JP5532015B2 - Wastewater treatment equipment - Google Patents

Description

  The present invention relates to a wastewater treatment apparatus. More specifically, the present invention relates to a wastewater treatment apparatus that reduces components that increase the COD (chemical oxygen demand) value contained in waste liquid.

Since the release of sulfur dioxide gas (SO2) into the atmosphere is strictly regulated by law, flue gas desulfurization that removes sulfur dioxide gas from exhaust gas is performed in the process that involves the generation of sulfur dioxide. In this flue gas desulfurization, there is an alkali absorption method, and a sodium hydroxide solution, a sodium sulfite solution, aqueous ammonia, etc. are used as an absorbent, and these are made to absorb sulfur dioxide (SO ₂ ), so that sodium sulfite, sulfur, sulfuric acid, Recovery is performed in the state of liquid SO ₂ , ammonium sulfate, or the like.

  As a method of removing sulfur dioxide gas in the absorption tower, a method of absorbing sulfur dioxide gas with a liquid absorbent is employed. For example, when a sodium hydroxide (NaOH) aqueous solution is used as the absorbent, sulfur dioxide gas reacts with the sodium hydroxide aqueous solution to form sodium sulfite, sodium bisulfite, or sodium sulfate (hereinafter referred to as the aqueous solution). (Referred to as waste liquid).

  However, sodium sulfite and sodium bisulfite produced by the reaction between sulfur dioxide gas and an aqueous sodium hydroxide solution increase the COD (chemical oxygen demand) value of the waste liquid. For this reason, the waste liquid from the absorption tower collects sodium sulfite as crystals. Alternatively, once the sodium sulfite is oxidized to sodium sulfate in the wastewater treatment apparatus and becomes less than the legal standard COD value, the waste liquid is drained into public water bodies. In other words, in facilities with processes that involve the generation of sulfur dioxide, in addition to flue gas desulfurization equipment, equipment that collects sodium sulfite, etc. as a product, or oxidizes sodium sulfite and sodium bisulfite to remove or reduce them from the waste liquid It is necessary to have a device to perform.

  As a wastewater treatment device that oxidizes waste liquid as described above, a container for storing the waste liquid, a fine bubble diffuser such as a diffused cylinder and a diffuser plate disposed in the container, and a finely forced through a nozzle An apparatus including a mechanism for blowing the formed bubbles and a mechanism for mixing and ejecting waste liquid and air with a nozzle have been developed (for example, Patent Document 1 and Non-Patent Document 1).

  However, in the case of the conventional waste water treatment apparatus, since it is the structure which blows in air compulsorily, air blowers, such as a blower, are needed, and an apparatus enlarges. In addition, bubbles formed by a nozzle or the like are not very good in reactivity with sodium sulfite or sodium bisulfite in the waste liquid, so that the oxidation efficiency is low and the waste liquid treatment efficiency is low.

JP-A-8-117551

Microbubble nanoplanet.co.jp Nano Planet Research Institute Taisei Journal of MMJ Vol23, p.90-93 (2007)

  An object of this invention is to provide the waste water treatment apparatus which can oxidize the substance in a waste liquid efficiently in view of the said situation.

A wastewater treatment apparatus according to a first aspect of the present invention is an apparatus that oxidizes a substance contained in a liquid, and includes an oxidation tank that contains the liquid, and a stirring means that is disposed in the oxidation tank. The means includes a cylindrical member disposed so that a tip end is immersed in the liquid in the oxidation tank and a base end is positioned above the liquid level of the liquid, and inside the cylindrical member. A rotating shaft disposed; a stirring member attached to an end portion of the cylindrical member on the rotating shaft; and an intake passage through which air can be introduced into the cylindrical member. A flange-shaped miniaturized plate is provided concentrically at the tip of the cylindrical member, and the miniaturized plate includes a plurality of bubbles for allowing air bubbles to pass through the annular plate. A through hole is formed along the outer periphery, and the stirring member includes a circular plate and the pre-plate. Consists stirring blade provided on preparative, the through hole is characterized in that located above the position where the stirring blade passes.
Wastewater treatment apparatus of the second invention, in the first shot bright, the interior of the tubular member, characterized in that it comprises a liquid supply passage for supplying the liquid from the outside of the oxidation tank.
Waste water treatment apparatus of the third invention, was first or the second aspect, the stirring means has a plurality of the oxide bath is provided, oxidation vessel wherein the plurality of the oxidation vessel positioned upstream The treated liquid is arranged to be sequentially supplied to the downstream oxidation tank, and the liquid treated in the upstream oxidation tank is stirred by the stirring means in the downstream oxidation tank. A communication passage is provided in the vicinity of the member.
Waste water treatment apparatus of the fourth invention, the first, was the second or the third invention comprises a pH adjusting means for adjusting the pH of the liquid, the pH adjusting means, the pH of the liquid, 7 It is characterized by being adjusted to be larger than 10 and larger.
Waste water treatment apparatus of the fifth invention, the first, second, was the third or the fourth invention is characterized in that it comprises a dilution means for diluting the liquid.
Waste water treatment apparatus of the sixth invention, the first, second, third, were fourth or the fifth invention, wherein the liquid, and characterized in that a liquid containing sodium sulphite and / or sodium bisulfite To do.

According to the first invention, the following effects are obtained.
a) When the rotating shaft rotates, a swirl flow from the proximal end to the distal end of the tubular member is formed inside the tubular member, so that the liquid inside the tubular member is discharged from the distal end of the tubular member. . Then, the pressure inside the cylindrical member decreases and air is introduced into the cylindrical member through the intake passage, so that the substance in the liquid, for example, sodium sulfite and sodium bisulfite, and oxygen are efficiently used. Since the contact can be made well, the substance can be oxidized efficiently. In addition, since a means for forcibly blowing air, such as a means such as a compressor, is unnecessary, the apparatus can be made compact.
b) Since the bubbles can be made fine by the interference between the micronized plate and the stirring blade, and when the bubbles pass through the through holes of the micronizing plate, the bubbles are sheared by the stirring blade and the micronization of the bubbles is further promoted. The interface between the processing liquid L and air can be further increased.
According to the second invention, the liquid to be oxidized can be directly supplied into the cylindrical member through the liquid supply passage. Then, since the intake air in the cylindrical member and the liquid just after introduction can be efficiently contacted, the substance can be oxidized quickly.
According to the third invention, in each oxidation tank, the liquid supplied from the upstream oxidation tank is supplied as it is to the vicinity of the stirring member of the downstream oxidation tank, so that the substance is reliably oxidized in each oxidation tank. be able to. And since the liquid supplied from the upstream oxidation tank can be made to contact efficiently with the liquid containing many bubbles, the oxidation process of a substance can be advanced reliably.
According to the fourth invention, the oxidation treatment efficiency of the substance can be improved.
According to the fifth invention, the oxidation treatment efficiency of the substance can be improved.
According to the sixth aspect of the invention, sodium sulfite and / or sodium bisulfite can be converted to sodium sulfate, so that deterioration of the COD value can be prevented even if the liquid is flowed into public waters.

(A) is schematic explanatory drawing of the waste water treatment equipment 1 of this embodiment, (B) is the principal part enlarged view of the stirring member 10 in the BB cross section of (A), (C) is the stirring member 10 FIG. (A) is a schematic explanatory drawing of the waste water treatment apparatus 1 of other embodiment, (B) is a principal part enlarged view. It is a schematic explanatory drawing of the waste water treatment equipment 1 of other embodiment. It is a schematic explanatory drawing of the waste water treatment equipment 1 of other embodiment. It is a schematic explanatory drawing of the waste water treatment equipment 1 of other embodiment. FIG. 6 is a diagram showing experimental results of Example 1. FIG. 6 is a diagram showing experimental results of Example 2.

Next, an embodiment of the present invention will be described with reference to the drawings.
The wastewater treatment apparatus of the present invention can reduce the COD value of a treatment liquid by oxidizing such a component in a liquid (treatment liquid) containing a component that increases the COD (chemical oxygen demand) value. It is.

The treatment liquid treated in the wastewater treatment apparatus of the present invention is a liquid containing, for example, sodium sulfite (Na ₂ SO ₃ ), sodium bisulfite (NaHSO ₃ ), sodium sulfate (Na ₂ SO ₄ ), etc. The liquid is not particularly limited. In other words, the treatment liquid is a liquid containing a component that raises the COD (chemical oxygen demand) value (hereinafter referred to as a COD component), and can reduce the COD value by oxidizing the COD component. If it is, it will not be specifically limited.

For example, in an installation having a process involving the generation of sulfur dioxide gas, a sodium hydroxide solution is used as an absorbent to remove the sulfur dioxide gas from the exhaust gas, and the sulfur dioxide gas is recovered in an aqueous solution in an absorption tower. The aqueous solution from which the sulfur dioxide gas is recovered (in the waste liquid of the absorption tower) contains sodium sulfite (Na ₂ SO ₃ ) and sodium bisulfite (NaHSO ₃ ). The waste liquid of such an absorption tower corresponds to the processing liquid processed in the wastewater treatment apparatus of the present invention.

Hereinafter, a case where a treatment liquid containing sodium sulfite (Na ₂ SO ₃ ) and / or sodium bisulfite (NaHSO ₃ ) is treated by the waste water treatment apparatus of the present invention will be described as a representative.

(Description of the wastewater treatment apparatus 1 of this embodiment)
As shown in FIG. 1, the waste water treatment apparatus 1 of the present embodiment includes an oxidation tank 2 that contains a treatment liquid L, and a stirring means 10 that is disposed in the oxidation tank 2.

(About oxidation tank 2)
As shown in FIG. 1, the oxidation tank 2 is a container having an accommodation space 2 h that contains a hollow processing liquid L therein, and is resistant to the processing liquid L such as sodium sulfite (Na2SO3) or sodium bisulfite (NaHSO3). Is made of high material.

(About the stirring means 10)
As shown in FIG. 1, an agitation means holding part 3 is provided at the upper end of the oxidation tank 2, and the agitation means 10 is oxidized at the tip of the cylindrical member 11 by the frame of the agitation means holding part 3. It is arranged so as to be located in the tank 2.
In addition, although the height which arrange | positions the front-end | tip of the cylindrical member 11 is not specifically limited, it is the height which can maintain the state where the front-end | tip of the cylindrical member 11 was immersed in the process liquid L during the operation | work which processes a process liquid. I just need it.

(Cylindrical member 11)
The tubular member 11 is a hollow tubular member having a through hole that communicates between the distal end and the proximal end. The base end portion 11a of the cylindrical member 11 is attached to the gantry of the stirring means holding portion 3 so that the cylindrical member 11 does not move in the axial direction or the radial direction or rotate around the axis.
The tubular member 11 is provided with an intake passage 11c that communicates between the inside and the outside of the distal end portion 11b of the tubular member 11. The intake passage 11c is a hollow tubular member, and is provided so that outside air can be introduced into the distal end portion 11b of the tubular member 11.

(Rotating shaft 12)
A rotating shaft 12 is inserted into the cylindrical member 11. The rotating shaft 12 has a length longer than the axial length of the cylindrical member 11, and is provided so that both end portions thereof are located outside the both end portions of the cylindrical member 11.
The proximal end portion of the rotary shaft 12 cannot be moved in the axial direction and the radial direction with respect to the cylindrical member 11, but is attached to the cylindrical member 11 so as to be able to rotate around the axis. Specifically, the upper and lower portions of the base end portion of the rotating shaft 12 are held by a pair of bearings provided in the base end portion 11 a of the cylindrical member 11.

The rotating shaft 12 is connected to a shaft rotating mechanism that rotates around the central axis. Specifically, a driven pulley 12p is provided at the base end portion of the rotating shaft 12, and the driven pulley 12p is connected to a driving pulley attached to the main shaft of the motor by a belt. For this reason, when the motor is operated, the driving force is transmitted in the order of the driving pulley → the belt → the driven pulley 12p, and the rotating shaft 12 can be rotated.
The driving mechanism for rotating the rotating shaft 12 is not particularly limited as long as the rotating shaft 12 can be rotated. For example, the base end of the rotating shaft 12 may be directly connected to the main shaft of the motor.

(Stirring member 15)
On the other hand, a stirring member 15 is provided at the tip of the rotating shaft 12 (the lower end in FIG. 1 and hereinafter referred to as the lower end of the rotating shaft 12).

  The stirring member 15 includes a plate 17 that is a substantially flat plate-like member. The plate 17 is circular in plan view, and is attached to the lower end of the rotary shaft 12 such that its center is located on the central axis of the rotary shaft 12 and its upper surface is orthogonal to the central axis of the rotary shaft 12. ing.

  A plurality of stirring blades 16 are provided on the upper surface of the plate 17. The plurality of stirring blades 16 are plate-like members provided upright on the upper surface of the plate 17, and are mounted on the plate 17 at intervals along the circumferential direction. Specifically, the stirring blade 16 is provided in such a shape and arrangement that a swirling flow around the rotating shaft 12 is formed when the rotating shaft 12 rotates.

On the other hand, a miniaturized plate 11 d is provided at the tip of the cylindrical member 11. The miniaturization plate 11d is a plate formed in an annular shape, and is provided so that the center thereof is located on the central axis of the cylindrical member 11. The miniaturization plate 11d is disposed such that a narrow gap (about several mm) is formed between the lower surface of the miniaturization plate 11d and the upper end of the stirring blade 16.
The miniaturization plate 11d is formed so that its outer diameter is larger than the outer diameter of the cylindrical member 11. That is, the cylindrical member 11 is formed to have a shape having a flange at the tip thereof by attaching the miniaturization plate 11d. Further, the miniaturization plate 11d is formed so that the inner diameter of the central hole is larger than the axial diameter of the rotary shaft 12 so that the rotary shaft 12 can be inserted into the central hole.
The miniaturization plate 11d has a plurality of through holes along the outer peripheral edge thereof. The plurality of through holes are provided above a position where the stirring blade 16 passes when the rotary shaft 12 rotates.
The reason why the miniaturized plate 11d is provided will be described later.

  Since the stirring member 15 has such a configuration, when the rotating shaft 12 rotates, the swirl flow around the rotating shaft 12 is accompanied by a flow from the rotating shaft 12 toward the inner surface of the oxidizing tank 2 when the rotating shaft 12 rotates. Can be formed. In other words, when the rotating shaft 12 rotates, the processing liquid L in the vicinity of the tip of the cylindrical member 11 is rotated from the tip of the cylindrical member 11 toward the inner surface of the oxidation tank 2 while rotating around the central axis of the rotating shaft 12. It is formed to flow.

  On the other hand, when the flow of the processing liquid L as described above is formed near the tip of the cylindrical member 11, the processing liquid L inside the cylindrical member 11 moves around the central axis of the rotating shaft 12 along with the flow. It flows toward the tip of the cylindrical member 11 while turning. That is, the plurality of stirring blades 16 of the stirring member 15 can form a swirling flow from the proximal end to the distal end of the tubular member 11 in the tubular member 11 as the rotary shaft 12 rotates. is there.

  The shape of the stirring member 15 is not limited to the above-described shape, and when the rotating shaft 12 rotates, a swirl flow around the rotating shaft 12 accompanied with a flow from the rotating shaft 12 toward the inner surface of the oxidation tank 2 can be formed. Any shape can be used. For example, the shape may be a general stirring member (for example, an impeller or the like) used when stirring the liquid, and is not particularly limited.

(Oxidation treatment by the wastewater treatment apparatus 1 of the present embodiment)
Since the wastewater treatment apparatus 1 of the present embodiment has the structure as described above, the COD component in the treatment liquid L is oxidized and the COD value of the treatment liquid L is reduced as follows. be able to.

  First, the processing liquid L is put into the oxidation tank 2. At this time, the processing liquid L is supplied so that the liquid level is located above the tip of the cylindrical member 11. Specifically, even if the stirring member 15 rotates and a swirling flow around the rotation shaft 12 is formed in the oxidation tank 2, an amount that does not expose the stirring member 15 from the liquid surface is supplied into the oxidation tank 2. .

  Next, the shaft rotating mechanism is operated to rotate the rotating shaft 12. Then, the stirring member 15 attached to the tip of the rotating shaft 12 rotates, and a swirl flow with a flow in a direction toward the inner surface of the oxidation tank 2 is generated in the oxidation tank 2.

  At this time, a swirl flow from the proximal end of the tubular member 11 to the distal end is formed inside the tubular member 11, so that the processing liquid L inside the tubular member 11 flows out from the distal end of the tubular member 11. To do. Then, the inside of the distal end portion 11b of the cylindrical member 11 (portion above the liquid surface) becomes a negative pressure compared to the atmospheric pressure. For this reason, air flows into the front end portion 11b of the cylindrical member 11 through the intake passage 11c, and the inflowed air comes into contact with the processing liquid L.

Then, sodium sulfite, sodium bisulfite and the like, which are COD components in the treatment liquid L, can be brought into contact with oxygen at the interface with the air, so that sodium sulfite and sodium bisulfite are oxidized to sodium sulfate (Na ₂ it can be a SO _4).

Further, since a swirl flow from the base end to the tip end of the tubular member 11 is formed inside the tubular member 11, the air flowing into the tubular member 11 due to the swirling flow is treated. Or mixed into the liquid L. As a result, the interface between the processing liquid L and air becomes large.
Moreover, when the air mixed in the processing liquid L flows out from the lower end of the cylindrical member 11, this air becomes bubbles and tends to float upward, but the lower surface of the miniaturized plate 11 d and the stirring blade 16 Since the gap between the upper end is narrow and the stirring blade 16 is rotating, the bubbles interfere with the lower surface of the miniaturization plate 11d and the upper end of the stirring blade 16 and are refined. In particular, when the bubbles are about to rise upward through the through holes of the miniaturization plate 11d, the bubbles are sheared by the stirring blades 16, so that the miniaturization of the bubbles is promoted. That is, the interface between the processing liquid L and air is further increased.

  As described above, in the wastewater treatment apparatus 1 of the present embodiment, the interface between the treatment liquid L and the air is greatly increased by the formation of a swirl flow in the cylindrical member 11 or the refinement of bubbles in the treatment liquid L. Therefore, sodium sulfite and sodium bisulfite in the treatment liquid L can be efficiently brought into contact with oxygen. Therefore, sodium sulfite and sodium bisulfite can be efficiently oxidized and converted to sodium sulfate.

  Since the interface between the processing liquid L and the air is increased only by rotating the rotating shaft 12, the compressor forcibly blows air into the processing liquid L as in the case of supplying bubbles to the processing liquid L. Therefore, the waste water treatment apparatus 1 can be made compact and energy can be saved.

In addition, if the lower end of the cylindrical member 11 is formed in a shape that expands toward the lower end opening (that is, a trumpet shape), the processing liquid L can be smoothly flowed from the cylindrical member 11 to the outside. Therefore, the advantage that the swirl | vortex flow in the cylindrical member 11 can be strengthened is acquired.
Further, the hole diameter of the central hole of the micronization plate 11d is not particularly limited, and may be approximately the same as the inner diameter of the cylindrical member 11 or may be smaller than the inner diameter of the cylindrical member 11. However, when it is smaller than the inner diameter of the cylindrical member 11, the flow velocity of the processing liquid L when passing through the central hole is increased, so that it is presumed that gas is easily mixed into the processing liquid L (FIG. 1 ( C)).
Further, the miniaturization plate 11d is not necessarily provided. However, if the miniaturization plate 11d is provided, there is an advantage that the miniaturization of bubbles can be promoted as described above.

(Equipment capable of continuous processing)
Further, the wastewater treatment apparatus 1 of the present embodiment performs the oxidation treatment by stirring the processing liquid L stored in the oxidation tank 2 by the stirring means 10, and discharges the processed liquid after the processing is completed. The structure which supplies the process liquid L to the oxidation tank 2, ie, the structure which batch-processes the process liquid L may be sufficient.
However, in order to improve the processing efficiency of the processing liquid L, it is preferable that the waste water treatment apparatus 1 of the present embodiment has a structure capable of continuously processing the processing liquid L.

  For example, a liquid supply passage for supplying the processing liquid L into the oxidation tank 2 and a discharge passage 22 for discharging the processing liquid L from the oxidation tank 2 (see FIG. 2A) are provided. Then, the opening (processing liquid discharge port) on the oxidation tank 2 side of the discharge passage 22 is provided at substantially the same height as the liquid surface of the processing liquid L. Specifically, the liquid level of the processing liquid L (hereinafter referred to as a reference liquid) in a state where the processing liquid L is not supplied from the liquid supply passage to the oxidation tank 2 and the agitation means 10 is not operated. It is disposed at a position (e.g., about 100 to 200 mm above) slightly higher than the substantially same height as the surface. Then, if the processing liquid L is supplied to the oxidation tank 2 from the liquid supply passage, an amount corresponding to the amount supplied from the liquid supply passage can be discharged from the processing liquid discharge port to the discharge passage 22. L can be processed continuously.

  When such a configuration is employed, the liquid supply passage is preferably configured as shown in FIG.

As shown in FIG. 2, the liquid supply passage 21 is in communication with the cylindrical member 11 of the stirring means 10. That is, the liquid supply passage 21 has a proximal end disposed outside the oxidation tank 2 and a distal end connected to the cylindrical member 11.
With this structure, the processing liquid L can be directly supplied to the inside of the cylindrical member 11 through the liquid supply passage 21, so that the gas mixed into the processing liquid L in the cylindrical member 11 and the immediately after introduction The processing liquid L can be reliably contacted and mixed. Then, the efficiency of oxidizing sodium sulfite and sodium bisulfite in the treatment liquid L to convert them into sodium sulfate can be further increased.
In the case of adopting the configuration as described above, the diameter of the enlarged portion of the cylindrical member 11 is prevented in order to prevent the processing liquid L flowing from the liquid supply passage 21 from obstructing the formation of the swirling flow in the cylindrical member 11. 11e is preferably provided to increase the internal volume of the portion to which the liquid supply passage 21 is connected (see FIG. 2B). The “tip portion of the cylindrical member” referred to in the claims is a concept including a portion provided with an enlarged diameter portion 11e.

Further, in the case of continuous processing, a plurality of oxidation tank 2 having 撹拌means 10 to the waste water treatment apparatus 1, treated treated liquid L in the oxidation tank 2 located on the upstream side is sequentially downstream It is preferable to be configured to be supplied to the oxidation tank 2. With such a configuration, a sufficient time for oxidizing the treatment liquid L can be taken, so that sodium sulfite and sodium bisulfite discharged without treatment can be reduced.

  For example, as shown in FIG. 3, a plurality of oxidation tanks 2 are arranged side by side, and an opening that communicates between the two tanks is provided at the same height as the reference liquid level on the wall surface between the adjacent tanks. deep. Then, when the processing liquid L is supplied from the liquid supply passage 21, the processing liquid L can be sequentially supplied from the oxidation tank 2 positioned on the upstream side to the oxidation tank 2 positioned on the downstream side. The processing liquid L can be discharged into the discharge passage 22 from the processing liquid discharge port provided in the oxidation tank 2 located on the most downstream side.

  Also in this case, if the communication passage 23 has a structure communicating with the cylindrical member 11 of the stirring means 10 in the downstream wastewater treatment apparatus 1 as shown in FIG. Since the treatment liquid L immediately after introduction can be reliably contacted and mixed, the efficiency of oxidizing sodium sulfite and sodium bisulfite in the treatment liquid L to convert them into sodium sulfate can be further increased.

  The communication passage 23 does not necessarily need to have a structure communicating with the tubular member 11 of the stirring means 10 in the downstream wastewater treatment apparatus 1. For example, as shown in FIG. 4, if a pipe having one end connected to the communication opening and the other end arranged at the lower part of the downstream oxidation tank 2 is provided, this pipe can function as the communication passage 23. .

  In addition, as shown in FIG. 5, instead of the communication opening, an opening is provided in the lower portion of the wall surface between adjacent tanks, one end is connected to this opening, and the other end is the upstream oxidation tank 2. It is good also as a connecting channel | path 23 by installing piping so that it may be located in the reference | standard liquid level. Even in this case, if the liquid level of the processing liquid L in the oxidation tank 2 becomes higher than the reference liquid level, the processing liquid L flows into the communication path 23 from the upper end of the communication path 23, It can flow into the downstream oxidation tank 2 from the lower part of the downstream oxidation tank 2.

  Furthermore, each oxidation tank 2 may be provided so that the liquid level of the processing liquid L is all the same height, but the liquid level of the processing liquid L is lowered as it becomes the downstream oxidation tank 2. This is preferable because the efficiency of processing the processing liquid L can be improved.

(Adjustment of treatment liquid L)
When the waste liquid discharged from the absorption tower or the like is used as the treatment liquid L, the waste liquid may be supplied as it is to the waste water treatment apparatus 1 of the present embodiment. If it supplies to 1, the efficiency of an oxidation process can be raised further.

  Specifically, the liquid supply passage 21 is provided with a concentration adjusting means for decreasing the concentration of sodium sulfite or sodium bisulfite in the processing liquid L, or the processing liquid L is diluted separately from the oxidation tank 2 or the pH is adjusted. It is preferable to adjust the concentration of sodium sulfite or sodium bisulfite in the treatment liquid L to be a predetermined concentration or less by providing a pretreatment tank. If water is added to the treatment liquid L and diluted by such concentration adjusting means, the efficiency of oxidizing these substances can be improved as compared with the case where the concentration of sodium sulfite or sodium bisulfite is high.

Furthermore, a pH adjusting means for adjusting the pH of the processing liquid L may be provided in the liquid supply passage 21, or an adjusting tank for adjusting the pH of the processing liquid L may be provided separately from the oxidation tank 2. That is, the treatment liquid L may be supplied to the oxidation tank 2 after adjusting the pH to a predetermined range. In this case, the efficiency of oxidizing sodium sulfite or sodium bisulfite can be improved as compared with the case where the pH of the treatment liquid L is out of the predetermined range.
For example, if the treatment liquid L is waste liquid discharged from an absorption tower that processes exhaust gas discharged from the exhaust desulfurization apparatus, the pH of the treatment liquid L is greater than 7 and less than 10, preferably 8 or more, 9 If adjusted to the following, the efficiency of oxidizing sodium sulfite and sodium bisulfite can be improved.

  Further, the liquid supply passage 21 may be provided with temperature adjusting means for cooling the processing liquid L to cool the processing liquid L. Even in this case, compared with the case where the temperature of the process liquid L is high, the efficiency of oxidizing a substance such as sodium sulfite and sodium bisulfite can be improved.

  Of course, the concentration adjusting means, the pH adjusting means, and the temperature adjusting means do not have to be provided as long as they are in the above state without diluting the treatment liquid L, adjusting the pH, or adjusting the temperature.

  The effectiveness of the oxidation treatment by the wastewater treatment apparatus of the present invention was confirmed by experiments.

The experiment confirmed the effect of pH and temperature on the oxidation treatment when a treatment liquid containing sodium sulfite (Na ₂ SO ₃ ) and sodium bisulfite (NaHSO ₃ ) was treated with the wastewater treatment apparatus of the present invention.
In the experiment, the amount of sodium sulfite (Na ₂ SO ₃ ) and / or sodium bisulfite (NaHSO ₃ ) contained in the treatment liquid was confirmed for the treatment liquid discharged from the waste water treatment apparatus.

The concentrations of sodium sulfate (Na ₂ SO ₄ ), sodium sulfite (Na ₂ SO ₃ ) and sodium bisulfite (NaHSO ₃ ) in the treatment liquid used in the experiment are as follows.
Sodium sulfate (Na ₂ SO ₄ ): 93 g / L
Sodium sulfite (Na ₂ SO ₃ ): 120 g / L
Sodium bisulfite (NaHSO ₃ ): 26 g / L

The experimental conditions are as follows.
(PH fluctuation test)
Treatment liquid temperature: Room temperature (25 ° C)
Residence time: 1 hour (temperature fluctuation test)
PH of treatment liquid: pH 9
Residence time: 1 hour

The amounts of sodium sulfate and sodium sulfite were measured by the following methods, respectively.
Sodium sulfate: precipitation weight method A
Sodium sulfite: Sodium thiosulfate back titration method B
In addition, sodium bisulfite was calculated by converting the amount of sulfur S calculated by the following formula to sodium bisulfite.
S = (Total amount obtained by ICP method−Sulfur amount) − (A sulfur amount + B sulfur amount)

Total is the total amount of sodium sulfate, sodium sulfite, and sodium bisulfite, as measured by the ICP method (ICP emission spectrometer SPS3100 manufactured by SII Nanotechnology).
The pH was measured with a glass electrode type hydrogen ion concentration indicator (manufactured by Toa Denpa Kogyo: HM-20J), and the temperature was measured with a glass rod thermometer.

The experimental results are shown in FIGS. 6 (A) and 6 (B).
As shown in FIG. 6 (A), when the pH is greater than 7 and less than 10, both sodium sulfite and sodium bisulfite can be sufficiently reduced.
On the other hand, when the pH is 7, both components are hardly reduced.
When the pH is 10, sodium bisulfite can be reduced, but sodium sulfite is hardly reduced.
From the above results, when the treatment liquid containing sodium sulfite (Na ₂ SO ₃ ) and sodium bisulfite (NaHSO ₃ ) is treated with the wastewater treatment apparatus of the present invention, the pH is preferably greater than 7 and less than 10. Can be confirmed.

Moreover, as shown to FIG. 6 (B), it can confirm that sodium sulfite can be decreased largely, so that the temperature of a process liquid becomes low.
From the above results, it can be confirmed that when the treatment liquid containing sodium sulfite (Na ₂ SO ₃ ) and sodium bisulfite (NaHSO ₃ ) is treated with the wastewater treatment apparatus of the present invention, a lower temperature is preferable. .

In the experiment, when the treatment liquid containing sodium sulfite (Na ₂ SO ₃ ) and sodium bisulfite (NaHSO ₃ ) is treated with the wastewater treatment apparatus of the present invention, the effect of the concentration of components in the treatment liquid on the oxidation treatment It was confirmed.
In the experiment, the amount of sodium sulfite (Na ₂ SO ₃ ) contained in the treated liquid was confirmed for the treated liquid after treatment.

  In the experiment, a wastewater treatment apparatus having three oxidation tanks and capable of continuously treating the treatment liquid was used (see FIGS. 3 to 5). In this wastewater treatment apparatus, the oxidation tank located on the upstream side (oxidation tank to which the treatment liquid is supplied from the outside) is an N0.1 oxidation tank (the tank on the left side in FIG. 2), and the liquid after oxidation treatment is exposed to the outside. The oxidation tank to be discharged is an N0.3 oxidation tank (the tank on the right side in FIG. 2), and the oxidation tank disposed between them is an N0.2 oxidation tank (the middle tank in FIG. 2).

The concentration of sodium sulfite (Na ₂ SO ₃ ) in the treatment liquid used in the experiment is as follows.
(1) Sodium sulfite (Na ₂ SO ₃ ): 240 g / L
(2) Sodium sulfite (Na ₂ SO ₃ ): 150 g / L
(3) Sodium sulfite (Na ₂ SO ₃ ): 50 g / L
In (3), a treatment liquid containing 100 g / L of sodium sulfite is diluted twice to obtain a liquid having the above concentration.

The experimental conditions are as follows.
Temperature of treatment liquid: washing tower 50 ° C., oxidation tank 50-60 ° C.
PH of treatment liquid: washing tower pH 8.0, oxidation tank pH 8.5

  The amount of sodium sulfite was measured by a sodium thiosulfate back titration method, the pH was measured by a glass electrode type hydrogen ion concentration indicator (manufactured by Toa Denpa Kogyo: HM-20J), and the temperature was measured by a glass rod thermometer. .

The experimental results are shown in FIG. In FIG. 7, NO.1, NO.2 and NO.3 correspond to the NO.1 to NO.3 oxidation tanks described above, respectively, and sodium sulfite (Na ₂ SO ₃ ) of each tank. A density | concentration is a density | concentration in the process liquid discharged | emitted from each tank.
As shown in FIG. 7, the lower the concentration of sodium sulfite (Na ₂ SO ₃ ) in the supplied processing liquid, the larger the amount of sodium sulfite that can be reduced, and the shorter the processing time can be. Can be confirmed.
Therefore, it can be confirmed that it is effective to dilute the treatment liquid before the treatment with the wastewater treatment apparatus of the present invention.

  The waste water treatment apparatus of the present invention is suitable for an apparatus for treating a liquid containing a component that increases a COD (chemical oxygen demand) value discharged from an absorption tower or the like.

DESCRIPTION OF SYMBOLS 1 Waste water treatment apparatus 2 Oxidation tank 10 Stirring means 11 Cylindrical member 11c Intake passage 12 Rotating shaft 13 Stirring member 21 Liquid supply passage 22 Discharge passage L Processing liquid

Claims (6)

An apparatus for oxidizing a substance contained in a liquid,
An oxidation tank containing liquid;
A stirring means disposed in the oxidation tank,
The stirring means includes
A cylindrical member disposed such that a tip end is immersed in the liquid in the oxidation tank and a base end is positioned above the liquid level of the liquid;
A rotating shaft disposed inside the tubular member;
A stirring member attached to the end of the cylindrical member on the tip side of the rotating shaft;
An intake passage through which air can be introduced into the cylindrical member, and
A flange-shaped refinement plate is provided concentrically at the tip of the cylindrical member,
In the miniaturized plate, a plurality of through holes for allowing bubbles to pass through the annularly formed plate are formed along the outer peripheral edge,
The stirring member is
It consists of a circular plate and a stirring blade provided on the plate,
The waste water treatment apparatus, wherein the through hole is located above a position through which the stirring blade passes . The interior of the tubular member, according to claim 1 Symbol placement of waste water treatment apparatus is characterized in that it comprises a liquid supply passage for supplying the liquid from the outside of the oxidation tank. A plurality of the oxidation tanks provided with the stirring means,
The plurality of oxidation tanks are
The liquid processed in the oxidation tank located on the upstream side is arranged so as to be sequentially supplied to the downstream oxidation tank,
The liquid which has been treated in an oxidation vessel positioned upstream, downstream of claim 1 or 2, wherein in that it comprises a stirring member near the supply communication passage of the stirring means in the oxidation vessel Wastewater treatment equipment. PH adjusting means for adjusting the pH of the liquid is provided,
The pH adjusting means is
Claim 1, 2 or 3 waste water treatment apparatus, wherein the pH of the liquid, and adjusts the greater than 10 than 7. According to claim 1, characterized in that it comprises a dilution means for diluting the liquid, waste water treatment apparatus 3 or 4, wherein. Wherein the liquid, waste water treatment apparatus according to claim 1, 2, 3, 4 or 5, wherein it is a liquid containing sodium sulphite and / or sodium bisulfite.

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