Intelligent detection and early warning system for tail gas of printing and dyeing workshop

Abstract

The present application relates to printing and dyeing workshop tail gas detection early warning technical field, disclose a kind of printing and dyeing workshop tail gas intelligent detection early warning system, comprising: dual-wavelength photoelectric concentration detection module, differential pressure acquisition module, explosion-proof alarm terminal module and alarm determination control module, the state machine in alarm determination control module determines the actual phase difference between the characteristic quantity pulse transition moment collected by dual-wavelength photoelectric concentration detection module and the pressure difference gradient jump moment collected by differential pressure acquisition module, and when the actual phase difference falls into transmission time delay interval, alarm trigger instruction is output to explosion-proof alarm terminal module, when the actual phase difference is less than or equal to common mode vibration delay tolerance, alarm trigger instruction is suppressed and the zero point reference of dual-wavelength photoelectric concentration detection module is corrected, the present application determines early warning boundary using transmission time delay law, eliminates zero point drift generated by oil mist contamination, suppresses common mode false alarm, improves early warning confidence.

Description

Technical Field

[0001] This invention relates to the field of exhaust gas detection and early warning technology in dyeing and printing workshops, and specifically to an intelligent exhaust gas detection and early warning system for dyeing and printing workshops. Background Technology

[0002] Industrial exhaust monitoring and safety control systems typically employ photoelectric attenuation detection to monitor changes in the concentration of specific gases within exhaust ducts. When the detected value reaches a preset threshold, the system outputs a linkage control signal and issues an early warning. Under relatively stable temperature and vibration conditions, such systems can continuously reflect the changing trends of gas concentration, providing assurance for environmental management and safe production in production workshops. The exhaust gas emitted from dyeing and finishing workshops contains high concentrations of highly adhesive oil mist particles and a large number of high-humidity suspended particles. These particles easily adhere to the surface of the photoelectric sampling probe and cause contamination during long-term operation. After the probe becomes contaminated, the transmittance of the detection optical path gradually decreases, resulting in a slow zero-point drift of the detection signal. When using a fixed threshold for alarm judgment, zero-point drift can easily cause continuous false alarms, leading to frequent shutdowns for cleaning or purging, reducing the continuity of system operation and increasing maintenance workload and costs.

[0003] Existing solutions typically remove deposits from the probe surface by shortening maintenance cycles or adding pneumatic purging components. However, this approach fails to effectively eliminate the detection response lag and safety risks during the interval between cleaning sessions. Furthermore, the strong vibrations generated by the main fan during operation can cause optical path deviations in the photoelectric detection device. To reduce such interference, existing systems usually combine pressure and current data from multiple detection points for judgment. However, when the entire pipeline experiences strong vibrations, each detection point often experiences instantaneous fluctuations in the same direction at almost the same moment. In contrast, when actual exhaust gas concentration changes propagate along the pipeline, the transmission delay caused by pipeline layout and propagation distance makes it easy to misjudge simultaneous vibration interference at each detection point as abnormal exhaust gas concentration. It is difficult to accurately distinguish between the sequential changes in signal caused by mechanical vibration and actual exhaust gas transmission. Moreover, existing stenter exhaust gas treatment systems primarily focus on physical processes. While mechanical optimization of filtration devices has been achieved, significant logical deficiencies remain in the monitoring of exhaust gas concentration. For example, Chinese invention patent application CN116139618A discloses an automatic fireproof stenter exhaust gas filtration system. By adding a filter brush and a rotary purging device, it achieves automated maintenance and cleaning of the filter components. However, this type of system mainly relies on mechanical actions to ensure filtration efficiency. Its monitoring of exhaust gas concentration uses a fixed threshold setting method. When the exhaust gas emission pipeline is contaminated with oil mist due to long-term operation or interfered with by common-mode vibration of the equipment, the fixed threshold warning scheme is prone to generating false alarms, leading to unnecessary equipment shutdowns. In addition, this type of technology does not provide real-time dynamic compensation for changes in exhaust gas composition produced by different materials. Therefore, it can be seen that the existing technology is still insufficient in handling signal drift and false alarm suppression under complex working conditions, and it is difficult to meet the actual needs of industrial environments for high confidence and high accuracy of detection and warning systems.

[0004] Therefore, it is difficult to balance operating energy consumption and millisecond-level emergency response. The technical problem to be solved by this invention is how to determine the transmission delay based on the pipeline distance between detection points and the normal flow rate of exhaust gas, compensate for the deviation of the detection signal, and complete the state switching and alarm judgment according to the sequence of different detection signals, so as to automatically eliminate vibration interference and ensure the accuracy of early warning and the timeliness of linkage response. Summary of the Invention

[0005] To address the problems in the background art, this invention proposes an intelligent detection and early warning system for exhaust gas in a dyeing and printing workshop, comprising: The dual-wavelength photoelectric concentration detection module is used to collect photoelectric sampling data from the exhaust gas emission pipeline. The photoelectric sampling data includes the characteristic pulse transition times composed of light intensity decay time series data. The differential pressure acquisition module is used to acquire differential pressure gradient data of the exhaust gas emission pipeline. The differential pressure gradient data includes the differential pressure gradient jump moments composed of pressure fluctuation sequences. The alarm determination and control module includes a state machine, which determines the actual phase difference between the characteristic quantity pulse transition time and the pressure gradient rise time. When the actual phase difference falls within the fluid transmission delay interval and is greater than the common-mode vibration delay tolerance, the state machine transitions from the monitoring steady state to the early warning high-confidence state and outputs an alarm trigger command to the explosion-proof alarm terminal module. When the actual phase difference is less than or equal to the common-mode vibration delay tolerance, the state machine suppresses the alarm trigger command and corrects the zero-point reference of the dual-wavelength photoelectric concentration detection module based on the transient attenuation deviation in the photoelectric sampling data. The explosion-proof alarm terminal module is used to emit audible and visual alarm signals.

[0006] Preferably, the alarm judgment control module further includes a threshold adaptive correction module, which is used to calculate the sliding average value of the absolute transmittance of photoelectricity within the calibration operation cycle, and to solve the degradation slope reflecting the physical contamination rate of the dual-wavelength photoelectric concentration detection module through the least squares sliding window method, so as to determine the adaptive correction amount of the warning threshold under the current contamination state; the threshold adaptive correction module is used to acquire the feed material category data, and when the feed material category data remains constant, to overwrite the warning threshold according to the adaptive correction amount of the warning threshold.

[0007] Preferably, the alarm judgment control module is also used to collect the probe operating current of the dual-wavelength photoelectric concentration detection module and obtain the time when the probe operating current deviates; when the actual phase difference falls within the fluid transmission delay interval and the time when the probe operating current deviates is later than the characteristic quantity pulse transition time, the state machine transitions from the monitoring steady state to the early warning high reliability state.

[0008] Preferably, the system also includes a linkage alarm control module connected to the alarm judgment control module; the state machine is also used to output the alarm confidence probability in the high confidence state of the alarm; the linkage alarm control module is used to receive the alarm confidence probability and output an over-limit control signal to the external emergency handling equipment when the alarm confidence probability is greater than the alarm confidence threshold and the duration is greater than the calibrated time threshold.

[0009] Preferably, the dual-wavelength photoelectric concentration detection module includes a first wavelength emitting module, a second wavelength emitting module, and a photoelectric receiving and detection module; the first wavelength emitting module and the second wavelength emitting module are used to emit detection beams with different center wavelengths into the exhaust gas emission pipe; the photoelectric receiving and detection module is used to receive the detection beams after passing through the exhaust gas emission pipe, so as to provide photoelectric sampling data to the alarm judgment and control module.

[0010] Preferably, the differential pressure acquisition module includes a pitot tube measurement module; the pitot tube measurement module is used to acquire the measured differential pressure signal inside the exhaust gas emission pipeline; the differential pressure acquisition module is used to generate differential pressure gradient data by time derivative calculation of the measured differential pressure signal.

[0011] Preferably, the state machine also includes a low-confidence warning state; when the actual phase difference value falls outside the fluid transmission delay interval and the photoelectric sampling data is greater than the first warning threshold, the state machine transitions from the monitoring steady state to the low-confidence warning state and outputs a low-confidence warning command to the explosion-proof alarm terminal module; when the actual phase difference value recovers to fall within the fluid transmission delay interval, the state machine transitions from the low-confidence warning state to the high-confidence warning state.

[0012] Preferably, the material category data includes at least one of polyester fiber fabric, cotton fiber fabric and polyester-cotton blended fabric; when the material category data changes, the threshold adaptive correction module is used to pause the update of the early warning threshold adaptive correction amount and load the transmittance benchmark value corresponding to the changed material category data to recalibrate the early warning threshold.

[0013] Preferably, the system also includes an emergency exhaust fan adjustment module connected to the explosion-proof alarm terminal module. The emergency exhaust fan adjustment module is installed at the diversion node of the exhaust gas emission pipeline. The emergency exhaust fan adjustment module is used to adjust the exhaust fan speed in the exhaust gas emission pipeline according to the alarm status of the explosion-proof alarm terminal module when the state machine is in a high-confidence warning state, so that the operating pressure in the exhaust gas emission pipeline is maintained within the safe pressure range.

[0014] The beneficial effects of this invention are: 1. In the intelligent detection and early warning of exhaust gas in the dyeing and printing workshop, by extracting the change characteristics of sudden changes in exhaust gas concentration from the photoelectric sampling data, the real concentration change can be distinguished from the zero-point drift caused by the slow adhesion of oil mist. Even if the transmittance of the photoelectric detection probe decreases after being contaminated, the system can still identify abnormal changes in exhaust gas concentration in a timely manner, reducing false alarms and response delays caused by probe surface contamination. While ensuring the sensitivity and reliability of the early warning, the cleaning and maintenance cycle of the probe can also be appropriately extended.

[0015] 2. The fluid transmission delay is determined based on the pipe distance between detection points and the exhaust gas velocity. Alarm judgment is made by combining the sequential relationship of pressure gradient rise, characteristic quantity pulse transition, and probe operating current deviation. This can more accurately distinguish between real exhaust gas anomalies and instantaneous interference caused by pipe vibration. When multiple detection signals change almost simultaneously, the system can identify them as common-mode vibration and suppress the alarm. At the same time, the zero-point reference of the dual-wavelength photoelectric concentration detection module is corrected, thereby reducing false alarms caused by aerodynamic interference in parallel pipelines and pipe vibration, improving the accuracy of alarm judgment and the system's self-calibration capability.

[0016] 3. The warning threshold is adaptively corrected based on the long-term changes in photoelectric transmittance, so that the alarm threshold can be adjusted in a timely manner according to the changes in the degree of probe contamination. This avoids the fixed threshold losing accuracy due to the gradual contamination of the probe. At the same time, the adjustment of the warning threshold is combined with the data of the feed material type. It is only updated when the feed material remains unchanged and recalibrated when the material changes. This reduces the impact of changes in the exhaust gas concentration benchmark caused by different fabric materials on alarm judgment. Therefore, while reducing the number of manual maintenance and threshold resetting, the system can still maintain a high warning sensitivity. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the control principle of the intelligent exhaust gas detection and early warning system of the present invention; Figure 2 This is a diagram showing the linkage adjustment structure of the intelligent exhaust gas detection and early warning system of the present invention. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] A smart detection and early warning system for exhaust gas in a dyeing and printing workshop includes: The dual-wavelength photoelectric concentration detection module is used to collect photoelectric sampling data from the exhaust gas emission pipeline. The photoelectric sampling data includes the characteristic pulse transition times composed of light intensity decay time series data. The differential pressure acquisition module is used to acquire differential pressure gradient data of the exhaust gas emission pipeline. The differential pressure gradient data includes the differential pressure gradient jump moments composed of pressure fluctuation sequences. The alarm determination and control module includes a state machine, which determines the actual phase difference between the characteristic quantity pulse transition time and the pressure gradient rise time. When the actual phase difference falls within the fluid transmission delay interval and is greater than the common-mode vibration delay tolerance, the state machine transitions from the monitoring steady state to the early warning high-confidence state and outputs an alarm trigger command to the explosion-proof alarm terminal module. When the actual phase difference is less than or equal to the common-mode vibration delay tolerance, the state machine suppresses the alarm trigger command and corrects the zero-point reference of the dual-wavelength photoelectric concentration detection module based on the transient attenuation deviation in the photoelectric sampling data. The explosion-proof alarm terminal module is used to emit audible and visual alarm signals.

[0021] Preferably, the alarm judgment control module further includes a threshold adaptive correction module, which is used to calculate the sliding average value of the absolute transmittance of photoelectricity within the calibration operation cycle, and to solve the degradation slope reflecting the physical contamination rate of the dual-wavelength photoelectric concentration detection module through the least squares sliding window method, so as to determine the adaptive correction amount of the warning threshold under the current contamination state; the threshold adaptive correction module is used to acquire the feed material category data, and when the feed material category data remains constant, to overwrite the warning threshold according to the adaptive correction amount of the warning threshold.

[0022] Preferably, the alarm judgment control module is also used to collect the probe operating current of the dual-wavelength photoelectric concentration detection module and obtain the time when the probe operating current deviates; when the actual phase difference falls within the fluid transmission delay interval and the time when the probe operating current deviates is later than the characteristic quantity pulse transition time, the state machine transitions from the monitoring steady state to the early warning high reliability state.

[0023] Preferably, the system also includes a linkage alarm control module connected to the alarm judgment control module; the state machine is also used to output the alarm confidence probability in the high confidence state of the alarm; the linkage alarm control module is used to receive the alarm confidence probability and output an over-limit control signal to the external emergency handling equipment when the alarm confidence probability is greater than the alarm confidence threshold and the duration is greater than the calibrated time threshold.

[0024] Preferably, the dual-wavelength photoelectric concentration detection module includes a first wavelength emitting module, a second wavelength emitting module, and a photoelectric receiving and detection module; the first wavelength emitting module and the second wavelength emitting module are used to emit detection beams with different center wavelengths into the exhaust gas emission pipe; the photoelectric receiving and detection module is used to receive the detection beams after passing through the exhaust gas emission pipe, so as to provide photoelectric sampling data to the alarm judgment and control module.

[0025] Preferably, the differential pressure acquisition module includes a pitot tube measurement module; the pitot tube measurement module is used to acquire the measured differential pressure signal inside the exhaust gas emission pipeline; the differential pressure acquisition module is used to generate differential pressure gradient data by time derivative calculation of the measured differential pressure signal.

[0026] Preferably, the state machine also includes a low-confidence warning state; when the actual phase difference value falls outside the fluid transmission delay interval and the photoelectric sampling data is greater than the first warning threshold, the state machine transitions from the monitoring steady state to the low-confidence warning state and outputs a low-confidence warning command to the explosion-proof alarm terminal module; when the actual phase difference value recovers to fall within the fluid transmission delay interval, the state machine transitions from the low-confidence warning state to the high-confidence warning state.

[0027] Preferably, the material category data includes at least one of polyester fiber fabric, cotton fiber fabric and polyester-cotton blended fabric; when the material category data changes, the threshold adaptive correction module is used to pause the update of the early warning threshold adaptive correction amount and load the transmittance benchmark value corresponding to the changed material category data to recalibrate the early warning threshold.

[0028] Preferably, the system also includes an emergency exhaust fan adjustment module connected to the explosion-proof alarm terminal module. The emergency exhaust fan adjustment module is installed at the diversion node of the exhaust gas emission pipeline. The emergency exhaust fan adjustment module is used to adjust the exhaust fan speed in the exhaust gas emission pipeline according to the alarm status of the explosion-proof alarm terminal module when the state machine is in a high-confidence warning state, so that the operating pressure in the exhaust gas emission pipeline is maintained within the safe pressure range.

[0029] Example 1: The intelligent detection and early warning system for exhaust gas in the dyeing and printing workshop in this example is arranged on the exhaust gas emission pipeline of the stenter. The pipeline contains high-temperature and high-humidity exhaust gas, as well as organosilicon carriers and volatile organic compounds. The real-time temperature fluctuates between 120°C and 180°C, and the exhaust gas velocity varies between 8 m / s and 15 m / s. The system includes a dual-wavelength photoelectric concentration detection module, a differential pressure acquisition module, an explosion-proof alarm terminal module, and an alarm judgment and control module. The alarm judgment and control module is connected to the other three modules respectively. The dual-wavelength photoelectric concentration detection module includes a first wavelength emission module, a second wavelength emission module, and a photoelectric receiving and detection module. The two wavelength emission modules alternately emit detection beams with different center wavelengths into the exhaust gas emission pipeline. The photoelectric receiving and detection module receives the detection beams after passing through the pipeline and outputs photoelectric sampling data. The explosion-proof alarm terminal module adopts an audible and visual alarm adapted to the explosion-proof area of ​​the workshop.

[0030] The differential pressure acquisition module includes a pitot tube measurement module. The pitot tube measurement point is located upstream of the dual-wavelength photoelectric concentration detection module, and the two are spaced at a fixed distance along the exhaust gas flow direction. The pitot tube measurement module collects the measured differential pressure signal in the pipeline. The differential pressure acquisition module performs time derivative on the measured differential pressure signal according to the sampling time to generate differential pressure gradient data. The alarm judgment and control module provides the same sampling clock to the dual-wavelength photoelectric concentration detection module and the differential pressure acquisition module, so that the photoelectric sampling data and the differential pressure gradient data adopt a unified time reference.

[0031] Within each sampling period, the alarm judgment and control module compares the received light intensity corresponding to the two center wavelengths with the received light intensity under the clean air calibration state to obtain the absolute photoelectric transmittance, and arranges it according to the sampling time to form light intensity attenuation time sequence data. When the change of adjacent sample values ​​first exceeds the upper limit of light intensity fluctuation during stable operation, the corresponding sampling time is determined as the characteristic quantity pulse transition time. The differential pressure acquisition module performs time derivative on the continuously sampled measured differential pressure signal. When the differential pressure gradient first exceeds the upper limit of pressure fluctuation gradient during stable operation, the corresponding sampling time is determined as the differential pressure gradient rise time.

[0032] A state machine is set up in the alarm judgment control module. Since the Pitot tube measurement point is located upstream of the dual-wavelength photoelectric concentration detection module, the state machine subtracts the pressure gradient rise time from the characteristic pulse transition time to obtain the actual time phase difference value. The fluid transmission delay interval is determined based on the pipeline distance and exhaust gas velocity between the two detection positions. Specifically, the lower limit of the interval is obtained by dividing the pipeline distance by 15m / s, and the upper limit of the interval is obtained by dividing the pipeline distance by 8m / s. The common mode vibration delay tolerance is calibrated based on the sampling clock error of the two acquisition channels, the signal processing delay, and the maximum synchronization deviation of the two detection signals in the pipeline vibration test.

[0033] The state machine initially operates in a monitoring steady state. When the actual phase difference falls within the fluid transmission delay range and exceeds the common-mode vibration delay tolerance, the state machine determines this signal change as an abnormal change propagating with the exhaust gas flow. It then transitions from the monitoring steady state to a high-confidence warning state and outputs an alarm trigger command to the explosion-proof alarm terminal module. When the actual phase difference is less than or equal to the common-mode vibration delay tolerance, the state machine determines the near-synchronous change of the two detection signals as common-mode vibration in the pipeline and suppresses the alarm trigger command. At this time, the alarm determination and control module calculates the common offset of the absolute transmittance of photoelectric signals relative to the zero-point reference within a short time window before and after the characteristic pulse transition moment. This common offset is used as the transient attenuation deviation, and the zero-point reference of the dual-wavelength photoelectric concentration detection module is corrected accordingly.

[0034] To detect the slow attenuation caused by deposits on the surface of the photodetector, the alarm judgment control module also collects the electrical relaxation response at the output of the photodetector module. When the detection cycle is reached, the alarm judgment control module applies a square wave voltage signal with an amplitude of 1.5V and a duration of 50ms to the driving terminals of the first wavelength transmitting module and the second wavelength transmitting module. After the square wave voltage signal is cut off, the analog-to-digital converter with a sampling frequency of 10kHz collects the residual voltage attenuation data at the output of the photodetector module. The discharge process of the photodetector module after the square wave is turned off follows the first-order RC exponential attenuation law, and its residual voltage satisfies the following relationship with time: ,in To cut off the initial voltage, The circuit time constant is determined by the equivalent junction capacitance of the detector and the load resistance of the loop. The acquired residual voltage decay timing data, after initial amplitude normalization, constitutes an electrical fingerprint signal characterizing the transient discharge characteristics of the optoelectronic device. The time interval corresponding to the exponential decay of the residual voltage from 0.8V to 0.1V is defined as the electrical relaxation time. ,satisfy This reflects the dynamic rate of carrier recombination and junction charge release in optoelectronic devices; the alarm judgment control module calculates the deviation compensation coefficient using the following formula. : ,in, This is the deviation compensation coefficient. For electrical relaxation time, The calibration factor is set to 0.05 per millisecond under the current operating conditions. It is a constant, set to 0.2 under the current operating conditions.

[0035] During the pre-calibration process, firstly, with the light-transmitting window in a clean and uncontaminated baseline state, a standard exhaust gas component with a known gradient was introduced to calibrate the baseline correspondence between the original output current of the dual-wavelength photoelectric concentration detection module and the actual gas concentration, obtaining the standard gas calibration curve. Simultaneously, a square wave voltage signal was applied in clean air, and the initial electrical relaxation time under uncontaminated conditions was measured to be 2 ms. Since the original current measurement value of the photoelectric receiving and detection module is linearly proportional to the received transmitted light intensity, and the attenuation caused by oil mist deposition on the surface of the light-transmitting window manifests as a linear and proportional reduction in transmitted light intensity and photocurrent, the deviation compensation coefficient... Used for linear gain restoration of light intensity attenuation in the original signal domain; under reference conditions, the reference deviation compensation coefficient is calculated by substituting the initial electrical relaxation time of 2ms into the formula. The value was 0.3, at which point the original current matched the gas calibration curve. Subsequently, a mixture of typical tar and auxiliaries from a dyeing and printing workshop of different thicknesses was uniformly coated on the surface of the light-transmitting window to simulate different degrees of physical contamination. The electrical relaxation time under each contamination state and the actual output current attenuation deviation of the photoelectric receiving and detection module when standard concentration tail gas was introduced were recorded. The calibration coefficient was obtained by linearly fitting multiple sets of electrical relaxation times and photocurrent attenuation ratios using the least squares method. It is 0.05 per millisecond, a constant. It is 0.2.

[0036] As the amount of deposits on the surface of the light-transmitting window increases, the received light intensity decreases, and the electrical relaxation time of the photoelectric receiving and detection module is correspondingly prolonged. When the ms is increased from 2ms to 5ms, the deviation compensation coefficient calculated according to the above formula is... The value was adjusted from 0.3 to 0.45, and the alarm judgment control module will use the deviation compensation coefficient between the original current measurement value collected by the photoelectric receiving and detection module and the currently calculated value. Multiplication is performed to eliminate the proportional attenuation caused by physical contamination of the window and restore the equivalent clean photocurrent. This photocurrent is then directly substituted into the preset standard gas calibration curve to convert it into corrected real exhaust gas concentration data, ensuring that the preset gas calibration curve remains effective throughout its entire lifespan without the need for recalibration. When the state machine determines that the two detection signals belong to common-mode vibration, it also utilizes the deviation compensation coefficient. The transient attenuation deviation is weighted, and the zero-point reference is corrected based on the weighted result.

[0037] The alarm judgment and control module also includes a threshold adaptive correction module. Within the calibrated operating cycle, the threshold adaptive correction module calculates the moving average of the absolute photoelectric transmittance and performs least squares sliding window fitting with the time and moving average corresponding to each sliding window. The slope of the resulting fitted line is the degradation slope. The absolute value of the degradation slope increases with the increase of the physical contamination rate of the light transmission window. The threshold adaptive correction module determines the adaptive correction amount of the warning threshold under the current contamination state based on the correspondence between the pre-calibrated degradation slope and the adaptive correction amount of the warning threshold. It also obtains the material category data of the feed material from the workshop production control terminal. When the material category data of the feed material remains constant within the calibrated operating cycle, the threshold adaptive correction module overwrites the current warning threshold with the adaptive correction amount of the warning threshold.

[0038] The alarm judgment and control module compares the corrected exhaust gas concentration data with the graded alarm thresholds. The first-level warning threshold is set to 50 ppm, and the second-level alarm threshold is set to 200 ppm. When the corrected exhaust gas concentration data is greater than the first-level warning threshold and less than the second-level alarm threshold for five consecutive sampling cycles, and the state machine has transitioned to the high-confidence warning state, the explosion-proof alarm terminal module sends a warning electrical signal to the workshop control terminal and illuminates the indicator light. When the corrected exhaust gas concentration data is greater than the second-level alarm threshold in any sampling cycle, and the state machine is in the high-confidence warning state, the explosion-proof alarm terminal module emits an audible and visual alarm signal with a sound intensity of 85 dB.

[0039] The alarm judgment control module adopts a sliding time window with a width of 10 seconds. When the arithmetic mean of the corrected exhaust gas concentration data within the sliding time window is greater than the first-level warning threshold, the system maintains the warning output. When the arithmetic mean is lower than the first-level warning threshold for 30 consecutive seconds, the explosion-proof alarm terminal module stops outputting the warning signal, the alarm execution circuit is reset, and the state machine returns to the monitoring steady state. When the actual phase difference is less than or equal to the common-mode vibration delay tolerance, the state machine suppresses the alarm trigger command and performs zero-point reference correction, regardless of whether the photoelectric sampling data produces instantaneous fluctuations.

[0040] During a continuous 168-hour high-temperature dyeing and printing exhaust gas scouring test, a tar and additive adhesion layer formed on the surface of the light-transmitting window of the dual-wavelength photoelectric concentration detection module in the stenter pipeline. The system determined the adhesion layer based on the electrical relaxation time after the square wave voltage signal was cut off within each detection cycle. Calculate the deviation compensation coefficient The system corrects the original current measurement value of the photoelectric receiving and detection module and the zero-point reference of the dual-wavelength photoelectric concentration detection module. At the same time, it performs state transition and alarm judgment based on the actual phase difference between the pressure gradient jump moment and the characteristic quantity pulse jump moment. The exhaust gas concentration curve output by the system is consistent with the control data obtained by the offline detection of the chromatograph. The number of false alarms during the operation test cycle is zero, the alarm response time is within 3 seconds, and the system continuously outputs monitoring data that meets the preset alarm standards under the condition that the light-transmitting window has deposits. It also maintains operation in a highly polluted dyeing exhaust gas environment.

[0041] Example 2: In this example, the anti-interference capability and early warning accuracy of the intelligent detection and early warning system for exhaust gas in the dyeing and finishing machine were tested at the exhaust port of the dyeing and finishing machine. At the test site, the relative humidity in the exhaust gas emission pipeline fluctuated between 80% and 98%, and the concentration of volatile organic compounds was 50 mg / m³. 3 Up to 300mg / m 3 Between 0.5μm and 10μm, the particle size of the dye particles is between 0.5μm and 10μm. The dual-wavelength photoelectric concentration detection module and the differential pressure acquisition module are installed along the exhaust gas flow direction. The alarm judgment and control module uses a unified sampling clock to collect photoelectric sampling data, differential pressure gradient data, and the probe operating current of the dual-wavelength photoelectric concentration detection module. After receiving the alarm trigger command, the explosion-proof alarm terminal module issues an audible and visual alarm signal.

[0042] The test platform includes a test chamber installed on the bypass of the exhaust gas pipeline, a multi-component gas sensor array, and an alarm judgment and control module. The multi-component gas sensor array serves as an independent calibration branch, used to record gas input and humidity interference in the test chamber, and does not participate in the alarm judgment of the state machine. Among them, the electrochemical gas sensor has a measurement range of 0ppm to 100ppm, a resolution of 0.1ppm, and a temperature control accuracy of 0.5℃; the semiconductor combustible gas sensor has a measurement range of 0%LEL to 100%LEL, a resolution of 1%LEL, and a data acquisition card serves as a signal conversion interface with an analog-to-digital conversion resolution of 16 bits and a sampling rate set to 10Hz.

[0043] During system testing, the alarm judgment and control module extracts the characteristic pulse transition time and the pressure difference gradient rise time from the light intensity attenuation time sequence data and the pressure fluctuation sequence, respectively, and calculates the actual phase difference between the two. When the actual phase difference falls within the fluid transmission delay interval and is greater than the common-mode vibration delay tolerance, the state machine continues to check the time when the probe's operating current deviates. When this time is later than the characteristic pulse transition time, the state machine transitions from the monitoring steady state to the early warning high-confidence state and outputs an alarm trigger command to the explosion-proof alarm terminal module. When the actual phase difference is less than or equal to the common-mode vibration delay tolerance, the state machine identifies the near-synchronous change as common-mode vibration, suppresses the alarm trigger command, and corrects the zero-point reference of the dual-wavelength photoelectric concentration detection module based on the transient attenuation deviation in the photoelectric sampling data.

[0044] When the actual phase difference falls outside the fluid transmission delay interval, and the photoelectric sampling data is greater than the first warning threshold, the state machine transitions from the monitoring steady state to the warning low confidence state and outputs a low confidence warning command to the explosion-proof alarm terminal module. When the actual phase difference recovers to within the fluid transmission delay interval, the state machine transitions from the warning low confidence state to the warning high confidence state. Thus, the near-synchronous fluctuations caused by pipeline vibration, the abnormal fluctuations in a single detection channel, and the concentration changes propagating along the exhaust gas flow direction enter different state processing paths.

[0045] To simulate electromagnetic radiation and interference from the stenter fan motor in the dyeing and printing workshop, Gaussian white noise with a signal-to-noise ratio of 20dB is injected into the voltage output terminals of the dual-wavelength photoelectric concentration detection module and the independent verification branch. A 50Hz power frequency sinusoidal interference wave with an amplitude of 15mV is introduced through a power frequency signal generator. At this time, the photoelectric sampling data and the differential pressure gradient data change instantaneously at approximately the same time. The actual time phase difference is within the common-mode vibration delay tolerance. The state machine maintains the alarm suppression state. Without using the time phase difference value for judgment, the glitches and baseline drift in the original sensor output signal will cause the fixed voltage threshold alarm to generate false warnings.

[0046] The independent verification branch records gas changes within the test chamber via an electrochemical sensor, and the modulation frequency of the sensor excitation signal... Electric double-layer capacitance at the electrode interface and charge transfer resistance When the modulation frequency is too high, the capacitive reactance of the double-layer capacitor decreases, and the current flowing through the electrode system is mainly formed by the charging and discharging of capacitive charges, thus affecting the charge transfer resistance. The resistance change is masked; when the modulation frequency is too low, the establishment time of the electrochemical polarization process is prolonged, and the measurement period increases accordingly. According to the electrochemical impedance spectroscopy model of the electrode system, when the modulation frequency satisfies the following equation, the charge transfer resistance... Its weight in the total impedance shall not be less than 70%. ,in, For modulation frequency, It is a double-layer capacitor, subscript Indicates the electric double layer; For charge transfer resistor, subscript Indicates charge transfer and measures the double-layer capacitance of the sensor electrodes used in the test. The limiting charge transfer resistance is 10 μF under the upper limit of the target gas concentration. The impedance is 1100Ω, and the cutoff frequency of the modulation frequency is set to 4.5Hz.

[0047] In industrial settings, parasitic capacitance and contact resistance are introduced by leads, connectors, and the input terminals of multi-channel acquisition modules, increasing the equivalent double-layer capacitance from the theoretically nominal 10μF to approximately 16μF. This is calculated using the theoretical cutoff frequency formula. The ideal cutoff frequency corresponding to a nominal capacitance of 10μF is approximately 7.23Hz. When distributed parameters are taken into account, causing the equivalent capacitance to increase to 16μF, the time constant of the actual system increases, and the theoretically permissible cutoff frequency of the system decreases to the nominal value. In engineering implementation, the setpoint of the capacitor increment attenuation ratio, 0.62, is taken as the engineering safety margin factor, i.e. This limits the maximum allowed modulation frequency of the independent verification branch to 4.5Hz. In this embodiment, the modulation frequency is... The frequency is set to 2Hz, and the detection response delay is less than or equal to 500ms, provided that the electrode reaction is responsive.

[0048] The dynamic impedance fingerprint of the independent verification branch is extracted at a modulation frequency of 2Hz, and the impedance characteristic value after temperature and humidity compensation is calculated. In high humidity environments, water molecules competitively adsorb onto the active sites of the sensitive electrode. Under a 2Hz modulation signal, the detection process is mainly controlled by charge transfer on the electrode surface. Adsorbed water molecules form a dipole barrier layer at the gas-solid interface, hindering carrier migration. The measured impedance of the electrode system increases with relative humidity. The measured impedance simultaneously includes the decrease in charge transfer impedance caused by target gas adsorption and the increase in impedance caused by water molecule adsorption. The independent verification branch subtracts a humidity compensation term proportional to the real-time relative humidity from the measured impedance and calculates the impedance characteristic value according to the following formula. : ,in, The impedance characteristic value after temperature and humidity compensation, subscript Indicates the compensation characteristic value; The measured impedance amplitude of the sensor at a modulation frequency of 2Hz is given by the subscript. Indicates the measured value; The humidity compensation factor is set to 15Ω / %RH; The value is the real-time relative humidity. When the relative humidity reaches 95%, a water film will condense on the surface of the sensitive electrode. Some target gas molecules are dissolved or blocked by the water film, and the impedance characteristic value will rise compared to the low humidity condition. The humidity compensation term is used to deduct the impedance change caused by the water film.

[0049] The test setup included three comparison groups. The system test group operated a dual-wavelength photoelectric concentration detection module, a differential pressure acquisition module, an alarm judgment and control module, and an explosion-proof alarm terminal module. Simultaneously, it recorded the impedance data obtained by the independent verification branch at a modulation frequency of 2Hz. Control group A did not extract impedance fingerprints or implement temperature and humidity compensation. It directly judged the alarm status based on the total current output value of the sensor under DC polarization and a fixed voltage threshold. Control group B set the sensor's operating modulation frequency to 20Hz, which is higher than the cutoff frequency of 4.5Hz. The relative humidity in the test chamber was set to 50%, 75%, and 95%, respectively. Xylene gas with initial concentrations of 50ppm and 150ppm was introduced under each humidity condition. The original signal fluctuation amplitude, measured impedance amplitude, compensated impedance characteristic value, and warning delay time were recorded.

[0050] At a relative humidity of 50% and a xylene gas concentration of 50 ppm, the original signal fluctuation amplitude of the system test group was 0.08V, and the measured impedance amplitude of the independent calibration branch was obtained. The impedance characteristic value is 1100Ω, after deducting the humidity compensation term. The impedance is 350Ω; the state machine completes the alarm judgment based on the actual phase difference value, and the warning delay time is 11s. The original signal fluctuation amplitude of the control group A is 0.12V, and the measured impedance amplitude and the compensation impedance characteristic value are not extracted. The warning delay time is 18s. The original signal fluctuation amplitude of the control group B is 0.09V, the measured impedance amplitude is 195Ω, the compensation impedance characteristic value is 180Ω, and the warning delay time is 35s.

[0051] When the relative humidity increased to 75% and the xylene gas concentration remained at 50ppm, the original signal fluctuation amplitude of the system test group was 0.18V, the measured impedance amplitude was 1345Ω, the compensated impedance characteristic value was 220Ω, and the warning delay time was 10s. The original signal fluctuation amplitude of control group A increased to 0.28V, no corresponding impedance data was extracted, and the warning delay time was 24s. The original signal fluctuation amplitude of control group B was 0.21V, the measured impedance amplitude was 202Ω, the compensated impedance characteristic value was 187Ω, and the warning delay time was 37s.

[0052] At a relative humidity of 95% and a xylene gas concentration of 150 ppm, condensed water mist forms a liquid film on the sensor surface, superimposed with 50 Hz electromagnetic interference. During the baseline drift observation phase, the baseline of the sensor output voltage of control group A drifted from 1.2V before the gas was introduced to 1.9V, with a fluctuation amplitude of 0.35V, which is close to the set 2V alarm threshold. In the complete comparison record, the original signal fluctuation amplitude of control group A was 0.52V, the warning delay time was 42s, and the corresponding impedance data was not extracted.

[0053] Under the same operating conditions, the original signal fluctuation amplitude of the system test group was 0.35V. The measured impedance amplitude at the 2Hz frequency point was extracted by the independent verification branch through Fast Fourier Transform. Its value is 1850Ω; real-time relative humidity 95%, humidity compensation item The impedance characteristic value is calculated to be 1425Ω. The Ω value is 425Ω, which is the warning characteristic threshold. Set to 500Ω, subscript Indicates the warning characteristic threshold, impedance characteristic value Below the warning characteristic threshold Afterwards, the independent verification branch outputs a high-level warning signal within 0.4s as a verification signal for the state machine's judgment result; the state machine outputs an alarm trigger command according to the actual phase difference and the moment when the probe's working current deviates, and the warning delay time of the system test group is 12s.

[0054] The impedance characteristic value calculated for the independent check branch when no gas is introduced and the relative humidity is 95%. The resistance is 880Ω, which is higher than the warning characteristic threshold. The state machine did not detect the sequential changes of signals that satisfy the fluid transmission time delay relationship, and therefore did not output an alarm trigger command. The control group A was affected by 50Hz power frequency interference and baseline drift. At 45s, the sensor output voltage reached 2.05V, which exceeded the 2V alarm threshold and generated an erroneous alarm signal.

[0055] When the relative humidity was 95% and the xylene gas concentration was 150ppm, the original signal fluctuation amplitude of control group B was 0.38V, the measured impedance amplitude at 20Hz was 210Ω, the compensated impedance characteristic value was 198Ω, and the warning delay time was 39s. Due to the decrease in capacitive reactance of the double-layer capacitor at the 20Hz modulation frequency, the resistance change caused by the gas reaction was affected by the capacitor leakage current. Before and after xylene gas adsorption, the impedance characteristic value fluctuated between 190Ω and 205Ω.

[0056] The xylene gas concentration was further adjusted to between 10 ppm and 500 ppm, and the system warning time and impedance characteristic value were recorded. The impedance characteristic value changes when the xylene gas concentration is between 50 ppm and 250 ppm. The system exhibits a linear relationship with the gas concentration, outputting a warning signal within 15 seconds after the exhaust gas concentration deviates from the normal level. When the xylene gas concentration exceeds 300 ppm, the impedance characteristic value... The rate of decrease slows down and plateaus at 350 ppm; the impedance characteristic values ​​are as follows when the xylene gas concentration is 350 ppm and 500 ppm, respectively. The thresholds for warning features are 120Ω and 118Ω respectively, and the thresholds are further reduced. To avoid shortening the response time under high concentration conditions and making it difficult to reset the system after overload, the measurement range was set to 50ppm to 300ppm.

[0057] In various tests conducted at relative humidity levels ranging from 50% to 95%, the impedance characteristic value of the independently verified branch at a modulation frequency of 2Hz was determined. The alarm judgment of the system test group is still based on the characteristic pulse transition time, the pressure gradient rise time, and the time when the probe working current deviates, and the impedance data of the independent verification branch does not participate in the state machine transition.

[0058] During the 240-hour continuous operation test, the state machine maintained alarm suppression for near-synchronous signal changes caused by condensed water mist and power frequency electromagnetic interference, and the explosion-proof alarm terminal module did not generate any false alarms. When the gas concentration exceeded the standard, the system output an alarm trigger command and issued an audible and visual alarm signal within 12 seconds. Under the high confidence state of the warning, the state machine simultaneously output the warning confidence probability. When the probability was greater than the warning confidence threshold and the duration was greater than the calibrated time threshold, the linkage alarm control module output an over-limit control signal to the pneumatic actuator valve, which is an external emergency handling device. During the continuous test, the hardware current output of each monitoring node remained stable, and the pneumatic actuator valve was in an interlocked state.

[0059] Example 3: In the current dyeing and printing workshop, multiple stenters are equipped with exhaust gas pipelines. The temperature at the exhaust outlet is maintained between 130°C and 170°C. The exhaust gas contains high concentrations of water vapor and volatile organic waste gas generated during the stenting process. Each exhaust outlet is equipped with a dual-wavelength photoelectric concentration detection module and a differential pressure acquisition module. Gas sensor nodes, temperature sensors, and humidity sensors are installed at adjacent locations. The processor in the alarm judgment and control module is connected to each monitoring node through a multi-channel acquisition module. After receiving the alarm trigger command, the explosion-proof alarm terminal module issues an audible and visual alarm signal. The alternation of temperature and humidity will cause the gas sensor to deviate from its resistance value, resulting in cross-sensitivity of temperature and humidity and cumulative zero-point drift. When using a fixed threshold for alarm, false alarms are likely to occur even when the exhaust gas does not exceed the standard.

[0060] Under steady-state monitoring, the minimum sampling frequency of each gas sensor node is 10Hz. The alarm judgment control module calculates the standard deviation of the exhaust gas concentration at each emission port using a 1-minute sliding time window. When the standard deviation is less than 0.5 mg / m³, the alarm is triggered. 3 At this time, the sampling frequency of the corresponding gas sensor node remains at 10Hz; when the standard deviation of any emission outlet is greater than or equal to 0.5mg / m³ 3 At that time, the sampling frequency of the gas sensor node corresponding to the emission port is increased to 50Hz, and 60% of the data transmission bandwidth is allocated to the node. The sampling frequency of the remaining gas sensor nodes is reduced to 2Hz. The dual-wavelength photoelectric concentration detection module and the differential pressure acquisition module continue to collect photoelectric sampling data and differential pressure gradient data. The state machine performs state determination based on the actual time phase difference between the characteristic quantity pulse transition time and the differential pressure gradient rise time.

[0061] When the gas sensor node collects data, the alarm judgment and control module simultaneously reads the measurement data of the adjacent temperature sensor and humidity sensor. The offline two-dimensional interpolation calibration table is filled according to the ratio of the gas sensor output resistance under different temperature and humidity combinations to the reference resistance under the preset reference state. The processor retrieves the table based on the current temperature and humidity data, obtains the corresponding temperature and humidity compensation correction coefficient, and uses the coefficient to correct the output data of the gas sensor.

[0062] The alarm determination and control module also calculates the real-time baseline drift compensation value of the gas sensor. During the maintenance cycle when the stenter is shut down and clean air is introduced into the exhaust gas pipeline, the processor records the initial stable output value of the gas sensor. In subsequent operation, the processor calculates the average output value of the gas sensor when standard clean gas is introduced within a 30-day sliding time window, then calculates the absolute deviation between this average output value and the initial stable output value, and uses this deviation as the baseline drift compensation value. subscript To indicate drift, for a dual-wavelength photoelectric concentration detection module, when the phase difference in actual time is less than or equal to the common-mode vibration delay tolerance, the state machine corrects the zero-point reference based on the transient attenuation deviation in the photoelectric sampling data; baseline drift compensation value. Used to correct long-term output drift of gas sensor nodes.

[0063] The processor calculates the dynamic early warning indicators according to the following formula. : ,in, It is a dimensionless dynamic early warning indicator; The rate of change in exhaust gas concentration is obtained by differential calculation using gas sensor data. This is the baseline drift compensation value for the gas sensor. The first coefficient, subscript This indicates that the coefficient is used in the calculation of dynamic early warning indicators; The second coefficient is the ratio of the exhaust gas concentration change rate to the first coefficient in the first term. The product is a dimensionless value; the second term contains the baseline drift compensation value. With the second coefficient The product is also dimensionless; the sum of the two values ​​yields a dynamic early warning index. The dimensions are consistent with those on both sides of the equal sign.

[0064] High temperature, high humidity, and oil mist contamination can reduce the activity of the sensitive material in gas sensors. As surface deposits increase, baseline drift compensation values ​​decrease. Increase the rate of change of exhaust gas concentration output by the gas sensor under the same abrupt change in exhaust gas concentration. Reduced due to delayed response, dynamic early warning indicators Baseline drift compensation value As a positive compensation term, it is used to compensate for the decrease in the concentration change rate caused by the decay of sensor sensitivity.

[0065] The rate of change of exhaust gas concentration measured in real time When the value exceeds the minimum trigger perturbation threshold and shows a monotonically increasing trend over multiple consecutive sampling periods, the processor activates a dynamic early warning indicator. The cumulative calculation; when the tail gas concentration change rate When the value is within zero or the noise fluctuation range, the processor will dynamically issue a warning. Maintaining at the safety threshold, the alarm judgment and control module will dynamically issue early warning indicators. As an auxiliary quantifier for the probability of confidence level in early warning, the state machine transition is still based on the actual phase difference and the moment when the probe's operating current deviates.

[0066] In a specific set of calculated data, the rate of change of exhaust gas concentration 1.5 mg / (m 3 ·s), baseline drift compensation value 0.2 mg / m 3 First coefficient Set to 0.8 (m) 3 ·s) / mg, second coefficient Set to 1.2m 3 / mg, the processor calculates the first item The second item is 1.2. The sum of the two values ​​is 0.24, which is the dynamic early warning indicator. The value is 1.44, and the warning trigger determination threshold is set to 1.2.

[0067] In dynamic early warning indicators When the value is 1.44 and greater than the warning trigger judgment threshold of 1.2, the actual phase difference falls within the fluid transmission delay range and is greater than the common mode vibration delay tolerance, and the time when the probe operating current deviates is later than the characteristic quantity pulse transition time, the state machine transitions from the monitoring steady state to the warning high reliability state. The alarm judgment control module outputs a 24V high-level alarm trigger command to the explosion-proof alarm terminal module within 3s. The explosion-proof alarm terminal module then flashes and emits an alarm sound of no less than 80dB. During the test process of the sensor zero point deviation, the system false alarm rate is controlled below 1%, and the response time of abnormal exhaust gas emission is controlled within 3s.

[0068] The emergency exhaust fan regulating module is connected to the explosion-proof alarm terminal module and installed at the diversion node of the exhaust gas pipeline. When the state machine is in the high-reliability warning state, the emergency exhaust fan regulating module adjusts the exhaust fan speed according to the alarm status of the explosion-proof alarm terminal module. The differential pressure acquisition module synchronously feeds back the pressure changes in the pipeline, so that the operating pressure in the exhaust gas pipeline is maintained within the safe pressure range.

[0069] Example 4: This example combines Figures 1 to 2 A description of an intelligent detection and early warning system for exhaust gas in a dyeing and printing workshop, such as... Figure 1 As shown, the system includes a dual-wavelength photoelectric concentration detection module, a differential pressure acquisition module, an alarm determination and control module (including a state machine), and an explosion-proof alarm terminal module. The dual-wavelength photoelectric concentration detection module is connected to the alarm determination and control module (including a state machine) to transmit photoelectric sampling data. The differential pressure acquisition module is also connected to the alarm determination and control module (including a state machine) to transmit differential pressure gradient data. The dual-wavelength photoelectric concentration detection module is used to collect photoelectric sampling data from the exhaust gas emission pipeline. This photoelectric sampling data includes characteristic pulse transition times composed of light intensity attenuation time series data. The differential pressure acquisition module is used to collect differential pressure gradient data from the exhaust gas emission pipeline. This differential pressure gradient data includes differential pressure gradient rise times composed of pressure fluctuation sequences. The alarm determination and control module (including a state machine) is connected to the dual-wavelength... The photoelectric concentration detection module and the explosion-proof alarm terminal module are connected. The alarm judgment and control module includes a state machine in the state machine to determine the actual phase difference between the characteristic quantity pulse transition time and the pressure difference gradient rise time. When the actual phase difference falls within the fluid transmission delay interval and is greater than the common-mode vibration delay tolerance, the state machine transitions from the monitoring steady state to the early warning high-confidence state and outputs an alarm trigger command to the explosion-proof alarm terminal module. When the actual phase difference is less than or equal to the common-mode vibration delay tolerance, the state machine suppresses the alarm trigger command and feeds back a correction zero-point reference signal to the dual-wavelength photoelectric concentration detection module to correct the zero-point reference of the dual-wavelength photoelectric concentration detection module based on the transient attenuation deviation in the photoelectric sampling data. The explosion-proof alarm terminal module is used to issue audible and visual alarm signals.

[0070] like Figure 2As shown, it includes an emergency exhaust fan adjustment module, an explosion-proof alarm terminal module, a differential pressure acquisition module, an alarm judgment and control module, a linkage alarm control module, and a dual-wavelength photoelectric concentration detection module. The dual-wavelength photoelectric concentration detection module is connected to the alarm judgment and control module, the differential pressure acquisition module is connected to the alarm judgment and control module, the alarm judgment and control module is connected to both the linkage alarm control module and the explosion-proof alarm terminal module, and the explosion-proof alarm terminal module is connected to the emergency exhaust fan adjustment module.

[0071] Example 5: Before the intelligent detection and early warning system for exhaust gas in the dyeing and printing workshop is put into operation, the dual-wavelength photoelectric concentration detection module, gas sensor node, temperature sensor, and humidity sensor are jointly calibrated. The above detection components are placed in a temperature and humidity alternating test chamber. The chamber temperature is controlled to switch at 10°C intervals within the range of 130°C to 170°C, and the relative humidity is adjusted at 20% intervals within the range of 10% to 90% at each temperature point. After the environmental conditions corresponding to each temperature and humidity combination stabilize, a concentration of 50 mg / m³ is introduced into the test chamber. 3 Calibration gas.

[0072] At each environmental node, the multi-channel acquisition module synchronously acquires the received light intensity corresponding to the first and second wavelength transmission modules, and obtains the output resistance value of the gas sensor node. The alarm judgment and control module calculates the absolute photoelectric transmittance based on the emitted and received light intensities, which is used to calibrate the zero-point reference of the dual-wavelength photoelectric concentration detection module under different temperature and humidity conditions. The gas sensor node serves as an auxiliary calibration branch, and the ratio of its output resistance value to the reference resistance value under the preset reference state is recorded as the temperature and humidity compensation correction coefficient. Temperature and humidity compensation correction coefficients for each temperature and humidity combination A two-dimensional matrix is ​​written into the internal memory of the alarm judgment and control module, thereby forming an offline two-dimensional interpolation calibration table, which is used to correct the resistance deviation of the auxiliary verification branch under high temperature and high humidity conditions.

[0073] After completing the temperature and humidity calibration, the corresponding material category data for polyester fiber fabric, cotton fiber fabric and polyester-cotton blended fabric are input respectively. When the various material categories remain stable, the threshold adaptive correction module records the absolute transmittance of the dual-wavelength photoelectric concentration detection module and uses the sliding average of the absolute transmittance of the photoelectric concentration during the calibration operation cycle as the transmittance benchmark value of the corresponding material category. The data of each material category and its transmittance benchmark value are stored in the alarm judgment control module according to the corresponding relationship.

[0074] After the system completes the on-site pipeline connections and electrical wiring, it keeps the stenter in a stopped state and introduces clean air into the exhaust gas pipeline. The alarm judgment and control module activates the dual-wavelength photoelectric concentration detection module and the gas sensor node. The multi-channel acquisition module continuously collects the raw voltage signal over 60 minutes. For the gas sensor node, the processor calculates the arithmetic mean of the raw voltage signal through mean filtering and uses this arithmetic mean as the initial stable output value. Write to non-volatile memory; The unit is V, representing the initial zero-point voltage signal value of the gas sensor node under clean air conditions, and is used as the subsequent baseline drift compensation value. For the comparison benchmark, the alarm judgment control module writes the absolute photoelectric transmittance obtained under clean air conditions into the zero-point benchmark for the dual-wavelength photoelectric concentration detection module.

[0075] When the material category data of the feed material remains constant, the threshold adaptive correction module determines the adaptive correction amount of the warning threshold based on the degradation slope of the absolute transmittance of photoelectric material, and overwrites the warning threshold accordingly. When the material category data of the feed material transmitted from the production control terminal changes, the threshold adaptive correction module pauses the update of the adaptive correction amount of the warning threshold, loads the transmittance reference value corresponding to the changed material category data from the memory, and recalibrates the warning threshold based on the transmittance reference value. After the recalibration is completed, the update of the adaptive correction amount of the warning threshold resumes.

[0076] During on-site calibration, the control port of the explosion-proof alarm terminal module is kept at a low level of 0V, the sampling frequency of each gas sensor node is kept at 10Hz, the state machine is in a monitoring steady state, and after the zero-point reference, transmittance reference value and warning threshold are calibrated, the alarm judgment control module begins to receive photoelectric sampling data and differential pressure gradient data, and the system enters normal monitoring state.

[0077] Example 6: In this example, the linkage alarm control module and the emergency exhaust fan adjustment module are used in the exhaust gas emission pipeline shared by multiple stenters. The exhaust branches of each stenter converge into the diversion node. The emergency exhaust fan adjustment module is installed at this node and is connected to the explosion-proof alarm terminal module and the alarm judgment control module respectively. The differential pressure acquisition module continuously acquires the measured differential pressure signal before and after the diversion node. The alarm judgment control module obtains the operating pressure of the exhaust gas emission pipeline according to the on-site calibration relationship. The safe pressure range is preset according to the allowable operating pressure of the exhaust gas emission pipeline and its connected equipment.

[0078] After the state machine enters the high confidence state of the early warning, it outputs the early warning confidence probability according to the ratio of the number of sampling periods that meet the conditions for entering the high confidence state of the early warning within the continuous observation period to the total number of sampling periods contained in the observation period. The early warning confidence threshold is calibrated based on the state judgment results obtained under normal emission conditions and abnormal exhaust gas emission conditions. The calibration time threshold is determined according to the duration of short-term fluctuations that need to be excluded.

[0079] When the probability of a warning is greater than the confidence threshold, but the duration has not yet reached the calibrated time threshold, the linkage alarm control module maintains its original output state, and the explosion-proof alarm terminal module continues to issue audible and visual alarm signals. When the probability of a warning is greater than the confidence threshold and the duration exceeds the calibrated time threshold, the linkage alarm control module outputs an over-limit control signal to the external emergency handling equipment. After receiving the signal, the external emergency handling equipment closes the external heating main valve, causing the stenter to stop generating high-temperature exhaust gas.

[0080] During the period when the state machine is in the high-reliability warning state, the explosion-proof alarm terminal module simultaneously transmits the alarm status to the emergency exhaust fan adjustment module. This module adjusts the exhaust fan speed in the exhaust gas emission pipeline based on the operating pressure fed back by the differential pressure acquisition module. When the operating pressure is close to or exceeds the upper limit of the safe pressure range, the exhaust fan speed is increased; when the operating pressure is lower than the lower limit of the safe pressure range, the exhaust fan speed is decreased; when the operating pressure is within the safe pressure range, the current exhaust fan speed is maintained.

[0081] After each adjustment of the exhaust fan speed, the emergency exhaust fan adjustment module continues to read the operating pressure and makes the next adjustment according to the same rules until the operating pressure is maintained within the safe pressure range. After the state machine exits the high-reliability warning state, the module stops emergency adjustment and the exhaust gas emission pipeline resumes normal exhaust operation.

[0082] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An intelligent detection and early warning system for exhaust gas in a dyeing and printing workshop, characterized in that, include: The dual-wavelength photoelectric concentration detection module is used to collect photoelectric sampling data from the exhaust gas emission pipeline. The photoelectric sampling data includes the characteristic pulse transition times composed of light intensity decay time series data. The differential pressure acquisition module is used to acquire differential pressure gradient data of the exhaust gas emission pipeline. The differential pressure gradient data includes the differential pressure gradient jump moments composed of pressure fluctuation sequences. The alarm determination and control module includes a state machine, which is used to determine the actual time phase difference between the characteristic quantity pulse transition time and the pressure difference gradient rise time. When the actual phase difference falls within the fluid transmission delay range and is greater than the common-mode vibration delay tolerance, the state machine transitions from the monitoring steady state to the early warning high-confidence state and outputs an alarm trigger command to the explosion-proof alarm terminal module; when the actual phase difference is less than or equal to the common-mode vibration delay tolerance, the state machine suppresses the alarm trigger command and corrects the zero-point reference of the dual-wavelength photoelectric concentration detection module based on the transient attenuation deviation in the photoelectric sampling data. The explosion-proof alarm terminal module is used to emit audible and visual alarm signals.

2. The intelligent detection and early warning system for exhaust gas in a dyeing and printing workshop according to claim 1, characterized in that, The alarm judgment and control module also includes a threshold adaptive correction module, which is used to calculate the sliding average value of absolute photoelectric transmittance within the calibration operation cycle, and to solve the degradation slope reflecting the physical contamination rate of the dual-wavelength photoelectric concentration detection module through the least squares sliding window method, so as to determine the adaptive correction amount of the warning threshold under the current contamination state. The threshold adaptive correction module is used to obtain the feed material category data, and when the feed material category data remains constant, it overwrites the warning threshold according to the adaptive correction amount of the warning threshold.

3. The intelligent detection and early warning system for exhaust gas in a dyeing and printing workshop according to claim 1, characterized in that, The alarm judgment control module is also used to collect the probe operating current of the dual-wavelength photoelectric concentration detection module and obtain the time when the probe operating current deviates. When the actual phase difference falls within the fluid transmission delay interval and the time when the probe operating current deviates is later than the characteristic pulse transition time, the state machine will transition from the monitoring steady state to the early warning high reliability state.

4. The intelligent detection and early warning system for exhaust gas in a dyeing and printing workshop according to claim 1, characterized in that, The system also includes a linkage alarm control module connected to the alarm judgment control module; the state machine is also used to output the alarm confidence probability in the high confidence state of the alarm; the linkage alarm control module is used to receive the alarm confidence probability and output an over-limit control signal to the external emergency handling equipment when the alarm confidence probability is greater than the alarm confidence threshold and the duration is greater than the calibrated time threshold.

5. The intelligent detection and early warning system for exhaust gas in a dyeing and printing workshop according to claim 1, characterized in that, The dual-wavelength photoelectric concentration detection module includes a first wavelength transmitting module, a second wavelength transmitting module, and a photoelectric receiving and detection module. The first wavelength transmitting module and the second wavelength transmitting module are used to emit detection beams with different center wavelengths into the exhaust gas emission pipe. The photoelectric receiving and detection module is used to receive the detection beams after they pass through the exhaust gas emission pipe, so as to provide photoelectric sampling data to the alarm judgment and control module.

6. The intelligent detection and early warning system for exhaust gas in a dyeing and printing workshop according to claim 1, characterized in that, The differential pressure acquisition module includes a pitot tube measurement module; the pitot tube measurement module is used to acquire the measured differential pressure signal inside the exhaust gas emission pipeline; the differential pressure acquisition module is used to generate differential pressure gradient data by time derivative calculation of the measured differential pressure signal.

7. The intelligent detection and early warning system for exhaust gas in a dyeing and printing workshop according to claim 1, characterized in that, The state machine also includes a low-confidence warning state; when the actual phase difference falls outside the fluid transmission delay interval and the photoelectric sampling data is greater than the first warning threshold, the state machine transitions from the monitoring steady state to the low-confidence warning state and outputs a low-confidence warning command to the explosion-proof alarm terminal module. When the actual time phase difference recovers to fall within the fluid transport delay interval, the state machine transitions from the low-confidence warning state to the high-confidence warning state.

8. The intelligent detection and early warning system for exhaust gas in a dyeing and printing workshop according to claim 2, characterized in that, The material category data includes at least one of polyester fiber fabric, cotton fiber fabric, and polyester-cotton blended fabric; when the material category data changes, the threshold adaptive correction module is used to pause the update of the early warning threshold adaptive correction amount and load the transmittance benchmark value corresponding to the changed material category data to recalibrate the early warning threshold.

9. The intelligent detection and early warning system for exhaust gas in a dyeing and printing workshop according to claim 1, characterized in that, The system also includes an emergency exhaust fan adjustment module connected to the explosion-proof alarm terminal module. The emergency exhaust fan adjustment module is installed at the diversion node of the exhaust gas emission pipeline. The emergency exhaust fan adjustment module is used to adjust the exhaust fan speed in the exhaust gas emission pipeline according to the alarm status of the explosion-proof alarm terminal module when the state machine is in a high-confidence warning state, so that the operating pressure in the exhaust gas emission pipeline is maintained within the safe pressure range.

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