A three-extraction temperature control method and control system for a pure condensing steam turbine

Abstract

The present invention discloses a three-extraction temperature control method and control system for a pure condensing steam turbine, and relates to the field of power generation equipment. The method comprises measuring the three-extraction temperature, the high-pressure cylinder temperature or the medium-pressure cylinder temperature; calculating the difference between the measured temperature value and the specified value; generating the opening control data of the first to fourth flow valves according to the difference; and adjusting the first to fourth flow valves according to the generated opening control data. The system comprises: a first flow valve arranged in the pipeline from the condenser to the deaerator; a second flow valve arranged in the pipeline from the normal temperature water tank to the deaerator; a third flow valve arranged in the pipeline from the heating return water tank to the deaerator; and a fourth flow valve arranged in the pipeline from the third steam extraction port of the steam turbine to the deaerator. The present invention keeps the three-extraction temperature of the steam turbine below 450°C for safe operation by optimizing the water replenishment and heating operation of the deaerator, and has the characteristics of simple adjustment, strong operability and good stability.

Description

Technical Field

[0001] The invention relates to the field of power generation equipment, and in particular to a three-extraction temperature control method and control system for a pure condensing steam turbine. Background Art

[0002] The overhaul of the steam pipe is an important part of the overhaul of the steam turbine. After the overhaul of the steam pipe, the gap between the steam pipe and the cylinder body becomes larger after the oxide scale is cleaned, and more steam leaks into the interlayer, causing the temperature of the outer cylinder to rise by about 50℃ compared with before the overhaul, causing the temperature of the three extractions to reach 470-490℃ during the operation of the pure condensing steam turbine. However, the three extraction pipes are made of 20G metal material, which is suitable for steam temperatures below 450℃. Long-term operation at 470-490℃ will cause pearlite spheroidization and graphitization.

[0003] The present invention proposes a solution to the above technical problems that occur after the overhaul of a pure condensing steam turbine. Summary of the invention

[0004] The object of the present invention is to provide a temperature control method and control system for the third extraction of a pure condensing steam turbine, so as to solve the technical problem of over-temperature of the third extraction after maintenance.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A three-extraction temperature control method for a pure condensing steam turbine, comprising:

[0007] Measure the temperature of the third extraction, high pressure cylinder or medium pressure cylinder;

[0008] Calculate the difference between the measured temperature value and the specified value;

[0009] Generate opening control data of the first to fourth flow valves respectively according to the difference; and

[0010] adjusting the first to fourth flow valves according to the generated opening control data;

[0011] Among them, the first flow valve is set in the pipeline from the condenser to the deaerator, the second flow valve is set in the pipeline from the normal temperature water tank to the deaerator, the third flow valve is set in the pipeline from the heating return water tank to the deaerator, and the fourth flow valve is set in the pipeline from the third steam extraction port of the turbine to the deaerator.

[0012] In the above control method, preferably, it also includes the step of controlling the water treatment equipment to supplement softened water to the condenser when the water level value of the deaerator is lower than the normal value.

[0013] In the above control method, preferably, it also includes the step of reducing the opening of the third flow valve and increasing the opening of the second flow valve and the opening of the fourth flow valve when the water level value of the heating return tank is lower than the set value.

[0014] In the above-mentioned control method, preferably, in the step of generating the opening control data of the first to fourth flow valves respectively according to the difference, the opening control data of the first flow valve is negatively correlated with the difference, and the opening control data of the second flow valve and the opening control data of the fourth flow valve are both positively correlated with the difference.

[0015] A three-extraction temperature control system for a pure condensing steam turbine, comprising:

[0016] A first flow valve is provided in the pipeline from the condenser to the deaerator;

[0017] A second flow valve is arranged in the pipeline from the normal temperature water tank to the deaerator;

[0018] A third flow valve is provided in the pipeline from the heating return water tank to the deaerator; and

[0019] The fourth flow valve is arranged in the pipeline from the third steam extraction port of the steam turbine to the deaerator.

[0020] In the above-mentioned control system, preferably, it also includes: a first water level sensor, used to detect the water level in the deaerator water tank; a water treatment device, used to convert raw water into softened water, the water treatment device is connected to the water supply port of the condenser; and a fifth valve, arranged in the water supply pipeline from the water treatment device to the condenser; when the water level of the deaerator is lower than the normal value, the fifth valve is opened, and the water treatment device replenishes softened water to the condenser.

[0021] In the above control system, preferably, it also includes a second water level sensor, which is used to detect the water level of the heating return water tank to adjust the opening of the second to fourth flow valves according to the water level of the heating return water tank.

[0022] In the above-mentioned control system, preferably, it also includes: a temperature sensor configured to measure the three-extraction temperature, the high-pressure cylinder temperature or the medium-pressure cylinder temperature; a microprocessor electrically connected to the temperature sensor and the first to fourth flow valves; and a memory storing a program that can be executed by the microprocessor; when the program is executed by the microprocessor, the control system executes the steps of the control method as described in any one of the above.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] The present invention optimizes the operation of water replenishment and heat supply to the deaerator to keep the third extraction temperature of the steam turbine below 450°C for safe operation, and has the characteristics of simple adjustment, strong operability and good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a water replenishment system diagram of a deaerator according to an embodiment;

[0026] Figure numerals: 1. Water treatment equipment; 2. Fifth valve; 3. Condenser; 4. #1 low-temperature heater; 5. #2 low-temperature heater; 6. #3 low-temperature heater; 7. #4 low-temperature heater; 8. First water supply branch; 9. First flow valve; 10. Deaeration water tank; 11. Deaerator head; 12. Deaerator; 13. Three steam extraction pipes; 14. Fourth flow valve; 15. Second flow valve; 16. Second water supply branch; 17. Third water supply branch; 18. Normal temperature water tank; 19. Third flow valve; 20. Heating return water tank. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0028] Reference Figure 1 The deaerator 12 includes a deaerator water tank 10 and a deaerator head 11. In the water supply system of the deaerator 12, on the one hand, the steam inlet of the condenser 3 is connected to the exhaust steam port of the steam turbine, and the condensate outlet of the condenser 3 is connected to the deaerator head 11 through the #1 low-temperature heater 4, the #2 low-temperature heater 5, the #3 low-temperature heater 6, and the #4 low-temperature heater 7 in sequence to form the first water supply branch 8. The deaerator head 11 is also connected to the normal temperature water tank 18 to form the second water supply branch 16. The deaerator head 11 is also connected to the heat return water tank 20 to form the third water supply branch 17. The three water supply branches constitute the water supply system of the deaerator 12. The three water supply branches are all equipped with pumps, and water is supplied to the deaerator 12 through the pumps. On the other hand, the deaerator head 11 is also connected to the third extraction of the steam turbine, that is, the third exhaust port, to provide a heating source for the deaerator 12. The water deoxygenated by the deaerator 12 is returned to the steam generator to generate high-temperature steam for the steam turbine, driving the operation of the steam turbine and then driving the generator to generate electricity. The water in the heating return water tank 20 is the high-temperature steam extracted from the steam turbine, which is returned as heating return water after providing heat to the user.

[0029] Among them, a first flow valve 9 is provided in the first water supply branch 8, that is, the pipeline from the condenser 3 to the deaerator 12. A second flow valve 15 is provided in the second water supply branch 16, that is, the pipeline from the normal temperature water tank 18 to the deaerator 12. A third flow valve 19 is provided in the third water supply branch 17, that is, the pipeline from the heating return water tank 20 to the deaerator 12. A fourth flow valve 14 is provided in the three-extraction pipeline 13 from the third steam extraction port of the turbine to the deaerator 12. The combination of the first to fourth flow valves constitutes a three-extraction temperature control system for the steam turbine. Through the above-mentioned three-extraction temperature control system, the three-extraction temperature of the steam turbine can be controlled at a specified value, for example, operating below 450°C.

[0030] As an embodiment, manual control may be adopted. Specifically, when the three-extraction temperature over-temperature fault occurs after the steam pipe is overhauled, the three-extraction temperature is measured, and the difference between the measured temperature value and the specified value is calculated, and the opening control data of the first to fourth flow valves are generated according to the difference, and then the first to fourth flow valves are adjusted according to the generated opening control data. The theoretical basis is: since the water temperatures of the three water replenishment branches are different, for example, in one embodiment, the water temperature of the first water replenishment branch 8 is about 130°C and the pressure is about 1Mpa, the water temperature of the second water replenishment branch 16 is room temperature and the pressure is about 1Mpa, and the water temperature of the third water replenishment branch 17 is about 80°C and the pressure is 1.5-2Mpa. By adjusting the water replenishment ratio of the three water replenishment branches to the deaerator 12, the pressure and temperature of the deaerator 12 can be reduced. When the pressure and temperature of the deaerator 12 are reduced, the steam extraction of the three extractions can be increased, so that the high-temperature steam source that leaks into the interlayer steam is cooled by the increased steam extraction of the three extractions, which can ensure that the temperature of the three extractions is maintained below 450°C for safe operation.

[0031] Among them, in the step of generating the opening control data of the first to fourth flow valves according to the difference, the opening control data of the first flow valve 9 is negatively correlated with the difference, and the opening control data of the second flow valve 15 and the opening control data of the fourth flow valve 14 are both positively correlated with the difference. That is, the larger the difference, the smaller the opening of the first flow valve 9 will be adjusted, and the larger the opening of the second flow valve 15 and the opening of the fourth flow valve 14 will be adjusted. The specific values ​​of the difference and the opening control data can be obtained through experiments.

[0032] The steam turbine three-extraction temperature control system may further include: a first water level sensor, a water treatment device 1 and a fifth valve 2. The first water level sensor is used to detect the water level in the deaerator water tank 10 of the deaerator 12; the water treatment device 1 is used to convert raw water into softened water, and the water treatment device 1 is connected to the water supply port of the condenser 3; the fifth valve 2 is arranged in the water supply pipeline from the water treatment device 1 to the condenser 3. When the water level of the deaerator 12 is lower than the normal value, for example, lower than 2400 mm, the fifth valve 2 is opened, and the water treatment device 1 supplies softened water to the condenser 3.

[0033] The steam turbine three-extraction temperature control system may further include a second water level sensor, which is used to detect the water level of the heating return water tank 20, so as to adjust the opening of the second to fourth flow valves according to the water level of the heating return water tank 20. Specifically, when the water level of the heating return water tank 20 is lower than the set value, the opening of the third flow valve 19 is reduced and the opening of the second flow valve 15 and the opening of the fourth flow valve 14 are increased. In this way, when the heating return water is reduced, the three-extraction temperature is still kept below 450°C for safe operation.

[0034] Automatic control can also be achieved. Specifically, in the above-mentioned steam turbine three-extraction temperature control system, it further includes: a temperature sensor configured to measure the three-extraction temperature; a microprocessor electrically connected to the temperature sensor and the first to fourth flow valves; and a memory storing a program that can be executed by the microprocessor, wherein when the program is executed by the microprocessor, the control system performs the following steps: measuring the three-extraction temperature; calculating the difference between the measured temperature value and the specified value; generating the opening control data of the first to fourth flow valves according to the difference; and adjusting the first to fourth flow valves according to the generated opening control data. Among them, the method of generating the opening control data of the first to fourth flow valves according to the difference is: storing a corresponding table with different differences and the opening control data of the first to fourth flow valves, and obtaining the opening control data of the first to fourth flow valves by a table lookup method.

[0035] When the program is executed by the microprocessor, the control system may further perform the following steps: detecting the water level of the deaerator 12 , and when the water level of the deaerator 12 is lower than a normal value, such as lower than 2400 mm, controlling the water treatment equipment 1 to add softened water to the condenser 3 .

[0036] When the program is executed by the microprocessor, the control system can also perform the following steps: detect the water level of the heating return tank 20, and when the water level value of the heating return tank 20 is lower than the set value, reduce the opening of the third flow valve 19 and increase the opening of the second flow valve 15 and the opening of the fourth flow valve 14.

[0037] Among them, the microprocessors that can be used include but are not limited to MCU (Microcontroller Unit), CPU (Central Processing Unit), FPGA (Field-Programmable Gate Array), DSP (Digital Signal Processing), PLC (Programmable Logic Controller), single-chip microcomputer, etc.

[0038] It should be noted that in the above embodiment, the temperature sensor is configured to measure the three-extraction temperature, and the over-temperature value of the three-extraction temperature is obtained by comparing the measured temperature value with the specified value of the three-extraction temperature (450° C. in some embodiments). Since the three-extraction temperature is related to both the high-pressure cylinder temperature and the medium-pressure cylinder temperature, the outer cylinder temperature of the high-pressure cylinder can also be measured, and compared with the specified value of the outer cylinder temperature of the high-pressure cylinder to obtain a difference, and the opening control data of the first to fourth flow valves can be generated according to the difference, or the outer cylinder temperature of the medium-pressure cylinder can also be measured, and compared with the specified value of the outer cylinder temperature of the medium-pressure cylinder to obtain a difference, and the opening control data of the first to fourth flow valves can be generated according to the difference.

[0039] The above scheme has been verified in a power plant in Luoding. Specifically, during the fourth A-level overhaul after the power plant was put into operation, after the steam pipe was overhauled, the gap between the steam pipe and the cylinder body was cleaned of the oxide scale, and more steam leaked into the interlayer, causing the outer cylinder temperature to rise by about 50°C compared with before the overhaul, causing the three-extraction temperature of the pure condensing steam turbine to reach 470-490°C during operation. By adopting the above scheme, the water temperature of the first water supply branch 8 is about 130℃ and the pressure is about 1Mpa, the water temperature of the second water supply branch 16 is room temperature and the pressure is about 1Mpa, and the water temperature of the third water supply branch 17 is about 80℃ and the pressure is 1.5-2Mpa. By reducing the opening of the first flow valve 9 and increasing the opening of the second flow valve 15 and the third flow valve 19, the pressure and temperature of the deaerator 12 are reduced. At the same time, the opening of the fourth flow valve 14 is increased to increase the extraction volume of the three extractions by about 10%-15%. The deaerator 12 can normally remove oxygen from the water, and the temperature of the three extractions is maintained below 450℃ for safe operation. Satisfactory results have been achieved so far, reducing various accidents caused by metal overheating and the number and time of unplanned shutdowns of the unit, improving the reliability of safe operation of the equipment, and extending the service life of the equipment.

[0040] It should be pointed out that, unless otherwise specified, the above-mentioned "first", "second", "third", "fourth" and other similar terms are used to distinguish different devices with the same name and cannot be interpreted as having meanings of order, priority, importance, etc.

[0041] The present invention is described in detail above through specific embodiments, and these detailed descriptions are only limited to helping those skilled in the art understand the content of the present invention, and cannot be understood as limiting the scope of protection of the present invention. Various modifications, equivalent transformations, etc. made by those skilled in the art to the above scheme under the conception of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for controlling the temperature of a pure condensing steam turbine, characterized in that: include: Measure the temperature of the third extraction, high pressure cylinder or medium pressure cylinder; Calculate the difference between the measured temperature value and the specified value; Generate opening control data of the first to fourth flow valves according to the difference, wherein the generated opening control data is configured to ensure that the temperature of the third extraction is kept below a specified value after adjusting the corresponding flow valve according to the generated opening control data; and adjusting the first to fourth flow valves according to the generated opening control data; Among them, the first flow valve is set in the pipeline from the condenser to the deaerator, the second flow valve is set in the pipeline from the normal temperature water tank to the deaerator, the third flow valve is set in the pipeline from the heating return water tank to the deaerator, and the fourth flow valve is set in the pipeline from the third steam extraction port of the turbine to the deaerator.

2. The three-extraction temperature control method for a pure condensing steam turbine according to claim 1, characterized in that: The control method further comprises the step of controlling a water treatment device to supplement softened water to the condenser when the water level value of the deaerator is lower than a normal value.

3. The three-extraction temperature control method for a pure condensing steam turbine according to claim 1, characterized in that: The control method further includes the step of reducing the opening of the third flow valve and increasing the opening of the second flow valve and the opening of the fourth flow valve when the water level of the heating return water tank is lower than a set value.

4. The three-extraction temperature control method for a pure condensing steam turbine according to claim 1, characterized in that: In the step of generating the opening control data of the first to fourth flow valves according to the difference, the opening control data of the first flow valve is negatively correlated with the difference, and the opening control data of the second flow valve and the opening control data of the fourth flow valve are both positively correlated with the difference.

5. A three-extraction temperature control system for a pure condensing steam turbine, characterized in that: include: A first flow valve is provided in the pipeline from the condenser to the deaerator; A second flow valve is arranged in the pipeline from the normal temperature water tank to the deaerator; A third flow valve is arranged in the pipeline from the heating return water tank to the deaerator; a fourth flow valve, arranged in a pipeline from a third steam extraction port of the steam turbine to the deaerator; A temperature sensor configured to measure a third-extraction temperature, a high-pressure cylinder temperature, or an intermediate-pressure cylinder temperature; a microprocessor electrically connected to the temperature sensor and the first to fourth flow valves; as well as a memory storing a program executable by the microprocessor; When the program is executed by the microprocessor, the control system performs the steps of the control method according to any one of claims 1 to 4.

6. The three-extraction temperature control system for a pure condensing steam turbine according to claim 5, characterized in that: The control system further comprises: a first water level sensor, used for detecting the water level in the deaerator water tank; a water treatment device, used for converting raw water into softened water, the water treatment device being connected to the water supply port of the condenser; and a fifth valve, arranged in a water supply pipeline from the water treatment equipment to the condenser; When the water level of the deaerator is lower than a normal value, the fifth valve is opened, and the water treatment equipment supplies softened water to the condenser.

7. The three-extraction temperature control system for a pure condensing steam turbine according to claim 5, characterized in that: The control system also includes a second water level sensor, which is used to detect the water level of the heating return water tank to adjust the opening of the second to fourth flow valves according to the water level of the heating return water tank.

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