JP2008051287A - Cold reserving system of liquefied natural gas facility - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce cost for cold reservation while securing a proper cooling capacity, when performing cold insulation to a receiving pipe in a liquefied natural gas facility such as an LNG receiving base. <P>SOLUTION: This cold reserving system of the liquefied natural gas facility 1 has the receiving pipe 4 reaching a storage tank 2 from a receiving destination of LNG, and a receiving circulating pipe 6 reaching the upstream side of the receiving pipe from its storage tank, and is constituted for selectively performing a circulating cooling mode of circulating the LNG in the storage tank via the receiving circulating pipe and the receiving pipe and a pressurizing cooling mode of holding the LNG in the receiving pipe in a pressurized state by introducing the LNG into the receiving pipe via the receiving circulating pipe in a state of holding the LNG in the receiving pipe, and reduces a quantity of LNG used for heat reservation, while securing the proper cooling capacity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cooling system for a liquefied natural gas facility such as a LNG receiving terminal.

  Conventionally, an LNG receiving terminal is provided with an LNG tank for storing LNG, and this LNG tank transports LNG from the LNG ship to the tank for receiving LNG, from the tank to LNG vaporization equipment, etc. A transport pipe such as a payout pipe is connected.

  The acceptance of LNG into the LNG tank is usually performed at intervals of several days to several weeks. The receiving pipe is kept at a low temperature during transportation of LNG (normal pressure of about −162 ° C.), but if LNG is not received for a certain period of time, the temperature of the receiving pipe is increased by natural heat input from the outside. If it gradually rises and starts transporting LNG again as it is, problems such as large-scale evaporation of LNG in the LNG tank and deformation and breakage of the transport pipe due to a rapid temperature change may occur.

  Therefore, as one of the means for avoiding such a problem, a circulation pipe for returning the LNG stored in the LNG tank through the receiving pipe and returning it to the tank is provided, and LNG is not accepted. For example, a technique is known in which an appropriate amount of LNG (circulating fluid) is forcedly circulated by a pump device to keep the piping system at a low temperature (cold insulation circulation).

However, when carrying out cold insulation circulation, pump power is required to circulate a relatively large amount (for example, several tens of tons / hr) of the circulating fluid, and the implementation cost is not small. There are techniques aimed at keeping the tube cool. For example, using a pipe in which a gas reservoir is formed at the uppermost end, while the vaporized gas generated by the vaporization of LNG left in the pipe is kept at a pressure that does not lift the LNG in the pipe, the vaporized gas reaches the gas reservoir. A control method of the LNG pipe that executes an operation mode (storage operation mode) in which an amount of gas equal to the vaporized gas is extracted from the gas reservoir and an amount of LNG equal to the vaporized gas is supplied from the storage tank into the pipe when it rises. Is known (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 7-119893 (FIG. 4)

  By the way, in the prior art as described in the above-mentioned Patent Document 1, the storage operation mode is executed after receiving LNG, and when the next LNG is received, the heated LNG in the pipe is replaced with a low-temperature LNG. The operation for replacing with is executed. However, when the frequency of accepting LNG is low (for example, at intervals of several weeks or more), the component of LNG in the piping changes in the storage operation mode (that is, the proportion of heavy components is reduced by evaporation of light components such as methane). This increases the saturation temperature of the LNG in the pipe and increases the cooling capacity.

  The present invention has been devised to solve such problems of the prior art, and the main purpose of the present invention is to cool the receiving pipe in a liquefied natural gas facility such as an LNG receiving terminal. An object of the present invention is to provide a refrigeration system for a liquefied natural gas facility that can reduce the amount of LNG used for cold insulation while ensuring an appropriate cooling capacity, and thus can reduce the costs associated with the implementation of cold insulation. .

  In order to solve such a problem, a refrigerated natural gas facility cold insulation system according to the present invention includes, as shown in claim 1, a receiving pipe from an LNG receiving destination to its storage tank, and a receiving pipe from the storage tank to the receiving pipe. A cooling system for a liquefied natural gas facility having a receiving circulation pipe extending to the upstream side of the refrigeration system, wherein the LNG in the storage tank is circulated through the receiving circulation pipe and the receiving pipe, and the receiving A configuration that selectively executes a pressurized cooling mode in which the LNG in the receiving pipe is held in a pressurized state while the LNG is introduced into the receiving pipe through the receiving circulation pipe while the LNG is held in the pipe. And

  According to this, sensible heat and latent heat of LNG can be obtained by appropriately selecting a circulation cooling mode and a pressurized cooling mode when performing cooling of the receiving pipe in a liquefied natural gas facility such as an LNG receiving terminal. Thus, it is possible to reduce the amount of LNG used for cold insulation while ensuring an appropriate cooling capacity, and to reduce the cost for carrying out the cold insulation.

  In the cooling system of the liquefied natural gas facility, as shown in claim 2, when the temperature of the LNG in the receiving pipe becomes a predetermined value or more in the pressurized cooling mode, the pressurized holding of the LNG is released. Thus, it can be configured to switch to the circulation cooling mode.

  According to this, when the temperature of the LNG in the receiving pipe becomes equal to or higher than a predetermined value, the low temperature LNG from the storage tank is introduced into the receiving pipe by executing the circulation cooling mode, and the LNG pressurized and held in the receiving pipe. It is possible to prevent the cooling capacity from being lowered due to the temperature rise.

  In the cooling system of the liquefied natural gas facility, as shown in claim 3, in the circulating cooling mode switched from the pressurized cooling mode, the LNG that has been pressurized and held in the receiving pipe in the pressurized cooling mode is stored. After replacing with the LNG to be circulated, it can be configured to switch to the pressurized cooling mode again.

  According to this, the amount of LNG used for cold insulation can be effectively reduced by minimizing the execution of the circulating cooling mode. In this case, whether or not the replacement of the LNG held in the receiving pipe in the pressure / cooling mode is completed is indicated by, for example, an elapsed time after releasing the pressurization or the temperature of the LNG in the receiving pipe. Can be determined appropriately.

  In the cooling system of the liquefied natural gas facility, as shown in claim 4, in the pressurized cooling mode, the vaporized gas generated from the LNG pressurized and held in the receiving pipe is discharged from the receiving pipe and the evaporation is performed. The LNG can be introduced into the receiving pipe through the receiving circulation pipe in accordance with the amount of vaporized gas.

  According to this, by performing pressure control of the receiving pipe, it is possible to prevent the pressure in the receiving pipe from rising and exceeding a predetermined allowable value. Also, the vaporized gas generated by heat input to the receiving pipe (natural heat and heat input by the pump device, etc.) is appropriately discharged out of the receiving pipe, and the discharged LNG is put into the receiving pipe through the receiving circulation pipe. By making up, it is possible to maintain a state where the receiving pipe is filled with LNG and to secure an appropriate cooling capacity.

  As described above, the present invention holds the operation mode in which the circulating fluid is circulated through the receiving pipe and the receiving pipe in a pressure-cooled state when the receiving pipe is cooled in a liquefied natural gas facility such as an LNG receiving terminal. By selectively executing the operation mode, it is possible to reduce the amount of LNG used for cold insulation while ensuring appropriate cooling capacity using sensible heat and latent heat of LNG. There is an excellent effect that the cost involved can be reduced.

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

  FIG. 1 is a configuration diagram schematically showing an outline of an LNG receiving terminal according to the present invention. The LNG receiving terminal 1 includes an LNG tank 2 for storing low-temperature LNG, an receiving pipe 4 for transporting LNG transported by the LNG ship 3 from the jetty to the tank 2, and an LNG stored in the tank 2. The discharge pipe 5 for transporting to the LNG vaporizer 43, the receiving circulation pipe 6 for circulating the LNG in the tank 2 through the receiving pipe 4, and the BOG (boil-off gas) in the tank 2 outside the tank 2 It mainly comprises a BOG pipe 7 for discharging.

  The receiving pipe 4 is provided with a loading arm 11 for receiving an LNG on a bridge located upstream thereof, a first horizontal portion 4a extending substantially horizontally from the loading arm 11 toward the tank 2, and a first horizontal portion 4a thereof. And a second horizontal portion 4c extending substantially horizontally from the rising portion 4b toward the top of the tank 2, and a downstream side of the rising portion 4b extending upward from the horizontal portion 4a. It is connected.

  Here, the first horizontal portion 4 a is provided with gas reservoirs 12 and 13 for discharging LNG vaporized gas generated in the receiving pipe 4, and the detection results of the liquid level detectors 14 and 15 are obtained. Based on this, the liquid level adjusting valves 16 and 17 are opened and closed so as to maintain the liquid level constant, and the vaporized gas in the receiving pipe 4 can be discharged through the gas vent pipes 18 and 19. Similarly, a gas reservoir 21 is provided above the rising portion 4b. By opening and closing the pressure control valve 26 connected to either the liquid level detector 24 or the pressure detector 25 by switching the switches 22 and 23 based on the detection result of the liquid level or pressure, the receiving pipe 4 The vaporized gas inside can be discharged through the gas vent pipe 27 and the pressure in the receiving pipe 4 can be adjusted.

  The first horizontal portion 4a includes a receiving operation valve 31 for switching communication with the loading arm 11 with respect to the LNG receiving operation, and a temperature detector 32 for detecting the temperature of the LNG in the receiving pipe 4. Is provided. Further, the second horizontal portion 4c is provided with a receiving operation valve 33 for switching communication with the tank 2 with respect to the LNG receiving operation, and a bypass pipe 34 arranged to bypass the receiving operation valve 33. Is provided with an operation valve 35. The bypass pipe 34 is configured by a pipe having a smaller diameter than the receiving pipe 4 and is used when a LNG having a smaller flow rate is allowed to flow.

  The upstream side of the discharge pipe 5 is connected to a discharge pump 41 provided in the liquid layer portion L of the tank 2, and an LNG vaporizer 43 for vaporizing LNG is provided on the downstream side. When paying out LNG from the LNG receiving terminal 1, the LNG in the tank 2 is sent out from the tank 2 by the payout pump 41, transported through the payout pipe 5, and sent to the LNG vaporizer 43. In the LNG vaporizer 43, a process for vaporizing LNG by heat exchange is performed, and the vaporized LNG vaporized gas is supplied to the payout destination through the gas supply pipe 44.

  The receiving circulation pipe 6 is branched from the upstream part of the dispensing pipe 5 and connected to the upstream part of the receiving pipe 4. The receiving circulation pipe 6 is provided with a flow rate controller 51 for adjusting the flow rate of LNG from the tank 2, a flow rate adjustment valve 52 for adjusting the opening degree based on a control signal from the controller 51, and an operation valve 53. It has been. Further, a bypass pipe 54 arranged so as to bypass the flow controller 51 and the flow control valve 52 is opened based on a flow meter 55 for confirming the flow rate of LNG and a control signal from the liquid level detector 24. A liquid level adjusting valve 56 for adjusting the degree is provided. The bypass pipe 54 is configured by a pipe having a smaller diameter than the receiving circulation pipe 6 and is used when a smaller flow rate of LNG is allowed to flow.

  The BOG pipe 7 has an upstream side connected to the gas layer part G of the tank 2, and has an intermediate part branched to the discharge side and the flare stack 64 side for performing the BOG combustion process. On the payout side, a BOG compressor 65 for compressing the BOG to be transported is provided, and is connected to a gas feed pipe 44 after the LNG vaporizer 43. On the other hand, the flare stack 64 side is provided with a pressure controller 66 for adjusting the pressure in the tank 2 and a pressure adjusting valve 67 for adjusting the opening degree based on a control signal from the controller 66. Further, a part of the BOG discharged from the tank 2 is compressed by the return gas blower 71 through the pipe 70 in order to adjust the pressure in the tank of the LNG ship 3 when receiving the LNG, and then the loading arm 72 returns to the LNG ship 3. The above-described gas vent pipe 18 is connected to the pipe 70, and the vaporized gas discharged from the gas reservoir 12 is sent to the flare stack 64 or the BOG compressor 65 through the pipe 70.

  The LNG receiving base 1 having the above-described configuration has three operation modes related to the LNG receiving operation and the cooling operation of the receiving pipe 4 executed from the end of the receiving operation to the next receiving operation. That is, in the LNG receiving base 1, when the LNG is received from the LNG ship 3 and when the LNG is not received and the LNG is not transported through the receiving pipe 4, the refrigeration system is selectively used. The pressure cooling mode and the circulation cooling mode are executed. Details of these operation modes will be described below.

  FIG. 2 is a diagram for explaining an outline of an accepting operation mode that is performed at the time of accepting LNG at the LNG accepting base shown in FIG. In this acceptance operation mode, by opening the acceptance operation valves 31 and 33, the pump device installed in the LNG ship 3 (not shown) causes the LNG from the LNG ship 3 to follow the acceptance route (indicated by a broken line in the figure). Then, the inside of the receiving pipe 4 is transported to the tank 2 through the loading arm 11 and supplied to the liquid layer portion L in the tank 2. At this time, the liquid level control valves 16, 17 and the pressure control valve 26 are closed, and the liquid level control and pressure control are not performed. Further, the flow rate adjustment valve 52 and the operation valve 53 in the receiving circulation pipe 6 are closed, and the LNG from the tank 2 is shut off.

  As shown in FIG. 2, by installing gas reservoirs 12 and 13 for degassing in the first horizontal portion 4a of the receiving pipe 4, a large amount of vaporized gas generated in the horizontal portion 4a flows into the rising portion 4b. It is possible to prevent the occurrence of Geysering. Further, by configuring the portion immediately before the transition from the horizontal portion 4a to the rising portion 4b (that is, from the position where the gas reservoir 13 is provided in the horizontal portion 4a to the connecting portion with the rising portion 4b) to be temporarily lowered. The occurrence of Geisering can be more effectively prevented.

  FIG. 3 is a diagram for explaining an outline of a pressurized cooling mode that is performed when the receiving pipe is kept cold at the LNG receiving terminal shown in FIG. 1. This pressurized cooling mode is executed after the above-described receiving operation mode, and the receiving operation valves 31 and 33 are fully closed so that LNG is held in the receiving pipe 4. By introducing the LNG in the tank 2 into the receiving pipe 4 via the receiving circulation pipe 6, the pressure in the receiving pipe 4 is adjusted by the pressure control valve 26 while keeping the liquid level of LNG in the receiving pipe 4 constant. Pressurized and held at a predetermined pressure.

  At this time, in the receiving circulation pipe 6, while closing the flow rate adjusting valve 52 and opening the operation valve 53 and the liquid level adjusting valve 56, LNG from the tank 2 is introduced into the receiving pipe 4 via the bypass pipe 54. By passing through this bypass pipe 54, unlike the case of the circulation cooling mode described later (for example, a flow rate of several tens of t / hr), a smaller flow rate (for example, about 1 to 2 t / hr) of LNG is easily introduced. be able to. In this case, since the amount of LNG supplied to the receiving pipe 4 in the pressurized cooling mode and the amount of LNG supplied to the receiving pipe 4 in the circulation cooling mode described later are greatly different, the liquid level control valve 56 is set in the receiving circulation pipe 6. By providing it separately from the flow rate adjustment valve 52 for introducing LNG to the receiving pipe 4 in the circulation cooling mode, optimal flow rate control is possible in each operation mode.

  In this way, with the LNG introduced from the receiving circulation pipe 6 to the receiving pipe 4, the opening degree of the pressure control valve 26 is adjusted based on the detection result of the pressure detector 25, thereby defining the pressure in the receiving pipe 4. The value is raised to a value (for example, about 100 kPaG at the position of the pressure detector 25), and the LNG in the receiving pipe 4 is held in a pressurized state. At this time, the pressure control valve 26 is connected to the pressure detector 25 by the switch 22. At the same time, the opening of the liquid level control valves 16 and 17 is adjusted based on the detection results of the liquid level detectors 14 and 15, and is generated in the receiving pipe 4 by heat input to the receiving pipe 4 from the discharge pump 41 and the surrounding environment. The vaporized gas to be discharged is appropriately discharged from the receiving pipe 4. In this case, LNG is introduced into the receiving pipe 4 via the receiving circulation pipe 6 so as to compensate for the amount of LNG that has been vaporized and discharged from the receiving pipe 4. Here, the discharge of the vaporized gas in the receiving pipe 4 uses the liquid level adjusting valves 16 and 17 and the liquid level detectors 14 and 15, and the pressure control in the receiving pipe 4 is performed by the pressure adjusting valve 26 and the pressure detection. Further, since the liquid level control of the rising portion 4b is performed individually using the control valve 56 and the liquid level detector 24, simple sequence control is possible.

  The end timing of this pressurized cooling mode depends on the temperature of the LNG in the receiving pipe 4 in order to ensure an appropriate liquid density or cooling capacity for the receiving pipe 4 in addition to the case of shifting to the circulation cooling mode described later before the receiving operation. It is determined. That is, the temperature of the LNG in the receiving pipe 4 is monitored by the temperature detector 32, and when the temperature of the LNG exceeds a specified value due to heat input to the receiving pipe 4 as time elapses, the LNG is maintained in a pressurized state. It cancels and it transfers to the circulation cooling mode mentioned later from a pressurized cooling mode. In the transition to the circulation cooling mode, the pressure of the LNG at the position of the pressure detector 25 (for example, 100 kPaG in the pressure cooling mode) is applied to the lower part of the receiving pipe 4 (first horizontal portion 4a). By further raising the pressure to a pressure sufficiently higher than the pressure at 300 m (for example, 300 kPaG in the pressure cooling mode), it is possible to prevent the occurrence of the Geisering phenomenon accompanying the generation of bubbles in the rising portion 4b.

  In such a pressurized cooling mode, the amount of LNG used for cooling (that is, LNG introduced into the receiving pipe 4 from the tank 2 through the receiving circulation pipe 6) is smaller than that in the circulation cooling mode described later. Since the load can be reduced, the load on the dispensing pump 41 can be reduced (or the number of pumps operated can be reduced), and the running cost can be reduced. In this case, since the heat input from the discharge pump 41 is also reduced, there is an advantage that the running cost of the compressor 65 can be reduced. Further, in the pressurized cooling mode, as shown in FIG. 4, not only sensible heat of LNG but also latent heat that contributes more to cooling can be used for cooling. Further, in the pressurized cooling mode, the saturation temperature rises by pressurizing the LNG held in the receiving pipe 4, so that the sensible heat of LNG can be used more effectively for cooling the receiving pipe 4. is there.

  As shown in FIG. 3, by providing the pressure detector 25 at the upper part of the rising portion 4b, stable adjustment can be achieved even when the density of the LNG in the receiving pipe 4 changes due to long-time operation in the pressurized cooling mode. The valve 26 differential pressure can be secured. On the other hand, when the pressure detector 25 is provided in the first horizontal portion 4a, the density of LNG in the receiving pipe 4 increases as the ratio of heavy components increases due to evaporation of light components such as methane. Since the liquid head in the rising portion 4b increases and the pressure in the first horizontal portion 4a increases, it is difficult to appropriately control the pressure control valve 26.

  FIG. 5 is a diagram for explaining the outline of the circulation cooling mode that is performed when the receiving pipe is kept cold at the LNG receiving terminal shown in FIG. 1. This circulating cooling mode is executed when the temperature of the LNG in the receiving pipe 4 exceeds the specified value in the above-described pressure cooling mode or when it is necessary to newly prepare for receiving LNG. Yes, the LNG in the tank 2 is forcedly circulated through the receiving circulation pipe 6 and the receiving pipe 4.

  Here, the circulation route of the LNG for cold insulation is configured as tank 2 → discharge pipe 5 → reception circulation pipe 6 → reception pipe 4 → tank 2. That is, the LNG for cold insulation is sent from the tank 2 to the discharge pipe 5 by the discharge pump 41 and then led to the upstream part of the reception pipe 4 via the reception circulation pipe 6 branched from the upstream part of the discharge pipe 5. Furthermore, it returns to the inside of the tank 2 via the bypass pipe 34 branched from the downstream part of the receiving pipe 4. Further, in the receiving circulation pipe 6, the liquid level adjusting valve 56 is closed, and the flow rate adjusting valve 52 is opened, whereby LNG from the tank 2 is introduced into the receiving pipe 4 through the receiving circulation pipe 6.

  In this circulating cooling mode, the pressure at the position of the pressure detector 25 is received by the pressure control valve 26 until the liquid in the receiving pipe 4 is replaced with low density and low temperature LNG. The liquid is circulated at a pressure sufficiently higher than the pressure in the lower portion of the receiving pipe 4 at the time. After the liquid replacement is completed, the pressure control valve 26 is connected to the liquid level detector 24 by switching the switches 22 and 23, and the detection result The degree of opening is adjusted based on the above and the liquid level is adjusted. At the same time, by opening the operation valve 35, the circulation of LNG is continued. Further, the opening of the liquid level control valves 16 and 17 is adjusted based on the detection results of the liquid level detectors 14 and 15 from the pressurized cooling mode, and the liquid level is adjusted. In addition, by raising the set pressure of the pressure control valve 26 at the time of shifting to the circulating cooling mode as described above, it is possible to reliably suppress the generation of vaporized gas at the beginning of shifting to the circulating cooling mode. Therefore, it is possible to avoid the problem that, when shifting to the circulation cooling mode, the LNG passing through the control valve 26 becomes a gas-liquid mixed phase flow, the liquid flow rate is not stabilized, and the pressure control becomes difficult.

  The switching from the pressure control of the pressure control valve 26 to the liquid level control and the opening operation of the operation valve 35 in the circulation cooling mode and the opening operation of the operation valve 35 are newly performed by the LNG held in pressure in the receiving pipe 4 in the pressure cooling mode. This is determined by determining whether or not the LNG introduced from the tank 2 to the receiving pipe 4 is sufficiently replaced. In the present embodiment, when the temperature of the LNG in the receiving pipe 4 is equal to or lower than a specified value and the measured time of the timer is equal to or longer than a predetermined time, it is determined that the replacement of LNG is completed. That is, in the circulating cooling mode, the temperature of the LNG in the receiving pipe 4 is monitored by the temperature detector 32, and the elapsed time after shifting to the circulating cooling mode is measured by a timer (not shown). When the temperature of the LNG is equal to or lower than the specified value and the time measured by the timer is equal to or longer than the predetermined time, the pressure control valve 26 is switched from the pressure control to the liquid level control, and the operation valve 35 is opened. Thereafter, the operator makes a transition from the circulating cooling mode to the pressurized cooling mode again at the operator's discretion. When preparation for receiving LNG becomes necessary, the operation mode shifts from the circulating cooling mode to the receiving operation mode without shifting to the pressurized cooling mode. Thereby, the cooler LNG in the tank 2 can be introduced into the receiving pipe 4 to reliably cool the receiving pipe 4 and prevent the occurrence of a Geisering phenomenon or the like.

  FIG. 6 is a flowchart showing an operation procedure for receiving LNG at the LNG receiving terminal shown in FIG. 1 and cooling the receiving pipe.

  First, an acceptance operation mode is executed when LNG is received from the LNG ship 3 (ST101). Next, when the acceptance of LNG is completed (ST102: YES), the operation mode is shifted from the receiving operation mode to the pressurized cooling mode (ST103).

  In this pressurized cooling mode, it is not necessary to start preparation for receiving LNG (ST104: YES), and when the temperature of the LNG held under pressure in the receiving pipe 4 is not more than a specified value (ST105: NO). Is continuously executed. Therefore, when the temperature of the LNG becomes equal to or higher than the specified value due to heat input to the receiving pipe 4 as time passes, the pressurized cooling mode is switched to the circulating cooling mode (ST106).

  This circulation cooling mode is continued until the temperature of the LNG in the receiving pipe 4 becomes a specified value or less and the elapsed time after the transition to the circulation cooling mode becomes a specified time or more. When the time condition is satisfied (ST107: YES), the process returns to ST103 again and shifts to the pressurized cooling mode.

  In addition, when it becomes necessary to newly prepare to receive LNG from the LNG ship 3 (for example, several hours before the start of the receiving operation), preparation for receiving LNG is started (ST104: YES), and circulation cooling is started from the pressurized cooling mode. The mode is shifted to (ST108). Therefore, after the receiving pipe 4 is appropriately cooled, the circulation cooling mode is stopped, and the reception of LNG is started. The mode selection as described above can be automatically executed by a control unit that controls LNG transportation or the like at the LNG receiving terminal 1 or may be manually selected by an operator.

  The cold storage system for a liquefied natural gas facility according to the present invention can reduce the circulation amount while ensuring an appropriate cooling capacity when carrying out cold cooling of the receiving pipe, and thus costs associated with carrying out cold storage. Therefore, it is useful as a cold storage system for a liquefied natural gas facility such as an LNG receiving terminal.

The figure which shows typically schematic structure of the LNG receiving base which concerns on this invention Explanatory drawing of the acceptance operation mode carried out when accepting LNG Explanatory drawing of pressurized cooling mode to be performed when the receiving pipe is kept cool Diagram showing the relationship between LNG enthalpy and temperature Explanatory drawing of the circulation cooling mode to be performed when the receiving pipe is kept cool Flow chart showing the operation procedure for receiving LNG and cooling the receiving pipe

Explanation of symbols

1 LNG receiving base 2 LNG tank 4 receiving pipe 5 discharging pipe 6 receiving circulation pipe 41 discharging pump

Claims (4)

A cold storage system for a liquefied natural gas facility comprising a receiving pipe from a receiving destination of liquefied natural gas (LNG) to a storage tank thereof, and a receiving circulation pipe extending from the storage tank to an upstream side of the receiving pipe,
A circulating cooling mode for circulating LNG in the storage tank through the receiving circulation pipe and the receiving pipe;
A pressure cooling mode in which the LNG in the receiving pipe is held in a pressurized state while the LNG is introduced into the receiving pipe through the receiving circulation pipe while the LNG is held in the receiving pipe is selectively executed. A cold storage system for liquefied natural gas equipment.   The pressurization cooling mode WHEREIN: When the temperature of the LNG in the said receiving pipe becomes more than predetermined value, the pressurization holding | maintenance of the said LNG is cancelled | released and it switches to the said circulation cooling mode. Cooling system for liquefied natural gas equipment.   In the circulating cooling mode switched from the pressurized cooling mode, the LNG that has been pressurized and held in the receiving pipe in the pressurized cooling mode is replaced with the circulating LNG, and then switched to the pressurized cooling mode again. The cold storage system for a liquefied natural gas facility according to claim 2. In the pressurized cooling mode, the vaporized gas generated from the LNG pressurized and held in the receiving pipe is discharged from the receiving pipe, and the inside of the receiving pipe is passed through the receiving circulation pipe according to the amount of the evaporated vaporized gas. 2. The refrigerated natural gas facility cold insulation system according to claim 1, wherein LNG is introduced into the LNG.

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