JPH06226047A - Ocean treatment of carbon dioxide - Google Patents

Abstract

PURPOSE:To make ocean treatment of CO2 in the sea where water depth is shallow by clathrating the CO2 and settling the clathrated CO2 into the sea. CONSTITUTION:An injection pipe 2 for liquid CO, is penetrated into the upper part of a clathrate forming container 1 of a vertical cylindrical shape closed in the upper part in such a manner that the liquid CO2 of the density smaller than the density of the sea water does not float and diffuse in the sea water. The clathrate forming container 1 is first arranged at about 700m water depth from the equipment on the sea. The equipment on the sea and the forming container 1 are then connected by the injection pipe 2. The CO2 accumulates in the upper part of the container 1 when is injected from an injection nozzle 3. The CO2 is stirred while the CO2 is so held as not to diffuse. The clathrate of the CO2 is formed when the CO2 solubility in the container 1 attains about 6wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CO ₂ ocean treatment method for treating a large amount of carbon dioxide (hereinafter referred to as “CO ₂ ”), which is one of the measures to prevent global warming.

[0002]

2. Description of the Related Art In recent years, global warming of the climate due to greenhouse effects such as artificially emitted CO ₂ and destruction of the ozone layer due to stable compounds such as CFCs have become a problem of environmental destruction at the global level. . As one of the measures to prevent this global environmental problem, since a large amount of CO ₂ is contained in the combustion exhaust gas discharged from a combustion device such as a boiler, the CO ₂ in the gas is discharged before the combustion exhaust gas is released to the atmosphere. Attempts have been made to separate and collect.

[0003]

[SUMMARY OF THE INVENTION Incidentally, in recent years, the combustion device and there are many in various fields, since the combustion exhaust gas amount exhausted many, particularly generated a large amount of flue gas in thermal power plants, the CO ₂ When separated and collected, a large amount of CO ₂
How to handle is one problem. This CO
_{As one of the two} treatment methods, it is considered to liquefy CO ₂ and inject it into the deep sea floor of a large-capacity ocean for storage.

When injecting CO ₂ into the sea, CO ₂ exists as a liquid in a place deeper than about 500 m in water depth. 500m
Since the density of liquid CO ₂ is smaller than that of seawater at the depth of
The O ₂ droplets are dissolved in the seawater while floating, but the CO ₂ droplets that cannot be dissolved and remain, when they float to a certain depth, suddenly become a gas and suddenly float and diffuse from the sea surface to the atmosphere.

Further, since liquid CO ₂ has a higher compressibility than seawater, the increase in density is larger than that of seawater when the water depth is deep, and at a water depth of 3000 m, the densities of seawater and CO ₂ are reversed and C
The O ₂ drop settles.

Therefore, for example, as shown in FIG. 5, the CO ₂ separation device 1 is separated from the combustion exhaust gas of the boiler 10.
1. In order to treat CO ₂ stored in a liquid state in the storage tank 13 via the CO ₂ liquefaction device 12, the CO ₂ transport ship 14 transports the water to a depth of more than 3000 m, and the offshore equipment 7
It is considered that the pipe 15 is lowered from the (sea level) to a depth deeper than 3000 m to inject a large amount of CO ₂ into the deep sea and store the CO ₂ in the deep sea bottom.

However, piping 1 to a depth of more than 3000m
Therefore, the construction cost and the running cost are increased, and the CO ₂ treatment cost is increased.

[0008] The present invention has been made in view of such circumstances, and its object is to provide a marine processing method CO ₂ capable of performing marine processing CO ₂ at shallow water .

[0009]

In order to achieve the above-mentioned object, the present invention dissolves liquid CO ₂ in the sea and stirs it while keeping it so as not to diffuse so that the CO ₂ is clathrated in the sea. , CO ₂ clathrate (inclusion compound)
It is to be submerged in the form of. That is, liquefied CO ₂ separated recovered from the exhaust gas such as a boiler as a measure of global warming prevention measures, injected into a large ocean volume, it intended to prevent the dissipation to the atmosphere simply liquefied CO ₂ Instead of storing it in the deep sea as it is, it is made into a clathrate and settled in the deep sea.

[0010]

[Action] The CO ₂ was clathrate of, by precipitating it in the sea, the state clathrate of the CO _2, the density is about 1.1 g / cm ^3, or less depth of about 700m is the clathrate stable Since it exists in the ocean and settles under its own weight, it is possible to perform ocean treatment of CO ₂ at a depth of about 700 m, which is relatively shallow.

By the way, it is difficult to generate the clathrate just by injecting liquid CO ₂ into the sea with a nozzle, and even if the clathrate is generated, only the surface of the CO ₂ droplets has the clathrate and the inside of the liquid CO ₂ is There is. Therefore, the liquid C
By dissolving O ₂ in the sea and stirring it while keeping it from diffusing, the droplets having only the surface clathrate are crushed. As a result, a clathrate is generated on the surface of a new CO ₂ droplet, and most of the CO ₂ is converted to a clathrate by repeating this, so that the clathrate is easily generated. This makes it possible to industrially generate a clathrate of CO _{2 on} the sea and to lower the treatment cost compared to the method of injecting this slurry-like material into the sea, thereby making it economically more economical.
Marine processing of O ₂ can be performed.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a clathrate generating container. This container 1 is, for example, a vertical cylinder whose upper part is closed so that liquid CO ₂ having a density lower than that of seawater does not float and diffuse in seawater. Formed into a shape.

The upper portion of the production container 1 is a liquid CO ₂ injection pipe 2
Is penetrated to form a bell shape, and CO ₂ is injected from the offshore equipment via the injection pipe 2, so that the tip of the injection pipe 2 in the container 1 is formed as an injection nozzle 3. Further, in the production container 1, a plurality of stirring devices 4 are arranged vertically and horizontally so that the liquid in the container 1 is sufficiently stirred.

Further, below the injection nozzle 3 in the container 1, since the clathrate-forming reaction is an exothermic reaction, the container 1
A cooling device 5 is arranged so that the internal temperature is maintained within an allowable range, and the cooling device 5 is configured to use seawater from a seawater pump 6 arranged outside the production container 1 as a cooling medium. Has been done.

Now, in order to carry out the ocean treatment of liquid CO ₂ ,
As shown in FIG. 2, first, the clathrate production container 1 is placed at a water depth of about 700 m from the offshore equipment 7, and the offshore equipment 7 and the production container 1 are connected by the injection pipe 2.

Next, liquid CO ₂ is injected from the offshore equipment 7 into the clathrate producing container 1 from the injection nozzle 3 through the injection pipe 2. At this time, since the density of the liquid CO ₂ is smaller than that of seawater, the CO ₂ droplets are floated and dissolved in the seawater.
Since the production container 1 is formed in a vertical cylindrical shape with the upper part closed, the CO injected from the injection nozzle 3 into seawater.
₂ accumulates in the upper part of the container 1 and its floating is prevented.
That is, as shown in FIG. 1, the portion above the nozzle 3 in the container 1 is a portion where the liquid CO ₂ is accumulated, and the portion appropriately below the nozzle 3 is a portion having a high CO ₂ solubility.

The CO ₂ solubility in the container 1 is about 6 wt.
%, The CO ₂ clathrate is generated. This is because the conditions that easily generate clathrates are created in the sea.

That is, from the temperature of seawater shown in FIG.
In the sea deeper than 500 m, it is in the region I in FIG. 4 showing the phase equilibrium diagram of CO ₂ -artificial seawater. This area of I is
As described below with reference to FIG. 4, the conditions are the temperature and pressure at which liquid CO ₂ , CO ₂ clathrate, and seawater coexist. Although CO ₂ clathrate be injected CO ₂ to the seawater make this condition experimentally can not facilitate, CO ₂ dissolved concentration of about 6
When it reaches wt%, the clathrate is generated. Further, if seawater having a CO ₂ dissolved concentration of about 4 wt% or more and up to about 6 wt% has a seed crystal (which may be a clathrate piece) that becomes the nucleus for starting the clathrate formation, the clathrate can be easily produced by stirring. It is possible.

Even if the above conditions are satisfied in the container 1, the clathrate is generated only on the surface of the CO ₂ droplet, and the inside remains the liquid CO ₂ . Droplets having a clathrate only on such a surface will float because the clathrate is very thin.

Therefore, the inside of the container 1 is agitated by the agitator 4 to crush the clathrate which is the skin of the droplet. This creates a clathrate on the surface of the new CO ₂ droplet. By repeating this, the clathrate generation speed increases. As a result, the generated clathrate has a large density of about 1.1 and settles under its own weight. At this time, CO ₂
Regarding the pressure of the clathrate generation condition, it is possible to easily satisfy the condition at the depth of the sea, but regarding the temperature, since the clathrate generation is an exothermic reaction, the seawater pump 6 is driven and the cooling device 5 is used. The temperature inside the container 1 is cooled so as to satisfy the above conditions. According to the experiment,
If a small amount of clathrate can be produced with the CO ₂ solubility raised to about 6 wt%, stirring in this state will promote clathrate production. The CO ₂ solubility in such a state drops to about 4 wt%.

Therefore, it is possible to easily convert CO ₂ into clathrates by utilizing the conditions such as the temperature and pressure in the sea. The clathrate CO ₂ has a density of about 1.1 g / cm ³ , and the clathrate remains stable at a water depth of about 700 m or less and settles under its own weight. Therefore, the depth of water is about 700 m, which is shallower than 3000 m. CO ₂ ocean treatment can be performed.

If the sea area for treating CO ₂ is properly selected, for example, in the Oyashio area near Japan, even if the water depth is 500 m, there are places where the water temperature is about 3 ° C. throughout the year.
CO ₂ treatment is possible even at 0 m.

Further, by dissolving liquid CO ₂ in the sea and stirring it while keeping it so that it does not diffuse, droplets having a clathrate only on the surface are crushed and new CO ₂ droplets are classified on the surface. Rate is generated, and by repeating this, C
Since most of O ₂ is converted to clathrate, CO _{2 in the} sea
It is possible to continuously classify. Therefore, the amount of CO ₂ injected into the production container 1 is adjusted according to the amount of the liquid CO ₂ that clathrates and settles due to its own weight, so that the inside of the container 1 is set to the above condition (condition that the clathrate is generated). By maintaining the liquid CO ₂ continuously in the container 1.
Is converted into clathrates, and CO ₂ can be efficiently treated in the form of clathrates. Therefore, the treatment cost is lower than that of the method of industrially producing a clathrate of CO ₂ and injecting this slurry into the sea or the method of injecting liquid CO ₂ into a water depth of 3000 m, which is more economical. It will be possible to perform ocean treatment of CO ₂ .

[0025]

According to the present invention, liquid CO ₂ is dissolved in the sea, and the CO ₂ is clathrated by stirring while maintaining it so as not to diffuse, so that CO ₂ is economically economical at a shallow water depth. Can process ₂ oceans.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a view showing a state in which the clathrate producing container of the present invention is submerged in the sea.

FIG. 3 is a diagram showing a relationship between water depth, seawater density, and seawater temperature.

FIG. 4 is a phase equilibrium diagram of CO ₂ -artificial seawater.

FIG. 5 is a configuration diagram showing an example previously proposed.

[Explanation of symbols]

 1 Clathrate container 2 Injection tube 4 Stirrer

Claims (1)

[Claims] 1. A method of dissolving liquid carbon dioxide in the sea, stirring the liquid carbon so as to keep it from diffusing, and clathrating the carbon dioxide to precipitate the carbon dioxide in the form of clathrate in the sea. Carbon dioxide marine treatment method.