartz glass to be used through exposure to an ultraviolet ray having a wave length of 200 nm or less, characterized in that it is produced from natural rock-crystal or silica sand, has a total content of sodium, potassium, titanium and iron of 2.5 ppm or less and contains an OH group in an amount of 10 ppm or more; and an ultraviolet irradiation apparatus wherein the quartz glass is used as the material of a bulb (11) of a light emitting tube of an ultraviolet discharge lamp (L), and as the material of an ultraviolet-transmittable outer tube or protecting tube (20) housing the ultraviolet discharge lamp. The quartz glass is improved with respect to the lowering of the transmittance of an ultraviolet ray in a shorter wave length region with the elapse of time, which leads to the provision of a discharge lump and an ultraviolet irradiation apparatus which are greatly improved in the degree of retention of ultraviolet ray strength, and thus can be operated at a reduced cost and with saving energy.

Description

Description Quartz glass for short wavelength ultraviolet light, discharge lamp using it, its container, and ultraviolet irradiation device

The present invention relates to an improvement of quartz glass used for an apparatus for decomposing organic substances by emitting ultraviolet energy in a wavelength range of 200 nm or less, and further relates to a discharge lamp, an ultraviolet irradiation apparatus and a method using the quartz glass. About. Background art

Ultraviolet light in the short wavelength region has a high level of energy, and is therefore widely used for decomposing harmful substances and organic substances. FIG. 4 shows an example of a conventionally known closed type ultraviolet irradiation bath for liquid treatment. The discharge lamp 30 is housed in an outer tube (protective tube) 20. The discharge lamp 30 is housed in a stainless steel cylinder 1 and the liquid to be treated is introduced into the cylinder 1 and irradiated with ultraviolet rays emitted from the discharge lamp 30. You. As the discharge lamp 30, for example, a low-pressure mercury vapor discharge lamp that efficiently emits ultraviolet rays in a wavelength range of 185 nm is used. The arc tube 10 of the discharge lamp 30 is also made of quartz glass having excellent ultraviolet transmittance. The discharge lamp 30 is housed inside an outer tube (protective tube) 20 that transmits ultraviolet light, and the discharge lamp 30 is liquid-tightly isolated from the liquid to be treated. The powerful outer tube 20 is also made of quartz glass with excellent ultraviolet transmittance! Both ends of the cylinder 1 are closed by flanges la and lb, and the liquid to be treated taken in from the water inlet lc is irradiated with ultraviolet rays while passing through the cylinder 11 and discharged from the water outlet Id. The liquid to be treated flows in the cylinder 1 from the water inlet lc toward the water outlet Id.Several pieces (five in the figure) of the liquid to be treated Flow plate le ~: Li is arranged. For the sake of convenience, FIG. 5 illustrates a device equipped with only one discharge lamp 30, but in practice, a multi-lamp type large-capacity device is often used. Ultraviolet light emitted from the discharge lamp 30 passes through the outer tube 20 and irradiates the liquid to be treated. Irradiated ultraviolet rays, for example, the organic matter present in the water in Succoth action decomposes were result into harmless CO, C0 _{_2,} H ₂ 0 as follows. H ₂₀ + hv (185 nm) → H + OH radical

CnHmOk + OH radio cane → CO, C〇 ₂ , H ₂ O

(n, m, k, are 1, 2, 3,...) FIG. 5 shows a configuration example of the discharge lamp 30. Both ends of the quartz glass arc tube 10 are hermetically closed by glass stems 2a and 2b. A pair of filaments 21a and 21b are coated with a barium oxide (BaO) emitter for the purpose of smooth discharge. The filaments 21a and 21b are held on the glass stems 2a and 2b, respectively, and are connected to the terminals 31a to 31d of the bases 3a and 3b via inner leads 22a to 22d, molybdenum foils 24a to 24d, and outer leads 25a to 25d. It is electrically connected. Also, an appropriate amount of mercury and argon gas are sealed in the valve. When the electric discharge lamp 30 is connected to a predetermined power supply (not shown) and power is applied, a discharge occurs between the filaments 21a and 21b, mercury is evaporated by the discharge heat, and ultraviolet rays are emitted by excitation of the mercury nuclear power. become.

By the way, in recent years, the density of ultraviolet light sources has been increased in order to increase the processing capacity. The densification is to increase the power of the discharge lamp and increase the total amount of ultraviolet rays. However, the present inventor has found that with this increase in density, a new problem arises in that the processing capacity is significantly reduced as the lighting time of the discharge lamp advances. Specifically, for example, TOC when raw water (organic matter) concentration lOppb expressed in power consumption of the discharge lamp needs to be decomposed into the following l _PP b, processing capacity of the initial Atsuta at 0. 3 kWh / ton On the other hand, about a year later, it was 0.7kWhZ tons, which required twice or more the amount of electricity, and noticed that the processing capacity was reduced by half. In the past, such a problem was not noticed and was neglected. Therefore, it is necessary to appropriately improve such problems. Disclosure of the invention

The present inventor has sought to determine the causes of various viewpoints and to devise a solution to solve the powerful problem. And found that there was a cause. Then, they came up with a clear measure to improve the aging of the transparent quartz glass. Therefore, the present invention has been made in view of the above points, and provides quartz glass with improved aging of ultraviolet transmittance in a short wavelength range, and maintains ultraviolet intensity by using strong quartz glass. It is an object of the present invention to provide a high-density discharge lamp having a significantly improved efficiency, and to provide an energy-saving ultraviolet irradiation apparatus and method by using such a quartz glass or a discharge lamp.

As a result of repeating experiments and analysis on the above problem, the inventor of the present invention has found that the short-wavelength ultraviolet light emitted by the discharge lamp itself alters the quartz glass forming the tube of the discharge lamp, lowers the transmittance, and reduces the ultraviolet intensity. It was concluded that the cause was that the retention rate decreased over time. In other words, while the conventionally known low-density light source has a small absolute amount of ultraviolet light and thus does not cause significant deterioration, the high-density discharge lamp causes the deterioration with time. It is understood that it appeared as a phenomena. The present inventor has found a quartz glass composition that can significantly improve the ultraviolet intensity maintenance rate. That is, the facts discovered by the present inventors are mainly the following three points. The first point is, in the silicon dioxide of the main component constituting the essence of silica glass (Si0 _2), sodium (Na), potassium (K), when many impurities exist titanium (Ti) and iron (Fe) Short Absorption of ultraviolet light of a wavelength, causing a decrease in the transmittance of quartz glass. Numerous glass samples were investigated and analyzed in terms of short-wavelength UV transmittance, and the fact that the decrease in transmittance over time of quartz glass due to these impurities was identified using statistical methods. The second point is that, even if the transmittance is slightly reduced at the beginning, the quartz glass is degraded with time during use of the discharge lamp, and the force gradually leads to a significant decrease in transmittance. . Third, the above-mentioned alteration of quartz glass can be reduced by the presence of OH groups. The following is the result of examining the mechanism of alteration and alteration mitigation of quartz glass. Alteration is a phenomenon that occurs because the “Si—O” bond of quartz glass is decomposed by ultraviolet energy and free silicon (Si) is generated, accompanied by a decrease in transmittance. Here, the dissociation energy of “Si—〇” is 145 kCal / mol, which corresponds to 200 nm ultraviolet energy. Therefore, when the quartz glass is exposed to ultraviolet light having a wavelength of 200 nm or less, dissociation of “Si-0” which causes a decrease in transmittance occurs. It is considered that the alteration relaxation is effective in suppressing the presence of free Si by free silicon (Si) being recombined with OH groups to form “Si—OHJ”.

In view of the above, the quartz glass for short-wavelength ultraviolet light according to the present invention is a quartz glass that is used by being exposed to ultraviolet light having a wavelength range of 200 nm or less. Using sand as a starting material, the total content of the four elements, sodium (Na), potassium (K), titanium (Ti), and iron (Fe), is 2.5 ppm or less and OH groups of 10 ppm or more It is characterized by including.

Various substances are contained as impurities in quartz glass starting from natural quartz or quartz sand. As described above, among these impurities, the presence of a large amount of the four elements of sodium, lithium (K), titanium (Ti), and iron (Fe) can reduce the transmittance of quartz glass. It can cause damage. On the other hand, the presence of OH groups can mitigate the alteration of quartz glass. In other words, the generation of free Si, which causes the transmittance to decrease due to the decomposition of the “Si-0” bond of silicon dioxide (Si〇 ₂ ), which is the main component of quartz glass, by the OH group Can be suppressed by recombining with free Si to form “Si—OH”. As a result of experiments conducted by the inventor, if the total content of these four elements is less than 2.5 ppm and OH groups are more than 10 ppm, the aging of quartz glass due to short-wavelength ultraviolet rays will occur. It has been found that can be improved considerably. Therefore, by selecting or setting the material of the quartz glass in such a manner, it is possible to obtain a quartz glass which has considerably improved the deterioration with time due to ultraviolet rays in a short wavelength region (that is, can maintain a good ultraviolet transmittance for a long period of time). Can be provided.

Note that, as described above, the dissociation of “Si-0” in quartz glass hardly occurs with respect to ultraviolet rays in a wavelength range longer than 200 nm, and thus was excluded from the present invention. The reason for setting the boundary value of the total content of the above four elements to “2.5 ppm or less” was set based on the experience of repeated experiments. For example, a total content of “4. Oppm” is clearly better than a total content of “3.06 ppm”. On the other hand, it was confirmed that those with a total content of “1.56 ppm” were good, and those with a total content of “1.20 ppm” were also good. Therefore, it was confirmed that good results could be obtained by setting a boundary at a total content of “2.5 ppm or less” by taking about halfway between these empirical data. Also, the reason why the boundary value of the OH group content was set to `` 10 _PP m or more '' was that there was an amount sufficient to capture free Si, Was set as follows.

The discharge lamp according to the present invention is characterized in that a substance that emits ultraviolet light in a wavelength range of 200 nm or less is enclosed in a container made of quartz glass configured as described above, It is. With this structure, it is possible to provide a discharge lamp with significantly improved ultraviolet intensity maintenance rate. It becomes possible.

An ultraviolet irradiation device according to the present invention is provided with the discharge lamp configured as described above. This makes it possible to provide an ultraviolet irradiation device capable of maintaining a high ultraviolet transmittance for a long period of time, and to provide an energy-saving ultraviolet irradiation device with low running cost.

The quartz glass according to the present invention is not limited to the container (bulb) itself of the ultraviolet discharge lamp as described above, but can be used as a material for protecting the discharge lamp, that is, as a material of an outer tube or a protective tube. In this case, the same operation and effect as described above can be expected. Further, the quartz glass according to the present invention may be used not only for the container (bulb) of the ultraviolet discharge lamp itself but also as a material for protecting the discharge lamp, that is, as a material of an outer tube or a protective tube. Then, it is possible to provide an energy-saving ultraviolet irradiating apparatus with further lower running cost.

Furthermore, the ultraviolet irradiation method according to the present invention emits ultraviolet light in a wavelength range of 200 nm or less from a discharge lamp using a discharge tube made of quartz glass as a material as described above, and irradiates the object to be treated. By doing so, processing such as sterilization, disinfection, and decomposition of organic substances is performed.

In another ultraviolet irradiation method according to the present invention, a discharge lamp that emits ultraviolet light having a wavelength range of 200 nm or less is housed in a container made of quartz glass having the above-described structure, and the discharge lamp in the container is used. By irradiating the object to be treated with ultraviolet light having a wavelength range of 200 nm or less emitted from an electric lamp, treatment such as sterilization, disinfection, or decomposition of organic substances is performed. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic partial cross-sectional view showing one embodiment of a discharge lamp according to the present invention,

Figure 2 shows various discharge lamps manufactured using the total content of sodium (Na), potassium (K), titanium (Ti), iron (Fe) and the content of OH groups as parameters of the composition of quartz glass. FIG. 3 is a graph showing an ultraviolet intensity maintenance rate curve obtained by performing a lighting experiment over a long period of time. A graph showing the experimental results comparing the possible processing capacity with the processing flow rate per unit of power,

FIG. 4 is a diagram showing an example of a conventional liquid ultraviolet irradiation apparatus, FIG. 5 is a schematic partial sectional view showing an example of a conventional discharge lamp. BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows an example of a discharge lamp L according to one embodiment of the present invention. The difference between the discharge lamp L shown in FIG. 1 and the conventional discharge lamp 30 shown in FIG. 5 is that the discharge lamp L according to one embodiment of the present invention has a material strength of the arc tube bulb 11 and a discharge lamp L of the conventional discharge lamp 30. It differs from the material of the arc tube 10 only in that it is different. Other configurations may be the same as those in the related art, and thus detailed description thereof will be omitted. The quartz glass constituting the material of the arc tube 11 of the discharge lamp L is made of natural quartz or quartz sand as a starting material, and includes sodium (Na), potassium), titanium, i) and iron. The total content of the four elements of (Fe) is less than 2.5 ppm, and some contain OH groups of more than 10 ppm. For example, the inner diameter of the arc tube bulb 11 is 22 mm, the wall pressure is 1 mm, and a pair of filaments 21 a and 21 b coated with a barium oxide emitter are arranged at both ends at intervals of 150 cm. Contains about 20 mg of mercury and 130 Pa of argon gas. Further, the discharge lamp L is configured to emit ultraviolet light in a wavelength range of 200 nm or less.

As described above, in the quartz glass constituting the material of the arc tube 11 of the discharge lamp L, there are four types of elements, namely, sodium (Na), potassium (K), titanium (Ti), and iron (Fe). Is not more than 2.5 ppm and contains not less than 10 ppm of OH groups, so that the aging of the quartz glass of the arc tube bulb 11 due to the short wavelength ultraviolet light emitted by the discharge lamp L is deteriorated. Can be considerably improved.

Figure 2 shows various types of quartz glass manufactured using the total content of sodium (Na), potassium (K), titanium (Ti), and iron (Fe) and the content of the base group as parameters. It is an ultraviolet intensity maintenance rate curve obtained by performing a lighting experiment for a long period of time. The shape and dimensions of the discharge lamp are the same, the horizontal axis represents the lighting time, and the vertical axis represents the ultraviolet intensity of 185 nm wavelength when the initial value of the intensity of the discharge lamp according to the present invention is 100%. The composition conditions of quartz glass in each discharge lamp corresponding to each song, B, C, D are as shown in the table below. [table 1]

Curve Total content of Na, K, Ti, Fe —OH group content

A2.5ppm or less lOOppm

B4.2 ppm lOOppm

C4.5 Less than 5ppm lOppm

D6.4 Less than lOppm Curve A is sodium (Na), potassium (K), titanium (Ti) and iron (Fe) as defined in the present invention, the total content of the four kinds of elements is 2.5 ppm The following satisfies the condition that an OH group contains 10 ppm or more, and the curves B, C, and D do not satisfy the condition. In Fig. 2, it is clear from the curve HA that the best result is obtained, and it is clear that the impurities in quartz glass are sodium (Na), potassium (K), titanium (Ti), and iron (Fe). By setting the total content of the four elements and the content of the OH group in accordance with the present invention, it is possible to greatly improve the ultraviolet light intensity maintenance rate over time. In the experiment shown in Fig. 2, ozone is generated by the reaction to ultraviolet light in the atmosphere, and if the generated ozone is interposed between the discharge lamp and the ultraviolet intensity meter, the measured value varies. The measurement was performed by directly attaching to the outer surface of the lamp.

In the technical field of UV sterilization and disinfection to which the present invention is applied, regardless of the magnitude of the input density of the discharge lamp, the system is generally designed assuming that the UV maintenance rate after use for one year is 70%. From that point of view, it is clear that quartz glass with a composition that gives the result of the curve in Fig. 2 is effective, and quartz glass with a composition that gives the result of curves B, C, and D is clearly not effective. As described above, the total content of the four elements of sodium (Na), potassium (K), titanium (Ti), and iron (Fe), which are impurities in quartz glass, is 2.5 ppm or less. For example, the UV maintenance rate after one year of use can be maintained at 70% or more. If we comment on the OH group content, less than 10 _PPm is insufficient for the Si-OH recombination effect.

In the above embodiment, as an example of using the quartz glass according to the present invention, not only the mercury vapor discharge lamp described for the mercury vapor discharge lamp using mercury as a luminescent substance but also a discharge lamp emitting light in a wavelength region of 200 nm or less. For example, the present invention is also applied to a discharge lamp or the like in which a substance capable of emitting excimer light such as xenon (Xe), chlorine (C1), bromine (Br), and fluorine (F) is sealed. By doing so, a similar function and effect can be obtained. Further, in the above embodiment, the description has been made using the discharge lamp having the filament. However, the present invention can be applied to a discharge lamp having any lighting method irrespective of the structure of the electrode, the electrode and the like. The same effect can be obtained.

Further, the quartz glass made of the material according to the present invention is used not only in the arc tube of the discharge lamp itself, but also in any part or component used when exposed to ultraviolet rays in a wavelength range of 200 nm or less. be able to. For example, the quartz glass according to the present invention can be used as the material of the ultraviolet-transparent glass wall in the outer tube (protective tube) 20 as shown in FIG. The shape of such an outer tube (protective tube) for accommodating the discharge lamp, that is, the container is not limited to a cylindrical shape, but may be any shape.

The discharge lamp L according to the embodiment of the present invention shown in FIG. 1 (the arc tube bulb 11 has an inner diameter of 22 mm, a wall thickness of lmm, a filament interval of 150 cm, and contains about 20 mg of mercury and 130 Pa of argon gas. ) In a quartz glass outer tube made of a raw material according to the present invention (hereinafter referred to as the device of the present invention), and a conventional discharge lamp in a quartz glass outer tube according to the prior art. Fig. 3 shows the results of an experiment comparing the ability of a stored ultraviolet irradiation device (hereinafter referred to as a conventional device and a laser) to process over time. Fig. 3 shows a comparison of the processing capacity per unit of electric power between the apparatus of the present invention and the conventional apparatus, which can reduce the raw water having a TOC concentration of lOppb to lppb or less. / kWH), and the horizontal axis indicates time. Here, the apparatus of the present invention and the conventional apparatus had the same configuration and dimensions except that the quartz glass used for the discharge lamp and the outer tube were different in material. From this figure, it can be seen that the capacity of the conventional device is reduced to about 40% after 8500 hours, which is a guideline for one year of use, while the device of the present invention maintains a capacity of nearly 80%. . In other words, it is clear that although the processing capacity of the two is small at the beginning, there is a significant difference as the usage time advances. Here, powerful UV irradiation equipment is used for a long time in various plants and factories for the purpose of sterilization and disinfection, etc., so the scale of the equipment is generally designed in consideration of the capacity after one year. ing. Therefore, in the conventional apparatus, initial equipment investment is increased, for example, by increasing the number of discharge lamps so as to be able to withstand a large capacity drop after one year, while the apparatus of the present invention requires such capacity. Since there is no reduction, initial capital investment can be reduced. Therefore, according to the present invention, not only energy saving but also reduction of capital investment is useful. It is profitable. The object to be processed by the ultraviolet irradiation apparatus according to the present invention is not limited to a liquid, but may be a solid or a gas.

As quartz glass having a good transmittance of ultraviolet rays, artificial quartz glass called so-called synthetic quartz, which is manufactured using tetrachlorosilane silicon (SiC14) as a starting material, is known. British glass is not limited to the four types of sodium (Na), potassium), titanium (Ti), and iron (Fe) described in the present invention. , Lithium (Li), magnesium (Mg), calcium (Ca), chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), lead (Pb), etc. The feature is that it is extremely small. However, their high cost makes them impractical in the field of the present invention. Therefore, they are out of the scope of the present invention.

As described above, according to the present invention, natural quartz or quartz sand is used as a starting material in quartz glass used by being exposed to ultraviolet light in a wavelength range of 200 nm or less, and sodium quartz, titanium, titanium, and iron are used. The total content of these elements is 2.5 ppm or less, and the composition is such that they contain OH groups of 10 ppm or less. An excellent effect of being able to provide a low-cost and energy-saving ultraviolet irradiation device is achieved.

Claims

The scope of the claims

1.Quartz glass that is used by being exposed to ultraviolet rays in the wavelength range of 200 nm or less, using natural quartz or quartz sand as the starting material and having a total content of four elements of sodium, potassium, titanium, and iron 2. A quartz glass for short-wavelength ultraviolet light, characterized in that the OH group is not more than 5 ppm and not less than 10 ppm.

2. A discharge lamp characterized in that a substance that emits ultraviolet light in a wavelength range of 200 nm or less is sealed in the container made of quartz glass according to claim 1.

3. the discharge lamp according to claim 2;

Means for processing the processing object by irradiating the processing object with ultraviolet light emitted from the discharge lamp

An ultraviolet irradiation device comprising:

4. A container made of the quartz glass according to claim 1, wherein the container is used for housing a discharge lamp that emits ultraviolet light having a wavelength range of 200 nm or less.

5. A discharge lamp comprising a container made of quartz glass according to claim 1 and containing a substance that emits ultraviolet light in a wavelength range of 200 nm or less,

A container made of quartz glass according to claim 1, wherein the discharge lamp is housed inside.

An ultraviolet irradiation device comprising: '

6. Using natural quartz or quartz sand as the starting material, the total content of the four elements of sodium, potassium, titanium and iron is 2.5 ppm or less, and it contains OH groups of 10 ppm or more. A quartz lamp for short wavelength ultraviolet light is used as an arc tube, and a substance that emits ultraviolet light in a wavelength range of 200 ηm or less is sealed inside the discharge tube. Emitting a light, Irradiating the object to be treated with the ultraviolet light generated by the discharge lamp power, and treating the object to be treated;

An ultraviolet irradiation method comprising:

7. Using natural quartz or quartz sand as the starting material, the total content of the four elements, sodium, potassium, titanium and iron, is 2.5 ppm or less and contains OH groups of 10 ppm or more. A step of storing a discharge lamp that emits ultraviolet light having a wavelength range of 200 nm or less in a container made of quartz glass for short wavelength ultraviolet light, and emitting ultraviolet light having a wavelength range of 200 nm or less with the discharge lamp;

Irradiating the object to be treated with ultraviolet light emitted from the discharge lamp cap in the container, and treating the object to be treated;

An ultraviolet irradiation method comprising: