Method for reusing non-regenerative mixed bed ion exchange resin, and double bed system

Abstract

Provided is a double bed system which reuses an ion exchange resin after being used as a non-regenerative mixed bed ion exchange resin. This double bed system has a preceding stage including a strongly acidic cation exchange resin and a subsequent stage including a strongly basic anion exchange resin, or has a preceding stage including a strongly basic anion exchange resin and a subsequent stage including a strongly acidic cation exchange resin. A strongly acidic cation exchange resin or a strongly basic anion exchange resin derived from a used non-regenerative mixed bed ion exchange resin is disposed in the preceding stage, and a new strongly basic anion exchange resin or a new strongly acidic cation exchange resin is disposed in the subsequent stage.

Description

Method for reusing non-regenerated mixed bed ion exchange resin and multiple bed system

[0001] The present invention relates to a method for recycling a non-regenerated mixed bed ion exchange resin and a multi-bed system in which a non-regenerated mixed bed ion exchange resin is recycled.

[0002] Ion exchange resins used in pure water production systems are disposed of as industrial waste by landfill or incineration after a certain period of use. On the other hand, studies have been conducted to carbonize the discarded ion exchange resins by dehydration or heating (Patent Document 1), or to crush them and reuse them as filter aids (Patent Document 2).

[0003] JP-A-08-012312, JP-A-57-099336, JP-A-59-066354

[0004] As described in Patent Documents 1 and 2, studies have already been conducted on the reuse of discarded ion exchange resins for purposes other than as ion exchange resins. However, in consideration of environmental and cost aspects, there is currently a demand for the development of a method for reusing discarded ion exchange resins as ion exchange resins.

[0005] An object of the present invention is to provide a method for reusing an ion exchange resin after its use as a non-regenerated mixed-bed ion exchange resin as an ion exchange resin for use in a multiple-bed system.An object of the present invention is also to provide a multiple-bed system in which an ion exchange resin after its use as a non-regenerated mixed-bed ion exchange resin is reused.

[0006] The present invention relates to a multi-bed system having an upstream stage containing a strongly acidic cation exchange resin and a downstream stage containing a strongly basic anion exchange resin, or having an upstream stage containing a strongly basic anion exchange resin and a downstream stage containing a strongly acidic cation exchange resin, characterized in that a strongly acidic cation exchange resin or a strongly basic anion exchange resin derived from used non-regenerated mixed-bed ion exchange resin is placed in the upstream stage, and a new strongly basic anion exchange resin or a new strongly acidic cation exchange resin is placed in the downstream stage.

[0007] The present invention also provides a method for reusing used non-regenerated mixed bed ion exchange resins in a multi-bed system having an upstream section containing a strongly acidic cation exchange resin and a downstream section containing a strongly basic anion exchange resin, or in a multi-bed system having an upstream section containing a strongly basic anion exchange resin and a downstream section containing a strongly acidic cation exchange resin, the method comprising a reuse step of using the strong acid cation exchange resin or strong basic anion exchange resin derived from the used non-regenerated mixed bed ion exchange resin as the strong acid cation exchange resin or strong basic anion exchange resin contained in the upstream section of the multi-bed system, and using new strong basic anion exchange resin or strong acid cation exchange resin as the strong basic anion exchange resin or strong acid cation exchange resin contained in the downstream section of the multi-bed system.

[0008] According to the present invention, an ion exchange resin that has been used as a non-regenerative mixed-bed ion exchange resin can be repeatedly reused as an ion exchange resin for use in a multiple-bed system. Also, according to the present invention, a multiple-bed system can be provided in which an ion exchange resin that has been used as a non-regenerative mixed-bed ion exchange resin is reused.

[0009] It is a schematic diagram for explaining a part of the technical idea according to the present invention.It is a schematic diagram showing an example of a multi-floor system according to the present invention.It is a schematic diagram showing an example of a multi-floor system according to the present invention.

[0010] In the electronics industry, such as liquid crystal and semiconductor manufacturing, where high-purity pure water and ultrapure water are required, non-regenerative ion exchange resin devices are often installed at the end of primary water purification systems or in subsystem water purification systems to remove trace amounts of ions. While single-bed and dual-bed ion exchange resin devices are sometimes used as non-regenerative ion exchange resin devices, mixed-bed ion exchange resin devices are commonly used. In this specification, the ion exchange resins used in mixed-bed non-regenerative ion exchange resin devices, i.e., the ion exchange resins used in mixed-bed non-regenerative ion exchange resin devices, are referred to as "non-regenerative mixed-bed ion exchange resins." When reusing used non-regenerative mixed-bed ion exchange resins after use in a mixed-bed non-regenerative ion exchange resin device, it is first necessary to separate the cation exchange resin (C) from the anion exchange resin (A) contained in the used non-regenerative mixed-bed ion exchange resin. In the process of separating the cation exchange resin (C) and the anion exchange resin (A), two patterns occur: (a) a pattern in which the cation exchange resin and the anion exchange resin (A) cannot be completely separated, and one resin is partially contaminated with the other resin (a different resin) (a different resin contamination pattern); and (b) a pattern in which the cation exchange resin (C) and the anion exchange resin are almost completely separated (a complete separation pattern). The present inventors have intensively investigated methods for reusing used non-regenerated ion exchange resins that have been separated and regenerated in this manner. As a result, they have found that various operations are possible, such as reusing used non-regenerated ion exchange resins assuming the presence of a different resin contamination (above (a)) and reusing used non-regenerated ion exchange resins assuming only a small amount of resin contamination and almost complete separation (above (b)). Based on these findings, they have completed a series of inventions, including the present invention.

[0011] Among these inventions, this specification describes an invention relating to the case where used non-regenerated mixed bed ion exchange resin is reused, assuming that a different resin is mixed in. The present invention will be described in detail below.

[0012] <Method for Reusing Non-Regenerated Mixed-Bed Ion Exchange Resins> The method for reusing non-regenerated mixed-bed ion exchange resins according to the present invention is a method for reusing used non-regenerated mixed-bed ion exchange resins in a multi-bed system having an upstream stage containing at least a strongly acidic cation exchange resin and a downstream stage containing at least a strongly basic anion exchange resin, or in a multi-bed system having an upstream stage containing at least a strongly basic anion exchange resin and a downstream stage containing at least a strongly acidic cation exchange resin, and comprises at least the following steps: a reuse step in which the strongly acidic cation exchange resin or strongly basic anion exchange resin derived from the used non-regenerated mixed-bed ion exchange resin is used as the strongly acidic cation exchange resin or strongly basic anion exchange resin in the upstream stage of the multi-bed system, and a new strongly basic anion exchange resin or strongly acidic cation exchange resin is used as the strongly basic anion exchange resin or strongly acidic cation exchange resin in the downstream stage of the multi-bed system; and a reuse step in which the method for reusing non-regenerated mixed-bed ion exchange resin according to the present invention preferably comprises the following step prior to the reuse step. A separation process for separating the strongly acidic cation exchange resin and the strongly basic anion exchange resin contained in the used non-regenerated mixed bed ion exchange resin. A regeneration process for regenerating the separated strongly acidic cation exchange resin and the strongly basic anion exchange resin.

[0013] [Non-regenerated mixed-bed ion exchange resin] As described above, a non-regenerated mixed-bed ion exchange resin is a non-regenerated ion exchange resin used in a mixed-bed state in a mixed-bed non-regenerated ion exchange resin device. Known mixed-bed ion exchange resins can be used as such non-regenerated mixed-bed ion exchange resins. Mixed-bed ion exchange resins are generally mixed-bed ion exchange resins that contain a strongly acidic H-type cation exchange resin and a strongly basic OH-type anion exchange resin. The mixed bed ion exchange resin is not particularly limited, and examples thereof include commercially available products such as ESP-2 (trade name, manufactured by Organo Corporation), AmberTec UP6040 H / OH (trade name, manufactured by DuPont de Nemours), DIAION SMT200L (trade name, manufactured by Mitsubishi Chemical Corporation), UltraClean UCW9966 (trade name, manufactured by Purolite Co., Ltd.), and LEWATIT UltraPure 1294MD (trade name, manufactured by Lanxess).

[0014] The mixing ratio (volume ratio) of the strongly acidic cation exchange resin and the strongly basic anion exchange resin in the non-regenerative mixed-bed ion exchange resin is preferably 1:0.5 to 4.0 (strongly acidic cation exchange resin:strongly basic anion exchange resin). Generally, in many commercially available mixed-bed ion exchange resins, the ion exchange capacity of the strongly acidic cation exchange resin is mixed with the exchange capacity of the strongly basic anion exchange resin in a ratio of 1:1. Therefore, for example, if the exchange capacity of the strongly acidic cation exchange resin is about 2.0 eq / L-R and the exchange capacity of the strongly basic anion exchange resin is about 1.0 eq / L-R, the volume ratio of the strongly acidic cation exchange resin to the strongly basic anion exchange resin will be about 1:2. The matrix of the ion exchange resin may be either a transparent gel type having small pore diameters, a macrolitercular type (MR type) having large pore diameters, or a macroporous type (also called a porous type or a hyperporous type) having large macropore diameters.

[0015] [Separation Process] The separation process separates the strongly acidic cation exchange resin and the strongly basic anion exchange resin contained in the used non-regenerated mixed-bed ion exchange resin used in purifying the treated water. Known methods can be appropriately selected and used to separate the strongly acidic cation exchange resin and the strongly basic anion exchange resin. Examples of separation methods include a method using a surface treatment agent or a method of converting the ion exchange resin's ionic form to a salt form (see Patent Document 3). As mentioned above, the present invention is based on the premise that one of the cation exchange resin and the anion exchange resin contains a portion of the other resin (a different resin). If a large amount of the different resin is present in each ion exchange resin after separation, the different resin may exchange with counterions of the regenerant in the regeneration process described below, potentially affecting the purity of the liquid to be purified when the regenerated ion exchange resin is reused. Therefore, it is preferable that the proportion of the different resin contained in each ion exchange resin obtained after the separation process is as low as possible. Specifically, the proportion of strongly basic anion exchange resins mixed in the strongly acidic cation exchange resin (i.e., the strongly acidic cation exchange resin derived from the used non-regenerated mixed-bed ion exchange resin) obtained after the separation step (foreign resin contamination rate) is preferably greater than 0% by volume and less than 5% by volume, more preferably less than 1% by volume, and even more preferably less than 0.1% by volume, relative to 100% by volume of the total ion exchange resins (the total volume of the strongly acidic cation exchange resin and the strongly basic anion exchange resin). Similarly, the proportion of strongly acidic cation exchange resins mixed in the strongly basic anion exchange resin (i.e., the strongly basic anion exchange resin derived from the used non-regenerated mixed-bed ion exchange resin) obtained after the separation step (foreign resin contamination rate) is preferably greater than 0% by volume and less than 5% by volume, more preferably less than 1% by volume, and even more preferably less than 0.1% by volume, relative to 100% by volume of the total ion exchange resins (the total volume of the strongly acidic cation exchange resin and the strongly basic anion exchange resin).

[0016] [Regeneration Step] The regeneration step is a step of regenerating the strongly acidic cation exchange resin and the strongly basic anion exchange resin derived from the used non-regenerated mixed bed ion exchange resin separated in the separation step. In the regeneration step, each ion exchange resin is regenerated using a known method. While the regeneration method for the strongly acidic cation exchange resin is not particularly limited, hydrochloric acid is typically used as the regenerant. Furthermore, while the regeneration method for the strongly basic anion exchange resin is not particularly limited, sodium hydroxide is typically used as the regenerant. Various conditions in the regeneration step can also be appropriately selected from known methods. By performing the regeneration step, the strongly acidic cation exchange resin derived from the used non-regenerated mixed bed ion exchange resin (including contaminated strongly basic anion exchange resin) is regenerated into the H-form strongly acidic cation exchange resin. Furthermore, the strongly basic anion exchange resin derived from the used non-regenerated mixed bed ion exchange resin (including contaminated strongly acidic cation exchange resin) is regenerated into the OH-form strongly basic anion exchange resin. As described above, in this regeneration step, for example, some of the ion exchange groups of the strongly basic anion exchange resin mixed in the strongly acidic cation exchange resin are converted to counter ions (e.g., Cl) contained in the regenerant. － ions) and is converted to the Cl form. － When the regenerated strongly acidic cation exchange resin (including the contaminated strongly basic anion exchange resin) is reused for purifying a liquid to be purified, the ions may affect the purity of the liquid to be purified.

[0017] [Recycling Process] In the recycling process, strongly acidic cation exchange resins or strongly basic anion exchange resins derived from used non-regenerated mixed-bed ion exchange resins are reused as strongly acidic cation exchange resins or strongly basic anion exchange resins in the first stage of the multi-bed system. On the other hand, as the strongly basic anion exchange resins or strongly acidic cation exchange resins in the second stage of the multi-bed system, the strongly acidic cation exchange resins or strongly basic anion exchange resins derived from used non-regenerated mixed-bed ion exchange resins according to the present invention are not used, but new strongly basic anion exchange resins or strongly acidic cation exchange resins are used. Here, the "used" strongly acidic cation exchange resins or strongly basic anion exchange resins derived from recycled non-regenerated mixed-bed ion exchange resins that have already been used to purify the treated liquid are preferably those that have undergone the separation and regeneration processes. As described above, the resins are preferably those that have undergone the separation and regeneration processes. Furthermore, "new" strongly basic anion exchange resin or strongly acidic cation exchange resin refers to an unused anion exchange resin or strongly acidic cation exchange resin that has not yet been used to purify a liquid to be treated and is free of any other resin contamination. In other words, in this recycling step, the ion exchange resin derived from a used non-regenerated mixed-bed ion exchange resin is reused for purifying the liquid to be purified. When the method for recycling a non-regenerated mixed-bed ion exchange resin according to the present invention includes the regeneration step, "strongly acidic cation exchange resin or strongly basic anion exchange resin derived from a used non-regenerated mixed-bed ion exchange resin" refers to the regenerated strongly acidic cation exchange resin or strongly basic anion exchange resin obtained through the regeneration step.

[0018] (Multiple-Bed System) The multiple-bed system is not limited as long as it has a front and rear stage, i.e., two or more resin towers (including mixed towers). Specifically, the multiple-bed system is a multiple-bed system having a front stage containing at least a strongly acidic cation exchange resin and a rear stage containing at least a strongly basic anion exchange resin, or a multiple-bed system having a front stage containing at least a strongly basic anion exchange resin and a rear stage containing at least a strongly acidic cation exchange resin. Hereinafter, specific examples of the multiple-bed system according to the present invention will be described with reference to Figs. 2 and 3.

[0019] (Reusing a Strongly Acidic Cation Exchange Resin Derived from a Used Non-Regenerated Mixed-Bed Ion Exchange Resin) First, we will explain the case where a strongly acidic cation exchange resin derived from a used non-regenerated mixed-bed ion exchange resin is reused in a multi-bed system having a front stage containing at least a strongly acidic cation exchange resin and a rear stage containing at least a strongly basic anion exchange resin. In this case, for example, as shown in Figures 2(a) to 2(g), a multi-bed system having a resin tower packed with a strongly acidic cation exchange resin (SACER) in the front stage can be exemplified. Figure 2(a) shows a multi-bed system having a resin tower packed with SACER in the front stage and a resin tower packed with a strongly basic anion exchange resin (SBAER) in the rear stage. As shown in Figure 2(b), the front and rear stages may be mixed towers. The second-stage strongly basic anion exchange resin may be a strongly basic anion exchange resin contained in a non-regenerative mixed-bed ion exchange resin (CP) or a regenerative mixed-bed ion exchange resin (mix bed) (FIGS. 2(c), (d), and (g)). The first-stage resin tower packed with a strongly acidic cation exchange resin may have a resin tower packed with an SBAER or a weakly acidic cation exchange resin (WACER) in the first stage (FIGS. 2(d) and (e)). The second-stage resin tower packed with a strongly basic anion exchange resin may have a resin tower packed with a weakly basic anion exchange resin (WBAER) in the first stage (FIG. 2(e)). In addition to these resin towers, the multi-bed system may also have a degassing device (DG) such as a decarbonation tower or a decarbonation membrane (FIGS. 2(e) and (f)). Furthermore, the multi-bed systems shown in FIGS. 2(a) to 2(g) can be used in combination. For example, after the recycling step is performed in the multi-bed system shown in Fig. 2(a), the recycling step may be further performed in the multi-bed system shown in Fig. 2(b). Although Fig. 2 shows all liquid passage directions as downward, the liquid passage direction may be upward as long as the liquid is passed through the front stage and then the rear stage in that order.

[0020] In a multiple-bed system such as that shown in Figure 2, the SACER in the first stage, preferably only the SACER in the first stage, is a strongly acidic cation exchange resin derived from the above-mentioned used non-regenerated mixed-bed ion exchange resin. The SBAER, SBAER-containing CP, and Mix Bed in the second stage are new single-bed anion exchange resins or new non-regenerated or regenerated mixed-bed ion exchange resins. While recycled resins can be used in the second stage, provided that they are free of any other resins (other resins) and can be considered equivalent to new single-bed anion exchange resins or new non-regenerated or regenerated mixed-bed ion exchange resins, it is preferable that the resin used in the second stage be new. The SBAER and WACER in the stage immediately preceding the SACER in the first stage, and the WBAER in the stage preceding the SBAER in the second stage, may be new or may be recycled by any method, including the method of the present invention.

[0021] (Reusing a Strongly Basic Anion Exchange Resin Derived from a Used Non-Regenerated Mixed-Bed Ion Exchange Resin) Next, we will explain the case where a strongly basic anion exchange resin derived from a used non-regenerated mixed-bed ion exchange resin is reused in a multi-bed system having a front stage containing at least a strongly basic anion exchange resin and a rear stage containing at least a strongly acidic cation exchange resin. In this case, for example, as shown in Figures 3(a) to 3(g), a multi-bed system having a resin tower packed with a strongly basic anion exchange resin (SBAER) in the front stage can be exemplified. Figure 3(a) shows a multi-bed system having a resin tower packed with SBAER in the front stage and a resin tower packed with a strongly acidic cation exchange resin (SACER) in the rear stage. As shown in Figure 3(b), the front and rear stages may be mixed towers. The second-stage strongly acidic cation exchange resin may be a strongly acidic cation exchange resin contained in a non-regenerated mixed bed ion exchange resin (CP) or a regenerated mixed bed ion exchange resin (Mix Bed) (FIGS. 3(c), (d), and (g)). The first-stage resin tower packed with a strongly basic anion exchange resin may have a second-stage resin tower packed with one or more resins selected from SACER, weakly acidic cation exchange resin (WACER), and weakly basic anion exchange resin (WBAER) (FIGS. 3(d) to (f)). The second-stage resin tower packed with a strongly acidic cation exchange resin may have a second-stage resin tower packed with an SBAER (second stage) in the first stage, for example, SACER (first stage) - SBAER (first stage) - SBAER (second stage) - SACER (second stage) (not shown). In addition to these resin towers, the multi-bed system may also have a degassing device (DG) such as a decarbonation tower or a decarbonation membrane (FIGS. 3(e) and (f)). Furthermore, a plurality of the multi-bed systems shown in FIGS. 3(a) to (g) can also be used in combination. For example, after a recycling step is performed in the multi-bed system shown in FIG. 3(a), a recycling step may be performed in the multi-bed system shown in FIG. 3(b). Although all liquid passage directions are shown downward in FIG. 3, the liquid passage direction may also be upward as long as the liquid is passed through the front stage and then the rear stage in that order.

[0022] In a multiple-bed system such as that shown in Figure 3, the SBAER contained in the first stage is a strong basic anion exchange resin derived from the above-mentioned used non-regenerated mixed-bed ion exchange resin. The SACER, SACER-containing CP, and Mix Bed contained in the second stage are new single-bed cation exchange resins or new non-regenerated or regenerated mixed-bed ion exchange resins. While recycled resins can be used in the second stage, provided that they are free of any other resins (other resins) and can be considered equivalent to new single-bed cation exchange resins or new non-regenerated or regenerated mixed-bed ion exchange resins, it is preferable that the resins used in the second stage are new. The SACER, WACER, and WBAER in the stage immediately preceding the SBAER contained in the first stage, as well as the SBAER in the stage preceding the SACER contained in the second stage, may be new or may be recycled by any method, including the method of the present invention.

[0023] As described above, examples of the upstream and downstream stages of a multi-bed system include a configuration having separate anion exchange resin towers (upper or lower) and cation exchange resin towers (lower or upper) or a configuration in which a single ion exchange resin tower is divided into a layer (e.g., a lower layer) that first comes into contact with the water to be treated when it is passed through, and a layer (e.g., an upper layer) that second comes into contact with the water to be treated, and these layers are filled with cation exchange resin and anion exchange resin, respectively. In the latter case, whether the upper or lower layer in the ion exchange resin tower is the upstream stage will depend on the direction of flow of the water to be treated. In addition to the upstream and lower stages, the multi-bed system may also have other components necessary for purifying the water to be treated. Other configurations include a degassing device such as the decarbonation tower or decarbonation membrane. When the ion exchange resin used in the first stage is the strongly acidic cation exchange resin (recycled product) according to the present invention, a new strongly basic anion exchange resin is used in the second stage, and when the ion exchange resin used in the first stage is the strongly basic anion exchange resin (recycled product) according to the present invention, a new strongly acidic cation exchange resin is used in the second stage. Of course, the strongly acidic cation exchange resin and the strongly basic anion exchange resin according to the present invention may be used in the first stage of different multiple-bed systems.

[0024] More specific examples of multi-bed systems include the following: a 2B3T-type pure water production system having a configuration including a cation exchange resin tower (front stage)-decarbonation tower or decarbonation membrane-anion exchange resin tower (rear stage); a pure water production system having an anion exchange resin layer (front stage)-cation exchange resin layer (rear stage) arranged in this order; and a pure water production system having a cation exchange resin layer (front stage)-anion exchange resin layer (rear stage) arranged in this order. Each system will be described below.

[0025] 1. 2B3T type pure water production system In the 2B3T type pure water production system, first, the water to be treated is passed through a cation exchange resin tower (front stage) filled with H-type strongly acidic cation exchange resin, and the H-type of the strongly acidic cation exchange resin is removed. ＋ However, Na in the treated water ＋ , Ca ＋ and Mg ＋ etc., and dissociates in the water to be treated. ＋ The water to be treated becomes acidic due to the influence of the following. ３ － But HCO ３ － +H ＋ →H ２ CO ３ →H ２ O+CO ２ By blowing air into this stage, the carbonic acid components are removed from the water to be treated. As a result, the load on the anion exchange resin used in the latter stage is reduced, and the amount of anion exchange resin used can be reduced. Finally, in the anion exchange resin tower (later stage) filled with a strongly basic anion exchange resin, Cl is removed. － and SO ４ ２－ As a result, pure water is obtained at the outlet of the anion exchange resin tower.

[0026] In one embodiment of the present invention, a strongly acidic cation exchange resin derived from a used non-regenerated mixed-bed ion exchange resin is reused in the cation exchange resin tower (first stage) of a 2B3T pure water production system. The recycled resin according to the present invention is not used in the anion exchange resin tower (second stage), but rather, a normal single-bed anion exchange resin (i.e., one not contaminated with cation exchange resin) is used. The single-bed anion exchange resin used in the second stage is a new single-bed anion exchange resin. While the single-bed anion exchange resin used in the second stage may be a recycled product, it is preferably new, provided that it is not contaminated with any cation exchange resin and can be considered the same as a new product. Known decarbonation towers and decarbonation membranes can be used.

[0027] 2. Pure Water Production System (Anion Exchange Resin Layer - Cation Exchange Resin Layer) In one embodiment of the present invention, a pure water production system is configured with an anion exchange resin layer (front layer) and a cation exchange resin layer (rear layer) arranged in this order, and a strongly basic anion exchange resin derived from a used non-regenerated mixed-bed ion exchange resin is reused in the anion exchange resin layer (front layer). The recycled resin according to the present invention is not used in the cation exchange resin layer (rear layer), but rather, a normal single-bed cation exchange resin (i.e., one not contaminated with anion exchange resin) is used. The single-bed cation exchange resin used in the rear layer is a new single-bed cation exchange resin. While the single-bed cation exchange resin used in the rear layer may be a recycled product, it is preferably new, provided that it is not contaminated with any anion exchange resin and can be considered the same as a new product. As described above, the anion exchange resin layer and the cation exchange resin layer may be provided in separate ion exchange resin towers, or may be provided as upper and lower layers within a single ion exchange resin tower. In the latter case, the anion exchange resin layer is configured so that the layer that first comes into contact with the water to be treated when the water to be treated is passed through the anion exchange resin layer.

[0028] 3. Pure Water Production System (Cation Exchange Resin Layer - Anion Exchange Resin Layer) In one embodiment of the present invention, a pure water production system is configured with a cation exchange resin layer (front layer) and anion exchange resin layer (rear layer) arranged in this order, and a strongly acidic cation exchange resin derived from a used non-regenerated mixed-bed ion exchange resin is reused in the cation exchange resin layer (front layer). In the anion exchange resin layer (rear layer), a recycled resin according to the present invention is not used, and instead, a normal single-bed anion exchange resin (i.e., one not contaminated with cation exchange resin) is used. The single-bed anion exchange resin used in the rear layer is a new single-bed anion exchange resin. While the single-bed anion exchange resin used in the rear layer may be a recycled product, it is preferably new, provided that it is not contaminated with any cation exchange resin and can be considered the same as a new product. As described above, the cation exchange resin layer and the anion exchange resin layer may be provided in separate ion exchange resin towers, or may be provided as upper and lower layers within a single ion exchange resin tower. In the latter case, the cation exchange resin layer is configured to be the first layer to come into contact with the water to be treated when the water is passed through the cation exchange resin layer.

[0029] As described above, the recycling method of the present invention allows the strongly acidic cation exchange resin and the strongly basic anion exchange resin derived from used non-regenerated mixed-bed ion exchange resin to be recycled in the upstream stage of a multi-bed system. As shown in the examples, the present invention can significantly improve the initial quality of treated water even when recycled non-regenerated mixed-bed ion exchange resin is used. Furthermore, the strongly acidic cation exchange resin and the strongly basic anion exchange resin recycled in the multi-bed system can be reused after undergoing the above-mentioned regeneration process.

[0030] <Multiple-Bed System> The multiple-bed system of the present invention is a multiple-bed system in which the strongly acidic cation exchange resin and the strongly basic anion exchange resin derived from used non-regenerated mixed-bed ion exchange resin are reused in the method for recycling non-regenerated mixed-bed ion exchange resins according to the present invention. That is, the multiple-bed system of the present invention has an upstream stage containing at least a strongly acidic cation exchange resin and a downstream stage containing at least a strongly basic anion exchange resin, or has an upstream stage containing at least a strongly basic anion exchange resin and a downstream stage containing at least a strongly acidic cation exchange resin. In the multiple-bed system of the present invention, the strongly acidic cation exchange resin or the strongly basic anion exchange resin derived from used non-regenerated mixed-bed ion exchange resin is placed in the upstream stage, and new strongly basic anion exchange resin or the strongly acidic cation exchange resin is placed in the downstream stage.

[0031] The term "strongly acidic cation exchange resin derived from a used non-regenerated mixed-bed ion exchange resin used in the upstream of a multi-bed system" refers to a strongly acidic cation exchange resin derived from a recycled non-regenerated mixed-bed ion exchange resin that has already been used to purify the water to be treated. The resin is preferably a strongly acidic cation exchange resin obtained by separating the strongly acidic cation exchange resin and the strongly basic anion exchange resin contained in a used non-regenerated mixed-bed ion exchange resin that has already been used to purify the water to be treated and then regenerating the separated strongly acidic cation exchange resin. Furthermore, the term "strongly basic anion exchange resin derived from a used non-regenerated mixed-bed ion exchange resin used in the upstream of a multi-bed system" refers to a strongly basic anion exchange resin derived from a recycled non-regenerated mixed-bed ion exchange resin that has already been used to purify the water to be treated. The resin is preferably a strongly acidic cation exchange resin obtained by separating the strongly acidic cation exchange resin and the strongly basic anion exchange resin contained in a used non-regenerated mixed-bed ion exchange resin that has already been used to purify the water to be treated and then regenerating the separated strongly basic anion exchange resin. For the method for separating the strongly acidic cation exchange resin and the strongly basic anion exchange resin contained in used non-regenerated mixed bed ion exchange resin and the method for regenerating the separated strongly acidic cation exchange resin or the strongly basic anion exchange resin, reference can be made to the explanations of the separation step and the regeneration step in the method for reusing non-regenerated mixed bed ion exchange resin according to the present invention.

[0032] The term "new strong basic anion exchange resin" used in the downstream of a multi-bed system refers to a new, unused, and uncontaminated strong basic anion exchange resin that has not yet been used to purify treated water. Such a strong basic anion exchange resin can be a new single-bed anion exchange resin or a new non-regenerated or regenerated mixed-bed ion exchange resin. While recycled resins can be used in the downstream, provided that they are completely free of contaminating resins and can be considered equivalent to new single-bed anion exchange resins, it is preferable that the strong basic anion exchange resin used in the downstream is new. Similarly, the term "new strong acid cation exchange resin" used in the downstream of a multi-bed system refers to a new, unused, and uncontaminated strong acid cation exchange resin that has not yet been used to purify treated water. Such a strong acid cation exchange resin can be a new single-bed cation exchange resin or a new non-regenerated or regenerated mixed-bed ion exchange resin. It is also possible to use a recycled product in the latter stage, provided that it is free from any other resin contamination and can be considered equivalent to a new single-bed cation exchange resin, but it is preferable that the strongly acidic cation exchange resin used in the latter stage is new.

[0033] The proportion of strongly basic anion exchange resins mixed in the strongly acidic cation exchange resins derived from used non-regenerated mixed-bed ion exchange resins obtained by separating the strongly acidic cation exchange resins and strongly basic anion exchange resins contained in used non-regenerated mixed-bed ion exchange resins (foreign resin contamination rate) is preferably more than 0% by volume and not more than 5% by volume, more preferably not more than 1% by volume, and even more preferably not more than 0.1% by volume, relative to 100% by volume of the total volume of the ion exchange resins (total volume of the strongly acidic cation exchange resins and the strongly basic anion exchange resins). Similarly, the proportion of strongly acidic cation exchange resins mixed in the strongly basic anion exchange resins derived from used non-regenerated mixed-bed ion exchange resins obtained by separating the strongly acidic cation exchange resins and strongly basic anion exchange resins contained in used non-regenerated mixed-bed ion exchange resins (foreign resin contamination rate) is preferably more than 0% by volume and not more than 5% by volume, more preferably not more than 1% by volume, and even more preferably not more than 0.1% by volume, relative to 100% by volume of the total volume of the ion exchange resins (total volume of strongly acidic cation exchange resins and strongly basic anion exchange resins).

[0034] Examples of the configuration of the multi-bed system include a 2B3T-type pure water production system having a configuration including a cation exchange resin tower-decarbonation tower or a decarbonation membrane-anion exchange resin tower, and a pure water production system having a configuration in which an anion exchange resin layer-cation exchange resin layer or a cation exchange resin layer-anion exchange resin layer are arranged in that order. For details regarding the multi-bed system according to the present invention, the respective descriptions regarding the method for reusing a non-regenerative mixed-bed ion exchange resin according to the present invention can be applied as appropriate.

[0035] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0036] [Examples 1 and 2 and Comparative Examples 1 and 2] (1. Resins Used) The following ion exchange resins were used as the H-type strongly acidic cation exchange resin (hereinafter abbreviated as "cation") and the OH-type strongly basic anion exchange resin (hereinafter abbreviated as "anion"): Cation: AMBERLITE HPR1500 H (trade name, manufactured by DuPont de Nemours) Anion: AMBERLITE HPR4200 OH (trade name, manufactured by DuPont de Nemours)

[0037] (2. Combinations) The above ion exchange resins were used in a multi-bed system having an upstream and downstream stages in the combinations shown in Table 1 below. The resin configuration, in which anions and cations are mixed, simulates ion exchange resins derived from non-regenerated mixed-bed ion exchange resins containing other resins, which are obtained by separating used non-regenerated mixed-bed ion exchange resins into cation exchange resins and anion exchange resins in a separation process. In the following examples and comparative examples, the foreign resin contamination rate of the recycled anion resins was 5% by volume, and the foreign resin contamination rate of the recycled cation resins was 5% by volume.

[0038]

[0039] (3. Regeneration Step) The resins shown in Table 1 were weighed out in the amounts shown, mixed appropriately, and then packed into a cation exchange resin tower (abbreviated as "cation tower") and an anion exchange resin tower (abbreviated as "anion tower"). The cation tower and anion tower were then regenerated under the following conditions. <Cation Tower Regeneration Conditions> 875 g of 4% by mass hydrochloric acid was passed through the resin packed in the cation tower at SV = 4, followed by extrusion and washing with ultrapure water at SV = 10 and BV = 10. <Anion Tower Regeneration Conditions> 1500 g of 4% by mass aqueous sodium hydroxide solution was passed through the resin packed in the anion tower at SV = 4, followed by extrusion and washing with ultrapure water at SV = 10 and BV = 10.

[0040] (4. Reuse Step) Ultrapure water was passed through the resin that had undergone the regeneration step, from the front to the rear, at SV = 50, and the resistivity of the treated water obtained from the outlet of the rear ion exchange resin tower was measured using a resistivity meter (trade name: Foxboro 871CR, manufactured by T&C Technical Co., Ltd.) after the elapse of each time period shown in Table 2. The results are shown in Table 2.

[0041]

[0042] As shown in Table 2, compared to the comparative example in which recycled resin containing foreign resins was used in both the front and back stages, the example in which recycled resin containing foreign resins was used only in the front stage and new resin was used in the back stage showed a significant improvement in the rise in treated water quality. Specifically, in the comparative example, even after 5 hours, the resistivity was about 60% of that after 20 hours, while in the example, the resistivity after 5 hours was already equivalent to that after 20 hours. Note that the above examples show examples in which the foreign resin contamination rate for each ion exchange resin was 5% by volume, but it is expected that effects equivalent to or better than those of the above examples will be obtained if the foreign resin contamination rate is even lower.

[0043] The present invention includes the following configurations. [Configuration 1] A multiple-bed system having an upstream section containing a strongly acidic cation exchange resin and a downstream section containing a strongly basic anion exchange resin, or an upstream section containing a strongly basic anion exchange resin and a downstream section containing a strongly acidic cation exchange resin, wherein a strongly acidic cation exchange resin or a strongly basic anion exchange resin derived from a used non-regenerated mixed-bed ion exchange resin is placed in the upstream section, and a new strongly basic anion exchange resin or a strongly acidic cation exchange resin is placed in the downstream section. [Configuration 2] The multiple-bed system according to Configuration 1, wherein the volume ratio of the strongly acidic cation exchange resin to the strongly basic anion exchange resin contained in the non-regenerated mixed-bed ion exchange resin is within the range of 1:0.5 to 4.0. [Configuration 3] The multi-bed system according to Configuration 1 or 2, wherein the proportion of strongly basic anion exchange resin in the strongly acidic cation exchange resin derived from the used non-regenerated mixed bed ion exchange resin ((volume of strongly basic anion exchange resin / total volume of strongly acidic cation exchange resin and strongly basic anion exchange resin) x 100) is 5% by volume or less, and the proportion of strongly acidic cation exchange resin in the strongly basic anion exchange resin derived from the used non-regenerated mixed bed ion exchange resin ((volume of strongly acidic cation exchange resin / total volume of strongly basic anion exchange resin and strongly acidic cation exchange resin) x 100) is 5% by volume or less. [Configuration 4] The multi-bed system according to any of Configurations 1 to 3, which is a 2B3T-type pure water production apparatus having a configuration including a cation exchange resin tower-decarbonation tower or a decarbonation membrane-anion exchange resin tower. [Configuration 5] The multi-bed system according to any one of Configurations 1 to 3, which is a pure water production apparatus having a configuration in which an anion exchange resin layer - a cation exchange resin layer, or a cation exchange resin layer - an anion exchange resin layer are arranged in this order.[Configuration 6] A method for reusing used non-regenerated mixed bed ion exchange resins in a multi-bed system having an upstream section containing a strongly acidic cation exchange resin and a downstream section containing a strongly basic anion exchange resin, or in a multi-bed system having an upstream section containing a strongly basic anion exchange resin and a downstream section containing a strongly acidic cation exchange resin, the method comprising the steps of: using the strong acid cation exchange resin or strong basic anion exchange resin derived from the used non-regenerated mixed bed ion exchange resin as the strong acid cation exchange resin or strong basic anion exchange resin contained in the upstream section of the multi-bed system; and using new strong basic anion exchange resin or strong acid cation exchange resin as the strong basic anion exchange resin or strong acid cation exchange resin contained in the downstream section of the multi-bed system. [Configuration 7] The method for recycling a non-regenerated mixed bed ion exchange resin according to Configuration 6, wherein the volume ratio of the strongly acidic cation exchange resin to the strongly basic anion exchange resin contained in the non-regenerated mixed bed ion exchange resin is within the range of 1:0.5 to 4.0. [Configuration 8] The method for recycling a non-regenerated mixed bed ion exchange resin according to Configuration 6 or 7, further comprising, before the recycling step, a separation step of separating the strongly acidic cation exchange resin and the strongly basic anion exchange resin contained in the used non-regenerated mixed bed ion exchange resin, and a regeneration step of regenerating each of the separated strongly acidic cation exchange resin and the strongly basic anion exchange resin. [Configuration 9] The method for reusing a non-regenerated mixed bed ion exchange resin according to Configuration 8, wherein the proportion of strongly basic anion exchange resin in the strongly acidic cation exchange resin after separation obtained after the separation step ((volume of strongly basic anion exchange resin / total volume of strongly acidic cation exchange resin and strongly basic anion exchange resin) × 100) is 5 vol% or less, and the proportion of strongly acidic cation exchange resin in the strongly acidic anion exchange resin after separation obtained after the separation step ((volume of strongly acidic cation exchange resin / total volume of strongly basic anion exchange resin and strongly acidic cation exchange resin) × 100) is 5 vol% or less.[Configuration 10] The method for reusing a non-regenerative mixed bed ion exchange resin according to any one of Configurations 6 to 9, wherein the double-bed system is a 2B3T-type pure water production apparatus having a configuration including a cation exchange resin tower-decarbonation tower or a decarbonation membrane-anion exchange resin tower. [Configuration 11] The method for reusing a non-regenerative mixed bed ion exchange resin according to any one of Configurations 6 to 9, wherein the double-bed system is a pure water production apparatus having a configuration in which an anion exchange resin layer-cation exchange resin layer, or a cation exchange resin layer-anion exchange resin layer are arranged in this order.

[0044] While certain preferred embodiments of the present invention have been shown and described in detail above, it should be understood that the present invention is not limited to the above-described embodiments, but that various changes and modifications are possible without departing from the spirit or scope of the appended claims.

[0045] This application claims priority based on Japanese Patent Application No. 2024-059612, filed April 2, 2024, the entire contents of which are incorporated herein by reference.

[0046] A: Anion exchange resin C: Cation exchange resin SACER: Strongly acidic cation exchange resin WACER: Weakly acidic cation exchange resin SBAER: Strongly basic anion exchange resin WBAER: Weakly basic anion exchange resin CP: Non-regenerated mixed bed ion exchange resin Mix Bed: Regenerated mixed bed ion exchange resin DG: Degasser

Claims

1. A multi-bed system having an upstream stage containing a strongly acidic cation exchange resin and a downstream stage containing a strongly basic anion exchange resin, or having an upstream stage containing a strongly basic anion exchange resin and a downstream stage containing a strongly acidic cation exchange resin, characterized in that the strongly acidic cation exchange resin or the strongly basic anion exchange resin derived from used non-regenerated mixed bed ion exchange resin is placed in the upstream stage, and new strongly basic anion exchange resin or the strongly acidic cation exchange resin is placed in the downstream stage.

2. The multi-bed system according to claim 1, wherein the volume ratio of the strongly acidic cation exchange resin to the strongly basic anion exchange resin contained in the non-regenerative mixed bed ion exchange resin is within the range of 1:0.5 to 4.

0.

3. The multi-bed system described in claim 1, wherein the proportion of strongly basic anion exchange resin in the strongly acidic cation exchange resin derived from the used non-regenerated mixed bed ion exchange resin ((volume of strongly basic anion exchange resin / total volume of strongly acidic cation exchange resin and strongly basic anion exchange resin) x 100) is 5 volume % or less, and the proportion of strongly acidic cation exchange resin in the strongly basic anion exchange resin derived from the used non-regenerated mixed bed ion exchange resin ((volume of strongly acidic cation exchange resin / total volume of strongly basic anion exchange resin and strongly acidic cation exchange resin) x 100) is 5 volume % or less.

4. The multi-bed system according to any one of claims 1 to 3, which is a 2B3T type pure water production system having a configuration including a cation exchange resin tower-decarbonation tower or a decarbonation membrane-anion exchange resin tower.

5. The multi-bed system according to any one of claims 1 to 3, which is a pure water production system having a configuration in which an anion exchange resin layer - a cation exchange resin layer, or a cation exchange resin layer - an anion exchange resin layer are arranged in that order.

6. A method for reusing used non-regenerated mixed bed ion exchange resins in a multiple bed system having an upstream section containing a strongly acidic cation exchange resin and a downstream section containing a strongly basic anion exchange resin, or in a multiple bed system having an upstream section containing a strongly basic anion exchange resin and a downstream section containing a strongly acidic cation exchange resin, the method comprising the steps of: using the strong acid cation exchange resin or strong basic anion exchange resin derived from the used non-regenerated mixed bed ion exchange resin as the strong acid cation exchange resin or strong basic anion exchange resin contained in the upstream section of the multiple bed system; and using new strong basic anion exchange resin or strong acid cation exchange resin as the strong basic anion exchange resin or strong acid cation exchange resin contained in the downstream section of the multiple bed system.

7. A method for recycling a non-regenerated mixed bed ion exchange resin according to claim 6, wherein the volume ratio of the strongly acidic cation exchange resin to the strongly basic anion exchange resin contained in the non-regenerated mixed bed ion exchange resin is within the range of 1:0.5 to 4.

0.

8. The method for recycling a non-regenerated mixed bed ion exchange resin according to claim 6, further comprising, before the recycling step, a separation step of separating the strong acid cation exchange resin and the strong basic anion exchange resin contained in the used non-regenerated mixed bed ion exchange resin, and a regeneration step of regenerating each of the separated strong acid cation exchange resin and strong basic anion exchange resin.

9. A method for reusing a non-regenerated mixed-bed ion exchange resin according to claim 8, wherein the proportion of strongly basic anion exchange resin mixed in the separated strongly acidic cation exchange resin obtained after the separation step ((volume of strongly basic anion exchange resin / total volume of strongly acidic cation exchange resin and strongly basic anion exchange resin) x 100) is 5 vol% or less, and the proportion of strongly acidic cation exchange resin mixed in the separated strongly basic anion exchange resin obtained after the separation step ((volume of strongly acidic cation exchange resin / total volume of strongly basic anion exchange resin and strongly acidic cation exchange resin) x 100) is 5 vol% or less.

10. A method for reusing non-regenerative mixed-bed ion exchange resins according to any one of claims 6 to 9, wherein the multi-bed system is a 2B3T-type pure water production system having a configuration including a cation exchange resin tower-decarbonation tower or a decarbonation membrane-anion exchange resin tower.

11. The method for reusing non-regenerative mixed-bed ion exchange resins according to any one of claims 6 to 9, wherein the multi-bed system is a pure water production apparatus having a configuration in which an anion exchange resin layer - a cation exchange resin layer, or a cation exchange resin layer - an anion exchange resin layer are arranged in that order.

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