WO2025104871A1 - Carbon dioxide emission reduction method and carbon dioxide emission reduction system - Google Patents

Abstract

Exhaust G discharged from an internal combustion engine 20 is injected into an alkaline solution A stored in a storage tank 2, the alkaline solution A and the exhaust G are brought into contact with each other inside the storage tank 2, and the alkaline solution A and the carbon dioxide contained in the exhaust G are subjected to a neutralizing reaction. This reduces the amount of carbon dioxide contained in the exhaust G discharged from the internal combustion engine 20, and the exhaust G with the reduced amount of carbon dioxide is discharged from an exhaust port 2c of the storage tank 2. This can effectively reduce the amount of carbon dioxide contained in the exhaust G discharged from the internal combustion engine 20.

Description

Carbon dioxide emission reduction method and carbon dioxide emission reduction system

The present invention relates to a method and system for reducing carbon dioxide emissions, and more specifically to a method and system for reducing carbon dioxide emissions that can effectively reduce the amount of carbon dioxide contained in exhaust gas emitted from an internal combustion engine.

In order to curb global warming, reducing carbon dioxide ( _CO2 ) emissions in construction work has become an important issue. Carbon dioxide emissions from internal combustion engines such as generators and diesel engines used in construction work account for a relatively large proportion of carbon dioxide emissions in construction work. Therefore, it is important to reduce the carbon dioxide contained in the exhaust gas emitted from internal combustion engines in construction work.

Conventionally, urea SCR systems have been used to purify the exhaust gas from internal combustion engines of automobiles and ships. However, the urea SRC system is a system that purifies nitrogen oxides ( _NOx ) in the exhaust gas and cannot reduce the carbon dioxide contained in the exhaust gas (see, for example, Patent Document 1).

Japanese Patent Application Publication No. 2012-240446

The object of the present invention is to provide a method and system for reducing carbon dioxide emissions that can effectively reduce the amount of carbon dioxide contained in exhaust gas discharged from an internal combustion engine.

In order to achieve the above object, the carbon dioxide emission reduction method of the present invention is characterized in that exhaust gas discharged from an internal combustion engine is injected into an alkaline solution stored in a storage tank, the alkaline solution is brought into contact with the exhaust gas inside the storage tank, and a neutralization reaction occurs between the alkaline solution and the carbon dioxide contained in the exhaust gas, thereby reducing the carbon dioxide contained in the exhaust gas, and the exhaust gas with reduced carbon dioxide is discharged from an exhaust port of the storage tank.

In order to achieve the above object, the carbon dioxide emission reduction system of the present invention is characterized in that it comprises a storage tank in which an alkaline solution is stored, and an injection means for injecting exhaust gas discharged from an internal combustion engine into the alkaline solution stored in the storage tank, and the alkaline solution comes into contact with the exhaust gas injected by the injection means inside the storage tank, causing a neutralization reaction between the alkaline solution and the carbon dioxide contained in the exhaust gas, thereby reducing the carbon dioxide contained in the exhaust gas, and the exhaust gas with the reduced carbon dioxide content is discharged from an exhaust port of the storage tank.

According to the present invention, the amount of carbon dioxide contained in the exhaust gas discharged from an internal combustion engine can be effectively reduced by injecting the exhaust gas discharged from an internal combustion engine into an alkaline solution stored in a storage tank and causing a neutralization reaction between the carbon dioxide contained in the exhaust gas and the alkaline solution inside the storage tank. Furthermore, the alkaline solution used to reduce the amount of carbon dioxide contained in the exhaust gas can reduce the hydrogen ion concentration by causing a neutralization reaction with carbon dioxide. Therefore, the alkaline solution can be easily disposed of after use.

FIG. 1 is an explanatory diagram that illustrates a carbon dioxide emission reduction system according to an embodiment of the present invention. FIG. 2 is an explanatory diagram illustrating a schematic cross-sectional view of the storage tank of FIG. FIG. 3 is an explanatory diagram that illustrates a schematic example of a plurality of storage tanks and a notch tank that are connected in series and that constitute the carbon dioxide emission reduction system of the present invention. FIG. 4 is an explanatory diagram that illustrates a schematic example of an exhaust gas supply line that constitutes the carbon dioxide emission reduction system of the present invention. FIG. 5 is an explanatory diagram that illustrates a schematic example of a solution supply line that constitutes the carbon dioxide emission reduction system of the present invention. FIG. 6 is a graph illustrating the transition of the hydrogen ion concentration of the alkaline solution and the transition of the cumulative amount of carbon dioxide absorbed from the exhaust gas in the carbon dioxide emission reduction system of the present invention. FIG. 7 is an explanatory diagram that illustrates a carbon dioxide emission reduction system according to another embodiment of the present invention. FIG. 8 is an explanatory diagram that illustrates a carbon dioxide emission reduction system according to still another embodiment of the present invention. FIG. 9 is an explanatory diagram that illustrates a carbon dioxide emission reduction system according to still another embodiment of the present invention.

Below, the carbon dioxide emission reduction method and carbon dioxide emission reduction system of the present invention will be explained based on the embodiment shown in the figure.

The carbon dioxide emission reduction method and carbon dioxide emission reduction system 1 of the present invention illustrated in Figures 1 to 5 reduce carbon dioxide (CO ₂ ) contained in exhaust G discharged from an internal combustion engine 20. Examples of the internal combustion engine 20 include a generator and a diesel engine. The carbon dioxide emission reduction system 1 of the present invention (hereinafter referred to as the reduction system 1) can be applied to internal combustion engines 20 such as generators used in land-based construction work and diesel engines equipped in construction machinery. This reduction system 1 can also be applied to internal combustion engines 20 such as generators and diesel engines equipped in work vessels used in marine construction work.

As illustrated in FIG. 1, the reduction system 1 includes a storage tank 2 in which an alkaline solution A is stored, and an injection means 3 for injecting exhaust gas G discharged from an internal combustion engine 20 into the alkaline solution A stored in the storage tank 2. In this reduction system 1, the alkaline solution A comes into contact with the exhaust gas G injected by the injection means 3 inside the storage tank 2, and a neutralization reaction occurs between the alkaline solution A and the carbon dioxide contained in the exhaust gas G, thereby reducing the carbon dioxide contained in the exhaust gas G. The exhaust gas G with reduced carbon dioxide is then discharged from the exhaust port 2c of the storage tank 2. In the figure, the flow of the exhaust gas G is shown diagrammatically by open arrows, and the flow of the alkaline solution A is shown diagrammatically by filled arrows.

Various solutions can be used as the alkaline solution A, so long as it is alkaline with a hydrogen ion concentration greater than pH 7 and undergoes a neutralizing reaction with carbon dioxide. Specifically, for example, a calcium hydroxide solution or a sodium hydroxide solution can be used as the alkaline solution A. It is advisable to use an alkaline solution A having a hydrogen ion concentration of, for example, pH 8 to 14, preferably pH 9 to 14, and more preferably pH 10 to 14. This embodiment illustrates the case where alkaline solution A (calcium hydroxide solution) is produced using recycled crushed stone R obtained by crushing concrete waste generated during demolition work, etc.

As shown in FIG. 1, the storage tank 2 is an airtight, hollow container. In this embodiment, the storage tank 2 has a cylindrical tubular portion that extends in the vertical direction, and below the tubular portion is a tapered portion that tapers downward. The shape of the storage tank 2 is not limited to the shape of this embodiment, and for example, a storage tank 2 having a polygonal cylindrical shape can also be used.

The bottom of the storage tank 2 is provided with an inlet 2a through which alkaline solution A flows in, and a connecting pipe 6 is connected to the inlet 2a. The top of the storage tank 2 is provided with a drain 2d through which alkaline solution A flows out, and a connecting pipe 6 is connected to the drain 2d. The drain 2d is located near the liquid level of the alkaline solution A stored in the storage tank 2. The alkaline solution A flows into the inside of the storage tank 2 from the solution supply line described below through the connecting pipe 6 connected to the inlet 2a of the storage tank 2 (2X), and the alkaline solution A near the liquid level stored in the storage tank 2 flows out into the connecting pipe 6 connected to the drain 2d.

In this embodiment, the injection means 3 is an injection port 2b provided at the bottom of the storage tank 2, and an air vent pipe 5 is inserted into the injection port 2b. The tip of the air vent pipe 5 is connected to the injection unit 4. The injection unit 4 is disposed at the bottom inside the storage tank 2. An exhaust port 2c through which exhaust gas G is discharged is provided at the top of the storage tank 2, and the air vent pipe 5 is connected to the exhaust port 2c. The exhaust port 2c is located above the liquid level of the alkaline solution A stored in the storage tank 2.

The exhaust G discharged from the internal combustion engine 20 is supplied to the injection unit 4 through an exhaust supply line (described later) and a vent pipe 5 inserted into the injection port 2b, and the supplied exhaust G is injected into the alkaline solution A by the injection unit 4. The exhaust G injected from the injection unit 4 and passed through the alkaline solution A is then discharged from the vent pipe 5 connected to the exhaust port 2c.

As shown in FIG. 2, the injection unit 4 of this embodiment is configured to have a plurality of ejection nozzles 4a and a branch pipe section 4b. The branch pipe section 4b is connected to the tip of the vent pipe 5 inserted into the injection port 2b. A plurality of ejection nozzles 4a are arranged on the branch pipe section 4b. The exhaust G supplied to the branch pipe section 4b from the vent pipe 5 is distributed to each ejection nozzle 4a by the branch pipe section 4b, and the exhaust G is ejected from each ejection nozzle 4a. The ejection of the exhaust G from each ejection nozzle 4a generates a swirling flow in which many bubbles of exhaust G rise in a spiral shape in the alkaline solution A inside the storage tank 2. In FIG. 1 and FIG. 3, the bubbles of exhaust G ejected from one ejection nozzle 4a are shown relatively large in schematic form, but in reality, many fine exhaust G are ejected from each ejection nozzle 4a, resulting in a state in which a large number of bubbles of exhaust G are ejected into the alkaline solution A.

More specifically, the branch pipe section 4b in this embodiment has a connecting section in the center in a plan view that is connected to the tip of the vent pipe 5. The branch pipe section 4b further has a number of distribution pipes that branch out radially from the connecting section provided in the center, and annular pipes located outside each distribution pipe and to which the outer ends of each distribution pipe are connected. A number of ejection nozzles 4a are disposed at equal intervals around the circumference of the annular pipe. In this embodiment, each ejection nozzle 4a is installed so as to eject exhaust gas G diagonally upward toward the inner surface of the storage tank 2. The number and arrangement of the ejection nozzles 4a that constitute the injection unit 4, the ejection direction, the shape of the branch pipe section 4b, etc. are not limited to this embodiment, and various other configurations are possible.

As shown in FIG. 1, a discharge pipe 11 is connected to the bottom of the storage tank 2 to discharge precipitate S generated by a neutralization reaction between the carbon dioxide contained in the exhaust gas G and the alkaline solution A. The discharge pipe 11 is provided with an openable and closable discharge valve 12. In this embodiment, calcium carbonate generated by a neutralization reaction between the carbon dioxide contained in the exhaust gas G and the alkaline solution A (aqueous calcium hydroxide solution) is precipitated as precipitate S at the bottom of the storage tank 2.

The storage tank 2 is provided with a hydrogen ion concentration meter 13 for measuring the hydrogen ion concentration of the stored alkaline solution A, and a carbon dioxide concentration meter 14 for measuring the carbon dioxide concentration of the exhaust gas G after it has passed through the alkaline solution A in the storage tank 2. In addition, a pressure meter 15 for measuring the pressure of the exhaust gas G flowing into the vent pipe 5 connected to the exhaust port 2c of the storage tank 2 is provided. The hydrogen ion concentration meter 13, the carbon dioxide concentration meter 14, and the pressure meter 15 are each communicatively connected to a management device 40, an example of which is shown in FIG. 3. The management device 40 is composed of a computer. The measurement data measured by the hydrogen ion concentration meter 13, the carbon dioxide concentration meter 14, and the pressure meter 15 are transmitted to the management device 40 as needed, and the transmitted measurement data is displayed on the monitor of the management device 40.

As shown in FIG. 3, in this embodiment, three storage tanks 2 (2X to 2Z) are connected in series via a vent pipe 5 through which exhaust gas G flows and a connecting pipe 6 through which alkaline solution A flows. The structure of each of the storage tanks 2X to 2Z and the configuration of the injection means 3 provided in each of the storage tanks 2X to 2Z are the same. Each of the storage tanks 2X to 2Z is provided with a hydrogen ion concentration meter 13, a carbon dioxide concentration meter 14, and a pressure gauge 15, and the measurement data of each is transmitted to the management device 40 as needed.

The downstream end of the vent pipe 5 connected to the exhaust port 2c of the upstream storage tank 2X (on the internal combustion engine 20 side) is connected to an injection unit 4 provided in the downstream storage tank 2Y. The downstream end of the connecting pipe 6 connected to the drain port 2d of the upstream storage tank 2X is connected to the inlet 2a of the downstream storage tank 2Y. The downstream end of the vent pipe 5 connected to the exhaust port 2c of the storage tank 2Y is further connected to an injection unit 4 provided in the downstream storage tank 2Z. The downstream end of the connecting pipe 6 connected to the drain port 2d of the storage tank 2Y is connected to the inlet 2a of the downstream storage tank 2Z.

An exhaust pipe 7 is connected to the exhaust port 2c of the most downstream storage tank 2Z, and the exhaust G discharged from the exhaust port 2c of the storage tank 2Z is discharged to the atmosphere via the exhaust pipe 7 as treated exhaust GP with reduced carbon dioxide. A connecting pipe 6 is connected to the drain port 2d of the most downstream storage tank 2Z, and the downstream end of the connecting pipe 6 is connected to the upstream inlet of the notch tank 17. The alkaline solution A that flows into the notch tank 17 is discharged as neutralized treated solution AP from the drain pipe 9 connected to the downstream outlet of the notch tank 17.

As shown in FIG. 4, in the exhaust supply line that supplies the exhaust G discharged from the internal combustion engine 20 to the injection means 3, a manifold 21 is connected downstream of the internal combustion engine 20 via an air duct 5. The exhaust G discharged from the internal combustion engine 20 flows into the manifold 21 through the air duct 5. In this embodiment, multiple internal combustion engines 20 are each connected to the manifold 21 via the air duct 5, and the exhaust G discharged from the multiple internal combustion engines 20 is collected in the manifold 21.

A dust collector 22 is connected to the downstream side of the manifold 21 via an air duct 5. The dust collector 22 is a device that removes dust contained in the exhaust gas G. A pressure feeder 24 is connected to the downstream side of the dust collector 22 via an air duct 5. A heat removal tank 23 that removes heat from the exhaust gas G is provided between the dust collector 22 and the pressure feeder 24.

Cooling water CW is stored in the heat removal tank 23, and the middle part of the vent pipe 5 connecting the dust collector 22 and the pumping device 24 is submerged in the cooling water CW stored in the heat removal tank 23. A supply pipe that supplies new cooling water CW to the heat removal tank 23 and a drain pipe that discharges the cooling water CW stored in the heat removal tank 23 are connected to the heat removal tank 23, and by replacing the cooling water CW, the temperature of the cooling water CW stored in the heat removal tank 23 is maintained below a predetermined temperature.

The exhaust gas G discharged from the dust collection device 22 is removed from heat in the heat removal tank 23, and then passes through the vent pipe 5 and is sucked into the compression device 24. The compression device 24 is a device that compresses the exhaust gas G to the injection means 3, and is composed of a gas pump such as a vacuum pump. The injection unit 4 is connected downstream of the compression device 24 via the vent pipe 5, and the exhaust gas G compressed by the compression device 24 is supplied to the injection unit 4.

As shown in FIG. 5, the solution supply line that supplies alkaline solution A to the storage tank 2 has a solution generation tank 30 that generates alkaline solution A on the upstream side. In this embodiment, water W is supplied to the solution generation tank 30, and recycled crushed stone R is added at predetermined time intervals. The solution generation tank 30 is provided with an agitator 31. An outlet is provided at the top of the solution generation tank 30 from which the generated alkaline solution A flows out. An outlet is provided at the bottom of the solution generation tank 30 from which the treated recycled crushed stone RP that has been used to generate the alkaline solution A and neutralized is discharged.

Downstream of the solution generation tank 30 is a raw water level adjustment tank 32 in which the alkaline solution A generated in the solution generation tank 30 is temporarily stored. The outlet of the solution generation tank 30 and the raw water level adjustment tank 32 are connected by a connecting pipe 6, and the alkaline solution A generated in the solution generation tank 30 flows into the raw water level adjustment tank 32 through the connecting pipe 6.

The raw water level adjustment tank 32 is provided with a hydrogen ion concentration meter 13, and the measurement data of the hydrogen ion concentration measured by the hydrogen ion concentration meter 13 is transmitted to the management device 40 at any time. An outlet from which the alkaline solution A flows out is provided at the top of the raw water level adjustment tank 32. A storage tank 2X is provided downstream of the raw water level adjustment tank 32, and the outlet of the raw water level adjustment tank 32 and the inlet 2a of the storage tank 2X are connected by a connecting pipe 6. The outlet of the raw water level adjustment tank 32 is positioned higher than the inlet 2a of the storage tank 2X.

The liquid level of alkaline solution A stored in the raw water level adjustment tank 32, the liquid level of alkaline solution A stored in each of the storage tanks 2X to 2Z, and the liquid level of alkaline solution A stored in the notch tank 17 are set to the same height.

Next, we will explain a method for reducing carbon dioxide emissions using this reduction system 1.

As shown in FIG. 5, in the solution supply line, water W is supplied to the solution generation tank 30 and recycled crushed stone R is added. The recycled crushed stone R accumulates at the bottom of the solution generation tank 30. The water W supplied to the solution generation tank 30 can be seawater, river water, groundwater, tap water, etc. at the construction site. The water W stored in the solution generation tank 30 is stirred by the mixer 31, so that the calcium hydroxide contained in the recycled crushed stone R dissolves in the water W and an alkaline solution A (calcium hydroxide solution) is generated. The calcium hydroxide contained in the recycled crushed stone R dissolves in the water W, so that the recycled crushed stone R accumulated at the bottom of the solution generation tank 30 is neutralized. The treated recycled crushed stone RP that has been used to generate the alkaline solution A and has been neutralized is discharged and collected from a discharge outlet provided at the bottom of the solution generation tank 30.

The alkaline solution A generated in the solution generation tank 30 flows into the raw water level adjustment tank 32 through the connecting pipe 6 connected to the outlet of the solution generation tank 30, and is stored in the raw water level adjustment tank 32. In the raw water level adjustment tank 32, the hydrogen ion concentration of the stored alkaline solution A is measured by the hydrogen ion concentration meter 13, and the amount of recycled crushed stone R to be added to the solution generation tank 30 is adjusted based on the measurement result. It is preferable to adjust the amount of recycled crushed stone R to be added to the solution generation tank 30 so that the hydrogen ion concentration of the alkaline solution A stored in the raw water level adjustment tank 32 is, for example, pH 8 to 14, preferably pH 9 to 14, more preferably pH 10 to 14. The alkaline solution A stored in the raw water level adjustment tank 32 flows into the inside of the storage tank 2X from the inlet 2a of the storage tank 2X through the connecting pipe 6 connected to the outlet of the raw water level adjustment tank 32. In the solution generation tank 30, the flow rate of the alkaline solution A supplied to the raw water level adjustment tank 32 is adjusted so that the liquid level of the alkaline solution A stored in the raw water level adjustment tank 32 is maintained at a predetermined height.

As shown in FIG. 4, in the exhaust supply line, when the target internal combustion engines 20 are operating, exhaust G discharged from each internal combustion engine 20 flows into the manifold 21 through the ventilation pipe 5. The exhaust G collected in the manifold 21 flows into the dust collector 22 through the ventilation pipe 5, and the dust contained in the exhaust G is removed by the dust collector 22.

The exhaust gas G from which dust has been removed by the dust collector 22 has heat removed by passing through an air vent pipe 5 submerged in the cooling water CW stored in the heat removal tank 23, and the heat-removed exhaust gas G is sucked into the pumping device 24. Seawater, river water, groundwater, tap water, industrial water, etc. at the construction site can be used as the cooling water CW for the heat removal tank 23. The exhaust gas G sucked into the pumping device 24 is pumped by the pumping device 24 to the injection means 3 provided in the storage tank 2X.

As illustrated in Figures 1 to 3, in the storage tank 2X, exhaust gas G pumped by the pumping device 24 is injected by the injection means 3 into the alkaline solution A stored in the storage tank 2X. In this embodiment, the exhaust gas G pumped by the pumping device 24 flows into the branch pipe section 4b of the injection unit 4, and the exhaust gas G that flows into the branch pipe section 4b is ejected from each ejection nozzle 4a. As the exhaust gas G is ejected from each ejection nozzle 4a, a swirling flow is generated inside the storage tank 2X, causing numerous bubbles of exhaust gas G to rise in a spiral shape into the alkaline solution A.

As the bubbles of the exhaust gas G rise in a spiral shape in the alkaline solution A, the alkaline solution A comes into contact with the exhaust gas G, and a neutralization reaction occurs between the alkaline solution A and the carbon dioxide contained in the exhaust gas G. Specifically, when a calcium hydroxide solution is used as the alkaline solution A, the carbon dioxide (CO ₂ ) contained in the exhaust gas G and the water (H ₂ O) contained in the calcium hydroxide solution react chemically to generate carbon dioxide (H ₂ CO ₃ ) (CO ₂ +H ₂ O→H ₂ CO ₃ ). Furthermore, the generated carbon dioxide (H ₂ CO ₃ ) and calcium hydroxide (Ca(OH) ₂ ) contained in the calcium hydroxide solution react chemically to generate calcium carbonate (CaCO ₃ ) (Ca(OH) ₂ +H ₂ CO ₃ →CaCO ₃ +2H ₂ O).

The carbon dioxide contained in the exhaust gas G is reduced by a neutralization reaction between the carbon dioxide contained in the exhaust gas G and the alkaline solution A. The exhaust gas G, which has passed through the alkaline solution A and has had its carbon dioxide content reduced, is accumulated in the upper part of the inside of the storage tank 2X. As shown in FIG. 3, the exhaust gas G that has accumulated in the upper part of the inside of the storage tank 2X flows from time to time through the vent pipe 5 connected to the exhaust port 2c of the storage tank 2X and into the injection means 3 provided in the downstream storage tank 2Y.

By continuously supplying new alkaline solution A to the inlet 2a of the storage tank 2X through the solution supply line, the alkaline solution A, whose hydrogen ion concentration has decreased due to a neutralization reaction with the carbon dioxide contained in the exhaust gas G, rises inside the storage tank 2X together with the exhaust gas G. Then, the alkaline solution A that has risen to the top of the storage tank 2X passes through the connecting pipe 6 connected to the drainage port 2d and flows into the inside of the storage tank 2Y from the inlet 2a provided at the bottom of the downstream storage tank 2Y.

The precipitate S (calcium carbonate) produced by the neutralization reaction settles to the bottom of the storage tank 2X. The precipitate S that has accumulated at the bottom of the storage tank 2X is discharged outside the storage tank 2X and collected by appropriately opening the discharge valve 12 of the discharge pipe 11 connected to the storage tank 2X.

The alkaline solution A, whose hydrogen ion concentration has been reduced by the neutralization reaction in the upstream storage tank 2X, flows into the downstream storage tank 2Y. Then, the exhaust G discharged from the exhaust port 2c of the upstream storage tank 2X flows into the branch pipe section 4b of the injection unit 4 provided in the downstream storage tank 2Y, and the exhaust G that flows into the branch pipe section 4b is ejected from each ejection nozzle 4a. Then, as with the upstream storage tank 2X, the exhaust G is ejected from each ejection nozzle 4a, creating a swirling flow in which numerous bubbles of exhaust G rise in a spiral shape in the alkaline solution A inside the downstream storage tank 2Y.

As the bubbles of exhaust gas G rise in a spiral shape through alkaline solution A, they come into contact with the exhaust gas G, causing a neutralization reaction between the alkaline solution A and the carbon dioxide contained in the exhaust gas G. This neutralization reaction further reduces the carbon dioxide contained in the exhaust gas G, and the hydrogen ion concentration of alkaline solution A decreases further. The exhaust gas G, which has passed through alkaline solution A and has had its carbon dioxide content further reduced, ends up accumulating at the top of the inside of storage tank 2Y. The exhaust gas G accumulating at the top of the inside of storage tank 2Y flows from time to time through vent pipe 5 connected to exhaust port 2c of storage tank 2Y and into injection means 3 provided in storage tank 2Z further downstream.

As alkaline solution A continues to flow into the inlet 2a of the storage tank 2Y, the alkaline solution A, which neutralizes with the carbon dioxide contained in the exhaust gas G and further reduces its hydrogen ion concentration, rises inside the storage tank 2Y together with the exhaust gas G. The alkaline solution A that has risen to the top of the storage tank 2Y passes through the connecting pipe 6 connected to the drain outlet 2d and flows further downstream into the inside of the storage tank 2Z from the inlet 2a provided at the bottom of the storage tank 2Z.

The precipitate S produced by the neutralization reaction settles to the bottom of the storage tank 2Y. The precipitate S that has accumulated at the bottom of the storage tank 2Y is discharged outside the storage tank 2Y and collected by appropriately opening the discharge valve 12 of the discharge pipe 11 connected to the storage tank 2Y.

The alkaline solution A, whose hydrogen ion concentration has been further reduced by the neutralization reaction in the storage tank 2Y, flows into and is stored in the storage tank 2Z on the most downstream side. Then, the exhaust gas G discharged from the exhaust port 2c of the storage tank 2Y flows into the branch pipe section 4b of the injection unit 4 provided in the storage tank 2Z, and the exhaust gas G that flows into the branch pipe section 4b is sprayed from each spray nozzle 4a. Then, just like the storage tank 2Y, a swirling flow is generated inside the storage tank 2Z in which many bubbles of exhaust gas G rise in a spiral shape, and a neutralization reaction occurs between the alkaline solution A and the carbon dioxide contained in the exhaust gas G.

This neutralization reaction further reduces the carbon dioxide contained in the exhaust gas G, further lowering the hydrogen ion concentration of the alkaline solution A. The exhaust gas G, which has passed through the alkaline solution A and has had its carbon dioxide content further reduced, ends up accumulating at the top of the inside of the storage tank 2Z. The exhaust gas G that has accumulated at the top of the inside of the storage tank 2Z is then discharged from the exhaust port 2c of the storage tank 2Z as needed, and is discharged to the atmosphere via the exhaust pipe 7 as treated exhaust gas GP with reduced carbon dioxide content.

As alkaline solution A continues to flow into the inlet 2a of the storage tank 2Z, it neutralizes with the carbon dioxide contained in the exhaust gas G, further reducing the hydrogen ion concentration, and rises inside the storage tank 2Z together with the exhaust gas G. The alkaline solution A that has risen to the top of the storage tank 2Z then flows into the notch tank 17 through the connecting pipe 6 connected to the drainage port 2d. The alkaline solution A that has flowed into the notch tank 17 has any remaining sediments removed, and is discharged into public water areas, sewers, etc. as a neutralized treated solution AP.

The precipitate S produced by the neutralization reaction settles to the bottom of the storage tank 2Z. The precipitate S that has accumulated at the bottom of the storage tank 2Z is discharged outside the storage tank 2Z and collected by appropriately opening the discharge valve 12 of the discharge pipe 11 connected to the storage tank 2Z.

The measurement data measured by each of the hydrogen ion concentration meter 13, carbon dioxide concentration meter 14, and pressure meter 15 is sent to the management device 40 as needed and displayed on the monitor of the management device 40. The administrator of the reduction system 1 can monitor the operating status of the reduction system 1 by checking the measurement data displayed on the monitor of the management device 40.

The vertical axis on the left side of the graph shown in FIG. 6 indicates the hydrogen ion concentration (pH) of alkaline solution A, and the vertical axis on the right side indicates the cumulative absorption amount of carbon dioxide contained in exhaust gas G. M0 on the horizontal axis of the graph indicates the hydrogen ion concentration of alkaline solution A stored in raw water level adjustment tank 32. M1 indicates the hydrogen ion concentration of alkaline solution A stored in storage tank 2X and the cumulative absorption amount of carbon dioxide absorbed in storage tank 2X. M2 indicates the hydrogen ion concentration of alkaline solution A stored in storage tank 2Y and the cumulative absorption amount of carbon dioxide absorbed in storage tanks 2X and 2Y. M3 indicates the hydrogen ion concentration of alkaline solution A stored in storage tank 2Z and the cumulative absorption amount of carbon dioxide absorbed in storage tanks 2X to 2Z. In FIG. 6, the change in the hydrogen ion concentration of alkaline solution A is shown by a dashed line, and the change in the cumulative absorption amount of carbon dioxide is shown by a solid line.

As shown in the graph in Figure 6, a neutralization reaction occurs between alkaline solution A and the carbon dioxide contained in the exhaust gas G in each of the storage tanks 2X to 2Z, causing the cumulative absorption of carbon dioxide contained in the exhaust gas G to increase and the hydrogen ion concentration of alkaline solution A to decrease. In the upstream storage tank 2X, the hydrogen ion concentration of alkaline solution A is relatively high and the proportion of carbon dioxide contained in the exhaust gas is also relatively high, so the neutralization reaction between alkaline solution A and the carbon dioxide contained in the exhaust gas G proceeds relatively actively and the amount of carbon dioxide absorbed from the exhaust gas G is also relatively large. The hydrogen ion concentration of alkaline solution A also decreases relatively significantly.

In the downstream storage tanks 2Y and 2Z, the proportion of carbon dioxide contained in the exhaust gas G and the hydrogen ion concentration of the alkaline solution A gradually decrease, so the amount of carbon dioxide absorbed from the exhaust gas G gradually decreases compared to the upstream storage tank 2X, but by the time it is finally released as treated exhaust gas GP, most of the carbon dioxide contained in the exhaust gas G has been absorbed by the neutralization reaction. In addition, by the time the alkaline solution A is finally processed into treated solution AP, the neutralization process is complete and the hydrogen ion concentration becomes close to neutral.

In this way, according to the present invention, the exhaust gas G discharged from the internal combustion engine 20 is injected into the alkaline solution A stored in the storage tank 2, and the carbon dioxide contained in the exhaust gas G is neutralized inside the storage tank 2 with the alkaline solution A, thereby effectively reducing the amount of carbon dioxide contained in the exhaust gas G discharged from the internal combustion engine 20. This contributes to reducing the amount of carbon dioxide emissions, which is a greenhouse gas that causes global warming. Furthermore, the alkaline solution A used to reduce the amount of carbon dioxide contained in the exhaust gas G can have its hydrogen ion concentration reduced by neutralizing it with carbon dioxide. Therefore, the alkaline solution A can be easily disposed of after use.

Construction work generates a large amount of alkaline wastewater with a relatively high hydrogen ion concentration. For example, demolition work generates a lot of concrete waste, and the recycled crushed stone obtained by crushing this concrete waste is alkaline, just like concrete. Therefore, a large amount of alkaline wastewater is generated when producing neutralized recycled crushed stone. In addition, construction work generates a large amount of alkaline wastewater (so-called cleaning water or wash water) during cleaning operations at manufacturing plants and transportation equipment for cement, mortar, and concrete.

When disposing of alkaline wastewater generated during construction work, it is necessary to carry out a neutralization process to adjust the hydrogen ion concentration of the alkaline wastewater to a pH of 5.8 to 8.6 or less. Generally, neutralization is carried out by adding an acidic neutralizing agent to the alkaline wastewater. In this reduction system 1, alkaline wastewater generated during construction work is used as alkaline solution A, which makes it possible to reduce the carbon dioxide contained in the exhaust G of the internal combustion engine 20 and to neutralize the alkaline wastewater.

The carbon dioxide emissions from internal combustion engines 20, such as generators and diesel engines, account for a large proportion of the carbon dioxide emissions from construction work, and a large amount of alkaline wastewater is generated during construction work. Therefore, the reduction system 1 of the present invention, which can effectively utilize the alkaline wastewater generated during construction work to reduce the amount of carbon dioxide emissions from the exhaust G of internal combustion engines 20, is extremely beneficial to those skilled in the art who carry out construction work.

In particular, as in this embodiment, by using recycled crushed stone R obtained by crushing concrete waste to generate alkaline solution A and storing the generated alkaline solution A in the storage tank 2, the alkaline recycled crushed stone R can be effectively used to generate the alkaline solution A while producing neutralized recycled crushed stone RP. If the alkaline recycled crushed stone R is used as it is as a paving material, the hydrogen ion concentration of the surrounding soil may increase, so the applications are limited. In contrast, the neutralized recycled crushed stone RP can be used for a wider range of applications. Therefore, concrete waste can be used more effectively. Furthermore, by using the alkaline wastewater generated when neutralizing the recycled crushed stone R as the alkaline solution A, the carbon dioxide emissions due to the exhaust G of the internal combustion engine 20 can be reduced and the alkaline wastewater can be neutralized. Therefore, it is very beneficial for those skilled in the art who carry out construction work.

Even when alkaline wastewater generated in the cleaning of cement, mortar, and concrete manufacturing plants and transport equipment is used as alkaline solution A, the alkaline wastewater can be effectively used as alkaline solution A to reduce carbon dioxide emissions from the exhaust G of the internal combustion engine 20 while neutralizing the alkaline wastewater. When using alkaline wastewater generated in cleaning operations, it is preferable to mix and stir a coagulant into the alkaline wastewater in advance to perform a coagulation process to remove the coagulated solids, and to supply the alkaline wastewater after the coagulation process as alkaline solution A to the raw water level adjustment tank 32 or the storage tank 2.

Construction sites often have excess cement and lime, but this reduction system 1 can be configured to use such excess cement and lime to generate alkaline solution A. This reduction system 1 can also be configured to generate alkaline solution A using slag produced during metal smelting.

In this way, the reduction system 1 of the present invention not only reduces the amount of carbon dioxide emissions from the exhaust G of the internal combustion engine 20, but also functions as a system for neutralizing alkaline wastewater and alkaline waste materials generated during construction work. Therefore, this reduction system 1 is extremely useful for those skilled in the art who carry out construction work.

In this embodiment, multiple ejection nozzles 4a are disposed at the bottom inside the storage tank 2, and exhaust G is ejected from each of the ejection nozzles 4a to generate a swirling flow in which numerous bubbles of exhaust G rise in a spiral shape into the alkaline solution A. With this configuration, the travel distance and time required for the bubbles of exhaust G to finish passing through the alkaline solution A can be secured longer than when the bubbles of exhaust G are caused to rise straight up in the alkaline solution A. Therefore, the carbon dioxide contained in the exhaust G can be more effectively neutralized in the storage tank 2 with the alkaline solution A.

In addition, the longer the vertical distance between the position where the exhaust gas G is ejected by the injection means 3 and the liquid surface of the alkaline solution A stored in the storage tank 2, the longer the travel distance and time required for the bubbles of the exhaust gas G to pass through the alkaline solution A, but on the other hand, the higher the pumping pressure required to inject the exhaust gas G into the alkaline solution A. The higher the pumping pressure of the exhaust gas G, the more power the pumping device 24 consumes, and the more carbon dioxide is emitted by the generator that supplies power to the pumping device 24.

In this respect, by configuring the alkaline solution A to generate a swirling flow in which many exhaust G bubbles rise in a spiral shape, as in this embodiment, it becomes possible to relatively shorten the vertical distance between the position at which the exhaust G is ejected by the injection means 3 and the liquid surface of the alkaline solution A, while ensuring a long travel distance and time required for the exhaust G bubbles to finish passing through the alkaline solution A. This makes it possible to set the pumping pressure of the exhaust G by the pumping device 24 relatively low, which is also advantageous for reducing the power consumption by the pumping device 24. This is therefore more advantageous for reducing carbon dioxide emissions.

As in this embodiment, when multiple storage tanks 2 (2X to 2Z) are connected in series via a vent pipe 5 through which exhaust G flows and a connecting pipe 6 through which alkaline solution A flows, the exhaust G is passed through the alkaline solution A stored in the multiple storage tanks 2, and the carbon dioxide contained in the exhaust G and the alkaline solution A can be neutralized more effectively. This is therefore more advantageous for reducing the carbon dioxide contained in the exhaust G discharged from the internal combustion engine 20. In addition, by flowing the alkaline solution A together with the exhaust G from the upstream storage tank 2 to the downstream storage tank 2, the alkaline solution A can be utilized more effectively. Furthermore, by neutralizing the alkaline solution A with the carbon dioxide contained in the exhaust G in each storage tank 2, it is also advantageous to advance the neutralization process of the alkaline solution A.

As in this embodiment, by configuring the raw water level adjustment tank 32 and the alkaline solution A stored in each storage tank 2 (2X to 2Z) to be at the same height, it is possible to naturally flow the alkaline solution A from the raw water level adjustment tank 32 to the most downstream storage tank 2Z by utilizing the siphon principle, without providing a power source such as a pump to the connecting pipe 6 connecting the raw water level adjustment tank 32 and the storage tank 2, or to the connecting pipe 6 connecting the storage tanks 2 to each other. This is therefore even more advantageous in reducing carbon dioxide emissions. Also, despite the simple configuration, it is possible to maintain a constant amount of alkaline solution A stored in each storage tank 2X to 2Z.

The reduction system 1 of the present invention can also be configured as shown in FIG. 7.

In this embodiment, separate exhaust pipes 7 are connected to the middle of the vent pipe 5 connecting the storage tank 2X and the storage tank 2Y, and to the middle of the vent pipe 5 connecting the storage tank 2Y and the storage tank 2Z. Each exhaust pipe 7 is provided with an openable and closable exhaust valve 8. Separate drain pipes 9 are connected to the middle of the connecting pipe 6 connecting the storage tank 2X and the storage tank 2Y, and to the middle of the connecting pipe 6 connecting the storage tank 2Y and the storage tank 2Z. Each drain pipe 9 is provided with an openable and closable drain valve 10. Furthermore, a control device 16 is provided for each of the storage tanks 2X and 2Y. The control device 16 is, for example, composed of a computer.

The hydrogen ion concentration meter 13 and carbon dioxide concentration meter 14 installed in the same storage tank 2 are each communicatively connected to a control device 16 installed in the same storage tank 2. The measurement data measured by the hydrogen ion concentration meter 13 and the carbon dioxide concentration meter 14 are input to the control device 16 as needed. In this embodiment, the opening and closing operations of the exhaust valves 8 and the drainage valves 10 are automatically controlled by the control devices 16 installed in the storage tanks 2 upstream of each other. The other configurations are the same as those of the reduction system 1 in the embodiment illustrated in Figures 1 to 5.

In this embodiment, the hydrogen ion concentration of the alkaline solution A stored in each storage tank 2 is measured by a hydrogen ion concentration meter 13, and alkaline solution A whose hydrogen ion concentration is below a preset threshold is not allowed to flow into the downstream storage tank 2 and is treated as treated solution AP. The threshold value for the hydrogen ion concentration of the alkaline solution A described above is set to, for example, about pH 7.0 to pH 8.6.

Specifically, for example, when the hydrogen ion concentration of alkaline solution A measured by hydrogen ion concentration meter 13 provided in storage tank 2X is higher than a preset threshold value, control device 16 provided in storage tank 2X controls drain valve 10 provided between storage tank 2X and downstream storage tank 2Y to be in a closed state. Then, alkaline solution A that flows from drain port 2d of storage tank 2X into connecting pipe 6 flows directly through connecting pipe 6 into downstream storage tank 2Y.

On the other hand, when the hydrogen ion concentration of alkaline solution A measured by the hydrogen ion concentration meter 13 provided in the storage tank 2X is equal to or lower than a preset threshold value, the control device 16 provided in the storage tank 2X controls the drain valve 10 provided between the storage tank 2X and the downstream storage tank 2Y to be open. Then, the alkaline solution A that flows into the connecting pipe 6 from the drain outlet 2d of the storage tank 2X flows into the drain pipe 9 halfway through the connecting pipe 6, and the neutralized alkaline solution A that flows into the drain pipe 9 and has a hydrogen ion concentration equal to or lower than the threshold value is discharged into the sewer as treated solution AP.

When the drain valve 10 is opened and alkaline solution A is discharged from the drain pipe 9, the flow rate of the alkaline solution A stored in the storage tank 2 downstream of the drain pipe 9 temporarily decreases, but the alkaline solution A continues to be supplied from the solution generation tank 30, so that the liquid level of the alkaline solution A stored in the raw water level adjustment tank 32 and each of the storage tanks 2X to 2Z remains consistent.

With this configuration, alkaline solution A, whose hydrogen ion concentration falls below a preset threshold and whose carbon dioxide absorption rate has decreased, does not flow into the downstream storage tank 2 but is treated as treated solution AP. Therefore, even without finely adjusting the hydrogen ion concentration of alkaline solution A generated in the solution generation tank 30, it is possible to reduce the fluctuation in the hydrogen ion concentration of alkaline solution A stored in each storage tank 2, and it is possible to reduce the fluctuation in the amount of carbon dioxide absorbed in each storage tank 2. Therefore, while the control is simple, it is more advantageous for stably reducing the carbon dioxide contained in the exhaust gas G.

In addition, in this embodiment, the carbon dioxide concentration of the exhaust G after passing through the alkaline solution A in each storage tank 2 is measured by a carbon dioxide concentration meter 14, and exhaust G whose carbon dioxide concentration is below a preset reference value is not injected into the alkaline solution A stored in the downstream storage tank 2, but is treated as treated exhaust GP. The reference value for the carbon dioxide concentration of the exhaust G mentioned above is set to, for example, about 5000 ppm.

Specifically, for example, when the carbon dioxide concentration of the exhaust gas G measured by the carbon dioxide concentration measuring device 14 provided in the storage tank 2X is higher than a preset reference value, the control device 16 provided in the storage tank 2X controls the exhaust valve 8 provided between the storage tank 2X and the downstream storage tank 2Y to be in a closed state. Then, the exhaust gas G that flows into the vent pipe 5 from the exhaust port 2c of the storage tank 2X flows directly through the vent pipe 5 into the injection means 3 provided in the downstream storage tank 2Y.

On the other hand, when the carbon dioxide concentration of the exhaust G measured by the carbon dioxide concentration measuring device 14 installed in the storage tank 2X is below a preset reference value, the control device 16 installed in that storage tank 2X controls the exhaust valve 8 installed between that storage tank 2X and the downstream storage tank 2Y to be in an open state. Then, the exhaust G that flows into the ventilation pipe 5 from the exhaust port 2c of the storage tank 2X flows into the exhaust pipe 7 halfway through the ventilation pipe 5, and the exhaust G that flows into the exhaust pipe 7 and has a carbon dioxide concentration below the reference value is released into the atmosphere as treated exhaust GP.

With this configuration, exhaust gas G whose carbon dioxide concentration falls below a preset reference value and which hardly undergoes a neutralization reaction with alkaline solution A is not injected into the alkaline solution A stored in the downstream storage tank 2, but is treated as treated exhaust gas GP. This makes it possible to reduce the fluctuation in the carbon dioxide concentration of the exhaust gas G injected into the alkaline solution A stored in each storage tank 2. This also makes it possible to reduce the fluctuation in the hydrogen ion concentration of the alkaline solution A stored in each storage tank 2. Therefore, while the control is simple, it is more advantageous for stably reducing the carbon dioxide contained in the exhaust gas G and stably neutralizing the alkaline solution A.

The reduction system 1 of the present invention can also be configured as shown in FIG. 8.

In this embodiment, a protrusion 2e is provided on the inner surface of the storage tank 2, and the protrusion 2e is used to slow down the rising speed of the exhaust G bubbles rising through the alkaline solution A. In other words, by providing the protrusion 2e on the inner surface of the storage tank 2, which acts as an obstacle when the exhaust G bubbles rise, the time that the exhaust G bubbles remain in the alkaline solution A is increased. In this embodiment, a protrusion 2e extending in a spiral shape is provided on the inner surface of the storage tank 2, and the protrusion 2e is used to guide the swirling flow of the many exhaust G bubbles that rise in a spiral shape, generated by the injection means 3.

The rest of the configuration is the same as the reduction system 1 of the embodiment illustrated in Figures 1 to 5. Note that the protrusion 2e is not limited to a spiral structure as in this embodiment, and can have various other configurations as long as the structure can slow down the rising speed of the exhaust gas G bubbles rising through the alkaline solution A.

In this way, by providing the protrusions 2e on the inner surface of the storage tank 2, the time that the bubbles of exhaust gas G injected into the alkaline solution A from the injection means 3 are in contact with the alkaline solution A can be lengthened, so that the carbon dioxide contained in the exhaust gas G and the alkaline solution A can be neutralized more effectively in the storage tank 2. Therefore, despite its simple configuration, it is even more advantageous for reducing the carbon dioxide contained in the exhaust gas G.

As in this embodiment, when the protrusion 2e is structured to guide the swirling flow of the many exhaust G bubbles generated by the injection means 3 rising in a spiral shape, the protrusion 2e makes the swirling flow more stable, which is more advantageous in ensuring a long distance and required time for the exhaust G bubbles to travel in the alkaline solution A. Therefore, the carbon dioxide contained in the exhaust G and the alkaline solution A can be more effectively neutralized in the storage tank 2, which is even more advantageous in reducing the carbon dioxide contained in the exhaust G.

The reduction system 1 of the present invention can also be configured as shown in FIG. 9.

In this embodiment, the configuration of the injection means 3 is different. The other configurations are the same as those of the reduction system 1 of the embodiment illustrated in Figures 1 to 5. In this embodiment, the injection means 3 is composed of multiple ejection nozzles 4a inserted laterally into the side wall of the storage tank 2. Four injection ports 2b are provided at equal intervals in the circumferential direction on the side wall of the storage tank 2, and an ejection nozzle 4a is inserted into each injection port 2b. Exhaust gas G is ejected laterally from each ejection nozzle 4a along the inner surface of the storage tank 2, generating a swirling flow inside the storage tank 2 in which numerous bubbles of exhaust gas G rise in a spiral shape into the alkaline solution A.

When using the injection means 3 configured as in this embodiment, it is possible to achieve substantially the same effects as when using the injection means 3 of the embodiment illustrated in Figures 1 to 5. In this way, the configuration of the injection means 3 that generates a swirling flow in which many exhaust G bubbles rise in a spiral shape in the alkaline solution A is not limited to the configuration of the injection means 3 of the embodiment illustrated in Figures 1 to 5, and various other configurations are possible. For example, the injection means 3 can be configured to generate many exhaust G bubbles in the alkaline solution A by providing a porous filter with many through holes at the bottom inside the storage tank 2 and passing the exhaust G sprayed from the spray nozzle 4a through the porous filter. By using a porous filter, many exhaust G bubbles can be efficiently formed.

The reduction system 1 of the present invention is not limited to the embodiment exemplified above, and can have various other configurations. The manifold 21, dust collector 22, and heat removal tank 23 that constitute the exhaust supply line are not essential components, and can be provided as needed. For example, in the case of a reduction system 1 that reduces carbon dioxide in the exhaust G of one internal combustion engine 20, it is not necessary to provide the manifold 21. For example, the exhaust port of the internal combustion engine 20 and the pumping device 24 can be directly connected by the vent pipe 5. Also, for example, a system for purifying the exhaust G of the internal combustion engine 20 (such as a urea SCR system) can be interposed between the exhaust port of the internal combustion engine 20 and the injection means 3.

The solution generation tank 30, the agitator 31, and the raw water level adjustment tank 32 that constitute the solution supply line are not essential components, and can be provided as necessary. The solution supply line may be configured in various ways as long as it can supply the alkaline solution A to the storage tank 2, in addition to the embodiment exemplified above. For example, the alkaline wastewater generated during construction work or the alkaline solution A that has been generated in advance can be directly flowed into the storage tank 2 (2X). In addition, although the above example shows a case in which three storage tanks 2X to 2Z are connected in series, the number of storage tanks 2 to be connected is not particularly limited. For example, it can be configured to connect two storage tanks 2, or to connect four or more storage tanks 2. The reduction system 1 of the present invention can also be configured with one storage tank 2.

1 Carbon dioxide emission reduction system 2, 2X to 2Z Storage tank 2a Inlet 2b Inlet 2c Exhaust port 2d Drain port 2e Projection 3 Injection means 4 Injection unit 4a Spray nozzle 4b Branch pipe section 5 Vent pipe 6 Connecting pipe 7 Exhaust pipe 8 Exhaust valve 9 Drain pipe 10 Drain valve 11 Drain pipe 12 Drain valve 13 Hydrogen ion concentration meter 14 Carbon dioxide concentration meter 15 Pressure gauge 16 Control device 17 Notch tank 20 Internal combustion engine 21 Manifold 22 Dust collector 23 Heat removal tank 24 Pressure feed device 30 Solution generation tank 31 Agitator 32 Raw water level adjustment tank 40 Management device G Exhaust GP Treated exhaust A Alkaline solution AP Treated solution CW Cooling water R Recycled crushed stone RP Treated recycled crushed stone S Sediment W Water

Claims (12)

A method for reducing carbon dioxide emissions, comprising: injecting exhaust gas discharged from an internal combustion engine into an alkaline solution stored in a storage tank; bringing the alkaline solution into contact with the exhaust gas inside the storage tank; causing a neutralization reaction between the alkaline solution and the carbon dioxide contained in the exhaust gas, thereby reducing the amount of carbon dioxide contained in the exhaust gas; and discharging the exhaust gas with reduced carbon dioxide from an exhaust port of the storage tank. The carbon dioxide emission reduction method according to claim 1, in which a plurality of ejection nozzles to which the exhaust gas is supplied are arranged at the bottom inside the storage tank, and the exhaust gas is ejected from each of the ejection nozzles, thereby generating a swirling flow in which a large number of bubbles of the exhaust gas rise in a spiral shape in the alkaline solution inside the storage tank. The method for reducing carbon dioxide emissions according to claim 1 or 2, in which a protrusion provided on the inner surface of the storage tank slows down the rate at which the exhaust gas bubbles rise through the alkaline solution. The method for reducing carbon dioxide emissions according to claims 1 to 3, in which the alkaline solution is generated using recycled crushed stone obtained by crushing waste concrete, and the generated alkaline solution is stored in the storage tank. A plurality of the storage tanks are connected in series via a vent pipe through which the exhaust gas flows and a connecting pipe through which the alkaline solution flows,
The method for reducing carbon dioxide emissions according to claims 1 to 4, wherein the alkaline solution stored in the upstream storage tank, whose hydrogen ion concentration has been reduced by a neutralization reaction with the carbon dioxide contained in the exhaust air in the upstream storage tank, is discharged from a drain port of the upstream storage tank, and the alkaline solution discharged from the drain port flows into the downstream storage tank via the connecting pipe and is stored therein, and the exhaust air discharged from the exhaust port of the upstream storage tank is injected into the alkaline solution stored in the downstream storage tank via the vent pipe, so that the alkaline solution and the exhaust air come into contact with each other inside the downstream storage tank, thereby causing a neutralization reaction between the alkaline solution and the carbon dioxide contained in the exhaust air, thereby further reducing the carbon dioxide contained in the exhaust air and further reducing the hydrogen ion concentration of the alkaline solution, and the exhaust air with the further reduced carbon dioxide is discharged from the exhaust port of the downstream storage tank, and the alkaline solution with the further reduced hydrogen ion concentration is discharged from the drain port of the downstream storage tank. The carbon dioxide emission reduction method according to claim 5, wherein the carbon dioxide concentration of the exhaust gas after passing through the alkaline solution in each of the storage tanks is measured, and the exhaust gas whose carbon dioxide concentration is equal to or lower than a preset reference value is treated as treated exhaust gas without being injected into the alkaline solution stored in the downstream storage tank. The method for reducing carbon dioxide emissions according to claim 5 or 6, wherein the hydrogen ion concentration of the alkaline solution stored in each of the storage tanks is measured, and the alkaline solution whose hydrogen ion concentration is equal to or lower than a preset threshold value is not allowed to flow into the downstream storage tank, but is treated as a treated solution. The method for reducing carbon dioxide emissions according to claims 1 to 7, in which the exhaust gas discharged from the internal combustion engine is subjected to heat removal in a heat removal tank, and the exhaust gas from which heat has been removed is injected into the alkaline solution stored in the storage tank. The method for reducing carbon dioxide emissions according to claims 1 to 8, in which dust contained in the exhaust gas discharged from the internal combustion engine is removed by a dust collector, and the exhaust gas from which the dust has been removed is injected into the alkaline solution stored in the storage tank. The carbon dioxide emission reduction method according to claims 1 to 9, in which a raw water level adjustment tank for temporarily storing the generated alkaline solution is connected to the storage tank with a connecting pipe, the alkaline solution stored in the raw water level adjustment tank is allowed to flow into the storage tank, and the height of the liquid level position of the alkaline solution stored in the raw water level adjustment tank and the height of the liquid level position of the alkaline solution stored in the storage tank are made to match. The method for reducing carbon dioxide emissions according to claim 10, wherein the flow rate of the alkaline solution supplied to the raw water level adjustment tank is adjusted so as to maintain the liquid level of the alkaline solution stored in the raw water level adjustment tank at a preset height. a storage tank in which an alkaline solution is stored; and an injection means for injecting exhaust gas discharged from an internal combustion engine into the alkaline solution stored in the storage tank;
a carbon dioxide emission reduction system configured such that the alkaline solution comes into contact with the exhaust gas injected by the injection means inside the storage tank, and a neutralization reaction occurs between the alkaline solution and the carbon dioxide contained in the exhaust gas, thereby reducing the carbon dioxide contained in the exhaust gas, and the exhaust gas with the reduced carbon dioxide content is discharged from an exhaust port of the storage tank.

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