Unit load lifting system based on high-enthalpy-value steam source driving feed pump turbine

Abstract

A unit load increasing system based on a high-enthalpy-value steam source driving water feeding pump turbine comprises a boiler, a main turbine, the water feeding pump turbine, a steam condensing system, a reheating steam extraction system, a heat regeneration system and a water feeding pump turbine steam distribution system. The reheating steam extraction system comprises N sections of extraction steam, hot section reheating steam and cold section reheating steam, the i-th section of extraction steam is a working steam source for driving the water feed pump turbine, the cold section reheating steam is a high-pressure low-enthalpy-value steam source of the water feed pump turbine, the i-1-th section of extraction steam and the hot section reheating steam are high-enthalpy-value steam sources of the water feed pump turbine, i is larger than 3 and smaller than N, and N and i are integers; the steam distribution system of the feed pump turbine comprises a working steam distribution unit, a high-pressure low-enthalpy-value steam distribution unit, a high-enthalpy-value steam distribution unit and a main steam distribution unit. When the unit operates with increased load, the high enthalpy value steam source is gradually merged into the working steam source, and the steam inlet enthalpy value of the feed pump turbine is increased, so that the work output of the feed pump turbine is increased, and the electrical load of the unit meets the requirements of a power grid.

Description

Technical Field

[0001] The utility model belongs to the technical field of feedwater pump turbines of generator sets, and in particular relates to a unit load-raising system based on a high-enthalpy steam source driving the feedwater pump turbine. Background Art

[0002] At present, thermal power plants generally use steam-driven feedwater pumps as the boiler feed water method, which requires the feedwater pump turbine to be equipped with a steam source with stable pressure, enthalpy and temperature to ensure good adjustment characteristics of the feedwater pump turbine speed; the steam source of the feedwater pump turbine in most coal-fired power plants generally includes cold-section reheat steam section extraction steam, four-section extraction steam and auxiliary steam; during normal operation, when the regulating valve opening of the feedwater pump turbine is below 80%, the four-section extraction steam is used as the working steam source, and when the regulating valve opening of the feedwater pump turbine is above 80%, in order to ensure the stability of the boiler feed water, the working steam source of the feedwater pump turbine is switched from four-section extraction steam to cold-section reheat steam.

[0003] The working output of the feedwater pump steam turbine mainly depends on the enthalpy of the steam source, while the enthalpy of the cold-end reheated steam is relatively small. This means that when the steam inlet volume of the feedwater pump steam turbine does not change much, the working capacity of the feedwater pump steam turbine cannot be significantly improved. In addition, due to the allowable stress limit of the last-stage blades of the small steam turbine, the steam flow rate of the feedwater pump steam turbine cannot be too large. This shows that the output effect brought by incorporating the cold-end reheated steam as the working steam source is extremely limited.

[0004] In recent years, with the vigorous promotion of deep peak regulation of thermal power generating units, ultra-low unit load has become the normal operation of thermal power generating units. When operating in the excessively low load section, the enthalpy and pressure of the cold reheat steam section extraction and the fourth stage extraction are very low, which brings new challenges to the stable work of the feedwater pump turbine.

[0005] Chinese patent application number 202410170146.4 proposes a 1000MW ultra-supercritical unit feedwater pump turbine steam inlet system and method, including: a four-stage extraction steam supply system, a cold re-extraction steam supply system, an auxiliary steam source steam supply system, a control system, and a normally closed hot re-extraction steam supply system, each connected to the feedwater pump turbine; wherein the control system is used to control the on-off and steam supply flow between the four-stage extraction steam supply system, the cold re-extraction steam supply system, the auxiliary steam source steam supply system, and the hot re-extraction steam supply system and the water pump turbine, thereby ensuring the safe operation of the unit under low grid load conditions and reducing the chance of unit downtime; Chinese patent application number 202122558200 .7 A feedwater pump steam turbine steam source modification system based on energy matching is proposed. The system is equipped with a new extraction steam pipeline for the feedwater pump steam turbine. The new extraction steam is taken from the high and medium pressure cylinders of the steam turbine. The new extraction port of the steam turbine is close to the four-stage extraction port. The steam source is switched through a connecting pipeline. By switching between the four-stage extraction steam and the new extraction steam pipeline, the output requirements of the feedwater pump steam turbine under different thermal load operating conditions can be met, avoiding the use of high-pressure main steam or reheated cold-section steam with excessively high parameters as the steam source of the feedwater pump steam turbine, thereby realizing the cascade utilization of energy.

[0006] Although the above-mentioned cited patents have explored new connection methods for the working steam source of the feedwater pump turbine, the problems they solve are respectively ensuring the safe operation of the unit under low grid load and the feedwater pump output requirements under different thermal load operating conditions; in summer, the generator set, especially the air-cooled generator set, has the problem of excessive back pressure of the unit resulting in limited output of the feedwater pump turbine and thus affecting the load-carrying capacity of the unit. Due to the volatility and instantaneous nature of grid-connected power generation of new energy, the grid has increasingly stringent requirements on the rapid high-load capacity of the generator set. In order to improve the load-carrying capacity and load response speed of the generator set, especially the air-cooled generator set, it is necessary to propose a unit load-raising system based on a high-enthalpy steam source to drive the feedwater pump turbine, and to distribute steam to the feedwater pump turbine according to the unit load demand, unit back pressure, steam distribution enthalpy, etc., and to integrate multiple steam distribution units to ensure that the unit electrical load can still meet the requirements under extreme working conditions. Summary of the Invention

[0007] A unit load-raising system based on a feedwater pump turbine driven by a high-enthalpy steam source provides a high-enthalpy steam source for the feedwater pump turbine. By adjusting each steam distribution unit according to the unit load and unit back pressure, the feedwater pump turbine inlet steam enthalpy determined by the unit load is gradually merged into the working steam source, and the two systems enter the feedwater pump turbine together, thereby improving the work output of the feedwater pump turbine, increasing the boiler feed water flow rate, and increasing the unit electrical load. At the same time, the steam flow rate of the feedwater pump turbine can be kept relatively stable, avoiding valve opening fluctuations and increased thermal stress caused by drastic changes in the steam pressure and temperature of the feedwater pump turbine.

[0008] A unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine comprises a boiler, a main steam turbine, a feedwater pump turbine, a condensing system, a reheat extraction system, a heat recovery system, and a feedwater pump turbine steam distribution system; the reheat extraction system comprises N sections of extraction steam and hot section reheat steam and cold section reheat steam, where N is an integer and 3<i<N; the i-th section of extraction steam is the working steam source for driving the feedwater pump turbine, the cold section reheat steam is the high-pressure and low-enthalpy steam source for driving the feedwater pump turbine, and the i-1-th section of extraction steam and the hot section reheat steam are the high-enthalpy steam sources for driving the feedwater pump turbine; the feedwater pump turbine steam distribution system comprises a working steam distribution unit, a high-pressure and low-enthalpy steam distribution unit, a high-enthalpy steam distribution unit, and a main steam distribution unit.

[0009] The superheated steam generated by the boiler enters the main steam turbine to perform work and is then discharged into the condensing system to condense into condensate. The condensate enters the boiler through the heat recovery system and becomes superheated steam again. The main steam turbine includes a high-pressure cylinder, a medium-pressure cylinder, and a low-pressure cylinder. The reheat extraction system extracts steam from the main steam turbine and enters the heat recovery system to heat the condensate entering the boiler.

[0010] The feedwater pump steam turbine can be a single feedwater pump steam turbine or two parallel feedwater pump steam turbines; the feedwater pump steam turbine steam distribution system sends the working steam source, high-pressure low-enthalpy steam source, and high-enthalpy steam source to the feedwater pump steam turbine to perform work, driving the condensate to be heated through the heat recovery system and enter the boiler.

[0011] The condensing system includes a condenser, a hot well, and a condensate pump; the condenser condenses steam into water and then sends the water to the heat recovery system through the hot well and the condensate pump.

[0012] The heat recovery system includes N heaters, 3<i<N, N and i are integers; wherein the i-th heater is a deaerator, the 1st to i-1th heaters are high-pressure heaters, and the i+1th to Nth heaters are low-pressure heaters; the i-th section of the reheat extraction steam system enters the deaerator, the 1st to i-1th sections of the extraction steam enter the 1st to i-1th heaters respectively, and the i+1th to Nth sections of the extraction steam enter the i+1th to Nth heaters respectively.

[0013] The main steam distribution unit can be divided into two types: external switching steam distribution and internal switching steam distribution; the main steam distribution unit of the external switching steam distribution type includes a main steam distribution pipeline, a regulating valve, and a main steam valve. The main steam distribution pipeline is first provided with a main steam valve and then a regulating valve along the direction of steam movement; the main steam distribution unit of the internal switching steam distribution type includes a main steam distribution pipeline, a regulating valve, and a main steam valve. The main steam distribution pipeline is divided into two branches, and each branch is successively provided with a main steam valve and a regulating valve along the direction of steam movement.

[0014] The working steam distribution unit includes a working steam source steam distribution pipeline, a check valve, and a first electric valve; the working steam source steam distribution pipeline is first provided with a first electric valve and then a check valve along the direction of steam movement; one end of the working steam source steam distribution pipeline is connected to the i-th section steam extraction, and the other end is connected to the main steam distribution unit; the first electric valve can accept an external power supply signal to perform steam cut-off and flow regulation actions.

[0015] The high-pressure, low-enthalpy steam distribution unit includes a high-pressure, low-enthalpy steam source steam distribution pipeline, a check valve, and a second electric valve; the high-pressure, low-enthalpy steam source steam distribution pipeline is first provided with a second electric valve and then provided with a check valve along the direction of steam movement; one end of the high-pressure, low-enthalpy steam source steam distribution pipeline is connected to the cold section reheat steam, and the other end is connected to the main steam distribution unit; the second electric valve can accept an external power supply signal to perform steam cut-off and flow regulation actions.

[0016] The high-enthalpy steam distribution unit includes a first high-enthalpy steam distribution pipeline, a second high-enthalpy steam distribution pipeline, a check valve, a third electric valve, and a fourth electric valve; the first high-enthalpy steam distribution pipeline is first provided with a third electric valve and then a check valve along the direction of steam movement; one end of the first high-enthalpy steam distribution pipeline is connected to the i-1th section steam extraction, and the other end is connected to the main steam distribution unit.

[0017] The second high-enthalpy steam distribution pipeline is first provided with a fourth electric valve and then a check valve along the direction of steam movement; one end of the second high-enthalpy steam distribution pipeline is connected to the hot section reheat steam, and the other end is connected to the main steam distribution unit; the third electric valve and the fourth electric valve can receive external power supply signals to perform steam cut-off and flow regulation actions. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention is a schematic diagram of a load-raising system for a unit based on a high-enthalpy steam source driving a feedwater pump turbine in accordance with an embodiment of the present invention.

[0019] Figure 2 、 Figure 3 、 Figure 4 This is a schematic diagram of a unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine, one of the other three implementation methods involved in the present utility model.

[0020] In the figure: 1 - boiler, 2 - high pressure cylinder, 3 - medium pressure cylinder, 4 - low pressure cylinder, 5 - feedwater pump turbine, 6 - condenser, 7 - hot well, 8 - condensate pump, 9 - first stage extraction steam, 10 - second stage extraction steam, 11 - third stage extraction steam, 12 - fourth stage extraction steam, 13 - fifth stage extraction steam, 14 - sixth stage extraction steam, 15 - seventh stage extraction steam, 16 - eighth stage extraction steam, 17 - hot section reheat steam, 18 - No. 1 high pressure heater, 19 - No. 2 high pressure heater, 20 - No. 3 high pressure heater, 21 - deaerator, 22 - No. 5 low pressure heater Heater, 23—No. 6 low-pressure heater, 24—No. 7 low-pressure heater, 25—No. 8 low-pressure heater, 26—shaft seal heater, 27—first high-enthalpy steam distribution pipeline, 28—second high-enthalpy steam distribution pipeline, 29—working steam source steam distribution pipeline, 30—main steam distribution pipeline, 31—regulating valve, 32—main steam valve, 33—check valve, 34—first electric valve, 35—third electric valve, 36—fourth electric valve, 37—second electric valve, 38—high-pressure and low-enthalpy steam source steam distribution pipeline, 39—cold section reheat steam. DETAILED DESCRIPTION

[0021] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0022] As attached Figure 1 As shown, a unit load-raising system for driving a feedwater pump turbine based on a high-enthalpy steam source includes a boiler 1, a main steam turbine, a feedwater pump turbine 5, a condensing system, a reheat extraction system, a heat recovery system, and a feedwater pump turbine steam distribution system; wherein the reheat extraction system includes eight sections of extraction steam and hot section reheat steam 17 and cold section reheat steam 39; the feedwater pump turbine steam distribution system includes a main steam distribution pipeline 30, a working steam source steam distribution pipeline 29, a first high-enthalpy steam distribution pipeline 27, a second high-enthalpy steam distribution pipeline 28, a main steam valve 32, a regulating valve 31, a check valve 33, a first electric valve 34, a third electric valve 35, a fourth electric valve 36, a second electric valve 37, and a high-pressure, low-enthalpy steam source steam distribution pipeline 38.

[0023] As attached Figure 1As shown, a unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine, the superheated steam generated by the boiler 1 enters the main steam turbine to perform work and is discharged into the condensing system to condense into condensate, and the condensate enters the boiler 1 again through the heat recovery system to become superheated steam; the main steam turbine includes a high-pressure cylinder 2, an intermediate-pressure cylinder 3, and a low-pressure cylinder 4; the condensing system includes a condenser 6, a hot well 7, and a condensate pump 8; the heat recovery system includes a No. 1 high-pressure heater 18, a No. 2 high-pressure heater 19, a No. 3 high-pressure heater 20, a deaerator 21, a No. 5 low-pressure heater 22, a No. 6 low-pressure heater 23, and a No. 7 low-pressure heater 2 4. No. 8 low-pressure heater 25, shaft seal heater 26; first-stage extraction steam 9 is extracted from high-pressure cylinder 2 to No. 1 high-pressure heater 18; second-stage extraction steam 10 is extracted from high-pressure cylinder 2 to No. 2 high-pressure heater 19; third-stage extraction steam 11 is extracted from intermediate-pressure cylinder 3 to No. 3 high-pressure heater 20; fourth-stage extraction steam 12 is extracted from intermediate-pressure cylinder 3 to deaerator 21; fifth-stage extraction steam 13 is extracted from intermediate-pressure cylinder 3 to No. 5 low-pressure heater 22; sixth-stage extraction steam 14, seventh-stage extraction steam 15, and eighth-stage extraction steam 16 are extracted from low-pressure cylinder 4 to No. 6 low-pressure heater 23, No. 7 low-pressure heater 24, and No. 8 low-pressure heater 25, respectively.

[0024] As attached Figure 1As shown, a unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine, the feedwater pump turbine is 100% capacity, and one unit is arranged; the fourth-section extraction steam is the working steam source for driving the feedwater pump turbine, the cold-section reheat steam is the high-pressure, low-enthalpy steam source for driving the feedwater pump turbine, the third-section extraction steam and the hot-section reheat steam are the high-enthalpy steam sources for driving the feedwater pump turbine; the main steam distribution unit is an external switching steam distribution type; the main steam distribution unit of the external switching steam distribution type includes a main steam distribution pipeline 30, a regulating valve 31, and a main steam valve 32. The main steam distribution pipeline is first provided with a main steam valve 32 along the direction of steam movement, and then a regulating valve 31 is provided; the working steam distribution unit includes a working steam source steam distribution pipeline 29, a check valve 33, and a first electric valve 34; the working steam source steam distribution pipeline is first provided with a first electric valve 34 along the direction of steam movement, and then a check valve 33 is provided; one end of the working steam source steam distribution pipeline is connected to the fourth-section extraction steam, and the other end The high-pressure low-enthalpy steam distribution unit includes a high-pressure low-enthalpy steam source steam distribution pipeline 38, a check valve 33, and a second electric valve 37; one end of the high-pressure low-enthalpy steam source steam distribution pipeline 38 is connected to the cold section reheat steam 39, and the other end is connected to the main steam distribution pipeline 30; the high-enthalpy steam distribution unit includes a first high-enthalpy steam distribution pipeline 27, a second high-enthalpy steam distribution pipeline 28, a check valve 33, a third electric valve 35, and a fourth electric valve 36; the A third electric valve 35 is first provided on a high-enthalpy steam distribution pipe 27 along the direction of steam movement, and a check valve 33 is then provided. One end of the first high-enthalpy steam distribution pipe 27 is connected to the third section extraction steam, and the other end is connected to the main steam distribution pipe 30. A fourth electric valve 34 is first provided on a second high-enthalpy steam distribution pipe 28 along the direction of steam movement, and a check valve 33 is then provided. One end of the second high-enthalpy steam distribution pipe 28 is connected to the hot section reheat steam, and the other end is connected to the main steam distribution pipe 30.

[0025] As attached Figure 1As shown, a unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine can adjust each steam distribution unit according to the unit load and the unit back pressure. When the unit load is limited, the high-enthalpy steam source is gradually merged into the working steam source, and enters the feedwater pump turbine together, thereby improving the work output of the feedwater pump turbine, increasing the boiler feed water flow rate, and increasing the unit electrical load. When the unit is running at high load, in order to ensure the boiler feed water efficiency, the high-enthalpy steam source is merged with the working steam source to improve the feedwater pump turbine. Work output; At this time, according to the enthalpy value required by the feedwater pump turbine, the third electric valve 35 on the first high-enthalpy steam distribution pipe 27 receives an electrical signal and opens to a certain opening, and the steam flow in the low-pressure steam distribution pipe 29 from the four-stage steam extraction is reduced accordingly. The main steam valve 32 on the main steam distribution pipe 30 ensures that the total steam volume of the feedwater pump turbine is relatively stable; When the unit load continues to increase, according to the boiler feed water situation, the opening of the third electric valve 35 is gradually increased to allow the high-enthalpy steam source and the working steam source to be gradually and slowly mixed; If it is still necessary to increase the boiler feed water, increase the feed water The feedwater pump turbine output, if the steam flow of the No. 3 high-pressure heater 20 at the end of the three-stage extraction steam is limited, an electrical signal is transmitted to the fourth electric valve 36, and the third electric valve 35 is closed at the same time, and the steam in the second high enthalpy steam distribution pipe 28 from the hot section reheated steam is merged with the working steam source, and the opening of the fourth electric valve 36 is gradually increased to increase the steam enthalpy in the feedwater pump turbine until the feedwater pump turbine output meets the high-load operation requirements of the boiler; when the unit is operating normally, the fourth stage extraction steam is used as the working steam source through the electric valve 34, the stop valve 35 and the stop valve 36 in sequence. The return valve 33, the main steam valve 32, and the regulating valve 31 enter to drive the feedwater pump turbine 5 to perform work, and the regulating valve adjusts the steam intake according to the boiler feed water demand. At this time, the second electric valve 37, the third electric valve 35, and the fourth electric valve 36 are all closed to block the steam circulation; when the unit is running at low load, the check valve on the high-pressure and low-enthalpy steam source steam distribution pipeline 38 is opened, the second electric valve 37 is opened, the check valve on the working steam source steam distribution pipeline is closed, and the first electric valve 34 is closed, switching to the high-pressure and low-enthalpy steam source to enter the feedwater pump turbine 5 to perform work.

[0026] As attached Figure 2 As shown, a unit load-raising system for driving a feedwater pump turbine based on a high-enthalpy steam source includes a boiler 1, a main steam turbine, a feedwater pump turbine 5, a condensing system, a reheat extraction system, a heat recovery system, and a feedwater pump turbine steam distribution system; wherein the reheat extraction system includes eight sections of extraction steam and hot section reheat steam 17 and cold section reheat steam 39; the feedwater pump turbine steam distribution system includes a main steam distribution pipeline 30, a working steam source steam distribution pipeline 29, a first high-enthalpy steam distribution pipeline 27, a second high-enthalpy steam distribution pipeline 28, a main steam valve 32, a regulating valve 31, a check valve 33, a first electric valve 34, a third electric valve 35, a fourth electric valve 36, a second electric valve 37, and a high-pressure, low-enthalpy steam source steam distribution pipeline 38.

[0027] As attached Figure 2 As shown, a unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine, the superheated steam generated by the boiler 1 enters the main steam turbine to perform work and is discharged into the condensing system to condense into condensate, and the condensate enters the boiler 1 again through the heat recovery system to become superheated steam; the main steam turbine includes a high-pressure cylinder 2, an intermediate-pressure cylinder 3, and a low-pressure cylinder 4; the condensing system includes a condenser 6, a hot well 7, and a condensate pump 8; the heat recovery system includes a No. 1 high-pressure heater 18, a No. 2 high-pressure heater 19, a No. 3 high-pressure heater 20, a deaerator 21, a No. 5 low-pressure heater 22, a No. 6 low-pressure heater 23, and a No. 7 low-pressure heater 2 4. No. 8 low-pressure heater 25, shaft seal heater 26; first-stage extraction steam 9 is extracted from high-pressure cylinder 2 to No. 1 high-pressure heater 18; second-stage extraction steam 10 is extracted from high-pressure cylinder 2 to No. 2 high-pressure heater 19; third-stage extraction steam 11 is extracted from intermediate-pressure cylinder 3 to No. 3 high-pressure heater 20; fourth-stage extraction steam 12 is extracted from intermediate-pressure cylinder 3 to deaerator 21; fifth-stage extraction steam 13 is extracted from intermediate-pressure cylinder 3 to No. 5 low-pressure heater 22; sixth-stage extraction steam 14, seventh-stage extraction steam 15, and eighth-stage extraction steam 16 are extracted from low-pressure cylinder 4 to No. 6 low-pressure heater 23, No. 7 low-pressure heater 24, and No. 8 low-pressure heater 25, respectively.

[0028] As attached Figure 2As shown, a unit load-raising system for driving a feedwater pump turbine based on a high-enthalpy steam source, the feedwater pump turbine is 100% capacity, and one unit is arranged; the fourth-section extraction steam is the working steam source for driving the feedwater pump turbine, the cold-section reheat steam is the high-pressure, low-enthalpy steam source for driving the feedwater pump turbine, and the third-section extraction steam and the hot-section reheat steam are the high-enthalpy steam sources for driving the feedwater pump turbine; the main steam distribution unit is an internal switching steam distribution type; the main steam distribution unit of the internal switching steam distribution type includes a main steam distribution pipeline 30, a regulating valve 31, and a main steam valve 32. The main steam distribution pipeline is divided into two branches, and each branch is successively provided with a main steam valve 32 and a regulating valve 31 along the direction of steam movement; the working steam distribution unit includes a working steam source steam distribution pipeline 29, a check valve 33, and a first electric valve 34; the working steam source steam distribution pipeline is first provided with a first electric valve 34 along the direction of steam movement, and then a check valve 33; one end of the working steam source steam distribution pipeline is connected to the fourth section The high-pressure low-enthalpy steam distribution unit includes a high-pressure low-enthalpy steam source steam distribution pipeline 38, a check valve 33, and a second electric valve 37; one end of the high-pressure low-enthalpy steam source steam distribution pipeline 38 is connected to the cold section reheat steam 39, and the other end is connected to the main steam distribution pipeline 30; the high-enthalpy steam distribution unit includes a first high-enthalpy steam distribution pipeline 27, a second high-enthalpy steam distribution pipeline 28, a check valve 33, a third electric valve 35, and a fourth electric valve 3 6; The first high-enthalpy steam distribution pipe 27 is first provided with a third electric valve 35 along the direction of steam movement, and then a check valve 33; one end of the first high-enthalpy steam distribution pipe 27 is connected to the third section extraction steam, and the other end is connected to the main steam distribution pipe 30; the second high-enthalpy steam distribution pipe 28 is first provided with a fourth electric valve 34 along the direction of steam movement, and then a check valve 33; one end of the second high-enthalpy steam distribution pipe 28 is connected to the hot section reheat steam, and the other end is connected to the main steam distribution pipe 30.

[0029] As attached Figure 2As shown, a unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine can adjust each steam distribution unit according to the unit load and the unit back pressure. When the unit load is limited, the feedwater pump turbine inlet enthalpy determined by the unit load is adjusted, so that the high-enthalpy steam source is gradually merged into the working steam source and enters the feedwater pump turbine together, thereby improving the work output of the feedwater pump turbine, increasing the boiler feed water flow rate, and improving the unit electrical load. When the unit is operating normally, the fourth stage extraction steam is used as the working steam source and passes through the electric valve 34, the check valve 33, the main steam valve 32, The regulating valve 31 enters to drive the feedwater pump turbine 5 to do work, and the regulating valve adjusts the steam intake according to the boiler feedwater demand. At this time, the second electric valve 37, the third electric valve 35, and the fourth electric valve 36 are all closed to block the steam circulation; when the unit is running at low load, the check valve on the high-pressure low-enthalpy steam source steam distribution pipeline 38 is opened, the second electric valve 37 is opened, the check valve on the working steam source steam distribution pipeline is closed, and the first electric valve 34 is closed, switching to the high-pressure low-enthalpy steam source to enter the feedwater pump turbine 5 to do work; when the unit is running at high load, the check valve on the high-pressure low-enthalpy steam source steam distribution pipeline 38 is opened, the second electric valve 37 is opened, the check valve on the working steam source steam distribution pipeline is closed, and the first electric valve 34 is closed, switching to the high-pressure low-enthalpy steam source to enter the feedwater pump turbine 5 to do work; During operation, in order to ensure the efficiency of boiler water supply, the high enthalpy steam source is combined with the working steam source to increase the work output of the feedwater pump turbine; at this time, according to the enthalpy value required by the feedwater pump turbine, the third electric valve 35 on the first high enthalpy steam distribution pipeline 27 receives an electrical signal and opens to a certain opening, and the steam flow in the low-pressure steam distribution pipeline 29 from the four-stage steam extraction is reduced accordingly. The main steam valve 32 on the main steam distribution pipeline 30 ensures that the total steam volume of the feedwater pump turbine is relatively stable; when the unit load continues to increase, according to the boiler water supply situation, the valve is gradually increased. The third electric valve 35 is opened to a large extent, so that the high enthalpy steam source and the working steam source are gradually and slowly mixed; if the boiler feed water still needs to be increased to improve the output of the feedwater pump turbine, if the steam flow of the No. 3 high-pressure heater 20 at the end of the three-stage steam extraction is limited, an electrical signal is transmitted to the fourth electric valve 36, and the third electric valve 35 is closed at the same time, and the steam in the second high enthalpy steam distribution pipe 28 from the hot section reheat steam is merged with the working steam source, and the opening of the fourth electric valve 36 is gradually increased at the same time until the output of the feedwater pump turbine meets the high-load operation requirements of the boiler.

[0030] As attached Figure 3As shown, a unit load-raising system for driving a feedwater pump turbine based on a high-enthalpy steam source comprises a boiler 1, a main steam turbine, a feedwater pump turbine 5, a condensing system, a reheat extraction system, a heat recovery system, and a feedwater pump turbine steam distribution system; wherein the reheat extraction system comprises eight sections of extraction steam and hot section reheat steam 17 and cold section reheat steam 39; the feedwater pump turbine steam distribution system comprises a main steam distribution pipeline 30, a working steam source steam distribution pipeline 29, a first high-enthalpy steam source steam distribution pipeline 31, a first high-enthalpy steam source steam distribution pipeline 32, a first high-enthalpy steam source steam distribution pipeline 33, a first high-enthalpy steam source steam distribution pipeline 34, a first high-enthalpy steam source steam distribution pipeline 35, a first high-enthalpy steam source steam distribution pipeline 36, a first high-enthalpy steam source steam distribution pipeline 37, a first high-enthalpy steam source steam distribution pipeline 38, a first high-enthalpy steam source steam distribution pipeline 39, a first high-enthalpy steam source steam distribution pipeline 30 ... Steam distribution pipeline 27, second high enthalpy steam distribution pipeline 28, main steam valve 32, regulating valve 31, check valve 33, first electric valve 34, third electric valve 35, fourth electric valve 36, second electric valve 37, high pressure low enthalpy steam source steam distribution pipeline 38; the superheated steam generated by boiler 1 enters the main steam turbine to perform work and is discharged into the condensing system to condense into condensate, and the condensate enters the boiler 1 through the heat recovery system to become superheated steam again; the main steam turbine includes a high pressure cylinder 2, an intermediate pressure cylinder 3, and a low pressure cylinder 4; the condensing system includes a condenser 6, a hot well 7, and a condensate pump 8; the heat recovery system includes a No. 1 high pressure heater 18, a No. 2 high pressure heater 19, a No. 3 high pressure heater 20, a deaerator 21, a No. 5 low pressure heater 22, a No. 6 low pressure heater 23, a No. 7 low pressure heater 24, a No. 8 low pressure heater 25, and a shaft seal heater 26; the first stage extraction 9 extracts steam from the high pressure cylinder 2 to the No. 1 high pressure heater 18; the second stage extraction 10 extracts steam from the high-pressure cylinder 2 to the No. 2 high-pressure heater 19; the third-stage steam extraction 11 extracts steam from the intermediate-pressure cylinder 3 to the No. 3 high-pressure heater 20; the fourth-stage steam extraction 12 extracts steam from the intermediate-pressure cylinder 3 to the deaerator 21; the fifth-stage steam extraction 13 extracts steam from the intermediate-pressure cylinder 3 to the No. 5 low-pressure heater 22; the sixth-stage steam extraction 14, the seventh-stage steam extraction 15, and the eighth-stage steam extraction 16 extract steam from the low-pressure cylinder 4 to the No. 6 low-pressure heater 23, the No. 7 low-pressure heater 24, and the No. 8 low-pressure heater 25 respectively.

[0031] As attached Figure 3As shown, a unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine, the feedwater pump turbine is 50% capacity, there are two feedwater pump turbines in total, and the two feedwater pump turbines are arranged in parallel; the fourth-stage extraction steam is the working steam source for driving the feedwater pump turbine, the cold-section reheat steam is the high-pressure, low-enthalpy steam source for driving the feedwater pump turbine, and the third-stage extraction steam and the hot-section reheat steam are the high-enthalpy steam sources for driving the feedwater pump turbine; each feedwater pump turbine is provided with a set of main steam distribution units, and the main steam distribution units are of the internal switching steam distribution type The main steam distribution unit of the internal switching steam distribution type includes a main steam distribution pipeline 30, a regulating valve 31, and a main steam valve 32. Each set of the main steam distribution pipeline is divided into two branches. Each branch is successively provided with a main steam valve 32 and a regulating valve 31 along the direction of steam movement; the working steam distribution unit includes a working steam source steam distribution pipeline 29, a check valve 33, and a first electric valve 34; the working steam source steam distribution pipeline is first provided with a first electric valve 34 along the direction of steam movement, and then a check valve 33; one end of the working steam source steam distribution pipeline is connected to the fourth section of extraction steam, and the other end is connected to the fourth section of extraction steam. The main steam distribution pipe 30 is connected to each feedwater pump turbine; the high-pressure low-enthalpy steam distribution unit includes a high-pressure low-enthalpy steam source steam distribution pipe 38, a check valve 33, and a second electric valve 37; one end of the high-pressure low-enthalpy steam source steam distribution pipe 38 is connected to the cold section reheat steam 39, and the other end is connected to the main steam distribution pipe 30 configured for each feedwater pump turbine; the high-enthalpy steam distribution unit includes a first high-enthalpy steam distribution pipe 27, a second high-enthalpy steam distribution pipe 28, a check valve 33, a third electric valve 35, and a fourth electric valve 36; A high-enthalpy steam distribution pipe 27 is first provided with a third electric valve 35 along the direction of steam movement, and then a check valve 33; one end of the first high-enthalpy steam distribution pipe 27 is connected to the third section extraction steam, and the other end is connected to the main steam distribution pipe 30 configured for each feedwater pump turbine; a second high-enthalpy steam distribution pipe 28 is first provided with a fourth electric valve 34 along the direction of steam movement, and then a check valve 33; one end of the second high-enthalpy steam distribution pipe 28 is connected to the hot section reheat steam, and the other end is connected to the main steam distribution pipe 30 configured for each feedwater pump turbine.

[0032] As attached Figure 3As shown, a unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine can adjust each steam distribution unit according to the unit load and the unit back pressure. When the unit load is limited, the feedwater pump turbine inlet enthalpy determined by the unit load is adjusted, so that the high-enthalpy steam source is gradually merged into the working steam source and enters the feedwater pump turbine together, thereby improving the work output of the feedwater pump turbine, increasing the boiler feed water flow rate, and improving the unit electrical load. When the unit is operating normally, the fourth stage extraction steam is used as the working steam source and passes through the electric valve 34, the check valve 33, the main steam valve 32, The regulating valve 31 enters to drive the feedwater pump turbine 5 to do work, and the regulating valve adjusts the steam intake according to the boiler feedwater demand. At this time, the second electric valve 37, the third electric valve 35, and the fourth electric valve 36 are all closed to block the steam circulation; when the unit is running at low load, the check valve on the high-pressure low-enthalpy steam source steam distribution pipeline 38 is opened, the second electric valve 37 is opened, the check valve on the working steam source steam distribution pipeline is closed, and the first electric valve 34 is closed, switching to the high-pressure low-enthalpy steam source to enter the feedwater pump turbine 5 to do work; when the unit is running at high load, the check valve on the high-pressure low-enthalpy steam source steam distribution pipeline 38 is opened, the second electric valve 37 is opened, the check valve on the working steam source steam distribution pipeline is closed, and the first electric valve 34 is closed, switching to the high-pressure low-enthalpy steam source to enter the feedwater pump turbine 5 to do work; During operation, in order to ensure the efficiency of boiler water supply, the high enthalpy steam source is combined with the working steam source to increase the work output of the feedwater pump turbine; at this time, according to the enthalpy value required by the feedwater pump turbine, the third electric valve 35 on the first high enthalpy steam distribution pipeline 27 receives an electrical signal and opens to a certain opening, and the steam flow in the low-pressure steam distribution pipeline 29 from the four-stage steam extraction is reduced accordingly. The main steam valve 32 on the main steam distribution pipeline 30 ensures that the total steam volume of the feedwater pump turbine is relatively stable; when the unit load continues to increase, according to the boiler water supply situation, the valve is gradually increased. The third electric valve 35 is opened to a large extent, so that the high enthalpy steam source and the working steam source are gradually and slowly mixed; if the boiler feed water still needs to be increased to improve the output of the feedwater pump turbine, if the steam flow of the No. 3 high-pressure heater 20 at the end of the three-stage steam extraction is limited, an electrical signal is transmitted to the fourth electric valve 36, and the third electric valve 35 is closed at the same time, and the steam in the second high enthalpy steam distribution pipe 28 from the hot section reheat steam is merged with the working steam source, and the opening of the fourth electric valve 36 is gradually increased at the same time until the output of the feedwater pump turbine meets the high-load operation requirements of the boiler.

[0033] As attached Figure 4As shown, a unit load-raising system for driving a feedwater pump turbine based on a high-enthalpy steam source comprises a boiler 1, a main steam turbine, a feedwater pump turbine 5, a condensing system, a reheat extraction system, a heat recovery system, and a feedwater pump turbine steam distribution system; wherein the reheat extraction system comprises eight sections of extraction steam and hot section reheat steam 17 and cold section reheat steam 39; the feedwater pump turbine steam distribution system comprises a main steam distribution pipeline 30, a working steam source steam distribution pipeline 29, a first high-enthalpy steam source steam distribution pipeline 31, a first high-enthalpy steam source steam distribution pipeline 32, a first high-enthalpy steam source steam distribution pipeline 33, a first high-enthalpy steam source steam distribution pipeline 34, a first high-enthalpy steam source steam distribution pipeline 35, a first high-enthalpy steam source steam distribution pipeline 36, a first high-enthalpy steam source steam distribution pipeline 37, a first high-enthalpy steam source steam distribution pipeline 38, a first high-enthalpy steam source steam distribution pipeline 39, a first high-enthalpy steam source steam distribution pipeline 30 ... Steam distribution pipeline 27, second high enthalpy steam distribution pipeline 28, main steam valve 32, regulating valve 31, check valve 33, first electric valve 34, third electric valve 35, fourth electric valve 36, second electric valve 37, high pressure low enthalpy steam source steam distribution pipeline 38; the superheated steam generated by boiler 1 enters the main steam turbine to perform work and is discharged into the condensing system to condense into condensate, and the condensate enters the boiler 1 through the heat recovery system to become superheated steam again; the main steam turbine includes a high pressure cylinder 2, an intermediate pressure cylinder 3, and a low pressure cylinder 4; the condensing system includes a condenser 6, a hot well 7, and a condensate pump 8; the heat recovery system includes a No. 1 high pressure heater 18, a No. 2 high pressure heater 19, a No. 3 high pressure heater 20, a deaerator 21, a No. 5 low pressure heater 22, a No. 6 low pressure heater 23, a No. 7 low pressure heater 24, a No. 8 low pressure heater 25, and a shaft seal heater 26; the first stage extraction 9 extracts steam from the high pressure cylinder 2 to the No. 1 high pressure heater 18; the second stage extraction 10 extracts steam from the high-pressure cylinder 2 to the No. 2 high-pressure heater 19; the third-stage steam extraction 11 extracts steam from the intermediate-pressure cylinder 3 to the No. 3 high-pressure heater 20; the fourth-stage steam extraction 12 extracts steam from the intermediate-pressure cylinder 3 to the deaerator 21; the fifth-stage steam extraction 13 extracts steam from the intermediate-pressure cylinder 3 to the No. 5 low-pressure heater 22; the sixth-stage steam extraction 14, the seventh-stage steam extraction 15, and the eighth-stage steam extraction 16 extract steam from the low-pressure cylinder 4 to the No. 6 low-pressure heater 23, the No. 7 low-pressure heater 24, and the No. 8 low-pressure heater 25 respectively.

[0034] As attached Figure 4As shown, a unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine, the feedwater pump turbine is 50% capacity, there are two feedwater pump turbines in total, and the two feedwater pump turbines are arranged in parallel; the fourth-stage extraction steam is the working steam source for driving the feedwater pump turbine, the cold-stage reheat steam is the high-pressure, low-enthalpy steam source for driving the feedwater pump turbine, and the third-stage extraction steam and the hot-stage reheat steam are the high-enthalpy steam sources for driving the feedwater pump turbine; each feedwater pump turbine is equipped with a main steam distribution unit, which is an externally switched steam distribution type Type; The main steam distribution unit of the external switching steam distribution type includes a main steam distribution pipeline 30, a regulating valve 31, and a main steam valve 32. The main steam distribution pipeline is provided with the main steam valve 32 first along the direction of steam movement, and then the regulating valve 31; The working steam distribution unit includes a working steam source steam distribution pipeline 29, a check valve 33, and a first electric valve 34; The working steam source steam distribution pipeline is provided with the first electric valve 34 and then the check valve 33 along the direction of steam movement; One end of the working steam source steam distribution pipeline is connected to the fourth section of steam extraction, and the other end is connected to each water supply pump The main steam distribution pipe 30 configured for the steam turbine; the high-pressure low-enthalpy steam distribution unit includes a high-pressure low-enthalpy steam source steam distribution pipe 38, a check valve 33, and a second electric valve 37; one end of the high-pressure low-enthalpy steam source steam distribution pipe 38 is connected to the cold section reheat steam 39, and the other end is connected to the main steam distribution pipe 30 configured for each feedwater pump turbine; the high-enthalpy steam distribution unit includes a first high-enthalpy steam distribution pipe 27, a second high-enthalpy steam distribution pipe 28, a check valve 33, a third electric valve 35, and a fourth electric valve 36; the first high-enthalpy A third electric valve 35 is first provided on the high-enthalpy steam distribution pipe 27 along the direction of steam movement, and a check valve 33 is then provided; one end of the first high-enthalpy steam distribution pipe 27 is connected to the third section extraction steam, and the other end is connected to the main steam distribution pipe 30 configured for each feedwater pump turbine; a fourth electric valve 34 is first provided on the second high-enthalpy steam distribution pipe 28 along the direction of steam movement, and a check valve 33 is then provided; one end of the second high-enthalpy steam distribution pipe 28 is connected to the hot section reheat steam, and the other end is connected to the main steam distribution pipe 30 configured for each feedwater pump turbine.

[0035] As attached Figure 4As shown, a unit load-raising system for driving a feedwater pump turbine based on a high-enthalpy steam source is provided. When the unit is running at high load, in order to ensure the boiler feedwater efficiency, the high-enthalpy steam source and the working steam source are combined to increase the work output of the feedwater pump turbine. At this time, according to the enthalpy required by the feedwater pump turbine, the third electric valve 35 on the first high-enthalpy steam distribution pipe 27 receives an electrical signal and opens to a certain opening, and the steam flow in the low-pressure steam distribution pipe 29 from the four-stage steam extraction is reduced accordingly. The main steam valve 32 on the main steam distribution pipe 30 ensures that the total steam volume of the feedwater pump turbine is relatively stable. When the unit load continues to increase, according to the boiler feedwater situation, the opening of the third electric valve 35 is gradually increased to allow the high-enthalpy steam source and the working steam source to be gradually and slowly mixed. If it is still necessary to increase the boiler feedwater and increase the feedwater pump turbine output, if the steam flow of the No. 3 high-pressure heater 20 at the end of the three-stage steam extraction is limited, an electrical signal is transmitted to the fourth electric valve 35. Valve 36 is opened, and the third electric valve 35 is closed at the same time. The steam in the second high enthalpy steam distribution pipe 28 from the hot section reheated steam is merged with the working steam source, and the opening of the fourth electric valve 36 is gradually increased until the output of the feedwater pump turbine meets the high-load operation requirements of the boiler; when the unit is operating normally, the fourth section extraction steam is used as the working steam source through the electric valve 34, the check valve 33, the main steam valve 32, and the regulating valve 31 in sequence to drive the feedwater pump turbine 5 to perform work, and the regulating valve adjusts the steam intake according to the boiler feed water demand. At this time, the second electric valve 37, the third electric valve 35, and the fourth electric valve 36 are all closed to block the steam circulation; when the unit is operating at low load, the check valve on the high-pressure and low-enthalpy steam source steam distribution pipe 38 is opened, the second electric valve 37 is opened, the check valve on the working steam source steam distribution pipe is closed, the first electric valve 34 is closed, and the high-pressure and low-enthalpy steam source is switched to enter the feedwater pump turbine 5 to perform work.

[0036] The above shows and describes the basic principles, main features and advantages of the utility model. For those skilled in the art, it is obvious that the utility model is not limited to the details of the above-mentioned exemplary implementation cases, and the utility model can be implemented in other specific forms without departing from the spirit or basic features of the utility model; therefore, no matter from which point of view, the implementation cases should be regarded as exemplary and non-restrictive. The scope of the utility model is limited by the attached claims rather than the above description. Therefore, it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims are included in the utility model, and any figure marks in the claims should not be regarded as limiting the claims involved.

[0037] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine, comprising a boiler, a main steam turbine, a feedwater pump turbine, a condensing system, a reheat extraction system, a heat recovery system, and a feedwater pump turbine steam distribution system; the reheat extraction system comprises N sections of extraction steam and hot section reheat steam and cold section reheat steam, 3<i<N, i, N are integers; the i-th section of extraction steam is the working steam source for driving the feedwater pump turbine, the cold section reheat steam is the high-pressure and low-enthalpy steam source for driving the feedwater pump turbine, the i-1th section of extraction steam and the hot section reheat steam are the high-enthalpy steam sources for driving the feedwater pump turbine; the feedwater pump turbine steam distribution system comprises a working steam distribution unit, a high-pressure and low-enthalpy steam distribution unit, a high-enthalpy steam distribution unit, and a main steam distribution unit.

2. The unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine according to claim 1, characterized in that: The superheated steam generated by the boiler enters the main steam turbine to perform work and is then discharged into the condensing system to condense into condensate. The condensate enters the boiler through the heat recovery system and becomes superheated steam again. The main steam turbine includes a high-pressure cylinder, a medium-pressure cylinder, and a low-pressure cylinder. The reheat extraction system extracts steam from the main steam turbine and enters the heat recovery system to heat the condensate entering the boiler.

3. The unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine according to claim 1, characterized in that: The feedwater pump steam turbine can be a single feedwater pump steam turbine or two parallel feedwater pump steam turbines; the feedwater pump steam turbine steam distribution system sends the working steam source, high-pressure low-enthalpy steam source, and high-enthalpy steam source to the feedwater pump steam turbine to perform work, driving the condensate to be heated through the heat recovery system and enter the boiler.

4. The unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine according to claim 1, characterized in that: The condensing system includes a condenser, a hot well, and a condensate pump; the condenser condenses steam into water and then sends the water to the heat recovery system through the hot well and the condensate pump.

5. The unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine according to claim 1, characterized in that: The heat recovery system includes N heaters, 3<i<N, N and i are integers; Among them, the i-th heater is a deaerator, the 1st to i-1th heaters are high-pressure heaters, and the i+1th to Nth heaters are low-pressure heaters; the i-th section of the reheat extraction steam system enters the deaerator, the 1st to i-1th sections of the extraction steam enter the 1st to i-1th heaters respectively, and the i+1th to Nth sections of the extraction steam enter the i+1th to Nth heaters respectively.

6. The unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine according to claim 1, characterized in that: The main steam distribution unit can be divided into two types: external switching steam distribution and internal switching steam distribution; the main steam distribution unit of the external switching steam distribution type includes a main steam distribution pipeline, a regulating valve, and a main steam valve. The main steam distribution pipeline is first provided with a main steam valve and then a regulating valve along the direction of steam movement; the main steam distribution unit of the internal switching steam distribution type includes a main steam distribution pipeline, a regulating valve, and a main steam valve. The main steam distribution pipeline is divided into two branches, and each branch is successively provided with a main steam valve and a regulating valve along the direction of steam movement.

7. The unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine according to claim 1, characterized in that: The working steam distribution unit includes a working steam source steam distribution pipeline, a check valve, and a first electric valve; the working steam source steam distribution pipeline is first provided with a first electric valve and then a check valve along the direction of steam movement; one end of the working steam source steam distribution pipeline is connected to the i-th section steam extraction, and the other end is connected to the main steam distribution unit; the first electric valve can accept an external power supply signal to perform steam cut-off and flow regulation actions.

8. The unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine according to claim 1, characterized in that: The high-pressure, low-enthalpy steam distribution unit includes a high-pressure, low-enthalpy steam source steam distribution pipeline, a check valve, and a second electric valve; the high-pressure, low-enthalpy steam source steam distribution pipeline is first provided with a second electric valve along the direction of steam movement, and then provided with a check valve; one end of the high-pressure, low-enthalpy steam source steam distribution pipeline is connected to the cold section reheat steam, and the other end is connected to the main steam distribution unit; the second electric valve can accept an external power supply signal to perform steam cut-off and flow regulation actions.

9. The unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine according to claim 1, characterized in that: The high-enthalpy steam distribution unit includes a first high-enthalpy steam distribution pipeline, a second high-enthalpy steam distribution pipeline, a check valve, a third electric valve, and a fourth electric valve; the first high-enthalpy steam distribution pipeline is first provided with a third electric valve and then a check valve along the direction of steam movement; one end of the first high-enthalpy steam distribution pipeline is connected to the i-1th section steam extraction, and the other end is connected to the main steam distribution unit.

10. The unit load-raising system based on a high-enthalpy steam source driving a feedwater pump turbine according to claim 9, characterized in that: The second high-enthalpy steam distribution pipeline is first provided with a fourth electric valve and then a check valve along the direction of steam movement; one end of the second high-enthalpy steam distribution pipeline is connected to the hot section reheat steam, and the other end is connected to the main steam distribution unit; the third electric valve and the fourth electric valve can receive external power supply signals to perform steam cut-off and flow regulation actions.

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