Mvr mechanical compression fan leak-proof shaft seal system and method

Abstract

The application discloses a kind of MVR mechanical compression fan leakproof shaft sealing system and method, including carbon ring sealing structure, labyrinth seal structure and nitrogen pressure sealing structure;The carbon ring sealing structure is adopted by multistage carbon ring, carbon ring sealing structure is arranged at the junction of main shaft and impeller, the labyrinth seal structure is arranged between bearing box end cover and main shaft, the nitrogen pressure sealing structure is arranged on bearing box end cover, the labyrinth seal structure and nitrogen pressure sealing structure form double sealing structure;The multistage carbon ring structure sealing main shaft and impeller are arranged in the application, while under the effect of additional pressure steam holding, balance internal and external pressure difference, greatly prolong the carbon ring sealing life and sealing effect, effectively avoid steam and condensate leakage;The labyrinth seal structure and nitrogen pressure sealing structure are arranged to double insurance sealing for bearing box end cover, effectively strengthen the operation safety guarantee of equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fan shaft seal, in particular to a MVR mechanical compression fan anti-leakage shaft sealing system and method. BACKGROUND

[0002] MVR is the abbreviation of Mechanica l Vapor Recompress ion, and the principle of the MVR evaporator is to use a high-energy-efficiency vapor compressor to compress the secondary vapor generated by evaporation, convert electrical energy into heat energy, and improve the enthalpy of the secondary vapor. The secondary vapor with improved heat energy is injected into the evaporation chamber for heating, so as to achieve the purpose of recycling the existing heat energy of the secondary vapor, thereby reducing or even eliminating the need for fresh steam, and realizing the purpose of evaporation and concentration through self-circulation of the evaporator.

[0003] The MVR mechanical compression fan is the core equipment of the technology, and the low-grade secondary vapor is improved in heat energy under the action of high-speed centrifugal motion of the compression fan impeller. At present, the shaft seal form of the centrifugal fan is single, and most of the sealing elements are packing seals or skeleton oil seals. Since the sealing element is fixed on the shell, there is relative motion between the sealing element and the main shaft. Therefore, when the equipment is continuously operated for a long time, the sealing element is prone to wear and leakage, and frequent shutdown is required for processing. This not only has high labor intensity, but also seriously affects the production efficiency. SUMMARY

[0004] In view of the problems existing in the prior art, the present application provides a MVR mechanical compression fan anti-leakage shaft sealing system and method, which realizes the shaft sealing of the compression fan through the cooperation of multiple sealing structures, and ensures the stable operation of the compression fan.

[0005] The technical scheme of the present application is as follows:

[0006] In the first aspect of the present application, a MVR mechanical compression fan anti-leakage shaft sealing system comprises a carbon ring sealing structure, a labyrinth sealing structure and a nitrogen pressure sealing structure. The carbon ring sealing structure is a multi-stage sealing structure composed of multiple carbon rings, and is arranged at the connection between the main shaft and the impeller. The labyrinth sealing structure is arranged between the bearing box end cover and the main shaft. The nitrogen pressure sealing structure is arranged on the bearing box end cover. The labyrinth sealing structure and the nitrogen pressure sealing structure form a double sealing structure.

[0007] In some embodiments of the present application, the carbon ring sealing structure comprises an annular shaft sealing shell and an annular shaft sleeve. The annular shaft sealing shell has an annular groove, and at least two carbon rings with rectangular cross sections are arranged in the annular groove.

[0008] In some embodiments of the present application, a steam buffer sealing structure is further arranged on the shaft seal housing, the steam buffer sealing structure comprises a sealing steam inlet and a steam condensate outlet, and the sealing steam inlet is filled with pressurized steam higher than or equal to the steam pressure at the inlet of the compression fan.

[0009] In some embodiments of the present application, a gap of 0.01-0.04mm is provided between the inner diameter of the carbon ring and the annular shaft sleeve, and a wear-resistant layer is coated on the outer surface of the shaft sleeve, the wear-resistant layer being made of aluminum oxide or chromium oxide.

[0010] In some embodiments of the present application, the carbon ring comprises a plurality of fan-shaped carbon rings, and a groove is arranged on the outer periphery of the fan-shaped carbon ring, and a tension spring is arranged in the groove, and the fan-shaped carbon rings are combined into an annular carbon ring by the tension spring.

[0011] In some embodiments of the present application, the nitrogen gas pressurized seal comprises a nitrogen gas channel, and the nitrogen gas channel is in communication with the bearing box.

[0012] In some embodiments of the present application, the nitrogen gas channel is arranged on the bearing end cover, a screw is arranged on the inner wall of the nitrogen gas inlet, and the screw is screwed into the bearing end cover.

[0013] In some embodiments of the present application, the nitrogen gas pressurized pressure is 0.2-0.5Mpa.

[0014] In some embodiments of the present application, the labyrinth seal comprises a plurality of annular sealing teeth arranged in sequence, and a series of interception gaps and expansion cavities are formed between the teeth.

[0015] In the second aspect of the present application, a MVR mechanical compression fan anti-leakage shaft sealing method is provided, comprising: adopting a multi-stage carbon ring sealing structure as the main shaft sealing, and cooperating with a pressurized steam buffer sealing structure to balance the internal and external pressure difference; adopting a labyrinth sealing structure and a nitrogen gas pressurized structure to seal between the bearing box and the main shaft, and when the carbon ring fails to leak, 0.2-0.5MPa nitrogen gas is introduced to form an air seal.

[0016] The one or more technical solutions of the present application have the following beneficial effects:

[0017] (1) The MVR mechanical compression fan anti-leakage shaft sealing system provided by the present application seals the connection between the main shaft and the impeller through the multi-stage carbon ring structure, balances the internal and external pressure difference on the impeller side and the bearing side under the effect of the additional pressurized steam, greatly prolongs the carbon ring sealing life and sealing effect, effectively avoids steam and condensate leakage, and double-insurance seals the bearing box end cover through the labyrinth sealing structure and the nitrogen gas pressurized sealing structure, and the nitrogen gas pressurization serves as an insurance measure after the carbon ring sealing leaks, thereby effectively improving the operation safety of the equipment.

[0018] (2) The MVR mechanical compression fan anti-leakage shaft sealing system and method can ensure long-period stable operation of the MVR mechanical compression fan, save fresh steam supplement, reduce energy consumption of the evaporation system, and save energy consumption cost of more than 1 million yuan per year for the enterprise. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Figure 1 is a structural schematic diagram of the MVR mechanical compression fan anti-leakage shaft sealing system of the present application;

[0020] Figure 2 Figure 2 is a structural schematic diagram of the multi-stage carbon ring installed on the shaft sleeve of the present application;

[0021] Figure 3 Figure 3 is an elevation view of the steam buffer sealing structure of the present application;

[0022] Figure 4 Figure 4 is a sectional view at A-A in Figure 3; Figure 3

[0023] Figure 5 Figure 5 is a structural schematic diagram of the carbon ring of the present application;

[0024] Figure 6 Figure 6 is a schematic diagram of the sealing structure at the bearing box of the present application.

[0025] In the figure: 1, impeller; 2, casing baffle; 3, shaft seal shell; 4, nitrogen pressure interface; 5, bearing box; 6, driving end bearing; 7, bearing labyrinth seal; 8, carbon ring; 81, groove; 9, shaft sleeve; 10, main shaft; 11, nitrogen channel; 12, steam inlet; 13, steam condensate outlet; 14, O-ring; 15, screw. DETAILED DESCRIPTION

[0026] The present application will be further described below in combination with the drawings and examples.

[0027] Example 1

[0028] ​Because the temperature required for evaporation of some special materials in the MVR system is relatively high, the steam compression fan matched is long-term operated under high pressure, and a large amount of steam leaks out of the shaft seal of the compressor, in this case, the steam leaked out condenses to form a large amount of water droplets, which enter the bearing box through the shaft sealing gap of the bearing box, and deteriorate the lubricating oil in the bearing box, seriously affecting the service life of the bearing box bearing; the inventor finds that the sealing of the existing steam compression fan focuses on the sealing between the impeller and the main shaft, and the existing technology is to set a carbon ring between the main shaft and the impeller to realize the sealing, this sealing structure is single, and because the carbon ring sealing is only suitable for a low pressure environment, when the gas pressure is too high, a certain amount of leakage still occurs, which leads to poor sealing effect of the compression fan, in addition, when leakage occurs at the carbon ring, there is no corresponding remedial measure, which leads to bearing damage, equipment failure caused by the contamination of the lubricating oil in the bearing due to steam leakage, and great loss is caused.

[0029] In view of the above problems, in a typical embodiment of the present application, as shown in Figure 1 , an MVR mechanical compression fan anti-leakage shaft sealing system is provided, which comprises a carbon ring sealing structure, a labyrinth sealing structure and a nitrogen pressure sealing structure; the carbon ring sealing structure adopts a multi-stage carbon ring, and is arranged at the connection between the main shaft 10 and the impeller 1; the labyrinth sealing structure is arranged between the end cover of the bearing box 5 and the main shaft 10; and the nitrogen pressure sealing structure is arranged on the end cover of the bearing box 5; the labyrinth sealing structure and the nitrogen pressure sealing structure form a double sealing structure, and the shaft seal of the compression fan is realized through the cooperation of the above various sealing structures.

[0030] As shown in Figure 2 , the carbon ring sealing structure comprises an annular shaft sealing shell 3 and an annular shaft sleeve 9, the shaft sealing shell 3 has an annular groove, and at least two carbon rings with a rectangular cross section are arranged in the annular groove; specifically, a multi-stage carbon ring is arranged in the shaft sealing shell, the carbon ring is sleeved on the shaft sleeve 9, the shaft sleeve 9 is installed on the main shaft 10 and rotates with the main shaft, and the shaft sleeve 9 and the static sealing part of the shaft sealing shell jointly form a sealing friction pair, so as to ensure that the steam on the impeller side does not leak. Further, a gap of 0.01-0.04mm is formed between the inner diameter of the carbon ring and the annular shaft sleeve, and a wear-resistant layer is coated on the outer surface of the shaft sleeve, and the wear-resistant layer can be aluminum oxide or chromium oxide.

[0031] As shown in Figure 3 and Figure 4As shown, the shaft seal housing is also provided with a sealing steam inlet 12 and a steam condensate outlet 13, the sealing steam inlet is filled with pressurized steam higher than or equal to the inlet steam pressure of the compression fan, the steam enters the shaft seal housing, which can be used to balance the internal and external pressure difference between the impeller side and the bearing side, to ensure that the high-temperature and high-pressure steam and condensate do not leak along the shaft during high-speed rotation of the shaft. By introducing high-pressure steam into the shaft seal housing, a buffer seal can be achieved. The shaft seal housing 3 is fixed on the machine shell baffle plate by screws 15, and an O-shaped sealing ring 14 is arranged between the shaft sleeve and the main shaft to achieve sealing.

[0032] As shown in Figure 5 The carbon ring includes a plurality of fan-shaped carbon rings, and the outer periphery of the fan-shaped carbon ring is provided with a groove 81. The fan-shaped carbon ring is composed of a ring-shaped carbon ring by a tension spring. By arranging a plurality of carbon rings, a gas film can be formed with the inlet sealing gas, a throttling pressure reduction is generated, and gas leakage is hindered. By arranging a compressible compression spring around the outer periphery of the carbon ring, the expansion of the carbon ring under the action of gas pressure can be prevented, and the gas leakage and the shortening of the service life caused by the deformation of the carbon ring can be prevented.

[0033] The sealing structure at the bearing box is as shown in Figure 6 The nitrogen pressurization sealing includes a nitrogen channel 11, which is in communication with the bearing box. The nitrogen channel is arranged on the bearing end cover, and a screw is arranged on the inner wall of the nitrogen inlet. When the carbon ring can achieve sealing, the nitrogen channel is blocked by the screw. When the carbon ring structure is damaged, the screw is removed, the nitrogen pressurization structure is connected with the nitrogen pressurization pipeline, and nitrogen is filled into the bearing box. The nitrogen pressurization pressure is 0.2-0.5Mpa.

[0034] The labyrinth seal includes a plurality of annular sealing teeth arranged in sequence, and a series of interception gaps and expansion cavities are formed between the teeth. The sealed medium generates a throttling effect when passing through the gaps of the labyrinth, thereby achieving the purpose of blocking leakage.

[0035] The MVR mechanical compression fan anti-leakage shaft sealing system provided by the embodiment is used for sealing the gap between the shaft and the opening on the back plate of the machine shell (opposite to the inlet pipeline). A multi-stage carbon ring system is adopted. The carbon ring sealing box is additionally filled with pressurized steam higher than or equal to the inlet steam pressure to balance the internal and external pressure difference, so as to ensure that the high-temperature and high-pressure steam and condensate do not leak along the shaft during high-speed rotation of the shaft. In addition, the bearing box adopts a labyrinth seal, and a nitrogen pressurization interface is arranged on the end cover. Once the carbon ring seal leaks, the nitrogen seal is used, and even if the leaked steam and condensate seep along the shaft to the end cover of the bearing box, it will be blocked outside the bearing box body by the double effects of the labyrinth seal and the nitrogen seal, thereby avoiding the bearing damage and equipment failure caused by the pollution of the lubricating oil in the bearing box due to leakage.

[0036] Example 2

[0037] In an exemplary embodiment of the present application, a method for preventing leakage of a shaft seal of an MVR mechanical compression fan is provided, comprising: using a multi-stage carbon ring seal structure as a main shaft seal, cooperating with a pressurized steam buffer seal structure to balance the internal and external pressure difference, and sealing between the main shaft and the impeller; using a labyrinth seal structure cooperating with a nitrogen pressurization structure to seal between the bearing box and the main shaft, and when the carbon ring fails to leak, 0.2-0.5 MPa nitrogen is introduced to form an air seal.

[0038] The sealing method provided by the present embodiment can, when the carbon ring seal leaks, through the double action of the nitrogen pressurization structure and the labyrinth seal, serve as an insurance measure after the carbon ring seal leaks, and effectively enhances the operation safety of the equipment.

[0039] The above-described embodiments have described the technical solutions of the present application in detail, and it should be understood that the above-described is only a specific embodiment of the present application and is not used to limit the present application. Any modification, supplement or similar replacement within the principle range of the present application should be included in the protection range of the present application.

Claims

1.A kind of MVR mechanical compression fan leakage prevention shaft seal system, characterized by: Including carbon ring sealing structure, labyrinth seal structure and nitrogen pressure seal structure; The carbon ring sealing structure is a multi-stage sealing structure composed of multiple carbon rings (8), and is arranged at the connection between the main shaft (10) and the impeller (1). The labyrinth seal structure is arranged between the bearing box (5) end cover and the main shaft (10). The nitrogen pressure seal structure is arranged on the bearing box (5) end cover. The labyrinth seal structure and the nitrogen pressure seal structure form a double seal structure. The carbon ring sealing structure includes an annular shaft seal housing (3) and an annular shaft sleeve (9). The shaft seal housing (3) has an annular groove. At least two carbon rings (8) with rectangular cross-section are arranged in the annular groove. The shaft seal housing (3) is also provided with a steam buffer seal structure. The steam buffer seal structure includes a sealing steam inlet (12) and a steam condensate outlet (13). The sealing steam inlet (12) is filled with pressurized steam higher than or equal to the inlet steam pressure of the compression fan. The inner diameter of the carbon ring (8) and the annular shaft sleeve (9) have a gap of 0.01-0.04mm. The outer surface of the shaft sleeve (9) is coated with a wear-resistant layer. The wear-resistant layer is made of aluminum oxide or chromium oxide. The carbon ring (8) includes multiple fan-shaped carbon rings (8). The outer periphery of the fan-shaped carbon ring (8) is provided with a groove (81). A tension spring is placed in the groove (81). The fan-shaped carbon ring (8) is assembled into a ring-shaped carbon ring (8) by the tension spring. The labyrinth seal includes multiple annular seal teeth arranged in sequence. A series of interception gaps and expansion cavities are formed between the teeth. The nitrogen pressure seal includes a nitrogen channel (11) which is in communication with the bearing box (5). The nitrogen channel (11) is arranged on the bearing end cover. A screw (15) is installed on the inner wall of the nitrogen inlet. When the carbon ring (8) can play a sealing role, the nitrogen channel (11) is plugged by the screw (15). When the carbon ring (8) structure is damaged, the screw (15) is removed. The nitrogen pressure interface (4) is connected to the nitrogen pressure pipeline. Nitrogen is filled into the bearing box (5). 2.The MVR mechanical compression fan leakage prevention shaft seal system according to claim 1, characterized by: The nitrogen pressure is 0.2-0.5MPa. 3.A MVR mechanical compression fan leakage prevention shaft sealing method, using the shaft sealing system according to any one of claims 1-2, characterized by: Including: Using a multi-stage carbon ring sealing structure as the main shaft (10) sealing, cooperating with the pressurized steam buffer sealing structure to balance the internal and external pressure difference, and sealing between the main shaft (10) and the impeller (1). Using the labyrinth seal structure and the nitrogen pressure structure to seal between the bearing box (5) and the main shaft (10). When the carbon ring (8) fails to leak, 0.2-0.5MPa nitrogen is introduced to form an air seal.

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