Marine environment improving method and calcium ion supply device used therefor

Abstract

To provide a marine environment improving method by reducing greenhouse gases by absorbing carbon dioxide and thereby improving the marine environment, and a calcium ion supply device used therefor.SOLUTION: A marine environment improving method includes: supplying lime water or calcium carbonate and water to a reaction tank 10; further supplying atmospheric air A; and supplying a calcium hydrogencarbonate aqueous solution obtained by reacting them to the sea S. A calcium ion supply device 1 includes: a supply device 2 that supplies lime water or water to the reaction tank; a gas-liquid contact device 3 that is equipped with a pump 31 for collecting atmospheric air, and contacts atmospheric air with the lime water or calcium carbonate and water filled in the reaction tank; a conveying device 4 that conveys the calcium hydrogencarbonate aqueous solution generated by the reaction of carbon dioxide in the atmosphere with the lime water or calcium carbonate and water from the reaction tank to the outside via a conveying pump 42, and conveys the calcium hydrogencarbonate aqueous solution to the sea via a conveying path 41 connected to the conveying pump; and a control device that controls each of these devices.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a marine environment improvement method that can reduce carbon dioxide emissions, and a calcium ion supply device used therein. [Background technology]

[0002] Currently, efforts are being made worldwide to reduce carbon dioxide emissions in order to prevent global warming.

[0003] One conventional technology proposed for reducing the concentration of carbon dioxide in the atmosphere involves capturing carbon dioxide from the exhaust gas outlets of factories and other facilities, and then mineralizing and fixing the captured carbon dioxide underground. A storage facility for this technology has already been tested (see, for example, Non-Patent Document 1).

[0004] Another proposed technology involves recovering carbon dioxide from the atmosphere, dissolving the recovered carbon dioxide in water, injecting it into the ground, allowing it to be absorbed and fixed in the ground, and then recovering hot spring water (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Non-Patent Document 1] IPCC (2005) Special Report on Carb on Dioxide Capture and Storage: Prepared by Working Group III of the International Panel on Climate Change. Cambridge University Press, Cambridge and New York, 422 pp. [Patent Document 1] Special table 2017-528318 publication Summary of the Invention [Problem to be solved by the invention]

[0006] However, when recovering carbon dioxide from the exhaust gas outlet, it is not possible to recover carbon dioxide that has already been released and diffused into the atmosphere.

[0007] Furthermore, whether capturing carbon dioxide from exhaust gas outlets or from the atmosphere, it is mineralized and fixed underground, and in both cases, it is thought that the calcium oxide contained in the basalt that makes up the Earth's crust reacts with carbon dioxide to form calcium carbonate, which is fixed underground. However, if carbon dioxide is directly transported from the atmosphere into the ground and mineralized and fixed in this way, while it may be possible to achieve the goal when considering only carbon dioxide reduction, it is far removed from the carbon dioxide reduction mechanism that the natural environment originally played, and so other issues arise, and there is concern that it will take time to improve the marine environment, which has been deteriorated by the increase in atmospheric carbon dioxide.

[0008] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a marine environment improvement method that can absorb carbon dioxide to reduce greenhouse gases and improve the marine environment, and a calcium ion supply device to be used therein. [Means for solving the problem]

[0009] In order to solve the above problems, the marine environment improvement method of the present invention comprises supplying limewater or calcium carbonate and water to a reaction tank, supplying air into the reaction tank, causing carbon dioxide in the air to react with the limewater or calcium carbonate and water in the reaction tank, and supplying the resulting aqueous solution of calcium bicarbonate to the sea.

[0010] In the above-described method for improving the marine environment, carbon dioxide in the atmosphere may be reacted with lime water or calcium carbonate and water in the reaction tank while the aqueous solution in the reaction tank is cooled.

[0011] In the marine environment improvement method, the limewater may be prepared by adding water to calcium oxide obtained by burning calcium carbonate in a closed system using renewable energy to recover carbon dioxide, or by adding water to calcium hydroxide obtained by slaked calcium oxide.

[0012] In the marine environment improvement method, the calcium carbonate may be obtained by burning calcium carbonate in a closed system using renewable energy to recover carbon dioxide, and then allowing the calcium oxide obtained to absorb carbon dioxide from the atmosphere, or by digesting the calcium oxide to obtain calcium hydroxide, and then allowing carbon dioxide from the atmosphere to absorb carbon dioxide.

[0013] The marine environment improvement method of the present invention, which solves the above-mentioned problems, involves calcining calcium carbonate in a closed system using renewable energy, recovering carbon dioxide, and adding water to the calcium oxide obtained to prepare limewater, or adding water to calcium hydroxide obtained by slaked the calcium oxide, and supplying the resulting limewater to the sea.

[0014] In the marine environment improvement method, each step may be carried out using renewable energy.

[0015] In the above-mentioned marine environment improvement method, the calcium carbonate may be obtained from seashells.

[0016] In the marine environment improvement method, limestone may be used as calcium carbonate.

[0017] In the above-mentioned method for improving the marine environment, the water used to prepare the limewater or the water used may be groundwater, stored water, rainwater, river water, or industrial wastewater.

[0018] In the above-mentioned marine environment improvement method, the obtained aqueous solution of calcium hydrogen carbonate may be supplied to sandy areas on the seabed.

[0019] In the above-mentioned marine environment improvement method, the obtained limewater may be supplied to sandy areas in the sea.

[0020] In the above marine environment improvement method, the obtained limewater may be supplied to the seabed.

[0021] A calcium ion supply device of the present invention for solving the above-mentioned problems includes a reaction tank that can be filled with lime water or calcium carbonate and water, a supply device that supplies lime water or water to the reaction tank, a gas-liquid contactor that has a pump that collects air and brings the air into contact with the lime water or calcium carbonate and water filled in the reaction tank, a transport device that transports an aqueous solution of calcium bicarbonate produced by the reaction of carbon dioxide in the air with the lime water or calcium carbonate and water from the reaction tank to the outside using a transport pump, and transports the aqueous solution of calcium bicarbonate to the sea via a transport path connected to the transport pump, and a control device that controls each of these devices.

[0022] The calcium ion supply device may further include a water temperature control device that controls the temperature of the aqueous solution in the reaction tank.

[0023] The calcium ion supplying device may further include a renewable energy supplying device that produces renewable energy and supplies the renewable energy to the device. [Effects of the Invention]

[0024] As described above, according to the present invention, calcium can be supplied to the ocean in the form of calcium ions by supplying limewater or calcium carbonate and water to a reaction tank, supplying atmospheric air to the aqueous solution in the reaction tank, reacting carbon dioxide in the air with the aqueous solution, and supplying the resulting aqueous solution of calcium bicarbonate to the ocean. Normally, atmospheric carbon dioxide dissolves in rainwater to form acid rain and is directly fixed in the ocean, which results in ocean acidification. However, in the present invention, atmospheric carbon dioxide reacts with the aqueous solution to form an aqueous solution of calcium bicarbonate, which is then supplied to the ocean. Therefore, ocean acidification is not caused, and atmospheric carbon dioxide can be captured and fixed in the ocean while preventing ocean acidification. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a diagram showing an outline of the overall configuration of a calcium ion supplying device according to the present invention. [Figure 2] 1 is a block diagram showing an outline of the overall configuration of a calcium ion supplying device according to the present invention. [Figure 3] 5(a) to 5(d) are configuration diagrams showing other embodiments of the reaction tank of the calcium ion supply device according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] 1 and 2 show an outline of the overall configuration of a calcium ion supplying device 1 used to carry out the marine environment improvement method according to the present invention.

[0027] That is, as shown in FIG. 1, the marine environment improvement method of the present invention involves supplying limewater L to a reaction tank 10, supplying the atmosphere A to the limewater L in this reaction tank 10, causing carbon dioxide CO2 in the atmosphere A to react with the limewater L, and supplying the resulting aqueous solution of calcium bicarbonate Ca(HCO3)2 to the sea S.

[0028] This marine environment improvement method can be carried out by a calcium ion supply device 1 including a reaction tank 10, a supply device 2, a gas-liquid contactor 3, a transport device 4, a control device 5, and a solar power generation device 6, as shown in Figures 1 and 2.

[0029] The reaction tank 10 is configured as a water tank that can be filled with limewater L. The reaction tank 10 is configured as an open-type water tank with an open top so that the limewater L in the reaction tank 10 can be brought into contact with the atmosphere A and the atmosphere A can be exhausted after contact. This may be a case where the top of the reaction tank 10 is simply open, or the top of the reaction tank 10 is sealed with a lid (not shown) having an exhaust path and is open to the atmosphere via this exhaust path. However, an open-type water tank with an open entire top is preferable because it increases the opportunity for the limewater L in the reaction tank 10 to come into direct contact with the atmosphere A. Furthermore, in order to increase the opportunity for direct contact between the limewater L and the atmosphere A, the reaction tank 10 is preferably shaped to have a large plane area and a shallow depth.

[0030] To this reaction tank 10, a supply path 21 of a supply device 2 for supplying limewater L into the inside of the reaction tank 10 is connected. The supply device 2 is configured to include a supply line 21, a supply pump 22, and a preparation tank 23, so that limewater L prepared in the preparation tank 23 is supplied to the reaction tank 10 via the supply line 21 via the supply pump 22. To prepare the limewater L in the preparation tank 23, water and calcium hydroxide Ca(OH)2 soluble in the amount of water added are charged into the preparation tank 23, stirred, and then the water and calcium hydroxide Ca(OH)2 are measured each time to prepare the limewater L. Alternatively, a large amount of calcium hydroxide Ca(OH)2 is charged into the preparation tank 23, an appropriate amount of water is added, stirred, and after allowing to stand, the supernatant limewater L is removed. Thereafter, water is added, and the preparation of limewater L is repeated in the same manner. The stirring may be performed by rotating an agitator blade 25 using a motor 24, by rotating a stirrer (not shown) using magnetic force, or by using a water pump (not shown). The water used to prepare this limewater L may be rainwater, reservoir water, river water, groundwater, tap water, industrial wastewater, or treated sewage. The water may be prepared by providing a heat pump, Peltier element, or other water temperature control device C in the preparation device 2 to obtain limewater L at a desired temperature depending on the environment. The solubility of calcium hydroxide (Ca(OH)2) in water increases with decreasing temperature (0.153 g / 100 ml water at 30°C, 0.176 g / 100 ml water at 10°C, and 0.185 g / 100 ml water at 0°C). Therefore, preparation of limewater L is facilitated by cooling the water with the water temperature control device C. Therefore, dissolving 1 mole (74 g) of calcium hydroxide (Ca(OH)2) in water to prepare limewater L requires 40 to 50 liters of water, assuming complete dissolution. With a margin of error, 50 to 60 liters of water can be used to obtain 1 mole (74 g) of calcium hydroxide (Ca(OH)2) in limewater L. Note that 50 to 60 liters is an example of a case where dissolution is performed with a margin of solubility, and the substance may be dissolved in a larger amount of water, or in an amount that completely dissolves the substance.If a large amount of calcium hydroxide (Ca(OH)2) is added to the preparation tank 23, an appropriate amount of water is added, the mixture is stirred, and the supernatant limewater (L) is removed, a volume of 40 to 50 liters (approximately the theoretical value) containing 74 g of calcium hydroxide (Ca(OH)2) dissolved in 1 mole of the limewater (L) can be prepared. It is not necessary to prepare limewater (L) with a saturated solubility; a solubility margin is acceptable because it prevents precipitation during temperature changes, but leaving too much solubility is not beneficial. The above example describes the preparation of 50 to 60 liters of limewater (L) containing 74 g of calcium hydroxide (Ca(OH)2) dissolved in 1 mole of the limewater (L). However, the scale of the supply device (2) is not particularly limited. For example, it may be 1,000 times larger (50 to 60 tons) or 10,000 times larger (500 to 600 tons). This can be determined depending on the amount of water to be procured, such as rainwater, reservoir water, river water, groundwater, tap water, industrial wastewater, or treated sewage water.

[0031] The gas-liquid contactor 3 is composed of a pump 31 for collecting atmospheric air A, a pressure-transfer path 32 extending from the atmosphere to the bottom of the reaction vessel 10 to pump the atmospheric air A into the reaction vessel 10 using the pump 31, and a bubbling head 33 provided at the bottom of the reaction vessel 10, which is the extended tip of the pressure-transfer path 32. The gas-liquid contactor 3 is configured to exhaust atmospheric air A from the bubbling head 33 into the limewater L supplied to the reaction vessel 10. The bubbling head 33 is provided at the bottom of the reaction vessel 10 so that the atmospheric air A exhausted into the reaction vessel 10 can sufficiently contact with the limewater L in the reaction vessel 10. Furthermore, the bubbling head 33 may extend over the entire bottom surface of the reaction vessel 10 and have many pores formed therein to generate as fine bubbles as possible, so that the atmospheric air A exhausted from the bubbling head 33 can contact the limewater L in the reaction vessel 10 as efficiently as possible. Specifically, an air stone, a nanobubble head, or the like can be used. However, if the pores are made too small, the load on the pump 31 that pumps the atmosphere A increases, reducing the absolute amount of atmosphere A supplied to the reaction tank 10. Therefore, it is possible to prioritize the supply of atmosphere A and adopt a bubbling head 33 with a large pore size that can supply as much atmosphere A as possible. In this case, the size of the bubbles increases, and the bubbles rise quickly and are released back into atmosphere A before they have fully come into contact with the limewater L in the reaction tank 10. However, this is advantageous in that the absolute amount of atmosphere A that can come into contact with the limewater L increases, allowing the carbon dioxide CO2 in the atmosphere A to react with the limewater L.

[0032] Furthermore, when the absolute amount of air A supplied by the pump 33 is increased in this manner, an obstacle wall 11 may be provided in the reaction tank 10 as shown in FIG. 3(a) to keep the air bubbles in contact with the limewater L in the reaction tank 10 for as long as possible. Alternatively, an agitator 12 for agitating the air bubbles may be provided in the reaction tank 10 as shown in FIG. 3(b). In this case, the obstacle wall 11 may be made of the same material as the reaction tank 10, and may be a plurality of plates or mesh plates arranged to block the rising of bubbles, or may be formed by forming a spiral flow path. Alternatively, as shown in FIG. 3(c), calcium carbonate (CaCO3) media, such as seashells, may be filled in and this filler material 13 may be used instead of the obstacle wall 11. The agitator 12 may be one that stirs the stirring blades 12b using a motor 12a, one that stirs a stirring bar (not shown) using magnetic force, or one that stirs using a water flow. Alternatively, as shown in Figure 3(d), it may be configured to rotate between the limewater L and the atmosphere A, like an aquaculture agitator 14, to generate bubbles of the atmosphere A in the limewater L and generate droplets of the limewater L in the atmosphere A, thereby bringing the limewater L into contact with the atmosphere A, or it may be a spray type in which the limewater L itself is sprayed from the reaction tank 10 into the atmosphere A and then received back in the reaction tank 10, and this process is repeated to bring the limewater L into contact with the atmosphere A.

[0033] However, in the case of a gas-liquid contactor 3 that supplies atmospheric air A using a pump 33, new atmospheric air A is continuously supplied, but in the case of a spray type, the existing atmospheric air A must be renewed in order to recover carbon dioxide CO2, so it is necessary to either close the space where the spraying is to be performed and continuously supply new atmospheric air A using a blower or to spray in a well-ventilated space. In either case, it is necessary to avoid a configuration in which the sprayed limewater L is blown away by the atmospheric air A and cannot be recovered in the reaction tank 10, so the droplets to be sprayed are determined depending on the environment. In particular, limewater L changes into a cloudy aqueous solution with calcium carbonate CaCO3 dispersed in it by absorbing carbon dioxide CO2, and then becomes a clear aqueous solution of calcium bicarbonate Ca(HCO3)2. In the case of a spray type, there is a concern that the calcium carbonate CaCO3 will aggregate and cause clogging if used over a long period of time, so while mist-like droplets are effective in that they come into contact with the atmosphere A, when considering the operation of the device, droplets that are on the borderline between flowing water like that in a chiller device and liquid droplets are preferable.

[0034] The size of the reaction vessel 10 is set so as to maximize the contact area with the atmosphere A. For example, when the supply amount of limewater L supplied from the supply device 2 is 50 to 60 tons, the reaction vessel 10 is preferably formed to have an effective water storage capacity of 50 to 60 tons, with dimensions of, for example, 10 m wide x 10 m long x 0.5 to 0.6 m deep. When the supply amount of limewater L supplied from the supply device 2 is 500 to 600 tons, the reaction vessel 10 is preferably formed to have an effective water storage capacity of, for example, 20 m wide x 25 to 30 m long x 1 m deep, with dimensions of 500 to 600 tons. However, the size of the reaction vessel 10 is not limited to the above and is determined depending on the supply amount of limewater L supplied from the supply device 2, the target treatment time, and the treatment capacity of the gas-liquid contactor 3. The concentration of carbon dioxide CO2 in the atmosphere A is 768.686 mg / m at 20°C. 3 743 mg / m at 30°C 3Therefore, 10,000 liters of atmosphere A can supply atmosphere A containing approximately 7.5 g of carbon dioxide CO2. Therefore, to supply 1 mole (44 g) of carbon dioxide CO2, approximately 58,700 liters of atmosphere A is required. If a pump 33 with an output of 1,000 liters / minute is used, atmosphere A containing 1 mole of carbon dioxide CO2 can be supplied in approximately one hour. Of course, this is for general atmosphere A, and in areas or places where the concentration of carbon dioxide CO2 is high, the amount of atmosphere A required will be less.

[0035] When limewater L is brought into contact with atmospheric air A in reaction vessel 10, the limewater L reacts with carbon dioxide CO2 in atmospheric air A, decomposing the limewater L into calcium carbonate CaCO3 and water. As carbon dioxide CO2 from atmospheric air A continues to be supplied, the limewater L becomes an aqueous solution of calcium bicarbonate Ca(HCO3). Even if the limewater L is sufficiently cooled by supply device 2, there is a concern that the temperature of the limewater L may gradually increase if the temperature of the atmospheric air A supplied from gas-liquid contactor 3 is high or due to heat from pump 33 of gas-liquid contactor 3. Therefore, like tank 23 of supply device 2, reaction vessel 10 may be equipped with a heat pump, Peltier element, or other water temperature control device C to obtain an aqueous solution of calcium bicarbonate Ca(HCO3)2 at a desired temperature depending on the environment. The aqueous solution of calcium bicarbonate Ca(HCO3)2 thus obtained can recover 2 moles of carbon dioxide CO2 from atmospheric air A during the process of converting the limewater L into an aqueous solution of calcium bicarbonate Ca(HCO3).

[0036] Therefore, for example, by supplying approximately 58,700 liters of air A containing 1 mole (44 g) of carbon dioxide CO2 to 50 to 60 liters of limewater L with 1 mole (74 g) of calcium hydroxide Ca(OH)2 dissolved in it, or approximately 117,400 liters of air A containing twice that amount (2 moles, 88 g) of carbon dioxide CO2, it is possible to obtain 50 to 60 liters of an aqueous solution of calcium bicarbonate Ca(HCO3)2 with 1 mole (approximately 162 g) of calcium bicarbonate Ca(HCO3)2 dissolved in it, and to recover 2 moles (88 g) of carbon dioxide CO2 from the air A. For example, in a case where one cycle is operated per day, to obtain 50 to 60 liters of an aqueous calcium bicarbonate solution Ca(HCO3)2 in which 1 mole (74 g) of calcium hydroxide Ca(OH)2 is dissolved, from, say, 50 to 60 liters of limewater L, it is necessary to supply approximately 117,400 liters of air A containing 2 moles (88 g) of carbon dioxide CO2. Even if air A is supplied from the gas-liquid contactor 3 for 10 hours, this can be achieved by using a pump 31 with a capacity of 196 liters / minute. Of course, it is possible that air A does not contain carbon dioxide CO2 as theoretically predicted, but in that case, the capacity of the pump 31 can be increased or the treatment time can be extended. When 50 to 60 liters of limewater L in which 1 mole (74 g) of calcium hydroxide Ca(OH)2 is dissolved is used in a reaction tank 11 with a capacity of 50 to 60 tons (1,000 times larger), or a reaction tank 11 with a capacity of 500 to 600 tons (10,000 times larger), similarly, the capacity of the pump 31 can be increased or the treatment time can be extended. The capacity of the pump 31 can be increased by increasing the capacity of the pump 31 itself, or by increasing the number of pumps. In either case, the power consumption of the pump 31 itself is small, so this can be easily achieved.

[0037] In the transport device 4, a transport path 41 is connected to the reaction tank 10, and the transport path 41 extends from the reaction tank 10 so as to supply the aqueous solution of calcium bicarbonate Ca(HCO3)2 obtained in the reaction tank 10 to the sea S. The supply to the sea S is performed by driving a transport pump 42 provided on the transport path 41. The position of the outlet 43 at the end of the transport path 41 for discharging the aqueous solution of calcium bicarbonate Ca(HCO3)2 is not particularly limited as long as it is configured to supply the aqueous solution of calcium bicarbonate Ca(HCO3)2 to the sea S.

[0038] By supplying the aqueous solution of calcium bicarbonate Ca(HCO3)2 to the sea S using the transport device 4, for example, 50 to 60 liters of the aqueous solution of calcium bicarbonate Ca(HCO3)2 described above can supply approximately 40 g of calcium ions per mole and 122 g of bicarbonate ions per mole to the sea S. Therefore, in a single treatment, for example, if 50 to 60 tons, a 1000-fold increase, is treated, 40 kg of calcium ions and 122 kg of bicarbonate ions can be supplied to the sea S, and if 500 to 600 tons, a 10,000-fold increase, is treated, 400 kg of calcium ions and 1,220 kg of bicarbonate ions can be supplied to the sea S.

[0039] Here, the sea S includes not only seawater but also sandy areas that the seawater reaches. For example, the outlet 43 may be located at a depth of less than 50 m where shallow groundwater joins, e.g., 20 to 30 m, or at a depth of 50 m or more where deep groundwater joins, e.g., 50 to 60 m, or in the deep sea at a depth of 200 m or more, or less than 10 m. Furthermore, the outlet 43 is not limited to being located in the sea, but may also be located on sandy areas of the same depth. Furthermore, the outlet 43 may be located on sandy areas in the intertidal zone between the high-tide shoreline and the low-tide shoreline, or on sandy areas in the shallow layer at a depth of less than 50 m, the deep layer at a depth of 50 m or more, or the deep-sea layer at a depth of 200 m or more. In particular, when considering supplying calcium ions to marine exoskeletal organisms, it is preferable to supply them to the intertidal zone or shallow waters, especially sandy areas less than 10 m deep where shellfish are likely to live, and more preferably less than 5 m deep. However, such intertidal zones and shallow waters, especially the morning zone, are susceptible to high and low water temperatures and are easily affected by air temperature. Depending on the location and season, calcium ions are prone to recalcification, and the ionized calcium is recalcified and immobilized. Therefore, it is preferable to supply calcium ions in a way that makes them more easily absorbed by marine exoskeletal organisms. In other words, when preparing the aqueous solution of calcium bicarbonate (Ca(HCO3)2) in the reaction tank 11, the temperature may be adjusted by heating or cooling the reaction tank 11 using a water temperature control device C, depending on the temperature and environment of the supply location. Considering the growth of marine exoskeletal organisms such as shellfish, these shellfish feed on phytoplankton, which are found in abundance at depths where light reaches, as they grow through photosynthesis, and therefore it is preferable that the outlet 43 for the aqueous solution of calcium bicarbonate Ca(HCO3)2 from the reaction tank 11 be supplied to a location where there is a large amount of phytoplankton. For this reason, it is preferable to supply the aqueous solution to the intertidal zone or shallow waters, particularly to sandy areas less than 10 m deep where shellfish are likely to live, and more preferably less than 5 m deep.However, when supplying an aqueous solution of calcium bicarbonate Ca(HCO3)2 from sandy soil, there is a concern that high water pressure from outlet 43 may dig up the sandy soil, so it is preferable to supply the water at a reduced water pressure, to branch outlet 43 into multiple outlets to reduce the water pressure, or to supply the water by merging it with an existing underground water vein flowing into the sea S.

[0040] The control device 5 is configured to control the overall operation of the calcium ion supply device 1. Specifically, it is configured to control a series of operations by at least the supply device 2, the gas-liquid contact device 3, and the transport device 4. The supply of power generated by the solar power generation device 6 to the supply device 2, the gas-liquid contact device 3, and the transport device 4 is also controlled by the control device 5. Although the control device 5 may control everything, other control methods are not excluded. Part of the control by the control device 5 may be manually operated artificially, or all of the control may be manually operated.

[0041] To explain the series of operations, first, the supply device 2 supplies water and calcium hydroxide to the preparation tank 23. At this time, when a pump (not shown) is used to supply water, the operation of this pump may be controlled by the control device 5, or the control device 5 may control the pump to stop operation when the tank is full of water. If water pressure can be used, the control device 5 may control the opening and closing of a valve (not shown) to supply water. Of course, this may be done manually, without using the control device 5.

[0042] Next, the water in the preparation tank 23 is stirred. The drive of the motor 24 that performs this stirring can also be controlled by the control device 5. Calcium hydroxide Ca(OH)2 is dissolved in the water by stirring, producing limewater L, which is then transferred to the reaction tank 10 from the supply line 21 via the supply pump 22. The operation of the supply pump 22 may be controlled by the control device 5. Calcium hydroxide Ca(OH)2 may be automatically added by the control device 5 in an amount corresponding to the amount of water to be supplied to the preparation tank 23. Alternatively, a large amount of calcium hydroxide Ca(OH)2 may be added to the preparation tank 23 in advance, and after stirring, the dispersed excess calcium hydroxide Ca(OH)2 may settle, and then the limewater L may be transferred to the reaction tank 10. However, when a large amount of calcium hydroxide Ca(OH) is added, it is necessary to wait for the dispersed excess calcium hydroxide Ca(OH) to settle after each stirring. Therefore, to prevent the settled calcium hydroxide Ca(OH) from being transferred, only the supernatant limewater L may be transferred using a strainer or the like. Alternatively, to prevent the dispersed excess calcium hydroxide Ca(OH) from dispersing, a large amount of calcium hydroxide Ca(OH) may be placed in a nonwoven bag or the like, and the calcium hydroxide Ca(OH) may be dissolved through the bag, preventing the dispersed excess calcium hydroxide Ca(OH) from dispersing in the reaction tank 10 in an amount greater than the dissolved amount. In this case, the dispersed excess calcium hydroxide Ca(OH) in the limewater L can be prevented from being transferred to the reaction tank 10, and the limewater L can be transferred to the reaction tank 10 without waiting for the dispersed excess calcium hydroxide Ca(OH) to settle.

[0043] When the supply of limewater L to the reaction tank 10 is completed, the supply pump 22 is stopped, and the pump 31 of the gas-liquid contactor 3 is operated to perform bubbling. At this time, the operation of the pump 31 may be controlled by the control device 5. When the limewater L is bubbling, it changes into a cloudy aqueous solution of calcium carbonate CaCO3, and then into a clear aqueous solution of calcium bicarbonate Ca(HCO3)2. At the stage when the aqueous solution of calcium bicarbonate Ca(HCO3)2 is obtained, the bubbling by the pump 31 is stopped. During this bubbling by the gas-liquid contactor 3, fresh limewater L to be used next is prepared in the supply device 2 in parallel. Whether or not the solution has become an aqueous solution of calcium bicarbonate (Ca(HCO3)2) can be determined simply by the bubbling time, or by detecting the color change with a sensor (the solution becomes cloudy as it changes from limewater L to an aqueous solution of calcium carbonate (CaCO3), and then becomes clear again when it becomes an aqueous solution of calcium bicarbonate (Ca(HCO3)2), or by detecting the change in pH with a pH meter. Because limewater L is strongly alkaline, it initially has a high pH value, but if carbon dioxide (CO2) is continued to be supplied even after the solution has finally become an aqueous solution of calcium bicarbonate (Ca(HCO3)2), the carbon dioxide (CO2) dissolves in the solvent water, causing the pH to change to the acidic side; this change in pH can be detected to determine whether or not the solution has become an aqueous solution of calcium bicarbonate (Ca(HCO3)2).

[0044] The aqueous solution of calcium bicarbonate Ca(HCO3)2 in the reaction tank 10 is then transported to the sea S by the transport device 4 and supplied to the sea. At this time, the operation of the transport pump 42 is controlled by the control device 5.

[0045] Thereafter, the above process is repeated by batch processing.

[0046] The solar power generation device 6 is charged with all driving energy when the control device 5 controls a series of operations of the calcium ion supply device 1. In this case, the solar power generation device 6 may operate the calcium ion supply device 1 while supplying generated power to the calcium ion supply device 1, or may charge the battery 61 and then operate the calcium ion supply device 1 with the charged power. Furthermore, although the present embodiment uses the solar power generation device 6, other renewable energy sources such as wind power generation, geothermal power generation, and power generation using biomass gas may also be used. Furthermore, the solar power generation device 6 may use electricity generated by fossil fuels, or may use such electricity in combination with renewable energy.

[0047] For example, when treating 50 to 60 liters of limewater L containing 1 mole (approximately 74 g) of dissolved calcium hydroxide Ca(OH)2, the calcium ion supply device 1 of the present invention can supply air A containing 2 moles (approximately 88 g) of carbon dioxide CO2 and supply 50 to 60 liters of an aqueous solution of calcium bicarbonate Ca(HCO3)2 containing 1 mole (approximately 40 g) of calcium ions and 2 moles (approximately 122 g) of bicarbonate ions to the sea S. Therefore, for example, when treating 50 to 60 tons, which is 1,000 times the amount, in a single treatment, 40 kg of calcium ions can be supplied to the sea S and 88 kg of carbon dioxide CO2 can be recovered. When treating 500 to 600 tons, which is 10,000 times the amount, 400 kg of calcium ions can be supplied to the sea S and 880 kg of carbon dioxide CO2 can be recovered. Solar power generation is said to emit 17–48 g of carbon dioxide (CO2) per kilowatt, while fossil fuel-fired electricity is said to emit 690 g of carbon dioxide (CO2) per kilowatt. Therefore, to process 50–60 tons of waste, the power required to emit 88 kg of CO2 (5176.47–1833.33 kW) would be achievable, while fossil fuel-fired electricity would require 12.75 kW. To process 500–600 tons of waste, the power required to emit 880 kg of CO2 (51764.7–18333.3 kW) would be achievable, while fossil fuel-fired electricity would require 127.5 kW. If the power consumption per process can be kept below these levels, the amount of CO2 recovered will be proportional to the reduction. Therefore, if the calcium ion supply device 1 not only supplies calcium ions to the sea (S) but also actively captures CO2, it is advisable to use renewable energy sources such as solar power.

[0048] In this embodiment, limewater L prepared by the supply device 2 is supplied to the reaction tank 10. However, the supply device 2 may be omitted and water may be supplied to the reaction tank 10. In this case, calcium carbonate CaCO3 is supplied to the reaction tank 10 in advance. This allows the water and calcium carbonate CaCO3 in the reaction tank 10 to react with carbon dioxide CO2 in the atmosphere supplied by the gas-liquid contactor 3 to form an aqueous solution of calcium bicarbonate Ca(HCO3)2. In this case, the supply device 2 for limewater L is not required, and the configuration and control can be simplified. However, when limewater L turns into a cloudy liquid of calcium carbonate CaCO3 and water and then turns into calcium bicarbonate Ca(HCO3)2, the calcium carbonate CaCO3 is cloudy at the molecular level and therefore easily reacts with carbon dioxide CO2 to become calcium bicarbonate Ca(HCO3)2. However, when calcium bicarbonate Ca(HCO3)2 is obtained from water and calcium carbonate CaCO3, calcium carbonate CaCO3 itself does not dissolve in water, so the carbon dioxide CO2 dissolves in the water to form carbonated water, and this carbonated water then dissolves calcium carbonate CaCO3 to become calcium bicarbonate Ca(HCO3)2, so it must be taken into account that this process is less efficient.

[0049] According to the marine environment improvement method of the present invention, the calcium ion supply device 1 recovers carbon dioxide (CO2) from the atmosphere (A) while preparing an aqueous solution of calcium bicarbonate (Ca(HCO3)2). The resulting aqueous solution of calcium bicarbonate (Ca(HCO3)2) is then supplied to the sea (S), thereby supplying calcium ions to the sea (S). Therefore, these calcium ions can be used to support the growth of marine organisms, particularly marine exoskeleton organisms. Specifically, when the sea (S) absorbs carbon dioxide (CO2) that has already been released and dispersed into the atmosphere (A), the carbon dioxide (CO2) dissolves in rainwater and falls into the sea (S), where it is absorbed. In this case, a large amount of hydrogen ions is generated, leading to the acidification of the sea (S), which has already caused problems such as inhibiting the formation of exoskeletons in marine exoskeletal organisms. However, when the calcium ion supply device 1 is used, the carbon dioxide (CO2) recovered from the atmosphere (A) by the calcium ion supply device 1 is converted into an aqueous solution of calcium bicarbonate (Ca(HCO3)2) and supplied to the sea (S). This converts the carbon dioxide (CO2) into calcium ions and bicarbonate ions, preventing the generation of hydrogen ions and preventing the acidification of the sea (S). Furthermore, it can supply calcium ions necessary for the formation of exoskeletons of marine exoskeleton organisms.

[0050] Furthermore, when the limewater L supply device 2 is eliminated and water is supplied to the reaction tank 10 containing calcium carbonate CaCO3 to prepare an aqueous solution of calcium bicarbonate Ca(HCO3)2, it is possible to use shells that are generated as waste after aquaculture or consumption as calcium carbonate CaCO3, thereby reducing waste.

[0051] In this embodiment, calcium hydroxide Ca(OH)2 and calcium carbonate CaCO3 may be calcium hydroxide Ca(OH)2 obtained by heating shells or limestone in a sealed furnace using renewable energy, recovering the carbon dioxide CO2 generated during heating, and digesting the resulting calcium oxide CaO, or calcium carbonate CaCO3 obtained by allowing the calcium hydroxide Ca(OH)2 obtained in this way to absorb carbon dioxide CO2 from the atmosphere.

[0052] By recovering CO2 from shells and limestone in this way, the CO2 immobilized in these shells and limestone is extracted. The resulting calcium hydroxide (Ca(OH)2) absorbs CO2 from the atmosphere (A) to become calcium carbonate (CaCO3), which then absorbs CO2 to become calcium bicarbonate (Ca(HCO3)2), which is then supplied to the sea (S). If the CO2 recovered from shells and limestone could be used for industrial purposes, it would be possible to recover 1 mole of CO2 from 1 mole of calcium carbonate (CaCO3), recover 2 moles of CO2 from the resulting calcium hydroxide, and supply this to the sea (S) as calcium bicarbonate (Ca(HCO3)2). Of these, 1 mole of CO2 is the CO2 originally contained in the shells or limestone, so 2 moles of CO2 can be recovered from 1 mole of calcium carbonate (CaCO3). This will also enable the creation of a recycling-based society in which seashells, which are generated in large quantities as industrial waste, are converted into calcium ions and returned to the sea S. Furthermore, industrial carbon dioxide CO2 can be obtained. This industrial carbon dioxide CO2 was produced during oil refining, but due to the current trend toward reducing carbon dioxide emissions worldwide, oil refineries are being closed, resulting in a shortage of industrial carbon dioxide CO2. In other words, while the amount of carbon dioxide CO2 in the atmosphere A is increasing, there is a shortage of industrial carbon dioxide CO2 for industrial use. Even in such a situation, by using the calcium ion supply device 1 of the present invention, it is possible to supply calcium ions to the sea S while recovering carbon dioxide CO2 from the atmosphere A and obtaining industrial carbon dioxide CO2.

[0053] Calcium bicarbonate Ca(HCO3)2 is a liquid that dissolves in water and decomposes into calcium ions and bicarbonate ions. However, if air A is supplied to the reaction vessel 10 and bubbling by the gas-liquid contactor 3 continues even after the calcium carbonate CaCO3 is consumed, carbon dioxide CO2 in the air A will dissolve in the water solvent, forming carbonated water, which will cause the water to become acidic. Supplying this to the sea S will contribute to ocean acidification. Therefore, it is preferable to continuously supply surplus calcium carbonate CaCO3 to the reaction vessel 10 so that carbon dioxide CO2 from the air A is still supplied even after the calcium carbonate CaCO3 in the reaction vessel 10 has turned into calcium bicarbonate Ca(HCO3)2, preventing the water from becoming acidic due to the dissolution of carbon dioxide CO2 in the water solvent.

[0054] The calcium ion supplying device 1 of the present invention may supply limewater L prepared in the supplying device 2 to the sea S, either in parallel with or separately from the aqueous solution of calcium bicarbonate Ca(HCO3)2 prepared in the reaction tank 10. In this case, simply supplying the limewater L to the sea S as is can supply calcium ions to the sea S, and because it is strongly alkaline, it can prevent ocean acidification caused by carbon dioxide (CO2). In other words, the sea S has become acidic due to the inflow of rainwater containing dissolved carbon dioxide (CO2), and the hydrogen ion concentration has increased. CO2+H2O→Ocean→HCO3 - +H +

[0055] Therefore, when limewater L is supplied to sea S, two hydroxy ions are produced per mole of limewater L. Ca(OH)2aq → Sea → Ca + +2OH -

[0056] One mole of limewater L acts as a buffer with the two hydrogen ions that are produced when two moles of carbon dioxide CO2 are supplied and the sea S becomes acidic, thereby preventing the sea S from becoming acidic. 2HCO3 - +2H+ +Ca + +2OH - →Ca + +2HCO3 - +2H2O

[0057] In other words, just as when 2 moles of carbon dioxide CO2 are absorbed into limewater L and supplied to sea S as an aqueous solution of calcium bicarbonate Ca(HCO3)2, when limewater L is supplied to sea S, 2 moles of carbon dioxide CO2 dissolve in sea S and act as a buffer with the oxidized hydrogen ions, resulting in the same effect as when 2 moles of carbon dioxide CO2 are recovered.

[0058] The calcium bicarbonate (Ca(HCO3)2) aqueous solution from the reaction tank 10 and the limewater (L) from the supply device 2 can be freely prepared and supplied as calcium bicarbonate (Ca(HCO3)2) aqueous solution alone, limewater (L) alone, or both, or even when both are supplied, the ratio of each can be varied. The supply location can also be varied accordingly, for example, supplying calcium bicarbonate (Ca(HCO3)2) aqueous solution to sandy areas where shellfish are likely to grow, and supplying limewater (L) to the cool seabed where carbon dioxide (CO2) dissolves easily and acidification is likely to occur. In particular, the carbon dioxide (CO2) dissolved in the sea (S) is higher in high-latitude regions near the Arctic and Antarctic, where the water temperature is low, and especially in the Northern Hemisphere, where economic activity is active. Therefore, supplying limewater (L) to these high-latitude regions and the Northern Hemisphere is highly effective. Therefore, the ratio of calcium bicarbonate (Ca(HCO3)2) aqueous solution to limewater (L) supplied can be varied for each region to increase the proportion of limewater (L) in these regions.

[0059] It should be noted that the present invention can be embodied in various other forms without departing from its spirit or essential features. Therefore, the above-described embodiments are merely illustrative in all respects and should not be interpreted as limiting. The scope of the present invention is defined by the claims and is not limited in any way by the text of the specification. Furthermore, all modifications and variations that fall within the scope of the claims are within the scope of the present invention. [Explanation of symbols]

[0060] 1. Calcium ion supply device 10 Reaction vessel 2 Feeding device 3 Gas-liquid contactor 31 Pump 4. Conveyor equipment 41 Transport Route 42 Transfer pump 5. Control device 6. Solar power generation equipment (renewable energy supply equipment) A. Atmosphere C. Water temperature control device L lime water S sea

Claims

1. A method for improving a marine environment, comprising: supplying lime water, or calcium carbonate and water, to a reaction tank; supplying atmospheric air into the reaction tank; causing carbon dioxide in the air to react with the lime water, or calcium carbonate and water in the reaction tank; and supplying the resulting aqueous solution of calcium bicarbonate to the sea.

2. 2. The method for improving a marine environment according to claim 1, wherein carbon dioxide in the atmosphere is reacted with lime water or calcium carbonate and water in the reaction tank while the reaction tank is cooled.

3. 2. The method for improving a marine environment according to claim 1, wherein the limewater is prepared by adding water to calcium oxide obtained by burning calcium carbonate in a closed system using renewable energy to recover carbon dioxide, or by adding water to calcium hydroxide obtained by slaked calcium oxide.

4. 2. The method for improving a marine environment according to claim 1, wherein the calcium carbonate is obtained by burning calcium carbonate in a closed system using renewable energy to recover carbon dioxide, and then allowing the calcium oxide obtained to absorb carbon dioxide from the atmosphere, or by digesting the calcium oxide to obtain calcium hydroxide, and then allowing carbon dioxide from the atmosphere to absorb carbon dioxide.

5. A method for improving the marine environment, characterized by: calcining calcium carbonate in a closed system using renewable energy; recovering carbon dioxide; and adding water to the calcium oxide obtained by calcining calcium carbonate in a closed system; or adding water to calcium hydroxide obtained by slaked the calcium oxide to prepare lime water; and supplying the lime water to the sea.

6. 3. The method for improving a marine environment according to claim 1 or 2, wherein each step is carried out using renewable energy.

7. 6. The method for improving a marine environment according to claim 1, wherein the calcium carbonate is obtained from seashells.

8. 6. The method for improving a marine environment according to claim 1, wherein limestone is used as calcium carbonate.

9. 6. The method for improving a marine environment according to claim 1, wherein the water used to prepare the lime water is selected from the group consisting of groundwater, stored water, rainwater, river water, and industrial wastewater.

10. 2. The method for improving a marine environment according to claim 1, wherein the obtained aqueous solution of calcium bicarbonate is supplied to sandy areas in the sea.

11. 6. The method for improving a marine environment according to claim 5, wherein the obtained lime water is supplied to sandy areas in the sea.

12. 6. The method for improving a marine environment according to claim 5, wherein the obtained lime water is supplied to the seabed.

13. a reaction vessel that can be filled with limewater or calcium carbonate and water; a supply device for supplying lime water or water to the reaction tank; a gas-liquid contactor including a pump for collecting atmospheric air and bringing the atmospheric air into contact with lime water or calcium carbonate and water filled in a reaction tank; a transport device that transports an aqueous solution of calcium bicarbonate produced by a reaction between carbon dioxide in the atmosphere and lime water or calcium carbonate and water from the reaction tank to the outside using a transport pump, and transports the aqueous solution of calcium bicarbonate to the sea via a transport path connected to the transport pump; A calcium ion supplying device characterized by comprising a control device that controls each of these devices.

14. 14. The calcium ion supplying device according to claim 13, further comprising a water temperature control device for controlling the temperature of the aqueous solution in the reaction tank.

15. 15. The calcium ion supplying device according to claim 13 or 14, further comprising a renewable energy supplying device that produces renewable energy and supplies the renewable energy to the device.

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