Method and device for carbon capture of low-sulfur flue gas, co-production of nitrogen fertilizer and control of ammonia escape

Abstract

A method and a device for carbon capture of low-sulfur flue gas, co-production of a nitrogen fertilizer and control of ammonia escape, which method and device are applied to carbon capture of low-sulfur flue gas (such as natural gas flue gas) and co-production of a nitrogen fertilizer. A sulfur-containing oxide and the process gas of CO2 firstly enter an ammonia desulfurization device to perform desulfurization, so as to generate an ammonium sulfate chemical fertilizer; the desulfurized gas enters an ammonia decarburization device, so as to remove carbon dioxide from the gas and generate an ammonium bicarbonate chemical fertilizer, wherein the decarburized gas contains free ammonia; and a desulfurization circulating liquid is used for washing, and a washing liquid is returned to the decarburization device. For the part having an insufficient acid content in a low-sulfur flue gas desulfurization circulating liquid, sulfuric acid is added into the desulfurization circulating liquid to control the pH of the washing liquid; and an ammonium sulfate chemical fertilizer is generated by means of washing and is returned to a desulfurization functional area along with the desulfurization liquid, and then recovered into an ammonium sulfate chemical fertilizer product.

Description

Method and device for controlling ammonia escape by carbon capture and co-production of nitrogen fertilizer from low-sulfur flue gas Technical field:

[0001] The present invention belongs to the field of environmental protection technology, and specifically relates to a device and method for removing sulfur oxides and CO2 using an ammonia process. Background technology:

[0002] Carbon dioxide is the most important greenhouse gas, with fossil energy use being the primary source. my country's total CO2 emissions already rank first in the world, and China's coal-dominated energy structure will continue for some time. Coal will remain the foundation for new energy peak regulation and energy security. my country has pledged to reach carbon peak by 2030 and achieve carbon neutrality by 2060. Capturing, storing, and utilizing CO2 in flue gas as a resource is crucial for controlling and reducing greenhouse gas emissions and addressing the greenhouse effect and global warming.

[0003] Ammonia-based carbon capture technology has long been a research priority and the best approach to addressing greenhouse gas emissions. However, ammonia is volatile, and decarbonization requires alkaline conditions, which increases ammonia escape. If unaddressed, this high level of ammonia escape not only increases decarbonization costs but also causes secondary pollution.

[0004] CN113262625A discloses an integrated ammonia-based desulfurization and decarbonization device and method. This process removes sulfur oxides and CO2 from the gas through ammonia-based desulfurization and ammonia-based decarbonization, and uses a desulfurization circulating fluid to control ammonia escape after decarbonization. However, this process does not address the issue of insufficient acid in the desulfurization circulating fluid for low-sulfur flue gas, which makes it impossible to effectively control ammonia escape after decarbonization.

[0005] CN104874272A discloses an integrated desulfurization and carbon dioxide capture device and method. The flue gas first passes through an ammonia desulfurization device to remove SO2, then enters a direct contact cooling device for cooling and cooling, and then enters a decarbonization tower for decarbonization. After decarbonization, the gas passes through an ammonia scrubber and is washed with water. After washing, the flue gas enters a direct contact heating device, and some ammonia is removed simultaneously during the spray contact heating process. The spray contact solution uses an aqueous solution discharged from the contact cooling tower. After the contact spray, the solution is cooled in the cooling tower and then used for contact cooling spray. The ammonia solution in the water scrubber enters the decarbonization tower for decarbonization, or enters the stripping tower for deammoniation. And the acidic reagent sulfuric acid is added during the spray contact heating process to strengthen the ammonia washing. Although this process uses strong acid washing to remove ammonia, it does not fully utilize the acidic solution of the ammonia desulfurization device, which increases the consumption of strong acid.

[0006] CN101909721A also adopts the method of adding sulfuric acid for cyclic washing to remove ammonia, and consumes a large amount of sulfuric acid.

[0007] CN101600489A discloses a gas cleaning system operable to clean a process gas containing carbon dioxide and sulfur dioxide, comprising a combined cooling and cleaning system (16) and a CO2 absorber. The combined cooling and cleaning system (16) comprises a first gas-liquid contact device (50) located upstream of the CO2 absorber and operable to cool the process gas with a cooling liquid and absorb sulfur dioxide from the process gas into the cooling liquid, thereby obtaining a cooling liquid containing sulfate. The combined cooling and cleaning system (16) further comprises a second gas-liquid contact device (94) located downstream of the CO2 absorber and operable to remove ammonia from the process gas treated in the CO2 absorber by contacting the process gas containing ammonia with the cooling liquid containing sulfate. Sulfuric acid may be added to the cooling liquid to control the pH value of the cooling liquid. However, this process uses cooling gas to obtain cooling liquid containing sulfate to remove ammonia. It does not mention an ammonia-based desulfurization device, nor does it provide any suggestion for using the acidic solution in the ammonia-based desulfurization device to remove ammonia.

[0008] In response to the above problems, the present invention develops a method and device for controlling ammonia escape by carbon capture and co-production of nitrogen fertilizer from low-sulfur flue gas.

[0009] Summary of the Invention

[0010] The present invention develops a method and device for controlling ammonia escape by carbon capture and co-production of nitrogen fertilizer from low-sulfur flue gas. The method is mainly applied to carbon capture and co-production of nitrogen fertilizer from low-sulfur flue gas (i.e., process gas, such as natural gas flue gas). The process gas containing sulfur oxides and CO2 first enters an ammonia desulfurization device for desulfurization to generate ammonium sulfate fertilizer. The desulfurized gas enters an ammonia decarbonization device to remove carbon dioxide from the gas and generate ammonium bicarbonate fertilizer. The decarbonized gas contains free ammonia, which is washed with a desulfurization circulating liquid, and the washing liquid is returned to the desulfurization device. The insufficient acid content in the low-sulfur flue gas desulfurization circulating liquid is washed by adding sulfuric acid to the desulfurization circulating liquid to control the pH of the washing liquid, and ammonium sulfate fertilizer is generated. The ammonium sulfate fertilizer is then returned to the desulfurization functional area with the desulfurization liquid and recovered as an ammonium sulfate fertilizer product. The technical process is simple, with low investment and operating costs. Ammonium sulfate and ammonium bicarbonate fertilizer are produced as by-products, truly realizing the transformation of waste into treasure and a circular economy.

[0011] A method for controlling ammonia escape by carbon capture and co-production of nitrogen fertilizer from low-sulfur flue gas comprises the following steps in sequence:

[0012] 1) Use ammonium salt solution to remove part of the SO2 in the process gas;

[0013] 2) using an ammonium salt solution to remove part of the CO2 in the process gas; and

[0014] 3) using the ammonium salt solution and sulfuric acid solution in step 1) to remove part of the free ammonia in the process gas to generate ammonium sulfate;

[0015] 4) returning at least a portion of the ammonium sulfate solution produced in step 3) to the desulfurization functional zone, and co-crystallizing with the desulfurization byproduct ammonium sulfate in the desulfurization functional zone to produce solid ammonium sulfate.

[0016] Step 2) produces solid ammonium bicarbonate.

[0017] In step 3), at least one gas-liquid contact device is provided for contacting the ammonium salt solution and the sulfuric acid solution with the process gas. The gas-liquid contact device can be a spraying method.

[0018] The pH of the solution in gas-liquid contact is controlled to be 1-10, preferably 1-7.5, more preferably 1-6.5, and most preferably 1-5.5.

[0019] In step 3), the sulfuric acid solution is added to the pipeline of the ammonium salt solution, and the mixed solution directly enters the gas-liquid contact device. Alternatively, in step 3), the sulfuric acid solution and the ammonium salt solution are directly entered into the gas-liquid contact device respectively.

[0020] Step 3) includes a solution collecting device, sulfuric acid solution and ammonium salt solution are added to the solution collecting device, and gas-liquid contact is carried out through forced circulation.

[0021] The amount of sulfuric acid solution added is controlled according to the pH value. The amount of flue gas after decarbonization and the ammonia escape concentration are also controlled.

[0022] The mass concentration of the sulfuric acid solution is 10%-50%, preferably 12%-40%, more preferably 15%-30%.

[0023] In step 4), the concentration of the ammonium sulfate solution is adjusted by adding water so that the difference in mass concentration between the ammonium sulfate solution and the ammonium salt solution from the desulfurization functional zone does not exceed 5%, preferably 3%, and more preferably 1%.

[0024] The SO2 content in the low-sulfur flue gas is not higher than 2000 mg / Nm 3 , preferably 1000mg / Nm 3 , more preferably 500 mg / Nm 3 .

[0025] In step 1), the ammonium salt solution is one or a combination of the concentrated circulating liquid, the absorption circulating liquid, and the washing circulating liquid of the ammonia desulfurization functional zone, the concentrated circulating liquid has a pH of 1-6, preferably 2-4.5, an ammonium sulfite concentration of 0-0.2wt%, and an ammonium sulfate concentration of 10-60wt%. The absorption circulating liquid has a pH of 4.5-6.5, preferably 4.8-6.2, an ammonium sulfite concentration of 0.1-3wt%, and an ammonium sulfate concentration of 10-38wt%. The washing circulating liquid has a pH of 1.5-6.5, preferably 2-5, and an ammonium sulfate concentration of 0-5wt%.

[0026] In step 2), the ammonium salt solution is one or a combination of an ammonium bicarbonate generation circulating liquid and a decarbonization absorption circulating liquid. The molar ratio of total ammonia to total CO2 in the ammonium bicarbonate generation circulating liquid is 1-1.8, and the molar ratio of total ammonia to total CO2 in the decarbonization absorption circulating liquid is 1.8-3. The total ammonia includes ammonia and ammonium ions, and the total CO2 includes free CO2 and carbonized CO2.

[0027] A device for controlling ammonia escape by carbon capture and co-production of nitrogen fertilizer from low-sulfur flue gas, characterized by being equipped with an ammonia desulfurization functional area, an ammonia decarbonization functional area, an ammonia washing functional area, and an acid addition system.

[0028] Among them, the ammonia desulfurization functional area, the ammonia decarbonization functional area, and the ammonia washing functional area are connected in sequence, the ammonia desulfurization functional area and the ammonia washing functional area are connected through a liquid phase pipeline, and the acid addition system is connected to the ammonia washing functional area.

[0029] The ammonia desulfurization functional area is divided into multiple sections, including a cooling, concentration and temperature reduction section, an absorption section, and a water washing section. Each section is provided with at least one layer of gas-liquid contact, and equipment / components that allow gas to pass through are provided between sections.

[0030] The ammonia desulfurization functional area is divided into multiple sections, including an ammonium bicarbonate generation section and a decarbonization absorption section. Each section is provided with at least one layer of gas-liquid contact, and equipment / components allowing gas to pass through are provided between sections.

[0031] The ammonia washing functional area is equipped with a pH detection device.

[0032] The ammonia desulfurization functional area also includes an ammonium sulfate production system.

[0033] The ammonia decarbonization functional area also includes an ammonium bicarbonate production system.

[0034] One or a combination of the cooling, concentration and temperature reduction section, the absorption section and the water washing section is connected to the ammonia washing functional area.

[0035] The ammonia washing functional area also includes a water washing section, which is connected to the water supply pipe and is provided with at least one layer of gas-liquid contact. Equipment / components that allow gas to pass through are provided between the water washing section and other sections of the ammonia washing functional area.

[0036] The ammonia washing functional area is equipped with a water replenishment device.

[0037] The acid adding system is equipped with an acid dilution device and an acid concentration measuring device.

[0038] The acid adding device is connected to the liquid phase connecting pipelines of the ammonia desulfurization functional area and the ammonia washing functional area, and is connected to the ammonia washing functional area.

[0039] The ammonia washing functional area includes a solution collecting device, and the acid adding device is directly connected to the solution collecting device.

[0040] Between step 2) and step 3), step 4) is included to remove some free ammonia from the process gas using process water, and / or after step 3), step 5) is included to further remove some free ammonia from the process gas using process water. The ammonia-containing process water after washing is used to replenish the decarbonization unit or desulfurization unit or as an absorbent.

[0041] The method for controlling ammonia escape by carbon capture and co-production of nitrogen fertilizer using low-sulfur flue gas of the present invention is preferably carried out in the device for controlling ammonia escape by carbon capture and co-production of nitrogen fertilizer using low-sulfur flue gas of the present invention.

[0042] This application also relates to the following implementation plans:

[0043] 1. A method for controlling ammonia escape by carbon capture and co-production of nitrogen fertilizer from low-sulfur flue gas, comprising the following steps:

[0044] 1) Use ammonium salt solution to remove part of the SO2 in the process gas;

[0045] 2) using an ammonium salt solution to remove part of the CO2 in the process gas; and

[0046] 3) using the ammonium salt solution and sulfuric acid solution in step 1) to remove part of the free ammonia in the process gas to generate ammonium sulfate;

[0047] 4) returning at least a portion of the ammonium sulfate solution produced in step 3) to the desulfurization functional zone, and co-crystallizing with the desulfurization byproduct ammonium sulfate in the desulfurization functional zone to produce solid ammonium sulfate.

[0048] 2. The method according to embodiment 1, wherein step 2) produces solid ammonium bicarbonate.

[0049] 3. The method according to embodiment 1 is characterized in that at least one layer of gas-liquid contact device is provided in step 3).

[0050] 4. The method according to embodiment 3, wherein the pH of the solution in gas-liquid contact is controlled to be 1-10, preferably 1-7.5, more preferably 1-6.5, and most preferably 1-5.5.

[0051] 5. The method according to embodiment 3 is characterized in that in step 3), the sulfuric acid solution is added to the pipeline of the ammonium salt solution, and the mixed solution directly enters the gas-liquid contact device.

[0052] 6. The method according to embodiment 3, characterized in that step 3) includes a solution collecting device, sulfuric acid solution and ammonium salt solution are added to the solution collecting device, and gas-liquid contact is carried out by forced circulation.

[0053] 7. The method according to embodiment 4, wherein the amount of sulfuric acid solution added is controlled according to the pH value.

[0054] 8. The method as described in Embodiment 1 is characterized in that the amount of sulfuric acid solution added is also controlled according to the flue gas volume after decarbonization and the ammonia escape concentration.

[0055] 9. The method according to embodiment 1, characterized in that the mass concentration of the sulfuric acid solution is 10%-50%, preferably 12%-40%, and more preferably 15%-30%.

[0056] 10. The method according to embodiment 1 is characterized in that in step 4), the concentration of the ammonium sulfate solution is further adjusted by adding water so that the difference in mass concentration between the ammonium sulfate solution and the ammonium salt solution from the desulfurization functional zone does not exceed 5%, preferably 3%, and more preferably 1%.

[0057] 11. The method according to embodiment 1, characterized in that the SO2 content in the low-sulfur flue gas is not higher than 2000 mg / Nm 3 , preferably 1000mg / Nm 3 , more preferably 500 mg / Nm 3 .

[0058] 12. The method according to embodiment 1 is characterized in that the ammonium salt solution in step 1) is one or a combination of the concentrated circulating liquid, the absorption circulating liquid, and the washing circulating liquid of the ammonia-based desulfurization functional zone, the concentrated circulating liquid has a pH of 1-6, preferably 2-4.5, an ammonium sulfite concentration of 0-0.2 wt%, and an ammonium sulfate concentration of 10-60 wt%. The absorption circulating liquid has a pH of 4.5-6.5, preferably 4.8-6.2, an ammonium sulfite concentration of 0.1-3 wt%, and an ammonium sulfate concentration of 10-38 wt%. The washing circulating liquid has a pH of 1.5-6.5, preferably 2-5, and an ammonium sulfate concentration of 0-5 wt%.

[0059] 13. The method as described in embodiment 1 is characterized in that the ammonium salt solution in step 2) is one or a combination of ammonium bicarbonate generation circulating liquid and decarbonization absorption circulating liquid, the molar ratio of total ammonia to total CO2 in the ammonium bicarbonate generation circulating liquid is 1-1.8, and the molar ratio of total ammonia to total CO2 in the decarbonization absorption circulating liquid is 1.8-3, the total ammonia includes ammonia and ammonium ions, and the total CO2 includes free CO2 and carbonized CO2.

[0060] 14. A device for controlling ammonia escape by carbon capture and co-production of nitrogen fertilizer from low-sulfur flue gas, characterized by the following features: an ammonia desulfurization functional area, an ammonia decarbonization functional area, an ammonia washing functional area, and an acid addition system.

[0061] Among them, the ammonia desulfurization functional area, the ammonia decarbonization functional area, and the ammonia washing functional area are connected in sequence, the ammonia desulfurization functional area and the ammonia washing functional area are connected through a liquid phase pipeline, and the acid addition system is connected to the ammonia washing functional area.

[0062] 15. The device as described in Embodiment 14 is characterized in that the ammonia desulfurization functional area is divided into multiple sections, including a cooling, concentration and temperature reduction section, an absorption section, and a water washing section. Each section is provided with at least one layer of gas-liquid contact, and equipment / components allowing gas to pass through are provided between the sections.

[0063] 16. The device as described in Embodiment 14 is characterized in that the ammonia desulfurization functional area is divided into multiple sections, including an ammonium bicarbonate generation section and a decarbonization absorption section. Each section is provided with at least one layer of gas-liquid contact, and equipment / components allowing gas to pass through are provided between the sections.

[0064] 17. The device as described in embodiment 14 is characterized in that the ammonia washing functional area is provided with a pH detection device.

[0065] 18. The device as described in Embodiment 14 is characterized in that the ammonia desulfurization functional area also includes an ammonium sulfate production system.

[0066] 19. The device as described in Embodiment 14 is characterized in that the ammonia decarbonization functional area also includes an ammonium bicarbonate production system.

[0067] 20. The device as described in embodiment 15 is characterized in that one or a combination of the cooling, concentration and temperature reduction section, the absorption section, and the water washing section is connected to the ammonia washing functional area.

[0068] 21. The device as described in Embodiment 14 is characterized in that the ammonia washing functional area also includes a water washing section, which is connected to the water supply pipe, is provided with at least one layer of gas-liquid contact, and is provided with equipment / components allowing gas to pass between the water washing section and other sections of the ammonia washing functional area.

[0069] 22. The device as described in Embodiment 14 is characterized in that a water replenishment device is provided in the ammonia washing functional area.

[0070] 23. The device as described in embodiment 14 is characterized in that the acid addition system is provided with an acid dilution device and an acid concentration measuring device.

[0071] 24. The device as described in Embodiment 14 is characterized in that the acid adding device is connected to the liquid phase connecting pipelines of the ammonia desulfurization functional area and the ammonia washing functional area, and is connected to the ammonia washing functional area.

[0072] 25. The device as described in embodiment 14 is characterized in that the ammonia washing functional area includes a solution collecting device, and the acid adding device is directly connected to the solution collecting device.

[0073] 26. The method according to embodiment 3, characterized in that in step 3), the sulfuric acid solution and the ammonium salt solution are directly introduced into the gas-liquid contact device respectively. Description of the drawings:

[0074] Figure 1 shows a device for controlling ammonia escape in a low-sulfur flue gas carbon capture and co-production of nitrogen fertilizer. 1. Process gas; 2. Desulfurization functional area; 3. Desulfurization circulation pump a; 4. Desulfurization heat exchanger-a; 5. Desulfurization circulation pump-b; 6. Desulfurization heat exchanger-b; 7. Oxidizing air; 8. Desulfurization system ammonia addition; 9. Ammonium sulfate treatment system; 10. Desulfurization circulation pump-c; 11. Desulfurization heat exchanger-c; 12. Exhaust gas after desulfurization; 13. Decarbonization cooling system; 14. Desulfurization circulation tank; 15. Ammonia wash pH meter; 16. Ammonia wash solution to desulfurization area; 17. Ammonia wash solution to decarbonization area; 18. Process water; 19. Decarbonization Functional area; 20. Particle washing circulation pump; 21. Decarbonization circulation pump; 22. Decarbonization heat exchanger; 23. Tail gas after decarbonization; 24. Adding ammonia to the decarbonization system; 25. Ammonia washing functional area; 26. Ammonia washing functional area circulation pump-a; 27. Ammonia washing functional area circulation pump-b; 28. Ammonia washing heat exchanger; 29. ​​Ammonia washing drainage 30. Clean flue gas; 31. Acidic desulfurization liquid (i.e., desulfurization circulating liquid used as deammoniation washing liquid); 32. Return desulfurization liquid; 33. Ammonium bicarbonate treatment system; 34. Sulfuric acid addition equipment. DETAILED DESCRIPTION

[0075] In the figure, process gas 1 containing sulfur oxides and CO2 enters the desulfurization zone 2, where it is spray-circulated by the desulfurization circulation pump-b 5. The temperature is controlled by the desulfurization heat exchanger-b 6. The exhaust gas is cooled while the ammonium sulfate solution is concentrated. The concentrated ammonium sulfate slurry, which has precipitated solids, is then passed through the ammonium sulfate treatment system 9 to produce finished ammonium sulfate. The desulfurization zone 2 desulfurization circulation pump-b 3 and desulfurization circulation tank 14 perform an absorption spray cycle to absorb sulfur oxides (sulfur dioxide and sulfur trioxide) from the exhaust gas. The desulfurization temperature is controlled by the desulfurization heat exchanger-a 4. The desulfurization circulation pump-c 10 performs a scrubbing spray cycle, and the scrubbing temperature is controlled by the desulfurization heat exchanger-c 11. Ammonia 8 is metered and then added to the desulfurization circulation tank 14. Oxidizing air 7 is then passed to the desulfurization circulation tank 14 to oxidize the solution.

[0076] After desulfurization, tail gas 12 is cooled by a decarbonization cooling system 13 before entering a decarbonization zone 19. Decarbonization circulation pump 21 conducts absorption spray circulation, and decarbonization heat exchanger 22 removes the decarbonization heat. The ammonium bicarbonate treatment system 33 produces finished ammonium bicarbonate. Ammonia 24 is metered and then added to the decarbonization zone 19.

[0077] Decarbonized tail gas 23 enters the ammonia scrubbing zone 25, where it undergoes primary scrubbing using ammonia scrubbing tower circulation pump-a 26. The primary scrubbing liquid, derived from the acidic desulfurization liquid 31 of the particulate matter scrubbing circulation pump in the desulfurization circulation tank 14, is continuously fed to the bottom of the ammonia scrubbing tower 25. After absorbing ammonia, the desulfurized liquid (i.e., the returned desulfurized liquid) 32 returns to the desulfurization circulation tank 14. Secondary scrubbing occurs using ammonia scrubbing zone circulation pump-b 27. The scrubbing temperature is controlled by the ammonia scrubbing heat exchanger 28. The secondary scrubbing liquid is supplied as process water 18. The post-scrubbing wastewater 29 is split into two routes: pipeline 16 and pipeline 17. Pipeline 16 returns to the desulfurization zone 2, while pipeline 17 returns to the decarbonization zone 19. The opening and closing of pipelines 16 and 17 are controlled by the water replenishment in the desulfurization zone 2 and decarbonization zone 19. Clean flue gas 30 is discharged after scrubbing.

[0078] The device also includes a sulfuric acid adding device 34 and an ammonia washing pH meter 15. Sulfuric acid is added to the bottom of the first-level washing section of the ammonia washing functional area 25 through the sulfuric acid adding device 34 to adjust the pH value of the inlet solution of the first-level washing circulation pump-a 26 of the ammonia washing tower.

[0079] Alternatively, as shown in Figure 2, sulfuric acid can be added to the acidic desulfurization liquid pipeline 31 through the sulfuric acid addition device 34, and the liquid is directly sprayed into the first washing cycle section of the ammonia scrubbing tower. The pH meter 15 is installed after the sulfuric acid addition point in the acidic desulfurization liquid pipeline 31.

[0080] Example

[0081] This application provides Examples 1-2 and Comparative Examples 1-2 to further illustrate the technical solutions of the present invention.

[0082] Example 1:

[0083] Gas-fired boiler flue gas (process gas) containing sulfur oxides and CO₂ enters the integrated desulfurization and decarbonization device described above. The process flow is shown in Figure 1. Gas-fired boiler flue gas 1 enters the desulfurization zone 2, where it is spray-circulated by the desulfurization circulation pump-b 5. The temperature is controlled by the desulfurization heat exchanger-b 6. While the exhaust gas is cooled, the ammonium sulfate solution is concentrated. The concentrated ammonium sulfate slurry, which has precipitated solids, is passed through the ammonium sulfate treatment system 9 to produce finished ammonium sulfate. The desulfurization zone 2 desulfurization circulation pump-b 3 and desulfurization circulation tank 14 perform an absorption spray circulation to absorb sulfur oxides (sulfur dioxide and sulfur trioxide) from the exhaust gas. The desulfurization temperature is controlled by the desulfurization heat exchanger-a 4. The desulfurization circulation pump-c 10 performs a scrubbing spray circulation, and the scrubbing temperature is controlled by the desulfurization heat exchanger-c 11. Ammonia 8 is metered and then added to the desulfurization circulation tank 14. Oxidizing air 7 is passed to the desulfurization circulation tank 14 to oxidize the solution.

[0084] After desulfurization, tail gas 12 is cooled by a decarbonization cooling system 13 before entering a decarbonization zone 19. Decarbonization circulation pump 21 conducts absorption spray circulation, and decarbonization heat is removed by a decarbonization heat exchanger 22. Finished ammonium bicarbonate is obtained by an ammonium bicarbonate treatment system 33. Ammonia 24 is metered and then added to the decarbonization zone 19.

[0085] Decarbonized tail gas 23 enters the ammonia scrubbing zone 25 for primary scrubbing using ammonia scrubbing tower circulation pump-a 26. The primary scrubbing liquid, supplied by the acidic desulfurization liquid 31 from the particulate matter scrubbing circulation pump in the desulfurization circulation tank 14, is continuously fed to the bottom of the ammonia scrubbing tower 25. After absorbing ammonia, the desulfurized liquid 32 returns to the desulfurization circulation tank 14. Secondary scrubbing occurs using ammonia scrubbing zone circulation pump-b 27. The scrubbing temperature is controlled by the ammonia scrubbing heat exchanger 28. The secondary scrubbing liquid comes from process water 18. After scrubbing, wastewater 29 returns to the desulfurization zone 2 (pipeline 16) and the decarbonization zone 19 (pipeline 17). Clean flue gas 30 is discharged after scrubbing. Ammonia 24 is metered and then sent to the decarbonization zone 19 for ammonia addition.

[0086] The device also includes a sulfuric acid addition device 34 and an ammonia washing pH meter 15. Sulfuric acid and acidic desulfurization liquid 31 are directly added respectively. The pH of the solution is significantly reduced after the addition of sulfuric acid, which better adjusts the pH value of the first-level washing circulating solution of the ammonia washing tower, thereby absorbing ammonia in the gas.

[0087] Ammonia is removed from the decarbonized tail gas 23 by scrubbing acidic desulfurization liquid 31 from the particle scrubbing pump in the desulfurization circulation tank 14. However, due to the low SO2 content in the process gas 1, the ammonia content in the decarbonized tail gas 23 cannot be fully consumed. Therefore, sulfuric acid is added to the acidic desulfurization liquid 31 to adjust the pH and produce ammonium sulfate. This ammonium sulfate is then returned to the desulfurization zone along with the desulfurization liquid 32 after absorbing ammonia, along with the ammonium sulfate produced by the ammonia-based desulfurization process, to be recovered as ammonium sulfate fertilizer. Because ammonium sulfate is produced in the first-stage deammonification scrubbing circulating liquid, the solution concentration increases. To ensure that the concentration does not exceed 3% of the incoming liquid, water replenishment is required. This replenishment is done with the water-based scrubbing liquid from the second-stage deammonification process.

[0088] The concentration of sulfuric acid used is 20%, and the pH value of the pH meter 15 is controlled to be 4.5-5.5.

[0089] Desulfurization and decarbonization use 99.6% liquid ammonia as the absorbent. The process gas 1 parameters are shown in the table below:

[0090] The main parameters of the gas 12 after being treated by the desulfurization system are shown in the following table:

[0091] The main parameters of the gas 23 after being treated in the decarbonization functional zone are shown in the following table:

[0092] The main parameters after treatment in the ammonia washing tower are shown in the table below:

[0093] Example 2:

[0094] As shown in Figure 2, compared to Example 1, sulfuric acid is added to the acidic desulfurization liquid pipeline 31 via sulfuric acid addition equipment 34, and the solution is sprayed directly into the primary scrubbing cycle of the ammonia scrubbing tower. A pH meter 15 is located after the sulfuric acid addition point in the acidic desulfurization liquid pipeline 31. The sulfuric acid concentration used is 20%, and the pH value of pH meter 15 is controlled at 2-4. All other conditions remain unchanged.

[0095] The main parameters after treatment in the ammonia washing tower are shown in the table below:

[0096] Comparative Example 1: Compared with Example 1, the sulfuric acid adding device 34 is omitted. Other conditions remain unchanged.

[0097] Without sulfuric acid, the pH meter 15 showed a pH value of 4.5-5.5, which was not controlled, and the actual pH value was 10.5-12. The ammonia concentration at the outlet remained high after ammonia scrubbing. To reduce ammonia escape, the only option was to increase the number of water scrubbing stages and the spray volume, which would obviously increase investment and operating costs.

[0098] Comparative Example 2: Compared with Example 2, the sulfuric acid adding device 34 is omitted. Other conditions remain unchanged.

[0099] The pH of the acidic desulfurization liquid is 4.5-6.5. Although ammonia can be removed in the initial stage, the desulfurization system cannot consume the large amount of ammonia absorbed, which will cause the desulfurization system to fail to operate normally.

[0100] It can be seen from the above embodiments and comparative examples of the present invention that the method and device for controlling ammonia escape through low-sulfur flue gas carbon capture and co-production of nitrogen fertilizer of the present invention can achieve efficient decarbonization while controlling ammonia escape, thereby achieving excellent technical and economic effects.

[0101] The above description is merely a preferred embodiment of the present invention. Those skilled in the art, once understanding the technical means of the present invention, will naturally be able to modify the present invention according to their actual needs. Therefore, all equivalent changes and modifications made within the scope of the present invention are still covered by the present invention.

Claims

1. A method for controlling ammonia escape by carbon capture and co-production of nitrogen fertilizer from low-sulfur flue gas, comprising the following steps in sequence: 1) Use ammonium salt solution to remove part of the SO2 in the process gas; 2) Use ammonium salt solution to remove part of the CO2 in the process gas; and 3) using the ammonium salt solution and sulfuric acid solution of step 1) to remove part of the free ammonia in the process gas to generate ammonium sulfate; 4) at least part of the ammonium sulfate solution produced in step 3) is returned to the desulfurization functional zone, and is co-crystallized with the desulfurization byproduct ammonium sulfate in the desulfurization functional zone to produce solid ammonium sulfate.

2. The method according to claim 1, characterized in that Step 2) produces solid ammonium bicarbonate.

3. The method according to claim 1, characterized in that In step 3), at least one layer of gas-liquid contact device is provided.

4. The method according to claim 3, characterized in that The pH of the solution in gas-liquid contact is controlled to be 1-10, preferably 1-7.5, more preferably 1-6.5, most preferably 1-5.

5.

5. The method according to claim 3, characterized in that In step 3), sulfuric acid solution is added to the pipeline of ammonium salt solution, and the mixed solution directly enters the gas-liquid contact device.

6. The method according to claim 3, characterized in that Step 3) includes a solution collecting device, sulfuric acid solution and ammonium salt solution are added to the solution collecting device, and gas-liquid contact is carried out through forced circulation.

7. The method according to claim 4, characterized in that The amount of sulfuric acid solution added is controlled according to the pH value.

8. The method according to claim 1, characterized in that The amount of sulfuric acid solution added is also controlled according to the flue gas volume after decarbonization and the ammonia escape concentration.

9. The method according to claim 1, characterized in that The mass concentration of the sulfuric acid solution is 10%-50%, preferably 12%-40%, more preferably 15%-30%.

10. The method according to claim 1, characterized in that In step 4), the concentration of the ammonium sulfate solution is adjusted by water replenishment so that the difference in mass concentration between the ammonium sulfate solution and the ammonium salt solution from the desulfurization functional area does not exceed 5%, preferably 3%, and more preferably 1%.

11. The method according to claim 1, characterized in that The SO2 content in the low-sulfur flue gas is not higher than 2000 mg / Nm 3 , preferably 1000mg / Nm 3 , more preferably 500 mg / Nm 3 .

12. The method according to claim 1, characterized in that In step 1), the ammonium salt solution is one or a combination of the concentrated circulating liquid, the absorption circulating liquid and the washing circulating liquid of the ammonia desulfurization functional zone, the concentrated circulating liquid has a pH of 1-6, preferably 2-4.5, an ammonium sulfite concentration of 0-0.2wt%, an ammonium sulfate concentration of 10-60wt%, an absorption circulating liquid has a pH of 4.5-6.5, preferably 4.8-6.2, an ammonium sulfite concentration of 0.1-3wt%, an ammonium sulfate concentration of 10-38wt%, and a washing circulating liquid has a pH of 1.5-6.5, preferably 2-5, and an ammonium sulfate concentration of 0-5wt%.

13. The method according to claim 1, characterized in that In step 2), the ammonium salt solution is one or a combination of ammonium bicarbonate generation circulating liquid and decarbonization absorption circulating liquid. The molar ratio of total ammonia to total CO2 in the ammonium bicarbonate generation circulating liquid is 1-1.8, and the molar ratio of total ammonia to total CO2 in the decarbonization absorption circulating liquid is 1.8-3. The total ammonia includes ammonia and ammonium ions, and the total CO2 includes free CO2 and carbonized CO2.

14. A device for controlling ammonia escape by carbon capture and co-production of nitrogen fertilizer from low-sulfur flue gas, characterized in that: Set up ammonia desulfurization functional area, ammonia decarbonization functional area, ammonia washing functional area, and acid addition system. Among them, the ammonia desulfurization functional area, the ammonia decarbonization functional area, and the ammonia washing functional area are connected in sequence, the ammonia desulfurization functional area is connected to the ammonia washing functional area through a liquid phase pipeline, and the acid addition system is connected to the ammonia washing functional area.

15. The device according to claim 14, characterized in that The ammonia desulfurization functional area is divided into multiple sections, including a cooling, concentration and temperature reduction section, an absorption section, and a water washing section. Each section is provided with at least one layer of gas-liquid contact, and equipment / components that allow gas to pass through are provided between the sections.

16. The device according to claim 14, characterized in that The ammonia desulfurization functional area is divided into multiple sections, including an ammonium bicarbonate generation section and a decarbonization absorption section. Each section is provided with at least one layer of gas-liquid contact, and equipment / components allowing gas to pass through are provided between the sections.

17. The device according to claim 14, characterized in that The ammonia washing functional area is equipped with a pH detection device.

18. The device according to claim 14, characterized in that The ammonia desulfurization functional area also includes an ammonium sulfate production system.

19. The device according to claim 14, characterized in that The ammonia decarbonization functional area also includes an ammonium bicarbonate production system.

20. The device according to claim 15, characterized in that One or a combination of the cooling, concentration and temperature reduction section, the absorption section and the water washing section is connected to the ammonia washing functional area.

21. The device according to claim 14, characterized in that The ammonia washing functional area also includes a water washing section, which is connected to the water replenishment pipe and is provided with at least one layer of gas-liquid contact. Equipment / components allowing gas to pass are provided between the water washing section and other sections of the ammonia washing functional area.

22. The device according to claim 14, characterized in that The ammonia washing functional area is equipped with a water replenishment device.

23. The device according to claim 14, characterized in that The acid adding system is equipped with an acid dilution device and an acid concentration measuring device.

24. The device according to claim 14, characterized in that The acid adding device is connected to the liquid phase connecting pipelines of the ammonia desulfurization functional area and the ammonia washing functional area, and is connected to the ammonia washing functional area.

25. The device according to claim 14, characterized in that The ammonia washing functional area includes a solution collecting device, and the acid adding device is directly connected to the solution collecting device.

26. The method of claim 3, wherein: In step 3), the sulfuric acid solution and the ammonium salt solution are directly introduced into the gas-liquid contact device respectively.

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