JPH09308881A - Washing of condensed water desalting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To wash a condensed water desalting apparatus within a short washing time by reducing the load of a suspension of a metal oxide leaked at the initial period of the passage of water after the regeneration of a desalting tower to an ion exchange resin bed. SOLUTION: In a condensed water treatment system wherein condensed is filtered by a filter 1 and filtered condensed water and unfiltered condensed water are parallelly passed through a plurality of desalting columns 2a, 2b... of a condensed water desalting apparatus 2 to be desalted, the anion and cation exchange resins of the mixed bed 7a of the desalting column 2a lowered in its desalting capacity are backward washed and separated to be regenerated and washed, and the washed resins are mixed in the desalting column 2a to form the mixed bed 7a to perform washing at the initial stage of water passage. At this time, the washing waste waster of the desalting column 2a is circulated to the filter 1 to be filtered before introduced into the desalting column 2a to perform circulating washing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a condensate demineralizer, and more particularly to a circulating cleaning method for the initial stage of water passage after regeneration of the condensate demineralizer.

[0002]

2. Description of the Related Art In a thermal power plant and a nuclear power plant, steam condenses to generate condensate. A condensate demineralizer is provided to reuse the condensate as boiler water. The condensate demineralizer removes dissolved salts and some metal oxides in the packed bed of anion and cation exchange resin, but a large amount of metal oxides and other suspended solids are removed. When it is included, it is filtered by the filtering device provided in the previous stage.

Generally, in a power plant, when metal impurities are brought into the boiler, corrosion by metal scales and a decrease in thermal efficiency occur. Therefore, it is necessary to supply as clean water as possible to the boiler (steam generator). Especially BW
In the R nuclear power plant, by preventing the increase in the radioactivity level of the system due to the metal oxide flowing into the reactor and being activated, and by suppressing the oxide adhesion to the fuel rod,
Iron removal is required for the purpose of reducing the radiation exposure of workers during maintenance work. In the PWR nuclear power plant, iron is removed for the purpose of preventing corrosion inside the steam generator and preventing clogging of the water flow path due to scale accumulation by suppressing the inflow of iron into the steam generator.

For this reason, in any case, as a device for condensate treatment, it is standard to install a filtration device in the front stage and a condensate desalination device in the rear stage. Here, the filtering device is also expected to have an effect of preventing metal contamination of the ion-exchange resin filled in the desalting device by removing the metal oxide and maintaining a good ion-exchange reaction.

In this configuration, the filtering device requires a large space as a facility for condensing water, and the cost increases due to the consumption of the filtering material. Therefore, the filtering device can process only a part of the condensate. Perform small capacity equipment often installed. In this case, perform filtration when there is a large amount of suspended matter, such as when starting up the device, and do not perform filtration when there is a small amount of suspended matter, such as during normal operation, and directly introduce condensate into the desalination device. It is configured.

In the condensate demineralizer, a plurality of mixed-bed type demineralization towers filled with anion and cation exchange resins are installed in parallel, and condensate is simultaneously passed through these to perform desalination. The demineralization tower with reduced capacity is separated from the desalination process and moved to the regeneration process. In the regeneration step, backwashing with water separates the anion and cation exchange resin layers, and each resin layer is regenerated in a separate regeneration tower. The regenerated resins are mixed in the desalting tower to form a mixed bed,
After washing, return to the desalting process.

By the way, the treated water quality of the condensate treatment apparatus composed of the filtration apparatus and the condensate demineralization apparatus is determined by the two-stage treatment of the filtration apparatus and the desalination apparatus, but the filtration apparatus can completely remove iron. Instead, about 1 to 50% of the inflow of iron and other metal oxides flows into the subsequent desalination unit,
A phenomenon of sticking to the surface of the ion exchange resin is recognized. The metal oxide adhered to the surface of the ion exchange resin is slightly dissolved by the regenerant of the ion exchange resin such as hydrochloric acid or sulfuric acid, but a large amount of metal oxide adheres to the surface of the resin during long-term use. In particular, an anion exchange resin using sodium hydroxide as a regenerant has a small metal-dissolving ability, and a large amount of metal adheres to the surface of the ion exchange resin.

For this reason, the metal oxide such as iron attached to the surface of the regenerated resin is easily peeled off,
Since the metal oxide is peeled off and leaks into the treated water for 3 to 24 hours from the start of water flow due to the flow rate shock, a circulating cleaning step is provided to reduce the iron concentration of the treated water. In the conventional circulation cleaning process, the treated water is circulated in the untreated water supply path in front of the desalting tower, so the circulated treated water also enters other desalting towers, and the metal oxides are used in the desalting tower. In addition to the above load, it takes time for the amount of metal oxide leaked from the ion-exchange resin layer to decrease, and there is a problem that long cleaning is required.

[0009]

The object of the present invention is to reduce the load on the ion-exchange resin layer of suspensions of metal oxides and the like that leak during the initial passage of water after regeneration of the desalting tower, and also to perform washing. It is to propose a cleaning method for a condensate demineralizer that can shorten the time.

[0010]

SUMMARY OF THE INVENTION The present invention provides a condensate treatment system comprising a filtering device for filtering condensate and a condensate desalting device for desalting condensate after filtering or not filtering. After regenerating the condensate desalination apparatus, the washing wastewater of the condensate desalination apparatus is circulated to the condensate deionization apparatus through the filtration device to perform washing at the initial stage of water passage. Is the cleaning method.

The condensate demineralizer to be cleaned in the present invention is installed in the latter stage of the filtering device in a system that uses condensed water in which steam is condensed as boiler water, such as thermal power or nuclear power generation, and is installed after the filtering device. This is a device for desalting the condensate before the filtration or the condensate after the filtration, and is composed of a mixed bed type ion exchange device filled with anion and cation exchange resins.

This condensate demineralizer demineralizes the condensate after filtering by the filtration device when the condensate contains a large amount of metal oxides and other suspensions, and in a steady operation state in which there are few suspensions. Although the condensate before filtering is directly desalted, the condensate filtered by a filtering device may always be desalted. Desalination may be carried out by mixing the subsequent condensate.

As the ion exchange resin to be filled in such a condensate demineralizer, a strongly basic anion exchange resin is used as the anion exchange resin and a strongly acidic cation exchange resin is used as the cation exchange resin, and both are mixed to form a mixed bed. Form. A condensate demineralizer is constructed by installing a plurality of desalting towers having a mixed bed in parallel.

The filter installed before the condensate demineralizer may be any one capable of removing metal oxides such as iron oxides and other suspended matter in the condensate, such as a precoat filter, an electromagnetic filter and a hollow fiber membrane. Although any type of filtration device such as a filter can be used, it is preferable to use a hollow fiber membrane filter, a cartridge filter, or the like that can be operated intermittently because filtration can be performed only when necessary.

The filtering device may be provided in the preceding stage of the desalting device and may be connected so that the condensate is always filtered and then supplied to the desalting device. It is preferable that the filter is provided in the above-mentioned item and the condenser is bypassed and the condensate is directly supplied to the desalination unit. In this case, when the amount of suspension in the condensate is small, the condensate is directly supplied to the desalting device, and when the amount of suspension is large, it is supplied to the desalting device after being filtered by the filtering device. Usually, the amount of suspended solids is large when the equipment is started up, such as after periodic inspection of the power plant, and it is small in the steady state.

In the condensate treatment system as described above, if necessary, condensate produced by steam condensation in a power plant or the like is filtered by a filter to remove metal oxides and other suspended matter. Then, the filtered condensate water or the unfiltered condensate water is desalted by ion exchange in a condensate desalination apparatus, and circulated to a boiler (steam generator) for reuse. Desalination equipment normally conducts condensate water in parallel to a plurality of desalination towers for desalting, and among them, the desalting towers with reduced ion exchange capacity are sequentially separated from the water passage (desalination) step for regeneration. To do.

In the regenerating step, a usual regenerating method used in a condensate demineralizer can be adopted. In a general method, a mixed resin of anion and cation exchange resin is transferred to a backwash separation column from a desalting column that is blocked from the condensate line and the treated water line. Here, the anion exchange resin layer and the cation exchange resin layer are separated by backwash separation with a difference in specific gravity, and each resin layer is transferred to an anion regeneration tower and a cation regeneration tower for regeneration. In this case, the backwash separation column can also be used as the cation regeneration column.

The regeneration operation in each regeneration tower is such that scrubbing is performed by backwashing with air to remove the deposits, chemicals of the regenerant are injected, extrusion is performed to regenerate each resin layer, and washing with pure water is sequentially performed. . The resin layers that have been washed are transferred to a desalting tower and mixed with stirring by introducing air to form a mixed bed.

Thereafter, in the desalting tower, washing is performed in the mixed bed state at the initial stage of water passage. As the cleaning at the beginning of water passage, after washing with pure water, the condensate is passed through at a low flow rate to collect and wash,
Circulation cleaning is performed by increasing the flow rate of the water passing process. In the first pure water cleaning step, pure water is passed at a low flow rate to wash away peeled substances and other impurities generated during the transfer and stirring and mixing of the resin, and the cleaning waste water is discharged to the outside of the system. In the recovery and cleaning process, condensate is passed at a low flow rate, and cleaning wastewater is returned to the condenser for recovery.

After the pure water cleaning and the recovery cleaning as described above, when the flow rate of the condensate is increased to the flow rate of the water-passing (desalting) step, the adhered matter is separated due to the shock of the flow rate. In order to do this, the cleaning waste water is circulated to perform circulation cleaning. Conventionally, the cleaning wastewater was circulated immediately before the desalting tower, but in the present invention, the cleaning wastewater is supplied to a filtering device, filtered by the filtering device, and then circulated immediately before the desalting tower to perform desalination. Introduce to the tower.

Although another filtration device may be used as the filtration device, it is preferable to use the filtration device provided in the condensate treatment system. Further, the filtration by the filtering device may be performed only on the washing wastewater of the desalting tower during washing, and the filtered water may be circulated to the desalting tower during washing, but the washing wastewater is filtered,
It is preferable to mix the filtered water with the condensate to be treated and to introduce it into other desalting towers in a divided manner because the filtering device can be effectively used.

When the wash drainage is filtered by the filter, the metal oxide and other suspensions in the wash drainage are captured by the filter medium, and the filtered water enters the desalting tower. In the desalting tower, the suspension remaining in the filtered water is removed, and the flowable suspension deposited on the resin layer is washed out. By performing circulation cleaning while circulating the cleaning wastewater, when the amount of the suspended matter flowing out into the cleaning wastewater becomes small, water is collected as treated water and the process proceeds to the water passing (desalting) step. At this stage, the filtration by the filtration device is stopped, and the condensate is directly passed through the desalting tower for desalting.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram showing a cleaning method for a condensate demineralizer according to an embodiment.

In FIG. 1, 1 is a filtering device, 2 is a condensate demineralizer, and a plurality of desalting towers 2a, 2b ... Are provided between the condensate line 3 and the treated water line 4, and valves 5a, 5b. Are provided in parallel via the condensate introduction passages 3a, 3b ... And the treatment water passages 4a, 4b. A filter medium 1 a is built in the filter device 1. Mixed beds 7a, 7b of anion and cation exchange resin are formed in the desalting towers 2a, 2b. The filtering device 1 is provided with a valve 9 of a bypass line 9 connecting before and after the valve 8 of the condensate line 3.
It is provided between a and 9b.

Compressed air passages 11a ... And 12a ... Are connected to the upper and lower portions of the desalting towers 2a, 2b ... Through valves 13a.
5a and the resin outlet 16a are valves 17a ... and 1
8a ... and communicate with each other through the treatment water channels 4a, 4
Circulation paths 20a having valves 19a are branched from b, but only the demineralization tower 2a and the treatment water path 4a are illustrated. The circulation paths 20a ... Are connected to the filtration device 1 via a circulation line 20 having a pump 21 and a valve 23. From the circulation line 20 a recovery line 25 with a valve 24 communicates with a condenser (not shown).

In the condensate treatment system as described above, the condensate generated by the condensation of steam in the power plant or the like is introduced from the condensate line 3 into the filtering device 1 and filtered when necessary depending on the condensate quality, Remove metal oxides and other suspensions. Then, the filtered condensate water or the unfiltered condensate water is returned to the condensate desalination device 2
In this, it is desalted by ion exchange and circulated to the boiler (steam generator) for reuse. In the desalination apparatus 2, condensate is passed in parallel to a plurality of desalting towers 2a, 2b ... to perform desalting, and a desalting tower having a reduced ion exchange capacity, for example, 2a water passing (desalination) step. Playback is performed by sequentially disconnecting from.

For the regeneration step, the usual regeneration method used in the condensate demineralizer is adopted. For example valves 5a, 6a
By closing, the compressed air passage 11a sends compressed air to the demineralization tower 2a which is shut off from the condensate line 3 and the treated water line 4, and the mixed resin of anion and cation exchange resin is backwashed and separated from the resin extraction passage 16a. Transfer to a tower (not shown). Here, the anion exchange resin layer and the cation exchange resin layer are separated by backwash separation with a difference in specific gravity, and each resin layer is transferred to an anion regeneration tower and a cation regeneration tower for regeneration. In this case, the backwash separation column can also be used as the cation regeneration column.

In the regeneration operation in each regeneration tower, scrubbing is performed by backwashing with air to remove the deposits, and then a regenerating agent (sodium hydroxide for anion exchange resin, sulfuric acid for cation exchange resin). Each of the resin layers is regenerated by performing chemical injection and extrusion with pure water, and washing with pure water is sequentially performed. Each resin layer after washing is desalting tower 2a
Then, the compressed air is introduced from the compressed air passage 12a and stirred and mixed to form the mixed bed 7a.

After that, in the desalting tower 2a, washing in the initial stage of water passage is performed in a mixed bed state. As the initial washing with water, washing with pure water is performed for 10 to 30 minutes, and then condensate is passed at a low flow rate to carry out recovery washing for 30 to 60 minutes. Circulation cleaning is performed for 24 hours.

In the first deionized water washing step, deionized substances and other impurities generated during the transfer and stirring and mixing of the resin are washed away by passing deionized water at a low flow rate, and the washing waste water is discharged to the outside of the system (pure water. The flow path for cleaning is not shown). In the recovery and washing step, the condensate is passed through the condensate passage 3a at a low flow rate without being filtered by the filtration device 1, and the cleaning wastewater is recovered from the treated water passage 4a through the recovery line 25 into a condenser (not shown).

After deionized water washing and recovery washing as described above, when the flow rate of the condensate is increased to the flow rate of the water-passing (desalting) step, the adhered matter is peeled off due to the shock of the flow rate. In order to do this, the cleaning waste water is circulated to perform circulation cleaning. In this case, with the valves 6a, 9a, 24 closed,
After opening the valves 9b, 19a, 23, the pump 21 circulates the washing wastewater from the circulation line 20 in front of the filtration device 1, and after filtering with the filtration device 1, the desalination towers 2a, 2b via the condensate line 3. Introduce to ...

When the wash drainage is filtered by the filter device 1, the metal oxide and other suspensions in the wash drainage are captured by the filter medium 1a, and the filtered water enters the desalting towers 2a, 2b ... Desalting tower 2a,
In 2b ..., the suspension remaining in the filtered water is removed, and in the desalting towers 2b, 2c ..., normal desalting is performed. In the desalting tower 2a, the flowable suspension accumulated on the resin layer is washed out.

When the amount of suspended matter flowing out into the cleaning drainage becomes small by performing the circulating cleaning while circulating the cleaning drainage in this way, the valve 19a is closed and the valve 6a is opened, so that the treated water in the desalting tower 2a is discharged. Water is collected in the treated water line 4, and the process proceeds to the water passing (desalting) step. At this stage, the filtration by the filtration device 1 is stopped, and the condensate is directly passed through the desalting towers 2a, 2b ...

Conventionally, in the case of circulation cleaning, the cleaning drainage was circulated from the circulation line 22 to the condensate passage 3 immediately before the desalting device 2, so that the suspension in the cleaning drainage is the entire desalting towers 2a, 2b. …
Load on each of the desalination towers and shorten the water sampling time.
In the desalting tower 2a, the suspension that cannot be captured leaks for a long time, the concentration of the washing waste water does not decrease, and the washing time becomes long.

On the other hand, when the washing wastewater is circulated from the circulation line 20 to the filtering device 1 for filtration, the suspension in the washing wastewater is captured by the filtering device 1, so that the desalting towers 2a, 2
The load of b ... is reduced and the water sampling time becomes longer. Then, in the desalting tower 2a, the amount of suspended matter leaking out becomes small, so that the circulation cleaning time becomes short. The washing wastewater of the desalting tower 2a is treated water that has been desalted, and by passing through the filtration device 1, ions are eluted from the trapped suspension, but the amount thereof is very small, The increase in the load on the towers 2a, 2b ... Can be almost ignored.

[0036]

EXAMPLES Examples and comparative examples of the present invention will be described below.

Example 1 In the condensate treatment system shown in FIG. 1 (condensate flow rate 2800 T / Hr), the performance of one desalting tower 2a deteriorated, so regeneration was carried out by the above operation. Since 5 desalting towers are installed, the processing flow rate per unit is 560 in normal desalting operation.
It is T / Hr, but the other processing flow rate when regenerating one unit is 700T.
/ Hr.

After regeneration, the resins are mixed in the desalting tower 2a,
Pure water was passed at 150 T / Hr for washing for 20 minutes, and condensate was passed at 200 T / Hr for 45 minutes for collecting and washing. Next, when the condensate flow rate was increased to 350 T / H and the cleaning wastewater was circulated through the filter device 1 to perform circulation cleaning, the iron concentration in the cleaning wastewater was 3 mg /
It became 1 and it became possible to shift to the water sampling (desalting) step. The iron concentration in the cleaning drainage water and the treated water from the water flow preparation step (pure water cleaning step) is shown in "invention method" of FIG.

Comparative Example 1 In Example 1, when the cleaning waste water was circulated before the condensate demineralization apparatus 2 (after the filtration apparatus 1) during circulation cleaning, about 12
After a lapse of time, the iron concentration in the washing wastewater became 3 mg / l, and it became possible to shift to the water sampling (desalting) step. The iron concentration in the cleaning drainage water and the treated water from the water flow preparation step (pure water cleaning step) is shown in "Conventional method" in FIG.

From the results shown in FIG. 2, the iron concentration was 3 in Comparative Example 1.
It takes about 12 hours to reach mg / l or less, whereas in Example 1, about 2 hours is required, and it can be seen that the cleaning time can be shortened.

[0041]

According to the present invention, after the condensate demineralizer is regenerated, the cleaning wastewater of the condensate demineralizer is circulated to the condensate demineralizer through the filtering device to perform the initial washing of the water. Therefore, it is possible to reduce the load on the ion-exchange resin layer of the suspension of metal oxides or the like that leaks out in the initial water passage after the regeneration of the desalting tower, and it is possible to shorten the washing time.

[Brief description of drawings]

FIG. 1 is a system diagram showing a method for cleaning a condensate desalination apparatus according to an embodiment.

FIG. 2 is a graph showing the results of examples and comparative examples.

[Explanation of symbols]

1 Filtration device 1a Filter medium 2 Condensate demineralizer 2a, 2b ... Desalting tower 3 Condensation line 3a, 3b ... Condensate channel 4 Treated water line 4a, 4b ... Treated channel 5a, 5b ..., 6a, 6b ..., 8, 9a, 9b, 13a
..., 14a ..., 17a ..., 18a ..., 19a, 23, 2
4 ... Valve 7a, 7b ... Mixed bed 9 Bypass passage 11a ..., 12a ... Compressed air passage 15a ... Resin introduction passage 16a ... Resin extraction passage 20, 22 Circulation line 20a ... Circulation passage 21 Pump 25 Recovery line

Claims (1)

[Claims] 1. A condensate treatment system comprising a filtering device for filtering condensate and a condensate desalting device for desalting condensate after filtering or unfiltered condensate. After that, a cleaning method for a condensate desalination device, characterized in that cleaning wastewater of the condensate desalination device is circulated through the filtration device to the condensate deionization device to perform cleaning at the initial stage of water passage.