CN104236471B - Y-type double FBG fiber optic vibration sensor for online monitoring of coking tower hydraulic decoking - Google Patents

Abstract

The Y-type double FBG optical fiber vibration sensor for on-line monitoring of coking tower hydraulic decoking of the present invention includes a vibration guide rod (2), a heat dissipation structure (3), a Y-type vibration part (4), a sealing shell (5), and a counterweight (6) And the fiber grating, and the connection base (1) supporting the whole sensor, wherein: the contact probe (10) at the left end of the vibration guide rod is in close contact with the wall of the coke tower, the heat dissipation structure is fixed on the vibration guide rod, and the sealing shell passes through the screw port Assembled on the fixing part (11) at the right end of the vibrating guide rod, the counterweight and the Y-shaped vibrating part are located in the sealed casing, the first fiber grating is fixed on the sealed casing after being led out from one end of the Y-shaped vibrating part, and the second fiber grating is drawn from the Y-shaped vibrating part. The other end of the Y-shaped vibrator is drawn out and pre-stretched and fixed on the sealed shell. The invention has the advantages of high response frequency, large measurement range, intrinsic safety, etc., and can pick up the high-frequency vibration signal generated by high-pressure water hitting the tower wall during the hydraulic decoking process, so as to obtain the hydraulic decoking process.

Description

Y-type double FBG fiber optic vibration sensor for online monitoring of coking tower hydraulic decoking

technical field

The invention relates to the field of sensing technology, in particular to a Y-type double FBG optical fiber vibration sensor for on-line monitoring of hydraulic decoking of coking towers in the petrochemical industry.

Background technique

The coking tower is one of the important equipment of the delayed coking unit in the oil refining industry. It is mainly used in the last link of production in petrochemical oil refining enterprises. The principle of hydraulic decoking is to use the powerful impact of high-pressure water jets from the nozzle of the hydraulic coke cutter The coke is cut off by force, and the nozzle of the hydraulic coke cutter moves up and down and rotates in the tower to make the coke in the tower fall off until all the coke in the coking tower is completely removed. At present, in the production process of the domestic petrochemical industry, almost all operators judge whether the coke in the coking tower is removed by observing the turbidity of the coke water in the chute at the bottom of the tower and listening to the sound of the coke cutting process based on work experience. Workers cannot accurately locate changes in the thickness of the focal layer and the position of the nozzle of the coke cutter, resulting in high frequency of repeated coke cutting operations and relatively low work efficiency, and the distance between the chute and the observation window is relatively long, which is less affected by weather conditions and day and night vision For example, in the weather of heavy rain or heavy fog, the operator cannot accurately observe the situation of the chute below, which causes a lot of trouble to the focus cutting work, affects the efficiency and safety of focus cutting, and causes huge power loss , increasing the labor intensity of workers.

In terms of online monitoring of the hydraulic decoking process, there are currently foreign reports that use a quartz tuning fork to measure the sound produced by the high-pressure water hitting the tower wall in the coking tower to judge the hydraulic decoking process. This system can monitor the cleanliness of the decoking process, but cannot monitor the hydraulic The change of coke layer thickness and the position of the nozzle of the coke cutter during the decoking process. In recent years, some units at home and abroad have begun to study the sensing measurement method for online monitoring of the process of hydraulic decoking. Wang Tao and others from East China University of Science and Technology have used quartz crystal sensors to detect vibration signals in the process of hydraulic decoking. Similarly, Luoyang Jianguang Petrochemical Equipment Co., Ltd. also uses piezoelectric vibration sensors to monitor the coke removal status on the tower wall. Because their monitoring methods mainly use piezoelectric crystal sensors to measure tower wall vibration signals, the sensors used are mainly electrical sensors, which are affected by electromagnetic interference and temperature, and the measurement accuracy is not high, and the sensor layout is limited (generally below 8 points) From the experimental results, it is only possible to monitor whether the high-pressure water coming out of the nozzle of the coke cutter hits the coke layer or the inner wall of the coking tower where the coke has been removed. It cannot really monitor the change of the thickness of the coke layer during the hydraulic decoking process. and the more accurate position of the coke cutter nozzle. In terms of technical means, since the electrical sensor is placed on the coking tower integrating various types of electrical equipment, electromagnetic interference is inevitable, and the high temperature of the coking tower will inevitably greatly reduce its measurement accuracy; The sensor needs to adopt explosion-proof and package measures to reduce the impact of temperature, resulting in large volume and high cost. In addition, the multiplexing characteristics of electrical sensors limit the number of points on the tower wall, which cannot truly reflect the change law of the thickness of the focal layer and the focal cut. The more accurate position of the injector nozzle.

Since Morey first used Fiber Bragg Grating (FBG) as a sensing element in 1989, fiber optic sensing technology has received extensive attention and developed rapidly. Compared with traditional sensors, FBG sensors have many advantages such as intrinsic explosion-proof, anti-electromagnetic interference, and long-distance signal transmission. However, up to now, no fiber grating vibration sensor has been applied to the monitoring of the hydraulic decoking process, mainly due to the limitation of the low response frequency of the existing fiber optic vibration sensor.

In order to improve the response frequency and working stability of the fiber grating vibration sensor, Zhang Dongsheng et al. proposed a vertical push-pull sensor; Xu Gang et al. also designed a new type of high-frequency sensor. However, the response frequency of these two sensors is still low (below 3000Hz, and the effective response frequency is below 2000Hz), which cannot meet the requirements of the sensor response frequency for hydraulic decoking process monitoring.

Contents of the invention

The technical problem to be solved by the present invention is to provide a Y-type double FBG optical fiber vibration sensor for on-line monitoring of coking tower hydraulic decoking in view of the above-mentioned defects of the prior art. It solves the problem that the thickness of the coke layer is difficult to distinguish in the monitoring system of the hydraulic decoking of the coking tower. At the same time, the optical fiber sensor can not be affected by temperature, electromagnetic interference, etc., and it is safer and more convenient to use.

The present invention solves its technical problem and adopts the following technical solutions:

The Y-type double FBG optical fiber vibration sensor for online monitoring of coking tower hydraulic decoking provided by the present invention includes a vibration guide rod, a heat dissipation structure, a Y-shaped vibration part, a sealing shell, a counterweight and an optical fiber grating, and a connection base supporting the entire sensor , wherein: the contact probe at the left end of the vibrating guide rod is in close contact with the wall of the coke tower, the heat dissipation structure is fixed on the vibrating guide rod, the sealing shell is assembled on the fixing piece at the right end of the vibrating guiding rod through the screw port, and the sealing shell is equipped with a counterweight and Y-shaped vibrating part, the counterweight is a part of the Y-shaped vibrating part, the first fiber grating is drawn out from one end of the Y-shaped vibrating part and fixed on the sealing shell, and the second fiber grating is drawn out and pre-tensioned from the other end of the Y-shaped vibrating part After being stretched, it is fixed on the sealing shell.

The Y-shaped vibrating element is composed of a strut and two fork-shaped arms fixedly connected to the upper end of the strut, and the lower end of the strut is fixed on the bottom of the sealed shell.

The Y-shaped vibrating element is located 150mm±5mm behind the position of the heat dissipation structure on the vibrating guide rod, which can eliminate the complex motion transmitted by the tower wall and only retain its normal vibration.

The vibration guide rod is composed of a contact probe and a stainless steel round tube, wherein: the contact probe has an arc, which is processed according to the arc of the tower wall; the middle part of the arc of the contact probe is connected to the stainless steel round tube by laser welding.

The heat dissipation structure is composed of several ring-shaped metal sheets, and these ring-shaped metal sheets are fixed on the vibrating guide rod through threads.

The heat dissipation structure reduces the temperature transmitted from the coke drum, so that the working temperature of the FBG optical fiber vibration sensor does not exceed 100°C.

The Y-type dual FBG optical fiber vibration sensor for on-line monitoring of coking tower hydraulic decoking in the present invention has a response frequency that is inversely proportional to the mass m of the counterweight body and proportional to the vibration position vector of the counterweight body.

The present invention can increase the response frequency of the FBG optical fiber vibration sensor of the present invention to 3000-5000 Hz by adjusting the mass and vibration potential vector of the weight body.

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

1. The Y-shaped vibrating part has a high response frequency, a large measurement range, and eliminates the influence of temperature on the experimental results; through the design of the Y-shaped vibrating part, the vibration interference in other directions is eliminated, and only the normal vibration is retained, so the focal layer can be accurately determined changes in thickness;

2. High sensitivity and high response frequency can be obtained by adjusting the mass of the counterweight in the Y-type dual FBG fiber optic sensor and the vibration vector of the Y-type vibrating element;

3. The vibration guide rod is in close contact with the coking tower wall, which facilitates the precise transmission of vibration;

4. The heat dissipation structure eliminates the influence of the temperature of the coking tower wall on the sensor;

5. The state of hydraulic defocusing can be obtained by measuring the optical signal change of the fiber grating, and the operation is more convenient;

Description of drawings

Figure 1 shows the overall structure of the Y-type double FBG fiber optic vibration sensor for monitoring the hydraulic decoking condition of the coking tower.

In the figure: 1. Connection base; 2. Vibration guide rod; 3. Heat dissipation structure; 4. Y-shaped vibrating part; 5. Sealed shell; Fiber; 10. Contact probe; 11. Fixing piece.

detailed description

The structure and realization principle of the sensor of the present invention will be further described below in conjunction with the accompanying drawings.

The Y-type double FBG optical fiber vibration sensor (hereinafter referred to as the sensor) for online monitoring of coking tower hydraulic decoking provided by the present invention has a structure as shown in Figure 1, including a connection base 1, a vibration guide rod 2, a heat dissipation structure 3, and a Y-type Vibrator 4, sealing shell 5, counterweight 6, fiber grating 7, fiber grating 8, pigtail 9, contact probe 10, and fixing piece 11, wherein: the connection base 1 is used for the installation and fixing of the entire sensor, and the connection base The seat 1 closely contacts the contact probe 10 at the left end of the vibrating guide rod 2 with the wall of the coke tower. The heat dissipation structure 3 is fixed on the vibrating guide rod 2 . The sealing shell 5 is assembled on the fixing part 11 at the right end of the vibrating guide rod 2 through a screw. The Y-shaped vibrating element 4 with the counterweight 6 is fixed on the sealing shell 5 of the sensor, and the fiber grating 8 is fixed on the sealing shell 5 through one end of the Y-shaped vibrating element 4 . The fiber grating 7 is led out from the other end of the Y-shaped vibrating element 4, and the fiber grating 7 is fixed on the sealing shell 5, and pre-stretched to a certain extent, and then the components are packaged in sequence, and the preparation work is completed.

The connection base 1 is composed of a chassis, a bracket, and a ring-shaped fixing member connected in sequence, wherein: the chassis is connected to the ground, and the ring-shaped fixing member penetrates into the vibration guide rod 2 and is fixedly connected through the side wings of the vibration guide rod. The two ends of the bracket are respectively connected with the chassis and the ring-shaped fasteners by welding.

Described vibrating guide bar 2 is a kind of is made up of contact probe 10 and stainless steel round pipe, wherein: one end (left side) of contact probe 10 has arc, and this arc is processed according to tower wall radian; One end is connected to the stainless steel round tube by laser welding to reduce the distortion of vibration in transmission and improve the accuracy of measurement. The rod body of the vibrating guide rod 2 passes through the annular fixing part connecting the base 1, and the fixing part 11 at the right end of the rod body is connected with the sealing shell 5 through a screw port.

The heat dissipation structure 3 is fixedly connected with the rod body of the vibrating guide rod 2 through threads. The heat dissipation structure 3 is composed of several circular metal sheets, and these circular metal sheets are fixed on the vibrating guide rod through threads.

The sealing shell 5 is provided with a counterweight 6 and a Y-shaped vibrating element 4 .

The Y-shaped vibrating element 4 is composed of a strut and two fork-shaped arms fixedly connected to the upper end of the strut, and the lower end of the strut is fixed on the bottom of the sealing shell 5 .

The counterweight 6 is a part of the Y-shaped vibrating part 4, and the two arms of the Y-shaped vibrating part 4 increase the arm length when the fiber grating is forced to vibrate, which enhances the sensitivity of the sensor, but then the response frequency decreases, which is reduced by the counterweight. The center of gravity of the Y-shaped vibration member 4 is to enhance its response frequency, so as to achieve the high technical index of high response frequency and high sensitivity of the sensor.

Described optical fiber grating comprises optical fiber grating 7 and optical fiber grating 8, wherein: after optical fiber grating 7 is drawn from the end of an arm of Y-shaped vibrator 4, its lower end is fixed on the sealing shell 5, and is pre-stretched to a certain extent . After the fiber grating 8 is drawn out from the end of the other arm of the Y-shaped vibrator 4 , its lower part is fixed on the sealing shell 5 , and its pigtail 9 passes through the bottom of the sealing shell 5 . The pigtail 9 is connected to the demodulation system through an external junction box.

According to elastic mechanics and optical fiber sensing theory, the present invention designs a Y-type double FBG optical fiber vibration sensor as shown in Figure 1, and the smart design of the structure and the selection of structural materials and grating length are carried out to the sensor. According to the vibration model Deduce the relationship between the vibration frequency and amplitude of the fiber grating vibration sensor and the fixed length of the two points of the optical fiber, the mass of the counterweight, the angle and size of the Y-shaped sensitivity compensation structure, and the tension of the optical fiber to achieve the dual excellence of high-frequency vibration and high sensitivity Selection, because the nature of the sensor itself is closely related to the quality of the vibrator and the elastic modulus of the elastic structure. With the vibration of the counterweight 6, the wavelengths of the fiber grating 7 and the fiber grating 8 drift accordingly, and the reflected light intensity changes with the change of the reflected wavelength difference of the grating, which is a linear relationship within a certain range and is consistent with the change rule of the object vibration . After the counterweight 6 is fixed, the vibration in the vertical direction of the vibration guide bar can be eliminated, and the normal high-frequency vibration generated by the high-speed water jet hitting the tower wall can be retained. With the swing of the counterweight 6 in the horizontal direction, the wavelength of the fiber grating drifts, and the reflected light intensity changes with the change of the wavelength drift, which is linear in a certain range and consistent with the vibration law of the furnace wall.

The working principle of the present invention is: the vibrating guide rod 2 with an arc-shaped contact probe in front is in close contact with the coking tower wall, and under the impact of high-pressure water jet, the coking tower wall generates local vibration, and the vibration signal of the coking tower will pass through the vibrating guide rod It acts on the fiber grating to change the optical signal reflected by the high-frequency vibration sensor of the fiber grating, and judges the state of the hydraulic defocusing by measuring the change of the signal.

Claims (8)

1. A Y-type double FBG fiber optic vibration sensor for on-line monitoring of hydraulic decoking of a coking tower, characterized in that it includes a vibration guide rod (2), a heat dissipation structure (3), a Y-shaped vibrating member (4), and a sealed shell (5) , a counterweight (6) and a fiber grating, and a connection base (1) supporting the entire sensor, wherein: the contact probe (10) at the left end of the vibration guide rod (2) is in close contact with the coke tower wall, and the heat dissipation structure (3) It is fixed on the vibrating guide rod (2), and the sealing shell (5) is assembled on the fixing part (11) at the right end of the vibrating guiding rod (2) through the screw port, and the sealing shell (5) is equipped with a counterweight (6) and a Y-shaped The vibrating element (4), the counterweight body (6) is a part of the Y-shaped vibrating element (4), and the first fiber grating (8) is fixed on the sealing shell (5) after being led out from one end of the Y-shaped vibrating element (4). The second optical fiber grating (7) is drawn out from the other end of the Y-shaped vibrator (4) and fixed on the sealing shell (5) after being pre-stretched. 2. The Y-type double FBG fiber optic vibration sensor for on-line monitoring of coking tower hydraulic decoking according to claim 1, is characterized in that said Y-type vibrating part (4) is fixedly connected with the upper end of the support rod by a support rod in the form of Two arms arranged in a fork shape are formed, and the lower end of the pole is fixed on the bottom of the sealing shell (5). 3. the Y-type double FBG fiber optic vibration sensor of coking tower hydraulic decoking on-line monitoring according to claim 2 is characterized in that said Y-type vibrating part (4) is positioned at the cooling structure (3) on the vibrating guide rod (2) ) at 150mm±5mm behind the position, which can eliminate the complex motion transmitted by the tower wall and only retain its normal vibration. 4. The Y-type double FBG optical fiber vibration sensor for on-line monitoring of coking tower hydraulic decoking according to claim 1, is characterized in that said vibration guide rod (2) is made up of contact probe (10) and stainless steel round pipe, wherein: The contact probe (10) has an arc, which is processed according to the radian of the tower wall; the arc middle part of the contact probe (10) is connected with the stainless steel round pipe by laser welding. 5. The Y-type double FBG fiber optic vibration sensor for on-line monitoring of coking tower hydraulic decoking according to claim 1, is characterized in that the heat dissipation structure (3) is made up of several annular metal sheets, and these annular The metal sheet is fixed on the vibrating guide rod through threads. 6. The Y-type double FBG optical fiber vibration sensor for on-line monitoring of coking tower hydraulic decoking according to claim 5, is characterized in that the heat dissipation structure (3) reduces the temperature delivered by the coke tower to make the FBG optical fiber vibrate The operating temperature of the sensor does not exceed 100°C. 7. the Y-type double FBG fiber optic vibration sensor of coking tower hydraulic decoking on-line monitoring according to claim 1 is characterized in that: the response frequency of this FBG fiber optic vibration sensor is inversely proportional to the quality m of counterweight body (6), and The vibration position vector of the counterweight is proportional. 8. The Y-type double FBG fiber optic vibration sensor for on-line monitoring of coking tower hydraulic decoking according to claim 7, is characterized in that: by adjusting the quality and the vibration potential vector of the counterweight (6), the FBG fiber optic vibration sensor The response frequency is increased to 3000-5000Hz.