Blowing device for inlet filter and liquid collecting tank of BOG (Boil Off Gas) compressor

Abstract

The utility model relates to a BOG compressor inlet filter and liquid collecting tank purging device which comprises a liquid separation tank, a liquid collecting tank and a plurality of compressors, the top of the liquid separation tank is communicated with one end of a gaseous natural gas pipeline, and the top of the liquid separation tank is further communicated with inlets of the compressors through a first pipeline; an outlet of the compressor is communicated with one end of a pipeline II; a filter is mounted on the pipeline I; the top of the liquid collection tank is communicated with one end of a nitrogen pipeline and is communicated with the bottom of the liquid separation tank through a pipeline III, and the bottom of the liquid collection tank is communicated with one end of a discharge pipeline; the pipeline II is communicated with the corresponding part of the pipeline I through a gas return pipeline I, and the part of the pipeline I corresponding to the position between the filter and the liquid separation tank is communicated with the nitrogen pipeline through a gas return pipeline II. According to the utility model, the filter at the inlet of the compressor is reversely purged to the filtering tank to be circulated back to the inlet of the BOG compressor for reuse, BOG is introduced by using the outlet of the BOG compressor to replace nitrogen to carry out pressurization emptying on the liquid collecting tank, the energy is saved, the consumption is reduced, and the production is safe.

Description

Technical Field

[0001] The utility model relates to the technical field of petroleum and natural gas processing, in particular to a BOG compressor inlet filter and a liquid collecting tank purge device. Background Art

[0002] During the operation of the low-temperature BOG compressor inlet at the LNG (liquid natural gas) receiving station, heavy hydrocarbons often clog the filter; when the pressure at the BOG compressor suction port is low, it is necessary to switch the BOG compressor to operate and purge the originally clogged inlet filter with nitrogen. When the liquid level in the inlet liquid collecting tank is high, the inlet liquid collecting tank needs to be drained. The common method used by LNG receiving stations is to use the room temperature nitrogen from the plant nitrogen pipeline network to purge the BOG compressor inlet filter and inject nitrogen to drain the liquid collecting tank. This method has the following problems:

[0003] 1. The inlet filter needs to be discharged on site when purging, which poses certain safety risks;

[0004] 2. Excessive nitrogen injection can easily lead to fluctuations in calorific value for downstream users;

[0005] 3. When the LNG receiving station uses the normal temperature nitrogen from the nitrogen pipeline network in the plant area to pressurize and drain the BOG compressor inlet collecting tank, it has a great impact on the nitrogen pipeline network pressure, and the nitrogen pipeline network needs to be filled with nitrogen through the liquid nitrogen system to maintain the pressure. During the drainage operation, the pressurization speed of the BOG compressor inlet collecting tank is slow, and the liquid nitrogen consumption is large;

[0006] 4. The nitrogen purge of the BOG compressor inlet filter lasts for a long time. When emptying on site, personnel must be arranged to conduct full-process control and inspection of the site. When the liquid collecting tank is drained, liquid nitrogen is needed to pressurize the nitrogen pipeline network. At least two operators are required to operate at the same time (excluding the vote counting or operation supervision personnel), and the operation manpower demand is large. Utility Model Content

[0007] The technical problem to be solved by the utility model is to provide

[0008] The technical solution of the utility model to solve the above technical problems is as follows:

[0009] A BOG compressor inlet filter and liquid collecting tank purge device, comprising a liquid separator, a liquid collecting tank and a plurality of compressors arranged in parallel, wherein the top of the liquid separator is connected to one end of a gaseous natural gas pipeline, and the top of the liquid separator is also connected to the inlet of each compressor through a pipeline 1; the outlet of each compressor is connected to one end of a pipeline 2, and a filter is fixedly installed on the pipeline 1 near the inlet of the compressor; the top of the liquid collecting tank is connected to one end of a nitrogen pipeline, and the top of the liquid collecting tank is connected to the bottom of the liquid separator through a pipeline 3, and the bottom of the liquid separator is connected to one end of a discharge pipeline;

[0010] The pipeline 2 is connected to the portion of the pipeline 1 corresponding to the filter and the compressor through the return air pipeline 1, and the portion of the pipeline 1 corresponding to the filter and the liquid separator tank is connected to the nitrogen pipeline through the return air pipeline 2.

[0011] The beneficial effects of the utility model are as follows: during the operation, after the liquefied natural gas is sent to the liquid separation tank, it is compressed by the compressor; at the same time, part of the compressed gaseous natural gas returns to the liquid collecting tank through the return gas pipeline 1 and the return gas pipeline 2, so that the pressure in the liquid collecting tank is increased to discharge the liquefied natural gas in the liquid collecting tank, which is convenient for drainage and saves energy and reduces consumption; during the gas return process, the filter at the compressor inlet will be purged to prevent the filter from being blocked and affecting the filtering effect.

[0012] The traditional technology is to directly introduce nitrogen into the liquid collecting tank to discharge the liquid, which consumes a lot of energy.

[0013] The utility model reversely purges the filter at the inlet of the compressor to the filter tank for circulation back to the inlet of the BOG compressor for repeated use, and uses the BOG compressor outlet to introduce BOG instead of nitrogen to pressurize and discharge the liquid collecting tank, thereby saving energy, reducing consumption and ensuring safe production.

[0014] On the basis of the above technical solution, the present invention can also be improved as follows.

[0015] Furthermore, a filter tank is fixedly installed on the second return air pipeline.

[0016] The beneficial effects of adopting the above further scheme are simple structure and reasonable design. The returned gaseous natural gas is filtered through the filter tank to remove impurities in the gas and ensure the cleanliness of the natural gas in the liquid collecting tank. The filter tank has its own sewage discharge function and pipeline, and sewage can be discharged through pressure difference indication or sight glass observation of filter blockage.

[0017] Furthermore, the return air pipeline 1 and / or the return air pipeline 2 are respectively fixedly installed with a temperature gauge at a location between the connection point between the return air pipeline 1 and the nitrogen pipeline and the filter tank.

[0018] The beneficial effects of adopting the above further solution are simple structure and reasonable design. The temperature on each pipeline is detected by a thermometer to monitor the temperature in the pipeline in real time to ensure the normal operation of the system.

[0019] Furthermore, the return gas pipeline 1 is also connected to the return gas pipeline 2 via the return gas pipeline 3, corresponding to the portion between the return gas pipeline 2 and the nitrogen pipeline and the filter tank.

[0020] The beneficial effect of adopting the above further solution is that during the operation, the natural gas compressed by the compressor can also be directly sent to the liquid collecting tank for drainage, which makes the drainage convenient.

[0021] Furthermore, valves 1 are fixedly installed at the connection point between the return air pipeline 3 and the return air pipeline 1 and the position between the two ends of the return air pipeline 1.

[0022] The beneficial effects of adopting the above further solution are simple structure, reasonable design, and setting various valves to control the path of natural gas so as to complete different operations.

[0023] Furthermore, a valve 2 is fixedly installed on the return air pipeline 2 near the portion where it is connected to the pipeline 1.

[0024] The beneficial effects of adopting the above further solution are simple structure, reasonable design, and setting each valve to control the path of natural gas so as to complete different operations.

[0025] Furthermore, valves three are fixedly installed on the return air pipeline two at locations close to the inlet and outlet of the filter tank.

[0026] The beneficial effects of adopting the above further solution are simple structure, reasonable design, setting each valve to control the on-off of the natural gas in the path, and convenient operation.

[0027] Furthermore, a valve four is fixedly installed on the return gas pipeline 2 near the portion where it is connected to the nitrogen pipeline.

[0028] The beneficial effects of adopting the above further solution are simple structure, reasonable design, setting each valve four to control the on and off of the natural gas in the path, and convenient operation.

[0029] Furthermore, a valve five is fixedly installed at the other end of the nitrogen pipeline.

[0030] The beneficial effects of adopting the above further solution are simple structure and reasonable design. By setting valve 5, natural gas can be prevented from being discharged from the other end of the nitrogen pipeline, ensuring that nitrogen can be discharged from the liquid collecting tank.

[0031] Furthermore, the number of the compressors is two.

[0032] The beneficial effect of adopting the above further solution is that the two compressors are arranged in parallel and can perform compression operations at the same time, which greatly improves the operating efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a process flow chart of the utility model.

[0034] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0035] 1. Liquid separation tank; 2. Liquid collecting tank; 3. Compressor; 4. Gaseous natural gas pipeline; 5. Filter; 6. Nitrogen pipeline; 7. Filter tank; 8. Thermometer; 9. Return gas pipeline one; 10. Return gas pipeline two; 11. Return gas pipeline three; 12. Valve one; 13. Valve two; 14. Valve three; 15. Valve four; 16. Valve five; 17. Liquid natural gas pipeline. DETAILED DESCRIPTION

[0036] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0037] In the description of the present utility model, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present utility model. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present utility model, unless otherwise specified, "multiple" means two or more.

[0038] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0039] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0040] Example 1

[0041] like Figure 1As shown, this embodiment provides a BOG compressor inlet filter and a liquid collecting tank purge device, comprising a liquid separator 1, a liquid collecting tank 2 and a plurality of compressors 3 arranged in parallel, wherein the top of the liquid separator 1 is connected to one end of a gaseous natural gas pipeline 4, and the top of the liquid separator 1 is also connected to the inlet of each compressor 3 through a pipeline 1; the outlet of each compressor 3 is connected to one end of a pipeline 2, and a filter 5 is fixedly installed on the pipeline 1 near the inlet of the compressor 3; the top of the liquid collecting tank 2 is connected to one end of a nitrogen pipeline 6, and the top of the liquid collecting tank 2 is connected to the bottom of the liquid separator 1 through a pipeline 3, and the bottom is connected to one end of a discharge pipeline;

[0042] The pipeline 2 is connected to the portion of the pipeline 1 corresponding to the filter 5 and the compressor 3 through the return air pipeline 1 9, and the portion of the pipeline 1 corresponding to the filter 5 and the liquid separator 1 is connected to the nitrogen pipeline 6 through the return air pipeline 2 10.

[0043] During the operation, the liquefied natural gas is sent to the liquid separator 1 and compressed by the compressor 3. At the same time, part of the compressed gaseous natural gas is returned to the liquid collecting tank 2 through the return gas pipeline 1 9 and the return gas pipeline 2 10, so that the pressure in the liquid collecting tank 2 is increased to discharge the liquefied natural gas in the liquid collecting tank 2, which is convenient for drainage and saves energy and reduces consumption. During the gas return process, the filter 5 at the inlet of the compressor 3 will be purged to prevent the filter from being blocked and affecting the filtering effect.

[0044] The traditional technology is to directly introduce nitrogen into the liquid collecting tank to drain the liquid, which consumes a lot of energy and requires a lot of workload for operators.

[0045] It should be noted that the compressor 3 is preferably a BOG compressor in the prior art. Both the compressor 3 and the filter 5 adopt the prior art, and their specific structures and principles are not described in detail here.

[0046] In addition, LNG in the drawings represents liquid natural gas, which is used for precooling; BOG represents gaseous natural gas, and GNI represents nitrogen.

[0047] Based on the above scheme, pressure regulating valves are fixedly installed on the two return gas pipelines 10, and the pressure regulating valves are preferably self-supporting regulating valves. The self-supporting regulating valves are set to adjust the pressure according to the design pressure of the downstream pipeline container to ensure safe operation of the downstream.

[0048] Based on the above scheme, the purpose of setting up multiple compressors 3 is: as long as one of the compressors 3 is guaranteed to perform normal compression operations, assuming that the filters 5 at the inlets of the remaining multiple compressors 3 are blocked, the gas generated by the normally compressed compressor 3 can be used to purge the filters 5 at the inlets of the remaining compressors 3.

[0049] In this embodiment, the filter at the compressor inlet is reversely purged to the filter tank and circulated back to the BOG compressor inlet for repeated use. The BOG compressor outlet is used to introduce BOG instead of nitrogen to pressurize and discharge the liquid collecting tank, thereby saving energy, reducing consumption and ensuring safe production.

[0050] Example 2

[0051] On the basis of Example 1, in this embodiment, a filter tank 7 is fixedly installed on the return air pipeline 10.

[0052] The scheme has a simple structure and a reasonable design. The returned gaseous natural gas is filtered by the filter tank 7 to remove impurities in the gas and ensure the cleanliness of the natural gas in the liquid collecting tank 2. The filter tank 7 has its own sewage discharge function and pipeline, and sewage can be discharged by pressure difference indication or by observing the filter blockage through a sight glass.

[0053] The above-mentioned filter tank 7 adopts the existing technology, and its specific structure and principle are not described in detail here.

[0054] Alternatively, a separator in the prior art may be used to replace the filter tank 7 .

[0055] Example 3

[0056] On the basis of Example 2, in this example, the return air pipeline 1 9 and / or the return air pipeline 2 10 are respectively fixedly installed with a temperature gauge 8 at the position corresponding to the connection point between the return air pipeline 1 9 and the nitrogen pipeline 6 and the filter tank 7 .

[0057] The scheme has a simple structure and a reasonable design. The temperature on each pipeline is detected by a temperature meter 8 to monitor the temperature in the pipeline in real time to ensure the normal operation of the system.

[0058] Example 4

[0059] On the basis of any one of Examples 2 to 3, in this embodiment, the return air pipeline 1 9 is also connected to the return air pipeline 2 10 via the return air pipeline 3 11 at a location between the return air pipeline 10 and the nitrogen pipeline 6 and the filter tank 7 .

[0060] During the operation, the natural gas compressed by the compressor 3 can also be directly sent to the liquid collecting tank 2 for drainage, which is convenient for drainage.

[0061] Based on the above solution, the temperature gauge 8 located on the return gas pipeline 10 is located between the connection point between the return gas pipeline 10 and the nitrogen pipeline 6 and the connection point between the return gas pipeline 11 and the return gas pipeline 10.

[0062] Example 5

[0063] On the basis of Example 4, in this embodiment, valves 12 are fixedly installed at the connection point between the return air pipeline 3 11 and the return air pipeline 1 9 and at the position between the two ends of the return air pipeline 1 9.

[0064] The solution has a simple structure and a reasonable design. The various valves 12 are arranged to control the path of the natural gas so as to complete different operations.

[0065] Example 6

[0066] On the basis of any one of Examples 2 to 5, in this embodiment, a second valve 13 is fixedly installed on the second return air pipeline 10 near the portion where the return air pipeline 10 is connected to the first pipeline.

[0067] The solution has a simple structure and a reasonable design. The arrangement of each valve 13 can control the path of the natural gas so as to complete different operations.

[0068] Example 7

[0069] On the basis of Example 6, in this embodiment, valves 3 14 are fixedly installed on the return air pipeline 2 10 near the inlet and outlet of the filter tank 7 respectively.

[0070] The solution has a simple structure and a reasonable design. The arrangement of each valve 14 can control the on-off of the natural gas in the path, and the operation is convenient.

[0071] Based on the above scheme, the two valves 14 are respectively represented as V11 and V12.

[0072] In addition, an interlocking cut-off valve is fixedly installed on the end of the return air pipeline 10 corresponding to the valve V11 away from the filter tank 7. The interlocking cut-off valve is interlocked and cut off at the design pressure alarm value of the downstream pipeline container to ensure safe operation downstream.

[0073] Example 8

[0074] On the basis of the above embodiments, in this embodiment, a valve 4 15 is fixedly installed on the return gas pipeline 2 10 near the portion where it is connected to the nitrogen pipeline 6 .

[0075] The solution has a simple structure and a reasonable design. The arrangement of each valve 15 can control the on-off of the natural gas in the path, and the operation is convenient.

[0076] Preferably, in this embodiment, the number of valves four 15 is preferably two, and the two valves four 15 are respectively represented as V15 and V16.

[0077] Example 9

[0078] On the basis of the above embodiments, in this embodiment, a valve 5 16 is fixedly installed at the other end of the nitrogen pipeline 6 .

[0079] The scheme has a simple structure and a reasonable design. The arrangement of each valve 16 can control the on-off of the natural gas in the path, and the operation is convenient.

[0080] The valve five 16 mentioned above is represented by V17.

[0081] Example 10

[0082] On the basis of the above embodiments, in this embodiment, the number of the compressors 3 is two, and the two compressors 3 are distributed in parallel.

[0083] The two compressors 3 are arranged in parallel and can perform compression operations simultaneously, which greatly improves the operating efficiency.

[0084] Based on the above solution, the other ends of the two pipelines 2 are connected to the same pipeline, which is connected to the next process. The pipelines are reasonably distributed, saving space and reducing costs.

[0085] Moreover, the two return air pipelines 1 9 are connected through a pipeline, and the two return air pipelines 2 10 are connected through a pipeline and then collected in the filter tank 7 .

[0086] One ends of the two pipelines 1 are connected to the top of the liquid separation tank 1 after merging, and valves V13 and V14 are fixedly installed on one ends of the two pipelines 1 respectively.

[0087] In addition, two valves 12 are respectively provided at both ends of the two return gas pipelines 9. The four valves 12 on one return gas pipeline 9 are represented by V1, V2, V5 and V7 in the direction of gas flow, and the four valves 12 on the other return gas pipeline 9 are represented by V3, V4, V6 and V7 in the direction of gas flow.

[0088] The two return gas pipelines 10 are respectively fixedly installed with valves 13, and the valves 13 on the two return gas pipelines 10 are respectively represented as V9 and V10 along the direction of their own gas flow.

[0089] Preferably, in this embodiment, each of the above-mentioned valves is preferably a solenoid valve, which is connected to a controller through a line, and the controller controls the opening and closing of each valve.

[0090] It should be noted that the valves mentioned above are prefixed with V, which is just a valve number for identification and has no other substantial meaning.

[0091] Based on the above scheme, the two pipelines 1 are connected to the other end of the gaseous natural gas pipeline 4 through pipelines, and the gaseous natural gas pipeline 4 is connected to one end of the liquid natural gas pipeline 17, and one end of the gaseous natural gas pipeline 4 is connected to pipeline 1 through a pipeline.

[0092] In addition, the other end of the gaseous natural gas pipeline 4 is also connected to the top of the liquid collecting tank 2 through a pipeline.

[0093] It should be noted that valves are installed on the above pipelines as required to meet production needs.

[0094] The principles of the BOG compressor inlet filter and the liquid collecting tank purge device in the utility model are as follows:

[0095] In the case that the inlet filter of the low-temperature BOG compressor is blocked due to heavy hydrocarbons and the suction port pressure is low, the outlet BOG of the low-temperature BOG compressor that operates normally after switching is used to replace the normal temperature nitrogen as the BOG compressor inlet filter purge gas and the inlet liquid collecting tank purge gas and booster exhaust gas. The BOG inlet filter purge work and liquid collecting tank exhaust operation can be completed safely and quickly, while saving liquid nitrogen resources and ensuring the stability of the calorific value of downstream BOG users.

[0096] The process operation flow of the above tank purging device is as follows:

[0097] 1. Low-temperature BOG compressor inlet filter purge operation (taking BOGC-A inlet filter blockage as an example):

[0098] Set up the process flow, follow the principle of downstream first and upstream later, and confirm that the pipeline flow of V4-V5-V7-V9-V11-V12-V15-V16 is connected;

[0099] Slowly open V3 to introduce BOG from the BOGC-B outlet to reversely purge the BOGC-A inlet filter. The light components filtered by the filter tank are returned to the BOG storage system through the balance pipeline connected to the liquid collecting tank and the BOG pipeline.

[0100] According to the change of BOG compressor outlet pressure, adjust the pressure and condensation ratio of the recondenser;

[0101] Continuously monitor the temperature and pressure during the purge process;

[0102] After the dew point at the filter tank test port is tested and found to be qualified, the process and BOG compressor A are restored to standby status.

[0103] 2. Purge and drain operation of the low-temperature BOG compressor inlet liquid collecting tank (taking BOGC-A operation as an example):

[0104] Set up the process flow, follow the principle of downstream first and upstream later, and confirm that the pipeline flow of V2-V15-V16 is connected;

[0105] Slowly open V1 to introduce BOG from the BOGC-A outlet to pressurize the inlet liquid collecting tank;

[0106] According to the change of BOG compressor outlet pressure, adjust the pressure and condensation ratio of the recondenser;

[0107] Continuously monitor the temperature and pressure during the pressurization process;

[0108] When the pressure of the liquid collecting tank reaches 5Bar, the liquid collecting tank draining operation begins;

[0109] When the liquid level in the inlet collecting tank is drained, the pressurization and inlet collecting tank process flow is restored.

[0110] The utility model analyzes the frequent increase in the pressure difference of the filter at the inlet of the BOG compressor and finds that the main reason for the filter clogging during normal operation is that the suction components contain heavy components such as ethane and propane that exceed the design content of the filter. The stored LNG is often LNG cargo with high density, and the generated boil-off gas contains more heavy components, which forms a liquid film on the pores of the filter at the suction port of the compressor, causing the filter pressure difference to increase.

[0111] Based on this situation, in line with the principles of safe production and energy conservation and consumption reduction, the original purging and exhaust process pipeline flow was technically transformed, the inlet filter was reversely purged to the filter tank and circulated back to the BOG compressor inlet for repeated use; the BOG compressor outlet was used to introduce BOG instead of nitrogen to pressurize and exhaust the liquid collecting tank.

[0112] The utility model is a process treatment method for purging and draining the inlet filter and liquid collecting tank of BOG compressor. By replacing normal temperature nitrogen with BOG as the purge gas for the inlet filter of BOG compressor and the booster gas for the inlet liquid collecting tank, the purging work of the inlet filter of BOG and the draining work of the liquid collecting tank can be completed safely and quickly, and at the same time, liquid nitrogen resources can be saved to ensure the stability of the calorific value of downstream BOG users.

[0113] The utility model is mainly suitable for the purging and pressurizing and draining operations of the inlet filter and the liquid collecting tank of the low-temperature BOG compressor.

[0114] The device can be applied to the drainage operations of LNG unloading pipelines and LNG export pipelines in LNG receiving stations. It is a pre-treatment measure for emptying the LNG pipeline or replacing and purging it.

[0115] It should be noted that all electronic components involved in the present invention adopt the existing technology, and the above-mentioned components are electrically connected to the controller, and the control circuit between the controller and each component is the existing technology.

[0116] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-restrictive from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention. Any reference numeral in a claim should not be regarded as limiting the claim to which it relates.

[0117] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0118] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A BOG compressor inlet filter and liquid collecting tank purge device, characterized in that: The invention comprises a liquid separation tank (1), a liquid collection tank (2) and a plurality of compressors (3) arranged in parallel, wherein the top of the liquid separation tank (1) is connected to one end of a gaseous natural gas pipeline (4), and the top of the liquid separation tank (1) is also connected to the inlet of each compressor (3) through pipeline 1; the outlet of each compressor (3) is connected to one end of pipeline 2, and a filter (5) is fixedly installed on pipeline 1 near the inlet of the compressor (3); the top of the liquid collection tank (2) is connected to one end of a nitrogen pipeline (6), and the top of the liquid collection tank (2) is connected to the bottom of the liquid separation tank (1) through pipeline 3, and the bottom of the liquid collection tank (2) is connected to one end of a discharge pipeline; The pipeline 2 is connected to the portion of the pipeline 1 corresponding to the filter (5) and the compressor (3) through the return air pipeline 1 (9), and the portion of the pipeline 1 corresponding to the filter (5) and the liquid separation tank (1) is connected to the nitrogen pipeline (6) through the return air pipeline 2 (10).

2. The BOG compressor inlet filter and liquid collecting tank purge device according to claim 1, characterized in that: A filter tank (7) is also fixedly mounted on the second return air pipeline (10).

3. The BOG compressor inlet filter and liquid collecting tank purge device according to claim 2, characterized in that: The return air pipeline 1 (9) and / or the return air pipeline 2 (10) are respectively fixedly mounted with a temperature gauge (8) at a location between the connection point with the nitrogen pipeline (6) and the filter tank (7).

4. The BOG compressor inlet filter and liquid collecting tank purge device according to claim 2, characterized in that: The return air pipeline 1 (9) is also connected to the return air pipeline 2 (10) via the return air pipeline 3 (11) at a location between the return air pipeline 2 (10) and the nitrogen pipeline (6) and the filter tank (7).

5. The BOG compressor inlet filter and liquid collecting tank purge device according to claim 4, characterized in that: A valve 1 (12) is fixedly installed at the connection point between the return air pipeline 3 (11) and the return air pipeline 1 (9) and at the positions between the two ends of the return air pipeline 1 (9).

6. The BOG compressor inlet filter and liquid collecting tank purge device according to any one of claims 2 to 5, characterized in that: A valve 2 (13) is fixedly installed on the return air pipeline 2 (10) near the connection point between the return air pipeline 2 and the pipeline 1.

7. The BOG compressor inlet filter and liquid collecting tank purge device according to claim 6, characterized in that: Valves 3 (14) are fixedly installed on the return air pipeline 2 (10) at locations close to the inlet and outlet of the filter tank (7).

8. The BOG compressor inlet filter and liquid collecting tank purge device according to any one of claims 1 to 5, characterized in that: A valve four (15) is fixedly installed on the return air pipeline two (10) near the point where it is connected with the nitrogen pipeline (6).

9. The BOG compressor inlet filter and liquid collecting tank purge device according to any one of claims 1 to 5, characterized in that: A valve five (16) is fixedly installed at the other end of the nitrogen pipeline (6).

10. The BOG compressor inlet filter and liquid collecting tank purge device according to any one of claims 1 to 5, characterized in that: The number of the compressors (3) is two.

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