JP2021063282A - Chemical agent application apparatus and chemical agent application method - Google Patents

Abstract

To enable an appropriate adhesion of a chemical agent injected into fluid, onto a surface of a structural material on which the fluid contacts and flows, regardless of a flow rate of the fluid.SOLUTION: A chemical agent application apparatus 40 is configured to adhere a chemical agent injected into fluid, onto a surface of a structural material on which the fluid having a flow velocity distribution contacts and flows. The chemical agent application apparatus includes: a first tank 41 storing a first chemical agent containing an ion or a particle with a particle size 10 nm or less; a second tank 42 storing a second chemical agent with a particle size 100 nm or more; and an injection pump 44 configured to inject the first chemical agent in the first tank and the second chemical agent in the second tank into a flow of the fluid.SELECTED DRAWING: Figure 2

Description

An embodiment of the present invention relates to a chemical application apparatus and a chemical application method for adhering a chemical injected into a fluid to the surface of a structural material in which a fluid having a flow velocity distribution flows in contact with the fluid.

Many industrial equipment, including boilers, power plants, and chemical plants, use cooling water to handle the heat generated by the equipment. Most of these cooling waters are tap water and river water, but there are events that hinder the operation of equipment, such as corrosion of structural materials, propagation of microorganisms, and precipitation of trace components in water called scales. It may occur.

In addition to the possibility that the corrosion phenomenon may lead to damage to the structural material, the accumulation of oxides of the structural material generated by the corrosion reaction may cause equipment failure due to blockage of piping and a decrease in cooling capacity. Similarly, the precipitation of scales and the propagation of microorganisms can cause a decrease in the capacity of the equipment.

As a preventive technique for these events, water purification and chemical treatment of cooling water are performed. In the case of scale, a precipitation inhibitor is added, and in the case of microorganisms, the oxygen concentration and organic matter concentration that cause the generation are controlled. In addition to water purification that removes scale and microorganisms, power plants are undergoing various treatments to control corrosion. Specific methods for suppressing corrosion include installing a deaerator to reduce oxygen and hydrogen peroxide that contribute to the corrosion reaction, injecting reducing substances such as hydrogen and hydrazine, and further reducing the corrosion reaction. Chemicals such as ammonia and lithium hydroxide are injected to create a pH environment.

Furthermore, stress corrosion cracking (SCC) is also a concern in equipment that operates at high temperatures. From the viewpoint of preventing stress corrosion cracking, precious metals and titanium oxide are injected. This injection technique reduces the rate of the corrosion reaction by lowering the potential of the structural material and prevents the development of SCC. Here, an example of the corrosion reaction is shown in Equation 1. The corrosion reaction of metal structural materials is accompanied by the emission of electrons, and when the potential drops and the environment becomes negative, the emission of negatively charged electrons is suppressed, so the corrosion reaction is an electron emission reaction. Is also suppressed.
Fe → Fe ²⁺ + 2e ⁻ ……… Equation 1

Most of the above-mentioned chemical construction techniques are effective when a chemical is injected into the flow of a fluid flowing in contact with the surface of the structural material and the injected chemical reaches the surface of the structural material. .. However, unlike simple piping, it is considered that the inside of the equipment that carries out these chemical treatments does not have a uniform flow. Therefore, it is considered that the effect of the construction agent differs depending on the surface portion of the structural material due to the difference in the flow velocity of the fluid and the difference in the surface shape of the structural material.

Here, the amount of substance (reaching amount or diffusion amount J) in which ions or particles having a particle diameter of 10 nm or less reach the surface of the structural material and adhere to the surface has a diffusion coefficient of D, a solution concentration of C0, and a surface concentration of C. Assuming that the diffusion layer thickness is δ, the following equation 2 can be used as an example for evaluation.
J = D × (C0-C) / δ ……… Equation 2
In the above formula 2, the diffusion layer thickness δ is represented by the following formula 3, where the Reynolds number is Re, the Schmid number is Sc, and the pipe diameter is d.
δ = 1 / (0.023 × d × Re ^0.8 × Sc ^0.33 ) ……… Equation 3
The Reynolds number Re and the Schmid number Sc in the above equation 3 are expressed in the following equations 4 and 5, respectively, where v is the fluid velocity, d is the pipe diameter, ν is the kinematic viscosity coefficient, μ is the kinematic viscosity, and D is the mass diffusivity. expressed.
Re = v × d / ν ……… Equation 4
Sc = μ / D ……… Equation 5

From these formulas 2 to 5, a relatively large amount of chemicals arrive at the surface of the structural material and adhere to the surface of the structural material as the diffusion layer thickness δ decreases due to the increase in the Reynolds number Re in the high flow velocity environment of the fluid flow. I understand. On the other hand, it is considered that the amount of the chemical adhered to the low flow velocity portion of the fluid flow is small.

JP-A-2007-192745

In chemical construction, it is assumed that the amount of chemicals reached will differ due to the influence of the flow velocity of the fluid and the surface shape of the structural material at each part of the surface of the structural material to which the fluid flows in contact. As a result, in the construction of chemicals such as precious metals and titanium oxide, there is a risk that a sufficient amount of chemicals adhered to the surface of the structural material in contact with the low flow velocity portion of the fluid flow.

The embodiment of the present invention has been made in consideration of the above circumstances, and the drug injected into the fluid is suitably attached to the surface of the structural material in which the fluid is in contact and flows regardless of the flow velocity of the fluid. It is an object of the present invention to provide a chemical construction apparatus and a chemical construction method capable of performing.

The chemical construction apparatus according to the embodiment of the present invention is a chemical construction apparatus that adheres a chemical injected into the fluid to the surface of a structural material in which a fluid having a flow velocity distribution flows in contact with the fluid, and has an ion or particle diameter of 10 nm or less. A first tank for storing the first drug as the drug containing the particles of the above, a second tank for storing the second drug as the drug having a particle diameter of 100 nm or more, and the first drug in the first tank. The chemical construction apparatus is characterized in that it is configured to have an injection means for injecting the second chemical in the second tank into the flow of the fluid.

The chemical application method according to the embodiment of the present invention is a chemical application method in which a chemical injected into the fluid is attached to the surface of a structural material in which a fluid having a flow velocity distribution flows in contact with the fluid, and the ion or particle size is 10 nm or less. The first drug as the drug containing the particles of the above and the second drug as the drug having a particle diameter of 100 nm or more are injected into the flow of the fluid.

According to the embodiment of the present invention, the drug injected into the fluid can be suitably attached to the surface of the structural material in which the fluid flows in contact with the fluid, regardless of the flow velocity of the fluid.

The system diagram which shows a part of the nuclear power plant to which the chemical construction apparatus which concerns on 1st Embodiment is applied. The block diagram which shows the chemicals construction apparatus of FIG. Explanatory drawing which shows the relationship between the particle of a drug and a dispersant, and explains the case where the concentration of a dispersant is high and the particle size of a drug is small. Explanatory drawing which shows the relationship between the particle of a drug and a dispersant, and explains the case where the concentration of a drug is low and the particle size of a drug is large. FIG. 6 is a schematic view of a chemical construction apparatus and a structural material for explaining the chemical construction method according to the third embodiment.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
[A] First Embodiment (FIGS. 1 to 4)
FIG. 1 is a system diagram showing a part of a nuclear power plant to which the chemical construction apparatus according to the first embodiment is applied. Further, FIG. 2 is a configuration diagram showing the chemical construction apparatus of FIG. The boiling water reactor 11 of the nuclear power plant 10 shown in FIG. 1 houses the core 13 in the reactor pressure vessel 12. A large number of fuel assemblies (not shown) constituting the core 13 are surrounded by the core shroud 14 and supported by the core support plate 15 and the upper lattice plate 16. The upper opening of the core shroud 14 is closed by the shroud head 17, and the steam separator 18 and the steam dryer 19 are sequentially arranged above the shroud head 17.

The reactor pressure vessel 12 includes a vessel body 20 and a lid 21 provided so as to close the upper opening of the vessel body 20. The container body 20 includes a cylindrical body 22 and a mirror 23 connected to the lower end of the body 22 to form a lower core plenum 24. The lower mirror 23 is provided with a through hole (both not shown) through which the control rod drive mechanism 25 and the in-core instrumentation pipe are inserted.

Inside the reactor pressure vessel 12, the core shroud 14, the core support plate 15, the upper lattice plate 16, the shroud head 17, the air-water separator 18 and the steam dryer 19, and the jet pump 36 described later, which will be described later, are not shown. Reactor internal structures such as shroud support and core spray system piping are housed.

Further, the reactor primary system piping that takes in the coolant as water supply and releases steam or the like is connected to the reactor pressure vessel 12. The reactor primary system piping includes the main steam system piping 27 of the main steam system 26, the water supply system piping 29 of the water supply system 28, the recirculation system piping 31 of the reactor recirculation system 30, and the cooling of the reactor coolant purification system 32. The material purification system pipe 33, the bottom drain pipe 34, and the like. The cooling material purification system pipe 33 is connected to the bottom drain pipe 34 and the recirculation system pipe 31.

The steam generated in the core 13 of the boiling water reactor 11 is separated by the steam separator 18 and dried by the steam dryer 19, and passes through the main steam system pipe 27 to the turbine system (not shown). Is supplied to. The steam that has worked in the turbine system is condensed into condensate, heated while passing through the water supply system 28 to become water supply, and is supplied from the water supply system pipe 29 into the reactor pressure vessel 12 as a coolant.

This coolant is boosted by the recirculation pump 35 of the reactor recirculation system 30, and is supplied by a plurality of jet pumps 36 installed in the downside section between the vessel body 20 of the reactor pressure vessel 12 and the core shroud 14. Together with the water separated by the air-water separator 18, it is guided into the lower core plenum 24 below the core 13. The coolant flows upward from the lower plenum 24 of the core, is heated by the nuclear reaction heat of the core 13, becomes a gas-liquid mixed flow of steam and water, and reaches the gas-water separator 18. The above cycle is repeated.

As described above, the coolant (coolant water) as a fluid flows in contact with the surface of the reactor pressure vessel 12, the equipment such as the reactor internal structure, and the structural material such as the reactor primary system piping. In the first embodiment, for the purpose of mainly preventing corrosion of the surface of the structural material to which the cooling water flows in contact with the cooling water, the chemical is injected into the flow of the cooling water from the chemical construction apparatus 40 to form the structural material. It is attached to the surface. This agent is an oxygen scavenger consisting of a reducing substance containing, for example, hydrogen or hydrazine.

The workability of adhering the chemical to the surface of the structural material is determined by the amount of the first chemical reaching the surface of the structural material (diffusion amount) when the chemical contains ions or particles having a particle size of 10 nm or less. Will be done. Since this amount of arrival (diffusion amount) is defined by the above formula 2, the first drug increases the Reynolds number Re in an environment of a high-speed flow of cooling water (for example, a speed exceeding 0.1 m / s). As the diffusion layer thickness δ decreases due to the above, it adheres well to the surface of the structural material.

On the other hand, when the drug is a second drug having a particle size of 100 nm or more, the second drug adheres in a deposited form in an environment where the cooling water has a low flow velocity (for example, 0.1 m / s or less), and has low peelability. Therefore, it has sufficient durability.

Therefore, in the chemical construction apparatus 40 of the first embodiment, when the chemical injected into the cooling water is adhered to the surface of the structural material in which the cooling water having the flow velocity distribution flows in contact with the cooling water, the flow velocity distribution of the cooling water is used. Drugs with different particle sizes (first drug, second drug) are attached.

At this time, each of the first drug and the second drug may be two or more kinds of drugs having different particle sizes within the range of the particle size of each drug. For example, as the first agent, two or more kinds of second agents having different particle sizes within a particle size range of 10 nm or less may be used at the same time. Further, the first drug and the second drug are preferably drugs of the same substance, but may be drugs of different substances as long as they do not adversely affect each other.

As shown in FIG. 2, the chemical construction apparatus 40 of the first embodiment as described above has a first tank 41 for storing the first chemical, a second tank 42 for storing the second chemical, and a first tank. A mixing tank 43 that mixes the first drug in the 41 and the second drug in the second tank 42, and an injection that injects the first drug and the second drug mixed in the mixing tank 43 into the flow of cooling water. It is configured to have one injection pump 44 as a means.

The storage of the chemicals in the first tank 41 and the second tank 42 and the mixing of the chemicals in the mixing tank 43 are performed in an environment of normal temperature and pressure. In particular, the mixing of the drug in the mixing tank 43 is performed by the injection pump 44 before (for example, immediately before) injection. Further, since it is assumed that the structural material to be injected with the drug is in a high temperature and high pressure environment, the injection pump 44 is configured to be compatible with this high temperature and high pressure environment. In the first embodiment, the injection pump 44 injects the first agent and the second agent at high pressure into the flow of the cooling water flowing through the cooling material purification system pipe 33.

Here, the particle size of each of the first agent and the second agent is controlled, for example, by changing the concentration of the dispersant 2 (FIGS. 3 and 4) present in these agents. That is, when the concentration of the dispersant 2 is high, as shown in FIG. 3, the dispersant 2 covers the entire surface of the drug particles 1, thereby inhibiting the binding between the drug particles 1 and the drug particles 1. The particle size becomes smaller. On the other hand, when the concentration of the dispersant 2 is low, as shown in FIG. 4, the dispersant 2 does not cover the entire surface of the drug particles 1, so that the drug particles 1 bind to each other and the drug particles 1 It is considered that the particle size of is large. The above-mentioned change in the concentration of the dispersant 2 reduces the concentration of the dispersant 2 by neutralization, oxidation, reduction, thermal decomposition, etc. of the dispersant 2, and the dispersant 2 is added by adding the dispersant 2. A method of increasing the concentration can be considered.

Further, the particle size of each of the first agent and the second agent may be adjusted by using the particle size changing means 45 shown in FIG. That is, the particle size changing means 45 is installed in the second tank 42, and the first drug stored in the second tank 42 is subjected to a treatment such as gas exposure (aeration) or heating. The dispersant 2 is separated from the drug particles 1 of the drug. As a result, the drug particles 1 of the first drug are bound to each other to increase the particle size of the drug particles 1, and the second drug is generated and stored in the second tank 42.

Since it is configured as described above, according to the first embodiment, the following effects (1) and (2) are obtained.
(1) Ions or particles with a particle diameter of 10 nm or less are contained from the injection pump 44 in the flow of cooling water having a flow velocity distribution that flows in contact with the surface of structural materials such as reactor internal structures and reactor primary system piping. By injecting the first agent and the second agent having a particle size of 100 nm or more, the first agent adheres to the surface of the structural material in contact with the high-speed flow cooling water, and the structural material comes into contact with the low-velocity cooling water. The second drug adheres to the surface of the. As a result, the chemical injected into the cooling water can be suitably adhered to the surface of the structural material in which the cooling water flows in contact with the cooling water regardless of the flow velocity of the cooling water.

(2) Before injecting the first drug and the second drug by the injection pump 44, the first drug in the first tank 41 and the second drug in the second tank 42 are mixed by the mixing tank 43, so that the injection is performed. The pump 44 does not have to prepare a plurality of dedicated pumps for each of the first agent and the second agent. As a result, since one injection pump 44 is sufficient, the cost can be reduced and the maintenance cost can be reduced.

[B] Second embodiment (FIG. 2)
In this second embodiment, the same parts as those in the first embodiment are designated by the same reference numerals as those in the first embodiment to simplify or omit the description.

The chemical application device 50 of the second embodiment is an environment in which the surface of the structural material in which the fluid having the flow velocity distribution flows in contact with the flow is irradiated with radiation or ultraviolet rays, and further, in this environment, the flow velocity of the fluid is low (the flow velocity of the fluid is low (). For example, 0.1 m / s or less), and in an environment where the first drug is difficult or does not adhere to the surface, the injection pump 51 as an injection means sets the injection rate of the first drug to the second drug. It is configured to be set higher than.

In an environment exposed to radiation or ultraviolet rays (for example, the nuclear power plant 10 in FIG. 1 to be irradiated with radiation), an oxidizing substance is generated by irradiation of water as a fluid with radiation or ultraviolet rays, and the oxidizing substance produces an oxidizing substance. There is concern about the effects of corrosion on the surface of structural materials. This tendency of corrosion is remarkable in an environment where the flow of water, which is exposed to radiation or ultraviolet rays for a long time, is low flow velocity (for example, 0.1 m / s or less).

Therefore, in the chemical construction apparatus 50 of the second embodiment, the second chemical having good adhesion even on the surface of the structural material in which the flow of water as a fluid is a low flow velocity (for example, 0.1 m / s or less). The mixing ratio of the first drug is higher than that of the first drug, the first drug and the second drug are mixed by the mixing tank 52, and the mixed drug is injected into the flow of the fluid (water) from the injection pump 51 to obtain the second drug. The injection rate of the drug is higher than that of the first drug.

Based on the above configuration, according to the second embodiment, in addition to the same effects as those of the first embodiment (1) and (2), the following effect (3) is obtained.

(3) The surface of the structural material to which the fluid having the flow velocity distribution flows in contact is in an environment where radiation or ultraviolet rays are irradiated, and in this environment, the flow velocity of the fluid is low (for example, 0.1 m / s or less). Therefore, when the environment is such that the first drug is difficult to adhere to or does not adhere to the surface, the injection pump 51 sets the injection rate of the second drug to be higher than that of the first drug. As a result, the second agent can be sufficiently adhered to the surface of the structural material which is exposed to radiation or ultraviolet rays for a long time in an environment where the flow of the fluid (for example, water) is low. As a result, both the surface of the structural material in contact with the fluid having a high flow velocity and the surface of the structural material in contact with the fluid having a low flow velocity can be reliably prevented from being corroded by the oxidizing substance.

[C] Third Embodiment (Fig. 5)
FIG. 5 is a schematic view of a chemical construction apparatus and a structural material for explaining the chemical construction method according to the third embodiment. In this third embodiment, the same parts as those in the first embodiment are designated by the same reference numerals as those in the first embodiment to simplify or omit the description.

The chemical application device 60 used in the chemical application method of the third embodiment has a chemical tank 61 for storing chemicals containing ions or particles having a particle diameter of 10 nm or less, and a flow velocity distribution that flows in contact with the surface of the structural material. It is configured to include one injection pump 62 for injecting the drug in the drug tank 61 into the flow of fluid.

In the chemical application method of the third embodiment, the chemical in the chemical tank 61 is injected from the injection pump 62 into the flow of the fluid having a flow velocity distribution flowing in contact with the surface of the structural material, and the chemical is flowed at a high speed of the fluid. While adhering to the surface of the structural material in contact with the fluid, when the flow of the fluid is stopped, the flow of the fluid becomes low flow velocity (for example, 0.1 m / s or less) on the surface of the structural material in contact with the fluid, and the flow of the fluid becomes low. Apply the chemical to the surface where the chemical is hard to adhere or does not adhere.

This drug can be sufficiently adhered to the surface of the structural material in contact with the fluid flowing at high speed by injecting the drug in the drug tank 61 from the injection pump 62 during the flow of the fluid. On the other hand, on the surface of the structural material in contact with the fluid flowing at a low flow velocity (for example, 0.1 m / s or less), the chemicals injected during the flow of the fluid are often difficult or non-adherent.

Here, as a condition for the fluid flow to have a low flow velocity, for example, when the structural material is a pipe, a large-diameter portion 64 having a large flow path area is assumed with respect to a small-diameter portion 63 having a narrow flow path area. Among the large-diameter portions 64, the corner portion 65 is a portion where the flow velocity is particularly slow. Since it is relatively easy to apply the drug to the large-diameter portion 64, for example, the drug is applied to the large-diameter portion 64 when the flow of the fluid is stopped.

Since it is configured as described above, according to the third embodiment, the following effect (4) is obtained.
(4) For example, for a small-diameter portion 63 where the flow path area is narrow and the fluid flows at a high speed, the drug in the drug tank 61 is injected into the fluid flow by the injection pump 62 to adhere the drug. Further, the chemical is applied to, for example, a large-diameter portion 64 in which the flow path area is wide and the fluid flows at a low flow velocity. As a result, the drug can be suitably attached to the entire surface area of the structural material.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention, and their replacements and changes can be made. Is included in the scope and gist of the invention, and is also included in the invention described in the claims and the equivalent scope thereof.

1 ... Chemical particles, 2 ... Dispersant, 40 ... Chemical construction equipment, 41 ... 1st tank, 42 ... 2nd tank, 43 ... Mixing tank, 44 ... Injection pump (injection means), 50 ... Chemical construction equipment, 51 ... Injection pump (injection means), 63 ... small diameter part, 64 ... large diameter part

Claims (9)

A chemical construction device that attaches a chemical injected into the fluid to the surface of a structural material in which a fluid having a flow velocity distribution flows in contact with the fluid.
A first tank for storing a first drug as a drug containing ions or particles having a particle size of 10 nm or less, and a first tank.
A second tank for storing the second drug as the drug having a particle size of 100 nm or more, and a second tank.
A chemical construction apparatus comprising: an injection means for injecting the first drug in the first tank and the second drug in the second tank into the flow of the fluid. .. The chemical construction apparatus according to claim 1, wherein the first and second chemicals are oxygen scavengers containing hydrogen or hydrazine. According to claim 1 or 2, the particle size of each of the first agent and the second agent is controlled by changing the concentration of the dispersant present in these agents. The drug construction equipment described. When the surface of the structural material is in an environment where the flow velocity of the fluid is low and the first drug does not adhere, the injection means sets the injection ratio of the second drug to be higher than that of the first drug. The chemical application apparatus according to any one of claims 1 to 3, characterized in that it is configured. The chemical application apparatus according to claim 4, wherein the environment in which the flow of the fluid becomes low and the first chemical does not adhere is an environment in which radiation or ultraviolet rays are irradiated. The injection means according to any one of claims 1 to 5, wherein the injection means is one injection pump that injects a drug in which a first drug and a second drug are mixed into a flow of a fluid. Chemical construction equipment. Any one of claims 1 to 6, wherein each of the first drug and the second drug is two or more kinds of drugs having different particle sizes within the range of the particle size of the respective drugs. The chemical construction equipment described in. This is a chemical application method in which a chemical injected into the fluid is attached to the surface of a structural material in which a fluid having a flow velocity distribution flows in contact with the fluid.
Chemical construction characterized by injecting a first drug as the drug containing ions or particles having a particle size of 10 nm or less and a second drug as the drug having a particle size of 100 nm or more into the flow of the fluid. Method. This is a chemical application method in which a chemical injected into the fluid is attached to the surface of a structural material in which a fluid having a flow velocity distribution flows in contact with the fluid.
While injecting the drug containing ions or particles having a particle size of 10 nm or less into the flow of the fluid,
A chemical application method, characterized in that, when the flow of the fluid is stopped, the chemical is applied to a surface of the surface of the structural material where the flow of the fluid becomes low and the chemical does not adhere.

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