Dry gas sealing device for liquid ammonia high-pressure pump

Abstract

The utility model discloses a dry gas sealing device for a liquid ammonia high-pressure pump, which comprises a rotating shaft, a first-stage seal, a second-stage seal and a third-stage seal are sequentially arranged on the rotating shaft, the first-stage seal and the second-stage seal are double-end-face dry gas seals, and the third-stage seal is single-end-face dry gas seal. The first-stage seal is connected with the second-stage seal and the third-stage seal in series, the double-end-face dry gas seal is connected with an ammonia gas pipeline with one inlet and one outlet, a heater is arranged on the ammonia gas pipeline, and an outlet pipeline of the circulation pipeline is connected with a pump inlet. The sealing structure is changed into three-end-face dry gas sealing, when the first-stage sealing fails, the second-stage sealing replaces the first-stage sealing to serve as the main sealing, the second-stage sealing and the third-stage sealing form a series connection structure, and safe shutdown of the pump is guaranteed; when the second-stage sealing fails, the third-stage sealing can replace the second-stage sealing, it is guaranteed that media do not leak out, safe shutdown is achieved, and meanwhile a heater is additionally arranged to guarantee that ammonia gas which does not flow in the double-end-face dry gas sealing cavity is condensed and forms liquid drops to damage the sealing.

Description

Technical Field

[0001] This utility model relates to the field of dry gas sealing, specifically to a dry gas sealing device for a liquid ammonia high-pressure pump. Background Technology

[0002] The liquid ammonia high-pressure pump is mainly used to transport and pressurize liquid ammonia from the ammonia synthesis section so as to deliver a quantitative and qualified amount of liquid ammonia to the urea synthesis tower and other stations. However, the equipment often stops and production cannot be carried out due to damage to the sealing structure in the liquid ammonia high-pressure pump.

[0003] Mechanical seals are key components that ensure the normal operation of equipment. However, traditional mechanical seals are limited by PV values ​​and have a short service life, making it difficult to meet the needs of long-term operation of equipment. Dry gas seals, as a new type of sealing product, have emerged. Their non-contact sealing end face feature greatly extends the service life of the seal and provides higher vibration resistance to equipment than mechanical seals.

[0004] Currently, in some application scenarios, externally introduced ammonia is used as the main sealing gas for Plan 74. However, to ensure on-site safety and environmental protection, the sealing scheme needs further optimization. The existing scheme has certain limitations in actual operation, such as insufficient filtration accuracy of the sealing gas, unstable main sealing gas pressure regulation, inaccurate leakage monitoring, and the possibility of ammonia condensate damaging the seal. Utility Model Content

[0005] To address the aforementioned problems, this utility model provides a dry gas sealing device for a liquid ammonia high-pressure pump.

[0006] This utility model is achieved through the following technical solution:

[0007] A dry gas sealing device for a liquid ammonia high-pressure pump includes a rotating shaft with a first-stage seal, a second-stage seal, and a third-stage seal sequentially arranged on the shaft. The first-stage and second-stage seals are double-end-face dry gas seals, and the third-stage seal is a single-end-face dry gas seal. The first-stage, second-stage, and third-stage seals are connected in series. An ammonia gas pipeline with one inlet and one outlet is connected to the double-end-face dry gas seal. A heater is installed on the ammonia gas pipeline, and the outlet pipeline of the circulating pipeline is connected to the pump inlet.

[0008] Alternatively, a sealing gas with a pressure 0.2-0.3 MPa higher than the pump chamber pressure can be injected into the sealing chambers of the first and second stage seals. The sealing gas is externally drawn ammonia, and the third stage seal uses room temperature nitrogen as a buffer gas.

[0009] Alternatively, the first and second stage seals can withstand the full pressure of the medium, while the third stage seal operates under low-pressure conditions.

[0010] Further optional features include a control system, which includes a filtration unit, a regulating unit, and a leakage monitoring unit.

[0011] Further optionally, the filtration unit includes a filter with a filter accuracy of micrometers.

[0012] Further optionally, the regulating unit includes a regulating valve, which is used to ensure that the pressure of the first-stage seal and the second-stage seal is higher than the pressure of the sealing cavity by - MPa.

[0013] Optionally, the leak monitoring unit includes a first flow meter and a second flow meter, as well as a first pressure sensor and a second pressure sensor, respectively installed on the ammonia pipeline and the nitrogen pipeline.

[0014] Compared with existing technologies, the advantages of this invention are as follows: The sealing structure is changed to a three-end-face dry gas seal. Under normal circumstances, the Plan74 double-end-face dry gas seal bears the full pressure of the medium, while the third-stage seal operates under low-pressure conditions. When the first-stage seal fails, the second-stage seal replaces it as the main seal, forming a series structure with the third stage to ensure safe pump shutdown. When the second-stage seal fails, the third-stage seal can replace the second-stage seal, ensuring no leakage of the medium and safe shutdown. Simultaneously, a heater is added to prevent the condensation of ammonia gas, which does not flow within the double-end-face dry gas seal cavity, from forming droplets that damage the seal. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the system of this utility model;

[0016] In the diagram: 1. Rotary shaft; 2. First-stage seal; 3. Second-stage seal; 4. Third-stage seal; 5. Ammonia pipeline; 6. Heater; 7. Filter; 8. Regulating valve; 9. Second flow meter; 10. Second sensor; 11. First flow meter; 12. First pressure sensor; 13. Nitrogen source; 14. Ammonia source; 15. Nitrogen pipeline. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0018] like Figure 1 As shown, a dry gas sealing device for a liquid ammonia high-pressure pump includes a rotating shaft 1. A first-stage seal 2, a second-stage seal 3, and a third-stage seal 4 are sequentially arranged on the rotating shaft 1. The first-stage seal 2 and the second-stage seal 3 are double-end dry gas seals, and the third-stage seal 4 is a single-end dry gas seal. The first-stage seal 2, the second-stage seal 3, and the third-stage seal 4 are connected in series. An ammonia gas pipeline 5 with one inlet and one outlet is connected to the double-end dry gas seal. A heater 6 is installed on the ammonia gas pipeline 5, and the outlet pipeline of the ammonia gas pipeline 5 is connected to the pump inlet.

[0019] like Figure 1As shown, the sealing chambers of the first-stage seal 2 and the second-stage seal 3 are injected with a sealing gas at a pressure 0.2-0.3 MPa higher than that of the pump chamber. The sealing gas is externally drawn ammonia, and the third-stage seal 4 uses room-temperature nitrogen as a buffer gas.

[0020] like Figure 1 As shown, the first-stage seal 2 and the second-stage seal 3 bear the full pressure of the medium, while the third-stage seal 4 operates under low-pressure conditions.

[0021] like Figure 1 As shown, it also includes a control system, which includes a filtration unit, an adjustment unit, and a leakage monitoring unit.

[0022] like Figure 1 As shown, the filtration unit includes a filter 7 with a filter accuracy of 2 micrometers.

[0023] like Figure 1 As shown, the regulating unit includes a regulating valve 8, which is used to ensure that the pressure of the first-stage seal 2 and the second-stage seal 3 is 0.2-0.3 MPa higher than the pressure of the sealing cavity.

[0024] like Figure 1 As shown, the leakage monitoring unit includes a first flow meter 11 and a second flow meter 9, as well as a first pressure sensor 12 and a second pressure sensor 10, which are respectively installed on the ammonia pipeline 5 and the nitrogen pipeline 15.

[0025] The implementation principle of a dry gas sealing device for a liquid ammonia high-pressure pump according to an embodiment of this application is as follows:

[0026] During the sealing process, the corresponding sealing gases enter the ammonia pipeline 5 and nitrogen pipeline 15 from the nitrogen source 13 and ammonia source 14. The nitrogen and ammonia in the ammonia pipeline 5 and nitrogen pipeline 15 are filtered by the filter 7 to become clean gases with a precision of 2 microns. The filtered nitrogen and ammonia are then regulated by the regulating valve 8 to stabilize the pressure of the nitrogen and ammonia in the ammonia pipeline 5 and nitrogen pipeline 15 at a fixed value, always ensuring that the pressure in the ammonia pipeline 5 and nitrogen pipeline 15 is 0.2 to 0.3 MPa higher than the sealing cavity pressure. After pressure regulation, the nitrogen and ammonia enter the sealing cavities of the corresponding first-stage seal 2, second-stage seal 3 and third-stage seal 4 for sealing operations.

[0027] Meanwhile, before the ammonia enters the sealed cavity, in order to prevent the ammonia from condensing and forming droplets that could damage the seal, the ammonia will be heated by heater 6.

[0028] During the sealing process, the second flow meter 9 and the second pressure sensor 10, as well as the first flow meter 11 and the first pressure sensor 12 installed on the ammonia pipeline 5 and the nitrogen pipeline 15, will monitor the pressure and flow rate of the corresponding ammonia pipeline 5 and nitrogen pipeline 15. When the gas leakage in the ammonia pipeline 5 and the nitrogen pipeline 15 exceeds the set value (the set value is set according to the site conditions), the flow rate of the second flow meter 9 and the first flow meter 11 will increase. This indicates that the dry gas seal is damaged, and the machine will be shut down for maintenance.

[0029] When the first-stage seal fails, the second-stage seal takes its place as the main seal, forming a series structure with the third stage to ensure safe pump shutdown; when the second-stage seal fails, the third-stage seal can replace the second-stage seal to ensure no leakage of the medium and safe shutdown.

[0030] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed utility model. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A dry gas sealing device for a liquid ammonia high-pressure pump, comprising a rotating shaft (1), characterized in that: The rotating shaft (1) is sequentially provided with a first-stage seal (2), a second-stage seal (3), and a third-stage seal (4). The first-stage seal (2) and the second-stage seal (3) are double-end dry gas seals, and the third-stage seal (4) is a single-end dry gas seal. The first-stage seal (2), the second-stage seal (3), and the third-stage seal (4) are connected in series. The double-end dry gas seal is connected to an ammonia gas pipeline (5) with one inlet and one outlet. The ammonia gas pipeline (5) is provided with a heater (6), and the outlet pipeline of the ammonia gas pipeline (5) is connected to the pump inlet.

2. The dry gas sealing device for a liquid ammonia high-pressure pump according to claim 1, characterized in that: The sealing chambers of the first-stage seal (2) and the second-stage seal (3) are filled with a sealing gas at a pressure 0.2-0.3 MPa higher than that of the pump chamber. The sealing gas is externally drawn ammonia. The third-stage seal (4) uses room-temperature nitrogen as a buffer gas.

3. The dry gas sealing device for a liquid ammonia high-pressure pump according to claim 2, characterized in that: The first-stage seal (2) and the second-stage seal (3) bear the full pressure of the medium, while the third-stage seal (4) operates under low-pressure conditions.

4. The dry gas sealing device for a liquid ammonia high-pressure pump according to claim 1, characterized in that; It also includes a control system, which includes a filtration unit, an adjustment unit, and a leakage monitoring unit.

5. A dry gas sealing device for a liquid ammonia high-pressure pump according to claim 4, characterized in that: The filtration unit includes a filter (7) with a precision of 2 micrometers.

6. The dry gas sealing device for a liquid ammonia high-pressure pump according to claim 4, characterized in that: The regulating unit includes a regulating valve (8), which is used to ensure that the pressure of the first-stage seal (2) and the second-stage seal (3) is 0.2-0.3 MPa higher than the pressure of the sealing cavity.

7. A dry gas sealing device for a liquid ammonia high-pressure pump according to claim 4, characterized in that: The leakage monitoring unit includes a first flow meter (11) and a second flow meter (9) installed on the ammonia pipeline (5) and the nitrogen pipeline (15), respectively, as well as a first pressure sensor (12) and a second pressure sensor (10).

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