A carbon isotope detection device for trace carbon monoxide in the early stage of spontaneous combustion of coal

Abstract

This invention provides a carbon isotope detection device for trace carbon monoxide in the early stage of coal spontaneous combustion, belonging to the field of coal mine safety and coal spontaneous combustion monitoring technology. It includes a multi-port rotary valve and a supply module. The input terminals of the multi-port rotary valve are respectively connected to a helium input module and a sample introduction module. The output terminals of the multi-port rotary valve are respectively connected to a moisture removal module and a CO enrichment module. The output terminal of the moisture removal module is connected to an elimination module, and the output terminal of the elimination module is connected to the input terminal of the CO enrichment module. The output terminal of the CO enrichment module is connected to a CO quantitative conversion module. The supply module is connected to the CO quantitative conversion module. The output terminal of the CO quantitative conversion module is connected to a conversion product purification module, and the output terminal of the conversion product purification module is connected to an isotope ratio mass spectrometry analysis module. This detection device can perform carbon isotope detection of CO at ppm levels or even lower concentrations during the early low-temperature oxidation stage of coal spontaneous combustion.

Description

Technical Field

[0001] This invention relates to the field of coal mine safety and coal spontaneous combustion monitoring technology, specifically to a carbon isotope detection device for trace carbon monoxide in the early stage of coal spontaneous combustion. Background Technology

[0002] Spontaneous combustion of coal is one of the major hazards affecting safe production in coal mines. The early, low-temperature oxidation stage of spontaneous combustion is a critical window for fire prevention and control. During this stage, the coal oxidation reaction is slow, the exothermic reaction is not obvious, and no gaseous products have yet appeared in the gaseous phase. If high-grade hydrocarbon indicators (CGEs) and above are not identified and addressed in a timely manner, they can easily evolve into accelerated oxidation or even violent combustion. Therefore, accurate monitoring and early warning of the early low-temperature oxidation stage of coal spontaneous combustion is of great significance. Currently, carbon monoxide is widely used as the most sensitive indicator gas for coal spontaneous combustion. However, in the early stages of spontaneous combustion, carbon monoxide concentrations are extremely low (typically at the ppm level), and the composition of underground gases is complex, affected by background concentration fluctuations and interference from the goaf environment. Relying solely on concentration monitoring has limitations in sensitivity and reliability.

[0003] In contrast, gas isotope ratios are not affected by the aforementioned factors. Existing gas carbon isotope detection technologies are mainly divided into two categories: gas chromatography-isotope ratio mass spectrometry (GC-IRMS) and pre-concentration-isotope ratio mass spectrometry (PreCon-IRMS). GC-IRMS requires CO concentrations of several thousand ppm to achieve chromatographic separation. Since carbon monoxide concentrations are typically in the ppm range during the early, low-temperature oxidation stage of coal combustion, GC-IRMS is difficult to use for carbon isotope detection of ppm-level CO during this stage. PreCon-IRMS is primarily designed for... , , Because of its greenhouse gas design, CO is considered an impurity gas and is removed during the testing process. Therefore, PreCon-IRMS is difficult to use for carbon isotope detection of ppm-level CO in the early low-temperature oxidation stage of coal spontaneous combustion. Although some researchers have developed automated CO purification and injection devices, they still rely on chromatographic functions to remove nitrogen, etc. The method does not consider moisture content, does not take into account methane interference, and requires a CO concentration of several thousand ppm, thus failing to meet the ppm-level CO detection requirements during the early low-temperature oxidation stage of coal spontaneous combustion.

[0004] Based on the similar physical properties of methane and carbon monoxide, they are difficult to separate during the low-temperature oxidation stage. Background carbon dioxide and moisture directly interfere with carbon isotope determination, making it impossible for existing technologies to obtain accurate results under conditions without chromatographic separation. Therefore, we propose a carbon isotope detection device for trace carbon monoxide in the early stage of coal spontaneous combustion. Summary of the Invention

[0005] The purpose of this invention is to provide a device for detecting trace carbon monoxide carbon isotopes in the early stage of spontaneous combustion of coal, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a device for detecting trace carbon monoxide carbon isotopes in the early stages of spontaneous combustion of coal, comprising a multi-channel rotary valve, The system includes a supply module and a control module. The input terminals of the multi-way rotary valve are connected to a helium input module and a sample introduction module, respectively. The output terminals of the multi-way rotary valve are connected to a moisture removal module and a CO enrichment module, respectively. The output terminal of the moisture removal module is connected to... Elimination module, the The output of the elimination module is connected to the input of the CO enrichment module, and the output of the CO enrichment module is connected to a CO quantitative conversion module. The supply module is connected to the CO quantitative conversion module. The output of the CO quantitative conversion module is connected to the conversion product purification module. The output of the conversion product purification module is connected to the isotope ratio mass spectrometry analysis module. The multi-way rotary valve... Supply module, helium input module, sample introduction module, moisture removal module, The elimination module, CO enrichment module, CO quantitative conversion module, conversion product purification module, and isotope ratio mass spectrometry analysis module are all electrically connected to the control module.

[0008] Furthermore, the helium input module includes a gas mass flow controller and a flow regulator valve. The output of the gas mass flow controller is connected to the input of the flow regulator valve, and the output of the flow regulator valve is connected to the input of the multi-way rotary valve.

[0009] Furthermore, the sample introduction module includes a flow limiting valve and a gas mass flow controller. The output end of the flow limiting valve is connected to the input end of the gas mass flow controller, and the output end of the gas mass flow controller is connected to the input end of the multi-way rotary valve.

[0010] Furthermore, the moisture removal module includes a Nafion membrane dehydration unit and a low-temperature cold trap, which is filled with anhydrous magnesium perchlorate desiccant.

[0011] Furthermore, the aforementioned The elimination module includes a filled absorption trap, which is filled with... Absorbent material.

[0012] Furthermore, the CO enrichment module includes a low-temperature cold trap filled with a CO selective adsorbent, and an electric heating jacket is provided on the outside of the low-temperature cold trap.

[0013] Furthermore, the CO selective adsorbent is one of activated carbon, carbon molecular sieve, or metal-organic framework materials.

[0014] Furthermore, the CO quantitative conversion module includes a quartz reaction tube, the interior of which is filled with a selective oxidation catalyst, and an electric heating temperature control unit is provided on the outside of the quartz reaction tube. The supply module is connected to the quartz reaction tube.

[0015] Furthermore, the aforementioned The supply module includes an oxygen cylinder, the output end of which is connected to a pressure reducing valve, the output end of which is connected to a gas mass flow controller, the output end of which is connected to a pulse solenoid valve, and the output end of which is connected to a CO quantitative conversion module.

[0016] Furthermore, the conversion product purification module includes a water removal unit and a controlled-temperature cold trap, with a temperature control unit provided on the outside of the controlled-temperature cold trap.

[0017] Compared with the prior art, the present invention has the following technical effects: In this invention, the detection device adopts the core idea of ​​co-capture, selective conversion, and phase purification. Without using gas chromatography separation, it first removes moisture and background carbon dioxide through fractional pretreatment, then uses a CO enrichment module to co-capture carbon monoxide and methane, and removes air matrix such as nitrogen and oxygen to achieve trace component concentration. Subsequently, through precise control of catalytic conditions, only carbon monoxide is quantitatively converted into carbon dioxide, while methane remains inert and does not react. Finally, phase separation is used to retain carbon dioxide and remove methane, ensuring that the carbon source entering the mass spectrometer is unique. This technology enables precise and stable detection of carbon isotopes of CO at concentrations of ppm or even lower during the early low-temperature oxidation stage of coal spontaneous combustion without gas chromatography separation. It overcomes the concentration threshold limitations of traditional gas chromatography techniques and fills the gap in existing technologies for CO carbon isotope detection during the early low-temperature oxidation stage of coal spontaneous combustion. It is suitable for a wide range of applications, including coal mine goaf areas and programmed temperature rise experiments, demonstrating strong specialization. By removing background carbon dioxide, matrix gases, and moisture and controlling CO conversion conditions under chromatographic-free conditions, carbon dioxide, methane, matrix gases, and moisture do not affect the carbon isotope detection of carbon monoxide, ensuring the accuracy and reliability of carbon isotope measurement results. Furthermore, by setting up a control module, it can achieve fully automated operation and quality control throughout the entire process. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the detection device according to an embodiment of the present invention; Figure 2This is a schematic diagram of the working process of the detection device according to an embodiment of the present invention.

[0019] In the diagram: 1. Helium input module, 2. Sample introduction module, 3. Multi-way rotary valve, 4. Moisture removal module, 5. 6. Elimination module, 7. CO enrichment module, 8. CO quantitative conversion module, 9. The modules are: 9. Supply module, 10. Conversion product purification module, and 11. Isotope ratio mass spectrometry analysis module. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention.

[0021] In this article, terms such as "left," "right," "up," "down," "front," and "back" are established based on the positional relationships shown in the attached drawings. Depending on the attached drawings, the corresponding positional relationships may also change. Therefore, they should not be interpreted as an absolute limitation on the scope of protection.

[0022] Please see Figure 1 This embodiment provides a device for detecting trace carbon monoxide carbon isotopes in the early stage of coal spontaneous combustion. This device is suitable for detecting trace carbon monoxide carbon isotopes at the ppm level generated during the low-temperature oxidation stage of early coal spontaneous combustion. It can be adapted to various detection scenarios such as on-site gas sampling in coal mine goaf areas and coal programmed temperature oxidation experiments. Without using gas chromatography separation technology, it can achieve accurate and stable determination of trace carbon monoxide carbon isotopes.

[0023] Specifically, this testing device includes a multi-way rotary valve 3, The supply module 8 and control module are connected to the input terminals of the multi-way rotary valve 3, which are respectively connected to the helium input module 1 and the sample introduction module 2. The output terminals of the multi-way rotary valve 3 are respectively connected to the moisture removal module 4 and the CO enrichment module 6. The output terminal of the moisture removal module 4 is connected to... Eliminate the input of module 5. The output of the elimination module 5 is connected to the input of the CO enrichment module 6, and the output of the CO enrichment module 6 is connected to the CO quantitative conversion module 7. The supply module 8 is connected to the CO quantitative conversion module 7. The output of the CO quantitative conversion module 7 is connected to the conversion product purification module 9, and the output of the conversion product purification module 9 is connected to the isotope ratio mass spectrometry analysis module 10. A multi-way rotary valve 3 is also included. Supply module 8, Helium input module 1, Sample introduction module 2, Moisture removal module 4 The elimination module 5, CO enrichment module 6, CO quantitative conversion module 7, conversion product purification module 9, and isotope ratio mass spectrometry analysis module 10 are all electrically connected to the control module.

[0024] Specifically, the helium input module 1 provides a continuous and adjustable supply of high-purity helium (purity ≥99.999%) as a carrier gas to the entire device, ensuring stable gas flow in the pipeline without additional carbon source contamination. The helium input module 1 includes a gas mass flow controller (MFC) and a flow stabilizing valve. The output of the gas mass flow controller is connected to the input of the flow stabilizing valve, and the output of the flow stabilizing valve is connected to the input of the multi-way rotary valve 3. The carrier gas flow rate is controlled by the MFC within the range of 20–100 mL / min, and can be flexibly adjusted according to the carbon monoxide concentration in the sample and enrichment requirements, ensuring that the residence time of the mixed gas in each module meets the processing requirements.

[0025] Specifically, sample introduction module 2 is used to introduce mixed gas samples generated during the early low-temperature oxidation stage of coal spontaneous combustion. These mixed gas samples can originate from coal mine goaf areas and coal programmed temperature oxidation experiments. The mixed gas samples include water, carbon monoxide (ppm level), carbon dioxide, trace amounts of methane, and air-based matrices such as nitrogen and oxygen. Sample introduction module 2 includes a flow-limiting valve and a gas mass flow controller. The output of the flow-limiting valve is connected to the input of the gas mass flow controller, and the output of the gas mass flow controller is connected to the input of the multi-way rotary valve 3. The sample injection flow rate is controlled at 5–50 mL / min to achieve stable and quantitative sample introduction. Depending on actual needs, a gas buffer tank can also be installed to avoid pressure fluctuations during on-site sampling affecting subsequent processing. The preferred volume of the gas buffer tank is 100–500 mL.

[0026] Specifically, the multi-way rotary valve 3 is resistant to low temperatures and trace corrosion, enabling the switching of pathways between the helium input module 1, the sample introduction module 2, and other modules, ensuring the continuous operation of the entire detection process without manual intervention. In this embodiment, the multi-way rotary valve 3 is a six-way or eight-way electromagnetic rotary valve with a switching response time ≤0.5s.

[0027] Specifically, the moisture removal module 4 removes free and bound water from the mixed gas, preventing moisture from adsorbing onto the surfaces of the adsorbents and catalysts in subsequent modules, thus avoiding impacts on enrichment, conversion efficiency, and isotope detection accuracy. The moisture removal module 4 includes a Nafion membrane and a cryogenic cold trap filled with anhydrous magnesium perchlorate desiccant. The Nafion membrane operates at 25~40℃ with a water removal efficiency ≥95%, while the cryogenic cold trap operates at -20~-40℃. During operation, initial water removal occurs first through the Nafion membrane, followed by deep water removal through the cryogenic cold trap, ultimately ensuring the dew point of the mixed gas is ≤-60℃.

[0028] Specifically, Elimination module 5 is used to quantitatively remove background from the mixed gas before CO enrichment. ,avoid Entering the subsequent isotope ratio mass spectrometry analysis module 10 results in carbon source mixing. Elimination module 5 includes a filled absorption trap, which is filled with... Absorbent material. The absorbent material can be soda lime, modified molecular sieve (13X molecular sieve) or potassium carbonate supported adsorbent. The absorbent material loading amount is 5–20 g. The mixed gas has a space velocity ≤ 500 m / s. Through a filled absorption trap The removal rate is ≥99.9%, and the absorbent has no adsorption effect on CO and methane, so it will not cause the loss of the target components.

[0029] Specifically, the CO enrichment module 6 is used for the efficient capture and enrichment of trace amounts of CO and methane, while simultaneously discharging them. , The CO enrichment module 6 includes a cryogenic cold trap cooled by liquid nitrogen (operating at 77K, i.e., liquid nitrogen temperature). The cold trap is filled with a CO-selective adsorbent, and an electrically heated jacket is provided on its outer side. In this embodiment, the CO-selective adsorbent can be one of activated carbon, carbon molecular sieves (5A / 13X), or metal-organic frameworks (MOFs). The CO-selective adsorbent has a strong physical adsorption effect on CO and methane, while... , The adsorption capacity of the air matrix is ​​extremely weak. During operation, the mixed gas remains in the low-temperature cold trap for 3–5 minutes (i.e., the optimal enrichment time is 3–5 minutes, which can be extended to 5–10 minutes for low-concentration samples), and trace amounts of CO and methane are completely captured by the absorbent. , After the air matrix is ​​purged out of the low-temperature cold trap along with the carrier gas, the low-temperature cold trap is heated by an electric heating mantle (heating rate of 10~20℃ / min). When the temperature reaches 50~100℃, the captured CO and methane are rapidly desorbed and released, forming a high-concentration pulsed gas flow, which enters the subsequent CO quantitative conversion module 7.

[0030] Specifically, the CO quantitative conversion module 7 is used to quantitatively oxidize the enriched CO to CO under preset reaction conditions. This ensures that methane does not undergo oxidation under the same conditions. The CO quantitative conversion module 7 includes a quartz reaction tube, which serves as the catalyst bed. In this embodiment, the inner diameter of the quartz reaction tube is 4–8 mm, and its length is 50–100 mm. The quartz reaction tube is filled with a selective oxidation catalyst, which can be selected from Cu–Mn oxides, etc. , , , Or a combination thereof, with a catalyst particle size of 20-40 mesh and a loading amount of 1-5g. An electric heating temperature control unit is provided on the outside of the quartz reaction tube. The electric heating temperature control unit adopts a programmable temperature rise furnace, which can accurately control the temperature of the catalyst bed within the range of 50-350℃. According to actual needs, the temperature can be further precisely controlled within 150-300℃, with a temperature control accuracy of ±1℃. Supply module 8 is connected to the quartz reaction tube. The supply module 8 is used to provide controllable high-purity oxygen (purity ≥99.99%) to the CO quantitative conversion module 7. The oxygen supply method adopts a combination of pulse oxygen supply and limited oxygen supply, and the molar ratio of oxygen to CO is controlled at 1.0~1.2:1.

[0031] Specifically, by synergistically controlling the reaction temperature, oxygen supply method, and gas residence time in the catalyst bed, carbon monoxide is quantitatively oxidized within a short contact time (conversion efficiency ≥ 99.9%), while methane, due to its high oxidation activation energy, is difficult to oxidize under the same conditions. The conversion rate is controlled below 1% or below the detection limit of the isotope ratio mass spectrometry analysis module 10, thus achieving differentiation between carbon monoxide and methane at the chemical reaction level. Preferably, the residence time of CO in the catalyst bed is controlled to ≤ 2 seconds by controlling the carrier gas flow rate.

[0032] Specifically, The supply module 8 includes an oxygen cylinder containing stored oxygen. A pressure reducing valve is connected to the output of the oxygen cylinder, which in turn is connected to a gas mass flow controller (MFC). The output of the MFC is connected to a pulse solenoid valve, which is then connected to a quartz reaction tube. The MFC controls the oxygen flow rate at 1–10 mL / min, and the pulse solenoid valve provides a pulsed oxygen supply, matching the desorption and release rhythm of CO to prevent excessive oxygen from interfering with subsequent purification and detection.

[0033] Specifically, the conversion product purification module 9 is used to process the CO oxidation products. Deep purification is performed to remove residual moisture, unreacted trace oxygen, and unreacted methane, ensuring that the carbon source entering the isotope ratio mass spectrometry analysis module 10 originates from a single CO. The conversion product purification module 9 includes a water removal unit and a controlled-temperature cold trap. A temperature control unit is located on the outside of the controlled-temperature cold trap to precisely control the temperature within it. The water removal unit uses a Nafion membrane or anhydrous magnesium perchlorate adsorption trap to remove water generated from the CO oxidation reaction and residual moisture from the gas, achieving a water removal efficiency of ≥99.9%.

[0034] Specifically, during operation, the first step is to remove any moisture that may have been carried over or generated during the conversion process using a dehydration unit. Then, the mixed gas enters a temperature-controlled cold trap, where a temperature control unit precisely maintains the cold trap temperature between -80°C and -100°C (this temperature range is within...). Located between the sublimation point and the boiling point of methane, in a low-temperature environment of -80℃ to -100℃, the carbon dioxide converted from carbon monoxide is rapidly solidified and retained, while the chemically stable and extremely low-boiling-point methane, along with trace amounts of oxygen and other non-condensable impurities, remain in a gaseous state and are discharged through the exhaust port with the carrier gas flow. After the impurities are completely removed, the temperature control unit rapidly heats the cold trap to 20~50℃, solidifying the... Rapid sublimation to form high purity The pulsed gas flow enters the isotope ratio mass spectrometry analysis module 10.

[0035] Specifically, the isotope ratio mass spectrometry analysis module 10 is used to determine the purified... The carbon isotope composition was determined to obtain the carbon isotope ratio of trace CO in the early stages of coal spontaneous combustion. 13 C). In this embodiment, the isotope ratio mass spectrometry analysis module 10 uses an isotope ratio mass spectrometer (IRMS) with an adapted gas sample introduction interface to obtain carbon monoxide by measuring the ion abundance ratio at m / z=45 and m / z=44. 13 C value, precise measurement 13 C ≤ ±0.1‰, repeatability RSD ≤ 1%. Achievable. The carbon isotope can be determined online and rapidly. The detection results of the mass spectrometer are recorded and analyzed in real time through the control module, and the carbon isotope composition data of CO are directly output.

[0036] Specifically, the control module is used to achieve fully automated operation of the entire process. It can achieve stable regulation of flow and pressure throughout the process, monitor and adjust the carrier gas flow, oxygen supply, and temperature of each module in real time, and has data recording and alarm functions. It can also use carbon dioxide standard gas with known carbon isotope ratios to complete calibration and data correction.

[0037] Please see Figure 2 The core of this detection device is to achieve carbon isotope detection of trace carbon monoxide in mixed gases through a process route of graded treatment, directional conversion, and purification, while avoiding interference from background carbon dioxide, methane, and air matrix. The entire process uses a multi-way rotary valve 3 to switch between pathways. A single detection cycle is 15–30 minutes, adjustable according to sample concentration. The workflow is as follows: Device preheating and carrier gas purging: Turn on helium input module 1, set the carrier gas flow rate to 50 mL / min, and purge the entire pipeline and each module of the device for 5 to 10 minutes; at the same time, start the electric heating temperature control unit of CO quantitative conversion module 7 to raise the temperature of the quartz reaction tube to 200°C, and start the temperature control unit of conversion product purification module 9 to precool the controlled temperature cold trap to -90°C to complete the device preheating.

[0038] Sample introduction and moisture removal: Switch to the sample channel via the multi-way rotary valve 3 and start the sample introduction module 2 to introduce the mixed gas of the early low-temperature oxidation stage of coal spontaneous combustion into the device at a flow rate of 20 mL / min. After passing through the multi-way rotary valve 3, the mixed gas first enters the moisture removal module 4. After being dehydrated by the combination of Nafion membrane and low-temperature cold trap, the dew point drops to below -60℃.

[0039] background Removal: The mixed gas after water removal enters Elimination module 5 quantitatively removes background by using soda lime adsorbent within a filled absorption trap. , Removal efficiency ≥99.9%, with no loss of CO, methane and air matrix.

[0040] CO Low-Temperature Enrichment and Matrix Separation: Removal The mixed gas enters CO enrichment module 6 and remains in a cryogenic cold trap at 77K for 4 minutes, where trace amounts of CO and methane are adsorbed and captured by carbon molecular sieves. , After the air matrix is ​​purged and discharged with the carrier gas, the low-temperature cold trap is heated to 80°C to desorb and release the captured CO and methane gases.

[0041] CO quantitative oxidation conversion: Subsequently, CO and methane gas enter CO quantitative conversion module 7, through... The supply module 8 pulses high-purity oxygen to the CO quantitative conversion module 7. With a molar ratio of 1.1:1 to CO, CO was quantitatively oxidized to [missing value] in the presence of a Cu–Mn oxide catalyst (200 °C). The conversion efficiency is ≥99.9%. Under these conditions, methane undergoes no oxidation reaction and enters the subsequent modules along with the conversion products.

[0042] Conversion product purification and methane removal: The conversion product enters the conversion product purification module 9, where it first passes through a dehydration unit to remove any moisture that may have been carried or generated during the conversion process. Then, it enters a -90°C controlled-temperature cold trap, where carbon dioxide is rapidly solidified and retained, while impurities such as methane and trace amounts of oxygen are purged out with the carrier gas. After impurity removal, the controlled-temperature cold trap is heated to 30°C to release high-purity methane. Pulsed airflow.

[0043] Carbon isotope detection and data output: high purity A pulsed gas flow enters the isotope ratio mass spectrometry analysis module 10, where the isotope ratio mass spectrometer determines its carbon isotope composition and records the data in real time. 13 C data (i.e., the carbon isotope ratio of trace CO in the early stage of coal spontaneous combustion) is transmitted to the control module.

[0044] Device reset: After a single test is completed, switch back to the carrier gas path through the multi-way rotary valve 3, continue to purge each module with helium for 5 minutes to remove residual gas in the pipeline, and complete the device reset. The next sample test can then be performed.

[0045] Specifically, in this invention, the detection device adopts the core idea of ​​co-capture, selective conversion, and phase purification. Without using gas chromatography separation, water and background carbon dioxide are first removed through fractional pretreatment. Then, carbon monoxide and methane are co-captured using CO enrichment module 6, and nitrogen, oxygen and other air matrix are removed to achieve trace component concentration. Subsequently, through precise control of catalytic conditions, only carbon monoxide is quantitatively converted into carbon dioxide, while methane remains inert and does not react. Finally, carbon dioxide is retained and methane is discharged through phase separation to ensure that the carbon source entering the mass spectrometer is unique. This technology enables precise and stable detection of carbon isotopes of CO at concentrations of ppm or even lower during the early low-temperature oxidation stage of coal spontaneous combustion without gas chromatography separation. It overcomes the concentration threshold limitations of traditional gas chromatography techniques and fills the gap in existing technologies for CO carbon isotope detection during the early low-temperature oxidation stage of coal spontaneous combustion. It is suitable for a wide range of applications, including coal mine goaf areas and programmed temperature rise experiments, demonstrating strong specialization. By removing background carbon dioxide, matrix gases, and moisture and controlling CO conversion conditions under chromatographic-free conditions, carbon dioxide, methane, matrix gases, and moisture do not affect the carbon isotope detection of carbon monoxide, ensuring the accuracy and reliability of carbon isotope measurement results. Furthermore, by setting up a control module, it can achieve fully automated operation and quality control throughout the entire process.

[0046] The following two simulated tests will be used as examples to describe the testing process of this device.

[0047] Trace CO carbon isotope simulation detection in coal temperature-programmed oxidation experiment Detection scenario: Simulated mixed gas detection for the early low-temperature oxidation stage (80 ℃) of bituminous coal spontaneous combustion. The simulated sample contains typical components of early coal spontaneous combustion: CO concentration 5 ppm. Concentration 200 ppm, methane concentration 0.5 ppm, / Air matrix, relative humidity 60%.

[0048] Device operating parameters: sample injection flow rate 20 mL / min, helium carrier gas flow rate 50 mL / min, CO enrichment time 4 min; CO quantitative conversion module 7 uses Cu–Mn oxide catalyst, reaction temperature 200 ℃. The molar ratio with CO is 1.1:1; the cold trap temperature of the conversion product purification module 9 is -90 ℃; the isotope ratio mass spectrometry analysis module 10 adopts the conventional detection mode.

[0049] Expected performance: Based on the module design and parameter matching of this device, it is expected to achieve complete enrichment of trace CO at 5 ppm, and directional oxidation of CO to... The efficiency is ≥99.9%; the conversion rate of methane under the controlled reaction conditions is ≤1% (below the detection limit of the isotope measurement system); after purification, the carbon source entering the isotope ratio mass spectrometry analysis module 10 is a single CO, which is expected to achieve accurate detection of CO carbon isotopes at this concentration, with a relative standard deviation of ≤±0.1‰.

[0050] On-site trace CO carbon isotope simulation detection in coal mine goaf areas Detection scenario: On-site mixed gas detection in shallow, closely spaced, multi-coal seam goaf areas with potential spontaneous combustion hazards, simulating complex on-site components: CO concentration 3 ppm, Concentration 350 ppm, methane concentration 1.2 ppm, contains trace amounts of hydrogen sulfide impurities, relative humidity 75%.

[0051] Operating parameters: To address the low concentration and high impurity characteristics at the site, the CO enrichment time was adjusted to 6 min, sample injection flow rate to 15 mL / min, and helium carrier gas flow rate to 40 mL / min; the CO quantitative conversion module 7 used a CuO / CeO2 composite catalyst, and the reaction temperature was 250 ℃. The molar ratio with CO is 1.2:1; the cold trap temperature of the conversion product purification module 9 is -85 ℃; the isotope ratio mass spectrometry analysis module 10 is in high-precision detection mode.

[0052] Expected performance: Based on the anti-interference design and parameter adaptation of this device, it is expected to achieve an enrichment efficiency of ≥99.9% for ultra-low concentration CO of 3 ppm and a CO conversion efficiency of ≥99.9%; methane conversion rate ≤1%; impurities such as hydrogen sulfide can be completely removed by the conversion product purification module 9; it is expected to meet the detection requirements of trace CO carbon isotopes in the complex environment of coal mine sites, with a detection accuracy of ≤±0.1‰.

[0053] The above embodiments merely illustrate the basic principles and characteristics of the present invention, but are not limited to the above implementation schemes. It should be understood that those skilled in the art can make various changes and modifications to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A device for detecting trace carbon monoxide carbon isotopes in the early stages of spontaneous combustion of coal, characterized in that, Including multi-way rotary valve (3), The supply module (8) and control module are connected to the input end of the multi-way rotary valve (3), which is connected to the helium input module (1) and the sample introduction module (2). The output end of the multi-way rotary valve (3) is connected to the moisture removal module (4) and the CO enrichment module (6). The output end of the moisture removal module (4) is connected to the control module. Elimination module (5), the The output of the elimination module (5) is connected to the input of the CO enrichment module (6), and the output of the CO enrichment module (6) is connected to the CO quantitative conversion module (7). The supply module (8) is connected to the CO quantitative conversion module (7), the output end of the CO quantitative conversion module (7) is connected to the conversion product purification module (9), the output end of the conversion product purification module (9) is connected to the isotope ratio mass spectrometry analysis module (10), and the multi-way rotary valve (3) is connected to the CO quantitative conversion module (7). Supply module (8), helium input module (1), sample introduction module (2), moisture removal module (4) The elimination module (5), CO enrichment module (6), CO quantitative conversion module (7), conversion product purification module (9) and isotope ratio mass spectrometry analysis module (10) are all electrically connected to the control module; The CO enrichment module (6) includes a low-temperature cold trap filled with a CO selective adsorbent, and an electric heating jacket is provided on the outside of the low-temperature cold trap. The CO quantitative conversion module (7) is used to quantitatively oxidize the enriched CO into To ensure that methane does not undergo oxidation under the same conditions, the CO quantitative conversion module (7) includes a quartz reaction tube, which is filled with a selective oxidation catalyst. An electric heating temperature control unit is provided on the outside of the quartz reaction tube. The supply module (8) is connected to the quartz reaction tube; The conversion product purification module (9) includes a water removal unit and a controlled-temperature cold trap. A temperature control unit is provided on the outside of the controlled-temperature cold trap, and the temperature control unit precisely controls the temperature of the controlled-temperature cold trap between -80°C and -100°C. The device does not contain a gas chromatography separation unit.

2. The carbon isotope detection device for trace carbon monoxide in the early stage of spontaneous combustion of coal according to claim 1, characterized in that, The helium input module (1) includes a gas mass flow controller and a flow regulator. The output end of the gas mass flow controller is connected to the input end of the flow regulator, and the output end of the flow regulator is connected to the input end of the multi-way rotary valve (3).

3. The carbon isotope detection device for trace carbon monoxide in the early stage of spontaneous combustion of coal according to claim 1, characterized in that, The sample introduction module (2) includes a flow limiting valve and a gas mass flow controller. The output end of the flow limiting valve is connected to the input end of the gas mass flow controller, and the output end of the gas mass flow controller is connected to the input end of the multi-way rotary valve (3).

4. The carbon isotope detection device for trace carbon monoxide in the early stage of spontaneous combustion of coal according to claim 1, characterized in that, The moisture removal module (4) includes a Nafion membrane dehydration unit and a low-temperature cold trap, which is filled with anhydrous magnesium perchlorate desiccant.

5. The carbon isotope detection device for trace carbon monoxide in the early stage of spontaneous combustion of coal according to claim 1, characterized in that, The The elimination module (5) includes a filled absorption trap, wherein the filled absorption trap is filled with Absorbent material.

6. The carbon isotope detection device for trace carbon monoxide in the early stage of spontaneous combustion of coal according to claim 1, characterized in that, The CO selective adsorbent is one of activated carbon, carbon molecular sieve, or metal-organic framework materials.

7. The carbon isotope detection device for trace carbon monoxide in the early stage of spontaneous combustion of coal according to claim 1, characterized in that, The The supply module (8) includes an oxygen cylinder, the output end of which is connected to a pressure reducing valve, the output end of which is connected to a gas mass flow controller, the output end of which is connected to a pulse solenoid valve, and the output end of which is connected to a CO quantitative conversion module (7).

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