A waste incinerator pollutant control method based on multi-layer coupling temperature measurement technology

Abstract

This invention relates to waste incineration pollution control technology, aiming to provide a method for controlling pollutants in waste incinerators based on multi-layer coupled temperature measurement technology. The method includes: reconstructing a three-dimensional temperature field by fusing temperature data from thermocouple and acoustic temperature measurement units; monitoring temperature changes in the three-dimensional temperature field in real time using a DCS system; adjusting the combustion status of the waste incinerator using a PLC control system to optimize combustion efficiency and reduce pollutant emissions; and constructing a pollutant correlation prediction model using a recurrent neural network. The real-time acquired incinerator temperature and pollutant detection values ​​are input into the optimized prediction model, which calculates based on the current three-dimensional temperature field distribution, outputting predicted pollutant data and suggested PLC control parameters, thus achieving full-process control of pollutant emissions in flue gas. This invention improves the accuracy of temperature measurement and environmental adaptability within waste incinerators, achieving comprehensive temperature monitoring, feedback control, and trace pollutant emission reduction.

Description

Technical Field

[0001] This invention relates to the field of waste incineration pollution control technology, and in particular to a multi-layer temperature measurement and pollutant control method for waste incinerators that combines acoustic and thermocouple temperature measurement. Background Technology

[0002] With the acceleration of urbanization in human society, the amount of urban domestic waste has also increased rapidly. Waste incineration technology has become one of the mainstream methods for treating urban domestic waste due to its high volume reduction rate and considerable low-grade heat recovery efficiency. It has significant environmental and economic benefits, but it also poses great challenges to the stable and efficient operation of disposal facilities, especially incinerators.

[0003] In existing waste incineration technologies, accurate temperature measurement is crucial for ensuring incineration efficiency and environmental compliance. Currently, temperature monitoring in waste incinerators primarily relies on thermocouples and infrared thermography. While thermocouples offer high measurement accuracy, they are a contact-based method and cannot measure the high-temperature flue gas temperature in the central area. Furthermore, they are susceptible to damage and shortened lifespan due to the high temperatures and corrosive environment within the furnace. Infrared thermography, on the other hand, is prone to accuracy issues in dusty and smoky environments and cannot provide a comprehensive view of the temperature distribution within the furnace.

[0004] While existing coupled temperature measurement technologies can overcome some of the shortcomings of single temperature measurement methods, none can fully reflect the overall temperature distribution inside the furnace. For example, acoustic coupled flame image temperature measurement technology is limited by flame image temperature measurement technology, and can only measure the temperature distribution of the flame portion, and is greatly affected by flame radiation intensity and image noise; acoustic coupled infrared temperature measurement technology is limited by acoustic wave temperature measurement technology, and can only measure the temperature distribution of a single cross-section, and cannot fully overcome the influence of harsh working environments on infrared temperature measurement technology. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a pollutant control method for waste incinerators based on multi-layer coupled temperature measurement technology.

[0006] To solve the technical problem, the solution of the present invention is:

[0007] A method for controlling pollutants in a waste incinerator based on multi-layer coupled temperature measurement technology is provided, comprising the following steps:

[0008] (1) Multiple thermocouple temperature measurement units are arranged in the furnace and flue of the waste incinerator, and multiple acoustic temperature measurement units are arranged in the flue. These two types of temperature measurement units are used to obtain temperature data at key locations during the waste incineration process. Pollutant monitoring sensors are set at the end of the chimney to obtain real-time ambient pollutant concentration data.

[0009] (2) Preprocess the detected temperature data and pollutant data; reconstruct the three-dimensional temperature field by fusing the temperature data to achieve quantitative characterization of the temperature field distribution and combustion state in the incinerator in the DCS system;

[0010] (3) The temperature data changes in the three-dimensional temperature field are monitored in real time by the DCS system, and the combustion status of the waste incinerator is adjusted by the PLC control system to optimize combustion efficiency and reduce pollutant emissions.

[0011] (4) Construct a pollutant correlation prediction model using a recurrent neural network; use historical temperature data, pollutant data and PLC control parameters as training set to train the prediction model; input the real-time acquired incinerator temperature and pollutant detection values ​​into the optimized prediction model, calculate based on the current three-dimensional temperature field distribution, and output the predicted data of pollutants and the suggested values ​​of PLC control parameters to achieve full-process control of pollutant emissions in flue gas.

[0012] As a preferred embodiment of the present invention, in step (1), there are at least four sets of thermocouple temperature measuring units, which are arranged alternately in the grate, rear arch, first flue, and second flue of the waste incinerator to collect direct temperature information of the measuring points; there are at least four sets of acoustic temperature measuring units, which are arranged in a single layer at the high-temperature section of the first flue inlet of the waste incinerator to indirectly calculate temperature data by measuring the flight time of sound waves at the corresponding cross section; the data acquired by the pollutant monitoring sensor includes the concentrations of particulate matter, nitrogen oxides, sulfur dioxide, hydrogen chloride, and carbon monoxide.

[0013] As a preferred embodiment of the present invention, the preprocessing of temperature data and pollutant data in step (2) specifically includes: aligning all measurement data on the time axis through time synchronization processing; using digital signal processing technology to smooth and filter the data to eliminate noise and outliers in the data; and reconstructing the internal temperature distribution of the incinerator based on limited temperature measurement point data using inverse distance weighted interpolation or radial basis function interpolation.

[0014] As a preferred embodiment of the present invention, step (2) of the fusion processing to reconstruct the three-dimensional temperature field specifically includes: calculating the discrete temperature distribution data on each cross section in the main combustion zone of the incinerator, and using the temperature distribution values ​​of different temperature measurement planes to construct a three-dimensional temperature field; using the least squares method to minimize the sum of square errors between the measured and theoretical values ​​of the sound wave transit time of each path for all three-dimensional sound wave propagation paths in the flue; obtaining the distribution temperature matrix T by solving the canonical equation; and obtaining the regional temperature function T(x,y) by multiquadric radial basis function interpolation calculation, and finally realizing the reconstruction of the three-dimensional temperature field.

[0015] As a preferred embodiment of the present invention, step (3), adjusting the combustion status of the waste incinerator based on the PLC control system specifically includes:

[0016] When the average flame temperature of a certain zone of the grate is lower than the set minimum temperature, and the average temperature of the corresponding zone in the flue exceeds the set threshold, it is considered that the combustion condition is abnormal and the pollutant concentration will exceed the standard; when the temperature of the area near the flue wall measured by the acoustic temperature measurement unit exceeds the set threshold, and the average flame temperature of the corresponding zone of the grate is normal, it is judged that the wall has serious coking.

[0017] In response to the above-mentioned abnormal conditions, the DCS system issues control signals according to the preset control strategy, and adjusts the feeding and air distribution of the relevant actuators through the PLC control system to ensure that the combustion conditions in the furnace are always in the best state, thereby reducing the emission intensity of pollutants from the source of combustion and controlling the emission concentration of pollutants at the end in advance.

[0018] As a preferred embodiment of the present invention, in step (4), the pollutant association prediction model is a comparative model for multivariate data prediction, and a standard RNN, LSTM or GRU model is selected for construction.

[0019] The temperature data and pollutant concentration data at each marked point in the incinerator are processed to obtain the multivariate prediction input set A, the multivariate output set B, and the matrix dataset E, as shown in the following formula:

[0020]

[0021] In the formula: m is the number of data sets, x mn Temperature value of the nth marked point in the entire furnace; y mi Let i be the concentration value of the i-th pollutant;

[0022] By constructing training and testing sets using sufficient historical data, the design of the training model is optimized to determine the number of hidden layers and neurons, which are then used to predict pollutant concentration and to recommend appropriate PLC control parameters.

[0023] The present invention further provides a system for implementing the aforementioned method for controlling pollutants in a waste incinerator based on multi-layer coupling temperature measurement technology, characterized in that the system comprises:

[0024] Acoustic temperature measurement unit, thermocouple temperature measurement unit and pollutant monitoring sensor are used to acquire temperature data at key locations during waste incineration and data on the concentration of environmental pollutants in exhaust gas.

[0025] The data governance unit preprocesses the received data, fuses and processes the temperature data to reconstruct a three-dimensional temperature field and achieve quantitative characterization; it also constructs a pollutant correlation prediction model and trains the model using historical data.

[0026] The pollutant feedback control unit monitors temperature data changes in the three-dimensional temperature field in real time through the DCS system and adjusts the combustion status of the waste incinerator through the PLC control system; it calculates pollutant prediction data and PLC control parameter recommendations based on the pollutant correlation prediction model to control pollutant emissions in the flue gas throughout the entire process.

[0027] As a preferred embodiment of the present invention, the acoustic temperature measurement unit comprises at least four sets, each set including a heat insulation gasket, a dustproof net, an acoustic duct, a metal membrane, a soot blower, an acoustic temperature sensor, a connecting flange, and a data acquisition device; the axial direction of the acoustic duct forms a 45° angle with the vertical flow direction of the flue gas in the flue; the thermocouple temperature measurement unit comprises at least four sets, each set including a thermocouple probe, a high-temperature resistant sheath, a signal amplifier, an isolation protection tube, a connecting cable, and a data transmission interface.

[0028] As a preferred embodiment of the present invention, the pollutant feedback control unit includes an interface between a PLC control system and an action actuator, and is used to automatically adjust the combustion air ratio, waste feeding rate and combustion zone configuration in the incinerator based on temperature data changes and pollutant correlation prediction model calculation results.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] 1. This invention obtains the incinerator temperature field by coupling thermocouple temperature measurement data with an acoustic temperature measurement system and then fusion processing it. This improves the accuracy of temperature measurement and environmental adaptability in the waste incinerator, enables comprehensive temperature monitoring and feedback control, and achieves more accurate and reliable in-furnace temperature monitoring and trace pollutant emission reduction.

[0031] 2. This invention innovatively integrates temperature measurement and pollutant control, which not only provides high-precision temperature monitoring but also enables environmental feedback control based on real-time monitoring data, significantly improving the operating efficiency and environmental performance of waste incinerators. This invention will provide the waste incineration industry with an efficient, economical, and environmentally friendly solution. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of an acoustically coupled thermocouple temperature measurement system for a waste incinerator.

[0033] Figure 2 A thermal accuracy calibration diagram for acoustic temperature measurement of simulated flue gas from waste incineration.

[0034] Figure 3 This is a feature importance diagram for a temperature-based end-of-pipe pollutant emission prediction model for the waste incineration process.

[0035] Figure 4 The relative error diagram of the BLS prediction model for pollutant emissions at the end of waste incineration.

[0036] Figure 5 The graph shows the relative error of the LSTM prediction model for pollutant emissions at the end of waste incineration.

[0037] Figure 6 A schematic diagram illustrating the correlation and control methods for trace organic pollutant emissions during waste incineration. Detailed Implementation

[0038] First, it should be noted that this invention relates to computer technology, specifically its application in data processing and control. This technology is primarily used for temperature measurement and pollutant control in waste incinerators. By combining acoustic temperature measurement technology and thermocouple technology, the accuracy of temperature measurement and the reliability of the system are improved. The implementation of this invention involves the application of multiple software functional modules, including but not limited to data preprocessing modules and pollutant correlation prediction models. All modules mentioned in this application fall within this scope, and the applicant will not list them all. The applicant believes that those skilled in the art, after understanding the principles and objectives of this invention, can implement it using their software programming skills in conjunction with existing technology.

[0039] Part One: Implementation Scheme of the Invention

[0040] 1. This invention provides a method for controlling pollutants in a waste incinerator based on multi-layer coupled temperature measurement technology, comprising the following steps:

[0041] (1) Multiple thermocouple temperature measurement units are arranged in the furnace and flue of the waste incinerator, and multiple acoustic temperature measurement units are arranged in the flue. These two types of temperature measurement units are used to obtain temperature data at key locations during the waste incineration process. Pollutant monitoring sensors are set at the end of the chimney to obtain real-time ambient pollutant concentration data.

[0042] To accurately monitor temperature changes in key parts of the incinerator, at least four thermocouple temperature measurement units are arranged alternately in the grate, rear arch, first flue, and second flue of the waste incinerator to collect direct temperature information at the measurement points. At least four acoustic temperature measurement units are arranged in a single layer at the high-temperature section of the first flue inlet of the waste incinerator, indirectly calculating temperature data by measuring the transit time of sound waves at the corresponding cross-section. Pollutant monitoring sensors are used to acquire real-time environmental pollution data, including at least the concentrations of particulate matter, nitrogen oxides, sulfur dioxide, hydrogen chloride, and carbon monoxide.

[0043] (2) Preprocess the detected temperature data and pollutant data; reconstruct the three-dimensional temperature field by fusing the temperature data to achieve quantitative characterization of the temperature field distribution and combustion state in the incinerator in the DCS system;

[0044] The preprocessing of temperature and pollutant data specifically includes: aligning all measurement data on the time axis through time synchronization processing; using digital signal processing technology to smooth and filter the data, eliminating noise and outliers; and reconstructing the internal temperature distribution of the incinerator based on limited temperature measurement point data using inverse distance weighted interpolation or radial basis function interpolation.

[0045] The fusion processing for reconstructing the three-dimensional temperature field specifically includes: calculating the discrete temperature distribution data and constructing a three-dimensional temperature field using the temperature distribution values ​​of different temperature measurement sections; for all three-dimensional sound wave propagation paths, using the least squares method to minimize the sum of squared errors between the measured and theoretical values ​​of the sound wave transit time for each path; obtaining the distributed temperature matrix T by solving the canonical equation; and obtaining the regional temperature function T(x,y) through Multiquadric radial basis function interpolation, ultimately achieving the reconstruction of the three-dimensional temperature field.

[0046] (3) Real-time monitoring of temperature data changes in the three-dimensional temperature field using a DCS system, and adjustment of the combustion status of the waste incinerator through a PLC control system to optimize combustion efficiency and reduce pollutant emissions; specifically including:

[0047] When the average flame temperature of a certain zone in the grate is lower than the set minimum temperature, and the average temperature of the corresponding zone in the flue exceeds the set threshold, the combustion condition is considered abnormal, and the pollutant concentration will exceed the standard. When the temperature of the area near the flue wall measured by the acoustic temperature measurement unit exceeds the set threshold, and the average flame temperature of the corresponding zone in the grate is normal, it is judged that severe coking has occurred on the wall. For the above abnormal conditions, the DCS system issues a control signal according to the preset control strategy, and adjusts the feeding and air distribution through the PLC control system to ensure that the combustion conditions in the furnace are always in the best state, reduce the emission intensity of pollutants from the source of combustion, and control the emission concentration of pollutants at the end in advance.

[0048] (4) Construct a pollutant correlation prediction model using a recurrent neural network; use historical temperature data, pollutant data and PLC control parameters as training set to train the prediction model; input the real-time acquired incinerator temperature and pollutant detection values ​​into the optimized prediction model, calculate based on the current three-dimensional temperature field distribution, and output the predicted data of pollutants and the suggested values ​​of PLC control parameters to achieve full-process control of pollutant emissions in flue gas.

[0049] Pollutant association prediction models are comparative models for predicting multivariate data, and are built using standard RNN, LSTM or GRU models.

[0050] The temperature data and pollutant concentration data at each marked point in the incinerator are processed to obtain the multivariate prediction input set A, the multivariate output set B, and the matrix dataset E, as shown in the following formula:

[0051]

[0052] In the formula: m is the number of data sets, x mn Temperature value of the nth marked point in the entire furnace; y mi Let i be the concentration value of the i-th pollutant;

[0053] By constructing training and testing sets using sufficient historical data, the design of the training model is optimized to determine the number of hidden layers and neurons, which are then used to predict pollutant concentration and to recommend appropriate PLC control parameters.

[0054] 2. To achieve the above-mentioned pollutant control method for waste incinerators, the present invention further provides a pollutant control system for waste incinerators based on multi-layer coupled temperature measurement technology; the system includes:

[0055] An acoustic temperature measurement unit, a thermocouple temperature measurement unit, and a pollutant monitoring sensor are used to acquire temperature data at key locations during waste incineration and the concentration of cyclic pollutants in the exhaust gas. The acoustic temperature measurement unit comprises at least four sets, each including a heat-insulating gasket, a dustproof net, an acoustic duct, a metal diaphragm, a soot blower, an acoustic temperature sensor, a connecting flange, and a data acquisition unit. The axial direction of the acoustic duct forms a 45° angle with the vertical flow direction of the flue gas within the flue to cope with the positive pressure and temperature conduction of the incinerator flue gas during start-up, shutdown, and abnormal operating conditions. The thermocouple temperature measurement unit comprises at least four sets, each including a thermocouple probe, a high-temperature resistant sheath, a signal amplifier, an isolation protection tube, a connecting cable, and a data transmission interface.

[0056] (1) Acoustic temperature measurement unit

[0057] An acoustic temperature measurement unit is welded and installed on the outside of the flue, serving as a non-contact temperature measurement device. It emits sound waves of a specific frequency band driven inward by an electroacoustic source or compressed air source. The acoustic duct has only a partially exposed section inside the flue, with the rest of the main body located on the outside, ensuring the maintenance cycle and durability of the acoustic temperature measurement unit. To adapt to the complex operating conditions inside the furnace, the acoustic temperature measurement unit is designed with a titanium diaphragm and a specifically angled acoustic duct to resist high temperatures, dust, and chemical corrosion. Furthermore, the layout of the acoustic temperature measurement unit should consider the flow characteristics of the flue gas inside the furnace to ensure accurate data acquisition and transmission. The acoustic temperature measurement unit indirectly calculates temperature by measuring the travel time of the sound wave, based on the physical relationship between the speed of sound and the temperature of the medium. The propagation speed of sound waves is directly affected by the temperature of the medium; by accurately measuring the propagation time of sound waves in the waste incineration flue gas, the average temperature along that path can be calculated.

[0058] (2) Thermocouple temperature measurement unit

[0059] A thermocouple is a commonly used temperature sensor that measures temperature by utilizing the thermoelectric electromotive force generated at the contact point of two different metal materials when the temperature changes. In this invention, thermocouple temperature sensing units are strategically placed in key locations within the waste incinerator, such as the grate, rear arch, first and second flue outlets, and other areas with high heat loads. By combining point and area measurements, the highly dynamic and easily deployable point measurement capabilities of thermocouples can be used to calibrate and verify the regional average temperature obtained from the acoustic temperature sensing unit, thereby significantly improving the temperature measurement accuracy and reliability of the entire system. Furthermore, the real-time temperature data from the thermocouples provides direct support for optimizing combustion control strategies, reducing pollution emissions, and enhancing the system's responsiveness and control flexibility.

[0060] This invention utilizes a temperature measurement technology combining acoustic and thermocouple methods, offering the following advantages: (a) More comprehensive temperature monitoring. Acoustic temperature measurement provides a wider range of temperature distribution within the furnace, while thermocouples provide precise temperature at specific points. The combination enables comprehensive and accurate monitoring of the furnace temperature. (b) Higher temperature measurement stability and reliability. As a non-contact measurement method, acoustic temperature measurement is unaffected by high-temperature corrosion and can operate stably for extended periods. The data provided by thermocouples can be used for calibration, improving the overall accuracy of the temperature measurement system. (c) Enhanced environmental adaptability. The combined use allows for stable operation under varying environmental conditions, making it particularly suitable for dusty, high-temperature waste incinerator environments.

[0061] The applicant's preliminary research revealed a strong correlation between the end-of-pipe trace pollutant concentrations in waste incinerators and the waste incineration temperature field. Incineration temperature reflects the incineration state and directly affects the generation and decomposition rates of pollutants. Controlling appropriate incineration temperatures helps reduce the generation of certain pollutants; however, excessively low or high temperatures, as well as uneven temperature field distribution, may lead to incomplete decomposition of some toxic substances, thereby increasing emission concentrations. Therefore, timely adjustment of incinerator configuration based on temperature measurements is essential for controlling pollutant emissions.

[0062] (3) Data Governance Unit

[0063] The temperature and pollutant concentration data collected in this invention require preprocessing by a data preprocessing module, which can employ existing techniques. For example, time synchronization aligns all measurement data along the time axis; digital signal processing smooths and filters the data to eliminate noise and outliers; and inverse distance weighted interpolation or radial basis function interpolation reconstructs the internal temperature distribution of the incinerator based on limited temperature measurement data. Preliminary filtering removes potential background noise and biases; further advanced algorithms such as weighted averaging and least squares are used to synthesize a more accurate and comprehensive temperature distribution, fully leveraging the advantages of multi-dimensional temperature data sensing to compensate for the shortcomings of single technologies.

[0064] An example of reconstructing a three-dimensional temperature field is as follows: Discrete temperature data from thermocouples at various cross-sections within the main combustion zone of the incinerator are calculated, and the temperature distribution values ​​from different measurement planes are used to construct a three-dimensional temperature field. For all three-dimensional acoustic wave propagation paths in the flue, the least squares method is used to minimize the sum of squared errors between the measured and theoretical values ​​of the acoustic wave transit time for each path, solving the canonical equation to obtain the distributed temperature matrix T. Further, based on the obtained distributed temperature matrix T, the temperature function T(x,y) of the area to be measured is calculated using Multiquadric radial basis function interpolation, ultimately achieving the reconstruction of the three-dimensional temperature field. The reconstructed three-dimensional temperature field is then coupled with the DCS system and presented on a display device in the form of isotherm maps or thermograms. By calculating and comparing the average temperatures of the corresponding areas measured by acoustic wave temperature measurement and thermocouple temperature measurement, the combustion state is quantitatively characterized.

[0065] The data governance unit also includes a pollutant association prediction model. This model is a comparative model for multivariate data prediction and can be built using standard RNN, LSTM, or GRU models; alternatively, these models can be modified to suit the actual conditions of the waste incinerator. Historical temperature data, pollutant data, and PLC control parameters are used as the training set to train the model, optimize its parameter design, determine its hidden layers and the number of neurons, and then apply it to predictions during actual production processes.

[0066] (4) Pollutant feedback control unit

[0067] The pollutant feedback control unit utilizes a DCS system to monitor temperature data changes in a three-dimensional temperature field in real time, and adjusts the combustion status of the waste incinerator through a PLC control system. Based on a pollutant correlation prediction model, it calculates predicted pollutant data and suggested values ​​for PLC control parameters to control pollutant emissions throughout the entire process. The pollutant feedback control unit includes an interface between the PLC control system and the actuators, used to automatically adjust the combustion air ratio, waste feeding rate, and combustion zone configuration within the incinerator based on temperature data changes and the results of the pollutant correlation prediction model calculations.

[0068] This section represents the most significant innovative aspect of the invention: feedback control is achieved through real-time temperature and pollutant concentration monitoring data. Specifically, based on real-time data on temperature changes and pollutant emissions, combustion parameters within the furnace, such as air supply, waste feed rate, and combustion zone configuration, are adjusted in advance to optimize combustion efficiency and reduce harmful gas emissions. This includes two main parts:

[0069] Part 1 Operation: Monitor the temperature data changes in the three-dimensional temperature field in real time through the DCS system, and adjust the combustion status in the waste incinerator through the PLC control system.

[0070] For example, if the average flame temperature of a certain zone in the grate is lower than the set minimum temperature, and the average temperature of the corresponding zone in the flue exceeds the set threshold, the combustion condition is considered abnormal, and the pollutant concentration will exceed the standard. If the temperature of the area near the flue wall measured by the acoustic temperature measurement unit exceeds the set threshold, and the average flame temperature of the corresponding zone in the grate is normal, then severe coking is judged to have occurred on the wall. When the above abnormal conditions occur, the DCS system issues a control signal according to the preset control strategy, and the PLC control system automatically adjusts the relevant actuators, such as the feeding and primary air distribution mechanism, and the secondary air distribution mechanism, to ensure that the combustion conditions in the furnace are always in the optimal state, thereby reducing the emission intensity of pollutants from the source and proactively controlling the emission concentration of pollutants at the end.

[0071] The second part of the operation involves calculating pollutant prediction data and recommended values ​​for PLC control parameters based on the pollutant correlation prediction model, and controlling the entire process of pollutant emissions in flue gas.

[0072] The system acquires real-time temperature data and various pollutant concentration data at all marked points in the entire furnace. After preprocessing, these data are combined into a matrix dataset for input. After calculation by the prediction model, the system outputs predicted pollutant data and suggested values ​​for PLC control parameters to achieve full-process control of pollutant emissions in flue gas.

[0073] By innovatively integrating acoustic and thermocouple-based temperature measurement and pollutant control in waste incinerators, this invention not only provides high-precision temperature monitoring but also enables environmental feedback control based on real-time monitoring data, significantly improving the operational efficiency and environmental performance of waste incinerators. The implementation of this system will provide the waste incineration industry with an efficient, economical, and environmentally friendly solution.

[0074] Part Two: A Specific Implementation Case

[0075] The following case study is based on a waste incinerator modification plan for a waste incineration plant in Zhejiang Province, and related tests were conducted.

[0076] In this example, there are seven acoustic temperature measurement units 1, arranged in a single layer in the flue area at the furnace outlet of the waste incinerator to measure the sound wave travel time. The sensors in each acoustic temperature measurement unit form cross-correlated sound wave transmission paths with the sensors in other units. Each acoustic temperature measurement unit 1 consists of a heat-insulating gasket, a dustproof net, an acoustic duct, a metal diaphragm, a soot blower, an acoustic temperature sensor, a connecting flange, and a data acquisition unit. Specifically, the heat-insulating gasket is flush against the flue wall, and a dustproof net is installed between it and the conical acoustic duct for protection. The acoustic duct's axis is angled upwards at 45° to the direction of flue gas flow in the flue. It has an exposed section inside the flue, with soot blowers on both sides of this exposed section. All components are connected by fasteners. The transceiver acoustic temperature sensor is placed at the end of the acoustic duct to collect and transmit signals, which are then transmitted to the data processing unit via a signal cable. The acoustic temperature sensor is a commercially available product.

[0077] Thermocouple temperature measurement units 2 are deployed in multiple stages of the waste incinerator, including the grate, rear arch, and first and second flues. Each unit consists of a thermocouple probe, a high-temperature resistant sheath, a signal amplifier, an isolation protection tube, a connecting cable, and a data transmission interface. The thermocouple temperature measurement units provide accurate temperature data at each point, supplementing the regional temperature information provided by the acoustic temperature measurement units, together achieving comprehensive temperature monitoring.

[0078] The hardware of data governance unit 3 consists of a relay cabinet and a terminal server. The relay cabinet receives acoustic wave transit time data from the acoustic temperature measurement unit, raw temperature signals from thermocouples, and data from pollutant monitoring sensors, and transmits them to the terminal server located in the waste incinerator's electronics room. The terminal server runs an operating system, a software-implemented data preprocessing module, and a pollutant correlation prediction model. The terminal server is also connected to the DCS and PLC control systems via data cables to transmit various data and control signals. The collected temperature and pollutant data undergoes preliminary signal processing, data filtering and calibration, and temperature strong correlation coupling in the data preprocessing module; then it is transmitted to the pollutant correlation prediction model in the pollutant feedback control unit.

[0079] The data preprocessing process involves multi-level data processing, including but not limited to: I. Time synchronization processing: ensuring all measurement data are aligned on the time axis for accurate historical data analysis and future trend prediction. II. Data smoothing and filtering: applying digital signal processing techniques to filter out noise and outliers in the data, ensuring data quality and measurement accuracy. III. Spatial interpolation: using advanced interpolation methods such as inverse distance weighted interpolation and radial basis function interpolation to reconstruct the temperature distribution inside the entire furnace based on limited measurement point data.

[0080] The flight time and fitting error of associated gas components for measuring the acoustic temperature field inside a waste incinerator were obtained beforehand through a hot-state experiment using simulated incineration flue gas in the laboratory. By changing the H2O, particulate matter concentration, and flue gas velocity of the simulated incineration flue gas, and comparing and weighting the results with standard thermocouples, a universal temperature measurement model under different operating conditions can be obtained. Specific data from the applicant's hot-state simulation experimental platform are attached. Figure 2 As shown. According to the applicant's research and verification results, the main component of flue gas, H2O, has a relatively small impact on the temperature measurement accuracy (<10%). The analysis shows that its average error is about 5% in the low temperature range (10-100℃); as the temperature increases (100-300℃), the relative error of temperature measurement under different moisture conditions further decreases.

[0081] The pollutant feedback control unit 4 consists of a DCS system, a PLC control system, actuator interfaces (such as valves, fans, and waste grabbers), pollutant monitoring sensors, and a decision support module based on optimization algorithms. The main function of this unit is to adjust the incinerator's operating parameters in real time based on the comprehensive temperature information received from the data governance unit and the calculation results of the pollutant correlation prediction model, in order to optimize combustion efficiency and control pollutant emissions.

[0082] First, based on temperature data changes in the three-dimensional temperature field and the calculation results of the prediction model, the optimal combustion state can be calculated to guide the PLC system in real-time adjustments. Simultaneously, real-time reports and predictions of furnace temperature and pollutant emissions can be generated and updated, and displayed intuitively on the control room screen through the DCS system, providing decision support information for operators. This feedback mechanism can further improve thermal efficiency and reduce pollutant emissions by finely adjusting the excess air supply and waste feeding speed during the incineration process, ensuring compliance with emission standards.

[0083] In this example, an acoustically coupled thermocouple temperature measurement system was applied in the field based on the actual operation of a large grate incinerator. Measurements were taken from April to June 2024, with a 5-minute interval, resulting in a total of 14,397 datasets collected from the incineration system. 80% of the total dataset was used as the training set, and the remaining 20% ​​as the test set. To eliminate errors in the magnitude and distribution of input feature parameters, normalization and data cleaning were performed before importing the data into the model for training, converting it into a standardized unified dataset. Figure 3 As shown, the characteristic importance of the dioxin emission prediction model was analyzed based on the normalized weight matrix. The results showed that the characteristic importance of temperature in the measurement area was 17.4%. The concentrations of HCl, CO, and PM, the average temperature of thermocouples in the furnace, the outlet flue gas temperature of the bag filter, the primary air volume, the primary air temperature, the outlet flue gas temperature of the semi-dry process, and the residence time of high-temperature flue gas were all significantly important for the toxic equivalent concentration of PCDD / Fs at the end of incineration. The relative error distribution of the pollutant association prediction model constructed using a width learning system (BLS) and a long short-term memory neural network (LSTM) is shown in the attached figure. Figure 4 and Figure 5 As shown. Therefore, as Figure 6 As shown, based on the constructed multi-layer temperature measurement results, real-time monitoring and precise control of the incineration temperature field ensure a uniform temperature distribution within the furnace, preventing local temperatures from falling below 900℃, thus preventing precursor increases due to incineration deterioration, and curbing excessive residence of tail gas temperature within the de novo synthesis temperature range (200-400℃). Key attention is paid to conventional pollutant parameters such as CO, HCl, and PM concentrations. A pollutant correlation prediction model is used to continuously analyze and predict PCDD / Fs I-TEQ emission concentrations, forming a comprehensive control over flue gas pollutant emissions to ensure the environmental benefits and compliance of the waste incineration process.

Claims

1. A method for controlling pollutants in a waste incinerator based on multi-layer coupled temperature measurement technology, characterized in that, Includes the following steps: (1) Multiple thermocouple temperature measurement units are arranged in the furnace and flue of the waste incinerator, and multiple acoustic temperature measurement units are arranged in the flue. These two types of temperature measurement units are used to obtain temperature data at key locations during the waste incineration process. Pollutant monitoring sensors are set at the end of the chimney to obtain real-time ambient pollutant concentration data. (2) Preprocess the detected temperature data and pollutant data; reconstruct the three-dimensional temperature field by fusing the temperature data to achieve quantitative characterization of the temperature field distribution and combustion state in the incinerator in the DCS system; (3) The temperature data changes in the three-dimensional temperature field are monitored in real time by the DCS system, and the combustion status of the waste incinerator is adjusted by the PLC control system to optimize combustion efficiency and reduce pollutant emissions. (4) Construct a pollutant correlation prediction model using a recurrent neural network; use historical temperature data, pollutant data and PLC control parameters as training set to train the prediction model; input the real-time acquired incinerator temperature and pollutant detection values ​​into the optimized prediction model, calculate based on the current three-dimensional temperature field distribution, and output the predicted data of pollutants and the suggested values ​​of PLC control parameters to achieve full-process control of pollutant emissions in flue gas.

2. The method according to claim 1, characterized in that, In step (1), there are at least four sets of thermocouple temperature measuring units, which are arranged alternately in the grate, rear arch, first flue, and second flue of the waste incinerator to collect direct temperature information at the measurement points; there are at least four sets of acoustic temperature measuring units, which are arranged in a single layer at the high-temperature section of the first flue inlet of the waste incinerator to indirectly calculate temperature data by measuring the flight time of sound waves at the corresponding cross section; the data acquired by the pollutant monitoring sensor includes the concentrations of particulate matter, nitrogen oxides, sulfur dioxide, hydrogen chloride, and carbon monoxide.

3. The method according to claim 1, characterized in that, In step (2), the preprocessing of temperature data and pollutant data specifically includes: aligning all measurement data on the time axis through time synchronization processing; using digital signal processing technology to smooth and filter the data, eliminating noise and outliers in the data; and using inverse distance weighted interpolation or radial basis function interpolation to reconstruct the internal temperature distribution of the incinerator based on limited temperature measurement point data.

4. The method according to claim 1, characterized in that, In step (2), the fusion processing to reconstruct the three-dimensional temperature field specifically includes: calculating the discrete temperature distribution data on each cross section in the main combustion zone of the incinerator, and using the temperature distribution values ​​of different temperature measurement planes to construct a three-dimensional temperature field; using the least squares method to minimize the sum of square errors between the measured and theoretical values ​​of the sound wave transit time for all three-dimensional layers in the flue; obtaining the distribution temperature matrix T by solving the canonical equation; and obtaining the regional temperature function T(x,y) by multiquadric radial basis function interpolation, thus finally realizing the reconstruction of the three-dimensional temperature field.

5. The method according to claim 1, characterized in that, In step (3), adjusting the combustion status of the waste incinerator based on the PLC control system specifically includes: When the average flame temperature of a certain zone of the grate is lower than the set minimum temperature, and the average temperature of the corresponding zone in the flue exceeds the set threshold, it is considered that the combustion condition is abnormal and the pollutant concentration will exceed the standard; when the temperature of the area near the flue wall measured by the acoustic temperature measurement unit exceeds the set threshold, and the average flame temperature of the corresponding zone of the grate is normal, it is judged that the wall has serious coking. In response to the above-mentioned abnormal conditions, the DCS system issues control signals according to the preset control strategy, and adjusts the feeding and air distribution of the relevant actuators through the PLC control system to ensure that the combustion conditions in the furnace are always in the best state, thereby reducing the emission intensity of pollutants from the source of combustion and controlling the emission concentration of pollutants at the end in advance.

6. The method according to claim 1, characterized in that, In step (4), the pollutant association prediction model is a comparative model for multivariate data prediction, and standard RNN, LSTM or GRU models are selected for construction. The temperature data and pollutant concentration data at each marked point in the incinerator are processed to obtain the multivariate prediction input set A, the multivariate output set B, and the matrix dataset E, as shown in the following formula: In the formula: m is the number of data sets, x mn Temperature value of the nth marked point in the entire furnace; y mi Let i be the concentration value of the i-th pollutant; By constructing training and testing sets using sufficient historical data, the design of the training model is optimized to determine the number of hidden layers and neurons, which are then used to predict pollutant concentration and to recommend appropriate PLC control parameters.

7. A system for implementing the pollutant control method for a waste incinerator based on multi-layer coupled temperature measurement technology as described in claim 1, characterized in that, The system includes: Acoustic temperature measurement unit, thermocouple temperature measurement unit and pollutant monitoring sensor are used to acquire temperature data at key locations during waste incineration and data on the concentration of environmental pollutants in exhaust gas. The data governance unit preprocesses the received data, fuses and processes the temperature data to reconstruct a three-dimensional temperature field and achieve quantitative characterization; it also constructs a pollutant correlation prediction model and trains the model using historical data. The pollutant feedback control unit monitors temperature data changes in the three-dimensional temperature field in real time through the DCS system and adjusts the combustion status of the waste incinerator through the PLC control system; it calculates pollutant prediction data and PLC control parameter recommendations based on the pollutant correlation prediction model to control pollutant emissions in the flue gas throughout the entire process.

8. The system according to claim 7, characterized in that, The acoustic temperature measurement unit comprises at least four sets, each including a heat insulation gasket, a dustproof net, an acoustic duct, a metal diaphragm, a soot blower, an acoustic temperature sensor, a connecting flange, and a data acquisition unit; the axial direction of the acoustic duct forms a 45° angle with the vertical flow direction of the flue gas in the flue; the thermocouple temperature measurement unit comprises at least four sets, each including a thermocouple probe, a high-temperature resistant sheath, a signal amplifier, an isolation protection tube, a connecting cable, and a data transmission interface.

9. The system according to claim 7, wherein the pollutant feedback control unit includes an interface between a PLC control system and an actuator, and is used to automatically adjust the combustion air ratio, waste feeding rate and combustion zone configuration in the incinerator based on temperature data changes and pollutant correlation prediction model calculation results.

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