JPS6260944B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a method for cleaning a cation exchange resin after treating the resin with an iron removing agent in which a hydrogen sulfite component and a sulfite component coexist in the solution and the pH of the solution is adjusted to 5.5 or higher. It is related to.

Conventionally, condensate treatment equipment filled with salt-type cation exchange resins such as Na type or NH ₄ type has been used to treat condensate from medium-low pressure boilers. The condensate treatment device is installed mainly for the purpose of removing insoluble iron oxide contained in condensate through the overaction of the cation exchange resin layer.

Most of the iron oxide passed through the cation exchange resin layer is removed during regeneration, such as when the cation exchange resin layer is agitated with air or backwashed with water, or when the regenerant is passed through the device. When used for a long period of time, iron oxide is deposited inside or outside of the cation exchange resin particles, resulting in so-called iron contamination. If a cation exchange resin is contaminated with iron in this way, conventionally, a solution of a reducing agent such as hydrosulfite, bisulfite, or sulfite is brought into contact with the cation exchange resin to prevent iron from depositing inside or outside the cation exchange resin particles. Iron removal operations have been carried out by reducing the iron oxide present in the liquid, removing it as soluble iron.However, the present inventors made hydrogen sulfite components and sulfite components coexist in the solution, and the PH of the solution was reduced.
It was found that iron remover with iron removal adjusted to 5.5 or higher has excellent iron removal effect. This iron remover achieves a synergistic iron removal effect due to the synergistic action of the hydrogen sulfite component and the sulfite component, which cannot be obtained with the hydrogen sulfite component alone or the sulfite component alone.However, in order for both components to coexist, it is necessary to add Achieved by mixing and dissolving a bisulfite such as sodium bisulfite or ammonium bisulfite with a sulfite such as sodium sulfite or ammonium sulfite, or by adding an alkali such as caustic soda or aqueous ammonia to a solution of bisulfite. can.

The pH of a solution containing only bisulfite is acidic, and the pH of a solution containing only sulfite is alkaline.
Therefore, a solution in which hydrogen sulfite and sulfite components coexist will be acidic if the hydrogen sulfite component is larger, and alkaline if the sulfite component is larger. When treating a cation exchange resin with such an iron remover, the pH of the solution is adjusted to a range of 5.5 to 7.0 by adjusting the mixing ratio of both components and brought into contact with the cation exchange resin to remove iron. It was found that cleaning after treatment with iron agent takes a long time.

The purpose of the present invention is to effectively clean the cation exchange resin treated with the above-mentioned iron removing agent and to significantly shorten the cleaning time. When cleaning the cation exchange resin after treating it with an iron remover whose pH has been adjusted to 5.5 or higher,
After replacing the iron removing agent in the cation exchange resin layer with extruded water, the cation exchange resin layer is mixed immediately after adding a small amount of acid to the cation exchange resin layer, or
Alternatively, it relates to a method for cleaning a cation exchange resin, which comprises mixing the cation exchange resin layer while adding a small amount of acid to the cation exchange resin layer, and then cleaning the cation exchange resin layer with cleaning water. .

The present invention will be explained in detail below.

In the present invention, when treating a cation exchange resin with the above-mentioned iron removing agent, the cation exchange resin layer is first air agitated or backwashed to remove relatively much of the material attached to the surface of the cation exchange resin particles. Removes easily iron oxide. Next, the cation exchange resin is brought into contact with an iron removing agent in which a hydrogen sulfite component and a sulfite component are made to coexist to adjust the pH of the liquid to 5.5 or higher. In this case, it is possible to simply pass the iron removing agent through the cation exchange resin layer, but it is better to replace the water in the cation exchange resin layer with the iron removing agent and then stir with air, etc. for a more effective iron oxide removal effect. Are better.

After the cation exchange resin and the iron removing agent are brought into sufficient contact, the iron removing agent in the cation exchange resin layer is replaced with extruded water. In conventional iron removal operations, pure water or condensate water to be treated is then used as cleaning water, and a cleaning process is performed in which the cleaning water is flowed through a cation exchange resin layer at a relatively high flow rate of SV10 to 20. As mentioned above, this conventional method requires a long time for cleaning.

In the present invention, after the iron removing agent remaining in the cation exchange resin layer is replaced with extruded water, the following operations are performed. That is, the cation exchange resin layer is mixed immediately after adding a small amount of acid to the cation exchange resin layer, or the cation exchange resin layer is mixed while adding a small amount of acid. As the acid to be added, it is preferable to use a mineral acid with a relatively high concentration of 1N to 2N, such as hydrochloric acid or sulfuric acid.
In some cases, an organic acid with a relatively small molecular weight such as acetic acid may be used. The amount of acid used is generally 1/10 to 1/100 of the ion exchange capacity. In other words, the ion exchange capacity is 1.9eq/R
In that case, it is preferable to use an acid of 0.19 to 0.019 eq/R.

Note that an appropriate amount of acid is used within the range depending on the degree of cleaning properties. However, if too much acid is used, the exchange group becomes H type, which is not preferable, and therefore the ion exchange capacity decreases. It is preferable not to use acids of 1/10 or higher.

Next, when adding the acid to the cation exchange resin layer, it is necessary to disperse the added acid throughout the cation exchange resin layer. For this purpose, the cation exchange resin layer is mixed immediately after adding the acid, or the cation exchange resin layer is mixed while adding the acid. For example, passing an acid through a bed of packed cation exchange resin, or contacting only a portion of a bed of packed cation exchange resin with an acid;
The acid is adsorbed only in a portion of the cation exchange resin layer, making it impossible to achieve the intended purpose. Therefore, in the present invention, the cation exchange resin layer is mixed immediately after adding the acid, or the cation exchange resin layer is mixed while adding the acid, but the latter is more effective in the present invention. In addition, when mixing the cation exchange resin layer, backwashing with water, mixing by mechanical stirring, air mixing, etc. are performed, but air mixing with good mixing efficiency is most preferable. After mixing the cation exchange resin layer in this way and dispersing the added acid throughout the cation exchange resin layer, the cation exchange resin layer is settled and then washed with washing water by a conventional method to improve the cleaning properties. This is a dramatic improvement and the cleaning time can be significantly shortened.

Examples of the present invention will be described below.

Example 1 A strongly acidic cation exchange resin Amberlite (registered trademark, hereinafter the same) 200.1 was placed in a column,
With a molar ratio of Na ₂ SO ₃ /NaHSO ₃ of 0.7 (PH = 6.2)
0.7N solution 1 as NaHSO ₃ concentration was passed through SV4, then extruded for 20 minutes at SV4 using pure water,
Water in the column was drained to the top of the cation exchange resin layer, 10 ml of 2N-HCl was added, and air was immediately supplied from the bottom of the column at a rate of 1 N/min for 3 minutes to thoroughly mix the cation exchange resin in the column. Thereafter, as a result of washing at SV10 using pure water, the electrical conductivity of the washing wastewater rapidly decreased as shown in FIG. 1, and it took about 2 minutes to reach 5 μS/cmat at 25°C.

As a comparative example, when cleaning with SV10 using pure water without adding acid after extrusion, the time required for the electrical conductivity to reach 5 μS/cmat 25°C is 23 minutes, as shown in Figure 1 and 2. Ta.

Example 2 Strongly acidic cation exchange resin Amberlite 200,
1 was placed in a column, and a 0.83N solution 1 was passed through the column using SV4 at a NaHSO ₃ concentration with a molar ratio of Na ₂ SO ₃ /NaHSO ₃ of 0.17 (PH = 5.5), and then purified water was used.
After extruding with SV4 for 20 minutes, drain the water in the column to the top of the cation exchange resin layer, add 10 ml of 2N-HCl,
Immediately, air was supplied from the bottom of the column at a rate of 1 N/min for 3 minutes to thoroughly mix the cation exchange resin in the column. Thereafter, as a result of washing at SV10 using pure water, the electrical conductivity of the washing waste water rapidly decreased as shown in FIG. 2, and it took about 2 minutes to reach 5 μS/cmat at 25°C.

As a comparative example, when the product was washed with SV10 using pure water without adding acid after extrusion, it took 14 minutes to reach the electrical conductivity of 5μS/cmat25℃ as shown in Figure 2. .

[Brief explanation of the drawing]

The drawings are all graphs showing the cleaning effect in the examples, FIG. 1 shows the cleaning effect in Example 1, and FIG. 2 shows the cleaning effect in Example 2.
In both figures, the vertical axis shows the electrical conductivity of the cleaning wastewater, and the horizontal axis shows the cleaning time. In both figures, curve 1 is the result of the cleaning method of the present invention, and curve 2 is the result of the conventional cleaning method.

Claims (1)

[Claims] 1. When cleaning the cation exchange resin after treating it with an iron removal agent in which hydrogen sulfite and sulfite components coexist and the pH of the liquid is adjusted to 5.5 or higher, extrude the iron removal agent in the cation exchange resin layer. After replacing with water, the cation exchange resin layer is mixed immediately after adding a small amount of acid to the cation exchange resin layer, or the cation exchange resin layer is mixed while adding a small amount of acid to the cation exchange resin layer. mix,
A method for cleaning a cation exchange resin, which comprises subsequently cleaning the cation exchange resin layer with cleaning water.