A chain grate coal-fired boiler flue gas treatment device and method

Abstract

The present invention relates to a chain grate coal-fired boiler flue gas treatment device and method, the device comprises a reaction tower, one side of the reaction tower is provided with a flue gas inlet, the top of the reaction tower is provided with a flue gas outlet, the reaction tower includes SO X Absorption spray layer, NO X Acidification spray layer, nitric acid absorption spray layer, coordinated dust removal device, flue gas inlet is located at SO X Below the absorption spray layer; at the bottom of the reaction tower there is a SO X Absorption tank, NO X Acidification tank, NO X Absorption tank, SO X Absorption tank, NO X Acidification tank, NO X The absorption tank is connected to SO X Absorption spray layer, NO X Acidification spray layer and nitric acid absorption spray layer are connected; SO X A flue gas liquid holding plate is also provided between the lower part of the absorption spray layer and the flue gas inlet. The chain grate coal-fired boiler flue gas treatment device and method of the present application removes NOx, SOx and smoke pollutants in one tower, with small engineering workload and high removal efficiency, meeting national air emission standards.

Description

Technical Field

[0001] The invention relates to the technical field of flue gas purification and treatment, and in particular to a device and method for treating flue gas from a chain grate coal-fired boiler. Background Art

[0002] Chain grate coal-fired boilers are the main heat source equipment for centralized heating and gas supply boiler rooms in my country (especially in the Northeast). The main pollutants produced by chain grate coal-fired boilers are smoke, NOx and SOx. The emission of smoke and SOx has long been strictly controlled in China, and various forms of mature dust removal and desulfurization equipment have been used. The flue gas of chain grate coal-fired boilers also contains a certain amount of NOx, but its concentration is lower than that of pulverized coal boilers and oil boilers. When no measures are taken, the NOx concentration in the flue gas is generally between 200 and 450 mg / m 3 , which is lower than the emission limits of most countries in the world. Since denitration of chain grate coal-fired boilers is more difficult, more complex and more costly than dust removal and desulfurization, the denitration treatment of chain grate coal-fired boilers has been progressing slowly.

[0003] At present, 90% of flue gas desulfurization projects use the wet limestone-gypsum method. Commonly used boiler denitrification treatment technologies include low nitrogen combustion technology (LNB), selective catalytic reduction technology (SCR), selective non-catalytic reduction technology (SNCR), wet complex absorption technology, liquid phase oxidation-absorption technology, gas phase oxidation-absorption technology, etc. Among them, the first two methods are widely used in power plants, cement and other industries.

[0004] The SNCR denitrification process requires a flue gas temperature range of 850℃~1150℃, and a residence time of the reductant and flue gas mixture of more than 0.5 seconds; the SCR denitrification process requires a flue gas temperature range of 320~420℃, and requires the unit to have the necessary transformation space. For large industrial boilers or power station boiler units, whether it is a pulverized coal boiler or a circulating fluidized bed boiler, they can basically meet the relevant transformation conditions, but a considerable number of small and medium-sized coal-fired boilers or other forms of kilns are difficult to meet the SCR or SNCR technical requirements due to their compact furnace structure (for example: currently most of my country's municipal heating boilers are 15t / h~150t / h layer-fired chain boilers. Due to the characteristics of this furnace type, the flue gas temperature at the furnace outlet is basically lower than 850℃, which cannot meet the SNCR reaction temperature window; limited by the boiler form, the internal space of the furnace cannot meet the residence time required by the SNCR process). In addition, the denitrification efficiency is low and cannot meet environmental protection requirements. The space of the rear heating surface of the chain boiler, economizer and air preheater is too compact to arrange the SCR reaction tower, making it difficult to complete the SCR transformation.

[0005] Oxidation absorption is a denitrification technology that mainly removes NO in a reaction tower by oxidizing NO. The formed NO2 is highly soluble in water and is combined with a desulfurization system. The byproducts generated are nitric acid compounds and other products. It is a flue gas treatment technology that is particularly suitable for small and medium-sized chain grate coal-fired boilers and has broad market prospects. Summary of the invention

[0006] In order to overcome the above-mentioned deficiencies in the prior art, the present invention proposes a chain grate coal-fired boiler flue gas treatment device and method to solve the problem that existing small and medium-sized coal-fired boilers or other forms of kilns are difficult to meet the SCR or SNCR technical requirements due to their compact furnace structure.

[0007] The present invention is achieved through the following technical solutions:

[0008] A chain grate coal-fired boiler flue gas treatment device comprises a reaction tower, one side of the reaction tower is provided with a flue gas inlet, the top of the reaction tower is provided with a flue gas outlet, and the reaction tower is characterized in that the inside of the reaction tower comprises SO X Absorption spray layer, NO X Acidification spray layer, nitric acid absorption spray layer, coordinated dust removal device, the flue gas inlet is located at SO X Below the absorption spray layer; at the bottom of the reaction tower there is a SO X Absorption cell, NO X Acidification tank, NO X Absorption tank, the SO X Absorption cell, NO X Acidification tank, NO X The absorption tank is connected to SO X Absorption spray layer, NO X The acidification spray layer and the nitric acid absorption spray layer are connected; the SO X A smoke liquid holding plate is also provided between the lower side of the absorption spray layer and the smoke inlet.

[0009] Furthermore, the SO X The absorption spray layer adopts liquid alkali, and a plurality of holes are opened on the smoke liquid holding plate.

[0010] Furthermore, the NO X The acidification spray layer uses sodium chlorite, and the NO X Acidification spray layer and SO X A collecting tray is provided between the absorption spray layers. The collecting tray is a flanged open hole structure. The bottom of the collecting tray is connected to the NO X Acidification pool.

[0011] Furthermore, the nitric acid absorption spray layer uses liquid alkali, and the nitric acid absorption spray layer and NOX A collection bowl is provided between the acidification spray layers. The collection bowl is fixed to the tower wall by profiles. A gap is provided between the collection bowl and the tower wall to facilitate the passage of flue gas. The bottom of the collection bowl is connected to the NO X Absorption tank.

[0012] Furthermore, the collaborative dust removal device includes a grid-type interceptor and a ridge-type demister.

[0013] Furthermore, the SO X Absorption tank and SO X There is SO on the pipes between the absorption spray layers. X Absorption circulation pump, the NO X Acidification pool and NO X There is NO in the pipeline between the acidification spray layers. X Acidification circulation pump, the NO X There is NO in the pipeline between the absorption tank and the nitric acid absorption spray layer. X Absorption circulation pump; the SO X Absorption cell, NO X Acidification tank, NO X The bottom outlets of the absorption tanks are connected to discharge pumps through pipelines.

[0014] Furthermore, the NO X There is NO between the absorption tank and the reaction tower. X The balance pipe of the absorption tank, the NO X There is NO between the acidification tank and the reaction tower. X Acidification tank balance pipe.

[0015] Furthermore, a booster fan is provided on one side of the smoke inlet.

[0016] Furthermore, the smoke outlet is connected to the chimney through a clean flue.

[0017] A method for treating flue gas from a chain grate coal-fired boiler, comprising the following steps:

[0018] S1: Flue gas enters the tower from the flue gas inlet on one side of the reaction tower, first passes through the flue gas holding plate, and the flue gas fully contacts the reaction liquid on the flue gas holding plate to precipitate dust, and then enters the SO X Absorbing spray layer, SO in flue gas X Reacts chemically with liquid alkali to absorb SO X After the flue gas enters NO X Acidification spray layer;

[0019] S2: NO X Sodium chlorite sprayed from the acidification spray layer removes NO in the flue gas. X Acidification, after acidified NOx Combines with water to form gaseous nitric acid that falls into NO X Acidification tank, the flue gas continues upward into the nitric acid absorption spray layer;

[0020] S3: The low-temperature flue gas containing nitric acid further undergoes a neutralization reaction with liquid alkali, and the nitric acid in the flue gas finally forms nitrate compounds and falls into NO X Absorption tank;

[0021] S4: Removal of NO X The flue gas goes upward into the coordinated dust removal device and is discharged after coordinated dust removal.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention proposes a chain grate coal-fired boiler flue gas treatment device and method, which can remove SO X 、NO X The removal of dust is completed in the same reaction tower. By adding a layer of porous alloy flue gas liquid holding plate at the entrance of the reaction tower, the flue gas entering the reaction tower is evenly distributed, the flow field is better, and the desulfurization and dust washing efficiency is increased; in order to ensure a higher utilization rate of the reaction reagent, the SO X A collection tray is set above the absorption spray layer to reduce the amount of reactant solution entering the SO X In the absorption section, desulfurization is performed first, followed by acidification reaction, which ensures that the reactants are less likely to interact with SO X reaction, and low temperature conditions are more suitable for acidification reaction; X A collection bowl is set above the acidification spray layer to reduce the amount of absorbent solution entering the NO X In the acidification section, part of the nitric acid solution is neutralized, and the collection bowl absorbs the nitric acid mist more fully. The various components in the tower are reasonably designed, and a coordinated dust removal device is used to effectively intercept and remove droplets, improve the demisting effect, reduce the secondary entrainment of droplets, and achieve efficient coordinated dust removal while efficiently desulfurizing and denitrifying, with higher efficiency and lower cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of a chain grate coal-fired boiler flue gas treatment device according to an embodiment of the present invention;

[0025] Figure 2 This is a schematic structural diagram of a chain grate coal-fired boiler flue gas treatment device according to an embodiment of the present invention.

[0026] In the figure:

[0027] 1. Booster fan; 2. Flue gas holding plate; 3. SO X Absorption spray layer; 4. Collection plate; 5. NO XAcidification spray layer; 6. Collection bowl; 7. Nitric acid absorption spray layer; 8. Coordinated dust removal device; 9. Clean flue; 10. NO X Absorption tank; 11. NO X Absorption circulation pump; 12. SO X Absorption tank; 13. SO X Absorption circulation pump; 14, NO X Acidification pool; 15, NO X Acidification circulation pump; 16, discharge pump; 17, chimney; 18, NO X Absorption tank balance pipe; 19, NO X Acidification tank balance pipe; 20. Reaction tower; 21. Flue gas inlet; 22. Flue gas outlet. DETAILED DESCRIPTION

[0028] Examples are shown to specifically illustrate certain embodiments of the present invention and should not be construed as limiting the scope of the present invention. The disclosed content of the present invention can be improved from materials, methods and reaction conditions at the same time, and all these improvements should fall within the spirit and scope of the present invention.

[0029] like Figure 1-2 As shown, a chain grate coal-fired boiler flue gas treatment device includes a reaction tower 20, a flue gas inlet 21 is provided on one side of the reaction tower 20, and the flue gas is pressurized by a booster fan 1 before entering the reaction tower through the flue gas inlet 21. The reaction tower 20 includes SO X Absorption spray layer 3, NO X Acidification spray layer 5, nitric acid absorption spray layer 7, coordinated dust removal device 8, the flue gas inlet 21 is located at SO X Below the absorption spray layer 3, a flue gas outlet 22 is provided on the top of the reaction tower 20, and the flue gas outlet 22 is connected to the chimney 17 through the clean flue 9; the flue gas entering the reaction tower 20 from the flue gas inlet 21 first passes through the SO X Absorption spray layer 3 desulfurization, and then through NO X The acidification spray layer 5 and the nitric acid absorption spray layer 7 complete the denitration, and finally enter the coordinated dust removal device 8 for coordinated dust removal. The purified flue gas after treatment is discharged into the air through the chimney 17.

[0030] In this embodiment, the SO X The absorption spray layer 3 includes two layers of spray pipe networks, each of which is composed of multiple branch pipes and a number of high-efficiency nozzles. The distance between each two layers of spray pipe networks is not less than 1.5m. X The absorbent used in the absorption spray layer 3 is liquid alkali (NaOH), and the SO X The absorption spray layer 3 is connected to the SO at the bottom of the reaction tower 20 through a pipeline. X The absorption tank 12 is connected, and the SOX Absorption spray layer 3 and SO X The connecting pipes between the absorption tanks 12 are also provided with SO X The absorption circulation pump 13, the SOX absorption spray layer 3, the SOX absorption tank 12, and the SOX absorption circulation pump 13 constitute the SO X The absorber section reactant circulation loop realizes SO X The reactants in the absorption section absorb the flue gas in a cycle. X A flue gas liquid retaining plate 2 is also provided between the lower part of the absorption spray layer 3 and the flue gas inlet 21. The flue gas liquid retaining plate 2 is arranged in the entire cross section of the reaction tower 20. The flue gas liquid retaining plate 2 is provided with a number of holes, and the total area of ​​the holes is 35% of the cross section of the reaction tower 20. The flue gas liquid retaining plate 2 rectifies and evenly distributes the flue gas entering the desulfurization tower. At the same time, the liquid film formed above the flue gas liquid retaining plate 2 prolongs the gas-liquid contact time. The action mechanism of the flue gas liquid retaining plate 2 is: the liquid sprayed from the spray pipe network is temporarily retained on the flue gas liquid retaining plate 2 to form a layer of liquid film. The flue gas forms a strong stirring effect in the process of passing through the liquid film. The gas and liquid collide violently to produce a large number of small bubbles, which increases the contact between gas and liquid. The contact between gas and liquid on the plate is much stronger than that in the spray layer, and dust is more likely to gather and precipitate in the liquid film; so that the SOX and dust in the flue gas are evenly removed, and low liquid-gas ratio high-efficiency desulfurization and synergistic dust removal are achieved. After the flue gas is absorbed at this stage, its SO X The concentration can be lower than 35mg / m 3 , SO X The liquid-gas ratio of the absorption section is between 6 and 8, and the pH value of the SOX absorption tank is controlled at 6 to 7. The specific value is adjusted according to the quality of the inlet coal. The desulfurization process is mainly a chemical reaction between sulfur dioxide (SO2) and sodium hydroxide (NaOH), and the reaction product sodium bisulfite (NaHSO3) dissolves in water. The reaction mechanism is the same as other wet desulfurization reaction mechanisms. The main reaction is that SO2 in the flue gas first dissolves in the absorption liquid and then dissociates into H + and HSO3 - , the reaction equation is as follows:

[0031]

[0032]

[0033]

[0034]

[0035]

[0036] Then H + With OH in solution —Neutralization reaction generates salt and water, which promotes the continuous absorption and neutralization of SO2. The specific reaction equation is as follows:

[0037] H + +OH - →H2O

[0038]

[0039]

[0040] In this embodiment, the NO X The acidification spray layer 5 includes two layers of spray pipe networks, each layer of spray pipe network is composed of multiple branch pipes and a number of high-efficiency nozzles, and the distance between each two layers of spray pipe network is not less than 1.5m. The reaction time is controlled within 1 to 1.5s according to the height. X The acidification spray layer 5 uses sodium chlorite (NaClO2), NO X The acidification spray layer 5 is connected to the NO at the bottom of the reaction tower 20 through a pipeline. X Acidification tank 14 connection, NO X Acidification spray layer 5 and NO X The connecting pipes between the acidification tanks 14 are also provided with NO X Acidification circulation pump 15, NO X Acidification spray layer 5, NO X Acidification pool 14, NO X Acidification circulation pump 15 forms NO X Acidification stage reactant circulation loop to achieve NO X The reactants in the acidification section acidify the flue gas in a cycle, NO X The liquid-gas ratio of the acidification section is 4 to 6. X Acidification spray layer 5 and SO X A collecting tray 4 is provided between the absorption spray layers 3. The collecting tray 4 is a flanged opening structure, and a water retaining ridge is provided above the opening. The reactant mixed solution cannot flow into the SO X In the absorption section, the flue gas flows upward from the holes in the flange to the reaction acidification section, and the liquid collected by the collecting tray 4 is connected to the NO X Acidification tank 14, NO X Acidification tank 14 adjusts pH value, NO X Acidification tank 14 controls pH to 6, NO X The acidification tank 14 controls the reaction potential ORP to be 500-600mv. X The acidification stage is a gas film controlled reaction, and the reaction mechanism is as follows:

[0041]

[0042] 2NO+ClO2 - →2NO2+Cl -

[0043] NO+ClO2 - →NO2+ClO -

[0044] 4NO2+ClO 2- +4OH - →4NO3 - +Cl - +2H2O

[0045] 2NO2+ClO2 - +4OH - →2NO3 - +Cl - +2H2O

[0046] Because HNO3 is generated, the pH value will drop rapidly in a short time, and the solution will become acidic. NaClO2 will decompose in the acidic solution, and the reaction is:

[0047] ClO2 - +H + →HClO2

[0048] 8HClO2→6ClO2+Cl2+4H2O

[0049] 2ClO2 - +Cl2→2Cl - +ClO2

[0050] 4ClO2 - +2H + →2ClO2+ClO3 - +Cl - +2H2O

[0051] The reaction of NO is as follows

[0052] 4NO+3ClO2 - +2H2O→4HNO3+3Cl -

[0053] 5NO+4HCl→4ClO2+5Cl - +2H2O

[0054] 5NO+3ClO2+4H2O→5HNO3+Cl -

[0055] In this embodiment, the nitric acid absorption spray layer 7 includes two layers of spray pipe networks, each layer of the spray pipe network is composed of multiple branch pipes and a number of high-efficiency nozzles, and the distance between each two layers of the spray pipe network is not less than 1.5m; the nitric acid absorption spray layer 7 uses liquid alkali (NaOH), and the nitric acid absorption spray layer 7 is connected to NO by a pipeline. X The absorption tank 10 is connected to the nitric acid absorption spray layer 7 and the NO X The pipes between the absorption tanks 10 are provided with NO X Absorption circulation pump 11, nitric acid absorption spray layer 7, NO X Absorption tank 10, NO X Absorption circulation pump 11 forms NO X The absorber section reactant circulation loop realizes NO X The reactants in the absorption section absorb the flue gas in a cycle, NO X The absorption section controls the liquid-gas ratio between 4 and 6; the nitric acid absorption spray layer 7 and NO X A collecting bowl 6 is provided between the acidification spray layers 5. The collecting bowl 6 is arranged in the entire cross section of the reaction tower 20 and is composed of a funnel. The collecting bowl 6 is fixed to the tower wall by a profile. A gap is provided between the collecting bowl 6 and the tower wall to facilitate the passage of flue gas. The total area of ​​the gap opening is more than 60% of the cross section of the reaction tower. At the same time, it is ensured that part of the absorption liquid enters the reaction acidification section to adjust the pH value of the reaction liquid to prevent the pH of the reaction liquid from being too low. The bottom of the collecting bowl 6 is connected to the NO X Absorption tank 10, NO X The pH value of the absorption tank 10 is controlled at 5.5 to 6.5, NO X The absorption cell 10 controls the reaction potential ORP to be 300-400 mv. X Reaction mechanism of absorption section:

[0056] H + +OH - →H2O

[0057] NO3 - +Na + →NaNO3

[0058] After the above three stages of reaction, 99.9% of the pollutants are washed into the reaction liquid and the absorption liquid. Since the droplets of the flue gas are accompanied by dust particles, in order to ensure that the dust emission concentration is lower than 5 mg / m3, a collaborative dust removal device 8 is set. The collaborative dust removal device 8 includes a grid interceptor and a ridge demister. The flue gas after collaborative dust removal finally achieves ultra-clean dust emission; The mechanism of the collaborative dust removal device 8: the flow field of the washed flue gas is uneven, and the droplets are unevenly distributed. The large droplets are settled by controlling the sedimentation time, and the small droplets undergo secondary rectification through the collaborative dust removal device 8, while inertial collision and direct interception occur to form large droplets that are easy to settle. The secondary improvement of the uniformity of the flue gas on the cross-section of the reaction tower and the increase of the sedimentation time reduce the burden on the above high-efficiency demister. Compared with the conventional treatment process with the emission requirement of particulate matter concentration value lower than 5 mg / Nm3, a multi-stage demister and wet electrostatic precipitator are adopted, which have high efficiency, low investment, less maintenance and low operating costs.

[0059] In this embodiment, the SO X Absorption tank 12, NO X Acidification pool 14, NO X The bottom outlet of the absorption tank 10 is connected to the discharge pump 16 through pipelines, the main purpose of which is to control the adjustment of the liquid level and the discharge of by-products.

[0060] In this embodiment, SO X Absorption tank 12, NO X Acidification pool 14, NO X The absorption tank 10 can be integrated with the reaction tower 20, or can be separately configured as a concrete structure; X NO needs to be connected between the absorption tank 10 and the reaction tower 20 X The absorption tank balance pipe 18, in NO X A NO connection is required between the acidification tank 14 and the reaction tower 20. X Acidification tank balance pipe 19, to ensure NO X Absorption tank 10, NO X The gas pressure in the acidification tank 14 and the reaction tower 20 is balanced.

[0061] A method for treating flue gas from a chain grate coal-fired boiler, comprising the following steps:

[0062] S1: Flue gas enters the tower from the flue gas inlet 21 on one side of the reaction tower 20, first passes through the flue gas holding plate 2, and the flue gas fully contacts the reaction liquid on the flue gas holding plate to precipitate dust, and then enters the SO X Absorbing spray layer 3, SO in flue gas X Reacts chemically with liquid alkali to absorb SO X After the flue gas enters NO X Acidification spray layer 5; SO XThe absorbent slurry in the absorption tank passes through SO X Absorption circulation pump to SO X The absorption spray layer 3 is evenly sprayed and contacts the desulfurized flue gas in reverse direction. During this process, SO x The particulate matter is captured by the desulfurization solution, and the solution that absorbs the pollutants falls back into the SO X In the absorption tank, the absorption liquid is repeatedly circulated to remove SO x Absorb and finally achieve desulfurization;

[0063] S2: NO X The sodium chlorite sprayed from the acidification spray layer 5 removes NO in the flue gas. X Acidification, after acidified NO x Combines with water to form gaseous nitric acid that falls into NO X The flue gas from the acidification tank 14 continues to move upwards and enters the nitric acid absorption spray layer 7; the flue gas from the nitric acid after the reaction is desulfurized and dusted and continues to move upwards through the collection plate and enters the NO X Acidification section, NO X The reaction reagent solution in the acidification tank 14 is passed through NO X Acidification circulation pump to NO X The acidification spray layer 5 is evenly sprayed and contacts the flue gas containing nitrogen oxides in reverse. During this process, NO in the flue gas is X The NO after the reaction is captured by the reactant solution; X Reacts with water to form dilute nitric acid and a mixed solution of reactants that falls back into the NO X In the acidification tank 14, the mixed liquid is repeatedly circulated to remove NO X The reaction finally achieves NO X Convert dilute nitric acid solution;

[0064] S3: The low-temperature flue gas containing nitric acid further undergoes a neutralization reaction with liquid alkali, and the nitric acid in the flue gas finally forms nitrate compounds and falls into NO X Absorption tank 10; NO X The absorbent solution in the absorption tank 10 is passed through NO X The absorption circulation pump is sent to the nitric acid absorption spray layer 7 for uniform spraying, and contacts the flue gas containing nitrogen reactants in reverse. During this process, the nitric acid and fine particles in the flue gas are captured by the absorbent solution; the solution that absorbs the pollutants falls back into the NO X In the absorption tank 10, the absorption liquid is repeatedly circulated to absorb the nitric acid mist, and finally the nitric acid mist is removed;

[0065] S4: Removal of NO XThe flue gas enters the collaborative dust removal device 8 upward, undergoes secondary rectification, interception and capture in the collaborative dust removal device 8, and then is removed by the high-efficiency demister to remove the entrained droplets, further reducing the dust concentration in the flue gas, and is finally discharged into the chimney 17 through the top reaction tower outlet.

[0066] In summary, the flue gas treatment device and method of the present application removes NOx, SOx and smoke pollutants in one tower, with small engineering workload and high removal efficiency, and meets national atmospheric emission standards.

[0067] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A chain grate coal-fired boiler flue gas treatment device, comprising a reaction tower (20), a flue gas inlet (21) is provided on one side of the reaction tower (20), and a flue gas outlet (22) is provided on the top of the reaction tower (20), characterized in that: The reaction tower (20) includes SO X Absorption spray layer (3), NO X Acidification spray layer (5), nitric acid absorption spray layer (7), coordinated dust removal device (8), the flue gas inlet (21) is located at SO X Below the absorption spray layer (3); at the bottom of the reaction tower (20) there is a SO X Absorption tank (12), NO X Acidification pool (14), NO X Absorption tank (10), the SO X Absorption tank (12), NO X Acidification pool (14), NO X The absorption tank (10) is connected to SO X Absorption spray layer (3), NO X The acidification spray layer (5) and the nitric acid absorption spray layer (7) are connected; the SO X A smoke liquid holding plate (2) is also provided between the lower part of the absorption spray layer (3) and the smoke inlet (21); The SO X The absorption spray layer (3) uses liquid alkali, and the smoke liquid holding plate (2) is provided with a plurality of holes; The NO X The acidification spray layer (5) uses sodium chlorite, and the NO X Acidification spray layer (5) and SO X A collecting tray (4) is provided between the absorption spray layers (3), the collecting tray (4) being a flanged open hole structure, and the bottom of the collecting tray (4) is connected to the NO X Acidification pond(14); The nitric acid absorption spray layer (7) uses liquid alkali, and the nitric acid absorption spray layer (7) and NO X A collecting bowl (6) is provided between the acidification spray layers (5), the collecting bowl (6) is fixed to the tower wall by a profile, a gap is provided between the collecting bowl (6) and the tower wall to facilitate the passage of flue gas, and the bottom of the collecting bowl (6) is connected to the NO X Absorption tank (10).

2. The chain grate coal-fired boiler flue gas treatment device according to claim 1 is characterized in that: The coordinated dust removal device (8) comprises a grid-type interceptor and a ridge-type demister.

3. The chain grate coal-fired boiler flue gas treatment device according to claim 1 is characterized in that: The SO X Absorption tank (12) and SO X The pipeline between the absorption spray layers (3) is provided with SO X Absorption circulation pump (13), the NO X Acidification pool (14) and NO X The pipeline between the acidification spray layers (5) is provided with NO X Acidification circulation pump (15), the NO X The pipeline between the absorption tank (10) and the nitric acid absorption spray layer (7) is provided with NO X Absorption circulation pump (11); the SO X Absorption tank (12), NO X Acidification pool (14), NO X The bottom outlets of the absorption tank (10) are connected to discharge pumps (16) through pipelines.

4. The chain grate coal-fired boiler flue gas treatment device according to claim 1 is characterized in that: The NO X A NO is connected between the absorption tank (10) and the reaction tower (20). X The absorption tank balance pipe (18), the NO X A NO is connected between the acidification tank (14) and the reaction tower (20). X Acidification tank balance pipe (19).

5. The chain grate coal-fired boiler flue gas treatment device according to claim 1 is characterized in that: A booster fan (1) is also provided on one side of the smoke inlet (21).

6. The chain grate coal-fired boiler flue gas treatment device according to claim 1, characterized in that: The smoke outlet (22) is connected to the chimney (17) via a clean smoke duct (9).

7. A chain grate coal-fired boiler flue gas treatment method, characterized in that: A chain grate coal-fired boiler flue gas treatment device as described in any one of claims 1 to 6 is used, specifically The following steps are involved: S1: Flue gas enters the tower from the flue gas inlet (21) on one side of the reaction tower (20), first passes through the flue gas holding plate (2), and then fully contacts the reaction liquid on the flue gas holding plate to precipitate dust, and then enters the SO X Absorption spray layer (3), SO in flue gas X Reacts chemically with liquid alkali to absorb SO X After the flue gas enters NO X Acidification spray layer (5); S2: NO X The sodium chlorite sprayed from the acidification spray layer (5) removes NO in the flue gas. X Acidification, after acidified NO x Combines with water to form gaseous nitric acid that falls into NO X Acidification tank (14), the flue gas continues upward to enter the nitric acid absorption spray layer (7); S3: The low-temperature flue gas containing nitric acid further undergoes a neutralization reaction with liquid alkali, and the nitric acid in the flue gas finally forms nitrate compounds and falls into NO X Absorption tank (10); S4: Removal of NO X The flue gas enters the coordinated dust removal device (8) upwards and is discharged after coordinated dust removal.

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