JPS5813229B2 - Condensate treatment method - Google Patents

Description

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

In general, as boiler operating conditions become higher in temperature and pressure, the importance of condensate treatment has become widely recognized, and good treatment is usually achieved with a condensate desalination device using a mixed bed type ion exchange resin tower.

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.
One is the H cycle treatment method in which the cation exchange resin is regenerated when it is saturated with ammonia in the condensate, and the other is a resin in which the cation exchange resin is continuously replaced with ammonia even after the resin has been saturated with ammonia in the condensate. There is an NH3 cycle treatment method that uses NH3 to continue treatment.

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

However, the operation of the NH3 cycle is subject to various limitations different from those of the H cycle, and there are drawbacks such as the equipment being complicated and regeneration taking a long time, so it cannot necessarily be said that it is a perfected technology. The current situation is that there is no such thing.

In other words, when operating a mixed bed type ion exchange resin bed in an ammonia cycle, the salt form resin present in the mixed bed causes impurity leakage during ammonia break, so the proportion of salt form resin contained in the mixed bed is It is necessary to keep it low.

In particular, the cation exchange resin mixed in the anion exchange resin layer is converted to the N form by caustic soda, which is a regenerating agent for the anion exchange resin, but the Na form cation exchange resin easily exchanges ions with NH4+ in the condensate, and the boiler N harmful to
The proportion of Na type cation exchange resin in the mixed bed must be kept extremely low in order to cause a+ leakage.

However, in the normal mixed-bed ion exchange resin regeneration method that uses the difference in specific gravity of the resin to perform backwash separation, it is difficult to completely separate the resin, and several percent of the salt-form resin is produced during regeneration. is difficult to avoid, and therefore operation on an ammonia cycle is impossible.

Various condensate treatment methods have been devised to enable operation in this ammonia cycle. One method involves passing slaked lime or ammonia through an anion exchange resin layer that has been regenerated by a conventional method to exchange Na-type cations generated during regeneration. NH resin
There are methods of converting to Ca type, which is difficult to exchange with 4+, or NH4 type, which is harmless to the boiler, adding an inert resin with an intermediate specific gravity between cation exchange resin and anion exchange resin, or using a solution with intermediate specific gravity. There is a known method in which the resin is completely separated, and a method in which only the completely separated and regenerated resin is filled by removing the portions where the resin has not been sufficiently separated.

However, these methods require extra chemical injection equipment, chemical costs, etc., and require a long time for regeneration, so they are not yet recognized as perfected technologies.

In order to eliminate these conventional drawbacks, the present inventors first developed an economical condensate treatment method that uses the entire amount of recycled resin without using any extra chemicals other than the usual recycling chemicals. However, the present invention relates to an effective method that further improves the condensate treatment method proposed previously.

That is, in recent years, two or three boiler accidents believed to be caused by trace amounts of Na+ leaking from condensate desalination equipment have been experienced, and water quality requirements regarding Na+ are becoming increasingly strict.

In the condensate treatment method proposed earlier, the entire amount of regenerated resin is charged again into the demineralization tower, so the second stage is filled with the remaining resin after removing the resin that does not substantially contain salt-form resin. The salt form resin content of the mixed bed is slightly higher than that of a normal mixed bed type ion exchange resin bed in which the entire amount of regenerated resin is mixed uniformly.

In a mixed bed that operates only on the H cycle, the allowable amount of salt resin content is much more relaxed than in a mixed bed that operates on the ammonia cycle. Although there is no problem even if the amount is slightly increased, considering the recent strict water quality requirements, it may not necessarily be a good idea to refill the desalination tower with the entire amount of regenerated resin.

The present invention does not charge part of the salt-form resin that occurs near the resin interface during backwash separation and causes impurity leaks into the demineralization tower.
By leaving it in the regeneration tower, the content of salt-form resin in the second mixed bed is mainly reduced, further reducing the leakage amount of Na+,
This is an attempt to meet high water quality requirements.

In view of the spirit of the present invention, the salt form resin content of the second mixed bed may be the same as or slightly lower than that of a normal mixed bed type ion exchange resin bed, and therefore a single mixed bed can be used for ammonia cycling. It is not necessary to leave a large amount of resin in the regeneration tower in order to significantly reduce the salt-form resin content, as is the case when operating in achieved.

Another object of the present invention is that it is possible to stably obtain high-purity treated water without using any extra chemicals other than ordinary regeneration chemicals, and to enable operation in the NH3 (ammonia) cycle as well as the H cycle. It is an object of the present invention to provide a treatment method that can be used in a variety of ways, and that can also facilitate maintenance and management.

The present invention uses two beds: a cation exchange resin bed that does not substantially contain salt form resin, and a mixed bed type ion exchange resin bed. The second mixed bed is filled with a resin containing a small amount of salt-form resin, and when the inflow condensate water quality is relatively good, water is passed in series from the cation exchange resin bed to the first mixed bed, and the treated water is When the water quality deteriorates, a second hot bed is added to the final stage, and when refilling the desalination tower in the desalination process where water is passed through these three beds in series, the entire regenerated resin layer is added to the upper layer of the anion exchange resin layer. The lower layer, the upper layer of the cation exchange resin layer, the middle layer, the lower layer, and the resin near the resin interface where both resins are significantly mixed are each divided into 6 parts, and a small amount of the resin that became salt form during resin regeneration is removed. The containing parts, that is, the upper layer of the cation exchange resin layer that was backwashed and classified during regeneration, and the lower layer of the anion exchange resin layer that was backwashed and classified during regeneration, are mixed, and a second mixed bed is prepared. The lower part of the cation exchange resin layer which was backwashed and classified during regeneration, and the upper part of the anion exchange resin layer which was backwashed and classified during regeneration. The middle layer of the cation exchange resin layer, which has been backwashed and classified during regeneration, is packed alone into the cation exchange resin bed, and the mixture of both resins is significantly mixed. The feature is that the area near the interface is left unfilled and is recycled in addition to the resin that has undergone the desalination process during the next resin regeneration.

One embodiment of the present invention will be described with reference to the drawings. The condensate treatment is continued, the demineralization tower 1 that has lost its processing capacity is removed from the demineralization process, and all the resin inside is demineralized by the resin transfer line 20. The salt is transferred from the salt tower 1 to the cation regeneration tower 2.

After separating the cation exchange resin and anion exchange resin by backwashing, mineral acid is passed upward through the cation exchange resin layer from the bottom of the cation regeneration tower, and waste acid is discharged from the acid discharge pipe 18 provided near the resin interface. It is extracted and the cation exchange resin layer is regenerated.

During this time, water is flowed from the upper part of the tower and discharged outside the tower from the acid discharge pipe 18 to prevent the acid from diffusing into the anion exchange resin layer in the upper layer and to maintain the cation exchange resin layer as a fixed bed.

When the drug is passed in an upward flow, it is expected that the regeneration rate of the lower layer of the cation exchange resin layer will be slightly higher, which is more convenient for the present invention.

After passing the medicine, the cation exchange resin layer was washed with water, and then the resin transfer line 21 opened slightly below the resin interface.
The anion exchange resin layer and the heavily mixed portion of the resin near the resin interface are transferred to the anion regeneration tower 3, and the transferred resin is backwashed again to separate the anion exchange resin and a small amount of cation exchange resin. After regenerating the anion exchange resin, the resin layer is washed with water.

Of the resin regenerated in the cation regeneration tower 2, the upper layer 6 of the cation exchange resin layer is sent to the demineralization tower 1 via the resin transfer line 22, and the middle layer 7 is transferred to the cation exchange resin layer 5 via the resin transfer line 23. The lower layer 8 is transferred to the resin mixing tank 4 via the resin transfer line 24, the upper layer 9 of the anion exchange resin layer in the anion regeneration tower 3 is transferred to the resin mixing tank 4 via the resin transfer line 25, and the lower layer 10 is transferred to the resin mixing tank 4. Desalination tower 1 in line 26
On the other hand, the resin interface portion 11 left at the bottom of the anion regeneration tower is transferred to the cation regeneration tower 2 via the resin transfer line 27 and added to the resin to be regenerated next time.

Next, in order to refill the resin into the demineralization tower 1, the demineralization tower 1
The transferred resins are mixed and washed with water to form a mixed bed 14 containing a small amount of salt-form resin at the bottom of the column, and a resin mixing tank 4 is placed at the top of the column.
The resin mixed and washed with water is filled through the transfer line 28,
A mixed bed 13 substantially free of salt-form resin is formed, and the resin transferred to the cation-exchange resin storage tank 5 is filled in the upper part of the mixed bed 13 via the resin transfer line 29 to form a cation-exchange bed 13 substantially free of salt-form resin. A resin bed 12 is formed as the top layer.

On the other hand, when passing water, condensate is allowed to flow in from the condensate inflow pipe 15 at the top of the desalination tower, and when the quality of the inflow condensate water is relatively good, the treated water is taken out from the treated water outflow pipe 16 at the middle of the tower. In this case, since the condensate is treated with the cation exchange resin bed 12 and the mixed bed 13, which do not substantially contain salt-form resin, treated water of extremely high purity can be obtained, and even when operated in an ammonia cycle, No hindrance will occur.

In addition, since the cation exchange resin bed 12 is provided, the performance of removing suspended substances such as metal oxides is excellent, and the contamination of the anion exchange resin in the mixed bed can be prevented.

Condensate treatment continues in this state, and the cation exchange resin bed 12
If treatment is no longer possible with only the mixed bed 13, or if a condenser leak occurs, the treated water outlet is switched from the treated water outlet pipe 16 to the treated water outlet pipe 17 at the bottom of the tower by opening and closing a valve, and all Processing will be performed using a resin layer.

In this case, since the mixed bed 14 contains a small amount of salt-form resin, it cannot be operated in the ammonia cycle, but since the significant portion of salt-form resin production due to resin mixing has been removed, as long as it is operated in the H cycle, It is possible to obtain treated water quality that is equal to or higher than that of a normal mixed bed desalination tower.

In addition, since it is not possible to operate in an ammonia cycle in a process using the entire resin layer, the desalting process ends immediately before the ammonia break, and all the resin is transferred from the desalting tower 1 to the cation regeneration tower 2, where the previous resin regeneration process is carried out. It is effective to add the resin interface portion 11 left at the time and perform a resin regeneration operation.

In the figure, 19 is a water collector, 30, 31, 32, 33, 34, 3
5, 36, 37, 38, 39, 40 are valves, 41 is a water collector, 42, 43 are regeneration liquid supply pipes, 44, 45 are drain pipes, 4
6, 47, 48 are valves, 49 is a cleaning water supply pipe, and 50 is a valve.

If condensate treatment is performed according to the present invention, it becomes possible to operate in an ammonia cycle without using extra chemicals, and since the mixed bed at the top of the demineralization tower does not substantially contain salt-form resin, Cl.
-, SO: Almost no leakage of first-class anions occurs.

In addition, since about half of the total amount of resin is normally kept in H type and OH type, it has sufficient treatment capacity against capacitor leaks, and also has the properties of two mixed beds. Slight changes can be made to make the process more economical.

Furthermore, if the cationic resin is regenerated in an upward flow, the cationic resin with a high regeneration rate will be delivered to the mixed bed type resin layer, which will be more convenient.

As described above, if the resin is regenerated and filled according to the present invention, it becomes possible to operate in an ammonia cycle without using any extra chemicals other than the usual regeneration chemicals, resulting in economical recovery. Water treatment can be performed, and suspended solids such as metal oxides can be efficiently removed because a cation exchange resin bed is provided at the front stage.Also, the amount of resin left in the regeneration tower is relatively small, so the resin It is also easy to maintain a balance, so highly purified treated water can be stably obtained.

In addition, Na leakage during ammonia break can be accurately prevented, condensate treatment can be performed with sufficient margin even in the event of capacitor leakage, and treatment efficiency can be significantly increased by performing condensate treatment continuously. The regeneration rate has been significantly increased, operation and maintenance has become easier, and the drawbacks of conventional condensate desalination methods have been eliminated, allowing stable and large amounts of extremely high-purity treated water to be produced not only in the H cycle but also in the NH3 cycle. There are also benefits that can be obtained and the processing costs are also economical.

[Brief explanation of the drawing]

The drawing is a system explanatory diagram showing one embodiment of the present invention. 1... Desalting tower, 2... Cation regeneration tower, 3... Anion regeneration tower, 4... Resin mixing tank, 5...・Cation exchange resin storage tank, 6...
... Upper layer of cation exchange resin layer, 7...
Middle part of the cation exchange resin layer, 8... Lower part of the cation exchange resin layer, 9... Upper part of the anion exchange resin layer, 10... Lower part of the anion exchange resin layer. Middle part, 11...Resin interface part, 12...
・Cation exchange resin bed, 13, 14...mixed bed,
15... Condensate inflow pipe, 16, 17...
Treated water outflow pipe, 20, 21, 22, 23, 24, 25
, 26, 27, 28, 29... Resin transfer line.

Claims (1)

[Scope of Claims] 1. A resin that has undergone a desalination process in a condensate desalination process in which impurities in the condensate are removed by passing condensate in series from a cation exchange resin layer to a mixed bed ion exchange resin layer. is transferred from the demineralization tower to the regeneration tower, and after performing backwash separation, chemical passage, and water washing, as in the case of normally regenerating mixed-bed ion exchange resins, when filling the demineralization tower again, The regenerated entire resin layer was divided into six regions, each with the upper and lower parts of the anion exchange resin layer, the upper part, middle part, and lower part of the cation exchange resin layer, and the resin near the resin interface where both resins were significantly mixed. The upper layer of the cation-exchange resin layer is divided into two parts and contains a small amount of resin that has become salt form during resin regeneration, namely, the upper layer of the cation-exchange resin layer that has been backwashed and classified during regeneration, and the anion-exchange resin layer that has been backwashed and classified during regeneration. The lower layer of the resin layer is mixed with the lower layer of the cation exchange resin layer, and the mixture is filled into a second mixed bed. and the upper layer of the anion exchange resin that was backwashed and classified during regeneration, and filled into the first mixed bed, and the middle layer of the cation exchange resin that was backwashed and classified during regeneration It is recommended to fill the cation exchange resin bed alone, leave the area near the resin interface where there is significant mixing of both resins without filling, and add it to the resin that has completed the desalination process during the next resin regeneration. Characteristic condensate treatment method. 2 A cation exchange resin bed that does not substantially contain a salt form resin and two mixed bed type ion exchange resin beds are used, the first mixed bed contains a resin that does not substantially contain a salt form resin, and the second The mixed bed is filled with a resin containing a small amount of salt-form resin, and when the inflow condensate water quality is relatively good, water is passed in series from the cation exchange resin bed to the first mixed bed to prevent deterioration of the treated water quality. The condensate treatment method according to claim 1, wherein a second mixed bed is sometimes added to the final stage and water is passed through these three beds in series. 3. In the desalination step, the middle layer of the cation exchange resin layer that has been backwashed and classified during regeneration is mixed with the upper layer of the anion exchange resin layer that has been backwashed and classified during regeneration, and a first mixed bed is formed. The condensate according to claim 1 or 2 is carried out by filling the lower layer of the cation exchange resin bed, which has been backwashed and classified during regeneration, alone into the cation exchange resin bed. Processing method. 4 The regeneration step uses two regeneration towers, and among the resin layers after backwashing and separation, the anion exchange resin layer and the resin layer near the resin interface where both resins are significantly mixed are treated with anion exchange resin respectively. The resin is transferred to the regeneration tower, and the cation exchange resin and anion exchange resin are passed through the resin separately. When filling the regenerated resin, the part located at the bottom of the anion exchange resin regeneration tower where the two resins are significantly mixed is not filled. Claims 1, 2, or 3, which are retained and recycled in addition to the resin that has undergone the desalting process during the next resin regeneration.
Condensate treatment method described in section. 5. Claims 1, 2, 3, or 4, wherein the cation exchange resin regeneration step involves passing mineral acid through the cation exchange resin layer in an upward flow. condensate treatment method. 6. In the regeneration step, after backwashing and separating the cation exchange resin and anion exchange resin in a cation exchange resin regeneration tower, the cation exchange resin layer is further treated with mineral acid in an upward flow and washed with water, and then the anion exchange resin layer is The condensate treatment method according to claim 4 or 5, wherein the condensate near the resin interface where both resins are significantly mixed is transferred to an anion exchange resin regeneration tower.