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

Abstract

This application provides an LNG receiving station gas-liquid mixed-phase light hydrocarbon separation process system, relating to the field of cryogenic light hydrocarbon separation technology. The system includes a first conveying pipeline, a second conveying pipeline, a demethanizer, a first heat exchanger, and a side-line output pipeline. Raw material natural gas and raw material LNG are respectively fed into the demethanizer through the first and second conveying pipelines. A side-line output pipeline is provided on one side of the demethanizer, connecting it to the first heat exchanger. Utilizing the thermosiphon principle, liquid hydrocarbons in the demethanizer flow through the side-line output pipeline into the first heat exchanger, absorbing heat from the exchanger. The partially vaporized liquid hydrocarbons are then transported back to the demethanizer. The side-line output pipeline provides cooling to the first heat exchanger, improving the temperature gradient in the cold box, and also reduces the heating load on the reboiler, thereby reducing equipment investment and energy consumption.

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] 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] The current 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, resulting in a large amount of energy being wasted. Summary of the Invention

[0005] This application provides a gas-liquid mixed-phase light hydrocarbon separation process system for LNG receiving terminals to solve the problem of a large amount of energy being wasted.

[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] The first transmission pipeline is used to transport raw material natural gas;

[0008] The second pipeline is used to transport the raw material LNG;

[0009] A demethanizing tower, the demethanizing tower having a first inlet and a second inlet, the first inlet being connected to a first conveying pipeline, and the second inlet being connected to a second conveying pipeline;

[0010] A first heat exchanger has at least two heat exchange channels for heat exchange, one of which is connected between the first delivery pipeline and the demethanizer, and the other of which is connected between the second delivery pipeline and the demethanizer.

[0011] A side-line output pipeline is connected to both the demethanizer and the first heat exchanger. Under thermosiphon action, the side-line output pipeline transports the liquid hydrocarbons in the demethanizer to the first heat exchanger and heats the liquid hydrocarbons to vaporize them. Part of the vaporized liquid hydrocarbons are then transported back to the demethanizer through the side-line output pipeline.

[0012] In one possible implementation, the side-line output pipeline includes a first side-line output pipeline and a second side-line output pipeline; the first heat exchanger is connected to the demethanizer via the first side-line output pipeline;

[0013] The first end of the first side-line output pipe forms a first communication port on the side wall of the demethanizer; the liquid hydrocarbon in the demethanizer is transported to the first heat exchanger through the first side-line output pipe, and the liquid hydrocarbon is heated; the first heat exchanger is connected to the demethanizer through the second side-line output pipe; the second end of the second side-line output pipe forms a second communication port on the side wall of the demethanizer; the partially vaporized liquid hydrocarbon flows back to the demethanizer through the second side-line output pipe; the first communication port is above the second communication port.

[0014] In one possible implementation, the second delivery pipeline includes a main line; one end of the main line is connected to the demethanizer, and the end of the main line forms a second inlet on the demethanizer; the second inlet is located above the first connection port.

[0015] In one possible implementation, the second delivery pipeline further includes a first branch, a first end of which is connected to the main pipeline; a second end of which is connected to the demethanizer, and a third inlet is formed on the demethanizer at the second end of the first branch; the third inlet is located above the first inlet.

[0016] In one possible implementation, it also includes:

[0017] A third conveying pipeline is connected to both the demethanizer and the first heat exchanger. Liquid hydrocarbons at the top of the demethanizer flow through the third conveying pipeline and exchange heat with the first heat exchanger. The first end of the third conveying pipeline is connected to the top of the demethanizer, and the second end of the third conveying pipeline forms a fourth inlet on the demethanizer.

[0018] Along the height direction of the demethanizer, the fourth inlet, the first inlet, the second inlet, the third inlet, the first connecting port, and the second connecting port are arranged sequentially from top to bottom.

[0019] In one possible implementation, the demethanizer has a plurality of tray structures arranged from top to bottom and at least one sealed tray arranged on one side of the tray structures; the liquid hydrocarbons on the sealed trays flow through the first heat exchanger via a side-line output pipeline and flow back to the tray structure at the next stage below the sealed trays.

[0020] In one possible implementation, the sealed tray is located between the first connecting port and the second connecting port. Under the action of thermosiphon, the liquid hydrocarbon on the sealed tray enters the first side line output pipeline through the first connecting port and is transported to the first heat exchanger, where the liquid hydrocarbon is heated to vaporize a portion of it. The partially vaporized liquid hydrocarbon flows through the second side line output pipeline and through the second connecting port to the next stage tray structure of the sealed tray.

[0021] In one possible implementation, the first connection port is always below the liquid hydrocarbon level on the sealed tray.

[0022] In one possible implementation, the sealed tray is provided with a groove; the first communication port is located within the groove.

[0023] In one possible implementation, it also includes:

[0024] An overflow structure is provided on the sealed tray; when the liquid hydrocarbon on the sealed tray exceeds a certain height, it flows through the overflow structure to the next stage tray structure.

[0025] In one possible implementation, it also includes:

[0026] A reboiler is connected to the bottom of the demethanizer; the reboiler heats the liquid hydrocarbons at the bottom of the demethanizer to vaporize the liquid hydrocarbons.

[0027] Secondly, an LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system includes:

[0028] The first transmission pipeline is used to transport raw material natural gas;

[0029] The second pipeline is used to transport the raw material LNG;

[0030] A demethanizing tower, the demethanizing tower having a first inlet and a second inlet, the first inlet being connected to a first conveying pipeline, and the second inlet being connected to a second conveying pipeline;

[0031] A first heat exchanger has at least two heat exchange channels for heat exchange, one of which is connected between the first delivery pipeline and the demethanizer, and the other of which is connected between the second delivery pipeline and the demethanizer.

[0032] A side-line output pipeline is connected to the demethanizer and the first heat exchanger, respectively.

[0033] This application provides an LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system, including a first conveying pipeline, a second conveying pipeline, a demethanizer, a first heat exchanger, and a side-line output pipeline. Raw material natural gas and raw material LNG are respectively fed into the demethanizer through the first and second conveying pipelines. A side-line output pipeline is provided on one side of the demethanizer, which is connected to the first heat exchanger. Utilizing the thermosiphon principle, liquid hydrocarbons in the demethanizer flow through the side-line output pipeline to the first heat exchanger, absorbing heat from the first heat exchanger. The partially vaporized liquid hydrocarbons are then transported back to the demethanizer. By providing the side-line output pipeline, cooling capacity can be provided to the first heat exchanger, improving the temperature gradient of the cold box. Furthermore, the heating load on the reboiler can be reduced, thereby reducing equipment investment and energy consumption. Attached Figure Description

[0034] 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.

[0035] Figure 1 A schematic diagram of a gas-liquid miscible light hydrocarbon separation process system for an LNG receiving station is provided in this application;

[0036] Figure 2 This is a schematic diagram of a second embodiment of an LNG receiving station gas-liquid miscible light hydrocarbon separation process system provided in this application;

[0037] Figure 3 This is a schematic diagram of the third embodiment of an LNG receiving station gas-liquid miscible light hydrocarbon separation process system provided in this application.

[0038] Figure label:

[0039] 100 - First heat exchanger;

[0040] 200 - Second heat exchanger;

[0041] 300 - Demethanizer; 310 - Tray structure; 320 - Sealed tray; 330 - Overflow structure;

[0042] 400 - Heating Component;

[0043] 410 - Air heater; 420 - Heater;

[0044] 500-Deethaner column;

[0045] 600 - Third heat exchanger;

[0046] 700-Rich Liquid Booster Pump;

[0047] 800-Lean Solution Booster Pump;

[0048] 900 - Fourth heat exchanger;

[0049] 1000-expansion compressor unit;

[0050] 1100-Ethane reflux branch;

[0051] 1110 - Reflux tank; 1120 - Reflux pump;

[0052] 1200 - Refrigerant circulation path;

[0053] 1210 - Suction tank; 1220 - Compressor; 1230 - Throttling valve;

[0054] 1300-Reboiler;

[0055] 1400 - First delivery pipeline; 1401 - First inlet;

[0056] 1500 - Second transmission pipeline; 1510 - Main road; 1511 - Second entrance; 1520 - First branch road; 1521 - Third entrance;

[0057] 1600 - Side line output pipeline; 1601 - First connection port; 1602 - Second connection port; 1610 - First side line output pipeline; 1620 - Second side line output pipeline;

[0058] 1700 - Third delivery pipeline; 1701 - Fourth inlet;

[0059] 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

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] With the continuous release of China's dual-carbon policy, natural gas consumption is increasing day by day. 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.

[0067] 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.

[0068] Currently, the light hydrocarbon separation processes applicable to LNG receiving terminals are: one is to pass the natural gas transported from the LNG receiving terminal into a light hydrocarbon separation unit for light hydrocarbon separation, but this method cannot fully utilize the cold energy of LNG, resulting in a large amount of energy waste.

[0069] To address the aforementioned issues, this application provides an LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system, comprising a first conveying pipeline, a second conveying pipeline, a demethanizer, a first heat exchanger, and a side-line output pipeline. Raw material natural gas and raw material LNG are respectively fed into the demethanizer via the first and second conveying pipelines. A side-line output pipeline is provided on one side of the demethanizer, connecting it to the first heat exchanger. Utilizing the thermosiphon principle, liquid hydrocarbons in the demethanizer flow through the side-line output pipeline into the first heat exchanger, absorbing heat from the exchanger. This partially vaporizes the liquid hydrocarbons, and the partially vaporized liquid hydrocarbons are returned to the demethanizer. By providing the side-line output pipeline, cooling capacity is provided to the first heat exchanger, improving the temperature gradient in the cold box. Furthermore, the heating load on the reboiler is reduced, thereby decreasing equipment investment and energy consumption.

[0070] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0071] like Figure 1As shown in the figure, this application provides a gas-liquid miscible light hydrocarbon separation process system for an LNG receiving station, including a first conveying pipeline 1400, a second conveying pipeline 1500, a demethanizer 300, a first heat exchanger 100, and a side-line output pipeline 1600. The first conveying pipeline 1400 is used to convey raw material natural gas; the second conveying pipeline 1500 is used to convey raw material LNG; the demethanizer 300 has a first inlet 1401 and a second inlet 1511, the first inlet 1401 being connected to the first conveying pipeline 1400, and the second inlet 1511 being connected to the second conveying pipeline 1500; wherein the first heat exchanger 100 has… The heat exchanger has at least two heat exchange channels, one of which is connected between the first delivery pipeline 1400 and the demethanizer 300, and the other is connected between the second delivery pipeline 1500 and the demethanizer 300. The side output pipeline 1600 is connected to the demethanizer 300 and the first heat exchanger 100 respectively. Under the action of thermosiphon, the side output pipeline 1600 transports the liquid hydrocarbon in the demethanizer 300 to the first heat exchanger 100 and heats the liquid hydrocarbon to vaporize it. The partially vaporized liquid hydrocarbon is transported back to the demethanizer 300 through the side output pipeline 1600.

[0072] It should be noted that there are no specific requirements for the structure of the 300 demethanizer tower; it can be a plate tower or a packed tower, and staff can choose according to their needs.

[0073] Specifically, the raw material natural gas enters the demethanizer 300 through the first transmission pipeline 1400 and the first inlet 1401 on the demethanizer 300. The raw material LNG enters the demethanizer 300 through the second transmission pipeline 1500 and the second inlet 1511 on the demethanizer 300. The liquid hydrocarbons in the demethanizer 300 are then flowed through the side output pipeline 1600 and output to the first heat exchanger 100 under the action of thermosiphon. The liquid hydrocarbons absorb heat and partially vaporize in the first heat exchanger 100. Subsequently, the partially vaporized liquid hydrocarbons are automatically transported back to the demethanizer 300 through the side output pipeline 1600.

[0074] It should be noted that the thermosiphon principle is a physical phenomenon that utilizes the density change caused by the temperature difference of a fluid to generate a natural circulation flow in a closed loop. It does not require external power such as a pump. In this embodiment, after the liquid hydrocarbon in the demethanizer 300 absorbs heat from the first heat exchanger 100, due to the partial vaporization of the liquid hydrocarbon, a density difference occurs between the liquid hydrocarbon before and after entering the first heat exchanger 100, thereby causing the liquid hydrocarbon to circulate along the side outlet pipeline 1600.

[0075] In this embodiment, the upper and lower sides are based on the height direction of the demethanizer 300. When one side is above the other, it means that its height on the demethanizer 300 is greater than that of the other.

[0076] Furthermore, in the LNG receiving station gas-liquid mixed light hydrocarbon separation process system provided in this application embodiment, the side output pipeline 1600 includes a first side output pipeline 1610 and a second side output pipeline 1620; the first heat exchanger 100 is connected to the demethanizer 300 through the first side output pipeline 1610.

[0077] The first end of the first side-line output pipe 1610 forms a first connection port 1601 on the side wall of the demethanizer 300; the liquid hydrocarbon in the demethanizer 300 is transported to the first heat exchanger 100 through the first side-line output pipe 1610 and the liquid hydrocarbon is heated; the first heat exchanger 100 is connected to the demethanizer 300 through the second side-line output pipe 1620; the second end of the second side-line output pipe 1620 forms a second connection port 1602 on the side wall of the demethanizer 300; the partially vaporized liquid hydrocarbon flows back to the demethanizer 300 through the second side-line output pipe 1620; the first connection port 1601 is above the second connection port 1602.

[0078] It should be noted that in this embodiment, there is one side output pipe 1600; in an alternative embodiment, there can be multiple side output pipes 1600, and there are multiple corresponding first connection ports 1601 and second connection ports 1602, which correspond one to one.

[0079] Specifically, the liquid hydrocarbons in the demethanizer 300 are transported to the first heat exchanger 100 through the first side line output pipeline 1610, thereby heating the liquid hydrocarbons. The heated liquid hydrocarbons then flow back into the demethanizer 300 through the second side line output pipeline 1620.

[0080] In one possible implementation, the first side line output pipe 1610 and the second side line are connected as two pipe sections. As a preferred embodiment, the first side line output pipe 1610 and the second side line output pipe 1620 share a single pipe.

[0081] It should be noted that by setting the first connecting port 1601 above the second connecting port 1602, the liquid hydrocarbon can be circulated along the side line output pipeline 1600, thereby ensuring the normal operation of the circulation.

[0082] Furthermore, in the LNG receiving station gas-liquid mixed light hydrocarbon separation process system provided in this application embodiment, the second conveying pipeline 1500 includes a main pipeline 1510; one end of the main pipeline 1510 is connected to the demethanizer 300, and the end of the main pipeline 1510 forms a second inlet 1511 on the demethanizer 300; the second inlet 1511 is located above the first connecting port 1601.

[0083] It should be noted that, in the embodiments of this application, 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 supercooled 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.

[0084] Specifically, the raw material LNG is fed into the main line 1510 of the second transmission pipeline 1500. Since one end of the main line 1510 is connected to the demethanizer 300, and the end of the main line 1510 forms a second inlet 1511 on the demethanizer 300, the raw material LNG can flow in the main line 1510 and enter the demethanizer 300 through the second inlet 1511.

[0085] Specifically, it is necessary to ensure that the second inlet 1511 is located above the first connecting port 1601.

[0086] Furthermore, the second delivery pipeline 1500 also includes a first branch 1520, the first end of which is connected to the main pipeline 1510; the second end of the first branch 1520 is connected to the demethanizer 300, and the second end of the first branch 1520 forms a third inlet 1521 on the demethanizer 300; the third inlet 1521 is located above the first inlet 1401.

[0087] Specifically, the first end of the first branch 1520 is connected to the main road 1510. Some of the raw material LNG in the main road 1510 will enter the first branch 1520. Since the second end of the first branch 1520 forms a third inlet 1521 on the demethanizer 300, the raw material LNG entering the first branch 1520 flows through the third inlet 1521 into the demethanizer 300.

[0088] In this embodiment, the third inlet 1521 is located above the first inlet 1401.

[0089] Furthermore, it also includes a third conveying pipeline 1700, which is connected to the demethanizer 300 and the first heat exchanger 100 respectively; the liquid hydrocarbon at the top of the demethanizer 300 flows through the third conveying pipeline 1700 and exchanges heat with the first heat exchanger 100; the first end of the third conveying pipeline 1700 is connected to the top of the demethanizer 300, and the second end of the third conveying pipeline 1700 forms a fourth inlet 1701 on the demethanizer 300;

[0090] Along the height of the demethanizer 300, from top to bottom, the fourth inlet 1701, the first inlet 1401, the second inlet 1511, the third inlet 1521, the first connecting port 1601, and the second connecting port 1602 are arranged sequentially.

[0091] Specifically, the first end of the third conveying pipeline 1700 is connected to the top of the demethanizer 300. The liquid hydrocarbons at the top of the demethanizer enter the first heat exchanger 100 along the third conveying pipeline 1700 and exchange heat with the first heat exchanger 100. The second end of the third conveying pipeline 1700 forms a fourth inlet 1701 with the side wall of the demethanizer 300. The liquid hydrocarbons in the third conveying pipeline 1700 flow back into the demethanizer 300 through the fourth inlet 1701.

[0092] It should be noted that in this embodiment, the fourth inlet 1701, the first inlet 1401, the second inlet 1511, the third inlet 1521, the first connecting port 1601 and the second connecting port 1602 are arranged from top to bottom.

[0093] The third inlet 1521, the first inlet 1401, the second inlet 1511, the fourth inlet 1701, the first connecting port 1601, and the second connecting port 1602 are not limited in the circumferential direction of the demethanizer 300 and can be reasonably allocated according to actual needs.

[0094] Furthermore, in this embodiment, an LNG receiving station gas-liquid mixed light hydrocarbon separation process system is provided, in which a number of tray structures 310 and at least one sealed tray 320 are arranged from top to bottom in the demethanizer 300; the liquid hydrocarbons on the sealed tray 320 flow through the first heat exchanger 100 through the side line output pipeline 1600 and flow back to the tray structure 310 at the next level below the sealed tray 320.

[0095] By setting up a sealed tray 320, the hydrocarbon liquid on the sealed tray 320 cannot flow into the next stage tray structure 310 through the downcomer, so that the hydrocarbon liquid on the sealed tray 320 can only enter the next stage tray structure 310 through the side line output pipeline 1600.

[0096] It should be noted that the shape of the sealed tray 320 can be reasonably adjusted according to actual needs. In this embodiment, a disc structure with the same diameter as the demethanizer 300 is adopted.

[0097] Furthermore, the sealed tray 320 is located between the first connecting port 1601 and the second connecting port 1602. Under the action of thermosiphon, the liquid hydrocarbon on the sealed tray 320 enters the first side line output pipeline 1610 through the first connecting port 1601, and is transported to the first heat exchanger 100, where the liquid hydrocarbon is heated to vaporize some of it. The partially vaporized liquid hydrocarbon flows through the second side line output pipeline 1620 and through the second connecting port 1602 to the next stage tray structure 310 of the sealed tray 320.

[0098] Specifically, the tray structure 310 above the sealed tray 320 drips hydrocarbon liquid onto the sealed tray 320. After the height of the hydrocarbon liquid exceeds the first connection port 1601, the hydrocarbon liquid is transported to the first side line output pipeline 1610 through the first connection port 1601 under the action of thermosiphon. Subsequently, the hydrocarbon liquid absorbs heat and partially vaporizes in the first heat exchanger 100. Then, the partially vaporized hydrocarbon liquid flows through the second side line pipeline and the second connection port 1602 to the next stage tray structure 310 of the sealed tray.

[0099] Furthermore, the first connecting port 1601 is always below the liquid level of the liquid hydrocarbon on the sealed tray 320.

[0100] Liquid sealing can enhance the mass transfer effect of the tray structure 310 and prevent gas blockage and open circuit.

[0101] It should be noted that if the first connecting port 1601 is not below the liquid level of the liquid hydrocarbon on the sealed tray 320, the upper space of the sealed tray 320 will not be sealed, thus affecting the entry of the liquid hydrocarbon on the sealed tray 320 into the side output pipeline 1600.

[0102] In this embodiment, in order to ensure that the first connection port 1601 is always below the liquid surface of the liquid hydrocarbon on the sealed tray 320, a groove is provided on the sealed tray 320; the first connection port 1601 is located in the groove.

[0103] By setting the first connection port 1601 in the recessed portion of the sealing tray 320, the liquid hydrocarbons on the sealing tray 320 will preferentially collect in the recessed portion, so that only a small amount of liquid hydrocarbons is needed to satisfy the liquid seal of the first connection port 1601, thus maximizing the liquid seal effect.

[0104] Specifically, placing the first connecting port 1601 at the bottom of the groove will result in a better liquid sealing effect.

[0105] Furthermore, it also includes an overflow structure 330, which is installed on the sealed tray 320; when the liquid hydrocarbon on the sealed tray 320 exceeds a certain height, it flows through the overflow structure 330 to the next stage tray structure 310 of the sealed tray 320.

[0106] In this embodiment, the overflow structure 330 includes a riser pipe. After the liquid level of the liquid hydrocarbon on the sealed tray 320 exceeds the height of the riser pipe, the liquid on the sealed tray 320 flows through the riser pipe to the lower side of the sealed tray 320, i.e., the next stage tray structure 310.

[0107] In this embodiment, the overflow structure 330 also includes an overflow cap, which is located above the riser pipe. The overflow cap prevents the liquid hydrocarbons of the upper stage tray structure 310 of the sealing tray 320 from directly passing through the riser pipe and entering the lower stage tray structure 310.

[0108] In this embodiment, a reboiler 1300 is also included, which is connected to the bottom of the demethanizer 300; the reboiler 1300 heats the liquid hydrocarbon at the bottom of the demethanizer 300 to vaporize the liquid hydrocarbon.

[0109] The reboiler 1300 provides the necessary gaseous feedstock for the operation of the demethanizer 300 and the deethanizer 500.

[0110] 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.

[0111] Secondly, this embodiment provides a gas-liquid mixed-phase light hydrocarbon separation process system for an LNG receiving station, including a first conveying pipeline 1400 for conveying raw material natural gas; a second conveying pipeline 1500 for conveying raw material LNG; a demethanizer 300 having a first inlet 1401 and a second inlet 1511, the first inlet 1401 being connected to the first conveying pipeline 1400 and the second inlet 1511 being connected to the second conveying pipeline 1500; a first heat exchanger 100 having at least two heat exchange channels, one heat exchange channel being connected between the first conveying pipeline 1400 and the demethanizer 300, and the other heat exchange channel being connected between the second conveying pipeline 1500 and the demethanizer 300; and a side-line output pipeline 1600 being connected to the demethanizer 300 and the first heat exchanger 100 respectively.

[0112] Reference Figure 2As 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] In the above embodiments, two additional paths are provided for the feedstock LNG to enter the demethanizer 300.

[0123] 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.

[0124] Of course, staff can reassemble the fourth heat exchanger 900 according to the actual situation (see reference). Figure 3 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] In some embodiments, both the demethanizer 300 and the deethanizer 500 are equipped with a reboiler 1300 at the bottom.

[0138] 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.

[0139] 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.

[0140] 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 2 As shown, it includes:

[0141] 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.

[0142] 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.

[0143] 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.

[0144] 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: The first transmission pipeline (1400) is used to transport raw material natural gas; The second transmission pipeline (1500) is used to transport the raw material LNG; A demethanizing tower (300) has a first inlet (1401) and a second inlet (1511), the first inlet (1401) being connected to the first delivery line (1400) and the second inlet (1511) being connected to the second delivery line (1500); The first heat exchanger (100) has at least two heat exchange channels for heat exchange, one of which is connected between the first delivery line (1400) and the demethanizer (300), and the other of which is connected between the second delivery line (1500) and the demethanizer (300). A side-line output pipeline (1600) is connected to the demethanizer (300) and the first heat exchanger (100) respectively. Under the action of thermosiphon, the side-line output pipeline (1600) transports the liquid hydrocarbon in the demethanizer (300) to the first heat exchanger (100) and heats the liquid hydrocarbon so that the liquid hydrocarbon in the side-line output pipeline (1600) is vaporized. Part of the vaporized liquid hydrocarbon is transported back to the demethanizer (300) through the side-line output pipeline (1600).

2. The LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system according to claim 1, characterized in that, The side-line output pipeline (1600) includes a first side-line output pipeline (1610) and a second side-line output pipeline (1620); the first heat exchanger (100) is connected to the demethanizer (300) through the first side-line output pipeline (1610); The first end of the first side-line output pipe (1610) forms a first communication port (1601) on the side wall of the demethanizer (300); the liquid hydrocarbon in the demethanizer (300) is transported to the first heat exchanger (100) through the first side-line output pipe (1610) and the liquid hydrocarbon is heated; the first heat exchanger (100) is connected to the demethanizer (300) through the second side-line output pipe (1620); the second end of the second side-line output pipe (1620) forms a second communication port (1602) on the side wall of the demethanizer (300); the partially vaporized liquid hydrocarbon is returned to the demethanizer (300) through the second side-line output pipe (1620); the first communication port (1601) is above the second communication port (1602).

3. The LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system according to claim 2, characterized in that, The second delivery pipeline (1500) includes a main line (1510); one end of the main line (1510) is connected to the demethanizer (300), and the end of the main line (1510) forms a second inlet (1511) on the demethanizer (300); the second inlet (1511) is located above the first connection port (1601).

4. The LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system according to claim 3, characterized in that, The second delivery pipeline (1500) also includes a first branch (1520), the first end of which is connected to the main road (1510); the second end of which is connected to the demethanizer (300), and the second end of which forms a third inlet (1521) on the demethanizer (300); the third inlet (1521) is located above the first inlet (1401).

5. The LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system according to claim 4, characterized in that, Also includes: A third delivery pipeline (1700) is connected to the demethanizer (300) and the first heat exchanger (100) respectively; the liquid hydrocarbon at the top of the demethanizer (300) flows through the third delivery pipeline (1700) and exchanges heat with the first heat exchanger (100); the first end of the third delivery pipeline (1700) is connected to the top of the demethanizer (300), and the second end of the third delivery pipeline (1700) forms a fourth inlet (1701) on the demethanizer (300). Along the height direction of the demethanizer (300), the fourth inlet (1701), the first inlet (1401), the second inlet (1511), the third inlet (1521), the first connecting port (1601) and the second connecting port (1602) are arranged sequentially from top to bottom.

6. The LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system according to any one of claims 2-5, characterized in that, The demethanizer (300) has several tray structures (310) arranged from top to bottom and at least one sealed tray (320) arranged on one side of the tray structure (310); the liquid hydrocarbon on the sealed tray (320) flows through the first heat exchanger (100) through the side line output pipeline (1600) and flows back to the tray structure (310) at the next level of the sealed tray (320).

7. The LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system according to claim 6, characterized in that, The sealed tray (320) is located between the first connecting port (1601) and the second connecting port (1602). Under the action of thermosiphon, the liquid hydrocarbon on the sealed tray (320) enters the first side line output pipeline (1610) through the first connecting port (1601) and is transported to the first heat exchanger (100) to heat the liquid hydrocarbon so that some of the liquid hydrocarbon is vaporized. The partially vaporized liquid hydrocarbon flows through the second side line output pipeline (1620) and through the second connecting port (1602) to the next stage tray structure (310) of the sealed tray (320).

8. The LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system according to claim 6, characterized in that, The first connection port (1601) is always below the liquid level of the liquid hydrocarbon on the sealed tray (320).

9. The LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system according to claim 6, characterized in that, The sealed tray (320) is provided with a groove; the first communication port (1601) is located in the groove.

10. The LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system according to claim 6, characterized in that, Also includes: An overflow structure (330) is provided on the sealed tray (320); Once the liquid hydrocarbon on the sealed tray (320) exceeds a certain height, it flows through the overflow structure (330) to the next stage tray structure (310) of the sealed tray (320).

11. The LNG receiving terminal gas-liquid miscible light hydrocarbon separation process system according to claim 6, characterized in that, Also includes: A reboiler (1300) is connected to the bottom of the demethanizer (300); the reboiler (1300) heats the liquid hydrocarbons at the bottom of the demethanizer (300) to vaporize the liquid hydrocarbons.

12. A gas-liquid miscible light hydrocarbon separation process system for an LNG receiving terminal, characterized in that, include: The first transmission pipeline (1400) is used to transport raw material natural gas; The second transmission pipeline (1500) is used to transport the raw material LNG; A demethanizing tower (300) has a first inlet (1401) and a second inlet (1511), the first inlet (1401) being connected to the first delivery line (1400) and the second inlet (1511) being connected to the second delivery line (1500); The first heat exchanger (100) has at least two heat exchange channels for heat exchange, one of which is connected between the first delivery line (1400) and the demethanizer (300), and the other of which is connected between the second delivery line (1500) and the demethanizer (300). A side-line output pipeline (1600) is connected to the demethanizer (300) and the first heat exchanger (100).

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