JP2005329329A - Air diffuser and air diffusing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air diffuser capable of reducing pressure loss while keeping a good air diffusing state, and an air diffusing method. <P>SOLUTION: The air diffuser is equipped with a membrane air diffusing body having an elastic film provided with venting holes or permitting air to pass and passing air through the elastic film to discharge the same into a liquid as air bubbles and further equipped with a dehumidifying mechanism capable of reducing the moisture of air. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an air diffuser that diffuses air in a liquid and a method thereof.

In an aeration tank that performs activated sludge treatment of sewage and a biological treatment tank that performs dephosphorization and denitrification treatment of organic wastewater, it has an elastic membrane made of synthetic resin provided with a large number of ventilation holes for gas to pass through. An air diffuser that pressurizes a gas such as air or oxygen with a pressurizer to a porous body of membrane diffused gas or ceramics, supplies it through a pipe, and diffuses it as fine bubbles with a diameter of about 1 mm in the liquid to be treated. It is used. Among these aeration devices, those using a ceramic porous body have a problem that clogging is likely to occur due to sludge entering the pores, algae, scales, and the like. On the other hand, in the case of using a membrane air diffuser, a large number of air holes that take an open state and a closed state due to elastic deformation of the elastic film and are opened by air supplied from a pressurizing device are elastic. Since it is provided on the body membrane, the vent is closed by a process called blowdown that stops operation at regular intervals, and the clogging that has entered the vent is pushed into the liquid to be treated. be able to. Thus, what used the membrane air diffuser has the outstanding point that a favorable air diffused state can be maintained by the blowdown, and in Patent Document 1, the gas to be diffused is humidified. It is also shown that clogging can be prevented and the blowdown interval can be increased.
JP 2003-170186 A

By the way, in such an aeration process, there is a problem that the pressure loss is large and a large amount of energy is required for operation of the pressurizer because bubbles are released from the vent holes in the liquid to be treated.
Further, the aeration process can increase the contact area and the contact time between the gas and the liquid to be processed by reducing the bubbles and setting the position where the gas is diffused to a deep position in the liquid to be processed. When bubbles are generated in a deep position in the liquid to be treated, there is a problem that pressure loss becomes larger and more operating energy is required in the air diffuser.
Thus, the problem that a great deal of operating energy is required in the aeration process is a problem common to the entire aeration process, not just the activated sludge process and the biological process.

  In view of the above problems, an object of the present invention is to provide an air diffuser and an air diffuser that can reduce pressure loss while maintaining a good air diffuse state.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the pressure loss in the aeration process can be reduced by reducing the absolute humidity in the gas, and the present invention has been completed. It is.
That is, the present invention is an air diffuser comprising a membrane air diffuser having an elastic membrane provided with a vent hole through which gas passes and releasing the gas into the liquid through the elastic membrane as a bubble, Furthermore, the present invention provides an air diffuser provided with a dehumidifying mechanism capable of reducing the moisture of the gas.
Further, the present invention provides the air diffuser comprising: a pressurizer that pressurizes the gas; and a pipe that supplies the gas pressurized by the pressurizer to the membrane air diffuser as a gas that passes through the vent hole. provide.
Further, the present invention provides a membrane gas diffuser having an elastic membrane provided with a vent hole for passing a pressurized gas, and releasing the pressurized gas into the liquid as bubbles through the elastic membrane. A gas diffusion method is provided, wherein at least a part of the contained water is removed, a gas is introduced in a pressurized state, and the gas is discharged as bubbles into the liquid through the vent hole.
Furthermore, the present invention provides the aeration method for removing at least a part of the contained water by a compressed air dryer.
In the present invention, the dehumidifying mechanism means a mechanism capable of removing moisture contained in a gas, such as a dehumidifier, an air conditioner, a hygroscopic agent, and a moisture adsorbent.

  According to the present invention, since a membrane air diffuser is used, a good air diffused state can be maintained, and a dehumidifying mechanism is provided to supply a gas with reduced moisture to the membrane air diffuser. Pressure loss can be reduced.

Hereinafter, preferred embodiments of the present invention will be described (based on the accompanying drawings).
As shown in FIG. 1, the air diffuser of the present embodiment includes a blower 4 that pressurizes air, a membrane diffuser 3 that diffuses the pressurized air, and the membrane from the pressurized blower 4 to the membrane. And a pipe 5 for introducing a pressurized gas to the diffused gas 3, and further a dehumidifier 2 for reducing the moisture of the air.
The membrane air diffuser 3 is disposed in an air diffuser tank 6 in which the liquid to be treated is stored in order to diffuse fine bubbles having a diameter of about 1 mm to the liquid 7 to be air diffused.
Further, in order to send air with reduced moisture to the membrane air diffuser 3, the pressurized blower 4 is installed together with the dehumidifier 2 in a chamber 1 into which outside air can be introduced.
Further, the pressurized blower 4 and the membrane gas diffuser 3 are arranged so that moisture is not added again until the air blown by the pressurized blower 4 is supplied to the membrane diffused gas 3. The pipe 5 is sealed from the outside air.

  In the present embodiment, it is suitable in that it is not necessary to adjust the operating condition of the dehumidifier according to the amount of air blown by the pressurized blower. Therefore, the chamber is used, and the air in the chamber is dehumidified by the dehumidifier. In order to blow air with reduced moisture without using a chamber, the blower outlet of the dehumidifier and the pressurized blower may be connected by piping, etc. It is also possible to provide a dehumidifier in the middle of the piping leading to the membrane gas.

  The dehumidifier may be a cooling dehumidifier that cools air below the dew point of the contained water to remove condensed water, an adsorption dehumidifier that uses a moisture adsorbent such as silica gel, or a contact with an aqueous lithium chloride solution. Absorption type dehumidifiers, compression type dehumidifiers that compress air and remove condensed water more than the water vapor partial pressure of the contained water reaches saturated water vapor pressure, and these combined dehumidifiers can be used, Instead of the dehumidifier, dehumidification may be performed using a general air conditioner, a hygroscopic agent, a moisture adsorbent, or the like, and dehumidification may be performed using these dehumidifying means in combination.

  Moreover, as said pressurization air blower, if the pressure of the air introduce | transduced in a membrane air diffuser can be pressurized more than the pressure in an air diffuser tank so that air can be discharge | released to an air diffuser tank However, it is not particularly limited, and a fan such as a propeller fan or a sirocco fan, a pump, a compressor, or the like can be employed.

  In addition, the pipe may be made of synthetic resin such as polyvinyl chloride, metal such as copper, lead, stainless steel or other materials as the material depending on the purpose. The pressure loss is preferably selected to be sufficiently smaller than the pressure loss at

Further, the piping may be branched and connected independently to each membrane gas diffuser, or may be connected to a manifold pipe or the like in which a plurality of membrane gas diffusers are integrated with one pipe.
In the case of adopting the form of independent piping, it is possible to blow down individual membrane diffused gas without interrupting the overall diffused gas process by providing a valve in each individual pipe. It will be something.

In addition, in this embodiment, although the said dehumidifier and the said pressurization air blower were used as a different thing, it can replace with these and can also use the pressurization type dehumidifier provided with the mechanism which pressurizes and ventilates.
As the pressurization type dehumidifier, a compression type air dryer can be exemplified, and when the compression type air dryer is used as equipment for blowing air with reduced moisture to the membrane air diffuser, The energy required for operation can be reduced as compared with the case where the blower is used separately.
Further, since the installation space can be made small, the installation work is also simplified, which is preferable.
Further, when the operation control of the dehumidifier is performed according to the temperature and humidity of the air to be blown, the energy consumption can be further reduced.

As shown in FIG. 2, the membrane gas is a plate-like membrane gas provided with a plate-like main body portion 31 and an elastic film 32, and between the plate-like main body portion 31 and the elastic film 32. The pipe 5 is connected to introduce air into the space.
In this embodiment, a plate-like membrane gas is used as the membrane gas, but in the present invention, a cylindrical membrane gas having a cylindrical elastic film on the outer periphery of the cylindrical main body, Various forms of membrane gas diffuser such as a hose-like membrane gas diffuser that is more elongated than the cylindrical membrane gas diffuser can be employed.

  The membrane air diffuser body has strength that does not cause damage or deformation due to pressure during the air diffusion treatment, etc., and is subject to corrosion by the liquid to be air diffused or air diffused. Anything can be used as long as it does not. That is, the material, the form, etc. are not limited as long as the elastic film can be held in the aeration process.

  The elastic membrane of the membrane air diffuser may be any one that can expand and contract the vent hole provided in the elastic membrane by expansion at the time of air diffusion and contraction at the time of blowdown. Elastic materials such as rubber, silicone rubber, fluorine rubber, styrene rubber, chloroprene, nitrile rubber, natural rubber, polyurethane, and thermoplastic elastomer, or those that have been reinforced and modified with fibers, fillers, and other resins It can be used alone or in a stacked manner.

  The vent hole provided in the elastic membrane opens as the elastic membrane is expanded by the pressurized air, releases air as bubbles into the liquid to be treated in the aeration treatment tank, and contracts during the blowdown. Any size and shape can be used as long as it can push out the clogging that has entered the vent hole into the liquid to be treated in the aeration treatment tank. A slit shape having a length of 0.1 to 0.5 mm or the slit shape is used in that it can be surely shrunk and cause clogging to be extruded into the liquid to be treated in the aeration tank. A cross-shaped shape that is orthogonal to each other is preferable.

  In the present embodiment, air is used as a gas for the aeration process. However, in the present invention, the gas is not limited to air, and a gas according to the purpose such as nitrogen, oxygen, carbon dioxide, or the like. Can be adopted.

Next, the air diffusion method by the air diffuser will be described with an example. The air in the chamber is dehumidified by the dehumidifier, and the collected water is discharged out of the chamber. The air inside is kept at a low absolute humidity.
The pressure blower blows air in the chamber maintained at this low absolute humidity into the pipe as pressurized air. At this time, fresh air is taken into the chamber from the outside air intake. Since moisture contained in newly introduced air is also dehumidified by the dehumidifier, the air in the chamber is kept at a low absolute humidity even if new air is introduced.
The compressed air is branched by a pipe, blown to each of a plurality of membrane air diffusers arranged at the bottom of the air diffusion treatment tank, spreads the air holes provided in the elastic body film from the inside, and becomes air bubbles. Released into the treatment tank. At this time, since dehumidified air is used, it passes through the elastic film with a lower pressure loss than when non-dehumidified air is used.

(Reference example)
As a reference of the present invention, FIG. 4 shows data obtained by measuring the pressure loss of the membrane air diffuser and the amount of water vapor in the air for 150 days continuously in an actual sewage treatment plant as follows.
<Installation>
A plate-like membrane air diffuser having a width of 0.15 m and a length of 2.0 m consisting of a polyurethane elastic membrane and a stainless plate-like main body was installed in three aerobic tanks (aerobic tanks 1 to 3).
Further, one section of the aerobic tank has a length of 6 m, a width of 6 m, and a water depth of 5 m, and the plate-like membrane air diffuser was installed at a position of 14 to 24 sheets / compartment at a water depth of 4.5 m.
<Measurement method of pressure loss>
During the measurement period, the aerobic tank is operated by controlling the air flow so that the air flow is constant, a Bourdon tube precision pressure gauge is attached to the piping, the total pressure is measured, and the diffused gas is calculated from the total pressure. The pressure corresponding to the water depth (4.5 m) was subtracted to obtain the pressure loss at that time.
<Method for measuring the amount of water vapor (absolute humidity) in the air>
The amount of water vapor (absolute humidity) in the air was determined by calculation based on the AMeDAS weather data at the nearest point to the sewage treatment plant where the test was conducted.
Specifically, the saturated water vapor pressure [Psat (Pa)] of the temperature is obtained from the relative humidity [Rh (%)] and temperature data of AMeDAS, and the water vapor partial pressure [Pw (Pa)] is obtained from (Equation 1). The absolute humidity [X (g / kg)] was calculated from the value of AMeDAS pressure data [P (Pa)] and the water vapor partial pressure [Pw (Pa)] according to (Equation 2).
Pw = Psat × Rh (Formula 1)
X = 622 × Pw / (P−Pw) (Formula 2)

Using the membrane air diffused from the aerobic tank 3 shown in the above-mentioned reference example, the air flow rate per unit area is ˜20 m ³ / (m ² · h), 20 to 32.5 m ³ / (m ² · h), It was divided into 32.5 to 37 m ³ / (m ² · h) and the amount of moisture in the air was changed to measure how the pressure loss becomes.
As a result, it was confirmed that the pressure loss could be reduced by removing moisture in the air as shown in FIGS.

The schematic diagram which shows the diffuser of one Embodiment. The external view which shows the membrane air diffuser of the embodiment. a) Membrane diffused gas sectional view showing an elastic membrane in a contracted state. b) Membrane gas cross-sectional view showing an elastic membrane in an expanded state. The relationship graph of the amount of water vapor of diffused air and pressure loss. The relationship graph of the amount of water vapor of diffused air and pressure loss.

Explanation of symbols

2 Dehumidifier 3 Membrane air diffuser 4 Pressure blower 5 Piping 6 Air diffuser tank 32 Elastic membrane 33 Ventilation hole

Claims (4)

An air diffuser comprising a membrane air diffuser having an elastic membrane provided with a vent hole for passing a gas and releasing the gas into the liquid through the elastic membrane as a bubble,
Furthermore, the diffuser provided with the dehumidification mechanism which can reduce the water | moisture content of the said gas. The diffuser according to claim 1, further comprising: a pressurizer that pressurizes the gas; and a pipe that supplies the gas pressurized by the pressurizer to the membrane air diffused as a gas that passes through the vent hole. At least one of the moisture contained in the membrane gas which has an elastic membrane provided with a vent hole for passing the pressurized gas and releases the pressurized gas into the liquid as bubbles through the elastic membrane. A gas diffusion method, wherein a gas is introduced in a pressurized state after being removed, and discharged as bubbles into the liquid through the vent hole. The aeration method according to claim 3, wherein at least a part of the contained water is removed by a compressed air dryer.

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