Method for measuring methane gas concentration and device for detecting methane concentration

Abstract

The invention relates to the technical field of gas measurement, in particular to a method for measuring the concentration of methane gas and a device for detecting the concentration of methane. The method for measuring the concentration of the methane gas comprises the following steps: acquiring the methane gas to be measured; methane gas is conveyed into the solid fuel cell to be circularly combusted; calculating an oxygen consumption amount in each cycle combustion in the solid fuel cell; and when the oxygen consumption is lower than a set threshold value, circulating combustion is stopped, and the concentration of the methane gas is calculated. According to the method, the consumption of oxygen is detected in real time in the circulating combustion process through an electrochemical measurement method based on the Nernst principle, and sufficient combustion of methane gas is ensured. Therefore, the method provided by the invention can effectively solve the problem that the methane concentration measurement is inaccurate due to the fact that the methane gas is directly conveyed to the solid fuel cell for combustion and cannot be completely combusted in the existing scheme, so that the methane gas concentration measurement with higher precision is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of gas measurement, in particular to a method for measuring methane gas concentration and a device for detecting methane concentration. Background Art

[0002] Currently, the detection of methane in human breath can assist diagnosis, so the concentration of methane gas needs to be accurately measured. However, in existing detection schemes, when solid fuel cells are used for detection, methane gas of the concentration to be measured is usually directly transported to the solid fuel cell for combustion. The problem with the current scheme is that it fails to ensure that methane gas is completely burned in the solid fuel cell, thus affecting the accuracy of methane concentration measurement. Summary of the invention

[0003] An object of the invention of the present application is to provide a method for measuring methane gas concentration so as to enable methane to be completely burned in a solid fuel cell, thereby improving the accuracy of methane gas concentration measurement.

[0004] According to an embodiment of the present application, a first aspect provides a method for measuring methane gas concentration, wherein the method for measuring methane gas concentration includes:

[0005] Obtaining methane gas to be tested;

[0006] transporting the methane gas to a solid fuel cell for cyclic combustion;

[0007] Calculating oxygen consumption during each combustion cycle in the solid fuel cell;

[0008] When the oxygen consumption is lower than a set threshold, the cyclic combustion is stopped and the concentration of the methane gas is calculated.

[0009] In one embodiment, obtaining the change in oxygen after each cyclic combustion in the solid fuel cell comprises:

[0010] The electromotive force output by the solid fuel cell when the methane gas is burned in each cycle is obtained to determine the oxygen consumption in each cycle.

[0011] In one embodiment, obtaining the oxygen content of the methane gas flowing through each cycle of combustion, obtaining the electromotive force output by the solid fuel cell during each cycle of combustion of the methane gas, and obtaining the oxygen consumption in each cycle includes:

[0012] The oxygen consumption is calculated according to the following expression:

[0013]

[0014] Among them, C x (t) represents the change of oxygen concentration over time during combustion, C0 represents the initial concentration of oxygen on the reference electrode side, E k (t) is the electromotive force output by the solid fuel cell in the kth cycle, and a is a proportional factor determined by the system constant R, T0, Faraday constant F and the number of electron transfers n.

[0015] In one embodiment, the sampled discrete electromotive force of the solid fuel cell is obtained, and the change value of the discrete electromotive force is calculated by a numerical integration method, and the oxygen consumption in each cycle is calculated according to the change value of the discrete electromotive force:

[0016]

[0017] Among them, the ΔS k is the change value of discrete electromotive force, C0 is the oxygen concentration;

[0018] The cumulative oxygen consumption of N cycles is:

[0019]

[0020] Where ΔQ represents the cumulative oxygen consumption of N cycles, and M is the number of cycles.

[0021] In one embodiment, when the oxygen consumption is lower than a set threshold, stopping the cyclic combustion and calculating the concentration of the methane gas includes:

[0022] The concentration of the methane gas to be measured is calculated according to the volume and pressure of the methane gas to be measured and the stoichiometric ratio of the methane gas to oxygen.

[0023] In one embodiment, the step of calculating the concentration of the methane gas to be measured according to the volume and pressure of the methane gas to be measured and the stoichiometric ratio of the methane gas to oxygen comprises:

[0024] The concentration of the methane gas to be measured is:

[0025]

[0026] Wherein, C is the concentration of the methane gas to be measured (μL / L); V0 is the volume of the methane gas to be measured (mL); L is the flow rate of the carrier gas (mL / min); and N is the stoichiometric ratio of the methane gas to be measured to oxygen.

[0027] According to an embodiment of the present application, a second aspect provides a device for detecting methane concentration, wherein the methane concentration detection device uses the methane measurement method, and the methane concentration detection device includes:

[0028] A collection module, used to obtain the methane gas to be tested;

[0029] A first separation module, used for separating the moisture in the methane gas to be tested;

[0030] A sampling module, used for quantitative sampling of the methane gas separated by the first separation module;

[0031] A second separation module is used to separate the quantitatively sampled methane gas;

[0032] A solid fuel cell module, used for burning the separated methane gas to obtain the concentration of the methane gas;

[0033] A gas circulation module is arranged between the second separation module and the solid fuel cell module, and is used to control the methane gas in the second separation module to circulate into the solid fuel cell.

[0034] In one embodiment, the first separation module includes a first-stage separation module and a second-stage separation module.

[0035] In one embodiment, the sampling module includes: a vacuum diaphragm pump and a gas quantitative tube.

[0036] In one embodiment, the gas circulation module includes a delay column and a one-way valve.

[0037] The method for measuring methane gas concentration in the present application, after obtaining the methane gas to be measured, transports the methane gas to be measured to a solid fuel cell for cyclic combustion, thereby ensuring that the methane gas is fully burned in the solid fuel cell, thereby further improving the accuracy of the calculated solid fuel cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a flow chart of a method for measuring methane gas concentration in one embodiment of the present invention;

[0039] Figure 2 Schematic diagram of a module of a device for detecting methane concentration in one embodiment of the present invention.

[0040] Description of the accompanying drawings:

[0041] 100, sampling module; 200, first separation module; 210, first stage separation module;

[0042] 220, second stage separation module; 300, sampling module; 400, second separation module;

[0043] 500, solid fuel module; 610, delay column; 620, one-way valve; DETAILED DESCRIPTION

[0044] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0045] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0046] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0047] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0048] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0049] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0050] As described in the background, currently, the detection of methane in human respiratory gas can assist diagnosis, so it is necessary to accurately measure the concentration of methane gas. However, in the existing detection scheme, when a solid fuel cell is used for detection, the methane gas of the concentration to be measured is usually directly transported to the solid fuel cell for combustion. The problem with the current scheme is that it fails to ensure that the methane gas is completely burned in the solid fuel cell, thereby affecting the accuracy of the methane concentration measurement. In order to better solve this problem, the researchers in this application propose a method for measuring the concentration of methane gas. In the method for measuring the concentration of methane gas, methane is allowed to circulate and burn in the solid fuel cell, so that the methane gas is completely burned in the solid fuel cell, thereby improving the accuracy of the methane gas concentration measurement.

[0051] See also Figure 1 , Figure 1 The flowchart of the method for measuring the methane gas concentration in one embodiment of the present invention is shown. The method for measuring the methane gas concentration includes:

[0052] S110: Obtaining methane gas to be tested;

[0053] S120: transporting methane gas to a solid fuel cell for cyclic combustion;

[0054] S130: Calculating oxygen consumption during each combustion cycle in the solid fuel cell;

[0055] S140: When the oxygen consumption is lower than the set threshold, the cyclic combustion is stopped and the concentration of methane gas is calculated.

[0056] In this embodiment, first, the methane gas to be tested is obtained through step S110. Then, the methane gas is transported to the solid fuel cell for cyclic combustion through step S120. In the process of burning methane in the solid fuel cell, the combustion reaction causes a change in electromotive force. Using the Nernst principle, the relationship between the output potential of the solid fuel cell and the partial pressure and concentration of oxygen can be used to detect the oxygen consumption, thereby realizing the monitoring of the methane combustion process. Among them, the solid fuel cell can use oxygen ion conductive materials (such as yttrium stabilized zirconia, YSZ) as the electrolyte. According to the Nernst equation, the output potential E(t) of the fuel cell can be expressed by the following formula:

[0057]

[0058] Where E(t) is the output potential of the fuel cell; R is the gas constant, which is 8.134 J / (mol·K); T0 is the operating temperature of the solid fuel cell, which is usually 973.15 K; n is the number of electrons transferred when each mole of fuel consumes oxygen, which is 4 in this application; and F is the Faraday constant, which is 96485.33289 C / mol. P0 and P x (t) represents the oxygen partial pressure on the reference electrode side and the measuring electrode side, respectively, and the two are related to the oxygen volume concentration C0 and C x (t). Based on this relationship, the oxygen concentration C x (t) can be further calculated by the following formula:

[0059]

[0060] in, C0 is the oxygen concentration on the reference electrode side, usually 209600 μL / L. Through the above formula relationship, the change of oxygen concentration during the combustion process can be measured in real time, thereby realizing effective monitoring of the combustion of methane gas.

[0061] In step S130, by calculating the amount of oxygen consumed in each cycle of combustion in the solid fuel cell, the degree of methane combustion can be accurately reflected. Combined with the output potential change in step S120, it can be determined whether the methane combustion has reached a sufficient state based on the amount of oxygen consumed in each cycle of the solid fuel cell.

[0062] In step S140, when it is detected that the oxygen consumption is lower than the preset threshold, it indicates that the methane gas is close to complete combustion. At this time, the cyclic combustion is stopped and the methane gas concentration is calculated. Since the oxygen consumption and the methane concentration have a direct quantitative relationship, the methane gas concentration value can be accurately calculated by the above formula. In step S140, by setting the threshold of oxygen consumption, the complete combustion of methane is effectively ensured, thereby improving the accuracy of the measurement.

[0063] This embodiment uses an electrochemical measurement method based on the Nernst principle to detect the oxygen consumption in real time during the cyclic combustion process, thereby ensuring the full combustion of methane gas. Therefore, the method proposed in this embodiment can effectively solve the problem of inaccurate methane concentration measurement caused by the failure to ensure complete combustion of methane gas due to direct delivery of methane gas to solid fuel cells for combustion in the existing solution, thereby achieving higher-precision methane gas concentration measurement.

[0064] In one embodiment, obtaining the change in oxygen after each cycle combustion in the solid fuel cell includes:

[0065] The electromotive force output by the solid fuel cell during the combustion of methane gas in each cycle is obtained to determine the oxygen consumption in each cycle.

[0066] In this embodiment, since there is a clear functional relationship between the output electromotive force of the solid fuel cell and the oxygen partial pressure, by obtaining the electromotive force of the solid fuel cell during each cycle of methane gas combustion, the oxygen consumption during the combustion process can be monitored in real time. Based on the electrochemical principle of the Nernst equation, the change in electromotive force is directly related to the change in oxygen partial pressure. Therefore, by monitoring the change in electromotive force in real time, the oxygen consumption can be accurately determined, thereby reflecting the sufficiency and stability of the combustion process. Because the oxygen consumption directly affects the complete combustion process of methane, real-time monitoring of oxygen consumption is of great significance for ensuring the sufficiency of the combustion process and the accuracy of measurement.

[0067] In each combustion cycle, by calculating the oxygen consumption, on the one hand, it is possible to determine whether methane is completely consumed within the cycle; on the other hand, by integrating the oxygen consumption within each cycle, the total oxygen consumption in the entire cycle can be obtained, so as to more accurately reflect the overall situation of the methane combustion process.

[0068] In one implementation, obtaining the oxygen content of the methane gas flowing through each cycle of combustion, obtaining the electromotive force output by the solid fuel cell during each cycle of combustion of the methane gas, and obtaining the oxygen consumption in each cycle include:

[0069] The oxygen consumption was calculated according to the following expression:

[0070]

[0071] Among them, C x (t) represents the change of oxygen concentration over time during combustion, C0 represents the initial concentration of oxygen on the reference electrode side, E k(t) is the electromotive force output by the solid fuel cell in the kth cycle, and a is a proportional factor determined by the system constant R, T0, Faraday constant F and the number of electron transfers n.

[0072] In this embodiment, by obtaining the electromotive force output by the solid fuel cell during each cycle of methane gas combustion and calculating the oxygen content flowing through the solid fuel cell, the oxygen consumption can be further accurately measured. Since there is a clear functional relationship between the electromotive force output by the solid fuel cell and the oxygen partial pressure according to the electrochemical principle of the Nernst equation, the oxygen consumption can be quantified by the change in the electromotive force.

[0073] Furthermore, according to the integral formula in expression (1):

[0074]

[0075] Among them, Q k represents the total oxygen consumption during the kth cycle combustion, P is the partial pressure of oxygen, L is the flow rate of the carrier gas, R is the gas constant, T0 is the operating temperature of the solid fuel cell, C x (t) represents the change of oxygen concentration over time during combustion, C0 represents the initial concentration of oxygen on the reference electrode side, E k (t) is the electromotive force output by the solid fuel cell in the kth cycle, and a is a proportional factor determined by the system constant R, T0, Faraday constant F and the number of electron transfers n.

[0076] The realization process of expression (1) is as follows: by real-time monitoring of the electromotive force E output by the solid fuel cell during each cycle of combustion k (t), and combined with the Nernst equation, the change in electromotive force is converted into the oxygen concentration C at the corresponding time point x (t). Then, by adjusting the oxygen concentration C x (t) is integrated over the time interval [t1, t2] to calculate the total oxygen consumption during this time period. The modified expression on the right side of the formula utilizes the exponential relationship between oxygen concentration and electromotive force, simplifying the calculation process of oxygen consumption.

[0077] Through the above calculation method, accurate calculation of oxygen consumption in each combustion cycle can be achieved, thereby ensuring the accuracy and reliability of the methane concentration measurement obtained by calculation.

[0078] In one embodiment, the sampled discrete electromotive force of the solid fuel cell is obtained, and the change value of the discrete electromotive force is calculated by a numerical integration method, and the oxygen consumption in each cycle is calculated according to the change value of the discrete electromotive force:

[0079]

[0080] Among them, ΔS k is the change value of discrete electromotive force, C0 is the oxygen concentration;

[0081] The cumulative oxygen consumption of N cycles is:

[0082]

[0083] Where ΔQ represents the cumulative oxygen consumption of N cycles, and M is the number of cycles.

[0084] In this embodiment, the oxygen consumption in each combustion cycle is accurately determined by obtaining discrete electromotive force sampling data of the solid fuel cell and calculating the change value of the discrete electromotive force using the numerical integration method. Since the electromotive force signal generated by the solid fuel cell in actual operation is a continuous change curve, and the sampling device can only obtain discrete data points, it is necessary to use discrete electromotive force data for calculation during the data processing process. By processing these discrete sampling points, the errors that may be caused by data discontinuity during the signal sampling process are overcome, ensuring the accurate calculation of oxygen consumption.

[0085] Specifically, according to expression (2):

[0086]

[0087] Among them, ΔS k represents the discrete electromotive force change value of the kth combustion cycle, C0 is the initial oxygen concentration, t1 and t2 are the sampling start and end time points, Δt k is the sampling time interval, E k (t) is the electromotive force of the kth cycle, and a is the proportional factor related to the system parameters. Through the trapezoidal integration method, the formula replaces the continuous integral with the discrete integral, which is used to quantitatively calculate the oxygen consumption in each cycle, making full use of the discrete sampling data while ensuring the accuracy of the calculation results.

[0088] Furthermore, the cumulative calculation of oxygen consumption over multiple combustion cycles is achieved through expression (3):

[0089]

[0090] Where ΔQ is the cumulative oxygen consumption of N cycles, M is the number of cycles, P is the oxygen partial pressure, L is the carrier gas flow rate, R is the gas constant, and T0 is the operating temperature of the solid fuel cell. The discrete electromotive force change ΔS of multiple cycles is calculated by formula (3): k The oxygen consumption in the whole cycle can be accurately calculated by cumulative calculation, and finally the concentration of methane gas can be calculated by the oxygen consumption.

[0091] In one embodiment, when the oxygen consumption is lower than a set threshold, the cyclic combustion is stopped, and the concentration of methane gas is calculated, including:

[0092] The concentration of the methane gas to be measured is calculated according to the volume and pressure of the methane gas to be measured and the stoichiometric ratio of the methane gas to oxygen.

[0093] In this embodiment, the concentration of the methane gas to be measured can be calculated by obtaining the oxygen consumption of the methane gas to be measured during the entire cycle and combining the volume, pressure and stoichiometric ratio of the methane gas to oxygen. Specifically, the combustion reaction of methane and oxygen follows the following chemical equation:

[0094] CH4+2O2→CO2+2H2O

[0095] This equation shows that under complete combustion conditions, one mole of methane is burned for every two moles of oxygen consumed. Therefore, by measuring the oxygen consumption, the number of moles of methane gas involved in the combustion can be indirectly derived. At the same time, combined with the volume and pressure of the methane gas to be measured, the concentration of methane gas can be further determined using the ideal gas state equation PV=nRT, where P is the gas pressure, V is the gas volume, n is the number of moles, R is the gas constant, and T is the temperature.

[0096] In the specific calculation process, the relationship between oxygen consumption and methane gas concentration is based on the stoichiometric ratio of the combustion reaction. By real-time monitoring of oxygen consumption, combined with the initial volume and pressure of methane gas, the oxygen consumption can be directly related to the number of moles of methane, and then the concentration of methane gas can be inferred based on the gas state equation.

[0097] In one embodiment, calculating the concentration of the methane gas to be measured according to the volume and pressure of the methane gas to be measured and the stoichiometric ratio of the methane gas to oxygen includes:

[0098] The concentration of methane gas to be measured is:

[0099]

[0100] Wherein, C is the concentration of the methane gas to be measured (μL / L); V0 is the volume of the methane gas to be measured (mL); L is the flow rate of the carrier gas (mL / min); and N is the stoichiometric ratio of the methane gas to be measured to oxygen.

[0101] In this embodiment, the calculation method of the methane gas concentration to be measured is obtained by combining the stoichiometric ratio of methane gas to oxygen and the oxygen consumption. According to the combustion reaction equation of methane and oxygen, it can be obtained that under complete combustion conditions, every two moles of oxygen consumed corresponds to the combustion of one mole of methane. Combined with this stoichiometric relationship, according to formula (4):

[0102]

[0103] Where C is the concentration of the methane gas to be measured, ΔQ represents the cumulative consumption of oxygen, V0 is the volume of the methane gas to be measured, L is the carrier gas flow rate, N is the stoichiometric ratio of methane to oxygen, and ΔS k is the discrete electromotive force change value of the kth cycle, and M is the number of combustion cycles.

[0104] The specific calculation process of formula (4) is as follows: First, the methane consumption is determined by the measured cumulative oxygen consumption and the stoichiometric ratio N of the methane gas. Then, based on the volume V0, pressure P and other known parameters of the methane gas to be measured, the oxygen consumption is converted into the concentration of the methane gas according to the formula. The integral deformation form on the right side of the formula further expresses the oxygen consumption as the cumulative amount of discrete electromotive force changes, and the quantification of oxygen consumption is achieved with the help of discrete electromotive force data of multiple combustion cycles.

[0105] Through this method, on the basis of clarifying the relationship between oxygen consumption and methane concentration, combined with the stoichiometric relationship between methane and oxygen and the volume parameters of the gas to be measured, the methane concentration can be accurately calculated.

[0106] The present application also proposes a device for detecting methane concentration, wherein the methane concentration detection device uses the above-mentioned methane measurement method, which can be found in Figure 2 As shown, the methane concentration detection device includes: a collection module, a first separation module 200, a sampling module 300, a second separation module 400, a solid fuel cell module and a gas circulation module. Among them, the collection module is used to obtain the methane gas to be tested; the first separation module 200 is used to separate the moisture of the methane gas to be tested; the sampling module 300 is used to quantitatively sample the methane gas separated by the first separation module 200; the second separation module 400 is used to separate the quantitatively sampled methane gas; the solid fuel cell module is used to burn the separated methane gas to obtain the concentration of the methane gas; the gas circulation module is arranged between the second separation module 400 and the solid fuel cell module, and the gas circulation module is used to control the circulation of the methane gas in the second separation module 400 into the solid fuel cell.

[0107] In this embodiment, the methane gas to be measured is first obtained through the acquisition module, and the acquisition module may include a gas sampling bag, a flow tube, and a sealing valve, and its main function is to collect human respiratory gas. Then, the first separation module 200 separates the moisture in the methane gas to avoid the influence of moisture on the subsequent combustion process and measurement accuracy. The methane gas after the separation of moisture is quantitatively sampled by the sampling module 300 to ensure that the methane gas entering the solid fuel cell has a stable volume and concentration, thereby enhancing the repeatability and accuracy of the measurement. The methane gas after quantitative sampling is further processed in the second separation module 400 to ensure the gas purity during the combustion process. The second separation module 400 may include a chromatographic separation module. Subsequently, the solid fuel cell module burns the separated methane gas and realizes the accurate detection of the methane concentration through the consumption of oxygen. The gas circulation module establishes a circulation channel between the second separation module 400 and the solid fuel cell module to ensure that the methane gas can continue to circulate in the solid fuel cell until it reaches a state of complete combustion.

[0108] The device in this embodiment effectively completes the detection of methane gas concentration through the functional coordination of each module, solving the measurement error problem caused by incomplete combustion of methane in the prior art. The combined design of each module ensures that the processing and circulation process of methane gas before and after combustion is more reasonable, further improving the accuracy and stability of concentration measurement.

[0109] In one embodiment, see Figure 2 As described above, the first separation module 200 includes a first-stage separation module 210 and a second-stage separation module 220 .

[0110] In this embodiment, by designing the first separation module 200 to include a first-stage separation module 210 and a second-stage separation module 220, the effect of removing moisture from the sample gas can be effectively improved. The first-stage separation module 210 uses adsorption materials such as molecular sieves or silica gel to preliminarily remove moisture from the gas by physical adsorption. The second-stage separation module 220 uses a condenser to further remove the remaining water vapor by lowering the gas temperature. In this embodiment, the dual separation design of the first-stage separation module 210 and the second-stage separation module 220 can significantly reduce the moisture content in the sample gas, so that the water vapor in the human breath is basically completely removed, thereby further improving the accuracy and stability of methane concentration detection.

[0111] In one embodiment, the sampling module 300 includes: a vacuum diaphragm pump and a gas quantitative tube.

[0112] In the present embodiment, the sampling module 300 includes a vacuum diaphragm pump and a gas quantitative tube, which are used to achieve accurate quantitative sampling of the sample gas. The vacuum diaphragm pump is used to evacuate the gas quantitative tube to ensure that there is no residual air in the gas quantitative tube, so as to eliminate the interference of external air on the sample gas measurement. A solenoid valve is arranged between the vacuum diaphragm pump and the gas quantitative tube, and the separation of the quantitative tube and the external gas is achieved by controlling the opening and closing of the solenoid valve. During the sampling process, the gas quantitative tube is first evacuated, and then the sample gas is introduced using the pressure difference principle to ensure that the sample gas enters the gas quantitative tube with a fixed volume. In order to further ensure the sampling accuracy, the vacuum process is repeated three times to minimize the influence of residual air in the quantitative tube on the sampling process.

[0113] In one embodiment, see Figure 2 As shown, the gas circulation module includes a delay column 610 and a one-way valve 620 .

[0114] In this embodiment, the combination of the delay column 610 and the one-way valve 620 in the gas circulation module can effectively ensure the full combustion of methane gas in the solid fuel cell. The delay column 610 prolongs the gas residence time in the gas circulation path and reduces the gas flow rate, so that the methane gas obtains a uniform and stable flow state before entering the solid fuel cell, thereby ensuring that the gas supply during the combustion process is continuous and balanced, and avoiding incomplete combustion caused by unstable air flow. At the same time, the one-way valve 620 is used to prevent external air or unburned gas from entering the inlet of the fuel cell in reverse, thereby maintaining the stability of the combustion environment. Through the synergistic effect of the delay column 610 and the one-way valve 620, the methane gas can be continuously and stably circulated in the solid fuel cell to achieve a complete combustion state. The technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the various technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0115] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for measuring methane gas concentration, characterized in that: The method of measuring the methane gas concentration comprises: Obtaining methane gas to be tested; transporting the methane gas to a solid fuel cell for cyclic combustion; Calculating oxygen consumption during each combustion cycle in the solid fuel cell; When the oxygen consumption is lower than a set threshold, the cyclic combustion is stopped and the concentration of the methane gas is calculated.

2. The methane measurement method according to claim 1, characterized in that: The step of obtaining the change in oxygen after each cyclic combustion in the solid fuel cell comprises: The electromotive force output by the solid fuel cell when the methane gas is burned in each cycle is obtained to determine the oxygen consumption in each cycle.

3. The methane measurement method according to claim 2, characterized in that: The step of obtaining the oxygen content of the methane gas flowing through each cycle of combustion, obtaining the electromotive force output by the solid fuel cell during each cycle of combustion of the methane gas, and obtaining the oxygen consumption in each cycle includes: The oxygen consumption is calculated according to the following expression: Among them, C x (t) represents the change of oxygen concentration over time during combustion, C0 represents the initial concentration of oxygen on the reference electrode side, E k (t) is the electromotive force output by the solid fuel cell in the kth cycle, and a is a proportional factor determined by the system constant R, T0, Faraday constant F and the number of electron transfers n.

4. The methane measurement method according to claim 3, characterized in that: The sampled discrete electromotive force of the solid fuel cell is obtained, and the change value of the discrete electromotive force is calculated by a numerical integration method, and the oxygen consumption in each cycle is calculated according to the change value of the discrete electromotive force: Among them, the ΔS k is the change value of discrete electromotive force, C0 is the oxygen concentration; The cumulative oxygen consumption of N cycles is: Where ΔQ represents the cumulative oxygen consumption of N cycles, and M is the number of cycles.

5. The methane measurement method according to claim 4, characterized in that: When the oxygen consumption is lower than a set threshold, the cyclic combustion is stopped, and the concentration of the methane gas is calculated, including: The concentration of the methane gas to be measured is calculated according to the volume and pressure of the methane gas to be measured and the stoichiometric ratio of the methane gas to oxygen.

6. The methane measurement method according to claim 5, characterized in that: The step of calculating the concentration of the methane gas to be measured according to the volume and pressure of the methane gas to be measured and the stoichiometric ratio of the methane gas to oxygen comprises: The concentration of the methane gas to be measured is: Wherein, C is the concentration of the methane gas to be measured (μL / L); V0 is the volume of the methane gas to be measured (mL); L is the flow rate of the carrier gas (mL / min); and N is the stoichiometric ratio of the methane gas to be measured to oxygen.

7. A device for detecting methane concentration, characterized in that: The methane concentration detection device uses the methane measurement method described in claim 1, and the methane concentration detection device includes: A collection module, used to obtain the methane gas to be tested; A first separation module, used for separating the moisture in the methane gas to be tested; A sampling module, used for quantitative sampling of the methane gas separated by the first separation module; A second separation module is used to separate the quantitatively sampled methane gas; A solid fuel cell module, used for burning the separated methane gas to obtain the concentration of the methane gas; A gas circulation module is arranged between the second separation module and the solid fuel cell module, and is used to control the methane gas in the second separation module to circulate into the solid fuel cell.

8. The device for detecting methane concentration according to claim 7, characterized in that: The first separation module includes a first-stage separation module and a second-stage separation module.

9. The device for detecting methane concentration according to claim 7, characterized in that: The sampling module comprises: a vacuum diaphragm pump and a gas quantitative tube.

10. The device for detecting methane concentration according to claim 7, characterized in that: The gas circulation module includes a delay column and a one-way valve.

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