JP5477364B2 - Method and apparatus for collecting and releasing gas using a hydrate containing a quaternary ammonium salt as a guest molecule - Google Patents

Description

  The present invention relates to a technique for collecting and releasing a gas using a hydrate containing a quaternary ammonium salt as a guest molecule, and more specifically, bringing an aqueous solution containing a quaternary ammonium salt as a solute into contact with the gas, By cooling at a temperature higher than 15 ° C., a hydrate that collects gas is generated, and further, the hydrate is dispersed or suspended in an aqueous solution or water to generate a hydrate slurry. Heating the hydrate slurry produced in step 1 and the first step to melt the hydrate therein, thereby removing gas from the hydrate produced in the first step. And a second step of generating an aqueous solution containing a quaternary ammonium salt as a solute and an apparatus for realizing the method.

In the present invention, the meanings or interpretations of the following terms are as follows. The meaning or interpretation of this term does not preclude the technical scope of the present invention from reaching an equivalent scope.
(1) “Hydrate” is an abbreviation for clathrate hydrate. In the structure (inclusion lattice) such as a tunnel shape, a layer shape, a network shape, and a cage shape formed by a molecule or a compound called a host or a host material (ie, host molecule) (ie, a host molecule), another molecule or compound called a guest material (ie, a host material) A substance formed and formed by entering or taking in a guest molecule) is called an inclusion compound. Examples of guest molecules include quaternary ammonium salts typified by alkyl ammonium salts such as tetra-n-butylammonium salt, tetra-isopentylammonium salt, tri-n-butyl-pentylammonium salt, alkylphosphonium salts, alkylsulfonium salts, and the like. is there. Examples of host molecules are water and cyclodextrins. An inclusion compound in which the host molecule is water is an inclusion hydrate. The “hydrate” in the present invention includes quasi-clathrate hydrate.
(2) An aqueous solution of a clathrate hydrate guest molecule, more specifically, an aqueous solution containing one or two or more guest molecules as a solute and water as a solvent may be abbreviated as “guest molecule aqueous solution”.
(3) “Slurry of hydrate” refers to a slurry in which a hydrate is dispersed or suspended in an aqueous solution or aqueous solvent of guest molecules. Even if the amount of hydrate is small (in other words, even if the proportion of hydrate is low), if it is dispersed or suspended in the aqueous solution or aqueous solvent, it corresponds to “a slurry of hydrate”. To do. The “hydrate slurry” may be simply referred to as “slurry” in context or for convenience.
(4) “Hydrate formation temperature” refers to the temperature at which a hydrate is formed in an aqueous solution of the hydrate guest molecule when cooled.

  A technique of using a hydrate containing a quaternary ammonium salt as a guest molecule as a gas separating agent and utilizing it for gas separation or concentration has been studied (Patent Documents 1 to 3, Non-Patent Documents 1 and 2). .

Japanese Patent No. 3826176 JP 2006-117485 A JP 2006-206635 A

AntoinChapoy, Ross Anderson, and Bahman Tohidi, “Low-PressureMolecular HydrogenStorage in Semi-clathrate Hydrates of Quaternary AmmoniumCompounds” Journal of American Chemical Society 2007, 129, pp. 746-747. NguyenHong Duc, Fabien Chauvy, Jean-Michel Herri, “CO2capture by hydratecrystallization-A potential solution for gas emission ofsteelmakingindustry,” Available online 30 November 2006, Internet <URL: http://www.emse.fr/spin/depscientifiques/GENERIC /hydrates/publications/abstract2006a.htm><URL: http://www.aseanenvironment.info/Abstract/43005208.pdf>

However, none of the prior arts are in the research stage and are not in a stage that can withstand realistic applications. In order to use a hydrate containing a quaternary ammonium salt as a guest molecule as a gas separating agent, one of the necessary conditions to be able to withstand practical applications is to use a quaternary ammonium salt as a guest. A cycle of collecting a gas using a hydrate contained as a molecule and releasing the gas collected from the hydrate to separate a desired gas and collect the guest molecule is more efficient or It is to be realized economically. Although the techniques described in Patent Documents 3 and 4 seem to be one of the candidates that can satisfy this necessary condition, the energy efficiency as a whole is not sufficient and there is room for improvement.
Conventionally, many substance names belonging to quaternary ammonium salts have been cited as hydrate guest molecules that can be used for gas separation and concentration. However, the quaternary ammonium salts actually used for research are tetra-n-butylammonium halides (particularly tetra-n-butylammonium bromide (TBAB), tetra-n-butylammonium hydroxide (TBAOH), tetra-n-fluoride). It can be said that it is generally limited to butylammonium (TBAF).

  The present invention has been made in view of the above points, and is a technique for collecting and releasing a gas using a hydrate containing a quaternary ammonium salt as a guest molecule in order to separate the gas, An object of the present invention is to provide a gas that can efficiently or economically collect and release a gas and recover a guest molecule.

  In order to achieve the above object, a method of collecting and releasing a gas according to the first embodiment of the present invention collects and releases a gas using a hydrate containing a quaternary ammonium salt as a guest molecule. In this method, an aqueous solution of the guest molecule is brought into contact with a gas and cooled at a temperature of 15 ° C. or higher to generate a hydrate that collects the gas, and the hydrate is further added to the aqueous solution or water. The first step for producing a slurry formed by dispersion or suspension, and the slurry produced in the first step is heated to melt the hydrate therein, thereby collecting the hydrate. And a second step of generating an aqueous solution of the guest molecule.

  The method for collecting and releasing the gas according to the second aspect of the present invention is the method according to the first aspect, wherein the aqueous solution of the guest molecule contains a tetraisopentylammonium salt or a tetraisopentylammonium salt. It contains two or more kinds of quaternary ammonium salts as a solute.

An apparatus for collecting and releasing a gas according to the third aspect of the present invention is an apparatus for collecting and releasing a gas using a hydrate containing a quaternary ammonium salt as a guest molecule, the guest molecule A slurry obtained by bringing the aqueous solution into contact with a gas and cooling at a temperature of 15 ° C. or more, thereby generating a hydrate that collects the gas, and further dispersing or suspending the hydrate in the aqueous solution or water. Gas to be generated and gas that heats the slurry generated in the gas collector and melts hydrates in the slurry, thereby releasing gas and generating an aqueous solution of the guest molecule And a discharge device.

  An apparatus for collecting and releasing a gas according to a fourth aspect of the present invention is the apparatus according to the third aspect, wherein the aqueous solution of the guest molecule contains a tetraisopentylammonium salt or a tetraisopentylammonium salt. It contains two or more kinds of quaternary ammonium salts as a solute.

  In each form of the present invention, when gas is collected using a hydrate containing a quaternary ammonium salt as a guest molecule, it is desirable to apply pressure in order to facilitate the collection. In this case, the pressure is less than 2 MPa (usually 1 MPa or less, preferably about 0.1 to 0.7 MPa), and no special high pressure is required (see Patent Documents 1 to 3).

  According to the present invention, gas is collected using a hydrate containing a quaternary ammonium salt as a guest molecule, the gas is separated by releasing the collected gas, and the guest molecule is recovered. A technique can be provided in which the cycle can be realized more efficiently or economically and thus can withstand realistic applications.

Furthermore, in this invention, when the hydrate formation temperature of the hydrate which uses a quaternary ammonium salt as a guest molecule belongs to the range of 15-30 degreeC, the temperature (about 15-30 degreeC at most) By adjusting, gas collection and release can be controlled, so that energy consumption is low and economical gas separation can be realized. For example, when the outside air temperature is higher than the hydrate formation temperature, the aqueous solution of the guest molecule is cooled to collect gas in the hydrate, and at least a part of the hydrate is removed using the thermal energy of the outside air. It is possible to melt and thereby release the gas. In addition, when the outside air temperature is lower than the hydrate formation temperature, the aqueous solution of the guest molecule is cooled using the thermal energy of the outside air, thereby collecting the gas in at least a part of the hydrate, and by heating. The hydrate can be melted and the gas released. In any case, since the thermal energy of the outside air is used, energy consumption is relatively reduced, and economical gas separation becomes possible.
The effect which each form of this invention has is as follows.

  According to the first aspect of the present invention, the temperature at which the aqueous solution is cooled in the first step is 15 ° C. or higher. The aqueous solution can be cooled using the thermal energy of the outside air while reducing the operating load of the cooling device without requiring a special cooling device or even when a cooling device is required. it can. This allows for relatively low energy consumption, gas collection that is efficient and economical and thus can withstand more realistic applications.

  According to the second aspect of the present invention, the aqueous solution of guest molecules contains tetraisopentylammonium salt or two or more kinds of quaternary ammonium salts including tetraisopentylammonium salt as solutes. Since the generation temperature can be set to a preferable temperature, an aqueous solution or hydrate slurry of guest molecules that can be applied to the method according to the first embodiment can be prepared, and thus the effectiveness of the present invention can be improved. Can be increased.

  According to the 3rd form of this invention, the apparatus with which the method which concerns on a 1st form is performed is realizable. In this case, the first and second steps are executed in the gas collection device and the gas discharge device, respectively.

According to the 4th form of this invention, the apparatus with which the method which concerns on a 2nd form is performed is realizable.
In addition, a guest molecule suitable in each form of the present invention is a tetraisopentylammonium salt or a tetraisopentylammonium salt and other quaternary ammonium salts (particularly, an alkylammonium salt typified by a tetra-nbutylammonium salt). It is.

It is explanatory drawing of the gas separation apparatus which concerns on embodiment of this invention. FIG. 2 is a detailed explanatory diagram of a part of the gas separation device shown in FIG. 1. It is explanatory drawing of the gas separation method in embodiment of this invention.

  Hereinafter, the present invention will be described in detail by embodiments. The technical scope of the present invention is not limited by these embodiments, and can be implemented in various forms without changing the gist of the invention. Further, the technical scope of the present invention extends to an equivalent range.

FIG. 1 is an explanatory diagram for explaining the equipment configuration when an apparatus for collecting and releasing a gas according to the present invention is realized as a gas separation apparatus.
The gas separation device according to the present embodiment uses a hydrate containing a quaternary ammonium salt as a guest molecule, separates and collects the gas A from the mixed gas containing the gas A, which is the purpose of collection, It is an apparatus for discharging the collected gas A, and includes a gas collection device 15 and a gas release device 17 as shown in FIG.
The aqueous solution of guest molecules is selected so that a hydrate can be generated by cooling the aqueous solution at a temperature of 15 ° C. or higher in the gas collector 15.

Examples of the aqueous solution of the quaternary ammonium salt selected in this embodiment include an aqueous solution of tetraisopentylammonium bromide (TiPAB) or an aqueous solution of two or more kinds of quaternary ammonium salts containing tetraisopentylammonium bromide. preferable. This is because the tetraisopentylammonium bromide has a harmonic melting point of 30 ° C., and it is easy to adjust the hydrate formation temperature to a temperature of 15 ° C. or higher.
One of the quaternary ammonium salts other than tetraisopentylammonium bromide is preferably tetra-n-butylammonium bromide. Since tetra-n-butylammonium bromide is relatively inexpensive and easy to obtain, by properly blending tetraisopentylammonium bromide and tetra-n-butylammonium bromide, the hydrate formation temperature can be raised to 15 ° C or higher. A method of collecting and releasing a gas that is easy to adjust and economically excellent can be configured.
Hereinafter, the configuration of each device according to the present embodiment will be described in detail.

<Gas collector>
The gas collection device 15 is mixed by mixing an aqueous solution of a quaternary ammonium salt introduced from the gas release device 17 and a mixed gas, cooling at a temperature higher than 15 ° C., and generating a hydrate containing the gas A. Gas A is collected from the gas. The gas collection device 15 has a function of generating a hydrate slurry.
The gas collection device 15 having such a function includes a mixer 9, a hydrate slurry generator 11, and a separator 13 (see FIG. 2).
Hereinafter, each of these devices will be described.

[Mixer]
An aqueous solution of a quaternary ammonium salt (hereinafter sometimes simply referred to as “aqueous solution”) is supplied, and a mixed gas is supplied to the aqueous solution to mix them.
The supply of the mixed gas to the aqueous solution is relative, and this applies to the case where the aqueous solution is discharged toward the mixed gas as well as the case where the gas is discharged toward the aqueous solution. A typical example of the former is bubbling of gas from outside the region to the region where the aqueous solution exists. In that case, the bubble diameter is preferably as small as possible. One aspect of the mixer 9 for realizing this is that the mixer 9 is composed of a tank filled with an aqueous solution and the gas is dispersed in the aqueous solution as fine bubbles. In this case, it is preferable that the bubble diameter is small so that the gas-liquid contact area can be increased.
A typical example in the case of discharging the aqueous solution toward the latter, that is, the mixed gas, is spraying of the aqueous solution from the outside of the region to the region where the gas exists. As an aspect of the mixer 9 for realizing this, there is a type in which an aqueous solution is sprayed by a spray nozzle into a gas-filled container and brought into contact with the gas to dissolve the gas in the aqueous solution.
In both the former and the latter cases, it is preferable that the gas supply to the aqueous solution is performed by a technique for further increasing the contact area between the gas and the aqueous solution.

  After the mixed gas is mixed with the aqueous solution of the quaternary ammonium salt by the mixer, the mixed fluid is sent to the hydrate slurry generator 11 by the pump.

[Hydrate slurry generator]
The hydrate slurry generator has a cooling function, and cools an aqueous solution containing an aqueous solution of a quaternary ammonium salt mixed with a mixer and a mixed gas, and contains gas A and a quaternary ammonium salt as a guest. Inclusion hydrate is produced.

In the hydrate slurry generator, the cooling temperature for cooling the aqueous solution is higher than 15 ° C. That is, the temperature of the slurry to be generated is set to a temperature higher than 15 ° C. If the cooling temperature is set to a temperature higher than 15 ° C., for example, in a season in which the outside air temperature is 15 ° C. or more (for example, spring or summer) in one year, a special cooling device is required for the aqueous solution. Even if it is a case where a cooling device is required, the aqueous solution can be cooled using the thermal energy of the outside air while reducing the operating load of the cooling device.
The hydrate slurry generator is preferably provided with a stirring mechanism.
In the hydrate slurry generator, clathrate hydrate is produced by cooling, and stirring is performed to produce a hydrate slurry in which clathrate hydrate particles are dispersed in an aqueous solution.
Moreover, since supercooling is cancelled | released rapidly by cooling while stirring aqueous solution, a hydrate slurry can be produced | generated efficiently.
Further, in the hydrate slurry generator, there is a remaining portion of the mixed gas that is not collected in the hydrate, but this is separated from the hydrate slurry by the separator 13 described later as the residual gas. The gas is collected from the gas collecting device 15.

[Separator]
The separator 13 receives the supply of the hydrate slurry and the unreacted residual gas from the hydrate slurry generator 11 and separates the unreacted residual gas.
The type of the separator 13 is arbitrary. For example, a cyclone separator or the like can be used. However, in order to minimize the mixing of slurry droplets into the separated residual gas, for example, a collision separation type mist separator is also used. It is desirable to use.

<Gas release device>
The gas release device 17 has a heating function, introduces the hydrate slurry generated by the gas collection device 15, further heats it, melts the hydrate to generate an aqueous solution, and hydrates The gas A collected in the object is released. As a heating function, it is preferable to provide a heat exchanger that supplies and heats a heat medium.
The mixed fluid composed of the gas A and the aqueous solution is introduced into a second separator (not shown), separated into the aqueous solution and the gas A, and the aqueous solution is sent to the gas collecting device 15. The separated gas A is discharged and appropriately stored in a storage tank or the like, or introduced into the next processing process.

FIG. 3 schematically shows the function of each device constituting the gas separation device and the state of the gas, aqueous solution, and slurry passing through each device. Hereinafter, a method of separating the gas A from the mixed gas by the gas separation device configured as described above will be described with reference to FIG.
Gas A, which is the purpose of collection, for example, a mixed gas containing carbon dioxide is introduced into the gas collector 15 (see FIG. 3), mixed with an aqueous solution of a quaternary ammonium salt by a mixer, and the mixed gas is dissolved in the aqueous solution. To do.
After the mixed gas is dissolved in the aqueous solution of the quaternary ammonium salt by the mixer, the mixed fluid is sent to the hydrate slurry generator by a pump. In the hydrate slurry generator, the mixed fluid is cooled at a temperature higher than 15 ° C. to produce an clathrate hydrate containing gas A and a quaternary ammonium salt as a guest. By stirring in the generator, a hydrate slurry in which clathrate hydrate particles are dispersed in an aqueous solution is generated.
The hydrate slurry generated by the hydrate slurry generator and the unreacted residual gas are supplied to the separator, and the hydrate slurry and the unreacted residual gas are separated. When the gas A remains in the residual gas, it is recirculated and used as a mixed gas, for example, until the residual amount becomes a certain amount or less.
The separated hydrate slurry is introduced into the gas release device 17 and heated in the gas release device 17 (see FIG. 3). By this heating, the hydrate melts and the gas A collected in the hydrate is released. When the gas A is released, a mixed fluid composed of the gas A and the aqueous solution exists in the gas release device 17, and this mixed fluid is introduced into a second separator (not shown), and the aqueous solution and the gas A are converted into the aqueous solution and the gas A. To be separated. The separated aqueous solution is sent to a gas collecting device, and the separated gas A is discharged and stored in a storage tank or the like as appropriate, or introduced into the next treatment process.

In the embodiment, by using the above-mentioned aqueous solution of the quaternary ammonium salt, the hydrate formation temperature can be easily adjusted to a temperature of 15 ° C. or more, and the following effects are obtained.
That is, according to the embodiment, since the temperature for cooling the aqueous solution in the gas collecting device 15 is 15 ° C. or higher, for example, in a season in which the outside air temperature is 15 ° C. or higher in one year (for example, spring or summer) The aqueous solution can be cooled using the thermal energy of the outside air while reducing the operating load of the cooling device without requiring a special cooling device or even when a cooling device is required. . This allows for relatively low energy consumption, gas collection that is efficient and economical and thus can withstand more realistic applications.

  In the above embodiment, the mixed gas and the aqueous solution are mixed by the separately provided mixer 9, but the mixed gas is added to the aqueous solution in the hydrate slurry generator 11 by omitting the mixer 9. By supplying, the aqueous solution and the mixed gas may be mixed.

Using the gas collection device and the gas release device shown in FIG. 1, an experiment was conducted to separate the gas from a mixed gas containing a specific gas.
The experimental method, the test aqueous solution used, and the test gas mixture are as follows.

[Gas separation experiment method]
A hydrate slurry generator that also serves as a mixer is filled with an aqueous solution of a quaternary ammonium salt (hereinafter referred to as a test aqueous solution). The mixed gas was introduced into the hydrate slurry generator filled with this aqueous test solution, and the valve provided on the mixed gas supply pipe was closed while the pressure was increased to 0.5 MPa at 30 ° C., and the heat exchange part of the hydrate slurry generator The refrigerant is supplied to the hydrate slurry generator and cooled from 30 ° C. to the test temperature (15 ° C., 20 ° C.) while stirring the liquid phase inside the hydrate slurry generator.
A hydrate containing a quaternary ammonium salt and a gas is generated by cooling, and the pressure inside the hydrate slurry generator is gradually reduced by collecting the gas.
After the pressure drop inside the hydrate slurry generator was completed, the residual gas remaining was extracted from the hydrate slurry generator, and the gas composition of the residual gas was measured by a gas chromatograph. In addition, the hydrate slurry was extracted from the hydrate slurry generator, introduced into the gas discharge device, and the hydrate slurry was melted by heating the hydrate slurry by supplying a heat medium to the heat exchange unit, and collected. The gas is released. Then, the released gas (referred to as recovered gas) was extracted, and the gas composition of the recovered gas was measured by a gas chromatograph.

[Test aqueous solution]
(1) Tetraisopentyl ammonium bromide (TiPAB) 5 wt% aqueous solution (2) Tetraisopentyl ammonium bromide (TiPAB) 2.5 wt% mixed aqueous solution of tetra n butyl ammonium bromide (TBAB) 2.5 wt% (3 ) As a comparative example, a mixed aqueous solution of tetra n-butylammonium bromide (TBAB) 5 wt%

[Test gas mixture]
Mixed gas containing 5% carbon dioxide (for example, mixed gas simulating blast furnace gas)
The separation target gas is carbon dioxide.

The experimental results are shown in Table 1.

As shown in Table 1, tetraisopentylammonium bromide (TiPAB) 5 wt% aqueous solution or tetraisopentylammonium bromide (TiPAB) 2.5 wt% and tetranbutylammonium bromide (TBAB) 2.5 wt% mixed aqueous solution It was confirmed that carbon dioxide can be selectively collected from the mixed gas and concentrated by increasing the concentration of carbon dioxide in the recovered gas by collecting and releasing the target gas.
It was also confirmed that the lower the cooling temperature, the more the target gas can be collected.
On the other hand, when the aqueous solution of tetra n-butylammonium bromide (TBAB) 5 wt% of the comparative example was used, the concentration of carbon dioxide in the recovered gas was slightly higher than the concentration of the test gas mixture before the experiment due to the dissolution of carbon dioxide in the aqueous solution. Although the temperature was higher, under the conditions of cooling temperature of 20 ° C or 15 ° C, tetra n-butylammonium bromide hydrate was not formed, and could the target gas be collected by forming the hydrate? I was not able to confirm clearly whether it was able to collect.

9 Mixer 11 Hydrate Slurry Generator 13 Separator 15 Gas Collector 17 Gas Release Device

Claims (2)

A method of collecting and releasing gas using a hydrate containing a quaternary ammonium salt as a guest molecule,
The aqueous solution of the guest molecule is brought into contact with a gas and cooled at a temperature of 15 ° C. or higher to generate a hydrate that collects the gas, and the hydrate is dispersed or suspended in the aqueous solution or water. A first step of generating a slurry comprising:
The slurry produced in the first step is heated to melt the hydrate therein, thereby releasing the gas collected by the hydrate and producing an aqueous solution of the guest molecule. have a and the second step,
A method for collecting and releasing a gas, wherein the aqueous solution of the guest molecule contains tetraisopentylammonium salt or two or more kinds of quaternary ammonium salts containing tetraisopentylammonium salt as a solute . An apparatus for collecting and releasing gas using a hydrate containing a quaternary ammonium salt as a guest molecule,
The aqueous solution of the guest molecule is brought into contact with a gas and cooled at a temperature of 15 ° C. or more, thereby producing a hydrate that collects the gas, and the hydrate is dispersed or suspended in the aqueous solution or water. A gas collector for producing a slurry,
The slurry generated in the gas collector is heated, the hydrate in the slurry is melted, thereby releasing the gas, and a gas releasing device for generating an aqueous solution of the guest molecule ,
An apparatus for collecting and releasing a gas, wherein the aqueous solution of the guest molecule contains tetraisopentylammonium salt or two or more kinds of quaternary ammonium salts containing tetraisopentylammonium salt as a solute .

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