A steam distribution device for a subcritical unit steam turbine

Abstract

The present invention provides a steam distribution device for a subcritical unit steam turbine, which includes a boiler, a steam turbine, and a No. 0 high-pressure heater. The boiler and the steam turbine are connected through a boiler steam outlet pipeline, and the steam turbine and the No. 0 high-pressure heater are connected through a No. 0 high-pressure heater pipeline. The beneficial effects of the present invention are as follows: The steam supply port of the high-pressure steam supply pipeline is the steam extraction port of the No. 0 high-pressure heater pipeline. Sharing a steam extraction / supply port increases the space in the high-pressure cylinder of the steam turbine, increases the number of flow stages, improves the efficiency of the entire high-pressure cylinder, and reduces one steam extraction / supply port, which is beneficial to the safety calculation of the high-pressure cylinder.

Description

Technical Field

[0001] The present invention relates to the field of steam turbine manufacturing, and particularly to a steam distribution device for a subcritical unit steam turbine. Background Art

[0002] For a long time, for subcritical parameter steam turbines with a power of 300MW - 600MW, there are two design styles for the high-pressure steam inlet end: the full-arc admission form with no nozzle grouping and the non-full-arc admission form with nozzle grouping.

[0003] When using the non-full-arc admission method, nozzle grouping and partial admission are likely to form a steam gap excitation source, which is not conducive to the safe operation of the unit under partial load. For impulse regulating stages, the high-speed steam flow and small steam admission angle under low load conditions are more likely to form serious hard particle erosion; when using full-arc admission, the first-stage high-pressure blades do not have the impact load caused by partial admission, and the blade stress changes synchronously with the unit load, making the blades of this stage in a safe state with a high temperature but a low stress level under any operating conditions, solving the strength problem of the first-stage high-pressure blades. The steam inlet pressure of the steam turbine is proportional to the flow rate, that is, the unit only reaches the rated value of the steam inlet pressure when operating at the maximum flow rate (usually called VWO) condition. Considering from the perspective of the thermal cycle and giving full play to the potential of the entire power plant equipment, the sliding pressure operation mode of full-arc admission does not fully utilize the steam pressure capacity. To enable the unit to have a frequency modulation function, full-arc admission must adopt a throttling method, which will cause a decrease in operating economy. For example, 5% of full-arc throttling increases the heat consumption by about 12kJ / kWh.

[0004] In current subcritical units, steam inlet, supplementary steam, and steam outlet are respectively carried out through three paths: the steam inlet pipe, the supplementary steam pipe, and the steam outlet pipe. In the transformation of such projects, due to many factors such as the original design structure layout, span, non-replacement of unit components, and external interfaces, when considering the scheme of adding the extraction steam of the No. 0 high-pressure heater, there is no suitable and sufficient space in the high-pressure inner cylinder of the unit to arrange the No. 0 high-pressure heater, which has many limitations compared with the design of new units. Summary of the Invention

[0005] In order to overcome the above problems existing in the prior art, the present invention provides a steam distribution device for a subcritical unit steam turbine.

[0006] The present invention discloses a steam distribution device for a subcritical unit steam turbine, which includes a boiler, a steam turbine, and a No. 0 high-pressure heater. The boiler and the steam turbine are connected through a boiler steam outlet pipeline, and the steam in the boiler is introduced into the steam turbine through the boiler steam outlet pipeline. The steam turbine and the No. 0 high-pressure heater are connected through a No. 0 high-pressure heater pipeline. When the unit needs to extract steam, the steam in the steam turbine is extracted through the No. 0 high-pressure heater pipeline. A first branch point is provided on the boiler steam outlet pipeline. The boiler steam outlet pipeline branches out a high-pressure steam pipeline and a high-pressure supplementary steam pipeline from the first branch point, and the high-pressure steam pipeline and the high-pressure supplementary steam pipeline share an outlet. The structure is simple and the layout is reasonable. Steam inlet holes and supplementary steam holes are respectively opened on the steam turbine for connecting the high-pressure steam pipeline and the high-pressure supplementary steam pipeline. A second branch point is provided on the high-pressure supplementary steam pipeline, and the No. 0 high-pressure heater pipeline extends from the second branch point. The supplementary steam port of the high-pressure supplementary steam pipeline is the steam extraction port of the No. 0 high-pressure heater pipeline. Since a common steam extraction / supplementary steam port can increase the number of flow stages, the efficiency of the entire high-pressure cylinder can be improved, the economic benefit can be increased, and one steam extraction / supplementary steam port is reduced, which is also beneficial to the safety calculation of the high-pressure cylinder.

[0007] On this basis, a steam outlet is opened on the boiler. One end of the boiler steam outlet pipeline is connected to the steam outlet, and the steam in the boiler is led out through the steam outlet. A main steam valve and a main control valve are sequentially installed on the boiler steam outlet pipeline. The first branch point is arranged in front of the main control valve. When the unit is operating normally, the main steam valve and the main control valve are opened, and all other valves are closed.

[0008] On this basis, the other end of the high-pressure steam pipeline is connected to the steam inlet hole of the high-pressure cylinder, and the high-pressure steam pipeline is in a normally open state to continuously supply steam to the steam turbine.

[0009] On this basis, a first stop valve and a supplementary steam valve are sequentially installed outward from the first branch point on the high-pressure supplementary steam pipeline. The other end of the high-pressure supplementary steam pipeline is connected to the supplementary steam hole of the high-pressure cylinder. When the unit needs to supplement steam, the first stop valve and the supplementary steam valve on the high-pressure supplementary steam pipeline are opened for supplementary steam. The supplementary steam valve can adjust the supplementary steam flow rate, thereby adjusting the unit power. At this time, the high-pressure steam pipeline is still in an open state.

[0010] On this basis, the second branch point is arranged between the supplementary steam hole and the supplementary steam valve. The No. 0 high-pressure heater 1 and the supplementary steam valve 10 share an inlet interface, and the supplementary steam or steam extraction is switched through the supplementary steam valve 10 and the steam extraction regulating valve 13 of the No. 0 high-pressure heater pipeline 14.

[0011] On this basis, a second stop valve, a steam extraction check valve, and a steam extraction regulating valve are sequentially installed on the No. 0 high-pressure heater pipeline outward from the second branch point. The other end of the No. 0 high-pressure heater pipeline is connected to the No. 0 high-pressure heater. Close the first stop valve and the steam supply valve on the high-pressure steam supply pipeline, and open the second stop valve, the steam extraction check valve, and the steam extraction regulating valve on the No. 0 high-pressure heater pipeline. At this time, the steam extraction regulating valve can adjust the steam extraction flow rate, and the unit extracts steam to the No. 0 high-pressure heater to reduce the heat consumption of the unit under low load conditions. The steam extraction check valve prevents gas from flowing back.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: The steam supply port of the high-pressure steam supply pipeline is the steam extraction port of the No. 0 high-pressure heater pipeline, sharing a steam extraction / supply port, which increases the effective axial space of the high-pressure cylinder of the steam turbine, increases the number of flow stages, improves the efficiency of the entire high-pressure cylinder, and reduces one steam extraction / supply port, which is beneficial to the safety calculation of the high-pressure cylinder; Sharing an outlet for the high-pressure steam pipeline and the high-pressure steam supply pipeline has a simple structure and reasonable layout, improves the cycle efficiency of the unit under low load conditions, is beneficial to the economy of partial loads, and at the same time, the increase in the feed water temperature at partial loads also meets the requirements of full-load denitration of the boiler. Description of the Drawings

[0013] Figure 1 is a schematic structural diagram of the steam distribution device of the subcritical unit steam turbine of the present invention;

[0014] Figure 2 is a top view structural diagram of the steam distribution device of the subcritical unit steam turbine of the present invention.

[0015] In the figure: 1. No. 0 high-pressure heater, 2. Boiler, 3. Steam turbine, 4. Steam outlet, 5. Boiler steam outlet pipeline, 6. Main steam valve, 7. Main regulating valve, 8. First branch point, 9. First stop valve, 10. Steam supply valve, 11. Second stop valve, 12. Steam extraction check valve, 13. Steam extraction regulating valve, 14. No. 0 high-pressure heater pipeline, 15. High-pressure steam supply pipeline, 16. Steam supply hole, 17. Steam inlet hole, 18. High-pressure steam pipeline, 19. Second branch point. Detailed Embodiments

[0016] The following further details the present invention in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] The present invention discloses a steam distribution device for a subcritical unit steam turbine. Refer to Figure 1, including boiler 2, steam turbine 3 and No. 0 high-pressure heater 1. The boiler 2 and the steam turbine 3 are connected through the boiler steam outlet pipeline 5. The steam in the boiler 2 is introduced into the steam turbine 3 through the boiler steam outlet pipeline 5. An outlet 4 is opened on the boiler 2. One end of the boiler steam outlet pipeline 5 is connected to the outlet 4, and the steam in the boiler 2 is led out through the outlet 4. A main steam valve 6 and a main regulating valve 7 are successively installed on the boiler steam outlet pipeline 5. A first branch point 8 is provided on the boiler steam outlet pipeline 5, and the first branch point 8 is arranged in front of the main regulating valve 7. The boiler steam outlet pipeline 5 branches out a high-pressure steam pipeline 18 and a high-pressure supplementary steam pipeline 15 from the first branch point 8, and the high-pressure steam pipeline 18 and the high-pressure supplementary steam pipeline 15 share an outlet; steam inlet holes 17 and supplementary steam holes 16 are respectively opened on the steam turbine 3, and are respectively connected to the high-pressure steam pipeline 18 and the high-pressure supplementary steam pipeline 15. The other end of the high-pressure steam pipeline 18 is connected to the steam inlet hole 17 of the steam turbine 3; a first stop valve 9 and a supplementary steam valve 10 are successively installed outward from the first branch point 8 on the high-pressure supplementary steam pipeline 15, and the other end of the high-pressure supplementary steam pipeline 15 is connected to the supplementary steam hole 16 of the steam turbine 3.

[0018] During normal operation of the unit, the main steam valve 6 and the main regulating valve 7 are opened, and all other valves are closed. The main steam valve 6 is opened before the main regulating valve 7 is fully opened. Otherwise, there will be double losses of throttling of the main regulating valve 7 and the main steam valve 6, resulting in a greater increase in the heat consumption of the unit. The main regulating valve 7 is fully opened to reach the flow rate at the rated inlet steam pressure. The main steam valve 6 determines that the flow rate value of the main regulating valve 7 should be equal to the flow rate under the heat consumption guarantee condition. Only when the flow rate is greater than this value, the main steam valve 6 is opened for steam supply. If the maximum flow rate setting of the main regulating valve is too large and the opening point of the supplementary steam valve is shifted backward, then under the heat consumption guarantee condition, the inlet steam pressure of the unit has not yet dropped to the rated pressure, and the potential of the steam pressure has not been fully utilized; refer to Figure 1 and Figure 2 , when the unit needs supplementary steam, the first stop valve 9 and the supplementary steam valve 10 on the high-pressure supplementary steam pipeline 15 are opened for supplementary steam. The supplementary steam valve 10 can adjust the supplementary steam flow rate, thereby adjusting the unit power. At this time, the high-pressure steam pipeline 18 is still in the open state.

[0019] Refer to Figure 2 , for subcritical-class units, the original configuration has two main steam valves 6. A pipeline is led out behind each main steam valve 6 and in front of the main regulating valve 7 and is connected to one or two external supplementary steam valves 10. The valve structure is a single-seat valve, located at the lower part / upper and lower parts of the high-pressure cylinder, and the opening degree is controlled by an electro-hydraulic control system and is safely closed by a spring. After the steam is led out from the valve and enters a certain intermediate stage, the high-pressure cylinder structure related to the supplementary steam valve 10 is as follows: There is a closed chamber between the high-pressure outer cylinder and the inner cylinder. This chamber is connected to the high-pressure flow path through the radial holes on the high-pressure inner cylinder. Specifically, which stage to connect to needs to be determined from aspects such as economy, temperature field thermal stress, and the influence of supplementary steam on the flow capacity of the main regulating valve, and is adjusted for different units.

[0020] Reference Figure 1 Figure 1 , as a preferred embodiment of the present invention, in this embodiment, the steam turbine 3 is connected to the No. 0 high-pressure heater 1 through the No. 0 high-pressure heater pipeline 14. When the unit needs to extract steam, the steam in the steam turbine 3 is extracted through the No. 0 high-pressure heater pipeline 14. In traditional retrofit projects, due to many factors such as the original design structure layout, span, non-replacement of unit components, and external interfaces, when considering adding a steam extraction scheme for the No. 0 high-pressure heater, there is no suitable and sufficient space in the high-pressure inner cylinder of the unit to arrange the No. 0 high-pressure heater. When retrofitting a subcritical unit for full-circumference steam admission and make-up steam valve configuration, since the flow-through retrofit scheme cancels the governing stage, and the governing stage is short and stout, the space in the high-pressure cylinder increases, and the flow-through span available for arranging the blades of the flow-through part and the steam extraction port is greatly improved compared with before the retrofit. It is easier to arrange the No. 0 high-pressure heater in the body structure.

[0021]

[0021] , as a preferred embodiment of the present invention, in this embodiment, a second branch point 19 is provided on the high-pressure make-up steam pipeline 15. The second branch point 19 is provided between the make-up steam hole 16 and the make-up steam valve 10. The No. 0 high-pressure heater pipeline 14 extends from the second branch point 19. The No. 0 high-pressure heater pipeline 14 is sequentially installed with a second stop valve 11, a steam extraction check valve 12, and a steam extraction regulating valve 13 outward from the second branch point 19. The other end of the No. 0 high-pressure heater pipeline 14 is connected to the No. 0 high-pressure heater 1. The make-up steam port of the high-pressure make-up steam pipeline 15 is the steam extraction port of the No. 0 high-pressure heater pipeline 14. Since sharing a single steam extraction / make-up steam port can increase the number of flow-through stages, thereby improving the efficiency of the entire high-pressure cylinder and reducing one steam extraction / make-up steam port, which is also beneficial for the safety calculation of the high-pressure cylinder. Close the first stop valve 9 and the make-up steam valve 10 on the high-pressure make-up steam pipeline 15, and open the second stop valve 11, the steam extraction check valve 12, and the steam extraction regulating valve 13 on the No. 0 high-pressure heater pipeline 14. At this time, the steam extraction regulating valve 13 can adjust the steam extraction flow rate, and the unit extracts steam to the No. 0 high-pressure heater 1 to reduce the heat consumption of the unit under low-load conditions. The steam extraction check valve 12 prevents gas from flowing back. At this time, the high-pressure steam pipeline 18 is still in the open state, continuously supplying steam to the steam turbine 3. The No. 0 high-pressure heater 1 and the make-up steam valve 10 share an intake interface, and the make-up steam or steam extraction is switched through the make-up steam valve 10 and the steam extraction regulating valve 13 of the No. 0 high-pressure heater pipeline 14.

[0022] Applied to the Jianbi Unit, it will communicate with the outlet of the 9th stage moving blade. The steam inlet of the supplementary steam valve and the extraction port of the No. 0 high-pressure heater are both arranged behind the 9th stage of the high pressure. When the steam inlet volume is much larger than the critical opening flow of the supplementary steam valve (i.e., the main steam flow under THA condition), part of the steam enters the flow path through the supplementary steam valve, so that the unit has a greater overload capacity; in the partial load condition, steam is extracted from this extraction port to supply the No. 0 high-pressure heater to increase the final feed water temperature of the unit. Compared with the general unit with full arc admission and No. 0 high-pressure heater configuration, due to sharing a single extraction / supplementary steam port, the number of flow stages can be increased by 3 stages, thereby improving the efficiency of the entire high-pressure cylinder. And because one extraction / supplementary steam port is reduced, it is more conducive to the safety calculation of the high-pressure cylinder and improves the economic benefits at the same time. As shown in Table 1, it is the economic benefit comparison between the case where the No. 0 high-pressure heater and the supplementary steam valve share one path and the case where the No. 0 high-pressure heater and the supplementary steam valve are separated into two paths.

[0023] Table 1

[0024]

[0025] After the transformation, an extraction / supplementary steam port is arranged behind the 9th stage of the high pressure of the unit, which can be used for the regenerative extraction of the added No. 0 high-pressure heater. This No. 0 high-pressure heater is put into operation at partial load to increase the feed water temperature under low load conditions. It can increase the feed water temperature by about 20 degrees under 75% THA condition and about 25 degrees under 50% THA load, thereby improving the cycle efficiency of the unit under low load conditions and being beneficial to the economy at partial load. As shown in Table 2, it is the economic benefit of adding the No. 0 high-pressure heater; at the same time, the increase in the feed water temperature at partial load also meets the requirements of full-load denitration of the boiler.

[0026] Table 2

[0027] Full - circumference steam admission and No. 0 HP heater Full - circumference steam admission Heat rate at THA condition (kJ / kWh) 0 Baseline Heat rate at 75% THA condition (kJ / kWh) -30 Baseline Heat rate at 50% THA condition (kJ / kWh) -35 Baseline Heat rate at 30% THA condition (kJ / kWh) -45 Baseline

[0028] To sum up, adding a high-pressure supplementary steam pipeline on the high-pressure side of the steam turbine can meet the requirement that the unit can generate the rated power under the summer back pressure condition. At the same time, it can also meet the operation of the No. 0 high-pressure heater at low load of the unit. After analyzing and calculating the structure and flow path of the high-pressure cylinder, it is considered that the scheme of adding the No. 0 high-pressure heater is completely feasible.

[0029] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inner", "front", "center", "both ends", etc. is the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying 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 construed as a limitation to the present invention.

[0030] In the present invention, unless otherwise clearly defined and limited, terms such as "installation", "setting", "connection", "fixation", "swivel connection", "padding", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two components or the interaction relationship between two components. Unless otherwise clearly defined, for those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] The above description shows and describes the preferred embodiments of the present invention. As mentioned above, it should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be changed within the scope of the inventive concept described herein through the above teachings or the techniques or knowledge in related fields. And any changes and modifications made by those skilled in the art without departing from the spirit and scope of the present invention shall fall within the protection scope of the appended claims of the present invention.

Claims

1. A steam distribution device for a subcritical unit steam turbine, comprising a boiler (2), a steam turbine (3) and a No. 0 high-pressure heater (1), characterized in that: The boiler (2) and the steam turbine (3) are connected through a boiler steam outlet pipeline (5), and the steam turbine (3) and the No. 0 high-pressure heater (1) are connected through a No. 0 high-pressure heater pipeline (14); A first branch point (8) is provided on the boiler steam outlet pipeline (5). The boiler steam outlet pipeline (5) branches out a high-pressure steam pipeline (18) and a high-pressure supplementary steam pipeline (15) from the first branch point (8). Steam inlet holes (17) and supplementary steam holes (16) are respectively opened on the steam turbine (3). A second branch point (19) is provided on the high-pressure supplementary steam pipeline (15), and the No. 0 high-pressure heater pipeline (14) extends from the second branch point (19). A first stop valve (9) and a supplementary steam valve (10) are sequentially installed outward from the first branch point (8) on the high-pressure supplementary steam pipeline (15). The other end of the high-pressure supplementary steam pipeline (15) is connected to the supplementary steam hole (16) of the steam turbine (3). The second branch point (19) is arranged between the supplementary steam hole (16) and the supplementary steam valve (10). The No. 0 high-pressure heater (1) shares an inlet interface with the supplementary steam valve (10), and supplementary steam or extraction steam is switched through the supplementary steam valve (10) and the extraction steam regulating valve (13) of the No. 0 high-pressure heater pipeline (14).

2. The steam distribution device of the subcritical unit steam turbine according to claim 1, characterized in that: A steam outlet (4) is opened on the boiler (2), and one end of the boiler steam outlet pipeline (5) is connected to the steam outlet (4).

3. The steam distribution device of the subcritical unit steam turbine according to claim 2, characterized in that: A main steam valve (6) and a main regulating valve (7) are sequentially installed on the boiler steam outlet pipeline (5), and the first branch point (8) is arranged in front of the main regulating valve (7).

4. The steam distribution device of the subcritical unit steam turbine according to claim 1, characterized in that: The other end of the high-pressure steam pipeline (18) is connected to the steam inlet hole (17) of the steam turbine (3).

5. The steam distribution device of the subcritical unit steam turbine according to claim 1, characterized in that: A second stop valve (11), a steam extraction check valve (12), and a steam extraction regulating valve (13) are sequentially installed outward from the second branch point (19) on the No. 0 high-pressure heater pipeline (14), and the other end of the No. 0 high-pressure heater pipeline (14) is connected to the No. 0 high-pressure heater (1).

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