JPH0445216B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention is applicable to mixed bed condensate desalination equipment for treating condensate in thermal power plants, nuclear power plants, etc., or for producing ultrapure water used in the electronics industry for manufacturing semiconductor devices, etc. The present invention relates to a method for preventing harmful ions from leaking into the treated water of a mixed bed type ion exchange device, such as a mixed bed type pure water production device, which is required to obtain highly purified treated water. <Conventional technology> In thermal power plants or nuclear power plants,
The generated steam drives a steam turbine to generate electricity, and then the steam is cooled with seawater to obtain condensate, which is then heated again to obtain steam. However, the condensate water contains small amounts of suspended matter such as iron oxide, and impurities such as sodium ions and chloride ions, and in order to constantly remove these impurities, or seawater used as cooling water is relatively A mixed-bed condensate desalination device is installed in the condensate system in preparation for what is called a seawater leak in a large amount of condensate. The mixed-bed condensate desalination equipment includes a plurality of water towers filled with a recycled mixed ion exchange resin of cation exchange resin and anion exchange resin and used only for the passage of condensate, and the water tower. It consists of a regeneration system used only for regeneration of used mixed ion exchange resin.
The used mixed ion exchange resin is backwashed and separated into a cation exchange resin and an anion exchange resin, then both ion exchange resins are regenerated, and the recycled both ion exchange resins are mixed and subjected to water flow. In this respect, it is the same as a normal mixed-bed pure water production system in which water passing and regeneration are performed in the same column. The flow of a mixed-bed condensate desalination apparatus in which the regeneration system is composed of a regeneration tower and a resin storage tank is as shown in FIG. That is, condensate 2 flows into each of the plurality of water towers 1a, 1b, and 1c, and the treated water 3 flows out. With such water flow, for example, the water tower 1a
When the mixed ion exchange resin filled in the tank reaches the end point of water flow, the water flow tower 1a is separated from the water flow and the mixed ion exchange resin is transported in the form of slurry to the regeneration tower 5 through the resin transfer pipe 4a. Next, the regenerated mixed ion exchange resin that has been kept on standby in the resin storage tank 6 is transferred in slurry form to the water tower 1a through the resin transfer pipe 4c, and when this transfer is completed, water flow through the water tower 1a is continued. On the other hand, the used mixed ion exchange resin transferred to the regeneration tower 5 is backwashed and separated and regenerated in the same tower, and the regenerated mixed ion exchange resin is transferred in the form of slurry to the resin storage tank 6 through the resin transfer pipe 4b. For example, the mixed ion exchange resin is kept on standby as a recycled mixed ion exchange resin to be transferred to the water tower 1b. In this way, in the conventional mixed bed condensate desalination equipment, the water flow times of the water towers 1, which have a plurality of towers, are staggered and adjusted so that each water tower reaches the end point of water flow at approximately regular intervals. The used mixed ion exchange resin of each water tower is sequentially regenerated in the regeneration system at approximately equal water flow intervals. Next, a conventional regeneration method in the regeneration tower 5 will be explained below. As shown in FIG. 3, the used mixed ion exchange resin transferred to the regeneration tower 5 is backwashed and separated into a cation exchange resin 7 and an anion exchange resin 8 by a conventional method. Next, a caustic soda solution, which is a regenerating agent for the anion exchange resin 8, is passed from the distributor 10 through the inflow pipe 9a, followed by extruded water, and supporting water is flowed in through the inflow pipe 9b, thereby dissolving the both ion exchange resins. The regenerated waste liquid flows out from an outflow pipe 13 through a collector 12 installed within the layer of anion exchange resin 8 slightly above the separation boundary surface 11 . Next, inflow pipe 9
Hydrochloric acid, which is a regenerating agent for the cation exchange resin 7, is passed through b, followed by extruded water, and support water flows in through the inflow pipe 9a, and the regenerated waste liquid flows out through the collector 12 through the outflow pipe 13. After such drug feeding and extrusion are completed, the inflow pipe 9
Washing water flows in from a and 9b, and the washing waste liquid flows out from the outflow pipe 13 via the collector 12,
Clean both ion exchange resins. After the specified cleaning (usually about 60 minutes) is completed, the recycled both ion exchange resins are immediately transferred to the resin storage tank 6 using the resin transfer pipe 4b, and both ion exchange resins are thoroughly mixed in the resin storage tank 6. Then, the mixed ion exchange resin and ion exchange resin are kept on standby until the time is right to transfer them to the water tower 1. In the regeneration tower 5 described above, the collector 12 is installed in the anion exchange resin 8 slightly above the separation boundary surface 11 of both ion exchange resins, and this is for the following reason. In other words, the factors that determine the harmful ions sodium ions and chloride ions that leak into the treated water are
Na type fraction (R-Na/R-H+R-Na) and Cl type fraction (R
-Cl/R-OH+R-Cl), and for example, in order to reduce the leakage amount of sodium ions to 0.06ppb or less, the Na fraction must be 0.02 or less, and the leakage amount of chloride ions must be 0.15ppb. In order to achieve the following, the Cl fraction must be 0.3 or less. As seen in the above values, the Na fraction is higher than the Cl fraction.
Because it is necessary to keep the form fraction to a fairly low value, the collector 12 is installed above the separation boundary surface 11 so that the caustic soda solution, which is a regenerating agent for the anion exchange resin 8, does not come into contact with the cation exchange resin 7. This is what we are doing. In conventional regeneration towers, the collector 12 is placed at a distance of 50 to 100 mm from the separation boundary surface 11 for the reasons mentioned above.
Sodium ions are removed by installing the ion exchange resin 8 above and first passing a caustic soda solution, which is a regenerating agent for the anion exchange resin 8, and then passing hydrochloric acid, which is a regenerating agent for the cation exchange resin 7. We are trying to reduce the amount of leakage as much as possible. <Problems with the prior art> However, in such a mixed bed type condensate desalination equipment, while the ion exchange resin used is relatively new, the above-mentioned regeneration method reduces the amount of sodium ions and chloride ions in the treated water. In both cases, high purity treated water can be obtained that is below the specified values, but if the anion exchange resin is contaminated, the amount of chloride ions leaking increases, especially at the initial stage of water flow. A problem arises in that the leakage amount of chloride ions does not fall within a specified value even if cleaning is performed for a fairly long time. The condensate contains lubricating oil from various machines, organic matter that has been thermally decomposed from oil that has adhered to the inner surface of new piping, or emulsion that is a combination of the aforementioned oil and iron oxide, etc., in small amounts, sometimes relatively. This is thought to be because when an anion exchange resin is contaminated with the above-mentioned substances, which may be present in large amounts, the reaction rate decreases, thereby increasing the leakage amount of chloride ions. In other words, as shown in FIG. 3, the anion exchange resin present in the lower part of the collector 12 becomes Cl form due to the hydrochloric acid passed therein to regenerate the cation exchange resin, and the Cl form anion exchange resin particles contain hydrochloric acid. However, if the anion exchange resin is not contaminated and the reaction rate is not reduced, there will be no particular problem even in this situation, but if the anion exchange resin is When the reaction rate decreases, the aforementioned hydrochloric acid in the particles cannot be easily washed out, and the amount of chloride ion leakage increases because the hydrochloric acid continues to leach into the treated water little by little during water flow. It is speculated that. Furthermore, when sulfuric acid is used as a regenerating agent for cation exchange resin, the leakage amount of sulfate ions increases due to the same reason, and even if the cation exchange resin is regenerated first and the anion exchange resin later. The same problem occurs in the lower part of the collector 12 because an anion exchange resin is produced in which the regenerant acid remains in the resin particles. Furthermore, even in mixed-bed pure water production equipment where regeneration and water flow are performed in the same column, the same phenomenon occurs in the anion exchange resin near the collector 12, so if the anion exchange resin is contaminated and the reaction rate decreases. The same problem occurs. Conventionally, in order to solve this problem, only the ion exchange resin that has been converted into a salt form by the other regenerating agent near the collector 12 after regeneration is taken out of the column, and the ion exchange resin taken out of the column is passed through. There is a method of reducing the leakage of harmful ions in treated water by not exposing it to water (Japanese Patent Publication No. 58-20312), but this method requires a tank to receive the ion exchange resin taken out, and an additional regeneration process This is not a very desirable method because it is complicated. <Means for Solving the Problems> The purpose of the present invention is to prevent, in a simple manner, the above-mentioned drawbacks of the mixed bed type ion exchange apparatus, namely, the drawback that the leakage amount of chloride ions, which are harmful ions, increases. The anion existing near the collector becomes a salt form by contacting the cation exchange resin regenerating agent while maintaining the separated state of the recycled anion exchange resin and cation exchange resin. The above object is achieved by bringing the exchange resin into contact with ammonia water, then mixing both ion exchange resins and passing water through the mixture. Embodiments of the present invention will be described in detail below using a mixed bed type condensate desalination apparatus as an example. As shown in Fig. 1, the used mixed ion exchange resin from the water tower (not shown) is transferred to the regeneration tower 5, backwash water is introduced from the bottom of the regeneration tower 5, and the resin is purified using a conventional method. It is backwashed and separated into an ion exchange resin 7 and an anion exchange resin 8. Next, caustic soda solution and extruded water are passed from the distributor 10 through the inflow pipe 9a, and support water is flowed in from the inflow pipe 9b to the shaded area slightly above the separation boundary surface 11 of both ion exchange resins. The regenerated waste liquid flows out from the outflow pipe 13 via the collector 12 installed in the ion exchange resin layer, and the anion exchange resin 8 is regenerated. Next, hydrochloric acid and extruded water are passed through the inflow pipe 9b, and the inflow pipe 9a
Support water flows in through the collector 12, and the regenerated waste liquid flows out from the outflow pipe 13 to regenerate the cation exchange resin 7. Next, washing water flows in from the inflow pipes 9a and 9b, and the washing waste liquid flows out from the outflow pipe 13 via the collector 12, thereby washing both ion exchange resins. The operations up to this point are exactly the same as conventional operations, and through these operations, the anion exchange resin 8' present below the collector 12 comes into contact with hydrochloric acid, which is a regenerant for the cation exchange resin 7. It is in the salt form, that is, the Cl form, and hydrochloric acid remains in the resin particles. Conventionally, after a specified cleaning process, the anion exchange resins 8, 8' and the cation exchange resin 7 are transferred to a resin storage tank (not shown), and both ion exchange resins are thoroughly mixed in the resin storage tank. However, in the present invention, the cation exchange resin 7 and the anion exchange resins 8 and 8' after washing are not mixed immediately, and the separation state of the cation exchange resin and anion exchange resin is maintained. While doing so, perform the following operations. That is, for example, 0.2% ammonia water flows in from the inflow pipe 9a, the ammonia water is brought into contact with the anion exchange resin 8' via the anion exchange resin 8, and the ammonia water after contact is sent slightly below the separation boundary surface 11. The water flows out through a collector 12' and an outflow pipe 13' installed in the water, and then the anionic and anionic ion exchange resins are mixed and used for water flow. If the operation of bringing aqueous ammonia into contact with the Cl-type anion exchange resin 8' while maintaining the separated state of both ion exchange resins in this way, the leakage amount of chloride ions cannot be reduced for any reason. It is not clear at present whether this is possible, but it is probably due to the following reasons. In other words, conventionally, the H-type cation exchange resin 7 and the OH-type anion exchange resin 8 after regeneration are combined with the above-mentioned
Since the Cl type anion exchange resin 8' is mixed with the anion exchange resin 8', even if a small amount of sodium ions or chloride ions are present in the pore water, the ions are removed by the both ion exchange resins and the mixed ions are The pore water of the exchange resin becomes pure water with almost no ions present, and therefore the pore water existing around the Cl type anion exchange resin 8' mixed in the mixed ion exchange resin also becomes pure water. If the mixed ion exchange resin is left in this condition, the hydrochloric acid remaining in the Cl-type anion exchange resin 8' particles will attempt to diffuse into the pore water, but if the anion exchange resin is contaminated, ions In addition to the fact that the diffusion rate within the particles of the anion exchange resin 8' is reduced, if the water in the system is pure water, the driving force in diffusion is further reduced, so hydrochloric acid remaining in the particles of the anion exchange resin 8' is easily removed. It is assumed that the particles do not diffuse outside the particle. On the other hand, when ammonia water is brought into contact with the Cl type anion exchange resin 8' while maintaining the separation state of the cation exchange resin and anion exchange resin as in the present invention, ammonium ions and hydroxide ions become a driving hose. In addition, it is thought that the neutralization reaction between the hydrochloric acid remaining in the particles and the aqueous ammonia that comes into contact with the particles also acts, making it easier for the hydrochloric acid remaining in the anion exchange resin 8' particles to diffuse out of the particles. The effect of the present invention is thought to be due to the phenomenon described above, but in any case, ammonia water is added to the Cl-type anion exchange resin 8' while maintaining the separation state of the cation exchange resin and anion exchange resin. By bringing these into contact with each other, the object of the present invention can be reliably achieved. Note that, considering only the effect of increasing the diffusion rate of hydrochloric acid remaining in the anion exchange resin 8' particles, a caustic soda aqueous solution can be used instead of ammonia water; This is not preferable because the sodium ion exchange resin 7 comes into contact with a portion of the cation exchange resin 7 and converts it into Na form, which increases the amount of sodium ions leaking from the treated water. In the present invention, Cl type anion exchange resin 8'
However, if the contact time is too short, the object of the present invention cannot be achieved, so the contact time must be at least 20 minutes or more. In addition to the method of bringing the ammonia water into contact with the anion exchange resin 8' by passing water as shown in FIG. 1, a dipping method as described later may be used. That is, ammonia water is introduced from the inflow pipe 9a or vice versa from the outflow pipe 13' to replace the pore water in the anion exchange resin 8' with ammonia water, and then left to stand. The object of the present invention can be achieved even when the anion exchange resin 8' is immersed in aqueous ammonia and left for at least 20 minutes. Next, the concentration of ammonia water to be used will be explained. In the present invention, it is not necessary to use ammonia water with a very high concentration, and a concentration of 2% or less is sufficient. That is, Cl type anion exchange resin 8'
Even the presence of a small amount of ammonium hydroxide in the pore water is effective in diffusing the hydrochloric acid in the particles, so it is not preferable to use highly concentrated ammonia water because it unnecessarily increases chemical costs. Note that condensate contains 500 to 2000 ppb of ammonium hydroxide, so for example, inflow pipe 9a
The condensate is brought into contact with the anion exchange resin 8' via the anion exchange resin 8, and the condensate after contact is discharged from the outflow pipe 13',
Alternatively, the ammonium ions in the condensate can be utilized by constantly passing water through the cation exchange resin 7 and flowing out from the lower part of the regeneration tower 5. Note that when condensate is consistently passed through the anion exchange resins 8, 8' and the cation exchange resin 7, a portion of the cation exchange resin 7 changes from the H form to the NH ₄ form, but the amount is extremely small. So there's no problem at all. In addition, when ammonia water is brought into contact with the anion exchange resin 8', it is possible to flow the ammonia water backward from the collector 12' in an upward flow and bring the anion exchange resin 8 into contact with the anion exchange resin 8' while expanding the anion exchange resin 8' to some extent. Also, anion exchange resin 8
Even if aqueous ammonia is brought into contact with the mixed anion exchange resin after sufficiently mixing 8' and 8', the effect will not change. Further, the anion exchange resins 8 and 8' may be brought into contact with ammonia water, and then both the anion exchange resins 8 and 8' may be sufficiently mixed and left to stand. Next, as another embodiment in which aqueous ammonia is brought into contact with the Cl type anion exchange resin 8' while maintaining the separation state of the cation exchange resin and anion exchange resin,
In addition to contacting in the regeneration tower 5 as shown in FIG. 1, the upper layer anion exchange resins 8 and 8' may be transferred to a resin storage tank (not shown), or the lower layer cation exchange resin 7 may be brought into contact with the resin storage tank. Alternatively, the anion exchange resins 8, 8' and the cation exchange resin 7 may be separated into separate columns by transferring the anion exchange resins to a separate column, and the ammonia water may be brought into contact with the anion exchange resin separated into the separate columns. In this case, even if a small amount of H-type cation exchange resin 7 is mixed into the anion exchange resin, the amount will not remove most of the ammonium ions in the ammonia water that is to be brought into contact with the anion exchange resin 8'. There is no problem as long as it is a moderate amount. As described above, the present invention provides a collector 1 which has become a salt form by contacting with a regenerating agent for a cation exchange resin.
After the ammonia water is brought into contact with the anion exchange resin 8' present in the vicinity of the anion exchange resin 8', it is washed if necessary, and then the anion and anion exchange resins are mixed and water is passed through. <Effects of the Present Invention> As explained above, the present invention is capable of converting recycled anion exchange resin and cation exchange resin into salt form by contacting with a regenerating agent of the cation exchange resin while maintaining the separated state. Chloride ions leaking into the treated water can be significantly reduced by a simple operation of bringing ammonia water into contact with the anion exchange resin present near the collector, then mixing both ion exchange resins and passing the water through the mixture. Therefore, if the present invention is applied to a mixed bed type condensate desalination apparatus where leakage of trace amounts of chloride ions is a problem, the problem can be successfully solved. Furthermore, even when the regenerant for the anion exchange resin is sulfuric acid, the leakage of sulfate ions can be reduced by the present invention, and it is also suitable for mixed-bed pure water production equipment in which water flow and regeneration are performed in the same tower. The invention can be applied. Examples will be described below to make the effects of the present invention more clear. Example 1 Mixed ion exchange of cation exchange resin Amberlite (registered trademark, hereinafter the same) 200CT and anion exchange resin Amberlite IRA-900 used in mixed bed condensate desalination equipment in pressurized water nuclear power plants. Collect the resin, separate the mixed ion exchange resin by a conventional method, and then add Amberlite.
200CT, 2, Amberlight IRA-900, 1
was regenerated under the regeneration conditions shown in Table 1.

[Table] Next played Amberlight IRA-900, 100
After taking out 1 ml of 1N hydrochloric acid 50/-R at SV10, using ion-exchanged water of about 1 μs/cm,
The effluent was washed with SV10 until the electrical conductivity reached 20 μs/cm, and Cl type Amberlite IRA-900 was prepared. Next, in the lower layer of a column with an inner diameter of 46.5 mm and a height of 1000 mm, Cl type Amberlite IRA-900, 100 ml was added, and in the upper layer, the above-mentioned regenerated Amberlite IRA-900, 900 was added.
Filled with ml. 0.2% ammonia water was passed through the upper part of the column using SV4 for 20 minutes, and then ion-exchanged water with an electrical conductivity of approximately 1 μS/cm was used to pass 0.2% ammonia water through the column.
Washing was performed until the electrical conductivity of the effluent water reached 20 μS/cm. Next, remove the Amberlite IRA-900 from the column and add the regenerated Amberlite to it.
200CT and 2 were mixed and packed into a column with an inner diameter of 56.5 mm and a height of 1500 mm as a mixed bed, and a water flow test was conducted. The Cl fraction of Amberlite IRA-900 is 25
It was %. In addition, the electrical conductivity of the water used in the water flow test was approximately
Ammonium and hydrazine were added to ion-exchanged water at 1 μs/cm by chemical injection, and the concentrations were approximately 500 μg NH ₄ / as ammonium and 150 μg N ₂ H ₄ / as hydrazine, respectively, and LV80 m/hr.
Water was passed through. The results are shown in Figure 4. Example 2 Ammonia water administration time in Example-1
Water was passed under exactly the same conditions as in Example-1, except that the time was 60 minutes. The results are shown in FIG. Example 3 Cl type Amberlite IRA-900 filled in the same manner as Example-1 and recycled Amberlite IRA-900
500ml of 0.1% ammonia water was circulated in SV4 for 60 minutes. Other than that, water was passed under exactly the same conditions as in Example-1. The results are shown in FIG. Example 4 Cl type Amberlite IRA-900, 100ml prepared in the same manner as Example-1 and recycled Amberlite IRA
-900, 900ml in a beaker, add 500ml of 1% ammonia water to it, mix well, leave it in that state for 60 minutes, inner diameter 46.5mm, height 1000mm.
The sample was packed in a column of 2.0 mm in diameter, and washed using ion-exchanged water with an electrical conductivity of approximately 1 μS/cm using SV10 until the electrical conductivity of the effluent water reached 20 μs/cm. Other than that, water was passed under exactly the same conditions as in Example-1. The results are shown in FIG. Example 5 Instead of ammonia water in Example-1, simulated condensate equivalent to condensate from a pressurized water nuclear power plant was used. In other words, Cl type Amberlite IRA−
900, 100ml and recycled Amberlite IRA-900,
Mix 900 ml, fill a column with an inner diameter of 46.5 mm and a height of 1000 mm, add ammonium and hydrazine to ion-exchanged water with an electrical conductivity of about 1 μs/cm, and add about 50 μg of ammonium _{NH 4} /150 μg of hydrazine.
Simulated condensate adjusted to 2 gN ₂ H ₄ / was circulated and washed at SV10 for 2 hours. Other than that, water was passed under exactly the same conditions as in Example-1. The results are shown in FIG. Comparative example Cl type Amberlite IRA-900 prepared in Example-1 and regenerated Amberlite IRA-900
Immediately mixed with the regenerated Amberlite 200CT without contacting it with ammonia water, then washed the mixed ion exchange resin with ion exchange water with an electrical conductivity of about 1 μS/cm at SV10 for 60 minutes, and then mixed it with Example-1. Water was passed under exactly the same conditions. The results are shown in FIG.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a flow of an example of an embodiment of the present invention, and is an explanatory diagram showing a state when a cation exchange resin and an anion exchange resin are regenerated in a regeneration tower. FIG. 3 is an explanatory diagram of the flow of a conventional mixed bed condensate desalination apparatus, and FIG. 3 is an explanatory diagram of the flow of a regeneration tower of a conventional mixed bed condensate desalination apparatus. Further, FIG. 4 is a graph showing the water flow results in the example, with the vertical axis showing the leakage amount of chloride ions in the treated water, and the horizontal axis showing the water flow time. 1... Water tower, 2... Condensate, 3... Treated water, 4
... Resin transfer pipe, 5 ... Regeneration tower, 6 ... Resin storage tank, 7 ... Cation exchange resin, 8 ... Anion exchange resin, 9 ... Inflow pipe, 10 ... Distributor, 11 ... Separation boundary surface, 12...Collector,
13...Outflow pipe.

Claims (1)

[Claims] 1. Backwash and separate the used cation exchange resin and anion exchange resin mixture, pass a regenerant through the anion exchange resin in the upper layer and the cation exchange resin in the lower layer, and pour the regenerated waste liquid into both. In a mixed bed type ion exchange device in which the recycled anion exchange resin flows out from a collector installed near the separation interface of the ion exchange resin and is regenerated, the recycled anion exchange resin is mixed and passed through water. Aqueous ammonia is brought into contact with the anion exchange resin present near the collector, which has become a salt form by contacting with a regenerating agent for the cation exchange resin while maintaining the state of separation from the cation exchange resin and the cation exchange resin. A method for preventing leakage of harmful ions in a mixed bed type ion exchange device, characterized in that an exchange resin is mixed and water is passed through the device.