A sealing device and method for a circulating fluidized bed boiler slag tap hole

Abstract

The application provides a sealing device for a slag outlet of a circulating fluidized bed boiler, and belongs to the technical field of auxiliary equipment of a coal-fired power station boiler and high-temperature solid material conveying, which comprises: a multistage sealing unit, which comprises a first-stage mechanical sealing structure arranged between an insert plate and a door frame, a second-stage air curtain sealing structure and a third-stage auxiliary contact sealing structure in sequence along a material flow direction; a wear self-adaptive compensation unit arranged corresponding to the first-stage mechanical sealing structure and used for applying a continuous and adjustable pressing force to the first-stage mechanical sealing structure to compensate for wear; and a cooling unit comprising a cooling flow channel arranged in the insert plate and / or a cooling structure arranged on the door frame. The application overcomes the defects of easy leakage, easy wear and easy jamming of the existing insert plate door of a slag outlet, and realizes "gas-solid collaborative sealing" and "dynamic wear compensation".

Description

Technical Field

[0001] This invention belongs to the field of auxiliary equipment for coal-fired power plant boilers and high-temperature solid material conveying technology, specifically relating to a highly reliable sealing device for the slag outlet of a circulating fluidized bed boiler drum slag cooler and a sealing method based on the device. Background Technology

[0002] Circulating fluidized bed (CFB) boilers are widely used in power generation, heating, and industrial sectors due to their significant advantages such as wide fuel adaptability, high combustion efficiency, and low pollutant emissions. During the operation of a CFB boiler, a large amount of high-temperature flue gas (approximately 850℃-950℃) generated in the furnace carries unburned solid particles. After gas-solid separation in a cyclone separator, the separated high-temperature solid material is returned to the furnace via a loop seal and a return leg to maintain material circulation and stable combustion within the furnace. Simultaneously, to meet the needs of boiler slag removal, maintenance, and emergency discharge in case of accidents, a discharge outlet is usually installed at the bottom of the return valve or return leg. This discharge outlet is connected to the downstream slag cooler or slag removal system via a discharge pipe. A sealing device (usually a gate valve) is required at the discharge outlet to reliably close the discharge channel during normal operation and prevent leakage of high-temperature, dust-laden flue gas.

[0003] The discharge outlet sealing device is a critical channel component at the pressure boundary of a circulating fluidized bed boiler. Its sealing reliability directly affects the personal safety of boiler operators, the thermal efficiency and operational stability of the boiler equipment, and environmental emission compliance. Because this sealing device operates under extreme conditions of high temperature (material temperature can reach over 850℃), high concentration of abrasive particles (median ash particle size is typically less than 0.1mm), and positive pressure (furnace pressure is typically positive), extremely stringent requirements are placed on the materials, structure, and control methods of the sealing device.

[0004] In existing technologies, circulating fluidized bed boilers typically use simple flat gate valves or ordinary slide gates as sealing devices at the discharge outlet. Their sealing principle mainly relies on the rigid contact between the slide gate and the frame or ordinary sealing packing. These conventional structures reveal the following significant drawbacks under long-term high-temperature and high-abrasion operating conditions: 1. Severe wear leading to seal failure: The sealing surfaces of the slide plate and the door frame are directly exposed to high-temperature, dusty flue gas. During frequent opening and closing, high-temperature fly ash particles cause severe erosion and abrasive wear on the sealing surfaces, leading to rapid wear and deformation, and a continuous increase in the clearance. When the clearance exceeds a certain limit, during positive pressure operation of the boiler, high-temperature flue gas carrying a large amount of dust leaks out from the sealing gap, seriously threatening the personal safety of on-site operators and causing environmental pollution.

[0005] 2. Inevitable leakage of fine dust: The flue gas from circulating fluidized bed boilers contains a large number of ultrafine fly ash particles with a diameter of less than 0.1 mm. Driven by the positive pressure airflow inside the furnace, these fine particles can easily penetrate even the smallest gaps between conventional mechanical seals, resulting in continuous dust leakage. The leaked dust not only pollutes the maintenance environment but also enters the transmission mechanism of the sealing device, accelerating the wear and jamming of moving parts.

[0006] 3. Rapid failure of sealing materials: Ordinary rubber seals or graphite fillers used in conventional sealing devices rapidly age, become brittle, and crack under high-temperature and abrasive conditions above 850℃, losing their sealing function. Even with high-temperature resistant materials, their effective service life is extremely limited without effective cooling and wear compensation mechanisms, requiring frequent shutdowns for replacement, which seriously affects the boiler's availability and economy.

[0007] 4. High risk of jamming and poor operational reliability: Uneven thermal expansion caused by high temperatures and dust accumulation in the sliding joint gap can easily cause the insert plate to jam or become stuck in the door frame, preventing normal opening and closing. In boiler accident conditions, if the discharge outlet sealing device cannot be opened in a timely and reliable manner, it will directly affect the safe shutdown of the boiler and the handling of the accident, causing serious safety hazards and economic losses.

[0008] Therefore, there is an urgent need to develop a new type of sealing device that can fundamentally overcome the above-mentioned defects and achieve long-term reliable sealing under high temperature and high abrasion conditions, so as to meet the needs of safe, efficient and environmentally friendly operation of circulating fluidized bed boilers. Summary of the Invention

[0009] The present invention aims to overcome the defects of existing cold slag machine outlet gates, such as easy leakage, easy wear, and easy jamming, and provides a sealing device and method based on the principles of "gas-solid synergistic sealing" and "dynamic wear compensation".

[0010] To achieve the above objectives, the present invention provides the following technical solution: a sealing device for the slag outlet of a circulating fluidized bed boiler slag cooler, wherein the slag outlet of the slag cooler is provided with a gate, the gate comprising a door frame, a gate plate, and a driving mechanism for driving the gate plate, comprising: The multi-stage sealing unit, along the material flow direction, sequentially includes a first-stage mechanical seal structure, a second-stage air curtain seal structure, and a third-stage auxiliary contact seal structure disposed between the insert plate and the door frame. The first-stage mechanical seal structure includes a hard, wear-resistant surface located around the slag-facing side of the insert plate and an elastic sealing body located on the door frame. The second-stage air curtain seal structure includes an air curtain sealing cavity formed within the door frame, with its air passage connected to a sealing gas inlet. The third-stage auxiliary contact seal structure is located on the outer side of the second-stage air curtain seal structure at the junction with the door stem of the insert plate door. A wear adaptive compensation unit, corresponding to the first-stage mechanical seal structure arrangement, is used to apply a continuous and adjustable clamping force to compensate for wear; and The cooling unit includes cooling channels disposed inside the insert plate and / or cooling structures disposed on the door frame.

[0011] The aforementioned sealing device achieves multiple barriers to high-temperature, dusty flue gas through the synergistic effect of three-stage sealing units. The first-stage contact mechanical seal performs the primary sealing function, blocking most of the high-temperature flue gas and coarse particles; the second-stage air curtain sealing cavity utilizes a positive pressure air curtain to form a dynamic sealing barrier, effectively preventing the penetration and leakage of fine dust; the third-stage auxiliary contact seal serves as the final safety barrier, ensuring that no leakage occurs even under extreme operating conditions. The three-stage sealing, progressively enhanced and synergistically working, fundamentally solves the problem of insufficient sealing reliability of traditional single mechanical seals under high-temperature and abrasive conditions. In other words, this solution, through the synergistic effect of multi-stage sealing, active maintenance of wear compensation, and systematic thermal management, fundamentally solves the problem of single-seal failure under harsh conditions, achieving high-performance and long-life sealing effects.

[0012] Preferably, the wear adaptive compensation unit includes a plurality of miniature hydraulic cylinders evenly distributed along the circumference of the door frame, with the piston rod end of the miniature hydraulic cylinder abutting against the back of the elastic seal.

[0013] Furthermore, the wear adaptive compensation unit also includes a pressure sensor for detecting the clamping force applied to the elastic seal. The pressure sensor is communicatively connected to the DCS control system. The DCS control system adjusts the hydraulic pressure of the micro hydraulic cylinder based on the feedback signal from the pressure sensor to apply a continuous and adjustable clamping force to the elastic seal. This preferred embodiment provides a concrete and effective way to achieve wear compensation. The micro hydraulic cylinder can provide stable and controllable thrust, ensuring that the elastic seal is always pressed against the wear-resistant surface of the insert plate at a set pressure, automatically compensating for gaps caused by wear, and further intelligentizing the wear compensation unit. Through linkage with the DCS system, real-time monitoring and closed-loop precise adjustment of the sealing pressure can be achieved, ensuring that the sealing performance is always in an optimal state, further improving adaptability and reliability.

[0014] More specifically, four miniature hydraulic cylinders are arranged on the four sides of the door frame. The hydraulic system pressure of the hydraulic cylinders is set to a constant value. The DCS control system performs closed-loop adjustment based on real-time feedback from the pressure sensor to automatically compensate for displacement when the elastic seal wears, maintaining effective contact clamping force between the elastic seal and the hard wear-resistant surface. This wear-adaptive compensation unit is one of the core innovations that distinguishes this invention from existing technologies. In traditional sealing devices, the sealing clamping force continuously decreases after the sealing surface wears, eventually leading to seal failure and requiring shutdown and replacement of the seal. This invention achieves real-time automatic compensation for the wear of the sealing surface by evenly arranging miniature hydraulic cylinders around the insert plate and cooperating with pressure sensors and a DCS closed-loop control system. When the sealing surface wears due to long-term use, causing a decrease in contact clamping force, the pressure sensor immediately detects the change in clamping force. The DCS system automatically increases the output displacement of the hydraulic cylinders, causing the elastic seal to move towards the hard wear-resistant surface, restoring and maintaining a constant effective contact clamping force. This "self-healing sealing pair" mechanism enables the sealing device to maintain good sealing performance throughout its entire life cycle, significantly extending maintenance intervals.

[0015] Preferably, the insert plate has a sandwich hollow structure, and the cooling channels inside it are provided with a cooling medium inlet and outlet; the cooling structure on the door frame is a cooling coil embedded inside the high-temperature zone. This provides a comprehensive cooling solution, with efficient cooling structures designed for the main components that bear heat radiation and come into contact with high-temperature slag—the insert plate and the door frame—effectively suppressing thermal deformation and ensuring long-term dimensional stability and material mechanical properties.

[0016] Specifically, the sealing gas inlet receives compressed air from a source through an airflow passage equipped with a pressure regulating valve. The pressure regulating valve is configured to control the pressure of the sealing gas entering the air curtain sealing cavity within a range 0.5-2 kPa higher than the pressure inside the slag cooler cavity.

[0017] Typically, the hard wear-resistant surface is a tungsten carbide wear-resistant surface, and the elastic seal is an elastic seal formed by wrapping flexible graphite with a high-temperature alloy bellows.

[0018] A second aspect of the present invention provides a sealing method for the slag outlet of a circulating fluidized bed boiler slag cooler, applicable to any of the aforementioned sealing devices for the slag outlet of a circulating fluidized bed boiler slag cooler, comprising the following steps: Close the insert plate to allow the first-stage mechanical seal structure to seal and fit together, forming an initial mechanical seal; Sealing gas is introduced into the second-stage air curtain sealing structure to form a positive airflow from the outside to the inside; The wear adaptive compensation unit applies and maintains a constant effective contact pressure on the first-stage mechanical seal structure. The cooling unit is operated to cool the target parts on the insert plate and the door frame.

[0019] This sealing method achieves fully automated and intelligent operation of the sealing device through a series of orderly steps: mechanical seal establishment, air curtain seal activation, automatic wear compensation, and active cooling maintenance. Each step has a clear temporal logic and collaborative relationship: first, the mechanical seal foundation is established; then, the air curtain seal is activated for enhancement; finally, continuous monitoring for wear compensation begins, while the cooling system operates throughout to ensure structural thermal stability. This method is simple to operate, highly automated, and achieves long-term reliable sealing without manual intervention.

[0020] Preferably, the step of introducing sealing gas is automatically executed after the insert plate is closed in place. The sealing gas is clean, dry compressed air. The cooling unit continues to operate during and after the slag discharge process of the slag cooler to control the temperature of the insert plate and the high-temperature zone of the door frame below a preset threshold. This preferred operation, through comprehensive cooling design, fundamentally solves the problem of high-temperature damage to the structure and materials of the sealing device. The combined cooling of the internal cooling channels of the door frame and the cooling channels of the insert plate significantly reduces the operating temperature of key sealing components from over 850°C to approximately 100°C, fundamentally avoiding thermal deformation, material aging, and thermal stress concentration caused by high temperatures. This ensures the long-term stability of the dimensional accuracy and fit clearance of each component of the sealing device, while significantly extending the service life of the sealing material.

[0021] Preferably, the step of applying and maintaining a constant effective contact pressure through the wear adaptive compensation unit specifically includes: preset the system pressure of the micro hydraulic cylinder of the wear adaptive compensation unit, and when the sealing surface is worn, the piston of the micro hydraulic cylinder automatically extends to compensate for the displacement, so that the sealing contact pressure is maintained at the design value.

[0022] The sealing device and method for the slag outlet of a circulating fluidized bed boiler slag cooler provided by the embodiments of the present invention have the following advantages compared with the prior art: First, multiple sealing guarantees ensure inherent safety and reliability: Through a three-stage synergistic sealing system consisting of a first-stage contact mechanical seal, a second-stage air curtain seal, and a third-stage auxiliary contact seal, each stage works in a progressive manner and performs its own function, forming a multi-layered protection architecture where "the mechanical seal blocks coarse particles, the air curtain seal blocks fine dust, and the auxiliary seal ensures the bottom line." Even if the sealing performance of one stage decreases, the other two stages can still ensure the overall sealing reliability, fundamentally achieving an inherently safe design.

[0023] Secondly, the dynamic air curtain barrier effectively prevents micro-dust leakage: filtered and dried compressed air is introduced into the second-stage air curtain sealing cavity to form a stable positive pressure air curtain barrier. This air curtain establishes a directional flow from the sealing cavity towards the material side at the sealing gap, effectively preventing the leakage path of fine dust (particle size <0.1mm) through the micro-gap of the mechanical seal pair under the positive pressure inside the furnace. At the same time, the sealing airflow has a continuous cooling and purging cleaning effect on the sealing surface, further extending the service life of the mechanical seal pair.

[0024] Third, automatic wear compensation enables maintenance-free long-term operation: A closed-loop wear compensation system, composed of miniature hydraulic cylinders, pressure sensors, and a DCS control system evenly arranged around the circumference of the sealing plate, can automatically detect and compensate for the wear of the sealing surface in real time, ensuring that the sealing contact clamping force remains constant throughout the entire equipment's lifespan. This innovative design completely solves the industry pain point of traditional sealing devices where wear leads to a continuous decrease in sealing force, necessitating frequent shutdowns to replace seals. It significantly extends the maintenance cycle and is expected to achieve the goal of maintenance-free operation with the same lifespan as the boiler body.

[0025] Fourth, comprehensive active cooling ensures structural thermal stability: By setting cooling channels inside the door frame wall and cooling channels in the high-temperature area of ​​the insert plate, cooling water is used to force-cool key parts, significantly reducing the working temperature of the sealing area from over 850℃ to about 100℃. This fundamentally avoids changes in fit clearance and jamming risks caused by high-temperature thermal deformation, ensuring the dimensional accuracy and movement flexibility of each component. At the same time, it significantly reduces the thermal aging and thermal stress damage of the sealing material, ensuring the long-term operational reliability of the device.

[0026] Fourth, significant safety, environmental protection, and economic benefits: It has achieved long-term, essentially zero-leakage operation at the discharge outlet, completely eliminating the safety hazards of high-temperature flue gas dust leakage on site, and meeting increasingly stringent environmental emission requirements; it has greatly reduced unplanned shutdowns and maintenance workload, lowered maintenance costs and power generation losses caused by boiler shutdowns, and brought significant economic benefits to users. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure of the sealing device at the slag outlet of the circulating fluidized bed boiler slag cooler in this embodiment of the invention.

[0028] Figure 2 This is an enlarged schematic diagram of the wear adaptive compensation unit according to an embodiment of the present invention. Figure 3 This is a flowchart illustrating the sealing method for the slag outlet of a circulating fluidized bed boiler slag cooler according to an embodiment of the present invention.

[0029] Explanation of reference numerals in this invention: 1. Door frame; 2. Insert plate; 3. Drive mechanism; 4. Hard wear-resistant surface; 5. Air curtain sealing cavity; 6. Air source interface; 7. Door frame cooling air inlet; 8. Sealing air inlet; 9. Insert plate cooling channel inlet; 10. Insert plate cooling channel outlet; 11. Third-stage auxiliary contact sealing structure; 12. Miniature hydraulic cylinder; 13. Elastic sealing body; 14. Pressure sensor. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] See Figure 1 and Figure 2 This embodiment provides a sealing device for the slag outlet of a circulating fluidized bed boiler slag cooler. The sealing device is integrally installed on the slag outlet flange of the drum slag cooler. The slag outlet of the slag cooler is equipped with a gate, which includes a door frame 1, a gate plate 2, and a driving mechanism 3 for driving the gate plate. The mechanism includes: The multi-stage sealing unit, along the material flow direction, includes a first-stage mechanical seal structure, a second-stage air curtain seal structure, and a third-stage auxiliary contact seal structure disposed between the insert plate 2 and the door frame 1. The first-stage mechanical seal structure includes a hard wear-resistant surface 4 disposed around the slag-facing side of the insert plate 2 and an elastic sealing body 13 disposed on the door frame. The second-stage air curtain seal structure includes an air curtain sealing cavity 5 opened within the door frame 1, with the air passage of the air curtain sealing cavity connected to the sealing air inlet 8. The third-stage auxiliary contact seal structure 7 is disposed on the outside of the second-stage air curtain seal structure at the joint with the door stem of the insert plate door. A wear-adaptive compensation unit, corresponding to the first-stage mechanical seal structure arrangement, is used to apply a continuous and adjustable clamping force to compensate for wear; and The cooling unit includes cooling channels disposed inside the insert plate 2 and / or cooling structures disposed on the door frame 1.

[0032] In the above basic embodiment, the door frame 1 may optionally be an integral cast or welded steel structure with sufficient rigidity and strength, and its interior may be precision machined with channels and cavities to accommodate multi-stage sealing units.

[0033] The insert plate 2 can be made of double-layer heat-resistant steel plates welded together to form a sandwich hollow structure. One end of the insert plate 2 is connected to the drive mechanism 3 (such as an electric push rod or hydraulic cylinder) through a three-dimensional spherical connecting mechanism. This three-dimensional spherical connecting mechanism can effectively eliminate the additional bending moment and stress between the drive mechanism 3 and the insert plate 2 caused by installation errors or thermal expansion and contraction, ensuring smooth movement of the insert plate 2 and preventing jamming.

[0034] The multi-stage sealing unit is a key technical concept of this invention. As a preferred embodiment, it comprises, from the slag side to the atmosphere side, the following components: The first-stage mechanical seal structure includes a hard, wear-resistant surface 4 located around the slag-facing side of the insert plate 2 and an elastic sealing body 13 located on the door frame 1. The hard, wear-resistant surface 4 is made of ultra-hard, wear-resistant materials such as tungsten carbide, which can be welded or bolted. The elastic sealing body 13 is preferably made of flexible graphite material wrapped in a high-temperature alloy bellows, combining elasticity and high-temperature resistance. When the insert plate 2 is closed, the two form a tight fit, achieving the main blocking of high-temperature slag and larger particles.

[0035] The second-stage air curtain sealing structure is located outside the first-stage mechanical seal structure (near the atmosphere). Specifically, it can be an annular, sealed air curtain sealing cavity 5 opened within the door frame 1. This air curtain sealing cavity 5 can be connected to an external air source via an air source interface 6. A shut-off valve, a filter pressure reducing valve, and a precision pressure regulating valve (not shown in the figure) can be sequentially installed on the pipeline of the air source interface 6. The precision pressure regulating valve stably controls the air source pressure (usually plant-use instrument compressed air) within a range 0.5-2 kPa higher than the internal pressure of the slag cooler, for example, higher than 1 kPa.

[0036] The third-level auxiliary contact sealing structure 7 is located outside the second-level air curtain sealing structure and at the junction of the door rod (i.e., the door rod) of the insert gate. This seal can be a simple felt, a rubber lip seal, or a flexible graphite packing. Its function is to prevent dust, moisture, and other impurities in the external environment from entering the precision second-level sealing cavity, while also serving as a final safety redundancy line of defense against micro-powder leakage.

[0037] In a preferred embodiment, the wear adaptive compensation unit may include four miniature hydraulic cylinders 12, evenly distributed circumferentially along the door frame 1 (e.g., one on each of the four sides of the door frame). The output end (piston rod) of each miniature hydraulic cylinder 12 directly abuts against the back of the elastic seal 13. These miniature hydraulic cylinders 12 are connected to an independent, pressure-adjustable hydraulic station (not shown in the figure). By setting the pressure of the hydraulic system, a constant, continuous thrust can be provided to one or more miniature hydraulic cylinders 12. For more precise control, a pressure sensor can also be integrated on the back of the seal or on the hydraulic pipeline, and the signal from the sensor can be connected to the distributed control system (DCS) of the power station. The DCS system adjusts the pressure of the hydraulic station or the opening of the proportional valve in a closed loop according to the deviation between the preset pressure value and the actual feedback value, thereby achieving dynamic and precise adjustment of the sealing clamping force.

[0038] As an alternative embodiment, the cooling unit may include two parts. The first part is the internal cooling channel of the insert plate, located in the interlayer of the insert plate 2, with an insert plate cooling channel inlet 9 and an insert plate cooling channel outlet 10, and the cooling medium may be cooling air or cooling water. The second part may be a door frame cooling structure, which may be a cooling coil connected to the door frame cooling air inlet 7, embedded in the part corresponding to the high-temperature zone (e.g., near the flange root near the slag outlet) during the casting or welding of the door frame 1, in which the cooling medium circulates. The cooling unit operates continuously throughout the entire life cycle of the device, effectively reducing the temperature of key parts of the insert plate 2 and door frame 1 from several hundred degrees to around 100 degrees or even lower.

[0039] The basic embodiments and preferred embodiments of the sealing device of the present invention have been described above in a hierarchical manner. To help those skilled in the art understand the present invention, the following references are made. Figure 1 and Figure 2 A relatively comprehensive and specific preferred embodiment of the present invention is described below.

[0040] like Figures 2 to 3 As shown, the present invention provides a sealing device for the slag outlet of a circulating fluidized bed boiler slag cooler. The sealing device is installed on the discharge outlet flange at the bottom of the return valve or return leg of the circulating fluidized bed boiler.

[0041] The sealing device includes a door frame 1, an insert plate 2, a drive mechanism 3, a multi-stage sealing unit, a wear adaptive compensation unit, and an active cooling unit. The door frame 1 is a rectangular welded structure, constructed from double-layered steel plates, with the cavity between the plates forming an internal cooling channel. Grooves and steps are machined on the door frame 1 for mounting the elastic sealing body 13. The side of the door frame 1 has a door frame cooling air inlet 7 and a door frame cooling air outlet. The cooling medium (preferably cooling air) enters the internal cooling channel (cooling coil) from the door frame cooling air inlet 7, flows through the cooling section of the door frame, and exits from the door frame cooling air outlet, achieving uniform cooling of the entire door frame 1. The door frame 1 also has a sealing gas inlet 8 for connecting to the sealing gas in the air curtain sealing cavity 5. The door frame 1 is preferably made of heat-resistant alloy steel to balance high-temperature strength, corrosion resistance, and weldability.

[0042] The insert plate 2 is a rectangular welded structure that is slidably installed inside the door frame 1. It can move horizontally between an open and closed position to open or close the inlet and outlet of the door frame 1. The insert plate 2 has a hard, wear-resistant surface 4 on the periphery of its slag-facing side. An insert plate cooling channel is provided inside the insert plate 2, which has an inlet 9 and an outlet 10. The cooling medium (preferably cooling water) enters from the inlet 9, flows through the high-temperature area inside the insert plate 2, and exits from the outlet 10, effectively cooling the critical high-temperature parts of the insert plate 2. The insert plate 2 is preferably made of the same or similar heat-resistant alloy steel as the door frame 1 to reduce differences in thermal expansion.

[0043] The drive mechanism 3 is installed on one side of the door frame 1 and mechanically connected to the insert plate 2, used to drive the insert plate 2 to move between the open and closed positions. The drive mechanism 3 can be an electric, hydraulic, or pneumatic actuator, preferably an electric actuator with a lead screw drive to achieve precise position control and sufficient driving force. The third-stage auxiliary contact sealing structure 7 is provided at the junction of the drive mechanism 3 and the door stem of the insert plate 2.

[0044] The multi-stage sealing unit includes three sealing structures in sequence along the direction in which flue gas may leak (i.e., from the inside of the inlet and outlet of the door frame 1 to the outside): (1) First-stage contact mechanical seal structure: including a hard wear-resistant surface 4 set on the inner edge of the material receiving surface of the inlet and outlet of the insert plate 2 and an elastic sealing body 13 set on the door frame 1. The hard wear-resistant surface 4 is made of tungsten carbide (WC) material, and can be fixed to the inner edge of the material receiving surface of the inlet and outlet of the insert plate 2 by bolts, and has extremely high hardness and excellent anti-abrasive wear performance. The elastic sealing body 13 is made of flexible graphite wrapped in a high-temperature alloy bellows and is embedded in the corresponding position of the door frame 1. When the insert plate 2 is in the closed position, the elastic sealing body 13 and the hard wear-resistant surface 4 form an interference fit, generating sufficient contact pressure to effectively block most of the coarse particles and flue gas in the high-temperature dusty flue gas. The advantages of using tungsten carbide material for the hard wear-resistant surface 4 are: Tungsten carbide has extremely high hardness (HV 1200-1800), which is much higher than the hardness of the main abrasive components (quartz, feldspar, etc.) in the circulating fluidized bed fly ash. Therefore, it has excellent anti-abrasive wear performance and can maintain the geometric accuracy of the sealing surface during long-term operation. The elastic sealing body 13 adopts a structure of flexible graphite wrapped with a high-temperature alloy bellows, which combines the elastic compensation capability of metal bellows with the excellent sealing performance and self-lubricating properties of flexible graphite. It can maintain good elasticity and sealing adaptability at high temperatures. (2) Second-stage air curtain sealing structure: Located on the downstream side of the first-stage contact mechanical seal structure (i.e., the side away from the material side), it includes an air curtain sealing cavity 5 defined between the door frame 1 and the insert plate 2. The air curtain sealing cavity 5 is a rectangular annular cavity. The air curtain sealing cavity 5 is provided with a sealing gas inlet 8, and the air curtain sealing cavity 5 is connected to the sealing gas supply system through the gas source interface 6 pipe. The sealing gas supply system includes a compressed gas source and a precision pressure regulating valve. Compressed air supplied by the compressed gas source (usually a plant-use compressed air system) is filtered to remove moisture and impurities, and then precisely regulated by the precision pressure regulating valve before entering the air curtain sealing chamber 5 through the gas source interface 6. The precision pressure regulating valve regulates and maintains the chamber pressure within the air curtain sealing chamber 5 within the range of 0.5-2 kPa, preferably around 1 kPa, ensuring that the pressure within the air curtain sealing chamber 5 is always higher than the material-side pressure at the inlet and outlet. Under the action of the positive pressure differential, the sealing gas forms a directional airflow within the air curtain sealing chamber 5, flowing from the air curtain sealing chamber 5 towards the first-stage contact mechanical seal (i.e., flowing from the sealing chamber towards the material side). This positive pressure air curtain has three functions: first, it forms a gas barrier, preventing fine dust from penetrating outwards through any microscopic gaps in the first-stage mechanical seal under the positive pressure within the furnace; second, it continuously cools the sealing surface of the first-stage mechanical seal with gas, reducing the sealing surface temperature; and third, it continuously purges and cleans the sealing surface, preventing dust accumulation on the sealing surface. The sealing gas is preferably filtered and dried compressed air to ensure that the gas is clean and will not cause secondary pollution or corrosion to the sealing surface.The chamber pressure setting value (0.5-2kPa) of the air curtain sealing cavity 5 is carefully selected: if the pressure is too low, an effective air curtain barrier cannot be formed; if the pressure is too high, the gas consumption will increase and may have an adverse effect on the first-stage mechanical seal. (3) Third-stage auxiliary contact seal 7: located downstream of the air curtain sealing cavity 5, specifically set at the valve stem joint of the door frame 1 and the insert plate 2, for isolation from the external atmosphere. The third-stage auxiliary contact seal 7 adopts a conventional packing seal or lip seal structure. Its function is to serve as a final safety barrier to prevent residual gas in the air curtain sealing cavity 5 from leaking into the atmosphere under extreme conditions (such as when the sealing gas supply system is unexpectedly interrupted), ensuring that no external leakage will occur under any circumstances. The setting of the third-stage auxiliary contact seal 7 reflects the "defense in depth" design concept of the present invention, further improving the reliability and safety of the sealing device.

[0045] The wear adaptive compensation unit includes multiple miniature hydraulic cylinders 12 evenly distributed circumferentially along the insert plate 2 and a pressure sensor 14 for detecting the clamping force applied to the elastic seal 13. There are four miniature hydraulic cylinders 12, arranged on the four sides of the door frame 1. The piston rod end of each miniature hydraulic cylinder 12 abuts against the back of the elastic seal 13 (i.e., the side away from the hard wear-resistant surface 4). The hydraulic system pressure of the hydraulic cylinders is set to a constant value, and the hydraulic system is connected to an external hydraulic station via hydraulic lines. The pressure sensor 14 is mounted on the elastic seal and is used to detect the contact clamping force between the elastic seal 13 and the hard wear-resistant surface 4 in real time. The pressure sensor 14 is communicatively connected to the DCS (Distributed Control System) and transmits the real-time detected clamping force signal to the DCS control system. Based on the feedback signal from the pressure sensor 14, the DCS control system adjusts the hydraulic pressure of the miniature hydraulic cylinders 12 through a closed-loop control algorithm, thereby adjusting the extension displacement of the piston rod to apply a continuous and adjustable clamping force to the elastic seal 13. The working principle of the wear adaptive compensation unit is as follows: During the long-term operation of the sealing device, the elastic sealing body 13 and the hard wear-resistant surface 4 will gradually wear down due to continuous contact friction and fly ash erosion, resulting in a gradual decrease in the contact clamping force. After the pressure sensor 14 monitors the decreasing trend of the clamping force in real time, the DCS control system automatically increases the output pressure of the micro hydraulic cylinder 12, causing the piston rod to extend further and push the elastic sealing body 13 towards the hard wear-resistant surface 4, compensating for the gap caused by wear and restoring and maintaining a constant effective contact clamping force. This process is continuous and automatic, requiring no manual intervention, realizing the "self-healing" function of the sealing device, and ensuring that the sealing performance remains stable throughout its entire life cycle.

[0046] The active cooling unit comprises two parts: an internal cooling channel within the door frame and a cooling channel within the insert plate. The internal cooling channel of the door frame 1 is formed within the double-layered steel plate wall of the door frame 1, and has a door frame cooling air inlet 7 and a cooling medium outlet. The cooling medium (preferably cooling air) enters the internal cooling channel of the door frame through the cooling medium inlet 7, flows circumferentially along the frame of the door frame 1, absorbs the heat conducted from the high-temperature flue gas side of the door frame 1, and is discharged from the cooling medium outlet, achieving uniform cooling of the entire door frame 1. The cooling channel of the insert plate 2 is located inside the insert plate corresponding to the high-temperature area, and has an insert plate cooling channel inlet 9 and an insert plate cooling channel outlet 10. The cooling medium (preferably cooling water) enters the cooling channel inside the insert plate 2 through the insert plate cooling channel inlet 9, flows through the high-temperature area of ​​the insert plate 2, absorbs heat, and is discharged from the insert plate cooling channel outlet 10. The arrangement path of the insert plate cooling channel is optimized to primarily cover the front end area and the sealing surface area of ​​the insert plate 2 that are in direct contact with the high-temperature flue gas. Through the combined cooling effect of the internal cooling channels of the door frame and the cooling channels of the insert plate, the active cooling unit significantly reduces the operating temperature of key parts (especially the sealing surface area) of the door frame 1 and the insert plate 2 from over 850°C to about 100°C. This significant cooling effect fundamentally avoids thermal deformation, thermal stress concentration, and accelerated material aging caused by high temperatures, ensuring the long-term stability of the dimensional accuracy, fitting clearance, and movement flexibility of each component of the sealing device, while also greatly extending the service life of the sealing material (especially the flexible graphite in the elastic sealing body 13).

[0047] The sealing gas supply system includes a compressed gas source (preferably a plant-grade compressed air system), a filter, a dryer, and a precision pressure regulating valve. The compressed air supplied by the compressed gas source first passes through a filter to remove solid particulate impurities, then through a dryer to remove moisture, and then is precisely regulated to a set pressure (0.5-2 kPa, preferably 1 kPa) by the precision pressure regulating valve. Finally, it enters the air curtain sealing chamber 5 through the gas source interface 6. The precision pressure regulating valve has high-precision pressure regulation capabilities, enabling it to stably maintain the chamber pressure within the air curtain sealing chamber 5 at the set value, unaffected by fluctuations in the compressed gas source pressure.

[0048] Based on the above sealing device, this embodiment provides a method for achieving long-term sealing, the specific working process of which is as follows: Preparation and initial state: During normal slag discharge from the slag cooler and during slag discharge intervals, the cooling unit is always in operation. The cooling medium continuously flows through the internal cooling channels of the insert plate and the door frame cooling structure, providing a stable low-temperature environment for the entire sealing system and suppressing thermal deformation.

[0049] Slag Discharge Initiation: When slag discharge is required, the drive mechanism 3 receives the command and smoothly pulls open the insert plate 2 through the three-dimensional spherical connecting mechanism. At this time, all sealing units are in a separated or non-working state, and the slag outlet is open.

[0050] Closure and Initial Sealing: After slag discharge, the drive mechanism 3 reverses its direction, pushing the slide plate 2 to close. The hard, wear-resistant surface 4 on the slide plate 2 first contacts and presses against the elastic sealing body 13 on the door frame 1, forming the initial first-stage mechanical seal. At the same time, the third-stage auxiliary contact seal 7 also passively comes into place.

[0051] Automatic activation of the air curtain seal: Triggered by the signal indicating that the gate plate 2 is closed, the valve on the air source interface 6 automatically opens. Clean sealing gas (e.g., compressed air with a pressure 1 kPa higher than the slag cavity) after filtering, drying, and pressure regulation enters the annular air curtain sealing cavity 5. Since there may still be microscopic gaps in the first-stage mechanical seal pair, this gas, under the influence of the pressure difference, forms a stable, minute, positive seepage flow from the atmospheric side into the slag cavity. This airflow acts like an invisible wall, effectively preventing any fine dust from escaping from the slag cavity. Simultaneously, the airflow also provides auxiliary cooling and purging for the sealing surface.

[0052] Dynamic Wear Compensation: During long-term operation, the hard wear-resistant surface 4 and the elastic seal 13 will inevitably wear. At this time, the miniature hydraulic cylinder 12 in the wear adaptive compensation unit, based on its set system pressure, will automatically push the piston rod outwards, pressing against the back of the elastic seal 13 to compensate for the gap caused by wear. Therefore, regardless of changes in wear, the contact pressure between the sealing surfaces can be dynamically maintained at the initially set optimal value. If DCS closed-loop control is configured, the system can even fine-tune the thrust of the hydraulic cylinder 12 in real time based on minute fluctuations in the pressure sensor, achieving the ultimate "seal as new" effect.

[0053] Long-term operation and maintenance: Through the synergistic effect of the above methods, the sealing device of the present invention can achieve long-term (e.g., synchronized with the boiler overhaul cycle) maintenance-free operation. When scheduled maintenance is required, operators can easily inspect or replace the modular sealing components.

[0054] As can be seen, in the above continuous dynamic operation process, the main core steps of the sealing method of the present invention in a single operation are: closing the insert plate to make the first-stage mechanical seal structure seal and form an initial mechanical seal; introducing sealing gas into the second-stage air curtain sealing structure to form a positive airflow from the outside to the inside; applying and maintaining a constant effective contact pressure on the first-stage mechanical seal structure through the wear adaptive compensation unit; and running the cooling unit to cool the target parts on the insert plate and the door frame.

[0055] In summary, this invention organically combines key technical features such as multi-stage sealing, active air curtain, dynamic wear compensation, and system cooling to form a novel, synergistic technical solution. This solution completely solves the long-standing problems of leakage, jamming, and short lifespan at the slag outlet of the circulating fluidized bed boiler slag cooler, significantly improving the equipment's safety and environmental performance, and bringing substantial economic and social benefits. The sealing device and method for the slag outlet of a circulating fluidized bed boiler slag cooler provided by the embodiments of the present invention have the following advantages compared with the prior art: First, multiple sealing guarantees ensure inherent safety and reliability: Through a three-stage synergistic sealing system consisting of a first-stage contact mechanical seal, a second-stage air curtain seal, and a third-stage auxiliary contact seal, each stage works in a progressive manner and performs its own function, forming a multi-layered protection architecture where "the mechanical seal blocks coarse particles, the air curtain seal blocks fine dust, and the auxiliary seal ensures the bottom line." Even if the sealing performance of one stage decreases, the other two stages can still ensure the overall sealing reliability, fundamentally achieving an inherently safe design.

[0056] Secondly, the dynamic air curtain barrier effectively prevents micro-dust leakage: filtered and dried compressed air is introduced into the second-stage air curtain sealing cavity to form a stable positive pressure air curtain barrier. This air curtain establishes a directional flow from the sealing cavity towards the material side at the sealing gap, effectively preventing the leakage path of fine dust (particle size <0.1mm) through the micro-gap of the mechanical seal pair under the positive pressure inside the furnace. At the same time, the sealing airflow has a continuous cooling and purging cleaning effect on the sealing surface, further extending the service life of the mechanical seal pair.

[0057] Third, automatic wear compensation enables maintenance-free long-term operation: A closed-loop wear compensation system, composed of miniature hydraulic cylinders, pressure sensors, and a DCS control system evenly arranged around the circumference of the sealing plate, can automatically detect and compensate for the wear of the sealing surface in real time, ensuring that the sealing contact clamping force remains constant throughout the entire equipment's lifespan. This innovative design completely solves the industry pain point of traditional sealing devices where wear leads to a continuous decrease in sealing force, necessitating frequent shutdowns to replace seals. It significantly extends the maintenance cycle and is expected to achieve the goal of maintenance-free operation with the same lifespan as the boiler body.

[0058] Fourth, comprehensive active cooling ensures structural thermal stability: By setting cooling channels inside the door frame wall and cooling channels in the high-temperature area of ​​the insert plate, cooling water is used to force-cool key parts, significantly reducing the working temperature of the sealing area from over 850℃ to about 100℃. This fundamentally avoids changes in fit clearance and jamming risks caused by high-temperature thermal deformation, ensuring the dimensional accuracy and movement flexibility of each component. At the same time, it significantly reduces the thermal aging and thermal stress damage of the sealing material, ensuring the long-term operational reliability of the device.

[0059] Fourth, significant safety, environmental protection, and economic benefits: It has achieved long-term, essentially zero-leakage operation at the discharge outlet, completely eliminating the safety hazards of high-temperature flue gas dust leakage on site, and meeting increasingly stringent environmental emission requirements; it has greatly reduced unplanned shutdowns and maintenance workload, lowered maintenance costs and power generation losses caused by boiler shutdowns, and brought significant economic benefits to users.

[0060] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A sealing device for the slag outlet of a circulating fluidized bed boiler slag cooler, wherein the slag outlet of the slag cooler is provided with a gate, the gate comprising a door frame, a gate plate, and a driving mechanism for driving the gate plate, characterized in that, Also includes: The multi-stage sealing unit, along the material flow direction, sequentially includes a first-stage mechanical seal structure, a second-stage air curtain seal structure, and a third-stage auxiliary contact seal structure disposed between the insert plate and the door frame. The first-stage mechanical seal structure includes a hard, wear-resistant surface located around the slag-facing side of the insert plate and an elastic sealing body located on the door frame. The second-stage air curtain seal structure includes an air curtain sealing cavity formed within the door frame, with its air passage connected to a sealing gas inlet. The third-stage auxiliary contact seal structure is located on the outer side of the second-stage air curtain seal structure at the junction with the door stem of the insert plate door. A wear adaptive compensation unit, corresponding to the first-stage mechanical seal structure arrangement, is used to apply a continuous and adjustable clamping force to compensate for wear; and The cooling unit includes cooling channels disposed inside the insert plate and / or cooling structures disposed on the door frame.

2. The sealing device for the slag outlet of the circulating fluidized bed boiler slag cooler according to claim 1, characterized in that, The wear adaptive compensation unit includes multiple miniature hydraulic cylinders evenly distributed along the circumference of the door frame, with the piston rod end of each miniature hydraulic cylinder abutting against the back of the elastic seal.

3. The sealing device for the slag outlet of the circulating fluidized bed boiler slag cooler according to claim 2, characterized in that, The wear adaptive compensation unit also includes a pressure sensor for detecting the clamping force on the elastic seal. The pressure sensor is communicatively connected to the DCS control system. The DCS control system adjusts the hydraulic pressure of the micro hydraulic cylinder according to the feedback signal of the pressure sensor to apply a continuous and adjustable clamping force to the elastic seal.

4. The sealing device for the slag outlet of the circulating fluidized bed boiler slag cooler according to claim 3, characterized in that, The number of miniature hydraulic cylinders is four, which are respectively arranged on the four sides of the door frame. The hydraulic system pressure of the hydraulic cylinders is set to a constant value. The DCS control system performs closed-loop adjustment based on the real-time feedback of the pressure sensor to automatically compensate for displacement when the elastic seal wears, and maintain the effective contact clamping force between the elastic seal and the hard wear-resistant surface.

5. The sealing device for the slag outlet of the circulating fluidized bed boiler slag cooler according to any one of claims 1 to 4, characterized in that, Also includes: The insert plate has a hollow sandwich structure, and the cooling channel inside it is provided with a cooling medium inlet and outlet; the cooling structure on the door frame is a cooling coil embedded inside the high-temperature zone.

6. The sealing device for the slag outlet of the circulating fluidized bed boiler slag cooler according to any one of claims 1 to 4, characterized in that, The sealing gas inlet receives compressed air from a source through an airflow passage equipped with a pressure regulating valve. The pressure regulating valve is configured to control the pressure of the sealing gas entering the air curtain sealing cavity within a range that is 0.5-2 kPa higher than the pressure inside the slag cooler cavity.

7. The sealing device for the slag outlet of the circulating fluidized bed boiler slag cooler according to any one of claims 1 to 4, characterized in that, The hard wear-resistant surface is a tungsten carbide wear-resistant surface, and the elastic seal is an elastic seal formed by wrapping flexible graphite with a high-temperature alloy bellows.

8. A sealing method for the slag outlet of a circulating fluidized bed boiler slag cooler, characterized in that, A sealing device applied to the slag outlet of a circulating fluidized bed boiler slag cooler according to any one of claims 1 to 7, comprising the following steps: Close the insert plate to allow the first-stage mechanical seal structure to seal and fit together, forming an initial mechanical seal; Sealing gas is introduced into the second-stage air curtain sealing structure to form a positive airflow from the outside to the inside; The wear adaptive compensation unit applies and maintains a constant effective contact pressure on the first-stage mechanical seal structure. The cooling unit is operated to cool the target parts on the insert plate and the door frame.

9. The sealing method for the slag outlet of the circulating fluidized bed boiler slag cooler according to claim 8, characterized in that, The step of introducing sealing gas is automatically executed after the gate is closed in place; the sealing gas is clean, dry compressed air. This ensures that the cooling unit continues to operate during and after the slag discharge process of the slag cooler, so as to control the temperature of the high-temperature zone of the insert plate and door frame below a preset threshold.

10. The sealing method for the slag outlet of the circulating fluidized bed boiler slag cooler according to claim 8 or 9, characterized in that, The steps of applying and maintaining a constant effective contact pressure through the wear adaptive compensation unit specifically include: preset the system pressure of the micro hydraulic cylinder of the wear adaptive compensation unit; when the sealing surface is worn, the piston of the micro hydraulic cylinder automatically extends to compensate for the displacement, so that the sealing contact pressure is maintained at the design value.

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