CN115849598A - Recycling system and process method for recycled water source circulating water of thermal power plant - Google Patents

Abstract

The invention relates to a recycling system and a process method of recycled water of a reclaimed water source of a thermal power plant. Wherein, the coagulation clarification system and the ultrafiltration system are connected with each other to form a first loop; the circulating cooling system, the advanced oxidation system, the softening system, the coagulation clarification system, the ultrafiltration system and the reverse osmosis system are sequentially connected to form a second loop; the reverse osmosis system, the desulfurization system and the tail end wastewater treatment system are connected in sequence. The invention has the beneficial effects that: the invention realizes zero discharge of the reclaimed water source circulating cooling system in the thermal power plant, reasonably recycles water resources by combining with the requirements of other systems in the thermal power plant, reduces the front-end water intake, avoids the discharge of sewage and pollutants to the water environment, and has remarkable environmental benefit.

Description

A system and process method for reclaiming reclaimed water source circulating water in a thermal power plant

technical field

The invention relates to the technical field of industrial sewage treatment, more precisely, it relates to a system and a process method for recycling water source circulating water in a thermal power plant.

Background technique

The open cycle cooling system of thermal power plants maintains a certain concentration ratio through regular drainage to prevent pollutants from enriching in circulating water. The sewage of the circulating cooling system has the characteristics of large water volume and poor water quality. Its salt content, alkalinity, hardness, and suspended solids concentration are several times that of the circulating water make-up water. The wastewater from the circulating cooling system that uses urban reclaimed water as the source of replenishment water is worse than the common river water and groundwater. Most of the thermal power plant's circulating cooling system directly discharges the sewage after reaching the discharge standard, which causes a lot of waste of water resources and discharges the concentrated pollutants to the environment. The sewage from the circulating cooling system is scientifically treated and rationally reused as industrial sewage Difficulties in governance.

Under the goal of zero discharge of wastewater from thermal power plants, a variety of circulating water wastewater treatment processes have been proposed, including softening and clarification-ultrafiltration-reverse osmosis, softening and clarification-nanofiltration-reverse osmosis, coagulation filtration-ion exchange-nanofiltration - reverse osmosis, etc. Although these processes can effectively treat conventional circulating sewage, there are many deficiencies: 1. Full softening processes such as double alkali method need to add a large amount of alkaline hardening agent and produce solid waste; when ion exchange method is hardening, cation exchange The resin regeneration process uses a large amount of concentrated acid and produces highly concentrated acidic wastewater. 2. The existing process does not include a COD control step, and the unremoved COD in the reclaimed water is enriched in the circulating cooling system, which will affect the reasonable reuse of the produced water and concentrated water. 3. A large amount of concentrated water enters the terminal thermal evaporation system, the water resource reuse method is unreasonable and the energy consumption is too high. 4. The final product water of the process is usually refined into demineralized water, but because the amount of circulating water effluent far exceeds the demand for boiler feed water in thermal power plants, a certain degree of waste of resources is caused.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art and provide a recycling system and process method for water source circulating water in a thermal power plant.

In the first aspect, there is provided a recirculating water recycling system for reclaimed water in a thermal power plant, including: a circulating cooling system, an advanced oxidation system, a softening system, a coagulation and clarification system, an ultrafiltration system, a reverse osmosis system, a desulfurization system and terminal waste water processing system;

Among them, the coagulation clarification system and the ultrafiltration system are connected to each other and form the first loop; the circulating cooling system, the advanced oxidation system, the softening system, the coagulation clarification system, the ultrafiltration system and the reverse osmosis system are connected in turn to form the second loop; The osmosis system, the desulfurization system and the terminal waste water treatment system are connected sequentially; the fresh water outlet of the reverse osmosis system is connected with the circulating cooling system, and the concentrated water outlet of the reverse osmosis system is connected with the desulfurization system.

Preferably, the advanced oxidation system is any one of an ozone oxidation system, an electrochemical oxidation system, an ultrasonic oxidation system, a Fenton oxidation system and an ultraviolet oxidation system.

Preferably, the softening system includes a dosing system for dosing and a dosing pool for stirring.

Preferably, the coagulation and clarification system includes a clarification tank and a filter press system, and the clarification tank is a mechanical acceleration clarification tank.

Preferably, the ultrafiltration system includes: an ultrafiltration water pump, an ultrafiltration membrane module and a backwash water pump.

Preferably, the reverse osmosis system includes a security filter, a water inlet pump and a reverse osmosis membrane module.

The second aspect provides a process method for reclaiming reclaimed water source circulating water in a thermal power plant, which is executed by a reclaimed reclaimed water source recirculating water recycling system in a thermal power plant described in the first aspect, including:

S1. Urban reclaimed water enters the circulating cooling system after preliminary biochemical treatment, and undergoes concentrated treatment, and is discharged from the circulating cooling system as sewage;

S2. The sewage enters the advanced oxidation system to remove most of the chemical oxygen demand COD and ammonia nitrogen and then enters the softening system;

S3. In the softening system, by adding milk of lime, Mg(OH)2 and CaF2 precipitates are formed, and HCO3- is removed; and the insoluble suspended matter in water is coagulated by adding flocculants and coagulants;

S4. The effluent of the softening system enters the coagulation and clarification system, and enters the ultrafiltration system through the clarification tank for turbidity removal, and obtains ultrafiltration backwash water and ultrafiltration effluent, and the ultrafiltration backwash water is returned to the coagulation and clarification system re-clarify;

S5. The ultrafiltered effluent passes through the reverse osmosis system to obtain reverse osmosis concentrated water and reverse osmosis fresh water. The reverse osmosis fresh water is reused as replenishment water to the circulating cooling system, and the reverse osmosis concentrated water is reused as replenishment water to the desulfurization system. ;

S6. The calcium ions and sulfate ions in the reverse osmosis concentrated water form desulfurized gypsum as a by-product in the desulfurization system, and other impurities in the reverse osmosis concentrated water are further concentrated in the desulfurization tower of the desulfurization system to form desulfurization wastewater and enter the terminal wastewater treatment system.

Preferably, in S5, the proportion of fresh water and concentrated water is adjusted by controlling the scale and operating conditions of the reverse osmosis system, and the amount of concentrated water production is preferentially controlled according to the actual water replenishment demand of the desulfurization system.

The beneficial effects of the present invention are:

1. The present invention realizes zero discharge of water source circulation cooling system in thermal power plants, rationally reuses water resources in combination with other system requirements in thermal power plants, reduces front-end water intake, and avoids the discharge of sewage and pollutants to the water body environment , significant environmental benefits.

2. The present invention adopts a partial softening process to remove impurities such as magnesium ions and fluorine ions, so that a large amount of calcium ions can be reused to the desulfurization system with concentrated water, reducing the generation of solid precipitation, reducing the dosage of limestone in the desulfurization system, and reducing the amount of desulfurization. The dosage of hard agent has remarkable economic and environmental benefits.

3. According to the characteristics of reclaimed water quality, the present invention sets up an advanced oxidation system to remove COD, which avoids unqualified water quality of reclaimed water caused by COD enrichment, and ensures the safe and stable operation of the water system of thermal power plants

4. The circulating water recycling system for reclaimed water in thermal power plants provided by the present invention is safe, reliable, and easy to maintain. It can be used as a complete set of new systems, and can also be upgraded on the basis of old systems.

5. The present invention is not only applicable to reclaimed water circulation cooling systems, but also can be used in circulation cooling systems of surface water sources, ground water sources, and mixed water sources, and has universal applicability and versatility.

Description of drawings

Fig. 1 is the structural representation of a kind of water source circulating water recycling system in a thermal power plant provided by the application;

Fig. 2 is the structural representation of the softening system provided by the present application;

Fig. 3 is a flow chart of a process for recycling water source circulating water in a thermal power plant provided by the present application.

Detailed ways

The present invention will be further described below in conjunction with the examples. The description of the following examples is provided only to aid the understanding of the present invention. It should be pointed out that for those skilled in the art, some modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Example 1:

This application provides a reclaimed water source circulating water reuse system in a thermal power plant. A reasonable process is set according to the characteristics of the reclaimed water recirculating water quality. Partial softening can concentrate the sewage, and the produced water can be reused as recirculating water system replenishment. The water is used as supplementary water for the desulfurization system to achieve zero discharge of the circulating water system. Specifically, as shown in Figure 1, it includes: circulating cooling system, advanced oxidation system, softening system, coagulation and clarification system, ultrafiltration system, reverse osmosis system , a desulfurization system and a terminal wastewater treatment system; the fresh water outlet of the reverse osmosis system is connected to the circulating cooling system, and the concentrated water outlet of the reverse osmosis system is connected to the desulfurization system;

Among them, the coagulation clarification system and the ultrafiltration system are connected to each other and form the first loop; the circulating cooling system, the advanced oxidation system, the softening system, the coagulation clarification system, the ultrafiltration system and the reverse osmosis system are connected in turn to form the second loop; The permeation system, the desulfurization system and the terminal wastewater treatment system are also connected in sequence.

The advanced oxidation system is an ozone oxidation system, an electrochemical oxidation system, an ultrasonic oxidation system, a Fenton oxidation system, an ultraviolet oxidation system or other advanced oxidation systems. It can effectively remove the high concentration of COD and ammonia nitrogen in the reclaimed water, avoid the enrichment of COD and ammonia nitrogen, and prevent microbial contamination of the back-end system.

As shown in Figure 2, the softening system includes a dosing system for dosing and a dosing pool for stirring. The dosing system is connected to the dosing pool. Condensation is connected to the clarification system. Among them, the dosing system can add lime milk, flocculant and coagulant aid, and the dosing pool has a stirring function. The softening system can precipitate magnesium ions, fluoride ions and suspended matter, remove temporary hardness, and adjust pH to weak alkaline.

The coagulation and clarification system includes a clarifier and a filter press system. The effluent of the softening system is used as the inflow of the clarifier, and enters the clarifier from the middle of the clarifier. The effluent from the clarifier overflows from the top and enters the ultrafiltration system as replenishment water for the ultrafiltration system. The filter press system receives the muddy water mixture at the bottom of the clarification tank, separates a large amount of solid sediment and discharges it out of the system, and obtains a small amount of filter press wastewater to return to the clarifier tank. The clarifier can be a mechanically accelerated clarifier or other types of clarifiers. It can remove most of the suspended solids and sediments, and form a solid filter residue through the filter press system.

The ultrafiltration system includes: ultrafiltration water pump, ultrafiltration membrane module and backwash water pump and other equipment. The effluent of the coagulation and clarification system (ie, the overflow water of the clarification tank) is the water inflow of the ultrafiltration system, and the water produced by the ultrafiltration system (ie, the effluent of the ultrafiltration membrane module) is the inflow of the reverse osmosis system. The ultrafiltration water pump and the ultrafiltration membrane module are in series mode, and the backwash water pump only acts on the ultrafiltration membrane module. It can further remove suspended solids in the influent and slow down the fouling rate of the back-end reverse osmosis system. Since the first loop is formed between the ultrafiltration system and the coagulation clarification system, the ultrafiltration backwash water returns to the clarification tank for re-clarification.

The reverse osmosis system includes a security filter, an inlet pump and a reverse osmosis membrane module. The effluent of the ultrafiltration system (ie, the effluent of the ultrafiltration membrane module) is the inlet water of the reverse osmosis system, the water produced by the reverse osmosis system is the replenishment water of the circulating cooling system, and the concentrated water of the reverse osmosis system is the replenishment water of the desulfurization system. The security filter, the water inlet pump and the reverse osmosis membrane module are connected in series. The reverse osmosis membrane module can be fresh water reverse osmosis, brackish water reverse osmosis, seawater reverse osmosis or other types of reverse osmosis membrane modules. The reverse osmosis system can be set up in one stage, two stages or multiple stages. The fresh water of the reverse osmosis system is reused as make-up water to the circulating cooling system, and the concentrated reverse osmosis water is reused as make-up water to the desulfurization system. Compared with the prior art where the concentrated water and fresh water of the reverse osmosis system are passed into the concentrated water tank and the fresh water tank respectively, this application rationally reuses the effluent of the reverse osmosis system, reduces the water intake at the front end, and avoids sewage discharge and pollution The material is discharged to the water body environment, and the environmental benefit is remarkable.

Example 2:

A process method for reclaimed water source circulating water recycling in a thermal power plant, performed by a reclaimed water source recirculating water recycling system in a thermal power plant according to the first aspect, comprising:

S1. Urban reclaimed water enters the circulating cooling system after preliminary biochemical treatment, and undergoes concentration treatment (the concentration ratio is usually 3 to 10 times), and is discharged from the circulating cooling system as sewage.

S2. The sewage enters the advanced oxidation system to remove most of the chemical oxygen demand COD and ammonia nitrogen and then enters the softening system.

S3. In the softening system, add lime milk to form Mg(OH)2 and CaF2 precipitates, and remove HCO3-; and add flocculants and coagulants to coagulate insoluble suspended matter in water.

S4. The effluent of the softening system enters the coagulation and clarification system, and enters the ultrafiltration system through the clarification tank for turbidity removal, and obtains ultrafiltration backwash water and ultrafiltration effluent, and the ultrafiltration backwash water returns to the coagulation and clarification system for re-clarification; The mass concentration of suspended solids in the effluent after the clarification tank should be less than 100mg/L.

S5. The ultrafiltration effluent passes through the reverse osmosis system to obtain reverse osmosis concentrated water and reverse osmosis fresh water. The reverse osmosis fresh water is reused as replenishment water to the circulating cooling system, and the reverse osmosis concentrated water is reused as replenishment water to the desulfurization system.

Among them, reverse osmosis fresh water can also be called desalination produced water, which is low in various anions and cations and can be reused in the circulating cooling system. Concentrated reverse osmosis water has high concentrations of calcium ions, chloride ions and sulfate ions, which can be recycled to the desulfurization system.

S6. Calcium ions and sulfate ions in reverse osmosis concentrated water form by-product desulfurization gypsum in the desulfurization system. Other impurities in reverse osmosis concentrated water are further concentrated in the desulfurization tower of the desulfurization system to form desulfurization wastewater and enter the terminal wastewater treatment system.

It is worth noting that in S5, the desulfurization system of the thermal power plant has far less water replenishment than the circulating cooling system. By controlling the scale and operating conditions of the reverse osmosis system, the ratio of fresh water and concentrated water is adjusted, and the concentrated water is prioritized according to the actual water replenishment demand of the desulfurization system. Water production.

Example 3:

An inland thermal power plant is equipped with an open circulation cooling system, and the urban reclaimed water treated by the Aerated Biological Fluidized Bed (ABFT) process is used as the main supply of circulating water. The water replenishment volume is about 2000t/h, the water replenishment TDS is about 600mg/L, the chloride ion concentration of the replenishment water is about 100mg/L, and the water replenishment COD is about 20mg/L. The concentration ratio of the circulating water system is about 4 times, the sewage volume is about 550t/h, the TDS of the drainage is about 2400mg/L, the chlorine ion concentration of the drainage is about 400mg/L, and the COD of the drainage is about 80mg/L. The limestone-gypsum wet desulfurization system of the thermal power plant uses miscellaneous water as supplementary water, and the supplemental water volume is 120t/h. A bypass flue gas drying tower is set up to treat terminal desulfurization wastewater.

In order to save water resources, reduce the burden on the environment, and realize zero discharge of waste water in the whole plant, the thermal power plant has built a circulating water reuse system to treat and reuse the sewage from the circulating cooling system. The ozone sterilization system, lime dosing system, coagulation clarification system, ultrafiltration system and reverse osmosis system are set up in sequence. Among them, the reverse osmosis system is divided into two sections, one is seawater reverse osmosis, and the other is disc tube high-pressure reverse osmosis. The volume of concentrated water in the second stage is about 120t/h, the TDS is about 9000mg/L, the concentration of chloride ion is about 1500mg/L, and the concentration of calcium ion is about 2000mg/L, which is used as replenishment water for the desulfurization system. A total of about 450t/h of water produced by the first stage of reverse osmosis and the second stage of reverse osmosis will be reused in the circulating cooling system. After the system of the present invention is applied to the thermal power plant, all the circulating water and sewage are absorbed and reused, which not only reduces the front-end water intake by 550t/h, but also avoids the waste water discharge. Combined with the terminal wastewater treatment system, the zero discharge of wastewater in the whole plant is truly realized.

Since the power plant's circulating water reuse system was put into normal operation for one year, the sewage treatment efficiency has been stable, the operation of the circulating cooling system and the quality of circulating cooling water have remained normal, and no obvious abnormalities have been seen in other systems including the desulfurization system, which has achieved expectations Process goals. The above results show that this reclaimed water source circulating water reuse system and process method have good applicability.

To sum up, the present invention sets up a reasonable process according to the water quality characteristics of reclaimed water circulating water. Partially softening can concentrate the sewage, reuse the produced water as replenishing water for the circulating water system, and reuse the concentrated water as replenishing water for the desulfurization system to realize circulation. Zero discharge from the water system.

Claims (8)

1. The utility model provides a water source circulating water recycling system in thermal power plant which characterized in that includes: a circulating cooling system, an advanced oxidation system, a softening system, a coagulation clarification system, an ultrafiltration system, a reverse osmosis system, a desulfurization system and a tail end wastewater treatment system;

wherein, the coagulation clarification system and the ultrafiltration system are connected with each other to form a first loop; the circulating cooling system, the advanced oxidation system, the softening system, the coagulation clarification system, the ultrafiltration system and the reverse osmosis system are sequentially connected to form a second loop; the reverse osmosis system, the desulfurization system and the tail end wastewater treatment system are also connected in sequence; and a fresh water outlet of the reverse osmosis system is connected with the circulating cooling system, and a concentrated water outlet of the reverse osmosis system is connected with the desulfurization system.

2. The system for recycling recycled water from a water source in a thermal power plant according to claim 1, wherein the advanced oxidation system is any one of an ozone oxidation system, an electrochemical oxidation system, an ultrasonic oxidation system, a Fenton oxidation system and an ultraviolet oxidation system.

3. The system for recycling recycled water from a reclaimed water source of a thermal power plant as claimed in claim 2, wherein the softening system comprises a dosing system for dosing and a dosing tank for stirring.

4. The system for recycling the circulating water of the reclaimed water source of the thermal power plant as claimed in claim 3, wherein the coagulation clarification system comprises a clarification tank and a filter pressing system, and the clarification tank is a mechanical accelerated clarification tank.

5. The system for recycling recycled water from a reclaimed water source of a thermal power plant as claimed in claim 4, wherein the ultrafiltration system comprises: an ultrafiltration water pump, an ultrafiltration membrane component and a backwashing water pump.

6. The system for recycling recycled water from a reclaimed water source of a thermal power plant as claimed in claim 5, wherein the reverse osmosis system comprises a cartridge filter, a water inlet pump and a reverse osmosis membrane module.

7. A process method for recycling recycled water from a reclaimed water source of a thermal power plant, which is performed by the recycled water recycling system for a reclaimed water source of a thermal power plant according to claim 1, and comprises the following steps:

s1, after primary biochemical treatment, urban reclaimed water enters a circulating cooling system, is subjected to concentration treatment and is discharged out of the circulating cooling system as sewage;

s2, enabling the sewage to enter an advanced oxidation system, removing most of Chemical Oxygen Demand (COD) and ammonia nitrogen, and then enabling the sewage to enter a softening system;

s3, adding lime milk into the softening system to form Mg (OH) ₂ And CaF ₂ Precipitating and adding HCO ₃ ^- -removing; adding flocculating agent and coagulant aid to coagulate the insoluble suspended matters in the water;

s4, enabling the effluent of the softening system to enter a coagulation clarification system, enabling the effluent to enter an ultrafiltration system through a clarification tank for turbidity removal to obtain ultrafiltration backwashing water and ultrafiltration effluent, and returning the ultrafiltration backwashing water to the coagulation clarification system for re-clarification;

s5, enabling the ultrafiltration outlet water to pass through a reverse osmosis system, and obtaining reverse osmosis concentrated water and reverse osmosis fresh water, wherein the reverse osmosis fresh water is recycled to the circulating cooling system as supplemented water, and the reverse osmosis concentrated water is recycled to the desulfurization system as supplemented water;

and S6, forming byproduct desulfurized gypsum in the desulfurization system by calcium ions and sulfate ions in the reverse osmosis concentrated water, and further concentrating other impurities in the reverse osmosis concentrated water in a desulfurization tower of the desulfurization system to form desulfurized wastewater to enter a tail-end wastewater treatment system.

8. The process method for recycling the circulating water of the reclaimed water source of the thermal power plant according to claim 7, wherein in S5, the ratio of the fresh water to the concentrated water is adjusted by controlling the scale and the operating condition of the reverse osmosis system, and the water making amount of the concentrated water is preferentially controlled according to the actual water replenishing requirement of the desulfurization system.

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