Shallow cold air cooling capacity coupling natural gas dehydration and dealkylation process and device

Abstract

The invention relates to the technical field of natural gas dehydration and dealkylation processes for refrigerating by coupling air cooling capacity, in particular to a shallow cold air cooling capacity coupling natural gas dehydration and dealkylation process and a shallow cold air cooling capacity coupling natural gas dehydration and dealkylation device. Comprising the step of carrying out cooling heat exchange treatment on feed gas by adopting a front cooling heat exchanger, an air cooler, a rear cooling heat exchanger, a low-temperature separator, a liquid hydrocarbon heat exchanger and a J-T valve or a propane evaporator so as to carry out dehydration and dealkylation treatment on the feed gas. According to the shallow cold air cooling capacity coupling natural gas dehydration and dealkylation process, the problem of high energy consumption of the existing J-T valve throttling refrigeration, propane external cooling dehydration and dealkylation process in the later period of gas field exploitation or in a peak regulation type underground gas storage is solved; the energy consumption of dehydration and dealkylation treatment of gas produced by a peak shaving type underground gas storage in the later period of gas field exploitation can be remarkably reduced.

Description

Technical Field

[0001] The invention relates to the technical field of a natural gas dehydration and dehydrocarbonization process coupled with air cooling, and is a natural gas dehydration and dehydrocarbonization process and device coupled with shallow air cooling. Background Art

[0002] As a clean and efficient energy source, natural gas can not only optimize the energy structure and ease the contradiction between supply and demand, but also play a very important role in improving the quality of cities, improving the environment, improving people's quality of life and achieving sustainable development. Natural gas extracted from gas fields usually needs to be treated by dehydration and dehydrogenation before being input into the finished gas pipeline network to meet the requirements of hydrocarbon and water dew point of finished gas. Commonly used natural gas dehydration and dehydrogenation treatment processes include JT valve throttling refrigeration and propane external cooling: when the raw gas pressure is high and pressure energy is available, the JT valve throttling refrigeration process is preferred; when the raw gas pressure is low and no pressure energy is available, the propane external cooling process is preferred. For gas fields that adopt depletion-type exploitation, JT valve throttling refrigeration can usually be used when the formation pressure is high in the early stage, but as the exploitation continues to deepen, there is a formation pressure attenuation in the later stage, resulting in the problem of insufficient JT valve throttling pressure difference. In addition, the formation pressure of the peak-shaving underground gas storage reservoir decreases significantly during the gas production period as the produced gas volume increases. In order to meet the standards for hydrocarbon and water dew point of gas transmission, gas fields often need to use compressors to increase the pressure of produced gas in the later stage of exploitation or underground gas storage to meet the throttling pressure difference of JT valves or add propane external cooling devices, which consumes a lot of energy and meets the increasingly stringent requirements of energy conservation and carbon reduction. Therefore, it is necessary to develop a new process technology that can effectively reduce the energy consumption of dehydration and dehydrogenation in the later stage of gas field exploitation or peak-shaving underground gas storage. Summary of the invention

[0003] The present invention provides a shallow cold air cooling capacity coupled natural gas dehydration and dehydrogenation process and device, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problem of high energy consumption in the existing JT valve throttling refrigeration, propane external cooling dehydration and dehydrogenation processes in the late stage of gas field exploitation or in peak-shaving underground gas storage.

[0004] One of the technical solutions of the present invention is achieved by the following measures: A shallow cold air cooling capacity coupled natural gas dehydration and dehydrocarbonization process comprises the following steps: Step 1: After the raw gas from the production separator is injected with ethylene glycol once, part of the raw gas enters the pre-cooling heat exchanger for cooling, and the other part of the raw gas enters the liquid hydrocarbon heat exchanger for cooling; Step 2: The raw gas from the pre-cooling heat exchanger enters the air cooler and is cooled using the cold energy in the winter air; Step 3: After the feed gas from the air cooler is injected with ethylene glycol for the second time, it enters the aftercooling heat exchanger for further cooling; Step 4: The raw gas from the aftercooling heat exchanger enters the JT valve or propane evaporator for further cooling; Step 5: The low-temperature gas from the JT valve or propane evaporator enters the low-temperature separator for gas-liquid separation, the separated liquid phase goes to the liquid hydrocarbon heat exchanger, and the separated low-temperature dry gas enters the after-cooling heat exchanger; Step 6: The low-temperature dry gas separated by the low-temperature separator enters the after-cooling heat exchanger for reheating; Step 7: The dry gas from the after-cooling heat exchanger enters the front-cooling heat exchanger, and then goes downstream after further reheating; Step 8: The low-temperature condensate separated by the low-temperature separator enters the liquid hydrocarbon heat exchanger for reheating and then goes downstream.

[0005] The following is a further optimization and / or improvement of one of the above-mentioned technical solutions: The above-mentioned shallow cold air cold capacity coupled with the natural gas dehydration and dehydrocarbonization process specifically includes the following steps: Step 1: After the raw gas from the production separator is injected with ethylene glycol once, part of the raw gas enters the pre-cooling heat exchanger to be cooled to 10°C to 25°C, and the other part of the raw gas enters the liquid hydrocarbon heat exchanger to be cooled to 10°C to 25°C; Step 2: The raw gas from the pre-cooling heat exchanger enters the air cooler and is cooled to -5℃ to 0℃ using the cold energy in the winter air; Step 3: After the feed gas from the air cooler is injected with ethylene glycol for the second time, it enters the aftercooling heat exchanger and is further cooled to -10℃ to -5℃; Step 4: The raw gas from the aftercooling heat exchanger enters the JT valve or propane evaporator and is cooled to -15℃ to -10℃; Step 5: The low-temperature gas from the JT valve or propane evaporator enters the low-temperature separator for gas-liquid separation, the separated liquid phase goes to the liquid hydrocarbon heat exchanger, and the separated low-temperature dry gas enters the after-cooling heat exchanger; Step 6: The temperature of the low-temperature dry gas separated by the low-temperature separator is -15℃ to -10℃, and it enters the after-cooling heat exchanger to be reheated to 0℃ to 5℃; Step 7: The dry gas from the after-cooling heat exchanger enters the front-cooling heat exchanger, and is further reheated to 10℃ to 30℃ before going downstream; Step 8: The temperature of the low-temperature condensate separated by the low-temperature separator is -15℃ to -10℃. It enters the liquid hydrocarbon heat exchanger to be reheated to 25℃ to 30℃ before going downstream.

[0006] The second technical solution of the present invention is achieved by the following measures: a device for coupling the shallow cold air cooling capacity of the natural gas dehydration and dehydrocarbonization process described in one of the technical solutions, including a front-cooling heat exchanger, an air cooler, a back-cooling heat exchanger, a low-temperature separator, a liquid hydrocarbon heat exchanger and a JT valve or a propane evaporator, the raw gas inlet of the front-cooling heat exchanger is connected with a raw gas pipeline, the raw gas outlet of the front-cooling heat exchanger and the air cooler inlet are connected with a front-cooling pipeline, the air cooler outlet and the inlet of the back-cooling heat exchanger are connected with an air cooling pipeline, the outlet of the back-cooling heat exchanger is connected with the inlet of the JT valve or the propane evaporator with a back-cooling pipeline, and the outlet of the JT valve or the propane evaporator is connected with a back-cooling pipeline. It is connected with the inlet of the low-temperature separator; the top outlet of the low-temperature separator is connected with the dry gas inlet of the after-cooling heat exchanger through a low-temperature separation pipeline, the dry gas outlet of the after-cooling heat exchanger is connected with the dry gas inlet of the front-cooling heat exchanger through a primary rewarming dry gas pipeline, and the dry gas outlet of the front-cooling heat exchanger is connected with a secondary rewarming dry gas pipeline; the raw gas pipeline and the raw gas inlet of the liquid hydrocarbon heat exchanger are connected through a raw gas branch pipeline, and the raw gas outlet of the liquid hydrocarbon heat exchanger and the front-cooling pipeline are connected with a cooling branch pipeline; the bottom outlet of the low-temperature separator is connected with the liquid phase inlet of the liquid hydrocarbon heat exchanger through a low-temperature liquid hydrocarbon pipeline, and the liquid phase outlet of the liquid hydrocarbon heat exchanger is connected with a rewarming liquid hydrocarbon pipeline.

[0007] The following is a further optimization and / or improvement of the second technical solution of the above invention: The raw gas pipeline is provided with a first alcohol injection atomizer, and the inlet of the first alcohol injection atomizer is connected with an ethylene glycol antifreeze pipeline.

[0008] A second alcohol injection atomizer is arranged on the above-mentioned aftercooling pipeline, and an ethylene glycol antifreeze pipeline is connected to the inlet of the second alcohol injection atomizer.

[0009] Compared with the prior art, the present invention has the following positive effects: 1) Compared with the existing JT valve throttling refrigeration and auxiliary compressor boosting process, the total heat exchange area of ​​the heat exchanger is not increased. Under the same hydrocarbon and water dew point conditions, this process technology can effectively reduce the JT valve throttling pressure difference by more than 1.5MPa during winter operation, thereby reducing the compressor boosting energy consumption by more than 65%; 2) Compared with the existing propane external cooling process, the total heat exchange area of ​​the heat exchanger is not increased. Under the same hydrocarbon and water dew point conditions, this process technology can effectively reduce the propane refrigeration energy consumption by more than 55% during winter operation.

[0010] As a result, the energy consumption of dehydration and dehydrogenation treatment of produced gas in the late stage of gas field exploitation or in peak-shaving underground gas storage can be significantly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Attached Figure 1 It is a schematic diagram of the process flow of the device of the present invention.

[0012] The codes in the accompanying drawings are: 1 is a front-cooling heat exchanger, 2 is an air cooler, 3 is an after-cooling heat exchanger, 4 is a low-temperature separator, 5 is a liquid hydrocarbon heat exchanger, 6 is a JT valve or a propane evaporator, 7 is a raw gas pipeline, 8 is a front-cooling pipeline, 9 is an air-cooling pipeline, 10 is a after-cooling pipeline, 11 is a low-temperature separation pipeline, 12 is a primary rewarming dry gas pipeline, 13 is a secondary rewarming dry gas pipeline, 14 is a raw gas branch pipeline, 15 is a cooling branch pipeline, 16 is a low-temperature liquid hydrocarbon pipeline, 17 is a rewarming liquid hydrocarbon pipeline, 18 is a first alcohol injection atomizer, 19 is a second alcohol injection atomizer, and 20 is an ethylene glycol antifreeze pipeline. DETAILED DESCRIPTION

[0013] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0014] In the present invention, for the convenience of description, the relative position relationship of each component is described according to the attached Figure 1 The layout is described in detail, such as the positional relationship of front, back, top, bottom, left, right, etc., which is based on the attached manual. Figure 1 It is determined by the layout direction.

[0015] The present invention will be further described below in conjunction with embodiments: Embodiment 1: As attached Figure 1 As shown, the shallow cold air cold capacity coupled natural gas dehydration and dehydrogenation process includes the following steps: Step 1: After the raw gas from the production separator is injected with ethylene glycol once, part of the raw gas enters the pre-cooling heat exchanger 1 for cooling, and the other part of the raw gas enters the liquid hydrocarbon heat exchanger 5 for cooling; Step 2: The raw gas from the pre-cooling heat exchanger 1 enters the air cooler 2 and is cooled by the cold energy in the winter air; Step 3: After the feed gas from the air cooler 2 is injected with ethylene glycol for the second time, it enters the aftercooling heat exchanger 3 for further cooling; Step 4: The raw gas from the aftercooling heat exchanger 3 enters the JT valve or propane evaporator 6 to continue cooling; Step 5: The low-temperature gas from the JT valve or propane evaporator 6 enters the low-temperature separator 4 for gas-liquid separation, the separated liquid phase goes to the liquid hydrocarbon heat exchanger 5, and the separated low-temperature dry gas enters the after-cooling heat exchanger 3; Step 6: The low-temperature dry gas separated by the low-temperature separator 4 enters the after-cooling heat exchanger 3 for reheating; Step 7: The dry gas from the after-cooling heat exchanger 3 enters the front-cooling heat exchanger 1, and then goes downstream after further reheating; Step 8: The low-temperature condensate separated by the low-temperature separator 4 enters the liquid hydrocarbon heat exchanger 5 for reheating and then goes downstream.

[0016] The shallow air cooling capacity coupled natural gas dehydration and dehydrogenation process described in the present invention solves the high energy consumption problem of the existing JT valve throttling refrigeration, propane external cooling dehydration and dehydrogenation processes in the late stage of gas field exploitation or in peak-shaving underground gas storages. It can significantly reduce the energy consumption of dehydration and dehydrogenation treatment of produced gas in the late stage of gas field exploitation or in peak-shaving underground gas storages.

[0017] Embodiment 2: As attached Figure 1 As shown, the shallow cold air cooling capacity is coupled with the natural gas dehydration and dehydrocarbonization process, which specifically includes the following steps: Step 1: After the raw gas from the production separator is injected with ethylene glycol once, part of the raw gas enters the pre-cooling heat exchanger 1 to be cooled to 10°C to 25°C, and the other part of the raw gas enters the liquid hydrocarbon heat exchanger 5 to be cooled to 10°C to 25°C; Step 2: The raw gas from the pre-cooling heat exchanger 1 enters the air cooler 2 and is cooled to -5℃ to 0℃ using the cold energy in the winter air; Step 3: After the feed gas from the air cooler 2 is injected with ethylene glycol for the second time, it enters the aftercooling heat exchanger 3 and is further cooled to -10°C to -5°C; Step 4: The raw gas from the aftercooling heat exchanger 3 enters the JT valve or propane evaporator 6 and is cooled to -15°C to -10°C; Step 5: The low-temperature gas from the JT valve or propane evaporator 6 enters the low-temperature separator 4 for gas-liquid separation, the separated liquid phase goes to the liquid hydrocarbon heat exchanger 5, and the separated low-temperature dry gas enters the after-cooling heat exchanger 3; Step 6: The temperature of the low-temperature dry gas separated by the low-temperature separator 4 is -15°C to -10°C, and enters the after-cooling heat exchanger 3 to be reheated to 0°C to 5°C; Step 7: The dry gas from the after-cooling heat exchanger 3 enters the front-cooling heat exchanger 1, is further reheated to 10°C to 30°C, and then goes downstream; Step 8: The temperature of the low-temperature condensate separated by the low-temperature separator 4 is -15°C to -10°C. It enters the liquid hydrocarbon heat exchanger 5 to be reheated to 25°C to 30°C before going downstream.

[0018] Embodiment 3: As attached Figure 1As shown, the device for implementing the shallow cold air cooling capacity coupled natural gas dehydration and dehydrocarbonization process described in the above embodiment comprises a front cooling heat exchanger 1, an air cooler 2, an after-cooling heat exchanger 3, a low-temperature separator 4, a liquid hydrocarbon heat exchanger 5 and a JT valve or a propane evaporator 6, the raw gas inlet of the front cooling heat exchanger 1 is connected with a raw gas pipeline 7, the raw gas outlet of the front cooling heat exchanger 1 and the inlet of the air cooler 2 are connected with a front cooling pipeline 8, the outlet of the air cooler 2 and the inlet of the after-cooling heat exchanger 3 are connected with an air cooling pipeline 9, the outlet of the after-cooling heat exchanger 3 and the inlet of the JT valve or the propane evaporator 6 are connected with an after-cooling pipeline 10, and the outlet of the JT valve or the propane evaporator 6 is connected with the inlet of the low-temperature separator 4; The top outlet of the warm separator 4 is connected to the dry gas inlet of the after-cooling heat exchanger 3 through a low-temperature separation pipeline 11, the dry gas outlet of the after-cooling heat exchanger 3 is connected to the dry gas inlet of the front-cooling heat exchanger 1 through a primary rewarming dry gas pipeline 12, and the dry gas outlet of the front-cooling heat exchanger 1 is connected to a secondary rewarming dry gas pipeline 13; the raw gas pipeline 7 and the raw gas inlet of the liquid hydrocarbon heat exchanger 5 are connected through a raw gas branch pipeline 14, and the raw gas outlet of the liquid hydrocarbon heat exchanger 5 and the front-cooling pipeline 8 are connected through a cooling branch pipeline 15; the bottom outlet of the low-temperature separator 4 is connected to the liquid phase inlet of the liquid hydrocarbon heat exchanger 5 through a low-temperature liquid hydrocarbon pipeline 16, and the liquid phase outlet of the liquid hydrocarbon heat exchanger 5 is connected to a rewarming liquid hydrocarbon pipeline 17.

[0019] The pre-cooling heat exchanger 1 is used to exchange heat between the raw gas (30°C to 45°C) from the production separator and the dry gas from the post-cooling heat exchanger 3, and to reheat the post-cooled dry gas to 15°C to 30°C to meet the requirements of the external transmission temperature to adapt to the material of the external transmission pipeline. While recovering the coldness in the dry gas from the post-cooling heat exchanger, the raw gas is pre-cooled to 10°C to 25°C.

[0020] A liquid hydrocarbon heat exchanger 5 is provided for exchanging heat between part of the raw gas (30°C to 45°C) from the production separator and the low-temperature condensate from the low-temperature separator 4, reheating the low-temperature condensate from the low-temperature separator 4 to 25°C to 30°C, recovering the cold in the low-temperature condensate from the low-temperature separator 4, and precooling the raw gas to 10°C to 25°C.

[0021] An air cooler 2 is arranged after the front cooling heat exchanger 1, and the cold energy in the winter air can be used to further cool the raw gas from the front cooling heat exchanger 1 to -5°C to 0°C.

[0022] An after-cooling heat exchanger 3 is arranged after the air cooler 2, which is used for exchanging heat between the raw gas cooled by the air cooler 2 and the low-temperature dry gas from the low-temperature separator 4, and reheating the low-temperature dry gas (-10℃ to -15℃) from the low-temperature separator 4 to 0℃ to 5℃ to recover the cold in the dry gas from the low-temperature separator 4. At the same time, the raw gas is after-cooled to -10℃ to -5℃ and enters the JT valve or propane evaporator 6 to be cooled to -15℃ to -10℃.

[0023] The low-temperature gas (-15°C to -10°C) cooled by the JT valve or propane evaporator 6 enters the low-temperature separator 4 for gas-liquid separation, the separated gas phase enters the aftercooling heat exchanger 3, and the separated liquid phase enters the liquid hydrocarbon separator.

[0024] Embodiment 4: As attached Figure 1 As shown, as an optimization of Example 3, a first alcohol injection atomizer 18 is provided on the raw gas pipeline 7, and the inlet of the first alcohol injection atomizer 18 is connected to an ethylene glycol antifreeze pipeline 20.

[0025] A first alcohol injection atomizer 18 is provided on the raw gas pipeline 7 at the inlet of the pre-cooling heat exchanger 1 for injecting ethylene glycol antifreeze to prevent freezing and blockage of the raw gas after pre-cooling and air cooling.

[0026] Embodiment 5: As attached Figure 1 As shown, as an optimization of embodiments 3 and 4, a second alcohol injection atomizer 19 is provided on the aftercooling pipeline 10, and the inlet of the second alcohol injection atomizer 19 is connected to an ethylene glycol antifreeze pipeline 20.

[0027] A second alcohol injection atomizer 19 is provided on the after-cooling pipeline 10 at the outlet of the after-cooling heat exchanger 3 for injecting ethylene glycol antifreeze to prevent freezing and blockage of the raw gas after after-cooling.

[0028] The practical application examples of the shallow cold air cooling capacity coupled with the natural gas dehydration and dehydrogenation process are as follows: Example 1: Application of JT valve throttling refrigeration, natural gas dehydration and dehydrocarbon removal: Step 1: The raw gas from the production separator is 30℃ to 45℃, 7.5MPa. After the ethylene glycol is injected once, 90% of the raw gas enters the front cooling heat exchanger 1 and is cooled to 10℃ to 25℃, and 10% of the raw gas enters the liquid hydrocarbon heat exchanger 5 and is cooled to 10℃ to 25℃; Step 2: The raw gas from the pre-cooling heat exchanger 1 enters the air cooler 2 and is cooled to -5℃ to 0℃ using the cold energy in the winter air; Step 3: After the feed gas from the air cooler 2 is injected with ethylene glycol for the second time, it enters the aftercooling heat exchanger 3 and is further cooled to -10°C to -5°C; Step 4: The raw gas from the aftercooling heat exchanger 3 enters the JT valve and is throttled to 6MPa, -15℃ to -10℃; Step 5: The low-temperature gas from the JT valve enters the low-temperature separator 4 for gas-liquid separation, the separated liquid phase goes to the liquid hydrocarbon heat exchanger 5, and the separated low-temperature dry gas enters the after-cooling heat exchanger 3; Step 6: The low-temperature dry gas separated from the low-temperature separator 4 at -15°C to -10°C enters the after-cooling heat exchanger 3 and is reheated to 0°C to 5°C; Step 7: The dry gas from the after-cooling heat exchanger 3 enters the front-cooling heat exchanger 1, and is further reheated to 10°C to 30°C before going downstream; Step 8: The low-temperature condensate separated from the low-temperature separator 4 at -15°C to -10°C enters the liquid hydrocarbon heat exchanger 5 for reheating to 25°C to 30°C and then goes downstream.

[0029] Example 2: Application of propane external cooling to dehydrate and dehydrogenate natural gas: Step 1: The raw gas from the production separator is 30℃ to 45℃, 6MPa. After the ethylene glycol is injected once, 90% of the raw gas enters the front cooling heat exchanger 1 and is cooled to 10℃ to 25℃, and 10% of the raw gas enters the liquid hydrocarbon heat exchanger 5 and is cooled to 10℃ to 25℃; Step 2: The raw gas from the pre-cooling heat exchanger 1 enters the air cooler 2 and is cooled to -5℃ to 0℃ using the cold energy in the winter air; Step 3: After the feed gas from the air cooler 2 is injected with ethylene glycol for the second time, it enters the aftercooling heat exchanger 3 and is further cooled to -10°C to -5°C; Step 4: The raw gas from the aftercooling heat exchanger 3 enters the propane evaporator and is cooled to -15°C to -10°C; Step 5: The low-temperature gas from the propane evaporator enters the low-temperature separator 4 for gas-liquid separation, the separated liquid phase goes to the liquid hydrocarbon heat exchanger 5, and the separated low-temperature dry gas enters the after-cooling heat exchanger 3; Step 6: The low-temperature dry gas separated from the low-temperature separator 4 at -15°C to -10°C enters the after-cooling heat exchanger 3 and is reheated to 0°C to 5°C; Step 7: The dry gas from the after-cooling heat exchanger 3 enters the front-cooling heat exchanger 1, and is further reheated to 10°C to 30°C before going downstream; Step 8: The low-temperature condensate separated from the low-temperature separator 4 at -15°C to -10°C enters the liquid hydrocarbon heat exchanger 5 for reheating to 25°C to 30°C and then goes downstream.

[0030] Example 3: Application of JT valve throttling refrigeration, natural gas dehydration and dehydrogenation: Step 1: The raw gas from the production separator is 45°C and 7.5MPa. After the ethylene glycol is injected once, 90% of the raw gas enters the front cooling heat exchanger 1 and is cooled to 10°C, and 10% of the raw gas enters the liquid hydrocarbon heat exchanger 5 and is cooled to 10°C; Step 2: The raw gas from the pre-cooling heat exchanger 1 enters the air cooler 2 and is cooled to -5°C using the cold energy in the winter air; Step 3: After the feed gas from the air cooler 2 is injected with ethylene glycol for the second time, it enters the aftercooling heat exchanger 3 and is further cooled to -10°C; Step 4: The raw gas from the aftercooling heat exchanger 3 enters the JT valve and is throttled to 6MPa, -15℃; Step 5: The low-temperature gas from the JT valve enters the low-temperature separator 4 for gas-liquid separation, the separated liquid phase goes to the liquid hydrocarbon heat exchanger 5, and the separated low-temperature dry gas enters the after-cooling heat exchanger 3; Step 6: The low-temperature dry gas separated by the low-temperature separator 4 at -15°C enters the after-cooling heat exchanger 3 and is reheated to 0°C; Step 7: The dry gas from the after-cooling heat exchanger 3 enters the front-cooling heat exchanger 1, is further reheated to 10°C and then goes downstream; Step 8: The low-temperature condensate separated from the low-temperature separator 4 at -15°C enters the liquid hydrocarbon heat exchanger 5 for reheating to 25°C and then goes downstream.

[0031] Example 4: Application of propane external cooling to dehydrate and dehydrogenate natural gas: Step 1: The raw gas from the production separator is 30℃, 6MPa. After the ethylene glycol is injected once, 90% of the raw gas enters the pre-cooling heat exchanger 1 and is cooled to 25℃, and 10% of the raw gas enters the liquid hydrocarbon heat exchanger 5 and is cooled to 25℃; Step 2: The raw gas from the pre-cooling heat exchanger 1 enters the air cooler 2 and is cooled to 0°C using the cold energy in the winter air; Step 3: After the feed gas from the air cooler 2 is injected with ethylene glycol for the second time, it enters the aftercooling heat exchanger 3 and is further cooled to -5°C; Step 4: The raw gas from the aftercooling heat exchanger 3 enters the propane evaporator and is cooled to -10°C; Step 5: The low-temperature gas from the propane evaporator enters the low-temperature separator 4 for gas-liquid separation, the separated liquid phase goes to the liquid hydrocarbon heat exchanger 5, and the separated low-temperature dry gas enters the after-cooling heat exchanger 3; Step 6: The low-temperature dry gas separated by the low-temperature separator 4 at -10°C enters the after-cooling heat exchanger 3 and is reheated to 5°C; Step 7: The dry gas from the after-cooling heat exchanger 3 enters the front-cooling heat exchanger 1, is further reheated to 30°C and then goes downstream; Step 8: The low-temperature condensate separated from the low-temperature separator 4 at -10°C enters the liquid hydrocarbon heat exchanger 5 for reheating to 30°C and then goes downstream.

[0032] Compared with the prior art, the present invention has the following positive effects: 1) Compared with the existing JT valve throttling refrigeration and auxiliary compressor boosting process, the total heat exchange area of ​​the heat exchanger is not increased. Under the same hydrocarbon and water dew point conditions, this process technology can effectively reduce the JT valve throttling pressure difference by more than 1.5MPa during winter operation, thereby reducing the compressor boosting energy consumption by more than 65% (see Example 3 for details); 2) Compared with the existing propane external cooling process, the total heat exchange area of ​​the heat exchanger is not increased. Under the same hydrocarbon and water dew point conditions, this process technology can effectively reduce the propane refrigeration energy consumption by more than 55% during winter operation (see Example 4 for details).

[0033] As a result, the energy consumption of dehydration and dehydrogenation treatment of produced gas in the late stage of gas field exploitation or in peak-shaving underground gas storage can be significantly reduced.

[0034] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A process for coupling the cooling capacity of shallow cold air with the dehydration and dehydrocarbonization of natural gas, characterized in that The following steps are involved: Step 1: After the raw gas from the production separator is injected with ethylene glycol once, part of the raw gas enters the pre-cooling heat exchanger for cooling, and the other part of the raw gas enters the liquid hydrocarbon heat exchanger for cooling; Step 2: The raw gas from the pre-cooling heat exchanger enters the air cooler and is cooled using the cold energy in the winter air; Step 3: After the feed gas from the air cooler is injected with ethylene glycol for the second time, it enters the aftercooling heat exchanger for further cooling; Step 4: The raw gas from the aftercooling heat exchanger enters the JT valve or propane evaporator for further cooling; Step 5: The low-temperature gas from the JT valve or propane evaporator enters the low-temperature separator for gas-liquid separation, the separated liquid phase goes to the liquid hydrocarbon heat exchanger, and the separated low-temperature dry gas enters the after-cooling heat exchanger; Step 6: The low-temperature dry gas separated by the low-temperature separator enters the after-cooling heat exchanger for reheating; Step 7: The dry gas from the after-cooling heat exchanger enters the front-cooling heat exchanger, and then goes downstream after further reheating; Step 8: The low-temperature condensate separated by the low-temperature separator enters the liquid hydrocarbon heat exchanger for reheating and then goes downstream.

2. The shallow cold air cold capacity coupled natural gas dehydration and dehydrocarbonization process according to claim 1 is characterized in that The specific steps include: Step 1: After the raw gas from the production separator is injected with ethylene glycol once, part of the raw gas enters the pre-cooling heat exchanger to be cooled to 10°C to 25°C, and the other part of the raw gas enters the liquid hydrocarbon heat exchanger to be cooled to 10°C to 25°C; Step 2: The raw gas from the pre-cooling heat exchanger enters the air cooler and is cooled to -5℃ to 0℃ using the cold energy in the winter air; Step 3: After the feed gas from the air cooler is injected with ethylene glycol for the second time, it enters the aftercooling heat exchanger and is further cooled to -10℃ to -5℃; Step 4: The raw gas from the aftercooling heat exchanger enters the JT valve or propane evaporator and is cooled to -15℃ to -10℃; Step 5: The low-temperature gas from the JT valve or propane evaporator enters the low-temperature separator for gas-liquid separation, the separated liquid phase goes to the liquid hydrocarbon heat exchanger, and the separated low-temperature dry gas enters the after-cooling heat exchanger; Step 6: The temperature of the low-temperature dry gas separated by the low-temperature separator is -15℃ to -10℃, and it enters the after-cooling heat exchanger to be reheated to 0℃ to 5℃; Step 7: The dry gas from the after-cooling heat exchanger enters the front-cooling heat exchanger, and is further reheated to 10℃ to 30℃ before going downstream; Step 8: The temperature of the low-temperature condensate separated by the low-temperature separator is -15℃ to -10℃. It enters the liquid hydrocarbon heat exchanger to be reheated to 25℃ to 30℃ before going downstream.

3. A device for implementing the shallow cold air cooling coupled natural gas dehydration and dehydrocarbonization process according to claim 1 or 2, characterized in that The invention comprises a front cooling heat exchanger, an air cooler, an after-cooling heat exchanger, a low-temperature separator, a liquid hydrocarbon heat exchanger and a JT valve or a propane evaporator. The raw gas inlet of the front cooling heat exchanger is connected with a raw gas pipeline, the raw gas outlet of the front cooling heat exchanger and the air cooler inlet are connected with a front cooling pipeline, the air cooler outlet and the after-cooling heat exchanger inlet are connected with an air cooling pipeline, the outlet of the after-cooling heat exchanger and the inlet of the JT valve or the propane evaporator are connected with an after-cooling pipeline, the outlet of the JT valve or the propane evaporator is connected with the inlet of the low-temperature separator; the top outlet of the low-temperature separator is connected with the after-cooling heat exchanger. The dry gas inlet of the after-cooling heat exchanger is connected through a low-temperature separation pipeline, the dry gas outlet of the after-cooling heat exchanger is connected to the dry gas inlet of the front-cooling heat exchanger through a primary rewarming dry gas pipeline, and the dry gas outlet of the front-cooling heat exchanger is connected to a secondary rewarming dry gas pipeline; the raw gas pipeline and the raw gas inlet of the liquid hydrocarbon heat exchanger are connected through a raw gas branch pipeline, and the raw gas outlet of the liquid hydrocarbon heat exchanger and the front-cooling pipeline are connected with a cooling branch pipeline; the bottom outlet of the low-temperature separator is connected to the liquid phase inlet of the liquid hydrocarbon heat exchanger through a low-temperature liquid hydrocarbon pipeline, and the liquid phase outlet of the liquid hydrocarbon heat exchanger is connected with a rewarming liquid hydrocarbon pipeline.

4. The device according to claim 3, characterized in that The raw gas pipeline is provided with a first alcohol injection atomizer.

5. The device according to claim 4, characterized in that The inlet of the first alcohol injection atomizer is connected with an ethylene glycol antifreeze pipeline.

6. The device according to claim 3, 4 or 5, characterized in that A second alcohol injection atomizer is provided on the aftercooling line.

7. The device according to claim 6, characterized in that The inlet of the second alcohol injection atomizer is connected with an ethylene glycol antifreeze pipeline.

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