JPS58216743A - Desalting method of condensate - Google Patents

Abstract

PURPOSE:To improve the treated water of condensate in passing condensate to a mixed bed type desalting column and desalting the same by transferring an upper layer to an anion regeneration column the transferring a middle layer into a resin layer. CONSTITUTION:A mixture of the anion exhange resin and cation exchange resin used in a mixed bed type desalting column is transferred into a sepn. and regeneration column, where the resin layers are developed by the water passed in upward current from the lower part to separate the resin layers to the three layers; the upper layer contg. only the anion exchange resin and cation exchange resin, the middle layer contg. a mixture of the anion exhange resin and cation exchange resin and the lower layer contg. only the cation exchange resin. After the upper layer is transferred into an anion regeneration tower, the middle layer is stransferred into a resin storage tank, and the lower layer is allowed to remain in the separation and regeneration tower. The transfer is accomplished by flowing the transfer water in upward current from the lowr part of the column and discharging the resin layer while developing the same from the mid-part of the column.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for desalinating condensate, and more particularly to a method for desalinating condensate using a mixed-bed desalination tower.

High purity water is required for power generation in thermal power generation and nuclear power plants, so condensate is desalinated in a mixed-bed desalination tower made of anion exchange resin and cation exchange resin. In this demineralization tower, the anion exchange resin is used in the OR form, the regeneration of which takes place by contacting with an alkali, and the cation exchange resin is used in the H form, the regeneration of which takes place by contacting with an acid. be exposed.

Regeneration of the mixed bed must first begin by separating the anion exchange resin IJiff and the cabion exchange resin, or if this separation is not completed, impurities may leak out when subjected to desalination after birth. The large number of stems causes various kinds of harm. For example, if a cation exchange resin is mixed into an anion exchange tree Qif, it can be regenerated with an alkali such as tttrium hydroxide to
4) The tI-converted tung fat becomes Na form, and this resin is
・Ri) When performing t^1t, sodium ions are released,
Causes corrosion damage to boiler tapes and turbines.

In addition, if an anion exchange resin is mixed into a cation exchange resin, the anion exchange resin becomes Ck type or SO2 type when regenerated with an acid such as hydrochloric acid or sulfuric acid, and when desalted using the resin, chloride ions or sulfuric acid Ions are released and cause corrosion and scale damage.

Conventionally, when regenerating this mixed bed outside the tower, the resin to be separated and regenerated is transferred to the separation and regeneration tower, and the resin layer is developed by flowing water upward from the first part of the tower, thereby separating the anion exchange resin and cation exchange resin. They were separated using the difference in specific gravity. However, because separation was incomplete near the boundary between the two resins, we weighed the harm caused by the mixing of the anion exchange resin into the cation exchange resin and the harm caused by the mixing of the cation exchange resin into the anion exchange resin A. Choosing the former, in the PT&S raw tower, some anion exchange resin remained on the top of the cation exchange resin j, and the cation exchange resin r
h Transfer the anion exchange resin with almost no contamination to the anion regeneration tower, and regenerate it by passing acid v and alkali through the separation regeneration tower and anion regeneration tower, respectively, and then transfer the regenerated resin to the resin storage tank. 12. Waited until desalting.

In this method, as mentioned above, since the anion exchange resin remains in the separation and regeneration tower above the cation exchange resin layer,
When the anion exchange resin is regenerated, the salt form is C! When subjected to desalination, a large amount of chlorine ions leaked out. For this reason, in the separation and regeneration tower, both resins are stratified and separated by upward flowing water, and the incompletely separated intermediate layer near the boundary is temporarily transferred to a resin receiving tank, and then transferred to the resin storage tank for the regenerated cation exchange resin. A method has been proposed in which the resin is returned to the separation and regeneration tower after completion of the transfer, and the resin is separated and regenerated together with the resin to be separated and regenerated next time.However, a resin receiving tank is required for temporary storage of the intermediate layer, and the resin In order to maintain the balance 7 of i, an extra resin corresponding to the intermediate layer was required, and the operation was further complicated.

The present invention focuses on the fact that during stratification separation using upward flowing water, the incomplete separation near the boundary reproduces the sound of the middle layer, which contaminates the resin, and provides ancillary equipment with simple operations. The purpose of this study is to propose a method for improving treated condensate water by regenerating it without any waste water.

The condensate is desalinated by passing through a mixed-bed desalination tower, and the loaded ion exchange resin in the demineralization tower is regenerated outside the tower.The resin is transferred to a separation and regeneration tower and then The flowing water separates into three layers: an upper layer containing only cyanion exchange resin, a middle layer containing a mixture of anion exchange resin and cation exchange resin, and a lower layer containing cation exchange resin, and the upper layer is transferred to an anion regeneration tower. Regenerate with alkali and transfer to the middle layer #'i resin storage barrel, regenerate the remaining lower layer with acid, and transfer the regenerated cation exchange resin h and anion exchange resin in the separation regeneration tower and anion regeneration tower to the resin storage tank. This condensate desalination method is characterized by further transferring the resin in this resin storage tank to a demineralization tower for desalination. The mixture of anion exchange resin and cation exchange resin used in 7 is transferred to a separation and regeneration tower, and water is passed upward from the bottom of the tower to develop a resin layer, making use of the difference in specific gravity between the 7 anion exchange resin and the cation exchange resin. Then, the mixture is separated into three layers: an upper layer containing only anion exchange resin, a middle layer containing a mixture of anion exchange resin and cation exchange resin, and a layer containing only cation exchange resin. Next, in the conventional method, the upper layer was transferred to the anion regeneration tower, and the middle and lower layers were left in the separation tower. However, in the present invention, after the upper layer is transferred to the anion regeneration tower, the middle layer is It is transferred to a storage tank, and the lower layer remains in the separation and regeneration tower. The transfer is carried out by flowing the transferred water upward from the lower part of the tower to develop the resin layer and discharging it from the middle part of the tower.

In this way, each layer is isolated from other layers, and □ of the main reagent is passed through the anion regeneration tower (h) and the separation tower (p), respectively. Regeneration is carried out according to a conventional method, and an alkali such as a 2 to 10% sodium hydroxide solution is passed through the anion regeneration tower containing the anion exchange resin in the upper layer, and the cation exchange resin in the lower layer is passed through the anion regeneration tower. The separation and regeneration tower has two
This is done by passing an acid such as ~10% hydrochloric acid or sulfuric acid,
Thereafter, extrusion and water washing are performed, and the regenerated upper layer ν and lower layer are each transferred to a resin storage tank. The resin reservoir already contains the middle layer, or the middle layer is mixed with the regenerated upper and lower layers and is ready for desalination.

In the present invention, although the middle layer is not regenerated, since the condensate usually contains ammonia as a component, the anion exchange resin in the middle layer is mostly #I OH type, and the cation exchange resin is extremely Since it is in the NH3 form, there is no risk that the anion exchange resin in the middle layer will be converted to the C8 type or 804 type by the cation exchange resin regenerant as in the conventional method. The cation exchange resin in the NkLa form is not harmful in itself, just because it cannot capture ammonium ions in the afterwater. In addition, since the middle layer consists of at most five layers in total, the ion exchange capacity of the desalting tower is hardly reduced.

The invention is effective for condensate treatment in secondary cooling water systems of nuclear power plants, particularly pressurized water nuclear power plants. This thread not only improves the purity of the condensate treated water, but also reduces the amount of N in the treated water.
It is required to control a/C13 (molar ratio) to 0.7-03. This is to prevent concentration of sodium ions in the thin tubes of the steam generator from causing embrittlement of the thin tubes due to sodium hydroxide.

In other words, while reducing the sodium ions in the treated water as much as possible,
This is to secure chlorine ions as counter ions and suppress the production of sodium hydroxide.

In the conventional method described above, the sodium ion concentration in the treated water can be lowered, but the chlorine ion linearity is high, and the Na''-/CI3 (molar ratio) is between 03 and 01.
Although it was not possible to satisfy the approval value, according to the present invention, in the case of a normal power plant that always uses multiple desalination towers and desalinates condensate in parallel, By adopting the operating method of the present invention for the required number of desalting towers out of a plurality of desalting towers and using the conventional operating method for the other towers, the quality of treated water and Na/C13 (molar ratio) can be improved. Both can be tailored to your needs. Of the plurality of desalination towers, whether or not the side towers are operated according to the method of the present invention depends on the water quality of the condensate, but usually two of the five towers are fertile.

That is, regarding the method of distributing condensate to several mixed-bed desalination towers and flowing them in parallel, regeneration method I is used for desalination of at least one tower.
The regenerated ion-exchange resin is poured and subjected to desalination.
The other desalting tower is filled with the ion exchange resin regenerated by the regeneration method ① and used for desalting.

Regeneration method I is a regeneration method according to the present invention, in which the ion exchange resin loaded in the desalination tower is regenerated outside the tower, the resin is transferred to the regeneration tower, and the resin is transferred to the upward flowing water. An upper layer containing only a cyanion exchange resin, a middle layer containing a mixture of an anion exchange resin and a cation exchange resin, and a Kanaon 9. Separate into three layers of f oil containing only resin, the upper layer is transferred to an anion regeneration tower and regenerated with alkali, the middle layer is transferred to a resin storage tank IC,
The first layer subjected to IA distillation is regenerated with acid, and the regenerated cation exchange resin and anion exchange resin in the separation and regeneration tower 2 and anion regeneration tower are transferred to a resin storage tank, and the resin in this resin storage tank is further transferred to a demineralization tower. and then subjected to desalination.

Regeneration method (■) is a regeneration method that falls under the conventional method. When regenerating the negatively charged ion exchange resin in the demineralization tower outside the tower, the resin is transferred to the N1 regeneration tower, and the anions are removed by upward flowing water. Soil layer containing only exchange resin, middle layer containing a mixture of anion exchange resin and cation exchange resin, cation exchange resin glue,
The soil layer is transferred to the anion regeneration tower and regenerated with alkali, and the afterglow middle layer ↓ and 1st layer are regenerated by the enemy, and separated into the raw tower and anion regeneration tower. The regenerated cation exchange fat and anion exchange resin in the tower are transferred to a resin storage tank, and the resin in this resin storage tank is further transferred to a demineralization tower for desalination. This is because the concentration of both sodium ions and chloride ions in the treated water can be lowered by the operating method of the present invention, but Na''/
Since C# (molar ratio) cannot necessarily be kept within the range of 9.7 to 0.3, trace amounts of chlorine ions can be secured by operating other towers in the conventional manner17. The requirements can be met by mixing.

The present invention has been described above, and according to the present invention, since the middle layer is brought into contact with a regenerating agent, there is no contamination of the resin during regeneration, and regeneration can be performed with simple operations without the need for additional equipment. It is possible to improve the quality of treated water and meet the strict demands seen in PWR.

Example 1 A portion of the condensate was desalinated in a desalination tower with an inner diameter of 3000 m.

In the desalination tower, cation exchange resin Tiymen PK22B (manufactured by Mitsubishi Chemical Industries, Ltd., commercially available) 7
The anion exchange resin Diaion PA3123300J, which had been regenerated into 00 (L and OH form), was filled and used for desalination.
The linear velocity (L
V) Flow pure water upward at 15m/h to drain the upper and middle layers.
The resin layer is stratified and separated into the upper layer and the lower layer, and the upper layer resin 3100i is transferred from the discharge port provided in the middle of the separation and regeneration tower to the anion regeneration tower with an inner diameter of 1800 mm, while the resin layer is expanded by flowing water upward. of resin 3001 with an inner diameter of 230
Transferred to a 0 mm resin storage tank, and added 5% sodium hydroxide to the anion regeneration tower at a regeneration level of 200 t-NaOH/l.
3-R, and 5% hydrochloric acid was passed through the separation and regeneration tower at a regeneration level of 140f-HCI3/13-R for regeneration, followed by extrusion and water washing, respectively. Each resin after regeneration is transferred to a resin storage tank, mixed with the resin in the middle layer, and returned to the desalination tower.
The condensate was passed through to obtain treated water. The results are shown in Table 1. For comparison, Table 1 also shows the case of the conventional method in which the middle layer is not transferred to the resin storage tank but left in the separation and regeneration tower and brought into contact with hydrochloric acid together with the first layer.

Table 1 Example 2 Five demineralization towers were used as in Example 1, and two towers were used in Example 1.
When operated in the same manner as above, the 1A 3 tower was operated in the conventional manner, and the treated water was mixed, the sodium ion concentration was 0.02 q.
/g/, chlorine ion once (1,01141q/ /-
Tonak) Na''/C/3 (molar ratio) was 037.

Applicant: Kurita Industries Co., Ltd.

Claims (1)

[Claims] In the method of desalinating condensate in a mixed-bed desalination tower, the condensate is desalted by passing through the mixed-bed desalination tower, and the ion exchange resin loaded in the desalination tower is regenerated outside the tower. The resin is transferred to a separation and regeneration tower, and the upper layer is made up of three layers: an upper layer containing only cyanion exchange resin, a middle layer containing a mixture of anion exchange resin and cation exchange resin, and one layer containing only cation exchange resin. The layers are separated, the upper layer is transferred to an anion regeneration tower and regenerated with alkali, the middle layer is transferred to a resin storage tank, the remaining lower layer is regenerated with rice, and the regenerated cation exchange resin in the anion regeneration tower is transferred to the separation and regeneration tower. Transferring the resin and anion exchange resin to a resin storage tank, and further transferring the resin in the resin storage tank to a demineralization tower for desalination.