Equipment and method for infrared pulse laser monitoring of vinyl chloride in long-distance open optical path

Abstract

The present invention discloses a mid-infrared pulse laser monitoring equipment and method for vinyl chloride in a long-distance open optical path, and relates to the technical field of vinyl chloride monitoring. The equipment comprises: a mid-infrared laser emission module, a mid-infrared filter module, a multi-point angle cone reflection prism array, an optical signal focusing receiving module, a phase-locked amplifier, and a data acquisition storage processing module. The device can obtain the characteristic peak value of a specific waveband of the mid-infrared laser before emission and the characteristic peak value of a specific waveband of the mid-infrared laser after emission, and then determine the difference and ratio of the characteristic peak values ​​of the specific waveband of the mid-infrared laser; finally, based on the difference and ratio of the characteristic peak values ​​of the specific waveband of the mid-infrared laser and the vinyl chloride concentration inversion algorithm, inversion is performed to obtain the inverted vinyl chloride concentration. Compared with the prior art, the present invention can achieve long-distance, high-precision and rapid measurement of the concentration of vinyl chloride.

Description

Technical Field

[0001] The invention relates to the technical field of vinyl chloride monitoring, and in particular to infrared pulse laser monitoring equipment and method for vinyl chloride in a long-distance open optical path. Background Art

[0002] Vinyl chloride is carcinogenic and flammable, and is a major hazard source of hazardous chemicals. Leakage monitoring is usually carried out using fixed-point catalytic combustion or electrochemical sensors, which can only sample and detect gases near the monitoring points. Generally, a high concentration is required for detection, and there are common problems such as slow measurement speed, low sensitivity, limited distance, and susceptibility to environmental interference. How to achieve simultaneous and highly sensitive detection over a large area is an important safety issue in the production, storage, and use of vinyl chloride.

[0003] There is currently no open optical path long-distance detection equipment for vinyl chloride in China. The difficulty lies in the interference of environmental interfering gases (ethylene, chlorine, ethyl chloride, water vapor, etc.) and system noise. Since the vibration-rotation energy level of vinyl chloride atoms / molecules is low, the absorption characteristic peak is located in the mid-infrared band. The continuous laser modulation speed in the mid-infrared band is slow and the power is low, which has a certain impact on the detection accuracy, dynamic range and detection speed.

[0004] Therefore, how to design an equipment and method that can achieve long-distance, high-precision and rapid measurement of vinyl chloride has become a technical problem that urgently needs to be solved in this field. Summary of the invention

[0005] The purpose of the present invention is to provide an infrared pulse laser monitoring device and method for vinyl chloride in a long-distance open optical path, which can realize long-distance, high-precision and rapid measurement of the concentration of vinyl chloride.

[0006] To achieve the above object, the present invention provides the following solution.

[0007] In a first aspect, the present invention provides an infrared pulse laser monitoring device for vinyl chloride in a long-distance open optical path, and the infrared pulse laser monitoring device for vinyl chloride in a long-distance open optical path includes.

[0008] The mid-infrared laser emission module is used to modulate a narrow-frequency mid-infrared laser beam to obtain a modulated narrow-frequency mid-infrared laser beam.

[0009] The mid-infrared filter module is used to filter the modulated narrow-frequency mid-infrared laser beam to obtain a filtered beam.

[0010] The multi-point angle pyramid reflection prism array is used to reflect the filtered light beam to obtain a reflected light beam.

[0011] The mid-infrared filter module is also used to perform secondary filtering on the reflected light beam to obtain a secondary filtered light beam.

[0012] The optical signal focusing receiving module is used to convert the optical signal after the secondary filtering into an optical signal to obtain a current signal.

[0013] The lock-in amplifier is used to convert the current signal into a voltage signal and amplify it, while suppressing noise to the maximum extent to obtain a maximum signal-to-noise ratio.

[0014] The data acquisition storage processing module is used to convert the current signal and the voltage signal into digital signals and store them; determine the characteristic peak value of the specific band of the mid-infrared laser after emission based on the digital signal; determine the difference and ratio of the characteristic peak value of the specific band of the mid-infrared laser based on the characteristic peak value of the specific band of the mid-infrared laser before emission and the characteristic peak value of the specific band of the mid-infrared laser after emission; and perform inversion based on the difference and ratio of the characteristic peak value of the specific band of the mid-infrared laser and a vinyl chloride concentration inversion algorithm to obtain the inverted vinyl chloride concentration; the vinyl chloride concentration inversion algorithm is a correlation relationship and function between the difference and ratio of the specific characteristic peak value of the narrow-band mid-infrared wavelength and the vinyl chloride concentration established based on a neural network method.

[0015] In the second aspect, the present invention provides a method for monitoring vinyl chloride in an open optical path over a long distance using infrared pulse laser. The method is implemented based on the above-mentioned equipment for monitoring vinyl chloride in an open optical path over a long distance using infrared pulse laser. The method includes:

[0016] A narrow-frequency mid-infrared laser beam is modulated by a mid-infrared laser emission module to obtain a modulated narrow-frequency mid-infrared laser beam.

[0017] The modulated narrow-frequency mid-infrared laser beam is filtered using a mid-infrared filter module to obtain a filtered beam.

[0018] The filtered light beam is reflected by using a multi-point angle pyramid reflection prism array to obtain a reflected light beam.

[0019] The reflected light beam is secondary filtered by the mid-infrared filter module to obtain a secondary filtered light beam.

[0020] The optical signal focusing receiving module is used to convert the optical beam after the secondary filtering into an optical signal to obtain a current signal.

[0021] The current signal is converted into a voltage signal and amplified by a lock-in amplifier, while noise is suppressed to the maximum extent to obtain a maximum signal-to-noise ratio.

[0022] The current signal and the voltage signal are converted into digital signals and stored by using a data acquisition storage processing module; a characteristic peak value of a specific waveband of a mid-infrared laser after emission is determined based on the digital signal; a difference and a ratio of the characteristic peak values ​​of a specific waveband of the mid-infrared laser are determined based on the characteristic peak value of the specific waveband of the mid-infrared laser before emission and the characteristic peak value of the specific waveband of the mid-infrared laser after emission; an inversion is performed based on the difference and the ratio of the characteristic peak values ​​of the specific waveband of the mid-infrared laser and a vinyl chloride concentration inversion algorithm to obtain an inverted vinyl chloride concentration; the vinyl chloride concentration inversion algorithm is a correlation relationship and a function between the difference and the ratio of the specific characteristic peak values ​​of a narrow-band mid-infrared wavelength and the vinyl chloride concentration established based on a neural network method.

[0023] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0024] The present invention provides a long-distance open optical path mid-infrared pulse laser monitoring equipment and method for vinyl chloride. Through the coordinated use of a mid-infrared laser emission module, a mid-infrared filter module, a multi-point angle cone reflection prism array, an optical signal focusing receiving module, a phase-locked amplifier, and a data acquisition storage processing module, the mid-infrared laser specific band characteristic peak value before emission and the mid-infrared laser specific band characteristic peak value after emission can be obtained, and then the difference and ratio of the mid-infrared laser specific band characteristic peak value can be determined; finally, based on the difference and ratio of the mid-infrared laser specific band characteristic peak value and the vinyl chloride concentration inversion algorithm, inversion can be performed to obtain the inverted vinyl chloride concentration. Compared with the prior art, the present invention can achieve long-distance, high-precision and rapid measurement of vinyl chloride concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 A schematic structural diagram of an infrared pulse laser monitoring device for long-distance open optical path of vinyl chloride provided by one embodiment of the present invention.

[0027] Figure 2 A schematic flow chart of a method for monitoring vinyl chloride in a long-distance open optical path using infrared pulse laser is provided in accordance with an embodiment of the present invention.

[0028] Figure numerals.

[0029] 1-mounting bracket; 2-vinyl chloride detector housing; 3-semiconductor temperature and humidity control module; 4-data wireless transmission module; 5-data acquisition storage and processing module; 6-phase-locked amplifier; 7-optical signal focusing receiving module; 8-mid-infrared laser emission module; 9-indicator laser emission module; 10-bypass reflector; 11-mid-infrared filter module; 12-reference air chamber filter; 13-reference air chamber; 14-reference air chamber pump suction and exhaust filling and discharge port; 15-reference air chamber reflection prism; 16-reference air chamber standard gas filling and discharge port; 17-multi-point angle adjustment reflector; 18-multi-point angle cone reflection prism array. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] In recent years, domestic and foreign studies have used quantum cascade lasers (QCL) to try to broaden the effective detection dynamic range, detection speed and accuracy through the regulation and demodulation of pulsed light. Quantum cascade lasers are semiconductor lasers that can emit infrared lasers. They have high output power, narrow linewidth, and tunable characteristics. The typical operating wavelength range is the mid-infrared region of 3.6~11µm. The mid-infrared region is precisely the fingerprint spectral region of many gas molecules. Therefore, after the emergence of QCL, it has become a powerful tool in the field of gas molecule identification and detection.

[0033] Therefore, the present invention proposes a long-distance open optical path mid-infrared laser monitoring equipment and method for vinyl chloride leakage, special designs such as high-power, high-frequency pulse quantum cascade mid-infrared laser, reference optical path, precision optical separation calibration module, noise reduction and anti-interference algorithm, and Beer-Lambert law concentration inversion method, which can achieve 50m long-distance, ppm-level vinyl chloride concentration high-precision second-level rapid measurement, and support risk warning and safety prevention and control of the entire chain of vinyl chloride production, storage and utilization.

[0034] In an exemplary embodiment, Figure 1 As shown, an infrared pulse laser monitoring device for vinyl chloride in a long-distance open optical path is provided, and the infrared pulse laser monitoring device for vinyl chloride in a long-distance open optical path includes.

[0035] The mid-infrared laser emission module 8 is used to modulate the narrow-frequency mid-infrared laser beam to obtain a modulated narrow-frequency mid-infrared laser beam.

[0036] The mid-infrared filter module 11 is used to filter the modulated narrow-frequency mid-infrared laser beam to obtain a filtered beam.

[0037] The multi-point angle pyramid reflection prism array 18 is used to reflect the filtered light beam to obtain a reflected light beam.

[0038] The mid-infrared filter module 11 is also used to perform secondary filtering on the reflected light beam to obtain a secondary filtered light beam.

[0039] The optical signal focusing receiving module 7 is used to convert the optical signal after the secondary filtering into an optical signal to obtain a current signal.

[0040] The lock-in amplifier 6 is used to convert the current signal into a voltage signal and amplify it, while suppressing noise to the maximum extent to obtain a maximum signal-to-noise ratio.

[0041] The data acquisition storage processing module 5 is used to convert the current signal and the voltage signal into digital signals and store them; determine the characteristic peak value of the specific band of the mid-infrared laser after emission based on the digital signal; determine the difference and ratio of the characteristic peak value of the specific band of the mid-infrared laser based on the characteristic peak value of the specific band of the mid-infrared laser before emission and the characteristic peak value of the specific band of the mid-infrared laser after emission; and perform inversion based on the difference and ratio of the characteristic peak value of the specific band of the mid-infrared laser and the vinyl chloride concentration inversion algorithm to obtain the inverted vinyl chloride concentration; the vinyl chloride concentration inversion algorithm is a correlation relationship and function between the difference and ratio of the specific characteristic peak value of the narrow-band mid-infrared wavelength and the vinyl chloride concentration established based on the neural network method.

[0042] The mid-infrared laser emission module 8 includes: a quantum cascade mid-infrared laser and a current temperature control adaptive adjustment module.

[0043] The quantum cascade mid-infrared laser is used to emit a narrow-frequency mid-infrared laser beam.

[0044] The current temperature control adaptive adjustment module is used to automatically control the operating temperature of the quantum cascade mid-infrared laser and to change the central wavelength of the narrow-frequency mid-infrared laser beam by temperature adjustment.

[0045] In order to accurately measure the concentration of vinyl chloride, the quantum cascade mid-infrared laser emits a narrow frequency mid-infrared laser beam. The collimated output power of the mid-infrared laser is not less than 10mW, the peak operating wavelength is in the range of 3.6um~16um, and the corresponding wave number is 625cm -1 ~2778cm -1, the spectral bandwidth is not higher than 3MHz. The current temperature control adaptive adjustment module, on the one hand, automatically adjusts the working temperature of the quantum cascade mid-infrared laser to prevent the deviation of the emitted mid-infrared center wavelength from causing measurement errors, the wavelength temperature coefficient is not higher than 3nm / K, and the wavelength current coefficient is not higher than 100nm / A; on the other hand, the center wavelength can be changed by temperature adjustment within a certain range, and the adjustable range is not less than 50nm.

[0046] In another exemplary embodiment of the present invention, the infrared pulse laser monitoring equipment for long-distance open optical path of vinyl chloride also includes.

[0047] The semiconductor temperature and humidity control module 3 is used to adjust the ambient temperature and humidity.

[0048] The semiconductor temperature and humidity control module 3 includes: a temperature and humidity sensor, a semiconductor temperature regulator and a dehumidifier.

[0049] The temperature and humidity sensor is used to monitor the temperature and humidity of the environment.

[0050] The semiconductor temperature regulator is used to adjust the temperature of the environment.

[0051] The dehumidifier is used to adjust the humidity of the environment.

[0052] The minimum temperature resolution of the temperature and humidity sensor shall not be higher than 5mA, and the minimum humidity resolution shall not be higher than 1%RH; the response time of the semiconductor temperature regulator and dehumidifier shall be less than 10s, the temperature range shall be 0~40℃, and the humidity range shall be 0~70%RH.

[0053] In an exemplary embodiment, the mid-infrared filter module 11 is mainly composed of a mid-infrared filter, which is located between the quantum cascade mid-infrared laser and the mid-infrared detector output port. The central wavelength of light transmission of the mid-infrared filter is consistent with the central wavelength of the mid-infrared laser of the quantum cascade mid-infrared laser, which is in the range of 3.6um~16um and the transmittance needs to be above 90%; in order to prevent the reflected light of the mid-infrared filter from affecting the measurement accuracy, the mid-infrared filter is fixed on a 3-degree-of-freedom adjustment platform, which has 2 inclination angle adjustments and forward and backward translation adjustment capabilities, which is equivalent to changing the 3-degree-of-freedom coordinate position of the light exit point, and the angle adjustment range is between 0~30°.

[0054] In an exemplary embodiment, the optical signal focusing receiving module 7 includes: a parabolic mirror and a mid-infrared photoelectric detector.

[0055] The parabolic mirror is used to enhance the receiving intensity of the mid-infrared laser reflected back from the open optical path.

[0056] The mid-infrared photoelectric detector is used to convert the light beam after secondary filtering into a photoelectric signal to obtain a current signal.

[0057] The diameter of the parabolic mirror shall not be less than Φ200mm and the surface shall be coated with infrared enhanced aluminum film to enhance the receiving intensity of the mid-infrared laser reflected back from the open optical path; the mid-infrared photoelectric detector converts the weak light signal into a current signal, and a photodiode photoelectric detector is selected with a wavelength response range of 3.6um~16um and a saturated light power of not less than 10mW.

[0058] In an exemplary embodiment, the phase-locked amplifier 6 mainly converts the received weak current signal into a voltage signal and amplifies it, while suppressing noise to the maximum extent to obtain the maximum signal-to-noise ratio; the output voltage range is within ±100mV.

[0059] In another exemplary embodiment of the present invention, the infrared pulse laser monitoring equipment for long-distance open optical path of vinyl chloride also includes.

[0060] The reference gas chamber 13 is used to calibrate the measurement accuracy of the instrument and eliminate external environmental interference using standard gas.

[0061] The reference chamber 13 uses standard gas to calibrate the instrument measurement accuracy on the one hand, and on the other hand, in actual measurement, measures the interference of stray light or particulate matter in the environment on the absorption spectrum and intensity of vinyl chloride in real time. The ultraviolet light beam collimated from the off-axis parabolic reflector is irradiated to a 45° plane reflector with a diameter of Φ10~100mm through the top control, and deflected 90° to the bottom reference chamber 13. A UV filter is also installed at the inlet of the reference chamber 13, and the central wavelength of light transmission is within the range of 3.6um~16um and the transmittance must be above 90%; the light beam after single or multiple reflections in the reference chamber 13 returns to the top plane reflector, and after being reflected again by the off-axis parabola, enters the optical signal focusing receiving module 7 and undergoes demodulation processing, thereby calibrating the accuracy and eliminating external environmental interference.

[0062] In an exemplary embodiment, the multi-point corner pyramid reflector array 18 includes.

[0063] The angle of incidence of mid-infrared light in the corner pyramid reflector array at different positions is 80-90°, and the reflectivity of mid-infrared laser is greater than 90%. In order to measure vinyl chloride at multiple positions, a reflective prism with precise automatic rotation adjustment is added at any position between the detector reflector and the corner pyramid reflector array to refract the outgoing light at a certain angle, thereby realizing the measurement of vinyl chloride concentration at multiple points in space.

[0064] In another exemplary embodiment of the present invention, the infrared pulse laser monitoring equipment for long-distance open optical path of vinyl chloride also includes.

[0065] The indicating laser emitting module 9 is used to indicate the aiming and alignment of the modulated narrow-frequency mid-infrared laser beam. The indicating laser emitting module adopts a visible laser, and the output laser power of the visible laser emitter is not less than 30mW.

[0066] In an exemplary embodiment, the data acquisition storage processing module 5 converts the voltage signal and the current signal into digital signals and stores them. The internally acquired and stored data at least includes the characteristic peak values ​​of the specific band of the mid-infrared laser before and after emission, the difference and ratio between the two, and the acquisition time; the internally processed data is to associate the difference and ratio of the characteristic peak values ​​of the specific band of the mid-infrared laser before and after emission with the corresponding concentration (BP / convolutional neural network and other methods) to invert the vinyl chloride concentration.

[0067] In another exemplary embodiment of the present invention, the infrared pulse laser monitoring equipment for long-distance open optical path of vinyl chloride also includes.

[0068] The data wireless transmission module 4 is used to use a local area network / Internet of Things to directly send the vinyl chloride concentration to a local server to store the vinyl chloride concentration; or use a 4G / 5G wireless network to send the vinyl chloride concentration to the cloud, and then transfer it to a local server or other storage area.

[0069] The present invention can achieve 50m long-distance, ppm-level high-precision second-level rapid measurement of vinyl chloride concentration through the special design of the equipment, such as high-power, high-frequency pulse quantum cascade mid-infrared laser, reference optical path, precision optical separation calibration module, noise reduction and anti-interference algorithm, and Beer-Lambert law concentration inversion method, effectively solving the problems of flammable and explosive vinyl chloride, slow measurement of carcinogenic media, high risk of personnel close-range measurement, and insufficient measurement accuracy of existing electrochemical / catalytic combustion methods, and supporting the risk warning and safety control of the whole chain of vinyl chloride production, storage and utilization. Through this equipment, the intensity of the harmonic signal of the narrow-band mid-infrared laser of vinyl chloride before emission, the attenuation intensity of the harmonic signal of the narrow-band mid-infrared laser in the standard gas chamber after emission, and the attenuation intensity of the harmonic signal of the narrow-band mid-infrared laser in the open optical path after emission are measured respectively to eliminate the interference of environmental stray light, and the difference of the attenuation intensity change before and after is used to invert the concentration of vinyl chloride; at the same time, the noise level of the signal system under different light intensities is measured and the algorithm is calibrated to eliminate its interference, so as to ensure the high-precision inversion of vinyl chloride concentration.

[0070] It should be noted that if Figure 1 As shown, the infrared pulse laser monitoring equipment for vinyl chloride long-distance open optical path also includes: a mounting bracket 1, a vinyl chloride detector housing 2, a reference gas chamber filter 12, a reference gas chamber pump suction and exhaust filling and discharge port 14, a reference gas chamber reflection prism 15, a reference gas chamber standard gas filling and discharge port 16 and a multi-point angle adjustment reflector 17.

[0071] Among them, the mounting bracket 1 plays a supporting role, the vinyl chloride detector housing 2 plays a protective role, the reference air chamber filter 12 is used to filter the light beam in the reference air chamber 13, the reference air chamber pump suction and exhaust filling and discharge port 14 is used for filling pump suction and exhaust, the reference air chamber reflection prism 15 is used to reflect the light beam in the reference air chamber 13, the reference air chamber standard gas filling and discharge port 16 is used to fill standard gas, and the multi-point angle adjustment reflector 17 is used to adjust the incident angle of the mid-infrared laser beam.

[0072] As an optional implementation, this embodiment designs a 50m long-distance, 200ppm minimum sensitivity, infrared second-level rapid monitoring equipment for vinyl chloride leakage in the open optical path according to the above content.

[0073] Among them, the mid-infrared laser emission module includes a quantum cascade mid-infrared laser and a current temperature control adaptive adjustment module. In order to accurately measure the concentration of vinyl chloride, the quantum cascade mid-infrared laser emits a narrow frequency mid-infrared laser beam. The collimated output power of the mid-infrared laser is 30~100mW, the peak operating wavelength is in the range of 8um~12um, and the corresponding wave number is 833cm -1 ~1250cm -1 , the spectral bandwidth is not higher than 2MHz. The current temperature control adaptive adjustment module, on the one hand, automatically adjusts the working temperature of the quantum cascade mid-infrared laser to prevent the deviation of the emitted mid-infrared center wavelength from causing measurement errors, the wavelength temperature coefficient is not higher than 3nm / K, and the wavelength current coefficient is not higher than 100nm / A; on the other hand, the center wavelength can be changed by temperature adjustment within a certain range, and the adjustable range is not less than 50nm.

[0074] The semiconductor temperature and humidity control module of this embodiment includes: a temperature and humidity sensor, a semiconductor temperature regulator and a dehumidifier. The temperature and humidity sensor has a minimum temperature resolution of no more than 3 mA, and a minimum humidity resolution of no more than 1% RH; the semiconductor temperature regulator and the dehumidifier have a response time of less than 10 seconds, a temperature range of 15-25°C, and a humidity range of 0-70% RH.

[0075] The mid-infrared filter module of this embodiment is mainly composed of a mid-infrared filter, which is located between the mid-infrared laser and the emission port of the mid-infrared detector. The central wavelength of light transmission of the filter is consistent with the central wavelength of the mid-infrared laser of the quantum cascade mid-infrared laser, which is in the range of 8um~12um and the transmittance needs to be above 90%; in order to prevent the reflected light of the filter from affecting the measurement accuracy, the filter is fixed on a 3-degree-of-freedom adjustment platform, which has the ability to adjust 2 inclination angles and forward and backward translation, which is equivalent to changing the 3-degree-of-freedom coordinate position of the light exit point, and the angle adjustment range is between 0~15°.

[0076] The optical signal focusing receiving module of this embodiment includes a parabolic mirror and a mid-infrared photoelectric detector. The parabolic mirror has a diameter of Φ400mm and the surface needs to be coated with infrared enhanced aluminum film to enhance the receiving intensity of the mid-infrared laser reflected back from the open optical path; the mid-infrared photoelectric detector converts weak light signals into current signals, and a photodiode photoelectric detector is selected, with a wavelength response range of 8um~12um and a saturated light power of 10~50mW.

[0077] The lock-in amplifier of this embodiment mainly converts the received weak current signal into a voltage signal and amplifies it, while suppressing noise to the maximum extent to obtain the maximum signal-to-noise ratio; the output voltage range is within ±100mV.

[0078] The reference gas chamber of this embodiment uses standard gas to calibrate the measurement accuracy of the instrument on the one hand, and on the other hand, in actual measurement, measures the interference of stray light or particulate matter in the environment on the absorption spectrum and intensity of vinyl chloride in real time. The ultraviolet light beam collimated from the off-axis parabolic reflector is irradiated to a 45° plane reflector with a diameter of Φ10~100mm through the top control, and deflected 90° to the bottom reference gas chamber. A UV filter is also installed at the inlet of the reference gas chamber, and the central wavelength of light transmission is within the range of 8um~12um and the transmittance must be above 90%; the light beam after single or multiple reflections in the reference gas chamber returns to the top plane reflector, and after being reflected again by the off-axis parabola, enters the optical signal focusing receiving module and undergoes demodulation processing, thereby calibrating the accuracy and eliminating external environmental interference.

[0079] The multi-point corner pyramid reflector array of this embodiment includes a plurality of corner pyramid reflector arrays at different positions, the incident angle of mid-infrared light is between 85° and 90°, and the reflectivity of mid-infrared laser is greater than 90%. In order to realize the measurement of chlorine gas at multiple positions, a reflective prism with precise and automatic rotation adjustment is added at any position between the detector reflector and the corner pyramid reflector array to refract the outgoing light at a certain angle, thereby realizing the measurement of vinyl chloride concentration at multiple points in space.

[0080] The indicating laser emitting module of this embodiment adopts visible laser, and the output laser power of the visible laser emitter is 50mW.

[0081] The data acquisition, storage and processing module of this embodiment converts the voltage and current signals into digital signals and stores them. The internally acquired and stored data at least includes the characteristic peak values ​​of the specific band of the mid-infrared laser before and after emission, the difference and ratio between the two, and the acquisition time; the internally processed data is to associate the difference and ratio of the characteristic peak values ​​of the specific band of the mid-infrared laser before and after emission with the corresponding concentration (BP / convolutional neural network and other methods) to invert the vinyl chloride concentration.

[0082] The data wireless transmission module of this embodiment uses a 4G / 5G wireless network to send data to the cloud, and then transfer it to a server or other storage area.

[0083] This equipment can be used to measure long-distance vinyl chloride leakage with high-precision quantitative perception and early warning, supporting risk warning and safety control for the entire chain of vinyl chloride production, storage and use.

[0084] like Figure 2 As shown, a method for infrared pulse laser monitoring of vinyl chloride in a long-distance open optical path is provided. The method for infrared pulse laser monitoring of vinyl chloride in a long-distance open optical path is implemented based on the above-mentioned infrared pulse laser monitoring equipment for vinyl chloride in a long-distance open optical path. The method for infrared pulse laser monitoring of vinyl chloride in a long-distance open optical path includes.

[0085] S1: using the mid-infrared laser emitting module 8 to modulate a narrow-frequency mid-infrared laser beam to obtain a modulated narrow-frequency mid-infrared laser beam.

[0086] S2: Filtering the modulated narrow-frequency mid-infrared laser beam using the mid-infrared filter module 11 to obtain a filtered beam.

[0087] S3: using the multi-point angle pyramid reflection prism array 18 to reflect the filtered light beam to obtain a reflected light beam.

[0088] S4: performing secondary filtering on the reflected light beam using the mid-infrared filter module 11 to obtain a secondary filtered light beam.

[0089] S5: using the optical signal focusing receiving module 7 to convert the light beam after the secondary filtering into an optical signal to obtain a current signal.

[0090] S6: using the lock-in amplifier 6 to convert the current signal into a voltage signal and amplify it, while suppressing noise to the maximum extent to obtain a maximum signal-to-noise ratio.

[0091] S7: using the data acquisition storage processing module 5 to convert the current signal and the voltage signal into digital signals and store them; determining the characteristic peak value of the specific band of the mid-infrared laser after emission based on the digital signal; determining the difference and ratio of the characteristic peak value of the specific band of the mid-infrared laser based on the characteristic peak value of the specific band of the mid-infrared laser before emission and the characteristic peak value of the specific band of the mid-infrared laser after emission; performing inversion based on the difference and ratio of the characteristic peak value of the specific band of the mid-infrared laser and the vinyl chloride concentration inversion algorithm to obtain the inverted vinyl chloride concentration; the vinyl chloride concentration inversion algorithm is a correlation relationship and function between the difference and ratio of the specific characteristic peak value of the narrow-band mid-infrared wavelength and the vinyl chloride concentration established based on the neural network method.

[0092] The present invention utilizes special designs such as high-power, high-frequency pulse quantum cascade mid-infrared laser, reference optical path, precision optical separation and calibration module, noise reduction and anti-interference algorithm, and Beer-Lambert's law concentration inversion method to achieve high-precision, second-level rapid measurement of 50m long-distance, ppm-level vinyl chloride concentration, and support risk warning and safety prevention and control of the entire chain of vinyl chloride production, storage and utilization.

[0093] This monitoring method is the key to ensure that the infrared laser monitoring equipment in the long-distance open optical path of vinyl chloride leakage can achieve long-distance, high-precision and rapid measurement. In this method, the narrow-frequency mid-infrared laser beam is modulated by the mid-infrared laser emission module 8. In order to ensure that the wavelength of the emitted narrow-frequency laser beam is constant, the semiconductor temperature and humidity control module 3 is used to further eliminate the influence of ambient temperature and humidity on the working temperature of the laser. The temperature is directly related to the mid-infrared wavelength and is generally maintained within the linear correlation range. The emitted mid-infrared laser beam is first filtered by the mid-infrared filter module 11 and then emitted to the atmospheric environment. The mid-infrared laser beam reflected back by the multi-point angle cone reflection prism array 18 is then filtered twice by the mid-infrared filter module 11 to eliminate ambient light interference. The reflected mid-infrared laser beam enters the optical signal focusing receiving module 7 after filtering for photoelectric signal conversion, and then undergoes signal processing by the phase-locked amplifier 6, and finally is sent to the data acquisition storage processing module 5.

[0094] In this process, since the system background noise and environmental particles will respectively affect the characteristic parameters of the intensity of the emitted and reflected mid-infrared laser beams (such as the absorption peak), a reference gas chamber 13 is required to calibrate the device background noise and eliminate the interference of environmental particles; in addition, in order to ensure the collimation of the multi-angle light beam, the visible laser emitted by the indicator laser emission module 9 is required for aiming and alignment.

[0095] Finally, all data are sent to the data acquisition, storage and processing module 5, and inverted by the vinyl chloride concentration inversion algorithm (based on the neural network method to establish the correlation and function between the difference and ratio of specific characteristic peak values ​​of narrow-band mid-infrared wavelengths and the vinyl chloride concentration). The inverted concentration signal and the original data before processing will be transmitted to the cloud server or local server through the data wireless transmission module 4 for display.

[0096] The core of the present invention is to first calibrate the equipment background noise law and correlation function by using different concentrations of vinyl chloride standard gas, on the one hand, eliminate the background noise influence and calibrate to zero by subtraction, and on the other hand, establish the correlation relationship and function between the difference and ratio of specific characteristic peak values ​​of narrow-band mid-infrared wavelength and vinyl chloride concentration by using the neural network method. (The inversion of vinyl chloride concentration is to reverse the concentration based on the vinyl chloride laser intensity attenuation rate before and after emission. 1. It is necessary to eliminate the background noise of the equipment itself, such as current interference. The background noise has an impact on the light intensity attenuation rate, so it needs to be calibrated first. 2. Calculate the laser intensity attenuation before and after emission, and use the absorption peak value and ratio to represent the attenuation intensity, which can reduce the error). Then, when measuring under the actual open optical path, on the one hand, the mid-infrared laser is reflected and received by the long-distance multi-point angle cone reflection prism array 18, and the characteristic peak value is obtained by the optical signal focusing receiving module 7; on the other hand, the bypass reflector 10 is adjusted regularly, and the atmosphere under the actual measurement environment is extracted by using the reference gas chamber, and the influence of interfering gases and particulate matter in the atmospheric environment on the measurement intensity is synchronously measured, and compared with the main optical path measurement data, and the interference of environmental interfering gases and particulate matter is eliminated. Finally, convolutional neural network + support vector machine + image recognition method and Beer-Lambert law are used to achieve high-precision inversion of vinyl chloride concentration, with a minimum sensitivity of no more than 300ppm.

[0097] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0098] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A long-distance open optical path infrared pulse laser monitoring equipment for vinyl chloride, characterized in that: The infrared pulse laser monitoring equipment for vinyl chloride long-distance open optical path includes: A mid-infrared laser emission module is used to modulate a narrow-frequency mid-infrared laser beam to obtain a modulated narrow-frequency mid-infrared laser beam; A mid-infrared filter module, used for filtering the modulated narrow-frequency mid-infrared laser beam to obtain a filtered beam; A multi-point angle pyramid reflection prism array, used for reflecting the filtered light beam to obtain a reflected light beam; The mid-infrared filter module is further used to perform secondary filtering on the reflected light beam to obtain a secondary filtered light beam; An optical signal focusing receiving module is used to convert the optical beam after the secondary filtering into an optical signal to obtain a current signal; A lock-in amplifier is used to convert the current signal into a voltage signal and amplify it, while suppressing noise to the maximum extent to obtain a maximum signal-to-noise ratio; The data acquisition storage processing module is used to convert the current signal and the voltage signal into digital signals and store them; determine the characteristic peak value of the specific band of the mid-infrared laser after emission based on the digital signal; determine the difference and ratio of the characteristic peak value of the specific band of the mid-infrared laser based on the characteristic peak value of the specific band of the mid-infrared laser before emission and the characteristic peak value of the specific band of the mid-infrared laser after emission; and perform inversion based on the difference and ratio of the characteristic peak value of the specific band of the mid-infrared laser and a vinyl chloride concentration inversion algorithm to obtain the inverted vinyl chloride concentration; the vinyl chloride concentration inversion algorithm is a correlation relationship and function between the difference and ratio of the specific characteristic peak value of the narrow-band mid-infrared wavelength and the vinyl chloride concentration established based on a neural network method.

2. The long-distance open optical path infrared pulse laser monitoring equipment for vinyl chloride according to claim 1 is characterized in that: The infrared pulse laser monitoring equipment for vinyl chloride in a long-distance open optical path also includes: Semiconductor temperature and humidity control module, used to adjust the ambient temperature and humidity.

3. The infrared pulse laser monitoring equipment for vinyl chloride in a long-distance open optical path according to claim 1 is characterized in that: The infrared pulse laser monitoring equipment for vinyl chloride in a long-distance open optical path also includes: Reference gas chamber is used to calibrate the instrument measurement accuracy and eliminate external environmental interference using standard gas.

4. The infrared pulse laser monitoring equipment for vinyl chloride in a long-distance open optical path according to claim 1 is characterized in that: The infrared pulse laser monitoring equipment for vinyl chloride in a long-distance open optical path also includes: The indicating laser emission module is used to indicate the aiming and alignment of the modulated narrow-frequency mid-infrared laser beam.

5. The infrared pulse laser monitoring equipment for vinyl chloride in a long-distance open optical path according to claim 1 is characterized in that: The infrared pulse laser monitoring equipment for vinyl chloride in a long-distance open optical path also includes: The data wireless transmission module is used to directly send the vinyl chloride concentration to a local server using a local area network / Internet of Things to store the vinyl chloride concentration; or use a 4G / 5G wireless network to send the vinyl chloride concentration to the cloud, and then transfer it to a local server or other storage area.

6. The long-distance open optical path infrared pulse laser monitoring equipment for vinyl chloride according to claim 1 is characterized in that: The mid-infrared laser emission module includes: a quantum cascade mid-infrared laser and a current temperature control adaptive adjustment module; The quantum cascade mid-infrared laser is used to emit a narrow-frequency mid-infrared laser beam; The current temperature control adaptive adjustment module is used to automatically control the operating temperature of the quantum cascade mid-infrared laser and to change the central wavelength of the narrow-frequency mid-infrared laser beam by temperature adjustment.

7. The long-distance open optical path infrared pulse laser monitoring equipment for vinyl chloride according to claim 1 is characterized in that: The multi-point angle pyramid reflector array comprises: The angle of incidence of mid-infrared light in the corner cone reflection prism array at different positions is 80~90°, and the reflectivity of mid-infrared laser is greater than 90%.

8. The long-distance open optical path infrared pulse laser monitoring equipment for vinyl chloride according to claim 1 is characterized in that: The optical signal focusing receiving module comprises: a parabolic mirror and a mid-infrared photoelectric detector; The parabolic mirror is used to enhance the receiving intensity of the mid-infrared laser reflected back from the open optical path; The mid-infrared photoelectric detector is used to convert the light beam after the secondary filtering into a photoelectric signal to obtain a current signal.

9. The long-distance open optical path infrared pulse laser monitoring equipment for vinyl chloride according to claim 2, characterized in that: The semiconductor temperature and humidity control module includes: a temperature and humidity sensor, a semiconductor temperature regulator and a dehumidifier; The temperature and humidity sensor is used to monitor the temperature and humidity of the environment; The semiconductor temperature regulator is used to adjust the temperature of the environment; The dehumidifier is used to adjust the humidity of the environment.

10. A method for monitoring vinyl chloride in a long-distance open optical path by infrared pulse laser, characterized in that: The infrared pulse laser monitoring method for vinyl chloride in a long-distance open optical path is implemented based on the infrared pulse laser monitoring equipment for vinyl chloride in a long-distance open optical path according to any one of claims 1 to 9, and the infrared pulse laser monitoring method for vinyl chloride in a long-distance open optical path comprises: Using a mid-infrared laser emission module to modulate a narrow-frequency mid-infrared laser beam to obtain a modulated narrow-frequency mid-infrared laser beam; Using a mid-infrared filter module to filter the modulated narrow-frequency mid-infrared laser beam to obtain a filtered beam; Reflecting the filtered light beam using a multi-point angle pyramid reflection prism array to obtain a reflected light beam; Using the mid-infrared filter module to perform secondary filtering on the reflected light beam to obtain a secondary filtered light beam; Using an optical signal focusing receiving module to convert the light beam after the secondary filtering into an optical signal to obtain a current signal; The current signal is converted into a voltage signal and amplified by using a lock-in amplifier, while suppressing noise to the maximum extent to obtain a maximum signal-to-noise ratio; The current signal and the voltage signal are converted into digital signals and stored by using a data acquisition storage processing module; a characteristic peak value of a specific waveband of a mid-infrared laser after emission is determined based on the digital signal; a difference and a ratio of the characteristic peak values ​​of a specific waveband of the mid-infrared laser are determined based on the characteristic peak value of the specific waveband of the mid-infrared laser before emission and the characteristic peak value of the specific waveband of the mid-infrared laser after emission; an inversion is performed based on the difference and the ratio of the characteristic peak values ​​of the specific waveband of the mid-infrared laser and a vinyl chloride concentration inversion algorithm to obtain an inverted vinyl chloride concentration; the vinyl chloride concentration inversion algorithm is a correlation relationship and a function between the difference and the ratio of the specific characteristic peak values ​​of a narrow-band mid-infrared wavelength and the vinyl chloride concentration established based on a neural network method.

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