WO2018179089A1 - Adsorbent, reaction vessel, carbon dioxide removal device, and carbon dioxide removal system - Google Patents

Abstract

An adsorbent used for removing carbon dioxide from a gas to be treated that contains carbon dioxide. The adsorbent includes particles 1 that comprise: a core 3 including a metal oxide; and a porous section 5 covering at least part of the core 3.

Description

Adsorbent, reaction vessel, carbon dioxide removal device and carbon dioxide removal system

The present invention relates to an adsorbent, a reaction vessel, a carbon dioxide removal device, and a carbon dioxide removal system.

One of the causes of global warming is the emission of greenhouse gases. Examples of the greenhouse gas include carbon dioxide (CO ₂ ), methane (CH ₄ ), and chlorofluorocarbons (CFCs and the like). Among greenhouse gases, the impact of carbon dioxide is the greatest, and the construction of a system for removing carbon dioxide (such as carbon dioxide discharged from thermal power plants and steelworks) has become an urgent issue.

Examples of a solution to the above problem include a method of removing carbon dioxide by a chemical absorption method, a physical absorption method, a membrane separation method, an adsorption separation method, a cryogenic separation method, or the like. For example, a method of separating and recovering carbon dioxide using a solid carbon dioxide adsorbent (CO ₂ separation and recovery method) can be mentioned.

In a carbon dioxide removal system using an adsorbent, a gas to be treated containing carbon dioxide is introduced into a reaction vessel filled with the adsorbent, and the adsorbent and the gas to be treated are brought into contact under atmospheric pressure or under pressure. To adsorb carbon dioxide to the adsorbent. Thereafter, for example, the adsorbent is heated or the inside of the reaction vessel is depressurized to desorb carbon dioxide from the adsorbent. The adsorbent from which carbon dioxide has been desorbed can be used again for removing carbon dioxide by cooling or pressurizing.

In such a carbon dioxide removal system, zeolite is mainly used as an adsorbent. For example, in Patent Document 1 below, carbon dioxide-containing gas is brought into contact with a zeolite-based adsorbent to adsorb carbon dioxide to the adsorbent, and then the adsorbent is heated to remove carbon dioxide. A method for removing carbon is described.

Special table 2010-527757

By the way, exhaust gas discharged from a plant or the like may contain nitrogen oxides (NOx) in addition to carbon dioxide, and even if the exhaust gas is subjected to a denitration process, tens of ppm of NOx may remain. . As a result of the study by the present inventors, when a gas to be treated containing moisture (water vapor, H ₂ O) together with a small amount of NOx is used as described above, an adsorbent (solid carbon dioxide capturing material) such as zeolite is poisoned. It was found that the CO ₂ adsorptivity decreases. In Patent Document 1, there is no discussion about such poisoning of the adsorbent, and there is no description about the configuration of the carbon dioxide removing device taking such circumstances into consideration.

Therefore, the present invention provides an adsorbent capable of suppressing a decrease in CO ₂ adsorptivity in repeated use even when the gas to be treated containing carbon dioxide further contains nitrogen oxides (NOx) and moisture. The purpose is to provide. Moreover, this invention aims at providing the carbon dioxide removal system provided with the reaction container provided with the said adsorption agent, the carbon dioxide removal apparatus provided with the said reaction container, and the said carbon dioxide removal apparatus.

The present invention is an adsorbent used for removing carbon dioxide from a gas to be treated containing carbon dioxide, and includes a core portion containing a metal oxide and a porous portion covering at least a part of the core portion. An adsorbent comprising particles comprising:

According to the adsorbent according to the present invention, even if the gas to be treated containing carbon dioxide further contains nitrogen oxides (NOx) and moisture, it is possible to suppress a decrease in CO ₂ adsorptivity in repeated use. be able to. That is, according to the adsorbent according to the present invention, excellent cycle characteristics can be obtained even when the gas to be treated containing carbon dioxide further contains NOx and moisture.

By the way, exhaust gas discharged from a plant or the like may contain sulfur oxide (SOx) in addition to carbon dioxide, and even if the exhaust gas is subjected to a desulfurization process, tens of ppm of SOx may remain. . As a result of the study by the present inventors, when a gas to be treated containing moisture together with a small amount of SOx is used as described above, an adsorbent (solid carbon dioxide capturing material) such as zeolite is poisoned, and the CO ₂ adsorptivity is low. It has been found to decrease. On the other hand, according to the adsorbent according to the present invention, even if the gas to be treated containing carbon dioxide further contains SOx and moisture, it is possible to suppress a decrease in CO ₂ adsorptivity in repeated use. . That is, according to the adsorbent according to the present invention, excellent cycle characteristics can be obtained even when the gas to be treated containing carbon dioxide further contains SOx and moisture.

The metal oxide may include cerium. In this case, it is possible to further suppress a decrease in CO ₂ adsorbability in repeated use.

The porous portion may include a carbon material. In this case, it is possible to further suppress a decrease in CO ₂ adsorbability in repeated use.

The molar ratio of carbon to cerium in the adsorbent may be 1.3 to 11.0. In this case, it is possible to further suppress a decrease in CO ₂ adsorbability in repeated use.

Further, the present invention is an adsorbent comprising particles comprising a core part containing a metal oxide and a porous part covering at least a part of the core part, the carbon adsorbing carbon to the metal element in the adsorbent An adsorbent having a molar ratio of 1.3 to 11.0 is provided.

The reaction container according to the present invention includes the adsorbent. In the adsorbent, even when carbon dioxide is repeatedly removed from the gas to be treated containing NOx or SOx, the CO ₂ adsorptivity of the adsorbent is unlikely to decrease. Therefore, according to the reaction container of the present invention, the carbon dioxide removal efficiency can be improved. In addition, when the CO ₂ adsorptivity of the adsorbent decreases due to repeated use, operations such as exchanging the adsorbent and removing NOx, SOx, etc. adsorbed on the adsorbent are necessary. According to such a reactor, such a work burden can be reduced.

The carbon dioxide removal apparatus according to the present invention includes the reaction vessel. The carbon dioxide removal apparatus according to the present invention is excellent in carbon dioxide removal efficiency.

The carbon dioxide removal system according to the present invention includes the carbon dioxide removal device. The carbon dioxide removal system according to the present invention is excellent in carbon dioxide removal efficiency.

According to the present invention, even if the gas to be treated containing carbon dioxide further contains nitrogen oxides (NOx) and moisture, it is possible to suppress a decrease in CO ₂ adsorption due to repeated use. Further, according to the present invention, even if the gas to be treated containing carbon dioxide further contains sulfur oxide (SOx) and moisture, it is possible to suppress a decrease in CO ₂ adsorptivity in repeated use. it can. According to the present invention, it is possible to provide an application of an adsorbent to the removal of carbon dioxide from a gas to be treated containing carbon dioxide, moisture and poisoning components (NOx and / or SOx).

FIG. 1 is a schematic view showing a cross section of an embodiment of an adsorbent particle. FIG. 2 is a schematic diagram illustrating an embodiment of a carbon dioxide removal system. FIG. 3 is a schematic view showing another embodiment of the carbon dioxide removal system. FIG. 4 is a graph showing the CO ₂ adsorption amount maintenance rate of the adsorbents of Examples and Comparative Examples. FIG. 5 is a graph showing the relationship between the cerium / carbon ratio (molar ratio) of the adsorbents of Examples and Comparative Examples and the CO ₂ adsorption amount retention rate.

In this specification, a numerical range indicated by using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in the present specification, the upper limit value or lower limit value of a numerical range of a certain step may be replaced with the upper limit value or lower limit value of the numerical range of another step. Further, in the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the values shown in the examples. The materials exemplified in the present specification can be used singly or in combination of two or more unless otherwise specified. In the present specification, the content of each component in the composition is the total amount of the plurality of substances present in the composition unless there is a specific notice when there are a plurality of substances corresponding to each component in the composition. Means.

Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

<Adsorbent>
The adsorbent (carbon dioxide scavenger) according to the present embodiment is an adsorbent used for removing (for example, recovering) carbon dioxide from a processing target gas (gas to be processed) containing carbon dioxide. And a particle (adsorbent particle) comprising a core part including a metal oxide and a porous part (porous covering part) covering at least a part of the core part.

The core portion has CO ₂ adsorptivity. Therefore, by bringing the gas to be treated containing carbon dioxide into contact with the adsorbent, carbon dioxide comes into contact with the core through the pores provided in the porous portion, and carbon dioxide is adsorbed on the core. Thereby, carbon dioxide is removed from the gas to be treated.

The adsorbent according to the present embodiment suppresses a decrease in CO ₂ adsorptivity in repeated use even when the gas to be treated containing carbon dioxide further contains nitrogen oxide (NOx) and moisture. (Excellent cycle characteristics can be obtained). Further, the adsorbent according to the present embodiment suppresses a decrease in CO ₂ adsorptivity in repeated use even when the gas to be treated containing carbon dioxide further contains sulfur oxide (SOx) and moisture. (Excellent cycle characteristics can be obtained). The adsorbent according to the present embodiment is particularly useful when removing carbon dioxide from a gas to be treated containing carbon dioxide, NOx, SOx, and moisture. The present inventors speculate as follows why the decrease in CO ₂ adsorptivity in repeated use can be suppressed even when the adsorbent according to the present embodiment uses the gas to be treated as described above. is doing.

First, the deterioration of the adsorbent (reduction in CO ₂ adsorptivity) when using a gas to be treated containing carbon dioxide, poisoning components (NOx or SOx) and moisture is caused by adsorption of moisture on the surface of the adsorbent. I think that. That is, when the gas to be treated comes into contact with the adsorbent, the poisoning component is adsorbed on the surface of the adsorbent particles, and then moisture is co-adsorbed on the surface, whereby the moisture and the poisoning component react to react with the acid ( Nitric acid or sulfuric acid) is generated (as an example, a reaction in which nitric acid is generated by NOx and moisture is shown in the following formula). Next, a metal salt (nitrate or sulfate) is generated by the reaction between this acid and the metal oxide contained in the adsorbent. And it is believed that the decrease in CO ₂ adsorptive adsorbents by the metal salt. On the other hand, in this embodiment, the core part of adsorbent particle | grains is coat | covered with the porous part, and the adsorption | suction of the water | moisture content to the core part surface is suppressed by the said porous part. For this reason, it is presumed that a decrease in CO ₂ adsorptivity in repeated use can be suppressed.
NO + 1 / 2O ₂ → NO ₂
3NO ₂ + H ₂ O → 2HNO ₃ + NO

The adsorbent according to the present embodiment may include particles having a core-shell structure having a core part and a layered porous part. The coverage of the porous part in the total surface area of the core part may be 10% or more, or 50% or more. The coverage of the porous portion may be 100% or less as shown in FIG. The adsorbent shown in FIG. 1 includes particles including a core portion 3 containing a metal oxide and a porous portion 5 covering at least a part of the core portion 3, and the entire core portion 3 is porous. Covered by the mass part 5.

(Core)
The core includes at least a metal oxide. The metal oxide may be a metal oxide containing one kind of metal element or a complex metal oxide containing multiple kinds of metal elements. A metal oxide can be used individually by 1 type or in combination of 2 or more types. The core part may be porous.

The metal element constituting the metal oxide is not particularly limited, and rare earth elements such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd); yttrium (Y), manganese (Mn), Transition metal elements such as iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), aluminum (Al), chromium (Cr), In (indium); sodium (Na), Typical metal elements such as magnesium (Mg) and silicon (Si) are listed. The metal oxide preferably contains at least one metal element selected from the group consisting of rare earth metal elements and transition metal elements, and more preferably contains cerium, from the viewpoint of further improving cycle characteristics. Examples of the metal oxide containing cerium include CeOx (x = 1.5 to 2.0), and specific examples include CeO ₂ and Ce ₂ O ₃ . The metal oxide may be silica (SiO ₂ ), alumina (Al ₂ O ₃ ), zeolite, or the like. The metal oxide is at least one selected from the group consisting of silica, alumina or zeolite, rare earth metal (for example, cerium) and zirconium from the viewpoints of improvement in specific surface area, improvement in heat resistance, reduction in the amount of metal used, and the like. An oxide (a composite oxide or the like) containing a seed metal may be supported.

By the way, if the zeolite contacts the gas to be treated containing moisture, the adsorptivity of carbon dioxide decreases. Therefore, it is common to remove moisture from the processing target gas before the processing target gas is brought into contact with the adsorbent. For example, in the carbon dioxide removal method described in Patent Document 1, when the gas to be treated contains moisture, the concentration of moisture in the gas to be treated is preferably reduced to 400 ppm or less, and reduced to 20 ppm or less. It is more preferable to do this. On the other hand, the metal oxide containing cerium has excellent CO ₂ adsorptivity even when the gas to be treated contains moisture.

The metal oxide may be, for example, a porous metal oxide (porous metal oxide) or a layered metal oxide (layered metal oxide). As the metal oxide, a metal oxide having a large specific surface area is preferable. From such a viewpoint, a porous metal oxide is preferable.

The layered metal oxide may be an oxide obtained by firing a layered double hydroxide, for example. The layered double hydroxide is also called a hydrotalcite compound and contains two or more kinds of metal elements, and the composition thereof can be represented by the following formula (1).
[M ⁽²⁺⁾ _1-x M ⁽³⁺⁾ _x (OH) ₂ ] [A ⁽ⁿ⁻⁾ _{x / n} · yH ₂ O] (1)

In the above formula, M ⁽²⁺⁾ is a divalent metal ion. For example, magnesium (Mg) ion, manganese (Mn) ion, iron (Fe) ion, cobalt (Co) ion, nickel (Ni) ion, copper ( It represents at least one metal ion selected from the group consisting of Cu) ions and zinc (Zn) ions. M ⁽³⁺⁾ is a trivalent metal ion, for example, selected from the group consisting of aluminum (Al) ion, chromium (Cr), iron (Fe) ion, cobalt (Co) ion, and indium (In) ion. Represents at least one ion. A ⁽ⁿ⁻⁾ is an n-valent anion and represents, for example, at least one ion selected from the group consisting of carbonate ion, nitrate ion and sulfate ion. In the above formula (1), M ⁽²⁺⁾ , M ⁽³⁺⁾ and A ⁽ⁿ⁻⁾ may each be a single ion or a plurality of types of ions.

Examples of methods for synthesizing metal oxides include preparation methods such as an impregnation method, a kneading method, a coprecipitation method, and a sol-gel method. For example, in the method of synthesizing a metal oxide containing cerium, the pH is adjusted to 7 to 7 by adding a basic compound such as ammonia, sodium hydroxide, calcium hydroxide to a solution containing an acidic salt of cerium (for example, nitrate). It may be adjusted to 10 for precipitation. When an oxide is formed by precipitation, the precipitate may be used as it is or may be further oxidized by baking the precipitate.

Examples of the method for synthesizing the layered double hydroxide include preparation methods such as an impregnation method, a kneading method, a coprecipitation method, and a sol-gel method. For example, in the method of synthesizing a layered double hydroxide, after adding sodium carbonate to a solution containing nitrate containing Mg and nitrate containing Al, a basic compound such as ammonia, sodium hydroxide, or calcium hydroxide is added. It may be precipitated by adjusting the pH to 8 to 11 by adding. The resulting precipitate is a layered double hydroxide, and a metal oxide or a composite metal oxide can be obtained by firing the precipitate. The firing temperature is not particularly limited, and may be, for example, 200 ° C. or higher.

The core part may contain components other than the metal oxide. Examples of such components include components derived from metal oxide precursors (for example, metal salts), solid organic compounds, and the like. As the solid organic compound, a basic organic compound is preferable, and examples thereof include an organic compound having an amino group.

The content of the metal oxide in the core part may be 80% by mass or more, 90% by mass or more, or 95% by mass or more based on the total mass of the core part. The content of the metal oxide may be 100% by mass or less based on the total mass of the core part.

(Porous part)
The porous part covers at least a part of the core part. The porous part is, for example, layered. The porous part has a plurality of pores that communicate with the core part from the outside of the adsorbent particles. The pores have a size that allows carbon dioxide to pass through, for example, and have a pore diameter of 0.001 to 1 μm, for example.

The porous portion includes at least one selected from the group consisting of a simple metal, a metal oxide, a carbon material, and an organic compound (resin or the like), for example. The porous portion preferably contains a carbon material. When the porous portion contains a carbon material, the moisture in the gas to be treated is easily adsorbed by the porous portion, and therefore the cycle characteristics are further excellent. When the porous part contains a carbon material, the porous part preferably further contains at least one element selected from the group consisting of alkali metals, alkaline earth metals, oxygen, nitrogen, boron and hydrogen. These elements may be contained in the porous portion separately from the carbon material, or may be incorporated in the carbon material. However, when a metal simple substance and a metal oxide come into contact with a poisoning component (NOx or SOx) and a gas to be treated containing moisture, it is considered that a metal salt (metal nitrate or metal sulfate) is generated by the mechanism described above. The surface of the adsorbent particles preferably does not contain a single metal or a metal oxide from the viewpoint of further improving cycle characteristics.

As the carbon material, at least one selected from the group consisting of graphite, amorphous carbon, carbon fiber, and carbon nanotube can be used. A carbon material can be used individually by 1 type or in combination of 2 or more types.

The carbon material may be a fired product of a carbon material precursor. As precursors of carbon materials, phenol resin, naphthalene sulfonic acid resin, polyvinylidene chloride, carboxymethyl cellulose, polyacrylonitrile resin, polyvinyl chloride, gilsonite coke, petroleum-based or coal-based mesophase pitch, pyrrole, polypyrrole, polyvinylpyrrole , 3-methylpolypyrrole, vinylpyridine, polyvinylpyridine, imidazole, 2-methylimidazole, aniline, polyaniline, polyaminobismaleimide, polyimide, benzimidazole, polybenzoimidazole, polyamide, acrylonitrile, polyacrylonitrile, chitin , Chitosan, silk, hair, polyamino acid, nucleic acid, DNA, RNA, hydrazine, hydrazide, urea, salen, polycarbazole, polybismaleimide, triazine Melamine, melamine resin, polyamide-imide resins, polyacrylic acid, sodium polyacrylate, potassium polyacrylate, phthalocyanine, phenanthroline, riboflavin, and the like. The precursor of a carbon material can be used individually by 1 type or in combination of 2 or more types.

The content of the carbon material in the porous part may be 80% by mass or more, 90% by mass or more, or 95% by mass or more based on the total mass of the porous part. . The content of the carbon material may be 100% by mass or less based on the total mass of the porous portion.

The thickness of the porous part is preferably 1 nm to 100 μm. If the thickness of the porous portion is 1 nm or more, excellent cycle characteristics are easily obtained. If the thickness of the porous portion is 100 μm or less, sufficient CO ₂ adsorption is easily obtained.

As a method of covering at least a part of the core portion with the porous portion, a physical preparation method such as an impregnation method, a kneading method, a coprecipitation method, a sol-gel method, an ion exchange method, and a vapor deposition method; a preparation method using a chemical reaction Etc. For example, in the impregnation method, after the material (core material) constituting the core part of the adsorbent particles is dispersed in the solvent after firing, the precursor of the porous part is added to the solvent, and the solvent is further removed. Thus, an adsorbent precursor (adsorbent particle precursor) is obtained. Next, the adsorbent (adsorbent particles) can be produced by firing the adsorbent precursor (adsorbent particle precursor). The firing temperature may be, for example, 200 ° C. or higher. The solvent is not particularly limited as long as it can dissolve the precursor of the porous portion. In the above method, the molar ratio of carbon to the metal element (for example, cerium) in the adsorbent is adjusted by adjusting the addition amount of the core material and the precursor of the porous portion, the kind of the precursor of the porous portion, and the like. The content of the carbon material in the part, the coverage and thickness of the porous part can be adjusted.

The precursor of the porous portion includes, for example, the above-described carbon material precursor. In this case, the carbon material is obtained by firing the precursor of the carbon material. The precursor of the porous portion includes, in addition to the precursor of the carbon material, an alkali metal or alkaline earth metal salt (for example, nitrate, carbonate, sulfate and acetate); oxygen, nitrogen, boron, hydrogen, etc. It may further contain an inorganic compound having an element. When the precursor of the porous part contains an alkali metal or alkaline earth metal salt, a porous part containing an alkali metal or alkaline earth metal is obtained. Moreover, when the precursor of a porous part contains the inorganic compound which has elements, such as oxygen, nitrogen, boron, and hydrogen, the porous part containing these elements is obtained. In addition to the above, as a method for obtaining a porous portion containing elements such as oxygen, nitrogen, boron, and hydrogen, firing is performed using a gas containing these elements (for example, oxygen gas, ammonia gas, and hydrogen gas). And a method using an organic compound containing these elements as a precursor of the carbon material. In the present embodiment, these methods may be combined.

The adsorbent particles according to this embodiment may be composed of only a core part and a porous part, and may further include parts other than the core part and the porous part.

The shape of the adsorbent particles is not particularly limited, and may be, for example, a powder shape, a pellet shape, a granular shape, a honeycomb shape, or the like. The shape of the adsorbent particles may be determined in consideration of the required reaction rate, pressure loss, purity of the gas (adsorbed gas) adsorbed on the adsorbent (CO ₂ purity), and the like.

The average particle diameter of the adsorbent particles may be, for example, 0.1 to 10 mm. The average particle diameter can be measured with a laser diffractometer, a scanning electron microscope, or the like.

The specific surface area of the adsorbent particles is preferably 10 to 500 m ² / g. When the specific surface area of the adsorbent particles is 10 m ² / g or more, the CO ₂ adsorption amount is high and desired performance as an adsorbent is easily obtained. When the specific surface area of the adsorbent particles is 500 m ² / g or less, the ratio of the porous portion does not become too high, the amount of CO ₂ adsorption per volume increases, and desired performance as an adsorbent is easily obtained. The specific surface area can be measured by the BET multipoint method using BELSORP-mini (made by Nippon Bell Co., Ltd.) using a nitrogen adsorption method. Specifically, the adsorption temperature is set to 77 K, the measured value is used for the saturated vapor pressure P ₀ , and the adsorption gas pressure P changes P with respect to P _{0 in} the range of 0.005 to 0.5. Note that the adsorption cross-sectional area of nitrogen is 0.162 nm ² .

The content of the adsorbent particles may be 80% by mass or more, 90% by mass or more, or 95% by mass or more based on the total mass of the adsorbent. The content of the carbon material may be 100% by mass or less based on the total mass of the porous portion.

The molar ratio of carbon to metal element in the adsorbent (carbon / metal element. Total amount of carbon components / total amount of metal element) is preferably in the following range. The molar ratio (carbon / metal element) is preferably 1.3 or more and more preferably greater than 1.3 from the viewpoint that a sufficient amount of coverage by the porous portion is easily obtained and excellent cycle characteristics are easily obtained. Preferably, 1.4 or more is more preferable, and 1.5 or more is particularly preferable. The molar ratio (carbon / metal element) is a case where the CO ₂ adsorption / desorption cycle is repeated because the amount of water remaining in the porous portion is not excessive and adsorption of carbon dioxide is difficult to be inhibited. However, from the viewpoint that the CO ₂ adsorptivity is hardly lowered, it is preferably 11.0 or less, more preferably less than 11.0, still more preferably 10.0 or less, and particularly preferably 8.0 or less. The molar ratio (carbon / metal element) is preferably 9.0 or less, more preferably 8.0 or less, still more preferably 7.0 or less, and 6.0 or less from the viewpoint of easily obtaining a high CO ₂ adsorption amount. Is particularly preferable, 4.0 or less is very preferable, 3.0 or less is very preferable, and 2.0 or less is even more preferable. From these viewpoints, the molar ratio (carbon / metal element) is preferably 1.3 to 11.0.

The molar ratio of carbon to cerium (carbon / cerium) in the adsorbent is preferably in the following range. The molar ratio (carbon / cerium) is preferably 1.3 or more, more preferably greater than 1.3, from the viewpoint that a sufficient amount of coating by the porous portion is easily obtained and excellent cycle characteristics are easily obtained. 1.4 or more is more preferable, and 1.5 or more is particularly preferable. The molar ratio (carbon / cerium) is such that even if the CO ₂ adsorption / desorption cycle is repeated because the amount of water remaining in the porous portion is not excessive and adsorption of carbon dioxide is difficult to be inhibited. From the viewpoint that the CO ₂ adsorptivity is hardly lowered, it is preferably 11 or less, more preferably less than 11.0, further preferably 10.0 or less, and particularly preferably 8.0 or less. The molar ratio (carbon / cerium) is preferably 9.0 or less, more preferably 8.0 or less, still more preferably 7.0 or less, and 6.0 or less from the viewpoint of easily obtaining a high CO ₂ adsorption amount. Particularly preferred is 4.0 or less, very preferred is 3.0 or less, and most preferred is 2.0 or less. From these viewpoints, the molar ratio (carbon / cerium) is preferably 1.3 to 11.0.

The molar ratio can be measured by composition analysis of the adsorbent using a fluorescent X-ray analyzer (ZSX Primus 2, manufactured by Rigaku Corporation). Measurement conditions and measurement methods are as follows.
X-ray tube: Rh target X-ray output: 3 kW
Measurement chamber atmosphere: Vacuum Analysis diameter: 10mmΦ
Measurement method: quantified by the fundamental parameter method using a sensitivity library

<Method for removing carbon dioxide>
Next, a method for removing carbon dioxide using the adsorbent according to the present embodiment will be described. The method for removing carbon dioxide includes an adsorption step in which a treatment target gas containing carbon dioxide is brought into contact with an adsorbent to adsorb carbon dioxide onto the adsorbent.

The gas to be treated contains, for example, at least carbon dioxide (CO ₂ ) and moisture (water vapor, H ₂ O). The gas to be treated may contain components other than carbon dioxide, for example, nitrogen oxide (NOx), sulfur oxide (SOx), oxygen (O ₂ ), nitrogen (N ₂ ), carbon monoxide (CO ), Volatile organic substances (VOC), and the like. The adsorbent according to the present embodiment can exhibit excellent cycle characteristics when the gas to be treated contains carbon dioxide, moisture, NOx and / or SOx. Specific examples of such a gas to be treated include gas discharged from a plant (particularly a large-scale plant).

The CO ₂ concentration in the gas to be treated is not particularly limited, and may be, for example, 0.0001 to 0.01% by volume, 0.011 to 0.1% by volume, or 0.11 to 0.1% by volume. It may be 10% by volume. On the other hand, when the adsorbent contains a metal oxide containing cerium, the CO ₂ concentration may be 1000 ppm or less, 750 ppm or less, or 500 ppm or less based on the total volume of the gas to be treated. Also good. The metal oxide containing cerium can exhibit excellent CO ₂ adsorption when the CO ₂ concentration is 1000 ppm or less. Therefore, when the adsorbent contains a metal oxide containing cerium and the CO ₂ concentration is in the above range, excellent CO ₂ adsorbability is easily confirmed. Further, when the adsorbent contains a metal oxide containing cerium, the CO ₂ concentration may be 100 ppm or more on the basis of the total volume of the gas to be treated, from the viewpoint of easy removal of carbon dioxide, and 200 ppm The above may be sufficient and 400 ppm or more may be sufficient.

When the processing target gas contains NOx, the NOx concentration in the processing target gas may be 0.0001% by volume or more based on the total volume of the processing target gas from the viewpoint of easy confirmation of excellent cycle characteristics. 0.001 volume% or more may be sufficient and 0.01 volume% or more may be sufficient. The NOx concentration may be 10% by volume or less, 1% by volume or less, or 0.1% by volume or less, based on the total volume of the gas to be treated, from the viewpoint of easily maintaining CO ₂ adsorption. It may be.

When the processing target gas contains SOx, the SOx concentration in the processing target gas may be 0.0001% by volume or more on the basis of the total volume of the processing target gas from the viewpoint of easy confirmation of excellent cycle characteristics. 0.001 volume% or more may be sufficient and 0.01 volume% or more may be sufficient. The SOx concentration may be 10% by volume or less, 1% by volume or less, or 0.1% by volume or less, based on the total volume of the gas to be treated, from the viewpoint of easily maintaining CO ₂ adsorption. It may be.

The moisture concentration in the gas to be processed may be 0.0001% by volume or more, or 0.001% by volume or more based on the total volume of the gas to be processed, from the viewpoint of easy confirmation of excellent cycle characteristics. It may be 0.01% by volume or more. The water concentration may be 10% by volume or less, 1% by volume or less, or 0.1% by volume or less, based on the total volume of the gas to be treated, from the viewpoint that the CO ₂ adsorptivity is easily maintained. It may be. In particular, when the adsorbent contains a metal oxide containing cerium, the moisture concentration is preferably in the above range.

The amount of CO ₂ adsorption can be adjusted by adjusting the temperature T ₁ of the adsorbent when the gas to be treated is brought into contact with the adsorbent in the adsorption step. The higher the temperature T _{1, the} smaller the CO ₂ adsorption amount of the adsorbent. The temperature T ₁ may be −20 to 100 ° C. or 10 to 40 ° C.

Temperature T ₁ of the adsorbent may be adjusted by heating or cooling the adsorbent may be used in combination of heating and cooling. Further, the temperature T ₁ of the indirect adsorbent may be adjusted by heating or cooling the processed gas. As a method of heating the adsorbent, a method in which a heat medium (for example, heated gas or liquid) is brought into direct contact with the adsorbent; a heat medium (for example, heated gas or liquid) is circulated through a heat transfer tube, Examples include a method of heating the adsorbent by heat conduction from the heat transfer surface; a method of heating the adsorbent by an electric furnace that generates heat electrically, and the like. As a method for cooling the adsorbent, a method in which a refrigerant (for example, a cooled gas or liquid) is directly brought into contact with the adsorbent; a refrigerant (for example, a cooled gas or liquid) is circulated through a heat transfer tube or the like, and heat transfer is performed. The method of cooling by the heat conduction from a surface etc. is mentioned.

In the adsorption step, the CO ₂ adsorption amount can be adjusted by adjusting the total pressure of the atmosphere in which the adsorbent is present (for example, the total pressure in the reaction vessel containing the adsorbent). The higher the total pressure, the greater the amount of CO ₂ adsorbed by the adsorbent. From the viewpoint of further improving the carbon dioxide removal efficiency, the total pressure is preferably 0.1 atm or more, and more preferably 1 atm or more. The total pressure may be 10 atm or less, 2 atm or less, or 1.3 atm or less from the viewpoint of energy saving. The total pressure may be 5 atmospheres or more.

The total pressure of the atmosphere in which the adsorbent is present may be adjusted by pressurization or depressurization, and pressurization and depressurization may be used in combination. Examples of a method for adjusting the total pressure include a method in which the pressure is mechanically adjusted by a pump, a compressor, and the like; a method in which a gas having a pressure different from the pressure in the ambient atmosphere of the adsorbent is introduced.

The carbon dioxide removal method according to this embodiment may further include a desorption step of desorbing (desorbing) carbon dioxide from the adsorbent after the adsorption step.

As a method for desorbing carbon dioxide from the adsorbent, a method using the temperature dependence of the adsorption amount (temperature swing method; a method using the difference in the CO ₂ adsorption amount of the adsorbent with temperature change); pressure of the adsorption amount The method using pressure dependence (pressure swing method. The method using the difference in the amount of CO ₂ adsorbed by the adsorbent accompanying the pressure change) can be used, and these methods may be used in combination (temperature / pressure swing method). .

In the method using the temperature dependency of the adsorption amount, for example, the temperature of the adsorbent in the desorption process is set higher than that in the adsorption process. Examples of the method for heating the adsorbent include the same method as the method for heating the adsorbent in the above-described adsorption step; the method using the peripheral exhaust heat, and the like. From the viewpoint of reducing the energy required for heating, it is preferable to use the peripheral exhaust heat.

The temperature difference (T ₂ −T ₁ ) between the adsorbent temperature T ₁ in the adsorption step and the adsorbent temperature T ₂ in the desorption step may be 200 ° C. or less, or 100 ° C. or less from the viewpoint of energy saving. It may be 50 degrees C or less. The temperature difference (T ₂ −T ₁ ) may be 10 ° C. or higher, 20 ° C. or higher, or 30 ° C. or higher from the viewpoint of easy desorption of carbon dioxide adsorbed on the adsorbent. Good. Temperature _{T 2} of the adsorbent in the desorption step, for example, may be 40 ~ 300 ° C., may be 50 ~ 200 ° C., may be 80 ~ 120 ° C..

In the method using the pressure dependency of the adsorption amount, the CO ₂ adsorption amount increases as the total pressure of the atmosphere in which the adsorbent exists (for example, the total pressure in the container containing the adsorbent) increases. It is preferable to change so that the total pressure in the desorption process is lower than the total pressure. The total pressure may be adjusted by pressurizing or depressurizing, and pressurization and depressurization may be used in combination. As a method for adjusting the total pressure, for example, a method similar to the adsorption step described above can be used. The total pressure in the desorption process may be the ambient atmospheric pressure (for example, 1 atmosphere) or less than 1 atmosphere from the viewpoint of increasing the amount of CO ₂ desorption.

The carbon dioxide desorbed and recovered by the desorption process may be reused in the field where carbon dioxide is used. For example, in greenhouse cultivation for house or the like, since the plant growth by increasing the CO ₂ concentration is accelerated, which may increase the CO ₂ concentration 1000ppm level. Therefore, the recovered carbon dioxide may be reused to increase the CO ₂ concentration.

The adsorbent after the desorption process can be used again in the adsorption process. In the carbon dioxide removal method according to this embodiment, the adsorption step and the desorption step may be repeatedly performed after the desorption step. When the adsorbent is heated in the desorption step, the adsorbent may be cooled by the above-described method and used in the adsorption step. The adsorbent may be cooled by bringing a gas containing carbon dioxide (for example, a treatment target gas containing carbon dioxide) into contact with the adsorbent.

When the gas to be treated contains SOx, NOx, dust, or the like (for example, when the gas to be treated is exhaust gas discharged from a coal-fired power plant or the like), the carbon dioxide removal method according to this embodiment uses adsorption. From the viewpoint of easily maintaining the CO ₂ adsorptivity of the agent, an impurity removal step of removing impurities such as SOx, NOx, and dust from the gas to be treated may be further provided before the adsorption step. The impurity removal step can be performed using a removal device such as a denitration device, a desulfurization device, or a dust removal device, and the gas to be treated can be brought into contact with the adsorbent on the downstream side of these devices. Further, when impurities such as SOx, NOx, and dust are adsorbed on the adsorbent, the adsorbent can be removed by heating the adsorbent as well as exchanging the adsorbent.

In the method for removing carbon dioxide according to the present embodiment, the adsorbent may be supported on a honeycomb-shaped base material or may be used by filling a reaction vessel. Further, a honeycomb-like base material carrying an adsorbent may be disposed and used in the reaction vessel. The method of using the adsorbent may be determined in consideration of the required reaction rate, pressure loss, purity of the gas (adsorbed gas) adsorbed on the adsorbent (CO ₂ purity), and the like.

When using an adsorbent, the smaller the void between adsorbent particles (the lower the porosity), the smaller the amount of gas other than carbon dioxide remaining in the void, so that the purity of carbon dioxide in the adsorbed gas can be increased. it can. On the other hand, the more voids between adsorbent particles (the higher the porosity), the smaller the pressure loss. When the adsorbent is supported on the honeycomb and used, the porosity can be increased, so that the pressure loss can be reduced.

<Reaction vessel>
Next, the reaction container according to this embodiment will be described. The reaction container according to the present embodiment includes the adsorbent according to the present embodiment. In the reaction vessel, the adsorbent is disposed (for example, filled) inside the reaction vessel. The filling amount and arrangement position of the adsorbent are not particularly limited. For example, the adsorbent may be filled in the central portion of the reaction vessel or may be disposed on a part of the inner wall surface.

The reaction vessel may be a fixed bed type, a rotor type, or a fluidized bed type. The rotor type and the fluidized bed type are systems in which the adsorbent itself is moved without switching the gas (circulation gas) to be circulated in the reaction vessel.

In a fixed bed type reaction vessel, for example, an adsorbent (for example, a granular adsorbent) is filled in the reaction vessel, and the temperature and pressure in the processing target gas or the reaction vessel are changed without moving the adsorbent itself. And configured to perform adsorption and desorption of carbon dioxide. In this method, since there is little movement of the adsorbent, wear of the adsorbent due to contact between the adsorbents or between the adsorbent and the reaction vessel can be reduced, and a decrease in the performance of the adsorbent can be suppressed. Moreover, since the packing density can be increased, the porosity is low, and the amount of carbon dioxide removed per volume of the reaction vessel can be increased.

Examples of the rotor-type reaction container include a reaction container including a container, an adsorbent filling unit provided inside the container, and a partition plate for partitioning the gas flowing in the container. The adsorbent filling portion is filled with an adsorbent. This reaction vessel is internally divided into a plurality of regions by partition plates, and is divided into a carbon dioxide adsorption region, an adsorbent heating region (CO ₂ desorption region), an adsorbent cooling region, etc., depending on the type of gas flowing. It has been. Therefore, in this manner, by rotating the adsorbent filling portion, it is possible to move the adsorbent carbon dioxide adsorption region, the adsorbent heated region (CO ₂ desorption region), the adsorbent cooling region like, CO ₂ Adsorption / desorption cycles such as adsorption of adsorbent, heating of the adsorbent (desorption of CO ₂ ), and cooling of the adsorbent can be performed. In this method, even when performing a temperature swing method in which heating gas is circulated to heat the adsorbent and CO ₂ is desorbed, it is not necessary to switch the gas circulated to the reaction vessel. The configuration of valves and the like is simplified. In addition, since the size of each region can be determined by changing the position where the partition plate is installed, the flow time of the gas to be treated (time for adsorbing carbon dioxide), the heating time of the adsorbent (desorbing carbon dioxide) Time) and the cooling time of the adsorbent can be easily determined.

In the rotor type, a honeycomb (for example, a honeycomb rotor) carrying an adsorbent may be disposed in the reaction vessel. In this case, since the adsorbent is supported on the honeycomb, wear of the adsorbent itself can be reduced, and a decrease in the performance of the adsorbent can be suppressed.

When two or more kinds of adsorbents are used in the rotor system, two or more reaction vessels may be installed, and different adsorbents may be disposed in each reaction vessel. You may arrange | position an adsorbent in a different location. For example, different adsorbents may be arranged on the upstream side and the downstream side in the reaction vessel. In this case, for example, an adsorbent containing cerium oxide may be arranged on the upstream side, and an adsorbent containing zeolite may be arranged on the downstream side. By adopting such a configuration, for example, the gas to be treated is circulated in the direction from the upstream side to the downstream side, and the heating gas is circulated in the direction from the downstream side to the upstream side. CO ₂ adsorption of the zeolite can be prevented to reduce. Further, when the adsorbent is supported on the honeycomb (honeycomb rotor), the place where each adsorbent is supported may be divided in the honeycomb.

The fluidized bed type reaction vessel is configured such that, for example, the adsorbent can flow by power (conveyor, blower, etc.) by reducing the filling amount of the adsorbent. In the case of using a fluidized bed type reaction vessel, for example, a reaction vessel in which a gas to be treated is circulated and a heating vessel in which a gas for heating is circulated are installed, and power (conveyor, blower, etc.) is used to adsorb the adsorbent ( For example, the adsorption and desorption of carbon dioxide may be repeated by moving a granular or powdery adsorbent between the reaction vessel and the heating vessel. In this method, since it is not necessary to switch the gas to be circulated in the reaction vessel, the configuration of piping, valves, etc. is simplified. Also, different porosity can be set during carbon dioxide adsorption and desorption. For example, the void ratio may be set to be low during desorption, and the purity (CO ₂ purity) of the gas (adsorbed gas) adsorbed by the adsorbent may be increased. When a gas having a very large gas flow rate (boiler exhaust gas or the like) is used as a processing target gas, carbon dioxide may be removed by blowing up the adsorbent with the gas instead of the conveyor. Since the number of machine parts is reduced compared to a conveyor, a simple configuration can be achieved.

According to the reaction container according to the present embodiment, even when the CO ₂ adsorption / desorption cycle is repeated, the CO ₂ adsorptivity of the adsorbent is unlikely to be lowered, so that the carbon dioxide removal efficiency can be improved. In addition, when the CO ₂ adsorptivity of the adsorbent decreases due to repeated use, operations such as exchanging the adsorbent and removing NOx, SOx, etc. adsorbed on the adsorbent are required. According to this, such work burden can be reduced.

<Carbon dioxide removal device and carbon dioxide removal system>
The carbon dioxide removal system according to the present embodiment includes the carbon dioxide removal device according to the present embodiment, and a control unit for comprehensively controlling the carbon dioxide removal device. The carbon dioxide removal system (air conditioning system etc.) concerning this embodiment may be provided with two or more carbon dioxide removal devices (air conditioning equipment etc.) concerning this embodiment. The carbon dioxide removal system according to the present embodiment may include a control unit that comprehensively controls the operation of the plurality of carbon dioxide removal devices. The carbon dioxide removal apparatus according to the present embodiment includes the reaction container according to the present embodiment.

In the carbon dioxide removal system and the carbon dioxide removal apparatus according to the present embodiment, carbon dioxide is adsorbed by the adsorbent when the gas to be treated introduced into the reaction container comes into contact with the adsorbent disposed in the reaction container. To do. The carbon dioxide removal system and the carbon dioxide removal device according to the present embodiment may be used to reduce the carbon dioxide concentration in the air-conditioning target space, and to reduce the carbon dioxide concentration in the gas discharged from the plant or the like to the outside air. May be used. The air-conditioning target space may be, for example, a building; a vehicle; an automobile; a space station; a submersible; a food or chemical production plant.

The carbon dioxide removing device according to this embodiment may be an air conditioner. The air conditioner according to the present embodiment is an air conditioner used in an air conditioning target space including a processing target gas containing carbon dioxide. The air conditioner according to the present embodiment includes a flow path connected to the air conditioning target space, and a removal unit (carbon dioxide removal unit) that removes carbon dioxide contained in the processing target gas as the reaction container according to the present embodiment. It is arranged in the flow path. In the air conditioner according to the present embodiment, the adsorbent according to the present embodiment is disposed in the removal unit, and the adsorbent comes into contact with the processing target gas and carbon dioxide is adsorbed by the adsorbent. According to the present embodiment, there is provided an air conditioning method including an adsorption process in which a processing target gas in an air conditioning target space is brought into contact with an adsorbent to adsorb carbon dioxide to the adsorbent. The details of the processing target gas containing carbon dioxide are the same as the processing target gas in the carbon dioxide removal method described above.

Hereinafter, an air conditioner and an air conditioning system will be described as examples of the carbon dioxide removal system and the carbon dioxide removal device with reference to FIGS. 2 and 3.

As shown in FIG. 2, the air conditioning system 200 includes an air conditioner 100 and a control device (control unit) 110. The air conditioner 100 includes a flow path 10, an exhaust fan (exhaust unit) 20, a concentration measuring device (concentration measuring unit) 30, an electric furnace (temperature control unit) 40, and a compressor (pressure control unit) 50. I have.

The flow path 10 is connected to an air-conditioning target space R including a processing target gas (indoor gas) containing carbon dioxide. The flow path 10 includes a flow path section 10a, a flow path section 10b, a removal section (flow path section, carbon dioxide removal section) 10c, a flow path section 10d, a flow path section (circulation flow path) 10e, The removal part 10c is arrange | positioned at the flow path 10 with the path part (exhaust flow path) 10f. The air conditioner 100 includes a removing unit 10c as a reaction container. In the flow path 10, a valve 70 a that adjusts the presence or absence of the inflow of the processing target gas in the removing unit 10 c and a valve 70 b that adjusts the flow direction of the processing target gas are arranged.

The upstream end of the flow path part 10a is connected to the air conditioning target space R, and the downstream end of the flow path part 10a is connected to the upstream end of the flow path part 10b via the valve 70a. The upstream end of the removal part 10c is connected to the downstream end of the flow path part 10b. The downstream end of the removal part 10c is connected to the upstream end of the flow path part 10d. A downstream side of the flow path portion 10d in the flow path 10 is branched into a flow path section 10e and a flow path section 10f. The downstream end of the flow path portion 10d is connected to the upstream end of the flow path portion 10e and the upstream end of the flow path portion 10f via the valve 70b. The downstream end of the flow path part 10e is connected to the air conditioning target space R. The downstream end of the flow path portion 10f is connected to the outside air.

The adsorbent 80, which is an adsorbent according to the present embodiment, is disposed in the removing unit 10c. The adsorbent 80 is filled in the central portion of the removal portion 10c. Two spaces are formed in the removal unit 10c via the adsorbent 80. The removal unit 10c includes an upstream space S1, a central portion S2 filled with the adsorbent 80, and a downstream space S3. And have. The space S1 is connected to the air conditioning target space R via the flow path portions 10a and 10b and the valve 70a, and the processing target gas containing carbon dioxide is supplied from the air conditioning target space R to the space S1 of the removal unit 10c. . The processing target gas supplied to the removing unit 10c moves from the space S1 to the space S3 via the central part S2, and is then discharged from the removing unit 10c.

At least part of the carbon dioxide is removed from the processing target gas discharged from the air conditioning target space R in the removing unit 10c. The processing target gas from which carbon dioxide has been removed may be returned to the air conditioning target space R by adjusting the valve 70b or may be discharged to the outside air outside the air conditioning apparatus 100. For example, the processing target gas discharged from the air conditioning target space R passes from upstream to downstream through the flow path part 10a, the flow path part 10b, the removal part 10c, the flow path part 10d, and the flow path part 10e. Can flow into R. Further, the processing target gas discharged from the air conditioning target space R is discharged from the upstream to the downstream via the flow path part 10a, the flow path part 10b, the removal part 10c, the flow path part 10d, and the flow path part 10f. May be.

The exhaust fan 20 is disposed at the discharge position of the processing target gas in the air conditioning target space R. The exhaust fan 20 discharges the processing target gas from the air conditioning target space R and supplies it to the removing unit 10c.

The concentration measuring device 30 measures the carbon dioxide concentration in the air conditioning target space R. The concentration measuring device 30 is disposed in the air conditioning target space R.

The electric furnace 40 is disposed outside the removing unit 10c of the air conditioner 100, and can raise the temperature of the adsorbent 80. The compressor 50 is connected to the removing unit 10c of the air conditioner 100, and can adjust the pressure in the removing unit 10c.

The control device 110 can perform overall operation control of the air conditioner 100. For example, based on the carbon dioxide concentration measured by the concentration measuring device 30, the presence or absence of inflow of the processing target gas in the removal unit 10c Can be controlled. Specifically, when the concentration measuring device 30 detects that the carbon dioxide concentration in the air-conditioning target space R has increased and reached a predetermined concentration due to exhalation or the like, concentration information is sent from the concentration measuring device 30 to the control device 110. Sent. The control device 110 that has received the concentration information opens the valve 70a and adjusts the gas discharged from the removal unit 10c so as to flow into the air-conditioning target space R through the flow channel unit 10d and the flow channel unit 10e. And the control apparatus 110 operates the exhaust fan 20, and supplies process target gas from the air-conditioning object space R to the removal part 10c. Furthermore, the control device 110 operates the electric furnace 40 and / or the compressor 50 as necessary to adjust the temperature of the adsorbent 80, the pressure in the removal unit 10c, and the like.

When the processing target gas supplied to the removing unit 10c moves from the space S1 to the space S3 via the central portion S2, the processing target gas comes into contact with the adsorbent 80, and carbon dioxide in the processing target gas is absorbed into the adsorbent 80. Adsorb to. Thereby, carbon dioxide is removed from the gas to be treated. In this case, the gas from which carbon dioxide has been removed is supplied to the air-conditioning target space R through the flow path part 10d and the flow path part 10e.

The carbon dioxide adsorbed on the adsorbent 80 may be recovered in a state of being adsorbed on the adsorbent 80 without being desorbed from the adsorbent 80, or may be recovered after being desorbed from the adsorbent 80. In the desorption process, the electric furnace 40 and / or the compressor 50 are operated to adjust the temperature of the adsorbent 80, the pressure in the removal unit 10c, etc. Carbon dioxide can be desorbed from 80. In this case, for example, the valve 70b is adjusted so that the gas discharged from the removing unit 10c (the gas containing the desorbed carbon dioxide) is discharged to the outside air through the flow path unit 10f. Thus, the discharged carbon dioxide can be recovered.

As shown in FIG. 3, the air conditioning system 210 includes a first air conditioner 100a, a second air conditioner 100b, a control device (control unit) 110, and a control device (control unit) 120. . The control device 120 controls the air conditioning operation of the first air conditioner 100a and the second air conditioner 100b by controlling the control device 110 described above in the first air conditioner 100a and the second air conditioner 100b. Control. For example, the control device 120 may adjust the air conditioning operations of the first air conditioner 100a and the second air conditioner 100b to be performed under the same conditions, and the first air conditioner 100a and the second air conditioner 100b. You may adjust so that air-conditioning operation may be performed on different conditions. The control device 120 can transmit information regarding the presence or absence of the inflow of the processing target gas in the removal unit 10c to the control device 110.

The carbon dioxide removal device and the carbon dioxide removal system are not limited to the above-described embodiment, and may be appropriately changed without departing from the gist thereof. For example, the control content of the control unit of the carbon dioxide removal device is not limited to controlling the presence or absence of the inflow of the processing target gas in the reaction vessel, and the control unit may adjust the inflow amount of the processing target gas in the reaction vessel. Good.

In the air conditioner, the gas to be processed may be supplied to the reaction vessel using a blower instead of the exhaust fan. When the gas to be processed is supplied to the reaction vessel by natural convection, the exhaust means may not be used. Good. Further, the temperature control means and the pressure control means are not limited to the electric furnace and the compressor, and various means described above can be used in the adsorption process and the desorption process. The temperature control means is not limited to the heating means, and may be a cooling means.

In the air conditioner, each of the air-conditioning target space, the carbon dioxide removal unit, the exhaust unit, the temperature control unit, the pressure control unit, the concentration measurement unit, and the like is not limited to one, and a plurality of units may be arranged. The air conditioner includes a humidity controller for adjusting the dew point and relative humidity of the gas to be treated; a humidity measuring device for measuring the humidity of the air conditioning target space; a removal device such as a denitration device, a desulfurization device, and a dust removal device. May be.

Hereinafter, the contents of the present invention will be described in more detail using examples and comparative examples. However, the present invention is not limited to the following examples.

<Manufacture of adsorbent>
Example 1
1.0 g of cerium oxide (CeO ₂ ) and 0.072 g of polyacrylic acid were added to 10 mL of pure water, and then stirred at room temperature for 30 minutes to obtain a mixed solution. The mixed solution was poured into a quartz boat and put into a box type electric furnace. After raising the temperature to 300 ° C. at 10 ° C./min in the air, firing was performed at 300 ° C. for 1 hour. Thereafter, the fired product obtained was naturally cooled and then taken out from the box-type electric furnace. Adsorbent powder was obtained by grinding the fired product using a mortar and pestle.

The above method was repeated a plurality of times to obtain a necessary amount of adsorbent powder. Thereafter, using a mold having a diameter of 40 mm, the adsorbent powder was pelletized at 500 kgf by a press machine. Next, after the pellets are crushed, the adsorbent particles (core part and porous part covering the core part) are granulated (particle size: 0.5 to 1.0 mm) using a sieve. And an adsorbent (hereinafter simply referred to as “adsorbent”). The molar ratio of carbon to cerium in the adsorbent (carbon / cerium) was 1.3. In this example, the molar ratio (carbon / cerium) was measured by composition analysis of the adsorbent using a fluorescent X-ray analyzer (ZSX Primus 2, manufactured by Rigaku Corporation). Measurement conditions and measurement methods were as follows.
X-ray tube: Rh target X-ray output: 3 kW
Measurement chamber atmosphere: Vacuum Analysis diameter: 10mmΦ
Measurement method: quantified by the fundamental parameter method using a sensitivity library

(Example 2)
An adsorbent was produced in the same procedure as in Example 1 except that the amount of polyacrylic acid used was changed to 0.143 g.

(Example 3)
An adsorbent was produced in the same procedure as in Example 1 except that the amount of polyacrylic acid used was changed to 0.286 g.

Example 4
An adsorbent was produced in the same procedure as in Example 1 except that the amount of polyacrylic acid used was changed to 0.429 g.

(Example 5)
An adsorbent was produced in the same procedure as in Example 1 except that the amount of polyacrylic acid used was changed to 0.500 g.

(Example 6)
An adsorbent was produced in the same procedure as in Example 1 except that the amount of polyacrylic acid used was changed to 0.572 g.

(Comparative Example 1)
An adsorbent was produced in the same procedure as in Example 1 except that no polyacrylic acid was added.

<Evaluation>
The CO ₂ adsorption test and the cycle test were carried out by the following methods, and the CO ₂ adsorption amount and the CO ₂ adsorption amount maintenance rate of the adsorbents of the examples and comparative examples were determined. Note that the gas to be treated in the CO ₂ adsorption test and the cycle test simulates the exhaust gas of a thermal power plant.

(Evaluation in the presence of NOx)
[CO ₂ adsorption test]
First, 20.0 mL of the adsorbent was weighed using a graduated cylinder and fixed in a SUS reaction tube. Then, after raising the temperature of the adsorbent to 50 ° C. using an electric furnace, the volume of the adsorbent is maintained at 50 ° C. in the electric furnace, and 15 vol% CO ₂ , 5 vol% O ₂ A mixed gas containing 150 ppm NO and 80% by volume of N ₂ containing saturated water vapor at about 50 ° C. was circulated through the reaction tube. The flow rate of the mixed gas was 2000 mL / min. The CO ₂ concentration at the outlet of the reaction tube was measured by a gas chromatograph (carrier gas: He), and gas introduction was continued until the CO ₂ concentration measured at the outlet of the reaction tube was saturated. CO ₂ concentration was measured inlet and CO ₂ adsorption amount from the difference between the CO ₂ concentration in the outlet side of the reaction tube until saturated. The CO ₂ adsorption amount was evaluated by a relative value with the CO ₂ adsorption amount in Comparative Example 1 being 1.00.

[Cycle test]
CO ₂ was adsorbed on the adsorbent by the same method as in the CO ₂ adsorption test. Subsequently, CO ₂ was desorbed from the adsorbent by raising the temperature of the adsorbent to 200 ° C. in an electric furnace. Thereafter, the temperature of the adsorbent was cooled to 50 ° C. while only N ₂ gas was passed through the reaction tube. This series of steps (CO ₂ adsorption, CO ₂ desorption and cooling) was repeated 24 cycles, and the CO ₂ adsorption amount maintenance rate was calculated based on the following formula. The evaluation results are shown in Table 1, FIG. 4 and FIG.
CO ₂ adsorption amount retention rate (%) = (CO ₂ adsorption amount at the first cycle) / (CO ₂ adsorption amount at the 24th cycle) × 100

(Evaluation in the presence of SOx)
For the adsorbents of Example 2 and Comparative Example 1, the mixed gas contained about 15% by volume of CO ₂ , 5% by volume of O ₂ , 300 ppm of SO ₂ , and about 50% saturated steam at about 50 ° C. Except for using a mixed gas containing 80% by volume of N ₂ , the CO ₂ adsorption amount and the CO ₂ adsorption amount maintenance rate were determined in the same procedure as the adsorption performance evaluation in the presence of NOx.

In the example in which the porous part covering the core part containing the metal oxide was formed using polyacrylic acid, it was confirmed that the CO ₂ adsorption amount retention rate after the cycle test was high and had high cycle characteristics. . On the other hand, in the comparative example using no polyacrylic acid, CO ₂ adsorption amount retention rate after cycle test was low as compared with Examples.

DESCRIPTION OF SYMBOLS 1 ... Adsorbent particle (particle), 3 ... Core part, 5 ... Porous part, 10c ... Removal part (reaction vessel), 80 ... Adsorbent, 100, 100a, 100b ... Air conditioner (carbon dioxide removal apparatus), 200 210 ... Air conditioning system (carbon dioxide removal system).

Claims (8)

1. An adsorbent used to remove carbon dioxide from a gas to be treated containing carbon dioxide,
   An adsorbent comprising particles comprising a core part containing a metal oxide and a porous part covering at least a part of the core part.
2. The adsorbent according to claim 1, wherein the metal oxide contains cerium.
3. The adsorbent according to claim 1 or 2, wherein the porous portion contains a carbon material.
4. The adsorbent according to any one of claims 1 to 3, wherein a molar ratio of carbon to cerium in the adsorbent is 1.3 to 11.0.
5. An adsorbent comprising particles comprising a core part containing a metal oxide and a porous part covering at least a part of the core part,
   The adsorbent, wherein the molar ratio of carbon to metal element in the adsorbent is 1.3 to 11.0.
6. A reaction vessel comprising the adsorbent according to any one of claims 1 to 5.
7. A carbon dioxide removing device comprising the reaction vessel according to claim 6.
8. A carbon dioxide removal system comprising the carbon dioxide removal device according to claim 7.

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