JP2006103974A - Carbon dioxide separation/recovery device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently separate and recover only carbon dioxide by using an absorbent mainly comprising lithium silicate. <P>SOLUTION: This carbon dioxide separation/recovery device is equipped with a reaction vessel housing a carbon dioxide absorbent comprising lithium silicate (Li<SB>4</SB>SiO<SB>4</SB>, Li<SB>2</SB>SiO<SB>3</SB>) as the principal component and containing LiOH or LiOH(H<SB>2</SB>O)<SB>n</SB>ä(H<SB>2</SB>O)<SB>n</SB>indicates crystallization water}, and a heating unit for heating the carbon dioxide absorbent. A mixed gas is introduced into the reaction vessel, the carbon dioxide in the mixed gas is absorbed by the carbon dioxide absorbent, and after discharging the mixed gas from the reaction vessel, heating the carbon dioxide absorbent to release carbon dioxide, and carbon dioxide is separated and recovered. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an apparatus for separating and collecting carbon dioxide from a mixed gas containing carbon dioxide.

  In order to preserve the global environment, there is an active movement to regulate carbon dioxide emissions. Carbon dioxide gas is contained in, for example, exhaust gas generated from combustion of fuels mainly composed of hydrocarbons, energy plants that use fossil fuels as raw materials, chemical plants, automobiles, etc., and these are released into the atmosphere. Therefore, efficient separation and removal is required.

  Conventionally, lithium silicate is known as a carbon dioxide absorbing material that absorbs such carbon dioxide. In the conventional method of using lithium silicate, the temperature range for absorbing carbon dioxide was 450 ° C. to 700 ° C.

  Moreover, soda lime exists as a carbon dioxide gas absorbent for room temperature. Soda lime contains calcium hydroxide as a main component, and the calcium hydroxide reacts with the carbon dioxide gas to form calcium carbonate, thereby absorbing the carbon dioxide gas. Calcium carbonate is a stable substance. For this reason, it is difficult to reuse soda lime after recycling (see Patent Document 1).

JP-A-8-24571

An object of the present invention is to provide a carbon dioxide gas separation and recovery apparatus that efficiently separates and recovers only carbon dioxide gas using an absorbent material mainly composed of lithium silicate.
Alternatively, an object of the present invention is to provide a carbon dioxide gas separation material recovery apparatus using a carbon dioxide gas absorption material having carbon dioxide gas absorption ability even at 450 ° C. or lower in a carbon dioxide gas absorption material mainly composed of lithium silicate.

The present invention is a carbonic acid containing lithium silicate (Li ₄ SiO ₄ , Li ₂ SiO ₃ ) as a main component and containing LiOH or LiOH (H ₂ O) _n {(H ₂ O) _n represents crystal water}. A carbon dioxide separation / recovery device comprising a reaction vessel having a gas absorption material, a heating device for heating the carbon dioxide absorption material, and a recovery vessel for recovering carbon dioxide.

The present invention can efficiently separate and recover only carbon dioxide from a mixed gas by using an absorbent containing lithium silicate as a main component and containing LiOH or LiOH (H ₂ O) _n .

(CO2 separation and recovery device)
The carbon dioxide gas separation and recovery device of the present invention is a device that separates and recovers carbon dioxide from a mixed gas containing carbon dioxide by a carbon dioxide absorber. For example, carbon dioxide (carbon dioxide) is separated and recovered from exhaust gas, fuel gas, and raw gas generated from energy plants, chemical plants, automobiles, fuel reformers etc. Or to increase the combustion efficiency and reaction efficiency, to separate and recover the carbon dioxide in the fuel and raw material supply section, or to reduce the carbon dioxide concentration in the enclosed space and circulating gas for life support and atmosphere control An apparatus for separating and recovering carbon dioxide gas.

  This carbon dioxide gas separation / recovery device can absorb carbon dioxide gas in a wide temperature range from room temperature to 700 ° C. When this absorbent material is stored in a reaction vessel and a mixed gas mixed with carbon dioxide gas is passed through the reaction vessel, the absorbent material absorbs only the carbon dioxide component, so that the carbon dioxide gas can be separated and recovered. Moreover, the absorber which absorbed the carbon dioxide gas can be used repeatedly by performing a regeneration process. In addition, by installing a carbon dioxide concentration meter, a valve, and a carbon dioxide supply device before and after the reaction vessel containing the carbon dioxide absorbent, the carbon dioxide concentration in a closed space or a closed system can be adjusted.

For example, as shown in FIG. 1, the carbon dioxide gas separation and recovery device includes a reaction vessel 1 that contains a carbon dioxide absorbent 2, a gas introduction pipe 5 that introduces a mixed gas containing carbon dioxide into the reaction vessel 1, and a reaction vessel 1. A gas discharge pipe 6 for discharging the mixed gas from, a carbon dioxide concentration meter 3 for measuring the concentration of carbon dioxide before and after the reaction vessel, a flow meter 4 for measuring the flow rate of the gas introduced into the reaction vessel 1, and a gas And a heating device 8 and the like. Moreover, the carbon dioxide gas separation and recovery apparatus includes a carbon dioxide gas supply source 11 in addition to the configuration of FIG. The carbon dioxide supply source 11 is connected to the heating device 8 via the valve 7 and further connected to the gas exhaust pipe 6 via the valve 7. The carbon dioxide gas supply source 11 can use a CO ₂ gas cylinder. The carbon dioxide supply source may be replaced with a CO ₂ recovery container.

  An example of the carbon dioxide separation and recovery device including the recovery container 10 and the humidifier 9 is shown in FIG. 3 having the same functions as those in FIG. 1 are denoted by the same reference numerals. The recovery container 10 is connected to the reaction container 1 via the gas discharge pipe 6. The humidifier 9 is connected to the reaction vessel 1 through a moisture gas introduction pipe 51 as shown in FIG. Alternatively, it is connected to the reaction vessel via the gas introduction pipe 5 as shown in FIG.

A carbon dioxide separation / recovery device provided with a plurality of reaction vessels 1 is shown, for example, in FIG. By providing a plurality of containers, one can absorb carbon dioxide and the other can regenerate the carbon dioxide absorbent, so that carbon dioxide can be continuously absorbed and separated and recovered. FIG. 4A shows a configuration in which two reaction vessels 1 of FIG. 3A are connected in parallel, and the number of pipes is increased accordingly. FIG. 4B similarly includes two reaction vessels 1 of FIG. 3B, and the number of pipes is increased. 3 to 4, the carbon dioxide concentration meters 3 and 3 and the flow meter 4 in FIG. 1 are omitted. However, when measuring the gas concentration and flow rate, they are attached as necessary. It is done.

(Carbon dioxide absorber)
The chemical reaction formula in which lithium silicate (Li ₄ SiO ₄ ) absorbs carbon dioxide is expressed by the following formula (1).

Li ₄ SiO ₄ + CO ₂ → Li ₂ SiO ₃ + Li ₂ CO ₃ (1)

  Formula (1) is a reversible reaction, and at a high temperature, the reverse reaction shown in Reaction Formula (2) occurs, and carbon dioxide gas is released.

Li ₂ SiO ₃ + Li ₂ CO ₃ → Li ₄ SiO ₄ + CO ₂ (2)

  By repeating such a reversible reaction, the lithium silicate can repeatedly absorb carbon dioxide. However, the area | region which absorbs a carbon dioxide gas was 450-700 degreeC. Therefore, by reacting water with lithium silicate, a part of the lithium silicate can be changed to LiOH and can be contained in the lithium silicate. The chemical reaction formula is represented by the following formula (3).

Li ₄ SiO ₄ + H ₂ 0 → Li ₂ SiO ₃ + 2LiOH (3)

LiOH present in the lithium silicate absorbs carbon dioxide at room temperature to 700 ° C. The reaction formula is represented by the following formula (4).

2LiOH + CO ₂ → Li ₂ CO ₃ + H ₂ O (4)

  Lithium carbonate produced by reacting with carbon dioxide gas is regenerated into lithium silicate according to formula (2) by heat treatment. Unreacted LiOH is regenerated into lithium silicate by the following formula (5).

Li ₂ SiO ₃ + 2LiOH → Li ₄ SiO ₄ + H ₂ O (5)

The regenerated lithium silicate reacts with moisture to cause the reaction of the formula (3), and is regenerated into a carbon dioxide gas absorbent containing LiOH in the lithium silicate. Since LiOH has a very high reactivity with carbon dioxide gas, the reaction of formula (4) occurs even at a dry room temperature and can absorb carbon dioxide gas. The above LiOH may be LiOH.H ₂ O _n ((H ₂ O) _n represents crystal water) with crystal water.

  Moreover, this carbon dioxide absorbing material can separate and collect carbon dioxide in a temperature range of room temperature to 700 ° C. Further, the absorbent that has reacted with the carbon dioxide gas can be repeatedly used by performing a regeneration treatment. When this absorbent material is stored in a reaction vessel and a mixed gas mixed with carbon dioxide gas is passed through the reaction vessel, the carbon dioxide gas can be separated and recovered. Further, by installing a carbon dioxide concentration meter, a valve, and a carbon dioxide supply device before and after the reaction vessel, it can be used as a device for adjusting the carbon dioxide concentration.

In the production of lithium silicate, pure water is added to lithium carbonate and silicon oxide and pulverized and mixed. After drying the slurry, a mixed powder is obtained. Next, pure water, mixed powder, and binder are put into an alumina mortar and kneaded. This kneaded product is molded. This molded body is fired to produce lithium silicate. In order to accelerate the synthesis reaction, a trace amount of alkali carbonate such as K ₂ CO ₃ or Na ₂ CO ₃ may be added.

Next, a carbon dioxide absorbent containing LiOH is produced as follows. The prepared lithium silicate is allowed to stand in an inert gas atmosphere such as nitrogen gas, water is introduced, and a part of the lithium silicate is allowed to react, whereby carbon dioxide containing LiOH or LiOH. (H ₂ O) _n is contained. A gas absorber is obtained.

For the reaction between moisture and lithium silicate, a humidifying dryer capable of controlling the temperature or an autoclave capable of controlling the pressure may be used. Moreover, when making it react with a carbon dioxide gas especially at room temperature, you may contain free water.

(Operation of carbon dioxide separation and recovery device)
In the carbon dioxide separator of FIG. 1, the mixed gas is introduced into the reaction vessel 1 from the gas introduction pipe 5. At that time, the introduction of the mixed gas is controlled to open and close by the valve 7, and the flow rate is measured by the flow meter 4. In the reaction vessel 1, the carbon dioxide gas reacts with the carbon dioxide absorbent according to the equations (1) and (4) in a temperature range where the carbon dioxide absorbent 2 reacts with the carbon dioxide, for example, from room temperature to 700 ° C. The mixed gas from which the carbon dioxide gas has been removed or whose concentration has been reduced is discharged through the gas discharge pipe 6. Next, in the case where the carbon dioxide gas that has reacted with the carbon dioxide absorbent 2 is released, in the temperature range where the carbon dioxide of the carbon dioxide absorbent 2 is released, for example, 800 ° C., To be released. The released carbon dioxide gas is discharged through the gas discharge pipe 6 by opening and closing the valve 7. In the carbon dioxide separator of FIG. 1, when the carbon dioxide concentration of the discharged gas becomes too low, the carbon dioxide supply source 11 can adjust the carbon dioxide concentration to a preferable one as in the carbon dioxide separator of FIG. Good. The carbon dioxide supply source 11 may be a carbon dioxide cylinder, a carbon dioxide absorbent that has absorbed carbon dioxide, or another device that generates carbon dioxide.

  In the carbon dioxide gas separation and recovery device of FIG. 3, after the carbon dioxide gas absorbent reacts with the carbon dioxide gas, the carbon dioxide gas absorbent material 2 is heated by the heating device 8 to release the carbon dioxide gas into the reaction vessel according to the equation (2). . The released carbon dioxide is transferred to the collection container 10 through the carbon dioxide discharge pipe 61 and collected.

  In order to return the carbon dioxide gas separation and recovery device to the initial state, water is supplied to the carbon dioxide gas absorbent. For this purpose, the humidifier 9 is operated to supply moisture to the reaction vessel 1. In the reaction vessel, the reaction of formula (3) proceeds, and the LiOH content in the carbon dioxide absorbent 2 increases. Water is supplied so as to obtain a desired content.

In the carbon dioxide gas separation and recovery apparatus of FIG. 4, when recovering carbon dioxide, one reaction vessel absorbs carbon dioxide in the mixed gas, and the other reaction vessel regenerates the absorbent that has absorbed carbon dioxide. When the regeneration process is performed, the reaction vessel 1 is heated to release carbon dioxide into the reaction vessel, and is transferred to the collection vessel 10 through the gas discharge pipe 6 and collected in the same manner as in the apparatus of FIG. When there are a plurality of reaction vessels, carbon dioxide can be separated and recovered continuously.

Example 1
The production of the carbon dioxide absorber is performed as follows. In a polypot, lithium carbonate and silicon oxide as raw materials were in a molar ratio of 2: 1, pulverized alumina balls and pure water were added, and pulverized and mixed in a pot mill for 20 hours (hours). The slurry was dried and passed through a # 60 nylon mesh to obtain a mixed powder having an average particle size of 240 μm or less. Next, pure water, mixed powder, polysaccharide binder, and a small amount of potassium carbonate were put into an alumina mortar and kneaded. The amount of binder added was 2% by weight with respect to the mixed powder, and 2 mol% of potassium carbonate was added to the synthesized lithium silicate. After the kneaded product was dried, a granular shaped product having an average particle size of 240 to 420 μm was produced. The obtained molded body was calcined by holding at 600 ° C. for 8 hours in a nitrogen flow atmosphere to produce lithium silicate granules.

  The produced lithium silicate was allowed to stand in a desiccator in a nitrogen atmosphere, and nitrogen gas that had been moistened by bubbling water was introduced into the lithium silicate so that the lithium silicate was kept at 25% by weight of water. Thus, the produced carbon dioxide absorbing material was housed in a reaction vessel, and the carbon dioxide absorbing performance was measured.

  Next, the reaction vessel after the completion of the reaction was kept at 600 ° C. for 4 hours, and then cooled to room temperature and the humidifier was operated to introduce moisture into the reaction vessel. The operation time of the humidifier was adjusted so that the water content of the carbon dioxide absorbent was 25% by weight, the same as the first time. The gas introduction time was 2 hours, and the carbon dioxide absorption rate was determined by the following equation.

  Carbon dioxide absorption rate (%) = Amount of carbon dioxide absorbed by the absorbent (g) / Amount of absorbent (g) × 100 (6)

The apparatus that performed the measurement this time is to install a carbon dioxide concentration meter before and after the reaction vessel, introduce a mixed gas with adjusted carbon dioxide concentration at 1 L (liter) / min, and carbon dioxide gas before and after the reaction vessel. The concentration was measured, and the absorption rate of the reaction vessel was evaluated. The volume of the reaction vessel is 7 cm ³ . The temperature of the mixed gas was 25 ° C., and the carbon dioxide concentration in the mixed gas was 3000 ppm.

(Comparative Example 1)
Comparative Example 1 is an example in which soda lime is used instead of lithium silicate as a carbon dioxide gas absorbent. As the carbon dioxide gas separation and recovery device, the same device as in Example 1 was used except that soda lime was accommodated in the reaction vessel.

(Measurement result 1)
From Table 1, it can be seen that the carbon dioxide separation and recovery apparatus used for the absorbent containing LiOH containing lithium silicate as a main component can be repeatedly used by performing the regeneration treatment. In Example 1, although the shape of lithium silicate uses the granule, it is not limited to it, Various shapes, such as spherical shape, disk shape, cylindrical shape, square shape, prismatic shape, can be selected.

As described above, the lithium silicate is subjected to regeneration treatment to obtain a carbon dioxide absorption performance almost equal to that of the first time, so that a carbon dioxide separation and recovery device that can be used for a long time without waste is obtained. be able to. Or it can use as an apparatus which adjusts a carbon dioxide gas concentration by installing a carbon dioxide gas concentration meter and a valve before and behind a reaction container. Alternatively, carbon dioxide gas can be separated and recovered in a wide temperature range from room temperature to 700 ° C., and even when dried, carbon dioxide gas can be separated and recovered without lowering the absorption performance.

  Examples that can efficiently absorb carbon dioxide gas even at high temperatures are shown below.

(Example 2)
The manufacture of the lithium silicate of Example 2 is performed as follows. Lithium carbonate and silicon oxide as raw materials were put in a polypot so as to have a molar ratio of 2: 1, pulverized alumina balls and pure water were added, and pulverized and mixed in a pot mill for 20 hours (h). The slurry was dried and passed through a nylon mesh 240 μm to obtain a mixed powder. Next, pure water, mixed powder, and binder (polysaccharide) were put into an alumina mortar and kneaded. The added amount of the binder was 2% by weight with respect to the mixed powder. This kneaded product was molded into a spherical shape of about 2 mm. This molded body was fired by holding at 650 ° C. for 8 hours in a nitrogen flow atmosphere to produce a spherical lithium silicate of about 2 mm.

  Next, a carbon dioxide absorbent containing LiOH is produced as follows. The produced lithium silicate was allowed to stand in a desiccator in a nitrogen atmosphere, and nitrogen gas in which water was published was introduced therein to react a part of the lithium silicate with water. Then, it hold | maintained at 120 degreeC in nitrogen atmosphere for 2 hours, the excess water | moisture content was removed, and the carbon dioxide gas absorber containing LiOH was obtained.

  The carbon dioxide absorption performance was measured by storing the produced carbon dioxide absorbent in a reaction vessel. The gas introduction time was 2 hours, and the carbon dioxide absorption rate was determined by the above formula (6).

As shown in FIG. 1, the apparatus which measured at room temperature (25 degreeC) installed the carbon dioxide gas concentration meter in front and behind the reaction container, and the standard gas adjusted to the carbon dioxide gas concentration of 3000 ppm to there is 1 L / min. The carbon dioxide concentration before and after the reaction vessel was measured, and the absorption rate of the carbon dioxide absorbent was evaluated. The volume of the reaction vessel is 7 cm ³ .

  The apparatus which measured at 200 degreeC and 600 degreeC accommodates the carbon dioxide gas absorption material in the reaction container, introduces 500 ml / min of standard gas with a carbon dioxide concentration of 20% by weight, and absorbs the carbon dioxide gas. The carbon dioxide absorption rate was evaluated based on the change in the weight of the absorbent.

(Comparative Example 2)
Lithium silicate was produced in the same manner as in Example 2, but it was not reacted with moisture and LiOH or LiOH (H ₂ 0) _n was not contained. In the same manner as in Example 1, this absorbent material was measured for carbon dioxide absorption at room temperature (25 ° C.), 200 ° C., and 600 ° C.

(Measurement result 2)
According to Table 2, the carbon dioxide absorption rate at room temperature was 8.7% in Example 2, but 0.1% in Comparative Example 2, and the carbon dioxide gas absorbent containing LiOH is carbon dioxide even at room temperature. It can be absorbed. The carbon dioxide absorption rate at 200 ° C. was 4.3% in Example 2, but 0% in Comparative Example 2. The carbon dioxide absorbent containing LiOH absorbs carbon dioxide even in an atmosphere at 200 ° C. Shows that you can. The carbon dioxide absorption rate at 600 ° C. was 22.5% in Example 2, but 23.3% in Comparative Example 2.

Schematic diagram of carbon dioxide separation and recovery device of the present invention Schematic of another carbon dioxide gas separation and recovery device of the present invention Schematic of another carbon dioxide gas separation and recovery device of the present invention Schematic of another carbon dioxide gas separation and recovery device of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Reaction container 2 ... Carbon dioxide gas absorption material 3 ... Carbon dioxide gas concentration meter 4 ... Flow meter 5 ... Gas introduction pipe 51 ... Humid gas introduction pipe 6 ... Gas discharge pipe 61 ..CO2 discharge pipe 7 ... Valve 8 ... Heating device 9 ... Humidifier 10 ... Recovery container 11 ... CO2 supply source

Claims (4)

A reaction having a carbon dioxide absorbent containing lithium silicate (Li ₄ SiO ₄ , Li ₂ SiO ₃ ) as a main component and containing LiOH or LiOH (H ₂ O) _n {(H ₂ O) _n represents crystal water}. A container,
A heating device for heating the carbon dioxide absorber;
A carbon dioxide separation / recovery device comprising a recovery container for recovering carbon dioxide.
A reaction having a carbon dioxide absorbent containing lithium silicate (Li ₄ SiO ₄ , Li ₂ SiO ₃ ) as a main component and containing LiOH or LiOH (H ₂ O) _n {(H ₂ O) _n represents crystal water}. A container,
A heating device for heating the carbon dioxide absorber;
A collection container for collecting carbon dioxide gas,
The mixed gas is introduced into the reaction vessel, and the carbon dioxide in the mixed gas is reacted with the carbon dioxide absorbent. Next, after the mixed gas in the reaction vessel is discharged, the carbon dioxide absorbent is heated to react the carbon dioxide. A carbon dioxide separation and recovery device, characterized in that it is generated in a container and recovered in a container.
The molar ratio of the lithium compound in the carbon dioxide absorbent is Li ₄ SiO ₄ : Li ₂ SiO ₃ : LiOH = 1-x: x: 2x (0 <x ≦ 1), The carbon dioxide gas separation and recovery device described in 1.
A gas introduction pipe for introducing gas into the reaction vessel;
A gas discharge pipe for discharging gas from the reaction vessel;
A humidifier that humidifies the carbon dioxide absorbent,
The carbon dioxide gas separation and recovery device according to claim 1 or 2, wherein H ₂ O is supplied to the reaction vessel by a humidifier and reacted with lithium silicate to produce LiOH in the reaction vessel.

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