An ammonia-ammonium sulfite combined desulfurization and denitrification system

Abstract

The present invention relates to an ammonia-ammonium sulfite combined desulfurization and denitrification system, comprising a reaction tower, a solid particle collecting device, a condensing dust collector, a flue gas post-treatment device, a regulating tank, an ammonium sulfite precipitation system, and an ammonium sulfite treatment system. The reaction tower is connected to an ammonia adding device, the flue gas outlet of the reaction tower is connected to the flue gas inlet of the solid particle collecting device, the flue gas outlet of the solid particle collecting device is connected to the inlet of the condensing dust collector, the outlet of the condensing dust collector is connected to the flue gas inlet of the flue gas post-treatment device, the condensate outlet of the condensing dust collector is connected to the regulating tank, and the regulating tank is connected to the ammonium sulfite precipitation system. Advantages: ammonium sulfite and ammonia are used as raw materials to achieve the purpose of desulfurization and denitrification. The regeneration cycle of the reaction materials and the supplementation of the reaction raw materials by the ammonium sulfite generated by desulfurization significantly reduce the material operating cost of the system. No catalyst is required, no high temperature reaction temperature window is required, no desulfurization wastewater treatment is required, and there is no disposal of low-value by-products.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas treatment equipment, and in particular to an ammonia-ammonium sulfite combined desulfurization and denitrification system. Background Art

[0002] Many industries burn coal to generate heat during industrial production. The flue gas produced by this process contains large amounts of SO2 and NOx. If left untreated, these gases can cause severe environmental pollution. Currently, atmospheric emission standards have strict requirements for SO2 and NOx emission concentrations.

[0003] There are many types of desulfurization processes, up to dozens of them. Based on whether water is added during the desulfurization process and the dry and wet forms of the desulfurization products, flue gas desulfurization is divided into three major desulfurization processes: wet, semi-dry, and dry. Wet desulfurization technology is relatively mature, highly efficient, and easy to operate. The traditional limestone / lime-gypsum flue gas desulfurization process uses calcium-based desulfurizers to absorb sulfur dioxide to generate calcium sulfite and calcium sulfate. Due to their low solubility, they are very prone to scaling and clogging in the desulfurization tower and pipelines. In terms of denitrification, the mainstream ones are mainly SCR and SNCR. The former requires a catalyst to proceed, while the latter does not require a catalyst, but the reaction temperature window is more demanding and is often easily restricted by the furnace structure.

[0004] Therefore, it is necessary to develop a new desulfurization and denitrification system to solve the above technical problems. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an ammonia-ammonium sulfite combined desulfurization and denitrification system, which effectively overcomes the defects of the prior art.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] An ammonia-ammonium sulfite combined desulfurization and denitrification system comprises a reaction tower, a solid particle collecting device, a condensing dust collector, a flue gas post-treatment device, a regulating tank, an ammonium sulfite precipitation system, and an ammonium sulfite treatment system. The reaction tower is connected to an ammonia adding device, the flue gas outlet of the reaction tower is connected to the flue gas inlet of the solid particle collecting device, the flue gas outlet of the solid particle collecting device is connected to the inlet of the condensing dust collector, the outlet of the condensing dust collector is connected to the flue gas inlet of the flue gas post-treatment device, the condensate outlet of the condensing dust collector is connected to the regulating tank, the regulating tank is connected to the ammonium sulfite precipitation system, the ammonium sulfite precipitation system is used to precipitate sulfite crystals, the ammonium sulfite treatment system is used to process the ammonium sulfite crystals precipitated by the ammonium sulfite precipitation system into dry and loose powder, and an ammonium sulfite powder inlet is provided at the bottom of the reaction tower.

[0008] On the basis of the above technical solution, the present invention can also be improved as follows.

[0009] Furthermore, the solid particle collection device is a bag dust collector.

[0010] Furthermore, the flue gas post-treatment device is a water washing tower, and the liquid outlet of the water washing tower is connected to the regulating tank.

[0011] Furthermore, an ammonia adding pipeline with a valve is connected to the bottom of the regulating tank, and the ammonia adding pipeline is connected to an ammonia source.

[0012] Furthermore, the ammonium sulfite precipitation system includes a liquid concentrator, a cooling crystallizer and a liquid filtration device. The inlet of the liquid concentrator is connected to the regulating tank, and the outlet is connected to the inlet of the cooling crystallizer. The slurry outlet of the cooling crystallizer is connected to the inlet of the liquid filtration device, and the filtrate discharge port of the liquid filtration device is connected to the inlet of the liquid concentrator.

[0013] Furthermore, the liquid concentration device is a flash tank.

[0014] Furthermore, the liquid filtering device is a vacuum belt or plate and frame filter press.

[0015] Furthermore, the ammonium sulfite processing system includes an anaerobic drying device and a grinding device. The discharge end of the anaerobic drying device is connected to the feed end of the grinding device through a material feeding device. The discharge end of the grinding device is connected to an ammonium sulfite storage bin. The ammonium sulfite storage bin is provided with a discharge port. The discharge port of the ammonium sulfite storage bin is connected to the ammonium sulfite powder inlet through a feeder.

[0016] Furthermore, the above-mentioned oxygen-free drying device is an oxygen-free drying machine, and the above-mentioned loader is a suction loader.

[0017] Furthermore, the ammonia adding device is a liquid ammonia tank.

[0018] The beneficial effects of the present invention are: using ammonium sulfite and ammonia as raw materials to achieve the purpose of desulfurization and denitrification, the regeneration cycle of the reaction materials and the supplementation of the reaction raw materials by the ammonium sulfite generated by desulfurization greatly reduce the material operation cost of the system, do not require a catalyst, do not require a high-temperature reaction temperature window, do not need to treat desulfurization wastewater, and do not have to deal with low-value by-products and other problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the ammonia-ammonium sulfite combined desulfurization and denitrification system of the present invention.

[0020] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0021] 1. Reaction tower; 2. Solid particle collection device; 3. Condensation dust collector; 4. Flue gas post-treatment device; 5. Equalization tank; 6. Ammonia addition device; 71. Liquid concentration device; 72. Cooling crystallizer; 73. Liquid filtration device; 81. Anaerobic drying device; 82. Grinding device; 83. Ammonium sulfite storage silo; 84. Loader. DETAILED DESCRIPTION

[0022] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0023] Example: Figure 1 As shown, the ammonia-ammonium sulfite combined desulfurization and denitrification system of this embodiment includes a reaction tower 1, a solid particle collecting device 2, a condensing dust collector 3, a flue gas post-treatment device 4, an adjusting tank 5, an ammonium sulfite precipitation system and an ammonium sulfite treatment system. The reaction tower 1 is connected to an ammonia adding device 6, the flue gas outlet of the reaction tower 1 is connected to the flue gas inlet of the solid particle collecting device 2, the flue gas outlet of the solid particle collecting device 2 is connected to the inlet of the condensing dust collector 3, the outlet of the condensing dust collector 3 is connected to the flue gas inlet of the flue gas post-treatment device 4, the condensate outlet of the condensing dust collector 3 is connected to the adjusting tank 5, the adjusting tank 5 is connected to the ammonium sulfite precipitation system, the ammonium sulfite precipitation system is used to precipitate sulfite crystals, and the ammonium sulfite treatment system is used to process the ammonium sulfite crystals precipitated by the ammonium sulfite precipitation system into dry and loose powder. An ammonium sulfite powder inlet is provided at the bottom of the reaction tower 1.

[0024] The ammonia-ammonium sulfite combined desulfurization and denitrification system of this embodiment is applicable to flue gas emissions from coal-fired boilers, steelmaking, aluminum smelting, ships, and other chemical and non-electrical plants. The specific treatment process is as follows:

[0025] Ammonia is metered into reaction tower 1 via ammonia dosing device 6. During operation, raw flue gas enters the lower portion of reaction tower 1. SO₂ and NOx in the flue gas first react with finely divided ammonium sulfite, obtained by the ammonium sulfite treatment system and fed into reaction tower 1, and NH₃ introduced into reaction tower 1 by ammonia dosing device 6, to produce ammonium sulfite, ammonium bisulfite, and ammonium sulfate, respectively. During this process, because the ammonium sulfite powder raw material is very small, its surface area in contact with the flue gas entering reaction tower 1 is large, resulting in high denitrification efficiency. However, finely divided ammonium sulfite is more sensitive to temperature and rapidly decomposes into SO₂ and NH₃ at elevated temperatures. Therefore, the temperature within reaction tower 1 is generally controlled between 60°C and 90°C. The flue gas at the exit of reaction tower 1 contains a mixture of solid powders of ammonium sulfate and ammonium bisulfate generated by the reaction, SO2 and NH3 produced by the decomposition of ammonium sulfite, SO2 carried by the original flue gas, and NH3 added by ammonia addition unit 6. The former solid particles are a denitrification byproduct and cannot be recycled, so they must be collected by the subsequent solid particle collection unit 2. The latter, mainly composed of SO2 and NH3, these two gaseous substances, begin to react to form ammonium sulfite when the temperature drops below 70°C. Therefore, after the flue gas discharged from the reaction tower 1 passes through the solid particle collecting device 2, it enters the condenser dust collector 3. The coil inside the condenser dust collector 3 is filled with low-temperature circulating water or other low-temperature refrigerant. After contact with the flue gas, the cooling capacity should be able to reduce the flue gas temperature to below 60°C, so that a large amount of ammonium sulfite particles can be generated. At the same time, due to the supersaturation of water vapor, condensed water will precipitate on the inner wall of the condenser dust collector 3, forming a liquid film. Ammonium sulfite has a very high solubility and dissolves into the liquid film once it contacts the liquid film. The rotation of the flue gas in the condenser dust collector 3 also causes the particulate matter and water vapor droplets to approach the wall due to centrifugation, accelerating the capture of ammonium sulfite particles. The condensate flowing out from the bottom of the condenser dust collector 3 contains a large amount of ammonium sulfite and some ammonium bisulfite. Both components are recyclable and are therefore merged into the subsequent regulating tank 5. In the flue gas passing through the condensing dust collector 3, there may still be a small amount of escaped ammonium sulfite particles and excess NH3. These components cannot be discharged directly, so they are treated by the subsequent flue gas post-treatment device 4 and then discharged normally. Among them, the regulating tank 5 serves as a collection, storage and component adjustment unit for the ammonium sulfite aqueous solution. When the content of ammonium bisulfite component in the tank is too much, ammonia is added to the regulating tank 5 to regenerate the ammonium bisulfite into ammonium sulfite. When the liquid level in the regulating tank 5 reaches the highest liquid level, the extraction of the ammonium sulfite component begins. Specifically: first, the relatively dilute solution in the regulating tank 5 enters the ammonium sulfite precipitation system to process the precipitated crystals (ammonium sulfite), and then is dried and processed into loose fine-grained powder by the ammonium sulfite treatment system, and then is sent to the reaction tower 1 as the ammonium sulfite raw material to continue the reaction. At this point, the ammonium sulfite is recovered and regenerated.It should be noted that when the SO2 concentration in the original flue gas is low, the amount of ammonium sulfite generated by the reaction of ammonia and SO2 is relatively small, and the denitrification product of ammonium sulfite is ammonium sulfate. This component has lost the ability to regenerate. Therefore, during the operation of the system, a small amount of ammonium sulfite needs to be added to the reaction tower 1 to maintain the denitrification reaction. However, when the SO2 concentration in the original flue gas is very high, NH3 reacts with SO2 in the flue gas to generate a large amount of ammonium sulfite. This part of ammonium sulfite can not only meet the amount of ammonium sulfite required for denitrification, but may even have a surplus. At this time, some ammonium sulfite can be regularly removed from the storage bin. This part of ammonium sulfite can be used as a high-value by-product for other industrial purposes.

[0026] It should be added that: in this embodiment, the equation involved in the reaction process in the reaction tower 1 is as follows:

[0027] The reaction equation is as follows:

[0028] 1) SO2 reacts with NH3 to produce (NH4)2SO4. The reaction equation is as follows:

[0029] SO2+2NH3+H2O=(NH4)2SO3

[0030] 2) (NH4)2SO3 further reacts with SO2:

[0031] (NH4)2SO3+SO2+H2O=2(NH4)HSO3

[0032] 3) Part of (NH4)2SO3 is oxidized by O2 in the flue gas:

[0033] 2(NH4)2SO3+O2=2(NH4)2SO4

[0034] 4) Part of (NH4)HSO3 is oxidized by O2 in the flue gas:

[0035] 2NH4HSO3+O2=2NH4HSO4

[0036] The denitrification part uses ammonium sulfite to react with NOx to generate N2. The reaction is designed in the following reaction stages:

[0037] 1) NO is oxidized to NO2 by O2 in the flue gas

[0038] 2NO+O2=2NO2

[0039] 2)(NH4)2SO3 reacts with NO in the presence of a catalyst to produce N2

[0040] 2(NH4)2SO3+2NO=(NH4)2SO4+N2

[0041] 3) (NH4) 2SO3 reacts with NO2 under the action of catalyst to produce N2

[0042] 4(NH4)2SO3+2NO2=4(NH4)2SO4+N2

[0043] 4)(NH4)2SO3 high temperature decomposition

[0044] (NH4)2SO3.H2O=2NH3+SO2+H2O

[0045] Therefore, the flue gas outlet of the reaction tower 1 contains not only solid powders of ammonium sulfate and ammonium bisulfate generated by the reaction, but also NH3 and SO2 generated by the decomposition of ammonium sulfite, as well as SO2 carried by the original flue gas and NH3 added by the ammonia addition device.

[0046] In this embodiment, in order to ensure uniform gas-solid mixing in the reaction tower 1 and prevent deviation and short-flow of materials and flue gas, orifice plates, hoods and other tower internal components that are beneficial to gas-solid mixing can be added to the tower.

[0047] In this embodiment, the solid particle collection device 2 is a bag filter. The specific model can be flexibly and reasonably selected based on actual usage requirements. This bag filter is used to remove ammonium sulfate generated by denitrification within the reaction tower 1. The internal temperature must be maintained above 60°C to prevent bag sticking due to condensation. Furthermore, the bag filter's large specific surface area allows it to serve as a secondary site for the desulfurization and denitrification reactions.

[0048] In this embodiment, the condenser dust collector 3 is an optimized version of a conventional cyclone dust collector, combining the functions of a cooling heat exchanger and a cyclone dust collector. The input of refrigerant lowers the flue gas temperature, causing the SO₂ and NH₃ in the flue gas to react and form ammonium sulfite particles. Furthermore, as the flue gas passes through the device, it undergoes centrifugal rotation, causing the resulting ammonium sulfite particles to accumulate on the outer wall of the condenser dust collector 3. These particles then dissolve into the condensate film formed by the cooling process, where they are then collected and flow into the subsequent regulating tank 5.

[0049] In this embodiment, the flue gas post-treatment device 4 is a water scrubber, the liquid outlet of which is connected to the regulating tank 5. The flue gas exiting the condenser dust collector 3 (which may contain a small amount of escaped ammonium sulfite particles and excess NH3) enters the water scrubber. The flue gas is then scrubbed by the scrubber's spray or gas-liquid contact layer, achieving final purification and meeting emission requirements. The circulating liquid in the scrubber can be maintained at a certain concentration by controlling the discharge flow rate and the amount of water replenished. This circulating liquid is ultimately introduced into the regulating tank 5.

[0050] It should be noted that the water washing tower is an existing technology equipment, and the specific model can be flexibly and reasonably selected according to actual usage requirements, so it will not be described in detail here.

[0051] In this embodiment, the regulating tank 5 is used to collect the condensate from the condensation dust collector 3 and the ammonium sulfite solution from the water washing tower. It is generally required to be able to continuously collect the volume of the collected liquid for more than 4 hours to avoid continuous low-load operation or frequent intermittent start and stop of subsequent processing units.

[0052] In this embodiment, an ammonia addition pipeline with a valve is connected to the bottom of the regulating tank 5 and is connected to an ammonia source. When the proportion of ammonium bisulfite in the solution ions in the regulating tank 5 exceeds 10% (which can be set by the user) during analysis, ammonia gas can be introduced into the regulating tank 5 through the ammonia addition pipeline. The added ammonia gas will cause the ammonium bisulfite in the solution in the regulating tank 5 to react to form ammonium sulfite.

[0053] As a preferred embodiment, the ammonium sulfite precipitation system includes a liquid concentrator 71, a cooling crystallizer 72 and a liquid filtration device 73, the inlet of the liquid concentrator 71 is connected to the regulating tank 5, and its outlet is connected to the inlet of the cooling crystallizer 72, the slurry outlet of the cooling crystallizer 72 is connected to the inlet of the liquid filtration device 73, and the filtrate discharge port of the liquid filtration device 73 is connected to the inlet of the liquid concentrator 71.

[0054] In the above embodiment, the concentrated liquid from the liquid concentrating device 71 enters the cooling crystallizer 72, where it is cooled and crystallized. Specifically, ammonium sulfite is supersaturated and precipitated in the cooling crystallizer 72. The cooling crystallizer 72 can reduce the saturated liquid or supersaturated mixed liquid above 50°C from the low-temperature evaporation section to room temperature or lower, so that the supersaturated ammonium sulfite crystals are fully precipitated. The slurry is then sent to the liquid filtering device 73 to filter the ammonium sulfite crystals from the slurry. The filtrate generated during the filtration process needs to be returned to the liquid concentrating device 71 for re-concentration. The entire system is simple and reasonable in design, and can effectively and quickly precipitate and reuse ammonium sulfite in the liquid from the regulating tank 5.

[0055] In this embodiment, the liquid concentrating device 71 is a flash tank. After the liquid in the regulating tank 5 enters the flash tank, the ammonium sulfite-rich slurry collected in the regulating tank 5 is evaporated and concentrated by controlling the vacuum level of the flash tank. The concentration process ensures that the temperature of the concentrated liquid in the flash tank is between 50 and 70°C. When the concentrated liquid reaches saturation or supersaturation, it is discharged into the cooling crystallizer 72 for crystallization. The concentrated liquid temperature is gradually cooled from above 50°C to room temperature or forced cooling is performed to a temperature lower than room temperature. During this process, a large amount of ammonium sulfite crystals will precipitate in the concentrated liquid. The concentrated liquid then enters the liquid filtration device 73 for filtration. The filtrate returns to the flash tank, and the filter residue enters the subsequent ammonium sulfite treatment system for further processing.

[0056] In this embodiment, the liquid filtration device 73 is a vacuum belt or plate-and-frame filter press. The specific model can be flexibly and reasonably selected according to actual use requirements. The obtained filtrate is returned to the liquid concentrator 71 through a pipeline, and the filtered filter cake enters the subsequent drying system.

[0057] As a preferred embodiment, the ammonium sulfite processing system includes an anaerobic drying device 81 and a grinding device 82. The discharge end of the anaerobic drying device 81 is connected to the feed end of the grinding device 82 through a material feeding device. The discharge end of the grinding device 82 is connected to an ammonium sulfite storage bin 83. The ammonium sulfite storage bin 83 is provided with a discharge port. The discharge port of the ammonium sulfite storage bin 83 is connected to the ammonium sulfite powder inlet through a feeder 84.

[0058] In the above embodiment, the ammonium sulfite crystals are dried in an oxygen-free drying device 81. The oxygen content in the oxygen-free drying device 81 is strictly controlled to prevent oxidation of the ammonium sulfite. After drying, the ammonium sulfite crystals are ground into a loose powder in a grinding device 82 and stored in an ammonium sulfite storage bin 83. When needed, the ammonium sulfite powder in the ammonium sulfite storage bin 83 is fed into the reaction tower 1 via the ammonium sulfite powder inlet by a feeder 84, thereby completing the complete process of drying, grinding, and feeding the crystals.

[0059] It should be emphasized that: when the SO2 content in the flue gas is high, the ammonium sulfite generated by the input of ammonia is sufficient to support the amount of ammonium sulfite required for denitrification, and there may even be a surplus. Therefore, according to different flue gas conditions, it is necessary to regularly replenish part of the ammonium sulfite material into the ammonium sulfite storage bin 83, or output part of the high-value by-product of ammonium sulfite.

[0060] In this embodiment, the above-mentioned oxygen-free drying device 81 is an oxygen-free dryer, and the specific model can be flexibly and reasonably selected according to actual use requirements. The filtered ammonium sulfite crystals are dried using an oxygen-free dryer in an oxygen-free environment below 60°C, which not only avoids the decomposition of ammonium sulfite, but also avoids the oxidation of ammonium sulfite by oxygen in the air. Among them, the oxygen-free dryer does not need to dry the material to a completely water-free state, but only needs to ensure that the attached water content of the material is less than 5% and the material is loose and not agglomerated. The above-mentioned grinding device 82 can adopt a Raymond mill or other grinding equipment currently available on the market that is suitable for the properties of ammonium sulfite. The specific model can be flexibly and reasonably selected according to actual use requirements. The feeder 84 can adopt a suction feeder to pump the ammonium sulfite powder in the ammonium sulfite storage bin 83 into the reaction tower 1 along with the air flow.

[0061] In this embodiment, the ammonia adding device 6 adopts a liquid ammonia tank with a valve.

[0062] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0063] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0064] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0065] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0066] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0067] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. An ammonia-ammonium sulfite combined desulfurization and denitrification system, characterized by: The invention comprises a reaction tower (1), a solid particle collecting device (2), a condensation dust collector (3), a flue gas post-treatment device (4), a regulating tank (5), an ammonium sulfite precipitation system and an ammonium sulfite treatment system. The reaction tower (1) is connected to an ammonia adding device (6). The flue gas outlet of the reaction tower (1) is connected to the flue gas inlet of the solid particle collecting device (2). The flue gas outlet of the solid particle collecting device (2) is connected to the inlet of the condensation dust collector (3). The outlet of the condensation dust collector (3) is connected to the flue gas inlet of the flue gas post-treatment device (4). The condensate outlet of the condensation dust collector (3) is connected to the regulating tank (5). The regulating tank (5) is connected to the ammonium sulfite precipitation system. The ammonium sulfite precipitation system is used to precipitate sulfurous acid crystals. The ammonium sulfite treatment system is used to process the ammonium sulfite crystals precipitated by the ammonium sulfite precipitation system into dry and loose powder. The bottom of the reaction tower (1) is provided with an ammonium sulfite powder inlet.

2. The ammonia-ammonium sulfite combined desulfurization and denitrification system according to claim 1, characterized in that: The solid particle collecting device (2) is a bag dust collector.

3. The ammonia-ammonium sulfite combined desulfurization and denitrification system according to claim 1, characterized in that: The flue gas post-treatment device (4) is a water washing tower, and the liquid outlet of the water washing tower is connected to the regulating tank (5).

4. The ammonia-ammonium sulfite combined desulfurization and denitrification system according to claim 1, characterized in that: The bottom of the regulating tank (5) is connected to an ammonia adding pipeline with a valve, and the ammonia adding pipeline is connected to an ammonia source.

5. The ammonia-ammonium sulfite combined desulfurization and denitrification system according to claim 1, characterized in that: The ammonium sulfite precipitation system comprises a liquid concentrating device (71), a cooling crystallizer (72) and a liquid filtering device (73); the inlet of the liquid concentrating device (71) is connected to the regulating tank (5), and the outlet thereof is connected to the inlet of the cooling crystallizer (72); the slurry outlet of the cooling crystallizer (72) is connected to the inlet of the liquid filtering device (73); and the filtrate discharge port of the liquid filtering device (73) is connected to the inlet of the liquid concentrating device (71).

6. The ammonia-ammonium sulfite combined desulfurization and denitrification system according to claim 5, characterized in that: The liquid concentration device (71) is a flash tank.

7. The ammonia-ammonium sulfite combined desulfurization and denitrification system according to claim 5, characterized in that: The liquid filtering device (73) is a vacuum belt or plate and frame filter press.

8. The ammonia-ammonium sulfite combined desulfurization and denitrification system according to claim 1, characterized in that: The ammonium sulfite processing system comprises an anaerobic drying device (81) and a grinding device (82), wherein the discharge end of the anaerobic drying device (81) is connected to the feed end of the grinding device (82) via a material feeding device, and the discharge end of the grinding device (82) is connected to an ammonium sulfite storage bin (83), wherein the ammonium sulfite storage bin (83) is provided with a discharge port, and the discharge port of the ammonium sulfite storage bin (83) is connected to the ammonium sulfite powder inlet via a feeder (84).

9. The ammonia-ammonium sulfite combined desulfurization and denitrification system according to claim 8, characterized in that: The oxygen-free drying device (81) is an oxygen-free drying machine, and the loader (84) is an air suction loader.

10. The ammonia-ammonium sulfite combined desulfurization and denitrification system according to claim 1, characterized in that: The ammonia adding device (6) is a liquid ammonia tank.

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