JP5334279B2 - Gas clathrate production accelerator and gas clathrate production method - Google Patents

Description

  The present invention relates to a gas clathrate production accelerator and a gas clathrate production method.

  As a method of storing gas or a method of transporting gas, a method of storing and transporting gas in the form of clathrate is considered. This method is practical because it can be handled at a lower pressure than the method of compressing, storing and transporting the same volume of gas, and it can be handled at a higher temperature than the method of storing and transporting by liquefaction at low temperature. It is a highly useful method.

  For example, when a large amount of natural gas is transported from a gas field having a large reserve, a method of liquefying natural gas at a low temperature and transporting it by a tanker has been conventionally employed. However, in this method, for example, in a small and small gas field with a small reserve, the construction and operation costs of a plant for liquefying natural gas may not be economically commensurate with the mining amount. On the other hand, the transportation method by clathrate has less economic restrictions such as plant construction and operation costs. Therefore, the transportation by clathrate is superior for small-scale transportation from small and medium gas fields. It can be said that there is.

  As a gas storage method and transportation method using a gas clathrate, for example, natural gas mined in a production area is used as a natural gas clathrate (that is, natural gas clathrate) in a gas clathrate production facility, and this is used as a transport ship. It is transported to storage bases in consuming regions and consuming countries, where it is decomposed again into natural gas and transported as natural gas to small-lot consumers. In this case, the natural gas clathrate produced in the production area may be temporarily stored in a storage facility, and then transported to a consuming area or a consuming country storage base by a transport ship or the like.

  Water is usually used to produce natural gas clathrate. At this time, the water simply generates clathrate and is used for transportation. If the gas is, for example, methane, theoretically the water in 1 kg of methane clathrate is 0.866 kg and the methane is only 0.134 kg, ie 13.4 wt%. In this respect, the same applies to the case of other lower hydrocarbons, carbon dioxide, hydrogen sulfide, halogen, rare gas, and the like. Thus, the proportion of water in the transported goods is very large. Also, in this method, the speed at which the natural gas clathrate is produced has an important effect on the economy.

  Here, a lower hydrocarbon clathrate will be described as an example. For example, methane clathrate has a three-dimensional network structure made of water molecules, that is, a structure in which methane molecules are incorporated in a cage structure. This is produced when water and methane coexist in a low temperature and high pressure state, and the property is a solid material such as a sherbet or snow. However, the lower hydrocarbon clathrate is an unstable substance and has a tendency to gradually decompose. To avoid this decomposition, it is necessary to maintain a low temperature state, a pressurized state, or a low temperature and a pressurized state. .

  In general, when a gas is made into a clathrate, it is necessary to make sufficient contact between water and gas under conditions of temperature and pressure at which the gas clathrate can be generated, but the temperature and pressure at which the clathrate can be generated. Various types of production promoters that relax the conditions have been proposed.

  Japanese Patent Laid-Open No. 4-316795 describes the use of, for example, fatty amines as hydrate formation accelerators when natural gas is converted into hydrates and stored. It is described that, for example, fatty amines are used as hydrate formation accelerators when BOG (Boil Off Gas) is converted into hydrates and stored in gas satellite bases.

  Japanese Patent Application Laid-Open No. 6-17069 describes that a cyclic compound having 2 to 6 carbon atoms and having an alcohol group, a carbonyl group, an ether group or an ester group as a functional group is used to stabilize a hydrocarbon hydrate. In JP-A-9-49600, ketones such as acetone and aliphatic amines are used as hydration accelerators when converting natural gas from a high-pressure pipeline into hydrates when demand is low. It is described.

  By such various hydrate formation accelerators, clathrate is generated under a milder temperature and pressure condition. In addition, in Tokuharu Okui, Journal of Petroleum Technology Association, Vol. 66, No. 2, p.168-174 (March 2001) “Expectation for gas hydrate transport technology” Tetrahydrofuran and 1,4-dioxane are disclosed as agents.

Japanese Patent Laid-Open No. 4-316795 JP-A-4-316797 JP-A-6-17069 JP-A-9-49600 Tomoharu Okui Journal of Petroleum Technology of Japan, Vol. 66, No. 2, p. 168-174 (March 2001) “Expectations for Gas Hydrate Transportation Technology”

  These clathrate formation accelerators are known to stabilize the cage structure when the formation accelerator itself enters the cage structure of the water molecule of the clathrate, and to produce clathrate under milder temperature and pressure conditions. It has been.

  In order to promote the generation of the gas clathrate, in addition to generating the gas clathrate at a milder temperature and pressure condition, it is also necessary to increase the generation rate of the clathrate. For this reason, various types of production accelerators that produce a clathrate faster have been proposed. For example, Japanese Patent Application Laid-Open No. 10-216505 discloses a silicone resin-containing surfactant as an accelerator that generates clathrate more quickly, and by using the silicone resin-containing surfactant, contact between gas and water is promoted. And is supposed to generate class rates faster. Japanese Patent Application Laid-Open No. 2002-60428 discloses a polymer obtained by polymerizing or copolymerizing a specific vinyl monomer. Japanese Patent Application Laid-Open No. 2003-105361 discloses a gel polymer containing a hydrophilic monomer unit and / or an amphiphilic monomer unit as a kinetic production promoter, and this production promoter is preferably an alkyl (meth) acrylate. And alkyl (meth) acrylamides. Japanese Patent Application Laid-Open No. 2004-115613 discloses salicylate as a kinetic production accelerator. By these production accelerators, the production of clathrate is promoted kinetically, and the produced clathrate is also stabilized as it is.

JP-A-10-216505 JP 2002-60428 A JP 2003-105361 A JP 2004-115613 A

  In addition to the above various clathrate production accelerators, Table 1 summarizes <materials for stabilizing the clathrate after clathrate production> described below, although it does not promote clathrate production. A part of the display is omitted due to the space in Table 1.

<Material to stabilize the clathrate after the clathrate is generated>
A material that stabilizes the clathrate has been developed, although the production is inhibited when the clathrate is generated. JP-A No. 2001-164276 describes a polymer obtained by copolymerizing the compounds shown in the publication column in Table 1, and JP-A No. 2001-139966 discloses three kinds of polymers shown in the publication column in Table 1. JP-A-2001-139965 describes a polymer obtained by copolymerizing two or more of the compounds, and JP-A-2001-139965 discloses that at least two or more of the monomers having a water / octanol distribution coefficient in the range of 0.5 to 1.5 are copolymerized. Polymerized polymers are described. These materials inhibit the generation when the clathrate is generated, and once the clathrate is generated, there is an effect of delaying the decomposition, that is, a stabilizing effect.

JP 2001-164276 A JP 2001-139966 A JP 2001-139965 A

  Japanese Patent Application Laid-Open No. 2002-60428 describes a polymer obtained by (co) polymerizing the vinyl monomers shown in the above-mentioned publication column in Table 1, and the vinyl monomer is particularly tetrahydrofurfuryl (meta). ) Acrylate, tetrahydrofurfuryl (meth) acrylamide and the like are preferred. Japanese Patent Application Laid-Open No. 2003-321689 discloses crosslinked polystyrene, and in the examples, crosslinked polystyrene beads are used. These materials are believed to inhibit kinetics during clathrate production and once the clathrate is produced, stabilize the clathrate, both kinetically and under temperature and pressure conditions (both in equilibrium). ing.

  Further, JP-A-2003-105361 discloses a hydrophilic monomer unit and / or an amphiphilic monomer unit as a material that accelerates the generation of clathrate and stabilizes it once the clathrate is generated and makes it difficult to decompose. A gel-like polymer containing is disclosed. The hydrophilic monomers are particularly preferably N- (meth) acrylamide and N-methyl (meth) acrylamide, and the amphiphilic monomers are particularly preferably N-ethyl (meth) acrylamide and N-methyl (meth) acrylamide. ing.

JP 2002-60428 A JP 2003-321689 A JP 2003-105361 A

  Among these production accelerators, ketones such as acetone and aliphatic amines, cyclic compounds having 2 to 6 carbon atoms and having an alcohol group, carbonyl group, ether group or ester group as a functional group, tetrahydrofuran, 1, 4 -Since the production promoters such as dioxane are contained in the clathrate cage structure, the ratio of gas entering the cage structure is low, and the storage performance is low.

  In addition, although silicone resin-containing surfactants and salicylates have a kinetic generation promoting effect, the equilibrium conditions of clathrate change to higher temperature and lower pressure, that is, temperature and pressure conditions necessary for clathrate generation. The temperature does not change to higher temperature and lower pressure side to promote the generation of clathrate, and the temperature and pressure conditions of conventional clathrate generation, that is, low temperature state, pressurized state, low temperature state, low temperature state and pressurization It is necessary to be in a state.

  Furthermore, gel polymers containing hydrophilic monomer units and / or amphiphilic monomer units are stabilized once the gas clathrate is formed, and the decomposition of the clathrate is suppressed. It acts to inhibit production. Therefore, when the gas is, for example, methane, it is disadvantageous when the clathrate is generated for the purpose of storage and transportation. In addition, a polymer obtained by polymerizing or copolymerizing a specific vinyl monomer is a substance obtained by polymerizing a compound of acrylates or acrylamides, and there is a concern about influence on the environment or carcinogenicity.

  In light of the above-mentioned problems in storing and transporting gas as clathrate, the present inventors have conducted extensive experiments and research. As a result, surfactants are effective as gas clathrate production accelerators. Thus, the inventors have found the present invention.

  That is, the present invention aims to provide a gas clathrate production accelerator comprising a surfactant (that is, an agent that promotes the production of gas clathrate), and a gas clathrate that uses this production accelerator. The object is to provide a manufacturing method.

  The present invention is (1) a gas clathrate production accelerator from gas and water, wherein the accelerator comprises a nonionic surfactant.

  The present invention is (2) a gas clathrate production accelerator from gas and water, wherein the accelerator comprises an anionic surfactant.

  The present invention is (3) a gas clathrate production accelerator from gas and water, wherein the accelerator comprises a cationic surfactant.

  The present invention is (4) a gas clathrate production promoter from gas and water, wherein the promoter comprises an amphoteric surfactant.

  In the present invention, (5) when a gas clathrate is produced from gas and water, a gas clathrate is produced at a higher temperature and a lower pressure side by using a nonionic surfactant as a gas clathrate production accelerator. This is a method for generating a gas clathrate.

  In the present invention, (6) when generating a gas clathrate from gas and water, an anionic surfactant is used as a gas clathrate generation accelerator, thereby generating a gas clathrate at a higher temperature and a lower pressure side. This is a method for generating a gas clathrate.

  According to the present invention, (7) when a gas clathrate is produced from gas and water, a gas clathrate is produced at a higher temperature and a lower pressure side by using a cationic surfactant as a gas clathrate production accelerator. This is a method for generating a gas clathrate.

  According to the present invention, (8) when a gas clathrate is produced from gas and water, an amphoteric surfactant is used as a gas clathrate production accelerator to produce a gas clathrate at a higher temperature and a lower pressure side. This is a characteristic gas clathrate generation method.

  The present invention (1) is a gas clathrate production accelerator from gas and water, wherein the accelerator comprises a nonionic surfactant. Preferred examples of the nonionic surfactant include an ether type nonionic surfactant, an oxyethylene chain / oxypropylene chain addition type nonionic surfactant, or a hydroxyl group-containing type nonionic surfactant. However, it is not limited to these. This also applies to the nonionic surfactant used in the gas clathrate production method of the present invention (5).

  The present invention (2) is a gas clathrate production accelerator from gas and water, wherein the accelerator comprises an anionic surfactant. Preferred examples of the anionic surfactant include a sulfate ester type anionic surfactant, a sulfonic acid type anionic surfactant, a polymerization type anionic surfactant, and a condensation polymerization type anionic surfactant. However, it is not limited to these. This also applies to the anionic surfactant used in the gas clathrate production method of the present invention (6).

  The present invention (3) is a gas clathrate production accelerator from gas and water, wherein the accelerator comprises a cationic surfactant. Preferable examples of the cationic surfactant include, but are not limited to, quaternary ammonium type cationic surfactants. The same applies to the cationic surfactant used in the gas clathrate production method of the present invention (7).

  The present invention (4) is a gas clathrate production accelerator from gas and water, wherein the accelerator comprises an amphoteric surfactant. Preferable examples of the amphoteric surfactant include amine oxide type amphoteric surfactants, but are not limited thereto. The same applies to the amphoteric surfactant used in the gas clathrate production method of the present invention (8).

  Table 2 shows the surfactants that are gas clathrate production accelerators in the present invention (1)-(4) and the gas clathrate production accelerator in the gas clathrate production method of the present invention (5)-(8). Each surfactant to be used is classified and shown, and in Table 2, specific examples are illustrated for each type of surfactant shown as a classification (medium classification).

  As shown in Table 1 above, in the conventional gas clathrate production technology, there is no technology that uses a surfactant as the production accelerator, and even in this respect, the gas clathrate comprising the surfactant according to the present invention is not used. It can be said that the production accelerator is different from conventional additives.

  In general, surfactants are classified into nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, nitrogen-containing surfactants, silicone surfactants, and fluorosurfactants. However, in the present invention, nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants are used as the clathrate formation accelerator, and the above-mentioned JP-A-10-216505 is used. This is different from the silicone resin-containing surfactant disclosed in the publication.

  In the present invention, the use of a nonionic surfactant, an anionic surfactant, a cationic surfactant, or an amphoteric surfactant as a gas clathrate production accelerator from gas and water makes it possible to stabilize the clathrate. It is possible to shift the temperature and pressure conditions necessary for the conversion to higher temperature and lower pressure.

  In addition, the gas clathrate production accelerator of the present invention does not deteriorate storage performance, impede its production at the time of clathrate production or have toxicity, which is a problem in the prior art. Since the surfactant used in the present invention is water-soluble, it is not necessary to handle a solid or gel substance.

  The clathrate production accelerator comprising the surfactant of the present invention includes water, at least one lower hydrocarbon selected from methane, ethane, ethylene, propane and butane, a mixed gas thereof, carbon dioxide gas, hydrogen sulfide, Effective and used to produce clathrates of these gases from halogens or noble gases.

  Examples of the present invention will be described below including experiments that have led to the present invention. In this embodiment, methane is described as an example, but the same applies to other gases.

  The measurement of the pressure and temperature conditions at which the methane clathrate was produced was in accordance with the operating method disclosed in “Clathlate Hydrate of Natural Gases” 2nd Ed. P.297 (1998) Marcel Dekker, Inc. by E.D.Sloan.

  The production vessel shown in FIG. 1, that is, the high-pressure cell, was charged with 500 cc of an accelerator solution, the cell temperature was set to 20 ° C., and the gas in the cell and piping was purged. In the purge operation, nitrogen gas was sealed, the inside of the cell was temporarily set to 1 MPa, and the pressure was further reduced twice. After purging, the inside of the cell was once set to 1 MPa with methane, which is a gas that generates clathrate, and the operation of further reducing the pressure was repeated twice, and then the pressure was adjusted to a range of 7 MPa to 12 MPa. The reason why the inside of the cell is once pressurized to 1 MPa with methane and then depressurized is to purge the nitrogen gas remaining in the cell or the piping with methane at the time of purging.

  After pressurizing the cell in the range of 7 MPa to 12 MPa, the temperature in the cell was lowered from 20 ° C. at a rate of 4 ° C./h while stirring in the cell. When the temperature in the cell was lowered to some extent, methane clathrate began to form in the cell, and the pressure in the cell decreased. When the decrease in the pressure in the cell was confirmed, the temperature in the cell was increased at a rate of 1 ° C./h. As the temperature increased, the clathrate in the cell decomposed and the pressure in the cell increased. When the clathrate in the cell was completely decomposed, the pressure in the cell returned to the state before clathrate generation at that temperature. This state becomes an equilibrium condition for the generation of the clathrate.

  FIG. 2 schematically shows the temperature and pressure of the experimental system in the above measurement method. The portion surrounded by a circle in the figure is a portion indicated as an equilibrium point. In general, this temperature and pressure condition is called an equilibrium point, and a plurality of equilibrium points illustrated is called an equilibrium curve.

  The aqueous solution of various surfactants used in the present invention is liquid, and can be easily stirred in a high-pressure cell together with methane due to the apparatus configuration. In addition, any surfactant used in the present invention has no problem with respect to carcinogenicity and influence on the environment and is safe, and is much smaller than conventional acrylamides and the like.

  Further, as is clear from the structural formulas of various surfactants shown in Table 2, these surfactants have such a large molecular size that they cannot enter the water cage forming the clathrate. Therefore, these surfactants do not enter the water basket in the formed clathrate, but are present around the outer periphery of the water basket. For this reason, unlike materials such as aliphatic amines, cyclic carbons, and ketones, the storage performance of methane does not deteriorate.

<Description of the fact that the production accelerator according to the present invention does not enter the cage structure of the production clathrate>
Here, it will be described that the production accelerator does not enter the gas clathrate cage structure formed by using the production accelerator comprising the surfactant in the present invention, and the gas storage amount does not decrease.

  FIG. 3 shows changes in temperature and pressure when a 0.1 wt% aqueous solution of alkylpolyglucoside is added, and FIG. 4 shows changes in temperature and pressure when only distilled water is used. The alkylpolyglucoside corresponds to the nonionic surfactant used in Example 4 described later.

As shown in FIG. 3, in the case of the alkyl polyglucoside aqueous solution, the pressure decreased from 7.24 MPa to 3.90 MPa and changed by 3.34 (= 7.24-3.90) MPa when the clathrate was produced. This is because the gas corresponding to the reduced pressure has become clathrate.
On the other hand, as shown in FIG. 4, in the case of distilled water, the pressure decreased from 7.10 MPa to 4.00 MPa and changed by 3.10 (= 7.10−4.00) MPa.

  That is, the pressure decrease amount is about 3 MPa in both cases of an aqueous solution of alkylpolyglucoside as a surfactant and distilled water. Thus, it can be seen that even when a surfactant is used, the surfactant does not enter the clathrate cage structure, and the amount of gas to be clathrated is substantially the same and does not decrease.

  Further, the production accelerator comprising the surfactant of the present invention stabilizes the cage structure by interacting with the cage structure from the outside after clathrate production, so that the decomposition of the produced clathrate is prevented and stabilized. There is also an effect.

<Example 1>
FIG. 5 shows an equilibrium curve obtained by the above-described measurement method when a 0.1 wt% aqueous solution of polyoxyethylene isodecyl ale, which is a nonionic surfactant, is used as an additive. There is a value called HLB (Hydrophile-Lipophile Balance) as the degree of expressing the hydrophilicity of the nonionic surfactant, and this value is obtained by the following formula.

  In this example, an aqueous solution of polyoxyethylene isodecyl ale having an HLB of 12.3 to 15.5 was used. FIG. 5 also shows an equilibrium curve of distilled water as a comparative example. From the results of FIG. 5, it was found that the equilibrium point changed to higher temperature and lower pressure side by this surfactant.

<Example 2>
FIG. 6 shows an equilibrium curve obtained by the above-described measurement method when a 0.1 wt% aqueous solution of polyoxyalkylene decyl ale, which is a nonionic surfactant, is used as an additive. In this example, an aqueous polyoxyalkylene decyl ale solution having an HLB of 13.2 to 16.3 was used. An equilibrium curve of distilled water is also shown as a comparative example. From the results of FIG. 6, it was found that the equilibrium point changed to higher temperature and lower pressure by this surfactant.

<Example 3>
FIG. 7 shows an equilibrium curve according to the above-described measurement method when a 0.1 wt% aqueous solution and a 10 wt% aqueous solution of polyoxyethylene tridecyl ale, which is a nonionic surfactant, are used as additives. An equilibrium curve of distilled water is also shown as a comparative example.

  In this example, a polyoxyethylene tridecyl ale aqueous solution having an HLB of 13.3 to 13.8 was used. From the results of FIG. 7, it was found that the equilibrium point changed to a higher temperature and a lower pressure side by the nonionic surfactant. Moreover, the critical micelle concentration of this nonionic surfactant is about 0.005 wt% at room temperature, and the concentration of this example is well above the critical micelle concentration. That is, it was found that the non-ionic surfactant aqueous solution exceeding the critical micelle concentration has the same effect of promoting clathrate formation.

<Example 4>
In FIG. 8, 0.1 wt% aqueous solution of polyoxyethylene polyoxypropylene block polymer which is a nonionic surfactant and 0.1 wt% aqueous solution of alkyl polyglucoside which is also a nonionic surfactant are added. The equilibrium curve by the above-mentioned measuring method is shown.

  In this example, an aqueous solution of a polyoxyethylene polyoxypropylene block polymer (nonionic surfactant) having an average molecular weight of 2000 and an ethylene oxide chain of 50% was used. An equilibrium curve of distilled water is also shown as a comparative example. From the result of FIG. 8, it was found that the equilibrium point changed to a higher temperature and a lower pressure side by this nonionic surfactant.

<Example 5>
In FIG. 9, an anionic surfactant, an aqueous solution of ammonium polyacrylate, an aqueous solution of sodium polyoxyethylene tridecyl ether sulfate, an aqueous solution of linear sodium dodecylbenzenesulfonate, and an aqueous solution of sodium formalin condensate of naphthalenesulfonate are added. The equilibrium curve by the above-mentioned measuring method is shown.

  In this example, a 2.0 wt% aqueous solution was used in all cases. An equilibrium curve of distilled water is also shown as a comparative example. From the results of FIG. 9, it was found that the equilibrium point changes to a higher temperature and a lower pressure side even with an anionic surfactant.

<Example 6>
FIG. 10 shows an equilibrium curve obtained by the above-described measurement method in the case where an aqueous solution of lauryldimethylamine oxide, which is an amphoteric surfactant, is used as an additive.

  In this example, a 2.0 wt% aqueous solution was used. FIG. 8 also shows an equilibrium curve of distilled water as a comparative example. From the results of FIG. 10, it was found that the equilibrium point changes to the higher temperature and lower pressure side even with the amphoteric surfactant.

<Example 7>
FIG. 11 shows an equilibrium curve according to the above-described measurement method when an alkyltrimethylammonium chloride aqueous solution, which is a cationic surfactant, is used as an additive.

  In this example, a 2.0 wt% aqueous solution was used. An equilibrium curve of distilled water is also shown as a comparative example. From the result of FIG. 11, it was found that the equilibrium point changes to a higher temperature and a lower pressure side even with the cationic surfactant.

  As described above, according to the present invention, the conditions for generating the gas clathrate can be increased at a higher temperature by any of the nonionic surfactants, anionic surfactants, amphoteric surfactants, and cationic surfactants. It is possible to shift to the low pressure side and to delay and stabilize the decomposition of the product gas clathrate.

Diagram showing the test equipment used for the clathrate generation rate test Diagram showing temperature and pressure as conditions for clathrate generation The figure explaining the positional relationship between the clathrate cage structure and the production accelerator according to the present invention The figure which shows the equilibrium point in the case of only distilled water compared with FIG. The figure which shows the equilibrium curve in Example 1 The figure which shows the equilibrium curve in Example 2 The figure which shows the equilibrium curve in Example 3 The figure which shows the equilibrium curve in Example 4 The figure which shows the equilibrium curve in Example 5 The figure which shows the equilibrium curve in Example 6 The figure which shows the equilibrium curve in Example 7

Claims (2)

A gas clathrate production promoter from gas and water, wherein the promoter comprises an amine oxide type amphoteric surfactant. When generating a gas clathrate from gas and water, an amine oxide type amphoteric surfactant is used as a gas clathrate generation accelerator, thereby generating a gas clathrate at a higher temperature and a lower pressure side. Gas clathrate generation method.

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