JP2000107512A - Method for reducing dissolved oxygen and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently reduce the content of a dissolved oxygen by performing the pressure boosting and the pressure reduction of a liquid containing the dissolved oxygen once or more, then mixing the liquid after the pressure boosting with an inert gas and separating the insert gas containing a dissipated oxygen from the liquid after the pressure reduction and exhausting the inert gas. SOLUTION: A liquid introduced into a liquid feed pump 1 through a valve 12 from a flow path 11 is pressurized to a preset pressure level using the liquid feed pump 1 and then is made to flow into liquid feed piping 2a in a gas introduction part 2 through a flow path 13, a valve 14 and a flow path 15. The liquid pressure is boosted by the pump 1 in such a manner that the difference between the primary side and the secondary side of the pump 1 side of a throttle part 3 is as specified. An inert gas introduced through valves 22, 23 from flow paths 21, 21 is adjusted to a specified pressure level using a pressure setter 23, and this pressure-adjusted inert gas is jetted into the liquid from a sparger 5 through an inert gas supply passage 6 to produce a fluid which is in a gas/liquid mixed state. The gas/liquid mixed fluid is fed into a tank 4 through a flow path 31 to be separated into a gas and a liquid after a dissolved oxygen is dissipated and then is loaded into inert gas bubbles, passing through the throttle part 3. After this process, the inert gas containing the oxygen is exhausted from an exhaust passage 8. Thus it is possible to remove the dissolved oxygen.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for reducing dissolved oxygen, and more particularly, to liquids such as edible oil, wine, sake, soy sauce, water for food processing, and photographic developers. The present invention relates to a method and an apparatus for reducing dissolved oxygen contained in, for example.

[0002]

2. Description of the Related Art As a method for reducing dissolved oxygen in various liquids, a gas degassing method in which an inert gas is bubbled in a liquid, a heat degassing method in which a liquid is heated, and a deoxidizing agent such as a sulfite in a liquid. There are known a chemical degassing method in which a liquid is stored in a container, a vacuum degassing method in which the pressure in a container storing a liquid is reduced, and a film type degassing method using a deoxygenation film.

[0003] Among these methods, the gas degassing method has various proposals for improving the efficiency of removing dissolved oxygen since it is difficult to remove oxygen sufficiently only by simple bubbling of an inert gas. Have been. For example, JP-A-6-2
In the dissolved oxygen reducing device described in US Pat.
Dissolved oxygen is gradually removed by arranging a plurality of bubbling tanks in series and bubbling nitrogen gas. In addition, Japanese Patent Application Laid-Open Nos. 5-184711, 1-297105, and 1-31
In the deoxygenation method described in JP 7586 and the like, dissolved oxygen is introduced into nitrogen gas by flowing a liquid containing fine bubbles such as nitrogen gas at an ultra-high speed or by vigorous stirring. Further, JP-A-62-29
In the degassing apparatus described in Japanese Patent No. 4482, vacuum degassing and gas degassing are combined.

In the degassing operation, it is desirable to form microbubbles such as nitrogen gas in the liquid.
The methods described in JP-A-63371 and JP-A-6-205813 are known.

[0005]

However, in the conventional method, the efficiency of deaeration of dissolved oxygen cannot be said to be sufficiently high. In the aging process of wine and the like, if the amount of dissolved oxygen is large, there is a disadvantage that the liquid is oxidized. On the other hand, it is necessary to secure a certain amount of dissolved oxygen for aging.

Accordingly, an object of the present invention is to provide a method and an apparatus for reducing dissolved oxygen which can efficiently reduce dissolved oxygen with a simple operation and can easily adjust the amount of oxygen removed.

[0007]

In order to achieve the above object, a method for reducing dissolved oxygen according to the present invention comprises performing at least one pressure raising operation and one pressure reducing operation on a liquid containing dissolved oxygen, and An inert gas mixing operation of introducing an inert gas into the liquid to mix the liquid and the inert gas,
A gas separation operation of separating and exhausting the liquid after the pressure reduction operation and the inert gas containing oxygen released from the liquid is performed.

Further, the method for reducing dissolved oxygen according to the present invention comprises:
The gas separated by the gas separation operation is reused as an inert gas introduced into a liquid by the inert gas mixing operation according to the oxygen concentration in the gas, and the pressure after the pressure increasing operation and the pressure reduction are reduced. The difference from the pressure after the operation is 0.1 MPa or more.

Further, the dissolved oxygen reducing device of the present invention comprises: a liquid sending pump for increasing the pressure of a liquid containing dissolved oxygen; a gas introducing unit for introducing an inert gas into the liquid after the pressure is increased by the liquid sending pump; And a throttle unit for reducing the pressure of the liquid after the introduction of the gas in the gas introduction unit.

[0010] Further, the apparatus for reducing dissolved oxygen of the present invention comprises:
A gas-liquid separator on the secondary side of the throttle unit, or a tank that stores a decompressed liquid and has a gas discharge path, wherein the tank contains an inert gas for purging. It is characterized by having a purge gas introduction path for introduction.

The gas inlet is provided at the center of the liquid feed pipe, and has a sparger for ejecting the inert gas radially from the center of the pipe. The ejection part is formed of a sintered metal.

[0012]

FIG. 1 is a system diagram showing one embodiment of a device for reducing dissolved oxygen to which the present invention is applied. This apparatus for reducing dissolved oxygen includes a liquid feed pump 1 for increasing the pressure of a liquid containing dissolved oxygen, a gas introduction unit 2 for introducing an inert gas into the liquid after the pressure increase, and a throttle unit 3 for reducing the pressure of the liquid after gas introduction. A tank 4 for storing the decompressed liquid, an inert gas supply path 6 for supplying an inert gas to a sparger 5 provided in the gas introduction unit 2, and an inert gas for purging in the tank 4. A purge gas introduction path 7 for introducing a gas and an exhaust path 8 for discharging an inert gas accompanied by oxygen separated from the liquid from the tank 4 are provided.

A sparger 5 provided at the tip of the inert gas supply passage 6 is formed so as to radially eject an inert gas from a central portion of a liquid feed pipe 2a constituting the gas introducing section 2. For example, as shown in FIG. 2, a cylindrical body is provided with a large number of injection ports 5 a formed of fine through holes on the peripheral surface, or as shown in FIG. Can be used.

By using the sparger 5 to form fine air bubbles and jetting the air bubbles radially, contact and mixing of gas and liquid can be promoted, and the liquid and the active gas can be efficiently mixed. Depending on the flow rate of the liquid and the degree of removal of the dissolved oxygen, it may be sufficient to simply connect the inert gas supply path to the liquid supply path.

The liquid introduced into the liquid feed pump 1 from the path 11 via the valve 12 is boosted to a predetermined pressure by the liquid feed pump 1, and then passed through the path 13, the valve 14, and the path 15 to the liquid introducing section 2. It flows into the liquid sending pipe 2a. The pressure increasing operation in the liquid feed pump 1 also differs depending on the primary pressure of the liquid feed pump 1 and the secondary pressure of the throttle unit 3, but the difference between the primary pressure and the secondary pressure in the throttle unit 3 is different. It is preferable to increase the pressure of the liquid so as to be 0.1 MPa or more. If this pressure difference is small, it will be difficult to obtain a sufficient separation effect. On the other hand, if the pressure difference is too large, the pressure resistance of the liquid feed path must be increased, and the cost of the apparatus increases. Therefore, 1 MPa or less, usually 0.5 MPa or less is appropriate. The pressure of the liquid after the pressure raising operation is measured by a pressure gauge (PI) 16, and the flow rate is measured by a flow meter (FI) 17.

On the other hand, the inert gas introduced from the passages 21 and 21 through the valves 22 and 22 is adjusted to a predetermined pressure by a pressure setter (regulator) 23 and then passes through the inert gas supply passage 6. And supplied to the sparger 5,
The gas is jetted into the liquid to generate a gas-liquid mixed fluid. The pressure of the inert gas is measured by a pressure gauge (PI) 24.

The supply amount of the inert gas varies depending on the flow rate of the liquid, the dissolved oxygen amount, and the desired oxygen removal amount. In general, if the supply amount of the inert gas is increased, that is, the gas in the gas-liquid mixed flow is increased. If the liquid ratio is increased, the amount of dissolved oxygen that can be removed can be increased, and the amount of dissolved oxygen after the treatment can be further reduced.

In the above inert gas mixing operation, sparger 5
The fluid in a gas-liquid mixed state entrained with the inert gas ejected from the nozzle is in contact with the liquid and the inert gas, and when passing through the throttle unit 3, the dissolved oxygen is diffused out of the liquid and becomes insoluble. The active gas flows into the tank 4 in a state of being taken in the bubbles, and is sent from the path 31 into the tank 4. At this time, the air bubbles mixed with the liquid are gradually gas-liquid separated in the path 31 by the difference in specific gravity from the liquid, and almost completely gas-liquid separated in the tank 4, and provided at the top of the tank 4. The inert gas containing oxygen is exhausted from the exhaust path 8.

The pressure of the liquid after decompression is measured by a pressure gauge (PI) 3
2, and the dissolved oxygen concentration in the liquid is measured by a dissolved oxygen concentration meter (DO) 33. In addition, tank 4
The dissolved oxygen concentration of the liquid in the tank is measured by a dissolved oxygen concentration meter (DO) 3.
4 measured.

The pressure in the tank 4 is controlled such that an inert gas, the pressure of which has been adjusted by a regulator 43 from a passage 41 via a valve 42, is introduced from the purge gas introduction passage 7, and the gas in the tank 4 is maintained at a pressure holding valve in an exhaust passage 8. It is kept at a predetermined pressure by being exhausted through 81. That is, when the pressure in the tank 4 becomes lower than the pressure set by the regulator 43 due to the consumption of the liquid in the tank 4, the inert gas is introduced into the tank 4 from the purge gas introduction path 7. In addition, the tank 4
When the internal pressure becomes higher than the pressure set by the pressure holding valve 81,
The gas in the tank 4 is exhausted from the exhaust path 8.

The pressure in the tank is within a range that can prevent the invasion of the atmosphere, is lower than the pressure in the pipe in consideration of the pressure loss, and is equal to or lower than the normal pressure of the tank 4. For example, about 500 mmAq is appropriate. It is. The pressure of the purge gas in the purge gas introduction path 7 is measured by a pressure gauge (PI) 4
4 measured.

Therefore, the pressure (secondary pressure) after the pressure reduction in the pressure reducing operation after the throttle unit 3 is set to be higher than the pressure at which the fluid after the pressure reduction can flow into the tank 4. As the difference between the primary side pressure and the secondary side pressure of the part 3 is increased, the dissolved oxygen reduction effect is also improved. That is, by appropriately setting the boost pressure of the liquid sending pump 1 in accordance with the effect of reducing dissolved oxygen in the throttle section 3 and thereafter, the removal and reduction of dissolved oxygen can be performed efficiently and effectively.

As described above, by introducing the inert gas into the pressurized liquid and then reducing the pressure at once, the dissolved oxygen concentration in the liquid can be reduced to 2 ppm or less, and further to about 0.8 ppm. By appropriately setting the boosting pressure, the amount of the inert gas introduced, and the like, the desired dissolved oxygen amount can be adjusted. In addition, even if the bubble diameter of the inert gas is large to a certain extent, a sufficient separation effect can be obtained, and
Since the flow rate is not made extremely fast, heated to a high temperature, or an oxygen scavenger is not used, it can be implemented with a simple apparatus configuration, and there is no problem in food hygiene.

FIG. 4 shows a gas-liquid separator 5 on the secondary side of the throttle section 3.
1 shows an example in which 1 is provided. As described above, by providing the gas-liquid separator 51, the inert gas containing oxygen mixed in the liquid is quickly separated by the gas-liquid separator 9 and exhausted from the passage 91. The amount of gas flowing into the tank 4, that is, the amount of oxygen can be significantly reduced. As a result, the increase in the oxygen concentration in the gas phase of the tank 4 is reduced, so that the amount of the inert gas introduced from the purge gas introduction path 7 can be reduced.

Various types of gas-liquid separators 9 can be used. For example, a centrifugal gas-liquid separator can be used. Since the other device configuration can be formed in the same manner as the embodiment shown in FIG. 1, the same reference numerals are given to the same components as those in the first embodiment, and the detailed description is omitted. .

It is also possible to arrange a plurality of sets of the liquid feed pump 1, the gas introduction section 2, the throttle section 3 and the gas-liquid separator 9 as described above, and to arrange them in parallel or in series. It is also possible to circulate the liquid in the upstream of the liquid feed pump 1 and reprocess the liquid.

Further, the inert gas (separated gas) separated from the liquid after the pressure reduction contains oxygen removed from the liquid, and the oxygen concentration is higher than that of the initial inert gas. Since the increase in the oxygen concentration is slight, the separated gas can be reused as an inert gas to be introduced into the liquid after the pressurization according to the oxygen concentration. As a result, the usage efficiency of the inert gas can be increased, and its consumption can be reduced.

The pressure of the liquid can also be increased by a liquid head, gas pressurization, or the like. The inert gas includes nitrogen gas, argon gas, carbon dioxide, etc., depending on the type of liquid and the supply environment of the inert gas. You can select the one that suits you. Also,
As the throttle portion, various types such as an orifice, a needle valve, and a diaphragm valve can be used as long as they can perform a predetermined depressurizing operation, and the degree of depressurization can be continuously adjusted by using a needle valve or the like. Can be. In addition, the pressure can be reduced by expanding the diameter of the piping at once, or by flowing it into a tank with a large volume.However, considering the pressure of the pressurized liquid and the cost and labor involved in installing the piping, the orifice A simple throttle portion such as described above is preferable.

[0029]

EXAMPLE An experiment was conducted in which water was used as a liquid and dissolved oxygen was removed by a dissolved oxygen reducing device having the structure shown in FIG. Water was normal temperature (about 20 ° C.) and normal pressure, the viscosity was 1 cP, and the dissolved oxygen concentration was 9 ppm. A high-purity nitrogen gas (oxygen content: 0.1 ppm or less) was used as the inert gas.

The discharge pressure of the liquid feed pump 1 and the amount of nitrogen gas introduced in the gas introduction unit 2 were variously set, and the concentration of dissolved oxygen contained in water after the pressure was reduced to approximately atmospheric pressure after the throttle unit 3 was measured. . Table 1 shows the results.

[0031]

[Table 1]

[0032]

As described above, according to the present invention,
Dissolved oxygen can be reliably removed with a simple device configuration, it is cheaper than conventional ones, and it does not adversely affect the liquid after treatment, so that foods etc. can be treated safely. it can. Further, since the apparatus main body can be formed in a small size, it can be easily attached to existing facilities.

[Brief description of the drawings]

FIG. 1 is a system diagram showing one embodiment of a dissolved oxygen reducing device of the present invention.

FIG. 2 is a cross-sectional view illustrating an example of a form of a sparger.

FIG. 3 is a cross-sectional view illustrating another example of a sparger.

FIG. 4 is a system diagram showing another embodiment of the dissolved oxygen reducing device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Liquid sending pump, 2 ... Gas introduction part, 3 ... Restriction part, 4 ... Tank, 5 ... Sparger, 6 ... Inert gas supply path, 7
... Purge gas introduction path, 8 ... Exhaust path, 9 ... Gas-liquid separator

Claims (9)

[Claims] 1. An inert gas that performs at least one pressurizing operation and a depressurizing operation on a liquid containing dissolved oxygen, and introduces an inert gas into the liquid after the pressurizing operation to mix the liquid with the inert gas. A method for reducing dissolved oxygen, comprising: performing a gas mixing operation and a gas separation operation of separating and exhausting a liquid after the pressure reduction operation and an inert gas containing oxygen released from the liquid. 2. The method for reducing dissolved oxygen according to claim 1, wherein the gas separated by the gas separation operation is reused as an inert gas introduced into a liquid by the inert gas mixing operation. 3. The method for reducing dissolved oxygen according to claim 1, wherein a difference between the pressure after the pressure increasing operation and the pressure after the pressure reducing operation is 0.1 MPa or more. 4. A liquid sending pump for increasing the pressure of a liquid containing dissolved oxygen, a gas introduction unit for introducing an inert gas into the liquid after the pressure is increased by the liquid sending pump, and a gas introduction unit for introducing the gas in the gas introduction unit. An apparatus for reducing dissolved oxygen, comprising: a throttle section for reducing the pressure of a liquid. 5. The apparatus for reducing dissolved oxygen according to claim 4, wherein a gas-liquid separator is provided on a secondary side of the throttle section. 6. The apparatus for reducing dissolved oxygen according to claim 4, wherein a tank having a gas discharge path and storing a liquid after decompression is provided on a secondary side of the throttle section. 7. The apparatus for reducing dissolved oxygen according to claim 6, wherein the tank has a purge gas introduction path for introducing an inert gas for purging. 8. The gas introduction part according to claim 4, wherein the gas introduction part includes a sparger that is provided at a central part of the liquid feed pipe and that jets the inert gas radially from the central part of the pipe. Equipment for reducing dissolved oxygen. 9. The apparatus for reducing dissolved oxygen according to claim 8, wherein the sparger has a spouted portion of an inert gas formed of a sintered metal.