LNG receiving station gas-liquid mixed phase light hydrocarbon separation process system

Abstract

The embodiment of the application provides a kind of LNG receiving station gas-liquid mixed phase light hydrocarbon separation process system, it is related to light hydrocarbon cryogenic separation technical field.The first heat exchanger is included;Demethanizer has gas phase outlet and liquid phase outlet, gas phase outlet is set in the top of demethanizer, and liquid phase outlet is set in the bottom of demethanizer, to guide the lean natural gas of demethanizer and demethanization liquid to the outside of demethanizer;First conveying pipeline is used to transport raw material natural gas, first conveying pipeline is connected with the first inlet of demethanizer by first heat exchanger;Second conveying pipeline is used to transport raw material LNG, second conveying pipeline is connected with the second inlet of demethanizer by first heat exchanger, in first heat exchanger, raw material natural gas and raw material LNG are heat exchanged.The light hydrocarbon separation process system provided in the application can improve the recovery rate of light hydrocarbon, reduce the energy consumption of light hydrocarbon separation process, in addition, the process system can gasify LNG, reduce the energy consumption of LNG gasification in the LNG receiving station export process.

Description

Technical Field

[0001] This application relates to the field of cryogenic separation technology for light hydrocarbons, and in particular to a gas-liquid mixed-phase light hydrocarbon separation process system for LNG receiving terminals. Background Technology

[0002] According to relevant statistics, my country relies on imports for about 60% of its natural gas, and the natural gas imported from abroad is usually delivered in the form of liquefied natural gas (LNG).

[0003] Besides methane, LNG-rich environments also contain small amounts of ethane and liquefied petroleum gas (LPG). Ethane can replace naphtha in ethylene production and is more economical than naphtha, diesel, and kerosene. Therefore, separating and recovering ethane from LNG is beneficial for improving the utilization efficiency of LNG and promoting the development of my country's ethylene industry.

[0004] Currently, the light hydrocarbon separation process applicable to LNG receiving terminals involves passing the natural gas exported from the LNG receiving terminal into a light hydrocarbon separation unit for light hydrocarbon separation. However, this method cannot fully utilize the cold energy of LNG, and the exported natural gas is in the gas phase, requiring pressurization for export. Pressurizing to the specified export pressure consumes a large amount of energy. Summary of the Invention

[0005] This application provides a gas-liquid mixed-phase light hydrocarbon separation process system for LNG receiving terminals, which can improve the light hydrocarbon recovery rate and reduce the energy consumption of the light hydrocarbon separation process. At the same time, this process system can vaporize LNG, reducing the energy consumption of LNG vaporization during the external transportation process of LNG receiving terminals.

[0006] In a first aspect, embodiments of this application provide a gas-liquid miscible light hydrocarbon separation process system for an LNG receiving station, comprising:

[0007] First heat exchanger;

[0008] A demethanizing tower has a gas phase outlet and a liquid phase outlet. The gas phase outlet is located at the top of the demethanizing tower, and the liquid phase outlet is located at the bottom of the demethanizing tower, so as to guide the lean natural gas and demethanized liquid from the demethanizing tower to the outside of the demethanizing tower.

[0009] The first transmission pipeline is used to transport raw material natural gas, and the first transmission pipeline is connected to the first inlet of the demethanizer through the first heat exchanger;

[0010] The second pipeline is used to transport raw material LNG. The second pipeline is connected to the second inlet of the demethanizer through the first heat exchanger. In the first heat exchanger, the raw material natural gas and the raw material LNG exchange heat.

[0011] In some embodiments, an expansion compressor unit is also included, which includes an expansion end and a compression end;

[0012] The first heat exchanger is connected to the first inlet of the demethanizer via a first connecting pipe, and the gas phase outlet of the demethanizer is connected to the first heat exchanger via a second connecting pipe. The expansion end is located on the first connecting pipe, and the compression end is located on the second connecting pipe.

[0013] In some embodiments, a third connecting pipe is also included, wherein the second connecting pipe is connected to the third connecting pipe via the first heat exchanger;

[0014] In the third connecting pipeline, the lean natural gas condenses into a liquid state, and the liquid lean natural gas is converted into a gaseous state through the first heat exchanger and transported to the outside.

[0015] Alternatively, in the third connecting pipeline, the lean natural gas condenses into a gas-liquid mixture, and the gas-liquid mixture is then converted into a gaseous state through the first heat exchanger and transported to the outside.

[0016] In some embodiments, a heating assembly is also included, and a third connecting pipe is connected to the inlet of the heating assembly via a first heat exchanger.

[0017] As the natural gas leaves the first heat exchanger and enters the heating assembly, the liquid lean natural gas in the third connecting pipe is vaporized into a gaseous state.

[0018] In some embodiments, the heating assembly includes an air heater and a heater connected to each other;

[0019] The inlet of the air heater is connected to the third connecting pipeline through the first heat exchanger, so that the gas phase outlet of the demethanizer is connected to the inlet of the air heater in sequence through the compression end, the first heat exchanger, the third connecting pipeline and the first heat exchanger.

[0020] In some embodiments, it also includes a second heat exchanger, a fourth connecting pipeline and a fifth connecting pipeline, wherein the second delivery pipeline is connected to the first heat exchanger through the second heat exchanger, and the first heat exchanger is connected to the third inlet of the demethanizer through the fourth connecting pipeline;

[0021] The third connecting pipeline is connected to the fourth inlet of the demethanizer via the fifth connecting pipeline. The second heat exchanger is installed on the fifth connecting pipeline, where the lean natural gas is in a liquid state.

[0022] In some embodiments, the system also includes a deethanizer, wherein the liquid phase outlet of the demethanizer is connected to the first inlet of the deethanizer, and the gas outlet of the deethanizer is connected to the first heat exchanger.

[0023] It also includes a third heat exchanger, with the gas outlet and liquid outlet of the deethaner connected to the two inlets on the sides of the third heat exchanger, respectively.

[0024] In some embodiments, an ethane reflux branch is also included, on which a reflux tank and a reflux pump are provided;

[0025] The outlet of the deethaner is connected to the second inlet of the deethaner in sequence through the first heat exchanger, the reflux tank and the reflux pump.

[0026] In some embodiments, a gas-liquid separator is provided on the first connecting pipeline. The inlet of the gas-liquid separator is connected to the first heat exchanger. The gas-liquid separator has a liquid outlet and a gas outlet. The gas outlet is connected to the first connecting pipeline, and the liquid outlet is guided to the outside of the gas-liquid separator.

[0027] In some embodiments, a rich solution booster pump and a lean solution booster pump are also included, with the rich solution booster pump located on the second delivery pipeline and the lean solution booster pump located on the third connecting pipeline.

[0028] Secondly, another embodiment of this application provides a gas-liquid miscible light hydrocarbon separation process system for an LNG receiving station, comprising:

[0029] First heat exchanger;

[0030] A demethanizing tower has a gas phase outlet and a liquid phase outlet. The gas phase outlet is located at the top of the demethanizing tower, and the liquid phase outlet is located at the bottom of the demethanizing tower, so as to guide the lean natural gas and demethanized liquid from the demethanizing tower to the outside of the demethanizing tower.

[0031] The first transmission pipeline is used to transport raw material natural gas, and the first transmission pipeline is connected to the first inlet of the demethanizer through the first heat exchanger;

[0032] The second pipeline is used to transport raw material LNG. The second pipeline is connected to the second inlet of the demethanizer through the first heat exchanger, and the raw material natural gas and raw material LNG exchange heat.

[0033] This application provides an LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system, which includes a first heat exchanger, a demethanizer, a first conveying pipeline, and a second conveying pipeline. The first heat exchanger establishes a heat exchange system between the feedstock LNG and feedstock natural gas, utilizing the cold energy contained in the feedstock LNG to cool the feedstock natural gas, replacing the additional refrigeration equipment that might be required in traditional processes. On one hand, the cold energy of the feedstock LNG is utilized in a cascade manner, improving the efficiency of cold energy utilization. On the other hand, the feedstock natural gas is cooled through heat exchange, eliminating the need for additional energy consumption for pre-cooling, significantly reducing the overall energy consumption of the process.

[0034] Furthermore, the independent transport of gaseous and liquid feedstocks is achieved through the first and second transport pipelines. After pretreatment in the first heat exchanger, the feedstock enters the demethanizer, forming a transport, heat exchange, and separation path. This avoids the complex multi-unit connections inherent in traditional processes, improving the long-term stability and reliability of the system. Therefore, the LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system provided in this application can solve the problems of insufficient utilization of LNG cold energy and the need for pressurization before exporting natural gas (which is in the gas phase and requires significant energy consumption to reach the specified export pressure). Attached Figure Description

[0035] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0036] Figure 1 A schematic diagram of one of the structural components of the LNG receiving station gas-liquid miscible light hydrocarbon separation process system provided in the embodiments of this application;

[0037] Figure 2 A second schematic diagram of the structure of the LNG receiving station gas-liquid miscible light hydrocarbon separation process system provided in the embodiments of this application;

[0038] Figure 3 The third schematic diagram of the gas-liquid mixed light hydrocarbon separation process system of the LNG receiving station provided in the embodiments of this application.

[0039] Explanation of reference numerals in the attached figures:

[0040] 100 - First heat exchanger;

[0041] 200 - Second heat exchanger;

[0042] 300-Demethanizer;

[0043] 400 - Heating Component;

[0044] 410 - Air heater; 420 - Heater;

[0045] 500-Deethaner column;

[0046] 600 - Third heat exchanger;

[0047] 700-Rich Liquid Booster Pump;

[0048] 800-Lean Solution Booster Pump;

[0049] 900 - Fourth heat exchanger;

[0050] 1000-expansion compressor unit;

[0051] 1100-Ethane reflux branch;

[0052] 1110 - Reflux tank; 1120 - Reflux pump;

[0053] 1200 - Refrigerant circulation path;

[0054] 1210 - Suction tank; 1220 - Compressor; 1230 - Throttling valve;

[0055] 1300-Reboiler;

[0056] 1400 - First delivery pipeline;

[0057] 1500 - Second delivery pipeline;

[0058] 1600 - First connecting pipe;

[0059] 1700 - Second connecting pipe;

[0060] 1800 - Third connecting pipe;

[0061] 1900 - Fourth connecting pipe;

[0062] 2000 - Fifth connecting pipeline;

[0063] 2100-Gas-Liquid Separator.

[0064] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0065] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application and how the technical solutions of the embodiments of this application solve the above-mentioned technical problems will be clearly and completely described below with reference to specific embodiments and the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0066] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection through an intermediate medium, or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0067] In the description of the embodiments of this application, it should be understood that the terms "upper", "lower", "front", "rear", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0068] The terms "first," "second," "third," "fourth," etc. (if present) in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein.

[0069] In this application, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0070] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion, such that a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or apparatus.

[0071] According to relevant statistics, my country relies on imports for about 60% of its natural gas, and the natural gas imported from abroad is usually delivered in the form of LNG.

[0072] Besides methane, LNG-rich LNG also contains small amounts of ethane and LPG. Ethane can replace naphtha in ethylene production and is more economical than naphtha, diesel, and kerosene. Therefore, separating and recovering ethane from LNG is beneficial for improving LNG utilization efficiency and promoting the development of my country's ethylene industry.

[0073] Currently, the light hydrocarbon separation process applicable to LNG receiving terminals involves passing the natural gas exported from the LNG receiving terminal into a light hydrocarbon separation unit for light hydrocarbon separation. However, this method cannot fully utilize the cold energy of LNG, and the exported natural gas is in the gas phase, requiring pressurization for export. Pressurizing to the specified export pressure consumes a large amount of energy.

[0074] This application embodiment constructs a heat exchange system between feedstock LNG and feedstock natural gas using a first heat exchanger. This utilizes the cold energy contained in the feedstock LNG to cool the feedstock natural gas, replacing the artificial refrigeration equipment that might be required in traditional processes. On one hand, the cold energy of the feedstock LNG is utilized in a cascade manner, avoiding the cold energy loss caused by direct LNG vaporization and transportation. On the other hand, the feedstock natural gas is cooled through heat exchange, eliminating the need for additional energy consumption for pre-cooling and significantly reducing the overall energy consumption of the process.

[0075] After heat exchange, the raw LNG is partially vaporized (or becomes liquid) and enters the demethanizer. The raw natural gas is cooled after heat exchange, and then the cooled raw natural gas and heated raw LNG are supplied to the demethanizer 300.

[0076] Furthermore, the gaseous and liquid raw materials are transported independently through the first and second transport pipelines. After pretreatment by the first heat exchanger, they enter the demethanizer, forming a path of transport, heat exchange, and separation. This avoids the complex problem of multi-unit connection in traditional processes and improves the stability and reliability of the system in long-term operation.

[0077] Therefore, the LNG receiving station gas-liquid mixed light hydrocarbon separation process system provided in the embodiments of this application can solve the problems that the cold energy of LNG cannot be fully utilized, and that the natural gas to be exported is in the gas phase, which requires pressurization for export, and that pressurization to the specified export pressure requires a large amount of energy.

[0078] The contents of this application will now be described in detail with reference to the accompanying drawings, so that those skilled in the art can have a clearer and more detailed understanding of the contents of this application.

[0079] like Figure 1 , Figure 2 and Figure 3 As shown in the embodiment of this application, a gas-liquid miscible light hydrocarbon separation process system for an LNG receiving station is provided. The gas-liquid miscible light hydrocarbon separation process system for an LNG receiving station includes a first heat exchanger 100, a demethanizer 300, a first conveying pipeline 1400, and a second conveying pipeline 1500.

[0080] Specifically, the raw material natural gas and raw material LNG circulate in the first heat exchanger 100, are cooled and reheated respectively after heat exchange, and then enter the demethanizer 300 together to separate the lean natural gas and demethanized liquid components through the principle of distillation.

[0081] The demethanizer 300 has a gas phase outlet and a liquid phase outlet. The gas phase outlet is located at the top of the demethanizer 300, and the liquid phase outlet is located at the bottom of the demethanizer 300, so as to guide the lean natural gas and demethanized liquid of the demethanizer 300 to the outside of the demethanizer 300.

[0082] The first transmission pipeline 1400 is used to transport raw material natural gas, and the first transmission pipeline 1400 is connected to the first inlet of the demethanizer 300 through the first heat exchanger 100.

[0083] The second pipeline 1500 is used to transport raw material LNG. The second pipeline 1500 is connected to the second inlet of the demethanizer 300 through the first heat exchanger 100. In the first heat exchanger 100, the raw material natural gas and the raw material LNG exchange heat.

[0084] In this application, the raw material natural gas (gas phase) is directionally transported along the first transmission pipeline 1400 to the corresponding medium channel of the first heat exchanger 100 under the action of the first transmission pipeline 1400. At the same time, the raw material LNG (liquid phase) is transported to another set of medium channels of the first heat exchanger 100 under the action of the second transmission pipeline 1500, where heat exchange takes place within the first heat exchanger 100.

[0085] Specifically, inside the first heat exchanger 100, the cold energy of the raw LNG itself is used to efficiently exchange heat with the relatively high-temperature raw natural gas. During this process, the raw LNG absorbs heat and its temperature rises, gradually transitioning to the gas phase. The raw natural gas releases heat and its temperature decreases, creating favorable conditions for subsequent efficient separation in the demethanizer 300.

[0086] Subsequently, the pretreated raw natural gas and raw LNG (in liquid state, or partially vaporized to form a gas-liquid mixed state) enter the demethanizer 300 through the first and second inlets, respectively. The demethanizer 300 separates the lean natural gas from the demethanized liquid through distillation.

[0087] In this process, the lean natural gas is diverted from the gas phase outlet at the top of the demethanizer 300 to the outside of the demethanizer 300. The demethanized liquid leaves the bottom of the demethanizer 300 in liquid phase.

[0088] Through the above configuration, this embodiment of the application constructs a heat exchange system between raw LNG and raw natural gas using a first heat exchanger 100. This utilizes the cold energy contained in the raw LNG to cool the raw natural gas, replacing the additional refrigeration equipment that might be required in traditional processes. On one hand, the cold energy of the raw LNG is utilized in a cascade manner, improving the efficiency of cold energy utilization. On the other hand, the raw natural gas is cooled through heat exchange, eliminating the need for additional energy consumption for pre-cooling and significantly reducing the overall energy consumption of the process.

[0089] Furthermore, the gaseous and liquid raw materials are independently transported through the first transport pipeline 1400 and the second transport pipeline 1500. After pretreatment by the first heat exchanger 100, they enter the demethanizer 300, forming a path of transport, heat exchange, and separation. This avoids the problem of complex multi-unit connection in traditional processes and improves the stability and reliability of the system in long-term operation.

[0090] In some embodiments, the system further includes an expansion compressor unit 1000, which includes an expansion end and a compression end. A first heat exchanger 100 is connected to the first inlet of a demethanizer 300 via a first connecting pipe 1600, and the gas phase outlet of the demethanizer 300 is connected to the first heat exchanger 100 via a second connecting pipe 1700. The expansion end is located on the first connecting pipe 1600, and the compression end is located on the second connecting pipe 1700.

[0091] The expansion end achieves cooling, depressurization, and energy recovery through material expansion, while the compression end achieves pressurization through material compression. Simultaneously, the energy recovered from the expansion end drives the compression end, reducing additional energy consumption. The first connecting pipeline 1600 connects the first heat exchanger 100 and the first inlet of the demethanizer 300, providing a channel for transporting the heat-exchanged feedstock natural gas to the demethanizer 300. The second connecting pipeline 1700 connects the gas phase outlet of the demethanizer 300 and the first heat exchanger 100, providing a path for the reflux heat exchange of the separated lean natural gas.

[0092] In this application, the raw material natural gas (gas phase) is directionally transported along the first transmission pipeline 1400 to the corresponding medium channel of the first heat exchanger 100 under the action of the first transmission pipeline 1400. Simultaneously, the raw material LNG (liquid phase) is independently transported to another set of medium channels in the first heat exchanger 100 under the action of the second transmission pipeline 1500. Inside the first heat exchanger 100, the raw material LNG and the relatively higher-temperature raw material natural gas undergo efficient heat exchange, utilizing the cooling capacity of the LNG to pre-cool the raw material natural gas.

[0093] Subsequently, the pre-treated feedstock natural gas (gaseous feedstock natural gas or gas-liquid mixed feedstock natural gas) is conveyed to the first inlet of the demethanizer 300 through the first connecting pipeline 1600. When it flows through the expansion end of the expansion compressor unit 1000 embedded in the first connecting pipeline 1600, the material pushes the expansion end to do work, achieving rapid cooling and depressurization. Then, the cooled and depressurized feedstock natural gas enters the demethanizer 300.

[0094] In this process, the lean natural gas separated by distillation in the demethanizer 300 is guided from the gas phase outlet at the top of the tower to the outside of the demethanizer 300. The demethanized liquid leaves the bottom of the demethanizer 300 in liquid phase.

[0095] Furthermore, the lean natural gas in the second connecting pipeline 1700 flows through the compression end of the expansion compressor unit 1000 embedded in the second connecting pipeline 1700. The mechanical energy generated by the work done at the expansion end directly drives the compression end to compress and pressurize the lean natural gas. The pressurized lean natural gas continues to flow back along the second connecting pipeline 1700 to the first heat exchanger 100, where it exchanges heat with the raw material LNG. After further recovering the cold energy contained in the LNG, the lean natural gas can absorb cold energy and liquefy.

[0096] With the above setup, the expansion end utilizes the pressure energy of the raw natural gas in the first connecting pipeline 1600 to expand and perform work, converting the pressure energy of the raw natural gas into mechanical energy. This mechanical energy directly drives the compression end to compress and pressurize the lean natural gas in the second connecting pipeline 1700, eliminating the need for additional drive equipment such as motors and avoiding the problem of consuming a large amount of electrical energy for methane export and pressurization in traditional processes. Simultaneously, the lean natural gas, after compression, enters the first heat exchanger 100 for heat exchange and cooling, fully utilizing the cold energy contained in the LNG to achieve cascaded energy utilization and significantly reduce the overall energy consumption of the system.

[0097] Furthermore, the expansion end expands the raw material natural gas in the first connecting pipeline 1600, which can further reduce the temperature of the raw material natural gas, ensuring the low-temperature environment necessary for the operation of the demethanizer 300 and improving the yield of the demethanizer 300.

[0098] In some embodiments, a third connecting pipe 1800 is also included, wherein the second connecting pipe 1700 is connected to the third connecting pipe 1800 through the first heat exchanger 100.

[0099] Within the third connecting pipeline 1800, lean natural gas condenses into a liquid state. The liquid lean natural gas is then converted into a gaseous state through the first heat exchanger 100 and transported to the outside.

[0100] Alternatively, within the third connecting pipe 1800, the lean natural gas condenses into a gas-liquid mixture, and the gas-liquid mixture is then converted into a gaseous state through the first heat exchanger 100 and transported to the outside.

[0101] The second connecting pipeline 1700 serves as a return and external transmission channel for the separated lean natural gas, connecting the gas phase outlet of the demethanizer 300 with the first heat exchanger 100. The compression end of the expansion compressor unit 1000 is embedded in the second connecting pipeline 1700 to realize the compression and pressurization of the lean natural gas and to perform heat exchange. It is also connected to the third connecting pipeline 1800 through the first heat exchanger 100.

[0102] Subsequently, the third connecting pipeline 1800 serves as the downstream processing and export terminal channel for lean natural gas. One end of the third connecting pipeline 1800 is connected to the second connecting pipeline 1700 through the first heat exchanger 100, so that the lean natural gas after heat exchange is condensed through the first heat exchanger 100 and enters the third connecting pipeline 1800, providing a path for the condensation, regasification and final export of lean natural gas.

[0103] Specifically, the lean natural gas discharged from the gas phase outlet of the demethanizer 300 is introduced into the first heat exchanger 100 via the second connecting pipeline 1700. After heat exchange in the first heat exchanger 100, the temperature decreases, and the lean natural gas condenses from the gas phase into a liquid state. The condensed liquid lean natural gas is then pressurized by a pump and re-enters the first heat exchanger 100 to absorb heat and revert to a gaseous state, meeting the pressure requirements for natural gas export and reducing the energy consumption of pressurized gaseous natural gas.

[0104] In this application, the lean natural gas, after being compressed and pressurized at the compression end of the expansion compressor unit 1000, flows back to the first heat exchanger 100 via the second connecting pipeline 1700, where it exchanges heat with the feedstock LNG, causing the lean natural gas to cool and condense into a liquid state. This liquid then enters the third connecting pipeline 1800 through the first heat exchanger 100. Subsequently, the liquid lean natural gas is pressurized by a pump and re-enters the first heat exchanger 100, where it absorbs heat, heats up, and is re-gasified, converting into a gaseous state before being transported to the outside, ultimately completing the external transmission process.

[0105] Through the above setup, the third connecting pipeline 1800 establishes a control system for the condensation, pressurization, and regasification of lean natural gas. It fully utilizes the cold energy of the raw material LNG to liquefy the lean natural gas, significantly reducing the pressurization energy consumption required for exporting natural gas. Then, it utilizes the heat of the raw material natural gas to regasify the liquefied lean natural gas for export, further reducing the energy consumption of regasifying the raw material LNG during the export process from the LNG receiving terminal.

[0106] In some embodiments, a heating assembly 400 is also included. A third connecting pipe 1800 is connected to the inlet of the heating assembly 400 through a first heat exchanger 100. When the natural gas in the third connecting pipe 1800 leaves the first heat exchanger 100 and enters the heating assembly 400, the liquid lean natural gas in the third connecting pipe 1800 is vaporized into a gaseous state.

[0107] The heating component 400 has an inlet and an outlet structure. The inlet of the heating component 400 is connected to the third connecting pipe 1800, which can provide stable heat to ensure that the liquid lean natural gas entering the heating component 400 is efficiently vaporized into a gaseous state, thus ensuring the stability of the form of the exported natural gas.

[0108] One end of the third connecting pipe 1800 is connected to the second connecting pipe 1700 through the first heat exchanger 100, and the other end of the third connecting pipe 1800 is connected to the inlet of the heating component 400, receiving the lean natural gas after heat exchange, and providing a path for its condensation and transportation to the heating component 400.

[0109] In this application, the lean natural gas, after being compressed and pressurized at the compression end, flows back to the first heat exchanger 100 along the second connecting pipeline 1700 to exchange heat with the raw material LNG. After being condensed into a liquid state by the cold energy, the lean natural gas is transported to the first heat exchanger 100 again through the third connecting pipeline 1800 for heat exchange again. This allows the liquid lean natural gas entering the first heat exchanger 100 through the third connecting pipeline 1800 to exchange heat with the raw material natural gas and be heated to a gaseous state or a gas-liquid mixture state, and then enters the inlet of the heating component 400 through the first heat exchanger 100.

[0110] Finally, the gaseous lean natural gas or the gas-liquid mixture lean natural gas enters the heating component 400, absorbs the heat provided by the heating component 400 to complete the gasification, and is converted into a stable gaseous state to meet the external transmission standard, and is finally transported to the outside.

[0111] With the above setup, the liquefied lean natural gas is transported to the first heat exchanger 100 via the third connecting pipeline 1800 for heat exchange, causing the liquefied lean natural gas to heat up to a gaseous state. This allows the heating component 400 to precisely adjust the vaporization temperature according to the export requirements, ensuring that the exported natural gas is always in a stable gaseous state.

[0112] Alternatively, the liquefied lean natural gas can be transported to the first heat exchanger 100 via the third connecting pipeline 1800 for heat exchange, so that the liquefied lean natural gas is heated to a gas-liquid mixed state and then introduced into the heating component 400. It can be completely vaporized by the stable heat provided by the heating component 400 without being affected by the fluctuation of the front-end heat exchange conditions, thus avoiding the inclusion of liquid components in the gaseous lean natural gas.

[0113] In some embodiments, the heating assembly 400 includes an air heater 410 and a heater 420 connected to each other. The inlet of the air heater 410 is connected to a third connecting pipe 1800 via a first heat exchanger 100, so that the gas phase outlet of the demethanizer 300 is connected to the inlet of the air heater 410 in sequence via the compression end, the first heat exchanger 100, the third connecting pipe 1800, and the first heat exchanger 100.

[0114] The heating assembly 400 includes an air heater 410 and a heater 420 connected to each other, forming a staged heating structure. The inlet of the air heater 410 is connected to the third connecting pipe 1800 through the first heat exchanger 100, and the outlet of the air heater 410 is connected to the heater 420. The outlet of the heater 420 is the final output end of the heating assembly 400. The air heater 410 can use air as a heat exchange medium or heating source to initially heat the gaseous lean natural gas transported by the third connecting pipe 1800. After that, the heater 420 is directly connected to the air heater 410, which can provide continuous and stable heat to achieve deep heating, thereby providing staged and stable heat and ensuring the stability of the output gas state.

[0115] In this application, the temperature of the lean natural gas decreases after heat exchange, transforming it from a gaseous state into a liquid or gas-liquid mixture, and then it enters the third connecting pipeline 1800 through the first heat exchanger 100. Subsequently, the third connecting pipeline 1800 guides the liquid or gas-liquid mixture of lean natural gas back into the first heat exchanger 100 to absorb heat and transform it into a gaseous state, which is then transported to the air heater 410 of the heating assembly 400 to be heated to the external output temperature.

[0116] With the above settings, the staged heating of the air heater 410 and heater 420 in the heating assembly 400 can dynamically adjust the heating intensity of the lean natural gas, avoiding the inability of a single heating device to reach the required temperature for external transmission due to load fluctuations.

[0117] In some embodiments, the system further includes a second heat exchanger 200, a fourth connecting pipe 1900, and a fifth connecting pipe 2000. A second delivery pipeline 1500 is connected to a first heat exchanger 100 via the second heat exchanger 200. The first heat exchanger 100 is connected to the third inlet of the demethanizer 300 via the fourth connecting pipe 1900. The third connecting pipe 1800 is connected to the fourth inlet of the demethanizer 300 via the fifth connecting pipe 2000. The second heat exchanger 200 is disposed on the fifth connecting pipe 2000, within which the lean natural gas is in a liquid state.

[0118] The second heat exchanger 200 connects the second transmission pipeline 1500 and the fifth connecting pipeline 2000. The second heat exchanger 200 precools the raw material LNG in the second transmission pipeline 1500, and at the same time utilizes the cold energy of the liquid lean natural gas in the fifth connecting pipeline 2000 to achieve secondary distribution and efficient utilization of cold energy, providing support for the state control of raw material LNG and liquid lean natural gas.

[0119] The fourth connecting pipeline 1900 serves as a transport channel for pre-treated raw material LNG. The fourth connecting pipeline 1900 connects the first heat exchanger 100 and the third inlet of the demethanizer 300, and transports the lean natural gas that has been cooled twice to the demethanizer 300.

[0120] The fifth connecting pipeline 2000 serves as a return channel for liquefied lean natural gas. The fifth connecting pipeline 2000 connects the third connecting pipeline 1800 and the fourth inlet of the demethanizer 300, providing a path for the liquefied lean natural gas to return to the demethanizer 300, and the lean natural gas in the fifth connecting pipeline 2000 remains stably liquid.

[0121] In this application, the feedstock LNG first enters the second heat exchanger 200 via the second transmission pipeline 1500, where it exchanges heat with the liquefied lean natural gas flowing in the fifth connecting pipeline 2000. The liquefied lean natural gas cools down and becomes subcooled, while the feedstock LNG absorbs heat and warms up, ensuring that cold energy is recovered across the path. The reheated feedstock LNG then enters the first heat exchanger 100 via the second transmission pipeline 1500, where it completes one heat exchange with the feedstock natural gas.

[0122] Afterwards, the raw material LNG (liquid or gas-liquid mixed state) after heat exchange in the first heat exchanger 100 is transported to the third inlet of the demethanizer 300 through the fourth connecting pipeline 1900, realizing separate inlet feeding from the raw material natural gas, improving the temperature distribution in the cold box and increasing the utilization efficiency of cold energy.

[0123] Furthermore, the lean natural gas is condensed into a liquid or gas-liquid mixture in the first heat exchanger 100 and enters the third connecting pipe 1800. Subsequently, it enters the second heat exchanger 200, absorbs cold energy, and is cooled down. The lean natural gas in this state is divided into two paths: one path is pumped into the first heat exchanger 100 and, after passing through the heating component 400, is converted into high-pressure lean natural gas; the other path passes through the fourth heat exchanger 900, absorbs cold energy, and is then returned to the demethanizer 300 as reflux liquid.

[0124] The liquid lean natural gas in the fifth connecting pipeline 2000 absorbs the cold energy released by the raw material LNG in the second heat exchanger 200, which further cools the liquid lean natural gas. The raw material LNG in the second transmission pipeline 1500 absorbs heat and heats up. After the cold energy transfer is completed, the liquid lean natural gas flows back to the demethanizer 300 through the fourth inlet of the demethanizer 300 along the fifth connecting pipeline 2000.

[0125] Through the above setup, the fifth connecting pipeline 2000 enables the reflux of liquefied lean natural gas to the demethanizer 300, making cascade use of the cold energy of the LNG feedstock, improving the cold energy utilization rate and further increasing the light hydrocarbon yield of the demethanizer.

[0126] In some embodiments, the system further includes a deethanizer 500, the liquid phase outlet of the demethanizer 300 being connected to the first inlet of the deethanizer 500, and the gas outlet of the deethanizer 500 being connected to the first heat exchanger 100.

[0127] The deethanizer 500 can perform deep separation of the demethanized liquid discharged from the bottom of the demethanizer 300 to extract ethane, while guiding the gas phase components separated by the deethanizer 500 back to the first heat exchanger 100 to recover cold energy.

[0128] Ethane in the gas phase is discharged through the outlet at the top of the deethaner 500 and transported through pipeline to the medium channel of the first heat exchanger 100 to exchange heat with the raw material LNG.

[0129] Ethane, after being liquefied by heat exchanger 100, is pressurized by reflux pump 1120 and returned to the top of the deethaner column to improve ethane recovery rate.

[0130] It also includes a third heat exchanger 600. The outlet of the deethaner 500 is divided into two branches. One branch and the liquid outlet are connected to the two inlets of the third heat exchanger 600, respectively. The other branch introduces ethane into the first heat exchanger 100 and returns it to the deethaner 500 via the reflux pump 1120.

[0131] In some embodiments, the system further includes an ethane reflux branch 1100, which is equipped with a reflux tank 1110 and a reflux pump 1120. The outlet of the deethaner 500 is connected to the second inlet of the deethaner 500 via a first heat exchanger 100, a reflux tank 1110, and a reflux pump 1120 in sequence.

[0132] To reduce the propane content in the ethane product, a portion of the ethane is refluxed to the deethaner 500 via the first heat exchanger 100, reflux tank 1110, and reflux pump 1120.

[0133] In practice, ethane is liquefied in the first heat exchanger 100 and introduced into the reflux tank 1110 for separation. The gas at the top of the reflux tank 1110 is output to the external environment, and the liquid at the bottom of the reflux tank 1110 is pressurized by the reflux pump 1120 and then refluxed back into the de-ethane tower 500. The reflux pump 1120 is used to increase the pressure of the liquid after ethane liquefaction to provide power for its reflux.

[0134] In some embodiments, a gas-liquid separator 2100 is provided on the first connecting pipe 1600. The inlet of the gas-liquid separator 2100 is connected to the first heat exchanger 100. The gas-liquid separator 2100 has a liquid outlet and a gas outlet. The gas outlet is connected to the first connecting pipe 1600, and the liquid outlet is guided to the outside of the gas-liquid separator 2100.

[0135] In this application, the raw natural gas, after heat exchange in the first heat exchanger 100, is introduced into the first connecting pipeline 1600. The raw natural gas in the first connecting pipeline 1600 may be in a gaseous state or a gas-liquid mixture. Gas-liquid separation is achieved using a gas-liquid separator 2100. The gaseous raw natural gas is introduced into the demethanizer 300, and the liquid outlet is directly discharged to the outside of the gas-liquid separator 2100, thereby achieving gas-liquid separation of the raw natural gas in the gas-liquid mixture state.

[0136] like Figure 1 As shown, in some embodiments, a rich liquid booster pump 700 and a lean liquid booster pump 800 are also included. The rich liquid booster pump 700 is installed on the second delivery line 1500, and the lean liquid booster pump 800 is installed on the third connecting line 1800.

[0137] In this application, the rich liquid booster pump 700 is used to increase the pressure of the feedstock LNG, providing power for the feedstock LNG to enter the demethanizer 300. The lean liquid booster pump 800 is used to increase the pressure of the liquefied lean natural gas to achieve the necessary export pressure.

[0138] At the same time, by using the cooling capacity of LNG to liquefy lean natural gas in advance, the energy consumed to increase the pressure of the liquid phase is much less than the energy consumed to pressurize the gas phase, which reduces the pressurization load of the lean liquid booster pump 800.

[0139] Reference Figure 1 As shown in the embodiment of this application, a gas-liquid miscible light hydrocarbon separation process system for an LNG receiving station is provided, including a first heat exchanger 100; a second heat exchanger 200; a demethanizer 300, wherein the feed natural gas is connected to the first inlet of the demethanizer 300 via the first heat exchanger 100; the feed LNG is connected to the second inlet of the demethanizer 300 via the second heat exchanger 200 and the first heat exchanger 100 in sequence; a heating assembly 400, wherein the gas outlet of the demethanizer 300 is connected to the inlet of the heating assembly 400 via the first heat exchanger 100, the second heat exchanger 200 and the first heat exchanger 100 in sequence; a deethanizer 500, wherein the liquid outlet of the demethanizer 300 is connected to the first inlet of the deethanizer 500; and a third heat exchanger 600, wherein the gas outlet and the liquid outlet of the deethanizer 500 are respectively connected to the two side inlets of the third heat exchanger 600.

[0140] It should be noted that there are no specific requirements for the structure of the demethanizer 300 and the deethaner 500; they can be plate towers or packed towers, and staff can choose according to their needs.

[0141] In practice, the raw material natural gas is fed into the demethanizer 300 via the first heat exchanger 100; the raw material LNG is fed into the demethanizer 300 via the second heat exchanger 200 and the first heat exchanger 100 in sequence; the gas at the top of the demethanizer 300 is heated by the first heat exchanger 100, the second heat exchanger 200, the first heat exchanger 100, and the heating component 400 in sequence to prepare lean natural gas and output; the liquid at the bottom of the demethanizer 300 is separated by the deethaner 500 and heat-treated by the third heat exchanger 600 to prepare LPG and ethane and output.

[0142] In this embodiment, since LNG has a large amount of cold energy, when the raw material LNG is introduced into the light hydrocarbon separation process system, its internal cold energy will first be transferred to the liquid lean natural gas from the first heat exchanger 100 through the second heat exchanger 200, so as to make it subcooled and prevent cavitation from occurring during the pressurization process of the liquid lean natural gas. Then, the raw material LNG flows through the first heat exchanger 100, transferring the cold energy to the lean natural gas from the demethanizer 300 to liquefy it. After the liquid natural gas rises to a suitable temperature, it is introduced into the demethanizer 300.

[0143] When the feedstock natural gas is fed into the light hydrocarbon separation process system, it will transfer heat to the pressurized liquefied lean natural gas, causing it to vaporize. After the feedstock natural gas is cooled to a suitable temperature, it is fed into the demethanizer tower 300.

[0144] Compared to existing light hydrocarbon separation processes, this application provides a gas-liquid miscible light hydrocarbon separation process system for LNG receiving terminals, which can improve the light hydrocarbon recovery rate of the light hydrocarbon separation process system. Using gaseous natural gas and LNG as raw materials, the cold energy contained in LNG is used as the sole cold source to provide cooling for the light hydrocarbon separation process system, reducing energy consumption in the light hydrocarbon separation process. Utilizing the cold energy of LNG to liquefy lean natural gas can significantly reduce the pressurization energy consumption required for exporting natural gas. Then, the heat of the raw material natural gas is used to vaporize the liquefied lean natural gas for export, further reducing the energy consumption for LNG vaporization during the export process from the LNG receiving terminal.

[0145] In some embodiments, the system further includes a rich liquid booster pump 700 and a lean liquid booster pump 800, with the second heat exchanger 200 connected to the first heat exchanger 100 via a first pipeline; the outlet of the rich liquid booster pump 700 is connected to the second inlet of the demethanizer 300 via the second heat exchanger 200 and the first heat exchanger 100 in sequence; and the lean liquid booster pump 800 is located on the first pipeline.

[0146] In practice, the rich liquid booster pump 700 is used to increase the pressure of the raw material LNG to provide power for the raw material LNG to enter the demethanizer 300; while the lean liquid booster pump 800 is used to increase the pressure of the liquid after lean natural gas liquefaction so that it reaches the necessary external transmission pressure.

[0147] At the same time, by using the cooling capacity of LNG to liquefy lean natural gas in advance, the energy consumed to increase the pressure of the liquid phase is much less than the energy consumed to pressurize the gas phase, which reduces the pressurization load of the lean liquid booster pump 800.

[0148] Furthermore, in some embodiments, the outlet of the rich liquid booster pump 700 is connected to the third inlet of the demethanizer 300 via the second heat exchanger 200; it also includes a fourth heat exchanger 900, and the gas outlet of the demethanizer 300 is connected to the fourth inlet of the demethanizer 300 in sequence via the first heat exchanger 100, the second heat exchanger 200 and the fourth heat exchanger 900; the outlet of the rich liquid booster pump 700 is connected to the fifth inlet of the demethanizer 300 via the fourth heat exchanger 900.

[0149] In the above embodiments, two additional paths are provided for the feedstock LNG to enter the demethanizer 300.

[0150] Meanwhile, in order to improve the recovery rate of light hydrocarbons, a portion of the liquid after liquefaction of lean natural gas is refluxed to the demethanizer tower 300 via the fourth heat exchanger 900. At this time, the internal cooling capacity of the raw material LNG will be transferred to the liquid through the fourth heat exchanger 900 to lower the liquid to a suitable temperature, thereby realizing the further utilization of the cold energy of the raw material LNG.

[0151] Of course, staff can reassemble the fourth heat exchanger 900 according to the actual situation (see reference). Figure 2 This allows the cold energy of the feedstock LNG to be concentrated for the liquefaction of lean natural gas and the cooling of the feedstock natural gas.

[0152] In some embodiments, the heating assembly 400 includes an air heater 410 and a heater 420 connected to each other; the outlet of the demethanizer 300 is connected to the inlet of the air heater 410 via a first heat exchanger 100, a second heat exchanger 200 and the first heat exchanger 100 in sequence.

[0153] Here, an air heater 410 is provided to heat the gasified lean natural gas and reheat it; the heater 420 then heats the reheated lean natural gas to the export temperature; the multi-stage heating system consisting of the air heater 410 and the heater 420 improves the heating efficiency of the lean natural gas and reduces the energy consumption of the process system; at the same time, the air heater 410 has the characteristics of small size and high heating efficiency.

[0154] In practice, the lean natural gas is divided into two streams by passing through the first heat exchanger 100 and the second heat exchanger 200. By controlling the flow rate of one stream, it can be directly heated by the first heat exchanger 100 to reach the specified export temperature. The other stream is vaporized by the first heat exchanger 100 and then heated by multiple stages of air heater 410 and heater 420 before being output.

[0155] In some embodiments, the system further includes an expansion compressor unit 1000, which includes an expansion end and a compression end; a first heat exchanger 100 is connected to the first inlet of a demethanizer 300 via a second pipeline, and the outlet of the demethanizer 300 is connected to the first heat exchanger 100 via a third pipeline; the expansion end of the expansion compressor unit 1000 is located on the second pipeline, and the compression end of the expansion compressor unit 1000 is located on the third pipeline.

[0156] In the above embodiment, an expansion compressor unit 1000 is provided. On the one hand, it recovers the pressure energy of the raw material natural gas to reduce it to a suitable temperature. On the other hand, it pressurizes the lean natural gas separated by the demethanizer tower 300 to increase the bubble point temperature of the lean natural gas, making it easier for the lean natural gas to be completely liquefied in the first heat exchanger 100 and the second heat exchanger 200.

[0157] In some embodiments, the first outlet of the demethanizer 300 is connected to the sixth inlet of the demethanizer 300 via a first heat exchanger 100.

[0158] To improve the recovery rate of light hydrocarbons, a portion of the liquid from the liquefaction of lean natural gas is subcooled in the fourth heat exchanger 900 and then refluxed into the demethanizer 300, which increases the heating load of the demethanizer 300. Therefore, in the above embodiment, a portion of the liquid is drawn from the demethanizer 300, vaporized in the heat exchange section of the first heat exchanger 100, and then introduced into the demethanizer 300 to reduce the proportion of liquid phase in the demethanizer 300, thereby reducing the heating load of the demethanizer 300.

[0159] In some embodiments, the system further includes an ethane reflux branch 1100, on which a reflux tank 1110 and a reflux pump 1120 are provided; the first heat exchanger 100 also has an eleventh channel capable of heat exchange; the outlet of the deethaner 500 is connected to the second inlet of the deethaner 500 in sequence via the first heat exchanger 100, the reflux tank 1110 and the reflux pump 1120.

[0160] To reduce the propane content in the ethane product, a portion of the ethane is refluxed to the deethaner 500 via the first heat exchanger 100, reflux tank 1110, and reflux pump 1120.

[0161] In practice, ethane is liquefied in the first heat exchanger 100 and introduced into the reflux tank 1110 for separation. The gas at the top of the reflux tank 1110 is output to the external environment, and the liquid at the bottom of the reflux tank 1110 is pressurized by the reflux pump 1120 and then refluxed back into the de-ethane tower 500. The reflux pump 1120 is used to increase the pressure of the liquid after ethane liquefaction to provide power for its reflux.

[0162] In some embodiments, a refrigerant circulation path 1200 is further included, on which a suction tank 1210, a compressor 1220 and a throttle valve 1230 are provided, so that the refrigerant inside the first heat exchanger 100 flows back to the first heat exchanger 100 in sequence through the suction tank 1210, the compressor 1220 and the throttle valve 1230.

[0163] As a bridge for heat transfer between raw material LNG and raw material natural gas and lean natural gas, in order to obtain different grades of cooling capacity, a refrigerant circulation path 1200 is set up in the above embodiment so that the refrigerant in the first heat exchanger 100 can circulate. The compressor 1220 is used to provide power for the flow of refrigerant.

[0164] In some embodiments, both the demethanizer 300 and the deethanizer 500 are equipped with a reboiler 1300 at the bottom.

[0165] In the above embodiment, a reboiler 1300 is provided to vaporize the liquid portion at the bottom of the demethanizer 300 and the deethanizer 500, providing the necessary gaseous feedstock for the operation of the demethanizer 300 and the deethanizer 500.

[0166] It should be noted that there are no requirements for the reboiler 1300; it can be natural gas, steam, heat transfer oil, or seawater, and the staff can choose the heat source according to the required temperature.

[0167] This application also proposes a method for separating gas-liquid miscible light hydrocarbons in an LNG receiving terminal based on the aforementioned process system, referring to... Figure 1 As shown, it includes:

[0168] Heat exchange section: After pre-cooling in the first heat exchanger 100, the raw natural gas is expanded and cooled by the expansion compressor unit 1000 to recover its pressure energy and further reduce its temperature before entering the demethanizer 300; the raw LNG is pressurized by the rich liquid booster pump 700 and divided into three streams: one stream enters the second heat exchanger 200 and the first heat exchanger 100 in sequence to provide cooling, and then serves as the liquid feed at the top of the demethanizer 300; another stream enters the second heat exchanger 200 to provide cooling and then serves as the liquid feed at the top of the demethanizer 300; and the third stream enters the third heat exchanger 600 to provide cooling and then serves as the liquid feed at the top of the demethanizer 300.

[0169] Demethanizing section: The lean natural gas exiting from the top of the demethanizer 300 is compressed and pressurized by the expansion compressor unit 1000, then enters the first heat exchanger 100 for liquefaction, and then enters the second heat exchanger 200 for subcooling, after which it is divided into two streams. One stream is further subcooled by the third heat exchanger 600 and serves as the liquid phase reflux at the top of the demethanizer 300. The other stream is pressurized by the lean liquid booster pump 800 and then divided into two streams entering the first heat exchanger 100. After the two lean liquid streams are vaporized and reheated by the first heat exchanger 100, one stream is directly heated to the external output temperature and then output, while the other stream is heated and reheated by the air heater 410 and then heated to the external output temperature by the heater 420 before being output. A stream of low-temperature hydrocarbon liquid is extracted from the middle of the demethanizer 300 and enters the first heat exchanger 100. After reheating, it returns to the demethanizer 300. The hydrocarbon liquid at the bottom of the demethanizer 300 is heated by the reboiler and then transported to the deethaner 500 in liquid phase.

[0170] De-ethane removal section: The demethanized liquid from the bottom of the demethanizer 300 is sent to the middle of the de-ethaner 500. The top gas phase of the de-ethaner 500 enters the first heat exchanger 100 for condensation and then enters the reflux tank 1110. It is then pressurized by the reflux pump 1120 and used as reflux for the de-ethaner 500. The bottom hydrocarbon liquid of the de-ethaner 500 is heated and separated in a reboiler. The liquid phase then exchanges heat with another portion of the gaseous ethane from the top of the de-ethaner 500 in the second heat exchanger 200 before being separately discharged.

[0171] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A gas-liquid miscible light hydrocarbon separation process system for an LNG receiving terminal, characterized in that, include: First heat exchanger (100); A demethanizer (300) has a gas phase outlet and a liquid phase outlet, the gas phase outlet being located at the top of the demethanizer (300) and the liquid phase outlet being located at the bottom of the demethanizer (300) to guide the lean natural gas and demethanized liquid of the demethanizer (300) to the outside of the demethanizer (300); The first transmission pipeline (1400) is used to transport raw material natural gas, and the first transmission pipeline (1400) is connected to the first inlet of the demethanizer (300) through the first heat exchanger (100); The second transport pipeline (1500) is used to transport raw material LNG. The second transport pipeline (1500) is connected to the second inlet of the demethanizer (300) through the first heat exchanger (100). In the first heat exchanger (100), the raw material natural gas and the raw material LNG exchange heat.

2. The LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system according to claim 1, characterized in that, It also includes an expansion compressor unit (1000), which includes an expansion end and a compression end; The first heat exchanger (100) is connected to the first inlet of the demethanizer (300) through the first connecting pipe (1600), and the gas phase outlet of the demethanizer (300) is connected to the first heat exchanger (100) through the second connecting pipe (1700). The expansion end is located on the first connecting pipe (1600), and the compression end is located on the second connecting pipe (1700).

3. The LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system according to claim 2, characterized in that, It also includes a third connecting pipe (1800), and the second connecting pipe (1700) is connected to the third connecting pipe (1800) through the first heat exchanger (100); In the third connecting pipeline (1800), the lean natural gas condenses into a liquid state, and the liquid lean natural gas is heat-exchanged into a gaseous state through the first heat exchanger (100) and transported to the outside. Alternatively, within the third connecting pipe (1800), the lean natural gas condenses into a gas-liquid mixture, and the gas-liquid mixture is then converted into a gaseous state by the first heat exchanger (100) and transported to the outside.

4. The LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system according to claim 3, characterized in that, It also includes a heating assembly (400), and the third connecting pipe (1800) is connected to the inlet of the heating assembly (400) through the first heat exchanger (100). As the natural gas leaves the first heat exchanger (100) and enters the heating assembly (400), the liquid lean natural gas in the third connecting pipe (1800) is vaporized into a gaseous state.

5. The LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system according to claim 4, characterized in that, The heating assembly (400) includes an air heater (410) and a heater (420) connected to each other. The inlet of the air heater (410) is connected to the third connecting pipe (1800) through the first heat exchanger (100), so that the gas phase outlet of the demethanizer (300) is connected to the inlet of the air heater (410) in sequence through the compression end, the first heat exchanger (100), the third connecting pipe (1800) and the first heat exchanger (100).

6. The LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system according to claim 3, characterized in that, It also includes a second heat exchanger (200), a fourth connecting pipe (1900) and a fifth connecting pipe (2000), the second delivery pipe (1500) being connected to the first heat exchanger (100) through the second heat exchanger (200), and the first heat exchanger (100) being connected to the third inlet of the demethanizer (300) through the fourth connecting pipe (1900); The third connecting pipe (1800) is connected to the fourth inlet of the demethanizer (300) through the fifth connecting pipe (2000), and the second heat exchanger (200) is installed on the fifth connecting pipe (2000). The lean natural gas is in liquid state in the fifth connecting pipe (2000).

7. The LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system according to claim 1, characterized in that, It also includes a deethanizer (500), the liquid phase outlet of the demethanizer (300) being connected to the first inlet of the deethanizer (500), and the gas outlet of the deethanizer (500) being connected to the first heat exchanger (100). It also includes a third heat exchanger (600), and the gas outlet and liquid outlet of the deethaner (500) are respectively connected to the two inlets of the third heat exchanger (600).

8. The LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system according to claim 7, characterized in that, It also includes an ethane reflux branch (1100), on which a reflux tank (1110) and a reflux pump (1120) are provided. The outlet of the deethaner (500) is connected to the second inlet of the deethaner (500) in sequence through the first heat exchanger (100), the reflux tank (1110) and the reflux pump (1120).

9. The LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system according to claim 2, characterized in that, A gas-liquid separator (2100) is provided on the first connecting pipe (1600). The inlet of the gas-liquid separator (2100) is connected to the first heat exchanger (100). The gas-liquid separator (2100) has a liquid outlet and a gas outlet. The gas outlet is connected to the first connecting pipe (1600), and the liquid outlet is guided to the outside of the gas-liquid separator (2100).

10. The LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system according to claim 4, characterized in that, It also includes a rich liquid booster pump (700) and a lean liquid booster pump (800), the rich liquid booster pump (700) being installed on the second delivery line (1500) and the lean liquid booster pump (800) being installed on the third connecting line (1800).

11. A gas-liquid miscible light hydrocarbon separation process system for an LNG receiving terminal, characterized in that, include: First heat exchanger (100); A demethanizer (300) has a gas phase outlet and a liquid phase outlet, the gas phase outlet being located at the top of the demethanizer (300) and the liquid phase outlet being located at the bottom of the demethanizer (300) to guide the lean natural gas and demethanized liquid of the demethanizer (300) to the outside of the demethanizer (300); The first transmission pipeline (1400) is used to transport raw material natural gas, and the first transmission pipeline (1400) is connected to the first inlet of the demethanizer (300) through the first heat exchanger (100); The second transmission pipeline (1500) is used to transport raw material LNG. The second transmission pipeline (1500) is connected to the second inlet of the demethanizer (300) through the first heat exchanger (100), and the raw material natural gas exchanges heat with the raw material LNG.

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