JP2001324096A - Control method of boil off-gas generation amount during receiving of liquefied natural gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce total cost of an entire base by controlling BOG generation amount by adequately combining respective feed pipes of a top, a bottom, and a bottom having a funnel part according to liquid density difference between LNG liquid in a ground tank and received LNG. SOLUTION: The tip of a bottom feed pipe 3 disposed through a side part 1a of the ground tank 1 is communicated with the LNG liquid 2 in the ground tank 1, and the top 1b of the ground tank 1 is provided with a top feed pipe 5 and a bottom feed pipe 6 having a funnel part of which lower end communicates with the LNG liquid 2 in the ground tank 1. When LNG 9 is received which has liquid density larger than that of the LNG liquid 2 in the ground tank 1, the top feed pipe 5 and the bottom feed pipe 6 are used in combination. When LNG 4 is received which has liquid density smaller than that of the LNG liquid 2 in the ground tank 1, the bottom feed pipe 3 and the bottom feed pipe 6 are used in combination. Thus, the BOG generating amount during the receiving of LNG is kept at a design level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the amount of boil-off gas (hereinafter referred to as BOG) generated when LNG is received into a ground tank for storing liquefied natural gas (hereinafter referred to as LNG).

[0002]

2. Description of the Related Art Conventionally, it has been known that the amount of components of LNG differs depending on which base is produced and paid out. For example, it is lightweight and has a boiling point of about -1.
The amount of methane or the like at 62 ° C. may be large, or the amount of ethane or the like having a relatively heavy boiling point of about −80 ° C. may be large. Therefore, in the conventional LNG storage ground tank, the LNG in the ground tank after receiving the LNG is taken into consideration in consideration of the liquid density difference between the LNG ship and the LNG in the ground tank.
Basically, the following receiving method is adopted so that NG is not stratified. This is because when the LNG in the ground tank is stratified, a rollover phenomenon occurs, and the amount of BOG generated increases extremely. As a result, the pressure in the ground tank also increases, and BOG may be ejected from a safety valve or the like. Happen
This is because it is necessary to prevent damage to the tank and improve safety by devising an LNG receiving method.

The method of receiving LNG shown in FIGS. 2 and 3 is for receiving LNG 53 having a larger (heavier) liquid density than the LNG liquid 52 in the ground tank 51. Therefore, an LN (not shown) is provided on the top 51a of the ground tank 51.
A top feed pipe 54 is installed, for example, by being routed from Vessel G.
NG 53 is supplied into the ground tank 51 and the LNG liquid 52
It is designed to be sprayed on the upper surface of the device. The LNG receiving method shown in FIGS. 4 and 5 has a smaller (lighter) liquid density than the LNG liquid 52 in the ground tank 51.
This is the case where LNG 55 is accepted. For this reason, a bottom feed pipe 56 is installed below the side portion 51b of the ground tank 51 by being routed from an LNG ship (not shown).
5 is supplied into the ground tank 51 and discharged into the LNG liquid 52 to be received. If there is almost no difference between the LNG liquid 52 in the ground tank 51 and the LNG of the LNG ship, the top feed pipe 54
Alternatively, LNG is received using either the bottom feed pipe 56.

On the other hand, in the method of receiving LNG, as shown in FIGS. 6 and 7, an underground tank or a PC (prestressed concrete) ground tank 61 is used instead of a normal ground tank due to the installation location and the like. Sometimes.
In this type of tank 61, an ordinary bottom feed pipe cannot be installed, so that a receiving nozzle 62 from an LNG ship is installed at the top 61a, and an interval is provided at the lower end of the receiving nozzle 62. A bottom feed pipe 63 with a funnel is continuously installed along the vertical direction. That is, an enlarged funnel tube portion 64 is provided at the upper end of the bottom feed tube 63, and the lower end thereof is
Is disposed in the LNG liquid 65 in the inside. Therefore, L
The LNG 66 of the NG ship receives the tank 61 from the receiving nozzle 62.
And is discharged from the lower end of the bottom feed pipe 63 into the LNG liquid 65 through the funnel pipe section 64 and received therein.

[0005]

However, among the conventional receiving methods described above, the top feed pipe 54 shown in FIG.
In the receiving method using the bottom feed pipe 56 shown in FIG. 4 and FIG. 4, as shown in FIG. 3 and FIG. 5, both of the BOG amount and the BOG amount that are considerably larger than the normal BOG amount are generated after the start of the reception. I couldn't control it. In addition, the LNG 53 after the start of receiving is LN at the top feed compared to the bottom feed.
Since it does not mix stably with the liquid G 52, a large amount of BOG is to be generated. As a countermeasure against this, conventionally, an operation plan of the entire base has been established so as to correspond to the BOG at the time of reception. That is, a compressor for reliquefying the generated BOG may be provided, or the top feed pipe 5 may be used.
The strength of the tank corresponding to the pressure of the receiving method using No. 4 is designed. Therefore, the total cost of the entire base increases, which is economically disadvantageous.

On the other hand, among the conventional receiving methods, FIG.
In the receiving method using the receiving nozzle 62 and the bottom feed pipe 63 with a funnel shown in FIG. 6, when the LNG 66 is discharged from the lower end of the receiving nozzle 62, as shown in FIG. Since the surrounding BOG is involved as shown by an arrow F, the involved BOG is reliquefied. Therefore, after the start of receiving the LNG 66, as shown in FIG.
Since the amount of OG generation is reduced, the inside of the tank 61 becomes a negative pressure, which may cause the tank 61 to be damaged.

[0007] The present invention has been made in view of such a situation, and an object thereof is to provide an LNG solution and a LNG solution in a ground tank.
Use of a compressor to control the amount of BOG generated and re-liquefy BOG by appropriately combining the top feed pipe, bottom feed pipe and bottom feed pipe with funnel according to the liquid density difference from LNG of NG ship It is an object of the present invention to provide a method for controlling the amount of BOG generated at the time of receiving LNG, which can reduce the total cost of the entire base, such as by reducing the number of units.

[0008]

In order to solve the problems of the prior art, according to the present invention, a bottom feed pipe is provided on a side of a ground tank for storing LNG, and a tip of the bottom feed pipe is connected to the bottom feed pipe. While communicating with the LNG liquid in the ground tank, a top feed pipe and a bottom feed pipe with a funnel are installed at the top of the ground tank,
The lower end of the bottom feed pipe with the funnel is communicated with the LNG liquid in the ground tank, and the LN liquid in the ground tank is
When receiving LNG having a liquid density higher than G, the top feed pipe and the bottom feed pipe with a funnel are used in combination, while when receiving LNG having a liquid density lower than LNG in the above-ground tank, By using the bottom feed pipe and the bottom feed pipe with the funnel in combination, the BO at the time of receiving the LNG is reduced.
The G generation amount is held at the design value level.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments. Here, FIG. 1 is a ground tank for implementing a method of controlling the amount of BOG generated during LNG reception according to an embodiment of the present invention, and a bottom feed pipe, a top feed pipe, and a bottom feed pipe with a funnel installed therein. It is a conceptual sectional view of.

[0010] BOG at the time of receiving LNG according to this embodiment
As shown in FIG. 1, the LNG storage tank that implements the method for controlling the generation amount is a dome-shaped ground tank 1 installed on the ground in a storage base G where an LNG ship or the like calls at the port. LNG liquid 2 is already stored in the lower half.

Below the side 1a of the above-mentioned ground tank 1,
A bottom feed pipe 3 is provided. The base end of the bottom feed pipe 3 is connected to a discharge pipe or the like of an LNG ship (not shown), is led therefrom, and is led to a place where the ground tank 1 is installed. L
The NG liquid 2 is provided in communication with the NG liquid 2. Therefore, L
The LNG 4 of the NG ship is discharged and received into the LNG liquid 2 from below the side portion 1a of the ground tank 1 via the bottom feed pipe 3. The liquid density of the LNG 4 is smaller (lighter) than that of the LNG liquid 2 in the ground tank 1.

On the other hand, on the top 1b of the above-mentioned ground tank 1,
A top feed pipe 5 and a bottom feed pipe 6 with a funnel are provided. Of these feed pipes, the base end of the top feed pipe 5 is connected to an unillustrated discharge pipe of an LNG carrier, similar to the bottom feed pipe 3, and is routed therefrom to lead to the installation location of the ground tank 1. The front end of the tank is communicated with the ground tank 1.

The upper end of the bottom feed pipe 6 with a funnel is connected to the middle of the top feed pipe 5 through a receiving nozzle 7, and the lower end thereof communicates with the LNG liquid 2 in the ground tank 1. It is arranged. That is, the bottom feed pipe 6 with the funnel and the receiving nozzle 7 are continuously arranged concentrically along the vertical direction. At the upper end of the bottom feed pipe 6 with a funnel, a funnel 8 having an increased diameter is provided to provide a reducer effect, and an inner peripheral wall of the funnel 8 and the receiving nozzle 7 are provided.
A predetermined interval is provided between the lower end of the lens. Therefore, the LNG 9 of the LNG ship is sprayed from the top 1b of the ground tank 1 via the top feed pipe 5 and the bottom feed pipe 6 with the funnel, and is discharged and received in the LNG liquid 2. . In addition, LNG
The liquid density of 9 is larger (heavier) than that of the LNG liquid 2 in the ground tank 1.

Next, the method for controlling the amount of BOG generated according to the embodiment of the present invention will be described with reference to FIG.
The procedure for receiving the vehicle in the ground tank 1 will be described. First, LNG having a higher liquid density than the LNG liquid 2 in the ground tank 1
When receiving 9, the top feed pipe 5 and the bottom feed pipe 6 with the funnel are used in combination. That is, LNG 9 is fed from the LNG ship to the top feed pipe 5 and sprayed from the tip of the top feed pipe 5 onto the upper surface of the LNG liquid 2 as shown by the arrow, and is received from the receiving nozzle 7 via the top feed pipe 5. To the funnel tube 8,
The BOG is discharged into the LNG liquid 2 from the lower end of the bottom feed pipe 6 with the funnel while entraining the surrounding BOG. Therefore, while considering the amount of BOG generated in the ground tank 1,
When the amounts of LNG 9 supplied from the two routes of the top feed pipe 5 and the bottom feed pipe 6 with the funnel are combined in a well-balanced manner, the LNG 9 of the LNG ship becomes LN 9
The BOG generation amount is received in the ground tank 1 in a state where the BOG generation amount is maintained at the design value level without being stratified with the G solution 2.

When receiving LNG 4 having a lower liquid density than the LNG liquid 2 in the ground tank 1, the bottom feed pipe 3 and the bottom feed pipe 6 with a funnel are used in combination. That is, LNG 4 is sent from the LNG ship to the bottom feed pipe 3 and discharged into the LNG liquid 2 from the tip of the bottom feed pipe 3 as shown by the arrow, and is sent to the funnel pipe section 8 via the receiving nozzle 7. , Surrounding B
Bottom feed pipe 6 with funnel while rolling OG
Is discharged into the LNG liquid 2 from the lower end of the liquid. Therefore, when the amount of LNG 4 supplied from the two routes of the bottom feed pipe 3 and the bottom feed pipe 6 with the funnel is combined in a well-balanced manner while taking into account the amount of BOG generated in the ground tank 1, the LNG 4 of the LNG ship becomes , And LNG liquid 2, the BOG generation amount is received in the ground tank 1 while being kept at the design value level.

In the method for controlling the amount of BOG generated when receiving LNG according to the embodiment of the present invention, the BNG generation amount in the ground tank 1 is changed according to the liquid density difference between the LNG liquid 2 in the ground tank 1 and the LNG 4, 9 of the LNG ship. When the LNGs 4 and 9 are received, the combination of the top feed pipe 5 and the bottom feed pipe 6 with the funnel is selected, or the combination of the bottom feed pipe 3 and the bottom feed pipe 6 with the funnel is selected. Therefore, L is supplied to the bottom feed pipe 3, the top feed pipe 5, and the bottom feed pipe 6 with the funnel, taking into account the amount of BOG generated in the ground tank 1.
By adjusting the amount of NG4 and NG, the LNG is stored in the ground tank 1 while the BOG generation amount is maintained at the design value level.
LNG 4 and 9 of Vessel G can be received, and LNG liquid 2 in ground tank 1 is uniformly mixed with LNG.
The stratification of the NG liquid 2 can be prevented, and this has a great advantage in the operation plan of the entire base including the number of BOG reliquefaction compressors used and the tank strength design.

While the embodiments of the present invention have been described above,
The present invention is not limited to the embodiments described above, and various modifications are possible based on the technical idea of the present invention.
For example, one end of the receiving nozzle 7 may be connected directly to the discharge pipe of the LNG ship or the like, instead of the top feed pipe 5, or may be connected to the middle of the bottom feed pipe 3.

[0018]

As described above, according to the method for controlling the amount of BOG generated during LNG reception according to the present invention, a bottom feed pipe is installed on the side of a ground tank for storing LNG.
Connect the tip of the bottom feed pipe to LNG in the ground tank.
While communicating with the liquid, a top feed pipe and a bottom feed pipe with a funnel are installed at the top of the ground tank, and the lower end of the bottom feed pipe with the funnel is communicated with the LNG liquid in the ground tank. When receiving LNG having a higher liquid density than the LNG in the ground tank, the top feed pipe and the bottom feed pipe with the funnel are used in combination while the LNG in the ground tank is used.
When receiving LNG having a smaller liquid density than the above, by using the bottom feed pipe and the bottom feed pipe with a funnel in combination, the amount of BOG generated at the time of receiving the LNG is maintained at a design value level. The following effects can be obtained. That is, according to the control method of the present invention, the LNG liquid in the ground tank and the LN of the LNG ship are
The top feed pipe, the bottom feed pipe and the bottom feed pipe with the funnel are combined in a well-balanced manner in accordance with the liquid density difference from G. Therefore, the amount of BOG generated while preventing stratification with the LNG liquid in the ground tank is prevented. And reduce the number of compressors used to reliquefy the BOG, and to design the tank strength in response to the pressure of the receiving method of the bottom feed pipe, thereby reducing the total cost of the entire station Can be.

[Brief description of the drawings]

FIG. 1 is a view for explaining a method of controlling the amount of BOG generated at the time of receiving LNG according to an embodiment of the present invention, and includes a ground tank, a bottom feed pipe, a top feed pipe, and a bottom with a funnel installed therein. It is sectional drawing which shows a feed pipe notionally.

FIG. 2 is a sectional view conceptually showing a conventional method for receiving LNG into a ground tank using a top feed pipe.

FIG. 3 is a diagram showing a relationship between a BOG amount and time when LNG is received by the top feed pipe of FIG. 2;

FIG. 4 is a sectional view conceptually showing a conventional method for receiving LNG into a ground tank using a bottom feed pipe.

FIG. 5 is a diagram showing a relationship between a BOG amount and time when LNG is received by the bottom feed pipe of FIG. 4;

FIG. 6A is a sectional view conceptually showing a conventional method for receiving LNG into a ground tank using a bottom feed pipe with a funnel, and FIG. 6B is an enlarged view of a part A in FIG.

FIG. 7 is a view showing the L by the bottom feed tube with the funnel of FIG. 6;
It is a diagram showing the relationship between the BOG amount and time at the time of NG reception.

[Explanation of symbols]

 Reference Signs List 1 ground tank 1a side 1b top 2 LNG liquid 3 bottom feed pipe 4 LNG 5 top feed pipe 6 bottom feed pipe with funnel 7 receiving nozzle 8 funnel pipe 9 LNG

Claims (1)

[Claims] 1. A bottom feed pipe is provided on a side of a ground tank for storing liquefied natural gas, and a tip of the bottom feed pipe is communicated with the liquefied natural gas liquid in the ground tank. A top feed pipe and a bottom feed pipe with a funnel are installed at the top, and the lower end of the bottom feed pipe with a funnel is communicated with the liquefied natural gas liquid in the above-mentioned tank above the liquefied natural gas in the above-mentioned above-ground tank. When receiving liquefied natural gas having a high liquid density, the top feed pipe and the bottom feed pipe with a funnel are used in combination, while liquefied natural gas having a lower liquid density than the liquefied natural gas in the above-ground tank is received. At the time of receiving the liquefied natural gas by using the bottom feed pipe and the bottom feed pipe with the funnel in combination. A method for controlling the amount of boil-off gas generated when liquefied natural gas is received, wherein the amount of boil-off gas generated is maintained at a design value level.