JPH10272336A - Carbon dioxide-absorbing material, and method for separating and recovering carbon dioxide in exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove CO2 generated from an equipment of such as a thermal power station, by preparing a CO2 absorption material from elements selected from the group of Ba, Sr, Ca, elements from the group of La, Pr, Ce, and elements from Ti, Mn, Fe. SOLUTION: As a material to absorb and remove CO2 selectively and directly from a high temperature exhaust gas, the CO2 absorbing material is prepared by using at least one kind of element selected from the group of Ba, Sr, Ca, Cs, K, one element selected from the group of La, Pr, Ce, Nd, Gd, Y, Pb, Bi, and at least one kind of element selected from the group of Ti, Mn, Fe, Co, Ni, Cu, Al, Sn, Zr. The CO2 absorbing material is prepared so as to have a perovskite complex oxide structure represented by a formula ABO3 (where A is a kind of element selected from Ba, Sr, Ca; B is a kind of element selected from Ti, Mn, Fe).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a material for absorbing and removing carbon dioxide (CO ₂ ) contained in flue gas at a high temperature, and to use the CO ₂ absorbing material to efficiently remove CO ₂ from exhaust gas. The present invention relates to a method for removing CO ₂ from CO ₂ and is particularly useful for removing CO ₂ generated from equipment such as a thermal power plant.

[0002]

_2. Description of the Related Art In recent years, a global warming phenomenon due to a greenhouse effect of CO ₂ has become a major problem, and there is an urgent need to establish a method for removing CO ₂ contained in exhaust gas from a combustion engine. Various methods for removing CO ₂ from exhaust gas have been proposed. Typical methods include contact removal with an aqueous solution of an amine compound, pressure swing adsorption, alkali,
Immobilization removal method with alkaline earth metal hydroxide, adsorption
There is a high-temperature carbon dioxide gas separation method using a desorption time difference.
As a contact removal method using an amine compound aqueous solution, for example, JP-A-8-257353 discloses a method in which an aqueous solution containing a diamine compound is brought into contact with combustion exhaust gas to remove CO _{2 in} exhaust gas. . The pressure swing adsorption, for example, in JP-A-1-180218, that the partial pressure is increased gas CO ₂ was supplied at a low temperature under normal pressure, allowed to adsorb CO ₂ in chestnut knob tyrosine-write adsorbent Is removed under reduced pressure and recovered, and a method of performing each step cyclically is disclosed. As an immobilization removal method using an alkali or alkaline earth metal hydroxide,
For example, Japanese Unexamined Patent Publication (Kokai) No. 3-245811 discloses that an alkali metal hydroxide and / or an alkaline earth metal hydroxide is brought into contact with a combustion exhaust gas to cause carbonation thereof, thereby reducing CO 2 in the exhaust gas.
₂ and the carbonate is transferred to an electrodialysis machine to remove CO ₂
A method for separating gas and alkali and reusing the separated alkali is disclosed. As a high-temperature carbon dioxide separation method utilizing the time difference between adsorption and desorption, for example, Japanese Patent Application Laid-Open No. 7-27
No. 7718 discloses a method of separating and recovering CO _{2 in} exhaust gas at a high temperature using a ceramics separation material.

[0003]

However, the methods disclosed in JP-A-1-180218 and JP-A-8-257353 both perform a separation operation after once cooling a high-temperature exhaust gas. Method, the cost of the cooling step is large, and the separated CO
_When converting ₂ to methanol or acetic acid for reuse,
The inefficiency in the process of heating and transferring to the catalytic reaction process again becomes a problem. As a method for solving such a problem, for example, Japanese Unexamined Patent Publication (Kokai) No. 3-245811 discloses a method in which a high-temperature exhaust gas is brought into direct contact with an alkali or alkaline earth metal hydroxide to reduce CO _2.
A method for immobilizing a gas is disclosed. However, this method requires electrodialysis in a solution in order to recover the immobilized CO ₂ and regenerate the absorbent.
There is a problem that the process cost becomes large. Japanese Patent Application Laid-Open No. Hei 7-277718 discloses a method of directly separating CO ₂ from high-temperature exhaust gas and eliminating the need for regeneration of a processing medium. However, this method has a problem that it is difficult to select a material having a significantly different CO ₂ emission retention time from other exhaust gas components such as NOx, and it is difficult to recover only CO ₂ .

[0004]

Means for Solving the Problems The present inventors have studied to solve the above problems, and as a result, as a material for directly and selectively absorbing and removing CO ₂ from high-temperature exhaust gas, alkali metals, It has been found that an oxide in which an alkaline earth metal and a transition metal are in a composite state is effective. Furthermore, the CO ₂ absorbing material, the boundary of 600 ° C. to 800 ° C., the absorption from the CO ₂ in the low temperature side which, CO ₂ at a high temperature side
Has the property of releasing, moreover, CO ₂ emission, newly found that absorption process has a property of proceeds reversibly, by utilizing this property, from the exhaust gas at a low temperature side than the temperature range CO ₂ was separated, consisting of the process to release CO ₂ into a collection stream at the high temperature side, which resulted in the invention a method of separating and recovering CO ₂ from exhaust gas. That is,
The CO ₂ absorbent according to claim 1 is Ba, Sr, Ca, C
at least one element selected from s and K;
a, Pr, Ce, Nd, Gd, Y, Pb, and one element selected from Bi, Ti, Mn, Fe, Co, N
and at least one element selected from the group consisting of i, Cu, Al, Sn, and Zr. The CO ₂ absorbent according to claim 2 has a general formula AB
O ₃ (A in the formula is Ba, Sr, Ca, Cs, K, L
a, Pr, Ce, Nd, Gd, Er, Y, Pb and B
B is composed of at least one element selected from i.
Represents Ti, Mn, Fe, Co, Ni, Cu, Al, S
a perovskite composite oxide structure represented by at least one selected from the group consisting of n and Zr). Further, C according to claim 3
The method of separating and recovering O ₂ is, when separating and recovering CO ₂ from the high-temperature combustion exhaust gas discharged as a combustion gas, after setting the hot gas as it is or a predetermined temperature, the CO ₂ absorbent material according to claim 1 or 2, wherein It is characterized by contacting and absorbing and removing CO ₂ , and then releasing and absorbing the absorbed CO ₂ by heating the CO ₂ absorbent in a recovery gas stream.

[0005]

The CO ₂ absorbent according to claim 1 is excellent in C.
The mechanism of exhibiting the O ₂ absorption effect is not necessarily clear yet, but is considered as follows. Action of the composite oxide according to claim 1 Ba, Sr, Ca, contained in the composite oxide of the present invention.
At least one element selected from the group consisting of La, Cs and K is, in the presence of CO ₂ gas at 600 ° C. or lower,
Although present as a carbonate in the composite oxide, it has a characteristic of releasing CO ₂ even in the presence of CO ₂ at 800 ° C. or higher.
This phenomenon is that the alkali, alkaline earth metal carbonate reacts at 800 ° C. or higher with a partially adjacent transition metal and releases CO ₂ because it becomes a perovskite precursor,
It is considered that this perovskite precursor is unstable at a temperature of 600 ° C. or lower in a CO ₂ atmosphere as compared with a carbonate structure, and is generated by absorbing CO ₂ because the above-mentioned element is carbonated. As described above, the absorption and release of CO ₂ accompanied by a crystal phase change occur at a temperature difference of about 100 ° C., but the absolute temperature depends on the crystal formation energy of the alkali, alkaline earth metal carbonate and perovskite precursor. , Depending on the composite composition. However, all composite oxides of claims 1 to 3, wherein, in order to perform the CO ₂ absorption release the boundary of the temperature range of 600 ° C. to 800 ° C., the practice of claim 1, the absorption control temperature 600 ° C. or less, Release control temperature 80
The purpose can be achieved by setting the temperature to 0 ° C. or higher. By performing the exhaust gas treatment by the method described in claim 3 utilizing the above characteristics, it is possible to efficiently absorb and remove only CO ₂ related to the change in the material structure in the high-temperature region from the exhaust gas. Action of the composite oxide according to claim 2 B contained in the perovskite composite oxide of the present invention
a, Sr, Ca, La, at least one element selected from the group consisting of Cs and K, of 600 ° C. or less CO ₂
The presence gases is present as carbonate in the composite oxide, having the property of releasing CO ₂ in the presence of CO ₂ at 800 ° C. or higher. The phenomenon is that the alkali and alkaline earth metals in the perovskite partially form a carbonate in the presence of CO _{2 at} 600 ° C. or lower, and the CO ₂ at 800 ° C. or higher.
It is considered that CO ₂ is released even in the presence, and a perovskite structure is formed. Therefore, by utilizing this characteristic and performing the exhaust gas treatment by the method of claim 3, it is possible to more efficiently absorb and remove only CO ₂ related to the change in the material structure in the high-temperature region than in the exhaust gas. The CO ₂ absorption and release processes according to claim 3 are performed at 600 ° C. or less, respectively.
Although it is completely carried out at 800 ° C. or higher, the temperature range in which the phase change occurs varies depending on the composition. Therefore, individual compositions can absorb and release CO ₂ even within this temperature range. is there. In claim 3, when the temperature in the CO ₂ absorption process is 450 ° C. or less, the coexisting NOx
In order to absorb gas, it is desirable to perform the treatment at 450 ° C. or higher for the purpose of removing only CO ₂ . In the case where the temperature of the CO ₂ releasing step is 1000 ° C. or less, the structure of the perovskite precursor is destroyed, and CO _{2 is} released again.
_Since the function of absorbing ₂ is lost, it is desirable to carry out at 1000 ° C. or lower.

[0006]

EXAMPLES Hereinafter, specific examples will be described with reference to examples and comparative examples. Composite oxide powder represented by (Example _{1) Ba 0.5 La 0.5 Co 0.5} Fe 0.5 O 3 was prepared by the following methods. Starting from barium, lanthanum, cobalt and iron carbonates or hydroxides, the respective molar ratios are 5:
The mixture was added in a ratio of 5: 5: 5, pulverized with a ball mill, and 500 g of an aqueous nitric acid solution was added to 100 g of the obtained mixture to cause a reaction. Then, the obtained slurry is heated to 120 ° C.
And calcined at 700 ° C. for 1 hour in the air.
_{A 0.5} La _0.5 Co _0.5 Fe _0.5 O ₃ composite oxide powder was obtained. 500 g of the obtained powder and 900 g of water were put into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry liquid was added to a cordierite monolithic carrier (1.0 L,
(400 cells), and the excess slurry in the cells was removed by an air flow, dried at 130 ° C., and fired at 400 ° C. for 1 hour. This operation was performed twice to obtain a CO ₂ absorbent having a coat layer weight of 200 g / L. The obtained CO ₂ absorbent is cut into a cylindrical shape of φ25 mm × L50 mm,
The simulated exhaust gas was attached to the catalytic reactor and the inlet temperature was 55
After flowing at 0 ° C. and a flow rate of 20 L / min for 3 minutes, a process of flowing the recovered gas at an inlet temperature of 850 ° C. and a flow rate of 20 L / min for 3 minutes was performed for two cycles to separate and recover CO ₂ from the simulated exhaust gas. . The component of the simulated exhaust gas is CO ₂ : 10
%, NO: 2000 ppm, O ₂ : 10%, N ₂ balance, and Air was used as the recovered gas. FIG. 1 shows the recovery rate of CO _{2 in} the exhaust gas into the recovered gas, as shown in the following equation.

[0007]

[Formula 1]

In the following Examples and Comparative Examples, composites were prepared in the same manner as in Example 1 except that the types and mixing ratios of carbonates and hydroxides as starting salts were changed unless otherwise specified. An oxide powder or a perovskite powder was produced. (Example _{2) Ba 0.18 La 0.7 2 Co} 0.5 Fe 0.5 O 3
The procedure was performed in the same manner as in Example 1 except for using the composite oxide powder represented by. But using composite oxide powder represented by (Example _{3) Y 0.47 Ca 0.47 Mn 0.9} Ti 0.1 O 3, was prepared as in Example 1. But using composite oxide powder represented by (Example _{4) Y 0.3 Ca 0.7 Mn 0.6} Ti 0.4 O 3, was prepared as in Example 1. (Example 5) Nd _0.31 La _0.09 Sr _0.5 Cu _0.2 Mn
_{The same} operation as in Example 1 was carried out except that a composite oxide powder represented by _0.8 O ₃ was used. (Example 6) Gd _0.31 La _0.09 Sr _0.5 Co _0.5 Mn
But using composite oxide powder represented by _0.5 O _3, was prepared as in Example 1. But using composite oxide powder represented by (Example _{7) La 0.5 K 0.5 Co 0.9} Al 0.1 O 3, was prepared as in Example 1. (Example 8) Example 1 was repeated except that a composite oxide powder represented by Ba _0.81 Pr _0.09 Co _0.5 Fe _0.5 O ₃ was used.
Was performed in the same manner as described above. Example 9 Example 1 was repeated except that a composite oxide powder represented by Ba _0.81 Pb _0.09 Co _0.5 Fe _0.5 O ₃ was used.
Was performed in the same manner as described above. But using composite oxide powder represented by (Example 10) Ba _1.0 CoO _3, was prepared as in Example 1. (Example 11) The same operation as in Example 1 was carried out except that a composite oxide powder represented by K _0.8 MnO ₃ was used. (Example _{12) Ba 0.6 La 0.2 Mn 0.5} Co 0.5 O 3
The procedure was performed in the same manner as in Example 1 except for using the composite oxide powder represented by. (Example 13) The same operation as in Example 1 was carried out except that a composite oxide powder represented by Ca _0.5 La _0.5 MnO ₃ was used. (Example 14) Sr _0.81 Bi _0.09 Ni _0.9 Mn _0.1 O ₃
The procedure was performed in the same manner as in Example 1 except for using the composite oxide powder represented by. (Example _{15) Ce 0.47 Ba 0.47 Zr 0.3} Cu 0.7 O 3
The procedure was performed in the same manner as in Example 1 except for using the composite oxide powder represented by. (Example _{16) Ce 0.47 Ba 0.47 Sn 0.3} Cu 0.7 O 3
The procedure was performed in the same manner as in Example 1 except for using the composite oxide powder represented by.

Comparative Example 1 The same operation as in Example 1 was performed except that calcium carbonate powder was used instead of the composite oxide powder. (Comparative Example 2) The same operation as in Example 1 was performed except that barium carbonate powder was used instead of the composite oxide powder. (Comparative Example 3) The same operation as in Example 1 was performed except that NiO powder was used instead of the composite oxide powder. (Comparative Example 4) The same operation as in Example 1 was performed except that Al ₂ O ₃ powder was used instead of the composite oxide powder. (Comparative Example 5) The same operation as in Example 1 was performed except that Mn ₂ O ₃ powder was used instead of the composite oxide powder. (Comparative Example 6) The same operation as in Example 1 was performed except that CeO ₂ was used instead of the composite oxide powder. But using a composite oxide powder represented by (Comparative Example _{7) La 1.0 Co 0.5 Fe 0.5} O 3 was prepared in the same manner as in Example 1. (Comparative Example 8) The same operation as in Example 1 was performed, except that a composite oxide powder represented by Ce _0.7 Zr _0.3 O ₃ was used. But using a composite oxide powder represented by (Comparative Example _{9) Nd 0.47 Y 0.47 Zr 0.3} Cu 0.7 O 3 was prepared in the same manner as in Example 1.

[0010]

As described above, according to the present invention,
In the method of separating and recovering CO _{2 in} the O ₂ absorber and the exhaust gas, only the CO ₂ relating to the change in the material structure in the high-temperature region can be absorbed and removed more efficiently than in the exhaust gas.

[Brief description of the drawings]

FIG. 1 is a view showing a recovery rate of CO _{2 in} an exhaust gas into a recovery gas according to an example of the present invention and a comparative example.

Claims (3)

[Claims] 1. At least one element selected from Ba, Sr, Ca, Cs, and K, and La, Pr, Ce,
One element selected from Nd, Gd, Y, Pb and Bi, and Ti, Mn, Fe, Co, Ni, Cu, Al, S
A carbon dioxide absorbent comprising: at least one element selected from the group consisting of n and Zr. 2. The general formula ABO ₃ (where A is Ba, S
r, Ca, Cs, K, La, Pr, Ce, Nd, Gd,
It is composed of at least one element selected from Er, Y, Pb and Bi, and B is Ti, Mn, Fe, Co,
A carbon dioxide absorbent having a perovskite composite oxide structure represented by at least one selected from the group consisting of Ni, Cu, Al, Sn, and Zr). 3. A method for separating and recovering carbon dioxide from a high-temperature combustion exhaust gas discharged as a combustion gas, wherein the high-temperature gas is brought into contact with the carbon dioxide absorbent according to claim 1 or after being set at a predetermined temperature, A method for separating and recovering carbon dioxide, wherein carbon dioxide is absorbed and removed, and then the carbon dioxide absorbent is heated in a recovery airflow to release and recover the absorbed carbon dioxide.