JPS6139849B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for separating mixed ion exchange resins, and more specifically, the present invention relates to a method for separating mixed ion exchange resins.
It relates to a method for separating each ion exchange resin with as high purity as possible. Water purification devices typically incorporate a mixed bed of cation exchange resins and anion exchange resins.
To regenerate the mixed bed, first, water is flowed upward in the bed to develop the resin layer and separate it into a lower cation exchange resin layer and an upper anion exchange resin layer.
This is done by passing a caustic soda aqueous solution through the upper part of the bed and a hydrochloric acid aqueous solution through the lower part of the bed, and extracting the chemical solution from a collection pipe provided at the interface between both resin layers. In recent years, with the demand for highly purified water, the coexistence of both resins near the interface between the two resin layers has become a problem. As a solution to this problem, resin extraction pipes are installed above and below the interface, and while water is flowing slowly upward from the bottom of the floor, only the anion exchange resin is extracted from the upper resin extraction pipe, and then the anion exchange resin is extracted from the lower resin extraction pipe. A method has been proposed for extracting the resin mixture existing between the two resin extraction tubes from the resin extraction tube (Japanese Patent Application Laid-open No.
52-88586). According to this method, the cation exchange resin and the anion exchange resin can be separated with extremely high purity. However, in this method, the resin is extracted while water is flowing upward, so if the water flow rate is reduced so that the resin does not flow, it takes a long time to extract the resin. Furthermore, when the water flow rate is increased, the resin layer expands, making the interface unclear and requiring a large amount of water for extraction. In the present invention, after a mixed bed is separated into a lower cation exchange resin layer and an upper anion exchange resin layer by upward flowing water, the upper layer anion exchange resin and the resin mixture near the interface are extracted by downward flowing water. This provides a method for efficiently extracting resin. According to the present invention, two resin transfer pipes each consisting of one collecting pipe and a plurality of extraction pipes branching from the collecting pipe and having resin extraction holes are installed horizontally with an appropriate interval above and below. In the separation tower, a mixture of cation exchange resin and anion exchange resin is separated into a lower cation exchange resin layer and an upper anion exchange resin layer by upward flowing water, and the interface between both resin layers is separated. After placing the resin in the middle between the upper and lower resin transfer pipes, first transfer the upper resin while flowing water downward and at a flow rate such that the pressure loss at each resin extraction hole is 0.2Kg/ ^cm2 or more. The anion exchange resin above the transfer tube is extracted together with water through the transfer tube, and then the ion exchange resin between the two transfer tubes is extracted together with water through the lower resin transfer tube. To explain the present invention in detail, in the present invention, resin is separated in a separation column in which resin transfer pipes are installed horizontally above and below so as to sandwich the interface between a cation exchange resin layer and an anion exchange resin layer. . The interval between the upper and lower resin transfer pipes is such that the cation exchange resin and anion exchange resin are separated after backwashing separation, and the mixing area that occurs near the separation interface between the two is sandwiched between them. It is preferable to keep the length as short as possible, taking into consideration the purity required for the ion exchange resin and anion exchange resin, and is usually 20 to 40 cm. Each resin transfer pipe consists of one collecting pipe and a plurality of extraction pipes branching from the collecting pipe and having resin extraction holes. The ion exchange resin enters the extraction pipe from the resin extraction hole and is sent to the resin regeneration tower via the collecting pipe. The resin extraction hole is sized to cause a pressure loss of 0.2 Kg/cm ² or more during resin extraction. If the pressure loss of the resin extraction holes is smaller than this, the resin cannot be uniformly extracted from each resin extraction hole due to fluctuations in the pressure loss in the pipes between the extraction tubes. The extraction tube is usually made into a thin tube so that the flow rate is higher than that of the collecting tube, so that the ion exchange resin does not settle in the tube and clog the extraction tube. Unlike when the resin layer is extracted with an upward flow while expanding, when extracted with a downward flow, resin remains in a mountain shape between the resin extraction holes depending on the angle of repose of the resin. . Therefore, the resin extraction holes are distributed as uniformly as possible in the cross section of the separation column so that the amount of the remaining resin is not locally non-uniform. For example, when the interval between the upper and lower resin transfer pipes is 30 cm, it is preferable that the distance from any point on the cross section to the nearest resin extraction hole be within 40 cm.
In this way, when the lower extraction pipe is operated, almost all of the resin above the middle between the upper and lower transfer pipes can be extracted in spite of the existence of the angle of repose. According to the present invention, since the resin is extracted under downward flowing water, separation at the interface between the cation exchange resin and the anion exchange resin is good. Furthermore, since the resin is extracted without expanding the resin layer, the extraction speed is fast and the amount of water required for extraction is small. Furthermore, since the resin transfer pipe is composed of a collecting pipe and multiple extraction pipes branching from the collecting pipe, resin can be extracted uniformly from the entire cross section, so that the resin remaining above the resin extraction hole surface is removed. The amount is small and there is no non-uniformity depending on location. Therefore, according to the present invention, the cation exchange resin and the anion exchange resin can be separated with high purity, and the amount of the mixed resin layer extracted as an intermediate component can also be kept to a small amount. In addition, in the method of the present invention, when the downward flow is accompanied by a gentle upward flow of about 1 to 2 m/hour, the angle of repose becomes small, and the amount of resin remaining above the resin extraction hole is further reduced. EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to the following Examples unless it exceeds the gist thereof. Example 1 In a separation column having an inner diameter of 100 cmφ, resin transfer pipes were installed horizontally at a height of 110 cm and a height of 130 cm from the lower resin support plate, respectively. The resin transfer pipe has an inner diameter of 4cm from a collecting pipe with an inner diameter of 6cmφ.
It is made by branching two extraction tubes of diameter 50cm, and each extraction tube has resin extraction holes with a diameter of 7mmφ at positions 22cm and 65cm from the front. There is. Diaion PK228L940 and this separation tower
PA312L470 and a mixture were added, water was passed through the water supply and drainage pipe at the bottom of the tower at a flow rate of 10 m/hour, and water was discharged from the water supply and drainage pipe at the top of the tower to separate the resin. Next, water was passed through the water supply and drainage pipe at the top of the tower at a flow rate of 7.4 m/hour, and the resin was extracted together with water from the upper resin transfer pipe. The pressure loss in each extraction hole was 0.5 Kg/cm ² . After 11 minutes, the resin had finished flowing out from the upper resin transfer tube, so the upper resin transfer tube was closed, the lower resin transfer tube was opened, and the resin was extracted. Resin flow ended after 7 minutes. The extracted anion exchange resin and the cation exchange resin remaining in the column were regenerated with caustic soda and hydrochloric acid in a conventional manner. Regeneration level is HCl 150
g/-R, NaOH 300g/-R. After thoroughly washing with water to ensure purity, it was packed into an ion exchange tower with an inner diameter of 100 cmφ to form a mixed resin bed. When raw water with the following composition was passed through this at a rate of 100 m/hour,
The quality of the treated water after 48 hours was as shown in Table 1. Composition of raw water NH ₃ 540ppb N ₂ H ₄ 100ppb Na 39ppb Cl 60ppb Comparative example 1 Resin transfer pipe is one pipe with an inner diameter of 4cmφ, and resin extraction holes with a diameter of 8mmφ are provided at positions 17cm, 50cm, and 83cm from the front. Separation, extraction, and regeneration of the resin were carried out in the same manner as in Example 1 using a separation column constructed in exactly the same manner as in Example 1, except that the column was replaced with a different one. A water flow test was conducted in exactly the same manner as in Example 1 using the recycled resin, and the quality of the treated water after 48 hours was as shown in Table 1. Comparative Example 2 Separation and extraction of resin were carried out in the same manner as in Example 1 using a separation tower configured exactly the same as in Example 1 except that the size of the resin extraction hole was 13 mmφ in diameter.
It was regenerated. The pressure loss at each extraction hole is
It was 0.04Kg/ ^cm2 . It took 45 minutes to extract the resin from the upper resin transfer tube and 26 minutes to extract the resin from the lower resin transfer tube. The reason why it took longer to extract the resin than in Example 1 is thought to be that the resin did not flow out uniformly from each extraction hole, and even after the extraction was completed, there was a large amount of resin around the extraction hole in front. The residual height of the resin was low, and the residual height of the resin was high around the extraction hole at the tip. Further, when a water flow test was conducted using the recycled resin in exactly the same manner as in Example 1, the quality of the treated water after 48 hours was as shown in Table 1.

[Table] From Table 1, it is clear that in the comparative example, the anion exchange resin was mixed into the cation exchange resin remaining in the column. This is because the resin transfer pipe was a straight pipe or the pressure loss at the resin extraction hole was too small, so the resin was not extracted uniformly from the entire cross section, and a large amount of resin was deposited above the lower extraction pipe. This shows that some resin remained.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical cross-sectional view showing the outline of the separation column used in the examples. FIG. 2 is also a schematic cross-sectional view. 1... Tower wall, 2... Resin support plate, 3, 4... Water supply and drainage pipe, 5, 6... Resin transfer pipe, 7... Upper surface of resin bed, 8... Separation interface, 9... Collection pipe, 10 ...Resin extraction tube.

Claims (1)

[Claims] 1 Inside a separation tower in which two resin transfer pipes, consisting of one collecting pipe and a plurality of extraction pipes branching from the collecting pipe and having resin extraction holes, are installed horizontally with an appropriate interval above and below. The mixture of cation exchange resin and anion exchange resin is separated into a lower cation exchange resin layer and an upper anion exchange resin layer by upward flowing water, and the interface between both resin layers is separated into upper and lower resin transfer tubes. After that, the water is flowed downward and at a flow rate such that the pressure loss at each resin extraction hole is 0.2Kg/ ^cm2 or more, first through the upper resin transfer pipe. A method for separating a mixed ion exchange resin, which comprises extracting the anion exchange resin above the transfer tube together with water, and then extracting the ion exchange resin between the two transfer tubes together with water via the lower resin transfer tube.