A shaft seal device and system

Abstract

This utility model relates to the field of shaft seals, particularly shaft seal devices and systems, including mechanical seals. A sealing cavity is provided on the outer side of the mechanical seal, and a material channel is provided on the inner side. The sealing cavity includes an annular channel and an inlet channel and an outlet channel connecting the ends of the annular channel. The sealing fluid contained in the sealing cavity is a trichlorosilane or silicon tetrachloride liquid with the same properties as the process material. An integrated sealing system is formed by the shaft seal device, a pressure stabilizing tank, and two staggered supply and return pipelines. Using a trichlorosilane or silicon tetrachloride liquid with the same properties as the process medium as the sealing fluid, a constant pressure difference is formed between the tank and the sealing cavity through natural circulation, allowing the sealing fluid to continuously lubricate, cool, and isolate the double-end mechanical seal. A level gauge provides real-time feedback on the leakage rate, and a nitrogen pressure regulating valve automatically compensates for the pressure, achieving "internal leakage without external leakage." This allows for online wear monitoring, significantly extends the mechanical seal's lifespan, and reduces the frequency of downtime for the filter cake dryer.

Description

Technical Field

[0001] This utility model relates to the field of shaft sealing, and in particular to a shaft sealing device and system. Background Technology

[0002] Traditional shaft seals for filter cake dryers generally employ a packing seal structure: flexible packing is filled between the rotating shaft and the end cover, and wear is reduced by continuously injecting grease. At the same time, nitrogen is introduced for cooling and purging to prevent solid and chlorine-containing process media from entering the packing area, thereby achieving the sealing purpose.

[0003] However, in actual operation, the packing is prone to wear due to long-term friction with the shaft. The grease deteriorates and hardens rapidly after contact with highly corrosive materials such as trichlorosilane and silicon tetrachloride, losing its lubricating and sealing properties. As the leakage gradually increases, media escape, equipment corrosion and environmental pollution occur on site. Replacing the packing requires stopping production and removing the cover, which is cumbersome, time-consuming and labor-intensive, significantly increasing maintenance costs and the risk of production interruption. Utility Model Content

[0004] Therefore, the technical problem to be solved by this utility model is that the packing seal is prone to wear and the lubricating grease deteriorates and hardens during the operation of the filter residue dryer, resulting in increased leakage, frequent maintenance, and the need to stop production for replacement.

[0005] The above-mentioned technical problems are solved by the following technical solution: This utility model proposes a shaft sealing device, including a mechanical seal, a sealing cavity is provided on the outer side of the mechanical seal, and a material channel is provided on the inner side.

[0006] The sealing cavity includes an annular channel and an inlet channel and an outlet channel connecting the ends of the annular channel. The sealing liquid contained in the sealing cavity is a trichlorosilane or silicon tetrachloride liquid with the same properties as the process material.

[0007] In a preferred embodiment of the shaft sealing device of this utility model: the shaft sealing device is a cartridge-type double-end mechanical seal, which further includes a main body and a first water-cooling channel, the sealing cavity and a second water-cooling channel arranged sequentially along the axial direction of the main body.

[0008] This utility model also proposes a shaft sealing system, including the aforementioned shaft sealing device and a pressure stabilizing tank, which is connected to the inlet channel of the sealing cavity through a liquid supply pipeline and to the outlet channel of the sealing cavity through a liquid return pipeline, forming a sealing liquid circulation loop.

[0009] In a preferred embodiment of the shaft sealing system of this utility model: the pressure stabilizing tank is provided with a nitrogen inlet at its top, and a nitrogen pressure regulating valve is installed on the nitrogen inlet.

[0010] In a preferred embodiment of the shaft sealing system of this utility model: the pressure stabilizing tank is further provided with a sealing liquid inlet at its top, and the sealing liquid in the pressure stabilizing tank is a trichlorosilane or silicon tetrachloride liquid with the same properties as the process material.

[0011] A level gauge is installed inside the pressure stabilizing tank to detect and output the liquid level signal of the sealing liquid inside the tank in real time.

[0012] In a preferred embodiment of the shaft sealing system of this utility model: the outlet of the liquid supply pipeline connected to the pressure stabilizing tank is lower in the vertical direction than the inlet of the return liquid pipeline connected to the pressure stabilizing tank.

[0013] In a preferred embodiment of the shaft sealing system of this utility model: the outlet pressure setting value of the nitrogen pressure regulating valve is 0.05 MPa higher than the working pressure of the filter residue dryer.

[0014] In a preferred embodiment of the shaft sealing system of this utility model: the pressure stabilizing tank is vertical, and an external discharge port is provided at its lowest point.

[0015] In a preferred embodiment of the shaft sealing system of this utility model: the mechanical seal is sleeved on the outer circumference of the rotating shaft of the filter residue dryer and located between the end cover and the housing of the filter residue dryer.

[0016] In a preferred embodiment of the shaft sealing system of this utility model: the level gauge is a magnetic plate level gauge equipped with a remote signal interface for connecting to a DCS system to realize low level alarm.

[0017] The beneficial effects of this utility model are as follows: This system is an integrated sealing system consisting of a mechanical seal, a pressure stabilizing tank, and two staggered supply and return pipelines. It uses trichlorosilane or silicon tetrachloride liquid with the same properties as the process medium as the sealing fluid, forming a natural circulation with a constant pressure difference between the tank and the sealing cavity. This allows the sealing fluid to continuously lubricate, cool, and isolate the double-end mechanical seal. The level gauge provides real-time feedback on the leakage rate, and the nitrogen pressure regulating valve automatically compensates for the pressure, achieving "internal leakage without external leakage." It can monitor wear online without the need for additional pumping, significantly extending the mechanical seal life and reducing the downtime frequency and maintenance costs of the filter cake dryer. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this utility model, the accompanying drawings of the embodiments of this utility model will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this utility model and are not intended to limit the scope of this utility model. Wherein:

[0019] Figure 1 A cross-sectional view of the shaft sealing device of the present invention is shown;

[0020] Figure 2 An overall view of the shaft sealing device of the present invention is shown.

[0021] Figure 3 A schematic diagram of the shaft sealing system connection of the present invention is shown. Figure 1 ;

[0022] Figure 4 A schematic diagram of the shaft sealing system connection of the present invention is shown. Figure 2 .

[0023] In the picture:

[0024] 100. Shaft sealing device; 101. Mechanical seal; 102. Sealing cavity; 102a. Annular channel; 102b. Inlet channel; 102c. Outlet channel; 103. Material channel; 104. Main body; 105. First water cooling channel; 106. Second water cooling channel; 200. Pressure stabilizing tank; 201. Nitrogen inlet; 202. Sealing liquid inlet; 203. Outlet; 300. Liquid supply pipeline; 400. Liquid return pipeline; 500. Nitrogen pressure regulating valve; 600. Liquid level gauge. Detailed Implementation

[0025] To enable those skilled in the art to better understand this utility model, the present utility model will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0026] The terminology used in this invention refers to those general terms currently widely used in the art in consideration of the functionality of this invention; however, these terms may vary according to the intent, precedent, or new technology of those skilled in the art. Furthermore, specific terms may be chosen by the applicant, and in such cases, their detailed meanings will be described in the detailed description of this invention. Therefore, the terminology used in this specification should not be construed as simple names, but rather based on the meaning of the terms and the overall description of this invention.

[0027] Reference Figures 1-2 This embodiment provides a shaft sealing device 100, including a mechanical seal 101. A sealing cavity 102 is provided on the outer side of the mechanical seal 101, and a material channel 103 is provided on the inner side. The sealing cavity 102 includes an annular channel 102a and an inlet channel 102b and an outlet channel 102c connecting the ends of the annular channel 102a. The sealing liquid contained in the sealing cavity 102 is a trichlorosilane or silicon tetrachloride liquid with the same properties as the process material. The shaft sealing device 100 is a cartridge-type double-end mechanical seal, which also includes a main body 104 and a first water-cooling channel 105, a sealing cavity 102, and a second water-cooling channel 106 arranged sequentially along the axial direction of the main body 104. The shaft sealing device 100 is sleeved on the outer circumference of the rotating shaft of the filter residue dryer and is located between the end cover and the shell of the filter residue dryer.

[0028] The mechanical seal 101 is used to initially seal the material in the material channel 103, and the sealing cavity 102 is used to seal the mechanical seal 101, forming a double seal of mechanical and liquid to prevent material leakage. The sealing cavity 102 is filled with trichlorosilane or silicon tetrachloride liquid with the same properties as the process material, which prevents the sealing liquid from reacting chemically with the process material when the sealing cavity 102 of the mechanical seal 101 leaks. In this way, it can safely "leak internally but not externally" in the event of a small amount of leakage.

[0029] In this embodiment, the shaft sealing device 100 uses a cartridge-type double-end mechanical seal as the core sealing element, aiming to solve the leakage and lifespan problems of the filter cake dryer under high temperature, solid content, and chlorine content conditions in one go. The term "cartridge-type" means that the entire sealing assembly, including the dynamic ring, stationary ring, spring, push ring, O-ring, and positioning sleeve, is pre-pressed into an independent cylinder. On-site, there is no need to adjust the compression of each component individually. Installation can be completed simply by hoisting it onto the shaft and tightening the bolts. This shortens maintenance time, eliminates human assembly errors, and significantly reduces the risk of early failure due to improper installation.

[0030] The shaft sealing device 100 has a double-end face structure with a first water-cooling channel 105, a sealing cavity 102, and a second water-cooling channel 106 arranged sequentially along the axial direction. The first water-cooling channel 105 is close to the end face of the medium side, which can quickly remove the instantaneous high heat generated by the friction of solid particles. The sealing cavity 102 is located between two pairs of friction pairs and is used to inject trichlorosilane or silicon tetrachloride liquid with the same properties as the process material to form a positive pressure isolation barrier. The second water-cooling channel 106 is close to the atmospheric side, which further reduces the end face temperature and avoids dry friction of the outer end face. The three cooling and lubrication paths are connected in series, so that each sealing surface works within the optimal temperature range, and the wear rate is reduced to less than one-third of that of a normal single-end face mechanical seal 101.

[0031] Furthermore, the cartridge-type double-end mechanical seal has a short axial dimension and good radial containment, allowing it to be directly fitted onto the outer circumference of the rotating shaft of the filter cake dryer and embedded between the end cover and the housing without altering the original equipment interface. In case of maintenance, it can be pulled out entirely without disassembling the bearings or couplings, truly achieving online core replacement. Considering its ease of installation, cooling redundancy, and zero-emission safety, the cartridge-type double-end mechanical seal is the optimal choice for meeting the long-cycle, maintenance-free operation requirements of cold hydrogenation filter cake dryers.

[0032] Reference Figure 3 This embodiment provides a shaft sealing system, including a shaft sealing device 100 and a pressure stabilizing tank 200. The device is connected to the inlet of the sealing cavity 102 through a liquid supply pipeline 300 and to the outlet of the sealing cavity 102 through a liquid return pipeline 400, thus forming a sealing liquid circulation loop.

[0033] In this embodiment, the shaft sealing system consists of a shaft sealing device 100, a pressure stabilizing tank 200, and two pipelines. The shaft sealing device 100 is directly fitted onto the outer circumference of the dryer's rotating shaft, located between the filter residue dryer's end cover and the housing, acting as the first barrier. An annular sealing cavity 102 is machined inside, providing space for the sealing liquid to flow and reside. The pressure stabilizing tank 200 is installed vertically near the dryer. The tank contains a trichlorosilane or silicon tetrachloride liquid with the same properties as the process material, preventing a chemical reaction between the sealing liquid and the process material in the event of leakage from the sealing cavity 102 of the mechanical seal 101. This ensures safe "internal leakage without external leakage" even in the event of minor leaks. One end of the supply line 300 is connected to the lower outlet of the pressure stabilizing tank 200, and the other end is connected to the inlet of the sealing cavity 102 of the shaft seal device 100; one end of the return line 400 is connected to the outlet of the sealing cavity 102, and the other end returns to the upper inlet of the pressure stabilizing tank 200, thus forming a closed sealing fluid circulation loop. This circulation loop can achieve natural circulation under the action of height difference or pressure difference, or it can be supplemented by a constant pressure difference provided by the nitrogen pressure regulating valve 500, so that the sealing fluid flows continuously and stably through the two end faces of the mechanical seal 101 to complete the functions of lubrication, cooling and isolation.

[0034] Since the liquid level in the pressure stabilizing tank 200 is directly related to the leakage rate of the shaft sealing device 100, operators only need to observe the reading of the magnetic plate level gauge 600 inside the pressure stabilizing tank 200 to determine the wear condition of the sealing surface online, thereby deciding when to perform maintenance. The entire system integrates the shaft sealing device 100, the pressure stabilizing tank 200, and the circulation pipeline into one unit through a simple structural connection. It retains the compactness of the traditional shaft sealing device 100 while leveraging the pressure stabilizing tank 200 to achieve multiple functions such as pressure buffering, liquid compensation, and condition monitoring, significantly extending the seal life and reducing the downtime frequency and maintenance costs of the filter cake dryer.

[0035] Reference Figure 3 , Figure 4 Furthermore, the pressure stabilizing tank 200 has a nitrogen inlet 201 at its top, and a nitrogen pressure regulating valve 500 is installed on the nitrogen inlet 201. The outlet pressure setting of the nitrogen pressure regulating valve 500 is 0.05 MPa higher than the working pressure of the filter cake dryer.

[0036] In this embodiment, a nitrogen inlet 201 is specially machined on the top of the pressure stabilizing tank 200 for introducing an external nitrogen source. A nitrogen pressure regulating valve 500 is installed at this inlet to ensure that the nitrogen pressure entering the tank can always be precisely set and kept constant. According to the actual operating conditions of the filter residue dryer, the outlet pressure of the nitrogen pressure regulating valve 500 is set to be higher than the internal working pressure of the dryer by at least 0.05 MPa. This creates a continuous positive pressure difference between the pressure stabilizing tank 200 and the dryer. This pressure difference ensures that the sealing liquid can preferentially flow to the sealing cavity 102 at any instant, preventing the process medium from seeping back. On the other hand, when a slight wear occurs on the end face of the shaft sealing device 100, causing the gap to increase, the sealing liquid will be forced into the equipment first, preventing the leakage of solid or chlorine-containing process gases or liquids, thus achieving a safe seal of "internal leakage without external leakage". The margin of 0.05MPa or more takes into account the pressure loss caused by pipeline resistance, temperature fluctuations and slight equipment vibration, and provides sufficient signal sensitivity for online monitoring. As soon as the liquid level starts to drop, it indicates that the inner end face has begun to wear. Maintenance personnel can arrange maintenance in advance based on this and avoid sudden leaks and downtime accidents.

[0037] Reference Figure 3 , Figure 4 Furthermore, the pressure stabilizing tank 200 is vertical in shape, and the top of the pressure stabilizing tank 200 is also provided with a sealing liquid inlet 202. The sealing liquid inside the pressure stabilizing tank 200 is a trichlorosilane or silicon tetrachloride liquid with the same properties as the process material, and an external discharge port 203 is provided at its lowest point.

[0038] In this embodiment, the pressure stabilizing tank 200 adopts a vertical cylindrical structure with a vertically arranged tank axis. This provides sufficient liquid static pressure height with minimal footprint, facilitating the smooth flow of sealing liquid into the sealing cavity 102 of the shaft sealing device 100 under gravity. A sealing liquid inlet 202 is provided at the top of the tank, serving as a channel for initial filling or replenishment during operation. This inlet 202 is equipped with a sealing joint compatible with trichlorosilane and silicon tetrachloride, ensuring that air, moisture, or foreign matter are not introduced during disassembly or replenishment, thus maintaining system purity. The pressure stabilizing tank 200 is entirely filled with trichlorosilane or silicon tetrachloride liquid of the same nature as the process materials. This prevents the formation of solid particles that could clog the circuit due to chemical reactions, and ensures complete compatibility with the materials in the dryer even in the event of minor leaks, avoiding byproduct deposition or corrosion. The pressure stabilizing tank 200 has an external drain port 203 at the lowest point of its bottom. Under normal operating conditions, it is sealed with a blind flange or valve. When maintenance or cleaning is required, it can be opened to completely drain the residual liquid and prevent the accumulation of sediment. The external drain port 203 is short-connected to the tank bottom with the same material to ensure complete drainage and reliable sealing. The vertical tank, top inlet, same-type sealing liquid, and bottom external drain port 203 together constitute a simple, easy-to-maintain, safe and reliable sealing liquid storage and replenishment unit, providing a basic guarantee for the long-term operation of the entire shaft sealing device 100.

[0039] Reference Figure 3 , Figure 4 Furthermore, the outlet of the liquid supply line 300 connected to the pressure stabilizing tank 200 is vertically lower than the inlet of the return line 400 connected to the pressure stabilizing tank 200.

[0040] In this embodiment, the outlet of the pressure stabilizing tank 200, which connects to the supply pipeline 300, is located in the lowest region of the tank body, while the inlet of the return pipeline 400, which connects back to the tank body, is located in the higher region of the upper tank body, creating a significant vertical difference between the two. This difference allows the sealing fluid inside the tank to flow continuously and without power along the supply pipeline 300 to the sealing cavity 102 of the mechanical seal 101 under the influence of gravity. After cooling, lubrication, and removal of frictional heat and small particles, the slightly warmer sealing fluid returns to the upper inlet of the tank body through the return pipeline 400, further promoting natural circulation through temperature and density differences. The high-level return inlet also prevents air bubble accumulation and avoids air lock, ensuring that the entire circulation loop is always filled with liquid, maintaining a stable positive pressure differential, reducing dependence on pumps or external power, thereby improving the reliability and energy efficiency of the system.

[0041] Reference Figure 3 , Figure 4 Furthermore, a level gauge 600 is installed inside the pressure stabilizing tank 200 to detect and output the liquid level signal of the sealing liquid inside the tank in real time. The level gauge 600 is a magnetic plate type level gauge 600, which is equipped with a remote signal interface for connection to the DCS system to realize low liquid level alarm.

[0042] In this embodiment, a magnetic plate level gauge 600 is installed inside the pressure stabilizing tank 200. Its measuring cylinder is directly connected to the side wall of the tank, and the float rises and falls synchronously with the level of the sealing fluid. The float has a built-in permanent magnet ring that drives an external indicating flap via magnetic coupling, allowing on-site personnel to visually read the liquid level without opening the tank. The magnetic plate level gauge 600 is equipped with a remote signal interface on its top, which can send analog or digital liquid level signals to the DCS system in real time. When the liquid level continues to drop due to wear on the end face of the shaft sealing device 100 and reaches the set low limit, the DCS immediately triggers an audible and visual alarm, reminding operators to replenish the liquid or arrange maintenance, thus eliminating potential leakage risks at the outset. The entire monitoring process does not contact the sealing fluid and has no sealing points, ensuring the purity of the trichlorosilane / silicon tetrachloride medium and avoiding the risks of easy breakage and leakage associated with traditional glass plate level gauges 600. This achieves dual functions of remote monitoring and local display, providing reliable data support for the safe and long-term operation of the shaft sealing device 100.

[0043] Reference Figures 1-4Furthermore, the sealing cavity 102 includes an annular channel 102a and an inlet channel 102b and an outlet channel 102c connecting the ends of the annular channel 102a. The inlet channel 102b is connected to the liquid supply line 300, and the outlet channel 102c is connected to the liquid return line 400.

[0044] In this embodiment, the sealing cavity 102 is designed as a circumferentially closed annular channel 102a, tightly fitted around the rotating shaft and located between the two end face friction pairs. The radial cross-section of the annular channel 102a is a rectangular or trapezoidal cavity, ensuring that the sealing fluid can uniformly surround the journal within a 360° range, quickly carrying away heat and lubricating the entire friction interface. In order to form a closed loop with the external pressure tank 200, radial or tangential inlet channels 102b and outlet channels 102c are respectively machined on the same axial end face of the annular channel 102a: the inlet channel 102b is located at a low position and directly connects to the liquid supply pipeline 300, so that the low temperature and high pressure sealing fluid first enters the vicinity of the medium side end face that is most prone to heat generation; the outlet channel 102c is located at a high position and connects to the return liquid pipeline 400, so as to promptly bring the sealing fluid carrying heat and a small amount of wear debris back to the pressure tank 200 for cooling and filtration. The arrangement of a low inlet and a high outlet utilizes the gravity difference to promote natural circulation and avoids air bubble retention, ensuring that the entire sealed cavity 102 is filled with liquid, thus achieving continuous and stable cooling and isolation effects.

[0045] Reference Figures 1-4 This patent constructs a completely closed sealed liquid circulation loop: the outlet of the pressure stabilizing tank 200 is connected to the inlet of the sealing cavity 102 of the shaft sealing device 100 via the liquid supply pipeline 300, and the outlet of the shaft sealing device 100 returns to the inlet of the pressure stabilizing tank 200 via the liquid return pipeline 400. The liquid supply pipeline 300 and the liquid return pipeline 400 form a natural height difference in the vertical direction. This height difference, together with the pressure difference of the injected nitrogen gas, allows trichlorosilane or silicon tetrachloride liquid to continuously flow by gravity between the tank, pipe, and cavity, which not only eliminates the need for power equipment but also ensures that the cavity is always full of liquid, laying the foundation for subsequent positive pressure flow.

[0046] The sealing fluid itself is made of trichlorosilane or silicon tetrachloride, which are of the same nature as the process materials, to avoid precipitation or corrosion due to chemical incompatibility; the pressure stabilizing tank 200 and all flow parts are made of stainless steel or fluoropolymer-lined structure that are compatible with it, to further ensure the purity of the system and the life of the equipment.

[0047] In terms of pressure maintenance, the top of the pressure stabilizing tank 200 is equipped with a nitrogen pressure regulating valve 500 and a pressure gauge interface. The outlet of the nitrogen pressure regulating valve 500 is set to 0.10MPa (example value), which is much higher than the working pressure of ≤0.05MPa inside the filter residue dryer. This ensures that the sealing cavity 102 is always under positive pressure. Once the end face of the shaft sealing device 100 is worn, the sealing liquid will be preferentially forced into the equipment, and the process medium cannot escape, thus achieving internal leakage without external leakage.

[0048] Condition monitoring relies on the magnetic plate level gauge 600 on the side wall of the tank. Its remote signal is connected to the DCS system. A continuous drop in the liquid level indicates a leak at the end face, and the operator can arrange maintenance in advance to avoid sudden shutdown.

[0049] Finally, routine maintenance is extremely simple: the top of the tank has a sealing fluid addition port, which can be replenished at any time; the bottom drain port 203 can completely drain residual fluid during maintenance. The whole set of equipment has a compact structure, operates without a pump, and can be inspected online, which can significantly extend the life of the shaft seal device by 100 and reduce the frequency of maintenance.

[0050] Finally, it should be noted that the methods and devices described in detail above are merely embodiments, and those skilled in the art can modify these embodiments in different ways as long as they do not depart from the scope of this utility model.

Claims

1. A shaft sealing device (100), characterized in that, It includes a mechanical seal (101), a sealing cavity (102) is provided on the outer side of the mechanical seal (101), and a material channel (103) is provided on the inner side. The sealing cavity (102) includes an annular channel (102a) and an inlet channel (102b) and an outlet channel (102c) connecting the ends of the annular channel (102a). The sealing liquid contained in the sealing cavity (102) is a trichlorosilane or silicon tetrachloride liquid with the same properties as the process material.

2. The shaft sealing device (100) according to claim 1, characterized in that: The shaft sealing device (100) is a cartridge-type double-end mechanical seal, which also includes a main body (104) and a first water-cooling channel (105), the sealing cavity (102) and a second water-cooling channel (106) arranged sequentially along the axial direction of the main body (104).

3. A shaft sealing system, characterized in that, The device includes the shaft sealing device (100) according to any one of claims 1 to 2 and a pressure stabilizing tank (200), which is connected to the inlet channel (102b) of the sealing cavity (102) through a liquid supply pipeline (300) and to the outlet channel (102c) of the sealing cavity (102) through a liquid return pipeline (400), thus forming a sealing liquid circulation loop.

4. The shaft sealing system according to claim 3, characterized in that: The pressure stabilizing tank (200) has a nitrogen inlet (201) at its top, and a nitrogen pressure regulating valve (500) is installed on the nitrogen inlet (201).

5. The shaft sealing system according to claim 3, characterized in that: The pressure stabilizing tank (200) is also provided with a sealing liquid inlet (202) at its top. The sealing liquid in the pressure stabilizing tank (200) is a trichlorosilane or silicon tetrachloride liquid with the same properties as the process material. The pressure stabilizing tank (200) is equipped with a level gauge (600) for real-time detection and output of the liquid level signal of the sealing liquid inside the tank.

6. The shaft sealing system according to any one of claims 3 to 5, characterized in that: The outlet of the supply pipeline (300) connected to the pressure stabilizing tank (200) is vertically lower than the inlet of the return pipeline (400) connected to the pressure stabilizing tank (200).

7. The shaft sealing system according to claim 4, characterized in that: The outlet pressure setting of the nitrogen pressure regulating valve (500) is at least 0.05 MPa higher than the working pressure of the filter residue dryer.

8. The shaft sealing system according to any one of claims 3, 4, 5, and 7, characterized in that: The pressure stabilizing tank (200) is vertical, and an external discharge port (203) is provided at its lowest point.

9. The shaft sealing system according to any one of claims 3, 4, 5, and 7, characterized in that: The mechanical seal (101) is fitted around the outer circumference of the rotating shaft of the filter residue dryer and is located between the end cover and the shell of the filter residue dryer.

10. The shaft sealing system according to claim 5, characterized in that: The level gauge (600) is a magnetic plate level gauge equipped with a remote signal interface for connecting to a DCS system to realize low level alarm.

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