Dechlorination system for realizing zero discharge of desulfurization wastewater

Abstract

The invention discloses a dechlorination system capable of realizing zero emission of desulfurization wastewater, which relates to the technical field of pollutant control of coal-fired power plants and comprises an alkali liquor injection device, a tail gas treatment device, a desulfurization wastewater recovery treatment device, a flue gas waste heat recovery device and an alkali liquor injection device. According to the dechlorination system capable of realizing zero discharge of the desulfurization wastewater, effective removal of target pollutants is realized, the reduced desulfurization wastewater and a basic solution are mixed in the sedimentation tank, precipitates in the desulfurization wastewater can be effectively removed, and then clear liquid at the upper part of the sedimentation tank is sprayed into a flue gas pipeline, so that the desulfurization wastewater is completely discharged. Suspended solids and soluble solids in the wastewater form fine solid particles after being heated by high-temperature flue gas, the fine solid particles enter an electrostatic dust collector under the entrainment action of airflow and are captured and removed by electrodes, precipitates are further subjected to solid-liquid separation through a filter press, waste liquid is recycled to a sedimentation tank, and finally efficient desulfurization wastewater zero discharge is achieved. The environment-friendly requirement is met; the economical efficiency and the operability are relatively high.

Description

Technical Field

[0001] The invention relates to the technical field of pollutant control in coal-fired power plants, in particular to a dechlorination system for achieving zero discharge of desulfurization wastewater. Background Art

[0002] Limestone-gypsum wet flue gas desulfurization technology has become the mainstream treatment process for flue gas desulfurization in my country's current power plants due to its high desulfurization efficiency, mature technology, compact equipment layout, and strong adaptability to water quality changes. However, in the process of removing sulfur dioxide, this technology will also absorb acidic gases such as HCl in the flue gas and transfer them to the desulfurization slurry. With the recycling of the desulfurization slurry, C1 - The gradually increased ion concentration affects the desulfurization efficiency, reduces the quality of gypsum, and causes corrosion problems to the desulfurization system pipelines.

[0003] Prior art 1 (publication number: CN212632246U, Chinese patent with publication date of 2021-03-02) A raw flue gas dechlorination system for a zero-emission process for desulfurization wastewater, comprising a fan, which is connected to a desulfurization absorption tower through an original flue, and an HCl absorption device is arranged in the original flue, the HCl absorption device comprises a packing layer and an absorption layer, the absorption layer comprises a horizontally arranged defogger, a liquid holding tank is installed at the lower part of the defogger, a circulating water branch pipe is arranged at the bottom of the liquid holding tank, a guide groove is arranged between the defogger and the liquid holding tank, the liquid outlet of the liquid holding tank is connected to a first graphite cooler, the first graphite cooler is connected to a dual-media filter, the dual-media filter is connected to a high-pressure pump, the high-pressure pump is connected to a DTRO membrane device, the concentrated water outlet of the DTRO membrane device is connected to a desorption tower, and the top of the desorption tower is connected to an industrial hydrochloric acid storage tank. The dechlorination device has opened up a new approach to zero-emission wastewater engineering for limestone-gypsum wet flue gas desulfurization, and has the characteristics of low operating cost, resource utilization of industrial hydrochloric acid, no impact on fly ash resource utilization, and optimized desulfurization system operation.

[0004] There is also prior art 2 (publication number: CN111018025B, Chinese patent with publication date of 2024-01-02), an intelligent wastewater zero-emission coupled dechlorination system utilizing flue gas waste heat, used in conjunction with a flue gas dust removal and desulfurization system, which includes a device layer, a control layer, a perception layer, and an optimization layer. The device layer is used to achieve wastewater dechlorination through boiler flue gas waste heat, the control layer is used to control the operation of the device layer and set control parameters, the perception layer is used to monitor the flue gas and wastewater information of the device layer and feed the information back to the optimization layer, and the optimization layer is used to receive information from the perception layer and optimize the set control parameters of the control layer. This is to reduce the chloride ions that re-enter the wastewater concentration system and desulfurization system with the flue gas when the wastewater evaporates, thereby achieving source reduction of wastewater; at the same time, the byproducts of concentrated wastewater evaporation are high-chloride salts and heavy metal substances, which are captured by an independently operated high-efficiency bag dust collector to avoid causing the original dust removal system to have a lower ash quality.

[0005] In my country's current coal-fired power plants, equipment specifically used to remove HCl has not been widely used. Currently, HCl is still processed through a wet desulfurization tower. In order to maintain the stable operation of the system and ensure the desulfurization efficiency, when the chloride ion concentration in the absorption tower slurry is close to the specified range, it will be extracted in time. However, this process will lead to the generation of a large amount of desulfurization wastewater. Existing equipment cannot treat the generated desulfurization wastewater. Direct discharge of desulfurization wastewater will cause secondary pollution to the environment and also pose a threat to human health.

[0006] Therefore, we proposed a dechlorination system that achieves zero discharge of desulfurization wastewater in order to solve the problems raised above. Summary of the invention

[0007] The purpose of the present invention is to provide a dechlorination system that achieves zero discharge of desulfurization wastewater, so as to solve the problem raised in the above background technology that the existing equipment on the market cannot treat the generated desulfurization wastewater, and directly discharging the desulfurization wastewater will cause secondary pollution to the environment and also pose a threat to human health.

[0008] To achieve the above purpose, the present invention provides the following technical solutions: a dechlorination system for achieving zero discharge of desulfurization wastewater, comprising an alkali liquid injection device, an exhaust gas treatment device, a desulfurization wastewater recovery and treatment device, and a flue gas waste heat recovery device.

[0009] The alkali liquid injection device comprises a sedimentation tank and an alkali liquid preparation tank connected to the top of the sedimentation tank; a water pump 1 is connected to the side of the sedimentation tank, and the water pump 1 injects the clarified liquid on the upper part of the sedimentation tank into the conveying pipeline through the conveying pipeline;

[0010] Tail gas treatment device: including an electrostatic precipitator acting after the above-mentioned conveying pipeline and a subsequent wet desulfurization tower;

[0011] Desulfurization wastewater recovery and treatment device: including a wastewater collection box, which is placed at the bottom of the wet desulfurization tower and is connected to the above-mentioned sedimentation tank;

[0012] A filter press is connected to the bottom of the sedimentation tank. The sediment discharged from the sedimentation tank is further separated from the solid by a filter press, and the waste liquid is recirculated to the sedimentation tank;

[0013] Flue gas waste heat recovery device: includes an annular outer pipe acting on the front and rear flue of the electrostatic precipitator, and circulating water in the annular outer pipe.

[0014] Preferably, the alkali solution injection device includes a sedimentation tank and an alkali solution preparation tank connected to the top of the sedimentation tank, and an agitator is installed inside the alkali solution preparation tank; the side of the sedimentation tank is connected to a conveying pipe that penetrates through it, and a plurality of nozzles are opened at the end of the conveying pipe, and the side of the sedimentation tank is connected to a water pump 1, and the water pump 1 sprays the clarified liquid on the upper part of the sedimentation tank into the flue gas pipe through the conveying pipe and the nozzle, and the alkali solution is transported from the alkali solution preparation tank to the sedimentation tank through the water pump 3.

[0015] Preferably, the alkali solution preparation tank contains a high-concentration alkali solution body, which is selected as a mixed solution of sodium hydroxide, magnesium hydroxide, calcium hydroxide and polymerized iron oxide. During the preparation of the alkali solution body, the solid particles and the liquid are fully mixed by mechanical force to help the solid to dissolve quickly in the water and ensure that the mixture is uniform and stable. The addition of magnesium hydroxide and calcium hydroxide allows the alkali solution to form magnesium chloride and calcium chloride that are not volatile and stable at high temperatures when removing chloride ions from the desulfurization wastewater, thereby avoiding the secondary release of chloride ions circulated from the wastewater to the flue gas duct under high temperature conditions. In addition, the addition of the alkali solution avoids the possible corrosion of the flue gas duct by the acidic desulfurization wastewater when it is sprayed into the flue gas duct.

[0016] Preferably, the nozzle sprays the alkali liquid body into the flue gas duct in an atomized form, thereby improving the uniformity of the alkali liquid body in the flue gas duct. The atomized alkali liquid body reacts with HCl in the flue gas duct to generate salt substances that are stable and non-volatile at high temperatures. The adsorbed products of the reaction and the alkali liquid body droplets are evaporated and dried by the acidic gas and further adhere to the surface of the fly ash, while the suspended matter and soluble solids originally dissolved in the desulfurization wastewater form fine solid particles.

[0017] Preferably, the electrostatic precipitator in the tail gas treatment device is used to remove fly ash attached with HCl and evaporate and dry to form fine solid particles, the wet desulfurization tower is used to remove SO2 in the flue gas, and the generated desulfurization wastewater is collected in a wastewater collection box. The addition of the alkali liquid body to the desulfurization wastewater makes the HCl in the flue gas entering the wet desulfurization tower reach a lower level, and the amount of desulfurization wastewater in the wastewater collection box at the bottom of the wet desulfurization tower will be greatly reduced.

[0018] Preferably, the desulfurization wastewater recovery and treatment device comprises a wastewater collection tank placed at the bottom of the wet desulfurization tower, and the water in the wastewater collection tank is transported to the sedimentation tank by a second water pump;

[0019] The filter press is connected to the bottom of the sedimentation tank. The sediment discharged from the sedimentation tank is subjected to a filter press operation to further achieve solid-liquid separation. At the same time, the liquid is recirculated to the sedimentation tank through water pump four, and the filter cake is discharged from the system.

[0020] Preferably, the desulfurization wastewater entering the sedimentation tank from the wastewater collection tank through the water pump 2 undergoes various chemical reactions with the alkali solution body therein, and the desulfurization wastewater contains a large number of impurities, including but not limited to heavy metals such as mercury, lead, nickel, and zinc, non-metals such as sulfates, fluoride ions, and chloride ions, suspended solids such as gypsum particles and silicon dioxide, and C1 - 、SO4 2- 、F - The anions will form corresponding salts and precipitates by fully mixing with the alkali solution. Due to the addition of polymerized iron oxide, most of the chloride ions are discharged from the system in the form of precipitates.

[0021] Preferably, the outer heat exchange tube in the flue gas waste heat recovery device adopts a countercurrent heat exchanger design, in which the flow direction of the circulating water in the tube is opposite to the flow direction of the acid gas, which helps to reduce the temperature of the acid gas, slow down the reaction rate of corrosive chemicals with the metal surface, and reduce the activity of acid gases such as HCl and SO2, thereby reducing corrosion. The low-temperature dechlorination environment helps to improve the fluidity of the acid gas, so that the acid gas and the alkali solution are fully mixed, and the sufficiency of the reaction is enhanced. The low-temperature reaction environment can also make the dechlorination reaction more stable, avoid the occurrence of side reactions (such as the re-release of chlorine), and the salts generated by the dechlorination reaction are also easier to separate and collect from the acid gas.

[0022] Preferably, the evaporation amount of the alkali liquid body is further reduced at a lower temperature, and a higher alkali liquid body concentration is maintained, which is beneficial to improving the dechlorination effect. The circulating water that absorbs the waste heat of the flue gas can also be used for other thermal energy needs, realizing waste heat recovery and improving the energy utilization rate of the system.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present application provides a dechlorination system that achieves zero discharge of desulfurization wastewater, which achieves efficient removal of HCl in flue gas by spraying atomized alkaline solution into the flue gas pipeline and utilizing the reaction of the alkaline solution with HCl, thereby achieving effective removal of target pollutants;

[0025] 2. The present application provides a dechlorination system that achieves zero discharge of desulfurization wastewater. By using an electrostatic precipitator to remove HCl attached to fly ash, the HCl content entering the wet desulfurization tower is effectively reduced. According to the principle of desulfurization wastewater generation, the discharge of desulfurization wastewater is reduced from the source, effectively reducing the negative impact of desulfurization wastewater on the environment;

[0026] 3. The present application provides a dechlorination system for achieving zero discharge of desulfurization wastewater, which mixes the reduced desulfurization wastewater with an alkaline solution in a sedimentation tank, and can effectively remove the sediment in the desulfurization wastewater. Subsequently, the clarified liquid at the upper part of the sedimentation tank is sprayed into the flue gas duct, and the suspended matter and soluble solids therein are formed into fine solid particles after being heated by the high-temperature flue gas. The fine solid particles are entrained by the airflow and enter the electrostatic precipitator and are captured and removed by the electrodes, and the sediment is further separated into solid and liquid by the filter press, and the waste liquid is recycled to the sedimentation tank, and finally the efficient zero discharge of desulfurization wastewater is achieved, which meets the environmental protection requirements and has high economy and operability.

[0027] 4. The dechlorination system provided by the present application achieves zero discharge of desulfurization wastewater. By setting a countercurrent heat exchanger outside the tail flue before the dust removal device, the flue temperature is reduced to a certain extent, which slows down the corrosion of the flue gas pipeline by acidic gases under high temperature conditions, and further ensures the dechlorination efficiency and avoids the secondary release of chlorine at high temperature. The circulating water that absorbs the waste heat of the flue gas can also be used for other thermal energy needs to achieve waste heat recovery and improve the energy utilization rate of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the dechlorination system structure to achieve zero discharge of desulfurization wastewater.

[0029] In the figure: 1. Sedimentation tank; 2. Alkali solution preparation tank; 3. Water pump one; 4. Delivery pipeline; 5. Flue gas pipeline; 6. Electrostatic precipitator; 7. Wet desulfurization tower; 8. Wastewater collection box; 9. Agitator; 10. Annular outer pipe; 11. Water pump four; 12. Alkali solution body; 13. Filter press; 14. Water pump two; 15. Water pump three; 16. Nozzle. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in 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. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Embodiment 1: The present invention provides the following technical solutions: a dechlorination system for achieving zero discharge of desulfurization wastewater, and a dechlorination device for achieving zero discharge of desulfurization wastewater:

[0032] The dechlorination device for achieving zero discharge of desulfurization wastewater includes an alkali liquid injection device, an exhaust gas treatment device, a desulfurization wastewater recovery treatment device, and a flue gas waste heat recovery device;

[0033] The alkali liquid injection device comprises a sedimentation tank 1 and an alkali liquid preparation tank 2 connected to the top of the sedimentation tank 1, wherein an agitator 9 is installed inside the alkali liquid preparation tank 2; a conveying pipe 4 is connected to the side of the sedimentation tank 1, and a plurality of nozzles 16 are opened at the end of the conveying pipe 4, and a water pump 3 is connected to the side of the sedimentation tank 1, and the water pump 3 sprays the clarified liquid on the upper part of the sedimentation tank 1 into the flue gas pipe 5 through the conveying pipe 4 and the nozzle 16, and the alkali solution is transported from the alkali liquid preparation tank 2 to the sedimentation tank 1 through the water pump 3 15;

[0034] The tail gas treatment device includes an electrostatic precipitator 6 acting on the above-mentioned conveying pipeline 4 and a subsequent wet desulfurization tower 7;

[0035] The desulfurization wastewater recovery and treatment device includes a wastewater collection tank 8 disposed at the bottom of the wet desulfurization tower 7, and the water in the wastewater collection tank 8 is transported to the sedimentation tank 1 by a water pump 2 14;

[0036] The filter press 13 is connected to the bottom of the sedimentation tank 1. The sediment discharged from the sedimentation tank 1 is subjected to a filter press operation to further achieve solid-liquid separation. At the same time, the liquid is recirculated to the sedimentation tank 1 through the water pump 4 11, and the filter cake is discharged from the system;

[0037] The flue gas waste heat recovery device comprises an annular outer pipe 10 acting on the flue gas duct at the front and rear of the electrostatic precipitator 6 , and circulating water in the annular outer pipe 10 .

[0038] Embodiment 2: Figure 1 The present invention provides the following technical solution: a dechlorination system for achieving zero discharge of desulfurization wastewater:

[0039] The alkali solution preparation tank 2 contains a high-concentration alkali solution body 12, which is a mixed solution of sodium hydroxide, magnesium hydroxide, calcium hydroxide and polymerized iron oxide. During the preparation of the alkali solution body 12, the solid particles are fully mixed with the liquid by mechanical force to help the solid quickly dissolve in the water and ensure that the mixture is uniform and stable. The addition of magnesium hydroxide and calcium hydroxide allows the alkali solution to form magnesium chloride and calcium chloride that are not volatile and stable at high temperatures when removing chloride ions from the desulfurization wastewater, thereby avoiding the secondary release of chloride ions from the wastewater circulation to the flue gas duct 5 under high temperature conditions. In addition, the alkali solution The addition of the liquid avoids possible corrosion to the flue gas duct 5 caused by the acidic desulfurization wastewater when it is sprayed into the flue gas duct 5. The nozzle 16 sprays the alkali liquid body 12 into the flue gas duct 5 in an atomized form, thereby improving the uniformity of the alkali liquid body 12 in the flue gas duct 5. The atomized alkali liquid body 12 reacts with HCl in the flue gas duct 5 to generate salt substances that are stable and non-volatile at high temperatures. The adsorbed products of the reaction and the droplets of the alkali liquid body 12 are evaporated and dried by the acidic gas, and further adhere to the surface of the fly ash, while the suspended matter and soluble solids originally dissolved in the desulfurization wastewater form fine solid particles.

[0040] The electrostatic precipitator 6 is used to remove the fly ash attached with HCl and evaporate and dry to form fine solid particles. The wet flue gas desulfurization tower 7 is used to remove SO2 from the flue gas. The generated desulfurization wastewater is collected in the wastewater collection box 8. Due to the addition of the alkali liquid body 12, the HCl in the flue gas entering the wet flue gas desulfurization tower 7 reaches a lower level, and the amount of desulfurization wastewater in the wastewater collection box 8 at the bottom of the wet flue gas desulfurization tower 7 will be greatly reduced.

[0041] The desulfurization wastewater entering the sedimentation tank 1 from the wastewater collection box 8 through the water pump 2 14 undergoes various chemical reactions with the alkali solution 12 therein. The desulfurization wastewater contains a large number of impurities, including but not limited to heavy metals such as mercury, lead, nickel, and zinc, non-metals such as sulfates, fluoride ions, and chloride ions, suspended solids such as gypsum particles and silicon dioxide, and C1-, SO4 2- 、F - The anions, etc., will form corresponding salts and precipitates by being fully mixed with the alkali solution body 12. Due to the addition of polymerized iron oxide, most of the chloride ions are discharged from the system in the form of precipitates;

[0042] The heat exchange outer tube adopts a counter-current heat exchanger design, in which the flow direction of the circulating water in the tube is opposite to the flow direction of the acid gas, which helps to reduce the temperature of the acid gas, slow down the reaction rate of the corrosive chemical substances with the metal surface, and reduce the activity of acid gases such as HCl and SO2, thereby reducing corrosion. The low-temperature dechlorination environment helps to improve the fluidity of the acid gas, so that the acid gas and the alkali liquid body 12 are fully mixed, and the sufficiency of the reaction is enhanced. The low-temperature reaction environment can also make the dechlorination reaction more stable, avoid the occurrence of side reactions such as the re-release of chlorine, and the salts generated by the dechlorination reaction are also easier to separate and collect from the acid gas;

[0043] The evaporation amount of the alkali solution body 12 is further reduced at a lower temperature, and maintaining a higher concentration of the alkali solution body 12 is beneficial to improving the dechlorination effect. The circulating water that absorbs the waste heat of the flue gas can also be used for other thermal energy needs, realizing waste heat recovery and improving the energy utilization rate of the system.

[0044] Embodiment 3: Figure 1 The technical solution shown in the figure, a method for realizing a dechlorination system with zero discharge of desulfurization wastewater comprises the following steps:

[0045] S1. Under the action of the agitator 9, a certain concentration of alkaline solution is prepared. The alkaline solution is transported from the alkaline solution preparation tank 2 to the sedimentation tank 1 through the water pump 3 15. At the same time, the desulfurized wastewater in the wastewater collection tank 8 is transported to the sedimentation tank 1 through the water pump 2 14 to react chemically with the alkaline solution to form precipitation and non-volatile high-temperature stable salts. The precipitate in the desulfurized wastewater is precipitated during the long stay in the sedimentation tank, and the upper clarified liquid is sprayed into the flue gas pipeline 5 through the nozzle 16 through the conveying pipeline 4 under the action of the water pump 1 3. The atomized alkaline solution body 12 reacts with the acidic gas in the flue to generate an adsorption product attached to the fly ash;

[0046] S2, the fly ash and small particles in the flue enter the electrostatic precipitator 6 to be captured and removed, the SO2 in the flue enters the wet desulfurization tower 7 to complete the removal, and the desulfurization wastewater formed during the desulfurization process is collected in the wastewater collection box 8;

[0047] S3, the desulfurization wastewater in the wastewater collection box 8 enters the sedimentation tank 1 under the action of the water pump 2 14, and the sediment at the bottom of the sedimentation tank 1 is discharged into the filter press 13 to achieve further solid-liquid separation, and the separation product filter cake is discharged from the system, and the wastewater is circulated to the sedimentation tank 1 through the water pump 4 11 to complete the circulation of the desulfurization wastewater in the system, achieving zero discharge of desulfurization wastewater;

[0048] S4. The circulating water in the annular outer tube 10 and the flue gas flow in countercurrent to form a countercurrent heat exchanger to reduce the flue gas temperature and realize waste heat recovery.

[0049] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A dechlorination system for achieving zero discharge of desulfurization wastewater, characterized in that: It includes alkali liquid injection device, tail gas treatment device, desulfurization wastewater recovery treatment device, flue gas waste heat recovery device; The desulfurization wastewater recovery and treatment device comprises a wastewater collection box (8) and a filter press (13), wherein the wastewater collection box (8) is placed at the bottom end of the wet desulfurization tower (7), and the wastewater collection box (8) is connected to the sedimentation tank (1); A filter press (13) is connected to the bottom of the sedimentation tank (1). The sediment discharged from the sedimentation tank (1) is subjected to a filter press operation to further achieve solid-liquid separation, and the waste liquid is recirculated to the sedimentation tank (1).

2. A dechlorination system for achieving zero discharge of desulfurization wastewater according to claim 1, characterized in that: The alkali solution injection device comprises a sedimentation tank (1) and an alkali solution preparation tank (2) connected to the top of the sedimentation tank (1), wherein an agitator (9) is installed inside the alkali solution preparation tank (2); a conveying pipeline (4) is connected to the side of the sedimentation tank (1), and a nozzle (16) is opened at the end of the conveying pipeline (4); and a water pump (3) is connected to the side of the sedimentation tank (1), and the water pump (3) sprays the clarified liquid on the upper part of the sedimentation tank (1) through the conveying pipeline (4) and the nozzle (16) into the flue gas pipeline (5), and the alkali solution is transported from the alkali solution preparation tank (2) to the sedimentation tank (1) through the water pump (15).

3. A dechlorination system for achieving zero discharge of desulfurization wastewater according to claim 2, characterized in that: The alkali solution preparation tank (2) contains a high-concentration alkali solution body (12), and the alkali solution body (12) is selected to be a mixed solution of sodium hydroxide, magnesium hydroxide, calcium hydroxide and polymerized iron oxide; The alkali solution body (12) is prepared to fully mix the solid particles with the liquid through mechanical force, thereby helping the solid to dissolve in the water. The addition of the alkali solution avoids possible corrosion of the flue gas pipeline (5) caused by the acidic desulfurization wastewater when it is sprayed into the flue gas pipeline (5).

4. A dechlorination system for achieving zero discharge of desulfurization wastewater according to claim 3, characterized in that: The nozzle (16) sprays the alkali liquid body (12) into the flue gas duct (5) in an atomized manner, thereby improving the uniformity of the alkali liquid body (12) in the flue gas duct (5); the alkali liquid body (12) reacts with HCl in the flue gas duct (5).

5. A dechlorination system for achieving zero discharge of desulfurization wastewater according to claim 1, characterized in that: The tail gas treatment device comprises an electrostatic precipitator (6) after the conveying pipeline (4) and a subsequent wet desulfurization tower (7); The electrostatic precipitator (6) is used to remove fly ash attached with HCl and evaporate and dry to form fine solid particles. The wet desulfurization tower (7) is used to remove SO2 in flue gas. The generated desulfurization wastewater is collected in a wastewater collection box (8). Due to the addition of the alkali liquid body (12), the HCl in the flue gas entering the wet desulfurization tower (7) is reduced, and the amount of desulfurization wastewater in the wastewater collection box (8) at the bottom of the wet desulfurization tower (7) is reduced.

6. A dechlorination system for achieving zero discharge of desulfurization wastewater according to claim 1, characterized in that: The desulfurization wastewater recovery and treatment device comprises a wastewater collection tank (8) disposed at the bottom of the wet desulfurization tower (7), and the water in the wastewater collection tank (8) is transported to the sedimentation tank (1) by a second water pump (14); The filter press (13) is connected to the bottom end of the sedimentation tank (1). The sediment discharged from the sedimentation tank (1) is subjected to a filter press operation to further achieve solid-liquid separation. At the same time, the liquid is recirculated to the sedimentation tank (1) through a water pump (11), and the filter cake is discharged from the system.

7. A dechlorination system for achieving zero discharge of desulfurization wastewater according to claim 6, characterized in that: The desulfurization wastewater entering the sedimentation tank (1) from the wastewater collection box (8) through the second water pump (14) undergoes a chemical reaction with the alkali liquid body (12) therein. The desulfurization wastewater contains impurities, which are fully mixed with the alkali liquid body (12) to form corresponding salts and precipitates. The addition of polymerized iron oxide allows the chloride ions to be discharged from the system in the form of precipitates.

8. A dechlorination system for achieving zero discharge of desulfurization wastewater according to claim 1, characterized in that: The flue gas waste heat recovery device comprises an annular outer pipe (10) acting on the front and rear flue of the electrostatic precipitator (6), and circulating water in the annular outer pipe (10); The outer heat exchange tube adopts a counter-current heat exchanger design, in which the circulating water flows in the tube in the opposite direction to the flow direction of the acid gas, which helps to reduce the temperature of the acid gas, slow down the reaction rate of corrosive chemicals with the metal surface, and reduce the activity of acid gases such as HCl and SO2, thereby reducing corrosion.

9. A dechlorination system for achieving zero discharge of desulfurization wastewater according to claim 3, characterized in that: The evaporation amount of the alkali liquid body (12) is further reduced under temperature control, and a relatively high concentration of the alkali liquid body (12) is maintained, which is beneficial to improving the dechlorination effect. The circulating water that absorbs the waste heat of the flue gas can also be used for other thermal energy needs, thereby realizing waste heat recovery and improving the energy utilization rate of the system.

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