JP3546704B2 - Gas storage method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for storing a gas such as natural gas by adsorption.
[0002]
[Prior art]
When storing a gas such as natural gas, it is important to store a low-density gas at a high density and efficiently under normal temperature and normal pressure. Among natural gas components, butane and the like can be liquefied at normal temperature by pressurizing at a relatively low pressure (CNG: compressed natural gas), but methane and the like are difficult to liquefy under pressure at normal temperature.
[0003]
Conventionally, as a method of storing a gas that is difficult to liquefy under pressure at around normal temperature, a method of liquefying while maintaining the temperature at an extremely low temperature, such as LNG (liquid natural gas), has been used. In this gas liquefaction method, a volume 600 times the normal temperature and normal pressure can be stored. However, in the case of LNG, for example, it is necessary to maintain the temperature at an extremely low temperature of -163 ° C. or lower, and both the equipment cost and the operation cost must be high.
[0004]
On the other hand, a method (ANG: absorbed natural gas) of storing gas by adsorption without using any special pressurization or cryogenic temperature is being studied.
JP-A-9-210295 proposes a storage method in which a gas such as methane or ethane is adsorbed on a porous material such as activated carbon at about room temperature in the presence of a host compound such as water. It is described that a large amount of gas can be stored by the synergistic effect of the adsorption capacity and pseudo high pressure effect of the compound and the formation of an inclusion compound by the host compound.
[0005]
However, even the method proposed above has not yet achieved a storage density that can be substituted for a storage method using cryogenic temperature such as LNG.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a gas storage method capable of realizing an extremely high storage density by adsorption without using an extremely low temperature.
[0007]
[Means for Solving the Problems]
According to the present invention, according to the present invention, the storage target gas and the adsorbent are maintained at a temperature lower than the liquefaction temperature of the storage target gas in the container, so that the storage target gas is liquefied and adsorbed by the adsorbent. The process of
By introducing a gaseous or liquid medium having a freezing temperature higher than the liquefaction temperature of the storage target gas into the container maintained at the low temperature and freezing the medium, the liquefied and adsorbent material is liquefied. The storage target gas that is adsorbed to the, the step of containing the frozen medium, and the container, the step of maintaining a temperature higher than the liquefaction temperature and lower than the freezing temperature,
Is achieved by a gas storage method comprising:
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, once liquefied by cryogenic temperature, the liquefied gas can be frozen and stored at a temperature higher than the cryogenic temperature required for the liquefaction by enclosing the liquefied gas with a freezing medium.
As the freezing medium, one that is gaseous or liquid, has a freezing temperature higher than the liquefaction temperature of the storage target gas, and does not react with the storage target gas, the adsorbent, the container, or the like at the storage temperature is used.
[0009]
By using a medium having a freezing temperature (melting point, sublimation point) close to room temperature, it is possible to realize storage that maintains high density at extremely low temperatures near room temperature.
Among such media, for example, those having a freezing temperature (generally "melting point") in the range of −20 ° C. to + 20 ° C. include water (Tm = 0 ° C.), dodecane (−9.6 ° C.), and phthalic acid. Representative examples include dimethyl acid (0 ° C), diethyl phthalate (-3 ° C), cyclohexane (6.5 ° C), and dimethyl carbonate (0.5 ° C).
[0010]
As the adsorbent, a conventional gas adsorbent can be used. Typically, any of inorganic or organic adsorbents such as activated carbon, zeolite, and silica gel may be used.
The storage target gas may be any gas that can be liquefied and adsorbed at a very low temperature, such as conventional LNG or liquid nitrogen, and can be applied to gases such as hydrogen, helium, nitrogen, and hydrocarbons. Typical examples of the hydrocarbon gas include methane, ethane, propane and the like.
[0011]
【Example】
[Example 1]
Using the apparatus having the configuration shown in FIG. 1, methane gas according to the present invention was stored in the following procedure.
First, 5 g of activated carbon powder (particle size: about 3 to 5 mm) was charged into a sample capsule (capacity: 10 cc) having an airtight structure, and the pressure in the capsule was reduced to 1 × 10 ⁻⁶ MPa by a rotary pump.
[0012]
Thereafter, methane was introduced into the capsule from a methane cylinder to adjust the pressure in the capsule to 0.5 MPa.
The capsule in this state was immersed in liquid nitrogen filled in a Dewar bin and kept at the liquid nitrogen temperature (-196 ° C) for 20 minutes. Thereby, all the methane gas in the capsule is liquefied and adsorbed on the activated carbon.
[0013]
Subsequently, the capsule was maintained in a state of being immersed in liquid nitrogen, and steam (temperature: 20 to 60 ° C.) generated from the water reservoir was introduced into the capsule. As a result, the water vapor immediately freezes at the liquid nitrogen temperature to become ice, and the liquefied and adsorbed methane gas is frozen and sealed in the ice.
As a comparative example, the steps up to liquefaction and adsorption of methane were performed in the same procedure as in Example 1, but thereafter no steam was introduced.
[0014]
FIG. 2 shows the desorption behavior of methane when the capsule temperature is naturally raised to room temperature from the methane storage state according to Example 1 and the comparative example. In the figure, the temperature on the horizontal axis and the pressure on the vertical axis are the temperature and pressure in the capsule, respectively, measured by the thermocouple and the pressure gauge in FIG.
<Adsorption and liquefaction process: common to Example 1 and Comparative Example (indicated by ● in FIG. 2)>
When the capsule after the introduction of methane is immersed in liquid nitrogen, adsorption proceeds with the temperature drop inside the capsule, and the pressure inside the capsule decreases linearly. It becomes 0 MPa, and reaches liquid nitrogen temperature -196 ° C as it is.
<Desorption process: Comparison between Example 1 and Comparative Example>
In the case of the comparative example in which water vapor was not introduced after the temperature of the liquid nitrogen was reached (indicated by a circle in FIG. 2), the capsule was taken out of the liquid nitrogen and the temperature was raised. Methane desorption begins and the pressure starts to rise.
[0015]
On the other hand, in the embodiment in which water vapor is introduced and frozen and confined by the present invention after reaching the temperature of liquid nitrogen (◇ in FIG. 2), desorption detected as an increase in pressure value is −50 ° C. It can be seen that the temperature rise has progressed to this point, and even under 0 ° C., a considerable portion of methane is maintained in an adsorbed state without being desorbed.
[Example 2]
After the liquid nitrogen temperature was reached, gas storage according to the present invention was performed in the same procedure as in Example 1 except that liquid water was introduced into the capsule from the water reservoir instead of water vapor.
[0016]
As a result, the same desorption behavior as in Example 1 shown in FIG. 2 was observed, and the low pressure was maintained at around 0 ° C.
[0017]
【The invention's effect】
As described above, according to the present invention, a gas storage method capable of realizing an extremely high storage density by adsorption without using an extremely low temperature is provided.
According to the method of the present invention, since the storage temperature does not need to be extremely low, it is possible to sufficiently store even a normal refrigerator operated at about −10 to 20 ° C., and the equipment cost and the operating cost for storage are sufficient. Can be reduced in cost.
[0018]
Further, the storage container and other equipment do not need to be made of a special material for cryogenic use, which is advantageous in terms of equipment material cost.
[Brief description of the drawings]
FIG. 1 is a layout diagram showing a configuration example of an apparatus for performing a gas storage method according to the present invention.
FIG. 2 is a graph showing the desorption behavior of a methane gas adsorbed and liquefied at a cryogenic temperature due to a rise in temperature of a sample of the present invention and a comparative example.

Claims (1)

In the container, by keeping the storage target gas and the adsorbent at a temperature lower than the liquefaction temperature of the storage target gas, liquefying the storage target gas and adsorbing the adsorbent on the adsorbent,
By introducing a gaseous or liquid medium having a freezing temperature higher than the liquefaction temperature of the storage target gas into the container maintained at the low temperature and freezing the medium, the liquefied and adsorbent material is liquefied. The storage target gas that is adsorbed to the, the step of containing the frozen medium, and the container, the step of maintaining a temperature higher than the liquefaction temperature and lower than the freezing temperature,
A gas storage method including:

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