An interstage self-circulating two-stage centrifugal steam compressor sealing system and operating method

Abstract

The present invention discloses an interstage self-circulating two-stage centrifugal steam compressor sealing system and operating method, comprising a compressor primary main unit and a compressor secondary main unit; the compressor primary main unit is provided with a primary shaft sealing mechanism for sealing the primary main shaft, the primary shaft sealing mechanism being provided with a primary steam isolation chamber; the compressor secondary main unit is provided with a secondary shaft sealing mechanism for sealing the secondary main shaft, the secondary shaft sealing mechanism being provided with a secondary steam isolation chamber; the primary steam isolation chamber is connected to the primary shaft seal air supply pipeline, the secondary steam isolation chamber is connected to the secondary shaft seal air extraction pipeline, a shaft seal interstage pipeline is provided between the primary shaft seal air supply pipeline and the secondary shaft seal air extraction pipeline, and a shaft seal interstage regulating valve is provided on the shaft seal interstage pipeline. The present invention effectively reduces overall energy consumption, improves energy efficiency, and also reduces system operating costs.

Description

Technical Field

[0001] The present invention relates to the technical field of steam compressors, and in particular to an interstage self-circulating two-stage centrifugal steam compressor sealing system and an operating method. Background Art

[0002] With the growing demand for energy conservation and emission reduction across various industrial sectors, the market is increasingly demanding compressors with high flow rates, high temperature rises, and enhanced energy efficiency, particularly two-stage steam centrifugal compressors. A significant difference between these products and traditional single-stage compressors is their superior energy efficiency and more significant pressure increase. This significant pressure increase, however, places higher demands on the compressor shaft seal.

[0003] Conventional single-stage compressors use steam as the medium for the shaft end seal, pumping air into the leak port on the negative pressure side and extracting air from the leak port on the positive pressure side. Whether injecting air on the negative pressure side or extracting air on the positive pressure side, this results in additional steam consumption. Two-stage steam compressors operate under more complex conditions, often with negative pressure at the first-stage impeller inlet and positive pressure at the second-stage impeller outlet. When faced with both positive and negative pressures, steam consumption for the shaft end seal is even more significant. This significant increase in steam consumption leads to significantly increased energy consumption and costs during the operation of two-stage steam compressors. Summary of the Invention

[0004] The purpose of the present invention is to solve the deficiencies in the prior art and to provide an interstage self-circulating two-stage centrifugal steam compressor sealing system and an operating method.

[0005] The objective of the present invention is achieved through the following technical solutions: an interstage self-circulating two-stage centrifugal steam compressor sealing system, comprising a first-stage compressor host and a second-stage compressor host, the first-stage main shaft of the first-stage compressor host and the second-stage main shaft of the second-stage compressor host are connected to a driving device at the same time, and a compressor interstage pipeline is arranged between the first-stage compressor host and the second-stage compressor host; the first-stage compressor host is provided with a first-stage shaft sealing mechanism for sealing the first-stage main shaft, and a first-stage steam isolation chamber is arranged at the first-stage shaft sealing mechanism; the second-stage compressor host is provided with a second-stage shaft sealing mechanism for sealing the second-stage main shaft, and a second-stage steam isolation chamber is arranged at the second-stage shaft sealing mechanism; the first-stage steam isolation chamber is connected to the first-stage shaft seal air supply pipeline, the second-stage steam isolation chamber is connected to the second-stage shaft seal exhaust pipeline, a shaft seal interstage pipeline is arranged between the first-stage shaft seal air supply pipeline and the second-stage shaft seal exhaust pipeline, and a shaft seal interstage regulating valve is arranged on the shaft seal interstage pipeline; the amount of steam flowing from the second-stage steam isolation chamber to the first-stage steam isolation chamber is adjusted by the shaft seal interstage regulating valve.

[0006] Preferably, the first-level shaft seal air supply pipeline is provided with a first-level shaft seal air supply regulating valve and a first-level shaft seal pipeline pressure monitoring instrument, and the second-level shaft seal air exhaust pipeline is provided with a second-level shaft seal air exhaust regulating valve and a second-level shaft seal pipeline pressure monitoring instrument.

[0007] Preferably, the first-level shaft sealing mechanism includes a first-level front end carbon ring and a first-level rear end carbon ring arranged on the casing of the first-level main engine of the compressor, the first-level main shaft passes through the first-level front end carbon ring and the first-level rear end carbon ring, and the first-level steam isolation chamber is arranged between the first-level front end carbon ring and the first-level rear end carbon ring; the second-level shaft sealing mechanism includes a second-level front end carbon ring and a second-level rear end carbon ring arranged on the casing of the second-level main engine of the compressor, the second-level main shaft passes through the second-level front end carbon ring and the second-level rear end carbon ring, and the second-level steam isolation chamber is arranged between the second-level front end carbon ring and the second-level rear end carbon ring.

[0008] Preferably, the outlet end of the secondary shaft seal exhaust pipeline is connected to the shaft seal cooling, and the shaft seal cooler is provided with a shaft seal cooler cooling water inlet pipeline, a shaft seal cooler cooling water outlet pipeline, and a shaft seal cooler drain pipeline. The shaft seal cooler cooling water inlet pipeline is provided with a cooling water inlet temperature sensor and a cooling water inlet regulating valve, and the shaft seal cooler cooling water outlet pipeline is provided with a cooling water outlet temperature sensor; the steam in the secondary shaft seal exhaust pipeline is discharged after being cooled by the shaft seal cooler.

[0009] As a preference, the opening of the cooling water inlet regulating valve is adjusted according to the water temperature in the cooling water inlet pipeline and the cooling water outlet pipeline of the shaft seal cooler. The specific method is as follows:

[0010] Set a preset temperature difference value Td. If the temperature difference between the water in the cooling water outlet pipe 23b of the shaft seal cooler and the water in the cooling water inlet pipe 23a of the shaft seal cooler is less than the preset temperature difference value Td, reduce the opening of the cooling water inlet regulating valve 29 to reduce the amount of circulating water, and finally keep the cooling water inlet regulating valve 29 at the minimum opening;

[0011] If the temperature difference between the water in the shaft seal cooler cooling water outlet pipe 23b and the shaft seal cooler cooling water inlet pipe 23a is greater than the temperature difference preset value Td, the opening of the cooling water inlet regulating valve 29 is gradually increased until the temperature difference between the water in the shaft seal cooler cooling water outlet pipe 23b and the shaft seal cooler cooling water inlet pipe 23a is equal to the temperature difference preset value Td.

[0012] Preferably, the driving device includes a gear box, the input shaft of the gear box is connected to the motor, and two output shafts are provided on the gear box, and the two output shafts are respectively connected to the primary main shaft and the secondary main shaft.

[0013] An operating method for an interstage self-circulating two-stage centrifugal steam compressor sealing system, the specific method is as follows:

[0014] The pressure value of the primary shaft seal pipeline pressure monitoring instrument is P1, the pressure value of the secondary shaft seal pipeline pressure monitoring instrument is P2, and the primary shaft seal air supply regulating valve is set to control the target value P 1tar1 , the shaft seal interstage regulating valve sets the control target value P 1tar2 To control the valve opening, the secondary shaft seal exhaust regulating valve sets the control target value P 2tar1 ; and there is P 1tar1 <P 1tar2 <P 2tar1 ;

[0015] When P1<P 1tar1 , the first-stage shaft seal air supply regulating valve is opened until P1≥P 1tar1 The rear stage shaft seal air supply regulating valve is closed;

[0016] When P2>P 2tar1 When P2≤P 2tar1 The valve is closed gradually;

[0017] The opening of the shaft seal interstage regulating valve is determined by the pressure value P1 of the first-level shaft seal pipeline pressure monitoring instrument and the pressure value P2 of the second-level shaft seal pipeline pressure monitoring instrument.

[0018] Preferably, the opening of the shaft seal interstage regulating valve is adjusted by the following method:

[0019] In the control system, the P1 and P2 monitoring values are used to check the saturated steam densities rho1 and rho2 corresponding to the pressure values P1 and P2 through the steam physical property database, and the average value of rho1 and rho2 is calculated as the average density rho_a of the shaft seal pipeline;

[0020] According to the average density rho_a of the shaft seal pipeline and the flow coefficient when the shaft seal interstage regulating valve is fully opened Calculate the flow rate mc when the shaft seal interstage regulating valve is fully open under the current pressure conditions. The calculation formula for the flow rate mc when the shaft seal interstage regulating valve is fully open is as follows:

[0021] ;

[0022] Calculate the reference opening of the shaft seal interstage regulating valve under the current pressure conditions based on the flow rate mc when the shaft seal interstage regulating valve is fully open, the compressor mass flow design value m_in, the shaft seal pipeline leakage rate α and the adjustable ratio R , reference opening of the shaft seal interstage regulating valve The calculation formula is as follows:

[0023] ;

[0024] Reference opening As a benchmark, adjust the opening of the shaft seal interstage regulating valve within the range of ±20%;

[0025] When the difference between the pressure value P2 of the secondary shaft seal pipeline pressure monitoring instrument and the pressure value P1 of the primary shaft seal pipeline pressure monitoring instrument increases, the opening of the shaft seal interstage regulating valve is increased; when the difference between the pressure value P2 of the secondary shaft seal pipeline pressure monitoring instrument and the pressure value P1 of the primary shaft seal pipeline pressure monitoring instrument decreases, the opening of the shaft seal interstage regulating valve is reduced.

[0026] Preferably, when the steam compressor is started, the first-stage shaft seal air supply regulating valve is in the open state, the shaft seal interstage regulating valve is fully opened, the second-stage shaft seal air extraction regulating valve is in the closed state, and the steam in the first-stage steam isolation chamber provides steam sealing for both the first-stage shaft seal mechanism and the second-stage shaft seal mechanism.

[0027] The beneficial effects of the present invention are:

[0028] 1. In the present invention, the high-pressure steam in the secondary steam isolation chamber can partially flow to the primary steam isolation chamber through the shaft seal interstage pipeline, which not only solves the steam leakage problem caused by the pressure increase in the secondary steam isolation chamber, but also provides the necessary steam source for the primary steam isolation chamber, thereby realizing the effective reuse of steam resources; by arranging a shaft seal interstage regulating valve on the shaft seal interstage pipeline, the amount of steam flowing from the secondary steam isolation chamber to the primary steam isolation chamber can be flexibly adjusted according to actual operating conditions, thereby ensuring the pressure balance and optimal working state in the steam isolation chambers of each stage, thereby improving the stability and adaptability of the system.

[0029] 2. When the steam compressor is operating normally, the air supply regulating valve can be completely closed. It does not rely on external steam replenishment, but only relies on the steam leakage from the secondary steam isolation chamber to replenish the steam pressure of the primary steam isolation chamber. A small amount of excess steam in the secondary steam isolation chamber is condensed in the shaft seal cooler and then discharged; part or all of the steam leaked from the secondary steam isolation chamber can be effectively reused within the system, reducing dependence on external steam supply, while reducing the final amount of steam discharged from the secondary shaft seal to the shaft seal cooler, which helps to reduce overall energy consumption, improve energy efficiency, and also reduce operating costs.

[0030] 3. Based on the actual pressure values of P1 and P2, the present invention calculates the saturated steam densities rho1 and rho2 in combination with the steam physical property database, and then determines the average density rho_a of the shaft seal pipeline; this method can more accurately reflect the actual working state of the system, ensure more precise adjustment of the opening of the shaft seal interstage regulating valve, and maintain stable operation of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the system structure of the present invention.

[0032] In the figure: 1. Compressor primary main engine, 2. Primary main shaft, 3. Primary front carbon ring seal, 4. Primary steam isolation chamber, 5. Primary rear carbon ring, 6. Gearbox, 7. Primary shaft seal air supply pipeline, 8. Primary shaft seal air supply regulating valve, 9. Primary shaft seal pipeline pressure monitoring instrument, 10. Shaft seal interstage regulating valve, 11. Shaft seal interstage pipeline, 12. Primary shaft seal drain pipeline, 13. Compressor inlet pipeline, 14. Compressor secondary main engine, 15. Secondary front carbon ring, 16. Secondary steam isolation chamber, 17. Secondary rear carbon ring, 18. Secondary shaft Sealing and exhaust pipeline, 19. Secondary shaft seal pipeline pressure monitoring instrument, 20. Secondary shaft seal exhaust regulating valve, 21. Shaft seal cooler, 22. Shaft seal fan, 23a. Shaft seal cooler cooling water inlet pipeline, 23b. Shaft seal cooler cooling water outlet pipeline, 24. Shaft seal cooler drain pipeline, 25. Secondary shaft seal drain pipeline, 26. Compressor interstage pipeline, 27. Compressor outlet pipeline, 28a. Cooling water inlet temperature sensor, 28b. Cooling water outlet temperature sensor, 29. Cooling water inlet regulating valve, 30. Secondary main shaft. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention are within the scope of protection of the present invention.

[0034] It should be understood by those skilled in the art that, in the disclosure of the present invention, the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0035] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the elements may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0036] like Figure 1As shown, an interstage self-circulating two-stage centrifugal steam compressor sealing system includes a compressor primary host 1 and a compressor secondary host 14, the primary main shaft 2 of the compressor primary host 1 and the secondary main shaft 30 of the compressor secondary host 14 are connected to the drive device at the same time, and a compressor interstage pipeline 26 is provided between the compressor primary host 1 and the compressor secondary host 14; the compressor primary host 1 is provided with a primary shaft sealing mechanism for sealing the primary main shaft 2, and the primary shaft sealing mechanism is provided with a primary steam isolation chamber 4; the compressor secondary host 14 is provided with a A secondary shaft sealing mechanism is provided for sealing the secondary main shaft 30, and a secondary steam isolation chamber 16 is provided at the secondary shaft sealing mechanism; the primary steam isolation chamber 4 is connected to the primary shaft seal air supply pipeline 7, and the secondary steam isolation chamber 16 is connected to the secondary shaft seal air extraction pipeline 18. A shaft seal interstage pipeline 11 is provided between the primary shaft seal air supply pipeline 7 and the secondary shaft seal air extraction pipeline 18, and a shaft seal interstage regulating valve 10 is provided on the shaft seal interstage regulating valve 10; the amount of steam flowing from the secondary steam isolation chamber 16 to the primary steam isolation chamber 4 is adjusted by the shaft seal interstage regulating valve 10.

[0037] A compressor inlet pipeline 13 is provided on the compressor first-stage main unit 1, and a compressor outlet pipeline is provided on the compressor second-stage main unit 14. The steam to be pressurized first enters the compressor first-stage main unit 1 through the compressor inlet pipeline 13 for primary pressurization. After the primary pressurization, the steam passes through the compressor interstage pipeline 26 to the compressor second-stage main unit 14 for secondary pressurization. The steam after the secondary pressurization is discharged through the compressor outlet pipeline.

[0038] The primary shaft seal mechanism includes a primary front carbon ring and a primary rear carbon ring 5 mounted on the housing of the compressor's primary main unit 1. The primary main shaft 2 passes through these rings, and a primary steam isolation chamber 4 is disposed between these rings. The secondary shaft seal mechanism includes a secondary front carbon ring 15 and a secondary rear carbon ring 17 mounted on the housing of the compressor's secondary main unit 14. The secondary main shaft 30 passes through these rings, and a secondary steam isolation chamber 16 is disposed between these rings. Both the primary steam isolation chamber 4 and the secondary steam isolation chamber 16 are annular chambers.

[0039] In the present invention, the shaft end seal of the two-stage centrifugal steam compressor adopts a combination of steam isolation chamber + carbon ring seal + front end (compressor first host 1) air supply + rear end (compressor second host 14) air extraction, and external steam is injected into the first-stage steam isolation chamber 4 as isolation gas to prevent air leakage into the compressor; since the steam pressure in the compressor second host 14 is significantly increased, the second-stage steam isolation chamber 16 is positive pressure, and the high-pressure steam in the second-stage steam isolation chamber 16 will leak outward, and a part of the leaked steam can be passed through the shaft seal inter-stage pipeline 11 to the first-stage steam isolation chamber 4 to meet the steam usage demand in the first-stage steam isolation chamber 4; the excess steam leaked from the second-stage steam isolation chamber 16 can be discharged through the second-stage shaft seal exhaust pipeline 18.

[0040] In the present invention, high-pressure steam in the secondary steam isolation chamber 16 can partially flow to the primary steam isolation chamber 4 via the shaft seal interstage piping 11. This not only solves the problem of steam leakage caused by increased pressure within the secondary steam isolation chamber 16, but also provides a necessary steam source for the primary steam isolation chamber 4, achieving effective reuse of steam resources. By providing a shaft seal interstage regulating valve 10 on the shaft seal interstage piping 11, the amount of steam flowing from the secondary steam isolation chamber 16 to the primary steam isolation chamber 4 can be flexibly adjusted according to actual operating conditions, ensuring pressure balance and optimal operating conditions within each steam isolation chamber, thereby improving the stability and adaptability of the system.

[0041] When the steam compressor is operating normally, the air supply regulating valve can be completely closed, without relying on external steam replenishment. The steam pressure of the primary steam isolation chamber 4 can be replenished by relying solely on the steam leaking from the secondary steam isolation chamber 16. A small amount of excess steam in the secondary steam isolation chamber 16 is condensed in the shaft seal cooler 21 and then discharged; part or all of the steam leaked from the secondary steam isolation chamber 16 can be effectively reused within the system, reducing dependence on external steam supply, and at the same time reducing the final amount of steam discharged from the secondary shaft seal leaking to the shaft seal cooler 21, which helps to reduce overall energy consumption, improve energy efficiency, and also reduce operating costs.

[0042] Among them, the first-level shaft seal air supply pipeline 7 is provided with a first-level shaft seal air supply regulating valve 8 and a first-level shaft seal pipeline pressure monitoring instrument 9, and the second-level shaft seal air exhaust pipeline 18 is provided with a second-level shaft seal air exhaust regulating valve 20 and a second-level shaft seal pipeline pressure monitoring instrument 19.

[0043] External steam can be introduced into the primary steam isolation chamber 4 through the primary shaft seal air supply line 7. The steam flow rate in the primary shaft seal air supply line 7 is regulated by the primary shaft seal air supply regulating valve 8. The primary shaft seal line pressure monitoring instrument 9 is used to monitor the steam pressure within the primary steam isolation chamber 4. Steam in the secondary steam isolation chamber 16 can be discharged externally through the secondary shaft seal exhaust line 18. The secondary shaft seal line pressure monitoring instrument 19 is used to monitor the steam pressure within the secondary steam isolation chamber 16. The secondary shaft seal exhaust regulating valve 20 is used to control the steam flow rate in the secondary shaft seal exhaust line 18.

[0044] The outlet of the secondary shaft seal exhaust pipeline 18 is connected to the shaft seal cooler. The shaft seal cooler 21 is equipped with a shaft seal cooler cooling water inlet pipeline 23a, a shaft seal cooler cooling water outlet pipeline 23b, and a shaft seal cooler drain pipeline 24. The shaft seal cooler cooling water inlet pipeline 23a is equipped with a cooling water inlet temperature sensor 28a and a cooling water inlet regulating valve 29, and the shaft seal cooler cooling water outlet pipeline 23b is equipped with a cooling water outlet temperature sensor 28b. The steam in the secondary shaft seal exhaust pipeline 18 is cooled by the shaft seal cooler 21 and then discharged. The shaft seal cooler 21 is also connected to the shaft seal blower 22.

[0045] In the present invention, the opening of the cooling water inlet regulating valve 29 is adjusted according to the water temperature in the cooling water inlet pipe 23a and the cooling water outlet pipe 23b of the shaft seal cooler. The specific method is as follows:

[0046] Set a preset temperature difference value Td. If the temperature difference between the water in the shaft seal cooler cooling water outlet pipe 23b and the shaft seal cooler cooling water inlet pipe 23a is less than the preset temperature difference value Td, reduce the opening of the cooling water inlet regulating valve 29 to reduce the amount of circulating water, and ultimately keep the cooling water inlet regulating valve 29 at the minimum opening; the minimum opening of the cooling water inlet regulating valve 29 is maintained at 2%-8%.

[0047] If the temperature difference between the water in the shaft seal cooler cooling water outlet pipe 23b and the shaft seal cooler cooling water inlet pipe 23a is greater than the temperature difference preset value Td, the opening of the cooling water inlet regulating valve 29 is gradually increased until the temperature difference between the water in the shaft seal cooler cooling water outlet pipe 23b and the shaft seal cooler cooling water inlet pipe 23a is equal to the temperature difference preset value Td.

[0048] The present invention can ensure that the shaft seal cooler 21 maintains the best cooling effect under various working conditions by dynamically adjusting the opening of the cooling water inlet regulating valve 29; when it is detected that the actual temperature difference is greater than the set preset value, the opening of the regulating valve is increased, and the cooling water flow rate is increased, thereby more effectively reducing the temperature, ensuring that the leaked steam discharged from the secondary shaft seal exhaust management can be fully condensed, and avoiding the steam from being directly discharged into the atmosphere; at the same time, this method can avoid unnecessary excessive cooling and only increase the cooling water flow rate when needed; this helps to reduce the use of cooling water, thereby reducing the energy consumption required to pump cooling water, and achieving the purpose of energy saving.

[0049] In this embodiment, the drive device includes a gearbox 6, the input shaft of which is connected to the motor. The gearbox 6 is provided with two output shafts, one connected to the primary spindle and the other to the secondary spindle. During system operation, the motor drives the gearbox 6, which in turn drives the primary spindle 2 and the secondary spindle 30 to rotate synchronously.

[0050] The primary steam isolation chamber 4 is connected to the primary shaft seal drain line 12, and the secondary steam isolation chamber 16 is connected to the secondary shaft seal drain line 25. Some steam condenses in the primary steam isolation chamber 4 to form liquid water, which is then drained through the primary shaft seal drain line 12. Similarly, some steam condenses in the secondary steam isolation chamber 16 to form liquid water, which is then drained through the secondary shaft seal drain line 25.

[0051] An operating method for an interstage self-circulating two-stage centrifugal steam compressor sealing system, the specific method is as follows:

[0052] The pressure value of the primary shaft seal pipeline pressure monitoring instrument is P1, the pressure value of the secondary shaft seal pipeline pressure monitoring instrument is P2, and the primary shaft seal air supply regulating valve is set to control the target value P 1tar1 , the shaft seal interstage regulating valve sets the control target value P 1tar2 To control the valve opening, the secondary shaft seal exhaust regulating valve sets the control target value P 2tar1 ; and there is P 1tar1 <P 1tar2 <P 2tar1 ;

[0053] When P1<P 1tar1 , the first-stage shaft seal air supply regulating valve is opened until P1≥P 1tar1 The rear stage shaft seal air supply regulating valve is closed;

[0054] When P2>P 2tar1 When P2≤P 2tar1The valve is closed gradually;

[0055] The opening of the shaft seal interstage regulating valve is determined by the pressure value P1 of the first-level shaft seal pipeline pressure monitoring instrument and the pressure value P2 of the second-level shaft seal pipeline pressure monitoring instrument.

[0056] Among them, the opening of the shaft seal interstage regulating valve is adjusted by the following methods:

[0057] In the control system, the saturated steam densities rho1 and rho2 corresponding to the pressure values P1 and P2 are obtained from the steam physical property database through the monitoring values of P1 and P2, and the average value of rho1 and rho2 is calculated as the average density rho_a of the shaft seal pipeline; that is, rho_a=(rho1+rho2) / 2;

[0058] According to the average density rho_a of the shaft seal pipeline and the flow coefficient when the shaft seal interstage regulating valve is fully opened Calculate the flow rate mc when the shaft seal interstage regulating valve is fully open under the current pressure conditions. The calculation formula for the flow rate mc when the shaft seal interstage regulating valve is fully open is as follows:

[0059] ;

[0060] Calculate the reference opening of the shaft seal interstage regulating valve under the current pressure conditions based on the flow rate mc when the shaft seal interstage regulating valve is fully open, the compressor mass flow design value m_in, the shaft seal pipeline leakage rate α and the adjustable ratio R , reference opening of the shaft seal interstage regulating valve The calculation formula is as follows:

[0061] ;

[0062] Reference opening As a benchmark, adjust the opening of the shaft seal interstage regulating valve within the range of ±20%;

[0063] When the difference between the pressure value P2 of the secondary shaft seal pipeline pressure monitoring instrument 19 and the pressure value P1 of the primary shaft seal pipeline pressure monitoring instrument 9 increases, the opening of the shaft seal interstage regulating valve 10 is increased; when the difference between the pressure value P2 of the secondary shaft seal pipeline pressure monitoring instrument 19 and the pressure value P1 of the primary shaft seal pipeline pressure monitoring instrument 9 decreases, the opening of the shaft seal interstage regulating valve 10 is reduced.

[0064] The shaft seal interstage control valve 10 is an equal percentage control valve. The compressor mass flow design value m_in, the shaft seal pipeline leakage rate α, the adjustable ratio R, and the flow coefficient of the shaft seal interstage control valve 10 when fully open are all known constants. In this embodiment, the shaft seal pipeline leakage rate α ranges from 0.001 to 0.003.

[0065] The present invention calculates the saturated steam densities rho1 and rho2 based on the actual pressure values of P1 and P2 in combination with the steam physical property database, and then determines the average density rho_a of the shaft seal pipeline; this method can more accurately reflect the actual working state of the system, ensure that the opening adjustment of the shaft seal interstage regulating valve 10 is more precise, and maintain stable operation of the system.

[0066] It's worth noting that during actual system operation, the shaft seal interstage regulating valve 10 is always set to a minimum opening, Lmin. That is, the opening of the shaft seal interstage regulating valve 10 never falls below this minimum opening, Lmin, in any situation. This ensures that steam always flows from the secondary steam isolation chamber 16 to the primary steam isolation chamber 4 for sealing, thus ensuring efficient steam utilization. In this embodiment, this minimum opening, Lmin, is set between 10% and 20%.

[0067] When the steam compressor system starts, the pressure at the primary shaft seal mechanism is lower than the set value P because the compressor host has not yet reached the predetermined operating condition. 1tar1 , the first-stage shaft seal air supply regulating valve 8 is in the open state and steam is supplied; because P 1tar1 <P 1tar2 <P 2tar1 At this time, the pressure at the first-stage shaft seal mechanism is also lower than the set value P 1tar2 , the shaft seal interstage regulating valve 10 is fully opened, the secondary shaft seal exhaust regulating valve 20 is closed, and the steam in the primary steam isolation chamber 4 provides steam sealing for both the primary and secondary shaft seal mechanisms; as the steam compressor gradually starts, the pressure in each pipeline increases, and the sealing system reaches a normal working state, each regulating valve is adjusted according to the change in the system pressure according to the adjustment method described above, and the pressure at each measuring point is maintained stable near the set value by opening or closing.

[0068] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, any technical solution that is the same or similar to that of the present application falls within the scope of protection of the present invention.

Claims

1. An operating method for an interstage self-circulating two-stage centrifugal steam compressor sealing system, characterized in that: The interstage self-circulating two-stage centrifugal steam compressor sealing system includes a compressor primary main unit and a compressor secondary main unit, the primary main shaft of the compressor primary main unit and the secondary main shaft of the compressor secondary main unit are connected to the drive device at the same time, and a compressor interstage pipeline is provided between the compressor primary main unit and the compressor secondary main unit; The compressor's primary main engine is provided with a primary shaft sealing mechanism for sealing the primary main shaft, and a primary steam isolation chamber is provided at the primary shaft sealing mechanism; The secondary main engine of the compressor is provided with a secondary shaft sealing mechanism for sealing the secondary main shaft, and a secondary steam isolation chamber is provided at the secondary shaft sealing mechanism; The first-level steam isolation chamber is connected to the first-level shaft seal air supply pipeline, the second-level steam isolation chamber is connected to the second-level shaft seal air extraction pipeline, a shaft seal interstage pipeline is provided between the first-level shaft seal air supply pipeline and the second-level shaft seal air extraction pipeline, and a shaft seal interstage regulating valve is provided on the shaft seal interstage pipeline; the amount of steam flowing from the second-level steam isolation chamber to the first-level steam isolation chamber is regulated by the shaft seal interstage regulating valve; the first-level shaft seal air supply regulating valve and the first-level shaft seal pipeline pressure monitoring instrument are provided on the first-level shaft seal air supply pipeline, and the second-level shaft seal air extraction regulating valve and the second-level shaft seal pipeline pressure monitoring instrument are provided on the second-level shaft seal air extraction pipeline; The operating method of the interstage self-circulating two-stage centrifugal steam compressor sealing system is as follows: The pressure value of the primary shaft seal pipeline pressure monitoring instrument is P1, the pressure value of the secondary shaft seal pipeline pressure monitoring instrument is P2, and the primary shaft seal air supply regulating valve is set to control the target value P 1tar1 , the shaft seal interstage regulating valve sets the control target value P 1tar2 To control the valve opening, the secondary shaft seal exhaust regulating valve sets the control target value P 2tar1 ; and there is P 1tar1 <P 1tar2 <P 2tar1 ; When P1<P 1tar1 , the first-stage shaft seal air supply regulating valve is opened until P1≥P 1tar1 The rear stage shaft seal air supply regulating valve is closed; When P2>P 2tar1 When P2≤P 2tar1 The valve is closed gradually; The opening of the shaft seal interstage regulating valve is determined by the pressure value P1 of the first-level shaft seal pipeline pressure monitoring instrument and the pressure value P2 of the second-level shaft seal pipeline pressure monitoring instrument.

2. The method for operating an interstage self-circulating two-stage centrifugal steam compressor sealing system according to claim 1, characterized in that: The first-level shaft sealing mechanism includes a first-level front carbon ring and a first-level rear carbon ring arranged on the shell of the first-level main engine of the compressor, the first-level main shaft passes through the first-level front carbon ring and the first-level rear carbon ring, and the first-level steam isolation chamber is arranged between the first-level front carbon ring and the first-level rear carbon ring; the second-level shaft sealing mechanism includes a second-level front carbon ring and a second-level rear carbon ring arranged on the shell of the second-level main engine of the compressor, the second-level main shaft passes through the second-level front carbon ring and the second-level rear carbon ring, and the second-level steam isolation chamber is arranged between the second-level front carbon ring and the second-level rear carbon ring.

3. The method for operating an interstage self-circulating two-stage centrifugal steam compressor sealing system according to claim 1, characterized in that: The outlet end of the secondary shaft seal exhaust pipeline is connected to the shaft seal cooler, and the shaft seal cooler is provided with a shaft seal cooler cooling water inlet pipeline, a shaft seal cooler cooling water outlet pipeline, and a shaft seal cooler drain pipeline. The shaft seal cooler cooling water inlet pipeline is provided with a cooling water inlet temperature sensor and a cooling water inlet regulating valve, and the shaft seal cooler cooling water outlet pipeline is provided with a cooling water outlet temperature sensor; the steam in the secondary shaft seal exhaust pipeline is discharged after being cooled by the shaft seal cooler.

4. The method for operating the interstage self-circulating two-stage centrifugal steam compressor sealing system according to claim 3, characterized in that: Adjust the opening of the cooling water inlet regulating valve according to the water temperature in the cooling water inlet pipeline and the cooling water outlet pipeline of the shaft seal cooler. The specific method is as follows: Set the temperature difference preset value Td. If the temperature difference between the water in the cooling water outlet pipeline of the shaft seal cooler and the cooling water inlet pipeline of the shaft seal cooler is less than the temperature difference preset value Td, reduce the opening of the cooling water inlet regulating valve to reduce the circulating water volume, and finally keep the cooling water inlet regulating valve at the minimum opening; If the temperature difference between the water in the cooling water outlet pipeline of the shaft seal cooler and the cooling water inlet pipeline of the shaft seal cooler is greater than the temperature difference preset value Td, gradually increase the opening of the cooling water inlet regulating valve until the temperature difference between the water in the cooling water outlet pipeline of the shaft seal cooler and the cooling water inlet pipeline of the shaft seal cooler is equal to the temperature difference preset value Td.

5. The method for operating an interstage self-circulating two-stage centrifugal steam compressor sealing system according to claim 1, characterized in that: The driving device includes a gear box, an input shaft of the gear box is connected to the motor, and two output shafts are provided on the gear box, and the two output shafts are respectively connected to the primary main shaft and the secondary main shaft.

6. The method for operating an interstage self-circulating two-stage centrifugal steam compressor sealing system according to claim 1, characterized in that: The opening of the shaft seal interstage regulating valve is adjusted by the following methods: In the control system, the P1 and P2 monitoring values are used to check the saturated steam densities rho1 and rho2 corresponding to the pressure values P1 and P2 through the steam physical property database, and the average value of rho1 and rho2 is calculated as the average density rho_a of the shaft seal pipeline; According to the average density rho_a of the shaft seal pipeline and the flow coefficient when the shaft seal interstage regulating valve is fully opened Calculate the flow rate mc when the shaft seal interstage regulating valve is fully open under the current pressure conditions. The calculation formula for the flow rate mc when the shaft seal interstage regulating valve is fully open is as follows: ； Calculate the reference opening of the shaft seal interstage regulating valve under the current pressure conditions based on the flow rate mc when the shaft seal interstage regulating valve is fully open, the compressor mass flow design value m_in, the shaft seal pipeline leakage rate α and the adjustable ratio R , reference opening of the shaft seal interstage regulating valve The calculation formula is as follows: ； Reference opening As a benchmark, adjust the opening of the shaft seal interstage regulating valve within the range of ±20%; When the difference between the pressure value P2 of the secondary shaft seal pipeline pressure monitoring instrument and the pressure value P1 of the primary shaft seal pipeline pressure monitoring instrument increases, the opening of the shaft seal interstage regulating valve is increased; when the difference between the pressure value P2 of the secondary shaft seal pipeline pressure monitoring instrument and the pressure value P1 of the primary shaft seal pipeline pressure monitoring instrument decreases, the opening of the shaft seal interstage regulating valve is reduced.

7. The method for operating an interstage self-circulating two-stage centrifugal steam compressor sealing system according to claim 1, characterized in that: When the steam compressor is started, the first-stage shaft seal air supply regulating valve is in the open state, the shaft seal interstage regulating valve is fully opened, the second-stage shaft seal air extraction regulating valve is in the closed state, and the steam in the first-stage steam isolation chamber provides steam sealing for both the first-stage shaft seal mechanism and the second-stage shaft seal mechanism.

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