Two-point dosing method for circulating water treatment of thermal power plant

Abstract

The invention relates to the technical field of thermal power plant water treatment, and discloses a thermal power plant circulating water treatment two-point chemical adding method which comprises the following steps: determining a chemical adding position; selecting a medicament adding position a and a medicament adding position b, selecting a pipeline for connecting a lifting pump and a mechanical acceleration clarification tank in the circulating water treatment system as the position a, and selecting a pipeline for connecting the mechanical acceleration clarification tank and a variable-porosity filter tank as the position b; determining an added medicament; adding a coagulant to the position a, and adding a bactericide and sulfuric acid to the position b; determining the dosing method of the medicament; the method comprises the following steps: initially operating a circulating water treatment system, adding a coagulant, a bactericide and sulfuric acid once for the first time, continuously operating the circulating water treatment system, and determining the daily adding times of the coagulant, the bactericide and the sulfuric acid according to the water temperature; determining the dosage of the medicament; the method has the advantages that the treatment effect is good, the medicament reaction is sufficient, and the treatment time is shortened.

Description

Technical Field

[0001] The invention relates to a two-point dosing method for circulating water treatment in a thermal power plant, belonging to the technical field of water treatment in thermal power plants. Background Art

[0002] The circulating water system of a thermal power plant is mainly responsible for the task of water supply, and it is an important "blood" for the normal operation of thermal power units. The main function of the circulating water system of a thermal power plant is to cool the exhaust steam of the steam turbine, maintain the normal temperature of the power generation equipment, and ensure the safe and stable operation of the unit. The common circulating water system of a thermal power plant has the characteristics of large water volume and long operation time, and can perform the corresponding cooling work well, but it has more impurities after cooling, which makes the water quality of the circulating water very unstable and needs to be treated. At present, the problems faced by circulating water treatment include high concentration ratio, high chloride ion concentration and high carbonate hardness.

[0003] To solve this problem, lime treatment, anti-scaling treatment and weak acid ion exchange methods have emerged in the prior art. The lime treatment method mainly adjusts the pH value of water by adding lime (calcium hydroxide) to water, while promoting the precipitation and removal of soluble substances. Lime reacts with bicarbonate ions in water to produce insoluble calcium carbonate, thereby purifying the water quality. The anti-scaling treatment method inhibits the precipitation and scaling of dissolved minerals in water by adding chemical agents (such as polymers, phosphates, organic acids, etc.), mainly to prevent the precipitation of calcium, magnesium and other ions in the circulating water system. The weak acid ion exchange method uses weak acid resins (for example, polystyrene sulfonic acid resins) to remove cations (such as calcium, magnesium, etc.) in water, so that they are replaced by hydrogen ions released by weak acids in the resin, thereby softening the water.

[0004] The above methods do not restrict the method of adding the reagents in actual use. The common method of adding the reagents is to directly put the reagents into the corresponding reaction tank or treatment tank for reaction. The water flow in the reaction tank or treatment tank is generally slow, which may lead to incomplete reaction between the reagent and water and a long reaction time. At the same time, the common method of adding the reagents is to add a fixed amount at a fixed period, which is not combined with the actual water conditions and should be improved. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a two-point dosing method for circulating water treatment in a thermal power plant.

[0006] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a circulating water treatment system for a thermal power plant, comprising a circulating water tank, a circulating water regulating tank, a lifting pump, a mechanical accelerated clarification tank, a variable pore filter, a clear water tank, a circulating water make-up pump, a lime system, a sludge treatment system and an online monitoring system, wherein the circulating water tank is respectively connected to the circulating water regulating tank and the lifting pump by pipelines, the circulating water regulating tank is connected to the lifting pump by pipeline, the lifting pump is connected to the mechanical accelerated clarification tank by pipeline, the mechanical accelerated clarification tank is connected to the variable pore filter by pipeline, the variable pore filter is connected to the clear water tank by pipeline, the clear water tank is connected to the circulating water make-up pump by pipeline, the circulating water make-up pump is used to input the circulating water in the clear water tank into the circulating water system of the thermal power plant for corresponding cooling work, and the circulating water after completing the corresponding cooling work will enter the circulating water tank from the circulating water system of the thermal power plant for collection, and the mechanical accelerated clarification tank is also respectively connected to the lime system and the sludge treatment system by pipelines.

[0007] The circulating water tank is used to store circulating water that needs to be treated.

[0008] The circulating water regulating tank is used to remove large particle impurities in the circulating water. The specific process is that the circulating water enters the circulating water regulating tank, and the large particle impurities and suspended matter in the water are removed through natural sedimentation and physical separation.

[0009] The lifting pump is used to lift and transport the circulating water that needs to be treated.

[0010] Mechanical accelerated clarification tanks are used to remove turbidity, hardness, alkalinity and chemical oxygen demand (COD) in water. The specific process is to add corresponding chemical agents into the mechanical accelerated clarification tank to form flocs. Mechanical stirring (commonly used stirring rods, etc.) can accelerate the formation and precipitation of flocs. After that, the flocs are precipitated in the mechanical accelerated clarification tank, the supernatant enters the subsequent treatment steps, and the precipitate enters the sludge treatment system for treatment.

[0011] The variable pore filter is used to remove most of the suspended matter in the circulating water, reduce the carbonate hardness, and increase the concentration rate of the circulating water. The specific process is that the circulating water passes through the variable pore filter, and the filter material in the filter (such as quartz sand) can effectively remove the suspended matter and some soluble impurities. When the variable pore filter is in use, it should be backwashed regularly to remove the impurities in the variable pore filter and restore the filtering capacity of the variable pore filter.

[0012] The clean water tank is used to store recycled water that can be used after treatment.

[0013] The circulating water make-up pump is used to lift and transport the treated circulating water so that the treated circulating water can be input into the circulating water system of the thermal power plant for make-up.

[0014] The lime system is used to produce lime milk. The lime system can be composed of a lime silo, a metering hopper, a preparation box, a conveying pump, a sand catcher, a metering box and a metering pump. A cone hopper is set at the bottom of the lime silo. The cone hopper is set in an eccentric shape. The eccentric shape of the cone hopper is conducive to the output of powdered granular materials. The output powdered granular materials can enter the metering hopper. The metering hopper is used to measure the amount of lime required for preparing lime milk. The powdered granular materials measured by the metering hopper can enter the preparation box. The preparation box can prepare the powdered granular materials into lime milk and input the lime milk into the metering box. The metering pump is connected to the metering box by a pipeline. The metering box and the metering pump are used to control the amount of lime milk added to the mechanical accelerated clarifier. A cyclone sand catcher can also be added so that the sand and gravel in the lime milk can be intercepted by the cyclone sand catcher by impurities to prevent the lime system from being blocked. The lime system can realize automatic control of the preparation, dosing and transportation of lime milk, which can greatly save human resources.

[0015] The sludge treatment system is used to treat the sediment in the mechanical accelerated clarifier. The sludge treatment system can be composed of a sludge delivery pump and a plate and frame filter press. The sludge delivery pump delivers the sediment in the mechanical accelerated clarifier to the plate and frame filter press for dehydration. The dehydrated sludge is regularly transported to the outdoors by car, which enables the sludge to be dehydrated in the bypass, without affecting the operation of the circulating water treatment system of the thermal power plant, and maintaining the continuous online treatment of the circulating water.

[0016] The online monitoring system is used to monitor various parameters of circulating water in the circulating water treatment system of thermal power plants in real time. It is composed of various sensors installed in the circulating water treatment system of thermal power plants, such as pH sensors, water temperature sensors, turbidity sensors, etc.

[0017] In a second aspect, the present invention further provides a two-point dosing method for circulating water treatment in a thermal power plant, comprising the following steps: Step 1: Determine the location for adding the reagent; select the reagent addition location a and location b. Location a is selected as the pipeline connecting the lifting pump and the mechanical accelerated clarifier in the circulating water treatment system, and location b is selected as the pipeline connecting the mechanical accelerated clarifier and the variable pore filter.

[0018] Step 2: Determine the reagents to be added; add a coagulant to point a, the coagulant may be polyaluminium chloride, and add a bactericide and sulfuric acid to point b, the bactericide may be sodium hypochlorite.

[0019] Step 3: Determine the method of adding the agent; the circulating water treatment system is initially operated, and the first addition is carried out. Coagulant, bactericide and sulfuric acid are all added once, and the treatment effect is observed in combination with the water quality parameters monitored by the online monitoring system. The circulating water treatment system is in continuous operation. When the water temperature is lower than 15°C, this is a low temperature environment, which will cause the affinity between particles in the circulating water to weaken. Therefore, coagulant is added 2 to 3 times a day. Low temperature will reduce bacterial activity and make sulfuric acid more stable. Therefore, bactericide is added once a day or every other day, and sulfuric acid is added once a day. When the water temperature is between 15 and 25°C, this is a medium temperature environment. The affinity between particles in the circulating water gradually increases. Therefore, coagulant is added 1 to 2 times a day. Medium temperature will gradually activate bacterial activity and make sulfuric acid tend to be unstable. Therefore, bactericide is added once a day, and sulfuric acid is added 1 to 2 times a day. When the water temperature is above 25°C, it is a high temperature environment. The affinity between particles in the circulating water is sufficient. Therefore, coagulant is added once a day. The high temperature environment will make bacteria very active and make sulfuric acid unstable. Therefore, fungicide is added 2 to 5 times a day and sulfuric acid is added 2 to 4 times a day.

[0020] Step 4: Determine the dosage of the reagent; the single dosage of coagulant is 10-50 mg per unit water volume L (calculated as aluminum ions), the single dosage of fungicide is 2-10 mg per unit water volume L (calculated as chloride ions), and the single dosage of sulfuric acid is 10-50 mg per unit water volume L (calculated as hydrogen ions). Furthermore, when the coagulant is added, a method of continuous addition is adopted every day, and the amount added each time is 5 to 20% of the total amount of the coagulant added at a single time.

[0021] Furthermore, when the fungicide is added, a method of continuous addition is adopted every day, and the amount added each time is 1 to 5% of the total amount of the fungicide added at a single time.

[0022] Furthermore, when sulfuric acid is added, a method of continuous addition is adopted every day, and the amount added each time is 1 to 3% of the total amount of sulfuric acid added at a single time.

[0023] Coagulant, lime milk and sodium carbonate may also be added to the mechanical accelerated clarification tank, and the coagulant may be polyacrylamide PAM.

[0024] Furthermore, when the coagulant is added, it is added continuously every day. When the water temperature is higher than 30°C, it is a high temperature environment. At high temperatures, the formation rate of flocs is accelerated. Therefore, the amount of coagulant added on the same day is 0.03-0.15 mg / L (in terms of effective ingredients) per unit water volume L. When the water temperature is lower than 30°C, it is a low temperature environment. At low temperatures, the formation rate of flocs is slowed down. Therefore, the amount of coagulant added on the same day is 0.1-0.3 mg / L (in terms of effective ingredients) per unit water volume L.

[0025] Furthermore, when lime milk is added, it is added continuously every day. When the water temperature is higher than 30°C, it is a high temperature environment. At high temperature, the formation rate of flocs is accelerated. Therefore, the amount of lime milk added on the day is 5-30 mg / L (in terms of hydroxide ions) per unit water volume L. When the water temperature is lower than 30°C, it is a low temperature environment. At low temperature, the formation rate of flocs is slowed down. Therefore, the amount of lime milk added on the day is 20-70 mg / L (in terms of hydroxide ions) per unit water volume L.

[0026] Furthermore, when sodium carbonate is added, an uninterrupted and continuous addition method is adopted every day. When the water temperature is higher than 30°C, this is a high temperature environment. At high temperature, the formation rate of flocs is accelerated. Therefore, the daily addition amount of sodium carbonate is 5-30 mg / L (in terms of carbonate ions) per unit water volume L. When the water temperature is lower than 30°C, this is a low temperature environment. At low temperature, the formation rate of flocs is slowed down. Therefore, the daily addition amount of sodium carbonate is 20-50 mg / L (in terms of carbonate ions) per unit water volume L.

[0027] When the aforementioned thermal power plant circulating water treatment system combines the aforementioned two-point dosing method to treat the circulating water, the lifting pump inputs the water to be treated in the circulating water pool into the circulating water regulating pool for primary treatment to remove large particle impurities in the circulating water. After the treatment is completed, the lifting pump pumps the circulating water into the mechanical accelerated clarification tank. When there is a shortage of circulating water in the circulating water system of the thermal power plant, the lifting pump can also directly pump the water to be treated in the circulating water pool into the mechanical accelerated clarification tank. When the circulating water is about to enter the mechanical accelerated clarification tank, a coagulant is added to position a. The coagulant helps to form flocs in the circulating water, so that the circulating water can be initially precipitated before entering the mechanical accelerated clarification tank, thereby shortening the required reaction time. After the circulating water enters the mechanical accelerated clarification tank, lime milk is added to the mechanical accelerated clarification tank through the lime system, and a coagulant and sodium carbonate are added. The coagulant can enhance the effect of the coagulant and promote the rapid sedimentation and flocculation of suspended particles in the circulating water. The lime milk and sodium carbonate can adjust the alkalinity of the circulating water and increase its pH value to accelerate the formation of flocs. The flocs generated in the mechanical accelerated clarifier enter the sludge treatment system for treatment, and the supernatant will enter the variable pore filter under the action of the lifting pump. When the supernatant is about to enter the variable pore filter, bactericide and sulfuric acid are added to position b. The bactericide can remove bacteria, fungi and algae in the supernatant, and sulfuric acid can adjust the acidity of the supernatant, reduce its pH value, and restore it to a neutral liquid to avoid damage to the pipeline system. The variable pore filter can remove most of the suspended matter in the supernatant, reduce the carbonate hardness, and increase the concentration rate of the supernatant. After the treatment is completed, the treated water will enter the clear water tank for collection, and will be input into the circulating water system of the thermal power plant for replenishment under the action of the circulating water replenishment pump.

[0028] The present invention has the following beneficial effects: 1. The present invention proposes a two-point dosing method, by setting the corresponding number of dosing and the appropriate dosage of the agent at different water temperatures, so as to ensure the treatment effect of the agent on the circulating water, and adopts the two-point dosing method, the dosing positions of the coagulant, the bactericide and the sulfuric acid are selected as position a and position b, and both position a and position b are areas with strong water flow, so that the agent and the circulating water can be fully contacted and mixed, so as to be able to fully react, which can not only improve the reaction efficiency of the added agent, reduce the dosage of the agent and the required reaction time, but also can well prevent the occurrence of scaling. Compared with the prior art, it has the advantages of good treatment effect, sufficient agent reaction and shortened treatment time.

[0029] 2. The present invention realizes the efficient utilization of circulating water. The circulating water completes the initial sedimentation in the circulating water regulating tank to remove large impurity particles; in the mechanical accelerated clarification tank, under the action of chemical agents and equipment operation, the floccules are gradually aggregated and precipitated, and the turbidity, hardness, alkalinity and chemical oxygen demand (COD) of the water are reduced by adjusting the pH. Then, the supersaturated alkalinity is adjusted by sulfuric acid and bactericide to remove bacteria, fungi and algae in the water, and then most of the suspended matter in the water is removed by the variable pore filter, so as to reduce the carbonate hardness and improve the concentration rate of circulating water; reduce the salt content, especially the chloride ion content, and reduce the corrosiveness of circulating water; reduce the suspended matter content and reduce the thermal resistance value of dirt; after the purification of the circulating water is completed, it can be transported back to the circulating water system of the thermal power plant to achieve efficient utilization of water resources.

[0030] 3. The sludge treatment system of the present invention can treat the sludge (floc) in the mechanical accelerated clarifier. The sludge is pumped out of the mechanical accelerated clarifier by a sludge delivery pump and sent to a plate and frame filter press for dehydration. The sludge is regularly transported to the outdoors by car. This ensures that the normal operation of the circulating water treatment system of the thermal power plant is not affected when the sludge is dehydrated in the bypass, thereby maintaining continuous online treatment of the circulating water.

[0031] 4. The lime system of the present invention can realize the mechanized preparation and addition of lime slurry when in use, thereby reducing the labor intensity of workers and greatly saving human resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the circulating water treatment system in the present invention.

[0033] The reference numerals in the figure are as follows: 1. Circulating water tank; 2. Circulating water regulating tank; 3. Lifting pump; 4. Mechanical accelerated clarification tank; 5. Variable pore filter; 6. Clear water tank; 7. Circulating water make-up pump; 8. Lime system; 9. Sludge treatment system; 10. Online monitoring system. DETAILED DESCRIPTION

[0034] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] Example: Please refer to Figure 1The present embodiment provides a circulating water treatment system for a thermal power plant, comprising a circulating water tank 1, a circulating water regulating tank 2, a lifting pump 3, a mechanical accelerated clarifier 4, a variable pore filter 5, a clean water tank 6, a circulating water replenishment pump 7, a lime system 8, a sludge treatment system 9 and an online monitoring system 10. The circulating water tank 1 is connected to the circulating water regulating tank 2 and the lifting pump 3 by pipelines, the circulating water regulating tank 2 is connected to the lifting pump 3 by pipelines, the lifting pump 3 is connected to the mechanical accelerated clarifier 4 by pipelines, the mechanical accelerated clarifier 4 is connected to the variable pore filter 5 by pipelines, the variable pore filter 5 is connected to the clean water tank 6 by pipelines, and the clean water tank 6 is connected to the variable pore filter 5 by pipelines. The water tank 6 is connected to the circulating water make-up pump 7 by a pipeline. The circulating water make-up pump 7 is used to input the circulating water in the clear water tank 6 into the circulating water system of the thermal power plant for corresponding cooling work. After completing the corresponding cooling work, the circulating water will enter the circulating water tank 1 from the circulating water system of the thermal power plant for collection. The mechanical acceleration clarification tank 4 is also connected to the lime system 8 and the sludge treatment system 9 by pipelines respectively. The online monitoring system 10 is composed of various sensors installed in the circulating water treatment system of the thermal power plant. The online monitoring system 10 is used to monitor various parameters of the circulating water in the circulating water treatment system of the thermal power plant in real time.

[0036] This embodiment also provides a two-point dosing method for circulating water treatment in a thermal power plant, comprising the following steps: Step 1: Determine the position for adding the reagent; select the reagent adding position a and position b, position a is selected as the pipeline connecting the lifting pump 3 and the mechanical accelerated clarification tank 4 in the circulating water treatment system, and position b is selected as the pipeline connecting the mechanical accelerated clarification tank 4 and the variable pore filter 5.

[0037] Step 2: Determine the reagents to be added; add a coagulant to point a, the coagulant may be polyaluminium chloride, and add a bactericide and sulfuric acid to point b, the bactericide may be sodium hypochlorite.

[0038] Step 3: Determine the method of adding chemicals; when the circulating water treatment system is initially put into operation, the first addition is carried out, and the coagulant, bactericide and sulfuric acid are all added once. When the circulating water treatment system is continuously operated, when the water temperature is below 15°C, the coagulant is added 2 to 3 times a day, the bactericide is added once a day or every other day, and the sulfuric acid is added once a day. When the water temperature is between 15 and 25°C, the coagulant is added 1 to 2 times a day, the bactericide is added once a day, and the sulfuric acid is added 1 to 2 times a day. When the water temperature is above 25°C, the coagulant is added once a day, the bactericide is added 2 to 5 times a day, and the sulfuric acid is added 2 to 4 times a day.

[0039] Step 4: Determine the dosage of the reagent; the single dosage of coagulant is 10-50 mg per unit of water L (calculated as aluminum ion), the single dosage of fungicide is 2-10 mg per unit of water L (calculated as chloride ion), and the single dosage of sulfuric acid is 10-50 mg per unit of water L (calculated as hydrogen ion). When the coagulant is added, it is added continuously every day, and the amount added each time is 5 to 20% of the total amount of the coagulant added at a single time.

[0040] When adding the fungicide, it is added continuously every day, and the amount added each time is 1 to 5% of the total amount of the fungicide added at a single time.

[0041] When sulfuric acid is added, it is added continuously every day, and the amount added each time is 1 to 3% of the total amount of sulfuric acid added at a single time.

[0042] A coagulant, lime milk and sodium carbonate are also added to the mechanical accelerated clarification tank 4. The coagulant may be polyacrylamide PAM.

[0043] When adding the coagulant, adopt the method of uninterrupted continuous addition every day. When the water temperature is higher than 30℃, the daily dosage of the coagulant is 0.03-0.15 mg / L (calculated as active ingredient) per unit water volume L. When the water temperature is lower than 30℃, the daily dosage of the coagulant is 0.1-0.3 mg / L (calculated as active ingredient) per unit water volume L.

[0044] When adding lime milk, adopt the method of uninterrupted continuous addition every day. When the water temperature is higher than 30℃, the amount of lime milk added on the same day is 5-30 mg / L (calculated as hydroxide ions) per unit water volume L. When the water temperature is lower than 30℃, the amount of lime milk added on the same day is 20-70 mg / L (calculated as hydroxide ions) per unit water volume L.

[0045] When sodium carbonate is added, the method of uninterrupted continuous addition is adopted every day. When the water temperature is higher than 30°C, the daily dosage of sodium carbonate is 5-30 mg / L (calculated as carbonate ions) per unit water volume L. When the water temperature is lower than 30°C, the daily dosage of sodium carbonate is 20-50 mg / L (calculated as carbonate ions) per unit water volume L.

[0046] Taking the treatment of 10 tons of water per hour as an example, the above-mentioned thermal power plant circulating water treatment system combined with the above-mentioned two-point dosing method was used as the experimental group, and the common lime treatment method, scale inhibition treatment method and weak acid ion exchange method were used as the comparison group to obtain the following values, as shown in Tables 1 and 2.

[0047] Table 1

[0048] Table 2

[0049] The water quality parameters and required treatment time of the circulating water after treatment of experimental groups 1 to 3 and comparative groups 1 to 3 were integrated to obtain the following values, as shown in Table 3. The water quality parameters of the circulating water before treatment were: pH 7, hardness (mg / L) 300, turbidity (NTU) 10, and COD (mg / L) 200.

[0050] Table 3

[0051] As can be seen from Table 3, the two-point dosing method provided in this embodiment requires a shorter treatment time when used. Compared with the traditional lime treatment method, it will not increase the pH value of the water body to avoid the occurrence of metal corrosion of the pipeline system caused by excessively high pH value. At the same time, the two-point dosing method provided in this embodiment can also effectively treat the hardness, turbidity and chemical oxygen demand (COD) of the circulating water, and the treatment effect is better than the traditional lime treatment method, scale inhibition treatment method and weak acid ion exchange method. This method has been used in the circulating water system of our company's thermal power plant.

[0052] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A two-point dosing method for circulating water treatment in a thermal power plant, characterized in that: The following steps are involved: Step A1: Determine the position for adding reagents; select positions a and b for adding reagents, position a is selected as the pipeline connecting the lifting pump and the mechanical accelerated clarifier in the circulating water treatment system, and position b is selected as the pipeline connecting the mechanical accelerated clarifier and the variable pore filter; Step A2: Determine the reagents to be added; add coagulant to position a, and add fungicide and sulfuric acid to position b; Step A3: Determine the method for adding reagents; the circulating water treatment system is initially operated, and the first addition is carried out, and the mixing Coagulant, fungicide and sulfuric acid are added once. The circulating water treatment system operates continuously. When the water temperature is below 15°C, coagulant is added 2 to 3 times a day, fungicide is added once a day or every other day, and sulfuric acid is added once a day. When the water temperature is between 15 and 25°C, coagulant is added 1 to 2 times a day, fungicide is added once a day, and sulfuric acid is added 1 to 2 times a day. When the water temperature is above 25°C, coagulant is added once a day, fungicide is added 2 to 5 times a day, and sulfuric acid is added 2 to 4 times a day. Step A4: Determine the dosage of the reagent; the single dosage of the coagulant is 10-50 mg per unit of water L, the single dosage of the bactericide is 2-10 mg per unit of water L, and the single dosage of sulfuric acid is 10-50 mg per unit of water L.

2. A two-point dosing method for circulating water treatment in a thermal power plant according to claim 1, characterized in that: When the coagulant is added, a method of continuous and uninterrupted addition is adopted every day, and the amount added each time is 5-20% of the total amount of the coagulant added at a single time.

3. A two-point dosing method for circulating water treatment in a thermal power plant according to claim 1, characterized in that: When the bactericide is added, a method of continuous and uninterrupted addition is adopted every day, and the amount added each time is 1 to 5% of the total amount of the bactericide added at a single time.

4. A two-point dosing method for circulating water treatment in a thermal power plant according to claim 1, characterized in that: When the sulfuric acid is added, a method of continuous addition is adopted every day, and the amount added each time is 1-3% of the total amount of sulfuric acid added at a single time.

5. A two-point dosing method for circulating water treatment in a thermal power plant according to claim 1, characterized in that: A coagulant, lime milk and sodium carbonate are also added to the mechanical accelerated clarification tank.

6. A two-point dosing method for circulating water treatment in a thermal power plant according to claim 5, characterized in that: When the coagulant is added, it is added continuously every day. When the water temperature is higher than 30°C, the daily dosage of the coagulant is 0.03-0.15 mg / L per unit water volume L. When the water temperature is lower than 30°C, the daily dosage of the coagulant is 0.1-0.3 mg / L per unit water volume L.

7. A two-point dosing method for circulating water treatment in a thermal power plant according to claim 5, characterized in that: When the lime milk is added, a method of uninterrupted continuous addition is adopted every day. When the water temperature is higher than 30°C, the amount of lime milk added on the same day is 5-30 mg / L per unit water volume L. When the water temperature is lower than 30°C, the amount of lime milk added on the same day is 20-70 mg / L per unit water volume L.

8. A two-point dosing method for circulating water treatment in a thermal power plant according to claim 5, characterized in that: When the sodium carbonate is added, a method of uninterrupted continuous addition is adopted every day. When the water temperature is higher than 30°C, the daily addition amount of sodium carbonate is 5-30 mg / L per unit water volume L. When the water temperature is lower than 30°C, the daily addition amount of sodium carbonate is 20-50 mg / L per unit water volume L.

9. A two-point dosing method for circulating water treatment in a thermal power plant according to claim 1, characterized in that: The sludge produced in the mechanically accelerated clarifier is discharged into a sludge treatment system for treatment.

10. A two-point dosing method for circulating water treatment in a thermal power plant according to claim 1, characterized in that: The added lime milk is produced by a lime system.

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