Air preheater stall protection device

Abstract

An embodiment of the present invention provides an air preheater stall protection device, comprising an air preheater body, a driven gear coaxially arranged on the main shaft of the air preheater body, at least one inductive proximity switch arranged circumferentially of the driven gear, a pulse counting module for receiving the output signal of the inductive switch, and a control module for controlling and outputting an alarm signal. This method uses an inductive proximity switch in conjunction with a pulse counting module to monitor the rotation state of the main shaft of the air preheater. An inductive proximity switch is a low-cost method for non-contact detection of metal objects. When a metal object moves toward or out of the proximity switch, the signal automatically changes, thereby achieving the purpose of detection. It has the characteristics of no contact, low power consumption, long service life, high response frequency, oil and dust resistance, etc., and can work reliably in various harsh environments.

Description

Technical Field

[0001] The invention relates to the technical field of air preheater stall protection, in particular to an air preheater stall protection device. Background Art

[0002] The air preheater is a heating surface that preheats the air before entering the boiler to a certain temperature through the internal heat sink in the flue gas at the tail end of the boiler. It is a device used to improve the heat exchange performance of the boiler and reduce energy consumption. The power station boiler usually adopts the rotary preheating of the heating surface. Its working principle is that the air preheater rotates slowly during operation, and the flue gas will enter the flue gas side of the air preheater and then be discharged. The heat carried by the flue gas will be absorbed by the heat sink in the air preheater. After that, the air will rotate slowly with the preheater, and the heat sink will move to the air side and transfer the heat to the air before entering the boiler. During the operation of the unit, the air preheater will stop rotating, which will cause the internal temperature field to expand freely with uneven sizes, and the shell and sealing sheet will also deform. At the same time, due to the sudden cooling of the rotor, the radial partition of the air preheater will be permanently deformed and the weld will crack. The high-temperature flue gas will directly enter the electrostatic precipitator, induced draft fan, and desulfurization absorption tower, which will reduce the efficiency of the electrostatic precipitator and damage the components of the absorption tower, seriously endangering the equipment and production safety. Therefore, the power plant will set up air preheater stall protection. The stall of one-side air preheater will interlock RB action, and the stall of both sides of the air preheater will trigger MFT protection action to protect the equipment from damage.

[0003] At present, the main way to directly measure the rotation of rotating equipment is to use inductive sensors, including variable reluctance and eddy current types. The rotation of the main shaft of the air preheater has the following characteristics: 1. The speed is slow, only 0.23rpm-0.99rpm. 2. The environment is harsh and the dust is large on site. 3. As the main auxiliary equipment, its speed protection needs to be set up redundantly to improve reliability. If the conventional method is used to measure the speed of the main shaft of the air preheater for stall protection, firstly, the measurement accuracy is a problem due to the low speed; secondly, due to the large dust on site, the measurement of the inductive sensor will be affected, affecting the reliability of the equipment; thirdly, the inductive sensor is expensive, and the price of a single probe ranges from 3,000 yuan to 20,000 yuan in the market. In addition, the price of the speed detection module of the distributed control system is about 50,000 yuan. If redundant settings are used, it will cause a large economic cost. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides an air preheater stall protection device, and the specific technical solution is as follows:

[0005] An embodiment of the present invention provides an air preheater stall protection device, comprising an air preheater body, a driven gear coaxially arranged on the main shaft of the air preheater body, at least one inductive proximity switch arranged circumferentially of the driven gear, a pulse counting module for receiving an output signal of the inductive switch, and a control module for controlling and outputting an alarm signal.

[0006] Furthermore, the number of the inductive proximity switches is 1-5.

[0007] Furthermore, the number of the pulse counting modules is 3, and each of the pulse counting modules is respectively connected to 1 or 2 of the inductive proximity switches.

[0008] Furthermore, the control module is a programmable controller.

[0009] Furthermore, each of the inductive proximity switches is arranged on a side of the driven gear that is not transmission-connected to the power output structure.

[0010] An embodiment of the present invention provides an air preheater stall protection device, comprising an air preheater body, a driven gear coaxially arranged on the main shaft of the air preheater body, at least one inductive proximity switch arranged circumferentially of the driven gear, a pulse counting module for receiving an output signal of the inductive switch, and a control module for controlling and outputting an alarm signal.

[0011] The method uses an inductive proximity switch in conjunction with a pulse counting module to monitor the rotation state of the main shaft of the air preheater. The inductive proximity switch is a low-cost method for non-contact detection of metal objects. When the metal object moves toward or out of the proximity switch, the signal will automatically change, thereby achieving the purpose of detection. It has the characteristics of no contact, low power consumption, long service life, high response frequency, oil and dust resistance, and can work reliably in various harsh environments. Because the state change of the inductive proximity switch is actually reflected in the output as a change in current / voltage (about 5V), conventional switch quantity and analog quantity input modules are not applicable. A pulse counting module can be selected to accept the voltage change, thereby obtaining the rotation state of the main shaft of the air preheater. In order to ensure the stability and reliability of the protection, a configuration mode of three out of two or five out of three can be used to trigger the air preheater stop protection. The present invention detects the rotation state of the main shaft of the air preheater by using a low-cost inductive proximity switch in conjunction with a pulse counting module, and designs a logic algorithm to reliably monitor the rotation state of the air preheater. This method is low-cost. A set of measuring equipment costs less than 20,000 yuan, which only accounts for a quarter of the detection method of the inductive sensor. Redundancy can be set to improve protection reliability. At the same time, it is more suitable for harsh environments such as air preheaters with a lot of dust and oil, greatly extending the life of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0013] Figure 1 A connection diagram of an air preheater stall protection device provided in an embodiment of the present invention.

[0014] Figure 2 A logical configuration diagram of a control module provided in an embodiment of the present invention.

[0015] Reference numerals:

[0016] 1 main shaft, 2 driven gear, 3 inductive proximity switch, 4 pulse counting module, 5 control module, 6 alarm signal. DETAILED DESCRIPTION

[0017] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and understandable, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0018] Example 1

[0019] See also Figure 1 , Figure 2 An embodiment of the present invention provides an air preheater stall protection device, including an air preheater body, a driven gear 2 is coaxially arranged on the main shaft 1 of the air preheater body, at least one inductive proximity switch 3 is circumferentially arranged on the driven gear 2, and also includes a pulse counting module 4 for receiving the output signal of the inductive switch, and a control module 5 for controlling and outputting an alarm signal 6.

[0020] It should be noted that the inductive proximity switch 3 consists of three parts: an oscillator, a switching circuit and an amplifier output circuit. The oscillator generates an alternating magnetic field. When a metal target approaches this magnetic field and reaches the sensing distance, eddy currents are generated in the metal target, causing the oscillation to attenuate and even stop. The changes in the oscillation and stop of the oscillator are processed by the post-amplifier circuit and converted into a switching signal, triggering the drive control device, thereby achieving the purpose of non-contact detection. The working principle of the above-mentioned inductive proximity switch 3 is as follows: When a metal or semiconductor sheet with current flowing through it is placed vertically in a magnetic field, a potential difference will be generated at both ends of the sheet. This phenomenon is called the Hall effect. The potential difference between the two ends is called the Hall potential U, and its expression is: U = K·I·B / d

[0021] Where K is the Hall coefficient, I is the current passing through the thin film, B is the magnetic induction intensity of the external magnetic field (Lorentz force), and d is the thickness of the thin film.

[0022] It can be seen from this that the sensitivity of the Hall effect is proportional to the magnetic induction intensity of the external magnetic field.

[0023] The Hall switch is such an active magnetoelectric conversion device. It is made based on the Hall effect principle and uses integrated packaging and assembly technology. It can easily convert magnetic input signals into electrical signals for practical applications, while also meeting the requirements of easy operation and reliability for practical applications in industrial situations.

[0024] The input end of the Hall switch is characterized by the magnetic induction intensity B. When the B value reaches a certain level (such as B1), the trigger inside the Hall switch flips, and the output level state of the Hall switch also flips. The output end generally uses transistor output, which is similar to other sensors and can be divided into NPN, PNP, normally open, normally closed, latch (bipolar), and dual signal output.

[0025] Hall switches have the characteristics of no contact, low power consumption, long service life, high response frequency, etc. The interior is sealed with epoxy resin to form an integrated whole, so it can work reliably in various harsh environments. Hall switches can be used in proximity sensors, pressure sensors, odometers, etc. as a new type of electrical accessories.

[0026] Principle of Linear Proximity Sensor

[0027] The linear proximity sensor is a linear device that senses metal. When the power is turned on, an alternating magnetic field will be generated on the sensing surface of the sensor. When a metal object approaches this sensing surface, eddy currents will be generated in the metal and absorb the energy of the oscillator, causing the oscillator output amplitude to decay linearly. Then, the purpose of contactless detection of objects is achieved based on the change in the attenuation amount.

[0028] The proximity sensor has no sliding contact, is not affected by non-metallic factors such as dust when working, has low power consumption and long life, and can be used in various harsh conditions. Linear sensors are mainly used in the intelligent control of analog quantities in automated equipment production lines.

[0029] Inductive proximity switch 3 working principle

[0030] The inductive proximity switch 3 consists of three parts: an oscillator, a switch circuit, and an amplifier output circuit. The oscillator generates an alternating magnetic field. When a metal target approaches this magnetic field and reaches the sensing distance, eddy currents are generated in the metal target, causing the oscillation to decay and even stop. The changes in the oscillation and stop of the oscillator are processed by the post-amplifier circuit and converted into a switch signal, triggering the drive control device, thereby achieving the purpose of non-contact detection.

[0031] It should be noted that the pulse counting module 4 has a strong anti-interference capability and has multiple output functions and control functions and multiple counting modes.

[0032] Please note that, see Figure 2 This embodiment provides a logic algorithm of a control module 5. Specifically, the signal sent by the field inductive proximity switch 3 is converted into the number of pulses detected in an execution cycle (an integer greater than or equal to 0) by the pulse counting module 4, introduced into the #1 high limit module, compared with 0.1, and the output enters the #1 delay break module and then enters the #1 delay pass module. The switch output of the delay pass module enters the #1 counting module. The signal conversion of the other four inductive proximity switches 3 is similar. Finally, after the five-out-of-three judgment, the output is used as the air preheater stop signal. Any signal is issued as an alarm to introduce the relevant alarm logic. With the above logic, the rotation state of the air preheater can be reliably monitored.

[0033] Specifically, the method uses an inductive proximity switch 3 in conjunction with a pulse counting module 4 to monitor the rotation state of the air preheater main shaft 1. The inductive proximity switch 3 is a low-cost method for non-contact detection of metal objects. When the metal object moves toward or out of the proximity switch, the signal will automatically change, thereby achieving the purpose of detection. It has the characteristics of no contact, low power consumption, long service life, high response frequency, oil and dust resistance, and can work reliably in various harsh environments. Because the state change of the inductive proximity switch 3 is actually reflected in the output as a change in current / voltage (about 5V), conventional switch quantity and analog quantity input modules are not applicable. The pulse counting module 4 can be selected to accept the voltage change, thereby obtaining the rotation state of the air preheater main shaft 1. In order to ensure the stability and reliability of the protection, a configuration mode of three out of two or five out of three can be used to trigger the air preheater stop protection. The present invention detects the rotation state of the air preheater main shaft 1 by using a low-cost inductive proximity switch 3 in conjunction with a pulse counting module 4, and designs a logic algorithm to reliably monitor the rotation state of the air preheater. This method is low-cost. A set of measuring equipment costs less than 20,000 yuan, which only accounts for a quarter of the detection method of the inductive sensor. Redundancy can be set to improve protection reliability. At the same time, it is more suitable for harsh environments such as air preheaters with a lot of dust and oil, greatly extending the life of the equipment.

[0034] In a specific implementation, the number of the inductive proximity switches 3 is 1-5.

[0035] In order to improve the protection reliability, 5 inductive proximity switches 3 can be installed to detect the rotation status of the air preheater.

[0036] In a specific embodiment, the number of the pulse counting modules 4 is 3, and each of the pulse counting modules 4 is respectively connected to 1 or 2 of the inductive proximity switches 3. The above configuration facilitates the implementation of the "three out of five" alarm logic, that is, any two pulse counting modules 4 alarm, and the control module 5 sends an alarm signal 6.

[0037] It should be noted that there are many ways to make the above-mentioned alarm. For example, it can be a remote alarm. By using the existing Internet of Things remote transmission system, the staff's mobile phone can be set as an existing terminal based on Internet of Things signal transmission to receive the above-mentioned alarm signal 6. The above-mentioned signal transmission module based on Internet of Things can be a LORA wireless transmission module, a NB-LOT data transmission module. Of course, it can also be other modules that can realize remote signal transmission, and the embodiments of the present invention do not limit it.

[0038] In a specific embodiment, the control module 5 is a programmable controller. By using a programmable controller, the functions required by the user can be written into the controller using existing programming methods. Specifically, in this embodiment, the logic principle of the programming that needs to be written is: the signal sent by the on-site inductive proximity switch 3 is converted into the number of pulses detected in an execution cycle (an integer greater than or equal to 0) by the pulse counting module 4, introduced into the #1 high limit module, compared with 0.1, and the output enters the #1 delay break module and then enters the #1 delay pass module. The switch output of the delay pass module enters the #1 counting module. The signal conversion of the other four inductive proximity switches 3 is similar. Finally, after the five-out-of-three judgment, the output is used as the air preheater stop signal. Any signal is issued as an alarm to introduce relevant alarm logic.

[0039] In a specific embodiment, Figure 1 As shown, each of the inductive proximity switches 3 is arranged on the side of the driven gear 2 that is not in transmission connection with the power output structure, so as to ensure that after the inductive proximity switch 3 is installed, the rotation of the main shaft 1 with the driven gear is not affected.

[0040] An embodiment of the present invention provides an air preheater stall protection device, comprising an air preheater body, a driven gear 2 coaxially arranged on the main shaft 1 of the air preheater body, at least one inductive proximity switch 3 circumferentially arranged on the driven gear 2, and a pulse counting module 4 for receiving the output signal of the inductive switch, and a control module 5 for controlling and outputting an alarm signal 6. In the prior art, the usual practice is to invert the shutdown signal or operation signal of the main and auxiliary motors of the air preheater and then AND the two to indirectly determine whether the air preheater is stalled. One of the disadvantages of this method is that there is a risk of misoperation or refusal of protection due to motor shutdown or abnormal operation signal. The second is that permanent magnet motors are increasingly used in power plants. After the air preheater motor is permanently magnetized, there is a situation where the motor is running but the transmission of the motor and the main shaft 1 of the air preheater is actually separated, causing the stall protection to fail. In order to solve this technical problem, the present embodiment uses an inductive proximity switch 3 to monitor the rotation of the gear coaxially arranged with the main shaft 1, and indirectly monitors the rotation of the main shaft 1. When the motor is running but the transmission of the motor and the air preheater main shaft 1 is actually separated, the driven gear 2 arranged on the main shaft 1 loses power and stops rotating. The existing detection means are used to detect that the main shaft 1 is still rotating, but the actual situation is that the main shaft 1 is idling. Therefore, the technical solution provided by this embodiment can also solve the situation when the motor is running but the transmission of the motor and the air preheater main shaft 1 is actually separated, and more comprehensive monitoring of the operating status of the air preheater is achieved.

[0041] The method uses an inductive proximity switch 3 in conjunction with a pulse counting module 4 to monitor the rotation state of the air preheater main shaft 1. The inductive proximity switch 3 is a low-cost method for non-contact detection of metal objects. When the metal object moves toward or out of the proximity switch, the signal will automatically change, thereby achieving the purpose of detection. It has the characteristics of no contact, low power consumption, long service life, high response frequency, oil and dust resistance, and can work reliably in various harsh environments. Because the state change of the inductive proximity switch 3 is actually reflected in the output as a change in current / voltage (about 5V), conventional switch quantity and analog quantity input modules are not applicable. The pulse counting module 4 can be selected to accept the voltage change, thereby obtaining the rotation state of the air preheater main shaft 1. In order to ensure the stability and reliability of the protection, a configuration mode of three out of two or five out of three can be used to trigger the air preheater stop protection. The present invention detects the rotation state of the air preheater main shaft 1 by using a low-cost inductive proximity switch 3 in conjunction with a pulse counting module 4, and designs a logic algorithm to reliably monitor the rotation state of the air preheater. This method is low-cost. A set of measuring equipment costs less than 20,000 yuan, which only accounts for a quarter of the detection method of the inductive sensor. Redundancy can be set to improve protection reliability. At the same time, it is more suitable for harsh environments such as air preheaters with a lot of dust and oil, greatly extending the life of the equipment.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An air preheater stall protection device, comprising an air preheater body, characterized in that: A driven gear is coaxially arranged on the main shaft of the air preheater body, at least one inductive proximity switch is arranged in the circumferential direction of the driven gear, and also includes a pulse counting module for receiving the output signal of the inductive switch, and a control module for controlling and outputting an alarm signal; the number of the pulse counting modules is 3, and each of the pulse counting modules is respectively connected to 1 or 2 of the inductive proximity switches; the control module is a programmable controller; The programming logic principle written into the programmable controller is: the signal sent by the inductive proximity switch is converted into the number of pulses detected in one execution cycle through the pulse counting module; The number of pulses is introduced into the high limit module and compared with the preset threshold value 0.1; if the number of pulses is lower than the preset threshold value, the output signal enters the delay break module; after being inverted, it enters the delay pass module; the switch output of the delay pass module enters the counting module; the alarm signal is triggered according to the alarm signal issuance logic, wherein the alarm signal issuance logic is: the control module 5 performs a "five-out-of-three" logic judgment based on the output signals of the three pulse counting modules, and if any two pulse counting modules alarm, the control module triggers the alarm signal.

2. The air preheater stall protection device according to claim 1, characterized in that: The number of the inductive proximity switches is 1-5.

3. The air preheater stall protection device according to claim 1, characterized in that: Each of the inductive proximity switches is arranged on a side of the driven gear that is not transmission-connected to the power output structure.

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