A solvent regeneration overhead reflux ammonia withdrawal to deamination column system and method

Abstract

The application discloses a system and method for extracting ammonia from solvent regenerator overhead reflux to a deamination tower, and belongs to the technical field of solvent regeneration. The system comprises a solvent regenerator, a deamination tower, a reboiler, a water cooler, a first circulating pump, a second circulating pump and a static mixer. The pipeline connecting the first circulating pump and the water cooler is connected with the pipeline connecting the second circulating pump and the static mixer through an ammonia extraction pipeline. The ammonia collected at the top of the regenerator affects the desulfurization effect of the solvent. In the application, the ammonia water collected at the top of the regenerator is sent to the deamination tower for treatment, so that the ammonia nitrogen and hydrogen sulfide contents in the amine solution after regeneration are reduced, and the amine regeneration effect is ensured. The application of the solvent regenerator overhead reflux ammonia extraction to the deamination tower to a hydrogenation device for removing hydrogen sulfide in circulating hydrogen can solve the common problem of poor desulfurization effect, and can also be applied to other naphthenic base distillate hydrogenation devices of various tonnages.

Description

Technical Field

[0001] This invention belongs to the field of solvent regeneration technology, and more specifically relates to a system and method for refluxing ammonia from the top of a solvent regeneration tower to a deammoniation tower. Background Technology

[0002] The 300,000-ton / year naphthenic distillate hydrotreating unit achieves a circulating hydrogen flow rate of 90,000 Nm³. 3 Although the ammonia content in the circulating hydrogen is not high, the large circulating flow rate causes the ammonia in the circulating hydrogen to be absorbed by the lean amine solution. As the rich amine solution accumulates in the regeneration tower, the ammonia content in the lean amine solution reaches as high as 3900 ppm, and the hydrogen sulfide content exceeds 1.2 g / L. This indirectly leads to a decrease in the desulfurization effect of the circulating hydrogen in the 300,000 kWh hydrogenation unit. Currently, the existing technology has repeatedly cut off the second-stage mixed hydrogen and switched the second-stage reactor to bypass mode due to the hydrogen sulfide content in the circulating hydrogen exceeding 25 ppm. The side-stream oil is then diverted to the unqualified line, which seriously affects the stable operation of the 300,000 kWh hydrogenation unit.

[0003] In the hydrotreating unit of cycloalkyl distillate oil, the amine-rich liquid at the bottom of the desulfurization tower is sent to the solvent regeneration tower for regeneration. Under normal circumstances, the feed to the solvent regeneration tower is a hydrogen sulfide-containing amine-rich liquid with a small amount of ammonia. Ammonia has low solubility at high temperatures, dissolving almost completely above 100°C. The bottom temperature of the solvent regeneration tower is around 115-130°C. Therefore, the small amount of ammonia dissolved in the amine-rich liquid entering the solvent regeneration tower will separate into gaseous ammonia gas, which will travel with the acidic gas to the top of the tower. The reflux temperature at the top of the solvent regeneration tower is controlled at around 40°C, and the reflux liquid contains about 70% water. At this temperature, a large amount of ammonia will dissolve and accumulate in the reflux liquid at the top of the tower, severely affecting the amine regeneration effect.

[0004] Therefore, how to develop a solvent regeneration tower top reflux ammonia extraction system and a reflux ammonia extraction method that can be applied to the hydrogen sulfide hydrogenation unit for the removal of hydrogen sulfide from amine liquid and solve the problem of poor amine liquid desulfurization caused by unqualified amine liquid regeneration is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a system and method for refluxing ammonia from the top of a solvent regeneration tower to a deammoniation tower.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A solvent regeneration tower top reflux ammonia extraction to a deammoniation tower system includes a solvent regeneration tower, a deammoniation tower, a reboiler, a water cooler, a first circulation pump, a second circulation pump, and a static mixer;

[0008] The solvent regeneration tower described above includes, from bottom to top, a liquid collector, lower packing, a collection tank, upper packing, and a first wire mesh demister. The top of the solvent regeneration tower has an acidic gas outlet. The upper part of the first wire mesh demister on the side wall of the solvent regeneration tower has a circulating low-temperature ammonia inlet. The side wall of the solvent regeneration tower also has a rich amine inlet and an ammonia outlet. The ammonia outlet is connected to the collection tank. The rich amine inlet is located at the bottom of the collection tank. The bottom of the solvent regeneration tower has a lean amine outlet. The ammonia outlet, the first circulating pump, the water cooler, and the circulating low-temperature ammonia inlet are connected sequentially via pipelines.

[0009] The lower part of the packing on the side wall of the solvent regeneration tower is provided with a rich amine liquid outlet. The rich amine liquid outlet is connected to the liquid collector through a pipeline. The bottom of the reboiler is provided with a lean amine liquid return tower lower inlet, a kettle liquid inlet and a condensate outlet in sequence from front to back. The top of the reboiler is provided with a lean amine liquid return tower upper inlet and a steam inlet in sequence from front to back. The rich amine liquid outlet is connected to the kettle liquid inlet through a pipeline. The lean amine liquid return tower lower inlet is connected to the bottom of the solvent regeneration tower through a pipeline. The lean amine liquid return tower upper inlet is connected to the lower part of the rich amine liquid outlet on the side wall of the solvent regeneration tower through a pipeline.

[0010] The aforementioned ammonia removal tower, from bottom to top, includes a lower packing layer, a lower distributor, an upper packing layer, an upper distributor, and a second wire mesh demister. The top of the ammonia removal tower is provided with an ammonia removal tail gas outlet, and the bottom of the side wall of the ammonia removal tower is provided with a concentrated sulfuric acid inlet and a circulating solution outlet. A circulating solution inlet is provided between the lower distributor and the upper packing layer on the side wall of the ammonia removal tower. The circulating solution outlet, the second circulating pump, the static mixer, and the circulating solution inlet are connected in sequence through pipelines.

[0011] The pipeline connecting the first circulating pump and the water cooler is connected to the pipeline connecting the second circulating pump and the static mixer via an ammonia extraction pipeline.

[0012] Furthermore, it also includes ball valves and check valves. The aforementioned pipelines connecting the first circulating pump and the water cooler, ball valves, check valves, and pipelines connecting the second circulating pump and the static mixer are connected in sequence through the ammonia extraction pipeline.

[0013] Furthermore, it also includes a temperature transmitter and a thermocouple, wherein the thermocouple is connected to a pipeline connecting the water cooler and the inlet of the circulating low-temperature ammonia water, and the temperature transmitter is connected to the thermocouple.

[0014] Furthermore, it also includes a level gauge and a thermometer. A level gauge is installed between the liquid collection tank on the side wall of the solvent regeneration tower and the upper packing, and a thermometer is installed at the bottom of the solvent regeneration tower.

[0015] Furthermore, the flanges connecting the pipe ends, the flanges connecting the valves and the pipelines, the ball valves, check valves, and the ammonia extraction pipelines in the system are all made of 316L stainless steel, and the diameter of the ammonia extraction pipelines is DN25.

[0016] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: Since the circulating liquid in the regeneration tower is highly corrosive, the risk of hydrogen sulfide leakage may increase after the technical transformation is completed. Therefore, materials with strong resistance to material corrosion, such as white steel or 316L stainless steel, are selected.

[0017] The present invention also provides a method for refluxing ammonia from the top of a solvent regeneration tower to a deammoniation tower, comprising the following steps:

[0018] The above-mentioned solvent regeneration tower top reflux pumps ammonia to the deammoniation tower system. The rich amine solution is sent to the solvent regeneration tower for regeneration. The bottom temperature of the solvent regeneration tower is 115-130℃. Some ammonia dissolves in the rich amine solution and enters the solvent regeneration tower, where it is separated into gaseous ammonia gas and discharged through the top of the tower along with the acid gas. The reflux temperature at the top of the solvent regeneration tower is controlled at 40℃ by a water cooler. At 40℃, the ammonia dissolves, causing the ammonia water to accumulate in the collection tank of the solvent regeneration tower. The ammonia water is sent into the pipeline connected to the second circulation pump and the static mixer to mix with the circulating solution and react with the sulfuric acid therein to generate ammonium sulfate solution, which is then sent to the deammoniation tower.

[0019] The beneficial effects of this invention: A large amount of ammonia accumulating at the top of the regeneration tower affects the solvent desulfurization effect. This invention sends the ammonia water accumulated at the top of the regeneration tower to the deammoniation tower for treatment, reducing the ammonia nitrogen and hydrogen sulfide content in the regenerated amine solution and ensuring the amine solution regeneration effect. Applying the reflux ammonia pumped from the top of the solvent regeneration tower to the deammoniation tower in a hydrogenation unit for removing hydrogen sulfide from circulating hydrogen in amine solution can solve the common problem of poor desulfurization effect. It can also be applied to other naphthenic distillate oil hydrogenation units of various tonnages. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the system structure of the solvent regeneration tower top reflux ammonia extraction to the deammoniation tower of the present invention;

[0021] Figure 2 This is a schematic diagram of the solvent regeneration tower and reboiler structure of the present invention;

[0022] Figure 3 This is a schematic diagram of the ammonia removal tower structure of the present invention;

[0023] In the diagram, 1-solvent regeneration tower, 2-ammonia removal tower, 3-reboiler, 4-water cooler, 5-first circulation pump, 6-second circulation pump, 7-static mixer, 8-liquid collector, 9-lower packing, 10-collecting tank, 11-upper packing, 12-first wire mesh demister, 13-lower packing, 14-lower distributor, 15-upper packing, 16-upper distributor, 17-second wire mesh demister, 18-ball valve, 19-check valve, 20-temperature transmitter, 21-thermocouple, 22- Level gauge, 23-Thermometer, 1-1-Acidic gas outlet, 1-2-Circulating low-temperature ammonia water inlet, 1-3-Rich amine liquid inlet, 1-4-Ammonia water outlet, 1-5-Lean amine liquid outlet, 1-6-Rich amine liquid outlet, 2-1-Deammoniation tail gas outlet, 2-2-Concentrated sulfuric acid inlet, 2-3-Circulating solution outlet, 2-4-Circulating solution inlet, 3-1-Lean amine liquid return to the lower part of the tower inlet, 3-2-Bottle liquid inlet, 3-3-Condensate outlet, 3-4-Steam inlet, 3-5-Lean amine liquid return to the upper part of the tower inlet. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The solvent regeneration tower top reflux pumps ammonia to the deammoniation tower system, which includes solvent regeneration tower 1, deammoniation tower 2, reboiler 3, water cooler 4, first circulation pump 5, second circulation pump 6 and static mixer 7;

[0026] The solvent regeneration tower 1 includes, from bottom to top, a liquid collector 8, a lower packing 9, a collection tank 10, an upper packing 11, and a first wire mesh demister 12. The top of the solvent regeneration tower 1 is provided with an acid gas outlet 1-1. The upper part of the first wire mesh demister 12 on the side wall of the solvent regeneration tower 1 is provided with a circulating low-temperature ammonia water inlet 1-2. The side wall of the solvent regeneration tower 1 is provided with a rich amine liquid inlet 1-3 and an ammonia water outlet 1-4. The ammonia water outlet 1-4 is connected to the collection tank 10. The rich amine liquid inlet 1-3 is located at the lower part of the collection tank 10. The bottom of the solvent regeneration tower 1 is provided with a lean amine liquid outlet 1-5. The ammonia water outlet 1-4, the first circulating pump 5, the water cooler 4, and the circulating low-temperature ammonia water inlet 1-2 are connected in sequence through pipelines.

[0027] The lower part of the packing 9 on the side wall of the solvent regeneration tower 1 is provided with a rich amine liquid outlet 1-6. The rich amine liquid outlet 1-6 is connected to the liquid collector 8 through a pipeline. The bottom of the reboiler 3 is provided with a lean amine liquid return tower lower inlet 3-1, a kettle liquid inlet 3-2 and a condensate outlet 3-3 in sequence from front to back. The top of the reboiler 3 is provided with a lean amine liquid return tower upper inlet 3-5 and a steam inlet 3-4 in sequence from front to back. The rich amine liquid outlet 1-6 is connected to the kettle liquid inlet 3-2 through a pipeline. The lean amine liquid return tower lower inlet 3-1 is connected to the bottom of the solvent regeneration tower 1 through a pipeline. The lean amine liquid return tower upper inlet 3-5 is connected to the lower part of the rich amine liquid outlet 1-6 on the side wall of the solvent regeneration tower 1 through a pipeline.

[0028] The interior of the ammonia removal tower 2, from bottom to top, includes a lower packing 13, a lower distributor 14, an upper packing 15, an upper distributor 16, and a second wire mesh demister 17. The top of the ammonia removal tower 2 is provided with an ammonia removal tail gas outlet 2-1. The bottom of the side wall of the ammonia removal tower 2 is provided with a concentrated sulfuric acid inlet 2-2 and a circulating solution outlet 2-3. A circulating solution inlet 2-4 is provided between the lower distributor 14 and the upper packing 15 on the side wall of the ammonia removal tower 2. The circulating solution outlet 2-3, the second circulating pump 6, the static mixer 7, and the circulating solution inlet 2-4 are connected in sequence through pipelines.

[0029] The pipeline connecting the first circulating pump 5 and the water cooler 4 is connected to the pipeline connecting the second circulating pump 6 and the static mixer 7 via an ammonia extraction pipeline.

[0030] In one embodiment, a ball valve 18 and a check valve 19 are also included. The pipeline connecting the first circulating pump 5 and the water cooler 4, the ball valve 18, the check valve 19, and the pipeline connecting the second circulating pump 6 and the static mixer 7 are connected in sequence through an ammonia extraction pipeline.

[0031] In one embodiment, the device further includes a temperature transmitter 20 and a thermocouple 21. The thermocouple 21 is connected to a pipeline connecting the water cooler 4 and the circulating low-temperature ammonia inlet 1-2, and the temperature transmitter 20 is connected to the thermocouple 21.

[0032] In one embodiment, a level gauge 22 and a thermometer 23 are also included. The level gauge 22 is installed between the liquid collection tank 10 on the side wall of the solvent regeneration tower 1 and the upper packing 11, and the thermometer 23 is installed at the bottom of the solvent regeneration tower 1.

[0033] In one embodiment, the flanges connecting the pipe ends, the flanges connecting the valves and the pipelines, the ball valve 18, the check valve 19, and the ammonia extraction pipeline in the system are all made of 316L stainless steel, and the diameter of the ammonia extraction pipeline is DN25.

[0034] The method for refluxing ammonia from the top of solvent regeneration tower 1 to ammonia removal tower 2 includes the following steps:

[0035] Ammonia is drawn from the top of the solvent regeneration tower and sent to the deammoniation tower system. The rich amine solution is sent to the solvent regeneration tower 1 for regeneration. The bottom temperature of the solvent regeneration tower 1 is 115-130℃. Some ammonia dissolves in the rich amine solution and enters the solvent regeneration tower 1, where it is separated into gaseous ammonia gas and discharged through the top of the tower along with the acid gas. The reflux temperature at the top of the solvent regeneration tower 1 is controlled to be 40℃ by the water cooler 4. At the temperature of 40℃, the ammonia dissolves and causes the ammonia water to accumulate in the collection tank 10 of the solvent regeneration tower 1. The ammonia water is sent into the pipeline connecting the second circulation pump 6 and the static mixer 7 to mix with the circulating solution and react with the sulfuric acid in it to generate ammonium sulfate solution, which is then sent to the deammoniation tower 2.

[0036] Working principle of the solvent regeneration tower top reflux ammonia pumping to the deammoniation tower system:

[0037] The rich amine solution enters solvent regeneration tower 1 for regeneration through rich amine solution inlet 1-3. It is then discharged into reboiler 3 through rich amine solution outlet 1-6 and bottom liquid inlet 3-2. 0.4 MPa steam is introduced into reboiler 3 through steam inlet 3-4. The lean amine solution obtained from heating in reboiler 3 is discharged into the bottom of the regeneration tower through lean amine solution return tower lower inlet 3-1, and into the lower part of rich amine solution outlet 1-6 in solvent regeneration tower 1 through lean amine solution return tower upper inlet 3-5. The temperature at the bottom of the regeneration tower is 115-130℃. Some ammonia dissolves in the rich amine solution and enters solvent regeneration tower 1, where it is separated into gaseous ammonia gas. This gas is discharged along with the acid gas through acid gas outlet 1-1 at the top of the tower. The reflux temperature at the top of solvent regeneration tower 1 is controlled at 40℃ by circulating cold water inlet and circulating hot water outlet through water cooler 4. This temperature is controlled by a temperature transmitter. 20. Thermocouple 21 monitors the liquid temperature in the pipeline between water cooler 4 and circulating low-temperature ammonia inlet 1-2. At 40℃, ammonia dissolves, causing ammonia to accumulate at the top of solvent regeneration tower 1. The ammonia collected in collection tank 10 is discharged through ammonia outlet 1-4 and enters circulating low-temperature ammonia inlet 1-2 via first circulation pump 5 and water cooler 4. Ball valve 18 and check valve 19 are opened to send the ammonia in the pipeline connecting first circulation pump 5 and water cooler 4 into the pipeline connecting second circulation pump 6 and static mixer 7. The ammonia is mixed with the circulating solution discharged from circulating solution outlet 2-3 and reacts with sulfuric acid to generate ammonium sulfate solution, which is sent to deammonium removal tower 2 through circulating solution inlet 2-4. Concentrated sulfuric acid is sent to deammonium removal tower 2 through concentrated sulfuric acid inlet 2-2. Deammonium removal tail gas is discharged through deammonium removal tail gas outlet 2-1.

[0038] The acceptable standard for hydrogen sulfide content in circulating hydrogen is less than 25 ppm.

[0039] Table 1

[0040] Hydrogen sulfide content after circulating hydrogen desulfurization before modification After modification, the hydrogen sulfide content after circulating hydrogen desulfurization in this invention is... 35.37ppm 4.35ppm 29.35ppm 3.28ppm 36.15ppm 2.96ppm 36.18ppm 3.68ppm 31.36ppm 3.42ppm 25.93ppm 2.68ppm 41.36ppm 4.60ppm 35.69ppm 3.78ppm

[0041] After modification, the ammonia content in the lean amine solution remained below 100 ppm, and the hydrogen sulfide content remained below 1.2 g / L.

[0042] Throughout 2018, due to substandard amine liquid regeneration, the 300,000-ton hydrogenation side-line oil conversion to substandard line lasted for 288 hours. At its most frequent, the second-stage bypass was cut off 7 times in one month. The hourly processing capacity was calculated at 37.5 tons (of which the substandard vacuum oil was calculated at 33.5 t / h), and the cost of refining each ton of substandard oil was calculated at 799.84 yuan.

[0043] Cost of refining substandard oil in 2018 = Total amount of substandard oil under reduced pressure * Cost of refining per ton of substandard oil = 288 hours * 33.5 tons / hour * 799.84 yuan / ton = 7,716,900 yuan.

[0044] After the project is implemented, it can save approximately 1,200 tons of alkali solution annually, with the following annual savings in alkali solution costs:

[0045] Savings on new alkali solution: 600 yuan / ton * 1200 tons = 720,000 yuan

[0046] Waste alkali solution savings: 3600 yuan / ton * 1200 tons = 4.32 million yuan

[0047] Through technological upgrades, the regeneration effect of amine solution was effectively guaranteed. After the upgrades were implemented, the number of times hydrogen sulfide exceeded the standard in the circulating hydrogen of the 300,000-ton hydrogenation unit due to unqualified amine solution regeneration was zero.

[0048] The description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A solvent regeneration tower top reflux ammonia extraction system to an ammonia removal tower, characterized in that, It includes a solvent regeneration tower, a deammoniation tower, a reboiler, a water cooler, a first circulation pump, a second circulation pump, and a static mixer; The solvent regeneration tower includes, from bottom to top, a liquid collector, lower packing, a collection tank, upper packing, and a first wire mesh demister. The top of the solvent regeneration tower has an acidic gas outlet. The upper part of the first wire mesh demister on the side wall of the solvent regeneration tower has a circulating low-temperature ammonia inlet. The side wall of the solvent regeneration tower has a rich amine inlet and an ammonia outlet. The ammonia outlet is connected to the collection tank. The rich amine inlet is located at the bottom of the collection tank. The bottom of the solvent regeneration tower has a lean amine outlet. The ammonia outlet, the first circulating pump, the water cooler, and the circulating low-temperature ammonia inlet are connected sequentially via pipelines. The lower part of the packing on the side wall of the solvent regeneration tower is provided with a rich amine liquid outlet, which is connected to the liquid collector through a pipeline. The bottom of the reboiler is provided with a lean amine liquid return tower lower inlet, a kettle liquid inlet, and a condensate outlet in sequence from front to back. The top of the reboiler is provided with a lean amine liquid return tower upper inlet and a steam inlet in sequence from front to back. The rich amine liquid outlet is connected to the kettle liquid inlet through a pipeline. The lean amine liquid return tower lower inlet is connected to the bottom of the solvent regeneration tower through a pipeline. The lean amine liquid return tower upper inlet is connected to the lower part of the rich amine liquid outlet on the side wall of the solvent regeneration tower through a pipeline. The deammonia removal tower includes, from bottom to top, a lower packing layer, a lower distributor, an upper packing layer, an upper distributor, and a second wire mesh demister. The top of the deammonia removal tower has a deammonia removal tail gas outlet, and the bottom of the side wall of the deammonia removal tower has a concentrated sulfuric acid inlet and a circulating solution outlet. A circulating solution inlet is provided between the lower distributor and the upper packing layer on the side wall of the deammonia removal tower. The circulating solution outlet, the second circulating pump, the static mixer, and the circulating solution inlet are connected in sequence through pipelines. The pipeline connecting the first circulating pump and the water cooler is connected to the pipeline connecting the second circulating pump and the static mixer via an ammonia extraction pipeline. The temperature at the bottom of the solvent regeneration tower is 115-130℃.

2. The solvent regeneration tower top reflux ammonia extraction to the deammoniation tower system according to claim 1, characterized in that, It also includes a ball valve and a check valve. The pipeline connecting the first circulating pump and the water cooler, the ball valve, the check valve, and the pipeline connecting the second circulating pump and the static mixer are connected in sequence through the ammonia extraction pipeline.

3. The solvent regeneration tower top reflux ammonia extraction to the deammoniation tower system according to claim 1, characterized in that, It also includes a temperature transmitter and a thermocouple, wherein the thermocouple is connected to a pipeline connecting the water cooler and the inlet of the circulating low-temperature ammonia water, and the thermocouple is connected to the temperature transmitter.

4. The solvent regeneration tower top reflux ammonia extraction to the deammoniation tower system according to claim 1, characterized in that, It also includes a level gauge and a thermometer. A level gauge is installed between the liquid collection tank on the side wall of the solvent regeneration tower and the upper packing, and a thermometer is installed at the bottom of the solvent regeneration tower.

5. The solvent regeneration tower top reflux ammonia extraction to the deammoniation tower system according to claim 2, characterized in that, The flanges connecting the pipe ends, the flanges connecting the valves and the pipelines, the ball valves, the check valves, and the ammonia extraction pipelines in the system are all made of 316L stainless steel, and the diameter of the ammonia extraction pipelines is DN25.

6. A method for refluxing ammonia from the top of a solvent regeneration tower to a deammoniation tower, characterized in that, The process includes the following steps: using a solvent regeneration tower top reflux pumping ammonia to a deammoniation tower system as described in any one of claims 1-5, sending rich amine solution to the solvent regeneration tower for regeneration, some ammonia dissolving in the rich amine solution and entering the solvent regeneration tower to be separated into gaseous ammonia gas and discharged through the top of the tower along with the acid gas, controlling the top reflux temperature of the solvent regeneration tower to 40°C through a water cooler, at 40°C the ammonia dissolves and causes the ammonia water to accumulate in the collection tank of the solvent regeneration tower, sending the ammonia water into the pipeline connected to the second circulation pump and the static mixer to mix with the circulating solution and react with the sulfuric acid therein to generate ammonium sulfate solution, which is then sent to the deammoniation tower.

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