Small steam turbine system

Abstract

The invention discloses a small steam turbine system, belongs to the technical field of thermal power generation, and mainly aims to guarantee efficient operation of a water feed pump steam turbine under the working condition of deep peak regulation of a main steam turbine and avoid the problem of large rotating speed fluctuation of the water feed pump steam turbine during high-pressure steam source switching. According to the main technical scheme, the small steam turbine system comprises a water feeding pump steam turbine, a first low-pressure steam pipe and a second low-pressure steam pipe; the power adjusting range of the water feeding pump steam turbine at least covers the steam parameter change requirement of the load of the main steam turbine within the range of 30%-100% of the rated load; the first low-pressure steam pipe and the second low-pressure steam pipe are arranged in parallel, and the first low-pressure steam pipe and the second low-pressure steam pipe are configured as follows: when the load of the main steam turbine is less than 90% of the rated load, the feed pump steam turbine is communicated with the first low-pressure steam pipe; when the load of the main steam turbine exceeds 90% of the rated load, the feed pump steam turbine is communicated with the first low-pressure steam pipe and the second low-pressure steam pipe at the same time.

Description

Technical Field

[0001] The present application belongs to the field of thermal power generation technology, and specifically relates to a small steam turbine system. Background Art

[0002] In modern thermal power generation systems, feedwater pumps are core equipment that ensure a stable supply of boiler feedwater. The performance of the feedwater pump turbine, which drives it, directly impacts the overall efficiency and reliability of the unit. As the power market continues to increase its demands for unit flexibility and economy, feedwater pump turbines must operate efficiently across a wide load range to meet the grid's peak load regulation needs and energy conservation and emission reduction targets.

[0003] Traditional feedwater pump steam turbine systems often use a "one high, one low" steam inlet scheme, whereby the feedwater pump steam turbine is driven by a combination of high-pressure and low-pressure steam. This scheme introduces the problem of feedwater pump steam turbine speed fluctuations when switching from a low-pressure steam source to a high-pressure steam source. Summary of the Invention

[0004] In view of this, the present application provides a small steam turbine system, the main purpose of which is to ensure the efficient operation of the feedwater pump turbine under the deep peak-shaving condition of the main steam turbine, while avoiding the problem of large fluctuations in the speed of the feedwater pump turbine caused by switching the high-pressure steam source.

[0005] To achieve the above objectives, this application mainly provides the following technical solutions:

[0006] The present application provides a small steam turbine system, comprising:

[0007] Feedwater pump turbine, first low-pressure steam pipe and second low-pressure steam pipe;

[0008] The power adjustment range of the feedwater pump steam turbine at least covers the steam parameter change requirements when the main steam turbine load is within the range of 30% to 100% of the rated load;

[0009] The first low-pressure steam pipe and the second low-pressure steam pipe are arranged in parallel and are configured as follows: when the load of the main steam turbine is below 90% of the rated load, the feedwater pump turbine is connected to the first low-pressure steam pipe; when the load of the main steam turbine exceeds 90% of the rated load, the feedwater pump turbine is connected to the first low-pressure steam pipe and the second low-pressure steam pipe at the same time.

[0010] Optionally, the small steam turbine system further includes:

[0011] Low-pressure steam source;

[0012] The low-pressure steam source is four-extraction steam pipes, and the four-extraction steam pipes are respectively connected to the first low-pressure steam pipe and the second low-pressure steam pipe.

[0013] Optionally, an electric isolation valve is provided on the four steam extraction pipes.

[0014] Optionally, a first main steam valve and a first regulating valve are provided on the first low-pressure steam pipe.

[0015] Optionally, the first regulating valve is arranged on the downstream side of the first main steam valve along the steam flow direction.

[0016] Optionally, a second main steam valve and a second regulating valve are provided on the second low-pressure steam pipe.

[0017] Optionally, the second regulating valve is arranged on the downstream side of the second main steam valve along the steam flow direction.

[0018] Optionally, a first regulating stage nozzle connected to the outlet of the first low-pressure steam pipe is provided in the feedwater pump turbine, and the nozzle area of the first regulating stage nozzle is adapted to the main steam turbine load in the range of 30% to 90% of the rated load.

[0019] Optionally, a second regulating stage nozzle connected to the outlet of the second low-pressure steam pipe is further provided in the feedwater pump turbine, and the nozzle area of the second regulating stage nozzle is smaller than the nozzle area of the first regulating stage nozzle.

[0020] Optionally, the small steam turbine system further includes:

[0021] exhaust pipe;

[0022] The exhaust pipe is connected to the feedwater pump turbine.

[0023] By means of the above technical solution, this application has at least the following beneficial effects:

[0024] The small steam turbine system provided in the embodiment of the present application, through the parallel setting of the first low-pressure steam pipe and the second low-pressure steam pipe and the flexible connection configuration according to the main steam turbine load, when the main steam turbine load is low (below 90% of the rated load), only the first low-pressure steam pipe is used to supply steam to the feedwater pump turbine, which can effectively utilize the energy of the low-pressure steam and keep the first regulation stage running in the high-efficiency range; when the main steam turbine load is high (exceeding 90% of the rated load), the first low-pressure steam pipe and the second low-pressure steam pipe are opened at the same time to increase the steam supply to meet the power demand of the feedwater pump turbine under high load. As a result, the small steam turbine system realizes the wide load and efficient operation of the small steam turbine in the deep peak regulation range, thereby improving the economy of the entire unit. At the same time, it avoids the problem of speed fluctuation of the feed pump turbine when the low-pressure steam source switches to the high-pressure steam source in the traditional "one high and one low" steam inlet scheme, so that the feed pump turbine can obtain the required steam smoothly under different loads, maintain stable speed and power output, improve the operating stability and reliability of the small steam turbine system, reduce equipment wear and failure caused by speed fluctuations, extend the service life of the equipment, and ensure the stable operation of the entire thermal power generation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic structural diagram of a small steam turbine system according to an optional embodiment of the present application.

[0026] The reference numerals indicate:

[0027] 1. Feedwater pump turbine; 2. First low-pressure steam pipe; 3. Second low-pressure steam pipe; 4. Four-extraction steam pipe; 5. Electric isolation valve; 6. First main steam valve; 7. First regulating valve; 8. Second main steam valve; 9. Second regulating valve; 10. Exhaust pipe. DETAILED DESCRIPTION

[0028] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0029] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0030] In this application, unless otherwise specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they can refer to fixed connection, detachable connection, or integral connection; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0031] The preferred embodiments of the present application are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present application and are not used to limit the present application.

[0032] See also Figure 1 As shown, according to an embodiment of the present application, a small steam turbine system is provided, including a feedwater pump turbine 1, a first low-pressure steam pipe 2 and a second low-pressure steam pipe 3; the power adjustment range of the feedwater pump turbine 1 at least covers the steam parameter change requirements when the main steam turbine load is in the range of 30% to 100% of the rated load; the first low-pressure steam pipe 2 and the second low-pressure steam pipe 3 are arranged in parallel, and are configured as follows: when the main steam turbine load is below 90% of the rated load, the feedwater pump turbine 1 is connected to the first low-pressure steam pipe 2; when the main steam turbine load exceeds 90% of the rated load, the feedwater pump turbine 1 is connected to the first low-pressure steam pipe 2 and the second low-pressure steam pipe 3 at the same time.

[0033] In the small steam turbine system provided in this embodiment, the power adjustment range of the feedwater pump turbine 1 covers at least the main steam turbine load in the range of 30% to 100% of the rated load, which can meet the steam parameter change requirements of the main steam turbine under different working conditions, so that the small steam turbine system can operate stably within a wide load range, improve the adaptability of the unit to different load conditions, and better meet the needs of power grid peak regulation.

[0034] The small steam turbine system provided in this embodiment, through the parallel arrangement of the first low-pressure steam pipe 2 and the second low-pressure steam pipe 3 and the flexible connection configuration according to the main steam turbine load, when the main steam turbine load is low (below 90% of the rated load), only the first low-pressure steam pipe 2 is used to supply steam to the feedwater pump turbine 1, which can effectively utilize the energy of the low-pressure steam and enable the first regulation stage to operate in the high-efficiency range; when the main steam turbine load is high (exceeding 90% of the rated load), the first low-pressure steam pipe 2 and the second low-pressure steam pipe 3 are opened at the same time to increase the steam supply to meet the power demand of the feedwater pump turbine 1 under high load. As a result, the small steam turbine system realizes the wide load and efficient operation of the small steam turbine in the deep peak regulation range, thereby improving the economy of the entire unit.

[0035] The small steam turbine system provided in this embodiment avoids the problem of speed fluctuation of the feedwater pump turbine 1 when the low-pressure steam source switches to the high-pressure steam source in the traditional "one high and one low" steam inlet scheme through the parallel arrangement of the first low-pressure steam pipe 2 and the second low-pressure steam pipe 3 and the flexible connection configuration according to the load of the main steam turbine. It enables the feedwater pump turbine 1 to smoothly obtain the required steam under different loads and maintain stable speed and power output, thereby improving the operating stability and reliability of the small steam turbine system, reducing equipment wear and failures that may be caused by speed fluctuations, extending the service life of the equipment, and ensuring the stable operation of the entire thermal power generation system.

[0036] In thermal power generation systems, the feedwater pump turbine 1, a key device that drives the feedwater pump, is often referred to as a small turbine compared to the main steam turbine. Its core function is to drive the feedwater pump, continuously delivering water from the deaerator to the boiler, ensuring stable power generation.

[0037] The feedwater pump steam turbine 1 in this embodiment has a wide range of power regulation capabilities, adapting to changes in steam parameters of the main steam turbine under different load conditions. Specifically, its power regulation range covers at least 30% to 100% of the main steam turbine's rated load, and can be expanded to wider load ranges such as 20% to 100%, 30% to 110%, or even 20% to 110%, to meet the operating requirements of different power generation scenarios.

[0038] Furthermore, to ensure efficient and stable steam supply, the small steam turbine system is equipped with two parallel pipelines: the first low-pressure steam pipe 2 and the second low-pressure steam pipe 3. These two pipelines work together to dynamically adjust steam input in response to changes in the main turbine load. When the main turbine is in a low-load state (90% or less of rated load), only the first low-pressure steam pipe 2 is activated. The steam parameters output by this pipeline precisely match the power requirements of the feedwater pump turbine 1 under these operating conditions, avoiding the speed fluctuations caused by the traditional "one high, one low" steam supply scheme when switching from a low-pressure steam source to a high-pressure source. For example, during periods of low grid power demand, if the main turbine load drops to 50% of rated load, the first low-pressure steam pipe 2 can independently supply sufficient steam to ensure stable operation of the feedwater pump turbine 1. When the main turbine load exceeds 90% of rated load and enters a high-load state, the system automatically activates the dual-pipeline parallel steam supply mode, with the first and second low-pressure steam pipes 2 and 3 operating synchronously, significantly increasing steam supply. When the main steam turbine is running at full load during the peak power consumption period of the power grid, the two pipelines work together to transport sufficient steam to ensure that the feedwater pump turbine 1 can output enough power to drive the feedwater pump to maintain stable boiler feed water pressure and flow, ensuring reliable operation of the unit under high load.

[0039] In some possible implementations disclosed in this application, see Figure 1 As shown, the small steam turbine system also includes a low-pressure steam source; the low-pressure steam source is four steam extraction pipes 4, and the four steam extraction pipes 4 are respectively connected to the first low-pressure steam pipe 2 and the second low-pressure steam pipe 3.

[0040] In this embodiment, the fourth extraction steam pipe 4 is a steam pipeline leading from the fourth extraction port of the main steam turbine. Its steam parameters are relatively stable. Using it as a low-pressure steam source, connected to the first low-pressure steam pipe 2 and the second low-pressure steam pipe 3, respectively, it can provide continuous and stable steam to the feedwater pump turbine 1, ensuring that the feedwater pump turbine 1 has a reliable power source under different main steam turbine loads, thereby improving the operational stability and reliability of the entire small steam turbine system.

[0041] As can be understood, using the fourth-stage extraction steam from the main steam turbine as the gas source for the feedwater pump steam turbine 1 achieves cascaded steam utilization. The fourth-stage extraction steam has already partially performed work in the main steam turbine. Introducing this steam into the small steam turbine system to drive the feedwater pump steam turbine 1 further utilizes the thermal energy of this steam, avoiding the energy waste caused by direct steam discharge, improving the energy utilization efficiency of the entire unit, and reducing energy consumption.

[0042] In some possible implementations disclosed in this application, see Figure 1 As shown, an electric isolation valve 5 is provided on the fourth steam extraction pipe 4.

[0043] Here, when it is necessary to inspect or maintain some equipment in the small steam turbine system (such as the first low-pressure steam pipe 2, the second low-pressure steam pipe 3, the feed water pump turbine 1, etc.), the electric isolation valve 5 can be closed to isolate the four-extraction steam pipe 4 from other components to prevent steam leakage, provide a safe working environment for maintenance personnel, facilitate inspection, repair and maintenance of related equipment, and improve the maintainability of the system.

[0044] It is understood that the electric isolation valve 5 can quickly cut off the steam supply in the event of an abnormal situation (such as a pipeline rupture, equipment failure, etc.), preventing large-scale steam leakage from causing safety accidents, reducing safety risks, protecting equipment and personnel, and improving the safety of the entire small steam turbine system. Specifically, the electric isolation valve 5 can flexibly control the opening and closing of the four-extraction steam pipe 4 according to actual operational needs. For example, during the system startup or shutdown process, the electric isolation valve 5 can be used to control the inflow and outflow of steam, ensuring smooth system startup and shutdown, and improving the system's operational flexibility and control accuracy.

[0045] In some possible implementations disclosed in this application, see Figure 1 As shown, the first low-pressure steam pipe 2 is provided with a first main steam valve 6 and a first regulating valve 7 .

[0046] In this embodiment, the first main steam valve 6 is used to control the on and off of steam. When the small steam turbine system is started, stopped or fails, by closing the first main steam valve 6, the steam supply of the first low-pressure steam pipe 2 can be quickly cut off to ensure the safety of the system. The first regulating valve 7 can accurately adjust the steam flow according to the actual operating requirements of the feedwater pump turbine 1. When the load of the main steam turbine changes, the first regulating valve 7 can adjust the opening accordingly so that the amount of steam entering the feedwater pump turbine 1 matches the operating conditions of the unit, ensuring the stable operation of the feedwater pump turbine 1, outputting appropriate power to drive the feedwater pump, and meeting the water supply needs of the boiler.

[0047] It is understood that the coordinated use of the first main steam valve 6 and the first regulating valve 7 can improve the precision of steam flow regulation. The first main steam valve 6 enables rapid steam shutoff and shutoff, while the first regulating valve 7 is responsible for fine flow regulation during steam flow. This combination enables more accurate steam flow control under various operating conditions, particularly at low loads or under conditions of frequent load fluctuations, thereby improving the operating efficiency and stability of the feedwater pump turbine 1.

[0048] In the above embodiment, see Figure 1 As shown, the first regulating valve 7 is arranged on the downstream side of the first main steam valve 6 along the steam flow direction.

[0049] Here, the first main steam valve 6 quickly shuts off the steam supply when the small steam turbine system starts, stops, or experiences a malfunction. Because the first regulating valve 7 is located downstream of the first main steam valve 6, damage to the first regulating valve 7 caused by the shock and high pressure generated during the steam on / off moment is avoided, extending its service life and improving its reliability.

[0050] It is understood that when the first main steam valve 6 is closed, the steam pressure on its upstream side is relatively high and stable, while the pressure on the downstream side is relatively low and fluctuates greatly. Placing the first regulating valve 7 on the downstream side allows flow regulation under a relatively stable pressure differential, which improves regulation accuracy and sensitivity, allowing for more accurate control of the steam flow entering the feedwater pump turbine 1 to meet operational requirements under varying operating conditions.

[0051] In some possible implementations disclosed in this application, see Figure 1 As shown, the second low-pressure steam pipe 3 is provided with a second main steam valve 8 and a second regulating valve 9.

[0052] In this embodiment, the second main steam valve 8 can independently control the steam on and off of the second low-pressure steam pipe 3. When the small steam turbine system needs to operate the second low-pressure steam pipe 3 separately, the steam can be cut off by closing the second main steam valve 8 to ensure the safety of related operations. At the same time, the second regulating valve 9 can accurately adjust the steam flow through the second low-pressure steam pipe 3 according to actual operating requirements. When the load of the main steam turbine increases, the second low-pressure steam pipe 3 is required to participate in the steam supply to meet the high-load operation of the feedwater pump turbine 1. The second regulating valve 9 can accurately control the steam flow so that the amount of steam entering the feedwater pump turbine 1 matches the required power.

[0053] It is understandable that the second main steam valve 8 and the second regulating valve 9 on the second low-pressure steam pipe 3 cooperate with the first main steam valve 6 and the first regulating valve 7 of the first low-pressure steam pipe 2 to achieve more flexible steam supply control. For example, under different main steam turbine load conditions, the steam supply method can be optimized by adjusting the main steam valve and the regulating valve on the two pipelines respectively, so as to make the operation of the feedwater pump turbine 1 more efficient. Under partial load conditions, the steam supply may mainly rely on the first low-pressure steam pipe 2, and fine adjustment may be performed through the first regulating valve 7; under high load conditions, in addition to the first low-pressure steam pipe 2 continuing to supply steam, the second main steam valve 8 can be opened, and the steam supply of the second low-pressure steam pipe 3 can be adjusted by the second regulating valve 9 to achieve dual-pipe coordinated steam supply, which can flexibly meet the steam demand of the feedwater pump turbine 1 under different working conditions.

[0054] In the above embodiment, see Figure 1 As shown, the second regulating valve 9 is arranged on the downstream side of the second main steam valve 8 along the steam flow direction.

[0055] Here, the second regulating valve 9 is located on the downstream side of the second main steam valve 8, which can avoid damage to the regulating valve caused by water hammer, high-pressure shock, etc. generated at the moment of steam on and off, thereby extending the service life of the second regulating valve 9 and improving its working stability and reliability.

[0056] In some possible embodiments disclosed in the present application, a first regulating stage nozzle connected to the outlet of the first low-pressure steam pipe 2 is provided in the feed water pump turbine 1, and the nozzle area of the first regulating stage nozzle is adapted to the main steam turbine load in the range of 30% to 90% of the rated load.

[0057] In this embodiment, the design of the first regulating stage nozzle abandons the disadvantages of the traditional large flow margin design scheme of the feed water pump turbine 1 (margin ≥ 30%). Its nozzle area is adapted to the operating conditions of the main steam turbine load in the range of 30% to 90% of the rated load, and can match the steam inlet flow of the first low-pressure steam pipe 2, thereby improving the operating efficiency of the feed water pump turbine 1 and ensuring the efficient operation of the feed water pump turbine 1 under deep peak-shaving conditions.

[0058] Understandably, due to excessive design margins, the low-pressure steam source inlet flow rate during actual operation is far below the maximum flow design capacity, causing the feedwater pump turbine 1 to operate in an inefficient state for a long period of time, with operating efficiency generally below 70%. However, the first regulating stage nozzle in this embodiment can match the inlet flow rate of the first low-pressure steam pipe 2, improving the operating efficiency of the feedwater pump turbine 1 and enabling it to maintain efficient and stable operation under deep peak-shaving conditions. This effectively solves the long-standing low efficiency problem of the traditional solution and helps the entire thermal power generation system achieve energy conservation, efficiency improvement, and stable operation.

[0059] In the above embodiment, a second regulating stage nozzle connected to the outlet of the second low-pressure steam pipe 3 is further provided in the feedwater pump turbine 1 , and the nozzle area of the second regulating stage nozzle is smaller than that of the first regulating stage nozzle.

[0060] Here, the second regulating stage nozzle has a smaller area and, in conjunction with the first regulating stage nozzle, can better adapt to changes in steam flow under different main turbine loads. When the main turbine load is between 30% and 90% of the rated load, the steam demand of the feedwater pump turbine 1 is primarily met by the first regulating stage nozzle in conjunction with the first low-pressure steam pipe 2. At this time, the first regulating stage nozzle has a larger area and can pass a larger steam flow. When the main turbine load exceeds 90% of the rated load, the second low-pressure steam pipe 3 is put into use. Although the second regulating stage nozzle has a smaller area, it can accurately supplement the appropriate amount of steam based on the current operating conditions. Working together with the first regulating stage nozzle, it ensures that the feedwater pump turbine 1 can obtain the appropriate amount of steam even under high load to meet the power output requirements.

[0061] In some possible implementations disclosed in this application, see Figure 1 As shown, the small steam turbine system further includes an exhaust pipe 10 ; the exhaust pipe 10 is connected to the feedwater pump turbine 1 .

[0062] In this embodiment, an exhaust pipe 10 is provided to provide a channel for the feedwater pump steam turbine 1 to discharge the steam after work, so that the steam can be smoothly discharged from the feedwater pump steam turbine 1, thereby ensuring the normal operation of the feedwater pump steam turbine 1.

[0063] It is understandable that during the working process of the feedwater pump steam turbine 1, after the steam drives the impeller to rotate, its energy decreases and needs to be discharged in a timely manner to maintain the pressure balance and normal working cycle within the feedwater pump steam turbine 1. Discharging the steam through the exhaust pipe 10 can avoid excessive pressure caused by steam accumulation inside the feedwater pump steam turbine 1, thereby ensuring the stability and safety of the operation of the feedwater pump steam turbine 1 and the entire small steam turbine system, and preventing damage to the equipment due to faults such as overpressure.

[0064] It is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0065] The above are merely preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application. The above are merely preferred embodiments of the present application. It should be noted that those skilled in the art may make various improvements and variations without departing from the technical principles of the present application, and such improvements and variations shall also be considered within the scope of protection of the present application.

Claims

1. A small steam turbine system, characterized in that: include: A feedwater pump turbine (1), a first low-pressure steam pipe (2), and a second low-pressure steam pipe (3); The power adjustment range of the feedwater pump steam turbine (1) at least covers the steam parameter change requirements when the main steam turbine load is within the range of 30% to 100% of the rated load; The first low-pressure steam pipe (2) and the second low-pressure steam pipe (3) are arranged in parallel and are configured such that: when the load of the main steam turbine is below 90% of the rated load, the feedwater pump steam turbine (1) is connected to the first low-pressure steam pipe (2); when the load of the main steam turbine exceeds 90% of the rated load, the feedwater pump steam turbine (1) is simultaneously connected to the first low-pressure steam pipe (2) and the second low-pressure steam pipe (3).

2. The small steam turbine system according to claim 1, characterized in that: Also includes: Low-pressure steam source; The low-pressure steam source is a four-extraction steam pipe (4), and the four-extraction steam pipe (4) is respectively connected to the first low-pressure steam pipe (2) and the second low-pressure steam pipe (3).

3. The small steam turbine system according to claim 2, characterized in that: The four-extraction steam pipe (4) is provided with an electric isolation valve (5).

4. The small steam turbine system according to claim 1, characterized in that: The first low-pressure steam pipe (2) is provided with a first main steam valve (6) and a first regulating valve (7).

5. The small steam turbine system according to claim 4, characterized in that: The first regulating valve (7) is arranged on the downstream side of the first main steam valve (6) along the steam flow path.

6. The small steam turbine system according to claim 1, characterized in that: The second low-pressure steam pipe (3) is provided with a second main steam valve (8) and a second regulating valve (9).

7. The small steam turbine system according to claim 6, characterized in that: The second regulating valve (9) is arranged on the downstream side of the second main steam valve (8) along the steam flow path.

8. The small steam turbine system according to claim 1, characterized in that: The feedwater pump turbine (1) is provided with a first regulating stage nozzle connected to the outlet of the first low-pressure steam pipe (2), and the nozzle area of the first regulating stage nozzle is adapted to the load of the main steam turbine in the range of 30% to 90% of the rated load.

9. The small steam turbine system according to claim 8, characterized in that: The feedwater pump turbine (1) is further provided with a second regulating stage nozzle connected to the outlet of the second low-pressure steam pipe (3), and the nozzle area of the second regulating stage nozzle is smaller than the nozzle area of the first regulating stage nozzle.

10. The small steam turbine system according to claim 1, characterized in that: Also includes: exhaust pipe (10); The exhaust pipe (10) is connected to the feedwater pump turbine (1).

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