Boiler steam-water system adapting to deep peak regulation of unit

Abstract

The invention belongs to the technical field of boilers, and particularly relates to a boiler steam-water system adapting to deep peak regulation of a unit. According to the technical scheme, the boiler steam-water system adapting to the deep peak regulation of the unit comprises a water supply pipeline, the other end of the water supply pipeline is connected with a boiler water-cooling wall pipeline, the other end of the boiler water-cooling wall pipeline is connected with a heat exchange pipeline, and the heat exchange pipeline is sequentially connected with a ceiling enclosure wall unit, a low-temperature superheater, a rear screen superheater and a high-temperature superheater. And part of steam extracted from the heat exchange pipeline and the residual steam on the heat exchange pipeline are introduced into the steam turbine to do work. According to the boiler steam-water system suitable for deep peak regulation of the unit, on the premise that safe and stable operation of the boiler is guaranteed, the load of the unit is further reduced, and the requirement for deep peak regulation of a new-generation coal power unit is met.

Description

Technical Field

[0001] This invention belongs to the field of boiler technology, and specifically relates to a boiler steam-water system adapted to deep peak shaving of power units. Background Technology

[0002] With the vigorous promotion and development of new energy sources, the proportion of new energy connected to the grid will continue to increase in the future. The peak-shaving load of current thermal power units may not be able to meet the requirements of the future new power system. In order to solve the greater volatility and uncertainty brought about by the increase in the proportion of renewable energy generation, future thermal power units will need to undertake lower and more extreme peak-shaving loads.

[0003] Conventional primary steam systems, such as Figure 2 As shown: The heating surface of the water-cooled wall of the power plant boiler is mainly composed of a lower spiral water-cooled wall 1 and an upper vertical water-cooled wall 2, wherein the spiral section of the water-cooled wall adopts an internally threaded tube; the lower spiral water-cooled wall 1 and the upper vertical water-cooled wall 2 are connected by an intermediate mixing header 3.

[0004] Superheated system steam-water flow: Feedwater supplied by feedwater pump 11 is heat-exchanged by economizer 10 and then flows into the water-cooled wall, sequentially passing through the lower spiral water-cooled wall 1, the intermediate mixing header 3, the upper vertical water-cooled wall 2, the water-cooled wall outlet mixing header 4, and the steam-water separator 5. The steam after steam-water separation sequentially passes through the roof wall unit 6, the low-temperature superheater 7, the rear screen superheater 8, and the high-temperature superheater 9 to absorb heat before entering the turbine to perform work. The boiler operates at the minimum direct-current load, for example, a counter-firing ultra-supercritical boiler operates at 20% load, without auxiliary combustion for stable combustion operation, and the water-cooled wall does not overheat.

[0005] Currently, the most advanced ultra-supercritical thermal power units can achieve a minimum load of approximately 20% for deep peak shaving. At this load, the working fluid inside the boiler water-cooled walls can switch to direct-flow dry operation, ensuring that film boiling does not occur and that the water-cooled walls operate safely and stably. If the peak load is further reduced, the working fluid inside the boiler water-cooled walls needs to operate in a wet state to avoid overheating and tube rupture. However, wet operation of the working fluid inside the water-cooled walls leads to heat and working fluid loss in the boiler, and frequent switching between dry and wet states makes unit control difficult, affecting the unit's safety and stability. Summary of the Invention

[0006] In order to solve the above-mentioned problems in the existing technology, the purpose of this invention is to provide a boiler steam-water system that is adapted to deep peak shaving of the unit, so as to further reduce the unit load while ensuring the safe and stable operation of the boiler and meet the needs of deep peak shaving of the new generation of coal-fired power units.

[0007] The technical solution adopted in this invention is as follows: A boiler steam-water system adapted to deep peak shaving of a power unit includes a feedwater pipeline, the other end of which is connected to a boiler water-cooled wall pipeline, and the other end of which is connected to a heat exchange pipeline. A roof wall unit, a low-temperature superheater, a rear screen superheater, and a high-temperature superheater are sequentially connected to the heat exchange pipeline. Part of the steam extracted from the heat exchange pipeline and the remaining steam in the heat exchange pipeline are fed into the steam turbine to do work.

[0008] To meet the requirements of deep-load operation and lower loads, this invention extracts a portion of steam from the superheater side. The remaining steam is then heated by the rear superheater and high-temperature superheater before being fed into the turbine to perform power, thereby meeting the grid peak-shaving requirements. The extracted steam can be used for different purposes depending on the steam parameters, improving steam utilization and unit efficiency. While the extracted steam volume is relatively small and can be adequately accommodated by the boiler, the high flue gas temperature reduces boiler-side economics during low-load operation. This invention efficiently utilizes the extracted steam without affecting the overall unit economy.

[0009] As a preferred embodiment of the present invention, the extraction points for the partial steam extraction on the heat exchange pipeline are before and after the low-temperature superheater, before and after the rear screen superheater, and before and after the high-temperature superheater. The selection of the partial steam extraction points can be flexibly designed; extraction from before and after the low-temperature superheater, before and after the rear screen superheater, or before and after the high-temperature superheater is all feasible, and the selection should be determined according to the actual needs of the project.

[0010] As a preferred embodiment of the present invention, a portion of steam is extracted from the heat exchange pipeline, and after heat exchange in the heat exchanger, it is discharged into the low-temperature heater, deaerator, or condenser of the unit.

[0011] As a preferred embodiment of the present invention, the heat exchanger is a steam-gas heat exchanger or a steam-water heat exchanger.

[0012] As a preferred embodiment of the present invention, a portion of the steam is extracted from the heat exchange pipeline and used to heat the inlet cold air or outlet hot air of the air preheater in the boiler system, specifically designed according to actual engineering requirements. Using extracted steam to heat the inlet cold air of the air preheater can prevent low-temperature corrosion. Using extracted steam to heat the outlet hot air of the air preheater can improve combustion stability.

[0013] As a preferred embodiment of the present invention, a portion of the steam is extracted from the heat exchange pipeline and directly introduced into the high-temperature heater of the boiler system before returning to the boiler.

[0014] As a preferred embodiment of the present invention, the counter-firing ultra-supercritical boiler operates at 20% load, with 5% of the steam extracted from the heat exchange pipeline and the remaining 15% of the steam fed into the turbine to perform work.

[0015] As a preferred embodiment of the present invention, a water supply pump and an economizer are connected to the water supply pipeline.

[0016] As a preferred embodiment of the present invention, the boiler water-cooled wall pipeline includes a spiral water-cooled wall located in the lower section of the boiler and a vertical water-cooled wall located in the upper section of the boiler. An intermediate mixing header is connected between the spiral water-cooled wall and the vertical water-cooled wall, and a water-cooled wall outlet mixing header is also connected to the top of the vertical water-cooled wall.

[0017] As a preferred embodiment of the present invention, the outlet end of the water-cooled wall outlet mixing header is connected to a steam-water separator via a pipeline, and one end of the heat exchange pipeline is connected to the gas phase outlet of the steam-water separator.

[0018] The beneficial effects of this invention are as follows: To meet the requirements of deep-load operation and lower loads, this invention extracts a portion of steam from the superheater side. The remaining steam is then heated by the rear superheater and high-temperature superheater before being fed into the turbine to perform power, thereby meeting the grid peak-shaving requirements. The extracted steam can be used for different purposes depending on the steam parameters, improving steam utilization and unit efficiency. While the extracted steam volume is relatively small and can be adequately accommodated by the boiler, the high flue gas temperature reduces boiler-side economics during low-load operation. This invention efficiently utilizes the extracted steam without affecting the overall unit economy. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of a conventional primary steam system.

[0020] In the diagram: 1-spiral water-cooled wall; 2-vertical water-cooled wall; 3-intermediate mixing header; 4-water-cooled wall outlet mixing header; 5-steam-water separator; 6-roof wall unit; 7-low-temperature superheater; 8-rear screen superheater; 9-high-temperature superheater; 10-economizer; 11-feed water pump; 12-heat exchanger. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the invention can be combined with each other.

[0023] like Figure 1 As shown, the boiler steam-water system adapted for deep peak shaving in this embodiment includes a feedwater pipeline. One end of the feedwater pipeline is connected to a boiler water-cooled wall pipeline, and the other end of the boiler water-cooled wall pipeline is connected to a heat exchange pipeline. The heat exchange pipeline is sequentially connected to a roof wall unit 6, a low-temperature superheater 7, a rear screen superheater 8, and a high-temperature superheater 9. A portion of the steam extracted from the heat exchange pipeline is used, while the remaining steam is fed into the turbine to perform work. In a counter-firing ultra-supercritical boiler operating at 20% load, 5% of the steam is extracted from the heat exchange pipeline, and the remaining 15% is fed into the turbine to perform work.

[0024] Specifically, a feedwater pump 11 and an economizer 10 are connected to the feedwater pipeline. The boiler water-cooled wall pipeline includes a spiral water-cooled wall 1 located in the lower section of the boiler and a vertical water-cooled wall 2 located in the upper section of the boiler. An intermediate mixing header 3 is connected between the spiral water-cooled wall 1 and the vertical water-cooled wall 2. A water-cooled wall outlet mixing header 4 is also connected to the top of the vertical water-cooled wall 2. The outlet end of the water-cooled wall outlet mixing header 4 is connected to a steam-water separator 5 through a pipeline, and one end of the heat exchange pipeline is connected to the gas phase outlet of the steam-water separator 5. The ceiling and wall enclosure unit 6 includes a ceiling and a wall enclosure.

[0025] The superheated system steam-water flow: The feedwater supplied by the feedwater pump 11 is heat exchanged through the economizer 10 and then enters the water-cooled wall. It flows sequentially through the lower spiral section water-cooled wall, the intermediate mixing header 3, the upper vertical section water-cooled wall, the water-cooled wall outlet mixing header 4, and the steam-water separator 5. The steam after steam-water separation passes sequentially through the roof wall unit 6, the low-temperature superheater 7, the rear screen superheater 8, and the high-temperature superheater 9 to absorb heat before entering the steam turbine to do work.

[0026] The boiler operates at the minimum direct-flow load, such as a counter-firing ultra-supercritical boiler operating at 20% load, without auxiliary combustion for stable combustion, and the water-cooled walls do not overheat. To meet the unit's deep-load regulation requirement of 15%, 5% of the steam is extracted from the superheater side, such as from the outlet of the low-temperature superheater 7. The remaining 15% of the steam is then heated and superheated by the rear screen superheater 8 and the high-temperature superheater 9 before being fed into the turbine to perform power, thereby meeting the grid peak-shaving requirements.

[0027] The 5% steam extracted from the heat exchange pipeline can have different uses depending on the steam parameters. First, some steam is extracted from the heat exchange pipeline, passes through heat exchanger 12, and then is discharged into the unit's low-temperature heater, deaerator, or condenser. Heat exchanger 12 can be a steam-gas heat exchanger or a steam-water heat exchanger. Second, some steam is extracted from the heat exchange pipeline to heat the inlet cold air or outlet hot air of the air preheater in the boiler system, specifically designed according to actual engineering requirements. When steam is extracted to heat the inlet cold air of the air preheater, it can prevent low-temperature corrosion. When steam is extracted to heat the outlet hot air of the air preheater, it can improve combustion stability. Third, some steam is extracted from the heat exchange pipeline and directly fed into the high-temperature heater of the boiler system before returning to the boiler.

[0028] The extraction points for some steam on the heat exchange pipelines are before and after the low-temperature superheater 7, before and after the rear screen superheater 8, and before and after the high-temperature superheater 9. The selection of the extraction points for some steam can be flexibly designed; extraction from before and after the low-temperature superheater 7, before and after the rear screen superheater 8, and before and after the high-temperature superheater 9 are all feasible, and the selection should be determined according to the actual needs of the project.

[0029] The 5% steam extraction volume is not large and the boiler side can basically adapt, but the flue gas temperature is relatively high, and the boiler side's economy decreases when operating at low load. If the 5% steam volume can be used efficiently, it will not affect the overall economic efficiency of the unit.

[0030] This invention, under the premise of ensuring the safe and stable operation of the boiler (e.g., a counter-firing boiler operating at 20% load), extracts approximately 5% of the steam from the superheater side, such as the outlet of the low-temperature superheater 7, for other purposes. The remaining steam (approximately 15%) is then reheated and fed into the turbine to perform work, meeting the unit's deep peak-shaving requirements, improving the unit's flexibility and peak-shaving capability, while ensuring the safe operation of the boiler at low loads. The selection of the steam extraction point can be flexibly designed and determined according to the actual needs of the project.

[0031] This invention is not limited to the above-described optional embodiments. Anyone can derive other various forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that falls within the scope of the claims of this invention shall be protected by this invention.

Claims

1. A boiler steam-water system adapted to deep peak shaving of generating units, characterized in that: It includes a water supply pipeline, the other end of which is connected to a boiler water-cooled wall pipeline, the other end of which is connected to a heat exchange pipeline, and the heat exchange pipeline is connected in sequence to a ceiling wall unit (6), a low-temperature superheater (7), a rear screen superheater (8) and a high-temperature superheater (9). Part of the steam extracted from the heat exchange pipeline and the remaining steam in the heat exchange pipeline are fed into the steam turbine to do work.

2. A boiler steam-water system adapted to deep peak shaving of a generating unit according to claim 1, characterized in that: The extraction points for extracting some steam on the heat exchange pipeline are before and after the low-temperature superheater (7), before and after the rear screen superheater (8), and before and after the high-temperature superheater (9).

3. A boiler steam-water system adapted to deep peak shaving of a generating unit according to claim 1, characterized in that: Some steam is drawn out from the heat exchange pipeline, and after heat exchange through the heat exchanger (12), it is discharged into the low-temperature heater, deaerator or condenser of the unit.

4. A boiler steam-water system adapted to deep peak shaving of a generating unit according to claim 3, characterized in that: The heat exchanger (12) is a steam-gas heat exchanger or a steam-water heat exchanger.

5. A boiler steam-water system adapted to deep peak shaving of a generating unit according to claim 1, characterized in that: Some steam is extracted from the heat exchange pipeline to heat the inlet cold air or outlet hot air of the air preheater in the boiler system.

6. A boiler steam-water system adapted to deep peak shaving of a generating unit according to claim 1, characterized in that: Some steam is extracted from the heat exchange pipeline and directly fed into the high-temperature heater of the boiler system before returning to the boiler.

7. A boiler steam-water system adapted to deep peak shaving of a generating unit according to claim 1, characterized in that: The counter-firing ultra-supercritical boiler operates at 20% load, with 5% of the steam extracted from the heat exchanger tubes and the remaining 15% of the steam fed into the turbine to perform work.

8. A boiler steam-water system adapted to deep peak shaving of a generating unit according to claim 1, characterized in that: A water supply pump (11) and an economizer (10) are connected to the water supply pipeline.

9. A boiler steam-water system adapted to deep peak shaving of a generating unit according to claim 1, characterized in that: The boiler water-cooled wall pipeline includes a spiral water-cooled wall (1) located in the lower section of the boiler and a vertical water-cooled wall (2) located in the upper section of the boiler. An intermediate mixing header (3) is connected between the spiral water-cooled wall (1) and the vertical water-cooled wall (2). A water-cooled wall outlet mixing header (4) is also connected to the top of the vertical water-cooled wall (2).

10. A boiler steam-water system adapted to deep peak shaving of a generating unit according to claim 9, characterized in that: The outlet end of the water-cooled wall outlet mixing header (4) is connected to a steam-water separator (5) via a pipeline, and one end of the heat exchange pipeline is connected to the gas phase outlet of the steam-water separator (5).

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