H2s measurement-based heated surface slagging corrosion monitoring control system and method

Abstract

This invention discloses a monitoring and control system and method for slagging corrosion of heated surfaces based on H2S measurement. The system includes: an H2S sampling unit: using a multi-stage filtered flue gas probe to extract flue gas from the near-wall surface of the boiler's water-cooled wall and introduce it into the flue gas chamber; an H2S measurement unit: calculating the H2S concentration value in the flue gas chamber online; a backflushing and zeroing unit: equipped with a backflushing gas tank, using the gas source in the tank to perform pulse backflushing cleaning treatment on the flue gas probe and flue gas chamber through a backflushing pump, and periodically introducing the gas source into the flue gas chamber to perform zero-point calibration of the H2S measurement unit; a data acquisition and control unit: acquiring the H2S concentration value and comparing it with preset multi-level thresholds to generate graded control commands; and an execution unit: according to the graded control commands, activating the corresponding actuators of the boiler to perform fixed-point soot blowing, damper adjustment, and ammonia injection operations. This invention can realize direct monitoring and graded coordinated control of boiler slagging corrosion, ensuring the safe and economical operation of the boiler.

Description

Technical Field

[0001] This invention belongs to the field of safety monitoring and control technology for coal-fired power plant boilers, and relates to a monitoring and control system and method for slagging corrosion of heated surfaces based on H2S measurement. Background Technology

[0002] When burning high-sulfur, low-volatile coals such as anthracite in coal-fired boilers, slagging and high-temperature corrosion easily occur on the furnace water-cooled walls and high-temperature heating surfaces. Slagging leads to deteriorated heat transfer, increased flue gas temperature, and in severe cases, can cause large coke collapse and damage to equipment; high-temperature corrosion, especially sulfide corrosion, directly causes thinning of the tube walls, threatening the safe operation of the boiler. Existing monitoring methods mainly include indirect inference from sensor data, infrared thermal imaging, wall temperature measurement, and analysis of multi-component flue gas such as CO and O2. However, these methods have the following problems: 1. Indirect monitoring parameters: The monitoring parameters mainly use indirect indicators such as temperature, images, and multi-component flue gas, which are difficult to directly reflect the high-temperature sulfide corrosion and slagging process dominated by H2S, resulting in delayed early warning and high misjudgment rate.

[0003] 2. Sampling system is prone to clogging: Boiler flue gas has a high dust content and high temperature, and conventional sampling probes are very prone to clogging, making it difficult to reflect the real state of slagging and corrosion in real time and accurately. In addition, maintenance is frequent and it cannot operate continuously for a long time.

[0004] 3. Limited control methods: Existing systems mostly only link soot blowing or adjust the air volume, lacking multi-level coordinated control strategies, especially lacking precise intervention methods for localized reducing atmosphere, and thus failing to achieve both safety and low-carbon goals.

[0005] Meanwhile, research shows a strong correlation between H2S concentration near the furnace wall and high-temperature corrosion and slagging tendency: as a key component of the reducing atmosphere, H2S concentration can directly characterize the intensity of the corrosive atmosphere and the ash deposition characteristics. Therefore, developing a device capable of online and reliable measurement of H2S concentration and realizing intelligent control based on this measurement is of great significance for ensuring the safe and economical operation of boilers. Summary of the Invention

[0006] To address the aforementioned technical problems in existing technologies, this invention proposes a monitoring and control system and method for boiler slagging corrosion based on H2S measurement. This system integrates sampling and filtration, laser spectroscopy detection, multi-level collaborative control, and targeted ammonia injection, achieving graded collaborative control of boiler slagging corrosion based on direct H2S monitoring. Furthermore, targeted ammonia injection enables precise intervention in localized reducing atmospheres. The specific technical solution is as follows: A monitoring and control system for slagging corrosion on heated surfaces based on H2S measurement, comprising: H2S sampling unit: It uses a flue gas probe with built-in multi-stage filter screen to extract flue gas from the near wall surface of the water-cooled wall of the boiler and introduce it into the flue gas chamber. H2S Measurement Unit: Utilizes tunable semiconductor laser absorption spectroscopy technology to calculate the H2S concentration in the flue gas chamber online; Backflush and zeroing unit: Equipped with a backflush gas tank, the gas source in the tank is used to perform pulse backflush cleaning of the flue gas probe and flue gas chamber through a backflush pump, and the gas source is periodically introduced into the flue gas chamber to perform zero-point calibration of the H2S measurement unit; Data acquisition and control unit: acquires the H2S concentration value and compares it with preset multi-level thresholds, and generates graded control commands based on the comparison results; Execution unit: According to the hierarchical control instructions, the corresponding actuator in the boiler is started to perform fixed-point soot blowing, damper adjustment and ammonia injection operations.

[0007] Preferably, several flue gas probes are evenly arranged on the four walls of the main combustion zone, reduction zone, and burnout zone in the height direction of the boiler furnace, and the sampling ports of the probes are set near the wall surface of the water-cooled wall.

[0008] Preferably, the H2S measurement unit includes: a laser driven by a tuning circuit, the laser output wavelength being near the H2S absorption peak, the laser signal scanning through the gas to be measured in the flue gas cavity at a fixed frequency, and the laser intensity signal after passing through the gas to be measured being detected by a receiver; The tuning circuit also provides a reference signal; The phase-locked amplifier module uses the reference signal to demodulate the signal detected by the receiver, extracts the second harmonic signal, and obtains the H2S absorption line shape. The data processing module acquires the temperature and pressure signals in the flue gas chamber and, in conjunction with the second harmonic signal, uses a wavelength modulation spectroscopy algorithm to calculate the H2S concentration value in real time.

[0009] Preferably, the actuator includes a secondary damper regulating mechanism, which regulates the damper opening and burnout air volume of the boiler burner.

[0010] Preferably, the actuator includes an ammonia blending mechanism, which regulates and injects the flow rate of ammonia gas that reacts with the flue gas in the boiler, the flow rate being proportional to the extent to which the H2S concentration exceeds the standard.

[0011] Preferably, the nozzle of the ammonia blending mechanism is provided in the adjacent area below each flue gas probe.

[0012] Preferably, the data acquisition and control unit adopts a DCS distributed control system.

[0013] Preferably, the DCS distributed control system automatically controls the backflush pump to perform pulse backflush cleaning of the flue gas probe and flue gas chamber based on the pressure signal in the flue gas chamber or a preset fixed time period.

[0014] Preferably, the DCS distributed control system periodically controls the backflush pump to draw gas from the backflush gas tank and introduce it into the flue gas chamber for zero-point calibration of the flue gas chamber.

[0015] A method for monitoring and controlling slagging corrosion on heated surfaces based on H2S measurement includes the following steps: S1: Multi-point sampling: Multiple flue gas probes are set on the near-wall surface of the water-cooled wall at different heights in the boiler furnace. The flue gas is introduced into the flue gas chamber after being filtered through a multi-stage filter by an exhaust pump. S2: Laser measurement: The tuning circuit controls the laser output wavelength to scan within the H2S characteristic absorption peak range. The laser passes through the flue gas cavity, the receiver detects the light intensity signal, and the lock-in amplifier module extracts the absorption line shape. S3: Concentration Calculation: The data processing module combines the temperature and pressure in the flue gas chamber and uses a wavelength modulation spectroscopy algorithm to calculate the H2S concentration value at each measuring point; S4: Grading Judgment and Command Generation: Compare the H2S concentration C with the preset thresholds of C1~C3 levels: When C < C1, it is judged as a normal state and the existing operation is maintained; when C1 ≤ C < C2, a soot blowing start command for the corresponding area is generated; when C2 ≤ C < C3, a combustion adjustment command is generated; when C ≥ C3, a fixed-point ammonia injection command is generated and an audible and visual alarm is issued. S5: Execution Control: The soot blowing mechanism, burner damper adjustment mechanism, and ammonia blending mechanism receive instructions from the DCS distributed control system and execute corresponding actions; the soot blowing mechanism performs fixed-point soot blowing according to the soot blowing start instruction, the burner damper adjustment mechanism adjusts its secondary damper opening and / or burnout damper opening according to the combustion adjustment instruction, and the ammonia blending mechanism injects ammonia into the flue gas near the wall at the set flow rate at the corresponding measuring point; S6: Self-cleaning and calibration: The system automatically starts the backflush pump 7 to perform pulse backflush on the flue gas chamber and flue gas probe according to the preset time or differential pressure signal, and periodically introduces gas from the backflush gas tank to perform zero-point calibration on the H2S measurement unit.

[0016] Compared with the prior art, the innovative aspects and beneficial effects of this invention are as follows: 1. Direct monitoring of characteristic gases improves early warning accuracy. Because this invention uses tunable semiconductor laser absorption spectroscopy (TDLAS) technology, it is the first to use H2S concentration as a direct characteristic parameter for online monitoring of boiler slagging and high-temperature sulfide corrosion. This overcomes the lag and misjudgment problems caused by traditional methods that use indirect indicators such as temperature, CO, and images. It can reflect the reducing atmosphere and ash deposition state near the water-cooled wall surface earlier and more accurately.

[0017] 2. The integrated design of multi-stage filtration and intelligent backflushing ensures long-term stable operation of the system. Because this invention incorporates multi-stage filters within the flue gas probe and automatically triggers a backflushing pump based on differential pressure signals or timed intervals for pulse backflushing, it effectively solves the problem of easy clogging of sampling probes in high-dust flue gas environments, significantly reducing maintenance workload and ensuring the continuous availability of the monitoring system. Simultaneously, the backflushing air source also serves as a zero-calibration air source, simplifying the system structure and reducing costs.

[0018] 3. Hierarchical and coordinated control enables progressive adjustment from localized cleaning to precise intervention. Because this invention triggers a three-tiered strategy—soot blowing, combustion optimization, and targeted ammonia injection—based on H2S concentration levels, it achieves a step-by-step response from localized ash removal to overall combustion condition adjustment, and then to precise intervention in micro-area atmosphere, avoiding the limitations of single control methods.

[0019] 4. Precise control of localized reducing atmosphere through targeted ammonia injection, resulting in low carbon emissions and high efficiency. This invention spatially links the ammonia-injection mechanism with H2S measurement points, injecting ammonia only into areas exceeding the standard. At high temperatures, the NH2 and NH radicals generated from the pyrolysis of NH3 competitively consume reactive species such as H and OH, inhibiting H2S dissociation and thus reducing the concentration of HS and S radicals near the wall, thereby decreasing the formation of FeS corrosion products. Compared to traditional ammonia-injected burners, the ammonia dosage is significantly reduced, effectively suppressing localized high-temperature sulfide corrosion while avoiding excessive ammonia escape and its impact on the flame stability of the main combustion zone, achieving a high degree of synergy between low carbon emissions and equipment safety.

[0020] 5. The measurement technology based on laser absorption spectroscopy has strong anti-interference ability. Because this invention uses tunable semiconductor laser absorption spectroscopy (TDLAS) technology combined with lock-in amplification and temperature and pressure compensation, it has high measurement accuracy, fast response (<10 seconds), and is not affected by cross-interference from other components in the flue gas, making it suitable for harsh furnace environments with high temperature and high dust.

[0021] 6. The device has a compact structure and is easy to retrofit onto existing boilers. Because the invention adopts a modular design for the flue gas probe and ammonia dosing nozzle, it can be retracted and installed, allowing for maintenance or replacement without shutting down the boiler; the multi-point distributed arrangement enables precise monitoring and control of different areas of the furnace, making it highly adaptable. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a monitoring and control system for slagging corrosion on heated surfaces based on H2S measurement, according to an embodiment of the present invention. Figure 2 This is a flowchart of a method for monitoring and controlling slag corrosion on heated surfaces based on H2S measurement, according to an embodiment of the present invention. In the diagram, 1. Water-cooled wall; 2. Laser; 3. Tuning circuit; 4. Flue gas chamber; 5. Exhaust pump; 6. Backflush gas tank; 7. Backflush pump; 8. Phase-locked amplifier module; 9. Receiver; 10. Data processing module; 11. DCS system; 12. Burner; 13. Temperature sensor; 14. Pressure sensor; 15. Soot blowing mechanism; 16. Ammonia blending mechanism; 17. Multi-stage filter; 18. Flue gas probe. Detailed Implementation

[0023] To make the objectives, technical solutions, and technical effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0024] like Figure 1 As shown, this embodiment discloses a monitoring and control system for slagging corrosion on heated surfaces based on H2S measurement, comprising: H2S sampling unit includes: flue gas probe 18, with multi-stage filter screen 17 inside the probe; flue gas chamber 4; and exhaust pump 5. The H2S measurement unit includes: laser 2, tuning circuit 3, receiver 9, lock-in amplifier module 8, data processing module 10, temperature sensor 13, and pressure sensor 14. The backflush and zero-point unit includes: a backflush gas tank 6, a backflush pump 7 and corresponding solenoid valves, with the backflush pump 7 connected to the flue gas chamber 4; The data acquisition and control unit, also known as the distributed control system (DCS), receives the H2S concentration signal output by the data processing module, compares it with a preset threshold, and generates graded control commands. The execution unit includes: a soot blowing mechanism 15, a damper adjustment mechanism for the burner 12, and an ammonia blending mechanism 16.

[0025] Continue to refer to Figure 1 The slagging corrosion monitoring and control system for heated surfaces based on H2S measurement, as described in this embodiment, is applied to a 600MW anthracite coal-fired power plant boiler, as follows: Device Installation: Three flue gas probes 18 are evenly arranged on each of the four walls of the main combustion zone, reduction zone, and burnout zone along the height of the boiler furnace. The sampling port of the probe is about 50 mm away from the surface of the water-cooled wall 1. An ammonia dosing mechanism 16 nozzle is installed 50 mm below each flue gas probe 18, with the nozzle facing the surface of the water-cooled wall 1. The rear ends of all flue gas probes 18 are connected to the flue gas chamber 4 and the exhaust pump 5 through high-temperature resistant stainless steel pipes. The laser 2, receiver 9, and other optical components are centrally installed in the constant temperature control cabinet on the boiler platform.

[0026] Sampling and Measurement: The exhaust pump 5 operates continuously, creating a slight negative pressure inside the flue gas probe 18. The flue gas in the furnace enters the flue gas chamber 4 after being filtered by the multi-stage filter 17. The first-stage filter of the multi-stage filter 17 has a pore size of 80μm, and the second-stage filter has a pore size of 10μm. The laser 2 is driven by the tuning circuit 3, and the output wavelength is at the H2S absorption peak, i.e., 6320-6350cm. -1 The laser is scanned at a frequency of 1 kHz in the vicinity. After passing through the gas to be measured in the flue gas chamber 4, it is detected by the receiver 9. The lock-in amplifier module 8 uses the reference signal provided by the tuning circuit 3 to demodulate the detected signal, extract the second harmonic signal, and obtain the H2S absorption curve. The data processing module 10 combines the data from the temperature sensor 13 and the pressure sensor 14, uses a wavelength modulation spectroscopy algorithm to calculate the H2S concentration in real time, and uploads it to the DCS system 11.

[0027] Hierarchical control: The DCS system 11 receives the H2S concentration values ​​at each measuring point, compares them with preset multi-level thresholds, and generates corresponding control commands. The multi-level thresholds are, for example, C1=100ppm, C2=300ppm, and C3=500ppm. When the concentration exceeds 100ppm, the corresponding area's soot blowing mechanism 15 is activated for targeted soot blowing; when it exceeds 300ppm, the secondary air damper adjustment mechanism of the burner 12 is triggered, increasing the opening of the secondary air damper in that area by 5%-15%, and adjusting the burnout air volume accordingly to optimize combustion; when it exceeds 500ppm, the ammonia blending mechanism 16 is activated, opening the flow regulating valve of the corresponding nozzle. Ammonia gas is injected into the flue gas near the wall at a pressure of 0.2~0.5MPa. The ammonia injection flow rate is proportional to the extent of H2S concentration exceeding the standard, and an audible and visual alarm is issued simultaneously. The injected ammonia gas undergoes pyrolysis at high temperature to generate free radicals. Through competitive reaction, the free radicals H* inhibit the formation of H2S and corrosion products FeS, achieving precise intervention in a localized reducing atmosphere, increasing the ash melting point, and controlling slagging corrosion.

[0028] Self-cleaning and calibration: The DCS system 11 automatically triggers a backflushing operation based on data from the pressure sensor 14 or every 30 minutes: the backflushing pump 7 is activated, drawing compressed air at a pressure of 0.7 MPa from the backflushing air tank 6, and pulse-backflushing the flue gas probe 18 for 5 seconds via the backflushing solenoid valve to remove the ash and slag accumulated on the multi-stage filter 17. Simultaneously, the gas in the backflushing air tank 6 also serves as a zero-point calibration source, periodically introduced into the flue gas chamber 4 for zero-point calibration. In this embodiment, zero-point calibration is automatically performed every 24 hours: the sampling gas path is closed, compressed air from the backflushing air tank 6 is introduced into the flue gas chamber 4, and the output at this time is recorded as the zero point for drift correction.

[0029] Based on the above system, such as Figure 2 As shown in the figure, this embodiment also discloses a method for monitoring and controlling slag corrosion on heated surfaces based on H2S measurement, including the following steps: S1: Multi-point sampling: Multiple flue gas probes 18 are set near the wall of the water-cooled wall 1 at different heights in the boiler furnace. The flue gas is introduced into the flue gas chamber 4 after being filtered by a multi-stage filter screen 17 through an exhaust pump 5. S2: Laser measurement: The tuning circuit 3 controls the output wavelength of the laser 2 to scan within the H2S characteristic absorption peak range. The laser passes through the flue gas cavity 4, the receiver 9 detects the light intensity signal, and the lock-in amplifier module 8 extracts the absorption line shape. S3: Concentration Calculation: The data processing module 10 combines the temperature and pressure collected by the temperature sensor 13 and the pressure sensor 14, and uses the wavelength modulation spectroscopy algorithm to calculate the H2S concentration value at each measuring point. S4: Grading Judgment and Command Generation: Compare the H2S concentration C with the preset thresholds of C1~C3 levels: When C < C1, it is judged as a normal state and the existing operation is maintained; when C1 ≤ C < C2, a soot blowing start command for the corresponding area is generated; when C2 ≤ C < C3, a combustion adjustment command is generated; when C ≥ C3, a fixed-point ammonia injection command is generated and an audible and visual alarm is issued. S5: Execution control: The soot blowing mechanism 15, the burner 12 damper adjustment mechanism, and the ammonia blending mechanism 16 receive instructions and execute corresponding actions respectively; the soot blowing mechanism 15 performs fixed-point soot blowing according to the soot blowing start instruction, the burner 12 damper adjustment mechanism adjusts its secondary damper opening and / or burnout damper opening according to the combustion adjustment instruction, and the ammonia blending mechanism 16 injects ammonia into the flue gas near the wall at the corresponding measuring point according to the fixed-point ammonia injection instruction at the set flow rate; S6: Self-cleaning and calibration: The system automatically starts the backflush pump 7 to perform pulse backflush on the flue gas chamber 4 and flue gas probe 18 according to the preset time or differential pressure signal, and periodically introduces gas from the backflush gas tank 6 to perform zero-point calibration on the measuring unit.

[0030] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Although the implementation process of the present invention has been described in detail above, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. All modifications and equivalent substitutions made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A system for monitoring and controlling the corrosion of a heat surface by slagging based on the measurement of H2S, characterized in that, include: H2S sampling unit: It uses a flue gas probe with built-in multi-stage filter screen to extract flue gas from the near wall surface of the water-cooled wall of the boiler and introduce it into the flue gas chamber. H2S Measurement Unit: Utilizes tunable semiconductor laser absorption spectroscopy technology to calculate the H2S concentration in the flue gas chamber online; Backflush and zeroing unit: Equipped with a backflush gas tank, the gas source in the tank is used to perform pulse backflush cleaning of the flue gas probe and flue gas chamber through a backflush pump, and the gas source is periodically introduced into the flue gas chamber to perform zero-point calibration of the H2S measurement unit; Data acquisition and control unit: acquires the H2S concentration value and compares it with preset multi-level thresholds, and generates corresponding hierarchical control commands based on the comparison results; Execution unit: According to the hierarchical control instructions, the corresponding actuator in the boiler is started to perform fixed-point soot blowing, damper adjustment and ammonia injection operations.

2. The monitoring and control system as described in claim 1, characterized in that, Several flue gas probes are evenly arranged on the four walls of the main combustion zone, reduction zone, and burnout zone in the height direction of the boiler furnace, with the probe sampling ports set near the wall surface of the water-cooled wall.

3. The monitoring and control system as described in claim 1, characterized in that, The H2S measurement unit includes: a laser driven by a tuning circuit, the laser output wavelength being near the H2S absorption peak, the laser signal scanning through the gas to be measured in the flue gas cavity at a fixed frequency, and the laser intensity signal after passing through the gas to be measured being detected by a receiver; The tuning circuit also provides a reference signal; The phase-locked amplifier module uses the reference signal to demodulate the signal detected by the receiver, extracts the second harmonic signal, and obtains the H2S absorption line shape. The data processing module acquires the temperature and pressure signals in the flue gas chamber and, in conjunction with the second harmonic signal, uses a wavelength modulation spectroscopy algorithm to calculate the H2S concentration value in real time.

4. The monitoring and control system as described in claim 1, characterized in that, The actuator includes a secondary damper regulating mechanism, which regulates the damper opening and burnout air volume of the boiler burner.

5. The monitoring and control system as described in claim 1, characterized in that, The actuator includes an ammonia blending mechanism, which regulates and injects the flow rate of ammonia gas that reacts with the flue gas in the boiler. This flow rate is proportional to the extent to which the H2S concentration exceeds the standard.

6. The monitoring and control system as described in claim 5, characterized in that, The nozzle of the ammonia blending mechanism is located in the adjacent area below each flue gas probe.

7. The monitoring and control system as described in claim 1, characterized in that, The data acquisition and control unit adopts a DCS distributed control system.

8. The monitoring and control system as described in claim 7, characterized in that, The DCS distributed control system automatically controls the backflush pump to perform pulse backflush cleaning of the flue gas probe and flue gas chamber based on the pressure signal in the flue gas chamber or a preset fixed time period.

9. The monitoring and control system as described in claim 7, characterized in that, The DCS distributed control system periodically controls the backflush pump to draw gas from the backflush gas tank and introduce it into the flue gas chamber for zero-point calibration of the flue gas chamber.

10. A control method for a monitoring and control system for slagging corrosion of heated surfaces based on H2S measurement as described in any one of claims 1 to 9, characterized in that, Includes the following steps: S1: Multi-point sampling: Multiple flue gas probes are set on the near-wall surface of the water-cooled wall at different heights in the boiler furnace. Flue gas is introduced into the flue gas chamber after being filtered through a multi-stage filter by an exhaust pump. S2: Laser measurement: The tuning circuit controls the laser output wavelength to scan within the H2S characteristic absorption peak range. The laser passes through the flue gas cavity, the receiver detects the light intensity signal, and the lock-in amplifier module extracts the absorption line shape. S3: Concentration Calculation: The data processing module combines the temperature and pressure in the flue gas chamber and uses a wavelength modulation spectroscopy algorithm to calculate the H2S concentration value at each measuring point; S4: Grading Judgment and Command Generation: Compare the H2S concentration C with the preset thresholds of C1~C3 levels: When C < C1, it is judged as a normal state and the existing operation is maintained; when C1 ≤ C < C2, a soot blowing start command for the corresponding area is generated; when C2 ≤ C < C3, a combustion adjustment command is generated; when C ≥ C3, a fixed-point ammonia injection command is generated and an audible and visual alarm is issued. S5: Execution Control: The soot blowing mechanism, burner damper adjustment mechanism, and ammonia blending mechanism receive instructions from the DCS distributed control system and execute corresponding actions; the soot blowing mechanism performs fixed-point soot blowing according to the soot blowing start instruction, the burner damper adjustment mechanism adjusts its secondary damper opening and / or burnout damper opening according to the combustion adjustment instruction, and the ammonia blending mechanism injects ammonia into the flue gas near the wall at the set flow rate at the corresponding measuring point; S6: Self-cleaning and calibration: The system automatically starts the backflush pump 7 to perform pulse backflush on the flue gas chamber and flue gas probe according to the preset time or differential pressure signal, and periodically introduces gas from the backflush gas tank to perform zero-point calibration on the H2S measurement unit.

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