JPS5841913B2 - Condensate treatment method - Google Patents

Description

Detailed Description of the Invention The present invention removes impurities present in condensate using a cation exchange resin layer and a mixed bed ion exchange resin layer in order to prevent scale formation and corrosion in boilers, turbines, etc. This invention relates to a condensate desalination treatment method.

As boiler operating conditions generally become higher temperature and higher pressure, the importance of condensate treatment has become widely recognized, and good treatment is usually achieved with a condensate desalination equipment filled with a mixed bed type ion exchange resin bed. .

This condensate desalination equipment uses a mixture of H type of strongly acidic cation exchange resin and OH type of strongly basic anion exchange resin.
The cation exchange resin undergoes an exchange reaction with ammonia in the condensate,
There is an H cycle treatment method in which regeneration is performed once ammonia has passed through, and an NH3 cycle treatment method in which treatment is continued using the resin that has been replaced with ammonia even after ammonia has broken through. be.

Recently, in order to save on regeneration chemicals for condensate desalination equipment and to improve operation management, many companies have adopted condensate treatment using the NH3 cycle, which requires less regeneration frequency.

However, the operation of the NH3 cycle is subject to various restrictions different from the H cycle, so the equipment is complicated, special regeneration chemicals are used, the cost is high, and regeneration takes a long time. At present, it cannot be said that this technology is necessarily perfected due to the following problems.

One of the problems when operating in a mixed bed type ion exchange resin layer NH3 cycle is that the salt form resin present in the mixed bed causes impurity leakage during ammonia break. It is necessary to adopt a resin recycling method that can keep the proportion of resin low.

Another problem is that during the NH3 cycle, the ability to remove impurity ions is slightly inferior to that during the H cycle.
In the event that a seawater leak occurs, impurity ions are likely to escape from the IJ, and the time it takes for the impurity ions to break through is shorter than during the H cycle, so there is concern about how to deal with seawater leaks. It is.

For this reason, at present, if a seawater leak is detected during the NH cycle, the regeneration of the resin is immediately started and the operation of the demineralization tower is sequentially switched from the NH3 cycle to the H cycle.

However, since it takes a certain amount of time to regenerate the resin, depending on the scale of the seawater leak, the resin may not be regenerated in time, and the power generation output may drop within a short time or the power generation may be forced to stop.

In order to avoid such dangers, it has been proposed that at least one tower should always be operated in the H cycle even during NH3 cycle operation, but in such an operating method,
The operating time of the desalination tower is naturally limited, and the actual situation is that the inherent advantages of the NH3 cycle cannot be fully demonstrated.

The present invention solves all of these drawbacks of conventional NH and cycle condensate desalination treatment methods, performs NH3 cycle condensate desalination without using any chemicals other than acids and alkalis, and The object of the present invention is to provide a condensate desalination treatment method that can safely deal with the occurrence of seawater leakage during a cycle without any adverse effects on the boiler or turbine.

In the present invention, condensate is introduced from the upper part of the demineralization tower, which is filled with a mixed bed type ion exchange resin layer at the bottom and a cation exchange resin is placed on top of the demineralization tower. In the process of regenerating the resin used in the condensate desalination equipment, which takes out the treated water from approximately the middle part and takes out the treated water from the bottom of the demineralization tower in the event of a seawater leak, this is added to the resin transferred from the demineralization tower. Separately prepared cation exchange resin and anion exchange resin are added and backwashed and separated in the cation exchange resin regeneration tower, and the anion exchange resin layer is sent to the anion exchange resin regeneration tower together with a part of the upper part of the cation exchange resin layer. By transporting the cation exchange resin, the generation of salt-form anion exchange resin during regeneration of the cation exchange resin is suppressed, and the cation exchange resin remaining in the cation exchange resin regeneration tower is regenerated by passing the regeneration agent through the anion exchange resin regeneration tower. The transferred resin is backwashed again to remove a part of the finely divided resin, and the cation exchange resin mixed in the anion exchange resin is separated, and the regenerating chemical is passed only through the anion exchange resin layer. This prevents the mixed cation exchange resin from being reversely regenerated, and once the resin has been washed with water for regeneration, the entire amount of resin in the cation exchange resin regeneration tower is transferred to the resin storage tank, and then the anion exchange resin regeneration tower is Transfer the required amount of the upper part of the anion exchange resin layer to a resin storage tank, introduce water, air, etc. from the approximately middle part of the cation exchange resin layer in the resin storage tank, and convert the upper part of the cation exchange resin into an anion exchange resin. Mix to form a mixed bed type ion exchange resin layer, fill the lower part of the desalination tower with this resin layer, fill the upper part with the cation exchange resin left in the resin storage tank, and then enter the desalination process again. This condensate treatment method is characterized in that the cation exchange resin and anion exchange resin left in the anion exchange resin regeneration tower are returned to the cation exchange resin regeneration tower and added to the resin to be regenerated.

In the present invention, when the anion exchange resin layer that has been backwashed and separated in the cation exchange resin regeneration tower is transferred to the anion exchange resin regeneration tower, the upper layer of the cation exchange resin is also transferred to the cation exchange resin regeneration tower. This is to avoid leaving any anion exchange resin, but since the allowable amount of anion exchange resin mixed into the cation exchange resin layer is relatively large, the height of the cation exchange resin layer for separation is 1007g711~
300 tomo is enough.

By this operation, the cation exchange resin layer left in the cation exchange resin regeneration tower contains almost no anion exchange resin, so no anion leak occurs even if it is used in the NH3 cycle after being regenerated with a mineral acid such as hydrochloric acid or sulfuric acid.

In the present invention, when the transferred resin is backwashed again in the anion exchange resin regeneration tower, removing a part of the pulverized resin to the outside of the tower along with the backwash waste water is a method that reduces the pressure loss during the desalination process. It is effective in reducing the amount of water and is also effective in removing the finely divided cation exchange resin mixed in the anion exchange resin layer.

As a guideline for the particle size for removing the resin in the form of fine powder, a particle size finer than 30 to 50 mesh is preferable.

In this case, in order to perform complete regeneration in the anion exchange resin regeneration tower, water must be introduced from the bottom of the regeneration tower during drug passage to prevent the regenerated chemicals from diffusing into the upper layer of the cation exchange resin used for separation. Bye.

The layer height of the anion exchange resin layer for separation affects the mixing rate of the cation exchange resin into the anion exchange resin (for desalination) or the reverse regeneration of the cation exchange resin for separation using regeneration chemicals, but it is usually 150. ~700 mm, or 20 to 50 mm relative to the total height of the anion exchange resin layer.

In the present invention, the bed height of the resin to be filled into the desalination tower must be determined in consideration of the quality of inflow condensate water, the quality of treated water, differential pressure, etc.

If the layer height (layer thickness) of the cation exchange resin layer filled at the top is too thin, the effect of removing suspended particles will be low, and it will be difficult to form a uniform layer. Generally, a range of 100 to 6001 m is appropriate since this results in an increase in pressure.

The height of the mixed-bed ion exchange resin layer in the middle area affects the quality of treated water during normal operation using the NH3 cycle, but since the concentration of ionic impurities during normal times is extremely low, it is lower than the resin layer height in conventional methods. Good, 300-11000
i is appropriate, and the total with the cation exchange resin layer is 6
A distance of about 0.00 to 12001 m is desirable.

The height of the mixed bed ion exchange resin layer at the bottom affects the treatment duration in the event of a seawater leak, but in the event of a seawater leak, water passes through all the resin layers, so if the layer height is too high, the differential pressure will increase. .

Therefore, the appropriate layer height is 300 to 1000+s, and the total resin layer height is 1000 to 1800n.
It becomes yx.

To explain the present invention with reference to the drawings, the first embodiment is as follows.
In the resin regeneration process shown in the figure, the resin that has completed the desalination process is transferred from the demineralization tower 1 to the cation exchange resin regeneration tower 2'\ by the resin transfer line 11, and the resin for separation (from the anion exchange resin regeneration tower 3 described later) Anion exchange resin AR returned
2 and cation exchange resin CR2)J are backwashed and separated into cation exchange resin layers CR, , CR2 and anion exchange resin layers (AR1+AR2')&.

Next, the amounts of the anion exchange resin layers AR1, AR, and the cation exchange resin CR2 for separation in the upper layer of the cation exchange resin layer (CRI + CR2) are transferred to the anion exchange resin regeneration tower 3 through the resin transfer line 12.

The cation exchange resin layer CR1 left in the cation exchange resin regeneration tower 2 is regenerated by passing hydrochloric acid and sulfuric acid through the regeneration chemical supply pipe 7.

On the other hand, the resin AR1 transferred to the anion exchange resin regeneration tower 3
, AR2, CR2 are backwashed again to form anion exchange resin layers AR0, AR2 and cation exchange resin CR217)3.
After separating into layers, the anion exchange resin layer AR1゜ARρ
Perform playback.

Note that the anion exchange resin AR□ is a resin used in the desalination process, and the anion exchange resin AR2 is not used in the desalination process but is a resin for efficiently and accurately performing the regeneration process, that is, a resin exclusively for regeneration. During the re-backwashing, AR1 and AR
2 is separated into layers due to the difference in specific gravity.

The anion exchange resin layers AR1, AR2 are regenerated by passing a caustic soda aqueous solution through the regenerating chemical supply pipe 8, and the waste liquid is extracted from the bottom of the separation anion exchange resin layer ARρ through the regenerated waste liquid pipe 23.

The thus obtained cation exchange resin layer CR0 containing almost no salt form resin is transferred to the resin storage tank 4 via the resin transfer line 13, and an anion exchange resin layer containing almost no salt form resin is transferred to the upper part of the resin layer CR1. AR1 is transferred by resin transfer line 14.

Next, the step of filling the resin into the desalting tower 1 and the desalting step are carried out in the second step.
To explain according to the diagram, air and water are introduced through the pipe 25 from approximately the middle of the cation exchange resin layer CR1 transferred to the resin storage tank 4, and the upper part of the cation exchange resin layer CR1 and the anion exchange resin AR1 are stirred and mixed. to form a mixed bed type ion exchange resin layer MB, and a cation exchange resin layer CR1.
The lower layer is directly used as the cation exchange resin layer CRs in the demineralization tower 1.

Next, the mixed bed type ion exchange resin layer MB is packed into the lower part of the demineralization tower 1 through the resin transfer line 15, and then the cation exchange resin layer CRY is packed into the upper part of the mixed bed type ion exchange resin layer MB through the resin transfer line 16. do.

Cation exchange resin C left in anion exchange resin regeneration tower 3
R2 and anion exchange resin layer ARJ resin transfer line 1
7, the resin is returned to the cation exchange resin regeneration tower 2, and in the next regeneration step, it is mixed with the resin from the demineralization tower 1 and reused for backwash separation, etc. in the demineralization tower 1.

Anion exchange resin AR for separation as well as cation exchange resin layer CR2 for separation left in the anion exchange resin regeneration tower 3
As the saw repeatedly regenerates the resin, fine cation exchange resin and large particle size anion exchange resin accumulate, making it gradually difficult to separate the resin.

The formation of fine resin particles also worsens resin separation.

Therefore, in the present invention, if the resin separation deteriorates, instead of transferring the resin from the anion exchange resin regeneration tower 3 to the cation exchange resin regeneration tower 2 only through the transfer line 17, first, the resin transfer line 18 , only the anion exchange resin AR2 for separation is transferred to the cation exchange resin regeneration tower 2, and then the cation exchange resin C for separation is transferred to the cation exchange resin regeneration tower 2.
R2 is backwashed, and only the fine resin in the resin layer CR2 is discharged to the outside of the column via the resin transfer line 19, and the remaining cation exchange resin is returned to the cation exchange resin regeneration column 2 via the resin transfer line 17, and the remaining cation exchange resin is returned to the cation exchange resin regeneration column 2 via the resin transfer line 17. New resin in an amount corresponding to the added resin is supplied from the resin hopper 5 through the resin transfer line 20.

As a guideline for the particle size of fine cation exchange resin discharge, 3
Preferably, the mesh is finer than 0 to 50 meshes.

Since the particle size distribution of the cation exchange resin in the separation cation exchange resin layer CB and part h and the particle size distribution of the cation exchange resin mixed in the anion exchange resin layer overlap considerably with each other, the separation cation By removing the fine cation exchange resin in the exchange resin layer CR, h portion, the proportion of the cation exchange resin mixed into the desalting anion exchange resin layer AR1 can be easily lowered to an appropriate level.

Note that the removal operation of the fine cation exchange resin is not normally performed, but if the fine cation exchange resin accumulates and becomes a hindrance to the backwashing separation of the resin, even if the removal operation is performed. good.

On the other hand, for the desalination process, condensate is introduced from the upper part of the desalination tower 1, and in normal times, the mixed bed type ion exchange resin layer M
The treated water A is taken out from approximately the middle of the water B through the outflow pipe 9.

In this treatment, suspended substances such as iron oxides in the condensate are more efficiently removed from the cation exchange resin layer CRsJ, thereby preventing contamination of the anion exchange resin in the mixed bed type ion exchange resin layer MB.

Furthermore, impurity ions are removed by passing water through the upper layer MB1 of the mixed bed type ion exchange resin layer MB.

The treatment using the cation exchange resin layer CRs and the upper layer MB1 continues even after the ammonia break, and the operation shifts from the H cycle to the NH3 cycle.

If a seawater leak is detected in this NH cycle, the valve 26 is closed, the valve 27 is opened to stop taking out the treated water A, and the inflowing condensate is transferred to the mixed bed type ion exchange resin layer MB. Water is also passed to the lower part MB2 and taken out as treated water B from the outflow pipe 10 at the bottom of the desalination tower 1.

Since the lower part MB2 was stored in the H-type immediately after regeneration, this operation allows the operation of the demineralization tower 1 to be switched to the H-cycle, which has a high ability to remove NH3-cycle impurity ions, within a short time.

In the figure, 6 is a condensate inflow pipe, 21.24 is a wash water pipe, and 22 is a recycled waste liquid pipe.

As described above, the condensate desalination treatment method according to the present invention reliably produces anion exchange resins and cation exchange resins containing almost no salt-form resin through simple regeneration operations, and uses a special regeneration agent. It has the characteristics that it enables NH3 cycle condensate desalination without having to regenerate the resin, and that it can switch from NH3 cycle to H cycle in a short time without regenerating the resin. In addition to fully demonstrating the advantages of NH3 cycle condensate desalination, it also eliminates concerns about seawater leaks that were associated with conventional NH3 cycle condensate desalination, making it possible to use seawater as condenser cooling water. It has extremely great utility value for the steam power plants that use it.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention; FIG. 1 is a flow sheet of the resin regeneration process, and FIG. 2 is a flow sheet of the resin filling process and the desalination process. 1...Demineralization tower, 2...Cation exchange resin regeneration tower, 3...Anion exchange resin regeneration tower, 4
... Resin storage tank, 5 ... Resin hopper 6
...... Inflow pipe, 7, 8... Regeneration chemical supply pipe, 9, 10... Outflow pipe, 11, 12゜13.
14, 15, 16, 17, 18, 19°20...
・Resin transfer line, 21, 22, 23゜24, 25・
...Piping, 26, 27...Valve, A, B
... Treated water, ARl - ... Anion exchange resin or resin layer for desalination, AR2 ... Anion exchange resin or resin layer for separation, CR1, CR8 ... Cation exchange resin or resin layer for desalting, CR2-...
Cation exchange resin or resin layer for separation, MB...
Mixed bed ion exchange resin layer, MBi... upper layer of the mixed bed ion exchange resin layer, MB2... lower layer of the mixed bed ion exchange resin layer.

Claims (1)

[Scope of Claims] 1. Condensate is introduced from the upper part of the desalination tower, which is filled with a mixed bed ion exchange resin layer in the lower part and a cation exchange resin is arranged in the upper part. In the condensate desalination process, the treated water is extracted from approximately the middle of the resin layer, and when a seawater leak occurs, the treated water is extracted from the bottom of the desalination tower. After backwashing and separation in advance, the anion exchange resin layer and a part of the upper part of the cation exchange resin layer are transferred to an anion exchange resin regeneration tower, and the cation exchange resin remaining in the cation exchange resin regeneration tower is regenerated by passing regeneration chemicals through it. On the other hand, these transferred resins are backwashed and separated again, and the regenerating chemicals are passed only through the anion exchange resin layer to regenerate the resin and wash with water.Then, the resin in the cation exchange resin regeneration tower is transferred to the resin storage tank. Then, the resin at the upper part of the anion exchange resin layer in the anion exchange resin regeneration tower is transferred to a resin storage tank, and approximately the middle part or more of the cation exchange resin layer in the resin storage tank is made into a mixed bed type ion exchange resin layer. , the resin of the mixed bed ion exchange resin layer is filled in the lower part of the desalination tower, and the cation exchange resin left in the resin storage tank is filled in the upper part of the desalination tower, and then the desalination process is started again, and the anion exchange resin is A condensate treatment method characterized in that the cation exchange resin and anion exchange resin left in the regeneration tower are returned to the cation exchange resin regeneration tower and reused in the cation exchange resin regeneration tower. 2. The backwash separation of the resin in the cation exchange resin regeneration tower is performed by using the anion exchange resin dedicated to the backwash separation and the cation exchange resin also dedicated to the backwash separation for each batch of the regeneration process in the cation exchange resin regeneration tower. The condensate treatment method according to claim 1, wherein the condensate treatment method is carried out by returning and mixing from an anion exchange resin regeneration tower. 3. The step of returning the resin from the anion exchange resin regeneration tower first transfers the anion exchange resin in the upper part of the anion exchange resin regeneration tower to the cation exchange resin regeneration tower, and then transports the fine cation exchange resin in the cation exchange resin layer. The condensate according to claim 1 or 2, wherein the cation exchange resin is removed by backwashing to the outside of the anion exchange resin regeneration tower, and then transferred to the cation exchange resin regeneration tower. Processing method. 4. The resin regeneration step in the cation exchange resin regeneration tower is performed by replenishing an amount of new resin corresponding to the amount discharged outside the anion exchange resin regeneration tower when the resin is returned. The condensate treatment method according to scope 3. 5. Only when the return process interferes with the backwash separation of the anion exchange resin and cation exchange resin in the anion exchange resin regeneration tower, after performing the operation to remove fine cation exchange resin, remove the remaining part. Claim 3 or 4 is carried out by transferring the normal crystal cation exchange resin to the cation exchange resin regeneration tower.
Condensate treatment method described in section. 6. The resin regeneration step in the anion exchange resin regeneration tower is carried out by passing a caustic soda aqueous solution only through the anion exchange resin layer, and during the passage, water is introduced from the lower end of the cation exchange resin layer. The condensate treatment method according to claim 1, 2, 3, 4, or 5, wherein: