High-pressure natural gas treatment efficient heat exchange device and using method thereof

Abstract

The invention relates to the technical field of natural gas heat exchange treatment, in particular to an efficient heat exchange device for high-pressure natural gas treatment and a using method of the efficient heat exchange device. The two heat exchangers are vertically installed in series, the length of the heat exchange tube bundle is increased, the heat exchange temperature difference is reduced, the cold and heat recovery efficiency is improved, condensate is discharged at the bottom end socket of the first heat exchanger, and the situation that natural gas with liquid climbs to enter the second heat exchanger to form slug flow is avoided; the device operation stability and the heat exchange efficiency of the second heat exchanger are influenced; meanwhile, liquid hydrocarbon and ethylene glycol condensed out of a bottom sealing head of the first heat exchanger are discharged into the low-temperature separator at the rear end in a self-pressure mode and enter the first heat exchanger and the second heat exchanger together with low-temperature condensation mixed liquid separated out of the low-temperature separator for reheating, energy consumption is low, the operation pressure is the same, no safety risk exists even if gas blow-by occurs in the liquid discharging process, and the safety coefficient is high. And the operation safety of the device is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of natural gas heat exchange processing, and is a high-efficiency heat exchange device for high-pressure natural gas processing and a use method thereof. Background Art

[0002] In general, the low-temperature dehydration and dehydrocarbonization process of natural gas is to reduce energy consumption by exchanging heat between low-temperature dry gas and raw gas, recovering the low-temperature cooling capacity and heat of raw gas at the back end, reducing the refrigeration load, and increasing the product gas transmission temperature to meet the requirement that the transmission temperature is greater than or equal to 0°C. When the heat exchange temperature of the raw natural gas is lower than the hydrate formation temperature at its operating pressure, in order to prevent freezing and blockage of natural gas hydrates generated by saturated water-containing wet raw gas, an appropriate amount of hydrate inhibitors such as methanol or ethylene glycol should be injected before the wet raw natural gas is heat exchanged to reduce the natural gas hydrate formation temperature to below the heat exchange temperature.

[0003] Some domestic high-pressure natural gas heat exchangers are installed in a horizontal stack. The tube side and shell side of the upper and lower heat exchangers are connected in series to increase the length of the heat exchange tube bundle and reduce the temperature difference between the cold and hot streams. However, the temperature drop in the entire heat exchange process is large, and the amount of water condensed during the heat exchange of saturated water-containing raw natural gas is large. The heat exchanger structure cannot separate and drain the liquid during the heat exchange process. Since antifreeze agents such as ethylene glycol are easily soluble in water, it is necessary to increase the amount of alcohol injection before the raw gas enters the heat exchanger. In addition, during the heat exchange process, due to the long heat exchange path of the shell side, the ethylene glycol injected into the natural gas and the condensed water and liquid hydrocarbons during the heat exchange and cooling process will sink and adhere to the lower part of the heat exchange tube bundle under the action of gravity, reducing the heat exchange efficiency of the entire heat exchanger. Due to the uneven distribution of ethylene glycol in the natural gas, the heat exchange tube bundle (diameter of about φ16) is easily frozen.

[0004] At the same time, when the natural gas processing volume is large, the existing heat exchanger usage method has the following problems if a smaller heat exchange temperature difference is to be obtained because the raw natural gas is wet and has high pressure: (1) The natural gas processing volume is large, and many heat exchange tube bundles are required, so the heat exchanger diameter is too large; (2) In order to reduce the heat exchange temperature difference and increase the amount of cold and heat recovery, the length of the heat exchange tube bundle needs to be increased, and the heat exchanger length is too long; (3) The raw gas heat exchange temperature drop is large, and a single large vertical heat exchanger or a horizontally stacked heat exchanger will condense a large amount of water in the saturated water-containing natural gas during the heat exchange and cooling process. Antifreeze agents such as ethylene glycol are easily soluble in water, and the amount of alcohol injected increases exponentially; (4) The vertical installation of the heat exchanger can avoid the problem of condensate adhering to the heat exchange tube bundle during horizontal installation, which reduces the heat exchange efficiency. However, there is also the problem that the liquid condensed from the saturated water-containing high-temperature wet natural gas during the heat exchange process will continue to deposit at the bottom of the heat exchanger. When the liquid volume accumulates to a certain level, it will cause slug flow in the export natural gas pipeline. If the condensed liquid is discharged regularly, the heat exchanger operating pressure is high, the discharge system pressure is low, and the risk of blowby gas overpressure during the discharge process at different pressure levels is high. Problems (1) and (2) directly lead to the large-scale use of high-efficiency heat exchangers with small heat exchange temperature differences in large natural gas processing units, which are difficult to process and manufacture and have high costs; problem (3) leads to a large amount of alcohol injection for heat exchanger antifreeze, high investment in the ethylene glycol injection system, and high energy consumption for ethylene glycol regeneration; problem (4) natural gas may be transported uphill with liquid, forming a slug flow that affects the stability of the device operation. If the sewage is discharged regularly, the operation risk is high. In the process of large-scale construction of natural gas processing units, the large size of the heat exchanger and the manufacturing bottleneck limit the minimum heat exchange temperature difference and the efficient recovery of cold and heat, and the large amount of ethylene glycol injection leads to high energy consumption in the operation of the device. Summary of the invention

[0005] The present invention provides a high-efficiency heat exchange device for high-pressure natural gas processing and a method for using the same, which overcomes the deficiencies of the above-mentioned prior art and can effectively solve the problems of existing natural gas processing such as excessively large heat exchanger diameters, high operating risks, and high costs caused by large amounts of alcohol injection.

[0006] One of the technical solutions of the present invention is achieved through the following measures: a high-efficiency heat exchange device for high-pressure natural gas processing, including a gas-liquid separator, a first heat exchanger, a second heat exchanger, a refrigeration device and a low-temperature separator, the top inlet of the gas-liquid separator is fixedly connected with a produced gas inlet pipeline, the top outlet of the gas-liquid separator and the top inlet of the first heat exchanger are fixedly connected with a wet natural gas outlet pipeline, the bottom outlet of the gas-liquid separator is fixedly connected with a first liquid discharge pipeline, the first outlet at the bottom of the first heat exchanger and the top inlet of the second heat exchanger are fixedly connected with a first pre-cooling natural gas outlet pipeline, the first outlet at the bottom of the second heat exchanger and the top inlet of the low-temperature separator are fixedly connected with a second pre-cooling natural gas outlet pipeline, the second pre-cooling natural gas outlet pipeline is fixedly installed with a refrigeration device, and the low-temperature separator is fixedly connected with the first outlet at the bottom of the second heat exchanger. A first low-temperature dry gas outlet pipeline is fixedly connected between the top outlet of the separator and the lower inlet of the second heat exchanger, a second low-temperature dry gas outlet pipeline is fixedly connected between the upper outlet of the second heat exchanger and the lower inlet of the first heat exchanger, a dehydration and dehydrocarbonization dry gas pipeline is fixedly connected to the upper outlet of the first heat exchanger, a first liquid hydrocarbon pipeline is fixedly connected between the bottom outlet of the low-temperature separator and the first upper inlet of the second heat exchanger, a second liquid hydrocarbon pipeline is fixedly connected between the second lower outlet of the second heat exchanger and the first upper inlet of the first heat exchanger, a third liquid hydrocarbon pipeline is fixedly connected to the second lower outlet of the first heat exchanger, a first ethylene glycol injection pipeline is fixedly connected to the second upper inlet of the first heat exchanger, and a second ethylene glycol injection pipeline is fixedly connected between the second upper inlet of the second heat exchanger and the first ethylene glycol injection pipeline.

[0007] The following is a further optimization and / or improvement of one of the above-mentioned technical solutions: A booster compressor is fixedly installed on the dehydrated and dehydrocarbonized dry gas pipeline, a flow control valve is fixedly installed on the first liquid hydrocarbon pipeline, and an orifice plate is fixedly installed on the first liquid hydrocarbon pipeline between the flow control valve and the second heat exchanger.

[0008] A second drainage pipeline is fixedly connected between the second precooling natural gas outlet pipeline between the refrigeration equipment and the low-temperature separator and the first outlet at the bottom of the first heat exchanger, and a third drainage pipeline is fixedly connected between the bottom outlet of the second heat exchanger and the second drainage pipeline.

[0009] A liquid level control valve is fixedly installed on the second liquid discharge pipeline, a remote liquid level gauge is arranged at the bottom of the first heat exchanger, and an interlock is arranged between the remote liquid level gauge and the liquid level control valve.

[0010] A remote thermometer is fixedly installed on the second pre-cooling natural gas outlet pipeline between the second liquid discharge pipeline and the refrigeration equipment, and an interlock is provided between the remote thermometer and the refrigeration equipment.

[0011] The third outlet at the lower part of the first heat exchanger is fixedly connected with the first sewage pipeline, the second outlet at the bottom of the first heat exchanger is fixedly connected with the first sewage pipeline, and the third sewage pipeline is fixedly connected between the first sewage pipeline outlet and the second sewage pipeline and the third outlet at the lower part of the second heat exchanger.

[0012] The second technical solution of the present invention is achieved by the following measures: a method for using a high-efficiency heat exchange device for high-pressure natural gas processing, which is carried out according to the following steps: in the first step, the raw gas from the produced gas inlet pipeline is initially separated by a gas-liquid separator to obtain a high-temperature water-containing natural gas and a mixed liquid phase; in the second step, the high-temperature water-containing natural gas is transported to the first pipe pass of the first heat exchanger through a wet natural gas outlet pipeline, and ethylene glycol is injected into the high-temperature water-containing natural gas once by atomization to obtain a natural gas injected with alcohol, and the mixed liquid phase is discharged through a first liquid discharge pipeline and then recycled; in the third step, The natural gas injected with alcohol once flows from top to bottom in the first tube side of the first heat exchanger, and countercurrently exchanges heat with the secondary low-temperature dry gas in the shell side of the first heat exchanger to reduce the temperature, thereby obtaining large-particle condensate and preliminary pre-cooled wet natural gas respectively; in the fourth step, the large-particle condensate settles naturally under the action of gravity and is collected at the bottom head of the first heat exchanger, and the preliminary pre-cooled wet natural gas enters the first tube side of the second heat exchanger through the first pre-cooling natural gas outlet pipeline, and ethylene glycol is injected into the preliminary pre-cooled wet natural gas for a second time to obtain the natural gas injected with alcohol twice; in the fifth step, the natural gas injected with alcohol twice is discharged from the second heat exchanger. The gas circulates from top to bottom in the first tube side of the heat exchanger, and countercurrently exchanges heat with the primary low-temperature dry gas in the shell side of the second heat exchanger to reduce the temperature, thereby obtaining secondary pre-cooled wet natural gas; in the sixth step, after the secondary pre-cooled wet natural gas is cooled in the refrigeration equipment, it is mixed with the large-particle condensate collected from the bottom head of the first heat exchanger, and is sent to the low-temperature separator through the second pre-cooling natural gas outlet pipeline to separate the low-temperature condensate mixture and the primary low-temperature dry gas; in the seventh step, the low-temperature condensate mixture is sent to the second tube side of the second heat exchanger through the first liquid hydrocarbon pipeline by the flow control valve for heat exchange, and then is sent to the second liquid hydrocarbon pipeline by the second liquid hydrocarbon pipeline. Heat exchange is performed again in the second tube side of the first heat exchanger, and the obtained mixed liquid after heat exchange is discharged from the third liquid hydrocarbon pipeline and sent to the downstream process for recovery of liquid hydrocarbons and ethylene glycol. The primary low-temperature dry gas returns to the shell side of the second heat exchanger through the first low-temperature dry gas outlet pipeline for heat exchange to obtain secondary low-temperature dry gas; in the eighth step, the secondary low-temperature dry gas is sent to the shell side of the first heat exchanger through the second low-temperature dry gas outlet pipeline for heat exchange again to obtain reheated dry gas; in the ninth step, the reheated dry gas is pressurized by the booster compressor to obtain high-pressure reheated dry gas, and the high-pressure reheated dry gas is discharged through the dehydration and dehydrocarbonization dry gas pipeline for external transmission.

[0013] The following is a further optimization and / or improvement of the second technical solution of the above invention: In the second step, the flow rate of high-temperature water-containing natural gas is 1500×10 4 m3 / d, the pressure is 10.3 to 10.5 MPa, the temperature is 28°C to 32°C, the mass concentration of ethylene glycol is 80% to 82%, and the injection rate of ethylene glycol is 290L / h to 295L / h; or / and, in the fourth step, the mass concentration of ethylene glycol is 80% to 82%, and the injection rate of ethylene glycol is 275L / h to 280L / h.

[0014] In the above-mentioned third step, the temperature of the initial pre-cooled wet natural gas is 6°C to 10°C; or / and, in the sixth step, the temperature of the secondary pre-cooled wet natural gas is -8°C to -10°C, and the temperature of the secondary pre-cooled wet natural gas after being cooled by the refrigeration equipment is -12°C to -16°C; or / and, in the eighth step, the temperature of the secondary low-temperature dry gas is 0°C to 5°C, and the temperature of the reheated dry gas is 20°C to 25°C.

[0015] In the seventh step, the temperature of the low-temperature condensate mixed liquid after heat exchange in the second tube pass of the second heat exchanger is -6°C to -10°C, and the temperature of the mixed liquid after heat exchange and the large particle condensate collected at the bottom head is 24°C to 28°C.

[0016] The present invention connects two heat exchangers in series and vertically installs them to increase the length of the heat exchange tube bundle, reduce the heat exchange temperature difference, and improve the cold and heat recovery efficiency. The condensate is discharged at the bottom head of the first heat exchanger, thereby avoiding the formation of slug flow in the process of natural gas carrying liquid climbing into the second heat exchanger, which affects the operating stability of the device and the heat exchange efficiency of the second heat exchanger. At the same time, the liquid hydrocarbons and ethylene glycol condensed from the bottom head of the first heat exchanger are discharged into the low-temperature separator at the rear end by self-pressure, and are reheated in the first heat exchanger and the second heat exchanger together with the low-temperature condensed mixed liquid separated by the low-temperature separator. The energy consumption is low, and the operating pressure is the same. There is no safety risk even if gas is blowby during the discharge process, which effectively improves the operating safety of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Attached Figure 1 This is a schematic diagram of the process flow of Example 1 of the present invention.

[0018] The codes in the attached drawings are: 1 is a gas-liquid separator, 2 is a first heat exchanger, 3 is a second heat exchanger, 4 is a refrigeration device, 5 is a booster compressor, 6 is a low-temperature separator, 7 is a produced gas inlet pipeline, 8 is a wet natural gas outlet pipeline, 9 is a first liquid discharge pipeline, 10 is a first precooling natural gas outlet pipeline, 11 is a second precooling natural gas outlet pipeline, 12 is a first low-temperature dry gas outlet pipeline, 13 is a second low-temperature dry gas outlet pipeline, 14 is a dehydration and degassing pipeline, Hydrocarbon dry gas pipeline, 15 is the first liquid hydrocarbon pipeline, 16 is the second liquid hydrocarbon pipeline, 17 is the third liquid hydrocarbon pipeline, 18 is the first ethylene glycol injection pipeline, 19 is the second ethylene glycol injection pipeline, 20 is the third liquid discharge pipeline, 21 is a flow control valve, 22 is the second liquid discharge pipeline, 23 is a liquid level control valve, 24 is a remote liquid level meter, 25 is a remote thermometer, 26 is the first sewage discharge pipeline, 27 is the second sewage discharge pipeline, 28 is the third sewage discharge pipeline, and 29 is an orifice plate. DETAILED DESCRIPTION

[0019] The present invention is not limited by the following embodiments, and specific implementation methods can be determined according to the technical scheme of the present invention and actual conditions. Unless otherwise specified, the various chemical reagents and chemicals mentioned in the present invention are all known and commonly used chemical reagents and chemicals in the prior art.

[0020] The present invention will be further described below in conjunction with embodiments: Embodiment 1: As attached Figure 1As shown, the high-efficiency heat exchange device for high-pressure natural gas processing comprises a gas-liquid separator 1, a first heat exchanger 2, a second heat exchanger 3, a refrigeration device 4 and a low-temperature separator 6. The top inlet of the gas-liquid separator 1 is fixedly connected with a produced gas inlet pipeline 7, the top outlet of the gas-liquid separator 1 and the top inlet of the first heat exchanger 2 are fixedly connected with a wet natural gas outlet pipeline 8, the bottom outlet of the gas-liquid separator 1 is fixedly connected with a first liquid discharge pipeline 9, the first outlet at the lower part of the first heat exchanger 2 and the top inlet of the second heat exchanger 3 are fixedly connected with a first pre-cooling natural gas outlet pipeline 10, the first outlet at the lower part of the second heat exchanger 3 and the top inlet of the low-temperature separator 6 are fixedly connected with a second pre-cooling natural gas outlet pipeline 11, the second pre-cooling natural gas outlet pipeline 11 is fixedly installed with the refrigeration device 4, the top outlet of the low-temperature separator 6 is connected to the second heat exchanger 3, and the second pre-cooling natural gas outlet pipeline 11 is fixedly connected with the refrigeration device 4. A first low-temperature dry gas outlet pipeline 12 is fixedly connected between the lower inlet of the heat exchanger 3, a second low-temperature dry gas outlet pipeline 13 is fixedly connected between the upper outlet of the second heat exchanger 3 and the lower inlet of the first heat exchanger 2, a dehydration and dehydrocarbonization dry gas pipeline 14 is fixedly connected to the upper outlet of the first heat exchanger 2, a first liquid hydrocarbon pipeline 15 is fixedly connected between the bottom outlet of the low-temperature separator 6 and the first upper inlet of the second heat exchanger 3, a second liquid hydrocarbon pipeline 16 is fixedly connected between the second lower outlet of the second heat exchanger 3 and the first upper inlet of the first heat exchanger 2, a third liquid hydrocarbon pipeline 17 is fixedly connected to the second lower outlet of the first heat exchanger 2, a first ethylene glycol injection pipeline 18 is fixedly connected to the second upper inlet of the first heat exchanger 2, and a second ethylene glycol injection pipeline 19 is fixedly connected between the second upper inlet of the second heat exchanger 3 and the first ethylene glycol injection pipeline 18.

[0021] According to the present invention, the number of heat exchangers connected in series can be increased as needed.

[0022] Embodiment 2: As an optimization of the above embodiment, as shown in the attached Figure 1 As shown, a booster compressor 5 is fixedly installed on the dehydrated and dehydrogenated dry gas pipeline 14 , a flow control valve 21 is fixedly installed on the first liquid hydrocarbon pipeline 15 , and an orifice plate 29 is fixedly installed on the first liquid hydrocarbon pipeline 15 between the flow control valve 21 and the second heat exchanger 3 .

[0023] As required, the dehydration and dehydrogenation dry gas pipeline 14 may also be provided with a flow meter, a flow control valve, a thermometer, etc., which are well known and used in the art.

[0024] Embodiment 3: As an optimization of the above embodiment, as shown in the attached Figure 1 As shown, a second drain line 22 is fixedly connected between the second pre-cooling natural gas outlet pipeline 11 between the refrigeration equipment 4 and the low-temperature separator 6 and the first outlet at the bottom of the first heat exchanger 2, and a third drain line 20 is fixedly connected between the bottom outlet of the second heat exchanger 3 and the second drain line 22.

[0025] Embodiment 4: As an optimization of the above embodiment, as shown in the attached Figure 1As shown, a liquid level control valve 23 is fixedly installed on the second liquid discharge pipeline 22 and the third liquid discharge pipeline 20 between the third liquid discharge pipeline 20 and the first heat exchanger 2, and a remote liquid level gauge 24 is provided at the bottom of the first heat exchanger 2 and the second heat exchanger 3, and an interlock is provided between the remote liquid level gauge 24 and the liquid level control valve 23.

[0026] Embodiment 5: As an optimization of the above embodiment, as shown in the attached Figure 1 As shown, a remote thermometer 25 is fixedly installed on the second pre-cooling natural gas outlet pipeline 11 between the second liquid discharge pipeline 22 and the refrigeration equipment 4 , and an interlock is provided between the remote thermometer 25 and the refrigeration equipment 4 .

[0027] According to the needs, in the present invention, during the process of cooling down the saturated water-containing high-temperature wet natural gas in each heat exchange tube bundle of the first tube pass of the first heat exchanger 2 from top to bottom, the condensed large particle droplets (ethylene glycol aqueous solution and liquid hydrocarbon) settle by gravity and fall into the bottom end cap of the first heat exchanger 2, and are sent to the inlet of the low-temperature separator 6 through the second drainage pipeline 22 at the bottom of the end cap. When the high-temperature wet natural gas coming out of the bottom end cap of the first heat exchanger 2 passes through the first tube pass of the second heat exchanger 3, a pressure loss of about 70KPa will be generated. Combined with the pressure loss of the wet natural gas flowing through the process pipeline and refrigeration equipment 4 at the rear end of the heat exchanger, the natural gas pressure at the bottom end cap of the first heat exchanger 2 is about 100KPa higher than the inlet and outlet pressure of the low-temperature separator 6. The pressure difference can be used to discharge the ethylene glycol aqueous solution and liquid hydrocarbon condensed and precipitated at the bottom end cap of the first tube pass of the first heat exchanger 2 into the inlet of the low-temperature separator 6 by self-pressure. A liquid level control valve 23 is provided on the drainage pipeline, and is interlocked with the remote liquid level meter 24 to control the drainage volume.

[0028] Embodiment 6: As an optimization of the above embodiment, as shown in the attached Figure 1 As shown, the third outlet at the bottom of the first heat exchanger 2 is fixedly connected to the first sewage pipeline 26, the second sewage pipeline 27 is fixedly connected between the second outlet at the bottom of the first heat exchanger 2 and the first sewage pipeline 26, and the third sewage pipeline 28 is fixedly connected between the first sewage pipeline 26 outlet and the second sewage pipeline 27 and the third outlet at the bottom of the second heat exchanger 3.

[0029] In the present invention, unless otherwise specified, the equipment and devices used are all the equipment and devices known and used in the art.

[0030] As required, the pipelines and equipment of the high-efficiency heat exchange device for high-pressure natural gas processing may be provided with conventional valves, thermometers, pressure gauges, etc. known and used in the art according to production needs.

[0031] Embodiment 7: As attached Figure 1As shown, the method for using the high-efficiency heat exchange device for high-pressure natural gas processing is carried out according to the following steps: in the first step, the raw gas from the produced gas inlet pipeline 7 is initially separated by the gas-liquid separator 1 to obtain high-temperature water-containing natural gas and a mixed liquid phase respectively; in the second step, the high-temperature water-containing natural gas is transported to the first pipe pass of the first heat exchanger 2 through the wet natural gas outlet pipeline 8, and ethylene glycol is injected into the high-temperature water-containing natural gas once by atomization to obtain natural gas after a single alcohol injection, and the mixed liquid phase is discharged through the first liquid discharge pipeline 9 and then recycled; in the third step, the natural gas after a single alcohol injection is discharged in the first The gas condensates flow from top to bottom in the tube pass, and countercurrently exchanges heat with the secondary low-temperature dry gas in the shell pass of the first heat exchanger 2 to cool down the temperature, thereby obtaining large-particle condensate and preliminary pre-cooled wet natural gas respectively; in the fourth step, the large-particle condensate settles naturally under the action of gravity, and is collected at the bottom head of the first heat exchanger 2, and the preliminary pre-cooled wet natural gas enters the first tube pass of the second heat exchanger 3 through the first pre-cooled natural gas outlet pipeline 10, and ethylene glycol is injected into the preliminary pre-cooled wet natural gas through secondary atomization to obtain natural gas after secondary alcohol injection; in the fifth step, the natural gas after secondary alcohol injection flows from top to bottom in the first tube pass of the second heat exchanger 3, The secondary pre-cooled wet natural gas is cooled by countercurrent heat exchange with the primary low-temperature dry gas in the shell side of the second heat exchanger 3 to obtain secondary pre-cooled wet natural gas; in the sixth step, after the secondary pre-cooled wet natural gas is cooled in the refrigeration equipment 4, it is mixed with the large particle condensate collected from the bottom head of the first heat exchanger 2, and sent to the low-temperature separator 6 through the second pre-cooling natural gas outlet pipeline 11 to separate the low-temperature condensate mixture and the primary low-temperature dry gas; in the seventh step, the low-temperature condensate mixture is sent to the second tube side of the second heat exchanger 3 through the first liquid hydrocarbon pipeline 15 and the flow control valve 21 for heat exchange, and then sent to the second pipe side of the first heat exchanger 2 through the second liquid hydrocarbon pipeline 16. Heat exchange is performed again in the tube side, and the obtained mixed liquid after heat exchange is discharged from the third liquid hydrocarbon pipeline 17 and sent to the downstream process for recovery of liquid hydrocarbons and ethylene glycol. The primary low-temperature dry gas returns to the shell side of the second heat exchanger 3 through the first low-temperature dry gas outlet pipeline 12 for heat exchange to obtain secondary low-temperature dry gas. In the eighth step, the secondary low-temperature dry gas is sent to the shell side of the first heat exchanger 2 through the second low-temperature dry gas outlet pipeline 13 for heat exchange again to obtain reheated dry gas. In the ninth step, the reheated dry gas is pressurized by the booster compressor 5 to obtain high-pressure reheated dry gas, and the high-pressure reheated dry gas is discharged through the dehydration and dehydrocarbonization dry gas pipeline 14 for external transmission.

[0032] Under a certain pressure, the saturated water content of natural gas increases exponentially with temperature. The saturated high-temperature wet natural gas with water produces the most condensed water during the condensation and cooling process in the first heat exchanger 2. The present invention discharges the condensate at the bottom head of the first heat exchanger 2, thereby avoiding the formation of slug flow in the process of natural gas carrying liquid climbing into the second heat exchanger 3, which affects the operating stability of the device and the heat exchange efficiency of the second heat exchanger 3. At the same time, the size of a single heat exchanger can be reduced, solving the problem of processing and manufacturing large heat exchange, small heat exchange temperature difference, and efficient heat recovery heat exchanger for large and high-pressure natural gas processing equipment.

[0033] Example 8: As an optimization of the above example, in the second step, the delivery flow rate of the high-temperature water-containing natural gas is 1500×10 4 m 3 / d, the pressure is 10.3 to 10.5 MPa, the temperature is 28°C to 32°C, the mass concentration of ethylene glycol is 80% to 82%, and the injection rate of ethylene glycol is 290L / h to 295L / h; or / and, in the fourth step, the mass concentration of ethylene glycol is 80% to 82%, and the injection rate of ethylene glycol is 275L / h to 280L / h.

[0034] Embodiment 9: As an optimization of the above embodiment, in the third step, the temperature of the initial pre-cooling wet natural gas is 6°C to 10°C; or / and, in the sixth step, the temperature of the secondary pre-cooling wet natural gas is -8°C to -10°C, and the temperature of the secondary pre-cooling wet natural gas after cooling by the refrigeration equipment 4 is -12°C to -16°C; or / and, in the eighth step, the temperature of the secondary low-temperature dry gas is 0°C to 5°C, and the temperature of the reheated dry gas is 20°C to 25°C.

[0035] Example 10: As an optimization of the above example, in the seventh step, the temperature of the low-temperature condensed mixed liquid after heat exchange in the second tube pass of the second heat exchanger 3 is -6°C to -10°C, and the temperature of the mixed liquid after heat exchange and the large particle condensate collected at the bottom head is 24°C to 28°C.

[0036] Example 11: In the high-efficiency heat exchange device for high-pressure natural gas processing, the raw gas is the wellhead produced natural gas (saturated water-containing wet gas) that has been initially separated at the station, with a pressure of 10.5 MPa, a temperature of 30°C, and a flow rate of 1500×10 4 m 3 / d, enters from the top head of the first heat exchanger 2, and ethylene glycol (mass concentration 82%) is injected into the natural gas in atomization at about 291.9L / h in the top head of the first heat exchanger 2 (the formation temperature of natural gas hydrate is controlled to be 0℃). The natural gas after alcohol injection is dispersed into each heat exchange tube bundle (diameter φ16) of the first tube side of the first heat exchanger 2, and circulates from top to bottom to countercurrently exchange heat with the secondary low-temperature dry gas in the shell side of the first heat exchanger 2. The temperature of the initially pre-cooled wet natural gas when it is discharged from the bottom head of the first heat exchanger 2 through the first pre-cooling natural gas outlet pipeline 10 is 7.96℃. The large particles of condensate condensed in the first tube side of the first heat exchanger 2 The droplets settle and fall into the bottom of the head of the first heat exchanger 2, and the preliminary pre-cooled wet natural gas enters from the top head of the second heat exchanger 3. Ethylene glycol (mass concentration 82%) is injected in the top head of the second heat exchanger 3 for secondary atomization at a rate of about 275.8 L / h (the formation temperature of natural gas hydrate is controlled to be -20°C). The natural gas after alcohol injection is dispersed into each heat exchange tube bundle (diameter φ16) of the first tube side of the second heat exchanger 3, and circulates from top to bottom for countercurrent heat exchange with the primary low-temperature dry gas in the shell side of the second heat exchanger 3. The temperature of the secondary pre-cooled wet natural gas when it is discharged from the bottom head of the second heat exchanger 3 through the second pre-cooling natural gas outlet pipeline 11 is -10°C. The secondary pre-cooled wet natural gas is further cooled to -15°C by the refrigeration equipment 4 and then enters the low-temperature separator 6 to separate the low-temperature condensed mixed liquid composed of low-temperature condensed ethylene glycol and liquid hydrocarbons in the natural gas. The low-temperature dry gas at the gas phase outlet of the low-temperature separator 6 goes to the bottom shell side inlet of the second heat exchanger 3, flows from bottom to top inside the shell side of the second heat exchanger 3, and is countercurrently heat exchanged with the raw gas (i.e., the natural gas after the second alcohol injection) in the first tube side of the second heat exchanger 3. It is discharged from the upper shell side outlet of the second heat exchanger 3 at a temperature of 2°C. Thereafter, it enters from the bottom shell side inlet of the first heat exchanger 2, flows from bottom to top, and is further countercurrently heat exchanged with the raw gas (i.e., the natural gas after the first alcohol injection) in the first tube side of the first heat exchanger 2. It is then discharged from the upper shell side outlet of the first heat exchanger 2 at a temperature of 23.53°C.

[0037] Among them, the amount of condensed water and ethylene glycol in the bottom head of the first heat exchanger 2 is 518.7L / h, and enters the low-temperature separator 6 together with the condensed liquid hydrocarbons through the second pre-cooling natural gas outlet pipeline 11. The liquid hydrocarbons separated by the low-temperature separator 6 enter the second tube side of the second heat exchanger 3 from the upper part of the second heat exchanger 3, and after heat exchange with the first tube side of the second heat exchanger 3 against the wall, the low-temperature condensed mixed liquid is discharged from the lower part of the second heat exchanger 3 through the second liquid hydrocarbon pipeline at a temperature of -6.9°C, and then enters the second tube side of the first heat exchanger 2 from the upper part of the first heat exchanger 2. After heat exchange with the first tube side of the first heat exchanger 2 against the wall, the mixed liquid after heat exchange is discharged from the lower part of the first heat exchanger 2 through the third liquid hydrocarbon pipeline 17 at a temperature of 26.8°C.

[0038] In Example 11 of the present invention, the injection amount of high-temperature wet raw natural gas ethylene glycol in the second heat exchanger 3 is reduced by about 60.8% compared with the injection amount when the bottom head of the first heat exchanger 2 is not drained, and the regeneration energy consumption of ethylene glycol is reduced by about 17.5%.

[0039] In summary, the present invention connects two heat exchangers in series and vertically installs them to increase the length of the heat exchange tube bundle, reduce the heat exchange temperature difference, improve the cold and heat recovery efficiency, and discharge the condensate at the bottom head of the first heat exchanger, thereby avoiding the formation of slug flow in the process of natural gas carrying liquid climbing into the second heat exchanger, which affects the operating stability of the device and the heat exchange efficiency of the second heat exchanger; at the same time, the liquid hydrocarbons and ethylene glycol condensed from the bottom head of the first heat exchanger are discharged into the low-temperature separator at the rear end by self-pressure, and are reheated in the first heat exchanger and the second heat exchanger together with the low-temperature condensed mixed liquid separated by the low-temperature separator, with low energy consumption and the same operating pressure. There is no safety risk even if gas blowby occurs during the discharge process, which effectively improves the operating safety of the device.

[0040] 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 high-efficiency heat exchange device for high-pressure natural gas processing, characterized in that The invention comprises a gas-liquid separator, a first heat exchanger, a second heat exchanger, a refrigeration device and a low-temperature separator. The top inlet of the gas-liquid separator is fixedly connected with a produced gas inlet pipeline. The top outlet of the gas-liquid separator and the top inlet of the first heat exchanger are fixedly connected with a wet natural gas outlet pipeline. The bottom outlet of the gas-liquid separator is fixedly connected with a first liquid discharge pipeline. The first outlet at the lower part of the first heat exchanger and the top inlet of the second heat exchanger are fixedly connected with a first pre-cooling natural gas outlet pipeline. The first outlet at the lower part of the second heat exchanger and the top inlet of the low-temperature separator are fixedly connected with a second pre-cooling natural gas outlet pipeline. The second pre-cooling natural gas outlet pipeline is fixedly installed with a refrigeration device. The top outlet of the low-temperature separator and the lower inlet of the second heat exchanger are fixedly connected with a first pre-cooling natural gas outlet pipeline. A first low-temperature dry gas outlet pipeline is fixedly connected, a second low-temperature dry gas outlet pipeline is fixedly connected between the upper outlet of the second heat exchanger and the lower inlet of the first heat exchanger, a dehydration and dehydrocarbonization dry gas pipeline is fixedly connected to the upper outlet of the first heat exchanger, a first liquid hydrocarbon pipeline is fixedly connected between the bottom outlet of the low-temperature separator and the first upper inlet of the second heat exchanger, a second liquid hydrocarbon pipeline is fixedly connected between the second lower outlet of the second heat exchanger and the first upper inlet of the first heat exchanger, a third liquid hydrocarbon pipeline is fixedly connected to the second lower outlet of the first heat exchanger, a first ethylene glycol injection pipeline is fixedly connected to the second upper inlet of the first heat exchanger, and a second ethylene glycol injection pipeline is fixedly connected between the second upper inlet of the second heat exchanger and the first ethylene glycol injection pipeline.

2. The high-efficiency heat exchange device for high-pressure natural gas processing according to claim 1 is characterized in that A booster compressor is fixedly installed on the dehydrated and dehydrocarbonized dry gas pipeline, a flow control valve is fixedly installed on the first liquid hydrocarbon pipeline, and an orifice plate is fixedly installed on the first liquid hydrocarbon pipeline between the flow control valve and the second heat exchanger.

3. The high-efficiency heat exchange device for high-pressure natural gas processing according to claim 1 or 2, characterized in that A second drainage pipeline is fixedly connected between the second precooling natural gas outlet pipeline between the refrigeration equipment and the low-temperature separator and the first outlet at the bottom of the first heat exchanger, and a third drainage pipeline is fixedly connected between the bottom outlet of the second heat exchanger and the second drainage pipeline.

4. The high-efficiency heat exchange device for high-pressure natural gas processing according to claim 3 is characterized in that A liquid level control valve is fixedly installed on the second liquid discharge pipeline, a remote liquid level gauge is arranged at the bottom of the first heat exchanger, and an interlock is arranged between the remote liquid level gauge and the liquid level control valve.

5. The high-efficiency heat exchange device for high-pressure natural gas processing according to claim 3 or 4, characterized in that A remote thermometer is fixedly installed on the second pre-cooling natural gas outlet pipeline between the second liquid discharge pipeline and the refrigeration equipment, and an interlock is provided between the remote thermometer and the refrigeration equipment.

6. The high-efficiency heat exchange device for high-pressure natural gas processing according to claim 5, characterized in that The third outlet at the lower part of the first heat exchanger is fixedly connected with the first sewage pipeline, the second outlet at the bottom of the first heat exchanger and the first sewage pipeline are fixedly connected with the second sewage pipeline, and the first sewage pipeline between the first sewage pipeline outlet and the second sewage pipeline is fixedly connected with the third outlet at the lower part of the second heat exchanger.

7. A method for using the high-efficiency heat exchange device for high-pressure natural gas processing according to any one of claims 1 to 6, characterized in that The process is carried out according to the following steps: in the first step, the raw gas from the produced gas inlet pipeline is preliminarily separated by a gas-liquid separator to obtain high-temperature water-containing natural gas and a mixed liquid phase respectively; in the second step, the high-temperature water-containing natural gas is transported to the first pipe side of the first heat exchanger through the wet natural gas outlet pipeline, and ethylene glycol is injected into the high-temperature water-containing natural gas once by atomization to obtain natural gas injected with alcohol once, and the mixed liquid phase is discharged through the first liquid discharge pipeline and then recycled; in the third step, the natural gas injected with alcohol once flows from top to bottom in the first pipe side of the first heat exchanger, and countercurrently exchanges heat with the secondary low-temperature dry gas in the shell side of the first heat exchanger to reduce the temperature, and obtains large particle condensate and preliminarily pre-cooled wet natural gas respectively; In the fourth step, the large-particle condensate settles naturally under the action of gravity and collects at the bottom head of the first heat exchanger. The pre-cooled wet natural gas enters the first pipe pass of the second heat exchanger through the first pre-cooled natural gas outlet pipeline. After secondary atomization and injection of ethylene glycol into the pre-cooled wet natural gas, the natural gas after secondary alcohol injection is obtained. In the fifth step, the natural gas after the second alcohol injection flows from top to bottom in the first tube side of the second heat exchanger, and countercurrently exchanges heat with the primary low-temperature dry gas in the shell side of the second heat exchanger to obtain secondary pre-cooled wet natural gas; in the sixth step, after the secondary pre-cooled wet natural gas is cooled in the refrigeration equipment, it is mixed with the large-particle condensate collected from the bottom head of the first heat exchanger, and sent to the low-temperature separator through the second pre-cooling natural gas outlet pipeline to separate the low-temperature condensate mixture and the primary low-temperature dry gas; In the seventh step, the low-temperature condensed mixed liquid is sent to the second tube side of the second heat exchanger through the first liquid hydrocarbon pipeline through the flow control valve for heat exchange, and then sent to the second tube side of the first heat exchanger through the second liquid hydrocarbon pipeline for heat exchange again. The obtained mixed liquid after heat exchange is discharged from the third liquid hydrocarbon pipeline and sent to the downstream process for recovery of liquid hydrocarbons and ethylene glycol. The primary low-temperature dry gas is returned to the shell side of the second heat exchanger through the first low-temperature dry gas outlet pipeline for heat exchange to obtain secondary low-temperature dry gas. In the eighth step, the secondary low-temperature dry gas is sent to the shell side of the first heat exchanger through the second low-temperature dry gas outlet pipeline for further heat exchange to obtain reheated dry gas; In the ninth step, the reheated dry gas is pressurized by a booster compressor to obtain high-pressure reheated dry gas, and the high-pressure reheated dry gas is discharged through a dehydration and dehydrocarbonization dry gas pipeline for external transmission.

8. The method for using the high-efficiency heat exchange device for high-pressure natural gas processing according to claim 7, characterized in that In the second step, the transmission flow rate of high-temperature water-containing natural gas is 1500×10 4 m 3 / d, the pressure is 10.3 to 10.5 MPa, the temperature is 28°C to 32°C, the mass concentration of ethylene glycol is 80% to 82%, and the injection rate of ethylene glycol is 290L / h to 295L / h; or / and, in the fourth step, the mass concentration of ethylene glycol is 80% to 82%, and the injection rate of ethylene glycol is 275L / h to 280L / h.

9. The method for using the high-efficiency heat exchange device for high-pressure natural gas processing according to claim 7 or 8, characterized in that In the third step, the temperature of the initial pre-cooled wet natural gas is 6°C to 10°C; or / and, in the sixth step, the temperature of the secondary pre-cooled wet natural gas is -8°C to -10°C, and the temperature of the secondary pre-cooled wet natural gas after cooling by the refrigeration equipment is -12°C to -16°C; or / and, in the eighth step, the temperature of the secondary low-temperature dry gas is 0°C to 5°C, and the temperature of the reheated dry gas is 20°C to 25°C.

10. The method for using the high-efficiency heat exchange device for high-pressure natural gas processing according to claim 7, 8 or 9, characterized in that In the seventh step, the temperature of the low-temperature condensed mixed liquid after heat exchange in the second tube pass of the second heat exchanger is -6°C to -10°C, and the temperature of the mixed liquid after heat exchange and the large particle condensate collected at the bottom head is 24°C to 28°C.

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