JP2008291885A - Natural gas storage tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform excellent storage of natural gas by suppressing separation/coagulation of components of the natural gas. <P>SOLUTION: A ratio (p:q), an area p of an inner cross section of a connection part of an NG flow pipe 11 connected to a gas reservoir for storing the natural gas and the largest area q of an inner cross section of the NG gas reservoir 12, is set to be 1:255-1:64. A natural gas adsorbent for adsorbing the natural gas is stored in the gas reservoir. Further, the reservoir is provided with a temperature-raising means for preventing decrease in temperature at the time of supplying the gas. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a natural gas storage tank suitable for storing and discharging natural gas.

  Conventionally, when storing natural gas, a method of compressing natural gas and filling it in a cylinder or using a material that adsorbs natural gas or the like has been widely used.

  However, since the cylinder has a large wall thickness for a large volume, its internal capacity is small and its weight is large. Therefore, studies on storage techniques using chemical or physical methods such as adsorption have been actively conducted. Such a storage technique can reduce the size and weight of storage tanks and devices, and is expected in applications such as in-vehicle use that are limited by the arrangement space.

In connection with the above, a vehicular compressed natural gas tank is disclosed comprising an elongate tubular member wound in a single plane about a central axis perpendicular to the plane formed by the longitudinal axis of the side wall (e.g., a patent). Reference 1).
Mito No. 3036588

  However, natural gas generally contains heavy components such as propane and butane in addition to methane, which is the main component, and these heavy components are usually in a mixed gas state with methane, but they are separated for some reason. Then, it is difficult to return to the mixed gas state again, and the storage performance of the material for storing natural gas is impaired. For example, in an adsorbent having pores that serve as adsorption sites for natural gas adsorption, heavy components after separation tend to aggregate in the pores, and when aggregated, the pores are blocked to obtain the original storage performance. I can't.

  For example, when natural gas is filled into a high-pressure tank or the like, if the natural gas is introduced into a high-pressure tank or the like having a larger volume than the gas pipe that circulates the natural gas, the gas temperature rapidly decreases due to rapid adiabatic expansion. Heavy components are separated from the mixed gas and agglomerated. This agglomeration is likely to occur inside the adsorbent and the like. For example, if agglomeration occurs in pores that contribute to the chemical or physical adsorption of the adsorbent, the pores are blocked and gas inflow into the adsorbent is hindered. Once agglomeration occurs, agglomeration is likely to occur along with this and is aggravated by this repetition. Therefore, as the filling and releasing of natural gas are repeated, the storage amount gradually decreases, and the amount of gas that can be used in one filling (release amount) also decreases.

  Thus, although chemical or physical methods such as adsorption are considered useful, it is the actual situation that the merit of storing by such a method is not obtained.

  The present invention has been made in view of the above, and an object of the present invention is to provide a natural gas storage tank capable of satisfactorily storing natural gas while suppressing component separation and aggregation from natural gas. The challenge is to achieve.

  In the present invention, natural gas is supplied from a pipe into a container with a large volume, such as propane, butane, etc. mixed in natural gas because cooling by adiabatic expansion is large in a supply system with rapid adiabatic expansion. Based on this knowledge, we have obtained the knowledge that the heavy components of the material are separated, and thus cause aggregation, thereby reducing the storage sites such as the pores of the storage material and reducing the storage / release efficiency and the storage / release amount. It has been achieved.

  In order to achieve the above object, a natural gas storage tank according to the first aspect of the present invention includes an area p of an inner cross section at a connection portion of a gas flow pipe connected to a gas storage container for storing natural gas, The ratio (p: q) with the maximum area q of the inner cross section orthogonal to the gas flow direction expanded in the gas flow direction from the connecting portion of the gas storage container is in the range of 1: 225 to 1:64. It is a thing.

  In the first invention, the ratio of the cross-sectional area of each inner cross section perpendicular to the gas flow direction between the gas flow tube for flowing natural gas and the gas storage container to which natural gas is supplied from the gas flow tube ( p: q), the area p of the inner cross section at the connection portion of the gas flow pipe connected to the gas storage container is expanded in the gas flow direction from the connection portion with the gas flow pipe of the gas storage container. By setting the area ratio (p: q) of both inner cross sections within the range of 1: 225 to 1:64 so that the maximum area q of the inner cross section orthogonal to the gas flow direction does not become too large, The temperature drop due to adiabatic expansion when flowing into the gas storage container from the gas distribution pipe is suppressed, the separation and aggregation of heavy components such as propane and butane from natural gas are suppressed, and the gas storage characteristics in the gas storage container (especially Natural gas storage / release and It is possible to reduce the deterioration of the warehouse / emission efficiency).

  This is particularly effective when an adsorbent (such as a carbon material such as carbon nanotube) having pores serving as natural gas adsorption sites is accommodated in the gas storage container. As described above, it is possible to avoid a decrease in adsorption sites due to the blockage of pores that are adsorption sites due to agglomeration of heavy components such as butane in natural gas. The gas storage / release performance can be maintained for a long time without significantly reducing the storage / release amount.

  The natural gas storage tank according to the second aspect of the present invention has at least one pipe wall between the one end of the gas flow pipe connected to the gas storage container with one end projecting inward from the container wall to the gas storage container. A ratio (r: s) between the total area r of the holes and the maximum area s of the inner cross section orthogonal to the gas flow direction expanded from the connection part of the gas storage container in the gas flow direction. It is configured to be 1: 225 to 1:64.

  In the second invention, paying attention to the ratio between the opening size of the hole for discharging the natural gas and the size of the gas storage container to which the natural gas is supplied from this hole, the gas distribution pipe for circulating the natural gas is provided. The maximum area s of the inner cross section perpendicular to the gas flow direction expanded in the gas flow direction from the connecting portion of the gas storage container to the gas flow pipe with respect to the total area r of the holes formed is not too large. By setting the area ratio (r: s) of the total area r and the maximum area s within the range of 1: 225 to 1:64, the temperature due to adiabatic expansion when natural gas flows into the gas storage container from the gas circulation pipe It is possible to suppress the degradation, suppress the separation and agglomeration of heavy components such as propane and butane from natural gas, and the characteristics of gas storage in gas storage containers (especially the storage / release amount and storage / release efficiency of natural gas) ) It is possible.

Further, the gas flow pipe in the second invention can be provided with a plurality of holes, and in the case of providing a plurality of holes, it is most at one end which is a protruding end protruding inward from the wall of the gas storage container. The ratio (s ¹ : s ⁿ ) between the area s ¹ of the near hole and the area s ⁿ (n> 2) of the furthest hole, that is, the hole closest to the vessel wall (connection portion) is 2: 1 to 3: It can suppress more effectively the temperature fall by adiabatic expansion when natural gas flows in into a gas storage container that it is 1.
Similar to the first invention, this is particularly effective when an adsorbent (carbon material such as carbon nanotube) having pores that become natural gas adsorption sites is accommodated in the gas storage container.

  The natural gas storage tank according to the first and second inventions can be provided with a temperature raising means for raising the temperature of the natural gas supplied from the gas distribution pipe to the gas storage container. When supplying natural gas to the gas storage container, the temperature of the supplied natural gas is heated by the temperature raising means so as not to be greatly reduced by adiabatic expansion at the time of supply. Separation and aggregation of heavy components in the gas can be suppressed. Suppression of aggregation reduces reduction in gas storage characteristics (especially natural gas storage / release amount and storage / release efficiency) such as adsorbents such as carbon nanotubes and other adsorbents, which have pores that become adsorption sites. be able to.

  The heating of the natural gas by the temperature raising means is performed so as to be raised to a temperature of 50 ° C. or more from the viewpoint of more effectively preventing separation and aggregation of heavy components generated by cooling accompanying adiabatic expansion. desirable.

  The natural gas storage tank of the present invention is generally constructed to have a structure in which an elongated tube is connected to a container having a larger internal volume when gas is supplied. In the case of filling, it is possible to construct a system with stable filling / release efficiency and filling / release amount.

  ADVANTAGE OF THE INVENTION According to this invention, the natural gas storage tank which can suppress a component separation and aggregation from natural gas and can store a natural gas favorably can be provided. In particular, it is possible to provide a natural gas storage tank with good natural gas storage / release amount and storage / release efficiency.

  Hereinafter, an embodiment of a natural gas storage tank of the present invention will be described in detail with reference to the drawings.

(First embodiment)
1st Embodiment of the natural gas storage tank of this invention is described with reference to FIGS. The natural gas storage tank of the present embodiment includes an area of an inner cross section (referred to as area p) of an NG distribution pipe through which natural gas (hereinafter sometimes abbreviated as NG) flows, and an NG storage container to which NG is supplied. The ratio (p: q) to the cross-sectional area of the inner cross-section (referred to as the maximum area q) is 1: 100, and the supplied natural gas is not separated or aggregated.

  In the present embodiment, a case where “yashigara charcoal” is accommodated as a natural gas adsorbent in the NG storage tank will be described as an example. However, the present invention is not limited to the following embodiment.

  As shown in FIG. 1, the natural gas storage tank of the present embodiment accommodates an NG distribution pipe 11 that is a gas distribution pipe through which NG (natural gas) circulates and “Yashigara Charcoal” that is a natural gas adsorbent. And an NG storage container 12 which is a gas storage container for storing NG supplied from the NG circulation pipe 11.

  The NG circulation pipe 11 is connected to the NG storage tank 12 at one end on the downstream side in the circulation direction of NG through which natural gas (NG) circulates. The other end can be connected to a natural gas supply device (not shown) installed outside the natural gas storage tank.

As shown in FIG. 1, the NG distribution pipe 11 has a cylindrical structure made of SUS316 (or SUS310 or the like) having an inner diameter A of 4 mm, and the cross section orthogonal to the NG distribution direction is a substantially uniform circular shape. It has become. Here, the circular cross section with an inner diameter of 4 mm is the inner cross section of the NG flow pipe, and the area p of the inner cross section is 4π mm ² .

  The NG storage container 12 has a structure in which both ends in the longitudinal direction of a cylindrical body made of SUS316 (or SUS310, etc.) having an inner diameter B of 40 mm, a length of 3.0 m, and an internal volume of 3.7 L are closed by curved surfaces. The NG supply / exhaust port 13 is formed on one curved surface (closed end), and one end of the NG circulation pipe 11 is connected to the NG supply / exhaust port 13. The filling of NG can be performed in 5 minutes from the start of the supply of NG. In addition, since weight reduction is important as a material for automobiles, CFRP and FRP pressure-resistant containers in which the periphery of an aluminum liner is reinforced with carbon fiber, glass fiber, or the like are also used.

As shown in FIG. 1, NG circulates in the NG storage container 12 from the NG distribution pipe 11 toward the other curved surface (closed end), but the NG storage container orthogonal to the NG distribution direction. Twelve cross sections, that is, a circular cross section with an inner diameter of 40 mm is the inner cross section of the NG storage container, and this inner cross section is formed in a substantially uniform circular shape from one end of both closed ends to the other. Therefore, the maximum area q of the inner cross section of the NG storage container 12 is 400πmm ² .

  Inside the NG storage container 12, “Yashigara Charcoal” 14, which is a natural gas adsorbent for adsorbing and storing natural gas, is accommodated, and circulates through the NG distribution pipe 11 to enter the NG storage container 12. When NG is supplied, the supplied NG is adsorbed by the coconut charcoal 14 in the NG storage container 12 and stored. Further, when there is an NG discharge request from an NG using device (not shown) that operates with natural gas installed outside (for example, an engine or an NG reformer), a valve (regulator valve) installed in the NG distribution pipe 11 NG stored for example by opening the) is supplied to the NG using device.

Natural gas adsorbents include, for example, carbon fibers such as carbon nanotubes, carbon materials such as activated carbon and fullerene, mesoporous materials such as FSM (SiO ₂ ), MOF (metal complex), etc. Etc. can be used.
In addition, there is no restriction | limiting in particular about the kind of natural gas adsorbent, and the accommodation amount in an NG storage container, It can select suitably according to cases, such as the filling amount at the time of full filling, and filling time.

  In addition, in the NG storage container 12, a heating medium passage 15 for circulating a heating medium (heated water or the like) is provided in order to raise the temperature of the internal atmosphere. Accordingly, a large temperature drop of NG due to adiabatic expansion can be suppressed. The circulation of the heat medium can be started, and the temperature of the supplied NG can be maintained in a temperature range where separation and aggregation of heavy components in natural gas do not occur. Note that the heating means is not limited to a heat medium, and may be a heater or the like.

It is preferable to raise the temperature of NG through the heat medium passage 15 so that the NG temperature becomes 50 ° C. or higher. In the case of supplying NG, it is possible to avoid the possibility that the NG temperature becomes larger than the temperature decrease range (temperature difference of 15 ° C. or more) that causes aggregation when the temperature decreases due to adiabatic expansion.
Among these, heating in the range of 50 ° C. to 70 ° C. is desirable in terms of component separation in natural gas and prevention of aggregation. Excessive heating is contrary to the original high density storage due to the expansion of the gas itself.

  In this embodiment, the ratio (p: q) of the area p of the inner cross section of the NG circulation pipe 11 to the maximum area q of the inner cross section of the NG storage container 12 is 1: 100, but the ratio (p: q) May be in the range of 1: 225 to 1:64, preventing NG separation and aggregation due to adiabatic expansion during NG supply, and maintaining good NG adsorption / release efficiency over a long period of time. Adsorption / release amount can be secured.

Here, it is desirable that the decrease in the storage amount (storage rate) of NG is within 1%. For example, assuming an NG storage tank where V / V ₀ (V: NG filling amount, V ₀ : tank internal volume) is 300 at the time of full filling, the storage amount is as shown in FIG. When the ratio of the maximum area q of the inner cross section of the NG storage container to the area p of the inner cross section is further reduced, and the ratio of p to q is greater than 1:64, the reduction in storage efficiency is reduced by more than 1%.
On the other hand, as shown in FIG. 3, the temperature drop during the supply of NG decreases as the ratio of the maximum area q of the inner cross section of the NG storage container to the area p of the inner cross section of the NG distribution pipe decreases. When the ratio to is further smaller than 1: 225, the temperature range ΔT at which heavy components such as propane and butane in the natural gas are separated and aggregated exceeds 15 (deg).

  That is, by setting the ratio (p: q) of the area p of the inner cross section of the NG flow pipe to the maximum area q of the inner cross section of the NG storage container to 1: 225 to 1:64, a significant temperature at the time of supplying NG The decrease can be suppressed, thereby preventing separation and aggregation of heavy components in NG. As a result, a decrease in the number of NG adsorption sites can be avoided, good NG adsorption / release efficiency can be maintained over a long period of time, and a desired amount of adsorption / release can be ensured.

  For the above reasons, the ratio (p: q) is more preferably in the range of 1: 144 to 1: 100.

  As in this embodiment, by attaching a heat medium passage to the NG storage container as a heater and maintaining the NG temperature supplied by circulating the heat medium as necessary, for example, at the time of supply It is possible to eliminate the tendency of NG to separate and aggregate due to the influence of NG temperature, filling speed, material of the NG storage container, internal structure, etc., and the ratio (p: q) range (1: 225 to the above) 1:64) makes it possible to supply (fill) NG more stably.

Heating means such as a heat medium passage and a heater for raising the temperature of the natural gas can be provided in the gas storage container and / or the gas distribution pipe. When provided in the gas storage container, the heating means is provided either inside or outside the container. May be. Specifically, for example, an electrical supply is made on the NG supply side of the gas storage container (in this case, for example, from the connection part (NG supply / exhaust port) of the NG distribution pipe to a partial region of the container body), the outer wall of the NG distribution pipe, etc. A heater can be attached.
Further, the heater may be configured to increase the temperature of the NG adsorbent (here, coconut charcoal) and apply heat from the coconut charcoal.

(Second Embodiment)
A second embodiment of the natural gas storage tank of the present invention will be described with reference to FIGS. In the present embodiment, the gas storage container is provided with six holes of different diameters on the pipe wall between the gas flow pipe connecting portion connected to the gas storage container with one end protruding inward from the container wall. The ratio (r: s) of the total area r of the pores of the gas and the cross-sectional area (referred to as the maximum area s) of the inner cross section of the gas storage container supplied with NG is 1: 100, and separation of the supplied natural gas; The composition does not cause aggregation.

  As the natural gas adsorbent, “Yashigara Charcoal” used in the first embodiment and other natural gas adsorbents described in the first embodiment can be used, and the same as in the first embodiment. Constituent elements are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 4, the natural gas storage tank of the present embodiment accommodates an NG distribution pipe 21 that is a gas distribution pipe through which NG (natural gas) circulates and “Yashigara Charcoal” that is a natural gas adsorbent. And an NG storage container 22 which is a gas storage container for storing NG supplied from the NG circulation pipe 21.

The NG flow pipe 21 has a cylindrical structure made of SUS316 (or SUS310 or the like) having a substantially uniform circular shape with a cross section perpendicular to the NG flow direction having an inner diameter of 4 mm, and natural gas (NG) is contained in the pipe. One end, which is the downstream side in the circulation direction of the NG that circulates, is provided so as to protrude inward from the vessel wall of the NG storage container 12. The other end can be connected to a natural gas supply device (not shown) installed outside the natural gas storage tank.
The NG distribution pipe 21 is fixed at a penetrating portion that penetrates the NG storage container 22 and the vessel wall.

  The pipe wall of the NG circulation pipe 21 has six holes (S1, S1) between a connection portion with the NG storage container 22 and one end (hereinafter also referred to as a protruding end) protruding from the connection portion into the container. S2, S3, S4, S5, S6) are opened, and NG that has flowed through the NG flow pipe 21 is discharged from each hole and supplied to the NG storage container 22.

As shown in FIG. 4, the holes S1, S2, S3, S4, S5 and S6 have a small opening area from the projecting end in the vessel of the NG circulation pipe 21 toward the connection portion (through portion) with the NG storage container 22. The area s ^{1 of the} hole S1 is 0.94πmm ² , and the areas s ² , s ^3, and s ⁴ of the hole S2 to the hole S4 are each an area s ² : 0.82πmm ² . s ³ : 0.71πmm ² , area s ⁴ : 0.60πmm ² , and areas s ⁵ and s ⁶ of hole S5 and hole S6 are area s ⁵ : 0.51πmm ² and area s ⁶ : 0.41πmm, respectively. ² .

Holes S1, S2, S3, S4, S5 and S6, the ratio of the area ^{s 6} of the area ^{s 1} farthest hole S6 in closest hole S1 to the one end of the vessel is a protruding end ^{(s 1: s} 6) 2.29: 1, cooling due to adiabatic expansion when NG is supplied is suppressed, so that NG component separation and aggregation can be avoided.

In the case where a plurality of holes are provided in the NG circulation pipe 12, all the holes may be opened with the same area, or some or all of the holes may be opened with different areas.
As in the latter case, it is desirable to provide a plurality of holes having a part or all of different areas. In this case, cooling due to adiabatic expansion of the supplied NG is suppressed, and heavy propane, butane, etc. in the NG is suppressed. It is farthest from the area s ^{1 of the} hole S1 closest to one end (protruding end) in the vessel, which is the protruding end of the NG flow pipe, in that the separation and aggregation of the components can be prevented and NG can be stored and released satisfactorily. The ratio (s ¹ : s ⁿ ) of the area s ⁿ (n> 2) of the hole S6 is preferably in the range of 2: 1 to 3: 1 from the viewpoint of obtaining a uniform flow rate. More preferably, it is in the range of 2.25: 1 to 2.56: 1.

  The interval between the holes can be selected without any particular limitation. However, as shown in FIG. 5, it is more uniform from the viewpoint of “gas diffusion into the entire tank” when the holes are provided spirally with respect to the cross section. A gas flow is desirable.

  The number of holes to be formed is not particularly limited, and the NG filling speed, the inner diameter and length of the NG flow pipe, the area of each hole, a combination of holes having different areas, and the maximum area of the inner cross section of the NG storage container s, etc. can be selected as appropriate.

As shown in FIG. 4, the NG storage container 22 has a structure in which both ends in the longitudinal direction of a cylindrical body made of SUS316 (or SUS310, etc.) having an inner diameter B of 40 mm and an internal volume of 3.7 L are closed by curved surfaces. An NG supply / exhaust port 13 is formed on one curved surface (closed end), and one end of the NG flow pipe 21 is connected to the NG supply / exhaust port 13. Further, a cross section of the NG storage container 22 orthogonal to the NG flow direction, that is, a circular cross section with an inner diameter of 40 mm is the inner cross section of the NG storage container, and this inner cross section is substantially uniform from one end to the other of the closed ends. It has a circular structure. That is, the maximum area s of the inner cross section of the NG storage container 22 is 400πmm ² .

  In this embodiment, the ratio (r: s) of the total area r of the holes S1, S2, S3, S4, S5 and S6 to the maximum area s of the inner cross section of the NG storage container 22 is 1: 100. In addition, cooling due to adiabatic expansion of supplied NG is suppressed, and separation and aggregation of heavy components such as propane and butane in NG are prevented, and NG can be stored and released satisfactorily.

In the present embodiment, the ratio (r: s) is 1: 100, but the ratio (r: s) may be in the range of 1: 225 to 1:64, and a significant temperature drop during NG supply can be achieved. This can prevent the separation and aggregation of heavy components in NG. As a result, a decrease in the number of NG adsorption sites can be avoided, good NG adsorption / release efficiency can be maintained over a long period of time, and a desired amount of adsorption / release can be ensured.
Among the ratio (r: s), the range of 1: 1144 to 1: 100 is more preferable.

  Also in the present embodiment, a heat medium passage (or a heater or the like) is attached as in the first embodiment, and the supplied NG temperature is kept high by circulating the heat medium (or turning on the heater) as necessary. By doing so, for example, NG can be more easily separated and aggregated due to the influence of the NG temperature at the time of supply, the filling rate, the material of the NG storage container, the internal structure, etc. In the range of the ratio (r: s) (1: 225 to 1:64), NG can be supplied (filled) more stably.

In the present embodiment, the case where a plurality of holes are provided in the tube wall located inside the NG storage container of one NG circulation pipe has been described, but instead of forming a hole in one pipe. In a structure in which one NG distribution pipe branches into a plurality of NG storage containers, and a plurality of branch ends (that is, the area of the end face of the branch end) are provided so as to satisfy the above-described ratio (r: s). The same applies when configured. For example, for example, one NG flow pipe first branches into two (or three or more) pipes having the same or different inner diameters, and the two branched pipes are further divided into three pipes having the same or different inner diameters (or 2 or 4 or more), and a total of 6 or more branch ends can be formed. Furthermore, a branched structure may be used.
Even when configured in such a branched structure, by configuring so as to satisfy the above-described ratio (r: s), it is possible to obtain the same effect as when a plurality of holes of the present embodiment are provided.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Natural gas is abbreviated as “NG”.

Example 1
First, an NG storage tank having a structure similar to that shown in FIG. 1 was prepared.
This NG storage tank contains “Yashigara Charcoal” 14 as a natural gas adsorbent, and NG storage container (inner diameter 40 mm, inner volume) that adsorbs and stores the supplied natural gas (NG) on the Yagiga Charcoal. 3.7L made of SUS310) 12 and an NG distribution pipe 11 that is connected to the NG supply / exhaust port 13 of the NG storage container 12 and circulates through a pipe having an inner diameter of 4 mm to supply NG to the NG storage container 12. It has been done. Further, a temperature sensor (not shown) for detecting the temperature of NG entering the container of the NG storage container is located in the NG storage container 12 located slightly downstream of the NG supply / exhaust port 13 in the NG distribution direction. Is attached so that the NG temperature can be detected at a predetermined timing.

The ratio p: q of the area p (4πmm ² ) of the inner cross section of the NG flow pipe and the maximum area q (400πmm ² ) of the inner cross section of the NG storage container in this example is 1: 100.
Further, the NG storage rate V / V ₀ (V: NG filling amount, V ₀ : tank internal volume) at the time of full filling was 300, and the filling time of NG was 5 minutes.

When 20 MPa of NG (composition of 13A) was passed through the NG distribution pipe 11 and blown into the NG storage container 12 at room temperature (15 ° C.), the NG storage tank was connected to the NG distribution pipe and the NG storage container. NG adiabatically expanded in the vicinity of the supply / discharge port 13, and the NG temperature decreased to 5 ° C. At this time, the decrease range of the NG temperature is 10 deg, the temperature decrease range (ΔT ≧ 15 deg) at which natural gas agglomerates is not reached, and there is a change in the NG storage rate V / V ₀ at the time of full filling. There wasn't. Further, separation of butane and the like in NG was observed by mass spectrum analysis of the released gas, but separation of butane and the like was not observed. This operation was repeated 10 times, but no NG component was separated, and the decrease in the NG storage rate V / V ₀ was less than 1%.

(Comparative Example 1)
In Example 1, the maximum area q of the inner cross section of the NG storage container was changed to 22500πmm ² (made of SUS310 having an inner diameter of 300 mm and an inner volume of 80 L), and the ratio p: q was set to 1: 5625 (NG at full filling) (Storage rate V / V ₀ = 300, filling time = 5 minutes) In the same manner as in Example 1, NG was filled and the NG temperature was measured.

As a result, the NG temperature decreased to -20 ° C. At this time, the decrease width of the NG temperature was 35 deg, which exceeded the temperature decrease width (ΔT ≧ 15 deg) at which the natural gas causes aggregation, and separation of butane in NG was confirmed. A decrease in the NG storage rate V / _{V 0} is seen, the decline was also about 15 deg.

(Comparative Examples 2-3)
In Example 1, the maximum area q of the inner cross section of the NG storage container was 960πmm ² (inner diameter 62 mm, inner volume 8.9 L; Comparative Example 2), 225πmm ² (inner diameter 30 mm, inner volume 2.1 L; Comparative Example 3) In the same manner as in Example 1 except that the ratio p: q was set to 1: 240 and 1:56, respectively (NG storage rate V / V ₀ at full filling = 300, filling time = 5 minutes), NG was filled and the NG temperature was measured.

As a result, the NG temperature decreased to −3 ° C. in Comparative Example 2, and the decrease width of the NG temperature was 18 deg. Moreover, in the comparative example 3, it fell to 10 degreeC and the fall width | variety of NG temperature was 5 deg. In Comparative Example 2, the temperature decrease range (ΔT ≧ 15 deg) at which natural gas causes aggregation is confirmed, butane separation in NG is confirmed, and a decrease in NG storage rate V / V ₀ is also observed. It was about 5 deg. In Comparative Example 3, no butane separation was observed, but a decrease of 1% or more occurred at the NG storage rate V / V ₀ based on the increase in the proportion of the meat part of the tank (FIG. 2).

It is a schematic sectional drawing which shows the structure of the NG storage tank which concerns on 1st Embodiment of this invention. It is a relationship diagram showing the relationship between the maximum area q and V / V ₀ the inner cross section of the inner cross-sectional area p / NG storage container NG flow pipe. It is a related figure which shows the relationship between the internal cross-sectional area p / NG storage container of the NG distribution | circulation pipe | tube, and the largest area q of the inner cross section of NG storage container, and (DELTA) T. It is a schematic sectional drawing which shows the structure of the NG storage tank which concerns on 2nd Embodiment of this invention. (A) is the schematic block diagram which looked at the NG distribution pipe from one end, (B) is the schematic block diagram which looked at the NG distribution pipe from the side.

Explanation of symbols

11, 21 ... NG flow pipes 12, 22 ... NG storage container 14 ... coconut charcoal 15 ... heat medium passages S1 to S6 ... holes

Claims (6)

  The area p of the inner cross section at the connection portion of the gas flow pipe connected to the gas storage container for storing natural gas, and the inner cross section orthogonal to the gas flow direction expanded in the gas flow direction from the connection portion of the gas storage container. A natural gas storage tank having a ratio (p: q) of 1: 225 to 1:64 with respect to the maximum area q.   The gas storage container has at least one hole in the tube wall between the one end of the gas flow pipe connected to the gas storage container with one end projecting inward from the container wall, and the total area r of the holes The natural gas storage in which the ratio (r: s) of the inner cross section orthogonal to the gas flow direction expanded in the gas flow direction from the connection part of the gas storage container (r: s) is 1: 225 to 1:64 tank. The gas flow pipe has a plurality of holes, and the ratio (s ¹ : s ⁿ ) between the area s ^{1 of the} hole closest to the one end that is the protruding end and the area s ⁿ (n> 2) of the furthest hole. The natural gas storage tank according to claim 2, wherein the ratio is 2: 1 to 3: 1.   The natural gas storage tank according to any one of claims 1 to 3, wherein the gas storage container contains a natural gas adsorbent that adsorbs natural gas in the vessel.   The natural gas storage tank according to any one of claims 1 to 4, further comprising a temperature raising means for raising the temperature of the natural gas supplied from the gas distribution pipe to the gas storage container. .   The natural gas storage tank according to claim 5, wherein the temperature raising means raises the temperature to 50 ° C. or higher.