A radio frequency moisture content measuring instrument and method under cyclonic state

Abstract

The present invention belongs to the technical field of measuring the water content of crude oil, and specifically relates to a radio frequency water content measuring instrument and method under a cyclonic state. A radio frequency water content measuring instrument under a cyclonic state comprises a casing, one end of which is horizontally connected to the cyclone, and the other end is vertically connected to the conduit; a radio frequency signal processing module and a communication wire protective cover are arranged on the outside of the casing, and the communication wire protective cover supplies power to the radio frequency signal processing module and transmits signals through internal wires; a radio frequency antenna connected to the radio frequency signal processing module is arranged inside the casing; the radio frequency signal processing module comprises an embedded single chip microcomputer, a signal source generator, a signal amplifier, a data detection module and a data acquisition card. The present invention uses a cyclonic state to measure the water content, which is less affected by unstable oil-water distribution and has more accurate measurement results. The detachable component design of the present invention can clean wax and scale on the antenna surface in time, and it is convenient to replace components, which can extend the service life.

Description

Technical Field

[0001] The invention belongs to the technical field of crude oil water content measurement, and in particular relates to a radio frequency water content measuring instrument and method under a cyclonic state. Background Art

[0002] The measurement of water content in crude oil has always been an important part of three-phase flow measurement technology. At present, the measurement technology of water content in crude oil is mainly divided into two categories: one is the manual measurement method, also known as the offline measurement method, which mainly includes the distillation method, the electro-desorption method and the Karl Fischer method; the other is the electrical measurement method, also known as the online measurement method, which mainly includes the conductivity method, the ray method, the capacitance method, the electromagnetic method and the radio frequency method.

[0003] At present, due to various unstable factors and imperfections in online measurement methods, manual measurement is still the main method for measuring water content in crude oil in the production line. The distillation method is mainly based on the difference in boiling points of different mixtures in the output fluid. After heating, cooling and condensation, the water content value in the output fluid is obtained. The main disadvantage of the distillation method is that due to the limitations of actual production conditions, the single sampling volume is small and the sampling cycle is long, which makes the test results unrepresentative and less convincing. The electro-desorption method and the Karl Fischer method also have the above problems, and the cost is high. Therefore, the current actual production is facing a dilemma. The manual method has accurate and high precision measurement results, but it is not representative and labor-intensive; the online method is convenient and timely, but the error is large and cannot meet the requirements of actual production. It will take some time to promote and apply it. Therefore, the research on the measurement technology of water content in crude oil urgently needs to be broken through and solved. Summary of the invention

[0004] In view of the above problems, the present invention provides a radio frequency moisture content measuring instrument and method under cyclonic state.

[0005] The first object of the present invention is to provide a radio frequency moisture content measuring instrument under a cyclonic state, comprising a sleeve, one end of the sleeve is horizontally connected to the cyclone, and the other end is vertically connected to the conduit; a radio frequency signal processing module and a communication wire protection cover are arranged outside the sleeve, and the communication wire protection cover supplies power to the radio frequency signal processing module and transmits signals through internal wires; a radio frequency antenna connected to the radio frequency signal processing module is arranged inside the sleeve; the radio frequency signal processing module comprises an embedded single-chip microcomputer, a signal source generator, a signal amplifier, a data detection module and a data acquisition card.

[0006] Furthermore, the radio frequency antenna is threadedly connected to the sleeve, and the radio frequency antenna is fixed at the axis of the sleeve by a fixer.

[0007] Furthermore, the structure of the RF antenna from outside to inside is a polytetrafluoroethylene antenna protection cover and a silver-plated copper core. One end of the RF antenna is provided with an external thread base, and the external thread base is provided with an internal feeding hole.

[0008] The second object of the present invention is to provide a method for measuring radio frequency moisture content under a cyclonic state, comprising the following steps:

[0009] S1, connect the cyclone end of the measuring instrument to the crude oil pipeline, pass the crude oil with known water content through the cyclone for measurement, and the crude oil will form a two-phase flow with oil as the inner ring and water as the outer ring through the casing after the cyclone.

[0010] S2, the RF antenna generates a 40MHz-50MHz RF signal under the action of the signal source generator and the signal amplifier of the RF signal processing module, and acts on the two-phase flow generated in step S1;

[0011] S3, the data detection module of the RF signal processing module detects the RF signal after passing through the crude oil, and inputs it into the receiving circuit in the RF signal processing module, obtains the voltage value across the measuring resistor, and records it in the data acquisition card;

[0012] S4, repeating the operations of S1 to S3 for multiple groups of crude oils with different water contents, and measuring the voltage values ​​corresponding to the different water contents;

[0013] S5, establishing a corresponding relationship between the measured voltage value data and the known water content of the crude oil, and fitting a water content prediction curve;

[0014] S6, repeating the operations of S1 to S3 for the crude oil whose water content is to be measured, calibrating the measured voltage value with the water content prediction curve obtained in S5, obtaining the water content value and outputting it for display.

[0015] The present invention has the following beneficial effects:

[0016] First, the radio frequency method for measuring the water content in crude oil is an effective method for measuring the water content in crude oil. Its measurement principle is based on the radio frequency impedance theory of the medium. It takes the water-containing crude oil as the dielectric and reflects the water content in the crude oil by measuring the change in the impedance characteristics of the oil-water mixture to the radio frequency signal. It has the advantages of high measurement accuracy, stable and reliable operation, and easy installation, which facilitates the online measurement of the water content in crude oil.

[0017] Secondly, the water content is measured by using the cyclone state. The oil and water are separated into layers under the cyclone cyclone, with the oil density being smaller and forming an outer ring, and the water density being larger and forming an inner ring. There will not be too much oil-water mixing to cause uneven distribution of capacitance, so the water content measuring instrument in the cyclone state is more accurate in value and less affected by unstable oil-water distribution.

[0018] Third, the detachable parts design can clean the wax and scale on the antenna surface in time, making it easy to replace parts and extend the service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1This is a schematic diagram of the three-dimensional structure of the measuring instrument provided by the present invention.

[0020] Figure 2 The present invention is a schematic cross-sectional view of the measuring instrument provided by the present invention.

[0021] Figure 3 Schematic diagram of the working process of the RF signal processing module.

[0022] Figure 4 It is a schematic cross-sectional view of the radio frequency antenna of the present invention.

[0023] Figure 5 It is a schematic diagram of the front view structure of the fixer of the present invention.

[0024] Figure 6 This is a flow chart of a method for measuring radio frequency moisture content under cyclonic state provided by the present invention.

[0025] Figure 7 It is a fitted moisture content-voltage value corresponding curve in step S5 of a radio frequency moisture content measurement method under a cyclonic state provided by the present invention.

[0026] Figure 8 This is a schematic diagram of the cross section of the crude oil in the casing after the swirl effect.

[0027] Among them: sleeve 1, radio frequency signal processing module 2, fixture 3, communication wire protection cover 4, radio frequency antenna 5, threaded port 6, antenna protection cover 7, silver-plated copper core 8, external thread base 9, internal feed hole 10, cyclone 11. DETAILED DESCRIPTION

[0028] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0029] like Figures 1-2 As shown, a radio frequency moisture content measuring instrument under cyclonic state comprises a sleeve 1, one end of the sleeve 1 is horizontally connected to the cyclone 11, and the other end is vertically connected to the conduit 1.1; a radio frequency signal processing module 2 and a communication wire protection cover 4 are arranged on the outside of the sleeve 1, and the communication wire protection cover 4 supplies power and transmits signals to the radio frequency signal processing module 2 through internal wires; a radio frequency antenna 5 connected to the radio frequency signal processing module 2 is arranged inside the sleeve 1; the radio frequency signal processing module 2 comprises an embedded single chip microcomputer, a signal source generator, a signal amplifier, a data detection module and a data acquisition card.

[0030] like Figure 3As shown, the RF signal processing module 2 is composed of an embedded single-chip microcomputer STM32F407 as the core, equipped with a signal source module AD9851 as a signal source generator, and uses an AD8310 signal amplifier to perform logarithmic amplification of the signal to provide an output frequency of 0MHz-70MHz to the RF antenna. At the same time, the receiver uses an instrument amplifier with two sections of measuring resistance and resistance for data detection of the RF outgoing signal and outputting a DC voltage, and a data acquisition card for recording data.

[0031] The diameter of the steel casing 1 is 25.4 mm, and the left side is connected to the cyclone 11. The cyclone 11 of different specifications is selected according to the required performance. The upper part of the steel casing 1 is provided with a radio frequency signal processing module 2 and a communication wire protection cover 4. The communication wire protection cover 4 supplies power and transmits signals to the radio frequency signal processing module 2 through internal wires. The specific size of the radio frequency signal processing module 2 is determined according to the selected communication module.

[0032] The radio frequency antenna 5 is screwed into the threaded opening on the right side of the steel sleeve 1 and fixed at the axis of the sleeve 1 by the fixer 3 .

[0033] like Figure 4 As shown, the RF antenna 5 is 210 mm long. The structure of the RF antenna 5 from outside to inside is a polytetrafluoroethylene antenna protection cover 7 and a silver-plated copper core 8. One end of the RF antenna 5 is provided with an external thread base 9, and the external thread base 9 is provided with an internal feed hole 10. The polytetrafluoroethylene antenna protection cover 7 has an outer diameter of 8 mm and a length of 203 mm; the internal silver-plated copper core 8 has a length of 200 mm and an outer diameter of 7 mm as a feed antenna; the external thread base 9 at the right tail has a length of 10 mm and an outer diameter of 10 mm, and the outer circle has threads corresponding to the threaded opening 6 of the pipe part, and the internal feed hole 10 at the axis has a diameter of 2 mm, which is used to power the RF antenna 5 and connect an external RF signal source.

[0034] Figure 5 The 3D structure diagram of the fixture 3 is shown in FIG. The center of the fixture 3 is a hollow circular ring with a diameter of 8 mm and a width of 1 mm. The outer side is composed of three rectangular brackets with a width of 1 mm and a length of 7.8 mm. The three brackets divide the circle into three equal parts. When the RF antenna 5 is installed, it passes through the axis of the fixture 3 to stabilize the antenna in the vortex.

[0035] like Figure 6 As shown, a method for measuring moisture content by a radio frequency moisture content measuring instrument under a cyclonic state comprises the following steps:

[0036] S1, connect the cyclone 11 end of the measuring instrument to the crude oil pipeline, pass the crude oil with known water content through the cyclone 11 for measurement, and the crude oil will form a two-phase flow with oil as the inner ring and water as the outer ring through the casing 1 after the action of the cyclone 11;

[0037] S2, the RF antenna 5 generates a 40MHz-50MHz RF signal under the action of the signal source generator and the signal amplifier of the RF signal processing module 2, and acts on the two-phase flow generated in step S1;

[0038] S3, the data detection module of the RF signal processing module 2 detects the RF signal after passing through the crude oil, and inputs it into the receiving circuit in the RF signal processing module 2, obtains the voltage value across the measuring resistor, and records it in the data acquisition card;

[0039] S4, repeating the operations of S1 to S3 for multiple groups of crude oils with different water contents, and measuring the voltage values ​​corresponding to the different water contents;

[0040] S5, establish a corresponding relationship between the measured voltage value data and the known crude oil water content, and fit the water content prediction curve (such as Figure 7 shown);

[0041] S6, repeating the operations of S1 to S3 for the crude oil whose water content is to be measured, calibrating the measured voltage value with the water content prediction curve obtained in S5, obtaining the water content value and outputting it for display.

[0042] Figure 8 It is a schematic diagram of the cross section of crude oil in casing 1 after cyclone action, and the central circle is the RF antenna. The outer interface of the RF antenna to the oil-water interface and the oil-water interface to the inner wall of the pipeline are regarded as two different cylindrical capacitors, r is the antenna radius, r0 is the radius of the oil section in the pipe, i.e. the oil-water interface position, R is the inner diameter of the pipeline, the antenna length is L, and the water content is D.

[0043] The cross-sectional area of ​​the annular oil is S 油 , the cross-sectional area of ​​the annular water is S 水 , the cross-sectional area of ​​the antenna is S 天 , the overall liquid cross-sectional area of ​​the pipeline is S 液 .

[0044] but

[0045]

[0046] S 液 =πR 2 -S 天 =π(R 2 -r 2 ) (2)

[0047] S 油 =S 液 -S 水 =(1-D)S 液 (3)

[0048] Where: V 水 V is the volume of pure water in the tube;液 is the volume of all liquid in the tube; l 管 is the measuring instrument pipeline length.

[0049] again

[0050] S 油 =πr0 2 -πr 2 (4)

[0051] According to equations (2) to (4), we can obtain:

[0052]

[0053] According to the cylinder capacitance calculation formula:

[0054]

[0055]

[0056] Where: C 天线-油 is the capacitance between the antenna and the oil-water interface; C 油-水 is the capacitance between the oil-water interface and the inner wall of the pipeline; L 天 is the antenna length; ε0 is the vacuum dielectric constant, which is approximately 8.854187817×10 -12 F / m; ε 油 is the dielectric constant of oil; ε 水 is the dielectric constant of water.

[0057] The two capacitors combined inside and outside can be regarded as series capacitors, and the total capacitance C is calculated as follows:

[0058]

[0059] When the RF signal penetrates the medium, the total system impedance Z is:

[0060]

[0061] R 接 is the equivalent resistance of the receiving sensor, f is the transmitting frequency of the RF antenna, C is the total capacitance, Z is the total system impedance, and J is a complex number, a purely mathematical symbol with no actual physical meaning.

[0062] When the system impedance is determined, the current in the receiver is:

[0063]

[0064] I is the current in the receiver and U is the overall voltage.

[0065] Adding the sense resistor R 测 After that, the detection resistor R测 The voltage across the terminals is:

[0066] U 测 =IR 测 (11)

[0067] U 测 To measure the voltage across a resistor, R 测 To measure the resistance of a resistor.

[0068] Due to the different water content D, the oil and water are separated after the swirl, and the oil cross-sectional radius r0 changes, which leads to the change of the two-part cylindrical capacitance value and the total capacitance, so the system current in the receiver changes. Since the frequency and length of the RF antenna are constants, the RF generator and the receiver voltage are fixed, so the voltage value U across the measuring resistor corresponds to the water content D of the oil used, and the water content is obtained by adjusting the coefficient.

[0069] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A method for measuring moisture content with a radio frequency moisture content measuring instrument under a cyclonic state, characterized in that: The radio frequency moisture content measuring instrument under the cyclonic state comprises a sleeve (1), one end of the sleeve (1) being horizontally connected to the cyclone (11), and the other end being vertically connected to the conduit (1.1); a radio frequency signal processing module (2) and a communication wire protection cover (4) are arranged outside the sleeve (1), and the communication wire protection cover (4) supplies power to the radio frequency signal processing module (2) and transmits signals through internal wires; a radio frequency antenna (5) connected to the radio frequency signal processing module (2) is arranged inside the sleeve (1); the radio frequency signal processing module (2) comprises an embedded single chip microcomputer, a signal source generator, a signal amplifier, a data detection module and a data acquisition card; The method for measuring moisture content comprises the following steps: S1, connecting the cyclone (11) end of the measuring instrument to the crude oil pipeline, passing crude oil with a known water content through the cyclone (11) for measurement, and the crude oil passing through the cyclone (11) forms a two-phase flow with oil as an inner ring and water as an outer ring and passes through the casing (1); S2, the radio frequency antenna (5) generates a 40 MHz to 50 MHz radio frequency signal under the action of the signal source generator and the signal amplifier of the radio frequency signal processing module (2), and acts on the two-phase flow generated in step S1; S3, the data detection module of the radio frequency signal processing module (2) detects the radio frequency signal after passing through the crude oil, and inputs it into the receiving circuit in the radio frequency signal processing module (2), obtains the voltage value across the measuring resistor, and records it in the data acquisition card; S4, repeating the operations of S1 to S3 for multiple groups of crude oils with different water contents, and measuring the voltage values ​​corresponding to the different water contents; S5, establishing a corresponding relationship between the measured voltage value data and the known water content of the crude oil, and fitting a water content prediction curve; S6, repeating the operations of S1 to S3 for the crude oil whose water content is to be measured, calibrating the measured voltage value with the water content prediction curve obtained in S5, obtaining the water content value and outputting it for display.

2. The method for measuring moisture content by a radio frequency moisture content measuring instrument under cyclonic flow state according to claim 1, characterized in that: The radio frequency antenna (5) is threadedly connected to the sleeve (1), and the radio frequency antenna (5) is fixed at the axis of the sleeve (1) by a fixer (3).

3. The method for measuring moisture content by a radio frequency moisture content measuring instrument under cyclonic state according to claim 2, characterized in that: The structure of the radio frequency antenna (5) from outside to inside is a polytetrafluoroethylene antenna protection cover (7) and a silver-plated copper core (8). An external thread base (9) is provided at one end of the radio frequency antenna (5), and the external thread base (9) is provided with an internal feeding hole (10).

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