Centrifugal separator having energy consumption reducing devices

Abstract

The invention relates to a centrifugal separator comprising a casing which delimits and seals off a space in which a rotor is arranged. The rotor forms a separation space which is sealed or isolated from the space, and in which separation space centrifugal separation of a higher density and a lower density component from a fluid takes place. An inlet extends into the rotor for introducing fluid to the separation space, and a first outlet extends from the rotor for discharge of a component separated from the fluid. The space is connected to a pump device which is arranged to remove gas, thereby maintaining negative pressure in said space. The rotor comprises at least one second outlet extending from the separation space to the space for discharge of at least one higher density component separated from the fluid. The invention also relates to a method in such a centrifugal separator.

Claims

1. A centrifugal separator comprising a casing which delimits a space which is sealed relative to a surrounding of the casing and in which a rotor is arranged for rotation, which rotor forms within itself a separation space, and in which separation space centrifugal separation of at least one higher density component and at least one lower density component from a fluid takes place during operation, into which rotor at least one inlet extends for introducing said fluid to the separation space, and from which rotor at least one first outlet extends for discharge of at least one component separated from the fluid during operation, wherein the space is connected to a pump device which is arranged to remove gas from the space during operation, thereby maintaining negative pressure in said space, and wherein the rotor comprises at least one second outlet extending from a portion of the separation space to the space for discharge of at least one higher density component separated from the fluid during operation; the at least one second outlet being configured to at least partially seal the separation space from the space or selectively isolate the separation space from the space.

2. A centrifugal separator according to claim 1, wherein the at least one second outlet is arranged to open and close allowing intermittent discharge of at least one higher density component separated from the fluid during operation.

3. A centrifugal separator according to claim 1, wherein the at least one second outlet is arranged as an open nozzle for continuous discharge of at least one higher density component separated from the fluid during operation.

4. A centrifugal separator according to claim 1, further comprising a discharge device in the form of a sludge pump being arranged to remove the at least one higher density component separated from the fluid from the space during operation.

5. A centrifugal separator according to claim 1, wherein the pump device is one of a water-filled liquid ring pump, a lamella pump and a vacuum pump.

6. A centrifugal separator according to claim 1, further comprising a device for supplying a medium to the space, which medium is brought into heat-transferring contact with the rotor in order to regulate the temperature of the rotor.

7. A centrifugal separator according to claim 6, wherein said medium comprises a liquid which in said heat-transferring contact is at least partly caused to evaporate and form a gas medium in the space.

8. A centrifugal separator according to claim 6, wherein said medium comprises a gas medium.

9. A centrifugal separator according to claim 7, wherein said gas medium has a density lower than the density of air and/or a viscosity lower than the viscosity of air.

10. A centrifugal separator according to claim 6, wherein said medium is sprayed towards the rotor.

11. A centrifugal separator according to claim 6, wherein said medium is finely divided in the space.

12. A centrifugal separator according to claim 6, wherein a flow of medium into the space is driven by pressure difference between a container for medium and the space and is controlled by a valve.

13. A centrifugal separator according to claim 7, further comprising a cold surface in the space for condensation of said gas medium to a condensate.

14. A centrifugal separator according to claim 13, wherein the condensate is brought into heat-transferring contact with the rotor in order to regulate the temperature of the rotor.

15. A centrifugal separator according to claim 13, wherein the casing comprises thermally insulating and/or sound-insulating material.

16. A centrifugal separator according to claim 13, wherein the space is sealed or isolated from an inlet chamber in the rotor or an outlet chamber in the rotor or both the inlet chamber and outlet chamber.

17. A centrifugal separator according to claim 13, wherein the space is sealed relative to a drive device which is arranged to provide torque to the rotor.

18. A centrifugal separator according to claim 13, wherein a discharge device is arranged to remove at least one component separated from the fluid during operation from the space.

19. A centrifugal separator according to claim 18, further comprising a vessel between the space and the discharge device for gathering at least one component separated from the fluid.

20. A method for operating a centrifugal separator, the method comprising: providing a centrifugal separator according to claim 1; removing gas from the space around the rotor, thereby maintaining negative pressure in said space; and discharging from a portion of the separation space to the space via said second outlet at least one higher density component separated from the fluid during operation.

21. A method according to claim 20, which further comprises the steps of: supplying a medium to said space, which medium is brought into heat-transferring contact with the rotor in order to regulate the temperature of the rotor.

22. A method according to claim 21, in which said medium comprises a liquid which in said heat-transferring contact with the rotor is at least partly caused to evaporate and form a gas medium in the space, and in which at least part of said gas medium is removed from the space.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and objects of the present invention, together with preferred embodiments which exemplify it, are described below in more detail with reference to the attached schematic drawings in which

(2) FIG. 1 depicts a centrifugal separator according to an embodiment of the invention,

(3) FIG. 2 depicts a centrifugal separator according to another embodiment of the invention,

(4) FIG. 3 depicts portions of a centrifugal separator according to a further embodiment of the invention,

(5) FIG. 4 depicts portions of a centrifugal separator according to a further embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(6) Mutually similar parts which appear in the various drawings have been given the same reference notations. An example of a centrifugal separator according to the invention is depicted in FIG. 1, which centrifugal separator 1 comprises a rotor 2 arranged for rotation about an axis of rotation by means of a spindle 3. The spindle is supported in the centrifugal separator's frame 4 in a bottom bearing 5 and a top bearing 6. The rotor 2 forms within itself a separation chamber 7 in which centrifugal separation of at least two components of a fluid takes place during operation. The separation space 7 is provided with a stack of frusto-conical separation discs 8 in order to achieve effective separation of said fluid. An inlet 9 for introducing the fluid for centrifugal separation extends into the rotor, providing fluid to the separation space. The inlet 9 extends through the spindle 3, which takes the form of a hollow, tubular member. A first outlet 10 for discharging at least one of the components of the fluid extends from the separation space. The rotor is provided at its outer periphery with a set of second outlets 11 in the form of intermittently openable sludge outlets for discharge of sludge and/or a higher density component in said fluid, or heavy phase, from a radially outer portion of the separation space to the space round the rotor.

(7) The centrifugal separator 1 further comprises a drive motor 12 connected to the spindle via a transmission means in the form of a worm gear which comprises a pinion 13 and an element 14 connected to the spindle in order to receive driving torque. The transmission means may alternatively take the form of a propeller shaft, drive belts or the like, and the drive motor may alternatively, as depicted in FIG. 2, be connected directly to the spindle.

(8) FIG. 1 further depicts a casing 15 which encloses the rotor 2 and is sealed round the spindle 3 by a top bearing seal 16 and at the outlet 10 by an outlet seal 17. The casing thus delimits a space 18 which contains the rotor and which is air-tightly sealed relative to the surroundings of the casing. The outlet seal 17 also seals the space 18 relative to the spaces in the rotor which contain at least one component of the fluid for centrifugal separation during operation, e.g. the separation space 7.

(9) The centrifugal separator is further provided with a pump device 19 for removal of gas from the space 18 round the rotor, which pump device takes the form of a water-filled liquid ring pump or, as an alternative, a lamella pump. The separator is further provided with a device 20 for supply of a liquid to said space, in the form of a reservoir or inlet line for supply of a liquid at a pressure higher than the operating pressure in the space 18. The supply device 20 is provided with a valve 21 for regulating a liquid flow to a nozzle 22 in connection to said space 18.

(10) The centrifugal separator further comprises a vessel 23 in the form of a cyclone connected to the space 18 and adapted to gathering sludge and liquid from the sludge outlet 11. The gathering vessel is further connected to a discharge device 24 in the form of a sludge pump for discharge of sludge and liquid present in the gathering vessel. The sludge pump is provided with a check valve function which prevents flow into the vessel 23 via the sludge pump.

(11) During operation of the separator in FIG. 1, the rotor 2 is caused to rotate by torque transmitted from the drive motor 12 to the spindle 3 via the worm gear 13 and 14. Gas is pumped out of the space 18 round the rotor by the vacuum pump 19, thereby maintaining in the space a pressure of 1-50 kPa, preferably 2-10 kPa. Via the inlet 9, a fluid at the temperature T.sub.0 is brought into the separation space 7 and between the conical separation discs 8 fitted in the separation space. Heavier components in the fluid, e.g. sludge particles and/or heavy phase, move radially outwards between the separation discs and accumulate within the sludge phase outlets 11. Sludge is emptied intermittently from the separation space by the sludge outlets 11 being opened, whereupon sludge and a certain amount of fluid is discharged from the separation space by means of centrifugal force. The discharge of sludge may also take place continuously, in which case the sludge outlets 11 take the form of open nozzles and a certain flow of sludge and/or heavy phase is discharged continuously by means of centrifugal force. Sludge which is discharged from the separation space via the sludge outlets is conveyed from the surrounding space 18 to the gathering vessel 23 connected thereto, in which the sludge accumulates and from which it is pumped out by the sludge pump 24.

(12) Lower density components of the fluid, e.g. the light phase, or the pure fluid, without the heavier components, move radially inwards between the separation discs and out through the outlet 10. Friction effects due to the rotation of the rotor in the gas remaining in the space 18, the flow of the fluid through the separation space and losses in bearings cause the separated fluid at the outlet to be at a somewhat higher temperature than T.sub.0. In order to affect the temperature of outgoing separated fluid, water is sprayed into heat-transferring contact with the rotor 2, e.g. towards its outer surface. Heat is removed from the rotor by the water vaporizing upon contact with the rotor, thereby consuming vaporization heat. The vaporization of the water is further facilitated by the negative pressure maintained in the space.

(13) Water vapor is removed from the space 18 round the rotor by the pump device 19, thereby maintaining said negative pressure. The vaporization of the water followed by water vapor being conveyed away from the space results in a transfer of heat away from the rotor 2 and the space 18 to the pump device 19.

(14) Another example of the centrifugal separator 1 according to the invention is depicted in FIG. 2, which differs from the above example as follows. An inlet 9 extends to the rotor 2 via a hollow, tubular spindle 3 for providing fluid to the separation space 7. The rotor has extending from it an outlet 25 for a lower density component, or light phase, separated from the fluid, and an outlet 26 for a higher density component, or heavy phase, separated from the fluid. The outlets 25 and 26 extend through the casing 15, and the space 18 is sealed by a seal 17. The rotor is provided with a sludge outlet 11 at an outer periphery for discharge of sludge phase to the space. The centrifugal separator is provided with a drive motor 12 comprising a stationary element 27 and a rotatable element 28, which rotatable element 28 surrounds and is so connected to the spindle 3 that during operation it transmits driving torque to the spindle and hence to the rotor 2. The drive motor is an electric motor, preferably of the hybrid permanent magnet motor (HPM motor) type. The centrifugal separator is further provided with a pump device 19 for removal of gas from the space 18 round the rotor, and with a device 20 for supply of a liquid to the space 18. This supply device is provided with a valve 21 for regulating a liquid flow to a nozzle 22 connected to said space 18. The centrifugal separator is further provided with a discharge device 24 in the form of a pump for removing sludge and other liquid from the space 18 round the rotor. The pump 24 is connected to a lower portion of the space 18 without any intermediate gathering vessel besides the pipe connections between the pump 24 and the space.

(15) A further example of portions of a centrifugal separator according to the invention is depicted in FIG. 3, which differs from the above examples as follows. The rotor 2 is supported by a spindle 3 which is solid. An inlet 9 in the form of a pipe extends into the rotor from above for providing fluid to the separation space 7. The rotor has extending from it an outlet 10 for discharge of at least one of the components of the fluid, which outlet surrounds the inlet pipe 9. The inlet 9 and the outlet 10 extend through the casing 15, and the space 18 round the rotor is sealed by a seal 30 round them. The rotor is provided with sludge outlets 11 at an outer periphery for discharge of sludge phase to the space. The centrifugal separator is provided with a device 20 for supply of coolant to the seal 30 for the latter's cooling, which coolant is thereafter brought into the space 18 and into contact with the rotor. The flow of coolant is regulated by the valve 21. The centrifugal separator is further provided with a pump 29 for removal of gas and liquid from the space, which pump maintains negative pressure in, and discharges sludge and other liquid from, the space 18.

(16) A further example of portions of a centrifugal separator according to the invention is depicted in FIG. 4, which differs from the above examples as follows. The centrifugal separator is provided with a pump device 19 for removal of gas from the space 18, which space is surrounded by the casing 15 and contains the rotor 2. The separator is further provided with a device 20 for supply of a liquid to the space 18, and with a discharge device in the form of a pump 24 for removal of sludge and other liquid from the space 18 round the rotor. A region of the casing in the space 18, above the rotor 2, is provided with cooling from at least one cold temperature source 33, thereby forming a cold surface 31. The region is provided with one or more inclined surfaces so that vapor which condenses on the cold surface accumulates and drops or runs down onto the rotor by gravity. During operation, a certain amount of cooling medium is brought into the space and into contact with the rotor, which in the example is the warmest surface in the space, whereby at least part of the coolant vaporizes. The vapor condenses against the cold surface 31 and accumulates before running back down onto the rotor in order to be vaporized again. The result is effective heat transfer between the rotor and the cold surface. The casing 15 is further provided with an outer shell 32 of thermally insulating and sound-insulating material, resulting in a further stable thermal environment in the space 18 and a good acoustic characteristic of the separator.