JPH0456668B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Fields> 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. 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 consists of a plurality of water passage 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; It consists of a regeneration system used only to regenerate the used mixed ion exchange resin in the water tower.
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 consists 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 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 time of the water tower 1, which has multiple towers, is staggered, and the water flow is adjusted so that each water tower reaches the end point of water flow at approximately regular intervals. The used mixed ion exchange resin in each water tower is sequentially regenerated in the early regeneration system at 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 regenerated 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 sodium ions and chloride ions, which are harmful ions leaking into treated water, are the factors in the cation exchange resin after regeneration.
Na type fraction (R-Na/R-H+R-Na) and C1 type fraction (R-C1/R-OH+R-C1) in the anion exchange resin after regeneration, for example, the leakage amount of sodium ions is 0.06 In order to keep it below ppb, the Na fraction needs to be below 0.02.
Furthermore, in order to keep the leakage amount of chloride ions below 0.15 ppb, it is necessary to keep the C1 fraction below 0.3. As seen in the above numbers, Na is lower than the C1 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 mixed-bed condensate desalination equipment, while the ion exchange resin used is relatively new, the aforementioned 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 C1 type due to the hydrochloric acid passed to regenerate the cation exchange resin, and the C1 type 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.
There is a method (Japanese Patent Publication No. 58-20312) of reducing the leakage amount of harmful ions in the treated water by not allowing the ion exchange resin taken out of the tower to pass through the water, but this method does not allow the ion exchange resin taken out of the tower to This is not a very desirable method because it requires a tank to receive the resin and the regeneration process is complicated. <Means for Solving the Problems> The purpose of the present invention is to prevent, in a simple manner, the disadvantage of the mixed bed ion exchange apparatus as described above, namely, the increase in the leakage amount of chloride ions, which are harmful ions. In this method, the regenerated anion and ion exchange resin is left to stand by for at least 3 hours while maintaining its separation from the cation exchange resin, and after the waiting period, both ion exchange resins are mixed and water is passed through. It accomplishes its purpose. 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 through the collector 12 installed in the ion exchange resin tank, 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 operation up to this point is exactly the same as the conventional operation. In the past, after the specified cleaning, the regenerated both ion exchange resins were immediately transferred to a resin storage tank (not shown), and the two ion exchange resins were sufficiently mixed and waited in the resin storage tank. However, in the present invention, the two ion exchange resins are not mixed immediately after washing, but are allowed to stand by for a relatively long time while maintaining the separated state of the two ion exchange resins. In this way, the separation state of both ion exchange resins is maintained for a relatively long time, specifically at least 3
Although it is not clear at present why the leakage amount of chloride ions can be reduced by waiting for a longer period of time, it is probably due to the following reasons. That is, as shown in FIG. 1, the cation exchange resin 7 after regeneration and cleaning is in the H type, and even after the cleaning is completed, the water existing in the voids of the cation exchange resin 7 contains a small amount of hydrochloric acid, which is a regenerant. Residual acidity. Furthermore, the anion exchange resin 8' present below the collector 12 is in the C1 form because it comes into contact with hydrochloric acid, which is a regenerating agent for the cation exchange resin 7, and furthermore, hydrochloric acid remains in the resin particles, and Similarly, the water existing in the voids of the anion exchange resin 8' is acidic, with a trace amount of hydrochloric acid remaining as a regenerating agent. On the other hand, the anion exchange resin 8 present above the collector 12 is in the OH type, and even if cleaning is completed in the same manner, the water present in the voids of the anion exchange resin 8 is contaminated with caustic soda, which is a regenerating agent. It is alkaline with a trace amount remaining. In the conventional operation, such both ion exchange resins 7, 8, and 8' are immediately mixed, so that the sodium ions caused by caustic soda and the chloride ions caused by hydrochloric acid present in the pore water are converted to H. The pore water of the mixed ion exchange resin becomes pure water with almost no ions, and is therefore mixed in the mixed ion exchange resin. The pore water existing around the C1 type anion exchange resin 8' also becomes pure water. If the mixed ion exchange resin is left in this condition, the hydrochloric acid remaining in the C1 type anion exchange resin 8' particles will try 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, if the anion exchange resin 8 and the cation exchange resin 7 are not mixed as in the present invention, trace amounts of sodium ions and chloride ions will exist in the pore water of the anion exchange resins 8 and 8' as described above. It is thought that the ions become a driving hose and the hydrochloric acid remaining in the anion exchange resin 8' particles easily diffuses out of the particles. The effect of the present invention is thought to be due to the phenomenon described above, but in any case, after waiting for a relatively long time while maintaining the separated state of the anion exchange resin 8 and the cation exchange resin 7, both ion exchange is performed. The object of the present invention can be reliably achieved by mixing the resins and passing water through them. Note that the longer you wait while maintaining the separation state of both ion exchange resins, the more you can reduce the amount of chloride ions leaking out. However, if this waiting time is less than 3 hours, the intended purpose may not be achieved. Since this cannot be achieved, it is necessary to wait for at least 3 hours or more, preferably for 10 hours or more. In addition, when the anion exchange resins 8 and 8' are placed on standby, water or air is passed upward from the lower part of the anion exchange resin 8', and the C1 type anion exchange resin 8' and OH type anions are It is more effective to mix the exchange resin 8, and such mixing can further reduce the leakage amount of chloride ions with the same waiting time. In addition, when mixing the anion exchange resins 8 and 8', it is desirable to attach a mixing positive distributor (not shown) to the lower part of the separation boundary surface 11 and pass water or air from there. When water flows upward from the inflow pipe 9b and expands the cation exchange resin 7 and the anion exchange resins 8 and 8' to some extent, the anion exchange resin 8' is mixed with the anion exchange resin 8, although incompletely. Even such incomplete mixing is effective. Furthermore, when water is introduced from the inflow pipe 9b and the anion exchange resins 8 and 8' are mixed, the cation exchange resin 7 may be mixed into the anion exchange resin, but if the amount is small, it is The effect of the invention remains the same. Next, as a mode of waiting while maintaining the separated state of both ion exchange resins, it is possible to make them wait in the regeneration tower 5 as shown in FIG. The anion exchange resins 8, 8' and the cation exchange resin 7 are separated into separate columns by transferring the resin to a storage tank (not shown) or transferring the lower layer cation exchange resin 7 to a resin storage tank. It may be kept on standby. In this case as well, there is no problem even if a small amount of the cation exchange resin 7 is mixed into the anion exchange resins 8, 8'. In the present invention, the recycled anion exchange resin is kept on standby for at least 3 hours while maintaining its separation from the cation exchange resin, and after the waiting period, both ion exchange resins are mixed in a resin storage tank. The ion exchange resin is transferred to the water tower and used for water flow. <Effects of the present invention> As explained above, the present invention allows the recycled anion exchange resin to stand by for at least 3 hours while maintaining its separation from the cation exchange resin, and after the waiting period, mixes both ion exchange resins. The chloride ions leaking into the treated water can be significantly reduced with the simple operation of passing water through the water.For example, mixed bed condensate desalination, where leakage of trace amounts of chloride ions is a problem, is possible. This problem can be successfully solved by applying the present invention to the device. 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 that performs feeding and regeneration in the same column. The invention can be applied. The present invention aims to solve the problem of an increase in the leakage of anions such as chloride ions that occurs when the anion exchange resin used in a mixed bed ion exchange device is contaminated and the reaction rate decreases. Although this is the main purpose, for example, when a cation exchange resin is contaminated, Na
Even if the diffusion of caustic soda in the cation exchange resin particles decreases and the amount of sodium ions in the treated water increases, wait for at least 3 hours while maintaining the separated state of both ion exchange resins after regeneration. By doing so, the leakage amount of sodium ions can be reduced. In this case, if the Na-type cation exchange resin near the collector is mixed with the H-type cation exchange resin on standby, the leakage amount of sodium ions can be further reduced. Examples will be described below to make the effects of the present invention more clear. Example 1 A cation exchange resin, Amberlite (registered trademark, hereinafter the same) 200CT, and an anion exchange resin, Amberlite IRA-900, used in a mixed bed condensate desalination equipment in a pressurized water nuclear power plant. Collect the mixed ion exchange resin, separate the mixed ion exchange resin by a conventional method, and then add 200CT and IRA.
-900 was reproduced under the reproduction conditions shown in Table 1.

[Table] Next, take out the regenerated IRA-900, 100ml,
After passing 1N-hydrochloric acid 50/-R at SV10, approx.
Pass 1μS/cm ion-exchanged water through SV10 and wash until the electrical conductivity of the cleaning wastewater becomes 20μS/cm.
Adjusted C1 type IRA-900. The above-mentioned recycled IRA-900, 900ml and C1 type
100 ml of IRA-900 was mixed in a beaker and allowed to stand for 3 hours. I then played this
200CT, adjust the mixed ion exchange resin by mixing 2, and prepare the mixed ion exchange resin with an inner diameter of 56.5 mm and a height of
It was packed into a 1500 mm column and the following water flow test was conducted. That is, ammonium and hydrazine were added by chemical injection to ion-exchanged water with an electrical conductivity of about 1 μS/cm, and each amount was about 500 μg as ammonium.
NH ₄ /, about 150 μg N ₂ H ₄ / as hydrazine
Adjust the raw water to a concentration of LV8.
Water was passed through the aforementioned column at m/h. The results are shown in Figure 4. Example 2 After mixing C1 type IRA-900 and regenerated IRA-900, water was passed under exactly the same conditions as in Example 1 except that the standing time was 5 hours. The results are shown in Figure 4. Example 3 After mixing C1 type IRA-900 and regenerated IRA-900, water was passed through the mixture under exactly the same conditions as in Example 1, except that the standing time was 15 hours. The results are shown in Figure 4. Example 4 200CT, 2 prepared in the same manner as in Example 1, in the lower layer, C1 type IRA-900, 100ml in the middle layer, and recycled IRA-900, 900ml in the upper layer, each with an inner diameter of 56.5
After filling a column with a height of 1500 mm and a height of 1500 mm, the upper layer
In order to mix IRA-900 and IRA-900 in the middle layer, ion-exchange water of about 1μS/cm was added from the bottom of the column to LV4.
Water was passed for 30 minutes at m/h to remove the entire ion exchange resin layer.
It was expanded by 20% and then settled. Next, after leaving this state as it is for 5 hours, all the ion exchange resins were sufficiently mixed to prepare a mixed ion exchange resin, and the mixed ion exchange resin was subjected to water flow. Note that the water flow conditions are exactly the same as in Example 1. The results are shown in Figure 4. Example 5 Water was passed under exactly the same conditions as in Example 4, except that the standing time was 15 hours. The results are shown in Figure 4. Example 6 200CT, 2 prepared in the same manner as in Example 1 was regenerated in the lower layer, and C1 type IRA-900, 100ml was regenerated in the middle layer.
IRA−900, 900ml on top layer each with inner diameter of 56.5mm,
After filling a column with a height of 1500 mm, it was left as it was for 15 hours. Next, all the ion exchange resins were sufficiently mixed to prepare a mixed ion exchange resin, and the mixed ion exchange resin was subjected to water flow. Note that the water flow conditions are exactly the same as in Example 1. The result is the fourth
Shown in the figure. Comparative Example 1 IRA-900, 900 regenerated under the same conditions as Example 1
After mixing 100 ml of C1 type IRA-900 and 100 ml of IRA-900, the mixture was immediately mixed with 200 CT, 2 without any standing time, and water was passed under exactly the same conditions as in Example 1. The result is the fourth
As shown in the figure. Comparative Example 2 IRA-900, 900 regenerated under the same conditions as Example 1
ml, C1 type IRA−900, 100ml and regenerated
After mixing 200CT and 2, leave it as it is for 15
After standing for a period of time, water was passed under exactly the same conditions as in Example 1.
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 mixed bed type condensate desalination apparatus, and FIG. 3 is an explanatory diagram of the flow of a regeneration tower of a conventional mixed bed type ascites 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)

[Scope of Claims] 1 A used cation exchange resin and an anion exchange resin are backwashed and separated, and a regenerating agent is passed through the anion exchange resin in the upper layer and the cation exchange resin in the lower layer. In a mixed bed type ion exchange device, the recycled waste liquid flows out from a collector installed near the separation interface of both ion exchange resins and is regenerated, and the recycled both ion exchange resins are mixed and water is passed through the mixed bed type ion exchange equipment. A mixed bed type ion system, characterized in that the anion exchange resin that has already been used is kept on standby for at least 3 hours while maintaining a state of separation from the cation exchange resin, and after the waiting period, both ion exchange resins are mixed and water is passed through the mixture. A method of preventing leakage of harmful ions in an exchanger. 2. A method for preventing the leakage of harmful ions in a mixed bed type ion exchange apparatus according to claim 1, which comprises passing water or gas through the recycled anion exchange resin, mixing the anion exchange resin, and then waiting.