CN107162260B

CN107162260B - Recycling process of circulating water and sewage of power plant

Info

Publication number: CN107162260B
Application number: CN201710392355.3A
Authority: CN
Inventors: 鹿泽安; 焦丽苹; 李万强; 杜善学; 杜宗超
Original assignee: Shandong Lantian Energy Reservation & Environmental Protection Technology Co ltd
Current assignee: Shandong Lantian Energy Reservation & Environmental Protection Technology Co ltd
Priority date: 2017-05-27
Filing date: 2017-05-27
Publication date: 2020-11-10
Anticipated expiration: 2037-05-27
Also published as: CN107162260A

Abstract

The invention provides a recycling process of circulating water and sewage of a power plant, which comprises the following steps: lifting the circulating water and sewage of the power plant to a shallow sand filter by a lift pump for filtering, and then passing through a fluidized bed type sodium ion softener, a cartridge filter, reverse osmosis treatment, nanofiltration system treatment, sea-fresh membrane treatment and a DTRO system; sodium chloride is added into the DTRO concentrated water to ensure that the concentration of sodium ions is 5 to 8 percent, and the DTRO concentrated water enters a fluidized bed type sodium ion softener for cyclic utilization. The process can effectively reduce the pollution and blockage of the sewage of the circulating water of the power plant to the reverse osmosis device, prolong the reverse osmosis operation period, reduce the chemical cleaning frequency, effectively improve the recovery rate of the sewage of the circulating water of the power plant, improve the recovery rate by 25 percent and ensure that the total recovery rate of the system can reach 90 percent.

Description

Recycling process of circulating water and sewage of power plant

Technical Field

The invention relates to a recycling process for circulating water and sewage of a power plant, belonging to the technical field of industrial sewage recycling.

Background

With the increasing strictness of the requirements for environmental protection, the restriction conditions for the discharge of circulating water from power plants are continuously improved. Effective advanced sewage treatment and recycling are important water-saving modes of power plants. China is seriously deficient in everyone water resources, the space and time distribution is seriously uneven, and the sewage treatment technology is relatively lagged, so that the originally scarce water resources are brought forward. How to effectively and thoroughly treat the wastewater generated in the production, even recycle the wastewater, has become a great development direction of current scientific research.

The recycling of the sewage of the circulating water is an effective way for solving the shortage of water resources of a power plant and realizing the emission reduction and the resource utilization of the sewage. The water quality components of the circulating water and the sewage are complex, the salt content, COD (chemical oxygen demand), Si02, hardness, alkalinity and other indexes in the water are multiplied compared with those of a natural water body, when the water is reused for reverse osmosis treatment, reverse osmosis is easy to cause pollution blockage, reverse osmosis output is reduced, the operation period is shortened, frequent chemical cleaning is carried out, the service life of a reverse osmosis membrane element is shortened in serious conditions, and the stability of reverse osmosis operation of a power plant is greatly influenced.

At present, the prior art has the following defects: in the power plant that adopts circulating water blowdown water retrieval and utilization, mostly adopt the ultrafiltration as reverse osmosis pretreatment process, the ultrafiltration takes up an area of great, the investment cost is high, and to this kind of complicated water of circulating water blowdown water, although the ultrafiltration falls to the requirement scope with reverse osmosis intake SDI value, the effect of getting rid of the organic matter of ultrafiltration to aquatic and microorganism is relatively poor, the condition that ultrafiltration and reverse osmosis are dirty stifled in succession often appears in the operation, the water yield descends in the reverse osmosis appearance, the pressure differential rises, the condition such as desalination decline, operating stability receives the influence. The reverse osmosis recovery rate of a power plant has to be reduced to operate normally, the reverse osmosis recovery rate is 75% in the prior art, the reverse osmosis recovery rate of some circulating water recycling systems is even reduced to 60%, namely more than one fourth of the inlet water is discharged as concentrated water, and the system wastes a lot. The reverse osmosis produced water can be directly used for the water supplement of a heat supply network of a power plant and the water supplement of circulating water.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a recycling process of the circulating water and sewage of the power plant, which has high overall recovery rate and strong system operation stability, aiming at the defects in the prior art, and provide a recycling process of the circulating water and sewage of the power plant, so as to realize the following purposes:

(1) the invention solves the double contradiction of organic matter pollution blockage under the reverse osmosis low-PH operation environment and inorganic salt scaling under the high-PH operation environment in the conventional treatment process under the condition of the coexistence of high inorganic salt and high organic matter of the circulating water, and improves the safe and stable operation level of the reverse osmosis in the circulating water sewage treatment system;

(2) the process adopts the fluidized bed type sodium ion softener, can reduce the pollution and blockage of the sewage of the circulating water of the power plant to the reverse osmosis device, prolong the reverse osmosis operation period and reduce the chemical cleaning frequency;

(3) the invention effectively improves the recovery rate of the circulating water and sewage of the power plant and effectively improves the overall water yield of the system;

(4) the invention can reasonably recycle all DTRO concentrated water for the regeneration of the fluidized bed type sodium ion softener, saves a large amount of water resources, reduces the salt consumption of sodium chloride, reduces the operation cost and reduces the treatment cost of the part of high-concentration brine;

(5) the reverse osmosis effluent obtained by the treatment process has good water quality, and can be directly used for replenishing water of a water source and circulating water of a chemical makeup water treatment system of a power plant.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

a recycling process of circulating water and sewage of a power plant comprises the following steps:

(1) lifting the circulating water and sewage of the power plant to a shallow sand filter by a lift pump for filtering to obtain clear effluent;

(2) feeding the clarified effluent obtained in the step (1) into a fluidized bed type sodium ion softener for treatment to obtain effluent;

(3) adding a reducing agent into the effluent of the fluidized bed type sodium ion softener in the step (2) for reduction, adding a scale inhibitor, and sequentially passing through a first-stage cartridge filter and a second-stage cartridge filter to obtain effluent of the cartridge filter;

(4) performing reverse osmosis treatment on the outlet water of the cartridge filter obtained in the step (3) to generate reverse osmosis pure water and reverse osmosis concentrated water, and recovering the reverse osmosis pure water;

(5) the reverse osmosis concentrated water generated in the reverse osmosis treatment in the step (4) enters a nanofiltration system for nanofiltration treatment, and nanofiltration salt separation is recovered to obtain nanofiltration concentrated water and nanofiltration pure water;

(6) performing sea-fresh membrane treatment on the nanofiltration pure water in the step (5), and allowing the treated water to enter a sea-fresh membrane system to obtain sea-fresh membrane concentrated water and sea-fresh membrane pure water; feeding the concentrated water of the sea-fresh membrane into a DTRO system to obtain DTRO pure water and DTRO concentrated water;

(7) and (4) adding sodium chloride into the DTRO concentrated water obtained in the step (6) to ensure that the concentration of sodium ions is 5-8%, and entering a fluidized bed type sodium ion softener for recycling.

The following is a further improvement of the above technical solution:

in the step (3), the reducing agent is sodium bisulfite, and the addition amount is 2-3 ppm; the addition amount of the scale inhibitor is 3 ppm.

In the step (3), the ORP value after the reducing agent is added for reduction is lower than 200 mV.

And (4) circularly refluxing the sea-fresh film pure water in the step (5) and the DTRO pure water in the step (6) to a water outlet of the No. 1 high-pressure pump, then entering a reverse osmosis system for reverse osmosis treatment, and entering a circulating system for recycling.

In the step (5), the conductivity of the pure water of the sea freshwater membrane and the DTRO pure water in the step (6) is between 800 and 1200 us/cm.

The concentration of the DTRO concentrated water in the step (5) is 5-8%.

And (6) carrying out water yield of the DTRO concentrated water at 6 m/h.

The circulating water of the power plant is discharged as Na⁺Concentration of 600-900mg/L, Cl^-The concentration is 700-1000 mg/L.

And (2) soaking the fluidized bed type sodium ion softener for 2-12 hours by using a hydrochloric acid solution every 10-15 periods of operation of the fluidized bed type sodium ion softener, then washing the sodium ion exchanger by using the produced water of the reverse osmosis membrane until the effluent has no hardness, regenerating the fluidized bed type sodium ion exchanger by using a sodium hydroxide solution, and then washing the effluent of the fluidized bed type sodium ion softener by using the produced water of the reverse osmosis membrane until the pH value is less than 10.0.

By adopting the technical scheme, the invention has the beneficial effects that:

(1) the fluidized bed type sodium ion softener is adopted, part of effluent water circulation is added, the hardness of inlet water is diluted by effluent water per se, the total hardness of the effluent water is reduced by 5-8mmol/L compared with that of a common sodium ion softener, and the pollution and blockage of sewage of circulating water of a power plant to a reverse osmosis device can be effectively reduced;

(2) the reverse osmosis operation period is prolonged; the original operation cycle is 1.5-2 years, and the current operation cycle can reach more than 3 years;

(3) the chemical cleaning frequency is reduced; the chemical cleaning frequency is prolonged from 1 month to 2 months;

(4) the recovery rate of the circulating water and sewage of the power plant is effectively improved, and the total recovery rate of the system can reach 90 percent;

(5) all DTRO concentrated water can be reasonably recycled for regeneration of the fluidized bed type sodium ion softener, a large amount of water resources and the salt consumption of sodium chloride are saved, the operation cost is reduced, and the treatment cost of the part of high-concentration brine is reduced; the water consumption is saved by about 24 Yuan/h according to 6m for regeneration water quantity per hour and 4 Yuan (including pollution discharge cost) for water per ton, and the salt consumption is saved by at least 400kg according to the calculation, and 120 Yuan/h according to 300 Yuan for sodium chloride per ton;

(6) the reverse osmosis effluent obtained by the recycling process has good water quality, and can be directly used for replenishing water of a water source and circulating water of a chemical makeup water treatment system of a power plant;

(7) by the recycling process, the water yield of the system is integrally improved by 25 percent.

Drawings

FIG. 1 is a schematic view of the process for recycling the sewage of the circulating water of the power plant.

Detailed Description

The following description of the preferred embodiments of the present invention is provided for the purpose of illustration and description, and is in no way intended to limit the invention.

Embodiment of a recycling process for circulating water and sewage of a power plant

The invention relates to a device for a recycling process of circulating water and sewage of a power plant, which forms an integral system, wherein the integral system consists of a pretreatment system, a reverse osmosis desalination system, a concentrated water purification system and a control system, and the flow description is as follows:

1. pretreatment system

The purpose of raw water pretreatment is to solve the following problems:

(1) preventing the pollution and blockage of colloidal substances and suspended solid particles;

(2) preventing the fouling of organic matters;

(3) preventing the fouling of microorganisms;

(4) preventing oxidative damage to the membrane by oxides;

(5) the water yield of the reverse osmosis device is kept stable.

Thereby ensuring the stable operation and the service life of the reverse osmosis device.

The pretreatment part of equipment mainly comprises a sewage disposal pool, a lift pump, a shallow sand filter, a fluidized bed type sodium ion softener, an intermediate pool and the like.

1.1 Sewage disposal pool

The method is mainly used for storing circulating water and sewage.

1.2 Lift Pump

This pretreatment systems needs certain pressure of intaking just can hold back material such as colloid, granule, bacterium, virus in the former aquatic, and according to this pretreatment systems's water inflow, pressure of intaking, the inflow is 150m year/h, and the pressure of intaking is 2.5kgf, supporting suitable lift pump.

1.3 shallow sand filter

The shallow sand filter is composed of a plurality of standard high-speed sand cylinder units, a unique water distributor and a unique water collector are arranged in the shallow sand filter, a unique bidirectional automatic flushing valve is provided, and the single back flushing of the plurality of standard high-speed sand cylinders one by one in the normal system operation can be realized and the full-automatic program control is realized. The device has the advantages of small water consumption for backwashing, convenient equipment installation, easy operation and the like, and has large flow and no need of maintenance.

The forward washing filtration state: when the system is in a filtering state, unfiltered water is uniformly distributed by a unique water distributor which is self developed, and the water passes through a packing layer (refined uniform-grain quartz sand/garnet) in the filter in a laminar flow state. As water flows through the packing layer, impurities are trapped within the packing layer. The bottom of the filter is provided with a plurality of water collectors which are uniformly distributed, so that the filtered water is uniformly collected and led out, and the filter can filter at high flow rate through advection filtration and still can achieve a better filtering effect.

And (3) backwashing state: as impurities accumulate in the packing layer, the internal head loss will increase. When the loss of the water inlet pressure head and the water outlet pressure head reaches a set value, the system automatically activates the constant pressure device to switch the constant pressure device to a backwashing state, and when the backwashing is finished, the hydraulic valve changes the water supply direction, so that the backwashing one by one is realized, and the accumulated impurities can be cleaned more conveniently.

When the system is in a backwashing state, the filtration is still continued, wherein the standard unit sand cylinder to be backwashed does not carry out the filtration, and other standard unit sand cylinders in the system are still filtering. The filtered clean water part is used for backwashing the standard unit sand cylinder, and the rest is still sent to a user. The backwashing sewage is discharged through a backwashing water outlet of the hydraulic valve. In a high-speed sand cylinder full-automatic high-efficiency filtering system, the filler can be mutually scrubbed by the special water collector design, the backwashing efficiency is improved to the maximum extent, the required backwashing water (clean water) is reduced, and meanwhile, the material leakage phenomenon does not occur during backwashing. And backwashing one standard unit sand cylinder for 2 minutes, finishing backwashing, reducing the loss of the pressure head in the standard unit sand cylinder to a reasonable range, giving a recovery signal by a constant pressure device, recovering the hydraulic valve to a filtering state, and preparing the next standard unit sand cylinder to enter a backwashing state.

1.4 fluidized bed type sodium ion softener

In order to prevent CaCO3, MgCO3, MgSO4, CaSO4, BaSO4, SrSO4 and SiSO4 from crystallizing out when the concentration of the concentrated water end, particularly the concentrated water side of the last membrane module of the RO device is greater than the equilibrium solubility constant, and the original characteristics of the membrane are damaged, a sodium type ion exchange resin is adopted in a system before a reverse osmosis membrane module for water inlet to carry out ion exchange adsorption so as to remove main hardness components in water, and after the adsorption is saturated, the resin is invalid, and the resin can be regenerated by industrial salt so as to recover the exchange capacity.

According to the conditions of the water quality of inlet and outlet water, the water consumption, the water quality of outlet water and the like, the outlet water of the shallow sand filter has certain pressure and automatically flows into the fluidized bed type sodium ion softener. The system adopts a double-valve double-tank type water softener to carry out softening treatment. The equipment belongs to a continuous liquid phase switching ion exchange treatment process, and is of a floating bed type. The design of the system integrates three systems of exchange, automatic control and regeneration.

1.5 intermediate tank

The effluent of the fluidized bed type sodium ion softener automatically flows into an intermediate tank, and the intermediate tank is mainly used for adjusting the water quality and the water quantity, has the functions of collecting and storing and provides uniform and stable water quality for entering a cartridge filter.

2. Reverse osmosis desalination system

The reverse osmosis desalination system mainly comprises a reverse osmosis booster pump, a scale inhibitor, a reducing agent, a bactericide dosing device, a cartridge filter, a high-pressure pump, a reverse osmosis device, a cleaning device, a pure water tank and the like.

2.1 reverse osmosis booster pump

The booster pump provides stable water inlet pressure for the water inlet of the cartridge filter.

2.2 Scale inhibitor dosing System

The scale inhibitor is added into reverse osmosis inlet water, and is mainly used for preventing scale formation separated out after concentration of insoluble salts such as calcium carbonate, magnesium carbonate, calcium sulfate, magnesium sulfate and the like on the reverse osmosis concentrated water side and blocking a reverse osmosis membrane so as to damage the function and application characteristics of a membrane element. Its main function is to relatively increase the solubility of structural substances in water to prevent the obstruction of calcium carbonate, magnesium carbonate, calcium sulfate, magnesium sulfate and other substances to the membrane, and at the same time it can also reduce the iron ion blocking of the micropores of the membrane. For general water quality, the addition amount of the scale inhibitor is 2-3 ppm. The specific adding amount is determined according to specific conditions.

2.3 reducing agent adding system (also can be used as a bactericide adding system and alternately operates)

In order to ensure that the residual chlorine of the inlet water of the membrane element is required to be less than 0.1ppm, a reducing agent (sodium bisulfite) is added in front of the membrane device to eliminate the residual chlorine in the water, so that the membrane element is prevented from being oxidized, the running safety of a subsequent membrane system is ensured, and the service life of the membrane is prolonged. The adding amount of the NaHSO3 is determined according to the content of residual chlorine in the raw water.

2.42 grade safety filter

In order to prevent fine particles in water from entering a reverse osmosis membrane component after being pressurized by a high-pressure pump to scratch the membrane surface, a security filter is specially arranged.

The system is provided with 2 security filters with the diameter of phi 600, the security filters are high-flow security filters, and the security filters have the advantages of low filtration resistance, high flux, strong dirt blocking capability, long service life and convenience in replacement. The material of the filter is 304, 5 filter elements made of 6 inches PP material are arranged in the filter, and the flux of each filter element is 30m 3/h. The filter can be maintained for about 1-6 months under normal working conditions, and when the pressure difference between the inlet and the outlet of the filter is more than 0.1MPa, the filter element needs to be replaced. The filter structure meets the requirement of quick assembly and disassembly.

2.5 high pressure pump

Reverse osmosis systems require high water inlet pressure to drive the separation of solution and solute, operating pressures of about 1.5-1.7Mpa are determined according to the reverse osmosis membrane design guidelines.

2.6 reverse osmosis device

The reverse osmosis device is the core part of the system pre-desalination, and the water after reverse osmosis treatment can remove most inorganic salts and almost all organic matters, microorganisms and colloids.

The principle of reverse osmosis desalination: reverse Osmosis (RO) is a membrane separation technique using pressure difference as driving force by virtue of the function of permselective (semi-permeable) membrane, and when the pressure applied in the system is greater than the osmotic pressure of the solution, water molecules continuously permeate the membrane, flow into the central tube through the water production flow channel, and then flow out at the water outlet end, and impurities in the inlet water, such as: ions, organic matters, bacteria, viruses and the like are intercepted on the water inlet side of the membrane and then flow out from the concentrated water end, thereby achieving the purposes of separation and desalination.

The membrane element of the reverse osmosis device is a polyamide composite membrane provided by Heidenen/Dow/CSM company representing the international highest standard, the element is compounded by three layers of membranes, the surface layer is made of aromatic polyamide material and has the thickness of about 2000 angstroms, and the membrane element is supported by a microporous polysulfone layer, can bear high pressure, has better resistance to mechanical tension and chemical erosion, has relatively larger water production flux, and has the removal rate of more than 99 percent on NaCl, CaCl2 and MgCl 2.

Reverse osmosis auxiliary configuration:

the reverse osmosis device is provided with a low-pressure flushing function, when the reverse osmosis device runs, concentrated water is deeply concentrated at the concentrated water side, inorganic salt, bacteria and the like are caused to deposit on the surface of the membrane, and in order to remove impurities such as the inorganic salt, the bacteria and the like in time and prevent the impurities from depositing on the surface of the membrane, the impurities can be loosened and flushed out before a pollution layer is adhered to the surface of the membrane, so that the cleaning frequency of the membrane element is reduced, the service life of the membrane element is prolonged, and the attenuation of performance parameters such as the water yield and the desalination rate. When the reverse osmosis device is started, shut down and operates for a certain time, the DCS controls the starting of the low-pressure flushing function, the automatic discharge valve on the concentrated water side is automatically opened, low-pressure flushing is carried out, pollutants on the surface of the reverse osmosis membrane are flushed away, the concentrated water is prevented from precipitating and scaling on the membrane surface, and the service life of the RO membrane is prolonged.

2.7 cleaning device

The more complete the pretreatment of reverse osmosis, the longer the membrane element cleaning cycle and the easier the cleaning. It is impractical to ensure that the reverse osmosis membrane elements are not contaminated at all. Therefore, when the membrane element causes pollution due to operation accumulation, the pressure difference of an inlet and an outlet of the reverse osmosis rises, the water yield is reduced, and the desalination rate is reduced. In order to ensure the long-term stable operation of reverse osmosis, a reverse osmosis chemical cleaning device is necessary.

The chemical cleaning process comprises the following steps:

cleaning solution tank → cleaning water pump → ultrafilter → reverse osmosis system.

2.8 pure water pool

The device is mainly used for storing reverse osmosis pure water.

3. Concentrated water purification system

The concentrated water purification system mainly comprises a 1# buffer tank, a 2# high-pressure pump, a nanofiltration system, a 2# buffer tank, a 3# high-pressure pump, a seawater-freshwater membrane system, a 3# buffer tank, a 4# high-pressure pump, a DTRO system and a cleaning device.

3.11 #, 2#, 3# buffer box

The 1#, 2#, 3# buffer boxes are respectively used for storing the concentrated water of the reverse osmosis system, the nanofiltration system and the sea-fresh water membrane system.

3.22 #, 3#, 4# high pressure pump

The 2#, 3#, 4# high pressure pumps are used for providing inlet water with sufficient pressure for a nanofiltration system, a seawater system, a DTRO system respectively.

3.3 nanofiltration System

Nanofiltration membranes are functional semipermeable membranes that allow the passage of solvent molecules or certain low molecular weight solutes or low valent ions. It is a special and promising kind of separation membrane, its name is that it can retain matter about nanometer in size, and its pore size is above 1nm, generally 1-2 nm. The molecular weight of the organic substance is about 150-500-.

The process adopts a nanofiltration system to mainly separate salt from reverse osmosis concentrated water. Monovalent ions such as Na + and Cl-are separated, and desalting treatment is continued.

3.4 sea freshwater membrane system

Because the pure water generated by the nanofiltration system contains organic matters and salts with small relative molecular mass, such as univalent ions Na & lt + & gt and Cl & lt- & gt in the wastewater, the COD and the conductivity of the nanofiltration water are high. And (3) allowing the pure water produced by nanofiltration to enter a seawater-freshwater membrane system, removing 98-99% of salt through a seawater-freshwater membrane, and returning the effluent water to a water outlet of a No. 1 high-pressure pump, and then allowing the effluent water to enter a reverse osmosis system for continuous desalination treatment because the effluent water still exceeds the quality of the pure water.

3.5 DTRO System

The concentrated water of the sea-thin film enters the DTRO system again, and pure water generated by the DTRO system also flows back to the water outlet of the 1# high-pressure pump due to relatively high conductivity and then enters the reverse osmosis system, so that the water yield of the system is integrally improved. The concentrated water quantity concentrated by the DTRO system can be just used as the regeneration water quantity of the fluidized bed type sodium ion softener, the concentration of sodium chloride in the concentrated water is relatively high, and a small amount (or no) of sodium chloride can be added into the regeneration water according to the content calculation of Na & lt + & gt and Cl & lt- & gt in the circulating water sewage to ensure that the concentration of sodium salt in the regeneration water is 5-8% and then the regeneration water is used for the regeneration of the sodium ion softener.

3.6 cleaning device

A cleaning device of the concentrated water purification system and the reverse osmosis desalination system are shared.

4. Control system

The control system has the following structural modes: centralized DCS control

In the control system, the program task mainly aims at the interlocking of other pumps and the liquid level controlled by the membrane system program, and the DCS in the control system realizes automatic control on the starting, stopping and protection of system equipment through signals fed back on site.

The invention relates to a process for recycling circulating water and sewage of a power plant, which comprises the following steps:

(1) the flow of circulating water and sewage in the power plant is 150 m/h, the circulating water and sewage in the power plant are directly lifted to a shallow sand filter through a lifting pump, a unique water distributor is arranged in the shallow sand filter to distribute water uniformly, water passes through a packing layer (refined uniform-grain quartz sand/garnet) in the filter in a laminar flow state, and impurities are trapped in the packing layer. The bottom of the filter is provided with a plurality of water collectors which are uniformly distributed, so that the filtered water is uniformly collected and led out, and the filter can filter at high flow rate through advection filtration and still can achieve a better filtering effect.

The unique structure of the filter can ensure that the turbidity of the effluent is below 0.5 NTU and the filtration precision of impurities can reach 5 microns.

(2) Feeding the clear effluent obtained in the step (1) into a fluidized bed type sodium ion softener; the hardness of the water discharged from the softener is reduced to 15 mmol/L; (the hardness of effluent treated by a common sodium ion softener is about 22 mmol/L)

(3) And (3) adding 2-3ppm of sodium bisulfite into the effluent of the sodium ion softener in the step (2) to reduce so that the ORP value is lower than 200mV, and adding 3ppm of scale inhibitor to prevent the reverse osmosis membrane from scaling. The water enters the reverse osmosis water treatment device sequentially through the first-stage security filter and the second-stage security filter to ensure the reverse osmosis water quality.

(4) And (4) performing reverse osmosis treatment on the effluent of the cartridge filter obtained in the step (3), and recycling the reverse osmosis produced water.

(5) The concentrated water generated by the reverse osmosis treatment in the step (4) is reused in a nanofiltration system, after the nanofiltration separated salt is recovered, the concentrated water is discharged outside, and the pure water generated by the nanofiltration system contains organic matters and salts with small relative molecular mass, such as monovalent ions Na & lt + & gt and Cl & lt- & gt in the wastewater, so that the COD and the conductivity of the nanofiltration produced water are high.

(6) And (3) enabling the pure water in the step (5) to enter a sea-fresh water membrane system, enabling concentrated water of the sea-fresh water membrane to enter a DTRO system (disc tube type reverse osmosis), wherein the pure water generated by the sea-fresh water membrane system and the DTRO system has relatively high conductivity, and the conductivity is between 800 and 1200us/cm, so that the part of water flows back to a water outlet of a No. 1 high-pressure pump and then enters the reverse osmosis system, the water production rate of the system is integrally improved, the water production rate is improved by 25 percent, and the water production rate is improved to 90 percent.

(7) And (3) carrying out dry distillation on the DTRO concentrated water at the speed of 6 m/h, and carrying out dry distillation on the DTRO concentrated water at the speed of 5-8% to obtain the DTRO concentrated water at the speed of 6 m/h. According to the calculation of Na + and Cl-content in the circulating water sewage, the Na + concentration is generally 900mg/L, the Cl-concentration is generally 1000mg/L and 600-L, and a small amount of (or no) sodium chloride can be added into the regeneration water to ensure that the sodium salt concentration in the regeneration water is 5-8% and then the regeneration water is used for the regeneration of the sodium ion softener.

(8) After the fluidized bed type sodium ion softener operates for 10-15 cycles, the fluidized bed type sodium ion softener is soaked in hydrochloric acid solution with the mass concentration of 3% -5% for 2-12 hours, then the produced water of the reverse osmosis membrane is used for washing the sodium ion exchanger until the effluent water has no hardness, then the sodium ion exchanger is regenerated by using sodium hydroxide solution with the mass concentration of 3% -5%, and then the produced water of the reverse osmosis membrane is used for washing the effluent water of the fluidized bed type sodium ion softener until the pH value is less than 10.0.

The obtained reverse osmosis water production can reach 135 m/h.

The water quality of the final system reuse water, namely reverse osmosis produced water, is as follows:

the fluidized bed type sodium ion softener is adopted, partial effluent circulation is added, the hardness of the inlet water is diluted by the effluent of the fluidized bed type sodium ion softener, the total hardness of the outlet water is reduced by 5-8mmol/L compared with the hardness of the outlet water of a common sodium ion softener, and the pollution and blockage of the sewage of the circulating water of the power plant to a reverse osmosis device can be effectively reduced; through the long-term practice of the inventor, the process for recycling the sewage of the circulating water of the power plant can prolong the reverse osmosis operation period: the original operation cycle is 1.5-2 years, and the current operation cycle can reach more than 3 years; the chemical cleaning frequency can be reduced: the chemical cleaning frequency is prolonged from 1 month to 2 months; the recovery rate of the circulating water and sewage of the power plant is effectively improved, and the total recovery rate of the system can reach 90 percent; all DTRO concentrated water can be reasonably recycled for regeneration of the fluidized bed type sodium ion softener, a large amount of water resources and the salt consumption of sodium chloride are saved, the operation cost is reduced, and the treatment cost of the part of high-concentration brine is reduced; the water consumption is saved by about 24 Yuan/h according to 6m for regeneration water quantity per hour and 4 Yuan (including pollution discharge cost) for water per ton, and the salt consumption is saved by at least 400kg according to the calculation, and 120 Yuan/h according to 300 Yuan for sodium chloride per ton; the reverse osmosis effluent obtained by the recycling process has good water quality, and can be directly used for replenishing water of a water source and circulating water of a chemical makeup water treatment system of a power plant; by the recycling process, the water yield of the system is integrally improved by 25 percent and 90 percent.

Unless otherwise stated, the percentages used in the present invention are percentages by weight, and the proportions described in the present invention are proportions by mass. The reverse osmosis produced water refers to pure water produced by the reverse osmosis system. The fluidized bed type sodium ion softener produces water, namely the effluent of the fluidized bed type sodium ion softener, namely the produced pure water.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A recycling process of circulating water and sewage of a power plant is characterized by comprising the following steps:

2. The recycling process of sewage of circulating water of power plant as claimed in claim 1, wherein in the step (3), the reducing agent is sodium bisulfite, and the addition amount is 2-3 ppm; the addition amount of the scale inhibitor is 3 ppm.

3. The recycling process of sewage of circulating water of power plant as claimed in claim 1, wherein in step (3), ORP value after adding reducing agent for reduction is lower than 200 mV.

4. The recycling process of sewage of circulating water of power plant as claimed in claim 1, wherein the pure water of desalination of sea in step (6) and the pure water of DTRO in step (6) are circulated and returned to the water outlet of the high pressure pump, and then enter a reverse osmosis system for reverse osmosis treatment, and then enter a circulation system for recycling.

5. The recycling process of sewage of circulating water of power plant as claimed in claim 4, wherein the conductivity of the pure water of sea desalination membrane in step (5) and the conductivity of the pure water of DTRO in step (6) are between 800-.

6. The recycling process of circulating water and sewage of power plant as claimed in claim 1, wherein the concentration of DTRO concentrated water in step (5) is 5-8%.

7. The recycling process of circulating water and sewage of power plants as claimed in claim 1, wherein in step (6), the water yield of DTRO concentrated water is 6m for cultivation/h.

8. The recycling process of sewage from circulating water of power plant as claimed in claim 1, wherein the concentration of Na + in the sewage from circulating water of power plant is 600-900mg/L, and the concentration of Cl-is 700-1000 mg/L.

9. The recycling process of sewage of circulating water of power plant as claimed in claim 1, wherein the fluidized bed type sodium ion softener is soaked with hydrochloric acid solution for 2-12 hours every 10-15 cycles, then the produced water of reverse osmosis membrane is used to wash the sodium ion softener until the effluent water has no hardness, then the fluidized bed type sodium ion softener is regenerated by sodium hydroxide solution, and then the effluent water of the fluidized bed type sodium ion softener is washed by reverse osmosis pure water until the pH value is less than 10.0.