Liquefied gas equipment

Abstract

A liquefied gas facility according to one aspect of the present disclosure is provided with: a storage area in which a boil off gas is present; a boil off gas carry-out piping through which the boil off gas in the storage area is carried out; a gas discharging tower which discharges the boil off gas carried out from the storage area into the atmosphere; and an inert gas supply piping through which an inert gas is supplied into the gas discharging tower in such a manner that the concentration of oxygen in the gas discharging tower is constantly lower than a limiting oxygen concentration or the concentration of the boil off gas in the gas discharging tower is constantly lower than a lower explosible concentration.

Description

Technical Field

[0001] This disclosure relates to liquefied gas equipment for handling liquefied gas.

Background Art

[0002] Regarding liquefied gas equipment, Patent Document 1 discloses a vent mast that discharges the volatile components (boil-off gas) of the liquefied gas stored in a liquefied gas tank from the liquefied gas tank to prevent a pressure increase inside the liquefied gas tank.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an exhaust tower such as a vent mast, if the boil-off gas in the exhaust tower touches an ignition source and catches fire, it may develop into a large fire accompanied by backfire or deflagration. Therefore, an object of this disclosure is to provide liquefied gas equipment that can prevent the ignition of boil-off gas in the exhaust tower.

Means for Solving the Problems

[0005] The liquefied gas equipment according to one aspect of this disclosure includes a storage area where boil-off gas exists, a boil-off gas discharge pipe for discharging the boil-off gas in the storage area, an exhaust tower for discharging the boil-off gas carried out from the storage area to the atmosphere, and an inert gas supply pipe for supplying an inert gas to the exhaust tower so that the oxygen concentration in the exhaust tower is always below the limiting oxygen concentration or the concentration of the boil-off gas in the exhaust tower is always below the lower explosive limit concentration.

Effects of the Invention

[0006] The above configuration makes it possible to prevent the ignition of boil-off gas inside the exhaust tower. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic diagram of a liquefied gas facility according to the first embodiment. [Figure 2] Figure 2 is a schematic diagram of a liquefied gas facility according to the second embodiment. [Figure 3] Figure 3 is a flow diagram of the inert gas supply control. [Figure 4] Figure 4 is a schematic diagram of the liquefied gas equipment according to the third embodiment. [Modes for carrying out the invention]

[0008] (First Embodiment) First, the liquefied gas equipment 100 according to the first embodiment will be described. Figure 1 is a schematic diagram of the liquefied gas equipment 100 according to the first embodiment. The liquefied gas equipment 100 according to this embodiment may be mounted on a ship or installed on land.

[0009] As shown in Figure 1, the liquefied gas equipment 100 includes a storage area 10, a boil-off gas discharge piping 20, a boil-off gas discharge valve 30, an exhaust tower 40, an inert gas supply piping 50, and a control device 60. These components will be described in order below.

[0010] The storage area 10 is the area where boil-off gas is present. The storage area 10 is located, for example, inside a liquefied gas tank, but it may also be located inside piping. Examples of liquefied gases stored in the storage area 10 include liquefied hydrogen, liquefied natural gas (LNG), and liquefied petroleum gas (LPG). In the storage area 10, boil-off gas may be present from the beginning, or it may be generated when a portion of the liquefied gas vaporizes. The boil-off gas in this embodiment is a flammable gas.

[0011] The boil-off gas discharge piping 20 is a pipe that discharges the boil-off gas from the storage area 10. In this embodiment, the boil-off gas discharge piping 20 is located between the storage area 10 and the exhaust tower 40. In other words, the boil-off gas from the storage area 10 is discharged to the exhaust tower 40 via the boil-off gas discharge piping 20.

[0012] The boil-off gas discharge valve 30 is a valve located in the boil-off gas discharge piping 20. In this embodiment, the boil-off gas discharge valve 30 is a safety valve that opens when the internal pressure of the storage area 10 exceeds a specified value. However, the boil-off gas discharge valve 30 may be a valve other than a safety valve, for example, a manual valve that can be opened and closed at will by an operator. When the boil-off gas discharge valve 30 opens, the boil-off gas from the storage area 10 is supplied to the exhaust tower 40.

[0013] The exhaust tower 40 is a device that releases the boil-off gas from the storage area 10 into the atmosphere. When the liquefied gas equipment 100 is installed on a ship, the ship's vent mast corresponds to this exhaust tower 40. The exhaust tower 40 extends vertically, and an exhaust port 41 is located at the top. The boil-off gas is released into the atmosphere from this exhaust port 41.

[0014] The inert gas supply piping 50 is a pipe that supplies inert gas to the exhaust tower 40. In this embodiment, the inert gas supply piping 50 supplies inert gas to the exhaust tower 40 via the boil-off gas discharge piping 20. Examples of inert gases include nitrogen gas and argon gas. The upstream end of the inert gas supply piping 50 is connected to an inert gas generator 101 that produces inert gas. However, the upstream end of the inert gas supply piping 50 may be connected to a cylinder or tank truck that stores inert gas instead of the inert gas generator 101. The downstream end of the inert gas supply piping 50 is connected to the portion of the boil-off gas discharge piping 20 downstream of the boil-off gas discharge valve 30.

[0015] Furthermore, the inert gas supply piping 50 of this embodiment includes a regulator 51 and a flow meter 52. The regulator 51 is a device that adjusts the amount of inert gas supplied to the exhaust tower 40. In this embodiment, the regulator 51 is controlled by a control device 60, but it may also be manually controllable. The regulator 51 may include, for example, an electrically operated, hydraulic, or pneumatic valve and an orifice. The flow meter 52 can measure the amount of inert gas supplied to the exhaust tower 40. In Figure 1, the flow meter 52 is located downstream of the regulator 51, but the flow meter 52 may be located upstream of the regulator 51, or between the components of the regulator 51.

[0016] The control device 60 is a device that controls the liquefied gas equipment 100. The control device 60 in this embodiment includes a processor, volatile memory, non-volatile memory, and an I / O interface. Various programs and various data are stored in the non-volatile memory of the control device 60, and the processor performs calculations using the volatile memory based on the various programs.

[0017] The functions of the elements disclosed in this specification can be executed using a circuit or processing circuit including a general-purpose processor, a dedicated processor, an integrated circuit, an ASIC (Application Specific Integrated Circuits), a conventional circuit, and / or a combination thereof that is configured or programmed to perform the disclosed functions. Since a processor includes transistors and other circuits, it is regarded as a processing circuit or a circuit. In the present disclosure, a circuit, unit, or means is hardware that performs the recited functions, or hardware programmed to perform the recited functions. The hardware may be the hardware disclosed in this specification, or other known hardware that is programmed or configured to perform the recited functions. When the hardware is a processor that is considered a type of circuit, the circuit, means, or unit is a combination of hardware and software, and the software is used for configuring the hardware and / or the processor.

[0018] The control device 60 is electrically connected to the flowmeter 52 and can obtain the supply amount of the inert gas based on the measurement signal received from the flowmeter 52. Further, the control device 60 is electrically connected to the regulator 51 and can adjust the supply amount of the inert gas supplied from the inert gas supply pipe 50 to the exhaust tower 40 by transmitting a control signal to the regulator 51.

[0019] The control device 60 of the present embodiment supplies an inert gas from the inert gas supply pipe 50 to the exhaust tower 40 so that the oxygen concentration in the exhaust tower 40 is always lower than the limiting oxygen concentration, or so that the concentration of the boil-off gas in the exhaust tower 40 is always lower than the lower explosion limit concentration. Here, the above-mentioned "limiting oxygen concentration" refers to the oxygen concentration at which a combustible gas does not explode when the oxygen concentration is lowered. Also, the "lower explosion limit concentration" refers to the lower limit concentration of a combustible gas that causes an explosion.

[0020] Thus, in this embodiment, instead of supplying an inert gas to the exhaust tower 40 to extinguish the fire after the boil-off gas catches fire, an inert gas is supplied to the exhaust tower 40 in advance. Therefore, according to this embodiment, it is possible to prevent the boil-off gas in the exhaust tower 40 from catching fire beforehand.

[0021] Furthermore, in order to maintain a state where the oxygen concentration in the exhaust tower 40 is always below the limiting oxygen concentration, or a state where the concentration of the boil-off gas in the exhaust tower 40 is always below the lower explosive limit concentration, the control device 60 of this embodiment always supplies an inert gas to the exhaust tower 40. That is, without sequentially acquiring the oxygen concentration and the concentration of the boil-off gas in the exhaust tower 40, an inert gas is always supplied to the exhaust tower 40. Here, the above "always" refers to the period from the state where the boil-off gas transfer pipe 20 may supply the boil-off gas to the exhaust tower 40 to the state where it is impossible to supply.

[0022] Therefore, according to the liquefied gas facility 100 according to this embodiment, it is possible to maintain a state where the oxygen concentration in the exhaust tower 40 is always below the limiting oxygen concentration, or a state where the concentration of the boil-off gas in the exhaust tower 40 is always below the lower explosive limit concentration, without using complex control.

[0023] 0000099Note that the control device 60 may control the regulator 51 so that the supply amount of the inert gas supplied to the exhaust tower 40 becomes a constant value or a desired target value. According to this configuration, an appropriate amount of inert gas can be quickly supplied into the exhaust tower 40, and the consumption amount of the inert gas can also be suppressed.

[0024] Furthermore, the control device 60 may acquire the supply amount (actual supply amount) of the inert gas supplied to the exhaust tower 40 based on the measurement signal received from the flow meter 52, and control the regulator 51 (that is, feedback control) based on the acquired actual supply amount. According to this configuration, an appropriate amount of inert gas can be efficiently supplied to the exhaust tower 40.

[0025] Furthermore, in this embodiment, the inert gas supply pipe 50 supplies inert gas to the exhaust tower 40 via the boil-off gas discharge pipe 20. Therefore, ignition of the boil-off gas within the boil-off gas discharge pipe 20 can be prevented.

[0026] Furthermore, the control described above may be performed manually by an operator rather than by the control device 60.

[0027] (Second Embodiment) Next, a liquefied gas equipment 200 according to the second embodiment will be described. Figure 2 is a schematic diagram of the liquefied gas equipment 200 according to the second embodiment. As shown in Figure 2, in the liquefied gas equipment 200 according to this embodiment, an oxygen concentration meter 42 capable of measuring the oxygen concentration inside the exhaust tower 40 is located in the exhaust tower 40. The control device 60 is electrically connected to this oxygen concentration meter 42 and can acquire the oxygen concentration inside the exhaust tower 40 based on the measurement signal received from this oxygen concentration meter 42.

[0028] Furthermore, the non-volatile memory of the control device 60 in this embodiment stores an inert gas supply control program, and calculation processing is performed using the volatile memory based on this inert gas supply control program. The inert gas supply control program will be described below.

[0029] Figure 3 is a flowchart of the inert gas supply control program. The inert gas supply control program is a program for supplying inert gas to the exhaust tower 40 and is executed by the control device 60.

[0030] As shown in Figure 3, when the inert gas supply control program is started, the control device 60 acquires the oxygen concentration in the exhaust tower 40 (step S1). As described above, the control device 60 can acquire the oxygen concentration in the exhaust tower 40 based on the measurement signal received from the oxygen concentration meter 42.

[0031] Next, the control device 60 determines whether the oxygen concentration obtained in step S1 exceeds the reference value (step S2). The "reference value" in step S1 is set to a value slightly smaller than the "limit oxygen concentration" mentioned above. Therefore, if the oxygen concentration exceeds the reference value, the boil-off gas in the exhaust tower 40 will not ignite, but there is a risk that it will approach the limit oxygen concentration. On the other hand, if the oxygen concentration does not exceed the reference value, the oxygen concentration is far from the limit oxygen concentration, and there is no risk of the boil-off gas igniting in the exhaust tower 40.

[0032] In step S2, if it is determined that the oxygen concentration has exceeded the standard value (YES in step S2), and there is a risk that the oxygen concentration will approach the critical oxygen concentration, the control device 60 starts supplying inert gas to the exhaust tower 40 (step S3). The control device 60 can start supplying inert gas to the exhaust tower 40 by transmitting a control signal to the regulator 51. Once the supply of inert gas to the exhaust tower 40 is started, the oxygen concentration inside the exhaust tower 40 will fall below the standard value without reaching the critical oxygen concentration. Therefore, the boil-off gas will not ignite inside the exhaust tower 40. In addition, at the same time as starting the supply of inert gas to the exhaust tower 40, the control device 60 may transmit a signal to an alarm device (not shown) to output a sound or image that can be recognized by the operator from the alarm device.

[0033] On the other hand, if in step S2 it is determined that the oxygen concentration does not exceed the standard value (NO in step S2), that is, the oxygen concentration is far from the limit oxygen concentration and there is no risk of boil-off gas igniting in the exhaust tower 40, the control device 60 returns to step S1 and repeats each of the above steps.

[0034] As described above, the liquefied gas equipment 200 according to this embodiment differs from the liquefied gas equipment 100 according to the first embodiment in that it acquires the oxygen concentration in the exhaust tower 40 and starts supplying inert gas to the exhaust tower 40 based on the acquired oxygen concentration. In all other respects, it has basically the same configuration as the liquefied gas equipment 100 according to the first embodiment.

[0035] In the second embodiment, a boil-off gas concentration meter for measuring the boil-off gas concentration may be installed in the exhaust tower 40 instead of the oxygen concentration meter 42. Then, the control device 60 may acquire the boil-off gas concentration inside the exhaust tower 40, and when the boil-off gas concentration exceeds a reference value (a value slightly smaller than the lower explosive limit concentration mentioned above), it may start supplying inert gas to the exhaust tower 40.

[0036] (Third embodiment) Next, the liquefied gas equipment 300 according to the third embodiment will be described. Figure 4 is a schematic diagram of the liquefied gas equipment 300 according to the third embodiment. The liquefied gas equipment 300 according to the third embodiment differs from the liquefied gas equipment 100 according to the first embodiment in that the inert gas supply piping 50 is not connected to the boil-off gas discharge piping 20, but is directly connected to the exhaust tower 40. Except for this point, the liquefied gas equipment 300 according to the third embodiment has the same configuration as the liquefied gas equipment 100 according to the first embodiment.

[0037] Even with the liquefied gas equipment 300 according to this embodiment, it is possible to prevent the boil-off gas from igniting inside the exhaust tower 40, just as with the liquefied gas equipment 100 according to the first embodiment.

[0038] Furthermore, as shown in Figure 4, the inert gas supply piping 50 in this embodiment is connected to the lower portion 43 (the shaded portion in Figure 4), which corresponds to the lower one-third of the exhaust tower 40 (if the height of the exhaust tower 40 is H, then the lower one-third H of the exhaust tower 40). With this configuration, the inert gas supplied to the lower portion 43 of the exhaust tower 40 flows toward the exhaust port 41, pushing the gas inside the exhaust tower 40 upwards and discharging it from the exhaust port 41. As a result, gases such as oxygen inside the exhaust tower 40 can be efficiently discharged.

[0039] (summary) The first item disclosed herein is a liquefied gas facility comprising: a storage area containing boil-off gas; a boil-off gas discharge pipe for discharging the boil-off gas from the storage area; an exhaust tower for releasing the boil-off gas discharged from the storage area into the atmosphere; and an inert gas supply pipe for supplying an inert gas to the exhaust tower such that the oxygen concentration in the exhaust tower is always below the critical oxygen concentration, or the concentration of boil-off gas in the exhaust tower is always below the lower explosive limit concentration.

[0040] This configuration makes it possible to prevent the ignition of boil-off gases inside the exhaust tower.

[0041] A second item disclosed herein is the liquefied gas equipment described in the first item, wherein the inert gas supply piping continuously supplies inert gas to the exhaust tower.

[0042] This configuration simplifies the control of supplying inert gas to the exhaust tower.

[0043] A third item disclosed herein is a liquefied gas system as described in the first or second item, wherein the inert gas supply piping starts supplying inert gas to the exhaust tower when the oxygen concentration in the exhaust tower exceeds a predetermined standard value.

[0044] This configuration allows for a reduction in the oxygen concentration within the exhaust tower, thereby preventing the ignition of boil-off gases within the exhaust tower.

[0045] The fourth item disclosed herein is a liquefied gas facility according to any one of the first to third items, wherein the inert gas supply piping is connected to the boil-off gas discharge piping.

[0046] This configuration also prevents the boil-off gas from igniting within the boil-off gas discharge piping.

[0047] The fifth item disclosed herein is a liquefied gas facility described in any one of the first to third items, wherein the inert gas supply piping is directly connected to the exhaust tower.

[0048] Even with this configuration, it is possible to prevent the ignition of boil-off gases inside the exhaust tower.

[0049] The sixth item disclosed herein is the liquefied gas equipment described in item 5, wherein the inert gas supply piping is connected to the lower one-third portion of the exhaust tower.

[0050] With this configuration, the inert gas flows through the exhaust tower from the lower part towards the exhaust port, allowing for efficient removal of air from within the exhaust tower.

[0051] The seventh item disclosed herein is a liquefied gas system according to any one of the first to sixth items, comprising a regulator capable of adjusting the amount of inert gas supplied to the exhaust tower.

[0052] This configuration allows for the rapid supply of an appropriate amount of inert gas into the exhaust tower, and also reduces the amount of inert gas consumed.

[0053] The eighth item disclosed herein is a liquefied gas system according to any one of the first to seventh items, comprising a flow meter capable of measuring the amount of inert gas supplied to the exhaust tower.

[0054] This configuration allows for the supply of an appropriate amount of inert gas to the exhaust tower.

[0055] The ninth item disclosed herein is the liquefied gas equipment described in the first item, which includes an oxygen concentration meter capable of measuring the oxygen concentration in the exhaust tower.

[0056] This configuration allows for the supply of the appropriate amount of inert gas into the exhaust tower at the appropriate time. [Explanation of Symbols]

[0057] 10 Storage Area 20 Boil-off gas discharge piping 30 Boil-off gas discharge valve 40 Exhaust tower 42. Oxygen concentration meter 50 Inert gas supply piping 51 Regulator 52 Flow meter 100 Liquefied gas equipment 200 Liquefied Gas Equipment 300 Liquefied Gas Equipment

Claims

1. Storage area where boil-off gas exists, A boil-off gas discharge piping for discharging boil-off gas from the aforementioned storage area, An exhaust tower for releasing the boil-off gas transported from the aforementioned storage area into the atmosphere, A liquefied gas apparatus comprising: an inert gas supply pipe that supplies an inert gas into the exhaust tower such that the oxygen concentration in the exhaust tower is always below the critical oxygen concentration, or the concentration of boil-off gas in the exhaust tower is always below the lower explosive limit concentration.

2. The liquefied gas equipment according to claim 1, wherein the inert gas supply piping continuously supplies inert gas to the exhaust tower.

3. The liquefied gas equipment according to claim 1, wherein the inert gas supply piping starts supplying inert gas to the exhaust tower when the oxygen concentration in the exhaust tower exceeds a predetermined standard value.

4. The liquefied gas equipment according to claim 1, wherein the inert gas supply piping is connected to the boil-off gas discharge piping.

5. The liquefied gas equipment according to claim 1, wherein the inert gas supply piping is directly connected to the exhaust tower.

6. The liquefied gas equipment according to claim 5, wherein the inert gas supply piping is connected to the lower one-third portion of the exhaust tower.

7. The liquefied gas equipment according to claim 1, further comprising a regulator capable of adjusting the amount of inert gas supplied to the exhaust tower.

8. The liquefied gas equipment according to claim 1, further comprising a flow meter capable of measuring the amount of inert gas supplied to the exhaust tower.

9. The liquefied gas equipment according to claim 1, further comprising an oxygen concentration meter capable of measuring the oxygen concentration in the exhaust tower.

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