JPH0437738B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a mixed ion exchange resin regeneration device in an external regeneration type mixed bed ion exchange desalination device, typified by a condensate desalination device. Specifically, in order to keep the concentration of sodium ions, chloride ions, and sulfate ions that leak into the treated water to an extremely low level when the recycled mixed ion exchange resin is used again for desalination treatment, the recycled cation exchange resin The present invention relates to a device for suppressing the abundance of sodium ion type exchange groups in a regenerated anion exchange resin, as well as chloride ion type and hydrogen sulfate ion type exchange groups in an anion exchange resin after regeneration. [Prior art] In recent years, requirements for the quality of treated water from condensate desalination equipment used in thermal power plants and nuclear power plants have become increasingly strict, and impurity ions such as sodium ions, chloride ions, and sulfate ions have become increasingly strict. It is often required to suppress the concentration of leakage into the treated water to 0.1μg/or less, and in some cases, the concentration of sodium ions is reduced to about 0.005μg/and the concentration of chloride or sulfate ions to about 0.01μg/. Sometimes you are asked to do something. This is thought to be due to the fact that the mechanisms of impurity ion concentration and corrosion in boilers and steam generators have gradually become clearer, and the accuracy of impurity ion analysis has improved, making analysis at extremely low concentrations possible. . Traditionally, mixed-bed ion exchange desalination equipment has been mainly used as condensate desalination equipment, and most of them use an outside-column regeneration method (no regeneration is performed inside the desalination tower, but ion exchange is carried out in a separate regeneration tower). This method uses a method in which replacement resin is transported and regenerated. In the case of external regeneration, when regenerating the mixed ion exchange resin, the resin in the demineralization tower is first transferred to the regeneration tower, and backwashed in the regeneration tower to separate the cation exchange resin and anion exchange resin into two layers. Then, the upper layer of anion exchange resin is transferred to another regeneration tower, and then hydrochloric acid or sulfuric acid is passed through the cation exchange resin, caustic soda is passed through the anion exchange resin, and both resins are washed. The basic procedure is to transfer both resins to a resin storage tank, mix them with air, and return the mixed resin to the desalination tower. However, as the leakage of impurity ions, particularly sodium ions, leaking into the treated water has become a problem, attention has been paid to the incompleteness of separation when separating both resins during regeneration. That is, the cation exchange resin mixed in the anion exchange resin layer comes into contact with caustic soda, which is a regenerating agent for the anion exchange resin, and becomes a sodium ion form, and this sodium ion form of the cation exchange resin is returned to the demineralization tower and passed through the water flow process. This is because it was found that when used in a chemical reaction, an ion exchange reaction occurs with cations such as hydrogen ions and ammonium ions, resulting in the leakage of sodium ions as shown in the following equation. R−Na+H ⁺ →R−H+Na ⁺ …(1) R−Na+NH ₄ ⁺ →R−NH ₄ +Na ⁺ …(2) (R means resin matrix) This phenomenon occurs especially after the breakthrough of ammonium ions. An operation method that continues water flow (so-called ammonia,
Although this problem is noticeable during cycle operation), it also occurs when water flow is stopped before ammonium ions break through (so-called H-OH cycle operation). However, in the H-OH cycle operation, the leakage of sodium ions that occurs is much smaller than in the ammonia cycle operation, so this has not been a problem in the past. However, under recent strict water quality requirements, even this minute leak has become a problem. On the other hand, the leakage of anions such as chloride ions and sulfate ions has traditionally been overlooked, partly because the means for detecting them have not been sufficiently developed. As analytical methods have developed and it has become possible to detect anions, it has become clear that chloride and sulfate ions leak more than expected. These leaks occur when the anion exchange resin mixed into the cation exchange resin layer during regeneration comes into contact with hydrochloric acid or sulfuric acid, which is a regenerant for the cation exchange resin, and becomes chloride ion form or hydrogen sulfate ion form, and this resin is desorbed. This is thought to be due to leakage of chloride ions and sulfate ions according to the following equation when the salt is returned to the salt tower and used in the water passing process. R-Cl+OH ^- →R-OH+Cl ^- ...(3) R=(HSO ₄ ) ₂ →R=SO ₄ +2H ⁺ +SO ₄ ^2-
...(4) The inventor conducted an experimental study and found that H-
It has been found that in order to reduce the sodium ion leakage to approximately 0.005 μg/degree in OH cycle operation, the abundance ratio of sodium ion exchange groups to all cation exchange groups needs to be 0.2 to 0.3%. It has also been found that in order to reduce the chloride ion leakage to about 0.01 μg/level, the abundance ratio of chloride ion exchange groups to all anion exchange groups needs to be 3 to 5%. The present inventors previously invented a method for improving the separation of cation exchange resins and anion exchange resins as shown in Japanese Patent Publication No. 58-41913. According to this method, the amount of cation exchange resin mixed into the anion exchange resin layer is 0.1% of the total cation exchange resin.
It becomes below. In addition, the amount of anion exchange resin mixed into the cation exchange resin layer is based on the total anion exchange resin.
It will be 0.5-2%. The reason why the contamination rate of anion exchange resin is relatively high is that after backwashing and separating both resins in the cation exchange resin regeneration tower, when the upper layer of anion exchange resin is transferred to the anion exchange resin regeneration tower, This is because even if the cation exchange resin is transferred together with the anion exchange resin, it is inevitable that some amount of the anion exchange resin remains. Now, the inventor conducted an experiment (experiment 1) in which water flow and regeneration were repeated using a model column, assuming a condensate desalination device with external regeneration, and obtained the results shown in Table 1. .

[Table] What is noticeable in Table 1 is that the abundance of chloride ion-type anion exchange resins is abnormally high, and a somewhat high chloride ion leak occurs accordingly. Considering that there is no load of chloride ions in flowing water and that the proportion of anion exchange resin mixed into the cation exchange resin layer during regeneration is 0.5 to 2%, this chloride ion type anion exchange resin is It can only be assumed that the 0.5 to 2% generated in the process accumulates each time it is regenerated. In fact, it is well known that the regeneration efficiency of chloride ion type anion exchange resins is poor, and in order to particularly reduce the proportion of chloride ion type anion exchange resins, it is necessary to flush a large excess of caustic soda. In addition, using the same model column as in Experiment 1, we conducted a water flow and regeneration experiment (Experiment 2) using sulfuric acid as a regenerant for the cation exchange resin.
The results shown are obtained.

[Table] What is noticeable in Table 2 is that the leakage of sulfate ions at the initial stage of water flow is abnormally high. Comparison with the results in Table 1 shows that the sulfate ion leak due to the hydrogen sulfate ion type exchange group is orders of magnitude larger than the chloride ion leak due to the chloride ion type exchange group. Note that hydrogen sulfate ion exchange groups cannot be analyzed separately from sulfate ion exchange groups, so they do not appear in the results in Table 2, but hydrogen sulfate ion exchange groups are commonly analyzed according to equation (4). It is thought that most of it has been converted into sulfate ion type exchange groups in water. By the way, the anion exchange resin used in Experiment 1 was regenerated by passing sulfuric acid through it, followed by passing caustic soda through it, and mixed with the cation exchange resin used in Experiment 1 regenerated with hydrochloric acid. When simulated condensate was passed through (Experiment 3), the results shown in Table 3 were obtained.

【table】

[Problem that the invention seeks to solve]

The present invention has been made in order to solve the above-mentioned problems. The objective is to suppress the abundance of exchange groups to a low level and to extremely reduce the concentration of sodium ions, chloride ions, and sulfate ions that leak into treated water when used for desalting treatment. [Means for Solving the Problems] The present invention is a mixed ion exchange resin regeneration device attached to an external regeneration type mixed bed ion exchange desalination device, which comprises a cation exchange resin regeneration tower 1, an anion exchange Resin regeneration tower 2, resin storage tank 3, hydrochloric acid supply device 4,
The cation exchange resin regeneration tower 1 is composed of a sulfuric acid supply device 5, a caustic soda supply device 6, and attached piping and valves; the cation exchange resin regeneration tower 1 is connected to a piping 901 for transferring the resin after the desalination process is completed from the demineralization tower, Resin extraction ports 11 and 12 are provided at the middle part of the tower and at the bottom of the tower, water collection and distribution mechanisms 13 and 14 are provided at the top and bottom of the tower, respectively, and a water collection and distribution mechanism at the top is provided above the resin extraction port 11 in the middle part of the tower. A hydrochloric acid inlet 15 is provided below 13, and the inlet 15
and the hydrochloric acid supply device 4 are connected by a pipe 103; the anion exchange resin regeneration tower 2 is equipped with resin extraction ports 21 and 22 at the middle part of the tower and at the bottom part of the tower, respectively, and has a water collection and distribution mechanism 23 at the top part and the bottom part of the tower, respectively. ,2
4, and is further provided with a sulfuric acid and caustic soda inlet 25 above the resin extraction port 21 in the middle part of the tower and below the water collection and distribution mechanism 23 at the top, and connects the inlet 25 with the sulfuric acid supply device 5 and the caustic soda supply device 6. Connected with piping 203; resin storage tank 3
is equipped with a resin extraction port 32 at the bottom, and a pipe 30 for transferring the resin in the tank to the desalination tower.
1 is connected, and water collection and distribution mechanisms 33 and 34 are provided at the top and bottom of the tank, respectively; the intermediate resin extraction port 11 of the cation exchange resin regeneration tower 1 and the upper part of the anion exchange resin regeneration tower 2 are connected by a resin transfer pipe 101. The bottom resin extraction port 12 of the cation exchange resin regeneration tower 1 and the top of the resin storage tank 3 are connected to the resin transfer pipe 10.
2, the intermediate resin withdrawal port 21 of the anion exchange resin regeneration tower 2 and the upper part of the resin storage tank 3 are connected by the resin transfer pipe 201, and the bottom resin withdrawal port 22 of the anion exchange resin regeneration tower 2 and the cation exchange resin regeneration tower 1 is characterized in that the upper part of the resin transfer pipe 202 is connected to the resin transfer pipe 202. [Embodiment] An embodiment of the present invention will be described with reference to the drawings. 1 is a cation exchange resin regeneration tower, 2 is an anion exchange resin regeneration tower, 3 is a resin storage tank, 4 is a hydrochloric acid supply device, and 5 is a A sulfuric acid supply device, 6 is a caustic soda supply device. The cation exchange resin regeneration tower 1 has a resin transfer pipe 901 connected to its upper part for transporting the resin after the desalination process of the demineralization tower (not shown) is completed, and a resin extraction port 11 is connected to the middle and bottom of the tower 1, respectively. 12, and a water collection and distribution mechanism 13 at the top and bottom, respectively.
and 14. Furthermore, a hydrochloric acid inlet 15 is provided above the intermediate resin withdrawal port 11 of the cation exchange resin regeneration tower 1 and below the top water collection and distribution mechanism 13, and this hydrochloric acid inlet 15 is connected to an ejector for sucking hydrochloric acid from the hydrochloric acid supply device 4. Piping 1 with valve at 41
It is connected at 03. The anion exchange resin regeneration tower 2 is equipped with resin extraction ports 21 and 22 at the middle and bottom, respectively, and a water collection and distribution mechanism 23 at the top and bottom, respectively.
and 24. Furthermore, a sulfuric acid and caustic soda inlet 25 is provided above the intermediate resin withdrawal port 21 of the anion exchange resin regeneration tower 2 and below the top water collection and distribution mechanism 23, and this inlet 25 sucks sulfuric acid from the sulfuric acid supply device 5. It is connected to an ejector 51 for sucking caustic soda from the caustic soda supply device 6 and an ejector 61 for sucking caustic soda from the caustic soda supply device 6 through a pipe 203 having a valve. The resin storage tank 3 is provided with a resin drawing port 32 at the bottom, a resin transfer pipe 301 having a valve for transferring the resin in the tank to a desalination tower (not shown) is connected to the bottom resin drawing port 32, and a resin transfer pipe 301 is connected to the resin drawing port 32 at the top of the tank. Water collection and distribution mechanisms 33 and 34 are provided at the bottom and the bottom, respectively. Further, the intermediate resin withdrawal port 11 of the cation exchange resin regeneration tower 1 and the upper part of the anion exchange resin regeneration tower 2 are connected by a resin transfer pipe 101 having a valve, and the bottom resin withdrawal port 12 and the upper part of the resin storage tank 3 are connected with a valve. The resin transfer pipe 102 is used for connection. In addition, the intermediate resin extraction port 21 of the anion exchange resin regeneration tower 2
and a resin transfer pipe 2 having a valve at the upper part of the resin storage tank 3.
01, and the bottom resin drawing port 22 and the upper part of the cation exchange resin regeneration tower 1 are connected by a resin transfer pipe 202 having a valve. In addition, the upper parts of the cation exchange resin regeneration tower 1, anion exchange resin regeneration tower 2, and resin storage tank 3 are connected to the air pipe 902 through valves, and are also connected to the exhaust valves 16, 26, and 36, and the top water collection and distribution mechanisms are connected to each other. 13, 23, 33 are connected to the water supply pipe 903 and the respective drain pipes 104, 204, 304 via valves, and each bottom water collection and distribution mechanism 14, 24, 34 is connected to the air pipe 904, the water supply pipe 905, and the respective drains. It is connected to pipes 105, 205, and 305 via valves. In the figure, CR indicates a cation exchange resin, and AR indicates an anion exchange resin. Next, to explain its operation, the mixed ion exchange resin after water passage in the demineralization tower (not shown) is received from the demineralization tower into the cation exchange resin regeneration tower 1 via the resin transfer pipe 901. . A mixed ion exchange resin for assisting separation (the same brand of resin as the desalting resin is used) is placed in advance in the cation exchange resin regeneration tower 1, and is backwashed together with the resin after the desalting process is completed. After backwashing, if left to stand still, it will separate into two layers, with the anion exchange resin in the upper layer and the cation exchange resin in the lower layer. At this time, the separation interface between the two layers is made to be above the intermediate resin extraction port 11. next,
Intermediate resin extraction port 1 via resin transfer piping 101
The resin above 1 is transferred to an anion exchange resin regeneration tower 2. By this operation, almost the entire amount of the anion exchange resin and the cation exchange resin near the separation interface are transferred to the anion exchange resin regeneration tower. After the transfer is completed, the resin in both regeneration towers is backwashed and left to stand still. At this time, a cation exchange resin CR layer is formed at the bottom of the anion exchange resin regeneration tower, but the separation interface between the two layers is made to be sufficiently below the intermediate resin extraction port. The drawing shows the progress of the process. Subsequently, hydrochloric acid flows into the cation exchange resin regeneration tower 1 through the pipe 103. At the same time, piping 20
3, sulfuric acid flows into the anion exchange resin regeneration tower 2. After passing the sulfuric acid, the pipe 203
The caustic soda solution flows into the anion exchange resin regeneration tower 2 through. After hydrochloric acid and caustic soda have been passed through, the insides of both regeneration towers are washed with pure water. Next, the resin in the cation exchange resin regeneration tower 1 is transferred to the resin storage tank 3 by the resin transfer pipe 102.
Further, the resin above the intermediate resin extraction port 21 in the anion exchange resin regeneration tower 2 is transferred to the resin storage tank 3 by the resin transfer piping 201 . Subsequently, air is introduced from the bottom water collection and distribution mechanism 34 in the resin storage tank 3 to mix the recycled cation exchange resin and the recycled anion exchange resin in the resin storage tank 3. Furthermore, the resin below the intermediate resin withdrawal port 21 in the anion exchange resin regeneration tower 2 is transferred to the cation exchange resin regeneration tower 1 through the resin transfer pipe 202, and used as a mixed ion exchange resin for separation aid during the next regeneration. use This completes the regeneration process and enters a standby state until the next regeneration. During the next regeneration, the resin transfer pipe 90
1, the mixed ion exchange resin after the completion of the desalination process is received into the cation exchange resin regeneration tower 1, and the regenerated mixed ion exchange resin in the resin storage tank 3 is transferred to the demineralization tower (not shown) through the resin transfer piping 301. performs the regeneration process in the same manner as the above procedure. If the device of the present invention is used in this way, the resin near the separation interface will be treated as a separation-aiding resin and will not be used in the next desalination process. The amount of cation exchange resin mixed in can be extremely reduced, and the amount of anion exchange resin mixed in the cation exchange resin layer can also be significantly reduced. Since hydrochloric acid is used to regenerate the cation exchange resin, it is possible to prevent the generation of hydrogen sulfate ion type exchange groups, and because the anion exchange resin is regenerated in two stages using sulfuric acid and caustic soda, it is possible to prevent generation of hydrogen sulfate ion exchange groups. There is no accumulation of chloride ion type exchange groups. Note that the hydrogen sulfate ion type exchange groups generated by passing sulfuric acid through the anion exchange resin layer are all converted into hydroxide ion form or sulfate ion form by the subsequent passage of caustic soda, and sulfuric acid No ion leakage occurs. Note that the illustrated example shows one embodiment of the present invention, and the present invention is not limited to this illustrated example. For example, although a measuring tank and an ejector are used as the regeneration chemical supply device in the illustrated example, the medicine may be directly supplied from the regeneration chemical storage tank using a metering pump without using a measuring tank. [Effects of the Invention] As described above, according to the present invention, the sodium ion type exchange group in the regenerated cation exchange resin and the chloride ion type or hydrogen sulfate ion type exchange group in the regenerated anion exchange resin can be reduced. It is possible to keep the abundance rate low, extremely low the concentration of sodium ions, chloride ions, and sulfate ions that leak into the treated water, and fully meet strict water quality requirements.

[Brief explanation of drawings]

The drawing is a system explanatory diagram showing an embodiment of the present invention. 1... Cation exchange resin regeneration tower, 2... Anion exchange resin regeneration tower, 3... Resin storage tank, 4... Hydrochloric acid supply device, 5... Sulfuric acid supply device, 6... Caustic soda supply device, 11, 21... Middle resin extraction port, 12, 22, 32...Bottom resin extraction port, 1
3, 23, 33... Top water collection and distribution mechanism, 14, 2
4, 34... Bottom water collection and distribution mechanism, 15... Hydrochloric acid inlet, 25... Sulfuric acid and caustic soda inlet, 1
6, 26, 36... Exhaust valve, 41, 51, 61...
...Ejector, 101, 102, 201, 202,
301,901...Resin transfer piping, 103,20
3...Piping, 104,204,304...Drain pipe, 105,205,305...Drain pipe, 90
2,904...Air piping, 903,905...Water supply piping, CR...Cation exchange resin, AR...Anion exchange resin.

Claims (1)

[Claims] 1. A mixed ion exchange resin regeneration device attached to an external regeneration type mixed bed ion exchange desalination device,
The cation exchange resin regeneration tower is composed of a cation exchange resin regeneration tower 1, an anion exchange resin regeneration tower 2, a resin storage tank 3, a hydrochloric acid supply device 4, a sulfuric acid supply device 5, a caustic soda supply device 6, and attached piping and valves; 1 is connected to a pipe 901 for transferring the resin after the desalination process is completed from the demineralization tower, is equipped with resin extraction ports 11 and 12 at the middle part of the tower and at the bottom part of the tower, respectively, and has a water collection and distribution mechanism at the top part and the bottom part of the tower, respectively. 13,1
4, and further provided with a hydrochloric acid inlet 15 above the resin extraction port 11 in the middle of the column and below the water collection and distribution mechanism 13 at the top, and connecting the inlet 15 and the hydrochloric acid supply device 4 with a pipe 103; The exchange resin regeneration tower 2 is equipped with resin withdrawal ports 21 and 22 at the middle part and the bottom part of the tower, respectively, and water collection and distribution mechanisms 23 and 24 at the top part and the bottom part of the tower, respectively.
Further, a sulfuric acid and caustic soda inlet 25 is provided above the resin extraction port 21 in the middle of the tower and below the water collection and distribution mechanism 23 at the top, and the inlet 25 is connected to the sulfuric acid supply device 5 and the caustic soda supply device 6 through piping 203. Connect; the resin storage tank 3 is equipped with a resin withdrawal port 32 at the bottom, and a pipe 301 for transferring the resin in the tank to the desalination tower is connected to the resin withdrawal port 32;
Furthermore, water collection and distribution mechanisms 33 and 34 are provided at the top and bottom of the tank, respectively; the intermediate resin extraction port 11 of the cation exchange resin regeneration tower 1 and the upper part of the anion exchange resin regeneration tower 2 are connected by a resin transfer pipe 101, and the cation exchange resin The bottom resin extraction port 12 of the regeneration tower 1 and the upper part of the resin storage tank 3 are connected by a resin transfer pipe 102,
Intermediate resin extraction port 2 of anion exchange resin regeneration tower 2
1 and the upper part of the resin storage tank 3 are connected by a resin transfer pipe 201, and the bottom resin extraction port 22 of the anion exchange resin regeneration tower 2 and the upper part of the cation exchange resin regeneration tower 1 are connected by a resin transfer pipe 202. Mixed ion exchange resin regeneration equipment.