JPH0763617B2 - Carbon dioxide ocean fixation device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a device for immobilizing carbon dioxide in the ocean, and particularly to directing carbon dioxide directly to the deep sea in the ocean to hydrate carbon dioxide and seawater. The present invention relates to a device for immobilizing carbon dioxide gas in the ocean by producing methane.

[Conventional technology]

Regarding global environmental problems, the phenomenon of global warming caused by greenhouse gases has become a problem. As a greenhouse gas,
Carbon dioxide (CO ₂ ), methane (CH ₄ ), nitrous oxide (N ₂ O), and chlorofluorocarbon in the atmosphere can be mentioned. Of these, chlorofluorocarbon was found to be the main cause of ozone layer depletion. Around the year 2000, it has been confirmed worldwide that it will be totally abolished.

CO ₂ is emitted as a result of consumption of fossil fuels such as coal, oil, and natural gas, and its concentration in the atmosphere is overwhelmingly large, and is a major cause of global warming, and its increase is a problem. As the effects of global warming, it has been pointed out that seawater expansion due to seawater temperature rise, sea level rise due to melting of ice in the Arctic and Antarctic, weather changes such as changes in precipitation, and their effects on biological systems. . For this reason, reduction of CO ₂ generation has become an important issue for suppressing global warming.

While alternative energy sources for reducing CO ₂ emissions are being studied, more than 70% of the earth's surface is the sea, and reduction by the “CO ₂ fixation method using the ocean” has been proposed. (Chemical Engineering Journal, Vol 54, No.1). For example 1)
Ocean fertilization method, 2) Deep water circulation, surface mixing method, 3) Subduction flow method, 4) Direct absorption method, 5) Seaweed fixation method, etc.

Of these, 1) the ocean fertilization method has a large amount of calcium ions dissolved in the ocean surface, but the nutrients such as phosphorus and nitrogen are close to zero, and phytoplankton does not grow.
Phosphorus and nitrogen fertilizers are sprinkled on the surface of the ocean to promote the absorption and fixation of atmospheric CO _{2 into} the ocean by the growth, death and decomposition of plankton.

In the deep water circulation and surface mixing method of 2), the dissolved concentration of phosphorus and nitrogen is higher than the surface layer in the deep water layer of the ocean where sunlight does not reach.
The artificial upwelling allows the plankton to circulate to the surface layer to promote the absorption of CO ₂ by the plankton.

3) The subduction flow method is that there is a general circulation flow in the earth's ocean, and the seawater cooled off Norway submerges deeply,
It is said to flow southward in the Atlantic Ocean to the Indian Ocean and the Pacific Ocean, appear in the surface layer in the process, and return to the coast of Norway again. For this reason, the possibility of absorbing and fixing CO ₂ in the sea by utilizing subduction flows off the coast of Norway has been proposed.

The direct absorption method of 4) is a method in which the emitted CO ₂ is directly introduced into seawater and absorbed. Similarly, the idea of dumping CO ₂ into the ocean has been previously reviewed. One is the study of spray absorption of CO ₂ by seawater and the bubbling method in the sea.
The other is a cost estimation for injecting liquefied carbon dioxide into the deep sea.

[Problems to be Solved by the Invention]

Regarding the above CO ₂ reduction measures, there are currently no technologies that can be embodied, and each has the following problems.

1) Ocean fertilization methods and deep water circulation methods that utilize the ocean
Since it is an indirect and generous CO ₂ fixation system, it cannot be used as an urgent reduction measure for the current increase in CO ₂ .

2) In the direct absorption method into the ocean, CO ₂ dissolves only in a saturated amount in seawater, and most of CO ₂ is released into the atmosphere.

3) In the above-mentioned absorption method into the ocean, the pH of seawater changes to acidic and directly affects the biological system of the ocean.

There are problems in processing and reducing CO ₂ .

An object of the present invention is to solve the above problems and to provide a carbon dioxide ocean fixation device capable of directly fixing CO ₂ to the ocean and rapidly processing a large amount of carbon dioxide.

[Means for Solving the Problems]

To achieve the above object, in the present invention, in a device for immobilizing carbon dioxide in the ocean, means for supplying carbon dioxide at a pressure of 13 atm or higher and a temperature of -4 ° C to 10 ° C at a pressure of 13 atm or higher.
A carbon dioxide gas ocean immobilization device comprising a gas introduction pipe capable of introducing gas into seawater, and a valve for preventing backflow of seawater that is opened and closed by water pressure is provided in the introduction pipe. It is a thing.

In the above-mentioned immobilization device, in order to generate a hydrate of carbon dioxide gas and water, it is preferable to react under the condition that carbon dioxide gas becomes liquefied carbon dioxide gas.
The reaction is preferably carried out at a pressure of 28 atm or higher and a temperature of -4 ° C to 10 ° C.

With the device of the present invention, CO ₂ is introduced into the ocean by an introduction pipe, and 1
By making a sea surface at a pressure of 3 atm or higher and a temperature in the range of -4 ° C to 10 ° C in the introduction pipe, and contacting CO ₂ with seawater at the sea surface to generate a hydrate of CO ₂ and water in seawater, It can be fixed in the sea by its own weight. Further, the CO ₂ density is made on the sea surface with a gas introduction pipe under the condition of the same as or larger than seawater, and liquefied CO ₂ is blown to generate the hydrate, and liquefied CO ₂ is put into the sea together with the hydrate. Can be fixed. Furthermore, a sea surface under the above conditions is created by a gas containing CO ₂ , liquefied CO ₂ is fixed in the sea, and other gas that is not liquefied can be appropriately released to the outside of the introduction pipe. CO ₂ can be directly and directly fixed in a large amount and rapidly fixed.

In the above-mentioned ocean immobilization device, the carbon dioxide gas supply means preferably has a supply amount control mechanism, and the gas introduction pipe draws out non-liquefied gas other than carbon dioxide gas when a mixed gas is used. It is better to provide a gas release mechanism,
Further, vibration or stirring means may be provided at the tip of the gas introducing pipe.

[Work]

The present invention has been made paying attention to the fact that when CO ₂ and seawater are brought into contact with each other, the CO ₂ molecule and the water molecule are bonded to each other to form a hydrate (clathrate). The CO ₂ bubbling method to sea, CO ₂ can not be absorbed only saturated dissolution amount in seawater, the excess CO ₂ is dissipated into the atmosphere from the sea. Also, due to CO ₂ dissolution, the pH of seawater changes to acidic and directly affects the biological system of the ocean. However, although the clathrate changes in salt concentration, it has little effect on seawater pH. Also, since it is heavier than seawater (specific gravity about 1.1) and settles due to its own weight, CO ₂ can be fixed in the sea.

FIG. 7 shows a CO ₂ pressure-temperature diagram. A gas phase and a liquid phase exist at the boundary of the boiling line. The clathrate is produced by contacting liquefied CO ₂ with seawater in a high-pressure vessel simulating the sea (for example, 50 atm and water temperature 5 ° C), and it is confirmed by experiments that the clathrate is produced at a temperature of 10 ° C or less. did.

FIG. 8 shows an example of the relationship between seawater temperature and water depth. Even in the Pacific Ocean Okinawa area, where the water temperature is relatively high, the water temperature is 10 ° C or less at 600 meters in the sea, and the temperature condition of 10 ° C or less can be easily obtained in the ocean. The clathrate is more likely to be generated when the seawater temperature is lower. The freezing temperature of seawater is about -4 ° C, but if frozen to ice, clathrate does not form. Therefore, the temperature range for clathrate production is -4 ° C to 10 ° C.

On the other hand, CO in deep water such as 3,000 meters (300 bar) of deep water
_{When 2} is introduced, the density of liquefied CO ₂ (about 1.05 mg / cc) is higher than that of seawater (1.03 mg / cc) when the water temperature is 5 ° C or lower.
For this reason, if CO ₂ is blown into the deep sea under the above conditions, the liquefied CO ₂ together with the clathrate can be precipitated and fixed on the sea floor due to its own weight. Here, CO directly on the sea surface of the introduction pipe
_{If 2} is pressed in and pushed down, a clathrate will be generated arbitrarily before reaching the sea surface of a predetermined water depth, and eventually the introduction pipe will be blocked. For this reason, it is necessary to provide a seawater backflow prevention mechanism, in particular, a valve for preventing seawater backflow that opens and closes by water pressure so that seawater does not enter the gas introduction pipe.

The main purpose of the present invention is to fix CO ₂ by clathrate generation, but in the sea, most of the carbon is dissolved in the form of HCO ₃ ⁻ , and the amount thereof increases if liquefied CO ₂ is blown in, 2HCO the following chemical equilibrium ^{_{3 - CO 2 + CO 3 2+}} H 2 O CO 3 2- reacts with Ca ²⁺ calcium carbonate (CaCO ₃₎ is produced, the possibility of fixing in a more stable form is there.

〔Example〕

Hereinafter, the present invention will be described by way of examples with reference to the drawings, but the present invention is not limited thereto.

Embodiment 1 FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention. In FIG. 1, it comprises a liquefied gas storage tank 1, a high-pressure pump 2 and a gas introduction pipe 3 into the sea. Liquefied C by compressing CO ₂
It is stored in the liquefied gas storage tank 1 as O ₂ , and is sent by the high-pressure pump 2 and is injected under pressure through the gas introduction pipe 3 and introduced into the sea.

2-a and 2-b show detailed sectional views of the tip of the gas introducing pipe, and the operation method will be described. The tip of the gas introduction pipe 3 is equipped with a valve 5, which is closed by water pressure to prevent backflow of seawater into the introduction pipe (state shown in FIG. 2-a). When the liquefied CO ₂ is sent by the high-pressure pump 2 and the pressure inside the introduction pipe is increased to a pressure equal to or higher than a predetermined water depth, the valve 5 opens (state shown in FIG. 2-b) and the liquefied CO ₂ flows into the sea. Liquefied CO ₂ 4 at this point
Sequentially generate clathrate 7 and settle to the sea floor.

Embodiment 2 FIG. 3 is a cross-sectional view showing an embodiment in which the tip of the gas introduction pipe 3 is flared. Example (however, experiment in high pressure vessel), 50 atm (equivalent to a water depth of 500 m) Water temperature 5 ° C
Under the conditions of, the density of liquefied CO ₂ (about 0.91 mg / cc) is
Less than 1.03 mg / cc), liquefied CO ₂ is in the upper layer and seawater is in the lower layer, and clathrate is generated and grows on the sea surface. That is, in FIG. 3, the clathrate 7 is sequentially generated, but excess liquefied CO ₂ floats. For this reason, liquefied CO ₂
To increase the area of the clathrate generating sea surface, and further attach a vibration transmitter 8 such as ultrasonic waves to add vibration to cause the clathrate layer to separate from and drop from the sea surface, and to increase clathrate generation efficiency. .

Embodiment 3 FIG. 4 is a sectional view showing an embodiment in which the check valve 9 and the nozzle 10 are combined at the tip of the gas introducing pipe. The liquefied CO ₂ 4 which has been pressurized and sent to a predetermined atmospheric pressure or more and jetted out from the nozzle 10 through the check valve 9 as droplets 4a. The finer the jetted droplets 4a, the better the contact efficiency with the seawater, and the droplets serve as nuclei to increase the clathrate generation rate.

Embodiment 4 FIG. 5 is a schematic configuration diagram showing an embodiment in which a gas containing carbon dioxide is directly fixed to the ocean. The gas is compressed by the gas compressor 11, passes through the gas storage tank 12, and is guided into the sea by the gas introduction pipe 3a. FIG. 6 shows a detailed sectional view of the gas introduction pipe 3a. CO ₂ in the gas is liquefied at an arbitrary position of the introduction pipe, and at a predetermined water depth, the valve 5 opens like the above and flows out into the sea to generate a clathrate. On the other hand, most of the unliquefied gas 4b (for example, nitrogen) in the gas is guided to the exhaust pipe 3b from an arbitrary position of the gas introduction pipe, and is pressure-controlled and released by the pressure holding valve 13 on the surface of the sea above the ground.

〔The invention's effect〕

 The present invention has the following effects.

1) By generating a hydrate of carbon dioxide and water, carbon dioxide can be fixed to the seabed because the hydrate settles due to its own weight.

2) Since carbon dioxide is a hydrate, there is little change in the pH of seawater and it has no direct effect on marine biological systems.

3) A large amount of carbon dioxide can be directly processed quickly, and the effect of reducing carbon dioxide is great.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention, FIGS. 2-a and 2-b are detailed sectional views of a gas introducing pipe, and FIGS. 3 and 4 are other embodiments. 5 is a detailed sectional view of the gas introducing pipe of FIG. 5, FIG. 5 is a schematic configuration diagram of another embodiment according to the present invention, FIG. 6 is a detailed sectional view of the gas introducing pipe used in FIG. 5, and FIG. 7 is the temperature of carbon dioxide gas. -Pressure phase equilibrium diagram, Fig. 8 is a graph showing the relationship between seawater temperature and water depth. 1 ... Liquefied gas storage tank, 2 ... High-pressure pump, 3 ... Gas introduction pipe, 4 ... Liquefied gas, 5 ... Valve, 6 ... Spring, 7 ...
Clathrate, 8 ... Vibration transmitter, 9 ... Check valve, 10 ...
… Nozzle, 11 …… Gas compressor, 12 …… Gas storage tank, 13 ……
Pressure-holding valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeoki Nishimura 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Hitate Manufacturing Co., Ltd.Hitachi Research Laboratories (72) Inventor Hiroshi Miyadera 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Hitsuru Corporation Hitachi Research Laboratory (72) Inventor Takao Hishinuma 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Hitachi, Ltd. (56) Reference JP-A-3-164420 (JP, A)

Claims (4)

[Claims] 1. In a device for immobilizing carbon dioxide in the ocean, means for supplying carbon dioxide at a water pressure of 13 atm or more and water pressure 13
A gas introducing pipe capable of introducing gas into seawater having a temperature of -4 ° C to 10 ° C at atmospheric pressure or higher, and a valve for preventing backflow of seawater opened and closed by water pressure is provided in the introducing pipe. Carbon dioxide ocean fixation device. 2. The ocean fixation device for carbon dioxide according to claim 1, wherein the carbon dioxide supply means has a supply amount control mechanism. 3. The carbon dioxide marine immobilization device according to claim 1, wherein the gas introduction pipe is provided with a gas release mechanism for extracting non-liquefied gas other than carbon dioxide gas. 4. The apparatus for immobilizing carbon dioxide in the ocean according to claim 1, wherein a means for vibrating or stirring is provided at the carbon dioxide emission end of the gas introduction pipe.