Rotary gas booster

Abstract

A rotary gas booster having a shaft (7) supported by a bearing arrangement (11,12) corrected to shaft driving means (14). The shaft drawing means are located within a chamber (8) having gas inlets and outlets. The gas booster is provided with integral gas cooling means (21).

Description

[0001] Rotary Gas Booster

[0002] Field of the Invention

[0003] This invention relates to rotary gas boosters which are used where gas has to be transported or circulated through a process or system.

[0004] Background to the Invention

[0005] Rotary gas boosters reduce the need for heat exchangers and similar devices to be incorporated within gas systems. They are considered as being more reliable than many competing booster designs which often work on different principles such as reciprocating or with differing type of rotors or screws. One inherent issue with boosting gases is that there is additional heat generated due to gas thermodynamics, bearing friction and other losses associated with couplings which can cause operational issues. Since these are generally considered unavoidable, the outcome tends to be to use an external heat exchanger or limit the operation of the booster to lesser duties (lower speed, lower pressure, process gas temperature and or molecular weight).

[0006] Statements of the Invention

[0007] According to the present invention there is provided a rotary gas booster comprising a shaft supported by a bearing arrangement, said shaft being connected to shaft driving means and to gas driving means, said gas driving means being located within a chamber having a gas inlet and a gas outlet, said gas booster being provided with integral gas cooling means.

[0008] The gas driving means may be an impeller and the chamber a casing or volute which may include a cooling jacket around the periphery of the casing so that the heat generation due to viscous shear and gas thermodynamic effects is minimised.

[0009] The bearing arrangement may include a housing provided with a cooling jacket to reduce the effects of frictional heat from the bearings where additional features are also provided to ensure that the gas pocket between the two sets of bearings is internally vented so that pressure and hence temperature increases are avoided. The other major source of heat generation in rotary gas boosters is due to losses in the magnetic drive coupling which produce eddy currents that raise the temperature of the gas within the booster in the vicinity of the coupling. Notch and fin like features can be included on certain coupling surfaces along with a two ply cannister design that permits cooling medium within the coupling itself.

[0010] Some or all of the above features can individually or collectively be applied so that the rotary gas booster can used in arduous duties where conventional designs would be compromised unless external heat exchangers were provided.

[0011] In addition the introduction of integral cooling will enable multistage units to be employed without the need for interstage external cooling where gas from one stage is send to a heat exchanger and then returned to the booster so that the subsequent stage can be conducted. The necessity for external heat exchanges introduces additional complexity and cost to the process.

[0012] Brief Description of the Drawings

[0013] The accompanying drawings are as follows:

[0014] Figures 1A and 1 B show a typical known rotary gas booster;

[0015] Figure 2 shows magnetic drive couplings for a gas booster of the invention;

[0016] Figure 3 shows a rotary gas booster of the invention with integral housing cooling;

[0017] Figure 4 shows a multistage rotary gas booster with integral cooling;

[0018] Figure 5 shows the housing with integral cooling;

[0019] Figure 6A shows the bearing integral cooling;

[0020] Figure 6B shows the bearing housing vent slot detail;

[0021] Figure 7 shows an exploded perspective view of a typical integrally cooled coupling; and

[0022] Figure 8 is a longitudinal section of the coupling of Figure 7. Detailed Description of the Invention

[0023] The present invention will now be described, by way of example only, with reference to the accompanying drawings.

[0024] A typical rotary gas booster is shown in Figure 1. It can be either vertically or horizontally mounted, in this case being vertically mounted. The booster can be driven by any rotating prime mover. In this case it is driven by an electrical motor 1 . The booster has a rotating shaft 7 which is supported by a bearing arrangement comprising of one radial bearing 11 plus a second bearing 12 which also withstands radial loads in addition to axial loads. The bearings can be mounted anywhere along the shaft however in this case they are mounted in close proximity to each other around an upper section of the shaft. The bearings are mounted within a purpose designed bearing housing 8 which has a slot like feature which allows gas flow / venting to prevent pressure and / or temperature increase within the interspace cavity. An impeller 14 is also mounted on the shaft. This can be located anywhere along the shaft. However in this case it is mounted at the lower end of the of the shaft. The impeller contains a series of periodic features which impart energy into the gas causing it to move through the surrounding control volume channel which is positioned within the confines of a housing. The housing surrounding the impeller has inlet and outlet nozzles allowing the gas to enter the booster where it is guided onto the impeller and control volume channel where it passes through the housing and exits. The shaft is driven by means of a magnetic coupling 5 which comprises a series of magnets placed around the booster shaft 7 and a corresponding set of magnets placed around the motor shaft. A cannister, fixed to the booster casing, separates the two sets of magnets. The cannister is a statically sealed unit which eliminates the need for a dynamic seal.

[0025] During normal operation heat is generated within the booster which in turn increases the gas temperature. The several sources of heat are; gas thermodynamics and viscous shear which occur heats the gas around the impeller, frictional heat from the bearings which can also affect any trapped gases within the bearing enclosure and eddy current losses generated by the magnetic drive coupling. Individually or collectively, these sources of heat can produce undesirable temperature rises in gases leaving the booster which usually dictate that an external cooling device (heat exchanger) becomes necessary. The introduction of integral cooling within the confines of the booster will mitigate the limiting effects of the heat sources.

[0026] Referring to Figures 3 to 5 of the accompanying drawings, the introduction of an additional cavity around the periphery of the impeller housing allows cooling medium which will combat the effects of heat generated by the impeller.

[0027] Referring to Figures 6A and 6B of the accompanying drawings, a jacket style arrangement 21 around the bearing housing provides cooling to prevent the bearings from overheating and reduce the likelihood of trapped gases overheating which would produce additional pressure. In addition to integral cooling the latter can be further prevented by the introduction of a vent slot 23 which prevents gases from becoming trapped.

[0028] Referring to Figures 2 and 7 of the accompanying drawings, heat generated by eddy current loses at the coupling are also alleviated. This can be addressed in several ways such as material selection, features which increase air circulation through the coupling and a two ply cannister where cooling medium can be circulated through the cannister itself without the overall design limiting the pressure rating for the equipment. The central coupling in Figure 2 shows such an integrally cooled magnetic coupling. Figures 7 and 8 also show a typical integrally cooled coupling.

[0029] As illustrated in Figure 4, the introduction of integral cooling also enables multistage boosters to be constructed without the need for external interstage cooling.

[0030] Overall having integral cooling is more efficient and productive. It saves on the additional expense and complications arising from external heat exchangers and also avoids the impact upon plant layout due to additional space requirements.

Claims

CLAIMS1 . A rotary gas booster comprising a shaft supported by a bearing arrangement, said shaft being connected to shaft driving means and to gas driving means, said gas driving means being located within a chamber having a gas inlet and a gas outlet, said gas booster being provided with integral gas cooling means.

2. A gas booster according to Claim 1 , wherein gas cooling means are provided to cool gas in the region of the gas driving means.

3. A gas booster according to Claim 1 or Claim 2, wherein gas cooling means are provided to cool gas in the region of the shaft driving means.

4. A gas booster according to any of the preceding claims, wherein gas cooling means are provided to cool gas in the region of the connection between the shaft driving means and the shaft.

5. A gas booster according to any of the preceding claims, wherein the gas driving means is an impeller.

6. A gas booster according to any of the preceding claims, wherein the shaft driving means is an electric motor.

7. A gas booster according to any of the preceding claims, wherein the connection between the shaft driving means and the shaft is a magnetic coupling.

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