Method for fixing carbon dioxide in management type disposal site

Abstract

To provide a method for fixing carbon dioxide in a management type disposal site capable of efficiently reducing carbon dioxide in the atmosphere toward carbon neutral as much as possible according to reclamation work when coal ash from a coal thermal power plant is reclaimed.SOLUTION: Wet ash or coal ash slurry is reclaimed in a land portion of a management type disposal site, and a surface in contact with the atmosphere is created in the reclaimed ground, and curing is performed, whereby carbon dioxide can be stored and fixed in the reclaimed ground of coal ash. As a result, carbon dioxide in the atmosphere can be efficiently reduced as much as possible toward carbon neutral according to reclamation work.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for fixing carbon dioxide in a controlled landfill site, in which carbon dioxide is stored and fixed in a coal ash landfill bed formed by filling the controlled landfill site. [Background technology]

[0002] As a countermeasure to global warming, which has long been a concern, it is necessary to reduce atmospheric carbon dioxide in order to achieve carbon neutrality. Meanwhile, coal ash emitted from coal-fired power plants is landfilled in controlled landfill sites on land or offshore. The following three methods are typically used to landfill coal ash in controlled landfill sites on land or offshore. Method 1 involves transporting wet ash using a dump truck or conveyor belt, and then using a shovel or backhoe to landfill the site with a single push. A distinctive feature of Method 1 is that, in locations where the landfill ground is not weak, no equipment such as pumps is required other than heavy machinery, making it the most inexpensive method of landfilling.

[0003] The second method involves mixing the coal ash with a low-concentration coal ash slurry (water content of 100% or more), transporting the coal ash slurry through a pressure pipe using a pressure pump, and discharging it from the end of the pressure pipe for landfill. A feature of this second method is that, compared to high-concentration coal ash slurry, the load during pumping is small, making it possible to pump the coal ash, eliminating the need for a high-pressure pump and enabling long-distance pumping. The third method involves mixing the coal ash with a high-concentration coal ash slurry (water content of 60% or less), transporting it through a pressure pipe using a pressure pump, and discharging it from the end of the pressure pipe for landfill. A feature of this third method is that, due to the high proportion of coal ash in the coal ash slurry and the high slurry density, a high-pressure pump is required. However, due to the high density of the landfill ground, a large amount of coal ash can be disposed of in a given volume. For details of the second and third methods, see Patent Document 1.

[0004] On the other hand, coal ash contains calcium, which is derived from coal and is converted into calcium oxide (CaO) by combustion, although the amount is small compared to cement or incineration ash. The calcium oxide contained in coal ash reacts with water on the particle surface or inside the porous coal ash particles to form calcium ions (CaO). 2+ Some of it is gradually dissolved in water (CaO + H2O → Ca 2+ +2OH - ) Here, this calcium ion Ca 2+ is the carbonate ion CO3 produced when carbon dioxide CO2 dissolves in water. 2- and calcium carbonate CaCO3 is produced (CO2 + H2O → 2H + +CO3 2- , and Ca 2+ +CO3 2- →CaCO3). This calcium carbonate crystallizes on the surface or inside of coal ash particles, or in water, and is stored in the coal ash landfill. In other words, coal ash can fix carbon dioxide. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-154127 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when coal ash discharged from coal-fired power plants is soaked in water, i.e., wet ash or coal ash slurry, and landfilled in a controlled disposal site using the first to third methods described above, no technology has been proposed to efficiently fix carbon dioxide to the coal ash, i.e., to efficiently store and fix carbon dioxide within the coal ash landfill, in order to reduce carbon dioxide in the atmosphere toward carbon neutrality.

[0007] The present invention has been made in view of the above-mentioned problems, and aims to provide a method for fixing carbon dioxide at a controlled disposal site that can efficiently reduce as much carbon dioxide in the atmosphere as possible during landfill work, with the aim of achieving carbon neutrality, when coal ash from coal-fired power plants is landfilled. [Means for solving the problem]

[0008] As a means for solving the above problems, the invention described in claim 1 is characterized in that wet ash or coal ash slurry is buried on land in a controlled disposal site, and a surface of the landfill that comes into contact with the atmosphere is created and cured, thereby storing and fixing carbon dioxide within the coal ash landfill. In the invention of claim 1, wet ash or coal ash slurry, including coal ash from coal-fired power plants, is buried on land in a controlled landfill site, creating a surface in contact with the atmosphere and allowing it to cure for a predetermined period. As a result, atmospheric carbon dioxide dissolves in the interstitial water within the landfill, causing calcium carbonate derived from the calcium contained in the coal ash to adhere to the surface or interior of the coal ash particles, or to crystallize in water and be stored within the coal ash landfill. In other words, atmospheric carbon dioxide can be stored and fixed as calcium carbonate within the coal ash landfill. This allows for efficient reduction of atmospheric carbon dioxide as much as possible toward carbon neutrality.

[0009] The invention described in claim 2 is characterized in that in the invention described in claim 1, the wet ash or coal ash slurry is mixed with cement and then buried. In the invention of claim 2, calcium oxide contained in cement contributes to increasing the amount of fixed carbon dioxide. Note that cement is mixed for reasons such as ensuring the strength of reclaimed land. Therefore, carbon dioxide is emitted during cement production, and this proposal is positioned to offset a portion of those emissions.

[0010] The invention described in claim 3 is characterized in that in the invention described in claim 1, excess water generated when wet ash or coal ash slurry is buried on land in a controlled landfill is stored in one section and carbon dioxide is fixed to the excess water. In the invention of claim 3, weakly alkaline surplus water is obtained from the coal ash slurry within the area flowing down from the discharge point on the landfill (land portion) of the controlled disposal site. The amount of surplus water is particularly large when the low-concentration slurry method (the second method) described above, which has a high water content, is used for landfilling. By storing this alkaline surplus water in a section, such as a reservoir, and using it as a dedicated dissolution pool, the dissolution of atmospheric carbon dioxide into the surplus water can be promoted. This makes it possible to increase the amount of carbon dioxide fixed throughout the controlled disposal site, including the amount fixed in the surplus water. Furthermore, when this surplus water is discharged, neutralization is promoted by the dissolution of atmospheric carbon dioxide, which has the effect of making it easier to meet discharge standards and reducing water treatment costs.

[0011] The invention described in claim 4 is characterized in that, in the invention of claim 1, the wet ash or coal ash slurry is buried on the land part of the managed disposal site by raising the pile with a plurality of ground layers, and carbon dioxide is stored and fixed within the coal ash landfill ground. In the invention of claim 4, when wet ash or coal ash slurry is piled up and filled with multiple thin ground layers on the land part of a controlled disposal site, a large contact area with carbon dioxide can be created in each ground layer, and as much carbon dioxide as possible can be efficiently stored and fixed in the coal ash landfill.

[0012] The invention described in claim 5 is characterized in that, in the invention described in claim 1, the reclaimed land is tilled. It is assumed that atmospheric carbon dioxide is mainly fixed in the top layer of the reclaimed land from a few centimeters to about 10 cm. Therefore, in the invention of claim 5, by tilling the surface layer of the reclaimed land, it is possible to move coal ash particles (coal ash slurry) containing water that have not come into contact with carbon dioxide to the surface layer, thereby increasing the amount of fixed carbon dioxide.

[0013] The invention described in claim 6 is characterized in that, in the invention described in claim 1, water is sprinkled on the reclaimed land. In addition, when the amount of sunlight is high and the humidity is low in a controlled disposal site, the drying of the surface of the landfill is accelerated. Since an appropriate amount of moisture is required for the reaction to calcium carbonate, the invention of claim 6 can increase the amount of fixed carbon dioxide by appropriately sprinkling water on the landfill during times when such environmental conditions occur.

[0014] The invention described in claim 7 is characterized in that when coal ash slurry is buried in a controlled disposal site through a pipeline using a pressure pump, carbon dioxide is supplied into the pipeline and the carbon dioxide is stored and fixed within the coal ash landfill. In the invention of claim 7, carbon dioxide is actively supplied into a pipeline through which coal ash slurry is flowing by a pressure pump, and carbon dioxide is dissolved in the coal ash slurry during pressure transport, thereby fixing the carbon dioxide as calcium carbonate in the coal ash slurry during the pressure transport process, and as a result, carbon dioxide can be stored and fixed in the coal ash landfill.

[0015] The invention described in claim 8 is characterized in that when coal ash slurry is buried in a controlled landfill site, carbon dioxide is supplied to a mixer section that produces the coal ash slurry, and the carbon dioxide is stored and fixed within the coal ash landfill site. In the invention of claim 8, carbon dioxide is actively supplied to the mixer section that generates the coal ash slurry, and the carbon dioxide is dissolved in the coal ash slurry being generated, thereby fixing the carbon dioxide in the coal ash slurry as calcium carbonate, and as a result, the carbon dioxide can be stored and fixed in the coal ash landfill.

[0016] The invention described in claim 9 is characterized in that, in the invention of claim 7 or 8, the carbon dioxide used is that emitted from a coal-fired power plant. In the invention of claim 9, a part of the exhaust gas from a coal-fired power plant is extracted and carbon dioxide with a relatively high concentration is supplied, thereby making it possible to fix carbon dioxide at a high reaction rate.

[0017] The invention described in claim 10 is characterized in that in any one of claims 1, 7 and 8, water other than seawater is used as the mixing water when producing the coal ash slurry. In the invention of claim 10, it is preferable to use water other than seawater as the mixing water, for example, water (alkaline water) stored in a controlled disposal site adjacent to a coal ash landfill (on land) where waste has already been buried in the underwater area. In short, the alkaline stored water already contains a large amount of carbonate ions CO3 2- is dissolved in the coal ash slurry, and calcium ions Ca are supplied when the coal ash slurry is mixed. 2+ This reacts with the coal ash slurry to produce calcium carbonate. Therefore, after mixing the coal ash slurry, a large amount of carbon dioxide can be fixed in addition to the carbon dioxide supplied from the atmosphere and exhaust gas. In other words, the amount of carbon dioxide fixed in the coal ash slurry can be further increased. [Effects of the Invention]

[0018] The method for fixing carbon dioxide at a controlled disposal site according to the present invention makes it possible to efficiently reduce as much carbon dioxide in the atmosphere as possible during landfill work, with the aim of achieving carbon neutrality, when coal ash from a coal-fired power plant is landfilled. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram of a controlled disposal site in which this embodiment is adopted. [Figure 2]FIG. 2 is a cross-sectional view showing a state in which coal ash from a coal-fired power plant is raised and buried on land in this embodiment. [Figure 3] FIG. 3 is a diagram showing how coal ash slurry from the nozzle (tip) of the pressure pipe is buried on land in a controlled disposal site in this embodiment. [Figure 4] FIG. 4 is a diagram showing how the coal ash slurry from the nozzle of the pressure pipe is buried and spread on land in a controlled landfill site in this embodiment. [Figure 5] FIG. 5 is a diagram showing how coal ash slurry from the nozzle of the pressure pipe is buried as a plurality of landfill layers on the land of a controlled landfill site in this embodiment. [Figure 6] FIG. 6 is a diagram showing how the surface layer of reclaimed land is being tilled by an excavation and stirring device in this embodiment. [Figure 7] FIG. 7 is a diagram showing the state in which water is being sprinkled onto the surface of reclaimed land by a sprinkler system in this embodiment. [Figure 8] FIG. 8 is a diagram showing an embodiment in which part of the exhaust gas is supplied to a pressure pipe from a smoke exhaust system (chimney) of a coal-fired power plant in this embodiment. [Figure 9] FIG. 9 is a diagram showing an embodiment in which part of the flue gas is supplied to the mixer unit from the flue gas exhaust system of a coal-fired power plant. [Figure 10] FIG. 10 is a diagram showing how carbon dioxide is fixed in surplus water stored within an area surrounded by a dam in a controlled disposal site in this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. The amount of coal ash emitted from coal-fired power plants 20 exceeds 10 million tons per year nationwide. Most of this coal ash is effectively used as a cement raw material or civil engineering material, but some of it is disposed of by landfill in controlled disposal site 1. In this embodiment, referring to FIG. 1 , coal ash from coal-fired power plant 20 is raised and buried in controlled marine disposal site 1 as controlled disposal site 1, on top of land portion 1A where waste has already been buried. Adjacent to this land portion 1A, there is a partitioned disposal site 1B where waste has already been buried underwater and where the surface of the retained water remains.

[0021] 1 and 2, when coal ash is piled up and buried on the land portion 1A of the controlled disposal site 1, the land portion 1A is surrounded by dams 4, 4, and wet ash or coal ash slurry is poured inside the dams 4, 4 to fill the land. When the height reaches the height of the dams 4, 4, the top of the landfill is again surrounded by dams 4, 4, and wet ash or coal ash slurry is poured inside the dams 4, 4 to fill the land. This process is repeated multiple times (for example, about six times) to pile up the coal ash from the coal-fired power plant 20 and fill it on the land portion 1A of the controlled disposal site 1. For example, the height of the dams 4 is about 5 m.

[0022] Referring to FIG. 3, in this embodiment, coal ash discharged from a coal-fired power plant 20 is mixed with mixing water (water supplied from a water supply facility 7 shown in FIGS. 8 and 9) in a mixer unit 6 to form coal ash slurry, which is then buried on the land portion 1A of the controlled landfill 1 (the aerial portion of the area surrounded by dams 4, 4). A low-concentration coal ash slurry with a water content of 100% or more is produced in the mixer unit 6. The coal ash slurry from the mixer unit 6 is transferred by a pressure pump 8 through a pressure pipe 9 (pipeline) and buried in the land portion 1A of the controlled landfill 1. This method requires less pumping load than a high-concentration coal ash slurry (water content of 60% or less), eliminating the need for a high-pressure pump and enabling long-distance pressure transportation. The nozzle (tip) of the pressure pipe 9 is installed facing the inside of the dam 4. The tip of the pressure pipe 9 can move along the direction in which the dam 4 extends, and can also move inside the dam 4 in a direction away from the dam 4. Note that cement may be added to the coal ash slurry in the mixer section 6 before landfilling. This increases the strength of the landfill, and the calcium oxide contained in the cement contributes to increasing the amount of carbon dioxide fixed.

[0023] Referring to FIG. 4, when the coal ash slurry is discharged from the tip of the pressure pipe 9 into the inside of the dam 4, the coal ash slurry spreads inside the dam 4 so as to assume a generally fan-shaped configuration in plan view. The slope gradient of the resulting volumetric ground is approximately 1:10 to 1:30. That is, by filling the coal ash slurry on the land portion 1A, a surface of the reclaimed ground that comes into contact with the atmosphere can be created. The reclaimed ground is then cured for a predetermined period in this state. The height (thickness) of this reclaimed ground (ground layer) is approximately 50 cm to 100 cm. The curing period may be, for example, one day, three days, or one week. In short, the curing period is, for example, within 10 days.

[0024] As a result, as mentioned above, calcium oxide contained in coal ash reacts with water on the particle surface or inside the porous coal ash particles to form calcium ions, Ca 2+ Some of it is gradually dissolved in water (CaO + H2O → Ca 2+ +2OH -) Here, this calcium ion Ca 2+ is the carbonate ion CO3 produced when carbon dioxide CO2 dissolves in water. 2- and calcium carbonate CaCO3 is produced (CO2 + H2O → 2H + +CO3 2- , and Ca 2+ +CO3 2- →CaCO3). In other words, atmospheric carbon dioxide is dissolved in the interstitial water within the landfill, and calcium carbonate derived from the calcium contained in the coal ash is fixed on the surface or inside of the coal ash particles, or crystallized in water and stored within the coal ash landfill; in other words, atmospheric carbon dioxide can be stored and fixed as calcium carbonate within the coal ash landfill.

[0025] Then, referring to FIG. 5, after a predetermined curing period has elapsed, the nozzle of pressure pipe 9 is moved in the intended direction, and coal ash slurry is again discharged from the nozzle, thereby creating a surface in contact with the atmosphere on the landfill site, and the landfill is then cured for a predetermined period. This landfill operation is repeated, and coal ash from coal-fired power plant 20 is successively buried as coal ash slurry in the area surrounded by the dams 4, 4 of managed landfill site 1. As a result, referring to FIGS. 2 and 5, multiple thin ground layers are formed along the vertical direction of the area surrounded by the dams 4, 4 as the landfill site. Furthermore, if the amount of landfill material to be buried per day is large, it is possible to increase the surface area in contact with the atmosphere while achieving a predetermined curing period by branching a single pressure pipe 9 to provide multiple nozzles (discharge portions). For example, by performing landfill at multiple discharge points on different days, the area in contact with the atmosphere can be increased.

[0026] The surface of the ground layer of this reclaimed land is soft due to the accumulation of low-concentration coal ash slurry. It is assumed that atmospheric carbon dioxide is mainly stored and fixed in the ground layer at a height of several centimeters to about 10 cm from the surface layer. For this reason, referring to Figure 6, it is preferable to till the ground layer with each of the excavation and mixing blades 13 of the excavation and mixing device 12. The depth of tilling is preferably equivalent to the thickness of the ground layer during the curing period (for example, 50 cm to 100 cm). This moves water-containing coal ash particles (coal ash slurry) that have not come into contact with carbon dioxide to the surface layer, thereby increasing the amount of carbon dioxide stored and fixed in the ground layer. The appropriate timing for tilling is, for example, about three days or one week after disposal in the landfill. That is, calcium ions Ca 2+ and carbonate ions CO3 2- It is necessary to leave the soil for a period of time to allow sufficient time for reaction with the soil, and tilling and stirring at the time when the reaction is reaching equilibrium will be efficient and effective.

[0027] Furthermore, referring to FIG. 7, during periods of high solar radiation and low humidity, the amount of carbon dioxide fixation can be increased by appropriately sprinkling water on the ground layer of the reclaimed land. The sprinkling equipment 15 can be a water truck, drone, sprinkler, or any other permanent or relocatable temporary sprinkling equipment 15. This sprinkling action is also effective as a dust control measure. Furthermore, it is preferable to use water other than seawater, such as reservoir water (alkaline water with a pH value of 8.3 or higher) from a managed landfill 1, where waste is already buried in the underwater portion adjacent to the land portion 1A where coal ash is buried. It has been confirmed that alkaline water dissolves carbon dioxide more easily than ordinary seawater (pH value of approximately 8.0). Sprinkling water containing dissolved carbon dioxide (reservoir water) increases the amount of carbon dioxide supplied to the ground layer of the reclaimed landfill, thereby promoting the storage and fixation of carbon dioxide in the ground layer. The water used for sprinkling may be industrial water, tap water, or the like.

[0028] 3 and 8, carbon dioxide may be supplied into the pressure pipe 9. As a result, carbon dioxide can be dissolved in the coal ash slurry being pumped, and the carbon dioxide can be fixed in the coal ash slurry as calcium carbonate. The total length of the pressure pipe 9 is 100 to 600 m, and the pumping time takes several minutes, ensuring sufficient reaction time. As a result, carbon dioxide can be fixed efficiently. Furthermore, as shown in FIGS. 3 and 9, carbon dioxide may be supplied to the mixer section 6. By dissolving carbon dioxide in the coal ash slurry being generated, the carbon dioxide can be fixed in the coal ash slurry as calcium carbonate. The mixing time in the mixer section 6 takes several minutes, and adding the subsequent pumping time in the pressure pipe 9 ensures sufficient reaction time. As a result, carbon dioxide can be fixed efficiently. In FIGS. 8 and 9, reference numeral 7 denotes a water supply facility.

[0029] 8 and 9, the carbon dioxide concentration in the exhaust gas emitted from a coal-fired power plant 20 is several to 10%. A portion of the exhaust gas from the coal-fired power plant 20 is extracted from a flue gas facility (chimney) 21, resulting in a relatively high concentration of carbon dioxide, and this carbon dioxide is actively supplied to the mixer section 6 or the pressure pipe 9. As a result, carbon dioxide can be fixed in the coal ash slurry at a high reaction rate. The method for extracting the exhaust gas is arbitrary, but one example is to suck the exhaust gas from the side of the flue gas facility 21 using a blower pump or the like and send it to the mixer section 6 or the pressure pipe 9. The amount of carbon dioxide supplied is set at approximately several to 10% per m of coal ash slurry based on the results of verification experiments. 3 The amount should be approximately 0.1 to 10g per serving.

[0030] Furthermore, it is preferable to use water other than seawater as the mixing water (water supplied from the water supply facility 7 shown in Figures 8 and 9) added to the coal ash in the mixer unit 6. For example, it is preferable to use water (alkaline water with a pH value of 8.3 or higher) stored in a disposal site 1B, where waste has already been buried underwater, adjacent to the land portion 1A (landfill) of the coal ash in the controlled disposal site 1. Note that industrial water or tap water may also be used as the mixing water. The water stored in the disposal site 1B, where waste has already been buried underwater, has had its original seawater components diluted by years of rainfall, making it freshwater or alkaline (pH value of 8.3 or higher).

[0031] Seawater (pH value of about 8.0) has the effect of buffering alkaline components from coal ash and cement, and when used as mixing water, coal ash slurry is less likely to become alkaline. On the other hand, when reserve water, industrial water, or tap water, which has a weakened buffering capacity, is used as mixing water for coal ash slurry, the coal ash slurry becomes weakly alkaline. This makes it easy for carbon dioxide to dissolve, and an improvement in the carbon dioxide fixation rate, or in other words, an increase in the amount of carbon dioxide fixed, is expected. In short, by producing a weakly alkaline coal ash slurry using water other than seawater, an increase in the amount of carbon dioxide fixed in the coal ash slurry is expected.

[0032] Referring to FIG. 10 , coal ash slurry discharged from the nozzle of pressure pipe 9 flows down from the discharge location within an area surrounded by dams 4, 4 on land portion 1A of managed landfill 1. Coal ash particles settle and accumulate in the low-concentration coal ash slurry, generating excess water. In this embodiment, low-concentration coal ash slurry is used, so more excess water can be obtained than with high-concentration coal ash slurry. This excess water is weakly alkaline due to the coal ash. By draining and removing this excess water, the surface of the landfill, which retains an appropriate amount of moisture, is exposed to the atmosphere.

[0033] This alkalized and discharged surplus water can be stored in a section of the controlled landfill 1, for example in a reservoir, which can function as a dedicated pool for dissolving carbon dioxide, thereby promoting the dissolution of atmospheric carbon dioxide into the surplus water. This makes it possible to increase the amount of carbon dioxide fixed throughout the controlled landfill 1, including the amount fixed in the surplus water. Furthermore, dissolving carbon dioxide into this surplus water makes it possible to neutralize the surplus water, making it possible to meet effluent standards for discharge into the open sea or to reduce the work and costs associated with water treatment. Most of the calcium carbonate produced during this process precipitates in a crystallized state in the reservoir, and can therefore be said to be stored within the controlled landfill 1.

[0034] In an experiment conducted by the inventors, in the case of a coal ash slurry with a water content of 100%, that is, a coal ash slurry mixed at a ratio of FA (fly ash):W (water) = 1:1, 2 / 3 of the pouring height becomes the pile height, and 1 / 3 becomes separated excess water. 3 When 50 kg of cement is mixed with the slurry, one-quarter of the water will be separated as excess water. This separated excess water flows down the slope of the ground layer of the landfill where the coal ash slurry has been deposited, and is stored in a section at the foot of the slope. This will function as a dedicated pool for dissolving carbon dioxide. The pH value of this coal ash slurry, or the excess water separated from coal ash slurry mixed with cement, is around 9 to 12, and compared to ordinary seawater (pH value of around 8.0), the amount of carbon dioxide that will dissolve in the excess water in the dedicated dissolution pool will be greater.

[0035] Here, approximately 22 g / t of carbon dioxide is required to neutralize alkaline water with a pH value of 11.0. As a result, it is expected that the amount of carbon dioxide fixed (reduced) in the atmosphere will be increased. In this embodiment, the surplus water is stored in one section within the managed disposal site 1 to function as a dedicated dissolution pool, but this surplus water may also be transferred to and stored in a separate enclosed section outside the area enclosed by the dams 4, 4 of the managed disposal site 1, to function as a dedicated dissolution pool.

[0036] In the present embodiment described above, wet ash or coal ash slurry is buried in the land area 1A of the controlled landfill 1, creating a surface in contact with the atmosphere on the landfill ground. After curing for a predetermined period of time, carbon dioxide in the atmosphere can be stored and fixed as calcium carbonate within the coal ash landfill ground. In this way, by adopting this embodiment, it is possible to efficiently reduce as much carbon dioxide in the atmosphere as possible, aiming for carbon neutrality.

[0037] In this embodiment, the amount of carbon dioxide fixed (reduction) can be increased by tilling the reclaimed land or sprinkling water on the surface of the reclaimed land. It is also possible to actively supply flue gas (carbon dioxide) emitted from the coal-fired power plant 20 to the mixer unit 6 or the pressure pipe 9. This increases the amount of carbon dioxide fixed, and also reduces the amount of carbon dioxide emitted into the atmosphere from the coal-fired power plant 20.

[0038] In addition, exhaust gas (carbon dioxide) emitted from a coal-fired power plant 20 is actively supplied into the mixer section 6 or the pressure pipe 9, and the supply amount (coal ash slurry 1 m 3 If the amount of carbon dioxide supplied per unit time (amount of carbon dioxide supplied per unit time) is sufficient, carbon dioxide is fixed in the coal ash slurry in the mixer section 6 or pressure pipe 9, and the reaction reaches equilibrium, it is not necessary to landfill the coal ash slurry in the onshore section 1A of the controlled disposal site 1, create a surface in contact with the atmosphere in the ground layer of the landfill, and allow it to cure for a specified period, and it is possible to landfill the coal ash slurry one after another. Furthermore, since a sufficient amount of carbon dioxide has been fixed, the amount stored in the landfill will increase even if the landfill is landfilled in the underwater part of a controlled sea surface disposal site, for example.

[0039] Furthermore, in this embodiment, it is preferable to use water other than seawater as the mixing water when forming the coal ash slurry, for example, water (alkaline water) stored in a landfill 1B adjacent to the coal ash landfill (land portion 1A) in the controlled landfill 1, where waste has already been buried in the underwater portion. By producing a weakly alkaline coal ash slurry using the stored water, it is expected that the amount of carbon dioxide fixed in the coal ash slurry will increase.

[0040] Furthermore, in this embodiment, surplus water generated when wet ash or coal ash slurry is landfilled in the controlled disposal site 1 is stored in one section, and carbon dioxide is fixed to the surplus water, and the surplus water is neutralized. This makes it possible to increase the amount of fixed carbon dioxide (reduction). Moreover, by neutralizing the surplus water, it becomes possible to satisfy effluent standards when discharging it into the open sea, or to reduce the work and costs related to water treatment.

[0041] In this embodiment, the controlled disposal site 1 is constructed by filling wet ash or coal ash slurry with a plurality of thin ground layers on top of the land area 1A where waste reclamation has already been completed at the controlled offshore disposal site, and storing and fixing carbon dioxide within the landfill ground. However, the wet ash or coal ash slurry may be buried in a controlled disposal site located on land and the carbon dioxide may be fixed within the landfill ground, or may be buried within a controlled offshore disposal site on a portion of the land area formed during the waste reclamation process and the carbon dioxide may be fixed within the landfill ground.

[0042] In addition, in this embodiment, a low-concentration coal ash slurry with a water content of 100% or more is produced in the mixer section 6, which allows for the production of more excess water and, as a result, contributes to an increase in the amount of carbon dioxide fixed (reduced). However, a high-concentration coal ash slurry with a water content of 60% or less may also be produced in the mixer section 6. [Explanation of symbols]

[0043] 1 Managed disposal site, 1A Land section, 6 Mixer section, 7 Water supply equipment, 8 Pressure pump, 9 Pressure pipe (pipeline), 12 Excavation and mixing equipment, 15 Sprinkler equipment, 21 Smoke exhaust equipment

Claims

1. A method for fixing carbon dioxide at a controlled landfill site, characterized in that wet ash or coal ash slurry is buried on land at the controlled landfill site, a surface of the landfill that comes into contact with the atmosphere is created, and the landfill is cured, thereby storing and fixing carbon dioxide within the coal ash landfill.

2. 2. The method for fixing carbon dioxide in a controlled landfill site according to claim 1, wherein the wet ash or coal ash slurry is mixed with cement and then buried.

3. 2. The method for fixation of carbon dioxide at a controlled landfill site according to claim 1, wherein excess water generated when wet ash or coal ash slurry is buried on land at the controlled landfill site is stored in one section, and carbon dioxide is fixed to the excess water.

4. 2. The method for fixing carbon dioxide at a controlled landfill site according to claim 1, wherein the wet ash or coal ash slurry is buried in the land area of ​​the controlled landfill site by raising the level of the wet ash or coal ash slurry with a plurality of ground layers, and carbon dioxide is stored and fixed within the coal ash landfill ground.

5. 2. The method for fixing carbon dioxide at a controlled landfill site according to claim 1, wherein the landfill ground is tilled.

6. 2. The method for fixing carbon dioxide at a controlled disposal site according to claim 1, wherein water is sprayed onto the landfill.

7. A method for fixing carbon dioxide at a controlled landfill site, comprising the steps of: supplying carbon dioxide into a pipeline to store and fix the carbon dioxide within the coal ash landfill bed when coal ash slurry is buried in the controlled landfill site using a pressure pump.

8. A method for fixing carbon dioxide at a controlled landfill site, comprising the steps of: supplying carbon dioxide to a mixer that produces coal ash slurry when the coal ash slurry is buried in the controlled landfill site; and storing and fixing the carbon dioxide within the coal ash landfill.

9. 9. The method for fixing carbon dioxide in a controlled disposal site according to claim 7 or 8, wherein the carbon dioxide used is that emitted from a coal-fired power plant.

10. 9. The method for fixing carbon dioxide in a controlled landfill site according to claim 1, wherein water other than seawater is used as mixing water when producing the coal ash slurry.

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