Method for preventing false shutdown of coking dry quenching steam boiler due to fault of liquid level sensor

Abstract

The invention discloses a method for preventing false shutdown of a coking dry quenching steam boiler due to faults of liquid level sensors, which comprises the following steps of: setting a plurality of liquid level sensors, setting an open circuit threshold value digital quantity signal and a short circuit threshold value digital quantity signal, and outputting a maximum value and a minimum value of the digital quantity signals in cooperation with the liquid level sensors; whether the current liquid level sensor has open circuit and short circuit faults or not is judged, meanwhile, the signal quality is judged, and if the signal quality is poor, the corresponding sensor signals are shielded, in this way, the false signals of the liquid level of the coking dry quenching steam boiler can be automatically judged and processed, equipment shutdown caused by the false signals is reduced, and the system reliability is improved. And efficient and stable normal operation of the system is ensured.

Description

Technical Field

[0001] The invention relates to a method for preventing a liquid level sensor from malfunctioning and shutting down, in particular to a method for preventing a liquid level sensor from malfunctioning and shutting down a coking dry quenching steam boiler, belonging to the technical field of coking dry quenching. Background Art

[0002] The coking dry quenching steam boiler is an energy converter. It uses a circulating fan to lead the hot air from the dry quenching furnace to the boiler, thereby heating the water to a certain parameter. The working fluid of the boiler is water, and the output working fluid is water vapor. The water vapor reaches the waste heat power generation through the steam pipe to generate electricity. There is a water inlet on the top of the boiler to replenish water to the boiler, so as to ensure the liquid level inside the boiler. There is a liquid level gauge next to the water inlet. The liquid level gauge converts the boiler liquid level height into a 4-20mA signal, which is transmitted to the dry quenching control PLC through a cable to monitor the liquid level inside the boiler in real time. In actual production operation, the liquid level of the boiler directly affects whether the boiler is operating normally and safely, and also affects the operation of the circulating fan, steam relief valve, and steam shut-off valve.

[0003] In actual use, the liquid level meter is an electronic product. With the increase of use time, the probability of damage also increases. Moreover, it is installed outdoors, and there are risks such as water ingress and aging. Even regular inspection and replacement cannot avoid sudden damage. The analog input module is also an electronic product. After a long period of use, input channel damage often occurs, so it cannot be guaranteed that it will not fail. Most of the CDQ control PLCs are Siemens brands. Siemens PLC only has the function of converting digital quantities into engineering quantities for analog processing, and does not have the function of judging whether the value of the current channel input is a normal value. If the current working condition is normal, the abnormal liquid level value caused by equipment failure will also cause the circulation fan to stop, the steam release valve to open, and the steam shut-off valve to close, which will greatly affect the stable operation of the CDQ furnace and waste heat power generation. Therefore, it is necessary to design a method to prevent the coking CDQ steam boiler from shutting down due to liquid level errors. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preventing a coking dry quenching steam boiler from shutting down due to a liquid level sensor failure, so as to prevent the coking dry quenching steam boiler from shutting down due to a liquid level sensor failure.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: A method for preventing a coking dry quenching steam boiler from shutting down due to a liquid level sensor failure comprises the following steps: S1. Several liquid level sensors are arranged in the coking dry quenching steam boiler, and the several liquid level sensors are connected to the PLC control system through analog modules respectively; S2. When the current digital signal received by the PCL control system is less than the circuit-breaking threshold digital signal, it is determined that the liquid level sensor and the analog module have a circuit-breaking fault, and the PLC control system shields the current digital signal and alarms on the host computer; S3, when the current digital signal received by the PCL control system is greater than the short-circuit threshold digital signal, it is determined that a short-circuit fault occurs in the liquid level sensor and the analog module, and the PLC control system shields the current digital signal and alarms on the host computer; S4, when the current digital signal received by the PCL control system is greater than the maximum value of the digital signal output by the analog module and less than the short-circuit threshold digital signal, or the current digital signal is less than the minimum value of the digital signal output by the analog module and greater than the open-circuit threshold digital signal, it is judged that the current digital signal is of poor quality, and the PLC control system shields the current digital signal and alarms in the upper computer; S5, sampling the current digital signal according to the first cycle, if the value of the current digital signal remains unchanged for several consecutive cycles, it is judged that the quality of the current digital signal is poor, the PLC control system shields the current digital signal and alarms on the host computer; S6. Sample the current digital quantity signal according to the second cycle, and cyclically record n ​​current digital quantity signals IN1-IN n , calculate the change rate of these n current number quality signals q = {|IN2-IN1|+|IN3-IN2|+…|IN n -IN n-1 |} / n, if the change rate q is greater than 1, it is judged that the current digital signal has poor quality, the PLC control system shields the current digital signal and alarms on the host computer; S7, if the PCL control system determines that the current digital signals of the several liquid level sensors are not of poor quality, then the current digital signals of the several liquid level sensors are averaged and output to the PID interlocking system; S8. If the PCL control system determines that the current digital signal of any one or more liquid level sensors is of poor quality, the current digital signal of the one or more liquid level sensors is shielded, and the PCL control system averages the current digital signals of the remaining liquid level sensors and outputs them to the PID interlocking system.

[0006] Furthermore, in step S1, the liquid level sensor includes a left liquid level sensor, a middle liquid level sensor and a right liquid level sensor, the left liquid level sensor and the right liquid level sensor are symmetrically arranged on both sides of the coking dry quenching steam boiler, and the middle liquid level sensor is arranged in the middle position of the coking dry quenching steam boiler.

[0007] Furthermore, the liquid level sensor adopts a double-chamber balance container and a differential pressure transmitter, and the measuring range of the liquid level sensor is -300-300mm.

[0008] Furthermore, the analog quantity module adopts Siemens SM331 analog quantity input module, with input current of 4-20mA and output digital quantity signal of 0-27648.

[0009] Furthermore, the step S2 is specifically as follows: measuring the first measurement digital signal emitted by the analog module received by the PLC control system when a circuit breakage fault occurs in the liquid level sensor and the analog module, setting a circuit breakage threshold digital signal and making sure that the value of the circuit breakage threshold digital signal is greater than the first measurement digital signal; when the current digital signal received by the PLC control system is less than the circuit breakage threshold digital signal, it is determined that a circuit breakage fault occurs in the liquid level sensor and the analog module, and the PLC control system shields the current digital signal and alarms the host computer.

[0010] Furthermore, the step S3 is specifically as follows: measuring a second measurement digital signal emitted by the analog module and received by the PLC control system when a short circuit fault occurs in the liquid level sensor and the analog module, setting a short circuit threshold digital signal and the value of the short circuit threshold digital signal is less than the second measurement digital signal, and when the current digital signal received by the PLC control system is greater than the short circuit threshold digital signal, it is determined that a short circuit fault occurs in the liquid level sensor and the analog module, and the PLC control system shields the current digital signal and alarms on the host computer.

[0011] Compared with the prior art, the present invention has the following advantages and effects: The present invention provides a method for preventing a coking dry quenching steam boiler from shutting down due to a liquid level sensor failure, which can monitor the quality status of the boiler liquid level in real time. When the boiler liquid level is a normal value, the circulating fan, steam relief valve and other equipment are interlocked. When the boiler liquid level is abnormal, the equipment is not interlocked and an alarm is given to prevent false signals of the boiler liquid level from causing production fluctuations and affecting the stable operation or shutdown of the system. The present invention can automatically judge and process false signals of the liquid level of a coking dry quenching steam boiler, reduce equipment shutdowns caused by false signals, and ensure the efficient and stable normal operation of the system; by setting multiple liquid level value measurement points and taking the average value of the multiple measurement points, the authenticity and correctness of the boiler liquid level are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The invention discloses a flow chart of a method for preventing a coking dry quenching steam boiler from shutting down due to a liquid level sensor failure. DETAILED DESCRIPTION

[0013] In order to elaborate on the technical scheme adopted by the present invention to achieve the predetermined technical purpose, 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 partial embodiments of the present invention, rather than all embodiments, and the technical means or technical features in the embodiments of the present invention can be replaced without paying creative work. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0014] like Figure 1 As shown, a method for preventing a coking dry quenching steam boiler from shutting down due to a liquid level sensor failure of the present invention comprises the following steps: S1. A plurality of liquid level sensors are arranged in the coking dry quenching steam boiler, and the plurality of liquid level sensors are connected to the PLC control system through analog quantity modules.

[0015] In this embodiment, three liquid level sensors are used, including a left liquid level sensor, a middle liquid level sensor and a right liquid level sensor. The left liquid level sensor and the right liquid level sensor are symmetrically arranged on both sides of the coking dry quenching steam boiler, and the middle liquid level sensor is arranged in the middle position of the coking dry quenching steam boiler.

[0016] The liquid level sensor adopts a double-chamber balance container and a differential pressure transmitter. The range of the liquid level sensor is -300-300mm. The liquid level sensor outputs a current value of 4-20mA to the analog module.

[0017] The analog module uses Siemens SM331 analog input module, with input current 4-20mA and output digital signal 0-27648.

[0018] The liquid level height value of -300mm corresponds to a 4mA current signal, which is then converted into a digital signal 0 by the analog module. The liquid level height value of 300mm corresponds to a 20mA current signal, which is then converted into a digital signal 27648 by the analog module.

[0019] S2. Measure the first measured digital signal sent by the analog module received by the PLC control system when a circuit breakage occurs in the liquid level sensor and the analog module. In this embodiment, the value of the first measured digital signal is -32768, so when the digital signal is detected to be equal to this value, it can be determined that a circuit breakage occurs. However, since the signal may have a small fluctuation, the circuit breakage threshold digital signal is set in this embodiment and the value of the circuit breakage threshold digital signal is greater than the first measured digital signal, such as -32000. When the current digital signal received by the PCL control system is less than the circuit breakage threshold digital signal, it is determined that a circuit breakage occurs in the liquid level sensor and the analog module, and the PLC control system shields the current digital signal and alarms the host computer.

[0020] S3, measure the second measurement digital signal sent by the analog module received by the PLC control system when a short circuit occurs in the liquid level sensor and the analog module. In this embodiment, the value of the second measurement digital signal is 32767, so when the digital signal is detected to be equal to this value, it can be determined that a short circuit occurs. However, since the signal may have a small fluctuation, the short circuit threshold digital signal is set in this embodiment and the value of the short circuit threshold digital signal is less than the second measurement digital signal, such as 32000. When the current digital signal received by the PCL control system is greater than the short circuit threshold digital signal, it is determined that a short circuit occurs in the liquid level sensor and the analog module, and the PLC control system shields the current digital signal and alarms in the host computer.

[0021] S4. When the current digital signal received by the PCL control system is greater than the maximum value 27648 of the digital signal output by the analog module and less than the short-circuit threshold digital signal, or the current digital signal is less than the minimum value 0 of the digital signal output by the analog module and greater than the open-circuit threshold digital signal, it is judged that the current digital signal is of poor quality, and the PLC control system shields the current digital signal and alarms on the host computer.

[0022] S5. Sample the current digital signal according to the first cycle (such as once per minute). If the value of the current digital signal remains unchanged for three consecutive cycles, it is judged that the quality of the current digital signal is poor. The PLC control system shields the current digital signal and alarms on the host computer.

[0023] S6. Sample the current digital quantity signal according to the second cycle (once per second), and cyclically record n ​​current digital quantity signals IN1-IN n , calculate the change rate of these n current number quality signals q = {|IN2-IN1|+|IN3-IN2|+…|IN n -IN n-1 |} / n, in this embodiment, n=60. If the rate of change q is greater than 1, it is determined that the quality of the current digital quantity signal is poor, and the PLC control system shields the current digital quantity signal and alarms in the host computer.

[0024] S7, if the PCL control system determines that the current digital signals of the three liquid level sensors are not of poor quality, then the current digital signals of the three liquid level sensors are averaged and output to the PID interlocking system; S8. If the PCL control system determines that the quality of the current digital signal of any one or two liquid level sensors is poor, the current digital signal of the one or two liquid level sensors is shielded, and the PCL control system averages the current digital signals of the remaining liquid level sensors and outputs them to the PID interlocking system.

[0025] The present invention provides a method for preventing a coking dry quenching steam boiler from shutting down due to a liquid level sensor failure, which can monitor the quality status of the boiler liquid level in real time. When the boiler liquid level is a normal value, the circulating fan, steam relief valve and other equipment are interlocked. When the boiler liquid level is abnormal, the equipment is not interlocked and an alarm is given to prevent the boiler liquid level false signal from causing production fluctuations and affecting the stable operation or shutdown of the system. The present invention can automatically judge and process the false signal of the coking dry quenching steam boiler liquid level, reduce the equipment shutdown caused by the false signal, and ensure the efficient and stable normal operation of the system; by setting multiple liquid level value measurement points and taking the average value of the multiple measurement points, the authenticity and correctness of the boiler liquid level are improved.

[0026] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement made to the above embodiments without departing from the content of the technical solution of the present invention, based on the technical essence of the present invention, within the spirit and principles of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preventing a coking dry quenching steam boiler from shutting down due to a liquid level sensor failure, characterized in that The following steps are involved: S1. Several liquid level sensors are arranged in the coking dry quenching steam boiler, and the several liquid level sensors are connected to the PLC control system through analog modules respectively; S2. When the current digital signal received by the PCL control system is less than the circuit-breaking threshold digital signal, it is determined that the liquid level sensor and the analog module have a circuit-breaking fault, and the PLC control system shields the current digital signal and alarms on the host computer; S3, when the current digital signal received by the PCL control system is greater than the short-circuit threshold digital signal, it is determined that a short-circuit fault occurs in the liquid level sensor and the analog module, and the PLC control system shields the current digital signal and alarms on the host computer; S4, when the current digital signal received by the PCL control system is greater than the maximum value of the digital signal output by the analog module and less than the short-circuit threshold digital signal, or the current digital signal is less than the minimum value of the digital signal output by the analog module and greater than the open-circuit threshold digital signal, it is judged that the current digital signal is of poor quality, and the PLC control system shields the current digital signal and alarms in the upper computer; S5, sampling the current digital signal according to the first cycle, if the value of the current digital signal remains unchanged for several consecutive cycles, it is judged that the quality of the current digital signal is poor, the PLC control system shields the current digital signal and alarms on the host computer; S6. Sample the current digital quantity signal according to the second cycle, and cyclically record n ​​current digital quantity signals IN1-IN n , calculate the change rate of these n current number quality signals q = {|IN2-IN1|+|IN3-IN2|+…|IN n -IN n-1 |} / n, if the change rate q is greater than 1, it is judged that the current digital signal has poor quality, the PLC control system shields the current digital signal and alarms on the host computer; S7, if the PCL control system determines that the current digital signals of the several liquid level sensors are not of poor quality, then the current digital signals of the several liquid level sensors are averaged and output to the PID interlocking system; S8. If the PCL control system determines that the current digital signal of any one or more liquid level sensors is of poor quality, the current digital signal of the one or more liquid level sensors is shielded, and the PCL control system averages the current digital signals of the remaining liquid level sensors and outputs them to the PID interlocking system.

2. A method for preventing a coking dry quenching steam boiler from shutting down due to a liquid level sensor failure according to claim 1, characterized in that: In step S1, the liquid level sensor includes a left liquid level sensor, a middle liquid level sensor and a right liquid level sensor. The left liquid level sensor and the right liquid level sensor are symmetrically arranged on both sides of the coking dry quenching steam boiler, and the middle liquid level sensor is arranged in the middle position of the coking dry quenching steam boiler.

3. A method for preventing a coking dry quenching steam boiler from shutting down due to a liquid level sensor failure according to claim 2, characterized in that: The liquid level sensor adopts a double-chamber balance container and a differential pressure transmitter, and the measuring range of the liquid level sensor is -300-300mm.

4. A method for preventing a coking dry quenching steam boiler from shutting down due to a liquid level sensor failure according to claim 3, characterized in that: The analog quantity module adopts Siemens SM331 analog quantity input module, with input current of 4-20mA and output digital quantity signal of 0-27648.

5. The method for preventing a coking dry quenching steam boiler from shutting down due to a liquid level sensor failure according to claim 1, characterized in that: The step S2 is specifically as follows: measuring the first measurement digital signal emitted by the analog module and received by the PLC control system when a circuit breakage fault occurs in the liquid level sensor and the analog module, setting a circuit breakage threshold digital signal and making sure that the value of the circuit breakage threshold digital signal is greater than the first measurement digital signal; when the current digital signal received by the PLC control system is less than the circuit breakage threshold digital signal, it is determined that a circuit breakage fault occurs in the liquid level sensor and the analog module, and the PLC control system shields the current digital signal and alarms the host computer.

6. A method for preventing a coking dry quenching steam boiler from shutting down due to a liquid level sensor failure according to claim 1, characterized in that: The step S3 is specifically as follows: measuring the second measurement digital signal emitted by the analog module received by the PLC control system when a short circuit fault occurs in the liquid level sensor and the analog module, setting a short circuit threshold digital signal and making sure that the value of the short circuit threshold digital signal is less than the second measurement digital signal; when the current digital signal received by the PLC control system is greater than the short circuit threshold digital signal, it is determined that a short circuit fault occurs in the liquid level sensor and the analog module, and the PLC control system shields the current digital signal and alarms the host computer.

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