Alcohol amine method purifies natural gas coupling pressure difference power generation cold energy utilization system

Abstract

The application discloses a kind of alcohol amine method purification natural gas coupling pressure difference power generation cold energy utilization system, including amine liquid natural gas heat exchanger, acid gas natural gas heat exchanger and natural gas expander;Amine liquid natural gas heat exchanger's amine liquid heat medium passage is accessed in the lean amine liquid pipeline of alcohol amine method purification natural gas system, and its amine liquid coolant passage import is connected high-pressure natural gas pipeline;Acid gas natural gas heat exchanger's acid gas heat medium passage is accessed in the acid gas pipeline of alcohol amine method purification natural gas system, and its acid gas coolant passage entrance is connected with the amine liquid coolant passage export of amine liquid natural gas heat exchanger;The gas inlet of natural gas expander is connected with the acid gas coolant passage export of acid gas natural gas heat exchanger, and the gas outlet of natural gas expander is connected with subsequent process system pipeline.The present application can make full use of existing resources, significantly reduce additional investment, and accurately control the parameter of expanded natural gas, ensure that it meets subsequent process requirements, so as to improve the system energy efficiency as a whole, reduce operating cost.

Description

Technical Field

[0001] This invention relates to the field of differential pressure power generation, specifically a system for utilizing cold energy in differential pressure power generation coupled with natural gas purification using the alcohol amine method. Background Technology

[0002] In the process of purifying natural gas using the amine method, the raw natural gas, after undergoing purification treatments such as desulfurization and decarbonization, typically still retains a high pressure. To recover the pressure energy of this high-pressure natural gas, differential pressure power generation technology has emerged, which uses a turbine expander to convert the pressure energy of the natural gas into mechanical energy and further generate electricity.

[0003] like Figure 1 As shown, the amine-based natural gas purification system includes a sour gas pipeline and a lean amine liquid pipeline. The sour gas pipeline includes the original regeneration tower top condenser 2, a sour gas inlet pipe 1 connected to the inlet of the original regeneration tower top condenser 2, and a sour gas outlet pipe 3 connected to the outlet of the original regeneration tower top condenser 2. The original process sour gas enters the sour gas outlet pipe 3 after heat exchange and cooling in the original regeneration tower top condenser 2 via the sour gas inlet pipe 1, and then enters the subsequent processes.

[0004] The lean amine solution pipeline includes a raw solution cooler 6, an amine inlet pipe 5 connecting to the inlet of the raw solution cooler 6, and an amine outlet pipe 7 connecting to the outlet of the raw solution cooler 6. A booster pump 4 is installed on the amine inlet pipe 5, and an amine pump 8 is installed on the amine outlet pipe 7. The lean amine solution from the original process enters the raw solution cooler 6 via the booster pump 4 and the amine inlet pipe 5 for heat exchange and cooling before entering the amine outlet pipe 7, and then via the amine pump 8 into the subsequent processes.

[0005] However, this technology presents a significant technical challenge: according to thermodynamic principles, when high-pressure natural gas undergoes adiabatic expansion in a turbine expander, its temperature drops significantly, typically by 20°C to 40°C or even higher. Although the expanded natural gas meets the pressure requirements of downstream pipelines, its temperature is often too low, easily leading to ice blockage in pipeline valves or adversely affecting subsequent processes, thus failing to meet the temperature parameters required for safe transportation and process control.

[0006] To address the aforementioned issue of reheating cryogenic natural gas, the commonly adopted technical solutions in the industry primarily involve installing natural gas heaters and utilizing the plant's circulating water system to heat the cryogenic natural gas. This method requires the addition of large heat exchange equipment and corresponding piping systems. Furthermore, the circulating water itself has limited heating capacity, resulting in poor performance during cold seasons or when higher reheating temperatures are required, leading to high energy consumption and equipment investment.

[0007] Heat pump units, either electrically or steam-driven, extract heat from low-temperature heat sources (such as ambient air or cooling water), upgrade its quality, and then use it to heat natural gas. While this method offers high reheating efficiency, it requires a complex and expensive heat pump system, significantly increasing initial investment and ongoing maintenance costs. Furthermore, the heat pump itself consumes a large amount of electricity or steam, offsetting some of the electricity generation revenue.

[0008] Therefore, the most commonly used methods for reheating low-temperature natural gas are circulating water reheating or heat pump reheating. Both of these methods require additional heat sources, which increases system investment.

[0009] In the amine regeneration unit, the acid gas separated from the top of the regeneration tower is at a high temperature (typically 80-100℃), and the lean amine liquid flowing out from the bottom of the regeneration tower also needs to be cooled (typically 40-60℃) before entering the absorption tower. In the current process, the waste heat of these two fluids is usually directly discharged into the environment through air coolers or water coolers, resulting in a large waste of low-grade heat energy.

[0010] In summary, existing processes for purifying natural gas using the amine method require additional heat sources to reheat low-pressure natural gas to ensure its parameters meet process requirements, thus increasing the cost of heat sources and related equipment. Furthermore, there is a waste of waste heat from the amine liquid and acid gas in the amine method for purifying natural gas. Summary of the Invention

[0011] The purpose of this invention is to address the shortcomings of existing technologies by providing a system for the coupled pressure difference power generation and cold energy utilization of natural gas through the amine method, which can effectively utilize existing resources, reduce system investment, and effectively control various parameters after the expansion of low-pressure natural gas to meet the requirements of subsequent processes.

[0012] The technical objective of this invention is achieved through the following technical solution: A cold energy utilization system for natural gas purification coupled with differential pressure power generation using the amine process includes an amine liquid natural gas heat exchanger, an acid gas natural gas heat exchanger, and a natural gas expander. The amine liquid heat medium channel of the amine liquid natural gas heat exchanger is connected to the lean amine liquid pipeline of the amine process natural gas purification system, and its amine liquid refrigerant channel inlet is connected to a high-pressure natural gas pipeline. The acid gas heat medium channel of the acid gas natural gas heat exchanger is connected to the acid gas pipeline of the amine process natural gas purification system, and its acid gas refrigerant channel inlet is connected to the amine liquid refrigerant channel outlet of the amine liquid natural gas heat exchanger. The inlet of the natural gas expander is connected to the acid gas refrigerant channel outlet of the acid gas natural gas heat exchanger, and the outlet of the natural gas expander is connected to a subsequent process system pipeline. The lean amine liquid and acid gas from the amine process natural gas purification system serve as heat sources, respectively, to perform staged heating of the high-pressure natural gas in the amine liquid natural gas heat exchanger and the acid gas natural gas heat exchanger. The heated high-pressure natural gas then enters the natural gas expander to expand and generate electricity.

[0013] Preferably, the inlet of the amine liquid heat medium channel of the amine liquid natural gas heat exchanger is connected to the amine liquid inlet pipe of the lean amine liquid pipeline, and its amine liquid heat medium channel outlet is connected to the amine liquid outlet pipe of the lean amine liquid pipeline.

[0014] Preferably, the acid gas heat medium channel inlet of the acid gas natural gas heat exchanger is connected to the acid gas inlet pipe of the acid gas pipeline, and its acid gas heat medium channel outlet is connected to the acid gas outlet pipe of the acid gas pipeline.

[0015] Preferably, it also includes a natural gas expander bypass pipeline; the inlet of the natural gas expander is connected to the outlet of the acid gas refrigerant channel of the acid gas natural gas heat exchanger via a natural gas expander inlet pipeline, and the outlet of the natural gas expander is connected to a natural gas expander outlet pipeline; the inlet end of the natural gas expander bypass pipeline is connected to the natural gas expander inlet pipeline, and its outlet end is connected to the natural gas expander outlet pipeline.

[0016] Preferably, it also includes a natural gas expansion pipeline, the inlet end of which is connected to a high-pressure natural gas pipeline, and the outlet end of which is connected to the outlet pipeline of the natural gas expander; a PV valve is installed on the natural gas expansion pipeline.

[0017] Preferably, a booster pump is provided on the amine liquid inlet pipe; the amine liquid heat medium channel inlet of the amine liquid natural gas heat exchanger is connected to the amine liquid inlet pipe through an amine liquid heat medium inlet pipe, and the inlet of the amine liquid heat medium inlet pipe is connected to the amine liquid inlet pipe between the original solution cooler and the booster pump.

[0018] Preferably, an amine liquid pump is provided on the amine liquid outlet pipe; the outlet of the amine liquid heat medium channel of the amine liquid natural gas heat exchanger is connected to the amine liquid outlet pipe through the amine liquid heat medium outlet pipe, and the outlet of the amine liquid heat medium outlet pipe is connected to the amine liquid outlet pipe between the original solution cooler and the amine liquid pump.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention effectively solves the technical problem of excessively low natural gas temperature after expansion power generation by using the waste heat from the lean amine liquid and acid gas generated in the amine purification process for cascade heating of natural gas before power generation, without relying on an external heat source. It achieves synergistic recovery of pressure energy and process waste heat. This system can fully utilize existing resources, significantly reduce additional investment, and precisely control the parameters of the expanded natural gas to ensure it meets the requirements of subsequent processes, thereby improving overall system energy efficiency and reducing operating costs. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the present invention; Attached reference numerals: 1—Acid gas inlet pipeline; 2—Original regeneration tower top condenser; 3—Acid gas outlet pipeline; 4—Booster pump; 5—Amine liquid inlet pipeline; 6—Original solution cooler; 7—Amine liquid outlet pipeline; 8—Amine liquid pump; 9—Acid gas heat transfer medium inlet pipeline; 10—Acid gas natural gas heat exchanger; 11—Acid gas heat transfer medium outlet pipeline; 12—Amine liquid heat transfer medium inlet pipeline; 13—Amine liquid natural gas heat exchanger; 14—Amine liquid heat transfer medium outlet pipeline; 15—High-pressure natural gas pipeline; 16—Connecting pipeline; 17—Natural gas expander inlet pipeline; 18—Natural gas expander; 19—Natural gas expander outlet pipeline; 20—Natural gas expander bypass pipeline; 21—Original natural gas expansion pipeline; 22—PV valve. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0023] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0024] like Figure 1 As shown, a cold energy utilization system for coupled pressure difference power generation from natural gas purified by the amine process includes an amine liquid natural gas heat exchanger 13, an acid gas natural gas heat exchanger 10, and a natural gas expander 18. The amine liquid heat medium channel of the amine liquid natural gas heat exchanger 13 is connected to the lean amine liquid pipeline of the amine process natural gas purification system, and its amine liquid coolant channel inlet is connected to the high-pressure natural gas pipeline 15. The acid gas heat medium channel of the acid gas natural gas heat exchanger 10 is connected to the acid gas pipeline of the amine process natural gas purification system, and its acid gas coolant channel inlet is connected to the amine liquid coolant channel outlet of the amine liquid natural gas heat exchanger 13. The inlet of the natural gas expander 18 is connected to the acid gas coolant channel outlet of the acid gas natural gas heat exchanger 10, and the outlet of the natural gas expander 18 is connected to the pipeline of the subsequent process system. The lean amine liquid and acid gas from the amine process natural gas purification system serve as heat sources, respectively, to perform staged heating of the high-pressure natural gas in the amine liquid natural gas heat exchanger 13 and the acid gas natural gas heat exchanger 10. The heated high-pressure natural gas then enters the natural gas expander 18 to expand and generate electricity. By utilizing the waste heat from the lean amine liquid and acid gas generated in the amine purification process to heat the natural gas before power generation in a cascade manner, the technical challenge of excessively low natural gas temperature after expansion power generation is effectively solved without relying on an external heat source. This achieves the synergistic recovery of pressure energy and process waste heat. The system can fully utilize existing resources, significantly reduce additional investment, and precisely control the parameters of the expanded natural gas to ensure it meets the requirements of subsequent processes, thereby improving overall system energy efficiency and reducing operating costs.

[0025] like Figure 1 As shown, the lean amine liquid pipeline includes a raw solution cooler 6, an amine liquid inlet pipe 5 connected to the inlet of the raw solution cooler 6, and an amine liquid outlet pipe 7 connected to the outlet of the raw solution cooler 6.

[0026] In practical implementation, the inlet of the amine liquid heat medium channel of the amine liquid natural gas heat exchanger 13 is connected to the amine liquid inlet pipe 5 of the lean amine liquid pipeline, and its outlet is connected to the amine liquid outlet pipe 7 of the lean amine liquid pipeline. This technical measure maximizes the recovery of waste heat from the high-temperature lean amine liquid for heating natural gas without affecting the original lean amine liquid cooling process, achieving efficient cascade utilization of energy and ensuring the stable operation of the main purification system. In practical use, the amine liquid heat medium channel inlet of the amine liquid heat exchanger 13 is connected to the amine liquid inlet pipe 5 via the amine liquid heat medium inlet pipe 12. A booster pump 4 is installed on the amine liquid inlet pipe 5. The inlet of the amine liquid heat medium inlet pipe 12 is connected to the amine liquid inlet pipe 5 between the original solution cooler 6 and the booster pump 4. This connection method allows high-temperature lean amine liquid with optimal pressure and temperature to be drawn from the outlet of the booster pump 4, before the original solution cooler 6. This ensures efficient and stable recovery of waste heat while completely avoiding interference with the original cooling process, thus ensuring the safe operation of the heat exchange equipment.

[0027] The outlet of the amine liquid heat medium channel of the amine liquid heat exchanger 13 is connected to the amine liquid outlet pipe 7 via an amine liquid heat medium outlet pipe 14. An amine liquid pump 8 is installed on the amine liquid outlet pipe 7; the outlet of the amine liquid heat medium outlet pipe 14 is connected to the amine liquid outlet pipe 7 between the original solution cooler 6 and the amine liquid pump 8. Returning the heat-exchanged amine liquid to the pipe between the original solution cooler 6 and the amine liquid pump 8 ensures that the temperature and pressure parameters of the amine liquid can be accurately and reliably regulated and guaranteed by the existing system before entering the downstream absorption tower. This achieves efficient waste heat recovery while maintaining the operational stability and safety of the main process system. The outlet of the amine liquid heat medium outlet pipe 14 is located on the inlet side of the amine liquid pump 8, ensuring that the amine liquid pump 8 can provide stable pressure for subsequent processes. Simultaneously, the temperature of the amine liquid after waste heat recovery and heat exchange may still be higher than the process requirements, allowing it to return to the original solution cooler 6 for final cooling. This ensures that the temperature of the amine liquid entering the absorption tower accurately meets the process parameters, which is crucial for achieving deep system coupling.

[0028] The inlet of the amine liquid refrigerant channel of the amine liquid natural gas heat exchanger 13 is connected to the high-pressure natural gas pipeline 15, and the outlet of the amine liquid refrigerant channel of the amine liquid natural gas heat exchanger 13 is connected to the inlet of the acid gas refrigerant channel of the acid gas natural gas heat exchanger 10 via a connecting pipeline 16. By connecting the refrigerant channels of the two heat exchangers in series, a cascade heating process for high-pressure natural gas is constructed, enabling it to absorb the waste heat of amine liquid and acid gas of different grades sequentially and orderly. This achieves efficient and reasonable matching of heat, thereby maximizing the overall energy recovery efficiency and ensuring the stable operation of the system.

[0029] like Figure 1As shown, the acid gas heat medium channel of the acid gas natural gas heat exchanger 10 is connected to the acid gas pipeline of the amine-based natural gas purification system, and its acid gas refrigerant channel inlet is connected to the amine liquid refrigerant channel outlet of the amine liquid natural gas heat exchanger 13; the gas inlet of the natural gas expander 18 is connected to the acid gas refrigerant channel outlet of the acid gas natural gas heat exchanger 10, and the gas outlet of the natural gas expander 18 is connected to the pipeline of the subsequent process system. By efficiently integrating the acid gas natural gas heat exchanger 10 into the original acid gas pipeline in a "bypass" manner, and directly connecting the power generation unit in series at the end of the heat exchange process, the ultimate recovery of the waste heat of the highest grade acid gas is achieved without interfering with the main process, and the efficient and direct conversion of pressure energy into electrical energy is ensured, ultimately forming a complete and smooth "cascade heating-expansion power generation" energy recovery closed loop.

[0030] In practical implementation, the acid gas heat medium channel inlet of the acid gas heat exchanger 10 is connected to the acid gas inlet pipe 1 of the acid gas pipeline, and its acid gas heat medium channel outlet is connected to the acid gas outlet pipe 3 of the acid gas pipeline. Specifically, the acid gas heat medium channel inlet of the acid gas heat exchanger 10 is connected to the acid gas inlet pipe 1 via an acid gas heat medium inlet pipe 9; and the acid gas heat medium channel outlet of the acid gas heat exchanger 10 is connected to the acid gas outlet pipe 3 via an acid gas heat medium outlet pipe 11.

[0031] The inlet of the natural gas expander 18 is connected to the outlet of the acid gas refrigerant channel of the acid gas heat exchanger 10 via the natural gas expander inlet pipe 17. The outlet of the natural gas expander 18 is connected to the subsequent process system pipeline via the natural gas expander outlet pipe 19.

[0032] The amine-based natural gas purification coupled with differential pressure power generation and cold energy utilization system also includes a natural gas expander bypass pipeline 20. The inlet of the natural gas expander 18 is connected to the outlet of the acid gas refrigerant channel of the acid gas heat exchanger 10 via a natural gas expander inlet pipeline 17, and the outlet of the natural gas expander 18 is connected to a natural gas expander outlet pipeline 19. The inlet end of the natural gas expander bypass pipeline 20 is connected to the natural gas expander inlet pipeline 17, and its outlet end is connected to the natural gas expander outlet pipeline 19. When the natural gas expander 18 malfunctions and shuts down, the natural gas can be directly discharged into the subsequent process system pipelines through the natural gas expander bypass pipeline 20. This technical measure provides crucial operational flexibility and safety assurance for the power generation system, ensuring that the main natural gas purification process can operate continuously and stably without any impact during expander failure or maintenance, thus decoupling the energy recovery function from the core requirements of safe production.

[0033] like Figure 1As shown, the natural gas purification coupled with differential pressure power generation cold energy utilization system using the amine method also includes the original natural gas expansion pipeline 21. The inlet end of the original natural gas expansion pipeline 21 is connected to the high-pressure natural gas pipeline 15, and its outlet end is connected to the natural gas expander outlet pipeline 19. A PV valve 22 is installed on the original natural gas expansion pipeline 21.

[0034] When the entire natural gas differential pressure power generation system experiences a malfunction or shutdown, natural gas can be expanded through the original natural gas expansion pipeline 21 via the PV valve group 22 and then enter the subsequent process system pipeline.

[0035] Working principle: The natural gas used for expansion power generation enters the amine liquid natural gas heat exchanger 13 through the high-pressure natural gas pipeline 15 for heat exchange. After the first heat exchange, the natural gas enters the acid gas heat exchanger 10 through the connecting pipe 16 for heat exchange. After the second heat exchange, the natural gas enters the natural gas expander 18 through the natural gas expander inlet pipe 17 for expansion power generation, and then enters the subsequent process system pipeline through the natural gas expander outlet pipe 19.

[0036] Implementation Case: Taking a natural gas purification plant with a daily transmission capacity of 3 million standard cubic meters as an example, its hourly natural gas transmission volume is approximately 125,000 Nm³ / h. The purified natural gas parameters are 5 MPa and 30℃, while the required transmission parameters are 3 MPa and 10℃. This pressure energy is recovered by installing a 1.5MW-class turbine expander (specific parameters are shown in Table 1). The annual power generation revenue is approximately 4.656 million yuan, the annual electricity saving revenue is 3.04 million yuan, and the total annual revenue is 8.0064 million yuan.

[0037] Table 1 Turbine Generator Set Parameter Table The technical solutions provided by the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the embodiments of the present invention. The descriptions of the embodiments above are only for helping to understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the embodiments of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An alcohol amine method purifies natural gas coupling pressure difference power generation cold energy utilization system, characterized in that, The system includes an amine liquid natural gas heat exchanger (13), an acid gas natural gas heat exchanger (10), and a natural gas expander (18). The amine liquid heat medium channel of the amine liquid natural gas heat exchanger (13) is connected to the lean amine liquid pipeline of the amine-based natural gas purification system, and its amine liquid coolant channel inlet is connected to the high-pressure natural gas pipeline (15). The acid gas heat medium channel of the acid gas natural gas heat exchanger (10) is connected to the acid gas pipeline of the amine-based natural gas purification system, and its acid gas coolant channel inlet is connected to the amine liquid coolant channel outlet of the amine liquid natural gas heat exchanger (13). The inlet of the natural gas expander (18) is connected to the acid gas coolant channel outlet of the acid gas natural gas heat exchanger (10), and the outlet of the natural gas expander (18) is connected to the subsequent process system pipeline. Among them, lean amine liquid and acid gas from the amine method natural gas purification system are used as heat sources to heat the high-pressure natural gas in the amine liquid natural gas heat exchanger (13) and acid gas natural gas heat exchanger (10). The heated high-pressure natural gas enters the natural gas expander (18) to expand and generate electricity. The inlet of the amine liquid heat medium channel of the amine liquid natural gas heat exchanger (13) is connected to the amine liquid inlet pipe (5) of the lean amine liquid pipeline, and the outlet of the amine liquid heat medium channel is connected to the amine liquid outlet pipe (7) of the lean amine liquid pipeline. The acid gas heat medium channel inlet of the acid gas heat exchanger (10) is connected to the acid gas inlet pipe (1) of the acid gas pipeline, and its acid gas heat medium channel outlet is connected to the acid gas outlet pipe (3) of the acid gas pipeline. A booster pump (4) is provided on the amine liquid inlet pipe (5); the amine liquid heat medium channel inlet of the amine liquid natural gas heat exchanger (13) is connected to the amine liquid inlet pipe (5) through the amine liquid heat medium inlet pipe (12), and the inlet of the amine liquid heat medium inlet pipe (12) is connected to the amine liquid inlet pipe (5) between the original solution cooler (6) and the booster pump (4); An amine pump (8) is provided on the amine outlet pipe (7); the outlet of the amine heat medium channel of the amine natural gas heat exchanger (13) is connected to the amine outlet pipe (7) through an amine heat medium outlet pipe (14), and the outlet of the amine heat medium outlet pipe (14) is connected to the amine outlet pipe (7) between the original solution cooler (6) and the amine pump (8).

2. The alcohol amine process purifying natural gas coupled with pressure difference power generation cold energy utilization system according to claim 1, characterized in that, It also includes a natural gas expander bypass pipe (20); the inlet of the natural gas expander (18) is connected to the outlet of the acid gas refrigerant channel of the acid gas heat exchanger (10) through a natural gas expander inlet pipe (17), and the outlet of the natural gas expander (18) is connected to a natural gas expander outlet pipe (19); the inlet end of the natural gas expander bypass pipe (20) is connected to the natural gas expander inlet pipe (17), and its outlet end is connected to the natural gas expander outlet pipe (19).

3. The alcohol amine process purified natural gas coupled pressure differential power generation cold energy utilization system according to claim 1, characterized in that, It also includes the original natural gas expansion pipeline (21), the inlet end of which is connected to the high-pressure natural gas pipeline (15), and the outlet end of which is connected to the natural gas expander outlet pipeline (19); a PV valve (22) is provided on the original natural gas expansion pipeline (21).

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