Combined gas storage natural gas shallow cooling treatment system and method

Abstract

The invention relates to the field of natural gas treatment, in particular to a combined gas storage natural gas shallow cooling treatment system and method. A first outlet of the pre-separator is connected with a first inlet of the heat exchanger; a first outlet of the heat exchanger is connected with an inlet of the production separator; a first outlet of the production separator is connected with a first inlet of the precooling heat exchanger; a first outlet of the precooling heat exchanger is connected with an inlet of the J-T valve; an outlet of the J-T valve is connected with an inlet of the low-temperature separator; a first outlet of the low-temperature separator is connected with a second inlet of the precooling heat exchanger; a second outlet of the precooling heat exchanger is connected with an inlet of the differential pressure power generation device; an outlet of the differential pressure power generation device is connected with a second inlet of the heat exchanger. Pressure energy in front of and behind the J-T valve is recycled through the differential pressure power generation device, cold natural gas subjected to expansion refrigeration exchanges heat with feed gas through the heat exchanger and exchanges heat with low-temperature dry gas through the pre-cooling heat exchanger, the temperature of the feed gas is further reduced, and the heat exchange area of the heat exchanger is reduced.

Description

Technical Field

[0001] The invention relates to the field of natural gas processing, and in particular to a combined gas storage natural gas shallow cold processing system and method. Background Art

[0002] At present, underground gas storage has a large flow rate and pressure difference during the gas production process. In order to meet the needs of raw gas deoiling and dehydration, the ethylene glycol injection antifreeze + JT valve throttling refrigeration process is generally adopted. Because the gas volume of the gas storage injection and production wells is large, the temperature of the produced gas is high. In order to meet the demand for water dew point transmission, the natural gas is generally cooled by an air cooler and then further cooled by a heat exchanger, and then the JT valve is used for expansion refrigeration to deoil and dehydrate. Since the cooling effect of the air cooler is greatly affected by the ambient temperature, the heat exchange area of ​​the heat exchanger is generally considered according to extreme conditions during design, resulting in a large heat exchange area, high investment, and high land occupation. Using the JT valve expansion refrigeration process, the pressure difference before and after the JT valve is less than 2MPa, and the pressure energy cannot be used. In order to meet the needs of deoiling and dehydration, a propane auxiliary refrigeration process is adopted, which has high investment, the pressure energy is not fully utilized, and the energy consumption is high. In summary, the existing related technologies have high equipment requirements, large investment, and the pressure energy cannot be used. Summary of the invention

[0003] The purpose of the present invention is to provide a combined gas storage natural gas shallow cold treatment system and method to solve the problems of high equipment requirements, large investment and unusable pressure energy in the existing related technologies.

[0004] A combined gas storage natural gas shallow cold treatment system comprises a pre-separator, a heat exchanger, a production separator, a pre-cooling heat exchanger, a JT valve, a low-temperature separator and a pressure difference power generation device; wherein: the inlet of the pre-separator is connected to the produced gas of the gas storage, the first outlet of the pre-separator is connected to the first inlet of the heat exchanger; the first outlet of the heat exchanger is connected to the inlet of the production separator; the first outlet of the production separator is connected to the first inlet of the pre-cooling heat exchanger; the first outlet of the pre-cooling heat exchanger is connected to the inlet of the JT valve; the outlet of the JT valve is connected to the inlet of the low-temperature separator; the first outlet of the low-temperature separator is connected to the second inlet of the pre-cooling heat exchanger; the second outlet of the pre-cooling heat exchanger is connected to the inlet of the pressure difference power generation device; the outlet of the pressure difference power generation device is connected to the second inlet of the heat exchanger; the second outlet of the heat exchanger is connected to the external transmission pipeline.

[0005] Optionally, the pressure difference power generation device includes a second JT valve, an expander, a generator and a grid-connected cabinet; wherein: the inlet of the expander is connected to the second outlet of the precooling heat exchanger and to the inlet of the second JT valve, the outlet of the expander is connected to the generator and the outlet of the second JT valve; the generator is connected to the grid-connected cabinet.

[0006] Optionally, the heat exchanger is a shell and tube heat exchanger or a plate heat exchanger.

[0007] Optionally, the production separator is a gravity separator or a rotary separator.

[0008] Optionally, it is characterized in that the pre-separator and the low-temperature separator are respectively provided with a second outlet, which is used to send the separated alcohol-containing liquid to the condensate oil stabilization device, and the production separator also includes a second outlet for transporting produced water to the flash tank in the gas gathering area.

[0009] Optionally, the first outlet of the production separator and the first outlet of the low-temperature separator are respectively connected to emergency venting pipelines.

[0010] Optionally, the pre-separator, the production separator and the low-temperature separator are respectively provided with liquid level detection devices, which are used to control the electric regulating valves of the second outlet of the pre-separator, the second outlet of the production separator and the second outlet of the low-temperature separator respectively.

[0011] Optionally, the first inlet of the precooling heat exchanger is connected to an ethylene glycol supply pipeline, and an ethylene glycol atomizer is provided at the connection between the precooling heat exchanger and the ethylene glycol supply pipeline.

[0012] A method for shallow cooling of natural gas in a combined gas storage facility comprises the following steps:

[0013] S1. The produced gas from the gas storage is separated from the produced water and the natural gas by a pre-separator to obtain raw natural gas. The raw natural gas is heat-exchanged with the product dry gas after expansion and power generation by a heat exchanger to heat the product dry gas after expansion and power generation to the second reheating temperature, and the temperature of the raw natural gas is reduced to the set first cooling temperature;

[0014] S2, transporting the cooled raw natural gas to a production separator to further separate produced water and condensate oil to obtain separated natural gas;

[0015] S3, the separated natural gas is cooled to the set second cooling temperature by the precooling heat exchanger, then expanded and cooled to the third cooling temperature by the JT valve, separated by the low-temperature separator to obtain low-temperature dry gas, and the low-temperature dry gas is reheated to the first reheating temperature by the precooling heat exchanger to obtain product dry gas;

[0016] S4. The product dry gas is expanded and refrigerated by the pressure difference power generation device. After power generation, it is transported to the heat exchanger for reheating to the second reheating temperature and then enters the external transmission pipeline.

[0017] Optionally, in step S3, the separated natural gas and atomized ethylene glycol enter the precooling heat exchanger together.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention adopts a pressure difference power generation device, which recovers the pressure energy before and after the JT valve, improves energy utilization efficiency and reduces operating costs;

[0020] 2. The present invention utilizes expansion refrigeration to cool natural gas after heat exchange with raw gas through a heat exchanger, thereby reducing the temperature of the raw gas, eliminating the air cooler, reducing investment, and avoiding the unstable factor of the air cooler being affected by the ambient temperature; by precooling the heat exchanger to exchange heat with low-temperature dry gas, the temperature of the raw gas is further reduced, the heat exchange area of ​​the heat exchanger is reduced, and the investment and land occupation are reduced;

[0021] 3. The present invention adopts an ethylene glycol atomizer to prevent the formation of hydrates after the JT valve expands and refrigerates; it fully utilizes the pressure energy that the JT valve cannot use to expand and refrigerate and generate electricity, replaces the propane auxiliary refrigeration system, reduces energy consumption, and realizes the green operation of the gas storage;

[0022] 4. The present invention optimizes the structure and parameters of equipment such as separators, heat exchangers, and JT valves, thereby improving the operational stability and safety of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a schematic diagram of a process flow of a combined gas storage natural gas shallow cold treatment system embodiment of the present invention.

[0024] Figure 2 The present invention is a schematic diagram of the steps of an embodiment of a method for shallow cold treatment of natural gas in a combined gas storage facility.

[0025] Among them, 1-pre-separator, 2-heat exchanger, 3-production separator, 4-pre-cooling heat exchanger, 5-JT valve, 6-low-temperature separator, 7-pressure difference power generation device. DETAILED DESCRIPTION

[0026] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict.

[0027] The following detailed description is an exemplary description, which is intended to provide further detailed description of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used in the present invention are only for describing specific embodiments, and are not intended to limit exemplary embodiments according to the present invention.

[0028] like Figure 1 As shown, an embodiment of a combined gas storage natural gas shallow cold treatment system includes a pre-separator 1, a heat exchanger 2, a production separator 3, a pre-cooling heat exchanger 4, a JT valve 5, a low-temperature separator 6 and a pressure difference power generation device 7; wherein: the inlet of the pre-separator 1 is connected to the produced gas of the gas storage, specifically, the produced gas of the gas storage is separated from the produced water and the natural gas through the pre-separator 1 to obtain the raw natural gas; the first outlet of the pre-separator 1 is connected to the first inlet of the heat exchanger 2; specifically, the temperature of the raw natural gas can be 40°C.

[0029] The first outlet of the heat exchanger 2 is connected to the inlet of the production separator 3. After the heat exchange, the temperature of the raw natural gas drops to the set first cooling temperature, and the specific first cooling temperature can be 20°C. The cooled raw natural gas is transported to the production separator 3 to further separate the produced water and condensate oil to obtain the separated natural gas; the first outlet of the production separator 3 is connected to the first inlet of the precooling heat exchanger 4; the separated natural gas is cooled to the set second cooling temperature through the precooling heat exchanger 4, and the specific second cooling temperature can be -5°C; the first outlet of the precooling heat exchanger 4 is connected to the inlet of the JT valve 5; and then expanded and cooled to the third cooling temperature through the JT valve 5, and the specific third cooling temperature can be -15°C.

[0030] The outlet of the JT valve 5 is connected to the inlet of the low-temperature separator 6; after separation in the low-temperature separator 6, low-temperature dry gas and alcohol-containing condensate are obtained.

[0031] The first outlet of the low-temperature separator 6 is connected to the second inlet of the precooling heat exchanger 4; specifically, the low-temperature dry gas is heat exchanged with the above-separated natural gas, and the low-temperature dry gas is reheated to a first reheating temperature through the precooling heat exchanger 4 to obtain the product dry gas; specifically, the first reheating temperature can be 10°C.

[0032] The second outlet of the precooling heat exchanger 4 is connected to the inlet of the pressure difference power generation device 7; the product dry gas is expanded and refrigerated by the pressure difference power generation device 7 to generate electricity, and the pressure energy is fully utilized for expansion and refrigeration to meet the water dew point and hydrocarbon dew point external transmission requirements; the pressure energy is converted into electrical energy for the power consumption of the injection station; the cold energy of the pressure difference power generation expansion and refrigeration is fully utilized to reduce the temperature of the reheated product dry gas, and the outlet of the pressure difference power generation device 7 is connected to the second inlet of the heat exchanger 2; the second outlet of the heat exchanger 2 is connected to the external transmission pipeline. The product dry gas is transported to the heat exchanger 2 and reheated to the second reheating temperature before entering the external transmission pipeline.

[0033] As a specific example, the pressure difference power generation device 7 includes a second JT valve, an expander, a generator and a grid-connected cabinet; wherein: the inlet of the expander is connected to the second outlet of the precooling heat exchanger 4 and to the inlet of the second JT valve, the outlet of the expander is connected to the generator and the outlet of the second JT valve; the generator is connected to the grid-connected cabinet.

[0034] After the first reheating, the product dry gas, when entering the second JT valve, uses the energy of expansion and refrigeration greater than 2MPa to remove oil and water. When the expander in the pressure difference power generation device 7 uses the pressure energy for expansion and refrigeration, it converts the pressure energy into electrical energy to start generating electricity.

[0035] As a specific example, the heat exchanger 2 may be a shell and tube heat exchanger or a plate heat exchanger.

[0036] As a specific example, the production separator 3 may be a gravity separator or a rotary separator.

[0037] As a specific example, the precooling heat exchanger 4 may be a coiled tube heat exchanger.

[0038] Optionally, it is characterized in that the pre-separator 1 and the low-temperature separator 6 are respectively provided with a second outlet, which is used to send the separated condensate oil and alcohol-containing liquid to the condensate oil stabilization device, and the production separator 3 also includes a second outlet for transporting the produced water to the flash tank in the gas gathering area, so as to recycle the generated waste or by-products.

[0039] As a preferred example, the first outlet of the production separator 3 and the first outlet of the low-temperature separator 6 are respectively connected to emergency venting pipelines. Specifically, emergency venting ball valves are also provided. When an emergency occurs, the emergency venting ball valves are opened for venting.

[0040] As a preferred example, the pre-separator 1, the production separator 3 and the low-temperature separator 6 are respectively provided with liquid level detection devices, which are interlocked with the pneumatic ball valves controlling the second outlet of the pre-separator 1, the second outlet of the production separator 3 and the second outlet of the low-temperature separator 6. When the liquid level of the separator is lower than the set value, the pneumatic ball valve is automatically closed; when the liquid level of the pre-separator 1, the production separator 3 and the low-temperature separator 6 reaches a preset high value, the electric regulating valve is automatically opened for discharge; when the preset low value is reached, the electric regulating valve is automatically closed.

[0041] As a preferred example, the first inlet of the precooling heat exchanger 4 is connected to the ethylene glycol supply pipeline, and an ethylene glycol atomizer is provided at the connection between the precooling heat exchanger 4 and the ethylene glycol supply pipeline. The ethylene glycol atomizer is used to prevent the formation of hydrates after expansion refrigeration of the JT valve; the pressure energy that the JT valve cannot use is fully utilized to expand refrigeration and generate electricity, which replaces the propane auxiliary refrigeration system, reduces energy consumption, and realizes green operation of the gas storage.

[0042] like Figure 2 As shown, an embodiment of a method for shallow cold treatment of natural gas in a combined gas storage facility comprises the following steps:

[0043] S1. The produced gas from the gas storage is separated from the produced water by the pre-separator 1 to obtain the raw natural gas. The raw natural gas is heat exchanged with the product dry gas after expansion and power generation by the heat exchanger 2, and the product dry gas after expansion and power generation is heated to the second reheating temperature, and the temperature of the raw natural gas is reduced to the set first cooling temperature; specifically, the cooling is completed when the temperature of the raw natural gas at the outlet of the heat exchanger 2 is 20°C. The 40°C raw natural gas is heat exchanged with the product dry gas after expansion and power generation by the heat exchanger 2, and the product dry gas is reheated to 5°C, and the temperature of the raw natural gas is reduced to 20°C.

[0044] S2. The cooled raw natural gas is transported to the production separator 3 to further separate the produced water and condensate oil to obtain separated natural gas; specifically, the separated natural gas does not contain liquid water.

[0045] S3. The separated natural gas is cooled to the set second cooling temperature through the precooling heat exchanger 4, and then expanded and cooled to the third cooling temperature through the JT valve 5. After separation through the low-temperature separator 6, low-temperature dry gas is obtained. The low-temperature dry gas is reheated to the first reheating temperature through the precooling heat exchanger 4 to obtain product dry gas. Specifically, when the pressure difference before and after the JT valve 5 is greater than 2MPa, the separated natural gas and the low-temperature dry gas are heat exchanged through the precooling heat exchanger 4. After the heat exchange, the temperature of the separated natural gas is reduced from 20°C to 5°C; the temperature of the low-temperature dry natural gas is increased from -15°C to 5°C, and the water dew point and hydrocarbon dew point of the natural gas are -15°C.

[0046] S4. The product dry gas is expanded and cooled by the pressure difference power generation device 7. After power generation, it is transported to the heat exchanger 2 for reheating to the second reheating temperature and then enters the external transmission pipeline. Specifically, the pressure difference power generation device 7 expands and cools, and the temperature of the low-temperature dry natural gas is not lower than -15°C. When the expander in the pressure difference power generation device 7 expands and cools, the pressure energy is converted into electrical energy to start power generation. When the pressure difference power generation device 7 fails, the dry natural gas can be adjusted to the external transmission pipeline through the regulating valve without affecting the operation of the system.

[0047] As a preferred example, in step S3 , the separated natural gas and the atomized ethylene glycol enter the precooling heat exchanger 4 together, which improves the heat exchange effect of the precooling heat exchanger 4 and reduces the throttling temperature of the JT valve 5 .

[0048] It is known from common technical knowledge that the present invention can be implemented by other embodiments that do not deviate from its spirit or essential features. Therefore, the above disclosed embodiments are only illustrative in all respects and are not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are included in the present invention.

Claims

1. A combined gas storage natural gas shallow cold treatment system, characterized in that: It comprises a pre-separator (1), a heat exchanger (2), a production separator (3), a pre-cooling heat exchanger (4), a JT valve (5), a low-temperature separator (6) and a pressure difference power generation device (7); wherein: The inlet of the pre-separator (1) is connected to the produced gas of the gas storage reservoir, and the first outlet of the pre-separator (1) is connected to the first inlet of the heat exchanger (2); The first outlet of the heat exchanger (2) is connected to the inlet of the production separator (3); The first outlet of the production separator (3) is connected to the first inlet of the precooling heat exchanger (4); The first outlet of the precooling heat exchanger (4) is connected to the inlet of the JT valve (5); The outlet of the JT valve (5) is connected to the inlet of the low-temperature separator (6); The first outlet of the low-temperature separator (6) is connected to the second inlet of the precooling heat exchanger (4); The second outlet of the precooling heat exchanger (4) and the inlet of the pressure difference power generation device (7); The outlet of the pressure difference power generation device (7) is connected to the second inlet of the heat exchanger (2); the second outlet of the heat exchanger (2) is connected to the external transmission pipeline.

2. A combined gas storage natural gas shallow cold treatment system according to claim 1, characterized in that: The pressure difference power generation device (7) comprises a second JT valve, an expander, a generator and a grid-connected cabinet; wherein: The inlet of the expander is connected to the second outlet of the precooling heat exchanger (4) and to the inlet of the second JT valve, and the outlet of the expander is connected to the generator and the outlet of the second JT valve; The generator is connected to the grid-connected cabinet.

3. The combined gas storage natural gas shallow cold treatment system according to claim 1 is characterized in that: The heat exchanger (2) is a shell and tube heat exchanger or a plate heat exchanger.

4. The combined gas storage natural gas shallow cold treatment system according to claim 1, characterized in that: The production separator (3) is a gravity separator or a rotary separator.

5. The combined gas storage natural gas shallow cold treatment system according to claim 1 is characterized in that: The pre-separator (1) and the low-temperature separator (6) are respectively provided with a second outlet for delivering the separated alcohol-containing liquid to the condensate stabilization device, and the production separator (3) also includes a second outlet for delivering the produced water to the flash tank in the gas gathering area.

6. The combined gas storage natural gas shallow cold treatment system according to claim 1, characterized in that: The first outlet of the production separator (3) and the first outlet of the low-temperature separator (6) are respectively connected to emergency venting pipelines.

7. A combined gas storage natural gas shallow cold treatment system according to claim 5, characterized in that: The pre-separator (1), the production separator (3) and the low-temperature separator (6) are respectively provided with liquid level detection devices, which are used to control the electric regulating valves of the second outlet of the pre-separator (1), the second outlet of the production separator (3) and the second outlet of the low-temperature separator (6).

8. The combined gas storage natural gas shallow cold treatment system according to claim 1, characterized in that: The first inlet of the precooling heat exchanger (4) is connected to the ethylene glycol supply pipeline, and an ethylene glycol atomizer is provided at the connection between the precooling heat exchanger (4) and the ethylene glycol supply pipeline.

9. A method for shallow cold treatment of natural gas in a combined gas storage according to claim 1, characterized in that: The steps include: S1. The produced gas from the gas storage is separated from the produced water by a pre-separator (1) to obtain raw natural gas. The raw natural gas is heat-exchanged with the product dry gas after expansion and power generation by a heat exchanger (2). The product dry gas after expansion and power generation is heated to a second reheating temperature, and the temperature of the raw natural gas is reduced to a set first cooling temperature. S2, transporting the cooled raw natural gas to a production separator (3) to further separate produced water and condensate oil to obtain separated natural gas; S3, the separated natural gas is cooled to a set second cooling temperature through a precooling heat exchanger (4), then expanded and cooled to a third cooling temperature through a JT valve (5), separated through a low-temperature separator (6) to obtain low-temperature dry gas, and the low-temperature dry gas is reheated to a first reheating temperature through a precooling heat exchanger (4) to obtain product dry gas; S4, the product dry gas is expanded and cooled by the pressure difference power generation device (7), after power generation, it is transported to the heat exchanger (2) to be reheated to the second reheating temperature and then enters the external transmission pipeline.

10. A method for shallow cold treatment of natural gas in a combined gas storage according to claim 9, characterized in that: In step S3, the separated natural gas and atomized ethylene glycol enter the precooling heat exchanger (4) together.

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