Coal-fired flue gas desulfurization system coupling decarburization pilot plant test system and method based on ammonia process

Abstract

The invention discloses a coal-fired flue gas desulfurization system coupling decarburization pilot plant test system and method based on an ammonia process, and belongs to the technical field of environmental protection. A process wastewater outlet of the cooling device is communicated with the ammonia washing tower; the cooling device is communicated with the decarburization tower; a gas outlet of the decarburization tower is communicated with the ammonia washing tower; the decarburization tower is communicated with an outlet of the buffer tank; a solid outlet of the solid-liquid separation device is communicated with the fluidized drying equipment, and the ammonia absorber is communicated with the buffer tank; high-temperature steam is introduced into a high-temperature steam inlet of the fourth heat exchanger, a mixed gas outlet of the fourth heat exchanger is communicated with fluidized drying equipment, the fluidized drying equipment is communicated with a condenser, a mixed gas outlet of the condenser is communicated with the fourth heat exchanger and an absorption tower, the absorption tower is communicated with a carbon dioxide storage tank through a compressor, and the absorption tower is communicated with a spray filler desulfurization tower. And the absorption tower is communicated with the spray filler desulfurization tower. The device is used for flue gas desulfurization and decarburization.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental protection, and particularly relates to a pilot system and method for coupling carbon dioxide removal in a coal-fired flue gas desulfurization system based on the ammonia method. Background Art

[0002] From the perspective of industrial applications, ammonia water or liquid ammonia is a reducing agent for selective catalytic reduction (SCR) denitrification and an absorbent for ammonia-based flue gas desulfurization (FGD). The ammonia-based flue gas desulfurization technology for coal-fired flue gas belongs to a new clean technology of circular economy. Since it does not produce any waste water, waste liquid, or waste residue and has no secondary pollution, it can meet the requirements of circular economy. By integrating an ammonia-based carbon capture system, power plants can achieve the integrated removal of acidic gases using only one absorbent, thereby reducing the retrofit cost of power plants. However, the regeneration of the absorbent in the traditional ammonia method is mainly a rich liquid regeneration process, in which the energy consumption of CO2 desorption accounts for 52% of the rich liquid regeneration carbon capture system, mainly due to the heat required to heat a large amount of water, and the regeneration effect of the ammonia-rich liquid at a lower temperature is not ideal. For example, the regeneration degree at 80°C is only 34.42%, and it still cannot achieve the goals of "efficient removal" and "low regeneration energy consumption". Summary of the Invention

[0003] The purpose of the present invention is to propose a pilot system and method for coupling carbon dioxide removal in a coal-fired flue gas desulfurization system based on the ammonia method to solve the above problems existing in the prior art.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0005] A pilot system for coupling carbon dioxide removal in a coal-fired flue gas desulfurization system based on the ammonia method, the pilot system includes a carbon dioxide removal system, a desulfurization system, and a CO2 purification system. The carbon dioxide removal system includes a cooling device, a heat exchanger I, a wash ammonia tower, a carbon dioxide removal tower, a solid-liquid separation device, an ammonia absorber, and a buffer tank; the desulfurization system includes a desulfurization tower; the CO2 purification system includes a heat exchanger IV, a fluidized drying device, a condenser, an absorption tower, a compressor, and a carbon dioxide storage tank;

[0006] The desulfurized flue gas outlet at the top of the desulfurization tower is connected to the desulfurized flue gas inlet of the cooling device. The cooling device is provided with a process water inlet. The process wastewater outlet at the lower end of the cooling device is connected to the process wastewater inlet of the ammonia scrubber through Heat Exchanger 1. The gas outlet of the cooling device is connected to the gas inlet of the decarbonization tower. The decarbonized flue gas outlet is provided at the upper end of the ammonia scrubber, and the liquid outlet is provided at the lower end of the ammonia scrubber; the gas outlet at the top of the decarbonization tower is connected to the gas inlet of the ammonia scrubber, the liquid inlet of the decarbonization tower is connected to the outlet of the buffer tank, the rich liquid outlet at the lower end of the decarbonization tower is connected to the liquid inlet of the solid-liquid separation device, the liquid outlet of the solid-liquid separation device is connected to the liquid inlet of the ammonia absorber, and the solid outlet of the solid-liquid separation device is connected to the solid inlet of the fluidized drying equipment; a supplementary liquid inlet is provided at the upper end of the ammonia absorber, and the absorbent outlet at the upper end of the ammonia absorber is connected to the inlet of the buffer tank; high-temperature steam is introduced into the high-temperature steam inlet of Heat Exchanger 4, the mixed gas outlet of Heat Exchanger 4 is connected to the mixed gas inlet of the fluidized drying equipment, the mixed gas outlet of the fluidized drying equipment is connected to the mixed gas inlet of the condenser, and the mixed gas outlet of the condenser is respectively connected to the mixed gas inlets of Heat Exchanger 4 and the absorption tower; the gas outlet of the absorption tower is connected to the gas inlet of the compressor, the gas outlet of the compressor is connected to the inlet of the carbon dioxide storage tank, the liquid inlet of the absorption tower is connected to the liquid outlet of the desulfurization tower, and the liquid outlet of the absorption tower is connected to the liquid inlet of the desulfurization tower; a flue gas inlet, a compressed air inlet and a desulfurized slurry outlet are provided at the lower part of the desulfurization tower, and a process water inlet is provided at the upper part of the desulfurization tower.

[0007] Further, the outlet of Heat Exchanger 1 is connected to the process wastewater inlet of the ammonia scrubber through Circulation Pump 1; the liquid outlet of the ammonia scrubber is connected to the liquid inlet of the cooling device through Circulation Pump 2; the rich liquid outlet at the lower end of the decarbonization tower is connected to the liquid inlet of the solid-liquid separation device through Circulation Pump 3; the outlet of the buffer tank is connected to the liquid inlet of the decarbonization tower through Circulation Pump 4; the liquid outlet of the absorption tower is connected to the liquid inlet of the desulfurization tower through Circulation Pump 5; the liquid outlet of the desulfurization tower is connected to the liquid inlet of the absorption tower through Circulation Pump 6.

[0008] Further, the outlet of the buffer tank is successively connected to the liquid inlet of the decarbonization tower through a flow meter and Circulation Pump 4.

[0009] Further, the tower body of the decarbonization tower is connected to Heat Exchanger 2; the ammonia absorber is connected to Heat Exchanger 3; the tower body of the desulfurization tower is connected to Heat Exchanger 5.

[0010] Further, the desulfurized flue gas outlet at the top of the desulfurization tower is connected to the desulfurized flue gas inlet of the cooling device through Fan 1, and the flue gas inlet of the desulfurization tower is connected to the coal-fired flue gas outlet of the coal-fired power unit through Fan 2; the compressed air inlet of the desulfurization tower is connected to the outlet of Fan 3.

[0011] Further, a butterfly valve is installed on the connecting pipeline between the desulfurized flue gas outlet at the top of the desulfurization tower and Fan 1.

[0012] Method for coupling decarbonization in a flue gas desulfurization system based on ammonia method, the method comprising the following steps:

[0013] Step 1: Decarbonize using a decarbonization system; the specific process is:

[0014] Step 1-1: The coal-fired flue gas after dust removal enters the desulfurization tower. After the sulfur-containing pollutants are removed by the ammonia method, the desulfurized flue gas is transported to a cooling device. The desulfurized flue gas countercurrently contacts the process water input into the cooling device by circulation pump 2 and is cooled to 10 - 20 °C, and then enters the decarbonization tower for decarbonization treatment;

[0015] Step 1-2: The gas entering the decarbonization tower contacts the absorbent countercurrently from bottom to top. In the absorption zone in the upper half of the decarbonization tower, the flue gas containing CO2 reacts with the absorbent. The decarbonized flue gas enters the ammonia washing tower from the top of the decarbonization tower, and the process water enters the ammonia washing tower from the top, countercurrently contacting the flue gas to remove the absorbent in the flue gas. The clean flue gas is discharged into the atmosphere from the decarbonized flue gas outlet of the ammonia washing tower; after the process water absorbs the escaping ammonia component in the flue gas, it becomes alkaline and is discharged from the liquid outlet of the ammonia washing tower for subsequent treatment; in the crystallization zone in the lower half of the decarbonization tower, the flue gas contacts the saturated absorbent, promoting the crystallization and precipitation of ammonium bicarbonate;

[0016] Step 1-3: The rich liquid discharged from the bottom of the decarbonization tower enters a solid-liquid separation device. The solid after centrifugal separation enters the CO2 purification system; the liquid after centrifugal separation enters an ammonia absorber, and at the same time, a supplementary liquid is added to the ammonia absorber;

[0017] Step 1-4: The absorbent enters a buffer tank from the top of the ammonia absorber for storage and then enters the upper part of the decarbonization tower;

[0018] Step 2: Desulfurize using a desulfurization system; the specific process is:

[0019] The flue gas output from the coal-fired unit enters the bottom of the desulfurization tower. The desulfurization absorbent enters the top of the desulfurization tower and contacts the flue gas countercurrently. SO2 is removed in the absorption zone. The flue gas continues to rise and contacts the process water entering through the process water inlet. The escaping ammonia in the flue gas is removed in the water washing zone and is discharged from the desulfurized flue gas outlet at the top of the desulfurization tower; part of the desulfurization absorbent in the desulfurization tower enters the absorption tower to supplement ammonia under the action of circulation pump 6 and enters the desulfurization tower for circulation under the action of circulation pump 5; part of the desulfurization absorbent reacts with the compressed air input by fan 3, and after the ammonium sulfite is oxidized, it flows out from the desulfurized slurry outlet for subsequent treatment; the desulfurization absorbent is ammonia water;

[0020] Step 3: Purify using a CO2 purification system; the specific process is:

[0021] Step 3-1: High-temperature steam countercurrently contacts and exchanges heat with the mixed gas in Heat Exchanger 4. After heat exchange, the low-temperature steam is discharged from the system, and the high-temperature mixed gas enters the fluidized drying equipment to heat the decarbonized solid product from the solid-liquid separation device. The solid decomposes into a mixed gas and is discharged from the top of the fluidized drying equipment. The moisture in the gas is removed by the condenser. Part of the mixed gas acts as a heating medium and enters Heat Exchanger 4 for circulation, and the other part of the mixed gas enters the absorption tower.

[0022] Step 3-2: The desulfurization absorbent from the desulfurization tower enters the absorption tower from the top under the action of Circulation Pump 6, countercurrently contacts with the gas to remove ammonia in the mixed gas, and enters the desulfurization tower for circulation under the action of Circulation Pump 5. High-purity carbon dioxide enters the compressor from the top of the absorption tower, is compressed into a liquid state, and then stored in the carbon dioxide storage tank.

[0023] Further, in Step 1-3, the composition of the supplementary liquid added to the ammonia absorber is ammonia, water, and a salting-out agent. Among them, the water in the supplementary liquid is supplemented by the condensate water of the condenser; ammonia is supplemented by liquid ammonia or ammonia gas; and a salting-out agent is supplemented to achieve material balance.

[0024] Further, in Step 3-1, the decarbonized solid product from the solid-liquid separation device is ammonium bicarbonate solid.

[0025] Further, in Step 3-1, the high-temperature steam countercurrently contacts and exchanges heat with the mixed gas in Heat Exchanger 4. After heat exchange, the high-temperature mixed gas at 120-130 °C enters the fluidized drying equipment to heat the decarbonized solid product from the solid-liquid separation device. The solid decomposes into a mixed gas and is discharged from the top of the fluidized drying equipment. The moisture in the gas is removed by the condenser. Part of the low-temperature mixed gas at 70-80 °C acts as a heating medium and enters Heat Exchanger 4 for circulation, and the other part of the mixed gas enters the absorption tower. The mixed gas is the decomposition product of ammonium bicarbonate, and its components are H2O, NH3, and CO2.

[0026] The beneficial effects of the present invention compared with the prior art are:

[0027] 1. The new ammonia-based carbon capture technology is adopted to mix the carbonated rich liquid with the salting-out agent. Under the salting-out effect, the carbon capture product precipitates from the solution in the form of crystals. Compared with the traditional rich liquid regeneration process, the energy consumption required for heating the solvent water can be saved, and the crystal product can be decomposed at room temperature and completely decomposed at 60 °C, breaking through the defect of high regeneration energy consumption in the traditional ammonia-based decarbonization technology.

[0028] 2. Utilize the low-quality steam from the power plant for waste energy utilization to provide heat for the decomposition of ammonium bicarbonate, exchange heat with the mixed gas generated by the decomposition, and use the high-temperature mixed gas as the fluidizing gas and heat source in the fluidized drying equipment to directly contact and heat ammonium bicarbonate, which can effectively improve the energy utilization rate and the product decomposition rate, and avoid the condensation energy consumption brought by the direct contact heating of steam to ammonium bicarbonate, further reducing the regeneration energy consumption of ammonia-based decarbonization.

[0029] 3. Utilize the existing ammonia-based desulfurization device in the power plant to achieve the combined removal of SO2 and CO2 to reduce the transformation cost. In addition, adjust the scale of the decarbonization system to match the ammonia in the product with the ammonia consumed by the desulfurization system, and make full use of the characteristics of the desulfurization slurry of the coal-fired unit to achieve high-efficiency and low-energy consumption purification of carbon dioxide. Brief Description of the Drawings

[0030] Figure 1 It is a schematic structural diagram of the pilot system for coupling desulfurization and decarbonization of coal-fired flue gas based on ammonia method of the present invention.

[0031] Figure 1 The names of the components involved and the reference numerals in the drawings are as follows:

[0032] 1 - First fan; 2 - Cooling device; 3 - Second circulation pump; 4 - First heat exchanger; 5 - First circulation pump; 6 - Decarbonized flue gas outlet; 7 - Ammonia washing tower; 8 - Decarbonization tower; 9 - Third circulation pump; 10 - Solid-liquid separation device; 11 - Second heat exchanger; 12 - Third heat exchanger; 13 - Ammonia absorber; 14 - Make-up liquid inlet; 15 - Buffer tank; 16 - Flowmeter; 17 - Fourth circulation pump; 18 - Fourth heat exchanger; 19 - Fluidized drying equipment; 20 - Condenser; 21 - Absorption tower; 22 - Compressor; 23 - Carbon dioxide storage tank; 24 - Fifth circulation pump; 25 - Sixth circulation pump; 26 - Desulfurization tower; 27 - Fifth heat exchanger; 28 - Second fan; 29 - Third fan; 30 - Desulfurization slurry outlet; 31 - Desulfurized flue gas outlet; 32 - Process water inlet; 33 - Liquid outlet of the ammonia washing tower. Detailed Embodiments

[0033] Detailed Embodiment 1: As Figure 1 shown, this embodiment describes a pilot system for coupling desulfurization and decarbonization of coal-fired flue gas based on ammonia method. The pilot system includes a decarbonization system (for removing CO2 from coal-fired flue gas and generating additional product ammonium bicarbonate), a desulfurization system (for removing circulating pollutants SO2 from coal-fired flue gas), and a CO2 purification system (for separating and obtaining high-purity CO2). The decarbonization system includes a cooling device 2, a first heat exchanger 4, an ammonia washing tower 7, a decarbonization tower 8, a solid-liquid separation device 10, an ammonia absorber 13, and a buffer tank 15; the desulfurization system includes a desulfurization tower 26; the CO2 purification system includes a fourth heat exchanger 18, a fluidized drying equipment 19, a condenser 20, an absorption tower 21, a compressor 22, and a carbon dioxide storage tank 23;

[0034] The desulfurized flue gas outlet 31 at the top of the desulfurization tower 26 is communicated with the desulfurized flue gas inlet of the cooling device 2. The cooling device 2 is provided with a process water inlet (the process water is transported from the power plant water source and is used to cool the desulfurized flue gas to the decarbonization reaction temperature). The process wastewater outlet at the lower end of the cooling device 2 is communicated with the process wastewater inlet of the ammonia washing tower 7 through the first heat exchanger 4. The gas outlet of the cooling device 2 is communicated with the gas inlet of the decarbonization tower 8. The upper end of the ammonia washing tower 7 is provided with a decarbonized flue gas outlet 6, and the lower end of the ammonia washing tower 7 is provided with a liquid outlet 33;

[0035] The gas outlet at the top of the decarbonization tower 8 is communicated with the gas inlet of the ammonia washing tower 7. The liquid inlet of the decarbonization tower 8 is communicated with the outlet of the buffer tank 15. The rich liquid outlet at the lower end of the decarbonization tower 8 is communicated with the liquid inlet of the solid-liquid separation device 10 (the solid-liquid separation device 10 is used to absorb CO2 in the flue gas and generate ammonium bicarbonate). The liquid outlet of the solid-liquid separation device 10 is communicated with the liquid inlet of the ammonia absorber 13. The solid outlet of the solid-liquid separation device 10 is communicated with the solid inlet of the fluidized drying device 19 (the ammonium bicarbonate solid from the solid-liquid separation device 10 enters the fluidized drying device 19 for heating, which is used for the solid-liquid separation of the carbonization slurry); The upper end of the ammonia absorber 13 is provided with a supplementary liquid inlet 14 (the supplementary liquid is added into the ammonia absorber 13 through the supplementary liquid inlet 14 of the ammonia absorber 13). The absorbent outlet at the upper end of the ammonia absorber 13 is communicated with the inlet of the buffer tank 15 (which is used to maintain the stability of the absorbent components);

[0036] The high-temperature steam inlet of the fourth heat exchanger 18 is introduced with high-temperature steam (the high-temperature steam is low-quality steam from the power plant). The mixed gas outlet of the fourth heat exchanger 18 is communicated with the mixed gas inlet of the fluidized drying device 19. The mixed gas outlet of the fluidized drying device 19 is communicated with the mixed gas inlet of the condenser 20. The mixed gas outlet of the condenser 20 is respectively communicated with the mixed gas inlets of the fourth heat exchanger 18 and the absorption tower 21 (the condenser 20 is used for condensing the high-temperature regeneration mixed gas and separating the steam and water. The high-temperature steam and the mixed gas (the mixed gas is the decomposition product of ammonium bicarbonate) are discharged from the system as low-temperature steam after countercurrent heat exchange in the fourth heat exchanger 18 for waste heat recovery. The high-temperature mixed gas enters the fluidized drying device 19, which is used as the fluidizing gas and provides heat to decompose the ammonium bicarbonate solid);

[0037] The gas outlet of the absorption tower 21 is communicated with the gas inlet of the compressor 22. The gas outlet of the compressor 22 is communicated with the inlet of the carbon dioxide storage tank 23 (the compressor 22 is used for compressing carbon dioxide gas and compressing it into a liquid state for storage in the carbon dioxide storage tank 23). The liquid inlet of the absorption tower 21 is communicated with the liquid outlet of the desulfurization tower 26. The liquid outlet of the absorption tower 21 is communicated with the liquid inlet of the desulfurization tower 26 (which is used to absorb ammonia in the mixed gas and output high-purity carbon dioxide gas);

[0038] The lower part of the desulfurization tower 26 is provided with a flue gas inlet, a compressed air inlet, and a desulfurization slurry outlet 30 (the slurry is discharged from the desulfurization slurry outlet 30 at the bottom of the desulfurization tower 26 for subsequent solid-liquid separation treatment), and the upper part of the desulfurization tower 26 is provided with a process water inlet 32 (the process water inlet 32 is communicated with the power plant water source outlet).

[0039] Optionally, the cooling device 2 is a packed tower or a spray tower.

[0040] Optionally, the decarbonization tower 8 is a packed tower, which is divided into an absorption zone and a crystallization zone.

[0041] Furthermore, the outlet of the first heat exchanger 4 is communicated with the process wastewater inlet of the ammonia scrubbing tower 7 through the first circulation pump 5; the liquid outlet 33 of the ammonia scrubbing tower is communicated with the liquid inlet of the cooling device 2 through the second circulation pump 3 (for cooling the desulfurized flue gas to the decarbonization reaction temperature); the rich liquid outlet at the lower end of the decarbonization tower 8 is communicated with the liquid inlet of the solid-liquid separation device 10 through the third circulation pump 9; the outlet of the buffer tank 15 is communicated with the liquid inlet of the decarbonization tower 8 through the fourth circulation pump 17; the liquid outlet of the absorption tower 21 is communicated with the liquid inlet of the desulfurization tower 26 through the fifth circulation pump 24; the liquid outlet of the desulfurization tower 26 is communicated with the liquid inlet of the absorption tower 21 through the sixth circulation pump 25.

[0042] Furthermore, the outlet of the buffer tank 15 is successively communicated with the liquid inlet of the decarbonization tower 8 through the flow meter 16 and the fourth circulation pump 17 (the flow rate of the absorbent in the decarbonization tower 8 is controlled by the flow meter 16 to achieve efficient removal of CO2 in the flue gas).

[0043] Furthermore, the tower body of the decarbonization tower 8 is communicated with the second heat exchanger 11 (the second heat exchanger 11 is arranged in the decarbonization tower 8 to collect the chemical heat released during the reaction process); the ammonia absorber 13 is communicated with the third heat exchanger 12 (the third heat exchanger 12 is arranged in the ammonia absorber 13 to absorb the chemical heat released when components such as ammonia dissolve in the absorbent); the tower body of the desulfurization tower 26 is communicated with the fifth heat exchanger 27 (the fifth heat exchanger 27 is arranged in the desulfurization tower 26 to obtain the chemical energy released during the desulfurization reaction process).

[0044] Furthermore, the desulfurized flue gas outlet 31 at the top of the desulfurization tower 26 is communicated with the desulfurized flue gas inlet of the cooling device 2 through the first fan 1 (a centrifugal fan) (the first fan 1 is used to transport the desulfurized flue gas of the coal-fired unit), and the flue gas inlet of the desulfurization tower 26 is communicated with the coal-fired flue gas outlet of the coal-fired unit through the second fan 28 (the second fan 28 is used to transport the dust-removed coal-fired flue gas to the desulfurization tower 26 for countercurrent contact with the absorbent to remove SO2); the compressed air inlet of the desulfurization tower 26 is communicated with the outlet of the third fan 29 (the third fan 29 is used to transport compressed air to the bottom of the packed desulfurization tower 26 to oxidize the desulfurization products).

[0045] Further, a butterfly valve is installed on the connecting pipeline between the desulfurized flue gas outlet 31 at the top of the desulfurization tower 26 and the first fan 1 (the precise control of the gas flow in the system is achieved by using the butterfly valve, and the opening degree of the butterfly valve is between 0° and 90°).

[0046] Specific Embodiment 2: As Figure 1 shown, this embodiment discloses a method for realizing the coupling of carbon dioxide removal in a coal-fired flue gas desulfurization system based on the ammonia method by using the pilot system described in Specific Embodiment 1. The method includes the following steps:

[0047] Step 1: Remove carbon dioxide using the carbon dioxide removal system; the specific process is:

[0048] Step 1-1: The coal-fired flue gas after dust removal enters the desulfurization tower 26. After the sulfur-containing pollutants are removed by the ammonia method, the desulfurized flue gas (transported by the first fan 1) is sent to the cooling device 2 (the desulfurized flue gas is discharged from the desulfurized flue gas outlet 31 at the top of the desulfurization tower 26, and a part is extracted for pilot demonstration). After the desulfurized flue gas countercurrently contacts the process water input into the cooling device 2 by the second circulation pump 3, it is cooled to 10 - 20°C and enters the carbon dioxide removal tower 8 for carbon dioxide removal treatment;

[0049] Step 1-2: The gas entering the carbon dioxide removal tower 8 flows upward and countercurrently contacts the absorbent (prepared by mixing ammonia water and the salting-out agent, and the mixing ratio of the two is not fixed and is adjusted according to needs). In the absorption zone in the upper half of the carbon dioxide removal tower 8, the flue gas containing CO2 (at a relatively low concentration) reacts with the absorbent (with relatively strong absorption capacity). The carbon dioxide-removed flue gas enters the ammonia washing tower 7 from the top of the carbon dioxide removal tower 8. The process water (after the high-temperature water from the cooling device 2 is cooled by the first heat exchanger 4 and under the action of the first circulation pump 5) enters the ammonia washing tower 7 from the top and countercurrently contacts the flue gas to remove the (readily soluble) absorbent in the flue gas. The clean flue gas is discharged into the atmosphere from the carbon dioxide-removed flue gas outlet 6 of the ammonia washing tower 7; after the process water absorbs the escaped ammonia component in the flue gas, it becomes alkaline and is discharged from the liquid outlet 33 of the ammonia washing tower for subsequent treatment; in the crystallization zone in the lower half of the carbon dioxide removal tower 8, the flue gas with a relatively high concentration contacts the saturated absorbent, promoting the crystallization of ammonium bicarbonate (a second heat exchanger 11 is arranged on the tower body of the carbon dioxide removal tower 8 to collect the chemical heat released during the reaction process);

[0050] Step 1-3: The rich liquid discharged from the bottom of the carbon dioxide removal tower 8 (under the action of the third circulation pump 9) enters the solid-liquid separation device 10. The solid after centrifugal separation enters the CO2 purification system; the liquid after centrifugal separation enters the ammonia absorber 13. At the same time, a supplementary liquid is added to the ammonia absorber 13 (the supplementary liquid is added to the ammonia absorber 13 through the supplementary liquid inlet 14 of the ammonia absorber 13 to supplement ammonia and water to maintain the stable concentration of the absorbent. A third heat exchanger 12 is arranged in the ammonia absorber 13 to absorb the chemical heat released when ammonia and other components dissolve in the absorbent);

[0051] Step 14: The absorbent enters the buffer tank 15 from the top of the ammonia absorber 13 for storage (the flow rate of the absorbent is adjusted under the action of the flowmeter 16), and (under the action of the circulation pump III 17) enters the upper part of the decarbonization tower 8;

[0052] Step 2: Desulfurize using the desulfurization system: The specific process is as follows:

[0053] The flue gas output from the coal-fired unit enters the bottom of the desulfurization tower 26 (under the action of the fan II 28), and the desulfurization absorbent (under the action of the circulation pump V 24) enters the top of the desulfurization tower 26 and contacts the flue gas countercurrently. SO2 is removed in the absorption zone. The flue gas continues to rise and contacts the process water entering through the process water inlet 32, and the escaping ammonia in the flue gas is removed in the water washing zone and discharged from the desulfurization flue gas outlet 31 at the top of the desulfurization tower 26; Part of the desulfurization absorbent in the desulfurization tower 26 enters the absorption tower 21 to supplement ammonia under the action of the circulation pump VI 25 and enters the desulfurization tower 26 for circulation under the action of the circulation pump V 24; Part of the desulfurization absorbent reacts with the compressed air input by the fan III 29, and the ammonium sulfite is oxidized and flows out through the desulfurization slurry outlet 30 for subsequent treatment (a heat exchanger V 27 is arranged on the tower body of the desulfurization tower 26 to absorb the chemical heat released during the desulfurization process); The desulfurization absorbent is ammonia water;

[0054] Step 3: Purify using the CO2 purification system; The specific process is as follows:

[0055] Step 3-1: High-temperature steam (low-quality steam from the power plant) contacts and exchanges heat with the mixed gas countercurrently in the heat exchanger IV 18. The exchanged low-temperature steam is discharged from the system (for waste heat recovery), and the high-temperature mixed gas enters the fluidized drying equipment 19 to heat the decarbonized solid product from the solid-liquid separation device 10. The solid decomposes into a mixed gas and is discharged from the top of the fluidized drying equipment 19. The moisture in the gas is removed through the condenser 20. Part of the mixed gas (the decomposition product of ammonium bicarbonate) acts as a heating medium and enters the heat exchanger IV 18 for circulation, and the other part of the mixed gas enters the absorption tower 21;

[0056] Step 3-2: The desulfurization absorbent from the desulfurization tower 26 enters the absorption tower 21 from the top under the action of the circulation pump VI 25, contacts the gas countercurrently to remove ammonia in the mixed gas, and enters the desulfurization tower 26 for circulation under the action of the circulation pump V 24. High-purity carbon dioxide enters the compressor 22 from the top of the absorption tower 21, is compressed to a liquid state, and stored in the carbon dioxide storage tank 23.

[0057] Further, in Step 13, the composition of the supplementary liquid added to the ammonia absorber 13 is ammonia, water, and a salting-out agent; among them: the water in the supplementary liquid is supplemented by the condensed water of the condenser 20; ammonia is supplemented by liquid ammonia or ammonia gas; and a salting-out agent is supplemented to achieve material balance.

[0058] Further, in Step 31, the decarbonized solid product from the solid-liquid separation device 10 is ammonium bicarbonate solid (the ammonium bicarbonate solid discharged from the solid outlet of the solid-liquid separation device 10 can be directly transported into the fluidized drying device 19 through the negative pressure environment realized by the fan inside the fluidized drying device 19, or can be fed through a conveyor such as a crawler).

[0059] Further, in Step 31, the high-temperature steam exchanges heat with the mixed gas in a countercurrent manner in the heat exchanger four 18, and the 120-130°C high-temperature mixed gas after heat exchange enters the fluidized drying device 19; the decarbonized solid product from the solid-liquid separation device 10 is heated, and the solid decomposes into a mixed gas and is discharged from the top of the fluidized drying device 19. The water in the gas is removed by the condenser 20. Among them, a part of the 70-80°C low-temperature mixed gas (the decomposition product of ammonium bicarbonate) acts as a heating medium and enters the heat exchanger four 18 for circulation, and the other part of the mixed gas enters the absorption tower 21; the mixed gas is the decomposition product of ammonium bicarbonate, and the components are H2O, NH3, and CO2.

[0060] Optionally, the clean flue gas is discharged into the atmosphere from the decarbonized flue gas outlet 6 of the ammonia scrubbing tower 7, and the ammonia concentration ≤ 10mg / Nm 3 , meeting the pollutant discharge standards.

[0061] Optionally, after the flue gas passes through wet desulfurization, the temperature is between 50 and 60°C, containing a large amount of saturated water vapor. After low-temperature heat exchange, the water vapor will condense and release a large amount of latent heat of vaporization, and the energy density is very high. This part of the heat can be recovered and utilized.

[0062] Optionally, in Step 12, a certain proportion of ammonia water - antisolvent is used. The ammonia water is low-concentration ammonia water with a mass concentration < 15%, the antisolvent is easily soluble in water, and the ammonium bicarbonate, the product of ammonia-based carbon capture, is hardly soluble in the antisolvent.

[0063] Optionally, the absorbent flows through the decarbonization tower 8 from top to bottom, and the flue gas flows through the decarbonization tower 8 from bottom to top, and the two contact in a countercurrent manner, so that the carbon dioxide removal rate in the flue gas > 90%. The absorbent with stronger absorption capacity removes carbon dioxide in the flue gas with lower concentration in the upper absorption area of the decarbonization tower 8. After the solubility of ammonium bicarbonate in the absorbent reaches saturation, it flows to the crystallization area. The absorbent contacts with carbon dioxide with a higher concentration, and the absorbent continues to remove carbon dioxide in the flue gas, and under the action of the antisolvent, ammonium bicarbonate solid is continuously precipitated. The absorbent slurry (rich liquid) is discharged from the bottom of the decarbonization tower 8.

[0064] Optionally, the height of the slurry at the bottom of the decarbonization tower 8 is controlled by a liquid level gauge, and a stirring device is used to prevent solid precipitation and blockage (the decarbonization tower 8 is an existing device).

[0065] Optionally, a densitometer is provided on the ammonia absorber 13 to control the absorbent concentration.

[0066] Optionally, the liquid inlet absorbent flow rate of the decarbonization tower 8 is controlled by the flow meter 16 to adjust the liquid-gas ratio of the decarbonization reaction.

[0067] Optionally, the heat exchanger IV 18 is an indirectly contacted steam heat exchanger. High-temperature steam and low-temperature mixed gas exchange heat countercurrently in the heat exchanger IV 18. The low-temperature steam is discharged from the system, while the high-temperature mixed gas enters the fluidized drying equipment 19 as the fluidizing gas and heat source, and directly contacts with the ammonium bicarbonate solid for heating.

[0068] Optionally, the ammonia desulfurization products in the desulfurization tower 26 are (NH4)2SO3 and NH4HSO3. (NH4)2SO3 becomes (NH4)2SO4 solid after air oxidation. Part of it is discharged from the desulfurization tower 26 through the desulfurization slurry outlet 30 to prepare ammonium sulfate products, while most of the absorbent needs to be supplemented with ammonia and then continue to participate in the desulfurization reaction. It is introduced into the absorption tower 21 to contact with the condensed mixed gas for ammonia supplementation, and the reaction NH3 + NH4HSO3 = (NH4)2SO3 occurs.

[0069] Optionally, high-purity carbon dioxide is discharged from the gas outlet of the absorption tower 21, and its concentration > 95%.

[0070] Optionally, carbon dioxide is compressed to a liquid state by the compressor 22 and stored in the carbon dioxide storage tank 23.

[0071] Those skilled in the art can understand that the low temperature and high temperature of the heat exchanger IV 18 are relative. In this case, the temperature of the low-temperature steam may be higher than that of the high-temperature mixed gas.

[0072] The present invention makes full use of the original ammonia absorber and desulfurization device in the power plant, adopts ammonia water to jointly remove the acidic components in the flue gas, realizes the combined removal of SO2 and CO2 in the coal-fired flue gas, and realizes the efficient utilization of various substances in the system. Combining with the new ammonia-based carbon capture technology can greatly reduce the regeneration energy consumption.

[0073] The coal-fired flue gas desulfurization system coupled with a decarbonization system based on the ammonia method of the present invention includes a decarbonization system, a desulfurization system, and a CO2 purification system. The ammonia water-solvent mixed absorbent is used to remove carbon dioxide in the coal-fired flue gas. Driven by the solvation effect, the carbonated rich liquid continuously absorbs carbon dioxide and precipitates ammonium bicarbonate crystals. After solid-liquid separation, the crystals are heated and decomposed and react with the desulfurization absorbent solution to supplement ammonia for the desulfurization system and realize the high-concentration purification of carbon dioxide. Based on the desulfurization and decarbonization of coal-fired flue gas, the new ammonia-based decarbonization technology can realize the decomposition of decarbonization products with a small amount of low-quality steam, which can reduce the regeneration energy consumption of the decarbonization system. Using the decomposed mixed gas to fluidize and heat the decarbonization products is beneficial to improving the heat utilization rate and decomposition rate. Combining with the ammonia-based desulfurization system, while supplementing ammonia for the desulfurization absorbent, the efficient separation of the mixed gas is realized.

[0074] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes should be covered within the protection scope of the present invention.

Claims

1. An ammonia-based pilot system for integrated desulfurization and decarbonization of coal-fired flue gas, characterized in that: The pilot-scale system includes a decarbonization system, a desulfurization system, and a CO2 purification system. The decarbonization system includes a cooling device (2), a first heat exchanger (4), an ammonia scrubber (7), a decarbonization tower (8), a solid-liquid separation device (10), an ammonia absorber (13), and a buffer tank (15); the desulfurization system includes a desulfurization tower (26); the CO2 purification system includes a fourth heat exchanger (18), a fluidized drying device (19), a condenser (20), an absorption tower (21), a compressor (22), and a carbon dioxide storage tank (23); The desulfurized flue gas outlet (31) at the top of the desulfurization tower (26) is communicated with the desulfurized flue gas inlet of the cooling device (2). A process water inlet is provided on the cooling device (2). The process wastewater outlet at the lower end of the cooling device (2) is communicated with the process wastewater inlet of the ammonia scrubber (7) through the first heat exchanger (4). The gas outlet of the cooling device (2) is communicated with the gas inlet of the decarbonization tower (8). The decarbonized flue gas outlet (6) is provided at the upper end of the ammonia scrubber (7), and the liquid outlet (33) is provided at the lower end of the ammonia scrubber (7); the gas outlet at the top of the decarbonization tower (8) is communicated with the gas inlet of the ammonia scrubber (7). The liquid inlet of the decarbonization tower (8) is communicated with the outlet of the buffer tank (15). The rich liquid outlet at the lower end of the decarbonization tower (8) is communicated with the liquid inlet of the solid-liquid separation device (10). The liquid outlet of the solid-liquid separation device (10) is communicated with the liquid inlet of the ammonia absorber (13). The solid outlet of the solid-liquid separation device (10) is communicated with the solid inlet of the fluidized drying device (19); a supplementary liquid inlet (14) is provided at the upper end of the ammonia absorber (13), and the absorbent outlet at the upper end of the ammonia absorber (13) is communicated with the inlet of the buffer tank (15); high-temperature steam is introduced into the high-temperature steam inlet of the fourth heat exchanger (18). The mixed gas outlet of the fourth heat exchanger (18) is communicated with the mixed gas inlet of the fluidized drying device (19). The mixed gas outlet of the fluidized drying device (19) is communicated with the mixed gas inlet of the condenser (20). The mixed gas outlet of the condenser (20) is respectively communicated with the mixed gas inlets of the fourth heat exchanger (18) and the absorption tower (21); the gas outlet of the absorption tower (21) is communicated with the gas inlet of the compressor (22). The gas outlet of the compressor (22) is communicated with the inlet of the carbon dioxide storage tank (23). The liquid inlet of the absorption tower (21) is communicated with the liquid outlet of the desulfurization tower (26). The liquid outlet of the absorption tower (21) is communicated with the liquid inlet of the desulfurization tower (26); a flue gas inlet, a compressed air inlet, and a desulfurization slurry outlet (30) are provided at the lower part of the desulfurization tower (26), and a process water inlet (32) is provided at the upper part of the desulfurization tower (26).

2. The pilot system according to claim 1, characterized in that: The outlet of heat exchanger 1 (4) is connected to the process wastewater inlet of the ammonia scrubbing tower (7) via circulation pump 1 (5); the liquid outlet (33) of the ammonia scrubbing tower is connected to the liquid inlet of the cooling device (2) via circulation pump 2 (3); the rich liquid outlet at the lower end of the decarbonization tower (8) is connected to the liquid inlet of the solid-liquid separation device (10) via circulation pump 3 (9); the outlet of the buffer tank (15) is connected to the liquid inlet of the decarbonization tower (8) via circulation pump 4 (17); the liquid outlet of the absorption tower (21) is connected to the liquid inlet of the desulfurization tower (26) via circulation pump 5 (24); the liquid outlet of the desulfurization tower (26) is connected to the liquid inlet of the absorption tower (21) via circulation pump 6 (25).

3. The pilot-scale system according to claim 2, wherein: The outlet of the buffer tank (15) is sequentially connected to the liquid inlet of the decarbonization tower (8) via a flow meter (16) and circulation pump 4 (17).

4. The pilot-scale system according to claim 1, wherein: The tower body of the decarbonization tower (8) is connected to heat exchanger 2 (11); the ammonia absorber (13) is connected to heat exchanger 3 (12); the tower body of the desulfurization tower (26) is connected to heat exchanger 5 (27).

5. The pilot-scale system according to claim 1, wherein: The desulfurized flue gas outlet (31) at the top of the desulfurization tower (26) is connected to the desulfurized flue gas inlet of the cooling device (2) via fan 1 (1), and the flue gas inlet of the desulfurization tower (26) is connected to the coal-fired flue gas outlet of the coal-fired unit via fan 2 (28); the compressed air inlet of the desulfurization tower (26) is connected to the outlet of fan 3 (29).

6. The pilot system according to claim 5, wherein: A butterfly valve is installed on the connecting pipeline between the desulfurized flue gas outlet (31) at the top of the desulfurization tower (26) and fan 1 (1).

7. A method for realizing the coupled decarbonization of a coal-fired flue gas desulfurization system based on the ammonia method by using the pilot-scale system described in any one of claims 1-6, characterized in that: The method includes the following steps: Step 1: Decarbonize using the decarbonization system; the specific process is: Step 1-1: The coal-fired flue gas after dust removal enters the desulfurization tower (26), and after the sulfur-containing pollutants are removed by the ammonia method, the desulfurized flue gas is transported to the cooling device (2). The desulfurized flue gas is cooled to 10 - 20 °C after counter-current contact with the process water input into the cooling device (2) by circulation pump 2 (3), and then enters the decarbonization tower (8) for decarbonization treatment; Step 1-2: The gas entering the decarbonization tower (8) contacts the absorbent counter-currently from bottom to top. In the absorption zone in the upper half of the decarbonization tower (8), the flue gas containing CO2 reacts with the absorbent. The decarbonized flue gas enters the ammonia scrubbing tower (7) from the top of the decarbonization tower (8), the process water enters the ammonia scrubbing tower (7) from the top, contacts the flue gas counter-currently to remove the absorbent in the flue gas, and the clean flue gas is discharged into the atmosphere from the decarbonized flue gas outlet (6) of the ammonia scrubbing tower (7); the process water becomes alkaline after absorbing the escaped ammonia component in the flue gas and is discharged from the liquid outlet (33) of the ammonia scrubbing tower for subsequent treatment; in the crystallization zone in the lower half of the decarbonization tower (8), the flue gas contacts the saturated absorbent, promoting the crystallization and precipitation of ammonium bicarbonate; Step 1-3: The rich liquid discharged from the bottom of the decarbonization tower (8) enters the solid-liquid separation device (10), and the solid after centrifugal separation enters the CO2 purification system; the liquid after centrifugal separation enters the ammonia absorber (13), and at the same time, a supplementary liquid is added to the ammonia absorber (13); Step 1-4: The absorbent enters the buffer tank (15) from the top of the ammonia absorber (13) for storage and then enters the upper part of the decarbonization tower (8); Step 2: Desulfurize using the desulfurization system: the specific process is: The flue gas output from the coal-fired unit enters the bottom of the desulfurization tower (26). The desulfurization absorbent enters the top of the desulfurization tower (26) and contacts the flue gas countercurrently. SO2 is removed in the absorption zone. The flue gas continues to rise and contacts the process water entering through the process water inlet (32). The escaped ammonia in the flue gas is removed in the water washing zone and discharged from the desulfurization flue gas outlet (31) at the top of the desulfurization tower (26). Part of the desulfurization absorbent in the desulfurization tower (26) enters the absorption tower (21) to supplement ammonia under the action of the sixth circulation pump (25), and enters the desulfurization tower (26) for circulation under the action of the fifth circulation pump (24). Part of the desulfurization absorbent reacts with the compressed air input by the third fan (29). After the ammonium sulfite is oxidized, it flows out through the desulfurization slurry outlet (30) for subsequent treatment. The desulfurization absorbent is ammonia water. Step 3: Purify using the CO2 purification system; the specific process is as follows: Step 3-1: High-temperature steam contacts and exchanges heat with the mixed gas countercurrently in the fourth heat exchanger (18). The cooled low-temperature steam is discharged from the system. The high-temperature mixed gas enters the fluidized drying equipment (19) to heat the decarbonized solid product from the solid-liquid separation device (10). The solid decomposes into a mixed gas and is discharged from the top of the fluidized drying equipment (19). The water in the gas is removed through the condenser (20). Part of the mixed gas acts as a heating medium and enters the fourth heat exchanger (18) for circulation, and the other part of the mixed gas enters the absorption tower (21). Step 3-2: The desulfurization absorbent from the desulfurization tower (26) enters the absorption tower (21) from the top under the action of the sixth circulation pump (25), contacts the gas countercurrently to remove ammonia in the mixed gas, and enters the desulfurization tower (26) for circulation under the action of the fifth circulation pump (24). High-purity carbon dioxide enters the compressor (22) from the top of the absorption tower (21), is compressed to a liquid state, and stored in the carbon dioxide storage tank (23).

8. The method for coupling decarbonization in an ammonia-based flue gas desulfurization system for coal-fired power plants according to claim 7, characterized in that: In Step 1-3, the components of the supplementary liquid added to the ammonia absorber (13) are ammonia, water, and the salting-out agent; among them: the water in the supplementary liquid is supplemented by the condensed water of the condenser (20); ammonia is supplemented by liquid ammonia or ammonia gas; and the salting-out agent is supplemented to achieve material balance.

9. The method for coupling decarbonization in a coal-fired flue gas desulfurization system based on the ammonia method according to claim 7, characterized in that: In Step 3-1, the decarbonized solid product from the solid-liquid separation device (10) is ammonium bicarbonate solid.

10. The method for coupling decarbonization in a coal-fired flue gas desulfurization system based on the ammonia method according to claim 7, characterized in that: In Step 3-1, the high-temperature steam contacts and exchanges heat with the mixed gas countercurrently in the fourth heat exchanger (18). The 120-130 °C high-temperature mixed gas after heat exchange enters the fluidized drying equipment (19); the decarbonized solid product from the solid-liquid separation device (10) is heated. The solid decomposes into a mixed gas and is discharged from the top of the fluidized drying equipment (19). The water in the gas is removed through the condenser (20). Part of the 70-80 °C low-temperature mixed gas acts as a heating medium and enters the fourth heat exchanger (18) for circulation, and the other part of the mixed gas enters the absorption tower (21). The mixed gas is the decomposition product of ammonium bicarbonate, and the components are H2O, NH3, and CO2.

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