JP2005351291A - Method and device for thermal insulating gas hydrate storage tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the entry of heat into a storage tank and also suppress thermal insulation cost. <P>SOLUTION: This method for thermally insulating a gas hydrate stored in the tank which stores the gas hydrate in a pellet shape. The gas hydrate storage tank 10 is formed in a double shell structure comprising an outer shell 12 and an inner shell 13. An inert gas b cooled to a specified temperature is allowed to flow in a gas passage 15 formed between the outer shell 12 and the inner shell 13 to exclude invaded heat invaded from the outer shell 12 by the inert gas b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat insulation method and apparatus for a gas hydrate storage tank.

  Considering the price of gas supplied to thermal power plants, LNG (gas hydrate) may be cheaper than LNG (liquefied natural gas), so LNG is used as fuel from the viewpoint of reducing fuel costs. An NGH storage tank for storing NGH is newly installed in the site of an existing thermal power plant, and LNG and NGH are being co-fired.

  Here, co-firing of LNG and NGH means that NGH is not directly mixed into LNG, but both are gasified and then mixed and burned.

  In addition, there is a high possibility of using NGH in combination with LNG from the viewpoint of measures to tighten LNG demand due to increased energy consumption in developing countries, etc., or to secure stable energy supply such as dispersion of fuel suppliers. .

  From the above viewpoint, it is conceivable to newly install an NGH storage tank for storing NGH on the site of an existing thermal power plant and store inexpensive NGH imported from abroad.

  NGH has the characteristic that it can be stably stored at a higher temperature level than LNG under normal pressure (specificity of the self-preserving effect at −20 ° C.), but it is necessary to remove the heat of entry into the NGH storage tank. (For example, refer to Patent Document 1).

  NGH can be stably stored at around −20 ° C., that is, −30 ° C. to −15 ° C. under normal pressure. For this reason, NGH is more economical than LNG and CNG (compressed natural gas) as a long-term storage means for natural gas. Moreover, since NGH is excellent also in terms of security, from the viewpoint of disaster prevention, the use of NGH is expected to be expanded in the future in conjunction with the spread of natural gas.

  As described above, although NGH can be stored stably for a long time, it is stored in the non-equilibrium region of gas hydrate, and is required to be decomposed slightly, and the storage temperature is −20 ° C. There is also decomposition due to heat entering from the outside.

Therefore, from the viewpoint of gas storage, gas discharge to the outside of the system should be suppressed as much as possible. Therefore, heat insulation is important. As a heat insulation method, there is a method of strengthening a heat insulating material or a minimum gas emission suppression method by vacuum insulation, etc., but there are problems such as an increase in heat insulation work cost or difficulty in shortening the construction period. was there.
JP 54-135708 (2nd page, Fig. 1)

  By the way, assuming that the decomposition of NGH pellets due to intrusion heat that has entered a tank filled with pellet-like gas hydrate (hereinafter referred to as NGH pellets) is mainly due to the temperature rise of the gas in contact with the side wall of the tank. As shown in FIG. 5, if the gas in the tank 1 is attracted by the blower 2 and is removed by the heat exchanger 3 outside the system, it can be assumed that heat can be prevented from entering the NGH pellet inside the tank.

  However, it is practically difficult to form the gas passage a along the inner wall of the tank 1 as shown in FIG. 5 in the tank 1 filled with the NGH pellet p. Rather, it is better to reduce the temperature of the intrusion heat that enters the tank by forming a gas flow between the inner shell and the outer shell while forming the tank by the inner and outer shells.

  The present invention has been made on the basis of such knowledge, and the object of the present invention is to suppress the intrusion of heat into the storage tank and the gas hydrate storage tank capable of suppressing the heat insulation work cost. It is to provide a heat insulation method and apparatus.

  In order to solve the above problems, the present invention is configured as follows.

  A heat insulation method for a gas hydrate storage tank according to claim 1 is a heat insulation method for a gas hydrate storage tank for storing pellet-like gas hydrate, wherein the gas hydrate storage tank is divided into an outer shell and an inner shell. An intrusion gas is formed between the outer shell and the inner shell, and an inert gas cooled to a predetermined temperature is caused to flow through the gas passage between the outer shell and the inner shell. A heat insulation method for a gas hydrate storage tank, wherein heat is excluded from the system.

  The method for heat insulation of a gas hydrate storage tank according to claim 2 is characterized in that the inert gas is cooled to a predetermined temperature using the cold of liquefied natural gas. This is a method for insulating a storage tank.

  A heat insulating device for a gas hydrate storage tank according to a third aspect of the present invention is a heat insulating device for a gas hydrate storage tank that stores pellet-like gas hydrate, wherein the gas hydrate storage tank includes an outer shell and an inner shell. And a gas passage is formed between the outer shell and the inner shell, an inert gas is allowed to flow through the gas passage, and an external circulation passage communicating with the gas passage is provided as the gas passage. A gas hydrate storage tank provided outside the hydrate storage tank and provided with an inert gas cooling device and a circulation blower in the external circulation path to eliminate intrusion heat entering from the outer shell outside the system. It is a heat insulation device.

  The heat insulating device for a gas hydrate storage tank according to the invention described in claim 4 is characterized in that a heat insulating material is provided outside the outer shell, and a gap with the inner shell is used as an inert gas passage. This is a heat insulation device for a gas hydrate storage tank.

  As described above, the heat insulation method for a gas hydrate storage tank according to the invention of claim 1 is a heat insulation method for a gas hydrate storage tank for storing pellet-like gas hydrate, wherein the gas hydrate storage tank is A double shell structure consisting of an outer shell and an inner shell is formed, and an inert gas cooled to a predetermined temperature is caused to flow through a gas passage provided between the outer shell and the inner shell. Since the intrusion heat entering from the shell is excluded from the system, the intrusion of heat into the gas hydrate storage tank can be suppressed in advance. For this reason, it is possible to store gas hydrate stably over a long period of time.

  Moreover, according to this invention, since it is not necessary to make the heat insulation work using a heat insulating material into complete heat insulation, it becomes possible to reduce the heat insulation work cost using a heat insulating material.

  In the heat insulation method for a gas hydrate storage tank according to the second aspect of the invention, the inert gas is cooled to a predetermined temperature using the cold heat of the liquefied natural gas, so that the refrigeration power corresponding to the intrusion heat is unnecessary. There is an advantage of becoming. Moreover, energy-saving gas storage becomes possible by utilizing the cold heat of LNG.

  A heat insulating device for a gas hydrate storage tank according to a third aspect of the present invention is a heat insulating device for a gas hydrate storage tank that stores pellet-like gas hydrate, wherein the gas hydrate storage tank includes an outer shell and an inner shell. And a gas passage is formed between the outer shell and the inner shell, an inert gas is allowed to flow through the gas passage, and an external circulation passage communicating with the gas passage is provided as the gas passage. Provided outside the hydrate storage tank, and provided with an inert gas cooling device and a circulation blower in the external circulation path to eliminate intrusion heat entering from the outer shell outside the system, so that it enters the gas hydrate storage tank. Intrusion heat can be blocked in advance. For this reason, gas hydrate can be stably stored over a long period of time.

  Moreover, according to this invention, since it is not necessary to make the heat-insulating work using a heat insulating material completely heat-insulating, it becomes possible to reduce the heat-insulating work cost using a heat insulating material, and it is economical.

  The heat insulation device for a gas hydrate storage tank according to the invention of claim 4 is provided with a heat insulating material on the outside of the outer shell, and the gap with the inner shell is used as an inert gas passage, so that the gas hydrate storage tank enters the gas hydrate storage tank. Heat can be blocked in advance, and the gas hydrate can be stably stored for a long time. Moreover, it becomes possible to handle an outer shell and a heat insulating material integrally, and the handleability of an outer shell improves dramatically.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In FIG. 2, reference numeral 10 denotes a storage tank (hereinafter referred to as a storage tank) for storing pellet-shaped gas hydrate (hereinafter referred to as NGH pellets) p imported from a foreign country. . However, there may be only one if desired.

  As shown in FIG. 3, the storage tank 10 is formed in a horizontally long shape, and a transport device (not shown) in which NGH pellets (not shown) stored therein are provided under a gantry 11 having a portal structure. Is sent to the next process (for example, gasifier).

  More specifically, as shown in FIG. 1, the storage tank 10 has a double shell structure composed of an outer shell 12 and an inner shell 13. The outside of the outer shell 12 is prevented from intruding heat from the outside by a heat insulating material 14. The outer shell 12 is attached to the gantry 11 (see FIG. 3) by a support member (not shown). The inner shell 13 is made of a strength member to support the NGH pellet p.

  Here, as a heat insulating material, hard polyethylene etc. are used preferably, for example, The plate | board thickness has preferable about 100-150 mm, for example.

  The storage tank 10 is provided with a gap between the outer shell 12 and the inner shell 13, and this gap serves as a gas passage 15. Further, the storage tank 10 includes an external circulation path 16 that communicates the upper end 15a and the lower end 15b of the gas passage 15 to the outside, and uses the circulation gas blower 17 provided in the external circulation path 16 to provide the gas. The inert gas b in the passage 15 and the external circulation path 16 is constantly circulated. Further, an inert gas cooling device 18 is provided in the external circulation path 16 so as to indirectly cool the inert gas b using the cold heat of LNG.

Here, examples of the inert gas include nitrogen gas and carbon dioxide. Carbon dioxide (CO ₂ ), which is easily available, has a high molecular weight, and can reduce the compression power, is preferably used. .

  The distance L between the outer shell 12 and the inner shell 13 is preferably in the range of 100 to 150 mm. When the distance L between the outer shell 12 and the inner shell 13 is less than 100 mm, the distance L between the outer shell 12 and the inner shell 13 is too small, and thus the manufacture becomes difficult. Conversely, when the distance L between the outer shell 12 and the inner shell 13 exceeds 150 mm, there is a problem that the outer shell 12 is enlarged and the amount of inert gas is increased.

The inert gas cooling device 18 includes two primary and secondary heat exchangers 19 and 20, a refrigerant enclosure tube 21 connecting the two heat exchangers 19 and 20, and a refrigerant provided in the refrigerant enclosure tube 21. An intermediate refrigerant (for example, ammonia (NH ₃ )) is sealed in the refrigerant sealing tube 21 formed by the pump 22. And the inert gas b is indirectly cooled using the cold of LNG (d). Here, the cooling temperature of the inert gas is preferably in the range of −20 ° C. to −30 ° C.

  The storage tank 10 also includes a BOG discharge pipe 23 communicating with the inner shell 13 and supplies BOG (e) to an existing gas consuming device (for example, a boiler for thermal power generation) using a low-pressure gas compressor (not shown). It is supposed to be. Further, the storage tank 10 is provided with a loading device 24 for introducing the NGH pellet p into the inner shell 13 at the top, and for discharging the NGH pellet p stored in the inner shell 13 at the bottom. An unloading device 25 is provided.

  Next, an operation method of the NGH storage tank will be described.

Now, when the circulating gas blower 17 and the inert gas cooling device 18 are operated, as shown in FIG. 4, the inert gas (CO ₂ ) cooled to a predetermined temperature (for example, −20 ° C.) by the inert gas cooling device 18. B) is supplied to the lower end 15 a of the gas passage 15 provided between the outer shell 12 and the inner shell 13 of the NGH storage tank 10.

The low-temperature inert gas (CO ₂ ) b absorbs intrusion heat that enters through the outer shell 12 while flowing from the lower end portion 15a of the gas passage 15 toward the upper end portion 15b. It is possible to prevent the temperature of the gas from rising.

  The present invention will be described in more detail with reference to FIG.

(Example)
・ Number of tanks: 3 ・ Tank capacity: 100,000 tons / base ・ Tank volume: 140,000 m ³ / base ・ Built-in gas volume: 14,000 tons / base ): 583 kg / h / group Here, BOG refers to a self-decomposing gas that does not depend on intrusion heat.
-BOR (ratio of the amount of gas generated by self-decomposition to the total amount of gas contained in NGH pellets): 0.1% / day-Area in contact with air: 31,000 m ²
・ Tank lower area: 9,019m ²
・ Tank outer surface temperature: 50 ℃ (average temperature of day and night considering radiant heat from solar radiation)
・ Outside temperature: 25 ℃
-Tank temperature: -20 ° C
Self-decomposition latent heat (cooled by NGH itself decomposition, but the temperature drop of the pellet is small): 437,500 kcal / h
・ Average heat transmission rate (surface affected by solar radiation): 0.35 kcal / m ² h ° C
-Average heat transmission rate (shaded surface): 0.25 kcal / m ² h ° C
・ Intrusion heat: 863,413 kcal / h
・ Amount of cracked gas: 3,454 kg / h
・ Power generation output (approximate): 23,112 kW
・ Total gas amount: 5,204 kg / h (gas amount when intrusion heat is not removed)
・ Intrusion heat equivalent BOG gas amount: 24,669 kg / h} 3 units ・ Intrusion heat equivalent refrigeration power: 612 kW (not required due to use of cold energy by LNG) ・ BOG amount: 1,750 kg / h
LNG usage (amount commensurate with intrusion heat from outside the system): 5996 kg / h (−150 ° C. to −50 ° C.)
-Circulating gas (CO ₂ ) amount: 693,504 kg / h
・ Required power for circulating gas blower: 2,003 kW

As described above, the required power required for suppressing the intrusion heat is 2003 kW. On the other hand, the power generation output (converted) by the generated gas when the intrusion heat is not suppressed is 23,112 kW.
Therefore, according to the present invention, the required power required for suppressing the intrusion heat can be reduced by about 20,000 kW (≈23,112 (kW) −2003 (kW)).

It is a principal part expanded sectional view of FIG. It is a schematic block diagram of the heat insulation apparatus of the gas hydrate storage tank which concerns on this invention. It is a perspective view of a gas hydrate storage tank. It is explanatory drawing of the heat insulation apparatus of the gas hydrate storage tank which concerns on this invention. It is heat removal explanatory drawing of an intrusion heat.

Explanation of symbols

b Inert gas p Pellet-shaped gas hydrate 10 Gas hydrate storage tank 12 Outer shell 13 Inner shell 15 Gas passage

Claims (4)

A heat insulation method for a gas hydrate storage tank for storing pellet-shaped gas hydrate, wherein the gas hydrate storage tank is formed into a double shell structure including an outer shell and an inner shell, and the outer shell and the inner shell Insulation of a gas hydrate storage tank, wherein an inert gas cooled to a predetermined temperature is caused to flow through a gas passage provided between the two and the intrusion heat entering from the outer shell by the inert gas is excluded from the system. Method. The heat insulation method for a gas hydrate storage tank according to claim 1, wherein the inert gas is cooled to a predetermined temperature by using the cold heat of liquefied natural gas. A heat insulating device for a gas hydrate storage tank for storing pellet-shaped gas hydrate, wherein the gas hydrate storage tank is formed into a double shell structure including an outer shell and an inner shell, and the outer shell and the inner shell are formed. A gas passage is formed between the gas passage, an inert gas is allowed to flow through the gas passage, an external circulation path communicating with the gas passage is provided outside the gas hydrate storage tank, and an inert gas is provided in the external circulation path. A heat insulation device for a gas hydrate storage tank, characterized in that a cooling device and a circulation blower are provided to eliminate intrusion heat entering from the outer shell to the outside of the system. The heat insulating device for a gas hydrate storage tank according to claim 3, wherein a heat insulating material is provided outside the outer shell, and a gap with the inner shell is used as an inert gas passage.

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