JPH0653273B2 - Condensate treatment method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for treating condensate of a steam engine plant such as a steam turbine using a mixed bed demineralization tower.

[Background of the Invention]

As a method for regenerating the ion-exchange resin loaded in the mixed bed type desalting tower outside the tower, for example, as shown in JP-A-58-216743, an upper layer of an anion-exchange resin, an anion-exchange resin in a separation and regeneration tower is used. And a cation exchange resin are mixed in the middle layer, and the cation exchange resin is separated into three layers of a lower layer, and the upper layer anion exchange resin is alkali,
A method is known in which the cation exchange resin in the lower layer is regenerated with an acid, and then the cation exchange resin is transferred to a mixed bed desalting tower together with the non-regenerated middle layer for desalting.

This method can prevent the reverse regeneration of the anion exchange resin and the cation exchange resin, but has a technical problem that it is difficult to avoid the leakage of loaded ions from the non-regenerated resin during the condensate treatment.

Furthermore, with regard to condensate of boiling water nuclear power plant (BWR plant), removal of iron cladding is strongly required,
In the conventional condensate treatment technology, it was difficult to completely remove the iron cladding.

Next, the cause of leakage of load ions from the recycled resin will be described.

Since high-purity water is required for power generation in thermal power plants and nuclear power generation, condensate is desalted by a mixed bed desalting tower composed of anion exchange resin and cation exchange resin. In the desalting tower in the BWR plant, the anion exchange resin is used in the OH type and the cation exchange resin is used in the H type, and when the desalination performance is lowered due to the ion load, the ion exchange resin is regenerated by the alkali and the acid, respectively.

Prior to regeneration of the mixed bed desalting tower, it is necessary to separate the anion exchange resin and the cation exchange resin. If this separation is incomplete, acid acts on the anion exchange resin or the cation exchange resin becomes alkaline. When the salt is subjected to desalination after regeneration, the amount of leaked impurity ions increases and various damages are caused. For example, when a cation exchange resin is mixed in an anion exchange resin, the mixed cation exchange resin becomes Na type by a regeneration operation with an alkali such as sodium hydroxide, and when this resin is subjected to desalting of condensate, sodium ion leaks. Occurs and causes corrosion damage to the turbine and the like. On the other hand, when an anion exchange resin is mixed in the cation exchange resin, the mixed anion exchange resin becomes SO ₄ type due to regeneration by acid such as sulfuric acid, and when this resin is subjected to desalination of condensate, a leak of sulfate ion occurs. Causes corrosion and scale failure.

Conventionally, when regenerating this mixed bed outside the tower, the regenerated resin to be separated is transferred to the separation and regeneration tower, and the resin layer is developed by upwardly circulating water from the lower part of the tower, whereby the anion exchange resin and the cation exchange resin They were separated using the difference in specific gravity. However, since the separation was incomplete near the boundary between both resins, it was difficult to avoid mixing the anion exchange resin into the cation exchange resin and the cation exchange resin into the anion exchange resin.

FIG. 2 is an explanatory diagram of a conventional method.

The ion exchange resin in the condensate demineralization tower 1 is transferred to the separation and regeneration tower 2, and is stratified into an upper layer 3 containing only anion exchange resin, a lower layer 5 containing only cation exchange resin, and a middle layer 4 in which both are mixed, After transferring the upper layer (anion resin) 3 to the anion regeneration tower 6, the middle layer (mixing) 4 is transferred to the mixing tower 7, and the lower layer (cation resin) 5 is left in the separation regeneration tower 2.

The upper layer (anion resin) 3 that has been separated by separating the layers into the respective columns as described above, has passed the alkaline regeneration liquid through the anion regeneration tower 6 and the acidic regeneration liquid through the separation regeneration tower 2 and has completed regeneration.
And the lower layer (cationic resin) 5 are transferred to the mixing tower 7.

In this way, the middle layer (mixed resin) 4 already contained in the mixing tower 7 and the regenerated upper layer 3 and lower layer 5 are mixed and packed in the desalting tower 1 for desalting. It was

In this way, the unregenerated middle layer (mixed resin) 4
Is mixed with the regenerated upper layer (anion resin) 3 and lower layer (cation resin) 5, so that a certain amount of ion leakage cannot be avoided.

[Object of the Invention]

The present invention has been made in view of the above circumstances, using the conventional condensate treatment equipment, there is no need for expansion or modification, and
There is no risk of load ions leaking from recycled resin,
Moreover, it is intended to provide a condensate treatment method capable of removing the iron cladding at a high rate.

[Outline of Invention]

Although the present inventors can prevent excessive contamination of the resin by not regenerating the middle layer (i) when the anion exchange resin and the cation exchange resin are separated by passing water,
It was experimentally shown that the leakage of impurity ions from the non-regenerated resin deteriorates the desalination performance, and (ii) the ion-cladding resin has a higher ability to remove the iron cladding than the anion-exchange resin. confirmed.

Further, from the results of the study conducted by the present inventors on the removal of iron cladding in the condensate demineralization tower, the iron cladding removal is an excess phenomenon in the ion exchange resin layer and an adhesion phenomenon to the ion exchange resin surface. It was found that the ion-exchange resin and the cation-exchange resin have significantly better iron-clad adhesion ability due to the difference in surface charge between the cation-exchange resin and the cation-exchange resin.
Further, it was found that the ion-exchange resin having the iron clad adhered thereto was difficult to be sufficiently regenerated, and the ion-exchange reaction was hindered so that the desalination performance was lowered.

The present inventors, based on the above experimental results, in order to achieve the above-mentioned object, in the state of the completion of the regeneration treatment, the regenerated cation exchange resin and the anion exchange resin are mixed and packed, and further, The processing method was created so that the non-regenerated resin was filled on the upstream side.

In the method of the present invention, first, a mixture of the anion exchange resin and the cation exchange resin used in the mixed bed desalting tower according to a conventional method is transferred to a separation regeneration tower, and the resin layer is developed by upward flowing water from the lower part of the tower, Utilizing the difference in specific gravity between the anion exchange resin and the cation exchange resin, it is stratified into three layers, an upper layer containing only the anion exchange resin, a middle layer containing the anion exchange resin and the cation exchange resin, and a lower layer containing only the cation exchange resin. To do.

After that, after transferring the upper layer to the anion regeneration tower and regenerating with alkali, the whole amount is transferred to the mixing tower and the anion regeneration tower is emptied, and then the middle layer is transferred to the empty anion regeneration tower. Then, the lower layer remaining in the separation and regeneration tower is regenerated with an acid and then transferred to a mixing tower, mixed with the anion exchange resin and filled in the desalting tower, and then the middle layer in the anion regeneration tower is filled in the desalting tower. Then, the ion exchange resin originally stored in the desalting tower is subjected to a regeneration treatment, and then the whole amount is returned to the desalting tower for restoration and used for condensate treatment. The above-mentioned ion exchange resin is regenerated according to a conventional method, and 2 to 10% is contained in the anion regeneration tower containing the anion exchange resin as the upper layer.
The separation and regeneration tower containing the cation exchange resin, which is the lower layer, contains 2 parts of alkali such as sodium hydroxide solution.
It is carried out by passing an acid such as sulfuric acid of about 10%, followed by extrusion and washing with water.

In the present invention, the unregenerated middle layer is filled upstream of the regenerated ion exchange resin, and as in the conventional method, the unregenerated middle layer ion exchange resin is never mixed in the middle layer or the lower layer in the desalting tower. Not in For this reason, in the conventional method, it was inevitable that a certain amount of the load ions leaked from the non-regenerated resin existing in the middle layer or the lower layer in the desalting tower. On the other hand, in the present invention, the non-regenerated resin is filled in the upstream side of the regenerated resin layer, and the load ions leaked from the non-regenerated resin are
It is reliably removed by the recycled resin in the lower layer. here,
The non-regenerated middle layer is at most 5-10% of the total,
The remaining 90 to 95% of the recycled resin has an extremely low ionic load.

INDUSTRIAL APPLICABILITY The present invention is effective for condensate treatment in a nuclear power plant, particularly in a primary cooling water system of a BWR plant. In this system, the treated water purity of condensate directly affects the reactor water quality. That is, the ions in the condensate are concentrated in the nuclear reactor, which increases the conductivity of the reactor water and promotes corrosion. In the above-mentioned conventional method, leak ions from the condensate demineralization tower are concentrated in the furnace and increase the reactor water conductivity, but according to the present invention, there is no ion leak from the condensate demineralization tower and the reactor water conductivity. Can be kept low, and the corrosion of internal structures can be suppressed.

Example of Invention

Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is an explanatory diagram of an embodiment of the present invention and is a diagram corresponding to FIG. 2 in the prior art. The cation exchange resin and the anion exchange resin in the desalination tower 1 whose desalination performance has been deteriorated by the treatment of condensate are transferred to the separation / regeneration tower 2, and the resin layer is developed by flowing water upward from the bottom of the tower to develop the anion. An upper layer 3 containing only an exchange resin, and a middle layer 4 containing an anion exchange resin and a cation exchange resin mixed therein,
The cation exchange resin alone is separated into the lower layer 5. After transferring the upper layer 3 to the anion regeneration tower 6 and regenerating with an alkali, the whole amount is moved to the mixing tower 7. As a result, the anion regeneration tower 6 is once emptied. Subsequently, the middle layer 4 is transferred to the empty anion regeneration tower 6 and the lower layer 5 in the separation regeneration tower is transferred.
Is regenerated with an acid, then transferred to a mixing tower 7 and thoroughly mixed with an anion exchange resin, and then charged into the desalting tower 1, and subsequently, the middle layer resin in the anion regeneration tower 6 is charged into the desalting tower 1. .
In this way, the entire amount of the ion exchange resin originally stored in the desalting tower 1 is returned to the desalting tower 1 for restoration, and the condensed water 8
Subject to processing.

FIG. 1 for explaining the method of the present invention, and FIG. 2 for explaining the prior art.
As is clear from comparison with the drawings, the method of the present invention can be carried out using the same device without adding or modifying the device of the conventional example.

The above-mentioned separation of the anion exchange resin and the cation exchange resin by water flow is performed by utilizing the difference in sedimentation speed.

The sedimentation velocity is a function of the particle size and density of the ion exchange resin according to Stokes's law, and the relationship between both resins is as shown in FIG. The particle size of the ion exchange resin packed in the desalting tower generally has a distribution of 200 to 1200 μm. Therefore, after the development of the resin layer, the cation exchange resin having a high sedimentation rate becomes the lower layer and the anion exchange resin having a low sedimentation rate becomes the upper layer due to the difference in density, but near the boundary between both resins, a small particle size cation exchange resin and a large particle size It can be seen that the sedimentation rate is close to the diameter anion exchange resin, the separation between the two is incomplete, and the formation of a middle layer in which the cation exchange resin and the anion exchange resin are mixed is inevitable.

FIG. 4 shows the relationship between the ratio of Na-type cation resin at the bottom of the desalting column and the leak Na ⁺ concentration from the exchange equilibrium constant of H ⁺ and Na ⁺ in the cation exchange resin.
The leak Na ⁺ concentration increases logarithmically as the proportion of Na-type cationic resin increases. The ratio of Cl-type anion resin shows a similar tendency. From this, it is understood that it is preferable to keep the ratio of the Na-type cation resin and the Cl-type anion resin at the bottom of the desalting column as low as possible. Since the middle layer in the separation / regeneration tower in the present invention is a non-regenerated resin, it is a load type ion exchange resin, for example, a Na-type cation resin or a Cl-type anion resin. At the upper part (upstream side) of the mixed bed of the H-type cation resin and the OH-type anion resin which have been regenerated in the above, since Na ⁺ and Cl ⁻ leaking from the non-regenerated resin are reliably removed in the lower layer, Impurity ions of the above never leak into the treated water.

FIG. 5 shows the amount of iron clad trapped in the depth direction of the resin layer in the desalting tower after condensate was passed through the desalting tower for about two months. It can be seen that the trapping of iron cladding in the desalination tower occurs mainly in the very surface layer. This is because the removal of iron clad is due to an excessive phenomenon. In the present invention, the surface layer resin in the desalting tower is filled with the non-regenerated resin, and the non-regenerated resin mainly captures the iron cladding. Therefore, the lowering of the ion exchange ability due to the adhesion of the cladding in the lower H-type cation and OH-type anion resin is prevented.

FIG. 6 shows the relationship between the resin particle size and the iron clad removal rate in the desalting tower. The removal rate improves as the resin particle size decreases. This is due to an increase in the excessive effect in removing the iron cladding due to the reduction in the resin particle size and an improvement in the adhesion efficiency due to an increase in the iron cladding adhesion surface with the increase in the resin outer surface area.

FIG. 7 shows the relationship between the filling rate of the cation exchange resin and the anion exchange resin in the desalting tower and the iron clad removal rate. The removal rate improves as the filling rate of the cation exchange resin increases. From this, it can be seen that the cation exchange resin has a higher iron clad removing ability than the anion exchange resin. It is considered that this is due to the difference in surface charge between the two resins.

From the results of Fig. 6 and Fig. 7, in order to improve the iron clad removing ability of the desalting tower, it is more important to reduce the particle size of the cation exchange resin having a high removing ability, because it causes an overeffect and an increase in the adhesion surface. It turns out to be preferable. In the present invention, the resin packed in the surface layer in the desalting tower is the one separated into the middle layer in the separation and regeneration tower, which has a large particle size for the anion resin and a small particle size for the cation exchange resin as described above. is there. Therefore, it can be seen that the iron clad is removed very effectively by the small particle size cation exchange resin on the surface layer.

The following Table 1 is a table in which the treated water quality in the above-mentioned embodiment and the treated water quality in the conventional example shown in FIG. 2 are compared.

From this table, according to the application of the present invention, Na ⁺ from the desalting tower is
It can be seen that the leak of Cl ⁻ and Cl ⁻ is reduced, and the iron-clad removal rate is also improved.

Even if the non-regenerated middle-layer resin is stored in a dedicated resin storage tank separately provided in the regeneration system by modifying this embodiment, the same effect can be obtained if the resin filling method for the desalting tower is the same. Is easy to understand.

〔The invention's effect〕

As described above in detail, when the method of the present invention is applied, the existing condensate treatment facility does not require any expansion or modification, and the leak of the load ion from the regenerated resin is caused only by the improvement of the operation method. There is no fear, and there is an excellent practical effect that the iron cladding can be removed with high efficiency.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of the method of the present invention, and FIG. 2 is an explanatory diagram of a conventional technique. Fig. 3 shows the relationship between the resin particle size and the sedimentation rate, Fig. 4 shows the relationship between the amount of Na-type resin and the leak Na ⁺ concentration, and Fig. 5 shows the relationship between the resin layer depth and the amount of trapped iron clad. 6 is a chart showing the relationship between the resin particle size and the iron clad removal rate, and FIG. 7 is a chart showing the relationship between the cationic resin / anion resin amount ratio and the iron clad removal rate. 1 ... Condensate demineralization tower, 2 ... Separation and regeneration tower, 3 ... Anion exchange resin layer, 4 ... Cation and anion exchange resin mixed layer, 5 ... Cation exchange resin layer, 6 ... Anion regeneration tower, 7 ... Mixing tower, 8 ... Condensate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroo Igarashi 3-2-1, Sachimachi, Hitachi City, Ibaraki Prefecture Hitachi Engineering Co., Ltd. (72) Inventor Yoshiaki Sato 3-2, Sachimachi, Hitachi City, Ibaraki Prefecture No. 1 in Hitachi Engineering Co., Ltd. (56) Reference JP-A-58-17884 (JP, A)

Claims (1)

[Claims] 1. A method of treating condensate of a steam engine with an ion exchange resin housed in a mixed bed type condensate demineralization tower, wherein the ion exchange resin loaded by the condensate treatment is separated and regenerated. In the method of regenerating outside the tower using the tower and the anion regeneration tower, (a) the ion exchange resin in the condensate demineralization tower is transferred to the separation and regeneration tower, and a. An upper layer consisting only of an anion exchange resin, b. A lower layer consisting only of a cation exchange resin, and c. The intermediate layer in which an anion exchange resin and a cation exchange resin are mixed is separated into layers, and (b) the upper layer consisting only of the anion exchange resin is transferred to an anion regeneration tower and subjected to regeneration treatment with an alkali,
The whole amount is transferred to a mixing tower to empty the anion regeneration tower, (c) the middle layer which is the mixture is transferred to an empty anion regeneration tower and temporarily stored, and (d) separation After regenerating the lower layer consisting of only the cation exchange resin remaining in the regeneration tower with an acid, it is transferred to the mixing tower, and the regeneration treatment that is previously transferred to the mixing tower in the step (b) is completed. Of the above anion exchange resin alone, and the mixed exchange resin is returned to the condensate demineralization tower, and (e) the whole amount of the middle layer, which is the mixture temporarily stored in the anion regeneration tower, is condensed. It is returned to the desalting tower, and is charged upstream of the regenerated upper and lower mixed layers that have been returned to the condensate desalting tower in the step (d), and At the start of the process, all the amount of ion exchange resin stored in the condensate demineralization tower is transferred to Recovery,
No need for any treatment tower other than the condensate demineralization tower, separation regeneration tower, anion regeneration tower, and mixing tower described above, and the entire amount of ion exchange resin filled in the condensate demineralization tower is reused. Then, the ion exchange capacity is restored, and the condensate is repeatedly subjected to desalination treatment of the condensate.