Flue gas denitration reaction process online monitoring method, system and device based on electron paramagnetic resonance

Abstract

The invention relates to the technical field of industrial flue gas treatment process monitoring and control, in particular to a flue gas denitration reaction process online monitoring method, system and device based on electron paramagnetic resonance, and aims to solve the problems of hysteresis of indirect monitoring and failure in diagnosis of fault root causes in the prior art. A high-temperature micro-reactor arranged in a flue is adopted as an external resonant cavity and is connected with a normal-temperature EPR detection unit arranged outside the flue through a waveguide, so that in-situ, online and direct monitoring on key free radical concentration and catalyst state in a denitration reaction process is realized. Through a multi-parameter fusion diagnosis method, EPR signals are converted into process parameters, intelligent diagnosis is carried out, and unprecedented process data support is provided for accurate control and fault early warning of a denitration system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial flue gas treatment process monitoring and control, and particularly relates to a flue gas denitration reaction process online monitoring method, system and device based on electron paramagnetic resonance. BACKGROUND

[0002] Currently, the operation monitoring of the flue gas denitration system mainly relies on the continuous emission monitoring system (CEMS) installed at the outlet of the reactor, which usually uses a NOx concentration analyzer of ultraviolet differential absorption spectroscopy (DOAS) technology. This scheme measures the NOx concentration value at the outlet and compares it with the set target value (such as the environmental protection emission limit value), and adjusts the ammonia injection amount through feedback control (such as a PID controller). This is an indirect and post-monitoring method, which cannot reflect the core chemical reaction process inside the reactor in real time. When the denitration efficiency decreases, it may be caused by catalyst poisoning, ammonia escape, temperature inappropriateness, insufficient generation of free radicals, etc., and the existing method is difficult to distinguish, and cannot provide direct process parameter guidance for precise ammonia injection, temperature control, etc.

[0003] In the flue gas denitration process, NH3 and NOx react to generate N2 and H2O under high temperature conditions or on the surface of the catalyst, and this process is accompanied by the generation and consumption of free radicals such as amino radical (·NH2), hydroxyl radical (·OH), and oxygen radical (·O). The concentration of these free radicals directly affects the denitration reaction efficiency; at the same time, the change of the valence state and coordination environment of the SCR catalyst can lead to the change of the catalytic efficiency. The electron paramagnetic resonance (EPR) technology is a direct method for directly detecting substances with unpaired electrons. Therefore, in the laboratory-level flue gas denitration reaction research, EPR can be used to detect and identify the key free radical intermediates (such as ·NH2, ·OH, etc.) generated in the reaction process, so as to reveal the reaction path; it can also be used to monitor the valence state, coordination environment and change rule of the active components (such as vanadium V 4+ , manganese Mn 2+ , copper Cu 2+ , etc.) in the SCR catalyst.

[0004] However, the current EPR spectrometer is a laboratory equipment, which is complex to operate and has poor environmental adaptability, and its sample processing method is offline and batch type, that is, the free radicals in the sample are first captured or frozen by a certain method, and then measured in the resonance cavity. EPR technology has never been successfully applied to online process monitoring in industrial sites, the main reasons are: Poor environmental adaptability: laboratory EPR equipment cannot be installed in the industrial site with complex vibration and electromagnetic interference; Sampling causes distortion: if the flue gas is introduced out and cooled to room temperature for EPR detection by traditional sampling method, the extremely active free radicals will be quenched before entering the detection chamber due to temperature change and contact with the pipe wall, etc., so that the true concentration cannot be measured. For catalysts, offline sampling will change their state in the actual reaction environment (such as re-oxidation), so that the laboratory measurement results cannot truly reflect the state of the running catalyst; Cannot withstand high temperature: the core component of EPR, the resonant cavity, is usually made of copper or other metals, which cannot withstand the high-temperature flue gas environment of SCR (260-400℃) or SNCR (850-1100℃) for a long time, resulting in component failure and inability to detect. SUMMARY

[0005] The purpose of the present application is to overcome the above-mentioned shortcomings of the prior art, and to provide a flue gas denitration reaction process in-situ online monitoring method, system and device based on electron paramagnetic resonance (EPR) technology. The scheme aims to realize direct, in-situ and online monitoring of the denitration reaction core intermediate (free radical) and catalyst state, change from "result monitoring" to "process monitoring", and overcome the limitations of EPR technology in high-temperature and high-dust industrial environments, to provide direct and advanced process parameter data support for fault early warning, root cause diagnosis and precise optimization control of the denitration system.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is: In a first aspect, the present application provides a flue gas denitration reaction process real-time monitoring method based on electron paramagnetic resonance, comprising the following steps: S1. In-situ sampling and environment maintenance step: make part of the flue gas continuously flow through a high-temperature-resistant cavity placed inside the flue duct, and control the environment in the cavity to be consistent with the main flue reaction environment; S2. In-situ EPR detection step: apply a static magnetic field and a microwave field to the cavity through an EPR detection unit placed outside the flue duct; S3. Resonance signal acquisition step: detect the EPR resonance signal generated by paramagnetic substances in the flue gas flowing through the cavity; S4. Signal processing and parameter extraction step: convert the EPR signal into at least one process parameter reflecting the denitration reaction progress, the process parameter including gas-phase free radical concentration and / or catalyst active center valence state information; S5. State diagnosis and control output step: based on the process parameters, diagnose the denitration reaction state in real time and generate control instructions or warning information.

[0007] Preferably, in the S1 step, the temperature inside the cavity is tracked to the actual temperature of the main flue gas by dynamic temperature tracking control through the heating insulation layer and temperature sensor arranged outside the cavity.

[0008] Preferably, the process parameters in the S4 step include the concentration of gas phase radicals and / or the information of valence state and coordination environment of paramagnetic active centers in the SCR catalyst.

[0009] Preferably, the S5 state diagnosis step includes diagnosing the root cause of the fault of the denitration system by analyzing the change trend of different process parameters and / or the correlation therebetween.

[0010] In the second aspect, the present application provides a device for in-situ online monitoring of a flue gas denitration reaction process, comprising a high-temperature micro-reactor unit and a normal-temperature EPR detection unit, wherein the high-temperature micro-reactor unit and the normal-temperature EPR detection unit are arranged inside and outside the flue, respectively. The high-temperature micro-reactor unit comprises a cavity, both ends of the cavity are provided with microwave suppression structures, both ends of the cavity are also provided with gas inlets and outlets in communication with the microwave suppression structures, flanges are connected between the gas inlets and outlets and the flue, a microwave penetration window is arranged on the side wall of the cavity, the cavity is wrapped by a heating insulation layer, and a temperature sensor is arranged between the surface of the heating insulation layer and the outside of the cavity.

[0011] The normal-temperature EPR detection unit comprises a main magnet system, a microwave system and a waveguide, wherein the main magnet system and the microwave system are arranged on one side of the flue, and the waveguide is connected to the microwave penetration window perpendicularly from the side of the cavity.

[0012] Preferably, an auxiliary system is arranged between the microwave system and the microwave penetration window, wherein the auxiliary system comprises a cooling system and a control and data processing system, and the cooling system is a cooling jacket and is sleeved on the surface of the waveguide.

[0013] Preferably, a gas curtain protection system is arranged on one side of the microwave penetration window.

[0014] Preferably, the control and data processing system is connected to the temperature sensor, the main magnet system, the microwave system and the waveguide through wires.

[0015] Preferably, a catalyst module is arranged inside the cavity.

[0016] In the third aspect, the present application provides a real-time monitoring system for a flue gas denitration reaction process, comprising the device according to any one of the second aspect, which is configured to execute the method according to any one of the first aspect.

[0017] Compared with the prior art, the present application has the following beneficial effects: The scheme is directly from the flue gas in the flue, measures the concentration of reaction intermediates (free radicals) and catalyst state, has no transmission lag, overcomes the lag of the prior art indirect monitoring, realizes the fundamental change from "black box monitoring" to "white box insight", realizes the direct, in-situ and online monitoring of the denitration reaction process.

[0018] The scheme adopts "physical separation and synergistic thermal management" design, actively insulates the metal cavity by using a heating insulation layer, makes it resistant to high temperature flue gas, sets a cooling system on the EPR side of the microwave transmission window, realizes heat isolation and microwave transmission through the microwave transmission window, ensures the stable and reliable operation of the device in high temperature environment, and solves the problem that the EPR technology cannot be applied to industrial high temperature environment.

[0019] The scheme realizes predictive maintenance and precise control by correlating and analyzing the directly monitored reaction core parameters, and realizes the real-time insight and intelligent diagnosis of the "white box" of the denitration reaction process. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a front view of a device for in-situ online monitoring of a flue gas denitration reaction process according to the present application; Figure 2 It is a top view of a device for in-situ online monitoring of a flue gas denitration reaction process according to the present application; Figure 3 It is a left view of a device for in-situ online monitoring of a flue gas denitration reaction process according to the present application; Figure 4 It is a front view of a high-temperature micro-reactor unit according to the present application; Figure 5 It is a top view of a high-temperature micro-reactor unit according to the present application; Figure 6 It is a left view of a high-temperature micro-reactor unit according to the present application; Figure 7 It is a flow chart of a real-time monitoring method for a flue gas denitration reaction process based on electron paramagnetic resonance according to the present application.

[0021] In the figure: flue 1, high-temperature micro-reactor unit 100, cavity 101, microwave suppression structure 102, gas inlet and outlet 103, microwave penetration window 104, heating and insulation layer 105, temperature sensor 106, catalyst module 107, flange 108, gas curtain protection system 109, normal-temperature EPR detection unit 200, main magnet system 201, microwave system 202, waveguide 203, auxiliary system 300, cooling system 301, control and data processing system 302. DETAILED DESCRIPTION

[0022] The following description is used to disclose the present application so that those skilled in the art can implement the present application. The preferred embodiments in the following description are only as examples, and other obvious modifications can be thought of by those skilled in the art.

[0023] As shown in Figures 1-6 A device for in-situ online monitoring of flue gas denitration reaction process, comprising a high-temperature micro-reactor unit 100 and a normal-temperature EPR detection unit 200, the high-temperature micro-reactor unit 100 and the normal-temperature EPR detection unit 200 are arranged inside and outside the flue 1 respectively. The high-temperature micro-reactor unit 1 comprises a cavity 101, which is a straight pipe structure made of high-temperature resistant alloy or ceramic, fixed to the flue wall through a flange 108, forming a flow-through reaction pool, and constituting a high-quality factor resonant cavity at the working frequency. Its inner diameter is 150 mm, length is 340 mm, and effective volume is about 6.0 L. This volume is optimized to ensure that the residence time of flue gas in the cavity is about 2 s.

[0024] Microwave suppression structures 102 are arranged at both ends of the cavity 101, which are cut-off waveguide arrays, realizing the dual functions of microwave shielding and airflow passing. The array is composed of micro-pipes with an inner diameter of 3 mm and a length of 30 mm in a triangular close-packed manner, which can effectively reflect microwaves (attenuation > 60 dB) and allow flue gas to pass at a flow rate of 2-5 L / s. The cut-off waveguide array used in the microwave suppression structure 102 can physically block most dust; the gas curtain protection system 109 can actively prevent dust from contacting and adhering to the window surface, solving the problem of probe window contamination and failure, greatly extending the maintenance period, and enabling long-term stable operation in high-dust flue gas environment.

[0025] Gas inlets and outlets 103 are also provided at both ends of the cavity 101, which communicate with the microwave suppression structures 102. The combination of the gas inlets and outlets 103 and 102 ensures the continuous flow of flue gas under pressure difference driving, while maintaining the cavity resonance condition.

[0026] The flanges 108 are connected between the microwave suppression structure gas inlets and outlets 103 and the flue 1, which are used to fix and seal the entire unit on the flue wall.

[0027] The side wall of the cavity 101 is provided with a microwave transmission window 104 made of sapphire or quartz glass as a transmission channel of microwaves.

[0028] The outer part of the cavity 101 is wrapped by a heating insulation layer 105, and a temperature sensor 106 is arranged between the surface of the heating insulation layer 105 and the outer part of the cavity 101. The temperature sensor 106 ensures that the temperature inside the cavity strictly tracks the actual temperature of the main flue in the range of 200-1000℃ by dynamically compensating for heat loss, and the temperature control accuracy is ±2℃. The heating insulation layer 105 reduces the emission of heat in the cavity 101, and the dynamic compensation for heat loss and the flow design of the cavity 101 enable the cavity 101 to dynamically track the real flue gas temperature, and the flue gas is continuously updated under pressure difference, ensuring that the gas in the cavity is consistent with the main flue gas, avoiding errors introduced by the measurement device itself, and ensuring the authenticity and representativeness of the measurement data.

[0029] The normal temperature EPR detection unit 200 includes a main magnet system 201, a microwave system 202 and a waveguide 203. The main magnet system 101 adopts a C-shaped or U-shaped water-cooled electromagnet design, and the pole distance is determined according to the flue width. A stable static magnetic field with a strength not less than 0.35T, a uniformity better than 10 -4 and a coverage diameter not less than 150mm can be generated in the central area of the poles. The main magnet system 201 and the microwave system 202 are arranged outside the flue 1, and the waveguide 203 is connected to the microwave transmission window 104 vertically from the side of the cavity 101. According to the feedback of the temperature sensor 106, the control and data processing system 302 dynamically controls the heating insulation layer 105, so that the internal temperature of the cavity of the high-temperature micro reactor 100 strictly tracks and maintains the actual reaction temperature of the main flue. At the same time, the flue gas continuously flows through the cavity under pressure difference; the control and data processing system 302 instructs the normal temperature EPR detection unit 200 to start, applies a static magnetic field through the main magnet system 201, generates a microwave of a specific frequency through the microwave system 202, and transmits the microwave through the waveguide 203, penetrates the microwave transmission window 104 and enters the cavity 101.

[0030] An auxiliary system 300 is arranged between the microwave system 202 and the microwave transmission window 104, and the auxiliary system 300 includes a cooling system 301 and a control and data processing system 302. The cooling system 301 is a cooling jacket and is sleeved on the surface of the waveguide 203.

[0031] One side of the microwave transmission window 104 is provided with an air curtain protection system 109, which blows a small amount of clean air to the outer surface of the microwave transmission window in the flue, with a gas consumption of 5-15 L / min, to form an air curtain to prevent dust and corrosion.

[0032] The control and data processing system 302 is connected to the temperature sensor 106, the main magnet system 201, the microwave system 202 and the waveguide 203 through wires. It is also connected to the gas curtain protection system 109 and the catalyst module 107 through wires.

[0033] The inside of the cavity 101 is provided with a catalyst module 107 for synchronous monitoring of the catalyst activity state.

[0034] As Figure 7 A flue gas denitration reaction process real-time monitoring method based on electron paramagnetic resonance is shown, which comprises the following steps: S1. In-situ sampling and environment maintaining step: part of the flue gas continuously flows through a high-temperature-resistant cavity 101 placed inside the flue, and dynamic temperature tracking control is performed through the heating insulation layer 105 and the temperature sensor 106 placed outside the cavity 101, so that the temperature inside the cavity 101 is consistent with the actual temperature environment of the main flue gas; S2. In-situ EPR detection step: through the EPR detection unit 200 placed outside the flue, a static magnetic field and a microwave field are applied to the cavity 101; S3. Resonance signal acquisition step: the EPR resonance signal generated by the paramagnetic substance in the flue gas flowing through the cavity 101 is detected; S4. Signal processing and parameter extraction step: the EPR signal is converted into at least one process parameter reflecting the denitration reaction process, the process parameters including the gas phase free radical concentration and / or the valence state information of the paramagnetic active center in the catalyst, the process parameters including the gas phase free radical concentration and / or the valence state and coordination environment information of the paramagnetic active center in the SCR catalyst; S5. State diagnosis and control output step: based on the process parameters, the denitration reaction state is diagnosed in real time and control instructions or warning information are generated, and by analyzing the change trend of different process parameters and / or the correlation between them, the root cause of the denitration system failure is diagnosed.

[0035] A flue gas denitration reaction process real-time monitoring system is configured by the monitoring device and the monitoring method.

[0036] The basic principles, main features and advantages of the present application are shown and described above. Those skilled in the art should understand that the present application is not limited to the above examples, and the above examples and descriptions in the specification are only the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection claimed by the present application is defined by the appended claims and their equivalents.

Claims

1. A method for real-time monitoring of a flue gas denitration reaction process based on electron paramagnetic resonance, characterized in that, The method comprises the following steps: S1. In-situ sampling and environment maintaining step: part of the flue gas continuously flows through a high-temperature-resistant cavity (101) placed inside the flue, and the environment in the cavity (101) is controlled to be consistent with the reaction environment of the main flue; S2. In-situ EPR detection step: a static magnetic field and a microwave field are applied to the cavity (101) by an EPR detection unit (200) placed outside the flue; S3. Resonance signal acquisition step: the EPR resonance signal generated by the paramagnetic substance in the flue gas flowing through the cavity (101) is detected; S4. Signal processing and parameter extraction step: the EPR signal is converted into at least one process parameter reflecting the denitration reaction progress, which includes the gas-phase free radical concentration and / or the valence state information of the active center of the catalyst; S5. State diagnosis and control output step: based on the process parameters, the denitration reaction state is diagnosed in real time, and control instructions or warning information are generated.

2. The method according to claim 1, wherein the method is characterized by, In the S1 step, the temperature inside the cavity (101) is tracked to the actual temperature of the main flue gas by dynamic temperature tracking control through the heating and insulation layer (105) and the temperature sensor (106) placed outside the cavity (101).

3. The method according to claim 1, wherein the method is characterized by, The process parameters in the S4 step include the gas-phase free radical concentration and / or the valence state and coordination environment information of the paramagnetic active center in the SCR catalyst.

4. The method according to claim 1, wherein the method is characterized by, The S5 state diagnosis step includes: by analyzing the change trend of different process parameters and / or their correlation, the root cause of the denitration system failure is diagnosed.

5. A device for in-situ online monitoring of a flue gas denitration reaction process, characterized in that, The method comprises a high-temperature micro-reactor unit (100) and a normal-temperature EPR detection unit (200), which are respectively arranged inside and outside the flue (1); The high-temperature micro-reactor unit (1) comprises a cavity (101), both ends of the cavity (101) are provided with microwave suppression structures (102), both ends of the cavity (101) are also provided with gas inlets and outlets (103) in communication with the microwave suppression structures (102), flanges (108) are connected between the gas inlets and outlets (103) and the flue (1), a microwave penetration window (104) is arranged on the side wall of the cavity (101), the cavity (101) is wrapped by a heating and insulation layer (105), and a temperature sensor (106) is arranged between the surface of the heating and insulation layer (105) and the outside of the cavity (101); The normal-temperature EPR detection unit (200) comprises a main magnet system (201), a microwave system (202) and a waveguide (203), the main magnet system (201) and the microwave system (202) are arranged on one side of the flue (1), and the waveguide (203) is connected with the microwave penetration window (104) vertically from the side of the cavity (101).

6. The device for in-situ online monitoring of flue gas denitration reaction process according to claim 1, characterized in that, An auxiliary system (300) is provided between the microwave system (202) and the microwave penetration window (104), the auxiliary system (300) comprising a cooling system (301) and a control and data processing system (302), the cooling system (301) being a cooling jacket and being sleeved on the surface of the waveguide (203).

7. The device for in-situ online monitoring of flue gas denitration reaction process according to claim 6, characterized in that, An air curtain protection system (109) is provided on one side of the microwave penetration window (104).

8. The device for in-situ online monitoring of flue gas denitration reaction process according to claim 6, characterized in that, The control and data processing system (302) is connected with the temperature sensor (106), the main magnet system (201), the microwave system (202) and the waveguide (203) through wires.

9. The device for in-situ online monitoring of flue gas denitration reaction process according to claim 6, characterized in that, A catalyst module (107) is arranged inside the cavity (101).

10. A flue gas denitration reaction process real-time monitoring system, characterized in that, The apparatus as claimed in any one of claims 5 to 9 is configured to perform the method as claimed in any one of claims 1 to 4.

Images