JPS6059037B2 - Condensate treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a condensate treatment method and apparatus for removing impurities present in condensate in order to prevent scale formation and corrosion in boilers and turbines.

In general, condensate desalination equipment uses strongly acidic cation exchange resin H
The other method is the H cycle treatment method, in which a mixture of the OH form and the OH form of a strongly basic anion exchange resin is used, and the cation exchange resin is regenerated when it is saturated with ammonia in the condensate. There is an NH3 cycle treatment method in which the treatment continues using the resin substituted into the ammonia form even after the ammonia in the condensate has broken through.

Recently, many companies have adopted condensate treatment using the NH3 cycle, which requires less frequency of regeneration, in order to save on regeneration chemicals for condensate desalination equipment and from the standpoint of operation and management. However, the operation of the NH3 cycle is subject to various limitations different from those of the H cycle, so it has disadvantages such as the equipment being complicated and regeneration taking a long time, so it is not necessarily a perfect technology. The current situation is that it is impossible to say. Conventionally done NH
In the 3rd cycle, ammonia in the demineralization tower inflow is not adsorbed and removed in the demineralization tower and is contained in the outflow water as it is, so if there are impurities remaining in the resin packed in the demineralization tower after regeneration, When these impurities react with ammonia in the condensate, the impurities are eluted from the resin and mixed with the treated water, deteriorating the quality of the treated water.

For example, when regenerating an anion exchange resin with caustic soda, some of the cation exchange resin comes into contact with the caustic soda and becomes Na.
One example is when this reacts with ammonia in the condensate during the water flow process, causing Na to leak into the treated water. Methods to reduce this sodium leakage have been put to practical use, such as passing a slaked lime solution through or using ammonia water, but both require special chemicals and require a long time for regeneration. There were some shortcomings. The present invention aims to eliminate the drawbacks of these conventional condensate desalination methods and provide an effective treatment method for stably obtaining treated water of extremely high purity not only in H cycle but also in NH3 cycle operation. There is.

Still another object of the present invention is to provide an effective treatment method that can greatly reduce the amount of regenerant in a condensate desalination device and facilitate maintenance. The present invention
A method for treating high-pressure boiler condensate using a condensate treatment device consisting of a precoat t-filter 1, a cation exchange resin 3, and a mixed bed demineralization tower 5 to remove dissolved solids and suspended solids in the condensate In Bo. When treating condensate containing a large amount of suspended solids, such as at the time of starting a furnace, the condensate can be treated with non-ion exchange powders such as powdered cellulose, powdered synthetic fiber, powdered synthetic resin or powdered activated carbon; The water is passed through the pre-coating filter 1 in the first tower, which has a double-layer pre-coating layer 2 containing one type of Oki filter aid or a mixture of several types of these Oki filter aids, to remove suspended solids in the condensate. After removing most of the resin, a granular H-type strongly acidic cation exchange resin layer 4 is added.
The remaining suspended solids 4 and soluble cations are adsorbed and separated through the cation exchange resin column 3 in the second column having This system is characterized in that the condensate is passed through the mixed bed demineralization tower 5 of the third tower, which has a mixed bed resin layer 6 mixed with exchange resin, for final finishing.

Normally, the main component of suspended solids contained in condensate when starting a boiler is iron oxide, and more than 50% of them are precoated with one type of non-ion exchange filter aid. 1, but in order to further increase the removal rate, the removal rate of suspended solids can be improved by using a precoat layer 2 that also includes several types of filter aids.

The type of the precoat offshore filter 1 is not particularly limited, and it may be of any type, such as a method in which a precoat layer is formed on a tubular element commonly used, or a method in which a precoat layer is formed on a leaf-shaped support. It can also be used. In addition, since the stream water discharged from the precoat p-filter 1 in the first column contains some suspended solids, these are removed by adsorption and p-filtration in the cation exchange resin column 3 of the second column. Separate and remove.

At this time, if the condensate contains cations such as sodium, magnesium, and calcium, these impurities are also adsorbed by the H-type strongly acidic cation exchange resin in the second column. The ionic form of the second column cation exchange resin is H-type strongly acidic cation-exchange resin, or NF [4-type] of resin substituted with ammonia form, but when there are many suspended solids such as when starting a boiler, H-type is more preferable because it has a high ability to adsorb metal oxides. Filtering machine 1 pre-coated in the front stage of the second tower
As a result, contamination of the ion exchange resin by suspended solids is significantly reduced. Furthermore, the water effluent from the second tower contains only trace amounts of suspended solids and soluble anions, which are almost completely removed while passing through the H and CR mixed bed desalination tower of the third tower. , from the third column, it is possible to obtain treated water of extremely high purity. When the boiler is started, the purity of the condensate flowing into the condensate treatment equipment gradually increases over time, and the concentration of soluble substances as well as suspended substances decreases. The purity of the effluent water from the two towers increases.

When such normal operation begins, the water quality of the second tower effluent is continuously monitored, and the water flow to the third tower is stopped from the moment the second tower effluent water quality reaches the boiler feed water standard value. The system is stopped and the method is changed to one in which condensate is treated in the first and second towers. In such normal operation, the resin in the second column, which was in H type at the beginning of water flow, adsorbs ammonia in the condensate and gradually becomes N.
Although it is replaced with H4 type resin, the condensate treatment with NH4 type resin can be continued to operate the ammonia cycle. If an increase in anions is detected in the inflowing condensate by measuring the quality of the condensate flowing into the condensate treatment equipment, the outflow water from the second tower is immediately passed to the mixed bed desalination tower 5 in the third tower for final treatment. Perform finishing touches. The resin in the third tower is always H type and 0H type.
Since the ionized solids are on standby in the ionic form, the method of the present invention can deal with a sudden increase in dissolved solids due to a major condenser leakage accident with sufficient margin. be. Another feature of the present invention is that condensate can be treated continuously. In the conventional condensate treatment method using only one mixed-bed demineralization tower, it was necessary to temporarily stop the water flow to the demineralization tower 5 during resin regeneration, but the method of the present invention According to the paper, continuous treatment is possible by switching the valves, so there is an advantage that there is no need for a standby desalination tower or the like. In other words, inside the first tower? During precoating of materials, condensate is treated in the second column alone or in the second column and the third column, and while the resin in the second column is being regenerated, the condensate is treated in the first column and the third column. During the regeneration of resin in the tower, the first
There are some that can perform condensate treatment in the tower and the second tower. In one illustrated embodiment of the invention, the precoat layer 2
A precoat filter 1 with a cation exchange resin layer 4, a cation exchange resin tower 3 with a cation exchange resin layer 4, and a mixed bed desalination tower 5 with a mixed bed resin layer 6 are connected in series through a piping route with a valve. In the condensate treatment equipment connected to the piping route, an inflow condensate water quality monitor Mj, a cation exchange resin tower effluent water quality monitor Mc, a mixed bed desalination tower effluent water quality monitor Me, and a valve 7 are installed in the piping route. ,8,9,10,11,12,13,14,15,1
6,17 are deployed.

In general, in a condensate treatment device, it is common to divide the water to be treated into a plurality of treatment devices and flow the water therethrough.

Although the method of the present invention similarly has a plurality of processing sequences, only one sequence is illustrated here, and the other sequences are omitted. When the wheeler is started, the condensate passes through valve 7 and whose water quality is checked by the inflow condensate water quality monitor Mi.The condensate passes through valve 8 and is introduced into the precoat overnight machine 1, where it is adsorbed while passing through the precoat layer 2. After the suspended solids are removed by the filtration action, the water is introduced into the cation exchange resin tower 3 via valves 9 and 13, and the water quality is measured by a water quality monitor Mc.
Subsequently, it is introduced into the mixed bed desalination tower 5 via the valve 14,
After receiving the final finishing, the water quality is continuously checked by a water quality monitor Me, and the water is led out of the system through a valve 16.

Pre-coat? When the differential pressure of the filter 1 exceeds the set value, the valve 8,
9 is closed and valves 10, 11, and 12 are opened to allow condensate to bypass the first column and flow to the second column, and at the same time, pressurized water is introduced from valve 11 into the first column to peel off the precoat layer 2. and discharged from the tower through valve 12. The valves 11 and 12 are then closed, and although not shown in the drawing, a non-ion-exchangeable filter aid is again precoated using a conventional method, and then the valves 8 and
The method of sequentially passing condensate from the first tower by opening valve 9 and closing valve 10 is repeated. In this way, even during the work of renewing the precoat layer 2, continuous treatment is possible without stopping the operation of the condensate treatment apparatus. The condensate at the time of boiler startup contains suspended solids in the range of tens to thousands of μy/l, but the amount of suspended solids in the effluent from the first column is several μ'/' to
The amount is on the order of several tens of μy/l, and the amount of water flowing out from the second tower is several μy/l at most.
/e decrease to the extent that it is detected. After the boiler is started, the purity of the inflow condensate gradually increases, and the purity of the second tower outflow water increases accordingly, but the water quality of the second tower outflow water satisfies the boiler feed water standard value according to the water quality monitor Mc. After confirming that
The valves 14 and 16 are closed and the valve 17 is opened to bypass the third column and proceed to normal operation.

In normal times, the pre-record layer 2 of the pre-coat filter 1 is renewed in the same way as before, but condensate is treated only in the cation exchange resin column 3 of the second column. is used not only in the H cycle but also in the NH3 cycle, but if regeneration is required by adsorption of impurities, valves 13 and 17 are closed and valves 15 and 16 are opened to temporarily release the condensate. The resin in the second column is treated by bypassing the second column and introducing it into the mixed bed desalination column 5 of the third column. Then, after being backwashed or regenerated with mineral acid, the water flow process is resumed. However, for a while after regeneration, the second tower is connected to the third tower for condensate treatment, and the second tower The third tower is disconnected from the point at which the purity of the outflow water satisfies the standard value.If the inflow condensate water quality monitor Mi detects an increase in dissolved solids, especially anions, in the inflow condensate, the valve is immediately shut off. It is reasonable to close valve 17 and open valves 14 and 16 to pass the second column effluent to the mixed bed demineralization column 5 of the third column to continue the treatment.

Regeneration of the resin in the mixed bed demineralization tower 5 is not shown in the figure, but it can be carried out by either an internal method or an external re-extraction method, and this method is similar to the normal H cycle condensate demineralization method. It may be carried out according to the method used in the salt method, and if the timing is selected when the third tower is on standby, it can be carried out without stopping the operation of the condensate treatment equipment. It is.

According to the method of the present invention, high purity treated water can be obtained even when operating an ammonia cycle by simply regenerating the resin in the second column, and special chemicals such as slaked lime and aqueous ammonia can be used. You can drive without needing any.

As described above, according to the method of the present invention, when the condensate purity is low, such as during boiler startup and condenser leakage,
Condensate treatment is carried out by serial treatment of pre-coat filter 1, cation exchange resin layer 4 and hotbed type resin layer 6, and in normal times when the purity of inflow condensate is high, by two-stage treatment excluding the mixed bed column. This method greatly reduces the use of regenerating chemicals in condensate treatment equipment, simplifies operation and maintenance, and eliminates the drawbacks of conventional condensate desalination methods, allowing it to be used not only in the H cycle but also in the N cycle.
Even in the operation of the H3 cycle, extremely high purity treated water can be stably obtained in large quantities.

[Brief explanation of drawings]

The drawing is a system explanatory diagram showing one embodiment of the present invention. 1: Precoat filter, 2: Precoat layer, 3: Cation exchange resin tower, 4: Cation exchange resin layer, 5: Mixed bed desalination tower, 6: Mixed bed resin layer, 7, 8, 9 ,10,11,1
2, 13, 14, 15, 16, 17: valve, M1: inflow condensate water quality monitor, MC: cation exchange resin tower effluent water quality monitor, Me: mixed bed desalination tower effluent water quality monitor.

Claims (1)

[Claims] 1. In a condensate treatment process in which impurities in condensate are removed by passing boiler condensate through a filter pre-coated with a non-ion exchange powder filter aid and an ion exchange resin tower filled with granular ion exchange resin, During normal times when the amount of impurities in condensate is low,
The condensate is passed through a pre-coat filter in the first column pre-coated with a non-ion exchange filter aid, and then undergoes a pre-coat filtration process, followed by a second column pre-coated with a granular cation exchange resin.
Water is passed through the tower and treated in an adsorption filtration process, and when the boiler starts up or the condenser leaks, when the amount of non-guns in the condensate is relatively large, the condensate treated in the first and second towers is turned into granules. A condensate treatment method characterized by passing water through a third column, a mixed-bed desalination tower, filled with a mixture of a cation exchange resin and an anion exchange resin, and treating the condensate in a desalination step. 2. While the precoat filtration process is renewing the precoat in the first column, the condensate is treated in the adsorption filtration process alone or from the adsorption filtration process through a desalination process. The condensate treatment method described in item 1. 3. During the adsorption filtration step, the resin in the second column is regenerated by backflow or drug flow, and the condensate is directly processed from the precoat filtration step through the desalination step, so that it is omitted from the actual condensate treatment step. The condensate treatment method according to claim 1, wherein: . 4. A patent claim in which the desalination step is omitted from the actual condensate treatment step by treating the condensate with a precoat filtration step and an adsorption filtration step during the regeneration of the resin in the third column. The condensate treatment method according to item 1.