A combined pressure stage external turbine unit and method of operation thereof

Abstract

The application provides a steam turbine unit with external combined pressure stages and a running method thereof. The steam turbine unit comprises a boiler (10), a high-pressure cylinder (11) and a first rotating shaft (12), a main steam valve (15) and a main path control valve (16) are arranged on a main steam pipeline in sequence along a steam flow direction; the steam turbine unit further comprises a second rotating shaft (13), an energy conversion device (14) and at least two regulating pressure stages (21, 22, 23), the regulating pressure stages (21, 22, 23) are connected in parallel, an inlet end of the main path control valve (16) is connected to a steam inlet branch of the regulating pressure stages (21, 22, 23), and an outlet end of the main path control valve (16) is connected to a steam outlet branch of the regulating pressure stages (21, 22, 23) through a bypass control valve (17), and each regulating pressure stage (21, 22, 23) can be selectively conducted. By combining the regulating pressure stages with different flow areas into multiple combination forms through different connection modes, and binding different combination forms with different load intervals one by one, under different load intervals, the steam turbine unit can actively adapt by switching to different external combined pressure stages, gradually increases working links under medium and low load conditions, improves the regulating capacity of the steam turbine unit and improves the operation energy efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of steam turbine power generation, and in particular relates to a steam turbine unit with an external combined pressure stage and an operating method thereof. Background Art

[0002] With the large-scale entry of new energy into the power grid, the power system needs to achieve a balance between the supply and demand of energy between the randomly fluctuating load demand and the randomly fluctuating power supply. Its structural form, operation and control mode, as well as planning, construction and management will undergo fundamental changes.

[0003] In the new generation of power systems, coal-fired power units are required to fully participate in deep peak regulation. During the process of participating in deep peak regulation, coal-fired power units need to operate for a long time under high, medium and low load conditions. However, coal-fired power units designed according to rated load conditions will have a sharp drop in power generation efficiency under medium and low load conditions, a significant increase in coal consumption, and poor regulation capabilities of the units, making it impossible to maintain efficient operation under various load conditions. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the purpose of the present invention is to provide a steam turbine unit with an external combined pressure stage and an operating method thereof, which is mainly used to solve the problems in the existing technology such as poor adjustment ability of the steam turbine unit, inability to adapt to variable load conditions, resulting in low energy efficiency, etc.

[0005] In order to solve the above problems, the technical solutions adopted by the present invention are as follows:

[0006] In a first aspect, the present invention provides a steam turbine unit with an external combined pressure stage, comprising a boiler, a high-pressure cylinder, and a first rotating shaft, wherein a main steam outlet of the boiler is connected to a steam inlet pipe of the high-pressure cylinder via a main steam pipe, a main steam valve and a main control valve being provided on the main steam pipe in sequence along the direction of steam flow, and the high-pressure cylinder is connected to the first rotating shaft;

[0007] It also includes a second rotating shaft, an energy conversion device and at least two regulating pressure stages. The regulating pressure stages and the energy conversion device are arranged in sequence along the central axis direction of the second rotating shaft. After the regulating pressure stages are connected in parallel, their steam inlet branches are connected to the inlet end of the main control valve, and their steam outlet branches are connected to the outlet end of the main control valve through a bypass control valve. Each of the regulating pressure stages can be selectively connected.

[0008] In some embodiments, a steam inlet regulating valve is provided between each of the regulating pressure stages and the steam inlet branch, and a steam outlet regulating valve is provided between each of the regulating pressure stages and the steam outlet branch.

[0009] In some embodiments, a steam inlet regulating valve is provided between each of the regulating pressure stages and the steam inlet branch, and a steam outlet regulating valve is provided between the steam outlet ends of two adjacent regulating pressure stages.

[0010] In some embodiments, along the central axis direction of the second rotating shaft, the steam outlet end of the preceding regulating pressure stage is connected to the steam inlet end of the succeeding regulating pressure stage through an intermediate regulating valve.

[0011] In some embodiments, the regulating pressure stages are arranged in the same direction or in pairs in opposite directions along the steam flow direction.

[0012] In some embodiments, the flow areas of the different regulating pressure levels become larger along the steam flow direction.

[0013] In some embodiments, a heat recovery system is further included, wherein the high-pressure cylinder is connected to the first high-pressure heater through a first heat recovery valve, and the outlet pipes of the main control valve and the bypass control valve are merged and connected to the first high-pressure heater through a second heat recovery valve.

[0014] In some embodiments, a condenser and a low-pressure heat exchange device are further included, and a steam outlet end of at least one of the regulating pressure stages is provided with a steam extraction valve, which is connected to the condenser or the low-pressure heat exchange device through a pipeline.

[0015] In some embodiments, a cooling steam valve is provided at the steam inlet end of at least one of the regulating pressure stages, and the cooling steam valve is connected to a steam source whose pressure is greater than the pressure at the steam extraction valve, and the steam source includes but is not limited to at least one of a main steam pipe, a reheat steam pipe, and a steam main pipe.

[0016] In a second aspect, the present invention further provides an operating method for the above-mentioned steam turbine unit with an external combined pressure stage, comprising:

[0017] Divide the control load interval according to the number of adjustment pressure levels, and the control load interval includes but is not limited to a high load interval, a medium-high load interval, a medium load interval and a low load interval;

[0018] Detect or set the operating interval point and determine the control load interval in which the operating interval point falls:

[0019] When the operating range point falls into the high load range, only the high-pressure cylinder is put into operation, and all the regulating pressure levels are idle or shut down;

[0020] When the operating range point falls into the medium-high load range, the pressure stages are adjusted to operate in parallel and then connected to the high-pressure cylinder;

[0021] When the operation interval point falls into the intermediate load interval, a single regulating pressure stage is put into operation, and the high-pressure cylinder is reconnected;

[0022] When the operation interval point falls into the low load interval, the regulating pressure stages are operated in series, and the high-pressure cylinder is reconnected.

[0023] In some embodiments, the intermediate load interval is divided into a plurality of sub-intermediate intervals;

[0024] According to the number and flow area of the regulating pressure stages, a plurality of pressure stage combination forms with unit steam enthalpy drop conversion capacity from small to large are combined;

[0025] A plurality of sub-intermediate intervals from high to low are bound to the pressure stage combination forms arranged in the order of unit steam enthalpy drop conversion capacity from small to large.

[0026] In some embodiments, the intermediate load interval is divided into a plurality of sub-intermediate intervals;

[0027] According to the unit steam enthalpy drop conversion capacity of the regulating pressure stages, the regulating pressure stages are arranged in the order of small to large;

[0028] A plurality of sub-intermediate intervals from high to low are bound to the regulating pressure stages arranged in the order of unit steam enthalpy drop conversion capacity from small to large.

[0029] In some embodiments, the low load interval is divided into a plurality of sub-low intervals;

[0030] According to the number and flow area of the regulating pressure stages, a plurality of pressure stage combination forms with unit steam enthalpy drop conversion capacity from small to large are combined;

[0031] A plurality of sub-low intervals from high to low are bound to the pressure stage combination forms arranged in the order of unit steam enthalpy drop conversion capacity from small to large.

[0032] In some embodiments, when the regulating pressure stage is in the state of being isolated into steam inlet and steam exhaust and entering the idle state, the corresponding steam extraction valve is opened.

[0033] In some embodiments, detection data is obtained to determine whether the cooling flow is sufficient;

[0034] If the cooling flow is insufficient, the cooling steam valve is opened.

[0035] Compared with the prior art, the present application at least has the following beneficial effects:

[0036] After connecting multiple regulating pressure stages in parallel at both ends of the main control valve, multiple regulating pressure stages can be switched into parallel connection mode, series connection mode or independent conduction connection mode through valves. By combining regulating pressure stages with different flow areas into multiple combination forms using different connection methods, and then binding different combination forms to different load ranges one by one, it is possible to actively adapt to different load ranges by switching to different external combined pressure stages, gradually increase the working links under medium and low load conditions, maintain a higher unit operating pressure, improve the unit's regulation capability, and improve operating energy efficiency.

[0037] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention is further described with reference to the accompanying drawings. However, the embodiments in the accompanying drawings do not constitute any limitation to the present invention. A person skilled in the art can obtain other drawings based on the following drawings without creative effort.

[0039] Figure 1 This is a structural diagram of a steam turbine unit with an external combined pressure stage provided in Example 1.

[0040] Figure 2 It is a structural schematic diagram of a steam turbine unit arranged in reverse under one embodiment.

[0041] Figure 3 This is a flow chart of an operating method of a steam turbine unit with an external combined pressure stage provided in Example 2.

[0042] Description of Figure Numbers:

[0043] 10 Boiler; 11 High-pressure cylinder; 12 First rotating shaft; 13 Second rotating shaft; 14 Energy conversion device; 15 Main steam valve; 16 Main line control valve; 17 Bypass control valve; 18 First reheat valve; 19 Second reheat valve; 21 First regulating pressure stage; 22 Second regulating pressure stage; 23 Third regulating pressure stage; 31 First steam inlet regulating valve; 32 Second steam inlet regulating valve; 33 Third steam inlet regulating valve; 41 First steam outlet regulating valve; 42 Second steam outlet regulating valve; 51 First intermediate regulating valve; 52 Second intermediate regulating valve; 61 Extraction valve; 62 Cooling steam valve; 63 First high-pressure heater; 64 Reheat system; 65 Condenser. DETAILED DESCRIPTION

[0044] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0045] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0046] In the description of the present invention, when a specific device is described as being located between a first device and a second device, an intervening device may or may not be present between the specific device and the first device or the second device. When a specific device is described as being connected to another device, the specific device may be directly connected to the other device without an intervening device, or may be directly connected to the other device but with an intervening device.

[0047] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0048] Example 1:

[0049] Reference Figure 1 This embodiment 1 provides a steam turbine unit with an external combined pressure stage, including a boiler 10, a high-pressure cylinder 11, and a first rotating shaft 12. The main steam outlet of the boiler 10 is connected to the steam inlet of the high-pressure cylinder 11 via a main steam pipe. A main steam valve 15 and a main control valve 16 are provided on the main steam pipe in the direction of steam flow. The main steam first passes through the main steam valve 15 and then through the main control valve 16. The high-pressure cylinder 11 is connected to the first rotating shaft 12. Of course, the first rotating shaft 12 is also connected to the intermediate-pressure cylinder, the low-pressure cylinder, and the generator.

[0050] More specifically, it also includes a second rotating shaft 13, an energy conversion device 14 and three regulating pressure stages, the regulating pressure stages are divided into a first regulating pressure stage 21, a second regulating pressure stage 22 and a third regulating pressure stage 23, the first regulating pressure stage 21, the second regulating pressure stage 22, the third regulating pressure stage 23 and the energy conversion device 14 are arranged in sequence from front to back along the central axis direction of the second rotating shaft 13, the steam inlet ends of the three regulating pressure stages are connected to a steam inlet branch, the steam outlet ends of the three regulating pressure stages are connected to a steam outlet branch, the steam inlet branch is then connected to the inlet end of the main control valve 16, the steam inlet branch is connected between the main steam valve 15 and the main control valve 16, and the steam outlet branch is connected to the outlet end of the main control valve 16 through the bypass control valve 17 Connection, the bypass control valve 17 can control whether the steam outlet of the three regulating pressure levels can be connected to the steam inlet end of the high-pressure cylinder 11. In the parallel path composed of the three regulating pressure levels, each regulating pressure level can be selectively turned on, that is, one of the regulating pressure level groups can be selected to be put into operation separately, or two or three of them can be put into operation at the same time. When different combinations are selected, the processing capacity of the working block composed of the three regulating pressure level groups will be different. The main steam coming out of the boiler 10 will undergo different degrees of work before entering the high-pressure cylinder 11. By constructing a working block with a processing capacity that can change according to the actual load conditions, the operating energy efficiency under different load conditions can be improved, and the adjustment ability and adaptability of the unit can be improved.

[0051] As an implementation method, a steam inlet regulating valve is provided between each regulating pressure stage and the steam inlet branch, and a steam outlet regulating valve is provided between each regulating pressure stage and the steam outlet branch. Through the steam inlet regulating valve and steam outlet regulating valve corresponding to each regulating pressure stage, the regulating pressure stage that does not need to be operated can be selectively isolated, and the control is precise.

[0052] As another embodiment, a steam inlet regulating valve is provided between each regulating pressure stage and the steam inlet branch, and a steam outlet regulating valve is provided between the steam outlet ends of two adjacent regulating pressure stages. Only two steam outlet regulating valves are required for three regulating pressure stages to achieve isolation between the steam outlet ends of adjacent regulating pressure stages. This method is preferred when there are fewer regulating pressure stages and they are opened in sequence from front to back.

[0053] Reference Figure 1 In this embodiment, a first steam inlet regulating valve 31 is provided before the first regulating pressure stage 21, a second steam inlet regulating valve 32 is provided before the second regulating pressure stage 22, and a third steam inlet regulating valve 33 is provided before the third regulating pressure stage 23. A first steam outlet regulating valve 41 is provided between the steam outlet ends of the first regulating pressure stage 21 and the second regulating pressure stage 22, and a second steam outlet regulating valve 42 is provided between the steam outlet ends of the second regulating pressure stage 22 and the third regulating pressure stage 23.

[0054] In this embodiment, along the central axis of the second rotating shaft 13 from front to back, the steam outlet end of the previous regulating pressure stage is connected to the steam inlet end of the next regulating pressure stage through an intermediate regulating valve, that is, the steam outlet end of the first regulating pressure stage 21 is connected to the outlet pipeline of the second steam inlet regulating valve 32 at the steam inlet end of the second regulating pressure stage 22 through the first intermediate regulating valve 51, and then connected to the steam inlet end pipeline of the second regulating pressure stage 22. Similarly, the steam outlet end of the second regulating pressure stage 22 is connected to the outlet pipeline of the third steam inlet regulating valve 33 at the steam inlet end of the third regulating pressure stage 23 through the second intermediate regulating valve 52, and then connected to the steam inlet end pipeline of the third regulating pressure stage 23. By opening the first intermediate regulating valve 51 and the second intermediate regulating valve 52 and closing the first steam outlet regulating valve 41 and the second steam outlet regulating valve 42, the parallel-connected regulating pressure stages can be switched to a series connection to increase the flow area to the maximum to adapt to lower working conditions.

[0055] As an embodiment, the regulating pressure stages are arranged in the same direction or in pairs in opposite directions along the steam flow direction; more specifically, Figure 1 In the middle, it is arranged in the same direction, and all the regulating pressure stages have steam inlet on the left and steam outlet on the right. Figure 2 In the reverse arrangement, they are arranged in pairs, and each pair is arranged in reverse. If there are four regulating pressure stages, the first two regulating pressure stages are arranged in reverse, and the last two regulating pressure stages are arranged in reverse. Figure 2 Two regulated pressure levels are shown.

[0056] Preferably, the flow areas of the different regulating pressure stages increase in size along the steam flow direction, i.e., the first regulating pressure stage 21 has the smallest flow area, the second regulating pressure stage 22 has the second largest flow area, and the third regulating pressure stage 23 has the largest flow area, arranged in ascending order. This arrangement facilitates opening the regulating pressure stages from smallest to largest as the load decreases. It should also be noted that the larger the flow area of ​​the regulating pressure stage, the greater its unit steam enthalpy drop conversion capacity.

[0057] In some embodiments, a heat recovery system 64 is further included, which includes a first high-pressure heater 63. The high-pressure cylinder 11 is connected to the first high-pressure heater 63 through a first heat recovery valve 18. The first heat recovery valve 18 is connected to the middle of the high-pressure cylinder 11 through a pipeline. The outlet pipelines of the main control valve 16 and the bypass control valve 17 are merged and connected to the first high-pressure heater 63 through a second heat recovery valve 19. That is, by controlling the first heat recovery valve 18 and the second heat recovery valve 19, steam in different states can be selected to enter the heat recovery. Even under extreme working conditions, the steam mainly enters the first high-pressure heater 63 through the second heat recovery valve 19, reducing the flow entering the high-pressure cylinder 11 to meet the set heat recovery requirements.

[0058] In some embodiments, a condenser 65 and a low-pressure heat exchange device are also included. The steam outlet end of at least one regulating pressure stage is provided with a steam extraction valve 61. The steam extraction valve 61 is connected to the condenser 65 or the low-pressure heat exchange device through a pipeline. When the corresponding regulating pressure stage is isolated from the steam intake and exhaust, it enters the idling state, and the corresponding steam extraction valve 61 can be opened to prevent steam from flowing back into the regulating pressure stage, resulting in its blast loss, and achieving basic cooling through steam leakage. The steam extraction valve 61 is connected to the condenser 65 or the low-pressure heat exchange device with lower pressure to guide the leaked steam through the pressure difference.

[0059] In some embodiments, a cooling steam valve 62 is provided at the steam inlet end of at least one regulating pressure stage. The cooling steam valve 62 is connected to a steam source whose pressure is greater than the pressure at the steam extraction valve 61. The steam source includes but is not limited to at least one of a main steam pipe, a reheat steam pipe, and a steam main pipe. This means that at the same regulating pressure stage, a steam extraction valve 61 and a cooling steam valve 62 are respectively provided. After the steam extraction valve 61 is opened, when the cooling flow is insufficient and the cooling effect is not ideal due to steam leakage cooling, the cooling steam valve 62 can be opened to introduce steam from a steam source with a higher pressure to realize steam circulation in the corresponding regulating pressure stage, thereby further improving the cooling flow.

[0060] Each regulating pressure stage can be provided with a steam extraction valve 61 and a cooling steam valve 62. When combined into different combinations according to actual needs, the isolated regulating pressure stage can also be cooled by the steam extraction valve 61 and the cooling steam valve 62 to reduce blast loss.

[0061] Example 2:

[0062] Reference Figure 3 This embodiment 2 provides an operating method for the steam turbine unit with an external combined pressure stage applied to the above embodiment, comprising:

[0063] According to the number of regulating pressure levels, the control load interval is divided, and the control load interval includes but is not limited to a high load interval, a medium-high load interval, an intermediate load interval and a low load interval;

[0064] Detect or set an operating interval point, and determine the control load interval within which the operating interval point falls. It should be noted that the operating interval point can be detected during actual operation. As the load of the actual unit changes, the operating interval point will also change accordingly and may fall into any control load interval. Of course, it can also be achieved through active control. When actively adjusting the load, by setting an operating interval point, the unit can be operated to the corresponding load point:

[0065] When the operating range point falls into the high-load range, only the high-pressure cylinder 11 is put into operation. The high-pressure cylinder 11 can be regarded as being in the rated operating state, and no other regulating pressure stages are required to be put into operation. Therefore, all regulating pressure stages are idle or shut down. More specifically, the main control valve 16 is opened, and the first steam inlet regulating valve 31, the second steam inlet regulating valve 32, the third steam inlet regulating valve 33, the first steam outlet regulating valve 41, the second steam outlet regulating valve 42 and the bypass control valve 17 are closed. This is equivalent to supplying steam to the high-pressure cylinder 11 only through the main steam pipeline, and the second rotating shaft 13 is not involved in the operation.

[0066] When the operating range falls into the medium-to-high load range, the regulating pressure stages are operated in parallel, and then connected to the high-pressure cylinder 11. The main control valve 16 is closed, and the specific regulating pressure stage for parallel operation is selected. The regulating valves before and after it are opened to connect it to the steam inlet branch and the steam outlet branch. Since the flow area of ​​the several regulating pressure stages operating in parallel is small, it is suitable to be put into operation when the load drops slightly. Therefore, a working block with smaller working capacity is connected in series before the high-pressure cylinder 11 to adapt to the load condition at this time.

[0067] When the operating range point falls into the intermediate load range, a single regulating pressure stage is put into operation, and then connected to the high-pressure cylinder 11. The main control valve 16 is closed, and the regulating pressure stage for separate operation is selected. The regulating valves before and after it are opened to connect it to the steam inlet branch and the steam outlet branch. At the same time, the regulating valves of other regulating pressure stages are closed. A single regulating pressure stage has a stronger work capacity than several regulating pressure stages connected in parallel. Therefore, a working unit with a larger work capacity is connected in series before the high-pressure cylinder 11 to adapt to the load condition at this time.

[0068] When the operating range point falls into the low load range, the regulating pressure stages are operated in series, and then connected to the high-pressure cylinder 11, the main control valve 16 is closed, the regulating pressure stage that needs to be operated in series is selected, and the corresponding steam outlet regulating valve and / or intermediate regulating valve are opened, so that the steam outlet end of the front regulating pressure stage is directly connected to the steam inlet end of the rear regulating pressure stage, and the regulating pressure stages with different working capacities are connected in series, and a working unit with greater working capacity is connected in series before the high-pressure cylinder 11 to adapt to the load conditions at this time.

[0069] This embodiment switches to different pressure-stage combinations based on actual operating ranges. By implementing parallel, independent, and series operation, and by controlling the number of units in operation, this approach enables adaptive adjustments in medium-to-high load, intermediate load, and low load ranges. The concept of unit steam enthalpy drop conversion capacity is used to describe the differences between different pressure-stage combinations. Lower loads and flow rates correspond to higher unit steam enthalpy drop conversion capacity for the corresponding pressure-stage combination.

[0070] As an implementation method, the medium-high load interval is divided into four sub-medium-high intervals;

[0071] According to the number of regulating pressure stages and the flow area, several pressure stage combinations with increasing unit steam enthalpy drop conversion capacity are formed. In this embodiment, since the flow areas of the first regulating pressure stage 21, the second regulating pressure stage 22, and the third regulating pressure stage 23 are increasingly larger, according to the order of increasing unit steam enthalpy drop conversion capacity, the first combination is the first regulating pressure stage 21, the second regulating pressure stage 22, and the third regulating pressure stage 23 connected in parallel, the second combination is the first regulating pressure stage 21 and the second regulating pressure stage 22 connected in parallel, the third combination is the first regulating pressure stage 21 and the third regulating pressure stage 23 connected in parallel, and the fourth combination is the second regulating pressure stage 22 and the third regulating pressure stage 23 connected in parallel;

[0072] The four sub-middle-high intervals from high to low are bound one by one to the pressure level combination forms arranged from small to large according to the unit steam enthalpy drop conversion capacity. When the operating interval point falls into a specific sub-middle-high interval, the corresponding pressure level combination form is operated.

[0073] In the medium and high load range, the main control valve 16 is closed, the bypass control valve 17 is opened, and the first intermediate regulating valve 51 and the second intermediate regulating valve 52 remain closed;

[0074] In the first sub-medium-high range, the first regulating pressure stage 21, the second regulating pressure stage 22, and the third regulating pressure stage 23 need to be put into operation, and the first steam inlet regulating valve 31, the second steam inlet regulating valve 32, the third steam inlet regulating valve 33, the first steam outlet regulating valve 41, and the second steam outlet regulating valve 42 are all opened;

[0075] In the second sub-medium-high range, the first regulating pressure stage 21 and the second regulating pressure stage 22 need to be put into operation, the first steam inlet regulating valve 31, the second steam inlet regulating valve 32, the first steam outlet regulating valve 41 and the second steam outlet regulating valve 42 are all opened, and the third steam inlet regulating valve 33 is closed;

[0076] In the third sub-medium-high range, the first regulating pressure stage 21 plus the third regulating pressure stage 23 need to be put into operation, the first steam inlet regulating valve 31, the third steam inlet regulating valve 33, the first steam outlet regulating valve 41 and the second steam outlet regulating valve 42 are all opened, and the second steam inlet regulating valve 32 is closed;

[0077] In the fourth sub-middle-high range, the second regulating pressure stage 22 plus the third regulating pressure stage 23 need to be put into operation, the second steam inlet regulating valve 32, the third steam inlet regulating valve 33 and the second steam outlet regulating valve 42 are all opened, and the first steam inlet regulating valve 31 and the first steam outlet regulating valve 41 are closed.

[0078] As an implementation method, the intermediate load interval is divided into three sub-intermediate intervals;

[0079] Arrange the regulating pressure stages from smallest to largest according to their unit steam enthalpy drop conversion capacity;

[0080] The three sub-intermediate intervals from high to low are bound one by one to the regulating pressure levels arranged from small to large according to the unit steam enthalpy drop conversion capacity;

[0081] In the intermediate load range, the main control valve 16 is closed, the bypass control valve 17 is opened, and the first intermediate regulating valve 51 and the second intermediate regulating valve 52 remain closed.

[0082] The first sub-intermediate interval corresponds to the first regulating pressure level 21. In this mode, the first steam inlet regulating valve 31, the first steam outlet regulating valve 41, and the second steam outlet regulating valve 42 are opened, and the second steam inlet regulating valve 32 and the third steam inlet regulating valve 33 are closed.

[0083] The second sub-intermediate interval corresponds to the second regulating pressure level 22. In this mode, the second steam inlet regulating valve 32 and the second steam outlet regulating valve 42 are opened, and the first steam inlet regulating valve 31, the third steam inlet regulating valve 33, and the first steam outlet regulating valve 41 are closed.

[0084] The third sub-intermediate interval corresponds to the second regulating pressure level 22. In this mode, the third steam inlet regulating valve 33 is opened, and the first steam inlet regulating valve 31, the second steam inlet regulating valve 32, the first steam outlet regulating valve 41, and the second steam outlet regulating valve 42 are closed.

[0085] As an implementation method, the low load interval is divided into four sub-low intervals;

[0086] According to the number of regulating pressure stages and the flow area, a plurality of pressure stage combinations with increasing unit steam enthalpy drop conversion capacity are formed; in order of increasing unit steam enthalpy drop conversion capacity, the first combination is the first regulating pressure stage 21 plus the second regulating pressure stage 22 connected in series, the second combination is the first regulating pressure stage 21 plus the third regulating pressure stage 23 connected in series, the third combination is the second regulating pressure stage 22 plus the third regulating pressure stage 23 connected in series, and the fourth combination is the first regulating pressure stage 21, the second regulating pressure stage 22 and the third regulating pressure stage 23 connected in series.

[0087] Bind a number of sub-low intervals from high to low to pressure level combinations arranged in ascending order of steam processing capacity;

[0088] In the low load range, the main control valve 16 is closed and the bypass control valve 17 is opened;

[0089] In the first sub-low range, the first regulating pressure stage 21 and the second regulating pressure stage 22 need to be put into operation, the first steam inlet regulating valve 31, the first intermediate regulating valve 51 and the second steam outlet regulating valve 42 are opened, and the second steam inlet regulating valve 32, the third steam inlet regulating valve 33, the second intermediate regulating valve 52 and the first steam outlet regulating valve 41 are closed;

[0090] In the second sub-low range, the first regulating pressure stage 21 and the third regulating pressure stage 23 need to be put into operation, the first steam inlet regulating valve 31, the first steam outlet regulating valve 41 and the second intermediate regulating valve 52 are opened, and the second steam inlet regulating valve 32, the third steam inlet regulating valve 33, the second steam outlet regulating valve 42 and the first intermediate regulating valve 51 are closed;

[0091] In the third sub-low range, the second regulating pressure stage 22 and the third regulating pressure stage 23 need to be put into operation, the second steam inlet regulating valve 32 and the second intermediate regulating valve 52 need to be opened, and the first steam inlet regulating valve 31, the third steam inlet regulating valve 33, the first steam outlet regulating valve 41, the second steam outlet regulating valve 42, and the first intermediate regulating valve 51 need to be closed;

[0092] In the fourth sub-low interval, it is necessary to put the first regulating pressure stage 21, the second regulating pressure stage 22 and the third regulating pressure stage 23 into operation, open the first steam inlet regulating valve 31, the first intermediate regulating valve 51 and the second intermediate regulating valve 52, and close the second steam inlet regulating valve 32, the third steam inlet regulating valve 33, the first steam outlet regulating valve 41 and the second steam outlet regulating valve 42.

[0093] Through the above connection method, the first regulating pressure stage 21, the second regulating pressure stage 22 and the third regulating pressure stage 23 can be connected in parallel, operated separately and in series. By combining them into various structural forms, work blocks with different unit steam enthalpy drop conversion capabilities can be formed to adapt to different actual operating load conditions.

[0094] As an implementation method, in the above three connection modes of parallel, single operation and series, there will be some isolated regulating pressure stages, which do not need to be put into operation at the current operating range point. Therefore, when the regulating pressure stage is in the state of isolated steam inlet and exhaust and enters the idling state, its corresponding steam extraction valve 61 is opened to allow steam to leak from the steam extraction valve to avoid steam backflow into the isolated regulating pressure stage, resulting in its blast loss, and basic cooling can be achieved through the steam leakage.

[0095] As an implementation method, detection data is obtained to determine whether the cooling flow rate is sufficient;

[0096] If the cooling flow is insufficient, open the cooling steam valve 62;

[0097] It should be noted that when the cooling flow is insufficient and the cooling effect is not ideal through steam leakage cooling, it is possible to determine whether the unit is properly cooled through detection data. If the data feedback shows that the cooling is insufficient, the cooling steam valve 62 is opened to introduce steam from a higher pressure steam source to achieve steam circulation within the corresponding regulated pressure level, thereby further improving the cooling flow.

[0098] In summary, compared with the prior art, the above embodiment provides a steam turbine unit with an external combined pressure stage and an operating method thereof, wherein a plurality of regulating pressure stages are connected in parallel at both ends of the main control valve 16, and the plurality of regulating pressure stages can be switched into a parallel connection mode, a series connection mode or an independent conduction connection mode through valves, and regulating pressure stages with different flow areas are combined into a plurality of combination forms using different connection methods, and then different combination forms are bound to different load intervals one by one, so that in different load intervals, active adaptation can be performed by switching to different external combined pressure stages, and the working links are gradually increased under medium and low load conditions, thereby maintaining a higher unit operating pressure, improving the unit's regulation capability, and improving operating energy efficiency.

[0099] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A steam turbine unit with an external combined pressure stage, comprising a boiler, a high-pressure cylinder, and a first rotating shaft, wherein the main steam outlet of the boiler is connected to the steam inlet of the high-pressure cylinder via a main steam pipe, the main steam pipe being provided with a main steam valve and a main control valve in sequence along the direction of steam flow, the high-pressure cylinder being connected to the first rotating shaft, characterized in that: The system further comprises a second rotating shaft, an energy conversion device, and at least two regulating pressure stages, wherein the regulating pressure stages and the energy conversion device are sequentially arranged along the central axis of the second rotating shaft, wherein the regulating pressure stages are connected in parallel, wherein the steam inlet branches thereof are connected to the inlet end of the main control valve, and the steam outlet branches thereof are connected to the outlet end of the main control valve via a bypass control valve, and each regulating pressure stage is selectively conductive; Along the central axis direction of the second rotating shaft, the steam outlet end of the preceding regulating pressure stage is connected to the steam inlet end of the following regulating pressure stage through an intermediate regulating valve.

2. The steam turbine unit with external combined pressure stages according to claim 1, characterized in that: A steam inlet regulating valve is provided between each of the regulating pressure stages and the steam inlet branch, and a steam outlet regulating valve is provided between each of the regulating pressure stages and the steam outlet branch.

3. The steam turbine unit with external combined pressure stages according to claim 1, characterized in that: A steam inlet regulating valve is provided between each of the regulating pressure stages and the steam inlet branch, and a steam outlet regulating valve is provided between the steam outlet ends of two adjacent regulating pressure stages.

4. The steam turbine unit with external combined pressure stages according to any one of claims 1 to 3, characterized in that: The regulating pressure stages are arranged in the same direction or in pairs in opposite directions along the steam flow direction.

5. The steam turbine unit with external combined pressure stages according to claim 4, characterized in that: The flow areas of the different regulating pressure levels become larger along the steam flow direction.

6. The steam turbine unit with external combined pressure stages according to claim 4, characterized in that: It also includes a heat recovery system provided with a first high-pressure heater, the high-pressure cylinder is connected to the first high-pressure heater through a first heat recovery valve, and the outlet pipelines of the main control valve and the bypass control valve are merged and connected to the first high-pressure heater through a second heat recovery valve.

7. The steam turbine unit with external combined pressure stages according to claim 4, characterized in that: It also includes a condenser and a low-pressure heat exchange device. The steam outlet end of at least one of the pressure regulating stages is provided with a steam extraction valve, and the steam extraction valve is connected to the condenser or the low-pressure heat exchange device through a pipeline.

8. The steam turbine unit with external combined pressure stages according to claim 7, characterized in that: A cooling steam valve is provided at the steam inlet end of at least one of the regulating pressure stages, and the cooling steam valve is connected to a steam source whose pressure is greater than the pressure at the steam extraction valve, and the steam source includes at least one of a main steam pipe, a reheat steam pipe, and a steam main pipe.

9. An operating method for a steam turbine unit with an external combined pressure stage according to any one of claims 1 to 8, characterized in that: include: Divide the control load interval according to the number of adjustment pressure levels, and the control load interval includes a high load interval, a medium-high load interval, an intermediate load interval and a low load interval; Detect or set the operating interval point and determine the control load interval in which the operating interval point falls: When the operating range point falls into the high load range, only the high-pressure cylinder is put into operation, and all the regulating pressure levels are idle or shut down; When the operating range point falls into the medium-high load range, the pressure stages are adjusted to operate in parallel and then connected to the high-pressure cylinder; When the operating interval point falls into the intermediate load interval, a single regulating pressure stage is put into operation and then connected to the high-pressure cylinder; When the operating range point falls into the low load range, the pressure stages are adjusted to operate in series and then connected to the high pressure cylinder.

10. The method for operating a steam turbine unit with an external combined pressure stage according to claim 9, characterized in that: Divide the medium-high load interval into several sub-medium-high intervals; According to the number of the regulating pressure stages and the flow area, a plurality of pressure stage combinations with increasing unit steam enthalpy drop conversion capacity are formed; Several sub-middle-high intervals from high to low are bound one by one to pressure level combinations arranged from small to large according to the unit steam enthalpy drop conversion capacity.

11. The method for operating a steam turbine unit with an external combined pressure stage according to claim 9, characterized in that: Divide the intermediate load interval into several sub-intermediate intervals; Arrange the regulating pressure levels from smallest to largest according to their unit steam enthalpy drop conversion capabilities; Several sub-intermediate intervals from high to low are bound one by one to the regulating pressure levels arranged from small to large according to the unit steam enthalpy drop conversion capacity.

12. The method for operating a steam turbine unit with an external combined pressure stage according to claim 9, characterized in that: Divide the low load interval into several sub-low intervals; According to the number of the regulating pressure stages and the flow area, a plurality of pressure stage combinations with increasing unit steam enthalpy drop conversion capacity are formed; Several sub-low intervals from high to low are bound one by one to pressure level combinations arranged from small to large according to the unit steam enthalpy drop conversion capacity.

13. The method for operating a steam turbine unit with an external combined pressure stage according to any one of claims 9 to 12, characterized in that: When the regulating pressure stage is isolated from the steam inlet and exhaust and enters the idling state, open the corresponding steam extraction valve.

14. The method for operating a steam turbine unit with an external combined pressure stage according to claim 13, characterized in that: Obtain test data to determine whether the cooling flow is sufficient; If the cooling flow is insufficient, open the cooling steam valve.

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