Desulfurization wastewater treatment method and treatment system

Abstract

The invention discloses a desulfurization wastewater treatment method and a desulfurization wastewater treatment system. The desulfurization wastewater treatment method comprises the following steps: S1, acquiring chloride ion concentration and calculating desulfurization wastewater discharge amount; s2, acquiring actual indexes of the flue gas and calculating the amount of treated desulfurization wastewater; s3, judging whether the desulfurization wastewater is completely consumed or not, if not, executing the step S4, and if yes, executing the step S5; s4, performing electrodialysis on the desulfurization wastewater; step S5, concentrating the desulfurization wastewater; and step S6, drying the desulfurization wastewater. According to the desulfurization wastewater treatment method disclosed by the invention, the synergistic cooperation with a desulfurization wastewater treatment system during desulfurization wastewater treatment is realized, and the problem of wastewater accumulation caused by limited drying capacity of high-temperature flue gas under low load is solved, so that excessive discharge or system corrosion caused by incapability of treating the wastewater in time is prevented.

Description

Technical Field

[0001] This invention relates to the field of desulfurization wastewater treatment technology, and in particular to a desulfurization wastewater treatment method and system. Background Technology

[0002] Related technologies indicate that flue gas desulfurization (FGD) is a crucial means of reducing sulfur dioxide emissions during the operation of coal-fired power plants. Wet FGD is widely used due to its high efficiency and mature technology. However, the FGD process generates a large amount of wastewater containing high concentrations of suspended solids, organic matter, salts, and heavy metals, posing a serious threat to the environment. Therefore, effectively treating FGD wastewater to achieve compliant discharge or resource utilization is an urgent problem for coal-fired power plants. Currently, there are two main routes for zero-discharge treatment of FGD wastewater from coal-fired power plants: one is "pretreatment + membrane concentration + evaporation crystallization," which requires large upfront investment, high operating costs, and high skill levels from operators, resulting in low overall adoption; the second route is "pretreatment + pre-concentration + high-temperature flue gas drying," which is more commonly used in coal-fired power plants due to its relatively simple system process, lower initial investment, and lower operating requirements. However, as the unit undergoes more frequent deep adjustments, the amount of concentrated water in the preheating flue gas shrinkage system and the amount of water that the high-temperature flue gas drying system can handle are limited under low load conditions. This results in the incomplete treatment of desulfurization wastewater, an imbalance in the plant's water system, and potential environmental hazards. Summary of the Invention

[0003] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a desulfurization wastewater treatment method, which enables coordinated operation between the desulfurization wastewater treatment process and the desulfurization wastewater treatment system, thereby solving the problem of wastewater accumulation caused by limited high-temperature flue gas drying capacity under low load conditions.

[0004] The present invention also proposes a desulfurization wastewater treatment system.

[0005] The desulfurization wastewater treatment method according to a first aspect of the present invention includes: Step S1: Obtain the chloride ion concentration and calculate the desulfurization wastewater discharge. Step S2: Obtain the actual indicators of the flue gas and calculate the amount of desulfurization wastewater to be treated; Step S3: Determine whether the desulfurization wastewater has been completely disposed of. If not, proceed to step S4; if yes, proceed to step S5. Step S4: Perform electrodialysis on the desulfurization wastewater; Step S5: Concentrate the desulfurization wastewater; Step S6: Dry the desulfurization wastewater.

[0006] According to the desulfurization wastewater treatment method of the present invention, by real-time monitoring of chloride ion concentration in desulfurization wastewater and boiler flue gas operating parameters, the desulfurization wastewater treatment volume and desulfurization wastewater discharge volume are dynamically calculated to determine the desulfurization wastewater disposal situation. When the treatment capacity is insufficient, electrodialysis pretreatment is introduced, and when the capacity is sufficient, a conventional concentration-drying path is adopted. This achieves synergistic cooperation between the desulfurization wastewater treatment process and the desulfurization wastewater treatment system, solves the problem of wastewater accumulation caused by limited high-temperature flue gas drying capacity under low load, and thus prevents excessive discharge or system corrosion caused by the inability to treat wastewater in a timely manner.

[0007] Furthermore, the chloride ion concentration includes the chloride ion concentration of the desulfurization slurry and the chloride ion concentration of the desulfurization process water.

[0008] Furthermore, the actual parameters of the flue gas include the flow rate of the electrodialysis flue gas, the temperature of the electrodialysis flue gas, the flow rate of the waste heat flue gas, and the temperature of the waste heat flue gas.

[0009] According to a desulfurization wastewater treatment system of a second aspect of the present invention, a desulfurization wastewater treatment method of a first aspect of the present invention is applied to the desulfurization wastewater treatment system, the desulfurization wastewater treatment system comprising: an integrated treatment device for treating suspended solids in the desulfurization wastewater; an electrodialysis device connected to the integrated treatment device and located downstream of the integrated treatment device in the flow direction of the desulfurization wastewater, the electrodialysis device being used for pre-concentrating the desulfurization wastewater; and a waste heat flue gas concentration tower connected to both the integrated treatment device and the electrodialysis device, the waste heat flue gas concentration tower being located downstream of the integrated treatment device and downstream of the electrodialysis device in the flow direction of the desulfurization wastewater, the waste heat flue gas concentration tower being used for concentrating the flue gas generated from the desulfurization wastewater.

[0010] According to the desulfurization wastewater treatment system of the present invention, by applying the desulfurization wastewater treatment method of the first aspect described above, zero discharge of desulfurization wastewater under all operating conditions is achieved, effectively coping with the flue gas heat fluctuations caused by deep peak shaving, eliminating the risk of wastewater accumulation under low load, making full use of boiler waste heat, and electrodialysis is only activated when necessary, thereby reducing treatment costs.

[0011] In some feasible embodiments, the integrated treatment equipment includes a reaction unit, a clarification unit, and a dosing unit. The reaction unit and the dosing unit are used to add dry powder to the desulfurization wastewater, and the clarification unit is used to precipitate sludge from the desulfurization wastewater.

[0012] In some feasible embodiments, the desulfurization wastewater treatment system further includes: a concentrate conditioning device, which is connected to the waste heat flue gas concentration tower. The concentrate conditioning device is located downstream of the waste heat flue gas concentration tower in the flow direction of the desulfurization wastewater, and is used to adjust the pH of the desulfurization wastewater.

[0013] In some feasible embodiments, the desulfurization wastewater treatment system further includes: a drying device, which is connected to the concentrate conditioning device and is located downstream of the concentrate conditioning device in the flow direction of the desulfurization wastewater; the drying device is used to dry the desulfurization wastewater.

[0014] In some feasible embodiments, the desulfurization wastewater treatment system further includes: a sludge treatment device, which is connected to the integrated treatment device, and the sludge treatment device is used to treat the sludge in the clarification unit.

[0015] In some feasible embodiments, the desulfurization wastewater treatment system further includes: a buffer tank located upstream of the integrated treatment equipment, the buffer tank being equipped with an aeration oxidation blower for reducing the chemical oxygen demand (COD) of the desulfurization wastewater; a clear water tank located between the integrated treatment equipment and the electrodialysis equipment for collecting the supernatant from the clarification unit; and a clear water to process water tank connected to the electrodialysis equipment for collecting the supernatant.

[0016] In some feasible embodiments, the desulfurization wastewater treatment system further includes: a first concentrate tank and a second concentrate tank. The first concentrate tank is located between the electrodialysis equipment and the waste heat flue gas concentration tower, and is used to collect the electrodialysis concentrate produced by the electrodialysis equipment. The second concentrate tank is located between the waste heat flue gas concentration tower and the concentrate conditioning equipment, and is used to collect the concentrated waste liquid produced by the waste heat flue gas concentration tower.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] Figure 1 This is a flowchart of a desulfurization wastewater treatment method according to a first aspect of the present invention; Figure 2 This is a flowchart of a desulfurization wastewater treatment system according to a second aspect of the present invention.

[0019] Figure label: 100. Desulfurization wastewater treatment system; 1. Buffer tank; 2. Integrated treatment equipment; 3. Clear water tank; 4. Electrodialysis equipment; 5. First concentrated water tank; 6. Waste heat flue gas concentration tower; 7. Second concentrated water tank; 8. Concentrated water conditioning equipment; 9. Drying equipment; 10. Sludge treatment equipment; 11. Clear water to process water tank. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] The following is for reference. Figure 1 A method for treating desulfurization wastewater according to an embodiment of the first aspect of the present invention is described.

[0022] like Figure 1 As shown, the desulfurization wastewater treatment method according to a first aspect embodiment of the present invention includes: Step S1: Obtain the chloride ion concentration and calculate the desulfurization wastewater discharge. Step S2: Obtain the actual indicators of the flue gas and calculate the amount of desulfurization wastewater to be treated; Step S3: Determine whether the desulfurization wastewater has been completely disposed of. If not, proceed to step S4; if yes, proceed to step S5. Step S4: Perform electrodialysis on the desulfurization wastewater; Step S5: Concentrate the desulfurization wastewater; Step S6: Dry the desulfurization wastewater.

[0023] Understandably, step S1, obtaining the chloride ion concentration and calculating the desulfurization wastewater discharge volume, involves chloride ions as a key control indicator in the desulfurization system. Excessive chloride ion concentration will exacerbate equipment corrosion. Typically, the chloride ion concentration in the absorption tower slurry or discharged wastewater is monitored in real time using an online chloride ion analyzer to calculate the volume of desulfurization wastewater to be discharged, i.e., the theoretical discharge volume, thus achieving precise quantification of wastewater discharge.

[0024] Step S2: Obtain the actual indicators of the flue gas and calculate the desulfurization wastewater treatment volume. Collect the actual operating parameters such as flue gas temperature, flow rate, and moisture content from the boiler tail flue. Combined with the heat balance model of the high-temperature flue gas drying system, calculate the maximum evaporable wastewater volume that can be treated under the current operating conditions. In this way, the wastewater treatment capacity is linked to the actual flue gas energy availability, avoiding a large error between the actual treated water volume and the theoretical treated water volume, and ensuring the accuracy of the actual treated water volume calculation.

[0025] Step S3: Determine whether the desulfurization wastewater has been completely absorbed. If not, proceed to step S4. If yes, proceed to step S5, which determines whether the desulfurization wastewater treatment volume is less than the desulfurization wastewater discharge volume. If the desulfurization wastewater treatment volume is less than the desulfurization wastewater discharge volume, it means that the wastewater has not been completely absorbed, and step S4 needs to be executed. If the desulfurization wastewater treatment volume is not less than the desulfurization wastewater discharge volume, it means that the wastewater has been completely absorbed, and step S5 needs to be executed. This achieves automatic switching of the treatment path and avoids forcibly injecting excessive wastewater when the flue gas heat is insufficient, which could lead to a sudden drop in flue gas temperature, a decrease in dust removal / desulfurization efficiency, or even equipment scaling and blockage.

[0026] Step S4: Electrodialysis is performed on the desulfurization wastewater. When it is determined that the system cannot completely absorb the wastewater, some or all of the desulfurization wastewater is introduced into the electrodialysis equipment 4. Electrodialysis uses ion exchange membranes and DC electric fields to selectively migrate sodium ions and chloride ions in the wastewater, thereby achieving salt concentration and freshwater reuse. This significantly reduces the volume of high-salt liquid that needs to be dried later, thus alleviating the bottleneck of insufficient flue gas drying capacity under low load. The produced freshwater can be reused in the desulfurization system or other processes, improving water resource utilization. Compared with evaporation and crystallization, electrodialysis has lower energy consumption, reducing operating costs during low load periods.

[0027] Step S5: Concentrate the desulfurization wastewater. After pretreatment, the desulfurization wastewater enters a conventional concentration unit (such as multi-effect evaporation, MVR, or membrane concentration) to increase the salt content of the wastewater to a concentration suitable for drying, thereby reducing the energy consumption of subsequent drying. Under high load and sufficient flue gas heat, the low-cost heat source is maximized for efficient concentration, providing a suitable feed concentration for subsequent drying and improving drying efficiency and system stability.

[0028] Step S6: Drying the desulfurization wastewater. The concentrated high-salt wastewater (or concentrated water after electrodialysis reduction) is sprayed into a high-temperature flue (such as the area before the air preheater, SCR outlet, etc.). The waste heat of the flue gas is used to instantly evaporate the wastewater. The salt is collected by the dust collector along with the fly ash in the form of solid particles, achieving zero discharge of wastewater. This completely realizes zero discharge of desulfurization wastewater, with no liquid discharge. It utilizes the existing flue gas system, eliminating the need for additional evaporation and crystallization equipment, resulting in low production costs. Furthermore, the solidified salt enters the fly ash system, facilitating unified disposal or resource utilization.

[0029] According to the desulfurization wastewater treatment method of the present invention, by real-time monitoring of chloride ion concentration in desulfurization wastewater and boiler flue gas operating parameters, the desulfurization wastewater treatment volume and desulfurization wastewater discharge volume are dynamically calculated to determine the desulfurization wastewater disposal status. When the treatment capacity is insufficient, electrodialysis pretreatment is introduced, and when the capacity is sufficient, a conventional concentration-drying path is adopted. This achieves coordinated cooperation between the desulfurization wastewater treatment method and the desulfurization wastewater treatment system 100, and solves the problem of wastewater accumulation caused by limited high-temperature flue gas drying capacity under low load, thereby preventing excessive discharge or system corrosion caused by the inability to treat wastewater in a timely manner.

[0030] Furthermore, the chloride ion concentration includes the chloride ion concentration in the desulfurization slurry and the chloride ion concentration in the desulfurization process water. It can be understood that the desulfurization slurry refers to the limestone-gypsum slurry in the absorption tower, whose chloride ions mainly originate from hydrogen chloride in the raw flue gas and dissolved chloride salts in the makeup process water. As the desulfurization reaction continues, water evaporates continuously, and chloride ions accumulate in the slurry. When the chloride ion concentration is too high, it inhibits limestone dissolution, reduces desulfurization efficiency, and exacerbates pitting corrosion and stress corrosion cracking of metal components. This directly reflects the degree of chloride salt accumulation within the desulfurization wastewater treatment system 100. Real-time monitoring can prevent a decrease in desulfurization efficiency and equipment corrosion failure. The desulfurization process water is used for slurry preparation, demister flushing, pump sealing, etc. Its source may be circulating water discharge, industrial water, or treated reclaimed water. If the water source itself contains high chloride ions (such as using high-salt reclaimed water), it will continuously input chloride ions into the desulfurization wastewater treatment system 100, causing a rapid increase in slurry chloride ions even without the addition of hydrogen chloride in the flue gas. Therefore, monitoring only the chloride ion concentration of the desulfurization slurry without considering the chloride ion concentration of the desulfurization process water will underestimate the chlorine load and result in insufficient wastewater discharge. At the same time, by combining the chloride ion concentration of the desulfurization slurry, a reasonable wastewater discharge rate can be deduced, so as to achieve on-demand sewage discharge and avoid excessive drainage that wastes water resources or insufficient sewage discharge that causes corrosion.

[0031] Furthermore, the actual indicators of the flue gas include the flow rate and temperature of the electrodialysis flue gas, as well as the flow rate and temperature of the waste heat flue gas. This enables precise quantification of heat source capacity, avoiding under- or over-treatment caused by experience or fixed settings. It supports adaptive scheduling under multiple operating conditions (especially deep adjustment under low load), optimizes the coordinated operation of electrodialysis and flue gas drying, achieves a balance between energy saving and reliability, and prevents operational risks such as incomplete spray drying, scaling, and corrosion caused by excessively low flue gas temperature or insufficient flow.

[0032] According to a second aspect of the present invention, a desulfurization wastewater treatment system 100 is provided, and the desulfurization wastewater treatment method according to the first aspect of the present invention is applied to the desulfurization wastewater treatment system 100. The desulfurization wastewater treatment system 100 includes: an integrated treatment device 2, an electrodialysis device 4, and a waste heat flue gas concentration tower 6.

[0033] like Figure 2As shown, specifically, the integrated treatment equipment 2 is used to treat suspended solids in the desulfurization wastewater. The electrodialysis equipment 4 is connected to the integrated treatment equipment 2 and is located downstream of the integrated treatment equipment 2 in the flow direction of the desulfurization wastewater. The electrodialysis equipment 4 is used to pre-concentrate the desulfurization wastewater. The waste heat flue gas concentration tower 6 is connected to both the integrated treatment equipment 2 and the electrodialysis equipment 4. The waste heat flue gas concentration tower 6 is located downstream of the integrated treatment equipment 2 in the flow direction of the desulfurization wastewater and downstream of the electrodialysis equipment 4 in the flow direction of the desulfurization wastewater. The waste heat flue gas concentration tower 6 is used to concentrate the flue gas generated from the desulfurization wastewater.

[0034] Understandably, the integrated treatment unit 2 is used to remove high concentrations of suspended solids (such as gypsum particles and dust), some heavy metals, and colloidal substances from desulfurization wastewater, protecting downstream precision equipment (such as electrodialysis membrane stacks) from clogging, fouling, or scaling, extending their service life, and reducing the cleaning frequency and maintenance costs of subsequent treatment units. The electrodialysis unit 4, located after the integrated treatment unit 2, uses a DC electric field to drive anions and cations in the wastewater through a selective ion exchange membrane, achieving salt migration and producing fresh water (which can be reused) and high-salt concentrate (which enters subsequent drying), reducing subsequent evaporation / The drying load alleviates the bottleneck of flue gas drying capacity under low load. The waste heat flue gas concentration tower 6 receives desulfurization wastewater from the integrated treatment equipment 2 (direct path) or the electrodialysis equipment 4 (concentrated water after volume reduction), and uses the high-temperature flue gas drawn from the tail of the boiler as a heat source. The wastewater is atomized through atomizing nozzles in the tower and comes into contact with the flue gas to achieve rapid evaporation of water. Salt is collected in the form of dry particles with the flue gas and enters the dust collector for capture. In this way, the waste heat of the boiler is directly utilized without the need for additional steam or electricity, which reduces the operating cost and achieves true zero liquid discharge. The solidified salt is easy to collect and dispose of.

[0035] According to the desulfurization wastewater treatment system 100 of the present invention, by applying the desulfurization wastewater treatment method of the first aspect embodiment described above, zero discharge of desulfurization wastewater under all operating conditions is achieved, effectively coping with the flue gas heat fluctuations caused by deep peak shaving, eliminating the risk of wastewater accumulation under low load, making full use of boiler waste heat, and electrodialysis is only activated when necessary, thereby reducing treatment costs.

[0036] In some embodiments of the present invention, the integrated treatment device 2 includes a reaction unit, a clarification unit, and a dosing unit. The reaction unit and the dosing unit work together to add dry powder to the desulfurization wastewater, and the clarification unit is used to settle the sludge in the desulfurization wastewater. It is understood that by precisely adding dry powder agents (such as lime, sodium carbonate, flocculants, etc.) to the desulfurization wastewater through the dosing unit, neutralization, softening, and flocculation reactions are completed in the reaction unit. Subsequently, the wastewater enters the clarification unit to achieve sludge settling and separation of clear water. This achieves efficient removal of suspended solids, hardness, and some heavy metals, reduces the sludge moisture content, facilitates subsequent dewatering, reduces the sludge treatment burden on the desulfurization wastewater treatment system, and improves the pretreatment effect of the desulfurization wastewater.

[0037] In some embodiments of the present invention, such as Figure 2 As shown, the desulfurization wastewater treatment system 100 also includes a concentrated water conditioning device 8, which is connected to the waste heat flue gas thickening tower 6. The concentrated water conditioning device 8 is located downstream of the waste heat flue gas thickening tower 6 in the flow direction of the desulfurization wastewater. The concentrated water conditioning device 8 is used to adjust the pH of the desulfurization wastewater. It can be understood that the concentrated water conditioning device 8, as a downstream unit of the waste heat flue gas thickening tower 6, is used to adjust the pH of the high-salt concentrated water after thickening or before drying. Since the pH of the desulfurization wastewater is usually strongly alkaline after pretreatment and thickening, if it is directly sprayed into the high-temperature flue for drying, it may cause scaling, corrosion, or affect the quality of fly ash in the flue gas system. This prevents scaling and corrosion in the high-temperature flue, avoids the precipitation of calcium hydroxide, magnesium hydroxide, and other deposits after evaporation of the alkaline concentrated water, improves the stability of fly ash quality, reduces equipment blockage or dust removal efficiency reduction caused by pH imbalance, and enhances the adaptability of the desulfurization wastewater treatment system 100 to water quality fluctuations.

[0038] For example, the pH value of the desulfurization wastewater before entering the concentrate conditioning equipment 8 is 1-2, and the pH value is adjusted to 6-8 after passing through the concentrate conditioning equipment 8.

[0039] In some embodiments of the present invention, such as Figure 2As shown, the desulfurization wastewater treatment system 100 also includes a drying device 9, which is connected to the concentrated water conditioning device 8. The drying device 9 is located downstream of the concentrated water conditioning device 8 in the flow direction of the desulfurization wastewater and is used to dry the desulfurization wastewater. It can be understood that the drying device 9, located downstream of the concentrated water conditioning device 8, is used to completely evaporate and dry the pretreated, concentrated, and conditioned high-salt concentrated water, converting it into solid salt particles, achieving true zero liquid discharge. Typically, high-temperature flue gas from the boiler tail is used as a heat source, and the concentrated water is instantly evaporated in the drying tower or flue through atomized spraying. The salt is captured by the dust collector along with the flue gas and finally discharged from the desulfurization wastewater treatment system 100 in the form of dry ash. This completely eliminates the discharge of liquid wastewater, reduces treatment costs, and produces solid salt that mixes into the fly ash system, facilitating unified collection, disposal, or resource utilization, thus simplifying solid waste management.

[0040] In some embodiments of the present invention, such as Figure 2 As shown, the desulfurization wastewater treatment system 100 also includes a sludge treatment device 10, which is connected to the integrated treatment device 2. The sludge treatment device 10 is used to treat the sludge in the clarification unit. It is understood that the sludge treatment device 10 is used to receive and dispose of the water-containing sludge discharged from the clarification unit. After the desulfurization wastewater undergoes the reaction and clarification process in the integrated treatment device 2, a large amount of chemical sludge, mainly composed of gypsum, calcium carbonate, magnesium hydroxide, and heavy metal hydroxides, is generated. If not treated in time, it not only occupies space but may also cause secondary pollution. The sludge treatment device 10 achieves solid waste reduction and harmlessness, avoids the environmental risks caused by sludge accumulation or overflow, reduces subsequent transportation and disposal costs, and prevents the clarification unit from experiencing efficiency decline or shutdown due to sludge accumulation.

[0041] In some embodiments of the present invention, such as Figure 2As shown, the desulfurization wastewater treatment system 100 also includes: a buffer tank 1, a clear water tank 3, and a clear water-to-process water tank 11. The buffer tank 1 is located upstream of the integrated treatment equipment 2 and is equipped with an aeration oxidation fan to reduce the chemical oxygen demand (COD) of the desulfurization wastewater. The clear water tank 3 is located between the integrated treatment equipment 2 and the electrodialysis equipment 4 and is used to collect the supernatant from the clarification unit. The clear water-to-process water tank 11 is connected to the electrodialysis equipment 4 and is used to collect the supernatant. It can be understood that the buffer tank 1 is located at the very front of the desulfurization wastewater treatment system 100 and uses aeration oxidation to reduce the COD of the wastewater; the clear water tank 3 receives the supernatant from the clarification unit of the integrated treatment equipment 2; and the clear water-to-process water tank 11 collects the fresh water (or high-quality supernatant) produced by the electrodialysis equipment 4 for reuse in the power plant's process system. This not only enhances the adaptability of the desulfurization wastewater treatment system 100 to fluctuations in influent water quality and quantity, but also stabilizes the upstream water quality, avoids the impact of shock loads on the operation of the integrated treatment equipment 2, effectively reduces wastewater COD, reduces the risk of organic pollution from subsequent membrane / electrodialysis, improves the overall plant water resource recycling rate, and reduces the cost of desulfurization wastewater treatment.

[0042] In some embodiments of the present invention, such as Figure 2 As shown, the desulfurization wastewater treatment system 100 also includes: a first concentrated water tank 5 and a second concentrated water tank 7. The first concentrated water tank 5 is located between the electrodialysis equipment 4 and the waste heat flue gas thickening tower 6, and is used to collect the electrodialysis concentrate produced by the electrodialysis equipment 4. The second concentrated water tank 7 is located between the waste heat flue gas thickening tower 6 and the concentrated water conditioning equipment 8, and is used to collect the concentrated waste liquid produced by the waste heat flue gas thickening tower 6. This improves the adaptability of the desulfurization wastewater treatment system 100 to load fluctuations, avoids equipment overload or shutdown due to sudden changes in instantaneous water volume / concentration, ensures stable water intake for subsequent units (such as the waste heat flue gas thickening tower 6 and the concentrated water conditioning equipment 8), facilitates water quality monitoring and emergency control, reduces pump start-up and shutdown frequency, extends the lifespan of the desulfurization wastewater treatment system 100, and reduces the energy consumption of the desulfurization wastewater treatment system 100.

[0043] For example, when the chloride ion content in the desulfurization process makeup water and coal is low, in order to ensure the quality of the desulfurization slurry, the desulfurization wastewater discharge is 10t / h, the unit is under high load, the preheating flue gas volume is large, and the heat is relatively sufficient. According to the calculation of the desulfurization wastewater treatment system 100, the drying equipment 9 can solidify 1 / h-2t / h of wastewater at this time. The heat of the waste heat flue gas thickening tower 6 is sufficient to concentrate 10t / h to 1 / h-2t / h. Therefore, the desulfurization wastewater in the clear water tank 3 can directly enter the waste heat flue gas thickening tower 6 without passing through the electrodialysis equipment 4. After being preheated and concentrated by 5-10 times by the flue gas, it enters the first concentrated water tank 5. At this time, the volume of desulfurization wastewater concentrate is about 1t / h-2t / h, and the pH value is relatively low (around 1-2). In order to prevent serious corrosion of the subsequent desulfurization wastewater treatment system 100, it is necessary to use an alkaline agent (sodium hydroxide) to adjust the pH to 6-8 before sending it to the drying equipment 9. The desulfurization wastewater concentrate directly enters the drying equipment 9 for treatment.

[0044] For example, when the discharge of desulfurization wastewater is large and the unit load is low (such as when the unit enters the deep peak shaving stage), the waste heat flue gas thickening tower 6 cannot completely concentrate the desulfurization wastewater discharged from the desulfurization tower. In this case, the desulfurization wastewater treatment system 100 automatically starts the electrodialysis equipment 4. After the desulfurization wastewater is reduced in volume, it enters the waste heat flue gas thickening tower 6. After being concentrated again, it enters the drying equipment 9 for solidification treatment. When the chloride ion content in coal increases in winter, in order to maintain the chloride ion concentration in the desulfurization tower slurry, the desulfurization wastewater discharge is 10t / h. At this time, due to the low boiler load and insufficient flue gas volume, the processing capacity of the drying equipment 9 is limited, and it can only process 0.5t / h-1t / h of desulfurization wastewater concentrate. Moreover, due to the small flue gas volume, the flue gas concentration system cannot directly concentrate the desulfurization wastewater from 10t / h to about 0.5t-1t / h. Therefore, it is necessary to start the electrodialysis equipment 4 to concentrate the desulfurization wastewater from 10t / h to 3t / h-4t / h. The clean water produced by the electrodialysis equipment 4 is returned to the clean water to the process water tank 11. The desulfurization wastewater enters the waste heat flue gas concentration tower 6 and is concentrated to about 0.5t / h-1t / h. Finally, after being conditioned by the concentrate conditioning equipment 8, it is sent to the drying equipment 9 for solidification treatment.

[0045] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0046] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0047] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0048] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0049] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for treating desulfurization wastewater, characterized in that, include: Step S1: Obtain the chloride ion concentration and calculate the desulfurization wastewater discharge. Step S2: Obtain the actual indicators of the flue gas and calculate the amount of desulfurization wastewater to be treated; Step S3: Determine whether the desulfurization wastewater has been completely disposed of. If not, proceed to step S4; if yes, proceed to step S5. Step S4: Perform electrodialysis on the desulfurization wastewater; Step S5: Concentrate the desulfurization wastewater; Step S6: Dry the desulfurization wastewater.

2. The desulfurization wastewater treatment method according to claim 1, characterized in that, The chloride ion concentration includes the chloride ion concentration of the desulfurization slurry and the chloride ion concentration of the desulfurization process water.

3. The desulfurization wastewater treatment method according to claim 2, characterized in that, The actual parameters of the flue gas include the flow rate of the electrodialysis flue gas, the temperature of the electrodialysis flue gas, the flow rate of the waste heat flue gas, and the temperature of the waste heat flue gas.

4. A desulfurization wastewater treatment system (100), characterized in that, The desulfurization wastewater treatment method according to any one of claims 1-3 is applied to the desulfurization wastewater treatment system (100), the desulfurization wastewater treatment system (100) comprising: An integrated treatment device (2) is used to treat suspended solids in desulfurization wastewater; An electrodialysis device (4) is connected to the integrated treatment device (2) and is located downstream of the integrated treatment device (2) in the direction of desulfurization wastewater flow. The electrodialysis device (4) is used to pre-concentrate desulfurization wastewater. Waste heat flue gas concentration tower (6) is connected to the integrated treatment equipment (2) and the electrodialysis equipment (4). The waste heat flue gas concentration tower (6) is located downstream of the integrated treatment equipment (2) in the direction of desulfurization wastewater flow and downstream of the electrodialysis equipment (4) in the direction of desulfurization wastewater flow. The waste heat flue gas concentration tower (6) is used to concentrate and treat the flue gas generated by desulfurization wastewater.

5. The desulfurization wastewater treatment system (100) according to claim 4, characterized in that, The integrated treatment equipment (2) includes a reaction unit, a clarification unit and a dosing unit. The reaction unit and the dosing unit are used to add dry powder to the desulfurization wastewater, and the clarification unit is used to precipitate sludge in the desulfurization wastewater.

6. The desulfurization wastewater treatment system (100) according to claim 5, characterized in that, Also includes: A concentrated water conditioning device (8) is connected to the waste heat flue gas thickening tower (6). The concentrated water conditioning device (8) is located downstream of the waste heat flue gas thickening tower (6) in the flow direction of the desulfurization wastewater. The concentrated water conditioning device (8) is used to adjust the pH of the desulfurization wastewater.

7. The desulfurization wastewater treatment system (100) according to claim 6, characterized in that, Also includes: A drying device (9) is connected to the concentrate conditioning device (8). The drying device (9) is located downstream of the concentrate conditioning device (8) in the flow direction of the desulfurization wastewater. The drying device (9) is used to dry the desulfurization wastewater.

8. The desulfurization wastewater treatment system (100) according to claim 7, characterized in that, Also includes: Sludge treatment equipment (10) is connected to the integrated treatment equipment (2) and is used to treat the sludge in the clarification unit.

9. The desulfurization wastewater treatment system (100) according to claim 8, characterized in that, Also includes: A buffer tank (1) is located upstream of the integrated treatment equipment (2). An aeration oxidation blower is installed inside the buffer tank (1) to reduce the chemical oxygen demand of the desulfurization wastewater. A clear water tank (3) is located between the integrated treatment device (2) and the electrodialysis device (4). The clear water tank (3) is used to collect the supernatant in the clarification unit. The water tank (11) is connected to the electrodialysis equipment (4) and is used to collect the supernatant.

10. The desulfurization wastewater treatment system (100) according to claim 9, characterized in that, Also includes: The first concentrated water tank (5) and the second concentrated water tank (7) are located between the electrodialysis equipment (4) and the waste heat flue gas concentration tower (6). The first concentrated water tank (5) is used to collect the electrodialysis concentrate produced by the electrodialysis equipment (4). The second concentrated water tank (7) is located between the waste heat flue gas concentration tower (6) and the concentrated water conditioning equipment (8). The second concentrated water tank (7) is used to collect the concentrated waste liquid produced by the waste heat flue gas concentration tower (6).

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