JPWO2008038484A1 - Carbon dioxide separation and recovery method - Google Patents

Abstract

The absorbed carbon dioxide can be efficiently released in a shorter time, and the carbon dioxide can be recovered by being converted to carbon monoxide, which is more versatile. After carbon dioxide is absorbed by the carbon dioxide absorbent, the carbon dioxide absorbent that has absorbed carbon dioxide is heated while supplying hydrogen gas or hydrocarbon gas to release carbon dioxide. Moreover, the heating temperature in a discharge | emission process shall be 800-1000 degreeC. Further, as the carbon dioxide absorbent, a material mainly composed of an alkaline earth metal oxide or a material mainly composed of a composite oxide containing an alkaline earth metal oxide is used. Further, as the carbon dioxide absorbing material, a material mainly composed of a composite oxide of Ba2TiO4, Sr2TiO4, and Ba3Ca2Ti2O9 is used.

Description

  The present invention relates to a method for separating and recovering carbon dioxide. Specifically, the present invention separates and recovers carbon dioxide using a carbon dioxide absorbent capable of absorbing carbon dioxide and releasing the carbon dioxide absorbed under predetermined conditions. Regarding the method.

As a method for separating carbon dioxide from high-temperature exhaust gas, for example, a method of separating carbon dioxide from exhaust gas at a temperature of 500 ° C. or higher using lithium silicate as a carbon dioxide absorbent has been proposed (Patent Literature). 1).

  Besides, lithium silicate is used as an absorbent for carbon dioxide, and a gas containing carbon dioxide after steam reforming of carbon-containing fuel is brought into contact with the absorbent at a temperature of 400 ° C. to 700 ° C. to absorb carbon dioxide and A method has been proposed in which carbon dioxide is absorbed by reacting the material, and then the absorbent that has absorbed carbon dioxide is regenerated at a temperature of 700 to 900 ° C. (see Patent Document 2).

  However, in the case of the methods described in Patent Documents 1 and 2, in order to recover carbon dioxide at a high concentration, it is necessary to perform treatment at a temperature higher than the absorption temperature, which consumes a great amount of energy. is there.

Even if it is possible to recover carbon dioxide at a high concentration, there is no clear policy for effective use of the recovered carbon dioxide, so technologies such as storage underground or in the sea are necessary. Therefore, there is a problem that the technical and economic burden is large.
JP 2000-262890 A JP 2003-054927 A

  The present invention solves the above-mentioned problems of the conventional technology, and can absorb the absorbed carbon dioxide more efficiently in a shorter time, and can further reduce carbon dioxide to a versatile monoxide. An object of the present invention is to provide a method for separating and recovering carbon dioxide that can be recovered by conversion to carbon.

In order to solve the above problems, the carbon dioxide separation and recovery method of the present invention (Claim 1) includes:
(a) an absorption step of causing the carbon dioxide absorbent to absorb carbon dioxide;
(b) a method for separating and recovering carbon dioxide, comprising the step of releasing carbon dioxide from a carbon dioxide absorbent that has absorbed carbon dioxide,
In the releasing step (b), the carbon dioxide absorbing material that has absorbed carbon dioxide is heated while supplying hydrogen gas or hydrocarbon gas to release carbon dioxide.

  The method for separating and recovering carbon dioxide according to claim 2 is characterized in that, in the configuration of the invention according to claim 1, the heating temperature in the releasing step (b) is 800 to 1000 ° C.

  According to a third aspect of the present invention, there is provided a method for separating and recovering carbon dioxide, wherein the carbon dioxide absorbent is mainly composed of an alkaline earth metal oxide, or an alkaline earth material. It is characterized in that the main component is a composite oxide containing a metal oxide.

According to a fourth aspect of the present invention, there is provided a method for separating and recovering carbon dioxide, wherein the carbon dioxide absorbent is composed of Ba ₂ TiO ₄ , Sr ₂ TiO ₄ , and Ba ₃ Ca ₂ Ti ₂ O ₉ . It is characterized in that any composite oxide is the main component.

  In the carbon dioxide separation and recovery method of the present invention (Claim 1), when carbon dioxide is released from the carbon dioxide absorbent that has absorbed carbon dioxide, the carbon dioxide absorbent that has absorbed carbon dioxide is treated with hydrogen gas or carbonization. Since carbon dioxide is released by heating while supplying the hydrogen-based gas, the carbon dioxide can be converted into carbon monoxide and recovered.

For example, methane, which is a hydrocarbon-based gas, is used as a sweep gas, and carbon dioxide is released by heating while supplying methane and releasing carbon dioxide in the carbon dioxide releasing step. ) Reacts with methane to produce carbon monoxide and hydrogen.
CO ₂ + CH ₄ → 2CO + 2H ₂ (1)

Further, when hydrogen gas is used as the sweep gas and carbon dioxide is released by heating while supplying hydrogen gas in the carbon dioxide releasing step, the carbon dioxide released is expressed by the following equation (2). It reacts with hydrogen to produce carbon monoxide and water.
CO ₂ + H ₂ → CO + H ₂ 0 (2)

In particular, when reacted with methane (see the above reaction formula (1)), the mixed gas of carbon monoxide and hydrogen is called synthesis gas, and the C number of methanol (CH ₃ OH), formaldehyde (HCHO), etc. Is useful as a basic material of so-called C1 chemistry for synthesizing a substance of 1. From this mixed gas of carbon monoxide and hydrogen, methanol is reacted by the reactions shown in the following formulas (3) and (4). And various hydrocarbons can be synthesized.
CO + 2H ₂ → CH ₃ OH (3)
CO + 2H ₂ → 1 / n-(-CH2-)- _n + H ₂ O (4)

  In addition, since the carbon dioxide released by the carbon dioxide absorbent reacts with methane, the increase in the partial pressure of carbon dioxide in the gas phase is suppressed. The carbon dioxide absorbent can be regenerated in a short time.

  Thus, according to the present invention, carbon dioxide can be recovered by converting it to carbon monoxide, which is more versatile than carbon dioxide, and the carbon dioxide absorbent is efficiently regenerated (carbon dioxide release). The carbon dioxide separation and recovery method of the present invention is extremely meaningful because the energy required for carbon dioxide emission and carbon dioxide absorbent regeneration can be suppressed as compared with conventional methods. It is.

  Further, as in the carbon dioxide separation and recovery method of claim 2, by setting the heating temperature in the carbon dioxide releasing step to 800 to 1000 ° C., the carbon dioxide is more efficiently converted into carbon monoxide in the carbon dioxide releasing step. Can be converted to hydrogen, and the present invention can be made more effective.

  In the carbon dioxide separation and recovery method of the present invention, it is preferable that the temperature condition of the releasing step is in the range of 800 to 1000 ° C. The carbon monoxide production ratio is when the temperature condition of the releasing step is less than 800 ° C. Further, when the temperature condition of the release process exceeds 1000 ° C., coking due to thermal decomposition of methane becomes intense and deterioration due to sintering of the carbon dioxide absorbent is likely to occur.

  In the method for separating and recovering carbon dioxide according to claim 3, the carbon dioxide absorbent is mainly composed of an alkaline earth metal oxide or a complex oxide containing an alkaline earth metal oxide. Since what is used as a component is used, the efficiency of conversion of carbon dioxide into carbon monoxide and hydrogen can be improved, and the present invention can be made more effective.

Examples of the alkaline earth metal oxide include CaO and SrO.
Examples of the main component of the composite oxide containing an alkaline earth metal oxide include Ba ₂ TiO ₄ , Sr ₂ TiO ₄ , Ba ₃ Ca ₂ Ti ₂ O _{9 and the} like.

Further, as in the carbon dioxide separation and recovery method of claim ₄ , the composite oxide of Ba ₂ TiO ₄ , Sr ₂ TiO ₄ , and Ba ₃ Ca ₂ Ti ₂ O ₉ is mainly used as the carbon dioxide absorbent. When the component is used, carbon dioxide can be absorbed at a high temperature, and the efficiency of conversion of carbon dioxide into carbon monoxide and hydrogen can be improved. It can be tightened.

As a carbon dioxide absorbing material, Ba ₂ TiO ₄ is one of the most effective materials from the viewpoint of the regeneration temperature and the reaction rate during regeneration, but other than that, Sr ₂ TiO ₄ and Ba ₃ Ca are used. ₂ Ti ₂ O ₉ or the like can also be used, and CaO having a normal regeneration temperature of 800 ° C. or lower can be regenerated under pressure to obtain the same effect.

  The features of the present invention will be described in more detail below with reference to examples of the present invention.

A cylindrical stainless steel container having an inner diameter of 22 mm and a length of 300 mm equipped with an external electric heater was filled with 22 g (about 10 mL) of Ba ₂ Ti0 ₄ (carbon dioxide absorbent) having an average particle diameter of 2 mm.
Then, nitrogen gas was circulated through this stainless steel container at a rate of 18 NL / h, and the nitrogen gas inlet temperature was controlled at 700 ° C. by a heat transfer heater.
After the circulated nitrogen gas temperature was stabilized, carbon dioxide was circulated at a rate of 2 NL / h (carbon dioxide concentration was 10 mol%), and carbon dioxide absorption was started.
Incidentally, the reaction of carbon dioxide absorption by Ba ₂ Ti0 ₄ (carbon dioxide absorbent) is defined in Equation (5) below.
Ba ₂ TiO ₄ + CO ₂ → BaTiO ₃ + BaCO ₃ (5)

  The change in carbon dioxide concentration in the gas that has passed through the carbon dioxide absorbent is measured with a gas analyzer (Gas Chromatograph manufactured by Shimadzu Corporation). Ended.

The carbon dioxide absorbing material that has absorbed carbon dioxide in this way is heated using an electric heater equipped in the container, and the temperature of the carbon dioxide absorbing material is controlled at 900 ° C., while methane is at a rate of 10 NL / h. The carbon dioxide absorbed in the carbon dioxide absorbent was released.
The release reaction of carbon dioxide from the carbon dioxide absorbing material that has absorbed carbon dioxide is represented by the following formula (6).
BaTiO ₃ + BaCO ₃ → Ba ₂ TiO ₄ + CO ₂ ↑ (6)

Then, the time-dependent change of the exhaust gas composition in the release process is measured by the gas analyzer, and the time until the release of carbon dioxide is completed and the ratio of carbon dioxide and carbon monoxide in the release process (CO / (CO ₂ + CO ): Volume ratio). The results are shown in Table 1.

  The ratio of carbon dioxide and carbon monoxide in the carbon dioxide releasing step was measured by the same method as in Example 1 except that the absorbent material temperature during carbon dioxide release was controlled to 800 ° C. The results are shown in Table 1.

The ratio of carbon dioxide and carbon monoxide in the carbon dioxide releasing step was measured by the same method as in Example 1 except that the absorbent material temperature during carbon dioxide release was controlled to 1000 ° C. The results are shown in Table 1.

  The ratio of carbon dioxide and carbon monoxide in the carbon dioxide releasing step was measured by the same method as in Example 1 except that hydrogen gas was used as the gas (sweep gas) to be circulated at the time of carbon dioxide release. The results are shown in Table 1.

A cylindrical stainless steel container having an inner diameter of 22 mm and a length of 300 mm equipped with an external electric heater was filled with 18 g (about 10 mL) of Sr ₂ Ti0 ₄ (carbon dioxide absorbent) having an average particle diameter of 2 mm.
Then, nitrogen gas was passed through the stainless steel container at 18 NL / h, and the nitrogen gas inlet temperature was controlled at 700 ° C. by a heat transfer heater.
After the circulated nitrogen gas temperature was stabilized, carbon dioxide was circulated at a rate of 2 NL / h (carbon dioxide concentration was 10 mol%), and carbon dioxide absorption was started.
The reaction of carbon dioxide absorption by Sr ₂ Ti0 ₄ (carbon dioxide absorbent) is as shown in the following formula (7).
Sr ₂ TiO ₄ + CO ₂ → SrTiO ₃ + SrCO ₃ (7)

  The change in carbon dioxide concentration in the gas that has passed through the carbon dioxide absorbent is measured with a gas analyzer (Gas Chromatograph manufactured by Shimadzu Corporation). Ended.

Then, the carbon dioxide absorbent that has absorbed carbon dioxide is heated using an electric heater equipped in the container, and the temperature of the carbon dioxide absorbent is controlled at 900 ° C., and methane is circulated at a rate of 10 NL / h. The carbon dioxide absorbed by the carbon dioxide absorbent was released.
The release reaction of carbon dioxide from the carbon dioxide absorbing material that has absorbed carbon dioxide is represented by the following formula (8).
SrTiO ₃ + SrCO ₃ → Sr ₂ TiO ₄ + CO ₂ ↑ (8)

  And the time-dependent change of the exhaust gas composition in a discharge process was measured with the said gas analyzer, and the ratio of the carbon dioxide and carbon monoxide in a discharge process was measured. The results are shown in Table 1.

A cylindrical stainless steel container having an inner diameter of 22 mm and a length of 300 mm equipped with an external electric heater was charged with 14 g (about 10 mL) of CaO (carbon dioxide absorbent) having an average particle diameter of 2 mm.
Then, nitrogen gas was circulated through this stainless steel container at 18 NL / h, and the nitrogen gas inlet temperature was controlled at 600 ° C. by a heat transfer heater.
After the circulated nitrogen gas temperature was stabilized, carbon dioxide was circulated at a rate of 2 NL / h (carbon dioxide concentration was 10 mol%), and carbon dioxide absorption was started.
The reaction of carbon dioxide absorption by CaO (carbon dioxide absorbent) is as shown in the following formula (9).
CaO + CO ₂ → CaCO ₃ (9)

  The change in carbon dioxide concentration in the gas that has passed through the carbon dioxide absorbent is measured with a gas analyzer (Gas Chromatograph manufactured by Shimadzu Corporation). Ended.

Then, the carbon dioxide absorbent that has absorbed carbon dioxide is heated using an electric heater equipped in the container, and the temperature of the carbon dioxide absorbent is controlled at 900 ° C., and methane is circulated at a rate of 10 NL / h. The carbon dioxide absorbed by the carbon dioxide absorbent was released.
The release reaction of carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide is represented by the following formula (10).
CaCO ₃ → CaO + CO ₂ ↑ …… (10)

  The time-dependent change of the exhaust gas composition in the release process was measured with the gas analyzer, and the ratio of carbon dioxide and carbon monoxide in the release process was measured. The results are shown in Table 1.

The ratio of carbon dioxide and carbon monoxide in the carbon dioxide releasing step was measured by the same method as in Example 6 except that the absorbent material temperature at the time of carbon dioxide release was controlled at 700 ° C. The results are shown in Table 1.
[Comparative Example 1]

Except that nitrogen gas was used as the gas to be circulated at the time of carbon dioxide release (nitrogen (N ₂ ) gas flow rate 10 NL / h), the time until the release of carbon dioxide was completed by the same method as in Example 1. The ratio of carbon dioxide and carbon monoxide in the release process was measured. The results are shown in Table 1.

[Evaluation]
Examples 1 to 7 and Comparative Example 1 were evaluated with reference to Table 1 showing the above measurement results for Examples 1 to 7 and Comparative Example 1.

As shown in Table 1, it was confirmed that carbon monoxide was produced at a high rate when methane was circulated at a temperature condition of 800 ° C. or higher in the carbon dioxide releasing step as in Examples 1 to 3. It was.
In addition, the reaction formula at this time is as the reaction formula of Formula (1).
CO ₂ + CH ₄ → 2CO + 2H ₂ (1)

In addition, as shown in Example 4, it was confirmed that carbon monoxide was produced at a high rate even when hydrogen was circulated instead of methane.
In addition, the reaction formula at this time is as the above-described reaction formula (2).
CO ₂ + H ₂ → CO + H ₂ 0 (2)

Further, as in Example 5, when a composite oxide containing other alkaline earth metal oxide (Sr ₂ Ti0 _{4 in} Example 5) is used as the carbon dioxide absorbent, or as in Example 6. In addition, even when an alkaline earth metal oxide (CaO in Example 6) is used as the carbon dioxide absorbent, the carbon dioxide releasing step (the temperature conditions in the releasing step are 900 ° C. in both Examples 5 and 6). Thus, it was confirmed that carbon monoxide was generated at a high rate by circulating a hydrocarbon-based gas (methane gas in Examples 5 and 6) as the sweep gas.

  In the case of Example 7 in which CaO is used as the carbon dioxide absorbent and the temperature condition of the carbon dioxide releasing step is 700 ° C., the rate of carbon monoxide generation is not necessarily as high as 0.38. Recognize. From this result, it can be seen that the reaction between carbon dioxide and methane tends to proceed at a high temperature (800 ° C. or higher). However, also in Example 7, it was confirmed that carbon monoxide was reliably generated, and it was confirmed that the basic effect of the present invention was obtained.

  As can be seen from the results of Example 7, the reaction between carbon dioxide and methane is likely to proceed at a high temperature, and carbon monoxide can be produced even at 700 ° C. However, as in Examples 1 to 6, The temperature condition of the carbon releasing process is desirably 800 ° C. or higher.

  It is possible to obtain carbon monoxide even when the temperature condition of the release process is a high temperature of 1000 ° C. or higher. However, coking due to thermal decomposition of methane becomes intense and the carbon dioxide absorbent is sintered. It is desirable to release at a temperature of 1000 ° C. or lower because deterioration tends to occur.

  Further, as in the present invention, in the carbon dioxide release step, when carbon dioxide is released by heating while circulating a hydrocarbon gas or hydrogen gas as a sweep gas, the released carbon dioxide Reacts with methane on the spot to become carbon monoxide, and the partial pressure of carbon dioxide in the gas phase is kept low, thus promoting the release of carbon dioxide.

  On the other hand, in the case of Comparative Example 1 in which nitrogen gas is used as a gas to be circulated at the time of carbon dioxide release without using a hydrocarbon-based gas or hydrogen gas as a sweep gas as in the prior art, the inside of the reaction tube is released by the carbon dioxide release. Since the carbon dioxide partial pressure of the carbon dioxide increases and the release of carbon dioxide is suppressed, the time required for carbon dioxide release in Example 1 is 300 times that of 30 minutes, that is, the invention of the present application (implemented). According to the method of Example 1), it was confirmed that the carbon dioxide release time can be shortened to 1/10 compared with the method of Comparative Example 1.

In the above embodiment, the case where methane is used as the hydrocarbon-based gas and the case where hydrogen is used as the sweep gas to be circulated in the release step has been described as an example. In the carbon dioxide releasing step, it is also possible to use hydrocarbon gases other than methane, such as propane and butane.
Further, depending on the purpose, it is possible to use a mixed gas in which a hydrocarbon gas and hydrogen are mixed, and further, a hydrocarbon gas or a mixed gas of hydrogen gas and another gas, for example, a hydrocarbon gas. It is also possible to use a mixed gas of carbon monoxide and water vapor or oxygen, or a mixed gas of carbon monoxide and hydrogen obtained by reforming it.

Further, in the above embodiment, the case where a granular carbon dioxide absorbent is used as the carbon dioxide absorbent has been described as an example. However, the carbon dioxide absorbent is not limited to a granular form, and is in a powder form. It is possible to use various forms such as a molded body formed into various shapes such as a cube, a rectangular parallelepiped, and a sphere, a sheet-shaped molded body, and a structure having a combination of them. .
In the above embodiment, use as a carbon dioxide _{absorbent, Ba 2 TiO 4, Sr 2} TiO 4, and has been described using the CaO, the carbon dioxide absorbent, the Ba ₃ Ca ₂ Ti ₂ O ₉ Even in this case, it has been confirmed that substantially the same effect as in the case of the above embodiment can be obtained.

  In addition, the invention of the present application is not limited to the configuration of each of the above embodiments in other respects, and various applications and modifications are made within the scope of the invention with respect to carbon dioxide absorption conditions and release conditions. It is possible.

As described above, according to the present invention, the absorbed carbon dioxide can be efficiently released in a shorter time, and the carbon dioxide can be recovered by converting it to carbon monoxide, which is more versatile. Is possible.
Therefore, the present invention can be widely applied to separation and recovery of carbon dioxide before combustion in the hydrogen production process and separation and recovery of carbon dioxide in combustion exhaust gas generated in a factory.

Claims (4)

(a) an absorption step of causing the carbon dioxide absorbent to absorb carbon dioxide;
(b) a method for separating and recovering carbon dioxide, comprising the step of releasing carbon dioxide from a carbon dioxide absorbent that has absorbed carbon dioxide,
In the release step of (b), the carbon dioxide absorbing material that has absorbed carbon dioxide is heated while supplying hydrogen gas or a hydrocarbon-based gas to release carbon dioxide. Method.   The method for separating and recovering carbon dioxide according to claim 1, wherein the heating temperature in the releasing step (b) is 800 to 1000 ° C.   The carbon dioxide absorbent is characterized in that the main component is an oxide of an alkaline earth metal or a composite oxide containing an alkaline earth metal oxide. 3. The method for separating and recovering carbon dioxide according to either 1 or 2. The carbon dioxide absorbent is mainly composed of a composite oxide of Ba ₂ TiO _4, Sr ₂ TiO ₄ , and Ba ₃ Ca ₂ Ti ₂ O _9. The method for separating and recovering carbon dioxide as described.