JPH0221312B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a power generation plant, and particularly relates to a water treatment method suitable for preventing corrosion of system equipment and piping caused by system water, and a power generation plant to which this method is applied. [Background of the Invention] Conventionally, in thermal power plants, etc., in order to prevent corrosion of system equipment, piping, etc., the amount of oxygen in system water has been reduced.
Degas to 10PPb or less, and add a trace amount of alkaline agent [e.g. NH ₄ OH, N ₂ H ₄ (to remove dissolved oxygen).
NH ₄ OH), NaOH, Na ₃ PO ₄ , Na ₂ HPO ₄
etc.] are added. As for the amount of alkaline agent added, the PH of the system water is determined as shown in Figure 1.
11.0 (HHUhlig, Corrosion Handbook
p.525 Fig3). Further, in thermal power plants, steel is the main material, but copper or an alloy containing copper is used in condensers and feed water heaters from the viewpoint of heat exchange efficiency. Therefore,
From the perspective of the elution amount at the PH value of steel and copper materials, it is important to consider
Considerations are being made as to what level the pH value should be.
One of the results is that, as shown in Figures 2 and 3, increasing the pH value of system water reduces the amount of iron eluted, but On the contrary, the amount of copper eluted will increase significantly (Rennosuke Okamoto, “Taketoyo Thermal Power Plant No. 1 Unit Water Treatment Characteristics Test Results”, Thermal Power Generation Vol. 20, No. 5, p. .498-517, May 1969). For this reason, the optimal PH value in the system water of a thermal power plant is 9.4, which minimizes the amount of iron and copper eluted. In addition, according to the Japanese Industrial Standards (JIS B8223-1977) "Boiler water supply and boiler water quality", the water supply pH of drum boiler type thermal power plants is specified to be 8 to 9.5, and if the water supply system has copper alloy equipment. teeth,
The upper limit of pH is kept at 9.0. Furthermore, the pH of the feed water for once-through boiler type thermal power plants is specified as 8.5 to 9.2 when the feed water heater pipe material is made of copper alloy, and 9.0 to 9.5 when the pipe material is steel pipe. As mentioned above, the upper limit for the pH value of water supplied to thermal power plants is 9.5. In addition, water quality in the secondary system of a pressurized water nuclear power plant, where water quality management is similar to that of a thermal power plant, is
The upper limit of the PH value is also 9.5 for the same reason as mentioned above. As described above, power generation plants are exposed to corrosion products leached from the constituent steel materials and copper alloys due to long-term use, such as in boiler water wall pipes, turbines, high-pressure feed water heaters, feed water flow meters, feed water regulating valves, etc. (1) Overheating of pipes, (2) Decrease in turbine output, (3) Decrease in heat exchange rate, (4) Overload of pump due to increase in differential pressure, (5) Improper flow rate indication. Causes homospecific species. This has resulted in the disadvantage that pickling of corrosion products, which requires manual labor and large amounts of chemicals, and jet cleaning, which involves spraying high-pressure water, must be carried out periodically. Pressurized water nuclear power plants have drawbacks such as corrosion products being carried into the steam generator and causing denting. On the other hand, in thermal power plants, there is a condensate desalination device downstream of the condensate pump, which uses an ammonia type ion exchange resin to purify the condensate. However, ammonia type ion exchange resin is used as a sodium type ion exchange resin (R-
This Na leaks out as Na ⁺ . The amount of Na ⁺ in the feed water of thermal power plants must be carefully considered and kept below 3 ppb, otherwise it may be carried into the turbine and cause cracks in the turbine rotor disk. Ion exchange resin outlet
As shown in Figure 4, the relationship between the Na ⁺ amount and the economizer inlet PH shows that the higher the PH value, the greater the Na ⁺ amount, and even at PH9.5, the Na ⁺ amount is 3 ppb or more. Therefore, it can be seen from this result that the PH value in the water supply of conventional thermal power plants cannot be made higher than 9.5. [Object of the Invention] The object of the present invention is to solve the above-mentioned drawbacks of conventional power plants, and to provide a condenser and a low-pressure feedwater heater made of copper-free materials, and Provides an effective water treatment method that can prevent corrosion of system equipment and piping and cracking of turbine rotor disks in power plants that use ammonia-type ion exchange resin in salt equipment, and power plants that apply the method. It's about doing. [Summary of the Invention] The present inventors have investigated the actual feed water PH value of a supercritical pressure thermal power plant where the condenser is made entirely of titanium tubes and the low pressure feed water heater is made of steel. Various studies were conducted on thermal power plants. Then, the pH of the water supply to the supercritical pressure thermal power plant is
Fe, Cr in the system when changed from 9.2 to 10.0,
Ni, Cu, Zn, Al, etc. were analyzed. As a result, Cr, Ni, Cu, Zn, and Al were below the analytical limit of 1 ppb in all water systems. Fe is the PH at the inlet of the boiler's Eco (carbon saver), which is the most important for water quality management.
When the value is 9.5 or less, Fe slightly increases at the Cp (condensate pump) outlet, but it decreases at the CBP (condensate booster pump) outlet because it is removed by DEM1 (condensate desalination equipment). However, the Fe at the deaerator inlet is
It increases due to the reflux of water and corrosion of the LP heater material.
In addition, at the deaerator outlet, Fe in the HP heater (high-pressure feed water heater) drain water is refluxed and further increases. After that, Fe decreases at the Eco inlet (boiler inlet) and main steam (turbine inlet) (see Figure 5). Therefore, Fe from the deaerator outlet to the Eco inlet
The decrease is due to Fe depositing as scale on the HP heater and boiler main water supply flowmeter, and
The decrease in Fe in the main steam from the Eco inlet is due to it adhering to the water wall tubes of the boiler. The adhesion of these scales shortens the time interval during which inconveniences occur, such as an increase in differential pressure, improper flow rate indication, and the need for boiler pickling. However, as shown in Figure 6, when the PH value of the Eco inlet is set to 9.6, 9.8, and 10.0,
Fe in the LP heater and HP heater drain water is significantly reduced, and corrosion of the equipment itself is also suppressed, resulting in a significant reduction in Fe at the deaerator inlet and outlet.
Especially when the PH of the Eco inlet is set to 9.8 and 10.0,
The increase in Fe after the CBP exit is very small, and
It was found that there was almost no decrease in Fe in the main steam from the Eco inlet (see Figures 5 and 6).
From this result, it can be seen that the Fe content in the system water when the PH value of the system water is increased is determined by the amount of Fe at the CBP outlet, that is, the condensate desalination equipment (DEM1) outlet. On the other hand, as shown in equation (1), the reaction of the ammonia-type ion exchange resin used in condensate desalination equipment with condensate is as follows:
Since only NH _{4 OH is removed by ion exchange and NH 4} OH is passed through, the amount of NH ₄ OH used can be reduced. R-NH ₄ NH ₄ OH→ R-Na + R-OH NaCl ←R-NH ₄ R-Na R-OH R-Cl+NH ₄ OH (1) However, R-NH ₄ :NH ₄ type cation exchange resin R- Na: Na type cation exchange resin R-OH: OH type anion exchange resin R-Cl: Cl type anion exchange resin However, from the perspective of the equilibrium relationship of ion exchange resins, equation (1) involves a reverse reaction, so after regeneration R on the resin of
When -Na is included, Na ⁺ leaks as NH ₄ OH passes through as shown in FIG. 4, and the leak amount of Na ⁺ increases especially when the PH value of the condensate is high. Therefore,
Various methods for reducing Na ⁺ leakage from ammonia-type resins were investigated. As a result, R in the ammonia-type resin used in conventional thermal power plants
Since the -Na content is 0.3% or more, as shown in FIG. 4, if the PH value is increased to 9.5 or more, Na ⁺ exceeds the control value of 3 ppb. However, when the content of R-Na in the ammonia type resin is reduced to 0.1% or less,
As shown in Fig. 7, it was found that even when the pH was set to 10.0, the amount of Na ⁺ leak was less than 3 ppb. The present invention was made based on the results of studies conducted in an actual supercritical pressure thermal power plant as described above, and includes a condenser and a low-pressure feed water heater made of materials that do not contain copper, and a condensate dewatering system. In power plants that use ammonia-type ion exchange resin in their salt equipment, an alkaline agent is injected into the system water.In this way, the PH value of the feed water in supercritical pressure thermal power plants can be adjusted.
By setting the value between 9.6 and 10.0, corrosion of system equipment and piping and cracking of the turbine rotor disk can be prevented. Furthermore, since corrosion can be prevented, conventionally eluted corrosion products can be removed from the boiler water wall pipes.
Problems caused by adhesion and precipitation on turbines, high-pressure feed water heaters, feed water flow meters, feed water adjustment valves, etc., such as (1) overheating of pipes, (2) decrease in turbine output, (3) heat exchange rate (4) Pump overload due to increased differential pressure, (5) Incorrect flow rate indication, etc. will be reduced, improving the performance and efficiency of the power plant and improving its reliability.
and extended pickling intervals to remove corrosion products;
There is no need for jet cleaning, and there are effects such as reducing wastewater treatment costs. [Embodiments of the Invention] Examples of the present invention will be described below based on the drawings. FIG. 8 shows a system diagram when the method and apparatus according to the present invention are used in a thermal power plant, and FIG. 9 similarly shows a system diagram when the method and apparatus according to the present invention are used in a pressurized water type nuclear power plant. In Figure 8, system water flows as follows.
Titanium condenser 2 → condenser hot well 3 → condensate piping 4 → condensate pump 5 → ammonia type condensate desalination device 6 → condensate heat exchanger 7a → condensate boost pump 7 → stainless steel low-pressure feed water heating Vessel 8 → Deaerator deaeration chamber 9 →
Deaerator water storage tank 10 → water supply piping 11 → water supply pump 12 → high pressure water supply heater 13 → boiler economizer 1
4 → Boiler water wall pipe 15 → Steam piping 16 → Turbine 1 → Condenser 2. In this flow, the system water is converted into steam by the boiler's economizer 14 and the boiler's water wall pipe 15, and flows into the turbine 1 to do work. According to the example shown in FIG. 8, in order to prevent corrosion of each device and each pipe, an alkaline agent is injected into the water supply downstream of the ammonia-type condensate desalination device 6 using an alkaline agent injection device 20. The alkaline agents in this example include ammonia (NH ₄ OH), hydrazine (N ₂ H ₄ ), and a volatile chemical mixture of ammonia, cyclohexylamine (C ₆ H ₁₁ NH ₂ ), and morpholine (C ₄ H ₉ NO). etc. are used. Corrosion of the entire system can be prevented by injecting this alkaline agent from upstream of the inlet of the economizer 14 so that the pH value is 9.6 to 10.0. FIG. 9 shows a system diagram of a pressurized water nuclear power plant. In this example, the flow of system water up to the high-pressure feed water heating pipe 13 is the same as in the example shown in FIG. After being heated in the furnace 22, it flows into the turbine 1 through the steam pipe 16, performs work, and returns to the condenser 2 again. Although ammonia and hydrazine are used as alkali agents in this example, chemicals such as those shown in the example shown in FIG. 8 may also be used.
Further, the injection point of the alkaline agent is upstream of the entrance of the steam generator 21. In both of the above two examples, the alkali agent is injected immediately after the condensate desalination device 6, but downstream from this and into the economizer 14 or the steam generator 2.
1 upstream, for example the bleed pipe 19 of the low pressure feed water heater 8
A, 19B, 19C and the bleed pipes 19D, 19E, 19F of the high-pressure feed water heater 13 also provide similar results. In this way, the inlet side of the economizer 14 in a thermal power plant (Fig. 8) or the steam generator 2 in a pressurized water nuclear power plant
The effects of the present invention can be achieved by injecting an alkaline agent into the system water on the inlet side (Fig. 9) of No. 1 to adjust the pH value to 9.6 to 10.0. Table 1 shows a comparison between the method according to the present invention and the conventional method. In addition, in the conventional method, materials containing copper are used for the condenser, condensate heat exchanger, and low-pressure feed water heater, and steel materials that do not contain copper are used for other equipment. An alkaline agent mixed with ammonia and hydrazine was injected from the feed water at the outlet of the condensate desalination equipment so that the PH value of the feed water at the inlet of the energy saver or the inlet of the steam generator in the case of a nuclear power plant was PH9.2. . Furthermore, the method of the present invention includes:
All equipment that comes into contact with system water is made of materials that do not contain copper, so that the PH value of the feed water at the entrance to the energy saver in the case of a thermal power plant and the inlet to the steam generator in the case of a nuclear power plant is PH10.0. In thermal power plants, an alkaline agent containing a mixture of ammonia, hydrazine, cyclohexylamine, and morpholine was injected from the inlet of the economizer, and in nuclear power plants, an alkaline agent containing a mixture of ammonia and hydrazine was injected from the inlet of the steam generator. According to Table 1, the present invention shows that the iron concentration in the water supply is significantly reduced, and no elution of copper or other ions is observed, achieving a sufficient anticorrosion effect.

〔Effect of the invention〕

According to the present invention, corrosion protection is provided for system equipment and piping of a power plant in which the condenser and low-pressure feedwater heater are constructed of materials that do not contain copper, and the condensate desalination device employs an ammonia-type ion exchange resin. can be achieved, and metal components in system water can be significantly reduced.
(1) Significantly extends the pickling interval to remove corrosion products, (2) Reduces wastewater treatment costs, (3) Eliminates the need for jet cleaning of high-pressure feed water heaters, (4) Eliminates scale deposition. This has the effect of greatly improving performance and efficiency. It goes without saying that the present invention is not limited to the above embodiments.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between PH value and corrosion amount.
Figure 2 is a diagram showing the total iron change in a thermal power plant system by the conventional method, Figure 3 is a diagram showing the total copper change in the thermal power plant system by the conventional method, and Figure 4 is a diagram showing the total copper change in the thermal power plant system by the conventional method.
The figure shows the Na ⁺
A diagram showing the relationship between the amount and the PH value at the inlet of the economizer,
Figure 5 is a diagram showing changes in total iron in a thermal power plant system at conventional PH values, Figure 6 is a diagram showing changes in total iron in a thermal power plant system at PH values according to the present invention, and Figure 7 is a diagram showing changes in total iron in a thermal power plant system at PH values according to the present invention. The ammonia type ion exchange resin outlet adopted in the condensate desalination equipment of the thermal power plant of the present invention
A diagram showing the relationship between Na ⁺ amount and Eco inlet PH, Figure 8 is a system diagram of a thermal power plant to which the method of the present invention is applied, and Figure 9 is a system diagram of a pressurized water type nuclear power plant to which the method of the present invention is applied. It is. 1...
Turbine, 2... Titanium condenser, 3... Condenser hot well, 4... Condensate piping, 5... Condensate pump, 6... Ammonia type condensate desalination device, 7... Condensate pressure booster Pump, 8... Stainless steel low pressure water heater, 9... Deaerator deaeration chamber, 10... Deaerator water storage tank, 11... Water supply piping, 12... Water supply pump,
13... High pressure feed water heater, 14... Boiler economizer, 15... Boiler water wall tube, 16... Steam piping, 17... Low pressure feed water heater drain piping, 18...
...High-pressure feed water heater drain piping, 19... Air extraction piping, 20... Alkali agent injection device, 21... Steam generator, 22... Nuclear reactor, 23... Primary coolant piping, 24... Primary coolant pump , 25...pressurizer.

Claims (1)

[Claims] 1. In a power generation plant in which all parts in contact with system water are made of materials that do not contain copper, and in which an ammonia-type ion exchange resin is used in a condensate desalination device, as the ammonia-type ion exchange resin, The content of sodium type ion exchange resin (R-Na) is
Add ammonia (NH ₄ OH), hydrazine (N ₂ H ₄ ), ammonia and cyclohexylamine (C ₆ H ₁₁ NH ₂ ), and morpholine (C ₄ H ₉ NO) to the system water using 0.1% or less. 1. A water treatment method for a power generation plant, characterized in that an alkaline agent containing at least one of mixed volatile chemicals is added to system water to adjust the pH to 9.6 to 10.0. 2. Add an alkaline agent to the system water from at least one of the following: the energy saver inlet, the steam generator inlet, the condensate desalination equipment outlet water supply pipe, the low-pressure feedwater heater bleed pipe, or the high-pressure feedwater heater bleed pipe. A water treatment method for a power plant according to claim 1, characterized in that: 3. In a power plant where all parts that come into contact with system water are made of copper-free materials, condensate dewatering using an ammonia-type ion-exchange resin with a sodium-type ion-exchange resin (R-Na) content of 0.1% or less salt equipment and at least one of the following volatile chemicals: ammonia (NH ₄ OH), hydrazine (N ₂ H ₄ ), a mixture of ammonia and cyclohexylamine (C ₆ H ₁₁ NH ₂ ) and morpholine (C ₄ H ₉ NO). and an alkaline agent injection device that adds an alkaline agent containing one to system water to adjust the pH to 9.6 to 10.0. 4 Among the parts that come into contact with system water, the condenser is made of materials such as austenitic, ferritic, austenitic and ferritic stainless steel, steel, titanium, and titanium alloys, and the low-pressure feed water heater is made of carbon steel, low alloy, etc. 4. The power generation plant according to claim 3, wherein the power plant is made of a material such as steel, stainless steel, or nickel-based alloy.