Industrial flue gas ammonia escape treatment system with heat recycling

Abstract

The utility model discloses an industrial flue gas ammonia escape treatment system of thermal power recycling, including the multifunctional ammonia removal tower, ammonia removal tower upper section circulating tank, ammonia removal tower middle section circulating tank, multifunctional rectifying tower, MVR compressor, reboiler, two stage rectifying tower, primary sedimentation tank, reaction tank, two stage sedimentation tank, pulping jar, ammonia removal tower upper section circulating pump, ammonia removal tower middle section circulating pump, ammonia removal tower lower section circulating pump, backflow pump, slurry delivery pump, WGGH circulating pump, WGGH heat exchanger, lean rich liquid heat exchanger, ammonia gas condensing cooler that connect gradually, the utility model discloses has realized the recycling of waste heat fully, has realized the energy -conserving of depth, in addition, on the basis of the utility model, SCR (selective catalytic reduction) and SNCR (non catalytic reduction) denitration device can adopt excess ammonia injection strategy, realizes the ultra -low emission of nitrogen oxides (NOx), and excess ammonia injection strategy leads to the further over standard of ammonia escape, and the ammonia escape control technology described in the utility model is used at the end of flue gas, can realize the full recovery of ammonia gas.

Description

Technical Field

[0001] This utility model relates to the field of environmental protection technology, specifically to an industrial flue gas ammonia escape treatment system that utilizes thermal recycling. Background Technology

[0002] In the process of producing cement from calcium carbide slag, calcium carbide slag with a moisture content of about 20-30% needs to be dried. The heat source used for drying calcium carbide slag is high-temperature flue gas, which is located at the back end of the denitrification device. A large amount of ammonia gas is generated during the drying process of calcium carbide slag, causing serious ammonia escape accidents. On the other hand, the SNCR denitrification of cement kilns requires a large amount of ammonia water as a denitrification agent. Enterprises usually purchase liquid ammonia or ammonia water from outside, which is costly. Utility Model Content

[0003] The purpose of this invention is to provide an industrial flue gas ammonia escape treatment system that utilizes thermal recycling to solve the problems mentioned in the background art.

[0004] This invention utilizes industrial waste sulfuric acid to absorb ammonia from flue gas. The resulting ammonium sulfate solution reacts with Ca(OH)2 in carbide slag, releasing ammonia gas again. After condensation and cooling, it forms ammonia water, which is supplied to SNCR denitrification. The generated calcium sulfate solid waste is used as a major raw material in cement production and is digested on-site. The process of treating ammonia escape from flue gas requires a large amount of heat energy. This invention fully realizes the recovery and reuse of waste heat, achieving deep energy saving. In addition, based on this invention, SCR (Selective Catalytic Reduction) and SNCR (Non-Catalytic Reduction) denitrification devices can adopt an excessive ammonia injection strategy to achieve ultra-low emissions of nitrogen oxides (NOx). Although the excessive ammonia injection strategy leads to further exceedances of ammonia escape, the ammonia escape control technology described in this invention can be used at the end of the flue gas treatment process to achieve full recovery of ammonia gas.

[0005] This utility model provides the following technical solution: a process for treating ammonia escape from industrial flue gas using thermal recycling, comprising a multi-functional ammonia removal tower, an upper circulation tank of the ammonia removal tower, a middle circulation tank of the ammonia removal tower, a multi-functional distillation tower, an MVR compressor, a reboiler, a secondary distillation tower, a primary sedimentation tank, a reaction tank, a secondary sedimentation tank, a slurry preparation tank, an upper circulation pump of the ammonia removal tower, a middle circulation pump of the ammonia removal tower, a lower circulation pump of the ammonia removal tower, a reflux pump, a slurry transfer pump, a WGGH circulation pump, a WGGH heat exchanger, a lean and rich liquid heat exchanger, and an ammonia condenser / cooler connected in sequence. The inlet of the multi-functional ammonia removal tower receives ammonia-containing flue gas from the outside. The flue gas undergoes three stages of scrubbing before being discharged. The multi-functional ammonia removal tower has a three-stage structure, from bottom to top: an ammonium sulfate concentration section, an ammonia scrubbing section, and an acid mist capture section. See [link to details] for the specific structure. Figure 2The upper section of the multi-functional ammonia stripping tower is connected to the upper section of the ammonia stripping tower circulation tank, the middle section of the multi-functional ammonia stripping tower is connected to the middle section of the ammonia stripping tower circulation tank, the upper full-flow port of the upper section of the ammonia stripping tower circulation tank is connected to the middle section of the multi-functional ammonia stripping tower, and the upper full-flow port of the middle section of the ammonia stripping tower circulation tank is connected to the lower section of the multi-functional ammonia stripping tower. The circulating washing liquid from the upper section of the deammoniation tower's circulating tank is pumped to the upper section of the multi-functional deammoniation tower via the upper section circulating pump. The circulating washing liquid from the middle section of the deammoniation tower's circulating tank is pumped to the middle section of the multi-functional deammoniation tower via the middle section circulating pump. The concentrated liquid at the bottom of the multi-functional deammoniation tower is pumped to the lower section of the deammoniation tower via the lower section circulating pump. A portion of the rich liquid in the lower section of the multi-functional deammoniation tower is drawn by the lower section circulating pump and sent to the lean-rich liquid heat exchanger, and further connected to the multi-functional distillation tower.

[0006] The bottom of the multi-functional distillation column is connected to the lean and rich liquid heat exchanger, and further connected to the primary sedimentation tank. The primary sedimentation tank is connected to the reaction tank, the reaction tank is connected to the secondary sedimentation tank, and the upper clear liquid of the secondary sedimentation tank is connected to the lower section of the multi-functional deammoniation column. The secondary steam at the top of the multi-functional distillation column is compressed by an MVR compressor, then connected to a reboiler, and further connected to a secondary distillation column. The bottom of the multi-functional distillation column is connected to a reboiler, then passes through a WGGH circulating pump and is connected to a WGGH heat exchanger, and further connected to a secondary distillation column, and finally connected to the multi-functional distillation column.

[0007] The secondary steam at the top of the secondary distillation column is connected to an ammonia condenser.

[0008] The multi-functional ammonia removal tower has a three-section structure. The lower section is the concentration section, used to concentrate the ammonia-rich washing solution. The middle section is the ammonia absorption section, used for deep washing of ammonia in the flue gas. The upper section is the acid mist capture section, used to fully capture sulfuric acid mist entrained in the flue gas. The structure of the multi-functional ammonia removal tower (1) is shown in the figure. Figure 2 ; The multi-functional distillation column has a two-section structure. The upper section is the rectification section, which fully rectifies the ammonia nitrogen in the ammonia-rich washing solution. The lower section is the steam generation section, which generates secondary steam to supply the rectification section. A liquid cut-off plate is installed between the rectification section and the steam generation section. The solution in the rectification section cannot enter the steam generation section, while the steam generated in the steam generation section can smoothly enter the rectification section through the liquid cut-off plate. The two-section structure design of the multi-functional distillation column avoids the slurry containing solid particles in the upper section from entering the reboiler, ensuring that the reboiler operates for a long time without scaling or clogging. The structure of the multifunctional distillation column is shown in the figure. Figure 3 .

[0009] The system of this utility model can be divided into a reactive distillation system, a deep energy-saving system, and an anti-clogging system. The reactive distillation system includes a multi-functional distillation column, a primary sedimentation tank, a reaction tank, a secondary sedimentation tank, a slurry preparation tank, a reflux pump, and a slurry transfer pump; The bottom of the multi-functional distillation column is connected to the lean and rich liquid heat exchanger, and further connected to the primary sedimentation tank. The primary sedimentation tank is connected to the reaction tank, the reaction tank is connected to the secondary sedimentation tank, and the upper clear liquid of the secondary sedimentation tank is connected to the lower section of the multi-functional deammoniation column. The deep energy-saving system includes a multi-functional distillation column, an MVR compressor, a reboiler, a secondary distillation column, a reflux pump, a WGGH circulating pump, a WGGH heat exchanger, a lean and rich liquid heat exchanger, and an ammonia condenser / cooler.

[0010] The secondary steam at the top of the multi-functional distillation column is compressed by an MVR compressor, then connected to a reboiler, and further connected to a secondary distillation column. The bottom of the multi-functional distillation column is connected to a reboiler, then passes through a WGGH circulating pump and is connected to a WGGH heat exchanger, and further connected to a secondary distillation column, and finally connected to the multi-functional distillation column.

[0011] The secondary steam at the top of the secondary distillation column is connected to an ammonia condenser. The high-temperature wastewater at the bottom of the secondary distillation column is pumped back and then connected to the multi-functional distillation column.

[0012] The anti-clogging system includes a primary sedimentation tank, a reaction tank, and a secondary sedimentation tank. The primary sedimentation tank is connected to the reaction tank, the reaction tank is connected to the secondary sedimentation tank, and the secondary sedimentation tank is connected to the bottom of the multi-functional deammoniation tower.

[0013] The process of this invention fully captures and recovers the ammonia gas escaping from the flue gas and uses it in the SNCR denitrification device of the cement kiln, achieving two goals at once. Furthermore, the secondary solid waste generated during the ammonia capture process can be used as an essential raw material in the cement production process, which can demonstrate higher economic and environmental value. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Among them: Figure 1 A flow chart of an industrial flue gas ammonia escape treatment system utilizing thermal recycling in this utility model; Figure 2 A simplified structural diagram of the multifunctional ammonia removal tower in this utility model; Figure 3 A simplified structural diagram of the multifunctional distillation column in this utility model.

[0015] In the diagram: 1. Multifunctional ammonia removal tower; 2. Upper circulation tank of the ammonia removal tower; 3. Middle circulation tank of the ammonia removal tower; 4. Multifunctional distillation tower; 5. MVR compressor; 6. Reboiler; 7. Secondary distillation tower; 8. Primary sedimentation tank; 9. Reaction tank; 10. Secondary sedimentation tank; 11. Slurry preparation tank; 12. Upper circulation pump of the ammonia removal tower; 13. Middle circulation pump of the ammonia removal tower; 14. Lower circulation pump of the ammonia removal tower; 15. Reflux pump; 16. Slurry transfer pump; 17. WGGH circulation pump; 18. WGGH heat exchanger; 19. Lean and rich liquid heat exchanger; 20. Ammonia condenser / cooler. Detailed Implementation

[0016] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings.

[0017] Many specific details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0018] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments.

[0019] Please see Figure 1 A process for treating ammonia escape from industrial flue gas using thermal recycling includes a multi-functional ammonia removal tower 1, an upper circulation tank 2, a middle circulation tank 3, a multi-functional distillation tower 4, an MVR compressor 5, a reboiler 6, a secondary distillation tower 7, a primary sedimentation tank 8, a reaction tank 9, a secondary sedimentation tank 10, a slurry preparation tank 11, an upper circulation pump 12, a middle circulation pump 13, a lower circulation pump 14, a reflux pump 15, a slurry transfer pump 16, a WGGH circulation pump 17, a WGGH heat exchanger 18, a lean and rich liquid heat exchanger 19, and an ammonia condenser / cooler 20, all connected in sequence. The inlet of the multi-functional ammonia removal tower 1 receives ammonia-containing flue gas from the outside. The flue gas passes through three stages of scrubbing in the multi-functional ammonia removal tower 1 before being discharged. The multi-functional ammonia removal tower 1 has a three-stage structure, from bottom to top: an ammonium sulfate concentration section, an ammonia scrubbing section, and an acid mist capture section. See [link to specific structure details] for details. Figure 2The upper washing liquid outlet of the multi-functional ammonia removal tower 1 is connected to the upper circulation tank 2 of the ammonia removal tower, the middle washing liquid outlet of the multi-functional ammonia removal tower 1 is connected to the middle circulation tank 3 of the ammonia removal tower, the upper full-flow port of the upper circulation tank 2 of the ammonia removal tower is connected to the middle section of the multi-functional ammonia removal tower 1, and the upper full-flow port of the middle circulation tank 3 of the ammonia removal tower is connected to the lower section of the multi-functional ammonia removal tower 1.

[0020] The circulating washing liquid in the upper section circulation tank 2 of the deammoniation tower is sent to the upper section circulation washing of the multi-functional deammoniation tower 1 via the upper section circulation pump 12. The circulating washing liquid in the middle section circulation tank 3 of the deammoniation tower is sent to the middle section circulation washing of the multi-functional deammoniation tower 1 via the middle section circulation pump 13. The concentrated liquid at the bottom of the multi-functional deammoniation tower 1 is sent to the lower section circulation washing of the deammoniation tower via the lower section circulation pump 14. A portion of the rich liquid in the lower section of the multi-functional deammoniation tower 1 is drawn by the lower section circulation pump 14 and sent to the lean and rich liquid heat exchanger (19), and further connected to the multi-functional distillation tower 4. The bottom of the multi-functional distillation column 4 is connected to the lean and rich liquid heat exchanger 19, and further connected to the primary sedimentation tank 8. The primary sedimentation tank 8 is connected to the reaction tank 9, the reaction tank 9 is connected to the secondary sedimentation tank 10, and the upper clear liquid of the secondary sedimentation tank 10 is connected to the lower section of the multi-functional deammoniation column 1.

[0021] The secondary steam at the top of the multifunctional distillation column 4 passes through the MVR compressor 5, then connects to the reboiler 6, and further connects to the secondary distillation column 7. The bottom of the multifunctional distillation column 4 is connected to the reboiler. The bottom of the multifunctional distillation column 4 passes through the WGGH circulating pump 17 and connects to the WGGH heat exchanger 18, and further connects to the secondary distillation column 7, and finally connects to the multifunctional distillation column 4.

[0022] The secondary steam at the top of the secondary distillation column 7 is connected to the ammonia condenser 20.

[0023] The high-temperature wastewater at the bottom of the secondary distillation column 7 is further connected to the multifunctional distillation column 4 via the reflux pump 15.

[0024] The specific implementation steps of this process are as follows: S1: The flue gas containing high concentrations of ammonia from the carbide slag cement production line is introduced into the lower section of the multi-functional deammoniation tower 1. Under the spraying action of the circulating absorbent liquid (material ①), the temperature of the flue gas drops instantly from 160℃ to about 60℃. At the same time, the ammonia in the flue gas reacts with the sulfuric acid in the circulating absorbent liquid to produce ammonium sulfate, as shown in the following reaction: NH3 + H2SO4 → (NH4)2SO4 At the same time, a large amount of circulating absorbent is evaporated, and when the concentration of ammonium sulfate solution approaches 30%, a portion of the feed liquid (material ②) is extracted and sent to the multi-functional distillation tower 4. The flue gas further enters the middle section of the multifunctional ammonia removal tower 1 from bottom to top, where it further absorbs the residual ammonia in the flue gas, and the reaction is as follows: NH3 + H2SO4 → (NH4)2SO4 After intermediate scrubbing, the ammonia concentration in the flue gas is less than 0.5 ppm, and it continues to enter the upper section of the multi-functional ammonia removal tower 1. The function of the upper section is to fully capture sulfuric acid mist in the flue gas; The upper section of the multi-functional ammonia removal tower 1 uses an intermittent water spray demister. The sprayed water is intercepted at the liquid cut-off plate between the upper and middle sections of the multi-functional ammonia removal tower 1, and flows by gravity into the upper section circulation tank 2 of the ammonia removal tower, causing its liquid level to rise. This water then flows fully into the middle section circulation tank 3 of the ammonia removal tower. The liquid level in the middle section circulation tank 3 rises, and then flows fully into the lower section of the multi-functional ammonia removal tower 1. The above-described liquid phase process ensures the ammonium sulfate concentration gradient in each tank and also achieves the liquid level balance of the multifunctional deammonia removal tower 1.

[0025] S2: Material ② is an ammonium sulfate solution with a concentration of 20~30% and a temperature of 50~60℃, containing a certain amount of solid impurities. Material ② is sent to the lean and rich liquor heat exchanger 19 by the side stream of the lower section circulation pump 14 of the deammoniation tower, and fully exchanges heat with the 100℃ high-temperature lean liquor discharged from the multi-functional distillation tower 4. After being preheated to ≥90℃, material ② is sent to the feed plate position of the multi-functional distillation tower 4. At the same time, the pre-prepared carbide slag slurry is also sent to the feed plate of the multi-functional distillation tower 4 via the slurry transfer pump 16.

[0026] The reactive distillation process that occurs within the multifunctional distillation column 4 is as follows: Ca(OH)2+(NH4)2SO4→CaSO4↓+NH3↑+H2O S3: The lean liquor ③ containing calcium sulfate CaSO4 solid particles discharged from the bottom of the multifunctional distillation column 4 should not be directly returned to the multifunctional deammoniation column 1 to avoid equipment blockage; The lean liquor ③ is first cooled in the lean-rich liquor heat exchanger 19. After the temperature drops from 100℃ to about 70℃, it flows by gravity into the primary sedimentation tank 8, where solid particles are fully separated by sedimentation. The supernatant flows by gravity into the reaction tank 9, where a certain amount of carbon dioxide and ammonia are simultaneously injected. The excess Ca(OH)2 in the lean liquor ③ reacts with CO2 and NH3 as follows: Ca(OH)₂ + CO₂ → CaCO₃↓ In this reaction process, NH3 acts as a catalyst, mainly playing a role in adjusting the pH value, which can effectively promote the formation of calcium carbonate, thereby deeply removing calcium ions from the aqueous solution. All the suspension in reaction tank 9 enters the secondary sedimentation tank 10, and the clear liquid after sedimentation and separation flows by gravity into the lower section of the multi-functional deammoniation tower 1. This process strictly controls the calcium ion concentration in the absorbent, ensuring that scaling and clogging are completely avoided in the multifunctional deammoniation tower 1.

[0027] S4: The secondary steam at the top of the multi-functional distillation column 4 contains about 5-10% ammonia. It enters an MVR compressor 5 for compression and heating, and then enters the shell side of the reboiler 6 for condensation and cooling to form a steam-water mixture ⑥, which then enters the secondary distillation column 7. The tube side of the reboiler 6 is supplied with soft water ⑤ from the lower section (steam generation section) of the multifunctional distillation column 4. The soft water ⑤ fully absorbs the latent heat of the secondary steam in the reboiler and partially vaporizes, returning to the multifunctional distillation column 4 to achieve the steam supply required for the distillation process. This step not only fully recovers the latent heat of the secondary steam at the top of the multifunctional distillation column 4, but also prevents the slurry containing a large amount of solid particles in the rectification section from directly entering the reboiler, ensuring that the reboiler will not be blocked.

[0028] S5: As the soft water ⑤ in the lower section of the multi-functional distillation column 4 continues to evaporate and form steam, the liquid level will inevitably drop. Therefore, the bottom liquid after the steam-water mixture entering the secondary distillation column 7 has been fully distilled and ammonia extracted is transported to the lower section of the multi-functional distillation column 4 by the reflux pump 15 to maintain the normal liquid level. The ammonia concentration in the secondary steam overflowing from the top of the secondary distillation column 7 is greater than 20%. It is fully condensed and cooled in the ammonia condenser 20, and the resulting liquid phase is ammonia water with an ammonia concentration greater than 20%. The non-condensable gas is returned to the lower section of the multi-functional deammoniation column 1.

[0029] S6: The MVR compressor 5 in the process flow achieves high efficiency and energy saving, but it is still insufficient to maintain the heat balance required for the production of the unit. Therefore, a portion of the soft water ⑦ in the lower section of the multifunctional distillation column 4 is transported by the WGGH circulating pump 17 to the WGGH heat exchanger 18 to fully absorb the sensible heat of the high temperature flue gas, and then further transported to the bottom of the secondary distillation column 7 for heating, and then returned to the lower section of the multifunctional distillation column 4.

[0030] This step achieves heat balance in the process flow, and the distillation process of the multifunctional distillation column 4 and the secondary distillation column 7 does not require additional heat energy supply.

[0031] Unless otherwise specified in the above description, all parts are prior art or can be implemented using existing technology. Furthermore, the specific embodiments described in this utility model are merely preferred embodiments and are not intended to limit the scope of this utility model. That is, all equivalent changes and modifications made within the scope of this utility model patent should be considered within the technical scope of this utility model.

Claims

1. A thermally recycled industrial flue gas ammonia escape treatment system, characterized in that, The system includes, in sequence, a multi-functional deammoniation tower (1), an upper circulation tank of the deammoniation tower (2), a middle circulation tank of the deammoniation tower (3), a multi-functional distillation tower (4), an MVR compressor (5), a reboiler (6), a secondary distillation tower (7), a primary sedimentation tank (8), a reaction tank (9), a secondary sedimentation tank (10), a slurry preparation tank (11), a WGGH heat exchanger (18), a lean and rich liquid heat exchanger (19), and an ammonia condenser (20). The upper section of the washing liquid outlet of the multi-functional deammonium stripper (1) is connected to the upper section circulation tank (2) of the deammonium stripper, the middle section of the washing liquid outlet of the multi-functional deammonium stripper (1) is connected to the middle section circulation tank (3) of the deammonium stripper, the upper full flow port of the upper section circulation tank (2) of the deammonium stripper is connected to the middle section of the multi-functional deammonium stripper (1), and the upper full flow port of the middle section circulation tank (3) of the deammonium stripper is connected to the lower section of the multi-functional deammonium stripper (1). The circulating washing liquid in the upper section of the deammoniation tower (2) is sent to the upper section of the multi-functional deammoniation tower (1) via the upper section circulating pump (12). The circulating washing liquid in the middle section of the deammoniation tower (3) is sent to the middle section of the multi-functional deammoniation tower (1) via the middle section circulating pump (13). The concentrated liquid at the bottom of the multi-functional deammoniation tower (1) is sent to the lower section of the deammoniation tower via the lower section circulating pump (14). A portion of the rich liquid in the lower section of the multi-functional deammoniation tower (1) is drawn by the lower section circulating pump (14) and sent to the lean and rich liquid heat exchanger (19), and further connected to the multi-functional distillation tower (4). The bottom of the multifunctional distillation column (4) is connected to the lean and rich liquid heat exchanger (19), and further connected to the primary sedimentation tank (8). The primary sedimentation tank (8) is connected to the reaction tank (9). The reaction tank (9) is connected to the secondary sedimentation tank (10). The upper clear liquid of the secondary sedimentation tank (10) is connected to the lower section of the multifunctional deammoniation column (1). The secondary steam at the top of the multifunctional distillation column (4) is connected to the reboiler (6) via the MVR compressor (5), and further connected to the secondary distillation column (7). The bottom of the multifunctional distillation column (4) is connected to the reboiler. The bottom of the multifunctional distillation column (4) is connected to the WGGH circulating pump (17) and the WGGH heat exchanger (18), and further connected to the secondary distillation column (7), and finally connected to the multifunctional distillation column (4).

2. The industrial flue gas ammonia escape treatment system based on thermal recycling according to claim 1, characterized in that, The multifunctional ammonia removal tower (1) is divided into three sections from bottom to top: the lower section is the concentration section, which is used to concentrate the ammonia-rich washing liquid; the middle section is the ammonia absorption section, which is used to deeply wash the ammonia in the flue gas; and the upper section is the acid mist capture section, which is used to fully capture the sulfuric acid mist entrained in the flue gas.

3. The industrial flue gas ammonia escape treatment system based on thermal recycling according to claim 1, characterized in that, The multifunctional distillation column (4) has a two-section structure. The upper section is the distillation section, which fully distills the ammonia nitrogen in the ammonia-rich washing solution. The lower section is the steam generation section, which generates secondary steam to supply the distillation section.

4. The industrial flue gas ammonia escape treatment system based on thermal recycling according to claim 3, characterized in that, A liquid cut-off plate is installed between the rectification section and the steam generation section. The solution in the rectification section cannot enter the steam generation section, while the steam generated in the steam generation section can smoothly pass through the liquid cut-off plate into the rectification section.

5. The industrial flue gas ammonia escape treatment system based on thermal recycling according to claim 1, characterized in that, The secondary steam at the top of the secondary distillation column (7) is connected to the ammonia condenser (20), and the high-temperature wastewater at the bottom is connected to the multifunctional distillation column (4) via the reflux pump (15).

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