JP5131721B2 - Carbon dioxide immobilization method - Google Patents

Description

The present invention contributes to environmental purification and relates to a method for immobilizing carbon dioxide.
Specifically, the present invention relates to a method capable of effectively fixing carbon dioxide at normal temperature and normal pressure using various metals such as iron and other metals and alloys, or mixtures of these metals.

  In recent years, environmental degradation on a global scale has become a problem. The prevention of global warming has been screamed and, as symbolized by the ratification of the Kyoto Protocol, it has developed into interests between countries over the conclusion of a treaty that controls carbon dioxide emissions under the fossil fuel and petroleum energy consumption regulations. In other words, global warming due to greenhouse gases such as carbon dioxide and environmental pollution due to exhaust gas have become obvious, and in order to suppress the emission of carbon dioxide into the atmosphere associated with the use of fossil fuels, carbon dioxide is absorbed and fixed. There is a need for means and technology to do this.

  As a method for absorbing and fixing carbon dioxide, various absorbing materials have been studied. For example, chemical absorption by a double oxide of lithium has been proposed (for example, Patent Document 1). Furthermore, as a method for fixing carbon dioxide, a method for storing in the deep sea or in the ground, and a method for fixing artificial photosynthesis that scientifically mimics photosynthesis of plants have been proposed.

  However, the above proposal of absorbing and fixing carbon dioxide with materials such as lithium double oxide has a limit in the amount of carbon dioxide absorbed per mass of the absorbent material, while taking into account the huge amount of carbon dioxide to be reduced In this case, it is necessary to secure an enormous amount of absorbent material, and the proposal depending on this material is a proposal that is practically effective because the cost and energy for producing the absorbent material are enormous. In fact, the lithium complex oxide used is actually a temporary separating agent that absorbs carbon dioxide and releases it to the next process rather than immobilizing it permanently. Use as a recovery agent is only the actual situation.

  Regarding the method of storing in the deep sea etc. mentioned last and the system by artificial photosynthesis etc., the former is difficult in the sense of immediate effect because the system is large-scale and complicated, and the latter is researched Since it has just begun and there are many issues for practical application, it is difficult to say that all of them are proposals with immediate effectiveness as a countermeasure against global warming.

  Under these backgrounds, the present inventors have intensively studied to develop effective carbon dioxide immobilization means, and as a result, strained metal bodies or substance bodies containing low-valent metals. Applying mechanical shocks or stresses that can be deformed or destroyed and bringing them into contact with water, the metal and water can react with each other to generate hydrogen. Together with the introduction of carbon dioxide, it was found that carbon dioxide was converted as a stable carbonate of metal and could be immobilized thereby, and a patent application was filed earlier based on these findings (Japanese Patent Application No. 2005-212332). ). However, the invention according to this earlier application is only required to promote a reaction by applying mechanical energy. As a result, when mechanical impact is applied as a mechanical energy application mode, even if a substance body containing a metal may become fine particles due to impact, the significance and effect of the mechanical energy are applied when mechanical energy is applied. Therefore, it was not considered that metal fine particles in a field to which no mechanical energy was applied can independently exhibit the same action and effect.

JP 2003-326159 A

  However, as a result of further examination of the invention according to the previous patent application proposed by the present inventors, the carbon dioxide fixation reaction due to the presence of metal and water does not give mechanical impact energy, but the form of the metal used as a raw material. I also found that it can proceed independently depending on the situation. That is, it was found that the reaction proceeds autonomously when the metal is fine particles. Of course, this finding does not deny the previous invention by applying mechanical energy, but it is significant to find out that a similar reaction can occur without applying mechanical energy. That is, it is clear that the invention has a special significance with respect to the invention by applying mechanical energy, and it can be distinguished and established as an independent invention.

The present invention has been made on the basis of the above findings, and is intended to propose a carbon dioxide absorption system that does not rely on mechanical energy application.
As a matter of course, establishing a carbon dioxide absorption system that does not require energy is significant in itself. As shown in the prior art, in the carbon dioxide fixation system using a specific absorbent material, it is necessary to secure a huge amount of absorbent in the future, and the absorbent has a special composition, structure, and form. cost, energy becomes enormous required for reserved for, while it is extremely problematic in terms of cost in energy, the inventors are those that attempt to provide a completely new carbon dioxide fixation system without such problems It is.

That is, as a result of intensive studies by the present inventors as described above, hydrogen is generated and carbon dioxide is produced by contacting fine particles or fine particle aggregates of a substance containing a metal or a low-valent metal with water and carbon dioxide. Has been found to be converted as a stable carbonate of metal and thereby be immobilized. This invention is made | formed based on these knowledge, Comprising: The structure is as follows.
(1) It is made of one metal selected from the group consisting of chromium, manganese, iron, cobalt, and copper, and a fine particle having a particle size of 50 μm or less , water, and carbon dioxide are brought into contact with each other, so that the metal has a higher valence. A method for immobilizing carbon dioxide is characterized in that a substance containing a carbonate of the metal is produced by reacting so that carbon dioxide becomes carbonate.
(2) pre-Symbol fine particles, characterized in that those made by a mechanical crushing method of immobilizing the carbon dioxide according to (1).
(3) The fine particles are placed in a container, carbon dioxide is filled in the container, and pure water is added to produce a substance containing the metal carbonate, (1) or (2) The method for immobilizing carbon dioxide described in 1.

  In the present invention, carbon dioxide can be immobilized as metal carbonate together with generation of hydrogen by the reaction of metal fine particles, water, and carbon dioxide with the above-described configuration. In other words, hydrogen is generated by the reaction with water on the metal surface, and the generated metal ions and carbonate ions can react to form carbonates. Conventionally, when carbon dioxide is chemically absorbed, special treatment is required. In contrast to the necessity of preparing a new absorbent material, the present invention has an exceptional effect of absorbing and fixing carbon dioxide without preparing an absorbent material having a special composition or structure. . Further, it can be efficiently absorbed even at room temperature around 20 ° C., and has the feature that heating may be unnecessary.

Hereinafter, the present invention will be described and referred to in detail based on embodiments.
In practicing the present invention, magnesium, aluminum, titanium, manganese, zinc, iron, chromium, cobalt, nickel, tin, lead, copper, silver, indium, gallium, germanium, lanthanum, cerium, and the like can be considered as the metal. . Among them, magnesium, aluminum, titanium, manganese, zinc, and iron are highly active, and since they are present on the earth in large quantities, metals containing a large amount of these are also widely used as metal materials, so they are used in the method and apparatus of the present invention. Cheap.

  Among them, iron is abundant in the earth's crust as an element, and is cheap and harmless, so it is used everywhere in life as a steel material and stainless steel. Since the amount of consumption is high, scrap is also increasing, and its effective use is a problem, but it can be used as a metal in the present invention.

  The metal that can be used in the present invention need not be a simple substance or a pure metal, and may be an alloy composed of two or more metal elements. Even if each metal is not separated and purified, each metal may exhibit the function of the present invention at the same time, or a metal that works more effectively may mainly function. Steel scrap in which metals such as copper, zinc and nickel are mixed with iron is not easy to reuse as a raw material for steel making, and thus the recycling rate is low. However, in the present invention, it can be used without worrying about the elemental composition. The produced carbonate corresponds to the metal particle-containing component used in the reaction, and a metal carbonate containing the metal particle-containing component can be produced. When the metal particles contain a plurality of elements, carbonates and composite carbonates containing a plurality of metal elements can be generated.

  The metal that can be used in the present invention may be an alloy phase containing a nonmetallic element, a composite material in which a fibrous or particulate material such as a resin is dispersed, a mixture containing a synthetic resin, oil, or the like. That is, the object can be achieved as long as the metal reacts even if impurities other than the metal are mixed, without extracting or refining the metal contained therein.

  In the present invention, a substance containing a low-valent metal is not only a so-called zero-valent metal but also a low valence in, for example, chromium, manganese, iron, cobalt, copper, etc. that can take a plurality of valences. Meaning those that can reduce water by changing to a higher valence state.

  Further, in the present invention, the fine particles refer to those having a small specific size and a large specific surface area which is a surface area per mass, and the larger the specific surface area, the easier the reaction proceeds. Examples of the size of the fine particles include those having a diameter of 1 to 50 micrometers, typically expressed as a diameter, as disclosed in Examples described later. However, the particle diameter is merely an example and is not limited by the disclosed example. That is, the fine particles in the present invention are determined depending on whether or not a reaction has occurred as a result, and can be defined as the fine particles of the present invention up to a limit that can cause a reaction.

  The shape of the fine particles is not limited to spherical or spherical, and may be any shape as long as the specific surface area is large, such as irregular shape, plate shape, film shape, needle shape, fiber shape, etc. There may be.

  Further, even if the fine particles are aggregated, it is sufficient that the specific surface area of the entire aggregate is large, and it may be a bulk or a porous body in appearance.

  In order to use a large solid or bulk metal such as scrap metal represented by scrap iron as a raw material as a metal of the present invention, it can be procured by making it fine by mechanical grinding.

  In carrying out the present invention, the temperature condition is not particularly limited. For example, the reaction can proceed even at room temperature of 20 ° C.

  As described above, the present invention has a distinctive effect by the above-described configuration, and it is clear that the present invention has a number of advantages as compared with the prior art. This proposal is very advantageous for the fixation of carbon dioxide exhaust gas, which has become a problem as a countermeasure against global warming, and has been proposed to fully meet the regulations expected in the future.

In principle, it is well known that metals are easily oxidized because they are electrically positive, and are dissolved in water as metal ions and water is reduced to generate hydrogen gas. On the other hand, it is also well known that carbon dioxide dissolves in water to produce carbonic acid, and carbonate ions (CO ₃ ²⁻ ) react with metal ions to produce carbonates.

For example, alkali metals such as sodium are very active. However, alkali metals react violently with water and are not easy to handle. In such a case, the reaction can be moderated by adding a base such as sodium hydroxide to water in advance to increase the pH and lowering the hydrogen ion concentration. Increasing the pH also promotes the production of carbonate ions from carbonic acid (H ₂ CO ₃ → 2H ⁺ + CO ₃ ²⁻ ), so dissolution / absorption of carbon dioxide in water (CO ₂ + H ₂₎
O → H ₂ CO ₃ ) and the formation of carbonates are also advantageously promoted. Of course, other than pH adjustment, it can be applied if a means capable of suppressing a violent reaction is taken.

  On the other hand, metals that have a relatively low ionization tendency compared to alkali metals are easy to handle, and as such, they are used as structural materials themselves. Can be used to cause the reaction as in the present invention.

  In order to give a practically sufficient reaction rate and increase the total reaction amount, it is an effective means to increase the surface area as a reaction field by, for example, miniaturizing a metal. Therefore, by using fine particles, carbonate can be efficiently generated even at room temperature.

  As described above, the present invention can fix carbon dioxide at room temperature, but as a metal used in the reaction, a used metal material such as scrap or a metal containing impurities is used as a raw material. Therefore, it is not necessary to secure a purified raw material that is refined as in an advanced chemical reaction operation, and it is extremely easy to secure the raw material, and the handling of the raw material is not required.

  The apparatus design for carrying out the method of the present invention is not limited at all as long as it has a structure that can accommodate reaction components and provide a reaction field, and the structure may be simple. For example, as shown in FIG. 1, metal powder (2) as a solid phase, water (3) as a liquid phase, and carbon dioxide (4) as a gas phase are supplied to a reaction vessel (1), and these reactions are carried out in the reaction vessel. Contact material. And metal carbonate (5) can be taken out after reaction. At the same time, hydrogen (6) is generated. Since there is no need to heat the reaction system, the apparatus does not require a heating mechanism and does not consume energy such as electric power. However, shaking the reaction vessel is preferable because contact, movement, and diffusion of the reaction components are promoted and the reaction can be performed efficiently. Alternatively, the reaction efficiency can be increased in a system that circulates reaction components regardless of shaking. There is no particular limitation on the reaction mode. Typically, a mode in which water is allowed to flow from above and carbon dioxide is bubbled from below onto a fixed bed on which metal particles are fixed may be employed. Or the aspect which forms the fluidized bed of a metal particle with the waste gas containing water or a carbon dioxide may be sufficient. Furthermore, the reaction material may be supplied continuously or batchwise to the shaking mill apparatus.

In any case, the scale-up in the device design is extremely simple, and the amount of carbon dioxide treated depends on the volume of the reaction vessel, the amount of reaction components accommodated, and the partial pressure of carbon dioxide. Carbon dioxide fixation is possible. There is no need to synthesize a substance as a carbon dioxide absorber or prepare a material as in the past, and it is only necessary to use a common metal, and carbon dioxide is the metal used. Fixed as carbonate.

That is, carbon dioxide is, for example, FeCO ₃ , MnC depending on the metal component of the metal used.
It can be fixed as a carbonate such as O ₃ . Moreover, in the case of FeCO ₃ , MnCO _3, etc., the amount of carbon dioxide is fixed at a ratio of 1 mole of carbon dioxide to 1 mole of metal, so about 800 grams of carbon dioxide is fixed by 1 kilogram of iron or manganese. can do. Therefore, it is mentioned as one of the advantages that it is extremely higher than the carbon dioxide absorption capacity of lithium orthosilicate described in Patent Document 1.

Incidentally, the reaction in carbon dioxide fixation in Patent Document 1 is represented by the reaction formula shown in (1) below.
Li ₄ SiO ₄ + CO ₂ → Li ₂ SiO ₃ + Li ₂ CO ₃ (1)
According to this reaction formula, Li ₄ S absorbs as much carbon dioxide as Fe and Mn.
The iO ₄ absorbent is twice or more in weight and corresponds to about 7 times in volume, and the immobilization of the present invention has an extremely high fixing ability.

Furthermore, the metal that can be used in carrying out the present invention is not particularly limited, and any metal may be used. It exists not only at factories and plants, but also at street corners and homes, that is, everywhere on the earth. Therefore, it is easy to proceed with fixing carbon dioxide on a large scale. Moreover, it is also possible to use metal waste materials that are no longer needed. Rather than being rusted, that is, just becoming an oxide, it can be said that it is a method and proposal suitable for resource saving because it will lead to effective use of waste if used for carbon dioxide absorption. In addition to carbonates and hydrogen carbonates, carbonates referred to here include other anions such as hydroxide carbonates and carbonates such as hydroxide carbonates M ₂ CO ₃ .nMOH. Can include, not exclude. Further, it may include fixing carbon dioxide in a state of carbonate aqueous solution in which carbonate is dissolved in a solvent such as water.

Carbon dioxide emitted in Japan is 32% of the total from the energy conversion sector, that is, power plants (data from 2003. Carbon dioxide emitted directly from power generation. Source: Greenhouse Gas Inventory Office) If an apparatus for carrying out the method of the present invention is installed in a power plant, carbon dioxide can be effectively reduced. When the above emissions are converted to the weight of carbon dioxide, it corresponds to about 400 million tons / year. On the other hand, 35 million tons of scrap are generated annually in Japan. If 20% (7 million tons) is used for carbon dioxide fixation, 5.6 million tons of carbon dioxide is fixed. Can do. This is equivalent to a 1.4% reduction in annual emissions.
For example, the amount of carbon dioxide emitted from a 1 million kW state-of-the-art thermal power plant using LNG (liquefied natural gas) as fuel is said to be 11,000 tons / day, and 460 tons per hour. It is. In order to absorb and immobilize this 1%, it is sufficient to supply about 5.8 tons / hour of iron or manganese.

  As an example of a method for installing the apparatus for carrying out the method of the present invention in a thermal power plant, carbon dioxide is effective by connecting an exhaust gas pipe to the reaction vessel (1) and introducing and passing the exhaust gas into the liquid phase. To be absorbed. From the reaction vessel (1), exhaust gas containing no carbon dioxide or containing a low concentration is discharged into the environment. By bubbling the gas while passing through the liquid phase, the reaction raw material in the reaction vessel is agitated, mass transfer / diffusion is promoted, and the reaction efficiency is also increased.

Carbonate obtained as a result of the carbon dioxide fixation is harmless, and thereafter, secondary treatment consuming cost, without the need for tertiary treatment, can be discharged remains fixed state. Alternatively, carbon dioxide may be stored and maintained after fixing, or carbon monoxide can be effectively used as various reaction raw materials by thermal decomposition into metal oxide and carbon monoxide. .

  Hereinafter, the present invention will be specifically described based on examples. However, these examples are merely for specifically disclosing and explaining the present invention, and are not intended to limit the present invention. Unless the gist of the invention is changed, the carbon dioxide immobilization conditions can be appropriately changed, and are not limited by the disclosed embodiments.

Example 1;
Put 20.0 g of commercially available iron powder with a particle size of 45 μm (097-04791, manufactured by Wako Pure Chemical Industries, Ltd., purity 99.9%, Lot: EWN0818) into a resin bottle with a lid with high airtightness of 300 ml capacity. After filling carbon dioxide with a purity of 99.95%, 12 ml of saturated carbon dioxide was added to pure water (collected from a pure water device Elix manufactured by Millipore), and the mixture was sealed to a carbon atmosphere of 1 atm. . The resin bottle was placed on a rotary table, and stirring was performed by performing a revolving motion of 200 revolutions per minute at room temperature and a rotational motion of the same rotational speed opposite to the rotational direction. After stirring for 16 hours, gas phase gas in the resin bottle was gas chromatographed (Shimadzu GC-8A, Polapack-N: 2m + Polapack-Q: 1m composite column and molecular sieve 5A column were used. ), No carbon dioxide was detected and all were absorbed. In addition, when analyzing air using this gas chromatography, carbon dioxide contained in the air (which is said to have a concentration of 330 ppm) can be easily detected, and the detection limit is at least lower than this concentration. The concentration was clearly lower than 330 ppm. As a result of analysis of the gas in the bottle by gas chromatography, hydrogen with a concentration of 96% or more was confirmed instead of carbon dioxide, and it was found that carbon dioxide was consumed and simultaneously filled with hydrogen. The remaining water was evaporated and removed by reducing the pressure inside the bottle while heating it to 50 ° C. When powder X-ray diffraction experiments (RINT-2500, Rigaku Electric Co., Ltd., CuKα ray, 12 kW) were performed on the powder remaining after drying, the X-ray diffraction pattern of FIG. 2 was obtained, and the raw material iron that remained unreacted The presence of iron carbonate (rhombohedral FeCO ₃ , mineral name: siderite) was confirmed along with (α-Fe).
The reaction formula is shown by the formula (2).
Fe + H ₂ O + CO ₂ → FeCO ₃ + H ₂ ↑ (2)
The number of moles of carbon dioxide at 1 atm filled in a resin bottle volume of 300 ml is approximately 13 mmol assuming an ideal gas, while 20 g of iron is 360 mmol, which is a large excess. Therefore, it is a reasonable result that all the carbon dioxide is fixed, but the raw material iron is left over. Further, 12 ml of water was 670 mmol, and this was too large because of excessive carbon dioxide. In this example, solid iron carbonate was obtained by removing by drying. In addition, although the diffraction pattern of iron oxide (Fe ₃ O ₄ ) is also confirmed in FIG. 2, this is because carbon dioxide is completely consumed at a stage earlier than 16 hours to produce carbonate, and then iron is produced. It was considered that the reaction between water and water continued without using carbon dioxide to produce hydroxide (Fe + 2H ₂ O → Fe (OH) ₂ + H ₂ ↑), and further oxide was formed by drying.

Example 2;
In the same bottle as in Example 1, 10.0 g of the same iron powder was charged to fill carbon dioxide, 10 ml of pure water saturated with carbon dioxide was added, and the mixture was sealed to a carbon atmosphere of 1 atm. Stirring was performed at 200 revolutions per minute at room temperature, 0.1 ml of gas was sampled from the gas phase every hour and analyzed by gas chromatography. The change in gas concentration is shown in FIG. From the change over time up to 8 hours later, it was confirmed that carbon dioxide was absorbed and that a volume of hydrogen approximately equal to the absorbed amount was generated. Stirring was continued, and it was confirmed that all carbon dioxide had already been absorbed after 20 hours.

Example 3;
In the same bottle as in Examples 1 and 2, 8.0 g of commercially available manganese powder having a particle size of 1 to 50 μm (manufactured by Furuuchi Chemical Co., Ltd., purity 99.9%, lot number: 67130) was charged to fill carbon dioxide. After that, 10 ml of pure water saturated with carbon dioxide was added and sealed in a carbon atmosphere of 1 atm. When stirring at 200 rpm for 3 hours and a half at room temperature and analyzing the gas in the gas phase by gas chromatography, carbon dioxide was not detected and hydrogen gas having a concentration of 97% was detected. A beige precipitate was produced in the bottle, and the powder was collected by filtration and drying, and a powder X-ray diffraction experiment was conducted. As shown in the X-ray diffraction pattern of FIG. 4, the presence of manganese carbonate (rhombohedral MnCO ₃ , mineral name: rhyoganite) was confirmed along with raw material manganese (α-Mn) remaining unreacted.
The reaction formula is shown by the formula (2).
Mn + H ₂ O + CO ₂ → MnCO ₃ + H ₂ ↑ (2)
Since 8 g of manganese is 150 millimoles, which is a large excess compared to 1 atm of carbon dioxide introduced before the start of the reaction, all of the carbon dioxide was fixed, while raw material manganese remaining unreacted was detected. I understand that. In FIG. 4, the line group other than the diffraction lines of manganese and manganese carbonate is identified as manganese oxide (Mn ₃ O ₄ and MnO ₂ ), and absorbs carbon dioxide as in the reaction with iron in Example 1. However, it was thought to have arisen as a result of the reaction between manganese and water.

  From the above results, it was confirmed that carbon dioxide was effectively absorbed and recovered as iron carbonate by reacting powdered iron or manganese with water and carbon dioxide at room temperature.

  As described above, it was confirmed that carbon dioxide can be immobilized as a carbonate by reacting fine metal particles, water, and carbon dioxide.

As described above, the present invention succeeds in immobilizing carbon dioxide by producing carbonate by reacting in the presence of carbon dioxide together with metal and water. Heating is also unnecessary and the reaction can proceed at room temperature. Today, we have developed a system that can meet the strong need for carbon dioxide fixation technology as a countermeasure against global warming, and its significance is extremely large.
Above all, the present invention does not require any energy by electric power or the like for immobilization, and does not discharge any problem by-products. Therefore, the present invention is an extremely excellent proposal, and is expected to receive much attention and be implemented. The In addition, it does not depend on raw materials or equipment that are particularly difficult to obtain, it only needs to have containers for reacting them with common raw materials, and it has many advantages such as being able to scale up arbitrarily. This technology is a meaningful proposal for the issue of carbon dioxide emission control, which has become a major problem internationally. In the future, this technology will become very popular worldwide and will be widely used not only by industry but also by human society in general. It is expected to be implemented.

1 is a schematic drawing of one embodiment of the carbon dioxide fixation process of the present invention. It is a solid X-ray diffraction pattern obtained after reacting iron powder, water, and carbon dioxide. It is a time-dependent change of the gas component density | concentration in a gaseous phase when iron powder, water, and a carbon dioxide are made to react. It is a solid X-ray diffraction pattern obtained after reacting manganese powder, water, and carbon dioxide.

Explanation of symbols

(1) Reaction vessel (2) Metal powder (3) Water (4) Carbon dioxide (5) Metal carbonate (6) Hydrogen

Claims (3)

Made of one metal selected from the group consisting of chromium, manganese, iron, cobalt, and copper, bringing fine particles having a particle size of 50 μm or less into contact with water and carbon dioxide, so that the metal has a higher valence. The method for immobilizing carbon dioxide is characterized in that a substance containing a carbonate of the metal is produced by reacting with the above, and carbon dioxide becomes carbonate. Before SL fine particles, characterized in that those made by a mechanical crushing method of immobilizing the carbon dioxide according to claim 1. The carbon dioxide according to claim 1 or 2, wherein the fine particles are placed in a container, carbon dioxide is filled in the container, and pure water is added to generate a substance containing the metal carbonate. Immobilization method.

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