Air pre-heater three-proofing solution system after thermal decomposition of ammonium bisulfate

Abstract

The utility model discloses a three-proofing solution system for an air pre-heater after thermal decomposition of ammonium bisulfate. A first group of nozzles for blowing high-temperature and high-speed airflow downwards from a flue gas inlet at the hot end of the air pre-heater is arranged at the part close to the flue gas side of an air flue isolation plate; a second group of nozzles which are used for purging the corrugated plate by high-temperature and high-speed airflow and blocking primary air from leaking to flue gas are arranged at the part, close to the flue gas side, of the primary air side; and a third group of nozzles for blowing high-temperature and high-speed air flow to the cold-end corrugated plate are arranged on the secondary air duct side and the part, close to the primary air side, of the secondary air inlet. The problem that the air pre-heater is corroded and blocked due to ammonium bisulfate is effectively solved.

Description

TECHNICAL FIELD

[0001] The utility model relates to a system for solving the corrosion and blockage hidden danger of air preheater. BACKGROUND

[0002] The air preheater is the main equipment of the boiler, and the three-proofing solution of the air preheater after thermal decomposition of ammonium bisulfate is subordinate to the technical field of boiler air preheater specification.

[0003] The most important thing in the combustion of the boiler is to have suitable coal fineness and temperature and sufficient oxygen to meet the combustion. The main functions of the air preheater are: first, to provide sufficient air quantity and heat to the pulverizing system to meet the drying output and hot air powder feeding of the pulverizing system; second, to provide sufficient oxygen and initial combustion air temperature to the furnace to facilitate coal ignition and burnout; and third, the working environment of the air preheater is harsh, and here is the heat absorption and heat release process of cold air and hot flue gas through rotating heat transfer elements, which transfers heat from the flue gas to the cold air, reduces the boiler flue gas temperature, improves the furnace heat value, meets the combustion demand, and improves the overall efficiency of the boiler.

[0004] However, a large amount of nitrogen oxides NOx is generated in the combustion of the boiler, and ammonia NH3 is needed to neutralize it into nitrogen N2 and water vapor H2O. In the denitration process, part of the ammonia inevitably escapes into the air preheater with the flue gas. In the process of burning coal in the boiler, sulfides SO2 and SO3 are inevitably generated, and when the sulfides are mixed and decomposed with ammonia and water vapor, ammonium bisulfate NH4HSO4 is generated and deposited on the air preheater dense corrugated board. Ammonium bisulfate is highly corrosive and is a temperature-unstable substance that exists in solid, liquid, and gaseous states. When it changes to liquid state due to temperature change, it sticks to the corrugated board like snot, not only corrodes the corrugated board, but also adsorbs fly ash particles in the flue gas and sticks to the corrugated board, causing the corrugated board of the air preheater to be blocked by dust, and the service life of the corrugated board is tied to the maintenance and use cycle time of the boiler. In addition, the corrosion and blockage of ammonium bisulfate on the corrugated board increase the differential pressure of the flue gas and air duct inlet and outlet, and the air preheater air leakage increases significantly. With the passage of time, the air leakage of the air preheater increases exponentially, and in severe cases, the air leakage rate reaches more than 30%, the fan output is limited, and the safety of the boiler combustion is directly affected. This problem is very common, but it has not been completely solved.

[0005] The flue gas temperature of the air preheater is reduced from about 390°C to about 120°C. The cold air is heated from about 20°C to about 340°C at the primary and secondary air sides of the air preheater. When the flue gas temperature is greater than 450°C, the ammonia NH3 and sulfuric acid H2SO4 in the flue gas do not react. The generation of ammonium bisulfate NH4HSO4 is reduced by controlling the water vapor content in the flue gas, which is one of the means to control the reaction between ammonia NH3 and sulfuric acid H2SO4. The high-temperature and high-speed airflow at 500°C is used to blow the accumulated dust on the corrugated plate at the flue gas side. The high-temperature airflow can reduce the generation of ammonium bisulfate in some areas, delay the change of gaseous ammonium bisulfate to liquid, and reduce the corrosion and blockage of the air preheater. At the primary and secondary air sides, the temperature of the large-area corrugated plate is lower than 147°C due to the influence of the inlet cold air temperature, which promotes the change of ammonium bisulfate from liquid to crystalline solid. The nose-shaped and viscous ammonium bisulfate in the flue gas side is connected with the fly ash particles, which rotate to the primary and secondary air sides. The fly ash-coated liquid ammonium bisulfate changes to more crystalline solid, which solidifies in the gap between the corrugated plates like cement pouring. The blockage not only hinders the smooth flow of the primary and secondary air, but also increases the resistance, which requires an increase in air pressure to overcome the resistance. The increase in air pressure further increases the positive pressure flow to the negative pressure side of the flue gas, which doubles the air leakage rate of the air preheater. The corrosion, blockage, and air leakage of the air preheater are causally related, and none of the existing blowing methods can eliminate the negative effects of blockage.

[0006] Steam blowing is the most common form of steam blowing. Taking steam blowing as an example, steam blowing is used to remove and clear the accumulated dust and scale on the corrugated plate by high-temperature and high-pressure heat. There is a group of steam blowing nozzles on the upper and lower parts of the air preheater. The steam consumption of a single steam blowing device is 6-8 tons / hour, which is about 72 tons per day. The higher the temperature of the blowing steam, the better. The steam pressure is limited by the blowing steam, and the steam pressure is limited by the pressure that the corrugated plate can withstand. Because the pressure is too high, it will directly blow off the corrugated plate. So far, there has been no report on the use of steam blowing devices for air preheaters to remove and clear the corrosion and blockage of the corrugated plate caused by ammonium bisulfate.

[0007] The steam blowing device of the air preheater uses jet blowing, which has a limited medium blowing area and cannot fully cover the required cleaning area. The diffusion of water vapor increases the moisture content in the flue gas, which increases the dew point temperature of the flue gas, thereby increasing the dust blockage and corrosion of the cold end of the corrugated plate of the air preheater. The operation cost of the steam blowing device of the air preheater is high, and the consumption of the working medium is large. Usually, it is blown three times a day, and the steam consumption is about 72 tons / hour. If we calculate for 300 days a year, the loss of high-quality steam is about 20,000 tons, and the loss of electricity is about several hundred thousand degrees. Because the cost is too high, steam blowing is not continuous, which provides conditions for the deposition and corrosion of ammonium bisulfate on the corrugated plate, as the generation of ammonium bisulfate is continuous and accumulative.

[0008] In thermal power generation technology, the air preheater plays a major role in thermal power generation, which not only improves the air temperature, reduces the exhaust gas temperature, but also helps to improve the boiler combustion, due to the improvement of the boiler combustion efficiency, reduces the water wall corrosion and ash deposition, improves the boiler thermal efficiency, thereby improves the efficiency and safety of the whole power generation system.

[0009] However, with the continuous running time of the coal-fired boiler air preheater, the corrosion and blockage of the air preheater corrugated plate affect the safe and efficient operation of the boiler. The reasons are as follows:

[0010] The sulfur content in the coal is greater than the design value, which will cause the dew point temperature of the tail flue gas to decrease, thereby causing the air preheater to condense. After condensation, the sticky flue gas particles are not continuous but intermittent, which causes the corrugated plate to be blocked and corroded.

[0011] B, in the operation of the SCR denitration system, due to equipment or operation reasons, or due to frequent load fluctuations of the power grid scheduling unit, NOx generation changes with load changes, and there is a certain lag in ammonia injection adjustment, which causes incomplete reaction of ammonia and causes a certain amount of ammonia escape. The oxidized sulfur in the flue gas and the ammonia escape and water vapor generate ammonium bisulfate under the action of a certain temperature.

[0012] C, since the air preheater is located upstream of the dust collector in the flue gas duct, the ash content in the flue gas is high, and the gap between the corrugated plates of the air preheater is very narrow, plus the fact that ammonium bisulfate is easily changed into a liquid state at a certain temperature, not only is it highly corrosive, but also is highly viscous. When the flue gas dust flows through the corrugated plate, it is adhered and accumulated by the viscous ammonium bisulfate. Once the accumulated dust cannot be removed, it will cause a vicious cycle and eventually lead to complete corrosion and blockage.

[0013] D, the blockage not only hinders the flow of primary and secondary air, but also increases the air leakage, which reduces the exhaust gas temperature and exacerbates the deposition of ammonium bisulfate, which exacerbates the corrosion and blockage of the air preheater body and the corrugated plate.

[0014] E, the steam soot blower cannot completely remove the viscous or hard ammonium bisulfate on the corrugated plate, and the steam soot blowing itself increases the water vapor in the flue gas, which promotes the combination of sulfides and ammonia escape to generate ammonium bisulfate. SUMMARY

[0015] The purpose of the present application is to provide a heat-decomposed ammonium bisulfate air preheater three-proofing solution system which can effectively prevent corrosion, blockage and air leakage of the air preheater.

[0016] The technical solution of the present application is:

[0017] A heat-decomposed ammonium bisulfate air preheater three-proofing solution system, characterized in that:

[0018] (1) in the flue gas side of the air duct partition plate, a first group of nozzles for blowing high-temperature and high-speed airflow from the hot end of the air preheater to the flue gas inlet are arranged;

[0019] (2) a second group of nozzles for blowing high-temperature and high-speed airflow to the wave-shaped plate on the primary air side close to the flue gas side are arranged to block the leakage of primary air to the flue gas.

[0020] Further, a third group of nozzles are arranged on the secondary air duct side and the secondary air inlet close to the primary air side to blow high-temperature and high-speed airflow to the cold end wave-shaped plate, so as to rapidly increase the temperature of the wave-shaped plate again, and when the temperature is above 120 DEG C, decomposition starts, ammonia gas and other substances are generated at about 270 DEG C, and the decomposition rate increases with the increase of the temperature, thereby reducing the corrosion and blockage of the wave-shaped plate by liquid ammonium bisulfate.

[0021] The nozzle openings of the nozzles are arranged in a line on the mother pipe, and the high-temperature and high-speed airflow nozzles are densely arranged on the left and right sides.

[0022] An ammonia gas monitoring device is arranged in the primary air duct and the secondary air outlet duct.

[0023] The air preheater three-proofing solution for the thermal decomposition of ammonium bisulfate provided by the utility model solves the problems of corrosion, blockage and increased air leakage of the air preheater in operation by changing the blowing form of high-temperature and high-speed airflow, and controls the corrosion, blockage and air leakage of the air preheater by the ammonium bisulfate from the generation and survival conditions of the ammonium bisulfate, so as to truly achieve the three-proofing purposes of corrosion prevention, blockage prevention and air leakage prevention of the air preheater.

[0024] The functions of the current steam blowing, acoustic blowing, high-pressure water flushing, compressed air blowing and gas shock wave blowing are only blowing, and they cannot solve the problems of the ammonium bisulfate. The root cause of the corrosion and blockage of the air preheater is that the ammonium bisulfate is in a liquid state and has a snotty and sticky property, is attached to the wave-shaped plate, the gap between the wave-shaped plates is small, and the dust in the flue gas is naturally stuck together, so that the corrosion and blockage of the air preheater cannot be solved, the blockage inevitably causes the increase of the inlet and outlet pressure difference, and the large pressure difference inevitably leads to large air leakage, which is always a hidden danger affecting the safe, economic and environmentally-friendly operation of the boiler.

[0025] The utility model aims to replace steam blowing with high-temperature and high-speed airflow blowing, and has the following characteristics:

[0026] The operation cost is almost zero, so the wave-shaped plate can be continuously blown, and the dryness, cleanliness and smoothness of the wave-shaped plate can be maintained.

[0027] The blowing device does not need to be stopped for operation, and is continuously blown, so the equipment maintenance amount is almost zero.

[0028] It is observable that the steam blowing avoids unnecessary water vapor in the flue gas, cuts off the combination of sulfide and ammonia escape in the flue gas, and reduces the generation of ammonium bisulfate.

[0029] d, 500℃ high temperature and high speed airflow, the flue gas flow direction is swept, high temperature forces the flue gas side partial area ammonium bisulfate decomposition reaction to stop, delay the generation of ammonium bisulfate, reduce the liquid state area of ammonium bisulfate, reduce the maximum liquid state ammonium bisulfate residence time of corrugated plate damage.

[0030] e, 500℃ high temperature and high speed airflow, the flue gas flow direction is swept, due to the nozzle is arranged in the flue gas side and the primary air side isolation plate primary air side, high speed cuts off the high primary air pressure to the negative pressure flue gas side flow formed by the air leakage. At this time, most of the liquid state ammonium bisulfate on the corrugated plate will be quickly converted into crystalline solid ammonium bisulfate due to the viscous adsorption of a large amount of fly ash dust particles in the flue gas, which is a phenomenon that cannot be removed by general soot blower. High temperature and high speed airflow sweeping immediately stops such situation from continuing in the corrugated plate.

[0031] f, 500℃ high temperature and high speed airflow, the flue gas flow direction is swept, the high temperature blowing of the primary air area is swept again by high temperature and high speed blowing, and the thermal decomposition reaction of liquid state ammonium bisulfate is awakened. Because ammonium bisulfate is an unstable object, when the temperature rises above 120℃, it begins to decompose, and when the temperature rises above 270℃, ammonia gas begins to be generated. At 370℃, the decomposition rate reaches the maximum. The decomposition products include ammonia, nitrogen, sulfur dioxide and water vapor. This is the key to solving the corrosion, blockage and air leakage of the air preheater corrugated plate by high temperature and high speed airflow sweeping of the air preheater corrugated plate. It is a special function that cannot be achieved by any other air preheater soot blower. BRIEF DESCRIPTION OF DRAWINGS

[0032] The utility model will be further described below in combination with the drawings and examples.

[0033] Figure 1 It is the schematic diagram of the flue gas, primary air and secondary air, high temperature and high speed airflow flow direction of the air preheater.

[0034] Figure 2 It is the schematic diagram of the air preheater structure of one embodiment of the utility model.

[0035] Reference signs:

[0036] 1. air preheater shaft, 2. air preheater hot end, 3. air preheater cold end, 4. air preheater shell, 5. first group high temperature high speed gas flow nozzle, 6. second group high temperature high speed gas flow nozzle, 7. cold end secondary air side sootblower, 8. hot end flue gas inlet flow direction, 9. cold end flue gas outlet flow direction, 10. cold end primary air inlet flow direction, 11. hot end primary air outlet flow direction, 12. cold end secondary air inlet flow direction, 13. hot end secondary air inlet flow direction, 14. air preheater high temperature section, 15. air preheater medium temperature section, 16. air preheater low temperature section, 17. hot end flue gas and air partition, 18. cold end flue gas and air partition, 19. hot end primary and secondary air partition, 20. cold end primary and secondary air partition, 21. hot gas flow manual total isolation valve, 22. hot gas flow total regulating valve, 23. flue gas sootblower regulating valve, 24. primary air sootblower regulating valve, 25. secondary air sootblower regulating valve, 26. secondary air outlet ammonia gas detection device. DETAILED DESCRIPTION

[0037] Air preheater flue gas and primary and secondary air and high temperature high speed gas flow direction schematic Figure 1 As shown in the figure, on the right side of the air preheater is the flue gas passage, flue gas flows from top to bottom 8, heat in the flue gas is transferred to the heat storage element wave-shaped plate, flue gas temperature decreases from top to bottom. The heat transfer element wave-shaped plate rotates to the left side of the air preheater, and on the left side is the primary and secondary air passage, cold air passes through the wave-shaped plate and absorbs the temperature on the wave-shaped plate. The primary air completes the pulverized coal feeding, and the secondary air completes the required air temperature and oxygen content, i.e. air volume, for boiler combustion.

[0038] The main cause of air preheater corrosion and blockage is the ammonium bisulfate generated in the flue gas. The flue gas contains SO2, SO3 and NH3, plus water vapor in the flue gas, when the flue gas temperature is below 450℃, the reaction begins, when the temperature reaches 370℃, the decomposition rate reaches a maximum. When the temperature is 270-370℃, the molecular decomposition reaction generates gaseous ammonium bisulfate, when the temperature drops below 270℃, the ammonium bisulfate changes to a viscous liquid state and sticks to the wave-shaped plate, at this time it has strong corrosive properties and can also stick to fly ash particles to form blockage. When the temperature drops below 147℃, ammonium bisulfate appears as a crystalline solid.

[0039] Ammonium bisulfate is a substance that exhibits instability with temperature changes. Controlling the hidden dangers of ammonium bisulfate corrosion and blockage of the air preheater using ammonium bisulfate chemical mechanism, when the temperature is greater than 450℃, ammonium bisulfate can be prevented from being generated, controlling the water vapor in the flue gas can control the generation of ammonium bisulfate. By using temperature changes again, the heat decomposition reaction of the generated ammonium bisulfate can generate ammonia, nitrogen, sulfur dioxide and water vapor, and the corrosive properties of ammonium bisulfate can be controlled.

[0040] The real cause of the air preheater corrosion and blockage is the liquid state of ammonium bisulfate, that is, the temperature is between 147-230℃. The chemical mechanism of ammonium bisulfate controls the hidden danger of ammonium bisulfate corrosion and blockage of air preheater, which is customized according to the chemical properties of ammonium bisulfate, and high-temperature and high-speed airflow is used to continuously and continuously sweep the wave plate, which can prevent the air preheater from being corroded and blocked.

[0041] As shown in Figure 1 、 Figure 2 , the wave plate of the air preheater body heat transfer element after boiler maintenance is neat and clean, the air preheater shaft 1 divides the air preheater into flue gas side and air duct side, the upper part of the air preheater is commonly known as the hot end 2 of the air preheater, and the lower part of the air preheater is commonly known as the cold end 3 of the air preheater. The generation of ammonium bisulfate is in the hot end of the flue gas side, where the temperature is suitable for mixing SO2, SO3 and NH3 in the flue gas with water H2O to generate ammonium bisulfate, and the flue gas side does not have the ability to generate ammonium bisulfate. Ammonium bisulfate is an unstable object, which has gaseous, liquid and solid states with temperature change. The most harmful one is the liquid state, which is a sticky and viscous state, which not only corrodes the wave plate, but more seriously, the adhered fly ash changes to solid state with temperature change, and the wave plate is like a hard plate cast with cement, causing the wave plate to rot and be unable to operate normally. After the wave plate is blocked, the inlet and outlet differential pressure of the air duct increases, especially the output of the primary air fan needs higher air pressure to overcome the large resistance of the differential pressure. The flue gas channel adjacent to the primary air is a negative pressure area, which increases the primary air leakage. The main reason for air preheater leakage is primary air leakage, because the primary air pressure is the highest.

[0042] A first group of high-temperature and high-speed airflow nozzles (blowers) 5 are installed on the baffle (hot end flue gas and air baffle) 17 flue gas side, and the high-temperature and high-speed airflow enters from the hot end and exits from the cold end along the flue gas flow. Make the air preheater high-temperature section 14 stop the generation of ammonium bisulfate temporarily, and the wave plate below 230℃ in the air preheater medium-temperature section 15 will also move down, which reduces the generation of ammonium bisulfate in the high-temperature section and the condensation and adhesion of the wave plate area. Use high-temperature and high-speed airflow to blow the wave plate on the flue gas side, dry the moisture on the wave plate, and more importantly, greatly reduce the water vapor in the flue gas, and prevent the generation of ammonium bisulfate caused by the water vapor generated by steam blowing.

[0043] When the air preheater rotates to the air duct side, the temperature of the primary air cold end inlet air is low, and the wave plate temperature is lower than 147℃, the liquid state ammonium bisulfate crystallizes and adheres to the wave plate, which is the most concerned phenomenon and the most harmful to the air preheater equipment. If it cannot be removed in time, the sticky ammonium bisulfate will continuously accumulate fly ash dust, and the crystalline solid state will be formed with the temperature decrease, and the wave plate will be like a hard cement cast, accompanied by the corrosion of ammonium bisulfate, and any blower will be unable to remove it. At the same time, the blockage causes the differential pressure to increase, and the fan needs higher air pressure to overcome the resistance, and the air preheater leakage increases exponentially.

[0044] In the primary air duct side partition (cold end flue gas and air partition) 18, the primary air inlet is close to the flue gas side, which is the low temperature section of the air preheater 16, and the second group of high temperature and high speed airflow nozzles (blower) 6 use high temperature and high speed airflow to cut off the cold end primary air leakage to the flue gas side of the negative pressure area, greatly reducing the air preheater leakage rate. Control the primary air leakage, control the air preheater leakage. The blower airflow sweeps the wave-shaped plate, cleaning the accumulated dust and adhering materials on the wave-shaped plate.

[0045] In the secondary air duct side partition (hot end primary and secondary air partition) 19, the secondary air inlet is close to the primary air side, which is the cold end section of the air preheater 16, and the ambient temperature is the lowest, and the ammonium bisulfate is converted to crystalline solid here. The cold end secondary air blower (the third group of high temperature and high speed airflow nozzles) 7 further strengthens the blowing, the maximum effect is to quickly raise the temperature of the wave-shaped plate to above 370℃, because the higher the ambient temperature is. The temperature of the upper wave-shaped plate of the air preheater is raised to 370℃ in advance, and there is sufficient oxygen in the secondary air, which can decompose the ammonium bisulfate into ammonia, nitrogen, sulfur dioxide and water vapor. Make ammonium bisulfate unable to take root in the wave-shaped plate. The ammonium bisulfate thermal decomposition reaction is a heating and then exothermic reaction, which is very helpful to improve the primary and secondary air temperature.

[0046] Use ammonium bisulfate chemical mechanism to control the hidden danger of ammonium bisulfate corrosion and blockage of air preheater, use high temperature and high speed airflow blower, continuous and uninterrupted blowing, always keep the wave-shaped plate dry and clean, from the ignition of the boiler, the wave-shaped plate cannot stick ammonium bisulfate and fly ash particles, and use temperature change to control the survival form of ammonium bisulfate. Control the conversion of ammonium bisulfate to thermal decomposition, eliminate the corrosion and blockage of ammonium bisulfate to the wave-shaped plate, and resolve the problem of increased leakage rate caused by high differential pressure, so as to protect the air preheater equipment and prolong its service life. For easy monitoring in operation, an ammonia gas detection device is installed on the primary and secondary air duct of the air preheater hot air outlet, which can effectively control the thermal decomposition of ammonium bisulfate. When there is no ammonia gas display on the primary air side, open the primary air blower valve 24, and when there is no ammonia gas display on the secondary air side, open the secondary air blower valve. In the initial stage of use, open the hot airflow total regulating valve 22 to meet the requirement of two ammonia gas detection table recording numerical display, and then close one by one for debugging.

[0047] Ammonium bisulfate is generated in the air preheater in the flue gas side. The flue gas at the inlet of the flue carries a large amount of fly ash dust, and also SO2, SO3, ammonia escape NH3 and water vapor H2O, which will generate ammonium bisulfate NH4HSO4 under the action of suitable temperature, causing the air preheater passage to be blocked and corroded, and increasing the air preheater air leakage. However, if there is no water in the flue, oxidized sulfur and ammonia gas will not generate ammonium bisulfate. Therefore, continuous uninterrupted cleaning of the wave-shaped plate by high-temperature high-speed airflow can reduce the generation of ammonium bisulfate. Because high-temperature high-speed airflow is used for blowing instead of steam blowing, the water vapor generated by steam blowing is eliminated, and controlling the water content in the flue gas is to control the generation of ammonium bisulfate.

[0048] The air preheater flue gas side is the main area where ammonium bisulfate is generated. The first group of high-temperature high-speed airflow nozzles is installed near the flue gas side of the air duct partition plate. High-temperature high-speed airflow sweeping is to use 500°C high-temperature airflow to sweep down from the air preheater hot end flue gas inlet in the same direction. The temperature of the wave-shaped plate in the swept area is increased to above 450°C. When the temperature in the flue is above 450°C, the oxidized sulfur in the flue gas and ammonia gas with water vapor will stop reacting ammonium bisulfate. Using high-temperature resistance to delay the generation of ammonium bisulfate in some areas, the purpose is to further control the amount of ammonium bisulfate generated.

[0049] The primary air pressure in the air preheater is high, and the adjacent is the negative pressure flue gas passage. The primary air leaks to the adjacent negative pressure flue gas side, and a small amount leaks to the secondary air side. When the primary air passage is partially blocked and the primary air inlet and outlet differential pressure increases, the primary air leakage increases with the differential pressure. The main reason for the large air preheater air leakage rate is the large primary air leakage. The second group of nozzles is installed near the flue gas side on the primary air side. High-temperature high-speed airflow not only sweeps the wave-shaped plate ash, but also has a straight-line barrier effect on the primary air leakage to the flue gas. Because the high-speed airflow makes it impossible for the primary air to cross horizontally, the primary air leakage is controlled, and the air preheater leakage is controlled.

[0050] The air preheater flue side does not have the ability to generate ammonium bisulfate, but every minute or so when the wave-shaped plate rotates, it carries ammonium bisulfate on it, which is thick liquid or solid. In a cold air environment, it further solidifies and crystallizes ammonium bisulfate on the wave-shaped plate, which is the main source of air preheater corrosion and blockage. The third group of high-temperature high-speed nozzles is close to the primary air side, using 500°C high-temperature high-speed airflow to sweep the cold end wave-shaped plate, and quickly raising the temperature of the wave-shaped plate again. Ammonium bisulfate is strongly dependent on temperature, and the decomposition products are different at different temperatures. High temperature awakens the thermal decomposition reaction of liquid ammonium bisulfate. When the temperature rises above 120°C, it begins to decompose, and when it rises above 270°C, ammonia gas begins to be produced. The decomposition rate reaches a maximum at 370°C. The decomposition products include ammonia, nitrogen, sulfur dioxide and water vapor. This is the key to high-temperature high-speed airflow sweeping the wave-shaped plate of the air preheater, solving the air preheater corrosion, blockage and air leakage. It is a special function that no other air preheater soot blower can have.

[0051] The air preheater rotates about one round per minute, and the ammonium bisulfate cannot stay in the air preheater and will float with the wind and smoke. There is no clogging of dust, and no corrosion. The high-temperature and high-speed airflow power mainly comes from the shape of the airflow nozzle, and the ratio of the flow area of the mother pipe to the flow area of the nozzle is the source of high speed. The airflow nozzle at the hot flue gas inlet, the primary air inlet, and the secondary air duct inlet uses this principle. The nozzle openings on the mother pipe are in the shape of a flat rectangle (or other suitable shape), arranged in a straight line, forming high-temperature and high-speed airflow nozzles connected on the left and right, densely covering each piece of wave-shaped plate, continuously and uninterruptedly blowing each piece of wave-shaped plate, and the freshly generated liquid ammonium bisulfate is blown away about twice per minute, like a cloth, so that the ammonium bisulfate cannot solidify and stick to the wave-shaped plate, and the clogging of the wave-shaped plate of the air preheater heat transfer element does not exist, and the corrosion of the ammonium bisulfate on the wave-shaped plate can be effectively controlled.

[0052] Ammonia monitoring devices are installed in the primary air duct and the secondary air outlet duct to monitor whether the air volume of the high-temperature and high-speed airflow soot blower is normal and whether the airflow temperature meets the requirements of thermal decomposition of ammonium bisulfate. The wave-shaped plate is blown by 500℃ high-temperature and high-speed airflow, and when the temperature rises to 270℃, the ammonium bisulfate is thermally decomposed into ammonia and sulfuric acid. Sulfuric acid still has strong corrosive properties, and rotates to the flue gas side, and will quickly combine with ammonia and water to form ammonium bisulfate. When the temperature in the hot airflow area reaches 400℃, the sulfuric acid is decomposed into sulfur trioxide and water. Subsequently, the sulfur trioxide reacts with ammonia, oxygen, and other substances to form ammonia and other substances. Two ammonia monitoring devices are installed in the secondary air outlet duct, which can detect ammonia, indicating that the high-temperature and high-speed airflow soot blower plays a protective role in blowing the wave-shaped plate, and solves the difficult problem of removing ammonium bisulfate. The cost of the air preheater three-protection solution after thermal decomposition of ammonium bisulfate is almost zero, and the wave-shaped plate can be continuously and uninterruptedly blown, the surface of the wave-shaped plate is always kept dry and clean, and the ammonium bisulfate on the wave-shaped plate has not solidified and crystallized, and is blown away by the hot airflow, thus eliminating the phenomenon of corrosion and clogging of the wave-shaped plate caused by the sticking of ammonium bisulfate. Since there is no need to start and stop the operation, the maintenance and operation labor is low, and the equipment has high reliability.

[0053] The above is only a specific implementation manner of the present application, but the protection scope of the present application is not limited to this, and any skilled person in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A system for preventing the air preheater from being damaged after thermal decomposition of ammonium bisulfate, characterized in that: (1) a first group of nozzles for blowing high-temperature and high-speed gas flow downward from the air preheater hot-end flue gas inlet is arranged near the flue gas side of the air duct partition; (2) a second group of nozzles for blowing high-temperature and high-speed gas flow to clean the wave-shaped plate and prevent the primary air from leaking into the flue gas is arranged near the flue gas side of the primary air side; and (3) a third group of nozzles for blowing high-temperature and high-speed gas flow to clean the cold-end wave-shaped plate is arranged near the primary air side of the secondary air inlet side of the secondary air duct. The nozzle openings of the nozzles are arranged in a line on the main pipe, and the high-temperature and high-speed gas flow nozzles are densely arranged left and right. An ammonia gas monitoring device is installed in the primary air duct and the secondary air outlet duct. ​ 2. The system according to claim 1, wherein the system is characterized by: ​ 3. The heat decomposition of ammonium bisulfate after the air preheater three-proofing solution system according to claim 1 or 2, characterized by: ​

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