JP7721466B2 - Irradiation device - Google Patents

Description

The present invention relates to an irradiation device for irradiating a fluid with ultraviolet light.

Ultraviolet light is known to have sterilizing properties, and devices that irradiate ultraviolet light are used for sterilization processes in medical and food processing facilities. Devices that continuously sterilize fluids, such as water, by irradiating them with ultraviolet light are also used. One such device is one in which ultraviolet LEDs are arranged on the inner wall at the end of a flow path formed by a straight metal pipe (see, for example, Patent Document 1).

JP 2011-16074 A

In order to irradiate the fluid flowing through the channel with ultraviolet light with high efficiency, it is desirable to have a structure with high ultraviolet light reflectivity on the channel's inner wall. However, bubbles may appear and disappear on the channel's inner wall depending on the state of the fluid. When bubbles appear, the ultraviolet light is scattered by the bubbles on the channel's inner wall, causing the intensity distribution of the ultraviolet light within the channel to change over time. This causes variations in the amount of ultraviolet light acting on the fluid, which in turn causes variations in the sterilization effect and organic matter decomposition effect of ultraviolet light irradiation.

The present invention was made in consideration of these problems, and one of its exemplary objectives is to provide an irradiation device that increases the irradiation efficiency of ultraviolet light while reducing variation in the irradiation amount.

An irradiation device according to one embodiment of the present invention comprises a flow path structure in which at least a portion of the inner wall surface of the flow path is made of a fluororesin material with an arithmetic mean roughness of 2 μm or less, and a light source that irradiates ultraviolet light toward the inside of the flow path structure.

According to this aspect, by using a fluororesin material for the inner wall surface of the flow channel, the flow channel structure is highly resistant to ultraviolet light, and the ultraviolet light reflectance on the inner wall surface of the flow channel is increased, allowing for efficient irradiation of the fluid with ultraviolet light. Furthermore, by setting the surface roughness of the fluororesin material to 2 μm or less, it is possible to prevent air bubbles from adhering to the inner wall surface of the flow channel and reduce changes over time in the irradiance distribution of ultraviolet light within the flow channel. This reduces variations in the amount of ultraviolet light acting on the fluid and stabilizes the irradiation performance of the irradiation device.

The fluorine-based resin material may be polytetrafluoroethylene (PTFE).

The flow path structure may include a straight tube made of a fluororesin material. The light source may be positioned to irradiate ultraviolet light toward the interior of the straight tube in the axial direction of the straight tube.

The light source may output ultraviolet light with a wavelength of 250 nm to 300 nm.

This invention can increase the efficiency of ultraviolet light irradiation within the flow channel while reducing variation in the amount of irradiation.

1 is a cross-sectional view schematically showing a configuration of an irradiation device according to an embodiment. 10 is a graph schematically showing an illuminance distribution in a flow channel according to a comparative example. 10 is a graph schematically showing the illuminance distribution in a flow channel according to an example. 1 is a diagram schematically illustrating a configuration of a purification device according to an embodiment.

The following describes in detail the embodiments of the present invention with reference to the drawings. Note that identical elements throughout the description will be designated by the same reference numerals, and redundant explanations will be omitted where appropriate.

Figure 1 is a cross-sectional view showing the schematic configuration of an irradiation device 10 according to an embodiment. The irradiation device 10 comprises a flow path structure 12 and a light source 14. The flow path structure 12 comprises a straight pipe 20, an inlet pipe 26, an outlet pipe 28, an irradiation window 30, and an end wall 32. The irradiation device 10 is used to irradiate a fluid such as water flowing inside the straight pipe 20 with ultraviolet light to perform sterilization or purification treatment.

The light source 14 is configured to irradiate the interior of the flow path structure 12 with ultraviolet light. The light source 14 is disposed at the first end 22 of the straight tube 20 and irradiates the ultraviolet light in the axial direction of the straight tube 20 toward the interior of the straight tube 20 through the irradiation window 30. The light source 14 includes, for example, an LED (Light Emitting Diode) that emits ultraviolet light, and outputs ultraviolet light with a wavelength of approximately 250 nm to 300 nm, which has high sterilization efficiency. When the target to be irradiated is water, the light source 14 is preferably configured to output ultraviolet light with a wavelength of 265 nm to 285 nm, for example, 270 nm, 275 nm, or 280 nm. The light source 14 may also include optical elements such as a lens or reflector to adjust the irradiation direction of the ultraviolet light output from the ultraviolet LED.

The straight tube 20 extends axially from the first end 22 to the second end 24. The straight tube 20 is made of a fluororesin material, such as polytetrafluoroethylene (PTFE), a fully fluorinated resin. PTFE is a chemically stable material that has excellent durability, heat resistance, and chemical resistance, and has a high reflectivity for ultraviolet light. By making the straight tube 20 out of a fluororesin material such as PTFE, the ultraviolet light from the light source 14 is reflected by the inner wall surface 18, allowing the ultraviolet light to propagate efficiently in the axial direction of the straight tube 20.

The straight pipe 20 does not need to be made entirely of PTFE; it is sufficient that the inner wall surface 18 that comes into contact with the fluid is made of PTFE. For example, the straight pipe 20 may be made by attaching a PTFE liner to the inner surface of a pipe made of another resin or metal material.

An irradiation window 30 that transmits ultraviolet light from the light source 14 is provided at the first end 22 of the straight tube 20. The irradiation window 30 is made of a material with high ultraviolet light transmittance, such as quartz ( _SiO2 ), sapphire ( _Al2O3 ), or amorphous _fluororesin . An end wall 32 is provided at the second end 24 of the straight tube 20. Like the straight tube 20, the end wall 32 is made of a fluororesin material such as PTFE. The end wall 32 does not have to be made entirely of PTFE; it is sufficient that at least the inner surface 34 of the end wall 32 is made of PTFE.

The inlet pipe 26 is provided near the first end 22 of the straight pipe 20 and extends radially, perpendicular to the axial direction of the straight pipe 20. The outlet pipe 28 is provided near the second end 24 of the straight pipe 20 and extends radially of the straight pipe 20. Therefore, in the irradiation device 10, fluid flows into the straight pipe 20 from a position close to the light source 14, flows inside the straight pipe 20 in a direction away from the light source 14, and is then discharged. Note that the direction of fluid flow may be reversed, and the inlet pipe 26 may be on the outlet side and the outlet pipe 28 on the inlet side.

In this embodiment, the straight pipe 20 is configured so that the arithmetic mean roughness Ra of the inner wall surface 18 is 2 μm or less. In order to achieve a surface roughness Ra of the inner wall surface 18 of 2 μm or less, for example, the inner wall surface 18 can be machined to remove minute irregularities on the inner wall surface 18. Alternatively, the surface roughness Ra of the inner wall surface 18 can be achieved by using a mold with a mirror finish on the surface that forms the inner wall surface 18 as the mold for molding the straight pipe 20.

The fluororesin material that makes up the inner wall surface 18 of the straight pipe 20 has high surface energy and is therefore extremely water-repellent. Therefore, if the inner wall surface 18 has minute irregularities, air bubbles tend to adhere to the irregularities, and once air bubbles form, they are difficult to remove. According to the inventors' findings, when the arithmetic mean roughness Ra of the PTFE surface exceeds 2 μm, air bubbles are observed adhering to the surface, and when Ra is 9 μm or greater, a large number of air bubbles adhere.

When air bubbles adhere to the inner wall surface 18 of the straight pipe 20, the difference in refractive index between the fluid and the air bubbles causes reflection or scattering at the bubble surface, affecting the UV light illuminance distribution inside the straight pipe 20. Because air bubbles do not necessarily occur in a fixed location, the illuminance distribution within the flow path changes depending on the number and location of the bubbles, resulting in variations in the amount of UV light irradiated onto the fluid. Furthermore, while the surface of a fluororesin material is primarily diffusely reflected, scattering incident UV light in various directions, the surface of an air bubble is primarily specularly reflected, tending to strongly reflect incident UV light in a specific direction. As a result, the formation of air bubbles can easily cause uneven illuminance distribution within the flow path. In this embodiment, the arithmetic mean roughness Ra of the inner wall surface 18 is set to 2 μm or less to reduce variations in the amount of irradiation due to the formation of air bubbles.

Figure 2 is a graph showing a schematic representation of the illuminance distribution within a flow channel according to a comparative example, illustrating the change over time in the radial illuminance distribution within the flow channel. In this comparative example, a PTFE tube with an inner diameter of 40 mm and an arithmetic mean roughness Ra of 4 μm on the flow channel inner wall surface was used, and the illuminance distribution was measured at a position 150 mm away from the light source. The inside of the PTFE tube was filled with pure water. Figure 2 shows a graph of the illuminance distribution measured at multiple times, with the intensity value at maximum light intensity normalized to 1. As shown in the figure, when the surface roughness of the flow channel inner wall surface is high, variations in light intensity are observed, with a maximum intensity change of approximately 30% occurring.

Figure 3 is a graph schematically illustrating the illuminance distribution within a flow channel according to an embodiment, showing the change over time in the illuminance distribution when PTFE with an arithmetic mean roughness Ra of 1.8 μm was used for the flow channel inner wall surface. In this example, a PTFE tube with an inner diameter of 40 mm was used, and the illuminance distribution was measured at a position 150 mm away from the light source with the PTFE tube filled with pure water. Figure 3 also shows a graph of the illuminance distribution measured at multiple times, with the intensity value at maximum light intensity normalized to 1. In this example, the small surface roughness of the flow channel inner wall surface resulted in small variations in light intensity, with a maximum intensity change of only approximately 5%. Thus, by setting the surface roughness to 2 μm or less, the change over time in the illuminance distribution within the flow channel can be minimized, reducing variations in the amount of irradiation.

Figure 4 is a diagram showing a schematic configuration of a purification device 70 according to an embodiment, illustrating an application example of the above-described irradiation device 10. The purification device 70 comprises an irradiation device 10 and a treatment device 60. The purification device 70 is a purification system for performing a two-stage purification process, in which pre-treatment is performed in the treatment device 60 and then post-treatment is performed in the irradiation device 10.

The treatment device 60 has a treatment tank 62 and an aeration device 64. The treatment device 60 is a device for purifying water using microorganisms. A contact material, to which aerobic microorganisms adhere, is provided inside the treatment tank 62. The aeration device 64 supplies air to the fluid inside the treatment tank 62, allowing the aerobic microorganisms to purify the fluid supplied from the inlet channel 71. After solids are removed from the fluid treated in the treatment tank 62, it is supplied to the irradiation device 10 via the connection channel 72.

The irradiation device 10 irradiates the fluid supplied from the treatment device 60 through the connection path 72 with ultraviolet light to purify the fluid, and discharges the treated fluid from the outlet path 73. Because air is supplied to the treatment device 60 through the aeration device 64, the fluid supplied through the connection path 72 has a relatively high dissolved air content and is prone to generating bubbles. However, in the irradiation device 10, the surface roughness of the flow path inner wall is set to 2 μm or less, so adhesion of bubbles to the flow path inner wall can be effectively suppressed even when a fluid with a high dissolved air content is supplied. As a result, the irradiation device 10 can irradiate ultraviolet light with high efficiency and suppress uneven irradiation caused by bubbles. Therefore, according to this embodiment, the processing capacity of the purification device 70 can be stabilized.

The present invention has been described above based on the embodiments. Those skilled in the art will understand that the present invention is not limited to the above embodiments, and that various design changes and modifications are possible, and that such modifications are also within the scope of the present invention.

In the above-described embodiment, a straight-pipe-shaped flow path structure is used, but the shape of the flow path structure is not particularly limited. In a modified example, the entire flow path may not be linear, but at least a portion of the flow path may have a bent section. Furthermore, the cross-sectional shape of the flow path may be circular or polygonal.

In the above-described embodiment, a fluororesin material is used for the entire inner wall surface of the flow path. In a modified example, a fluororesin material may be used for only a portion of the inner wall surface of the flow path. By setting the surface roughness Ra of the fluororesin material used for a portion of the inner wall surface of the flow path to 2 μm or less, it is possible to suppress the adhesion of air bubbles to the fluororesin surface and stabilize the reflection characteristics of ultraviolet light on the fluororesin surface.

In the above-described embodiment, an ultraviolet LED is used as the light source 14. In a modified example, an ultraviolet lamp may be used as the light source, and an ultraviolet lamp with a center or peak wavelength of 250 nm to 260 nm, for example 254 nm, may be used.

10...Irradiation device, 12...Flow path structure, 14...Light source, 18...Inner wall surface, 20...Straight tube.

Claims (4)

a flow path structure including a straight pipe, an inlet pipe for introducing water into the straight pipe, and an outlet pipe for discharging water from the straight pipe, wherein at least a portion of the inner surface of the straight pipe is made of polytetrafluoroethylene (PTFE) having an arithmetic mean roughness of 2 μm or less by cutting ;
an irradiation device comprising: a light source that irradiates ultraviolet light toward the water flowing inside the straight pipe. a flow path structure including a straight pipe, an inlet pipe for introducing water into the straight pipe, and an outlet pipe for discharging water from the straight pipe, wherein at least a portion of the inner surface of the straight pipe is made of polytetrafluoroethylene (PTFE) having an arithmetic mean roughness of 1.8 μm;
a light source that irradiates ultraviolet light toward the water flowing inside the straight pipe,
The light source is an irradiation device that irradiates ultraviolet light in the axial direction of the straight tube. the flow path structure further includes an irradiation window provided at a first end of the straight pipe;
The irradiation device according to claim 1 or 2, wherein the light source irradiates the inside of the straight tube with ultraviolet light through the irradiation window. the flow path structure further includes an end wall provided at a second end of the straight pipe;
4. The illumination device of claim 1, wherein the inner surface of the end wall is made of PTFE.