A kind of staged ammonia adding device and method for ammonia flue gas desulfurization

Abstract

The present invention relates to a staged ammonia addition device for ammonia flue gas desulfurization, comprising: a primary absorption circulation loop, a secondary absorption circulation loop, pipelines and valves; the primary absorption circulation loop is composed of an absorption tower slurry pool, a primary absorption circulation pump, a primary absorption spray layer and an absorption tower ammonia addition pipe; the absorption tower slurry pool is arranged at the bottom of the absorption tower, a flue gas inlet is arranged on the absorption tower, a primary absorption spray layer is arranged above the flue gas inlet, one end of the primary absorption circulation pump is connected to the outlet pipe of the absorption tower slurry pool, and the other end of the primary absorption circulation pump is divided into two ways to respectively connect the primary absorption spray layer and one end of the primary absorption to secondary absorption connecting pipe, and the other end of the primary absorption to secondary absorption connecting pipe is connected to the secondary absorption circulation box. The beneficial effects of the present invention are: the present invention selects a large-volume absorption tower slurry pool to ensure the full dissolution and uniform distribution of the added ammonia; the secondary absorption circulation box of the present invention is provided with an oxidizing air pipe network to reduce the escape of ammonia and reduce its corrosiveness at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of wet ammonia flue gas desulfurization, and in particular relates to a device and method including primary ammonia addition and secondary ammonia addition. Background Art

[0002] As a resource recovery and environmentally friendly process, wet ammonia-ammonium sulfate flue gas desulfurization process has been applied and promoted in the fields of flue gas desulfurization in the power, chemical and metallurgical industries due to its advantages of fast gas-liquid reaction, easy to obtain high desulfurization efficiency and recyclable desulfurization by-products. However, ammonia flue gas desulfurization technology has long been plagued by problems such as ammonia escape, aerosol, difficulty in oxidation of ammonium sulfite and strong corrosiveness.

[0003] Aerosols in ammonia flue gas desulfurization are mainly composed of submicron inorganic salt aerosol particles such as ammonium sulfite and ammonium sulfate generated by gaseous ammonia volatilized from the absorption liquid (i.e. ammonia escape) and sulfur dioxide and sulfur trioxide in the flue gas. The amount of ammonia escape is determined by the method of adding ammonia and the pH value control of the absorption liquid.

[0004] At present, the ammonia addition method for ammonia-based flue gas desulfurization is basically to add all the ammonia required for the desulfurization reaction into the absorber slurry pool, or into a small ammonia addition chamber with a small volume, or into the inlet pipe of the absorption circulation pump. Such ammonia addition device and method are prone to uneven ammonia addition, excessively high local pH value of the absorption liquid, unstable pH value during operation, and large fluctuations in outlet sulfur dioxide, which makes it difficult to control the amount of ammonia added during operation. In order to ensure that the outlet sulfur dioxide meets the emission standards, it is easy to add excessive ammonia, resulting in a large amount of ammonia escape and the generation of aerosols, which will not only cause secondary pollution, but also lead to a significant increase in operating costs. Summary of the invention

[0005] The object of the present invention is to overcome the deficiencies in the prior art and to provide a staged ammonia addition device and method for ammonia-based flue gas desulfurization.

[0006] The hierarchical ammonia addition device for ammonia-based flue gas desulfurization comprises: a primary absorption circulation loop, a secondary absorption circulation loop, pipelines and valves; the primary absorption circulation loop consists of an absorption tower slurry pool, a primary absorption circulation pump, a primary absorption spray layer and an absorption tower ammonia addition pipe; the absorption tower slurry pool is arranged at the bottom of the absorption tower, a flue gas inlet is arranged on the absorption tower, a primary absorption spray layer is arranged above the flue gas inlet, one end of the primary absorption circulation pump is connected to the outlet pipe of the absorption tower slurry pool, the other end of the primary absorption circulation pump is divided into two paths and respectively connected to the primary absorption spray layer and one end of the primary absorption to secondary absorption connecting pipe, the other end of the primary absorption to secondary absorption connecting pipe is connected to the secondary absorption circulation box, and an absorption tower ammonia addition pipe is arranged in the upper middle part of the absorption tower slurry pool; the secondary absorption circulation loop consists of a secondary absorption circulation box, a secondary absorption circulation pump, a secondary absorption spray layer, a liquid collector, a secondary absorption ammonia addition pipe and an oxidation air pipe network; a liquid collector is arranged above the primary absorption spray layer in the absorption tower, and a collector A secondary absorption spray layer is arranged above the liquid collector; one end of the secondary absorption circulation pump is connected to the outlet pipe at the bottom of the secondary absorption circulation box, and the other end of the secondary absorption circulation pump is divided into two ways to connect the secondary absorption spray layer and one end of the secondary absorption to primary absorption connecting pipe respectively, and the other end of the secondary absorption to primary absorption connecting pipe is connected to the absorption tower; an air lift cap and a liquid collecting tank are arranged on the liquid collector, and the flue gas from the primary absorption circulation enters the secondary absorption circulation through the air lift cap, and the secondary absorption circulation liquid collected in the liquid collecting tank is connected to the secondary absorption circulation box through a pipe; an oxidation air pipe network is arranged at the bottom of the secondary absorption circulation box, and the oxidation air pipe network is connected to the intersection pipe of the secondary absorption ammonia adding pipe and the oxidation air inlet pipe; an air outlet is arranged on the top of the secondary absorption circulation box, and the air outlet is connected to the absorption tower through a pipe (the oxygen in the oxidation air, after the oxidation reaction with ammonium sulfite in the secondary absorption circulation box, the remaining oxygen, nitrogen and carbon dioxide are passed to the absorption tower through this pipe).

[0007] Preferably, the absorber slurry pool has no internal components, and the absorber slurry pool has a large volume to ensure that ammonia is fully dissolved and evenly distributed.

[0008] Preferably, the oxidation air duct network is provided with evenly distributed small holes.

[0009] The working method of the staged ammonia addition device for ammonia flue gas desulfurization comprises the following steps:

[0010] Step 1, performing step 1.1 and step 1.2 simultaneously, adding different amounts of ammonia to the absorber slurry pool and the secondary absorption circulation box at the same time, and controlling the amount of ammonia added to the absorber slurry pool to be greater than the amount of ammonia added to the secondary absorption circulation box;

[0011] Step 1.1, adding ammonia to the absorption tower slurry pool through the absorption tower ammonia adding pipe, the ammonia is fully dissolved and mixed evenly in the absorption tower slurry pool, and has a large buffering capacity, which is convenient for maintaining the stability of the pH value; the primary absorption liquid is sent to the primary absorption spray layer of the absorption tower by the primary absorption circulation pump;

[0012] Step 1.2, adding ammonia through the secondary absorption ammonia adding pipe, the ammonia and the oxidizing air in the oxidizing air inlet pipe are pre-mixed in the intersection pipe outside the secondary absorption circulation box, and then added to the cross section of the secondary absorption circulation box evenly and at multiple points through the oxidizing air pipe network, and the ammonia is fully dissolved and mixed evenly in the secondary absorption circulation box; the secondary absorption liquid in the secondary absorption circulation box is sent to the secondary absorption spray layer of the absorption tower by the secondary absorption circulation pump;

[0013] Step 2, the high-temperature raw flue gas from the boiler enters the absorption tower and flows through the primary absorption spray layer. The primary absorption liquid sprayed from the primary absorption spray layer cools the high-temperature raw flue gas to the adiabatic saturation temperature, and the acidic gases (sulfur dioxide, hydrogen chloride and hydrogen fluoride) in the flue gas are absorbed and removed by a large amount of primary absorption liquid; the pH value of the primary absorption liquid is controlled to minimize the volatilization of ammonia in the primary absorption liquid; the pH value of the secondary absorption liquid in the secondary absorption circulation box is controlled to be lower than the pH value of the primary absorption liquid in the absorption tower slurry pool;

[0014] Step 3: The flue gas cooled to the adiabatic saturation temperature enters the secondary absorption cycle through the gas lift cap of the liquid collector. A small amount of gaseous ammonia in the flue gas is captured by the secondary absorption liquid with a lower pH value sprayed from the secondary absorption spray layer. After passing through the primary absorption spray layer and the secondary absorption spray layer, the sulfur dioxide in the original flue gas is efficiently absorbed and the ammonia escape is also controlled.

[0015] Step 4, the sulfur dioxide absorbed by the primary absorption liquid reacts with ammonia to generate ammonium sulfite. Since ammonium sulfite is unstable, it needs to be oxidized into stable ammonium sulfate. The newly generated ammonium sulfite is pumped into the secondary absorption circulation box through the primary absorption circulation pump for forced oxidation to obtain ammonium sulfate. A portion of the secondary absorption liquid in the secondary absorption circulation box is pumped into the absorption tower slurry pool through the secondary absorption circulation pump to maintain the liquid level balance between the absorption tower slurry pool and the secondary absorption circulation box.

[0016] Preferably, the amount of ammonia added to the absorption tower slurry pool in step 1 is 70% to 90% of the amount of ammonia required for desulfurization, and the primary absorption plays a major sulfur dioxide absorption function; the amount of ammonia added to the secondary absorption circulation box is 10% to 30% of the amount of ammonia required for desulfurization, and the secondary absorption plays a secondary sulfur dioxide absorption function.

[0017] Preferably, in step 1.1, the residence time of ammonia in the absorption tower slurry pool is 3 to 5 minutes, and the volume of the absorption tower slurry pool is set according to the residence time of ammonia in the absorption tower slurry pool.

[0018] Preferably, the position where the oxidation air inlet pipe and the secondary absorption ammonia adding pipe intersect in step 1.2 is a position in the oxidation air inlet pipe after the oxidation air has been cooled to the adiabatic saturation temperature.

[0019] Preferably, the liquid-to-gas ratio of the primary absorption cycle in the absorption tower in step 1.1 is in the range of 8.0 to 15.0, and a large liquid-to-gas ratio is beneficial to reducing the operating pH value of the primary absorption liquid; the liquid-to-gas ratio of the secondary absorption cycle in the secondary absorption circulation box in step 1.2 is in the range of 2.0 to 5.0, and a suitable secondary liquid-to-gas ratio can provide sufficient droplet surface area required for absorbing ammonia; the pH value of the primary absorption liquid in the absorption tower slurry pool in step 2 is 5.0 to 6.0, which is beneficial to the absorption of sulfur dioxide; the pH value of the secondary absorption liquid in the secondary absorption circulation box is 4.0 to 5.0, which is beneficial to reducing the volatilization of ammonia, and is also beneficial to the oxidation of sulfites and reducing the corrosiveness of the absorption liquid; the primary absorption cycle is a cycle consisting of the absorption tower slurry pool, the primary absorption circulation pump and the primary absorption spray layer, and the secondary absorption cycle is a cycle consisting of the secondary absorption circulation box, the secondary absorption circulation pump and the secondary absorption spray layer.

[0020] Preferably, the liquid-to-gas ratio of the primary absorption cycle in the absorption tower is in the range of 10.0-12.0; the liquid-to-gas ratio of the secondary absorption cycle in the secondary absorption circulation box is in the range of 3.0-4.0; the pH value of the primary absorption liquid in the absorption tower slurry pool is 5.2-5.8, and the pH value of the secondary absorption liquid in the secondary absorption circulation box is 4.5-5.0.

[0021] The beneficial effects of the present invention are:

[0022] 1) The present invention can achieve stable ammonia addition, maintain uniform and stable operating pH value of the absorption liquid, and realize pH zoning of the primary absorption liquid and the secondary absorption liquid. The high pH absorption cycle is beneficial to the efficient removal of sulfur dioxide, and the low pH absorption cycle is beneficial to the control of ammonia escape and the oxidation of ammonium sulfite. The functional zoning of efficient desulfurization and ammonia escape control is achieved through graded ammonia addition, and ammonia escape and aerosol generation in ammonia-based flue gas desulfurization are truly reduced from the process source. The effect is remarkable, the operation is stable and reliable, and it has high practicality and broad application prospects.

[0023] 2) By selecting a suitable primary absorption liquid-gas ratio, the pH of the primary absorption liquid is controlled below 6.0 while ensuring the desulfurization effect, thereby reducing the volatilization of ammonia. By selecting a large-volume absorption tower slurry pool and a longer residence time, the added ammonia is fully dissolved and evenly distributed; most of the ammonia is added to the large-volume absorption tower slurry pool, and the primary absorption is controlled to have a uniform, stable and high operating pH value, thereby ensuring the removal effect of sulfur dioxide.

[0024] 3) A small amount of ammonia is added to the secondary absorption circulation box at multiple points and evenly through the oxidation air network (oxidation air is mixed with ammonia), which increases the pH value of the secondary absorption to 3.0 to 5.0, reduces the escape of ammonia, and reduces its corrosiveness; realizes multi-point and even addition of ammonia in the secondary absorption circulation box to avoid the formation of local high pH areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a process flow chart of the present invention.

[0026] Explanation of the reference numerals: absorption tower slurry pool 1, primary absorption circulation pump 2, primary absorption spray layer 3, secondary absorption circulation box 4, secondary absorption circulation pump 5, secondary absorption spray layer 6, liquid collector 7, secondary absorption to primary absorption connecting pipe 8, primary absorption to secondary absorption connecting pipe 9, absorption tower ammonia adding pipe 10, secondary absorption ammonia adding pipe 11, oxidation air pipe network 12, flue gas inlet 13. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with embodiments. The description of the following embodiments is only used to help understand the present invention. It should be noted that for ordinary persons in the art, without departing from the principle of the present invention, the present invention can also be modified in some ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0028] As an example, a process flow of a staged ammonia addition device for ammonia flue gas desulfurization is as follows: Figure 1 As shown: the staged ammonia addition device of ammonia flue gas desulfurization mainly consists of two different absorption circulation loops (primary absorption circulation loop and secondary absorption circulation loop) composed of absorption tower slurry pool 1, secondary absorption circulation box 4, primary absorption circulation pump 2, secondary absorption circulation pump 5, pipelines and valves, etc. Different ammonia amounts are added to the absorption tower slurry pool 1 and the secondary absorption circulation box 4 at the same time.

[0029] 1. Process steps

[0030] The process of the present invention can be divided into two systematic steps:

[0031] (1) Primary absorption circulation system

[0032] The primary absorption circulation system includes an absorption tower slurry pool 1, a primary absorption circulation pump 2, a primary absorption spray layer 3 and an absorption tower ammonia adding pipe 10. Its purpose is to remove sulfur dioxide from the original flue gas entering the absorption tower and at the same time reduce the escape of ammonia to a minimum.

[0033] (2) Secondary absorption circulation system

[0034] The secondary absorption circulation system includes a secondary absorption circulation box 4, a secondary absorption circulation pump 5, a secondary absorption spray layer 6, a liquid collector 7, a secondary absorption ammonia pipe 11 and an oxidation air pipe network 12. Its purpose is to remove the ammonia volatilized in the primary absorption liquid and to efficiently oxidize ammonium sulfite into stable ammonium sulfate in the secondary absorption circulation box 4.

[0035] 2. Main process parameters:

[0036] (1) The liquid-to-gas ratio of the primary absorption cycle is in the range of 8.0 to 15.0, the pH value of the absorption tower slurry pool 1 is 5.0 to 6.0, and the circulation residence time of ammonia in the absorption tower slurry pool 1 is 3.0 to 5.0 minutes.

[0037] (2) The liquid-to-gas ratio of the secondary absorption cycle is in the range of 2.0 to 5.0, the pH value of the secondary absorption cycle box 4 is in the range of 4.0 to 5.0, and the oxidation rate is not less than 99%.

[0038] (3) The sulfur dioxide concentration at the outlet of the absorption tower is less than 35 mg / m 3 , ammonia escape concentration is less than 3.0 mg / m 3 , total dust concentration is less than 5.0mg / m 3 .

[0039] 3. Process flow:

[0040] The high-temperature raw flue gas from the boiler enters the absorption tower. After passing through the primary absorption spray layer 3, the flue gas is cooled to the adiabatic saturation temperature. At the same time, the acidic gases such as sulfur dioxide, hydrogen chloride and hydrogen fluoride in the flue gas are absorbed and removed by a large amount of primary absorption liquid. The pH value of the primary absorption liquid is controlled below 6.0 to minimize the volatilization of ammonia in the absorption liquid. Then the flue gas passes through the gas lifting cap of the liquid collector 7 and enters the secondary absorption section. The small amount of gaseous ammonia in the flue gas is captured by the lower pH absorption liquid sprayed from the secondary absorption spray layer 6. After passing through the primary absorption spray layer 3 and the secondary absorption spray layer 6, the sulfur dioxide in the raw flue gas is efficiently absorbed and the ammonia escape is also controlled.

[0041] The ammonia required for desulfurization comes from the ammonia preparation system. Most of the ammonia is added from the middle and upper part of the absorber slurry pool 1 through the absorber ammonia adding pipe 10. The relatively small amount of ammonia is fully dissolved and evenly distributed in the relatively large amount of absorption liquid in the absorber slurry pool 1. The absorber slurry pool 1 has a large capacity and strong buffering capacity. It can maintain a stable pH value during operation and does not fluctuate with the fluctuation of the amount of ammonia added. A small part of the ammonia is added to the oxidation air inlet pipe through the secondary absorption ammonia adding pipe 11. The ammonia is fully premixed with the cooled oxidation air and then evenly added to the bottom of the secondary absorption circulation box 4 through the oxidation air pipe network 12. A small amount of ammonia is added to the secondary absorption circulation box 4 to control the pH value of the secondary absorption liquid to be close to 5.0, thereby reducing the corrosiveness of the absorption liquid; adding ammonia through the evenly distributed small holes in the oxidation air pipe network 12 can avoid the formation of local high pH value areas, which is beneficial to the oxidation of ammonium sulfite and the control of ammonia escape.

[0042] The sulfur dioxide absorbed by the primary absorption liquid reacts with ammonia to generate ammonium sulfite. Since ammonium sulfite is unstable, it needs to be oxidized into stable ammonium sulfate. Therefore, the newly generated ammonium sulfite is pumped into the secondary absorption circulation box 4 through the primary absorption circulation pump 2 for forced oxidation, and a part of the absorption liquid in the secondary absorption circulation box 4 is pumped into the absorption tower slurry pool 1 through the secondary absorption circulation pump 5 to maintain the liquid level balance between the absorption tower slurry pool 1 and the secondary absorption circulation box 4.

[0043] 4. Application examples:

[0044] Ammonia desulfurization project for 480t / h boiler flue gas, with a flue gas treatment volume of 650000Nm 3 / h, the inlet SO2 concentration is 6000mg / Nm 3 , the inlet dust concentration is 30mg / Nm 3 , use 15% concentration of ammonia water as the desulfurization agent.

[0045] The main features of the staged ammonia addition device for ammonia flue gas desulfurization are:

[0046] (1) Liquid-to-gas ratio of primary absorption: 9.0L / m 3 The ammonia gas stays in the absorption tower slurry pool 1 for 3.5 minutes and the volume of the absorption tower slurry pool 1 is 500m 3 .

[0047] (2) Secondary absorption liquid-gas ratio 3.0L / m 3 .

[0048] (3) The amount of ammonia water added to the absorption tower slurry pool 1 is 10.5 t / h, and the amount of ammonia water added to the secondary absorption circulation box 4 is 1.2 t / h.

[0049] The operating parameters and results are:

[0050] (1) The pH value of the absorber slurry pool 1 is 5.8, and the pH value of the secondary absorption circulation box 4 is 4.9. The oxidation rate of the solution in the secondary absorption circulation box is 99.5%.

[0051] (2) The SO2 concentration in the net flue gas at the outlet of the absorption tower is 26 mg / Nm 3 , dust concentration is 4.2mg / Nm 3 , ammonia escape 2.3mg / Nm 3 .

Claims

1. A working method of a staged ammonia addition device for ammonia flue gas desulfurization, characterized in that: include: Primary absorption circulation loop, secondary absorption circulation loop, pipelines and valves; The primary absorption circulation loop is composed of an absorption tower slurry pool (1), a primary absorption circulation pump (2), a primary absorption spray layer (3) and an absorption tower ammonia adding pipe (10); the absorption tower slurry pool (1) is arranged at the bottom of the absorption tower, a flue gas inlet (13) is provided on the absorption tower, a primary absorption spray layer (3) is provided above the flue gas inlet (13), one end of the primary absorption circulation pump (2) is connected to the outlet pipe of the absorption tower slurry pool (1), the other end of the primary absorption circulation pump (2) is connected to the primary absorption spray layer (3) and one end of the primary absorption to secondary absorption connecting pipe (9) in two ways, the other end of the primary absorption to secondary absorption connecting pipe (9) is connected to the secondary absorption circulation box (4), and an absorption tower ammonia adding pipe (10) is provided in the middle and upper part of the absorption tower slurry pool (1); The secondary absorption circulation loop is composed of a secondary absorption circulation box (4), a secondary absorption circulation pump (5), a secondary absorption spray layer (6), a liquid collector (7), a secondary absorption ammonia adding pipe (11) and an oxidation air pipe network (12); a liquid collector (7) is provided above the primary absorption spray layer (3) in the absorption tower, and a secondary absorption spray layer (6) is provided above the liquid collector (7); one end of the secondary absorption circulation pump (5) is connected to the outlet pipe of the secondary absorption circulation box (4), and the other end of the secondary absorption circulation pump (5) is connected to the outlet pipe of the secondary absorption spray layer in two ways. (6) and one end of the secondary absorption to primary absorption connecting pipe (8), and the other end of the secondary absorption to primary absorption connecting pipe (8) is connected to the absorption tower; the liquid collector (7) is provided with an air lifting cap and a liquid collecting tank, and the liquid collecting tank is connected to the secondary absorption circulation box (4) through a pipeline; the bottom of the secondary absorption circulation box (4) is provided with an oxidation air pipe network (12), and the oxidation air pipe network (12) is connected to the intersection pipe of the secondary absorption ammonia adding pipe (11) and the oxidation air inlet pipe; the top of the secondary absorption circulation box (4) is provided with an air outlet, and the air outlet is connected to the absorption tower through a pipeline; The following steps are involved: Step 1, performing step 1.1 and step 1.2 simultaneously, adding different amounts of ammonia to the absorber slurry pool (1) and the secondary absorption circulation box (4), and controlling the amount of ammonia added to the absorber slurry pool (1) to be greater than the amount of ammonia added to the secondary absorption circulation box (4); in step 1, the amount of ammonia added to the absorber slurry pool (1) is 70% to 90% of the amount of ammonia required for desulfurization; the amount of ammonia added to the secondary absorption circulation box (4) is 10% to 30% of the amount of ammonia required for desulfurization; Step 1.1, adding ammonia to the absorption tower slurry pool (1) through the absorption tower ammonia adding pipe (10), and the ammonia is fully dissolved and mixed evenly in the absorption tower slurry pool (1); the primary absorption liquid is sent to the primary absorption spray layer (3) of the absorption tower by the primary absorption circulation pump (2); Step 1.2, ammonia is added through the secondary absorption ammonia adding pipe (11), ammonia and oxidizing air in the oxidizing air inlet pipe are pre-mixed in the intersection pipe outside the secondary absorption circulation box (4), and then added to the cross section of the secondary absorption circulation box (4) evenly and at multiple points through the oxidizing air pipe network (12), and ammonia is fully dissolved and mixed evenly in the secondary absorption circulation box (4); the secondary absorption liquid in the secondary absorption circulation box (4) is sent to the secondary absorption spray layer (6) of the absorption tower by the secondary absorption circulation pump (5); The liquid-to-gas ratio of the primary absorption cycle in the absorption tower in step 1.1 is in the range of 8.0 to 15.0; the liquid-to-gas ratio of the secondary absorption cycle in the secondary absorption circulation box (4) in step 1.2 is in the range of 2.0 to 5.0; the pH value of the primary absorption liquid in the absorption tower slurry pool (1) in step 2 is in the range of 5.0 to 6.0, and the pH value of the secondary absorption liquid in the secondary absorption circulation box (4) is in the range of 4.0 to 5.0; Step 2, the high-temperature raw flue gas from the boiler enters the absorption tower and flows through the primary absorption spray layer (3). The primary absorption liquid sprayed from the primary absorption spray layer (3) cools the high-temperature raw flue gas to an adiabatic saturation temperature, and the acidic gas in the flue gas is absorbed and removed by the primary absorption liquid; the pH value of the primary absorption liquid is controlled to minimize the volatilization of ammonia in the primary absorption liquid; the pH value of the secondary absorption liquid in the secondary absorption circulation box (4) is controlled to be lower than the pH value of the primary absorption liquid in the absorption tower slurry pool (1); Step 3, the flue gas cooled to the adiabatic saturation temperature passes through the gas lift cap of the liquid collector (7) and enters the secondary absorption cycle, and a small amount of gaseous ammonia in the flue gas is captured by the secondary absorption liquid with a lower pH value sprayed from the secondary absorption spray layer (6); Step 4: The sulfur dioxide absorbed by the primary absorption liquid reacts with ammonia to generate ammonium sulfite, and the newly generated ammonium sulfite is pumped into the secondary absorption circulation box (4) through the primary absorption circulation pump (2) for forced oxidation to obtain ammonium sulfate. A portion of the secondary absorption liquid in the secondary absorption circulation box (4) is pumped into the absorption tower slurry pool (1) through the secondary absorption circulation pump (5) to maintain the liquid level balance between the absorption tower slurry pool (1) and the secondary absorption circulation box (4).

2. The working method of the staged ammonia addition device for ammonia flue gas desulfurization according to claim 1 is characterized in that: In step 1.1, the residence time of ammonia in the absorption tower slurry pool (1) is 3 to 5 minutes, and the volume of the absorption tower slurry pool (1) is set according to the residence time of ammonia in the absorption tower slurry pool (1).

3. The working method of the staged ammonia addition device for ammonia flue gas desulfurization according to claim 1 is characterized in that: The position where the oxidation air inlet pipe and the secondary absorption ammonia adding pipe (11) intersect in step 1.2 is the position after the oxidation air in the oxidation air inlet pipe has been cooled to the adiabatic saturation temperature.

4. The working method of the staged ammonia addition device for ammonia flue gas desulfurization according to claim 1 is characterized in that: The primary absorption cycle is composed of an absorption tower slurry pool (1), a primary absorption circulation pump (2) and a primary absorption spray layer (3), and the secondary absorption cycle is composed of a secondary absorption circulation box (4), a secondary absorption circulation pump (5) and a secondary absorption spray layer (6).

5. The working method of the staged ammonia addition device for ammonia flue gas desulfurization according to claim 1 is characterized in that: The liquid-to-gas ratio of the primary absorption cycle in the absorption tower is in the range of 10.0 to 12.0; the liquid-to-gas ratio of the secondary absorption cycle in the secondary absorption circulation box (4) is in the range of 3.0 to 4.0; the pH value of the primary absorption liquid in the absorption tower slurry pool (1) is in the range of 5.2 to 5.8, and the pH value of the secondary absorption liquid in the secondary absorption circulation box (4) is in the range of 4.5 to 5.0.

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