JP3420036B2 - Carbon dioxide absorbing material and carbon dioxide absorbing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon dioxide absorbent, and particularly to carbon dioxide in an exhaust gas generated from an energy plant or a chemical plant using a fuel containing hydrocarbon as a main component at 200 to 500 ° C. It relates to a carbon dioxide absorbent used for repeated separation and recovery in a temperature range.

[0002]

2. Description of the Related Art For example, in an apparatus such as an engine for burning a fuel containing hydrocarbon as a main component, the temperature of a place suitable for carbon dioxide recovery is often as high as 300 ° C. or higher.

By the way, as a method for separating carbon dioxide gas, a method using cellulose acetate, a chemical absorption method using an alkanolamine-based solvent, and the like have been conventionally known. However, in any of the above-mentioned separation methods, the introduced gas temperature is set to 2
It is necessary to keep the temperature below 00 ° C. Therefore, exhaust gas that needs to be recycled at a high temperature needs to be once cooled to 200 ° C. or lower by a heat exchanger or the like, resulting in a large amount of energy consumption for carbon dioxide separation. .

On the other hand, Japanese Patent Application Laid-Open No. 9-99214 discloses a carbon dioxide gas absorbent made of lithiated zirconia. Lithiated zirconia enables recovery of carbon dioxide in a temperature range exceeding about 500 ° C., It is not always possible to absorb and recover carbon dioxide from all exhaust gases.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a carbon dioxide gas that can be separated and recovered directly at a high temperature, with low energy consumption, and with high efficiency, carbon dioxide gas in exhaust gas from a device for burning hydrocarbons. It is intended to provide an absorbent material.

[0006]

The carbon dioxide absorbent according to the present invention is an oxide in which lithium is solid-dissolved .
Is a small amount selected from titanium, iron nickel and silicon.
It is characterized by containing at least an oxide containing one kind of metal and reacting with carbon dioxide gas to produce lithium carbonate.

[0007]

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The carbon dioxide absorbent of the present invention contains an oxide in which lithium is solid-dissolved, and reacts with carbon dioxide at a temperature of 450 ° C. or less to produce lithium carbonate.

Examples of the gas containing carbon dioxide include a device such as an engine using a fuel containing hydrocarbon as a main component, a gas generated in a process of a power plant or a chemical plant, and the like.

Examples of the oxide in which lithium is solid-dissolved include a lithiated oxide containing at least one selected from aluminum, titanium, iron, nickel and silicon. In particular, lithiated oxides of titanium and nickel are preferable in view of stability at high temperature and reactivity with carbon dioxide gas, and lithiated oxides of aluminum and iron are preferable in consideration of mass treatment of carbon dioxide gas and cost. Further, as the composite containing the above-mentioned element, for example, Ti
Examples thereof include lithiated complex oxides of -V, Ni-Co, and Ni-Fe.

It is permissible to add an alkali carbonate selected from lithium, sodium and potassium to the oxide. By adding such a carbonate, the absorption / desorption reaction of carbon dioxide gas of the obtained absorbent can be promoted at a temperature of 350 ° C. or higher.
The amount of the carbonate added is preferably 5 to 30 mol% with respect to the lithium oxide. When the amount of the carbonate added is less than 5 mol%, it becomes difficult to sufficiently exert the effect of promoting the absorption reaction of carbon dioxide gas. On the other hand, when the amount of the carbonate added exceeds 30 mol%, not only the effect of promoting the absorption reaction of carbon dioxide gas is saturated, but also the absorption amount of carbon dioxide gas per volume of the absorbent may decrease. More preferable addition amount of the carbonate is 10 to 20 mol% with respect to the lithium oxide.

The carbon dioxide absorbent of the present invention has the form of a porous body composed of particles having an average particle size of 0.1 to 5.0 μm, for example. The porosity of this porous body is preferably around 40. In such a porous body, the added alkali carbonate selected from lithium, sodium and potassium is retained in the pores.

The carbon dioxide absorbent having such a porous structure is produced, for example, by the following method. First, a granular lithiated oxide is produced by reacting an oxide containing at least one selected from aluminum, titanium, iron, nickel, and silicon with lithium carbonate in the atmosphere at a temperature of about 900 ° C. Subsequently, lithium oxide particles having an average particle diameter of 0.1 to 5.0 μm are put into a mold having a diameter of 10 to 20 mm, and compression-molded to obtain a porosity of 4
A carbon dioxide absorbent having a porous structure is produced by making the green compact around 0%.

The carbon dioxide absorbent according to the present invention described above contains an oxide in which lithium is solid-solved, for example, a lithiated oxide containing at least one selected from aluminum, titanium, iron and nickel. Such a lithiated oxide reacts with carbon dioxide gas to produce lithium carbonate as shown in the following formulas (1) to (4).

2LiAlO ₂ (s) + CO ₂ (g) → Al ₂ O ₃ (s) + Li ₂ CO ₃ (l) (1) Li ₂ TiO ₃ (s) + CO ₂ (g) → TiO ₂ (s) + Li ₂ CO ₃ (l) (2) Li ₂ NiO ₂ (s) + CO ₂ (g) → NiO (s) + Li ₂ CO ₃ (l) (3) 2LiFeO ₂ (s) + CO ₂ (g) → Fe ₂ O ₃ (s) + Li ₂ CO ₃ (l) (4) Here, the reaction of the formula (1) is particularly likely to occur at a temperature of 350 ° C. or lower.

The reaction of the above formula (2) is particularly likely to occur at a temperature of 310 ° C. or lower. The reaction of the formula (3) is particularly likely to occur at a temperature of 400 ° C. or lower. The reaction of the formula (4) is 450
It is especially likely to occur at temperatures below ℃.

When each of the lithiated oxides is heated to the above-mentioned reaction temperature or higher, the reaction proceeds from right to left to release carbon dioxide, so that carbon dioxide can be recovered. Therefore, the carbon dioxide absorbent according to the present invention can separate and recover carbon dioxide with a small amount of energy in the temperature range of 200 to 500 ° C. or lower, which has been difficult in the past.

Further, by adding an alkali carbonate selected from lithium, sodium and potassium, it is possible to obtain a carbon dioxide absorbent capable of more efficiently carrying out a carbon dioxide absorption / desorption reaction. become.

[0019]

The preferred embodiments of the present invention will be described in detail below. (Examples 1 to 5) First, aluminum oxide, titanium oxide, iron oxide (Fe ₂ O ₃ ), nickel oxide and silicon oxide each having an average particle size of about 1 μm, 1 mol each, and lithium carbonate 1
The mixture was mixed with mol and baked in the atmosphere at 900 ° C. to produce particles of lithiated aluminum oxide, lithiated titanium oxide, lithiated iron oxide, lithiated nickel oxide and lithiated silicon oxide. Subsequently, 5 g of the carbon dioxide gas absorbent made of a green compact having a porosity of 40% was manufactured by introducing 1 g of each of the granules into a mold having a diameter of 12 mm and performing pressure molding.

(Comparative Example 1) Magnesium oxide particles having an average particle size of 1 μm were pressure-molded in the same manner as in Example 1 to give a porosity of 40.
% Carbon dioxide absorbent made of green compact was manufactured.

Comparative Example 2 Lithiated zirconia particles having an average particle size of 1 μm were pressure-molded in the same manner as in Example 1 to produce a carbon dioxide absorbent made of a green compact having a porosity of 40%.

The obtained Examples 1 to 5 and Comparative Examples 1 and 2 were obtained.
The carbon dioxide absorbent of No. 1 was installed in an electric furnace, and while flowing a mixed gas of 20 vol% carbon dioxide and 80 vol% nitrogen gas in the electric furnace, 300 ° C.
The amount of carbon dioxide gas absorbed was measured by keeping the temperature at 0 ° C. and 500 ° C. for 1 hour and examining the weight increase of the absorbent before and after that. The results are shown in Table 1 below. In this measurement, a similar experiment was carried out by supplying only nitrogen gas into the electric furnace in which the absorber was installed, and it was confirmed that no increase in the weight of the absorber was observed.

The absorbents of Examples 1 to 5 and Comparative Example 1 were held at 300 ° C. for 5 hours while flowing a mixed gas of carbon dioxide gas of 20 vol% and nitrogen gas of 80 vol%, and once returned to room temperature. The weight was measured, and the amount of carbon dioxide gas released was measured by maintaining the same gas conditions at 600 ° C. for 1 hour to measure the weight reduction. In the absorbent of Comparative Example 2, the temperature condition for absorbing carbon dioxide was set to 500 ° C., and then carbon dioxide was released at the same temperature of 600 ° C. The results are shown in Table 1 below.

[0024]

[Table 1]

As is clear from Table 1, Examples 1 to 5
The absorbent material of No. 3 is 300 to 4 as compared with the absorbent materials of Comparative Examples 1 and 2.
It can be seen that the amount of carbon dioxide gas absorbed at 50 ° C. per hour is large, and the carbon dioxide gas has excellent carbon dioxide gas absorbability. In particular, it can be seen that the absorbents of Examples 1 to 4 composed of lithium aluminum oxide, lithium titanium oxide, lithium iron oxide, and lithium nickel oxide have a high absorption rate of carbon dioxide gas.

(Examples 6 to 8) 1 mol of lithium carbonate was added to 1 mol of iron oxide having an average particle size of about 1 μm, and alkaline carbonates of the types and amounts shown in Table 2 below were mixed, and 900 ° C. Lithiated iron oxide was produced by firing in air. Subsequently, 1 g of each of the granules was put into a mold having a diameter of 12 mm and pressure-molded to produce three kinds of carbon dioxide absorbents made of a green compact having a porosity of 40%.

The carbon dioxide absorbents of Examples 6 to 8 thus obtained were placed in an electric furnace, and a mixed gas of 20 vol% carbon dioxide and 80 vol% nitrogen gas was passed through the electric furnace at 450 ° C. The amount of carbon dioxide absorbed was measured by keeping the temperature for 1 hour and examining the weight increase of the absorbent before and after that. The results are also shown in Table 2 below. Table 2 also shows the results of Comparative Example 3 described above.

[0028]

[Table 2]

As is clear from Table 2, the absorbents of Examples 6 to 8 in which the amount of alkali carbonate added was large, compared with the absorbent of Example 3, the absorption of carbon dioxide gas at 450 ° C. per hour. It can be seen that the amount is larger and it has excellent carbon dioxide absorption.

[0030]

As described in detail above, according to the present invention, carbon dioxide in exhaust gas from a device for burning hydrocarbons can be separated and recovered directly at high temperature with low energy consumption and high efficiency. A possible carbon dioxide absorbent can be provided.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiro Akasaka 1 Komukai Toshiba Town, Komukai-ku, Kawasaki City, Kanagawa Prefecture Toshiba Research and Development Center, Inc. (72) Inventor Shigehiro Tomimatsu Toshiba Komukai Toshiba, Kawasaki City, Kanagawa Prefecture 1-City, Toshiba Research & Development Center Co., Ltd. (56) Reference JP-A-2-43917 (JP, A) JP-A-9-99214 (JP, A) JP-A-49-22391 (JP, A) (58) ) Fields surveyed (Int.Cl. ⁷ , DB name) B01J 20/00-20/34

Claims (10)

(57) [Claims] 1. An oxide in which lithium is solid-dissolved, here
Oxide of titanium is selected from titanium, iron, nickel and silicon.
Demonstrating an oxide containing at least one metal selected from
A carbon dioxide absorbent, characterized by having a reaction with carbon dioxide to produce lithium carbonate. Wherein oxide wherein lithium is dissolved, the Li
The carbon dioxide absorbent according to claim 1, wherein the carbon dioxide absorbent is a solid solution silicon oxide . 3. The carbon dioxide absorbent according to claim 1, further comprising an alkali carbonate selected from lithium, sodium and potassium. 4. A lithiated oxide containing silicon which reacts with and absorbs carbon dioxide (a), and (b) an alkali carbonate selected from the group consisting of sodium carbonate, lithium carbonate and potassium carbonate. containing
An absorbent material, wherein the absorbent material is a porous material or a green compact, and the silicon is converted into silicon oxide when reacting with the carbon dioxide gas. 5. A formula Li containing particles which react with and absorb carbon dioxide gas and contain silicon-containing lithiated oxide, said lithiated oxide containing particles having an average particle size of 0.1 to 5 μm.
An absorbent material which is a compound having ₂ SiO ₃ , wherein the absorbent material is porous or a green compact, and the silicon is converted into silicon oxide upon reaction with the carbon dioxide gas. Carbon dioxide absorbent. 6. A step of forming lithium carbonate and silicon oxide by selectively reacting the carbon dioxide with the carbon dioxide absorbent according to claim 4 and absorbing the carbon dioxide as carbonate. A method for absorbing carbon dioxide from a gas containing carbon dioxide, comprising: By 7. be selectively reacted with carbon dioxide gas absorbent according to claim 5, wherein the carbon dioxide to form a lithium carbonate and silicon oxide, and the step of absorbing the carbon dioxide as carbonate A method for absorbing carbon dioxide from a gas containing carbon dioxide, comprising: 8. Lithium is absorbed by reacting with carbon dioxide,
Dissolved oxide, where oxide refers to oxide containing iron
Carbon dioxide gas absorbent and having to, a. 9. Lithium is absorbed by reacting with carbon dioxide,
Dissolved oxide, where the oxide contains titanium
And an alkali carbonate selected from the group consisting of sodium carbonate, lithium carbonate and potassium carbonate. 10. An oxide in which lithium is solid-dissolved, which reacts with carbon dioxide to be absorbed to form a reaction product composed of lithium carbonate and nickel oxide, wherein the oxide is nickel.
A carbon dioxide absorbent characterized by having an oxide containing Kel .