Absorption spectral line interference elimination method and system

Abstract

The invention discloses a method and a system for eliminating absorption spectral line interference. The method comprises the following steps: establishing a corresponding standard second harmonic signal sub-function library for various gases to be detected in mixed gas; performing laser detection on the mixed gas to obtain a corresponding second harmonic signal, and taking the to-be-detected gas with the maximum second harmonic signal amplitude in the mixed gas as a separated gas; performing function decomposition on the separated gas to obtain a separated gas function expression; and performing iterative calculation based on the threshold value corresponding to the residual mixed gas to obtain a final remainder function and a final function term. The method can solve the problem of overlapping interference of absorption spectral lines in laser detection of multiple mixed gases in the coal mine goaf, improves the measurement precision of the mixed gases in the goaf, can accurately predict the occurrence of the fire in the goaf, and has very important significance for avoiding the occurrence of the fire in the goaf and guaranteeing the safety production in the coal mine.

Description

Technical Field

[0001] The invention belongs to the technical field of coal mine monitoring and surveillance, and relates to a method and system for eliminating absorption spectrum line interference. Background Art

[0002] The traditional ground-type bundle pipe monitoring system has both the air pump and the detection equipment placed on the ground, and the gas in the goaf is transmitted to the ground through a pipeline of no less than 10 km. Due to the long pipeline, it has a large air extraction resistance and requires a high-power air pump. There are many pipe joints and it is easy to leak. The ground pipeline is prone to ice and blockage in winter. The gas is generally analyzed by a chromatograph, which has a long analysis cycle and complex maintenance. At present, the underground mine spontaneous combustion gas bundle pipe monitoring system has gradually been applied. The gas analysis equipment, gas path control equipment, sampling pump, power box, switch and other equipment that make up the system are all installed in the underground chamber, which effectively solves the problem of long sampling distance and shortens the sampling distance of the monitoring system to less than 2 km. However, the environment of the coal mine goaf has the characteristics of large water vapor, high dust and complex mixed gas composition. In the ground environment, there has never been a situation where nine gases such as carbon dioxide, oxygen, acetylene, methane, ethylene, carbon monoxide, ethane, ammonia, and hydrogen sulfide are measured simultaneously. In this case, it is very easy to cause overlapping interference of the absorption spectra of each gas, resulting in inaccurate gas concentration measurement. In ground applications, there is no such environment, so there is no good strategy to deal with the overlapping interference of the absorption lines of the nine gases, which has become the main "bottleneck" for the application of laser detection technology in the monitoring of mixed gases in coal mine goafs. The current methods of eliminating interference, such as reference gas chambers and reducing spectral line broadening, cannot be applied to the detection of multiple gas mixtures with water vapor, and most of these methods require hardware modification, with a complex overall structure, resulting in increased costs. Summary of the invention

[0003] In order to solve the deficiencies in the prior art, the present invention provides a method and system for eliminating absorption line interference.

[0004] The present invention adopts the following technical solution.

[0005] A first aspect of the present invention provides a method for eliminating interference of coal mine gas laser detection absorption spectrum lines, comprising:

[0006] Step 1: Perform standard gas laser detection tests on various gases to be tested in the mixed gas of the coal mine goaf to obtain standard second harmonic signals as sub-functions of the corresponding gases, and establish a sub-function library;

[0007] Step 2: Perform laser detection on the mixed gas to obtain the second harmonic signal function of the mixed gas, and use the gas to be tested with the largest second harmonic signal amplitude in the second harmonic signal function as the separation gas;

[0008] Step 3: Obtain the sub-function of the separated gas from the sub-function library, and obtain the function item corresponding to the separated gas using a polynomial fitting algorithm;

[0009] Step 4: Subtract the second harmonic signal function of the mixed gas from the function term corresponding to the separated gas to obtain the remainder function;

[0010] Step 5: Compare the amplitude of the remainder function with the preset decomposition thresholds of various types of gases to be tested. If the amplitude of the remainder function is greater than the decomposition threshold, the gas to be tested with the largest second harmonic signal amplitude in the remainder function is used as the new separation gas, and return to step 3-step 4 for iterative calculation. During the iterative calculation, the remainder function is used to replace the second harmonic signal function of the mixed gas in step 4 for remainder function calculation until the amplitude of the remainder function is less than all decomposition thresholds. The final remainder function is determined according to the sub-function corresponding to the current non-separated gas, and the final remainder function and the function terms obtained in each iteration are output.

[0011] Preferably, in step 1, the following standard second harmonic signal is obtained through a standard gas laser detection test:

[0012] L γ (t) = cL(tb) (3)

[0013] Where γ=(a,p,b) is the subfunction L γ (t), a is the expansion range, b is the translation scale, p is the modulation frequency, the standard second harmonic signal has a = 1, p = 1, c is the standard gas concentration corresponding to the gas to be measured, and t is time;

[0014] L(tb) is the window function belonging to the Hilbert space, expressed as

[0015]

[0016] Where x(tb) is the original second harmonic signal function after translation.

[0017] Preferably, in step 2, laser detection is performed on the mixed gas to obtain a second harmonic signal function of the mixed gas:

[0018]

[0019] In the formula, is the nth gas sub-function to be measured, k n is the analytical coefficient of the nth gas to be measured, and N is the type of gas to be measured.

[0020] Preferably, in step 3, the sub-function L for separating the gas is obtained from the sub-function library. γ(t), and use the polynomial fitting algorithm to obtain the function term corresponding to the separated gas:

[0021]

[0022] Among them, ρ i are polynomial fitting coefficients, and i,M are polynomial orders.

[0023] Preferably, in step 4, the second harmonic signal function f(t) of the mixed gas minus the function term y corresponding to the separated gas z (t), and obtain the remainder function:

[0024]

[0025] Preferably, in step 5, the decomposition threshold of the gas to be tested is determined as follows:

[0026] Calculate the detection noise of the gas to be tested, and compare the calculated noise value with the initial setting value of the decomposition threshold. If the calculated noise value is greater than the initial setting value of the decomposition threshold, set the calculated noise value as the decomposition threshold of the detected gas; otherwise, set the initial setting value of the decomposition threshold as the decomposition threshold of the detected gas.

[0027] Preferably, the calculation formula of the gas detection noise to be measured is:

[0028]

[0029] Where ε is the gas detection noise to be measured, △f is the laser modulation bandwidth, p is the modulation frequency, β is the modulation frequency index, is the laser fluctuating power at the modulation frequency p, σ is the detection efficiency, e is the charge of the detection circuit, h is the Planck constant, and w0 is the laser center frequency.

[0030] Preferably, the initial setting value of the decomposition threshold is the sum of the detection resolution of the gas to be detected and the absolute value of the detection error of the gas to be detected under ideal conditions.

[0031] Preferably, in step 5, after iterative calculation, the final function remainder and the function term obtained in each iteration are output to form the second harmonic signal function of the mixed gas after the absorption line interference is eliminated:

[0032]

[0033] Where m is the number of iterations;

[0034] y zn (t) is the corresponding function term obtained by using the polynomial fitting algorithm when the nth gas to be tested is used as the separation gas;

[0035] R m(t) is the final remainder function output after m iterations of calculation.

[0036] A second aspect of the present invention provides a system for eliminating interference of absorption spectrum lines of coal mine gas laser detection, comprising:

[0037] The sub-function library construction module is used to obtain standard second harmonic signals of various gases to be tested in the mixed gas of the coal mine goaf through standard gas laser detection test, and use them as sub-functions of corresponding gases to establish a sub-function library;

[0038] The laser detection module is used to perform laser detection on the mixed gas to obtain the second harmonic signal function of the mixed gas, and the gas to be tested with the largest second harmonic signal amplitude in the second harmonic signal function is used as the separation gas;

[0039] A function item fitting module, used for obtaining the sub-function of the separated gas from the sub-function library, and obtaining the function item corresponding to the separated gas by using a polynomial fitting algorithm;

[0040] The remainder function calculation module performs subtraction calculation on the second harmonic signal function of the mixed gas and the function term corresponding to the separated gas to obtain the remainder function;

[0041] The iterative calculation module is used to compare the amplitude of the remainder function with the preset decomposition thresholds of various types of gases to be tested. If the amplitude of the remainder function is greater than the decomposition threshold, the gas to be tested with the largest second harmonic signal amplitude in the remainder function is used as the new separation gas, and the function item fitting module and the remainder function calculation module are returned for iterative calculation. During the iterative calculation, the remainder function is used to replace the second harmonic signal function of the mixed gas in the remainder function calculation module for the remainder function calculation until the amplitude of the remainder function is less than all decomposition thresholds. The final remainder function is determined according to the sub-function corresponding to the current non-separated gas, and the final remainder function and the function items obtained in each iteration are output.

[0042] A terminal comprises a processor and a storage medium; the storage medium is used to store instructions; the processor is used to operate according to the instructions to execute the steps of the method.

[0043] A second aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which implements the steps of the method when executed by a processor.

[0044] Compared with the prior art, the beneficial effects of the present invention include at least:

[0045] The method of the present invention establishes a second harmonic sub-function library of each standard gas, and iteratively separates the gas with the largest second harmonic signal amplitude in the mixed gas in turn, thereby realizing accurate extraction of the second harmonic function of each gas. This method can not only accurately analyze the concentration of each main component of the mixed gas, and has high detection accuracy, but also does not require modification of the hardware circuit, thus reducing costs and improving efficiency. This method can achieve good detection effect and accuracy, and provides a guarantee for the detection device to accurately analyze the mixed gas in the goaf.

[0046] When the present invention determines the threshold value corresponding to the mixed gas used for iterative separation, taking into account the inevitable existence of noise in the detection device, the initial set threshold value is not simply adopted. Instead, the detection noise of the gas to be detected is calculated, and the calculated value is compared with the initial set value. If the noise is greater than the initial set value, the noise is set as the decomposition threshold value of the detection gas, which can effectively avoid the decomposition calculation of the noise, reduce the deviation of the calculation result, and achieve effective convergence.

[0047] The present invention quantifies the various factors of gas detection noise generated by the noise through the calculation model of the gas detection noise to be measured, thereby realizing the calculation of the gas detection noise to be measured. Due to the inevitable existence of noise in the detection device, when the initial decomposition threshold of the gas to be measured is less than the noise value, the system will decompose and calculate the noise, and the calculation result will have a large deviation. The parameters in the calculation model provide clear guidance for system design, which is helpful to design a more efficient and sensitive laser gas detection system. Given the system parameters, the noise calculation model can predict the detection limit and sensitivity of the system. The multiple parameters in the noise calculation model provide rich possibilities for system optimization. By adjusting the parameters in the calculation model formula, the performance of the detection system can be systematically optimized. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a flow chart of the method for eliminating interference of absorption spectrum lines of coal mine gas laser detection according to the present invention;

[0049] Figure 2 This is a flow chart of the implementation of the method for eliminating interference of absorption spectrum lines of coal mine gas laser detection according to the present invention;

[0050] Figure 3 is a second harmonic signal diagram of standard methane gas in an embodiment of the present invention;

[0051] Figure 4 is a second harmonic signal diagram of a mixed gas of methane and carbon monoxide in an embodiment of the present invention;

[0052] Figure 5 is a second harmonic signal diagram of methane gas separated in an embodiment of the present invention;

[0053] Figure 6 is a residual function signal diagram in an embodiment of the present invention;

[0054] Figure 7 is a second harmonic signal diagram of carbon monoxide gas separated in an embodiment of the present invention;

[0055] Figure 8 It is a structural diagram of the coal mine gas laser detection device of the present invention. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0057] Embodiment 1 of the present invention provides a method for eliminating interference of absorption spectrum lines in coal mine gas laser detection. In specific implementation, TDLAS detection includes direct absorption method and harmonic detection method. The harmonic detection method can well realize the extraction of second harmonic through a phase-locked amplifier, and can realize noise suppression through frequency modulation, which can significantly improve the detection accuracy, and thus is increasingly widely used.

[0058] The present invention adopts harmonic detection method to realize the detection of mixed gas in goaf. The mixed gas is decomposed into second harmonics, and the conversion amplitude of the sub-function is set to γ ​​= (a, p, b). Then the decomposed sub-function is

[0059]

[0060] Where θ is the concentration of the gas to be measured, a is the expansion range, p is the modulation frequency, and b is the translation scale.

[0061] The second harmonic function f(t) of multi-component gas can be expressed as:

[0062]

[0063] In the formula, is the nth gas subfunction, k n It is the analysis coefficient of the nth gas, where n represents the sequence number of the gas.

[0064] Based on formula (1), the second harmonic function of the standard gas (a=1, p=1) is obtained as

[0065] L γ (t) = cL(tb) (3)

[0066] In the formula, c is the standard gas concentration corresponding to the gas to be measured, and t is the time.

[0067] Based on the above analysis, taking the mixed gas of CH4 and CO as an example, Figure 1-2 As shown, the implementation steps of the method of the present invention are specifically as follows:

[0068] Step 1: Perform standard gas laser detection tests on various gases to be tested in the mixed gas of the coal mine goaf to obtain standard second harmonic signals as sub-functions of the corresponding gases, and establish a sub-function library;

[0069] This step establishes a corresponding standard second harmonic signal sub-function library for each type of gas to be tested in the mixed gas;

[0070] Further preferably, a standard second harmonic signal as shown in the above formula (3) is obtained through a standard gas laser detection test;

[0071] Where L(tb) is the window function belonging to the Hilbert space, expressed as

[0072]

[0073] Where x(tb) is the original signal function after translation.

[0074] For example, the laser detection experiment of standard methane gas (100ppm) obtains its second harmonic signal function as L CH (t);

[0075] The laser detection experiment of standard carbon monoxide gas (1000ppm) obtains its second harmonic signal function as L CO (t);

[0076] According to the HITRAN2016 database, the second harmonic signal (i.e., 2f signal) of methane gas with a concentration of 100 ppm under the conditions of pressure 1 atm, temperature 290 K, and optical path length 30 m was extracted, i.e., the second harmonic signal of standard methane gas, with the absorption line center at 4284.51 cm -1 ,like Figure 3 shown.

[0077] Step 2: Perform laser detection on the mixed gas to obtain the second harmonic signal function of the mixed gas, and use the gas to be tested with the largest second harmonic signal amplitude in the second harmonic signal function as the separation gas;

[0078] Further preferably, in this step, laser detection is performed on the mixed gas to obtain a corresponding second harmonic signal, and the gas to be tested having the largest second harmonic signal amplitude in the mixed gas is used as the separation gas, as follows:

[0079] Laser detection is performed on the mixed gas to obtain the second harmonic signal function of the mixed gas:

[0080]

[0081] In the formula, is the nth gas sub-function to be measured, determined based on the above equations (3)-(4), k n is the analytical coefficient of the nth gas to be measured, and N is the type of gas to be measured.

[0082] For example, in an experiment on a mixture of methane and carbon monoxide, the second harmonic y CO+CH (t).

[0083] Under the same conditions, the database was used to extract the second harmonic signal of a mixed gas of 300 ppm methane and 0.3 ppm carbon monoxide. The absorption line center of carbon monoxide gas is 4285 cm -1 ,like Figure 4 shown.

[0084] Since the concentration of methane gas is very high, it has a great influence on the second harmonic waveform of carbon monoxide as a separation gas.

[0085] Step 3: Obtain the sub-function of the separated gas from the sub-function library, and obtain the function item corresponding to the separated gas using a polynomial fitting algorithm;

[0086] Further preferably, the separated gas is subjected to functional decomposition to obtain a separated gas functional expression:

[0087] Obtain the gas separation sub-function L from the sub-function library γ (t), and use the polynomial fitting algorithm to obtain the function term corresponding to the separated gas:

[0088]

[0089] Among them, ρ i are polynomial fitting coefficients, and i,M are polynomial orders.

[0090] The second harmonic signal of the separated gas methane is obtained by using the polynomial fitting algorithm, such as Figure 5 shown.

[0091] Step 4: Subtract the second harmonic signal functions of the mixed gas and the separated gas to obtain the remainder function;

[0092] Further preferably, the second harmonic signal function f(t) of the mixed gas minus the function term y corresponding to the separated gas z (t), and get the decomposed remainder function:

[0093]

[0094] The residual function signal after decomposition is as follows Figure 6 shown.

[0095] Step 5: Determine the threshold corresponding to the remaining mixed gas. If the amplitude of the remainder function is greater than the threshold, the gas to be tested with the largest amplitude of the second harmonic signal in the remainder function is used as the new separated gas for further decomposition. Otherwise, determine the final remainder function and output the final remainder function and the obtained function terms:

[0096] The amplitude of the remainder function is compared with the preset decomposition thresholds of various types of gases to be tested. If the amplitude of the remainder function is greater than the decomposition threshold, the gas to be tested with the largest second harmonic signal amplitude in the remainder function is used as the new separation gas, and the process returns to step 3-step 4 for iterative calculation. During the iterative calculation, the remainder function is used to replace the second harmonic signal function of the mixed gas in step 4 for remainder function calculation until the amplitude of the remainder function is less than all decomposition thresholds. The final remainder function is determined according to the sub-function corresponding to the current non-separated gas, and the final remainder function and the function terms obtained in each iteration are output.

[0097] Further preferably, the decomposition threshold of the gas to be tested is determined as follows: the detection noise of the gas to be tested is calculated, and the calculated noise value is compared with the initial setting value of the decomposition threshold; if the calculated noise value is greater than the initial setting value of the decomposition threshold, the calculated noise value is set as the decomposition threshold of the detected gas; otherwise, the initial setting value of the decomposition threshold is set as the decomposition threshold of the detected gas.

[0098] The decomposition threshold of the gas to be measured is initially set to: the sum of the detection resolution of the gas to be measured and the absolute value of the detection error of the gas to be measured under ideal conditions.

[0099] Due to the unavoidable existence of noise in the detection device, if the initial setting is used alone, when the initial decomposition threshold of the gas to be tested is less than the noise value, the system will decompose and calculate the noise, and the calculation result will have a large deviation and cannot achieve effective convergence. Therefore, the detection noise of the gas to be tested is calculated, and the calculated value is compared with the initial setting value. If the noise is greater than the initial setting value, the noise is set as the decomposition threshold of the detection gas.

[0100] The gas detection noise ε is defined as

[0101]

[0102] In the formula, △f is the laser modulation bandwidth, p is the modulation frequency, and β is the modulation frequency index. is the laser fluctuating power, σ is the detection efficiency, e is the detection circuit charge, h is the Planck constant, and w0 is the laser center frequency.

[0103] When the amplitude of the remainder function is smaller than all decomposition thresholds, the iteration is stopped.

[0104] After iterative calculation, the final residual function and the function terms obtained in each iteration are output, which constitute the second harmonic signal function of the mixed gas after the absorption line interference is eliminated. It can be expressed as:

[0105]

[0106] Where m is the number of iterations;

[0107] y zn (t) is the corresponding function term obtained by using the polynomial fitting algorithm when the nth gas to be tested is used as the separation gas;

[0108] R m (t) is the final remainder function output after m iterations of calculation.

[0109] Set the decomposition threshold of methane gas to YZ1 and the decomposition threshold of carbon monoxide gas to YZ2.

[0110] When r When the maximum amplitude of (t) is greater than YZ2, the remainder function needs to be decomposed twice, and the second harmonic signal of carbon monoxide gas is obtained by the second polynomial fitting. Figure 7 shown.

[0111] It can be seen from the above embodiments that due to the overlapping interference of the spectral lines of carbon monoxide and methane, when the concentration difference between methane and carbon monoxide is large, the signal of carbon monoxide cannot be identified. By separating the methane gas signal, the carbon monoxide signal is extracted from the residual function.

[0112] The present invention can solve the problem of overlapping interference of absorption spectral lines in mixed multi-gas laser detection in coal mine goafs, improve the measurement accuracy of mixed gases in goafs, lay a foundation for the application of laser gas detection technology in underground coal mines, provide a guarantee for the accuracy of mixed gas detection in goafs by detection devices, and can accurately predict the occurrence of goaf fires, which is of great significance for coal mines to avoid the occurrence of goaf fires and ensure safe production.

[0113] Embodiment 2 of the present invention provides a system for eliminating interference of absorption spectrum lines of coal mine gas laser detection, comprising:

[0114] The sub-function library construction module is used to obtain standard second harmonic signals of various gases to be tested in the mixed gas of the coal mine goaf through standard gas laser detection test, and use them as sub-functions of corresponding gases to establish a sub-function library;

[0115] The laser detection module is used to perform laser detection on the mixed gas to obtain the second harmonic signal function of the mixed gas, and the gas to be tested with the largest second harmonic signal amplitude in the second harmonic signal function is used as the separation gas;

[0116] A function item fitting module, used to obtain the sub-function of the separated gas from the sub-function library, and obtain the function item corresponding to the separated gas by using a polynomial fitting algorithm;

[0117] The remainder function calculation module performs subtraction calculation on the second harmonic signal function of the mixed gas and the function term corresponding to the separated gas to obtain the remainder function;

[0118] The iterative calculation module is used to compare the amplitude of the remainder function with the preset decomposition thresholds of various types of gases to be tested. If the amplitude of the remainder function is greater than the decomposition threshold, the gas to be tested with the largest second harmonic signal amplitude in the remainder function is used as the new separation gas, and the function item fitting module and the remainder function calculation module are returned for iterative calculation. During the iterative calculation, the remainder function is used to replace the second harmonic signal function of the mixed gas in the remainder function calculation module for the remainder function calculation until the amplitude of the remainder function is less than all decomposition thresholds. The final remainder function is determined according to the sub-function corresponding to the current non-separated gas, and the final remainder function and the function items obtained in each iteration are output.

[0119] Embodiment 3 of the present invention provides a coal mine gas laser detection device, such as Figure 8 As shown, it includes a monitoring host, an air extraction and water filtration control box, a power box, a network interface and a host computer; wherein the monitoring host, the air extraction and water filtration control box and the power box are arranged in the goaf of the underground coal mine; the host computer is arranged above the well and communicates with the monitoring host through the network interface;

[0120] The monitoring host is powered by a power supply box and is used for on-site detection, display, and over-limit warning of the flow rate of the bundle pipe gas, the concentration of multiple gases to be measured in the bundle pipe gas, and the temperature, as well as remote communication with the host computer, and controls the gas extraction and water filtration of the gas extraction and water filtration control box. The concentration of multiple gases to be measured in the bundle pipe gas is detected based on the above-mentioned coal mine gas laser detection particle influence suppression method;

[0121] Further preferably, the monitoring host is mainly composed of a housing, a liquid crystal display, a flow sensor, a temperature sensor, a solenoid valve, a water filter, a main control board and 9 laser gas detection modules (carbon dioxide, oxygen, acetylene, methane, ethylene, carbon monoxide, ethane, ammonia, hydrogen sulfide). It is powered by a power box to realize manual and automatic detection of 9 gases, flow and temperature detection of pipeline gas, local control function through infrared remote control, remote control function through host computer, and local display of detection data and working status through liquid crystal display.

[0122] The monitoring host uses a laser gas detection module (laser sensor module), utilizes the coal mine gas laser detection particle impact suppression method, and adopts tunable laser spectral absorption technology TDLAS to detect the concentration of 9 gases to be tested, including carbon dioxide, oxygen, acetylene, methane ethylene, carbon monoxide, ethane, ammonia, and hydrogen sulfide, to achieve the analysis and measurement of the hazardous gas components in the gases to be tested at the corresponding monitoring points in the goaf of underground coal mines, and upload the measurement results in real time to provide early warning for coal mine spontaneous combustion fires. Specifically, the host computer can be used for early warning, and the monitoring host can be used to realize the on-site over-limit alarm of the hazardous gas concentration.

[0123] Further preferably, the temperature sensor of the monitoring host tests the temperature of the drawn gas to determine whether the gas in the pipeline is burning. This is because the temperature of the gas will drop after passing through a long pipeline and is not the actual temperature in the goaf. For this purpose, the laser sensor module and the goaf distributed temperature measurement system integrate monitoring and goaf fire warning analysis.

[0124] The laser sensor module measures the concentration of nine gases. The distributed optical fiber temperature measurement system in the goaf directly places the optical fiber in the goaf and directly measures the temperature of the goaf through the optical fiber. When the upper computer conducts fire warning analysis in the goaf, it can conduct a comprehensive analysis of the two data to improve the accuracy of the warning.

[0125] The monitoring host is connected to the nearby network interface through optical fiber underground, uploads data to the host computer through Ethernet, and receives commands from the host computer; communicates with the air extraction and water filtration control box through RS485, and sends the start and stop control commands of the sampling pump in the control box to the air extraction and water filtration control box.

[0126] The micro air pump is a negative pressure suction type intrinsically safe micro air pump.

[0127] The air extraction and water filtration control box is powered by the power box and is used for extraction, water filtration and flow measurement of the gas from the 8-way bundle pipes. The extracted and water-filtered gas is transported to the monitoring host through the air pipe. Each bundle pipe is equipped with a micro air pump to extract the gas from the 8-way bundle pipes synchronously.

[0128] Further preferably, the air extraction and water filtration control box is mainly composed of a shell, a micro air pump, a solenoid valve, a water filter, a control panel, a bus and a float flowmeter. Power is supplied by a power supply box to realize the extraction of gas from 8-way bundle tubes, realize the water filtration of gas, measure the flow rate through a float flowmeter, transmit the extracted and filtered gas to the monitoring host through a pipeline, and communicate with the monitoring host through an RS485 communication line. One bundle tube is connected by a micro air pump for gas extraction, and 8-way bundle tubes share 8 micro air pumps. The 8 pumps are controlled by the host and can perform air extraction at the same time, which shortens the air extraction time and solves the problem of very long air extraction time caused by conventional single pump polling air extraction. In addition, the present invention adopts the design of an intrinsically safe micro air pump, breaking the conventional explosion-proof vacuum pump or water circulation pump mode, greatly reducing product costs and reducing equipment size.

[0129] The host computer is used for data collection, display and remote control of multiple monitoring hosts, realizing data collection and display of multiple monitoring hosts and remote control of the hosts.

[0130] Each air extraction and water filtration control box is connected to an 8-channel bundle pipe to extract gases from 8 bundle pipes. The power supply is provided by a power supply box. The air extraction and water filtration control box transmits the extracted and filtered gas to the monitoring host through the air pipe, and the monitoring host detects 9 kinds of gases. The monitoring host is connected to the air extraction and water filtration control box via RS485 and sends the sampling pump start and stop control command to the control box. A monitoring host can be connected to up to 2 control boxes to detect up to 16 bundle pipe gases. The monitoring host is connected to the nearby network interface through optical fiber in the well, uploads data to the host computer through Ethernet, and receives commands from the host computer.

[0131] The monitoring host, air extraction and water filtration control box and power supply box are arranged underground and installed in the electromechanical chamber of the mining area. The upper computer is installed in the monitoring room above the well.

[0132] Embodiment 4 of the present invention provides a terminal, including a processor and a storage medium; the storage medium is used to store instructions; the processor is used to operate according to the instructions to execute the steps of the method.

[0133] Embodiment 5 of the present invention provides a computer-readable storage medium having a computer program stored thereon, which implements the steps of the method when executed by a processor.

[0134] Compared with the prior art, the beneficial effects of the present invention include at least:

[0135] The method of the present invention establishes a second harmonic sub-function library of each standard gas, and iteratively separates the gas with the largest second harmonic signal amplitude in the mixed gas in turn, thereby realizing accurate extraction of the second harmonic function of each gas. This method can not only accurately analyze the concentration of each component of the mixed gas, and has high detection accuracy, but also does not require modification of the hardware circuit, thus reducing costs and improving efficiency. This method can achieve good detection effect and accuracy, and provides a guarantee for the detection device to accurately analyze the mixed gas in the goaf.

[0136] The present invention quantifies the various factors of gas detection noise generated by the noise through the calculation model of the gas detection noise to be measured, thereby realizing the calculation of the gas detection noise to be measured. Due to the inevitable existence of noise in the detection device, when the initial decomposition threshold of the gas to be measured is less than the noise value, the system will decompose and calculate the noise, and the calculation result will have a large deviation. The parameters in the calculation model provide clear guidance for system design, which is helpful to design a more efficient and sensitive laser gas detection system. Given the system parameters, the noise calculation model can predict the detection limit and sensitivity of the system. The multiple parameters in the noise calculation model provide rich possibilities for system optimization. By adjusting the parameters in the calculation model formula, the performance of the detection system can be systematically optimized.

[0137] The device of the present invention uses laser detection technology to effectively conduct full laser real-time online on-site accurate and reliable monitoring and analysis of the nine gas components in the mixed gas in the underground goaf, realize early warning and forecasting of coal mine spontaneous combustion fires, and provide real-time upload and warning alarm functions, providing a new generation of solutions for the monitoring of coal mine spontaneous combustion fires and escorting the safe production of coal mines. It has the following characteristics:

[0138] Full laser detection of 9 types of gases improves detection accuracy and is calibration-free for 6 months, reducing maintenance workload.

[0139] Realizing underground distributed layout shortens pipeline distance and reduces the risk of blockage and gas leakage.

[0140] It has pipeline fault diagnosis function, can automatically remind when leakage and blockage occur, and can perform back-blowing operation through air pump to blow through the pipeline.

[0141] The design of intrinsically safe micro air pump breaks the conventional mode of flameproof vacuum pump or water circulation pump, greatly reduces product cost and equipment size.

[0142] It is designed that one bundle tube is connected to one micro air pump for gas extraction, and eight bundle tubes share eight micro air pumps. The eight pumps are controlled by the main engine and can perform gas extraction work at the same time, which shortens the gas extraction time and solves the problem of very long gas extraction time caused by conventional single pump polling gas extraction.

[0143] It can realize integrated monitoring and analysis with the distributed temperature measurement system in the goaf, thus improving the accuracy and precision of monitoring.

[0144] If the gas content at the monitoring point exceeds the limit, an audible and visual alarm will be given on site.

[0145] The laser spectrum analysis technology that can eliminate the interference of absorption spectrum lines is used to analyze the index gas in the goaf area. It has no drift, no calibration, no maintenance, fast measurement speed, high accuracy and strong reliability. The system has the characteristics of advanced technology, continuous monitoring, multiple functions, easy operation and fault diagnosis.

[0146] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0147] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples of computer-readable storage media (a non-exhaustive list) include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium is not to be interpreted as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

[0148] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in the computer-readable storage medium in each computing / processing device.

[0149] The computer program instructions for performing the operation of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. Computer-readable program instructions may be executed completely on a user's computer, partially on a user's computer, as an independent software package, partially on a user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), may be customized by utilizing the state information of the computer-readable program instructions, and the electronic circuit may execute the computer-readable program instructions, thereby realizing various aspects of the present disclosure.

[0150] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for eliminating interference of absorption lines in coal mine gas laser detection, characterized in that: include: Step 1: Perform standard gas laser detection tests on various gases to be tested in the mixed gas of the coal mine goaf to obtain standard second harmonic signals as sub-functions of the corresponding gases, and establish a sub-function library; Step 2: Perform laser detection on the mixed gas to obtain the second harmonic signal function of the mixed gas, and use the gas to be tested with the largest second harmonic signal amplitude in the second harmonic signal function as the separation gas; Step 3: Obtain the sub-function of the separated gas from the sub-function library, and obtain the function item corresponding to the separated gas using a polynomial fitting algorithm; Step 4: Subtract the second harmonic signal function of the mixed gas from the function term corresponding to the separated gas to obtain the remainder function; Step 5: Compare the amplitude of the remainder function with the preset decomposition thresholds of various types of gases to be tested. If the amplitude of the remainder function is greater than the decomposition threshold, the gas to be tested with the largest second harmonic signal amplitude in the remainder function is used as the new separation gas, and return to step 3 for iterative calculation. During the iterative calculation, the remainder function is used to replace the second harmonic signal function of the mixed gas in step 4 for remainder function calculation until the amplitude of the remainder function is less than all decomposition thresholds. The final remainder function is determined according to the sub-function corresponding to the current non-separated gas, and the final remainder function and the function terms obtained in each iteration are output.

2. The method for eliminating interference of coal mine gas laser detection absorption spectrum lines according to claim 1, characterized in that: In step 1, the following standard second harmonic signal is obtained through a standard gas laser detection test: L γ (t)=cL(t-b)(3) In the formula, b is the translation scale, c is the standard gas concentration corresponding to the gas to be measured, and t is the time; L(tb) is the window function belonging to the Hilbert space, expressed as Where x(tb) is the original second harmonic signal function after translation.

3. The method for eliminating interference of coal mine gas laser detection absorption spectrum lines according to claim 1, characterized in that: In step 2, the mixed gas is laser detected to obtain the second harmonic signal function of the mixed gas: In the formula, is the nth gas sub-function to be measured, k n is the analytical coefficient of the nth gas to be measured, and N is the type of gas to be measured.

4. The method for eliminating interference of coal mine gas laser detection absorption spectrum lines according to claim 3, characterized in that: In step 3, the sub-function L for separating the gas is obtained from the sub-function library. γ (t), and use the polynomial fitting algorithm to obtain the function term corresponding to the separated gas: Among them, ρ i are polynomial fitting coefficients, and i,M are polynomial orders.

5. A method for eliminating interference of coal mine gas laser detection absorption spectrum lines according to claim 4, characterized in that: In step 4, the second harmonic signal function f(t) of the mixed gas is subtracted from the function term y corresponding to the separated gas z (t), and obtain the remainder function:

6. The method for eliminating interference of coal mine gas laser detection absorption spectrum lines according to claim 1, characterized in that: In step 5, the decomposition threshold of the gas to be tested is determined as follows: Calculate the detection noise of the gas to be tested, and compare the calculated noise value with the initial setting value of the decomposition threshold. If the calculated noise value is greater than the initial setting value of the decomposition threshold, set the calculated noise value as the decomposition threshold of the detected gas; otherwise, set the initial setting value of the decomposition threshold as the decomposition threshold of the detected gas.

7. A method for eliminating interference of coal mine gas laser detection absorption spectrum lines according to claim 6, characterized in that: The calculation formula of the gas detection noise to be tested is: Where ε is the gas detection noise to be measured, △f is the laser modulation bandwidth, p is the modulation frequency, β is the modulation frequency index, is the laser fluctuating power at the modulation frequency p, σ is the detection efficiency, e is the charge of the detection circuit, h is the Planck constant, and w0 is the laser center frequency.

8. The method for eliminating interference of coal mine gas laser detection absorption spectrum lines according to claim 6, characterized in that: The initial setting value of the decomposition threshold is the sum of the detection resolution of the gas to be detected and the absolute value of the detection error of the gas to be detected under ideal conditions.

9. The method for eliminating interference of coal mine gas laser detection absorption spectrum lines according to claim 1, characterized in that: In step 5, after iterative calculation, the final function remainder and the function terms obtained in each iteration are output to form the second harmonic signal function of the mixed gas after the absorption line interference is eliminated: Where m is the number of iterations; y zn (t) is the corresponding function term obtained by using the polynomial fitting algorithm when the nth gas to be tested is used as the separation gas; R m (t) is the final remainder function output after m iterations of calculation.

10. A system for eliminating interference of absorption spectrum lines of coal mine gas laser detection, using the method according to any one of claims 1 to 9, characterized in that: The system comprises: The sub-function library construction module is used to obtain standard second harmonic signals of various gases to be tested in the mixed gas of the coal mine goaf through standard gas laser detection test, and use them as sub-functions of corresponding gases to establish a sub-function library; The laser detection module is used to perform laser detection on the mixed gas to obtain the second harmonic signal function of the mixed gas, and the gas to be tested with the largest second harmonic signal amplitude in the second harmonic signal function is used as the separation gas; A function item fitting module, used for obtaining the sub-function of the separated gas from the sub-function library, and obtaining the function item corresponding to the separated gas by using a polynomial fitting algorithm; The remainder function calculation module performs subtraction calculation on the second harmonic signal function of the mixed gas and the function term corresponding to the separated gas to obtain the remainder function; The iterative calculation module is used to compare the amplitude of the remainder function with the preset decomposition thresholds of various types of gases to be tested. If the amplitude of the remainder function is greater than the decomposition threshold, the gas to be tested with the largest second harmonic signal amplitude in the remainder function is used as the new separation gas, and the function item fitting module and the remainder function calculation module are returned for iterative calculation. During the iterative calculation, the remainder function is used to replace the second harmonic signal function of the mixed gas in the remainder function calculation module for the remainder function calculation until the amplitude of the remainder function is less than all decomposition thresholds. The final remainder function is determined according to the sub-function corresponding to the current non-separated gas, and the final remainder function and the function items obtained in each iteration are output.

11. A terminal comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the steps of the method according to any one of claims 1-9.

12. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 9 are implemented.

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