CN112194298A - System and method for recycling wastewater of whole power plant - Google Patents

System and method for recycling wastewater of whole power plant Download PDF

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Publication number
CN112194298A
CN112194298A CN202010787405.XA CN202010787405A CN112194298A CN 112194298 A CN112194298 A CN 112194298A CN 202010787405 A CN202010787405 A CN 202010787405A CN 112194298 A CN112194298 A CN 112194298A
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treatment
wastewater
concentration
pretreatment
communicated
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邓毅
梁全勋
鲁涛
金黄
付平
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Dongfang Boiler Group Co Ltd
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Dongfang Boiler Group Co Ltd
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    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00Multistage treatment of water, waste water, or sewage
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F5/00Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
    • C02F5/02Softening water by precipitation of the hardness
    • C02F5/04Softening water by precipitation of the hardness using phosphates
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F5/00Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
    • C02F5/02Softening water by precipitation of the hardness
    • C02F5/06Softening water by precipitation of the hardness using calcium compounds
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/001Processes for the treatment of water whereby the filtration technique is of importance
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/02Treatment of water, waste water, or sewage by heating
    • C02F1/04Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/44Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/441Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/44Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/444Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/46Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/469Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
    • C02F1/4693Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis electrodialysis
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/52Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/66Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/18Nature of the water, waste water, sewage or sludge to be treated from the purification of gaseous effluents

Abstract

The invention discloses a system and a method for recycling wastewater from a whole power plant, belonging to the technical field of wastewater treatment of power plants, wherein a circulating water sewage treatment system is matched with a bypass treatment system, a sewage outlet of the circulating water sewage treatment system is communicated with an A pretreatment device, the outlet end of the A pretreatment device is communicated with a membrane concentration device, and the outlet end of the membrane concentration device is communicated with a deep concentration system; the concentrated water discharge port of the feed water wastewater treatment system is respectively communicated with the deep concentration system and the desulfurization wastewater treatment system, and the desulfurization wastewater outlet of the desulfurization wastewater treatment system is communicated with the pretreatment device B; the system is characterized by further comprising an evaporation concentration system, wherein the inlet end of the evaporation concentration system is communicated with the deep concentration system and the pretreatment device B respectively, the outlet end of the evaporation concentration system is communicated with the pretreatment device C, the outlet end of the pretreatment device C is communicated with the membrane filtration device, the membrane filtration device is communicated with the post-treatment device and is prepared into a final product through the post-treatment device, so that zero discharge of wastewater of a whole plant is realized, industrial pure salt is finally prepared, and high-purity chemical raw materials such as acid and alkali and the like with higher economic values can be prepared.

Description

System and method for recycling wastewater of whole power plant
Technical Field
The invention belongs to the technical field of power plant wastewater treatment, and particularly relates to a system and a method for recycling wastewater from a whole power plant.
Background
The technical policy of pollution control of the thermal power plant in 2017 also makes the following requirements: the method has the advantages of preventing the pollution caused by the waste water discharged by the thermal power plant, determining that the water pollution prevention and control of the thermal power plant are in accordance with the principles of classification treatment and one water with multiple purposes, and encouraging the thermal power plant to realize the recycling of the waste water without discharging. Driven by similar relevant policies, the whole plant wastewater of the power plant is comprehensively treated and gradually utilized in a gradient manner, and finally zero discharge of the wastewater is imperative. For power plants, the whole plant has large wastewater discharge amount, the final aim of zero emission needs to be achieved in the most economic mode, and the resource utilization of the wastewater becomes the best choice for the zero emission treatment.
In the prior art, on one hand, various kinds of waste water in a power plant cannot be treated cooperatively, so that unnecessary investment or repeated investment is brought to the waste water treatment of the whole plant, and if the quantity of circulating water sewage is large, if zero discharge is to be realized, the economy is greatly influenced; on the other hand, the conventional resource utilization modes of pretreatment, membrane concentration and evaporative crystallization are adopted, SO that the problems that the investment cost is high, the operation cost is high, the economic value of the final product salt (mainly NaCl and Na2SO 4) is not high, and the product salt is always sold everywhere are caused.
Meanwhile, the difficulty of treating the desulfurization wastewater of the power plant terminal is high, and the method is a great problem which restricts the development of zero discharge of the wastewater of the whole power plant at present. Desulfurization waste water concentration is high, and the composition is complicated, and the salinity of waste water can not be handled to traditional triplex case, if the triplex case goes out the direct discharge of water and will cause very big harm to the environment. The desulfurization wastewater has high salt concentration (TDS: 30000-. Conventional treatment methods are classified into a membrane method and a thermal method.
The technical route adopted by the membrane method technology is as follows: softening, salt separation, membrane concentration and crystallization. The technical route has long flow, high investment and operation cost (the investment cost is more than 200 ten thousand per ton of water according to the water amount per hour, and the treatment cost per ton of water is more than 80 yuan), poor overall economy and difficult later maintenance of the membrane.
Thermal methods are divided into multiple-effect evaporation and flue gas evaporation. The multi-effect evaporation is as follows: concentrating or evaporating the desulfurized wastewater into mixed salt by adopting steam after the wastewater is softened; the flue gas is evaporated into: the desulfurization waste water is directly dried into mixed salt by adopting high-temperature (the smoke gas is above 300 ℃ in front of the air preheater) or low-temperature (the smoke gas is about 150 ℃ at the inlet of the dust remover). Multiple-effect evaporation needs strict softening pretreatment, the operation cost is high, CaSO4 is easy to scale in the evaporation process to block a heat exchange tube, and the heat exchange tube is generally cleaned thoroughly once a year; the evaporation of flue gas mixes the waste water miscellaneous salt into the fly ash, which will certainly affect the fly ash.
Disclosure of Invention
In view of the above, in order to solve the above problems in the prior art, the present invention provides a system and a method for recycling wastewater from a whole power plant to achieve the purpose of realizing zero discharge of wastewater from the whole plant, fully recovering water, reducing the water intake of the power plant, and lowering the overall operation cost, and simultaneously fully recovering salt in the wastewater to finally prepare industrial pure salt, and also prepare high-purity acid, alkali and other chemical raw materials with higher economic value.
The technical scheme adopted by the invention is as follows: a power plant whole-plant wastewater recycling treatment system comprises a circulating water and sewage treatment system, a water supply and wastewater treatment system and a desulfurization and wastewater treatment system, wherein the circulating water and sewage treatment system is matched with a bypass treatment system, a sewage outlet of the circulating water and sewage treatment system is communicated with an A pretreatment device, an outlet end of the A pretreatment device is communicated with a membrane concentration device, and an outlet end of the membrane concentration device is communicated with a deep concentration system;
the concentrated water discharge port of the feed water wastewater treatment system is respectively communicated to the deep concentration system and the desulfurization wastewater treatment system, and the desulfurization wastewater outlet of the desulfurization wastewater treatment system is communicated with the pretreatment device B;
the device is characterized by further comprising an evaporation concentration system, wherein the inlet end of the evaporation concentration system is respectively communicated with the depth concentration system and the pretreatment device B, the outlet end of the evaporation concentration system is communicated with the pretreatment device C, the outlet end of the pretreatment device C is communicated with the membrane filtration device, the membrane filtration device is communicated with the post-treatment device, and the final product is prepared through the post-treatment device.
Further, the post-treatment device is a bipolar membrane electrodialysis device, the bipolar membrane electrodialysis device is respectively communicated with the membrane concentration device and the C pretreatment device, and a NaOH solution and an HCl solution are prepared and generated through the bipolar membrane electrodialysis device, so that the added value is high, the post-treatment device can be consumed in a factory, the related cost is reduced, and the post-treatment device is convenient to sell.
Furthermore, the post-treatment device is an evaporative crystallization device which is communicated with the membrane filtration device, and industrial-grade NaCl pure salt can be prepared through the evaporative crystallization device.
The invention also provides a recycling treatment method for the wastewater of the whole power plant, which comprises the following steps:
treating the circulating water sewage treatment system through a bypass treatment system to reduce the sewage discharge amount of the circulating water system, and sequentially carrying out pretreatment process A and membrane concentration process on the sewage discharge of the circulating water sewage treatment system to obtain a product A after the membrane concentration process; wherein, the bypass treatment is adopted, so that the water quality and the concentration ratio can be improved, and the water intake and the sewage discharge can be reduced;
supplementing one part of concentrated water discharged by the feed water wastewater treatment system to the desulfurization wastewater treatment system, and taking the other part of the concentrated water as a product B;
performing a deep concentration process on the product A and the product B to obtain a product C, so as to realize deep concentration of concentrated water and recover moisture as much as possible;
performing a B pretreatment process on the desulfurization wastewater discharged by the desulfurization wastewater treatment system to obtain a product D; the desulfurization wastewater is taken as the wastewater of the whole plant to be considered uniformly, the conventional triple-header treatment is not adopted, and the pretreatment process B is carried out to control suspended matters, so that the treatment cost is saved;
carrying out a seed crystal evaporation concentration process on the product C and the product D to obtain a product E, and sequentially carrying out a pretreatment process C and a membrane filtration process on the product E to obtain a product F; the product E is pretreated and purified by adopting a pretreatment process C, salt separation by a membrane method is not adopted, the final concentrated water amount is small, and the overall investment and operation cost is low;
the F product is prepared into a final product through a post-treatment process, and the full recovery and high-added-value resource utilization of the wastewater of the whole power plant are realized.
Furthermore, the post-treatment process adopts a bipolar membrane electrodialysis process, a high-purity NaOH solution and a high-purity HCl solution are generated through the bipolar membrane electrodialysis process, fresh water generated by the bipolar membrane electrodialysis process is returned to the membrane concentration process, part of the NaOH solution generated by the bipolar membrane electrodialysis process can be recycled to the C pretreatment process, the NaOH solution and the HCl solution have high additional values, and full recovery and high-additional-value resource utilization of wastewater of the whole power plant are realized.
Furthermore, the post-treatment process adopts an evaporative crystallization process, and NaCl pure salt is prepared by the evaporative crystallization process, is of an industrial grade and has better economy, so that the full recovery of the wastewater of the whole plant of the power plant and the resource utilization with high added value are realized.
Furthermore, the pretreatment process A and the pretreatment process C both comprise a coagulating sedimentation process and a chemical dosing softening process, the pretreatment purification is carried out through the pretreatment process C, salt separation is not carried out by adopting a membrane method, the final concentrated water amount is small, and the overall investment and operation cost is low;
and the pretreatment process B comprises the steps of firstly adding lime to adjust the pH value and then carrying out coagulating sedimentation treatment, so that the desulfurization wastewater with high suspended matter content can be effectively treated.
Furthermore, the membrane concentration process comprises an ultrafiltration process and a low-pressure reverse osmosis process, and can enable the concentration TDS of the concentrated water to reach about 30000 mg/L.
Furthermore, the deep concentration process adopts a DTRO process or a high-pressure reverse osmosis process, so that the water is recovered as much as possible and the concentration TDS of the concentrated water is more than 60000 mg/L.
Further, the evaporation concentration process adopts a seed crystal method evaporation concentration process, and the seed crystal method evaporation concentration process takes the existing calcium sulfate crystals in the wastewater and newly configured calcium sulfate slurry (added when the system is started) as seed crystals. The crystal seed method is adopted for evaporation, crystallization and concentration, so that crystals newly generated in the evaporation and concentration process are preferentially attached to the surface of the crystal seed, and the scaling of an evaporation system can be delayed to the greatest extent, thereby chemical softening pretreatment is not needed, equipment and softening dosing of the traditional chemical softening and the like are saved, and the investment cost and the operating cost are saved.
The invention has the beneficial effects that:
1. by adopting the system and the method for treating the wastewater of the whole power plant as the resource, the circulating water of the circulating water sewage treatment system is treated by the bypass treatment system, so that the wastewater discharge of the power plant is greatly reduced from the source, and simultaneously, the water quality and the concentration rate are improved and the water intake is reduced; compared with the prior art, the system saves the traditional triple box, saves the investment cost, greatly reduces the operation cost, has low investment cost and low operation cost in the whole scheme, and realizes the full recovery of the wastewater of the whole power plant and the resource utilization with high added value.
2. By adopting the system and the method for recycling the wastewater of the whole power plant provided by the invention, the high-salinity concentrated water part (the deeply concentrated terminal wastewater, the desulfurization wastewater and the like) of the wastewater of the power plant adopts a method of firstly concentrating (a seed crystal method) and then subsequently treating (preprocessing and recycling). The pretreatment investment and the running cost of the high-salinity concentrated water can be reduced by times, and the whole economy is good.
3. By adopting the system and the method for recycling the wastewater of the whole power plant, the wastewater of the power plant can be finally recycled by bipolar membrane electrodialysis, and the final products are NaOH solution and HCl solution, or can be prepared into industrial-grade NaCl products with high purity by evaporation crystallization, so that the characteristics of good economical efficiency and high added value of byproducts are realized.
4. By adopting the system and the method for recycling the wastewater of the whole power plant, which are provided by the invention, a recycling treatment technical route with good economy and high added value is adopted, the wastewater can be recycled to the maximum extent, and the zero discharge of the wastewater is really realized. The whole system is simple, for the whole plant wastewater zero discharge project, the investment cost can be saved by more than 30%, the operation cost can be saved by more than 50%, the added value of the resource final product is high, and particularly, the acid and the alkali are prepared, so that the acid and the alkali can be absorbed in a plant, the related cost is reduced, and the outward sale is also convenient.
Drawings
FIG. 1 is a schematic system configuration diagram of a plant wastewater recycling system provided by the invention in example 1;
FIG. 2 is a schematic system structure diagram of a plant wastewater recycling treatment system provided by the invention in example 2;
FIG. 3 is a block flow diagram of a method for recycling wastewater from a whole plant of a power plant according to the present invention in example 1;
FIG. 4 is a block flow diagram of a method for recycling wastewater from a whole plant of a power plant in example 2.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
Example 1
The method aims at comprehensively treating three kinds of common wastewater difficult to treat in the power plant at present, and finally realizes resource utilization and zero emission. The three kinds of waste water are mainly circulating sewage generated by a circulating sewage treatment system, sewage generated by a water supply and waste water treatment system and desulfurization waste water generated by a desulfurization waste water treatment system. In order to solve the problems of high investment, high operation cost, incapability of treating miscellaneous salts, easiness in scaling of a system and the like commonly existing in other treatment routes at present, a method for recycling wastewater from a whole plant of a power plant is specifically provided in this embodiment, as shown in fig. 3, the method includes:
s1: because circulating water blowdown water processing system can produce a large amount of sewages, handle circulating water blowdown water processing system through bypass processing system to improve circulating water quality of water, and then can improve concentrated multiplying power and reduce the blowdown yield. The bypass treatment system treats 1-2% of the circulating water to reduce suspended matters, sludge, algae and temporary hardness in the wastewater, and the method is 'sand filter tank + active carbon + weak acid resin softening'. After the circulating water sewage treatment system adopts the bypass treatment system, the concentration ratio of circulating water can be improved to about 6.5, so that the wastewater discharge of the circulating water sewage treatment system can be reduced by more than 20%, and the water intake of the system can be reduced.
S2: sequentially carrying out pretreatment process A and membrane concentration process on the sewage of the circulating water sewage treatment system to obtain product A; the pretreatment process a includes a coagulation precipitation process and a chemical dosing softening process, both of which are commonly used treatment methods, and are not described herein again, in this embodiment, the chemical dosing softening process of the pretreatment process a uses lime + Na2CO3The double base method. The membrane concentration process comprises an ultrafiltration process and a low-pressure reverse osmosis processThe treated A product is recycled, the recovery rate is over 80 percent, and the concentration TDS of the A product reaches about 30000 mg/L.
S3: supplementing one part of concentrated water discharged by a feed water wastewater treatment system to a desulfurization wastewater treatment system, wherein the common reuse rate is 20-100%, and the other part (the part which cannot be absorbed by the desulfurization wastewater treatment system) is used as a product B;
s4: performing a deep concentration process on the product A and the product B to obtain a product C, so as to realize deep concentration of concentrated water and recover moisture as much as possible; wherein, the deep concentration process adopts a DTRO process or a high-pressure reverse osmosis process, the treated C product is recycled, the recovery rate is more than 50 percent, and the concentration TDS of the C product reaches more than 60000 mg/L.
S5: the concentration of the desulfurization wastewater discharged by the desulfurization wastewater treatment system is high, the TDS is more than 30000mg/L, the components are complex, the content of solid impurities such as suspended matters is high, the content of heavy metals is high, and the desulfurization wastewater cannot directly enter a deep concentration system, so that the desulfurization wastewater is subjected to a B pretreatment process to remove impurities such as suspended matters to obtain a D product; the desulfurization wastewater is taken as the wastewater of the whole plant to be considered uniformly, the conventional triple-header treatment is not adopted, and the B pretreatment process is carried out to control suspended matters, so that the treatment cost is saved. In this embodiment, the pretreatment process B is to add lime to adjust the PH, generally to about 9, and then perform a coagulating sedimentation treatment, wherein the suspended matter content of the product D is controlled below 100mg/L after the pretreatment process B.
S6: and (2) carrying out a seed crystal evaporation concentration process on the product C and the product D to obtain a product E, treating the product E by a seed crystal evaporation concentration system, evaporating most of water to obtain a recovered product, concentrating the product E until the concentration TDS reaches about 200000mg/L, carrying out a C pretreatment process and a membrane filtration process on the product E in sequence to obtain a product F, wherein the membrane filtration process mainly adopts an ultrafiltration device and is used for further removing impurities such as colloid in concentrated water to protect subsequent electrodialysis equipment, and the ultrafiltration recovery rate is more than 95%. Most of the factory wastewater is recycled through the step, and finally a small amount of concentrated water is a high-concentration NaCl solution (namely an E product), so that resource treatment can be further realized.
The evaporation concentration process adopts a crystal seed method evaporation concentration process, the crystal seed method evaporation concentration process takes existing calcium sulfate crystals and newly configured calcium sulfate slurry in the wastewater as crystal seeds, the crystal seeds are added when an evaporation system is started, 0.1-1 Wt% of calcium sulfate is added according to the water amount, the crystal seeds are recovered through a cyclone during the operation of the system, the crystal seeds do not need to be added, and the scaling of a heat exchange tube of the evaporation concentration system is avoided. Because the seed crystal method is adopted for evaporation, crystallization and concentration, chemical softening pretreatment is not needed, the scaling of an evaporation system can be prevented, and the operation cost is low.
The pretreatment process comprises coagulating sedimentation process and chemical agent softening process, and adopts NaOH (sodium hydroxide) and Na2CO3(calcium carbonate), BaCl2The treatment method of (calcium chloride) and coagulating sedimentation removes the sediment, hardness, sulfate radical, heavy metal and most suspended matters in the wastewater, and at the moment, the water quantity is small, and the whole operation cost is low. Because the content of Cl ions in the E product is high and the content of sulfate radicals is low, the sulfate radicals and other impurities are removed from the final high-salt concentrated water through a C pretreatment process, only NaCl is reserved, and the wastewater treated by the C pretreatment process mainly contains NaCl. Meanwhile, the final water amount is small, so that the cost of the treated medicament is low.
S7: the wastewater treated by the membrane filtration process is a high-concentration NaCl solution (namely, an F product), and the F product is prepared into a final product by a post-treatment process. In the implementation, the post-treatment process adopts a bipolar membrane electrodialysis process, NaOH solution and HCl solution with the concentration of more than 10% are generated through the bipolar membrane electrodialysis process, fresh water generated by the bipolar membrane electrodialysis process is returned to a membrane concentration process for continuous treatment, part of NaOH solution generated by the bipolar membrane electrodialysis process is recycled to the C pretreatment process, and the NaOH solution and the HCl solution have high added values.
By adopting the process route provided by the embodiment, the wastewater discharge of a power plant can be reduced to the greatest extent, the traditional triple box system is cancelled, the system is simple, the wastewater resource treatment is finally realized, the zero discharge is realized, and the problems that the investment is high, the operation cost is high, the mixed salt cannot be treated, the system is easy to scale and the like commonly existing in other treatment routes at present are solved.
In order to realize the above-mentioned method for recycling wastewater from the whole plant of the power plant, in practical application, the following system for recycling wastewater from the whole plant of the power plant is adopted, as shown in fig. 1, the system is designed as follows:
the system mainly comprises a circulating water and sewage treatment system, a water supply and wastewater treatment system and a desulfurization and wastewater treatment system, wherein the circulating water and sewage treatment system is matched with a bypass treatment system, a sewage discharge outlet of the circulating water and sewage treatment system is communicated with an A pretreatment device, chemical dosing softening and coagulating sedimentation are carried out through the A pretreatment device, an outlet end of the A pretreatment device is communicated with a membrane concentration device through a pipeline, the wastewater is further concentrated through the membrane concentration device, the concentration TDS reaches about 30000mg/L, and an outlet end of the membrane concentration device is communicated with a deep concentration system through a pipeline;
the concentrated water discharge port of the feed water wastewater treatment system is respectively communicated to the deep concentration system and the desulfurization wastewater treatment system through pipelines, the concentrated water of the feed water wastewater treatment system and the concentrated water treated by the membrane concentration device are concentrated again through the deep concentration system, the concentration TDS of the concentrated water can reach more than 60000mg/L, the desulfurization wastewater outlet of the desulfurization wastewater treatment system is communicated with a pretreatment device B, and after the pH value of the wastewater is adjusted through the pretreatment device B, coagulation and precipitation treatment is carried out to precipitate suspended matters in the desulfurization wastewater;
the evaporation concentration system adopts a crystal seed method evaporation concentration system, chemical softening treatment is not adopted, slurry prepared by calcium sulfate powder is used as crystal seeds, and scaling of a heat exchange tube of the evaporation concentration system is avoided. Through a seed crystal evaporation concentration system, the wastewater is finally concentrated until the concentration TDS reaches about 200000 mg/L. The evaporation form of the seed crystal evaporation and concentration system adopts forced circulation multiple-effect evaporation, the flow rate of circulating liquid is in the range of 2.5-3 m/s, the evaporation efficiency is reasonably selected according to the treated water quantity, the treated water quantity of a single set of system is controlled to be below 40t/h, and the evaporation efficiency is 2-4.
The inlet end of the evaporation concentration system is respectively communicated with the depth concentration system and the pretreatment device B through pipelines, the outlet end of the evaporation concentration system is communicated with the pretreatment device C through a pipeline, the outlet end of the pretreatment device C is communicated with a membrane filtration device through a pipeline, the membrane filtration device is communicated with a bipolar membrane electrodialysis device, and NaOH solution and HCl solution are prepared and generated through the bipolar membrane electrodialysis device. And the bipolar membrane electrodialysis device is respectively communicated with the membrane concentration device and the C pretreatment device so as to return the fresh water generated by the bipolar membrane electrodialysis device to the membrane concentration device for continuous treatment, and the NaOH solution is recycled to the C pretreatment device. Wherein, carry out chemistry through C preprocessing device and add medicine softening and coagulating sedimentation, add the medicine and be: NaOH (sodium hydroxide), Na2CO3 (calcium carbonate) and BaCl2 (calcium chloride) to remove the sediment, hardness, sulfate radical, heavy metal and most suspended substances in the wastewater, and the wastewater treated by the C pretreatment device mainly contains NaCl.
Example 2
Based on the embodiment 1, another post-treatment process is adopted for the wastewater treated by the membrane filtration process, namely the high-concentration NaCl solution, as shown in fig. 4, the post-treatment process adopts an evaporative crystallization process, and the high-concentration NaCl solution is re-evaporated and crystallized by the evaporative crystallization process to prepare NaCl pure salt, wherein the NaCl pure salt is industrial grade and has better economical efficiency.
The process route can reduce the wastewater discharge of a power plant to the maximum extent, a traditional triple box system is cancelled, the system is simple, the wastewater resource treatment is finally realized, the zero discharge is realized, and the problems that the investment is high, the operation cost is high, the mixed salt cannot be treated, the system is easy to scale and the like commonly existing in other treatment routes at present are solved.
Accordingly, the post-treatment apparatus in example 1 was replaced accordingly, and as shown in fig. 2, the post-treatment apparatus was set as an evaporative crystallization apparatus, and the evaporative crystallization apparatus was communicated with a membrane filtration apparatus through a pipe. The industrial-grade NaCl pure salt is prepared through the post-treatment device, the purity reaches more than 98.5%, the purity requirement of the industrial-grade NaCl salt is met, the rest structures of the system are the same, and the description is omitted.
The invention is not limited to the above alternative embodiments, and any other various forms of products can be obtained by anyone in the light of the present invention, but any changes in shape or structure thereof, which fall within the scope of the present invention as defined in the claims, fall within the scope of the present invention.

Claims (10)

1. A power plant whole plant wastewater recycling treatment system comprises a circulating water and sewage treatment system, a water supply and wastewater treatment system and a desulfurization and wastewater treatment system, and is characterized in that the circulating water and sewage treatment system is matched with a bypass treatment system, a sewage outlet of the circulating water and sewage treatment system is communicated with a pretreatment device A, an outlet end of the pretreatment device A is communicated with a membrane concentration device, and an outlet end of the membrane concentration device is communicated with a deep concentration system;
the concentrated water discharge port of the feed water wastewater treatment system is respectively communicated to the deep concentration system and the desulfurization wastewater treatment system, and the desulfurization wastewater outlet of the desulfurization wastewater treatment system is communicated with the pretreatment device B;
the device is characterized by further comprising an evaporation concentration system, wherein the inlet end of the evaporation concentration system is respectively communicated with the depth concentration system and the pretreatment device B, the outlet end of the evaporation concentration system is communicated with the pretreatment device C, the outlet end of the pretreatment device C is communicated with the membrane filtration device, the membrane filtration device is communicated with the post-treatment device, and the final product is prepared through the post-treatment device.
2. The plant-wide wastewater recycling treatment system according to claim 1, wherein the post-treatment device is a bipolar membrane electrodialysis device, and the bipolar membrane electrodialysis device is respectively communicated with the membrane concentration device and the C pretreatment device.
3. The plant-wide wastewater resource treatment system according to claim 1, wherein the post-treatment device is an evaporative crystallization device, and the evaporative crystallization device is communicated with the membrane filtration device.
4. A method for recycling wastewater from a whole power plant is characterized by comprising the following steps:
treating the circulating sewage treatment system through a bypass treatment system, sequentially carrying out pretreatment process A and membrane concentration process on the sewage of the circulating sewage treatment system, and obtaining product A after the membrane concentration process;
supplementing one part of concentrated water discharged by the feed water wastewater treatment system to the desulfurization wastewater treatment system, and taking the other part of the concentrated water as a product B;
performing a deep concentration process on the product A and the product B to obtain a product C;
performing a B pretreatment process on the desulfurization wastewater discharged by the desulfurization wastewater treatment system to obtain a product D;
carrying out a seed crystal evaporation concentration process on the product C and the product D to obtain a product E, and sequentially carrying out a pretreatment process C and a membrane filtration process on the product E to obtain a product F;
and (4) carrying out a post-treatment process on the F product to prepare a final product.
5. The method for recycling wastewater from a whole plant of a power plant according to claim 4, wherein the post-treatment process adopts a bipolar membrane electrodialysis process, NaOH solution and HCl solution are produced by the bipolar membrane electrodialysis process, fresh water produced by the bipolar membrane electrodialysis process is returned to the membrane concentration process, and part of NaOH solution produced by the bipolar membrane electrodialysis process is returned to the C pretreatment process.
6. The resource treatment method for wastewater from whole plants in power plants according to claim 4, characterized in that the post-treatment process adopts an evaporative crystallization process, and NaCl pure salt is prepared by the evaporative crystallization process.
7. The method for recycling the wastewater from the whole plant of the power plant according to any one of claims 4 to 6, wherein the pretreatment process A and the pretreatment process C both comprise a coagulation precipitation process and a chemical dosing softening treatment process; and the pretreatment process B comprises the steps of firstly adding lime to adjust the pH value and then carrying out coagulating sedimentation treatment.
8. The method for recycling wastewater from a whole plant of a power plant according to claim 4, wherein the membrane concentration process comprises an ultrafiltration process and a low-pressure reverse osmosis process.
9. The method for recycling wastewater from a whole plant of a power plant according to claim 4, wherein the deep concentration process adopts a DTRO process or a high pressure reverse osmosis process.
10. The method for recycling wastewater from a whole plant of a power plant according to claim 4, wherein the evaporation concentration process adopts a seed crystal method evaporation concentration process, and the seed crystal method evaporation concentration process uses existing calcium sulfate crystals and newly configured calcium sulfate slurry in the wastewater as seed crystals.
CN202010787405.XA 2020-08-07 2020-08-07 System and method for recycling wastewater of whole power plant Pending CN112194298A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113060887A (en) * 2021-04-01 2021-07-02 大唐环境产业集团股份有限公司 Low-cost thermal power plant wastewater treatment device and method

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113060887A (en) * 2021-04-01 2021-07-02 大唐环境产业集团股份有限公司 Low-cost thermal power plant wastewater treatment device and method

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