Full-scale methane gas detector

Abstract

The invention discloses a methane gas detector which comprises a first element, a second element, a third element and an electronic circuit, the first element comprises a first resistor with a thermosensitive characteristic, and the second element comprises a first heating resistor and a catalyst. According to the scheme, the advantages of a catalytic sensor and a thermal conductivity sensor are combined, the catalytic combustion principle is utilized under concentration gas, the gas thermal conductivity difference is utilized under high concentration, the measurement range is wide, response recovery is fast, sensitivity is high, and stability is good; moreover, the first element simultaneously serves as a compensation piece with catalytic performance and a sensitive piece with thermal conductivity, the number of the whole elements of the sensor is reduced, the manufacturing cost is reduced, the service life of the catalytic element is prolonged, the preheating effect is achieved due to the heat conduction effect during switching, the thermal efficiency is improved, and the advantages of being short in preheating time, high in sensitivity and the like are achieved. And the size is small.

Description

Technical Field

[0001] This application relates to methane monitoring and early warning technology, specifically to a methane gas detector. Background Technology

[0002] Methane, the main component of coal mine gas, is an important associated gas in coal mines. It is a flammable and explosive gas that often emerges from coal and rock formations. When the concentration of methane in the air reaches 5-16%, an explosion may occur, posing a threat to the safety of people and property. When the concentration of methane in the air exceeds 40%, it can cause immediate asphyxiation and death.

[0003] Real-time online monitoring of methane is a primary means of preventing coal mine gas accidents. However, most existing online methane sensors are thermocatalytic methane sensors, which detect concentrations of 0-5% by volume. When a gas outburst or gas surge occurs underground, these sensors are prone to false alarms or failure, failing to provide accurate warnings. With increasing coal mining depth, such hazards are on the rise, necessitating sensors capable of simultaneously monitoring both high and low concentrations of methane to ensure safe coal mine production. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application provides a methane gas detector, which includes a first element, a second element, a third element, and an electronic circuit connected to the first element, the second element, and the third element. The first element includes a first resistor with thermistor characteristics, the second element includes a first heating resistor and a catalyst, and the third element includes a second resistor.

[0005] The electronic circuit is configured to operate in a first mode and a second mode. The first mode is used to measure a first methane volume concentration range, and the second mode is used to measure a second methane volume concentration range. In the first mode, the first element and the second element are connected to the electronic circuit, the second element serves as a catalytic performance sensor, wherein the catalyst is used to catalyze the combustion of the analyte gas, and the first element serves as a catalytic performance compensation element. In the second mode, the first element and the third element are connected to the electronic circuit, the first element serves as a thermal conductivity sensor, wherein the analyte gas is in contact with the first element, and the third element serves as a thermal conductivity compensation element.

[0006] Based on the above embodiments, this application combines the advantages of catalytic and thermal conductivity sensors in a methane gas detector. It utilizes the principle of catalytic combustion under low gas concentrations and operates based on the difference in gas thermal conductivity under high concentrations, resulting in a wide measurement range, fast response recovery, high sensitivity, and good stability. Furthermore, this application sets the first element to a metal with thermosensitive properties, using it as a compensating element for catalytic performance and a sensitive element for thermal conductivity, reducing the overall number of sensor elements, thereby reducing manufacturing costs and extending the lifespan of the catalytic element. Moreover, during switching, the thermal conduction effect serves as a preheating function, improving thermal efficiency and offering advantages such as short preheating time and small size.

[0007] In some implementations, the first resistor is a thermistor.

[0008] In some embodiments, the methane gas detector further includes a carrier, wherein the first element, the second element, and the third element are all disposed on the carrier, and the carrier is an Al2O3 ceramic nanotube.

[0009] In some embodiments, the first element and / or the second element further include an isolation groove disposed on the carrier and surrounding all or part of the first resistor and / or the first heating resistor.

[0010] In some embodiments, the first heating resistor is a Pt film.

[0011] In some embodiments, the thickness of the Pt film is 10-20 μm.

[0012] In some embodiments, the Al2O3 ceramic nanotubes have a pore size of 50-150 nm and a pore spacing of 100-150 nm.

[0013] In some embodiments, the methane gas detector further includes a gas chamber, wherein the first element is disposed in the gas chamber, or the first element is in contact with the gas chamber.

[0014] In some embodiments, the catalyst is a Pt / Pd catalyst.

[0015] In some embodiments, the catalyst is attached to the first heating resistor. Attached Figure Description

[0016] Figure 1 This is a circuit diagram of a methane gas detector according to an embodiment of this application; Figure 2 This is a schematic diagram of the structure of the second element in a methane gas detector according to an embodiment of this application; Figure 3 This is the low-concentration response recovery curve of Example 1 of this application; Figure 4 This is the high-concentration response recovery curve of Example 1 of this application; Figure 5 This is the 1% response recovery curve for Example 1 of this application. Detailed Implementation

[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0019] Currently, commercially available sensors for measuring full-range (0-100%) methane (CH4), or methane gas detectors, mainly fall into two categories. One type uses thermal conductivity sensors and catalytic sensors to measure high and low concentrations of methane separately. However, these sensors suffer from drawbacks such as large device size, high power consumption, the need for switching at critical points, long sensor warm-up time, cumbersome calibration, and low measurement accuracy. The other type combines a catalytic sensor with a thermistor. It is usually an infrared remote-controlled intelligent detection instrument controlled by a microcontroller. However, this type of instrument uses a pair of carrier catalytic elements for infrared remote calibration under constant temperature control, which requires operation by professionals. The practicality of the product is relatively low, and these sensors also have high power consumption and low accuracy at high concentrations.

[0020] Therefore, there is an urgent need for a methane gas detector that has a wide measurement range, fast response recovery, high sensitivity, good stability, short preheating time, and small size.

[0021] This application provides a full-range methane gas detector, including a first element, a second element, a third element, and electronic circuitry connected to the first element, the second element, and the third element. The first element includes a first resistor with thermistor characteristics; the second element includes a first heating resistor and a catalyst; and the third element includes a second resistor. The electronic circuit is configured to operate in a first mode and a second mode, the first mode being used to measure a first methane volume concentration range, and the second mode being used to measure a second methane volume concentration range. In the first mode, the first element and the second element are connected to an electronic circuit, the second element serves as a sensitive element for catalytic performance, wherein the catalyst is used to catalyze the combustion of the analyte gas, and the first element serves as a compensating element for catalytic performance. In the second mode, the first element and the third element are connected to an electronic circuit. The first element serves as a sensor for thermal conductivity, wherein the analyte gas is in contact with the first element, and the third element serves as a compensator for thermal conductivity.

[0022] Based on the above embodiments, this application combines the advantages of catalytic and thermal conductivity sensors in a methane gas detector. It utilizes the principle of catalytic combustion under low-concentration gas conditions and operates based on the difference in thermal conductivity of gases under high concentration conditions. It has a wide measurement range, fast response recovery, high sensitivity, and good stability. Furthermore, this application sets the first element to a metal with thermosensitive properties, using it as a compensating element for catalytic performance and a sensitive element for thermal conductivity. This reduces the overall number of sensor elements, thereby reducing manufacturing costs and extending the lifespan of the catalytic element. Moreover, during switching, the thermal conduction effect serves as a preheating function, improving thermal efficiency and offering advantages such as short preheating time and small size.

[0023] The methane gas detector can also be called a methane sensor. It is understood that in the first mode, the third element may not be connected to the electronic circuit; in the second mode, the second element may not be connected to the electronic circuit.

[0024] In some embodiments, the first resistor may be a thermistor, such as a platinum wire, a nickel resistor, or a platinum-rhodium alloy resistor.

[0025] In some embodiments, the first heating resistor may be a platinum wire. Further, the first heating resistor may be an arc-shaped platinum wire.

[0026] In some embodiments, the catalyst is attached to the first heating resistor. Exemplarily, the catalyst can be coated or impregnated onto the surface of the first heating resistor. Specifically, an impregnation technique can be used to ensure uniform catalyst coating. The catalyst is capable of catalyzing flameless combustion when a low-concentration gas contacts the second element, thereby facilitating the chemical reaction.

[0027] The first heating resistor is used to provide heat to meet the sensor's operating temperature requirements. Specifically, the first heating resistor converts electrical energy into thermal energy to provide the temperature required for catalytic reaction and heat conduction.

[0028] Schematic, the catalytic principle in the first mode is as follows: The catalytic sensing element, i.e., the aforementioned second element, comprises a first heating resistor and a catalyst coated on its surface. When it operates, the first heating resistor comes into contact with a combustible gas (e.g., methane), resulting in flameless combustion and releasing heat. Since the first heating resistor is a platinum wire, a temperature-sensitive material, changes in the heat it receives cause a change in its platinum resistance. The sensor compensation element, i.e., the aforementioned first element, has no catalytic material on its surface and does not react with the combustible gas; it serves as a reference compensation. Using a Wheatstone bridge measurement circuit, the resistance changes of the sensing element and the compensation element can be measured, thereby further determining the change in methane concentration.

[0029] The catalytic reaction described above occurs on the catalyst surface. To ensure the catalytic reaction continues, the products must dissociate on the catalyst surface in a timely manner. In some embodiments, the catalyst can be a hydrodeoxygenation catalyst. For example, the catalyst can be a Pt / Pd catalyst. This catalyst can cause methane gas to be adsorbed and dissociated, i.e., dissociative chemisorption occurs.

[0030] In the formula, M represents the surface catalyst metal atom.

[0031] In some embodiments, the methane gas detector further includes a gas chamber, in which the first element is disposed, or in which the first element is in contact with the gas chamber.

[0032] Schematic, the heat conduction principle in the second mode is as follows: The thermally conductive element, i.e., the first element mentioned above, functions under high methane concentration conditions. Utilizing the difference in thermal conductivity between methane gas and air, an electrical signal related to the concentration of the gas being measured is obtained, thus determining the gas concentration. In this mode, the methane gas detector sends the gas to be measured into the gas chamber, and the thermally conductive element comes into contact with the gas. The methane gas detector energizes the first element, heating it to a certain temperature. Because the thermal conductivity of methane is higher than that of air (approximately 2.296 times that of air), when the first element encounters a methane-containing air mixture, it dissipates heat more quickly as a thermistor. The thermistor's temperature decreases, reducing its resistance. The change in the thermistor's resistance is measured using a Wheatstone bridge to obtain the concentration of the gas being measured. The stability of the measurement using the heat conduction method generally increases with increasing methane gas concentration.

[0033] In some embodiments, the methane gas detector further includes a carrier and a packaging shell, wherein the first element, the second element, and the third element are all disposed on the carrier and packaged in the packaging shell.

[0034] The outer casing can be made of ceramic material.

[0035] In some embodiments, the support is alumina (Al2O3) ceramic. Further, the support can be Al2O3 ceramic nanotubes, exemplarily having a pore size of 50-150 nm and a pore spacing of 100-150 nm. Specifically, the Al2O3 ceramic nanotube support can be prepared using a double anodic oxidation technique. Based on the above scheme, this support, due to its nanotube-permeable structure, exhibits excellent physical properties, resulting in higher sensor thermal efficiency and shorter response recovery time.

[0036] In some embodiments, the first element and / or the second element further includes an isolation groove. Specifically, the isolation groove is disposed on the carrier and surrounds all or part of the first resistor and / or the first heating resistor, thereby helping to reduce heat loss.

[0037] In some embodiments, the first heating resistor is specifically a Pt film. Preferably, the thickness of the Pt film is 10-20 μm.

[0038] In some embodiments, the first methane volume concentration range and the second methane volume concentration range can cover 0-100% of the methane volume concentration, thereby enabling the methane gas detector of this application to achieve efficient measurement of the full range of 0-100% methane gas volume concentration.

[0039] In some implementations, the first methane volume concentration range and the second methane volume concentration range may overlap. The first mode range is suitable for scenarios with low methane concentrations, while the second mode is suitable for scenarios with high methane concentrations. For example, the first mode may be used initially during testing, and the second mode may be switched as the methane concentration increases.

[0040] For example, the first methane volume concentration range can be 0-5%, and the second methane volume concentration range can be 5-100%. The first mode can detect a methane volume concentration of 0-5%; the second mode can detect a methane volume concentration of 5-100%.

[0041] like Figure 1 The diagram shown is a working circuit diagram of a methane gas detector according to an embodiment of this application. R1 is a thermal conductivity voltage divider resistor, operating in constant voltage mode, with a heating voltage range of 2-3V; proportional resistors R2 and R3 are fixed resistors, using 2KΩ precision metal film resistors; R4 is an adjustable resistor of 1KΩ, used to adjust the zero point of the bridge output. The first element 1 serves as a compensation element for the catalytic performance of the sensor and a sensitive element for thermal conductivity performance; the second element 2 is a sensitive element for catalytic performance; and the third element 3 is a compensation element for thermal conductivity performance. Switches K1 and K3 are interlocked, and switches K2 and K4 are interlocked. The rated voltage of the sensitive element is 2.6-3.0V.

[0042] The operation process is as follows: At low concentration, switches K1 and K3 are closed, and the system is in the first mode. Methane undergoes flameless combustion in the second element 2, resulting in an output voltage U`. The value of this output voltage is calculated as follows:

[0043] Where U is the input voltage, and r1 and r2 are the resistance values ​​of the compensation element and the sensing element of the catalytic sensor, respectively.

[0044] As the methane concentration increases, switches K2 and K4 close, entering the second mode and switching to the thermal conductivity principle. Methane then comes into contact with the first element 1, resulting in an output voltage U`. This output voltage value is calculated as follows:

[0045] Where U is the input voltage, and r1 and r3 are the resistance values ​​of the sensing element and the compensation element of the thermal conductivity sensor, respectively.

[0046] like Figure 2 The diagram shown is a schematic representation of the structure of the second element in a methane gas detector according to an embodiment of this application. It includes a Pt wire lead 100, an isolation groove 200, a heating electrode 300, a first heating resistor 400, and a support 500. The first heating resistor is a Pt film heating resistor, composed of an arc-shaped platinum resistance thermometer and a catalyst impregnated on its surface. The Pt film is 15 μm thick, and the catalyst is a Pt / Pd catalyst. The support 500 is a nanotube-permeable Al₂O₃ support, wherein the nanotube pore size is 100 nm and the pore spacing is 110 nm. The second element is encapsulated in a ceramic material encapsulation shell.

[0047] Figure 3 This is the low-concentration response recovery curve of Example 1 of this application. Figure 4 This is the high-concentration response recovery curve of Example 1 of this application. Figure 5 This is the 1% response recovery curve for Example 1 of this application.

[0048] Combined with soil Figure 5 As can be seen, the working circuit and structural model of the three-unit array full-range methane sensor in this application embodiment utilize the excellent mechanical processing performance of the ceramic micro-hot plate substrate, which has advantages such as high dielectric constant, low power consumption, and high-temperature operation. Combining silicon MEMS (microelectromechanical systems) technology and Pt thick film technology, a nanotube permeable structure full-range methane sensor with Al2O3 ceramic as substrate is proposed and fabricated. This improves the pairing success rate of the sensing element and the compensation element, enhances the stability of the sensor, and gives the sensor advantages such as wide measurement range, fast response recovery, high sensitivity, good stability, short preheating time, and small size.

[0049] It is understandable that the acquisition and processing of experimental data parameters in this application can be automatically controlled by a computer.

[0050] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A methane gas detector, characterized in that, It includes a first element, a second element, a third element, and electronic circuitry connected to the first element, the second element, and the third element. The first element includes a first resistor with thermistor properties; the second element includes a first heating resistor and a catalyst; and the third element includes a second resistor. The electronic circuit is configured to operate in a first mode and a second mode, the first mode being used to measure a first methane volume concentration range, and the second mode being used to measure a second methane volume concentration range. In the first mode, the first element and the second element are connected to an electronic circuit, the second element serves as a sensitive element for catalytic performance, wherein the catalyst is used to catalyze the combustion of the analyte gas, and the first element serves as a compensating element for catalytic performance. In the second mode, the first element and the third element are connected to an electronic circuit. The first element serves as a sensor for thermal conductivity, wherein the analyte gas is in contact with the first element, and the third element serves as a compensator for thermal conductivity.

2. The methane gas detector according to claim 1, characterized in that, The first resistor is a thermistor.

3. The methane gas detector according to claim 1 or 2, characterized in that, The methane gas detector also includes a carrier, on which the first element, the second element, and the third element are all disposed. The carrier is an Al2O3 ceramic nanotube.

4. The methane gas detector according to claim 1 or 2, characterized in that, The first element and / or the second element further include an isolation groove disposed on the carrier and surrounding all or part of the first resistor and / or the first heating resistor.

5. The methane gas detector according to claim 1 or 2, characterized in that, The first heating resistor is a Pt film.

6. The methane gas detector according to claim 5, characterized in that, The thickness of the Pt film is 10-20 μm.

7. The methane gas detector according to claim 3, characterized in that, The Al2O3 ceramic nanotubes have a pore size of 50-150 nm and a pore spacing of 100-150 nm.

8. The methane gas detector according to claim 1 or 2, characterized in that, It also includes air chambers, The first element is disposed in the air chamber, or the first element is able to contact the air chamber.

9. The methane gas detector according to claim 1 or 2, characterized in that, The catalyst is a Pt / Pd catalyst.

10. The methane gas detector according to claim 1 or 2, characterized in that, The catalyst is attached to the first heating resistor.

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