JPS5926143A - Iron removing restoration of ion exchange resin - Google Patents

Abstract

PURPOSE:To effectively carry out iron removing restoration treatment and to smoothly perform a regeneration process and water sampling process thereafter, in performing the iron removing restoration of ion exchange resin having clad adhered thereto, by passing an inorg. acid through the ion exchange resin treated with a liquid containing oxalic acid and/or oxalate. CONSTITUTION:In performing the iron removing restoration of ion exchange resin to which a clad, for example, a corrosive product based on an iron compound such as iron oxide is adhered, said ion exchange resin is treated with a liquid containing oxalic acid and/or oxalate and an inorg. acid is passed through the treated one. The iron removing restoration effect due to this method is remarkably high as compared with a conventional method and a removal ratio of about 70% is obtained by this method using sulfuric acid as a regenerating agent as compared with such a case that a regeneration level is 50% or less even if a conventional iron removing restoration agent is used in an amount two times relative to a usual one. This method has high effect in the point of iron removing restoration as well as said ion exchange resin after treatment operation is not converted to a salt form as in a conventional method and this iron removing restoration method is suitable for regeneration and water sampling thereafter.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing crud adhering to an ion exchange resin, that is, corrosion products mainly consisting of iron compounds such as iron oxide.

When crud adheres to the ion exchange resin, not only does the exchange capacity decrease, but iron content constantly leaks out and the quality of the treated water deteriorates. To avoid such a situation, for example, in a condensate desalination equipment at a thermal power plant, the amount of crud deposited is 500%.
■/1. When the amount exceeds -RasFe, crud removal treatment (hereinafter referred to as "°iron removal regeneration treatment") is performed.

Conventionally, various iron removal and regeneration agents have been proposed and put into practical use for iron removal and regeneration treatment, but they have the following major problems.

In other words, the following explanation will be given using a condensate desalination equipment as an example, but in Example λ-, a reducing agent such as hydrosulfite, sulfite, hydrogen sulfite, hydrazine salt, etc. is brought into contact with an ion exchange resin, and the cladding attached to the resin is removed. It is being removed as a soluble substance by reducing it. At this time, in addition to these reducing agents, we also adjust the resin ion type and process liquid p.
Adjustment of H.

Salt or other Na for removing organic matter, etc.

Since salts, alkalis, and acids containing K, CL, S04, etc. are used in combination, depending on the salts contained in the iron removal regeneration agent used, the cation exchange resin is Na type, and the anion exchange resin is Ct after iron removal regeneration treatment. It turns into a salt type, such as a mold.

In condensate desalination equipment, resins that have been converted into salt forms are a major hindrance in carrying out the ammonia cycle. The exchange resin needs to be converted into an OH type button, but a large amount of regenerating agent is required to regenerate these salt type resins.

For example, 10 eq/l-R of cation exchange resin (porous type strongly acidic cation exchange resin) in which 80 parts are converted to Na type.
Even if it is regenerated with H2SO4, only one Na type remains, and it is almost impossible to reduce it to less than 0.1%, which is necessary to carry out an ammonia cycle. In addition, anion exchange resin (
It is more difficult to convert porous type, type I strongly basic anion exchange resins to OH type, and converting 100 Ct type resin to 1 oe
Even if it is regenerated with q/L-R Naoli, about 25 coefficients remain, and it is impossible to reduce the amount of Ct leakage to less than 3 parts, which is necessary to reduce the leakage amount to 1.5 ppb or less.

As described above, in the conventional iron removal regeneration treatment method, a large amount of salt remains even after regeneration, and if the ammonia cycle currently used in thermal power plants is implemented, a large amount of Na and CL will leak. Therefore, the resin after iron removal regeneration treatment is
The actual situation is that the ammonia cycle cannot be carried out immediately, so the H-011 twcycle is carried out for 5 or more cycles, for about one month or more, and then the ammonia cycle is carried out after the salt type has decreased.

It is an object of the present invention to provide a method that eliminates the drawbacks of such conventional methods, performs extremely effective iron removal regeneration processing, and allows the subsequent regeneration process and water sampling process to be performed smoothly. It is something.

According to the present invention: i. When regenerating iron removal from the ion exchange resin to which the cladding has adhered (7), after treating oxalic acid and/or oxalate with a proprietary solution, passing an inorganic acid through the resin. This is a featured iron removal regeneration method for ion exchange resins.

Hereinafter, the present invention will be explained in detail using a condensate desalination equipment as an example.
20g) + a-Fe20s + r-FeOol
(+α-Fe00I [and amorphous. It is said that magnetic iron oxide, γ-Ji'eOO, It is said that the form of the cladding in - is different between cationic resins and anionic resins, but the details are currently unknown.

However, as a result of intensive research into iron removal regeneration methods using resin chemicals actually used in thermal power plants, the present inventors found that oxalic acid and oxalate have a great effect on iron removal regeneration from cation exchange resins. The present invention has been completed by discovering that this is the case.

In other words, when a cation exchange resin is treated with oxalic acid (salt), the cladding becomes ferrous oxalate, and since this compound has low solubility, only a small amount of iron is eluted into the treated supernatant, but oxalic acid (salt) After treatment with inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid, the ferrous oxalate that has precipitated or adhered to the resin is completely removed. This method achieves the above goals and has significantly higher effects than conventional methods. In addition, instead of using oxalic acid (salt) alone, treating with a mixture of oxalic acid (Jaf) and inorganic acid and then passing it through with inorganic acid has an even greater iron removal effect. Even if the mixed waste liquid with inorganic acid is reused, there is a sufficient effect.

In contrast to the conventional method in which the cladding is removed as a soluble compound at once by the action of a reducing agent, the method of the present invention uses a compound with low solubility such as ferrous oxalate and then regenerates the inorganic cladding. The feature is that these are removed using acid. Monoke inorganic acid precipitated as ferrous oxalate (regenerant)
For example, if you use sulfuric acid, adjust the concentration to 4 to 8, and use a cation exchange resin with an SV of 2 to 4.
It can be completely dissolved and removed by passing 0 to 400 tons of medicine.
After passing the sulfuric acid, ferrous oxalate precipitates and does not remain at all, causing no problems with subsequent water sampling.

As mentioned above, it is very preferable that the ionic type of the resin is maintained as Il type or OH type even after iron removal regeneration treatment, but in the present invention, it is preferable to use oxalic acid and inorganic acid. Conversion to the salt type completely avoids iron removal, and the iron removal effect is greater than that of conventional methods.

Oxalates such as sodium oxalate and potassium oxalate have the same iron removal effect as oxalic acid. The oxalic acid (salt) used in the present invention is extremely easy to handle and does not generate harmful sulfur dioxide gas during treatment, unlike the conventional iron removal regeneration agents such as ruhytrolphite and sulfite. be.

On the other hand, for anion exchange resins, the effect of iron removal by oxalic acid (salt) is not as great as that for cation exchange resins. This is probably due to the fact that the form of the deposited cladding is different between the two. -t h Therefore, a conventional iron removal regenerating agent may be used for the anion exchange resin if desired. In this case, the anion exchange resin is usually in the I''iC4 type after treatment because salt is used to remove organic matter and adjust the ionic type.Even if the anion exchange resin is regenerated as the Ct type, <It is difficult to reduce the Ct type to less than 3%, which is required for ammonia cycle operation.Therefore, it is necessary to cation-exchange the inorganic acid (especially sulfuric acid in the case of cation-exchange resin), which also serves as iron removal regeneration and regeneration of the cation-exchange resin. It is preferable to convert the cyanion exchange resin to the easily regenerated SO4 type by passing the resin and anion exchange resin in that order, and then convert it to 0) type 1 with caustic soda.In this case, the regeneration level of the caustic soda is the usual 2 ~3 times the amount is sufficient, and some S04 type remains, but SO4 remains even during the ammonia cycle.
Since it is difficult to leak, it can be transferred directly to the ammonia cycle.

Next, an embodiment of the present invention will be described with reference to FIG.

(1) After transferring the resin from the demineralization tower (not shown) to the cation regeneration tower/separation tower (hereinafter abbreviated as rCRTJ), the anion exchange resin undergoes a normal backwashing separation operation, and the anion exchange resin becomes anion exchange resin. , 7IJ grinding tower (hereinafter abbreviated as rART J) 2 by opening the valve 3 of the transfer line.

(2) After the transfer is completed, transfer the cation exchange resin 11 VC to 1 from the oxalic acid saturated solution tank 4 to the CR
Inject 1 to 202 degrees of oxalic acid and adjust the dilution to a concentration of 0.5 to 8 degrees. Further, if necessary, an inorganic acid with a concentration of 0.5 to 15% is injected from a normal regeneration line. Then, open valve 7 to introduce air and perform air scrubbing for 5 minutes.
Run for ~10 minutes to mix the resin. Then, perform air scrubbing for 1 to 2 minutes every 30 minutes and leave it for 30 minutes to 5 hours. At this time, even if the ion type of the cation exchange resin is H type, NH,! It doesn't matter if it's a type. The higher the concentration of oxalic acid is, the more appropriate it is 1 to 4 liters, and the higher the concentration of inorganic acid (4 to 10 LI), the greater the iron removal effect.

(:'l) Regarding ART 2, a conventional iron removal regeneration agent is added for treatment. Normal table salt and iron removal regeneration agent are added.

(4) Both CRTI and ART2 are extruded after being left for a certain period of time, and then 4 to 10 inorganic acids (
In the case of sulfuric acid, the amount is 2 to 3 times the normal regeneration level, 200 to 4
00 Y/l-Ras 66°Bb H2SO4) through the normal regeneration line, l:, 9SV3-4. At this time, the regenerated waste liquid is discharged by opening the valve 5 of the drug passage line 6 for the restricted waste liquid and passing the medicine also to -rART2, and then opening the valve 8.

Next, extrusion and washing are performed. CR1' with the operations so far
Iron removal and regeneration of the cation exchange resin No. 1 is completed. ARC
' The anion exchange resin in step 2 is once removed by iron removal regeneration treatment.
Becomes type t, but from CRT 1 ) lzsO + endogenous waste fluid is passed and SO,! Convert to type.

(5) Further to AR1' 2 and normal playback level 2-3
Regenerate by passing twice the amount of 1J to 1Nda.

In this way, in the illustrated example, the conventional playback device is equipped with CR'
By passing the regenerated waste liquid of l' 1 through AiζT2, there is no generation of salt types such as Na type in the cation exchange resin after iron removal and regeneration, and the anion exchange resin is also converted to OH type, and some SO+ Although the mold remains, it has no effect and can be moved to the ammonia cycle as is.

Next, examples of the present invention will be described.

EXAMPLE When a cation exchange resin used for 5 years at a thermal power plant was subjected to the iron removal regeneration treatment of the present invention, the results shown in FIGS. 2 and 3 were obtained. FIG. 4 shows the results of treatment with inorganic acid only.

Figure 2 shows a mixture of oxalic acid with a concentration of 4% and sulfuric acid with a concentration of 8% so that the amount of treated liquid per 1 ton of cation exchange resin is 100 f of oxalic acid and 200 Y of Th5Oa.
After treatment for a period of time, each inorganic acid (4 types) with a concentration of 8.
The results are shown below. H2SO4 (1) shows the effect when treated with a new mixed solution, and H2SOa (2) shows the effect when the mixed solution is recovered and reused. The conventional method involves passing J (2SO4) after treatment with a conventional iron removal regeneration agent, that is, one mainly composed of sulfur oxide, and is said to be the most effective.

Figure 3 shows the case where the sample was treated with a 4% oxalic acid solution for 5 hours and passed through the heat exchanger. It can be seen from FIGS. 2 and 3 that the method of the present invention is more effective in removing iron by 20 to 30 inches than the conventional method. The broken lines in FIGS. 2 and 3 indicate the iron removal effect of the oxalic acid/sulfuric acid mixture and the iron removal effect of oxalic acid, respectively. In the conventional method, the iron regenerating agent dissolves the iron and turns it into an ionic form.This ionic iron is exchanged with a cation exchange resin, and the ion-exchanged iron is desorbed by an inorganic acid. It is considered that the effect of the conventional method is small because it is difficult to obtain a precise image. In the method of the present invention, the cladding is attached to the resin as a precipitate such as ferrous oxalate due to the action of oxalic acid, so the proportion of image-like formation is lower than in the conventional method, and therefore the cladding is strongly ion-exchanged with the kathymene exchange resin. It is thought that the iron removal effect is greater than that of the conventional method because there is less iron removal.

In the method of the present invention, when hydrochloric acid is used, an iron removal effect of 9056 or more can be obtained. The same effect as shown in FIG. 2 was also obtained when sodium oxalate was used as the oxalate.

Furthermore, from FIG. 2, it was found that repeated use of a mixed solution of oxalic acid and I(2SO4) was sufficiently effective.

Figure 3 shows the case of treatment with oxalic acid alone, which is slightly inferior to the case of treatment with the mixture shown in Figure 2, but 1dII better than the conventional method.
In case of 2S04! 5-10 has a large iron removal effect.

The exchange capacity was measured for both the cation exchange resin treated with sulfuric acid shown in Figure 2 and the anion exchange resin soaked in the same mixed solution + c for 7 days and regenerated with caustic soda. . When condensate was treated in a mixed bed of both resins, the treated water had an electrical conductivity of 0.055 to 006/'S/cm, indicating that the method of the present invention would not cause the resin to deteriorate. It was confirmed that there was no

As mentioned above, the iron removal regeneration effect of the method of the present invention is significantly greater than that of the conventional method, and when sulfuric acid is used as a regenerating agent and 17, the iron removal regeneration effect with the conventional iron removal regenerating agent is twice that of the normal method. amount(
Approximately 300 y/l-Ras CaCO5)
In contrast, the method of the present invention provides a removal rate of about 70%. Like Jin, the method of the present invention is not only highly effective in terms of iron removal regeneration, but unlike conventional methods, it does not turn into a salt type after treatment, making it very convenient for subsequent regeneration and water sampling. This is an iron removal regeneration method, and its benefits are significant. The present invention is not only useful for condensate desalination equipment, but can also be effectively applied to cleaning crud-attached pure water equipment, powdered ion exchange resins, and other crud-attached fillers.

[Brief explanation of the drawing]

Fig. 1 is a flow sheet showing an embodiment of the present invention, and Figs. 2 to 4 are graphs showing the results of an embodiment of the present invention, and show the correspondence between iron removal regeneration conditions and iron removal efficiency. be. 1... Cation regeneration tower/separation tower (CRT), 2...
・Anion regeneration tower (ART), 3, 5, 7, 8
... Valve, 4... Oxalic acid saturated solution tank, 6... Medication line. Patent applicant: Patent attorney representing Ebara Infilco Co., Ltd.
Go Hayama - Patent attorney Sen 1) Minoru

Claims (1)

[Claims] 1. During the iron removal and regeneration of the ion exchange resin with the cladding attached, it is characterized by treating it with a solution containing oxalic acid and/or oxalate, and then passing it through with an inorganic acid. Iron removal regeneration method for ion exchange resin. 2. The liquid containing oxalic acid or oxalate is
Or the method according to claim 1, which is a mixed solution of oxalate and an inorganic acid. 6. When the cladding's ion exchange resin is a mixed resin of a cation exchange resin and an anion exchange resin, the mixed resin is heated in separate columns, and then the cation exchange resin is heated. A method according to claim 1 or 2, which performs an iron removal regeneration operation. 4. The method according to claim 3, wherein the inorganic acid discharged liquid after being passed through the iron removal regeneration operation for the force t-on exchange resin is passed through the anion exchange resin.