Wide-load efficient steam turbine

Abstract

The wide-load efficient steam turbine comprises a high-pressure cylinder, a first intermediate-pressure cylinder and a second intermediate-pressure cylinder, the first intermediate-pressure cylinder and the second intermediate-pressure cylinder are distributed in parallel, the first intermediate-pressure cylinder is communicated with a first low-pressure cylinder in an exhaust mode to form a first load path, and the second intermediate-pressure cylinder is communicated with a second low-pressure cylinder in an exhaust mode to form a second load path. Steam discharged from the high-pressure cylinder enters the first load path and the second load path respectively; different load ratios can be selected according to the current load working condition, and the stability of the main output pressure can still be kept under the condition that the total load is reduced.

Description

Technical Field

[0001] The present invention relates to the field of steam turbines, in particular to a wide-load high-efficiency steam turbine. Background Art

[0002] Existing steam turbine units primarily consist of a high-pressure (HP) cylinder, an intermediate-pressure (IP) cylinder, a low-pressure (LP) cylinder, a regenerative heater, a condenser, and a feedwater pump. Steam from the boiler sequentially passes through the HP, IP, and LP cylinders, performing work before entering the condenser and condensing into water. This condensed water is then heated by the regenerative heater, boosted by the feedwater pump, and heated by the boiler to produce steam, forming a thermodynamic cycle. Existing large steam turbines typically consist of one HP cylinder, one IP cylinder, and one or two LP cylinders.

[0003] Since the existing steam turbines are designed according to the rated power generation load, in order to ensure the lowest coal consumption when supplying power at the rated load, the coal consumption when supplying power at low load is not taken into consideration, resulting in a high coal consumption of the existing steam turbine generator sets when supplying power at low load.

[0004] However, with the rapid increase in installed capacity of renewable energy power generation, coal-fired power generation units operate under low-load conditions most of the time, which significantly increases the disadvantage of high coal consumption at low load, resulting in a further increase in the low-load power supply coal consumption of steam turbine generator sets, affecting the economic benefits of steam turbine generator sets. Summary of the Invention

[0005] The object of the present invention is to provide a wide load and high efficiency steam turbine which can select different load ratios according to the current load conditions and can maintain a stable main output pressure when the total load decreases.

[0006] In order to solve the above technical problems, the present invention provides a wide-load and high-efficiency steam turbine, including a high-pressure cylinder, a first intermediate-pressure cylinder and a second intermediate-pressure cylinder distributed in parallel, the exhaust of the first intermediate-pressure cylinder is connected to the first low-pressure cylinder to form a first load path, and the exhaust of the second intermediate-pressure cylinder is connected to the second low-pressure cylinder to form a second load path, so that the steam discharged from the high-pressure cylinder enters the first load path and the second load path respectively.

[0007] Furthermore, it also includes a boiler connected to the high-pressure cylinder, the boiler and the high-pressure cylinder are connected through a first pipeline, the boiler is connected to the flexible adjustable turbine through a second pipeline, the flexible adjustable turbine is connected to the high-pressure cylinder through a third pipeline, and the design flow rate of the flexible adjustable turbine is less than the rated flow rate of the high-pressure cylinder.

[0008] Furthermore, a fourth pipeline is connected to the flexible adjustable turbine, and the fourth pipeline is connected to the condenser and the atmospheric discharge port.

[0009] Furthermore, the first intermediate-pressure cylinder, the first low-pressure cylinder, and the second low-pressure cylinder are connected to a heat recovery system.

[0010] Furthermore, under high load conditions, the first pipeline and the second pipeline are activated to keep the high-pressure cylinder in operation and the flexible adjustable turbine enters the warm-up state; when under medium and low load conditions, the second pipeline and the third pipeline are started to put the flexible adjustable turbine into operation, and the steam enters the high-pressure cylinder after passing through the flexible adjustable turbine; when the flexible adjustable turbine is in the switching state, the first pipeline, the second pipeline and the third pipeline are started to make the high-pressure cylinder and the flexible adjustable turbine operate in parallel.

[0011] Furthermore, the design flow rate of the flexible adjustable turbine is 60%-80% of the rated flow rate of the high-pressure cylinder.

[0012] Furthermore, the high-pressure cylinder is connected to the first intermediate-pressure cylinder and the second intermediate-pressure cylinder through a circulating reheating loop, and the circulating reheating loop flows through the boiler.

[0013] Furthermore, under low load and high back pressure conditions, the second intermediate pressure cylinder and the second low pressure cylinder enter a low-output operation state.

[0014] Furthermore, the operating loads of the first load path and the second load path are configured in proportion.

[0015] Furthermore, the high-pressure cylinder, the first intermediate-pressure cylinder, the second intermediate-pressure cylinder, the first low-pressure cylinder and the second low-pressure cylinder are coaxially arranged.

[0016] The beneficial effects of the present invention are: 1. A flexible variable turbine is placed in front of the high-pressure cylinder. Under medium and low load conditions, the flexible variable turbine can be switched to the flexible variable turbine. The flexible variable turbine, which has a lower flow rate than the high-pressure cylinder, can increase the main steam pressure by reducing the flow area, thereby maintaining the output load pressure under medium and low load conditions, thereby improving the thermal efficiency of the entire steam turbine thermodynamic cycle and reducing coal consumption under medium and low load conditions. 2. By connecting the dual intermediate-pressure cylinders to the upper low-pressure cylinder to form two load paths, different load path usage ratios can be selected under high-load, medium- and low-load conditions, ensuring both stability under high-load conditions and output pressure under medium- and low-load conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the present invention.

[0018] Figure numerals: 1. high-pressure cylinder; 2. first intermediate-pressure cylinder; 3. second intermediate-pressure cylinder; 4. first low-pressure cylinder; 5. second low-pressure cylinder; 6. boiler; 7. first pipeline; 8. second pipeline; 9. flexible adjustable turbine; 10. third pipeline; 11. fourth pipeline; 12. condenser; 13. atmospheric discharge port. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention are within the scope of protection of the present invention.

[0020] It should be understood by those skilled in the art that, in the disclosure of the present invention, the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, which are only for the convenience of describing the present invention 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 operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0021] It is understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the elements may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0022] like Figure 1 The present invention provides a wide-load, high-efficiency steam turbine, comprising a high-pressure cylinder 1, a first intermediate-pressure cylinder 2 and a second intermediate-pressure cylinder 3 distributed in parallel, wherein the exhaust of the first intermediate-pressure cylinder 2 is connected to the first low-pressure cylinder 4 to form a first load path, and the exhaust of the second intermediate-pressure cylinder 3 is connected to the second low-pressure cylinder 5 to form a second load path, so that the steam discharged from the high-pressure cylinder 1 enters the first load path and the second load path respectively.

[0023] Specifically, steam from the high-pressure cylinder enters the two intermediate-pressure cylinders in parallel, with the steam inlet valves in these two cylinders controlling the steam flow. A regulating valve is not required for the low-pressure cylinder. Under low- to medium-load conditions, the steam inlet valve in the second intermediate-pressure cylinder is closed to the minimum steam flow to ensure safe operation of the second low-pressure cylinder. The majority of the steam enters the first intermediate- and low-pressure cylinders to perform work, ensuring stable output pressure.

[0024] Preferably, it also includes a boiler 6 connected to the high-pressure cylinder 1, the boiler 6 and the high-pressure cylinder 1 are connected through a first pipeline 7, the boiler 6 is connected to the flexible adjustable turbine 9 through a second pipeline 8, the flexible adjustable turbine 9 is connected to the high-pressure cylinder 1 through a third pipeline 10, and the design flow rate of the flexible adjustable turbine 9 is less than the rated flow rate of the high-pressure cylinder 1; the flexible adjustable turbine 9 is connected to a fourth pipeline 11, and the fourth pipeline 11 is connected to the condenser 12 and the atmospheric discharge port 13.

[0025] In a preferred embodiment of this scheme, the design flow rate of the flexible variable turbine 9 is 60%-80% of the rated flow rate of the high-pressure cylinder 1. In actual operation, the steam flow of the flexible variable turbine is from the flexible variable turbine to the high-pressure cylinder, then to the intermediate-pressure cylinder, and finally to the low-pressure cylinder. The design flow rate of the flexible variable turbine can be set to 70% of the rated flow rate. While the main steam flow rate remains unchanged, the steam flow area through the flexible variable turbine changes, thereby reconstructing the main steam parameters. By placing the flexible variable turbine before the high-pressure cylinder, the main steam pressure can be increased from the main steam pressure corresponding to 70% load (set capacity) to 28 MPa (relative output pressure at 100% load).

[0026] If the main steam flow exceeds 70% load (set capacity), the main steam directly enters the high-pressure cylinder, and the flexible adjustable turbine enters partial steam warm-up standby.

[0027] In one embodiment of the present scheme, under high-load conditions, the first pipeline 7 and the second pipeline 8 are activated to keep the high-pressure cylinder 1 in operation and the flexible adjustable turbine 9 enters the warm-up state; under medium and low load conditions, the second pipeline 8 and the third pipeline 10 are started to put the flexible adjustable turbine 9 into operation, and the steam enters the high-pressure cylinder 1 after passing through the flexible adjustable turbine 9; when the flexible adjustable turbine 9 is in the switching state, the first pipeline 7, the second pipeline 8 and the third pipeline 10 are started to make the high-pressure cylinder 1 and the flexible adjustable turbine 9 operate in parallel.

[0028] Among them, the flexible adjustable turbine can be designed to adapt to 32MPa pressure, adopting intermediate steam inlet, double split and double exhaust structure; the exhaust pressure can reach up to 28MPa.

[0029] Specifically, valves are provided at the first pipeline, the second pipeline, the third pipeline, and the fourth pipeline to control the opening and closing states of the corresponding pipelines. In actual use, the following operations can be adopted for each working condition: Under high load conditions, the first pipeline valve is opened, the second pipeline valve is opened, the third pipeline valve is closed, and the fourth pipeline valve is closed to stop the flexible adjustable turbine from running and maintain the warm-up state; Under low to medium load conditions, close the first pipeline valve, open the second pipeline valve, open the third pipeline valve, and close the fourth pipeline valve to put the flexible adjustable turbine into operation; And when the flexible adjustable turbine needs to be switched under medium and low load conditions, open the first pipeline valve, open the second pipeline valve, open the third pipeline valve, close valve 3, close the fourth pipeline valve, and the flexible adjustable turbine and the high-pressure cylinder are put into operation in parallel.

[0030] It is worth mentioning that the state in which the flexible adjustable turbine and the high-pressure cylinder operate in parallel is usually used: 1) during the commissioning and exiting process of the flexible adjustable turbine, such as the flexible adjustable turbine switching from the warm-up state to the operating state; 2) when it is necessary to adjust the turbine load increase and decrease rate, that is, the turbine output, the generated power can be distributed between the turbine and the flexible adjustable turbine.

[0031] At the same time, when an accident occurs in this scheme, the remaining pipelines can be cut off, only the second pipeline and the fourth pipeline are opened, and the valve at the atmospheric discharge port is opened simultaneously, so that steam can be discharged from the atmospheric discharge port under the accident condition, thereby improving safety.

[0032] Preferably, the first intermediate-pressure cylinder 2 , the first low-pressure cylinder 4 and the second low-pressure cylinder 5 are connected to a heat recovery system.

[0033] Specifically, the first intermediate-pressure cylinder is provided with a heat recovery system, while the second intermediate-pressure cylinder is not provided with a heat recovery system, and the two intermediate-pressure cylinders can be designed to have a large and a small volume, that is, different flow cross-sectional areas. Both intermediate-pressure cylinders have a double-flow steam inlet in the middle and exhaust steam at both ends, so that the exhaust steam pressures of the two intermediate-pressure cylinders are different, and the two intermediate-pressure cylinders are each provided with an independent valve to control the steam intake amount. The exhaust steam of the two intermediate-pressure cylinders enters their respective low-pressure cylinders, and the flow area of each corresponding low-pressure cylinder is designed to have a capacity corresponding to the preceding intermediate-pressure cylinder; both low-pressure cylinders are provided with a heat recovery system, and the designed volumes of the two low-pressure cylinders are different. The two low-pressure cylinders have a double-flow steam inlet in the middle and exhaust steam at both ends, and the exhaust steam enters their respective cooling devices.

[0034] Among them, the heat recovery system refers to the steam extracted from the steam turbine entering the heaters at each stage to heat the feed water; the purpose is to extract part of the steam with similar pressure and temperature levels to heat the feed water, realize the cascade heating of the feed water, reduce the cold end loss, and improve the thermal cycle efficiency.

[0035] Since the second intermediate pressure cylinder is designed for low output or shut-off, it cannot extract steam during this period. Therefore, the system does not extract steam from the second intermediate pressure cylinder to the regenerative heat system. Even under high load conditions, steam extraction from the first intermediate pressure cylinder can still meet the regenerative heat system requirements. Both low-pressure cylinders must be designed for regenerative heat extraction to meet the high-load steam extraction requirement for feedwater heating.

[0036] Preferably, the high-pressure cylinder 1 is connected to the first intermediate-pressure cylinder 2 and the second intermediate-pressure cylinder 3 through a circulating reheating loop, and the circulating reheating loop flows through the boiler 6 .

[0037] Specifically, the exhaust steam from the high-pressure cylinder of the unit is heated by the boiler and then enters the medium and low-pressure cylinders. The main purpose of reheating is to optimize the thermal cycle process, reduce the exhaust steam humidity to improve the overall efficiency of the unit, and the parameter change law is synchronized with the unit load.

[0038] Preferably, under low load and high back pressure conditions, the second intermediate pressure cylinder 3 and the second low pressure cylinder 5 enter a micro-output operation state; the operating loads of the first load path and the second load path are configured proportionally.

[0039] Specifically, under medium and high load conditions, both the first and second load paths are normally intake steam (the output of the two sets of medium and low pressure cylinders can be configured in a ratio of 5:5 or 4:6, and the design ratio is determined based on the normal operating load of the unit); under low load and high back pressure conditions, the second load path enters a micro-output operation state, and the medium-pressure main steam regulation controllable bypass valve controls the steam intake of the second load path. At this time, the steam intake pressure and steam volume of the first load path increase accordingly (the steam originally flowing through the second load path is transferred to the first load path), thereby maintaining a relatively high flow efficiency of the unit.

[0040] The main benefit of designing different ratios for the first and second load paths is that they can be tailored to the local electricity load factor. For example, if the local electricity load factor for the unit frequently operates below 60%, the two load paths can be designed with a 4:6 ratio. During actual operation, the second load path with a ratio of 4 is disconnected or operated at low output, allowing all reheated steam to flow into the first load path with a ratio of 6, thereby improving the overall efficiency of the first load path. Compared to existing designs in which one intermediate-pressure cylinder drives two low-pressure cylinders with equal ratios, steam is evenly distributed between the two low-pressure cylinders, resulting in low steam flow and low efficiency. This design, by configuring the two load paths in a proportional manner, allows steam to flow into the first load path (e.g., the first load path with a ratio of 6) below 60% load (or other different operating loads), nearly doubling the steam flow and improving overall efficiency.

[0041] In particular, when the steam flow rate is reduced to the set load, you can choose to completely cut out the second load path or operate the second load path at micro-output. The difference between the two is that: on the basis of considering the actual operation safety, the micro-output operation state of the second load path can ensure that the last-stage blades of the low-pressure cylinder of the second load path are safer.

[0042] Preferably, the high-pressure cylinder 1 , the first intermediate-pressure cylinder 2 , the second intermediate-pressure cylinder 3 , the first low-pressure cylinder 4 and the second low-pressure cylinder 5 are coaxially arranged.

[0043] Specifically, the high-pressure cylinder, the first intermediate-pressure cylinder, the second intermediate-pressure cylinder, the first low-pressure cylinder and the second low-pressure cylinder are arranged in series on a single axis. However, in the steam flow, the first load path and the second load path through which the reheated steam flows are in parallel. The advantage of this arrangement is that the above-mentioned components can be driven by the same device, and the steam can be divided into two paths for proportional configuration.

[0044] In one embodiment of this solution, the flexible adjustable turbine can be arranged coaxially with the above-mentioned components, or a small generator can be arranged separately.

[0045] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, any technical solution that is the same or similar to that of the present application falls within the scope of protection of the present invention.

Claims

1. A wide load and high efficiency steam turbine, characterized by: The invention comprises a high-pressure cylinder (1), a first intermediate-pressure cylinder (2) and a second intermediate-pressure cylinder (3) which are distributed in parallel. The exhaust of the first intermediate-pressure cylinder (2) is connected to the first low-pressure cylinder (4) to form a first load path. The exhaust of the second intermediate-pressure cylinder (3) is connected to the second low-pressure cylinder (5) to form a second load path, so that the steam exhausted from the high-pressure cylinder (1) enters the first load path and the second load path respectively.

2. The wide load and high efficiency steam turbine according to claim 1, characterized in that: The invention also includes a boiler (6) connected to the high-pressure cylinder (1), wherein the boiler (6) and the high-pressure cylinder (1) are connected via a first pipeline (7), the boiler (6) is connected to a flexible adjustable turbine (9) via a second pipeline (8), and the flexible adjustable turbine (9) is connected to the high-pressure cylinder (1) via a third pipeline (10), and the design flow rate of the flexible adjustable turbine (9) is less than the rated flow rate of the high-pressure cylinder (1).

3. The wide load and high efficiency steam turbine according to claim 2, characterized in that: The flexible adjustable turbine (9) is connected to a fourth pipeline (11), and the fourth pipeline (11) is connected to a condenser (12) and an atmospheric discharge port (13).

4. The wide load and high efficiency steam turbine according to claim 1, characterized in that: The first intermediate-pressure cylinder (2), the first low-pressure cylinder (4) and the second low-pressure cylinder (5) are connected to a heat recovery system.

5. The wide load and high efficiency steam turbine according to claim 1, characterized in that: Under high-load conditions, the first pipeline (7) and the second pipeline (8) are activated to keep the high-pressure cylinder (1) in operation and the flexible adjustable turbine (9) enters a warm-up state; under medium- and low-load conditions, the second pipeline (8) and the third pipeline (10) are activated to keep the flexible adjustable turbine (9) in operation and steam enters the high-pressure cylinder (1) after passing through the flexible adjustable turbine (9); When the flexible adjustable turbine (9) is in a switching state, the first pipeline (7), the second pipeline (8) and the third pipeline (10) are started to enable the high-pressure cylinder (1) and the flexible adjustable turbine (9) to be in a parallel operation state.

6. The wide load and high efficiency steam turbine according to claim 2, characterized in that: The design flow rate of the flexible adjustable turbine (9) is 60%-80% of the rated flow rate of the high-pressure cylinder (1).

7. The wide load and high efficiency steam turbine according to claim 1, characterized in that: The high-pressure cylinder (1) is connected to the first intermediate-pressure cylinder (2) and the second intermediate-pressure cylinder (3) through a circulating reheating circuit, and the circulating reheating circuit flows through a boiler (6).

8. The wide load and high efficiency steam turbine according to claim 1, characterized in that: Under low-load and high-back-pressure operating conditions, the second medium-pressure cylinder (3) and the second low-pressure cylinder (5) enter a low-output operating state.

9. The wide load and high efficiency steam turbine according to claim 1, characterized in that: The operating loads of the first load path and the second load path are configured in proportion.

10. The wide load and high efficiency steam turbine according to claim 1, characterized in that: The high-pressure cylinder (1), the first medium-pressure cylinder (2), the second medium-pressure cylinder (3), the first low-pressure cylinder (4) and the second low-pressure cylinder (5) are coaxially arranged.

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