JP2011005378A - Method of storing carbon dioxide in the ground - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably store/isolate undissolved carbon dioxide in an aquifer for a long time, and to greatly reduce the amount of a solvent used therefor.SOLUTION: The mass ratio of undissolved carbon dioxide to be mixed into water saturated with carbon dioxide is determined by the following steps (1) to (3) so that a first storage zone for storing undissolved carbon dioxide together with water saturated with carbon dioxide is formed around the circumference of an injection well in an aquifer and a second storage zone for exclusively storing water saturated with carbon dioxide is roughly concentrically formed in a manner of surrounding the first storage zone in the aquifer respectively, under a condition of storing/isolating water saturated with carbon dioxide as well as undissolved carbon dioxide: (1) a step of measuring the degree of saturation by volume of carbon dioxide, which is defined as the volume ratio of undissolved carbon dioxide storable relative to the volume of the void present in the aquifer, (2) a step of setting the volume of the first storage zone and the volume of the second storage zone, and (3) a step of determining the mass ratio of the undissolved carbon dioxide to be mixed into the water saturated with carbon dioxide based on the degree of saturation by volume of carbon dioxide measured in the step (1), and on the volumes of the first and the second storage zones set in the step (2).

Description

  The present invention contributes to the reduction of carbon dioxide, which is one of the greenhouse gases that cause global warming, so that the carbon dioxide separated and recovered from a large-scale emission source of carbon dioxide, etc. is treated with seawater and / or When dissolved in a solvent consisting of water and injected into the ground, by mixing undissolved carbon dioxide gas at a predetermined ratio with respect to carbon dioxide-dissolved water in which carbon dioxide gas is dissolved in the vicinity of the saturated concentration in the solvent, The present invention relates to a carbon dioxide underground storage method in which carbon dioxide gas is stably stored and the amount of solvent used is reduced.

  Conventionally, when storing carbon dioxide separated and recovered from exhaust gas in an oil field, gas field, or aquifer that is depleted in the ground, as described in Non-Patent Documents 1 and 2 below, Attempts have been made to compress it into a liquid or supercritical state and press it into the ground through an injection well. In general, this carbon dioxide gas is injected into a reservoir with a depth of 800 m or more to maintain the supercritical state of carbon dioxide gas (in the case of carbon dioxide, the temperature is 31 ° C or higher, the pressure is 7.4 MPa or higher), and the density of the carbon dioxide gas is increased. And efficient storage.

  However, supercritical carbon dioxide has a lower specific gravity than the surrounding groundwater and moves upward by buoyancy, so the shape of the aquifer that stores carbon dioxide is dome-shaped, and the carbon dioxide that has floated in the upper center is It was necessary to form a sealing layer (cap lock) to be trapped. However, in oil and gas fields, it is generally confirmed that the reservoir has a trap structure that is a combination of the seal layer and the dome shape, but it is possible to find an aquifer that meets the conditions in nature. It has become a challenge. For this reason, there has been a demand for a method for expanding the applicable conditions and storing and isolating carbon dioxide in the ground for a long term and stably without rising.

On the other hand, as a method of pressurizing carbon dioxide into the ground, carbon dioxide boosted by a CO ₂ booster and water pressurized by a pump are introduced into the pipe from the top of the pipe penetrating from the ground surface into the ground. Including the method described in Patent Document 1 described below, which is injected while being mixed and mixed, and the method described in Patent Document 2 described below, wherein carbon dioxide is dissolved in water by a mixer in the underground layer of a gas field or oil field, including carbon dioxide gas There exists the method of the following patent document 3, etc. which make gas microbubble and disperse | distribute it in water or seawater, and isolate | separate the carbon dioxide gas made into microbubble on the ground. In any of these methods, a seawater or water solvent and carbon dioxide are injected into the aquifer, and the carbon dioxide is dissolved in the solvent and stored in the aquifer.

  However, in the methods described in Patent Documents 1 to 3, carbon dioxide gas is dissolved in a solvent at a high concentration level, so that the specific gravity is heavier than that of the surrounding groundwater. It can be stably stored and sequestered, but if the solvent is only water or the dissolution means is “Merging”, “Mixer”, “Microbubble generator”, depending on the dissolution conditions, the dissolution concentration of carbon dioxide gas The level was considered insufficient, and there was a risk that the specific gravity could not be increased more than the surrounding groundwater.

  Therefore, in the following Patent Document 4, the applicant of the present invention disclosed a carbon dioxide gas compression device that compresses carbon dioxide gas to a liquid or supercritical state, a pressure feed pump that compresses and conveys a solvent composed of seawater and / or water, and the compressed gas. One or a plurality of dissolution tanks in which carbon dioxide gas and a solvent are injected, and the carbon dioxide gas is dissolved in the solvent to form carbon dioxide-dissolved water, and the generated carbon dioxide-dissolved water is pressed into the ground aquifer. A carbon dioxide underground storage system composed of an injection well penetrating from the surface to the aquifer is proposed, and as a second configuration pattern, the maximum weight of the solvent is expected in the hope of dissolving carbon dioxide in groundwater. We proposed a carbon dioxide underground storage system that injects 5% undissolved carbon dioxide into the underground aquifer.

  Further, in the following Patent Document 5, the applicant of the present invention has provided a carbon dioxide gas supply line inside a main flow line through which a solvent is flowed at a predetermined high flow rate, and the like, and a wall surface of the pipe line that partitions the solvent and the carbon dioxide gas. A high-pressure carbon dioxide gas bubbler was proposed, in which pores are formed in the gas and mixed while the carbon dioxide gas is bubbled by the shearing force of the solvent flowing through the main flow line. According to such a fine foaming apparatus, carbon dioxide gas can be finely foamed and mixed in a solvent with high processing capacity under a high pressure condition.

  Also, in recent years, as disclosed in Patent Document 6 below, there is an underground feeding method of liquefied carbon dioxide gas in which liquefied carbon dioxide gas is mixed into fine water droplets and mixed, and a two-component mixed fluid is injected into the ground. Proposed. At this time, carbon dioxide in the form of fine droplets is trapped as residual droplets in the rock when adsorbed on the surface of rock minerals or due to the capillary effect, but becomes fine bubbles due to changes in pressure and temperature conditions It is described that carbon dioxide is easily dissolved in the surrounding groundwater.

JP-A-6-170215 JP-A-3-258340 JP 2004-50167 A JP 2008-238054 A JP 2009-112995 A JP 2009-11964 A

IPCC, “IPCC Special Report on Carbon Dioxide Capture and Storage”, Chapter 5, 2005, Cambridge University Press Shinichi Ozeki, Koji Kano, “Towards the realization of“ CO2 underground storage ”business-Expectations for upstream oil and natural gas technologies”, “Oil / Natural gas review”, Independent administrative agency Petroleum natural gas and metal minerals Resource Organization, 2006.7, vol.40 No.4, p57-70

  As disclosed in Patent Documents 4 to 6, even when carbon dioxide is not dissolved in a solvent and is injected into an underground aquifer in the state of undissolved carbon dioxide, It has been clarified that it is trapped in the aquifer as residual droplets in the rock due to adsorption to the surface and capillary effect, and it is stably stored and isolated.

  Based on this knowledge, as a result of further extensive research by the present inventors, the ground conditions and the pressure / temperature conditions in the aquifer, If the mass ratio of undissolved carbon dioxide gas to carbon dioxide-dissolved water is not properly controlled according to the storage area of carbon dioxide-dissolved water and undissolved carbon dioxide gas formed in the water layer, it will be pressed into the aquifer. It has been predicted that there may be cases where it becomes impossible or wastes energy.

  Moreover, it can also be expected that the amount of the solvent used is reduced by increasing the mass ratio of the undissolved carbon dioxide mixed in the carbon dioxide-dissolved water from 5% of the solvent weight.

  Therefore, the main problem of the present invention is to stabilize the undissolved carbon dioxide gas in the aquifer by determining the appropriate mass ratio of undissolved carbon dioxide gas mixed in the carbon dioxide-dissolved water according to the ground conditions of the aquifer. It is intended to provide a method for underground storage of carbon dioxide gas that can be stored and sequestered for a long period of time and in which the amount of solvent used is greatly reduced.

In order to solve the above-mentioned problem, as the present invention according to claim 1, undissolved carbon dioxide gas is mixed in a predetermined ratio with respect to carbon dioxide-dissolved water obtained by dissolving carbon dioxide in a solvent at a saturation concentration. A carbon dioxide underground storage method for press-fitting into an aquifer and storing and isolating the carbon dioxide-dissolved water and undissolved carbon dioxide in the ground,
In the aquifer, the carbon dioxide dissolved water and the undissolved carbon dioxide gas are stored and separated around the injection well, and the carbon dioxide is concentrically formed so as to surround the first reservoir area. Under the condition of storing and isolating the carbon dioxide-dissolved water and the undissolved carbon dioxide so as to form the second storage region only by the gas-dissolved water, the undissolved carbon dioxide mixed in the carbon dioxide-dissolved water is obtained. Provided is a method for underground storage of carbon dioxide gas, wherein the mass ratio is determined by the following procedures (1) to (3).
(1) The volume saturation rate of carbon dioxide gas, defined as the volume ratio of undissolved carbon dioxide gas that can be stored in the gap volume of the aquifer, is measured by laboratory tests using raw ground material collected from the aquifer. Or a first procedure for estimating the volume saturation of the carbon dioxide gas based on the accumulated performance data.
(2) A second procedure for setting the volume of the first storage area and the volume of the second storage area.
(3) A third procedure for determining a mass ratio of undissolved carbon dioxide mixed in carbon dioxide-dissolved water based on the volume saturation rate of the carbon dioxide and the volumes of the first storage region and the second storage region.

  In the first aspect of the invention, in determining the mass ratio of the undissolved carbon dioxide mixed in the carbon dioxide-dissolved water, the first procedure for measuring or estimating the volume saturation of the carbon dioxide, the volume of the first storage region And the second procedure for setting the volume of the second storage area, based on the volume saturation of the carbon dioxide gas and the volumes of the first storage area and the second storage area, undissolved carbon dioxide mixed into the carbon dioxide dissolved water The third procedure for determining the mass ratio of gas is a constituent element.

  Specifically, in the first procedure, the characteristics of the ground material are measured or estimated in consideration of the aquifer porosity, groundwater pressure, temperature, and the like.

  In the second procedure, the aquifer is considered in consideration of the aquifer distribution (area, layer thickness), porosity, groundwater pressure, temperature, carbon dioxide saturation, carbon dioxide mass ratio of carbon dioxide dissolved water, etc. The volume of each storage area in the layer is set.

  In the third procedure, aquifer distribution (area, layer thickness), porosity, groundwater pressure, temperature, permeability, carbon dioxide dissolved water and carbon dioxide relative permeability, capillary pressure characteristics, groundwater salt concentration, etc. Checking the storage status of undissolved carbon dioxide and carbon dioxide dissolved water in the aquifer by intrusion flow analysis considering various characteristics in the aquifer and the amount of carbon dioxide dissolved water and undissolved carbon dioxide injected. To determine whether it can be injected or not, and evaluate the effects of mixing undissolved carbon dioxide mainly from the economic point of view, such as equipment construction costs, energy usage, and solvent (seawater, etc.) usage. The mass ratio of undissolved carbon dioxide mixed in the final carbon dioxide-dissolved water is determined by determining whether or not the storage conditions are satisfied.

  By injecting carbon dioxide-dissolved water mixed with undissolved carbon dioxide at an optimal mass ratio in this way, undissolved carbon dioxide is captured at a constant rate in the gap of the aquifer in addition to dissolving in groundwater. (traps) is, it becomes possible storage and sequestration stably and long-term.

  As will be described in detail later, the mass proportion of undissolved carbon dioxide mixed in the carbon dioxide-dissolved water is the amount of carbon dioxide stored in the aquifer, the carbon dioxide saturation rate, the porosity of the aquifer, and the groundwater pressure.・ It can be increased up to about 25% depending on temperature and other conditions, and can be increased from 5% of the solvent weight so far, and the energy consumption can be reduced by reducing the amount of solvent used. become able to.

As the present invention according to claim 2, a carbon dioxide gas compression device that compresses carbon dioxide gas to a liquid or supercritical state, a pressure feed pump that compresses and conveys a solvent composed of seawater and / or water, and the compressed carbon dioxide and In order to press-fit one or a plurality of dissolution tanks in which a solvent is injected and the carbon dioxide gas is dissolved in the solvent to form carbon dioxide-dissolved water, and the carbon dioxide-dissolved water and undissolved carbon dioxide are injected into the underground aquifer. And an injection well penetrating from the ground surface to the aquifer,
The dissolution tank includes a carbon dioxide gas inlet through which a carbon dioxide gas sent from the carbon dioxide compressor is injected into a lower part of a sealed container, and a solvent inlet through which a solvent sent from the solvent pump is injected. And a carbon dioxide underground storage system in which a discharge port for discharging the carbon dioxide-dissolved water is formed in an upper portion of the container, and the container is filled with a granular filler. make use of,
In the middle of the flow path from the dissolution tank to the injection well, undissolved carbon dioxide gas and carbon dioxide-dissolved water in which carbon dioxide gas is dissolved at a saturated concentration are separated from the total amount of carbon dioxide-dissolved water fed. A separation tank, an undissolved carbon dioxide pressure feeding device that pumps the undissolved carbon dioxide gas separated in the separation tank, a branching device that branches the undissolved carbon dioxide gas fed from the undissolved carbon dioxide pressure feeding device, and the separation The carbon dioxide dissolved water separated in the tank is provided with a junction for mixing the undissolved carbon dioxide branched by the branching device, and mixed in the carbon dioxide dissolved water among the undissolved carbon dioxide by the branching device. A predetermined amount to be branched and pumped to the merging point so that undissolved carbon dioxide gas is mixed into the carbon dioxide dissolved water at a predetermined ratio and press-fitted into the underground aquifer. A method for underground storage of carbon dioxide is provided.

  The invention described in claim 2 is defined for the first embodiment of the underground storage system used in the underground storage method described in claim 1, and is sent in the middle of the flow path from the dissolution tank to the injection well. A separation tank that separates undissolved carbon dioxide gas and carbon dioxide-dissolved water in which carbon dioxide gas is dissolved at a saturated concentration with respect to the total amount of carbon dioxide-dissolved water supplied, and undissolved carbon dioxide gas separated in the separation tank An undissolved carbon dioxide gas feeding device for feeding the water, a branch device for branching the undissolved carbon dioxide gas fed from the undissolved carbon dioxide gas feed device, and the carbon dioxide dissolved water separated in the separation tank by the branch device. The underground storage system provided with the junction where the branched undissolved carbon dioxide gas is mixed is used. When this underground storage system is used, the carbon dioxide-dissolved water is obtained by branching a predetermined amount mixed in the carbon dioxide-dissolved water out of the undissolved carbon dioxide by the branching device and pumping it to the junction. On the other hand, undissolved carbon dioxide gas is mixed at a predetermined ratio and pressed into the underground aquifer.

  Thus, by providing the separation tank in the middle of the flow path from the dissolution tank to the injection well, the carbon dioxide dissolved water separated in the separation tank can be used as the carbon dioxide dissolved water to be pressed into the aquifer, Carbon dioxide-dissolved water in which carbon dioxide is dissolved in a state that is close to saturation concentration can be surely injected into the ground, and undissolved carbon dioxide separated in the separation tank can be accurately added to this carbon dioxide-dissolved water at a specified ratio. It becomes possible to mix well.

As the present invention according to claim 3, a carbon dioxide gas compression device that compresses carbon dioxide gas to a liquid or supercritical state, a pressure feed pump that compresses and conveys a solvent composed of seawater and / or water, and the compressed carbon dioxide and In order to press-fit one or a plurality of dissolution tanks in which a solvent is injected and the carbon dioxide gas is dissolved in the solvent to form carbon dioxide-dissolved water, and the carbon dioxide-dissolved water and undissolved carbon dioxide are injected into the underground aquifer And an injection well penetrating from the ground surface to the aquifer,
The dissolution tank includes a carbon dioxide gas inlet through which a carbon dioxide gas sent from the carbon dioxide compressor is injected into a lower part of a sealed container, and a solvent inlet through which a solvent sent from the solvent pump is injected. And a discharge port through which the carbon dioxide-dissolved water is discharged is formed at the top of the container, and the container is filled with a granular filler,
Using the carbon dioxide underground storage system in which the carbon dioxide dissolved water discharged from the dissolution tank is injected into the underground aquifer in the state containing undissolved carbon dioxide as it is,
By controlling the mass of the carbon dioxide gas fed by the carbon dioxide compressor and the mass of the solvent fed by the solvent pump, respectively, undissolved carbon dioxide is mixed in the carbon dioxide-dissolved water at a predetermined ratio. Then, the underground storage method for carbon dioxide gas according to claim 1, which is press-fitted into the underground aquifer.

  The invention according to claim 3 is defined for the second embodiment of the underground storage system used in the underground storage method according to claim 1, and the carbon dioxide dissolved water discharged from the dissolution tank is undissolved. It uses an underground storage system that press-fits the underground aquifer while containing carbon dioxide. When this underground storage system is used, the mass of carbon dioxide pumped by the carbon dioxide compressor and the mass of solvent pumped by the solvent pump are respectively controlled, so that Dissolved carbon dioxide gas can be mixed at a predetermined ratio and injected into the underground aquifer. Therefore, the amount of carbon dioxide supplied to the underground storage system can be managed in an integrated manner.

  As a fourth aspect of the present invention, the carbon dioxide gas supply line is disposed in the main stream line in which the solvent is allowed to flow at a predetermined high flow rate, or the main stream line is disposed upstream of the dissolution tank. The carbon dioxide gas supply pipe line that fits outside is provided, pores are formed on the wall surface of the pipe line that partitions the solvent and carbon dioxide gas, and the carbon dioxide gas is finely bubbled by the shearing force of the solvent flowing through the main flow pipe line. The carbon dioxide gas underground storage method according to claim 3, wherein a high-pressure carbon dioxide gas bubble generation device that is mixed while being converted is installed.

  In the invention described in claim 4, the underground storage system according to the second embodiment in which the carbon dioxide dissolved water discharged from the dissolution tank is press-fitted into the underground aquifer while containing undissolved carbon dioxide as it is. In the above, the high-pressure carbon dioxide gas bubble generation device is installed in the previous stage of the dissolution tank. By installing the high-pressure carbon dioxide fine foaming device, carbon dioxide-dissolved water can be injected into the aquifer in a state where carbon dioxide is dissolved in a solvent (such as seawater) at a high concentration near the saturation concentration level. become.

  The high-pressure carbon dioxide gas bubbler has a structure in which carbon dioxide gas is mixed into the solvent while making it finer by the shearing force of the solvent flowing through the main flow line, so that the high pressure state is maintained without pressure release. In this state, carbon dioxide gas can be mixed into the solvent efficiently and with high processing capacity. Furthermore, since the structure is a combination of pipe lines, it can be easily incorporated into the pipeline.

The present invention according to claim 5 is characterized in that the flow rate of the solvent and the pore diameter of the pores are set so that the Weber number (We) obtained by the following formula (5) is 10 or more. A method for underground storage of carbon dioxide gas is provided.

  In the invention according to the fifth aspect, in accordance with Example 2-3 described later, when setting the flow rate of the solvent and the pore diameter of the pores, the Weber number (We) is set to 10 or more so that the carbon dioxide gas is efficiently and and fine foaming at a high throughput, it is possible to provide a high dissolution efficiency.

  The present invention according to claim 6 is the carbon dioxide gas according to any one of claims 2 to 5, wherein the granular filler filled in the dissolution tank is any one or a combination of sand, crushed stone, Raschig ring, and saddle. An underground storage method is provided.

  In the invention described in claim 6, as the granular filler filled in the dissolution tank, for example, any one of sand, crushed stone, Raschig ring, and saddle or a combination thereof is used.

  As the present invention according to claim 7, the granular filler to be filled in the dissolution tank is, for each type of filler, a carbon dioxide dissolution amount determined based on the flow rates of carbon dioxide and solvent and the shape of the dissolution tank. A carbon dioxide underground storage method according to any one of claims 2 to 6, wherein the average particle size is determined based on the pressure loss in the dissolution tank.

  In the invention of claim 7, the granular filler is, for each type of filler, the amount of carbon dioxide dissolved based on the flow rates of carbon dioxide and solvent and the shape of the dissolution tank, and the pressure loss in the dissolution tank. The average particle size determined from the above is used, and when the average particle size is the above-mentioned optimal average particle size, the dissolution efficiency is excellent.

  As the present invention according to claim 8, in the melting tank, one or a plurality of rectifying plates in which a large number of openings are formed so as to partition the flow path are provided in the filling region of the filler. 7-geological storage method carbon dioxide according to any one is provided.

  In the invention according to the eighth aspect, by providing the current plate, the dissolution of carbon dioxide gas in the dissolution tank is promoted.

  As described above in detail, according to the present invention, the undissolved carbon dioxide gas is removed from the aquifer by determining the appropriate mass ratio of the undissolved carbon dioxide gas mixed in the carbon dioxide-dissolved water according to the ground conditions of the aquifer. In addition, it is possible to provide a method for underground storage of carbon dioxide gas that can be stored and sequestered stably and for a long period of time and the amount of solvent used is greatly reduced.

It is a key map of underground storage system 1A (the 1st form example). It is a longitudinal cross-sectional view of the dissolution tank 4. 3 is a longitudinal sectional view of a separation tank 6. FIG. It is a plane conceptual diagram of the storage area in an aquifer. It is a cross-sectional conceptual diagram of the storage area | region in an aquifer. It is a schematic diagram which shows the storage state of the carbon dioxide gas in an aquifer. It is a flowchart (1st form example) which determines the mass ratio R of the undissolved carbon dioxide mixed in carbon dioxide dissolved water. It is a conceptual diagram of an experimental apparatus. It is a graph which shows the time-dependent change of the volume saturation of the carbon dioxide gas in the filler A and the test temperature of 25 degreeC. It is a graph which shows the time-dependent change of the volume saturation of the carbon dioxide gas in the filler A and the test temperature of 33 degreeC. It is a graph which shows the time-dependent change of the volume saturation of the carbon dioxide gas in the filler B and the test temperature of 25 degreeC. It is a graph which shows the time-dependent change of the volume saturation of the carbon dioxide gas in the filler B and the test temperature of 33 degreeC. Fillers A, is a graph showing the time course of the amount of dissolution of carbon dioxide in the test temperature 25 ° C.. Fillers A, is a graph showing the time course of the amount of dissolution of carbon dioxide in the test temperature 33 ° C.. Fillers B, and a graph showing the temporal change of the amount of dissolution of carbon dioxide in the test temperature 25 ° C.. Fillers B, and a graph showing the temporal change of the amount of dissolution of carbon dioxide in the test temperature 33 ° C.. Is a graph showing an example of calculation of the mass ratio R of undissolved carbon dioxide gas to be mixed into the carbon dioxide gas dissolved water. It is a conceptual diagram of underground storage system 1B (second embodiment). It is a longitudinal cross-sectional view of 7 A of fine foaming apparatuses. It is a longitudinal cross-sectional view of the fine foaming apparatus 7B. It is a longitudinal cross-sectional view of 7 C of fine bubble apparatuses. 3 is a longitudinal sectional view of the dissolution tank 4. FIG. It is a flowchart (2nd form example) which determines the mass ratio R of the undissolved carbon dioxide mixed in carbon dioxide dissolved water. It is a graph which shows the relationship between the carbon dioxide gas / salt water weight ratio when changing the conditions of the particle size and salt water flow rate in the temperature of 29 degreeC in Example 1, and a carbon dioxide dissolved amount. It is a graph which shows the relationship between the carbon dioxide gas / salt water weight ratio when changing the conditions of the particle size and salt water flow rate in the temperature of 33 degreeC in Example 1, and a carbon dioxide dissolved amount. It is a graph which shows the relationship between the carbon dioxide gas / salt water weight ratio when changing the conditions of the pressure in 25 degreeC in Example 1, and the flow rate of salt water, and a carbon dioxide dissolved amount. It is a graph which shows the relationship between the carbon dioxide gas / salt water weight ratio and the amount of carbon dioxide dissolved when the pressure at a temperature of 29 ° C. and the salt water flow rate in Example 1 are changed. It is a graph which shows the relationship between the carbon dioxide gas / salt water weight ratio when changing the conditions of the pressure in 33 degreeC in Example 1, and the flow rate of salt water, and a carbon dioxide dissolved amount. It is a graph which shows the relationship between the temperature in Example 1, and a carbon dioxide gas dissolution amount. It is a graph which shows the relationship between the average particle diameter of the filler in Example 1, and the relationship between a carbon dioxide gas dissolution amount. It is a graph which shows a verification experiment result quantitatively about the melt | dissolution effect in the fine foaming apparatus 7 in Example 2-1, and the melt | dissolution effect in the dissolution tank 4. Graph showing the relationship between the overall capacity coefficient K _{X a} water cross section molar flow rate in Example 2-2; FIG. Is a graph (part 2) showing the relationship between overall capacity coefficient K _{X a} water cross section molar flow rate in Example 2-2. Graph showing the relationship between the overall capacity coefficient K _{X a} water cross section molar flow rate in Example 2-2 is a third. Is a graph showing the relationship between the overall capacity coefficient ratio _{K x a (B) / K} x a (NB) and Weber number We in Example 2-3.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In the underground storage method for carbon dioxide gas according to the present invention, carbon dioxide gas separated and recovered from a large-scale emission source of carbon dioxide gas, etc. is dissolved in a solvent (seawater and / or water) at a high concentration near the saturation concentration level. Undissolved carbon dioxide gas is mixed in a predetermined ratio with respect to the carbon dioxide-dissolved water and pressed into the underground aquifer, and the carbon dioxide-dissolved water and undissolved carbon dioxide are brought into the ground stably and for a long time. It is for storage and isolation.

[First embodiment]
First, the carbon dioxide underground storage method according to the first embodiment will be described. In this 1st form example, compared with the below-mentioned 2nd form example, the underground storage system to be used is different. Specifically, in the first embodiment, a junction where undissolved carbon dioxide gas is mixed with carbon dioxide-dissolved water in which carbon dioxide gas is dissolved at a saturated concentration is provided in the middle of the flow path from the dissolution tank to the injection well. It has been.

Hereinafter, the underground storage system 1A for carbon dioxide and the underground storage method using the same will be described in this order.
(Carbon dioxide underground storage system 1A)
The carbon dioxide underground storage system 1A shown in FIG. 1 converts carbon dioxide separated and recovered from a large-scale emission source of carbon dioxide into a solvent (seawater and / or water) at a high concentration near the saturation concentration level. It is for containment in the ground aquifer in a dissolved state, and for long-term and stable storage and isolation.

That is, by dissolving carbon dioxide in the solvent at a high saturation concentration level, the specific gravity is heavier than that of the surrounding groundwater, and carbon dioxide is stored and sequestered in the aquifer for a long time and stably. . For this reason, the amount of carbon dioxide dissolved is 40 to 50 kg, preferably 45 to 50 kg per 1 m ³ of the solvent.

  The pressure in the system is such that the carbon dioxide is dissolved in a liquid or supercritical state, and the carbon dioxide dissolved water is injected into the underground aquifer. Considering the injection pressure and the pressure loss of the piping system, it is desirable to maintain a high pressure state of 8 MPa or more. In general, in an aquifer, if a groundwater pressure of 5 MPa or more can be secured, it can be efficiently stored.

  As shown in FIG. 1, the underground storage system 1 </ b> A includes a carbon dioxide gas compression device 2 that compresses carbon dioxide gas to a liquid or supercritical state, and a pressure feed pump 3 that compresses and conveys a solvent composed of seawater and / or water. The compressed carbon dioxide gas and solvent are injected, the carbon dioxide gas is dissolved in the solvent to form carbon dioxide-dissolved water, and the generated carbon dioxide-dissolved water is submerged in the ground. In order to press fit into the aquifer, it is mainly composed of an injection well 5 that penetrates from the ground surface to the aquifer.

  Further, in the middle of the flow path from the dissolution tanks 4, 4... To the injection well 5, undissolved carbon dioxide and carbon dioxide dissolved at a saturated concentration with respect to the total amount of carbon dioxide dissolved water fed. The separation tank 6 for separating the carbon dioxide-dissolved water in the state, the undissolved carbon dioxide pumping apparatus 8 for pumping the undissolved carbon dioxide separated in the separation tank 6, and the pumping from the undissolved carbon dioxide pump A branch device 32 for branching undissolved carbon dioxide gas, and a junction 9 for mixing the undissolved carbon dioxide gas branched in the branch device 32 into the carbon dioxide-dissolved water separated in the separation tank 6 are provided. A predetermined amount of the undissolved carbon dioxide gas mixed into the carbon dioxide-dissolved water is branched and pumped to the junction 9 by the device 32, whereby the undissolved carbon dioxide gas is predetermined with respect to the carbon dioxide-dissolved water. Will mix and press into the underground aquifer It is obtained by the.

  Of the undissolved carbon dioxide separated in the separation tank 6, the remaining undissolved carbon dioxide branched to the junction 9 by the branch device 32 is returned to the dissolution tank 4.

  In the present embodiment, a plurality of dissolution tanks 4 are installed to promote the dissolution of carbon dioxide gas, but the number may be set according to the processing capacity.

  Moreover, in order to accelerate | stimulate melt | dissolution to the solvent of the carbon dioxide gas in the melt | dissolution tank 4 in the front | former stage of the said dissolution tank 4, you may provide the foaming apparatus 7 explained in full detail in the 2nd form example of a back | latter stage.

  As shown in FIG. 2, the dissolution tank 4 includes a carbon dioxide gas inlet 11 into which a carbon dioxide gas sent from the carbon dioxide gas compression device 2 is injected into a lower portion of a sealed container 10, and the solvent pressure pump. 3 is formed, and a discharge port 13 for discharging the carbon dioxide-dissolved water is formed in the upper portion of the container 10. The perforated plates 14 and 14 partitioning the inside of the container 10 in the vertical direction are respectively arranged on the upper side, and a granular filler 16 is filled between the perforated plates 14 and 14.

  The filler 16 is for accelerating the stirring of the solvent and the carbon dioxide gas and improving the efficiency of the dissolution of the carbon dioxide gas. For example, the filler 16 may be any one or a combination of sand, crushed stone, Raschig ring, and saddle. it can. The Raschig ring is a cylinder-shaped packing made of ceramic, plastic, metal, carbon, etc., which is used in packed towers and can be used in general. The saddle is a horseshoe-shaped packing made of ceramic or the like, and is generally formed so that the pressure loss is smaller than that of the Raschig ring.

Moreover, the said filler 16 is the optimal average determined from the amount of carbon dioxide dissolution determined based on the flow volume of a carbon dioxide gas and a solvent, and the shape of the said dissolution tank, and the pressure loss in the said dissolution tank for every kind of filler. It is preferable to use a particle size. Specifically, for each type of filler, the following two relations (1) and (2) with respect to the average particle diameter of the filler are obtained experimentally, and then the pressure loss (dissolution) allowed in the dissolution tank With respect to the pressure difference between the inlet and the outlet of the tank), an average particle size that has the largest amount of dissolution is selected as the optimum average particle size.
(1) The relationship of the amount of carbon dioxide dissolved with respect to the average particle diameter of the filler in the predetermined flow rate of carbon dioxide gas and solvent and the shape of the dissolution tank.
(2) Relationship between dissolution tank pressure loss and average filler particle size.

  Generally, the properties of the filler with respect to the average particle size are as follows: (1) Given the flow rate of carbon dioxide gas and solvent and the shape of the dissolution tank, the smaller the average particle size of the filler, the more the dissolved amount of carbon dioxide gas. To increase. (2) On the other hand, as the average particle size of the filler becomes finer, the pressure loss due to the flow of carbon dioxide and solvent in the dissolution tank increases, and the energy used to secure a constant flow rate tends to increase. There is. Therefore, the average particle size of the filler is selected after comprehensively considering the flow rates of the carbon dioxide gas and the solvent and the shape of the dissolution tank. By using the filler 16 having the optimum average particle diameter, the carbon dioxide gas is efficiently dissolved.

  As shown in FIG. 2, the container 10 is preferably a sealed vertically long tube. Thereby, it becomes possible to ensure the residence time of the carbon dioxide gas and the solvent in the dissolution tank 4. Moreover, it can be set as the structure which has pressure | voltage resistance with respect to the said setting pressure in a system, and the production | generation of a carbon dioxide dissolved water can be continuously and stably in a short time.

  Here, the flow in the dissolution tank 4 will be described. The carbon dioxide gas and the solvent pumped into the container 10 from the carbon dioxide injection port 11 and the solvent injection port 12 are mixed in the lower hopper 17 and the lower side porous. The plate 14 uniformly enters the filling region of the filler 16. In the filling region of the filler 16, the solvent and carbon dioxide are sufficiently stirred together with the flow between the fillers 16 to dissolve the carbon dioxide in the solvent and flow upward. By this action, when the upper porous plate 14 is reached, carbon dioxide-dissolved water in which carbon dioxide is substantially dissolved in the solvent is generated, and reaches the saturated dissolution level of the solvent. Thereafter, the carbon dioxide-dissolved water that has entered the upper hopper 18 from the upper porous plate 14 is discharged from the discharge port 13.

  In the dissolution tank 4, it is desirable to provide one or a plurality of rectifying plates 19 in which a large number of openings are formed so as to partition the flow path in the filling region of the filler 16. By providing the rectifying plate 19, the flow of the carbon dioxide gas and the solvent by the filler 16 is made uniform, and the dissolution of the carbon dioxide gas in the dissolution tank 4 is improved by increasing the chance of contact between them. The residence time in the dissolution tank 4 and the carbon dioxide gas dissolution amount are in a generally proportional relationship up to the saturation concentration level. Therefore, the apparatus scale is set so that the residence time according to the target dissolution amount is obtained under predetermined operating conditions. It is desirable to set.

  As shown in FIG. 3, the separation tank 6 is erected in a sealed container 20 at a predetermined height from the lower surface and connected to a flow path of carbon dioxide dissolved water that has passed through the dissolution tank 4. A tube 21 is provided, and the inside of the container 20 is substantially filled with the carbon dioxide-dissolved water so that the undissolved carbon dioxide is gravity separated upward, and the undissolved carbon dioxide gas is discharged to the upper part of the container 20. An undissolved carbon dioxide gas discharge port 22 is formed, and a carbon dioxide gas-dissolved water discharge port 23 for discharging the carbon dioxide-dissolved water after the undissolved carbon dioxide gas is separated is formed below the container 20. Yes.

  Each flow rate of the solvent and carbon dioxide gas per dissolution tank is the weight of the injected carbon dioxide gas and solvent with respect to the total flow rate determined by the volume of the dissolution tank 4 and the residence time of the carbon dioxide gas and solvent in the dissolution tank 4. It can be determined from the ratio (carbon dioxide weight / solvent weight). At this time, the weight ratio between the carbon dioxide gas and the solvent is determined based on the desired amount of carbon dioxide dissolved. The relationship between the weight ratio of the carbon dioxide gas and the solvent and the dissolved amount of the carbon dioxide gas is determined by a water flow test performed in advance.

  As will be described in detail in an example at a later stage, the dissolution concentration in the dissolution tank 4 affects the weight ratio of the injected carbon dioxide gas and the solvent (carbon dioxide weight / solvent weight). Specifically, as the weight ratio to be injected increases, the dissolution concentration in the dissolution tank 4 tends to increase. For the purpose of promoting the dissolution of carbon dioxide, the injection weight ratio of carbon dioxide and solvent is: It is preferable to set it larger than the target value of the carbon dioxide gas dissolution concentration.

(Carbon dioxide underground storage method)
Next, an underground storage method for storing and isolating carbon dioxide-dissolved water and undissolved carbon dioxide in the ground using the underground storage system 1A according to the first embodiment will be described.

  First, the principle of storage / separation in the aquifer of carbon dioxide dissolved water and undissolved carbon dioxide injected by the underground storage system 1A will be described.

  When carbon dioxide-dissolved water mixed with the undissolved carbon dioxide gas at a predetermined ratio is pressed into the aquifer in the ground, the carbon dioxide-dissolved water and undissolved carbon dioxide gas are relative to the two-phase fluid in the aquifer. according permeability, it is stored, isolated by forming a predetermined storage area. Specifically, as shown in FIGS. 4 and 5, a first storage region for storing and isolating the undissolved carbon dioxide gas together with the carbon dioxide dissolved water is formed around the injection well 5. A second storage region for storing and isolating only the carbon dioxide-dissolved water is formed substantially concentrically so as to surround one storage region. In FIG. 5, each storage region is schematically illustrated so as to form the same cross-sectional area A1 and A2 over the height h and spread evenly in a planar shape. It is predicted that the first storage region and the second storage region will diffuse substantially concentrically around the opening in the aquifer.

  More specifically, the flow in the aquifer will be described in detail. As shown in FIG. 6, undissolved carbon dioxide mixed in the carbon dioxide-dissolved water is ground material (sand) from the vicinity of the injection well 5. , Sandstone, etc.) are trapped at a certain rate of carbon dioxide saturation depending on the ground conditions. When undissolved carbon dioxide gas is injected into a section over a certain rate of carbon dioxide saturation according to the ground conditions, the range in which the undissolved carbon dioxide gas is captured (trapped) is gradually distant from the injection well 5. Expand.

  On the other hand, the carbon dioxide-dissolved water is replaced with groundwater in the gap between the ground material from the vicinity of the injection well 5 by the press-fitting, and the injection range is gradually expanded farther from the injection point.

  That is, by appropriately determining the mass ratio of the carbon dioxide-dissolved water and the undissolved carbon dioxide and press-fitting it into the ground, the undissolved carbon dioxide can be trapped at a constant rate in the gap between the ground materials. Carbon dioxide dissolved at a high concentration near the saturation concentration level can be dissolved and trapped in the aquifer. Thus, the injected carbon dioxide-dissolved water and undissolved carbon dioxide can be stored and isolated in the aquifer for a long time and stably.

  Under such conditions, the method for determining the mass ratio R of the undissolved carbon dioxide mixed in the carbon dioxide-dissolved water in the underground storage method will be described in detail.

The procedure for determining the mass ratio R is roughly divided into the following three procedures as shown in FIG.
(1) First procedure: Setting of carbon dioxide gas volume saturation rate S _{CO2 in} the aquifer In the first procedure, the aquifer was taken from the aquifer in consideration of porosity, groundwater pressure, temperature, etc. The volume saturation rate S _CO2 of carbon dioxide gas, which is defined as the volume ratio of undissolved carbon dioxide gas that can be stored in the gap volume of the aquifer, is measured or accumulated by laboratory tests using raw ground materials. Based on the above, the volume saturation rate S _CO2 of the carbon dioxide gas is estimated.

The method for setting the volume saturation rate S _CO2 of the carbon dioxide gas by the laboratory test will be described. In the experiment, as shown in FIG. 8, the carbon dioxide gas in the carbon dioxide cylinder 30 is pressurized by the carbon dioxide gas compression device 33 and is added to the dissolution tank 35. When the salt water in the salt water tank 31 is pressurized by the solvent pressure pump 34 and injected into the dissolution tank 35, the filler filled in the dissolution tank 35 is regarded as the ground material in the aquifer. By estimating the amount of undissolved carbon dioxide gas present in 35, the change with time in the volume saturation of carbon dioxide gas was determined. Here, the volume of the dissolution tank 35 is 410 ml, and the filler simulating the ground material is made of glass beads as the filler A, an average particle size of 0.60 mm, and the material as the filler B is granular sand, Experiments were conducted on two types having an average particle size of 0.18 mm. A separation tank 36 that separates into “carbon dioxide-dissolved water” and “undissolved carbon dioxide” is installed at the subsequent stage of the dissolution tank 35. When the test pressure is 10 MPa, the salt water flow rate is constant at 15 ml / min, and the test temperature and the type of the filler 16 are changed, the carbon dioxide volume saturation and the carbon dioxide dissolved water separated in the separation tank 36 are atmospheric pressure. The change over time in the amount of carbon dioxide dissolved was measured.

The volume saturation rate S _CO2 of the carbon dioxide gas was obtained from [volume of undissolved carbon dioxide gas existing in the dissolution tank 4] / [gap volume of the porous body]. Here, [volume of undissolved carbon dioxide gas existing in the dissolution tank 4] is σ ₁ : amount of carbon dioxide gas injected into the dissolution tank 4, σ ₂ : amount of undissolved carbon dioxide gas flowing out from the dissolution tank 4, Assuming that σ _{3 is the} amount of carbon dioxide dissolved in the solvent from the dissolution tank 4 and σ ₄ is the amount of carbon dioxide present dissolved in the solvent in the dissolution tank 4, (σ ₁ − (σ ₂ + σ ₃ + Σ ₄ )).

As a result, as shown in FIGS. 9 to 12, the volume of undissolved carbon dioxide gas (volume saturation rate of carbon dioxide gas) remaining in the gap between the ground materials (fillers) increases with time, and then reaches a constant value. Converge to. This converged value can be used as the volume saturation rate S _{CO2 of the} carbon dioxide gas.

  On the other hand, as is clear from the results of FIGS. 9 to 12, in the ground such as the porous body, the undissolved carbon dioxide gas is injected into the underground gap by mixing and injecting the undissolved carbon dioxide gas. remaining trapped, it was confirmed that a stable capturable.

  Further, as shown in FIGS. 13 to 16, the volume saturation rate of the undissolved carbon dioxide gas remaining in the gap between the porous bodies becomes constant, so that the amount of carbon dioxide dissolved in the solvent becomes constant.

(2) Second procedure: Setting the volume V ₁ of the first reservoir region and the volume V ₂ of the second reservoir region in the aquifer In the second procedure, the distribution (area, layer thickness), porosity, In consideration of the groundwater pressure, temperature, carbon dioxide saturation rate, carbon dioxide mass ratio of carbon dioxide dissolved water, etc., in the aquifer, undissolved carbon dioxide is stored around the injection well 5 together with carbon dioxide dissolved water. Volume ratio V ₂ / V between the volume V ₁ of the first storage area to be isolated and the volume V ₂ of the second storage area that stores and isolates the carbon dioxide-dissolved water substantially concentrically so as to surround the first storage area. ₁ is set. Here, as shown in FIGS. 4 and 5, the first storage region and the second storage region formed in the aquifer have the same cross-sectional areas A ₁ and A ₂ over a predetermined height h. Then, since the volume V ₁ = A ₁ × h of the first storage region and the volume V ₂ = A ₂ × h of the second storage region, the volume ratio V ₂ / V ₁ is the area ratio A ₂ / A _1. Can be expressed as

By setting the volume ratio V ₂ / V ₁ (area ratio A ₂ / A ₁ ), the stored mass of carbon dioxide gas in each region is obtained from the following formulas (1) and (2), and the necessary undissolved carbon dioxide gas The amount of injection can be set.

(3) Third procedure: Determination of mass ratio R of undissolved carbon dioxide mixed in carbon dioxide dissolved water to be injected In the third procedure, aquifer distribution (area, layer thickness), porosity, groundwater pressure, temperature In consideration of various characteristics in the aquifer such as permeability, relative permeability of carbon dioxide-dissolved water and carbon dioxide, capillary pressure characteristics, groundwater salt concentration, and the amount of pressurization of carbon dioxide-dissolved water and undissolved carbon dioxide The mass ratio R of undissolved carbon dioxide mixed in the carbon dioxide-dissolved water to be injected is determined.

The mass ratio R is based on the following calculation method.
S _CO2 : Volume saturation of undissolved carbon dioxide (volume ratio of undissolved carbon dioxide in the aquifer gap)
S _S : Volume saturation of carbon dioxide-dissolved water (volume ratio of carbon dioxide-dissolved water in the aquifer gap)
ρ _CO2 : density of undissolved carbon dioxide ρ _S : density of carbon dioxide dissolved water X _CO2 ^S : mass ratio of carbon dioxide dissolved in carbon dioxide dissolved water (mass fraction of carbon dioxide)
A ₁ × h: Volume of the first storage region A ₂ × h: Volume of the second storage region φ: Porosity of the aquifer In this case, carbon dioxide gas in the first storage region (undissolved carbon dioxide and carbon dioxide dissolved water) reservoir mass W ₁ of the carbon dioxide gas) dissolved in can be calculated by the following equation (1). Note that the subscript I indicates each value in the first storage area.

In addition, the storage mass W ₂ of carbon dioxide gas (carbon dioxide dissolved in carbon dioxide-dissolved water) in the second storage region can be calculated by the following equation (2). The subscript II indicates each value in the second storage area.

From the above formulas (1) and (2), the mass ratio R of the undissolved carbon dioxide mixed in the carbon dioxide dissolved water to be injected can be calculated by the following formula (3).

Here, in order to see the change of the mass ratio R,
S _SI = 1-S _CO2I
S _SII = 1
ρ _SI = ρ _SII
X _CO2I ^S = X _{CO2 II} ^S
Then, the mass ratio R can be transformed as the following formula (4).

As described above, the volume saturation rate S _CO2 of the carbon dioxide gas in the aquifer is set, and the volume ratio V ₂ / V ₁ (area ratio A ₂ / A ₁₎ of the first storage region and the second storage region in the aquifer. ), The mass ratio R of the undissolved carbon dioxide mixed in the carbon dioxide-dissolved water to be injected can be calculated from the above formula (3) or (4).

At this time, using the area ratio A ₂ / A _{1 of} the second storage region and the first storage region and the volume saturation rate S _CO2 of _{carbon dioxide} as parameters, the water pressure of the aquifer is 10 MPa, and the temperature is 40 ° C. FIG. 17 shows the result of calculating the change in the mass ratio R of the undissolved carbon dioxide mixed in the carbon dioxide-dissolved water.

  As shown in FIG. 17, undissolved carbon dioxide mixed in carbon dioxide-dissolved water according to the ground conditions by setting the volumes of the first storage region and the second storage region targeted in the second procedure. Mass ratio R can be calculated. As a result of FIG. 17, the ratio of the undissolved carbon dioxide gas and the solvent mass that are simultaneously injected depends on conditions such as the amount of carbon dioxide stored in the aquifer, the carbon dioxide saturation rate, the porosity of the aquifer, the groundwater pressure, and the temperature. depending on, is determined can be increased up to about 25%.

  In this way, since undissolved carbon dioxide can be injected into the aquifer together with carbon dioxide-dissolved water dissolved near the saturation concentration, the amount of solvent used can be reduced, and the cost required to secure the solvent In addition, the cost of pumping the solvent can be reduced. For example, if the mass of the undissolved carbon dioxide gas injected into the aquifer is 5% of the solvent mass, the mass ratio of the carbon dioxide gas dissolved in the solvent is 4 to 5%, and the mass ratio of the undissolved carbon dioxide gas is 5%. In this case, the mass ratio of the solvent necessary for storage can be suppressed to about 44 to 50%, compared with the case where the entire amount of carbon dioxide gas is dissolved.

  In addition, when the geological situation of the aquifer is complex (such as when the ground conditions vary depending on the location), the storage status of carbon dioxide gas in each division is calculated and aggregated by dividing according to the geological situation. It can be obtained similarly.

  Regarding the mass ratio R calculated by the above equation (3) or (4), the mass of undissolved carbon dioxide mixed in the carbon dioxide-dissolved water injected into the aquifer is considered in consideration of various judgment factors as described below. The ratio R is finally determined.

  As a first determination factor, as shown in FIG. 7, it is determined whether or not injection is possible after confirming the storage state of carbon dioxide-dissolved water and undissolved carbon dioxide gas in the aquifer by the intrusion flow analysis. That is, for the ground conditions of the aquifer, a graph showing the relative permeability of carbon dioxide-dissolved water relative to the water saturation and the relative permeability of undissolved carbon dioxide is obtained, and the carbon dioxide-dissolved water at an arbitrary water saturation is obtained. The flow in the aquifer is simulated from the permeability of undissolved carbon dioxide gas, and it is determined whether or not injection is possible. For example, when the injection pressure exceeds a realizable pressure, the mixing ratio of undissolved carbon dioxide gas and / or the injection range is changed, and the mass ratio R is calculated again.

  As a second determination factor, as shown in FIG. 7, when an injectable injection condition is obtained, the effect of mixing undissolved carbon dioxide gas is evaluated mainly from the aspect of economy. For example, considering the construction cost and energy used for mixing undissolved carbon dioxide, and the amount of solvent used (seawater and / or water) to be mixed, are these costs and energy excessive? Determine whether the storage conditions are optimal. If it is not the optimum storage condition, the mixing ratio of undissolved carbon dioxide gas is changed and the mass ratio R is calculated again. In the case of the optimal storage conditions, the mass ratio R is determined as the mass ratio R of the undissolved carbon dioxide mixed in the carbon dioxide-dissolved water to be injected.

[Second embodiment]
Next, the underground storage method for carbon dioxide gas according to the second embodiment will be described. The second embodiment is different from the first embodiment described above in the underground storage system to be used. Specifically, in the second embodiment, the carbon dioxide-dissolved water discharged from the dissolution tank is pressed into the underground aquifer while containing undissolved carbon dioxide.

(Carbon dioxide underground storage system 1B)
As shown in FIG. 18, the carbon dioxide underground storage system 1 </ b> B includes a carbon dioxide compression device 2 that compresses carbon dioxide to a liquid or supercritical state, and a pressure feed that compresses and conveys a solvent composed of seawater and / or water. The pump 3, the compressed carbon dioxide gas and the solvent are injected, a plurality of dissolution tanks 4, 4... To dissolve the carbon dioxide gas in the solvent to obtain carbon dioxide-dissolved water, and the generated carbon dioxide-dissolved water It is mainly composed of an injection well 5 that penetrates from the ground surface to the aquifer in order to press-fit it into the underground aquifer. Carbon dioxide dissolved water discharged from the dissolution tank 4 is converted into undissolved carbon dioxide. In this state, it is pressed into the underground aquifer. Further, in the previous stage of the dissolution tank 4, there are provided fine foaming devices 7, 7... For finely forming a liquid or carbon dioxide gas compressed to a supercritical state and mixing it into a solvent.

  The fine foaming device 7 is used to promote the dissolution of carbon dioxide gas by increasing the contact area between the carbon dioxide gas and the solvent by making the carbon dioxide gas compressed to a liquid or supercritical state into fine bubbles and mixing in the solvent. Is. This fine foaming device 7 is used alone or preferably in combination with the dissolution tank 4 as described later.

  As shown in FIG. 19, the fine foaming device 7 is externally fitted to a main flow line 30 in which seawater and / or water is used as a solvent and these solvents are flowed at a predetermined high flow rate. A carbon dioxide gas supply pipe 31 is provided, and pores 30a, 30a... Are formed on a pipe wall surface for partitioning the solvent and carbon dioxide gas, in the illustrated example, on the pipe wall surface of the main flow pipe 30. By the shearing force of the solvent flowing through the passage 30, it is possible to obtain a fine foaming device 7A that mixes liquid or carbon dioxide gas compressed to a supercritical state while fine foaming.

  When a plurality of the pores 30a are arranged, as shown in the figure, it is desirable that the pores 30a are arranged on the pipe wall surface of the mainstream pipe 30 uniformly in the circumferential direction and in a multistage arrangement at intervals in the axial direction. .

The flow rate of the solvent and the pore diameter of the pores 30a are desirably set so that the Weber number (We) obtained by the following formula (5) is 10 or more according to Example 2-3 described later. However, the flow rate of the carbon dioxide gas from the pore is required to be 8 × 10 ⁻² m / s or more.

  The diameter of the fine carbon dioxide gas is about 0.05 to 0.2 mm, and it is not necessary to make it fine up to the micro level (10 to several tens of μm).

  Further, as shown in FIG. 20 and FIG. 21, as the foaming devices 7B and 7C, a carbon dioxide gas supply line 31 is disposed inside the main flow line 30 in which the solvent is flowed at a predetermined high flow rate. The pores 31 a, 31 a... Are formed on the wall surface of the pipe line that separates the solvent and the carbon dioxide gas, in the illustrated example, the pipe wall surface of the carbon dioxide gas supply pipe 31, and the shearing force of the solvent flowing through the main flow line 30 A carbon dioxide gas compressed to a liquid state or a supercritical state may be mixed while being finely bubbled.

  When this fine foaming device 7 is incorporated into the underground storage system 1B, as shown in FIG. 22, it is installed in the lower part of each dissolution tank 4 and is placed inside the main flow line 30 through which the solvent flows at a predetermined high flow rate. The carbon dioxide gas supply pipe 31 is disposed, and pores 31a, 31a,... Are formed on the pipe wall surface of the carbon dioxide gas supply pipe 31 that partitions the solvent and the carbon dioxide gas, and the solvent flowing through the main flow pipe 30 is formed. It can be set as the fine foaming apparatus 7 which mixes liquid or the carbon dioxide gas compressed to the supercritical state by shear force, making it fine foam.

  In the dissolution tank 4, as shown in FIG. 22, an inlet 9 into which a solvent mixed with carbon dioxide gas finely bubbled by the fine bubbler 7 is injected into the lower part of a sealed container 10. And a discharge port 13 through which the carbon dioxide-dissolved water is discharged is formed in the upper part of the container 10, and a porous partitioning the inside of the container 10 vertically in the lower and upper parts of the container 10, respectively. Plates 14 and 14 are arranged, respectively, and a granular filler 16 is filled between the porous plates 14 and 14. Furthermore, the mesh plate 15 is installed on the inlet 9.

(Carbon dioxide underground storage method)
Next, regarding the underground storage method for carbon dioxide using the underground storage system 1B according to the second embodiment, differences from the underground storage method according to the first embodiment will be described.

  As shown in FIG. 23, the underground storage method according to the second embodiment is the first in the procedure for determining the mass ratio R of the undissolved carbon dioxide gas with respect to the underground storage method according to the first embodiment. It differs between the 1 procedures and second procedures in that it has a first 'procedure.

In the first 'procedure, the underground storage system 1B according to the second embodiment is used to convert the carbon dioxide dissolved water discharged from the dissolution tank 4 into the underground aquifer while containing undissolved carbon dioxide. In order to press-fit, the mass ratio X _CO2 ^S of the carbon dioxide dissolved in the carbon dioxide-dissolved water in the dissolution tank 4 is set. Thereby, the mass ratio of the undissolved carbon dioxide gas mixed in the carbon dioxide-dissolved water can be calculated.

The mass ratio X _CO2 ^S dissolved in the carbon dioxide-dissolved water is the mass fraction of carbon dioxide dissolved in the solvent in the dissolution tank 4, and the water pressure, temperature, dilution, etc. in the aquifer after injection Set in consideration.

By setting the mass ratio X _CO2 ^S of the carbon dioxide dissolved in the carbon dioxide-dissolved water, the amount of carbon dioxide is the sum of the amount of carbon dioxide dissolved in the solvent and the amount of undissolved carbon dioxide mixed. The amount of carbon dioxide supplied to the underground storage system 1B can be centrally managed by pumping with the carbon dioxide compressor 2.

  In order to verify the state of carbon dioxide dissolution by the underground storage system 1, a carbon dioxide dissolution experiment was performed using the experimental apparatus shown in FIG. In addition, the fine foaming apparatus 7 was installed in the case with the fine foaming apparatus of Example 2 mentioned later.

  The experimental apparatus pressurizes the carbon dioxide gas in the carbon dioxide gas cylinder 30 by the carbon dioxide gas compression device 33 and injects it into the dissolution tank 35, and pressurizes the salt water in the salt water tank 31 by the solvent pressure pump 34 and injects it into the dissolution tank 35 to dissolve it. Carbon dioxide dissolved in the tank 35 is sampled, and the carbon dioxide-dissolved water after the undissolved carbon dioxide is separated in the separation tank 36 is sampled. Here, the volume of the dissolution tank 35 was 850 ml, and the filler 16 used was a sand-like one having an average particle size of 0.18 mm (particle size 1), 0.63 mm (particle size 2), and 1.32 mm (particle size 3). In the experiment, when the temperature, pressure, salt water flow rate, particle size of the filler 16 and the weight ratio of carbon dioxide and salt water (carbon dioxide weight / salt water weight) were changed, the amount of carbon dioxide dissolved in the sampled carbon dioxide dissolved water was changed. It was measured.

  24 and 25 show the weight ratio of carbon dioxide gas and salt water (carbon dioxide gas weight / salt water weight) injected into the dissolution tank 35 and the dissolution of carbon dioxide gas when the flow rate of salt water at each temperature and the particle size of the filler 16 are changed. It is a graph which shows the relationship with quantity. As a result, at any of the test temperatures of 29 ° C. and 33 ° C., the amount of carbon dioxide dissolved tends to increase as the weight ratio of carbon dioxide to salt water increases and the particle size of the filler 16 decreases.

  26 to 28 are graphs showing the relationship between the weight ratio and the amount of dissolved carbon dioxide gas when the salt water flow rate and pressure at each temperature are changed. As a result, as described above, as the weight ratio of carbon dioxide and salt water increases, the amount of dissolved carbon dioxide tends to increase, but at a certain weight ratio or more, the amount of dissolved carbon dioxide becomes a substantially constant saturation concentration level, The effectiveness of the underground storage system was confirmed.

  Figure 29 is a graph showing the relationship between temperature and carbon dioxide dissolved amount at each pressure. As a result, it was confirmed that, under general temperature conditions in the range of 25 ° C. to 40 ° C., the carbon dioxide dissolution amount was not greatly affected. Further, it was confirmed that the dissolution of carbon dioxide gas was promoted at a relatively low temperature condition of 15 ° C. to 20 ° C.

  FIG. 30 is a graph showing the relationship between the average particle diameter of the filler and the amount of carbon dioxide dissolved at each brine flow rate. As a result, in this example, the average particle size of the filler is excellent in the dissolution efficiency of carbon dioxide gas by setting the average particle size to 1.0 mm or less.

(Example 2-1)
In Example 2-1, an experiment for quantitatively verifying the dissolution effect in the fine foaming device 7 and the dissolution effect in the dissolution tank 35 by the underground storage system 1 was performed.

  The experiments were: Case 1: No filler in the dissolution tank 35 and no foaming device 7, Case 2: No filler in the dissolution tank 35 and a fine foaming device 7, Case 3: With a filler in the dissolution tank 35, and (1) Test pressure: 15 MPa, test temperature: 29 ° C., (carbon dioxide / brine water) weight ratio: about 8%, (2) Test pressure: 15 MPa, test temperature: 33 A dissolution test was conducted on two types of C, and (carbon dioxide / salt water) weight ratio: about 8%.

  The result is shown in FIG. From FIG. 31, the dissolution of carbon dioxide gas is considerably promoted by the fine foaming device 7 alone, and further, the dissolution is further promoted by combining the fine foaming device 7 and the dissolution tank 35. I was able to prove.

(Example 2-2)
In the present Example 2-2, verification experiment of the melt | dissolution promotion effect by the said bubble reduction apparatus 7 was conducted.

In general, it has been found that the relationship of the following equation (6) holds between the amount of carbon dioxide dissolved and the container height Z of the dissolution tank.

The height Z of the container required for dissolution is dependent on overall capacity coefficient K _{X a,} and the overall capacity coefficient K _{X a} as an index representing the dissolution efficiency. The experiment is for each case without a foaming device and with a foaming device. (1) Test pressure: 15 MPa, Test temperature: 29 ° C, (Carbon dioxide / salt water) Weight ratio: About 8%, (2) Test Pressure: 15 MPa, test temperature: 29 ° C., (carbon dioxide / salt water) weight ratio: about 10%, (3) test pressure: 15 MPa, test temperature: 33 ° C., (carbon dioxide / salt water) weight ratio: about 8% As shown in FIGS. 32 to 34, tests were performed on three types. The vertical axis represents the overall capacity coefficient K _x a (mol / m ³ · s), and the horizontal axis represents the cross-sectional molar flow velocity (mol / (m A graph of ² · s)) was obtained. According to the graphs of FIGS. 32 to 34, in the region where the cross-sectional molar flow velocity (mol / (m ² · s)) of water is high, the case with the foaming device is compared with the case without the foaming device. Thus, it has been found that the overall capacity coefficient K _x a is 1.5 times or more.

(Example 2-3)
The experimental results of Example 2-2 were rearranged using the Weber number We shown in the above equation (5), and as shown in FIG. 35, the vertical axis represents the overall capacity coefficient ratio K _x a (B) / K _x a (NB) [where K _x a (B): overall capacity coefficient with a finer, K _x a (NB): overall capacity without a finer], the horizontal axis is the Weber coefficient A graph of We was obtained.

From FIG. 35, it was found that the dissolution efficiency by the fine bubble formation is high in the region where the Weber number We is 10 or more. Therefore, in the fine foaming device 7, the solvent flow rate and the pore diameter of the pores 30a (31a) are preferably set so that the Weber number (We) is 10 or more. However, according to the same experiment, the flow rate of carbon dioxide from the pores is 8 × 10 ⁻² m / s or more.

  1 · 1A · 1B: underground storage system, 2 ... carbon dioxide compression device, 3 ... solvent pump, 4 ... dissolution tank, 5 ... injection well, 6 ... separation tank, 7 ... foaming device, 8 ... undissolved Carbon dioxide gas feeding device, 9 ... confluence, 10 ... container, 11 ... carbon dioxide gas inlet, 12 ... solvent inlet, 13 ... discharge port, 14 ... porous plate, 15 ... mesh plate, 16 ... filler, 19 ... rectifying Plate 20, container 21, inflow pipe 22, undissolved carbon dioxide gas outlet 23, carbon dioxide gas outlet 30, main stream pipe 31, carbon dioxide supply pipe, 30 a, 31 a, pore 32, Branching device

Claims (8)

Carbon dioxide gas dissolved in a solvent in the vicinity of the saturated concentration is mixed with undissolved carbon dioxide gas at a predetermined ratio and pressed into the underground aquifer. A carbon dioxide underground storage method for storing and sequestering carbon dioxide underground,
In the aquifer, the carbon dioxide dissolved water and the undissolved carbon dioxide gas are stored and separated around the injection well, and the carbon dioxide is concentrically formed so as to surround the first reservoir area. Under the condition of storing and isolating the carbon dioxide-dissolved water and the undissolved carbon dioxide so as to form the second storage region only by the gas-dissolved water, the undissolved carbon dioxide mixed in the carbon dioxide-dissolved water is obtained. A method for underground storage of carbon dioxide, wherein the mass ratio is determined by the following procedures (1) to (3).
(1) The volume saturation rate of carbon dioxide gas, defined as the volume ratio of undissolved carbon dioxide gas that can be stored in the gap volume of the aquifer, is measured by laboratory tests using raw ground material collected from the aquifer. Or a first procedure for estimating the volume saturation of the carbon dioxide gas based on the accumulated performance data.
(2) A second procedure for setting the volume of the first storage area and the volume of the second storage area.
(3) A third procedure for determining a mass ratio of undissolved carbon dioxide mixed in carbon dioxide-dissolved water based on the volume saturation rate of the carbon dioxide and the volumes of the first storage region and the second storage region. A carbon dioxide gas compression device that compresses carbon dioxide gas to a liquid or supercritical state, a pressure feed pump that compresses and conveys a solvent composed of seawater and / or water, and the compressed carbon dioxide gas and solvent are injected, and the solvent is One or more dissolution tanks that dissolve carbon dioxide to form carbon dioxide-dissolved water, and from the ground surface to the aquifer in order to press-fit the carbon dioxide-dissolved water and undissolved carbon dioxide into the underground aquifer It consists of an injection well that penetrates,
The dissolution tank includes a carbon dioxide gas inlet through which a carbon dioxide gas sent from the carbon dioxide compressor is injected into a lower part of a sealed container, and a solvent inlet through which a solvent sent from the solvent pump is injected. And a carbon dioxide underground storage system in which a discharge port for discharging the carbon dioxide-dissolved water is formed in the upper part of the container, and the container is filled with a granular filler. make use of,
In the middle of the flow path from the dissolution tank to the injection well, undissolved carbon dioxide gas and carbon dioxide-dissolved water in which carbon dioxide gas is dissolved at a saturated concentration are separated from the total amount of carbon dioxide-dissolved water fed. A separation tank, an undissolved carbon dioxide pressure feeding device that pumps the undissolved carbon dioxide gas separated in the separation tank, a branching device that branches the undissolved carbon dioxide gas fed from the undissolved carbon dioxide pressure feeding device, and the separation The carbon dioxide dissolved water separated in the tank is provided with a junction for mixing the undissolved carbon dioxide branched by the branching device, and mixed in the carbon dioxide dissolved water among the undissolved carbon dioxide by the branching device. 2. A predetermined amount to be branched and pumped to the confluence point to mix the undissolved carbon dioxide with the carbon dioxide dissolved water at a predetermined ratio and press-fit into the underground aquifer. Of underground storage of carbon dioxide gas. A carbon dioxide gas compression device that compresses carbon dioxide gas to a liquid or supercritical state, a pressure feed pump that compresses and conveys a solvent composed of seawater and / or water, and the compressed carbon dioxide gas and solvent are injected, and the solvent is One or more dissolution tanks that dissolve carbon dioxide to form carbon dioxide-dissolved water, and from the ground surface to the aquifer in order to press-fit the carbon dioxide-dissolved water and undissolved carbon dioxide into the underground aquifer It consists of an injection well that penetrates,
The dissolution tank includes a carbon dioxide gas inlet through which a carbon dioxide gas sent from the carbon dioxide compressor is injected into a lower part of a sealed container, and a solvent inlet through which a solvent sent from the solvent pump is injected. And a discharge port through which the carbon dioxide-dissolved water is discharged is formed at the top of the container, and the container is filled with a granular filler,
Using the carbon dioxide underground storage system in which the carbon dioxide dissolved water discharged from the dissolution tank is injected into the underground aquifer in the state containing undissolved carbon dioxide as it is,
By controlling the mass of the carbon dioxide gas fed by the carbon dioxide compressor and the mass of the solvent fed by the solvent pump, respectively, undissolved carbon dioxide is mixed in the carbon dioxide-dissolved water at a predetermined ratio. The underground storage method for carbon dioxide gas according to claim 1, which is press-fitted into the underground aquifer.   The carbon dioxide gas supply pipe is disposed in the main stream line through which the solvent is flowed at a predetermined high flow rate, or the carbon dioxide gas supply pipe is externally fitted to the main stream line. A high-pressure carbon dioxide gas fine particle is formed in which a channel is formed, pores are formed on the wall surface of the pipeline that partitions the solvent and carbon dioxide gas, and the carbon dioxide gas is mixed while being bubbled by the shearing force of the solvent flowing through the mainstream pipeline. underground storage method of claim 3 wherein the carbon dioxide gas bubbling device is installed. The carbon dioxide underground storage method according to claim 4, wherein the flow rate of the solvent and the pore diameter are set so that the Weber number (We) obtained by the following formula (5) is 10 or more.

  The method for underground storage of carbon dioxide gas according to any one of claims 2 to 5, wherein the granular filler filled in the dissolution tank is any one or a combination of sand, crushed stone, Raschig ring, and saddle.   For each type of filler, the granular filler filled in the dissolution tank is calculated from the amount of carbon dioxide dissolved based on the flow rates of carbon dioxide and solvent and the shape of the dissolution tank, and the pressure loss in the dissolution tank. The carbon dioxide underground storage method according to any one of claims 2 to 6, wherein the optimum average particle diameter is determined.   The carbon dioxide gas according to any one of claims 2 to 7, wherein in the dissolution tank, one or a plurality of rectifying plates in which a large number of openings are formed so as to partition the flow path are provided in the filling region of the filler. Underground storage method.

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