A regenerative system based on a back-pressure steam turbine

Abstract

The present invention belongs to the technical field of heat recovery system, and specifically relates to a heat recovery system based on a back-pressure steam turbine, including a high-pressure heater, a deaerator, a filter device, a feed water pump, a low-pressure heater, a steam extraction pipeline and valves on the pipeline, and a drain pipeline and a drain valve before and after the valve. The exhaust pipeline is connected to the middle stage of the back-pressure steam turbine for extracting steam and conveying steam to the high-pressure heater and the low-pressure heater for heating the feed water inside the high-pressure heater and the low-pressure heater. The heat recovery system based on the back-pressure steam turbine effectively improves the use effect of the tube bundle, thereby making the use of the high-pressure heater safer and more stable, effectively avoiding the occurrence of accidents, effectively purifying the water source entering the tube bundle, and effectively avoiding the blockage of the tube bundle. At the same time, the inclined state is set to facilitate the subsequent cleaning of the inside of the tube bundle.

Description

Technical Field

[0001] The present invention belongs to the technical field of regenerative systems, and particularly relates to a regenerative system based on a back-pressure steam turbine. Background Art

[0002] The regenerative system refers to the system between the steam extraction ports of the steam turbine and each heater. The regenerative system is not only the basis of the steam turbine thermal system but also the core of the whole plant thermal system, playing a decisive role in the thermal economy of the unit and the power plant. The cycle of the regenerative system mainly consists of a heating system composed of high-pressure heaters, low-pressure heaters, regenerative steam extraction pipelines, water pipelines, and drain pipelines. The high-pressure heater is the core of this system, and the stable and safe operation thereof is related to the efficient operation of the whole system.

[0003] However, in the actual regenerative system during the heating treatment of feed water, the heating treatment of the feed water in the internal tube bundles of the high-pressure heater or low-pressure heater is mainly achieved by extracting some steam from the steam turbine to the high-pressure heater and the low-pressure heater. However, since the water source of the feed water has been transported multiple times and contains certain impurities, when it enters the internal tube bundles of the high-pressure heater, due to the parallel distribution of the tube bundles, it is easy to cause the accumulation and blockage of the tube bundles, thereby affecting the heat transfer performance. At the same time, the connection method between the water inlet end and the water outlet end of the internal tube bundles of the high-pressure heater often uses ordinary welding. In the use inside the high-pressure heater tank, corrosion will occur at the welded joints, resulting in feed water leakage. This will cause more tube bundles around the leaking pipe to leak due to the impact of high-pressure feed water, and the leakage will be more serious. After the leakage, since the water side pressure is 20 MPa, which is much higher than the steam side pressure of 4 MPa, when the water level in the high-pressure heater rises sharply and the water level protection does not act, the water level will submerge the steam extraction inlet pipeline, and the steam with water will return to the steam pipeline and even enter the intermediate pressure cylinder, causing a water hammer accident in the steam turbine, directly affecting the economy and safety of large units. Therefore, it is urgent to design a regenerative system based on a back-pressure steam turbine to solve the above problems. Summary of the Invention

[0004] The purpose of the present invention is to provide a regenerative system based on a back-pressure steam turbine to solve the problems in the above background art that the water source of the feed water easily causes the accumulation and blockage of the tube bundles, thereby affecting the heat transfer performance, and the feed water leakage causes a water hammer accident in the steam turbine, directly affecting the economy and safety of large units.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a heat recovery system based on a back-pressure steam turbine, the heat recovery system of the back-pressure steam turbine includes a high-pressure heater, a deaerator, a filtering device, a feed water pump, a low-pressure heater, a steam extraction pipe and valves on the pipe, and a drain pipe and a drain valve before and after the valve. The steam extraction pipe is connected to the middle stage of the back-pressure steam turbine for extracting steam and transporting steam to the high-pressure heater and the low-pressure heater for heating the feed water inside the high-pressure heater and the low-pressure heater. The filtering device is installed at the front end of the feed water pipe of the high-pressure heater group for filtering and cleaning the feed water.

[0006] Preferably, the No. 1, 2 and 3 high-pressure heaters are externally connected to a large water supply bypass system for water supply treatment inside the high-pressure heaters, and the No. 5 and 6 low-pressure heaters are externally connected to small condensate bypasses respectively; the No. 7 and No. 8 combined low-pressure heaters are arranged at the throat of the recovery device and are externally connected to a condensate bypass.

[0007] Preferably, the steam extraction pipeline is equipped with a steam extraction check valve and an electric isolating valve, and thermocouples are provided on the upper and lower parts of the pipeline in front of each section of the steam extraction check valve, so as to detect whether water accumulates in the pipe according to the temperature difference between the upper and lower parts of the pipeline, and there are eight groups of steam extraction pipelines in total, the first, second and third groups of steam extraction are respectively supplied to three high-pressure heaters, the fourth group of steam extraction is supplied to a deaerator, a steam-driven feed water pump and an auxiliary steam manifold, the fifth, sixth, seventh and eighth groups of steam extraction are respectively supplied to four low-pressure heaters, and the water of each stage of heater is drained by gravity step by step.

[0008] Preferably, the heat recovery system includes a low-pressure heat recovery system and a high-pressure heat recovery system, and the low-pressure heat recovery system includes a pipeline system from the recovery device to the low-pressure heater and the deaerator, and the high-pressure heat recovery system includes a pipeline system from the high-pressure heater unit after the recovery device to the boiler economizer. Conventionally, the deaerator is used as the boundary, and the feed water heating system after the deaerator to the boiler economizer is called a high-pressure heat recovery heating system, and the condensate water system from the recovery device to the deaerator is called a low-pressure heat recovery heating system.

[0009] Preferably, the high-pressure heater includes a high-pressure heater main body, a sealing assembly, a support assembly, a tube bundle, a positioning rod, and a support plate. The high-pressure heater main body includes a tank body. A feed water outlet, a steam inlet, and a drain inlet are provided at the top of the tank body. A feed water inlet, a normal drain outlet, and an emergency drain outlet are provided below the tank body. The sealing assembly is arranged at the manhole of the tank body. The support assembly is installed inside the tank body. The support assembly includes a flow dividing partition plate. A sealing door is connected to the inclined end of the flow dividing partition plate. A first support sealing plate is connected to the horizontal end of the flow dividing partition plate. A positioning ring is connected to the side of the first support sealing plate away from the flow dividing partition plate. A second support sealing plate is connected to the inner wall of the positioning ring. The inlet end and the outlet end of the tube bundle are clamped between the second support sealing plate and the first support sealing plate. The tube bundle is in a U-shaped structure and is inclined as a whole.

[0010] Preferably, a filter screen layer is arranged inside the feed water inlet. A partition plate is arranged below the drain inlet. Threaded columns are arranged on one side of the flow dividing partition plate close to the sealing door, and positioning holes are provided on the sealing door corresponding to the threaded columns. The first support sealing plate is in a stepped shape. A guiding hole is provided on the first support sealing plate, and the inner diameter of the guiding hole is smaller than the inner diameter of the tube bundle. The side of the guiding hole of the first support sealing plate close to the tube bundle is in a stepped shape. The inlet end and the outlet end of the tube bundle are in a stepped shape, and this stepped shape is clamped between the first support sealing plate and the second support sealing plate. Sealing gaskets are arranged on the sides of the second support sealing plate and the first support sealing plate close to each other.

[0011] Preferably, positioning holes are evenly provided on the positioning ring, and positioning rods penetrate through the positioning holes. Support plates are evenly sleeved on the outer part of the positioning rods, and the support plates are evenly distributed outside the tube bundle. Both ends of the support plate are in a stepped shape, and both ends of the support plate are respectively fastened to the positioning rod and the positioning ring through nuts.

[0012] Preferably, the sealing assembly includes a first hinged plate. The first hinged plate is connected to the inner wall of the tank body through a hinge seat. The other end of the first hinged plate is hinged to a second hinged plate. The other end of the second hinged plate is connected to a first sealing plate through a hinge seat. The other side of the first sealing plate is connected to a second sealing plate through a threaded column. The second sealing plate and the first sealing plate are respectively clamped on both sides of the manhole of the tank body, and sealing gaskets are arranged on the sides of the first sealing plate and the second sealing plate close to the manhole. A handle is arranged on the outer wall of the second sealing plate.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: For a regenerative system based on a back-pressure steam turbine, through the addition of a filtering device, it is possible to filter the water source entering the high-pressure heater, thereby ensuring the cleanliness of the water source entering the interior of the high-pressure heater, effectively avoiding the accumulation of impurities inside the water source in the tube bundle, which may lead to the blockage of the tube bundle and, in severe cases, cause the bursting of the tube bundle, thus effectively improving the service effect of the tube bundle, and further making the use of the high-pressure heater safer and more stable, effectively avoiding the occurrence of accident hazards.

[0014] The present invention improves the connection method of the tube bundle inside the high-pressure heater, effectively reducing the welding points of the internal components of the high-pressure heater, thereby effectively avoiding the corrosion of its welding points. Furthermore, the connection and sealing of the tube bundle are achieved through the clamping of two support sealing plates, greatly improving the sealing performance of the tube bundle connection, effectively reducing the leakage at the tube bundle connection, further greatly reducing the occurrence of unnecessary accidents, improving the safety of the high-pressure heater during use. At the same time, through the inclined setting of the tube bundle, in cooperation with the filter screen provided at the water inlet and the external filtering device, the water source entering the tube bundle is effectively purified, effectively avoiding the blockage of the tube bundle. Moreover, the inclined state setting facilitates the subsequent cleaning inside the tube bundle. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a block diagram of the regenerative system of the present invention;

[0016] Figure 2 is a schematic diagram of the overall structure of the high-pressure heater of the present invention;

[0017] Figure 3 is a schematic sectional view of the high-pressure heater of the present invention;

[0018] Figure 4 is a schematic diagram of the structure of the sealing component of the present invention;

[0019] Figure 5 is a schematic diagram of the structure of the support component of the present invention;

[0020] Figure 6 is a partial sectional view of the support component of the present invention;

[0021] Figure 7 is an exploded sectional view of the support component of the present invention;

[0022] In the figure: 1. High-pressure heater body; 11. Tank body; 12. Water supply outlet; 13. Water supply inlet; 14. Steam inlet; 15. Normal drain outlet; 16. Drain inlet; 17. Accident drain outlet; 2. Sealing assembly; 21. First hinged plate; 22. Second hinged plate; 23. First sealing plate; 24. Second sealing plate; 3. Support assembly; 31. Diverter baffle; 32. Sealing door; 33. First supporting sealing plate; 34. Positioning ring; 35. Second supporting sealing plate; 4. Tube bundle; 5. Positioning rod; 6. Support plate. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Please see attached Figure 1-7 , several embodiments provided by the present invention:

[0025] A heat recovery system based on a back-pressure steam turbine comprises a high-pressure heater, a deaerator, a filtering device, a feed water pump, a low-pressure heater, a steam extraction pipeline and valves on the pipeline, and a drain pipeline and a drain valve before and after the valve. The steam extraction pipeline is connected to the middle stage of the back-pressure steam turbine for extracting steam and conveying steam to the high-pressure heater and the low-pressure heater for heating the feed water inside the high-pressure heater and the low-pressure heater. The filtering device is installed at the front end of the feed water pipeline of the high-pressure heater group for filtering and cleaning the feed water.

[0026] Furthermore, the No. 1, 2, and 3 high-pressure heaters are externally connected to a large water supply bypass system for water supply treatment inside the high-pressure heaters, and the No. 5 and 6 low-pressure heaters are externally connected to small condensate bypasses respectively; the No. 7 and 8 combined low-pressure heaters are arranged at the throat of the recovery device, and are externally connected to a condensate bypass.

[0027] Furthermore, a steam extraction check valve and an electric isolating valve are installed on the steam extraction pipeline, and thermocouples are arranged on the upper and lower parts of the pipeline in front of each section of the steam extraction check valve, so as to detect whether there is water accumulation in the pipe according to the temperature difference between the upper and lower parts of the pipeline, and there are eight groups of steam extraction pipelines in total, the first, second and third groups of steam extraction are respectively supplied to three high-pressure heaters, the fourth group of steam extraction is supplied to a deaerator, a steam-driven feed water pump and an auxiliary steam manifold, the fifth, sixth, seventh and eighth groups of steam extraction are respectively supplied to four low-pressure heaters, and the water of each stage of heater is drained step by step.

[0028] Further, the regenerative system includes a low-pressure regenerative system and a high-pressure regenerative system. The low-pressure regenerative system includes a pipeline system for the output of the recuperator to the low-pressure heaters and the deaerator. The high-pressure regenerative system includes a pipeline system from the high-pressure heater unit after the recuperator to the economizer of the boiler. Conventionally, with the deaerator as the boundary, the feed water heating system from the deaerator to the economizer of the boiler is called the high-pressure regenerative heating system, and the condensate water system from the output of the recuperator to the deaerator is called the low-pressure regenerative heating system.

[0029] Further, the high-pressure heater includes a high-pressure heater main body 1, a sealing assembly 2, a support assembly 3, a tube bundle 4, a positioning rod 5, and a support plate 6. The high-pressure heater main body 1 includes a tank body 11. A feed water outlet 12, a steam inlet 14, and a drain inlet 16 are provided at the top of the tank body 11. A feed water inlet 13, a normal drain outlet 15, and an emergency drain outlet 17 are provided below the tank body 11. The sealing assembly 2 is arranged at the manhole of the tank body 11. The support assembly 3 is installed inside the tank body 11. The support assembly 3 includes a flow dividing partition 31. A sealing door 32 is connected to the inclined end of the flow dividing partition 31. A first support sealing plate 33 is connected to the horizontal end of the flow dividing partition 31. A positioning ring 34 is connected to the side of the first support sealing plate 33 away from the flow dividing partition 31. A second support sealing plate 35 is connected to the inner wall of the positioning ring 34. The inlet end and the outlet end of the tube bundle 4 are clamped and connected between the second support sealing plate 35 and the first support sealing plate 33. The tube bundle 4 is of a U-shaped structure, and the tube bundle 4 is integrally distributed in an inclined shape. The inclined distribution can effectively avoid the residue of water source inside the tube bundle 4, further reduce the residue of impurities inside the tube bundle 4, thus effectively avoiding the blockage inside the tube bundle 4. At the same time, the inclined distribution is convenient for subsequent flushing of the tube bundle 4 and the discharge of sewage.

[0030] Furthermore, a filter screen layer is provided inside the water inlet 13. The setting of the filter screen layer further realizes the filtration treatment of the feed water and filters out impurities. A partition plate is provided below the drain inlet 16. Threaded posts are provided on one side of the shunt partition plate 31 close to the sealing door 32, and positioning holes are provided on the sealing door 32 corresponding to the threaded posts. The two are fastened by nuts, which is convenient for maintaining the internal parts and plays a role in blocking water. The first support sealing plate 33 is in a stepped shape. A guiding hole is provided on the first support sealing plate 33, and the inner diameter of the guiding hole is smaller than the inner diameter of the tube bundle 4. The side of the guiding hole of the first support sealing plate 33 close to the tube bundle 4 is in a stepped shape. The water inlet end and the water outlet end of the tube bundle 4 are in a stepped shape, and this stepped shape is clamped between the first support sealing plate 33 and the second support sealing plate 35. A sealing gasket is provided on the side where the second support sealing plate 35 and the first support sealing plate 33 are close to each other. Through the mutual clamping of the first support sealing plate 33 and the second support sealing plate 35, the connection and sealing of the end of the tube bundle 4 are realized. By setting this structure to replace the traditional welding method, the sealing performance is better and the safety of the high-pressure heater during use is improved.

[0031] Furthermore, positioning holes are evenly provided on the positioning ring 34, and positioning rods 5 penetrate through the positioning holes. Support plates 6 are evenly sleeved on the outside of the positioning rods 5, and the support plates 6 are evenly distributed outside the tube bundle 4. Both ends of the support plate 6 are in a stepped shape, and both ends of the support plate 6 are respectively fastened and connected to the positioning rod 5 and the positioning ring 34 by nuts. Through the uniform distribution of the support plates 6, the auxiliary positioning of the tube bundle 4 can be realized, effectively avoiding the shaking of the tube bundle 4 due to local fracture and preventing collisions between them, further improving its safety during use.

[0032] Furthermore, the sealing assembly 2 includes a first hinged plate 21. The first hinged plate 21 is connected to the inner wall of the tank body 11 through a hinge seat. The other end of the first hinged plate 21 is hinged to a second hinged plate 22. The other end of the second hinged plate 22 is connected to a first sealing plate 23 through a hinge seat. The other side of the first sealing plate 23 is connected to a second sealing plate 24 through a threaded post. The second sealing plate 24 and the first sealing plate 23 are respectively clamped on both sides of the manhole of the tank body 11, and sealing gaskets are provided on the sides of the first sealing plate 23 and the second sealing plate 24 close to the manhole. A handle is provided on the outer wall of the second sealing plate 24. The setting of this structure is used for the sealing treatment of the tank body 11. At the same time, the manhole is provided to facilitate personnel to carry out internal maintenance. Through the connection between the nuts and the threaded posts of the second sealing plate 24 and the first sealing plate 23, the first sealing plate 23 and the second sealing plate 24 clamp and seal the edge of the manhole.

[0033] Working principle:

[0034] By extracting part of the steam of the steam turbine to the high-pressure heater and the low-pressure heater, the heating treatment of the feed water inside the high-pressure heater or the low-pressure heater is realized, and the steam is collected inside the tank body 11 through the connection with the steam inlet 14. The feed water inlet 13 is connected to the external feed water pipe to convey water to the temporal part of the tank body 11. Through the arrangement of the first support sealing plate 33 and the second support sealing plate 35, the water source is conveyed to the upper half of the shunt partition plate 31 through the tube bundle 4, and further discharged through the feed water outlet 12. And during the process of the feed water passing through the tube bundle 4, it is heated by the steam from the steam inlet 14.

[0035] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

Claims

1. A regenerative system based on a back-pressure steam turbine, characterized in that: The regenerative system of a back-pressure steam turbine includes high-pressure heaters, deaerators, filtering devices, feed pumps, low-pressure heaters, extraction steam pipelines, valves on the pipelines, and drain pipelines and drain valves before and after the valves. The extraction steam pipeline is connected to the intermediate stage of the back-pressure steam turbine for extracting steam and transporting it to the high-pressure heater and the low-pressure heater for heating the feed water inside the high-pressure heater and the low-pressure heater. The filtering device is installed at the front end of the feed water pipeline of the high-pressure heater group for filtering and cleaning the feed water. The high-pressure heater includes a high-pressure heater main body (1), a sealing assembly (2), a support assembly (3), a tube bundle (4), a positioning rod (5), and a support plate (6). The high-pressure heater main body (1) includes a tank body (11). A feed water outlet (12), a steam inlet (14), and a drain inlet (16) are provided at the top of the tank body (11). A feed water inlet (13), a normal drain outlet (15), and an accident drain outlet (17) are provided below the tank body (11). The sealing assembly (2) is arranged at the manhole of the tank body (11). The support assembly (3) is installed inside the tank body (11). The support assembly (3) includes a flow dividing partition plate (31). A sealing door (32) is connected to the inclined end of the flow dividing partition plate (31). A first support sealing plate (33) is connected to the horizontal end of the flow dividing partition plate (31). A positioning ring (34) is connected to the side of the first support sealing plate (33) away from the flow dividing partition plate (31). A second support sealing plate (35) is connected to the inner wall of the positioning ring (34). The inlet end and the outlet end of the tube bundle (4) are clamped and connected between the second support sealing plate (35) and the first support sealing plate (33). The tube bundle (4) is of a U-shaped structure and is integrally distributed in an inclined shape. A filter screen layer is arranged inside the feed water inlet (13). A partition plate is arranged below the drain inlet (16). A threaded column is arranged on the side of the flow dividing partition plate (31) close to the sealing door (32), and the sealing door (32) is provided with a positioning hole corresponding to the threaded column. The first support sealing plate (33) is of a stepped shape. A guiding hole is provided on the first support sealing plate (33), and the inner diameter of the guiding hole is smaller than the inner diameter of the tube bundle (4). The side of the guiding hole of the first support sealing plate (33) close to the tube bundle (4) is of a stepped shape. The inlet end and the outlet end of the tube bundle (4) are of a stepped shape, and this stepped shape is clamped between the first support sealing plate (33) and the second support sealing plate (35). Sealing gaskets are arranged on the sides of the second support sealing plate (35) and the first support sealing plate (33) close to each other.

2. The regenerative system based on a back-pressure steam turbine according to claim 1, characterized in that: A large feed water bypass system is externally connected to the first, second, and third high-pressure heaters for feed water treatment inside the high-pressure heaters. Small condensate bypasses are externally connected to the fifth and sixth low-pressure heaters respectively. The seventh and eighth combined low-pressure heaters are arranged in the throat of the recovery device and are externally connected to a condensate bypass.

3. The regenerative system based on a back-pressure steam turbine according to claim 1, characterized in that: A steam extraction check valve and an electric isolating valve are installed on the steam extraction pipeline. Thermocouples are provided above and below the pipeline in front of each steam extraction check valve to detect whether there is water accumulation in the pipeline based on the temperature difference between the upper and lower parts of the pipeline. There are a total of eight groups of steam extraction pipelines. The steam extraction of the first, second, and third groups is respectively supplied to three high-pressure heaters. The steam extraction of the fourth group is supplied to the deaerator, the motor-driven feed water pump, and the auxiliary steam header. The steam extraction of the fifth, sixth, seventh, and eighth groups is respectively supplied to four low-pressure heaters. The drain water of each stage of the heater flows by gravity step by step.

4. The regenerative system based on a back-pressure steam turbine according to claim 1, characterized in that: The regenerative system includes a low-pressure regenerative system and a high-pressure regenerative system. The low-pressure regenerative system includes a pipeline system for the output of the recuperator to the low-pressure heaters and the deaerator. The high-pressure regenerative system includes a pipeline system from the high-pressure heater unit after the recuperator to the economizer of the boiler. Conventionally, with the deaerator as the boundary, the feed water heating system from the deaerator to the economizer of the boiler is called the high-pressure regenerative heating system, and the condensate water system from the output of the recuperator to the deaerator is called the low-pressure regenerative heating system.

5. The regenerative system based on a back-pressure steam turbine according to claim 1, characterized in that: The positioning ring (34) is evenly provided with positioning holes, and positioning rods (5) penetrate through the inside of the positioning holes. Support plates (6) are evenly sleeved on the outside of the positioning rods (5), and the support plates (6) are evenly distributed on the outside of the tube bundle (4). Both ends of the support plate (6) are in a stepped shape, and both ends of the support plate (6) are respectively fixedly connected to the positioning rod (5) and the positioning ring (34) through nuts.

6. The regenerative system based on a back-pressure steam turbine according to claim 1, characterized in that: The sealing assembly (2) includes a first hinged plate (21). The first hinged plate (21) is connected to the inner wall of the tank body (11) through a hinge seat. The other end of the first hinged plate (21) is hinged to a second hinged plate (22). The other end of the second hinged plate (22) is connected to a first sealing plate (23) through a hinge seat. The other side of the first sealing plate (23) is connected to a second sealing plate (24) through a threaded column. The second sealing plate (24) and the first sealing plate (23) are respectively clamped on both sides of the manhole of the tank body (11), and sealing gaskets are provided on the sides of the first sealing plate (23) and the second sealing plate (24) close to the manhole. A handle is provided on the outer wall of the second sealing plate (24).

Images