JP2001289398A - Liquefied gas reservoir - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a BOG generation amount during receiving LNG in a LNG reservoir. SOLUTION: A feed pipe 13 for introducing LNG into a LNG reservoir 11 is inserted into a communication port 16. A lower portion of a turkey red oil pipe 14 having the communication port 16 is skewed and a slit 17 is opened to the side face at the upper side of the inclined pipe. BOG which is swirled from surroundings during carrying LNG from the feed pipe 13 to the turkey red oil pipe 14 through the communication port 16 is gathered to an upper portion with buoyancy during carrying the LNG in the turkey red oil pipe 14 and returned from the slit 17 to a gas layer 11G in the LNG reservoir 11. A gas in the LNG to be discharged from a discharge port 15 at the lower end of the turkey red oil pipe 14 into a liquid layer 11L is reduced, therefore restricting a temporary increase in BOG generation amount after receiving the LNG.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to liquefied natural gas (hereinafter, referred to as "liquefied natural gas").
The present invention relates to a liquefied gas storage tank for storing a low-temperature liquefied gas such as “LNG”.

[0002]

FIG. 3 shows a conventional LNG storage tank 1 and a conventional LNG storage tank.
1 shows a schematic configuration of a receiving pipe. LNG storage tank 1
LNG from an LNG transport ship or LNG from another LNG storage tank is transported via the NG pipe 2. LNG
The receiving pipe for receiving the LNG transported by the pipe 2 into the LNG storage tank 1 penetrates the LNG storage tank 1 and transports the LNG.
And a funnel 4 for guiding LNG to the bottom of the LNG storage tank 1. A discharge port 5 is provided at the lower end of the funnel 4.

When a single receiving pipe is used, the flow rate of the LNG flowing downward in the receiving pipe gradually increases, so that the LNG is rapidly gasified in the pipe, causing vibrations and excessive force. Becomes In order to prevent this phenomenon, conventionally, LNG is not introduced into the bottom of the LNG storage tank 1 with a single receiving pipe, but is introduced from the feed pipe 3 into the funnel 4 having a funnel-shaped communication port 6 and introduced. LN around the part
It communicates with the gas layer in the G storage tank 1. The communication port 6 is arranged at a position higher than the maximum liquid level of the LNG storage tank 1 so that it can always communicate with the gas layer.

When LNG flows through the feed pipe 3 and the funnel pipe 4, the pressure at the communication port 6 decreases due to the flow rate of LNG, and the gas in the LNG storage tank 1 is involved.
The amount of entrainment depends on the falling speed when LNG reaches the liquid level. As the falling speed increases, the amount of entrainment increases. The entrained gas is discharged into the LNG storage tank 1 from the T-shaped discharge port 5 at the tip of the funnel 4. The shape of the discharge port 5 may be L-shaped or the like in addition to the T-shaped illustrated. All or part of the discharged gas is crushed by the LNG head pressure and reliquefied. LNG existing around the discharge port 5 before receiving LNG is in a supercooled state corresponding to the head pressure of the liquid. However, the accepted LN
G is boosted by a pump (not shown),
When transported by the pipe 2, the temperature has risen due to the heat input. In addition, the LNG that has been entrained and reliquefied also emits heat to the surroundings when condensed, and thus has a higher temperature than the LNG that originally existed. Therefore, the liquid discharged from the discharge port 5 has a low degree of supercooling and is in a state where it is likely to be gasified again.

As the time for receiving LNG into the LN storage tank 1 elapses, the liquid having a low degree of supercooling also diffuses upward as described above. Since the head pressure of the LNG decreases as it goes upward, it is gasified again and boil-off gas (hereinafter, “BOG”)
).

FIG. 4 shows a temporal change in the amount of BOG generated observed at the part A in FIG. 3 when LNG is received in the LNG storage tank 1. The solid line shows the change when LNG is received in the 140,000 kL LNG storage tank 1 at a rate of 11,000 m ³ / h for 12 hours. Before receiving, 2t / h BOG for natural heat input from outside to LNG storage tank 1.
Has occurred. Since the entrainment of gas becomes dominant after the start of LNG reception at 0:00, the BO observed in Part A
The amount of G generation decreases and decreases to -5 t / h. BOG
Is negative, that is, BOG outside the LNG storage tank 1 is LN
It is sucked into the G storage tank 1. Thereafter, as time passes, the reliquefied liquid having a relatively high temperature begins to diffuse and reach the liquid surface, and the amount of BOG generated increases.
t / h. Even after the end of receiving LNG, LNG with a high liquid temperature continues to reach the liquid level, so that a large amount of BOG continues to be generated.
It calms down to the amount of BOG generated at t / h.

[0007]

The LN as shown in FIG.
The BOG generated in the G storage tank 1 is usually a BOG (not shown).
It is pressurized by an OG compressor and used as a raw material for city gas. BOG compressor capacity is the maximum amount of BOG generated,
That is, in the case of FIG. 4, equipment having a capacity of 40 t / h is required. When LNG is not received, a processing capacity of 2 t / h may be sufficient, but equipment having a capacity of 40 t / h is required at the peak, and considerable equipment installation costs are required.

Conventionally, this type of low-temperature liquefied gas storage tank has
Since the low-temperature liquefied gas is received through the upper feed pipe 3 and the funnel 4, the gas in the storage tank is entrained from the opening at the connection portion between the feed pipe 3 and the funnel 4, and the entrained gas receives the low-temperature liquefied gas. Gasification occurs again with the passage of time, and the amount of boil-off gas generated temporarily increases.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide an easy-to-use liquefied gas storage tank which suppresses the temporarily increased amount of boil-off gas when liquefied gas is received. It is assumed that.

[0010]

In order to achieve the above object, the liquefied gas storage tank according to the present invention is configured as follows.

According to the present invention, there is provided a liquefied gas storage tank for receiving a liquefied gas from above a liquid level, wherein the liquefied gas is installed so that at least a part thereof is skewed and has an opening on a pipe side which is on the upper side in the skewed state. A liquefied gas storage tank comprising a receiving pipe.

According to the present invention, in the liquefied gas storage tank for receiving the liquefied gas from above the liquid level, a part or all of the liquefied gas receiving pipe is installed obliquely, and the liquefied gas receiving pipe is skewed. And an opening is provided on the tube side on the upper side. When the liquefied gas flows in the skewed receiving pipe, the gas entrained in the liquefied gas floats in the liquefied gas and gathers on the pipe side that is on the upper side in the skewed state. Since the opening is provided on the upper pipe side, the gas is extracted from the receiving pipe and returns to the gas layer in the liquefied gas storage tank. The gas entrained in the liquefied gas is transported to the bottom of the liquefied gas storage tank and discharged into the liquid, and it is less likely to diffuse to the liquid surface over time. The amount of generation can be suppressed. Since fluctuations in the amount of boil-off gas generated can be suppressed, an easy-to-use liquefied gas storage tank can be obtained.

Further, the liquefied gas receiving pipe of the present invention has a communicating portion with a gas layer in the liquefied gas storage tank. It is characterized by being wide.

According to the present invention, the cross-sectional area of the flow passage of the receiving pipe is larger in the upper part than in the lower part in the range below the communicating part between the inside of the receiving pipe and the gas layer of the liquefied gas storage tank. Since the cross-sectional area of the flow path at the upper part of the receiving pipe is widened, if the gas entrapped in the liquid floats, it can easily return to the gas layer of the liquefied gas storage tank, providing a convenient liquefied gas storage tank. be able to.

[Detailed Description of the Invention] FIG. 1 shows a schematic configuration of an LNG storage tank 11 as one embodiment of the present invention. In the LNG storage tank 11 of the present embodiment, the funnel pipe 1 which is connected to the tip of the LNG pipe for transporting LNG and penetrates the LNG storage tank 11, is disposed at an oblique lower portion and is disposed.
LNG is led to 4. That is, a T-shaped discharge port 15 is provided at the lower end of the funnel 14 installed obliquely among the feed pipe 13 and the funnel 14 which are receiving pipes. At the upper end of the funnel 14, a communication port 16 opened upward is provided as a communication part. The inner diameter of the opening of the communication port 16 is larger than the outer diameter of the lower end of the feed pipe 13.
The communication port 16 serving as a joint portion between the feed pipe 13 and the funnel pipe 14 has an LNG storage tank 11 like the conventional LNG storage tank 1.
It communicates with the gas layer 11G inside. The position of the opening 16 is arranged at a position higher than the highest liquid level of the liquid layer 11L of the LNG storage tank 11.

Since the communication port 16 is always in communication with the gas layer 11G, when LNG flows from the feed pipe 13 to the funnel 14, the surrounding BOG is involved. A plurality of long holes 17 are provided as openings along the length direction on the upper side of the oblique funnel 14. Note that the opening may be formed as one long hole or notch by continuously connecting the entire plurality of long holes 17.

The gas trapped from the communicating portion 16 where the feed pipe 13 and the funnel pipe 14 are connected collects upward due to buoyancy when flowing through the oblique funnel pipe 14, and flows into the LNG storage tank from the long hole 17. It returns to the gas layer 11G in 11. Since about 50% of the BOG entrapped at the communication port 16 at the junction between the feed pipe 13 and the funnel 14 returns to the gas layer 11G, the maximum BOG generation amount is 20 t / h as shown by the dashed line in the figure. Become. Therefore, BOG to be installed
The compressor only needs to have a processing capacity of 20 t / h, and it is possible to greatly reduce equipment installation costs.

FIG. 2 shows a schematic configuration of an LNG storage tank 21 according to another embodiment of the present invention. Also in this embodiment, LNG
Is transported into the LNG storage tank 21 by the feed pipe 23 of the feed pipe 23 and the funnel pipe 24 serving as the receiving pipe, and is introduced into the bottom of the liquid layer 21L via the funnel pipe 24. The lower end of the funnel 24 is a discharge port 25 for discharging LNG at the bottom of the LNG storage tank 21. The upper part of the funnel 24 is funnel-shaped, and a communication port 26 is formed at the upper end. Is inserted into the communication port 26. The funnel tube 24 of this embodiment is installed along the spiral shape on the inner wall 27 of the cylindrical LNG storage tank 21, and a fastener 28
It is fixed at. In the funnel-shaped upper portion of the funnel 24, the diameter continuously decreases from the communication port 26 to a predetermined pipe diameter portion, and after reaching the predetermined pipe diameter, the pipe diameter portion becomes the discharge port 25. Continue until. However, the cross section of the funnel 24 remains circular until halfway. Most of the helical range has an arc-shaped cross section in which a part of a circle is removed at an upper tube side portion, and a notch 29 is formed as an opening. Note that, instead of the cutout 29 that continuously opens along the axis of the funnel 24, a plurality of long holes as shown in FIG. 1 can be provided.

In this embodiment, as in the embodiment of FIG.
Communication port 26 for joining feed pipe 23 and funnel pipe 24
The gas entrapped in the gas flows from the notch 29 to the upper portion when flowing through the funnel 24, and returns to the gas layer 21 </ b> G in the LNG storage tank 21. The notch 29 of the present embodiment is
The aperture ratio can be made larger than that of the long hole 17 of the embodiment of FIG. Moreover, the inclination of the funnel tube 24 can be arranged gently. That is, since the flow rate of LNG can be suppressed, the effect of returning the entrained BOG to the gas layer 21G is further enhanced. Under the same conditions as in FIG. 3 and FIG. 1, the maximum BOG generation amount is further reduced to 15 t / h, and the installation cost of the BOG compressor can be greatly reduced.

In the above description, the case where LNG is stored as a liquefied gas is described. However, other types of liquefied gas such as liquefied petroleum gas (LPG) are also described.
The invention is equally applicable.

[0021]

As described above, according to the present invention, the generation of the boil-off gas, which temporarily increases, can be suppressed, so that an easy-to-use liquefied gas storage tank can be provided.

Further, according to the present invention, a communication portion communicating with the gas tank in the liquefied gas storage tank is provided while the liquefied gas is being received in the liquefied gas storage tank by the liquefied gas receiving pipe. Since the cross-sectional area of the flow path of the receiving pipe is made wider at the upper part than at the lower part, if the gas caught in the liquid floats, it can easily return to the gas layer of the liquefied gas storage tank, An increase in the amount of boil-off gas generated can be suppressed.

[Brief description of the drawings]

FIG. 1 shows an LNG storage tank 11 according to an embodiment of the present invention.
FIG. 2 is a partial cross-sectional view showing a schematic configuration of FIG.

FIG. 2 shows an LNG storage tank 21 according to another embodiment of the present invention.
FIG. 2 is a partial cross-sectional view showing a schematic configuration of FIG.

FIG. 3 is a simplified sectional view showing a schematic configuration of a conventional LNG storage tank.

FIG. 4 is a graph showing a temporal change of BOG generated when LNG is received in the LNG storage tank.

[Explanation of symbols]

 11, 21 LNG storage tank 11G, 21G Gas layer 11L, 21L Liquid layer 13, 23 Feed pipe 14, 24 Funnel 15, 25 Discharge port 16, 26 Communication port 17 Long hole 27 Inner wall 28 Fastener 29 Notch

Claims (2)

[Claims] 1. A liquefied gas storage tank for receiving a liquefied gas from above a liquid surface, wherein the liquefied gas receiving pipe is installed so that at least a part thereof is skewed and has an opening on a pipe side which is upper in a skewed state. A storage tank for liquefied gas, comprising: 2. The liquefied gas receiving pipe has a communication portion with a gas layer in a liquefied gas storage tank, and in a range below the communication portion, a cross-sectional area of a flow path is larger at an upper portion than at a lower portion. The liquefied gas storage tank according to claim 1, wherein: