Method for drying up and cooling down a submersible pump

Abstract

To provide a method for preventing gas introduced into a suction container for the purpose of drying up or cooling down a pump from idling the pump.SOLUTION: In a dry-up method for removing air from a suction vessel 2 in which a submerged pump 1 is housed, a first flow passage 41 communicating with a discharge port 1b of the submerged pump 1 is closed by a valve body 47, and a second flow passage 42 communicating with the inside of the suction vessel 2 and a third flow passage 43 communicating with a discharge port 8 of the suction vessel 2 communicate with each other, and the purge gas is transferred to the discharge port 8 through the second flow passage 42 and the third flow passage 43 while bypassing the submerged pump 1.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for drying up and a method for cooling down a submersible pump used to transport liquefied gases such as liquefied ammonia, liquefied hydrogen, liquid nitrogen, liquefied natural gas, liquefied ethylene gas, and liquefied petroleum gas. [Background technology]

[0002] Natural gas is widely used in thermal power generation and as a chemical raw material. Ammonia and hydrogen are also expected to be energy sources that do not produce carbon dioxide, a cause of global warming. Applications of hydrogen as an energy source include fuel cells and turbine power generation. Natural gas, ammonia, and hydrogen are in a gaseous state at room temperature, so they are cooled and liquefied for storage and transportation. Liquefied gases such as liquefied natural gas (LNG), liquefied ammonia, and liquefied hydrogen are first stored in liquefied gas storage tanks and then pumped to power plants, factories, etc.

[0003] FIG. 12 is a schematic diagram showing a conventional example of a pump system for pumping liquefied gas. Pump 500 is installed in a vertical suction vessel 505 connected to a liquefied gas storage tank (not shown) in which liquefied gas is stored. Liquefied gas is introduced into suction vessel 505 through suction port 501, and suction vessel 505 is filled with liquefied gas. Pump 500 is entirely immersed in liquefied gas. Therefore, pump 500 is a submersible pump that can operate in liquefied gas. When pump 500 is operating, the liquefied gas is discharged by pump 500 through discharge port 502. During operation of pump 500, part of the liquefied gas in suction vessel 505 evaporates and becomes gas, which is discharged from suction vessel 505 through vent line 503.

[0004] Before operating the pump 500, a drying-up process is performed in which air is removed from the suction container 505 using a purge gas, and a cooling-down process is performed in which the pump 500 is cooled with liquefied gas. When the air present in the suction container 505 comes into contact with the ultra-low temperature liquefied gas, the moisture in the air is cooled by the liquefied gas and solidifies, hindering the rotation of the pump 500. Furthermore, if the pump 500 is at room temperature when the pump 500 is started, the ultra-low temperature liquefied gas will vaporize when it comes into contact with the pump 500. To prevent such an event, the drying-up process and the cooling-down process are performed before operating the pump 500.

[0005] Drying up is performed by injecting a purge gas (e.g., nitrogen gas) into the suction vessel 505, and cooling down is performed by injecting a liquefied gas (e.g., liquefied natural gas) into the suction vessel 505. The purge gas or liquefied gas injected into the suction vessel 505 fills the suction vessel 505, flows into the pump 500 through the suction port 500a of the pump 500, and is then discharged through the discharge port 502. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Utility Model Application Publication No. 59-159795 [Patent Document 2] Jpn. Jpn. Appl. KOKAI Publication No. 62-031680 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the purge gas supplied into the suction vessel 505 for drying up flows through the pump 500 and may cause the pump 500 to run idle. When the pump 500 runs idle, it may damage the bearings and other sliding parts. Furthermore, the liquefied gas supplied into the suction vessel 505 for cooling down comes into contact with the room-temperature pump 500 and generates a large amount of gas. This gas may cause the impeller of the pump 500 to run idle, damaging the bearings and other sliding parts.

[0008] Therefore, the present invention provides a method for preventing gas introduced into the suction vessel for the purpose of drying up or cooling down the pump from causing the pump to run idle. [Means for solving the problem]

[0009] In one aspect, a drying-up method for removing air from a suction container containing a submersible pump is provided, the drying-up method including: closing a first flow path communicating with the discharge port of the submersible pump with a valve body; and supplying a purge gas into the suction container while a second flow path communicating with the interior of the suction container and a third flow path communicating with the discharge port of the suction container are in communication; and transporting the purge gas to the discharge port through the second flow path and the third flow path while bypassing the submersible pump.

[0010] In one aspect, a cool-down method for cooling a submersible pump housed in a suction container is provided, which includes closing a first flow path communicating with the discharge port of the submersible pump with a valve body, and supplying liquefied gas into the suction container while a second flow path communicating with the interior of the suction container and a third flow path communicating with the discharge port of the suction container are connected, and transferring the product gas generated by evaporation of the liquefied gas in the suction container to the discharge port through the second flow path and the third flow path while bypassing the submersible pump. [Effects of the Invention]

[0011] According to the present invention, gases introduced into the suction vessel during drying-up and cooling-down (such as purge gas and gas generated from liquefied gas) are not introduced into the submersible pump by the flow path switching device, but are instead directed to the discharge port. This prevents the impeller of the submersible pump from idling, thereby preventing damage to the bearings and other sliding parts of the submersible pump. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 illustrates an embodiment of a pump system for transferring liquefied gas. [Figure 2] FIG. 2 is a cross-sectional view showing a detailed configuration of a flow path switching device according to an embodiment. [Figure 3] This shows the state of the flow path switching device when the submersible pump is operating. [Figure 4] FIG. 1 is a diagram for explaining an embodiment of drying up. [Figure 5] FIG. 10 is a diagram for explaining another embodiment of the drying-up method. [Figure 6] FIG. 10 is a diagram for explaining still another embodiment of drying up. [Figure 7] FIG. 10 is a diagram for explaining an embodiment of a cool-down process. [Figure 8] FIG. 1 is a diagram illustrating an embodiment in which multiple submersible pumps are cooled simultaneously. [Figure 9] FIG. 10 is a cross-sectional view showing another embodiment of the flow path switching device. [Figure 10] FIG. 1 illustrates an embodiment of a pump system with a rotation detector. [Figure 11] FIG. 1 illustrates an embodiment of a pump system with an anti-rotation device. [Figure 12] FIG. 1 is a schematic diagram showing a conventional example of a pump system for pumping liquefied gas. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a diagram showing one embodiment of a pump system for transferring liquefied gas. Examples of liquefied gas that can be transferred by the pump system shown in Fig. 1 include liquefied ammonia, liquefied hydrogen, liquid nitrogen, liquefied natural gas, liquefied ethylene gas, and liquefied petroleum gas.

[0014] As shown in Figure 1, the pump system includes a submersible pump 1 for transferring liquefied gas, a suction vessel 2 in which the submersible pump 1 is housed, and a flow path switching device 5 for preventing the submersible pump 1 from running idle. The suction vessel 2 has a suction port 7 and a discharge port 8. Liquefied gas is introduced into the suction vessel 2 through the suction port 7, and the suction vessel 2 is filled with the liquefied gas. During operation of the submersible pump 1, the entire submersible pump 1 is immersed in the liquefied gas. Therefore, the submersible pump 1 is configured to be able to operate in liquefied gas.

[0015] The submersible pump 1 includes an electric motor 11 having a motor rotor 11A and a motor stator 11B, a rotating shaft 12 connected to the electric motor 11, bearings 14A, 14B, and 14C that rotatably support the rotating shaft 12, an impeller 15 fixed to the rotating shaft 12, and a pump casing 16 that houses the impeller 15. The flow path switching device 5 is disposed within the suction vessel 2. More specifically, the flow path switching device 5 is connected to both the discharge port 1b of the submersible pump 1 and the discharge port 8 of the suction vessel 2. The specific configuration of the flow path switching device 5 will be described later.

[0016] When power is supplied to the electric motor 11 through a power cable (not shown), the electric motor 11 rotates the rotating shaft 12 and impeller 15 together. As the impeller 15 rotates, liquefied gas is sucked into the submersible pump 1 from the suction port 1a and discharged into the flow path switching device 5 through the discharge flow path 17 and the discharge port 1b. The liquefied gas then flows through the flow path switching device 5 and into the discharge port 8 of the suction container 2. A discharge pipe 20 is connected to the discharge port 8, and the liquefied gas that flows through the discharge port 8 is transported through the discharge pipe 20.

[0017] A suction valve 22 is connected to the suction port 7, and a discharge valve 23 is connected to the discharge port 8. A drain line 25 is connected to the bottom of the suction vessel 2, and a drain valve 26 is connected to the drain line 25. The suction port 7 is provided on the side wall of the suction vessel 2 and is located higher than the bottom of the suction vessel 2. The discharge port 8 is provided on the top of the suction vessel 2 and is located higher than the suction port 7. When the submersible pump 1 is operating, the suction valve 22 and the discharge valve 23 are open, and the drain valve 26 is closed. A vent line 31 is connected to the top of the suction vessel 2. When the submersible pump 1 is operating, part of the liquefied gas evaporates and becomes gas due to heat generation by the submersible pump 1, and this gas is discharged from the suction vessel 2 through the vent line 31. A vent valve 32 is connected to the vent line 31. In one embodiment, this gas may be directed to a gas treatment device (not shown) through vent line 31. A gas treatment device is a device that processes gas (e.g., natural gas, hydrogen gas, or ammonia gas) vaporized from liquefied gas. Examples of gas treatment devices include gas incineration devices (flaring devices), chemical gas treatment devices, and gas adsorption devices.

[0018] FIG. 2 is a cross-sectional view showing a detailed configuration of one embodiment of the flow path switching device 5. As shown in FIG. 2, the flow path switching device 5 includes a flow path structure 45 having a first flow path 41, a second flow path 42, and a third flow path 43, and a valve body 47 disposed within the flow path structure 45. The first flow path 41 communicates with the discharge port 1b of the submersible pump 1, the second flow path 42 communicates with the interior of the suction container 2, and the third flow path 43 communicates with the discharge port 8 of the suction container 2. The valve body 47 is disposed so as to selectively connect the third flow path 43 to either the first flow path 41 or the second flow path 42. The configuration of the flow path switching device 5 is not limited to the embodiment shown in FIG. 2 as long as it can perform its intended function.

[0019] 2 shows the state of the flow path switching device 5 when the submersible pump 1 is not operating. The valve element 47 is pressed against the flow path structure 45 by the spring 50 to close the first flow path 41. More specifically, the flow path structure 45 has a valve seat 51 formed around the outlet of the first flow path 41, and the valve element 47 is pressed against the valve seat 51 by the spring 50. Therefore, while the valve element 47 is pressed against the valve seat 51, the first flow path 41 is closed, and the second flow path 42 and the third flow path 43 are connected to each other. The second flow path 42 opens inside the suction container 2 and is connected to the suction port 7 through the inside of the suction container 2.

[0020] 3 shows the state of the flow path switching device 5 when the submersible pump 1 is operating. When the submersible pump 1 is operating, liquefied gas is discharged from the discharge port 1b of the submersible pump 1 and flows into the first flow path 41 of the flow path switching device 5. The liquefied gas flowing through the first flow path 41 moves the valve element 47 against the force of the spring 50, opening the first flow path 41 and closing the second flow path 42 with the valve element 47. As a result, the first flow path 41 and the third flow path 43 are connected to each other.

[0021] When the submersible pump 1 stops operating, the valve element 47 is pressed against the valve seat 51 by the spring 50. As a result, as shown in FIG. 2, the first flow path 41 is closed, and the second flow path 42 and the third flow path 43 are connected. In this manner, the flow path switching device 5 of this embodiment is operated only by the spring 50 and the flow of liquefied gas. In one embodiment, the flow path switching device 5 may have an actuator (e.g., an electric actuator or a fluid actuator) that moves the valve element 47.

[0022] Before operating the submersible pump 1, a drying-up process is performed in which air is removed from the suction vessel 2 using a purge gas, and a cooling-down process is performed in which the submersible pump 1 is cooled with liquefied gas. The drying-up and cooling-down processes are performed in the state shown in Figure 2, i.e., in the state in which the first flow path 41 is closed by the valve body 47 and the second flow path 42 and the third flow path 43 are connected to each other.

[0023] Drying-up is an operation in which room-temperature purge gas is introduced into the suction vessel 2 to dry out the submersible pump 1. One embodiment of drying-up will be described below with reference to FIG. 4. When the submersible pump 1 is not operating (i.e., the state shown in FIG. 2), purge gas is supplied into the suction vessel 2 through the suction port 7. The discharge valve 23 and the vent valve 32 are closed, and the suction valve 22 and the drain valve 26 are open. The vent valve 32 may be open. The purge gas pushes out any air present in the suction vessel 2 and is discharged together with the air through the drain line 25. The suction vessel 2 is eventually filled with purge gas, thereby drying out the submersible pump 1.

[0024] In one embodiment, drying may be performed as follows. As shown in FIG. 5, when the submersible pump 1 is not operating (i.e., the state shown in FIG. 2), purge gas is supplied into the suction vessel 2 through the suction port 7. The drain valve 26 and the vent valve 32 are closed, and the suction valve 22 and the discharge valve 23 are open. The vent valve 32 may be open. The purge gas pushes out air present in the suction vessel 2 and is discharged together with the air through the second flow path 42 and the third flow path 43 of the flow path switching device 5 and the discharge port 8. The interior of the suction vessel 2 is eventually filled with purge gas, thereby drying the submersible pump 1.

[0025] Furthermore, in one embodiment, drying may be performed as follows. As shown in FIG. 6, when the submersible pump 1 is not operating (i.e., the state shown in FIG. 2), purge gas is supplied into the suction vessel 2 through the drain line 25. The suction valve 22 and the vent valve 32 are closed, and the drain valve 26 and the discharge valve 23 are open. The vent valve 32 may be opened. The purge gas pushes out air present in the suction vessel 2 and is discharged together with the air through the second flow path 42 and the third flow path 43 of the flow path switching device 5 and the discharge port 8. Eventually, the interior of the suction vessel 2 is filled with purge gas, thereby drying the submersible pump 1.

[0026] 4 to 6, the first flow path 41 is closed by the valve body 47. Therefore, the purge gas introduced into the suction vessel 2 does not flow through the submersible pump 1. As a result, the impeller 15 of the submersible pump 1 is prevented from idling, and damage to the sliding parts such as the bearings 14A, 14B, and 14C is prevented.

[0027] The purge gas used for drying up is an inert gas composed of elements with a boiling point lower than that of the elements constituting the liquefied gas. This is to prevent the purge gas from liquefying when it comes into contact with the cryogenic liquefied gas introduced after drying up. For example, when the liquefied gas is liquefied natural gas (LNG) or liquefied ammonia, the purge gas used is nitrogen gas. In another example, when the liquefied gas is liquefied hydrogen, the purge gas used is helium gas.

[0028] Cooling down is an operation performed after the drying up step to introduce liquefied gas into the suction vessel 2 to cool the submersible pump 1. One embodiment of the cool down process will be described below with reference to FIG. 7. As shown in FIG. 7, when the submersible pump 1 is not operating (i.e., the state shown in FIG. 2), liquefied gas is supplied into the suction vessel 2 through the suction port 7. The drain valve 26 and the vent valve 32 are closed, and the suction valve 22 and the discharge valve 23 are open. The vent valve 32 may be open. The liquefied gas vaporizes upon contact with the room-temperature submersible pump 1 and the suction vessel 2, generating gas (hereinafter, referred to as "generated gas"). The generated gas is discharged through the second flow path 42 and the third flow path 43 of the flow path switching device 5 and the discharge port 8. As the temperatures of the submersible pump 1 and the suction vessel 2 decrease, the liquefied gas no longer vaporizes. Eventually, the suction vessel 2 is filled with liquefied gas, thereby cooling the submersible pump 1.

[0029] 7, the first flow path 41 is also closed by the valve body 47. Therefore, the produced gas in the suction vessel 2 does not flow through the submersible pump 1. As a result, the impeller 15 of the submersible pump 1 is prevented from idling, and damage to the sliding parts such as the bearings 14A, 14B, and 14C is prevented.

[0030] As shown in FIG. 7, the produced gas is discharged through the discharge port 8 and the discharge pipe 20. Typically, the discharge port 8 and the discharge pipe 20 have larger diameters than the vent line 31 and the drain line 25. Therefore, the liquefied gas for cooling the submersible pump 1 can be introduced into the suction vessel 2 at a high flow rate. As a result, the cool-down can be completed in a short time. In particular, according to this embodiment, even if the liquefied gas is introduced into the suction vessel 2 at a high flow rate, the produced gas (gas produced by evaporation of the liquefied gas) does not flow inside the submersible pump 1 due to the flow path switching device 5, so the submersible pump 1 does not run idle.

[0031] In one embodiment, the product gas generated in the suction vessel 2 may be led to a gas treatment device (not shown) through the discharge port 8 and the discharge pipe 20. The gas treatment device is a device that treats gas (e.g., natural gas, hydrogen gas, or ammonia gas) vaporized from the liquefied gas. Examples of the gas treatment device include a gas incineration device (flaring device), a chemical gas treatment device, and a gas adsorption device.

[0032] As shown in Figure 8, it is also possible to connect multiple suction vessels 2 in series to simultaneously cool multiple submersible pumps 1. Specifically, the discharge port 8 of one suction vessel 2 housing one submersible pump 1 is connected to the suction port 7 of another suction vessel 2 housing another submersible pump 1. In the same manner, three or more suction vessels 2 can be connected in series. Liquefied gas is introduced from the suction port 7 of one of the multiple suction vessels 2, flows through each suction vessel 2, and is discharged from the discharge port 8 of another of the multiple suction vessels 2. The liquefied gas flowing through these suction vessels 2 can simultaneously cool multiple submersible pumps 1.

[0033] FIG. 9 is a cross-sectional view showing another embodiment of the flow path switching device 5. The configuration and operation of this embodiment, which are not specifically described, are the same as those of the embodiment described with reference to FIGS. 2 and 3, and therefore, redundant description will be omitted. As shown in FIG. 9, the flow path structure 45 includes a bypass flow path 55 that connects the first flow path 41 and the third flow path 43. The cross-sectional area of ​​the bypass flow path 55 is smaller than the cross-sectional area of ​​the first flow path 41. More specifically, the cross-sectional area of ​​the bypass flow path 55 is such that, when the valve element 47 closes the first flow path 41 and gas (purge gas or generated gas) flows through the submersible pump 1 and the bypass flow path 55, the impeller 15 of the submersible pump 1 does not rotate due to the flow of the gas.

[0034] The bypass flow path 55 may be a through hole as shown in FIG. 9 or a groove formed in the valve seat 51. Multiple bypass flow paths 55 may be provided as long as the gas does not rotate the impeller 15. According to this embodiment, purge gas or liquefied gas can be smoothly introduced into the submersible pump 1 during drying up and cooling down. As a result, the drying up and cooling down of the submersible pump 1 can be completed in a shorter time.

[0035] As shown in FIG. 10 , in one embodiment, the pump system may include a rotation detector 60 that detects the rotation of the submersible pump 1. The specific configuration of the rotation detector 60 is not particularly limited as long as it can detect the rotation of the submersible pump 1 (i.e., the rotation of the rotating shaft 12 or the impeller 15). In the example shown in FIG. 10 , the rotation detector 60 is an induced electromotive force detector that detects the induced electromotive force generated when the electric motor 11 is rotating. In another example (not shown), the rotation detector 60 may be a rotation detector that directly detects the rotation of the rotating shaft 12 or the impeller 15. Based on the output value from the rotation detector 60, the cross-sectional area of ​​the bypass flow path 55 in which the submersible pump 1 does not rotate can be determined.

[0036] As shown in FIG. 11 , in one embodiment, the pump system may further include an anti-rotation device 70 for preventing rotation of the submersible pump 1. The specific configuration of the anti-rotation device 70 is not particularly limited as long as it can prevent rotation of the submersible pump 1 (i.e., rotation of the rotating shaft 12 or the impeller 15). For example, the anti-rotation device 70 may be a mechanical anti-rotation device that presses brake pads against the rotating shaft 12 to prevent rotation of the rotating shaft 12 and the impeller 15. Examples of actuators that drive the brake pads include fluid actuators (e.g., gas cylinders) and electric actuators (e.g., electromagnetic solenoids). In another example, the anti-rotation device 70 may be an electromagnetic anti-rotation device that prevents rotation of the rotating shaft 12 and the impeller 15 by electromagnetic force generated by energizing a coil.

[0037] The above-described embodiments have been described for the purpose of enabling a person of ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments would be obvious to a person skilled in the art, and the technical concept of the present invention may be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical concept defined by the claims. [Industrial Applicability]

[0038] The present invention can be used in technology for preventing idling of submersible pumps used to transport liquefied gases such as liquefied ammonia, liquefied hydrogen, liquid nitrogen, liquefied natural gas, liquefied ethylene gas, and liquefied petroleum gas. [Explanation of symbols]

[0039] 1 Submersible pump 1a Intake port 1b Discharge port 2. Suction vessel 5. Flow path switching device 7. Suction port 8 Discharge port 11 Electric motor 12 Rotation axis 14A, 14B, 14C bearings 15 Impeller 16 Pump casing 17 Discharge channel 20 Discharge pipe 22 Suction valve 23 Discharge valve 25 Drain line 26 Drain valve 31 Vent Line 32 Vent valve 41 First Channel 42 Second Channel 43 Third Channel 45 Flow path structure 47 Valve body 50 springs 51 Valve seat 55 Bypass flow path 60 Rotation detector 70 Anti-rotation device

Claims

1. A dry-up method for removing air from a suction vessel in which a submersible pump is housed, comprising the steps of: a first flow path communicating with a discharge port of the submersible pump is closed by a valve body, and a second flow path communicating with the interior of the suction container and a third flow path communicating with a discharge port of the suction container are in communication with each other, and a purge gas is supplied into the suction container; The purge gas is transferred to the discharge port through the second flow path and the third flow path while bypassing the submersible pump.

2. The drying-up method according to claim 1 , wherein the purge gas is supplied into the suction container from a suction port of the suction container or a drain line connected to the suction container.

3. A cool-down method for cooling a submersible pump housed in a suction vessel, comprising the steps of: a valve body that closes a first flow path that communicates with a discharge port of the submersible pump, and a second flow path that communicates with the interior of the suction container and a third flow path that communicates with a discharge port of the suction container are in communication with each other, and liquefied gas is supplied into the suction container; A cool-down method in which a product gas generated by vaporization of the liquefied gas in the suction container is transferred to the discharge port through the second flow path and the third flow path while bypassing the submersible pump.

Images