Interstage self-circulation type two-stage centrifugal vapor compressor sealing system and operation method

Abstract

The invention discloses an inter-stage self-circulation type two-stage centrifugal vapor compressor sealing system and an operation method. The inter-stage self-circulation type two-stage centrifugal vapor compressor sealing system comprises a compressor first-stage main machine and a compressor second-stage main machine. The compressor first-stage main machine is provided with a first-stage shaft sealing mechanism used for sealing the first-stage main shaft, and a first-stage steam isolation cavity is formed in the first-stage shaft sealing mechanism. The compressor second-stage main machine is provided with a second-stage shaft seal mechanism used for sealing the second-stage main shaft, and a second-stage steam isolation cavity is formed in the second-stage shaft seal mechanism; the first-stage steam isolation cavity is connected with a first-stage shaft seal air supply pipeline, the second-stage steam isolation cavity is connected with a second-stage shaft seal air exhaust pipeline, a shaft seal interstage pipeline is arranged between the first-stage shaft seal air supply pipeline and the second-stage shaft seal air exhaust pipeline, and a shaft seal interstage adjusting valve is arranged on the shaft seal interstage pipeline. The overall energy consumption is effectively reduced, the energy efficiency ratio is increased, and meanwhile the system operation cost is reduced.

Description

Technical Field

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

[0002] With the development of energy conservation and emission reduction requirements in various industrial fields, the market demand for compressor products with large flow rates, large temperature rises, and higher energy-saving effects is becoming increasingly urgent, especially for two-stage steam centrifugal compressors. A significant difference between such products and traditional single-stage compressors is that the energy-saving effect is more prominent and the pressure increase is more significant. However, while the pressure increase effect is more significant, higher requirements are imposed on the shaft end seal of the compressor.

[0003] Conventional single-stage compressors use steam as the medium at the shaft end seal. The method is to inject air from the negative pressure side to the leakage port and extract air from the positive pressure side to the leakage port. Whether it is air supplementation on the negative pressure side or air extraction on the positive pressure side, it will cause additional consumption of steam. The working conditions of two-stage steam compressors are more complex, and there are many working conditions where the inlet of the first-stage impeller is in a negative pressure state and the outlet of the second-stage impeller is in a positive pressure state. In the face of the coexistence of positive and negative pressures, the steam consumption for shaft end sealing is also more significant. The substantial increase in steam consumption will greatly increase the energy consumption and cost 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 provide a stage-interconnected self-circulating two-stage centrifugal steam compressor sealing system and an operation method thereof.

[0005] The purpose of the present invention is achieved through the following technical solutions: A stage-interconnected self-circulating two-stage centrifugal steam compressor sealing system includes a first-stage main body of the compressor and a second-stage main body of the compressor. The first-stage main shaft of the first-stage main body of the compressor and the second-stage main shaft of the second-stage main body of the compressor are simultaneously connected to a driving device. A compressor inter-stage pipeline is provided between the first-stage main body of the compressor and the second-stage main body of the compressor; the first-stage main body of the compressor is provided with a first-stage shaft seal mechanism for sealing the first-stage main shaft, and a first-stage steam isolation chamber is arranged at the first-stage shaft seal mechanism; the second-stage main body of the compressor is provided with a second-stage shaft seal mechanism for sealing the second-stage main shaft, and a second-stage steam isolation chamber is arranged at the second-stage shaft seal mechanism; the first-stage steam isolation chamber is connected to a first-stage shaft seal air supply pipeline, the second-stage steam isolation chamber is connected to a second-stage shaft seal air extraction pipeline, a shaft seal inter-stage pipeline is arranged between the first-stage shaft seal air supply pipeline and the second-stage shaft seal air extraction pipeline, and a shaft seal inter-stage regulating valve is provided on the shaft seal inter-stage pipeline; the steam flow rate flowing from the second-stage steam isolation chamber to the first-stage steam isolation chamber is regulated through the shaft seal inter-stage regulating valve.

[0006] Preferably, a primary shaft seal air supply regulating valve and a primary shaft seal pipeline pressure monitoring instrument are provided on the primary shaft seal air supply pipeline, and a secondary shaft seal air extraction regulating valve and a secondary shaft seal pipeline pressure monitoring instrument are provided on the secondary shaft seal air extraction pipeline.

[0007] Preferably, the primary shaft seal mechanism includes a primary front carbon ring and a primary rear carbon ring provided on the housing of the primary host of the compressor. The primary main shaft passes through the primary front carbon ring and the primary rear carbon ring, and a primary steam isolation chamber is arranged between the primary front carbon ring and the primary rear carbon ring; the secondary shaft seal mechanism includes a secondary front carbon ring and a secondary rear carbon ring provided on the housing of the secondary host of the compressor. The secondary main shaft passes through the secondary front carbon ring and the secondary rear carbon ring, and a secondary steam isolation chamber is arranged between the secondary front carbon ring and the secondary rear carbon ring.

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

[0009] Preferably, the opening of the cooling water inlet regulating valve is adjusted according to the water temperatures in the shaft seal cooler cooling water inlet pipeline and the shaft seal cooler cooling water outlet pipeline. The specific method is as follows: Set a temperature difference preset value Td. If the temperature difference between the water in the shaft seal cooler cooling water outlet pipeline 23b and the water in the shaft seal cooler cooling water inlet pipeline 23a is less than the temperature difference preset value Td, then reduce the opening of the cooling water inlet regulating valve 29 to reduce the circulating water volume, and finally keep the cooling water inlet regulating valve 29 at the minimum opening; If the temperature difference between the water in the shaft seal cooler cooling water outlet pipeline 23b and the water in the shaft seal cooler cooling water inlet pipeline 23a is greater than the temperature difference preset value Td, then gradually increase the opening of the cooling water inlet regulating valve 29 until the temperature difference between the water in the shaft seal cooler cooling water outlet pipeline 23b and the water in the shaft seal cooler cooling water inlet pipeline 23a is equal to the temperature difference preset value Td.

[0010] Preferably, the driving device includes a gearbox. The input shaft of the gearbox is connected to the motor, and the gearbox is provided with two output shafts, which are respectively connected to the primary main shaft and the secondary main shaft.

[0011] An operation method of a stage-interconnected self-circulating two-stage centrifugal steam compressor sealing system is as follows: The pressure value of the pressure monitoring instrument for the primary shaft seal pipeline is P1, the pressure value of the pressure monitoring instrument for the secondary shaft seal pipeline is P2, and the set control target value of the primary shaft seal air supply regulating valve is P 1tar1 , and the set control target value of the shaft seal inter-stage regulating valve is P 1tar2 to control the valve opening. The set control target value of the secondary shaft seal air extraction regulating valve is P 2tar1 ; and there is P 1tar1 <P 1tar2 <P 2tar1 ; When P1 < P 1tar1 , the primary shaft seal air supply regulating valve opens until P1 ≥ P 1tar1 and then the primary shaft seal air supply regulating valve closes; When P2 > P 2tar1 , the secondary shaft seal air extraction regulating valve opens, and the steam in the secondary shaft seal air extraction pipeline flows to the shaft seal cooler at the outlet end of the secondary shaft seal air extraction pipeline for condensation until P2 ≤ P 2tar1 and the valve gradually closes; The opening of the shaft seal inter-stage regulating valve is determined by the pressure value P1 of the pressure monitoring instrument for the primary shaft seal pipeline and the pressure value P2 of the pressure monitoring instrument for the secondary shaft seal pipeline.

[0012] Preferably, the opening of the shaft seal inter-stage regulating valve is adjusted by the following method: In the control system, based on the monitored values of P1 and P2, the saturated steam densities rho1 and rho2 corresponding to the pressure values P1 and P2 are obtained 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 inter-stage regulating valve is fully open, calculate the through-flow capacity mc when the shaft seal inter-stage regulating valve is fully open under the current pressure condition. The calculation formula for the through-flow capacity mc when the shaft seal inter-stage regulating valve is fully open is as follows: ; According to the through-flow capacity mc when the shaft seal inter-stage 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, calculate the reference opening of the shaft seal inter-stage regulating valve under the current pressure condition. The calculation formula for the reference opening of the shaft seal inter-stage regulating valve is as follows: ; Taking the reference opening as the benchmark, adjust the opening of the shaft seal inter-stage regulating valve within the range of ±20%; When the difference between the pressure value P2 of the pressure monitoring instrument for the secondary shaft seal pipeline and the pressure value P1 of the pressure monitoring instrument for the primary shaft seal pipeline increases, the opening degree of the regulating valve between the shaft seal stages is increased; when the difference between the pressure value P2 of the pressure monitoring instrument for the secondary shaft seal pipeline and the pressure value P1 of the pressure monitoring instrument for the primary shaft seal pipeline decreases, the opening degree of the regulating valve between the shaft seal stages is decreased.

[0013] Preferably, when the steam compressor starts, the air supply regulating valve for the primary shaft seal is in the open state, the regulating valve between the shaft seal stages is fully open, the air extraction regulating valve for the secondary shaft seal is in the closed state, and the steam in the primary steam isolation chamber provides steam seals for both the primary shaft seal mechanism and the secondary shaft seal mechanism simultaneously.

[0014] The beneficial effects of the present invention are as follows: 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 pipeline between the shaft seal stages, which not only solves the problem of steam leakage in the secondary steam isolation chamber due to increased pressure, but also provides a necessary steam source for the primary steam isolation chamber, realizing the effective reuse of steam resources; by setting a regulating valve between the shaft seal stages on the pipeline between the shaft seal stages, the steam flow rate from the secondary steam isolation chamber to the primary steam isolation chamber can be flexibly adjusted according to the actual operating conditions, ensuring the pressure balance and the best working state in each steam isolation chamber, and improving the stability and adaptability of the system.

[0015] 2. When the steam compressor is operating normally, the air supply regulating valve can be completely closed, without relying on external steam supplementation, and only relying on the steam leaked from the secondary steam isolation chamber to supplement the steam pressure in the primary steam isolation chamber. A small part of the excess steam in the secondary steam isolation chamber is condensed by 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 the dependence on external steam supply, while reducing the final external discharge steam volume of the secondary shaft seal leaked to the shaft seal cooler, which helps to reduce the overall energy consumption, improve the energy efficiency ratio, and also reduce the operating cost.

[0016] 3. Based on the actual pressure values of P1 and P2 in the present invention, the saturated steam densities rho1 and rho2 are calculated by combining with the steam physical property database, and then the average density rho_a of the shaft seal pipeline is determined; this method can more accurately reflect the real working state of the system, ensure that the opening degree adjustment of the regulating valve between the shaft seal stages is more accurate, and maintain the stable operation of the system. Description of the Drawings

[0017] Figure 1 It is a schematic structural diagram of the system of the present invention.

[0018] In the figure: 1. The first-stage main unit of the compressor; 2. The first-stage main shaft; 3. The first-stage front carbon ring seal; 4. The first-stage steam isolation chamber; 5. The first-stage rear carbon ring; 6. The gearbox; 7. The first-stage shaft seal gas supply pipeline; 8. The first-stage shaft seal gas supply regulating valve; 9. The first-stage shaft seal pipeline pressure monitoring instrument; 10. The shaft seal inter-stage regulating valve; 11. The shaft seal inter-stage pipeline; 12. The first-stage shaft seal drain pipeline; 13. The compressor inlet pipeline; 14. The second-stage main unit of the compressor; 15. The second-stage front carbon ring; 16. The second-stage steam isolation chamber; 17. The second-stage rear carbon ring; 18. The second-stage shaft seal extraction pipeline; 19. The second-stage shaft seal pipeline pressure monitoring instrument; 20. The second-stage shaft seal extraction regulating valve; 21. The shaft seal cooler; 22. The shaft seal fan; 23a. The shaft seal cooler cooling water inlet pipeline; 23b. The shaft seal cooler cooling water outlet pipeline; 24. The shaft seal cooler drain pipeline; 25. The second-stage shaft seal drain pipeline; 26. The compressor inter-stage pipeline; 27. The compressor outlet pipeline; 28a. The cooling water inlet temperature sensor; 28b. The cooling water outlet temperature sensor; 29. The cooling water inlet regulating valve; 30. The second-stage main shaft. Detailed implementation manners

[0019] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present invention.

[0020] Those skilled in the art should understand that in the disclosure of the present invention, the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting the present invention.

[0021] It can 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 one element can be one, and in other embodiments, the number of this element can be multiple. The term "one" should not be construed as limiting the quantity.

[0022] Such as Figure 1As shown in the figure, an inter-stage self-circulating two-stage centrifugal steam compressor sealing system includes a first-stage main compressor 1 and a second-stage main compressor 14. The first-stage main shaft 2 of the first-stage main compressor 1 and the second-stage main shaft 30 of the second-stage main compressor 14 are simultaneously connected to a driving device. A compressor inter-stage pipeline 26 is arranged between the first-stage main compressor 1 and the second-stage main compressor 14. The first-stage main compressor 1 is provided with a first-stage shaft sealing mechanism for sealing the first-stage main shaft 2, and a first-stage steam isolation chamber 4 is arranged at the first-stage shaft sealing mechanism. The second-stage main compressor 14 is provided with a second-stage shaft sealing mechanism for sealing the second-stage main shaft 30, and a second-stage steam isolation chamber 16 is arranged at the second-stage shaft sealing mechanism. The first-stage steam isolation chamber 4 is connected to a first-stage shaft seal supply gas pipeline 7, and the second-stage steam isolation chamber 16 is connected to a second-stage shaft seal extraction gas pipeline 18. An inter-stage shaft seal pipeline 11 is arranged between the first-stage shaft seal supply gas pipeline 7 and the second-stage shaft seal extraction gas pipeline 18, and an inter-stage shaft seal regulating valve 10 is arranged on the inter-stage shaft seal pipeline 11. The amount of steam flowing from the second-stage steam isolation chamber 16 to the first-stage steam isolation chamber 4 is regulated by the inter-stage shaft seal regulating valve 10.

[0023] A compressor inlet pipeline 13 is arranged on the first-stage main compressor 1, and a compressor outlet pipeline is arranged on the second-stage main compressor 14. The steam to be pressurized first enters the first-stage main compressor 1 through the compressor inlet pipeline 13 for first-stage pressurization. After the first-stage pressurization, the steam passes through the compressor inter-stage pipeline 26 to the second-stage main compressor 14 for second-stage pressurization, and the steam after the second-stage pressurization is discharged through the compressor outlet pipeline.

[0024] Among them, the first-stage shaft sealing mechanism includes a first-stage front carbon ring and a first-stage rear carbon ring 5 arranged on the housing of the first-stage main compressor 1. The first-stage main shaft 2 passes through the first-stage front carbon ring and the first-stage rear carbon ring 5, and the first-stage steam isolation chamber 4 is arranged between the first-stage front carbon ring and the first-stage rear carbon ring 5. The second-stage shaft sealing mechanism includes a second-stage front carbon ring 15 and a second-stage rear carbon ring 17 arranged on the housing of the second-stage main compressor 14. The second-stage main shaft 30 passes through the second-stage front carbon ring 15 and the second-stage rear carbon ring 17, and the second-stage steam isolation chamber 16 is arranged between the second-stage front carbon ring 15 and the second-stage rear carbon ring 17. Both the first-stage steam isolation chamber 4 and the second-stage steam isolation chamber 16 are annular chambers.

[0025] In the present invention, the shaft end seal of the two-stage centrifugal steam compressor adopts a combined mode of steam isolation chamber + carbon ring seal + air supplement at the front end (the first-stage main body 1 of the compressor) + air extraction at the rear end (the second-stage main body 14 of the compressor). By injecting external steam into the first-stage steam isolation chamber 4 as the isolation gas, air leakage into the compressor is prevented. Since the steam pressure in the second-stage main body 14 of the compressor increases significantly and the second-stage steam isolation chamber 16 is under positive pressure, the high-pressure steam in the second-stage steam isolation chamber 16 will leak outwards. A part of the leaked steam can pass through the inter-stage shaft seal pipeline 11 to the first-stage steam isolation chamber 4 to meet the steam usage requirements 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 air extraction pipeline 18.

[0026] In the present invention, the high-pressure steam in the second-stage steam isolation chamber 16 can partially flow to the first-stage steam isolation chamber 4 through the inter-stage shaft seal pipeline 11, which not only solves the problem of steam leakage in the second-stage steam isolation chamber 16 caused by increased pressure, but also provides a necessary steam source for the first-stage steam isolation chamber 4, realizing the effective reuse of steam resources. By setting an inter-stage shaft seal regulating valve 10 on the inter-stage shaft seal pipeline 11, the steam flow rate from the second-stage steam isolation chamber 16 to the first-stage steam isolation chamber 4 can be flexibly adjusted according to the actual operating conditions, ensuring the pressure balance and the best working state in each steam isolation chamber, and improving the stability and adaptability of the system.

[0027] When the steam compressor operates normally, the air supplement regulating valve can be completely closed, without relying on external steam supplement. Only the steam leaked from the second-stage steam isolation chamber 16 is used to supplement the steam pressure in the first-stage steam isolation chamber 4. A small part of the excess steam in the second-stage steam isolation chamber 16 is condensed by the shaft seal cooler 21 and then discharged. Some or all of the steam leaked from the second-stage steam isolation chamber 16 can be effectively reused within the system, reducing the dependence on external steam supply, while reducing the final external discharge steam volume of the second-stage shaft seal leaked to the shaft seal cooler 21, which helps to reduce the overall energy consumption, improve the energy efficiency ratio, and also reduce the operating cost.

[0028] Among them, an air supplement regulating valve 8 and a pressure monitoring instrument 9 for the first-stage shaft seal pipeline are provided on the first-stage shaft seal air supplement pipeline 7, and a second-stage shaft seal air extraction regulating valve 20 and a pressure monitoring instrument 19 for the second-stage shaft seal pipeline are provided on the second-stage shaft seal air extraction pipeline 18.

[0029] External steam can enter the first-stage steam isolation chamber 4 through the first-stage shaft seal make-up gas pipeline 7. The steam flow in the first-stage shaft seal make-up gas pipeline 7 is regulated by the first-stage shaft seal make-up gas regulating valve 8. The first-stage shaft seal pipeline pressure monitoring instrument 9 is used to monitor the steam pressure in the first-stage steam isolation chamber 4. The steam in the second-stage steam isolation chamber 16 can be discharged outward through the second-stage shaft seal extraction pipeline 18. The second-stage shaft seal pipeline pressure monitoring instrument 19 is used to monitor the steam pressure in the second-stage steam isolation chamber 16, and the second-stage shaft seal extraction regulating valve 20 is used to control the steam flow in the second-stage shaft seal extraction pipeline 18.

[0030] The outlet end of the second-stage shaft seal extraction pipeline 18 is connected to the shaft seal cooler. The shaft seal cooler 21 is provided 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 provided with a cooling water inlet temperature sensor 28a and a cooling water inlet regulating valve 29. The shaft seal cooler cooling water outlet pipeline 23b is provided with a cooling water outlet temperature sensor 28b. The steam in the second-stage shaft seal extraction pipeline 18 is discharged after being cooled by the shaft seal cooler 21. The shaft seal cooler 21 is also connected to the shaft seal fan 22.

[0031] In the present invention, the opening degree of the cooling water inlet regulating valve 29 is adjusted according to the water temperatures in the shaft seal cooler cooling water inlet pipeline 23a and the shaft seal cooler cooling water outlet pipeline 23b. The specific method is as follows: Set a temperature difference preset value Td. If the temperature difference between the water in the shaft seal cooler cooling water outlet pipeline 23b and the water in the shaft seal cooler cooling water inlet pipeline 23a is less than the temperature difference preset value Td, then reduce the opening degree of the cooling water inlet regulating valve 29 to reduce the circulating water volume, and finally keep the cooling water inlet regulating valve 29 at the lowest opening degree. The lowest opening degree of the cooling water inlet regulating valve 29 is maintained at 2% - 8%.

[0032] If the temperature difference between the water in the shaft seal cooler cooling water outlet pipeline 23b and the water in the shaft seal cooler cooling water inlet pipeline 23a is greater than the temperature difference preset value Td, then gradually increase the opening degree of the cooling water inlet regulating valve 29 until the temperature difference between the water in the shaft seal cooler cooling water outlet pipeline 23b and the water in the shaft seal cooler cooling water inlet pipeline 23a is equal to the temperature difference preset value Td.

[0033] By dynamically adjusting the opening degree of the regulating valve 29 at the cooling water inlet, the present invention can ensure that the shaft seal cooler 21 maintains the best cooling effect under various working conditions; when it is detected that the actual temperature difference is greater than the set preset value, the opening degree of the regulating valve is increased to increase the cooling water flow rate, so as to more effectively reduce the temperature and ensure that the leakage steam discharged from the secondary shaft seal extraction management can be fully condensed, avoiding direct discharge of steam 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 usage of cooling water, thereby reducing the energy consumption required for pumping cooling water and achieving the purpose of energy conservation.

[0034] In this embodiment, the driving device includes a gearbox 6. The input shaft of the gearbox 6 is connected to the motor, and two output shafts are provided on the gearbox 6. The two output shafts are respectively connected to the primary main shaft and the secondary main shaft. When the system operates, the gearbox 6 is driven by the motor to drive the primary main shaft 2 and the secondary main shaft 30 to rotate synchronously.

[0035] The primary steam isolation chamber 4 is connected to the primary shaft seal drain pipe 12, and the secondary steam isolation chamber 16 is connected to the secondary shaft seal drain pipe 25. Part of the steam condenses in the primary steam isolation chamber 4 to form liquid water, and the liquid water in the primary steam isolation chamber 4 will be discharged through the primary shaft seal drain pipe 12. Similarly, part of the steam condenses in the secondary steam isolation chamber 16 to form liquid water, and the liquid water in the secondary steam isolation chamber 16 will be discharged through the secondary shaft seal drain pipe 25.

[0036] An operation method for a stage-interconnected self-circulating two-stage centrifugal steam compressor sealing system is as follows: The pressure value of the pressure monitoring instrument for the primary shaft seal pipeline is P1, the pressure value of the pressure monitoring instrument for the secondary shaft seal pipeline is P2, and the primary shaft seal air supplement regulating valve sets a control target value P 1tar1 , the shaft seal stage-interconnected regulating valve sets a control target value P 1tar2 to control the valve opening degree, and the secondary shaft seal extraction regulating valve sets a control target value P 2tar1 ; and there is P 1tar1 <P 1tar2 <P 2tar1 ; When P1<P 1tar1 , the primary shaft seal air supplement regulating valve opens until P1≥P 1tar1 and then the primary shaft seal air supplement regulating valve closes; When P2>P 2tar1 , the secondary shaft seal extraction regulating valve opens, and the steam in the secondary shaft seal extraction pipeline flows to the shaft seal cooler at the outlet end of the secondary shaft seal extraction pipeline for condensation until P2≤P 2tar1 This valve gradually closes; The opening of the inter-stage regulating valve of the shaft seal is determined by the pressure value P1 of the pressure monitoring instrument of the primary shaft seal pipeline and the pressure value P2 of the pressure monitoring instrument of the secondary shaft seal pipeline.

[0037] Among them, the opening of the inter-stage regulating valve of the shaft seal is adjusted by the following method: In the control system, through the monitored values of P1 and P2, the saturated steam densities rho1 and rho2 corresponding to the pressure values P1 and P2 are obtained by querying 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; that is, rho_a = (rho1 + rho2) / 2; According to the average density rho_a of the shaft seal pipeline and the flow coefficient when the inter-stage regulating valve of the shaft seal is fully open Calculate the through-flow capacity mc when the inter-stage regulating valve of the shaft seal is fully open under the current pressure condition; the calculation formula for the through-flow capacity mc when the inter-stage regulating valve of the shaft seal is fully open is as follows: ; According to the through-flow capacity mc when the inter-stage regulating valve of the shaft seal is fully open, the designed value m_in of the compressor mass flow rate, the leakage rate α of the shaft seal pipeline, and the adjustable ratio R, calculate the reference opening of the inter-stage regulating valve of the shaft seal under the current pressure condition , the reference opening of the inter-stage regulating valve of the shaft seal The calculation formula is as follows: ; Taking the reference opening as the benchmark, adjust the opening of the inter-stage regulating valve of the shaft seal within the range of ±20%; When the difference between the pressure value P2 of the pressure monitoring instrument 19 of the secondary shaft seal pipeline and the pressure value P1 of the pressure monitoring instrument 9 of the primary shaft seal pipeline increases, the opening of the inter-stage regulating valve 10 of the shaft seal is increased; when the difference between the pressure value P2 of the pressure monitoring instrument 19 of the secondary shaft seal pipeline and the pressure value P1 of the pressure monitoring instrument 9 of the primary shaft seal pipeline decreases, the opening of the inter-stage regulating valve 10 of the shaft seal is decreased.

[0038] Among them, the inter-stage regulating valve 10 of the shaft seal adopts an equal percentage regulating valve, and the designed value m_in of the compressor mass flow rate, the leakage rate α of the shaft seal pipeline, the adjustable ratio R, and the flow coefficient when the inter-stage regulating valve 10 of the shaft seal is fully open are all known constants. In this embodiment, the value range of the leakage rate α of the shaft seal pipeline is 0.001 - 0.003.

[0039] Based on the actual pressure values of P1 and P2, the present invention calculates the saturated steam densities rho1 and rho2 by combining with the steam physical property database, and further determines the average density rho_a of the shaft seal pipeline; this method can more accurately reflect the true working state of the system, ensure that the opening adjustment of the shaft seal inter-stage regulating valve 10 is more accurate, and maintain the stable operation of the system.

[0040] It is worth mentioning that during the actual operation of the system, the shaft seal inter-stage regulating valve 10 is always set to the minimum opening Lmin, that is, the opening of the shaft seal inter-stage regulating valve 10 is not less than this minimum opening Lmin under any circumstances during the operation of the system, so as to ensure that there is always steam flowing from the secondary steam isolation chamber 16 to the primary steam isolation chamber 4 for sealing, and to ensure the utilization efficiency of the steam. In this embodiment, the minimum opening Lmin is set to 10% - 20%.

[0041] When the steam compressor system starts, at this time, since the main compressor has not reached the predetermined working condition, the pressure at the primary shaft seal mechanism is lower than the set value P 1tar1 , and the primary shaft seal air supplement regulating valve 8 is in the open state and steam is supplemented; because P 1tar1 < P 1tar2 < P 2tar1 , at this time, the pressure at the primary shaft seal mechanism is also lower than the set value P 1tar2 , the shaft seal inter-stage regulating valve 10 is fully open, the secondary shaft seal air extraction regulating valve 20 is in the closed state, and the steam in the primary steam isolation chamber 4 provides steam seals for both the primary shaft seal mechanism and the secondary shaft seal mechanism at the same time; as the steam compressor gradually starts, the pressure in each pipeline increases, and the sealing system reaches the normal working state, and each regulating valve is adjusted according to the regulation method described above according to the change of the pressure in the system, and maintains the pressure at each measuring point stable near the set value by opening or closing.

[0042] The present invention is not limited to the above best embodiment, and anyone can obtain other various forms of products under the inspiration of the present invention. However, no matter what changes are made in its shape or structure, as long as it has the same or similar technical solutions as the present application, it falls within the protection scope of the present invention.

Claims

1. A seal system for an inter-stage self-circulating two-stage centrifugal steam compressor, characterized in that, It includes the first-stage main unit of the compressor and the second-stage main unit of the compressor. The first-stage main shaft of the first-stage main unit of the compressor and the second-stage main shaft of the second-stage main unit of the compressor are simultaneously connected to the driving device. A compressor inter-stage pipeline is arranged between the first-stage main unit of the compressor and the second-stage main unit of the compressor; The first-stage main unit of the compressor is provided with a first-stage shaft seal mechanism for sealing the first-stage main shaft, and a first-stage steam isolation chamber is arranged at the first-stage shaft seal mechanism; The second-stage main unit of the compressor is provided with a second-stage shaft seal mechanism for sealing the second-stage main shaft, and a second-stage steam isolation chamber is arranged at the second-stage shaft seal mechanism; The first-stage steam isolation chamber is connected to the first-stage shaft seal make-up gas pipeline, the second-stage steam isolation chamber is connected to the second-stage shaft seal extraction gas pipeline. An inter-stage pipeline for shaft seal is arranged between the first-stage shaft seal make-up gas pipeline and the second-stage shaft seal extraction gas pipeline, and an inter-stage regulating valve for shaft seal is arranged on the inter-stage pipeline for shaft seal; The steam flow from the second-stage steam isolation chamber to the first-stage steam isolation chamber is regulated by the inter-stage regulating valve for shaft seal.

2. The inter-stage self-circulating two-stage centrifugal steam compressor sealing system according to claim 1, wherein, A first-stage shaft seal make-up gas regulating valve and a pressure monitoring instrument for the first-stage shaft seal pipeline are arranged on the first-stage shaft seal make-up gas pipeline, and a second-stage shaft seal extraction gas regulating valve and a pressure monitoring instrument for the second-stage shaft seal pipeline are arranged on the second-stage shaft seal extraction gas pipeline.

3. The inter-stage self-circulating two-stage centrifugal steam compressor sealing system according to claim 1, wherein, The first-stage shaft seal mechanism includes a first-stage front carbon ring and a first-stage rear carbon ring arranged on the housing of the first-stage main unit of the compressor. The first-stage main shaft passes through the first-stage front carbon ring and the first-stage rear carbon ring, and the first-stage steam isolation chamber is arranged between the first-stage front carbon ring and the first-stage rear carbon ring; The second-stage shaft seal mechanism includes a second-stage front carbon ring and a second-stage rear carbon ring arranged on the housing of the second-stage main unit of the compressor. The second-stage main shaft passes through the second-stage front carbon ring and the second-stage rear carbon ring, and the second-stage steam isolation chamber is arranged between the second-stage front carbon ring and the second-stage rear carbon ring.

4. A sealing system for an inter-stage self-circulating two-stage centrifugal steam compressor according to claim 1, characterized in that, The outlet end of the second-stage shaft seal extraction gas pipeline is connected to a shaft seal cooler. A cooling water inlet pipeline, a cooling water outlet pipeline and a drain pipeline for the shaft seal cooler are arranged on the shaft seal cooler. A cooling water inlet temperature sensor and a cooling water inlet regulating valve are arranged on the cooling water inlet pipeline for the shaft seal cooler, and a cooling water outlet temperature sensor is arranged on the cooling water outlet pipeline for the shaft seal cooler; The steam in the second-stage shaft seal extraction gas pipeline is discharged after being cooled by the shaft seal cooler.

5. The sealing system of an inter-stage self-circulating two-stage centrifugal steam compressor according to claim 1, characterized in that, 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: Set a temperature difference preset value Td. If the temperature difference between the water in the cooling water outlet pipeline 23b and the cooling water inlet pipeline 23a of the shaft seal cooler is less than the temperature difference preset value Td, then reduce the opening of the cooling water inlet regulating valve 29 to reduce the circulating water volume, and finally keep the cooling water inlet regulating valve 29 at the minimum opening; If the temperature difference between the water in the cooling water outlet pipeline 23b and the cooling water inlet pipeline 23a of the shaft seal cooler is greater than the temperature difference preset value Td, then gradually increase the opening of the cooling water inlet regulating valve 29 until the temperature difference between the water in the cooling water outlet pipeline 23b and the cooling water inlet pipeline 23a of the shaft seal cooler is equal to the temperature difference preset value Td.

6. The sealing system of an inter-stage self-circulating two-stage centrifugal steam compressor according to claim 1, characterized in that, The driving device includes a gearbox. The input shaft of the gearbox is connected to the motor, and two output shafts are arranged on the gearbox. The two output shafts are respectively connected to the primary main shaft and the secondary main shaft.

7. A method for operating a sealing system of an inter-stage self-circulating two-stage centrifugal steam compressor, based on the inter-stage self-circulating two-stage centrifugal steam compressor sealing system according to claim 2, characterized in that, The specific method is as follows: The pressure value of the pressure monitoring instrument for the primary shaft seal pipeline is P1, and the pressure value of the pressure monitoring instrument for the secondary shaft seal pipeline is P2. The control target value P is set for the primary shaft seal air supply regulating valve 1tar1 , and the control target value P is set for the shaft seal inter-stage regulating valve 1tar2 to control the valve opening. The control target value P is set for the secondary shaft seal air extraction regulating valve 2tar1 ; and there is P 1tar1 < P 1tar2 < P 2tar1 ; When P1 < P 1tar1 , the first-stage shaft seal air supply regulating valve opens until P1 ≥ P 1tar1 and then the first-stage shaft seal air supply regulating valve closes; When P2 > P 2tar1 the secondary shaft seal steam extraction regulating valve opens, allowing the steam in the secondary shaft seal steam extraction pipeline to flow to the shaft seal cooler at the outlet end of the secondary shaft seal steam extraction pipeline for condensation until P2 ≤ P 2tar1 this valve closes gradually; Determine the opening degree of the inter-stage regulating valve of the shaft seal through the pressure value P1 of the pressure monitoring instrument of the primary shaft seal pipeline and the pressure value P2 of the pressure monitoring instrument of the secondary shaft seal pipeline.

8. The operating method of a sealing system for an inter-stage self-circulating two-stage centrifugal steam compressor according to claim 7, characterized in that, The opening degree of the inter-stage regulating valve of the shaft seal is adjusted by the following method: In the control system, through the monitored values of P1 and P2, the saturated steam densities rho1 and rho2 corresponding to the pressure values P1 and P2 are obtained from 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 stage regulating valve is fully open Calculate the through-flow mc when the shaft seal stage regulating valve is fully open under the current pressure condition; the calculation formula for the through-flow mc when the shaft seal stage regulating valve is fully open is as follows: ； Calculate the reference opening of the shaft seal inter-stage regulating valve under the current pressure conditions based on the through-flow rate mc when the shaft seal inter-stage regulating valve is fully open, the designed value m_in of the compressor mass flow rate, the shaft seal pipeline leakage rate α, and the adjustable ratio R , the reference opening of the shaft seal inter-stage regulating valve The calculation formula is as follows: ； With the reference opening degree as the reference, adjust the opening degree of the shaft seal stage regulating valve within the range of ±20%; When the difference between the pressure value P2 of the pressure monitoring instrument of the secondary shaft seal pipeline and the pressure value P1 of the pressure monitoring instrument of the primary shaft seal pipeline increases, the opening degree of the inter-stage regulating valve of the shaft seal is increased; when the difference between the pressure value P2 of the pressure monitoring instrument of the secondary shaft seal pipeline and the pressure value P1 of the pressure monitoring instrument of the primary shaft seal pipeline decreases, the opening degree of the inter-stage regulating valve of the shaft seal is decreased.

9. The operating method of a stage-interconnected self-circulating two-stage centrifugal steam compressor sealing system according to claim 7, characterized in that, When the steam compressor starts, the primary shaft seal air supplement regulating valve is in the open state, the inter-stage regulating valve of the shaft seal is fully open, the secondary shaft seal air extraction regulating valve is in the closed state, and the steam in the primary steam isolation chamber provides steam seals for both the primary shaft seal mechanism and the secondary shaft seal mechanism at the same time.

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