Steam recovery system suitable for liquefied hydrocarbon storage tank

Abstract

The invention provides a steam recovery system suitable for a liquefied hydrocarbon storage tank. The steam recovery system comprises a pre-filter, a sweeping line compressor, a cooler and an oil-water separator. When the liquefied hydrocarbon storage tank is maintained, the liquefied hydrocarbon storage tank needing to be maintained is communicated with the pre-filter, a liquid phase of product steam is filtered out in the pre-filter, a gas phase enters the sweeping line compressor to be compressed and then enters the cooler, the gas phase enters the oil-water separator after being cooled in the cooler, the oil-water separator carries out gas-liquid separation on the product steam, and the oil-water separator carries out oil-water separation on the product steam. And the separated gas phase can enter a fuel gas system for combustion and use, or enter a similar liquefied hydrocarbon storage tank which is not in a maintenance state, and the liquid phase enters the similar liquefied hydrocarbon storage tank which is not in the maintenance state. According to the steam recovery system suitable for the liquefied hydrocarbon storage tank, product steam in the liquefied hydrocarbon storage tank to be maintained can be utilized or transferred into other similar liquefied hydrocarbon storage tanks, and the problem of environmental pollution or resource waste caused by emptying of the product steam through torch combustion is solved.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas engineering, and in particular to a steam recovery system suitable for a liquefied hydrocarbon storage tank. Background Art

[0002] The liquefied hydrocarbon products of existing natural gas land terminals are often produced and sold by storing them in tanks and loading them onto trucks for transportation. When the liquefied hydrocarbon product storage tanks of land terminals are repaired or overhauled, the large amount of product vapor remaining in the tanks is mostly released into the flare and then discharged after combustion, which on the one hand brings environmental risks, and on the other hand also causes waste of resources. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a steam recovery system suitable for a liquefied hydrocarbon storage tank, which aims to solve the environmental problems and resource waste caused by the residual product steam in the liquefied hydrocarbon storage tank being discharged to a flare for combustion in the related art.

[0004] The present invention provides a steam recovery system suitable for a liquefied hydrocarbon storage tank, comprising: A pre-filter, wherein the inlet of the pre-filter is used to be connected to the top of a plurality of liquefied hydrocarbon storage tanks; A sweeping line compressor, the inlet of which is connected to the first gas phase outlet of the pre-filter; a cooler, wherein the inlet of the cooler is connected to the outlet of the sweeping compressor; An oil-water separator, wherein the inlet of the oil-water separator is connected to the outlet of the cooler, the second gas phase outlet of the oil-water separator is used to connect to the fuel gas system and the top of each of the liquefied hydrocarbon storage tanks, and the second liquid phase outlet of the oil-water separator is used to connect to the bottom of each of the liquefied hydrocarbon storage tanks.

[0005] According to the steam recovery system suitable for liquefied hydrocarbon storage tanks provided by the present invention, the inlet of the pre-filter is also used to connect to the normal temperature venting manifold at the loading pumps of the plurality of liquefied hydrocarbon storage tanks.

[0006] The steam recovery system suitable for liquefied hydrocarbon storage tanks provided by the present invention also includes a flare system, which is connected to the normal temperature vent manifold, the top of the pre-filter and the top of the oil-water separator through a vent line.

[0007] According to the steam recovery system applicable to the liquefied hydrocarbon storage tank provided by the present invention, safety valves are provided between the pre-filter and the venting pipeline, and between the oil-water separator and the venting pipeline.

[0008] According to the steam recovery system applicable to the liquefied hydrocarbon storage tank provided by the present invention, a first liquid phase outlet is further provided at the bottom of the pre-filter, and a first control valve is provided at the first liquid phase outlet.

[0009] According to the steam recovery system suitable for liquefied hydrocarbon storage tanks provided by the present invention, a second control valve is provided between the second gas phase outlet of the oil-water separator and the fuel gas system and the plurality of liquefied hydrocarbon storage tanks.

[0010] According to the steam recovery system applicable to liquefied hydrocarbon storage tanks provided by the present invention, a third control valve is provided between the second liquid phase outlet of the oil-water separator and the plurality of liquefied hydrocarbon storage tanks.

[0011] According to the steam recovery system suitable for liquefied hydrocarbon storage tanks provided by the present invention, a branch pipeline is connected to the normal temperature vent manifold at the loading pump of each liquefied hydrocarbon storage tank, and one end of a plurality of branch pipelines away from the normal temperature vent manifold is connected to a gas main pipe, and the other end of the gas main pipe is respectively connected to the vent line and the inlet of the pre-filter, and a fourth control valve is arranged between the gas main pipe and the vent line, and a fifth control valve is arranged between the gas main pipe and the pre-filter.

[0012] According to the steam recovery system applicable to the liquefied hydrocarbon storage tank provided by the present invention, a pressure gauge and a thermometer are provided at the inlet of the pre-filter.

[0013] According to the steam recovery system applicable to liquefied hydrocarbon storage tanks provided by the present invention, a one-way valve is provided between the cooler and the oil-water separator, and the conducting direction of the one-way valve is from the cooler to the oil-water separator.

[0014] The present invention adopts the above technical solution, which has the following advantages: The steam recovery system for liquefied hydrocarbon storage tanks provided by the present invention comprises a pre-filter, a sweep compressor, a cooler and an oil-water separator. The inlet of the pre-filter is used to connect with the tops of multiple liquefied hydrocarbon storage tanks, the first gas phase outlet of the pre-filter is connected with the inlet of the sweep compressor, the outlet of the sweep compressor is connected with the inlet of the cooler, the outlet of the cooler is connected with the inlet of the oil-water separator, the second gas phase outlet of the oil-water separator is used to connect with the fuel gas system and the tops of each liquefied hydrocarbon storage tank, and the second liquid phase outlet of the oil-water separator is used to connect with the bottom of each liquefied hydrocarbon storage tank. When inspecting or repairing a liquefied hydrocarbon storage tank, the liquefied hydrocarbon storage tank to be repaired is connected to the pre-filter, and the sweep compressor is turned on. Driven by the sweep compressor, the product vapor in the liquefied hydrocarbon storage tank connected to the pre-filter enters the pre-filter, and the product vapor filtered out of the liquid phase in the pre-filter enters the sweep compressor and is compressed before entering the cooler. The product vapor is cooled and partially liquefied in the cooler, and then enters the oil-water separator. The oil-water separator separates the gas and liquid of the incoming product, and the separated gas phase is discharged from the second gas phase outlet at the top. Under the control of the staff, the gas phase enters the fuel gas system for combustion or enters the top of the same liquefied hydrocarbon storage tank that is not under repair or overhaul. The liquid phase separated in the oil-water separator enters the bottom of the same liquefied hydrocarbon storage tank that is not under repair or overhaul. The steam recovery system for liquefied hydrocarbon storage tanks provided by the present invention can utilize or transfer the residual product steam in the liquefied hydrocarbon storage tank to be repaired or overhauled to other similar liquefied hydrocarbon storage tanks, thereby solving the problem of environmental pollution or resource waste caused by the residual product steam being discharged through flare combustion. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 It is a schematic diagram of a steam recovery system applicable to a liquefied hydrocarbon storage tank provided in one embodiment of the present invention.

[0017] Reference numerals: 110: pre-filter; 111: first gas phase outlet; 112: first liquid phase outlet; 120: sweep line compressor; 130: cooler; 140: oil-water separator; 141: second gas phase outlet; 142: second liquid phase outlet; 200: liquefied hydrocarbon storage tank; 310: sweep line gas branch pipeline; 320: sweep line gas main pipeline; 400: fuel gas system; 500: flare system; 510: vent pipeline; 600: safety valve; 710: first control valve; 720: second control valve; 730: third control valve; 740: fourth control valve; 750: fifth control valve; 810: branch pipeline; 820: gas main pipeline; 900: one-way valve. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0020] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0021] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like 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 an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0022] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0023] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0024] The steam recovery system for liquefied hydrocarbon storage tanks provided by the present invention comprises a pre-filter, a sweep compressor, a cooler and an oil-water separator. The inlet of the pre-filter is used to connect with the top of each liquefied hydrocarbon storage tank, the first gas phase outlet of the pre-filter is connected with the inlet of the sweep compressor, the outlet of the sweep compressor is connected with the inlet of the cooler, the outlet of the cooler is connected with the inlet of the oil-water separator, the second gas phase outlet of the oil-water separator is used to connect with the fuel gas system and the top of each liquefied hydrocarbon storage tank, and the second liquid phase outlet of the oil-water separator is used to connect with the bottom of multiple liquefied hydrocarbon storage tanks. When inspecting or repairing a liquefied hydrocarbon storage tank, the liquefied hydrocarbon storage tank to be repaired is connected to the pre-filter, and the sweep compressor is turned on. Driven by the sweep compressor, the product vapor in the liquefied hydrocarbon storage tank connected to the pre-filter enters the pre-filter, and the product vapor filtered out of the liquid phase in the pre-filter enters the sweep compressor and is compressed before entering the cooler. The product vapor is cooled and partially liquefied in the cooler, and then enters the oil-water separator. The oil-water separator separates the gas and liquid of the incoming product, and the separated gas phase is discharged from the second gas phase outlet at the top. Under the control of the staff, the gas phase enters the fuel gas system for combustion or enters the top of the same liquefied hydrocarbon storage tank that is not under repair or overhaul. The liquid phase separated in the oil-water separator enters the bottom of the same liquefied hydrocarbon storage tank that is not under repair or overhaul. The steam recovery system for liquefied hydrocarbon storage tanks provided by the present invention can utilize or transfer the residual product steam in the liquefied hydrocarbon storage tank to be repaired or overhauled to other similar liquefied hydrocarbon storage tanks, thereby solving the problem of environmental pollution or resource waste caused by the residual product steam being discharged through flare combustion.

[0025] Combine the following Figure 1 A vapor recovery system for use with a liquefied hydrocarbon storage tank of the present invention is described.

[0026] An embodiment of the present invention provides a vapor recovery system applicable to a liquefied hydrocarbon storage tank, the system comprising a pre-filter 110 , a sweep compressor 120 , a cooler 130 and an oil-water separator 140 .

[0027] The liquefied hydrocarbon storage tank 200 includes multiple, for example, n butane storage tanks for containing butane and m propane storage tanks for containing propane. A sweep gas branch pipeline 310 is provided on the top of the n butane storage tanks and the top of the m propane storage tanks. The multiple sweep gas branch pipelines 310 are gathered at one point away from the ends of the liquefied hydrocarbon storage tank 200 and connected to one end of the sweep gas main pipe 320 at this point. The other end of the sweep gas main pipe 320 is connected to the inlet of the pre-filter 110. The inlet of the pre-filter 110 can be set at the middle position of the pre-filter 110, and the pre-filter 110 is used to filter the liquid phase in the product vapor.

[0028] Since the density of the gas phase of the product steam is lower than that of the liquid phase, a first gas phase outlet 111 is provided at the top of the prefilter 110, and the first gas phase outlet 111 of the prefilter 110 is connected to the inlet of the sweep line compressor 120 through a pipeline. The sweep line compressor 120 is used to provide power for the flow of the product steam.

[0029] The outlet of the sweeping compressor 120 is connected to the inlet of the cooler 130. When the product steam enters the cooler 130, it exchanges heat with the condensate and is cooled. At this time, the product steam is partially liquefied. The cooled product steam is in a state where gas and liquid phases coexist. Driven by the sweeping compressor 120, it enters the oil-water separator 140, and the separation of gas and liquid phases is realized in the oil-water separator 140.

[0030] The top of the oil-water separator 140 is provided with a second gas phase outlet 141, which is connected to the fuel gas system 400 through a pipeline, and the separated gas phase can enter the fuel gas system 400 through the pipeline for combustion and reuse. At the same time, the second gas phase outlet 141 can also be connected to the top of each liquefied hydrocarbon storage tank 200 through a pipeline, and the separated gas phase can enter the top of the corresponding liquefied hydrocarbon storage tank 200 through the corresponding pipeline for collection.

[0031] The bottom of the oil-water separator 140 is provided with a second liquid phase outlet 142 , which is connected to the bottom of each liquefied hydrocarbon storage tank 200 through a pipeline, and the separated liquid phase can enter the bottom of the corresponding liquefied hydrocarbon storage tank 200 through the corresponding pipeline for collection.

[0032] When a liquefied hydrocarbon storage tank 200 is inspected or repaired, the liquefied hydrocarbon storage tank 200 to be repaired or inspected can be connected to the pre-filter 110, and then the sweeping compressor 120 is turned on. Under the drive of the sweeping compressor 120, the residual product vapor in the liquefied hydrocarbon storage tank 200 to be inspected or repaired is extracted and enters the pre-filter 110, the liquid phase in the product vapor is filtered by the pre-filter 110, and the gas phase in the product vapor enters the sweeping compressor 120 through the first gas phase outlet 111 at the top of the pre-filter 110.

[0033] The product vapor entering the sweep compressor 120 is compressed and then enters the cooler 130, where it is cooled. During the cooling process, part of the product vapor is liquefied. At this time, the product vapor is in a state where gas and liquid coexist.

[0034] After being cooled by the cooler 130, the product steam enters the oil-water separator 140, where gas-liquid separation is completed. The separated gas phase is discharged from the second gas phase outlet 141 at the top of the oil-water separator 140, and under the control of the staff, the gas phase is selectively introduced into the fuel gas system 400 for combustion and reuse, or selectively introduced into the liquefied hydrocarbon storage tank 200 that is not in a state of waiting for maintenance or overhaul and contains liquefied hydrocarbons of the same type as the product steam for collection.

[0035] The steam recovery system for liquefied hydrocarbon storage tanks provided by the present invention can burn and reuse the product steam remaining in the liquefied hydrocarbon storage tank 200 to be inspected or repaired, or transfer it to other liquefied hydrocarbon storage tanks 200 of the same type that are not in a state of being inspected or repaired for collection, thereby solving the problem of environmental pollution and waste of resources caused by the combustion and venting of residual product steam in the related art.

[0036] In some embodiments, the inlet of the pre-filter 110 is also used to connect to the normal temperature venting manifold at the loading pumps of the plurality of liquefied hydrocarbon storage tanks 200 .

[0037] Specifically, a loading pump is installed on each liquefied hydrocarbon storage tank 200. When the loading pump pumps liquefied hydrocarbon, part of the liquefied hydrocarbon is vaporized. Currently, the vaporized hydrocarbon gas is transported to the flare system 500 through a normal temperature venting manifold for combustion and venting, which will cause environmental pollution and waste of resources.

[0038] The steam recovery system suitable for liquefied hydrocarbon storage tanks provided by the present invention connects the normal temperature vent manifold to the pre-filter 110. Under the drive of the sweeping line compressor 120, the vaporized product steam is transported to the pre-filter 110, the liquid phase in the product steam is filtered by the pre-filter 110, and the gas phase in the product steam enters the sweeping line compressor 120 through the first gas phase outlet 111 at the top of the pre-filter 110.

[0039] The product vapor entering the sweep compressor 120 is compressed and then enters the cooler 130, where it is cooled. During the cooling process, part of the product vapor is liquefied. At this time, the product vapor is in a state where gas and liquid coexist.

[0040] After being cooled by the cooler 130, the product steam enters the oil-water separator 140, where gas-liquid separation is completed. The separated gas phase is discharged from the second gas phase outlet 141 at the top of the oil-water separator 140, and under the control of the staff, the gas phase is selectively introduced into the fuel gas system 400 for combustion and reuse, or selectively introduced into the liquefied hydrocarbon storage tank 200 that is not in a state of waiting for maintenance or overhaul and contains liquefied hydrocarbons of the same type as the product steam for collection.

[0041] In some embodiments, the steam recovery system further includes a flare system 500 , which is connected to the normal temperature vent manifold, the top of the pre-filter 110 , and the top of the oil-water separator 140 through a vent line 510 .

[0042] The technical solution provided in this embodiment allows the staff to selectively control the product steam discharged from the normal temperature vent manifold to directly enter the flare system 500 through the vent pipeline 510 for combustion and venting, or selectively control the product steam discharged from the normal temperature vent manifold to enter the pre-filter 110, and after the above-mentioned series of treatments, enter the fuel gas system 400 for combustion and reuse, or enter the liquefied hydrocarbon storage tank 200 for collection.

[0043] Moreover, under extreme working conditions, the gas phase in the pre-filter 110 and the oil-water separator 140 can also directly enter the flare system 500 through the venting pipeline 510 for direct combustion and venting treatment.

[0044] In some embodiments, a safety valve 600 is provided between the pre-filter 110 and the vent line 510 and between the oil-water separator 140 and the vent line 510. When the sweep compressor 120 fails and the pressure in the pre-filter 110 or the oil-water separator 140 is too high and exceeds the conduction pressure of the safety valve 600, the safety valve 600 opens to release the pressure into the vent line 510, and the gas enters the flare system 500 through the vent line 510 for combustion and venting, so as to ensure the safe operation of the system.

[0045] In some embodiments, a first liquid phase outlet 112 is further provided at the bottom of the pre-filter 110, a drain pipe is connected to the first liquid phase outlet 112, and a first control valve 710 is provided on the drain pipe, and the first control valve 710 may be a ball valve. The drain pipe may be opened to discharge the liquid phase of the product vapor filtered out of the pre-filter 110.

[0046] In some embodiments, a second control valve 720 is provided between the second gas phase outlet 141 of the oil-water separator 140 and the fuel gas system 400 and between the second gas phase outlet 141 and the plurality of liquefied hydrocarbon storage tanks 200 . The second control valve 720 may also be a ball valve.

[0047] The staff can selectively open one or more of the second control valves 720 to connect the fuel gas system 400 or the corresponding liquefied hydrocarbon storage tank 200 to the second gas phase outlet 141, and then the product vapor discharged from the second gas phase outlet 141 enters the connected fuel gas system 400 or the connected liquefied hydrocarbon storage tank 200.

[0048] In some embodiments, a third control valve 730 is disposed between the second liquid phase outlet 142 of the oil-water separator 140 and the plurality of liquefied hydrocarbon storage tanks 200 . The third control valve 730 may also be a ball valve.

[0049] The staff can selectively open one or more of the second control valves 720 to connect the corresponding liquefied hydrocarbon storage tank 200 with the second liquid phase outlet 142 , so that the product vapor discharged from the second liquid phase outlet 142 enters the connected liquefied hydrocarbon storage tank 200 .

[0050] In some embodiments, a branch pipeline 810 is connected to the normal temperature vent manifold at the loading pump of each liquefied hydrocarbon storage tank 200, and multiple branch pipelines 810 converge at one point away from one end of the normal temperature vent manifold, at which point they are connected to one end of a gas main pipe 820, and the other end of the gas main pipe 820 is connected to the vent air pipeline and the inlet of the pre-filter 110.

[0051] A fourth control valve 740 may be provided at the location where the gas main pipe 820 is connected to the vent line 510, and a fifth control valve 750 may be provided at the location where the gas main pipe 820 is connected to the pre-filter 110. During operation, the staff may conduct the fourth control valve 740 and close the fifth control valve 750, so that the product steam discharged from the normal temperature vent manifold directly enters the flare system 500 through the vent line 510 for combustion and venting. The staff may also close the fourth control valve 740 and conduct the fifth control valve 750, so that the product steam discharged from the normal temperature vent manifold enters the pre-filter 110, and enters the fuel gas system 400 for combustion and reuse through the above-mentioned subsequent treatment, or transfers to other liquefied hydrocarbon storage tanks 200 for collection.

[0052] In some embodiments, a pressure gauge and a thermometer may be provided at the inlet of the pre-filter 110 , and the staff may observe the inlet pressure of the pre-filter 110 through the pressure gauge, and may observe the temperature of the product steam entering the pre-filter 110 through the thermometer.

[0053] In some embodiments, a one-way valve 900 is further provided between the cooler 130 and the oil-water separator 140 . The conducting direction of the one-way valve 900 is from the cooler 130 to the oil-water separator 140 , which can prevent the gas in the oil-water separator 140 from flowing back into the cooler 130 .

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; 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, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A vapor recovery system suitable for a liquefied hydrocarbon storage tank, characterized in that: include: A pre-filter (110), wherein an inlet of the pre-filter (110) is used to be connected to the tops of a plurality of liquefied hydrocarbon storage tanks (200); A sweeping compressor (120), wherein an inlet of the sweeping compressor (120) is connected to a first gas phase outlet (111) of the pre-filter (110); A cooler (130), wherein an inlet of the cooler (130) is connected to an outlet of the sweeping compressor (120); An oil-water separator (140), wherein the inlet of the oil-water separator (140) is connected to the outlet of the cooler (130), the second gas phase outlet (141) of the oil-water separator (140) is used to be connected to the fuel gas system (400) and the top of each of the liquefied hydrocarbon storage tanks (200), and the second liquid phase outlet (142) of the oil-water separator (140) is used to be connected to the bottom of each of the liquefied hydrocarbon storage tanks (200).

2. The vapor recovery system for a liquefied hydrocarbon storage tank according to claim 1, characterized in that: The inlet of the pre-filter (110) is also used to be connected to the normal temperature venting manifold at the loading pumps of the plurality of liquefied hydrocarbon storage tanks (200).

3. The vapor recovery system for a liquefied hydrocarbon storage tank according to claim 2, characterized in that: It also includes a flare system (500), wherein the flare system (500) is connected to the normal temperature vent manifold, the top of the pre-filter (110), and the top of the oil-water separator (140) via a vent line (510).

4. The vapor recovery system for a liquefied hydrocarbon storage tank according to claim 3, characterized in that: Safety valves (600) are provided between the pre-filter (110) and the venting pipeline (510), and between the oil-water separator (140) and the venting pipeline (510).

5. The vapor recovery system for a liquefied hydrocarbon storage tank according to claim 1, characterized in that: A first liquid phase outlet (112) is also provided at the bottom of the pre-filter (110), and a first control valve (710) is provided at the first liquid phase outlet (112).

6. The vapor recovery system for a liquefied hydrocarbon storage tank according to claim 1, characterized in that: A second control valve (720) is provided between the second gas phase outlet (141) of the oil-water separator (140), the fuel gas system (400), and the plurality of liquefied hydrocarbon storage tanks (200).

7. The vapor recovery system for a liquefied hydrocarbon storage tank according to claim 1, characterized in that: A third control valve (730) is provided between the second liquid phase outlet (142) of the oil-water separator (140) and the plurality of liquefied hydrocarbon storage tanks (200).

8. The vapor recovery system for a liquefied hydrocarbon storage tank according to claim 3, characterized in that: A branch pipeline (810) is connected to the normal temperature venting manifold at the loading pump of each liquefied hydrocarbon storage tank (200); one end of each of the branch pipelines (810) away from the normal temperature venting manifold is connected to a gas main pipe (820); the other end of the gas main pipe (820) is respectively connected to the venting pipeline (510) and the inlet of the pre-filter (110); a fourth control valve (740) is provided between the gas main pipe (820) and the venting pipeline (510); and a fifth control valve (750) is provided between the gas main pipe (820) and the pre-filter (110).

9. The vapor recovery system for a liquefied hydrocarbon storage tank according to claim 1, characterized in that: A pressure gauge and a thermometer are provided at the inlet of the pre-filter (110).

10. The vapor recovery system for a liquefied hydrocarbon storage tank according to claim 1, characterized in that: A one-way valve (900) is provided between the cooler (130) and the oil-water separator (140), and the conducting direction of the one-way valve (900) is from the cooler (130) to the oil-water separator (140).

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