JP2019011814A - Liquefied gas discharge system and discharge method - Google Patents

Abstract

To stably discharge liquefied gas accumulated in a floating hose on the sea, regardless of performance of a gas production device configured to produce discharge gas.SOLUTION: A liquefied gas discharge system 5 comprises: a gas production device 15 configured to produce discharge gas having a condensation point lower than liquefied gas; a compressor 22 configured to compress the discharge gas produced by the gas production device 15; a pressure accumulation container 25 filled with the discharge gas compressed by the compressor 22; and a discharge gas supply line 31 configured to supply to a floating hose 3 the discharge gas with which the pressure accumulation container 25 is filled.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a floating hose used for transferring liquefied gas from a dispensing facility to a receiving facility, and a discharge system and method for discharging liquefied gas remaining in a marine hose after completing the transfer of liquefied gas. About.

  Natural gas consists mostly of methane, with other major components being nitrogen, ethane, propane and butane. Examples of the liquefied gas include LNG mainly composed of methane, ethane, propane, and butane.

  Conventionally, in the case of liquefied gas transfer from the land delivery facility to the hull, from the hull to the land receiving facility, or from the hull to the hull, the hull is placed next to the pier attached to the land dispensing / receiving facility, or the liquefied gas transfer between the hulls The hulls are placed side by side and are implemented by an articulating loading arm or by a flexible hose having a shorter length. For the purpose of ensuring safety in the separation work after the completion of transfer, a process of discharging the liquefied gas remaining in the transfer line connecting between the dispensing equipment and the receiving equipment is generally performed. When the liquefied gas is discharged from the loading arm or the like, an inert gas (nitrogen gas or the like) is used as the discharge gas.

  However, the liquefied gas transfer between the hulls can be arranged side by side only under the condition that the sea is extremely calm. Therefore, in the case of rough seas, a proposal has been proposed in which a floating hose is used to move the hulls apart by a safe distance of at least about 50 m to 300 m. In addition, a transfer facility using a floating hose similar to the transfer of liquefied gas between hulls has been proposed as an alternative to the pier attached to the liquefied gas on-site delivery / reception facility.

  When the floating hose is used, the shipping hose becomes longer and a rising portion is formed at the connecting portion between the hull and the hose. In order to discharge LNG (Liquefied Natural Gas) and the like from such a transfer line, a larger amount of exhaust gas is required than in the past. For example, a gas having the same composition as LNG (Defrost Gas) Alternatively, a method using boil-off gas (BOG) or the like is also conceivable. On the other hand, when a gas having the same composition as LNG is used as the exhaust gas, when the exhaust gas is injected into the transfer line, the exhaust gas in contact with the cryogenic LNG remaining in the transfer line is Abrupt condensation may cause troubles such as hammering.

  On the other hand, a technique using an inert gas (nitrogen gas or the like) as a discharge gas is known. For example, after the liquefied gas is transferred from the tank of the carrier ship to the receiving base, the inside of the loading arm constituting the transfer line is There is a technique for automatically replacing with an inert gas (see Patent Document 1).

Japanese Utility Model Publication No. 5-34399

  By the way, in the prior art described in the above-mentioned Patent Document 1, it is necessary to prepare an inert gas used as a discharge gas. However, for the purpose of discharging only the liquefied gas remaining in the loading arm of the transfer line, FLNG (Floating Liquefied Natural Gas) is not intended for the discharge of liquefied gas remaining in the entire transfer line from the production base to the transport ship and from the transport ship to the receiving base, and the liquefied gas remaining in the entire transfer line is discharged. There is a problem that the necessary amount of the inert gas is large, and it is not suitable for the cost to install the production apparatus of the inert gas corresponding to the necessary amount at the production base, the transport ship or the receiving base.

  On the other hand, it may be possible to divert the production equipment for inert gas used for other purposes in production facilities, transport ships or receiving terminals, but ensure the flow rate and pressure necessary for discharging the liquefied gas remaining in the transfer line. There is a problem that it is difficult.

  In particular, when a floating hose floating on the sea surface is used for a transfer line, there is a large difference in height depending on the discharge path of the liquefied gas (for example, the liquefied gas in the floating hose on the sea Therefore, it may be necessary to ensure a larger flow rate and pressure for the exhaust gas.

  The present invention has been devised in view of such problems of the prior art, and stably stabilizes the liquefied gas remaining in the floating hose at sea regardless of the performance of the gas production apparatus for producing the exhaust gas. The main object of the present invention is to provide a liquefied gas discharge system and discharge method that can be discharged.

  In the first aspect of the present invention, there is provided a discharge system (5) for liquefied gas remaining in the floating hose (3) at sea used for transferring the liquefied gas from the dispensing facility (1) to the receiving facility (2). A gas production device (15) for producing an exhaust gas having a lower condensation point than the liquefied gas, a compressor (22) for compressing the exhaust gas produced by the gas production device, and the compressor An accumulator container (25) filled with the exhaust gas compressed by the exhaust gas supply line (31) for supplying the exhaust gas filled in the accumulator container to the floating hose; It is provided with.

  According to this, by using the pressure accumulating container filled with the discharge gas compressed by the compressor, it is possible to easily ensure the flow rate and pressure required for the discharge gas. Therefore, it becomes possible to stably discharge the liquefied gas remaining in the floating hose at sea regardless of the performance of the gas manufacturing apparatus for manufacturing the exhaust gas.

  In the second aspect of the present invention, the exhaust gas filling amount in the pressure accumulating vessel can complete the discharge of the liquefied gas remaining in the floating hose using the entire amount of the exhaust gas filled. It is set as follows.

  According to this, since the entire amount of the filled exhaust gas is used for the discharge of the liquefied gas, it is not necessary to perform control, operation, or the like such as stopping the delivery of the exhaust gas from the pressure accumulating container at an appropriate timing. In addition, since it is easy to adjust the amount of exhaust gas used, excess exhaust gas is sent to the receiving equipment, adversely affecting the receiving equipment (for example, exceeding the design pressure of the storage tank for liquefied gas) Can be prevented. Alternatively, troubles such as increasing the inert gas concentration in the boil-off gas by mixing excess boil-off gas generated from the pay-out facility by returning the exhaust gas as return gas from the receiving facility to the discharge facility Can do.

  In the third aspect of the present invention, the capacity of the pressure accumulating vessel is such that the amount of the exhaust gas necessary for discharging the liquefied gas remaining in the floating hose only once can be filled. It is characterized by being set.

  According to this, the size of the pressure accumulating container is prevented from becoming unnecessarily large, and a compact facility can be realized.

  In the fourth aspect of the present invention, a flow rate adjusting device (37, 62, 162) provided in the exhaust gas supply line and for adjusting the flow rate of the exhaust gas supplied from the pressure accumulator to the floating hose. Is further provided.

  According to this, it is possible to easily realize the flow rate required for the discharge gas, and it is possible to discharge the liquefied gas remaining in the floating hose at sea more stably.

  In the fifth aspect of the present invention, the liquefied gas is liquefied natural gas, and the exhaust gas is nitrogen.

  According to this, it becomes easy to divert the manufacturing apparatus of the nitrogen gas used for other uses in the liquefied natural gas paying-out facility or receiving facility.

  The sixth aspect of the present invention is characterized in that the pressure accumulating container is installed in the dispensing facility or the receiving facility together with the floating hose winding device (4).

  According to this, since the floating hose used for the transfer of the liquefied gas is limited, the size required for the pressure accumulating container can be set more reliably.

  The seventh aspect of the present invention is characterized in that the exhaust gas supply line is connected to a liquefied gas transfer line (32) to which the floating hose is connected in the dispensing facility or the receiving facility. .

  According to this, after the liquefied gas transfer process is completed, it is possible to easily shift to the liquefied gas discharge process.

  In the eighth aspect of the present invention, the liquefied gas transfer line is provided on the upstream side of the connection portion (33) of the exhaust gas supply line in the liquefied gas transfer line, and shuts off the supply of the liquefied gas to the floating hose. Further, a shut-off valve is provided.

  According to this, a part of the liquefied gas transfer line can be used for discharging the liquefied gas, and the system configuration is simplified.

  According to a ninth aspect of the present invention, there is provided a method for discharging liquefied gas remaining in a floating hose (3) at sea used for transferring liquefied gas from a dispensing facility (1) to a receiving facility (2), A production process for producing an exhaust gas having a lower condensation point than the liquefied gas; a compression process for compressing the exhaust gas produced in the production process; and the exhaust gas compressed in the compression process. A filling step of filling the pressure accumulating vessel (25), and a discharging step of discharging the liquefied gas remaining in the floating hose by supplying the exhaust gas filled in the pressure accumulating vessel to the floating hose. It is characterized by including.

  According to this, by filling the pressure accumulating container with the discharge gas compressed by the compressor, it is possible to easily ensure the flow rate and pressure required for the discharge gas. Therefore, it is possible to stably discharge the liquefied gas remaining in the floating hose at sea regardless of the performance of the gas manufacturing apparatus that performs the manufacturing process for manufacturing the exhaust gas.

  The tenth aspect of the present invention is characterized in that the discharge step is performed using the entire amount of the discharge gas filled in the pressure accumulating container in the filling step.

  According to this, since the entire amount of the filled exhaust gas is used for the discharge of the liquefied gas, it is not necessary to perform control, operation, or the like such as stopping the delivery of the exhaust gas from the pressure accumulating container at an appropriate timing. In addition, since the amount of exhaust gas used can be easily adjusted, it is possible to prevent the exhaust facility from being adversely affected by sending excessive exhaust gas to the accept facility. Alternatively, troubles such as increasing the inert gas concentration in the boil-off gas by mixing excess boil-off gas generated from the pay-out facility by returning the exhaust gas as return gas from the receiving facility to the discharge facility Can do.

  As described above, according to the present invention, the liquefied gas remaining in the floating hose at sea can be discharged with a simple configuration.

Explanatory drawing which shows the example of application of the discharge system of the liquefied gas which concerns on embodiment The block diagram which shows the detail of the discharge system of the liquefied gas which concerns on embodiment Explanatory drawing which shows the discharge method of LNG remaining in the floating hose The block diagram which shows the modification of the discharge system of the liquefied gas shown in FIG.

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

  FIG. 1 is an explanatory view showing an application example of a liquefied gas discharge system 5 according to an embodiment of the present invention, FIG. 2 is a configuration diagram showing details of the liquefied gas discharge system 5, and FIG. It is explanatory drawing which shows the discharge method of LNG which remains in the inside.

  In LNG sea transportation, for example, as shown in FIG. 1, LNG is transferred via a floating hose 3 from FLNG 1 as a payout facility for paying out LNG to LNG ship 2 as a receiving facility for receiving LNG.

  FLNG1 is a floating type LNG liquefaction facility, and generates LNG by refining and liquefying natural gas (raw material gas) produced from a gas field on the sea floor. The FLNG 1 includes a floating hose 3 for transferring the generated LNG to the LNG ship 2 and the like, and a winding device 4 for receiving it. Further, the FLNG 1 includes a discharge system 5 (see FIG. 2) for discharging the LNG remaining in the floating hose 3 after completion of the transfer of the LNG.

  The floating hose 3 is a known flexible hose that constitutes an LNG transfer line and is used in a state of floating on the sea surface 6. When the LNG is transferred from the FLNG 1 to the LNG ship 2, the floating hose 3 is unwound from the winding device 4 toward the LNG ship 2 anchored, and as shown in FIG. 2 (piping for receiving LNG (not shown)).

  The floating hose 3 includes two LNG supply hoses 3A for supplying LNG from the FLNG 1 to the LNG ship 2, and one return gas hose for returning the return gas from the LNG ship 2 side to the FLNG 1. 3B. However, the configuration of the floating hose 3 (number of hoses, diameter, length, etc.) can be variously changed.

  The LNG ship 2 is a known LNG tanker used for transporting LNG, and includes an LNG tank 11 capable of storing LNG transferred from the FLNG 1.

  As shown in FIG. 2, the exhaust system 5 includes a nitrogen production apparatus (gas production apparatus) 15 that produces nitrogen having a condensation point lower than that of LNG. The nitrogen produced by the nitrogen production apparatus 15 is usually used for sealing lubricant oil for compressors in FLNG1, for preventing backflow of air in main piping in flare vent facilities, and for combustible gas during maintenance. It can be used for purging and the like. Here, nitrogen produced by the nitrogen production apparatus 15 is used as a discharge gas for discharging the liquefied gas remaining in the floating hose 3. Note that the nitrogen used as the exhaust gas may be any gas that does not affect the characteristics (particularly, having a lower condensation point than the liquefied gas).

  Thus, by using nitrogen as the exhaust gas, it is possible to divert the existing nitrogen production apparatus 15 used for other purposes in FLNG1. In addition, since nitrogen has a lower condensation point than LNG, nitrogen does not rapidly condense even when it comes into contact with the cryogenic LNG remaining in the floating hose 3, and troubles such as hammering do not occur.

  Further, in the exhaust system 5, the nitrogen produced by the nitrogen production device 15 is compressed (that is, increased in pressure) by being introduced into the compressor 22 through the nitrogen transport pipe 21. Further, the nitrogen compressed by the compressor 22 is introduced into the pressure accumulating vessel 25 through a nitrogen transport pipe 24 provided with a valve 23. Thereby, the pressure accumulation container 25 is filled with nitrogen having a pressure higher than that of nitrogen produced by the nitrogen production apparatus 15.

  Further, in the discharge system 5, the nitrogen filled in the pressure accumulating vessel 25 is supplied to the floating hose 3 (LNG supply hose 3 </ b> A) through a nitrogen transport pipe (discharge gas supply line) 31. More specifically, the downstream end of the nitrogen transport pipe 31 extends to a connection portion 33 to an LNG transport pipe (liquefied gas transfer line) 32 used in the transfer of LNG. The nitrogen is supplied to the floating hose 3 via a part of the LNG transport pipe 32 (downstream part of the connection portion 33 in the LNG transport pipe 32). With such a configuration, it is possible to easily shift to the LNG discharge process after the LNG transfer process described later is completed.

  Further, the nitrogen transport pipe 31 includes a flow rate adjusting unit (flow rate adjusting device) 35 for adjusting the flow rate of nitrogen supplied to the floating hose 3. The flow rate adjusting unit 35 is arranged on the upstream side of the flow meter 36 for detecting the flow rate of nitrogen supplied to the floating hose 3, and controls the flow rate of nitrogen based on the detected value of the flow meter 36. A flow control valve 37 is provided. Further, in the flow rate adjustment unit 35, the valves 38 and 39 are arranged so as to sandwich the flow meter 36 and the flow rate control valve 37.

  With such a flow rate adjusting unit 35, the flow rate of nitrogen required for discharging the LNG remaining in the floating hose 3 can be easily realized, and the LNG can be discharged more stably. The pressure in the pressure accumulating vessel 25 can be detected by a pressure gauge 42 connected to the nitrogen transport pipe 31 (or the pressure accumulating vessel 25) via the valve 41.

  In the LNG transport pipe 32, valves 51 and 52 are provided on the upstream side and the downstream side of the connection part 33, respectively. The downstream end 53 of the LNG transport pipe 32 is connected to the upstream end 54 of the floating hose 3 (LNG supply hose 3A). In FIG. 2, the winding device 4 in which the floating hose 3 is accommodated is omitted.

  In the discharge system 5, before the LNG transfer process from the FLNG 1 to the LNG ship 2, the amount of nitrogen required in the transfer process is manufactured in advance by the nitrogen manufacturing apparatus 15 (manufacturing process). The produced nitrogen is sequentially compressed by the compressor 22 (compression process) and sequentially introduced into the pressure accumulating vessel 25 (filling process). At this time, the valve 23 of the nitrogen transport pipe 24 is in an open state, and the valves 38 and 39 of the nitrogen transport pipe 31 are in a closed state.

  Thereafter, when filling of the pressure accumulating vessel 25 with nitrogen at a specified pressure (or capacity) is completed, the valve 23 is closed, and preparation for the step of discharging LNG from the floating hose 3 is completed.

  Next, in the LNG transfer step, LNG is supplied from the LNG transport pipe 32 to the LNG supply hose 3A with the valves 51 and 52 opened. At this time, in parallel with the supply of LNG, BOG generated in the LNG ship 2 is returned to the FLNG1 side via the return gas hose 3B.

  When the transfer process is completed, the valve (shutoff valve) 51 is closed while the valve 52 is kept open. At this time, since the inside of the floating hose 3 is almost filled with the remaining LNG, a process of discharging the remaining LNG from the floating hose 3 before disconnecting the floating hose 3 from the LNG ship 2 (discharge process) Is required.

  In the LNG discharging process, the valves 38 and 39 are opened, and nitrogen is supplied from the pressure accumulating vessel 25 to the floating hose 3 (LNG supply hose 3A) by opening the valve 37. Thereby, as shown in FIG. 3, the LNG in the floating hose 3 is gradually pushed out to the LNG ship 2 side by the nitrogen supplied from the FLNG1 side. Finally, when LNG in the floating hose 3 is replaced with nitrogen, the pressure in the pressure accumulating vessel 25 is reduced to a pressure close to the pressure of the floating hose, the valves 38 and 39 are closed, and the LNG discharging process is completed.

  Thus, in the LNG discharge system 5, the flow rate and pressure required for discharging the LNG from the floating hose 3 can be easily achieved by using the pressure accumulating vessel 25 filled with the discharge gas (here, nitrogen). Can be secured. Therefore, regardless of the performance of the nitrogen production apparatus 15 (that is, even when it is difficult to discharge LNG from the floating hose 3 with the flow rate or pressure of nitrogen from the existing nitrogen production apparatus 15), The remaining LNG can be discharged stably.

  In this case, the filling amount of nitrogen in the pressure accumulating vessel 25 may be set so that the discharge process of LNG remaining in the floating hose 3 can be completed using the whole amount of filled nitrogen. Thereby, control, operation, etc., such as stopping sending nitrogen from pressure accumulation container 25 at an appropriate timing, become unnecessary. Further, since it becomes easy to adjust the amount of nitrogen used as an exhaust gas, excess nitrogen is sent to the LNG ship 2 to adversely affect the facilities of the LNG ship 2 (for example, the design of the LNG tank 11). Overpressure) can be prevented. In addition, excessive nitrogen returns to FLNG1 as return gas via the return gas hose 3B, thereby preventing troubles such as increasing the inert gas concentration in the boil-off gas by mixing with the boil-off gas generated from the dispensing equipment. can do. In the exhaust process, when the pressure of nitrogen in the pressure accumulating vessel 25 (for example, the pressure of the pressure gauge 42) is equal to or lower than a predetermined pressure, it can be determined that the entire amount of filled nitrogen has been used.

  Moreover, the capacity | capacitance of the pressure accumulation container 25 is good to set so that the quantity of nitrogen required in order to implement the discharge | emission process of LNG remaining in the floating hose 3 only once can be filled. Thereby, the size (capacity) of the pressure accumulating vessel 25 is prevented from becoming unnecessarily large, and a compact facility can be realized.

  Further, the pressure accumulating vessel 25 may be installed in the FLNG 1 (or the LNG ship 2) together with the winding device 4 of the floating hose 3. Thereby, since the floating hose 3 used for the transfer of LNG is limited, the required size of the pressure accumulating vessel 25 can be set more reliably. Therefore, LNG remaining in the floating hose 3 at sea can be discharged more stably.

Example 1
Next, the simulation result based on the CFD analysis regarding the discharge process by the above-mentioned LNG discharge system 5 will be described. Here, the floating hose 3 has an inner diameter of 20 inches, a length of 280 m, and a height difference between the sea surface and the hose end 7 on the LNG ship 2 side (see length H in FIG. 3) is 25 m. . Moreover, about the supply conditions of the nitrogen from the pressure accumulation container 25 to the floating hose 3, the pressure was set to 3.0 bara (0.3 MPa) and the flow rate was set to 3.0 kg / s (about 8600 Nm ³ / h).

  Under such conditions, in the LNG discharging step, LNG remaining in the floating hose 3 was reduced to about 10 vol% or less by continuing to supply nitrogen to the floating hose 3 for about 3 minutes.

In order to prevent a large amount of nitrogen from flowing to the LNG ship 2 side, the total supply amount of nitrogen is about 56 m ^{3 under} the condition of −163 ° C. and 3.0 bara nitrogen. In this case, regarding the pressure accumulating vessel 25, if the pressure accumulating condition of nitrogen is 30 ° C. and 25 bara (2.5 MPa), and the pressure of nitrogen in the pressure accumulating vessel 25 after the discharging process is 4.0 bara, the pressure accumulating vessel 25 For example, the inner diameter of the cylindrical cross section can be 2300 mm, and the length between tangent lines (see length L in FIG. 2) can be 5000 mm. In the general nitrogen production apparatus 15, for example, the pressure of the produced nitrogen is 6 to 8 bara, and the supply amount is about 1000 to 2000 Nm ³ / h. Is insufficient.

(Example 2)
A simulation result in the case where the form of the floating hose 3 is changed under the same nitrogen supply conditions as in Example 1 will be described. Here, the floating hose 3 had an inner diameter of 6 inches, a length of 280 m, and a height difference of 15 m between the sea surface and the hose end portion 7 on the LNG ship 2 side.

In order to prevent a large amount of nitrogen from blowing through the LNG ship 2 as described above, the total supply amount of nitrogen is 5.2 m ^{3 under} the condition of −163 ° C. and 3.0 bara nitrogen. Moreover, about the size of the pressure accumulation container 25, it can be set as 1000 mm and the internal diameter of a cylindrical cross section, and the length between tangent lines can be 2500 mm.

  The discharge system 5 is not limited to the above-described example, and can perform a discharge process on various forms of the floating hose 3 and the receiving facility 2.

  FIG. 4 is a block diagram showing a modification of the liquefied gas discharge system 5 shown in FIG. Here, the same code | symbol is attached | subjected about the component similar to the discharge system 5 shown in FIG. Further, items not particularly mentioned below are the same as those of the discharge system 5 shown in FIG.

  4 differs from the discharge system 5 shown in FIG. 2 in the configuration of the flow rate adjustment unit 35. The flow rate adjusting unit 35 of the nitrogen transport pipe 31 is provided with a restriction orifice 62 on the downstream side of the valve 38, and a branch pipe 131 that branches from the main body of the nitrogen transport pipe 31 and extends in parallel on the upstream side of the valve 38. Are also provided with a similar configuration (valve 138 and restriction orifice 162). The downstream end of the branch pipe 131 is connected to the main body of the nitrogen transport pipe 31 on the upstream side of the valve 39.

  In the LNG discharging process, the valves 38 and 39 are first opened, and after the pressure in the pressure accumulating vessel gradually decreases, the valve 138 is then opened, and the flow rate of nitrogen supplied to the floating hose 3 is plural. Adjusted by limiting orifices 62 and 162.

  As mentioned above, although this invention was demonstrated based on specific embodiment, these embodiment is an illustration to the last, Comprising: This invention is not limited by these embodiment. In the above-described embodiment, an example in which FLNG is a payout facility and an LNG ship is a receiving facility is shown. However, the present invention is not limited to this, and any facility (for example, as long as LNG transfer using a floating hose is possible) FSO (Floating Storage & Offloading Unit): Floating storage and loading facility, FSU (Floating Storage Unit): Floating LNG receiving terminal, FSRU (Floating Storage & Regasification Unit): Floating storage regasification facility, FPSO (Floating Production, Storage & Offloading Unit): Floating production storage / loading equipment, etc.) can be the delivery equipment and receiving equipment, respectively. In addition, a configuration in which one of the payout facility and the receiving facility is installed on land is also possible.

  In the above-described embodiment, the liquefied gas to be discharged is LNG. However, the liquefied gas is not limited to this, and other liquefied gases (for example, LPG (Liquefied Petroleum Gas), for example, as long as transfer using a floating hose is possible. ) May be subject to discharge.

  In the above-described embodiment, an example in which nitrogen is used as the exhaust gas has been described. However, the present invention is not limited to this, and any other gas (for example, any gas that has a condensation point lower than the liquefied gas to be discharged) , Inert gas other than nitrogen, or a mixed gas thereof) may be used.

  Moreover, although the example which provided the discharge system 5 of LNG in the delivery equipment (FLNG1) side was shown in the above-mentioned embodiment, it is not restricted to this, At least one part of the component of the discharge system 5 is received equipment (LNG ship). 2) A configuration provided on the side is also possible. In that case, the LNG can be discharged so that the LNG remaining in the LNG supply hose 3A flows backward with respect to the transfer direction.

  It should be noted that the components of the liquefied gas discharge system and discharge method according to the present invention shown in the above-described embodiments are not necessarily essential, and may be appropriately selected as long as they do not depart from the scope of the present invention. Is possible.

1: FLNG (dispensing equipment)
2: LNG ship (receiving facility)
3: Floating hose 3A: LNG supply hose 3B: Return gas hose 4: Winding device 5: Discharge system 7: Hose end 11: LNG tank 15: Nitrogen production device 21: Nitrogen transport pipe 22: Compressor 23: Valve 24: Nitrogen transport pipe 25: Pressure accumulator 31: Nitrogen transport pipe (exhaust gas supply line)
32: LNG transport pipe (liquefied gas transfer line)
33: Connection part 35: Flow rate adjusting unit 36: Flow meter 37: Flow rate control valve (flow rate adjusting device)
38: Valve 39: Valve 41: Valve 42: Pressure gauge 51: Valve 52: Valve 53: Downstream end 54: Upstream end 62: Restriction orifice (flow rate adjusting device)
131: Bypass line 138: Valve 162: Restriction orifice (flow rate adjusting device)

Claims (10)

A system for discharging liquefied gas remaining in a floating hose at sea used to transfer liquefied gas from a dispensing facility to a receiving facility,
A gas production apparatus for producing an exhaust gas having a lower condensation point than the liquefied gas;
A compressor for compressing the exhaust gas produced by the gas production device;
A pressure accumulator filled with the exhaust gas compressed by the compressor;
An exhaust gas supply line for supplying the exhaust gas filled in the pressure accumulator to the floating hose;
A liquefied gas discharge system comprising:   The filling amount of the exhaust gas in the accumulator is set so that the discharge of the liquefied gas remaining in the floating hose can be completed using the whole amount of the exhaust gas filled. The liquefied gas discharge system according to claim 1.   The capacity of the pressure accumulating container is set so as to be able to be filled with the amount of the exhaust gas necessary for discharging the liquefied gas remaining in the floating hose only once. The liquefied gas discharge system according to claim 1 or 2.   4. The apparatus according to claim 1, further comprising a flow rate adjusting device that is provided in the exhaust gas supply line and adjusts a flow rate of the exhaust gas supplied from the pressure accumulating vessel to the floating hose. The liquefied gas discharge system according to any one of the above.   The liquefied gas discharge system according to any one of claims 1 to 4, wherein the liquefied gas is liquefied natural gas, and the discharge gas is nitrogen.   The liquefied gas discharge system according to any one of claims 1 to 5, wherein the pressure accumulating container is installed in the dispensing facility or the receiving facility together with the winding device for the floating hose.   7. The exhaust gas supply line is connected to a liquefied gas transfer line to which the floating hose is connected in the payout facility or the receiving facility. Liquefied gas discharge system.   The apparatus further comprises a shutoff valve provided on the upstream side of the connection portion of the exhaust gas supply line in the liquefied gas transfer line, and for shutting off the supply of the liquefied gas to the floating hose. The liquefied gas discharge system according to claim 7. A method for discharging liquefied gas remaining in a floating hose at sea used to transfer liquefied gas from a dispensing facility to a receiving facility,
A production process for producing an exhaust gas having a lower condensation point than the liquefied gas;
A compression step of compressing the exhaust gas produced in the production step;
A filling step of filling a pressure accumulating container with the exhaust gas compressed in the compression step;
A liquefied gas discharging method comprising: a discharging step of discharging the liquefied gas remaining in the floating hose by supplying the discharging gas filled in the pressure accumulating container to the floating hose.   The method of discharging liquefied gas according to claim 9, wherein the discharging step is performed using the entire amount of the discharge gas charged in the pressure accumulating container in the filling step.

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