JP2018034088A - Adsorbent, method of removing carbon dioxide, and air conditioning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adsorbent that can improve the amount of adsorption of carbon dioxide.SOLUTION: An adsorbent is used for removing carbon dioxide from a treatment gas containing the carbon dioxide. The adsorbent contains cerium oxide, and has an average pore diameter, measured by BET method using a nitrogen gas as an adsorption gas, of 40 nm or less.SELECTED DRAWING: None

Description

  The present invention relates to an adsorbent, a method for removing carbon dioxide, and an air conditioner.

In recent years, global warming due to greenhouse gas emissions has become a global problem. Examples of the greenhouse gas include carbon dioxide (CO ₂ ), methane (CH ₄ ), and chlorofluorocarbons (CFCs and the like). Among the greenhouse gases, carbon dioxide has the greatest influence, and construction of a method for removing carbon dioxide (for example, carbon dioxide discharged from thermal power plants, steelworks, etc.) is required.

Carbon dioxide is known to affect the human body. For example, when a gas containing carbon dioxide at a high concentration is sucked, drowsiness, health damage and the like are caused. In spaces with high human density (buildings, vehicles, etc.), the concentration of carbon dioxide in the room (hereinafter referred to as “CO ₂ concentration” in some cases) is likely to increase due to human expiration, and the CO ₂ concentration is adjusted by ventilation. There is a case.

In order to quickly ventilate indoor air and outside air, it is necessary to operate a blower such as a blower. Moreover, since the temperature and humidity of the air taken in from the outside (outside air) are not adjusted, it is necessary to operate the cooling in the summer and to operate the heating in the winter. For these reasons, an increase in indoor CO ₂ concentration is a factor in increasing power consumption associated with air conditioning.

The amount of reduction of carbon dioxide in the room due to ventilation (CO ₂ reduction amount) is expressed by the following equation. In the following equation, the CO ₂ concentration can be kept constant if the amount of CO ₂ decrease on the left side is equivalent to the amount of CO ₂ increase due to human expiration.
CO ₂ reduction amount = (CO ₂ concentration in the chamber - external air CO ₂ concentration) × ventilation

However, in recent years, since the CO ₂ concentration in the outside air has increased, the difference in CO ₂ concentration from the room has become smaller. For this reason, the amount of ventilation required to adjust the CO ₂ concentration is also increasing. In the future, when the CO ₂ concentration in the outside air further increases, it is considered that the power consumption increases by adjusting the CO ₂ concentration by ventilation.

  The said subject arises by ventilation with external air. Therefore, if carbon dioxide can be selectively removed using a method other than ventilation, the amount of ventilation can be reduced, and as a result, power consumption associated with air conditioning may be reduced.

  Also, in spaces (air stations, submersibles, etc.) shielded from the outside air in which air exists, it is difficult to ventilate the outside air and room air, so it is necessary to selectively remove carbon dioxide by methods other than ventilation. There is.

Examples of a solution to the 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 CO ₂ adsorbent (hereinafter simply referred to as “adsorbent”) (CO ₂ separation and recovery method) can be mentioned. For example, zeolite is known as an adsorbent (see, for example, Patent Document 1 below).

JP 2000-140549 A

  By the way, with respect to a carbon dioxide removal method using an adsorbent, it is required to improve the amount of carbon dioxide adsorbed on the adsorbent from the viewpoint of improving the carbon dioxide removal efficiency.

  This invention is made | formed in view of the said situation, and aims at providing the adsorption agent which can improve the adsorption amount of a carbon dioxide. Another object of the present invention is to provide a carbon dioxide removal method and an air conditioner using the adsorbent.

  The adsorbent according to the present invention is an adsorbent used for removing carbon dioxide from a gas to be treated containing carbon dioxide, contains cerium oxide, and is subjected to a BET method using nitrogen gas as the adsorbed gas. The average pore diameter measured is 40 nm or less.

According to the adsorbent according to the present invention, the amount of carbon dioxide adsorbed on the adsorbent can be improved. Such an adsorbent is excellent in CO ₂ adsorptivity (carbon dioxide adsorptivity, carbon dioxide scavenging ability).

By the way, in the method using a conventional adsorbent such as zeolite, when the CO ₂ concentration of the gas to be treated is low, the carbon dioxide removal efficiency tends to decrease. On the other hand, according to the adsorbent according to the present invention, the amount of carbon dioxide adsorbed to the adsorbent can be improved when the CO ₂ concentration of the gas to be treated is low. According to such an adsorbent, carbon dioxide can be efficiently removed when the CO ₂ concentration of the gas to be treated is low.

  The content of the cerium oxide is preferably 90% by mass or more based on the total mass of the adsorbent. In this case, the adsorption amount of carbon dioxide can be further improved.

  The method for removing carbon dioxide according to the present invention includes a step of bringing the adsorbent mentioned above into contact with a gas to be treated containing carbon dioxide to adsorb carbon dioxide to the adsorbent. According to the carbon dioxide removal method of the present invention, the amount of carbon dioxide adsorbed on the adsorbent can be improved, and the carbon dioxide removal efficiency can be improved.

  An air conditioner according to the present invention is an air conditioner used in an air conditioning target space including a processing target gas containing carbon dioxide, and includes a flow path connected to the air conditioning target space, and carbon dioxide contained in the processing target gas. The removal part which removes is arrange | positioned at the flow path, and the adsorbent mentioned above is arrange | positioned at the removal part, and an adsorbent contacts process target gas and a carbon dioxide adsorb | sucks to an adsorbent. According to the air conditioner according to the present invention, the amount of carbon dioxide adsorbed on the adsorbent can be improved, and the carbon dioxide removal efficiency can be improved.

The CO ₂ concentration of the processing object gas may be 5000 ppm or less, or 1000 ppm or less.

According to the present invention, the amount of carbon dioxide adsorbed on the adsorbent can be improved. In particular, according to the present invention, when the CO ₂ concentration of the gas to be processed is low, the amount of carbon dioxide adsorbed on the adsorbent can be improved.

FIG. 1 is a schematic diagram showing an air conditioner according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing an air conditioning system according to an embodiment of the present invention. FIG. 3 is a graph showing the relationship between the average pore diameter of the adsorbents of Examples and Comparative Examples and the CO ₂ adsorption amount.

  In this specification, the numerical range indicated 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.

  In this specification, the term “process” is not limited to an independent process, and is included in this term if the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes. It is. 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 this embodiment contains cerium oxide (cerium oxide) and has an average pore diameter (hereinafter simply referred to as “average fine particle size”) measured by the BET method using nitrogen gas as an adsorbed gas. (Also referred to as “pore diameter”) is 40 nm or less. The adsorbent according to the present embodiment is used for removing (for example, recovering) carbon dioxide from a processing target gas (gas to be processed) containing carbon dioxide.

As a result of intensive studies, the present inventors have found that when the adsorbent containing cerium oxide has an average pore diameter measured by the BET method using nitrogen gas as an adsorbed gas of 40 nm or less, excellent CO ₂ It was found to have adsorptive properties.

The reason why the adsorbent according to the present embodiment has excellent CO ₂ adsorptivity is not clear, but the adsorbent has pores having an average pore diameter of 40 nm or less, so that carbon dioxide and fine particles in the pores are reduced. Adsorption of carbon dioxide is promoted by improving the frequency of contact with the pore walls, improving the adsorption energy of carbon dioxide derived from the curvature of the pore walls, etc., and thus obtaining excellent CO ₂ adsorption. It is guessed. The adsorbent according to the present embodiment has excellent CO ₂ adsorbability particularly when the CO ₂ concentration of the gas to be processed is low.

  Here, the average pore diameter is specifically measured by the following procedure. First, as a pretreatment, the adsorbent is heated at 200 ° C. while vacuuming. Next, after measuring an adsorption isotherm of nitrogen at −196 ° C., an average pore diameter (4 V / A) is calculated from the specific surface area and total pore volume measured by the BET method.

Examples of the cerium oxide include CeOx (x = 1.5 to 2.0), and specific examples include CeO ₂ and Ce ₂ O ₃ .

  The content of cerium oxide in the adsorbent may be 30% by mass or more, 70% by mass or more, or 90% by mass or more based on the total mass of the adsorbent. The adsorbent may be an embodiment made of cerium oxide (an embodiment in which the content of cerium oxide is substantially 100% by mass based on the total mass of the adsorbent). The greater the content of cerium oxide, the more the carbon dioxide adsorption can be improved. The content of cerium oxide can be adjusted by, for example, the content of cerium salt in the raw material for obtaining the adsorbent.

  The average pore diameter of the pores of the adsorbent is 40 nm or less, preferably 30 nm or less, more preferably 10 nm or less, still more preferably 5 nm or less, particularly preferably 4.5 nm or less from the viewpoint of improving the amount of carbon dioxide adsorbed. is there. The average pore diameter of the pores of the adsorbent may be, for example, 1 nm or more. The average pore diameter of the pores of the adsorbent can be measured according to the method described in the examples. The average pore diameter can be adjusted by the firing temperature, the oxygen concentration, etc. when firing the raw material for obtaining the adsorbent.

  The adsorbent may be chemically treated, and may have a high specific surface area, for example, by mixing a filler (alumina, silica, etc.) as a binder.

Examples of the shape of the adsorbent include powder, pellets, granules, and honeycombs. The shape of the adsorbent may be determined in consideration of the required reaction rate, pressure loss, adsorption amount of the adsorbent, purity of the gas (adsorbed gas) adsorbed on the adsorbent (CO ₂ purity), and the like. The shape of the adsorbent may be the same as the shape of the raw material.

<Method for producing adsorbent>
The method for producing an adsorbent according to the present embodiment includes, for example, a firing step of firing a raw material containing at least one cerium salt selected from the group consisting of cerium carbonate and cerium bicarbonate. In such a method for producing an adsorbent, by firing a raw material containing at least one cerium salt selected from the group consisting of cerium carbonate and cerium bicarbonate, the cerium salt is decomposed, and cerium is obtained. Oxidize.

According to the method for producing an adsorbent, the adsorbent according to the present embodiment can be easily obtained. The cause of this is not clear, but the present inventors presume that it is as follows. In the method for producing the adsorbent, carbon dioxide (CO ₂ ) and water (H ₂ O) are discharged by decomposition of cerium carbonate and / or cerium bicarbonate during firing. It is assumed that an adsorbent having pores advantageous for adsorption of carbon dioxide is easily obtained by the carbon dioxide and water.

  The cerium salt may be, for example, a compound containing cerium ions and at least one ion selected from the group consisting of carbonate ions and hydrogen carbonate ions. The cerium carbonate is a compound containing, for example, cerium ions and carbonate ions. Cerium hydrogen carbonate is a compound containing, for example, cerium ions and hydrogen carbonate ions.

  Examples of the cerium carbonate include cerium carbonate and cerium oxycarbonate. Examples of cerium bicarbonate include cerium bicarbonate. The cerium salt may be at least one salt selected from the group consisting of cerium carbonate, cerium bicarbonate, and cerium oxycarbonate from the viewpoint of further improving the amount of carbon dioxide adsorbed. Cerium carbonate and / or cerium bicarbonate may be used in combination with cerium salts other than carbonate and carbon hydrogen salt.

  The raw material may contain a compound other than the cerium salt. Examples of other compounds include compounds containing lanthanides (excluding cerium; lanthanum, neodymium, praseodymium, etc.), iron, sodium and the like. Cerium salt can be prepared by a known method. Further, as the cerium salt, commercially available cerium carbonate and / or cerium bicarbonate may be used.

  The content of the cerium salt may be 90% by mass or more, or 99% by mass or more based on the total mass of the raw materials. The raw material containing a cerium salt may be in an aspect composed of a cerium salt (an aspect in which the content of the cerium salt is substantially 100% by mass based on the total mass of the raw material). The greater the content of cerium salt, the more the carbon dioxide adsorption can be improved.

  The firing temperature in the firing step is not particularly limited as long as it can decompose the cerium salt. The firing temperature may be 150 ° C. or higher, 200 ° C. or higher, or 225 ° C. or higher from the viewpoint of shortening the production time of the adsorbent because decomposition of the cerium salt is likely to proceed. Good. The firing temperature may be 400 ° C. or less, 350 ° C. or less, or 300 ° C. or less from the viewpoint that the specific surface area of the adsorbent tends to increase because sintering of cerium oxide hardly occurs. It may be 275 ° C. or less. From these viewpoints, the firing temperature may be 150 to 400 ° C, 200 to 350 ° C, 225 to 300 ° C, or 225 to 275 ° C.

  The firing time in the firing step may be, for example, 10 minutes or longer, although it depends on the firing amount, firing device, or the presence or absence of mixing during firing. The firing time may be, for example, 10 hours or less, 3 hours or less, or 1 hour or less.

  The firing process may be performed in one stage or in multiple stages including two or more stages. In addition, when performing multi-stage baking, it is preferable that at least one stage is the said baking temperature and / or baking time. The firing step can be performed, for example, in an air atmosphere or an oxygen atmosphere.

  In the firing step, the dried raw material may be fired. In the baking step, the solvent may be removed and the raw material may be fired by heating a solution containing the raw material (for example, a solution in which a cerium salt is dissolved).

  The manufacturing method of the adsorbent according to the present embodiment may include a step of forming the raw material before firing into a predetermined shape (for example, the shape of the adsorbent described later), and the raw material after baking into a predetermined shape. You may provide the process to shape | mold.

<Method for removing carbon dioxide>
The carbon dioxide removal method according to the present embodiment includes an adsorption process in which the adsorbent according to the present embodiment is brought into contact with a processing target gas containing carbon dioxide to adsorb carbon dioxide to the adsorbent.

The CO ₂ concentration in the processing target gas may be 5000 ppm or less (0.5% by volume or less) based on the total volume of the processing target gas. According to the carbon dioxide removal method according to the present embodiment, carbon dioxide can be efficiently removed when the CO ₂ concentration is 5000 ppm or less. The reason why such an effect is achieved is not clear, but the present inventors speculate that it is as follows. In the adsorption step, carbon dioxide is not physically adsorbed on the surface of the cerium oxide, but carbon dioxide is considered to be adsorbed to the adsorbent by chemically bonding with the surface of the cerium oxide. In this case, in the carbon dioxide removal method according to this embodiment, the carbon dioxide partial pressure dependency in the adsorption to the adsorbent is small, and even if the CO ₂ concentration of the gas to be treated is 5000 ppm or less, the carbon dioxide is efficiently removed. It is assumed that carbon can be removed.

CO ₂ concentration from the viewpoint of even if the CO ₂ concentration is low the effect of removing efficiently the carbon dioxide easily identified, based on the total volume of untreated gas may also be 2000ppm or less, 1500 ppm or less It may be 1000 ppm or less, 750 ppm or less, or 500 ppm or less. The CO ₂ concentration may be 100 ppm or more, 200 ppm or more, or 400 ppm or more on the basis of the total volume of the gas to be treated from the viewpoint of easily increasing the amount of carbon dioxide removed. From these viewpoints, the CO ₂ concentration may be 100 to 5000 ppm, 100 to 2000 ppm, 100 to 1500 ppm, or 100 to 1000 ppm, based on the total volume of the gas to be treated. It may be 200 to 1000 ppm, 400 to 1000 ppm, 400 to 750 ppm, or 400 to 500 ppm. In addition, the office hygiene standard rule of the Industrial Safety and Health Law stipulates that the indoor CO ₂ concentration should be adjusted to 5000 ppm or less. In addition, it is known that sleepiness is induced when the CO ₂ concentration exceeds 1000 ppm, and the building environmental hygiene management standard stipulates that the CO ₂ concentration should be adjusted to 1000 ppm or less. Therefore, the CO ₂ concentration may be adjusted by ventilating so that the CO ₂ concentration does not exceed 5000 ppm or 1000 ppm. The CO ₂ concentration in the gas to be treated is not limited to the above range, and may be 500 to 5000 ppm or 750 to 5000 ppm.

The gas to be treated is not particularly limited as long as it contains carbon dioxide, and may contain a gas component other than carbon dioxide. Examples of gas components other than carbon dioxide include water (water vapor, H ₂ O), oxygen (O ₂ ), nitrogen (N ₂ ), carbon monoxide (CO), SOx, NOx, and volatile organic substances (VOC). It is done. Specific examples of the processing target gas include air in a room such as a building or a vehicle. In the adsorption step, when the gas to be treated contains water, carbon monoxide, SOx, NOx, volatile organic matter, etc., these gas components may be adsorbed by the adsorbent.

By the way, in the conventional adsorbents such as zeolite, when the gas to be treated contains water, the CO ₂ adsorptivity tends to be greatly reduced. Therefore, in order to improve the CO ₂ adsorptivity of the adsorbent in the conventional method using the adsorbent, it is necessary to perform a dehumidification step of removing moisture from the target gas before bringing the target gas into contact with the adsorbent. The dehumidifying step is performed using, for example, a dehumidifying device, which leads to an increase in equipment and an increase in energy consumption. On the other hand, the adsorbent according to the present embodiment has excellent CO ₂ adsorptivity compared to conventional adsorbents even when the gas to be treated contains water. Therefore, the carbon dioxide removal method according to the present embodiment does not require a dehumidification step, and carbon dioxide can be efficiently removed even when the gas to be treated contains water.

The dew point of the gas to be treated is, for example, from −40 ° C. to 50 ° C., preferably from 0 ° C. to 40 ° C., more preferably from the viewpoint of increasing the hydroxyl group on the cerium oxide surface and increasing the reactivity with CO _2. It is not lower than 30 ° C and not lower than 30 ° C.

  From the viewpoint of reducing energy consumption due to dehumidification, the relative humidity of the gas to be treated is preferably 100% or less (that is, no condensation occurs on the adsorbent), preferably 0.1% or more and 90% or less, more preferably Is 10% or more and 80% or less. The relative humidity is a relative humidity at 30 ° C., for example.

By adjusting the temperature T ₁ of the adsorbent at the time of contact with the adsorbent untreated gas in the adsorption process, it is possible to adjust the amount of adsorption of carbon dioxide. The higher the temperature T _{1, the} lower the amount of CO ₂ adsorbed by the adsorbent. Temperatures _{T 1} may be a -20 to 100 ° C., it may be 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 amount of carbon dioxide adsorbed can be adjusted by adjusting the total pressure of the atmosphere in which the adsorbent is present (for example, the total pressure in the container containing the adsorbent). As the total pressure is higher, the amount of CO ₂ adsorbed by the adsorbent tends to increase. 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.

In the carbon dioxide removal method according to the present embodiment, the adsorbent may be supported on a honeycomb-shaped base material or may be used by filling the adsorbent into a container. The use method of the adsorbent may be determined in consideration of the required reaction rate, pressure loss, the amount of adsorbent adsorbed, the purity of the gas (adsorbed gas) adsorbed on the adsorbent (CO ₂ purity), and the like.

  When the adsorbent is filled in a container and used, the porosity is preferably as small as possible when increasing the purity of carbon dioxide in the adsorbed gas. In this case, since the amount of gas other than carbon dioxide remaining in the gap is reduced, the purity of carbon dioxide in the adsorbed gas can be increased. On the other hand, when reducing the pressure loss, it is preferable that the porosity is large.

  The carbon dioxide removal method according to the present 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 utilizing the difference in the adsorption amount of the adsorbent with temperature change); Examples include a method of using (pressure swing method, a method of using a difference in the amount of adsorbent adsorbed due to a pressure change) and the like, 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 to 300 ° C., may be 50 to 200 ° C., may be 80 to 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 discharged to the outside as it is, but may be reused in the field using carbon dioxide. For example, in greenhouse cultivation for house or the like, since the plant growth by increasing the CO ₂ concentration is accelerated, because they may increase the CO ₂ concentration 1000ppm level, the recovered carbon dioxide, the CO ₂ concentration May be reused to enhance.

When SOx, NOx, dust, or the like is adsorbed on the adsorbent, the CO ₂ adsorptivity of the adsorbent in the adsorption process may be lowered. Therefore, it is preferable that the gas to be treated does not contain SOx, NOx, dust, or the like. 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, it is preferable to further include an impurity removal step of removing impurities such as SOx, NOx, and dust from the gas to be treated before the adsorption step. In the impurity removing step, the impurities adsorbed on the adsorbent can be removed by heating the adsorbent. 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. .

  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.

The carbon dioxide removal method according to the present embodiment can be preferably carried out in a sealed space where the CO ₂ concentration needs to be managed. Examples of the space in which the CO ₂ concentration needs to be managed include a building, a vehicle, an automobile, a space station, a submersible, a food or chemical production plant, and the like. The carbon dioxide removal method according to this embodiment can be preferably carried out particularly in a space where the CO ₂ concentration is limited to 5000 ppm or less (for example, a space where the density of people such as buildings and vehicles is high). In addition, since carbon dioxide may adversely affect the production of food or chemical products, the carbon dioxide removal method according to the present embodiment is preferably implemented in a food or chemical production plant or the like. Can do.

<Air conditioning equipment and air conditioning system>
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 is disposed 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 example of the air conditioner will be described with reference to FIG.

  As shown in FIG. 1, an air conditioner 100 according to this embodiment includes a flow path 10, an exhaust fan (exhaust unit) 20, a concentration measuring device (concentration measuring unit) 30, and an electric furnace (temperature control unit) 40. And a compressor (pressure control means) 50 and a control device (control unit) 60.

  The flow path 10 is connected to the air conditioning target space R including the 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. 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.

  An adsorbent 80 that 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 60 can control the operation of the air conditioner 100. For example, based on the carbon dioxide concentration measured by the concentration measuring device 30, the control device 60 controls the presence or absence of inflow of the processing target gas in the removal unit 10c. be able to. 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 60. Sent. The control device 60 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 60 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 60 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.

  The air conditioning system according to the present embodiment includes a plurality of air conditioning apparatuses according to the present embodiment. The air conditioning system which concerns on this embodiment may be provided with the control part which controls the air conditioning driving | operation of several air conditioner. For example, the air conditioning system according to the present embodiment comprehensively controls the air conditioning operation of a plurality of air conditioners.

  For example, as shown in FIG. 2, the air conditioning system 1 according to the present embodiment includes a first air conditioner 100a, a second air conditioner 100b, and a control device (control unit) 62. The control device 62 controls the air conditioning operation of the first air conditioner 100a and the second air conditioner 100b by controlling the above-described control device 60 in the first air conditioner 100a and the second air conditioner 100b. For example, the control device 62 may adjust the air conditioning operations of the first air conditioner 100a and the second air conditioner 100b 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 62 can transmit information regarding the presence / absence of inflow of the processing target gas in the removal unit 10c to the control device 60.

  The air conditioner and the air conditioning system are not limited to the above-described embodiment, and may be appropriately changed without departing from the spirit thereof. For example, the adsorbent only needs to be disposed in the removal portion, and may be disposed in a part of the inner wall surface without being filled in the central portion of the removal portion. The control content of the control unit of the air conditioner is not limited to controlling the presence or absence of inflow of the processing target gas in the removal unit, and the control unit may adjust the inflow amount of the processing target gas in the removal unit.

  In the air conditioner, the gas to be processed may be supplied to the carbon dioxide removing unit using a blower instead of the exhaust fan, and when the gas to be processed is supplied to the carbon dioxide removing unit by natural convection, an exhaust means is provided. It may not be used. 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, the control device, etc. is not limited to one, and a plurality of them may be arranged. Good. 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.

  EXAMPLES Hereinafter, although the content of this invention is demonstrated in detail using an Example and a comparative example, this invention is not limited to a following example.

<Preparation of adsorbent>
Example 1
According to the following procedure, 20 g of cerium carbonate (Ce ₂ (CO ₃ ) ₃ · 8H ₂ O) was calcined in air. First, after raising the temperature to 120 ° C. at 5 ° C./min in an electric furnace, the temperature was maintained at 120 ° C. for 1 hour. Thereafter, the temperature was raised to a firing temperature of 300 ° C. at 5 ° C./min, and the temperature was maintained at the temperature (300 ° C.) for 1 hour. Thereby, the adsorbent of Example 1 was obtained.

(Example 2)
The following cerium oxalate by the procedure _{(Ce 2 (H 2 O 4} ) 3 · 9H 2 O) 20g was calcined in air. First, after raising the temperature to 120 ° C. at 5 ° C./min in an electric furnace, the temperature was maintained at 120 ° C. for 1 hour. Thereafter, the temperature was raised to a firing temperature of 300 ° C. at 5 ° C./min, and the temperature was maintained at the temperature (300 ° C.) for 1 hour. Thereby, the adsorbent of Example 2 was obtained.

(Example 3)
20 g of commercially available cerium oxide (A) was used as the adsorbent.

Example 4
According to the following procedure, 20 g of cerium hydroxide (Ce (OH) ₄ ) was calcined in air. First, after raising the temperature to 120 ° C. at 5 ° C./min in an electric furnace, the temperature was maintained at 120 ° C. for 1 hour. Thereafter, the temperature was raised to a firing temperature of 300 ° C. at 5 ° C./min, and the temperature was maintained at the temperature (300 ° C.) for 1 hour. Thereby, the adsorbent of Example 4 was obtained.

(Comparative Example 1)
20 g of commercially available cerium oxide (B) was used as the adsorbent.

<Measurement of average pore diameter>
For the adsorbents of Examples 1 to 4 and Comparative Example 1, the average pore diameter was measured by the following procedure. First, as a pretreatment, the adsorbent was heated at 200 ° C. while vacuuming. Next, after measuring an adsorption isotherm of nitrogen at −196 ° C., an average pore diameter (4 V / A) was calculated from the specific surface area and total pore volume measured by the BET method. The results are shown in Table 1.

<Measurement of carbon dioxide adsorption>
For the adsorbents of Examples 1 to 4 and Comparative Example 1, the amount of carbon dioxide adsorbed was measured.

First, using a metal mold having a diameter of 40 mm, the adsorbent was pelletized with a press at 2850 kgf / cm ² . Next, the pellets were crushed and then sized into granules (particle size: 0.5 to 1.0 mm) using a sieve. Thereafter, 1.0 mL of the adsorbent was measured using a graduated cylinder and fixed in a reaction tube made of quartz glass.

  Next, as a pretreatment, the temperature of the adsorbent was raised to 200 ° C. using an electric furnace while flowing helium (He) through the reaction tube at 150 mL / min, and then held at 200 ° C. for 1 hour. Thereby, impurities and gas adsorbed on the adsorbent were removed.

Next, after cooling the adsorbent to 50 ° C., the CO ₂ adsorption amount was measured by a CO ₂ pulse adsorption test while maintaining the adsorbent temperature at 50 ° C. in an electric furnace. Specifically, the CO ₂ pulse adsorption test was performed by the following method.

[CO ₂ pulse adsorption test]
As a sample gas, 10 mL of a mixed gas containing 12% by volume of CO ₂ and 88% by volume of He was used. The sample gas was introduced in a pulsed manner every 4 minutes for 2 minutes. At this time, the total pressure in the reaction tube was adjusted to 1 atmosphere. Next, the CO ₂ concentration at the outlet of the reaction tube was measured by a gas chromatograph (carrier gas: He). The introduction of the sample gas was continued until the CO ₂ concentration measured at the outlet of the reaction tube was saturated. CO ₂ concentration is the amount of carbon dioxide adsorbed in until saturated (unit: g) of the CO ₂ adsorption amount (unit: g / L) was determined. The results are shown in Table 1.

FIG. 3 shows the relationship between the average pore diameter of the adsorbent and the CO ₂ adsorption amount in Examples 1 to 4 and Comparative Example 1. By comparing Examples 1 to 4 with Comparative Example 1, when the adsorbent containing cerium oxide has a pore diameter having an average pore diameter of 40 nm or less, an effect of being excellent in CO ₂ adsorption amount is obtained. I understand that.

  DESCRIPTION OF SYMBOLS 1 ... Air conditioning system, 10 ... Channel, 10a, 10b, 10d, 10e, 10f ... Channel part, 10c ... Removal part, 20 ... Exhaust fan, 30 ... Concentration measuring device (concentration measuring part), 40 ... Electric furnace, 50 ... Compressor, 60, 62 ... Control device (control unit), 70a, 70b ... Valve, 80 ... Adsorbent, 100, 100a, 100b ... Air conditioner, R ... Air-conditioning target space, S1, S3 ... Space, S2 ... Center Department.

Claims (8)

An adsorbent used to remove carbon dioxide from a gas to be treated containing carbon dioxide,
Contains cerium oxide,
An adsorbent having an average pore diameter of 40 nm or less as measured by a BET method using nitrogen gas as an adsorbing gas.   The adsorbent according to claim 1, wherein the content of the cerium oxide is 90% by mass or more based on the total mass of the adsorbent.   A method for removing carbon dioxide, comprising: bringing the adsorbent according to claim 1 or 2 into contact with a gas to be treated containing carbon dioxide to adsorb carbon dioxide to the adsorbent.   The method for removing carbon dioxide according to claim 3, wherein the concentration of carbon dioxide in the gas to be treated is 5000 ppm or less.   The method for removing carbon dioxide according to claim 3, wherein the carbon dioxide concentration of the gas to be treated is 1000 ppm or less. An air conditioner used in an air conditioning target space containing a processing target gas containing carbon dioxide,
A flow path connected to the air-conditioned space,
A removal section for removing carbon dioxide contained in the processing target gas is disposed in the flow path,
The adsorbent according to claim 1 or 2 is disposed in the removal unit,
An air conditioner in which the adsorbent comes into contact with the gas to be treated and the carbon dioxide is adsorbed on the adsorbent.   The air conditioner of Claim 6 whose carbon dioxide concentration of the said process target gas is 5000 ppm or less.   The air conditioner according to claim 6 whose carbon dioxide concentration of said processing object gas is 1000 ppm or less.

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