Combined heat and power generation system and method for realizing flexible peak regulation of nuclear power unit

Abstract

The invention relates to the technical field of new energy power generation and energy storage, in particular to a combined heat and power generation system and method for achieving flexible peak regulation of a nuclear power unit. Thermoelectric decoupling is achieved through heat storage, meanwhile, waste heat of a power plant is comprehensively recycled, electric-heat conversion is achieved through heat pump temperature rising, and an ORC generator set is coupled to assist power peak regulation. In the peak period of power utilization, the nuclear power unit generates power in a full-power mode, the high-temperature heat storage tank serves as a high-temperature heat source to drive the ORC unit to generate power or supply heat to the outside, hot water returns to the medium-temperature heat storage tank to be stored after heat is released, and in addition, dead steam waste heat generated during power generation is stored through the low-temperature heat storage tank. In the electricity consumption trough period, steam extraction and heat storage are achieved as much as possible, the heat pump is driven by means of multiple electricity, waste heat of dead steam and waste heat stored in the peak period are heated by means of the heat pump, then heat is supplied, and redundant high-temperature heat is stored. In this way, the heat supply capacity is improved, deep peak regulation of electric power is achieved, and the whole combined heat and power generation system can be flexibly adjusted to operate according to changes of heat loads and electric loads.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy power generation and energy storage, and particularly relates to a cogeneration system and method for realizing flexible peak shaving of nuclear power units. Background Art

[0002] Limited by the safety factors of the nuclear island, the power adjustment range of nuclear power units is small, and the load change rate is slow. Generally, they operate at the rated working conditions and basically do not participate in peak shaving. Nuclear energy cogeneration can not only avoid the waste of nuclear power resources but also reduce the nuclear safety risks brought by rapid and large fluctuations in reactor power. It can achieve peak shaving of nuclear power while supplying power and heat to the outside, and reduce carbon emissions in the fields of power generation and heating.

[0003] In related technologies, when nuclear power is used for heating, some high-quality steam needs to be extracted from the nuclear power unit, and the power of the unit will change with the change of the extraction steam volume. Increasing the heating steam extraction will cause the power generation of the nuclear power unit to decrease linearly. However, the thermal and electrical loads are respectively affected by the demands on the user side and do not change inversely. There are problems such as thermoelectric coupling and low regulation flexibility in cogeneration units. In addition, the heat after the primary conversion of the high-grade steam used for cogeneration is not fully utilized, and a large amount of waste steam waste heat is discharged into the environment, resulting in a low comprehensive utilization rate of nuclear energy.

[0004] Therefore, there is an urgent need to provide a cogeneration system and method for realizing flexible peak shaving of nuclear power units to solve the above technical problems. Summary of the Invention

[0005] In order to solve the problems that nuclear power cannot be frequently peak-shaved, there is thermoelectric coupling during cogeneration, and a large amount of waste steam waste heat is wasted, the embodiments of the present invention provide a cogeneration system and method for realizing flexible peak shaving of nuclear power units.

[0006] In a first aspect, an embodiment of the present invention provides a cogeneration system for realizing flexible peak shaving of a nuclear power unit, including a steam turbine, a condenser, a steam-water heat exchanger, a heat pump unit, a low-temperature heat storage tank, a medium-temperature heat storage tank, a high-temperature heat storage tank, and an ORC power generation unit. The steam turbine is connected to the steam-side inlet and outlet of the steam-water heat exchanger through an extraction steam pipeline and a drain pipeline. The exhaust steam pipeline of the steam turbine is connected to the condenser. The condenser is connected to the inlet and outlet of the evaporator side of the heat pump unit and the inlet and outlet of the low-temperature heat storage tank through a cooling circulating water pipeline. The inlet of the condenser side of the heat pump unit is connected to a hot water return pipeline, and the outlet of the condenser side is respectively connected to a hot water supply pipeline and the water-side inlet pipeline of the steam-water heat exchanger. The inlet and outlet pipelines of the medium-temperature heat storage tank are respectively connected to the hot water return pipeline, the water-side inlet pipeline of the steam-water heat exchanger, and the outlet pipeline of the evaporator side of the ORC power generation unit. The inlet and outlet pipelines of the high-temperature heat storage tank are respectively connected to the water-side outlet pipeline of the steam-water heat exchanger, the hot water supply pipeline, and the inlet pipeline of the evaporator side of the ORC power generation unit.

[0007] In a second aspect, an embodiment of the present invention provides a cogeneration method for realizing flexible peak shaving of a nuclear power unit, which is applied to the method described in the above embodiment. During the peak electricity consumption period, the regulating valves of the extraction steam pipeline, the drain pipeline, the water-side inlet and outlet pipelines of the steam-water heat exchanger, the evaporator side inlet and outlet pipelines of the heat pump unit, and the condenser side inlet and outlet pipelines are closed, and the regulating valve of the inlet and outlet pipelines of the low-temperature heat storage tank is opened. At this time, the nuclear power unit generates electricity at full capacity, and the waste heat of the exhaust steam after the steam turbine generates electricity is stored in the low-temperature heat storage tank through heat exchange by the condenser via the cooling circulating water pipeline.

[0008] During the low electricity consumption period, the regulating valves of the extraction steam pipeline, the drain pipeline, the water-side inlet and outlet pipelines of the steam-water heat exchanger, the evaporator side inlet and outlet pipelines of the heat pump unit, and the condenser side inlet and outlet pipelines are opened, and the regulating valve of the evaporator side inlet and outlet pipelines of the ORC power generation unit is closed. The high-temperature steam extracted by the steam turbine enters the steam-water heat exchanger through the extraction steam pipeline to heat the water discharged from the medium-temperature heat storage tank, then returns to the exhaust steam pipeline of the steam turbine and enters the condenser to continue cooling. The heat of the high-temperature steam is stored in the high-temperature heat storage tank through the steam-water heat exchanger, and the waste heat of the exhaust steam is exchanged to the cooling circulating water. At the same time, the heat stored in the low-temperature heat storage tank is released and recovered as the low-temperature heat source of the heat pump unit.

[0009] An embodiment of the present invention provides a cogeneration system and method for realizing flexible peak shaving of a nuclear power unit. Thermal electrolysis decoupling is achieved through heat storage, while the waste heat of the power plant is fully recovered. Heat pump temperature increase is used to realize electro-thermal conversion, and an ORC generator set is coupled to assist in power peak shaving. During the peak electricity consumption period, the nuclear power unit generates electricity with all its strength. The high-temperature heat storage tank serves as a high-temperature heat source to drive the ORC unit to generate electricity or supply heat externally. After the heat is released, the hot water returns to the medium-temperature heat storage tank for storage (discharge process). In addition, the waste heat of the exhaust steam during power generation is stored in the low-temperature heat storage tank. During the low electricity consumption period, as much extraction steam heat storage as possible is carried out, and the extra generated electricity is used to drive the heat pump. The waste heat of the exhaust steam and the waste heat stored during the peak period are heated by the heat pump to increase the temperature and then supply heat, and the excess high-temperature heat is stored (charging process). In this way, both the heating capacity is improved and deep power peak shaving is achieved. The entire cogeneration system can be flexibly adjusted according to the changes in heat and electricity loads. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0011] Figure 1 It is a schematic diagram of a cogeneration system for realizing flexible peak shaving of a nuclear power unit provided by an embodiment of the present invention.

[0012] Reference Signs:

[0013] 1 - steam turbine; 2 - condenser; 3 - steam-water heat exchanger; 4 - heat pump unit; 5 - low-temperature heat storage tank; 6 - medium-temperature heat storage tank; 7 - high-temperature heat storage tank; 8 - ORC generator set;

[0014] 301, 302, 303, 304, 401, 402, 403, 404, 405, 406, 501, 502, 601, 701, 801, 802, 901, 902 - regulating valve. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0016] As Figure 1As shown in the figure, the cogeneration system for realizing flexible peak shaving of nuclear power units provided by the embodiments of the present invention includes a steam turbine 1, a condenser 2, a steam-water heat exchanger 3, a heat pump unit 4, a low-temperature heat storage tank 5, a medium-temperature heat storage tank 6, a high-temperature heat storage tank 7, and an ORC generator set 8. The steam turbine 1 is connected to the steam-side inlet and outlet of the steam-water heat exchanger 3 through an extraction steam pipeline and a drain pipeline. The exhaust steam pipeline of the steam turbine 1 is connected to the condenser 2. The condenser 2 is connected to the inlet and outlet of the evaporator side of the heat pump unit 4 and the inlet and outlet of the low-temperature heat storage tank 5 through a cooling circulating water pipeline. The inlet of the condenser side of the heat pump unit 4 is connected to the hot water return pipeline, and the outlet of the condenser side is respectively connected to the hot water supply pipeline and the water-side inlet pipeline of the steam-water heat exchanger 3. The inlet and outlet pipelines of the medium-temperature heat storage tank 6 are respectively connected to the hot water return pipeline, the water-side inlet pipeline of the steam-water heat exchanger 3, and the outlet pipeline of the evaporator side of the ORC generator set 8. The inlet and outlet pipelines of the high-temperature heat storage tank 7 are respectively connected to the water-side outlet pipeline of the steam-water heat exchanger 3, the hot water supply pipeline, and the inlet pipeline of the evaporator side of the ORC generator set 8.

[0017] In this embodiment, heat-electric decoupling is realized through heat storage, while the waste heat of the power plant is fully recovered. The heat pump is used to raise the temperature to realize electro-thermal conversion, and the ORC generator set is coupled to assist in power peak shaving. During the peak electricity consumption period, the nuclear power unit generates electricity with full capacity. The high-temperature heat storage tank serves as a high-temperature heat source to drive the ORC unit to generate electricity or supply heat to the outside. After the heat is released, the hot water returns to the medium-temperature heat storage tank for storage (discharge process). In addition, the waste heat of the exhaust steam during power generation is stored in the low-temperature heat storage tank. During the low electricity consumption period, as much extraction steam as possible is stored for heat storage, and the excess generated electricity is used to drive the heat pump. The waste heat of the exhaust steam and the waste heat stored during the peak period are heated by the heat pump to raise the temperature and then supply heat, and the excess high-temperature heat is stored (charging process). In this way, both the heating capacity is improved and the deep peak shaving of electricity is realized, and the entire cogeneration system can be flexibly adjusted according to the changes of heat and electricity loads.

[0018] In an embodiment of the present invention, regulating valves for regulating the flow rate are provided on the extraction steam pipeline, the drain pipeline, the water-side inlet and outlet pipelines of the steam-water heat exchanger 3, the cooling circulating water pipeline, the evaporator-side inlet and outlet pipelines of the heat pump unit 4, the condenser-side inlet and outlet pipelines of the heat pump unit 4, the hot water supply pipeline, the hot water return pipeline, the inlet and outlet pipelines of the medium-temperature heat storage tank 6, the inlet and outlet pipelines of the high-temperature heat storage tank 7, and the evaporator-side inlet and outlet pipelines of the ORC generator set 8 (that is Figure 1 the regulating valves numbered 301, 302, 303, 304, 401, 402, 403, 404, 405, 406, 501, 502, 601, 701, 801, 802, 901, 902 in the figure).

[0019] In an embodiment of the present invention, the water temperature in the low-temperature heat storage tank 5 is 20-40°C, the water temperature in the medium-temperature heat storage tank 6 is 60-80°C, and the water temperature in the high-temperature heat storage tank 7 is 120-150°C.

[0020] For example, during the peak electricity consumption period, high-temperature steam at about 260°C expands and does work in the steam turbine to drive the generator to generate electricity. The exhausted steam discharged from the steam turbine enters the condenser for condensation, and the heat of condensation is carried away by the cooling circulating water. The temperature of the circulating water is about between 20-40°C. This part of the waste heat is stored in the low-temperature heat storage tank and recycled during the low electricity consumption period as the low-temperature heat source of the heat pump unit. Further, the high-temperature heat storage tank, as the high-temperature heat source, can drive the ORC unit to generate electricity or supply high-temperature hot water according to the demand of the thermal and electric loads.

[0021] During the low electricity consumption period, as much steam is extracted as possible and less electricity is generated. The extraction steam temperature is about 170°C. The steam heats the medium-temperature hot water in the medium-temperature heat storage tank 6 at 60-80°C to 120-150°C through the steam-water heat exchanger and stores it in the high-temperature heat storage tank. Further, the extra electricity generated drives the heat pump unit to recover the heat of the exhausted steam of the steam turbine and the low-temperature waste heat stored during the peak electricity consumption period, raising the return water temperature of the hot water from 50-60°C to 80-95°C. It can directly supply heating hot water or further enter the steam-water heat exchanger to be heated to 120-150°C by steam to supply high-temperature hot water to meet municipal heating or other industrial heat consumption, and the excess high-temperature heat is stored in the high-temperature heat storage tank.

[0022] In addition, the embodiment of the present invention also provides a cogeneration method for realizing flexible peak shaving of a nuclear power unit, which is applied to the method mentioned in the embodiment and includes:

[0023] During the peak electricity consumption period, close the regulating valves of the steam extraction pipeline, the drain pipeline, the water-side inlet and outlet pipelines of the steam-water heat exchanger 3, the evaporator-side inlet and outlet pipelines of the heat pump unit 4, and the condenser-side inlet and outlet pipelines (i.e., regulating valves 301, 302, 303, 304, 401, 402, 403, and 404), and open the regulating valves of the inlet and outlet pipelines of the low-temperature heat storage tank 5 (i.e., regulating valves 501 and 502). At this time, the nuclear power unit generates electricity with all its strength, and the waste heat of the exhausted steam after the steam turbine 1 generates electricity is stored in the low-temperature heat storage tank 5 through the heat exchange of the condenser 2 and the cooling circulating water pipeline;

[0024] During the low electricity consumption period, open the regulating valves of the extraction steam pipeline, the drain pipeline, the water inlet and outlet pipelines on the water side of the steam-water heat exchanger 3, the evaporator side inlet and outlet pipelines of the heat pump unit 4, and the condenser side inlet and outlet pipelines (i.e., regulating valves 301, 302, 303, 304, 401, 402, 403, and 404), and close the regulating valves of the evaporator side inlet and outlet pipelines of the ORC power generation unit 8 (i.e., regulating valves 801 and 802). The high-temperature steam extracted by the steam turbine 1 enters the steam-water heat exchanger 3 through the extraction steam pipeline, heats the water discharged from the high-temperature heat storage tank 6, then returns to the exhaust steam pipeline of the steam turbine 1 and enters the condenser 2 to continue cooling. The heat of the high-temperature steam is stored in the high-temperature heat storage tank 7 through the steam-water heat exchanger 3, and the waste heat of the exhaust steam is exchanged to the cooling circulating water through the condenser 2. At the same time, the heat stored in the low-temperature heat storage tank 5 is released and recovered as the low-temperature heat source of the heat pump unit 4.

[0025] In an embodiment of the present invention, it further includes:

[0026] During the high electricity consumption period, according to the demand of the nuclear power unit's thermal and electric load, control the opening degrees of the regulating valves of the evaporator side inlet and outlet pipelines, the hot water supply pipeline, and the hot water return pipeline of the ORC power generation unit 8 (i.e., regulating valves 801, 802, 901, and 902). Using the high-temperature heat storage tank 7 as the high-temperature heat source, drive the ORC power generation unit 8 to generate electricity or supply high-temperature hot water. After the heat is released, the hot water returns to the medium-temperature heat storage tank 6 for storage.

[0027] In an embodiment of the present invention, it further includes:

[0028] During the low electricity consumption period, according to the demand of the nuclear power unit's thermal and electric load, control the opening degrees of the regulating valves of the inlet and outlet pipelines of the medium-temperature heat storage tank 6, the inlet and outlet pipelines of the high-temperature heat storage tank 7, the hot water supply pipeline, and the hot water return pipeline (i.e., regulating valves 601, 701, 901, and 902) to adjust the proportion of heat supply and energy storage.

[0029] In an embodiment of the present invention, it further includes:

[0030] During the low electricity consumption period, control the opening degrees of the regulating valves of the condenser side outlet pipeline of the heat pump unit 4 and the pipeline connecting it to the water side inlet and outlet pipelines of the steam-water heat exchanger 3 (i.e., regulating valves 404, 405, and 406) to adjust the supply temperature of the hot water.

[0031] In summary, the present invention has the following beneficial effects:

[0032] 1) According to the principle of temperature matching and energy cascade utilization, the present invention couples a heat pump energy storage device and an ORC power generation device that match the steam parameters of the nuclear power unit, realizes the flexible peak shaving of the nuclear power unit, achieves thermal and electric decoupling during cogeneration, and comprehensively recovers the waste heat of the steam turbine exhaust steam, improving the comprehensive utilization efficiency of nuclear energy.

[0033] 2) The present invention can flexibly adjust the power generation and heat supply according to the changes in thermal and electrical loads. During the peak electricity consumption period, the maximum power generation capacity is increased by 15%, and the maximum heat supply capacity is increased by 30% compared with the extraction steam heating. During the low electricity consumption period, zero power output to the grid can be achieved, which not only avoids the waste of nuclear power resources but also realizes the peak regulation of electricity on the basis of ensuring nuclear power safety, thus improving the economic efficiency of nuclear power plants.

[0034] It should be noted that in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the said element.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. However, such modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cogeneration system for realizing flexible peak load regulation of nuclear power units, characterized in that: The invention comprises a steam turbine (1), a condenser (2), a steam-water heat exchanger (3), a heat pump unit (4), a low-temperature heat storage tank (5), a medium-temperature heat storage tank (6), a high-temperature heat storage tank (7) and an ORC generator unit (8), wherein the steam turbine (1) is connected to the steam side inlet and outlet of the steam-water heat exchanger (3) via a steam extraction pipeline and a drain pipeline, the exhaust steam pipeline of the steam turbine (1) is connected to the condenser (2), the condenser (2) is respectively connected to the evaporator side water inlet and outlet of the heat pump unit (4) and the water inlet and outlet of the low-temperature heat storage tank (5) via a cooling circulating water pipeline, and the heat pump unit (8) is connected to the steam side inlet and outlet of the evaporator side of the heat pump unit (4) and the water inlet and outlet of the low-temperature heat storage tank (5). The condenser side water inlet of the group (4) is connected to the hot water return pipe, and the condenser side water outlet is respectively connected to the hot water supply pipe and the water side water inlet pipe of the steam-water heat exchanger (3); the inlet and outlet water pipes of the medium temperature heat storage tank (6) are respectively connected to the hot water return pipe, the water side water inlet pipe of the steam-water heat exchanger (3) and the evaporator side water outlet pipe of the ORC generator set (8); the inlet and outlet water pipes of the high temperature heat storage tank (7) are respectively connected to the water side water outlet pipe of the steam-water heat exchanger (3), the hot water supply pipe and the evaporator side water inlet pipe of the ORC generator set (8).

2. The system according to claim 1, characterized in that The steam extraction pipeline, the drain pipeline, the water side inlet and outlet water pipelines of the steam-water heat exchanger (3), the cooling circulation water pipeline, the evaporator side inlet and outlet water pipelines of the heat pump unit (4), the condenser side inlet and outlet water pipelines of the heat pump unit (4), the hot water supply pipeline, the hot water return pipeline, the medium temperature heat storage tank (6) inlet and outlet water pipelines, the high temperature heat storage tank (7) inlet and outlet water pipelines and the evaporator side inlet and outlet water pipelines of the ORC generator set (8) are all provided with regulating valves for regulating flow.

3. The system according to claim 2, characterized in that The water temperature of the low-temperature heat storage tank (5) is 20-40°C, the water temperature of the medium-temperature heat storage tank (6) is 60-80°C, and the water temperature of the high-temperature heat storage tank (7) is 120-150°C.

4. A cogeneration method for realizing flexible peak regulation of nuclear power units, characterized in that: The method as claimed in claim 3 comprises: During the peak period of electricity consumption, the regulating valves of the steam extraction pipeline, the drain pipeline, the water side inlet and outlet water pipelines of the steam-water heat exchanger (3), the evaporator side inlet and outlet water pipelines and the condenser side inlet and outlet water pipelines of the heat pump unit (4) are closed, and the regulating valves of the inlet and outlet water pipelines of the low-temperature heat storage tank (5) are opened. At this time, the nuclear power unit generates electricity at full capacity, and the waste heat of the exhaust steam after the steam turbine (1) generates electricity is stored in the low-temperature heat storage tank (5) through the heat exchange of the condenser (2) and the cooling circulating water pipeline; During the off-peak period of electricity consumption, the regulating valves of the steam extraction pipeline, the drain pipeline, the water side inlet and outlet water pipeline of the steam-water heat exchanger (3), the evaporator side inlet and outlet water pipeline of the heat pump unit (4), and the condenser side inlet and outlet water pipeline are opened, and the regulating valve of the evaporator side inlet and outlet water pipeline of the ORC generator unit (8) is closed. The high-temperature steam extracted from the steam turbine (1) enters the steam-water heat exchanger (3) through the steam extraction pipeline to heat the outlet water of the medium-temperature heat storage tank (6), and then returns to the exhaust steam pipeline of the steam turbine (1) and enters the condenser (2) to continue cooling. The heat of the high-temperature steam is stored in the high-temperature heat storage tank (7) through the steam-water heat exchanger (3), and the waste heat of the exhaust steam is exchanged into the cooling circulating water through the condenser (2). At the same time, the heat stored in the low-temperature heat storage tank (5) is released and recovered as a low-temperature heat source of the heat pump unit (4).

5. The method according to claim 4, characterized in that Also includes: During the peak period of electricity consumption, according to the demand of the thermal power load of the nuclear power unit, the opening of the regulating valves of the evaporator-side water inlet and outlet pipes, the hot water supply pipe and the hot water return pipe of the ORC generator set (8) is controlled, and the high-temperature heat storage tank (7) is used as a high-temperature heat source to drive the ORC generator set (8) to generate electricity or supply high-temperature hot water. After the heat is released, the hot water returns to the medium-temperature heat storage tank (6) for storage.

6. The method according to claim 5, characterized in that Also includes: During the off-peak period of electricity consumption, according to the demand of the thermal power load of the nuclear power unit, the opening of the regulating valves of the water inlet and outlet pipes of the medium-temperature heat storage tank (6), the water inlet and outlet pipes of the high-temperature heat storage tank (7), the hot water supply pipe and the hot water return pipe are controlled to adjust the ratio of heat supply and energy storage. The hot water return water and the water outlet of the medium-temperature heat storage tank (6) are gradually heated by the heat pump unit (4) and the steam-water heat exchanger (3) to become high-temperature hot water. A part of the high-temperature hot water enters the high-temperature heat storage tank (7) for storage, and the other part returns to the hot water supply.

7. The method according to claim 6, characterized in that Also includes: During the off-peak period of electricity consumption, the opening of the regulating valve of the water outlet pipe on the condenser side of the heat pump unit (4) and the pipe connected to the water inlet and outlet pipes on the water side of the steam-water heat exchanger (3) is controlled to adjust the water supply temperature of the hot water.

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