Coal-fired power plant flue gas carbon capture and ammonium fertilizer co-production system based on ammonia process

Abstract

The utility model discloses a coal-fired power plant flue gas carbon capture and ammonium fertilizer co-production system based on an ammonia process, desulfurized flue gas sequentially passes through a saturation area, an absorption area and an ammonia washing area of a decarburization system, passes through a first-stage ammonia washing spraying layer and a second-stage ammonia washing spraying layer, and finally, the purified flue gas is discharged to the atmosphere. After sodium hydroxide, sodium carbonate and a flocculating agent are added into desulfurization wastewater, obtained clear liquid is pumped into a first-stage ammonia washing spraying layer through a clear liquid conveying pump to spray and absorb escape ammonia gas, enters an absorption area slurry box after the pH value reaches the upper limit, and enters a saturation area after the pH value of the absorption area slurry box reaches the upper limit; slurry in the saturation area is subjected to solid-liquid separation through a cyclone and a centrifugal machine, and clear liquid returns to the saturation area again. And the slurry in the saturation area is separated twice by a cyclone and a centrifugal machine to obtain solid ammonium bicarbonate. The device disclosed by the utility model can be used for cooperatively treating partial desulfurization wastewater and carbon dioxide in desulfurized flue gas, and the produced ammonium bicarbonate fertilizer can be used for producing ammonium fertilizer or compound fertilizer, so that the device has higher economic value.

Description

Technical Field

[0001] The utility model relates to the field of carbon dioxide capture, and more specifically, to a system for capturing carbon dioxide from flue gas of a coal-fired power plant and co-producing ammonium fertilizer based on an ammonia process. Background Art

[0002] Most existing carbon dioxide capture and utilization methods directly use CO2 to produce dry ice, refrigeration, beverages, etc. Due to insufficient market demand, the cost of purification and pressurization is higher than the revenue from selling CO2. The traditional MEA process has problems such as degradation, corrosion, and high regeneration energy consumption, which seriously affect the application of this process. Due to oxidation, thermal degradation, irreversible reactions and evaporation, MEA is lost during the process. In addition, MEA has strict limits on the concentration of SO2 in flue gas (no more than 10ppm), and existing flue gas desulfurization (FGD) is difficult to meet the ultra-low SO2 concentration requirements. The above problems lead to high initial investment and operating costs of the MEA process. Therefore, there is an urgent need to further research and application of CO2 capture, hoping to complete the capture of flue gas CO2 at an acceptable low cost.

[0003] In view of the characteristics of flue gas from coal-fired power plants, the goal of the new absorbent is not high removal efficiency, but low absorbent cost and regeneration energy consumption. The by-products produced should be products with a large market and utilization value.

[0004] Regarding absorbent sources, ammonia is a major chemical product, and the production capacity and demand for synthetic ammonia are enormous. Ammonia is readily available, with synthetic ammonia plants, coal chemical plants, petrochemical companies, and other enterprises of varying sizes near nearly every power plant selling ammonia. Regarding absorbent applications in power plants, ammonia or liquid ammonia is used as a reducing agent in selective catalytic reduction (SCR) denitrification and as an absorbent in ammonia-based flue gas desulfurization (FGD). Some power plants have ammonia storage systems. Regarding price, ammonia is only one-sixth the price of MEA. Regarding ammonia's decarbonization absorption capacity, research has shown that its absorption capacity for removing CO2 from power plant flue gas is three times that of MEA. Regarding the treatment of decarbonization products, the byproduct of the ammonia decarbonization circulating slurry, after liquid-solid separation, is NH4HCO3, a widely used nitrogen fertilizer in agriculture with high economic value. In summary, ammonia offers significant advantages as a decarbonization absorbent and co-production of ammonium fertilizer.

[0005] CN220554641U discloses a device for controlling ammonia escape by capturing carbon from low-sulfur flue gas and producing nitrogen fertilizer. The device comprises an ammonia desulfurization zone, an ammonia decarbonization zone, an ammonia washing zone, and an acid addition system. The ammonia desulfurization zone, the ammonia decarbonization zone, and the ammonia washing zone are sequentially connected, the ammonia desulfurization zone and the ammonia washing zone are connected via a liquid phase pipeline, and the acid addition system is connected to the ammonia washing zone. To address the ammonia escape problem, the process system passes the desulfurization circulating fluid from the ammonia desulfurization process system into the decarbonization system to wash ammonia. However, this requires the use of an ammonia desulfurization system in conjunction with it. However, ammonia desulfurization systems are rarely used in China, making this system less widely applicable.

[0006] CN116272329B discloses a deamination device suitable for ammonia-based carbon capture and its application. The deamination slurry tank is connected to a first bubbling unit and a second bubbling unit, each of which is equipped with a forced oxidation blower. The second bubbling unit is located at the top of the organic amine decarbonization device and is equipped with a deamination absorbent. The first bubbling unit absorbs SO2 to form sulfurous acid, which is forcibly oxidized to sulfuric acid in the deamination slurry tank. The sulfuric acid is then used to capture escaping ammonia gas. This system requires a large amount of energy for forced oxidation, and the product ammonium sulfate may be mixed with volatile organic amines, making it difficult to reuse. Utility Model Content

[0007] The utility model discloses a system for capturing carbon from flue gas of a coal-fired power plant and co-producing ammonium fertilizer based on an ammonia process. The system can be used for an integrated process route of capture and utilization, and can collaboratively treat part of the desulfurization wastewater and CO2 in the flue gas after desulfurization. The generated ammonium bicarbonate fertilizer can be used to produce ammonium fertilizer or compound fertilizer, and has high economic value.

[0008] The designed ammonia-based coal-fired power plant flue gas carbon capture and co-production of ammonium fertilizer system can couple the treatment of CO2, Mg in desulfurization wastewater and flue gas. 2+ Most of the escaped ammonia can be suppressed, and the water volume in the decarbonization system can be kept balanced.

[0009] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0010] Ammonia-based flue gas carbon capture and co-production of ammonium fertilizer system for coal-fired power plants, including a desulfurization wastewater treatment system, a decarbonization system, and a dehydration system;

[0011] The decarbonization system includes a decarbonization tower;

[0012] The top exhaust port of the decarbonization tower is connected to the flue gas duct of the branch after decarbonization;

[0013] The decarbonization tower is equipped with a secondary ammonia washing spray layer, a secondary ammonia washing slurry divider, a primary ammonia washing spray layer, a primary ammonia washing slurry divider, an absorption zone spray layer, an absorption zone slurry divider and a saturation zone spray layer from top to bottom. The absorption zone is located above the absorption zone slurry divider. The bottom of the decarbonization tower is the saturation zone.

[0014] The decarbonization system is further provided with an ammonia washing area, which includes a secondary ammonia washing process water tank and a primary ammonia washing slurry tank;

[0015] The secondary ammonia washing spray layer, the secondary ammonia washing slurry divider and the secondary ammonia washing process water tank form a circulation through the secondary ammonia washing slurry circulation pump; the secondary ammonia washing process water tank is connected to the process water tank;

[0016] The first-level ammonia washing spray layer, the first-level ammonia washing slurry divider and the first-level ammonia washing slurry tank form a circulation through the first-level ammonia washing circulation pump; the desulfurization wastewater treatment system is connected to the first-level ammonia washing spray layer; the low-temperature flue gas concentrated acid slurry tank is connected to the first-level ammonia washing spray layer through the concentrated acid slurry delivery pump;

[0017] The absorption zone spray layer, the absorption zone slurry divider and the absorption zone slurry tank form a circulation through the absorption zone slurry circulation pump; the absorption zone slurry tank is connected to the concentrated ammonia solution replenishment tank;

[0018] The saturated zone spray layer and the saturated zone form a circulation through the saturated zone slurry circulation pump;

[0019] The flue gas duct of the post-desulfurization branch is connected below the spray layer of the saturated zone;

[0020] The saturated zone is also connected to the dewatering system through a saturated slurry discharge pump.

[0021] The desulfurization wastewater treatment system comprises a desulfurization wastewater tank, a heavy metal precipitation tank, a calcium precipitation tank, a colloid precipitation tank and a sedimentation tank connected in sequence;

[0022] The heavy metal precipitation tank is equipped with a sodium hydroxide delivery pipeline and a heavy metal precipitation discharge pipeline;

[0023] The calcium precipitation tank is equipped with a sodium carbonate delivery pipeline and a precipitated calcium discharge pipeline;

[0024] The colloid sedimentation tank is equipped with a flocculant delivery pipeline and a precipitated colloid discharge pipeline;

[0025] The sedimentation tank is connected to the clear liquid tank, and the clear liquid tank is connected to the first-level ammonia washing spray layer of the decarbonization tower through a clear liquid delivery pump.

[0026] The dehydration system comprises a saturated slurry box, a cyclone, a centrifuge and an ammonium bicarbonate storage bin which are connected in sequence.

[0027] The absorption zone, saturation zone and ammonia washing zone of the decarbonization system are all equipped with pH online monitoring devices, and the absorption zone and saturation zone are equipped with density online monitoring devices.

[0028] The utility model provides a system for capturing carbon in flue gas from coal-fired power plants and producing ammonium fertilizers in conjunction with an ammonia process. The system has the function of simultaneously treating CO2 from thermal power plants and desulfurization wastewater, and producing ammonium bicarbonate fertilizers with added value. After heavy metals, calcium ions, and colloids are precipitated in the desulfurization wastewater, it is used to enter the first-level ammonia spray layer in the ammonia washing area to absorb ammonia gas; the saturated solid-liquid mixed ammonium bicarbonate slurry in the saturation area is separated by a cyclone and a centrifuge for two-stage solid-liquid separation to produce ammonium bicarbonate fertilizers; the amount of ammonia water to be supplied and the timing of supply are determined based on pH and density; the first-level ammonia spray layer and the second-level ammonia spray layer in the ammonia washing area are respectively added with the clear liquid after desulfurization wastewater treatment and the process water for circulating spraying and washing ammonia. Sodium hydroxide is added to the desulfurization wastewater to precipitate heavy metals, calcium oxalate is added to precipitate calcium, and flocculants are added to precipitate colloids to obtain a slurry mainly containing Mg. 2+ 、SO4 2- 、Cl - of clear liquid.

[0029] Furthermore, for power plants equipped with a low-temperature flue gas concentration desulfurization wastewater system, low-temperature flue gas concentration slurry can be introduced into the decarbonization system, and the escaped ammonia can be recovered by spraying through the first-level ammonia washing spray layer.

[0030] The utility model provides a production method for a system for capturing carbon from flue gas of a coal-fired power plant and co-producing ammonium fertilizer based on an ammonia process, which includes three processing routes: gas, liquid, and solid:

[0031] 1. Gas processing route;

[0032] The desulfurized flue gas generated by industrial combustion is drawn into the branch flue gas duct by the induced draft fan and enters the decarbonization system. The flue gas contains carbon dioxide, water vapor and a small amount of impurity particles. The decarbonization system is divided into three functional areas, and the flue gas passes through the following areas in sequence:

[0033] (1) Saturated zone: In the saturated zone, the flue gas is directly contacted and absorbed by the spray slurry, the temperature is reduced, and a small amount of CO2 in the flue gas is initially captured.

[0034] (2) Absorption zone: The flue gas absorbed by the saturated zone slurry spray enters the absorption zone. In the absorption zone, most of the CO2 in the flue gas is efficiently absorbed by the absorption liquid.

[0035] (3) Ammonia washing area: After passing through the absorption area, the flue gas enters the ammonia washing area, and the spray layer captures the ammonia escaping from the flue gas. Secondary ammonia washing spray layer: The secondary spray layer further improves the absorption efficiency and ensures that the emission concentration of ammonia in the flue gas meets the standard.

[0036] The flue gas after multi-stage absorption is discharged through the exhaust pipe, and the ammonia concentration of the flue gas is controlled to be lower than 3ppm.

[0037] 2. Liquid handling routes;

[0038] (1) Pretreatment of wastewater: The wastewater generated during the desulfurization process is pretreated with chemical agents, including the addition of sodium hydroxide and sodium carbonate to adjust the pH value of the wastewater. Flocculants are added to precipitate and separate suspended particles and impurities in the wastewater to obtain clear liquid and flocs.

[0039] (2) Recycling of ammonia washing liquid. The pre-treated clear liquid is sent to the primary ammonia washing spray layer of the ammonia washing area to capture the remaining escaped ammonia in the flue gas. When the pH of the ammonia washing liquid in the secondary ammonia washing area reaches the upper limit, it is transported to the primary ammonia washing area. The ammonia washing liquid in the primary ammonia washing area is sent to the secondary ammonia washing spray layer of the ammonia washing area to capture the escaped ammonia in the flue gas for the first time. When the pH of the ammonia washing liquid in the primary ammonia washing area reaches the upper limit, it is transported to the slurry tank in the absorption area and mixed with ammonia water for CO2 absorption reaction. Furthermore, after running for a period of time, the saturated area slurry density is lower than 1050kg / m 3 When the water content of the system is high, the ammonia washing process water tank is required to absorb the saturated ammonia washing liquid and concentrate it through reverse osmosis. The 15% concentrated ammonium bicarbonate solution can be passed into the absorption area slurry tank to obtain low-concentration clear liquid.

[0040] (3) Cascade utilization of decarbonized slurry. The slurry in the absorption zone absorbs CO2 in the first cycle, playing the main role in CO2 absorption. When the pH of the slurry in the absorption zone slurry tank reaches the upper limit, the slurry is transferred to the saturation zone. The main components of the slurry in the absorption zone are ammonia water, ammonium carbonate, etc. In the saturation zone, the slurry absorbs CO2 in the first cycle to improve the absorption efficiency. The main components of the slurry in the absorption zone are ammonium bicarbonate, ammonium carbonate, etc.

[0041] (4) Solid-liquid separation of liquid: The slurry in the saturated zone is separated through a two-stage solid-liquid separation process. The cyclone separation separates the ammonium bicarbonate solid particles from the slurry to obtain a portion of low-concentration slurry. The centrifuge separation further separates the liquid and the ammonium bicarbonate solid particles after cyclone separation by high-speed centrifugation to obtain a low-concentration slurry and concentrated solid matter.

[0042] (5) The low-concentration slurry is recycled. The separated low-concentration slurry is transported back to the saturated area slurry tank to achieve recycling.

[0043] 3. Solids handling routes;

[0044] (1) The formation of by-product ammonium bicarbonate. The concentrated solid obtained by solid-liquid separation is mainly composed of ammonium bicarbonate.

[0045] (2) Treatment and utilization of by-products: After further dehydration and drying, the solid matter is packaged and made into ammonium bicarbonate by-product, which can be directly used as agricultural fertilizer or other industrial purposes.

[0046] Furthermore, the pH value of the low-temperature flue gas concentrated slurry is controlled to be in the range of 2-3; the pH value of the desulfurization wastewater in the heavy metal precipitation tank of the desulfurization wastewater treatment system is controlled to be in the range of 8-9, preferably, the pH is optimal at 8.4; the pH value of the slurry in the saturated zone of the decarbonization system is controlled to be in the range of 8-8.5, preferably, the pH is optimal at 8.3, and the slurry density of the saturated zone of the decarbonization system is 1100-1120 kg / m 3 , preferably, the slurry density is controlled to 1103kg / m 3 The optimal pH range is 9.5-10 in the decarbonization system's absorption zone. The pH of the ammonia wash solution in the primary ammonia wash tank in the ammonia wash zone is controlled between 10-10.5, and the pH of the ammonia wash solution in the secondary ammonia wash process tank in the ammonia wash zone is controlled between 8-9. Once the pH of the clear solution in the secondary ammonia wash process tank reaches the upper limit, it enters the primary ammonia wash process tank. Once the pH of the clear solution in the primary process tank reaches the upper limit, it enters the absorption zone slurry tank. Once the slurry in the absorption zone slurry tank reaches saturation, it enters the saturation zone slurry tank.

[0047] The utility model calculates the concentration of ammonium bicarbonate in the solution based on the control relationship between the measured density and the saturation of ammonium bicarbonate. Combined with the monitored pH value, a balance equation can be established to calculate the effective ammonia concentration in the absorption zone. The reference value C is introduced and there is a positive correlation with the CO2 absorption efficiency, that is, a one-to-one correspondence. Substituting it into the formula:

[0048] C=738.58[NH3] 2 +11.32[NH3],

[0049] [NH3] represents the effective ammonia concentration;

[0050] C is calculated and the C value of the absorption slurry is adjusted by adding concentrated ammonia water in the concentrated ammonia water replenishment tank (30) to maintain the decarbonization system efficiency above 80%.

[0051] This utility model proposes a method that utilizes carbon capture byproducts as fertilizer, making it one of the most viable byproduct utilization options currently available, linking carbon emission reduction with ecological regulation. NH4HCO3 recycling not only offsets operating expenses but also significantly reduces operating costs through simplified processes. Replacing existing NH4HCO3 production also improves the environment and reduces energy consumption.

[0052] The beneficial effects of the present invention are as follows:

[0053] (1) The CO2 removal efficiency can be stably controlled to be above 80%;

[0054] (2) The ammonia emission concentration in the flue gas at the outlet of the decarbonization system can be controlled within 3ppm;

[0055] (3) It can collaboratively treat desulfurization wastewater, with a treatment capacity of up to 3t / h;

[0056] (4) No wastewater is generated during the operation of the decarbonization system;

[0057] (5) The system is highly practical and can be used for ultra-low carbon emission reduction layout of thermal power plants under various circumstances. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a schematic diagram of the system structure of the utility model;

[0059] Legend: 1-decarbonization tower, 2-desulfurization wastewater tank, 3-sodium hydroxide delivery pipeline, 4-heavy metal precipitation tank, 5-heavy metal precipitation discharge pipeline, 6-sodium carbonate delivery pipeline, 7-calcium precipitation tank, 8-precipitated calcium discharge pipeline, 9-flocculant delivery pipeline, 10-colloid precipitation tank, 11-precipitated colloid discharge pipeline, 12-sedimentation tank, 13-clear liquid tank, 14-clear liquid delivery pump, 15-low-temperature flue gas concentrated acid slurry tank, 16-concentrated acid slurry delivery pump, 17-post-desulfurization branch flue gas duct, 18-secondary ammonia washing spray layer, 19-secondary ammonia washing slurry splitter, 20-primary ammonia washing spray layer, 2 1-first-stage ammonia washing slurry divider, 22-absorption zone spray layer, 23-absorption zone slurry divider, 24-saturation zone spray layer, 25-saturation zone, 26-second-stage ammonia washing process water tank, 27-process water tank, 28-first-stage ammonia washing slurry tank, 29-absorption zone slurry tank, 30-concentrated ammonia water replenishment tank, 31-second-stage ammonia washing slurry circulation pump, 32-first-stage ammonia washing circulation pump, 33-absorption zone slurry circulation pump, 34-saturation zone slurry circulation pump, 35-saturated slurry discharge pump, 36-saturated slurry tank, 37-cyclone, 38-centrifuge, 39-ammonium bicarbonate storage tank, 40-branch flue gas duct after decarbonization.

[0060] Figure 2 2 is a graph of the outlet escaped ammonia concentration under different MgCl2 concentration conditions of the embodiment. DETAILED DESCRIPTION

[0061] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other similar device diagrams can be obtained based on the drawings without creative work. The situation of simply adjusting the circulation pump, slurry supply pump, and the number and installation position of the spray layers are all protected by this patent.

[0062] like Figure 1As shown, the desulfurization system generates desulfurization wastewater. The outlet pipeline of desulfurization wastewater tank 2 is connected to the inlet of heavy metal precipitation tank 4. Heavy metal precipitation tank 4 is equipped with sodium hydroxide delivery pipeline 3 and heavy metal precipitation discharge pipeline 5. The outlet pipeline of heavy metal precipitation tank 4 is connected to the inlet of calcium precipitation tank 7. Calcium precipitation tank 7 is equipped with sodium carbonate delivery pipeline 6 and calcium precipitation discharge pipeline 8. The outlet pipeline of calcium precipitation tank 7 is connected to the inlet of colloid precipitation tank 10. Colloid precipitation tank 10 is equipped with flocculant delivery pipeline 9 and precipitated colloid discharge pipeline 8. The outlet pipeline of colloid precipitation tank 10 is connected to the inlet of sedimentation tank 12. The outlet pipeline of sedimentation tank 12 is connected to the inlet pipeline of clear liquid tank 13. The outlet pipeline of clear liquid tank 13 is connected to the primary spray layer 20, and a clear liquid delivery pump is installed in the pipeline. The outlet pipeline of low-temperature flue gas concentrated slurry tank 15 is connected to the primary spray layer 20, and a concentrated acidic slurry delivery pump 16 is installed in the pipeline.

[0063] A post-desulfurization branch flue gas duct 17 is provided at the bottom of the decarbonization tower 1, and a post-decarbonization branch flue gas duct 40 is provided at the top of the decarbonization tower 1. Below the bottom opening of the decarbonization tower 1 is a saturated zone. The external circulation pipeline of the saturated zone 25 is connected to the saturated zone spray layer 24, and a saturated zone slurry circulation pump 34 is installed in the pipeline.

[0064] An absorption zone slurry divider 23 is installed above the saturation zone spray layer 24. The absorption zone slurry divider 23 is connected to the inlet of the absorption zone slurry tank 29. The outlet pipeline of the absorption zone slurry tank 29 is connected to the absorption zone spray layer 22. An absorption zone slurry circulation pump 33 is installed in the pipeline. The outlet of the concentrated ammonia solution replenishment tank 30 is connected to the inlet of the absorption zone slurry tank 29 via a pipeline.

[0065] A first-level ammonia washing slurry divider 21 is provided on the upper part of the absorption zone spray layer 22. The absorption zone slurry divider 21 is connected to the inlet of the absorption zone slurry tank 28. The outlet pipeline of the first-level ammonia washing slurry tank 28 is connected to the first-level ammonia washing spray layer 22. A first-level ammonia washing slurry circulation pump 32 is installed in the pipeline.

[0066] A secondary ammonia wash slurry divider 19 is provided above the primary ammonia wash spray layer 20. The secondary ammonia wash slurry divider 19 is connected to the inlet of the secondary ammonia wash process water tank 26. The outlet pipeline of the secondary ammonia wash process water tank 26 is connected to the secondary ammonia wash spray layer 18. A secondary ammonia wash slurry circulation pump 31 is installed in the pipeline. The outlet of the process water tank 27 is connected to the inlet of the secondary ammonia wash process water tank 29 through a pipeline.

[0067] The outlet of the saturated zone 25 is connected to the inlet of the saturated zone slurry tank 36, a saturated slurry discharge pump 35 is installed in the pipeline, the outlet of the saturated zone slurry tank 36 is connected to the inlet of the cyclone 37, the bottom flow outlet of the cyclone 37 is connected to the inlet of the centrifuge 38, and the outlet of the centrifuge 38 is connected to the inlet of the ammonium bicarbonate storage tank 39.

[0068] The utility model provides a method for capturing carbon from flue gas of coal-fired power plants and co-producing ammonium fertilizer based on the ammonia process, which includes three processing routes: gas, liquid and solid:

[0069] The gas treatment route includes: the flue gas undergoes multi-stage absorption in the saturation zone, absorption zone and ammonia washing zone of the decarbonization system to remove part of the CO2 and escaped ammonia, and the concentration of the emitted ammonia is controlled below 3ppm; the slurry pH in the saturation zone 25 of the decarbonization system is 8-8.5, the slurry pH in the absorption zone is 9.5-10, the pH in the first-level ammonia washing water tank 28 of the ammonia washing zone is 10-10.5, and the pH in the second-level ammonia washing process water tank 26 is 8-9.

[0070] The liquid treatment route includes: in the desulfurization wastewater treatment system, the wastewater undergoes pretreatment, recycling of ammonia washing liquid, cascade utilization of decarbonization slurry and solid-liquid separation to ensure that the desulfurization wastewater and ammonia washing liquid are treated and recycled; the pretreatment step of the desulfurization wastewater includes adding sodium hydroxide and sodium carbonate to adjust the pH value, and adding flocculants to remove suspended particles and impurities to obtain clear liquid and flocs, and the clear liquid is used for recycling of ammonia washing liquid.

[0071] The solid processing route includes: obtaining ammonium bicarbonate solid by-product through solid-liquid separation in a dehydration system, and forming ammonium bicarbonate fertilizer that can be used in agriculture or industry after dehydration and drying.

[0072] The utility model calculates the concentration of ammonium bicarbonate in the solution based on the control relationship between the measured density and the saturation of ammonium bicarbonate. Combined with the monitored pH value, a balance equation can be established to calculate the effective ammonia concentration in the absorption zone. The reference value C is introduced and there is a positive correlation with the CO2 absorption efficiency, that is, a one-to-one correspondence. Substituting it into the formula:

[0073] C=738.58[NH3] 2 +11.32[NH3]

[0074] [NH3] represents the effective ammonia concentration;

[0075] C is calculated and the C value of the absorption slurry is adjusted by adding concentrated ammonia water in the concentrated ammonia water replenishment tank (30) to maintain the decarbonization system efficiency above 80%.

[0076] Table 1 is a comparison table of ammonium bicarbonate slurry concentration and density, which is used to calculate the ammonium bicarbonate concentration in the absorption zone slurry.

[0077] Table 1 is a comparison table of ammonium bicarbonate slurry concentration and density

[0078]

[0079] In this embodiment, the pH of the absorption zone is set to 10, the ammonium bicarbonate concentration is 10%, the absorption efficiency is 82%, and the slurry density is 1.057 kg / m3 In order to maintain the absorption efficiency within the range of 85-90%, at this time, the effective ammonia concentration is 1.08mol / L, the C value is 891.20, and according to operating experience, the C value needs to be controlled to be greater than 2000 so that the absorption efficiency can be greater than 85%. In this case, ammonia water is added to the absorption zone until the pH is greater than 10.1. The pH value of the absorption zone can be adjusted at any time according to the amount of ammonia water added, and the real-time C value is calculated to maintain the absorption efficiency within the range of 85-90%. Figure 2 shown.

Claims

1. A system for capturing carbon dioxide from flue gas of coal-fired power plants and co-producing ammonium fertilizer based on the ammonia process, characterized by: Including desulfurization wastewater treatment system, decarbonization system and dehydration system; The decarbonization system comprises a decarbonization tower (1); The top exhaust port of the decarbonization tower (1) is connected to the flue gas duct (40) of the post-decarbonization branch; The decarbonization tower (1) is provided with a secondary ammonia washing spray layer (18), a secondary ammonia washing slurry divider (19), a primary ammonia washing spray layer (20), a primary ammonia washing slurry divider (21), an absorption zone spray layer (22), an absorption zone slurry divider (23), and a saturation zone spray layer (24) in order from top to bottom; the absorption zone is located above the absorption zone slurry divider (23); and the bottom of the decarbonization tower (1) is the saturation zone (25); The decarbonization system is further provided with an ammonia washing area, which includes a secondary ammonia washing process water tank (26) and a primary ammonia washing slurry tank (28); The secondary ammonia washing spray layer (18), the secondary ammonia washing slurry divider (19) and the secondary ammonia washing process water tank (26) form a circulation through the secondary ammonia washing slurry circulation pump (31); the secondary ammonia washing process water tank (26) is connected to the process water tank (27); The primary ammonia washing spray layer (20), the primary ammonia washing slurry divider (21) and the primary ammonia washing slurry tank (28) form a circulation through the primary ammonia washing circulation pump (32); the desulfurization wastewater treatment system is connected to the primary ammonia washing spray layer (20); the low-temperature flue gas concentrated acid slurry tank (15) is connected to the primary ammonia washing spray layer (20) through the concentrated acid slurry delivery pump (16); The absorption zone spray layer (22), the absorption zone slurry divider (23) and the absorption zone slurry tank (29) form a circulation through the absorption zone slurry circulation pump (33); the absorption zone slurry tank (29) is connected to the concentrated ammonia solution replenishment tank (30); The saturated zone spray layer (24) and the saturated zone (25) form a circulation through the saturated zone slurry circulation pump (34); The lower portion of the saturated zone spray layer (24) is connected to a post-desulfurization branch flue gas duct (17); The saturated zone (25) is also connected to the dewatering system via a saturated slurry discharge pump (35).

2. The system for capturing carbon dioxide from flue gas of a coal-fired power plant and co-producing ammonium fertilizer based on an ammonia process according to claim 1, characterized in that: The desulfurization wastewater treatment system comprises a desulfurization wastewater tank (2), a heavy metal precipitation tank (4), a calcium precipitation tank (7), a colloid precipitation tank (10) and a sedimentation tank (12) connected in sequence; The heavy metal precipitation tank (4) is provided with a sodium hydroxide delivery pipeline (3) and a heavy metal precipitation discharge pipeline (5); The calcium precipitation tank (7) is provided with a sodium carbonate delivery pipeline (6) and a precipitated calcium discharge pipeline (8); The colloid precipitation tank (10) is provided with a flocculant delivery pipeline (9) and a precipitated colloid discharge pipeline (11); The sedimentation tank (12) is connected to the clear liquid tank (13), and the clear liquid tank (13) is connected to the first-level ammonia washing spray layer (20) of the decarbonization tower (1) through a clear liquid delivery pump (14).

3. The system for capturing carbon dioxide from flue gas of a coal-fired power plant and co-producing ammonium fertilizer based on an ammonia process according to claim 1, characterized in that: The dehydration system comprises a saturated slurry tank (36), a cyclone (37), a centrifuge (38) and an ammonium bicarbonate storage bin (39) which are connected in sequence.

4. The system for capturing carbon dioxide from flue gas of a coal-fired power plant and co-producing ammonium fertilizer based on an ammonia process according to claim 1, characterized in that: The absorption zone, saturation zone (25) and ammonia washing zone of the decarbonization system are all equipped with pH online monitoring devices, and the absorption zone and saturation zone (25) are equipped with density online monitoring devices.

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