JPH0511495B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is a method for producing pure water using both anion and cation exchange resins in a mixed state. The invention relates to a method for separating and extracting anion and cation exchange resins, respectively. [Prior Art] In an ion exchange apparatus that desalinates water using an ion exchange resin, the cation exchange resin and anion exchange resin used for desalination are regenerated and used again for desalination. For regeneration, a multi-bed type ion exchange equipment that uses cation exchange resin and anion exchange resin in separate columns can be used as is, but it can be regenerated as is, but both anion exchange resin and cation exchange resin are used in a mixed state. In mixed bed type or mono-bed type ion exchange equipment, both anion and cation exchange resins are
Must be separated separately. When regenerating a mixed-bed ion exchange device, first, the mixed anion and cation exchange resins are backwashed in a tank (usually a separation tower, which is separate from the demineralization tower). At the same time, it is separated into two layers, the anion exchange resin in the upper layer and the cation exchange resin in the lower layer, due to the difference in specific gravity.
The anion exchange resin in the upper layer is introduced into an anion exchange resin regeneration tower and regenerated with a caustic soda aqueous solution, etc., and the cation exchange resin remaining in the tank is regenerated with sulfuric acid etc. in the tank, and then the regenerated both After each resin is washed and both resins are mixed, they are returned from the tank to the desalination tower and used again for desalination. In this conventional method, after the anion exchange resin and the anion exchange resin are separated into two layers, one resin extraction tube is installed near the separation surface of both resins and within the anion exchange resin layer. The anion exchange resin is extracted from the anion exchange resin to an anion exchange resin regeneration tower. When extracting the anion exchange resin using this resin extraction tube, resin particles are affected by the resin transfer state from the demineralization tower to the separation tower, the state of the desalination treatment, and the difference in surface potential of the anion and cation exchange resins. Due to mutual entanglement (clamping), the separation surface may be vertically displaced from a predetermined position with respect to the resin extraction tube, and therefore, the upper layer anion exchange resin may be removed from the resin extraction tube provided near the separation surface. When extracting the ion exchange resin, a portion of the cation exchange resin may also be extracted, and the anion exchange resin may not be completely extracted and a portion thereof may remain in the separation column. In this case, the cation exchange resin extracted together with the anion exchange resin is reversely regenerated (completely
Also, the anion exchange resin remaining in the cation exchange resin is reversely regenerated with sulfuric acid, which reduces the ion exchange capacity of the entire ion exchange resin during desalination. At the same time, it is predicted that the sodium ions or sulfate ions used to regenerate the ion exchange resin will dissociate from the ion exchange resin while the water is flowing through the demineralization tower and leak to the downstream side, adversely affecting the water quality of the primary system. One way to solve this problem is to use an ion exchange resin for separation and replenishment, and use multiple resin extraction tubes to separate both the negative and positive ion exchange resins. There is a problem. (1) Even if the fluctuation range of the level of the separation plane of the anion and cation exchange resin is predicted and designed in advance, if it deviates from this range, problems such as reverse regeneration may occur. (2) In plants such as nuclear power plants that do not have sufficient installation space, it is quite difficult to install incidental equipment such as storage tanks for separation and replenishment resin, resulting in space problems. (3) Since multiple resin extraction pipes are installed in the separation tower, when separating anion and cation exchange resins by backwashing, they become an obstacle to the water flow for backwashing, making it difficult to separate the two resins cleanly. There is a risk. (4) Filling with extra ion exchange resin increases the number of operations and requires a larger volume of the separation column. [Problems to be Solved by the Invention] This invention solves the problems of the prior art described above, and is capable of sufficiently dealing with the range of fluctuations in the level of the resin separation surface, which could not be dealt with conventionally. possible, always completely separate the cation exchange resin and anion exchange resin from the mixture of anion and cation exchange resins, so that both resins can be regenerated in their respective pure states and returned to the desalination tower. The present invention provides a method. Furthermore, the present invention provides a method for separating both resins, which can be used in a nuclear power plant where installation space is comparatively limited, and which can be used in the same amount of space as conventional methods. [Means for Solving the Problems] As a result of various studies in order to improve the above-mentioned drawbacks of the conventional method, the present inventor has found that the level of the separation surface of the anion and cation exchange resin formed in the separation column has been improved. A portion of the cation exchange resin in the lower layer is extracted from the bottom of the separation column so that it is below the position of the anion exchange resin extraction pipe, and by adjusting the position of the above level, the anion exchange resin of the cation exchange resin is removed. Achieved prevention of contamination into the regeneration tower. Furthermore, for the anion exchange resin remaining in the separation tower, backwash water is injected from the bottom of the separation tower to develop the resin layer and raise the level of the separation surface, and only the anion exchange resin is removed from the anion exchange resin extraction pipe. By extracting the anion exchange resin, the amount of anion exchange resin remaining in the separation column was minimized. That is, the present invention provides a method for separating an ion exchange resin in a mixed state of a cation exchange resin and an anion exchange resin after a water sampling operation into each resin in order to regenerate the resin through (i) desalination. A mixed ion exchange resin is introduced from the column into a separation column (which also serves as a cation exchange resin regeneration column), and the introduced ion exchange resin is backwashed.
A first step of forming two layers: an anion exchange resin layer and a cation exchange resin layer. (ii) The cations in the cation exchange resin layer are removed so that the separation surface of the anion exchange resin and cation exchange resin is below the anion exchange resin extraction pipe installed in the middle of the separation column. A second step in which a part of the exchange resin is extracted from the cation exchange resin extraction pipe provided at the bottom of the separation tower to a resin storage tank; (iii) the anion exchange resin in the separation tower is extracted from the anion exchange resin extraction pipe through the anion exchange resin extraction pipe; The third step is to extract the resin to the regeneration tower. (iv) The anion exchange resin remaining in the separation tower is gently backwashed from the bottom of the separation tower, and the amount of backwash water is adjusted to develop and raise the level of the resin separation surface. (v) a fifth step in which the cation exchange resin extracted into the resin storage tank in the second step is returned to the separation tower; This is a method for separating ion exchange resins. This method makes it possible to fully manage and control the range of fluctuations in the resin separation level, which was not possible with conventional methods, and it is possible to always completely separate and regenerate cation exchange resins and anion exchange resins. It became. In the case of separation by backwashing of both anion exchange resin and anion exchange resin, even if the anion exchange resin extraction pipe is designed in advance to be installed near the level of the separation surface of both resins, the actual separation will be difficult as will be explained later. The surface level tends to rise above the target level, and when sluicing water is sent to send the anion exchange resin to the anion exchange resin regeneration tower, the cation exchange resin layer expands somewhat due to the water flow. , as the level of the separation surface rises upwards, normally the cation exchange resin tends to enter the anion exchange resin extraction pipe, but in this invention, the level of the separation surface is raised to a part of the cation exchange resin. Since the separation surface level is lowered to the target separation surface level by extracting the separation surface, even if the actual separation surface level fluctuates, separation can be performed perfectly in the same manner every time. The operation of this separation method can be carried out visually and manually, but as a means of checking the level of the resin separation surface, it is possible to check the color difference (brightness) or electrical conductivity of the cation exchange resin and anion exchange resin. By using a device that continuously detects differences in temperature (μS/cm), etc., the level of the resin separation surface is automatically monitored, and valves and pumps that are linked to a program timer or sequence controller, etc. , by controlling the extraction level of the cation exchange resin in the second step, and by controlling the separation level in the fourth step by controlling the amount of backwash water from the lower part of the separation tower using a control valve. Driving is also possible. [Example] Next, an example of the present invention will be described, but the present invention is not limited to this example. FIG. 1 illustrates each step in the separation method of the present invention. (1) shows the first step of separating the cation exchange resin and the anion exchange resin by backwashing the ion exchange resin in a mixed state of both anion and cation exchange resins. 1 is a separation tower (cation exchange resin regeneration tower), into which the saturated,
When the ion exchange resin in a mixed state is introduced and backwash water is introduced from the pipe 9 at the bottom of the column for backwashing, a layer of anion exchange resin 4 in the upper part and a layer of cation exchange resin 5 in the lower part are formed.
It is assumed that the separation surface 6, which is the boundary between the two layers, is slightly above the anion exchange resin extraction pipe 11 provided at a predetermined position in the middle of the separation column. 7 is an overflow outlet pipe, 8 is a water collection pipe, 10
is a distribution pipe. (2) shows the second step of transferring a portion of the cation exchange resin from the cation exchange resin layer to the resin storage tank. While air is being fed through the pipe 12 and pressurized, sluicing water is fed through the pipe 9, and the tower 1 is
When the valve of the cation exchange resin extraction pipe 14 provided at the bottom of the cation exchange resin is opened, the cation exchange resin in the cation exchange resin layer is sent from the pipe 14 to the resin storage tank 3. As the level of the separation surface 6 decreases with this transfer, when the level falls to the target level, the valve of the pipe 14 is closed to stop the transfer of the cation exchange resin. (3) shows the third step of transferring the anion exchange resin from the separation tower to the anion exchange resin regeneration tower. When air is introduced through the pipe 12 to pressurize it, sluicing water is introduced through the pipe 9, and the valve of the pipe 13 connected to the anion exchange resin extraction pipe 11 is opened.
Anion exchange resin 4 is transferred to anion exchange resin regeneration tower 2 through pipes 11 and 13. Depending on this transfer, the portion of the anion exchange resin layer above the tube 11 is sent. The lower part of the layer is not transferred from the pipe 11 because the flow of the sluicing water is weak and does not rise to the pipe 11. (4) shows the fourth step of sending the anion exchange resin remaining in the separation tower to the anion exchange resin regeneration tower. Backwash water is sent from the pipe 9 while air is fed from the pipe 12 under pressure, and the backwash water does not disturb the separation surface, but both resin layers expand upward and rise. When adjusting the amount of water, the anion exchange resin rises and is transferred to the column 2 through pipes 11 and 13. When the transfer of the anion exchange resin is completed, the cation exchange resin will be mixed in, so the supply of backwash water is stopped. (5) shows the fifth step of returning the cation exchange resin in the resin storage tank to the separation tower. Air is fed into the resin storage tank 3 from the pipe 15 and pressurized, and sluicing water is fed into the lower part of the storage tank from the pipe 16, and when the valve of the pipe 17 is opened, the cation exchange resin in the storage tank 3 is Sent to separation column 1. Through the above-mentioned steps, the cation exchange resin is separated in an almost pure state in the separation column, and the anion exchange resin is separated in an almost pure state in the anion exchange resin regeneration column. (6) shows the regeneration process for both resins. Sulfuric acid is fed into the separation column 1 through a tube 18, and a caustic soda aqueous solution is fed into the anion exchange resin regeneration column 2 through a tube 19 to regenerate both resins. The above operation can be carried out by visual inspection and manual operation, but as a means of checking the resin separation level,
By using a device that continuously detects the difference in color (brightness) or electrical conductivity (μS/cm) between cation exchange resins and anion exchange resins, the resin separation level can be automatically monitored, and the program timer or sequence Automatic operation is possible using valves and pumps that are linked to a controller. In this case, especially the above-mentioned (2), which is a feature of this invention,
The operation control method in the steps shown in and (4) will be explained. FIG. 2 shows the operation control system when transferring a part of the cation exchange resin to the resin storage tank in the second step of (2), and the numbers up to 14 are the same as in FIG. 1. When the color difference type resin separation level detection device 24 is activated by an instruction from the program timer or sequence controller 23, the scanning type detection unit 25 moves up and down to detect the actual separation level Lr, and the signal is sent to the calculation device 26. Then, the difference l between the target separation level Lo and the actual separation level Lr is calculated, and the signal is sent to the calculation device 27 (which may be the same device as the calculation device 26), where the resin withdrawal speed is calculated. The opening times of the air inlet valve 20, through jig water inlet valve 21, and resin outlet valve 22 are calculated, and the signals are sent to the program timer or sequence controller 23, which instructs the operating times of the valves and pumps. The output from there is sent to each of the above-mentioned valves 20, 21 and 22, so that they can be operated automatically. FIG. 3 shows the operation control system when transferring the residual anion exchange resin to the anion exchange resin regeneration tower in the fourth step (4). When the type resin level detection device 24 is activated, the scanning type detection unit 25 moves up and down to detect the actual separation level Ls in this process, and the signal is sent to the calculation device 26, where the separation level Ls is detected.
The difference l' between the level Lt of the anion exchange resin extraction pipe 11 and the level Lt of the anion exchange resin extraction pipe 11 is calculated, and the signal is sent to the calculation device 27. There, based on the relationship between the backwash expansion rate and the backwash flow rate, a The control value of the flow rate adjustment valve 29 is calculated and set. At this time, the difference in expansion rate due to water temperature should also be taken into account. The signal is then sent to the program timer or sequence controller 23, which instructs the operation of valves and pumps. This allows automatic operation. [Effects of the Invention] By having the above-mentioned steps, the present invention can always completely separate the cation exchange resin and the anion exchange resin. Furthermore, it is possible to deal with fluctuations in the resin separation level, which could not be dealt with conventionally. Further, since the cation exchange resin and anion exchange resin can be subjected to regeneration in an almost pure state, the regeneration efficiency is high. Furthermore, both resins can be returned to the desalination tower with very little reverse regeneration, making it possible to ensure good treated water quality during desalination. In an example of a BWR plant that adopted this separation method, the quality of water used in the reactor was improved in the following ways compared to the conventional method. 【table】

[Brief explanation of drawings]

FIG. 1 illustrates each step in the separation method of the present invention, and FIG. 2 shows the operation control system when transferring a part of the cation exchange resin to the resin storage tank in the second step, FIG. 3 shows the operation control system when transferring the residual anion exchange resin to the anion exchange resin regeneration tower in the fourth step. 1: Separation tower, 2: Anion exchange resin regeneration tower,
3: resin storage tank, 4: anion exchange resin, 5: cation exchange resin, 6: separation surface, 9: tube, 11: anion exchange resin extraction tube, 13: tube, 14: cation exchange resin extraction tube, 17: Tube.

Claims (1)

[Scope of Claims] 1. In a method of separating a mixed ion exchange resin of a cation exchange resin and an anion exchange resin after a water sampling operation into respective resins in order to regenerate the ion exchange resin through drug passage, the method includes: (i) desorption. A mixed ion exchange resin is introduced from the salt tower into a separation tower (which also serves as a cation exchange resin regeneration tower), and the introduced ion exchange resin is backwashed.
The first step is to form two layers, an anion exchange resin layer and a cation exchange resin layer. A second step in which a part of the cation exchange resin in the cation exchange resin layer is extracted from the cation exchange resin extraction pipe provided at the bottom of the separation column into the resin storage tank so that the separation surface with the resin goes below it; (iii) ) The third step is to extract the anion exchange resin in the separation tower from the anion exchange resin extraction pipe to the anion exchange resin regeneration tower, (iv) the anion exchange resin remaining in the separation tower is removed from the bottom of the separation tower by (v) A fourth step in which the anion exchange resin is extracted from the anion exchange resin extraction pipe and sent to the anion exchange resin regeneration tower by washing and adjusting the amount of backwash water to develop and raise the level of the resin separation surface. A method for separating ion exchange resins, comprising: a fifth step of returning the cation exchange resin extracted to the resin storage tank in the second step to the separation column. 2 When extracting the cation exchange resin in the second step, the difference in color (brightness) or electrical conductivity (μS/cm) between the cation exchange resin and anion exchange resin is used as a means of checking the level of the resin separation surface. The level at the resin separation surface is automatically monitored by using a device that continuously detects cation exchange resin, etc., and the level of cation exchange resin withdrawn is controlled by valves and pumps that are linked to a program timer or sequence controller, etc. In the same way, in the fourth step, when removing the residual anion exchange resin,
2. The method for separating ion exchange resins according to item 1, wherein the level of the resin separation surface is controlled by controlling the amount of backwash water from the lower part of the separation tower using a control valve.