Continuous monitoring system and method for emission of non-methane total hydrocarbon in waste gas

Abstract

The invention discloses a waste gas non-methane total hydrocarbon emission continuous monitoring system and method, and relates to the related technical field of environmental monitoring, and the system comprises: a connection collection device, which is used for extracting to-be-detected gas from a waste gas source; carrying out gas chromatographic separation, and determining separated components; detecting through a hydrogen flame ionization detector to generate an ion current, and converting the ion current to obtain a current signal; weak current analysis is carried out, and a concentration-signal relation is established through fitting; extracting real-time to-be-detected gas for passing treatment, and generating real-time concentration in combination with the concentration-signal relationship; and the real-time concentration is output through a monitoring interface. The technical problem that in the prior art, continuous monitoring is difficult to conduct to effectively extract and separate different pollutant components, and consequently the accuracy and timeliness of the emission monitoring result are insufficient is solved, and the technical effect of improving the accuracy and timeliness of the emission monitoring result is achieved.

Description

Technical Field

[0001] This application relates to the technical field of environmental monitoring, and particularly relates to a continuous monitoring system and method for the emission of non-methane total hydrocarbons in waste gas. Background Art

[0002] Waste gas emission monitoring is an important part of environmental protection and pollution control. During industrial production and energy consumption processes, non-methane total hydrocarbons (NMHCs) are one of the important pollutants. Non-methane total hydrocarbons mainly include hydrocarbon substances (such as olefins, aromatic hydrocarbons, and alkanes, etc.), which pose potential hazards to environmental air quality and human health, and have strong volatility and flammability. Therefore, it is necessary to accurately and real-time monitor them. Currently, the monitoring methods for non-methane total hydrocarbons in waste gas mainly include gas chromatography, infrared absorption method, chemiluminescence method, etc., which usually rely on relatively complex equipment and time-consuming analysis processes, and have problems such as insufficient real-time performance, difficult equipment maintenance, and poor environmental adaptability. With the increasingly strict environmental protection requirements and high requirements for monitoring accuracy, traditional monitoring methods cannot achieve real-time online monitoring and rapid response, and it is difficult to meet the needs of efficient and continuous monitoring during the industrial waste gas emission process.

[0003] Therefore, in the related technologies at the present stage, there are technical problems that it is difficult to conduct continuous monitoring to effectively extract and separate different pollutant components, resulting in insufficient accuracy and timeliness of emission monitoring results. Summary of the Invention

[0004] This application provides a continuous monitoring system and method for the emission of non-methane total hydrocarbons in waste gas, solves the technical problem in the prior art that it is difficult to conduct continuous monitoring to effectively extract and separate different pollutant components, resulting in insufficient accuracy and timeliness of emission monitoring results, and achieves the technical effect of improving the accuracy and timeliness of emission monitoring results.

[0005] This application provides a continuous monitoring system for the emission of non-methane total hydrocarbons in waste gas. The system includes: a module for extracting the gas to be measured, which is used to connect to a collection device and extract the gas to be measured from a waste gas source; a module for determining separated components, which is used to inject the gas to be measured into a gas chromatograph for gas chromatography separation to determine the separated components; a module for obtaining a current signal, which is used to detect the separated components when flowing out of the gas chromatograph through a hydrogen flame ionization detector to generate an ion current and convert it into a current signal; a module for analyzing weak current, which is used to conduct weak current analysis based on the current signal, compare it with the relationship between the standard gas concentration and the standard gas response signal, and fit to establish a concentration-signal relationship; a module for generating real-time concentration, which is used to extract the real-time gas to be measured for passing through the gas chromatograph and the hydrogen flame ionization detector, and generate a real-time concentration in combination with the concentration-signal relationship; a module for outputting real-time concentration, which is used to output the real-time concentration through a monitoring interface.

[0006] In a possible implementation, the separation component determination module further performs the following processes: identifying the components of the gas to be measured through the air inlet, heating and evaporating the non-gaseous components according to a preset heating temperature until the non-gaseous components are completely turned into gaseous components, obtaining a sample gas, wherein the air inlet is connected to the gas chromatograph; calculating the amount of separated components per unit time according to the column capacity of the chromatographic column in the gas chromatograph to obtain the injection volume; injecting the sample gas into the gas chromatograph with the injection volume.

[0007] In a possible implementation, the separation component determination module further performs the following processes: calculating the interaction time through the interaction between the chromatographic column and the sample gas to obtain the retention time; identifying the gas components in the sample gas according to the retention time to obtain the separated components, wherein the gas components are quantified based on the response signal of the detector to obtain the component concentration, and the component concentration is associated with the separated components.

[0008] In a possible implementation, the weak current analysis module further performs the following processes: identifying the current signal based on the weak current signal threshold to obtain a weak current signal; extracting a first weak current signal according to the weak current signal; performing signal enhancement and noise suppression on the first weak current signal to obtain a first gain current signal; calculating the ratio of the first gain current signal to the standard gas concentration-standard gas response signal relationship to generate a first weak concentration; using the first weak concentration to traverse the weak current signal to calculate the concentration until the Nth weak concentration, obtaining N weak concentrations; performing polynomial fitting according to the proportionality coefficients of the N weak current signals and the N weak concentrations to establish the concentration-signal relationship.

[0009] In a possible implementation, the weak current analysis module further performs the following processes: dividing the proportionality coefficients into a training set and a validation set, wherein the training set is used to train the model architecture of the concentration-signal relationship, and the validation set is used to validate the model architecture of the concentration-signal relationship and output a predicted value; calculating the mean absolute error between the predicted value and the true value in the training set; combining the error range, evaluating the prediction accuracy of the model architecture of the concentration-signal relationship with the mean absolute error, and adjusting the proportionality coefficients through the evaluation coefficient to obtain the concentration-signal relationship.

[0010] In a possible implementation, the weak current analysis module further performs the following processes: introducing an online standard gas through the hydrogen flame ionization detector for real-time calibration response; calculating an offset of the relationship between the online standard gas and the standard gas concentration-standard gas response signal based on the trigger of the real-time calibration response; performing incremental calibration on the concentration-signal relationship with the offset to obtain a locally optimized concentration-signal relationship; and fusing the locally optimized concentration-signal relationship into the concentration-signal relationship.

[0011] In a possible implementation, the real-time concentration output module further performs the following processes: generating a real-time trend graph of the real-time concentration according to the monitoring interface; setting an environmental protection concentration threshold according to environmental protection standards and setting a safety concentration threshold based on a safety range; generating a first warning by identifying the real-time trend graph with the environmental protection concentration threshold and generating a second warning by identifying the real-time trend graph with the safety concentration threshold; and respectively outputting the first warning and the second warning through the monitoring interface.

[0012] The present application also provides a method for continuously monitoring the non-methane total hydrocarbon emissions of waste gas. The method includes: connecting a collection device to extract a gas to be measured from a waste gas source; injecting the gas to be measured into a gas chromatograph for gas chromatographic separation to determine separated components; detecting the separated components when flowing out of the gas chromatograph through a hydrogen flame ionization detector to generate an ion current and converting it into a current signal; performing weak current analysis on the current signal, comparing it with the relationship between the standard gas concentration and the standard gas response signal, and fitting to establish a concentration-signal relationship; extracting the real-time gas to be measured for the passing process of the gas chromatograph and the hydrogen flame ionization detector, and combining with the concentration-signal relationship to generate a real-time concentration; and outputting the real-time concentration through a monitoring interface.

[0013] It is intended to connect a collection device through a continuous monitoring system and method for non-methane total hydrocarbon emissions of waste gas proposed by the present application to extract a gas to be measured from a waste gas source; perform gas chromatographic separation to determine separated components; detect through a hydrogen flame ionization detector to generate an ion current and convert it into a current signal; perform weak current analysis and fit to establish a concentration-signal relationship; extract the real-time gas to be measured for the passing process and combine with the concentration-signal relationship to generate a real-time concentration; and output the real-time concentration through a monitoring interface. This solves the technical problem in the prior art that it is difficult to perform continuous monitoring to effectively extract and separate different pollutant components, resulting in insufficient accuracy and timeliness of emission monitoring results, and achieves the technical effect of improving the accuracy and timeliness of emission monitoring results. Description of the Drawings

[0014] To more clearly illustrate the technical solutions of the embodiments of the present disclosure, the accompanying drawings of the embodiments of the present disclosure will be briefly introduced below. Flowcharts are used in this application to illustrate the operations performed by the systems according to the embodiments of the present application. It should be understood that the operations described above or below do not necessarily need to be performed precisely in sequence. On the contrary, as needed, various steps can be performed in reverse order or simultaneously. At the same time, other operations can also be added to these processes, or one or more steps can be removed from these processes.

[0015] Figure 1 It is a schematic structural diagram of a continuous monitoring system for the emission of non-methane total hydrocarbons in waste gas provided by an embodiment of the present application.

[0016] Figure 2 It is a schematic flowchart of a continuous monitoring method for the emission of non-methane total hydrocarbons in waste gas provided by an embodiment of the present application.

[0017] Explanation of reference numerals: The extracted gas to be measured module 10, the separation component determination module 20, the current signal acquisition module 30, the weak current analysis module 40, the real-time concentration generation module 50, and the real-time concentration output module 60. Detailed implementation manners

[0018] The above description is only an overview of the technical solutions of the present application. In order to be able to understand the technical means of the present application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of the present application more obvious and understandable, the following specifically gives the detailed implementation manners of the present application.

[0019] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings. The described embodiments should not be regarded as limitations of the present application. All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0020] In the following description, reference is made to "some embodiments", which describe a subset of all possible embodiments. However, it is understood that "some embodiments" may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict. The terms "first" and "second" are only used to distinguish similar objects and do not represent a specific order for the objects. The terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, system, product or server that includes a series of steps or units need not be limited to those steps or units clearly listed, but may include other steps or modules not clearly listed or inherent to these processes, products or devices. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used herein are only for the purpose of describing the embodiments of this application.

[0021] An embodiment of the present application provides a continuous monitoring system for the total non-methane hydrocarbon emissions of exhaust gas, as Figure 1 shown, the system includes: A module 10 for extracting the gas to be measured, which is used to connect to a collection device and extract the gas to be measured from an exhaust gas source.

[0022] Preferably, the gas to be measured is collected from an exhaust gas source (such as an exhaust gas discharge pipe or an industrial chimney of a factory) through a gas sampling device. Specifically, the collection device at the exhaust gas source is connected, and the collection probe installed at the discharge port or pipeline of the exhaust gas source is used to directly contact the exhaust gas and collect the gas to be measured, and then the gas to be measured is extracted in real time.

[0023] A module 20 for determining the separated components, which is used to inject the gas to be measured into a gas chromatograph for gas chromatographic separation and determine the separated components.

[0024] Preferably, the gas to be measured extracted by the collection device is injected into a gas chromatograph for gas chromatographic separation. The gas chromatograph is used to analyze the components in a gas sample and separates them depending on the different distribution characteristics of the components in the stationary phase and the mobile phase. Specifically, the gas to be measured is injected into the chromatographic column (a slender pipe) through a microsyringe (such as in a gas sample bottle). Gas chromatographic separation utilizes the difference in the distribution coefficients of gas components in the chromatographic column. The chromatographic column is filled with a stationary phase (usually a solid or liquid material coated inside a thin tube), and the mobile phase is a gas carrier gas (such as nitrogen, helium, etc.). After the gas to be measured is injected, as the carrier gas flows, the gas components interact with the stationary phase in the column. Each component has a different migration rate due to its different affinity for the stationary phase, and thus is separated. Specifically, the gas to be measured enters the chromatographic column through the injection port of the gas chromatograph. Different components in the sample have different degrees of interaction with the stationary phase of the chromatographic column according to their physicochemical properties (such as volatility, polarity, molecular weight, etc.), resulting in different residence times of them in the chromatographic column. Inside the chromatographic column, the components go through processes such as distribution, adsorption, and desorption, and move forward together with the carrier gas. Eventually, different components are separated and leave the chromatographic column at different time points. Through the separation of gas chromatography, each component in the gas to be measured will be detected separately, and finally the separated components are determined, so as to efficiently and accurately separate and determine the gas components such as non-methane total hydrocarbons (such as organic compounds like olefins, aromatic hydrocarbons, etc.) in the waste gas sample.

[0025] The current signal acquisition module 30 is used to detect the separated components when they flow out of the gas chromatograph through a hydrogen flame ionization detector, generate an ion current, and convert it into a current signal.

[0026] Preferably, a hydrogen flame ionization detector is used to detect the separated components and then convert them into corresponding electrical signals. Among them, after the gas sample to be measured is separated by the chromatographic column, different gas components are formed and will flow out of the chromatographic column in sequence at different times (i.e., retention time). The hydrogen flame ionization detector is arranged after the gas chromatograph and detects when the separated components flow out. The hydrogen flame ionization detector is a commonly used detector in gas chromatography, used to detect organic gas components, especially suitable for analyzing organic gases such as non-methane total hydrocarbons. The core of the hydrogen flame ionization detector is the flame, which is usually a flame formed by the mixed combustion of hydrogen (H2) and air (O2). Specifically, when an organic compound (the gas to be measured, such as hydrocarbon substances) passes through the flame, an ionization reaction will occur. The gas molecules react with the hydrogen atoms in the flame to produce positively charged ions and free electrons, that is, positive ions (H⁺) and free electrons (e⁻) are generated. The collision of ions and electrons generates an electric current, and this current signal is proportional to the gas concentration. The hydrogen flame ionization detector has two electrodes, one is the combustion electrode and the other is the collection electrode. When the separated organic gas (such as the hydrocarbon components in non-methane total hydrocarbons) contacts the flame, it undergoes a chemical reaction with the hydrogen in the flame to generate positively charged ions and free electrons. These charged particles (ion current) will be guided to the collection electrode through the electric field, thereby generating an electric current signal, which reflects the concentration of the analyzed gas component. The greater the intensity of the signal, the higher the concentration of the organic gas in the sample.

[0027] The weak current analysis module 40 is used to perform weak current analysis based on the current signal, compare it with the relationship between the standard gas concentration and the standard gas response signal, and fit to establish the concentration-signal relationship.

[0028] Preferably, weak current analysis is performed on the current signal generated by the hydrogen flame ionization detector. Specifically, the current signal is amplified and filtered by an electronic circuit to obtain more stable current data, and then compared with the relationship between the standard gas concentration and the standard gas response signal. Among them, the standard gas (also called the standard gas sample) refers to a standard gas sample with a known concentration. The relationship between the standard gas concentration and the standard gas response signal refers to the corresponding relationship between the concentration of the standard gas and the current signal generated by it, that is, the change in gas concentration will cause a change in the current signal, and this change is predictable. The detector is calibrated with the standard gas of known concentration. By using standard gases with different concentrations, the response curve between the concentration and the current signal can be plotted; then the concentration of the standard gas is compared with the output current signal data to obtain a set of corresponding data, and then these data are fitted through a mathematical model (such as linear regression, non-linear regression, etc.) to obtain the functional relationship between the concentration and the current signal, that is, a non-linear regression model (such as an exponential model, a polynomial model, etc.) is used for fitting to represent the proportional relationship between the concentration and the current signal, that is, the concentration-signal relationship is established.

[0029] A real-time concentration generation module 50 is configured to extract the real-time gas to be measured, process it through the gas chromatograph and the hydrogen flame ionization detector, and generate a real-time concentration in combination with the concentration-signal relationship.

[0030] Preferably, by performing real-time sampling and processing of the gas sample to be measured, using the combined action of the gas chromatograph and the hydrogen flame ionization detector, and combining the previously established concentration-signal relationship (i.e., the calibration curve), the immediate analysis and calculation of the gas concentration are carried out, and then the real-time concentration is generated. Specifically, the collection device continuously collects the gas to be measured from the waste gas source during the waste gas monitoring process, including pollutants such as non-methane total hydrocarbons (NMHC). Then, the collected gas sample is injected into the gas chromatograph. The function of the gas chromatograph is to separate the different components in the gas to be measured (such as various hydrocarbon compounds). After each component is separated in the chromatographic column, it will flow out in sequence and enter the downstream detector for detection. The high-temperature flame generated by the combustion of hydrogen ionizes the organic components in the gas, generating an ion current, and an electric current signal will be generated under the action of the electric field. The intensity of the signal is proportional to the concentration of the organic components in the gas. Finally, the electric current signal of the gas to be measured is compared with the established concentration-signal relationship, and then the concentration of the gas to be measured is calculated in real time. For example, if the real-time signal is a certain specific electric current value, the system will convert the electric current value into the corresponding concentration (such as ppm or ppb) through this relationship, so as to realize the continuous, real-time, and accurate monitoring of the concentration of harmful substances (such as non-methane total hydrocarbons, etc.) in the waste gas.

[0031] A real-time concentration output module 60 is configured to output the real-time concentration through the monitoring interface.

[0032] Preferably, the real-time gas concentration data obtained through the processing of the hydrogen flame ionization detector and the gas chromatograph are displayed and monitored through the monitoring interface, that is, presented to the user in a visual and operable manner. Specifically, the monitoring interface is usually a visual graphical user interface, which provides the display of real-time data through a computer or a dedicated monitoring device. For example, the monitoring interface will display the real-time gas concentration data (such as ppm or ppb values) and show the change trend of the concentration over time. In addition to real-time data display, the monitoring interface has an alarm and warning function, enabling the management personnel to always grasp the emission status and make a quick response. For example, when the gas concentration exceeds the preset threshold, the system will issue an alarm to remind the staff to take appropriate measures to deal with the emission of high-concentration polluted gas, which helps to monitor the real-time and accurate emission of pollutants and also improves the environmental protection and compliance of the production process.

[0033] Furthermore, the specific configuration of the separation component determination module 20 further includes identifying the components of the gas to be measured through the air inlet, heating and evaporating the non-gaseous components according to a preset heating temperature until the non-gaseous components are completely converted into gaseous components, obtaining a sample gas, wherein the air inlet is connected to the gas chromatograph; calculating the amount of separated components per unit time according to the column capacity of the chromatographic column in the gas chromatograph to obtain the injection volume; and injecting the sample gas into the gas chromatograph with the injection volume.

[0034] Preferably, the air inlet may be equipped with a sensor or a simple gas analysis device to identify the components of the gas to be measured. The gas to be measured may contain some non-gaseous components (such as solid or liquid pollutants, particulate matter or moisture, etc.), which must be converted into gas by heating and evaporation before subsequent gas analysis. Specifically, by controlling the heating temperature, the non-gaseous components (such as liquid or solid substances) are completely converted into gas at a certain temperature to ensure that all components are completely converted into gas before entering the gas chromatograph. The gas sample after heating treatment is called a sample gas, that is, the gas to be measured that has been completely vaporized, and can be sent into the gas chromatograph for detailed detection. Among them, the air inlet is connected to the gas chromatograph through a pipeline or a sampling device to ensure that the sample gas can enter the gas chromatograph for separation and detection.

[0035] Preferably, during the gas chromatography analysis process, the chromatographic column separates the gas components according to the physical and chemical properties of the components (such as molecular weight, volatility, polarity, etc.). Through the design and capacity of the chromatographic column, the analytical instrument can calculate how many components of the gas sample the chromatographic column can separate per unit time (usually expressed in volume or mass), and then determine the injection volume, that is, the volume of the sample gas injected into the chromatograph each time. It is necessary to ensure that this volume matches the separation ability of the chromatographic column to ensure accurate and stable separation results; finally, according to the calculated appropriate injection volume, the sample gas is accurately injected into the gas chromatograph. The size of the injection volume determines the amount of sample gas entering the chromatograph. Specifically, after the sample gas is injected into the injection port of the gas chromatograph, it will quickly pass through the chromatographic column and be separated in the column according to the different gas components. The separated components will be displayed as peaks on the gas chromatogram. Finally, the concentration and characteristics of each component can be determined according to these signals, ensuring the accuracy and efficiency of the analysis and providing accurate gas component analysis results.

[0036] Furthermore, the specific configuration of the separation component determination module 20 further includes calculating the interaction time to obtain the retention time through the interaction between the chromatographic column and the sample gas; identifying the gas components in the sample gas according to the retention time to obtain the separated components, wherein the gas component quantification is based on the response signal of the detector to obtain the component concentration, and is associated with the separated components.

[0037] Preferably, the components in the sample gas are analyzed by the interaction between the chromatographic column and the sample gas, the concentration of each component is determined, and quantitative analysis is performed based on the response signal of the detector. Among them, the chromatographic column is the core component of the gas chromatograph. It interacts with the components of the gas sample through the packed or coated stationary phase (such as silica gel, polymer, or metal, etc.). Each gas component has a different affinity for the stationary phase of the chromatographic column according to its physical and chemical properties (such as molecular weight, polarity, volatility, etc.), resulting in different flow rates in the chromatographic column. Specifically, in the gas chromatograph, after each component in the sample gas enters the chromatographic column, it will experience an interaction with the stationary phase. This interaction time is called the retention time, that is, the time required for the sample gas to be injected into the chromatograph until this component passes through the chromatographic column and reaches the detector. The retention time of a component is the result of its interaction with the stationary phase. The component with a stronger affinity has a longer retention time; the component with a weaker affinity has a shorter retention time.

[0038] Preferably, after the gas sample is separated by the chromatographic column, each component will flow out of the chromatographic column at different times (i.e., retention times). By recording and analyzing these retention times, the instrument can identify based on the known standard sample data. For example, by plotting a chromatogram in the chromatograph, each gas component will form a peak, and the position where the peak appears corresponds to a specific retention time. By comparing these peaks with the retention times of the known standard gases, the analyst can determine which components are contained in the sample gas. Among them, when the gas component passes through the chromatographic column, it is sent to the hydrogen flame ionization detector, and the detector will perform quantitative analysis of the gas component, that is, generate a response signal, usually an electric current signal proportional to the gas concentration. The intensity of the signal (the magnitude of the current) reflects the concentration of the component. Then, based on the response signal generated by the detector, quantitative analysis is performed on each gas component. Specifically, through the concentration-signal relationship (calibration curve), according to the peaks and retention times in the chromatogram, the signal of each component is automatically associated with its corresponding concentration, so as to provide accurate gas component analysis and concentration measurement.

[0039] Furthermore, the specific configuration of the weak current analysis module 40 further includes identifying the current signal based on the weak current signal threshold to obtain a weak current signal; extracting a first weak current signal according to the weak current signal; performing signal enhancement and noise suppression on the first weak current signal to obtain a first gain current signal; calculating the ratio of the first gain current signal to the standard gas concentration-standard gas response signal relationship to generate a first weak concentration; using the first weak concentration to traverse the weak current signal to calculate the concentration until the Nth weak concentration, obtaining N weak concentrations; performing polynomial fitting according to the proportionality coefficients of the N weak current signals and the N weak concentrations to establish the concentration-signal relationship.

[0040] Preferably, the weak current signal threshold is a preset standard value for distinguishing effective current signals and noise. Specifically, the current signal is compared with the weak current signal threshold to identify weak current signals, which are usually very small currents (possibly in the microampere range). Due to their low intensity, they may be interfered by background noise. A weak current signal is randomly selected from the obtained weak current signals as the first weak current signal, and then the first weak current signal is subjected to signal enhancement and noise suppression, that is, the intensity of the effective signal is increased through specific algorithms (such as amplification, filtering, etc.), and at the same time, filtering techniques (such as low-pass filtering, high-pass filtering, band-pass filtering, etc.) are used to remove the background noise in the signal (such as electrical noise, environmental noise, etc.), thereby retaining the effective current signal, that is, obtaining the first gain current signal. By calculating the ratio of the first gain current signal to the concentration-response signal during calibration, the weak concentration corresponding to this current signal (i.e., the first weak concentration) can be obtained, which reflects the relationship between the signal intensity and the concentration, thus realizing the quantification of the concentration.

[0041] Preferably, starting from the first weak concentration, the same calculation method is used to traverse other weak current signals, so as to calculate the concentration corresponding to each current signal. Each weak current signal is associated with a specific concentration value. The concentration corresponding to each current signal is continuously calculated based on the signal until N weak concentrations are obtained, where N is a positive integer representing the total number of weak current signals. Finally, polynomial fitting is performed on the proportionality coefficients of the N weak current signals and the N weak concentrations. The proportionality coefficient refers to the conversion coefficient between the current signal and the concentration. Specifically, through mathematical methods (such as the least squares method), the relationship between the signal and the concentration is transformed into a mathematical model, usually a polynomial function. For example, assuming that the relationship between the concentration and the signal is non-linear, a quadratic, cubic or higher-order polynomial may be used to represent this relationship during the fitting process. Through fitting, the system obtains a mathematical relationship between the concentration and the current signal, that is, the concentration-signal relationship, which is used to convert the current signals collected in the future into concentration data to achieve accurate measurement of the gas sample concentration.

[0042] Furthermore, the specific configuration of the weak current analysis module 40 also includes dividing the proportionality coefficient into a training set and a validation set. The training set is used to train the model architecture of the concentration-signal relationship, and the validation set is used to validate the model architecture of the concentration-signal relationship and output a predicted value; calculating the mean absolute error between the predicted value and the true value in the training set; combining the error range, and evaluating the prediction accuracy of the model architecture of the concentration-signal relationship based on the mean absolute error, and adjusting the proportionality coefficient through the evaluation coefficient to obtain the concentration-signal relationship.

[0043] Preferably, the proportionality coefficient is divided into a training set and a validation set. The training set is used to train the model architecture, that is, to adjust the parameters of the model (such as the proportionality coefficient) according to the training data (including current signals and corresponding concentration data), so that the model can learn the relationship between the signal and the concentration. The validation set is used to verify the model architecture of the concentration-signal relationship and help detect the prediction ability of the model on unseen data. By inputting the current signal of the validation set, the model will generate a predicted value (i.e., the predicted concentration). By calculating the absolute value of the difference between the predicted value and the true value, and then obtaining the average of these differences, the prediction performance of the model can be quantitatively evaluated. The smaller the error, the more accurate the prediction of the model. Finally, combined with the error range, the prediction accuracy of the model architecture of the concentration-signal relationship is evaluated using the mean absolute error, that is, the mean absolute error is used to evaluate the accuracy of the model. If the error is large, it means that the prediction accuracy of the model is poor; if the error is small, it means that the model has a high accuracy. Then, the proportionality coefficient is adjusted through the evaluation coefficient. Among them, the prediction accuracy of the model is reflected by the mean absolute error, and the evaluation coefficient can be used to indicate whether the model needs to be optimized, that is, by analyzing the mean absolute error and the error range, the proportionality coefficient of the model (the conversion coefficient between concentration and signal) can be adjusted. For example, if the prediction error of the model is too large, it may be necessary to readjust the proportionality coefficient, or adjust the model architecture, training method, etc. to improve the accuracy, and finally obtain the concentration-signal relationship, which can accurately convert the weak current signal into the gas concentration in practical applications and ensure the prediction accuracy, realizing real-time and accurate concentration measurement.

[0044] Furthermore, the specific configuration of the weak current analysis module 40 further includes introducing an online standard gas through the hydrogen flame ionization detector for real-time calibration response; calculating the offset of the online standard gas from the standard gas concentration-standard gas response signal relationship based on the trigger of the real-time calibration response; incrementally calibrating the concentration-signal relationship with the offset to obtain a locally optimized concentration-signal relationship; and fusing the locally optimized concentration-signal relationship into the concentration-signal relationship.

[0045] Preferably, the on-line standard gas is a gas sample with a known concentration, which is usually used to determine the response of a gas detector (such as a flame ionization detector) to ensure the accuracy of the device. Specifically, by introducing the on-line standard gas into the flame ionization detector, the response signal (usually a current signal) of this standard gas is measured. By comparing the response of the detector and the known concentration of the on-line standard gas, the device can be calibrated in real time to ensure that the detector maintains an accurate response to cope with changes in gas concentration. Each time the standard gas is introduced, the detector triggers a calibration response, generating a corresponding current signal, and then detecting the deviation between the current detector response and the known concentration of the standard gas, and further calculating the offset. The offset refers to the gap between the current standard gas concentration-standard gas response signal relationship and the on-line standard gas, which may cause the response of the detector to deviate due to various factors (such as environmental changes, equipment aging, temperature and humidity, etc.). Then, the calculated offset is used to perform incremental calibration on the concentration-signal relationship, that is, by making small adjustments to make the response of the detector more precisely match the concentration of the standard gas. Specifically, the parameters (such as the proportionality coefficient) in the concentration-signal model are adjusted according to the calculated offset to ensure that the model can accurately reflect the relationship between the actual concentration of the standard gas and the detection signal, thereby obtaining a locally optimized concentration-signal relationship, and finally integrating it into the original concentration-signal relationship to form a more accurate global concentration-signal relationship, which not only calibrates the response in the current state, but also ensures the consistency of the original model under new data, thus ensuring that the instrument can maintain a stable and high-precision response at different times and conditions.

[0046] Furthermore, the specific configuration of the real-time concentration output module 60 further includes generating a real-time trend graph of the real-time concentration according to the monitoring interface; setting an environmental protection concentration threshold according to environmental protection standards and setting a safety concentration threshold based on a safety range; generating a first warning by identifying the real-time trend graph with the environmental protection concentration threshold and generating a second warning by identifying the real-time trend graph with the safety concentration threshold; and respectively outputting the first warning and the second warning through the monitoring interface.

[0047] Preferably, a real-time trend graph is generated based on the real-time concentration data of the monitoring interface (i.e., the change of gas concentration over time), which shows the dynamic trend of gas concentration changing with time, helping the operator visually view the change of pollutant concentration, so as to make a timely response. Set an environmental protection concentration threshold according to the environmental protection standard (the maximum safety value that the gas concentration shall not exceed) to indicate when the concentration reaches or exceeds the environmental protection standard. For example, certain harmful gases such as sulfur dioxide and nitrogen oxides have clear environmental protection concentration limits. Once the concentration exceeds this value, it may cause harm to the environment and human health. Then set a safety concentration threshold according to the safety range (based on operation and personnel safety), which is usually set higher than the environmental protection threshold to ensure that measures can be taken as early as possible when the concentration is too high to prevent harm to staff or facilities.

[0048] Preferably, when the concentration data in the real-time trend graph exceeds the set environmental protection concentration threshold, a first warning is generated, which is usually a warning in terms of environmental protection, prompting the staff to take measures to reduce pollution emissions, adjust the production process or perform other environmental control operations; when the concentration data in the real-time trend graph exceeds the set safety concentration threshold, a second warning is generated, notifying the relevant personnel that the gas concentration has exceeded the safety range and may have a direct impact on the operator or equipment. This warning is more urgent and usually triggers stronger response measures, such as personnel evacuation, equipment shutdown, emission source closure, etc., to ensure that personnel safety and equipment operation are not threatened; finally, the first warning and the second warning are respectively displayed through the monitoring interface, and the operator is prompted through a warning box or graphical interface on the interface. For example, the colors of the warning box or icon will be different, such as green indicating normal, yellow / orange indicating the first warning, and red indicating the second warning; a sound alarm may be issued to ensure that the staff can respond quickly, prevent environmental pollution and personnel injury, and ensure the safety of the production process and compliance with environmental protection regulations.

[0049] In the above text, reference is made to Figure 1 A continuous monitoring system for waste gas non-methane total hydrocarbon emissions according to an embodiment of the present invention is described in detail. Next, a continuous monitoring method for waste gas non-methane total hydrocarbon emissions according to an embodiment of the present invention will be described with reference to Figure 2 A continuous monitoring method for waste gas non-methane total hydrocarbon emissions is as follows

[0050] A continuous monitoring method for waste gas non-methane total hydrocarbon emissions, as Figure 2As shown, the method includes: connecting a collection device to extract a gas to be measured from an exhaust gas source; injecting the gas to be measured into a gas chromatograph for gas chromatography separation to determine the separated components; detecting the separated components when flowing out of the gas chromatograph through a hydrogen flame ionization detector to generate an ion current and converting it into a current signal; performing weak current analysis based on the current signal, comparing it with the relationship between the standard gas concentration and the standard gas response signal, and fitting to establish a concentration-signal relationship; extracting the real-time gas to be measured for processing by the gas chromatograph and the hydrogen flame ionization detector, and combining the concentration-signal relationship to generate a real-time concentration; outputting the real-time concentration through a monitoring interface.

[0051] In a possible implementation manner, the method for continuously monitoring the non-methane total hydrocarbon emissions of exhaust gas further includes: identifying the components of the gas to be measured through an intake port, heating and evaporating the non-gaseous components according to a preset heating temperature until the non-gaseous components are completely turned into gaseous components to obtain a sample gas, where the intake port is connected to the gas chromatograph; calculating the amount of separated components per unit time according to the chromatographic column capacity of the chromatographic column in the gas chromatograph to obtain an injection volume; injecting the sample gas into the gas chromatograph with the injection volume.

[0052] In a possible implementation manner, the method for continuously monitoring the non-methane total hydrocarbon emissions of exhaust gas further includes: calculating the interaction time to obtain a retention time through the interaction between the chromatographic column and the sample gas; identifying the gas components in the sample gas according to the retention time to obtain separated components, where the gas components are quantitatively determined based on the response signal of the detector to obtain the component concentration and are associated with the separated components.

[0053] In a possible implementation manner, the method for continuously monitoring the non-methane total hydrocarbon emissions of exhaust gas further includes: identifying the current signal based on a weak current signal threshold to obtain a weak current signal; extracting a first weak current signal according to the weak current signal; performing signal enhancement and noise suppression on the first weak current signal to obtain a first gain current signal; calculating the ratio of the first gain current signal to the relationship between the standard gas concentration and the standard gas response signal to generate a first weak concentration; using the first weak concentration to traverse the weak current signal to calculate the concentration until the Nth weak concentration to obtain N weak concentrations; performing polynomial fitting according to the proportionality coefficient between the N weak current signals and the N weak concentrations to establish the concentration-signal relationship.

[0054] In a possible implementation, the method for continuously monitoring the non-methane total hydrocarbon emissions of waste gas further includes: dividing the proportionality coefficient into a training set and a validation set, where the training set is used to train the model architecture of the concentration-signal relationship, and the validation set is used to validate the model architecture of the concentration-signal relationship and output a predicted value; calculating the mean absolute error between the predicted value and the true value in the training set; combining the error range, evaluating the prediction accuracy of the model architecture of the concentration-signal relationship based on the mean absolute error, and adjusting the proportionality coefficient through an evaluation coefficient to obtain the concentration-signal relationship.

[0055] In a possible implementation, the method for continuously monitoring the non-methane total hydrocarbon emissions of waste gas further includes: introducing an on-line standard gas through the flame ionization detector for real-time calibration response; calculating the offset of the relationship between the on-line standard gas and the standard gas concentration-standard gas response signal based on the trigger of the real-time calibration response; performing incremental calibration on the concentration-signal relationship with the offset to obtain a locally optimized concentration-signal relationship; and fusing the locally optimized concentration-signal relationship into the concentration-signal relationship.

[0056] In a possible implementation, the method for continuously monitoring the non-methane total hydrocarbon emissions of waste gas further includes: generating a real-time trend graph of the real-time concentration according to the monitoring interface; setting an environmental protection concentration threshold based on environmental protection standards and setting a safety concentration threshold based on a safety range; generating a first warning by identifying the real-time trend graph with the environmental protection concentration threshold, and generating a second warning by identifying the real-time trend graph with the safety concentration threshold; and respectively outputting the first warning and the second warning through the monitoring interface.

[0057] The continuous monitoring system for non-methane total hydrocarbon emissions of waste gas provided by the embodiments of the present invention can execute the method for continuously monitoring the non-methane total hydrocarbon emissions of waste gas provided by any embodiment of the present invention, and has corresponding functional modules and beneficial effects for executing the method.

[0058] Although the present application makes various references to certain modules in the system according to the embodiments of the present application, however, any number of different modules can be used and run on the user terminal and / or the server. The included individual units and modules are only divided according to functional logic, but are not limited to the above division as long as the corresponding functions can be achieved; in addition, the specific names of the functional units are only for the convenience of mutual distinction and do not limit the protection scope of the present invention.

[0059] The above specific embodiments do not constitute a limitation on the protection scope of this application. Those skilled in the art should understand that various modifications, combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims

1. A continuous monitoring system for exhaust gas non-methane total hydrocarbon emissions, characterized in that: The system comprises: The gas extraction module to be tested is used to connect to the collection device to extract the gas to be tested from the exhaust gas source; A separation component determination module is used to inject the gas to be tested into a gas chromatograph for gas chromatography separation to determine the separation components; A current signal acquisition module, used to detect the separated components flowing out of the gas chromatograph through a hydrogen flame ionization detector, generate an ion flow, and convert it into a current signal; A weak current analysis module, used for performing weak current analysis based on the current signal, comparing it with the standard gas concentration-standard gas response signal relationship, and fitting to establish a concentration-signal relationship; A real-time concentration generating module, used for extracting the real-time gas to be tested for passing through the gas chromatograph and the hydrogen flame ionization detector, and generating the real-time concentration in combination with the concentration-signal relationship; The real-time concentration output module is used to output the real-time concentration through a monitoring interface.

2. A method for continuous monitoring of exhaust gas non-methane total hydrocarbon emissions as claimed in claim 1, characterized in that: The separation component determination module comprises: A heating evaporation unit, used for identifying the components of the gas to be tested through an air inlet, heating and evaporating non-gaseous components according to a preset heating temperature until the non-gaseous components are completely converted into gaseous components, thereby obtaining a sample gas, wherein the air inlet is connected to the gas chromatograph; An injection volume obtaining unit, used to calculate the amount of separated components per unit time according to the chromatographic column capacity of the chromatographic column in the gas chromatograph to obtain the injection volume; A sample gas injection unit is used to inject the sample gas into the gas chromatograph with the injection volume.

3. A method for continuous monitoring of exhaust gas non-methane total hydrocarbon emissions as claimed in claim 2, characterized in that: The separation component determination module comprises: A retention time calculation unit, used to calculate the interaction time to obtain the retention time through the interaction between the chromatographic column and the sample gas; The gas component quantification unit is used to identify the gas components in the sample gas according to the retention time to obtain separated components, wherein the gas component quantification is performed based on the response signal of the detector to obtain the component concentration and associate it with the separated component.

4. A method for continuous monitoring of exhaust gas non-methane total hydrocarbon emissions as claimed in claim 1, characterized in that: The weak current analysis module comprises: A current signal identification unit, used to identify the current signal based on a weak current signal threshold to obtain a weak current signal; A first weak current signal extraction unit, used to extract a first weak current signal according to the weak current signal; A first gain current signal obtaining unit, used for performing signal enhancement and noise suppression on the first weak current signal to obtain a first gain current signal; A first weak concentration generating unit, used for calculating the ratio of the first gain current signal to the relationship between the standard gas concentration and the standard gas response signal, to generate a first weak concentration; A weak concentration obtaining unit, configured to calculate the concentration by traversing the weak current signal with the first weak concentration until the Nth weak concentration, and obtain N weak concentrations; The polynomial fitting unit is used to perform polynomial fitting according to the proportionality coefficients of the N weak current signals and the N weak concentrations to establish the concentration-signal relationship.

5. A method for continuous monitoring of exhaust gas non-methane total hydrocarbon emissions as claimed in claim 4, characterized in that: The weak current analysis module comprises: A proportionality coefficient division unit, used to divide the proportionality coefficient into a training set and a validation set, wherein the training set is used to train the model framework of the concentration-signal relationship, and the validation set is used to validate the model framework of the concentration-signal relationship and output a predicted value; A mean absolute error calculation unit, used to calculate the mean absolute error between the predicted value and the true value in the training set; The proportionality coefficient adjustment unit is used to evaluate the prediction accuracy of the model framework of the concentration-signal relationship in combination with the error range with the mean absolute error, and to adjust the proportionality coefficient through the evaluation coefficient to obtain the concentration-signal relationship.

6. A method for continuous monitoring of exhaust gas non-methane total hydrocarbon emissions as claimed in claim 5, characterized in that: The weak current analysis module comprises: A real-time calibration response unit, used for introducing online standard gas through the hydrogen flame ionization detector to perform real-time calibration response; An offset calculation unit, used for calculating the offset of the relationship between the online standard gas and the standard gas concentration-standard gas response signal based on the triggering of the real-time calibration response; An incremental calibration unit, used for performing incremental calibration on the concentration-signal relationship with the offset to obtain a locally optimized concentration-signal relationship; A relationship fusion unit is used to fuse the locally optimized concentration-signal relationship into the concentration-signal relationship.

7. A method for continuous monitoring of exhaust gas non-methane total hydrocarbon emissions as claimed in claim 1, characterized in that: The real-time concentration output module comprises: A real-time trend graph generating unit, used for generating a real-time trend graph of the real-time concentration according to the monitoring interface; A safety concentration threshold setting unit, used to set an environmental protection concentration threshold according to an environmental protection standard and to set a safety concentration threshold based on a safety range; A real-time trend graph recognition unit, configured to generate a first warning by recognizing the real-time trend graph through the environmental protection concentration threshold, and generate a second warning by recognizing the real-time trend graph through the safety concentration threshold; An early warning output unit is used to output the first early warning and the second early warning respectively through the monitoring interface.

8. A method for continuous monitoring of exhaust gas non-methane total hydrocarbon emissions, characterized in that: The method is applied to any one of the exhaust gas non-methane total hydrocarbon emission continuous monitoring systems according to claims 1-7, and the method comprises: Connect the collection device to extract the gas to be tested from the exhaust gas source; Injecting the gas to be tested into a gas chromatograph for gas chromatography separation to determine the separated components; The separated components are detected by a hydrogen flame ionization detector when they flow out of the gas chromatograph to generate an ion flow, which is converted into a current signal; Performing weak current analysis based on the current signal, comparing it with the standard gas concentration-standard gas response signal relationship, and fitting to establish a concentration-signal relationship; Extracting real-time gas to be tested for passing through the gas chromatograph and the hydrogen flame ionization detector, and generating real-time concentration in combination with the concentration-signal relationship; The real-time concentration is output through a monitoring interface.

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