A CO laser detection system based on thermal radiation background

Abstract

The invention relates to the technical field of acetylene cracking furnace production monitoring, and specifically discloses a CO laser detection system based on thermal radiation background, which is used to solve the problem that thermal radiation and water vapor generated by high temperature in an existing ethylene cracking furnace interfere with infrared absorption measurement of CO, resulting in the difficulty of the existing monitoring system to accurately distinguish CO and water vapor signals. The system comprises a quantum cascade laser, a pyroelectric detector, a data processing unit and a signal analysis module. A reference light intensity adjustment module uses temperature, humidity and pressure data acquired in real time by an environmental parameter sensing module, adjusts the absorption coefficient of CO by an environmental correction factor, and dynamically calculates and corrects the reference light intensity based on the data. The data processing unit uses the data for dynamic correction of CO concentration monitoring. The system effectively extracts CO signals under the thermal radiation background by using quantum cascade lasers and beam modulation technology, accurately identifies abnormal CO concentration and issues an early warning in combination with environmental correction and real-time monitoring, and improves monitoring sensitivity and reliability.

Description

Technical Field

[0001] The invention relates to the technical field of acetylene cracking furnace production monitoring, and more specifically to a CO laser detection system based on thermal radiation background. Background Art

[0002] In an ethylene cracking furnace fueled by natural gas, the operating temperature usually exceeds 800°C, which will produce strong thermal radiation, especially in the mid-infrared region. This thermal radiation will overlap with the infrared absorption characteristic wavelength of CO, thereby affecting the monitoring accuracy. In addition, the high-temperature gas generated by the combustion of natural gas and the cracking reaction itself will also enhance the thermal radiation background of the flue gas, bringing additional thermal noise interference to the CO monitoring equipment in the exhaust pipe. Compared with other fuels, natural gas combustion is closer to complete combustion and usually operates within a narrow range of air excess coefficient. When the air volume is insufficient, it is easy to cause local hypoxia, thereby increasing the generation of CO, while excess air will reduce the combustion efficiency. Therefore, in the ethylene cracking furnace, the slight change of CO concentration is particularly sensitive, and the sensitivity of the CO monitoring equipment is required to be high. At the same time, natural gas combustion will produce a large amount of water vapor. At high temperature, water vapor has a strong infrared absorption peak, and the absorption spectrum of water vapor will overlap with the infrared absorption spectrum of CO, increasing the spectral interference in CO monitoring. The existing CO monitoring system usually lacks the spectral analysis ability to effectively identify and eliminate water vapor interference under complex spectral backgrounds, which makes it more difficult to distinguish the absorption signals of water vapor and CO. Summary of the invention

[0003] In order to overcome the above-mentioned defects of the prior art, the present invention provides a CO laser detection system based on thermal radiation background, which effectively extracts CO signals under thermal radiation background through quantum cascade laser and beam modulation technology.

[0004] In the acetylene production workshop of a large petrochemical plant, there are multiple acetylene cracking furnaces fueled by natural gas. Specifically, during daily operation monitoring, operators detected abnormal fluctuations in the CO concentration curve from the control system, but it was still within the range permitted by environmental protection standards, but slightly higher than historical data. The cause of the increase is still unclear. In order to prevent the situation from worsening, real-time monitoring of CO in the exhaust duct is required to better assist in problem analysis and diagnosis.

[0005] In order to solve the technical problems in the above situation and achieve the above purpose, the present invention provides the following technical solutions:

[0006] A CO laser detection system based on thermal radiation background comprises a quantum cascade laser, a pyroelectric detector, a data processing unit and a signal analysis module. The quantum cascade laser emits a 4.6 μm laser beam, the pyroelectric detector receives the beam after passing through a flue gas transmission pipeline, converts a photoelectric signal into an electrical signal, and transmits the electrical signal to the data processing unit. The data processing unit filters, performs analog-to-digital conversion, and performs signal demodulation on the signal from the pyroelectric detector, and monitors the CO concentration of the exhaust pipe in an acetylene cracking furnace in real time. The data processing unit is connected to a reference light intensity adjustment module, which is connected to an environmental parameter sensing module. The reference light intensity adjustment module uses the temperature, humidity and pressure data acquired in real time by the environmental parameter sensing module to adjust the absorption coefficient of CO through an environmental correction factor. The environmental correction factor is obtained by analyzing the real-time monitoring temperature, humidity and pressure data of the exhaust pipe of an ethylene cracking tank, and dynamically calculates and corrects the reference light intensity based on the environmental correction factor. The data processing unit uses the reference light intensity for dynamic correction of CO concentration monitoring to compensate for the light intensity fluctuation caused by water vapor absorption and thermal radiation background. In the data processing unit, the real-time monitoring correction formula of CO concentration is:

[0007] ;

[0008] Where: It is the real-time monitoring concentration correction value of CO in the exhaust pipe of the ethylene cracking furnace. is the absorption coefficient of CO, that is, the absorption coefficient of CO in flue gas to 4.6μm laser beam after correction by temperature, humidity and pressure data, is the optical path length, and the physical length of the smoke exhaust duct that the laser passes through is taken. is the dynamic reference light intensity of CO, obtained by the reference light intensity adjustment module, It is the actual measured laser intensity after CO passes through the exhaust duct, obtained by the pyroelectric detector.

[0009] As a further solution of the present invention, the quantum cascade laser includes a laser light source generator capable of emitting 4.6 μm, the laser light source generator is connected to a beam modulator and a first temperature control module, and the beam modulator is connected to a collimating lens.

[0010] At the beginning of the system, the laser light source generator provides a stable current and control signal for the quantum cascade laser, and the QCL begins to emit a 4.6μm laser beam. The laser beam passes through the beam modulator, which modulates the laser frequency or pulse, so that the laser beam carries specific modulation information. During the operation of the quantum cascade laser, the first temperature control module maintains the temperature stability of the quantum cascade laser to ensure that the wavelength of the laser emission is precisely stable at 4.6μm and is not affected by changes in ambient temperature. The modulated laser beam passes through the collimating lens, which collimates the beam into a parallel beam to ensure the stable propagation of the beam in the flue gas transmission pipeline. The collimated laser beam passes through the flue gas transmission pipeline containing CO. The CO molecules absorb part of the laser energy at a specific wavelength, and the remaining beam intensity is transmitted to the pyroelectric detector. The pyroelectric detector receives the beam after passing through the flue gas pipeline and converts it into an electrical signal. The subsequent signal is demodulated by phase-locked amplification technology to separate the pure CO absorption signal.

[0011] As a further solution of the present invention, the laser beam of the quantum cascade laser is transmitted to the pyroelectric detector through a smoke transmission pipe, the inlet and outlet of the smoke transmission pipe are both provided with optical windows, and the pyroelectric detector is provided with a low-noise preamplifier and a second temperature control module.

[0012] As a further solution of the present invention, the data processing unit includes a signal filter, an analog-to-digital converter, a signal demodulator and a gas concentration calculation unit. The signal filter is connected to the analog-to-digital converter, the analog-to-digital converter is connected to the signal demodulator, and the signal demodulator is connected to the gas concentration calculation unit.

[0013] After passing through the flue gas transmission pipeline, the laser beam reaches the pyroelectric detector. The detector receives the beam intensity signal after CO absorption and converts the optical signal into a corresponding electrical signal. The low-noise preamplifier on the pyroelectric detector amplifies the electrical signal. The second temperature control module maintains the stable working temperature of the pyroelectric detector to avoid changes in detector sensitivity and signal drift caused by ambient temperature fluctuations, thereby improving measurement accuracy and signal stability. After receiving the amplified electrical signal, the data processing unit first removes noise through a signal filter, and then converts the analog signal into a digital signal through an analog-to-digital converter to facilitate subsequent digital signal processing. The data processing unit uses phase-locked amplification technology to demodulate the modulated signal, extract pure signals related to CO concentration, and effectively separate interference signals from water vapor and thermal radiation background. The demodulated signal is sent to the gas concentration calculation unit, and the actual CO concentration value is calculated by the formula, and compared and analyzed with historical data.

[0014] Temperature changes directly affect the energy state and movement speed of gas molecules, thereby affecting the absorption characteristics of CO molecules to lasers. Under high temperature conditions, the frequency of collisions between molecules increases, resulting in broadening of absorption lines and slight shifts in the center frequency. Therefore, the absorption coefficient of CO needs to be adjusted according to the real-time temperature to compensate for this effect. Pressure changes affect the density and molecular collision frequency of the gas, which in turn affects the intensity of light absorption and the broadening of absorption lines. Higher pressures usually lead to broadening of absorption lines, so the absorption coefficient needs to be corrected according to the real-time pressure during measurement. Changes in humidity (especially water vapor concentration) have a significant effect on the propagation and absorption of light. Water vapor has strong absorption lines in the mid-infrared band, which overlap with the absorption lines of CO, thereby interfering with the measurement. Therefore, changes in humidity need to be adjusted through correction factors to offset the impact of this interference on CO measurement results.

[0015] As a further solution of the present invention, in the reference light intensity adjustment module, the environmental correction factor is obtained by using a predefined environmental correction factor formula through real-time monitoring of temperature, humidity and pressure data of the exhaust pipe of the ethylene cracking tank. The predefined environmental correction factor formula is:

[0016] ;

[0017] Where: , , They are real-time monitoring of temperature, humidity and pressure of the exhaust pipe of the ethylene cracking tank. is the environmental correction factor, , , They are reference temperature, reference humidity and reference pressure, which are 293K, absolute humidity corresponding to 50% relative humidity under standard conditions, and 101325Pa, respectively. , , They are temperature influence index, pressure influence index and humidity influence index, which are obtained through experimental calibration.

[0018] The absorption characteristics of CO molecules change with changes in temperature, pressure and humidity. High temperature will lead to intensified molecular motion, affecting the broadening of the absorption spectrum; pressure changes will affect the density of the gas and the frequency of molecular collisions, thereby affecting the absorption intensity; humidity changes will introduce interference from water vapor, especially in the mid-infrared band, where the absorption of water vapor overlaps with the absorption of CO. In order to accurately measure the concentration of CO under different environmental conditions, the absorption coefficient of CO must be environmentally corrected. This requires that the absorption coefficient under standard conditions be adjusted through an environmental correction factor to reflect the impact of the actual environment on the absorption coefficient.

[0019] As a further solution of the present invention, in the reference light intensity adjustment module, the absorption coefficient of CO in the flue gas to the 4.6 μm laser beam after correction by the temperature, humidity and pressure data is equal to the product of the CO absorption coefficient under standard conditions and the environmental correction factor. The formula for the absorption coefficient of CO in the flue gas to the 4.6 μm laser beam after correction by the temperature, humidity and pressure data is:

[0020] ;

[0021] Where: is the CO absorption coefficient under standard conditions, obtained by experimental calibration.

[0022] When the laser passes through the flue gas transmission pipeline containing CO gas, the light intensity will attenuate as the optical path increases. This attenuation follows the Beer-Lambert law, and the light intensity decays exponentially with the propagation distance. The initial light intensity provided by the quantum cascade laser is the starting point of the system measurement, reflecting the intensity of the laser before any absorption. The absorption coefficient is a value corrected for temperature, humidity and pressure, and accurately reflects the actual absorption capacity of CO to the laser under the current environmental conditions. The optical path length is the physical distance that the laser propagates in the flue gas transmission pipeline, which directly affects the degree of attenuation of the light intensity. This length is fixed and determined according to the physical length of the pipeline.

[0023] As a further solution of the present invention, in the reference light intensity adjustment module, the dynamic reference light intensity of CO is obtained by correcting the initial light intensity of CO by the exponential attenuation term of the product of the absorption coefficient of CO in the flue gas to the 4.6 μm laser beam and the optical path length after correction by the temperature, humidity and pressure data. The dynamic reference light intensity formula of CO is:

[0024] ;

[0025] Where: is the initial light intensity of CO, provided by a quantum cascade laser.

[0026] The gradual increase in CO concentration is the result of gradual changes in process or equipment operating conditions, such as a slow increase in cracking temperature, a gradual deviation of reaction conditions from the normal range, or reduced efficiency due to equipment wear. Such changes often do not cause serious problems immediately, but if not handled in time, they can lead to equipment overload, uncontrolled reactions, and ultimately safety accidents or product quality problems. By promptly identifying the gradual increase in CO concentration, the system can issue an early warning signal in advance to remind operators to check process parameters or equipment status, so as to take necessary adjustments or maintenance measures to prevent potential risks from further development. The instantaneous spike in CO concentration is caused by sudden abnormal events, such as raw material fluctuations, feed system abnormalities, equipment failures, or operating errors. This spike is short-lived, but if not handled in time, it can lead to more serious chain reactions, such as deflagration in the cracking furnace, over-reaction or incomplete reaction, affecting product quality, and even causing equipment damage or personal injury. By quickly identifying the instantaneous spike in CO concentration, the system can immediately trigger an early warning signal to remind operators to quickly check and handle abnormal conditions to prevent short-term abnormalities from evolving into major accidents.

[0027] As a further solution of the present invention, the signal analysis unit identifies CO concentration gradually increasing events and CO concentration instantaneous peak events through real-time monitoring of CO concentration and historical data analysis, and issues a warning signal.

[0028] As a further solution of the present invention, in the signal analysis unit, the method for identifying the CO concentration gradually increasing event is to compare the trend signal used to identify the CO concentration gradually increasing in the observation time window with the preset CO concentration increasing threshold. If it is greater than the preset CO concentration increasing threshold, it is determined to be a CO concentration gradually increasing event. Otherwise, it is determined not to be a CO concentration gradually increasing event. The trend signal formula used to identify the CO concentration gradually increasing in the observation time window is:

[0029] ;

[0030] Where: For the current moment, To identify the trend signal of the gradual increase of CO concentration within the observation time window, The average time window size for identifying rising trends can be set according to requirements. The index of the time point in the time window for identifying the rising trend, , They are the first and CO concentration at each time point.

[0031] As a further solution of the present invention, in the signal analysis unit, the CO concentration instantaneous peak event is identified by comparing the signal used to identify the CO concentration instantaneous peak with a preset CO concentration instantaneous peak threshold. If the signal is greater than the preset CO concentration instantaneous peak threshold, it is determined to be a CO concentration instantaneous peak event. Otherwise, it is determined not to be a CO concentration instantaneous peak event. The signal formula for identifying the CO concentration instantaneous shoulder in the observation time window is:

[0032] ;

[0033] Where: is a signal used to identify instantaneous peaks in CO concentration. For the moment Real-time monitoring value of CO concentration, The reference time window size for peak identification is set according to the requirements. is the time point index in the reference time window for spike identification, The first CO concentration at each time point.

[0034] Compared with the prior art, in order to solve the technical problem, the technical effect of the present invention is as follows: the present invention emits a 4.6μm wavelength laser through a quantum cascade laser, combined with beam modulation and phase-locked amplification technology, which can effectively separate and extract the absorption signal of CO under a strong thermal radiation background, and eliminate the spectral interference of water vapor. The reference light intensity adjustment module uses the real-time monitored temperature, humidity and pressure data to dynamically adjust the CO absorption coefficient and the reference light intensity through the environmental correction factor to ensure the accuracy of the measurement results under different working conditions. The signal analysis unit specifically identifies the gradual increase in CO concentration and instantaneous spike events through real-time monitoring of CO concentration and historical data analysis, and promptly issues early warning signals, thereby enhancing the system's response capability to sudden anomalies and long-term trend anomalies, helping to prevent and solve potential process problems and equipment failures, and significantly improving the sensitivity, accuracy and reliability of CO concentration monitoring in high temperature and complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a system block diagram of the present invention. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the present invention to clearly and completely describe the technical solutions in the present invention. Obviously, the described technical solutions are only part of the present invention but not all of it. Based on the content of the present invention, all other technical solutions obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0037] like Figure 1As shown, a CO laser detection system based on thermal radiation background proposed by the present invention includes a quantum cascade laser, a pyroelectric detector, a data processing unit and a signal analysis module. The quantum cascade laser emits a 4.6μm laser beam, and the pyroelectric detector receives the beam after passing through the flue gas transmission pipeline, converts the photoelectric signal into an electrical signal, and transmits the electrical signal to the data processing unit. The data processing unit filters, performs analog-to-digital conversion, and demodulates the signal from the pyroelectric detector to monitor the CO concentration of the exhaust pipe in the acetylene cracking furnace in real time. The data processing unit is connected to a reference light intensity adjustment module, and the reference light intensity adjustment module is connected to an environmental parameter sensing module. The reference light intensity adjustment module uses the temperature, humidity and pressure data obtained in real time by the environmental parameter sensing module to adjust the absorption coefficient of CO through an environmental correction factor. The environmental correction factor is obtained by analyzing the real-time monitoring temperature, humidity and pressure data of the exhaust pipe of the ethylene cracking tank, and dynamically calculates and corrects the reference light intensity based on the environmental correction factor. The data processing unit uses it for dynamic correction of CO concentration monitoring to compensate for the light intensity fluctuation caused by water vapor absorption and thermal radiation background. In the data processing unit, the real-time monitoring correction formula of CO concentration is:

[0038] ;

[0039] Where: It is the real-time monitoring concentration correction value of CO in the exhaust pipe of the ethylene cracking furnace. is the absorption coefficient of CO, that is, the absorption coefficient of CO in flue gas to 4.6μm laser beam after correction by temperature, humidity and pressure data, is the optical path length, and the physical length of the smoke exhaust duct that the laser passes through is taken. is the dynamic reference light intensity of CO, obtained by the reference light intensity adjustment module, It is the actual measured laser intensity after CO passes through the exhaust duct, obtained by the pyroelectric detector.

[0040] The present invention uses a quantum cascade laser to emit a laser with a wavelength of 4.6 μm, combined with beam modulation and phase-locked amplification technology, to effectively separate and extract the absorption signal of CO under a strong thermal radiation background, while eliminating the spectral interference of water vapor. The reference light intensity adjustment module uses the real-time monitored temperature, humidity and pressure data to dynamically adjust the CO absorption coefficient and the reference light intensity through the environmental correction factor to ensure the accuracy of the measurement results under different working conditions. The signal analysis unit specifically identifies the gradual increase in CO concentration and instantaneous peak events through real-time monitoring of CO concentration and historical data analysis, and promptly issues early warning signals, thereby enhancing the system's response capability to sudden anomalies and long-term trend anomalies, helping to prevent and solve potential process problems and equipment failures, and significantly improving the sensitivity, accuracy and reliability of CO concentration monitoring in high-temperature and complex environments.

[0041] It should be noted that the quantum cascade laser includes a laser light source generator capable of emitting 4.6 μm, the laser light source generator is connected to a beam modulator and a first temperature control module, and the beam modulator is connected to a collimating lens.

[0042] By emitting precise 4.6μm laser light through a quantum cascade laser and combining it with a beam modulator, a first temperature control module and a collimating lens, the system significantly improves the accuracy of CO measurement, enhances the ability to separate CO signals from high-temperature thermal radiation background, and effectively reduces the interference of water vapor and thermal noise.

[0043] It should be noted that the laser beam of the quantum cascade laser is transmitted to the pyroelectric detector through the smoke transmission pipe. The inlet and outlet of the smoke transmission pipe are both provided with optical windows. The pyroelectric detector is provided with a low-noise preamplifier and a second temperature control module.

[0044] By setting optical windows at the inlet and outlet of the flue gas transmission duct, the light beam of the quantum cascade laser can be transmitted to the pyroelectric detector without interference. Combined with the application of a low-noise preamplifier and a second temperature control module, the detection accuracy and stability of the CO signal are effectively improved, and the interference caused by environmental noise and temperature changes is reduced, thereby achieving more reliable CO concentration monitoring in complex industrial environments.

[0045] It should be noted that the data processing unit includes a signal filter, an analog-to-digital converter, a signal demodulator and a gas concentration calculation unit. The signal filter is connected to the analog-to-digital converter, the analog-to-digital converter is connected to the signal demodulator, and the signal demodulator is connected to the gas concentration calculation unit.

[0046] The pyroelectric detector receives the optical signal after passing through the flue gas transmission duct and converts it into an electrical signal, which is first transmitted to the signal filter of the data processing unit. The signal filter is used to remove high-frequency noise, low-frequency drift and other unwanted interference signals in the electrical signal to ensure that the retained signal is an effective component related to the CO concentration. This process helps to improve the quality and stability of the signal. The filtered analog signal is transmitted to the analog-to-digital converter (ADC). The analog-to-digital converter converts the analog signal into a digital signal for subsequent digital signal processing and analysis. The converted digital signal retains the important information in the original signal, but is represented in digital form, which is suitable for further calculation and processing. The digital signal enters the signal demodulator. The signal demodulator uses phase-locked amplification technology to demodulate the digital signal. Since the laser beam is modulated during transmission, the role of the demodulator is to extract the characteristic signal related to CO absorption from the received signal and effectively separate the water vapor absorption signal and other thermal noise interference. This step ensures that the CO absorption information in the signal can be accurately extracted for subsequent concentration calculation. The demodulated signal is transmitted to the gas concentration calculation unit. The gas concentration calculation unit calculates the CO concentration in the flue gas based on the Beer-Lambert law, by using the calculated reference light intensity, the actual measured light intensity, and the CO absorption coefficient. This unit uses the corrected parameters to ensure that the final CO concentration calculation result is highly accurate. Through comparative analysis, the system can identify the gradual increase trend of CO concentration or instantaneous spike events. When an abnormality is detected, the system will issue an early warning signal. This function helps operators to understand the changes in working conditions in a timely manner and take corresponding measures to ensure the safety and reliability of the system.

[0047] It should be noted that in the reference light intensity adjustment module, the environmental correction factor is obtained by using the predefined environmental correction factor formula through the real-time monitoring temperature, humidity and pressure data of the exhaust pipe of the ethylene cracking tank. The predefined environmental correction factor formula is:

[0048] ;

[0049] Where: , , They are real-time monitoring of temperature, humidity and pressure of the exhaust pipe of the ethylene cracking tank. is the environmental correction factor, , , They are reference temperature, reference humidity and reference pressure, which are 293K, absolute humidity corresponding to 50% relative humidity under standard conditions, and 101325Pa, respectively. , , They are temperature influence index, pressure influence index and humidity influence index, which are obtained through experimental calibration.

[0050] In the high temperature and complex environment of the ethylene cracking tank, the infrared absorption characteristics of CO are significantly affected by changes in temperature, humidity and pressure. In order to ensure the accuracy of CO concentration measurement, the reference light intensity adjustment module monitors the temperature, humidity and pressure data in the exhaust duct in real time and applies the predefined environmental correction factor formula to correct the CO absorption coefficient. The temperature influence index in the formula is , Pressure Impact Index and humidity impact index The environmental correction factors are obtained through experimental calibration and reflect the specific effects of environmental parameters on CO absorption characteristics. The environmental correction factors are dynamically calculated by comparing the real-time monitored environmental conditions with the standard reference conditions. , and adjust the absorption coefficient of CO accordingly, thereby correcting the reference light intensity. This approach effectively compensates for the measurement errors caused by changes in environmental conditions, allowing the system to maintain high-precision monitoring of CO concentration under high temperature, humidity fluctuations and pressure changes. By correcting the impact of environmental factors on the absorption coefficient, the system can more accurately separate the absorption signal of CO, solve the technical problems caused by thermal radiation and water vapor interference, and significantly improve the reliability and accuracy of CO concentration measurement.

[0051] It should be noted that in the reference light intensity adjustment module, the absorption coefficient of CO in flue gas to 4.6μm laser beam after correction by temperature, humidity and pressure data is equal to the product of CO absorption coefficient under standard conditions and environmental correction factor. The formula of the absorption coefficient of CO in flue gas to 4.6μm laser beam after correction by temperature, humidity and pressure data is:

[0052] ;

[0053] Where: is the CO absorption coefficient under standard conditions, obtained by experimental calibration.

[0054] In the reference light intensity adjustment module, the formula The CO absorption coefficient is dynamically adjusted to compensate for measurement errors caused by changes in temperature, humidity and pressure. As a benchmark, combined with environmental correction factors To reflect the impact of real-time environmental conditions, it can accurately correct the absorption characteristics of CO under complex working conditions of high temperature, humidity fluctuations and pressure changes, ensure the accuracy and reliability of measurement, thereby effectively solving the problems of thermal radiation and water vapor interference and improving the accuracy of CO concentration monitoring.

[0055] It should be noted that in the reference light intensity adjustment module, the dynamic reference light intensity of CO is obtained by correcting the initial light intensity of CO by the exponential attenuation term of the product of the absorption coefficient of CO in the flue gas to the 4.6μm laser beam and the optical path length after correction by temperature, humidity and pressure data. The dynamic reference light intensity formula of CO is:

[0056] ;

[0057] Where: is the initial light intensity of CO, provided by a quantum cascade laser.

[0058] By real-time correction of the absorption coefficient , the system can dynamically adjust the reference light intensity according to the current environmental conditions (such as temperature, humidity and pressure) to ensure that the measured value accurately reflects the actual CO concentration. The formula takes into account the optical path length and the corrected absorption coefficient The product of the energy loss of the laser in the flue gas transmission process is accurately compensated by the exponential decay model, thereby reducing the measurement error. By correcting the initial light intensity, the system can maintain high-precision CO concentration measurement under complex conditions of high temperature, humidity fluctuation and pressure change, solving the technical problems caused by thermal radiation and water vapor interference, and ensuring the reliability and stability of monitoring.

[0059] It should be noted that the signal analysis unit identifies CO concentration gradual increase events and CO concentration instantaneous peak events through real-time monitoring of CO concentration and historical data analysis, and issues a warning signal.

[0060] The signal analysis unit identifies CO concentration gradual increase events and instantaneous spike events through real-time monitoring of CO concentration and historical data analysis, and issues early warning signals. The technical effect of this method is that the system can detect and identify abnormal changes in CO concentration in real time, including gradual increases and instantaneous spikes, and quickly respond to potential process problems; through early warning, the system can take necessary measures to prevent possible safety hazards before abnormal changes evolve into more serious problems; through monitoring and analysis, the system helps to ensure the operational stability of the ethylene cracking furnace, prevent production interruptions or equipment damage caused by abnormal CO concentration, and improve overall production efficiency and safety.

[0061] It should be noted that in the signal analysis unit, the method for identifying the CO concentration gradually increasing event is to compare the trend signal used to identify the CO concentration gradually increasing in the observation time window with the preset CO concentration increasing threshold. If it is greater than the preset CO concentration increasing threshold, it is determined to be a CO concentration gradually increasing event. Otherwise, it is determined not to be a CO concentration gradually increasing event. The trend signal formula used to identify the CO concentration gradually increasing in the observation time window is:

[0062] ;

[0063] Where: For the current moment, To identify the trend signal of the gradual increase of CO concentration within the observation time window, The average time window size for identifying rising trends can be set according to requirements. The index of the time point in the time window for identifying the rising trend, , They are the first and CO concentration at each time point.

[0064] By calculating the CO concentration change trend within the observation time window , the system can identify the slow and continuous increase in CO concentration, which is usually an early sign of potential process or equipment problems. The gradual increase trend reflects the slow change of reaction conditions in the cracking furnace, such as the gradual increase in temperature or the gradual deterioration of combustion conditions; by setting a reasonable threshold, the system can issue an early warning signal when the CO concentration change has not reached a dangerous level, reminding operators to check and adjust, so as to prevent the problem from further deteriorating. This early warning mechanism can effectively reduce the risk of accidents; the observation time window and threshold can be flexibly set according to process requirements and historical data, making the system highly adaptable and can be adjusted for different operating conditions, thereby improving the accuracy and reliability of identification. This method can effectively solve the problem that traditional monitoring systems are difficult to identify slowly changing hidden dangers, improve the sensitivity and adaptability of the CO monitoring system under high temperature and complex working conditions, help prevent potential process anomalies and equipment failures, and ensure the safe and stable operation of the cracking furnace.

[0065] It should be noted that in the signal analysis unit, the identification method of the CO concentration instantaneous spike event is to compare the signal used to identify the CO concentration instantaneous spike with the preset CO concentration instantaneous spike threshold. If it is greater than the preset CO concentration instantaneous spike threshold, it is determined to be a CO concentration instantaneous spike event. Otherwise, it is determined not to be a CO concentration instantaneous spike event. The signal formula for identifying the CO concentration instantaneous shoulder in the observation time window is:

[0066] ;

[0067] Where: is a signal used to identify instantaneous peaks in CO concentration. For the moment Real-time monitoring value of CO concentration, The reference time window size for peak identification is set according to the requirements. is the time point index in the reference time window for spike identification, The first CO concentration at each time point.

[0068] This method monitors the CO concentration in real time. By comparing with the average value over the past period of time, sudden spikes in CO concentration can be quickly identified. This is particularly critical for detecting sudden process fluctuations or operational anomalies, such as unstable fuel supply or sudden changes in combustion conditions; by setting a reasonable spike recognition threshold, the system can distinguish between normal concentration fluctuations and abnormal spike events, thereby reducing the false alarm rate. Only when the signal exceeds the preset threshold will the system trigger an alarm to avoid operator fatigue or erroneous reactions caused by frequent false alarms; since this method can detect instantaneous abnormal changes in CO concentration in real time, the system can issue an early warning signal at the first time, prompting operators to check and respond to possible faults or abnormal conditions in a timely manner, thereby preventing serious accidents. This method solves the problem that traditional monitoring systems are difficult to capture and respond to in a timely manner when facing instantaneous abnormal fluctuations in CO concentration. By identifying sudden CO concentration spike events, the system can detect and respond to sudden abnormal conditions in the operation of the cracking furnace in a timely manner, ensure the safety and stability of the system, and avoid potential process accidents.

[0069] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

[0070] Finally: The above description is only an implementation scheme of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A CO laser detection system based on thermal radiation background, characterized in that: The invention comprises a quantum cascade laser, a pyroelectric detector, a data processing unit and a signal analysis module. The quantum cascade laser emits a 4.6 μm laser beam. The pyroelectric detector receives the beam after passing through the flue gas transmission pipeline, converts the photoelectric signal into an electrical signal, and transmits the electrical signal to the data processing unit. The data processing unit filters, performs analog-to-digital conversion and signal demodulation on the signal from the pyroelectric detector, and monitors the CO concentration of the exhaust pipe in the acetylene cracking furnace in real time. The data processing unit is connected with a reference light intensity adjustment module, and the reference light intensity adjustment module is connected with an environmental parameter sensing module. The reference light intensity adjustment module uses the temperature, humidity and pressure data obtained in real time by the environmental parameter sensing module to adjust the absorption coefficient of CO through the environmental correction factor. The environmental correction factor is obtained by analyzing the real-time monitoring temperature, humidity and pressure data of the exhaust pipe of the ethylene cracking tank, and dynamically calculates and corrects the reference light intensity based on the environmental correction factor. The data processing unit uses it for dynamic correction of CO concentration monitoring to compensate for the light intensity fluctuation caused by water vapor absorption and thermal radiation background. In the data processing unit, the real-time monitoring correction formula of CO concentration is: ； Where: It is the real-time monitoring concentration correction value of CO in the exhaust pipe of the ethylene cracking furnace. is the absorption coefficient of CO, that is, the absorption coefficient of CO in flue gas to 4.6μm laser beam after correction by temperature, humidity and pressure data, is the optical path length, and the physical length of the smoke exhaust duct that the laser passes through is taken. is the dynamic reference light intensity of CO, obtained by the reference light intensity adjustment module, It is the actual measured laser intensity after CO passes through the exhaust duct, obtained by the pyroelectric detector.

2. A CO laser detection system based on thermal radiation background according to claim 1, characterized in that the quantum The cascade laser comprises a laser light source generator capable of emitting 4.6 μm, the laser light source generator is connected with a beam modulator and a first temperature control module, and the beam modulator is connected with a collimating lens.

3. A CO laser detection system based on thermal radiation background according to claim 2, characterized in that the quantum The laser beam of the cascade laser is transmitted to the pyroelectric detector through a smoke transmission pipeline. The inlet and outlet of the smoke transmission pipeline are both provided with optical windows. The pyroelectric detector is provided with a low-noise preamplifier and a second temperature control module.

4. The CO laser detection system based on thermal radiation background according to claim 3, characterized in that: The data processing unit comprises a signal filter, an analog-to-digital converter, a signal demodulator and a gas concentration calculation unit. The signal filter is connected to the analog-to-digital converter, the analog-to-digital converter is connected to the signal demodulator, and the signal demodulator is connected to the gas concentration calculation unit.

5. The CO laser detection system based on thermal radiation background according to claim 1, characterized in that: In the reference light intensity adjustment module, the real-time monitoring temperature, humidity and pressure data of the exhaust pipe of the ethylene cracking tank are used to obtain the environmental correction factor using a predefined environmental correction factor formula. The predefined environmental correction factor formula is: ； Where: , , They are real-time monitoring of temperature, humidity and pressure of the exhaust pipe of the ethylene cracking tank. is the environmental correction factor, , , They are reference temperature, reference humidity and reference pressure, which are 293K, absolute humidity corresponding to 50% relative humidity under standard conditions, and 101325Pa, respectively. , , They are temperature influence index, pressure influence index and humidity influence index, which are obtained through experimental calibration.

6. The CO laser detection system based on thermal radiation background according to claim 5, characterized in that: In the reference light intensity adjustment module, the absorption coefficient of CO in flue gas to 4.6 μm laser beam after correction by temperature, humidity and pressure data is equal to the product of CO absorption coefficient under standard conditions and environmental correction factor. The formula of the absorption coefficient of CO in flue gas to 4.6 μm laser beam after correction by temperature, humidity and pressure data is: ； Where: is the CO absorption coefficient under standard conditions, obtained by experimental calibration.

7. The CO laser detection system based on thermal radiation background according to claim 6, characterized in that: In the reference light intensity adjustment module, the dynamic reference light intensity of CO is obtained by correcting the initial light intensity of CO by the exponential attenuation term of the product of the absorption coefficient of CO in the flue gas to the 4.6μm laser beam and the optical path length after correction by temperature, humidity and pressure data. The dynamic reference light intensity formula of CO is: ； Where: is the initial light intensity of CO, provided by a quantum cascade laser.

8. The CO laser detection system based on thermal radiation background according to claim 1, characterized in that: The signal analysis unit identifies CO concentration gradual increase events and CO concentration instantaneous peak events through real-time monitoring of CO concentration and historical data analysis, and issues early warning signals.

9. The CO laser detection system based on thermal radiation background according to claim 8, characterized in that: In the signal analysis unit, the method for identifying the CO concentration gradually increasing event is to compare the trend signal used to identify the CO concentration gradually increasing in the observation time window with the preset CO concentration increasing threshold. If it is greater than the preset CO concentration increasing threshold, it is determined to be a CO concentration gradually increasing event. Otherwise, it is determined not to be a CO concentration gradually increasing event. The trend signal formula used to identify the CO concentration gradually increasing in the observation time window is: ； Where: For the current moment, To identify the trend signal of gradually increasing CO concentration within the observation time window, The average time window size for identifying rising trends can be set according to requirements. The index of the time point in the time window for identifying the rising trend, , They are the first and CO concentration at each time point.

10. The CO laser detection system based on thermal radiation background according to claim 9, characterized in that: In the signal analysis unit, the identification method of the CO concentration instantaneous spike event is to compare the signal used to identify the CO concentration instantaneous spike with the preset CO concentration instantaneous spike threshold. If it is greater than the preset CO concentration instantaneous spike threshold, it is determined to be a CO concentration instantaneous spike event. Otherwise, it is determined not to be a CO concentration instantaneous spike event. The signal formula used to identify the CO concentration instantaneous spike in the observation time window is: ； Where: is a signal used to identify instantaneous peaks in CO concentration. For the moment Real-time monitoring value of CO concentration, The reference time window size for peak identification is set according to the requirements. is the time point index in the reference time window for spike identification, The first CO concentration at each time point.

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