Opencast coal mine methane emission monitoring equipment

Abstract

According to the open pit coal mine methane emission monitoring equipment, the pretreatment device, the sampling air pump and the CH4 analyzer are arranged through the mounting column, and the stability of the mounting column is ensured through the base of the triangular structure support. The pretreatment device is a three-stage progressive filtering unit, dust and steam in the open pit coal mine gas can be removed, and the obtained sample gas can be cleaner and drier and is appropriate in temperature. By utilizing suction force generated by the sampling air pump, air enters an optical cavity of the CH4 analyzer after being treated by the pretreatment device. The CH4 analyzer further comprises a laser and a CH4 optical analysis module, the laser emits a laser beam with a specific wavelength to the optical cavity, and multiple reflections are formed in the optical cavity, so that the effective optical path of the laser beam reaches a preset range; the CH4 optical analysis module measures the concentration of methane in the sample gas by detecting the light intensity change of the laser beam after the laser beam passes through the optical cavity containing the sample gas. According to the scheme, the methane emission condition of the open pit coal mine can be accurately monitored.

Description

Technical Field

[0001] The present application relates to the field of open-pit coal mine monitoring equipment, and in particular, to an open-pit coal mine methane emission monitoring device. Background Art

[0002] Greenhouse gas emissions are a major contributor to global climate change. Methane, a potent greenhouse gas, plays a key role in global warming. Methane emissions from the coal mining industry are a significant and significant source of methane emissions. Open-pit coal mining is a key method of coal mining. Compared to underground mining, open-pit coal mining utilizes larger scales and involves more complex operations, releasing significant amounts of methane during the production process. First, once coal seams are exposed, methane previously adsorbed within the coal mass gradually desorbs and releases into the atmosphere. Second, microbial activity in coal gangue deposits within open-pit coal mining areas also produces methane. Gangue contains a significant amount of organic matter, which, under suitable environmental conditions, releases methane as microorganisms decompose it. As a significant source of anthropogenic methane emissions, accurate monitoring of methane emissions from open-pit coal mines helps coal companies accurately understand their own methane emissions and provides data support for developing scientific emission reduction plans.

[0003] At present, methane emission monitoring technology for the special environment of open-pit coal mines mainly relies on handheld monitoring, mobile observation vehicle measurement, and drone inspection. When dealing with complex environments such as high dust, variable temperature and humidity in open-pit coal mines, it will lead to problems such as optical sensor sensitivity attenuation, gas path condensation, and inability to continuously monitor, affecting the measurement effect and insufficient accuracy. Summary of the Invention

[0004] The technical problem to be solved by this application is that the existing technical solutions for monitoring methane emissions in open-pit mines are difficult to adapt to the complex environment of high dust, variable temperature and humidity, resulting in low accuracy of monitoring results, and thus provide an open-pit coal mine methane emission monitoring device.

[0005] The technical solution of the present application provides an open-pit coal mine methane emission monitoring device, the device comprising a mounting column, a base, a pretreatment device, a sampling gas pump and a CH4 analyzer;

[0006] The pretreatment device, the sampling gas pump and the methane analyzer are arranged on the mounting column;

[0007] The base is a triangular structure bracket, the top of each bracket is fixed on the mounting column, and the bottom of each bracket is provided with an anchor bolt mounting hole;

[0008] The pretreatment device is a three-stage progressive filtration unit, wherein: the first-stage filtration unit uses multiple dust filters to remove coarse dust particles in the air, and the diameter of the coarse dust particles is in the first range; the second-stage filtration unit uses a PTFE membrane filter to remove fine dust particles in the air, and the diameter of the fine dust particles is in the second range; the third-stage filtration unit uses a molecular sieve drying cartridge to remove moisture from the air;

[0009] The air inlet of the sampling air pump is connected to the air outlet of the pretreatment device, and the air outlet of the sampling air pump is connected to the air inlet of the CH4 analyzer; the sampling air pump delivers the sample gas to be tested to the CH4 analyzer;

[0010] The CH4 analyzer includes a laser, an optical chamber, and a CH4 optical analysis module. The sample gas to be measured enters the optical chamber; the laser emits a laser beam of a specific wavelength into the optical chamber, causing multiple reflections in the optical chamber so that the effective optical path of the laser beam reaches a preset range; the CH4 optical analysis module measures the methane concentration in the sample gas by detecting the change in light intensity of the laser beam after passing through the optical chamber containing the sample gas.

[0011] Preferably, in the open-pit coal mine methane emission monitoring equipment, the optical chamber in the CH4 analyzer is composed of a pair of toroidal mirrors with matching curvature radii, and the reflectivity of the toroidal mirrors is ≥99.99%; the laser beam is incident on the optical chamber at a specific off-axis angle and forms 50-200 reflections in the optical chamber, and the preset range of the effective optical path is 180-220m.

[0012] Preferably, in the open-pit coal mine methane emission monitoring equipment, a flow meter is provided at the air inlet end of the CH4 analyzer, and the flow meter is used to adjust the flow rate of the sample gas delivered to the optical chamber.

[0013] Preferably, the open-pit coal mine methane emission monitoring equipment further includes an anemometer:

[0014] The anemometer is arranged on the top of the installation column, and the anemometer detects the wind speed in real time.

[0015] Preferably, in the open-pit coal mine methane emission monitoring equipment, the anemometer sends the wind speed to the CH4 analyzer, and the CH4 analyzer calculates the methane flux based on the methane concentration and the wind speed.

[0016] Preferably, in the open-pit coal mine methane emission monitoring equipment, the CH4 analyzer is integrated with a temperature and humidity sensor for monitoring ambient temperature and humidity.

[0017] Preferably, in the open-pit coal mine methane emission monitoring equipment, the CH4 analyzer calculates the methane flux F in the following manner:

[0018] F = K · ∫ [C (w) · U (w)] dw;

[0019] Wherein, K represents the humidity temperature compensation coefficient, which is obtained by looking up the table according to the ambient temperature and humidity; C(w) represents the line integral concentration of methane; U(w) represents the ultrasonic wind speed; and w represents the position where the detection device is set.

[0020] Preferably, in the open-pit coal mine methane emission monitoring equipment, the molecular sieve drying cylinder is equipped with a temperature control heating component, and the temperature control heating component controls the internal temperature of the molecular sieve drying cylinder within a preset range.

[0021] Preferably, in the open-pit coal mine methane emission monitoring equipment, an automatic condensate discharge valve is provided at the bottom of the molecular sieve drying cylinder. When the accumulated amount of liquid water in the cylinder reaches a preset threshold, the automatic condensate discharge valve automatically opens to discharge the liquid water.

[0022] Preferably, the open-pit coal mine methane emission monitoring device further includes a communication module and an early warning module:

[0023] The communication module is used to transmit the methane concentration to a host computer for the host computer to determine whether the methane concentration exceeds a threshold value, and the host computer outputs an indication signal when the methane concentration exceeds the threshold value;

[0024] The early warning module issues an alarm prompt after receiving the indication signal from the host computer indicating that the methane concentration exceeds the threshold.

[0025] Compared with the existing technology, the above technical solution provided by this application has the following technical effects:

[0026] The open-pit coal mine methane emission monitoring equipment provided in this application utilizes a mounting column to set up a pretreatment device, a sampling gas pump, and a CH4 analyzer, and utilizes the base of a triangular structure bracket to ensure the stability of the mounting column. The pretreatment device is a three-stage progressive filtration unit, wherein: the first-stage filtration unit uses multiple dust filters to remove coarse dust particles in the air, and the diameter of the coarse dust particles is in the first range; the second-stage filtration unit uses a PTFE membrane filter to remove fine dust particles in the air, and the diameter of the fine dust particles is in the second range; the third-stage filtration unit uses a molecular sieve drying cylinder to remove moisture from the air. Therefore, the pretreatment device can remove dust and moisture from the open-pit coal mine gas, and the obtained sample gas can be cleaner, drier, and at a suitable temperature. Utilizing the suction generated by the sampling gas pump, the air is processed by the pretreatment device and then enters the optical chamber of the CH4 analyzer. The CH4 analyzer also includes a laser and a CH4 optical analysis module. The laser emits a laser beam of a specific wavelength into an optical chamber, where multiple reflections occur, reducing the effective optical path of the laser beam to a preset range. The CH4 optical analysis module measures the methane concentration in the sample gas by detecting changes in the laser beam's intensity after it passes through the optical chamber containing the sample gas. This application solution enables monitoring of methane emissions from open-pit coal mines, and the sample gas analyzed by the CH4 analyzer is pre-treated, eliminating the effects of dust, temperature, and humidity. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic structural diagram of an open-pit coal mine methane emission monitoring device according to one embodiment of the present application;

[0028] Figure 2 This is a schematic structural diagram of a pre-processing device according to an embodiment of the present application;

[0029] Figure 3 This is a schematic block diagram of the modules of the CH4 analyzer according to one embodiment of the present application;

[0030] Figure 4 This is a structural schematic diagram of an open-pit coal mine methane emission monitoring device described in another embodiment of the present application. DETAILED DESCRIPTION

[0031] The specific implementation of this application is further described below with reference to the accompanying drawings.

[0032] It is easy to understand that according to the technical solution of this application, a variety of structural methods and implementation methods can be replaced with each other by those skilled in the art without changing the essential spirit of this application. Therefore, the following specific embodiments and drawings are only exemplary descriptions of the technical solution of this application and should not be regarded as the entire application or as a limitation or restriction of the technical solution of the application.

[0033] This embodiment provides an open-pit coal mine methane emission monitoring device, such as Figure 1 As shown, the equipment includes a mounting column 100, a base 200, a pretreatment device 300, a sampling gas pump 400 and a CH4 analyzer 500; the pretreatment device 300, the sampling gas pump 400 and the methane analyzer 500 are arranged on the mounting column 100, the mounting column 100 has a diameter of not less than 80 mm and is made of Q355B high-strength low-alloy steel; the base 200 is a triangular structure bracket, the top of each bracket 201 is fixed to the mounting column 100, and the bottom of each bracket 201 is provided with an anchor bolt mounting hole 202, which has high strength and wind resistance, and the height is usually 2.5-5m; Figure 2 As shown, the pretreatment device 300 is a three-stage progressive filtration unit, wherein: the first-stage filtration unit adopts multiple dust filters to remove coarse dust particles in the air, and the diameter of the coarse dust particles is in the first range, for example, it is used to remove dust particles with a diameter greater than 1 μm, and is provided with a differential pressure sensor (measuring range 0-10 kPa, accuracy ±1% FS), which outputs a replacement prompt signal when the filtration resistance is ≥5 kPa; the second-stage filtration unit adopts a PTFE membrane filter to remove fine dust particles in the air, and the diameter of the fine dust particles is in the second range, for example, it can be used to remove dust with a diameter less than or equal to 1 μm, the PTFE membrane filter adopts a folded structure, the filtration efficiency (for 1 μm particles) is ≥99.9%, and the dust holding capacity is ≥50 g; the third-stage filtration unit adopts a molecular sieve drying cylinder to remove moisture from the air, which is used for dehydration and drying and has its own temperature control heating to prevent condensation when the temperature is too low.

[0034] The air inlet of the sampling gas pump 400 is connected to the air outlet of the pretreatment device 300 , and the air outlet of the sampling gas pump 400 is connected to the air inlet of the CH 4 analyzer 500 ; the sampling gas pump 400 delivers the sample gas to be tested to the CH 4 analyzer 500 .

[0035] like Figure 3 As shown, the CH4 analyzer 500 includes a laser, an optical chamber, and a CH4 optical analysis module. The sample gas to be measured enters the optical chamber. The laser has an output power of 5mW and a linewidth of ≤1MHz, and emits a laser beam of a specific wavelength (1650nm) into the optical chamber. Multiple reflections are generated within the optical chamber, resulting in the effective optical path of the laser beam reaching a preset range. The CH4 optical analysis module measures the methane concentration in the sample gas by detecting the change in the laser beam's intensity after passing through the optical chamber containing the sample gas. Based on optical principles, the CH4 optical analysis module emits a laser beam of a specific wavelength through a laser transmitter. Through multiple reflection resonance within the chamber, it measures the line-integrated spatial methane concentration and outputs the line-integrated spatial methane concentration to the communication module.

[0036] When implementing it specifically, Figure 3 As shown, the CH4 analyzer 500 also includes a control circuit board, which is equipped with a calculation module, an early warning module, and a communication module. The calculation module is used to measure the line-integrated spatial methane concentration based on the methane concentration laser telemetry beam and output the line-integrated spatial methane concentration to the early warning module and communication module. The methane concentration is calculated based on the line-integrated spatial methane concentration and the spatial distance or effective optical path. The output end of the communication module is connected to a host computer via an RS485 / Modbus dual-protocol interface to output the methane concentration to the host computer. Communication can use 485 signals, 4G, or 5G. The early warning module is used to compare the methane concentration with a preset value and, if the concentration value exceeds the preset value, can issue an alarm. In other words, the device of this application has its own alarm function. Alternatively, the communication module is used to transmit the methane concentration to the host computer for determination of whether the methane concentration exceeds a threshold. The host computer outputs an indication signal when the methane concentration exceeds the threshold. The early warning module issues an alarm after receiving the indication signal from the host computer indicating that the methane concentration exceeds the threshold. That is, the device of the present application is controlled by a host computer to realize the alarm function.

[0037] In addition, the function of the sampling gas pump 400 is to provide power for the sample gas. The relative positions of the pretreatment device 300, the deoxygenation pump 400 and the CH4 analyzer 500 can be changed according to the specific application scenario.

[0038] The open-pit coal mine methane emission monitoring equipment provided in the above-mentioned embodiment utilizes a mounting column 100 to install a pretreatment device 300, a sampling gas pump 400, and a CH4 analyzer 500. The stability of the mounting column 100 is ensured by the base 200 of the triangular structure bracket. The pretreatment device 300 is a three-stage progressive filtration unit, wherein: the first-stage filtration unit uses multiple dust filters to remove coarse dust particles from the air; the second-stage filtration unit uses a PTFE membrane filter to remove fine dust particles from the air; and the third-stage filtration unit uses a molecular sieve drying cartridge to remove moisture from the air. Therefore, the pretreatment device 300 can remove dust and moisture from the open-pit coal mine gas, and the resulting sample gas can be cleaner, drier, and at a suitable temperature. Using the suction generated by the sampling gas pump 400, the air is processed by the pretreatment device 300 and then enters the optical chamber of the CH4 analyzer 500. The CH4 analyzer 500 also includes a laser and a CH4 optical analysis module. The laser emits a laser beam of a specific wavelength into an optical chamber, where it undergoes multiple reflections, extending the effective optical path of the laser beam to a preset range. The CH4 optical analysis module measures the methane concentration in the sample gas by detecting changes in the laser beam's intensity after it passes through the optical chamber containing the sample gas. This solution is capable of monitoring methane emissions from open-pit coal mines, and the CH4 analyzer analyzes pre-treated sample gas to eliminate the influence of dust, temperature, and humidity.

[0039] Furthermore, the molecular sieve drying cylinder is equipped with a temperature-controlled heating component, which controls the temperature inside the cylinder of the molecular sieve drying cylinder within a preset range (20±5°C). The temperature-controlled heating component can be started and stopped by a temperature and humidity sensor, so that the sample gas can reach an optimal temperature that is dry and suitable for methane measurement. Preferably, an automatic condensate discharge valve is provided at the bottom of the molecular sieve drying cylinder. When the accumulated amount of liquid water in the cylinder reaches a preset threshold, the automatic condensate discharge valve automatically opens to discharge liquid water. In specific implementation, the molecular sieve rotor (diameter 80mm, thickness 20mm) of the molecular sieve drying cylinder is controlled by an SHT30 humidity sensor (measuring range 0-100% RH). When the intake humidity is ≥60% RH, the rotor is started to rotate (speed 1r / min), and the regeneration fan power is 5W.

[0040] Preferably, in the open-pit coal mine methane emission monitoring equipment of the above scheme, the optical chamber in the CH4 analyzer 500 is composed of a pair of toroidal mirrors with matching curvature radii, the length of which can be 0.5m, and the reflectivity of the toroidal mirrors is ≥99.99%. The laser beam is incident on the optical chamber at a specific off-axis angle (2°-5°) and forms 50-200 reflections within the optical chamber, and the preset range of the effective optical path is 180-220m. In specific implementation, the CH4 chamber is a cylindrical stainless steel cavity (inner diameter 50mm, length 500mm), with a pair of toroidal reflectors with a curvature radius of 500mm assembled at both ends, and the reflector surface is coated with a multilayer dielectric film. The toroidal mirror uses a fused quartz substrate with a surface roughness of Ra ≤ 0.5nm and a coating layer that can withstand 500 wipes or more. The inner wall of the chamber is electropolished (surface roughness Ra ≤ 0.8μm) and coated with a polytetrafluoroethylene anti-corrosion coating that can withstand 1000ppm hydrogen sulfide gas corrosion.

[0041] like Figure 3 As shown, in the open-pit coal mine methane emission monitoring equipment, the air inlet end of the CH4 analyzer is provided with a flow meter, and the flow meter is used to adjust the flow of the sample gas delivered to the optical chamber.

[0042] Furthermore, if Figure 4 As shown, the open-pit coal mine methane emission monitoring equipment also includes an anemometer 600, which is installed at the top of the mounting column 100 and detects wind speed in real time. The anemometer 600 sends the wind speed to the CH4 analyzer 500, and the CH4 analyzer 500 calculates the methane flux based on the methane concentration and the wind speed. In a specific implementation, the CH4 analyzer 500 is also integrated with a temperature and humidity sensor for monitoring the ambient temperature and humidity. The CH4 analyzer 500 calculates the methane flux F in the following manner:

[0043] F = K · ∫ [C (w) · U (w)] dw;

[0044] Where K represents the humidity-temperature compensation coefficient, obtained by looking up the ambient temperature and humidity; C(w) represents the line-integrated concentration of methane; U(w) represents the ultrasonic wind speed; and w represents the location of the detection device. The above algorithm can be implemented in the calculation module on the control circuit board of the CH4 analyzer 500.

[0045] In addition, the open-pit coal mine methane emission monitoring equipment also includes a power supply system, which can use supporting photovoltaic panels and batteries, or wired power supply based on actual conditions.

[0046] The open-pit coal mine methane emission monitoring equipment disclosed in this application has been verified to have a detection range of 0.1-10,000 ppm, a response time of less than 2 seconds, a monitoring accuracy of ppm level, and an error of less than 0.01%. The verification process is as follows:

[0047] In a certain open-pit coal mine in production, in order to test the methane flux in the mining area, combined with the on-site mining and transportation conditions, a point was selected in the east, west, south and north directions of the open-pit coal mine, and each point was equipped with a set of monitoring equipment in this application. Priority was given to key methane emission areas such as the coal mining face area, the crushing station area, and the downwind area (north side). The base 200 uses a triangular bracket, which is fixed by a simple foundation and expansion bolts. Activated alumina is used as a desiccant for dehydration in the pretreatment device 300, and the filter disc adopts 4-stage filtration with accuracies of 100μm, 50μm, 10μm, and 1μm respectively. The desiccant and filter disc are replaced every month or so. The CH4 analyzer 500 is fixed to a height of 4 meters, and the sampling gas pump 400 uses a vacuum pump with a flow rate of 0.3L / M. Photovoltaic power supply is used for power supply, and battery energy storage is used. After testing, the highest environmental methane concentration in the north test point area was about 4 ppm, the highest methane concentration in the south test point area was about 2.7 ppm, the highest methane concentration in the west test point area was about 3.3 ppm, and the highest methane concentration in the east test point area was about 3.5 ppm.

[0048] As needed, the above technical solutions can be combined to achieve the best technical effect.

[0049] The above are only the principles and preferred embodiments of the present application. It should be noted that, for those skilled in the art, on the basis of the principles of the present application, several other modifications can be made, which should also be considered as the scope of protection of the present application.

Claims

1. An open-pit coal mine methane emission monitoring device, characterized in that: The equipment includes a mounting column, a base, a pretreatment device, a sampling gas pump and a CH4 analyzer; The pretreatment device, the sampling gas pump and the methane analyzer are arranged on the mounting column; The base is a triangular structure bracket, the top of each bracket is fixed on the mounting column, and the bottom of each bracket is provided with an anchor bolt mounting hole; The pretreatment device is a three-stage progressive filtration unit, wherein: the first-stage filtration unit uses multiple dust filters to remove coarse dust particles in the air, and the diameter of the coarse dust particles is in the first range; the second-stage filtration unit uses a PTFE membrane filter to remove fine dust particles in the air, and the diameter of the fine dust particles is in the second range; the third-stage filtration unit uses a molecular sieve drying cartridge to remove moisture from the air; The air inlet of the sampling air pump is connected to the air outlet of the pretreatment device, and the air outlet of the sampling air pump is connected to the air inlet of the CH4 analyzer; the sampling air pump delivers the sample gas to be tested to the CH4 analyzer; The CH4 analyzer includes a laser, an optical chamber, and a CH4 optical analysis module. The sample gas to be measured enters the optical chamber; the laser emits a laser beam of a specific wavelength into the optical chamber, causing multiple reflections in the optical chamber so that the effective optical path of the laser beam reaches a preset range; the CH4 optical analysis module measures the methane concentration in the sample gas by detecting the change in light intensity of the laser beam after passing through the optical chamber containing the sample gas.

2. The open-pit coal mine methane emission monitoring device according to claim 1, characterized in that: The optical cavity in the CH4 analyzer is composed of a pair of toroidal mirrors with matching curvature radii, and the reflectivity of the toroidal mirrors is ≥99.99%; the laser beam is incident on the optical cavity at a specific off-axis angle and forms 50-200 reflections in the optical cavity, and the preset range of the effective optical path is 180-220m.

3. The open-pit coal mine methane emission monitoring device according to claim 1, characterized in that: The CH4 analyzer is provided with a flow meter at the gas inlet end, and the flow meter is used to adjust the flow of the sample gas delivered to the optical chamber.

4. The open-pit coal mine methane emission monitoring equipment according to claim 1, characterized in that: Also includes anemometer: The anemometer is arranged on the top of the installation column, and the anemometer detects the wind speed in real time.

5. The open-pit coal mine methane emission monitoring device according to claim 4, characterized in that: The anemometer sends the wind speed to the CH4 analyzer, and the CH4 analyzer calculates the methane flux according to the methane concentration and the wind speed.

6. The open-pit coal mine methane emission monitoring device according to claim 5, characterized in that: The CH4 analyzer is integrated with a temperature and humidity sensor for monitoring ambient temperature and humidity.

7. The open-pit coal mine methane emission monitoring device according to claim 6, characterized in that: The CH4 analyzer calculates the methane flux F in the following manner: F = K · ∫ [C (w) · U (w)] dw; Wherein, K represents the humidity temperature compensation coefficient, which is obtained by looking up the table according to the ambient temperature and humidity; C(w) represents the line integral concentration of methane; U(w) represents the ultrasonic wind speed; and w represents the position where the detection device is set.

8. The open-pit coal mine methane emission monitoring device according to any one of claims 1 to 7, characterized in that: The molecular sieve drying cylinder is equipped with a temperature-controlled heating component, which controls the temperature inside the molecular sieve drying cylinder within a preset range.

9. The open-pit coal mine methane emission monitoring device according to claim 8, characterized in that: The bottom of the molecular sieve drying cylinder is provided with an automatic condensed water discharge valve. When the accumulated amount of liquid water in the cylinder reaches a preset threshold, the automatic condensed water discharge valve automatically opens to discharge the liquid water.

10. The open-pit coal mine methane emission monitoring equipment according to claim 8, characterized in that: It also includes communication module and early warning module: The communication module is used to transmit the methane concentration to a host computer for the host computer to determine whether the methane concentration exceeds a threshold value, and the host computer outputs an indication signal when the methane concentration exceeds the threshold value; The early warning module issues an alarm prompt after receiving the indication signal from the host computer indicating that the methane concentration exceeds the threshold.

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