CN109141561B - Device and method for measuring moisture of natural gas in real time based on in-pipe phase separation technology - Google Patents

Abstract

The natural gas moisture real-time measurement device based on in-pipe phase separation technology mainly comprises a gas-liquid coarse separation system, a two-stage cyclone, a two-stage pipeline type compact gas-liquid separator, a racemizer, a gas flowmeter, a temperature sensor, a pressure sensor, a U-shaped liquid collecting pipe, a liquid flowmeter and an injection type gas-liquid mixer; the measuring method of the device of the invention realizes the complete separation of gas and liquid through a plurality of separation steps by utilizing the internal phase separation technology in the multiphase flow pipe and combining the gravity separation effect, and then measures the flow of the gas phase and the liquid phase in the natural gas moisture by utilizing the single-phase flowmeter. The invention can remarkably improve the separation efficiency of gas and liquid in the wet gas, ensure the measurement accuracy of the gas and the liquid, greatly reduce the volume of the separator and increase the real-time performance of the wet gas measurement. In addition, the moisture measuring device and the moisture measuring method have the advantages of wide applicable flow parameter range, high safety performance and low production and manufacturing cost, and are very suitable for popularization and application in engineering.

Description

Device and method for measuring moisture of natural gas in real time based on in-pipe phase separation technology

Technical Field

The invention belongs to the technical field of multiphase flow measurement, and particularly relates to a natural gas moisture real-time measurement device based on an in-pipe phase separation technology, and a natural gas moisture real-time measurement method based on the in-pipe phase separation technology.

Background

Often, natural gas is produced from the subsurface to the surface with a portion of the liquids that may be crude oil in the formation, condensate from temperature and pressure reductions during production, formation water, injection or fracturing flowback fluids, and the like. In the oil and gas industry, the mixture of natural gas and liquid phases produced in such gas wells is referred to as "wet gas", the volumetric gas fraction of the gas in wet gas is often greater than 90%, the volumetric gas fraction of most gas wells is above 97%, and the Lockhart-MARTINELLI NUMBER is referred to as wet gas when the Lockhart is less than or equal to 0.3 as specified in the "wet gas metering guidelines" issued by the American society of mechanical Engineers. It follows that moisture falls within the category of multiphase streams, which in fact is a multiphase stream morphology of high volumetric gas fraction. The production of offshore oil and gas fields and shale gas fields is moisture.

Along with the increasing demand for natural gas, the requirement of refined management is also put forward for the production of natural gas at present, and the acquisition of single well gas production and liquid production volume through moisture measurement is basic data for realizing gas well monitoring, gas reservoir management, production process optimization, gas well drainage and gas production measure optimization, effect evaluation and the like, and the method is free from loss. From the measurement perspective, natural gas wet gas measurement is a special case of multiphase flow measurement, and the uncertainty of parameters such as speed slippage between gas and liquid phases, random change of internal phase distribution and flow pattern, temperature pressure and the like determines that wet gas measurement is a complex multiphase flow problem, and the ratio of liquid phases is very small, is particularly sensitive to measurement errors, and often generates huge measurement errors. Therefore, moisture cannot generally be measured directly by using a conventional single-phase gas flowmeter, and special researches on a measuring device and a measuring method thereof are required.

The conventional wet gas measurement method can be mainly divided into two main types, namely gas-liquid separation measurement and gas-liquid separation measurement. The measurement of gas-liquid separation is to directly measure the moisture by using a single-phase gas flowmeter, and correct the measured value by using an empirical formula or measure the moisture flow rate and the phase content by adopting a method of combining two sensors at the same time. The moisture measurement methods introduced by the Chinese patent applications CN103353319A, CN105675070A, CN104266702A, CN105890689A, CN105157766A and CN106979808A and the like belong to gas-liquid separation measurement. Measuring the wet gas flow rate by using a gas ultrasonic flowmeter as in CN103353319A, and correcting the virtual high flow rate according to an empirical formula; in CN105675070A, the moisture flow is measured by utilizing a special-shaped Venturi nozzle and combining the relation between multiphase flow pressure difference and flow and phase content; in CN104266702a, the flow rate of moisture was measured using a V-cone flowmeter and the liquid phase content was measured using a capacitance probe; CN105890689a uses a differential pressure flowmeter to measure the moisture flow and gamma ray sensors to measure the phase contents; CN105157766a measures the moisture flow rate and the phase content by using a method of combining a venturi flowmeter and a spindle flowmeter; CN106979808a measures moisture flow and phase content using an ultrasonic flow meter and target flow meter combination method. Furthermore, U.S. patent No. 7454981B2 describes an apparatus and method for measuring moisture flow and phase content in combination with an acoustic flowmeter and a gamma ray densitometer; the European patent EP2775272A1 describes a device and a method for measuring the moisture flow by using a combination method of a Coriolis flowmeter and a Venturi flowmeter; the international patent WO2005040732A1 describes the measurement of moisture flow using a combination of an ultrasonic flow meter and a differential pressure flow meter. While the moisture in the above related patents is measured using conventional gas flowmeters, which has the advantage of being small and easy to meter for installation applications, this measurement method requires reliance on a model of the response of conventional gas flowmeters versus moisture flow and phase fractions. Because of the complexity of multiphase flow and the randomness of flow field distribution, so far, theoretical research on the flow mechanism of multiphase flow is insufficient, and a reliable and universal flow model cannot be established theoretically, so that the relation model of multiphase flow parameters and instrument response is often obtained through fitting laboratory data. Because the flow working conditions of different gas wells are different, the expression obtained by laboratory data lacks universality, and if the field working condition data is applied to fit the relation, the limitation of the field conditions lacks magnitude transfer standards, and the method is basically not realized. Therefore, the conventional flowmeter is used for measuring the gas-liquid coexisting wet gas flow, the measurement model has certain limitation, the measurement model has higher measurement accuracy only in a narrow parameter range, and larger measurement errors which are difficult to predict are generated when the measurement model deviates from the parameter range. The liquid phase content in the wet gas is generally measured by a capacitance probe method, a gamma ray attenuation method, a microwave method and the like under the condition of no gas-liquid separation, and the resolution of the capacitance probe is difficult to reach the measurement requirement due to the extremely low liquid phase content in the wet gas, so that a larger liquid phase error can be caused; while radiation and microwave methods have radiation pollution and safety problems, their application is limited by national or local relevant policy laws.

The method for measuring the gas-liquid separation of the wet gas is to measure the wet gas by using a single-phase gas flowmeter and a liquid flowmeter respectively after the wet gas is subjected to the gas-liquid separation. The measuring method has high measuring precision for measuring the flow rate of each separated phase of the wet gas by the single-phase flowmeter because the gas and the liquid are completely separated, but the method also has higher requirements on the gas and the liquid separating device. The moisture measurement methods described in chinese patent application CN105020585A, CN106996289a, patent CN206414929U, international patent WO2017044538A1, etc. all belong to this type. The gas-liquid separators disclosed in these patents rely on cyclone separation or gravity separation, and for wet gas, the gas velocity is high, the liquid amount is small, the following property of the liquid flowing along with the gas flow is strong, in order to complete the complete separation of the gas and the liquid, the diameter of the separator needs to be increased to reduce the gas velocity, the height of the separator needs to be increased to increase the residence time of the wet gas in the separator, and some structures for strengthening the gas-liquid separation are often required to be arranged in the separator, so that the separator has a large volume and a complex structure, and is inconvenient for gas well wellhead measurement. In addition, the large-diameter gas-liquid separator belongs to a pressure vessel, has high manufacturing cost and has higher requirements on production process and operation environment.

In summary, the existing wet gas-liquid separation-free measurement method has the defects of low measurement precision and narrow application range because of too much depending on an empirical multiphase measurement model in spite of small device volume; the existing method for measuring after gas-liquid separation has the defects of large volume, complex structure, high manufacturing cost, high process and operation requirements and inconvenience in wellhead installation of the separator despite higher measurement precision.

Disclosure of Invention

Aiming at the defects and shortcomings of the prior art, the invention aims to provide a natural gas moisture real-time measurement device and method based on the in-pipe phase separation technology.

In order to achieve the above purpose, the invention adopts the following technical scheme:

the first object of the present invention is to provide a natural gas moisture real-time measurement device based on in-pipe phase separation technology, which comprises a horizontal inlet pipe, an upper horizontal pipeline, a lower horizontal pipeline and a horizontal outlet pipe, and is characterized in that: the system also comprises a gas-liquid coarse separation system, a gas-liquid separation system, a gas metering system, a gas-liquid mixing system and a liquid metering system; the gas-liquid coarse separation system is arranged between the horizontal inlet pipe and the upper horizontal pipeline; the gas-liquid separation system and the gas metering system are sequentially arranged on a vertical pipeline between an upper horizontal pipeline and a lower horizontal pipeline; the gas-liquid mixing system is arranged between the lower horizontal pipeline and the horizontal outlet pipe; the liquid metering system is arranged in parallel between the gas-liquid separation system and the gas-liquid mixing system;

the gas-liquid coarse separation system comprises a declining pipe, an ascending pipe and a steel wire mesh assembly; one end of the declining pipe is closed, and the other end of the declining pipe is connected with the horizontal inlet pipe; one end of the upper inclined pipe is positioned at the inlet side of the lower inclined pipe and is communicated with the lower inclined pipe, and the other end of the upper inclined pipe is communicated with an upper horizontal pipeline; the steel wire mesh assembly is positioned in the inlet side of the tilt-up pipe;

The gas-liquid separation system comprises a first-stage cyclone, a first-stage separator, a second-stage cyclone and a second-stage separator; the primary cyclone, the primary separator and the secondary separator are sequentially arranged on the vertical pipeline; the secondary cyclone is arranged inside the primary separator;

the gas metering system comprises a racemizer, a gas flowmeter, a pressure sensor and a temperature sensor; the racemizer and the gas flowmeter are sequentially arranged on the vertical pipeline; the pressure sensor and the temperature sensor are arranged between the racemizer and the gas flowmeter;

The gas-liquid mixing system comprises an injection type gas-liquid mixer;

The liquid metering system comprises a U-shaped liquid collecting pipe, a liquid path elbow, a vertical downcomer liquid level meter, an electric control valve and a liquid flowmeter; the U-shaped liquid collecting pipe is connected with the injection type gas-liquid mixer through a liquid path elbow and a vertical downcomer; the primary liquid guide pipe is communicated with the declining pipe and the U-shaped liquid collecting pipe; a first-stage liquid guide pipe is communicated with the first-stage separator and the U-shaped liquid collecting pipe; a second-stage liquid guide pipe is arranged to communicate the second-stage separator with the U-shaped liquid collecting pipe; the liquid flowmeter is arranged on the vertical downcomer; the liquid level meter and the electric control valve are arranged on the U-shaped liquid collecting pipe; the liquid level meter is connected with the electric control valve through a control line.

Further, the inclination angle of the declining pipe is 15-40 degrees; the tilt angle of the tilt-up pipe is larger than 30 degrees.

Further, the primary cyclone and the secondary cyclone are formed by surrounding a central shaft by four to eight spiral blades or straight blades; the inner edge of the blade is connected with the central shaft into a whole; the outer edges of the blades are closely contacted with the inner wall of the pipeline, and no gap exists; the diameter of the central shaft is smaller than 6mm.

Further, the primary separator consists of an outer cylinder, a first thin-wall inner partition pipe and a first air duct, wherein the first thin-wall inner partition pipe and the first air duct are coaxial with the outer cylinder; the inner wall of the outer cylinder and the outer wall of the first thin-wall inner partition tube form a first annular liquid discharge cavity; the bottom of the first annular liquid drainage cavity is communicated with a primary liquid guide pipe through a primary liquid drainage hole; a first liquid film circumferential seam is formed between the outer wall of the first thin-wall inner partition pipe and the inner wall of the pipeline; the first air duct is of an inverted L shape, an inlet of the first air duct is communicated with the top of the first annular liquid draining cavity, and an outlet of the first air duct is downward and is positioned at the center of the first thin-wall inner partition tube.

Further, the secondary separator consists of a pipeline, a second thin-wall inner partition pipe coaxial with the pipeline and a second air duct; the inner wall of the pipeline and the outer wall of the second thin-wall inner partition pipe form a second annular liquid discharge cavity; the bottom of the second annular liquid drainage cavity is communicated with a second liquid guide pipe through a second liquid drainage hole; a second liquid film circumferential seam is formed between the outer wall of the second thin-wall inner partition tube and the inner wall of the first thin-wall inner partition tube; the second air duct is of an inverted L shape, an inlet of the second air duct is communicated with the top of the second annular liquid draining cavity, and an outlet of the second air duct is downward and is positioned at the center of the second thin-wall inner partition tube.

Further, the racemization device is a group of thin flat plates which are arranged in parallel with the axis of the inner pipe of the pipeline; the spacing between the thin flat plates is equal.

Further, the injection type gas-liquid mixer is a venturi jet pipe, the outer diameter of the venturi jet pipe is equal to that of a pipeline, the venturi jet pipe is fixedly connected with the pipeline in a welding or flange mode, and the venturi jet pipe consists of an upstream contraction section, a downstream diffusion section and a straight throat section; an annular cavity is arranged between the inner wall and the outer wall of the throat part, the outer side of the annular cavity is communicated with the vertical downcomer through a hole on the outer wall of the throat part, and the inner side of the annular cavity is communicated with the venturi throat flow passage through a hole on the inner wall of the throat part; the holes on the inner wall of the throat part are distributed at equal intervals along the circumferential direction, at least one circle of holes are arranged, and at least two holes are arranged in each circle.

A second object of the present invention is to provide a measurement method of a natural gas moisture real-time measurement device based on in-pipe phase separation technique, characterized by comprising the steps of:

firstly, gas-liquid coarse separation:

when the natural gas wet gas flow enters the declining pipe from the inlet of the device through the horizontal inlet pipe, most liquid phase or liquid bullet in the slug flow type flows into the bottom of the declining pipe under the action of gravity and enters the U-shaped liquid collecting pipe through the primary liquid guide pipe, and the gas phase in the wet gas flow carries a small amount of liquid and enters the declining pipe after being further dehumidified through the liquid removing effect of the steel wire mesh assembly, so that the primary coarse separation of the gas and the liquid of the wet gas flow is completed.

And secondly, completely separating gas from liquid:

Moisture in the upward inclined pipe flows through the horizontal inlet pipe and then enters the primary cyclone, most of liquid phase flows in a liquid film form along the pipe wall under the action of centrifugal force, and gas phase flows in the middle of the pipe; the liquid film and a small amount of gas phase formed after passing through the primary cyclone fall into the first annular liquid discharge cavity through the first liquid film circumferential seam, the liquid phase enters the U-shaped liquid collecting pipe from the primary liquid discharge hole through the primary liquid guide pipe, and a small amount of gas entering the first annular liquid discharge cavity is discharged into the first thin-wall inner partition pipe through the first gas guide pipe to be converged with the main gas flow; the air flow in the first thin-wall inner partition pipe flows through the second-stage cyclone, liquid drops with smaller particle sizes are separated from the air flow under the action of further centrifugal force, so that the liquid drops flow along the inner wall of the first thin-wall inner partition pipe in a liquid film mode, then a small amount of air is carried along and falls into the second annular liquid discharge cavity through the second liquid film circumferential gap, liquid phase enters the U-shaped liquid collecting pipe from the second liquid discharge hole through the second liquid guide pipe, and a small amount of air is discharged into the second thin-wall inner partition pipe through the second air guide pipe to be combined with the main air flow;

Thirdly, gas and liquid metering:

after the dry gas from the second thin-wall inner separation pipe is racemized by the racemizer, the dry gas flows through the gas flowmeter for metering, and the pressure and the temperature of the gas flow are measured by the pressure sensor and the temperature sensor respectively;

The liquid in the U-shaped liquid collecting pipe is measured by a liquid flowmeter on the vertical downcomer;

Fourth, mixing gas and liquid:

The air flow after metering enters a venturi jet pipe type injection type gas-liquid mixer through a lower horizontal pipeline, and low pressure is generated at the throat part; the liquid after metering flows into the gas-liquid mixer under the low pressure of the throat part generated by the air flow, and the gas-liquid two phases are mixed again and then flow out of the measuring device through the horizontal outlet pipe.

Compared with the prior art, the invention has the following advantages:

(1) The moisture measurement accuracy is high. Because the two-stage separation based on the in-pipe phase separation technology is adopted and the gas-liquid coarse separation system is combined, the complete separation of gas and liquid can be realized, and the measurement precision of the single-phase flowmeter is ensured.

(2) The separator has small volume and compact structure. The gas-liquid separation efficiency based on the in-pipe phase separation technology is high, the diameter of the separator is similar to the diameter of a pipeline, the maximum diameter of the separator is only 15-20 mm larger than the outer diameter of the pipeline, compared with a traditional gas-liquid separation tank, the volume is greatly reduced, the structure is more compact, the occupied area is small, and the gas-liquid separation tank is very suitable for wellhead metering of a gas well.

(3) The application range is wide. The rough separation system of the device considers the slug flow condition of wet gas flow, can eliminate liquid and bullet, and the two-stage rotational flow and two-stage separation structure based on the in-pipe phase separation technology can separate liquid drops carried by gas, so that the gas and liquid are completely separated, and the device and the method have wider application range to multiphase flow working conditions.

(4) The safety performance is good. The gas-liquid separator of the device has small diameter, strong pressure resistance and high operation safety; the method does not need to measure the phase content by adopting a method such as microwaves or gamma rays, and the radiation safety problem does not exist.

(5) The economy is good. The device does not belong to a pressure vessel and has lower requirements on the processing technology and production by adopting a compact pipeline type gas-liquid separation structure; meanwhile, compared with the traditional large-scale gas-liquid separator, the structure is simpler, and the production and manufacturing cost is lower.

Drawings

FIG. 1 is a schematic structural diagram of a real-time measurement device for natural gas moisture based on in-pipe phase separation technology according to the present invention, wherein arrows indicate the flow direction of a fluid;

FIG. 2 is an enlarged partial view of a two-stage pipelined compact separator, wherein the arrows indicate the direction of fluid flow;

FIG. 3 is a schematic structural view of an ejector gas-liquid mixer, wherein arrows indicate the flow direction of the fluid;

Wherein: 1. a horizontal inlet pipe; 2. a downdip tube; 3. an upward tilting tube; 4. a steel wire mesh assembly; 5. a U-shaped liquid collecting pipe; 6. an upper horizontal pipeline; 7. a primary cyclone; 8. a primary separator; 9. a secondary cyclone; 10. a secondary separator; 11. a racemizer; 12. a gas flow meter; 13. a pressure sensor; 14. a temperature sensor; 15. a lower horizontal pipeline; 16. an injection type gas-liquid mixer; 17. a liquid flow meter; 18. a horizontal outlet pipe; 19. an inlet flange; 20. an outlet flange; 51. a primary catheter; 52. a primary catheter; 53. a secondary catheter; 54. a liquid path elbow; 55. a vertical downcomer; 56. a liquid level gauge; 57. an electric control valve; 58. a control line; 81. an outer cylinder; 82. a first thin-walled inner separator tube; 83. a first air duct; 84. a first annular drain chamber; 85. a first liquid film circumferential seam; 86. a primary liquid discharge hole; 101. a pipe; 102. a second thin-walled inner separator tube; 103. a second air duct; 104. a second annular drain chamber; 105. a second liquid film circumferential seam; 106. a secondary liquid discharge hole; 161. an upstream constriction section; 162. a downstream diffuser section; 163. a straight throat; 1631. an annular cavity; 1632. a hole in the outer wall; 1633. and a hole on the inner wall.

Detailed Description

The following detailed description of the invention, taken in conjunction with the accompanying drawings, is not to be taken as limiting the invention, but is made merely by way of example and the invention may be more clearly and easily understood by way of illustration.

As shown in fig. 1, the natural gas moisture real-time measurement device based on in-pipe phase separation technology comprises a horizontal inlet pipe 1, an upper horizontal pipeline 6, a lower horizontal pipeline 15 and a horizontal outlet pipe 18, and is characterized by further comprising a gas-liquid coarse separation system, a gas-liquid separation system, a gas metering system, a gas-liquid mixing system and a liquid metering system; the gas-liquid coarse separation system is arranged between the horizontal inlet pipe 1 and the upper horizontal pipeline 6; the gas-liquid separation system and the gas metering system are sequentially arranged on a vertical pipeline between the upper horizontal pipeline 6 and the lower horizontal pipeline 15; the gas-liquid mixing system is arranged between the lower horizontal line 15 and the horizontal outlet pipe 18; the liquid metering system is arranged in parallel between the gas-liquid separation system and the gas-liquid mixing system; the moisture measuring device is connected with the natural gas pipeline through an inlet flange 19 and an outlet flange 20;

The gas-liquid coarse separation system comprises a declining pipe 2, an ascending pipe 3 and a steel wire mesh assembly 4; one end of the declining pipe 2 is closed, and the other end is connected with the horizontal inlet pipe 1; one end of the upper inclined pipe 3 is positioned at the inlet side of the lower inclined pipe 2 and is communicated with the lower inclined pipe 2, and the other end of the upper inclined pipe is communicated with the upper horizontal pipeline 6; the steel wire mesh assembly 4 is positioned in the inlet side of the tilting pipe 3;

The gas-liquid separation system comprises a primary cyclone 7, a primary separator 8, a secondary cyclone 9 and a secondary separator 10; the primary cyclone 7, the primary separator 8 and the secondary separator 10 are sequentially arranged on a vertical pipeline; the secondary cyclone 9 is arranged inside the primary separator 8;

The gas metering system comprises a racemizer 11, a gas flowmeter 12, a pressure sensor 13 and a temperature sensor 14; the racemizer 11 and the gas flowmeter 12 are sequentially arranged on a vertical pipeline; the pressure sensor 13 and the temperature sensor 14 are arranged between the racemizer 11 and the gas flow meter 12;

the gas-liquid mixing system comprises an injection type gas-liquid mixer 16;

The liquid metering system comprises a U-shaped liquid collecting pipe 5, a liquid path elbow 54, a liquid level meter 56 of a vertical downcomer 55, an electric control valve 57 and a liquid flowmeter 17; the U-shaped liquid collecting pipe 5 is connected with the injection type gas-liquid mixer 16 through a liquid path elbow 54 and a vertical downcomer 55; a primary liquid guide pipe 51 is arranged to communicate the declining pipe 2 with the U-shaped liquid collecting pipe 5; a primary liquid guide pipe 52 is arranged to communicate the primary separator 8 with the U-shaped liquid collecting pipe 5; a secondary liquid guide pipe 53 is arranged to communicate the secondary separator 10 with the U-shaped liquid collecting pipe 5; the liquid flow meter 17 is mounted on a vertical downcomer 55; the liquid level meter 56 and the electric control valve 57 are arranged on the U-shaped liquid collecting pipe 5; the liquid level gauge 56 is connected with the electric control valve 57 through a control line 58.

The inclination angle of the declining pipe 2 is 15-40 degrees; the tilt angle of the tilt-up tube 3 is greater than 30 °.

When the liquid level gauge 56 shows that the liquid level in the U-shaped liquid collecting pipe 5 is lower than a set value, the opening of the electric valve 57 is closed to prevent gas from being led into a liquid path; and when the liquid level gauge 56 shows that the liquid level in the U-shaped liquid collecting pipe 5 is higher than the set value, the opening degree of the electric valve is increased so as to reduce the liquid path resistance and ensure that the separated liquid is smoothly discharged.

The primary cyclone 7 and the secondary cyclone 9 are formed by surrounding a central shaft by four to eight spiral blades or straight blades; the inner edge of the blade is connected with the central shaft into a whole; the outer edges of the blades are closely contacted with the inner wall of the pipeline, and no gap exists; the diameter of the central shaft is smaller than 6mm.

As shown in fig. 2, the primary separator 8 is composed of an outer cylinder 81, a first thin-wall inner partition pipe 82 coaxial with the outer cylinder, and a first air duct 83; the inner diameter of the outer cylinder 81 is 8-10 mm larger than the outer diameter of the pipeline; the inner wall of the outer cylinder 81 and the outer wall of the first thin-wall inner partition tube 82 form a first annular liquid discharge cavity 84; the bottom of the first annular drain cavity 84 communicates with the primary catheter 52 through a primary drain hole 86; the outer diameter of the first thin-wall inner separation pipe 82 is smaller than the inner diameter of the pipeline by 3-5 mm, and the inlet section stretches into the upstream pipeline by 5-8 mm; a first liquid film circumferential seam 85 is formed between the outer wall of the first thin-wall inner partition tube 82 and the inner wall of the pipeline; the first air duct 83 is of an inverted L shape, an inlet of the air duct is communicated with the top of the first annular liquid draining cavity 84, and an outlet of the air duct is downward and is positioned at the center of the first thin-wall inner partition 82.

The secondary separator 10 consists of a pipeline 101, a second thin-wall inner partition pipe 102 coaxial with the pipeline 101 and a second air duct 103; the inner wall of the pipeline 101 and the outer wall of the second thin-wall inner partition pipe 102 form a second annular liquid discharge cavity 104; the bottom of the second annular drain cavity 104 is communicated with the secondary liquid guide tube 53 through a secondary drain hole 106; the outer diameter of the second thin-wall inner separation tube 102 is 2-3 mm smaller than the inner diameter of the first thin-wall inner separation tube 82, and the inlet section penetrates into the first thin-wall inner separation tube 82 by 5-8 mm; a second liquid film circumferential gap 105 is formed between the outer wall of the second thin-wall inner separation tube 102 and the inner wall of the first thin-wall inner separation tube 82; the second air duct 103 is in an inverted L shape, an inlet of the second air duct is communicated with the top of the second annular liquid draining cavity 104, and an outlet of the second air duct is downward and is positioned at the center of the second thin-wall inner partition tube 102.

The racemizer 11 is a set of thin flat plates which are arranged in parallel with the axis of the inner pipe of the pipeline, and the thin flat plates are kept at equal intervals.

The gas flow meter 12 is a conventional single-phase gas flow meter, and may be a vortex shedding flow meter, a differential pressure flow meter, a thermal mass flow meter, or an ultrasonic flow meter.

The liquid flowmeter 17 is a conventional single-phase liquid flowmeter, and may be a vortex shedding flowmeter, a differential pressure flowmeter, a coriolis force flowmeter, an ultrasonic flowmeter, or an electromagnetic flowmeter.

As shown in fig. 3, the injection type gas-liquid mixer 16 is a venturi nozzle type, the outer diameter of which is equal to the outer diameter of the pipeline and is fixedly connected with the pipeline by welding or a flange; the ejector gas-liquid mixer 16 is comprised of an upstream constriction 161, a downstream diffuser 162, and a flat throat 163. As a preferred embodiment of the present invention, the upstream contraction section 161 is a conical tube, the diameter of the inlet is larger than that of the outlet, and the included angle between the inner wall and the axis is 10 ° to 23 °; the downstream diffusion section 162 is a conical tube, the diameter of the inlet is smaller than that of the outlet, and the included angle between the inner wall and the axis is 3-7 degrees; the throat 163 is a straight circular tube with a length of about 1-4 times the inner diameter thereof; an annular cavity 1631 is disposed between the inner wall and the outer wall of the throat 163; the outer side of the annular cavity 1631 is communicated with the vertical downcomer 55 through a hole 1632 on the outer wall of the throat 163, and the inner side is communicated with the venturi throat flow channel through a hole 1633 on the inner wall of the throat 163; the holes 1633 on the inner wall of the throat 163 are distributed at equal intervals along the circumferential direction, at least one circle is arranged, and at least two holes are arranged in each circle.

The measurement method of the natural gas moisture real-time measurement device based on the in-pipe phase separation technology comprises the following steps:

firstly, gas-liquid coarse separation:

When the natural gas wet gas flow enters the declining pipe 2 from the inlet of the device through the horizontal inlet pipe 1, most liquid phase or liquid bomb in the slug flow type flows into the bottom of the declining pipe 2 through the primary liquid guide pipe 51 to enter the U-shaped liquid collecting pipe 5, and a small amount of liquid carried by gas phase in the wet gas flow enters the declining pipe 3 after being further dehumidified through the liquid removing effect of the steel wire mesh assembly 4, so that the primary coarse separation of the gas and the liquid of the wet gas flow is completed.

And secondly, completely separating gas from liquid:

Moisture in the upward-inclined pipe 3 flows through the horizontal inlet pipe 6 and then enters the primary cyclone 7, most of liquid phase flows in a liquid film form and clings to the pipe wall under the action of centrifugal force, and gas phase flows in the middle of the pipe, so that the separation state in the pipe is realized; the liquid film and a small amount of gas phase formed after passing through the primary cyclone 7 fall into the first annular liquid discharge cavity 84 through the first liquid film circumferential seam 85, the liquid phase enters the U-shaped liquid collecting pipe 5 from the primary liquid discharge hole 86 through the primary liquid guide pipe 52, and a small amount of gas entering the first annular liquid discharge cavity 84 is discharged into the first thin-wall inner partition pipe 82 through the first gas guide pipe 83 to be converged with the main gas flow; the air flow in the first thin-wall inner separation tube 82 flows through the secondary cyclone 9, liquid drops with smaller particle sizes are separated from the air flow under the action of further centrifugal force, so that the liquid drops flow along the inner wall of the first thin-wall inner separation tube 82 in the form of a liquid film, then a small amount of air is carried into the second annular liquid discharge cavity 104 through the second liquid film circumferential gap 105, the liquid phase enters the U-shaped liquid collecting tube 5 from the secondary liquid discharge hole 106 through the secondary liquid guide tube 53, and a small amount of air is discharged into the second thin-wall inner separation tube 102 through the second air guide tube 103 to be converged with the main air flow;

Thirdly, gas and liquid metering:

after the dry gas from the second thin-wall inner separation tube 102 is racemized by the racemizer 11, the dry gas flows through the gas flowmeter 12 for metering, and the pressure and the temperature of the gas flow are respectively measured by the pressure sensor 13 and the temperature sensor 14 so as to supplement the measured value of the gas flowmeter and improve the measurement accuracy;

the liquid in the U-shaped liquid collecting pipe 5 is measured by a liquid flowmeter 17 on a vertical downcomer 55;

Fourth, mixing gas and liquid:

The air flow after metering enters a venturi jet pipe type injection type gas-liquid mixer 16 through a lower horizontal pipeline 15, and low pressure is generated at the throat part; the metered liquid flows into the gas-liquid mixer 16 under the low pressure of the throat part generated by the gas flow, and the gas-liquid two phases are recombined and then flow out of the measuring device through the horizontal outlet pipe 18.

The invention adopts two-stage separation based on in-pipe phase separation technology and combines a gas-liquid coarse separation system, so that the separation efficiency of gas and liquid in wet gas can be remarkably high, the complete separation of gas and liquid is realized, and the measurement accuracy of measuring the flow of each phase of gas and liquid by using a single-phase flowmeter is further ensured. Meanwhile, the volume of the separator is also greatly reduced, and the real-time performance of moisture measurement is improved. In addition, the moisture measurement device and the moisture measurement method have the advantages of wide applicable flow parameter range, high safety performance and low production and manufacturing cost, and are very suitable for popularization and application in engineering, and particularly are applied to natural gas wellhead measurement in the field of petroleum and natural gas engineering. Of course, in other engineering applications, when multiphase flow problems of high volumetric gas content are involved, the device and method of the present invention can also be used to measure the flow of each phase.

What is not described in detail in this specification is prior art known to those skilled in the art.

Claims (6)

1. Natural gas moisture real-time measurement device based on intraductal phase separation technique, including horizontal import pipe (1), go up horizontal pipeline (6), lower horizontal pipeline (15), horizontal outlet pipe (18), its characterized in that: the system also comprises a gas-liquid coarse separation system, a gas-liquid separation system, a gas metering system, a gas-liquid mixing system and a liquid metering system; the gas-liquid coarse separation system is arranged between the horizontal inlet pipe (1) and the upper horizontal pipeline (6); the gas-liquid separation system and the gas metering system are sequentially arranged on a vertical pipeline between an upper horizontal pipeline (6) and a lower horizontal pipeline (15); the gas-liquid mixing system is arranged between a lower horizontal pipeline (15) and a horizontal outlet pipe (18); the liquid metering system is arranged in parallel between the gas-liquid separation system and the gas-liquid mixing system;

The gas-liquid coarse separation system comprises a declining pipe (2), an ascending pipe (3) and a steel wire mesh assembly (4); one end of the declining pipe (2) is closed, and the other end is connected with the horizontal inlet pipe (1); one end of the upward-tilting pipe (3) is positioned at the inlet side of the downward-tilting pipe (2) and is communicated with the downward-tilting pipe (2), and the other end of the upward-tilting pipe is communicated with the upper horizontal pipeline (6); the steel wire mesh assembly (4) is positioned in the inlet side of the upward-inclined tube (3);

The gas-liquid separation system comprises a primary cyclone (7), a primary separator (8), a secondary cyclone (9) and a secondary separator (10); the primary cyclone (7), the primary separator (8) and the secondary separator (10) are sequentially arranged on a vertical pipeline; the secondary cyclone (9) is arranged inside the primary separator (8);

The primary separator (8) consists of an outer cylinder (81), a first thin-wall inner partition pipe (82) coaxial with the outer cylinder and a first air duct (83); the inner wall of the outer cylinder (81) and the outer wall of the first thin-wall inner separation pipe (82) form a first annular liquid discharge cavity (84); the bottom of the first annular liquid drainage cavity (84) is communicated with the primary liquid guide tube (52) through a primary liquid drainage hole (86); a first liquid film circumferential seam (85) is formed between the outer wall of the first thin-wall inner partition pipe (82) and the inner wall of the pipeline; the first air duct (83) is of an inverted L shape, an inlet of the first air duct is communicated with the top of the first annular liquid discharge cavity (84), and an outlet of the first air duct is downward and is positioned at the center of the first thin-wall inner partition tube (82);

The secondary separator (10) consists of a pipeline (101), a second thin-wall inner partition pipe (102) coaxial with the pipeline (101) and a second air duct (103); the inner wall of the pipeline (101) and the outer wall of the second thin-wall inner partition pipe (102) form a second annular liquid discharge cavity (104); the bottom of the second annular liquid drainage cavity (104) is communicated with the secondary liquid guide tube (53) through a secondary liquid drainage hole (106); a second liquid film circumferential seam (105) is formed between the outer wall of the second thin-wall inner separation tube (102) and the inner wall of the first thin-wall inner separation tube (82); the second air duct (103) is of an inverted L shape, an inlet of the second air duct is communicated with the top of the second annular liquid discharge cavity (104), and an outlet of the second air duct is downward and is positioned at the center of the second thin-wall inner partition tube (102);

The gas metering system comprises a racemizer (11), a gas flowmeter (12), a pressure sensor (13) and a temperature sensor (14); the racemizer (11) and the gas flowmeter (12) are sequentially arranged on the vertical pipeline; the pressure sensor (13) and the temperature sensor (14) are arranged between the racemizer (11) and the gas flowmeter (12);

the gas-liquid mixing system comprises an injection type gas-liquid mixer (16);

The liquid metering system comprises a U-shaped liquid collecting pipe (5), a liquid path elbow (54), a liquid level meter (56) of a vertical downcomer (55), an electric control valve (57) and a liquid flowmeter (17); the U-shaped liquid collecting pipe (5) is connected with the injection type gas-liquid mixer (16) through a liquid path elbow (54) and a vertical downcomer (55); a primary liquid guide pipe (51) is arranged to communicate the declining pipe (2) with the U-shaped liquid collecting pipe (5); a primary liquid guide pipe (52) is arranged to communicate the primary separator (8) with the U-shaped liquid collecting pipe (5); a secondary liquid guide pipe (53) is arranged to communicate the secondary separator (10) with the U-shaped liquid collecting pipe (5); the liquid flow meter (17) is mounted on a vertical downcomer (55); the liquid level meter (56) and the electric control valve (57) are arranged on the U-shaped liquid collecting pipe (5); the liquid level meter (56) is connected with the electric control valve (57) through a control line (58).

2. The in-pipe phase separation technology-based natural gas moisture real-time measurement device according to claim 1, wherein: the inclination angle of the declination pipe (2) is 15-40 degrees; the inclination angle of the upward-inclined pipe (3) is larger than 30 degrees.

3. The device for real-time measurement of natural gas moisture based on intra-tube phase separation technique according to claim 1 or 2, characterized in that: the primary cyclone (7) and the secondary cyclone (9) are formed by surrounding a central shaft by four to eight spiral blades or straight blades; the inner edge of the blade is connected with the central shaft into a whole; the outer edges of the blades are closely contacted with the inner wall of the pipeline, and no gap exists; the diameter of the central shaft is smaller than 6mm.

4. The in-pipe phase separation technology-based natural gas moisture real-time measurement device according to claim 1, wherein: the racemizer (11) is a group of thin flat plates which are arranged in parallel with the axis of the inner pipe of the pipeline; the spacing between the thin flat plates is equal.

5. The in-pipe phase separation technology-based natural gas moisture real-time measurement device according to claim 1, wherein: the injection type gas-liquid mixer (16) is a Venturi nozzle, has the outer diameter equal to the outer diameter of a pipeline, is fixedly connected with the pipeline in a welding or flange mode, and consists of an upstream contraction section (161), a downstream diffusion section (162) and a straight throat section (163); an annular cavity (1631) is arranged between the inner wall and the outer wall of the throat (163), the outer side of the annular cavity (1631) is communicated with the vertical downcomer (55) through a hole (1632) on the outer wall of the throat (163), and the inner side of the annular cavity is communicated with the venturi throat runner through a hole (1633) on the inner wall of the throat (163); the holes (1633) on the inner wall of the throat (163) are distributed at equal intervals along the circumferential direction, at least one circle is arranged, and at least two holes are arranged in each circle.

6. A measurement method using the natural gas moisture real-time measurement device based on the in-pipe phase separation technique according to any one of claims 1 to 5, characterized by comprising the steps of:

firstly, gas-liquid coarse separation:

When natural gas wet gas flow enters the declining pipe (2) from the inlet of the device through the horizontal inlet pipe (1), most liquid phase or liquid bullet in the slug flow type flows into the bottom of the declining pipe (2) under the action of gravity and enters the U-shaped liquid collecting pipe (5) through the primary liquid guide pipe (51), and a small amount of liquid carried by gas phase in the wet gas flow enters the declining pipe (3) after being further dehumidified by the liquid removal action of the steel wire mesh assembly (4), so that the primary coarse separation of the gas and the liquid of the wet gas flow is completed;

And secondly, completely separating gas from liquid:

Moisture in the upward inclined pipe (3) flows through the horizontal inlet pipe (1) and then enters the primary cyclone (7), most of liquid phase flows in the form of a liquid film along the pipe wall under the action of centrifugal force, and gas phase flows in the middle of the pipe; the liquid film and a small amount of gas phase formed after passing through the primary cyclone (7) fall into a first annular liquid discharge cavity (84) through a first liquid film circumferential seam (85), the liquid phase enters a U-shaped liquid collecting pipe (5) from a primary liquid discharge hole (86) through a primary liquid guide pipe (52), and a small amount of gas entering the first annular liquid discharge cavity (84) is discharged into a first thin-wall inner partition pipe (82) through a first gas guide pipe (83) to be combined with main gas flow; the air flow in the first thin-wall inner partition tube (82) flows through the secondary cyclone (9), liquid drops with smaller particle sizes are separated from the air flow under the action of further centrifugal force, so that the liquid drops flow along the inner wall of the first thin-wall inner partition tube (82) in the form of a liquid film, then a small amount of air is carried into the second annular liquid discharge cavity (104) through the second liquid film circumferential gap (105), liquid phase enters the U-shaped liquid collecting tube (5) from the secondary liquid discharge hole (106) through the secondary liquid guide tube (53), and a small amount of air is discharged into the second thin-wall inner partition tube (102) through the second air guide tube (103) to be converged with the main air flow;

Thirdly, gas and liquid metering:

Dry gas from the second thin-wall inner separation tube (102) flows through the gas flowmeter (12) for metering after racemization of the racemizer (11), and the pressure and the temperature of the gas flow are measured through the pressure sensor (13) and the temperature sensor (14) respectively;

The liquid in the U-shaped liquid collecting pipe (5) is metered by a liquid flowmeter (17) on a vertical downcomer (55);

Fourth, mixing gas and liquid:

The air flow after metering enters a venturi jet pipe type injection type gas-liquid mixer (16) through a lower horizontal pipeline (15), and low pressure is generated at the throat part; the liquid after metering flows into the gas-liquid mixer (16) under the action of the low pressure of the throat part generated by the air flow, and the gas-liquid two phases are mixed again and then flow out of the measuring device through the horizontal outlet pipe (18).