JPH0119930B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gas dissolving method for efficiently dissolving gases such as oxygen and ozone into liquids such as tap water or sewage.

[Conventional technology]

Conventional gas dissolution methods involve ejecting the gas to be dissolved into the liquid as fine bubbles, as seen in the dissolution of ozone into tap water and the dissolution of oxygen into sewage during activated sludge treatment. It's just that it's being done.

[Problem that the invention seeks to solve]

However, these methods require a large amount of energy to make the bubbles smaller, and the bubbles usually grow at a depth of 4 m.
rises in about 10 seconds, so in order to increase the gas-liquid contact efficiency it is necessary to constantly generate bubbles, which has the disadvantage of requiring a large amount of energy to generate this large amount of bubbles.

[Means for solving problems]

In view of the current situation, the present invention has been developed to eject gas as bubbles from an aeration member having holes with a diameter of 1 to 3 mm provided at the bottom of a gas dissolving tank filled with a liquid in which gas is to be dissolved. As the thickness of the gas layer that is constantly formed under each porous member, which has pores with a diameter of 0.2 to 2.0 mm, are arranged in multiple stages at intervals above, a part of the gas layer is intermittently made fine. This is a gas dissolving method characterized by causing gas bubbles to rise one after another in a liquid to maintain high contact efficiency and dissolution efficiency with the liquid.

[Effect]

In the present invention, gas is ejected into the liquid as bubbles from a relatively simple aeration member having holes with a diameter of 1 to 3 mm provided at the bottom of the gas dissolving tank, so bubbles can be generated with relatively little energy. Moreover, the air bubbles rising from the air diffuser are held in multi-stage gas layers by the porous member provided in multiple stages and rise, so a gas layer is always formed at the bottom of the porous member, and both the upper and lower sides Since the method is constantly in contact with the liquid, it is possible to obtain high dissolution efficiency with a smaller amount of gas supplied than in the conventional method of generating microbubbles.

〔Example〕

Hereinafter, the present invention will be explained in detail according to examples.

In the figure, reference numeral 1 denotes a gas dissolving tank containing a liquid to be gas-dissolved, and the bottom of the gas dissolving tank 1 is provided with aeration pipes 2, which are equipped with a large number of holes with a diameter of 1 to 3 mm. . The pore diameter of these diffuser pipes 2,... is approximately 1
3 mm, no microbubbles are generated, but the energy consumption required for bubble generation can be significantly reduced compared to an air diffuser that generates microbubbles.

3,... is a gas layer forming member formed by attaching a frame body 5,..., which prevents air bubbles from escaping to the side and forms a gas layer, to the lower part of the outer periphery of the porous member 4,...
The frames 5, . . . are fixed to columns 6, . The porous members 4,... have pores that temporarily hold the air bubbles that have risen from the air diffuser tubes 2,... and through which fine bubbles can pass, so the air bubbles gradually form below the porous members 4,... The maximum thickness of the gas layer A,... that is actually formed depends on the size of the pores of the porous member 4,... and the material of the porous member 4,... It changes depending on the hydrophilicity of the liquid, the surface tension of the liquid, etc., but when these factors are specified,
When the gas layer A,... reaches a predetermined thickness determined by the aforementioned factors, the equilibrium is broken and the porous member 4,
Bubbles are generated all at once from the entire surface of ... and rise to the upper stage. Therefore, if the thickness (length in the vertical direction) of the frame body 5,... is set larger than the maximum thickness of the gas layer A,... that is actually formed, the gas forming the gas layer A,... is always retained as a gas layer without deviating from the sides,
It will pass through the pores of the porous members 4, . . . intermittently to form bubbles. If the gas layer is formed to be excessively thick due to reasons such as small pore sizes in the porous members 4, etc., the gas layer forming member 3 may be subjected to intermittent impact, for example, as described below. If given, the gas layer can be kept relatively thin. Even when the gas layer reaches a predetermined thickness and the equilibrium is broken and bubbles are formed, some of the gas remains on the lower surface of the porous member 4, and at least some gas layer is always retained. . Therefore, the gas layer and the liquid are always in contact over a fairly wide area, and the gas dissolution efficiency can be maintained at a high rate even though no energy consumption is required. The porous members 4, . . . are, for example, perforated plates, net-like materials, cloth-like materials, etc., and the pore size thereof must be 0.2 to 2.0 mm in order to form a gas layer. Also, the thickness of the frame 5,... is 30 to 100 mm.
is preferred.

Figure 3 shows an example of the relationship between the pore size (opening) of a porous member and the thickness of the gas layer in fresh water.
It can be seen that an appropriate gas layer is formed when the thickness is ~2.0 mm. As mentioned above, the thickness of the gas layer varies depending on various factors, but in FIG. 3, A shows an example in which polyester taffeta is used, B shows cotton gauze, and C shows an example in which polyvinylidene chloride net is used.

Reference numeral 7 denotes an impact applying member for applying an impact to the gas layer forming member 3, and the impact applying member 7 is a protrusion provided on a vertical rod 9 that is movable only in the vertical direction by movement regulating members 8, . . . 10, the claw portion 12 of the rotationally driven rotating member 11 intermittently contacts from below, lifts it up, and releases it to cause the vertical rod 9 to fall onto the tip of the support column 6, thereby forming a gas layer via the support column 6. This applies an impact accompanied by vertical movement to the member 3 to prevent an excessive increase in the thickness of the gas layer.

As an example of sewage treatment, a 6-stage gas layer forming member is installed in a standard activated sludge method treatment equipment for domestic wastewater with a BOD of 200 ppm, and the air supply amount is 1/3 of the standard activated sludge method. As a result, treated water with a BOD removal rate of 97% was obtained.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, air bubbles are generated using a simple air diffuser member having holes with a relatively large diameter, so that air bubbles can be generated with energy saving, and the air bubbles can be removed from the air diffuser member. The rising air bubbles are held in the multi-stage porous member from the first stage, and a gas layer is constantly formed, so the gas not only acts as bubbles generated when passing through the porous member, but also as a gas layer. Since both the upper and lower surfaces are constantly in contact with the liquid, it is possible to maintain high gas-liquid contact efficiency and dissolution efficiency with a smaller gas supply amount than in the conventional case of generating microbubbles.

[Brief explanation of drawings]

Figure 1 of the drawings is a side cross-sectional view showing an example of a gas dissolving tank used in carrying out the present invention, Figure 2 is a slope view of the porous member, and Figure 3 is a diagram showing the size of the pores of the porous member and the gas layer. It is a graph showing the relationship between thickness and thickness. 1: Gas dissolution tank, 2: Diffusion tube, 4: Porous member, A: Gas layer.

Claims (1)

[Claims] 1. Gas is ejected as bubbles from a diffuser member having holes with a diameter of 1 to 3 mm provided at the bottom of a gas dissolving tank filled with a liquid in which gas is to be dissolved, and in multiple stages spaced apart above the diffuser member. The installed hole diameter is 0.2
As the thickness of the gas layer that is constantly formed under each porous member with pores of ~2.0 mm increases, a portion of the gas layer is intermittently formed into fine bubbles that rise one after another in the liquid, forming a A gas dissolution method characterized by maintaining high contact efficiency and dissolution efficiency.