JP2005155668A - Cryogenic liquid shipping piping line - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cryogenic liquid shipping piping line capable of reducing facility cost and operation cost and preventing loss of cryogenic liquid. <P>SOLUTION: This cryogenic liquid shipping piping line 1 is provided with a vent means 6 for evaporation gas whose one end part is connected with the halfway of a shipping pipe 3 and an evaporation gas return pipe 7 connecting a carrying vessel BOG return pipe 5 with the other end part of the vent means 6 for evaporation gas to return evaporation gas in the vent means 6 for evaporation gas into an upper part of a cryogenic liquid tank 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

    The present invention is used for shipping and receiving cryogenic liquids, and is always kept at a low temperature for standby, particularly cryogenic liquid shipping piping such as LNG shipping piping lines for loading LNG products from LNG manufacturing plants onto LNG carriers. About the line.

    The shipping piping line for loading LNG in the LNG (liquefied natural gas) storage tank onto the LNG carrier ship is for the purpose of preventing the generation of BOG (Boil Off Gas) due to heat input to the LNG. A small amount of LNG increased in pressure is circulated and cooled by sensible heat of LNG, so that the temperature is always kept low.

  Although there are no documents, patents, etc. published regarding the cold insulation of this LNG shipping piping etc., the following Patent Literature 1 is disclosed for the piping received from the LNG carrier to the LNG storage tank.

  Conventionally, the receiving pipe for transporting LNG from the LNG carrier to the base receiving LNG tank is always kept in a full liquid state. Therefore, when a large-capacity circulation pump is installed, there is a problem that the operation cost increases. It was.

  Therefore, according to Patent Document 1, in order to keep the receiving pipe pre-cooled, the entire amount of the LNG liquid is extracted from the receiving pipe, the BOG compressor is operated, BOG is introduced into the receiving pipe, and the low temperature gas is filled with BOG. It is cooling.

  Although a detailed description of the piping configuration for transporting LNG from the LNG carrier to the base receiving LNG tank is not made, according to FIG. 1, it is composed of an LNG receiving piping, a BOG piping, and a bypass piping connecting them.

On the other hand, the cooling method for shipping piping and the like when shipping the product LNG in the LNG manufacturing plant is not essentially different from the above-described configuration. In practice, the shipping piping is about 76 cm (30 inches) in diameter. By providing a return-only LNG circulation pipe with a diameter of about 20 cm (8 inches) and two shipping pipes with a diameter of about 61 cm (24 inches), one of the pipes is used as a return LNG circulation pipe during circulation cooling. Two forms are used.
No. 6-33872

    By the way, as described above, in the cold insulation by the LNG circulation, a small amount of LNG is circulated by a dedicated circulation pump having a capacity much smaller than that of the shipping pump.

  In this way, since a dedicated circulation pump that is unnecessary for the purpose of transporting LNG is provided, heat input to the LNG from the motor that drives the dedicated circulation pump is inevitable, and the vaporization of LNG to BOG is promoted. And incurs a loss of LNG.

  On the other hand, even when the shipping pump and the dedicated circulation pump are combined, the shipping / dedicated circulation pump is installed in the LNG tank, and once it is pumped up to the top of the LNG tank and loaded on the LNG carrier, Larger ones are required, as well as increasing excess heat input leading to LNG loss.

  In addition, a return LNG circulation (CIRCULATION) pipe for circulating LNG is required.

  In view of the above circumstances, the present invention eliminates the need for a dedicated circulation pump, circulation piping, etc., reduces the equipment cost by simplifying the equipment and reduces the operating cost, and can prevent the loss of the cryogenic liquid. The purpose is to provide.

    In order to achieve the above object, a cryogenic liquid shipping piping line according to claim 1 of the present invention includes a shipping piping for delivering a cryogenic liquid stored in a cryogenic liquid tank to a carrier ship, an upper portion of the carrier ship and the cryogenic liquid tank. And a transport ship BOG return pipe for returning the evaporated gas in the transport ship to the upper part of the cryogenic liquid tank, and an evaporative gas having one end connected in the middle of the shipment pipe A venting means, an evaporative gas return pipe for connecting the other end of the evaporative gas vent means and the transport ship BOG return pipe, and returning the evaporative gas in the evaporative gas vent means to the upper part of the cryogenic liquid tank. It is characterized by comprising.

  The cryogenic liquid shipping piping line according to claim 2 of the present invention is the cryogenic liquid shipping piping line according to claim 1, wherein the discharge pump for delivering the cryogenic liquid in the cryogenic liquid tank to the carrier ship is the cryogenic liquid tank. And is also used for the circulation of the cryogenic liquid in the shipping piping and the cryogenic liquid tank.

  The cryogenic liquid shipping piping line according to claim 3 of the present invention is the cryogenic liquid shipping piping line according to claim 1 or 2, wherein the evaporative gas vent means has a liquid level control function. Yes.

    As described above in detail, according to the low-temperature liquid shipping piping line according to claim 1 of the present invention, the evaporative gas vent means whose one end is connected to the middle of the shipping piping, and the other end of the evaporating gas vent means And an evaporative gas return pipe connecting the carrier BOG return pipe, a low-temperature liquid circulation pipe is not required, and the equipment cost can be reduced.

  According to the cryogenic liquid shipping piping line according to claim 2 of the present invention, since the dispensing pump is installed outside the cryogenic liquid tank, the heat input to the cryogenic liquid is reduced during the dispensing operation, and the loss of the cryogenic liquid is reduced. To reduce.

  Further, at the time of non-dispensing operation, the dispensing pump is not operated, and the liquid head is used for circulation of the low temperature liquid, so that a dedicated circulation pump is unnecessary.

  Thus, the equipment cost is reduced and the power consumption of the dedicated circulation pump is eliminated.

  According to the low-temperature liquid shipping piping line according to claim 3 of the present invention, since the evaporative gas vent means has a liquid level control function, the liquid level control of the low temperature liquid corresponding to the pressure of the evaporative gas is possible.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  An LNG shipping piping line (low temperature liquid shipping piping line) 1 in an LNG manufacturing plant of an embodiment of the present invention is shown in FIG.

  The LNG shipping piping line 1 includes an LNG tank (cold liquid tank) 2 in which manufactured LNG (low temperature liquid) products are stored, and an LNG connecting the LNG tank 2 and an LNG carrier ship (transport ship) S which is an LNG tanker. Shipping piping (shipping piping) 3, discharge pump 4 for passing LNG in the LNG tank 2 through the LNG shipping piping 3 and paying it to the LNG carrier S, loading arm 8 and LNG carrier for connecting the LNG to the LNG carrier S One end is connected to the loading arm 8 ′ for returning the BOG generated in S, the carrier ship BOG return pipe 5 for returning the BOG (evaporated gas) in the LNG carrier S to the upper part of the LNG tank 2, and the LNG shipping pipe 3. BOG extraction vent device (evaporation gas vent means) 6 and the other end of the BOG extraction vent device 6 are connected to the carrier BOG return pipe 5 That BOG return pipe is constituted and a (evaporative gas return line) 7.

  In the LNG tank 2, LNG is stored at a lower temperature of −160 ° C., and BOG generated by vaporization of LNG is −140 ° C. to −120 ° C. Stored at temperature.

  The payout pump 4 is installed outside the LNG tank 2, and heat generated in the drive motor of the payout pump 4 is prevented from entering the LNG and causing BOG.

  When the LNG is not loaded onto the LNG carrier S, the LNG in the LNG tank 2 is circulated through the LNG shipping pipe 3, the BOG return pipe 7, and the carrier BOG return pipe 5 by gravity (gravity) without operating the discharge pump 4. And returned to the LNG tank 2 as a BOG. That is, at the time of non-loading to the LNG carrier S, the LNG shipping pipe 3, the BOG return pipe 7 and the like are cooled by latent heat when LNG evaporates into BOG.

  The LNG shipping pipe 3 is connected to the lower part of the LNG tank 2, and one or a plurality of BOG extraction vent devices 6 are provided in the middle of the LNG shipping pipe 3 to extract BOG generated by LNG vaporization. .

  The BOG extraction vent device 6 includes a level controller LC for controlling the liquid level of the LNG, and has a liquid level control function of the LNG corresponding to the BOG pressure.

  This liquid level control function enables LNG liquid level control corresponding to the BOG pressure of the carrier ship BOG return pipe 5.

  The carrier BOG return pipe 5 connects the LNG carrier S and the upper part of the LNG tank 2, returns the BOG in the LNG carrier S to the LNG tank 2, and vents the BOG for the LNG in the LNG shipping pipe 3. The BOG of the apparatus 6 is returned into the LNG tank 2 via the BOG return pipe 7.

  Next, the operating state of the LNG shipping piping line 1 having the above-described configuration will be described.

  The LNG manufactured in the LNG manufacturing plant is transported and stored in the LNG tank 2 that is temperature-controlled at a low temperature.

  The LNG in the LNG tank 2 is loaded on the LNG carrier S through the LNG shipping pipe 3 by driving the discharge pump 4. At this time, the BOG generated by heat input to the LNG in the shipping pipe 3 is extracted by the BOG extraction vent device 6, passes through the BOG return pipe 7 and the transport ship BOG return pipe 5, and returns to the LNG tank 2. ing.

  By the way, the shipping pipe 3 is filled with LNG by the LNG liquid head in the LNG tank 2.

  When the LNG is not loaded onto the LNG carrier S, a small amount of LNG boosted by gravity is driven through the shipping pipe 3, the BOG return pipe 7, and the carrier BOG return pipe 5 without driving the discharge pump 4. Is returned to the LNG tank 2 and circulated.

  As described above, when the LNG is not loaded, the shipping piping 3, the BOG return piping 7, and the like are maintained at a predetermined low temperature by being circulated by gravity.

  Therefore, when LNG is loaded, loss due to vaporization of LNG to BOG due to the temperature rise of the shipping pipe 3 is prevented.

  According to the said structure, the return LNG circulation piping conventionally required is unnecessary.

  In addition, since the discharge pump 4 is installed outside the LNG tank 2, the LNG shipping pipe 3 can be filled with LNG by the LNG liquid head in the LNG tank 2, and the equipment such as a dedicated circulation pump can be used. Contributes to reduction.

  Furthermore, a dedicated circulation pump is unnecessary, and consumption of electric power for driving the pump is eliminated.

  Therefore, the facility is simplified, the facility cost is reduced, and the operation cost is reduced.

  In this way, the dedicated circulation pump is not installed in the LNG tank 2, and the LNG discharge and the discharge pump 4 that is used for both LNG circulation are installed outside the LNG tank 2. There is no heat, vaporization of LNG is prevented, and loss of LNG is eliminated.

  Therefore, according to the present invention, it is possible to reduce the facility cost and the operating cost with a simple configuration, and it is possible to provide the LNG shipping piping line 1 that prevents loss.

  In the above embodiment, LNG is exemplified as the low temperature liquid. However, the present invention is also applicable to low temperature liquids other than LNG such as LPG (liquefied petroleum gas).

    As an application example of the present invention, it is suitable for facilities that are always kept at a low temperature for shipment / acceptance of cryogenic liquid, such as a piping line for loading LNG into an LNG carrier in the LNG manufacturing plant exemplified in the embodiment.

The conceptual diagram which shows the LNG shipping piping line of the Example in connection with this invention.

Explanation of symbols

1 ... Low-temperature liquid shipping piping line (LNG shipping piping line),
2 ... Low temperature liquid tank (LNG tank),
3 ... Shipping piping (LNG shipping piping),
4 ... Dispensing pump,
5… Transport ship BOG return piping,
6 ... Vapor means for evaporative gas (vent device for extracting BOG),
7 ... Evaporative gas return pipe (BOG return pipe),
8 ... LNG shipping loading arm,
8 '... Evaporative gas (BOG) return loading arm,
S: Carrier (LNG carrier).

Claims (3)

A transport ship BOG for connecting the transport ship and the upper part of the cryogenic liquid tank by returning the cryogenic liquid stored in the cryogenic liquid tank to the transport ship and returning the evaporated gas in the transport ship to the upper part of the cryogenic liquid tank A cryogenic liquid shipping piping line comprising a return piping,
Vapor means for evaporating gas with one end connected in the middle of the shipping piping;
An evaporative gas return pipe for connecting the other end of the evaporative gas vent means to the transport ship BOG return pipe and returning the evaporative gas in the evaporative gas vent means to the upper part of the low-temperature liquid tank. A low-temperature liquid shipping piping line. The discharge pump for discharging the low-temperature liquid in the low-temperature liquid tank to the carrier ship is installed outside the low-temperature liquid tank, and is also used for circulation of the low-temperature liquid in the shipping pipe and the low-temperature liquid tank. The low-temperature liquid shipping piping line according to claim 1, wherein The low temperature liquid shipping piping line according to claim 1 or 2, wherein the evaporative gas vent means has a liquid level control function.

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