An indirect air cooling system for a nuclear power plant

Abstract

The invention discloses an indirect air cooling system for a nuclear power plant, comprising a condenser, a bypass processing device, a circulating water pump, an indirect cooling tower and an air cooling radiator; the air cooling radiator is arranged at the bottom of the indirect cooling tower, the exhaust port of an external steam turbine is connected to the shell side inlet of the condenser, the shell side outlet of the condenser is connected to the external condensate pump, the water outlet of the air cooling radiator is connected to the tube side inlet of the condenser, and the tube side outlet of the condenser is connected to the water inlet of the air cooling radiator via the circulating water pump. The system solves the problems of large water consumption and corrosion of open circulating water in nuclear power plants.

Description

Technical Field

[0001] The invention belongs to the field of nuclear power and relates to an indirect air cooling system of a nuclear power plant. Background Art

[0002] my country's nuclear power plants are generally located near the sea. In addition to the stable geological conditions of the site, the most critical factor is that the nuclear power plant needs a large amount of cold source as the exhaust steam of the circulating water cooling steam turbine. 3 / h, the circulating water volume is about 1.2×10 5 m 3 / h, the exhaust volume of a 1000WM nuclear power unit is 3500m 3 / h, the circulating water volume is about 2.2×10 5 m 3 / h, and directly discharged into the sea, which has a significant thermal effect on the ocean and will cause thermal pollution. The exhaust volume of the low-pressure cylinder of a 1000WM thermal power unit is 1600m 3 / h, the circulating water flow rate is about 4×10 4 m 3 / h. The water loss of cooling tower cooling mainly includes evaporation loss, sewage loss and wind loss, which is generally 3%-5% of the circulation volume. 3 / h-2000m 3 / h, and the consumption of circulating water accounts for more than 90% of the water consumption of the entire power plant. If nuclear power is developed inland, according to the cooling tower cooling method of thermal power, the consumption of circulating water of a 1000WM nuclear power unit will reach 1.1×10 4 m 3 / h; if direct seawater cooling is adopted, the circulating water volume is about 2.2×10 5 m 3 / h, which will increase investment, cause thermal pollution of water resources, and greatly restrict the choice of site. In addition, the direct-discharge seawater cooling method is prone to problems such as high circulating water consumption and corrosion because the system is in contact with circulating water in an open manner. Summary of the invention

[0003] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide an indirect air cooling system for a nuclear power plant, which solves the problems of high water consumption and corrosion of open circulating water in nuclear power plants.

[0004] To achieve the above-mentioned object, the indirect air cooling system of a nuclear power plant described in the present invention comprises a condenser, a bypass flow treatment device, a circulating water pump, an indirect cooling tower and an air cooling radiator;

[0005] The air-cooled radiator is arranged at the bottom of the intercooling tower, the exhaust port of the external steam turbine is connected with the shell side inlet of the condenser, the shell side outlet of the condenser is connected with the external condensate pump, the water outlet of the air-cooled radiator is connected with the tube side inlet of the condenser, and the tube side outlet of the condenser is connected with the water inlet of the air-cooled radiator through the circulating water pump.

[0006] A forced circulation fan is installed in the indirect cooling tower.

[0007] It also includes a side stream processing device, wherein the side stream processing device is connected in parallel with the pipeline between the circulating water pump and the air-cooled radiator.

[0008] The side stream treatment device comprises a filter and a desalination device, wherein the filter and the desalination device are connected in series.

[0009] According to equations (1), (2) and (3), the average heat transfer temperature difference Δt is calculated. m , calculate the heat exchange area S of the air-cooled radiator according to formula (4);

[0010] t 1 =t s -t d (1)

[0011]

[0012]

[0013]

[0014] Among them, Q is the heat transfer capacity of the air-cooled radiator, K is the total heat transfer coefficient, S is the heat transfer area of ​​the air-cooled radiator, Δt m is the average temperature difference of heat transfer, m a is the headwind mass velocity through the air-cooled radiator, t s is the saturated steam temperature corresponding to the turbine exhaust pressure, t 1 is the water inlet temperature of the air-cooled radiator, t 2 is the outlet water temperature of the air-cooled radiator, T 1 is the inlet air temperature of the air-cooled radiator, T 2 is the outlet air temperature of the air-cooled radiator, t d is the terminal difference of the condenser, F c is the circulating cooling water flow rate, c pw is the specific heat capacity of water, F k is the exhaust volume of the main steam turbine, h k is the exhaust enthalpy of the main steam turbine, h c is the enthalpy of condensed water in the main engine, Q s To dissipate heat for hydrophobicity.

[0015] The height H of the intercooling tower 4 is:

[0016]

[0017] Among them, ρ 1 is the density of cold air outside the intercooler, ρ 2 is the density of hot air in the intercooler, g is the acceleration of gravity, H is the effective height of the intercooler, m a is the headwind mass velocity through the air-cooled radiator.

[0018] The present invention has the following beneficial effects:

[0019] The indirect air cooling system of the nuclear power plant described in the present invention uses closed-loop circulating water to cool the exhaust steam of the steam turbine during specific operation, without evaporation loss. For the water-scarce northern region, it saves water resources, solves the technical problem of inland site selection of nuclear power plants, and makes the site selection of inland nuclear power plants more flexible. At the same time, the quality of water is easy to control, and high-quality water contributes to a good heat exchange effect, avoiding a series of problems such as pipe scaling, pipe blockage, and pipe corrosion. In addition, the air density difference inside and outside the intercooling tower drives the air to flow from the bottom of the outer edge of the intercooling tower to the top of the intercooling tower. During this period, the intercooling circulating water is cooled by natural air circulation, and there is no need to use a fan for forced cooling. The circulating water can be continuously cooled, saving electric energy, and also in line with the passive safety concept of nuclear power. The intercooling circulating water system is physically isolated from the secondary circuit water, and has good safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural diagram of the prior art;

[0021] Figure 2 It is a structural schematic diagram of the present invention;

[0022] Figure 3 It is a structural diagram of the intercooling tower 4.

[0023] Among them, 1 is a condenser, 2 is a side stream treatment device, 3 is a circulating water pump, 4 is an intercooler, 5 is a forced circulation fan, and 6 is an air-cooled radiator. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only an embodiment of a part of the present invention, not all embodiments, and is not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concepts disclosed in the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0025] The accompanying drawings show schematic diagrams of structures according to embodiments disclosed in the present invention. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0026] refer to Figure 2 and Figure 3 The indirect air cooling system of a nuclear power plant described in the present invention comprises a condenser 1, a bypass processing device 2, a circulating water pump 3, an indirect cooling tower 4, a forced circulation fan 5 and an air cooling radiator 6;

[0027] Among them, the air-cooled radiator 6 is arranged at the bottom of the intercooling tower 4, and the forced circulation fan 5 is arranged in the intercooling tower 4; the exhaust port of the steam turbine is connected to the shell side inlet of the condenser 1, the shell side outlet of the condenser 1 is connected to the condensate pump, the water outlet of the air-cooled radiator 6 is connected to the tube side inlet of the condenser 1, and the tube side outlet of the condenser 1 is connected to the water inlet of the air-cooled radiator 6 through the circulating water pump 3. In the present invention, desalted water is used as the cooling medium. After the circulating water passes through the condenser 1 to condense the exhaust steam of the steam turbine, the temperature of the intercooling circulating water increases by 8-10°C. After the circulating water is pressurized by the circulating water pump 3, it enters the air-cooled radiator 6 at the bottom of the intercooling tower 4. The air-cooled radiator 6 is composed of finned tubes, tube bundles, cooling triangles and cooling fan-shaped sections. The circulating water flows in the tube bundles and finned tubes of the air-cooled radiator 6 to exchange heat with the cold air outside the air-cooled radiator 6. The circulating water temperature is reduced by 8-10°C. The cooled circulating water enters the tube side of the condenser 1 to cool the exhaust steam of the steam turbine, completing the circulation process. The air heated by heat exchange in the air-cooled radiator 6 has a lower density, and the air naturally rises, forming a suction force in the intercooling tower 4, and finally discharged from the intercooling tower 4. At the same time, the cold air is sucked from the bottom of the air-cooled radiator 6 into the intercooling tower 4 to form a circulating suction process of air. In addition, the present invention is provided with a bypass treatment device 2, wherein the bypass treatment device 2 is connected in parallel with the pipeline between the circulating water pump 3 and the air-cooled radiator 6, and the bypass treatment device 2 includes a filter and a desalination device. The function of the filter is to remove particulate matter in the water, and the function of the desalination device is to remove ions in the water. The function of the bypass treatment device 2 is to put the bypass treatment device 2 into operation online after overhaul or when the water quality deteriorates under extreme working conditions to improve the water quality; in addition, the present invention is provided with a forced circulation fan 5 in the intercooling tower 4 to ensure that the forced circulation fan 5 is started under extreme working conditions to achieve the purpose of rapid cooling of the circulating water.

[0028] It should be noted that the core of the present invention lies in the design of the heat exchange area S of the air-cooling radiator 6 and the height H of the indirect cooling tower 4 .

[0029] According to equations (1), (2) and (3), the average heat transfer temperature difference Δt is calculated. m , calculate the heat exchange area S of the air-cooled radiator 6 according to formula (4).

[0030] t 1 =t s -t d (1)

[0031]

[0032]

[0033]

[0034] Wherein, Q is the heat transfer capacity of the air-cooled radiator 6 (W); K is the total heat transfer coefficient [W / (㎡·℃)]; S is the heat transfer area of ​​the air-cooled radiator 6 (m); Δt m is the average temperature difference of heat transfer (℃); m a is the oncoming mass wind speed passing through the air-cooled radiator 6 [kg / (s·m 2 )]; t s is the saturated steam temperature corresponding to the turbine exhaust pressure (°C); t 1 is the water inlet temperature of the air-cooled radiator 6 (°C); t 2 is the outlet water temperature of the air-cooled radiator 6 (°C); T 1 is the inlet air temperature of the air-cooled radiator 6, i.e., the ambient dry-bulb temperature (°C); T 2 is the outlet air temperature of the air-cooled radiator 6 (°C); t d is the terminal difference of condenser 1 (℃); F c is the circulating cooling water flow rate (kg / s); c pw is the specific heat capacity of water, 4187 [J / (kg·℃)]; F k is the exhaust volume of the main steam turbine (kg / s); h k is the exhaust enthalpy of the main steam turbine (J / kg); h c is the enthalpy of condensed water in the main engine (J / kg); Q s is the heat dissipation of the hydrophobic element (W).

[0035] The height H of the intercooling tower 4 is:

[0036]

[0037] Among them, ρ 1 is the density of the external cooling air in the intercooler 4 (kg / m 3 );ρ 2 is the density of hot air in intercooler 4 (kg / m 3); g is the acceleration due to gravity (m / s 2 ); H is the effective height of the intercooler 4 (m); m a is the oncoming mass wind speed passing through the air-cooled radiator 6 [kg / (s·m 2 )].

[0038] It should be noted that the present invention is provided with a forced circulation fan 5 in the intercooling tower 4. The forced circulation fan 5 can be an axial flow fan to ensure that the forced circulation fan 5 is started under extreme working conditions to achieve the purpose of rapid cooling of the circulating water. The main design parameters of the forced circulation fan 5 are the air volume and the fan position. According to the simulation results of the simulation software, the design air volume is ≧2% of the normal air intake through the windward surface of the air-cooling radiator 6; the central position is on the central axis of the intercooling tower 4, and the horizontal position is within the range from the horizontal plane of the bottom of the air-cooling radiator 6 to 1 / 2 of the height of the air-cooling radiator 6. The specific position is as follows: Figure 3 shown.

Claims

1. An indirect air cooling system for a nuclear power plant, characterized in that: It comprises a condenser (1), a side stream treatment device (2), a circulating water pump (3), an intercooler (4) and an air-cooling radiator (6); The air-cooling radiator (6) is arranged at the bottom of the intercooling tower (4); the exhaust port of the external steam turbine is connected to the shell side inlet of the condenser (1); the shell side outlet of the condenser (1) is connected to the external condensate pump; the water outlet of the air-cooling radiator (6) is connected to the tube side inlet of the condenser (1); and the tube side outlet of the condenser (1) is connected to the water inlet of the air-cooling radiator (6) via the circulating water pump (3); According to equations (1), (2) and (3), the average heat transfer temperature difference Δt is calculated. m , calculate the heat exchange area S of the air-cooled radiator (6) according to formula (4); （1） （2） （3） （4） Wherein, Q is the heat transfer capacity of the air-cooled radiator (6), K is the total heat transfer coefficient, S is the heat transfer area of ​​the air-cooled radiator (6), Δt m is the average temperature difference of heat transfer, m a is the headwind mass velocity through the air-cooled radiator (6), t s is the saturated steam temperature corresponding to the turbine exhaust pressure, t1 is the water inlet temperature of the air-cooled radiator (6), t2 is the water outlet temperature of the air-cooled radiator (6), T1 is the inlet air temperature of the air-cooled radiator (6), T2 is the outlet air temperature of the air-cooled radiator (6), t d is the terminal difference of condenser (1), F c is the circulating cooling water flow rate, c pw is the specific heat capacity of water, F k is the exhaust volume of the main steam turbine, h k is the exhaust enthalpy of the main engine steam turbine, h c is the enthalpy of condensed water in the main engine, Q s To dissipate heat for hydrophobicity; The height H of the intercooler (4) is: （5） Wherein, ρ1 is the cold air density outside the intercooler (4), ρ2 is the hot air density inside the intercooler (4), g is the gravitational acceleration, H is the effective height of the intercooler (4), m a is the headwind mass velocity passing through the air-cooled radiator (6).

2. The indirect air cooling system for a nuclear power plant according to claim 1, characterized in that: A forced circulation fan (5) is arranged in the intercooling tower (4).

3. The indirect air cooling system for a nuclear power plant according to claim 1, characterized in that: It also includes a side stream processing device (2), wherein the side stream processing device (2) is connected in parallel with a pipeline between the circulating water pump (3) and the air-cooling radiator (6).

4. The indirect air cooling system for a nuclear power plant according to claim 3, characterized in that: The side stream treatment device (2) comprises a filter and a desalination device, wherein the filter and the desalination device are connected in series.

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