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

Abstract

The invention discloses a washing and heavy hydrocarbon removal process and equipment for an LNG (liquefied natural gas) device, and relates to the technical field of pretreatment of natural gas liquefying devices.The washing and heavy hydrocarbon removal process comprises the following steps that dry natural gas is subjected to primary cooling, then heavy hydrocarbon and aromatic hydrocarbon are removed through washing, and a liquid phase obtained after heavy hydrocarbon and aromatic hydrocarbon are removed through washing is a liquid heavy hydrocarbon product; washing to remove the heavy hydrocarbon and the aromatic hydrocarbon to obtain a gas phase, condensing and separating the gas phase, washing the dry natural gas by using the separated condensate hydrocarbon as a washing solution for removing the heavy hydrocarbon and the aromatic hydrocarbon, condensing the separated gas, and carrying out flash evaporation, a liquid phase generated by flash evaporation is directly used as a liquefied natural gas product or a washing solution for removing heavy hydrocarbon and aromatic hydrocarbon to wash the dry natural gas, and a gas phase generated by flash evaporation is reheated to obtain a nitrogen-rich tail gas product. The heavy hydrocarbon and aromatic hydrocarbon removal function can be realized at the same time, the equipment consumption and consumption of the device are comprehensively reduced, and the overall reduction of the device investment and the production cost is realized.

Description

Technical Field

[0001] The invention relates to the technical field of pretreatment of a natural gas liquefaction device, and in particular to a washing and heavy hydrocarbon removal process and equipment for an LNG device. Background Art

[0002] At present, the raw natural gas of natural gas liquefaction equipment is diverse, mainly pipeline natural gas, scattered wellhead natural gas, shale gas, tight gas, etc. In the process of natural gas liquefaction, since the raw natural gas contains heavy hydrocarbons such as pentane and above and various aromatic hydrocarbons, and the content of heavy hydrocarbons and aromatic hydrocarbons varies greatly, if the heavy hydrocarbons and aromatic hydrocarbons are not completely removed, it will cause problems such as blockage and freezing of cold boxes and pipelines under low temperature conditions. Therefore, they must be completely removed before low-temperature condensation and liquefaction or during the condensation process.

[0003] Under the existing technology, the commonly used heavy hydrocarbon removal technologies mainly include: adsorption process of solid adsorbent, low-temperature liquid hydrocarbon washing process, etc.

[0004] The adsorption process of solid adsorbents utilizes the strong adsorption selectivity of solid adsorbent molecules and their high adsorption characteristics under low partial pressure to adsorb and remove heavy hydrocarbons. Many existing patent applications use this type of process, but the adsorption process of solid adsorbents is limited by the saturation, adsorption capacity and regeneration degree of the solid adsorbents, and is not suitable for situations where the raw natural gas processing volume is large and the heavy hydrocarbon content in the raw natural gas increases sharply.

[0005] The low-temperature liquid hydrocarbon washing process is a method of removing heavy hydrocarbons by utilizing the high solubility of heavy hydrocarbons and aromatic hydrocarbons in liquid hydrocarbons above C2. In the existing technologies, CN103031169A "Natural gas liquefaction and heavy hydrocarbon processing method and device", CN104087357A "A method and system for removing heavy hydrocarbons from natural gas liquefaction process", CN106978226A "A process and system for separating heavy hydrocarbons from natural gas by cryogenic method", CN211199147U "A heavy hydrocarbon removal device", CN111964353A "A natural gas liquefaction and condensate recovery integrated device and method", CN212680113U "A method for separating heavy hydrocarbons and separating heavy hydrocarbons by distillation using a dividing wall distillation tower ...7357A "A method and system for removing heavy hydrocarbons from natural gas by distillation using a dividing wall distillation tower", CN212680113U "A method for separating heavy hydrocarbons and separating heavy hydrocarbons by distillation using a dividing wall distillation tower", CN212687357A "A method and system for removing heavy hydrocarbons and removing heavy hydrocarbons from natural gas by distillation using a dividing wall distillation tower", CN212680113U "A method and system for removing heavy hydrocarbons and separating heavy hydrocarbons by distillation using a "Device", 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 oil field associated gas", all cool the natural gas from the scrubbing tower to a certain temperature to produce condensed liquid hydrocarbons, and then use a cryogenic pump to pressurize the condensed liquid hydrocarbons and send them to the top of the scrubbing tower as a scrubbing liquid. However, this process, at the set condensation temperature, when the C2 and above components in the raw natural gas decrease, the amount of condensed liquid hydrocarbons decreases, making It is difficult to establish a washing liquid circulation; CN105890284A "Liquefied natural gas heavy hydrocarbon removal device and method thereof" also allows the natural gas from the washing tower to enter the reflux condenser placed on the top of the washing tower to be cooled to a certain temperature to produce condensed liquid hydrocarbons, and then the liquid hydrocarbons are sent to the top of the washing tower as washing liquid by static pressure, so that there is no need for a reflux cryogenic pump. However, this process also reduces the amount of condensed liquid hydrocarbons at the set condensing temperature when the C2 and above components in the raw natural gas decrease, making it difficult to establish a washing liquid circulation; CN103351896A "A shale gas dehydration and heavy hydrocarbon removal method and device" uses The condensate of the distilled gas from the top of the deethanizer tower is used for washing; CN103409188A "A process device and method for removing heavy hydrocarbons in the process of natural gas liquefaction" uses a top reflux condenser and expansion refrigeration for washing. However, the pressure of the natural gas decreases after expansion and the energy consumption in the subsequent natural gas liquefaction process increases; CN105695015A "A new natural gas heavy hydrocarbon removal device and method" uses an LNG circulating pump to pressurize a small amount of LNG into a washing tower as a washing liquid. During the washing process, the new pentane cannot be completely washed off, and the natural gas containing new pentane will still freeze at low temperatures.

[0006] Therefore, there is an urgent need for a washing and heavy hydrocarbon removal process and equipment that can completely remove heavy hydrocarbons and aromatic hydrocarbons in LNG devices. Summary of the invention

[0007] The purpose of the present invention is to provide a washing and heavy hydrocarbon removal process and equipment for an LNG device, which can simultaneously achieve the removal functions of heavy hydrocarbons and aromatic hydrocarbons, comprehensively reduce the equipment usage and consumption of the device, and achieve an overall reduction in device investment and production costs.

[0008] To achieve the purpose of the present invention, the technical solution adopted is:

[0009] A washing and heavy hydrocarbon removal process for an LNG device comprises the following steps:

[0010] After the initial cooling, the dry natural gas is washed to remove heavy hydrocarbons and aromatic hydrocarbons. The liquid phase obtained after washing and removing the heavy hydrocarbons and aromatic hydrocarbons is a liquid heavy hydrocarbon product. The gas phase obtained after washing and removing the heavy hydrocarbons and aromatic hydrocarbons is condensed and separated. The condensed liquid hydrocarbons obtained by separation are used as a washing liquid for removing heavy hydrocarbons and aromatic hydrocarbons to wash the dry natural gas. The separated gas is condensed and flashed. The liquid phase produced by the flashing is directly used as a liquefied natural gas product or as a washing liquid for removing heavy hydrocarbons and aromatic hydrocarbons to wash the dry natural gas. The gas phase produced by the flashing is reheated to obtain a nitrogen-rich tail gas product.

[0011] Furthermore, the condensed liquid hydrocarbons separated from the gas phase obtained by washing and removing heavy hydrocarbons and aromatic hydrocarbons are transported by relying on their static pressure.

[0012] Furthermore, the pressure of the dry natural gas before the initial cooling ranges from 3.0 MPa to 6.5 MPa.

[0013] Furthermore, the primary cooling temperature of the dry natural gas is -40°C to 20°C.

[0014] Furthermore, the condensation temperature of the gas phase obtained after washing and removing heavy hydrocarbons and aromatic hydrocarbons is -80°C to -35°C.

[0015] A washing and heavy hydrocarbon removal device for an LNG unit comprises a main heat exchanger, a heavy hydrocarbon washing tower, a low-temperature separator and an LNG flash tank, wherein a cooling channel, a condensing channel and a condensation supercooling channel are arranged in the main heat exchanger; the inlet end of the cooling channel is connected to a dry natural gas feed pipeline for conveying raw gas, the outlet end of the cooling channel is communicated with a gas phase inlet of the heavy hydrocarbon washing tower, the gas phase outlet of the heavy hydrocarbon washing tower and the inlet of the low-temperature separation tank are respectively communicated with the two ends of the condensing channel, the gas phase outlet of the low-temperature separation tank and the inlet of the LNG flash tank are respectively communicated with the two ends of the condensation supercooling channel, and the liquid phase outlet of the LNG flash tank and the liquid phase outlet of the low-temperature separation tank are both communicated with a washing liquid feed port of the heavy hydrocarbon washing tower.

[0016] Furthermore, the heavy hydrocarbon washing tower is provided with two sections of packing or two sections of tower plates arranged up and down, and the heavy hydrocarbon washing tower has two washing liquid feed ports, the two washing liquid feed ports on the heavy hydrocarbon washing tower are respectively located above the two sections of packing or above the two sections of tower plates, and the liquid phase outlet of the LNG flash tank and the liquid phase outlet of the low-temperature separation tank are respectively connected to the two washing liquid feed ports on the heavy hydrocarbon washing tower.

[0017] Furthermore, the low-temperature separation tank is located at the top of the heavy hydrocarbon washing tower, and the liquid phase outlet of the low-temperature separation tank is connected to the washing liquid feed port in the middle of the heavy hydrocarbon washing tower.

[0018] Furthermore, an LNG reflux pump is provided between the liquid phase outlet of the LNG flash tank and the washing liquid feed inlet of the heavy hydrocarbon washing tower.

[0019] Furthermore, the heavy hydrocarbon washing tower is also connected to a liquid heavy hydrocarbon pipeline for transporting liquid heavy hydrocarbons to the outside.

[0020] Furthermore, a reboiler is installed on the heavy hydrocarbon washing tower.

[0021] Furthermore, the LNG flash tank is also connected to a liquefied natural gas pipeline for transporting liquefied natural gas to the outside.

[0022] Furthermore, the LNG flash tank is also equipped with a control valve four.

[0023] Furthermore, a control valve 1 is provided on the nitrogen-rich tail gas pipeline.

[0024] Furthermore, the main heat exchanger is provided with a reheating channel, the gas phase outlet of the LNG flash tank is connected to one end of the reheating channel, and the other end of the reheating channel is also connected to a nitrogen-rich tail gas pipeline for transporting nitrogen-rich tail gas to the outside.

[0025] Furthermore, the main heat exchanger also has a refrigerant channel for the refrigerant to flow.

[0026] Furthermore, the gas pressure entering the dry natural gas feed pipeline is 3.0 MPa to 6.5 MPa.

[0027] Furthermore, the cooling temperature range of the cooling channel is -40°C to 20°C.

[0028] Furthermore, the condensation temperature of the condensation channel is -80°C to -35°C.

[0029] The beneficial effects of the present invention are:

[0030] (1) The present invention has the characteristics of a double washing liquid circulation process and can completely remove heavy hydrocarbons and aromatic hydrocarbons. Compared with the prior art, the principle is easy to understand and suitable for technicians and operators to systematically master the device and process. At the same time, the present invention can simultaneously achieve the removal function of heavy hydrocarbons and aromatic hydrocarbons, comprehensively reducing the equipment usage and consumption of the device, and achieving an overall reduction in device investment and production costs.

[0031] (2) In the present invention, the liquid phase outlet of the LNG flash tank and the liquid phase outlet of the cryogenic separation tank are connected to the washing liquid feed port of the heavy hydrocarbon washing tower, so that the liquid phase of the LNG flash tank and the liquid phase of the cryogenic separation tank enter the heavy hydrocarbon washing tower for use as washing liquid, which is suitable for a wide range of changes in the components of dry natural gas.

[0032] (3) The present invention also has the function of recovering heavy hydrocarbons and aromatic hydrocarbons, and can produce LPG and light oil, thereby significantly improving economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings illustrate exemplary embodiments of the present invention and together with the description serve to explain the principles of the present invention. These drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification.

[0034] Figure 1 The present invention provides a system flow chart of a washing and heavy hydrocarbon removal device for an LNG device.

[0035] Markings and corresponding parts names in the attached drawings:

[0036] T101-heavy hydrocarbon scrubber, E101-main heat exchanger, V101-low temperature separator, V102-LNG flash tank, P101-LNG reflux pump;

[0037] G1-dry natural gas feed pipeline, G2-condensate hydrocarbon pipeline, G3-liquid heavy hydrocarbon pipeline, G4 liquefied natural gas pipeline, G5-nitrogen-rich tail gas pipeline;

[0038] T1-cooling channel, T2-condensing channel, T3-condensing subcooling channel, T4-reheating channel, T5-refrigerant channel;

[0039] PV101-control valve one, TV101-control valve two, LV101-control valve three, LV102-control valve four. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below in conjunction with the accompanying drawings and implementation methods. It is understood that the specific implementation methods described herein are only used to explain the relevant content, rather than to limit the present invention. It is also necessary to explain that, for ease of description, only the parts related to the present invention are shown in the accompanying drawings.

[0041] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0042] like Figure 1 As shown, the present invention provides a washing and heavy hydrocarbon removal equipment for an LNG device, comprising a main heat exchanger E101, a heavy hydrocarbon washing tower T101, a low-temperature separator V101, and an LNG flash tank V102, wherein the main heat exchanger E101 is provided with a cooling channel T1, a condensing channel T2, a condensing supercooling channel T3, a reheating channel T4, and a refrigerant channel T5, wherein the cooling channel T1, the condensing channel T2, and the condensing supercooling channel T3 are used for cooling the circulating medium, the reheating channel T4 is used for heating the circulating medium, and the refrigerant channel T5 is used for transporting the refrigerant medium.

[0043] The inlet end of the cooling channel T1 in the main heat exchanger E101 is connected to a dry natural gas feed pipe G1, and the feed pipe is used to transport the dry natural gas to 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 lower part of the heavy hydrocarbon washing tower T101 through a pipeline, so that the dry natural gas is cooled and lowered through the cooling channel T1 through the pipeline and is fed to the lower part of the heavy hydrocarbon washing tower T101.

[0044] The heavy hydrocarbon washing tower T101 has two sections of packing arranged up and down, with a certain distance between the two sections of packing, and the heavy hydrocarbon washing tower T101 also has two groups of spray devices for spraying washing liquid, and each section of packing corresponds to a spray device above. When the cooled natural gas just enters the heavy hydrocarbon washing tower T101, the cooled natural gas is located below the packing and passes through the packing to move to the upper part of the heavy hydrocarbon washing tower T101. In this process, the washing liquid sprayed by the spray device washes the natural gas, and the natural gas and the washing liquid transfer heat and mass, so that the heavy hydrocarbons and aromatic hydrocarbons in the natural gas are completely condensed and 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 produced after washing is discharged through the top of the heavy hydrocarbon washing tower T101. The liquid phase remaining 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 bottom of the heavy hydrocarbon washing tower T101 is connected to a liquid heavy hydrocarbon pipeline G3, and a control valve LV101 is also installed on the liquid heavy hydrocarbon pipeline G3.

[0045] The top of the heavy hydrocarbon washing tower T101 is connected to the inlet end of the condensation channel T2 through a pipeline, and the outlet end of the condensation channel T2 is connected to the inlet end of the low-temperature separator V101 through a pipeline. The natural gas from which heavy hydrocarbons have been washed and removed is discharged from the top of the heavy hydrocarbon washing tower T101 and enters the condensation channel T2 of the main heat exchanger E101 through a pipeline for condensation, and enters the low-temperature separator V101 after condensation.

[0046] When the low temperature separator V101 is installed, the low temperature separator V101 can be placed on the top of the heavy hydrocarbon washing tower T101. The gas phase outlet of the low temperature separator V101 is connected to the inlet end of the condensation supercooling channel T3 through a pipeline, and the outlet end of the condensation supercooling channel T3 is connected to 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 to one of the spray devices in the heavy hydrocarbon washing tower T101 through the condensed liquid hydrocarbon pipeline G2.

[0047] Since the low-temperature separator V101 is installed on the top of the heavy hydrocarbon washing tower T101, the liquid phase outlet of the low-temperature separator V101 can be preferentially connected to the spray device at the bottom of the heavy hydrocarbon washing tower T101 through the condensed liquid hydrocarbon pipeline G2. At this time, the liquid phase separated by the low-temperature separator V101 is directly sent to the spray device at the bottom of the heavy hydrocarbon washing tower T101 through the condensed liquid hydrocarbon pipeline G2 by the static pressure of the condensed liquid hydrocarbon. This design makes the condensed liquid hydrocarbon pipeline G2 a liquid seal structure on the low-temperature separator V101 to prevent gas backflow, thereby effectively preventing gas backflow in the low-temperature separator V101.

[0048] The low-temperature separator V101 separates gas and liquid, and the separated gas is sent from the top of the low-temperature separator V101 to the condensation subcooling channel T3 in the main heat exchanger E101 for condensation, and enters the LNG flash tank V102 after condensation; the gas phase separated by the low-temperature separator V101 is sent to 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 by the spray device.

[0049] A control valve 2 TV101 is installed on the pipeline connecting the outlet end of the condensation subcooling channel T3 in the main heat exchanger E101 and the inlet end of the LNG flash tank V102, and a control valve 4 LV102 is also provided on the LNG flash tank V102. The bottom of the LNG flash tank V102 is connected to a liquefied natural gas pipeline G4, and the bottom of the LNG flash tank V102 is also connected to another spray device in the heavy hydrocarbon washing tower T101 through a pipeline. The upper part of the LNG flash tank V102 is connected to the inlet end of the reheating channel T4 in the main heat exchanger E101 through a pipeline, and the outlet end of the reheating channel T4 is also connected to a nitrogen-rich tail gas pipeline G5. A control valve 1 PV101 is installed on the nitrogen-rich tail gas pipeline G5, and a pressure control valve can be selected for the control valve 1 PV101.

[0050] The control valve 4 LV102 is a liquid level control valve. The liquid level in the LNG flash tank V102 can be observed through the control valve 4 LV102, thereby preventing the LNG reflux pump from being damaged by cavitation. The control valve 4 LV102 can be directly installed on the liquefied natural gas pipeline G4 during installation. Of course, when the control valve 4 LV102 is directly installed on the liquefied natural gas pipeline G4 and is only used as a switch 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.

[0051] The gas phase entering the LNG flash tank V102 continues to undergo gas-liquid separation in the LNG flash tank V102. The separated gas is sent out from the top of the LNG flash tank V102 and enters the reheating channel T4 of the main heat exchanger E101 through a pipeline for heating. After heating, the nitrogen-rich tail gas is sent out of the device through the delivery 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 transported to the uppermost spray device in the heavy hydrocarbon washing tower T101, and the spray device is sprayed on the natural gas in the heavy hydrocarbon washing tower T101 to wash the natural gas.

[0052] In order to ensure that the liquid phase in the LNG flash tank V102 can be fed into the top spray 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 top spray device in the heavy hydrocarbon washing tower T101. The LNG reflux pump P101 pressurizes the liquid phase in the LNG flash tank V102 and transports it to the heavy hydrocarbon washing tower T101 as the top washing liquid.

[0053] In this embodiment, the two sections of fillers in the heavy hydrocarbon washing tower T101 can also be replaced by two sections of tower plates.

[0054] In this embodiment, the pressure range of the dry natural gas before entering the cooling channel T1 is 3.0 MPa to 6.5 MPa, the cooling temperature range of the cooling channel T1 is -40°C to 20°C, and the condensing temperature range of the condensing channel T2 is -80°C to -35°C.

[0055] In this 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 hydrocarbons separated by V101 in the low-temperature separator will increase significantly. The condensed liquid hydrocarbons enter the lower spray device of the heavy hydrocarbon washing tower T101 through the connecting channel G2. The packing or tower plate in the lower section of the heavy hydrocarbon washing tower T10 is sufficient to completely wash out the heavy hydrocarbons and aromatic hydrocarbons in the natural gas. At this time, the LNG reflux pump can be stopped.

[0056] The washing and heavy hydrocarbon removal equipment based on the above LNG unit has the following washing process:

[0057] The dry natural gas is fed into the cooling channel T1 in the main heat exchanger E101 through the dry natural gas feed pipeline G1 and cooled to -10°C. The BOG sent out from the cooling channel T1 in the main heat exchanger E101 is fed into the lower part of the heavy hydrocarbon washing tower T101 through a pipeline. The washed natural gas returns to the condensation channel T2 in the main heat exchanger E101 and is cooled to -65°C. It is then sent to the low-temperature separator V101 for gas-liquid separation. The separated gas phase returns to the condensation and supercooling channel T3 in the main heat exchanger E101 to be cooled, condensed and supercooled to -162°C. It is throttled and depressurized and sent to the LNG flash tank V102 for flash evaporation. The flashed nitrogen-rich tail gas returns to the reheating channel T4 in the main heat exchanger E101 to be reheated to room temperature and finally sent out through the nitrogen-rich tail gas pipeline G5.

[0058] 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 sent to the top of the heavy hydrocarbon washing tower T101 as the top washing liquid; the condensed liquid hydrocarbons separated by the low-temperature separator V101 are sent to the middle part of the heavy hydrocarbon washing tower T101 through the condensed liquid hydrocarbon pipeline G2 as the middle washing liquid of the tower.

[0059] Through the action of the washing liquid, the heavy hydrocarbons and aromatic hydrocarbons 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. Finally, the liquid heavy hydrocarbons at the bottom of the heavy hydrocarbon washing tower T101 are sent out through the liquid heavy hydrocarbon pipeline G3.

[0060] Application Example 1

[0061] This application example 1 is based on the washing and heavy hydrocarbon removal equipment provided in Example 1. The material balance data of the natural gas flow path of the device are as follows:

[0062] Table 1 Material balance data of natural gas flow path

[0063]

[0064]

[0065] After washing and removing heavy hydrocarbons, pentane and heavier hydrocarbons and aromatic hydrocarbons have been completely removed.

[0066] Application Example 2

[0067] This application example 2 is based on the washing and heavy hydrocarbon removal equipment provided in Example 1. When the raw natural gas composition changes, the material balance data of the natural gas flow path of the device is as follows:

[0068] Table 2 Material balance data of natural gas flow path

[0069]

[0070]

[0071] After washing and removing heavy hydrocarbons, pentane and heavier hydrocarbons and aromatic hydrocarbons have been completely removed.

[0072] In the description of this specification, the description with reference to the terms "one embodiment / method", "some embodiments / methods", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments / methods or examples. In addition, those skilled in the art may combine and combine the different embodiments / methods or examples described in this specification and the features of the different embodiments / methods or examples, unless they are contradictory.

[0073] 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 at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0074] It should be understood by those skilled in the art that the above embodiments are only for the purpose of clearly illustrating the present invention, and are not intended to limit the scope of the present invention. For those skilled in the art, other changes or modifications may be made based on the above disclosure, and these changes or modifications are still within the scope of the present invention.

Claims

1. A heavy hydrocarbon washing and removal process for an LNG device, characterized in that: The steps include: After the initial cooling, the dry natural gas is washed to remove heavy hydrocarbons and aromatic hydrocarbons. The liquid phase obtained after washing and removing the heavy hydrocarbons and aromatic hydrocarbons is a liquid heavy hydrocarbon product. The gas phase obtained after washing and removing the heavy hydrocarbons and aromatic hydrocarbons is condensed and separated. The condensed liquid hydrocarbons obtained by separation are used as a washing liquid for removing heavy hydrocarbons and aromatic hydrocarbons to wash the dry natural gas. The separated gas is condensed and flashed. The liquid phase produced by the flashing is directly used as a liquefied natural gas product or as a washing liquid for removing heavy hydrocarbons and aromatic hydrocarbons to wash the dry natural gas. The gas phase produced by the flashing is reheated to obtain a nitrogen-rich tail gas product.

2. The heavy hydrocarbon washing and removal equipment for the LNG device according to claim 1, characterized in that: After washing and removing heavy hydrocarbons and aromatic hydrocarbons, the gas phase is obtained and the condensed liquid hydrocarbons separated after condensation are transported depending on their static pressure.

3. The heavy hydrocarbon removal process of the LNG device according to claim 1, characterized in that: The pressure range of the dry natural gas before the initial cooling is 3.0MPa to 6.5MPa; preferably, the initial cooling temperature of the dry natural gas is -40°C to 20; preferably, the condensation temperature of the gas phase obtained after washing and removing heavy hydrocarbons and aromatic hydrocarbons is -80°C to -35°C.

4. A washing and heavy hydrocarbon removal device for implementing any one of the washing and heavy hydrocarbon removal processes of claims 1 to 3, characterized in that: The invention comprises a main heat exchanger (E101), a heavy hydrocarbon washing tower (T101), a low temperature separator (V101) and an LNG flash tank (V102), wherein the main heat exchanger (E101) is provided with a cooling channel (T1), a condensing channel (T2) and a condensing subcooling channel (T3); the inlet end of the cooling channel (T1) is connected to a dry natural gas feed pipeline (G1) for conveying raw gas, and the outlet end of the cooling channel (T1) is connected to 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 separation tank (V101) are respectively connected to the two ends of the condensation channel (T2), the gas phase outlet of the low-temperature separation tank (V101) and the inlet of the LNG flash tank (V102) are respectively connected to the two ends of the condensation supercooling channel (T3), and the liquid phase outlet of the LNG flash tank (V102) and the liquid phase outlet of the low-temperature separation tank (V101) are both connected to the washing liquid feed port of the heavy hydrocarbon washing tower (T101).

5. The heavy hydrocarbon washing and removal equipment for the LNG plant according to claim 4, characterized in that: The heavy hydrocarbon washing tower (T101) is provided with two sections of packing or two sections of tower plates arranged in an upper and lower manner, and the heavy hydrocarbon washing tower (T101) has two washing liquid feed ports, the two washing liquid feed ports on the heavy hydrocarbon washing tower (T101) are respectively located above the two sections of packing or above the two sections of tower plates, and the liquid phase outlet of the LNG flash tank (V102) and the liquid phase outlet of the low-temperature separation tank (V101) are respectively connected to the two washing liquid feed ports on the heavy hydrocarbon washing tower (T101).

6. The heavy hydrocarbon washing and removal equipment for the LNG plant according to claim 5, characterized in that: The low temperature separation tank (V101) is located at the top of the heavy hydrocarbon washing tower (T101), and the liquid phase outlet of the low temperature separation tank (V101) is connected to the washing liquid feed port in the middle of the heavy hydrocarbon washing tower (T101).

7. The heavy hydrocarbon washing and removal equipment for an LNG device according to claim 5 or 6, characterized in that: An LNG reflux pump (P101) is provided between the liquid phase outlet of the LNG flash tank (V102) and the washing liquid feed port of the heavy hydrocarbon washing tower (T101).

8. The heavy hydrocarbon washing and removal equipment for an LNG device according to claim 4, 5 or 6, characterized in that: The heavy hydrocarbon washing tower (T101) is also connected to a liquid heavy hydrocarbon pipeline (G3) for transporting liquid heavy hydrocarbons to the outside; preferably, a reboiler is also installed on the heavy hydrocarbon washing tower (T101).

9. The heavy hydrocarbon washing and removal equipment for an LNG device according to claim 4, 5 or 6, characterized in that: The LNG flash tank (V102) is also connected to a liquefied natural gas pipeline (G4) for transporting liquefied natural gas to the outside; preferably, the LNG flash tank (V102) is also equipped with a control valve four (LV102).

10. The heavy hydrocarbon washing and removal equipment for an LNG device according to claim 4, 5 or 6, characterized in that: The main heat exchanger (E101) further comprises a reheating channel (T4), the gas phase outlet of the LNG flash tank (V102) is connected to one end of the reheating channel (T4), and the other end of the reheating channel (T4) is also connected to a nitrogen-rich tail gas pipeline (G5) for transporting nitrogen-rich tail gas to the outside; preferably, a control valve 1 (PV101) is provided on the nitrogen-rich tail gas pipeline (G5); preferably, the main heat exchanger (E101) further comprises a refrigerant channel (T5) for the refrigerant to flow.

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