Gas seal cooling system

Abstract

A seal gas cooling circuit system (100) includes a gas seal (102) comprising: a seal gas inlet (106); and a seal gas outlet (108). The system (100) also includes a recirculation flow path (110) disposed between the seal gas inlet (106) and the seal gas outlet (108) for recirculating a seal gas through the gas seal (102); and a heat exchanger (112) disposed in the recirculation flow path (110) for cooling a temperature of the seal gas.

Description

GAS SEAL COOLING SYSTEMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to US provisional application number 63 / 607,168 filed on December 7, 2023.BACKGROUND

[0002] Double opposed dry gas seals and tandem dry gas seals, when used in combination with a very low leakage process side seal, are not typically used for rotating equipment with high operating pressures, for example, greater than 40 bar. This is due to excessive heat generated in the seal cavity due to windage resulting from the large fluid shear forces between the rotating and the stationary components that are exposed to high pressure gas.BRIEF SUMMARY

[0003] In one aspect, a seal gas cooling circuit system includes a gas seal, a seal gas inlet, and a seal gas outlet; a recirculation flow path disposed between the seal gas inlet and the seal gas outlet for recirculating a seal gas through the gas seal. The gas cooling circuit system also includes a heat exchanger disposed in the recirculation flow path for cooling a temperature of the seal gas.

[0004] In another aspect, a method of cooling a seal gas in a gas seal cooling circuit includes recirculating a seal gas from gas seal outlet of a dry gas seal to an inlet of the dry gas seal; cooling the seal gas in the recirculation circuit; and pressurizing the seal gas to a seal gas pressure greater than a sealing pressure of the gas seal.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.

[0006] FIG. 1 is a cross sectional view of a double opposed, dry gas seal including a gas cooling circuit in accordance with one embodiment.

[0007] FIG. 2 is a cross sectional view of a gas seal including a gas cooling circuit in accordance with one embodiment.

[0008] FIG. 3 illustrates a method in accordance with one embodiment.DETAILED DESCRIPTION

[0009] In the following detailed description, various specific details are set forth to provide a thorough understanding of such embodiments. However, those skilled in the art will understand that disclosed embodiments may be practiced without these specific details that the aspects of the present invention are not limited to the disclosed embodiments, and that aspects of the present invention may be practiced in a variety of alternative embodiments. In other instances, methods, procedures, and components, which would be well-understood by one skilled in the art have not been described in detail to avoid unnecessary and burdensome explanation.

[0010] Furthermore, various operations may be described as multiple discrete steps performed in a manner that is helpful for understanding embodiments of the present invention. However, the order of description should not be construed as to imply that these operations need be performed in the order they are presented, nor that they are even order dependent, unless otherwise indicated. Moreover, repeated usage of the phrase “in one embodiment” or "in an aspect" does not necessarily refer to the same embodiment, although it may.

[0011] It is noted that disclosed embodiments need not be construed as mutually exclusive embodiments, since aspects of such disclosed embodiments may be appropriately combined by one skilled in the art depending on the needs of a given application. Typically, the leakage rate through the rotating and stationary seal faces of conventional double opposed dry gas seals is relatively low. Consequently, there is insufficient flow of seal gas within sealing gas flow passages of the gas seal to remove the heat that will be produced in the seal cavity when subjected to high pressure and high rotating speed and the temperature can increase rapidly therein and may exceed the allowable temperatures for the seal components. The same is true for applications that utilize dry gas seals with a low leakage process side seal. As of now, there are no known efforts across the industry to increase the pressure limit established (and generally accepted throughout the OEMs and end users) for the double opposed dry gas seal. The proposed invention has the potential to change this and to enable the application of a cooled seal gas configuration having application over a wide range of gas seal operating parameters, such as higher operating pressures and high speeds, that were typically not considered in the past.

[0012] The present inventors have innovatively conceived and developed a system in which the primary seal gas may be used to remove the heat generated in the seal cavity, without the need to increase the leakage flow through the seal. Furthermore, the innovative system may beimplemented without having to perform major changes to conventional dry gas seal and seal housing configurations. Since seal gas needs to be supplied at a pressure above the process pressure, it is preferred that the pressure of the seal gas does not drop below the seal gas supply pressure level. The proposed innovative system advantageously allows raising the pressure limit of double opposed gas seals and other low leakage alternative seals. Unlike prior mechanical seals that are based on handling incompressible fluids in a fully closed loop system, the presently disclosed system can advantageously be applied to gas seal systems which are usually open loop type systems constantly being feed with seal gas, which is a compressible fluid. In another advantageous aspect, the ability to offer emissions free dry gas seal alternatives to the market is of paramount importance to meet decarbonization goals applications requiring zero emissions of HC gas into, for example, the primary vent of the turbo-compressor trains.

[0013] Advantageously, the proposed solution allows to raise the pressure limit of the double opposed seal and other low leakage alternatives, which may open different markets for this technology. The proposed solution is similar to systems used for liquid based mechanical seals (API Plan 53 and API Plan 54) but it is believed the first time that such an approach is applied in the dry gas seal domain to eliminate a known limitation of low leakage solutions such as the double opposed seal. It is important to note that liquid sealing systems are based on handling incompressible fluids in a fully closed loop system, in contrast, this concept is applied to gas seal systems which are usually open loop type systems constantly being feed with seal gas, which is a compressible fluid. The application of this type of solution is of particular importance to allow us to offer products from our current SE DGS portfolio to applications requiring zero emissions of HC gas into the primary vent of the turbo-compressor trains that we offer to the market. The ability to offer emissions free DGS alternatives to the market is of paramount importance to support our decarbonization goals.

[0014] The flow of seal gas required to remove excess heat is expected to be low enough to fall within the capabilities of commercially available seal gas boosters. A seal gas booster can be used to circulate the primary seal gas that will be used for cooling through a closed loop system composed of the return line, a small heat exchanger (available technology) and a connection to the seal gas supply line. The pressure drop through said components should be well within the capabilities of existing booster technology. Figure 1 shows one configuration of the system using an external booster. Since the windage losses are only present during theoperation of the turbo-compressor at high pressures, in another embodiment shown in Fig. 2, aerodynamic blading is added to the dry gas seal rotating shaft sleeve in order to drive the cooling flow though the cooling circuit without requiring the external booster.

[0015] In one aspect, the above described system may be retrofitted to existing dry gas seals. For example, a conventional seal gas cavity may have a seal gas supply port, so in principle, an additional connection can be used at the seal housing to connect to a seal gas return line. For example, API-692 recommended practice requires an additional port (low point of the seal gas supply annulus), it may be possible use that existing port for the cooling loop.

[0016] As depicted in FIG. 1, in one aspect, a seal gas cooling circuit system 100 includes a gas seal 102 a seal gas inlet 106, and a seal gas outlet 108. A recirculation flow path 110 disposed between the seal gas inlet 106 and the seal gas outlet 108 for recirculating a seal gas through the gas seal 102. The seal gas cooling circuit system 100 system also includes a heat exchanger 112 disposed in the recirculation flow path 110 for cooling a temperature of the seal gas 104 effective to remove at least a portion of heat imparted to the seal gas in the seal cavity 130 resulting from fluid shear forces between rotating and stationary components in the gas seal 102.

[0017] In one aspect, the seal gas cooling circuit system 100 may include a booster 114 disposed in the recirculation flow path 110 for maintaining a desired flow of the seal gas injected into the seal gas inlet 106.

[0018] In one aspect, the seal gas cooling circuit system 100 may include a seal gas 104 vent leakage flow path 120 for conducting a vent leakage portion of the seal gas from the seal gas inlet 106 to a vent leakage outlet 122,

[0019] In one aspect, the seal gas cooling circuit system 100 may include a process leakage flow path 116 for conducting a process leakage portion of the seal gas 104 from the seal gas inlet 106 to a process leakage outlet 118.

[0020] In one aspect, the seal gas cooling circuit system 100 may include a makeup seal gas flow 128 connected to the recirculation flow path 110 for adding make-up seal gas 104 to compensate for seal gas 104 leakage from the gas seal 102.

[0021] In one aspect, the seal gas 104 is pressurized to a seal gas pressure greater than a sealing pressure of the gas seal 102.

[0022] In one aspect, a pressure of the seal gas 104 entering the seal gas inlet 106 is greater than 40 Bar.

[0023] In one aspect, the recirculation flow path 110 is connected to at least one existing seal gas port 132 of the gas seal 102.

[0024] As depicted in FIG. 2, in one aspect, the seal gas cooling circuit system 100 may include aerodynamic blading 124 attached to a rotating shaft sleeve 126 of the gas seal 102 for maintaining a desired flowrate in the seal gas cooling circuit system 100. For example, the aerodynamic blading 124 may include a plurality of blades disposed around a circumference of the rotating shaft sleeve 126 and configured to maintain the flow rate of the seal gas passing thereover and maintaining the required flow through the cooling loop. The aerodynamic blading 124 may be used instead of booster 114.

[0025] A method of cooling a seal gas in a gas seal cooling circuit comprises, in block 302, routine 300 recirculates a seal gas from gas seal outlet of a dry gas seal to an inlet of the dry gas seal. In block 304, routine 300 cools the seal gas in the recirculation circuit. In block 306, routine 300 provides sufficient pressure rise through the system to overcome the pressure losses experienced by the flow of the seal gas through the cooling circuit (for example, heat exchanger 112 and piping connecting the inlet 106 to the outlet 108) of the gas seal.

[0026] The features of the present description which are believed to be novel are set forth below with particularity in the appended claims. However, modifications, variations, and changes to the exemplary embodiments described above will be apparent to those skilled in the art, and the seal gas cooling system and method described herein thus encompasses such modifications, variations, and changes and are not limited to the specific embodiments described herein.

Claims

CLAIMSWhat is claimed is:

1. A seal gas cooling circuit system comprising: a gas seal comprising: a seal gas inlet; and a seal gas outlet; a recirculation flow path disposed between the seal gas inlet and the seal gas outlet for recirculating a seal gas through the gas seal; and a heat exchanger disposed in the recirculation flow path for cooling a temperature of the seal gas effective to remove at least a portion of heat imparted to the seal gas in the seal cavity resulting from fluid shear forces between rotating and stationary components in the gas seal.

2. The system of claim 1, further comprising a booster disposed in the recirculation flow path for maintaining a desired flow of the seal gas injected into the seal gas inlet.

3. The system of claim 1, further comprising a seal gas vent leakage flow path for conducting a vent leakage portion of the seal gas from the seal gas inlet to a vent leakage outlet.

4. The system of claim 3, further comprising a process leakage flow path for conducting a process leakage portion of the seal gas from the seal gas inlet to a process leakage outlet.

5. The system of claim 1, further comprising aerodynamic blading attached to a rotating shaft sleeve of the gas seal for maintaining a desired flow in the seal gas cooling circuit.

6. The system of claim 1, further comprising a makeup seal gas flow connected to the recirculation flow path for adding make-up seal gas to compensate for seal gas leakage from the gas seal.

7. The system of claim 1, wherein the seal gas is pressurized to a seal gas pressure greater than a sealing pressure of the gas seal to promote the flow of gas through the cooling loop.

8. The system of claim 1, wherein a pressure of the seal gas entering the seal gas inlet is greater than 40 Bar.

9. The system of claim 1 , wherein the recirculation flow path is connected to at least one existing seal gas port of the gas seal.

10. A method of cooling a seal gas in a gas seal cooling circuit comprising: recirculating a seal gas from gas seal outlet of a dry gas seal to an inlet of the dry gas seal; cooling the seal gas in the recirculation circuit effective to remove at least a portion of heat imparted to the seal gas resulting from fluid shear forces between rotating and stationary components in the gas seal; and pressurizing the seal gas to a seal gas pressure greater than a sealing pressure of the gas seal to promote the flow of gas through the cooling loop.

11. The method of claim 10, further comprising injecting a make-up seal gas into the seal gas cooling circuit to compensate for seal gas leakage from the gas seal.

12. The method of claim 10, wherein pressurizing the seal gas comprises disposing a booster in the recirculation flow path for maintaining a desired flow of the seal gas injected into the seal gas inlet.

13. The method of claim 10, wherein pressurizing the seal gas comprises disposing aerodynamic blading on a rotating shaft sleeve of the gas seal for maintaining a desired flow in the seal gas cooling circuit.

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