JP6721020B2 - CO2 removal device - Google Patents

Description

The present invention relates to an apparatus for removing CO ₂ from a gas containing CO ₂ such as combustion exhaust gas and the atmosphere, and particularly to a technique for reducing energy required for CO ₂ removal.

Global warming due to greenhouse gas emissions has become a global problem. Greenhouse gases include carbon dioxide (CO ₂ ), methane (CH ₄ ), fluorocarbons (CFCs) and the like. Of these, CO ₂ has the greatest influence, and construction of a CO ₂ separation and removal system from a thermal power plant, a steel mill, etc. is an urgent issue.

CO ₂ also affects the human body. For example, when a gas containing a high concentration of CO ₂ is inhaled, it causes a health hazard. Therefore, it is necessary to control the CO ₂ concentration in a closed space such as a room. Especially in an environment where it is difficult to ventilate outside air and indoor air, such as a space station, a device for removing CO ₂ is particularly required. In addition, since CO ₂ may adversely affect the production of foods and chemical products, a system for removing CO ₂ is required.

As a solution to the above problems, there are a chemical absorption method, a physical absorption method, a membrane separation method, an adsorption separation method, a cryogenic separation method, and the like. Among them is a CO ₂ separation and recovery method using a solid CO ₂ capturing material. The CO ₂ removal system using CO ₂ capturing material, introducing CO ₂ containing gas to the capturing material container filled with CO ₂ capturing material, contacting the CO ₂ capturing material gas by pressure atmospheric or pressurized, Capture and remove CO ₂ . Then, the trapping material is heated or the inside of the trapping material container is depressurized to desorb and remove the captured CO ₂ . CO ₂ The desorbed was CO ₂ capturing material is cooled, or is used to capture and removal of by circulating again CO ₂ containing gas after vacuum CO _2.

In these CO ₂ capturing/removing devices, zeolite is mainly used as a CO ₂ capturing material. For example a gas containing CO ₂ in Patent Document 1 adsorbed CO ₂ by contacting the CO ₂ adsorbent zeolite, it is described thereafter CO ₂ removal method of the CO ₂ desorbed by heating There is.

Japanese Patent Publication No. 2010-527757

When zeolite is brought into contact with a gas containing water vapor (H ₂ O), the amount of captured CO ₂ decreases, so it is common to remove H ₂ O before the stage of capturing CO ₂ . For example, in the method for capturing and removing CO ₂ described in Patent Document 1, when the CO ₂ -containing gas contains water vapor (H ₂ O), the concentration of H ₂ O is set to 400 ppm or less, more preferably 20 ppm or less. It is preferable to reduce the amount.

Depending on the type of solid CO ₂ scavenger, it is considered that there is a preferable effect of bringing the gas containing H ₂ O into contact, such as an increase in the amount of CO ₂ scavenging or a lowering of the CO ₂ desorption temperature, or both. .. However, in Patent Document 1, these are not discussed, and further, there is no description about a device configuration using the same.

An object of the present invention is to provide a CO ₂ separation/removal device with reduced energy consumption.

For the above-mentioned purpose, the CO ₂ removal device of the present invention is a CO ₂ trap material for trapping H ₂ O and CO ₂ in a gas, a reaction container having the trap material inside, and a H ₂ gas in the gas. and H _{2 O} measurement device for measuring the O concentration, and H _{2 O} concentration adjusting device for adjusting of H _{2 O} concentration on the basis of information obtained by the H _{2 O} instrument, from the H _{2 O} concentration adjusting device A gas introduction path for introducing the gas into the reaction vessel to bring it into contact with the CO ₂ capturing material, and a first gas exhaust path for discharging the mixed gas from the reaction vessel after bringing the mixed gas into contact with the capturing material. And a second gas discharge path for discharging the gas desorbed from the CO ₂ trap material from the reaction vessel.

According to the present invention, it is possible to provide a CO ₂ separation/removal device that consumes less energy than before.

6 is a graph comparing the amount of CO ₂ trapped in cerium oxide with and without H ₂ O flowing. The CO ₂ desorption rate during the temperature increase in the cerium oxide is a graph comparing the presence or absence of H _{2 O} flow. Is a graph of the correlation of the energy and temperature were compared with and without H _{2 O} flow consumed for heating the capturing material when CO ₂ desorption of cerium oxide. The CO ₂ desorption rate during the temperature increase in the zirconium oxide is a graph comparing the presence or absence of H _{2 O} flow. It is a graph showing the correlation of the H _{2 O} concentration and the H _{2 O} adsorption in cerium oxide. Is an example of a CO ₂ removal device when the trapping agent is a fixed bed system. It is an example of a CO ₂ removal device capable of continuously removing CO ₂ when the trapping material is a fixed bed type. It is an example of a CO ₂ removal device when the capturing material is a rotor type. In an example of a CO ₂ removal device for removing H ₂ O or CO ₂ or both in another reaction container by using two reaction containers and switching a valve when trap saturation occurs in one reaction container is there. Using two reaction vessels, an example of a CO ₂ removal device for the flow direction of the flow direction and the heating gases CO ₂ and H _{2 O} containing gas with reverse.

The best mode for carrying out the present invention is shown below. The scope of the present invention is not limited to the examples given below.

As a result of diligent studies of the above problems, the present inventors have found that in a device for separating and removing CO _{2 and/} or H ₂ O from a gas containing CO ₂ and H ₂ O by using a solid CO ₂ capturing material. A trapping material capable of trapping H ₂ O and CO ₂ by the apparatus, a reaction vessel having the trapping material installed therein, an H ₂ O measuring instrument for measuring the H ₂ O concentration in the gas, and H _{2 O} concentration adjusting device for adjusting of H _{2 O} concentration, and means for controlling of H _{2 O} concentration adjusting device on the basis of the information obtained by the H _{2 O} instrument, CO into the reaction vessel A pipe for introducing a mixed gas containing ₂ and H ₂ O into contact with the capturing material, and a pipe for discharging the mixed gas from the reaction vessel after contacting with the capturing material, _It was found that the energy required for separating and removing CO ₂ can be reduced by leaving H ₂ O in the ₂ O concentration adjusting device. This is because the surface state of the solid changes due to the flow of H ₂ O, a trapped state of CO _{2 having} a low desorption temperature can be formed, and the energy required for heating necessary for desorbing CO ₂ can be reduced. I'm thinking of it. Further, it is considered that the energy required for removing H ₂ O can be reduced as compared with the case of removing the entire amount of H ₂ O.

The scavenger used to trap CO ₂ and H ₂ O can be any substance. Examples thereof include metal oxides, activated carbon, alkali metal carbonates, alkali metal hydroxides, layered double hydroxides, and solid organic compounds. As the CO ₂ capturing material, a single type may be used, or a plurality of types may be combined. Alternatively, one may be used as a carrier and the other may be supported by a method such as impregnation.

The metal oxide is preferably a porous metal oxide, particularly preferably an oxide or a composite oxide containing at least one metal selected from Ce, rare earth metals other than Ce, and zirconium. When the oxides of the combination are used, CO ₂ can be adsorbed even after contacting with H ₂ O, and the CO ₂ desorption temperature can be lowered. This is because in the above oxide, the surface of the oxide reacts with H ₂ O to form a hydroxyl group (—OH), and the reaction of this functional group with CO ₂ causes hydrogen carbonate (—CO ₃ H) on the surface. This is because it is possible to adsorb CO ₂ in the shape of Examples of the method for synthesizing the present capturing material include preparation methods such as an impregnation method, a kneading method, a coprecipitation method, and a sol-gel method. For example, the pH may be adjusted to 7 to 10 by adding a basic compound such as aqueous ammonia, Na hydroxide, and Ca hydroxide to a solution containing a nitrate of Ce, and precipitation may be performed. When an oxide is formed by precipitation, it may be used as it is or may be further oxidized by firing.

As the metal oxide, an oxide obtained by firing layered double hydroxide may be used. The layered double hydroxide is also called a hydrotalcite-like compound, and is a substance containing two or more kinds of metal elements and the composition of which can be represented by the following formula (1). In the formula below, M(2+) is a divalent metal ion such as Mg, Mn, Fe, Co, Ni, Cu and Zn, and M(3+) is a trivalent metal ion such as Al, Cr, Fe, Co and In, and A(n−) represents an n-valent anion, for example, carbonate ion, nitrate ion, and sulfate ion. Each of the M(2+), M(3+), and A(n−) may be a single ion or a plurality of ions.

M(2+) _1-x M(3+) _x (OH) ₂ A(n−) _x/n ·yH ₂ O... (1)
Examples of the method for synthesizing the layered double hydroxide include an impregnation method, a kneading method, a coprecipitation method, and a sol-gel method. For example, the pH is adjusted to 8 to 11 by adding sodium carbonate to a solution containing nitrates of Mg and Al and then adding basic compounds such as ammonia water, Na hydroxide, and Ca hydroxide. , May be obtained by precipitation. Since the substance obtained by this precipitation is a layered double hydroxide, it may be calcined to obtain a metal oxide and a metal composite oxide. The firing temperature may be any temperature, but a metal oxide can be obtained, for example, when firing at 400° C. or higher.

As the metal oxide and the metal composite oxide, silica (SiO ₂ ), alumina (Al ₂ O ₃ ), zeolite, or the like may be used. Further, in order to improve the specific surface area, heat resistance, and the amount of used metal, etc., an oxide or mixed oxide containing at least one metal selected from Ce, rare earth metal, and zirconium in the above silica, alumina, and zeolite. Etc. may be supported.

Any activated carbon may be used as the trapping material. When activated carbon contains nitrogen element (N) in its interior, its basicity may be increased and CO ₂ adsorption performance may be improved. Therefore, activated carbon containing a large amount of N may be preferable. When synthesizing such activated carbon, a method of contacting the activated carbon with a gas containing ammonia (NH ₃ ), and a method of synthesizing the activated carbon from an organic molecule containing a large amount of N can be considered.

As the solid organic compound, a basic organic compound is preferable, and examples thereof include an organic compound having an amino group.

Downstream of the reaction vessel filled with CO ₂ capturing material, may be installed different CO ₂ capturing material or H _{2 O} capturing material or reaction vessel filled with both. Further, a method may be used in which a valve for switching a flow path is installed in a pipe portion connecting the reaction vessels, and a reaction vessel at a subsequent stage is used as necessary. For example, when the scavenger capable of trapping both CO ₂ and H ₂ O is filled in the reaction vessel at the preceding stage, first, either gas of CO ₂ and H ₂ O is trapped and saturated first, and then discharged from the outlet of the reaction vessel. It is thought to be done. In the case where CO ₂ is captured and saturated first, a scavenger that reduces the CO ₂ scavenging performance when H ₂ O flows may be used in the reaction vessel installed in the latter stage. Examples of such a trapping material include zeolite and activated carbon. Further, when H ₂ O is captured and saturated first, a capturing material having a low CO ₂ capturing performance may be used in the reaction vessel installed in the subsequent stage. Examples of such a capturing material include silica and alumina. If the concentration ratio of H ₂ O and CO ₂ in the gas is likely to fluctuate and it is unclear which gas is likely to be trapped and saturated, two reaction vessels are installed in the latter stage, and the trapped and saturated gas type is installed. A method of selecting a reaction container to be used according to the above may be adopted. When H ₂ O and CO ₂ can be removed using only the trapping vessel of the first stage, it is not necessary to perform the desorption treatment of H ₂ O or CO ₂ from the reaction vessel of the second stage, and the energy consumption can be reduced.

As an example of the combination of the reaction vessel and the CO ₂ capturing material, a CO ₂ capturing material using an oxide or a composite oxide containing at least one metal selected from Ce, a rare earth metal other than Ce, and zirconium in the preceding stage. The reaction vessel filled with CO ₂ may be installed, and the reaction vessel filled with the CO ₂ capturing material using zeolite may be installed in the latter stage. When this configuration is used, only CO ₂ is captured and saturated in the reaction vessel at the front stage, and even when the CO ₂ is discharged from the outlet gas, CO ₂ can be captured at the reaction vessel at the rear stage. Even when H ₂ O is trapped and saturated at the front stage of the reaction vessel and is discharged from the outlet gas, it can be trapped by the zeolite at the rear stage, but since zeolite generally adsorbs H ₂ O more strongly than CO ₂ , To desorb H ₂ O, the load required for heating and decompression is higher than that for desorbing CO ₂ . Thus, in this configuration so that H _{2 O} in a reaction vessel of the preceding stage does not become trapped saturation, it is considered to be better to adjust of H 2 _O concentration can be reduced energy consumption.

As an example of the combination of the reaction vessel and the CO ₂ capturing material, a CO ₂ capturing material using an oxide or a composite oxide containing at least one metal selected from Ce, a rare earth metal other than Ce, and zirconium in the preceding stage. The reaction container filled with the above may be installed, and the reaction container filled with the H ₂ O scavenger using silica or alumina may be installed in the subsequent stage. When this configuration is used, only H ₂ O is trapped and saturated in the reaction vessel at the front stage, and even when discharged from the outlet gas, H ₂ O can be trapped at the reaction vessel at the rear stage. When CO ₂ becomes saturated in the reaction container in the first stage and flows into the second stage, CO ₂ removal may be incomplete because silica and alumina have low CO ₂ capturing performance. Therefore, in this configuration, it is necessary to prevent the CO ₂ trapping and saturation in the preceding stage, for example, by measuring the CO ₂ concentration distribution in the preceding reaction vessel.

The mixed gas containing CO ₂ and H ₂ O may be any gas, for example, a boiler exhaust gas of a coal-fired power plant, a combustion exhaust gas of an automobile, a gas generated by fermentation of microorganisms, the atmosphere, or the exhalation of living organisms. And so on. The composition is not limited, but in the case of boiler exhaust gas or combustion exhaust gas, for example, in addition to CO ₂ and H ₂ O, nitrogen (N ₂ ), oxygen (O ₂ ), nitrogen oxide (NOx), sulfur oxide (SOx). ), carbon monoxide (CO), hydrocarbons such as methane (CH ₄ ), and ash dust. Among these gases, NOx, SOx, and ash dust are considered to reduce the CO ₂ trapping performance of the trapping material, and therefore, if a large amount of these is contained, it is preferable to remove them in advance.

As the H ₂ O concentration adjusting device in the CO ₂ removing device, any device may be used. For example, the H _{2 O} concentration regulator that utilizes the temperature dependence of of H 2 _O saturated vapor pressure, cooled condensers and the like. This equipment generally are used for the purpose of reducing of H _{2 O} concentration increases the saturation vapor pressure of H _{2 O} by adjusting, for example, temperature increase of H _{2 O} concentration of the CO ₂ containing gas You may use it to let. The H _{2 O} concentration regulator that utilizes the temperature dependence of of H 2 _O saturated vapor pressure, and other temperature is adjusted to the liquid water (H 2 _O) in the gas by circulating the gas in There is a device for adjusting the H ₂ O concentration. In the case of using the device, a foaming device such as a bubbler may be installed in order to increase the contact area between water and gas to improve the efficiency. By using such a configuration, it is possible to control the H ₂ O concentration to be appropriate.

As the H _{2 O} concentration adjusting device include H _{2 O} concentration regulator for installing a timber for capturing of H _{2 O} to another. Any material may be used for adsorbing H ₂ O, but examples thereof include a porous material and a resin having a function of absorbing water. Any component may be used for the porous body, but examples thereof include silica (SiO ₂ ), alumina (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), cerium oxide (CeO ₂ ), and hydrotalcite. Organic compounds such as layered double hydroxide, zeolite, activated carbon and resin materials can be used.

When using these adsorbents, the when high H _{2 O} concentration in the gas adsorbs H _{2 O,} when H 2 _O is less of H _{2 O} in the capturing material conversely desorbed considered Therefore, even when the H ₂ O concentration in the CO ₂ -containing gas suddenly changes, it is possible to suppress the change in the H ₂ O concentration in the gas contacting the CO ₂ capturing material.

As the device for adjusting the H ₂ O concentration, a single device may be used, or a plurality of types of devices may be used in combination. For example, when using the temperature dependence of of H 2 _O saturated vapor pressure adjusting of H _{2 O} concentration, water (H 2 _O) vaporization or heat absorption or heat generation due to condensation of water vapor occurs, the If the amount is large, the temperature difference with the heat transfer part becomes large, and it is considered that the temperature cannot be controlled appropriately. In such a case, it is preferable to accurately control the H ₂ O concentration using a plurality of H ₂ O concentration adjusting devices.

Any device may be used as the device for measuring the H ₂ O concentration, and examples thereof include a dew point hygrometer, an electric resistance hygrometer, a thermal conductivity hygrometer, and a dry-humidity hygrometer. To adjust of H _{2 O} concentration using the H _{2 O} concentration regulator based of H _{2 O} concentration measured outputs of H 2 _O concentration as an electric signal, the H ₂ O based on the signal It is preferable to control the concentration adjuster.

The place where the device for measuring the H ₂ O concentration is installed is not limited, but, for example, a method of measuring at the upstream side of the reaction container filled with a CO ₂ capturing material, or measuring the distribution of the captured amount of H ₂ O, and capturing saturation. For example, a method of measuring inside the packed bed of the CO ₂ capturing material inside the reaction tube to predict the above, a method of measuring downstream of the reaction tube to observe the capture saturation, and the like can be mentioned.

The H ₂ O concentration in the mixed gas after the H ₂ O concentration adjuster adjusts the H ₂ O concentration is not particularly limited, but as an example, it is preferably 20 ppm or more, and may be 2000 ppm or more.

The H ₂ O concentration may be determined from the CO ₂ concentration. In this case, the molar ratio with CO ₂ is preferably 0.5 or more and 40 or less. By controlling the molar ratio with CO ₂ to be 0.5 or more, the surface state of the solid is changed, a trapped state of CO _{2 having} a low desorption temperature can be formed, and heating required for desorbing CO ₂ is performed. The energy required for the can be reduced. By controlling the 40 following mol ratio of CO _2, CO ₂ and _{H 2} O capture capture saturated _{H 2} O in the material is CO ₂ can be prevented from occurring to the capture before saturation.

Any method may be used as a method of desorbing CO ₂ after the CO ₂ is captured by the capturing material. For example, raising the temperature of the trapped material, CO ₂ temperature swing method desorb, or pressure swing method desorb the CO ₂ by reducing the pressure of the atmosphere in capturing material, or temperature and pressure swing method using both Are listed. These desorption methods may be determined in consideration of the pressure of the CO ₂ -containing gas, the CO ₂ partial pressure, and the temperature.

Examples of the heating method of the CO ₂ capturing material when using the temperature swing method include a method of directly contacting a heating medium such as a heated gas or liquid with the CO ₂ capturing material, or a method of heating a gas or a liquid heated in a heat transfer tube or the like. Examples thereof include a method in which a heat medium is circulated and heated by heat conduction from a heat transfer surface, and a method in which a CO ₂ capturing material is heated by electrically generating heat with an electric furnace or the like.

When the heating gas having a high temperature is brought into contact with the capturing material, the heating gas may be determined in consideration of the use of CO ₂ separation and removal. For example, if desired to increase the CO ₂ concentration recovered after the desorption may be used CO ₂ as a heating gas. When it is desired to separate the heating gas and the desorbed gas, H ₂ O whose saturated vapor pressure largely changes depending on the temperature is used, and H ₂ O may be removed by cooling the recovered gas. If there is no problem even if the CO ₂ concentration in the desorbed gas decreases, N2, O2, or atmospheric gas, which is relatively inexpensive, may be used.

In a configuration in which two or more reaction vessels are filled with different CO ₂ trapping materials or H ₂ O trapping materials, and heating gas is circulated to desorb CO ₂ and H ₂ O, the heating gases are separated in each reaction vessel. It may be distributed to. In this case, there is an advantage that the gas desorbed from one trapping material does not affect the other trapping material. Alternatively, the heating gas may be introduced from one side while the reaction vessels are connected to each other, and the heating gas may be circulated to the other reaction vessel and then discharged. In this case, since the gas used for heating one of the trapping materials is reused, there is an advantage that energy consumption can be reduced and the amount of gas used can be reduced. In this configuration, for example, H in the case where CO ₂ capture performance is by using a capturing material to decrease by _{2 O} inflow, control the flow direction of the heating gas so as not to contact desorbed H _{2 O} within said capturing material Preferably. For example, when cerium oxide is used as the CO ₂ trap in the first stage and zeolite is used as the CO ₂ trap in the _second stage, it is preferable to change the gas flow direction between trapping and desorption. When capturing CO ₂ and H ₂ O, the CO ₂ and H ₂ O-containing gas is made to flow from the front stage to the rear stage to make it difficult for H ₂ O to flow to the rear stage, and at the time of desorption, heating gas is transferred from the rear stage to the front stage. The H ₂ O desorbed from the cerium oxide in the former stage is less likely to come into contact with the zeolite in the latter stage by the circulation, and the CO ₂ trapping performance in the reaction vessel in the latter stage can be easily maintained.

As the method of decompressing when the pressure swing method or the temperature/pressure swing method is used, there is a mechanical means using a compressor such as a pump. When there is an influence such as pulverization of a material due to vibration generated by a mechanical means, a method of reducing the saturated vapor pressure by cooling to condense the water vapor in the atmosphere of the capturing material, and reducing the pressure can be mentioned. Examples of the method for reducing the partial pressure of CO _{2 in the} atmosphere around the CO ₂ capturing material include a method of circulating a gas other than CO ₂ in addition to the above method. As the gas used at this time, a gas that can be easily separated from CO ₂ is preferable, and in particular, there is a method of using steam from the viewpoint of being easily condensed by cooling.

Examples of the method of pressurizing the atmosphere around the CO ₂ capturing material include a method of mechanically pressurizing with a pump or a compressor, and a method of introducing a gas whose pressure is higher than that of the ambient atmosphere.

The trapping material may be used in any shape. For example, a method of molding into a powder form, a pellet form, or a granular form, or a method of supporting it on a honeycomb can be mentioned. These shapes may be determined in consideration of the required reaction rate, pressure loss and CO ₂ purity in the desorbed gas. Further, regarding the porosity, the porosity may be decreased when the purity of CO ₂ in the desorbed gas is increased. For example, when the particles are granular and the porosity is small, there is a drawback that the pressure loss increases, but the amount of gas other than CO ₂ remaining in the voids decreases, so that the purity of CO ₂ in the recovered gas can be increased. There are advantages. On the other hand, when loaded on a honeycomb, the porosity is high, so the pressure loss can be reduced, but the amount of gas other than CO ₂ remaining in the voids is large, so the purity of CO ₂ in the desorbed gas is low. There is.

The reaction container filled with the CO ₂ capturing material may have any configuration and operation method. For example, a granular or powdery CO ₂ capturing material is filled in the reaction container, and the gas introduced into the CO ₂ capturing material container without changing the CO ₂ capturing material itself and the temperature/pressure inside the reaction container are fixed. A floor system is mentioned. In this configuration, since the movement of the trapping material is small, there is an advantage that the deterioration of the performance due to the abrasion between the trapping materials or between the trapping material and the reaction vessel can be suppressed. Further, since the packing density can be increased, it is considered that the porosity is low and the amount of CO ₂ removed per volume can be increased. On the other hand, in the case of performing the temperature swing method in which the heating gas is circulated to heat the trapping material and CO ₂ is desorbed by using the present configuration, it is necessary to switch the circulated gas, and thus the piping or the valve is required. However, there is a drawback that the configuration of is complicated.

As a method for moving the CO ₂ capturing material itself without switching the distribution gas, for example, a honeycomb rotor carrying the CO ₂ capturing material and a reaction container, and a partition plate for partitioning gas distribution in the reaction container are installed. However, there is a rotor system in which the inside of the reaction vessel is divided into a CO ₂ capture zone, a CO ₂ thermal desorption zone, a CO ₂ capture material cooling zone, etc., depending on the flowing gas. By rotating the honeycomb, the internal CO ₂ trap material moves to each zone, and a cycle of CO ₂ trap, CO ₂ heat desorption, and CO ₂ trap material cooling can be performed. In this configuration, the CO ₂ trapping material is supported on the honeycomb, and there is an advantage that the CO ₂ trapping material itself is less worn and performance deterioration can be suppressed to a low level. In addition, since it is not necessary to switch the circulating gas, the structure of the pipes and valves is simplified. Further, the size of each zone can be determined by changing the installation of the partition plate, and thus the ratio of the CO ₂ capture time, the heat desorption time, the cooling time, etc. can be easily determined. On the other hand, high porosity, low CO ₂ removal amount per volume, also CO ₂ CO ₂ concentration in the desorbed gas is the disadvantage that low. When two or more trapping materials are used in this method, two or more reaction vessels may be installed and a honeycomb rotor carrying different trapping materials may be used, or one trapping material may be used in one honeycomb rotor. Two or more kinds of capturing materials may be carried by dividing the place for carrying. CO ₂ capturing material examples containing cerium oxide on the upstream side of the honeycomb rotor, and a method of carrying the CO ₂ capturing material containing zeolite downstream. In this configuration, CO ₂ and H _{2 O} containing gas is allowed to flow from the upstream side toward the downstream side, the heating gas can be circulated from the downstream side to the upstream direction, in contact H _{2 O} is the zeolite It is preferable from the viewpoint of suppressing a decrease in CO ₂ capture performance.

Without switching and distribution gas, as a way of moving the CO ₂ capturing material itself, and CO ₂ capture reaction vessel CO ₂ containing gas to other flows, capturing the CO ₂ gas for capturing material heated flows There is a fluidized bed system in which a material heating container is installed, and a granular or powdery trapping material is moved between the containers by using a power of a conveyor or a blower to repeat trapping and desorption. In this configuration, it is not necessary to switch the circulating gas, so the configurations of the pipes and valves are simplified. Further, since different porosities can be set at the time of trapping and at the time of desorption, for example, the porosity may be set to be low at the time of desorption and the CO ₂ concentration in the CO ₂ desorbed gas may be increased. On the other hand, since the trapping material itself moves, it is considered that the performance deteriorates due to wear when used for a long period of time. When the flow rate of gas such as boiler exhaust gas is very large, a method of blowing up the trapping material with gas may be used instead of the conveyor. In this case, since the number of mechanical parts is reduced as compared with the conveyor, the structure can be simplified.

Hereinafter, examples of the present invention will be described in detail.

Incidentally, cerium nitrate hexahydrate _{(Ce (NO 3) 3 ·} 6H 2 O), for the 28 wt% aqueous ammonia, either was made of Wako Pure Chemical Industries.
[Example 1]

(CO ₂ capture material using cerium oxide)
26.05 g of cerium nitrate hexahydrate was dissolved in 1080 g of purified water at room temperature with vigorous stirring. While stirring the aqueous solution, a 28% by weight aqueous ammonia solution was added dropwise to adjust the pH to 9.0. After stirring for 8 hours, the mixture was allowed to stand for 1 hour, and the precipitate was collected by washing filtration. Then, the precipitate was dried at 120° C. in a drying furnace and fired at 400° C. for 1 hour in an electric furnace in the air atmosphere, and the obtained cerium oxide was used as a CO ₂ capturing material.
[Example 2]

(CO ₂ capturing material using zirconium oxide)
Zirconium oxide (RSC-100) made by Daiichi Rare Element was used as a CO ₂ trap.

(CO ₂ adsorption test-no H ₂ O flow)
The test conditions when CO ₂ is adsorbed without passing H ₂ O are shown below.

Molding and installation:
The CO ₂ capturing material was pelletized at 200 kgf by a pressing machine using a mold having a diameter of 40 mm, crushed, and then sized into 0.5 to 1.0 mm particles using a sieve. Then, 1.0 ml was measured using a graduated cylinder and fixed in a quartz glass reaction tube.

Heat pretreatment:
While flowing He at 150 ml/min, the temperature of the CO ₂ capturing material was raised to 400° C. using an electric furnace and held for 1 hour to remove impurities and the gas adsorbed by the capturing material.

cooling:
After the heating pretreatment, the temperature was lowered by cooling to lower the CO ₂ capturing material temperature to 50°C.

adsorption:
The amount of CO ₂ trapped was measured by a CO ₂ pulse trap test while maintaining the sample temperature at 50° C. in an electric furnace. As a sample gas, 10 ml of a mixed gas consisting of 12% by volume of CO ₂ and 88% by volume of He was introduced in a pulse form every 4 minutes for 2 minutes, and the CO ₂ concentration at the outlet of the reaction tube was measured by gas chromatography. Pulse introduction was carried out until the CO ₂ measured at the reaction tube outlet was saturated. He was used as the carrier gas.

Thermal desorption:
The sample temperature was heated to 400° C. at a heating rate of 10° C./min in an electric furnace, and the amount of desorbed CO ₂ was measured.

(CO ₂ adsorption test-with H ₂ O distribution)
The test conditions when CO ₂ is adsorbed after H ₂ O is circulated are shown. CO ₂ adsorption test -H 2 _O without circulation, in the measurement method in, after cooling, it was evaluated CO ₂ adsorption amount in the same manner except that went of H _{2 O} distribution processing in the preceding adsorption.

H ₂ O distribution process:
He was passed through the bubbler container containing water at 25° C. at 150 ml/min for 1 hour. The temperature of the CO ₂ capturing material during the treatment was set to 50° C. in the electric furnace.

FIG. 1 is a graph comparing the CO ₂ trapping amounts of the CO ₂ trapping material of Example 1 with and without H ₂ O flowing. Due to the flow of H ₂ O, the amount of captured CO ₂ was reduced by about 10%.

FIG. 2 is a graph comparing the CO ₂ desorption ratio of the CO ₂ capturing material of Example 1 at the time of temperature rise with and without H ₂ O flow. When H ₂ O was distributed, the amount of CO ₂ desorbed at a relatively low temperature from 50° C. to 200° C. was large, and almost all the CO ₂ was desorbed by 200° C. On the other hand, when there was no H ₂ O flow, CO ₂ desorption was not completed even if the temperature was raised to 300°C. From this result, it was found that the flow of H ₂ O has the effect of lowering the CO ₂ desorption temperature.

FIG. 3 shows the amount of heat required to raise the temperature of the cerium oxide, and shows the amount of heat per desorbed CO ₂ amount. The specific heat of the cerium oxide was 382 J/K·kg, and the heat quantity H required for raising the temperature was calculated by the following formula. The bulk density of the cerium oxide in this test was 1.41 (kg/L), the CO ₂ desorption amount was Q _d , and the desorption temperature was T _d , and was calculated by the following formula (2).

H=1000 (g)/44 (g/mol)×1000/Q _d (mmol/L)
X 1.41 (kg/L) x ( _Td- 50) (K) x 382 (J/K*kg)... (2)
From this result, it was found that the energy required for heating can be lowered when H ₂ O is distributed.

FIG. 4 is a graph comparing the CO ₂ desorption ratio of the CO ₂ trapping material of Example 2 at the time of temperature rise with and without H ₂ O flow. When H ₂ O was distributed, the amount of CO ₂ desorption at 50° C. to 200° C. was large, and it was found from this result that H ₂ O distribution has the effect of lowering the CO ₂ desorption temperature.

(Evaluation method of specific surface area)
Using the BET (Brunauer-Emmett-Teller) method in the cerium oxide of Example 1, the adsorption isotherm of nitrogen at -196°C was measured to measure the specific surface area. As a pretreatment, it was heated at 200° C. while vacuuming. The specific surface area of Example 1 was 130 m ² /g.

(Measurement of H ₂ O adsorption isotherm)
The H ₂ O adsorption isotherm of the cerium oxide of Example 1 was measured. As a pretreatment, it was heated at 200° C. while vacuuming. After that, the sample was cooled while being evacuated, and H ₂ O was adsorbed while the sample temperature was kept at 25°C.

(Calculation of H ₂ O monolayer adsorption amount)
The adsorption amount Q _ml for forming the H ₂ O monolayer on the surface of the cerium oxide of Example 1 was calculated. The specific surface area obtained by the BET method is S _A , the Avogadro number is N _A =6.02×10 ²³ , and the adsorption cross-sectional area of H ₂ O is 1.25×10 ⁻¹⁹ m ² , and the following formula (3) is calculated. It was calculated using.

Q _ml =S _A ÷1.25×10 ⁻¹⁹ ÷6.02×10 ²³ ×1000 (3)
As a result of this calculation, the H ₂ O monolayer adsorption amount Q _ml was calculated to be 1.8 mol/kg.

FIG. 5 is a graph showing the H ₂ O adsorption isotherm of the cerium oxide of Example 1. From this result, the H ₂ O adsorption amount of the cerium oxide in Example 1 is equal to or more than the CO ₂ adsorption amount (300 mol/L÷1.41 kg/L=0.22 mol/kg) so that H ₂ O can be absorbed. The partial pressure was 0.002 kPa or less. In order to reach the main H ₂ O partial pressure under atmospheric pressure, the H ₂ O concentration should be about 20 ppm. That is, it is considered that the introduction of the gas having the H ₂ O concentration is a condition for H ₂ O/CO ₂ to react at a molar ratio of 1 or more. In order to form 1 mol of the above-mentioned hydrogen carbonate, it is considered that 1 mol of hydroxyl group (—OH) is required on the surface. Assuming that 1 mol of surface oxygen (O) reacts with 1 mol of H ₂ O to generate 2 mol of hydroxyl group as a mechanism of forming a hydroxyl group, if H ₂ O/CO ₂ is 0.5 or more in molar ratio, It is presumed that the reaction proceeds sufficiently when H ₂ O/CO ₂ is 1.0 or more in terms of mol ratio. If _{H 2} O concentration of the above 20ppm _{H 2} O / CO 2 can exceed 1.0 in mol ratio. Further, it is considered that the formation of hydroxyl groups is further promoted if the surface of the cerium oxide can be covered with the H ₂ O monolayer. The H ₂ O partial pressure required for making the H ₂ O adsorption amount equal to the H ₂ O monomolecular adsorption amount was 0.2 kPa. In order to reach the H ₂ O partial pressure in the atmosphere, the H ₂ O concentration should be about 2000 ppm.

Regarding the above calculation, if the specific surface area of the cerium oxide is increased, the CO ₂ adsorption amount is increased, but the H ₂ O adsorption amount is also considered to be increased in proportion to the specific surface area. It is considered that the correlation of H ₂ O concentration obtained based on 1 can be used.

The correlation between the H ₂ O concentration and the H ₂ O adsorption amount differs depending on the temperature of the trapping material, but in H ₂ O, if the relative pressure P/P ₀ with the saturated vapor pressure at that temperature is equal, H ₂ O It has the property that the adsorption amounts are almost the same. Therefore, when the temperature of the trapping material changes, the H ₂ O concentration may be determined based on the saturated vapor pressure at that temperature.
[Example 3]

FIG. 6 shows an example of introducing the CO ₂ removal gas into the room by using the CO ₂ capturing material of Example 1 in the fixed bed type CO ₂ removal apparatus of the present invention. The CO ₂ removal device according to the third embodiment includes a pipe 301 for circulating the H ₂ O and CO ₂ containing gas 101, a condenser 501, and a pipe 305 for discharging the water 201 condensed by the condenser 501. An H ₂ O densitometer 601, a means 1001 for inputting a signal from the H ₂ O densitometer 601 to the calculator 1002, and a means 1003 for outputting a signal for controlling the condenser 501 from the calculator 1002. , A valve 401 for controlling the flow of the H ₂ O and CO ₂ containing gas 101, a reaction vessel 701, and a CO ₂ scavenger 801 containing the cerium oxide of Example 1 filled in the reaction vessel 701 in a granular form. , A pipe 302 for circulating the gas in the reaction container into the room, a valve 402 for controlling the gas flow in the pipe 302, a heater 901, and the heating gas 103 taken from the atmosphere into the reaction container 701. And a valve 403 for controlling gas flow in the pipe 303, a pipe 304 for discharging gas in the reaction container to the atmosphere, and a valve 404 for controlling gas flow in the pipe 304. To be done.

When capturing CO ₂ , by opening the valves 401 and 402 and closing the valves 403 and 404, the H ₂ O and CO ₂ containing gas 101 is captured by the CO ₂ capturing material 801 by the CO ₂ and H ₂ O. The gas from which H ₂ O and CO ₂ have been removed flows through the room.

When the desorbing the captured CO ₂ in CO ₂ capturing material is a valve 403 and 404 opens, the valve 401 and 402 by a closed, gas 102 taken in from the atmosphere is heated by the heater 901 reaction The CO ₂ capturing material 801 flows into the container 701, the CO ₂ capturing material 801 is heated, and the captured CO ₂ is desorbed. The desorbed gas flows through the pipe 304 and is released to the atmosphere.
[Example 4]

FIG. 7 shows an example in which the CO ₂ capturing material of Example 1 is used in the fixed bed type CO ₂ removal apparatus of the present invention, and the CO ₂ removal gas is continuously circulated in the chamber by using two reaction vessels. In the configuration of Example 3, in order to flow the reaction container 702, the CO ₂ capturing material 802 containing the cerium oxide that is granularly filled in the reaction container 702, and the H ₂ O- and CO ₂ -containing gas 101 into the reaction container 702. Pipe 306, a valve 406 for controlling the gas flow in the pipe 306, a pipe 307 for circulating the gas in the reaction container indoors, a valve 407 for controlling the gas flow in the pipe 307, and the atmosphere. A pipe 308 for letting the taken-in heating gas 102 into the reaction container 702, a valve 408 for controlling gas flow in the pipe 308, a pipe 309 for discharging the gas in the reaction container to the atmosphere, and a pipe. It is composed of a valve 409 for controlling the gas flow of 309.

When CO ₂ is captured by the reaction tube 701 and CO ₂ is desorbed from the reaction tube 702, the valves 401, 402, 408 and 409 may be opened and the valves 403, 404, 406 and 407 may be closed. When CO ₂ is desorbed in the reaction tube 701 and CO ₂ is captured in the reaction tube 701, the valves 403, 404, 406 and 407 may be opened and the valves 401, 402, 408 and 409 may be closed. With this configuration and the operating method, the gas from which CO ₂ has been removed can be continuously circulated in the room.
[Example 5]

FIG. 8 shows an example of introducing the CO ₂ removal gas into the room in the rotor-type CO ₂ removal device of the present invention. A honeycomb rotor 801 carrying a CO ₂ capturing material containing the cerium oxide of Example 1 is installed inside the reaction vessel 701 in the present CO ₂ removal apparatus, and the partition plate 702 in the reaction vessel is used for gas circulation. Routes are becoming restricted. Zones 701A, 701B, and 701C in the reaction vessel 701 are gas distribution ranges defined by the partition plate 702. Even when the honeycomb rotor 801 is rotated, the position of the partition plate 702 does not change, but as the honeycomb rotor 801 rotates, the location where the gas contacts the honeycomb rotor changes. In this configuration, a gas containing H ₂ O and CO ₂ is passed through the zone 701A to trap CO ₂ (trapping zone), and a gas heated in the heater 901 is passed through the zone 701C to desorb CO ₂ ( The gas 103 taken from the atmosphere is circulated in the desorption zone) and the zone 701B to be cooled (cooling zone).

This CO ₂ removal device includes a pipe 301 for circulating the H ₂ O- and CO ₂ -containing gas 101 to the zone 701A in the reaction vessel 701, a condenser 501, and a pipe 305 for discharging the condensed water 201 from the condenser. An H ₂ O densitometer 601, a means 1001 for inputting a signal from the H ₂ O densitometer to the calculator 1002, a means 1002 for outputting a signal from the calculator 1002 to control the condenser 501, A reaction container 701, a rotatable honeycomb rotor 801 that carries a CO ₂ capturing material installed in the reaction container 701, a partition plate 702 installed in the reaction container for partitioning gas flow, and a gas discharged from the zone 701A A pipe 302 for circulating indoors, a pipe 303 for circulating the gas 103 taken in from the atmosphere to the zone 702B, a heater 901, and a pipe for circulating gas discharged from the zone 701B to the heater 901. 304, a pipe 306 for allowing the gas discharged from the heater 901 to flow to the zone 701C, and a pipe 307 for discharging the gas discharged from the zone 701C to the atmosphere.

In the present apparatus, the H ₂ O and CO ₂ containing gas flows through the zone 701A to be captured by the CO ₂ capturing material in the honeycomb rotor, and the gas from which the H ₂ O and CO ₂ have been removed flows inside the chamber. Due to the rotation of the honeycomb rotor, the portion that has captured CO ₂ moves to the zone 701C, and the heated gas is circulated to desorb CO ₂ . The portion that has been heated and desorbed CO ₂ moves to the zone 701B and is cooled using the gas taken in from the atmosphere. The cooled portion moves to the zone 701A to capture CO ₂ again.

In this configuration, the gas 103 taken in from the atmosphere is used to cool the honeycomb rotor, so that this gas is heated. Since the gas is further heated by the heater 901, the load on the heater 901 can be reduced.
[Example 6]

FIG. 9 shows a configuration for removing H ₂ O and CO ₂ by using a plurality of CO ₂ capturing materials and a plurality of reaction vessels in the present invention. In this embodiment, cerium oxide and zeolite are used as the CO ₂ capturing material. This apparatus comprises a pipe 301 for circulating the H ₂ O and CO ₂ containing gas 101 into the reaction tube 701, a CO ₂ trap material 801 containing the cerium oxide of Example 1 filled in the reaction tube 701, and a condenser. 501, a pipe 305 for discharging condensed water from the condenser, an H ₂ O concentration meter 601, a means 1001 for inputting a signal from the H ₂ O concentration meter to the calculator 1002, and the condenser 501. Means 1002 for outputting a signal from the computer 1002, a pipe 302 for circulating the heating gas, a pipe 303 for circulating the gas discharged from the reaction pipe 701 indoors, and a gas for the pipe 303 A valve 403 for controlling the flow, a pipe 304 for releasing the gas from the reaction tube 701 to the atmosphere, a valve 404 for controlling the gas flow through the pipe 304, and a gas discharged from the reaction tube 701. and _{H 2} O concentration meter 602 for measuring the _{H 2} O concentration, and CO ₂ concentration meter 603, and the reaction tube 702, and the capture member 802 that includes a zeolite charged to the reaction tube, the reaction tube from the reaction tube 701 A pipe 306 for circulating gas to 702, a valve 406 for controlling the gas circulation of the pipe 306, a pipe 307 for circulating the gas discharged from the reaction pipe 702 into the room, and a gas circulation of the pipe 307. 407 for controlling the gas, a pipe 309 for releasing gas from the reaction tube 702 to the atmosphere, a valve 409 for controlling gas flow in the pipe 309, and a heating gas for flowing to the reaction tube 701. The pipe 308 and a valve 408 for controlling the gas flow in the pipe 308.

For example, when only H ₂ O is likely to be trapped and saturated in the CO ₂ trapping material 801, the trapping material 802 in the subsequent reaction tube 702 may be filled with a trapping material that selectively traps H ₂ O. If only CO ₂ in CO ₂ capturing material 801 tends to be complementary saturation Conversely, by filling the capturing material to selectively complement the CO ₂ to the capturing material 802 in the latter stage of the reaction tube 702, _{H 2} O and The gas from which CO ₂ has been removed can be stably distributed in the room.
[Example 7]

FIG. 10 shows a configuration for removing H ₂ O and CO ₂ by using a plurality of CO ₂ capturing materials and a plurality of reaction vessels in the present invention. In this configuration, cerium oxide and zeolite are used as the CO ₂ capturing material. The CO ₂ capturing material 801 containing cerium oxide in the reaction vessel 701 in this configuration, the reaction vessel 702 is used CO ₂ capturing material containing zeolite. From H ₂ O and CO ₂ containing gas is in removing _{H 2} O and CO ₂ is the flow direction of the gas flow has a reaction vessel 702 from the reaction vessel 701, the heated gas of _{H 2} O and CO ₂ The opening and closing of each valve is adjusted so that the flow of the heating gas flow from the reaction vessel 702 to the reaction vessel 701 when removing it by circulation. This is to prevent H ₂ O desorbed from the CO ₂ capturing material 801 containing cerium oxide from coming into contact with the zeolite in the reaction vessel 702, so that H ₂ O is strongly captured in the zeolite. ..

101... H ₂ O and CO ₂ containing gas 103... Heating gas 301, 302, 303, 304... Piping 401, 402, 403, 404... Valve 501... Condenser 601... H ₂ O concentration meter 701... Reaction vessel 801, 802... CO ₂ capturing material 901... Heater

Claims (7)

A CO ₂ trapping material that traps H ₂ O and CO ₂ in the target gas;
A reaction vessel having the CO ₂ trap material installed therein;
And H _{2 O} concentration adjusting device for adjusting of H _{2 O} concentration of the object gas,
A gas introduction path for introducing the target gas into the reaction vessel from the H ₂ O concentration adjusting device to bring it into contact with the CO ₂ capturing material;
A first gas discharge path for discharging the target gas from the reaction vessel after contacting the target gas with the CO ₂ capturing material;
A second gas discharge path for discharging the desorbed gas desorbed from the CO ₂ capturing material from the reaction container,
The gas introduction path and the second gas discharge path are arranged on the upstream side of the reaction container in the flow direction of the target gas,
The first gas discharge path is disposed on the downstream side of the reaction container in the flow direction of the target gas,
The CO ₂ capturing material is
A capturing material A containing an oxide or a composite oxide containing at least one metal selected from cerium, rare earth metals other than cerium, and zirconium;
A capturing material B containing at least one metal oxide selected from silica, alumina and zeolite;
The CO 2 from the target _{gas, H} 2 _O, or in the case of removing both of these, the flow direction of the target gas is up direction der of capturing material B from the capture material A,
A heating fluid is configured to contact the CO2 trap,
The heating fluid is a fluid containing at least one gas selected from CO ₂ , steam, N ₂ , combustion exhaust gas, and a gas obtained by heating after taking in from the atmosphere,
The circulation direction of the heating fluid is opposite to the circulation direction of the target gas,
The target gas is introduced into the reaction container from the upstream side, and is discharged to the outside of the reaction container from the first gas discharge path on the downstream side,
The CO ₂ removal device , wherein the heating fluid is introduced into the reaction container from the downstream side and is discharged to the outside of the reaction container as the desorbed gas from the second gas discharge passage on the upstream side . Further comprising an H ₂ O measuring device for measuring the H ₂ O concentration in the target gas,
The H _{2 O} concentration adjusting device, the H _{2 O} instrument with the information obtained CO ₂ removing device according to claim 1, wherein adjusting of H _{2 O} concentration before Symbol object gas based on. The CO ₂ removal device according to claim 1 or 2, wherein the H ₂ O concentration adjusting device is a condenser that cools the target gas. The reaction container has a first reaction container in which the trapping material A is arranged, and a second reaction container in which the trapping material B is arranged,
The target gas is circulated from the first reaction container to the second reaction container and discharged from the second reaction container to the outside,
The heating fluid, CO ₂ removal of any one of claims 1 to 3 in circulation from the second reaction vessel to the first reaction vessel is discharged to the outside from the first reaction vessel apparatus. CO ₂ removal device of any one of claims 1-4, further comprising a decompression device for decompressing said reaction vessel. CO ₂ removal device of any one of claims 1-5, further comprising a pressurized pressure device for pressurizing the reaction vessel. CO ₂ removal device of any one of claims 1-6 wherein the target gas is at a higher pressure than the atmospheric pressure around.