Main steam gradient utilization peak regulation system

Abstract

The utility model discloses a peak shaving system for gradient utilization of main steam, which belongs to the field of steam turbine application and comprises a boiler, a flue gas heater, a high-pressure cylinder, an intermediate-pressure cylinder, a first high-pressure heater, a second high-pressure heater and a third high-pressure heater. A main steam gradient utilization system isolation door is installed at a main steam outlet of the boiler and connected with a steam inlet of the smoke heater, and a steam outlet of the smoke heater is connected with a steam inlet of the first high-pressure heater and a steam inlet of the second high-pressure heater. A first high-pressure heater isolation door is mounted at a steam inlet of the first high-pressure heater; a second high-pressure heater isolation door is mounted at a steam inlet of the second high-pressure heater; during deep peak regulation, extra main steam of the flue gas heater flows to the high-pressure heater to heat feed water, the feed water is preheated before entering the boiler, the temperature of flue gas before entering the SCR system is increased, the problem that operation of a denitration system is affected due to low flue gas temperature is effectively solved, and the flue gas temperature and the energy utilization rate are increased.

Description

Technical Field

[0001] The utility model relates to the application field of steam turbines, in particular to a main steam step utilization peak regulation system. Background Art

[0002] At present, the deep peak-shaving capacity of coal-fired units in thermal power plants during the non-heating period is often restricted by the boiler's emission indicators. During the non-heating period, the electricity demand is relatively low, but in order to ensure the stability of the power grid and meet the minimum electricity demand, the boiler still needs to operate to meet the basic load requirements. Under this low-load operation state, the boiler combustion efficiency will decrease. Because the SCR system requires a certain temperature of flue gas to operate effectively, the flue gas concentration and temperature emitted by the boiler may exceed environmental protection requirements. Therefore, the peak-shaving capacity is limited by emission indicators. Utility Model Content

[0003] The purpose of the utility model is to overcome the deficiencies of the above-mentioned prior art and to provide a main steam cascade utilization peak-shaving system that can deeply regulate boiler emission indicators under peak regulation and achieve deeper peak-shaving capacity of coal-fired units.

[0004] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0005] A main steam cascade utilization peak-shaving system comprises a boiler, a flue gas heater, a high-pressure cylinder, a medium-pressure cylinder, a first high-pressure heater, a second high-pressure heater and a third high-pressure heater. The flue gas outlet of the boiler is connected to the flue gas inlet of the flue gas heater, the main steam outlet of the boiler is connected to the steam inlet of the high-pressure cylinder, and a main steam cascade utilization system isolation door is installed at the main steam outlet of the boiler, and the main steam cascade utilization system isolation door is connected to the steam inlet of the flue gas heater.

[0006] The steam outlet of the flue gas heater is connected to the steam inlet of the first high-pressure heater and the steam inlet of the second high-pressure heater respectively, and a first high-pressure heater isolation door is installed at the steam inlet of the first high-pressure heater and a second high-pressure heater isolation door is installed at the steam inlet of the second high-pressure heater.

[0007] The steam outlet of the high-pressure cylinder is connected to the reheat steam inlet of the boiler, the reheat steam outlet of the boiler is connected to the steam inlet of the medium-pressure cylinder, and the exhaust port of the medium-pressure cylinder is connected to the steam inlet of the flue gas heater.

[0008] The high-pressure cylinder is also equipped with a first-stage exhaust electric door and a second-stage exhaust electric door. The steam outlet of the first-stage exhaust electric door is connected to the steam inlet of the first high-pressure heater, and the steam outlet of the second-stage exhaust electric door is connected to the steam inlet of the second high-pressure heater.

[0009] The first high-voltage heater, the second high-voltage heater and the third high-voltage heater are connected in sequence.

[0010] The feed water outlet of the first high pressure heater is connected to the feed water inlet of the boiler.

[0011] The beneficial effects of the utility model are:

[0012] During deep peak shaving, the utility model opens the isolation door of the main steam cascade utilization system, allowing the main steam to enter the flue gas heater to heat the low-temperature flue gas, and the flue gas temperature is increased to meet the environmental protection standard for discharge. The remaining main steam is cooled and still maintains an overheated state. The first high-pressure heater isolation door and the second high-pressure heater isolation door are opened, and the feed water in the first high-pressure heater and the second high-pressure heater are heated by pressure regulation and flow matching, thereby indirectly increasing the temperature of the flue gas. The advantage of the utility model system is that when the new energy green electricity is connected to the grid, the coal-fired power generation unit needs to perform deep peak shaving, and during the deep peak shaving during the pure condensing operation, the denitrification system cannot be put into use due to the low flue gas temperature, which limits the peak shaving depth of the unit. This system can effectively solve the problem of low flue gas temperature during deep peak shaving, and at the same time, the cooled main steam is connected to the high-pressure heater system, and the feed water temperature is greatly increased to further increase the flue gas temperature. At the same time, the energy utilization capacity of the unit can be improved, and the main steam cascade utilization can be realized. Through the cascade utilization of the main steam, this system further improves the peak shaving capacity of the unit, and utilizes the latent heat of vaporization to improve the energy utilization efficiency, thereby maximizing the operating benefits of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the structure of the utility model;

[0014] In the figure: 1. Boiler; 2. Flue gas heater; 3. High-pressure cylinder; 4. Medium-pressure cylinder; 5. First high-pressure heater; 6. Second high-pressure heater; 7. Third high-pressure heater; 8. Main steam cascade utilization system isolation door; 9. First-stage steam extraction electric door; 10. First high-pressure heater isolation door; 11. Second-stage steam extraction electric door; 12. Second high-pressure heater isolation door. DETAILED DESCRIPTION

[0015] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0016] In a specific implementation of this embodiment, as shown in the attached Figure 1As shown, the system includes a boiler 1, a flue gas heater 2, a high-pressure cylinder 3, an intermediate-pressure cylinder 44, a first high-pressure heater 5, a second high-pressure heater 6 and a third high-pressure heater 7. The flue gas outlet of the boiler 1 is connected to the flue gas inlet of the flue gas heater 2, the main steam outlet of the boiler 1 is connected to the steam inlet of the high-pressure cylinder 3, and a main steam step utilization system isolation door 8 is installed at the main steam outlet of the boiler 1, and the main steam step system isolation door 8 is connected to the steam inlet of the flue gas heater 2. The steam outlet of the flue gas heater 2 is connected to the steam inlet of the first high-pressure heater 5 and the steam inlet of the second high-pressure heater 6, respectively, and a first high-pressure heater isolation door 10 is installed at the steam inlet of the first high-pressure heater 5, and a second high-pressure heater isolation door 12 is installed at the steam inlet of the second high-pressure heater 6. The steam outlet of the high-pressure cylinder 3 is connected to the reheat steam inlet of the boiler 1, and the reheat steam outlet of the boiler 1 is connected to the steam inlet of the intermediate-pressure cylinder 4, and the exhaust port of the intermediate-pressure cylinder 4 is connected to the steam inlet of the flue gas heater 2. The high-pressure cylinder 3 is also equipped with a first-stage exhaust electric door 9 and a second-stage exhaust electric door 11. The steam outlet of the first-stage exhaust electric door 9 is connected to the steam inlet of the first high-pressure heater 5, and the steam outlet of the second-stage exhaust electric door 11 is connected to the steam inlet of the second high-pressure heater 6. The first high-pressure heater 5, the second high-pressure heater 6 and the third high-pressure heater 7 are connected in sequence. The feed water outlet of the first high-pressure heater 5 is connected to the feed water inlet of the boiler 1.

[0017] The working principle of the utility model is:

[0018] The main steam generated by the boiler 1 first enters the high-pressure cylinder 3. The steam energy in the high-pressure cylinder 3 is converted into mechanical energy, which drives the turbine to rotate and generate electricity. After the high-pressure cylinder 3 does work, the temperature and pressure of the steam drop. Part of the steam is sent back to the boiler 1 for reheating. The reheated steam enters the medium-pressure cylinder 4 and continues to convert energy into mechanical energy, further driving the turbine to generate electricity. The steam discharged from the medium-pressure cylinder 4 is guided to the flue gas heater 2 to heat the flue gas discharged from the boiler 1, increase the flue gas temperature, and ensure that the SCR system can operate effectively to reduce emission pollutants. The steam extracted from the high-pressure cylinder 3 is respectively sent to the first high-pressure heater 5 and the second high-pressure heater 6 through the first-stage steam extraction electric door 9 and the second-stage steam extraction electric door 11. The first high-pressure heater 5 and the second high-pressure heater 6 use the waste heat of the steam to heat the feed water of the boiler 1, increase the temperature of the feed water, and make it have a higher initial temperature before entering the boiler 1, thereby improving the efficiency of the boiler.

[0019] When the power demand is low, the main steam is adjusted to flow to the flue gas heater 2 instead of all entering the high-pressure cylinder 3 and the medium-pressure cylinder 4, thereby reducing the power generation and achieving a balance between power supply and demand.

[0020] In a specific implementation of this embodiment, during deep peak regulation, the main steam cascade utilization system isolation door 8 is opened to allow the main steam to enter the flue gas heater 2 to heat the low-temperature flue gas. The flue gas temperature is increased to meet the environmental protection standard for discharge. The remaining main steam is cooled and still maintains an overheated state. The first high-pressure heater isolation door 10 and the second high-pressure heater isolation door 12 are opened to heat the feed water in the first high-pressure heater 5 and the second high-pressure heater 6 through pressure regulation and flow matching, thereby indirectly increasing the temperature of the flue gas.

[0021] In a specific implementation of this embodiment, after the main steam stage peak-shaving system is put into operation, for a conventional 350MW supercritical unit, the main and reheat steam temperatures are increased by more than 20°C compared with the design conditions, the boiler secondary air temperature and feed water temperature are significantly increased, and the boiler transition point is greatly moved forward; the boiler denitrification SCR inlet flue gas temperature is maintained above 300°C under a load of 25-30%; the unit's minimum electrical load can reach 70MW.

[0022] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A main steam cascade utilization peak shaving system, characterized by: The invention comprises a boiler (1), a flue gas heater (2), a high-pressure cylinder (3), a medium-pressure cylinder (4), a first high-pressure heater (5), a second high-pressure heater (6) and a third high-pressure heater (7); the flue gas outlet of the boiler (1) is connected to the flue gas inlet of the flue gas heater (2); the main steam outlet of the boiler (1) is connected to the steam inlet of the high-pressure cylinder (3); a main steam step utilization system isolation door (8) is installed at the main steam outlet of the boiler (1); the main steam step utilization system isolation door (8) is connected to the steam inlet of the flue gas heater (2); the steam outlet of the flue gas heater (2) is respectively connected to the steam inlet of the first high-pressure heater (5) and the steam inlet of the second high-pressure heater (6); and a first high-pressure heater isolation door (10) is installed at the steam inlet of the first high-pressure heater (5) and a second high-pressure heater isolation door (12) is installed at the steam inlet of the second high-pressure heater (6).

2. A main steam cascade utilization peak shaving system according to claim 1, characterized in that: The steam outlet of the high-pressure cylinder (3) is connected to the reheat steam inlet of the boiler (1), the reheat steam outlet of the boiler (1) is connected to the steam inlet of the medium-pressure cylinder (4), and the exhaust port of the medium-pressure cylinder (4) is connected to the steam inlet of the flue gas heater (2).

3. A main steam cascade utilization peak shaving system according to claim 2, characterized in that: The high-pressure cylinder (3) is also equipped with a first-stage exhaust electric door (9) and a second-stage exhaust electric door (11), the steam outlet of the first-stage exhaust electric door (9) is connected to the steam inlet of the first high-pressure heater (5), and the steam outlet of the second-stage exhaust electric door (11) is connected to the steam inlet of the second high-pressure heater (6).

4. The main steam cascade utilization peak shaving system according to claim 1, characterized in that: The first high-pressure heater (5), the second high-pressure heater (6) and the third high-pressure heater (7) are connected in sequence.

5. A main steam cascade utilization peak shaving system according to claim 4, characterized in that: The feed water outlet of the first high-pressure heater (5) is connected to the feed water inlet of the boiler (1).

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