A water supply recirculation pipeline system suitable for deep peak regulation of coal-fired power units

Abstract

The present invention discloses a water supply recirculation pipeline system adapted to deep peak regulation of coal-fired power units, comprising a water supply mechanism, the water supply mechanism comprising a main water supply pump, a heater and a steam-driven water supply pump, and also comprising a recirculation mechanism, the recirculation mechanism being arranged between the water supply pump and the heater, the recirculation mechanism comprising a first circulation pipeline and an electric regulating valve, one end of the first circulation pipeline being connected to the steam-driven water supply pump, and the other end being introduced into the main water supply pump. The water supply recirculation pipeline system adapted to deep peak regulation of coal-fired power units provided by the present application, when the coal-fired power units are deeply peak regulated to below 35% of the rated power, the opening of the electric regulating valve is set to above 50%, and water is circulated through the first circulation pipeline, so as to adapt to the safe and stable operation of the coal-fired power units from deep peak regulation to low load and ensure the load response capability of the units during deep peak regulation, avoid the tripping of the steam-driven water supply pump due to the minimum flow protection to cause a production safety accident, and avoid the cavitation of the steam-driven water supply pump under low load conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of water supply systems, and in particular to a water supply recirculation pipeline system suitable for deep peak regulation of coal-fired power units. Background Art

[0002] At present, most of the supercritical coal-fired power units in my country have two steam-driven feedwater pumps with a capacity of 50% BMCR in the water supply system. Some units are designed to install a 30% BMCR electric feedwater pump as a backup. Usually, each steam-driven feedwater pump is equipped with a pre-pump, which runs at a fixed speed and the feedwater pump speed is adjustable. The water supply system plays an extremely important role in the safe and stable operation of the unit. The steam-driven feedwater pump group belongs to the most special type of main water pumps in the power generation process. It transports water from the deaerator to the boiler. It itself includes a complex system and corresponding control process. Under the condition of emergency peak load regulation to extremely low load, once an accident occurs, it may directly cause abnormal operation of the boiler or even directly cause the unit to stop, which has a great impact on the safety of the entire system and even the entire unit. In order to ensure the safe and stable operation of the feedwater pump, the feedwater pump is required to operate above the minimum flow rate. When the inlet flow rate of the water feed pump is lower than the minimum flow rate of the water feed pump operation, it is necessary to open the minimum flow regulating valve of the water feed pump to allow part of the water at the outlet of the water feed pump to return to the deaerator to ensure that the inlet flow rate of the water feed pump is greater than the required minimum flow rate, thereby ensuring the safe and stable operation of the water supply system.

[0003] Existing coal-fired power units participate in deep peak-shaving operation. When the deep peak-shaving is below 35%-30% of the rated power load condition, two steam-driven feedwater pumps are in operation, and the inlet flow of a single feedwater pump may drop below the minimum flow required for safe operation. During the deep peak-shaving period, the minimum flow valve is opened to ensure that the two feedwater pumps run in parallel, or a single steam-driven feedwater pump is loaded, while the other steam-driven feedwater pump maintains the minimum flow and runs idle. At this time, it is necessary to pay attention to the inlet and outlet pressure difference of the steam-driven feedwater pump to avoid cavitation of the feedwater pump, damage to the steam-driven feedwater pump, and production safety accidents. When the coal-fired power units frequently perform deep peak-shaving, the minimum flow valve of the feedwater pump will be frequently opened or maintained at the minimum opening, which is likely to cause the valve core and cage of the minimum flow valve to be eroded, resulting in internal leakage of the valve, posing a safety hazard to the operation of the unit. Summary of the invention

[0004] The present application provides a water supply recirculation pipeline system suitable for deep peak regulation of coal-fired power units, which solves the technical problem in the prior art that cavitation occurs in the steam-driven water supply pump under low-load conditions, the minimum flow valve of the water pump will be frequently opened or maintained at the minimum opening, which may easily cause scouring of the valve core and cage of the minimum flow valve, resulting in internal leakage of the valve.

[0005] The present application provides a water supply recirculation pipeline system that is adaptable to deep peak regulation of coal-fired power units, the system comprising a water supply mechanism, the water supply mechanism comprising a main feed water pump, a heater and a steam-driven feed water pump, the steam-driven feed water pump being arranged between the main feed water pump and the heater, the system further comprising a recirculation mechanism, the recirculation mechanism being arranged between the main feed water pump and the heater, the recirculation mechanism comprising a first circulation pipeline and an electric regulating valve, one end of the first circulation pipeline being connected to the steam-driven feed water pump, and the other end of the first circulation pipeline being introduced into the main feed water pump.

[0006] In some embodiments, the flow rate of the first circulation pipeline is 150 t / h.

[0007] In some embodiments, a deaerator is connected between the main feed water pump and the first circulation pipeline, the first circulation pipeline is connected to the inlet of the deaerator, and the main feed water pump is connected to the outlet of the deaerator.

[0008] In some embodiments, the recycling mechanism also includes a first check valve, an electric valve, a first gate valve and a first flow orifice, the first check valve and the electric valve are arranged between the electric regulating valve and the deaerator; the first gate valve and the first flow orifice are arranged between the pneumatic feed water pump and the electric regulating valve.

[0009] In some embodiments, the water supply mechanism further includes a water supply bypass and a minimum flow valve, the water supply bypass is connected between the steam-driven water supply pump and the deaerator, and the minimum flow valve is arranged on the water supply bypass.

[0010] In some embodiments, the water supply mechanism further includes a second check valve and two second gate valves, the two second gate valves are arranged on both sides of the minimum flow valve, and the second check valve is arranged between the minimum flow valve and the deaerator.

[0011] In some embodiments, the water supply mechanism also includes a third check valve, a second flow orifice and two third gate valves, one of the third gate valves is arranged between the main feed water pump and the deaerator, the other third gate valve and the third check valve are both arranged between the pneumatic feed water pump and the electric regulating valve, and the second flow orifice is arranged between the main feed water pump and the pneumatic feed water pump.

[0012] In some embodiments, a fourth gate valve and a fourth check valve are provided between the heater and the steam-driven water supply pump.

[0013] In some embodiments, the water supply mechanism is divided into two groups, and the pneumatic water supply pumps of the two groups of the water supply mechanism are both connected to the first circulation pipeline.

[0014] In some embodiments, the pressure difference of the electric regulating valve is 16 MPa.

[0015] The beneficial effects of this application are as follows:

[0016] The present application provides a water supply recirculation pipeline system that is suitable for deep peak regulation of coal-fired power units. When the coal-fired power units are deeply peak-regulated to below 35% of the rated power, the opening of the electric regulating valve is set to above 50%, and water is circulated through the first circulation pipeline to adapt to the safe and stable operation of the coal-fired power units during deep peak regulation to low loads and to ensure the load response capability of the units during deep peak regulation, avoid safety accidents caused by tripping of the steam-driven water supply pump due to minimum flow protection, avoid cavitation of the steam-driven water supply pump under low load conditions, and alleviate the problems of scouring and internal leakage of the minimum flow valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for describing the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention.

[0018] Figure 1 A schematic diagram of the overall structure of a recirculation piping system provided in this application.

[0019] Among them, 10-water supply mechanism; 11-main water supply pump; 12-heater; 13-pneumatic water supply pump; 14-water supply bypass; 15-minimum flow valve; 16-second check valve; 17-second gate valve; 18-third check valve; 19-second flow orifice; 191-third gate valve; 20-recirculation mechanism; 21-first circulation pipeline; 22-electric regulating valve; 23-electric valve; 24-first gate valve; 25-first flow orifice; 30-deaerator. DETAILED DESCRIPTION

[0020] The embodiment of the present application solves the technical problem in the prior art that cavitation occurs in the steam-driven water supply pump under low-load conditions, and the minimum flow valve of the water pump will be frequently opened or maintained at the minimum opening, which may easily cause scouring of the valve core and cage of the minimum flow valve and lead to internal leakage of the valve, by providing a water supply recirculation pipeline system that is suitable for deep peak regulation of coal-fired power units.

[0021] The technical solution in the embodiment of the present application is to solve the above technical problems, and the overall idea is as follows:

[0022] like Figure 1As shown, the present application provides a water supply recirculation pipeline system suitable for deep peak regulation of coal-fired power units, the system includes a water supply mechanism 10, the water supply mechanism 10 includes a main feed water pump 11, a heater 12 and a steam-driven feed water pump 13, the steam-driven feed water pump 13 is arranged between the main feed water pump 11 and the heater 12, the system also includes a recirculation mechanism 20, the recirculation mechanism 20 is arranged between the main feed water pump 11 and the heater 12, the recirculation mechanism 20 includes a first circulation pipeline 21 and an electric regulating valve 22, one end of the first circulation pipeline 21 is connected to the steam-driven feed water pump 13, and the other end of the first circulation pipeline 21 is introduced into the main feed water pump 11; specifically, the flow rate of the first circulation pipeline 21 is 150t / h, and the pressure difference of the electric regulating valve 22 is 16MPa.

[0023] In addition, a deaerator 30 is connected between the main feedwater pump 11 and the first circulation pipeline 21 . The first circulation pipeline 21 is connected to an inlet of the deaerator 30 , and the main feedwater pump 11 is connected to an outlet of the deaerator 30 .

[0024] When the coal-fired power unit is deeply peak-shaving to below 35% of the rated power, the opening of the electric regulating valve 22 is set to be above 50%, and water is circulated through the first circulation pipeline 21 to adapt to the safe and stable operation of the coal-fired power unit from deep peak-shaving to low load and to ensure the load response capability of the unit during deep peak-shaving, avoid the tripping of the steam-driven water supply pump 13 due to minimum flow protection and cause production safety accidents, avoid cavitation of the steam-driven water supply pump 13 under low load conditions, and alleviate the scouring and internal leakage problems of the minimum flow valve 15.

[0025] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0026] The recirculation mechanism 20 further includes a first check valve, an electric valve 23, a first gate valve 24 and a first flow orifice plate 25. The first check valve and the electric valve 23 are arranged between the electric regulating valve 22 and the deaerator 30; the first gate valve 24 and the first flow orifice plate 25 are arranged between the steam-driven feed water pump 13 and the electric regulating valve 22. The first flow orifice plate 25 reserves a straight pipe section of 10 times the outer diameter of the pipeline in the front and 5 times the outer diameter of the pipeline in the back to ensure accurate flow measurement. The control data of the electric valve 23 and the electric regulating valve 22 and the measurement data of the first flow orifice plate 25 are introduced into the unit DCS control system to facilitate the overall control of the system.

[0027] The water supply mechanism 10 also includes a water supply bypass 14, a minimum flow valve 15, a second check valve 16, two second gate valves 17, a third check valve 18, a second flow orifice 19 and two third gate valves 191. The water supply bypass 14 is connected between the steam-driven water supply pump 13 and the deaerator 30. The minimum flow valve 15 is arranged on the water supply bypass 14; the two second gate valves 17 are arranged on both sides of the minimum flow valve 15, and the second check valve 16 is arranged between the minimum flow valve 15 and the one of the third gate valves 191 is arranged between the main feed water pump 11 and the deaerator 30, the other third gate valve 191 and the third check valve 18 are both arranged between the steam-driven feed water pump 13 and the electric regulating valve 22, the second flow orifice 19 is arranged between the main feed water pump 11 and the steam-driven feed water pump 13, the feed water bypass 14, the minimum flow valve 15, the second check valve 16, and the two second gate valves 17 are all arranged on the deaerator 30 platform for easy operation.

[0028] Preferably, there are two groups of water supply mechanisms 10, and the steam-driven water supply pumps 13 of the two groups of water supply mechanisms 10 are connected to the first circulation pipeline 21. The minimum flow valves 15 of the steam-driven water supply pumps 13 of the two groups of water supply mechanisms 10 are mainly used for starting, stopping and in case of accidents of the main water supply pump 11, which can ensure that at least one group of water supply mechanisms 10 works and can meet the actual production needs of the generator set during the peak load period.

[0029] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0030] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A water supply recirculation pipeline system adapted to deep peak regulation of coal-fired power units, the system comprising a water supply mechanism, the water supply mechanism comprising a main water supply pump, a heater and a steam-driven water supply pump, the steam-driven water supply pump being arranged between the main water supply pump and the heater, characterized in that: The system further comprises a recirculation mechanism, which is arranged between the main feedwater pump and the heater, and comprises a first circulation pipeline and an electric regulating valve, one end of the first circulation pipeline is connected to the steam-driven feedwater pump, and the other end of the first circulation pipeline is introduced into the main feedwater pump; A deaerator is connected between the main feed water pump and the first circulation pipeline, the first circulation pipeline is connected to the inlet of the deaerator, and the main feed water pump is connected to the outlet of the deaerator; The water supply mechanism further comprises a water supply bypass and a minimum flow valve, wherein the water supply bypass is connected between the steam-driven water supply pump and the deaerator, and the minimum flow valve is arranged on the water supply bypass; The minimum flow valve is in an open state when the main water supply pump is started, stopped or encounters an accident.

2. The water supply recirculation pipeline system adapted to deep peak regulation of coal-fired power units according to claim 1, characterized in that: The flow rate of the first circulation pipeline is 150t / h.

3. The water supply recirculation pipeline system adapted to deep peak regulation of coal-fired power units according to claim 1, characterized in that: The recycling mechanism also includes a first check valve, an electric valve, a first gate valve and a first flow orifice plate. The first check valve and the electric valve are arranged between the electric regulating valve and the deaerator; the first gate valve and the first flow orifice plate are arranged between the steam-driven water supply pump and the electric regulating valve.

4. The water supply recirculation pipeline system adapted to deep peak regulation of coal-fired power units according to claim 1, characterized in that: The water supply mechanism further includes a second check valve and two second gate valves, wherein the two second gate valves are arranged on both sides of the minimum flow valve, and the second check valve is arranged between the minimum flow valve and the deaerator.

5. The water supply recirculation pipeline system adapted to deep peak regulation of coal-fired power units according to claim 1, characterized in that: The water supply mechanism also includes a third check valve, a second flow orifice plate and two third gate valves, one of the third gate valves is arranged between the main water supply pump and the deaerator, the other third gate valve and the third check valve are both arranged between the steam-driven water supply pump and the electric regulating valve, and the second flow orifice plate is arranged between the main water supply pump and the steam-driven water supply pump.

6. The water supply recirculation pipeline system adapted to deep peak regulation of coal-fired power units according to claim 1, characterized in that: A fourth gate valve and a fourth check valve are arranged between the heater and the steam-driven water supply pump.

7. The water supply recirculation pipeline system adapted to deep peak regulation of coal-fired power units according to claim 1, characterized in that: There are two groups of water supply mechanisms, and the steam-driven water supply pumps of the two groups of water supply mechanisms are both connected to the first circulation pipeline.

8. The water supply recirculation pipeline system adapted to deep peak regulation of coal-fired power generation units according to claim 1, characterized in that: The pressure difference of the electric regulating valve is 16MPa.

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