Circulating water lime softening system and method based on seed crystal circulation and intelligent control

Abstract

The invention belongs to the technical field of thermal power plant circulating water and sewage pretreatment, and relates to a circulating water lime softening system and method based on seed crystal circulation and intelligent control. Comprising a raw water tank, a lime softening tank, a flocculation reaction tank, a clarification tank and a softened water tank, through the synergistic effect of the seed crystal reflux circulation and the intelligent control technology, the softening efficiency is remarkably improved, the medicament consumption and the sludge output are reduced, and the resource utilization of the calcium carbonate byproduct is realized; according to the system, through organic connection of the raw water tank, the lime softening tank, the flocculation reaction tank, the clarification tank and the softening water tank, accurate adding of lime, sodium carbonate, seed crystal and a flocculating agent is combined, and whole-process water quality on-line monitoring and intelligent regulation and control are matched, so that efficient softening treatment of circulating water blow-down water is realized, stable and up-to-standard effluent quality is ensured, and the quality of discharged water is improved. Meanwhile, the operation cost and the treatment effect are optimized.

Description

Technical Field

[0001] The invention belongs to the technical field of pretreatment of circulating water and sewage in thermal power plants, and relates to a circulating water lime softening system and method based on seed crystal circulation and intelligent control. Background Art

[0002] During the operation of wet-cooled thermal power plants, the treatment of circulating water wastewater has always been a key and challenging issue in the water treatment field; this type of wastewater accounts for 70% to 80% of the total wastewater volume. During the operation of open industrial circulating cooling water systems, water continuously evaporates, causing various impurities in the water to continuously concentrate, leading to the continuous accumulation of hardness and a greater tendency for water scaling.

[0003] If it is discharged directly, it will not only cause waste of water resources, but may also have adverse effects on the environment; if it is reused for production, the high hardness of the water will cause problems such as pipe scaling and equipment corrosion, seriously affecting the normal operation and service life of the production equipment.

[0004] Directly using reverse osmosis technology to desalinate and reuse circulating water wastewater increases the risk of system blockage and scaling, thereby reducing system performance and seriously threatening the safe and stable operation of the circulating water system. Currently, common methods for softening circulating water wastewater include chemical precipitation and ion exchange. Traditional chemical precipitation methods require excessive dosage of reagents, making treatment results significantly affected by water quality fluctuations. They also generate large amounts of sludge, increasing the burden on subsequent solid waste disposal.

[0005] Ion exchange treatment is effective, but the resin requires frequent regeneration, resulting in high operating costs. Furthermore, existing softening treatment systems have a low degree of automation, lack intelligent control, and are unable to dynamically adjust to real-time changes in incoming water quality and quantity. This results in poor treatment results and the risk of scaling and clogging in subsequent membrane treatment systems.

[0006] Therefore, it is of great practical significance to develop an efficient, intelligent and environmentally friendly circulating water sewage softening pretreatment system and method. Summary of the Invention

[0007] In order to solve the problems of low treatment efficiency, high operating cost and low intelligence level in the existing pretreatment technology of circulating water and sewage, the present invention provides a circulating water lime softening system and method based on seed circulation and intelligent control, which can achieve efficient softening treatment of circulating water and sewage, and reduce the cost of reagents and sludge generation, so as to reduce environmental pollution.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a circulating water lime softening system based on seed crystal circulation and intelligent control, comprising a raw water tank, a lime softening tank, a flocculation reaction tank, a clarifier tank, and a softened water tank; The outlet of the raw water tank is connected to the first inlet of the lime softening tank; the first outlet of the lime softening tank is connected to the first inlet of the flocculation reaction tank; the outlet of the flocculation reaction tank is connected to the first inlet of the clarification tank; the first outlet of the clarification tank is connected to the softened water tank; The lime softening tank is provided with a lime inlet, a sodium carbonate inlet and a seed crystal inlet; the lime inlet is connected to the lime dosing device; the sodium carbonate inlet is connected to the sodium carbonate dosing device; the seed crystal inlet is connected to the seed crystal dosing device; The flocculation reaction tank is provided with a PAC inlet and a PAM inlet; the PAC inlet is connected to the PAC dosing device; the PAM inlet is connected to the PAM dosing device; The clarifier is provided with a sulfuric acid inlet; the sulfuric acid inlet is connected to a sulfuric acid dosing device.

[0009] Preferably, the second outlet of the lime softening tank is connected to a seed separation device; the seed separation device is provided with a seed outlet and a calcium carbonate outlet; the seed outlet is connected to the first inlet of the lime softening tank through a seed circulation pump; the calcium carbonate outlet is connected to a calcium carbonate particle recovery device.

[0010] Preferably, a raw water pump, a water inlet flow meter and a first water quality online monitoring device are sequentially arranged between the raw water pool outlet and the first inlet of the lime softening pool.

[0011] Preferably, a second water quality online monitoring device is provided between the first outlet of the clarifier and the softening water tank.

[0012] Preferably, the first water quality online monitoring device and the second water quality online monitoring device both include a pH sensor, a hardness sensor and a turbidity sensor.

[0013] Preferably, it includes an intelligent control system; the intelligent control system includes a data analysis module and a control decision module; the water inlet flow meter, the first water quality online monitoring device and the second water quality online monitoring device are all connected to the data analysis module; the data analysis module is connected to the control decision module; the control decision module is respectively connected to the raw water pump, the lime dosing device, the sodium carbonate dosing device, the seed dosing device, the PAC dosing device, the PAM dosing device and the sulfuric acid dosing device.

[0014] Preferably, the second outlet of the clarifier is connected to a sludge treatment device.

[0015] Preferably, an inclined tube sedimentation device is provided in the clarification tank.

[0016] Preferably, the seed crystals are CaCO3 seed crystals; the particle size of the CaCO3 seed crystals is 2-3 mm.

[0017] In a second aspect, the present invention provides a circulating water lime softening method based on seed crystal circulation and intelligent control, comprising the following steps: Circulating water wastewater enters the lime softening tank from the raw water tank; The lime dosing device, the sodium carbonate dosing device and the seed crystal dosing device respectively add lime, sodium carbonate and seed crystals to the lime softening tank, so that calcium and magnesium ions in the circulating water wastewater crystallize and grow on the surface of the seed crystals to form a precipitate of the first particle size and a precipitate of the second particle size; The second particle size precipitate and the circulating water wastewater enter the flocculation reaction tank, and PAC and PAM are sequentially added to the flocculation reaction tank through the PAC dosing device and the PAM dosing device to aggregate the second particle size precipitate to form flocs; The remaining circulating water wastewater enters the clarifier, and sulfuric acid is added to the clarifier through the sulfuric acid dosing device to adjust the water quality, thereby generating sludge and supernatant; The supernatant enters the softening water tank for treatment.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The present invention adds lime through a lime dosing device to adjust the pH value, so that substances such as calcium bicarbonate and magnesium bicarbonate in the water undergo a chemical reaction to generate precipitates such as calcium carbonate and magnesium hydroxide; sodium carbonate is added through a sodium carbonate dosing device to remove non-carbonate hardness; crystal seeds are added through a crystal seed dosing device to promote crystallization reaction, and the three act synergistically to achieve efficient removal of hardness components in the water; PAC and PAM are added respectively through a PAC dosing device and a PAM dosing device in a flocculation reaction tank to flocculate tiny precipitates formed in the water into larger flocs, thereby improving the subsequent precipitation effect; solid-liquid separation is achieved in a clarifier, and sulfuric acid is added through a sulfuric acid dosing device to adjust the pH value of the effluent, thereby ensuring stable effluent quality; a softening water tank is used to discharge circulating water after softening treatment, thereby providing a stable effluent guarantee for the system.

[0019] Furthermore, the seed crystal separation device is used to efficiently separate and realize graded recovery of the seed crystals and calcium carbonate products; the seed crystal outlet returns the separated seed crystals to the lime softening tank through the seed crystal circulation pump, forming a closed-loop seed crystal circulation system, which not only maintains the seed crystal concentration required by the reaction system, but also reduces the amount of fresh seed crystals added; the calcium carbonate outlet is connected to the calcium carbonate particle recovery device to centrally recover the by-product calcium carbonate particles to realize resource utilization.

[0020] Furthermore, the intelligent control system monitors the water quality parameters of each treatment link in real time, and automatically adjusts the dosage and equipment operating parameters according to changes in water quality to ensure the stable operation of the entire treatment system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 Schematic diagram of the structure of the system of the present invention.

[0023] Among them: 1. Raw water tank; 2. Raw water pump; 3. Water inlet flow meter; 4. First water quality online monitoring device; 5. Lime dosing device; 6. Sodium carbonate dosing device; 7. Seed dosing device; 8. Lime softening tank; 9. Flocculation reaction tank; 10. PAC dosing device; 11. PAM dosing device; 12. Sulfuric acid dosing device; 13. Clarification tank; 14. Second water quality online monitoring device; 15. Softened water tank; 16. Sludge treatment device; 17. Sludge transportation device; 18. Seed separation device; 19. Calcium carbonate particle recovery device; 20. Seed circulation pump; 21. Data analysis module; 22. Control decision module; 23. Intelligent control system. DETAILED DESCRIPTION

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0026] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0027] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "horizontal," "inner," etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the inventive product is typically placed when in use. These terms are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0028] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0029] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0030] The present invention is described in further detail below with reference to the accompanying drawings: The first purpose of the present invention is to provide a circulating water lime softening system based on seed crystal circulation and intelligent control. The system significantly improves the softening efficiency, reduces the consumption of reagents and the amount of sludge produced, and realizes resource utilization through seed crystal reflux circulation and intelligent control technology. Figure 1 As shown, the system of the present invention includes a raw water tank 1, a lime softening tank 8, a flocculation reaction tank 9, a clarifier 13 and a softened water tank 15; The outlet of the raw water tank 1 is connected to the first inlet of the lime softening tank 8; the first outlet of the lime softening tank 8 is connected to the first inlet of the flocculation reaction tank 9; the outlet of the flocculation reaction tank 9 is connected to the first inlet of the clarification tank 13; the first outlet of the clarification tank 13 is connected to the softened water tank 15; The lime softening tank 8 is provided with a lime inlet, a sodium carbonate inlet and a seed crystal inlet; the lime inlet is connected to the lime dosing device 5; the sodium carbonate inlet is connected to the sodium carbonate dosing device 6; the seed crystal inlet is connected to the seed crystal dosing device 7; The flocculation reaction tank 9 is provided with a polyaluminium chloride (PAC) inlet and a polyacrylamide (PAM) inlet; the PAC inlet is connected to a PAC dosing device 10; and the PAM inlet is connected to a PAM dosing device 11; A sulfuric acid inlet is provided on the clarifier 13 ; the sulfuric acid inlet is connected to the sulfuric acid dosing device 12 .

[0031] The circulating water lime softening system provided by the present invention achieves efficient softening treatment through the synergistic effect of various treatment units: the raw water tank 1 is used to store and regulate the circulating water sewage, providing a stable water inlet flow and water quality conditions for subsequent treatment processes; the lime softening tank 8 adds lime through the lime dosing device 5 to adjust the pH value, so that substances such as calcium bicarbonate and magnesium bicarbonate in the water undergo chemical reactions to generate precipitates such as calcium carbonate and magnesium hydroxide; the sodium carbonate dosing device 6 adds sodium carbonate to remove non-carbonate hardness, and the seed crystal dosing device 7 adds seeds to promote crystallization reaction. The three work together to achieve efficient removal of hardness components in the water; the flocculation reaction tank 9 adds PAC and PAM through the PAC dosing device 10 and the PAM dosing device 11 respectively, so that tiny precipitates formed in the water flocculate into larger flocs, thereby improving the subsequent precipitation effect; the clarifier 13 realizes solid-liquid separation, and adds sulfuric acid through the sulfuric acid dosing device 12 to adjust the pH value of the effluent, ensuring stable effluent water quality; the softened water tank 15 is used for the circulating water sewage after softening treatment, providing stable water outlet guarantee for the system.

[0032] In one embodiment of the present invention, the second outlet of the lime softening tank 8 is connected to the seed crystal separation device 18; the seed crystal separation device 18 is provided with a seed crystal outlet and a calcium carbonate outlet; the seed crystal outlet is connected to the first inlet of the lime softening tank 8 via a seed crystal circulation pump 20; and the calcium carbonate outlet is connected to the calcium carbonate particle recovery device 19. The second outlet of the lime softening tank 8 conveys the mixed liquid containing the reaction product to the seed crystal separation device 18, which achieves graded recovery of the seed crystals and calcium carbonate products through efficient separation; the seed crystal outlet returns the separated seed crystals to the lime softening tank 8 via the seed crystal circulation pump 20, forming a closed seed crystal circulation system, which not only maintains the seed crystal concentration required by the reaction system but also reduces the amount of fresh seed crystals added; the calcium carbonate outlet is connected to the calcium carbonate particle recovery device 19, which centrally recovers the by-product calcium carbonate particles for resource utilization.

[0033] In one embodiment of the present invention, a raw water pump 2, a water inlet flowmeter 3, and a first online water quality monitoring device 4 are sequentially disposed between the outlet of the raw water tank 1 and the first inlet of the lime softening tank 8. A second online water quality monitoring device 14 is disposed between the first outlet of the clarifier 13 and the softened water tank 15. Both the first online water quality monitoring device 4 and the second online water quality monitoring device 14 include a pH sensor, a hardness sensor, and a turbidity sensor.

[0034] Raw water pump 2 provides stable water inflow power to the system, ensuring continuous operation of the treatment process. Inlet flowmeter 3 monitors the inlet flow in real time, providing data support for subsequent dosing and process parameter adjustments. A first online water quality monitoring device 4, located at the softening tank inlet, detects raw water quality parameters in real time, providing a basis for the precise addition of lime, sodium carbonate, and seed crystals. A second online water quality monitoring device 14, located at the clarifier tank outlet 13, monitors the treated water quality in real time to ensure that indicators such as effluent hardness and turbidity meet standards. This present invention achieves precise control and stable operation of the treatment system through full-process water quality and flow monitoring.

[0035] The system of the present invention also includes an intelligent control system 23; the intelligent control system 23 includes a data analysis module 21 and a control decision module 22; the water inlet flow meter 3, the first water quality online monitoring device 4 and the second water quality online monitoring device 14 are all connected to the data analysis module 21; the data analysis module 21 is connected to the control decision module 22; the control decision module 22 is respectively connected to the raw water pump 2, the lime dosing device 5, the sodium carbonate dosing device 6, the seed dosing device 7, the PAC dosing device 10, the PAM dosing device 11 and the sulfuric acid dosing device 12.

[0036] The data analysis module 21 collects monitoring data from the inlet flow meter 3, the first water quality online monitoring device 4 and the second water quality online monitoring device 14 in real time, and conducts a comprehensive analysis of the inlet water quality and treatment effect; the control decision module 22 dynamically adjusts the flow of the raw water pump 2 according to the analysis results, and accurately controls the dosage of the lime dosing device 5, the sodium carbonate dosing device 6, and the seed crystal dosing device 7 to optimize the softening effect, and at the same time intelligently adjusts the flocculant dosage ratio of the PAC dosing device 10 and the PAM dosing device 11 and the pH callback amount of the sulfuric acid dosing device 12.

[0037] A liquid level sensor is installed in the raw water tank 1 to monitor the water level in real time and transmit the signal to the intelligent control system 23, so as to realize the real-time collection and analysis of water level data and provide key parameter basis for system start-up and shutdown and flow regulation.

[0038] In one embodiment of the present invention, the second outlet of clarifier 13 is connected to sludge treatment device 16, and an inclined tube settling device is installed within clarifier 13. The inclined tube settling device significantly increases the settling area, greatly improving the solid-liquid separation efficiency and ensuring that the effluent turbidity meets the standard. The second outlet of clarifier 13 transports the settled sludge to sludge treatment device 16 for centralized treatment, and then transports it for external use via sludge transport device 17.

[0039] The seed crystals are CaCO3 seed crystals; the particle size of the CaCO3 seed crystals is 2~3mm. The CaCO3 seed crystals have the same crystal structure as the reaction product, providing ideal nucleation sites for the crystallization of calcium and magnesium ions in water; the particle size range of 2~3mm not only ensures sufficient specific surface area to promote the crystallization reaction, but also avoids the loss of too small seed crystals with water flow or the reduction of reaction activity by too large seed crystals. Secondly, the lime softening tank 8 volume load is 5~8kg CaCO3 / m 3 ·d.

[0040] A second object of the present invention is to provide a circulating water lime softening method based on seed crystal circulation and intelligent control, comprising the following steps: Circulating water wastewater enters the raw water tank 1 for water quality and quantity adjustment, and is then transported to the lime softening tank 8 via the raw water pump 2. Simultaneously, the inlet flow meter 3 monitors the flow rate in real time, and the first online water quality monitoring device 4 detects the raw water pH, hardness, and turbidity parameters. The lime dosing device 5, the sodium carbonate dosing device 6 and the seed crystal dosing device 7 respectively add lime (to adjust the pH to 10.5-11.0), sodium carbonate (to remove non-carbonate hardness) and seed crystals (preferably 2-3 mm CaCO3 seed crystals) to the lime softening tank 8, so that the calcium and magnesium ions in the circulating water wastewater crystallize and grow on the surface of the seed crystals to form a first particle size precipitate and a second particle size precipitate; wherein the first particle size precipitate is a larger particle size precipitate, and the second particle size precipitate is a smaller second particle size precipitate; The mixed liquid containing the reaction product enters the seed crystal separation device 18, and the separation efficiency of the seed crystal separation device 18 is ≥90%. The separated seed crystals are returned to the lime softening tank 8 for recycling through the seed crystal circulation pump 20, and the seed crystal recovery rate is ≥95%. The separated calcium carbonate particles are transported to the calcium carbonate particle recovery device 19 for resource utilization as a desulfurization agent. The second particle size precipitate and the circulating water wastewater enter the flocculation reaction tank 9, and PAC (to form flocs) and PAM (to enhance flocculation) are added to the flocculation reaction tank 9 in sequence through the PAC dosing device 10 and the PAM dosing device 11, so that the second particle size precipitate aggregates to form flocs; The remaining circulating water enters the clarifier 13, where solid-liquid separation is achieved through an inclined tube sedimentation device, generating sludge and supernatant. Sulfuric acid is then added to the clarifier 13 through a sulfuric acid dosing device 12 to adjust the water pH to approximately 8.0. A second online water quality monitoring device 14 detects the pH, hardness, and turbidity parameters of the effluent. The water that meets the standards enters the softening water tank 15 for storage and reuse. The precipitated sludge is discharged through the second outlet of the clarifier 13 to the sludge treatment device 16 for dehydration to reduce the sludge moisture content to below 60%. After treatment, it is transported to the sludge transportation device 17 for utilization. The data analysis module 21 processes the data of the first water quality online monitoring device 4 and the second water quality online monitoring device 14 in real time, and controls the decision module 22 to dynamically adjust the operating parameters of each unit according to the analysis results to ensure that the outlet water hardness is ≤100mg / L and the turbidity is <5NTU.

[0041] Example Taking the softening treatment of circulating water blowdown from a power plant as an example, the initial hardness of the circulating water blowdown is 800 mg / L (calcium carbonate) and the pH is 7.0. This circulating water blowdown is pumped via raw water pump 2 to the raw water tank 1 of the present system for subsequent treatment. A first water quality monitoring device 4 monitors the incoming water quality in real time and transmits the data to an intelligent control system 23. Based on the water quality data, intelligent control system 23 controls a lime dosing device 5 to add lime to a lime softening tank 8, adjusting the wastewater's pH to 10.5-11. At this point, substances such as calcium bicarbonate and magnesium bicarbonate in the water react chemically to form precipitates such as calcium carbonate and magnesium hydroxide. A sodium carbonate dosing device 6 adds sodium carbonate to further remove non-carbonate hardness from the water. Simultaneously, calcium carbonate seeds are added via a seed crystal dosing device 7. A stirring device stirs the water at a speed of 100 rpm to ensure thorough mixing and reaction of the seeds, reagent, and wastewater. The post-reaction water enters the flocculation reaction tank 9, where PAC and PAM are added to further remove colloids, suspended solids, and some organic matter. The supernatant enters the clarification tank 13 for solid-liquid separation. Acid is added to adjust the pH to approximately 8.0, and the supernatant flows by gravity into the softening water tank 15. The hardness is required to be reduced to 100 mg / L and the turbidity to less than 5 NTU, meeting the water quality standards for reused water. The seed crystals sieved by the seed separation device 18 are returned to the lime softening tank 8 via the seed circulation pump 20 for recycling.

[0042] The intelligent control system 23 monitors water quality parameters at each treatment stage in real time, automatically adjusting dosing and equipment operating parameters based on water quality changes to ensure stable operation of the entire treatment system. Long-term operational monitoring has demonstrated that this treatment system delivers stable results, reduces treatment costs by approximately 30% compared to traditional treatment methods, and reduces sludge production by approximately 40%, resulting in significant economic and environmental benefits.

[0043] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A circulating water lime softening system based on seed crystal circulation and intelligent control, characterized in that: It includes a raw water tank (1), a lime softening tank (8), a flocculation reaction tank (9), a clarifier (13) and a softened water tank (15); The outlet of the raw water tank (1) is connected to the first inlet of the lime softening tank (8); the first outlet of the lime softening tank (8) is connected to the first inlet of the flocculation reaction tank (9); the outlet of the flocculation reaction tank (9) is connected to the first inlet of the clarification tank (13); the first outlet of the clarification tank (13) is connected to the softened water tank (15); The lime softening tank (8) is provided with a lime inlet, a sodium carbonate inlet and a seed crystal inlet; the lime inlet is connected to the lime dosing device (5); the sodium carbonate inlet is connected to the sodium carbonate dosing device (6); the seed crystal inlet is connected to the seed crystal dosing device (7); The flocculation reaction tank (9) is provided with a PAC inlet and a PAM inlet; the PAC inlet is connected to a PAC dosing device (10); the PAM inlet is connected to a PAM dosing device (11); The clarifier (13) is provided with a sulfuric acid inlet; the sulfuric acid inlet is connected to the sulfuric acid dosing device (12).

2. A circulating water lime softening system based on seed crystal circulation and intelligent control according to claim 1, characterized in that: The second outlet of the lime softening tank (8) is connected to the seed crystal separation device (18); the seed crystal separation device (18) is provided with a seed crystal outlet and a calcium carbonate outlet; the seed crystal outlet is connected to the first inlet of the lime softening tank (8) via a seed crystal circulation pump (20); and the calcium carbonate outlet is connected to the calcium carbonate particle recovery device (19).

3. A circulating water lime softening system based on seed crystal circulation and intelligent control according to claim 1, characterized in that: A raw water pump (2), a water inlet flow meter (3) and a first water quality online monitoring device (4) are sequentially arranged between the outlet of the raw water pool (1) and the first inlet of the lime softening pool (8).

4. A circulating water lime softening system based on seed crystal circulation and intelligent control according to claim 1, characterized in that: A second water quality online monitoring device (14) is provided between the first outlet of the clarifier (13) and the softened water tank (15).

5. A circulating water lime softening system based on seed crystal circulation and intelligent control according to claim 3 or 4, characterized in that: The first water quality online monitoring device (4) and the second water quality online monitoring device (14) both comprise a pH sensor, a hardness sensor, and a turbidity sensor.

6. A circulating water lime softening system based on seed crystal circulation and intelligent control according to claim 5, characterized in that: The intelligent control system (23) includes a data analysis module (21) and a control decision module (22); the water inlet flow meter (3), the first water quality online monitoring device (4) and the second water quality online monitoring device (14) are all connected to the data analysis module (21); the data analysis module (21) is connected to the control decision module (22); the control decision module (22) is respectively connected to the raw water pump (2), the lime dosing device (5), the sodium carbonate dosing device (6), the seed crystal dosing device (7), the PAC dosing device (10), the PAM dosing device (11) and the sulfuric acid dosing device (12).

7. A circulating water lime softening system based on seed crystal circulation and intelligent control according to claim 1, characterized in that: The second outlet of the clarifier (13) is connected to the sludge treatment device (16).

8. A circulating water lime softening system based on seed crystal circulation and intelligent control according to claim 1, characterized in that: An inclined tube sedimentation device is provided in the clarification tank (13).

9. The circulating water lime softening method based on seed crystal circulation and intelligent control according to claim 1, characterized in that: The seed crystals are CaCO3 seed crystals; the particle size of the CaCO3 seed crystals is 2-3 mm.

10. A circulating water lime softening method based on seed crystal circulation and intelligent control, characterized in that: The system according to any one of claims 1 to 9 comprises the following steps: Circulating water wastewater flows from the raw water tank (1) into the lime softening tank (8); The lime dosing device (5), the sodium carbonate dosing device (6) and the seed crystal dosing device (7) respectively add lime, sodium carbonate and seed crystals to the lime softening tank (8), so that calcium and magnesium ions in the circulating water wastewater crystallize and grow on the surface of the seed crystals to form a precipitate of the first particle size and a precipitate of the second particle size; The second particle size precipitate and the circulating water wastewater enter the flocculation reaction tank (9), and PAC and PAM are sequentially added to the flocculation reaction tank (9) through the PAC dosing device (10) and the PAM dosing device (11), so that the second particle size precipitate aggregates to form flocs; The remaining circulating water wastewater enters the clarifier (13), and sulfuric acid is added to the clarifier (13) through the sulfuric acid dosing device (12) to adjust the water quality, thereby generating sludge and supernatant; The supernatant enters the softening water tank (15) for treatment.

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