JP2007160162A - Method for operating power plant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for operating a power plant, by which the deterioration of strength of a hollow fiber membrane filter which is used in an apparatus for purifying a steam condensate and comprises polysulfone can be prevented. <P>SOLUTION: The method for operating the power plant in which a copper alloy is used as the constituent material of a steam condensate system and all volatile chemical treatment is executed comprises: a step of adjusting the pH of the water at the inlet of the apparatus for purifying the steam condensate to ≥9 by using an alkaline chemical other than hydrazine or adjusting the dissolved oxygen of the water at the inlet of the apparatus for purifying the steam condensate to ≤1 ppm or a step of: beforehand capturing iron oxide or/and iron hydroxide on the surface of a filtration membrane of the apparatus for purifying the steam condensate before the apparatus for purifying the steam condensate is operated and then making the steam condensate pass through the apparatus for purifying the steam condensate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power plant operation method, and more particularly, to a power plant operation method suitable for a pressurized water nuclear power plant or a thermal power plant using a condensate system apparatus using a copper alloy.

  In pressurized water nuclear power plants and thermal power plants, in plants where the installation year is old, copper alloys with good heat transfer efficiency (aluminum brass, aluminum bronze, Cupronickel etc.) are used. In order to suppress iron inflow to the steam generator, the system water is degassed with hydrazine for the purpose of corrosion protection of secondary equipment and piping, and the pH is adjusted to 9 with ammonia and ethanolamine (ETA). All volatile chemical treatment (AVT) controlled to about 2 is implemented.

In recent years, for the purpose of condensate system water purification, condensate purification devices, particularly condensate filtration devices, have been applied, and hollow fiber membrane filters have been applied as condensate filtration devices (for example, patents). Literature 1), hollow fiber membrane filters installed in power plants that apply copper alloys to system components such as condensers and heat exchangers and perform all volatile chemical treatments have extremely high physical strength. The hollow fiber membrane filter is broken, and the filtration accuracy is lowered.
JP 2002-346346 A

As a result of various studies on the factors that cause a sudden decrease in the physical strength of the hollow fiber membrane filter as described above, the cause was estimated as follows.
(1) Hydrazine added for the purpose of reducing dissolved oxygen in condensate water reacts with dissolved oxygen to produce hydrogen peroxide.
(2) The generated hydrogen peroxide reacts with copper ions eluted from the copper alloy to generate hydroxyl radicals having a strong oxidizing power.
(3) The generated hydroxyl radical oxidizes polysulfone, which is a material of the hollow fiber membrane filter, and sharply lowers the physical strength.
Here, copper ions are eluted from the copper alloy of the system constituent material.

  The subject of this invention is providing the operating method of the power plant which can prevent the strength reduction of the filter used for a condensate purification apparatus, especially the hollow fiber membrane filter which consists of polysulfone based on the above knowledge. .

  In order to solve the above problems, the operation method of the power plant according to the present invention is an operation method in a power plant that uses a copper alloy as a constituent material of the condensate system and performs total volatile chemical treatment. The pH of the condensate purification apparatus inlet water is adjusted to 9 or more with an alkaline chemical other than hydrazine.

  That is, by adjusting the inlet water of the condensate purification apparatus, particularly the condensate filtration apparatus, to pH 9 or higher with an alkaline chemical other than hydrazine, the decomposition of hydrogen peroxide, which is an oxidative factor, is promoted, and thus the generation of hydroxyl radicals is promoted. It suppresses and reduces oxidative degradation of a filter, particularly a hollow fiber membrane filter made of polysulfone.

  Here, adjusting to pH 9 or higher with an alkaline chemical other than hydrazine does not exclude the addition of hydrazine, but means that an alkaline chemical other than hydrazine is used to adjust the pH to 9 or higher. There are both cases where the pH is adjusted to 9 or more only with an alkaline chemical other than hydrazine, and cases where the pH is adjusted to 9 or higher by adding an alkaline chemical other than hydrazine after adding hydrazine. As alkaline chemicals other than hydrazine, ammonia or ethanolamine can be used.

  The operation method of the power plant according to the present invention is an operation method in a power plant that uses a copper alloy as a constituent material of the condensate system and performs all volatile chemical treatment, and is provided at the inlet of the condensate purification apparatus. It consists of the method characterized by adjusting the dissolved oxygen of water to 1 ppm or less.

  That is, by adjusting the dissolved oxygen at the inlet of the condensate purification device, particularly the condensate filtration device, to 1 ppm or less, the generation of hydrogen peroxide, which is an oxidative factor, is reduced, and the generation of hydroxyl radicals is suppressed. It is intended to reduce oxidative degradation of a hollow fiber membrane filter made of polysulfone.

  In order to adjust the dissolved oxygen to 1 ppm or less, for example, degassed pure water can be supplied. Further, in order to adjust the dissolved oxygen to 1 ppm or less, the condensate system and / or the water supply system can be sealed with nitrogen.

  Further, the power plant operating method according to the present invention is a power plant operating method using a copper alloy as a constituent material of the condensate system and carrying out the treatment of all volatile chemicals. It consists of a method characterized in that iron or / and iron hydroxide is trapped on the surface of the filtration membrane of the condensate purification apparatus, and then water passing treatment is performed.

  That is, before passing water through a condensate purification device, in particular before passing through the condensate filtration device, iron oxide, iron hydroxide, etc. are captured in advance on the filtration surface of the hollow fiber membrane filter, and the surface of the hollow fiber membrane against oxidation of the generated hydroxyl radicals. Protects against oxidative degradation.

  The operation method of the power plant according to the present invention as described above can be carried out by using any two or more methods in combination.

  Such a power plant operating method according to the present invention is effective particularly when a filter made of a polysulfone membrane is used in the condensate purification apparatus, and particularly when a hollow fiber membrane filter is used.

  According to the operation method of the power plant according to the present invention, it is possible to suppress a decrease in physical strength of the polysulfone membrane by adjusting the inlet pH of the hollow fiber membrane filter to 9 or more using ammonia or the like. Moreover, the fall of the physical strength of a polysulfone membrane can be suppressed by adjusting the inlet dissolved oxygen of a hollow fiber membrane filter to 1 ppm or less. Further, by preliminarily capturing iron oxide or iron hydroxide on the filtration surface before passing through the hollow fiber membrane filter, it is possible to suppress a decrease in physical strength of the polysulfone membrane.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
A first mode of a power plant operation method according to the present invention is a power plant operation method using a copper alloy as a constituent material of a condensate system and performing a total volatile chemical treatment, except for hydrazine. The pH of the condensate purification apparatus inlet water is adjusted to 9 or more with the above alkaline chemicals. Therefore, first, the effect of pH was examined in the case of pH adjustment with hydrazine as in the past.

A hollow fiber membrane filter made of polysulfone was passed through under the following water quality conditions, and changes in physical strength over time were confirmed. As a result, it was confirmed that a decrease in physical strength in the hollow fiber membrane filter made of polysulfone material was suppressed under water quality conditions having a high pH (9 or more). The physical strength was evaluated by the tensile elongation retention rate of the hollow fiber membrane filter.
Water quality conditions:
Hydrazine concentration: 1000mg / L
Copper ion concentration: 500mg / L
Dissolved oxygen concentration: 10μg / L
pH: 8 (Effect of pH shown in FIG. 1)
9 (Effect of pH shown in FIG. 2-2)

  Thus, it was confirmed that by adjusting the pH to 9 or more, the tensile elongation retention rate of the hollow fiber membrane filter made of polysulfone material can be maintained high. However, as pH adjusting chemicals, hydrazine and alkalis other than hydrazine were used. In order to examine how the influence of the hollow fiber membrane filter on the tensile elongation differs from that of chemicals, a forced immersion test was conducted. The measurement results are shown in FIG. As shown in FIG. 3, the tensile elongation retention rate is maintained higher when contacted (immersed) with alkaline chemicals other than hydrazine for a long time than when contacted (immersed) with hydrazine alone for a long time. (That is, it is possible to suppress the progress of film deterioration).

Therefore, when only hydrazine (N ₂ H ₄ ) is added (FIG. 4: substantially the same as the characteristics of FIG. 1, the pH is adjusted to 8 by adding a small amount of hydrazine), and an alkali other than hydrazine. When the pH was adjusted to 9 or more by adding a chemical (FIGS. 5 and 6), a comparative test of the influence of the polysulfone material on the tensile elongation retention rate of the hollow fiber membrane filter was performed. As can be seen from FIG. 5 and FIG. 6, there is no influence of film deterioration due to alkaline chemicals other than hydrazine (ammonia (NH ₃ ) and ethanolamine (ETA)), and in addition to FIG. It was confirmed that the deterioration was alleviated.

  Such alkaline chemicals other than hydrazine are preferably added, for example, at the initial stage of condensate cleanup in the condensate system. When degassed pure water described later is not used, at least after the vacuum level in the system is increased, It is preferable to add until the time when the water-soluble oxygen concentration (DO concentration) becomes 1 ppm or less. Although an addition place is not specifically limited, The addition in the back | latter stage of the condenser in a condensate system | strain and the back | latter stage of a condensate demineralizer can be illustrated.

  A second form of operation method of a power plant according to the present invention is an operation method in a power plant that uses a copper alloy as a constituent material of a condensate system and performs total volatile chemical treatment. The method is characterized in that the dissolved oxygen in the purification apparatus inlet water is adjusted to 1 ppm or less. Therefore, a polysulfone-based hollow fiber membrane filter was passed under the water flow rate and water quality conditions shown in FIG. 7, and the relationship between dissolved oxygen concentration and physical strength over time (tensile elongation retention) was examined. As a result, it was confirmed that the decrease in physical strength of the hollow fiber membrane filter made of polysulfone material was suppressed under water quality conditions where the dissolved oxygen was 1 ppm or less.

  In order to adjust the dissolved oxygen of the condensate purification apparatus inlet water to 1 ppm or less, for example, a method of supplying degassed pure water into the condensate system, a method of sealing the condensate system and / or the water supply system with nitrogen, etc. Can be adopted.

  A third mode of the operation method of the power plant according to the present invention is an operation method in a power plant that uses a copper alloy as a constituent material of the condensate system and performs total volatile chemical treatment, In this method, iron oxide and / or iron hydroxide is previously captured on the filtration membrane surface of the condensate purification apparatus, and then water passing treatment is performed. Therefore, in the case where water is passed through a hollow fiber membrane filter made of a polysulfone material under the conditions shown in FIG. 8, and as shown in FIG. 9, the surface of the filtration membrane of the condensate purification device is pre-treated with iron oxide or / and iron hydroxide before operation. A comparative test was conducted in which the water was trapped and then subjected to water treatment. As a result, it was confirmed that the decrease in physical strength (tensile elongation retention) in the hollow fiber membrane filter made of a polysulfone material was suppressed by preliminarily capturing iron oxide on the filtration surface before water flow.

  In addition, the said 1st, 2nd, 3rd form of the operating method of the power plant which concerns on this invention can be combined arbitrarily two or more.

  The present invention is a power plant operation method suitable for use in a condensate system of a pressurized water nuclear power plant or a thermal power plant using equipment using a copper alloy.

It is a time-dependent change characteristic figure which shows the test result in the case of pH = 8 which investigates the influence by pH. It is a time-dependent change characteristic figure which shows the test result in the case of pH = 9 which investigates the influence by pH. It is a tensile elongation characteristic view of the membrane filter which shows the immersion result for investigating the influence by a chemical species. It is a time-dependent change characteristic figure which shows the test result at the time of adding only the hydrazine for investigating the influence by chemical | medical agent kind. It is a time-dependent change characteristic figure which shows the test result at the time of adding chemicals (ammonia) other than hydrazine in addition to hydrazine. It is a time-dependent change characteristic figure which shows the test result at the time of adding chemicals (ammonia and ethanolamine) other than hydrazine in addition to hydrazine. It is a characteristic view which shows the relationship between dissolved oxygen concentration and tensile elongation retention. It is a time-dependent change characteristic view of the tensile elongation retention rate when not capturing iron oxide and / or iron hydroxide. It is a time-dependent change characteristic view of the tensile elongation retention when iron oxide and iron hydroxide are captured in advance.

Claims (9)

  An operation method in a power plant that uses a copper alloy as a constituent material of a condensate system and performs all volatile chemical treatments, and the pH of the condensate purification apparatus inlet water is increased to 9 or more by an alkaline chemical other than hydrazine. A method of operating a power plant characterized by adjusting.   The method for operating a power plant according to claim 1, wherein ammonia or / and ethanolamine are used as alkaline chemicals other than hydrazine.   An operation method in a power plant that uses a copper alloy as a constituent material of a condensate system and performs all volatile chemical treatments, wherein the dissolved oxygen in the condensate purification apparatus inlet water is adjusted to 1 ppm or less. How to operate the power plant.   The operating method of a power plant according to claim 3, wherein degassed pure water is supplied to adjust dissolved oxygen to 1 ppm or less.   The method for operating a power plant according to claim 3 or 4, wherein the condensate system and / or the water supply system is sealed with nitrogen in order to adjust dissolved oxygen to 1 ppm or less.   An operation method in a power plant that uses a copper alloy as a constituent material of a condensate system and performs all volatile chemical treatment, and before the operation, iron oxide and / or iron hydroxide is previously added to the condensate purification device. A method of operating a power plant characterized in that it is trapped on the surface of a filtration membrane and then subjected to water passage treatment.   An operation method for a power plant, wherein any two or more of the operation methods according to claim 1, 3 and 6 are carried out.   The method for operating a power plant according to any one of claims 1 to 7, wherein a filter made of a polysulfone membrane is used for the condensate purification apparatus.   The operating method of the power plant in any one of Claims 1-8 which uses a hollow fiber membrane filter for a condensate purification apparatus.

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