JPH0785763B2 - Method of removing dissolved oxygen - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing dissolved oxygen in a liquid, and more particularly to a method for removing dissolved oxygen having a relatively low concentration.

[0002]

2. Description of the Related Art As a method for removing dissolved oxygen (hereinafter referred to as DO) in water, a physical method such as vacuum degassing by a packed tower or a membrane, nitrogen gas purging, etc., and a chemical method of adding a reducing agent, And methods of combining these are known. For the purpose of improving these methods, the present inventors have proposed a method of first dissolving hydrogen in water and then reacting oxygen with hydrogen by ultraviolet irradiation to remove dissolved oxygen. However, the contact probability between hydrogen and oxygen becomes smaller as the dissolved oxygen concentration becomes lower, and ultraviolet rays with a wavelength of 200 nm or less, which is important in this reaction, are greatly attenuated by the absorption of ultraviolet rays by water. Was done.

[0003]

As described above, in the method of irradiating ultraviolet rays in the presence of hydrogen, it is important to increase the reaction efficiency between hydrogen and oxygen and increase the efficiency of ultraviolet ray irradiation. Met. Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a method for removing dissolved oxygen more easily and efficiently.

[0004]

In order to achieve the above object, in the present invention, in a method for removing dissolved oxygen in a liquid, in the presence of bubbles of a mixed gas of hydrogen and an inert gas in the liquid, It is intended to irradiate with ultraviolet rays. Here, as the inert gas, a gas that transmits ultraviolet rays and is inert to the liquid to be irradiated may be used, and nitrogen, argon, CO _2, or the like can be used. As the concentration of the mixed gas, a concentration below the explosion limit of hydrogen is desirable, and when the concentration of dissolved oxygen in the water to be treated is low, in order to suppress excess unreacted hydrogen remaining, It is desirable to reduce the hydrogen concentration to the necessary minimum. As a method for injecting the mixed gas into the liquid, any means such as an air diffuser, an air diffuser nozzle, and an ejector can be used. After the reaction, excess hydrogen and inert gas may be separated from the liquid, and the separated gas may be circulated and supplied again into the liquid. A wavelength of 20 for an ultraviolet light source
Any light source capable of irradiating vacuum ultraviolet rays of 0 nm or less may be used, and a low-pressure mercury lamp using synthetic quartz for the lamp tube and the protection tube can be usually used.

[0005]

The action of irradiating the liquid with ultraviolet rays in the presence of bubbles of a mixed gas of hydrogen and an inert gas has the following actions. The bubbles promote the diffusion and mixing of water.
Further, since light is dispersed on the surface of the bubble and the bubble moves, unevenness of irradiation intensity is reduced. In addition, the thickness of the liquid in the irradiation device is substantially reduced by the addition of the ultraviolet-transparent inert gas. Further, hydrogen has a higher moving speed in the gas phase than in the liquid phase of the same volume, and since the bubbles themselves move with respect to the liquid, the contact efficiency with dissolved oxygen in water is high. Therefore, the amount of hydrogen gas in the mixed gas is usually about 0.01 to 4%. Further, the contact time may be appropriately adjusted depending on the reaction container. Thus, by irradiating with ultraviolet rays in the presence of bubbles of a mixed gas of hydrogen and an inert gas, dissolved oxygen can be efficiently removed.

[0006]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. Example 1 FIG. 1 is a schematic diagram showing an example of an embodiment of the present invention. FIG. 2 is a schematic flow chart showing an example of a secondary pure water treatment apparatus incorporating the dissolved oxygen removing apparatus of the present invention. In FIG. 1, the water 14 to be treated is introduced into the apparatus through a water inlet 4 to be treated which is opened on the upper side wall of the apparatus jacket 1. The deoxygenated mixed gas 16 is introduced into the tank through the diffuser 7 from the mixed gas inflow port 6 opened on the side wall below the jacket. Thus, the water to be treated and the gas are countercurrently contacted and exposed to ultraviolet rays. Ultraviolet rays are radiated into the tank from a UV lamp 2 inserted in a lamp protection tube 3 made of synthetic quartz and purged with N ₂ gas, and the dissolved oxygen is efficiently removed by the above-mentioned action. The treated water flows out from the treated water outlet 5 at the bottom of the jacket, is introduced into the mixed bed ion exchange column 12 by the pressurizing pump 17 in FIG. 2, and is then treated by the ultrafiltration device 13 to become pure water 15. Further, the hydrogen-containing gas that has finished contacting is sent to the purge tank 9 through the purge pipe 8. The remaining gas may be returned to the mixed gas inflow port 6 again.

In the experiment, pure water obtained by subjecting tap water to microfiltration, RO treatment, ion exchange and membrane degassing treatment was used as treated water, and water was passed through a secondary pure water treatment device at a flow rate of 1 m ³ / h. I went. As a mixed gas to be added, nitrogen gas containing 0.9% of hydrogen was used, and the mixed gas was added at a flow rate of 0.2 m ³ / h by a diffuser tube method. As the ultraviolet irradiation device, three low-pressure mercury lamps made of synthetic quartz and having an output of 70 w were used. The results are shown in Table 1.
Shown in. As the inert gas, argon gas, carbon dioxide or the like may be appropriately used in addition to nitrogen gas, and the same result is obtained.

Comparative Example 1 FIG. 3 is a schematic flow chart of the secondary pure water treatment apparatus used in the comparative example. In FIG. 3, reference numeral 21 is a degassing film, 22 is a hydrogenation film, and 23 is a dissolved oxygen removing device. Hydrogen is dissolved in a part of the water 14 to be treated, and the dissolved oxygen removing device 23 irradiates ultraviolet rays. In the experiment, pure water similar to that used in the example was used as water to be treated, and water was passed at a flow rate of 1 m ³ / h. Pure hydrogen was added at a rate of about 30 ml / min through the gas permeable membrane, and the same ultraviolet irradiation device as in the example was used. The results are shown in Table 1.

[Table 1]

[0009]

[Effect] As described above, by irradiating with ultraviolet light in the presence of bubbles of a mixed gas of hydrogen and an inert gas, the mixing state of water in the device is improved and the contact efficiency between hydrogen and oxygen is increased. Therefore, dissolved oxygen in water can be efficiently removed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an apparatus used in the method for removing dissolved oxygen of the present invention.

FIG. 2 is a schematic flow chart showing an example of a secondary pure water treatment apparatus using the dissolved oxygen removing method of the present invention.

FIG. 3 is a schematic flow diagram of a secondary deionized water treatment apparatus using a hydrogenation by a membrane and a dissolved oxygen removal apparatus by ultraviolet irradiation.

[Explanation of symbols] 1: Jacket, 2: UV lamp, 3: Lamp protection tube,
4: treated water inlet, 5 treated water outlet, 6: mixed gas inlet, 7: diffuser, 8: purge pipe, 9: purge tank, 11: dissolved oxygen removing device (present invention), 12: mixed bed ion Exchange tower, 13: ultrafiltration device, 14: treated water,
15: treated water (pure water), 16: mixed gas, 17: pressure pump, 21: degassing film, 22: hydrogenation film, 23: dissolved oxygen removing device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Ken Nakajima Ken 6-6 27 Konan, Minato-ku, Tokyo Ebara Infilco Co., Ltd. (56) Reference JP-A-63-236593 (JP, A)

Claims (1)

[Claims] 1. A method for removing dissolved oxygen in a liquid, which comprises irradiating with ultraviolet rays in the presence of bubbles of a mixed gas of hydrogen and an inert gas in the liquid. .