JPS6150675B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for treating condensate when seawater leaks into condensate and the amount of sodium ions increases. Conventionally, in thermal power plants, condensate dewatering is performed using a mixed bed ion exchange tower (hereinafter referred to as ammonium mixed bed ion exchange tower) consisting of a combination of an ammonium type cation exchange resin and a hydroxyl group type anion exchange resin. Condensate desalination equipment that uses a mixed bed ion exchange tower (hereinafter referred to as hydrogen mixed bed ion exchange tower) consisting of a salt unit, a hydrogen type cation exchange resin, and a hydroxyl group type anion exchange resin is used. It was hot.
The advantages and disadvantages of both types of condensate desalination equipment are explained below.
is now maintained at a high level of 9.4 or higher, so ammonia is injected into the condensate system, and the concentration of ammonia in the condensate reaches 3000 ppb as CaCO ₃ or higher. This phenomenon is particularly noticeable in subcritical or supercritical pressure thermal power plants. However, in this case, the total amount of impurities other than ammonia present in the condensate is only a few tens of ppb as CaCO ₃ as long as the condensate cooling system is operating normally.
Therefore, when this condensate is treated with, for example, a hydrogen mixed ion exchange column, ammonia is also removed at the same time as the impurities in the condensate are removed. Naturally, the higher the condensate pH, in other words, the higher the concentration of ammonia in the condensate, the more frequently the resin in the hydrogen mixed bed ion exchange tower must be regenerated, leading to an increase in chemical costs. In addition, since ammonia in the condensate is removed, ammonia must be added to the treated water again. However, with the hydrogen type mixed bed ion exchange tower, even if a large amount of seawater leaks into the condensate, highly purified treated water can be obtained, and almost no sodium ions leak until the ion exchange resin reaches the flow-through point, resulting in stable water. It has the advantage that treated water can be obtained. Next, regarding the ammonium type mixed bed ion exchange tower, since it removes impurities other than ammonia without removing the ammonia in the condensate, compared to the hydrogen type mixed bed ion exchange tower that treats condensate, the ion exchange resin The regeneration frequency is significantly reduced, which naturally reduces the chemical cost, and since ammonia in the condensate is not removed, the PH of the treated water changes only slightly, and therefore the hydrogen mixed bed ion exchange tower This method has the advantage that it is not necessary to add ammonia to the treated water for pH control, unlike when using water. However, if a large amount of seawater leaks into the condensate, sodium ions may leak unless the proportion of the sodium-type cation exchange resin after regeneration is minimized. The amount of sodium leaked is largely controlled by the ratio of the sodium form cation exchange resin to the total amount of cation exchange resin after regeneration, and if the ratio of the ion exchange resin is constant, the condensate at the entrance of the ion exchange tower The more total cations there are, the greater the sodium leak. Various methods have been used in the past to minimize the proportion of sodium cation exchange resin after regeneration of an ammonium mixed bed ion exchange tower. The current situation is that the exchanged resin remains. Therefore, a seawater leak occurs in the condenser,
There is a drawback that when the amount of cations in the condensate increases, sodium leakage from the treated water inevitably increases. The present invention aims to solve the above-mentioned drawbacks of the ammonium type mixed bed ion exchange tower, and to provide a condensate treatment method that enables highly purified treated water to be obtained even when seawater leaks into the condensate. It's a method. That is, the present invention provides a condensate treatment apparatus in which high-temperature, high-pressure boiler condensate containing ammonia is passed in parallel through several ammonium-type mixed bed ion exchange towers.
When seawater, which is cooling water, leaks into condensate, one of the mixed bed ion exchange towers is immediately converted into a hydrogen type mixed bed ion exchange tower to treat the condensate containing seawater, and then sequentially converts the condensate into hydrogen. This is a method for treating condensate in the event of a seawater leak, which is characterized by increasing the proportion occupied by a mixed bed type ion exchange column and decreasing the proportion occupied by an ammonium type mixed bed type ion exchange column. The present invention will be explained in detail below using the drawings. The drawing is an explanatory diagram showing the flow of a condensate desalination apparatus which is an example of an embodiment of the present invention, and includes four ion exchange towers A to D and a separation tower/regeneration tower 10.
and a regeneration system consisting of a resin storage tank 11. To explain the basic flow when this condensate desalination equipment is used as an ammonium type mixed bed desalination equipment, for example, condensate 1, which is the water to be treated, is filled with mixed ion exchange resins 2 to 5. Water is passed through each of the ion exchange towers A to D to obtain treated water 6. For example, when the ion exchange tower A reaches the end point of water flow, the valves 7 and 8 attached to the inlet and outlet of the ion exchange tower A are closed, and only the ion exchange tower A is cut off from the water flow. The mixed ion exchange resin 2 in the ion exchange tower A is made into a slurry and is transferred to a separation tower/regeneration tower 10 via a resin transfer pipe 9. Next, after the entire amount of the mixed ion exchange resin 2 in the ion exchange tower A is transferred, the recycled mixed ion exchange resin 12 previously stored in the resin storage tank 11 is ionized in slurry form through the resin transfer pipe 9'. The exchange tower A is filled with water, and after this filling is completed, valves 7 and 8 are opened to continue water flow. The recycled mixed ion exchange resin 12 stored in the resin storage tank 11 is usually a mixed ion exchange resin consisting of a hydrogen type cation exchange resin and a hydroxyl group type anion exchange resin. The ion exchange tower A is filled with the resin, and condensate is passed through it, and the ammonium ions contained in the condensate convert the cation exchange resin in the hydrogen form into the ammonium form. That is, it has conventionally been the case that an ammonium type mixed bed ion exchange tower is operated as a hydrogen type mixed bed ion exchange tower at the initial stage of water flow. It usually takes 3 to 7 days to turn this condensate into ammonium form by passing water through it, depending on the amount of resin, and then it is operated as an ammonium type mixed bed ion exchange tower.
It will be operated for 20-50 days. As mentioned above, in an ammonium type mixed bed ion exchange tower, it is necessary to minimize the proportion of sodium type cation exchange resin after regeneration in order to prevent sodium from leaking into the water to be treated. Unlike condensate desalination plants using hydrogen mixed bed ion exchange columns, special regeneration methods have been implemented. That is, in regenerating the used mixed ion exchange resin 2 transferred to the separation tower/regeneration tower 10, the method disclosed in Japanese Patent Publication No. 47-5085, Japanese Patent Publication No. 47-4035, Japanese Patent Publication No. 47-14441, etc. is used. will be played.
In all of these methods, when regenerating the cation exchange resin and anion exchange resin that have been backwashed and separated with water, the cation exchange resin at the separation interface is used as a regenerating agent for the anion exchange resin as much as possible. After regenerating the anion exchange resin, the fine cation exchange resin mixed in the anion exchange resin becomes sodium form when the anion exchange resin is regenerated. The desired purpose is achieved by passing an ammonia solution through this resin layer to convert the cation exchange resin, which is in the sodium form, into the ammonium form. Another method is to separate a cation exchange resin from an anion exchange resin by adding a liquid having a specific gravity between those of both ion exchange resins, such as an approximately 10% caustic soda solution, to the two ion exchange resins to determine the difference in specific gravity. There is also a method of separately regenerating both ion exchange resins after separation. This method has the advantage of being able to separate fine cation exchange resins more effectively than backwashing with water, but it requires an extra operation of specific gravity separation before regeneration, and the It has a drawback that the cation exchange resin becomes completely in the sodium form when the ion exchange resin comes into contact with the separated caustic soda solution. Through the various methods described above, the ratio of sodium-type cation exchange resin to the total cation exchange resin after regeneration (hereinafter referred to as the sodium fraction) is minimized. It is economically impossible to set the value to 0, and currently it is around 0.002. For example, an ammonium type mixed bed ion exchange column with a sodium fraction of 0.002 is fed with ordinary condensate, for example, an ammonia content of about 3200 ppb as CaCO ₃ ,
Sodium ion content is approximately 5ppb as CaCO ₃ ,
If condensate with a pH of 9.4 enters, the amount of sodium leaking into the treated water will be approximately 2 ppb as CaCO ₃ . However, condensate water leaked from seawater as cooling water to the ammonium type mixed bed ion exchange tower has an ammonia content of about 3200 ppb as CaCO ₃ , a sodium ion content of about 1000 ppb as CaCO ₃ , PH
If 9.4% condensate flows in, the amount of sodium leaking into the treated water will be approximately 5 ppb as CaCO ₃ . In this way, in an ammonium type mixed bed ion exchange tower, when the sodium fraction is constant,
The greater the amount of total cations in the water to be treated, the greater the sodium leakage, and this is due to the following reasons. In other words, the principle of cation exchange in an ammonium type mixed bed ion exchange column is shown as equation (1), and the product of the reaction in the liquid shown on the right side also contains ammonium ions. Due to the presence of This is because it moves to the left. By the way, as mentioned above, for example, when normal condensate flows into an ammonium type mixed bed ion exchange tower with a sodium fraction of 0.002, the sodium leak in the treated water is approximately 2 ppb as CaCO ₃ , and the sodium leak in the treated water is approximately 2 ppb as CaCO 3. Sodium in condensate
When increasing to 1000ppb, the sodium leakage of treated water will be about 5ppb, and the difference is about 3ppb as
CaCO ₃ , a value that hardly causes any problems in so-called normal water treatment equipment. However, in subcritical pressure or supercritical pressure boilers where all of the water supplied is steam, even a slight increase in sodium cannot be ignored. In other words, in a thermal power plant with such a boiler, the amount of condensate treated is enormous, and usually around 400 m ³ /H of condensate is treated per ion exchange tower shown in the drawing. Three or four towers are operated in parallel, and their total processing capacity ranges from 1200m ³ /H to 1600m ³ /H, with some large ones reaching 2000m ³ /H. Since all of the large volume of condensate is converted into steam, even if the concentration of non-volatile substances such as sodium present in the condensate is minute, it becomes a value that cannot be ignored when converted to the total amount.
This must be reduced as much as possible. Therefore, in the present invention, when seawater, which is cooling water, leaks into condensate, one of the several ammonium type mixed bed ion exchange towers is immediately converted into a hydrogen type mixed bed ion exchange tower. That is, one arbitrarily selected column among the ion exchange columns A to D shown in the drawing, for example, column B, is unconditionally connected to valve 7' even if the column has not reached the end point of condensate flow. , 8' are closed to cut off the condensate flow, and the mixed ion exchange resin 3, which has not yet reached the end point of the condensate flow, is made into a slurry and sent to the separation tower/regeneration tower 10 via the resin transfer pipe 9. Transport. After the entire mixed ion exchange resin 3 in the ion exchange tower B is transferred, the recycled mixed ion exchange resin 12 previously stored in the resin storage tank 11 is ion-exchanged in slurry form through the resin transfer pipe 9'. Charge column B. As mentioned above, the recycled mixed ion exchange resin 12 stored in the resin storage tank 11 is composed of a hydrogen type cation exchange resin and a hydroxyl group type anion exchange resin, so water flow is restarted after this transfer is completed. Then, the ion exchange tower B will be operated as a hydrogen type mixed bed ion exchange tower. When the ion exchange column B is converted into a hydrogen mixed bed ion exchange column, the amount of sodium in the treated water of the column becomes almost undetectable. In other words, in the case of a hydrogen mixed bed ion exchange column, the principle of cation exchange is shown as equation (2), and the liquid in the liquid shown on the right side is Hydrogen ions, which are the reaction products, combine with hydroxyl ions, which are the reaction products of the hydroxyl group-type anion exchange resin, to form water, so the reaction progresses to the right to the limit, and the ammonium-type mixed bed ions described above Unlike an exchange column, a reverse reaction does not occur, and sodium ions as well as ammonium ions are removed to the maximum extent, regardless of the sodium fraction in the resin and the total amount of cations in the influent water. The ion exchange tower B has a point at which ammonia begins to leak into the treated water as the end point of the water flow. On the other hand, the mixed ion exchange resin 3 transferred to the separation tower/regeneration tower 10 is immediately regenerated into a hydrogen type cation exchange resin and a hydroxyl group type anion exchange resin by a conventional method. Transfer to resin storage tank 11. After this transfer is completed, the ion exchange towers A, C, and D
One arbitrarily selected tower is unconditionally cut off from condensate water flow in the same way as tower B, even if that tower has not reached the end point of condensate water flow, and the mixing inside the tower is The ion exchange resin is transferred to the separation tower/regeneration tower 10, and then the regenerated mixed ion exchange resin stored in the resin storage tank 11 is transferred to the ion exchange tower where the condensate water flow is cut off. Restart condensate water flow in the same way as tower B. Thereafter, by sequentially repeating such a procedure, the ion exchange towers A to D are sequentially converted into hydrogen mixed bed type ion exchange towers. In this way, when seawater, which is cooling water, leaked into condensate, several ion exchange towers A to D, which had been used as ammonia mixed bed ion exchange towers,
Immediately convert any one of the columns into a hydrogen type mixed bed ion exchange column, and then immediately reduce the proportion of the ammonium type mixed bed ion exchange column and increase the proportion of the hydrogen type mixed bed ion exchange column. This allows the amount of sodium in the treated water to be gradually reduced. In this case, the regeneration of the ion exchange resin in the separation tower/regeneration tower 10 uses the regenerated ion exchange resin as a hydrogen type mixed bed type ion exchange tower, so the regeneration of the ion exchange resin in the separation tower/regeneration tower 10 is carried out in accordance with Japanese Patent Publication No. 47-5085 as mentioned above. It is not necessary to particularly reduce the sodium fraction by such methods, and regeneration by ordinary methods may be used. Next, to explain seawater leaks in the condensate cooling system, in normal thermal power plants, the condenser is divided into several parts, and each of the divided condensers has an acid conductor on the outlet side. A conductivity meter is installed, and the leakage of seawater from each condenser is monitored based on the value of this acid conductivity meter. An acid conductivity meter takes a small amount of condensate and passes it through a cation exchange resin layer that has been completely regenerated.
It measures the conductivity of the treated water, and if seawater leaks into the condensate and salt is mixed in, hydrochloric acid corresponding to the amount of salt will be detected. The acid conductivity value of normal condensate without seawater leaking into the condensate is usually 0.1 to 0.15 μυ/cm, but if seawater leaks into the condensate, the acid conductivity will naturally change depending on the amount of seawater leakage. The value of conductivity varies, but in the case of a normal thermal power plant, the value of acid conductivity is 0.5μυ/
When the seawater level exceeds cm, it is considered an abnormal condition and the cooler that is displaying that value is shut off and the seawater leak location is inspected. Therefore, the method of the present invention is effective when carried out immediately after the acid conductivity value of the condensate system becomes abnormal as described above. If the value of the acid conductivity increases, convert all of the several ion exchange towers to hydrogen type mixed bed ion exchange towers, and if the acid conductivity value is an abnormal value but does not increase significantly, the acid The rate at which the hydrogen type mixed bed ion exchange tower is increased may be appropriately determined depending on the value of conductivity. Examples of the present invention will be described below. Example Amberlite (registered trademark) 200CT was used as the cation exchange resin, Amberlite IRA-900 was used as the anion exchange resin, and hydrogen form cations were used at a mixing ratio of 1:1 for each ion composition shown in Table 1. A mixed ion exchange resin of an exchange resin and a hydroxyl type anion exchange resin, and a mixed ion exchange resin of an ammonium type cation exchange resin and a hydroxyl type anion exchange resin at a mixing ratio of 1:1 were prepared, and each mixed ion exchange resin was prepared. 500 ml was packed into several experimental columns so that the resin bed height was 1 m, and several hydrogen type mixed bed ion exchange towers and several ammonium type mixed bed ion exchange towers were prepared respectively.

[Table] Next, dissolve 28% ammonia water and salt, which are special reagents, in pure water of 0.1 μυ/cm or less, and add 4000 ppb of ammonium hydroxide as CaCO ₃ and 3000 ppn of salt.
Synthetic condensate water was prepared assuming a CaCO ₃ seawater leak, and this synthetic water was sent to each set of four ion exchange towers at 125 m/H (62.5/H) in the combinations shown in Table 2. ) at a flow rate of
The sodium content of the mixed treated water from each set of four ion exchange towers was measured and shown in Table 2.

[Table] As shown in Table 2, under condensation conditions assuming a seawater leak, it is better to increase the proportion of the hydrogen type mixed bed ion exchange tower than to use the ammonium type mixed bed ion exchange tower alone. It was confirmed that the amount of sodium leakage can be reduced.

[Brief explanation of the drawing]

The drawing is an explanatory diagram showing the flow of a condensate desalination apparatus that is an example of an embodiment of the present invention. 1... Condensate, 2, 3, 4, 5... Mixed ion exchange resin, 6... Treated water, 7, 8... Valve, 9... Resin transfer pipe, 10... Separation tower and regeneration tower, 11 ... Resin storage tank, 12 ... Regenerated mixed ion exchange resin.

Claims (1)

[Claims] 1. In a condensate desalination device in which high-temperature, high-pressure boiler condensate containing ammonia is passed in parallel through several mixed-bed ion exchange towers made of a combination of an ammonium-type cation exchange resin and a hydroxyl-type anion exchange resin. When seawater, which is cooling water, leaks into the condensate, one of the mixed bed ion exchange towers is immediately replaced with a mixed bed type ion exchange tower consisting of a combination of a hydrogen type cation exchange resin and a hydroxyl group type anion exchange resin. The condensate is treated as an ion exchange column, and then the proportion of a mixed bed ion exchange column consisting of a combination of a hydrogen type cation exchange resin and a hydroxyl group type anion exchange resin is increased, and ammonium type cations are treated. A method for treating condensate at the time of a seawater leak, characterized by reducing the proportion occupied by a mixed-bed ion exchange tower made of a combination of an exchange resin and a hydroxyl anion exchange resin.