JPS6140462B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is directed to an external regeneration type mixed bed ion exchange equipment in which fine cation exchange resins, especially 80 mesh, are mixed into the anion exchange resin when regenerating used cation and anion mixed ion exchange resins. This article concerns a method for efficiently separating the following cation exchange resins. When backwashing used cation and anion mixed ion exchange resins with water, a new anion exchange resin is added to the water. Backwashing is performed to separate the cation exchange resin into two layers: a cation exchange resin at the bottom and an anion exchange resin at the top. By removing the anion exchange resin from the upper layer of the system together with the anion exchange resin, the amount of sodium cation exchange resin that enters the water flow system of the mixed bed ion exchange equipment is minimized, and highly purified treated water is produced. The purpose is to obtain. Conventionally, in order to obtain high-purity treated water using a mixed bed ion exchange device, it is necessary to completely separate both ion exchange resins and anion exchange resins before regenerating them with acid and alkali. It is well known among those skilled in the art that it is a necessary factor to not leave unregenerated ion exchange resins such as sodium type cation exchange resins and chloro type anion exchange resins in the regenerated state. Furthermore, the first condition for not leaving these unregenerated ion exchange resins is to completely separate the cation exchange resin and the anion exchange resin. However, in practice, it is difficult to achieve complete separation of both ion exchange resins. In other words, backwash separation using water is normally performed to separate the cation exchange resin and anion exchange resin, but in this operation, both ion exchange resins must be placed between the anion exchange resin layer and the cation exchange resin layer. A mixed layer is formed, and fine cation exchange resin is further mixed into the anion exchange resin layer. The inventor previously proposed Japanese Patent Application No. 53-4391 as a method for separating cation exchange resins with small particle sizes mixed in such anion exchange resins. This is done by flowing an upward flow of 2 to 8% by weight caustic soda solution from the bottom of the ion exchange resin layer at a flow rate of LV 0.5 to 4 m/H to separate the cation exchange resin and anion exchange resin. , a clear laminated layer is formed with an anion exchange resin layer on the top and a cation exchange resin layer on the bottom, and then a caustic soda solution having a density intermediate between the two ion exchange resins is added in an upward flow at a low flow rate. By flowing in, only the upper anion exchange resin is floated, and a liquid layer of caustic soda solution having an intermediate density is formed between the floated anion exchange resin and the precipitated cation exchange resin. This is a method in which the anion exchange resin and the cation exchange resin that have been floated are separately taken out of the system. This method works particularly effectively when the particle size of the fine cation exchange resin contained in the anion exchange resin layer is around 60 mesh, and it is possible to completely separate the cation and anion exchange resins. However, if it contains a large amount of fine cation exchange resin with a particle size smaller than 60 mesh, especially less than 80 mesh, 2 to 8% by weight of caustic soda can be added to LV 0.5.
When flowing upward from the bottom of the ion exchange resin at a flow rate of 4 m/h to 4 m/h, fine cation exchange resin tends to float to the upper layer of the anion exchange resin.
It has the disadvantage that it takes a long time to completely separate into two layers, an anion exchange resin and a cation exchange resin. As a result of repeated experiments to improve the shortcomings of the prior application method in cases where a large amount of fine cation exchange resin of 80 mesh or less is contained, the present inventor found that When the mixed ion exchange resin is backwashed with water and separated into two layers: a cation exchange resin at the bottom and an anion exchange resin at the top, fine cation exchange particles are mixed in the upper anion exchange resin layer. When looking at the distribution state of the resin, it was noted that the fine cation exchange resin of 80 mesh or less is mostly mixed in the upper layer region of the anion exchange resin layer, and the present invention was constructed based on this finding. That is, the present invention provides an external regeneration type mixed bed type ion exchange apparatus in which when backwashing a used cation-exchange resin and an anion-exchange resin with water, 15 to 60% by volume of the anion-exchange resin is Anion exchange resin is newly added and backwashed and separated with water to form an anion exchange resin layer on the top and a cation exchange resin layer on the bottom, and then the upper layer of the anion exchange resin layer that has been backwashed and separated. Mixed into an anion exchange resin characterized in that after removing an anion exchange resin in an amount equivalent to the amount of anion exchange resin added during backwash separation, both cation and anion exchange resins are regenerated. This is a method for separating fine cation exchange resins. The present invention will be explained below using a condensate desalination apparatus as an example with reference to the drawings. In carrying out the present invention, first, a used mixed ion exchange resin of an anion exchange resin and a cation exchange resin is passed through a water flow tower (not shown) of a condensate desalination apparatus to a separation tower 1 shown in FIG. Then, backwash water 2 is introduced from the lower part of the separation column 1 and backwashed and separated by a conventional method.The cation exchange resin 3 is placed in the bottom of the separation column 1, and the anion exchange resin is placed in the top of the separation column 1. Form 4. Note that the cation exchange resin 3 and anion exchange resin 4 cannot be completely separated by backwashing with water, and a mixed ion exchange resin of both ion exchange resins is placed between the cation exchange resin 3 and anion exchange resin 4. Resin 5 is formed, and as described above, fine cation exchange resin K of 80 mesh or less is mixed into the upper layer of anion exchange resin 4. Anion exchange resin 4 containing fine cation exchange resin K separated by backwashing in this way
The entire amount of the mixed ion exchange resin 5 and a portion of the cation exchange resin 3' present below it are transferred by a water stream to the anion exchange resin regeneration tower 6 shown in FIG. 2, and then to the separation tower 1. The remaining cation exchange resin 3 is regenerated with acid in a conventional manner. On the other hand, after the transfer of these ion exchange resins to the anion exchange resin regeneration tower 6 is completed, new anion exchange resin corresponding to 15 to 60% by volume of the anion exchange resin 4 is added to the anion exchange resin regeneration tower 6. and backwash water 2 is introduced from the lower part of the anion exchange resin regeneration tower 6 to carry out backwash separation again in a conventional manner.
When main backwashing is performed, as shown in Fig. 2, the cation exchange resin 3' is placed in the lower part of the anion exchange resin regeneration tower 6, the mixed ion exchange resin 5 is placed in the upper part of the cation exchange resin 3', and the resin amount is 15 to 60% by volume in the upper part. An increased amount of anion exchange resin 4' is formed, and fine cation exchange resin K is contained in the upper layer of the anion exchange resin 4'. The sedimentation rate of fine cation exchange resin K of 80 mesh or less is lower than that of anion exchange resin with a normal particle size, and such fine cation exchange resin K does not float to the surface during backwashing with normal water. However, since it is easy to mix between the upper surface of the upper anion exchange resin layer and the resin layer height of about 15 to 40% from above, when backwashing and separating, 15 to 60 volume % of the used anion exchange resin, Preferably, when 30 to 40% by volume of anion exchange resin is newly added and backwash separation with water is performed, fine cation exchange resin K is removed.
is mixed into a portion corresponding to the amount of newly added anion exchange resin from above the anion exchange resin 4. Next, an anion exchange resin corresponding to the amount of anion exchange resin added when backwashing and separating the upper part of the anion exchange resin 4' is taken out from a take-out pipe 7 provided in the anion exchange resin regeneration tower 6. Through this operation, the fine cation exchange resin K mixed in the upper layer of the anion exchange resin 4' can also be taken out at the same time, and the fine cation exchange resin K is transferred to the anion exchange resin regeneration tower 6 as shown in FIG. Remove cation exchange resin K,
A layer of anion exchange resin 4 can be formed in an amount equivalent to the amount of anion exchange resin used in the water tower. The anion exchange resin containing the fine cation exchange resin K taken out from the anion exchange resin regeneration tower 6 may be added as is to the next backwash separation and used repeatedly; The amount of fine cation exchange resin gradually accumulates in the anion exchange resin taken out, so depending on the content of fine cation exchange resin K, the taken out anion exchange resin is either discarded or cation exchanged. It can be added when the cation exchange resin K is separated using a liquid having an intermediate density between that of the ion exchange resin and the anion exchange resin, and then backwashed and separated again. Further, as another method of the present invention, as shown in FIG. 4, the used positive and negative mixed ion exchange resin is transferred to the separation tower 1 by water flow in the water passing tower,
An anion exchange resin of 15 to 60% by volume of the anion exchange resin is newly added to the cation and anion mixed ion exchange resin, backwash water 2 is introduced from the lower part of the separation column 1, and the mixture is washed using a conventional method. cation exchange resin 3,
A mixed ion exchange resin 5 of a cation exchange resin and an anion exchange resin and an anion exchange resin 4' in which the resin amount has been increased by 15 to 60% by volume are formed, and then anions are extracted from a take-off pipe 8 provided in the separation column 1. An anion exchange resin corresponding to the amount of anion exchange resin added when backwashing and separating the upper layer of the exchange resin 4' may be taken out. By doing this, the fine cation exchange resin K mixed in the upper layer of the anion exchange resin 4' is also removed, and the anion exchange resin 4 that is not contaminated with fine cation exchange resin K is transferred to the separation column 1. It can be left behind. Next, the anion exchange resin 4 obtained in this way, the mixed ion exchange resin 5 of a cation exchange resin and an anion exchange resin, and a part of the cation exchange resin 3' present in the lower part are subjected to anion exchange using a water stream. When the resin is transferred to the resin regeneration tower 6, backwash water 2 is introduced from the lower part of the anion exchange resin regeneration tower 6, and backwash separation is performed again using the conventional method, as shown in FIG. 3 of the method of the present invention described above. In the anion exchange resin regeneration tower 6, layers of a cation exchange resin 3', a mixed ion exchange resin 5 of a cation exchange resin and an anion exchange resin, and an anion exchange resin 4 can be formed from the bottom to the top.
Furthermore, as in the embodiment of the present invention described later, when an anion exchange resin is newly added to the mixed ion exchange resin of cation and anion transferred from the water tower in the separation column 1, the total amount of ion exchange resin increases, Since a large separation column 1 is required, as in the embodiment of the method of the present invention described above, the anion exchange resin 4 is separated and transferred to the anion exchange resin regeneration column 6, and new anions are added to the anion exchange resin 4. It is easier to perform backwash separation by adding exchange resin. Next, according to the present invention, fine cation exchange resin K
To regenerate the anion exchange resin from which the cation exchange resin K has been removed, a regenerating agent 9 is passed downward from the upper part of the anion exchange resin regeneration tower 6, as shown in FIG. 3, to remove fine cation exchange resin K. Then, the recycled anion exchange resin 4 is transferred from the anion exchange resin regeneration tower 6 to an ion exchange resin storage tank (not shown) and thoroughly washed in the storage tank. Then, the cation exchange resin 3 that has been regenerated and washed in the separation column 1 described above may be transferred from the separation column 1 to the same storage tank by a water stream and sufficiently mixed to prepare for the passage of condensate water. By the way, in the present invention, the fine cation exchange resin of 80 mesh or less mixed in the upper layer of the anion exchange resin 4' as shown in FIG. 2 is recycled together with the anion exchange resin in the upper layer. The cation exchange resin is taken out of the column from column 6, but if it contains cation exchange resin with a relatively small particle size of around 60 mesh, such cation exchange resin is separated into anion exchange resin by backwash separation with water. It is difficult to remove it in the present invention because it tends to get mixed into the lower layer of 4'. Therefore, if such cation exchange resin with a relatively small particle size of around 60 meshes remains in the anion exchange resin 4 shown in FIG. If the anion exchange resin 4 is regenerated without removing the exchange resin, a sodium-type cation exchange resin will be produced, and if this is supplied as it is to the water tower, it will cause a decrease in the purity of the treated water. In addition, in the above-mentioned regeneration method, the mixed ion exchange resin 5 and cation exchange resin 3' remaining in the anion exchange resin column 1 are returned to the separation column 1, but the mixed ion exchange resin 5 is only subjected to backwashing and separation with water. Since this method contains anion exchange resin that cannot be completely separated, there is a drawback that the recovery rate of the anion exchange resin regenerated in the anion exchange resin regeneration tower 6 and transferred to the ion exchange resin storage tank is low. Therefore, when the anion exchange resin is subjected to backwash separation to remove fine cation exchange resin of 80 mesh or less mixed in the anion exchange resin according to the present invention, the following regeneration method is performed. The effects of the present invention are further improved, and highly purified treated water can be obtained. In regenerating anion exchange resin from which fine cation exchange resin of 80 meshes or less has been removed according to the present invention, 2 to 8% by weight is used as the first step.
As shown in Fig. 5, the caustic soda solution 10 is
It is introduced from the lower part of the anion exchange resin regeneration tower 6 at a flow rate of LV 0.5 to 4 m/H. As a result, the anion exchange resin 4 becomes fluid, so that the cation exchange resin with a relatively small particle size of around 60 mesh mixed in the lower layer of the anion exchange resin 4 gradually becomes anionic. The ion exchange resin settles at the bottom of the ion exchange resin regeneration tower 6, and at the same time, the anion exchange resin in the mixed ion exchange resin 5 moves to the top of the anion exchange resin regeneration tower 6, and finally as shown in FIG. In the anion exchange resin regeneration tower 6, the lower part is the cation exchange resin 3', and the upper part is the anion exchange resin 4, so that a clear stack of anion exchange resin and cation exchange resin can be formed.
In addition, since the anion exchange resin 4 has already removed the fine cation exchange resin of 80 mesh or less which is particularly difficult to separate, this operation can completely separate both the cation and anion exchange resin in a short time. can do. In this operation, the anion exchange resin 4 is sufficiently fluidized to allow the cation exchange resin with a relatively small particle size to settle at the bottom of the anion exchange resin regeneration tower 6, thereby producing a more complete cation and anion exchange resin. Since the purpose is to perform separation, it is inconvenient if the density of the caustic soda solution used in this operation is higher than the density of the anion exchange resin. Even if it is an approximation, it is inconvenient.
Furthermore, when the caustic soda solution is caused to flow upward from the lower part of the anion exchange resin regeneration tower 6, if it flows in at too high a flow rate, not only will the cation exchange resin with a relatively small particle size not settle, but the anion exchange resin If the flow rate is extremely low, the anion exchange resin 4 will not flow, which will prevent the cation exchange resin 4, which has a relatively small particle size, from settling. There is also a correlation between the concentration of the caustic soda solution used in this operation and the flow rate at which the solution flows in an upward flow, and it is preferable to use the combinations of concentration and upward flow rate shown in Table 1.

[Table] Note that if the concentration of the caustic soda solution used in this operation is low, the separation efficiency of the cation exchange resin, which has a relatively small particle size, will decrease slightly as described above, and conversely, if the concentration is high, the separation efficiency of the cation exchange resin will decrease slightly. Since the flow of the anion exchange resin becomes slow, it takes a long time for the cation exchange resin, which has a relatively small particle size, to settle, so the concentration of the caustic soda solution is preferably selected in the range of 3 to 6%. good. In addition, in the previously filed Japanese Patent Application No. 53-4391, when separating both ion exchange resins with an upward flow of 2 to 8% by weight caustic soda solution, the increase in LV was 0.5.
However, since the anion exchange resin 4 removes the fine cation exchange resin K of 80 mesh or less according to the present invention, the LV increases a little more.
Even if the value is increased, the separation effect does not substantially change, and it can be achieved up to LV8m/H. However, LV8m/
If the rising flow rate is higher than H, as mentioned above, not only the cation exchange resin having a relatively small particle size will not settle, but also the cation exchange resin 3' will be mixed into the anion exchange resin 4, which is not preferable. On the contrary, LV1.5m/
At a rising flow rate of less than H, separation is possible up to LV 0.5 m/H, but this is not preferable because separation takes a long time. For these reasons, it is most preferable that the upward flow rate of the 2 to 8% by weight caustic soda solution in this operation be around LV4 m/H. Through this operation, as shown in FIG. 5, the anion exchange resin and cations are formed such that the cation exchange resin 3' is in the lower part of the anion exchange resin regeneration tower 6, and the anion exchange resin 4 is in the upper part. A distinct stack of exchange resins can be formed, thus comparing the mixed ion exchange resin 5 contained in the anion exchange resin 4 and the cation exchange resin 3', and in the lower layer of the anion exchange resin 4. It becomes possible to almost completely separate the cation exchange resin having a small target particle size from the anion exchange resin 4. Next, as a second step, as shown in FIG. 6, a caustic soda solution 11 having a density lower than that of the anion exchange resin 4 flows downward from the upper part of the anion exchange resin regeneration tower 6 to exchange anions. The resin 4 is regenerated, and the regenerated waste liquid 12 is discharged from the lower part of the anion exchange resin regeneration tower 6. In this way, by flowing the caustic soda solution 11 in a downward flow, 2 to 8% by weight of the caustic soda remaining in the anion exchange resin 4 and the free board 13 is removed at the end of the first step. The solution 10 is pushed out by the caustic soda solution 11 flowing from the upper part of the column and passes through the layer of anion exchange resin 4 again in a downward flow, so the pre-operation is mainly used to separate the cation exchange resin and anion exchange resin. was used for 2
to 8% by weight caustic soda solution 10 can be effectively used again for regenerating the anion exchange resin 4,
Then, the new caustic soda solution 11 flowing from the upper part of the anion exchange resin regeneration tower 6 passes through the four layers of anion exchange resin to further regenerate the anion exchange resin 4. Usage can be measured. The caustic soda solution 11 used in the second step must always have a density lower than that of the anion exchange resin 4.
This is because if a caustic soda solution with a density higher than that of the anion exchange resin 4 is used, the anion exchange resin 4 will float to the surface due to the density difference during the passage of the solution.
This is because the regeneration efficiency is extremely reduced. The concentration of the caustic soda solution 11 having a density lower than that of the anion exchange resin 4 used in the second step is generally desirably a concentration that regenerates the anion exchange resin, that is, about 5% by weight. In addition, in the second step, the caustic soda solution 1
1 may be flowed in from the upper part of the tower to extrude the caustic soda solution 10 used in the first step remaining in the anion exchange resin regeneration tower 6 in advance. . After the inflow of the caustic soda solution 11 is completed in this manner, extrusion and washing are performed using pure water in a conventional manner. By the above-described two operations, it is possible to separate the cation exchange resin having a relatively small particle size contained in the lower layer of the anion exchange resin, and to efficiently regenerate the anion exchange resin. Therefore, if only the regenerated anion exchange resin 4 shown in FIG. 6 is taken out from the anion exchange resin regeneration tower 6, no sodium-type cation exchange resin will be mixed into the ion exchange resin storage tank. As a method for taking out the anion exchange resin 4 from the anion exchange resin regeneration tower 6, as shown in FIG. At the same time, air or pure water 14 is introduced from the upper part of the column through the anion exchange resin take-out nozzle 16 provided in the lower part of the anion exchange resin 4. Replacement resin 4
It is preferable to take out the resin in the form of a slurry and transfer it to a resin storage tank. When this method is carried out, the anion exchange resin 4 is gradually taken out, and as the amount of the anion exchange resin remaining in the column becomes smaller, the anion exchange resin 4 floats up as shown in FIG. and a liquid layer 17 of caustic soda solution having an intermediate density between the anion exchange resin 4 and the cation exchange resin 3'.
is formed, and finally all of this floating anion exchange resin 4 is transferred to the ion exchange resin storage tank by the inflow pressure of air or pure water 14 flowing from the upper part of the column. To further explain this method in detail, the concentration of the caustic soda solution 15, which has an intermediate density between the cation exchange resin and anion exchange resin used in this operation, depends on the density of the cation exchange resin and anion exchange resin used. Therefore, it is best to select the optimum concentration for the purpose, usually from 10 to 20% by weight, although there is some variation. Moreover, if the flow rate when flowing the caustic soda solution 15 having an intermediate density into the anion exchange resin regeneration tower 6 in an upward flow is too high, the cation exchange resin may be separated as shown in FIG. 3' is fluidized, and the cation exchange resin with small particle size present in the upper layer of the cation exchange resin 3' becomes the caustic soda solution 15.
This is not preferable because it gets mixed into the anion exchange resin 4 along with the upward flow of the water. Therefore, when the caustic soda solution 15 flows in an upward flow, it is preferable that the flow rate is low so as not to fluidize the cation exchange resin 3'.
It is best to keep it below m/H. Further, the caustic soda solution 15 having an intermediate density used for separating the anion exchange resin and the cation exchange resin can be used repeatedly by recovering it. That is, the state after the anion exchange resin is transferred using the caustic soda solution is as shown in FIG. A liquid layer 17 of the sodium chloride solution is formed, and the free board 13 above it becomes an air layer when air is introduced from the top of the column when taking out the anion exchange resin. When pure water is introduced from the top of the tower, it forms a pure water layer. Therefore, as shown in FIG. 9, by flowing air or pure water 14 from the upper part of the anion exchange resin regeneration tower 6, it is possible to recover almost undiluted caustic soda solution from the lower part of the tower. It is. Moreover, since the medium density caustic soda solution thus recovered has been regenerated by the previous regeneration operation of the anion exchange resin, its purity has hardly decreased. Therefore, the recovered caustic soda solution can be used repeatedly,
This makes it possible to reduce the overall amount of caustic soda used. After taking out the regenerated anion exchange resin in the anion exchange resin regeneration tower 6 into the ion exchange resin storage tank by the method explained above, the anion exchange resin in the ion exchange resin storage tank is washed with water as necessary. Then, the cation exchange resin that has been regenerated and washed in the separation tower 1 is transferred to the same tower, where it is thoroughly mixed and prepared for the next transfer to the water tower. On the other hand, the cation exchange resin 3' remaining at the bottom of the anion exchange resin regeneration tower 6 is washed with water and then transferred to the separation tower 1, which is empty after the transfer of the cation exchange resin 3 has already been completed.
Used solar cells transferred from the next water tower
The capacity balance of the ion exchange resin is maintained by combining it with the anion and mixed ion exchange resin and providing it for the next regeneration. As explained above, the present invention enables the removal of fine particles of cation exchange resin that are mixed into the anion exchange resin that cannot be separated by simple backwashing with water, especially 80 mesh or less that are mixed in the upper layer of the anion exchange resin. Since fine cation exchange resin can be almost completely separated by relatively simple operations, the amount of sodium cation exchange resin mixed into the water flow system of an external regeneration type mixed bed ion exchange equipment can be reduced. This makes it possible to significantly reduce the amount of water, thereby making it possible to obtain highly purified treated water. Examples of the present invention will be described below. Example: Condensate from a thermal power plant using strong basic anion exchange resin Amberlite (registered trademark, same hereinafter) IRA-900 (density 1.09) and strong acidic cation exchange resin Amberlite 200C (density 1.21) The used mixed ion exchange resins were sampled from the desalination equipment in the water tower and used in the following experiment. First, add Amberlite IRA-900 24, which has been colored blue with thymolphthalein, to Amberlite.
80-100 mesh 150ml at 200C, 60-70 mesh
150ml and 2.5 particles with a particle size of 50 mesh or less
2.8 in total and packed into an acrylic separation column (diameter 160 mm, total length 4000 mm). Pure water was allowed to flow upward from the bottom of the column at a flow rate of LV 9 m/H for about 20 minutes to backwash and separate both ion exchange resins. As a result, there is a layer of only brown cation exchange resin at the bottom of the column, a mixed layer of brown cation exchange resin and blue anion exchange resin at the top, and a layer of fine brown cation exchange resin above that. A layer of blue anion exchange resin was formed. Next, Amberlite IRA-900 9.6, which was colored blue with thymolphthalein, was newly added to the above column, and pure water was flowed from the bottom of the column at an upward flow rate of LV 9 m/H for about 20 minutes, and both ion The exchange resin was backwashed and separated. As a result, there is again a layer of brown cation exchange resin at the bottom of the column, a mixed layer of brown cation exchange resin and blue anion exchange resin at the top, and a layer of fine brown cation exchange resin in the upper layer. A layer of blue anion exchange resin containing cation exchange resin was formed. Next, 9.6 anion exchange resin present above the take-out tube was taken out from the take-out tube provided at a position 480 mm downward from the surface of the anion exchange resin layer of the column. Transfer 9.6 of the anion exchange resin taken out into a separating funnel in two portions, add caustic soda solution adjusted to a density of approximately 1.16 (approximately 15% by weight), and stir thoroughly to separate the anion exchange resin. It was completely floated to the top of the liquid. Thereafter, the anion exchange resin that had been floated was stirred again after a period of time and allowed to stand still, which was repeated five times each to check whether the cation exchange resin had settled at the bottom of the separating funnel. As a result, the cation exchange resin precipitated at the bottom of the separating funnel, and the combined volume of the cation exchange resin divided into two portions was 202 ml. Of these, 138 particles have a particle size of 80 to 100 mesh.
ml, there are 64ml of particles with a particle size of 60 to 70 mesh, and of the fine cation exchange resin originally contained, 92% of the particles with a particle size of 80 to 100 mesh and
42% of particles with a particle size of 60-70 mesh were removed. Next, from the bottom of the column above, the density at a temperature of 20℃ is
LV 4 5% by weight caustic soda solution of 1.054g/ ^cm3
The inflow was carried out for 20 minutes at an upward flow rate of m/H. As a result, the blue anion exchange resin at the top of the column expanded by about 40% and was in a fluid state, although the amount was less than during backwashing. Furthermore, it was observed that the brown cation exchange resin with small particle size contained in the mixed layer and the lower layer of the anion exchange resin layer gradually settled to the bottom of the column. Finally, the upper part of the column is a blue anion exchange resin, and the lower part is a brown cation exchange resin whose particle size gradually increases from top to bottom. A laminate of ion exchange resin was formed. After settling for 10 minutes, reduce the temperature from the top of the column to 20
A 5% caustic soda solution with a density of 1.054g/ ^cm3 is approximately
After flowing for 30 minutes in a downward flow at a flow rate of LV 6 m/H,
Extrusion and washing were performed by flowing pure water from the top of the column in a downward flow at a flow rate of LV9 m/H for 30 minutes.
Next, from the bottom of the column, a sample with a density of 1.131 g/cm ³ at a temperature of 20°C is
A 12% by weight caustic soda solution was introduced at an upward flow of LV 2 m/H, and pure water was flowed from the top at a flow rate of LV 9 m/H to position the anion exchange resin layer 200 mm above the top surface of the cation exchange resin. The entire amount of anion exchange resin was taken out of the column from an anion exchange resin take-out nozzle provided at a certain point while floating the anion exchange resin on a 12% by weight caustic soda solution. About 50% of the anion exchange resin taken out was transferred to a separatory funnel together with the accompanying caustic soda solution, and the concentrated caustic soda solution was added to the separating funnel until the density of the accompanying caustic soda solution was about 1.16 (about 15% by weight). ) and stirred sufficiently to completely float the anion exchange resin to the top of the liquid. Thereafter, the anion exchange resin that had floated to the surface after a while was stirred again and allowed to stand still, which was repeated five times to check whether the cation exchange resin had settled at the bottom of the separating funnel. As a result, it was confirmed that a small amount of cation exchange resin had settled at the bottom of the separating funnel, and this volume was 0.7
It was less than ml. On the other hand, 500 ml of the removed anion exchange resin was separately collected and thoroughly washed with pure water, and the regeneration rate of the OH type anion exchange resin was measured and found to be over 95%. The amount of caustic soda required in this example was 5
% caustic soda solution flowing upward for 20 minutes at LV 4 m/H, and 5% caustic soda solution flowing upward for 20 minutes.
Total amount of flow flowing down for 30 minutes at LV 6m/H, calculated as 100% per anion exchange resin.
Although 190 g of the 12% by weight caustic soda solution used to separate the anion exchange resin and cation exchange resin was recovered, the equivalent of about 1.5 was diluted and could not be recovered. This unrecoverable caustic soda amounts to approximately 9 g on a 100% basis per anion exchange resin, and therefore the total amount of caustic soda required to regenerate the anion exchange resin is 100%.
It was converted to about 200g/-R. Moreover, the purity of the recovered caustic soda did not decrease at all, and it was sufficiently usable for the next separation. As is clear from this example, according to the present invention, the fine cation exchange resin mixed in the anion exchange resin layer could be almost completely removed.

[Brief explanation of the drawing]

Figures 1, 2, 3, 4, 5, 6, 7, 8, and 9 show anions for each operation in the embodiment of the present invention. FIG. 2 is an explanatory diagram showing a state of separation of an exchange resin and a cation exchange resin. 1... Separation tower, 2... Backwash water, 3... Cation exchange resin, 4... Anion exchange resin, 5... Mixed ion exchange resin, 6... Anion exchange resin regeneration tower, 7... Take-out pipe, 8... Take-out pipe, 9...
... Regenerating agent, 10 ... 2 to 8% by weight caustic soda solution, 11 ... Caustic soda solution having a density lower than the density of the anion exchange resin, 12 ... Regeneration waste liquid, 13 ... Freeboard, 14 ... ...air or pure water, 15...caustic soda solution having a density intermediate between anion exchange resin and cation exchange resin, 1
6... Anion exchange resin take-out nozzle, 17...
...liquid layer, K...fine cation exchange resin.

Claims (1)

[Claims] 1 In an off-column regeneration type mixed bed ion exchange equipment, when backwashing and separating a used cation-exchange resin and an anion-exchange resin with water, 15% of the anion exchange resin is
Or 60% by volume of anion exchange resin is newly added and backwashed and separated with water to form an anion exchange resin layer on the top and a cation exchange resin layer on the bottom, and then the backwashed and separated anions After removing an anion exchange resin in an amount corresponding to the amount of anion exchange resin added during backwash separation of the upper layer of the exchange resin layer,
A method for separating fine cation exchange resins mixed into an anion exchange resin, characterized by regenerating both cation and anion exchange resins.