A nuclear power plant extraction heating system configured with a steam accumulator

Abstract

The application discloses a nuclear power plant steam extraction heat supply system with a steam heat accumulator, comprising a power generation module, a steam extraction module, a heat supply module and a heat accumulator module: a steam generator is connected with a high-pressure cylinder, a low-pressure cylinder and a condenser in sequence; the low-pressure cylinder is connected with a generator; a steam extraction inlet is connected with a steam pipeline between the high-pressure cylinder and the low-pressure cylinder; a first steam extraction outlet and a second steam extraction outlet are connected with a first steam inlet, the second steam extraction outlet is connected with a second steam inlet, a steam outlet of the low-pressure cylinder and the first steam extraction outlet are connected with a steam inlet of the condenser, a condensate outlet of the condenser is connected with an inlet of a feed water pump through a water extraction port, and an outlet of the feed water pump is connected with a second water inlet. The application uses condenser warm drainage as the water inlet of the steam heat accumulator, can enhance the flexibility of the nuclear power plant heat supply, improve the upper limit of the heat supply capacity, improve the heat utilization efficiency of the reactor and prolong the service life of the steam heat accumulator under the premise of no adjustment of the steam extraction amount and stable power operation of the reactor.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power technology, and specifically relates to a steam extraction heating system for nuclear power plants equipped with a steam thermal storage device. Background Technology

[0002] Nuclear energy is a clean energy source with no greenhouse gas emissions. Steam extraction heating is a combined heat and power (CHP) scheme used in nuclear power plants, which can meet the clean heating needs of towns while simultaneously supplying electricity. Nuclear power plants employ a dual-loop intermediate steam extraction heating technology, with the extraction point located between the high-pressure and low-pressure cylinders. High-quality steam enters the high-pressure cylinder of the turbine to generate electricity, while low-quality steam, in addition to entering the low-pressure cylinder for power generation, is partially extracted as a heat source and supplied to town users through a steam-water heat exchanger.

[0003] To ensure reactor safety, the maximum extraction steam rate is limited by the unit's load step safety threshold. For example, in a pressurized water reactor designed for a 10% load step adaptability, the maximum extraction steam rate accounts for approximately 6% of the total steam intake into the low-pressure cylinder. In a nuclear power plant's combined heat and power (CHP) mode, generator load and heating extraction steam load affect reactor operating power. Excessive extraction steam rate may cause potential accidents such as primary loop overheating, and fluctuations in extraction steam rate can also affect the reactor's stable operation. Currently, user heating demand varies at different times of day and night. Existing extraction steam heating technology lacks the flexibility to respond to fluctuations in heating steam load under CHP mode, and can only supply limited heat during peak demand periods.

[0004] A search of publicly available patents related to nuclear power extraction heating reveals that, under the premise of ensuring stable reactor operating power, combining steam accumulators is one of the effective methods for regulating extraction heating. This method can meet changes in heat demand without adjusting the secondary loop extraction steam volume, enhancing the flexibility of nuclear power plant heating. Furthermore, by releasing heat stored during off-peak hours during peak hours, it can provide users with an additional heat source, increasing the upper limit of the nuclear power plant's heating capacity. Examples include "A Nuclear Heating System for a Floating Offshore Reactor with a Steam Accumulator" (CN 110160112A), "A Reactor Steam Storage and Heating System" (CN208817098 U), and "A Nuclear Cogeneration System for a Floating Offshore Reactor with a Thermal Storage Device" (CN 208817098 U).

[0005] However, existing technologies still have the following problems:

[0006] (1) Steam accumulators achieve convective heat transfer through circulation pipes. If there is a cold water zone with a large temperature difference in the water volume at the bottom of the accumulator shell, a large temperature gradient will be generated, which may induce uneven thermal expansion of the metal shell wall and cause cracking. At present, there is no report on the method of controlling the temperature gradient by water inlet.

[0007] (2) Nuclear power plant condensers discharge a large amount of warm wastewater, which is generally 6 to 12°C higher than the temperature of the receiving water in the environment. Its heat accounts for about 60% of the reactor’s heat output, and its heat utilization efficiency is not high. At present, there are no reports on the method of combining warm wastewater with steam accumulators. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing a nuclear power plant extraction steam heating system equipped with a steam thermal storage device. This system enhances the flexibility of nuclear power plant heating and increases the upper limit of heating capacity while ensuring stable reactor power operation without adjusting the extraction steam volume. Simultaneously, it extracts warm wastewater as the inlet water for the steam thermal storage device, thereby improving reactor thermal utilization efficiency and extending the service life of the steam thermal storage device.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A nuclear power plant steam extraction and heating system equipped with a steam thermal storage device includes a power generation module, a steam extraction module, a heating module, and a thermal storage module.

[0011] The power generation module includes a steam generator, a high-pressure cylinder, a low-pressure cylinder, a generator, and a condenser; the steam extraction module includes a steam extraction inlet, and the steam extraction inlet outlet is divided into a first steam extraction outlet and a second steam extraction outlet; the heating module includes a steam-water heat exchanger, which is equipped with a first steam inlet, a first steam outlet, a first water inlet, and a first water outlet; the heat storage module includes a steam accumulator and a feedwater pump, which is equipped with a second steam inlet, a second steam outlet, a second water inlet, and a second water outlet, and the feedwater pump inlet is connected to a water extraction port;

[0012] The steam generator is connected in sequence to the high-pressure cylinder, the low-pressure cylinder, and the condenser; the low-pressure cylinder is connected to the generator; the extraction steam inlet is connected to the steam pipeline between the high-pressure cylinder and the low-pressure cylinder; the first extraction steam outlet and the second steam outlet are connected to the first steam inlet, the second extraction steam outlet is connected to the second steam inlet, the steam outlet of the low-pressure cylinder and the first steam outlet are connected to the steam inlet of the condenser, the condensate outlet of the condenser is connected to the inlet of the feedwater pump through the water extraction port, and the outlet of the feedwater pump is connected to the second water inlet.

[0013] A further improvement of the present invention is that the steam accumulator adopts a horizontal variable pressure steam accumulator, which is equipped with steam nozzles and circulation pipes, and the heat storage medium is water. During operation, the upper part of the accumulator is a steam space and the lower part is a water volume.

[0014] A further improvement of the present invention is that the water inlet of the steam accumulator is drawn from the condenser temperature drainage pipeline.

[0015] A further improvement of the invention is that the steam generator is also connected to the reactor.

[0016] A further improvement of the present invention is that the first extraction steam outlet is connected to the first steam inlet via a first regulating valve.

[0017] A further improvement of the present invention is that the second extraction steam outlet is connected to the second steam inlet via a second regulating valve.

[0018] A further improvement of the present invention is that a third regulating valve is provided at the second steam outlet.

[0019] A further improvement of the present invention is that a fourth regulating valve is provided at the inlet of the water pump.

[0020] A further improvement of the present invention is that a fifth regulating valve is provided at the second water outlet.

[0021] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0022] (1) The steam accumulator draws out warm water from the inlet, avoiding the need for the nuclear power plant to supply additional water to the accumulator and improving the water resource utilization rate.

[0023] (2) It reduces the amount of warm wastewater discharged into natural water bodies, which can alleviate the thermal pollution problem caused by the direct discharge of warm wastewater into natural water bodies around nuclear power plants.

[0024] (3) Recovering and utilizing the waste heat of the warm water can avoid the presence of a cold water zone with a large temperature difference in the lower water volume of the accumulator, prevent uneven expansion of the metal cylinder wall and cracking, and extend the service life of the steam accumulator.

[0025] (4) The accumulator inlet water line is led out from the condenser hot water drain line and directly connected to the accumulator through the feed water pump. The required new equipment is small and the technical transformation cost of the existing nuclear power plant is low. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a nuclear power plant steam extraction heating system equipped with a steam thermal storage device, according to the present invention.

[0027] Explanation of reference numerals in the attached figures:

[0028] 1-Steam generator, 2-High-pressure cylinder, 3-Low-pressure cylinder, 4-Generator, 5-Condenser, 6-Steam-water heat exchanger, 7-Steam accumulator, 8-Feed water pump, 9-Circulation pipe, 10-First regulating valve, 11-Second regulating valve, 12-Third regulating valve, 13-Fourth regulating valve, 14-Fifth regulating valve, 1.1-Steam extraction inlet, 1.2-First steam extraction outlet, 1.3-Second steam extraction outlet, 2.1-First steam inlet, 2.2-First steam outlet, 2.3-First water inlet, 2.4-First water outlet, 3.1-Second steam inlet, 3.2-Second steam outlet, 3.3-Water extraction port, 3.4-Second water inlet, 3.5-Second water outlet. Detailed Implementation

[0029] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0030] like Figure 1 As shown, the present invention provides a nuclear power plant steam extraction heating system with a steam thermal storage device, comprising a power generation module, a steam extraction module, a heating module and a thermal storage module.

[0031] The power generation module includes a steam generator 1, a high-pressure cylinder 2, a low-pressure cylinder 3, a generator 4, and a condenser 5; wherein the steam generator 1 is connected in sequence to the high-pressure cylinder 2, the low-pressure cylinder 3, and the condenser 5; the low-pressure cylinder 3 is connected to the generator 4.

[0032] The steam extraction module includes a steam extraction inlet 1.1, a first steam extraction outlet 1.2, and a second steam extraction outlet 1.3; wherein the steam extraction inlet 1.1 is connected to the steam pipeline between the high-pressure cylinder 2 and the low-pressure cylinder 3; the first steam extraction outlet 1.2 is connected to the first regulating valve 10; and the second steam extraction outlet 1.3 is connected to the second regulating valve 11.

[0033] The heating module includes a steam-water heat exchanger 6, a first steam inlet 2.1, a first steam outlet 2.2, a first water inlet 2.3, and a first water outlet 2.4; wherein the first steam inlet 2.1 is connected to the steam-water heat exchanger 6 via a first regulating valve 10; the first steam outlet 2.2 is connected to the condenser 5 via the steam-water heat exchanger 6; the first water inlet 2.3 is connected to the steam-water heat exchanger 6 via the heating network return water pipeline; and the first water outlet 2.4 is connected to the heating network supply water pipeline via the steam-water heat exchanger 6.

[0034] The heat storage module includes a steam accumulator 7, a feed water pump 8, a second steam inlet 3.1, a second steam outlet 3.2, a water extraction port 3.3, a second water inlet 3.4, and a second water outlet 3.5; wherein the second steam inlet 3.1 is connected to the steam accumulator 7 via a second regulating valve 11; the second steam outlet 3.2 is connected to the third regulating valve 12 via the steam accumulator 7; the water extraction port 3.3 is connected to the fourth regulating valve 13 via the condenser 5's hot water drain line; the second water inlet 3.4 is connected to the steam accumulator 7 via the feed water pump 8; and a fifth regulating valve 14 is provided at the second water outlet 3.5.

[0035] If the steam load is lower than the extraction capacity, there is no need to adjust the extraction rate between the high-pressure cylinder 2 and the low-pressure cylinder 3. Steam flows out from the first extraction outlet 1.2 and the second extraction outlet 1.3 through the extraction inlet 1.1. The first part is used for heating, and the second part is used for heat storage. The amount of steam used for heating is controlled by the first regulating valve 10, so that the steam that meets the load enters the steam-water heat exchanger 6 through the first steam inlet 2.1 to exchange heat energy with the heating network. After heat exchange, it enters the condenser 5 through the first steam outlet 2.2, and the condensate enters the secondary loop of the conventional island. The third regulating valve 12, the fourth regulating valve 13, and the fifth regulating valve 14 are closed, and the excess steam is controlled by the second regulating valve 11 to enter the steam accumulator 7 through the second steam inlet 3.1. Steam is injected into the water from the nozzle, and the water in the circulation pipe 9 is heated. Some of the water is replaced by steam bubbles to form a lighter steam-water mixture, which diffuses and rises through the upper opening of the circulation pipe 9. Under the action of the pressure difference inside and outside the circulation pipe 9, the water at the lower opening of the circulation pipe 9 flows upward into the circulation pipe 9. The water circulation convection continuously carries the heat of the steam to the outside of the circulation pipe 9 and fully transfers it to the water in the water volume of the heat storage tank 9. The water temperature in each part of the water volume gradually becomes more uniform, thus completing the storage of heat.

[0036] If the steam load equals the extraction capacity, all extracted steam flows out through the first extraction outlet 1.2 for heating, and no longer flows out through the second extraction outlet 1.3 for heat storage. The second regulating valve 11 is closed, and the first regulating valve 10 is fully opened, controlling all steam extracted between the high-pressure cylinder 2 and the low-pressure cylinder 3 to enter the steam-water heat exchanger 6 to exchange heat energy with the heating network. After heat exchange, the steam enters the condenser 5 through the first steam outlet 2.2, and the condensate flows into the secondary loop of the conventional island.

[0037] If the steam load exceeds the extraction capacity, in addition to all the extracted steam flowing out through the first extraction outlet 1.2 for heating, the steam accumulator 7 is used for auxiliary heating. The second regulating valve 11 is closed, and the third regulating valve 12 near the accumulator 7 is opened. Because the pressure inside the accumulator 7 is greater than the pressure in the outlet pipeline, the steam in the steam space of the accumulator 7 flows out of the accumulator 7, through the second steam outlet 3.2, and into the steam-water heat exchanger 6 through the first steam inlet 2.1, exchanging heat energy with the heating network. The saturated water pressure inside the accumulator 7 decreases, causing the water temperature to exceed the saturation temperature after pressure reduction, becoming superheated water. The superheated water flashes to generate steam. The pressure and water temperature inside the accumulator decrease, the water level and enthalpy decrease, completing the heat release. The pumping rate is controlled by the fourth regulating valve 13, drawing water from the condenser 5 hot water drain line pumping port 3.3, and then pumping it into the accumulator 7 through the feedwater pump 8 from the second inlet 3.4 to replenish the water level. When the steam accumulator needs to be inspected, open the fifth regulating valve 14 and drain the water vapor mixture stored in the steam accumulator 7 from the second outlet 3.5.

[0038] This invention has been described through embodiments. Those skilled in the art will understand that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the guidance of this invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of this invention.

Claims

1. A steam extraction heating system for a nuclear power plant equipped with a steam thermal storage device, characterized in that, Includes power generation modules, steam extraction modules, heating modules, and thermal storage modules: The power generation module includes a steam generator (1), a high-pressure cylinder (2), a low-pressure cylinder (3), a generator (4), and a condenser (5); the steam extraction module includes a steam extraction inlet (1.1), and the outlet of the steam extraction inlet (1.1) is divided into a first steam extraction outlet (1.2) and a second steam extraction outlet (1.3); the heating module includes a steam-water heat exchanger (6), which is provided with a first steam inlet (2.1), a first steam outlet (2.2), a first water inlet (2.3), and a first water outlet (2.4); the heat storage module includes a steam accumulator (7) and a feed water pump (8), which is provided with a second steam inlet (3.1), a second steam outlet (3.2), a second water inlet (3.4), and a second water outlet (3.5), and the feed water pump (8) is connected to a water extraction port (3.3); The steam generator (1) is connected in sequence to the high-pressure cylinder (2), the low-pressure cylinder (3) and the condenser (5); the low-pressure cylinder (3) is connected to the generator (4); the extraction steam inlet (1.1) is connected to the steam pipeline between the high-pressure cylinder (2) and the low-pressure cylinder (3); the first extraction steam outlet (1.2) and the second steam outlet (3.2) are connected to the first steam inlet (2.1), the second extraction steam outlet (1.3) is connected to the second steam inlet (3.1), the steam outlet of the low-pressure cylinder (3) and the first steam outlet (2.2) are connected to the steam inlet of the condenser (5), the condenser (5) warm water outlet is connected to the inlet of the feed water pump (8) through the water inlet (3.3), and the outlet of the feed water pump (8) is connected to the second water inlet (3.4); The steam accumulator (7) adopts a horizontal variable pressure steam accumulator, which is equipped with steam nozzles and circulation pipes. The heat storage medium is water. During operation, the upper part of the accumulator is the steam space and the lower part is the water volume.

2. A nuclear power plant steam extraction heating system equipped with a steam thermal storage device according to claim 1, characterized in that, Extract the inlet water of the steam accumulator (7) from the condenser (5) temperature drainage pipeline.

3. A nuclear power plant steam extraction heating system with a steam thermal storage device as described in claim 1, characterized in that, The steam generator (1) is also connected to the reactor.

4. A nuclear power plant steam extraction heating system equipped with a steam thermal storage device according to claim 1, characterized in that, The first extraction steam outlet (1.2) is connected to the first steam inlet (2.1) via the first regulating valve (10).

5. A nuclear power plant steam extraction heating system equipped with a steam thermal storage device according to claim 4, characterized in that, The second extraction steam outlet (1.3) is connected to the second steam inlet (3.1) via the second regulating valve (11).

6. A nuclear power plant steam extraction heating system equipped with a steam thermal storage device according to claim 5, characterized in that, A third regulating valve (12) is installed at the second steam outlet (3.2).

7. A nuclear power plant steam extraction heating system with a steam thermal storage device as described in claim 6, characterized in that, A fourth regulating valve (13) is installed at the inlet of the water pump (8).

8. A nuclear power plant steam extraction heating system with a steam thermal storage device as described in claim 7, characterized in that, A fifth regulating valve (14) is provided at the second outlet (3.5).

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