JP2008080190A - Mixed bed ion-exchange resin column - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mixed bed ion-exchange resin column comprising a cation-exchange resin and an anion-exchange resin which are uniform in particle size distribution, while the ion-exchange resin column being capable of performing efficient regeneration and separation. <P>SOLUTION: The mixed bed ion-exchange resin column, which comprises a main cation-exchange resin and a main anion-exchange resin which are both uniform in particle size distribution, contains at least either a sub-cation-exchange resin which is smaller in particle size than the main cation-exchange resin and is uniform in particle size or a sub-anion-exchange resin which is larger in particle size than the main anion-exchange resin and is uniform in particle size distribution. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a mixed bed ion exchange resin tower, and more particularly to a mixed bed ion exchange resin tower capable of efficiently separating a cation exchange resin and an anion exchange resin during regeneration separation of the ion exchange resin.

  Mixed-bed ion exchange resin towers are used to remove or separate impurities in water or solvents in, for example, pure water equipment, condensate desalination equipment at power plants, soft water equipment, food production processes, chemical production processes, etc. Used as a purpose.

  For example, in a condensate demineralization apparatus, a cation exchange resin and an anion exchange resin are mixed in a single column, and the condensed water is passed through the mixed bed ion exchange resin tower, thereby removing impurities in the condensate. In the apparatus to remove, since the quality of treated water is good, a cation resin and an anion resin are used for desalting in a mixed state. When the ion exchange capacity is saturated, regeneration is performed with an acid / alkali agent to restore the ion exchange capacity, and it is repeatedly used for desalting. In this regeneration, it is required to separate the cation resin and the anion resin more completely and regenerate each.

  Especially in the condensate demineralizer of a power plant, the separation of both resins is made more complete, the cationic resin comes into contact with the NaOH solution that is a regenerant of the anionic resin and becomes R-Na form, and the anionic resin is the cationic resin. It is necessary to reduce as much as possible the R-Cl and R2-SO4 forms (which are referred to as "reverse regeneration" for convenience) that come into contact with the HCl or H2SO4 solution. The generation of such a reversely regenerated resin makes the regeneration incomplete, the amount of treated water becomes insufficient, and the quality of the treated water deteriorates. Therefore, it is necessary to prevent reverse regeneration as much as possible.

  In the regeneration operation, acid resin and alkali resin are used to regenerate the cation resin and anion resin, respectively. Therefore, the desalting tower and the regeneration tower are usually configured as completely separate towers so that this regenerant does not mix with the condensate. It is transferred through piping. In the regeneration tower, the resin is separated based on the specific gravity difference and the particle size difference between the cation exchange resin and the anion exchange resin by flowing water upward from the bottom of the tower. A cation exchange resin having a large specific gravity exists in the lower layer part of the resin layer, and an anion exchange resin having a light specific gravity exists in the upper part of the resin layer. The separated resin is regenerated by injecting acid from the bottom of the tower into the cation exchange resin layer and alkali from the top of the tower into the anion exchange resin layer, and discharging it from the intermediate drain pipe installed at the interface between the two resin layers. There is a regeneration system with one tower. In this method, when the resin amount balance between the cation resin and the anion resin deviates, it is difficult to make the upper part of the intermediate drain pipe installed near the boundary surface between the two resins completely anion resin and the lower part completely cationic resin. And because the interface between the cation resin and the anion resin is difficult to keep completely horizontal, the anion resin at the top of the cation resin layer is transferred to another regeneration tower and separated in each regeneration tower. A reproduction method is common. In any case, in an apparatus that mixes a cation resin and an anion resin and uses it for desalting, such as a condensate desalination facility, it is very important to reliably separate the two layers during regeneration.

  As described above, the separation of the cation exchange resin and the anion exchange resin is generally performed by flowing water from the bottom to the top of the mixed cation exchange resin and the anion exchange resin, and the difference in the terminal velocity between the cation resin and the anion resin. Are used to separate and form layers of only the respective resins. The particle size of a general ion exchange resin is not single but has a width, which is an abundance ratio like a Gaussian frequency curve. For this reason, when water backwash separation is performed, among the lower cationic resin layers, a cationic resin having a relatively large particle size gathers in the lowermost layer, and a cationic resin having a relatively small particle size gathers on the upper portion of the cationic resin layer. It will be. The same applies to the anion resin layer.

  In particular, anion resins with a large particle size and cation resins with a particularly small particle size are difficult to separate from the cation resin layer and the anion resin layer, respectively. Therefore, the average particle diameter of cation exchange resin is usually 0.6 to 0.75 mm (maximum diameter 1.18 mm, minimum diameter 0.5 mm), and the average particle diameter of anion exchange resin 0.5 to 0.65 mm (maximum diameter). 1.18 mm, minimum diameter 0.42 mm) and a particle size distribution rule are used.

  Conventionally, in such a mixed bed type ion exchange resin tower, a cation exchange resin or anion exchange resin having a wide Gaussian distribution (normal distribution) as described above has been used as the resin particle diameter. Narrow and uniform particle size resins have been used. There are various reasons why such a uniform particle size resin is adopted, that is, good cleanability after resin regeneration, high exchange capacity in production, low water flow differential pressure, uniform reactivity and resin. The utilization rate is high. However, when a uniform particle size resin is used, the flow state by backwashing of the ion exchange resin is not necessarily good compared to a resin having a conventional Gaussian particle size distribution, and the actual resin separation performance is worsened. The tendency to do was recognized. This is because when a mixed bed layer composed of a cation exchange resin and an anion exchange resin having a uniform particle size is separated by water back-washing using a difference in sedimentation speed, the conventional Gaussian distribution due to the uniformity of the particle size. Compared with a resin having a cation (hereinafter referred to as a conventional resin), the cation and anion layers flow violently, and the resin of the mating layer is drawn into each layer, and the drawn resin is resin together with the mating resin. It is estimated that the phenomenon of large flow in the bed occurs.

  The resin once drawn in this way is not easily separated again by this flow, and it takes a long time to return to the original layer from the resin interface again. Therefore, in addition to the cation exchange resin and the anion exchange resin having a uniform particle size distribution, an intermediate layer is formed at the time of development by backwashing with water, and the average particle size is smaller than the particle size of the cation exchange resin and wide. Separation can be improved by adding at least one of a cation exchange resin having a particle size distribution and an anion exchange resin having an average particle size larger than that of the anion exchange resin and a wide particle size distribution. It has been proposed (see, for example, Patent Document 1).

In addition, when a new ion exchange resin is used, the cation exchange resin and the anion exchange resin tend to be entangled at the beginning of use, and therefore the above-described pulling phenomenon tends to occur remarkably. Furthermore, even a slight fluctuation in the flow rate of the backwash water is greatly affected, and this flow is greatly disturbed, causing the separation layer to be broken and the resin to be drawn deeply. For this reason, a careful operation and a longer separation time than before are required to handle the uniform particle size resin. In addition, a method of improving the separability by adding a resin having an intermediate specific gravity between the cation exchange resin and the anion exchange resin and having no ion exchange ability is also performed. However, since a resin having an intermediate specific gravity and no ion exchange ability is added, the uniformity of the packed bed is disturbed, and the apparatus performance such as ion exchange ability and fine particle removal ability is deteriorated.
JP-A-10-202119 (Claims)

  In view of such circumstances, the present invention provides an ion exchange resin tower having further improved separability in a mixed bed type ion exchange resin tower comprising a cation exchange resin and / or an anion exchange resin having a uniform particle size distribution. Is an issue.

  A first aspect of the present invention for solving the above problems is a mixed bed ion exchange resin tower comprising a main cation exchange resin having a uniform particle size distribution and a main anion exchange resin having a uniform particle size distribution. A secondary cation exchange resin having a particle size smaller than that of the cation exchange resin and a uniform particle size, and a secondary anion exchange resin having a particle size larger than that of the main anion exchange resin and a uniform particle size distribution. It is in a mixed bed type ion exchange resin tower characterized by including at least one of them.

  According to a second aspect of the present invention, in the first aspect, the mixed cation type is characterized in that the particle size of the secondary cation exchange resin is 0.88 to 0.92 times the particle size of the main cation exchange resin. Located in the ion exchange resin tower.

  According to a third aspect of the present invention, in the first or second aspect, the mixed anion exchange resin has a particle size of 1.08 to 1.12 times the particle size of the main anion exchange resin. It is in the type ion exchange resin tower.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the mixed cation is characterized in that the resin amount of the secondary cation exchange resin is 5 to 25% of the main secondary total cation exchange resin amount. It is in the type ion exchange resin tower.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the mixed anion exchange resin amount is 5 to 35% of the main auxiliary total anion exchange resin amount. It is in the type ion exchange resin tower.

  According to the present invention, an intermediate layer is formed in a mixed bed type ion exchange resin tower composed of a main cation exchange resin having a uniform particle size distribution and a main anion exchange resin having a uniform particle size distribution when deployed by backwashing with water, A cation exchange resin having an average particle size smaller than the particle size of the cation exchange resin and a wide particle size distribution, and an average particle size larger than the particle size of the anion exchange resin and a wide particle size distribution Instead of adding at least one of the anion exchange resins having, a secondary cation exchange resin having a uniform particle size smaller than the particle size of the main cation exchange resin, and more than the particle size of the main anion exchange resin Since a mixed bed is formed by adding at least one of the secondary anion exchange resins having a large particle size and a uniform particle size distribution, It is possible to reduce the ratio of anion exchange resin the resin and the cation exchange resin to be mixed respectively to the exchange resin layer and the anion exchange resin layer.

  Hereinafter, the present invention will be described in detail.

  In the present invention, the uniform particle size distribution means that the center particle size of the distribution is ± 0.05 mm and the width of the distribution is within 0.1 mm. The central particle size of the particle size distribution of the main cation exchange resin having a uniform particle size distribution used in a pure water device or a condensate desalination device is 0.60 to 0.70 mm. The cation exchange resin can be displayed as 0.65 mm ± 0.05 mm. Further, the main anion exchange resin having a uniform particle size distribution has a center particle size of 0.50 to 0.60 mm, for example, the resin particle size can be expressed as 0.55 mm ± 0.05 mm. .

  The secondary cation exchange resin having a particle size smaller than that of the main cation exchange resin and having a uniform particle size has a center particle size of 0.55 to 0.63 mm, for example, a uniform particle size distribution. The main cation exchange resin having can be expressed as 0.60 mm ± 0.05 mm. It is preferable to use a secondary cation exchange resin having a central particle size of 0.88 to 0.92 times the central particle size of the particle size distribution of the main cation exchange resin. Further, the secondary cation exchange resin having a particle size smaller than that of the main anion exchange resin and having a uniform particle size has a center particle size of 0.55 to 0.70 mm, for example, a uniform particle size. The main cation exchange resin having a distribution can be expressed as 0.65 mm ± 0.05 mm. It is preferable to use a secondary anion exchange resin having a central particle size of 1.08 to 1.12 times the central particle size of the particle size distribution of the main anion exchange resin. By selecting these particle diameters, when developing layers are separated by backwashing with water, each fluid developing layer, zone, or layer zone is configured for the same resin, and the cation exchange resin layer and the anion exchange resin layer are separated from each other. Separation at the separation interface is improved.

  In the present invention, the ratio of adding the secondary cation exchange resin or secondary anion exchange resin to the mixed bed of uniform particle size resin is 5 to 25% (volume) of the primary secondary secondary cation exchange resin in the case of the secondary cation exchange resin. In the case of a secondary anion exchange resin, it is preferably 5 to 35% (capacity) of the main and secondary total anion exchange resin. With such a resin addition amount, each fluidized bed has little contact during separation of the development layer by backwashing with water. Outside these ranges, the effect of using a uniform particle size resin is reduced, which is not preferable.

  In a general pure water device or a condensate demineralizer, the amount of the cation resin and the amount of the anion resin are used in a volume ratio of about 2: 1 to 1: 2. Therefore, the same applies to the case where a mixed bed is formed by mixing uniform particle size resins.

  When this mixed bed ion exchange resin layer is back-washed with water, all the resins develop and flow uniformly in each resin layer, and the main anion exchange resin layer, the secondary anion exchange resin layer, and the secondary cation exchange resin in the top-down direction. Forming a layer and a main cation exchange resin layer. The in-layer flow rates of the secondary anion exchange resin layer and the secondary cation exchange resin layer have a smaller difference in flow rate than when the main anion exchange resin layer and the main cation exchange resin layer are in contact with each other, and the separation performance is improved. In contrast, when a resin having a conventional Gaussian distribution is used for the secondary anion exchange resin layer and / or the anion exchange resin layer, the difference in flow velocity between the fluidized beds of adjacent resins is large, and the flow turbulence (turbulent flow) is reduced. Occurs and the separation performance is poor.

Hereinafter, the present invention will be described based on examples.
(Examples 1-8, Comparative Examples 1-5)
An ion exchange resin layer was formed by mixing and filling the following resins in a column having an inner diameter of 40 mm and a height of 2000 mm. The cation exchange resin was ammonia type, and the anion exchange resin was OH type.
Example 1
Main cation exchange resin: Gel type cation exchange resin Dowex 650C 685 mL
Uniform particle size 650μm ± 50μm
Secondary cation exchange resin: Cation resin Diaion SK112 sieve (Note) 15mL
Uniform particle size 600μm
Main anion exchange resin: Gel type anion exchange resin Dowex 550A 300mL
Secondary anion exchange resin: Not used (Note) A resin clogged with a sieve having a JIS nominal size of 600 and clogged with a sieve was used.
Example 2
Main cation exchange resin: Gel type cation exchange resin Dowex 650C 665 mL
Uniform particle size 650μm ± 50μm
Secondary cation exchange resin: Cation resin Diaion SK112 sieve 35mL
Uniform particle size 600μm
Main anion exchange resin: Gel type anion exchange resin Dowex 550A 300mL
Secondary anion exchange resin: Non-use Example 3
Main cation exchange resin: Gel type cation exchange resin Dowex 650C 525 mL
Uniform particle size 650μm ± 50μm
Secondary cation exchange resin: cation resin Diaion SK112 sieve 175mL
Uniform particle size 600μm
Main anion exchange resin: Gel type anion exchange resin Dowex 550A 300mL
Secondary anion exchange resin: Non-use Example 4
Main cation exchange resin: Gel type cation exchange resin Dowex 650C 700mL
Uniform particle size 650μm ± 50μm
Secondary cation exchange resin: Not used Main anion exchange resin: Gel anion exchange resin Dowex 550A 288 mL
Secondary anion exchange resin: Anion resin Diaion SA10A sieve (Note) 12mL
Uniform particle size 600μm
(Note) A JIS nominal size 600 sieve was used, and a resin clogged with a sieve was used.
Example 5
Main cation exchange resin: Gel type cation exchange resin Dowex 650C 700mL
Uniform particle size 650μm ± 50μm
Secondary cation exchange resin: Not used Main anion exchange resin: Gel anion exchange resin Dowex 550A 270 mL
Secondary anion exchange resin: Anion resin Diaion SA10A sieving 30mL
Uniform particle size 600μm
Example 6
Main cation exchange resin: Gel type cation exchange resin Dowex 650C 700mL
Uniform particle size 650μm ± 50μm
Secondary cation exchange resin: Not used Main anion exchange resin: Gel type anion exchange resin Dowex 550A 195 mL
Secondary anion exchange resin: Anion resin Diaion SA10A sieving 105mL
Uniform particle size 600μm
Example 7
Main cation exchange resin: Gel type cation exchange resin Dowex 650C 665 mL
Uniform particle size 650μm ± 50μm
Secondary cation exchange resin: Cation resin Diaion SK112 sieve 35mL
Uniform particle size 600μm
Main anion exchange resin: Gel type anion exchange resin Dowex 550A 285 mL
Secondary anion exchange resin: Anion resin Diaion SA10A sieve 15 mL
Uniform particle size 600μm
Example 8
Main cation exchange resin: Gel type cation exchange resin Dowex 650C 665 mL
Uniform particle size 650μm ± 50μm
Secondary cation exchange resin: Cation resin Diaion SK112 sieve 35mL
Uniform particle size 600μm
Main anion exchange resin: Gel type anion exchange resin Dowex 550A 255 mL
Secondary anion exchange resin: Gel type anion resin Diaion SA10A sieving 45 mL
Comparative Example 1
Main cation exchange resin: Porous cation exchange resin PK228G 700mL
Particle size 500-1180μm
Secondary cation exchange resin: Not used Main anion exchange resin: Porous anion exchange resin PA312L 300mL
Particle size 420-1180μm
Secondary anion exchange resin: non-use comparative example 2
Main cation exchange resin: Gel type cation exchange resin Dowex 650C 700mL
Uniform particle size 650μm ± 50μm
Secondary cation exchange resin: Not used Main anion exchange resin: Gel type anion exchange resin Dowex 550A 300 mL
Uniform particle size 550μm ± 50μm
Secondary anion exchange resin: non-use comparative example 3
Main cation exchange resin: Gel type cation exchange resin Dowex 650C 665 mL
Uniform particle size 650μm ± 50μm
Secondary cation exchange resin: Cationic resin Diaion SK112 35mL
Particle size 300-1180μm
Main anion exchange resin: Gel type anion exchange resin Dowex 550A 300mL
Uniform particle size 550μm ± 50μm
Secondary anion exchange resin: non-use comparative example 4
Main cation exchange resin: Gel type cation exchange resin Dowex 650C 700mL
Uniform particle size 650μm ± 50μm
Secondary cation exchange resin: Not used Main anion exchange resin: Gel anion exchange resin Dowex 550A 285 mL
Uniform particle size 550μm ± 50μm
Secondary anion exchange resin: Gel type anion exchange resin Diaion SA10A 15 mL
Particle size 300-1180μm
Comparative Example 5
Main cation exchange resin: Gel type cation exchange resin Dowex 650C 665 mL
Uniform particle size 650μm ± 50μm
Secondary cation exchange resin: Cationic resin Diaion SK112 35mL
Particle size 300-1180μm
Main anion exchange resin: Gel type anion exchange resin Dowex 550A 285 mL
Uniform particle size 550μm ± 50μm
Secondary anion exchange resin: Gel type anion exchange resin Diaion SA10A 15 mL
Particle size 300-1180μm
[experimental method]
Pure water was passed from the bottom to each column mixed and packed with the ion exchange resins of Examples 1 to 8 and Comparative Examples 1 to 5 described above, back-washed with an upward flow of LV 10 m / h for 30 minutes, and subsequently LV 15 m / h Back washed with h for 45 minutes. About 90% of the anion exchange resin was collected from the upper part of the resin layer in the flow developed state by a siphon tube, and about 90% of the cation exchange resin was collected from the lowermost part of the resin layer in the flow developed state by the siphon tube. Next, each collected resin was separated into a cation exchange resin and an anion exchange resin with a 20% strength aqueous sodium hydroxide solution, and each volume was measured with a graduated cylinder. Since the volume of the mixed resin was small, the amount of resin less than 0.5 mL was determined by measuring the particle size and calculating the volume of the sphere from the particle size by microscopic observation.

  The results are shown in Table 1.

表１より、比較例１に示す従来樹脂(ポーラス型ガウス分布カチオン樹脂とアニオン樹脂の組み合わせ)では、アニオン樹脂逆再生：０．０８%、カチオン樹脂逆再生：０．０２%の樹脂分離が実現できている。これに対し、比較例２に示す、均一粒径樹脂の組み合わせでは各々０．８６%、０．４３%の逆再生樹脂が発生し、比較例１よりも樹脂再生状態が悪化してしまう。

From Table 1, the conventional resin shown in Comparative Example 1 (combination of porous Gaussian distribution cation resin and anion resin) achieves resin separation of 0.08% anion resin reverse regeneration and 0.02% cation resin reverse regeneration. is made of. On the other hand, in the combination of the uniform particle size resins shown in Comparative Example 2, 0.86% and 0.43% reversely regenerated resins are generated, respectively, and the resin regeneration state is worse than that in Comparative Example 1.

On the other hand, the reverse regeneration amount in the case where 2.1%, 5.0%, and 25% of a uniform particle size resin having a smaller particle size as a secondary cation resin is mixed is 0.12 for the anionic resin reverse regeneration. %, 0.06%, 0.09%, and the reverse regeneration of the cationic resin were 0.016%, 0.017%, 0.023%, and a separation state comparable to that of Comparative Example 1 was obtained.
In the case of Example 1 in which the mixing amount of the secondary cation resin is reduced to 2.1%, it is judged that the separation improvement effect is slightly insufficient.

  In Example 3 in which the amount of the secondary cation resin was increased to 25%, the separation improvement effect was sufficient, but it was determined that the characteristics of the uniform particle size resin were easily lost. However, it can be said that these separated states can realize a better separated state as compared with Comparative Example 3.

  Similarly, when the 4%, 10%, and 35% of a uniform particle size resin having a larger particle size is mixed as a secondary anion resin, the reverse regeneration amounts are 0.13% and 0.11 for anion resin reverse regeneration, respectively. %, 0.10%, and cationic resin reverse regeneration were 0.049%, 0.024%, and 0.031%, respectively, and a separation state equivalent to that of Comparative Example 1 was obtained.

When the amount of secondary anion resin is 4%, the reverse regeneration of the cationic resin is 0.0049%, and the improvement degree of the separation effect is small, and it can be determined that the amount of secondary anion resin is preferably 5% or more.

Claims (5)

  A mixed bed ion exchange resin tower comprising a main cation exchange resin having a uniform particle size distribution and a main anion exchange resin having a uniform particle size distribution, wherein the particle size is smaller than the main cation exchange resin and uniform. A mixed bed type comprising: a secondary cation exchange resin having a particle size; and at least one of a secondary anion exchange resin having a uniform particle size distribution and a particle size larger than that of the main anion exchange resin Ion exchange resin tower.   The mixed bed ion exchange resin tower according to claim 1, wherein the particle size of the secondary cation exchange resin is 0.88 to 0.92 times the particle size of the main cation exchange resin.   The mixed bed ion exchange resin tower according to claim 1 or 2, wherein the particle size of the secondary anion exchange resin is 1.08 to 1.12 times the particle size of the main anion exchange resin.   The mixed bed type ion exchange resin tower according to any one of claims 1 to 3, wherein the amount of the secondary cation exchange resin is 5 to 25% of the amount of the main and secondary total cation exchange resin. The mixed-bed type ion exchange resin tower according to any one of claims 1 to 4, wherein the amount of the secondary anion exchange resin is 5 to 35% of the amount of the main secondary total anion exchange resin.