LNG unloading arm purging system
By setting first and second nitrogen injection ports on the unloading arm body and dividing it into two sections, nitrogen purging is performed independently on the shore-side and ship-side pipelines, solving the problems of slow pressurization speed and high nitrogen consumption in the prior art, and realizing a more efficient purging process.
Patent Information
- Application Number
- CN202520288668.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-21
- Publication Date
- 2026-03-27
- Estimated Expiration
- 2035-02-21
AI Technical Summary
In the existing LNG unloading arm purging method, nitrogen purging is carried out simultaneously on the shore-side and ship-side pipelines, resulting in slow pressurization speed, time-consuming and labor-intensive process, and large nitrogen consumption.
First and second nitrogen injection ports are set on the unloading arm body, and the unloading arm is divided into two sections by the first valve system. The shore-side and ship-side pipelines are purged independently with nitrogen. The rapid pressurization characteristic of the short pipeline is utilized to reduce the amount of nitrogen used and the purging time.
By using segmented purging, the purging time of the unloading arm was significantly shortened, nitrogen consumption was reduced, and purging efficiency was improved.
Smart Images
Figure CN224050148U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to LNG ship unloading technology field especially is related to a kind of LNG unloading arm purging system. BACKGROUND
[0002] LNG unloading arm is a kind of loading and unloading equipment, is installed on the wharf for unloading hinged pipe system, including process pipe section and its support structure and all accessories, unloading arm usually includes three-dimensional rotary joint, outer arm, inner arm, top end rotary joint base riser and the rotary joint between connecting inner arm and base riser and other components are made of component group.When LNG ship reaches LNG receiving station wharf, by liquid phase unloading arm and unloading pipeline, LNG is transported into the storage tank of receiving station by the help of unloading pump on ship.
[0003] In LNG (liquefied natural gas) ship receiving and unloading operation, because LNG has the characteristics of low temperature (-162 DEG C), flammable and explosive, and its vapor can form explosive gas after mixing with air, nitrogen purging can effectively eliminate the risk of oxygen and combustible gas residue.The purging process of LNG unloading arm includes nitrogen purging before unloading and nitrogen purging after unloading, and safety control throughout the whole process of LNG receiving and unloading.Before unloading, nitrogen purging is used to ensure the inert environment to guarantee the "safe start" of system, to avoid the harm of oxygen and moisture;After unloading, gas replacement is used to realize "safe ending", to prevent combustible residue and air intrusion, wherein:
[0004] Nitrogen purging before unloading can eliminate the oxygen residue in LNG storage tank and pipeline system before unloading, prevent explosion;Prevent air from entering low-temperature system, which can cause water vapor to freeze or form natural gas hydrate, block pipeline or valve;Expel moisture to ensure normal operation of equipment in low-temperature environment;Form inert barrier between LNG and air to avoid the risk of pressure fluctuation or gas mixing caused by temperature difference in the early stage of unloading.
[0005] Nitrogen purging after unloading can remove the LNG vapor that may be left in the pipeline after unloading, replace combustible gas, prevent vapor leakage or contact with air to cause explosion when disconnected;Nitrogen can be injected to maintain the positive pressure inert environment of the system, prevent air from being sucked into the system to cause oxygen to enter the system, provide a safe environment for subsequent maintenance or restart;Prevent incomplete removal of LNG residue, which can cause low-temperature damage to valve or sealing element.
[0006] Therefore, nitrogen purging of unloading arm is a key link in LNG receiving station unloading operation, and the efficiency of unloading arm purging directly affects the total length of LNG ship receiving and unloading.Whether unloading arm is purged on time and successfully determines the subsequent unloading work arrangement and ship departure time.
[0007] In the prior art purging mode, after the LNG ship unloading is completed, nitrogen is injected from the original ammonia injection point at the top of the unloading arm body, and the bottom of the pipeline from the rear of the ship unloading horizontal pipe cut-off valve is used as a discharge port for ammonia gas purging. During purging, the double ball valve is in an open state, and the shore side pipeline and the ship side pipeline are simultaneously purged, nitrogen is injected into the unloading arm through the nitrogen injection pipeline of the unloading arm to increase the pressure, and the LNG is discharged to the shore side three times, then to the ship side three times, and then replaced by nitrogen gas to BOG until the methane content detected by the ship unloading valve downstream is qualified.
[0008] However, since the shore side pipeline and the ship side pipeline are simultaneously purged and replaced, the pipeline space is large, and the pressure increasing speed is slow. The horizontal pipeline at the bottom of the shore side unloading arm is long, and the unloading arm vertical pipeline is as high as 21.5 meters, so that the LNG remaining in the horizontal pipeline of the shore side unloading arm is gasified and discharged to the ship side unloading arm vertical pipeline during purging, which is time-consuming and laborious. Practical new type
[0009] The purpose of the present application is to provide a LNG unloading arm purging system which can save purging time and reduce nitrogen consumption.
[0010] The present application provides a LNG unloading arm purging system, which comprises an unloading arm body, a first valve system, a first nitrogen injection port and a second nitrogen injection port arranged on the unloading arm body, the first nitrogen injection port is located between the first valve system and the shore side LNG unloading manifold, and the second nitrogen injection port is located between the first valve system and the ship side LNG unloading manifold.
[0011] Further, the first valve system is a double ball valve, which comprises a first valve and a second valve connected in series.
[0012] Further, a second valve system is arranged on one side of the unloading arm body adjacent to the shore side LNG unloading manifold.
[0013] Further, the second valve system comprises a third valve and a fourth valve connected in parallel.
[0014] Further, a shore side BOG pipeline is connected to the unloading arm body, the shore side BOG pipeline is located between the first nitrogen injection port and the second valve system, and a fifth valve is arranged on the shore side BOG pipeline.
[0015] Further, a thermometer and a first pressure gauge are arranged between the first valve system and the second valve system.
[0016] Further, a sixth valve is arranged on the first nitrogen injection port, and a seventh valve is arranged on the second nitrogen injection port.
[0017] Further, a third valve system is arranged on one side of the unloading arm body adjacent to the ship side LNG unloading manifold.
[0018] Further, a detection interface and a second pressure gauge are arranged between the first valve system and the third valve system, and the detection interface is provided with an eighth valve.
[0019] Further, the third valve system comprises a ninth valve and a tenth valve connected in parallel.
[0020] The technical scheme of the utility model discloses a first nitrogen injection interface and a second nitrogen injection interface are arranged on the upstream and downstream sides of the first valve system on the unloading arm body. When the BOG gas replacement purging process is carried out, the first valve system is closed, the unloading arm body is divided into two sections, nitrogen is injected into the area adjacent to the shore side pipeline through the first nitrogen injection interface, and the pipeline and the unloading arm on the shore side can stop purging when the temperature reaches the unloading arm detection temperature (interlocking temperature of the unloading arm) -80 degrees Celsius or above, and the remaining residual liquid is evaporated by natural evaporation. The area adjacent to the ship side pipeline is injected with nitrogen through the second nitrogen injection interface, and the nitrogen gas and time consumed in purging are less because the pipeline is shorter and the pressure rises faster. BRIEF DESCRIPTION OF DRAWINGS
[0021] In order to more clearly illustrate the technical scheme in the specific embodiment or prior art of the utility model, the drawings needed in the specific embodiment or prior art description will be briefly introduced below, and obviously, the drawings in the following description are some embodiments of the utility model, and other drawings can also be obtained by those skilled in the art without creative labor.
[0022] Figure 1 It is a schematic diagram of the overall arrangement of the LNG unloading arm purging system of the utility model;
[0023] MARK NUMBER EXPLANATION:
[0024] 1-unloading arm body; 2-first valve system; 3-second valve system; 4-third valve system; 5-first nitrogen injection interface; 6-second nitrogen injection interface; 7-shore side LNG unloading manifold; 8-ship side LNG unloading manifold; 9-shore side BOG pipeline;
[0025] V1-first valve; V2-second valve; V3-third valve; V4-fourth valve; V5-fifth valve; V6-sixth valve; V7-seventh valve; V8-eighth valve; V9-ninth valve; V10-tenth valve; P1-first pressure gauge; P2-second pressure gauge; T1-thermometer; SPECIFIC EMBODIMENT
[0026] The technical solutions of the present application will be described clearly and completely below in connection with the embodiments. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.
[0027] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.
[0028] In addition, the terms "first" and "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the present application, "a plurality of" means two or more, unless otherwise specifically limited. In addition, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.
[0029] Embodiment 1
[0030] As Figure 1 shown, the present application provides a LNG unloading arm purging system, which comprises an unloading arm body 1, a first valve system 2, a first nitrogen injection port 5 and a second nitrogen injection port 6 are arranged on the unloading arm body 1, the first nitrogen injection port 5 is located between the first valve system 2 and the shore side LNG unloading manifold 7, and the second nitrogen injection port 6 is located between the first valve system 2 and the ship side LNG unloading manifold 8.
[0031] Specifically, LNG refers to liquefied natural gas (Liquefied Natural Gas, LNG for short), which is natural gas compressed and cooled to its condensation point (-161.5℃) to become a liquid. BOG refers to natural gas formed by evaporation of part of LNG due to external heat input during LNG storage. The specific structure of the unloading arm is the content of the prior art, and will not be described here.
[0032] If the first valve system 2 is closed during the unloading arm purge, the unloading arm body 1 is divided into two sections, and the shore side pipeline and the ship side pipeline are separated for purging, which can save a lot of time. Of course, the first valve system 2 is still in the open state during the liquid discharge process, and after three times of liquid discharge to the shore side and three times of liquid discharge to the ship side, it is confirmed that there is no liquid in the pipeline, and then the first valve system 2 is closed for segmented purging process. Because the pipeline pressure rises quickly when the pipeline is full of LNG, the amount of nitrogen used is small, and there is no need to segment the purge. However, when nitrogen is used to replace BOG gas, the pressure rise becomes very slow, and it takes tens of minutes to rise to the target pressure each time, and a large amount of nitrogen is consumed, so it is necessary to close the first valve system 2 for segmented purging.
[0033] The first nitrogen injection port 5 and the second nitrogen injection port 6 are nitrogen joints with three-way fittings added to the unloading arm body 1, two of which are connected to the unloading arm body 1, and the remaining one is used to connect a nitrogen hose.
[0034] After the first valve system 2 is closed, the second nitrogen injection port 6 at the upstream of the first valve system 2 is connected to a nitrogen hose, and nitrogen is connected from a nitrogen joint on the three-layer platform on the shore side, which is used for purging the ship side pipeline. This section of pipeline is short, the pressure rises quickly, and the nitrogen consumption is small. The first nitrogen injection port 5 at the downstream of the first valve system 2 is connected to a nitrogen hose, and the shore side pipeline and the unloading arm can stop purging as long as the temperature reaches the unloading arm detection temperature (interlock temperature of the unloading arm) -80 degrees Celsius or above.
[0035] In this system, the first valve system 2 is closed after the liquid discharge process is completed to perform the segmented purging process, which speeds up the time for the unloading arm to pass the purging. The original purging time of the unloading arm is more than 1 hour, and according to the modified method, the purging time of the unloading arm can be controlled to be less than half an hour. The original purging of the unloading arm consumes about 1 ton of nitrogen each time, and using the modified method can save at least half of the nitrogen consumption.
[0036] Furthermore, the system can also effectively save time during segmented purging before unloading. For example, if the first valve system 2 (first valve V1 and second valve V2) is kept closed after unloading, then before the next unloading, the pipeline close to the shore side can not be replaced by nitrogen, and only the pipeline close to the ship side needs to be replaced by nitrogen, thereby improving the purging efficiency and saving the amount of nitrogen used.
[0037] Embodiment 2
[0038] The first valve system 2 is a double ball valve, which comprises a first valve V1 and a second valve V2 connected in series.
[0039] Specifically, the double ball valve is composed of the first valve V1 and the second valve V2 connected in series, which makes the inside of the unloading arm body 1 communicate when both the first valve V1 and the second valve V2 are opened, and which makes the inside of the unloading arm body 1 separate into two sections when both the first valve V1 and the second valve V2 are closed.
[0040] Embodiment 3
[0041] The second valve system 3 is also arranged on one side of the unloading arm body 1 adjacent to the shore side LNG unloading manifold 7. The second valve system 3 comprises a third valve V3 and a fourth valve V4 connected in parallel. The unloading arm body 1 is connected with a shore side BOG pipeline 9, which is located between the first nitrogen injection port 5 and the second valve system 3, and the shore side BOG pipeline 9 is provided with a fifth valve V5. A thermometer and a first pressure gauge are arranged between the first valve system 2 and the second valve system 3.
[0042] Specifically, by closing both the first valve system 2 and the second valve system 3, the area adjacent to the shore side pipeline in the unloading arm body 1 is sealed, and the exhaust is carried out after the nitrogen is injected and the pressure is increased.
[0043] After the shore side pipeline and the unloading arm temperature reaches the unloading arm detection temperature (the interlocking temperature of the unloading arm operation) -80 degrees Celsius or above, the remaining residual liquid is evaporated by natural evaporation, and in this process, the fifth valve V5 of the shore side BOG pipeline 9 on the unloading arm is opened to connect with the BOG manifold, and the residual liquid is directly introduced into the BOG manifold after evaporation, which not only saves the time of blowing, but also reduces the amount of nitrogen used.
[0044] Embodiment 4
[0045] The first nitrogen injection port 5 is provided with a sixth valve V6, and the second nitrogen injection port 6 is provided with a seventh valve V7.
[0046] Specifically, the sixth valve V6 and the seventh valve V7 are used to control the connection of nitrogen of the two nitrogen injection ports.
[0047] Embodiment 5
[0048] The third valve system 4 is also arranged on one side of the unloading arm body 1 adjacent to the ship side LNG unloading manifold 8. A detection port and a second pressure gauge are arranged between the first valve system 2 and the third valve system 4, and the detection port is provided with an eighth valve V8. The third valve system 4 comprises a ninth valve V9 and a tenth valve V10 connected in parallel.
[0049] Specifically, by closing the first valve system 2 and the third valve system 4, the area adjacent to the ship side pipeline in the unloading arm body 1 is sealed, and nitrogen injection is carried out after pressure rise.
[0050] The eighth valve V8 can be equipped with detection instruments, such as methane content detection instruments, and when the methane content detected by the eighth valve V8 is less than 1%, it represents that the exhaust is qualified, and the exhaust process of the area adjacent to the ship side pipeline in the unloading arm body 1 is stopped.
[0051] The implementation process of the utility model:
[0052] 1. Confirm that the first valve system 2 (the first valve V1, the second valve V2) is in an open state, the second valve system 3 (the third valve V3, the fourth valve V4), the fifth valve V5, the sixth valve V6, the seventh valve V7, the eighth valve V8 and the third valve system 4 (the ninth valve V9, the tenth valve V10) are in a closed state.
[0053] 2. Open the sixth valve V6 to inject nitrogen to increase pressure, close the sixth valve V6 when the first pressure gauge reaches 5bar, open the shore side cut-off valve bypass fourth valve V4 to discharge liquid, close the fourth valve V4 when the first pressure gauge reaches 3bar (higher than the unloading pipeline pressure), and repeat three times.
[0054] 3. Open the sixth valve V6 to inject nitrogen to increase pressure, close the sixth valve V6 when the first pressure gauge reaches 5bar, open the ship side cut-off valve bypass tenth valve V10 to discharge liquid, close the tenth valve V10 when the first pressure gauge reaches 3bar, and repeat three times.
[0055] 4. Close the unloading arm double ball valve (the first valve V1, the second valve V2).
[0056] 5. Observe the temperature of the thermometer, if the temperature of the thermometer is higher than-80 DEG C, the shore side can be stopped blowing, open the fifth valve V5, if the temperature of the thermometer is lower than-80 DEG C, continue to open the sixth valve V6 to inject nitrogen to increase pressure, close the sixth valve V6 when the first pressure gauge reaches 5bar, open the fifth valve V5 to exhaust, until the temperature of the thermometer is higher than-80 DEG C.
[0057] 6. Connect the nitrogen hose to the seventh valve V7, open the seventh valve V7 to continue to inject nitrogen to increase pressure in the ship shore connection part, close the seventh valve V7 when the second pressure gauge reaches 5bar, open the ship side cut-off valve bypass tenth valve V10 to exhaust, repeat 2-3 times, until the eighth valve V8 checks that the methane content is less than 1%.
[0058] Finally, it should be noted that: the above embodiments are used to illustrate the technical solutions of the present application, but not limited to them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.
Claims
1. An LNG offloading arm purge system, characterized by, The unloading arm body is provided with a first valve system, a first nitrogen injection port and a second nitrogen injection port.
2. The LNG offloading arm purge system of claim 1, wherein, The first valve system is a double ball valve, comprising a first valve and a second valve connected in series.
3. The LNG offloading arm purge system of claim 1, wherein, The unloading arm body is further provided with a second valve system on one side adjacent to the shore side LNG unloading manifold.
4. The LNG offloading arm purge system of claim 3, wherein, The second valve system comprises a third valve and a fourth valve connected in parallel.
5. The LNG offloading arm purge system of claim 3, wherein, The unloading arm body is connected with a shore side BOG pipeline, which is located between the first nitrogen injection port and the second valve system, and is provided with a fifth valve.
6. The LNG offloading arm purge system of claim 3, wherein, A thermometer and a first pressure gauge are arranged between the first valve system and the second valve system.
7. The LNG offloading arm purge system of claim 1, wherein, The first nitrogen injection port is provided with a sixth valve, and the second nitrogen injection port is provided with a seventh valve.
8. The LNG offloading arm purge system of claim 1, wherein, The unloading arm body is further provided with a third valve system on one side adjacent to the ship side LNG unloading manifold.
9. The LNG offloading arm purge system of claim 8, wherein, A detection port and a second pressure gauge are arranged between the first valve system and the third valve system, and the detection port is provided with an eighth valve.
10. The LNG offloading arm purge system of claim 8, wherein, The third valve system comprises a ninth valve and a tenth valve connected in parallel.