Alkaline wastewater neutralization system

Abstract

To improve the neutralization efficiency of alkali waste water.SOLUTION: An alkaline wastewater neutralization system 1 for neutralizing alkaline wastewater includes a raw water tank 31 for storing alkaline wastewater discharged from a construction site, a neutralization apparatus 33 for neutralizing the alkaline wastewater supplied from the raw water tank 31 using carbon dioxide gas, an exhaust gas storage tank 51 for storing exhaust gas discharged from a boiler 4 at the construction site, and a bubble generator 56 for bubbling the exhaust gas supplied from the exhaust gas storage tank 51 to aerate the alkaline wastewater in the raw water tank 31.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an alkaline wastewater neutralization system for performing a neutralization treatment of alkaline wastewater. [Background technology]

[0002] Alkaline wastewater neutralization systems that perform alkaline wastewater neutralization treatment are known. For example, Patent Document 1 discloses a technology that uses the exhaust gas (carbon dioxide in the exhaust gas) of a ready-mixed concrete truck to lower the pH of alkaline wastewater generated by washing the ready-mixed concrete truck. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-165694 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the technology disclosed in Patent Document 1 is only effective when washing ready-mixed concrete vehicles, so its effect in reducing the pH of alkaline wastewater is limited. Also, the ready-mixed concrete vehicle needs to be kept in an engine-driven (idling) state during washing. [Means for solving the problem]

[0005] The present invention was created in view of the above-mentioned current situation and with the aim of solving these problems. The invention of claim 1 is an alkaline wastewater neutralization system that neutralizes alkaline wastewater, and is characterized by comprising: a raw water tank that stores alkaline wastewater discharged from a construction site; a neutralization treatment device that neutralizes alkaline wastewater supplied from the raw water tank using carbon dioxide; an exhaust gas storage tank that stores exhaust gas discharged from a boiler at the construction site; and a bubble generator that bubbles the exhaust gas supplied from the exhaust gas storage tank and aerates the alkaline wastewater in the raw water tank. The invention of claim 2 is an alkaline wastewater neutralization system according to claim 1, characterized in that the bubble generator is a fine bubble generator that converts exhaust gas supplied from the exhaust gas storage tank into fine bubbles and aerates the alkaline wastewater in the raw water tank. The invention of claim 3 is the alkaline wastewater neutralization system according to claim 1, characterized in that air is bubbled and aerated into the alkaline wastewater when the boiler is stopped. The invention of claim 4 is an alkaline wastewater neutralization system according to claim 3, characterized in that the exhaust gas storage tank comprises an exhaust gas inlet section for introducing exhaust gas, an air inlet section for introducing air, and a supply section for supplying exhaust gas to the bubble generator when exhaust gas is stored, and for supplying air to the bubble generator when exhaust gas is not stored. Furthermore, the invention of claim 5 is an alkaline wastewater neutralization system according to claim 3, characterized in that the exhaust gas storage tank comprises an exhaust gas inlet for introducing exhaust gas, an air inlet for introducing air, and a supply switching means capable of switching between a first state for supplying exhaust gas and a second state for supplying air to the bubble generator. Furthermore, the invention of claim 6 is the alkaline wastewater neutralization system according to claim 5, characterized in that it further comprises a control device that automatically switches the supply switching means in response to operation and stoppage of the boiler. Furthermore, the invention of claim 7 is an alkaline wastewater neutralization system as described in claim 1, characterized in that it further comprises a Roots blower that supplies exhaust gas in the exhaust gas storage tank to the bubble generator. Furthermore, the invention of claim 8 is the alkaline wastewater neutralization system described in claim 7, characterized in that the bubble generator is an aeration pipe that diffuses exhaust gas supplied from the exhaust gas storage tank via the Roots blower into the alkaline wastewater in the raw water tank to create bubbles. [Effects of the Invention]

[0006] According to the invention of claim 1, alkaline wastewater in a raw water tank is neutralized (pH reduction treatment) using exhaust gas from a boiler used at a construction site. Therefore, at construction sites where boilers are operated for long periods of time, alkaline wastewater in the raw water tank can be neutralized over a long period of time. In addition, this system stores the boiler exhaust gas in an exhaust gas storage tank and aerates the stored exhaust gas into the alkaline wastewater in the raw water tank, thereby ensuring a stable supply of exhaust gas for use in the neutralization treatment. As a result, this system efficiently lowers the pH of alkaline wastewater stored in the raw water tank and reduces the amount of carbon dioxide used by the neutralization treatment device. According to the invention of claim 2, the exhaust gas is converted into fine bubbles and aerated into the alkaline wastewater, thereby lengthening the time the exhaust gas remains in the liquid and promoting the neutralization reaction of the alkaline wastewater. Furthermore, according to the invention of claim 3, when the boiler is shut down, air is bubbled and aerated into the alkaline wastewater, so that the alkaline wastewater neutralization system can continue to operate stably even if the boiler is shut down frequently. Furthermore, according to the invention of claim 4, the exhaust gas storage tank supplies exhaust gas to the bubble generator when exhaust gas is stored, and supplies air to the bubble generator when exhaust gas is not stored. Therefore, there is no need to stop the operation of the alkaline wastewater neutralization system or to switch the supply flow path to the bubble generator when the boiler is stopped, thereby simplifying the system. Furthermore, according to the invention of claim 5, the exhaust gas storage tank is provided with a supply switching means that can switch between a first state in which exhaust gas is supplied to the bubble generator and a second state in which air is supplied, so that the aeration state using exhaust gas and the aeration state using air can be appropriately switched in the exhaust gas storage tank. Furthermore, according to the invention of claim 6, a control device is further provided that automatically switches the supply switching means depending on the operation and shutdown of the boiler, thereby eliminating the need for manual switching of the supply switching means and reducing the workload of the system administrator, and also preventing a decrease in neutralization processing efficiency due to incorrect operation or forgetting to operate the supply switching means. Furthermore, according to the invention of claim 7, a Roots blower is further provided to supply exhaust gas in the exhaust gas storage tank to the bubble generator, thereby increasing the amount of exhaust gas supplied to the bubble generator and improving the recovery rate of exhaust gas compared to when a compressor is used. Furthermore, according to the invention of claim 8, the bubble generator is an aeration pipe that diffuses exhaust gas supplied from the exhaust gas storage tank via a Roots blower into the alkaline wastewater in the raw water tank to create bubbles. Therefore, compared to using a fine bubble generator, not only can it easily cope with an increase in exhaust gas, but it also eliminates the need for a pump, reducing costs. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram showing the configuration of an alkaline wastewater neutralization system according to a first embodiment of the present invention. [Figure 2] FIG. 1 is a schematic cross-sectional view showing the structure of a fine bubble generator. [Figure 3] FIG. 10 is a block diagram showing input and output of a control device provided in an alkaline wastewater neutralization apparatus according to a second embodiment of the present invention. [Figure 4] 4 is a flowchart showing a control procedure of the control device. [Figure 5] FIG. 10 is a diagram showing the configuration of an alkaline wastewater neutralization system according to a third embodiment of the present invention. [Figure 6] (a) is a cross-sectional view of the Roots blower in the rotor axial direction, and (b) is a cross-sectional view of the Roots blower in the direction perpendicular to the rotor axis. [Figure 7] (a) is a front view of the coarse bubble diffusing pipe, and (b) is a side view of the coarse bubble diffusing pipe. [Figure 8] (a) is a side view of the fine bubble diffuser (the lower half is a cross-section), and (b) is the back side of the fine bubble diffuser. [Figure 9] 10 is a graph showing an experimental example of an alkaline wastewater neutralization system according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] [First embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In Fig. 1, reference numeral 1 denotes an alkaline wastewater neutralization system, which neutralizes alkaline wastewater discharged from a construction site. For example, the alkaline wastewater neutralization system 1 of this embodiment is applied to neutralizing alkaline wastewater discharged from a tunnel site.

[0009] At tunnel construction sites, a large amount of alkaline wastewater containing alkaline components dissolved from excavated materials such as bedrock is discharged. This type of alkaline wastewater is usually separated from the soil and sand in a settling basin 2 and then neutralized in a neutralization treatment facility 3.

[0010] Furthermore, at tunnel construction sites, boilers 4 (e.g., stable hot water equipment) may be used. For example, at tunnel construction sites in cold regions, boilers 4 are used to heat the mixing water for shotcrete. Boilers 4 use kerosene or other fuel to heat water, and therefore emit exhaust gases containing carbon dioxide when in operation.

[0011] As shown in FIG. 1, the alkaline wastewater neutralization system 1 of this embodiment is realized by adding a pre-neutralization treatment facility 5 to an existing neutralization treatment facility 3, and the pre-neutralization treatment facility 5 is a key part of the present invention.

[0012] The existing neutralization treatment facility 3 is configured to include a raw water tank 31 that stores alkaline wastewater discharged from a tunnel site (alkaline wastewater separated from sediment in the settling basin tank 2), and a neutralization treatment device 33 that neutralizes the alkaline wastewater supplied from the raw water tank 31 using liquefied carbon dioxide gas 32. Note that although the neutralization treatment device 33 shown in Fig. 1 is configured to include a neutralization reaction tower 331 and a neutralization reaction tank 332, the configuration of the neutralization treatment device 33 is not limited to this.

[0013] The pre-neutralization treatment equipment 5 includes an exhaust gas storage tank 51 , a compressor 52 , a regulator 53 , an air filter 54 , a pump 55 , and a bubble generator 56 .

[0014] Exhaust gas storage tank 51 stores exhaust gas discharged from boiler 4 and supplies the stored exhaust gas to compressor 52. For example, exhaust gas storage tank 51 is configured to include an exhaust gas inlet 511 that introduces exhaust gas discharged from boiler 4, an air inlet 513 that introduces air, a supply unit 512 that supplies exhaust gas to compressor 52 when exhaust gas is stored and that supplies air to compressor 52 when exhaust gas is not stored, a carbon dioxide concentration sensor (not shown) that detects the carbon dioxide concentration of the stored exhaust gas, and a carbon dioxide concentration display unit (not shown) that displays the detected carbon dioxide concentration.

[0015] The compressor 52 compresses the exhaust gas or air supplied from the exhaust gas storage tank 51 and supplies it to the regulator 53 .

[0016] The regulator 53 reduces the pressure of the exhaust gas or air supplied from the compressor 52 to a constant level, and supplies the gas to an air filter 54 .

[0017] The air filter 54 filters the exhaust gas or air supplied from the regulator 53 and supplies it to the bubble generator 56 .

[0018] The pump 55 sucks the alkaline wastewater in the raw water tank 31 and supplies it to the bubble generator 56. The pump 55 is configured, for example, by a submersible pump installed in the raw water tank 31.

[0019] The bubble generator 56 bubbles the exhaust gas or air supplied from the exhaust gas storage tank 51 and aerates the alkaline wastewater in the raw water tank 31. In this embodiment, a fine bubble generator that turns the exhaust gas or air supplied from the exhaust gas storage tank 51 into fine bubbles is used as the bubble generator 56. Fine bubbles are tiny bubbles less than 100 μm in size, which increase the residence time of the exhaust gas in the liquid and promote the neutralization reaction. Although a fine bubble generator is used as the bubble generator 56 in this embodiment, a bubble generator that generates bubbles of 100 μm or larger may also be used.

[0020] 2, the bubble generator 56, which is a fine bubble generator, is configured to include a liquid inlet 561 that introduces alkaline wastewater supplied from a pump 55, a gas inlet 562 that introduces exhaust gas or air supplied from an exhaust gas storage tank 51 via a compressor 52, a regulator 53, and an air filter 54, an air chamber 564 that supplies the exhaust gas or air introduced from the gas inlet 562 to the alkaline wastewater to generate fine bubbles, and an outlet 563 that discharges the alkaline wastewater containing the exhaust gas or air that has been converted into fine bubbles. The bubble generator 56 is installed in the raw water tank 31, thereby enabling the exhaust gas or air that has been converted into fine bubbles to be aerated into the alkaline wastewater in the raw water tank 31.

[0021] According to this embodiment configured as described above, the alkaline wastewater in the raw water tank 31 is neutralized using exhaust gas from the boiler 4 used at the construction site, so that at construction sites where the boiler 4 is operated for long periods of time, the alkaline wastewater in the raw water tank 31 can be neutralized for a long period of time.

[0022] Furthermore, this system stores exhaust gas from the boiler 4 in the exhaust gas storage tank 51 and aerates the stored exhaust gas into the alkaline wastewater in the raw water tank 31, thereby enabling a stable supply of exhaust gas to be used in the neutralization treatment. As a result, this system can efficiently lower the pH of the alkaline wastewater stored in the raw water tank 31 and reduce the amount of carbon dioxide gas used by the neutralization treatment device 33.

[0023] Furthermore, in this embodiment, the exhaust gas is converted into fine bubbles and aerated into the alkaline wastewater, which increases the time the exhaust gas remains in the liquid and promotes the neutralization reaction of the alkaline wastewater.

[0024] Furthermore, when the boiler 4 is stopped, air is bubbled and aerated into the alkaline wastewater, so that the system can continue to operate stably even if the boiler 4 is frequently stopped.

[0025] Furthermore, when exhaust gas is stored in the exhaust gas storage tank 51, the tank supplies the exhaust gas to the bubble generator 56, and when exhaust gas is not stored in the tank, the tank supplies air to the bubble generator 56. This eliminates the need to stop the operation of the system or to switch the supply flow path to the bubble generator 56 when the boiler 4 is stopped, thereby simplifying the system.

[0026] [Second embodiment] Next, an alkaline wastewater neutralization system 1 according to a second embodiment of the present invention will be described with reference to Figures 3 and 4. However, for configurations common to the above-described embodiment, the same reference numerals as in the above-described embodiment will be used, and the description of the above-described embodiment may be used.

[0027] 3, the alkaline wastewater neutralization system 1 of the second embodiment further includes a supply switching means 514 and a control device 57. The supply switching means 514 is provided in the exhaust gas storage tank 51, and switches between a first state in which exhaust gas is supplied to the bubble generator 56 and a second state in which air is supplied to the bubble generator 56.

[0028] 3, the control device 57 receives an ON / OFF signal from the main switch 58 and an operation signal from the boiler 4, and controls the supply switching means 514, the compressor 52, and the pump 55 in response to these signals. A specific control procedure of the control device 57 will be described below with reference to FIG.

[0029] As shown in Figure 4, in pre-neutralization control, the control device 57 first determines whether the main switch 58 is ON or not (S1), and if the result of this determination is NO, it turns off the compressor 52 and the pump 55 to stop operation of the pre-neutralization treatment equipment 5 (S2).

[0030] Furthermore, if the control device 57 determines that the main switch 58 is ON (S1: YES), it turns on the compressor 52 and the pump 55 to operate the pre-neutralization treatment equipment 5 (S3), and determines whether the boiler 4 is operating (S4).

[0031] Then, when the control device 57 determines that the boiler 4 is operating (S4: YES), it sets the supply switching means 514 to the first state and causes the fine bubble generator 56 to supply exhaust gas.

[0032] Furthermore, when the control device 57 determines that the boiler 4 is not operating (S4: NO), it sets the supply switching means 514 to the second state and causes air to be supplied to the fine bubble generator 56.

[0033] According to the second embodiment described above, the exhaust gas storage tank 51 is provided with a supply switching means 514 that can switch between a first state in which exhaust gas is supplied to the bubble generator 56 and a second state in which air is supplied, so that the exhaust gas storage tank 51 can appropriately switch between an aeration state using exhaust gas and an aeration state using air.

[0034] Furthermore, according to the second embodiment, a control device 57 is further provided that automatically switches the supply switching means 514 depending on whether the boiler 4 is operating or stopped. This not only eliminates the need for manual switching of the supply switching means 514, thereby reducing the workload of the system administrator, but also prevents a decrease in neutralization processing efficiency due to incorrect operation or forgetting to operate the supply switching means 514.

[0035] [Third embodiment] Next, an alkaline wastewater neutralization system 1 according to a third embodiment of the present invention will be described with reference to Fig. 5 and subsequent figures. However, for configurations common to the above-described embodiments, the same reference numerals as those in the above-described embodiments will be used, and the description of the above-described embodiments may be used.

[0036] As shown in Figure 5, the alkaline wastewater neutralization system 1 of the third embodiment differs from the first embodiment in that a Roots blower 61 (rotary blower) is used as an exhaust gas supply means for supplying the exhaust gas in the exhaust gas storage tank 51 to the bubble generator 56B, and in that aeration pipes 62, 63 are used as the bubble generator 56B for aerating the exhaust gas supplied from the exhaust gas storage tank 51 into the alkaline wastewater in the raw water tank 31.

[0037] The alkaline wastewater neutralization system 1 of the third embodiment is equipped with an air filter 515 provided in the exhaust gas storage tank 51 to filter exhaust gas and air, a water drain 516 provided at the bottom of the exhaust gas storage tank 51 to drain water accumulated in the tank, an air pressure gauge 64 provided in the exhaust gas supply path from the Roots blower 61 to the bubble generator 56B to measure the pressure of the exhaust gas and air, an air flow meter 65 provided in the exhaust gas supply path to measure the flow rate of the exhaust gas and air, valves such as an air valve 66, a valve 67, and a check valve 68 provided in the exhaust gas supply path, and a pH meter 69 provided in the raw water tank 31 to measure the pH of the alkaline wastewater, but the presence or absence of these can be selected as desired.

[0038] As shown in Figure 6, the Roots blower 61 comprises a casing 611, an intake port 612 for drawing exhaust gas and air into the casing 611, an exhaust port 613 for expelling exhaust gas and air from within the casing 611, a first rotor 614 and a second rotor 615 rotatably mounted within the casing 611, an input pulley 616 for inputting power supplied from a power source such as an electric motor to the first rotor 614, and a timing gear 617 for transmitting the power of the first rotor 614 to the second rotor 615 and rotating the second rotor 615 synchronously in the opposite direction to the first rotor 614.

[0039] The Roots blower 61 draws in exhaust gas and air through the intake port 612 and discharges the drawn-in exhaust gas and air from the discharge port 613 due to the synchronous rotation of the first rotor 614 and the second rotor 615. The Roots blower 61 configured in this way has a lower discharge pressure (e.g., 20 kPa) than a compressor, but a higher discharge volume (e.g., 3.07 m 3 / min) is large, the amount of exhaust gas supplied to the bubble generator 56B can be increased, and the recovery rate of the exhaust gas can be improved.

[0040] The aeration pipes 62, 63 may be, for example, a coarse bubble aeration pipe 62 shown in Fig. 7 or a fine bubble aeration pipe 63 shown in Fig. 8. The aeration pipes 62, 63 diffuse the exhaust gas supplied from the exhaust gas storage tank 51 into the alkaline wastewater in the raw water tank 31 to form bubbles. Therefore, unlike a fine bubble generator, the exhaust gas can be aerated into the alkaline wastewater to neutralize the alkaline wastewater using the exhaust gas, without using a pump 55. Furthermore, the system can easily accommodate an increase in the amount of exhaust gas supplied by the Roots blower 61.

[0041] As shown in FIG. 7 , the coarse bubble diffusing pipe 62 is formed entirely using a metal material such as stainless steel, and includes a diffusing pipe body 621 having a large number of bubble holes 621a, an inlet cap 622 covering the front opening of the diffusing pipe body 621, an air supply port 623 that passes through the inlet cap 622 and sends exhaust gas and air into the diffusing pipe body 631, and an end cap 624 that covers the rear opening of the diffusing pipe body 621.

[0042] When this coarse bubble diffuser 62 is installed in the raw water tank 31 and exhaust gas or air is sent into the diffuser body 621 through the air supply port 623, the sent exhaust gas or air is diffused into the alkaline wastewater through the numerous bubble holes 621a and turned into bubbles. Although the coarse bubble diffuser 62 generates coarse bubbles, it has a high standard airflow rate, which indicates the amount of gas that can be turned into bubbles. For example, a 610 mm long coarse bubble diffuser 62 has a standard airflow rate of 700 L / min. Therefore, when the coarse bubble diffuser 62 is used as the bubble generator 56B of the alkaline wastewater neutralization system 1, it can easily accommodate an increase in the amount of exhaust gas supplied by the Roots blower 61. Furthermore, a coarse bubble diffuser 62 made entirely of a metal material such as stainless steel is not only highly durable but also easy to maintain, thereby reducing operating costs.

[0043] As shown in FIG. 8, the fine bubble diffusing pipe 63 is made of synthetic rubber such as EPDM, and includes a diffuser pipe body 631 having numerous bubble slits 631a, a support member 632 that supports the diffuser pipe body 631 from the inner periphery, clamps 633 that secure both ends of the diffuser pipe body 631 to the support member 632, and an air supply port 634 that sends exhaust gas and air into the diffuser pipe body 631.

[0044] When this fine bubble diffuser 63 is installed in the raw water tank 31 and exhaust gas or air is sent into the diffuser body 631 through the air supply port 634, the exhaust gas or air is diffused into the alkaline wastewater through the numerous bubble slits 631a and turned into bubbles. The fine bubble diffuser 63 generates fine bubbles, but has a high standard airflow rate, which indicates the amount of gas that can be bubbled. For example, a fine bubble diffuser 63 with a diameter of 91 mm and a length of 762 mm has a standard airflow rate of 570 L / min. Therefore, when the fine bubble diffuser 63 is used as the bubble generator 56B in the alkaline wastewater neutralization system 1, it can easily accommodate an increase in the amount of exhaust gas supplied by the Roots blower 61. Furthermore, the fine bubble diffuser 63 can turn exhaust gas into fine bubbles more efficiently than the coarse bubble diffuser 62, thereby shortening the time required for neutralization.

[0045] FIG. 9 shows the time required for neutralization treatment using the coarse bubble diffuser 62 and the fine bubble diffuser 63 when alkaline water (6,000 L) with a pH of 12 was placed in an experimental tank. The time required for neutralization treatment using the coarse bubble diffuser 62 was 1 hour, 0 minutes, and 50 seconds, while the time required for neutralization treatment using the fine bubble diffuser 63 was 44 minutes and 40 seconds. As a result, if priority is given to the time required for neutralization treatment, it is considered advantageous to select the fine bubble diffuser 63. Furthermore, if priority is given to operating costs over the time required for neutralization treatment, it is considered advantageous to select the coarse bubble diffuser 62.

[0046] According to the third embodiment described above, a Roots blower 61 is further provided to supply exhaust gas in the exhaust gas storage tank 51 to the bubble generator 56B, thereby increasing the amount of exhaust gas supplied to the bubble generator 56B and improving the recovery rate of the exhaust gas compared to when the compressor 52 is used.

[0047] Furthermore, according to the third embodiment, the bubble generator 56B is constituted by aeration pipes 62, 63 that diffuse exhaust gas supplied from the exhaust gas storage tank 51 via the Roots blower 61 into the alkaline wastewater in the raw water tank 31 to create bubbles. Therefore, compared to the case where a fine bubble generator is used, not only can it easily cope with an increase in exhaust gas, but it can also eliminate the need for the pump 55, reducing costs. [Explanation of symbols]

[0048] 1. Alkaline wastewater neutralization system 2 Sediment basin tank 3 Neutralization treatment equipment 31 Raw Water Tank 32 Liquefied carbon dioxide 33 Neutralization treatment equipment 331 Neutralization reaction tower 332 Neutralization reactor 4 boilers 5 Pre-neutralization treatment equipment 51 Exhaust gas storage tank 511 Exhaust gas introduction section 512 Supply section 513 Air intake section 514 Supply switching means 52 Compressor 53 Regulator 54 Air filter 55 Pump 56 Bubble generator (fine bubble generator) 56B Bubble generator (aeration pipe) 561 Liquid introduction section 562 Gas inlet 563 Outlet 564 Air Chamber 57 Control Device 58 Main switch 61 Roots Blower 62 Coarse air bubble diffuser (aeration pipe) 63 Fine bubble diffuser (aeration tube)

Claims

1. An alkaline wastewater neutralization system for performing neutralization treatment of alkaline wastewater, A raw water tank that stores alkaline wastewater discharged from construction sites, a neutralization treatment device that neutralizes the alkaline wastewater supplied from the raw water tank using carbon dioxide gas; an exhaust gas storage tank for storing exhaust gas discharged from a boiler at the construction site; and a bubble generator that bubbles the exhaust gas supplied from the exhaust gas storage tank and aerates the alkaline wastewater in the raw water tank.

2. The alkaline wastewater neutralization system according to claim 1, characterized in that the bubble generator is a fine bubble generator that converts exhaust gas supplied from the exhaust gas storage tank into fine bubbles and aerates the alkaline wastewater in the raw water tank.

3. 2. The alkaline wastewater neutralization system according to claim 1, wherein air is bubbled and aerated into the alkaline wastewater when the boiler is stopped.

4. The exhaust gas storage tank is an exhaust gas introduction section that introduces exhaust gas; an air introduction section that introduces air; The alkaline wastewater neutralization system according to claim 3, further comprising a supply unit that supplies exhaust gas to the bubble generator when exhaust gas is stored, and that supplies air to the bubble generator when exhaust gas is not stored.

5. The exhaust gas storage tank is an exhaust gas introduction section that introduces exhaust gas; an air introduction section that introduces air; 4. The alkaline wastewater neutralization system according to claim 3, further comprising a supply switching means capable of switching between a first state for supplying exhaust gas to the bubble generator and a second state for supplying air to the bubble generator.

6. 6. The alkaline wastewater neutralization system according to claim 5, further comprising a control device that automatically switches the supply switching means in response to operation and shutdown of the boiler.

7. 2. The alkaline wastewater neutralization system according to claim 1, further comprising a Roots blower that supplies exhaust gas in the exhaust gas storage tank to the bubble generator.

8. The alkaline wastewater neutralization system described in claim 7, characterized in that the bubble generator is an aeration pipe that diffuses exhaust gas supplied from the exhaust gas storage tank via the Roots blower into the alkaline wastewater in the raw water tank to create bubbles.

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