JPH09294974A - Water treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the efficiency of the whole of a water treatment system. SOLUTION: Waste water such as desulfurization waste water in a power plant is treated in a waste treatment apparatus 300. This waste water treatment apparatus 300 has an evaporative concn. apparatus and condensed water is obtained from the evaporative concn. apparatus and supplied to a replenishing water treatment apparatus 200 forming high purity water necessary in the power plant 100 as raw water. Since condensed water is relatively good in quality, the replenishing water treatment apparatus 200 can be constituted of a reverse osmosis membrane apparatus, an electric deionizing apparatus or the like and the treated water therefrom is supplied as the replenishing water of the power plant. The conc. soln. of the reverse osmosis membrane apparatus or the electric deionizing apparatus is utilized as miscellaneous water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a facility having both a makeup water treatment device for obtaining highly purified makeup water and a waste water treatment device for treating waste water, for example, a water treatment system suitable for a thermal power plant. .

[0002]

2. Description of the Related Art Conventionally, in factories and the like, raw water received from the outside is used in various facilities to purify wastewater generated by the use of water and discharge the wastewater. Therefore, if the raw water quality is not sufficient, a water treatment device is required to purify the raw water to obtain water of a specified quality, and a wastewater treatment device is required to keep the drainage water quality below the standard value. . Therefore, it often has two water treatment devices, a water treatment device and a wastewater treatment device.

For example, a power plant has two water treatment devices, a wastewater treatment device for treating wastewater generated in various facilities and a makeup water treatment device for producing makeup water required for the power generation device. ing.

Particularly, in a thermal power plant, there are flue gas desulfurization effluent and cleaning effluent for various facilities as wastewater, and coagulation sedimentation filtration is generally used as a wastewater treatment device. If necessary, other treatment equipment may be added, and the treated water is usually p
It is discharged after H adjustment.

On the other hand, in power generation equipment, high-purity water is usually heated by a boiler to generate steam, which drives a turbine to operate a generator. High-purity water is reduced by drainage and the like due to power generation and periodic inspections, and thus make-up water is required. Therefore, a makeup water treatment device for producing high-purity makeup water is provided.

This make-up water treatment device treats river water, industrial water, city water, etc. as raw water and purifies it into high-purity water (pure water). Therefore, after performing pretreatment such as coagulation-sedimentation, filtration and treatment with activated carbon according to the quality of raw water, various ions are removed with an ion exchange resin to produce pure water. If the water source cannot be secured and the raw water is insufficient, a seawater desalination device may be installed.

Further, the ion exchange resin is regenerated at the time when a predetermined amount of water is reached or when the outlet water quality exceeds a specified value. Usually, the cation resin is regenerated with hydrochloric acid or sulfuric acid, and the anion resin is regenerated with caustic soda. Therefore, due to the regeneration of the ion exchange resin, waste water is generated from the makeup water treatment device, and this is also treated in the waste water treatment device.

Incidentally, a general treatment facility in a power plant is as described above, but it is disclosed in Japanese Patent Laid-Open No. 51-1023.
Japanese Patent Publication No. 57 etc. proposes to use the evaporative concentration treatment for the treatment of desulfurization wastewater in a thermal power plant. Further, this publication also discloses that the water quality of the condensed water is relatively good, so that the condensed water is reused as boiler water or other water.

As the makeup water treatment device, not only the usual treatment using an ion exchange resin but also the reverse osmosis membrane (R
O), a method using an electric deionization treatment (EDI or EDR), or a combination thereof is proposed. Such processing is performed, for example, in Japanese Patent Laid-Open No. 6-1344.
No. 90 publication.

Furthermore, the magazine "Thermal Nuclear Power Vol.
46 No. 9 September 1995 ”, it is shown that sewage is treated with a reverse osmosis membrane + ion exchange resin to be used as power plant boiler water. Further, in this document, the concentrated liquid (RO concentrated liquid) generated in the reverse osmosis membrane and the ion-exchange resin regeneration wastewater are treated with EDI and RO, and the treated water is recovered and used, and also generated by EDI and RO. It is shown that the concentrated liquid is evaporated and concentrated, and the condensed water is ion-exchanged and reused as boiler water.

[0011]

As described above, there are various proposals for water treatment systems in power plants.
However, there is a demand for effective use of water as a whole facility, to reduce the amount of drainage, and also to reduce the installation area and improve economic efficiency in terms of equipment, and a more efficient water treatment system is required. ing.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a suitable water treatment system in which a waste water treatment device and a makeup water treatment device are combined to enable efficient treatment as a whole. To do.

[0013]

A water treatment system according to the present invention comprises a makeup water treatment apparatus for purifying raw water to produce makeup water and supplying the produced makeup water to a water consumption facility, and a water consumption facility. It is characterized in that it includes an evaporative concentrator for treating the wastewater from the water, and a circulation system for returning condensed water generated in the treatment process in the evaporative concentrator to the raw water supply side of the makeup water treatment device. In this way, the condensed water obtained by evaporative concentration is supplied to the makeup water treatment device. Therefore, the waste water can be reused and the water can be effectively used. In addition, since the water quality of condensed water is higher than that of industrial water, efficient treatment can be performed in the makeup water treatment device.

Another aspect of the present invention is characterized in that the makeup water treatment device includes a reverse osmosis membrane treatment device. The reverse osmosis membrane treatment has a low removal rate of silica, but the condensed water is
Since the content of silica is low, no problem occurs. Therefore, it is highly preferable to perform the reverse osmosis treatment on the condensed water of the evaporative concentrator.

Still another invention is characterized in that the makeup water treatment apparatus includes an electric deionization apparatus.
Although the electric deionization device has a small ability to remove weak electrolytes, the condensed water has a small content of weak electrolytes, so that no problem occurs. Therefore, it is highly preferable to perform the reverse osmosis treatment on the condensed water of the evaporative concentrator.

Still another aspect of the present invention is to provide a condensed water storage tank in the middle of the circulation system, and to provide a gas dissolution preventing means for preventing the dissolution of oxygen and carbon dioxide gas in the atmosphere in the condensed water storage tank. Is characterized by. Condensed water contains almost no oxygen and carbon dioxide, and by preventing the subsequent dissolution, the contents of oxygen and carbon dioxide in the makeup water can be reduced. Therefore, the oxygen-carbon dioxide content in the makeup water of the boiler of the power plant can be reduced.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

[Overall System] FIG. 1 shows the overall configuration of a water treatment system applied to a thermal power plant according to an embodiment of the present invention.

The power station 100 is a facility for generating steam from high-purity water by a boiler and rotating a turbine with the generated steam to generate power. In addition, a lime-fired power plant also includes a flue gas desulfurization device that treats exhaust gas accompanying combustion of fuel for heating a boiler.

In order to replenish the required high-purity water by operating the power plant 100, the power plant 100 receives pure water as supplementary water. This makeup water is obtained by treating the raw water in the makeup water treatment device 200. As raw water for the makeup water treatment device 200, river water, industrial water, city water, or the like is used. Further, the makeup water treatment device is composed of, for example, a reverse osmosis device RO, an electric deionization device EDI, and a cartridge polisher (cartridge type non-regeneration type ion exchange device).

In addition to the flue gas desulfurization wastewater, the power station 100 discharges floor cleaning, drain wastewater of various equipment, and the like, and flows into the wastewater treatment device 300. The wastewater treatment device 300 is composed of an evaporative concentration device, evaporates and condenses the wastewater, and discharges the concentrated liquid or the evaporation residue. Wastewater containing a large amount of ammonia discharged from the condensate demineralizer for desalting boiler condensate is also processed by the evaporative concentrator by appropriately adjusting the pH. The evaporative concentrator has an operating temperature of about 70 ° C. and an operating pressure of about −50, for example.
It is operated at 0 to -600 mmHg (negative pressure).

Here, in the present embodiment, the wastewater treatment device 3
The condensed water obtained by the evaporative concentration in No. 00 is returned to the raw water side of the makeup water treatment apparatus 200. Therefore, the makeup water treatment device 200 receives the condensed water as the raw water, and the shortage will be covered by the industrial water from the outside.

That is, in the present embodiment, the raw water of the makeup water treatment device 200 is basically condensed water supplied from the wastewater treatment device 300, and industrial water or the like is supplemented for the shortage.

The electric conductivity of industrial water, river water, and city water, which is raw water for supplementing the shortage, is 100 μS / cm.
The electrical conductivity of the condensed water generated in the wastewater treatment device 300 is 10 to 20 μS / cm, although it is a degree. Therefore, the raw water of the makeup water treatment device 200 has a very high quality, which is about 1/10 of that of the conventional raw water. The turbidity of condensed water is usually 1 or less.

Particularly, in the condensed water, calcium, magnesium, silica and the like which are scaling components are very small. This is because the scaling component is less likely to evaporate and less likely to exist in the condensed water.

Therefore, in the makeup water treatment device 200,
When a reverse osmosis membrane is used, the recovery rate (ratio of treated water to raw water), which was about 80 to 90% in the conventional method using industrial water as raw water, can be further increased.

In the reverse osmosis membrane, the removal rate of silica is poor, and silica has a serious adverse effect on the boiler, turbine, etc. of the power plant 100. Therefore, the fact that the condensed water, which is the raw water, contains less silica is a great advantage in utilizing the reverse osmosis membrane.

Further, in the makeup water treatment device 200,
It is also suitable to use an electric deionization device. That is, the electric deionization method uses electrodialysis,
The ability to remove weakly dissociated weak electrolytes such as bicarbonate and silica ions is small. Since the condensed water contains few such components, a pretreatment for removing silica or the like is not necessary even in the electric deionization method in which an ion exchange resin is filled between the electrodialysis membranes.

Further, since the scale component is small, the reverse osmosis membrane and the electrodialysis membrane in the electric deionization method are less contaminated, so that the useful life of them can be extended.

Further, in order to improve the quality of the treated water (pure water) of the makeup water treatment device 200, a mixed bed ion exchange resin type cartridge polisher is provided at the subsequent stage of the treatment device as described above. Is preferred. This cartridge polisher is of a disposable type (non-regeneration type), does not generate regeneration waste liquid, and is suitable for removing a minute amount of ions.

The reverse osmosis membrane and the electric deionization method do not require chemical regeneration. In particular, in the present embodiment, the raw water quality is improved, and especially the components that are difficult to remove by the reverse osmosis membrane or the electric deionization method are very small. Therefore, by constructing the makeup water treatment device 200 with a treatment device of reverse osmosis membrane → electric deionization → cartridge polisher, wastewater from the makeup water treatment device 200 is generated in the reverse osmosis membrane device and the electric deionization device. It becomes only concentrated liquid. Further, this concentrated liquid can be treated in the wastewater treatment device 300, but can be used as it is as miscellaneous water. That is, the concentrate has an electric conductivity of 300 μS.
It is of a degree and can be suitably used as washing water.

As described above, a very efficient water treatment system is obtained by combining the wastewater treatment device 300 consisting of the evaporative concentration device and the makeup water treatment device 200 consisting of the reverse osmosis membrane, the electric deionization and the cartridge polisher. can get.

In addition, in the makeup water treatment device 200, a normal regenerated ion exchange resin can be used. Even in this case, since the quality of the condensed water from the wastewater treatment device 300 is high, the efficiency of the treatment with the ion exchange resin can be improved. That is, when the same amount of ion exchange resin as the conventional one is used, the interval between chemical regenerations becomes longer and the amount of chemicals used can be reduced. Further, when the same chemical regeneration interval is maintained, the amount of ion exchange resin may be small and the apparatus can be downsized. In addition, the effluent of the chemical regeneration is the wastewater treatment equipment 30 together with the wastewater of the power plant 100
It is introduced to 0 and processed.

[Wastewater Treatment Device] FIG. 2 shows an example of the configuration of a wastewater treatment device 300 suitable for this embodiment. The waste water from the power plant 100 flows into the pH adjusting tank 1 through the waste water supply line aa. The pH adjusting tank 1 adjusts the pH of the waste water from weak acid to neutral, and acid or alkali is added from the pH adjusting chemical storage tank 5 by the pH adjusting agent pump 8 as needed. It is preferable that the pH in the pH adjusting tank 1 is measured and the pH adjusting agent pump 8 is controlled.

The waste water in the pH-adjusted tank 1 whose pH has been adjusted is
It is supplied to the evaporative concentrator 2 by the drainage supply pump 9. The evaporative concentrator 2 is depressurized to about -500 to -600 mmHg by the vacuum pump 12 via the condenser 3. Further, the steam supplied from the heated steam line bb is used as a heating source, and the operating temperature is set to about 70 ° C.

The vapor evaporated in the evaporative concentrator 2 is condensed in the condenser 3 and discharged to the outside of the system by the condensed water pump 13. In the present embodiment, the water is once stored in the condensed water storage tank and then supplied to the makeup water treatment apparatus 200.

The capacitor 3 has lines cc and d
d is connected, and cooling water is circulated from here.

On the other hand, the concentrated liquid concentrated in the evaporative concentrator 2 is constantly circulated through the concentrated liquid circulation pump 10 and is discharged to the concentrated liquid tank 4 by the concentrated liquid discharge pump 11 when a certain concentration is reached. . Further, the drain of the heated steam is discharged by the steam drain pump 14.

The evaporative concentrator 2 is supplied with different kinds of water-soluble polymers from the water-soluble polymer storage tanks 6 and 7. As a result, the dispersibility of the solid matter in the concentrated liquid is improved, and the generation of scale in the evaporation concentrator 2 is prevented.
Further, the concentrated liquid may be further evaporated, and the residue may be disposed of by landfill or the like.

The evaporative concentrator 2 may be of a horizontal heat transfer tube type or a vertical thin film type. Further, the heating may be performed by the external heating method as described above or the self vapor compression type.

"Reverse Osmosis Membrane Treatment" As the reverse osmosis membrane, various materials such as cellulose acetate type membrane, polyamide type composite membrane, polyvinyl alcohol type membrane can be adopted. Further, as the shape, any shape such as a hollow fiber, a spiral, and a tubular can be applied. In this embodiment, a low-pressure type reverse osmosis membrane device is preferable because the ionic impurity concentration of raw water is low and the osmotic pressure is low.

FIG. 3 shows a configuration example of the reverse osmosis membrane treatment apparatus.
The condensed water from the evaporative concentrator 2 of the wastewater treatment device 300 is supplied to the condensed water storage tank 15 from the condensed water supply line ee,
It is stored here. Here, the condensed water storage tank 15 has, for example, a nitrogen seal structure, is shielded from the atmosphere, and is prevented from dissolving carbon dioxide gas and oxygen in the condensed water.

Then, the condensed water in the condensed water storage tank 15 is passed through the water pump 16 to the safety filter 1 for protecting the reverse osmosis membrane.
Water is passed to 7. The condensed water filtered by these is passed through the high pressure pump (booster pump) 18 to the reverse osmosis membrane device 19 at a predetermined pressure.

The treated water desalted by the reverse osmosis membrane device 19 is stored in the reverse osmosis membrane treated water tank 20.
On the other hand, the concentrated liquid in which the salt content has been concentrated by the desalting treatment is stored in the reverse osmosis membrane concentration tank 21.

"Electrical Deionization Device" The electrical deionization device is a pure water production technique in which ion exchange and electrodialysis are combined to move ions as impurities in water by direct current to remove them. And an ion exchanger (ion exchange resin or ion exchange fiber) filled between the electrodialysis membranes
Various configurations such as a mixed bed of a cation resin and an anion resin or a combination of single beds can be adopted.

FIG. 4 shows a structural example of the electric deionization apparatus. In this example, the condensed water from the wastewater treatment device 300 is passed through the condensed water storage tank 15 to the electric deionization device 22. Then, the treated water desalted by the electric deionizer 22 is supplied as makeup water for the power plant 100 through the treated water tank 23 of the electric deionizer. on the other hand,
The concentrated liquid produced by the desalting treatment is stored in the electric deionizer concentrated liquid tank 24 and used as miscellaneous water.

"Reverse Osmosis Membrane Device + Electrical Deionization Device" FIG. 5 shows a constitution in which condensed water is treated by the reverse osmosis membrane device and then treated by the electric deionization device. In this way, the treated water obtained in the reverse osmosis membrane device 19 is passed through the reverse osmosis membrane treated water tank 20 and the electric deionization water pump 21 to the electric deionization device 22. Then, the treated water desalted by the electric deionizer 22 is supplied from the electric deionizer treated water tank 23 as make-up water for the power plant 100, and the electric deionizer concentrate and the reverse osmosis membrane concentrate are concentrated. It is used as miscellaneous water via the tank 24.

[0048]

【Example】

"Condensed water" First, Table 1 shows the water quality of condensed water when desulfurization wastewater discharged from a coal-fired power plant is evaporated and concentrated by the above-described evaporative concentration apparatus.

[0049]

[Table 1] "Example 1" Table 2 shows the treated water quality and the amount of water when the condensed water shown in Table 1 was treated with a reverse osmosis membrane.

[Table 2] Thus, it was possible to make the recovery rate of the treated water as high as 95%, and the treated water quality was good at 3 μS / cm.

Example 2 Table 3 shows the quality of treated water and the flow rate when the condensed water shown in Table 1 was treated with an electric deionization apparatus.

[0051]

[Table 3] In this way, it was confirmed that the treated water quality was as good as 0.3 μS / cm.

[Example 3] Table 4 shows the treated water quality and flow rate when the condensate shown in Table 1 was treated with a reverse osmosis membrane and an electric deionization apparatus.

[0053]

[Table 4] As described above, it was confirmed that the treated water quality in the two-stage treatment by the reverse osmosis membrane device and the electric deionization device was 0.1 μS / cm, which was a very good water quality.

[0054]

As described above, the evaporative concentration device is applied to the wastewater treatment device, and the makeup water treatment device that uses the condensed water generated in the evaporative concentration process as raw water is combined to achieve effective use of water. In addition, it is possible to obtain an economically advantageous water treatment device that can reduce the amount of wastewater generated and can reduce the installation area.

Further, a reverse osmosis membrane device is added to the makeup water treatment device,
By using the electric deionization device, the concentrated liquid discharged from the makeup water treatment device can also be used as miscellaneous water.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a water treatment system.

FIG. 2 is a diagram showing a configuration of a wastewater treatment device including an evaporative concentrator.

FIG. 3 is a diagram showing a configuration of a reverse osmosis device.

FIG. 4 is a diagram showing a configuration of an electric deionization apparatus.

FIG. 5 is a diagram showing a configuration of a reverse osmosis device + electric deionization device.

[Explanation of symbols]

2 evaporative concentrator, 19 reverse osmosis membrane device, 22 electric deionization device, 100 power plant, 200 makeup water treatment device,
300 wastewater treatment equipment.

Claims (5)

[Claims] 1. A makeup water treatment apparatus for purifying raw water to generate makeup water and supplying the generated makeup water to a water consumption facility, an evaporative concentration apparatus for treating wastewater from the water consumption facility, and the evaporation A water treatment system comprising: a circulation system that returns condensed water generated in the treatment process of the concentrator to the raw water supply side of the makeup water treatment device. 2. The system according to claim 1, wherein the makeup water treatment device includes a reverse osmosis membrane treatment device. 3. The water treatment system according to claim 1, wherein the makeup water treatment device includes an electric deionization device. 4. The water treatment system according to claim 1, wherein the makeup water treatment device includes a reverse osmosis membrane treatment device and an electric deionization device. 5. The system according to any one of claims 1 to 4, wherein a condensate water storage tank is provided in the middle of the circulation system, and gas is dissolved in the condensed water storage tank to prevent dissolution of oxygen and carbon dioxide gas in the atmosphere. A water treatment system comprising a prevention means.