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

Abstract

The invention discloses a coal-fired power plant flue gas carbon capture and ammonium fertilizer co-production system and method 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, 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. According to the invention, part of desulfurization wastewater and carbon dioxide in desulfurized flue gas can be cooperatively treated, and the produced ammonium bicarbonate fertilizer can be used for producing ammonium fertilizer or compound fertilizer, and has high economic value.

Description

Technical Field

[0001] The present invention relates to the field of carbon dioxide capture, and more specifically, to a system and method for capturing flue gas carbon from 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 directly utilizes CO 2 Preparation of dry ice, refrigeration, beverages, etc. Due to insufficient market demand, the cost of purification and pressurization is higher than selling CO 2 The traditional MEA process has problems such as degradation, corrosion, and high regeneration energy consumption, which seriously affect the application of the process; MEA is lost during the process due to oxidation, thermal degradation, irreversible reactions, and evaporation; and MEA has a negative impact on SO in flue gas. 2 The concentration of SO is strictly limited (no more than 10 ppm), and the existing flue gas desulfurization (FGD) is difficult to meet the ultra-low SO 2 The above problems lead to high initial investment and operating costs of MEA process. Therefore, it is urgent to further develop CO 2 The research and application of capture is expected to achieve the goal of capturing flue gas CO at an acceptable low cost. 2 of capture.

[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] From the source of absorbents, ammonia water is a bulk chemical product, and the production capacity and demand for synthetic ammonia are very huge. The supply of ammonia sources is quite convenient. Almost every synthetic ammonia plant, coal chemical industry, petrochemical industry and other enterprises of varying sizes around every power plant have ammonia water for sale. From the application of absorbents in power plants, ammonia water or liquid ammonia is a reducing agent for selective catalytic reduction denitrification and an absorbent for ammonia flue gas desulfurization. Some power plants have built ammonia water storage systems. From the price point of view, the price of ammonia water is only 1 / 6 of that of MEA. From the absorption capacity of ammonia water for decarbonization, studies have shown that ammonia water can remove CO from power plant flue gas. 2 When the absorption capacity of ammonia solution is 3 times that of MEA, the byproduct obtained after liquid-solid separation of ammonia decarbonization circulating slurry is NH 4 HCO 3 , which is one of the nitrogen fertilizers widely used in agriculture and has high economic value. In summary, ammonia water has obvious advantages as a decarbonization absorbent and co-production of ammonium fertilizer.

[0005] CN220554641U discloses a device for controlling ammonia escape by carbon capture and co-production of nitrogen fertilizer in low-sulfur flue gas, which is provided with an ammonia desulfurization functional area, an ammonia decarbonization functional area, an ammonia washing functional area, and an acid adding system, wherein the ammonia desulfurization functional area, the ammonia decarbonization functional area, and the ammonia washing functional area are connected in sequence, the ammonia desulfurization functional area is connected to the ammonia washing functional area through a liquid phase pipeline, and the acid adding system is connected to the ammonia washing functional area. In order to solve the ammonia escape problem, the process system passes the desulfurization circulating fluid of the ammonia desulfurization process system into the decarbonization system for ammonia washing, but an ammonia desulfurization system needs to be used in conjunction with it, and the domestic ammonia desulfurization system is less used, so the system is generally less usable.

[0006] CN116272329B discloses a deamination device suitable for ammonia carbon capture and its application, wherein the deamination slurry pool is connected to the first bubbling unit and the second bubbling unit respectively, and a forced oxidation blower is arranged inside the second bubbling unit; the second bubbling unit is arranged at the top of the organic amine decarbonization device and a deamination absorbent is arranged inside. The first bubbling unit absorbs SO 2 Sulfite is formed and forced to be oxidized into sulfuric acid in the deammoniation slurry pool, which is then used to capture the escaped ammonia. This system requires forced oxidation and consumes a lot of energy, and the product ammonium sulfate may be mixed with volatile organic amines, which is difficult to reuse. Summary of the invention

[0007] The present invention discloses a system and method for capturing carbon dioxide from flue gas of coal-fired power plants and producing ammonium fertilizer based on an ammonia process. The system can be used for an integrated process route of capturing and utilizing carbon dioxide, and can synergistically treat part of the desulfurization wastewater and CO in the flue gas after desulfurization. 2 The produced ammonium bicarbonate fertilizer can be used to produce ammonium fertilizer or compound fertilizer and has high economic value.

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

[0009] To achieve the above object, the present invention adopts the following technical solution:

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

[0011] The decarbonization system comprises 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 provided 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 also 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 primary ammonia washing spray layer, the primary ammonia washing slurry divider and the primary ammonia washing slurry tank form a circulation through the primary ammonia washing circulation pump; the desulfurization wastewater treatment system is connected to the primary ammonia washing spray layer; the low-temperature flue gas concentrated acid slurry tank is connected to the primary 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 water 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 branch after desulfurization 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 precipitation tank which are 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 provided 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 primary 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 system for capturing carbon dioxide from flue gas of coal-fired power plants and producing ammonium fertilizer based on the ammonia method provided by the present invention has the function of simultaneously treating the CO 2 , and at the same time treat desulfurization wastewater to produce ammonium bicarbonate fertilizer with added value. After heavy metals, calcium ions, and colloids are precipitated, the desulfurization wastewater is used to enter the first-level ammonia spray layer in the ammonia washing area to absorb ammonia; the saturated solid-liquid mixed ammonium bicarbonate slurry in the saturated area passes through a cyclone and a centrifuge for two-stage solid-liquid separation to produce ammonium bicarbonate fertilizer; the amount and timing of ammonia replenishment 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 spray 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 the colloids to obtain a precipitate mainly containing Mg. 2+ 、SO 4 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 present invention provides a method 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 turn:

[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 CO in the flue gas is 2 Get initial capture.

[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 CO in the flue gas is 2 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 to ensure 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 duct, 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: Chemical agents are added to the wastewater generated during the desulfurization process for pretreatment, including: adding sodium hydroxide and sodium carbonate to adjust the pH value of the wastewater. Adding flocculants 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 CO 2 Furthermore, after a period of operation, the slurry density in the saturated zone is lower than 1050 kg / 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 decarbonization slurry: the slurry in the absorption zone is circulated for the first time to absorb CO 2 , the main CO 2 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 first circulates to absorb CO 2 , in order to improve the absorption efficiency. The main components of the slurry in the absorption area are ammonium bicarbonate, ammonium carbonate, etc.

[0041] (4) Solid-liquid separation of liquid: the saturated zone slurry is separated by a two-stage solid-liquid separation process. The cyclone separation separates the ammonium bicarbonate solid particles in the slurry to obtain a portion of low-concentration slurry. The centrifuge separation centrifuges the liquid after cyclone separation at high speed to further separate the liquid and the ammonium bicarbonate solid particles 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 zone slurry tank for recycling.

[0043] 3. Solids handling routes;

[0044] (1) The formation of by-product ammonium bicarbonate. The concentrated solid obtained by solid-liquid separation mainly contains 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 value is optimal at 8.3, and the slurry density of the saturated zone of the decarbonization system is 1100-1120kg / m 3 Preferably, the slurry density is controlled to be 1103kg / m 3 The pH value of the ammonia washing liquid in the primary ammonia washing water tank in the ammonia washing area is controlled to be 10-10.5, and the pH value of the ammonia washing liquid in the secondary ammonia washing process water tank in the ammonia washing area is controlled to be 8-9. After the pH value of the clear liquid in the secondary ammonia washing process water tank reaches the upper limit, it enters the primary ammonia washing process water tank. After the pH value of the clear liquid in the primary process water tank reaches the upper limit, it enters the slurry tank in the absorption area. After the slurry in the slurry tank in the absorption area reaches saturation, it enters the slurry tank in the saturated area.

[0047] The present invention calculates the concentration of ammonium bicarbonate in the solution based on the measured density and the comparison relationship between the ammonium bicarbonate saturation, and can establish a balance equation and calculate the effective ammonia concentration in the absorption zone by combining the pH value monitoring; the reference value C and CO are introduced 2 There is a positive correlation between the absorption efficiency, that is, a one-to-one correspondence, substituting into the formula:

[0048] C = 738.58 [NH 3 ] 2 +11.32[NH 3 ],

[0049] [NH 3 ] represents the effective ammonia concentration;

[0050] C is solved, 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] The method proposed in the present invention can use the carbon capture byproduct as fertilizer, which is one of the most feasible byproduct utilization schemes at present, linking carbon emission reduction with ecological regulation. 4 HCO 3 Recycling not only makes up for the operating costs, but also greatly reduces the operating costs by simplifying the process; replacing the existing NH 4 HCO 3 Production can also improve the environment and reduce energy consumption.

[0052] The beneficial effects of the present invention are embodied in:

[0053] (1) Can stably convert CO 2 The removal efficiency is controlled 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 synergistically 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 It is a schematic diagram of the system structure of the present invention;

[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 divider, 20-primary ammonia washing spray layer, 2 1-first-level ammonia washing slurry divider, 22-absorption zone spray layer, 23-absorption zone slurry divider, 24-saturation zone spray layer, 25-saturation zone, 26-second-level ammonia washing process water tank, 27-process water tank, 28-first-level ammonia washing slurry tank, 29-absorption zone slurry tank, 30-concentrated ammonia water replenishment tank, 31-second-level ammonia washing slurry circulation pump, 32-first-level 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 bin, 40-branch flue gas duct after decarbonization.

[0060] Figure 2 Examples of different MgCl 2 Figure 2. Ammonia concentration diagram of outlet escape under concentration conditions. 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 ordinary technicians in this field, 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 spraying layer are all protected by this patent.

[0062] Embodiment 1:

[0063] like Figure 1 As shown, the desulfurization wastewater generated by the desulfurization system, the outlet pipeline of the desulfurization wastewater tank 2 is connected to the inlet of the heavy metal precipitation tank 4, the heavy metal precipitation tank 4 is provided with a sodium hydroxide delivery pipeline 3 and a heavy metal precipitation discharge pipeline 5, the outlet pipeline of the heavy metal precipitation tank 4 is connected to the inlet of the calcium precipitation tank 7, the calcium precipitation tank 7 is provided with a sodium carbonate delivery pipeline 6 and a calcium precipitation discharge pipeline 8, the outlet pipeline of the calcium precipitation tank 7 is connected to the inlet of the colloid precipitation tank 10, the colloid precipitation tank 10 is provided with a flocculant delivery pipeline 9 and a precipitated colloid discharge pipeline 8, the outlet pipeline of the colloid precipitation tank 10 is connected to the inlet of the sedimentation tank 12, the outlet pipeline of the sedimentation tank 12 is connected to the inlet pipeline of the clear liquid tank 13, the outlet pipeline of the clear water tank 13 is connected to the primary spray layer 20, and a clear liquid delivery pump is provided in the pipeline. The outlet pipeline of the 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 provided in the pipeline.

[0064] 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.

[0065] An absorption zone slurry divider 23 is provided on the upper part of the saturated zone spray layer 24, and 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, and 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 through a pipeline.

[0066] A primary 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 primary ammonia washing slurry tank 28 is connected to the primary ammonia washing spray layer 22. A primary ammonia washing slurry circulation pump 32 is installed in the pipeline.

[0067] A secondary ammonia washing slurry divider 19 is provided on the upper part of the primary ammonia washing spray layer 20, and the secondary ammonia washing slurry divider 19 is connected to the inlet of the secondary ammonia washing process water tank 26, and the outlet pipeline of the secondary ammonia washing process water tank 26 is connected to the secondary ammonia washing spray layer 18, and a secondary ammonia washing 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 washing process water tank 29 through a pipeline.

[0068] 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 underflow 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.

[0069] Embodiment 2:

[0070] The present invention provides a method for capturing carbon from flue gas of a coal-fired power plant and co-producing ammonium fertilizer based on the ammonia process, which includes three processing routes: gas, liquid and solid:

[0071] 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 CO 2 and escaped ammonia, and the emitted ammonia concentration is controlled below 3ppm; the slurry pH in the saturated 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 in the ammonia washing zone is 10-10.5, and the pH in the second-level ammonia washing process water tank 26 is 8-9.

[0072] 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 the recycling of ammonia washing liquid.

[0073] 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.

[0074] The present invention calculates the concentration of ammonium bicarbonate in the solution based on the measured density and the comparison relationship between the ammonium bicarbonate saturation, and can establish a balance equation and calculate the effective ammonia concentration in the absorption zone by combining the pH value monitoring; the reference value C and CO are introduced 2 There is a positive correlation between the absorption efficiency, that is, a one-to-one correspondence, substituting into the formula:

[0075] C = 738.58 [NH 3 ] 2 +11.32[NH3 ]

[0076] [NH 3 ] represents the effective ammonia concentration;

[0077] C is solved, 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%.

[0078] 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.

[0079] Table 1 is a comparison table of ammonium bicarbonate slurry concentration and density

[0080]

[0081] 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 / m 3 In order to keep 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 flue gas carbon from coal-fired power plants and co-producing ammonium fertilizer based on the ammonia process, characterized in that: 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 post-decarbonization branch flue gas duct (40); The decarbonization tower (1) is provided with a secondary ammonia washing spray layer (18), a secondary ammonia washing slurry separator (19), a primary ammonia washing spray layer (20), a primary ammonia washing slurry separator (21), an absorption zone spray layer (22), an absorption zone slurry separator (23) and a saturation zone spray layer (24) in order from top to bottom; the absorption zone is located above the absorption zone slurry separator (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 a 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 a 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 water 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 part of the saturated zone spray layer (24) is connected to the 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 from flue gas of a coal-fired power plant and co-producing ammonium fertilizer based on the 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 precipitation tank (12) which are 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 a clear liquid tank (13), and the clear liquid tank (13) is connected to a primary ammonia washing spray layer (20) of a decarbonization tower (1) via a clear liquid delivery pump (14).

3. The system for capturing flue gas carbon and co-producing ammonium fertilizer in a coal-fired power plant 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 flue gas carbon and co-producing ammonium fertilizer in a coal-fired power plant 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.

5. A method for capturing flue gas carbon from coal-fired power plants and co-producing ammonium fertilizer based on an ammonia process, characterized in that: Including three processing routes: gas, liquid and solid: The gas treatment route includes: wherein the flue gas undergoes multi-stage absorption in the saturation zone, absorption zone and ammonia washing zone of the decarbonization system to remove CO2 and escaped ammonia; 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 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.

6. The method for capturing flue gas carbon from coal-fired power plants and co-producing ammonium fertilizer based on the ammonia process according to claim 5, characterized in that: 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. The clear liquid is used for the recycling of ammonia washing liquid.

7. The method for capturing flue gas carbon from coal-fired power plants and co-producing ammonium fertilizer based on the ammonia process according to claim 5, characterized in that: In the gas treatment route, the ammonia washing area is divided into primary and secondary ammonia washing areas to ensure that the emission concentration of ammonia is within 3ppm.

8. The method for capturing flue gas carbon from coal-fired power plants and co-producing ammonium fertilizer based on the ammonia process according to claim 5, characterized in that: The pH value of the slurry in each unit is controlled within the following range: the pH value of the slurry in the saturated zone (25) of the decarbonization system is 8-8.5, the pH value of the slurry in the absorption zone is 9.5-10, the pH value in the primary ammonia washing water tank (28) of the ammonia washing zone is 10-10.5, and the pH value in the secondary ammonia washing process water tank (26) is 8-9.

9. The method for capturing flue gas carbon from coal-fired power plants and co-producing ammonium fertilizer based on the ammonia process according to claim 5, characterized in that: The concentration of ammonium bicarbonate in the solution is calculated based on the measured density and the saturation of ammonium bicarbonate. The equilibrium equation is established in combination with the monitored pH value to calculate the effective ammonia concentration in the absorption zone.

10. The method for capturing flue gas carbon from coal-fired power plants and co-producing ammonium fertilizer based on the ammonia process according to claim 5, characterized in that: The reference value C is positively correlated with the CO2 absorption efficiency, that is, a one-to-one correspondence. Substituting it into the formula: C=738.58[NH3] 2 +11.32[NH3] [NH3] represents the effective ammonia concentration; C is solved, 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%.

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