A system and method for improving the final feed water temperature of a steam turbine under part load

Abstract

The present invention discloses a system and a usage method for improving the final feed water temperature of a steam turbine under partial load, belonging to the technical field of steam turbine power generation in thermal power units, aiming to solve the technical problem of low final feed water temperature of the steam turbine under the existing load. Through the combination of the first desuperheating and pressure reducing device and the second desuperheating and pressure reducing device, steam with an intermediate pressure is generated and enters the high-pressure heating device through the first triple valve for heating, thereby increasing the feed water temperature at the outlet of the high-pressure heater, and ultimately being able to supply heat to the steam turbine. The operation is simple and easy to implement. When the first desuperheating water regulating valve and the second desuperheating water regulating valve need to be overhauled, the first manual valve and the second manual valve can be closed, facilitating the overhaul of the first desuperheating water regulating valve and the second desuperheating water regulating valve. The first desuperheating water regulating valve and the second desuperheating and pressure reducing device can automatically adjust the opening degree for desuperheating and pressure reducing. The No. 1 high-pressure heater is connected to the boiler, which can solve the problems of unstable boiler water dynamics and poisoning of the SCR catalyst.

Description

Technical Field

[0001] The invention belongs to the technical field of steam turbine power generation in thermal power units, and relates to a system and a usage method for increasing the final feed water temperature of a steam turbine under part load. Background Art

[0002] The flexibility of thermal power units has been increasingly emphasized. The task of base load will be borne by new energy, and coal-fired units will be more involved in the deep regulation task, and undertaking part load will become the main task. Under lower load conditions, the final feed water temperature of the steam turbine decreases significantly, the feed water under-enthalpy is large, which is likely to cause unstable boiler water dynamics. At the same time, the SCR inlet flue gas temperature decreases, which may lead to SCR catalyst poisoning, and the final feed water temperature of the steam turbine is low under part load. Summary of the Invention

[0003] The purpose of the invention is to solve the problem of low final feed water temperature of the steam turbine under load in the prior art, and provide a system for increasing the final feed water temperature of the steam turbine under part load.

[0004] To achieve the above purpose, the invention adopts the following technical solutions:

[0005] A system for increasing the final feed water temperature of a steam turbine under part load proposed by the invention includes a first desuperheating and pressure reducing device, a heat exchanger, a first triple valve, a second triple valve, a second desuperheating and pressure reducing device, and a high-pressure heating device;

[0006] Steam is extracted from the main steam pipeline of the boiler to the first desuperheating and pressure reducing device for desuperheating and pressure reducing treatment to obtain desuperheated and pressure-reduced steam, the desuperheated and pressure-reduced steam is injected into the heat exchanger for heat exchange to obtain heat-exchanged steam, and then the heat-exchanged steam is injected into the first triple valve. The exhaust steam of the first triple valve is divided into two paths. The first path of steam of the first triple valve sequentially passes through the second triple valve and the second desuperheating and pressure reducing device for desuperheating and pressure reducing treatment, and the treated steam is introduced into the heat exchanger. The second path of steam of the first triple valve is introduced into the high-pressure heating device.

[0007] Preferably, the first desuperheating and pressure reducing device includes a first regulating valve, a first pneumatic gate valve, and a first desuperheating and pressure reducing valve;

[0008] The first path of the first regulating valve is connected to the main steam pipeline, the second path of the first regulating valve is connected to the first path of the first pneumatic gate valve, and the second path of the first pneumatic gate valve is connected to the first path of the first desuperheating and pressure reducing valve; the second path of the first desuperheating and pressure reducing valve is connected to the heat exchanger.

[0009] Preferably, the third path of the first desuperheating and pressure reducing valve is sequentially connected with a first manual valve and a first desuperheating water regulating valve.

[0010] Preferably, a check valve is connected between the second triple valve and the second desuperheating and pressure reducing device.

[0011] Preferably, a safety valve is connected between the second triple valve and the check valve.

[0012] Preferably, the second desuperheating and pressure reducing device includes a second desuperheater and pressure reducer, a second regulating valve, and a second pneumatic gate valve;

[0013] The first path of the second desuperheater and pressure reducer is connected to the heat exchanger, the second path of the second desuperheater and pressure reducer is connected to the first path of the second regulating valve, the second path of the second regulating valve is connected to the first path of the second pneumatic gate valve, and the second path of the second pneumatic gate valve is connected to the check valve.

[0014] Preferably, the third path of the second desuperheater and pressure reducer is sequentially connected with a second manual valve and a second desuperheating water regulating valve.

[0015] Preferably, the steam passing through the heat exchanger is introduced into the first triple valve at high speed.

[0016] Preferably, the high-pressure heating device includes a No. 1 high-pressure heater and a No. 2 high-pressure heater;

[0017] The first path of the No. 1 high-pressure heater is connected to the second path of the first triple valve, the second path of the No. 1 high-pressure heater is connected to the boiler, the third path of the No. 1 high-pressure heater is connected to the first path of the No. 2 high-pressure heater, and the second path of the No. 2 high-pressure heater is connected to the steam turbine.

[0018] A method for using a system for increasing the final feed water temperature of a steam turbine at partial load proposed by the present invention includes the following steps:

[0019] Steam is extracted from the main steam pipeline of the boiler to the first desuperheating and pressure reducing device for desuperheating and pressure reducing treatment to obtain desuperheated and pressure-reduced steam, the desuperheated and pressure-reduced steam is injected into the heat exchanger for heat exchange to obtain heat-exchanged steam, and then the heat-exchanged steam is injected into the first triple valve;

[0020] The steam in the first path of the first triple valve is sequentially subjected to desuperheating and pressure reducing treatment through the second triple valve and the second desuperheating and pressure reducing device, and the treated steam is introduced into the heat exchanger, and the steam in the second path of the first triple valve is introduced into the high-pressure heating device.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] A system for improving the final feed water temperature of a steam turbine under partial load proposed by the present invention, in a state of low load (because the feed water temperature is already high under high load), extracts a part of the steam from the main steam pipeline and conducts preliminary desuperheating and pressure reduction treatment through a first desuperheating and pressure reduction device to obtain desuperheated and depressurized steam suitable for user use. Then, the desuperheated and depressurized steam is injected into a heat exchanger. After the steam undergoes heat exchange treatment in the heat exchanger and expands, its potential energy is converted into kinetic energy and it flows out from the nozzle of the heat exchanger and into a first triple valve. The first triple valve processes the steam and conducts secondary desuperheating and pressure reduction treatment through a second triple valve and a second desuperheating and pressure reduction device. After obtaining the desuperheated and depressurized steam, it enters the heat exchanger. At this time, the velocity of the mixed fluid after the first desuperheated and depressurized steam flowing in from the main steam pipeline is mixed with the second desuperheated and depressurized steam gradually becomes balanced, and the kinetic energy is conversely converted into potential energy to generate steam with an intermediate pressure, which enters a high-pressure heating device through the first triple valve for heating, thereby raising the feed water temperature at the outlet of the high-pressure heater and ultimately being able to supply heat to the steam turbine. Therefore, the system for improving the final feed water temperature of a steam turbine under partial load proposed by the present invention has good thermal performance economy, a simple thermal system, improves the final feed water temperature, and is beneficial to improving the efficiency of the steam turbine generator set.

[0023] Further, the second path of the first desuperheating and pressure reducing valve is sequentially connected with a first manual valve and a first desuperheating water regulating valve. The first desuperheating water regulating valve can automatically adjust the opening degree for desuperheating and pressure reduction. When the first desuperheating water regulating valve needs to be overhauled, the first manual valve can be closed to facilitate the overhaul of the first desuperheating water regulating valve.

[0024] Further, a check valve is connected between the second triple valve and the second desuperheating and pressure reduction device, which can prevent steam from flowing back.

[0025] Further, a safety valve is connected between the second triple valve and the check valve, which can play a safety role.

[0026] Further, the third path of the second desuperheating and pressure reducing valve is sequentially connected with a second manual valve and a second desuperheating water regulating valve. The second desuperheating water regulating valve can automatically adjust the opening degree for desuperheating and pressure reduction. When the second desuperheating water regulating valve needs to be overhauled, the second manual valve can be closed to facilitate the overhaul of the second desuperheating water regulating valve.

[0027] Further, the steam passing through the heat exchanger is introduced into the first triple valve at a high speed. In fact, this is the principle of a jet heat exchanger. Only at a very high speed can a lower pressure be formed, thereby generating a suction effect.

[0028] Furthermore, the first path of the No. 1 high-pressure heater is connected to the second path of the first triple valve, and the second path of the No. 1 high-pressure heater is connected to the boiler, which can solve the problems of unstable boiler water dynamics and SCR catalyst poisoning.

[0029] A method for using a system for improving the final feed water temperature of a steam turbine under partial load proposed by the present invention generates steam at an intermediate pressure through the combination of a first desuperheating and pressure reducing device and a second desuperheating and pressure reducing device, and enters a high-pressure heating device through a first triple valve for heating, thereby raising the feed water temperature at the outlet of the high-pressure heater, and finally being able to supply heat to the steam turbine. The operation is simple and easy to implement. Brief Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0031] Figure 1 It is a system diagram of the present invention for improving the final feed water temperature of a steam turbine under partial load.

[0032] Wherein: 1 - First regulating valve, 2 - First pneumatic gate valve, 3 - First desuperheating and pressure reducing device, 4 - First desuperheating water regulating valve, 5 - First manual valve, 6 - Heat exchanger, 7 - First triple valve, 8 - Second desuperheating water regulating valve, 9 - Second manual valve, 10 - Second desuperheating and pressure reducing device, 11 - Second regulating valve, 12 - Second manual gate valve, 13 - Check valve, 14 - Safety valve, 15 - Second triple valve. Detailed Embodiments

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0035] It should be noted that similar reference numerals and letters indicate similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0036] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the invention product is usually placed during use. This 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. Therefore, it should not be construed as a limitation to the present invention. In addition, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0037] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0038] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, if terms such as "set", "installed", "connected", "connected" are used, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. 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 situations.

[0039] The following further describes the present invention in detail with reference to the drawings:

[0040] A system for improving the final feed water temperature of a steam turbine under partial load proposed by the present invention, as Figure 1 shown, includes a first desuperheating and pressure reducing device, a heat exchanger 6, a first triple valve 7, a second triple valve 15, a second desuperheating and pressure reducing device, and a high-pressure heating device.

[0041] Steam is extracted from the main steam pipeline of the boiler and sent to the first desuperheating and pressure-reducing device for preliminary desuperheating and pressure-reducing treatment to obtain desuperheated and pressure-reduced steam suitable for user use. The desuperheated and pressure-reduced steam is injected into the heat exchanger 6 for heat exchange treatment and then expands, converting potential energy into kinetic energy and flowing out from the nozzle of the heat exchanger 6 and into the first triple valve 7. The exhaust steam of the first triple valve 7 is divided into two paths. The first path of steam of the first triple valve 7 successively passes through the second triple valve 15 and the second desuperheating and pressure-reducing device for secondary desuperheating and pressure-reducing treatment, and after obtaining the secondary desuperheated and pressure-reduced steam, it is introduced into the heat exchanger 6. At this time, the velocity of the mixed fluid after the first desuperheated and pressure-reduced steam flowing in from the main steam pipeline and the second desuperheated and pressure-reduced steam is gradually balanced, and the kinetic energy is conversely converted into potential energy to generate steam with an intermediate pressure, which is introduced into the high-pressure heating device through the second path of steam of the first triple valve 7 for heating, thereby raising the feed water temperature at the outlet of the high-pressure heater and ultimately being able to supply heat to the steam turbine.

[0042] Among them, the first desuperheating and pressure-reducing device includes a first regulating valve 1, a first pneumatic gate valve 2 and a first desuperheating and pressure-reducing valve 3. The first path of the first regulating valve 1 is connected to the main steam pipeline, the second path of the first regulating valve 1 is connected to the first path of the first pneumatic gate valve 2, and the second path of the first pneumatic gate valve 2 is connected to the first path of the first desuperheating and pressure-reducing valve 3; the second path of the first desuperheating and pressure-reducing valve 3 is connected to the heat exchanger 6, and the third path of the first desuperheating and pressure-reducing valve 3 is successively connected with a first manual valve 5 and a first desuperheating water regulating valve 4. The first desuperheating water regulating valve 4 of the spray desuperheating and pressure-reducing valve can automatically adjust the opening degree for desuperheating and pressure-reducing; when the first desuperheating water regulating valve 4 needs to be overhauled, the first manual valve 5 can be closed to facilitate the overhaul of the first desuperheating water regulating valve 4.

[0043] A check valve 13 is connected between the second triple valve 15 and the second desuperheating and pressure-reducing device, which can prevent steam from flowing back. The second desuperheating and pressure-reducing device includes a second desuperheating and pressure-reducing valve 10, a second regulating valve 11 and a second pneumatic gate valve 12; the first path of the second desuperheating and pressure-reducing valve 10 is connected to the heat exchanger 6, the second path of the second desuperheating and pressure-reducing valve 10 is connected to the first path of the second regulating valve 11, the second path of the second regulating valve 11 is connected to the first path of the second pneumatic gate valve 12, and the second path of the second pneumatic gate valve 12 is connected to the check valve 13. The third path of the second desuperheating and pressure-reducing valve 10 is successively connected with a second manual valve 9 and a second desuperheating water regulating valve 8. The second desuperheating water regulating valve 8 of the spray desuperheating and pressure-reducing valve can automatically adjust the opening degree for desuperheating and pressure-reducing; when the second desuperheating water regulating valve 8 needs to be overhauled, the second manual valve 9 can be closed to facilitate the overhaul of the second desuperheating water regulating valve 8.

[0044] The high-pressure heating device includes the No. 1 high-pressure heater and the No. 2 high-pressure heater; the first path of the No. 1 high-pressure heater is connected to the second path of the first triple valve 7, and the second path of the No. 1 high-pressure heater is connected to the boiler, which can solve the problems of unstable boiler water dynamics and SCR catalyst poisoning. The third path of the No. 1 high-pressure heater is connected to the first path of the No. 2 high-pressure heater, and the second path of the No. 2 high-pressure heater is connected to the steam turbine, thereby increasing the feed water temperature at the outlet of the high-pressure heater and ultimately being able to supply heat to the steam turbine.

[0045] A safety valve 14 is connected between the second triple valve 15 and the check valve 13, which can play a safety role.

[0046] A method for using a system for increasing the final feed water temperature of a steam turbine under partial load proposed by the present invention includes the following steps:

[0047] Steam is extracted from the main steam pipeline of the boiler to the first desuperheating and pressure reducing device for desuperheating and pressure reducing treatment to obtain desuperheated and pressure-reduced steam. The desuperheated and pressure-reduced steam is injected into the heat exchanger 6 for heat exchange to obtain heat exchange steam, and then the heat exchange steam is injected into the first triple valve 7;

[0048] The first path steam of the first triple valve 7 is successively subjected to desuperheating and pressure reducing treatment through the second triple valve 15 and the second desuperheating and pressure reducing device, and the treated steam is introduced into the heat exchanger 6. The second path steam of the first triple valve 7 is introduced into the high-pressure heating device.

[0049] The specific working principle of a system for increasing the final feed water temperature of a steam turbine under partial load proposed by the present invention is as follows:

[0050] When the load is lower than 40% (because the feed water temperature is already high at high loads), a part of the steam is extracted from the high-pressure main steam pipeline and enters the jet heat exchanger 6 through the first regulating valve 1, the first pneumatic gate valve 2, and the first desuperheating and pressure reducing device 3. The high-pressure main steam expands in the nozzle of the heat exchanger 6, converting potential energy into kinetic energy and spraying out from the nozzle of the heat exchanger 6 at a very high speed and only flowing into the first triple valve 7. A section of extraction steam flows out from the first triple valve 7, passes through the second triple valve 15, the check valve 13, the second manual gate valve 12, and the second regulating valve 11, and enters the jet heat exchanger 6 after being desuperheated and pressure reduced by the second desuperheating and pressure reducing device 10. The velocity of the mixed fluid after the high-pressure main steam and the extraction steam are mixed gradually becomes balanced, and the kinetic energy is conversely converted into potential energy to generate steam with an intermediate pressure, which enters the No. 1 high-pressure heater through the first triple valve 7 for heating. Since the inlet steam pressure of the No. 1 high-pressure heater is greater than the pressure of the extraction steam in the first stage, the feed water temperature at the outlet of the No. 1 high-pressure heater can be effectively increased. Connecting the No. 1 high-pressure heater and the No. 2 high-pressure heater can ultimately achieve the cascaded utilization of energy and improve the efficiency of the steam turbine generator set. Among them, the cooled steam flowing out of the No. 1 high-pressure heater condenses into water and then flows into the No. 2 high-pressure heater to heat the feed water, realizing the cascaded utilization of energy.

[0051] Steam is ejected from the nozzle of the heat exchanger 6 at a very high speed to the first triple valve 7. In fact, this is the principle of the jet heat exchanger. Only at a very high speed can a lower pressure be formed, which can generate a suction effect.

[0052] After being desuperheated and depressurized by the second desuperheating and depressurizing device 10, it enters the jet heat exchanger 6 (sucking the steam with a lower pressure into the heat exchanger 6), which can generate a suction effect.

[0053] A system and a usage method for improving the final feed water temperature of a steam turbine under partial load proposed by the present invention generate steam with an intermediate pressure through the combination of the first desuperheating and depressurizing device and the second desuperheating and depressurizing device. The steam enters the high-pressure heating device through the first triple valve 7 for heating, thereby raising the feed water temperature at the outlet of the high-pressure heater. Ultimately, it can supply heat to the steam turbine, and the operation is simple and easy to implement. It can solve the problem of the relatively low final feed water temperature under partial load conditions and avoid problems such as unstable boiler water dynamics and poisoning of the SCR catalyst.

[0054] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A system for increasing the final feed water temperature of a steam turbine under part load, characterized in that, It comprises a first temperature-reducing and pressure-reducing device, a heat exchanger (6), a first triple valve (7), a second triple valve (15), a second temperature-reducing and pressure-reducing device, and a high-pressure heating device; Steam is extracted from the main steam pipeline of the boiler and sent to the first temperature reduction and pressure reduction device for temperature reduction and pressure reduction treatment to obtain temperature reduction and pressure reduction steam. The temperature reduction and pressure reduction steam is injected into the heat exchanger (6) for heat exchange to obtain heat exchange steam. The heat exchange steam is then introduced into the first triple valve (7) at a high speed. The exhaust steam of the first triple valve (7) is divided into two paths. The first path of steam from the first triple valve (7) is sequentially passed through the second triple valve (15) and the second temperature reduction and pressure reduction device for temperature reduction and pressure reduction treatment. The treated steam is introduced into the heat exchanger (6) and mixed with the main steam to form steam of intermediate pressure. The second path of steam from the first triple valve (7) is introduced into the high-pressure heating device. The heat exchanger (6) is a jet heat exchanger.

2. The system for increasing the final feed water temperature of a steam turbine under partial load according to claim 1, characterized in that, The first temperature and pressure reduction device comprises a first regulating valve (1), a first pneumatic gate valve (2) and a first temperature and pressure reduction device (3); The first path of the first regulating valve (1) is connected to the main steam pipeline, the second path of the first regulating valve (1) is connected to the first path of the first pneumatic gate valve (2), the second path of the first pneumatic gate valve (2) is connected to the first path of the first temperature reducing and pressure reducing device (3); and the second path of the first temperature reducing and pressure reducing device (3) is connected to the heat exchanger (6).

3. The system for increasing the final feed water temperature of a steam turbine under part load according to claim 2, characterized in that, The third circuit of the first temperature reducing and pressure reducing device (3) is connected in sequence to a first manual door (5) and a first temperature reducing water regulating valve (4).

4. The system for increasing the final feed water temperature of a steam turbine under part load according to claim 1, wherein, A check valve (13) is connected between the second triple valve (15) and the second temperature and pressure reduction device.

5. The system for increasing the final feed water temperature of a steam turbine under partial load according to claim 4, characterized in that, A safety valve (14) is connected between the second triple valve (15) and the check valve (13).

6. The system for increasing the final feed water temperature of a steam turbine under part load according to claim 4, characterized in that, The second temperature and pressure reduction device comprises a second temperature and pressure reduction device (10), a second regulating valve (11) and a second pneumatic gate valve (12); The first path of the second temperature-reducing and pressure-reducing device (10) is connected to the heat exchanger (6), the second path of the second temperature-reducing and pressure-reducing device (10) is connected to the first path of the second regulating valve (11), the second path of the second regulating valve (11) is connected to the first path of the second pneumatic gate valve (12), and the second path of the second pneumatic gate valve (12) is connected to the check valve (13).

7. The system for increasing the final feed water temperature of a steam turbine under part load according to claim 6, characterized in that, The third path of the second temperature-reducing and pressure-reducing device (10) is connected in sequence to a second manual door (9) and a second temperature-reducing water regulating valve (8).

8. The system for increasing the final feed water temperature of a steam turbine under part load according to claim 1, wherein The high-pressure heating device includes high-pressure heater No. 1 and high-pressure heater No. 2; The first line of the No. 1 high-pressure heater is connected to the second line of the first triple valve (7), the second line of the No. 1 high-pressure heater is connected to the boiler, the third line of the No. 1 high-pressure heater is connected to the first line of the No. 2 high-pressure heater, and the second line of the No. 2 high-pressure heater is connected to the turbine.

9. A method for using the system for increasing the final feed water temperature of a steam turbine under partial load according to any one of claims 1 to 8, characterized in that: The steps include: Extract steam from the main steam pipeline of the boiler to the first desuperheating and decompression device for desuperheating and decompression to obtain desuperheated and decompressed steam, inject the desuperheated and decompressed steam into the heat exchanger (6) for heat exchange to obtain heat exchange steam, and then inject the heat exchange steam into the first triple valve (7); The first path of steam from the first triple valve (7) sequentially passes through the second triple valve (15) and the second desuperheating and pressure reducing device for desuperheating and pressure reducing treatment, and the treated steam is introduced into the heat exchanger (6). The second path of steam from the first triple valve (7) is introduced into the high-pressure heating device.

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