JPS60125598A - Desalting device for condensate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a condensate purification system having a mixed bed type condensate desalination device incorporating a granular cation exchange resin and an anion exchange resin, and particularly relates to a condensate purification system having a mixed bed type condensate desalination device containing a granular cation exchange resin and an anion exchange resin. The present invention relates to a condensate desalination device suitable for effective regeneration of resin.

[Background of the invention]

Conventional nuclear reactor systems, especially boiling water reactors (referred to as BWRs)
The system has a configuration as shown in FIG. 1, in which steam flowing out from a reactor pressure vessel 1 equipped with a reactor purification system 10 passes through a high pressure turbine 2, a moisture separator 3, and a low pressure turbine 4, and is condensed in a condenser. ★)-f,s-mr t'! /
l'F LG - pin 4 light τ production★Pi L: # is condensed and becomes condensate. The low pressure turbine 4 is an oil-air system I.
It communicates via I with a feedwater heater 9, which in turn communicates with a condenser via a heater drain system 12. Therefore, corrosion products (mainly iron oxides, hereinafter referred to as crud) and impurity ions generated in the condenser 5, bleed system 11, feed water heater 9, etc. are removed by the condensate desalination device 7. The condensate flows into the reactor pressure vessel 1 via the feed water heater 9, and thereafter the condensate is repeatedly circulated in the same manner.

As shown in FIG. 2, the condensate desalination apparatus 7 has a container 13 connected to a water supply system 18 and a condensate system 19, and an ion exchange μ fat 15 and a Johnson screen 17 provided on a water sprinkling plate 14 and a batten 16. The condensate containing impurities passes through the condensate system 19 to the water spray plate 14 in the container 13.
The water flows down to the ion exchange resin 15 to remove impurities, and then flows through the Johnson screen 17 to the main system 18. The ion exchange resin 15 is B
It is well known that WR uses an H-type cation exchange resin and an OH-type anion exchange resin, and the particle size is approximately 300 to 1200 μm, and that it is a mixed bed that combines a cation exchange resin and an anion exchange resin with approximately the same diameter. That's right.

By the way, in order to regenerate the resin in the condensate desalination equipment, in order to avoid contamination of the condensate and water supply lines, the resin must be removed from the condensate desalination equipment.
An external regeneration system in which resin is regenerated separately is common, and an increase in the amount of waste such as recycled waste liquid accompanying resin regeneration has become a problem. Resin regeneration is divided into two parts: mechanically removing oxides trapped in the resin; The former is performed by scrubbing with air and water, and the latter is performed by chemical injection.

FIG. 3 shows a regeneration system of a mixed bed type condensate desalination apparatus using the conventional outside-column regeneration method. The ion exchange resin, which is backwashed and regenerated by differential pressure or periodic control, is transferred to the cation hexaconversion resin tower 21 and oxides trapped on the resin surface are removed by the injected water and air. The stripped oxides are discharged to the waste treatment system using wash water. Thereafter, the resins are transferred to the resin mixing tower 23, where they are mixed and then charged into the condensate desalination device 7 again. In addition, for regeneration by chemical injection, the cation exchange resin is separated into a cation exchange resin and an anion exchange resin in the cation exchange resin column 21, the anion exchange resin is transferred to the anion exchange resin column 22, and the cation exchange resin is transferred to a sulfuric acid solution, The anion exchange resins are each regenerated with a sodium hydroxide solution, mixed in a resin mixing tower 23, and then charged into a condensate demineralization tower 7.

Regeneration by backwashing is 20 days/tower, and regeneration by chemicals is 1 time.
It is performed at an increasing frequency of 00 days/time.

Incidentally, the amount of radioactive waste generated during chemical regeneration reaches about 20% of the amount generated in the entire plant, and reduction of this amount is required as part of reducing the amount of waste generated.

In the final treatment stage, the waste liquid from chemical regeneration is treated as sodium sulfate (mirabilite) by neutralizing the sulfuric acid used to regenerate the cation exchange resin and the sodium hydroxide used for the anion exchange resin. : There is a limit to volume reduction through a-condensation treatment, etc., and currently the waste liquid generated during chemical regeneration is approximately 60m3/
The waste liquid is transferred to a waste treatment system, concentrated approximately 20 times, and then canned in drums for treatment. For this reason, 11
A 00MW We class plant has about 10 desalination towers, and the annual amount of drums generated is about 1000, which is a large amount, and reducing this is a problem.

In addition, in backwash regeneration, the waste liquid mainly consists of crud (iron oxide).
Although the amount of waste can be considerably reduced through concentration treatment and there are few problems, the amount of waste liquid generated per year in a 1100 MWe class plant is enormous, approximately 12000 m3, so concentration equipment is rarely used in waste treatment systems. , it is in a state close to full operation, and there is a demand for reducing the burden on this equipment.

[Purpose of the invention]

An object of the present invention is to provide a condensate desalination apparatus that can effectively regenerate chemicals from an ion exchange resin filled in the condensate desalination apparatus and reduce the amount of chemicals and waste.

[Summary of the invention]

The condensate desalination equipment is filled with a mixture of cation exchange resin and anion exchange resin, and the following findings have been obtained from actual equipment data.

Figure 4 shows the relationship between the depth of the ion exchange resin layer and the ion load in the condensate desalination equipment during chemical regeneration.
Both cation exchange resin 27 and anion exchange resin 28 are 1
It was found that about 30 to 50 cm from the surface layer was used for removing ionic impurities, and the rest was hardly used.

This actual machine data is from normal plant operation, but
The amount of ion exchange resin filled in the condensate desalination equipment was determined based on the assumption that seawater would leak from the condenser cooling pipe. Therefore, during normal operation, there is a considerable ion exchange capacity as shown in FIG. 4, and furthermore, it can be seen that only the upper part of the resin layer is used for removing ionic impurities. On the other hand, the amount of chemical liquid injected during chemical regeneration is determined based on the ion exchange capacity with respect to the total amount of resin, so it is used in excess.

Based on these findings, the ion exchange resin of the condensate desalination equipment is used in the upper part of the ion exchange resin layer (3
It is sufficient to carry out only 0 cm to 50 cm), and since the ion exchange resin layer is approximately 1 m long, it is effective in reducing the amount of chemicals and waste.

Figure 5 shows the distribution of the amount of trapped iron in the depth direction of the ion-exchange resin layer during backwash regeneration, and as with the negative ion amount in Figure 4, it is large up to about 30 to 50 cm from the surface layer. It can be seen that the portion is captured.

Backwash regeneration is performed to remove crud such as iron oxides trapped in the ion exchange resin layer and to prevent a rise in differential pressure. It is thought that the differential pressure contributes to the upper part of the ion exchange resin layer. For this reason, it is generally considered sufficient to carry out washing and regeneration only on the upper part of the ion exchange resin layer, which is effective in reducing waste liquid during backwashing and regeneration.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

FIG. 5 is a diagram showing a conventional condensate demineralizer and a regeneration system in which a screen 29 for separating an ion exchange resin layer is provided in the condensate demineralizer.

The condensate flowing into the condensate desalination device 7 from the condensate system 19 is purified by an ion exchange resin layer in the upper part of the separation screen 29 and an ion exchange resin layer in the lower part, and then flows out to the water supply system 18. Here, assuming that the height of the upper ion exchange resin layer is 50 cm, the resin layer height is usually about 1 rn, and the resin amounts (layer heights) at the upper and lower portions of the screen are the same. Impurity ions and cladding (iron oxide, etc.) in the condensate are mostly removed by the resin layer above the screen. Therefore, chemical regeneration of the resin is performed only on the upper resin layer, and the resin is transferred to the cation exchange resin column 21 via the resin transfer line 3o, and after separation into the cation exchange resin and the anion exchange resin, the anion exchange resin is changed to the anion exchange resin. The chemicals are transferred to the tower 22 and regenerated respectively. At this time, the amount of recycled resin in the chemical injection tray is 1/2 that of the conventional one, so
Simply use 1/2 the amount. Resin mixing tower 23 after completion of regeneration
, and mix the cation exchange resin and anion exchange emollient. The resin filled in the lower part of the next screen is transferred to the cation exchange resin 214C, and the resin from the resin mixing tower 23, which has been regenerated as a chemical, is filled in the lower part of the screen. Thereafter, the resin transferred to the cation exchange resin column 21 passes through the resin mixing column 23 and is filled into the upper part of the screen. By exchanging the resin at the top and bottom of the screen during chemical regeneration, the balance between resin deterioration and the like depending on the usage status of the resin is resolved.

On the other hand, in backwash regeneration, only the resin at the top of the screen is transferred to the cation exchange resin 21, and after being regenerated with air and backwash water,
The resin passes through the resin mixing column 23 and is filled again into the upper part of the screen. In this case, since the amount of resin is reduced to 172, the amount of waste liquid can be reduced to 1/2 of the conventional amount, and the concentration operation of the waste liquid can be halved.

The installation of the separation screen 29 increases the differential pressure in the condensate desalination device 7, but the current ion exchange resin particle size is limited to 2% of 420 μm or less due to the resin specifications, so the screen mesh is 300 μm 0 to 400 μm. The pressure difference should be as large as possible to minimize the rise in differential pressure. Furthermore, even if the resin leaks from this screen, the Johnson screen 17 at the bottom of the condensate desalination device [7] has a thickness of about 150 μm, so that resin leakage outside the device can be prevented.

〔Effect of the invention〕

According to the present invention, among the ion-exchange resins in the condensate desalination equipment, only the resin used for removing ionic impurities in condensate during normal operation can be regenerated. This has the effect of reducing waste. In terms of waste volume, approximately 10 drums are generated per year.
00 lines, it can be reduced to 1/2 to 1/3.

In addition, backwashing regeneration can be performed only on the resin layer where iron oxides, etc. are removed, so the amount of waste liquid can be reduced by 1/2 to 1/3.
It is possible to reduce the burden on the concentrator.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a conventional boiling water nuclear power plant, Figure 2 is an explanation of a conventional condensate desalination system, and Figure 3 is a conventional hotbed type condensate desalination system using an external regeneration system. Figure 4 is a diagram showing the relationship between resin layer depth and ion load during chemical regeneration, Figure 5 is a distribution diagram of trapped iron in the resin depth direction, and Figure 6 is a diagram showing the amount of trapped iron in the resin depth direction. FIG. 2 is a configuration diagram showing a desalting device and a regeneration system when a screen for separating a resin layer is installed inside the condensate desalting device according to an embodiment of the invention. 7... Condensate desalination device, 15... Ion exchange resin, 2
DESCRIPTION OF SYMBOLS 1... Cation exchange resin column, 22... Anion exchange resin column, 23... Resin mixing column, 29... Resin layer separation screen.耀 1 Country 19 26 謬(+语謬 50 Continuation of page 1 @ inventor Art materials Masterpiece Hitachi Shiji Office)

Claims (1)

[Claims] 1. A condensate demineralizer characterized in that a mixed-bed condensate demineralizer containing a granular cation exchange resin and an anion exchange resin is provided with a screen that separates the ion exchange resin layer.