Gas replacement method and liquefied gas plant

Abstract

A gas replacement method according to one embodiment of the present disclosure is a method implemented in a liquefied gas plant provided with: a connection joint connected to an external transfer device; a transfer pipe that connects the connection joint and a liquefied gas tank and transfers liquefied gas; a first valve located in the transfer pipe; a return pipe that connects the liquid gas tank to an end region, which is a region of the transfer pipe closer to the connection joint than the first valve; and a return pressure relief valve which is located in the return pipe and which is opened when the internal pressure of the end region exceeds a return reference value, the return pressure relief valve being closed after the return pressure relief valve is not functioned in a state where the first valve is closed, and the return pressure relief valve being closed after the return pressure relief valve is functioned in a state where the return pressure relief valve is not functioned in a state where the first valve is closed. The internal pressure of the end region is increased or decreased to displace the gas in the end region.

Description

Technical Field

[0001] The present disclosure relates to a gas replacement method and a liquefied gas device. Background Art

[0002] Patent Document 1 discloses a gas replacement method for replacing the gas in a pipe before and after the transfer of liquefied hydrogen. This gas replacement method employs a pressure swing adsorption method in which the operation of pressurizing the pipe and then depressurizing the pipe is repeated multiple times.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-19552 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, in a liquefied gas facility having a transfer facility for transferring liquefied gas, the internal pressure of the transfer pipe may excessively increase, that is, exceed the assumed pressure, when the liquefied gas in the transfer pipe is vaporized to generate vaporized gas, when the liquid temperature in the transfer pipe rises and the liquefied gas expands, or when the liquefied gas is supplied to the transfer pipe from another facility at a high supply pressure. Therefore, the liquefied gas facility has a pressure relief valve for returning the vaporized gas in the transfer pipe to the liquefied gas tank when the internal pressure of the transfer pipe exceeds a reference value.

[0008] However, in a liquefied gas device having such a pressure relief valve, if a gas replacement is carried out accompanied by an increase or decrease in the internal pressure of the transfer piping such as a pressure swing adsorption method, there is a possibility that the pressure will rise excessively during the gas replacement and the pressure relief valve will operate, thereby causing air and inert gas to flow into the liquefied gas tank and contaminate the liquefied gas in the liquefied gas tank.

[0009] Therefore, an object of the present disclosure is to provide a gas replacement method and a liquefied gas equipment that do not contaminate the liquefied gas in the liquefied gas tank during gas replacement.

[0010] Means for solving problems

[0011] One embodiment of a gas replacement method disclosed herein is a method implemented in a liquefied gas device, which comprises: a connecting joint, which is connected to an external transfer device; a transfer pipe, which connects the connecting joint to a liquefied gas tank and transfers liquefied gas; a first valve, which is located in the transfer pipe; a return pipe, which connects an area of ​​the transfer pipe that is closer to the connecting joint than the first valve, i.e., an end area, to the liquefied gas tank; and a return pressure relief valve, which is located in the return pipe, and when the internal pressure of the end area exceeds a return reference value, the return pressure relief valve opens, wherein the return pressure relief valve is rendered inoperative when the first valve is closed, and the gas in the end area is replaced after the return pressure relief valve is rendered inoperative.

[0012] In addition, a liquefied gas device of one embodiment of the present invention comprises: a connecting joint, which is connected to an external transfer device; a transfer piping, which connects the connecting joint to a liquefied gas tank and transfers liquefied gas; a first valve, which is located in the transfer piping; a return piping, which connects an area of ​​the transfer piping that is closer to the connecting joint than the first valve, i.e., an end area, to the liquefied gas tank; a return pressure relief valve, which is located in the return piping and opens when the internal pressure of the end area exceeds a return reference value; a waste piping, which connects a waste device for waste liquefied gas to the end area; a waste pressure relief valve, which is located in the waste piping and opens when the internal pressure of the end area exceeds a waste reference value that is lower than the return reference value; and a waste opening and closing valve, which is located in the waste piping.

[0013] Effects of the Invention

[0014] According to the present disclosure, it is possible to provide a gas replacement method and a liquefied gas facility that do not contaminate liquefied gas in a liquefied gas tank during gas replacement. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the liquefied gas equipment and its surroundings.

[0016] Figure 2 This is a flow chart of the liquefied gas transfer procedure.

[0017] Figure 3 This is a schematic diagram of a liquefied gas facility and its surroundings according to a modified example.

[0018] Figure 4 This is a schematic diagram of liquefied gas equipment and its surroundings according to another modified example. DETAILED DESCRIPTION

[0019] <Overall structure of liquefied gas equipment>

[0020] First, the overall structure of the liquefied gas equipment 100 according to the embodiment will be described. Figure 1 1 is a schematic diagram of a liquefied gas facility 100 and its surroundings. The liquefied gas facility 100 of this embodiment includes a liquefied gas tank 101, a disposal facility 102, and a transfer facility 103 for transferring liquefied gas between the liquefied gas tank 101 of a ship and an external liquefied gas tank 111 on land. Liquefied gas is liquefied hydrogen, liquefied natural gas (LNG), liquefied petroleum gas (LPG), etc. In addition, the liquefied gas facility 100 of this embodiment is a facility on the ship side and is mounted on the ship. However, the liquefied gas facility 100 may also be a facility on the land side and be installed on land.

[0021] like Figure 1 As shown, the transfer equipment 103 of the liquefied gas equipment 100 of the present embodiment includes a connection joint 10, a transfer pipe 20, a return pipe 30, a waste pipe 40, and a connection pipe 50. These components will be described in order below.

[0022] The connection joint 10 is a device connected to the external transfer equipment 112. For example, the manifold of a liquefied gas tanker corresponds to the connection joint 10. The external transfer equipment 112 of this embodiment is a land-side device, and includes an external connection joint 113 connected to the connection joint 10, an external transfer piping 114 connecting the external connection joint 113 and the external liquefied gas tank 111, and an external first valve 115 located in the external transfer piping 114. The external transfer piping 114 may also include a deformable loading arm.

[0023] The transfer pipe 20 is a pipe that connects the connection joint 10 and the liquefied gas tank 101 to transfer the liquefied gas. The transfer pipe 20 can transfer the liquefied gas in the direction from the liquefied gas tank 101 to the external liquefied gas tank 111, and can also transfer the liquefied gas in the direction from the external liquefied gas tank 111 to the liquefied gas tank 101. The first valve 21 is located in the transfer pipe 20. The first valve 21 is the valve closest to the connection joint 10 among the valves located in the transfer pipe 20. In addition, hereinafter, the area of ​​the transfer pipe 20 that is closer to the connection joint 10 than the first valve 21 is referred to as the "end area 22".

[0024] The return piping 30 is a piping that connects the end area 22 to the liquefied gas tank 101. The return pressure relief valve 31 is located in the return piping 30. The return pressure relief valve 31 is set to open when the internal pressure of the end area 22 exceeds a predetermined "return reference value". For example, during the transfer of liquefied gas, gasified gas (hereinafter referred to as "gasified gas") is generated by the gasification of the liquefied gas being transferred, and the internal pressure of the transfer piping 20 rises. When the internal pressure of the end area 22 exceeds the return reference value, the return pressure relief valve 31 opens, and the gasified gas in the transfer piping 20 returns to the liquefied gas tank 101. In this way, the excessive increase in the internal pressure of the transfer piping 20 can be prevented, and the transfer piping 20 can be prevented from being damaged.

[0025] The waste piping 40 is a piping that connects the waste equipment 102 to the end area 22. The waste equipment 102 of the present embodiment is a vent mast that releases the gasified gas to the atmosphere. However, the waste equipment 102 may also be a flare device that burns the gasified gas, etc. That is, the waste equipment 102 is a device that discards the gasified gas. The waste pressure relief valve 41 and the waste on-off valve 42 are located in the waste piping 40. The waste pressure relief valve 41 is set to open when the internal pressure of the end area 22 exceeds a predetermined "waste reference value". The "waste reference value" is lower than the above-mentioned "return reference value". In addition, the waste on-off valve 42 is located upstream of the waste pressure relief valve 41. However, the waste on-off valve 42 may also be located downstream of the waste pressure relief valve 41.

[0026] The connecting pipe 50 is connected to the end region 22 of the transfer pipe 20, and is a pipe for supplying replacement gas to the end region 22 and discharging replaced gas. In addition, the connecting pipe valve 51 is located in the connecting pipe 50. The replacement gas is a gas supplied when replacing the gas, and changes according to the method of gas replacement. In addition, the replaced gas is a gas discharged when replacing the gas, and changes according to the method of gas replacement. The specific description of the replacement gas and the replaced gas will be described later.

[0027] <Liquid Gas Transfer Procedure>

[0028] Next, the transfer procedure of the liquefied gas including the gas replacement method will be described. Figure 2 This is a flow chart of the liquefied gas transfer procedure.

[0029] like Figure 2As shown, in the case of transferring liquefied gas, the transfer device 103 is first connected to the external transfer device 112 (step S1). Specifically, the connection joint 10 is connected to the external connection joint 113 while the first valve 21 and the external first valve 115 are closed. Thus, a closed space is formed between the first valve 21 and the external first valve 115. The end region 22 constitutes a part of the closed space. Immediately after the transfer device 103 is connected to the external transfer device 112, the interior of the end region 22 is filled with air containing oxygen (external air).

[0030] Next, the return pressure relief valve 31 is disabled (step S2). In the present embodiment, the return pressure relief valve 31 is disabled by opening the discard opening and closing valve 42. That is, the discard pressure relief valve 41 can be enabled to function by opening the discard opening and closing valve 42, but as described above, the return reference value, which is the reference for opening the return pressure relief valve 31, is higher than the discard reference value, which is the reference for opening the discard pressure relief valve 41. Therefore, if the discard pressure relief valve 41 is enabled to function, the discard pressure relief valve 41 operates before the internal pressure of the end region 22 reaches the return reference value, so the internal pressure of the end region 22 does not reach the return reference value, and the return pressure relief valve 31 does not open.

[0031] Next, the first gas replacement is implemented (step S3). In the first gas replacement, the air filling the interior of the end region 22 is replaced with an inert gas. That is, air is the replaced gas, and the inert gas is the replacement gas. In the first gas replacement, an inert gas generating device that generates an inert gas is connected to the connecting pipe 50. In this state, the connecting pipe valve 51 is opened. Thus, an inert gas is supplied to the end region 22 via the connecting pipe 50, and the internal pressure of the end region 22 rises. Thereafter, the connecting pipe valve 51 is closed, and the above-mentioned inert gas generating device is removed from the connecting pipe 50 in this state. Then, the connecting pipe valve 51 is opened again. Thus, the inert gas is violently discharged from the end region 22 together with the air, and the internal pressure of the end region 22 is reduced. By repeatedly increasing and decreasing the internal pressure of the end region 22 based on the inert gas, the air filling the interior of the end region 22 is replaced with an inert gas. In addition, as an inert gas, for example, nitrogen, argon, helium, carbon gas, and a mixed gas thereof can be used. In the first gas replacement, the inert gas may be supplied to the end region 22 from the external transfer device 112 via the connection joints 113 and 10 instead of being supplied to the end region 22 via the connection pipe 50 .

[0032] Next, the second gas replacement is performed (step S4). In the second gas replacement, the inert gas filling the interior of the end region 22 is replaced with the gasified gas. That is, the inert gas is the replaced gas, and the gasified gas is the replacement gas. In the second gas replacement, a gasification gas generating device that generates the gasified gas is connected to the connecting pipe 50. Using the gasification gas generating device, the inert gas in the end region 22 is replaced with the gasified gas by repeatedly increasing and decreasing the internal pressure of the end region 22 based on the gasified gas as the replacement gas, as in the first gas replacement.

[0033] Next, the return pressure relief valve 31 is made functional (step S5). Specifically, by closing the waste on-off valve 42, the waste pressure relief valve 41 is made inoperative and the return pressure relief valve 31 is made functional. Thus, there is a case where the internal pressure of the end region 22 reaches the return reference value. In this case, the return pressure relief valve 31 is opened, and the gasified gas in the end region 22 is supplied to the liquefied gas tank 101.

[0034] Next, the transfer of the liquefied gas is started (step S6). Specifically, the first valve 21 and the external first valve 115 are opened, and the transfer pump and the like are operated to transfer the liquefied gas. Thus, the liquefied gas is transferred via the transfer pipe 20 and the external transfer pipe 114. As described above, the end area 22 is filled with the gasified gas through the second gas replacement in step S4, so when the transfer of the liquefied gas starts, air, inert gas, etc. will not flow into the liquefied gas tank 101 and the external liquefied gas tank 111. In addition, the air in the end area 22 is not directly replaced with the gasified gas because, if the gasified gas is mixed with the oxygen in the air, it is possible to explode when it comes into contact with an ignition source.

[0035] Next, the transfer of the liquefied gas is terminated (step S7). Specifically, the pump for transferring the liquefied gas is stopped, and the first valve 21 and the external first valve 115 are closed. Immediately after the transfer of the liquefied gas is terminated, the end region 22 is filled with the vaporized gas.

[0036] Next, the return pressure relief valve 31 is disabled (step S8). Specifically, similarly to step S2, the return pressure relief valve 31 is disabled by opening the discard on-off valve 42.

[0037] Next, the third gas replacement is performed (step S9). The third gas replacement replaces the gasified gas filling the interior of the end region 22 with an inert gas. That is, the gasified gas is the replaced gas, and the inert gas is the replacement gas. In the third gas replacement, an inert gas generating device that generates an inert gas is connected to the connecting pipe 50. Using the inert gas generating device, the gasified gas in the end region 22 is replaced with an inert gas by repeatedly increasing and decreasing the internal pressure of the end region 22 based on the inert gas as the replacement gas, as in the first and second gas replacements.

[0038] Next, the transfer device 103 and the external transfer device 112 are disconnected (step S10). Specifically, the connection joint 10 and the external connection joint 113 are disconnected. Assuming that the transfer device 103 and the external transfer device 112 are disconnected directly after the transfer of the liquefied gas is completed, the flammable gasified gas in the end area 22 will be released to the periphery of the connection joint 10, which is not preferred. Therefore, before the transfer device 103 and the external transfer device 112 are disconnected, the third gas replacement of the above-mentioned step S9 is performed to replace the gasified gas of the liquefied gas in the end area 22 with an inert gas. The above is the step of transferring the liquefied gas.

[0039] As described above, in the present embodiment, in steps S3, S4, and S9, the internal pressure of the end region 22 is increased or decreased to replace the gas in the end region 22, but before that, in steps S2 and S8, the return pressure relief valve 31 is not made to function. Therefore, even if the internal pressure of the end region 22 increases due to the gas replacement, air and inert gas will not flow into the liquefied gas tank 101 through the return pipe 30. Therefore, the liquefied gas in the liquefied gas tank 101 will not be contaminated.

[0040] <Modification>

[0041] like Figure 1 As shown, in the above-mentioned embodiment, the waste pipe 40 is connected to the end region 22 of the transfer pipe 20. Figure 3 As shown, the waste pipe 40 may be connected to the portion of the return pipe 30 upstream of the return pressure relief valve 31. That is, the waste pipe 40 may connect the waste equipment 102 to the end area 22 via the return pipe 30. In this case, the same gas replacement method as in the above-mentioned embodiment can be implemented, and the same effect can be obtained.

[0042] In addition, Figure 3 In the liquefied gas equipment 100 shown, a switching valve may be arranged at the portion of the return pipe 30 connected to the waste pipe 40, and the waste on-off valve 42 may be omitted. In this case, if the flow direction of the liquefied gas is switched by a switching valve such as a three-way valve, for example, the return pressure relief valve 31 can be made to function or not function.

[0043] In addition, if Figure 4 As shown, the return on-off valve 32 may be arranged on the return pipe 30 and the waste pipe 40, the waste pressure relief valve 41 and the waste on-off valve 42 may be omitted (see Figure 1 ). In this case, by closing the return on-off valve 32, the return pressure relief valve 31 can be disabled, and by opening the return on-off valve 32, the return pressure relief valve 31 can be enabled. Figure 4 The structure shown can simplify the liquefied gas equipment 100 and enable the return pressure relief valve 31 to function or not function.

[0044] Summary

[0045] Item 1 disclosed in the present specification is a gas replacement method, which is a method implemented in a liquefied gas device, the liquefied gas device comprising: a connecting joint, which is connected to an external transfer device; a transfer piping, which connects the connecting joint to a liquefied gas tank and transfers liquefied gas; a first valve, which is located in the transfer piping; a return piping, which connects an area of ​​the transfer piping that is closer to the connecting joint than the first valve, i.e., an end area, to the liquefied gas tank; and a return pressure relief valve, which is located in the return piping, and when the internal pressure of the end area exceeds a return reference value, the return pressure relief valve opens, wherein, after the return pressure relief valve is not functioning in a closed state of the first valve, the internal pressure of the end area is increased or decreased to replace the gas in the end area.

[0046] According to this method, the return pressure relief valve is disabled before gas replacement, so that gas other than gasified gas can be prevented from flowing into the liquefied gas during gas replacement. As a result, contamination of the liquefied gas in the liquefied gas tank can be prevented.

[0047] Item 2 disclosed in this specification is a gas replacement method according to Item 1, wherein the liquefied gas equipment has a waste pipe connecting a waste device for waste gasified gas to the end area, and when the internal pressure of the end area exceeds a waste reference value that is lower than the return reference value, the gas in the end area is discharged to the waste device via the waste pipe, thereby rendering the return pressure relief valve inoperative.

[0048] According to this method, when the internal pressure of the end region exceeds the disposal reference value during gas replacement, the gas in the end region is discharged to the disposal device, thereby preventing the internal pressure of the end region from increasing excessively.

[0049] Item 3 disclosed in this specification is a gas replacement method according to Item 2, wherein the liquefied gas equipment comprises: a waste pressure relief valve located in the waste piping, which opens when the internal pressure in the end area exceeds the waste reference value; and a waste on-off valve located in the waste piping, which makes the return pressure relief valve inoperative by opening the waste on-off valve.

[0050] According to this method, when the internal pressure of the end region exceeds the disposal reference value during gas replacement, the disposal pressure release valve operates to discharge the gas in the end region to the disposal device, thereby preventing the internal pressure of the end region from increasing excessively.

[0051] Item 4 disclosed in this specification is the gas replacement method according to Item 1, wherein the liquefied gas equipment has a return on-off valve located in the return pipe, and the return pressure release valve is disabled by closing the return on-off valve.

[0052] According to this method, the liquefied gas equipment can be simplified and the return pressure relief valve can be made non-functional.

[0053] Item 5 disclosed in the present specification is a liquefied gas device, which comprises: a connecting joint, which is connected to an external transfer device; a transfer piping, which connects the connecting joint to a liquefied gas tank and transfers liquefied gas; a first valve, which is located in the transfer piping; a return piping, which connects an area of ​​the transfer piping that is closer to the connecting joint than the first valve, i.e., an end area, to the liquefied gas tank; a return pressure relief valve, which is located in the return piping, and opens when the internal pressure of the end area exceeds a return reference value; a waste piping, which connects a waste device for waste liquefied gas to the end area; a waste pressure relief valve, which is located in the waste piping, and opens when the internal pressure of the end area exceeds a waste reference value that is lower than the return reference value; and a waste opening and closing valve, which is located in the waste piping.

[0054] According to this structure, if the waste on-off valve is opened during gas replacement, the return pressure relief valve can be disabled, thereby preventing gas other than gasified gas from flowing into the liquefied gas during gas replacement, thereby preventing contamination of the liquefied gas in the liquefied gas tank.

[0055] Description of symbols

[0056] 10: Connecting joint; 20: Transfer piping; 21: First valve; 22: End area; 30: Return piping; 31: Return pressure relief valve; 32: Return on-off valve; 40: Abandonment piping; 41: Abandonment pressure relief valve; 42: Abandonment on-off valve; 100: Liquefied gas equipment; 101: Liquefied gas tank; 102: Abandonment equipment; 103: Transfer equipment; 111: External liquefied gas tank; 112: External transfer equipment.

Claims

1. A gas replacement method, the gas replacement method is a method implemented in a liquefied gas device, the liquefied gas device having: A connection connector connected to an external transfer device; A transfer pipe that connects the connection joint to the liquefied gas tank and transfers the liquefied gas; a first valve located in the transfer pipe; a return pipe that connects an end region of the transfer pipe that is a region closer to the connection joint than the first valve to the liquefied gas tank; and a return pressure relief valve located in the return pipe, which opens when the internal pressure of the end region exceeds a return reference value, in, The return pressure relief valve is disabled in a state where the first valve is closed. The gas in the end region is displaced after the return pressure relief valve has been deactivated.

2. The gas replacement method according to claim 1, wherein: The liquefied gas equipment has a waste pipe connecting a waste device for waste gasified gas to the end area. When the internal pressure of the end region exceeds a disposal reference value lower than the return reference value, the gas in the end region is discharged to the disposal device via the disposal pipe, thereby disabling the return pressure relief valve.

3. The gas replacement method according to claim 2, wherein: The liquefied gas equipment comprises: a waste pressure relief valve located in the waste pipe, which opens when the internal pressure of the end region exceeds the waste reference value; and A waste on-off valve is located in the waste pipe. The return pressure relief valve is rendered inoperative by opening the waste on-off valve.

4. The gas replacement method according to claim 1, wherein: The liquefied gas equipment has a return on-off valve located in the return pipe. The return pressure relief valve is disabled by closing the return on-off valve.

5. A liquefied gas device, comprising: A connection connector connected to an external transfer device; A transfer pipe that connects the connection joint to the liquefied gas tank and transfers the liquefied gas; a first valve located in the transfer pipe; a return pipe that connects a region of the transfer pipe that is closer to the connection joint than the first valve, that is, an end region, to the liquefied gas tank; a return pressure relief valve located in the return pipe, the return pressure relief valve opening when the internal pressure of the end region exceeds a return reference value; a waste pipe connecting a waste device for waste liquefied gas to the end region; a waste pressure relief valve located in the waste pipe, the waste pressure relief valve opening when the internal pressure of the end region exceeds a waste reference value lower than the return reference value; as well as A waste on-off valve is located in the waste pipe.

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