A system and method for deep coupling of high and low salt water in a coal-fired power plant for deep treatment and reuse of zero discharge

Abstract

The application provides a coal-fired power plant high-low salinity water deep coupling zero-emission deep treatment and recycling method, which comprises the following steps: step 1: sending the fine treatment iron and manganese removal filter backwash water into an industrial wastewater storage tank A, sending the low salinity water of mixed bed regeneration wastewater into an industrial wastewater storage tank B, and sending the high salinity water of mixed bed regeneration wastewater into an industrial wastewater storage tank C for storage; and according to the water quality, the water is recycled in different qualities; step 2: sending into an industrial wastewater treatment system for treatment; step 3: the water of the fine treatment iron and manganese removal filter backwash water and the low salinity water of mixed bed regeneration wastewater after being treated by the industrial wastewater treatment system is collectively referred to as low salinity water, and after being treated by a clean water tank, the low salinity water is pumped into an iron and manganese removal filter by a lifting pump to remove the iron and manganese affecting the operation of a desulfurization system for the second time, and is sent into the desulfurization system for water supplement; and step 4: the high salinity water of the mixed bed regeneration wastewater after being treated by the industrial wastewater treatment system is pumped into a thermal zero-emission system by a lifting pump to realize the treatment of the high salinity water and the recycling of water resources.

Description

Technical Field

[0001] This invention relates to the field of high and low saline water reuse in coal-fired power plants, and more particularly to a system and method for deep coupling of high and low saline water in coal-fired power plants for zero-emission deep treatment and reuse. Background Technology

[0002] Mixed bed regeneration wastewater is generally treated to meet discharge standards, or treated and used as makeup water for desulfurization. However, this also leads to discoloration of gypsum, a byproduct of desulfurization. Furthermore, the entry of high saline water increases the ion content of the desulfurization system, resulting in incomplete sulfur oxidation, affecting desulfurization efficiency, and causing a surge in desulfurization wastewater, among other problems.

[0003] Reverse osmosis can be used as an alternative to zero-discharge for deep treatment of mixed-bed regeneration wastewater, but it requires a separate setup. The typical regeneration cycle for a mixed-bed system is 45 days, which leads to long-term shutdowns of the reverse osmosis system, resulting in significant maintenance challenges.

[0004] In non-zero emission coal-fired power plants, the backwash water from the fine treatment iron and manganese removal filter, the high-salt water and low-salt water from the mixed bed regeneration wastewater are mixed and then treated with conventional industrial wastewater to meet the standards before being discharged. This can basically achieve normal treatment, but it also poses certain environmental risks and wastes a large amount of low-salt water resources (a large amount of demineralized water is required for each regeneration of the mixed bed).

[0005] In zero-emission coal-fired power plants, the backwash water from the iron and manganese removal treatment, the high-salt water from the mixed-bed regeneration wastewater, and the low-salt water are mixed and treated using conventional industrial wastewater treatment methods. All of this is used as makeup water for desulfurization. However, the high- and low-salt water from the backwash water and the mixed-bed regeneration wastewater contain large amounts of iron and manganese ions, causing discoloration of the desulfurization slurry, slightly affecting desulfurization efficiency, and discoloring the byproduct gypsum, impacting its sale. Simultaneously, the high-salt water enters the desulfurization system directly without any treatment, leading to a significant increase in the ion content of the desulfurization slurry. This results in insufficient dissolution of calcium and sulfur dioxide, impairing the desulfurization system's absorption of sulfur dioxide and affecting desulfurization efficiency. Furthermore, since the oxidation of iron and manganese ions requires oxygen, sulfur oxidation is incomplete, affecting gypsum quality. The large influx of ions necessitates increased wastewater discharge from the desulfurization system, leading to a dramatic increase in desulfurization wastewater. Summary of the Invention

[0006] To address the aforementioned problems, this invention discloses a system and method for deep coupling of high and low saline water in coal-fired power plants, achieving zero-discharge deep treatment and reuse. By separating and recycling the backwash water (for iron and manganese removal), the high-salinity wastewater from the mixed-bed regeneration wastewater, and the low-salinity wastewater from the mixed-bed regeneration wastewater, the conventional industrial wastewater treatment system is improved. The backwash water and low-salinity wastewater, after being filtered by an iron and manganese removal filter, are directly reused in the desulfurization system. The high-salinity wastewater from the mixed-bed regeneration wastewater is discharged into an existing desulfurization wastewater treatment facility, thus achieving reuse.

[0007] A method for deep coupling of high and low saline water in coal-fired power plants for zero-emission deep treatment and reuse includes the following steps: Step 1: Modify the drainage pipelines for the backwash water from the fine treatment iron and manganese removal filter, the low-salinity wastewater from the mixed bed regeneration wastewater, and the high-salinity wastewater from the mixed bed regeneration wastewater. Send the backwash water from the fine treatment iron and manganese removal filter to industrial wastewater storage tank A, the low-salinity wastewater from the mixed bed regeneration wastewater to industrial wastewater storage tank B, and the high-salinity wastewater from the mixed bed regeneration wastewater to industrial wastewater storage tank C for storage. Appropriate anti-corrosion measures must be taken for the tank bodies and equipment of the industrial wastewater storage tanks according to the water quality conditions to achieve separate recycling. After the mixed bed regeneration is completed, first drain the water, then fill it with water, and then drain it again. This portion of the water is discharged to the high-salinity industrial wastewater storage tank to minimize the amount of high-salinity water.

[0008] A method for reducing the salinity of low-salinity brine is proposed. After mixed-bed regeneration, the mixed bed is first filled with water, and this water is then discharged into a high-salinity industrial wastewater storage tank. This is done instead of directly flushing with large amounts of water after regeneration. Instead, a portion of the water is sacrificed to allow for thorough mixing with the mixed bed and is discharged as high-salinity brine. Following this, a large-volume flush is performed. The resulting low-salinity brine has a significantly reduced salinity and a near-neutral pH. This reduces the amount of acid and alkali needed for subsequent mixed-bed regeneration of low-salinity brine, saving on reagents. More importantly, it lowers the salt ion content of this water, increasing its reuse value.

[0009] Step 2: The water in industrial wastewater storage tank A, industrial wastewater storage tank B, and industrial wastewater storage tank C is sent to the industrial wastewater treatment system for treatment through the effluent pipes. Step 3: The backwash water from the fine treatment iron and manganese removal filter and the low-salt water from the mixed bed regeneration wastewater are collectively referred to as low-salt water after being treated by the industrial wastewater treatment system. After passing through the clean water tank, the water is pumped into the iron and manganese removal filter for secondary removal of iron and manganese that affect the operation of the desulfurization system, and then sent to the desulfurization system for makeup water. Step 4: The high-salinity wastewater from the mixed bed regeneration process is pumped into the thermal zero-discharge system after industrial wastewater treatment, thus achieving the treatment of high-salinity water and the reuse of water resources.

[0010] Furthermore, the industrial wastewater treatment system process flow is as follows: the effluent pipe is connected to a pH adjustment tank via a water pump; the pH adjustment tank is used to adjust the acid-base balance; the pH adjustment tank is connected to a reaction tank, and the effluent pipe of the reaction tank is connected to a flocculation tank; the flocculation tank is connected to a clarifier, and the outlet of the clarifier is connected to a final neutralization tank and a clean water tank; the final neutralization tank and the clean water tank adopt a rotary overflow design; the volume ratio of the clean water tank to the final neutralization tank is 4:1, and the final neutralization tank is cleaned regularly using a submersible lift pump.

[0011] Furthermore, based on the characteristics of the three types of water, automatic valves are installed at the outlet of each industrial wastewater storage tank, and different dosing methods and retention times are adopted. The retention time is changed by adjusting the manual valve of the booster pump or by using a frequency converter to change the flow rate of the treated water.

[0012] Mixed-bed regeneration of low-salinity water requires only the addition of a small amount of acid or alkali to achieve a pH between 6 and 9, and sometimes no acid or alkali needs to be added to achieve the pH between 6 and 9. Mixed-bed regeneration of low-salinity water involves the largest water volume, requiring a large amount of water for rinsing after each regeneration, hence the high flow rate during each treatment. Although the treatment flow rate is high, the water quality reaching the purification tank is optimal.

[0013] The mixed-bed regeneration high-salinity wastewater consists of two streams of wastewater, one acidic and one alkaline, from the mixed-bed regeneration acid and alkaline wastewater. The industrial wastewater storage tank C is used to achieve maximum acid-base self-balancing. However, self-balancing is generally not achieved during operation, mainly due to metering errors in acid and alkali addition during mixed-bed regeneration and on-site operational errors. A certain amount of acid and alkali must be added to adjust the pH, but the volume is small. It serves as the source of high-salinity wastewater downstream of the booster pump and has no reuse value, requiring thermal zero-discharge treatment.

[0014] The backwash water from the fine treatment process for iron and manganese removal contains a large amount of suspended solids and a certain amount of iron and manganese ions. It must be aerated and oxidized in industrial wastewater storage tank A to convert the iron and manganese ions into suspended solids. In subsequent treatment, a certain amount of flocculant and coagulant aid is added, and the treatment flow rate is reduced to allow for sufficient sedimentation. The pH is generally neutral; only pH monitoring is needed, and a small amount of acid or alkali is added if it exceeds the limit. Incomplete precipitation of iron and manganese ions will cause the gypsum in the desulfurization system to turn red, affecting gypsum sales and slightly reducing desulfurization efficiency.

[0015] Furthermore, a conductivity meter is installed after the booster pump in the clean water tank to determine the salinity of the water. If the salinity is higher than the set value, it is judged as high salinity and treated using a zero-discharge system. Otherwise, it is filtered and reused using an iron and manganese removal filter.

[0016] Furthermore, the conductivity value is generally set at around 20 mS / cm to reduce the proportion of fresh water in the drying system, reduce heat consumption, and save energy.

[0017] Furthermore, the final neutralization tank is cleaned periodically using a submersible lift pump.

[0018] Furthermore, since the backwashing and mixed bed regeneration of the fine treatment iron and manganese removal filter have long cycles, the industrial wastewater treatment equipment needs to be emptied each time the treated water quality is switched between backwashing and mixed bed regeneration. The pH adjustment tank, reaction tank, flocculation tank, clarifier, clean water tank, and final neutralization tank need to be emptied. The emptying method is as follows: the pH adjustment tank, reaction tank, flocculation tank, and clarifier are all equipped with bottom drain valves. The bottom sediment is first discharged to the sludge pit. The sludge is then transported to the sludge treatment room for centralized dewatering, and the upper clean water is discharged back to the original industrial wastewater storage tank.

[0019] A deep-coupled zero-emission deep treatment and reuse system for high and low salinity water in a coal-fired power plant includes an industrial wastewater storage tank A, an industrial wastewater storage tank B, and an industrial wastewater storage tank C. The outlets of industrial wastewater storage tanks A, B, and C are all connected to a main outlet pipe via automatic valves. The main outlet pipe is connected in sequence to a pH adjustment tank, a reaction tank, a flocculation tank, a clarifier, a purified water tank, and a final neutralization tank via a first booster pump. The outlet of the purified water tank is connected to a second booster pump. The outlet of the second booster pump is equipped with a low-salinity water outlet pipe and a high-salinity water outlet pipe, wherein the low-salinity water outlet pipe is connected to an iron and manganese removal filter, and the high-salinity water outlet pipe is connected to a thermal zero-emission system.

[0020] Industrial wastewater storage tanks A, B, and C are used to store backwash water from the iron and manganese removal filter, low-salinity mixed-bed regeneration wastewater, and high-salinity mixed-bed regeneration wastewater, respectively.

[0021] The final neutralization tank and the purification tank adopt a rotary overflow design.

[0022] The beneficial effects of this invention are: 1. It achieves advanced treatment of iron and manganese removal backwash water, high salinity mixed bed regeneration wastewater, and low salinity mixed bed regeneration wastewater, and also recycles water resources.

[0023] 2. It solves a series of problems caused by iron and manganese in the backwash water of fine treatment and the reuse of fine treatment mixed bed reclaimed water in the desulfurization system.

[0024] 3. Coupled with the zero-emission system of coal-fired power plants, it treats and reuses high-salinity wastewater from mixed-bed regeneration, avoiding the adverse effects of high-salinity water on the desulfurization system. Attached Figure Description

[0025] Figure 1 The process flow diagram of this invention.

[0026] List of reference numerals in the attached diagram: 1- Fine treatment of iron and manganese removal filter backwash water; 2- Mixed bed regeneration of low-salinity water; 3- Mixed bed regeneration of high-salinity water; 4- Industrial wastewater storage tank A; 5- Industrial wastewater storage tank B; 6- Industrial wastewater storage tank C; 7- Atmosphere; 8- Roots blower; 9- pH adjustment tank; 10- Reaction tank; 11- Flocculation tank; 12- Clarifier; 13- Final neutralization tank; 14- Clean water tank; 15- Low-salinity water outlet pipe; 16- High-salinity water outlet pipe; 17- Iron and manganese removal filter; 18- Reuse to desulfurization system makeup water; 19- Thermal method zero discharge. Detailed Implementation

[0027] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, and the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0028] like Figure 1 As shown, where Figure 1 The list of intermediate components is as follows:

[0029]

[0030] This embodiment of a method for deep coupling of high and low saline water in a coal-fired power plant to achieve zero-emission deep treatment and reuse includes the following steps: Step 1: Modify the drainage pipelines for the backwash water from the fine treatment iron and manganese removal filter, the low-salinity wastewater from the mixed bed regeneration wastewater, and the high-salinity wastewater from the mixed bed regeneration wastewater. Send the backwash water from the fine treatment iron and manganese removal filter to industrial wastewater storage tank A, the low-salinity wastewater from the mixed bed regeneration wastewater to industrial wastewater storage tank B, and the high-salinity wastewater from the mixed bed regeneration wastewater to industrial wastewater storage tank C for storage. Appropriate anti-corrosion measures must be taken for the tank bodies and equipment of the industrial wastewater storage tanks according to the water quality conditions to achieve separate recycling. After the mixed bed regeneration is completed, first drain the water, then fill it with water, and then drain it again. This portion of the water is discharged to the high-salinity industrial wastewater storage tank to minimize the amount of high-salinity water.

[0031] Because the backwashing and mixed bed regeneration of the fine treatment iron and manganese removal filter have long cycles, the industrial wastewater treatment equipment needs to be emptied each time the treated water quality is switched between backwashing and mixed bed regeneration. The pH adjustment tank, reaction tank, flocculation tank, clarifier, clean water tank, and final neutralization tank need to be emptied. The emptying method is as follows: the pH adjustment tank, reaction tank, flocculation tank, and clarifier are all equipped with bottom drain valves. The bottom sediment is first discharged to the sludge pit. The sludge is then transported to the sludge treatment room for centralized dewatering. The upper clean water is discharged back to the original industrial wastewater storage tank. The final neutralization tank is cleaned regularly using a submersible lift pump.

[0032] Step 2: Water from industrial wastewater storage tanks A, B, and C is sent to the industrial wastewater treatment system through effluent pipes for treatment. The process flow of the industrial wastewater treatment system is as follows: the effluent pipe is connected to a pH adjustment tank via a water pump; the pH adjustment tank is used to adjust the acid-base balance; the pH adjustment tank is connected to a reaction tank, and the effluent pipe of the reaction tank is connected to a flocculation tank; the flocculation tank is connected to a clarifier, and the outlet of the clarifier is connected to a final neutralization tank and a purified water tank; the final neutralization tank and the purified water tank adopt a rotary overflow design; the volume ratio of the purified water tank to the final neutralization tank is 4:1; according to the characteristics of the three water qualities, an automatic valve is installed at the outlet of each industrial wastewater storage tank, using different dosing methods and residence times; (the residence time is adjusted by the lift pump through its manual valve or by the lift pump through frequency conversion to change the treated water flow rate.) A conductivity meter is installed after the booster pump in the clean water tank to determine the salt content in the water. If the concentration is higher than the set value, it is judged as high salinity and treated using a zero-discharge system. Otherwise, it is filtered and reused using an iron and manganese removal filter. The conductivity value is set at 20 mS / cm.

[0033] Step 3: The backwash water from the fine treatment iron and manganese removal filter and the low-salt water from the mixed bed regeneration wastewater are collectively referred to as low-salt water after being treated by the industrial wastewater treatment system. After passing through the clean water tank, the water is pumped into the iron and manganese removal filter for secondary removal of iron and manganese that affect the operation of the desulfurization system, and then sent to the desulfurization system for makeup water. Step 4: The high-salinity wastewater from the mixed bed regeneration process is pumped into the thermal zero-discharge system after industrial wastewater treatment, thus achieving the treatment of high-salinity water and the reuse of water resources.

[0034] A deep treatment and reuse system for high and low saline water in a mixed-bed regeneration system for coal-fired power plants includes an industrial wastewater storage tank A4, an industrial wastewater storage tank B5, and an industrial wastewater storage tank C6. The industrial wastewater storage tanks A4, B5, and C6 are respectively used to store backwash water 1 from the fine treatment iron and manganese removal filter, low saline water 2 from the mixed-bed regeneration system, and high saline water 3 from the mixed-bed regeneration system.

[0035] The outlets of industrial wastewater storage tanks A4, B5, and C6 are all connected to a main outlet pipe via automatic valves. The main outlet pipe is connected in sequence to pH adjustment tank 9, reaction tank 10, flocculation tank 11, clarifier 12, final neutralization tank 13, and clean water tank 14 via a booster pump 1. The outlet of clean water tank 14 is connected to booster pump 2. The outlet of booster pump 2 is equipped with a low-salinity water outlet pipe 15 and a high-salinity water outlet pipe 16. The low-salinity water outlet pipe 15 is connected to the iron and manganese removal filter 17, and the high-salinity water outlet pipe 16 is connected to the thermal zero-discharge system 19.

[0036] In this embodiment, the backwash water from the finely treated iron and manganese removal filter is typically backwashed every 45 days. Its ion content is low, around 0.1 mS / cm in the Yangtze River region. The mixed bed is generally regenerated using an acid concentration controlled at 4-5% and an alkali concentration controlled at 3-4%. After regeneration, the wastewater is discharged, followed by a large volume of water for rinsing. The wastewater discharged after regeneration and the initial rinse water (3-10 minutes) are defined as high-salinity mixed bed regeneration wastewater, with a conductivity exceeding 100 mS / cm. The subsequent large-volume rinsing is low-salinity mixed bed regeneration wastewater, with a conductivity generally around 1-5 mS / cm after mixing.

[0037] List of main equipment for zero-emission (low-temperature flash concentration + evaporation drying) construction and industrial wastewater upgrading of a coal-fired power plant:

[0038]

[0039]

[0040]

[0041]

[0042] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A method for deep coupling of high and low saline water in coal-fired power plants, characterized in that: Includes the following steps: Step 1: Modify the drainage pipelines for the backwash water from the fine treatment iron and manganese removal filter, the low-salinity wastewater from the mixed bed regeneration wastewater, and the high-salinity wastewater from the mixed bed regeneration wastewater. Send the backwash water from the fine treatment iron and manganese removal filter to industrial wastewater storage tank A, the low-salinity wastewater from the mixed bed regeneration wastewater to industrial wastewater storage tank B, and the high-salinity wastewater from the mixed bed regeneration wastewater to industrial wastewater storage tank C for storage. Appropriate anti-corrosion measures must be taken for the tank bodies and equipment of the industrial wastewater storage tanks according to the water quality conditions to achieve separate recycling. Step 2: The water in industrial wastewater storage tank A, industrial wastewater storage tank B, and industrial wastewater storage tank C is sent to the industrial wastewater treatment system for treatment through the effluent pipes. Step 3: The backwash water from the fine treatment iron and manganese removal filter and the low-salt water from the mixed bed regeneration wastewater are collectively referred to as low-salt water after being treated by the industrial wastewater treatment system. After passing through the clean water tank, the water enters the iron and manganese removal filter for a second time to remove the iron and manganese that affect the operation of the desulfurization system, and is then sent to the desulfurization system for makeup water. Step 4: The high-salinity wastewater from the mixed-bed regeneration process passes through the industrial wastewater treatment system. After treatment, the high-salinity water is sent to the thermal zero-discharge system via a second booster pump after passing through a clean water tank, thus achieving the treatment of high-salinity water and the reuse of water resources. The process flow of the industrial wastewater treatment system is as follows: the effluent pipe is connected to the pH adjustment tank via the first booster pump; the pH adjustment tank is used to adjust the acid-base balance; the pH adjustment tank is connected to the reaction tank, and the effluent pipe of the reaction tank is connected to the flocculation tank; the flocculation tank is connected to the clarifier, and the outlet of the clarifier is connected to the final neutralization tank and the clean water tank; the final neutralization tank and the clean water tank adopt a rotary overflow design; the volume ratio of the clean water tank and the final neutralization tank is 4:1; the outlet of the clean water tank (14) is connected to the second booster pump; the outlet of the second booster pump is equipped with a low-salinity water outlet pipe (15) and a high-salinity water outlet pipe (16), wherein the low-salinity water outlet pipe (15) Connect to the iron and manganese removal filter (17); connect the high saline water outlet pipe (16) to the thermal zero discharge system (19); install a conductivity meter after the clean water tank lift pump, use the conductivity meter to determine the salt content in the water, when it is higher than the set value, it is judged as high saline water, and the zero discharge system is used for disposal, otherwise it is filtered by the iron and manganese removal filter and reused; since the backwashing and mixed bed regeneration of the fine treatment iron and manganese removal filter are both long, the industrial wastewater treatment equipment needs to be emptied each time the treatment water quality filter backwashes and mixed bed regeneration water is switched; empty the pH adjustment tank, reaction tank, flocculation tank, clarifier, clean water tank and final neutralization tank. Emptying method: the pH adjustment tank, reaction tank, flocculation tank and clarifier are all equipped with bottom drain valves. First, discharge the bottom sediment to the sludge pit. The sludge will be transported to the sludge treatment room for centralized dewatering. The upper clear water is discharged back to the original industrial wastewater storage tank.

2. The method for deep coupling of high and low saline water in a coal-fired power plant with zero-emission deep treatment and reuse according to claim 1, characterized in that: Based on the characteristics of the three types of water, automatic valves are installed at the outlet of each industrial wastewater storage tank, and different dosing methods and retention times are adopted. The retention time is changed by adjusting the manual valve of the booster pump or by using the frequency converter of the booster pump to change the flow rate of the treated water.

3. The method for deep coupling of high and low saline water in a coal-fired power plant with zero-emission deep treatment and reuse according to claim 1, characterized in that: The setting is set at 20ms / cm.

4. The method for deep coupling of high and low saline water in a coal-fired power plant for zero-emission deep treatment and reuse according to claim 1, characterized in that: The final neutralization tank is cleaned periodically using a submersible lift pump.

5. A deep-coupling zero-emission deep treatment and reuse system for high and low saline water in a coal-fired power plant for implementing the method of claim 1, characterized in that: The system includes industrial wastewater storage tank A (4), industrial wastewater storage tank B (5), and industrial wastewater storage tank C (6); the outlets of industrial wastewater storage tank A (4), industrial wastewater storage tank B (5), and industrial wastewater storage tank C (6) are all connected to the main outlet pipe through automatic valves. The main outlet pipe is connected to the pH adjustment tank (9), reaction tank (10), flocculation tank (11), clarifier (12), final neutralization tank (13), and clean water tank (14) in sequence through a booster pump one; the outlet of clean water tank (14) is connected to booster pump two; the outlet of booster pump two is equipped with a low-salinity water outlet pipe (15) and a high-salinity water outlet pipe (16), wherein the low-salinity water outlet pipe (15) is connected to the iron and manganese removal filter (17); and the high-salinity water outlet pipe (16) is connected to the thermal zero-discharge system (19).

6. The zero-emission deep treatment and reuse system for high and low saline water in a coal-fired power plant according to claim 5, characterized in that: Industrial wastewater storage tank A (4), industrial wastewater storage tank B (5) and industrial wastewater storage tank C (6) are used to store backwash water (1) from the fine treatment iron and manganese removal filter, low saline water (2) from mixed bed regeneration wastewater and high saline water (3) from mixed bed regeneration wastewater, respectively.

7. A deep-coupled zero-emission deep treatment and reuse system for high and low saline water in a coal-fired power plant according to claim 5, characterized in that: The final neutralization pool (13) and the purification pool (14) adopt a rotary overflow design.

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