Synchronous treatment system and method for low-concentration N2O and CH4

Abstract

The invention discloses a synchronous treatment system and method for low-concentration N2O and CH4, and the method realizes efficient degradation of low-concentration N2O and CH4 through the technical links of collection, pretreatment, dynamic regulation and control of incineration, online monitoring, carbon accounting and the like of odor containing N2O and CH4 in municipal facilities, thereby achieving the purposes of reducing greenhouse gas emission and realizing carbon emission reduction. According to the specific scheme, the system comprises an odor collection system, an odor pretreatment unit, an incineration air volume dynamic regulation and control system, a staged combustion system, an online monitoring system and a carbon accounting module based on a database. Compared with the prior art, through the incineration dynamic regulation and control and staged combustion technology, the combustion efficiency is guaranteed, thorough oxidation of greenhouse gases N2O and CH4 can be achieved under the low-concentration condition, a carbon emission reduction accounting method is provided, and data support can be provided for carbon emission permit trading or policy evaluation.

Description

Technical Field

[0001] The present invention relates to the technical field of greenhouse gas treatment and carbon emission reduction, and in particular to a method for synchronously removing low-concentration N2O and CH4 from the odor of municipal or chemical facilities, as well as the supporting online carbon emission accounting technology, belonging to the cross technical field of environmental governance and energy conservation and emission reduction. Background Art

[0002] With the increasingly severe global climate change problem, the emissions of greenhouse gases have attracted wide attention. Among them, nitrous oxide (N2O) and methane (CH4), as potent greenhouse gases, have greenhouse effects 273 and 27 times that of carbon dioxide respectively on a 100-year time scale. Especially in the fields of chemical industry, municipal administration, agriculture and waste treatment, the problem of low-concentration but large-flow N2O and CH4 fugitive emissions is particularly prominent, bringing huge challenges to the industry's carbon emission reduction and the goal of achieving carbon neutrality.

[0003] The existing methods for removing low-concentration N2O and CH4 mainly include combustion method, physical and chemical method and biological method. Although the combustion method has good effects in the treatment of high-concentration gases, when the gas concentration is low, due to reasons such as heat transfer and combustion stability, the removal efficiency is low and the cost is high; physical and chemical methods such as adsorption and absorption processes have large equipment investment and high operating costs, and are not suitable for large-scale low-concentration gas treatment; although the biological method shows certain potential at the laboratory stage, there are problems such as poor stability and limited treatment capacity in industrial promotion. Therefore, there is an urgent need for a new method with low cost, stability and suitable for removing large-flow low-concentration greenhouse gases.

[0004] In the existing patent literature, Patent CN111957719B provides a system and method for co-processing kitchen waste in a waste incineration plant. Incineration is only used for the treatment of the solid residue after the pressing of kitchen waste, and no greenhouse gas emission reduction effect is achieved. Patent CN111365715B provides a system and method for co-incinerating kitchen waste. This patent shares the odor suction system of incineration for odor treatment and does not pay attention to the emission reduction benefits of greenhouse gas removal. Although the above patents have proposed technical solutions for the co-processing of kitchen waste and domestic waste respectively, they have not been able to simultaneously achieve the synchronous removal of low-concentration greenhouse gases N2O and CH4 and accurate carbon emission accounting, which limits their application and promotion in the municipal and carbon emission reduction fields. Summary of the Invention

[0005] The object of the present invention is to overcome the problems existing in the above-mentioned prior art, such as low efficiency and high cost of removing low-concentration greenhouse gases and lack of accurate carbon emission reduction accounting, and to propose a method for synchronously removing low-concentration N2O and CH4 based on incineration cooperative technology.

[0006] The object of the present invention can be achieved by the following technical solutions:

[0007] As the first aspect of the present invention, there is provided a synchronous treatment system for low-concentration N2O and CH4, including, connected in sequence:

[0008] An odor collection system, which is connected to the enclosed space of the municipal facilities through a negative pressure pipeline to collect the odor containing low-concentration N2O and CH4;

[0009] An incineration air volume dynamic regulation system, including a PLC controller and a variable frequency fan; the incineration air volume dynamic regulation system adjusts the speed of the variable frequency fan through a feedforward-feedback composite proportional-integral-derivative control algorithm to dynamically regulate the mixing ratio of the odor and the primary air;

[0010] A staged combustion system, including a furnace and a secondary combustion chamber, and the dynamically regulated mixed gas enters the staged combustion system for staged combustion;

[0011] An on-line monitoring system, which is arranged in the incineration tail gas flue and is used to monitor the concentrations of N2O and CH4 and the tail gas flow rate in the incineration tail gas in real time.

[0012] As a preferred technical solution, an odor pretreatment system is arranged between the odor collection system and the incineration air volume dynamic regulation system, and the odor pretreatment system includes a cyclone dust removal device for purifying the collected odor.

[0013] As a preferred technical solution, the temperature of the furnace is controlled at 850-900 °C, and the temperature of the secondary combustion chamber is maintained above 900 °C.

[0014] As a preferred technical solution, a secondary air nozzle is arranged in the secondary combustion chamber to form a turbulent flow field during the combustion process, so that the residence time of the mixed gas in the secondary combustion chamber is greater than the set duration.

[0015] As a preferred technical solution, an FTIR spectrometer is installed in the incineration air volume dynamic regulation system to monitor the concentration data of N2O and CH4 at the front end of the odor;

[0016] The on-line monitoring system includes: an NDIR gas analyzer, which is installed in the incineration tail gas discharge chimney to monitor the concentration data of N2O and CH4 in the incineration tail gas; an ultrasonic flowmeter, which is installed in the incineration tail gas discharge chimney to monitor the tail gas flow rate data.

[0017] As a preferred technical solution, the treatment system is also configured with a carbon emission reduction accounting module, which includes a carbon accounting calculation unit and an emission factor database, and is respectively connected to the FTIR spectrometer and the on-line monitoring system in signal.

[0018] As a second aspect of the present invention, there is provided a method for synchronously treating low-concentration N2O and CH4 based on the above-mentioned synchronous treatment system for low-concentration N2O and CH4, characterized in that the steps include:

[0019] Collect the odor containing low-concentration N2O and CH4 by using an odor collection system;

[0020] After pretreatment, the odor enters the incineration air volume dynamic regulation system, and the concentration and flow data of N2O and CH4 in the odor before combustion are monitored in real time, and the rotational speed of the variable-frequency fan is adjusted by a feedforward-feedback composite proportional-integral-derivative control algorithm to dynamically regulate the mixing ratio of the odor and the primary air;

[0021] The mixed gas after dynamic regulation enters the staged combustion system for staged combustion, and at the same time, the air volume ejected from the secondary air nozzle is adjusted to form a turbulent flow field, so that the residence time of the mixed gas in the secondary combustion chamber reaches the set duration;

[0022] Monitor the concentrations of N2O and CH4 and the tail gas flow in the incineration tail gas in real time, and conduct carbon emission accounting.

[0023] As a preferred technical solution, the rotational speed of the variable-frequency fan is adjusted by a feedforward-feedback composite proportional-integral-derivative control algorithm as follows:

[0024] The feedforward control estimates the preliminary adjustment value of the fan frequency to reach the ideal mixing ratio based on the real-time concentration data of N2O and CH4 in the odor before combustion;

[0025] The feedback control is based on the deviation between the actual mixing ratio and the target mixing ratio range, and uses the PID algorithm to track the target mixing ratio range to obtain the fan frequency adjustment amount;

[0026] The final fan frequency adjustment value is obtained by combining the feedforward control and the feedback control output, and the rotational speed of the variable-frequency fan is adjusted in real time.

[0027] As a preferred technical solution, the preliminary adjustment value of the fan frequency is specifically calculated as follows:

[0028] Based on the concentration data of N2O and CH4 in the odor before combustion, the combustion chamber temperature and pressure, the fan frequency, the fan air volume, and the odor inlet air volume collected in real time, predict the N2O concentration and CH4 concentration in the tail gas emission in advance;

[0029] For the predicted N2O concentration and CH4 concentration in the tail gas emission, based on the empirical relationship model between the N2O and CH4 concentrations in the tail gas and the required air volume calibrated by experiments, obtain the additional air volume ΔQ;

[0030] Based on the additional air volume ΔQ, obtain the preliminary adjustment value of the fan frequency for the feedforward control part.

[0031] As an optimal technical solution, the carbon emission accounting is specifically as follows:

[0032] Obtain the concentration data of N2O and CH4 in the pre-combustion odor monitored by the FTIR spectrometer, the concentration data of N2O and CH4 in the incineration exhaust gas monitored by the NDIR gas analyzer, and the exhaust gas flow data monitored by the ultrasonic flowmeter;

[0033] Utilize the concentration and flow data of N2O and CH4 monitored in real time to calculate the mass flow rates of N2O and CH4 removed by incineration;

[0034] Convert the total amounts of N2O and CH4 removed during the treatment process into the corresponding carbon emission reduction amounts according to the emission factor database.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1) The present invention proposes a low-cost and highly efficient solution for synchronously removing low-concentration N2O and CH4 odors in municipal or industrial facilities. By centrally collecting the odors in the enclosed spaces of each municipal or industrial facility through a negative-pressure pipeline, and adopting the incineration dynamic regulation and staged combustion process, both the combustion efficiency is ensured, and the complete oxidation of greenhouse gases N2O and CH4 can be achieved under low-concentration conditions.

[0037] 2) The staged combustion system adopted by the present invention optimizes the oxidation and decomposition of greenhouse gases by forming a temperature difference between the furnace (850 - 900 °C) and the secondary combustion chamber (>900 °C). The furnace increases the gas temperature through preliminary combustion, while the secondary combustion chamber provides a higher temperature for the complete combustion of low-concentration greenhouse gases. At the same time, the secondary combustion chamber is specially equipped with secondary air nozzles to form a turbulent flow field, so that the residence time of the gas exceeds 2 seconds. Ensure that greenhouse gases such as N2O and CH4 are completely decomposed in a high-temperature environment, thereby improving the incineration efficiency and reducing the emission of greenhouse gases.

[0038] 3) The present invention proposes an intelligent regulation scheme for odor combustion. The system integrates a PLC controller, an FTIR spectrometer, and a variable-frequency fan. Based on the concentration of N2O and CH4 in the odor obtained by the FTIR spectrometer, the rotation speed of the variable-frequency fan is controlled by feedforward, and the given odor mixing ratio is tracked through feedback control. The intelligent regulation of the incineration air supply strategy is realized through a feedforward-feedback composite control loop and a PID algorithm. It can automatically adjust the blending ratio according to the changes in the concentrations of N2O and CH4 in the odor in real time, so that the combustion conditions are always in the best working condition, thereby ensuring that greenhouse gases are fully decomposed in the combustion chamber.

[0039] 4) In the feedforward part of the present invention, based on the real-time acquisition of the concentration data of N2O and CH4 in the pre-combustion odor, the combustion chamber temperature and pressure, the fan frequency, the fan air volume, and the odor inlet air volume, the N2O concentration in the exhaust gas is predicted in advance and CH4 concentration Thereby, an advance amount can be reserved for the air volume regulation of the fan, and the response speed of adjusting the mixing and incineration ratio of the odor can be improved; and based on the N2O concentration of the tail gas emissions predicted in advance and CH4 concentration The incineration control carried out can also avoid the problem of incomplete combustion of the tail gas.

[0040] 5) The present invention can also achieve high-precision on-line monitoring and carbon accounting. By configuring equipment such as NDIR gas analyzers and ultrasonic flow meters, the concentration changes of N2O and CH4 in the incineration tail gas are monitored in real time, and the dynamic calculation of the total emissions is realized in combination with the flow data. Based on the IPCC emission factor database, the carbon accounting module automatically generates an emission reduction report to meet the verification requirements of various domestic and foreign carbon emission reduction projects, providing transparent and traceable carbon emission data support for municipal or chemical facilities.

[0041] 6) The solution of the present invention has a wide range of applications. The technology for synchronously removing low-concentration N2O and CH4 of the present invention is not only applicable to conventional scenarios in the municipal industry such as sewage treatment plants, leachate treatment plants, composting plants, and anaerobic digestion plants, but also applicable to the treatment of large-flow and low-concentration greenhouse gas emissions in other industries. For example, for some industrial facilities with large-scale greenhouse gas emissions, combined with the method of the present invention, the reduction of greenhouse gases can be effectively achieved. At the same time, the modular design of the system enables it to be seamlessly integrated with existing equipment, improving the removal efficiency of strong greenhouse effect gases and reducing the operating cost without having a significant impact on the existing facilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a schematic diagram of the system for synchronously removing low-concentration N2O and CH4 of the present application;

[0043] Figure 2 is a flowchart of the air volume regulation of the present application;

[0044] Figure 3 is a control block diagram of the feedforward-feedback composite PID control in the present application;

[0045] Figure 4 is an effect diagram of the N2O and CH4 emission reduction potential in an embodiment of the present application; 4a) is the N2O release rate of the tail gas of the odor collection system and the staged incineration system, and 4b) is the CH4 release rate of the tail gas of the odor collection system and the staged incineration system;

[0046] As shown by the reference numerals in the figure: 101, odor collection system; 102, odor pretreatment system; 103, cyclone dust removal device; 201, dynamic regulation system for incineration air volume; 202, PLC controller; 203, FTIR spectrometer; 204, variable-frequency fan; 301, staged combustion system; 302, furnace; 303, secondary combustion chamber; 401, online monitoring system; 402, NDIR gas analyzer; 403, ultrasonic flowmeter; 501, carbon accounting module; 502, carbon accounting calculation unit; 503, emission factor database. Specific embodiments

[0047] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and gives detailed implementation manners and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0048] Embodiment 1

[0049] The present invention proposes a system and method for synchronously combusting and removing low-concentration greenhouse gases N2O and CH4 based on dynamic regulation of the incineration air supply strategy for low-concentration greenhouse gases N2O and CH4 in municipal facilities. Figure 1 A system schematic block diagram is shown. The overall system is divided into the following modules: an odor collection system 101, an odor pretreatment system 102, a dynamic regulation system 201 for incineration air volume, a staged combustion system 301, an online monitoring system 401, and a carbon accounting module 501. The method is based on the suction head to dynamically adjust the air volume and the mixing ratio of the odor by real-time monitoring the concentrations of N2O and CH4 in the odor and combining with the working state of the combustion system. The staged combustion system synchronously removes N2O and CH4, and the online monitoring system provides greenhouse gas removal data for the carbon emission reduction accounting module.

[0050] During specific implementation, the odor collection system 101 realizes the centralized collection of odors by setting negative pressure pipelines in the enclosed spaces of municipal facilities (such as sewage treatment plants, anaerobic digestion plants, etc.) or chemical facilities. To ensure the high efficiency of odor collection, all pipelines and collection chambers are designed with anti-corrosion and anti-leakage, and flow rate and concentration monitoring sensors are arranged at appropriate positions on the pipelines to realize real-time monitoring of the parameters of the collected gas.

[0051] For the odor pretreatment system 102, to prevent large particle impurities from entering the subsequent combustion equipment, this unit adopts a cyclone dust removal device 103 to preliminarily purify the collected odor. The design of the dust removal device can effectively remove particles with a diameter greater than 50 μm, ensuring that the gas entering the incineration chamber has high uniformity and stability.

[0052] Such as Figure 2As shown in the figure, the dynamic regulation system 201 of the incineration air volume consists of a PLC controller 202, an FTIR spectrometer 203, and a variable-frequency fan 204. The system collects the concentration data of N2O and CH4 in the odor gas in real time through a feedforward-feedback composite control loop, and uses the PID algorithm to regulate the fan speed to ensure that the mixing ratio of the odor gas and the primary air is maintained between 15% and 55%, thereby providing ideal intake conditions for subsequent combustion. Through this intelligent regulation, it can ensure that under different operating conditions, the combustion process is always in the best working condition, thus ensuring the efficient removal of low-concentration N2O and CH4.

[0053] During specific implementation, as Figure 3 shown, when the system is initialized, the PLC controller 202 pre-sets a series of key parameters, including the target mixing ratio range, various parameters of the PID algorithm (proportional coefficient K p , integral time constant T i , derivative time constant T d ), the frequency range of the variable-frequency fan 204 (minimum frequency f min and maximum frequency f max ), etc. The FTIR spectrometer 203 monitors the concentration data of N2O and CH4 in the odor gas in real time. After being processed by the signal conditioning circuit, the digital signal is transmitted to the PLC controller 202 through the communication interface. After receiving these data, the PLC controller 202 processes the data using the feedforward-feedback composite control method.

[0054] Furthermore, the feedforward control part preliminarily estimates the initial adjustment value of the fan frequency required to achieve the ideal mixing ratio based on the concentration data of N2O and CH4 in the odor gas collected in real time.

[0055] Based on the concentration data of N2O and CH4 in the odor gas before combustion, the combustion chamber temperature and pressure, the fan frequency, the fan air volume, and the odor gas intake air volume collected in real time, predict the N2O concentration and CH4 concentration

[0056] Specifically, in this embodiment, in order to achieve the advance prediction of the incineration state and the concentrations of N2O and CH4 in the tail gas, the system introduces the Gradient Boosting Decision Tree (GBDT) algorithm. GBDT is an ensemble learning method based on decision trees. By gradually optimizing the loss function, multiple weak learners (decision trees) are constructed, and their prediction results are linearly superimposed to achieve accurate prediction of the tail gas concentration.

[0057] GBDT trains multiple decision trees through iterative training, and each tree attempts to correct the prediction error of the previous tree. Its prediction process can be expressed as:

[0058] F(X) = F m-1 (X) + γ m × h m (X)

[0059] Wherein, F(X) is the final predicted concentration of tail gas N2O and CH4, and F m-1 (X) represents the predicted value of the (m - 1)th iteration, and h m (X) represents the predicted value of the mth decision tree, and γ m represents the weight of the mth tree and is calculated by minimizing the loss function.

[0060] In each iteration, GBDT updates the model by optimizing the following loss function:

[0061]

[0062] Wherein, represents the L2 regularization term used to prevent overfitting, Y i is the true value of the ith sample, and F(X i ) represents the predicted value of the ith sample, and W represents the weight parameter of the model.

[0063] In the prediction of incineration gas concentration, the input features of the system include:

[0064]

[0065] Wherein, and are the inlet air N2O and CH4 concentrations of the odor collection pipeline, T and P are the combustion chamber temperature and pressure respectively, f is the fan frequency, Q is the fan air volume, and Q odor is the odor inlet air volume.

[0066] Then, through experiments and data analysis, the approximate linear relationship between the N2O concentration C N2O and CH4 concentration C CH4 in the tail gas and the required additional air volume ΔQ is obtained. The empirical relationship model between the N2O and CH4 concentrations and the required air volume can be expressed by the following formula:

[0067]

[0068] Wherein, k1 and k2 are proportionality coefficients obtained through experimental calibration, reflecting the influence degree of the changes in N2O and CH4 concentrations on the required additional air volume.

[0069] There is also a certain relationship between the fan frequency f and the air volume ΔQ. In a variable frequency speed regulation system, it is usually assumed that the air volume is approximately proportional to the rotational speed (frequency):

[0070] ΔQ = k3×(f - f0)

[0071] Wherein, k3 is a proportionality constant, and f0 is the initial frequency of the fan.

[0072] Therefore, the calculation formula for the initial adjustment value Δf of the fan frequency in the feedforward control part can be derived:

[0073]

[0074] On the other hand, the feedback control part tracks the deviation between the actual mixing ratio and the target range, and feeds the deviation information back to the PLC controller 202 as a feedback signal, and then uses the PID algorithm to calculate the frequency adjustment amount. The specific formula of the PID algorithm is:

[0075]

[0076] Wherein, u(t) represents the output frequency adjustment amount; e is the deviation value between the actual mixing ratio and the target range, and K P is the proportionality coefficient, T i is the integral time constant, and T d is the differential time constant.

[0077] The PLC controller 202 comprehensively considers the preliminary adjustment value of the feedforward control and the deviation signal obtained by feedback to obtain the final frequency adjustment amount. The PLC controller 202 generates a corresponding frequency command signal according to the result calculated by the feedforward-feedback, and sends this signal to the variable-frequency fan 204 through the frequency converter communication interface. This frequency command signal can prompt the variable-frequency fan 204 to automatically adjust the operating frequency within the specified range f min to f max thereby changing the fan speed and air supply volume, and realizing precise control of the mixing ratio of the odor and the primary air.

[0078] During the actual operation process, the PLC controller 202 continuously monitors the mixing ratio and the changes of various working conditions. Once it is found that the mixing ratio deviates from the target range, or there is a certain fluctuation during long-term operation, the PLC controller will automatically fine-tune and optimize the parameters of the PID algorithm to improve the control accuracy and stability of the system, and ensure that the system can always maintain the dynamic balance of the incineration air volume under different working conditions.

[0079] In addition, to ensure the reliable operation of the entire incineration air volume dynamic regulation system 201, the system also has a perfect fault handling and alarm function. The PLC controller 202 monitors the working status of the FTIR spectrometer 203, variable frequency fan 204 and various sensors in real time. Once a device fault or signal anomaly is detected, such as a sensor disconnection or fan fault, a mechanism will be triggered immediately. On the one hand, an alarm signal is sent through an audible and visual alarm; on the other hand, detailed fault information is uploaded to the upper computer monitoring system to facilitate maintenance personnel to quickly locate and solve problems.

[0080] The staged combustion system 301 adopts a two-stage combustion structure, equipped with a furnace 302 and a secondary combustion chamber 303. In the furnace 302, the mixed gas is preheated and undergoes preliminary combustion, with the temperature controlled between 850 and 900 °C; subsequently, the gas enters the secondary combustion chamber 303, where the temperature is maintained above 900 °C to ensure the complete decomposition of greenhouse gases such as N2O and CH4. At the same time, a secondary air nozzle 304 is set in the secondary combustion chamber 303 to form a uniform turbulent flow field with the secondary air, ensuring that the gas residence time exceeds 2 seconds, ensuring that greenhouse gases such as N2O and CH4 are completely decomposed in a high-temperature environment, thereby improving the incineration efficiency and reducing greenhouse gas emissions.

[0081] In order to grasp the combustion status and tail gas emission situation in real time, the on-line monitoring system 401 installs an NDIR gas analyzer 402 and an ultrasonic flowmeter 403 in the incineration tail gas flue 404. The system can realize the real-time monitoring of N2O, CH4 and other related pollutants in the tail gas. When the detected N2O decomposition rate is lower than 99%, the system will automatically trigger an audible and visual alarm and start emergency measures to reduce the odor mixing ratio to ensure that the tail gas emissions meet environmental protection requirements.

[0082] The carbon accounting module 501 relies on the IPCC emission factor database 503 to dynamically count and calculate the data collected by the on-line monitoring system 401 in the carbon accounting calculation unit 502, and automatically generate a carbon emission reduction report. This module not only provides data support for project declaration, but also can realize the tracking and management of long-term carbon emission reduction benefits. The carbon emission reduction accounting module 502 calculates the emissions based on the concentration and flow data of N2O and CH4 during the incineration process, and combines with the IPCC (Intergovernmental Panel on Climate Change) emission factor database 503 to calculate the emission reduction amount of greenhouse gases through real-time monitoring data. The emission reduction report generated by the carbon accounting module 501 meets the certification requirements of various domestic and foreign carbon emission reduction projects (such as Clean Development Mechanism CDM projects). The report data is transparent and traceable, meeting the requirements of environmental supervision and carbon trading.

[0083] The accuracy and real-time nature of this module enable municipal facilities to accurately evaluate their carbon emission reduction effects and provide data support for participation in the carbon market.

[0084] To ensure a stable and efficient combustion process of the odor gas mixed with the primary air under low-concentration conditions, the following incineration air supply strategy is adopted for dynamic regulation:

[0085] Step S1: Real-time acquisition of the demand for incineration primary air

[0086] The system uses the PLC controller 202 to achieve feedforward control. Based on the real-time acquired concentration data of N2O and CH4 in the odor gas before combustion, the preliminary adjustment value of the fan frequency required to achieve the ideal mixing ratio is estimated in advance.

[0087] Based on the real-time acquired concentration data of N2O and CH4 in the odor gas before combustion, the temperature and pressure of the combustion chamber, the fan frequency, the fan air volume, and the odor gas inlet air volume, the N2O concentration in the tail gas emission is predicted in advance and the CH4 concentration Then, through experiments and data analysis, the N2O concentration in the tail gas CH4 concentration The approximate linear relationship between the concentration of N2O and CH4 and the required additional air volume ΔQ, and the empirical relationship model between the concentration of N2O and CH4 and the required air volume can be expressed by the following formula:

[0088]

[0089] where k1 and k2 are proportionality coefficients obtained through experimental calibration, reflecting the influence degree of the change in the concentration of N2O and CH4 on the required additional air volume.

[0090] There is also a certain relationship between the fan frequency f and the air volume ΔQ. In the variable frequency speed regulation system, it is usually assumed that the air volume is approximately proportional to the rotational speed (frequency):

[0091] ΔQ = k3×(f - f0)

[0092] where k3 is a proportionality constant and f0 is the initial frequency of the fan.

[0093] Therefore, the calculation formula for the initial adjustment value Δf of the fan frequency in the feedforward control part can be deduced:

[0094]

[0095] At the same time, the secondary air nozzle adjusts the ejected air volume in real time, coordinates with the temperature regulation of the furnace chamber 302 and the secondary combustion chamber 303, forms a suitable turbulent flow field, and enables the mixed gas to achieve the optimal residence time in the combustion chamber.

[0096] Step S2: Feedback adjustment of incineration primary air

[0097] The system adjusts the speed of the variable-frequency fan 204 according to the real-time collected data through the PID control algorithm to ensure that the odor mixing ratio is always controlled between 15% and 55% of the primary air volume.

[0098] When the air volume exceeds the preset range, the system will activate the feedback control loop. By adjusting the frequency of the variable-frequency fan 204, precise control of the air volume is achieved to ensure the stability of the oxygen content and temperature in the combustion chamber. Specifically, the feedback control part tracks the deviation between the actual mixing ratio and the target range, and takes the deviation information as a feedback signal to the PLC controller 202. Subsequently, calculations are performed using the PID algorithm. The PLC controller 202 comprehensively considers the preliminary adjustment value of the feedforward control and the deviation signal obtained from the feedback to obtain the final frequency adjustment amount. The specific formula of the PID algorithm is:

[0099]

[0100] Step S3: Prediction of the concentrations of N2O and CH4 in the tail gas based on the Gradient Boosting Decision Tree (GBDT)

[0101] To achieve the advance prediction of the incineration state and the concentrations of N2O and CH4 in the tail gas, the Gradient Boosting Decision Tree (GBDT) algorithm is introduced into the system in this embodiment. GBDT is an ensemble learning method based on decision trees. By gradually optimizing the loss function, multiple weak learners (decision trees) are constructed, and their prediction results are linearly superimposed to achieve precise prediction of the tail gas concentration.

[0102] GBDT iteratively trains multiple decision trees, and each tree attempts to correct the prediction error of the previous tree. Its prediction process can be expressed as:

[0103] F(X) = F m-1 (X) + γ m ×h m (X)

[0104] where F(X) is the final predicted concentration of N2O and CH4 in the tail gas, F m-1 (X) represents the predicted value of the (m - 1)-th iteration, h m (X) represents the predicted value of the m-th decision tree, and γ m represents the weight of the m-th tree, which is calculated by minimizing the loss function.

[0105] In each iteration, GBDT updates the model by optimizing the following loss function:

[0106]

[0107] where, Represents the L2 regularization term, which is used to prevent overfitting, Y i is the true value of the i-th sample, F(X i ) represents the predicted value of the i-th sample, and W represents the weight parameters of the model.

[0108] In the prediction of incineration gas concentration, the input features of the system include:

[0109]

[0110] Among them, and are the inlet N2O and CH4 concentrations of the odor collection pipeline, T and P are the combustion chamber temperature and pressure respectively, f is the fan frequency, Q is the fan air volume, and Q odor is the odor inlet air volume.

[0111] When the gradient boosting decision tree predicts the incineration tail gas concentration, first preprocess and standardize the historical data set (such as N2O and CH4 concentrations, combustion chamber temperature and pressure, fan frequency, etc.). Then use the historical data to train the gradient boosting decision tree model, and adjust hyperparameters such as the maximum depth and learning rate of the decision tree to optimize the model prediction effect.

[0112] The present invention not only realizes the efficient incineration removal of greenhouse gases, but also accurately accounts for carbon emissions. The process is as follows:

[0113] Step S41: Odor collection data acquisition

[0114] Install an FTIR spectrometer and a gas flow probe on the odor collection pipeline to collect the concentration and flow data of greenhouse gases N2O and CH4 in the odor in real time.

[0115] The data is transmitted to the central control system after passing through the preprocessing module and used as an important basis for subsequent carbon accounting.

[0116] Step S42: Incineration tail gas data acquisition and accounting

[0117] The on-line monitoring system 401 monitors the N2O and CH4 concentrations in the incinerated gas in the tail gas flue and uses the ultrasonic flowmeter 403 to collect the gas emission flow rate.

[0118] The system compares the real-time data with the IPCC emission factor database 503, calculates the carbon emission reduction achieved by incineration removal using the carbon accounting module 501, and automatically generates a detailed emission reduction report, which can be used for carbon trading, project declaration or policy evaluation.

[0119] To ensure that the solution of the present invention achieves the best effect in practical applications, the following are the key process parameters and safety measures:

[0120] 1. Temperature control: Furnace temperature: 850 - 900 °C to ensure sufficient initial combustion of the gas; Secondary combustion chamber temperature: greater than 900 °C to ensure complete decomposition of greenhouse gases (N2O and CH4) under high-temperature conditions.

[0121] 2. Gas residence time: Use CFD numerical simulation to optimize the air duct structure of the combustion chamber to ensure that the gas residence time in the combustion chamber is greater than 2 seconds, thereby improving the combustion efficiency and the decomposition rates of N2O and CH4.

[0122] 3. Sensors and control system: The system uses high-precision NDIR and ultrasonic flowmeter 403 to achieve real-time monitoring of the combustion conditions and the exhaust gas emissions; when the on-line monitoring system 401 detects abnormal combustion (the decomposition rate of N2O is lower than the set value), the system automatically triggers the emergency response procedure to reduce the odor mixing ratio and ensure that the combustion process is always in a safe, stable and efficient state.

[0123] 4. Data storage and transmission: All on-line collected data are transmitted to the central control system through the industrial Ethernet and data backup is performed; the system has remote monitoring and alarm functions to ensure that maintenance personnel are notified in a timely manner in case of abnormalities and measures are taken to avoid incomplete combustion of greenhouse gases due to equipment failures.

[0124] Example 2

[0125] In this example, a scheme for the collaborative treatment of anaerobic digestion and incineration using the above method for synchronously removing low-concentration N2O and CH4 is provided. Taking a municipal food waste anaerobic digestion and domestic waste collaborative treatment plant as an example, the plant processes approximately 800 tons of food waste and approximately 3000 tons of domestic waste for incineration every day. Low-concentration N2O and CH4 are emitted during the processes of food waste storage, mechanical pretreatment, anaerobic digestion, digestate dewatering and biogas slurry advanced treatment. Using the technology of the present invention, the transformed facility realizes the synchronous removal of the strong greenhouse effect gases N2O and CH4 and carbon emission reduction accounting through the following steps:

[0126] Based on the existing odor collection system 101 inside the anaerobic digestion plant, it is connected to the odor collection pipeline, and the escaped gas is concentrated into the odor pretreatment system 102 through negative pressure suction.

[0127] After cyclone dust removal, the gas enters the incineration air volume dynamic regulation system 201, and the PLC controller 202 combines with the FTIR spectrometer 203 to perform real-time regulation on the variable frequency fan 204 to ensure a stable gas mixing ratio.

[0128] The mixed gas enters the staged combustion system 301, the furnace temperature is controlled at about 850 °C, the temperature of the secondary combustion chamber is increased to above 900 °C, and the secondary air nozzle 304 ensures the formation of turbulence, and the gas residence time in the combustion chamber exceeds 2 seconds.

[0129] The on-line monitoring system 401 collects the data of N2O and CH4 in the tail gas in real time and transmits it to the carbon accounting module 501. The system automatically generates daily, monthly and annual carbon emission reduction reports. The data is true and reliable, providing data support for subsequent carbon emission verification and the approval of environmental protection departments.

[0130] The implementation results are as Figure 4 shown, indicating that after the transformation, the greenhouse gas emissions of the anaerobic digestion plant have been significantly reduced, and the N2O decomposition rate has reached more than 99.9%. At the same time, the carbon emission reduction obtained through carbon accounting enables the enterprise to obtain corresponding carbon credit benefits in the future, providing an effective solution for the low-cost and long-term greenhouse gas treatment in the municipal industry.

[0131] Example 3

[0132] In this embodiment, a collaborative treatment solution for greenhouse gases in sewage and garbage is provided by using the above method for simultaneously removing low-concentration N2O and CH4. In an underground sewage treatment plant, due to the limitations of the production process and the closed environment, a large amount of low-concentration odors are generated, including greenhouse gases such as low-concentration N2O and CH4. The traditional process has limited treatment effect, resulting in a relatively prominent problem of greenhouse gas emissions. Therefore, in this embodiment, the technical solution of the present invention is adopted. The odors generated inside the sewage treatment plant are collected from each key process area (such as sedimentation tanks, aeration tanks and other closed spaces) through a set of airtight and corrosion-resistant negative pressure pipeline system and stably transported to a dedicated incineration plant on the ground. The negative pressure pipeline system is made of high molecular composite materials, with excellent corrosion resistance and compressive capacity. At the same time, flow and concentration sensors are configured at key nodes of the pipeline to realize real-time monitoring of the state of the transported odors, and the negative pressure state inside the pipeline is uniformly regulated by a dedicated transport control unit to ensure that the odor transport process is always in a stable state.

[0133] After entering the ground incineration plant, the odor first passes through the odor pretreatment system (102) set at the entrance of the plant area. The pretreatment unit uses a cyclone dust removal device 103 to preliminarily filter large particle impurities in the odor to remove solid particles with a diameter exceeding 50μm, and further reduces the impurity content through a preliminary filtration module, so as to ensure the stability and efficiency of the subsequent incineration process. The odor after pretreatment enters the incineration air volume dynamic regulation system 201. This system consists of a PLC controller 202, an FTIR spectrometer 203 and a variable frequency fan 204. The system collects the concentration data of N2O and CH4 in the odor in real time, calculates the optimal adjustment amount through the built-in PID algorithm, and then sends the adjustment signal to the variable frequency fan 204, so that the mixing ratio of the primary air and the odor is stably maintained between 15% and 55%, thus ensuring sufficient oxygen supply and uniform combustion in the incineration chamber.

[0134] After the odorous gas and air are dynamically regulated, they enter the staged combustion system 301. This system is designed with a two-stage combustion structure, where the temperature in the furnace 302 is controlled between 850 and 900 °C to complete the preliminary combustion and preheating. Subsequently, the combustion gas enters the secondary combustion chamber 303, where the temperature is maintained above 900 °C to achieve the deep combustion and complete decomposition of greenhouse gases. To improve the combustion efficiency, secondary air nozzles are specially configured in the secondary combustion chamber 303 to form a uniform turbulent flow field with secondary air, so that the residence time of the gas in the combustion chamber exceeds 2 seconds, ensuring that greenhouse gases such as N2O and CH4 are fully oxidized and decomposed in a high-temperature environment.

[0135] The real-time monitoring of the incineration process is completed by the on-line monitoring system 401 installed in the tail gas flue 404. This system is equipped with an NDIR gas analyzer 402 and an ultrasonic flowmeter 403 to achieve accurate measurement of the concentration and flow rate of greenhouse gases in the tail gas. The NDIR gas analyzer 402 can collect the concentration data of N2O and CH4 in real time, while the ultrasonic flowmeter 403 records the emission flow rate of the tail gas. When the detected N2O decomposition rate is lower than 99%, the system will automatically trigger an audible and visual alarm and start auxiliary measures. All the collected data is transmitted to the central control system through the industrial Ethernet to achieve real-time monitoring, storage and remote management of the data, providing data support for the dynamic regulation and fault warning of the system.

[0136] On this basis, the incineration plant is also equipped with a carbon emission reduction accounting module 501. This module combines the real-time monitoring data and the IPCC emission factor database 503, and uses the carbon accounting calculation unit 502 to automatically calculate the total amount of N2O and CH4 removed during the treatment process and convert it into the corresponding carbon emission reduction amount. The system can generate daily, monthly and annual carbon emission reduction reports in real time. These report data are transparent and traceable, which not only meet the requirements of carbon verification projects (such as CDM projects), but also provide reliable data support for the municipal carbon emission statistics. The entire system realizes the information interconnection between the underground sewage treatment plant and the ground incineration plant through the linkage control unit. When any abnormal situation (such as abnormal temperature, low N2O decomposition rate or air volume deviation from the preset range) is detected, the system will immediately adjust the parameters of the variable-frequency fan or start emergency combustion measures to ensure the safe, stable and efficient operation of the entire incineration process.

[0137] The components not detailed in this embodiment are all existing components that can be purchased from public channels.

[0138] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art shall fall within the protection scope determined by the claims.

Claims

1. A synchronous treatment system for low-concentration N2O and CH4, characterized in that, Comprising, connected in sequence: An odor collection system (101), connected to the enclosed space of the municipal facility through a negative pressure pipeline to collect the odor containing low-concentration N2O and CH4; An incineration air volume dynamic regulation system (201), including a PLC controller (202) and a variable-frequency fan (204); the incineration air volume dynamic regulation system (201) adjusts the rotation speed of the variable-frequency fan (204) through a feedforward-feedback composite proportional-integral-derivative control algorithm to dynamically regulate the mixing ratio of the odor and the primary air; A staged combustion system (301), including a furnace (302) and a secondary combustion chamber (303), and the mixed gas after dynamic regulation enters the staged combustion system (301) for staged combustion; An on-line monitoring system (401), arranged in the incineration tail gas flue, for real-time monitoring of the concentrations of N2O and CH4 and the tail gas flow rate in the incineration tail gas.

2. The synchronous treatment system for low-concentration N2O and CH4 according to claim 1, wherein, A odor pretreatment system (102) is arranged between the odor collection system (101) and the incineration air volume dynamic regulation system (201) of the treatment system, and the odor pretreatment system (102) includes a cyclone dust removal device (103) for purifying the collected odor.

3. The synchronous treatment system for low-concentration N2O and CH4 according to claim 1, wherein The temperature of the furnace (302) is controlled at 850 - 900 °C, and the temperature of the secondary combustion chamber (303) is maintained above 900 °C.

4. The synchronous treatment system for low-concentration N2O and CH4 according to claim 3, characterized in that, A secondary air nozzle (304) is arranged in the secondary combustion chamber (303) for forming a turbulent flow field during the combustion process, so that the residence time of the mixed gas in the secondary combustion chamber (303) is greater than the set duration.

5. The synchronous treatment system for low-concentration N2O and CH4 according to claim 1, wherein An FTIR spectrometer (203) is installed in the incineration air volume dynamic regulation system (201) for monitoring the concentration data of N2O and CH4 at the front end of the odor; The on-line monitoring system (401) includes: a NDIR gas analyzer (402), installed in the incineration tail gas emission chimney for monitoring the concentration data of N2O and CH4 in the incineration tail gas; an ultrasonic flowmeter (403), installed in the incineration tail gas emission chimney for monitoring the tail gas flow rate data.

6. The synchronous treatment system for low-concentration N2O and CH4 according to claim 5, wherein, The treatment system is also configured with a carbon emission reduction accounting module (501), and the carbon emission reduction accounting module (501) includes a carbon accounting calculation unit (502) and an emission factor database (503), and is respectively connected to the FTIR spectrometer (203) and the on-line monitoring system (401) by signals.

7. A method for synchronously treating low-concentration N2O and CH4 based on the synchronous treatment system of low-concentration N2O and CH4 as described in any one of claims 1-6, characterized in that the steps Including: Using the odor collection system (101) to collect the odor containing low-concentration N2O and CH4; After pretreatment, the odor enters the incineration air volume dynamic regulation system (201), and the concentration and flow rate data of N2O and CH4 in the odor before combustion are monitored in real time, and the rotation speed of the variable-frequency fan (204) is adjusted through a feedforward-feedback composite proportional-integral-derivative control algorithm to dynamically regulate the mixing ratio of the odor and the primary air; The mixed gas after dynamic regulation enters the staged combustion system (301) for staged combustion, and at the same time, the air volume sprayed by the secondary air nozzle (304) is adjusted to form a turbulent flow field, so that the residence time of the mixed gas in the secondary combustion chamber (303) reaches the set duration; Monitor the concentrations of N2O and CH4 and the exhaust gas flow rate in the incineration exhaust gas in real time, and conduct carbon emission accounting.

8. A method for synchronously treating low-concentration N2O and CH4 according to claim 7, characterized in that, Adjust the speed of the variable-frequency fan through the feedforward-feedback composite proportional-integral-derivative control algorithm as follows: The feedforward control is based on the real-time N2O and CH4 concentration data of the odor before combustion, and estimates the preliminary adjustment value of the fan frequency to reach the ideal mixing ratio. The feedback control is based on the deviation between the actual mixing ratio and the target mixing ratio range, and uses the PID algorithm to track the target mixing ratio range to obtain the fan frequency adjustment amount. Combine the output of the feedforward control and the feedback control to obtain the final fan frequency adjustment value, and adjust the speed of the variable-frequency fan (204) in real time.

9. A synchronous treatment method for low-concentration N2O and CH4 according to claim 7, characterized in that, The specific calculation of the preliminary fan frequency adjustment value is as follows: Based on the real-time collected concentration data of N2O and CH4 in the odor before combustion, the temperature and pressure in the combustion chamber, the fan frequency, the fan air volume, and the odor inlet air volume, predict the N2O concentration and CH4 concentration in the exhaust gas emission in advance. For the predicted N2O concentration and CH4 concentration in the exhaust gas emission, based on the empirical relationship model between the N2O and CH4 concentrations and the required air volume in the exhaust gas calibrated by experiments, obtain the additional air volume ΔQ. Obtain the preliminary fan frequency adjustment value of the feedforward control part based on the additional air volume ΔQ.

10. A synchronous treatment method for low-concentration N2O and CH4 according to claim 7, characterized in that, The specific carbon emission accounting is as follows: Obtain the concentration data of N2O and CH4 in the odor before combustion monitored by the FTIR spectrometer (203), the concentration data of N2O and CH4 in the incineration exhaust gas monitored by the NDIR gas analyzer (402), and the exhaust gas flow rate data monitored by the ultrasonic flowmeter (403). Use the real-time monitored N2O and CH4 concentration and flow rate data to calculate the mass flow rates of N2O and CH4 removed by incineration. Convert the total amounts of N2O and CH4 removed during the treatment process into the corresponding carbon emission reduction amounts according to the emission factor database (503).

Images