Gas replacement method and liquefied gas equipment

Abstract

In a liquefied gas facility comprising a connection fitting that connects to an external transfer facility, a transfer pipe that connects the connection fitting and a liquefied gas tank and that transfers liquefied gas, a first valve that is positioned in the transfer pipe, a return pipe that connects the liquefied gas tank and an end part section which is positioned closer to the connection fitting than is the first valve of the transfer pipe, and a return pressure relief valve that is positioned in the return pipe and that opens when the internal pressure of the end part section exceeds a return reference value, a gas replacement method according to one aspect of the present disclosure causes the return pressure relief valve not to function in a state in which the first valve is closed, and then increases / decreases the internal pressure of the end part section to replace gas in the end part section.

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a gas replacement method for replacing gas in a pipe before and after the transfer of liquefied hydrogen. This gas replacement method employs a pressure swing system in which the pipe is pressurized and then depressurized multiple times. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-19552 Summary of the Invention [Problem to be solved by the invention]

[0004] In a liquefied gas facility equipped with a transfer facility for transferring liquefied gas, the internal pressure of the transfer pipe may rise excessively, i.e., exceed the expected pressure, if the liquefied gas vaporizes in the transfer pipe, if the liquid temperature rises in the transfer pipe and the liquefied gas expands, or if liquefied gas is supplied to the transfer pipe from another facility at a high supply pressure, etc. For this reason, the liquefied gas facility is equipped with a pressure relief valve to return the vaporized gas in the transfer pipe to the liquefied gas tank when the internal pressure of the transfer pipe exceeds a reference value.

[0005] However, in liquefied gas equipment equipped with such a pressure relief valve, when gas replacement is performed using a method such as a pressure swing method that involves increasing and decreasing the internal pressure of the transfer piping, an excessive increase in pressure during gas replacement may activate the pressure relief valve, causing air or inert gas to flow into the liquefied gas tank and contaminating the liquefied gas inside the liquefied gas tank.

[0006] Therefore, an object of the present disclosure is to provide a gas replacement method and liquefied gas equipment that do not contaminate the liquefied gas in the liquefied gas tank during gas replacement. [Means for solving the problem]

[0007] A gas replacement method according to one aspect of the present disclosure is provided in a liquefied gas facility including a connection fitting connected to external transfer equipment, a transfer pipe connecting the connection fitting to a liquefied gas tank and transferring liquefied gas, a first valve located on the transfer pipe, a return pipe connecting an end area of ​​the transfer pipe that is on the connection fitting side of the first valve to the liquefied gas tank, and a return pressure relief valve located on the return pipe that opens when the internal pressure of the end area exceeds a return reference value, the method comprising: closing the first valve to disable the return pressure relief valve; and disabling the return pressure relief valve and replacing the gas in the end area.

[0008] In addition, a liquefied gas facility according to one embodiment of the present disclosure includes a connection fitting for connecting to external transfer equipment, a transfer pipe connecting the connection fitting to a liquefied gas tank and transferring liquefied gas, a first valve located on the transfer pipe, a return pipe connecting the liquefied gas tank to an end area that is an area of ​​the transfer pipe closer to the connection fitting than the first valve, a return pressure relief valve located on the return pipe and opening when the internal pressure of the end area exceeds a return reference value, a waste pipe connecting the end area to a waste device that disposes of the liquefied gas, a waste pressure relief valve located on the waste pipe and opening when the internal pressure of the end area exceeds a waste reference value that is lower than the return reference value, and a waste on-off valve located on the waste pipe. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a gas replacement method and liquefied gas equipment that do not contaminate the liquefied gas in the liquefied gas tank during gas replacement. [Brief explanation of the drawings]

[0010] [Figure 1] Figure 1 is a schematic diagram of a liquefied gas facility and its surroundings. [Figure 2] FIG. 2 is a flow diagram of the liquefied gas transfer procedure. [Figure 3] FIG. 3 is a schematic diagram of a liquefied gas facility and its surroundings according to a modified example. [Figure 4] FIG. 4 is a schematic diagram of a liquefied gas facility and its surroundings according to another modified example. DETAILED DESCRIPTION OF THE INVENTION

[0011] <Overall configuration of liquefied gas equipment> An embodiment will be described below. First, the overall configuration of a liquefied gas facility 100 according to an embodiment will be described. FIG. 1 is a schematic diagram of the liquefied gas facility 100 and its surroundings. The liquefied gas facility 100 according to this embodiment includes a liquefied gas tank 101, disposal equipment 102, and transfer equipment 103 that transfers liquefied gas between the liquefied gas tank 101 on the ship and an external liquefied gas tank 111 on land. The liquefied gas may be liquefied hydrogen, liquefied natural gas (LNG), liquefied petroleum gas (LPG), or the like. The liquefied gas facility 100 according to this embodiment is a ship-side facility and is installed on the ship. However, the liquefied gas facility 100 may also be a land-side facility and installed on land.

[0012] As shown in Fig. 1, the transfer facility 103 of the liquefied gas facility 100 according to this 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 below in order.

[0013] The connection fitting 10 is a device that connects to external transfer equipment 112. For example, a manifold on a liquefied gas carrier corresponds to the connection fitting 10. The external transfer equipment 112 in this embodiment is a land-side facility, and includes an external connection fitting 113 that connects to the connection fitting 10, an external transfer piping 114 that connects the external connection fitting 113 and the external liquefied gas tank 111, and an external first valve 115 located on the external transfer piping 114. The external transfer piping 114 may include a deformable loading arm.

[0014] The transfer piping 20 is a piping that connects the connection fitting 10 and the liquefied gas tank 101 and transfers liquefied gas. The transfer piping 20 can transfer liquefied gas in a direction from the liquefied gas tank 101 toward the external liquefied gas tank 111, and can also transfer liquefied gas in a direction from the external liquefied gas tank 111 toward the liquefied gas tank 101. A first valve 21 is located in the transfer piping 20. Of the valves located in the transfer piping 20, the first valve 21 is the valve closest to the connection fitting 10. In the following, the area of ​​the transfer piping 20 on the connection fitting 10 side of the first valve 21 will be referred to as the "end area 22."

[0015] The return pipe 30 connects the end section 22 and the liquefied gas tank 101. A return pressure relief valve 31 is located in the return pipe 30. The return pressure relief valve 31 is set to open when the internal pressure of the end section 22 exceeds a predetermined "return reference value." For example, during the transfer of liquefied gas, the liquefied gas being transferred vaporizes to generate vaporized gas (hereinafter simply referred to as "vaporized gas"), causing the internal pressure of the transfer pipe 20 to rise. If the internal pressure of the end section 22 exceeds the return reference value, the return pressure relief valve 31 opens, and the vaporized gas in the transfer pipe 20 is returned to the liquefied gas tank 101. This prevents the internal pressure of the transfer pipe 20 from rising excessively, thereby preventing damage to the transfer pipe 20.

[0016] The waste piping 40 connects the waste equipment 102 and the end section 22. In this embodiment, the waste equipment 102 is a vent mast that releases vaporized gas into the atmosphere. However, the waste equipment 102 may also be a flare facility that burns the vaporized gas. In other words, the waste equipment 102 is a facility that disposes of the vaporized gas. A waste pressure relief valve 41 and a 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 section 22 exceeds a predetermined "waste reference value." This "waste reference value" is lower than the aforementioned "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.

[0017] The connection pipe 50 is connected to the end section 22 of the transfer pipe 20, and is a pipe that supplies a replacement gas to the end section 22 and discharges the gas to be replaced. In addition, a connection pipe valve 51 is located in the connection pipe 50. The replacement gas is a gas that is supplied when replacing a gas, and varies depending on the mode of gas replacement. In addition, the gas to be replaced is a gas that is discharged when replacing a gas, and varies depending on the mode of gas replacement. A specific explanation of the replacement gas and the gas to be replaced will be given later.

[0018] <Liquefied gas transfer procedure> Next, a procedure for transferring liquefied gas including a gas replacement method will be described. Figure 2 is a flow chart of the procedure for transferring liquefied gas.

[0019] As shown in Fig. 2, when transferring liquefied gas, first, the transfer facility 103 and the external transfer facility 112 are connected (step S1). Specifically, with the first valve 21 and the external first valve 115 closed, the connection joint 10 and the external connection joint 113 are connected. This forms a closed space between the first valve 21 and the external first valve 115. The end section 22 constitutes a part of this closed space. Immediately after the transfer facility 103 and the external transfer facility 112 are connected, the inside of the end section 22 is filled with air (outside air) containing oxygen.

[0020] Next, the return pressure relief valve 31 is deactivated (step S2). In this embodiment, the return pressure relief valve 31 is deactivated by opening the waste on-off valve 42. In other words, the waste pressure relief valve 41 can be activated by opening the waste on-off valve 42, but as described above, the return reference value, which is the criterion for opening the return pressure relief valve 31, is higher than the waste reference value, which is the criterion for opening the waste pressure relief valve 41. Therefore, when the waste pressure relief valve 41 is activated, the waste pressure relief valve 41 operates before the internal pressure of the end section 22 reaches the return reference value, and the internal pressure of the end section 22 does not reach the return reference value, so the return pressure relief valve 31 does not open.

[0021] Next, a first gas replacement is performed (step S3). In the first gas replacement, the air filling the inside of the end zone 22 is replaced with an inert gas. That is, air is the gas to be replaced, and the inert gas is the replacement gas. In the first gas replacement, an inert gas generator that generates an inert gas is connected to the connection pipe 50. In this state, the connection pipe valve 51 is opened. As a result, the inert gas is supplied to the end zone 22 through the connection pipe 50, and the internal pressure of the end zone 22 increases. Thereafter, the connection pipe valve 51 is closed, and in this state, the inert gas generator is removed from the connection pipe 50. Then, the connection pipe valve 51 is opened again. As a result, the inert gas is forcefully discharged from the end zone 22 together with the air, and the internal pressure of the end zone 22 decreases. By repeatedly increasing and decreasing the internal pressure of the end zone 22 with this inert gas, the air filling the inside of the end zone 22 is replaced with the inert gas. Note that, for example, nitrogen gas, argon gas, helium gas, carbon dioxide gas, and mixtures thereof can be used as the inert gas. In addition, in the first gas replacement, instead of supplying the inert gas to the end section 22 via the connection piping 50, the inert gas may be supplied to the end section 22 from the external transfer equipment 112 via the connection joints 113, 10.

[0022] Next, a second gas replacement is performed (step S4). In the second gas replacement, the inert gas filling the inside of end zone 22 is replaced with vaporized gas. That is, the inert gas is the gas to be replaced, and the vaporized gas is the replacement gas. In the second gas replacement, a vaporized gas generator that generates vaporized gas is connected to connection pipe 50. Using this vaporized gas generator, the inert gas in end zone 22 is replaced with vaporized gas by repeatedly increasing and decreasing the internal pressure of end zone 22 with the vaporized gas, which is the replacement gas, as in the first gas replacement.

[0023] Next, the return pressure relief valve 31 is made to function (step S5). Specifically, by closing the waste on-off valve 42, the waste pressure relief valve 41 is made to function inactive, and the return pressure relief valve 31 is made to function. As a result, there may be a case where the internal pressure of the end section 22 reaches the return reference value, in which case the return pressure relief valve 31 opens and the vaporized gas in the end section 22 is supplied to the liquefied gas tank 101.

[0024] 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 a transfer pump or the like is operated to transfer the liquefied gas. As a result, the liquefied gas is transferred via the transfer piping 20 and the external transfer piping 114. As described above, the end zone 22 is filled with vaporized gas by the second gas replacement in step S4, so that when the transfer of the liquefied gas is started, air, inert gas, etc. do not flow into the liquefied gas tank 101 and the external liquefied gas tank 111. The reason why the air in the end zone 22 is not directly replaced with vaporized gas is that if the vaporized gas mixes with oxygen in the air, it may explode when it comes into contact with an ignition source.

[0025] Next, the transfer of the liquefied gas is terminated (step S7). Specifically, the transfer pump or the like 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 section 22 is filled with vaporized gas.

[0026] Next, the return pressure relief valve 31 is made inoperative (step S8). Specifically, similarly to step S2, the waste on-off valve 42 is opened to make the return pressure relief valve 31 inoperative.

[0027] Next, a third gas replacement is performed (step S9). In the third gas replacement, the vaporized gas filling the inside of the end zone 22 is replaced with an inert gas. That is, the vaporized gas is the gas to be replaced, and the inert gas is the replacement gas. In the third gas replacement, an inert gas generator that generates an inert gas is connected to the connection pipe 50. Using this inert gas generator, the internal pressure of the end zone 22 is repeatedly increased and decreased by the inert gas, which is the replacement gas, as in the first and second gas replacements, thereby replacing the vaporized gas in the end zone 22 with the inert gas.

[0028] Next, the transfer equipment 103 is disconnected from the external transfer equipment 112 (step S10). Specifically, the connection joint 10 is disconnected from the external connection joint 113. If the transfer equipment 103 and the external transfer equipment 112 were disconnected immediately after the transfer of the liquefied gas was completed, this would undesirably release flammable vaporized gas in the end area 22 into the vicinity of the connection joint 10. Therefore, before disconnecting the transfer equipment 103 and the external transfer equipment 112, the third gas replacement in step S9 above is performed to replace the vaporized liquefied gas in the end area 22 with an inert gas. This completes the procedure for transferring liquefied gas.

[0029] As described above, in this embodiment, the internal pressure of the end section 22 is increased or decreased to replace the gas in the end section 22 in steps S3, S4, and S9, but before that, the return pressure relief valve 31 is disabled in steps S2 and S8. Therefore, even if the internal pressure of the end section 22 increases due to gas replacement, air or 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.

[0030] <Modification> As shown in Fig. 1, in the above embodiment, the waste pipe 40 is connected to the end section 22 of the transfer pipe 20. However, as shown in Fig. 3, the waste pipe 40 may be connected to a portion of the return pipe 30 upstream of the return pressure relief valve 31. In other words, the waste pipe 40 may connect the waste equipment 102 and the end section 22 via the return pipe 30. Even in this case, the same gas replacement method as in the above embodiment can be implemented, and the same effects can be obtained.

[0031] 3, a switching valve may be disposed at the portion of the return pipe 30 where the waste pipe 40 is connected, and the waste on-off valve 42 may be omitted. In this case, by switching the flow direction of the liquefied gas using a switching valve such as a three-way valve, the return pressure relief valve 31 can be made to function and not function.

[0032] Furthermore, as shown in Fig. 4, the return on-off valve 32 may be disposed in the return piping 30, and the waste piping 40, the waste pressure relief valve 41, and the waste on-off valve 42 (see Fig. 1) may be omitted. In this case, the return pressure relief valve 31 can be made inoperative by closing the return on-off valve 32, and the return pressure relief valve 31 can be made to function by opening the return on-off valve 32. Therefore, with the configuration shown in Fig. 4, it is possible to simplify the liquefied gas facility 100 while making the return pressure relief valve 31 function and not function.

[0033] <Summary> The first item disclosed in this specification is a gas replacement method in a liquefied gas facility including a connection fitting connected to external transfer equipment, a transfer pipe connecting the connection fitting to a liquefied gas tank and transferring liquefied gas, a first valve located on the transfer pipe, a return pipe connecting an end area of ​​the transfer pipe that is on the connection fitting side of the first valve to the liquefied gas tank, and a return pressure relief valve located on the return pipe that opens when the internal pressure of the end area exceeds a return reference value, in which the return pressure relief valve is made inoperative with the first valve closed, and then the internal pressure of the end area is increased or decreased to replace the gas in the end area.

[0034] According to this method, the return pressure relief valve is disabled before gas replacement, so that gas other than the vaporized gas can be prevented from flowing into the liquefied gas tank during gas replacement, thereby preventing contamination of the liquefied gas in the liquefied gas tank.

[0035] The second item disclosed in this specification is a gas replacement method described in claim 1, wherein the liquefied gas facility includes a waste pipe connecting the end area with a waste device that disposes of vaporized gas, 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 through the waste pipe, thereby rendering the return pressure relief valve inoperative.

[0036] According to this method, if the internal pressure in the end region exceeds the standard value for disposal during gas replacement, the gas in the end region is discharged to the disposal device, thereby preventing the internal pressure in the end region from rising excessively.

[0037] The third item disclosed in this specification is the gas replacement method according to the second item, which includes a waste pressure relief valve located in the waste pipe that opens when the internal pressure in the end region exceeds the waste reference value, and a waste on-off valve located in the waste pipe, and the return pressure relief valve is rendered inoperative by opening the waste on-off valve.

[0038] According to this method, if the internal pressure of the end section exceeds the standard value for waste disposal during gas replacement, the waste pressure relief valve is activated and the gas in the end section is discharged to the waste device, thereby preventing the internal pressure of the end section from rising excessively.

[0039] A fourth item disclosed in this specification is the gas replacement method according to the first item, wherein the liquefied gas facility is provided with a return on-off valve located in the return piping, and the return pressure relief valve is rendered inoperative by closing the return on-off valve.

[0040] This method simplifies the liquefied gas equipment while disabling the return pressure relief valve.

[0041] The fifth item disclosed in this specification is a liquefied gas facility comprising: a connection fitting for connecting to external transfer equipment; a transfer pipe connecting the connection fitting to a liquefied gas tank and transferring liquefied gas; a first valve located on the transfer pipe; a return pipe connecting the liquefied gas tank to an end area that is the area of ​​the transfer pipe closer to the connection fitting than the first valve; a return pressure relief valve located on the return pipe and opening when the internal pressure of the end area exceeds a return reference value; a waste pipe connecting the end area to a waste device that disposes of liquefied gas; a waste pressure relief valve located on the waste pipe and opening when the internal pressure of the end area exceeds a waste reference value that is lower than the return reference value; and a waste on-off valve located on the waste pipe.

[0042] With this configuration, the return pressure relief valve can be disabled by opening the waste on-off valve during gas replacement, which prevents gases other than vaporized gas from flowing into the liquefied gas tank during gas replacement, thereby preventing contamination of the liquefied gas in the liquefied gas tank. [Explanation of symbols]

[0043] 10 Connection joint 20 Transfer piping 21 First Valve 22 End area 30 Return pipe 31 Return pressure relief valve 32 Return valve 40 Waste pipe 41 Waste pressure relief valve 42 Waste on-off valve 100 Liquefied gas facilities 101 Liquefied gas tank 102 Disposal Facilities 103 Transfer equipment 111 External liquefied gas tank 112 External transfer equipment

Claims

1. a connection joint for connecting to an external transfer facility; a transfer pipe that connects the connection joint and a liquefied gas tank and transfers the liquefied gas; a first valve located in the transfer pipe; a return pipe connecting an end section of the transfer pipe, which is a section on the connection joint side of the first valve, to the liquefied gas tank; a return pressure relief valve located in the return pipe and opening when the internal pressure in the end region exceeds a return reference value, Disabling the return pressure relief valve when the first valve is closed; A gas replacement method, comprising displacing the gas in the end region after disabling the return pressure relief valve.

2. the liquefied gas facility includes a waste pipe connecting the end area with a waste device for disposing of the vaporized gas; 2. The gas replacement method according to claim 1, wherein when the internal pressure of the end section exceeds a waste reference value that is lower than the return reference value, the return pressure relief valve is rendered inoperative by discharging the gas in the end section to the waste device through the waste piping.

3. a waste pressure relief valve located in the waste pipe that opens when the internal pressure of the end section exceeds the waste reference value; a waste on-off valve located in the waste pipe, 3. The gas replacement method according to claim 2, wherein the return pressure relief valve is disabled by opening the waste on-off valve.

4. The liquefied gas facility includes a return on-off valve located in the return pipe, 2. The gas replacement method according to claim 1, wherein the return pressure relief valve is disabled by closing the return on-off valve.

5. a connection joint for connecting to an external transfer facility; a transfer pipe that connects the connection joint and a liquefied gas tank and transfers the liquefied gas; a first valve located in the transfer pipe; a return pipe connecting an end section of the transfer pipe, which is a section on the connection joint side of the first valve, to the liquefied gas tank; a return pressure relief valve located in the return line that opens when the internal pressure of the end section exceeds a return reference value; a waste pipe connecting the end section to a waste device for disposing of the liquefied gas; a waste pressure relief valve located in the waste line that opens when the internal pressure of the end section exceeds a waste reference value that is lower than the return reference value; A liquefied gas facility comprising: a waste on-off valve located on the waste pipe.

Images