Limestone-gypsum wet desulphurization system

Abstract

The invention relates to the technical field of flue gas desulfurization, and provides an efficient limestone-gypsum wet desulfurization system, which comprises an absorption tower, an absorbent unit, a by-product treatment unit, a process water unit, an accident discharge unit and a wastewater treatment unit, the absorption tower adopts a multi-stage spraying and oxidation combined countercurrent absorption structure; the by-product treatment unit realizes efficient dehydration and recovery of gypsum through a gypsum cyclone and a vacuum belt dehydrator; the wastewater is discharged after reaching the standard after being subjected to multi-stage treatment. The desulfurization efficiency of the system is greater than or equal to 98.5%, the water content of gypsum is less than or equal to 10%, the treated wastewater meets the environmental protection requirement, and the system has the remarkable advantages of high efficiency, energy conservation and environmental protection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flue gas desulfurization, in particular to a limestone-gypsum wet desulfurization system. BACKGROUND

[0002] With the increasingly stringent requirements of relevant regulations on SO2 emission in flue gas, limestone-gypsum wet desulfurization technology is widely used due to its high desulfurization efficiency and utilization of by-products. However, in the existing wet desulfurization system, the poor dewatering effect of by-product gypsum is a prominent problem. The traditional gypsum dewatering equipment and process cannot fully remove the water in gypsum, resulting in a high water content of dewatered gypsum, usually more than 15%, which seriously affects the comprehensive utilization of gypsum. For example, as a building material raw material, high water content increases the subsequent drying and other processing costs, reduces product quality, and even limits its application range. Therefore, the present application is proposed. SUMMARY

[0003] The purpose of the present application is to provide a limestone-gypsum wet desulfurization system that can realize efficient dewatering and recovery of gypsum while ensuring desulfurization efficiency and wastewater treatment.

[0004] The present application provides a limestone-gypsum wet desulfurization system, comprising an absorption tower, an absorbent unit, a process water unit, a by-product disposal unit, and a wastewater treatment unit, The absorbent unit is used to prepare limestone slurry and transport the limestone slurry to the absorption tower; The process water unit is used to add process water to the absorption tower; The by-product disposal unit comprises a gypsum cyclone, the inlet of the gypsum cyclone is connected to the slurry pool of the absorption tower through a first slurry discharge pump, the underflow of the gypsum cyclone is connected to a vacuum belt dewatering machine, the filtrate of the vacuum belt dewatering machine is connected to a filtrate tank, and the filtrate tank is connected to the absorption tower through a filtrate pump; The wastewater treatment unit is connected to the vacuum belt dewatering machine and is used to treat wastewater.

[0005] Further, an emergency discharge unit is also included, which comprises an emergency slurry tank, a second slurry discharge pump, and a slurry return pump, the inlet of the second slurry discharge pump is connected to the slurry pool of the absorption tower, the outlet of the second slurry discharge pump is connected to the emergency slurry tank, and the emergency slurry tank is connected to the absorption tower through a slurry return pump.

[0006] Further, the volume of the emergency slurry tank is 1.2-1.5 times the volume of the slurry pool of the absorption tower, and a stirrer is provided inside to prevent slurry sedimentation.

[0007] Further, the wastewater treatment unit comprises a gas-liquid separator, a filtrate outlet of the vacuum belt dewatering machine is communicated with the gas-liquid separator, a liquid phase outlet of the gas-liquid separator is communicated with a wastewater feeding tank, the wastewater feeding tank is communicated with a wastewater buffer tank through a wastewater cyclone station, and the wastewater buffer tank is communicated with a wastewater treatment device.

[0008] Further, a gypsum slurry overflow tank connected with the gypsum cyclone is further included, and outlets of the gypsum slurry overflow tank are respectively connected with the wastewater feeding tank and the absorption tower.

[0009] Further, the absorption tower is a countercurrent spray tower, at least three spray layers are arranged in the absorption tower, a plurality of circulating pumps are arranged outside the absorption tower, an inlet of each circulating pump is communicated with a slurry pool of the absorption tower, and an outlet of each circulating pump is communicated with a spray layer in the absorption tower.

[0010] Further, the absorption agent unit comprises a limestone storage, an outlet of the limestone storage is communicated with a limestone slurry tank, and the limestone slurry tank is communicated with a slurry inlet of the absorption tower through a limestone slurry pump.

[0011] Further, an outlet of the filtrate pump is further connected with a water inlet of the limestone slurry tank through a pipeline.

[0012] Further, the process water unit comprises a process water tank and a process water pump, and the process water tank is communicated with a demister and a process water point in the absorption tower through the process water pump.

[0013] Further, a dust removal and flue gas unit is further included, the dust removal and flue gas unit comprises a flue gas pipeline connected with a flue gas inlet of the absorption tower, a booster fan is arranged on the flue gas pipeline, an inlet of the booster fan is connected with a dust remover through a pipeline, an inlet of the dust remover is connected with a boiler flue gas outlet through a pipeline, and a flue gas outlet of the absorption tower is communicated with a chimney.

[0014] Compared with the prior art, the application has the following advantages: The technical scheme provided by the application can efficiently dewater gypsum through the by-product treatment unit, the gypsum cyclone and the vacuum belt dewatering machine, the water content of the dewatered gypsum is less than or equal to 10%, the problem of high water content of gypsum in the traditional system is solved, and the gypsum is conducive to comprehensive utilization; the filtrate tank can recycle the filtrate of the vacuum belt dewatering machine, and the recycling rate is greater than or equal to 98%. The application optimizes the by-product treatment unit, realizes efficient dewatering and recycling of gypsum, ensures desulfurization efficiency and wastewater treatment, has significant economic and environmental benefits, and is suitable for desulfurization treatment of various industrial flue gases. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the specific embodiments of the present application or the prior art, the accompanying drawings needed to be used in the description of the specific embodiments or the prior art will be briefly introduced. Obviously, the accompanying drawings in the following description are some embodiments of the present application, and based on these drawings, other drawings can be obtained by those skilled in the art without any creative effort.

[0016] Figure 1 Flow chart of the desulfurization system in Embodiment 1 of the present application; Legend: 1 - absorption tower; 2 - dust remover; 3 - booster fan; 4 - limestone storage bin; 5 - limestone slurry tank; 6 - limestone slurry pump; 7 - oxidation fan; 8 - process water tank; 9 - process water pump; 10 - circulating pump; 11 - chimney; 12 - emergency slurry tank; 13 - second slurry discharge pump; 14 - slurry return pump; 15 - first slurry discharge pump; 16 - gypsum cyclone; 17 - gypsum slurry overflow tank; 18 - filtrate water tank; 19 - filtrate pump; 20 - vacuum belt dewaterer; 21 - gas-liquid separator; 22 - waste water feeding tank; 23 - waste water cyclone station; 24 - waste water buffer tank; 25 - waste water treatment device. DETAILED DESCRIPTION

[0017] The technical solutions of the present application will be described in detail below in conjunction with the embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort fall within the scope of the present application.

[0018] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the present application and simplify the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0019] Furthermore, the terms "first", "second", "third", etc. are used herein for descriptive purposes only and should not be construed as indicating or implying relative importance or an ordered sequence. Thus, features defined with "first", "second" or "third" can include one or more of the described features, either explicitly or implicitly. In the description of the application, the meaning of "a plurality" is two or more, unless explicitly specified otherwise. Furthermore, the terms "mounting", "connected", "connecting" should be construed broadly, for example, can be fixed connection, can also be detachable connection, or integrally connected; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0020] Embodiment A limestone-gypsum wet desulfurization system, as shown in Figure 1 , includes a dusting and flue gas unit, an absorption tower 1, an absorbent unit, a process water unit, a by-product disposal unit, a wastewater treatment unit and an emergency discharge unit, the specific content is as follows: Dusting and flue gas unit: This unit is responsible for the pretreatment and transportation of flue gas, including flue gas pipeline, dust collector 2, booster fan 3 and chimney 11. The inlet of dust collector 2 is connected with the outlet of boiler flue gas through pipeline, and the inlet and outlet of booster are connected with the outlet of dust collector 2 and the flue gas inlet of absorption tower 1 through flue gas pipeline respectively. Dust-containing flue gas first enters dust collector 2, after dust removal treatment (outlet dust concentration <20mg / Nm 3 ), it is sent to the flue gas inlet of the lower part of absorption tower 1 by booster fan 3, after the desulfurization reaction in absorption tower 1, the clean flue gas removes liquid droplets (liquid droplet content <75mg / Nm 3 ) through the demister at the top of absorption tower 1, and finally is discharged through chimney 11. This unit adopts a series design of dust removal and desulfurization to avoid the interference of dust on the desulfurization system, while ensuring the stability of flue gas transportation. The chimney 11 and the absorption tower 1 of the present application are designed as an integrated design.

[0021] Absorbent unit: This unit is responsible for the preparation and supply of limestone slurry, including limestone storage 4, limestone slurry tank 5 and limestone slurry pump 6. The limestone powder with particle size <0.044mm is purchased, stored in limestone storage 4, sent to limestone slurry tank 5 through unloading device, mixed with process water to prepare limestone slurry with solid content of 10%-15%, and then delivered to the slurry inlet of absorption tower 1 by limestone slurry pump 6 to provide absorbent for desulfurization reaction.

[0022] The absorption tower 1 is the core device of the desulfurization reaction. The absorption tower 1 in the application adopts a countercurrent spray tower structure, is lined with scale resin or rubber anticorrosion. The tower is provided with three spray layers, each spray layer corresponds to a circulating pump 10, the circulating pump 10 sends the slurry in the slurry pool of the absorption tower 1 to the spray layer, is atomized after the silicon carbide hollow cone nozzle, forms fine droplets, fully contacts with the flue gas from bottom to top, realizes the high-efficiency absorption of SO2, the nozzle coverage rate is greater than or equal to 300%, and the gas-liquid dead angle contact is ensured.

[0023] The oxidation fan 7 is a Roots fan, the outlet is provided with an oxidation air pipe, the oxidation air pipe is located in front of the slurry pool stirrer of the absorption tower 1, the oxidation air is broken into micro-bubbles by the stirrer, fully reacts with the calcium sulfite generated in the slurry, the oxidation efficiency is greater than or equal to 95%, and finally generates dihydrate gypsum. The demister at the top of the absorption tower 1 is a folded plate demister, after three-stage demisting, the clean flue gas contains less than 75 mg / Nm 3 , and the phenomenon of white smoke from the chimney is avoided.

[0024] The by-product disposal unit: the unit realizes the efficient dehydration and recovery of gypsum, including a first slurry discharge pump 15, a gypsum cyclone 16, a gypsum slurry overflow tank 17, a filtrate water tank 18, a filtrate pump 19 and a vacuum belt dewatering machine 20. The gypsum cyclone 16 adopts a double-cone type cyclone. The gypsum slurry in the slurry pool of the absorption tower 1 is sent into the gypsum cyclone 16 by the first slurry discharge pump 15, after separation by the gypsum cyclone 16, the underflow gypsum slurry with a solid content greater than or equal to 45% enters the vacuum belt dewatering machine 20, and after dehydration, the gypsum has a water content of less than or equal to 10%, and can be directly utilized comprehensively, such as building material production.

[0025] The overflow of the gypsum cyclone 16 is connected with the gypsum slurry overflow tank 17 through a pipeline, and is sent into the slurry pool in the absorption tower 1 by a gypsum slurry overflow pump, to participate in the reaction again.

[0026] The filtrate of the vacuum belt dewatering machine 20 is collected into the filtrate water tank 18, and is sent back to the absorption tower 1 by the filtrate pump 19 for recycling, so that the slurry and process water are recycled, and resource consumption is reduced.

[0027] The water outlet of the filtrate water tank 18 is also connected with the water inlet of the limestone slurry tank 5 through the filtrate pump 19, for preparation of the limestone slurry.

[0028] The gypsum slurry discharged from the absorption tower 1 is composed of gypsum (CaS04·2H20), a salt mixture (MgS04, CaCl2), limestone (CaC03), calcium fluoride (CaF2) and ash particles. The solid content of the gypsum slurry discharged from the absorption tower 1 is about 18%-25%, and in order to facilitate the transportation, storage and utilization of the gypsum, dehydration treatment is required. The gypsum slurry is concentrated to a solid content of ≥45% by the gypsum cyclone 16, and is self-flowed to the vacuum belt dehydrator 20 from the bottom tank of the gypsum cyclone 16 for dehydration treatment. Under normal conditions, the surface moisture content of the gypsum solid after dehydration treatment is less than 10%, and the gypsum is sent to the gypsum storage room by the multi-point distribution belt machine, and is loaded by the loader and then transported to the comprehensive utilization user; under abnormal conditions, the high-concentration gypsum slurry is self-flowed to the gypsum slurry overflow tank 17 after being adjusted by the electric three-way baffle below the bottom tank of the gypsum cyclone 16, while the valve at the front end of the feed tank of the gypsum cyclone 16 is closed, and the gypsum slurry overflow pump 18 is used to send the gypsum slurry in the absorption tower 1 to the accident slurry tank 12 for storage. The overflow liquid separated by the gypsum cyclone 16 is overflowed to the gypsum slurry overflow tank 17 and is sent back to the absorption tower 1 by the gypsum slurry overflow pump to participate in the reaction again.

[0029] Process water unit: This unit provides process water for the whole process, including the process water tank 8 and the process water pump 9. The process water tank 8 stores industrial water or treated recycled water of the power plant, which is delivered to the demister, limestone slurry tank 5, equipment and pipeline flushing and other process water points in the absorption tower 1 by the process water pump 9, to ensure the normal operation of the system.

[0030] Emergency discharge unit: This unit ensures the temporary storage and recovery of the slurry when the desulfurization system fails or is under maintenance. It includes the accident slurry tank 12, the second slurry discharge pump 13 and the slurry return pump 14. When the system needs to be shut down for maintenance, the slurry in the absorption tower 1 is sent to the accident slurry tank 12 by the second slurry discharge pump 13, and the volume of the accident slurry tank 12 is 1.2-1.5 times the volume of the slurry pool in the absorption tower 1, and an agitator is arranged inside to prevent gypsum from precipitating; after the maintenance is completed, the accident slurry is sent back to the absorption tower 1 by the slurry return pump 14, realizing zero waste of the slurry and shortening the system restart time.

[0031] Wastewater treatment unit: the unit is used for treating desulfurization wastewater, realizing standard treatment of desulfurization wastewater. Including gas-liquid separator 21, wastewater feeding tank 22, wastewater cyclone station 23, wastewater buffer tank 24 and wastewater treatment device 25. Desulfurization wastewater is derived from two parts: one is the filtrate generated by the vacuum belt dewatering machine 20, and the other is part of the overflow of the gypsum slurry cyclone 16, both of which are discharged into the wastewater feeding tank 22 for unified treatment. The filtrate generated by the vacuum belt dewatering machine 20 is separated by the gas-liquid separator 21, and the liquid phase enters the wastewater feeding tank 22, and then the solid matter in the wastewater is separated by the three-stage wastewater cyclone station 23 (separation efficiency ≥ 85%), and the separated wastewater enters the wastewater buffer tank 24, and finally enters the wastewater treatment device 25 for neutralization, flocculation, precipitation and other treatments, and is discharged or reused after reaching the standard.

[0032] The outlet of the gypsum slurry overflow tank 17 is connected with the wastewater feeding tank 22 through a pipeline, and the water outlet of the wastewater cyclone station 23 is connected with the gypsum slurry overflow tank 17 through a pump. According to the requirements of the desulfurization process, the desulfurization system needs to continuously discharge a certain amount of wastewater to maintain the appropriate Cl - ion concentration in the slurry pool of the absorption tower. Part of the overflow of the gypsum slurry cyclone 16 is used as desulfurization wastewater, which is pumped into the wastewater cyclone station 23 for further concentration after being discharged into the wastewater feeding tank 22, and the underflow of the wastewater cyclone station 23 returns to the gypsum overflow slurry tank 17, which is sent back to the absorption tower 1 by the gypsum overflow slurry pump 19. The maximum amount of wastewater continuously generated by the system is about 1.0 t / h.

[0033] The process flow of the limestone-gypsum wet desulfurization system provided by the application is as follows: I. Smoke enters and pretreatment The original flue gas containing sulfur dioxide, dust and other pollutants generated by boiler combustion first enters the dust remover 2 in the dust and flue gas unit, and the dust particles in the flue gas are removed by using the principles of filtration, centrifugation and the like in the dust remover 2, so that the dust concentration at the outlet is <20 mg / Nm 3 , and the preliminary purification of the flue gas is completed. The flue gas after dust removal enters the booster fan 3, and the booster fan 3 pressurizes the flue gas so that it has enough power to be transported to the flue gas inlet at the lower part of the absorption tower 1 through the flue gas pipeline.

[0034] II. Desulfurization reaction process The absorbent unit starts to work, and according to the requirements of the desulfurization reaction, the limestone powder enters the limestone slurry tank 5 from the limestone storage bin 4 through the unloading device, and at the same time, the process water in the process water tank 8 or the filtrate water in the filtrate water tank 18 is also introduced into the limestone slurry tank 5. In the limestone slurry tank 5, the limestone powder and the process water or the filtrate water are fully mixed by stirring and the like to prepare limestone slurry containing 10%-15% solid content. The prepared limestone slurry is transported to the slurry inlet of the absorption tower 1 by the limestone slurry pump 6.

[0035] In the absorption tower 1, the flue gas sent into the bottom of the absorption tower 1 by the booster fan 3 flows upwards, the circulating pump 10 transports the limestone slurry in the slurry pool of the absorption tower 1 to the corresponding spray layer, and the slurry is atomized into fine droplets by the nozzle to fully contact with the rising flue gas. In this process, the sulfur dioxide in the flue gas reacts with the calcium carbonate in the limestone slurry to generate calcium sulfite and other substances.

[0036] The oxidation fan 7 sends air into the slurry pool of the absorption tower 1 to fully react with the calcium sulfite in the slurry to oxidize it into calcium sulfate. The clean flue gas after the desulfurization reaction continues to rise, passes through the demister at the top to remove the liquid droplets carried in the clean flue gas, so that the liquid droplet content in the clean flue gas is <75 mg / Nm 3 , and finally discharged into the atmosphere through the chimney 11.

[0037] III. By-product treatment The gypsum slurry containing calcium sulfate and other substances in the slurry pool of the absorption tower 1 is sent into the gypsum cyclone 16 by the first slurry discharge pump 15, and the gypsum slurry is separated in the gypsum cyclone 16 by using the centrifugal force. The underflow obtains gypsum slurry with a solid content ≥45%, and the overflow is a liquid with a lower solid content.

[0038] The gypsum slurry in the underflow of the gypsum cyclone 16 enters the vacuum belt dewatering machine 20, and in the vacuum belt dewatering machine, the water in the gypsum is further removed by vacuum suction and other methods, so that the water content of the dewatered gypsum is ≤10%, and the gypsum product can be directly utilized.

[0039] The filtrate generated by the vacuum belt dewatering machine 20 is collected into the filtrate tank 18 and sent back to the absorption tower 1 or the limestone slurry tank 5 by the filtrate pump 19 for recycling, realizing the recycling of the slurry and process water and reducing resource consumption. The overflow of the gypsum cyclone 16 is sent back to the absorption tower 1 by the gypsum slurry overflow pump to participate in the reaction again.

[0040] IV. Accident treatment When the desulfurization system needs to be shut down for maintenance or needs to be emptied due to abnormal conditions, the slurry in the slurry pool of the absorption tower 1 is sent into the accident slurry tank 12 in the accident discharge unit by the second slurry discharge pump 13; after the system maintenance is completed, the slurry in the accident slurry tank 12 is sent back to the absorption tower 1 by the slurry return pump 14, realizing the recycling of the slurry, shortening the system restart time, and avoiding the waste of the slurry.

[0041] V. Waste water treatment The filtrate generated by the vacuum belt dewatering machine 20 first enters a gas-liquid separator 21, separates the gas in the filtrate, and the liquid phase enters a waste water feeding tank 22. The waste water in the waste water feeding tank 22 is sent to a waste water cyclone station 23, and the solid in the waste water is separated by cyclone separation. The waste water after cyclone separation enters a waste water buffer tank 24, which plays a role of buffering and adjusting water quality and quantity.

[0042] Finally, the waste water in the waste water buffer tank 24 is sent to a waste water treatment device 25, and neutralization, flocculation, precipitation and other treatments are carried out in the waste water treatment device to remove harmful substances in the waste water, so that the treated waste water meets the discharge standard or the recycling standard, and can be discharged or recycled.

[0043] The limestone-gypsum wet desulfurization system provided by the application has the following advantages: I. Good gypsum dewatering effect: through the synergistic effect of the gypsum cyclone and the vacuum belt dewatering machine, the water content of the dewatered gypsum is ≤10%, solving the problem of high water content of gypsum in the traditional system, which is beneficial to the comprehensive utilization of gypsum.

[0044] II. High desulfurization efficiency: the absorption tower adopts multi-stage spraying and high-efficiency oxidation design, and the desulfurization efficiency is ≥98.5%; III. High resource utilization rate: the recovery rate of the overflow of the gypsum cyclone and the filtrate of the vacuum belt dewatering machine is ≥98%, realizing the recovery of slurry and process water; IV. Strong accident response capability: the accident slurry tank has sufficient volume and is provided with a stirring device to ensure that the slurry does not precipitate during temporary storage and is not wasted during recovery; a separate slurry discharge pump and a slurry return pump are also provided; V. High system integration: each system is modularly designed, the layout is compact, the land occupation area is small, and the installation and maintenance are convenient.

[0045] The application optimizes the by-product disposal unit and the waste water treatment unit, and additionally provides an accident discharge unit, realizes efficient dewatering and recovery of gypsum, ensures desulfurization efficiency and standard treatment of waste water, has significant economic and environmental benefits, and is suitable for desulfurization treatment of various industrial flue gas.

[0046] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the application, but not to limit them; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application.

Claims

1. A limestone-gypsum wet desulphurization system, characterized by, The system comprises an absorption tower (1), an absorbent unit, a process water unit, a by-product disposal unit and a wastewater treatment unit; The absorbent unit is used for preparing limestone slurry and transporting the limestone slurry into the absorption tower (1); The process water unit is used for adding process water into the absorption tower (1); The by-product disposal unit comprises a gypsum cyclone (16), the inlet of the gypsum cyclone (16) is communicated with the slurry pool of the absorption tower (1) through a first slurry discharge pump (15), the underflow of the gypsum cyclone (16) is communicated with a vacuum belt dewatering machine (20), the filtrate of the vacuum belt dewatering machine (20) is communicated with a filtrate tank (18), and the filtrate tank (18) is communicated with the absorption tower (1) through a filtrate pump (19). The wastewater treatment unit is connected with the vacuum belt dewatering machine (20) and is used for treating wastewater.

2. The limestone-gypsum wet desulphurization system according to claim 1, characterized in that, The system further comprises an accident discharge unit, the accident discharge unit comprises an accident slurry tank (12), a second slurry discharge pump (13) and a slurry return pump (14), the inlet of the second slurry discharge pump (13) is communicated with the slurry pool of the absorption tower (1), the outlet of the second slurry discharge pump (13) is communicated with the accident slurry tank (12), and the accident slurry tank (12) is communicated with the absorption tower (1) through the slurry return pump (14).

3. The limestone-gypsum wet desulphurization system according to claim 2, characterized in that, The volume of the accident slurry tank (12) is 1.2-1.5 times of the volume of the slurry pool of the absorption tower (1), and a stirrer is arranged in the accident slurry tank (12) to prevent the slurry from precipitating.

4. The limestone-gypsum wet desulphurization system according to claim 1, characterized in that, The wastewater treatment unit comprises a gas-liquid separator (21), the filtrate outlet of the vacuum belt dewatering machine (20) is communicated with the gas-liquid separator (21), the liquid phase outlet of the gas-liquid separator (21) is communicated with a wastewater feed tank (22), the wastewater feed tank (22) is communicated with a wastewater cyclone station (23) through a wastewater buffer tank (24), and the wastewater buffer tank (24) is communicated with a wastewater treatment device (25).

5. The limestone-gypsum wet desulphurization system according to claim 4, characterized in that, The system further comprises a gypsum slurry overflow tank (17) connected with the gypsum cyclone (16), the outlet of the gypsum slurry overflow tank (17) is connected with the wastewater feed tank (22) and the absorption tower (1), and the outlet of the wastewater cyclone station (23) is connected with the gypsum slurry overflow tank (17).

6. The limestone-gypsum wet desulphurization system according to claim 1, characterized in that, The absorption tower (1) is a countercurrent spray tower, at least three spray layers are arranged in the absorption tower (1), a plurality of circulating pumps (10) are arranged outside the absorption tower (1), the inlet of the circulating pump (10) is communicated with the slurry pool of the absorption tower (1), and the outlet of the circulating pump (10) is communicated with the spray layer in the absorption tower (1).

7. The limestone-gypsum wet desulphurization system according to claim 1, characterized in that, The absorbent unit comprises a limestone storage bin (4), the outlet of the limestone storage bin (4) is communicated with a limestone slurry tank (5), and the limestone slurry tank (5) is communicated with the slurry inlet of the absorption tower (1) through a limestone slurry pump (6).

8. The limestone-gypsum wet desulphurization system according to claim 7, characterized in that, The outlet of the filtrate pump (19) is also connected with the water inlet of the limestone slurry tank (5) through a pipeline.

9. The limestone-gypsum wet desulphurization system according to claim 1, characterized in that, The process water unit comprises a process water tank (8) and a process water pump (9), the process water tank (8) is communicated with a demister in the absorption tower (1) and a process water point through the process water pump (9).

10. The limestone-gypsum wet FGD system according to claim 1, characterized by, Further comprising a dust removal and flue gas unit, the dust removal and flue gas unit comprises a flue gas pipeline connected with a flue gas inlet of the absorption tower (1), a booster fan (3) is arranged on the flue gas pipeline, an inlet of the booster fan (3) is connected with a dust remover (2) through a pipeline, an inlet of the dust remover (2) is connected with a boiler flue gas outlet through a pipeline; a flue gas outlet of the absorption tower (1) is communicated with a chimney (11).

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