Device for producing liquefied natural gas using pressure energy of high-pressure natural gas

Abstract

The application discloses a device for preparing liquefied natural gas by using pressure energy of high-pressure natural gas; a first precooling pipeline is connected with a high-pressure section of a high-medium pressure regulating station, natural gas is introduced and pre-cooled, and then is input into a heavy hydrocarbon separation tank; the natural gas from the heavy hydrocarbon separation tank is divided into three paths and is input into a first expansion generator set, a second expansion generator set and a third precooling pipeline; the natural gas after the first expansion generator set is input into a first deep cooling pipeline of a deep cooling section for cooling, and is input into a gas-liquid separation tank after a first throttling valve; the natural gas after the second expansion generator set is input into the gas-liquid separation tank; after gas-liquid separation, the liquid natural gas is reduced in pressure and temperature by a second throttling valve, and is finally input into an LNG storage tank; and the gaseous natural gas is sequentially input into a second deep cooling pipeline of the deep cooling section and a second precooling pipeline of a precooling section. The application can reduce energy consumption of a liquefaction system and greatly reduce energy consumption during hourly peak regulation or daily peak regulation.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of liquefied natural gas storage and transportation, in particular to a device for producing liquefied natural gas by using pressure energy of high-pressure natural gas. BACKGROUND

[0002] Liquefied natural gas, i.e. LNG, is more convenient to store and transport, and is increasingly widely used in natural gas peak shaving.

[0003] In the prior art, a mixed refrigerant liquefaction process is usually used in a peak shaving type liquefaction plant, and a large amount of energy is consumed for refrigeration for liquefied natural gas.

[0004] Meanwhile, high-pressure natural gas has abundant pressure energy, which can be used to provide energy for natural gas liquefaction. With the development of cryogenic expander technology and the continuous reduction of cost, the use of natural gas pressure energy is increasingly valued.

[0005] Therefore, how to use the pressure of high-pressure natural gas to provide energy for natural gas liquefaction and reduce the energy consumption of the liquefaction system has become a technical problem to be solved by those skilled in the art. SUMMARY

[0006] In view of the above defects of the prior art, the present application provides a device for producing liquefied natural gas by using pressure energy of high-pressure natural gas, which realizes the purpose of reducing the energy consumption of the liquefaction system, is suitable for a high-medium pressure regulating station with a natural gas inlet pressure of more than 5 MPa and a medium-low pressure output, and can greatly reduce the energy consumption during hourly peak shaving or daily peak shaving.

[0007] To achieve the above purpose, the present application discloses a device for producing liquefied natural gas by using pressure energy of high-pressure natural gas; characterized in that it comprises a cold box, a heavy hydrocarbon separation tank, a first expansion generator set, a second expansion generator set and a gas-liquid separation tank.

[0008] The cold box comprises a precooling section in the upper part and a cryogenic section in the lower part.

[0009] The first precooling pipeline in the precooling section is connected with the high-pressure section of the high-medium pressure regulating station, introduces natural gas and performs precooling, and then inputs the heavy hydrocarbon separation tank.

[0010] The heavy hydrocarbon separation tank separates the input natural gas from heavy hydrocarbons and divides it into three paths to input the first expansion generator set, the second expansion generator set and the third precooling pipeline in the precooling section, respectively.

[0011] The natural gas generates electric energy through the first expansion generator set, reduces pressure and temperature, is then input into the first cryogenic pipeline of the cryogenic section for cooling, and is input into the gas-liquid separation tank after pressure reduction and temperature reduction through a first throttling valve.

[0012] The natural gas is input into the gas-liquid separation tank after being separated into gas and liquid, and the liquid natural gas is input into the LNG storage tank after being depressurized and cooled by the second throttling valve, and the gaseous natural gas is input into the second deep cooling pipeline and the second pre-cooling pipeline of the pre-cooling stage in sequence and is output through the medium pressure output pipeline of the high-medium pressure regulating station after being warmed up.

[0013] The natural gas input into the gas-liquid separation tank is separated into gas and liquid, and the liquid natural gas is input into the LNG storage tank after being depressurized and cooled by the second throttling valve, and the gaseous natural gas is input into the second deep cooling pipeline and the second pre-cooling pipeline of the pre-cooling stage in sequence and is output through the medium pressure output pipeline of the high-medium pressure regulating station after being warmed up.

[0014] The output port of the heavy hydrocarbon separation tank bottom outputting the separated heavy hydrocarbon is connected with the input port of the third pre-cooling pipeline through a pipeline, and the heavy hydrocarbon is mixed with the natural gas input into the third pre-cooling pipeline, and then is input into the third pre-cooling pipeline after being depressurized and cooled by the third throttling valve.

[0015] The natural gas passing through the third pre-cooling pipeline is output through the medium pressure or sub-high pressure output pipeline of the high-medium pressure regulating station after passing through the pre-cooling stage of the cold box.

[0016] Preferably, the first pre-cooling pipeline introduces natural gas with a pressure of 5MPa to 10MPa and pre-cools it to -30℃ to -40℃, and then inputs it into the heavy hydrocarbon separation tank.

[0017] Preferably, the natural gas is output through the first expansion generator after being output through the first expansion generator, and the pressure is reduced to 3MPa to 4MPa, and the temperature is reduced to -50℃ to -60℃, and then the natural gas is input into the first deep cooling pipeline and is cooled to below -110℃, and is depressurized to 0.1MPa to 0.4MPa and cooled to below -140℃ by the first throttling valve, and then is input into the gas-liquid separation tank.

[0018] The natural gas is output through the second expansion generator after being output through the second expansion generator, and the pressure is reduced to 0.3MPa to 0.4MPa, and the temperature is reduced to -110℃ to -120℃, and then the natural gas is input into the gas-liquid separation tank.

[0019] Preferably, the natural gas input into the gas-liquid separation tank is separated into gas and liquid, and the liquid natural gas is depressurized to 20kPa and cooled to below -160℃ by the second throttling valve, and then is input into the LNG storage tank, and the gaseous natural gas is input into the second deep cooling pipeline and the second pre-cooling pipeline in sequence, and is output through the medium pressure output pipeline after the temperature is increased to 20℃.

[0020] Preferably, the heavy hydrocarbon is mixed with the natural gas input into the third pre-cooling pipeline, and then is input into the third pre-cooling pipeline after being depressurized to 1.6MPa and cooled to below -65℃ by the third throttling valve.

[0021] Preferably, a first flow control valve and a shutoff valve are arranged on the pipeline between the first pre-cooling pipeline and the high-pressure section of the high-medium pressure regulating station.

[0022] Preferably, the outlet pressure of the first throttle valve is interlocked with the outlet pressure of the second expansion generator set, and the pressure values are adjusted to be the same.

[0023] A third flow control valve is arranged between the heavy hydrocarbon separation tank and the first expansion generator set.

[0024] The opening degree of the third flow control valve is interlocked with the temperature of the natural gas in the pipeline between the first deep cooling pipeline and the gas-liquid separation tank.

[0025] The higher the temperature of the natural gas in the pipeline between the first deep cooling pipeline and the gas-liquid separation tank, the smaller the opening degree of the third flow control valve.

[0026] The lower the temperature of the natural gas in the pipeline between the first deep cooling pipeline and the gas-liquid separation tank, the greater the opening degree of the third flow control valve.

[0027] Preferably, the LNG storage tank selects a pressure type storage tank or an atmospheric pressure type storage tank according to the set value of the outlet pressure of the second throttle valve.

[0028] Preferably, a second flow control valve and a check valve are arranged on the pipeline between the heavy hydrocarbon separation tank and the position where the heavy hydrocarbon and the natural gas input into the third pre-cooling pipeline are mixed.

[0029] Preferably, the outlet pressure of the third throttle valve is 1.6 MPa of a sub-high pressure or 0.1 MPa to 0.4 MPa of a medium pressure.

[0030] The present application has the following beneficial effects:

[0031] The present application can reduce the energy consumption of the liquefaction system, is suitable for a high-medium pressure regulating station with a natural gas inlet pressure of 5 MPa or above and a medium-low pressure output pressure, and can greatly reduce the energy consumption during hourly peak shaving or daily peak shaving.

[0032] The concept, specific structure and generated technical effects of the present application will be further described below with reference to the accompanying drawings, so as to fully understand the purposes, features and effects of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 A structure schematic diagram of an embodiment of the present application is shown. DETAILED DESCRIPTION

[0034] EMBODIMENT

[0035] As Figure 1As shown, the device for producing liquefied natural gas by using pressure energy of high-pressure natural gas comprises a cold box 29, a heavy hydrocarbon separation tank 5, a first expansion generator set 8, a second expansion generator set 23 and a gas-liquid separation tank 25;

[0036] The cold box 29 comprises a pre-cooling section in the upper part and a deep cooling section in the lower part;

[0037] The first pre-cooling pipeline in the pre-cooling section is connected with the high-pressure section of the high-medium pressure regulating station, and the natural gas is introduced and pre-cooled, and then input into the heavy hydrocarbon separation tank 5;

[0038] The heavy hydrocarbon separation tank 5 separates the input natural gas from heavy hydrocarbons, and then divides the natural gas into three paths and inputs into the first expansion generator set 8, the second expansion generator set 23 and the third pre-cooling pipeline in the pre-cooling section respectively;

[0039] The natural gas is output electric energy by the first expansion generator set 8, and then input into the first deep cooling pipeline of the deep cooling section after the pressure and temperature are reduced, and then input into the gas-liquid separation tank 25 after the pressure and temperature are reduced by the first throttling valve 11;

[0040] The natural gas is output electric energy by the second expansion generator set 23, and then input into the gas-liquid separation tank 25 after the pressure and temperature are reduced;

[0041] The natural gas input into the gas-liquid separation tank 25 is separated into liquid natural gas and gaseous natural gas, the liquid natural gas is input into the LNG storage tank 15 after the pressure and temperature are reduced by the second throttling valve 13, and the gaseous natural gas is input into the second deep cooling pipeline of the deep cooling section and the second pre-cooling pipeline of the pre-cooling section in sequence after the temperature is increased, and then output by the medium-pressure output pipeline of the high-medium pressure regulating station;

[0042] The output port of the heavy hydrocarbon separated from the bottom of the heavy hydrocarbon separation tank 5 is connected with the input port of the third pre-cooling pipeline by a pipeline, and the heavy hydrocarbon is mixed with the natural gas input into the third pre-cooling pipeline, and then input into the third pre-cooling pipeline after the pressure and temperature are reduced by the third throttling valve 20;

[0043] The natural gas passing through the third pre-cooling pipeline is output by the medium-pressure or sub-high pressure output pipeline of the high-medium pressure regulating station after passing through the pre-cooling section of the cold box 29.

[0044] In actual application, the natural gas in the application is expanded, one path of which is used as raw material gas to produce LNG after being cooled, and the other path of which is used as refrigerant to return to the natural gas pipeline network after being throttled and expanded, without setting a refrigerant circulation process, and completely relying on the pressure energy of the natural gas to refrigerate.

[0045] The LNG is produced by using the pressure energy of the natural gas, the energy consumption of the liquefaction system is reduced, the high-medium pressure regulating station is suitable for the natural gas with a pressure of more than 5 MPa and an output pressure of medium-low pressure, and the energy consumption during hourly peak regulation or daily peak regulation can be greatly reduced.

[0046] In some embodiments, natural gas at a pressure of 5 MPa to 10 MPa is introduced into the first precooling pipeline and precooled to -30°C to -40°C before being fed into the heavy hydrocarbon separator 5.

[0047] In some embodiments, after the natural gas generates electricity through the first expansion generator set 8, the pressure drops to 3MPa to 4MPa and the temperature drops to -50°C to -60°C. It is then fed into the first cryogenic pipeline to be cooled to below -110°C, and after being depressurized to 0.1MPa to 0.4MPa and cooled to below -140°C by the first throttle valve 11, it is fed into the gas-liquid separator 25.

[0048] After the natural gas generates electricity through the second expansion generator unit 23, the pressure drops to 0.3MPa to 0.4MPa and the temperature drops to -110℃ to -120℃ before being fed into the gas-liquid separator 25.

[0049] In some embodiments, after the natural gas entering the gas-liquid separator 25 is separated into gas and liquid, the liquid natural gas is then depressurized to 20 kPa and cooled to below -160°C through the second throttle valve 13, and finally fed into the LNG storage tank 15. The gaseous natural gas enters the second cryogenic pipeline and the second precooling pipeline in sequence. After the temperature rises to 20°C, it is output through the medium-pressure output pipeline.

[0050] In some embodiments, after the heavy hydrocarbons are mixed with the natural gas entering the third precooling pipeline, they are depressurized to 1.6 MPa and cooled to below -65°C by the third throttle valve 20 before being entered into the third precooling pipeline.

[0051] In some embodiments, a first flow control valve 3 and a shut-off valve 2 are provided on the pipeline between the first precooling pipeline and the high-pressure section of the high-pressure regulating station.

[0052] In practical applications, the flow rate of the introduced natural gas can be controlled by adjusting the opening of the first flow control valve 3, which facilitates the adjustment of the process load according to the production load of the high and medium pressure regulating station or the storage capacity of the storage tank.

[0053] In some embodiments, the outlet pressure of the first throttle valve 11 is interlocked with the outlet pressure of the second expansion generator set 23, and the pressure values ​​are adjusted to be the same.

[0054] A third flow control valve 7 is provided between the heavy hydrocarbon separator 5 and the first expansion generator set 8;

[0055] The opening degree of the third flow control valve 7 is interlocked with the temperature of the natural gas in the pipeline between the first cryogenic pipeline and the gas-liquid separator 25;

[0056] The higher the temperature of the natural gas in the pipeline between the first cryogenic pipeline and the gas-liquid separator 25, the smaller the opening of the third flow control valve 7;

[0057] The lower the temperature of the natural gas in the pipeline between the first cryogenic pipeline and the gas-liquid separator 25, the greater the opening degree of the third flow control valve 7.

[0058] In some embodiments, the LNG storage tank 15 is selected as either a pressure tank or an atmospheric pressure tank based on the outlet pressure setting of the second throttle valve 13.

[0059] In some embodiments, a second flow control valve 18 and a check valve 19 are provided on the pipeline from the heavy hydrocarbon separator 5 to the location where the heavy hydrocarbons are mixed with the natural gas input to the third precooling pipeline.

[0060] In practical applications, the second flow control valve 18 can be set to adjust the load distribution between the precooling section at the top and the cryogenic section at the bottom of the cold box 29 by controlling the flow of natural gas.

[0061] In practical applications, the check valve 19 can prevent liquid from entering the second expansion generator set 23 and causing equipment damage.

[0062] In some embodiments, the outlet pressure of the third throttle valve 20 is a sub-high pressure of 1.6 MPa or a medium pressure of 0.1 MPa to 0.4 MPa.

[0063] In practical applications, the outlet pressure of the third throttle valve 20 can be adjusted according to the function of the high and medium pressure regulating station.

[0064] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. An apparatus for producing liquefied natural gas using the pressure energy of high-pressure natural gas; characterized in that, It includes a cold box (29), a heavy hydrocarbon separator (5), a first expansion generator set (8), a second expansion generator set (23), and a gas-liquid separator (25); The cold box (29) includes an upper precooling section and a lower cryogenic section; The first precooling pipeline in the precooling section is connected to the high-pressure section of the high-pressure regulating station. After natural gas is introduced and precooled, it is fed into the heavy hydrocarbon separator (5). The heavy hydrocarbon separator (5) separates the heavy hydrocarbons from the input natural gas and then divides it into three streams, which are respectively fed into the first expansion generator set (8), the second expansion generator set (23), and the third precooling pipeline in the precooling section. The natural gas generates electricity through the first expansion generator set (8), and after reducing its pressure and temperature, it is then fed into the first cryogenic pipeline of the cryogenic section for cooling. After being depressurized and cooled by the first throttle valve (11), it is fed into the gas-liquid separator (25). The natural gas is powered by the second expansion generator set (23) to generate electricity, and after the pressure and temperature are reduced, it is then fed into the gas-liquid separator (25). After the natural gas enters the gas-liquid separator (25) and undergoes gas-liquid separation, the liquid natural gas is depressurized and heated by the second throttle valve (13) and then finally input into the LNG storage tank (15). The gaseous natural gas enters the second cryogenic pipeline of the cryogenic section and the second precooling pipeline of the precooling section in sequence for heating, and finally outputs through the medium-pressure output pipeline of the high-pressure regulating station. The outlet of the heavy hydrocarbon separator (5) at the bottom is connected to the inlet of the third precooling pipeline through a pipeline. The heavy hydrocarbon is mixed with the natural gas input into the third precooling pipeline. After being depressurized and cooled by the third throttle valve (20), it is input into the third precooling pipeline. The natural gas, after passing through the pre-cooling section of the cold box (29) via the third pre-cooling pipeline, is output through the medium-pressure or sub-high-pressure output pipeline of the high-medium-pressure regulating station.

2. The apparatus for producing liquefied natural gas using the pressure energy of high-pressure natural gas according to claim 1, characterized in that, The first precooling pipeline introduces natural gas at a pressure of 5MPa to 10MPa and precools it to -30°C to -40°C before it is fed into the heavy hydrocarbon separator (5).

3. The apparatus for producing liquefied natural gas using the pressure energy of high-pressure natural gas according to claim 1, characterized in that, After the natural gas generates electricity through the first expansion generator set (8), the pressure drops to 3MPa to 4MPa and the temperature drops to -50℃ to -60℃. It is then fed into the first cryogenic pipeline to be cooled to below -110℃, and then reduced to 0.1MPa to 0.4MPa and cooled to below -140℃ by the first throttle valve (11) before being fed into the gas-liquid separator (25). After the natural gas generates electricity through the second expansion generator set (23), the pressure drops to 0.3MPa to 0.4MPa and the temperature drops to -110℃ to -120℃ before being fed into the gas-liquid separator (25).

4. The apparatus for producing liquefied natural gas using the pressure energy of high-pressure natural gas according to claim 1, characterized in that, After the natural gas enters the gas-liquid separator (25) and undergoes gas-liquid separation, the liquid natural gas is then depressurized to 20 kPa and cooled to below -160°C through the second throttle valve (13), and finally fed into the LNG storage tank (15). The gaseous natural gas enters the second cryogenic pipeline and the second precooling pipeline in sequence. After the temperature rises to 20°C, it is output through the medium-pressure output pipeline.

5. The apparatus for producing liquefied natural gas using the pressure energy of high-pressure natural gas according to claim 1, characterized in that, After the heavy hydrocarbons are mixed with the natural gas input into the third precooling pipeline, they are depressurized to 1.6 MPa and cooled to below -65°C by the third throttle valve (20) before being input into the third precooling pipeline.

6. The apparatus for producing liquefied natural gas using the pressure energy of high-pressure natural gas according to claim 1, characterized in that, A first flow control valve (3) and a shut-off valve (2) are provided on the pipeline between the first precooling pipeline and the high-pressure section of the high-pressure regulating station.

7. The apparatus for producing liquefied natural gas using the pressure energy of high-pressure natural gas according to claim 1, characterized in that, The outlet pressure of the first throttle valve (11) is interlocked with the outlet pressure of the second expansion generator set (23), and the pressure values ​​are adjusted to be the same. A third flow control valve (7) is provided between the heavy hydrocarbon separator (5) and the first expansion generator set (8); The opening degree of the third flow control valve (7) is interlocked with the temperature of the natural gas in the pipeline between the first cryogenic pipeline and the gas-liquid separator (25); The higher the temperature of the natural gas in the pipeline between the first cryogenic pipeline and the gas-liquid separator (25), the smaller the opening of the third flow control valve (7); The lower the temperature of the natural gas in the pipeline between the first cryogenic pipeline and the gas-liquid separator (25), the greater the opening degree of the third flow control valve (7).

8. The apparatus for producing liquefied natural gas using the pressure energy of high-pressure natural gas according to claim 1, characterized in that, The LNG storage tank (15) is selected as a pressure tank or an atmospheric pressure tank according to the outlet pressure setting value of the second throttle valve (13).

9. The apparatus for producing liquefied natural gas using the pressure energy of high-pressure natural gas according to claim 1, characterized in that, A second flow control valve (18) and a check valve (19) are provided on the pipeline from the heavy hydrocarbon separator (5) to the mixing position of the heavy hydrocarbon and the natural gas input to the third precooling pipeline.

10. The apparatus for producing liquefied natural gas using the pressure energy of high-pressure natural gas according to claim 1, characterized in that, The outlet pressure of the third throttle valve (20) is a sub-high pressure of 1.6 MPa or a medium pressure of 0.1 MPa to 0.4 MPa.

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