JP2023140554A - Method for storing carbon dioxide in soil - Google Patents

Abstract

To provide a method for storing carbon dioxide in soil that can contribute to reducing carbon dioxide, which is a cause of global warming.SOLUTION: In a construction work to improve soil such as the ground G, a gas CG in which the volume ratio of carbon dioxide C is higher than that of the air at a construction site or a carbonic acid solution CW in which carbon dioxide C is dissolved is mixed with a mixture of at least one of the soil before improvement, a mixture to be mixed with the soil to be improved, or the soil after improvement. By mixing carbon dioxide C into the mixture, carbon dioxide C is stored in the improved soil.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for storing carbon dioxide in soil, and more particularly, to a method for storing carbon dioxide in soil that can contribute to reducing carbon dioxide, which is a greenhouse gas that causes global warming.

In order to suppress global warming, reducing carbon dioxide (CO ₂ ) emissions in civil engineering and construction work has become an important issue. BACKGROUND ART Conventionally, various ground improvement methods such as a deep mixing method and a high-pressure injection method have been used in civil engineering and construction works (for example, see Patent Document 1). However, conventional ground improvement methods have not been able to contribute to reducing carbon dioxide emissions.

Japanese Patent Application Publication No. 2011-256541

An object of the present invention is to provide a method for storing carbon dioxide in soil, and more specifically, to provide a method for storing carbon dioxide in soil that can contribute to reducing carbon dioxide, which is a greenhouse gas that causes global warming. be.

In order to achieve the above object, the method for storing carbon dioxide in soil of the present invention includes adding at least one of the soil before improvement, the mixed material to be mixed into the soil to be improved, or the soil after improvement at a construction site. By mixing a gas with a higher volume ratio of carbon dioxide than air or a carbonic acid solution in which carbon dioxide is dissolved, and incorporating the carbon dioxide into the mixture, the carbon dioxide can be removed from the soil after improvement. It is characterized by being stored in.

According to the present invention, a gas having a higher volume ratio of carbon dioxide than the air at the construction site is added to at least one of the soil before improvement, the mixed material mixed with the soil to be improved, and the soil after improvement. Alternatively, carbon dioxide is mixed into the mixture by mixing a carbonic acid solution in which carbon dioxide is dissolved. As a result, carbon dioxide, which is a cause of global warming, can be stored in the improved soil, contributing to the reduction of carbon dioxide during civil engineering and construction work.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram schematically illustrating an embodiment in which the carbon dioxide underground storage method of the present invention is applied to the SGM lightweight earthwork method. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram schematically illustrating an embodiment in which the carbon dioxide underground storage method of the present invention is applied to a gas injection unsaturated construction method. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram schematically illustrating an embodiment in which the method for storing carbon dioxide in soil of the present invention is applied to a deep mixing treatment method. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram schematically illustrating an embodiment in which the carbon dioxide underground storage method of the present invention is applied to a pumping system of a pneumatic transport ship. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram schematically illustrating an embodiment in which the method for storing carbon dioxide in soil of the present invention is applied to an in-pipe mixing solidification method. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram schematically illustrating an embodiment in which the carbon dioxide underground storage method of the present invention is applied to a high-pressure injection stirring method.

EMBODIMENT OF THE INVENTION Hereinafter, the method for storing carbon dioxide in soil according to the present invention will be described based on the embodiment shown in the drawings.

The method for storing carbon dioxide in the soil of the present invention involves adding at least one of the soil before improvement, the mixed material to be mixed with the soil to be improved, or the soil after improvement to the air at the construction site (atmospheric air near the ground surface). ), or a carbonated solution (carbonated water or a solution of carbonated water with additives added) in which carbon dioxide (carbon dioxide gas) is dissolved, to add carbon dioxide to the mixture. By incorporating carbon, carbon dioxide is stored in the improved soil.

In the present invention, for example, carbon dioxide stored in advance in a high-pressure container (for example, a cylinder) is used as the carbon dioxide in the above-mentioned gas or in the carbonic acid solution. Further, for example, carbon dioxide emitted by machines used at a construction site is used as the carbon dioxide in the gas or carbonic acid solution described above. Examples of machines used at construction sites that emit carbon dioxide include construction machines, vehicles, diesel engines of ships, and various machines used for construction (eg, generators). When using carbon dioxide emitted by machinery at the construction site, in construction sites where it is not acceptable to contain pollutants contained in the exhaust gas emitted by the machinery at the construction site, the exhaust gas emitted by the machinery must be used. After removing pollutants such as particulate matter (PM), nitrogen oxides (e.g. NO and NO ₂ ), and volatile organic compounds (VOC) from the exhaust gas using a filter, etc., Preference is given to using carbon dioxide.

Although the volume percentage of carbon dioxide contained in the air (atmosphere near the ground surface) varies somewhat depending on the altitude of the construction site, etc., the volume percentage of carbon dioxide in normal air is about 0.03 to 0.04%. When mixing a gas with a higher volume ratio of carbon dioxide than the air at the construction site into the above-mentioned mixture, for example, the volume ratio of carbon dioxide in the mixture should be 0.4% or more, more preferably 2% or more. , more preferably 10% or more of the gas. Alternatively, a gas in which the volume ratio of carbon dioxide is, for example, 10 times or more, more preferably 50 times or more, still more preferably 250 times or more of the volume ratio of carbon dioxide contained in the air at the construction site is mixed with the mixture. . The upper limit of the volume ratio of carbon dioxide contained in the gas with a higher volume ratio of carbon dioxide mixed into the mixture is, for example, 97% or less.

FIG. 1 illustrates an embodiment in which the method for storing carbon dioxide in the soil of the present invention is applied to the SGM lightweight earth construction method, which is a soil improvement method. Although illustrated later as another embodiment, the present invention is not limited to the SGM lightweight earth construction method, but can be applied to various other construction methods for improving soil (ground).

The SGM lightweight earth construction method uses a slurry-like muddy water 11 made by adding water to soil collected from the bottom of the water or on land (raw material soil 10), a lightweight material such as expanded foam 13 or styrene beads, and a solidifying material 12 such as cement. This is a ground improvement method in which a lightweight ground material 15 in the form of slurry is prepared and poured by mixing the following materials. The foam 13 is made by coating cells with a film of a highly surface-active substance. In this embodiment, a case where lightweight ground material 15 mixed with expanded foam 13 is poured will be illustrated.

As illustrated in FIG. 1, in the SGM lightweight earthwork method, a slurry-like muddy water 11, a solidification material 12 (for example, cement), and an expanded foam 13 (air bubbles) are supplied to a lightweight soil mixer 14. In the line that supplies muddy water 11 to the lightweight soil mixer 14, soil from the bottom of the water or on land (raw soil 10) is collected, and gravel and foreign matter contained in the raw material soil 10 (soil before improvement) are removed. Next, the raw soil 10 is put into a vibrating sieve 18 using a construction machine 17, etc., and the raw soil 10 is classified by the vibrating sieve 18, so that particles with relatively large particle sizes (for example, Remove particles with a particle size of 5 mm to 10 mm or more. Thereafter, the raw material soil 10 that has been classified by the vibrating sieve 18 is desilted by the desilting machine 19, and the desilted raw material soil 10 is put into the mud storage tank 20. In the mud storage tank 20, water is added to the raw material soil 10 to produce muddy water 11 in the form of slurry.

In this embodiment, the water added to the raw material soil 10 is a carbonated solution CW (carbonated water) in which carbon dioxide C is dissolved. For example, by connecting the high-pressure container 1 in which carbon dioxide C has been stored in advance to the mud storage tank 20 and supplying carbon dioxide C into the mud storage tank 20 from the high-pressure container 1, carbon dioxide C can be added to the muddy water 11. It is also possible to have a configuration in which the liquid is mixed and dissolved.

Next, the mud water 11 stored in the mud storage tank 20 is sent to a lightweight soil conditioning mud machine 22 by a mud pump 21. Then, the density and flow value of the muddy water 11 are adjusted using the lightweight soil conditioning mud machine 22. When the raw material soil 10 is sandy soil, additives such as bentonite are added as necessary to adjust the muddy water 11 to a predetermined density and flow value. The muddy water 11 (adjusted mud) whose density and flow value have been adjusted by the lightweight soil conditioning mud machine 22 is pumped to the lightweight soil kneading machine 14 .

In the line that supplies the solidifying material 12 (mixed material to be mixed with the soil to be improved) to the lightweight soil kneading machine 14, the solidifying material 12 is supplied to the lightweight soil kneading machine 14 from the storage facility 23 (silo) in which the solidifying material 12 is stored. do. In this embodiment, the high-pressure container 1 (1A) in which carbon dioxide C is stored in advance is connected to the storage equipment 23, and carbon dioxide C is mixed and dissolved in the solidification material 12 stored in the storage equipment 23. I have to.

In the line that supplies the foam foam 13 (mixture material to be mixed with the soil to be improved) to the lightweight soil kneading machine 14, a diluted liquid 26 obtained by diluting the foaming agent 24 with water 25 is supplied to the foaming machine 28 by a diluted liquid pump 27. . In this embodiment, a carbonic acid solution CW (carbonated water) in which carbon dioxide is dissolved is used as the water 25 used for dilution. For example, by connecting a high-pressure container 1 in which carbon dioxide C is stored in advance to a water storage tank 29 storing water 25 used for dilution, and supplying carbon dioxide C into the water storage tank 29 by the high-pressure container 1, the dilution can be performed. It is also possible to adopt a configuration in which carbon dioxide C is mixed and dissolved in the water 25 used for this purpose. Further, for example, by connecting the high-pressure container 1 to the liquid storage tank 30 storing the foaming agent 24 and supplying carbon dioxide C into the liquid storage tank 30 by the high-pressure container 1, the foaming agent 24 can be filled with carbon dioxide. It is also possible to have a structure in which C is mixed and dissolved.

The foaming machine 28 is further supplied with gas CG compressed by the compressor 2 (2A). Conventionally, air supplied at a construction site is compressed by an air compressor, and the compressed air is sent to the foaming machine 28. In contrast, in this embodiment, the high-pressure container 1 (1B) in which carbon dioxide C is stored in advance is connected to the compressor 2A, and the carbon dioxide C is compressed by supplying the compressor 2A from the high-pressure container 1B. The compressed gas CG having a higher volume ratio of carbon dioxide C than the air at the construction site is supplied from the blower 2A to the foamer 28. The compressor 2 to which the high-pressure container 1B can be connected can be easily manufactured, for example, by improving the air supply structure of a conventionally used air compressor. The foaming machine 28 uses the supplied diluent 26 and the compressed gas CG to generate the foam 13 having a large number of fine bubbles. The foam 13 produced by the foamer 28 is sent to the lightweight soil mixer 14.

In the lightweight soil kneading machine 14, the supplied mud water 11 (adjusted mud), solidification material 12, and foam 13 are stirred and mixed by a mixer, and a slurry-like lightweight ground material 15 (improved soil) containing many air bubbles is produced. generate. Then, the lightweight ground material 15 before solidification produced by the lightweight soil kneading machine 14 is pumped to a pouring machine 16, and the pouring machine 16 pours the lightweight soil material 15 onto the water bottom or land where soil improvement is to be performed.

In this embodiment, a pressure pump 31 pumps the lightweight ground material 15 before solidification into a pressure pipe 32, and a compressor 2 (2B) pumps a volume proportion of carbon dioxide C into the pressure pipe 32 compared to the air at the construction site. The structure is such that the lightweight ground material 15 before solidification is force-fed to the pouring machine 16 by sending compressed gas CG with increased CG. In this embodiment, a high-pressure container 1 (1C) storing carbon dioxide C is connected to the compressor 2B, and carbon dioxide C is supplied from the high-pressure container 1C to the compressor 2B. Note that when the amount of compressed gas CG sent by the compressor 2 exceeds the amount of gas supplied from the high-pressure container 1 with a high volume ratio of carbon dioxide C, the compressor 2 is supplied with the gas CG from the high-pressure container 1. It is also possible to supply air at the construction site together with a gas having a high volume ratio of carbon dioxide C, and to supply compressed gas CG with a higher volume ratio of carbon dioxide C than the air at the construction site. .

When the cast lightweight ground material 15 solidifies, a lightweight ground is formed in which a large number of independent voids formed by air bubbles are maintained. Inside the lightweight ground, gas containing carbon dioxide C is retained in a large number of independent voids. The unit volume weight of the lightweight ground material 15 in a hardened state is approximately 8 to 13 kN/m ³ , which is lighter than general ground materials, and the lightweight ground material 15 has sufficient strength against ground subsidence, earthquakes, liquefaction, etc. have. Therefore, by placing the lightweight ground material 15 using the SGM lightweight earthwork method, a stable ground can be formed.

As described above, according to the present invention, at least one of the soil before improvement, the mixed material mixed with the soil to be improved, or the soil after improvement has a volume of carbon dioxide C that is higher than the air at the construction site. Carbon dioxide C is mixed into the mixture by mixing gas CG with an increased proportion or carbonic acid solution CW in which carbon dioxide C is dissolved. As a result, carbon dioxide C, which is a cause of global warming, can be stored in the improved soil, contributing to the reduction of carbon dioxide C during civil engineering and construction work.

As a method of reducing carbon dioxide, carbon dioxide recovery is a method of separating and collecting carbon dioxide emitted from thermal power plants, chemical factories, etc. from other gases, and then storing the collected carbon dioxide by injecting it deep underground. - Carbon dioxide storage technology (CCS) is being researched, but since CCS injects carbon dioxide deep underground, special and large-scale equipment is required, and a large amount of energy is required. On the other hand, in the present invention, when improving the soil (ground) in civil engineering and construction work, the soil before improvement, the mixed material mixed with the soil to be improved, and the soil after improvement are made to have a higher temperature than the air at the construction site. Since it is only necessary to mix gas CG with a high volume ratio of carbon dioxide C and carbonic acid solution CW, large-scale equipment is not required, and a large amount of energy is not required compared to conventional construction methods. Furthermore, in the present invention, most of the carbon dioxide C mixed in the improved soil (soil + mixed material) becomes calcium carbonate (CaCO ₃ ) by reacting with calcium (Ca) contained in the improved soil. , becomes stably immobilized in the soil. Therefore, unlike CCS, carbon dioxide C can be stably stored in the soil without having to be injected into the ground at great depths. Therefore, it is very useful for those skilled in the art as a method for reducing carbon dioxide C in civil engineering and construction work.

As in this embodiment, in the SGM lightweight earth construction method, carbon dioxide C is mixed with water added to raw soil 10, solidifying agent 12, water 25 diluting foaming agent, etc., to create lightweight ground material 15 (improved It is possible to mix a large amount of carbon dioxide C into the soil (after soil). In addition, by supplying compressed gas CG with a higher volume ratio of carbon dioxide C than the air at the construction site from the compressor 2A to the foaming machine 28, a large amount of carbon dioxide is added to the foam 13 produced by the foaming machine 28. Carbon C can be mixed. In addition, the lightweight ground material 15 is pumped by sending compressed gas CG with a higher volume ratio of carbon dioxide C than the air at the construction site from the compressor 2B to the pipe that pumps the lightweight ground material 15 before solidification. In the process of doing so, carbon dioxide C can be effectively mixed into the lightweight ground material 15.

As described above, by applying the present invention to the SGM lightweight earthwork method and mixing carbon dioxide C into the mixture in the production process and pumping process of the lightweight ground material 15, a large amount of carbon dioxide C can be added to the lightweight ground material 15. Can be mixed. Furthermore, since gas containing a large amount of carbon dioxide C is retained in the numerous independent voids of the lightweight ground formed after the lightweight ground material 15 has solidified, it is difficult for carbon dioxide C to flow to the ground, and a large amount of carbon dioxide C is Carbon dioxide C can be stably stored in the soil.

Furthermore, since carbon dioxide C is relatively easily dissolved in water or the alkaline solidification material 12, by mixing gas CG, which has a higher volume ratio of carbon dioxide C than air, into the lightweight ground material 15. It becomes possible to form a larger number of finer air bubbles in the lightweight ground material 15 than when air is mixed in. Therefore, it is advantageous to form a high-quality lightweight ground. Further, as in this embodiment, if carbon dioxide C is mixed into the mixture in multiple steps in the SGM lightweight earthwork method, it is advantageous to increase the dissolution rate of carbon dioxide C contained in the lightweight ground material 15.

As in this embodiment, carbon dioxide C stored in advance in a high-pressure container 1 or the like is stored in a gas CG having a higher volume ratio of carbon dioxide C than the air at the construction site, or by dissolving carbon dioxide C. When used as carbon dioxide C in a carbonic acid solution CW, carbon dioxide C can be mixed into the mixture relatively easily. In particular, when the high-pressure container 1 is used, gas CG having a high volume ratio of carbon dioxide C can be easily supplied, so that a large amount of carbon dioxide C can be efficiently mixed into the mixture. Therefore, it is advantageous to increase the amount of carbon dioxide C stored in the soil after improvement. Furthermore, by using the high-pressure container 1, it is also possible to store carbon dioxide C discharged outside the construction site in the soil.

The method of mixing carbon dioxide C into the mixture is not limited to the case of using the high-pressure container 1 or the carbonic acid solution CW, and various other methods can be used to mix carbon dioxide C into the mixture. Specifically, for example, carbon dioxide C emitted by machines used at the construction site may be converted into gas CG with a higher volume ratio of carbon dioxide C than the air at the construction site, or carbon dioxide within carbon dioxide solution CW. It can also be used as C.

When using carbon dioxide C discharged by a machine at a construction site, for example, the exhaust port of the machine that discharges carbon dioxide C and the air supply port of the compressor 2 that supplies carbon dioxide C are connected by piping. Further, for example, piping is provided to send carbon dioxide C from an exhaust port of a machine that discharges carbon dioxide C to a material to be mixed (such as muddy water 11 stored in mud storage tank 20). At construction sites where contaminants contained in exhaust gas emitted by machinery cannot be contained in the soil, for example, filters are installed in piping to remove contaminants from exhaust gas emitted by machinery.

The machines used at the construction site mentioned above include, in the SGM lightweight earthwork method, construction machines used for collecting soil from the bottom of the water or on land, diesel engines from ships (crane ships equipped with grab buckets, etc.), vibrating sieves 18 Examples include a construction machine 17 that inputs the raw soil 10 into the soil, and each machine (compressor 2A, diluent pump 27, foaming machine 28, etc.) used to generate the lightweight ground material 15. Examples include a compressor 2B that pumps the lightweight ground material 15 to the pouring machine 16, a generator that supplies power to each machine used in construction, and the pouring machine 16.

By using carbon dioxide C discharged from these machines as carbon dioxide C mixed into the mixture, carbon dioxide C discharged into the atmosphere can be effectively reduced during construction using the SGM lightweight earthwork method. In particular, in the SGM lightweight earthwork method, since the amount of carbon dioxide C emitted by the pouring machine 16 and compressor 2 is relatively large, the carbon dioxide C discharged by the pouring machine 16 and compressor 2 is recovered and mixed When used as carbon dioxide C mixed in, the amount of carbon dioxide C emitted in the SGM lightweight earthwork method can be effectively reduced. In addition, when exhaust gas emitted by machines used at the construction site is used, the heat of the exhaust gas can heat the lightweight ground material 15 before solidification during the process of pumping the lightweight ground material 15 in the pressure feeding pipe 32. I can do it. Being able to heat the lightweight ground material 15 before solidification is advantageous in shortening the curing period until the cast lightweight ground material 15 solidifies.

In the embodiment illustrated in FIG. 2, the carbon dioxide underground storage method of the present invention is applied to the gas injection unsaturated construction method.

The gas injection unsaturated method is a ground improvement method that unsaturates the ground G by injecting gas into the soil using an injection pipe 40 inserted into the ground G to be improved, thereby increasing the liquefaction strength of the ground G. be. Conventionally, air supplied at a construction site is compressed using an air compressor, and the compressed air is sent to an injection pipe 40 inserted into the ground. By injecting air into the soil through the air supply hole 40a provided at the tip of the injection pipe 40, a large number of air bubbles 41 are formed in the soil. On the other hand, in the gas injection unsaturated construction method to which the present invention is applied, compressed gas CG having a higher volume ratio of carbon dioxide C than the air at the construction site is sent from the compressor 2C to the injection pipe 40.

Specifically, in the gas injection unsaturated construction method to which the present invention is applied, a hole is formed in the ground G using an excavator such as a boring machine. Then, the injection pipe 40 is inserted into the hole formed in the ground G, so that the injection pipe 40 is buried in the ground G. In this embodiment, a high-pressure container 1 (1D) in which carbon dioxide C is stored in advance is connected to a compressor 2 (2C), and carbon dioxide C is supplied from the high-pressure container 1D to the compressor 2C. Then, a compressed gas CG with a higher volume ratio of carbon dioxide C than the air at the construction site is supplied from the compressor 2C to the injection pipe 40, and is poured into the soil from the air supply hole 40a provided at the tip of the injection pipe 40. By injecting the compressed gas CG described above, a large number of air bubbles 41 are formed in the soil to make the ground G unsaturated.

The pressure of the compressed gas CG supplied from the compressor 2C to the injection pipe 40 is adjusted by the pressure regulating valve 42 based on the measured value of the pressure gauge 43. The flow rate of the compressed gas CG supplied from the compressor 2C to the injection pipe 40 is sequentially measured by a flow meter 44, and the pressure of the compressed gas CG is sequentially measured by a pressure gauge 45. Measurement data measured by the flow meter 44 and pressure gauge 45 is input to a data recorder 46, and the measurement data input to the data recorder 46 is displayed on a management monitor 47.

In the improved ground G in which many air bubbles 41 have been formed, when an earthquake occurs, the gas (air bubbles) in the soil is compressed and the volume is reduced. Even if the ground G undergoes shear deformation due to an earthquake, the volume of gas only decreases, and the soil particles of the ground G maintain contact with each other and remain entangled. Therefore, even if an earthquake occurs, the strength and rigidity of the soil of the ground G is maintained. Thereby, an increase in pore water pressure can be suppressed, and liquefaction of the ground G can be prevented.

As described above, when the present invention is applied to the gas injection unsaturated construction method, gas CG with a higher volume ratio of carbon dioxide C than the air at the construction site is injected into the ground G using the injection pipe 40 to inject the soil before improvement. By mixing carbon dioxide C into the mixture, a large amount of carbon dioxide C can be stored in the improved soil. Therefore, it can contribute to reducing carbon dioxide C in civil engineering and construction work.

In the gas injection unsaturated construction method to which the present invention is applied, some or all of the carbon dioxide C contained in the air bubbles 41 formed in the ground G dissolves in the moisture in the soil, so compared to the conventional method of injecting air, It becomes possible to make the bubbles 41 that remain in the soil finer (microbubbles). The finer the air bubbles 41 are, the easier they are to be adsorbed between soil particles, and the more difficult it is for them to escape to the ground surface. Therefore, by injecting gas CG with a higher volume ratio of carbon dioxide C than the air at the construction site into the ground G, it is more advantageous to maintain the unsaturation of the ground G, and the liquid state of the ground G It is also more advantageous to prevent the

If carbon dioxide C is supplied to the compressor 2C using the high-pressure container 1D as in this embodiment, the gas injection unsaturation method to which the present invention is applied can be implemented very easily. Moreover, by using the high-pressure container 1D, it is advantageous to increase the volume ratio of carbon dioxide C in the compressed gas CG sent from the compressor 2C.

The method of supplying carbon dioxide C to the compressor 2C is not limited to the case of using the high-pressure container 1D, and for example, carbon dioxide C discharged by a machine used at a construction site can also be supplied to the compressor 2C. In the gas injection unsaturation method, for example, carbon dioxide C emitted by the compressor 2C or the generator that supplies power to the compressor 2C is used as carbon dioxide C mixed into the mixture. Carbon dioxide C emitted into the atmosphere can be effectively reduced during construction using the saturation method.

In the embodiment illustrated in FIG. 3, the carbon dioxide underground storage method of the present invention is applied to the deep mixing treatment method.

The deep mixing method uses a deep mixing machine 50 to inject an improvement material 51 into the soft ground G to be improved, and also stirs and mixes the soil in the ground G with the improvement material 51 to form the improved soil. This is a construction method that improves the ground G by solidifying it. In the deep mixing method, in addition to the deep mixing machine 50, there is a mixer 52 (mixer) that mixes materials constituting the improved material 51, and the improved material 51 produced by the mixer 52 is sent to the deep mixing machine 50. A pressure pump 53 is used.

The deep mixing processor 50 includes a rotationally driven rod 50a, a stirring blade 50b provided at the tip of the rod 50a, and a discharge port 50c provided in the rod 50a or the stirring blade 50b. Stirring blades 50b are attached to the rod 50a at multiple locations spaced apart vertically. A discharge port 50c is provided at the tip of each stirring blade 50b. The rod 50a is equipped with a supply pipe to which the improved material 51 is supplied, and the improved material 51 produced by the mixer 52 is forced into the supply pipe by a pressure pump 53, and the improved material 51 that is pressure-fed is mixed into each of the improved materials 51. It is configured to be discharged from the discharge port 50c.

In this embodiment, the deep mixing processing machine 50 having two rods 50a is illustrated, but the number of rods 50a that the deep mixing processing machine 50 has, the stirring blades 50b provided on each rod 50a, and the discharge port The number, arrangement, etc. of 50c are not limited to this embodiment, and various other configurations can be made.

In the deep mixing method to which the present invention is applied, gas CG with a higher volume ratio of carbon dioxide C than the air at the construction site, or carbon dioxide C, is dissolved in the improvement material 51 (mixed material) to be mixed with the soil to be improved. By mixing the carbonic acid solution CW and incorporating carbon dioxide C into the improvement material 51, carbon dioxide C is stored in the soil after improvement.

There are various types of improvement material 51 used in the deep mixing method, but in this embodiment, a case where a cement-based improvement material 51 is used will be exemplified. The cement-based improvement material 51 is prepared by mixing water 54, a hardening material (cement material) 55, and an additive (hardening material retardant) 56 using a mixer 52.

In this embodiment, the water 54 supplied to the mixer 52 is a carbonated solution CW (carbonated water or a solution of carbonated water with additives added) in which carbon dioxide C (carbon dioxide gas) is dissolved. In addition, the high-pressure container 1 (1E) in which carbon dioxide C is stored in advance is connected to the mixer 52, and the carbon dioxide C is supplied from the high-pressure container 1E to the mixer 52. It has a structure in which carbon C is mixed. The improved material 51 formed in the mixer 52 is supplied to the deep mixing processor 50 by a pressure pump 53.

In construction to improve the ground G, each rod 50a of the deep mixing treatment machine 50 is rotated, and the soft ground G is excavated using the excavating blade and stirring blade 50b provided at the tip of the rod 50a. Then, in the ground, while the rod 50a is being rotated, the improvement material 51 is discharged from the discharge port 50c provided in the stirring blade 50b, and the soil of the ground G and the improvement material 51 are stirred by the rotating stirring blade 50b. Mix. Then, the improved soil mixed with the improving material 51 is solidified, thereby improving the strength of the ground G.

As described above, when the present invention is applied to the deep mixing method, gas CG with a higher volume ratio of carbon dioxide C than the air at the construction site or carbonic acid solution CW in which carbon dioxide C is dissolved is added to the improvement material 51. By mixing carbon dioxide C into the improvement material 51, carbon dioxide C can be stored in the improved soil. In the improvement material 51 that has alkalinity, such as the cement-based improvement material 51 that is mainly used in the deep mixing method, carbon dioxide C reacts with the alkali, so it is difficult to dissolve a large amount of carbon dioxide C in the improvement material 51. can. Therefore, when the present invention is applied to the deep mixing method, it is possible to store a large amount of carbon dioxide C in the improved soil.

If carbon dioxide C is supplied to the mixer 52 using the high-pressure container 1E as in this embodiment, the deep mixing method to which the present invention is applied can be implemented very easily. Further, by using the high-pressure container 1E, carbon dioxide C can be mixed into the improvement material 51 in the mixer 52 very efficiently.

In this embodiment, carbonic acid solution CW is used as the water 54 which is the material of the improving material 51, and carbon dioxide C is mixed into the improving material 51 in the mixer 52. By mixing gas CG with a higher volume ratio of carbon dioxide C than the air at the construction site or carbonic acid solution CW in which carbon dioxide C is dissolved into the material 55 and additive 56, carbon dioxide C can be added to the improvement material 51. can also be mixed in.

The method of mixing carbon dioxide C into the improvement material 51 or its material is not limited to the case where the high-pressure container 1 is used. It is also possible to supply the respective materials constituting 51 to a storage section. Examples of machines used in the deep mixing process include the deep mixing process machine 50, mixer 52, pressure pump 53, and a generator that supplies power to each machine. In particular, in the deep mixing treatment method, the amount of carbon dioxide C emitted by the generator that supplies electricity to the deep mixing treatment machine 50 is relatively large. When C is used as carbon dioxide C to be mixed into the mixture, carbon dioxide C emitted into the atmosphere can be effectively reduced in the deep mixing method. Furthermore, when exhaust gas discharged from machines used at the construction site is used, the improvement material 51 can be heated by the heat contained in the exhaust gas. Being able to heat the improvement material 51 is advantageous in shortening the curing period until the improved soil mixed with the improvement material 51 solidifies.

In the embodiment illustrated in FIG. 4, the carbon dioxide underground storage method of the present invention is applied to a mud feeding system 60 of a pneumatic conveying ship.

The pneumatic mud transport system 60 is a system that improves soil 70 (unimproved soil) dredged by a dredger or the like, and continuously transports a large amount of the improved soil 70 over long distances. The mud feeding system 60 includes a shearing machine 61, a vibrating sieve 62, an agitator 63, a quantitative feeder 64, an assisting pump 65, a pressure feeding pipe 66, and a compressor 2 (2D). A prime mover 67 is connected to the assisting pump 65 via a clutch.

In the mud feeding system 60, dredged soil 70 (soil before improvement) is put into a shearer 61, and the soil 70 is crushed by the shearer 61 and sent to a vibrating screen 62. The vibrating sieve 62 removes obstacles 71 such as gravel of a predetermined particle size or more contained in the soil 70, and sends the soil 70 that has passed through the vibrating sieve 62 to an agitator 63. The agitator 63 further refines the soil 70 by stirring it, and sends the refined soil 70 (improved soil) to the quantitative feeder 64 . The fixed amount feeder 64 sends a fixed amount of soil 70 to the assisting pump 65 every unit time. Then, the assisting pump 65 sends the sent soil 70 to the pressure feeding pipe 66. The compressor 2D sends compressed gas CG into the pressure feed pipe 66, thereby forcefully transporting the soil 70 sent to the pressure feed pipe 66 to a landfill or the like.

Conventionally, air compressed by an air compressor is sent into the pressure feed pipe 66. On the other hand, in the mud feeding system 60 to which the present invention is applied, compressed gas CG having a higher volume ratio of carbon dioxide C than the air at the construction site is fed into the pressure feeding pipe 66 by the compressor 2D. In this embodiment, a high-pressure container 1 (1F) in which carbon dioxide C is stored in advance is connected to the compressor 2D, and carbon dioxide C is supplied from the high-pressure container 1F to the compressor 2D.

As described above, when the present invention is applied to the mud feeding system 60 of a pneumatic feeding ship, the compressed gas CG, which has a higher volume ratio of carbon dioxide C than the air at the construction site, is fed into the pressure feeding pipe 66 by the compressor 2D. By doing so, carbon dioxide C can be mixed into the soil 70 (improved soil) that is fed in the pressure feeding pipe 66. Then, by using the soil 70 mixed with carbon dioxide C for the creation of a landfill, etc., carbon dioxide C can be stored in the improved soil. In the pneumatic transport system 60, the soil 70 is transported over a long distance in the pressure pipe 66, so by transporting the soil 70 with compressed gas CG with a high volume ratio of carbon dioxide C, the gas can be removed. Carbon dioxide C contained in CG can be effectively mixed into the soil 70.

If carbon dioxide C is supplied to the compressor 2D using the high-pressure container 1F as in this embodiment, the mud feeding system 60 to which the present invention is applied can be configured very simply. Furthermore, the use of the high-pressure container 1F is advantageous in increasing the volume ratio of carbon dioxide C in the compressed gas CG sent from the compressor 2D.

The method of supplying carbon dioxide C to the compressor 2D is not limited to the case of using the high-pressure container 1F. It can also be supplied in 2D. Machines used in the pneumatic transport ship mud feeding system 60 include a construction machine that feeds the soil 70 into the shearing machine 61, a crane equipped with a grab bucket, a shearing machine 61, a vibrating sieve 62, an agitator 63, and a quantitative feeder 64. , an auxiliary pump 65, a prime mover 67, a compressor 2D, a generator that supplies power to each machine, a diesel engine for a pneumatic ship, and the like. In particular, in the mud feeding system 60, the amount of carbon dioxide C emitted by the prime mover 67 and the diesel engine of the pneumatic transport ship is relatively large. When used as carbon dioxide C mixed in (mixture), it is possible to effectively reduce carbon dioxide C discharged into the atmosphere in the pneumatic transport system 60 of the pneumatic transport vessel. Furthermore, when exhaust gas discharged by machines used at the construction site is utilized, the soil 70 can be heated during the process of pumping the soil 70 within the pumping pipe 66 due to the heat contained in the exhaust gas. Being able to heat the soil 70 is advantageous in shortening the curing period of improved soil (solidified soil) formed using the soil 70.

In the embodiment illustrated in FIG. 5, the carbon dioxide underground storage method of the present invention is applied to the in-pipe mixing solidification method (hereinafter referred to as the in-pipe mixing method).

In the pipe mixing method, a solidifying agent 91 is added during the process of pumping relatively soft soil 90 such as dredged soil inside the pipe. Then, using a plug flow (turbulent flow) generated by sending compressed gas into the tube, the soil 90 and the solidification material 91 are stirred and mixed inside the tube to form improved soil 92. This is a construction method in which improved soil 92 is pumped to a landfill or the like.

The in-pipe mixing system 80 used in the in-pipe mixing method includes a first pressure feed pipe 81, a compressor 2 (2E), an expansion pipe 82, a solidification material supply device 83, and a second pressure feed pipe 84. ing. An expansion tube 82 having a larger diameter than the expansion tube 81 is connected to the rear of the first pressure-feeding tube 81, and a second pressure-feeding tube 84 having a smaller diameter than the expansion tube 82 is connected to the rear of the expansion tube 82. The compressor 2E is connected to the first pressure feed pipe 81 via an air feed pipe. A solidifying material supply device 83 is connected to the expansion tube 82 via a supply pipe.

In the in-pipe mixing method, unimproved soil 90 with a relatively high moisture content, such as dredged soil, is sent to the first pressure feeding pipe 81 using a mud pump or the like. When the compressor 2E sends compressed gas CG into the first pressure feed pipe 81, a plug flow (turbulent flow) is generated inside the first pressure feed pipe 81, and the air flows toward the expansion pipe 82. A state is reached in which the phase portion 93 (compressed gas CG) and the liquid phase portion 94 (soil 90) alternately flow through the first pressure feeding pipe 81. When the soil 90 is sent from the first pressure feed pipe 81 to the expansion pipe 82, the internal pressure in the expansion pipe 82, which has a relatively large diameter, is lower than that in the first pressure feed pipe 81, so that no plug flow is temporarily generated. state.

In the expansion tube 82, a solidification material 91 is added to the soil 90 by a solidification material supply device 83. The soil 90 to which the solidification material 91 has been added gradually flows toward the second pressure feeding pipe 84 by the compressed gas CG sent from the compressor 2E. In the second pressure feeding pipe 84, the internal pressure is higher than that of the expansion pipe 82, so that a plug flow is generated, and the gas phase part 93 (compressed gas CG) and the liquid phase part 94 (soil 90 and solidified material 91) alternately flow through the second pressure feed pipe 84. Due to the plug flow generated within the second pressure feed pipe 84, the soil 90 and the solidification material 91 are stirred and mixed during the process of being fed within the second pressure feed pipe 84, and improved soil 92 is formed. The improved soil 92 formed within the second pumping pipe 84 is then pumped to a landfill or the like.

Conventionally, air compressed by an air compressor is sent into the first pressure feed pipe 81. On the other hand, in the in-pipe mixing method to which the present invention is applied, the compressor 2E sends compressed gas CG, which has a higher volume ratio of carbon dioxide C than the air at the construction site, to the first pressure-feeding pipe 81. . In this embodiment, a high-pressure container 1 (1G) in which carbon dioxide C is stored in advance is connected to a compressor 2E, and carbon dioxide C is supplied from the high-pressure container 1G to the compressor 2E.

As described above, when the present invention is applied to the in-pipe mixing system 80, compressed gas CG having a higher volume ratio of carbon dioxide C than the air at the construction site is sent to the first pressure-feeding pipe 81 by the compressor 2E. By doing so, the unimproved soil 90 that is fed in the first pressure feeding pipe 81, the unimproved soil 90 and solidification material 91 (mixed material) that is fed in the expansion pipe 82, and the second forced feeding pipe 84. Carbon dioxide C can be effectively mixed into the improved soil 92 (improved soil) sent inside the soil. By using the improved soil 92 mixed with carbon dioxide C for the creation of a landfill, etc., carbon dioxide C can be stored in the improved soil. In addition, in the in-pipe mixing system 80, since the internal pressure in the first pressure feed pipe 81 and the second pressure feed pipe 84 is relatively high, by delivering compressed gas CG with a high volume ratio of carbon dioxide C, Carbon dioxide C can be effectively mixed into the soil 90 before improvement and the improved soil 92.

If carbon dioxide C is supplied to the compressor 2E using the high-pressure container 1G as in this embodiment, the in-pipe mixing method to which the present invention is applied can be implemented very simply. Further, the use of the high-pressure container 1G is advantageous in increasing the volume ratio of carbon dioxide C in the compressed gas CG sent from the compressor 2E.

The method of supplying carbon dioxide C to the compressor 2E is not limited to the case where the high-pressure container 1G is used. Carbon dioxide C can also be supplied to the compressor 2E. The machines used in the in-pipe mixing method include a mud pump and compressor 2E that feed the soil 90 before improvement to the first pressure feed pipe 81, a solidification material supply device 83, and a generator that supplies electricity to each device. For example, In particular, in the in-pipe mixing method, the amount of carbon dioxide C emitted by the compressor 2E and the diesel engine of the ship is relatively large, so the carbon dioxide C emitted by the compressor 2E and the diesel engine of the ship is mixed into the mixture. When used as carbon dioxide C, it is possible to effectively reduce carbon dioxide C emitted into the atmosphere in the in-pipe mixing method. Furthermore, when exhaust gas emitted by machines used at the construction site is used, the soil 90 and improved soil 92 can be heated by the heat contained in the exhaust gas during the process of pumping the soil 90 and improved soil 92. Being able to heat the improved soil 92 is advantageous in shortening the curing period of the improved soil 92.

In the embodiment illustrated in FIG. 6, the carbon dioxide underground storage method of the present invention is applied to the high-pressure injection stirring method.

In the high-pressure injection stirring method, a rod 101 inserted into the ground is rotated and water is injected from an injection port 101a provided at the tip of the rod 101, and water is compressed from an injection port 101b provided at the tip of the rod 101. The gas and improving material 110 are ejected. As a result, the soil in the ground G is cut, most of the cut soil is discharged to the ground by the air lift effect, and the remaining soil is mixed with the improvement material 110. (improved soil).

The high-pressure injection stirring system 100 used in the high-pressure injection stirring method includes a rod 101 inserted into the ground G, a control device 102 that supports the rod 101 and controls the vertical movement and rotational drive of the rod 101, and It includes a water pressure feeding device 104 that pumps water to a water pipe 103 connected to the injection port 101a. The high-pressure injection stirring system 100 further includes a compressor 2 (2F) that supplies compressed gas CG to an air supply pipe 105 connected to the jet port 101b of the rod 101, and an improved material to a supply pipe 106 connected to the jet port 101b. 110, and a mud removal pump 108 that discharges muddy water 111. An excavation blade 101c is provided at the tip of the rod 101, and an injection port 101a and an injection port 101b are provided above the excavation blade 101c, respectively.

Conventionally, air compressed by an air compressor is sent to the air pipe 105. In contrast, in this embodiment, the compressor 2F sends compressed gas CG, which has a higher volume ratio of carbon dioxide C than the air at the construction site, to the air pipe 105. In this embodiment, a high-pressure container 1 (1H) in which carbon dioxide C is stored in advance is connected to the compressor 2F, and carbon dioxide C is supplied from the high-pressure container 1H to the compressor 2F.

In addition, conventionally, the water pressure feeding device 104 is configured to force feed water to the water pipe 103, but in this embodiment, the water pressure feeding device 104 is used to pump water into the water pipe 103 using a carbonic acid solution CW (carbon dioxide solution) in which carbon dioxide C is dissolved. water).

The specific work procedure of the high-pressure injection stirring method is explained below. The rod 101 is rotated by the control device 102, and the rod 101 is inserted into the ground while cutting the ground G with the excavation blade 101c. When the tip of the rod 101 reaches a predetermined depth to be improved, water is transferred from the water pressure feeding device 104, compressor 2F, and improvement material supply device 107 to the water pipe 103, air pipe 105, and supply pipe 106, which are connected to each other, respectively. A carbonic acid solution CW, a gas CG compressed by increasing the volume ratio of carbon dioxide C, and an improvement material 110 are supplied. Then, while rotating and moving the rod 101 up and down, the carbonic acid solution CW is injected from the injection port 101a provided at the tip of the rod 101, and the compressed gas CG and the improvement material 110 are ejected from the injection port 101b.

The carbonate solution CW injected laterally from the injection port 101a and the compressed gas CG ejected laterally from the injection port 101b cut the soil in the ground, and most of the cut soil is removed. rises toward the ground through the gap on the side of the rod 101 due to the air lift effect caused by the carbonic acid solution CW and the compressed gas CG. The muddy water 111 that has risen to the ground is discharged to the outside by the mud removal pump 108. As the improvement material 110 is ejected from the spout 101b of the rotating rod 101, the soil remaining in the ground and the improvement material 110 are mixed, and an improved body is formed in the ground G. Then, after forming the improved body, the rod 101 is pulled out from the ground G to complete the construction.

As described above, when the present invention is applied to the high-pressure injection stirring construction method, the compressor 2F blows out gas CG with a higher volume ratio of carbon dioxide than the air at the construction site into the ground G, thereby improving the soil after improvement. Carbon dioxide C can be effectively mixed into the mixture and the surrounding soil, and carbon dioxide C can be stored in the improved soil. Since carbon dioxide C contained in gaseous CG dissolves in the soil after improvement and the moisture in the soil, a large amount of carbon dioxide C can be stored in the soil after improvement.

In addition, by injecting the carbonic acid solution CW in which carbon dioxide C is dissolved into the ground G using the water pumping device 104, it is possible to mix carbon dioxide C into the improved soil (mixture material) and the surrounding soil. It is possible to store carbon dioxide C in the soil after improvement. Furthermore, by using the carbonic acid solution CW, it is possible to enhance the air lift effect of lifting the cut soil, which is advantageous for discharging the cut soil more efficiently. For example, the high pressure container 1 may be connected to the water pressure feeding device 104, and the carbon dioxide C supplied from the high pressure container 1 to the water pressure feeding device 104 may be dissolved in the water force fed from the water pressure feeding device 104.

If carbon dioxide C is supplied to the compressor 2F using the high-pressure container 1H as in this embodiment, the high-pressure injection stirring method to which the present invention is applied can be implemented very simply. Further, the use of the high-pressure container 1H is advantageous in increasing the volume ratio of carbon dioxide C in the compressed gas CG sent from the compressor 2F.

The method of supplying carbon dioxide C to the compressor 2F is not limited to the case where the high-pressure container 1H is used. For example, carbon dioxide C discharged by a machine used at a construction site can also be supplied to the compressor 2F. Examples of machines used in the high-pressure injection stirring method include the control device 102, the water pressure feeding device 104, the compressor 2F, the improvement material supply device 107, the sludge pump 108, and the generator that supplies electricity to each device. In particular, in the high-pressure injection agitation method, the amount of carbon dioxide emitted by the compressor 2F is relatively large, so using the carbon dioxide C emitted by the compressor 2F can effectively reduce carbon dioxide C in the high-pressure injection agitation method. . Further, when exhaust gas discharged from machines used at the construction site is used, the improvement material 110 can be heated by the heat contained in the exhaust gas. Being able to heat the improvement material 110 is advantageous in shortening the curing period of the soil after improvement. For example, a configuration may be adopted in which the water pressure feeding device 104 is supplied with carbon dioxide C discharged by machines used at the construction site.

Note that the method of mixing carbon dioxide C in each of the construction methods exemplified above can be appropriately selected and adopted depending on the construction conditions and the like. Furthermore, the method for storing carbon dioxide in soil of the present invention is not limited to the methods exemplified above, but can be applied to other methods as long as they improve soil.

1, 1A to 1H High pressure container 2, 2A to 2F Compressor 10 Raw soil 11 Mud water 12 Solidifying material 13 Foaming foam 14 Lightweight soil kneading machine 15 Lightweight ground material 16 Casting machine 24 Foaming agent 25 Water 26 Diluent 28 Foaming machine 31 Pressure pump 32 Pressure pipe 40 Injection pipe 41 Bubbles 50 Deep mixing machine 50a Rod 50b Stirring blade 50c Discharge port 51 Improved material 52 Mixer 53 Pressure pump 54 Water 55 Hardening material 56 Additive 60 Sludge feeding system 61 Shearing machine 62 Vibration Sieve 63 Stirrer 64 Quantitative feeder 65 Assisting pump 66 Pressure feed pipe 67 Prime mover 70 Soil 80 In-pipe mixing system 81 First pressure feed pipe 82 Expansion tube 83 Solidifying material supply device 84 Second pressure feeding pipe 90 Soil 91 Solidifying material 92 Improvement Soil 100 High-pressure injection stirring system 101 Rod 102 Control device 103 Water pipe 104 Water pressure feeding device 107 Improvement material supply device 110 Improvement material 111 Mud water C Carbon dioxide CG (with a higher volume ratio of carbon dioxide than air) Gas CW Carbonic acid solution G ground

Claims (4)

A gas with a higher volume ratio of carbon dioxide than the air at the construction site, or carbon dioxide, is added to at least one of the soil before improvement, the mixed material to be mixed with the soil to be improved, or the soil after improvement. A method for storing carbon dioxide in soil, characterized in that the carbon dioxide is stored in improved soil by mixing a dissolved carbonic acid solution and mixing the carbon dioxide into the mixture. 2. The method for storing carbon dioxide in soil according to claim 1, wherein the carbon dioxide stored in advance is used as the carbon dioxide in the gas or in the carbonic acid solution. 3. The method for storing carbon dioxide in soil according to claim 1, wherein the carbon dioxide discharged by a machine used at a construction site is used as the carbon dioxide in the gas or in the carbonic acid solution. The method for storing carbon dioxide in soil according to claim 1 or 2, wherein the gas having a volume ratio of carbon dioxide of 0.4% or more is mixed with the mixture.

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