A system and method for preventing high temperature corrosion of boiler water-cooled wall

Abstract

The system and method for preventing high-temperature corrosion of the boiler water-cooled wall provided by the present invention can spray the high-temperature and high-pressure air after the compressor is boosted and the heater is heated toward the water-cooled wall through the air duct, which can effectively penetrate the flue gas in the furnace and form a protective air film with good anti-corrosion effect on the water-cooled wall, and will not form a large degree of cooling in the furnace, thereby achieving the technical effect of improving the atmosphere near the water-cooled wall, preventing the water-cooled wall from high-temperature corrosion, and not affecting the performance of the boiler; the compressed air flow directed to the water-cooled wall can also purge the water-cooled wall to prevent the flame from scouring the water-cooled wall, and remove the accumulated dust and slag on the water-cooled wall; by setting a sensor to detect the concentration of oxygen, carbon monoxide and hydrogen sulfide in the atmosphere attached to the water-cooled wall, and then adjusting the opening of the regulating valve on the pipeline according to the detection value of the sensor through the controller, it is possible to monitor the atmosphere attached to the water-cooled wall online, and to reasonably optimize the amount of compressed air injected in real time, thereby improving the economy.

Description

Technical Field

[0001] The invention relates to the technical field of water-cooled wall protection, and in particular to a system and method for preventing high-temperature corrosion of a boiler water-cooled wall. Background Art

[0002] In recent years, with the annual increase in coal prices, coal-fired power plants often use the blending of high-sulfur low-quality coal as an important way to effectively reduce fuel costs. Studies have shown that when the sulfur content in coal is lower than 0.7%, it generally does not cause high-temperature corrosion of the water-cooled wall. When it is higher than 0.7%, the probability of high-temperature corrosion of the water-cooled wall gradually increases. The greater the content of sulfur, alkali metals and their oxides in the coal, the greater the corrosiveness and the higher the probability of high-temperature corrosion. With the advancement of ultra-clean emissions, most power plants have carried out low-nitrogen combustion technology transformation, which makes the main combustion zone of the boiler in an oxygen-deficient state, and the strong reducing atmosphere further aggravates the occurrence of high-temperature corrosion.

[0003] The main type of high-temperature corrosion of boiler water-cooled walls is sulfide type. The cause of corrosion is that coal powder burns under oxygen-deficient conditions to produce H2S and free sulfur [S], which react with the iron metal and iron oxides of the water-cooled wall to form iron sulfides, thereby causing corrosion and making the oxide film of the water-cooled wall loose, cracked, or even falling off. High-temperature corrosion will cause the water-cooled wall to become thinner and the metal strength to decrease. Under the action of alternating thermal stress, the corrosion products will also accelerate the expansion of transverse cracks, greatly increasing the risk of water-cooled wall tube bursts, causing unplanned shutdowns of the unit and seriously threatening the safe and stable operation of the unit.

[0004] The high temperature corrosion of the water-cooled wall is mainly affected by the quality of the coal, the atmosphere near the water-cooled wall, the temperature of the water-cooled wall and the material. Since the quality of the coal will affect the dye cost and is not controllable, and the water-cooled wall has been built, it is not realistic to change its material. The temperature of the water-cooled wall will affect the performance of the boiler and cannot be easily adjusted. In order to solve the problem of high temperature corrosion of the water-cooled wall, we can only start from improving the atmosphere near the water-cooled wall. For example, Chinese patents CN104456538B, CN106989411A, and CN113776047A disclose such solutions. Such solutions basically directly supply air through air supply holes opened on the furnace wall or the water-cooled wall fins to form an air film that isolates the water-cooled wall and the coal powder combustion gas, thereby improving the atmosphere near the water-cooled wall. However, the wind of this solution flows in a direction away from the water-cooled wall, and most of the wind blows toward the middle of the furnace. Only a small amount of wind remains near the water-cooled wall to form an air film, resulting in a large amount of air consumed and a small coverage area of ​​the air film, poor economy, and poor anti-corrosion effect. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a system and method for preventing high-temperature corrosion of boiler water-cooled walls with good anti-corrosion effect and good economy.

[0006] To achieve the above-mentioned purpose, the product in the technical solution provided by the present invention is a system for preventing high-temperature corrosion of boiler water-cooled walls, comprising:

[0007] An air compressor, wherein the air compressor is used to provide dry, clean compressed air;

[0008] An air storage tank, the air storage tank is connected to the air compressor and is used to store the compressed air;

[0009] An injection assembly, which is connected to the air storage tank through a pipeline and is arranged on the fin of the water-cooled wall, and is used to inject the compressed air to form an air film. A pressure reducing valve and a regulating valve are sequentially arranged on the pipeline along the flow direction of the compressed air;

[0010] A controller, the controller is electrically connected to the sensor and the regulating valve, and the controller adjusts the opening of the regulating valve according to the detection value of the sensor;

[0011] The injection assembly includes a nozzle and a bell-shaped nozzle, the two ends of the nozzle are respectively connected to the pipeline and the bell-shaped nozzle, the nozzle is axially movable and vertically penetrates the fin, the bell-shaped nozzle is located in the furnace, and an air passage aligned with the water-cooled wall is opened on the bell-shaped nozzle; the sensor is vertically penetrated on the fin and spaced apart from the nozzle, and is used to detect the concentration of oxygen, carbon monoxide and hydrogen sulfide in the atmosphere attached to the water-cooled wall; the pipeline is also provided with a heater for heating the compressed air, and the heater is arranged between the pressure reducing valve and the regulating valve.

[0012] Preferably, the bell-shaped nozzle comprises a nozzle seat and a bell-shaped cap, the nozzle seat is fixedly connected to the end of the nozzle and exposes the radial air outlet holes provided on the nozzle, the bell-shaped cap is axially movably connected to the sealing plate on the end face of the nozzle by a tension spring, the circumferential gap between the bell-shaped cap and the nozzle seat forms the air passage, and the opening of the air passage is positively correlated with the opening of the regulating valve.

[0013] Further preferably, an annular guide plate is sleeved on the nozzle, and the annular guide plate is located in the inner cavity of the bell cap, and there is a gap between the edge of the annular guide plate and the inner wall of the bell cap.

[0014] Further preferably, a mounting hole for mounting the tension spring is provided at the top center of the bell cap, and a plug is threadedly connected to the mounting hole.

[0015] Further preferably, the opening of the mounting hole toward the interior of the bell cap is a bell mouth.

[0016] Preferably, the angle between the air duct and the water-cooled wall is 48-58°.

[0017] Preferably, the heater is a surface heater, and the heater uses the auxiliary steam generated by the water-cooled wall to heat the compressed air.

[0018] To achieve the above-mentioned purpose, the method in the technical solution provided by the present invention is a method for preventing high-temperature corrosion of a boiler water-cooled wall by using the system described in any one of the above items, characterized in that: the sensor is used to detect the oxygen concentration V1, carbon monoxide concentration V2, and hydrogen sulfide concentration V3 within 10 mm from the water-cooled wall. If V1≤2% or V2≥2000ppm or V3≥100ppm, the opening of the regulating valve is increased by the controller; if V1>4%, the opening of the regulating valve is decreased by the controller. The interval time of the sensor detection is 5-10s.

[0019] Preferably, the temperature of the compressed air when flowing out through the air passage is 150-250°C.

[0020] Preferably, the flow rate of the compressed air when flowing out through the air passage is 10-15 m / s.

[0021] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0022] The system and method for preventing high-temperature corrosion of the boiler water-cooled wall provided by the present invention can spray the high-temperature and high-pressure compressed air that has been boosted by a compressor and heated by a heater toward the water-cooled wall through an air duct, which can effectively penetrate the flue gas in the furnace and form a protective air film with good anti-corrosion effect on the water-cooled wall, and will not form a large degree of cooling in the furnace, thereby achieving the technical effect of improving the atmosphere near the water-cooled wall, preventing the water-cooled wall from high-temperature corrosion, and not affecting the performance of the boiler; the compressed air flow directed toward the water-cooled wall can also purge the water-cooled wall to prevent the flame from scouring the water-cooled wall, and remove the dust and slag accumulated on the heating surface of the water-cooled wall; by setting a sensor to detect the concentration of oxygen, carbon monoxide and hydrogen sulfide in the atmosphere attached to the water-cooled wall, and then adjusting the opening of the regulating valve on the pipeline according to the detection value of the sensor through a controller, it is possible to monitor the atmosphere attached to the water-cooled wall online, and to reasonably optimize the amount of compressed air injected in real time, thereby reducing the energy consumption of the system and improving the economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a system schematic diagram of embodiment 1 of the present invention.

[0024] Figure 2 yes Figure 1 Schematic cross-sectional view of the injection assembly.

[0025] Figure 3 It is a cross-sectional schematic diagram of the injection assembly in the second embodiment of the present invention.

[0026] Among them: 10. Air compressor; 20. Air storage tank; 21. Pipeline; 211. Pressure reducing valve; 212. Regulating valve; 30. Injection assembly; 31. Nozzle; 311. Radial air outlet; 312. Sealing plate; 313. Annular guide plate; 314. Gap; 32. Bell nozzle; 321. Nozzle seat; 322. Bell cap; 323. Mounting hole; 324. Plug; 325. Bell mouth; 33. Air duct; 34. Tension spring; 40. Controller; 41. Sensor; 50. Heater; 60. Water-cooled wall; 61. Fins. DETAILED DESCRIPTION

[0027] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0028] Embodiment 1

[0029] like Figure 1As shown, the system for preventing high temperature corrosion of boiler water-cooled wall provided by the present invention comprises: an air compressor 10, an air storage tank 20, an injection assembly 30, a controller 40, and a heater 50, wherein the air compressor 10 is an air compressor, and the air compressor 10 is used to provide dry and clean compressed air. Specifically, the air compressor 10 adopts a screw type or a centrifugal air compressor, and a dryer and a filter are arranged at its outlet; the air storage tank 20 is connected to the air compressor 10, and is used to store the compressed air produced by the air compressor 10, and its set pressure is 50kPa~100kPa, and the start and stop of the air compressor are controlled according to the set pressure. There are 3 to 6 gas storage tanks 20, and a connecting pipe is provided between each gas storage tank 20. A drainage device is provided at the bottom of the gas storage tank 20, and a heat preservation material is laid on the outside (not shown in the figure); the injection assembly 30 is connected to the gas storage tank 20 through the pipeline 21 and is arranged on the fin 61 of the water-cooled wall 60, and is used to spray compressed air to the water-cooled wall 60 to form a protective air film. Specifically, a pressure reducing valve 211 and a regulating valve 212 are sequentially provided on the pipeline 21 along the flow direction of the compressed air. The pressure of the compressed air after being reduced by the pressure reducing valve 211 is 20kPa~50kPa. The injection assembly 30 includes a nozzle 31 and a bell nozzle 32. The two ends of the nozzle 31 are divided into The nozzle 31 is axially movable and vertically penetrates the fin 61. The nozzle 32 is located in the furnace. The edge of the nozzle 32 is provided with an air passage 33 aimed at the water-cooled wall 60. The angle between the air passage 33 and the water-cooled wall 60 is 48-58°. In the present embodiment, the angle between the air passage 33 and the water-cooled wall 60 is 57°. The flow rate of the compressed air flowing out of the air passage 33 is 10-15 m / s. The controller 40 is electrically connected to the sensor 41 and the regulating valve 212. The sensor 41 is vertically penetrated on the fin 61 and is spaced apart from the nozzle 31. The sensor There are multiple sensors 41 distributed in a grid pattern on the fins 61. The sensors 41 are used to detect the concentrations of oxygen, carbon monoxide and hydrogen sulfide in the atmosphere adjacent to the water-cooled wall 60. The controller 40 adjusts the opening of the regulating valve 212 according to the detection value of the sensor 41. The heater 50 is arranged on the pipeline 21 and is located between the pressure reducing valve 211 and the regulating valve 212. The heater 50 is used to heat the compressed air flowing through the pipeline 21. The heater 50 is a surface heater, which uses the auxiliary steam generated by the water-cooled wall 60 to heat the compressed air. The temperature of the compressed air heated by the heater 50 is controlled at 150-250°C.

[0030] The advantage of such a setting is that it can utilize the injection of high-temperature and high-pressure compressed air aimed at the water-cooled wall to effectively penetrate the flue gas in the furnace and form a protective gas film with good anti-corrosion effect on the water-cooled wall, while not causing a large degree of cooling in the furnace, thereby minimizing the impact on the combustion effect in the furnace, achieving the technical effect of improving the atmosphere near the water-cooled wall, preventing high-temperature corrosion of the water-cooled wall, and not affecting the performance of the boiler; the position of the compressed air flow can be adjusted by moving the nozzle, so that it can be blown along the outer circle of the water pipe of the water-cooled wall to the water-cooled wall to remove the ash and slag on the heating surface of the water-cooled wall, and prevent the flame from scouring the water-cooled wall; by setting sensors to detect the concentrations of oxygen, carbon monoxide and hydrogen sulfide in the atmosphere attached to the water-cooled wall, and then adjusting the opening of the regulating valve on the pipeline according to the detection value of the sensor through the controller, it is possible to monitor the atmosphere attached to the water-cooled wall online, and to reasonably optimize the amount of compressed air injected in real time, reduce system energy consumption, and improve economy.

[0031] Embodiment 2

[0032] The second embodiment is basically the same as the first embodiment, except that the structure of the bell nozzle 32 is as follows: Figure 2 As shown, the bell-shaped nozzle 32 of the second embodiment includes a nozzle seat 321 and a bell-shaped cap 322. The nozzle seat 321 is fixedly connected to the end of the nozzle 31 and exposes the radial air outlet 311 opened on the nozzle 31. The bell-shaped cap 322 has a cavity inside. The bell-shaped cap 322 is connected to the sealing plate 312 on the end face of the nozzle 31 through a tension spring 34. There are multiple tension springs 34, which are distributed in a ring array along the axis of the nozzle 31. With the deformation of the tension spring 34, the bell-shaped cap 322 can move along the axial direction of the nozzle 31. The circumferential gap between the bell-shaped cap 322 and the nozzle seat 321 forms an airway 33. The opening of the airway 33 is positively correlated with the opening of the regulating valve 212.

[0033] The advantage of such a setting is that it can utilize the tapered angle characteristic of the airway. When the system stops, the bell cap is tightened with the tension spring to make it fit with the nozzle seat and realize automatic centering, thereby closing the airway and preventing dust from entering; when the system starts, the pressure exerted on the bell cap by the compressed air can push the bell cap to move in the direction away from the nozzle seat, open the airway, spray compressed air flow and form an air film; when the controller adjusts the opening of the regulating valve to a small extent, since the inner diameter dimensions of the pipeline and the nozzle at the rear section of the regulating valve do not change, the pressure of the compressed air in the nozzle is reduced, and under the action of the tension spring, the opening of the airway becomes smaller (the airway becomes narrower), thereby achieving the technical effect of adaptively adjusting the opening of the airway, so that the flow rate of the compressed air ejected through the airway does not drop significantly, and the flow rate is controlled at 12 to 13 m / s, thereby ensuring that the area of ​​the air film is formed does not change significantly, that is, the air film area is compensated by reducing the thickness of the air film, thereby avoiding high-temperature corrosion of the water-cooled wall.

[0034] In this embodiment, in order to further improve the stability of the bell cap 322 when moving, an annular guide plate 313 is also provided on the nozzle 31. The annular guide plate 313 is located in the inner cavity of the bell cap 322, and there is a gap between its edge and the inner wall of the bell cap 322.

[0035] To facilitate the installation of the tension spring 34, in this embodiment, a mounting hole 323 for mounting the tension spring 34 is opened at the top center of the bell cap 322, a plug 324 is threadedly connected to the mounting hole 323, and the opening of the mounting hole 323 toward the inside of the bell cap 322 is a bell mouth 325.

[0036] It should be noted that, in the above embodiments, the bell-shaped nozzle may be made of high temperature resistant steel or provided with a high temperature resistant coating on the surface to avoid burning.

[0037] The method for preventing high temperature corrosion of boiler water-cooled wall of the present invention is implemented by using the system provided by any of the above embodiments, and the specific method includes:

[0038] Sensors are used to detect the oxygen concentration V1, carbon monoxide concentration V2, and hydrogen sulfide concentration V3 within 10mm from the water-cooled wall. If V1≤2% or V2≥2000ppm or V3≥100ppm, the controller will increase the opening of the regulating valve. If V1>4%, the controller will decrease the opening of the regulating valve. The sensor detection interval is 5-10s.

[0039] The advantage of this setting is that it can realize online monitoring of the atmosphere of the water-cooled wall and predict the tendency of high-temperature corrosion of the water-cooled wall, so as to automatically change the opening of the regulating valve to achieve automatic adjustment, improve the atmosphere of the wall, prevent high-temperature corrosion, and reduce the consumption of compressed air.

[0040] Preferably, the temperature of the compressed air when it flows out through the air passage is 150-250°C.

[0041] Preferably, the flow rate of the compressed air when flowing out through the airway is 10-15 m / s.

[0042] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A system for preventing high temperature corrosion of a boiler water wall, comprising: An air compressor, wherein the air compressor is used to provide dry, clean compressed air; An air storage tank, the air storage tank is connected to the air compressor and is used to store the compressed air; An injection assembly, which is connected to the air storage tank through a pipeline and is arranged on the fin of the water-cooled wall, and is used to inject the compressed air to form an air film. A pressure reducing valve and a regulating valve are sequentially arranged on the pipeline along the flow direction of the compressed air; A controller, the controller is electrically connected to the sensor and the regulating valve, and the controller adjusts the opening of the regulating valve according to the detection value of the sensor; Features: The injection assembly includes a nozzle and a bell nozzle, the two ends of the nozzle are respectively connected to the pipeline and the bell nozzle, the nozzle is axially movable and vertically penetrates the fin, the bell nozzle is located in the furnace, and an air channel aligned with the water-cooled wall is opened on the bell nozzle; The sensor is vertically installed on the fin and spaced apart from the nozzle to detect the concentration of oxygen, carbon monoxide and hydrogen sulfide in the atmosphere attached to the water-cooled wall; The pipeline is also provided with a heater for heating the compressed air, and the heater is arranged between the pressure reducing valve and the regulating valve; the bell-shaped nozzle comprises a nozzle seat and a bell-shaped cap, the nozzle seat is fixedly connected to the end of the nozzle and exposes the radial air outlet hole opened on the nozzle, the bell-shaped cap is axially movably connected to the sealing plate on the end face of the nozzle through a tension spring, the circumferential gap between the bell-shaped cap and the nozzle seat forms the air channel, and the opening of the air channel is positively correlated with the opening of the regulating valve; The heater is a surface heater, and the heater uses the auxiliary steam generated by the water-cooled wall to heat the compressed air.

2. The system for preventing high temperature corrosion of boiler water wall according to claim 1, characterized in that: The nozzle is also sleeved with an annular guide plate, which is located in the inner cavity of the bell cap, and there is a gap between the edge of the annular guide plate and the inner wall of the bell cap.

3. The system for preventing high temperature corrosion of boiler water wall according to claim 1, characterized in that: A mounting hole for mounting the tension spring is provided at the top center of the bell cap, and a plug is threadedly connected to the mounting hole.

4. The system for preventing high temperature corrosion of boiler water wall according to claim 3 is characterized in that: The opening of the mounting hole toward the interior of the bell cover is a bell mouth.

5. The system for preventing high temperature corrosion of boiler water wall according to claim 1, characterized in that: The included angle between the air duct and the water-cooled wall is 48-58°.

6. A method for preventing high temperature corrosion of boiler water wall using the system according to any one of claims 1 to 5, characterized in that: The sensor is used to detect the oxygen concentration V1, carbon monoxide concentration V2, and hydrogen sulfide concentration V3 within 10 mm from the water-cooled wall. If V1≤2% or V2≥2000ppm or V3≥100ppm, the controller increases the opening of the regulating valve. If V1>4%, the controller decreases the opening of the regulating valve. The sensor detection interval is 5-10s.

7. The method for preventing high temperature corrosion of boiler water wall according to claim 6, characterized in that: The temperature of the compressed air when flowing out through the air passage is 150-250°C.

8. The method for preventing high temperature corrosion of boiler water wall according to claim 7, characterized in that: The flow rate of the compressed air when flowing out through the air passage is 10-15 m / s.

Images