JP2001280591A - Bog return method to tanker for transporting low- temperature liquid, and pipe used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce piping work and cost by integrating a reception piping and return BOG piping into one, as viewed from the outside in a low tempera ture liquid (LNG or the like) receiving station, and prevent the generation of troubles, such as liquid shock phenomenon caused by the condensated return BOG in the piping. SOLUTION: A piping line of double pipe structure composed of Invar (R) material is arranged at a part between an LNG tanker and an LNG storage tank, and the LNG is passed to be received in the storage tank form the tanker 1, on the side of the inner pipe 11 of the double pipe, while the BOG is passed to be received in the tank in the LNG tanker from the LNG storage tank, on the side of the outer pipe 12. The sides of inner and outer pipe 11, 12 are composed of invar material having a small linear expansion coefficient. A part of a cold insulator 13 on the side of outer pipe 12 is cut to expose the outer pipe 12 to the atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of returning a BOG to a low-temperature liquid such as LNG, which is carried out when the low-temperature liquid is received into a low-temperature liquid storage tank from a tanker that has transported the low-temperature liquid. The present invention relates to a piping material used in the return method.

[0002]

2. Description of the Related Art For example, LNG transported from a place of origin by an LNG tanker comes in contact with a quay of a receiving base,
It is designed to be received in a storage tank on the ground via a receiving pipe. FIG. 4 shows an outline of this receiving base, where 1 is an LNG tanker, 2 is a quay, 3 is a storage tank on the ground, 4 is an LNG receiving pipe, 5 is a BOG return pipe, and the inside of the LNG tanker 1 is shown. LNG is received into the storage tank 3 via the receiving pipe 4. Further, in the LNG tanker 1, since the pressure in the tank at the side of the ship decreases due to the discharge of the LNG, the BOG generated in the storage tank 3 is passed through the BOG return pipe 5 in order to prevent the pressure from decreasing. In order to maintain the pressure in the tank by receiving it in the tank on the side of the ship. FIG. 5 is an example of a piping rack provided between the tanker 1 and the storage tank 3,
The LNG receiving pipe 4 and the BOG
The return pipe 5 is separately supported, and the LNG receiving pipe 4
As shown in FIG. 6, the BOG return pipe 5 is covered with a cooling material 7 on its outside.

[0003]

For this reason, the conventional LN
The method of receiving G and returning BOG has the following disadvantages. 1. Since the LNG receiving pipe 4 and the BOG return pipe 5 are separately constructed, the construction takes time and effort. 2. It is necessary to separately cover the LNG receiving pipe 4 and the BOG return pipe 5 with the heat insulating material 7, and this cold insulating work requires cost, time and trouble. 3. It is necessary to make the piping rack 6 large, and a lot of cost is required for construction. 4. The area occupied by piping equipment in the base will increase. 5. If a crack or the like occurs in the LNG receiving pipe 4 and the BOG return pipe 5, there is a concern that LNG or BOG leaks directly into the atmosphere. 6. When the condensed liquid accumulates in the BOG return pipe, there is a concern that a liquid hammer phenomenon may occur.

A first object of the present invention is to provide a double pipe for a pipe for receiving a low temperature liquid from a tanker into a storage tank and a return pipe for a BOG to be returned to the tanker, thereby reducing the time and cost involved in the pipe. The problem is to reduce problems such as location, location, etc. A second purpose is to ensure safety in the event of a leak from the receiving pipe. A third object is to prevent the occurrence of a liquid hammer phenomenon in the piping that occurs when the returned BOG is recondensed.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, in a method of returning BOG to a low-temperature liquid transport tanker, a double pipe is formed of an invar material, A pipe material in which the outside of the heavy pipe is covered with a cold insulator is piped between the tanker side and the storage tank on the ground, and the low-temperature liquid is received from the tanker into the storage tank via the inner pipe side of the double pipe, and the outer pipe is The BOG generated in the storage tank is returned to the tanker via the storage tank.

Further, in the invention according to claim 2,
According to the first aspect of the present invention, a condensed liquid reservoir is formed in a part of the piping system path, and the cooling material outside the outer tube including the condensed liquid reservoir is omitted to remove the condensed liquid reservoir and the double pipe. When the tube side is exposed to the atmosphere and a part of the returned BOG is condensed due to the cold heat of the LNG flowing in the inner tube, the condensed BOG is temporarily stored in the condensate reservoir, and then B condensed by the atmospheric heat.
The OG is re-vaporized, mixed into the BOG being returned, and supplied for return.

Further, in the invention according to claim 3,
The invention according to claim 1 or 2, characterized in that the condensed BOG flows toward the condensate pool by making a part of the pipe have a downward slope toward the condensate pool. It is.

Further, in the invention according to claim 4,
In the BOG return pipe material for the low-temperature liquid transport tanker, a double pipe composed of an inner pipe and an outer pipe is formed by an invar material, and a condensed liquid reservoir is formed in a part of the outer pipe, and the condensate pool is further lowered. The heat insulating material coated on the outside of the outer tube is removed at a portion including the condensate reservoir to expose the condensate reservoir and the outer tube to the atmosphere.

Further, in the invention described in claim 5,
The invention according to claim 4 is characterized in that a part of the outer tube is inclined toward the condensate pool.

[0010]

The low-temperature liquid discharged from the tanker is received in the storage tank via the inner pipe side of the double pipe. On the other hand, the BOG generated in the storage tank is returned to the tank on the side of the tanker via the outer pipe side. Since the condensed liquid pool exposed to the atmosphere exists in a part of the piping system path, when the BOG being returned is liquefied by the cold heat of the low-temperature liquid, it is temporarily stored in the condensed liquid pool. The condensed BOG in the condensate reservoir is vaporized by atmospheric heat because the condensate reservoir and the outer tube side are partially exposed to the atmosphere, and the vaporized BOG is returned to the tanker along with the returned BOG. Will be returned.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The double piping material of the present invention
Both are made of an invar material having a small linear expansion coefficient value of 1.4 × 10 ⁻⁶ / ° C., and the outside of the outer tube is covered with a cold insulator such as a foam.

[0012] A part of the piping system path (optimal location) is partially cut off to expose the outer pipe to the atmosphere by removing a part of the cold insulator, and BOG is liquefied in the exposed part by the cold heat of the low-temperature liquid. A condensate pool that accumulates in some cases is formed. Also, by making a gentle downward slope toward this condensate pool,
Allow the condensed BOG to flow naturally. In this case, depending on the heat balance, the returned BOG may be condensed due to the cold heat of the low-temperature liquid in the inner tube, and this can be temporarily stored in the condensed liquid reservoir. Since the condensed liquid pool has no cooling material and is open to the atmosphere, the liquefied BOG in the condensed liquid pool is re-evaporated by atmospheric heat and returned to the tanker together with the returned BOG. Is done.

[0013]

Embodiment 1 An embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1 is a conceptual diagram of an LNG receiving pipe and a BOG return pipe at an LNG receiving terminal, FIG. 2 is a sectional view of a pipe material, and FIG. 3 is an explanatory view of a condensate pool. 1 is LNG tanker, 2 is quay, 3 is L
In the NG storage tank, the LNG tanker 1 and the LNG storage tank 3 are connected by a piping line 10 having a double pipe structure. The piping line 10 is, as shown in FIG.
1, an outer tube 12, and a cold insulator 13 covering the outer tube 12. LNG is received via the inner tube 11, and BOG is returned via the outer tube 12.

FIG. 3 is an explanatory view of a condenser 14 provided in a part of the piping line 10. The condenser 14 is provided with a part of the outer pipe 12 without the cooling material 13. While being exposed to the atmosphere, the lower surface of the outer tube 12 is formed one step lower to form a condensed liquid reservoir 15.
When a part of the returned BOG is condensed due to the heat balance with the inner tube 11 side, the condensed BOG is removed from the condensed liquid pool 15 by the heat balance with the inner tube 11 side.
It is allowed to flow inside and is temporarily stored here. Since the outer tube 12 is exposed to the atmosphere in the condensed liquid reservoir 15 at the outer tube 12, the accumulated BOG is vaporized by the heat input of atmospheric heat, and the vaporized BOG is mixed with the returned BOG and is returned to the tanker 1 again. Sent to the side.

In this embodiment, the condensed BO
Although G is vaporized by atmospheric heat, it may be vaporized by artificial heat using an electric heater or the like for the vaporization. Also,
The condensate reservoir 15 is not necessarily provided when the piping line 10 is relatively short, or when the return BOG does not condense due to better heat balance design.

[0016]

As described above, according to the present invention, a double pipe made of invar is piped between a tanker for transporting a low-temperature liquid and a storage tank, the low-temperature liquid being received is flowed to the inner pipe side, and the outer pipe is flown to the outer pipe side. By causing the return BOG to flow, the following effect can be obtained in the first aspect of the present invention. 1. Since the inner tube and the outer tube are made of Invar material, there is almost no difference in heat shrinkage between the inner tube and the outer tube. Therefore, there is no positional displacement between the inner pipe and the outer pipe, and almost no stress is generated at the spacer for maintaining the interval between the inner pipe and the outer pipe or at the joint of the pipes, and leakage can be prevented. 2. Piping work for receiving cryogenic liquid and returning BOG
Since the number of pipes is one, the labor and cost of piping work including cold insulation work can be greatly reduced. 3. For example, an outer tube through which the return BOG passes is located outside the inner tube through which LNG at -162 ° C. passes, and the BOG flows in this outer tube, so that the heat of the LNG is insulated by the BOG layer on the outer tube side. As a result, the heat insulating material can be made thinner than in the case of the conventional LNG receiving pipe, and the cost can be reduced accordingly. 4. Even if a crack or the like occurs in the inner tube and LNG leaks, the LNG is blocked by the outer tube, so there is no fear of leaking to the outside, and the safety is high. 5. Large piping space and piping racks are not required. 6. In the invention according to claims 2 to 5, even if the BOG being returned in the outer tube is condensed, it is temporarily stored in the condensed liquid pool, and is re-evaporated by atmospheric heat or the like, and is returned together with the BOG being returned. Since it is provided for re-return, it is possible to prevent a trouble such as a liquid hammer phenomenon from occurring in the outer tube due to the condensed BOG. Also, if you try to re-vaporize with atmospheric heat,
There is no cost for the heat source.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention in which a receiving pipe and a return BO of an LNG receiving terminal are used.
Explanatory drawing of the example implemented to G piping.

FIG. 2 is a cross-sectional view of a piping material.

FIG. 3 is an explanatory view of an embodiment in which a condensate reservoir is provided on the outer tube side.

FIG. 4 is an explanatory diagram of an LNG receiving pipe and a BOG returning method at a conventional LNG receiving base.

FIG. 5 is an explanatory view of a piping rack.

FIG. 6 is an explanatory diagram of a cold insulator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Piping line 11 Inner pipe 12 Outer pipe 13 Cooling material 14 Condenser 15 Condensate pool 16 Slope a Condensed BOG

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3E073 DD06 3H111 AA01 CA17 CB14 CB23 DA15 DA23 DB08 DB11 3J071 AA23 BB11 CC04 CC06 DD04 FF02

Claims (5)

[Claims] 1. A double pipe made of an invar material, and a pipe material whose outside is covered with a cooling material is piped between a tanker side and a storage tank on the ground, and an inner pipe side of the double pipe. B for the low-temperature liquid transport tanker that receives the low-temperature liquid from the tanker into the storage tank via the outer pipe and returns the BOG generated in the storage tank to the tanker side via the outer tube
OG return method. 2. A condensed liquid reservoir is formed in a part of a piping system passage, and a cooling material outside the outer tube including the condensed liquid reservoir is omitted to remove the condensed liquid reservoir and the outer tube side of the double tube from the outside. Exposed inside,
When a part of the returned BOG is condensed due to the cold heat of the LNG flowing in the inner tube, the condensed BOG is temporarily stored in the condensate reservoir, and then the BOG condensed by atmospheric heat is re-vaporized to be returned to the returned BOG. The method for returning BOG to a low-temperature liquid transport tanker according to claim 1, wherein the BOG is mixed and supplied for return. 3. The low-temperature liquid transport tanker according to claim 1, wherein the condensed BOG flows toward the condensed liquid reservoir by making a part of the pipe have a downward slope toward the condensed liquid reservoir. To return BOG to 4. A double pipe composed of an inner pipe and an outer pipe is formed by using an invar material, and a condensed liquid reservoir is formed on a part of the outer pipe, the condensate being lowered one step further, and further, the outer pipe is coated on the outside of the outer pipe. A BOG return piping material for a low-temperature liquid transport tanker, wherein a cold insulator is omitted in a portion including the condensate reservoir to expose the condensate reservoir and an outer tube to the atmosphere. 5. The piping material for returning a BOG to a low-temperature liquid transport tanker according to claim 4, wherein a part of the outer pipe is inclined toward the condensate pool.