Ammonia desulfurization device and method based on spray tower heat exchange

Abstract

The invention belongs to the technical field of flue gas desulfurization and resource recovery, and discloses an ammonia desulfurization device and method based on spray tower heat exchange, and the device comprises a spray tower, an absorption tower, a primary washing tank, a secondary washing tank, a slurry circulating pump, a wastewater pump, a steam generator and a slurry cooler. Compared with a traditional process, on the premise of ensuring that ammonia does not escape and sulfur does not exceed the standard, water balance accurate control is achieved in the mode that the spray tower exchanges heat with the ammonia-nitrogen wastewater and part of the ammonia-nitrogen wastewater returns to the tower, the problem that the water supplementing amount of the traditional process is large in fluctuation is solved, meanwhile, flue gas waste heat recovery is conducted, and wastewater discharge is reduced. In addition, the ammonia-nitrogen wastewater is recycled, wastewater recycling is achieved, liquid ammonia consumption is reduced, and the yield of the product ammonium sulfate is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas desulfurization and resource recovery, and specifically relates to an ammonia-based desulfurization device and method based on heat exchange in a spray tower. Background Art

[0002] The secondary water washing is a part after the absorption stage of ammonia-based desulfurization. Fresh process water is used for secondary spraying to further remove the escaped ammonia gas and reduce the emission of aerosols, more thoroughly purify the flue gas, and ensure compliance with emissions standards.

[0003] The ammonia-nitrogen wastewater generated by the secondary water washing (mainly containing NH3, NH4 + , a small amount of ammonium sulfate and impurities) is recycled back to the absorption tower to recover ammonia resources, reduce the supplement of fresh liquid ammonia, or introduced into the ammonium sulfate mother liquor circulation system to generate ammonium sulfate crystals, realizing resource utilization.

[0004] Problems in the prior art:

[0005] (1) Excessively high flue gas temperature: The high-temperature flue gas (120 - 180 °C) directly enters the absorption tower, resulting in a decrease in the desulfurization reaction efficiency (the absorption of SO2 is significantly affected by temperature);

[0006] (2) Waste of waste heat: The waste heat of the flue gas is not effectively utilized, and additional energy consumption is required for cooling;

[0007] (3) High cost of wastewater treatment: Traditional ammonia-nitrogen wastewater treatment relies on processes such as stripping and membrane separation, with high energy consumption and chemical agent costs;

[0008] (4) Fluctuation of water balance: In the ammonia-based desulfurization system, the reuse of secondary water washing wastewater is likely to cause the accumulation of impurities (Cl - , F - , heavy metals), leading to equipment corrosion and a decline in crystal quality; discharging or independently treating the wastewater disrupts the water balance of the system, increasing the makeup water volume and operating costs. The imbalance between wastewater reuse and discharge ratios results in unstable makeup water volume of the system. Summary of the Invention

[0009] Considering the above problems, the present invention uses the secondary ammonia-nitrogen wastewater as a cooling medium and sets up a spray tower heat exchange system before the flue gas enters the tower to realize an ammonia-based desulfurization device and method based on heat exchange in a spray tower. A device and method for heat exchange between a spray tower and secondary ammonia-nitrogen wastewater are set up before the flue gas enters the absorption tower, which is used to improve the desulfurization efficiency, recover waste heat, optimize the water balance, and achieve wastewater reduction.

[0010] (1) Flue gas cooling + waste heat recovery: The high-temperature flue gas directly contacts and exchanges heat with the low-temperature wastewater to improve the desulfurization efficiency and recover waste heat;

[0011] (2) Wastewater pretreatment + reduction: Utilize the heat of the flue gas to evaporate part of the wastewater, reducing the subsequent treatment load;

[0012] (3) Intelligent regulation of water balance: By dynamically matching the evaporation volume of wastewater and the makeup water volume, the system water balance is stabilized.

[0013] The technical solution of the present invention is as follows: An ammonia desulfurization device based on spray tower heat exchange includes a spray tower T101, an absorption tower T102, a primary water washing tank V101, a secondary water washing tank V102, a slurry circulation pump P101, a wastewater pump P102, a primary water washing pump P103, a secondary water washing pump P104, a steam generator E101, and a slurry cooler E102;

[0014] The side of the spray tower T101 is provided with a flue gas inlet, and the top is provided with a flue gas outlet, which is connected to the inlet of the absorption tower T102; The bottom of the spray tower T101 is provided with a concentrated liquid outlet, which is connected to the steam generator E101; n spray layers are arranged inside the spray tower T101;

[0015] The bottom of the absorption tower T102 is provided with an air inlet; n spray layers are arranged in the middle and lower part of the absorption tower T102; The bottom of the absorption tower T102 is provided with an outlet, which is divided into two branches; One branch passes through the slurry circulation pump P101 and is divided into two strands, one strand is used as a product ammonium sulfate extraction device, and the other strand is divided into n pipelines, which are respectively connected to each spray layer of the absorption tower T102; The other branch passes through the slurry cooler E102 and is connected to the bottom of the absorption tower T102;

[0016] Above the n spray layers of the absorption tower T102, a primary water washing spray layer and a secondary water washing spray layer are provided;

[0017] The first outlet of the primary water washing tank V101 is connected to the primary water washing spray layer through the primary water washing pump P103; The side of the absorption tower T102 is provided with a primary water washing outlet at the height of the bottom of the primary water washing spray layer, and the primary water washing outlet is connected to the first inlet of the primary water washing tank V101; Fresh process water is introduced into the second inlet of the primary water washing tank V101, and the second outlet of the primary water washing tank V101 is connected to the first inlet of the secondary water washing tank V102;

[0018] The first outlet of the secondary water washing tank V102 is connected to the secondary water washing spray layer through the secondary water washing pump P104; The side of the absorption tower T102 is provided with a secondary water washing outlet at the height of the bottom of the secondary water washing spray layer, and the secondary water washing outlet is connected to the second inlet of the secondary water washing tank V102;

[0019] The second outlet of the secondary water washing tank V102 is divided into two branches. The first branch passes through the wastewater pump P102 and is respectively connected to the n spray layers of the spray tower T101, and the second branch is connected to the bottom of the absorption tower T102;

[0020] The top of the absorption tower T102 is provided with a flue gas outlet.

[0021] Among the n pipelines connecting each spray layer of the absorption tower T102, two of the pipelines are connected to the liquid ammonia inlet.

[0022] Further, n = 4.

[0023] A method for an ammonia-based desulfurization device based on spray tower heat exchange, the specific process is as follows:

[0024] The high-temperature flue gas 100 enters from the bottom of the spray tower T101 and directly contacts the part of the secondary ammonia-nitrogen wastewater 101 sprayed by the spray layer in the middle of the spray tower T101 in a countercurrent manner; the temperature of the high-temperature flue gas 100 decreases, and at the same time, part of the SO2 in the high-temperature flue gas 100 is initially absorbed and becomes the flue gas cooling gas 102, which is introduced into the absorption tower T102 from the top of the spray tower T101;

[0025] Part of the secondary ammonia-nitrogen wastewater 101 is evaporated into the concentrated liquid 103 by the flue gas waste heat and discharged from the bottom of the spray tower T101; the concentrated liquid 103 obtains medium-pressure steam 104 through the steam generator E101 to recover the waste heat; the medium-pressure steam 104 is extracted, and the concentrated liquid 103 becomes the wastewater 105 and is discharged externally;

[0026] In the absorption tower T102, the flue gas cooling gas 102 directly contacts the 4 circulating slurries sprayed countercurrently by the spray layer of the absorption tower T102, and a chemical reaction occurs to absorb SO2. After the flue gas cooling gas 102 obtains the preliminarily purified gas, it enters the primary water washing spray layer and contacts the primary water washing water 110 from the primary water washing pump P103 in a countercurrent manner to wash the preliminarily purified gas and reduce ammonia escape; after spraying, the primary water washing water returns to the first inlet of the primary water washing tank V101; then it enters the secondary water washing spray layer and contacts the secondary water washing water 111 from the secondary water washing pump in a countercurrent manner for further washing to reduce ammonia escape; after spraying, the secondary water washing water returns to the second inlet of the secondary water washing tank V102;

[0027] After passing through the primary water washing spray layer and the secondary water washing spray layer in sequence, the final flue gas purified gas 112 is obtained and discharged from the top of the absorption tower T102;

[0028] Two slurries are drawn from the bottom of the absorption tower T102, the first slurry 113 and the second slurry 115. A part of the first slurry 113 is taken out as the product ammonium sulfate 114 out of the device through the slurry circulation pump P101, and the other part is divided into four slurries and connected to the four spray layers of the absorption tower T102 to return to the tower for absorption; the four slurries are successively called the primary circulation slurry 106, the secondary circulation slurry 107, the tertiary circulation slurry 108, and the quaternary circulation slurry 109 from bottom to top; the second slurry 115 is cooled by the slurry cooler E102 and returned to the bottom of the absorption tower T102;

[0029] Liquid ammonia is replenished into the primary circulation slurry 106 and the secondary circulation slurry 107 respectively;

[0030] Fresh process water 118 is supplemented through the second inlet of the first - stage water - washing tank V101, and a part of the first - stage ammonia - nitrogen wastewater 119 at the second outlet of the first - stage water - washing tank V101 is supplemented to the first inlet of the second - stage water - washing tank V102;

[0031] The second - stage ammonia - nitrogen wastewater discharged from the second - stage water - washing tank V102 is divided into two streams. One stream, the recycled ammonia - nitrogen wastewater 120, returns to the bottom of the absorption tower T102 to maintain the water balance. The other stream, the second - stage ammonia - nitrogen wastewater 121, is divided into four streams by the wastewater pump P102 and connected to the four - layer spray layer of the spray tower T101, contacting the high - temperature flue gas in counter - current. This part of the technology should be understood as follows: Considering that recycling ammonia - nitrogen wastewater can save liquid ammonia and water resources, but there is a risk of impurity accumulation, while discharging or treating it externally will disrupt the water balance of the system and increase the makeup water volume. In order to reduce the addition of fresh process water, by recycling a part of the ammonia - nitrogen wastewater, the recycling ratio of the wastewater is controlled to maintain the water balance of the desulfurization system.

[0032] Air 122 is introduced from the bottom of the absorption tower T102 to oxidize ammonium sulfite.

[0033] In the device of the present invention, the connection and inter - connection methods between each device, as well as between pipelines and devices, and the fluid transportation device can be set as required, and each device is not limited to the connection methods described above.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] On the premise of ensuring that ammonia does not escape and sulfur does not exceed the standard, through the heat exchange between the spray tower and the ammonia - nitrogen wastewater and the way of returning part of the ammonia - nitrogen wastewater to the tower, the water balance is accurately controlled, solving the problem of large fluctuations in makeup water volume in the traditional process. At the same time, the waste heat of the flue gas is recovered and the wastewater discharge is reduced. In addition, by recycling the ammonia - nitrogen wastewater, the wastewater is recycled, the consumption of liquid ammonia is reduced, and the output of the product ammonium sulfate is increased. Brief Description of the Drawings

[0036] Figure 1 It is a schematic flow diagram of an ammonia - based desulfurization method based on heat exchange in a spray tower according to the present invention.

[0037] In the figure: T101 - spray tower; T102 - absorption tower; V101 - primary water wash tank; V102 - secondary water wash tank; P101 - slurry circulation pump, P102 - waste water pump; E101 - steam generator; E102 - slurry cooler; 100 - high-temperature flue gas; 101 - secondary ammonia-nitrogen waste water; 102 - flue gas cooling gas; 103 - concentrated liquid; 104 - medium-pressure steam; 105 - waste water; 106 - primary circulating slurry; 107 - secondary circulating slurry; 108 - tertiary circulating slurry; 109 - quaternary circulating slurry; 110 - primary water wash water; 111 - secondary water wash water; 112 - finally flue gas purified gas; 113 - first slurry; 114 - product ammonium sulfate; 115 - second slurry; 116 - first liquid ammonia; 117 - second liquid ammonia; 118 - fresh process water; 119 - primary ammonia-nitrogen waste water; 120 - circulating ammonia-nitrogen waste water; 121 - one stream of secondary ammonia-nitrogen waste water; 122 - air. Detailed implementation manners

[0038] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art through improvement or adjustment belong to the protection scope of the present invention.

[0039] An ammonia desulfurization device based on heat exchange in a spray tower, as Figure 1 shown, includes a spray tower T101, an absorption tower T102, a primary water wash tank V101, a secondary water wash tank V102, a slurry circulation pump P101, a waste water pump P102, a primary water wash pump P103, a secondary water wash pump P104, a steam generator E101 and a slurry cooler E102;

[0040] The side of the spray tower T101 is provided with a flue gas inlet, and the top is provided with a flue gas outlet, which is connected to the inlet of the absorption tower T102; the bottom of the spray tower T101 is provided with a concentrated liquid outlet, which is connected to the steam generator E101; 4 spray layers are arranged in the tower body of the spray tower T101;

[0041] The bottom of the absorption tower T102 is provided with an air inlet; 4 spray layers are arranged in the middle and lower part of the absorption tower T102; the bottom of the absorption tower T102 is provided with an outlet, which is divided into two branches; one branch passes through the slurry circulation pump P101 and is divided into two streams, one stream is used as a product ammonium sulfate extraction device, and the other stream is divided into 4 pipelines, which are respectively connected to each spray layer of the absorption tower T102; the other branch passes through the slurry cooler E102 and is connected to the bottom of the absorption tower T102;

[0042] Above the 4 spray layers of the absorption tower T102, a primary water wash spray layer and a secondary water wash spray layer are provided;

[0043] The first outlet of the first-stage water washing tank V101 is connected to the first-stage water washing spray layer through the first-stage water washing pump P103; on the side of the absorption tower T102, a first-stage water washing outlet is provided at the height of the bottom of the first-stage water washing spray layer, and the first-stage water washing outlet is connected to the first inlet of the first-stage water washing tank V101; fresh process water is introduced into the second inlet of the first-stage water washing tank V101, and the second outlet of the first-stage water washing tank V101 is connected to the first inlet of the second-stage water washing tank V102;

[0044] The first outlet of the second-stage water washing tank V102 is connected to the second-stage water washing spray layer through the second-stage water washing pump P104; on the side of the absorption tower T102, a second-stage water washing outlet is provided at the height of the bottom of the second-stage water washing spray layer, and the second-stage water washing outlet is connected to the second inlet of the second-stage water washing tank V102;

[0045] The second outlet of the second-stage water washing tank V102 is divided into two branches. The first branch is connected to the 4-layer spray layers of the spray tower T101 through the waste water pump P102 respectively, and the second branch is connected to the bottom of the absorption tower T102;

[0046] A flue gas outlet is provided at the top of the absorption tower T102.

[0047] Among the 4 pipelines connecting each spray layer of the absorption tower T102, two of the pipelines are connected to the liquid ammonia inlet.

[0048] A method of an ammonia-based desulfurization device based on spray tower heat exchange, the specific process is as follows:

[0049] The high-temperature flue gas 100 enters from the bottom of the spray tower T101 and directly contacts the part of the secondary ammonia nitrogen wastewater 101 sprayed by the middle spray layer of the spray tower T101 in a reverse direction; the temperature of the high-temperature flue gas 100 decreases, and at the same time, part of the SO2 in the high-temperature flue gas 100 is preliminarily absorbed and becomes the flue gas cooling gas 102, which is introduced into the absorption tower T102 from the top of the spray tower T101;

[0050] Part of the secondary ammonia nitrogen wastewater 101 is evaporated into a concentrated liquid 103 by the waste heat of the flue gas and discharged from the bottom of the spray tower T101; the concentrated liquid 103 obtains medium-pressure steam 104 through the steam generator E101 to recover the waste heat; the medium-pressure steam 104 is taken out, and the concentrated liquid 103 becomes wastewater 105 and is discharged;

[0051] The flue gas cooler 102 is in the absorption tower T102, and directly contacts with 4 streams of circulating slurry sprayed reversely by the spray layer of the absorption tower T102, and a chemical reaction occurs to absorb SO2. After the flue gas cooler 102 obtains the preliminary purified gas, it enters the primary water washing spray layer and contacts countercurrently with the primary water washing water 110 from the primary water washing pump P103 to wash the preliminary purified gas and reduce ammonia escape; after spraying, the primary water washing water returns to the first inlet of the primary water washing tank V101; then it enters the secondary water washing spray layer and contacts countercurrently with the secondary water washing water 111 from the secondary water washing pump to further wash and reduce ammonia escape; after spraying, the secondary water washing water returns to the second inlet of the secondary water washing tank V102;

[0052] It successively passes through the primary water washing spray layer and the secondary water washing spray layer to obtain the final flue gas purified gas 112, which is discharged from the top of the absorption tower T102;

[0053] Two streams of slurry are drawn out from the bottom of the absorption tower T102, the first slurry 113 and the second slurry 115. A part of the first slurry 113 is taken out as the product ammonium sulfate 114 out of the device by the slurry circulation pump P101, and the other part is divided into four streams of slurry and connected to the four spray layers of the absorption tower T102 to return to the tower for absorption; the four streams of slurry are successively called the primary circulating slurry 106, the secondary circulating slurry 107, the tertiary circulating slurry 108 and the quaternary circulating slurry 109 from bottom to top; the second slurry 115 is cooled by the slurry cooler E102 and returns to the bottom of the absorption tower T102;

[0054] Liquid ammonia is replenished into the primary circulating slurry 106 and the secondary circulating slurry 107 respectively;

[0055] Fresh process water 118 is replenished into the second inlet of the primary water washing tank V101, and a part of the primary ammonia-nitrogen wastewater 119 at the second outlet of the primary water washing tank V101 is replenished into the first inlet of the secondary water washing tank V102;

[0056] The secondary ammonia-nitrogen wastewater coming out of the secondary water washing tank V102 is divided into two streams. One stream of circulating ammonia-nitrogen wastewater 120 returns to the bottom of the absorption tower T102 to maintain the water balance, and the other stream of secondary ammonia-nitrogen wastewater 121 is divided into four streams by the wastewater pump P102 and connected to the four spray layers of the spray tower T101 to contact countercurrently with the high-temperature flue gas; this part of the technology should be understood that considering that recycling ammonia-nitrogen wastewater can save liquid ammonia and water resources, but there is a risk of impurity accumulation, while discharging or treating it will disrupt the water balance of the system and increase the makeup water volume. In order to reduce the addition of fresh process water, by recycling a part of the ammonia-nitrogen wastewater, the recycling ratio of the wastewater is controlled to maintain the water balance of the desulfurization system.

[0057] Air 122 is introduced from the bottom of the absorption tower T102 to oxidize ammonium sulfite.

[0058] Example 1

[0059] An ammonia desulfurization system in a coking plant adopts the processes of spray tower heat exchange and partial return of part of the ammonia-nitrogen wastewater to the tower. The flue gas volume flow rate is 175,892.83 m 3 / h, the temperature is 125.6 °C, the SO2 is 156.78 kg / h. Finally, through the spray and absorption unit, 312.42 kg / h of ammonium sulfate product is obtained, 94 kg / h of liquid ammonia is consumed, 10 m 3 / h of fresh process water is supplemented, and 14.99 m 3 / h of secondary ammonia-nitrogen wastewater is returned to the tower. 6.89 kg / h more ammonium sulfate product is obtained, 1.15 m 3 / h less ammonia-nitrogen wastewater is discharged, the reuse rate of ammonia-nitrogen wastewater is 66.7%, and 187.38 kW / h less cooling capacity is supplemented.

[0060] The above embodiments only represent the implementation modes of the present invention, but should not be construed as limiting the scope of the present invention patent. It should be noted that for those skilled in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. An ammonia-based desulfurization device based on heat exchange in a spray tower, characterized in that, The ammonia desulfurization device based on spray tower heat exchange includes a spray tower (T101), an absorption tower (T102), a primary water wash tank (V101), a secondary water wash tank (V102), a slurry circulation pump (P101), a waste water pump (P102), a primary water wash pump (P103), a secondary water wash pump (P104), a steam generator (E101), and a slurry cooler (E102); The spray tower (T101) is provided with a flue gas inlet on the side of the tower and a flue gas outlet at the top of the tower, which is connected to the inlet of the absorption tower (T102); the bottom of the spray tower (T101) is provided with a concentrated liquid outlet, which is connected to the steam generator (E101); n spray layers are arranged in the tower body of the spray tower (T101); The bottom of the absorption tower (T102) is provided with an air inlet; n spray layers are arranged in the middle and lower part of the absorption tower (T102); The bottom of the absorption tower (T102) is provided with an outlet, which is divided into two branches; one branch passes through the slurry circulation pump (P101) and is divided into two streams, one stream is used as the product ammonium sulfate extraction device, and the other stream is divided into n pipelines, which are respectively connected to each spray layer of the absorption tower (T102); the other branch passes through the slurry cooler (E102) and is connected to the bottom of the absorption tower (T102); Above the n spray layers of the absorption tower (T102), a primary water wash spray layer and a secondary water wash spray layer are arranged; The first outlet of the primary water wash tank (V101) is connected to the primary water wash spray layer through the primary water wash pump (P103); On the side of the absorption tower (T102), a primary water wash outlet is provided at the height of the bottom of the primary water wash spray layer, and the primary water wash outlet is connected to the first inlet of the primary water wash tank (V101); fresh process water is introduced into the second inlet of the primary water wash tank (V101), and the second outlet of the primary water wash tank (V101) is connected to the first inlet of the secondary water wash tank (V102); The first outlet of the secondary water wash tank (V102) is connected to the secondary water wash spray layer through the secondary water wash pump (P104); On the side of the absorption tower (T102), a secondary water wash outlet is provided at the height of the bottom of the secondary water wash spray layer, and the secondary water wash outlet is connected to the second inlet of the secondary water wash tank (V102); The second outlet of the secondary water wash tank (V102) is divided into two branches. The first branch passes through the waste water pump (P102) and is respectively connected to the n spray layers of the spray tower (T101), and the second branch is connected to the bottom of the absorption tower (T102); The top of the absorption tower (T102) is provided with a flue gas outlet.

2. The ammonia desulfurization device based on heat exchange in a spray tower according to claim 1, wherein Among the n pipelines connecting each spray layer of the absorption tower (T102), two of the pipelines are connected to the liquid ammonia inlet.

3. The ammonia desulfurization device based on heat exchange in a spray tower according to claim 1 or 2, characterized in that, n＝4。 4. A method using the ammonia desulfurization device based on spray tower heat exchange according to any one of claims 1-3, characterized in that, The specific process is as follows: The high-temperature flue gas (100) enters from the bottom of the spray tower (T101) and directly contacts the part of the secondary ammonia nitrogen wastewater (101) sprayed by the spray layer in the middle of the spray tower (T101) in a reverse direction; the temperature of the high-temperature flue gas (100) decreases, and at the same time, part of the SO2 in the high-temperature flue gas (100) is preliminarily absorbed and becomes the flue gas cooling gas (102), which is introduced into the absorption tower (T102) from the top of the spray tower (T101); Part of the secondary ammonia nitrogen wastewater (101) is evaporated into concentrated liquid (103) by the waste heat of the flue gas and discharged from the bottom of the spray tower (T101); the concentrated liquid (103) is fed into the steam generator (E101) to obtain medium-pressure steam (104) and recover the waste heat; the medium-pressure steam (104) is extracted, and the concentrated liquid (103) becomes wastewater (105) and is discharged externally. In the absorption tower (T102), the flue gas cooling gas (102) is in direct contact with 4 streams of circulating slurry sprayed reversely by the spray layer of the absorption tower (T102), and a chemical reaction occurs to absorb SO2. After the flue gas cooling gas (102) is preliminarily purified, it enters the primary water washing spray layer and is in countercurrent contact with the primary water washing water (110) from the primary water washing pump (P103) to wash the preliminarily purified gas and reduce ammonia escape; after spraying, the primary water washing water returns to the first inlet of the primary water washing tank (V101); then it enters the secondary water washing spray layer and is in countercurrent contact with the secondary water washing water (111) from the secondary water washing pump to further wash and reduce ammonia escape; after spraying, the secondary water washing water returns to the second inlet of the secondary water washing tank (V102). After passing through the primary water washing spray layer and the secondary water washing spray layer in sequence, the final flue gas purified gas (112) is obtained and discharged from the top of the absorption tower (T102). Two streams of slurry are drawn out from the bottom of the absorption tower (T102), the first slurry (113) and the second slurry (115). A part of the first slurry (113) is extracted by the slurry circulation pump (P101) as the product ammonium sulfate (114) to leave the device, and the other part is divided into four streams of slurry and connected to the four-layer spray layer of the absorption tower (T102) to return to the tower for absorption; the four streams of slurry are successively called the primary circulating slurry (106), the secondary circulating slurry (107), the tertiary circulating slurry (108), and the quaternary circulating slurry (109) from bottom to top; the second slurry (115) is cooled by the slurry cooler (E102) and returned to the bottom of the absorption tower (T102). Liquid ammonia is replenished into the primary circulating slurry (106) and the secondary circulating slurry (107) respectively. Fresh process water (118) is replenished into the second inlet of the primary water washing tank (V101), and a part of the primary ammonia nitrogen wastewater (119) at the second outlet of the primary water washing tank (V101) is replenished into the first inlet of the secondary water washing tank (V102). The secondary ammonia nitrogen wastewater coming out of the secondary water washing tank (V102) is divided into two streams. One stream of circulating ammonia nitrogen wastewater (120) returns to the bottom of the absorption tower (T102) to maintain the water balance, and one stream of secondary ammonia nitrogen wastewater (121) is divided into four streams by the wastewater pump (P102) and connected to the four-layer spray layer of the spray tower (T101) to be in countercurrent contact with the high-temperature flue gas. Air (122) is introduced from the bottom of the absorption tower (T102) to oxidize ammonium sulfite.

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