JPH09220590A - Oxygen gas dissolving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxygen gas dissolving method enhanced in the dissolving power of O2 into a soln. and capable of being operated in low cost. SOLUTION: In a method dissolving O2 gas in a soln. by utilizing oxygen- containing gas as a raw material, the high purity oxygen enriched gas separated by an air separator 1 is compressed to be supplied into a pressure liquid tank 3 and the soln. is supplied to the pressure liquid tank 1 from the upper part thereof to dissolve O2 gas in the supplied soln. and the supplied soln. is supplied to the bottom part of an outside soln. from the pressure liquid tank 3 to increase dissolved oxygen in the soln. by liquid pressure.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for dissolving oxygen gas (O ₂ gas) for supplying oxygen used in wastewater treatment equipment (oxidation process or biological treatment), bioreactors and the like.

[0002]

2. Description of the Related Art Aerobic microorganisms are used to decompose pollutants and to reduce COD-causing substances for the treatment of industrial wastewater, lake purification, river purification, fish farm environment improvement, etc. The method of using O ₂ in the air such as oxidation is widely used in the industrial world. The method of supplying O ₂ is to blow the air directly into water or pressurize and dissolve the air in some water. The pressurized water method of supplying the water is generally adopted.

For example, in the case of water at room temperature, about 8 ppm of dissolved oxygen can be obtained by blowing air into the water. About 20.5% O ₂ is contained in the air, but if it is replaced with 85% O ₂ gas, the dissolving power is increased about 4 times and the dissolved oxygen is improved to about 30 ppm. Furthermore, if pressurized water is used, the amount of dissolved oxygen increases in proportion to the pressure, and the shortage of dissolved oxygen, which is a drawback of the conventional method, is eliminated.

[0004]

In the above conventional method, O ₂ is affected by the effect of N ₂ and Ar contained in the air at about 80%.
The dissolving power (O ₂ partial pressure) is only about 1/4 of the supply pressure, that is, the O ₂ concentration is low. Furthermore, inactive N ₂ and Ar are simultaneously dissolved in water.

Particularly in the case of the conventional pressurized water method, N ₂ and Ar are generated as white turbid bubbles when the supply air is depressurized, which causes agitation or floating separation of suspended matter, which makes wastewater treatment conditions extremely difficult. .

Further, in the pressurized water method, O is used instead of air.
_{If two} gas cylinders are used, the amount of dissolved oxygen will increase. However, when the O ₂ gas cylinder is used, the operating cost becomes high, and therefore it is practically used only for a special purpose.

The present invention is intended to provide an O ₂ gas melting method capable of solving the above-mentioned drawbacks.

[0008]

The present invention relates to an oxygen gas dissolving method for dissolving O ₂ gas in a solution using a gas containing O ₂ gas as a raw material, and enriching highly pure oxygen separated by an air separation device. The gas is compressed and supplied into the pressurized liquid tank, and the solution is supplied from the upper part of the pressurized liquid tank to dissolve the O ₂ gas in the supplied solution, and then the supplied solution is removed from the pressurized liquid tank. It is characterized in that it is supplied to the bottom of the external solution to increase the dissolved oxygen of the solution by hydraulic pressure.

In the present invention, the high-purity oxygen-enriched gas separated by the air separation device is dissolved in the solution under pressure in the pressurized liquid tank instead of air, so that the dissolving power of O ₂ is remarkably improved. Can be made. In addition, the pressure of the high-purity oxygen-enriched gas can be lowered and the power for compressing the oxygen-enriched gas can be reduced with the improvement of the dissolving power of O ₂ .

Further, a pressurized liquid in which O ₂ gas is dissolved is supplied to the bottom of the solution outside the pressurized liquid tank, and the liquid pressure of the solution suppresses the dissolution of the pressurized liquid O ₂ into air bubbles as much as possible. It can be easily dissolved and diffused in.

At the same time, as compared with the case where air is used, the N ₂ gas and Ar gas in the high-purity oxygen-enriched gas become minute amounts, so that the O ₂ gas is dissolved at the bottom of the solution outside the pressurized liquid tank. When the above pressurized liquid is supplied, foaming of N ₂ gas, Ar gas, etc. is remarkably reduced, and troubles due to foaming bubbles can be minimized.

The high-purity oxygen-enriched gas can be supplied on-site at a lower cost than the air separation device, and
The operating cost can be reduced as compared with the case where the O ₂ gas is supplied using a cylinder in which the O ₂ gas is compressed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIG. Reference numeral 10 is water used for a purification device by aerobic microorganisms such as lakes and rivers, a bioreactor, forced oxidation treatment of waste liquid, etc., part of which is a pressurized water pump 4
The upper nozzle 3 of the pressurized water tank 3 via the pipe 11
-1 is supplied to the upper part of the pressurized water tank 3.

The first method is to use an adsorbent having a property of preferentially adsorbing N ₂ gas, and perform an adsorption step and a desorption step alternately by a pressure swing method (hereinafter referred to as PSA method) to carry out O ₂ gas in air. Is a multi-tower pressure swing type (hereinafter referred to as PSA type) O ₂ production apparatus for continuously concentrating
The O ₂ gas (oxygen-enriched gas) having a purity of 85 to 97% produced by the SA type O ₂ production apparatus 1 is compressed to a pressure of 3 to 5 kg / cm ² G by the O ₂ gas compressor 2 and the compressed water It is designed to be supplied into the tank 3.

If necessary, the pressurized water tank 3 may be filled with a ring-shaped filling material in order to improve the contact efficiency of gas and liquid.

The lower nozzle 3-2 of the pressurized water tank 3
Is connected to a pipe 12 having a pressure reducing valve 5, and the pipe 12 is connected to a plurality of jet nozzles 6 provided near the bottom of the water 10 outside the pressurized water tank 3.

[0017] Incidentally, 1a Hara air compressor for sending feed air to the PSA formula O ₂ production apparatus 1, 1b is N ₂ gas compression for discharging the N ₂ (nitrogen) gas separated in PSA expression O ₂ production apparatus 1 It is a machine.

The gas follows Henry's law when dissolved in a solution such as water. Henry's law is given by p '= Hx, where p'is the partial pressure of the dissolved gas in the gas phase, x is the equilibrium molar concentration in the liquid phase, and H is the Henry's constant. This expression is
It shows that the gas dissolves in the liquid phase in proportion to the partial pressure of the gas in the gas phase.

On the other hand, the relationship between the partial pressure p'a of a specific gas and the total pressure P is represented by p'a = Pxa. For example, atmospheric condition 1
If the atm contains 20% O ₂ gas, p′o ₂
= 1 atm × 0.2 = 0.2 atm. 100% O
_In case of ₂ gases, p'o ₂ = 1 atm × 1.0 = 1.0a
tm and increase. As a result, if the O ₂ concentration in the gas phase is increased and the total pressure is also increased, O ₂ is proportionally increased.
The amount of gas dissolved in the solution increases. Further, if the total pressure is reduced, the dissolved gas is released as bubbles until the equilibrium state is reached.

In the present embodiment, as described above, the pressurized water tank 3 has a purity of 8% produced by the PSA type O ₂ production apparatus.
5 to 97% of O ₂ gas is 3 to 5 k by the O ₂ compressor 2.
Since the water is supplied after being compressed to a pressure of g / cm ² G, when the water supplied from the upper nozzle 3-1 into the pressurized water tank 3 descends in the pressurized water tank 3, the gas and liquid come into contact with each other, and the Henry O ₂ gas is dissolved under pressure in water according to the above rule, and the amount of dissolution increases.

The water obtained by pressurizing and dissolving O ₂ gas in the pressurized water tank 1 as described above is stored in the lower portion of the pressurized water tank 1. The dissolved oxygen in the pressurized water when it is pressurized to 5 kg / cm ² G by the compressed O ₂ gas is about 150 ppm.

O is stored in the lower part of the pressurized water tank 1._Two
Pressurized water obtained by pressurizing and dissolving gas is depressurized at the lower nozzle 3-2.
Provided near the bottom of the water 10 through the pipe 12 with the valve 5.
Of the water 10 outside the pressurized water tank 1 from the ejected nozzle 6
Released inside. Here, the pressurized water is the water of water 10.
The pressure is reduced to p, but when mixed with surrounding water, O _Two
The gas dissolves in the surrounding water 10. Fine white turbidity
Bubbles, but further contact with water 10 while slowly rising
And dissolve on the water side. In this case, N_TwoGas, A
Only a small amount of r gas is included, and foaming is remarkable.
Decrease.

Further, since the pressurized water bubbles are very fine as compared with ordinary nozzle blowing bubbles, the contact area with water is large and the residence time in water is long, so that the dissolution efficiency in water is extremely high. .

The O ₂ gas thus dissolved in the water 10 has the function of oxidizing water and maintaining the aerobic state of microorganisms.

In the present embodiment, as described above, the PSA
Since the high-purity O ₂ gas produced by the formula O ₂ production apparatus 1 is dissolved in water under pressure in the pressurized water tank 3, the dissolving power of oxygen is four times or more as compared with the case of using air. Can be improved. Further, as compared with the case where air is used, nitrogen gas is contained in the O ₂ gas having a high concentration,
Since the amount of the argon gas is very small, when the pressurized water in which the O ₂ gas is dissolved is ejected from the ejection nozzle 6 into the water 10 outside the pressurized water tank, the foaming amount is significantly reduced and the bubbles become finer, thereby suppressing the troubles caused by the foaming bubbles. Moreover, the O ₂ gas can be efficiently dissolved in the water 10 outside the pressurized water tank.

In order to dissolve the O ₂ gas, the high-purity and inexpensive O ₂ gas produced by the PSA O ₂ production apparatus is used instead of air, so that the dissolution pressure of the O ₂ gas is reduced. The power of the O ₂ gas compressor 2 can be reduced and the cost can be reduced.

[0027]

As described above, according to the present invention, by having the constitution described in the claims, the amount of dissolved oxygen in the solution can be increased and the O ₂ supply amount can be greatly increased. At the same time, it is possible to eliminate the influence of bubbles generated by unnecessary N ₂ and Ar. Further, it is possible to use an inexpensive high-purity oxygen-enriched gas separated by an oxygen separation device, and further reduce the dissolution pressure of the solution of the gas,
The operating cost can be reduced.

[Brief description of drawings]

FIG. 1 is a flow chart of an embodiment of the present invention.

[Explanation of symbols]

1 PSA type O ₂ production apparatus 2 O ₂ gas compressor 3 pressurized water tank 3-1 upper nozzle 3-2 lower nozzle 4 pressurized water pump 5 pressure reducing valve 6 jet nozzle 10 water 11, 12 pipe

Claims (1)

[Claims] 1. In an oxygen gas dissolving method of dissolving oxygen gas in a solution using a gas containing oxygen gas as a raw material, a highly pure oxygen-enriched gas separated by an air separator is compressed and supplied into a pressurized liquid tank. At the same time, the solution is supplied from the upper part inside the pressurized liquid tank to dissolve oxygen gas in the supplied solution, and then the supplied solution is supplied from the pressurized liquid tank to the bottom of the external solution by hydraulic pressure. A method for dissolving oxygen gas, which comprises increasing the dissolved oxygen of a solution.