Energy-saving ammonia-process carbon capture and nitrogen fertilizer co-production method and device

Abstract

The invention relates to an energy-saving ammonia-process carbon capture and nitrogen fertilizer co-production method and device. According to the method, ammonia is adopted as an absorbent, CO2 in flue gas is captured through a normal pressure method, ammonium bicarbonate fertilizer is co-produced, the temperature in the absorption process is controlled to range from 25 DEG C to 40 DEG C, and air is adopted as a cold source to remove and absorb heat generated. The device comprises an ammonia-process decarburization device and an air cooler, the ammonia-process decarburization device sequentially comprises a cooling functional area, an ammonium bicarbonate generation area, a carbon dioxide absorption area and an ammonia removal functional area in the flue gas flowing direction, the ammonia-process decarburization device is configured to be used for removing CO2 from flue gas containing CO2 through an ammonia absorbent to generate ammonium bicarbonate, and the air cooler is configured to be used for cooling the flue gas containing CO2. The air cooler is connected with the carbon dioxide absorption area of the ammonia process decarburization device and is configured to be used for extracting heat from the carbon dioxide absorption area of the ammonia process decarburization device.

Description

TECHNICAL FIELD

[0001] The present application relates to a method and device for energy-saving ammonia-based carbon capture and nitrogen fertilizer co-production. BACKGROUND

[0002] Ammonia-based decarbonization technology has always been the focus of research and the best method to solve greenhouse gases. However, ammonia is volatile, and decarbonization needs to be carried out under slightly alkaline conditions, resulting in an increase in ammonia escape. If not addressed, large amounts of ammonia escape not only increase the cost of decarbonization, but also cause secondary pollution.

[0003] CN200880122376.2 discloses a multi-stage CO2 removal system and method for treating a flue gas stream, using an absorber vessel to contact the flue gas stream with an ionic solution containing ammonia at a low temperature of 0-20℃, while the solution of the first absorption stage has a higher temperature and a lower ammonia-to-carbon ratio than the solution of the third absorption stage. By controlling the lower temperature, and the third stage has a lower temperature, ammonia escape can be reduced, but the third stage has a higher ammonia-to-carbon ratio, which will increase ammonia escape. This process is carried out at a low temperature of 0-20℃, and there are problems of low decarbonization efficiency and high energy consumption.

[0004] CN201110039363.2 discloses an ammonia-based atmospheric capture and absorption of sulfur dioxide and carbon dioxide system and process, which first carries out desulfurization and then decarbonization, and multiple heat exchangers are provided in the desulfurization and decarbonization units for controlling the absorption temperature, wherein the decarbonization temperature is controlled at 40℃-50℃, and high-concentration ammonia water is used for desulfurization and decarbonization, and then dilute-concentration ammonia water is used for desulfurization and decarbonization, and the gas after decarbonization is directly discharged. This process only uses temperature control and low-concentration ammonia water absorption, and cannot solve the problem of ammonia escape, in addition, the ammonia water concentration cannot be too low, and low-concentration ammonia water will bring in a large amount of water, causing the desulfurization product ammonium sulfate and the decarbonization product ammonium bicarbonate to be unable to crystallize.

[0005] 202223487588.7 discloses an ammonia-based decarbonization system, which comprises an ammonia-based decarbonization device and a cooling tower connected with the ammonia-based decarbonization device, along the flue gas flow direction, the ammonia-based decarbonization device comprises a cooling functional area (2), an ammonium bicarbonate generation area (5), a carbon dioxide absorption area (7) and an ammonia removal functional area (15) in sequence, the ammonia-based decarbonization device is configured to remove CO2 from flue gas containing CO2 with ammonia absorbent to produce ammonium bicarbonate, and the cooling tower is configured to extract heat from the ammonia-based decarbonization device, wherein the temperature of the decarbonization absorption circulating liquid is controlled at 20℃-30℃. The temperature control of this process needs a lower ambient temperature to be realized, and the process requires a large amount of cooling water, the cooling tower occupies a large area, and the water consumption is also large. SUMMARY

[0006] Technical problems solved and beneficial effects

[0007] For the economic and efficient production of ammonium bicarbonate by capturing carbon dioxide with ammonia, the present solution adopts a solution gradient control method, and under specific ammonia addition and ammonia washing conditions, ammonium bicarbonate is produced by ammonia method carbon capture at a higher temperature. The reaction temperature can be controlled at 25-40℃ by using an air cooler. The specific operations of the solution gradient control, ammonia addition and ammonia washing in the technical solution of the present application are as follows.

[0008] An energy-saving ammonia method carbon capture co-production nitrogen fertilizer device, comprising an ammonia method decarbonization device and an air cooler, the air cooler is connected with the ammonia method decarbonization device, along the flue gas flow direction, the ammonia method decarbonization device comprises a cooling function area 2, an ammonium bicarbonate generation area 5, a carbon dioxide absorption area 7 and an ammonia removal function area 15 in sequence, and the ammonia method decarbonization device is configured to remove CO2 from flue gas containing CO2 with ammonia absorbent to produce ammonium bicarbonate.

[0009] Regarding the solution gradient control, the carbon dioxide absorption area 7 in the technical solution of the present application can be designed with multiple stages of spraying according to the carbon dioxide concentration in the process gas and the decarbonization efficiency requirement, at least 2 stages are provided, along the flue gas flow direction, the flue gas upper source is the first stage, then in sequence is the second stage, the third stage, …, and the stages are separated by a liquid collector that only allows gas to pass through.

[0010] Regarding ammonia addition, in the technical solution of the present application, ammonia is mainly added from the second stage of the carbon dioxide absorption area 7, and the ammonia source in the first stage of the carbon dioxide absorption area 7 is only added through the second stage. If multiple stages of spraying are provided, the circulating liquid of the previous stage is sequentially supplemented into the next stage, so that the carbonate concentration gradually accumulates.

[0011] The supplement of the ammonium bicarbonate generation area 5 is supplemented through the first stage of the carbon dioxide absorption area. No ammonia is added to the ammonium bicarbonate generation area 5 to promote the generation of ammonium bicarbonate.

[0012] The carbon dioxide absorption area 7 is provided with at least 3 stages, and the amount of ammonia added after the third stage is sequentially reduced.

[0013] Regarding ammonia washing (i.e. ammonia removal), the ammonia removal function area 15 in the technical solution of the present application is provided with at least two stages of spraying 15-1 and 15-2, wherein 15-1 is process water washing to remove ammonia, the circulating liquid is forced to circulate through a pump 17-1, cooled through a heat exchange device 22, and the solution obtained by washing is supplemented into the second stage 7-2 of the carbon dioxide absorption area as an ammonia source. 15-2 is acid washing to remove ammonia, which can directly supplement sulfuric acid, or supplement the condensate obtained from the cooling function area 2, or supplement the acidic desulfurization circulating liquid of the desulfurization device 23.

[0014] The present application also relates to the following embodiments:

[0015] 1. A method for energy saving ammonia based carbon capture co-production of nitrogen fertilizer, characterized in that ammonia is used as absorbent, CO2 in flue gas is captured by atmospheric pressure method, ammonium bicarbonate fertilizer is co-produced, the temperature of absorption process is controlled at 25-40℃, preferably 28-40℃, more preferably 30-38℃, most preferably 32-38℃, and air is used as cold source to remove the heat generated by absorption.

[0016] 2. The method according to embodiment 1, characterized in that air cooler is used for temperature control.

[0017] 3. The method according to embodiment 2, characterized in that the air cooler is in the form of wet air cooler.

[0018] 4. The method according to embodiment 1, characterized in that the heat is removed directly by air cooler or indirectly by heat exchanger.

[0019] 5. The method according to embodiment 3, characterized in that the heat is removed directly by wet air cooler, wherein the circulating liquid directly enters the inlet of wet air cooling solution, and returns to the ammonia based carbon capture device from the outlet after cooling.

[0020] 6. The method according to embodiment 1, characterized in that the ammonia based carbon capture includes cooling unit, ammonium bicarbonate generation unit, absorption unit, ammonia escape control unit, and at least the absorption unit uses air cooler for temperature control.

[0021] 7. The method according to embodiment 6, characterized in that the cooling unit uses air cooler for temperature control, preferably wet air cooling.

[0022] 8. The method according to embodiment 7, characterized in that the temperature is controlled at 25-40℃.

[0023] 9. The method according to embodiment 6, characterized in that the ammonium bicarbonate generation unit uses air cooler for temperature control, preferably wet air cooling.

[0024] 10. The method according to embodiment 6, characterized in that the absorption unit includes at least 2 absorption stages, and ammonia is added to the second stage in the flue gas flow direction.

[0025] 11. The method according to embodiment 6, characterized in that the temperature of cooling unit is controlled at 25-40℃.

[0026] 12. The method according to embodiment 1, characterized in that the capture pressure is less than 90kpa (gauge pressure).

[0027] 13. The method according to embodiment 1, characterized in that after absorption, water is used to wash the escaped ammonia in flue gas, and the washing temperature is 20-40℃.

[0028] 14. The method of embodiment 13, wherein the scrubbing liquid is returned to the absorption unit.

[0029] 15. An energy-saving apparatus for carbon capture and nitrogen co-production by ammonia process, wherein the apparatus comprises an ammonia process decarbonization unit and an air cooler, the ammonia process decarbonization unit comprises a cooling functional zone, an ammonium bicarbonate generation zone, a carbon dioxide absorption zone and an ammonia removal functional zone in sequence along the flue gas flow direction, the ammonia process decarbonization unit is configured to remove CO2 from flue gas containing CO2 with ammonia absorbent to produce ammonium bicarbonate, the air cooler is connected with the carbon dioxide absorption zone of the ammonia process decarbonization unit and is configured to extract heat from the carbon dioxide absorption zone of the ammonia process decarbonization unit.

[0030] 16. The apparatus of embodiment 15, wherein the air cooler is a wet air cooler, and a circulation liquid pipeline of the carbon dioxide absorption zone of the ammonia process decarbonization unit is connected with the wet air cooler.

[0031] 17. The apparatus of embodiment 15, wherein the air cooler is connected with the ammonium bicarbonate generation zone of the ammonia process decarbonization unit and is configured to extract heat from the ammonium bicarbonate generation zone of the ammonia process decarbonization unit.

[0032] 18. The apparatus of embodiment 17, wherein the air cooler is a wet air cooler, and a circulation liquid pipeline of the ammonium bicarbonate generation zone of the ammonia process decarbonization unit is connected with the wet air cooler.

[0033] 19. The apparatus of embodiment 15, wherein the air cooler is connected with the cooling functional zone of the ammonia process decarbonization unit and is configured to extract heat from the cooling functional zone of the ammonia process decarbonization unit.

[0034] 20. The apparatus of embodiment 19, wherein the air cooler is a wet air cooler, and a circulation liquid pipeline of the cooling functional zone of the ammonia process decarbonization unit is connected with the wet air cooler.

[0035] 21. The apparatus of embodiment 15, wherein the air cooler is connected with the ammonia removal functional zone of the ammonia process decarbonization unit and is configured to extract heat from the ammonia removal functional zone of the ammonia process decarbonization unit.

[0036] 22. The apparatus of embodiment 21, wherein the air cooler is a wet air cooler, and a circulation liquid pipeline of the ammonia removal functional zone of the ammonia process decarbonization unit is connected with the wet air cooler. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a schematic diagram illustrating an embodiment of the present application.

[0038] Figure 2 is a schematic diagram of a cooling tower cooling device used as a heat exchange device in an embodiment of the present application.

[0039] Figure 3 is a schematic diagram of the air cooling device used as the heat exchange device in the embodiment of the present application.

[0040] Figure 4 is a schematic diagram of the wet air cooling device used as the heat exchange device in the embodiment of the present application.

[0041] The following reference signs are used in the figure:

[0042] Process gas 1, cooling function zone 2, cooling circulating pump 3, heat exchange device 4, ammonium bicarbonate generating zone 5, liquid collector 6, carbon dioxide absorption zone 7, heat exchange device 8, ammonium bicarbonate generating zone circulating pump 9, carbon dioxide absorption zone circulating pump 10, heat exchange device 11, scrubbing liquid second section to carbon dioxide absorption zone 12, process water 13, ammonium bicarbonate fertilizer 14, ammonia removal function zone 15, decarbonated gas 16, ammonia removal function zone water washing circulating pump 17, mother liquor return pipe 18, ammonia adding device 19, ammonia 20, ammonium bicarbonate discharge pump 21, heat exchange device 22, desulfurization device 23, ammonium sulfate fertilizer 24, circulating liquid in 25, circulating liquid out 26, tube and shell heat exchanger 27, cooling water in 28, cooling water out 29, circulating water pump 30, cooling tower 31, air cooler 32, wet air cooler 33. DETAILED DESCRIPTION

[0043] The process gas containing SO2 and CO2 (also referred to as flue gas) 1 is sent to the ammonia desulfurization device 23 to remove SO2 to produce ammonium sulfate 24, and then to the ammonia decarbonization device, which includes the cooling function zone 2, the ammonium bicarbonate generating zone 5, the carbon dioxide absorption zone 7, and the ammonia removal function zone 15.

[0044] The process gas containing SO2, CO2 and ammonium sulfate particles after desulfurization is first sent to the cooling function zone 2 to control the temperature of the process gas to 25-40°C, preferably 30-38°C.

[0045] The cooling function zone 2 can be indirect heat exchange between heat exchangers to cool the process gas.

[0046] The cooling function zone 2 can also be spray type direct contact cooling, where the gas is cooled by countercurrent spray contact with circulating liquid, which is circulated by the cooling circulating pump 3 and cooled by the heat exchange device 4. The cooling function zone is provided with at least 2 layers of spray.

[0047] The cooled gas enters the ammonium bicarbonate formation zone 5 where it is contacted with the circulating liquid in counter current spray to form ammonium bicarbonate. The circulating liquid is circulated by the circulating pump 9 and cooled by the heat exchange equipment 8. The gas leaving the ammonium bicarbonate formation zone 5 enters the carbon dioxide absorption zone 7. The circulating liquid of the carbon dioxide absorption zone 7 is circulated by the circulating pump 9. The carbon dioxide absorption zone 7 is separated from the ammonium bicarbonate formation zone 5 by a gas passable collector 6. Part of the circulating liquid of the carbon dioxide absorption zone 7 flows into the ammonium bicarbonate formation zone 5. The ammonium bicarbonate formation zone 5 is provided with 1-3 layers of spray. The temperature is controlled at 30-35°C.

[0048] In the carbon dioxide absorption zone 7, CO2 in the gas reacts with ammonia in the circulating liquid to form ammonium carbonate or carbamic acid. Part of the circulating liquid of the carbon dioxide absorption zone 7 flows into the ammonium bicarbonate formation zone 5. In the ammonium bicarbonate formation zone 5, CO2 in the gas reacts with ammonium carbonate or carbamic acid in the circulating liquid to form ammonium bicarbonate. The carbon dioxide absorption zone 7 is provided with 2 sections of spray 7-1 and 7-2 separated by a gas passable collector 6-2. The temperature is controlled at 25-40°C, preferably 28-40°C, more preferably 30-38°C, most preferably 32-38°C. The temperature is controlled by the heat exchange equipment 11.

[0049] The ammonia adding equipment 19 can be an ammonia tank. The ammonia 20 is 99.8wt% liquid ammonia added to 7-2.

[0050] The carbon dioxide absorption zone 7 can be designed with multiple sections of spray according to the concentration of CO2 in the gas and the requirement of decarbonization efficiency. At least 2 sections are provided. The sections are separated by a gas passable collector. Ammonia is mainly added to the second section of the carbon dioxide absorption zone. The first section of the carbon dioxide absorption zone is only supplied with make-up liquid from the second section. If multiple sections of spray are provided, the circulating liquid of the previous section is sequentially fed into the next section so that the concentration of carbonate gradually accumulates.

[0051] The gas after the carbon dioxide absorption zone 7 enters the ammonia removal function zone 15 where it is contacted with the circulating liquid in counter current spray to absorb free ammonia. The circulating liquid is circulated by the circulating pump 17. The process gas 16 after the ammonia removal is discharged from the top of the tower.

[0052] The ammonia removal function zone 15 is provided with 2 sections of spray 15-1 and 15-2. 15-1 is a water wash to remove ammonia. The circulating liquid is forced to circulate by the pump 17-1 and cooled by the heat exchange equipment 22. The solution obtained by the washing is fed into the second section 7-2 of the carbon dioxide absorption zone. The temperature of the process gas is controlled at 20-30°C by the heat exchange equipment 22. 15-2 is an acid wash to remove ammonia. Sulfuric acid can be directly fed into 15-2. Alternatively, condensed water obtained from the cooling function zone 2 or the acidic desulfurization circulating liquid obtained from the desulfurization equipment 23 can be fed into 15-2.

[0053] The circulating liquid of the ammonium bicarbonate generating zone 5 is pumped into the ammonium bicarbonate treatment system to produce solid ammonium bicarbonate 14 by the ammonium bicarbonate discharge pump 11. The ammonium bicarbonate treatment system comprises a crystallization device 12, a solid-liquid separation device 13, and the mother liquor 18 is returned to the carbon dioxide absorption zone 7.

[0054] The heat exchange devices 4, 8, 11, 22 can use air as a cold source to remove heat, and these heat exchange devices are used to cool the respective circulating liquid 25. As shown in Figure 2 The circulating liquid 25 that needs to be cooled enters the heat exchanger 27, and the cooled circulating liquid 26 is sprayed in the device. The cooling tower 31 produces circulating cooling water 28, which is pumped into the heat exchanger 27 by the circulating water pump 30, and the cooled cooling water 29 is returned to the cooling tower 31 for cooling.

[0055] As shown in Figure 3 The circulating liquid 25 that needs to be cooled enters the heat exchanger 27, and the cooled circulating liquid 26 is sprayed in the device. The air cooler 32 produces circulating cooling water 28, which is pumped into the heat exchanger 27 by the circulating water pump 30, and the cooled cooling water 29 is returned to the air cooler 32 for cooling.

[0056] As shown in Figure 4 The circulating liquid 25 that needs to be cooled enters the wet air cooling 33, and the cooled circulating liquid 26 is sprayed in the device. The wet air cooling 33 is sprayed by the circulating water pump 30 to cool the circulating liquid flowing inside.

[0057] Key points

[0058] In the embodiment of the present application, "using air as a cold source to remove heat generated by absorption", such devices usually include cooling towers, air coolers (including dry air coolers and wet air coolers). The heat exchange mode of the cooling tower is indirect heat exchange between the circulating liquid and the cooling water medium, and the heat transfer efficiency is reduced through the medium; the cooling limit of the dry air cooler is the dry bulb temperature, which is greater than the wet bulb temperature; the wet air cooler can directly pass the circulating liquid for cooling, and the limit temperature is the wet bulb temperature.

[0059] 1. The temperature of the carbon dioxide absorption zone 7 is controlled at 25-40℃, preferably 28-40℃, more preferably 30-38℃, and most preferably 32-38℃. However, the temperature of about 25℃ for the cooling tower is generally only achieved under the condition of very low ambient temperature (such as in northern China in winter), so the application also illustrates that the ammonia-based decarbonization system can be operated with particularly low energy consumption and low cost, especially in winter when the ambient temperature is relatively low. In this patent, it is found in the experiment that under the solution gradient control mode and under the specific conditions of ammonia addition and ammonia washing, the ammonia escape can still be effectively controlled at a temperature beyond the previous experience (20-30℃). At a higher temperature, the chemical reaction rate will increase, and the corresponding decarbonization efficiency will increase; at a higher temperature, the cooling cost of decarbonization can be saved, and especially in the range of 30-40℃, the temperature control can be completely achieved by using air cooling source. Because it is at a higher temperature, it can be achieved by using an air cooler, preferably a wet air cooler, which is referred to as a wet air cooler.

[0060] The working principle of the wet air cooler is based on the characteristic that water absorbs heat instantaneously when evaporating. When air passes through the filler layer, water will evaporate into water vapor, thereby absorbing heat and reducing the temperature of the air. Compared with a dry air cooler, a wet air cooler is more advantageous in hot summer or when the ambient temperature is relatively high. This is because the wet air cooler utilizes the latent heat exchange of water evaporation and the air cooling by humidification to strengthen heat transfer, and the presence of water mist can make the inlet air temperature of the air cooler close to the ambient wet-bulb temperature, thereby increasing the average temperature difference of heat transfer.

[0061] Therefore, the heat exchange efficiency of the wet air cooler is improved, and the investment and operating costs are reduced. Moreover, the wet air cooler design is flexible, and one pump can be provided with one set of wet air cooler, which is convenient for arrangement.

[0062] 2. The temperature of the cooling function zone 2 is controlled at 25-40℃, preferably 30-38℃, because it is at a higher temperature, it can be achieved by using an air cooler, preferably a wet air cooler.

[0063] 3. The temperature of the ammonium bicarbonate generation zone 5 is controlled at 25-40℃, preferably 30-38℃.

[0064] 4. The temperature of the process water ammonia washing section 15-1 is controlled at 20-40℃, which can be achieved by using an air cooler, preferably a wet air cooler.

[0065] 5. The present application adopts a solution gradient control mode, and under the specific conditions of ammonia addition and ammonia washing, the ammonia-based carbon capture is realized at a higher temperature to produce ammonium bicarbonate.

[0066] EMBODIMENT

[0067] The present application provides Example 1 and Comparative Example 1 to further illustrate the technical solutions of the present application.

[0068] EMBODIMENT 1

[0069] As Figure 1 The device, the gas 1 flue gas amount 420000 Nm 3 / h, CO2 content 12.9% (volume), SO2 content 3000 mg / Nm 3 , temperature 132℃. After desulfurization, SO2 and NH3 content is less than 10 mg / Nm 3 and 2 mg / Nm 3 , temperature 45℃, into ammonia decarburization device, in ammonia decarburization device through cooling function area 2, ammonium bicarbonate generation area 5, carbon dioxide absorption area 7, ammonia removal function area 15. Wet air cooling is used to control the temperature of cooling function area 2, ammonium bicarbonate generation area 5, carbon dioxide absorption area 7, process water washing ammonia removal section 15-1 at 32-38℃. No refrigerated water is needed. Decarburization efficiency is 92%, ammonia escape is 1.5 mg / Nm 3 .

[0070] Comparative example 1

[0071] The same process and parameters, such as control cooling function area 2, ammonium bicarbonate generation area 5, carbon dioxide absorption area 7, process water washing ammonia removal section 15-1 temperature at 15-20℃. Due to low temperature, air cooling equipment cannot be used completely, and must be used to pre-cool, then use refrigeration equipment to produce refrigerated water to cool down. In the case of achieving the same decarburization efficiency and ammonia escape as in example 1, the refrigerated water consumption is 1919 t / h.

[0072] The above only for the preferred embodiments of the present application, for those skilled in the art after understanding the technical means of the present application, naturally can be according to the actual needs, under the guidance of the present application to change. Therefore, any equivalent changes and modifications made in the scope of the present application patent application, should still belong to the scope of the present application patent.

Claims

1. A method of energy-efficient ammonia-based carbon capture co-production of nitrogen fertilizer, characterized in that, The temperature control is 25-40°C, preferably 28-40°C, more preferably 30-38°C, most preferably 32-38°C, using air as the cooling source to remove the heat generated by the absorption process.

2. The method of claim 1, wherein, The temperature control is performed using an air cooler.

3. The method of claim 2, wherein, The air cooler is a wet air cooler.

4. The method of claim 1, wherein, The heat is removed directly using an air cooler or indirectly using a heat exchanger.

5. The method of claim 3, wherein, The heat is removed directly using a wet air cooler, wherein the circulating liquid enters the wet air cooling solution inlet directly, and returns to the ammonia carbon capture device from the outlet after cooling.

6. The method of claim 1, wherein, The ammonia carbon capture includes a cooling unit, an ammonium bicarbonate generation unit, an absorption unit, and an ammonia escape control unit, and at least the absorption unit uses an air cooler for temperature control.

7. The method of claim 6, wherein, The cooling unit uses an air cooler for temperature control, preferably a wet air cooler.

8. The method of claim 7, wherein, The temperature control is 25-40°C.

9. The method of claim 6, wherein, The ammonium bicarbonate generation unit uses an air cooler for temperature control, preferably a wet air cooler.

10. The method of claim 6, wherein, The absorption unit includes at least 2 stages of absorption, and ammonia is added to the second stage in the flow direction of the flue gas.

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