KR102675281B1 - Seawater electrolysis system of nuclear power plant and operation method thereof - Google Patents

Abstract

Provides a seawater electrolysis system for a nuclear power plant and its operation method. The seawater electrolysis system of a nuclear power plant is a seawater electrolysis facility for a nuclear power plant, including a seawater supply pump that supplies seawater; A constant current power supply unit that supplies power to the consumer; an aeration tank for supplying the seawater and aerating carbon dioxide into the supplied seawater; And an electrolyzer in which the seawater is supplied and the power is supplied from the constant current power supply, and a reaction including a first reaction and a second reaction based on the first reaction is performed through electrolysis, wherein the electrolyzer is , hydrogen, chlorine, and sodium carbonate are produced, and sodium hypochlorite can be produced based on the reaction of the produced hydrogen and the chlorine.

Description

Seawater electrolysis system of nuclear power plant and operation method thereof}

The present invention relates to a seawater electrolysis system for a nuclear power plant and a method of operating the same.

Large-scale power plants such as nuclear power plants use seawater for cooling in the condenser at the rear of the turbine. The heat-exchanged seawater is discharged back into the sea, and the temperature near the seawater outlet is relatively high, providing a good environment for marine life to inhabit. For this reason, there is a problem in that marine life flows into the seawater system and causes damage to various facilities of the power plant, including seawater cooling pipes and heat exchangers.

To solve this problem, nuclear power plants and large-scale power plants can install seawater electrolysis facilities to produce sodium hypochlorite (NaOCl) for sterilization and add it to seawater to prevent the growth or attachment of marine organisms that have entered heat exchangers or piping. Seawater contains about 3.5% sodium chloride (NaCl), and when this is electrolyzed, chlorine (Cl ₂ ) gas is generated at the anode, and hydrogen (H ₂ ) and sodium hydroxide (NaOH) are generated at the cathode. The generated chlorine and sodium hydroxide react again to produce sodium hypochlorite (NaOCl), which has sterilizing and disinfecting properties. The seawater electrolysis facility installed in the power plant has a water level sensor inside the stored sodium hypochlorite tank, so it starts when the water level is low, but when the water level is high, it automatically stops and remains stopped for a long time. When it is stopped, the seawater cooling system is drained and raw water (raw water) is installed. In order to clean with water and restart, the chlorine concentration is measured periodically and resupplied during startup. However, there is a problem in that sodium hypochlorite must be manually re-injected when necessary to maintain a sufficient chlorine concentration.

Hydrogen has a faster molecular motion than air, so it has a high heat transfer rate and the density of hydrogen is 1/4 of the density of air, so the frictional wind loss caused by the rotating body and gas flow is small, cooling the heat generated in the stator and rotor windings inside the generator. Hydrogen is widely used in power plants as a medium. In addition, hydrogen is used to prevent metal corrosion and adjust pH in power plants. Hydrogen is needed in various systems within the power plant, but the amount of hydrogen (H ₂ ) generated at the cathode during seawater electrolysis is very small, so the produced hydrogen is not utilized because the economic value is low compared to the investment cost of installing utilization facilities. Due to the risk, methods of releasing hydrogen into the atmosphere or converting it to water through a catalytic reaction are used to maintain the hydrogen concentration below 1%. In addition, it can be implemented as a fuel cell system that produces electricity using the generated by-product hydrogen as fuel, but there is currently a problem that commercialization is not easy due to the small amount of hydrogen generated.

Korean Patent Publication No. 10-2014-0076540

The problem to be solved by the present invention is that when the seawater electrolysis facility produces more than the required amount of sodium hypochlorite (NaOCl), which is the intended purpose, it is kept in an idle state due to the high level of the storage tank, which reduces the equipment operation rate and the standstill state lasts for a long time. The goal is to provide a seawater electrolysis system for nuclear power plants that can omit additional management work, including cleaning.

In addition, idle time generated during additional management work is utilized to process carbon dioxide (CO ₂ ), a greenhouse gas, and react with dissolved carbon dioxide (CO ₂ ) with sodium hydroxide (NaOH) to produce sodium carbonate (Na ₂ CO ₃ ). The goal is to provide a seawater electrolysis system for nuclear power plants that can produce nuclear power plants.

In addition, the goal is to provide a seawater electrolysis system for nuclear power plants that overcomes the fact that the hydrogen generated in general seawater electrolysis facilities is small and therefore is not economically feasible to collect and utilize.

In particular, hydrogen is continuously produced as a by-product when producing sodium hydroxide (NaOH), which is needed when converting carbon dioxide (CO ₂ ) into sodium carbonate (Na ₂ CO ₃ ), so this is a nuclear power plant that can produce hydrogen and by-products by increasing the capacity of the facility. To provide a seawater electrolysis system.

In addition, it can produce and store sodium hypochlorite (NaOCl) needed for power plants in a short period of time and produce hydrogen and chemically decompose carbon dioxide (CO ₂ ) without idle time. Sodium carbonate (Na ₂ CO ₃ ), a by-product generated at this time, It provides a seawater electrolysis system for nuclear power plants that can be used as a pH regulator, food additive, or raw material for industrial product production.

The problems of the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

A seawater electrolysis system for a nuclear power plant according to an aspect of the present invention for achieving the above task includes a seawater supply pump for supplying seawater; A constant current power supply unit that supplies power to the consumer; an aeration tank for supplying the seawater and aerating carbon dioxide into the supplied seawater; An electrolyzer in which a reaction including a first reaction and a second reaction based on the first reaction is performed through electrolysis by receiving the seawater and receiving the power from the constant current power supply; And a sodium hypochlorite tank in which sodium hypochlorite produced in the electrolyzer is stored, wherein the electrolyzer produces hydrogen, chlorine, and sodium carbonate, and sodium hypochlorite is produced based on the reaction of the produced hydrogen and chlorine. Generated, the first reaction includes a seawater electrolysis system of a nuclear power plant, including a reaction equation.

In addition, the overall reaction is a seawater electrolysis facility for nuclear power plants based on the following reaction equation. [Full reaction formula 1] 2NaCl + H ₂ O +2e- → NaOCl + NaCl + H ₂ (g) + Heat

In addition, the reaction is a hydrogen production and carbon dioxide conversion system using seawater electrolysis, where the overall reaction is based on the following reaction equation. [Full reaction formula 2] 2NaCl + H ₂ O + CO ₂ +2e- → Na ₂ CO ₃ + H ₂ (g) + Cl ₂ (g)+ Heat

In addition, the storage tank stores the sodium hypochlorite generated in a commercial electrolyzer, and is equipped with a low water level sensor and a high water level sensor, so that when the stored amount of sodium hypochlorite exceeds a standard value, the operation of at least part of the seawater electrolysis facility is stopped. When the storage amount of sodium hypochlorite satisfies the standard value, the operation of the seawater electrolysis facility is resumed. The seawater electrolysis facility for nuclear power plants includes a carbon dioxide storage tank that supplies carbon dioxide to the aeration tank, and surplus that is not dissolved in the aeration tank. It further includes a circulation pump that recovers carbon dioxide and supplies it to the carbon dioxide storage tank, and the seawater supply pump is configured to operate the seawater electrolysis facility when an idle time in which the sodium hypochlorite is not produced occurs due to the stoppage of operation of the seawater electrolysis facility. The seawater is supplied to the aeration tank from time to time.

In addition, the carbon dioxide generated from industrial plants, including steelmaking, cement, petrochemical, and hydrogen production, is collected and transferred to the carbon dioxide storage tank of the storage tank depot for storage, and the aeration tank is connected to an aeration pipe provided at the bottom. The carbon dioxide is aerated in the form of micro-bubbles and supplied until it is saturated in the seawater of the aeration tank.

In addition, the conditions under which the carbon dioxide is supplied to the aeration tank include the supply conditions in which the saturated solubility of carbon dioxide in seawater at 0°C and 1 atm is 3 to 4 kg_CO ₂ /kg, and the carbon dioxide is supplied until saturation is reached, and the seawater electrolysis The equipment further includes a temperature control device that controls the temperature, salinity, and saturation of the seawater depending on the external environment.

In addition, the seawater electrolysis facility further includes a sodium carbonate storage tank in which the sodium carbonate is stored, and the electrolyzer is supplied with a second seawater in which carbon dioxide is dissolved in the aeration tank during the idle time, and the carbon dioxide in the second seawater is supplied. Sodium carbonate is generated by reacting with sodium hydroxide, and the hydrogen and chlorine are continuously generated together in the process of generating the sodium carbonate during the idle time.

A seawater electrolysis system for a nuclear power plant according to another aspect of the present invention for achieving the above problem is a method of operating a seawater electrolysis system for a nuclear power plant, comprising: supplying seawater by a seawater supply pump; Receiving the seawater from an electrolyzer and electrolyzing the seawater based on power supplied from a constant current power supply to generate sodium hypochlorite; The sodium hypochlorite produced in the electrolyzer is stored in the storage tank, and when the water level of the stored sodium hypochlorite exceeds the standard value, the seawater electrolysis facility switches to a process for producing sodium carbonate, hydrogen, and chlorine so that it does not remain idle. Includes steps.

In addition, in the aeration tank of the seawater electrolysis facility, in the idle state, the seawater filled therein is aerated in the form of micro-bubbles through an aeration pipe provided at the bottom until the carbon dioxide is saturated in the seawater of the aeration tank, The electrolyzer is supplied with second seawater in which carbon dioxide is dissolved in the aeration tank during the idle time, and the carbon dioxide in the second seawater reacts with sodium hydroxide to produce sodium carbonate. In the process of generating the sodium carbonate during the idle time, The hydrogen and chlorine are also continuously generated.

According to the present invention as described above, one or more of the following effects are achieved.

The present invention is a seawater electrolysis facility that produces more than the required amount of sodium hypochlorite (NaOCl), which is the intended purpose, and is kept in an idle state due to the high level of the storage tank, which reduces the equipment operation rate and includes cleaning while the stationary state continues for a long time. It is possible to provide a seawater electrolysis system for nuclear power plants that can omit additional management work.

In addition, idle time generated during additional management work is utilized to process carbon dioxide (CO ₂ ), a greenhouse gas, and react with dissolved carbon dioxide (CO ₂ ) with sodium hydroxide (NaOH) to produce sodium carbonate (Na ₂ CO ₃ ). We can provide a seawater electrolysis system for nuclear power plants that can produce

In addition, it is possible to provide a seawater electrolysis system for nuclear power plants that overcomes the fact that the hydrogen generated in general seawater electrolysis facilities is small and therefore is not economically feasible to collect and utilize.

In particular, hydrogen is continuously produced as a by-product when producing sodium hydroxide (NaOH), which is needed when converting carbon dioxide (CO ₂ ) into sodium carbonate (Na ₂ CO ₃ ), so this is a nuclear power plant that can produce hydrogen and by-products by increasing the capacity of the facility. can provide a seawater electrolysis system.

In addition, it can produce and store sodium hypochlorite (NaOCl) needed for power plants in a short period of time and produce hydrogen and chemically decompose carbon dioxide (CO ₂ ) without idle time. Sodium carbonate (Na ₂ CO ₃ ), a by-product generated at this time, It is possible to provide a seawater electrolysis system for nuclear power plants that can be used as a pH regulator, food additive, or raw material for industrial product production.

Figure 1 is a block diagram showing the configuration of a seawater electrolysis system for a nuclear power plant according to an embodiment of the present invention.
FIG. 2 is a configuration diagram showing the configuration of the seawater electrolysis system of the nuclear power plant according to FIG. 1.
Figure 3 is a flow chart sequentially showing a method of operating a seawater electrolysis system for a nuclear power plant according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. The advantages and features of the present invention and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. The present embodiments are merely intended to ensure that the disclosure of the present invention is complete and to provide common knowledge in the technical field to which the present invention pertains. It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Referring to Figure 1, the seawater electrolysis system of a nuclear power plant according to an embodiment of the present invention includes a seawater supply pump 110, a seawater supply valve 115, a temperature control module 118, an aeration tank 120, and an electrolyzer 130. , constant current power supply unit (140), carbon dioxide first supply valve (145), carbon dioxide recovery supply pump (150), carbon dioxide tank (155), carbon dioxide second supply valve (160), hydrogen tank (170), hydrogen tank valve ( 175), chlorine tank (180), chlorine tank valve (185), sodium hypochlorite valve (190), tartrium hypochlorite tank (195), sodium carbonate valve (200), and sodium carbonate tank (205).

Referring to Figures 1 and 2, the seawater electrolysis system of a nuclear power plant uses a seawater supply pump 110 to supply seawater. In addition, the constant current power supply unit 140 supplies power to the demand source.

The aeration tank 120 supplies the seawater and aerates carbon dioxide in the supplied seawater. The electrolyzer 130 receives the seawater and receives the power from the constant current power supply unit 140, and an electrochemical reaction occurs through electrolysis.

More specifically, the reaction in the electrolyzer 130 corresponds to a reaction including a first reaction and a second reaction based on the first reaction. In addition, the sodium hypochlorite tank 195 stores sodium hypochlorite produced in the electrolyzer 130.

The electrolyzer 130 produces hydrogen, chlorine, and sodium carbonate (see overall reaction equation 1 below), and sodium hypochlorite is produced based on the reaction of the hydrogen and chlorine. (See full Scheme 2 below)

Here, the first reaction including the cathode reaction and the anode reaction and the resulting second reaction are performed based on the following reaction formulas 1-1 to 3-2.

Anodic reaction

[Reaction Scheme 1-1]

2Na ⁺ +2e ^- -> 2Na

[Scheme 1-2]

2H ₂ O + 2Na -> 2NaOH + H ₂

Cathodic Reaction

[Reaction Scheme 2] 2Cl ^- -> Cl ₂ +2e ^-

2nd reaction

[Reaction Scheme 3-1]

Cl ₂ + 2NaOH → NaOCl + NaCl + H ₂ O (△H = -100.11 kJ/mol)

[Reaction Scheme 3-2]

CO ₂ + 2NaOH → Na ₂ CO ₃ + H ₂ O (△H = -169.80 kJ/mol)

Ultimately, the reaction has the following overall reaction formula 1 including Reaction Schemes 1-1, 1-2, 2, and 3-1, and the following overall Reaction Scheme including Reaction Schemes 1-1, 1-2, 2, and 3-2. It is based on 2.

[Full reaction formula 1]

2NaCl + H ₂ O +2e- → NaOCl + NaCl + H ₂ (g) + Heat

[Full reaction formula 2]

2NaCl + H ₂ O + CO ₂ +2e- → Na ₂ CO ₃ + H ₂ (g) + Cl ₂ (g)+ Heat

Meanwhile, the sodium hypochlorite tank 195 stores the sodium hypochlorite produced in the commercial electrolyzer 130. The sodium hypochlorite tank 195 is equipped with a low water level sensor 151 and a high water level sensor 152, so that when the storage amount of sodium hypochlorite exceeds the standard value, sodium carbonate and hydrogen are used to prevent the seawater electrolysis facility from remaining idle. , convert to a process that produces chlorine.

That is, the sodium hypochlorite tank stores the sodium hypochlorite produced in a commercial electrolyzer and is equipped with a low water level sensor and a high water level sensor, so that when the stored amount of sodium hypochlorite exceeds the standard value, at least a portion of the seawater electrolysis facility The operation is stopped, and operation of the seawater electrolysis facility is resumed when the stored amount of sodium hypochlorite satisfies the standard value.

In addition, in the idle state, the aeration tank 120 of the seawater electrolysis facility allows the seawater filled inside to bubble through an aeration pipe provided at the bottom until the carbon dioxide is saturated in the seawater of the aeration tank 120. ), the electrolyzer () is supplied with second seawater containing dissolved carbon dioxide from the aeration tank (120) during the idle time, and the carbon dioxide in the second seawater reacts with sodium hydroxide to produce sodium carbonate. Here, in the process of generating the sodium carbonate during the idle time, the hydrogen and the chlorine are also continuously generated.

In addition, when the stored amount of sodium hypochlorite satisfies the standard value, the operation of the seawater electrolysis facility 100 can be restarted. The carbon dioxide tank 155 supplies carbon dioxide to the aeration tank 120.

The circulation pump 165 recovers undissolved excess carbon dioxide from the aeration tank 120 and supplies it to the carbon dioxide tank 155. In addition, when an idle time occurs in which the sodium hypochlorite is not produced based on the stop signal of the seawater electrolysis facility 100, the seawater supply pump 110 supplies the seawater to the aeration tank 120 during the idle time. supply.

At this time, the aeration tank 120 may be supplied with seawater having a salinity of 3 to 5% through the seawater supply pump 110 during the idle time. The carbon dioxide generated in industrial plants, including steelmaking, cement, petrochemical, and hydrogen production, is captured, transferred to the carbon dioxide tank 155, and stored.

The carbon dioxide is aerated in the form of micro-bubbles by an aeration pipe provided at the bottom of the aeration tank 120, and the carbon dioxide is supplied until the seawater in the aeration tank 120 is saturated.

Here, the conditions under which the carbon dioxide is supplied to the aeration tank 120 include the supply conditions in which the saturated solubility of carbon dioxide in seawater at 0°C and 1 atm is 3 to 4 kg_CO ₂ /kg, and the carbon dioxide is supplied until saturation is reached.

The temperature control module 118 of the seawater electrolysis system 100 performs temperature control for the aeration tank 120 to control saturation, which varies depending on the temperature, salinity, and external environment of the seawater.

The sodium carbonate tank 205 of the seawater electrolysis system 100 stores the sodium carbonate. The electrolyzer 130 is supplied with second seawater containing dissolved carbon dioxide from the aeration tank 120 during the idle time, and the carbon dioxide in the second seawater reacts with sodium hydroxide to produce sodium carbonate.

Here, in the process of generating the sodium carbonate during the idle time, the hydrogen and the chlorine are continuously generated together. The electrolyzer 130 generates the hydrogen and the chlorine based on electrolysis of the second seawater during the idle time.

The hydrogen tank 170 of the seawater electrolysis system 100 stores the hydrogen generated during the idle time, and the chlorine tank 180 stores the chlorine generated during the idle time.

Referring to FIG. 3, the seawater electrolysis system operation method of a nuclear power plant (S100) includes a supply stage (S110), a generation stage (S120), and an idle state stage (S130).

In S110, the seawater supply pump 110 supplies seawater, and in S120, the electrolyzer 130 receives the seawater and electrolyzes the seawater based on the power supplied from the constant current power supply unit 140 to produce sodium hypochlorite. Create.

S130 stores the sodium hypochlorite produced in the electrolyzer 130 in the sodium hypochlorite tank 195. If the level of the sodium hypochlorite stored here exceeds the reference value, the operation of at least part of the seawater electrolysis facility 100 is stopped to make the seawater electrolysis facility 100 in an idle state.

Here, the carbon dioxide is aerated in the form of microbubbles by an aeration pipe provided at the bottom of the aeration tank 120, and the carbon dioxide is supplied until the seawater in the aeration tank 120 is saturated.

The electrolyzer 130 is supplied with second seawater containing dissolved carbon dioxide from the aeration tank 120 during the idle time, and the carbon dioxide in the second seawater reacts with sodium hydroxide to produce sodium carbonate. In addition, in the process of generating the sodium carbonate during the idle time, the hydrogen and the chlorine are also continuously generated.

Although embodiments of the present invention have been described with reference to the above and the attached drawings, those skilled in the art will understand that the present invention can be implemented in other specific forms without changing its technical idea or essential features. You will understand that it exists. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive.

110: Seawater supply pump
115: Seawater supply valve
118: Temperature control module
120: Aeration tank
130: electrolyzer
140: Constant current power supply unit

Claims (8)

As a seawater electrolysis facility for nuclear power plants,
A seawater supply pump that supplies seawater;
A constant current power supply unit that supplies power to the consumer;
an aeration tank for supplying the seawater and aerating carbon dioxide into the supplied seawater; and
An electrolyzer that receives the seawater and receives the power from the constant current power supply, and performs an overall reaction including a first reaction and a second reaction based on the first reaction through electrolysis,
The electrolyzer produces hydrogen, chlorine, and sodium carbonate,
When sodium chloride contained in the seawater is electrolyzed in the electrolyzer, chlorine, hydrogen, and sodium hydroxide are generated, and the generated chlorine and sodium hydroxide react again to produce sodium hypochlorite,
The overall reaction is based on the following reaction equations,
[Full reaction formula 1]
2NaCl + H ₂ O +2e- → NaOCl + NaCl + H ₂ (g) + Heat
[Full reaction formula 2]
2NaCl + H ₂ O + CO ₂ +2e- → Na ₂ CO ₃ + H ₂ (g) + Cl ₂ (g)+ Heat
It further includes a sodium hypochlorite tank,
The sodium hypochlorite tank,
The sodium hypochlorite produced in the electrolyzer is stored, and a low water level sensor and a high water level sensor are provided to stop the operation of at least part of the seawater electrolysis facility when the stored amount of sodium hypochlorite exceeds a reference value,
The operation of the seawater electrolysis facility is resumed when the stored amount of sodium hypochlorite satisfies the standard value,
Seawater electrolysis equipment for nuclear power plants,
A carbon dioxide storage tank that supplies carbon dioxide to the aeration tank,
It further includes a circulation pump that recovers undissolved excess carbon dioxide from the aeration tank and supplies it to the carbon dioxide storage tank,
The seawater supply pump,
A seawater electrolysis facility for a nuclear power plant that supplies the seawater to the aeration tank even during the idle time when an idle time in which the sodium hypochlorite is not produced occurs due to the stoppage of operation of the seawater electrolysis facility. delete delete delete According to paragraph 1,
The carbon dioxide is collected from industrial plants including steelmaking, cement, petrochemicals, and hydrogen production, and is transferred to the carbon dioxide storage tank and stored,
The aeration tank is a seawater electrolysis facility for a nuclear power plant in which the carbon dioxide is aerated in the form of microbubbles by an aeration pipe provided at the bottom of the aeration tank and supplied until it is saturated in the seawater of the aeration tank. According to paragraph 1,
The conditions under which the carbon dioxide is supplied to the aeration tank are:
The saturated solubility of carbon dioxide in seawater at 0℃ and 1 atm is 3~4kg_CO ₂ /kg, including the supply condition of supply until saturation is reached.
The seawater electrolysis facility,
A seawater electrolysis facility for a nuclear power plant, further comprising a temperature control device that controls saturation that varies depending on the temperature, salinity, and external environment of the seawater. According to clause 6,
The seawater electrolysis facility further includes a sodium carbonate storage tank in which the sodium carbonate is stored,
The electrolyzer is,
During the idle time, second seawater in which carbon dioxide is dissolved is supplied from the aeration tank, and the carbon dioxide in the second seawater reacts with sodium hydroxide to produce sodium carbonate,
A seawater electrolysis facility for a nuclear power plant in which the hydrogen and the chlorine are continuously generated during the process of generating the sodium carbonate during the idle time. As a method of operating a seawater electrolysis facility for a nuclear power plant,
A step where the seawater supply pump supplies seawater;
Receiving the seawater from an electrolyzer and electrolyzing the seawater based on power supplied from a constant current power supply to generate sodium hypochlorite;
The sodium hypochlorite generated in the electrolyzer is stored in the storage tank, and when the stored water level of the sodium hypochlorite exceeds the standard value, stopping the operation of at least part of the seawater electrolysis facility to put the seawater electrolysis facility in an idle state. Including,
In the idle state, the aeration tank of the seawater electrolysis facility aerates the seawater filled therein in the form of micro-bubbles through an aeration pipe provided at the bottom until carbon dioxide saturates the seawater of the aeration tank,
The electrolyzer is supplied with second seawater in which carbon dioxide is dissolved in the aeration tank, and carbon dioxide in the second seawater reacts with sodium hydroxide to produce sodium carbonate,
A method of operating a seawater electrolysis facility for a nuclear power plant in which hydrogen and chlorine are continuously generated in the process of generating the sodium carbonate.

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