A steam supply system and method for stabilizing the steam source pressure of a feedwater pump turbine in a coal-fired power plant

Abstract

The present invention provides a steam supply system and method for a feedwater pump turbine in a coal-fired power plant with stable steam source pressure, comprising a low-pressure steam source supply system, a four-stage extraction steam supply system, an auxiliary steam source supply system and a cold re-extraction steam supply system; one end of the low-pressure steam source supply system is connected to the auxiliary steam source supply system and the four-stage extraction steam supply system connected in parallel, and the other end is respectively connected in parallel with the cold re-extraction steam supply system and connected to the feedwater pump turbine; the auxiliary steam source supply system comprises a first auxiliary steam source supply pipeline, a second auxiliary steam source supply pipeline and a third auxiliary steam source supply pipeline; the application can maintain the steam source pressure of a steam-driven feedwater pump stable when the coal-fired unit is running under an ultra-low load state or during accident handling, so that the steam-driven feedwater pump has a good linear adjustment characteristic, thereby achieving the purpose of stabilizing the feedwater flow and ensuring the safety of the unit; the application scheme is reasonable, the structure is simple, it is easy to implement, and the modification cost is low.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal power generation, and in particular relates to a steam supply system and method for a feedwater pump steam turbine in a coal-fired power plant with stable steam source pressure. Background Art

[0002] At present, thermal power plants generally use steam-driven feedwater pumps as boiler feedwater, which requires the feedwater pump steam turbine to be equipped with a steam source with stable pressure and temperature to ensure good regulation characteristics of the small steam turbine speed. Especially with the vigorous promotion of deep peak regulation of thermal power generating units, ultra-low unit load has become the norm. When operating in the low load section, the extraction pressure of the cold reheat steam section and the fourth stage extraction steam is very low, which is a test for the stability of the steam source pressure of the feedwater pump steam turbine.

[0003] The steam source for the feedwater pump turbine of a coal-fired power plant is generally taken from the cold reheat steam section extraction steam, the fourth stage extraction steam and the auxiliary steam. During normal operation, the fourth stage extraction steam is used to supply steam. When the fourth stage extraction steam pressure is insufficient, the cold reheat steam is used to supply steam. The auxiliary steam is used to supply steam during the commissioning of the feedwater pump or the start and stop of the unit and accident handling.

[0004] In the prior art, the switching process between auxiliary steam supply and four-extraction and cold re-supply requires a long time to warm up the pipes, and the entire process requires personnel to manually adjust the steam supply electric door to maintain the stability of the air source pressure of the feed water pump, which is very time-consuming and labor-intensive. Especially in the accident handling process, if the adjustment is not timely, it is very easy to cause boiler feed water flow disturbance, resulting in severe accidents such as boiler water shortage or even water overflow, causing equipment damage, and seriously threatening the safety of the unit. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a steam supply system and method with stable steam source pressure for a feedwater pump turbine in a coal-fired power plant, so as to solve the potential safety hazard caused by steam source pressure fluctuation during deep peak regulation or accident handling of the unit.

[0006] The present invention is achieved through the following technical solutions:

[0007] A steam supply system with stable steam source pressure for a feedwater pump steam turbine in a coal-fired power plant, comprising a low-pressure steam source steam supply system, a four-stage steam extraction steam supply system, an auxiliary steam source steam supply system and a cold re-extraction steam supply system;

[0008] One end of the low-pressure steam source steam supply system is connected to the auxiliary steam source steam supply system and the four-stage steam extraction steam supply system in parallel, and the other end is connected to the cold re-extraction steam supply system in parallel and connected to the feedwater pump turbine;

[0009] The auxiliary steam source steam supply system comprises a first auxiliary steam source steam supply pipeline and a second auxiliary steam source steam supply pipeline connected in parallel, the first auxiliary steam source steam supply pipeline is provided with an auxiliary steam source steam supply electric door and an auxiliary steam source steam supply check valve, the two ends of the second auxiliary steam source steam supply pipeline are respectively connected to the two ends of the auxiliary steam source steam supply electric door, and the second auxiliary steam source steam supply pipeline is sequentially provided with a manual door before the auxiliary steam source steam supply bypass regulating valve, an auxiliary steam source steam supply bypass regulating valve and an electric door after the auxiliary steam source steam supply bypass regulating valve;

[0010] A third auxiliary steam source steam supply pipeline is connected between the manual door in front of the auxiliary steam source steam supply bypass regulating valve and the auxiliary steam source steam supply bypass regulating valve, and a drain temperature measuring point in front of the auxiliary steam source steam supply bypass regulating valve, a manual drain door in front of the auxiliary steam source steam supply bypass regulating valve and a drain pneumatic door in front of the auxiliary steam source steam supply bypass regulating valve are sequentially arranged on the third auxiliary steam source steam supply pipeline.

[0011] Furthermore, the other end of the steam supply pipeline of the third auxiliary steam source is connected to the hydrophobic expansion tank.

[0012] Furthermore, the four-stage steam extraction and steam supply system includes four-stage steam extraction and steam supply pipelines, on which four-stage steam extraction and steam supply check valves are arranged; one end of the auxiliary steam source steam supply check valve is respectively connected to the auxiliary steam source steam supply electric door and the auxiliary steam source steam supply bypass regulating valve rear electric door, and the other end is merged with the four-stage steam extraction and steam supply check valve.

[0013] Furthermore, the low-pressure steam source steam supply system comprises a low-pressure steam source steam supply pipeline, and the low-pressure steam source steam supply pipeline is sequentially provided with a low-pressure steam source steam supply electric door and a low-pressure steam source steam supply check valve;

[0014] Both ends of the low-pressure steam source steam supply electric door are provided with a first drain pipeline, and the first drain pipeline is sequentially provided with front and rear drain manual doors of the low-pressure steam source steam supply electric door and front and rear drain pneumatic doors of the low-pressure steam source steam supply electric door;

[0015] A second drain pipeline is provided at one end of the low-pressure steam source steam supply check valve, and the second drain pipeline is sequentially provided with a manual drain door behind the low-pressure steam source steam supply check valve and a pneumatic drain door behind the low-pressure steam source steam supply check valve.

[0016] Further, the cold re-extraction steam supply system comprises a cold re-extraction steam supply pipeline, wherein the cold re-extraction steam supply pipeline is provided with a cold re-extraction steam supply check valve, a cold re-extraction steam supply electric door and a cold re-extraction steam supply high-pressure regulating valve in sequence;

[0017] A manual cold re-extraction steam supply check valve rear drain manual door and a pneumatic cold re-extraction steam supply check valve rear drain pneumatic door connected in sequence are provided between the cold re-extraction steam supply check valve and the cold re-extraction steam supply electric door;

[0018] A manual drain door after the cold re-extraction steam supply electric door and a pneumatic drain door after the cold re-extraction steam supply electric door, which are connected in sequence, are arranged between the cold re-extraction steam supply electric door and the cold re-extraction steam supply high-pressure regulating valve.

[0019] Furthermore, the low-pressure steam source steam supply check valve and the cold re-extraction steam supply high-pressure regulating valve are merged and connected to the feedwater pump turbine pipeline; the feedwater pump turbine pipeline is sequentially provided with a feedwater pump turbine main steam valve and a feedwater pump turbine low-pressure regulating valve.

[0020] Furthermore, the feedwater pump turbine pipeline is also provided with a turbine steam supply main pipe temperature measuring point and a feedwater pump turbine steam supply main pipe pressure measuring point.

[0021] Furthermore, a feedwater pump steam turbine exhaust electric door is provided at the exhaust end of the feedwater pump steam turbine.

[0022] A method for supplying steam with a stable steam source pressure for a feedwater pump turbine in a coal-fired power plant comprises the following steps:

[0023] During unit start-up and shutdown and deep peak regulation, the auxiliary steam source steam supply system supplies steam to the feedwater pump turbine, and the pressure of the four-stage extraction steam supply system is reduced; the auxiliary steam source steam supply electric door remains closed, the auxiliary steam source steam supply bypass regulating valve front manual door, the auxiliary steam source steam supply bypass regulating valve and the auxiliary steam source steam supply bypass regulating valve rear electric door remain open, and the auxiliary steam source steam supply bypass regulating valve maintains the feedwater pump turbine low-pressure steam source steam supply pressure;

[0024] When the unit encounters RB and the load suddenly drops, causing the main steam pressure to drop rapidly, the pressure of the four-stage extraction steam supply system drops rapidly, and the auxiliary steam source steam supply bypass regulating valve maintains the low-pressure steam source steam supply pressure of the feedwater pump turbine stable. The drain pneumatic door in front of the auxiliary steam source steam supply bypass regulating valve automatically opens to discharge the drain, and the low-pressure steam source of the feedwater pump turbine is quickly switched from the four-stage extraction steam supply system to the auxiliary steam source steam supply system;

[0025] The manual drain valve in front of the auxiliary steam source steam supply bypass regulating valve in front of the auxiliary steam source steam supply system feed water pump turbine regulating valve is kept open. When the drain pneumatic valve in front of the auxiliary steam source steam supply bypass regulating valve is in automatic mode, the drain temperature target threshold is manually preset. When the temperature is higher than the target threshold, the drain is automatically closed, and when it is lower than the target threshold, it is automatically opened to prevent water from entering the feed water pump turbine when the steam source is switched;

[0026] When the unit is below 40% of the rated load, the auxiliary steam source steam supply system switches to the four-stage extraction steam supply system; when the unit is above 40% of the rated load, the four-stage extraction steam supply system supplies steam to the feedwater pump turbine;

[0027] The auxiliary steam source steam supply electric door has the function of stop and pulse operation, and has an opening display. When the auxiliary steam source steam supply bypass regulating valve fails, the auxiliary steam source steam supply electric door stops and pulses to automatically switch the steam supply from the four-stage steam extraction steam supply system to the auxiliary steam source steam supply system.

[0028] Furthermore, the auxiliary steam source is connected to the electric door of the DCS control system, and the steps of realizing the stop and pulse include:

[0029] S1: The low-pressure steam supply system supplies steam, and the manual drain doors before and after the low-pressure steam supply electric door and the manual drain door after the low-pressure steam supply check valve remain open; the pneumatic drain doors before and after the low-pressure steam supply electric door and the pneumatic drain door after the low-pressure steam supply check valve are opened;

[0030] S2: The DCS control system pulses the auxiliary steam source steam supply electric door, so that the auxiliary steam source steam supply electric door remains slightly open;

[0031] S3: If the temperature of the first drain pipe and the second drain pipe is greater than 200°C, and the output of the feedwater pump turbine is normal, continue to pulse the auxiliary steam source steam supply electric door at intervals until the auxiliary steam source steam supply electric door is fully opened;

[0032] S4: If the temperature of the first drain pipeline and the second drain pipeline is greater than 250°C, the drain pneumatic doors before and after the low-pressure steam source steam supply electric door and the drain pneumatic door after the low-pressure steam source steam supply check valve are closed.

[0033] Compared with the prior art, the present invention has the following beneficial technical effects:

[0034] The present invention provides a steam supply system and method for a feedwater pump steam turbine in a coal-fired power plant with a stable steam source pressure, comprising a low-pressure steam source steam supply system, a four-stage extraction steam supply system, an auxiliary steam source steam supply system and a cold re-extraction steam supply system; one end of the low-pressure steam source steam supply system is connected to the auxiliary steam source steam supply system and the four-stage extraction steam supply system connected in parallel, and the other end is respectively connected in parallel to the cold re-extraction steam supply system and connected to the feedwater pump steam turbine; the auxiliary steam source steam supply system comprises a first auxiliary steam source steam supply pipeline and a The second auxiliary steam source steam supply pipeline, the first auxiliary steam source steam supply pipeline is provided with an auxiliary steam source steam supply electric door and an auxiliary steam source steam supply check valve, the two ends of the second auxiliary steam source steam supply pipeline are respectively connected to the two ends of the auxiliary steam source steam supply electric door, the second auxiliary steam source steam supply pipeline is sequentially provided with an auxiliary steam source steam supply bypass regulating valve front manual door, an auxiliary steam source steam supply bypass regulating valve and an auxiliary steam source steam supply bypass regulating valve rear electric door; the auxiliary steam source steam supply bypass regulating valve front manual door and the auxiliary steam source steam supply bypass regulating valve are connected It is connected to a third auxiliary steam source steam supply pipeline, on which a drain temperature measuring point in front of the auxiliary steam source steam supply bypass regulating valve, a drain manual door in front of the auxiliary steam source steam supply bypass regulating valve and a drain pneumatic door in front of the auxiliary steam source steam supply bypass regulating valve are sequentially arranged; the present application can maintain the steam source pressure of the steam-driven feed water pump to be stable when the coal-fired unit is operating under ultra-low load or during accident handling, thereby achieving the purpose of stabilizing the feed water flow and ensuring the safety of the unit; at the same time, the present application has an automatic pipe heating function, which can effectively speed up the speed of steam source switching of the steam-driven feed water pump, ensure the stability of the steam source pressure, and thus make the steam-driven feed water pump have good linear adjustment characteristics; the present application adopts a large number of regulating valves with automatic adjustment function to replace manual operation of operating personnel, with a high degree of automation, which can reduce the operation amount of operating personnel during unit accident handling, and overcome the shortcomings of untimely and inadequate manual adjustment by personnel. The present application scheme is reasonable, simple in structure, easy to implement, and low in transformation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention is a schematic structural diagram of a steam supply system with stable steam source pressure for a feedwater pump turbine in a coal-fired power plant.

[0036] In the figure: cold re-extraction steam supply check valve 1, cold re-extraction steam supply electric valve 2, cold re-extraction steam supply high-pressure regulating valve 3, cold re-extraction steam supply check valve back drain manual valve 4, cold re-extraction steam supply check valve back drain pneumatic valve 5, cold re-extraction steam supply electric valve back drain manual valve 6, cold re-extraction steam supply electric valve back drain pneumatic valve 7, four-stage steam supply check valve 8, low-pressure steam source steam supply electric valve 9, low-pressure steam source steam supply check valve 10, low-pressure steam source steam supply electric valve front and rear drain manual valve 11, low-pressure steam source steam supply electric valve front and rear drain pneumatic valve 12, low-pressure steam source steam supply check valve back drain manual valve 13, low-pressure steam source steam supply check valve back drain pneumatic valve Drain pneumatic door 14, steam source steam supply electric door 15, auxiliary steam source steam supply check valve 16, manual door 17 in front of auxiliary steam source steam supply bypass regulating valve, auxiliary steam source steam supply bypass regulating valve 18, electric door 19 after auxiliary steam source steam supply bypass regulating valve, drain temperature measuring point 20 in front of auxiliary steam source steam supply bypass regulating valve, drain manual door 21 in front of auxiliary steam source steam supply bypass regulating valve, drain pneumatic door 22 in front of auxiliary steam source steam supply bypass regulating valve, turbine steam supply main pipe temperature measuring point 23, feedwater pump turbine steam supply main pipe pressure measuring point 24, feedwater pump turbine main steam valve 25, feedwater pump turbine low pressure regulating valve 26, feedwater pump turbine exhaust electric door 27. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0038] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0039] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0040] The present invention provides a steam supply system with stable steam source pressure for a feedwater pump turbine in a coal-fired power plant, characterized in that it comprises a low-pressure steam source steam supply system, a four-stage steam extraction steam supply system, an auxiliary steam source steam supply system and a cold re-extraction steam supply system;

[0041] One end of the low-pressure steam source steam supply system is connected to the auxiliary steam source steam supply system and the four-stage steam extraction steam supply system in parallel, and the other end is connected to the cold re-extraction steam supply system in parallel and connected to the feedwater pump turbine;

[0042] The auxiliary steam source steam supply system comprises a first auxiliary steam source steam supply pipeline and a second auxiliary steam source steam supply pipeline connected in parallel, the first auxiliary steam source steam supply pipeline is provided with an auxiliary steam source steam supply electric door 15 and an auxiliary steam source steam supply check valve 16, two ends of the second auxiliary steam source steam supply pipeline are respectively connected to two ends of the auxiliary steam source steam supply electric door 15, and the second auxiliary steam source steam supply pipeline is sequentially provided with an auxiliary steam source steam supply bypass regulating valve front manual door 17, an auxiliary steam source steam supply bypass regulating valve 18 and an auxiliary steam source steam supply bypass regulating valve rear electric door 19;

[0043] A third auxiliary steam source steam supply pipeline is connected between the auxiliary steam source steam supply bypass regulating valve manual door 17 and the auxiliary steam source steam supply bypass regulating valve 18, and the third auxiliary steam source steam supply pipeline is sequentially provided with a drain temperature measuring point 20 in front of the auxiliary steam source steam supply bypass regulating valve, a drain manual door 21 in front of the auxiliary steam source steam supply bypass regulating valve, and a drain pneumatic door 22 in front of the auxiliary steam source steam supply bypass regulating valve.

[0044] Preferably, the other end of the steam supply pipeline of the third auxiliary steam source is connected to the hydrophobic expansion tank.

[0045] Preferably, the four-stage steam extraction and steam supply system includes four-stage steam extraction and steam supply pipelines, on which four-stage steam extraction and steam supply check valves 8 are arranged; one end of the auxiliary steam source steam supply check valve 16 is respectively connected to the auxiliary steam source steam supply electric door 15 and the auxiliary steam source steam supply bypass regulating valve rear electric door 19, and the other end is merged with the four-stage steam extraction and steam supply check valve 8.

[0046] Preferably, the low-pressure steam source steam supply system comprises a low-pressure steam source steam supply pipeline, and the low-pressure steam source steam supply pipeline is sequentially provided with a low-pressure steam source steam supply electric door 9 and a low-pressure steam source steam supply check valve 10;

[0047] Both ends of the low-pressure steam source steam supply electric door 9 are provided with a first drain pipeline, and the first drain pipeline is sequentially provided with a front and rear drain manual door 11 of the low-pressure steam source steam supply electric door and a front and rear drain pneumatic door 12 of the low-pressure steam source steam supply electric door;

[0048] A second drain pipeline is provided at one end of the low-pressure steam source steam supply check valve 10, and the second drain pipeline is sequentially provided with a low-pressure steam source steam supply check valve rear drain manual door 13 and a low-pressure steam source steam supply check valve rear drain pneumatic door 14.

[0049] Further, the cold re-extraction steam supply system comprises a cold re-extraction steam supply pipeline, and the cold re-extraction steam supply pipeline is sequentially provided with a cold re-extraction steam supply check valve 1, a cold re-extraction steam supply electric door 2 and a cold re-extraction steam supply high-pressure regulating valve 3;

[0050] A cold re-extraction steam supply check valve rear drain manual door 4 and a cold re-extraction steam supply check valve rear drain pneumatic door 5 connected in sequence are arranged between the cold re-extraction steam supply check valve 1 and the cold re-extraction steam supply electric door 2;

[0051] A manual drain door 6 after the cold re-extraction steam supply electric door and a pneumatic drain door 7 after the cold re-extraction steam supply electric door, which are connected in sequence, are arranged between the cold re-extraction steam supply electric door 2 and the cold re-extraction steam supply high-pressure regulating valve 3.

[0052] Furthermore, the low-pressure steam source steam supply check valve 10 and the cold re-extraction steam supply high-pressure regulating valve 3 are connected to the feedwater pump turbine pipeline after merging; the feedwater pump turbine pipeline is sequentially provided with a feedwater pump turbine main steam valve 25 and a feedwater pump turbine low-pressure regulating valve 26.

[0053] Furthermore, the feedwater pump steam turbine pipeline is also provided with a steam turbine steam supply main pipe temperature measuring point 23 and a feedwater pump steam turbine steam supply main pipe pressure measuring point 24.

[0054] Preferably, a feedwater pump steam turbine exhaust electric door 27 is provided at the exhaust end of the feedwater pump steam turbine.

[0055] The present invention provides a method for supplying steam with a stable steam source pressure for a feedwater pump turbine in a coal-fired power plant, comprising the following steps:

[0056] During unit start-up and shutdown and deep peak regulation, as the pressure of the four-stage steam extraction steam supply system decreases, it is gradually switched to the auxiliary steam source steam supply system to supply steam to the feedwater pump turbine; the auxiliary steam source steam supply electric door 15 remains closed, the auxiliary steam source steam supply bypass regulating valve front manual door 17, the auxiliary steam source steam supply bypass regulating valve 18 and the auxiliary steam source steam supply bypass regulating valve rear electric door 19 remain open, and the auxiliary steam source steam supply bypass regulating valve 18 maintains the feedwater pump turbine low-pressure steam source steam supply pressure; it is used to achieve fast and automatic switching of the feedwater pump turbine low-pressure steam source during normal operating adjustment, so that the steam-driven feedwater pump has good linear adjustment characteristics.

[0057] When the unit encounters RB or a sudden drop in load causes the main steam pressure to drop rapidly, the pressure of the four-stage extraction steam supply system drops rapidly, and the auxiliary steam source steam supply bypass regulating valve 18 maintains the low-pressure steam source steam supply pressure of the feedwater pump turbine stable. The drain pneumatic door 22 in front of the auxiliary steam source steam supply bypass regulating valve automatically opens to discharge drain, and the low-pressure steam source of the feedwater pump turbine is quickly switched from the four-stage extraction steam supply system to the auxiliary steam source steam supply system; it is used to achieve rapid and automatic switching of the low-pressure steam source of the feedwater pump turbine during unit fault handling to ensure the stability of the feedwater flow.

[0058] The auxiliary steam source steam supply system feeds the water pump turbine regulating valve in front of the auxiliary steam source steam supply bypass regulating valve. The manual drain door 21 is kept open. The auxiliary steam source steam supply bypass regulating valve in front of the water pump turbine regulating valve is manually preset to the drain temperature target threshold when the temperature is higher than the target threshold. It is automatically closed when the temperature is lower than the target threshold. It is automatically opened to ensure that the auxiliary steam source steam supply system pipeline is always in the warm pipe standby state to prevent water from entering the feed pump turbine when the steam source is quickly switched.

[0059] When the unit is less than 40% of the rated load, the auxiliary steam source steam supply system supplies steam to the feedwater pump turbine; when the unit is more than 40% of the rated load, the four-stage steam extraction steam supply system supplies steam to the feedwater pump turbine;

[0060] The auxiliary steam source steam supply electric door 15 has the function of stop and pulse operation, and has an opening display. When the auxiliary steam source steam supply bypass regulating valve 18 fails, the auxiliary steam source steam supply electric door 15 stops and pulses to automatically switch the steam supply from the four-stage steam extraction steam supply system to the auxiliary steam source steam supply system. It is used as a backup steam source switching measure for the normal steam source switching mode to fully ensure the safety of the unit.

[0061] Furthermore, the auxiliary steam source steam supply electric door 15 is connected to a DCS control system, and the steps of realizing the intermediate stop and pulse include:

[0062] S1: The low-pressure steam supply system supplies steam, the front and rear drain manual doors 11 of the low-pressure steam supply electric door and the rear drain manual door 13 of the low-pressure steam supply check valve remain open; the front and rear drain pneumatic doors 12 of the low-pressure steam supply electric door and the rear drain pneumatic door 14 of the low-pressure steam supply check valve are opened;

[0063] S2: The DCS control system pulses the auxiliary steam source steam supply electric door 15, so that the auxiliary steam source steam supply electric door 15 remains in a slightly open state;

[0064] S3: If the temperature of the first drain pipe and the second drain pipe is greater than 200°C, the output of the feedwater pump turbine is normal, and the steam flow of the four-stage extraction steam supply system decreases, continue to pulse the auxiliary steam source steam supply electric door 15 at intervals until the auxiliary steam source steam supply electric door 15 is fully opened;

[0065] S4: If the temperature of the first drain pipeline and the second drain pipeline is greater than 250°C, close the front and rear drain pneumatic doors 12 of the low-pressure steam source steam supply electric door and the rear drain pneumatic door 14 of the low-pressure steam source steam supply check valve.

[0066] Specifically, in step S2, the DCS control system opens the pulse auxiliary steam source steam supply electric door 15;

[0067] The judgment conditions in step S3 specifically include:

[0068] A: Confirm that the temperature of the drain header rises to above 200°C;

[0069] B: Confirm that the output of the feedwater pump turbine is normal (abs (the difference between the small machine speed command and the actual speed) <50rpm; abs (the difference between the feedwater flow command and the actual flow) <50KG / S).

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for supplying steam with stable steam source pressure for a feedwater pump turbine in a coal-fired power plant, characterized in that: The steam supply system includes low-pressure steam source supply system, four-stage steam extraction supply system, auxiliary steam source supply system and cold re-extraction steam supply system; One end of the low-pressure steam source steam supply system is connected to the auxiliary steam source steam supply system and the four-stage steam extraction steam supply system in parallel, and the other end is connected to the cold re-extraction steam supply system in parallel and connected to the feedwater pump turbine; The auxiliary steam source steam supply system comprises a first auxiliary steam source steam supply pipeline and a second auxiliary steam source steam supply pipeline connected in parallel, the first auxiliary steam source steam supply pipeline is provided with an auxiliary steam source steam supply electric door (15) and an auxiliary steam source steam supply check valve (16), two ends of the second auxiliary steam source steam supply pipeline are respectively connected to two ends of the auxiliary steam source steam supply electric door (15), and the second auxiliary steam source steam supply pipeline is provided with an auxiliary steam source steam supply bypass regulating valve front manual door (17), an auxiliary steam source steam supply bypass regulating valve (18) and an auxiliary steam source steam supply bypass regulating valve rear electric door (19); A third auxiliary steam source steam supply pipeline is connected between the auxiliary steam source steam supply bypass regulating valve front manual door (17) and the auxiliary steam source steam supply bypass regulating valve (18), and the third auxiliary steam source steam supply pipeline is provided with a drain temperature measuring point (20) in front of the auxiliary steam source steam supply bypass regulating valve, a drain manual door (21) in front of the auxiliary steam source steam supply bypass regulating valve, and a drain pneumatic door (22) in front of the auxiliary steam source steam supply bypass regulating valve in sequence; When the unit is started and stopped and deep peak regulation is performed, the auxiliary steam source steam supply system supplies steam to the feedwater pump turbine, and the pressure of the four-stage extraction steam supply system is reduced; the auxiliary steam source steam supply electric door (15) remains closed, the auxiliary steam source steam supply bypass regulating valve front manual door (17), the auxiliary steam source steam supply bypass regulating valve (18) and the auxiliary steam source steam supply bypass regulating valve rear electric door (19) remain open, and the auxiliary steam source steam supply bypass regulating valve (18) maintains the feedwater pump turbine low-pressure steam source steam supply pressure; When the unit encounters RB and the load suddenly drops, causing the main steam pressure to drop rapidly, the pressure of the four-stage extraction steam supply system drops rapidly, the auxiliary steam source steam supply bypass regulating valve (18) maintains the low-pressure steam source steam supply pressure of the feedwater pump turbine stable, and the drain pneumatic door (22) in front of the auxiliary steam source steam supply bypass regulating valve automatically opens to discharge the drain, and the low-pressure steam source of the feedwater pump turbine is quickly switched from the four-stage extraction steam supply system to the auxiliary steam source steam supply system; The auxiliary steam source steam supply system feeds the water pump turbine regulating valve in front of the auxiliary steam source steam supply bypass regulating valve. The manual drain door (21) is kept in an open state. When the auxiliary steam source steam supply bypass regulating valve is in the automatic mode, the drain temperature target threshold is manually preset. When the temperature is higher than the target threshold, the drain is automatically closed. When the temperature is lower than the target threshold, the drain is automatically opened to prevent water from entering the feed pump turbine when the steam source is switched. When the unit is below 40% of the rated load, the auxiliary steam source steam supply system switches to the four-stage extraction steam supply system; when the unit is above 40% of the rated load, the four-stage extraction steam supply system supplies steam to the feedwater pump turbine; The auxiliary steam source steam supply electric door (15) has a stop and pulse operation function and an opening display. When the auxiliary steam source steam supply bypass regulating valve (18) fails, the auxiliary steam source steam supply electric door (15) stops and pulses, so that the four-stage steam extraction steam supply system is automatically switched to the auxiliary steam source steam supply system.

2. A method for supplying steam with stable steam source pressure for a feedwater pump turbine in a coal-fired power plant according to claim 1, characterized in that: The other end of the steam supply pipeline of the third auxiliary steam source is connected to the hydrophobic expansion tank.

3. A method for supplying steam with stable steam source pressure for a feedwater pump turbine in a coal-fired power plant according to claim 1, characterized in that: The four-stage steam extraction and supply system comprises a four-stage steam extraction and supply pipeline, on which a four-stage steam extraction and supply check valve (8) is arranged; one end of the auxiliary steam source steam supply check valve (16) is respectively connected to the auxiliary steam source steam supply electric valve (15) and the auxiliary steam source steam supply bypass regulating valve rear electric valve (19), and the other end is combined with the four-stage steam extraction and supply check valve (8).

4. A method for supplying steam with stable steam source pressure for a feedwater pump turbine in a coal-fired power plant according to claim 1, characterized in that: The low-pressure steam source steam supply system comprises a low-pressure steam source steam supply pipeline, and the low-pressure steam source steam supply pipeline is provided with a low-pressure steam source steam supply electric door (9) and a low-pressure steam source steam supply check valve (10) in sequence; Both ends of the low-pressure steam source steam supply electric door (9) are provided with a first drain pipeline, and the first drain pipeline is provided with front and rear drain manual doors (11) of the low-pressure steam source steam supply electric door and front and rear drain pneumatic doors (12) of the low-pressure steam source steam supply electric door in sequence; A second drain pipeline is provided at one end of the low-pressure steam source steam supply check valve (10), and the second drain pipeline is provided with a low-pressure steam source steam supply check valve rear drain manual door (13) and a low-pressure steam source steam supply check valve rear drain pneumatic door (14) in sequence.

5. A method for supplying steam with stable steam source pressure for a feedwater pump turbine in a coal-fired power plant according to claim 4, characterized in that: The cold re-extraction steam supply system comprises a cold re-extraction steam supply pipeline, wherein the cold re-extraction steam supply pipeline is provided with a cold re-extraction steam supply check valve (1), a cold re-extraction steam supply electric valve (2) and a cold re-extraction steam supply high-pressure regulating valve (3) in sequence; A cold re-extraction steam supply check valve rear drain manual door (4) and a cold re-extraction steam supply check valve rear drain pneumatic door (5) which are connected in sequence are arranged between the cold re-extraction steam supply check valve (1) and the cold re-extraction steam supply electric door (2); A manual cold re-extraction steam supply electric door (6) and a pneumatic cold re-extraction steam supply electric door drain pneumatic door (7) are provided between the cold re-extraction steam supply electric door (2) and the cold re-extraction steam supply high-pressure regulating valve (3), which are connected in sequence.

6. A method for supplying steam with stable steam source pressure for a feedwater pump turbine in a coal-fired power plant according to claim 5, characterized in that: The low-pressure steam source steam supply check valve (10) and the cold re-extraction steam supply high-pressure regulating valve (3) are connected to the feedwater pump steam turbine pipeline after converging; the feedwater pump steam turbine pipeline is provided with a feedwater pump steam turbine main steam valve (25) and a feedwater pump steam turbine low-pressure regulating valve (26) in sequence.

7. A method for supplying steam with stable steam source pressure for a feedwater pump turbine in a coal-fired power plant according to claim 5, characterized in that: The feedwater pump steam turbine pipeline is also provided with a steam turbine steam supply main pipe temperature measuring point (23) and a feedwater pump steam turbine steam supply main pipe pressure measuring point (24).

8. The steam supply system with stable steam source pressure for feedwater pump turbine of coal-fired power plant according to claim 1, characterized in that: The exhaust end of the feedwater pump steam turbine is provided with a feedwater pump steam turbine exhaust electric door (27).

9. A method for supplying steam with stable steam source pressure for a feedwater pump turbine in a coal-fired power plant according to claim 1, characterized in that: The auxiliary steam source steam supply electric door (15) is connected to a DCS control system, and the steps of realizing the intermediate stop and pulse include: S1: The low-pressure steam supply system supplies steam, the front and rear drain manual doors (11) of the low-pressure steam supply electric door and the rear drain manual door (13) of the low-pressure steam supply check valve remain open; the front and rear drain pneumatic doors (12) of the low-pressure steam supply electric door and the rear drain pneumatic door (14) of the low-pressure steam supply check valve are opened; S2: The DCS control system pulses the auxiliary steam source steam supply electric door (15), so that the auxiliary steam source steam supply electric door (15) remains in a slightly open state; S3: If the temperature of the first drain pipe and the second drain pipe is greater than 200°C and the output of the feedwater pump turbine is normal, continue to pulse the auxiliary steam source steam supply electric door (15) at intervals until the auxiliary steam source steam supply electric door (15) is fully opened; S4: If the temperature of the first drain pipeline and the second drain pipeline is greater than 250° C., the drain pneumatic doors (12) before and after the low-pressure steam source steam supply electric door and the drain pneumatic door (14) after the low-pressure steam source steam supply check valve are closed.

Images