A light hydrocarbon separation device for liquefied natural gas
By installing a reflux pipeline and a condenser in the LNG light hydrocarbon separation unit, the cascade utilization of cold energy is achieved, solving the problems of poor separation efficiency and high energy consumption, and improving separation efficiency and economy.
Patent Information
- Application Number
- CN202522690418.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-18
- Publication Date
- 2026-11-03
- Estimated Expiration
- 2035-12-18
AI Technical Summary
Existing liquefied natural gas (LNG) light hydrocarbon separation units suffer from poor separation efficiency and high energy consumption, and are particularly uneconomical for small and medium-sized LNG gasification stations.
By setting up a return pipeline from the liquid phase outlet of the secondary separator to the primary separator, combined with a heat exchanger and a condenser, the cascade utilization and efficient separation of cooling capacity can be achieved, reducing energy consumption and improving separation efficiency.
It significantly improved the efficiency of primary separation, reduced the load on subsequent distillation columns, reduced the power consumption of external refrigeration units, lowered operating costs, and improved the recovery rate and product purity of light hydrocarbon components.
Smart Images
Figure CN224930507U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the technical field of liquefied natural gas processing equipment, and in particular to a light hydrocarbon separation device for liquefied natural gas. Background Technology
[0002] In the process of gasifying and utilizing liquefied natural gas (LNG), it is first necessary to separate the heavy hydrocarbon components. This is because these heavy hydrocarbon components may condense in the subsequent pipeline system after gasification, leading to equipment blockage and increasing operational risks and safety hazards. The separation of heavy hydrocarbons is not only a key step to ensure the stable operation of the system, but also effectively prevents failures and maintenance costs caused by condensation. In addition, the separated light hydrocarbon components, such as propane and butane, have high economic value and can be reused as efficient energy sources or chemical feedstocks, thereby bringing additional economic benefits. Through this separation process, the safe transportation of natural gas can be guaranteed, and considerable additional revenue can be generated for enterprises.
[0003] Liquefied natural gas (LNG) light hydrocarbon separation units mainly employ two processes: simple flash separation and relatively complex cryogenic distillation. Flash separation is a simpler method, which is easy to operate and requires less equipment investment, but its separation effect is not ideal. It often fails to completely remove heavy hydrocarbon components, resulting in low product purity that is difficult to meet market demands. This method may suffer from insufficient separation efficiency when processing large volumes of LNG. Conversely, cryogenic distillation provides higher separation efficiency and can effectively improve product purity to meet stricter quality requirements. However, it is complex, requires expensive equipment investment, and has high energy consumption during operation, leading to higher operating costs. Especially for small and medium-sized LNG regasification stations, the high equipment investment and operating costs make this distillation process uneconomical.
[0004] In the existing technology, the equipment adopts a combination of multi-stage flash evaporation and distillation column, but the system does not fully consider the integrated utilization of energy, resulting in a large loss of cold energy, and the synergistic effect between the separators at each stage is limited, leading to high overall energy consumption and room for improvement in separation efficiency. Utility Model Content
[0005] In view of the aforementioned problem of poor separation efficiency in existing methods, this utility model is proposed.
[0006] Therefore, the purpose of this utility model is to provide a light hydrocarbon separation device for liquefied natural gas, which aims to significantly improve the efficiency and effect of the first-stage separation and reduce the load on the subsequent distillation column by setting up a reflux pipeline from the liquid phase outlet of the secondary separator to the primary separator.
[0007] To solve the above-mentioned technical problems, this utility model provides the following technical solution: a light hydrocarbon separation device for liquefied natural gas, comprising a primary separator, a secondary separator and a distillation column connected sequentially along the flow direction, wherein the gas phase outlet of the primary separator is connected to the feed inlet of the secondary separator through a first pipeline; The liquid phase outlet of the secondary separator is connected to the feed inlet of the primary separator or the feed zone inside the primary separator via a reflux pipeline. The gas phase outlet of the secondary separator is connected to the feed inlet of the distillation column via a second pipeline; The bottom outlet of the distillation column outputs heavy hydrocarbons through a heavy hydrocarbon output pipeline.
[0008] In a preferred embodiment of the liquefied natural gas light hydrocarbon separation device of this utility model, a reflux pump is provided on the reflux pipeline.
[0009] In a preferred embodiment of the liquefied natural gas light hydrocarbon separation device of this utility model, a flow control valve for controlling the return flow is provided on the return pipeline.
[0010] As a preferred embodiment of the liquefied natural gas light hydrocarbon separation device of this utility model, it further includes a heat exchanger having a first flow channel and a second flow channel that are isolated from each other. The first flow channel is connected to the heavy hydrocarbon output pipeline, and the second flow channel is connected to the raw material LNG input pipeline located before the first-stage separator.
[0011] As a preferred embodiment of the liquefied natural gas light hydrocarbon separation device of this utility model, a condenser is provided at the top of the distillation column, and the refrigerant inlet of the condenser is connected to the gas phase outlet of the secondary separator through a third pipeline.
[0012] In a preferred embodiment of the liquefied natural gas light hydrocarbon separation device of this utility model, the refrigerant outlet of the condenser is connected to the top reflux port of the distillation column via a fourth pipeline.
[0013] As a preferred embodiment of the liquefied natural gas light hydrocarbon separation device of this utility model, the primary separator and the secondary separator are both gas-liquid cyclone separators or packed separators.
[0014] As a preferred embodiment of the liquefied natural gas light hydrocarbon separation device of this utility model, the distillation column is provided with multiple layers of trays or structured packing.
[0015] As a preferred embodiment of the liquefied natural gas light hydrocarbon separation device of the present invention, wherein: the bottom of the primary separator is provided with a primary liquid phase outlet for outputting liquefied natural gas products.
[0016] Compared with the prior art, the present invention has at least the following beneficial effects: 1. This utility model, by setting up a reflux pipeline from the liquid phase outlet of the secondary separator to the primary separator, returns the liquid containing a large number of light components but entrained to the primary separator for further separation, which is equivalent to "distillation" of the primary separation, significantly improving the efficiency and effect of the primary separation and reducing the load on the subsequent distillation column.
[0017] 2. This utility model effectively recovers the cold energy of the heavy hydrocarbon liquid by using the relatively high temperature of the heavy hydrocarbon liquid at the bottom of the distillation column to exchange heat with the raw material LNG, which greatly reduces the energy consumption required for the pre-cooling of the raw material. At the same time, it uses the low temperature gas phase at the outlet of the secondary separator as the refrigerant for the condenser at the top of the distillation column, realizing the self-sufficiency and efficient cascade utilization of the internal cold energy of the device, eliminating or reducing the power consumption of the external refrigeration unit.
[0018] 3. This utility model integrates separation, distillation and heat exchange into one unit, which occupies a small area and has low modification costs. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of the overall structure of the light hydrocarbon separation device for liquefied natural gas of this utility model; Figure 2 This is a schematic diagram of the reflux pipeline, reflux pump, and flow control valve structure of the light hydrocarbon separation device for liquefied natural gas of this utility model. Figure 3 This is a schematic diagram of the heat exchanger and condenser structure of the light hydrocarbon separation device for liquefied natural gas of this utility model; Figure 4 This is a schematic diagram of the overall external structure of the liquefied natural gas light hydrocarbon separation device of this utility model.
[0020] Explanation of reference numerals in the attached figures: 1. LNG feedstock inlet pipeline; 2. Primary separator; 3. Primary liquid phase outlet; 4. First pipeline; 5. Secondary separator; 6. Reflux pipeline; 7. Reflux pump; 8. Second pipeline; 9. Distillation column; 10. Condenser; 11. Third pipeline; 12. Fourth pipeline; 13. Heavy hydrocarbon output pipeline; 14. Heat exchanger; 15. First flow channel; 16. Second flow channel; 17. Flow control valve. Detailed Implementation
[0021] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings. Example 1
[0022] Reference Figures 1-2This is the first embodiment of the present invention, which provides a light hydrocarbon separation device for liquefied natural gas. The light hydrocarbon separation device for liquefied natural gas includes a primary separator 2, a secondary separator 5 and a distillation column 9 connected in sequence along the flow direction. The gas phase outlet of the primary separator 2 is connected to the feed inlet of the secondary separator 5 through a first pipeline 4. The liquid phase outlet of the secondary separator 5 is connected to the feed inlet of the primary separator 2 or the feed zone inside the primary separator 2 via a return pipe 6. The gas phase outlet of the secondary separator 5 is connected to the feed inlet of the distillation column 9 via the second pipeline 8; The bottom outlet of distillation column 9 outputs heavy hydrocarbons through a heavy hydrocarbon output pipeline 13; By setting up two-stage separators before the feedstock enters the distillation column, the feedstock LNG is separated step by step and gradually. Most of the heavier components can be removed in the first and second stage separators, reducing the processing load of the subsequent distillation column, thereby improving the separation efficiency and operational stability of the entire unit. The liquid phase in the secondary separator still contains a considerable amount of volatile components. Recirculating these components allows them to be revaporized in the primary separator and enter subsequent processes, rather than being discharged as heavier components. This significantly improves the recovery rate of high-value light hydrocarbon components. By recirculating, the light components that may be entrained in the secondary liquid phase are "purified," ensuring that the LNG product discharged from the bottom of the primary separator has higher purity.
[0023] A reflux pump 7 is installed on the reflux pipeline 6. The reflux pump provides the power required to force the liquid phase of the secondary separator back to the primary separator, ensuring that the reflux process can be carried out stably and controllably, and overcoming the resistance caused by the system pressure drop.
[0024] A flow control valve 17 is installed on the reflux pipeline 6 to control the reflux flow rate, which allows the operator to adjust the reflux flow rate precisely and flexibly according to the changes in raw material composition and product purity requirements. This enables refined control of the reflux process and helps to optimize the separation effect under different operating conditions, thereby achieving optimal operation and automated control of the equipment. Example 2
[0025] Reference Figures 1-4 This is the second embodiment of the present invention. The difference between this embodiment and the first embodiment is that it also includes a heat exchanger 14. The heat exchanger 14 has a first flow channel 15 and a second flow channel 16 that are isolated from each other. The first flow channel 15 is connected to the heavy hydrocarbon output pipeline 13, and the second flow channel 16 is connected to the raw material LNG input pipeline 1 located before the first stage separator 2. By using the high-temperature bottom heavy hydrocarbon products to pre-cool the low-temperature feedstock LNG, the cold energy inside the unit is recovered, which greatly reduces the load and energy consumption required by the external refrigeration system, making the entire process more energy-efficient and economical. Precooling the LNG feedstock allows it to enter the primary separator at a more suitable temperature, which helps improve the separation effect. At the same time, it also reduces the output temperature of heavy hydrocarbon products, making them easier to store or transport later.
[0026] A condenser 10 is installed at the top of the distillation column 9. The refrigerant inlet of the condenser 10 is connected to the gas phase outlet of the secondary separator 5 through a third pipeline 11. By directly using the low-temperature gaseous stream from the secondary separator as the refrigerant for the top condenser of the distillation column, the use of external refrigerant is reduced or eliminated, further lowering the operating cost and complexity of the unit.
[0027] The refrigerant outlet of the condenser 10 is connected to the top reflux port of the distillation column 9 via the fourth pipe 12.
[0028] Both the primary separator 2 and the secondary separator 5 are gas-liquid cyclone separators or packing separators.
[0029] The distillation column 9 is equipped with multiple layers of trays or structured packing.
[0030] The bottom of the primary separator 2 is provided with a primary liquid phase outlet 3 for outputting liquefied natural gas products.
[0031] The remaining structure is the same as that in Example 1.
[0032] Based on embodiments 1-2, the working principle of this utility model is as follows: the raw material LNG first enters the second flow channel 16 of the heat exchanger 14 through the raw material LNG input pipeline 1, and exchanges heat with the warm heavy hydrocarbon product from the heavy hydrocarbon output pipeline 13 that flows through the first flow channel 15, and is initially pre-cooled; The pre-cooled LNG feedstock enters the first-stage separator 2 for the first gas-liquid separation; after separation, the heavier liquid phase component is discharged from the first-stage liquid phase outlet 3; the lighter gas phase component enters the second-stage separator 5 through the first pipeline 4. In the secondary separator 5, the gas phase undergoes a second separation; the separated liquid phase flows back to the feed inlet of the primary separator 2 through the return pipeline 6, driven by the return pump 7, and mixes with the raw material LNG for a second separation. This process can improve the yield of components such as ethane and ensure the purity of the LNG product; the flow control valve 17 is used to precisely adjust the return flow rate. The gas phase exiting from the top of the secondary separator 5 enters the middle of the distillation column 9 through the second pipeline 8; at the same time, this part of the low-temperature gas phase is also led to the condenser 10 at the top of the distillation column 9 through the third pipeline 11, and used as a refrigerant; in the condenser 10, it condenses the rising vapor of the distillation column 9; the refrigerant after heat exchange returns to the top of the distillation column 9 as reflux liquid through the fourth pipeline 12. Inside the distillation column 9, the gas and liquid phases fully contact and transfer mass on the trays or packing, and finally obtain a high-purity heavy hydrocarbon product at the bottom of the column. The heavy hydrocarbon product is discharged through the heavy hydrocarbon output pipeline 13 and flows through the first flow channel 15 of the heat exchanger 14 to pre-cool the raw material LNG before being sent out of the unit.
[0033] It should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and are not intended to limit it. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of this utility model without departing from the spirit and scope of the technical solution of this utility model, and all such modifications or substitutions should be covered within the scope of the claims of this utility model.
Claims
1. A light hydrocarbon separation device for liquefied natural gas, comprising a primary separator (2), a secondary separator (5), and a distillation column (9) connected sequentially along the flow direction, characterized in that: The gas phase outlet of the primary separator (2) is connected to the feed inlet of the secondary separator (5) through the first pipeline (4); The liquid phase outlet of the secondary separator (5) is connected to the feed inlet of the primary separator (2) or the feed zone inside the primary separator (2) via a return pipe (6). The gas phase outlet of the secondary separator (5) is connected to the feed inlet of the distillation column (9) via a second pipeline (8); The bottom outlet of the distillation column (9) outputs heavy hydrocarbons through a heavy hydrocarbon output pipeline (13).
2. The liquefied natural gas light hydrocarbon separation device according to claim 1, characterized in that: A return pump (7) is installed on the return pipeline (6).
3. The liquefied natural gas light hydrocarbon separation device according to claim 1, characterized in that: The return pipeline (6) is equipped with a flow control valve (17) for controlling the return flow.
4. The liquefied natural gas light hydrocarbon separation device according to claim 1, characterized in that: It also includes a heat exchanger (14) having a first flow channel (15) and a second flow channel (16) that are isolated from each other. The first flow channel (15) is connected to the heavy hydrocarbon output pipeline (13), and the second flow channel (16) is connected to the raw material LNG input pipeline (1) located before the first-stage separator (2).
5. The liquefied natural gas light hydrocarbon separation device according to claim 1, characterized in that: The distillation column (9) is equipped with a condenser (10) at the top. The refrigerant inlet of the condenser (10) is connected to the gas phase outlet of the secondary separator (5) through a third pipeline (11).
6. The liquefied natural gas light hydrocarbon separation device according to claim 5, characterized in that: The refrigerant outlet of the condenser (10) is connected to the top reflux port of the distillation column (9) via a fourth pipeline (12).
7. The liquefied natural gas light hydrocarbon separation device according to claim 1, characterized in that: Both the primary separator (2) and the secondary separator (5) are gas-liquid cyclone separators or packed separators.
8. The liquefied natural gas light hydrocarbon separation device according to claim 1, characterized in that: The distillation column (9) is equipped with multiple layers of trays or structured packing.
9. The liquefied natural gas light hydrocarbon separation device according to claim 1, characterized in that: The bottom of the primary separator (2) is provided with a primary liquid phase outlet (3) for outputting liquefied natural gas products.