Bypass switching device for main condenser of steam turbine and using method of bypass switching device

Abstract

The invention discloses a bypass switching device for a main condenser of a steam turbine and a using method thereof, and belongs to the technical field of steam condensing systems of steam turbines. The device comprises a steam turbine exhaust port, a condenser throat part, a sealing plate mounting inlet / outlet, a split type sealing flange plate and a safety valve. The detachable sealing plate mounting opening is formed in the side wall of the condenser throat, the split type sealing flange plate passes through the detachable sealing plate mounting opening and is spliced and fixed, a steam exhaust opening of a steam turbine and a condenser body can be isolated, and a main condenser is switched into a bypass condenser; the functions of the main condenser can be recovered by dismounting the flange plate. Welding and cutting are not needed in the switching process, and the switching time of a single device is short. The relief valve provides overpressure protection during bypass operation. An independent bypass condenser does not need to be additionally arranged, compared with a traditional scheme, the initial investment cost is reduced, the system structure is simplified, the maintenance workload is reduced, the unit operation flexibility and safety are improved, and the method is suitable for waste incineration power generation and other machine-along-furnace operation scenes.

Description

Technical Field

[0001] The present invention relates to the technical field of steam turbine condensing systems, and specifically to a bypass switching device for a main condenser of a steam turbine and its usage method, which is applicable to steam turbine generator sets that require "the turbine following the boiler" operation, such as waste incineration power generation and cogeneration of heat and power. Background Art

[0002] In fields such as waste incineration power generation and industrial waste heat utilization, steam turbine generator sets often adopt the "turbine following the boiler" operation mode, that is, the operating state of the steam turbine is adjusted with the operation of the boiler (or waste heat boiler). When the steam turbine is shut down due to the need for core components such as the rotor and cylinder to be returned to the factory for maintenance, in order to maintain the continuous operation of the incinerator or waste heat boiler and avoid garbage accumulation or waste heat waste, a bypass steam condensation system needs to be set up to receive the steam generated by the boiler.

[0003] In traditional technical solutions, usually a set of independent bypass condensers is equipped, and this bypass condenser needs to be independently configured with a complete system such as a cooling water pipeline, a vacuum pump, and a condensate pump. However, this design has significant defects:

[0004] High initial investment cost: The purchase and installation costs of the independent bypass condenser and its supporting system significantly increase the project cost. Especially for small and medium-sized units, the proportion of equipment investment is significantly increased.

[0005] High system complexity: The dual-condenser system leads to a complex pipeline layout, an increase in the number of accessories such as valves and instruments, and increases the design difficulty and failure rate of the control system.

[0006] Large maintenance workload: The two condensers need to be separately subjected to daily maintenance, cleaning, and anti-corrosion treatment, consuming a large amount of manpower and material resources. Moreover, the long-term idle bypass condenser is prone to problems such as pipeline blockage and seal aging.

[0007] Space occupation problem: The independent bypass condenser needs to additionally occupy the plant space. Especially in renovation projects, it may lead to a compact equipment layout and affect the operation convenience.

[0008] In the prior art, there have also been attempts to achieve the function conversion of the condenser through valve switching. However, such solutions require permanent modification to the main condenser body structure (such as welding isolation baffles), and there are the following deficiencies:

[0009] Time-consuming switching process: Welding or cutting operations require the unit to be shut down for a long time, affecting the unit availability;

[0010] Risk of structural damage: Welding thermal stress may cause deformation of the condenser throat, affecting the sealing performance and long-term operation reliability;

[0011] Limited function recovery: After permanent modification, the original high-efficiency operation performance of the main condenser may not be fully restored.

[0012] Therefore, how to achieve a fast and lossless switch between the main condenser and the bypass condenser without adding an independent bypass condenser, while ensuring the safety and economy of the system, has become a technical problem to be solved urgently in this field. Summary of the Invention

[0013] The present invention aims to overcome the above-mentioned disadvantages of the prior art and provides a bypass switching device for a steam turbine main condenser and its usage method.

[0014] The technical solution adopted by the present invention is as follows:

[0015] A bypass switching device for a steam turbine main condenser includes:

[0016] A steam turbine exhaust port, connected to the inlet end of the condenser throat;

[0017] A sealing plate installation inlet / outlet, arranged on the side wall of the condenser throat, for detachably sealing the flange plate to enter or exit the condenser throat;

[0018] At least one set of sealing flange plates, fed into the condenser throat through the sealing plate installation inlet / outlet, for isolating the steam turbine exhaust port from the condenser body when the steam turbine is shut down;

[0019] A safety valve, connected to the condenser throat or the condenser body, for overpressure protection during bypass operation.

[0020] Further, the sealing flange plate is of a multi-piece split structure, and the sealing flange plates are sequentially spliced along the axial direction of the condenser throat to form a complete isolation sealing surface.

[0021] Further, a sealing gasket installation groove is arranged on the edge of the sealing flange plate for installing a sealing gasket with high temperature resistance and steam erosion resistance.

[0022] Further, the number of the sealing plate installation inlet / outlets is 2, symmetrically distributed on both side walls of the condenser throat.

[0023] Further, a sealing plate is arranged at the sealing plate installation inlet / outlet to keep it sealed during the working state of the condenser.

[0024] Further, the opening pressure of the safety valve is set to 1.1 - 1.3 times the normal operating pressure of the condenser for releasing the excess steam pressure under accident conditions.

[0025] Further, a usage method of a bypass switching device for a steam turbine main condenser, switching to a bypass condenser includes the following steps:

[0026] S1: Feed the sealing flange plates into the condenser throat one by one through the sealing plate installation inlet / outlet;

[0027] S2: Assemble the sealing flange plates in a predetermined order, and install sealing gaskets between adjacent flange plates and between the flange plates and the inner wall of the condenser throat;

[0028] S3: Fix the sealing flange plates at the preset installation positions on the condenser throat through bolts to form a complete isolation and sealing structure;

[0029] S4: Start the bypass steam pipeline, condense the steam through the condenser body, and put the safety valve into the standby protection state.

[0030] Furthermore, the steps for restoring to the main condenser include the following:

[0031] Close the bypass steam pipeline and stop the condenser;

[0032] Remove the connecting bolts and sealing gaskets of the sealing flange plates;

[0033] Take out the sealing flange plates one by one through the installation inlets / outlets of the sealing plates, and restore the connection between the steam exhaust port of the steam turbine and the condenser body.

[0034] Furthermore, the splicing order of the sealing flange plates starts from one end of the condenser throat far away from the installation inlets / outlets of the sealing plates to ensure uniform stress on the seal.

[0035] Furthermore, when fixing the sealing flange plates in step S3, the bolts are tightened symmetrically and step by step.

[0036] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows:

[0037] Through the detachable sealing isolation device and the standardized switching process, the present invention realizes the rapid and non-destructive functional conversion between the main condenser of the steam turbine and the independent bypass condenser, and has significant technical advantages and economic value:

[0038] Greatly reduce the initial investment cost: There is no need to add an independent bypass condenser and supporting systems. Utilize the existing cooling pipelines and equipment of the main condenser, reduce the investment in the bypass system compared with the traditional scheme, and save the occupied space of the plant at the same time.

[0039] Rapid switching and non-destructive restoration: Through the modular installation of the split sealing flange plates, the switching time of a single set of devices is short, and the switching process does not involve permanent modifications such as welding and cutting. Only the isolation or connection is achieved through bolt connection. After restoration, the performance parameters of the main condenser are the same as the original state, ensuring the long-term reliability of the equipment.

[0040] System Simplification and Convenient Maintenance: The dual-condenser configuration is cancelled, reducing the number of accessories such as valves and pipelines, and lowering the complexity of the control system; The detachable structure enables daily maintenance to only check the status of the sealing gaskets and bolts, reducing the maintenance workload compared to traditional dual systems, and significantly enhancing the operation flexibility and availability of the unit. Description of the Drawings

[0041] Figure 1 is the overall structural schematic diagram of the present invention;

[0042] Figure 2 is the structural schematic diagram of the sealing flange plate of the present invention.

[0043] Markings in the figure:

[0044] 1 - Steam turbine exhaust port; 2 - Condenser throat; 3 - Inlet / Outlet for installing the sealing plate; 4 - Sealing flange plate; 5 - Safety valve.

[0045] Specific Examples

[0046] The present invention will be described in detail below with reference to the accompanying drawings.

[0047] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying 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.

[0048] Example 1

[0049] In this embodiment, as Figure 1 shown, a bypass switching device for the main condenser of a steam turbine includes:

[0050] A steam turbine exhaust port, connected to the inlet end of the condenser throat;

[0051] Inlet / Outlet for installing the sealing plate, provided on the side wall of the condenser throat, for the detachable sealing flange plate to enter or exit the condenser throat;

[0052] At least one set of sealing flange plates, inserted into the condenser throat through the inlet / outlet for installing the sealing plate, for isolating the steam turbine exhaust port from the condenser body when the steam turbine is shut down;

[0053] A safety valve, connected to the condenser throat or the condenser body, for overpressure protection during bypass operation.

[0054] As Figure 1As shown in the figure, the bypass switching device of the main condenser of the steam turbine includes: the steam exhaust port of the steam turbine is rigidly connected to the inlet end of the condenser throat through a flange to form a steam flow channel; the installation in / export of the sealing plate is a rectangular opening structure, symmetrically arranged on the side walls in the middle section of the condenser throat, and the opening size is adapted to the single-piece split size of the sealing flange plate, which is convenient for manual insertion or removal; at least one group of sealing flange plates is a metal flat plate, the thickness of which matches the bearing strength of the inner wall of the condenser throat, and bolt holes are provided at the edges; the safety valve is welded to the top of the condenser throat through a short pipe, the valve port faces outward, and is communicated with the internal cavity of the condenser.

[0055] When the steam turbine is shut down for maintenance, the sealing flange plate is inserted into the condenser throat through the installation in / export of the sealing plate, and the flange plate is fixed to the preset annular flange seat on the throat through bolts to form an isolation barrier, cutting off the connection between the steam exhaust port of the steam turbine and the main body of the condenser. At this time, the bypass steam generated by the boiler is directly connected to the main body of the condenser through the bypass pipeline, and the main condenser undertakes the condensation function. The safety valve automatically opens to relieve pressure when the steam pressure rises abnormally, avoiding overpressure damage to the condenser. This setting does not require the addition of an independent bypass condenser, utilizes the existing cooling system and pipelines of the main condenser, reduces the initial investment cost, and at the same time avoids the maintenance complexity brought by the dual system.

[0056] Furthermore, the sealing flange plate is a multi-piece split structure, and each sealing flange plate is sequentially spliced along the axial direction of the condenser throat to form a complete isolation sealing surface.

[0057] The sealing flange plate is designed as a 4-piece split structure, and each flange plate is sequentially spliced along the axial direction (vertical direction) of the condenser throat. The upper and lower edges of each flange plate are provided with tenon and mortise structures with convex and concave fits. When splicing, the convex tenon is embedded in the concave mortise to form axial positioning; bolt holes are provided at the two side edges of the flange plate, and adjacent flange plates are tightly connected by passing through bolts, and finally a complete annular isolation sealing surface is formed inside the condenser throat, fitting the inner wall radian of the throat.

[0058] The split structure solves the problem that the whole flange plate cannot pass through the installation in / export of the sealing plate due to its too large size, and the weight of a single piece is controlled within the range that can be carried by hand. When splicing axially, the flange plates are installed one by one from deep to shallow, and each flange plate is fixed by both the tenon and mortise structure and bolts, ensuring the flatness and tightness of the isolation surface. Compared with the integral flange plate, the split design shortens the installation time and avoids stress concentration on the inner wall of the throat caused by welding fixation, achieving the core goal of "damage-free switching" - that is, the original structure of the condenser is not damaged during the switching process, and only the bolts need to be removed for complete restoration during recovery.

[0059] Furthermore, a sealing gasket installation groove is provided at the edge of the sealing flange plate for installing high-temperature and steam erosion-resistant sealing gaskets.

[0060] An annular sealing gasket installation groove is provided at the edge (outer periphery on all sides) of the sealed flange plate, and a wound metal gasket (or rubber asbestos gasket) is embedded in the groove. The gasket material is selected according to the steam temperature and pressure, and its compression and resilience performance meets the sealing requirements between the flange plate and the inner wall of the throat and between adjacent flange plates.

[0061] During installation, the sealing gaskets are respectively placed in the outer peripheral groove where the flange plate contacts the inner wall of the throat and the inner peripheral groove at the splicing joint of adjacent flange plates. The gasket is compressed and deformed by the bolt tightening force to fill the tiny gaps. The gasket material with high temperature resistance and cavitation resistance can effectively resist the long-term scouring of steam and avoid the crack leakage problem caused by thermal expansion and contraction in the traditional welding isolation method. This structure enables a low leakage rate of the sealing surface, ensures the stability of the condenser vacuum during bypass operation, and improves the condensation efficiency.

[0062] Furthermore, the number of inlets / outlets for installing the sealing plates is 2, which are symmetrically distributed on both side walls of the condenser throat.

[0063] Two inlets / outlets for installing the sealing plates are provided, which are symmetrically distributed in the middle of both side walls of the condenser throat, and the height from the ground is 1.5 - 2 m, which is convenient for manual standing operation. Each inlet / outlet is a circular or rectangular through-hole, and a flange flanging is provided inside, and a detachable sealing cover plate (not shown in the figure) is connected by bolts.

[0064] The inlets / outlets arranged symmetrically on both sides realize an "in-one-out" installation path: a flange plate is inserted on one side, and the other side serves as an observation or auxiliary channel, avoiding the visual blind area and inconvenient operation during single-port installation and improving the splicing efficiency. The symmetrical layout also balances the forces on both sides of the throat, prevents local stress concentration caused by a single-side opening, and extends the service life of the condenser.

[0065] Furthermore, a sealing plate is provided at the inlets / outlets for installing the sealing plates to keep them sealed under the working state of the condenser.

[0066] A detachable sealing plate is provided outside the inlets / outlets for installing the sealing plates. The sealing plate is connected to the inlet / outlet flange by bolts, and a rubber sealing gasket is provided inside. During normal operation (in the main condenser state), the sealing plate is fastened to the inlet / outlet by bolts to form a complete sealing surface to prevent air leakage in the condenser vacuum system; when switching to the bypass condenser, the sealing plate can be removed to expose the inlet / outlet for the installation or disassembly of the flange plate.

[0067] The sealing plate structure ensures good sealing performance of the condenser in both modes: when the main condenser is operating, the inlet / outlet sealing plates are flush with the inner wall of the throat and do not affect the steam flow; when operating in bypass, after the sealing plate is removed, the flange plate can be quickly installed through the inlet / outlet. Compared with the traditional open-type opening, the sealing plate design avoids sundries from entering the condenser and prevents air from leaking into the vacuum system during operation, maintaining the stability of the condenser vacuum and ensuring the efficient operation of the main condenser.

[0068] Furthermore, the opening pressure of the safety valve is set to 1.1 - 1.3 times the normal operating pressure of the condenser, which is used to release the excess steam pressure under accident conditions.

[0069] As the "last line of defense", this protection mechanism compensates for the possible minor leaks or system control deviations of the sealed flange plate, reduces the accident risk, and ensures the safety of the bypass operation.

[0070] Embodiment 2

[0071] A method of using a bypass switching device for a steam turbine main condenser. Switching to the bypass condenser includes the following steps:

[0072] S1: Pass the sealed flange plates one by one into the condenser throat through the inlet / outlet of the sealing plate.

[0073] S2: Splice the sealed flange plates in a predetermined order, and install sealing gaskets between adjacent flange plates and between the flange plates and the inner wall of the condenser throat.

[0074] S3: Fix the sealed flange plates to the preset installation positions on the condenser throat through bolts to form a complete isolation and sealing structure.

[0075] S4: Start the bypass steam pipeline, allow the steam to condense through the condenser body, and the safety valve enters the standby protection state.

[0076] The specific steps for switching to the bypass condenser are as follows:

[0077] Insert the flange plates: Remove the sealing plate of the inlet / outlet of the sealing plate, and insert 4 split sealed flange plates in sequence from the left inlet. The right inlet is used as the observation port to ensure that the flange plates smoothly enter the throat.

[0078] Splice and seal: Place the first flange plate on the preset support angle steel in the throat, and vertically splice it with the second flange plate through the mortise and tenon structure. Insert sealing gaskets at the splicing seam and at the contact between the flange plate and the throat.

[0079] Bolt fixation: Use a torque wrench to tighten the connecting bolts at the edge of the flange plate in a symmetric order by removing the inlet / outlet of the sealing plate, ensuring that the torque of each bolt is consistent to form a sealing surface.

[0080] Start the bypass: Open the valve of the bypass steam pipeline, the steam enters the body through the condenser inlet, the cooling water system runs synchronously, the safety valve is on standby, and the pressure sensor monitors the throat pressure in real time.

[0081] Furthermore, restoring to the main condenser includes the following steps:

[0082] Close the bypass steam pipeline and stop the condenser.

[0083] Remove the connecting bolts and sealing gaskets of the sealing flange plate;

[0084] Take out the sealing flange plates one by one through the installation inlets / outlets of the sealing plates, and restore the connection between the steam exhaust port of the steam turbine and the main body of the condenser.

[0085] The steps to restore it to the main condenser are as follows:

[0086] Shut down the bypass: Close the bypass steam valve, shut down the cooling water pump, and wait until the internal pressure of the condenser drops to atmospheric pressure;

[0087] Remove the bolts and gaskets: Loosen the connecting bolts of the flange plate in the order of "from outside to inside", and take out the sealing gasket, paying attention to avoid the gasket fragments falling into the condenser tube bundle;

[0088] Take out the flange plates: Take out the split flange plates in sequence from the right-side outlet, check whether the flange plates and the inner wall of the throat are worn, and after confirming that there is no foreign object remaining, reinstall the inlet / outlet sealing plates and tighten them to restore the connection between the steam exhaust port of the steam turbine and the main body of the condenser.

[0089] The restoration process does not involve any cutting or welding operations, and completely relies on the detachable structure to ensure that the original strength and sealing performance of the condenser throat are not damaged.

[0090] Furthermore, the splicing sequence of the sealing flange plates starts from one end of the condenser throat far away from the installation inlets / outlets of the sealing plates to ensure uniform force on the seal.

[0091] Splicing from the far end can avoid the installation difficulties caused by the narrow space near the inlets / outlets, and at the same time make the gravity of the flange plate and the bolt tightening force be evenly transmitted along the axis, preventing the problem of the far end warping due to the proximal end being fixed first.

[0092] Furthermore, when fixing the sealing flange plate in step S3, the bolts are tightened symmetrically and step by step.

[0093] Symmetrically tightening step by step avoids the deformation of the flange plate caused by a single bolt being too tight, makes the sealing gasket be evenly compressed, and the gaps be evenly distributed.

[0094] The above are only the preferred embodiments of the invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A steam turbine main condenser bypass switching device, characterized in that: include: The steam turbine exhaust port (1) is connected to the inlet end of the condenser throat (2); A sealing plate installation inlet / outlet (3) is arranged on the side wall of the condenser throat (2) and is used for a detachable sealing flange plate (4) to enter or remove the condenser throat (2); at least one set of sealing flange plates (4) which are inserted into the throat (2) of the condenser through the sealing plate installation inlet / outlet (3) and are used to isolate the turbine exhaust port (1) from the condenser body when the turbine is shut down; A safety valve (5) is connected to the throat (2) of the condenser or the condenser body and is used for overpressure protection during bypass operation.

2. A steam turbine main condenser bypass switching device according to claim 1, characterized in that: The sealing flange plate (4) is a multi-piece split structure, and the sealing flange plates are spliced ​​in sequence along the axial direction of the condenser throat (2) to form a complete isolation sealing surface.

3. A steam turbine main condenser bypass switching device according to claim 2, characterized in that: The edge of the sealing flange plate (4) is provided with a sealing gasket installation groove for installing a high temperature resistant and cavitation resistant sealing gasket.

4. A steam turbine main condenser bypass switching device according to claim 1, characterized in that: The number of the sealing plate installation inlet / outlet (3) is 2, which are symmetrically distributed on the two side walls of the condenser throat (2).

5. A steam turbine main condenser bypass switching device according to claim 1, characterized in that: The sealing plate installation inlet / outlet (3) is provided with a sealing plate to keep the sealing when the condenser is in working state.

6. A steam turbine main condenser bypass switching device according to claim 1, characterized in that: The opening pressure of the safety valve (5) is set to 1.1 to 1.3 times the normal operating pressure of the condenser, and is used to release excess steam pressure under accident conditions.

7. A method for using a steam turbine main condenser bypass switching device, applied to a steam turbine main condenser bypass switching device as claimed in any one of claims 1 to 6, characterized in that: Switching to bypass the condenser involves the following steps: S1: Insert the sealing flange plates (4) one by one into the throat of the condenser (2) through the sealing plate installation inlet / outlet (3); S2: Splice the sealing flange plates (4) in a predetermined order, and install sealing gaskets between adjacent flange plates and between the flange plates and the inner wall of the condenser throat (2); S3: fixing the sealing flange plate (4) to the preset installation position of the throat of the condenser (2) by means of bolts to form a complete isolation sealing structure; S4: Start the bypass steam pipeline to allow the steam to condense through the condenser body, and the safety valve (5) enters the standby protection state.

8. The method for using the steam turbine main condenser bypass switching device according to claim 7, characterized in that: Restoring the main condenser includes the following steps: Close the bypass steam pipeline and shut down the condenser; Remove the connecting bolts and sealing gasket of the sealing flange plate (4); The sealing flange plates (4) are removed one by one through the sealing plate installation inlet / outlet (3) to restore the connection between the steam turbine exhaust port (1) and the condenser body.

9. The method for using the steam turbine main condenser bypass switching device according to claim 7, characterized in that: The order of splicing the sealing flange plate (4) is to start from the end of the condenser throat (2) away from the sealing plate installation inlet / outlet (3) to ensure that the seal is evenly stressed.

10. The operating method according to claim 7, characterized in that: When the sealing flange plate is fixed in step S3, the bolts are tightened symmetrically and step by step.

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