Washing and heavy hydrocarbon removal equipment of LNG (Liquefied Natural Gas) device

Abstract

The utility model discloses washing and heavy hydrocarbon removal equipment of an LNG (Liquefied Natural Gas) device, which relates to the technical field of pretreatment of natural gas liquefaction devices and comprises a main heat exchanger, a heavy hydrocarbon washing tower, a low-temperature separator and an LNG flash tank, and a cooling channel, a condensation channel and a condensation supercooling channel are arranged in the main heat exchanger; an inlet end of the cooling channel is connected with a dry natural gas feeding pipeline for conveying raw material gas, an outlet end of the cooling channel is communicated with a gas phase inlet of the heavy hydrocarbon washing tower, and a gas phase outlet of the heavy hydrocarbon washing tower and an inlet of the low-temperature separator are respectively communicated with two ends of the condensation channel; a gas phase outlet of the low-temperature separator and an inlet of the LNG flash tank are respectively communicated with two ends of the condensation supercooling channel, and a liquid phase outlet of the LNG flash tank and a liquid phase outlet of the low-temperature separator are both communicated with a washing liquid inlet of the heavy hydrocarbon washing tower. The device can realize the function of removing heavy hydrocarbon and aromatic hydrocarbon at the same time, and the equipment consumption and consumption of the device are comprehensively reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of natural gas liquefaction device pretreatment, specifically, relate to a kind of washing and heavy hydrocarbon equipment of LNG device. BACKGROUND

[0002] At present, the raw material natural gas of natural gas liquefaction device is various, mainly for pipe transportation natural gas, scattered wellhead natural gas, shale gas, tight gas etc..In the natural gas liquefaction process, due to the heavy hydrocarbon and various aromatic hydrocarbons of pentane and above in raw material natural gas, and heavy hydrocarbon and aromatic hydrocarbon content change greatly, if heavy hydrocarbon and aromatic hydrocarbon are not removed thoroughly, it will cause cold box and pipeline blockage and freezing problem under low temperature working condition, therefore, it must be removed thoroughly before low temperature condensation, liquefaction or in condensation process.

[0003] Under prior art, commonly used heavy hydrocarbon removal technology mainly has: adsorption process of solid adsorbent, low temperature liquid hydrocarbon washing process etc..

[0004] Adsorption process of solid adsorbent is the adsorption removal of heavy hydrocarbon using the strong molecular adsorption selectivity and high adsorption characteristics of solid adsorbent under low partial pressure;Many patent applications in prior art are using this kind of process, but adsorption process of solid adsorbent is limited by solid adsorbent saturation, adsorption capacity and regeneration degree, not suitable for the case that raw material natural gas treatment capacity is large and heavy hydrocarbon content in raw material natural gas increases sharply.

[0005] Low-temperature liquid hydrocarbon washing process is a method that uses the characteristics of heavy hydrocarbons and aromatic hydrocarbons having high solubility in liquid hydrocarbons above C2 to remove heavy hydrocarbons. In the prior art, CN103031169A "natural gas liquefaction and heavy hydrocarbon treatment method and device", CN104087357A "a method and system for removing heavy hydrocarbons from a natural gas liquefaction process", CN106978226A "a process and system for separating heavy hydrocarbons from natural gas by deep cooling method", CN211199147U "a heavy hydrocarbon removal device", CN111964353A "a natural gas liquefaction and condensate recovery integrated device and method", CN212680113U "a hydrocarbon separation device using a divided wall column for rectification and dehydrocarbon", CN213514662U "a small-scale flare gas to LNG heavy hydrocarbon removal device", CN213977590U "a mixed hydrocarbon recovery and LNG modular device", CN112812806A "a process and system for producing light hydrocarbons and LNG from oilfield associated gas", all cool the natural gas coming out of the washing tower to a certain temperature to produce condensed liquid hydrocarbons, and then use a low-temperature pump to pressurize the condensed liquid hydrocarbons and send them to the top of the washing tower as washing liquid. However, when the C2 or higher components in the raw natural gas become less at the set condensation temperature, the amount of condensed liquid hydrocarbons becomes less, making it difficult to establish a washing liquid circulation. CN105890284A "liquefied natural gas heavy hydrocarbon removal device and method" also cools the natural gas coming out of the washing tower in the reflux condenser placed at the top of the washing tower to a certain temperature to produce condensed liquid hydrocarbons, and then uses the static pressure of the liquid hydrocarbons to send them to the top of the washing tower as washing liquid, thus eliminating the need for a reflux low-temperature pump. However, when the C2 or higher components in the raw natural gas become less at the set condensation temperature, the amount of condensed liquid hydrocarbons becomes less, making it difficult to establish a washing liquid circulation. CN103351896A "a shale gas dehydration and heavy hydrocarbon removal method and device" uses the de-ethane tower top distillate gas condensate for washing, and CN103409188A "a process device and method for removing heavy hydrocarbons in a natural gas liquefaction process" uses a tower top reflux condenser and expansion refrigeration for washing. However, the pressure of the expanded natural gas is reduced, and the energy consumption of the subsequent natural gas liquefaction process is increased. CN105695015A "a new natural gas heavy hydrocarbon removal device and method" uses an LNG circulating pump to pressurize a small amount of LNG and send it to the washing tower as washing liquid. However, new pentane cannot be completely washed out during the washing process, and natural gas containing new pentane will still freeze at low temperatures.

[0006] Therefore, there is an urgent need for a washing heavy hydrocarbon removal process and equipment that can completely remove heavy hydrocarbons and aromatic hydrocarbons from an LNG device. Invention content

[0007] The utility model discloses a kind of washing heavy hydrocarbon equipment of LNG device, can simultaneously realize heavy hydrocarbon and aromatic hydrocarbon removal function, and the equipment consumption of device is reduced comprehensively, and the overall reduction of device investment and production cost is realized.

[0008] To achieve the purpose of the utility model, the technical scheme adopted is: a kind of washing heavy hydrocarbon equipment of LNG device, including main heat exchanger, heavy hydrocarbon washing tower, low temperature separator and LNG flash tank, and main heat exchanger has cooling channel, condensation channel, condensation supercooling channel in;The import end of the cooling channel is connected with the dry natural gas feed pipe of conveying raw material gas, and the outlet end of cooling channel is communicated with the gas phase inlet of heavy hydrocarbon washing tower, and the gas phase outlet of heavy hydrocarbon washing tower, the inlet of low temperature separator is communicated with the two ends of condensation channel respectively, and the gas phase outlet of low temperature separator, the inlet of LNG flash tank is communicated with the two ends of condensation supercooling channel respectively, and the liquid phase outlet of LNG flash tank, with the liquid phase outlet of low temperature separator are all communicated with the washing liquid feed port of heavy hydrocarbon washing tower.

[0009] Further, two sections of packing or two sections of tray are arranged in the heavy hydrocarbon washing tower in up-down arrangement, and the washing liquid feed port of heavy hydrocarbon washing tower is two, and the two washing liquid feed ports on heavy hydrocarbon washing tower are located above two sections of packing or two sections of tray respectively, and the liquid phase outlet of LNG flash tank, with the liquid phase outlet of low temperature separator are communicated with the two washing liquid feed ports on heavy hydrocarbon washing tower respectively.

[0010] Further, the low temperature separator is located at the top of heavy hydrocarbon washing tower, and the liquid phase outlet of low temperature separator is communicated with the washing liquid feed port in the middle of heavy hydrocarbon washing tower.

[0011] Further, LNG reflux pump is arranged between the liquid phase outlet of LNG flash tank and the washing liquid feed port of heavy hydrocarbon washing tower.

[0012] Further, the heavy hydrocarbon washing tower is also communicated with liquid heavy hydrocarbon pipeline for conveying liquid heavy hydrocarbon outward.

[0013] Further, reboiler is installed on the heavy hydrocarbon washing tower.

[0014] Further, the LNG flash tank is also communicated with liquefied natural gas pipeline for conveying liquefied natural gas outward.

[0015] Further, the LNG flash tank is also provided with control valve four.

[0016] Further, control valve one is arranged on the nitrogen-rich tail gas pipeline.

[0017] Further, the main heat exchanger further has a reheating channel, the gas phase outlet of the LNG flash tank is communicated with one end of the reheating channel, and the other end of the reheating channel is further communicated with a nitrogen-rich tail gas pipeline for conveying the nitrogen-rich tail gas outward.

[0018] Further, the main heat exchanger further has a refrigerant channel for refrigerant flow.

[0019] Further, the gas pressure in the dry natural gas feeding pipeline is 3.0-6.5 MPa.

[0020] Further, the cooling temperature of the cooling channel ranges from -40 DEG C to 20 DEG C.

[0021] Further, the condensing temperature of the condensing channel ranges from -80 DEG C to -35 DEG C.

[0022] The beneficial effects of the present application are as follows:

[0023] (1) The present application has the characteristics of double washing liquid circulation process and complete removal of heavy hydrocarbon and aromatic hydrocarbon, and compared with the prior art, the principle is simple and easy to understand, and is suitable for technical personnel and operators to master the system of the device and process; meanwhile, the present application can simultaneously realize the heavy hydrocarbon and aromatic hydrocarbon removal function, comprehensively reduces the equipment consumption and consumption of the device, and realizes the overall reduction of device investment and production cost.

[0024] (2) In the present application, the liquid phase outlet of the LNG flash tank and the liquid phase outlet of the low-temperature separator are both communicated with the washing liquid feeding port of the heavy hydrocarbon washing tower, so that the liquid phase of the LNG flash tank and the liquid phase of the low-temperature separator are used as washing liquid in the heavy hydrocarbon washing tower, which is suitable for the wide variation of dry natural gas components.

[0025] (3) The present application also has the heavy hydrocarbon and aromatic hydrocarbon recovery function, and can produce LPG and light oil, so that the economic benefit is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0026] The accompanying drawings illustrate exemplary embodiments of the present application and, together with the general description of the application given above, and the detailed description of the embodiments given below, serve to explain the principles of the present application. These drawings are included herewith and constitute a part of this specification.

[0027] Figure 1 is a system flow chart of the heavy hydrocarbon washing equipment of the LNG device provided by the present application.

[0028] Markings in the drawings and corresponding component names:

[0029] T101 – Heavy hydrocarbon scrubbing tower, E101 – Main heat exchanger, V101 – Cryogenic separator, V102 – LNG flash tank, P101 – LNG reflux pump;

[0030] G1 - Dry natural gas feed pipeline, G2 - Condensed hydrocarbon pipeline, G3 - Liquid heavy hydrocarbon pipeline, G4 - Liquefied natural gas pipeline, G5 - Nitrogen-rich tail gas pipeline;

[0031] T1 - Cooling passage, T2 - Condensation passage, T3 - Condensation subcooling passage, T4 - Reheating passage, T5 - Refrigerant passage;

[0032] PV101 - Control Valve 1, TV101 - Control Valve 2, LV101 - Control Valve 3, LV102 - Control Valve 4. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present invention are shown in the accompanying drawings.

[0034] It should be noted that, where there is no conflict, the embodiments and features described in these embodiments can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] like Figure 1 As shown, the present invention provides a washing and heavy hydrocarbon removal device for an LNG plant, including a main heat exchanger E101, a heavy hydrocarbon washing tower T101, a cryogenic separator V101, and an LNG flash tank V102. The main heat exchanger E101 has a cooling channel T1, a condensing channel T2, a condensing subcooling channel T3, a reheating channel T4, and a refrigerant channel T5. The cooling channel T1, condensing channel T2, and condensing subcooling channel T3 are used to cool the flowing medium, the reheating channel T4 is used to heat the flowing medium, and the refrigerant channel T5 is used to transport the refrigerant.

[0036] The inlet end of the cooling channel T1 in the main heat exchanger E101 is connected to a dry natural gas feed pipe G1. The feed pipe is used to transport the dry natural gas into the cooling channel T1 in the main heat exchanger E101 for cooling. The outlet end of the cooling channel T1 is connected to the gas phase inlet at the bottom of the heavy hydrocarbon scrubbing tower T101 through a pipe, so that the dry natural gas is cooled down after passing through the cooling channel T1 and then sent to the bottom of the heavy hydrocarbon scrubbing tower T101 through the pipe.

[0037] The heavy hydrocarbon washing tower T101 has two sections of fillers arranged in an up-down manner, and a certain spacing is provided between the two sections of fillers, and the heavy hydrocarbon washing tower T101 further has two groups of spraying devices for spraying the spraying liquid, and each section of filler corresponds to one spraying device, and the cooled natural gas is located below the fillers when entering the heavy hydrocarbon washing tower T101, and the cooled natural gas moves upward through the fillers to the upper part of the heavy hydrocarbon washing tower T101, in the process, the spraying liquid sprayed by the spraying device washes the natural gas, and the natural gas exchanges heat and mass with the spraying liquid, so that the heavy hydrocarbon and the aromatic hydrocarbon in the natural gas are completely condensed to flow to the bottom of the heavy hydrocarbon washing tower T101, and then the liquid phase is heated by the reboiler, and the methane in the liquid phase evaporates, at this time, the gas phase generated after washing is discharged through the top of the heavy hydrocarbon washing tower T101. The remaining liquid phase at the bottom of the heavy hydrocarbon washing tower T101 is liquid heavy hydrocarbon, in order to facilitate the delivery of the liquid heavy hydrocarbon, the heavy hydrocarbon washing tower T101 is connected with a liquid heavy hydrocarbon pipeline G3, and a control valve three LV101 is further installed on the liquid heavy hydrocarbon pipeline G3.

[0038] The top of the heavy hydrocarbon washing tower T101 is connected with the inlet end of the condensation channel T2 through a pipeline, the outlet end of the condensation channel T2 is connected with the inlet end of the low-temperature separator V101 through a pipeline, and the natural gas after removing the heavy hydrocarbon by washing is discharged from the top of the heavy hydrocarbon washing tower T101, enters the condensation channel T2 of the main heat exchanger E101 through a pipeline, and enters the low-temperature separator V101 after condensation.

[0039] When the low-temperature separator V101 is installed, the low-temperature separator V101 can be placed at the top of the heavy hydrocarbon washing tower T101. The gas phase outlet of the low-temperature separator V101 is connected with the inlet end of the condensation supercooling channel T3 through a pipeline, the outlet end of the condensation supercooling channel T3 is connected with the inlet section of the LNG flash tank V102 through a pipeline; at the same time, the liquid phase outlet of the low-temperature separator V101 is connected with one of the spraying devices in the heavy hydrocarbon washing tower T101 through a condensation liquid hydrocarbon pipeline G2.

[0040] Since the low-temperature separator V101 is installed at the top of the heavy hydrocarbon washing tower T101, the liquid phase outlet of the low-temperature separator V101 can be connected with the lowermost spraying device in the heavy hydrocarbon washing tower T101 through the condensation liquid hydrocarbon pipeline G2, at this time, the liquid phase separated out by the low-temperature separator V101 is directly sent to the lowermost spraying device in the heavy hydrocarbon washing tower T101 by the static pressure of the condensation liquid hydrocarbon, and this design makes the condensation liquid hydrocarbon pipeline G2 become a liquid seal structure for preventing gas backflow on the low-temperature separator V101, thereby effectively preventing the gas backflow in the low-temperature separator V101.

[0041] The low temperature separator V101 separates gas and liquid, the separated gas is sent into the condensation supercooling channel T3 in the main heat exchanger E101 from the top of the low temperature separator V101 to be condensed, and after being condensed, is sent into the LNG flash tank V102; the gas phase separated by the low temperature separator V101 is sent into one of the spray devices in the heavy hydrocarbon washing tower T101 through a pipeline, and the natural gas in the heavy hydrocarbon washing tower T101 is washed through the spray device.

[0042] The pipeline connected between the outlet end of the condensation supercooling channel T3 in the main heat exchanger E101 and the inlet end of the LNG flash tank V102 is provided with a control valve two TV101, and the LNG flash tank V102 is further provided with a control valve four LV102, the tank bottom of the LNG flash tank V102 is communicated with a liquefied natural gas pipeline G4, the tank bottom of the LNG flash tank V102 is also communicated with another spray device in the heavy hydrocarbon washing tower T101 through a pipeline, the upper part of the LNG flash tank V102 is communicated with the inlet end of the reheating channel T4 in the main heat exchanger E101 through a pipeline, the outlet end of the reheating channel T4 is further communicated with a nitrogen-rich tail gas pipeline G5, and the nitrogen-rich tail gas pipeline G5 is provided with a control valve one PV101, which can be a pressure control valve.

[0043] The control valve four LV102 is a liquid level control valve, and the liquid level in the LNG flash tank V102 can be observed through the control valve four LV102, so as to prevent the LNG return pump from being damaged by cavitation. The control valve four LV102 can be directly installed on the liquefied natural gas pipeline G4 during installation. Of course, when the control valve four LV102 is directly installed on the liquefied natural gas pipeline G4 and is only used as an on-off valve, the liquid level in the LNG flash tank V102 can also be observed by installing a liquid level meter on the LNG flash tank V102.

[0044] The gas phase entering the LNG flash tank V102 continues to separate gas and liquid in the LNG flash tank V102, the separated gas is sent out from the top of the LNG flash tank V102 and then enters the reheating channel T4 in the main heat exchanger E101 through a pipeline to be heated, and after being heated, the nitrogen-rich tail gas is sent out through the conveying pipeline G5; the liquid phase separated in the LNG flash tank V102 is the product LNG, most of which can be sent out through the liquefied natural gas pipeline G4, and the remaining part of the product LNG is conveyed to the uppermost spray device in the heavy hydrocarbon washing tower T101, and is sprayed in the heavy hydrocarbon washing tower T101 by the spray device to wash the natural gas.

[0045] In order to ensure that the liquid phase in the LNG flash tank V102 can be fed into the uppermost spraying device in the heavy hydrocarbon washing tower T101, an LNG reflux pump P101 is installed on the pipeline connecting the liquid phase outlet of the LNG flash tank V102 and the uppermost spraying device in the heavy hydrocarbon washing tower T101, and the LNG reflux pump P101 pressurizes and feeds the liquid phase in the LNG flash tank V102 to the heavy hydrocarbon washing tower T101 as the top washing liquid.

[0046] In the present embodiment, the two sections of packing in the heavy hydrocarbon washing tower T101 can also be replaced by two sections of trays.

[0047] In the present embodiment, the pressure of the dry natural gas before entering the cooling passage T1 is in the range of 3.0 MPa to 6.5 MPa, the cooling temperature of the cooling passage T1 is in the range of -40℃ to 20℃, and the condensing temperature of the condensing passage T2 is in the range of -80℃ to -35℃.

[0048] In the present embodiment, in order to adapt to different production conditions, when the content of ethane and heavier components in the raw gas (dry natural gas) increases significantly, the condensed liquid hydrocarbon separated by the V101 in the low-temperature separator will increase significantly, and the condensed liquid hydrocarbon enters the lower spraying device in the heavy hydrocarbon washing tower T101 through the communication passage G2. Only the packing or trays in the lower section of the heavy hydrocarbon washing tower T101 is enough to completely wash the heavy hydrocarbons and aromatic hydrocarbons in the natural gas, and at this time, the LNG reflux pump can be stopped.

[0049] Based on the heavy hydrocarbon washing equipment of the LNG device, the washing process is as follows:

[0050] The dry natural gas is fed into the cooling passage T1 in the main heat exchanger E101 through the dry natural gas feeding pipeline G1 and is cooled to -10℃. The BOG sent out from the cooling passage T1 in the main heat exchanger E101 is sent to the lower part of the heavy hydrocarbon washing tower T101 through the pipeline, and the washed natural gas returns to the condensing passage T2 in the main heat exchanger E101 and is cooled to -65℃. The natural gas is sent to the low-temperature separator V101 for gas-liquid separation, and the separated gas phase returns to the condensing supercooling passage T3 in the main heat exchanger E101 and is cooled, condensed and supercooled to -162℃. The natural gas is throttled and depressurized to be sent to the LNG flash tank V102 for flashing, the flashed nitrogen-rich tail gas returns to the reheating passage T4 in the main heat exchanger E101 and is reheated to normal temperature, and is finally sent out through the nitrogen-rich tail gas pipeline G5.

[0051] Most of the LNG in the LNG flash tank V102 is sent out as product LNG through the liquefied natural gas pipeline G4; the remaining LNG in the LNG flash tank V102 is pressurized by the LNG reflux pump P101 and is fed into the top of the heavy hydrocarbon washing tower T101 as the top washing liquid; the condensed liquid hydrocarbon separated by the low-temperature separator V101 is sent to the middle part of the heavy hydrocarbon washing tower T101 through the condensed liquid hydrocarbon pipeline G2 as the middle part washing liquid.

[0052] By the action of the washing liquid, the heavy hydrocarbon and aromatic hydrocarbon in the natural gas are completely condensed and flow to the bottom of the heavy hydrocarbon washing tower T101, and the reboiler on the heavy hydrocarbon washing tower T101 evaporates the methane at the bottom of the heavy hydrocarbon washing tower T101, and finally, the liquid heavy hydrocarbon at the bottom of the heavy hydrocarbon washing tower T101 is sent out by the liquid heavy hydrocarbon pipeline G3.

[0053] In the description of the present specification, the description of the terms "one embodiment / way", "some embodiments / ways", "example", "specific example" or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment / way or example are included in at least one embodiment / way or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment / way or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments / ways or examples. In addition, the person skilled in the art can combine and combine the different embodiments / ways or examples described in the present specification and the features of the different embodiments / ways or examples, without contradiction.

[0054] In addition, the terms "first", "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", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically limited.

[0055] The person skilled in the art should understand that the above-mentioned embodiments are only for clearly illustrating the present application, and not for limiting the scope of the present application. Based on the above disclosure, other changes or modifications can be made by those skilled in the art, and these changes or modifications are still within the scope of the present application.

Claims

1. A heavy hydrocarbon removal apparatus of a LNG plant, characterized by, The main heat exchanger (E101), the heavy hydrocarbon washing tower (T101), the low-temperature separator (V101) and the LNG flash tank (V102) are included, and the main heat exchanger (E101) has a cooling channel (T1), a condensation channel (T2) and a condensation supercooling channel (T3) therein; the inlet end of the cooling channel (T1) is connected with a dry natural gas feeding pipeline (G1) for conveying raw material gas, the outlet end of the cooling channel (T1) is communicated with the gas phase inlet of the heavy hydrocarbon washing tower (T101), the gas phase outlet of the heavy hydrocarbon washing tower (T101) and the inlet of the low-temperature separator (V101) are communicated with two ends of the condensation channel (T2) respectively, the gas phase outlet of the low-temperature separator (V101) and the inlet of the LNG flash tank (V102) are communicated with two ends of the condensation supercooling channel (T3) respectively, and the liquid phase outlet of the LNG flash tank (V102) and the liquid phase outlet of the low-temperature separator (V101) are communicated with the washing liquid feeding port of the heavy hydrocarbon washing tower (T101) respectively.

2. The LNG plant's wash heavy hydrocarbon removal apparatus according to claim 1, characterized in that, The heavy hydrocarbon washing tower (T101) is arranged with two sections of fillers or two sections of trays arranged in an up-down mode, and the heavy hydrocarbon washing tower (T101) has two washing liquid feeding ports, the two washing liquid feeding ports of the heavy hydrocarbon washing tower (T101) are located above the two sections of fillers or above the two sections of trays respectively, and the liquid phase outlet of the LNG flash tank (V102) and the liquid phase outlet of the low-temperature separator (V101) are communicated with the two washing liquid feeding ports of the heavy hydrocarbon washing tower (T101) respectively.

3. The LNG plant's wash heavy hydrocarbon removal apparatus according to claim 2, characterized in that, The low-temperature separator (V101) is located at the top of the heavy hydrocarbon washing tower (T101), and the liquid phase outlet of the low-temperature separator (V101) is communicated with the washing liquid feeding port in the middle of the heavy hydrocarbon washing tower (T101).

4. The LNG plant's wash heavy hydrocarbon removal apparatus according to claim 1 or 2 or 3, characterized in that, The LNG flash tank (V102) is provided with an LNG reflux pump (P101) between the liquid phase outlet and the washing liquid feeding port of the heavy hydrocarbon washing tower (T101).

5. The LNG plant's wash heavy hydrocarbon removal apparatus of claim 1, wherein, The heavy hydrocarbon washing tower (T101) is further communicated with a liquid heavy hydrocarbon pipeline (G3) for conveying liquid heavy hydrocarbon outward.

6. The LNG plant's wash heavy hydrocarbon removal apparatus of claim 1, wherein, The heavy hydrocarbon washing tower (T101) is further provided with a reboiler.

7. The LNG plant's wash heavy hydrocarbon removal apparatus of claim 1, wherein, The LNG flash tank (V102) is further communicated with a liquefied natural gas pipeline (G4) for conveying liquefied natural gas outward.

8. The LNG plant's wash heavy hydrocarbon removal apparatus of claim 1, wherein, The LNG flash tank (V102) is further provided with a control valve four (LV102).

9. The LNG plant's wash heavy hydrocarbon removal apparatus of any one of claims 1, 2, 3, or 5-8, wherein, The main heat exchanger (E101) further has a reheating channel (T4) therein, the gas phase outlet of the LNG flash tank (V102) is communicated with one end of the reheating channel (T4), and the other end of the reheating channel (T4) is further communicated with a nitrogen-rich tail gas pipeline (G5) for conveying nitrogen-rich tail gas outward.

10. The LNG plant's wash heavy hydrocarbon removal apparatus of claim 9, wherein, The nitrogen-rich tail gas pipeline (G5) is provided with a control valve one (PV101).

11. The LNG plant's wash heavy hydrocarbon removal apparatus of any one of claims 1, 2, 3, or 5-8, wherein, The main heat exchanger (E101) further has a refrigerant channel (T5) for refrigerant flow.

12. The LNG plant's wash heavy hydrocarbon removal apparatus of any one of claims 1, 2, 3, or 5-8, wherein, The gas pressure in the dry natural gas feeding pipeline (G1) is 3.0-6.5 MPa.

13. The LNG plant's wash heavy hydrocarbon removal apparatus of any one of claims 1, 2, 3, or 5-8, wherein, The cooling temperature of the cooling channel (T1) ranges from-40℃ to 20℃.

14. The LNG plant's wash heavy hydrocarbon removal apparatus of any one of claims 1, 2, 3, or 5-8, wherein, The condensation temperature of the condensation channel (T2) ranges from-80℃ to-35℃.

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