Coal-fired unit peak shaving system based on boiler extraction steam heat storage and operation method

Abstract

The application discloses a coal-fired unit peak regulation system and operation method based on boiler extraction steam heat storage, and additionally adds a steam storage tank and a steam ejector. When the unit is in load reduction operation, main steam is extracted and stored in the steam storage tank, so that the steam amount entering the steam turbine is reduced, and the unit is rapidly reduced in load. When the unit is in load increase operation, the steam in the steam storage tank is used as the power steam source of the steam ejector, the steam ejector is used to inject the cylinder exhaust steam, the actual steam pressure at the outlet of the steam ejector is higher than the steam pressure corresponding to the current load of the coal-fired boiler, the steam amount entering the steam turbine is increased, and thus the unit load is rapidly increased. If the boiler is in high load operation, the outlet steam of the steam ejector is introduced into the medium-pressure cylinder to do work; if the boiler is in low load operation, the outlet steam of the steam ejector is introduced into the low-pressure cylinder to do work. The application stores the main steam in the steam storage tank and uses the steam ejector to inject the cylinder exhaust steam, so that the load variation rate of the unit is improved, and the unit can be operated at an extremely low load.

Description

Technical Field

[0001] This invention relates to the field of coal-fired power generation technology, specifically to a peak-shaving system and operation method for coal-fired power units based on boiler steam extraction and thermal storage, in order to improve the operational flexibility of coal-fired power units. Background Technology

[0002] Of all energy sources, electricity is the most attractive and important. As the world continues to electrify, electricity consumption is steadily increasing. Currently, renewable energy accounts for about half of electricity growth, and its share of total generation is projected to grow from the current 7% to a quarter by 2050. However, electricity generated from renewable energy is discontinuous, unpredictable, and has low energy density. It is difficult to control and is easily affected by climate, seasons, and weather. Balancing generation and consumption is crucial for the smooth operation of the power grid. Therefore, it is necessary to retrofit coal-fired power plants to improve their operational flexibility to cope with the current complex operating environment. Summary of the Invention

[0003] In order to overcome the problems existing in the prior art, the purpose of this invention is to provide a peak-shaving system and operation method for coal-fired power units based on boiler steam extraction and heat storage, which can enable the unit to operate at a lower load and increase the rate of load change, thereby improving the flexibility of the unit.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A peak-shaving system and operation method for a coal-fired power unit based on boiler extraction steam thermal storage, comprising a coal-fired system and a steam thermal storage system. The coal-fired system includes a coal-fired boiler 1, a high-pressure cylinder 2, an intermediate-pressure cylinder 3, a low-pressure cylinder 4, a generator 5, a deaerator 6, a high-pressure heater 7, a low-pressure heater 8, a condenser 9, a condensate pump P1, a feedwater pump P2, and a fourth valve V4. The main steam outlet of the coal-fired boiler 1 is connected to the inlet of the high-pressure cylinder 2; the reheat steam outlet of the coal-fired boiler 1 is connected to the inlet of the intermediate-pressure cylinder 3; the exhaust outlet of the high-pressure cylinder 2 is connected to the cold end inlet of the reheat steam of the coal-fired boiler 1 through the fourth valve V4; the extraction steam outlet of the high-pressure cylinder 2 is connected to the hot end inlet of the high-pressure heater 7; the exhaust steam outlet of the intermediate-pressure cylinder 3 is connected to the inlet of the low-pressure cylinder 4; the extraction steam outlet of the intermediate-pressure cylinder 3... The steam outlet of the high-pressure cylinder 3 is connected to the hot end inlet of the high-pressure heater 7; the steam extraction outlet of the intermediate-pressure cylinder 3 is connected to the inlet of the deaerator 6; the outlet of the deaerator 6 is connected to the inlet of the feedwater pump P2; the outlet of the feedwater pump P2 is connected to the cold end inlet of the high-pressure heater 7; the cold end outlet of the high-pressure heater 7 is connected to the feedwater inlet of the coal-fired boiler 1; the steam extraction outlet of the low-pressure cylinder 4 is connected to the hot end inlet of the low-pressure heater 8; the exhaust outlet of the low-pressure cylinder 4 is connected to the inlet of the condenser 9; the outlet of the condenser 9 is connected to the inlet of the condensate pump P1; the outlet of the condensate pump P1 is connected to the cold end inlet of the low-pressure heater 8; the cold end outlet of the low-pressure heater 8 is connected to the inlet of the deaerator 6; the high-pressure cylinder 2, intermediate-pressure cylinder 3, low-pressure cylinder 4 and generator 5 share a common bearing connection.

[0006] The steam thermal storage system includes a steam storage tank 10, a steam ejector 11, a first valve V1, a second valve V2, a third valve V3, a fifth valve V5, and a sixth valve V6. The main steam outlet of the coal-fired boiler 1 is connected to the inlet of the steam storage tank 10 through the first valve V1. The outlet of the high-pressure steam storage tank 10 is connected to the power steam inlet of the steam ejector 11 through the second valve V2. The exhaust outlet of the high-pressure cylinder 2 is connected to the ejector extraction end of the steam ejector 11 through the third valve V3. The steam outlet of the steam ejector 11 is connected to the inlet of the intermediate-pressure cylinder 3 through the fifth valve V5. The steam outlet of the steam ejector 11 is connected to the inlet of the low-pressure cylinder 4 through the sixth valve V6.

[0007] In the coal-fired system, a main steam distributor F1 is installed between the main steam outlet of the coal-fired boiler 1 and the steam storage tank 10 and the high-pressure cylinder 2; a first steam distributor F2 is installed between the steam ejector 11 and the intermediate-pressure cylinder 3 and the low-pressure cylinder 4; a second steam distributor F3 is installed between the high-pressure cylinder 2 and the steam ejector 11 and the coal-fired boiler 1; a high-pressure steam combiner M1 is installed between the intermediate-pressure cylinder 3 and the reheat steam outlet of the steam ejector 11 and the coal-fired boiler 1; and a low-pressure steam combiner M2 is installed between the low-pressure cylinder 4 and the intermediate-pressure cylinder 3 and the steam ejector 11.

[0008] When a coal-fired unit needs to increase its load, if the current load of the coal-fired boiler 1 is between 50% and 100% THA, that is, when the coal-fired boiler 1 is operating at a high load, the outlet steam pressure of the steam ejector 11 is higher, and the power generation efficiency of the steam entering the intermediate pressure cylinder 3 is higher. Therefore, the fifth valve V5 is opened to allow the outlet steam of the steam ejector 11 to be fed into the intermediate pressure cylinder 3 to do work. If the current load of the coal-fired boiler 1 is between 25% and 50% THA, that is, when the coal-fired boiler 1 is operating at a low load, the outlet steam pressure of the steam ejector 11 is lower, and the power generation efficiency of the steam entering the low pressure cylinder 4 is higher. Moreover, it is necessary to increase the steam flow into the low pressure cylinder 4 to ensure that it does not blow air. Therefore, the sixth valve V6 is opened to allow the outlet steam of the steam ejector 11 to enter the low pressure cylinder 4 to do work.

[0009] When a coal-fired power unit needs to increase its load, the outlet steam flow of the steam ejector 11 can be adjusted by regulating the opening of the second valve V2 and the third valve V3, so that the steam flow entering the turbine can meet the turbine load change rate and enable the unit to meet the flexible load change requirements.

[0010] When a coal-fired unit needs to operate normally and stably, only the coal-fired system should be operated, the steam thermal storage system should not be operated, and the first valve V1, the second valve V2, the third valve V3, the fifth valve V5 and the sixth valve V6 should be closed, while the fourth valve V4 should be opened.

[0011] When the coal-fired unit needs to reduce its load, the first valve V1 is opened first. The main steam in the coal-fired boiler 1 enters the steam storage tank 10 through the first valve V1 for storage. The first valve V1 can be used to regulate the flow rate of the main steam into the steam storage tank 10, thereby controlling the load reduction rate of the coal-fired unit. During this period, the second valve V2, the third valve V3, the fifth valve V5 and the sixth valve V6 are closed, and the fourth valve V4 is open.

[0012] When the coal-fired unit needs to increase its load, the second valve V2 and the third valve V3 are opened, and the opening of the fourth valve V4 is reduced. Main steam is released from the steam storage tank 10 and enters the power steam inlet of the steam ejector 11. Exhaust steam from the high-pressure cylinder 2 enters the ejector extraction end of the steam ejector 11. If the current load of the coal-fired boiler 1 is between 50% and 100% THA, the fifth valve V5 is opened, allowing the outlet steam of the steam ejector 11 to enter the intermediate-pressure cylinder 3 to perform work. If the current load of the coal-fired boiler 1 is between 25% and 50% THA, the sixth valve V6 is opened, allowing the outlet steam of the steam ejector 11 to enter the low-pressure cylinder 4 to perform work. The actual outlet steam pressure of the steam ejector 10 must be higher than the steam pressure corresponding to the current load of the coal-fired boiler 1, and this can significantly increase the amount of steam entering the turbine, thereby rapidly increasing the unit load.

[0013] Compared with the prior art, the present invention has the following advantages: The present invention adds a steam storage tank 10 and a steam ejector 11. When the unit is operating at reduced load, the main steam is extracted and stored in the steam storage tank 10, rapidly reducing the amount of steam entering the turbine and achieving rapid load reduction. When the unit is operating at increased load, the steam in the steam storage tank 10 is used as the power steam source for the steam ejector 11. The steam ejector 11 is used to eject steam from the cylinder. The actual outlet steam pressure of the steam ejector 10 is higher than the steam pressure corresponding to the current load of the coal-fired boiler 1, and it can significantly increase the amount of steam entering the turbine, thereby rapidly increasing the unit load. Furthermore, if the current load of the coal-fired boiler 1 is between 50% and 100% THA, i.e., the coal-fired boiler 1 is operating at high load, the outlet steam pressure of the steam ejector 11 is higher, resulting in higher power generation efficiency when it enters the intermediate pressure cylinder 3. Therefore, the fifth valve V5 is opened to allow the outlet steam of the steam ejector 11 to be introduced into the intermediate pressure cylinder 3 to perform work. If the current load of the coal-fired boiler 1 is between 30% and 50% THA, that is, when the coal-fired boiler 1 is operating at a low load, the outlet steam pressure of the steam ejector 11 is relatively low, and the power generation efficiency of the steam entering the low-pressure cylinder 4 is higher. Moreover, it is necessary to increase the steam flow into the low-pressure cylinder 4 to ensure that it does not blow air. Therefore, the sixth valve V6 is opened to allow the outlet steam of the steam ejector 11 to enter the low-pressure cylinder 4 to do work. By selecting whether the outlet steam of the steam ejector 11 enters the intermediate-pressure cylinder 3 or the low-pressure cylinder 4 to do work according to the current operating load of the coal-fired boiler 1, the power generation efficiency of the system can be improved. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the peak-shaving system for coal-fired power units based on boiler steam extraction and heat storage, according to the present invention.

[0015] In the diagram: 1. Coal-fired boiler; 2. High-pressure cylinder; 3. Medium-pressure cylinder; 4. Low-pressure cylinder; 5. Generator; 6. Deaerator; 7. High-pressure heater; 8. Low-pressure heater; 9. Condenser; 10. Steam storage tank; 11. Steam ejector; P1. Condensate pump; P2. Feedwater pump; V1-V6. Valves; M1. High-pressure steam combiner; M2. Low-pressure steam combiner; F1. Main steam distributor; F2. First steam distributor; F3. Second steam distributor. Detailed Implementation

[0016] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. The solutions in the embodiments are not intended to limit the scope of protection of the present invention. All equivalent implementations or modifications that do not depart from the present invention are included within the scope of protection of the present invention.

[0017] like Figure 1As shown, this invention relates to a peak-shaving system and operation method for coal-fired power units based on boiler steam extraction and thermal storage, comprising a coal-fired system and a steam thermal storage system. The coal-fired system includes a coal-fired boiler 1, a high-pressure cylinder 2, an intermediate-pressure cylinder 3, a low-pressure cylinder 4, a generator 5, a deaerator 6, a high-pressure heater 7, a low-pressure heater 8, a condenser 9, a condensate pump P1, a feedwater pump P2, and a fourth valve V4. The main steam outlet of the coal-fired boiler 1 is connected to the inlet of the high-pressure cylinder 2; the reheat steam outlet of the coal-fired boiler 1 is connected to the inlet of the intermediate-pressure cylinder 3; the exhaust outlet of the high-pressure cylinder 2 is connected to the cold end inlet of the reheat steam of the coal-fired boiler 1 via the fourth valve V4; the extraction steam outlet of the high-pressure cylinder 2 is connected to the hot end inlet of the high-pressure heater 7; the exhaust steam outlet of the intermediate-pressure cylinder 3 is connected to the inlet of the low-pressure cylinder 4; and the extraction steam outlet of the intermediate-pressure cylinder 3 is connected to the hot end inlet of the high-pressure heater 7. The extraction steam outlet of the intermediate-pressure cylinder 3 is connected to the inlet of the deaerator 6; the outlet of the deaerator 6 is connected to the inlet of the feedwater pump P2; the outlet of the feedwater pump P2 is connected to the cold end inlet of the high-pressure heater 7; the cold end outlet of the high-pressure heater 7 is connected to the feedwater inlet of the coal-fired boiler 1; the extraction steam outlet of the low-pressure cylinder 4 is connected to the hot end inlet of the low-pressure heater 8; the exhaust steam outlet of the low-pressure cylinder 4 is connected to the inlet of the condenser 9; the outlet of the condenser 9 is connected to the inlet of the condensate pump P1; the outlet of the condensate pump P1 is connected to the cold end inlet of the low-pressure heater 8; the cold end outlet of the low-pressure heater 8 is connected to the inlet of the deaerator 6; the high-pressure cylinder 2, intermediate-pressure cylinder 3, low-pressure cylinder 4 and generator 5 share a common bearing connection.

[0018] The steam thermal storage system includes a steam storage tank 10, a steam ejector 11, a first valve V1, a second valve V2, a third valve V3, a fifth valve V5, and a sixth valve V6. The main steam outlet of the coal-fired boiler 1 is connected to the inlet of the steam storage tank 10 through the first valve V1. The outlet of the high-pressure steam storage tank 10 is connected to the power steam inlet of the steam ejector 11 through the second valve V2. The exhaust outlet of the high-pressure cylinder 2 is connected to the ejector extraction end of the steam ejector 11 through the third valve V3. The steam outlet of the steam ejector 11 is connected to the inlet of the intermediate-pressure cylinder 3 through the fifth valve V5. The steam outlet of the steam ejector 11 is connected to the inlet of the low-pressure cylinder 4 through the sixth valve V6.

[0019] In the coal-fired system, a main steam distributor F1 is installed between the main steam outlet of the coal-fired boiler 1 and the steam storage tank 10 and the high-pressure cylinder 2; a first steam distributor F2 is installed between the steam ejector 11 and the intermediate-pressure cylinder 3 and the low-pressure cylinder 4; a second steam distributor F3 is installed between the high-pressure cylinder 2 and the steam ejector 11 and the coal-fired boiler 1; a high-pressure steam combiner M1 is installed between the intermediate-pressure cylinder 3 and the reheat steam outlet of the steam ejector 11 and the coal-fired boiler 1; and a low-pressure steam combiner M2 is installed between the low-pressure cylinder 4 and the intermediate-pressure cylinder 3 and the steam ejector 11.

[0020] When a coal-fired unit needs to increase its load, if the current load of the coal-fired boiler 1 is between 50% and 100% THA, that is, when the coal-fired boiler 1 is operating at a high load, the outlet steam pressure of the steam ejector 11 is higher, and the power generation efficiency of the steam entering the intermediate pressure cylinder 3 is higher. Therefore, the fifth valve V5 is opened to allow the outlet steam of the steam ejector 11 to be fed into the intermediate pressure cylinder 3 to do work. If the current load of the coal-fired boiler 1 is between 25% and 50% THA, that is, when the coal-fired boiler 1 is operating at a low load, the outlet steam pressure of the steam ejector 11 is lower, and the power generation efficiency of the steam entering the low pressure cylinder 4 is higher. Moreover, it is necessary to increase the steam flow into the low pressure cylinder 4 to ensure that it does not blow air. Therefore, the sixth valve V6 is opened to allow the outlet steam of the steam ejector 11 to enter the low pressure cylinder 4 to do work.

[0021] When a coal-fired power unit needs to increase its load, the outlet steam flow of the steam ejector 11 can be adjusted by regulating the opening of the second valve V2 and the third valve V3, so that the steam flow entering the turbine can meet the turbine load change rate and enable the unit to meet the flexible load change requirements.

[0022] When a coal-fired unit needs to operate normally and stably, only the coal-fired system should be operated, the steam thermal storage system should not be operated, and the first valve V1, the second valve V2, the third valve V3, the fifth valve V5 and the sixth valve V6 should be closed, while the fourth valve V4 should be opened.

[0023] When the coal-fired unit needs to reduce its load, the first valve V1 is opened first. The main steam in the coal-fired boiler 1 enters the steam storage tank 10 through the first valve V1 for storage. The first valve V1 can be used to regulate the flow of the main steam into the steam storage tank 10, thereby controlling the load reduction rate of the coal-fired unit. During this period, the second valve V2, the third valve V3, the fifth valve V5 and the sixth valve V6 are closed, and the fourth valve is open.

[0024] When the coal-fired unit needs to increase its load, the second valve V2 and the third valve V3 are opened, and the opening of the fourth valve V4 is reduced. Main steam is released from the steam storage tank 10 and enters the power steam inlet of the steam ejector 11. Exhaust steam from the high-pressure cylinder 2 enters the ejector extraction end of the steam ejector 11. If the current load of the coal-fired boiler 1 is between 50% and 100% THA, the fifth valve V5 is opened, allowing the outlet steam of the steam ejector 11 to enter the intermediate-pressure cylinder 3 to perform work. If the current load of the coal-fired boiler 1 is between 25% and 50% THA, the sixth valve V6 is opened, allowing the outlet steam of the steam ejector 11 to enter the low-pressure cylinder 4 to perform work. The actual outlet steam pressure of the steam ejector 10 must be higher than the steam pressure corresponding to the current load of the coal-fired boiler 1, and this can significantly increase the amount of steam entering the turbine, thereby rapidly increasing the unit load.

Claims

1. A peak-shaving system for coal-fired power units based on boiler steam extraction and thermal storage, characterized in that, Including coal-fired systems and steam thermal storage systems; The coal-fired system includes a coal-fired boiler (1), a high-pressure cylinder (2), a medium-pressure cylinder (3), a low-pressure cylinder (4), a generator (5), a deaerator (6), a high-pressure heater (7), a low-pressure heater (8), a condenser (9), a condensate pump (P1), a feedwater pump (P2), and a fourth valve (V4). The main steam outlet of the coal-fired boiler (1) is connected to the inlet of the high-pressure cylinder (2). The reheat steam outlet of the coal-fired boiler (1) is connected to the inlet of the medium-pressure cylinder (3). The exhaust outlet of the high-pressure cylinder (2) is connected to the cold end inlet of the reheat steam of the coal-fired boiler (1) through the fourth valve (V4). The extraction steam outlet of the high-pressure cylinder (2) is connected to the hot end inlet of the high-pressure heater (7). The exhaust steam outlet of the medium-pressure cylinder (3) is connected to the inlet of the low-pressure cylinder (4). The extraction steam outlet of the medium-pressure cylinder (3) is connected to the hot end inlet of the high-pressure heater (7). The steam extraction outlet of the intermediate pressure cylinder (3) is connected to the inlet of the deaerator (6); the outlet of the deaerator (6) is connected to the inlet of the feed water pump (P2); the outlet of the feed water pump (P2) is connected to the cold end inlet of the high pressure heater (7); the cold end outlet of the high pressure heater (7) is connected to the feed water inlet of the coal-fired boiler (1); the steam extraction outlet of the low pressure cylinder (4) is connected to the hot end inlet of the low pressure heater (8); the exhaust outlet of the low pressure cylinder (4) is connected to the inlet of the condenser (9); the outlet of the condenser (9) is connected to the inlet of the condensate pump (P1); the outlet of the condensate pump (P1) is connected to the cold end inlet of the low pressure heater (8); the cold end outlet of the low pressure heater (8) is connected to the inlet of the deaerator (6); the high pressure cylinder (2), the intermediate pressure cylinder (3), the low pressure cylinder (4) and the generator (5) share a common bearing connection; The steam thermal storage system includes a steam storage tank (10), a steam ejector (11), a first valve (V1), a second valve (V2), a third valve (V3), a fifth valve (V5), and a sixth valve (V6). The main steam outlet of the coal-fired boiler (1) is connected to the inlet of the steam storage tank (10) through the first valve (V1). The outlet of the high-pressure steam storage tank (10) is connected to the power steam inlet of the steam ejector (11) through the second valve (V2). The exhaust outlet of the high-pressure cylinder (2) is connected to the ejector extraction end of the steam ejector (11) through the third valve (V3). The steam outlet of the steam ejector (11) is connected to the inlet of the medium-pressure cylinder (3) through the fifth valve (V5). The steam outlet of the steam ejector (11) is connected to the inlet of the low-pressure cylinder (4) through the sixth valve (V6).

2. The peak-shaving system for coal-fired power units based on boiler steam extraction and thermal storage according to claim 1, characterized in that, In the coal-fired system, a main steam splitter (F1) is provided between the main steam outlet of the coal-fired boiler (1) and the steam storage tank (10) and the high-pressure cylinder (2); a first steam splitter (F2) is provided between the steam ejector (11) and the intermediate-pressure cylinder (3) and the low-pressure cylinder (4); a second steam splitter (F3) is provided between the high-pressure cylinder (2) and the steam ejector (11) and the coal-fired boiler (1); a high-pressure steam combiner (M1) is provided between the intermediate-pressure cylinder (3) and the steam ejector (11) and the reheat steam outlet of the coal-fired boiler (1); and a low-pressure steam combiner (M2) is provided between the low-pressure cylinder (4) and the intermediate-pressure cylinder (3) and the steam ejector (11).

3. The peak-shaving system for coal-fired power units based on boiler steam extraction and thermal storage according to claim 1, characterized in that, When a coal-fired unit needs to increase its load, if the current load of the coal-fired boiler (1) is between 50% and 100% THA, that is, when the coal-fired boiler (1) is running at a high load, the outlet steam pressure of the steam ejector (11) is high, and the power generation efficiency of the steam entering the intermediate pressure cylinder (3) is high. Therefore, the fifth valve (V5) is opened to allow the outlet steam of the steam ejector (11) to be fed into the intermediate pressure cylinder (3) to do work. If the current load of the coal-fired boiler (1) is between 25% and 50% THA, that is, when the coal-fired boiler (1) is running at a low load, the outlet steam pressure of the steam ejector (11) is low, and the power generation efficiency of the steam entering the low pressure cylinder (4) to do work is high. Moreover, it is necessary to increase the steam flow into the low pressure cylinder (4) to ensure that it does not blow air. Therefore, the sixth valve (V6) is opened to allow the outlet steam of the steam ejector (11) to enter the low pressure cylinder (4) to do work.

4. The peak-shaving system for coal-fired power units based on boiler steam extraction and thermal storage according to claim 1, characterized in that, When the coal-fired unit needs to increase its load, the steam flow rate at the outlet of the steam ejector (11) is adjusted by regulating the opening of the second valve (V2) and the third valve (V3), so that the steam flow rate entering the turbine can meet the turbine load change rate and the coal-fired unit can meet the flexible load change requirements.

5. The operation method of the peak-shaving system of a coal-fired unit based on boiler steam extraction and thermal storage as described in any one of claims 1 to 4, characterized in that, When a coal-fired unit needs to operate normally and stably, only the coal-fired system should be operated, the steam thermal storage system should not be operated, and the first valve (V1), the second valve (V2), the third valve (V3), the fifth valve (V5) and the sixth valve (V6) should be closed, while the fourth valve (V4) should be opened. When the coal-fired unit needs to reduce its load, the first valve (V1) is opened first. The main steam in the coal-fired boiler (1) enters the steam storage tank (10) through the first valve (V1) for storage. The first valve (V1) is used to regulate the flow rate of the main steam flowing into the steam storage tank (10), thereby controlling the load reduction rate of the coal-fired unit. During this period, the second valve (V2), the third valve (V3), the fifth valve (V5) and the sixth valve (V6) are closed, and the fourth valve (V4) is open. When the coal-fired unit needs to increase its load, the second valve (V2) and the third valve (V3) are opened, and the opening of the fourth valve (V4) is reduced. The main steam is released from the steam storage tank (10) and enters the power steam inlet of the steam ejector (11). The high-pressure cylinder (2) exhausts steam into the ejector extraction end of the steam ejector (11). If the current load of the coal-fired boiler (1) is between 50% and 100% THA, the fifth valve (V5) is opened so that the outlet steam of the steam ejector (11) enters the intermediate-pressure cylinder (3) to do work. If the current load of the coal-fired boiler (1) is between 25% and 50% THA, the sixth valve (V6) is opened so that the outlet steam of the steam ejector (11) enters the low-pressure cylinder (4) to do work. The actual pressure of the outlet steam of the steam ejector (11) is higher than the steam pressure corresponding to the current load of the coal-fired boiler (1), and it can greatly increase the amount of steam entering the turbine, thereby rapidly increasing the load of the coal-fired unit.

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