KR20200142789A - Inert Gas Close Cycle for Insulation Space of Cargo Tank - Google Patents

Abstract

The present invention relates to a storage tank which stores low-temperature cargo. The present invention also relates to an inert gas injection system for an insulation space of a storage tank which can be applied to cause an insulation space of a storage tank for storing low-temperature cargo to become inert. According to the present invention, the inert gas injection system for an insulation space of a storage tank includes a liquefied gas storage tank to store liquefied gas in a body. The liquefied gas storage tank includes: one or more barriers to seal a leak of liquefied gas stored in the body; and one or more insulation spaces formed between the body of the liquefied gas storage tank and the one or more barriers. An argon gas circulation unit for circulating argon gas to the insulation spaces is further included. The argon gas circulation unit includes: an argon buffer tank to store forcibly evaporated argon gas and argon gas recovered from the insulation spaces; an argon supply line connecting the argon buffer tank and the insulation spaces, and allowing argon gas to flow from the argon buffer tank to the insulation spaces; and an argon discharge line connecting the insulation spaces and the argon buffer tank, and allowing argon gas to flow from the insulation spaces to the argon buffer tank.

Description

Inert Gas Close Cycle for Insulation Space of Cargo Tank}

The present invention relates to a storage tank for storing low-temperature cargo. In addition, the present invention relates to an inert gas injection system of a storage tank insulation space that can be applied to inactivate the insulation space of a storage tank storing low temperature cargo.

Natural gas is transported in gaseous form through gas pipelines on land or sea, or stored in a carrier as liquefied liquefied natural gas (LNG) and transported to remote consumers. Liquefied natural gas is obtained by cooling natural gas to a cryogenic temperature of about -163°C, and its volume is reduced to about 1/600 compared to when it is in a gaseous state, making it very suitable for long-distance transportation through sea.

LNG carriers that transport LNG by sea are equipped with an LNG storage tank (also called a'cargo hold') that can store LNG that has been liquefied by cooling natural gas. LNG storage tanks of LNG carriers should be equipped with an insulation system to keep LNG in a cryogenic liquid state.

However, even if an insulation system is applied, heat intrusion from the outside cannot be completely blocked, so the LNG stored in the LNG storage tank is spontaneously vaporized as external heat invades the LNG storage tank during the operation of the LNG carrier. The boil-off gas generated by natural vaporization of LNG is referred to as NBOG (Natural Boil-Off Gas), and the amount of LNG vaporized per day in the LNG storage tank is referred to as BOR (Boil-Off Rate).

When LNG is continuously evaporated in the LNG storage tank and NBOG is generated, the internal pressure of the LNG storage tank increases, eventually exceeding the safe pressure, and as a result, the generation of NBOG leads to loss of LNG.

Accordingly, there is a need for an effort to prevent NBOG from being generated as much as possible, that is, to improve the insulation performance in order to lower the BOR.

LNG storage tanks can be classified into stand-alone tanks and membrane tanks depending on whether the load of cargo directly acts on the insulation. In addition, the independent tank is divided into MOSS type and IHI-SPB type, and the membrane type tank is divided into GTT (Gaztransport & Technigaz) No.96. type and Mark III type.

In general, a membrane type tank includes a structure in which a plurality of barriers are installed inside a hull, an inner wall of the hull and a barrier, and an insulating space is formed between each barrier and the barrier.

The insulation space forms a double insulation structure so that even if one barrier is damaged, the other barrier can prevent the leakage of LNG. At this time, each insulation space is filled with insulation materials such as polyurethane foam (PUF), perlite, or glass wool to secure insulation performance.

The heat source from the outside of the ship passes through each insulated space, and heat enters the LNG. Therefore, the BOR varies depending on the insulation performance of the insulation space. In general, in the case of a type in which glass wool is filled in the insulating space of the GTT guarantee standard No.96. type storage tank, the BOR is known to be about 0.123%/day.

The present invention is to provide an inert gas injection system in a storage tank insulated space for reducing the BOR of the liquefied gas, that is, the natural vaporization rate by improving the insulation performance in a liquefied gas storage tank that stores liquefied gas at cryogenic temperatures. The purpose.

According to an aspect of the present invention for achieving the above object, a liquefied gas storage tank in which liquefied gas is stored in a body; and the liquefied gas storage tank is one for sealing leakage of the liquefied gas stored in the body More barriers; And one or more insulating spaces each formed between the liquefied gas storage tank body and the at least one barrier, and further comprising an argon gas circulation unit for circulating argon gas in the insulating space, and the argon gas circulation unit , An argon buffer tank for storing the forcibly vaporized argon gas and the argon gas recovered from the adiabatic space; An argon supply line connecting the argon buffer tank to the adiabatic space and flowing argon gas from the argon buffer tank to the adiabatic space; And an argon discharge line connecting the insulating space and the argon buffer tank and flowing argon gas from the insulating space to the argon buffer tank. The inert gas injection system of the storage tank insulating space is provided.

Preferably, the argon gas circulation unit, a pressure measuring device for measuring the pressure of the adiabatic space; An argon supply valve installed in the argon supply line and controlling a flow rate of argon gas flowing along the argon supply line; And an argon discharge valve installed in the argon discharge line and controlling the flow rate of the argon gas flowing along the argon discharge line, further comprising, any one of the argon supply valve and the argon discharge valve according to the pressure measured value of the pressure measuring device. It may include; a control unit for controlling one or more opening and closing and opening amount.

Preferably, in the argon discharge line, a gas detector that is installed upstream of the argon discharge valve and detects a component of the argon gas transferred along the argon discharge line may be installed.

Preferably, the control unit analyzes the components of the argon gas discharged from the insulating space using the gas detector, and if it is determined that the argon gas discharged from the insulating space cannot be recovered to the argon buffer tank, the The argon discharge valve can be closed.

Preferably, one or more of the argon supply line, the argon discharge line, a pressure measuring device, a gas detector, an argon supply valve, and an argon discharge valve may be provided to correspond to the one or more insulation spaces, respectively.

Preferably, the argon gas circulation unit may further include a compressor for compressing the argon gas recovered from the adiabatic space to the argon buffer tank along the argon supply line.

Preferably, the argon gas circulation unit may further include a pressure reducing valve for depressurizing the argon gas supplied from the argon buffer tank to the adiabatic space along the argon supply line.

Preferably, the argon gas circulation unit includes a liquid argon storage tank for storing liquid argon; A pump to pressurize the liquid argon discharged from the liquid argon storage tank; A vaporizer for generating argon gas by vaporizing liquid argon pressurized by the pump; And an argon replenishing line connecting the vaporizer and the argon buffer tank so that the argon gas vaporized by the vaporizer is supplied to the argon buffer tank.

According to another aspect of the present invention for achieving the above object, in the liquefied gas storage tank for storing the liquefied gas, the storage tank body in which the liquefied gas is stored; At least one barrier for sealing leakage of the liquefied gas stored in the storage tank body; And at least one insulating space each formed between the storage tank body and the at least one barrier, wherein the insulating space is filled with argon gas, and the argon gas is the insulating space according to pressure or temperature in the insulating space. A storage tank is provided that is discharged from or supplied to and circulates in the insulating space.

Preferably, the argon gas discharged from the insulating space may be compressed and depressurized and then resupplied to the insulating space.

The inert gas injection system and method of the storage tank insulation space according to the present invention can improve the insulation performance of the liquefied gas storage tank.

In particular, it is possible to reduce the BOR by filling the thermal insulation space of the liquefied gas storage tank with argon gas having low thermal conductivity.

In addition, by configuring the inert gas injection system in a closed cycle, it is possible to circulate expensive argon gas in the heat insulation space.

In addition, it is safe because the heat insulation space is filled with argon gas while maintaining a certain pressure, so that even if the liquefied gas leaks, the explosion lower limit concentration can be prevented.

1 is a block diagram schematically showing a storage tank and an inert gas injection system of an insulating space of the storage tank according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of an inert gas injection system in an insulating space of a storage tank to which an open cycle is applied.

In order to fully understand the operational advantages of the present invention and the object achieved by the implementation of the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, the configuration and operation of a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Here, in adding reference numerals to elements of each drawing, it should be noted that only the same elements are marked with the same numerals as possible, even if they are indicated on different drawings.

In an embodiment of the present invention to be described later, the liquefied gas may be obtained by liquefying a gas in a gaseous state at normal pressure and room temperature at a low temperature, for example, LNG (Liquefied Natural Gas), LEG (Liquefied Ethane Gas), LPG. It may be a liquefied petrochemical gas such as (Liquefied Petroleum Gas), Liquefied Ethylene Gas, and Liquefied Propylene Gas. However, in the embodiments to be described later, a representative liquefied gas, LNG, is applied as an example.

In addition, in an embodiment of the present invention to be described later, the ship may be any type of ship equipped with a liquefied gas storage tank (cargo hold) for storing liquefied gas. For example, LNG carriers, liquid hydrogen carriers, ships with self-propelled capabilities such as LNG Regasification Vessels (RVs), LNG Floating Production Storage Offloading (FPSO), LNG Floating Storage Regasification Unit (FSRU) and It may include offshore structures that do not have the same propulsion capability but are floating on the sea. In the embodiments to be described later, it will be described as an example of an LNG carrier.

In addition, the LNG storage tank according to an embodiment of the present invention is a membrane tank, in particular, No. 96. It will be described with an example of a type.

1 is a block diagram schematically showing a storage tank and an inert gas injection system of an insulating space of the storage tank according to an embodiment of the present invention. Hereinafter, a system and method for injecting an inert gas into a storage tank insulating space according to an embodiment of the present invention will be described with reference to FIG. 1.

The inert gas injection system of the storage tank insulation space according to the present embodiment includes an LNG storage tank 100 for storing LNG; And an inert gas circulation unit for circulating the inert gas into the insulation space of the LNG storage tank 100.

First, the LNG storage tank 100 according to the present embodiment includes a first barrier 101 that directly contacts the LNG and primarily seals the leakage of LNG; Including a second barrier 102 that is provided between the first barrier 101 and the inner wall 103 of the hull and secondaryly seals the leakage of LNG, the first barrier 101 and the second barrier A first heat insulating space 110 formed between 102 and primarily insulating LNG; And a second insulating space 120 formed between the second barrier 102 and the inner wall 103 of the hull and secondarily insulating LNG.

The first barrier 101 and the second barrier 102 of the present embodiment are from the innermost of the LNG storage tank 100 in which LNG is stored, to the first and second insulating spaces 110 and 120. Prevent leakage of LNG or natural gas.

The first barrier 101 and the second barrier 102 have almost the same degree of liquid tightness and strength, and therefore, when a leakage occurs in the first barrier 101, the second barrier 102 alone is used for a considerable period of time. In other words, it can safely support LNG.

As shown in FIG. 1, the first barrier 101 is a membrane provided on the outermost part of the body of the LNG storage tank 100, and the LNG stored in the body of the LNG storage tank 100 leaks out of the body. Prevent it.

The material of the first barrier 101 and the second barrier 102 may be INVAR steel (38% nickel steel), and the thickness may be about 0.5 to 1.5 mm. In the present embodiment, the first barrier 101 and the second barrier 102 will be described as an example of each 0.7 mm.

In addition, although not shown in the drawings, the first heat insulating space 110 and the second heat insulating space 120 of the present embodiment, perlite (perlite), polyurethane foam (PUF) or glass wool (glass wool) thermal conductivity It may include an insulation box filled with low insulation. The structural material of the insulation box may be plywood.

The first insulating space 110 and the second insulating space 120 are insulated so that heat transfer does not occur between the LNG stored in the storage tank body and outside air, as shown in FIG. 1.

In addition, the first heat insulating space 110 and the second heat insulating space 120 of the present embodiment are filled with an inert gas together with the above-described heat insulating material. The inert gas is not continuously injected and discharged, but is regulated to maintain an appropriate pressure, and is additionally supplemented when the pressure drops and discharged when the pressure rises.

In this embodiment, since the LNG storage tank 100 is described as an example as a membrane tank, an inert gas may be applied to the inside of the insulating space. On the other hand, when the LNG storage tank is a standalone tank, the inert gas may be applied to the outside of the insulating space.

In this embodiment, the inert gas may be argon (Ar, Argon).

The inert gas circulation unit of this embodiment includes a liquid argon storage tank 210 for storing liquid argon; And an argon buffer tank 310 for storing gaseous argon.

The liquid argon storage tank 210 and the argon buffer tank 310 are connected by an argon supplement line FL, and the argon buffer tank 310 and the first insulation space 110 are provided with a first supply line SL1 and It is connected by the first discharge line DL1, and the argon buffer tank 310 and the second insulation space 120 are connected by a second supply line SL2 and a second discharge line DL2.

The liquid argon storage tank 210 may include a supply connection 211 connected to the liquid argon supply unit to receive the liquid argon from the liquid argon supply unit outside the ship, before or during the operation of the ship. The supply connection part 211 may be detachably connected to the liquid argon supply part as necessary, and may be sealed from the outside after the connection with the argon supply part is released.

In addition, the inert gas circulation unit of the present embodiment includes: a first pressure measuring device 341 for measuring the internal pressure of the first heat insulating space 110; And a second pressure measuring device 342 for measuring the internal pressure of the second insulating space 120, and supplying the first using the pressure measured values of the first pressure measuring device 341 and the second pressure measuring device 342 It further includes a control unit 500 for controlling the flow of argon gas to the line SL1, the first discharge line DL1, the second supply line SL2, and the second discharge line DL2.

The control unit 500 supplies argon to the first heat insulating space 110 and the second heat insulating space 120 using the measured values of the first pressure measuring device 341 and the second pressure measuring device 342 and By controlling the discharge of argon from the heat insulation space 110 and the second heat insulation space 120, the pressure of the first heat insulation space 110 and the second heat insulation space 120 can be maintained within a set range.

The first pressure meter 341 and the second pressure meter 342 may be pressure transmitters.

The inert gas circulation unit of this embodiment includes a pump 220 for pressurizing liquid argon discharged from the liquid argon storage tank 210; And a vaporizer 230 for vaporizing liquid argon pressurized by the pump 220 into gaseous argon.

The liquid argon stored in the liquid argon storage tank 210 is discharged to the argon supplement line FL, if necessary, for example, when the internal pressure of the argon buffer tank 310 is lower than the set value, and the argon supplement line FL ) Is supplied to the vaporizer 230 by the pump 220 while flowing along, vaporized by the vaporizer 230, and then transferred to the argon buffer tank 310.

In the argon supplement line FL, it is installed between the vaporizer 230 and the argon buffer tank 310, and the argon gas vaporized in the vaporizer 230 is prevented from flowing backward from the argon buffer tank 310 side to the vaporizer 230 side. A first check valve 240 to prevent; may be installed.

In addition, the inert gas circulation unit according to the present embodiment may include a pressure reducing valve 320 for depressurizing the argon gas stored in the argon buffer tank 310.

As the pressure is reduced by the pressure reducing valve 320, the temperature of the argon gas may also be lowered.

When there is a need to supply argon gas to the first heat insulating space 110 and/or the second heat insulating space 120, the argon gas is discharged from the argon buffer tank 310 and decompressed by the pressure reducing valve 320, It flows along the first supply line SL1 and/or the second supply line SL2 to be supplied to the first insulating space 110 and/or the second insulating space 120.

The first supply line SL1 is provided with a first supply valve 331 in which the amount of opening and closing and opening is controlled by the control unit 500. When the first supply valve 331 is opened, the argon gas depressurized by the pressure reducing valve 320 is introduced into the first supply line SL1 and into the first thermal insulation space 110 along the first supply line SL1. Is transported. In addition, the flow rate of the argon gas transferred to the first thermal insulation space 110 may be adjusted by controlling the opening amount of the first supply valve 331.

In addition, the second supply line SL2 is provided with a second supply valve 332 in which the amount of opening and closing is controlled by the control unit 500. When the second supply valve 332 is opened, the argon gas depressurized by the pressure reducing valve 320 flows into the second supply line SL2 and goes to the second insulation space 120 along the second supply line SL2. Is transported. In addition, the flow rate of the argon gas transferred to the second thermal insulation space 120 may be adjusted by controlling the opening amount of the second supply valve 332.

In addition, a first discharge valve 361 is installed in the first discharge line DL1, in which the amount of opening and closing and opening is controlled by the control unit 500. When the first discharge valve 361 is opened, argon gas is introduced from the first insulating space 110 to the first discharge line DL1, and argon from the first insulating space 110 along the first discharge line DL1. It is transferred to the buffer tank 310. In addition, the flow rate of the argon gas transferred from the first thermal insulation space 110 to the argon buffer tank 310 may be adjusted by controlling the opening amount of the first discharge valve 361.

In addition, a second discharge valve 362 for controlling the amount of opening and closing and opening by the control unit 500 is installed in the second discharge line DL2. When the second discharge valve 362 is opened, argon gas is introduced from the second insulating space 120 into the second discharge line DL2, and argon from the second insulating space 120 along the second discharge line DL2. It is transferred to the buffer tank 310. In addition, the flow rate of argon gas transferred from the second thermal insulation space 210 to the argon buffer tank 310 may be adjusted by controlling the opening amount of the second discharge valve 362.

In addition, the first discharge line DL1 is installed upstream of the first discharge valve 361 and detects a component of the fluid discharged from the first insulation space 110 to the first discharge line DL1. A gas detection system 351 is installed.

In addition, in the second discharge line DL2, a second discharge valve is installed upstream of the second discharge valve 362 and detects a component of the fluid discharged from the second insulation space 120 to the second discharge line DL2. A gas detection system 352 is installed.

In addition, the inert gas circulation unit according to the present embodiment compresses the argon gas transferred by the first discharge line DL1 and/or the second discharge line DL2 to a temperature suitable for storage in the argon buffer tank 310. Compressor 370; may further include.

In addition, a second check is installed between the argon buffer tank 310 and the compressor 370 and prevents the argon recovery gas compressed by the compressor 370 from flowing back to the compressor 370 from the argon buffer tank 310 side. Valve 380; may further include.

That is, according to the present embodiment, the argon gas discharged from the first heat insulating space 110 and the second heat insulating space 120 is not vented when in a normal operation state, but is recovered into the argon buffer tank 310.

When argon gas recovered to the argon buffer tank 310 needs to be supplied to the first insulating space 110 and/or the second insulating space 120, the first insulating space 110 and/or 2 It can be resupplied to the heat insulation space 120.

That is, the argon gas stored in the argon buffer tank 310 of this embodiment is discharged from the argon gas vaporized by the vaporizer 230 and the first insulating space 110 and/or the second insulating space 120 It contains argon gas compressed by the compressor 370.

The temperature of the first insulating space 110 and the second insulating space 120 changes depending on whether LNG is loaded in the LNG storage tank 100. That is, when LNG is loaded in the LNG storage tank 100, the temperatures of the first and second thermally insulating spaces 110 and 120 may be lowered, and thus the first and second thermally insulating spaces 110 and 120 ), the volume of the argon gas filled in is changed, and accordingly, the pressure of the first insulating space 110 and the second insulating space 120 is also changed. This is sensed by the first pressure meter 341 and/or the second pressure meter 342.

When the pressure in the first insulation space 110 is lowered below the set pressure, the control unit 500 opens the first supply valve 331 to allow the argon gas to be discharged from the argon buffer tank 310, and the argon buffer tank The argon gas discharged from 310 is depressurized by the pressure reducing valve 320 and supplied to the first thermal insulation space 110.

In addition, when the pressure of the second thermal insulation space 120 is lowered below the set pressure, the control unit 500 opens the second supply valve 332 so that the argon gas is discharged from the argon buffer tank 310, and The argon gas discharged from the buffer tank 310 is depressurized by the pressure reducing valve 320 and supplied to the second insulating space 120.

Conversely, when the pressure in the first insulating space 110 increases, the control unit 500 opens the first discharge valve 361 so that the fluid is discharged from the first insulating space 110, and the compressor 370 is operated. After compressing the fluid by using, it is recovered into the argon buffer tank 310.

In addition, when the pressure in the second insulating space 120 increases, the control unit 500 opens the second discharge valve 362 so that the fluid is discharged from the second insulating space 120, and the compressor 370 is operated. After compressing the fluid by using, it is recovered into the argon buffer tank 310.

In this way, even if the pressure of the first heat insulation space 110 and/or the second heat insulation space 120 rises to discharge the argon gas from the first heat insulation space and/or the second heat insulation space 120, venting it Rather, by recovering it to the argon buffer tank 310, it is possible to reduce the loss of expensive argon.

In FIG. 1, a supply point is shown so that the fluid supplied to the first heat insulating space 110 through the first supply line SL1 is supplied to a relatively upper point within the first heat insulating space 110, and the second A supply point is shown so that the fluid supplied to the second insulating space 120 through the supply line SL2 is supplied to a relatively lower point within the second insulating space 120.

In addition, in FIG. 1, a discharge point is shown so that the fluid discharged from the first insulating space 110 through the first discharge line DL1 is discharged from a relatively upper point in the first insulating space 110, A discharge point is shown so that fluid discharged from the second insulating space 120 through the second discharge line DL2 is also discharged from a relatively upper point in the second insulating space 120.

Likewise, the fluid discharged to the venting unit 430 through the first venting line (VL1) and the fluid discharged to the venting unit 430 through the second discharge line (VL2) are also 2 The discharge point is shown so as to be discharged from the upper point in the insulating space 120 relatively.

As shown in FIG. 1, argon is supplied to an upper point in the first insulating space 110 and discharged from an upper point opposite to the supply point in the first insulating space 110. In addition, argon is supplied to a lower point in the second insulating space 120 and discharged from an upper point opposite to the supply point in the second insulating space 120. The supply point and the discharge point in the adiabatic space are not particularly limited, but the supply point and the discharge point may be located opposite to each other so as to spread the fluid as well as possible.

The gas detectors 351 and 352 of this embodiment may detect methane (CH ₄ ) and/or propane (C ₃ H ₈ ).

The controller 500 analyzes the gas component of the fluid discharged from the heat insulation spaces 110 and 120 using the first gas detector 351 and the second gas detector 352, and from the heat insulation spaces 110 and 120 When the discharged fluid contains a natural gas component or the concentration of natural gas contained in the fluid is greater than or equal to the set value, the first discharge valve 361 and/or the second discharge valve 362 are closed so that the fluid is an argon buffer. It is prevented from being recovered to the tank 310, and the fluid may be discharged to the venting unit 430 by the first venting line 410 and/or the second venting line 420 to be described later.

On the other hand, the inert gas circulation unit of the present embodiment, as a safety device, in the case of an abnormal situation in which the fluid cannot be recovered from the first insulating space 110 to the argon buffer tank 310, the fluid is vented from the first insulating space 110. A first venting line (VL1) connecting the first insulating space 110 and the venting part 430 to be transferred to the venting part 430; A first safety valve 410 installed in the first venting line VL1 and controlling opening and closing of the first venting line VL1; When the fluid cannot be recovered from the second insulating space 120 to the argon buffer tank 310, the second insulating space 120 and the venting unit are so that the fluid is transferred from the second insulating space 120 to the venting unit 430. A second venting line VL2 connecting the 430; And a second safety valve 420 installed on the second venting line VL2 and controlling opening and closing of the second venting line VL2.

The first safety valve 410 of this embodiment is automatically opened when the pressure in the first insulation space 110 is greater than or equal to the set pressure, and the second safety valve 420 is the pressure in the second insulation space 120 or more. In this case, it may be an automatic valve that is automatically opened.

That is, when the pressure of the first insulating space 110 is greater than or equal to the set pressure, the first safety valve 410 is opened so that the fluid from the first insulating space 110 flows into the venting part 430 along the first venting line VL1. Can be transported to and released into the atmosphere.

In addition, when the pressure of the second insulating space 120 is greater than or equal to the set pressure, the second safety valve 420 is opened so that the fluid from the second insulating space 120 flows into the venting part 430 along the second venting line VL2. Can be transported to and released into the atmosphere.

The venting part 430 of this embodiment may be a vent mast that is generally installed on a ship.

As described above, when argon gas is filled in the first and second insulating spaces 110 and 120, the thermal conductivity of argon is low, and the insulating performance may be improved.

In addition, even if LNG leaks from the first barrier 101 or the second barrier 102, since argon gas is filled while maintaining a constant pressure, the first insulating space 110 and the second insulating space The oxygen concentration in 120 is low, so that an explosion does not occur.

In addition, according to this embodiment, the inert gas discharge line branched between the discharge valves 361 and 362 of the discharge lines DL1 and DL2 and the compressor 370 and connected to the venting lines 410 and 420; And a venting valve 440 installed on the inert gas discharge line and controlling opening/closing of the inert gas discharge line by displacement control. The venting valve 440 may be controlled by the control unit 500 or may be automatically controlled according to a preset mode.

The venting valve 440 is opened when the measured value of the pressure measuring devices 341 and 342 exceeds the set value, and is controlled to discharge the fluid discharged through the discharge lines DL1 and DL2 to the venting unit 430. I can.

In addition, the venting valve 440 is opened when natural gas is detected by the gas detectors 351 and 352, and is controlled so that the fluid discharged through the discharge lines DL1 and DL2 is discharged to the venting unit 430. have.

FIG. 2 shows an embodiment in which nitrogen is applied as an inert gas filled together with an insulating material in the first and second insulating spaces.

In the inert gas injection system of the insulating space of the storage tank using nitrogen as the inert gas, as shown in FIG. 2, a first barrier 601 that directly contacts the LNG and first seals the leakage of LNG. ; Including a second barrier 602 provided between the first barrier 601 and the inner wall 603 of the hull and secondarily sealing the leakage of LNG, the first barrier 601 and the second barrier A first insulating space 610 formed between the 602 and primarily insulating LNG; And a second insulating space 620 formed between the second barrier 602 and the inner wall 603 to insulate LNG secondary; and the first insulating space 610 of the LNG storage tank 600 including Nitrogen gas other than argon is filled in the second insulating space 620.

In the case of using nitrogen, a nitrogen generator 710 for generating nitrogen to fill nitrogen gas in the heat insulation spaces 610 and 620; A nitrogen buffer tank 720 for storing the generated nitrogen gas in a gaseous state; And a nitrogen pressure reducing valve 730 for reducing nitrogen gas discharged from the nitrogen buffer tank 720 when it is necessary to supply nitrogen to the heat insulating spaces 610 and 620.

The nitrogen gas depressurized by the nitrogen pressure reducing valve 730 is supplied to the first insulating space 610 along the first nitrogen supplement line NL1 and the first nitrogen line NL3, or the second nitrogen supplement line NL2. ) And is supplied to the second thermal insulation space 620 along the second nitrogen line NL4.

In addition, nitrogen discharged from the heat insulation spaces 610 and 620 is not recovered to the nitrogen buffer tank 720 but is transferred to the venting unit 430 and discharged into the atmosphere for treatment.

As described above, when nitrogen is used as the inert gas, when argon is used as in the above-described embodiment of the present invention, unlike forming the closed cycle, the inert gas cycle is formed in an open type.

That is, the injection of nitrogen gas into the first heat insulation space 610 and discharge from the first heat insulation space 620 are both performed by the first nitrogen line NL3, and the first heat insulation from the nitrogen buffer tank 720 The purpose of supplying nitrogen gas to the space 610 and the purpose of discharging the nitrogen gas from the first heat insulating space 610 to the venting unit 430 are achieved by the first nitrogen line NL3.

When the first nitrogen supplement valve 741 installed in the first nitrogen supplement line NL1 is opened, nitrogen gas is supplied to the first heat insulation space 610, and a first nitrogen valve installed in the first nitrogen line NL3 When 751 is opened, nitrogen gas is discharged from the first heat insulating space 610 to the venting part 430.

Also, in the same way, both injection of nitrogen gas into the second insulating space 620 and discharge from the second insulating space 620 are performed by the second nitrogen line NL4, and from the nitrogen buffer tank 720 The purpose of supplying nitrogen gas to the second insulating space 620 and the purpose of discharging nitrogen gas from the second insulating space 620 to the venting unit 430 are achieved by the second nitrogen line NL4. .

When the second nitrogen supplement valve 742 installed in the second nitrogen supplement line NL2 is opened, nitrogen gas is supplied to the second insulating space 620 and a second nitrogen valve installed in the second nitrogen line NL4 When the 752 is opened, nitrogen gas is discharged from the second insulating space 620 to the venting unit 430.

In addition, a first venting line TL1 connecting the first insulating space 610 and the venting unit 430 so that nitrogen gas is transferred from the first insulating space 610 to the venting unit 430; A first safety valve 810 installed in the first venting line TL1 and controlling opening and closing of the first venting line TL1; A second venting line TL2 connecting the second insulating space 620 and the venting unit 430 so that nitrogen gas is transferred from the second insulating space 620 to the venting unit 430; And a second safety valve 820 installed on the second venting line TL2 and controlling opening and closing of the second venting line TL2.

The first safety valve 810 is automatically opened when the pressure in the first insulating space 610 is greater than or equal to the set pressure, and the second safety valve 820 is automatically opened when the pressure in the second insulating space 620 is greater than the set pressure. It may be an automatic valve that becomes.

The venting part 430 of this embodiment may be a vent mast that is generally installed on a ship.

The thermal conductivity of argon is 7.4 mW/mK at -160°C, 12.1 mW/mK at -80°C, and 16.2 mW/mK at 0°C. The thermal conductivity of argon is significantly lower than that of nitrogen (10.5 mW/mK at -160°C, 17.7 mW/mK at -80°C, 23.9 mW/mK at 0°C), so use nitrogen. Insulation performance can be improved more.

Therefore, when argon is filled in the adiabatic space, the BOR can be lowered by about 8 to 9% or more than that of using nitrogen.

It is obvious to those of ordinary skill in the art that the present invention is not limited to the above embodiments, and can be implemented with various modifications or variations within the scope of the technical gist of the present invention. I did it.

100: LNG storage tank
101: first barrier 102: second barrier 103: inner wall of the hull
110: first insulating space 120: second insulating space
210: liquid argon storage tank
220: pump
230: carburetor
240: first check valve
310: argon buffer tank
320: pressure reducing valve
370: compressor
380: second check valve
331: first supply valve 332: second supply valve
341: first pressure meter 342: second pressure meter
351: first gas detector 352: second gas detector
361: first discharge valve 362: second discharge valve

Claims (10)

Including; a liquefied gas storage tank in which the liquefied gas is stored in the body,
The liquefied gas storage tank,
At least one barrier for sealing leakage of the liquefied gas stored in the body; And
Includes; at least one insulating space each formed between the liquefied gas storage tank body and the at least one barrier,
Further comprising an argon gas circulation unit for circulating argon gas in the heat insulating space,
The argon gas circulation unit,
An argon buffer tank for storing the forcibly vaporized argon gas and the argon gas recovered from the adiabatic space;
An argon supply line connecting the argon buffer tank to the adiabatic space and flowing argon gas from the argon buffer tank to the adiabatic space; And
An inert gas injection system in the storage tank insulation space comprising a; an argon discharge line connecting the insulation space and the argon buffer tank and flowing argon gas from the insulation space to the argon buffer tank. The method according to claim 1,
The argon gas circulation unit,
A pressure measuring device for measuring the pressure in the adiabatic space;
An argon supply valve installed in the argon supply line and controlling a flow rate of argon gas flowing along the argon supply line; And
An argon discharge valve installed on the argon discharge line and controlling a flow rate of the argon gas flowing along the argon discharge line; further comprising,
Containing, inert gas injection system of the storage tank insulation space, a control unit for controlling the opening and closing amount of at least one of the argon supply valve and the argon discharge valve according to the pressure measured value of the pressure measuring device. The method according to claim 2,
In the argon discharge line,
A gas detector installed upstream of the argon discharge valve and detecting a component of the argon gas transferred along the argon discharge line; is installed, an inert gas injection system in the storage tank insulation space. The method of claim 3,
The control unit analyzes the components of the argon gas discharged from the adiabatic space using the gas detector, and when it is determined that the argon gas discharged from the adiabatic space cannot be recovered to the argon buffer tank, the argon discharge valve is closed. Closed, inert gas injection system of the storage tank insulation space. The method of claim 3,
The argon supply line, argon discharge line, pressure meter, gas detector, argon supply valve and argon discharge valve,
Inert gas injection system of the storage tank insulation space provided at least one to correspond to each of the at least one insulation space. The method according to claim 1,
The argon gas circulation unit,
A compressor for compressing the argon gas recovered from the adiabatic space to the argon buffer tank along the argon supply line; further comprising, inert gas injection system of the storage tank insulation space. The method according to claim 1,
The argon gas circulation unit,
A pressure reducing valve for depressurizing the argon gas supplied from the argon buffer tank to the insulating space along the argon supply line; further comprising, an inert gas injection system in the storage tank insulating space. The method according to claim 1,
The argon gas circulation unit,
A liquid argon storage tank for storing liquid argon;
A pump to pressurize the liquid argon discharged from the liquid argon storage tank;
A vaporizer for generating argon gas by vaporizing liquid argon pressurized by the pump; And
An argon replenishment line connecting the vaporizer and the argon buffer tank so that the argon gas vaporized by the vaporizer is supplied to the argon buffer tank; further comprising, an inert gas injection system of the storage tank insulation space. In the liquefied gas storage tank for storing liquefied gas,
A storage tank body in which the liquefied gas is stored;
At least one barrier for sealing leakage of the liquefied gas stored in the storage tank body; And
Includes; at least one insulating space each formed between the storage tank body and the at least one barrier,
Argon gas is filled in the insulating space,
The argon gas is discharged from the insulating space or supplied to the insulating space and circulated according to the pressure or temperature in the insulating space. The method of claim 9,
Argon gas discharged from the insulated space is compressed and depressurized and then resupplied to the insulated space.

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