WO2008111909A1

WO2008111909A1 - A particle separator

Info

Publication number: WO2008111909A1
Application number: PCT/SE2008/050274
Authority: WO
Inventors: Thomas Davidsson
Original assignee: Centriclean Systems Ab
Priority date: 2007-03-12
Filing date: 2008-03-12
Publication date: 2008-09-18
Also published as: SE0700640L; SE532661C2

Abstract

A particle separator with a centrifugal separator for separation of particles from a gas, said particles having a higher density than the gas, and said separator comprising: a rotor (24), a driving device (8) for rotation of the rotor (24) about s rotation axis (A), a housing (4) with a wall (1) that surrounds the rotor (24) a chamber (19) defined between an outer periphery of the rotor (24) and an inner periphery of the wall (1) of the housing (4), an outlet (15) of the rotor (24), a separating unit ( 13 with a plurality of separating passages (22), at least one inlet (5) for introduction of unclean gas into said chamber (19), said inlet (5) being situated in the wall (1) of said housing (4), wherein the centrifugal separator of the particle separator is arranged for a counter flow separation of dry and humid particles from the gas. The inlet (5) for introduction of unclean gas into the chamber (19) is arranged as a tangential cyclone inlet.

Description

A particle separator

The field of the invention

The present invention relates to a particle separator with a centrifugal separator for separation of particles from a gas, where the particles have a higher density than the gas. The particles may be dry or humid.

In particular the invention relates to a particle separator with a centrifugal separator for separation of particles from a gas, said particles having a higher density than the gas, and said separator comprising

• a rotor, that is rotatable about a rotation axis (A) and has an outlet for clean gas, the rotor having an inner space communicating with said outlet,

• a driving device for rotation of the rotor about the rotation axis,

• a housing with a wall that surrounds the rotor and the rotation axis, a chamber for reception of unclean gas being defined between an outer periphery of the rotor and an inner periphery of the wall of the housing,

• an outlet of the housing, arranged so as to permit cleaned gas gathered in the inner space of the rotor to leave the housing, and

• a separating unit with a plurality of separating channels, integrated in the rotor and arranged around the inner space of the rotor and with a plurality of separating passages, at one end communicating directly with the inner space of the rotor and at the other end communicating with the chamber, and

• at least one inlet for introduction of unclean gas into said chamber, said inlet being situated in the wall of said housing • wherein, the particle separator is arranged for a counter flow separation of dry and humid particles.

The term "counter flow" is referred to as when the flow of the separated particles and the gas flow have or are brought in opposite directions. According to the invention, gas and particles will enter the housing of the separator through the inlet provided in the separator wall, i.e. a wall arranged radially outside and adjacent the rotor of the separator. Since the rotor comprises a wall designed so as to permit gas to pass through it, but to prevent a vast majority of the particles from passing through it, the gas will move in a radial direction into the central space defined by the rotor, while the particles are thrown out from the rotor. Accordingly, a "counter flow" of gas and particles in opposite directions is obtained in the separating unit of the centrifugal separator thanks to the rotation of the rotor thereof, and thanks to the design of the separating channels provided therein.

Background of the invention and prior art

Different types of cyclones may be used as particle separators. They are commonly used since they are uncomplicated devices. The degree of purification is rarely over 85%, and therefore they are combined with stationary filters to separate the finest particles. Centrifugal separators are traditionally used mainly for the cleaning of liquids, or liquid droplets from gas. When the separator is used for cleaning of liquid droplets from gas it is a great advantage to have parallel flow separation, since the gas is sucked through the separating device without help from other equipment. A freestanding centrifugal separator is disclosed in WO02/34407. In the separator described therein unclean gas, i.e. gas contaminated with solid particles, is gathered inside the rotor, whereby larger particles will be subjected to a cyclone effect and separated from the gas, while smaller particles will follow the gas to a filter in which they are separated from the latter. However, this kind of separator does not operate in accordance with the counter flow principle.

Another centrifuge for separation is known from US 7.250.066. This separation device differs from the separator of the present invention in that it has an axial inlet, making it primarily adapted for the purpose of separating soot from an exhaust gas of an internal combustion engine. The suggested design of the device makes it unsuitable for separation of coarser particles, in particular due to the inline arrangement of the rotor/ centrifuge in relation to the gas inlet and outlet.

EP1785081 discloses another type of separator, in which no rotating part is used. The gas inlet is arranged tangentially in the mantle wall of a housing, from where the unclean gas is permitted to follow a helical path downwards in the housing and then a helical path upwards through a central cylinder, and out through an axial outlet at the end of said cylinder and further out of the housing.

SE 101 843 discloses a centrifugal particle separator in accordance with the preamble of the present application. Gas is introduced into a chamber between the outer periphery of a centrifugal rotor and the inner periphery of a housing from an inlet that seems to be directed in a radial direction, i.e. straight towards the centre of the device, where the rotor is located. However, if larger particles are introduced at high velocity into the chamber through the inlet, they might damage the rotor. There is also a possibility that particles introduced into the separator will be ejected back towards or even into the incoming flow of gas and particles to a relatively high degree, thereby disturbing the flow and effecting the separation in a negative manner.

The object of the invention

One object of the invention is to provide a particle separator that will not get clogged by the particles it is supposed to handle, such as is the case with centrifugal separators of prior art provided with conventional filters of, e.g., paper. These problems are most common when dust containing dry or semi dry particles is separated from a gas.

Another object of the invention is to provide a compact and efficient particle separator that needs a minimum amount of service, where there is a reduced need of separation filters or where no or reduced changing of filters is needed.

It is also an object of the present invention to present a particle separator that uses the principle of counter flow and which efficiently separates both finer and coarser particles from a gas.

Summary of the invention

The object of the invention is achieved by means of the initially defined particle separator, characterised in that the inlet for introduction of unclean gas into the chamber is arranged as a tangential cyclone inlet. Thereby, the flow of gas and particles, coarse as well as fine, will be guided along the inner periphery of the wall of the housing. The coarser particles may be separated due to the gravitational forces acting thereupon, and finer particles may follow the gas in a subsequent upwards motion to the centrifugal separator, in which they are separated from the gas.

Preferably the separating unit comprises a plurality of separating disks, distance elements being provided between said disks and delimiting a plurality of flow channels between each pair of disks. Preferably, the disks are conical.

According to one embodiment, the inlet points towards a bottom of the housing. Thereby, as a consequence of the directing thereof, the flow of gas and particles entering the chamber of the separator are guided downwards and prevented from further disturbing the flow at the inlet. A clearer cyclone-effect is achieved.

According to one embodiment, the inlet is located at an altitude below a lower end of the rotor. Thereby, particles carried by the gas entering the chamber are prevented from hitting the rotor as they are introduced into the chamber of the separator. However, the invention also includes alternative embodiments in which the only inlet, or one or more inlets among a plurality of such inlets, is/ are located at an altitude opposite to the region between two opposite axial ends of the rotor or, more precisely, the separating unit of the latter.

According to yet another embodiment, the separator comprises a guide rail extending from the inlet as a downwards sloping helix along a wall of the housing. Thereby, a further preferred guiding of the flow of gas and particles entering the chamber of the housing is achieved, and collisions between previously introduced and newly introduced particles are prevented.

According to a preferred embodiment, the inlet is arranged so as to direct incoming unclean gas such that the gas enters the separator with the same direction of rotation as the rotor.

It is also preferred that the channel of the inlet has a rectangular shape at the entrance of the housing. It should also be mentioned that, preferably, the outlet of the rotor is provided at an end of the rotor, preferably an upper end thereof. Preferably, the lower end of the rotor is closed, thereby preventing any significant entrance of gas or particles that way into the inner space of the rotor. The inner space of the rotor may be subdivided into two or more spaces, each one in communication with the outlet of the rotor. The inner space of rotor may also be defined as a central space, even though not necessarily provided in the absolute centre of the rotor. Preferably, the rotation axis of the rotor is also the central axis of the rotor. The gas outlet of the housing may either be an outlet through which the rotor itself extends out of the housing or an outlet that communicates with the outlet of the rotor. Preferably, the gas outlet of the housing is arranged in the same end of the separator as the one in which the end of the rotor is arranged. Preferably, the rotation axis of the rotor is other than horizontal, preferably generally vertical, and the outlet of the rotor, as well as the outlet of the housing, is provided in the region of an upper end of the rotor and housing respectively.

Preferably, the housing is stationary. Stationary in this context means that it is not rotating. According to the invention, the rotor, the driving unit and a cyclone function are integrated in the same stationary housing. The separation channels of the centrifugal separator will not get clogged since the separator is of a counter flow type where the gas flow goes from a big radius towards a smaller in the separating unit. Coarse particles will fall down along the inner periphery of the wall of the housing, and particles that are bigger than the separating channels might never clog the channels. Instead they are immediately leaving the rotor and are thrown against the wall of the receiving chamber. Further, the number of revolutions of the rotor is chosen to get, in each situation, an efficient separation, of about 99%.

A particle separator of the described kind is especially appropriate e.g. for separation of stone dust at rock drilling. The stone dust is guided by a tube to the cyclone inlet of the separator.

The dust particles separated from the gas are moving along the inner wall of the stationary housing and downwards and are collected in a suitable receptacle connected to the bottom of the separator. The rotor is suitably driven by an electric motor, but other alternatives are of course possible, such as turbine propulsion, hydraulic propulsion or jet propulsion (so called Heron propulsion).

Short description of the drawings

In the detailed description of the present invention reference will be made to the accompanying drawing, wherein, Fig 1 is a side view, partly in cross-section, of a separator according to a preferred embodiment of the invention, Fig. 2 is a further side view of the separator shown in fig. 1 , Fig. 3 is a top view of the separator shown in figs. 1 , and 2, with the cross-section taken in fig. 1 indicated, Fig. 4 is an exploded view of a separating unit of the separator shown in figs. 1-3, Fig. 5 is a cross section showing two adjacent elements of the separating unit of the separator, according to V-V in fig. 4, and Fig. 6 is a perspective view showing the separator according to figs. 1-

5.

Detailed description of the invention

A particle separator according to the invention is shown in figure 1. The separator comprises a stationary housing 4, comprising a cylindrical surrounding wall 1 , an engine support 3 supporting rubber dampers 7 that are attached to an engine plate 2, into which a driving device 8 is secured. The driving device 8 is driving a rotor 24. The rotor 24 has an axial end 10a that by means of spokes is connected to a hub part 10b, which is secured into the engine axis 9. Further, the rotor comprises an axially situated symmetrical rotation sealed end plate 12.

An inlet 5, preferably of a rectangular shape, is connected to the cylindrical surrounding wall 1 so that the flow of unclean gas hits a wall 14 in the lower part of the housing as tangential as possible and preferably in a somewhat inclined angle pointing downwardly in the figure. For achieving a pre separation in the best possible way, a guide rail 23 may be mounted in a downward helix, reaching from the wall 1 to the housing 4 and thereby forming a helix with the length of one turn. This construction ensures that the particles, on their second turn along the wall 14, under the pre separation not will collide with incoming gas from the inlet 5. According to the shown embodiment, a cyclone part is provided since the wall 14 is constructed as the lower part of a cone, in a well known way of constructing a cyclone.

Further, an independent cyclone may be constructed in a central part 20, separately from the housing 4 and the wall 14. Thereby, the inlet 5 leads directly into the built-in cyclone. Thereby, the conceived cyclone part and the centrifugal rotor part has a common collecting container 6 for separated particles. At its lower part the wall 14 has fastening means 21 for the collecting container 6 for out separated dust and particles. For certain kinds of abrasive particles, e.g. stone dust, the wall 1 and 14 should be coated with a resistant coating, of rubber for example. An outlet 15 for clean gas, which has left the rotor, is found under the engine plate 2.

Reference is now made to fig. 1 in combination with fig. 4. A separating unit 13 is situated between the axial end 10a and the end plate 12 of the rotor 24. In an internal, central space 17 for clean gas there is provided a wing-shaped axial element 26 (see fig. 4) which holds both ends 10a and 12 of the rotor 24, and centres the separating unit 13. Preferably, the wing- shaped axial element 26 comprises a plurality of conical separating disks 27, which between themselves have radially extending spacer elements 28 that delimit several flow channels 22 in a way known per se within this field of technology. The spacer elements 28 are formed by ribs attached to an outer surface of each disk 27. The disks 27 are arranged as a stack, thereby forming the functional part of a centrifugal separator that forms part of the particle separator. In other words, the inner space 17 is delimited by inner peripheries of the upper end part 10a, the lower end part 12, and the radially inner periphery of the stack of disks 27 arranged between said end parts 10a, 12. Fig. 5 is a cross section showing three adjacent disks 27. It should be understood that, for the sake of clarity, the number of disks shown in the figures are reduced.

For the purpose of ensuring that unclean gas will not pass from a chamber 19, delimited by the inner periphery of the housing and the outer periphery of the rotor 24, to the central space 17, without passing the flow channels 22, there is provided a gas sealing, e.g. a suitable slot, between an upper end plate of the housing 4 and the axial end 10a of the separating unit 13.

Apart from the elements mentioned above, the separator according to the invention also comprises a collecting container 6 provided below the housing 4. Moreover it comprises support members, formed by legs 29, for keeping the separator in an upright operational position. In the operational position, the rotational axis A of the rotor 24 is vertical. There is also provided a fan 30 connected to and driven by the driving device 8. The fan 30 is provided downstream an outlet 16 of the rotor and upstream an outlet 15 of the housing 4, as seen in the flow direction of the clean gas.

The operation of the particle separator is as follows.

The rotor 24 is driven by the driving device 8, preferably a frequency controlled electric engine, or other driving devices mentioned above. The rotor is secured to the axis 9 of the driving device and uses the bearing of the driving device to rotate. Unclean gas that shall be cleaned from particles is guided into the gas inlet 5 with an appropriate flow rate. The particles in the gas are thereby forced up against the wall 14 by the centrifugal forces being the result of the particles being forced to rotate in a helically shaped orbit downwards into the collecting container 6. The gas is thereby pre separated and contains no bigger particles. The gas is moving upwardly through a central part of the inner volume of the housing 4 and further up into the chamber 19. The gas is partly cleaned and contains, at this stage, smaller particles.

The partly cleaned gas is flowing into the flow channels 22 of the separating unit 13, which is rotated by the rotor 24. The particles that remain in the gas and that have a density higher than that of the gas is now separated by the generated centrifugal forces. If the separating unit 13 is constructed by conical separating disks, as is the case here, the particles will get into contact with the conical surface of the disks. The particles are forced into the boundary layer and slide, out in the opposite direction, from the gas flowing inwards. The particles are travelling further away from the rotor 24 and hitting the wall 1 , and moving in helical path downwardly as seen in fig. 1. They are flocculated. The particles are getting mixed with the initially separated, bigger particles from the inlet 5 and are collected in the collecting container 6.

In another embodiment of the invention the gas inlet is placed at the same altitude as the rotor 24, whereby the first out separated bigger particles that are moving in the helical shaped orbit downwardly, are helping the surrounding wall 1 to get free from the smaller particles, secondary out separated from the separating unit 13. These smaller particles have a tendency to adhere on all surfaces, among others due to that they are electrically charged.

When the gas is finally cleaned and has passed the separating unit 13 and has reached the central space 17, it continues through the passage 16 and leaves the particle separator through the outlet 15. It should be understood that the above description of an embodiment of the invention is only exemplifying, and that the claimed scope of protection is defined by the annexed claims, supported by the description and the drawing.

Claims

PATENT CLAIMS

1. A particle separator with a centrifugal separator for separation of particles from a gas, said particles having a higher density than the gas, and said separator comprising

• a rotor (24), that is rotatable about a rotation axis (A) and has an outlet (16) for cleaned gas, the rotor having an inner space (17) communicating with said outlet (16),

• a driving device (8) for rotation of the rotor (24) about the rotation axis (A),

• a housing (4) with a wall (1) that surrounds the rotor (24) and the rotation axis (A), a chamber (19) for reception of unclean gas, said chamber (19) being defined between an outer periphery of the rotor (24) and an inner periphery of the wall (1) of the housing (4),

• an outlet (15) of the housing (4), arranged so as to permit cleaned gas gathered in the inner space (17) of the rotor (24) to leave the housing (4), and

• a separating unit (13) with a plurality of separating channels, integrated in the rotor (24) and arranged around the inner space (17) of the rotor (24) and with a plurality of separating passages (22), at one end communicating directly with the inner space (17) of the rotor (24), and at the other end communicating with the chamber (19), • at least one inlet (5) for introduction of unclean gas into said chamber (19), said inlet (5) being situated in the wall (1) of said housing (4),

• wherein the centrifugal separator of the particle separator is arranged for a counter flow separation of dry and humid particles from the gas, characterised in that the inlet (5) for introduction of unclean gas into the chamber (19) is arranged as a tangential cyclone inlet.

2. A particle separator according to claim 1 , characterised in that the separating unit (13) comprises a plurality of separating disks, distance elements being provided between said disks and delimiting a plurality of flow channels (22) between each pair of disks.

3. A particle separator according to any one of claims 1-2, characterised in that the inlet (5) points towards a bottom of the housing (4).

4. A particle separator according to any one of claims 1-3, characterised in that the inlet (5) is located at an altitude below a lower end (12) of the rotor (24).

5. A particle separator according to any one of claims 1-4, characterised in that it comprises a guide rail (23) extending as a downwards sloping helix along a wall (14) of the housing (4)

6. A particle separator according to any of the preceding claims, characterised in that the inlet (5) is arranged so as to direct incoming unclean gas such that the gas enters the separator with the same direction of rotation as the rotor (24).

7. A particle separator according to any of the preceding claims, characterised in that, under operational conditions, the pressure by means of which the unclean gas is driven through the inlet (5) is higher than the atmospheric pressure, said pressure being sufficient to drive the gas in a counter flow direction through the separating unit (13) and further through the outlet (15).

8. A particle separator according to any of the preceding claims, characterised in that the inlet (5) has a rectangular channel shape at the entrance of the housing (4) .