CN114933384A - Selective electrodialysis concentration salt separation recycling system and method for power plant desulfurization wastewater treatment - Google Patents

Selective electrodialysis concentration salt separation recycling system and method for power plant desulfurization wastewater treatment Download PDF

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Publication number
CN114933384A
CN114933384A CN202210574824.4A CN202210574824A CN114933384A CN 114933384 A CN114933384 A CN 114933384A CN 202210574824 A CN202210574824 A CN 202210574824A CN 114933384 A CN114933384 A CN 114933384A
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water
desulfurization wastewater
selective electrodialysis
power plant
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张萌
王晓鹏
李海红
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Shanghai Power Station Auxiliary Equipment Works Co ltd
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Shanghai Power Station Auxiliary Equipment Works Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
    • C02F1/4693—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis electrodialysis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F2001/007—Processes including a sedimentation step
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/20—Heavy metals or heavy metal compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/30—Organic compounds
    • C02F2101/40—Organic compounds containing sulfur
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124—Water desalination
    • Y02A20/131—Reverse-osmosis

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  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

The invention discloses a selective electrodialysis concentration salt separation recycling system and method for power plant desulfurization wastewater treatment. The concentration salt separation recycling system comprises a triple box unit, a clarification tank, a sand filter unit, an ultrafiltration unit, a selective electrodialysis unit, a nanofiltration unit and a reverse osmosis unit which are sequentially connected in series; the selective electrodialysis unit and the nanofiltration unit are respectively provided with a concentrated water outlet, the reverse osmosis unit is provided with a concentrated water outlet and a water production port, and the concentrated water outlet of the reverse osmosis unit is connected with the water inlet end of the triple box unit; the selective electrodialysis unit is provided with an electrodialysis membrane stack which is formed by connecting a plurality of modules of monovalent anion permselective membranes and cation membranes in series or in parallel. The selective electrodialysis unit firstly adopts an electrodialysis membrane stack formed by alternately arranging anion permselective membranes and common cation membranes to treat the desulfurization wastewater, and carries out a salt separation process while carrying out electrodialysis concentration, thereby reducing the operating pressure of a subsequent membrane system.

Description

Selective electrodialysis concentration salt separation recycling system and method for power plant desulfurization wastewater treatment
Technical Field
The invention relates to a selective electrodialysis concentration salt separation recycling system and method for power plant desulfurization wastewater treatment, and belongs to the technical field of environment-friendly water treatment.
Background
The desulfurization wastewater has complex water quality and high salinity treatment difficulty, the existing treatment process generally realizes the zero discharge target of pretreatment, membrane concentration and solidification treatment, but has unstable operation, large reagent adding amount and higher cost. The existing electrodialysis process in the market is used as a new process in the desulfurization wastewater, but is generally used as a concentration function or a cation separation for reducing the scaling problem, and is generally based on the improvement of the existing process without greatly changing the existing process. The desulfurization wastewater recycling treatment process and method have patent application of 'a desulfurization wastewater recycling treatment system and method for a coal-fired power plant' (CN201911381482.9), a nanofiltration system is adopted to separate divalent ions in the desulfurization wastewater, and the whole process chain is long. The acid and alkali are prepared by an electrodialysis process for resource utilization. In addition, there is also relevant patent application "power plant desulfurization waste water zero release treatment process and system based on electrodialysis technique" (CN202111127310.6), and the power plant desulfurization waste water zero release treatment adopts the process: triple box treatment → -nanofiltration → monovalent cation selective electrodialysis → reverse osmosis concentration → freezing crystallization, wherein in the process, the cation is separated through electrodialysis after the salt is separated through nanofiltration, and the scaling risk is reduced. After reverse osmosis concentration, freezing crystallization and solidification are carried out to obtain magnesium sulfate for sale, and sodium chloride crystallization mother liquor enters a flue for evaporation. The process of the patent is long in chain, and unstable operation is easily caused. The salinity of water is high, the pressure of a membrane system is higher, and the operation cost is higher and needs to be improved.
Above two patents all use to receive and strain the salt processing as the prerequisite, and under the relatively poor, the higher condition of salinity of desulfurization waste water quality of water, the pressure of intaking of membrane system is great, and the operation easily causes unstablely. The electrodialysis process in the second patent is based on the reduction of scaling of a reverse osmosis membrane system, the effect is more basic, and the whole system is based on the existing process and has no major breakthrough.
Disclosure of Invention
The invention aims to overcome the defects of long process chain, unstable process package operation and the like of the conventional desulfurization wastewater treatment process, provides a system and a method for selective electrodialysis recycling treatment of power plant desulfurization wastewater, combines with the conventional process of a power plant, and develops a new idea of recycling desulfurization wastewater treatment by a simple, ingenious and green process.
In order to achieve the aim, the invention provides a selective electrodialysis concentration salt separation recycling system for power plant desulfurization wastewater treatment, which comprises a triple box unit 1, a clarification tank 2, a sand filter unit 3, an ultrafiltration unit 4, a selective electrodialysis unit 5, a nanofiltration unit 6 and a reverse osmosis unit 7 which are sequentially connected in series; the selective electrodialysis unit 5 and the nanofiltration unit 6 are respectively provided with a concentrated water outlet, the reverse osmosis unit 7 is respectively provided with a concentrated water outlet and a water producing port, and the concentrated water outlet of the reverse osmosis unit 7 is connected with the water inlet end of the triple box unit 1; the selective electrodialysis unit 5 is provided with an electrodialysis membrane stack formed by connecting a plurality of modules of monovalent anion permselective membranes and cation membranes which are alternately arranged in series or in parallel.
Preferably, the device also comprises a plate-and-frame filter press 8 which is connected with the bottoms of the triple box unit 1 and the clarification tank 2, wherein the plate-and-frame filter press 8 is provided with a filtrate outlet and a sludge outlet, and the filtrate outlet is connected with the water inlet end of the triple box unit 1.
Preferably, the device also comprises a medicament adding system II 9 and a medicament adding system II 10, wherein the medicament adding system II is respectively connected with the triple box unit 1, and the medicament adding system II is connected with the clarification tank 1.
Preferably, the device also comprises a back washing pipeline 11 connected with the ultrafiltration unit 4, and the water outlet end of the back washing pipeline is connected with the water inlet end of the triple box unit 1.
The invention also provides a selective electrodialysis concentration salt separation recycling method for power plant desulfurization wastewater treatment, which adopts the selective electrodialysis concentration salt separation recycling system for power plant desulfurization wastewater treatment for treatment and comprises the following steps:
step 1: raw water of the desulfurization wastewater enters a triple-box unit 1 for treatment, and lime milk (Ca (OH) is added through a medicament adding system 2 Calcium hydroxide) to make partial heavy metal be completely precipitated in the form of hydroxide, then adding organic sulfide to make heavy metal of cadmium and mercury be combined into sulfide which is difficult to dissolve in water, then adding flocculant to make most heavy metal be combined into water-insoluble sulfidePrecipitating suspended matters, and adsorbing heavy metal hydroxide precipitate; the water produced by the triple box unit 1 enters a clarification tank 2, and sodium hydroxide and sodium carbonate are added to further remove residual Ca 2+ Adding a flocculating agent for precipitation, and then adding hydrochloric acid for regulating the pH value;
step 2: the effluent of the clarification tank 2 enters a sand filter unit 3 for treatment, and after large-particle precipitates are further removed, the effluent enters an ultrafiltration unit 4 for further removal of suspended matters and COD reduction;
and step 3: the effluent of the ultrafiltration unit 4 enters a selective electrodialysis unit 5 for carrying out divalent anion concentration and salt separation treatment, so as to obtain fresh water containing sulfate and sodium chloride and concentrated water containing sodium chloride; the electrodialysis fresh water is mainly sulfate water containing partial sodium chloride, and the electrodialysis concentrated water is mainly sodium chloride (NaCl) brine and then is sent to an ash yard in a yard for consumption treatment;
and 4, step 4: the fresh water of the selective electrodialysis unit 5 enters a nanofiltration unit 6 for treatment to generate nanofiltration concentrated water and nanofiltration fresh water, the nanofiltration fresh water enters a reverse osmosis unit 7 for treatment to generate reverse osmosis produced water and reverse osmosis concentrated water, the reverse osmosis concentrated water flows back to the triple box unit (1) for water inlet, and the reverse osmosis produced water is recycled to the circulating sewage. The nanofiltration concentrated water contains sulfate radicals with higher concentration, and can be sent to a desulfurization slurry preparation system for reaction consumption by combining a desulfurization slurry system process of a power plant; the nanofiltration fresh water is mainly low-concentration sodium chloride (NaCl) brine, and the concentration of chloride ions is about 1500 mg/L.
Preferably, the precipitated sludge generated by treatment in the triple box unit 1 and the clarification tank 2 in the step 1 enters a plate-and-frame filter press 8 for filter pressing, filter-pressed effluent returns to the water inlet end of the triple box unit 1 to be mixed with the raw desulfurization wastewater to enter the triple box unit 1, and the filter-pressed sludge cake is loaded on a truck and sent out for treatment.
Preferably, the ultrafiltration unit 4 in the step 2 is periodically back flushed, and back-flushed back-flushing water is returned to the triple box unit 1 for water inlet.
Preferably, the TDS (dissolved total solids) concentration of the effluent of the ultrafiltration unit 4 (i.e. the feed water of the selective electrodialysis unit 5) in the step 3 is 20000-45000mg/L and the hardness is 5000-10000 mg/L.
Preferably, the recovery rate of the selective electrodialysis unit 5 is 90-96%; the recovery rate of the nanofiltration unit 6 is 75-85%; the recovery rate of the reverse osmosis unit 7 is 60-75%.
Compared with the prior art, the invention has the beneficial effects that:
(1) the selective electrodialysis unit adopts an electrodialysis membrane stack formed by alternately arranging anion selective permeable membranes and common cation membranes for the first time to treat the desulfurization wastewater, and carries out a salt separation process while carrying out electrodialysis concentration, thereby reducing the operating pressure of a subsequent membrane system;
(2) the method has short process chain, can operate the nanofiltration unit under lower pressure, and reduces the operation energy consumption by 10-35%;
(3) the concentrated water discharged by the membrane system is combined with the existing process of the power plant, and a novel concept of desulfurization wastewater treatment and recycling is developed by a simple, ingenious and green process.
Drawings
FIG. 1 is a schematic structural diagram of a selective electrodialysis concentration salt separation recycling system for desulfurization wastewater treatment of a power plant according to the present invention;
FIG. 2 is a process flow diagram of the selective electrodialysis concentration salt separation recycling method for power plant desulfurization wastewater treatment according to the present invention;
reference numerals: 1. a triple box unit; 2. a clarification tank; 3. a sand filter unit; 4. an ultrafiltration unit; 5. a selective electrodialysis unit; 6. a nanofiltration unit; 7. a reverse osmosis unit; 8. a plate-and-frame filter press; 9. the medicament adding system is uniform; 10. a second medicament adding system; 11. and (4) backwashing the pipeline.
Detailed Description
In order to make the invention more comprehensible, preferred embodiments are described in detail below with reference to the accompanying drawings.
Example 1
The embodiment provides a selective electrodialysis concentration salt separation recycling system for power plant desulfurization wastewater treatment, which comprises a triple box unit 1, a clarification tank 2, a sand filter unit 3, an ultrafiltration unit 4, a selective electrodialysis unit 5, a nanofiltration unit 6, a reverse osmosis unit 7, a plate-and-frame filter press 8, a first reagent adding system 9, a second reagent adding system 10 and a back flush pipeline 11, as shown in figure 1; wherein, the triple box unit 1, the clarification tank 2, the sand filter unit 3, the ultrafiltration unit 4, the selective electrodialysis unit 5, the nanofiltration unit 6 and the reverse osmosis unit 7 are connected in series in sequence; the selective electrodialysis unit 5 and the nanofiltration unit 6 are respectively provided with a concentrated water outlet, the reverse osmosis unit 7 is provided with a concentrated water outlet and a water production port, and the concentrated water outlet of the reverse osmosis unit 7 is connected with the water inlet end of the triple box unit 1; the selective electrodialysis unit 5 is provided with an electrodialysis membrane stack formed by connecting a plurality of modules of monovalent anion permselective membranes and cation membranes which are alternately arranged in series or in parallel.
The bottoms of the triple box unit 1 and the clarification tank 2 are connected with a plate-and-frame filter press 8, the plate-and-frame filter press 8 is provided with a filtrate outlet and a sludge outlet, and the filtrate outlet is connected with the water inlet end of the triple box unit 1;
the upper part of the triple box unit 1 is connected with a medicament adding system I9, and the upper part of the clarification tank 2 is connected with a medicament adding system II 10.
The bottom of the ultrafiltration unit 4 is connected with a back flush pipeline 11, and the water outlet end of the back flush pipeline 11 is connected with the water inlet end of the triple box unit 1.
Example 2
The embodiment provides a selective electrodialysis concentration salt-separation recycling method for power plant desulfurization wastewater treatment, which is implemented by using the selective electrodialysis concentration salt-separation recycling system for power plant desulfurization wastewater treatment described in embodiment 1, and the process flow is shown in fig. 2, and the specific treatment process is as follows:
the selective electrodialysis concentration salt separation recycling process and system for the power plant desulfurization wastewater treatment have the following requirements on water inlet: the inlet water can be and is not limited to the desulfurization wastewater of a coal-fired power plant, the salt content of the inlet water is 40000-60000mg/L, the concentration of the chlorine ion is 5000-25000mg/L, the concentration of the sulfate radical is 4500-10000mg/L, the hardness of the calcium and magnesium is 5000-20000mg/L, the pH value is 4-9, the turbidity is less than 5NTU, the suspension is 500-1000mg/L, and the temperature is 5-35 ℃.
Raw water of the desulfurization wastewater enters a triple-box unit 1 for process treatment and is added into a medicament adding systemUnify 9 adding lime cream (Ca (OH) 2 Calcium hydroxide) to make partial heavy metal completely precipitate in the form of hydroxide, then adding organic sulfide to make heavy metal of cadmium and mercury combine into sulfide which is difficult to dissolve in water, then adding flocculant to make most suspended substance precipitate and adsorbing heavy metal hydroxide precipitate. The water produced in the triple box unit enters a clarification tank 2, and then sodium hydroxide and sodium carbonate are added through a second medicament adding system 10 to further remove residual Ca 2+ And COD, adding a flocculating agent for precipitation, and then adding hydrochloric acid for adjusting the pH.
Precipitated sludge is generated in the process treatment of the triple box unit 1 and the clarification tank 2, then the precipitated sludge enters a plate-and-frame filter press 8 for filter pressing, filter pressing effluent flows back to the front end of the triple box unit 1 to be mixed with raw desulfurization wastewater to enter the triple box unit 1, and the filter-pressed sludge cake is loaded on a truck and sent out for treatment.
And then, the effluent of the triple box unit 1 enters a sand filter unit 3, after large-particle precipitates are further removed, the effluent enters an ultrafiltration unit 4, and suspended matters are further removed and COD is reduced. The ultrafiltration unit 4 periodically carries out back washing through a back washing water channel 11, and the back washing water returns to the triple box unit 1 for water inlet.
The effluent of the ultrafiltration unit 4 enters a selective electrodialysis unit 5 to carry out a divalent anion concentration and salt separation process. At this time, the recovery rate of the selective electrodialysis unit 5 was selected to be 93%, and electrodialysis fresh water and electrodialysis concentrated water were generated.
The electrodialysed fresh water, which is mainly sulphate water, contains part of the sodium chloride, and then enters the nanofiltration unit 6.
The electrodialysis concentrated water is mainly sodium chloride (NaCl) brine and is then sent to an ash field in a field for consumption treatment.
The nanofiltration concentrated water contains sulfate radicals with higher concentration, and can be sent to a desulfurization slurry preparation system for reaction consumption by combining the desulfurization slurry system process of a power plant.
The concentrated water of the nanofiltration unit 6 is sent to an ash field for consumption treatment, the fresh water of the nanofiltration unit 6 is mainly low-concentration sodium chloride (NaCl) brine, the concentration of chloride ions is about 1500mg/L, and then the nanofiltration fresh water enters the reverse osmosis unit 7. The reverse osmosis unit 7 processes at a recovery rate of 75% to produce two liquids, reverse osmosis produced water and reverse osmosis concentrated water.
And recycling reverse osmosis produced water to circulating sewage.
The high-concentration reverse osmosis concentrated water obtained after concentration by the reverse osmosis unit 7 is mainly a mixed solution of sodium chloride (NaCl) and sulfate and flows back to the triple box unit 1 to enter water.

Claims (9)

1. A selective electrodialysis concentration salt separation recycling system for power plant desulfurization wastewater treatment is characterized by comprising a triple box unit (1), a clarification tank (2), a sand filter unit (3), an ultrafiltration unit (4), a selective electrodialysis unit (5), a nanofiltration unit (6) and a reverse osmosis unit (7) which are sequentially connected in series; the selective electrodialysis unit (5) and the nanofiltration unit (6) are respectively provided with a concentrated water outlet, the reverse osmosis unit (7) is provided with a concentrated water outlet and a water production port, and the concentrated water outlet of the reverse osmosis unit (7) is connected with the water inlet end of the triple box unit (1); the selective electrodialysis unit (5) is provided with an electrodialysis membrane stack which is formed by connecting a plurality of modules of monovalent anion selective permeable membranes and cation membranes in series or in parallel in an alternating way.
2. The selective electrodialysis concentration salt separation recycling system for the power plant desulfurization wastewater treatment according to claim 1, further comprising a plate-and-frame filter press (8) connected with the triple box unit (1) and the clarification tank (2), wherein the plate-and-frame filter press (8) is provided with a filtrate outlet and a sludge outlet, and the filtrate outlet is connected with a water inlet end of the triple box unit (1).
3. The selective electrodialysis concentration salt separation recycling system for the power plant desulfurization wastewater treatment according to claim 1, further comprising a second reagent dosing system (9) connected to the triple box unit (1) and a second reagent dosing system (10) connected to the clarifier (2).
4. The selective electrodialysis concentration salt separation recycling system for power plant desulfurization wastewater treatment according to claim 1, further comprising a back-washing pipeline (11) connected to the ultrafiltration unit (4), wherein a water outlet end of the back-washing pipeline is connected to a water inlet end of the triple box unit (1).
5. A selective electrodialysis concentration salt separation recycling method for power plant desulfurization wastewater treatment is characterized in that the selective electrodialysis concentration salt separation recycling system for power plant desulfurization wastewater treatment as claimed in any one of claims 1-4 is adopted for treatment, and the method comprises the following steps:
step 1: raw water of the desulfurization wastewater enters a triple box unit (1) for treatment, lime milk is added through a medicament adding system, part of heavy metals are completely precipitated in the form of hydroxides, organic sulfides are added, heavy metals such as cadmium and mercury are combined into sulfides which are insoluble in water, and then a flocculating agent is added, so that most suspended matters are precipitated, and heavy metal hydroxides are adsorbed for precipitation; the water produced by the triple box unit (1) enters a clarification tank (2), and sodium hydroxide and sodium carbonate are added to further remove residual Ca 2+ Adding a flocculating agent for precipitation, and then adding hydrochloric acid for regulating the pH value;
and 2, step: the effluent of the clarification tank (2) enters a sand filter unit (3) for treatment, and after large-particle precipitates are further removed, the effluent enters an ultrafiltration unit (4) for further removal of suspended matters and reduction of COD;
and 3, step 3: the effluent of the ultrafiltration unit (4) enters a selective electrodialysis unit (5) for carrying out divalent anion concentration and salt separation treatment, so that fresh water containing sulfate and sodium chloride and concentrated water containing sodium chloride are obtained;
and 4, step 4: the fresh water of the selective electrodialysis unit (5) enters the nanofiltration unit (6) for treatment to generate nanofiltration concentrated water and nanofiltration fresh water, the nanofiltration fresh water enters the reverse osmosis unit (7) for treatment to generate reverse osmosis produced water and reverse osmosis concentrated water, the reverse osmosis concentrated water flows back to the triple box unit (1) for water inlet, and the reverse osmosis produced water is recycled to the circulating sewage.
6. The selective electrodialysis concentration salt separation recycling method for power plant desulfurization wastewater treatment according to claim 5, wherein the precipitated sludge generated in the step 1 through treatment by the triple box unit (1) and the clarification tank (2) enters a plate-and-frame filter press (8) for filter pressing, the filter-pressed effluent returns to the water inlet end of the triple box unit (1) to be mixed with the desulfurization wastewater raw water and enters the triple box unit (1), and the filter-pressed sludge cake is loaded on a truck and sent out for treatment.
7. The method for selective electrodialysis concentration salt separation resource utilization of power plant desulfurization wastewater treatment according to claim 5, wherein the ultrafiltration unit (4) in the step 2 is periodically subjected to back washing, and back washing water after back washing is returned to the triple box unit (1) for water inlet.
8. The method for recycling the selective electrodialysis concentration salt separation in the power plant desulfurization wastewater treatment as claimed in claim 5, wherein the TDS concentration of the effluent of the ultrafiltration unit (4) in the step 3 is 20000-45000mg/L, and the hardness is 5000-10000 mg/L.
9. The method for recycling the selective electrodialysis concentration salt separation in the power plant desulfurization wastewater treatment according to claim 5, wherein the recovery rate of the selective electrodialysis unit (5) is 90-96%; the recovery rate of the nanofiltration unit (6) is 75-85%; the recovery rate of the reverse osmosis unit (7) is 60-75%.
CN202210574824.4A 2022-05-25 2022-05-25 Selective electrodialysis concentration salt separation recycling system and method for power plant desulfurization wastewater treatment Pending CN114933384A (en)

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