Steam turbine regenerative system

Abstract

The utility model discloses a steam turbine regenerative system which comprises a boiler, a steam turbine high-pressure cylinder, a steam turbine intermediate-pressure cylinder, a first high-pressure heater, a second high-pressure heater, a third high-pressure heater, a deaerator and the like. The method aims at solving the problem that in the peak-shaving working condition variable-load operation process, due to the fact that the temperature change of water entering a high-pressure heater cannot follow the change rate of steam pressure, the high-pressure heater breaks down. According to the utility model, the communicating pipeline between the steam inlet pipe of the third high-pressure heater and the steam inlet pipe of the deaerator and the valve of the communicating pipeline are additionally arranged, and when the valve is opened, part of high-pressure and high-temperature steam in the steam inlet pipe of the third high-pressure heater enters the steam inlet pipe of the deaerator, so that the steam inlet pressure and temperature of the deaerator are increased, and the water inlet temperature of the third high-pressure heater is increased; the temperature difference between the water inlet temperature and the steam extraction temperature of the third high-pressure heater is reduced, the working environment of the third high-pressure heater is improved, the fault risk of the third high-pressure heater is effectively reduced, and the high practical value is achieved.

Description

Technical Field

[0001] The utility model relates to a steam turbine heat regeneration system, belonging to the technical field of steam turbine heat regeneration in thermal power plants. Background Art

[0002] High-pressure heaters are key auxiliary equipment in power plants, utilizing their heat recovery extraction steam to heat feedwater and improve the unit's thermal efficiency. It's worth noting that the frequency of failure of high-pressure heaters, particularly the high-pressure heater system and its piping, ranks second only to boiler tube bursts as a common power plant failure. Once a high-pressure heater fails and ceases operation, feedwater can only enter the boiler through a bypass pipe, causing the feedwater temperature to drop and increasing fuel consumption. For steam turbines, the pressure on the water side of the high-pressure heater is greater than the pressure on the steam side. If a leak occurs, feedwater will rush into the casing, causing the steam side to flood. Water could then flow back into the turbine cylinder along the extraction pipe, potentially causing cylinder deformation, differential expansion, unit vibration, dynamic and static friction, shaft bending, and even blade breakage.

[0003] The typical heat recovery system of a large coal-fired unit steam turbine includes three high-pressure heaters. Since the No. 3 high-pressure heater has the highest steam inlet temperature and the lowest feed water temperature, the temperature difference is the largest and the operating conditions are the most severe, it is the equipment with the highest incidence of high-pressure heater failure accidents.

[0004] In recent years, thermal power companies, as the main force in peak load regulation, have experienced large load fluctuations. Steam temperature, steam pressure, and boiler evaporation volume are constantly changing, resulting in constant changes in the extraction pressure, temperature, and extraction volume of the high-pressure heater. The temperature and flow rate of the high-pressure heater feed water cannot keep up with the rate of change of steam pressure. The U-shaped tubes inside the No. 3 high-pressure heater generate thermal stress due to the rapid changes in temperature and pressure, which will aggravate the fatigue of the heat exchange tubes and cause damage and leakage. At the same time, the heat exchange tubes of the high-pressure heater are supported and installed by various levels of baffles. There is a gap between the baffles and the heat exchange tubes. During operation, due to operating conditions such as water level fluctuations caused by gas-liquid two-phase flow, system hot and cold shocks, and rapid load fluctuations, the tube bundle will vibrate, causing the tube bundle to rub against the baffles. Long-term rubbing will cause pipeline leakage.

[0005] In summary, timely adjusting the water inlet temperature of the No. 3 HP heater or adopting other means to reduce the temperature difference are effective measures to prevent the failure of the No. 3 HP heater. Utility Model Content

[0006] The purpose of the utility model is to overcome the above-mentioned deficiencies in the prior art and to provide a steam turbine heat recovery system which has a reasonable structural design and is conducive to the safe operation of the unit.

[0007] The technical solution adopted by the present invention to solve the above problems is: a steam turbine heat recovery system, including a boiler, a steam turbine high-pressure cylinder and a steam turbine intermediate-pressure cylinder, the main steam outlet of the boiler is connected to the steam turbine high-pressure cylinder through a main steam pipe, and the reheat steam outlet of the boiler is connected to the steam turbine intermediate-pressure cylinder through a hot reheat steam pipe; it is characterized in that: it also includes a No. 1 high-pressure heater, a No. 2 high-pressure heater, a No. 3 high-pressure heater and a deaerator, the water sides of the deaerator, the No. 3 high-pressure heater, the No. 2 high-pressure heater and the No. 1 high-pressure heater are connected in sequence through a water feed pipe, the water outlet of the No. 1 high-pressure heater is connected to the boiler through a water feed pipe; the steam side of the No. 1 high-pressure heater is connected to the steam turbine high-pressure cylinder through the No. 1 high-pressure heater steam inlet pipe The steam side of the No. 2 high-pressure heater is connected to the high-pressure cylinder of the steam turbine through the No. 2 high-pressure heater steam inlet pipe, the steam side of the No. 3 high-pressure heater is connected to the medium-pressure cylinder of the steam turbine through the No. 3 high-pressure heater steam inlet pipe, and the steam side of the deaerator is connected to the medium-pressure cylinder of the steam turbine through the deaerator steam inlet pipe; the drain side of the No. 1 high-pressure heater is connected to the No. 2 high-pressure heater through the No. 1 high-pressure heater drain pipe, the drain side of the No. 2 high-pressure heater is connected to the No. 3 high-pressure heater through the No. 2 high-pressure heater drain pipe, the drain side of the No. 3 high-pressure heater is connected to the deaerator through the No. 3 high-pressure heater drain pipe, the No. 3 high-pressure heater steam inlet pipe is connected to the deaerator steam inlet pipe through a branch, and a valve is installed on the branch.

[0008] Preferably, the valve is connected to a control device that can control the valve to open or close.

[0009] The working method is as follows:

[0010] 1) When it is detected that the temperature difference between the inlet temperature of the No. 3 HP heater and the inlet water temperature of the No. 3 HP heater is large and exceeds the maximum temperature difference allowed by the design, the valve is opened, and part of the high-pressure and high-temperature steam in the steam inlet pipe of the No. 3 HP heater enters the steam inlet pipe of the deaerator, thereby increasing the inlet steam pressure and temperature of the deaerator, increasing the inlet water temperature of the No. 3 HP heater, and reducing the temperature difference.

[0011] 2) When the steam-measured temperature of the No. 3 high-pressure heater and the water-measured temperature of the No. 3 high-pressure heater are not significantly different and exceed the maximum temperature difference allowed by the design, other equipment and systems operate in accordance with conventional methods.

[0012] 3) When leakage occurs in the high-pressure heater, it is necessary to isolate all high-pressure heaters from operation and open the valve to avoid the risk of damage to the high-pressure heater due to deformation of the No. 3 high-pressure heater tube sheet caused by a loose steam inlet valve of the No. 3 high-pressure heater.

[0013] Compared with the existing technology, the present invention has the following advantages and effects: Based on the elastic heat recovery technology, the present invention adds a connecting pipe and valve between the No. 3 high-pressure heater steam inlet pipe and the deaerator steam inlet pipe, and rationally designs a system in which the steam inlet thermal parameters of the No. 3 high-pressure heater and the deaerator are consistent. When the valve is opened, part of the high-pressure and high-temperature steam in the No. 3 high-pressure heater steam inlet pipe enters the deaerator steam inlet pipe, increasing the steam inlet pressure and temperature of the deaerator, increasing the water inlet temperature of the No. 3 high-pressure heater, and reducing the temperature difference between the water inlet temperature of the No. 3 high-pressure heater and the extraction temperature. This is equivalent to moving the heating steam source of the No. 3 high-pressure heater backward, improving the working environment of the No. 3 high-pressure heater, ensuring the safe and stable operation of the No. 3 high-pressure heater, and has high practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural diagram of the system in the utility model.

[0015] In the figure: boiler 1, steam turbine high-pressure cylinder 2, steam turbine intermediate-pressure cylinder 3, No. 1 high-pressure heater 4, No. 2 high-pressure heater 5, No. 3 high-pressure heater 6, deaerator 7, main steam pipe 8, hot resteam pipe 9, No. 1 high-pressure heater steam inlet pipe 10, No. 2 high-pressure heater steam inlet pipe 11, No. 3 high-pressure heater steam inlet pipe 12, deaerator steam inlet pipe 13, No. 1 high-pressure heater drain pipe 14, No. 2 high-pressure heater drain pipe 15, No. 3 high-pressure heater drain pipe 16, valve 17, water supply pipe 18. DETAILED DESCRIPTION

[0016] The present invention will be further described in detail below with reference to the accompanying drawings and through examples. The following examples are provided to explain the present invention, but the present invention is not limited to the following examples.

[0017] Example

[0018] See also Figure 1In this embodiment, a steam turbine reheat system is provided, comprising a boiler 1, a steam turbine high-pressure cylinder 2 and a steam turbine intermediate-pressure cylinder 3. The main steam outlet of the boiler 1 is connected to the steam turbine high-pressure cylinder 2 through a main steam pipe 8, and the reheat steam outlet of the boiler 1 is connected to the steam turbine intermediate-pressure cylinder 3 through a hot reheat steam pipe 9; the system also comprises a No. 1 high-pressure heater 4, a No. 2 high-pressure heater 5, a No. 3 high-pressure heater 6 and a deaerator 7. The water sides of the deaerator 7, the No. 3 high-pressure heater 6, the No. 2 high-pressure heater 5 and the No. 1 high-pressure heater 4 are connected in sequence through a water feed pipe 18, and the water outlet of the No. 1 high-pressure heater 4 is connected to the boiler 1 through the water feed pipe 18; the steam side of the No. 1 high-pressure heater 4 is connected to the steam turbine high-pressure cylinder 2 through the No. 1 high-pressure heater steam inlet pipe 10, and the steam side of the No. 2 high-pressure heater 5 is connected to the steam turbine high-pressure cylinder 2 through the No. 2 high-pressure heater steam inlet pipe 10. The steam pipe 11 is connected to the high-pressure cylinder 2 of the steam turbine, the steam side of the No. 3 high-pressure heater 6 is connected to the intermediate-pressure cylinder 3 of the steam turbine through the No. 3 high-pressure heater steam inlet pipe 12, and the steam side of the deaerator 7 is connected to the intermediate-pressure cylinder 3 of the steam turbine through the deaerator steam inlet pipe 13; the drain side of the No. 1 high-pressure heater 4 is connected to the No. 2 high-pressure heater 5 through the No. 1 high-pressure heater drain pipe 14, the drain side of the No. 2 high-pressure heater 5 is connected to the No. 3 high-pressure heater 6 through the No. 2 high-pressure heater drain pipe 15, and the drain side of the No. 3 high-pressure heater 6 is connected to the deaerator 7 through the No. 3 high-pressure heater drain pipe 16. The No. 3 high-pressure heater steam inlet pipe 12 is connected to the deaerator steam inlet pipe 13 through a branch line, and a valve 17 is installed on the branch line. The valve 17 is connected to a control device (existing product) that can control the valve 17 to be opened or closed.

[0019] The working method is as follows:

[0020] 1) When it is detected that the temperature difference between the inlet temperature of the No. 3 HP heater 6 and the inlet water temperature of the No. 3 HP heater 6 is large and exceeds the maximum temperature difference allowed by the design, the valve 17 is opened, and part of the high-pressure and high-temperature steam in the No. 3 HP heater steam inlet pipe 12 enters the deaerator steam inlet pipe 13, thereby increasing the inlet steam pressure and temperature of the deaerator 7, increasing the inlet water temperature of the No. 3 HP heater 6, and reducing the temperature difference.

[0021] 2) When the steam temperature measured by the No. 3 high-pressure heater 6 and the water temperature measured by the No. 3 high-pressure heater 6 are not significantly different and exceed the maximum temperature difference allowed by the design, other equipment and systems operate in accordance with conventional methods.

[0022] 3) When leakage occurs in the high-pressure heater and all high-pressure heaters need to be isolated from operation, open valve 17 to avoid the risk of deformation of the No. 3 high-pressure heater 6 tube sheet due to a loose steam inlet valve of the No. 3 high-pressure heater 6, which may lead to damage to the high-pressure heater.

[0023] This design has little impact on the axial thrust of the unit. Only the first few stages (usually the first three stages) of the intermediate pressure cylinder have slightly changed the thermal characteristics of the unit, while other parts remain unchanged. A connecting pipe and its valve 17 are added between the No. 3 high-pressure heater steam inlet pipe 12 and the deaerator steam inlet pipe 13 in the heat recovery system, which does not affect the thermal characteristics of the original heat recovery system.

[0024] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0025] In addition, it should be noted that the above content described in this specification is merely an example of the structure of the present utility model. Any equivalent changes made based on the structure, features and principles described in the concept of the present utility model patent are included in the scope of protection of the present utility model patent. Those skilled in the art of the present utility model can make various modifications, supplements or replace the specific embodiments described in the present utility model with similar methods. As long as they do not deviate from the structure of the present utility model or exceed the scope defined by the claims, they should fall within the scope of protection of the present utility model.

Claims

1. A steam turbine reheat system, comprising a boiler (1), a steam turbine high-pressure cylinder (2), and a steam turbine intermediate-pressure cylinder (3), wherein the main steam outlet of the boiler (1) is connected to the steam turbine high-pressure cylinder (2) via a main steam pipe (8), and the reheat steam outlet of the boiler (1) is connected to the steam turbine intermediate-pressure cylinder (3) via a hot reheat steam pipe (9); characterized in that: The boiler also includes a No. 1 high-pressure heater (4), a No. 2 high-pressure heater (5), a No. 3 high-pressure heater (6) and a deaerator (7). The water sides of the deaerator (7), the No. 3 high-pressure heater (6), the No. 2 high-pressure heater (5) and the No. 1 high-pressure heater (4) are connected in sequence through a water supply pipe (18). The water outlet of the No. 1 high-pressure heater (4) is connected to the boiler (1) through the water supply pipe (18); the steam side of the No. 1 high-pressure heater (4) is connected to the high-pressure cylinder (2) of the steam turbine through the No. 1 high-pressure heater steam inlet pipe (10), the steam side of the No. 2 high-pressure heater (5) is connected to the high-pressure cylinder (2) of the steam turbine through the No. 2 high-pressure heater steam inlet pipe (11), and the steam side of the No. 3 high-pressure heater (6) is connected to the high-pressure cylinder (2) of the steam turbine through the No. 3 high-pressure heater steam inlet pipe (12). The steam inlet pipe (12) of the high-pressure heater is connected to the intermediate-pressure cylinder (3) of the steam turbine, and the steam side of the deaerator (7) is connected to the intermediate-pressure cylinder (3) of the steam turbine through the deaerator steam inlet pipe (13); the drain side of the No. 1 high-pressure heater (4) is connected to the No. 2 high-pressure heater (5) through the No. 1 high-pressure heater drain pipe (14), the drain side of the No. 2 high-pressure heater (5) is connected to the No. 3 high-pressure heater (6) through the No. 2 high-pressure heater drain pipe (15), and the drain side of the No. 3 high-pressure heater (6) is connected to the deaerator (7) through the No. 3 high-pressure heater drain pipe (16). The No. 3 high-pressure heater steam inlet pipe (12) is connected to the deaerator steam inlet pipe (13) through a branch line, and a valve (17) is installed on the branch line.

2. The steam turbine heat recovery system according to claim 1, characterized in that: The valve (17) is connected to a control device for controlling the valve (17) to open or close.

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