EP3463674A1

EP3463674A1 - Cyclone for the separation of particles from a fluid

Info

Publication number: EP3463674A1
Application number: EP17726940.4A
Authority: EP
Inventors: Michael Missalla; Robert MADUTA; Isabella Vandermaelen; Linus PERANDER; Torsten Liebmann
Original assignee: Outotec Finland Oy
Current assignee: Outotec Finland Oy
Priority date: 2016-06-01
Filing date: 2017-05-31
Publication date: 2019-04-10
Anticipated expiration: 2037-05-31
Also published as: BR112018074331B1; UA122721C2; EP3463674B1; DE202016102924U1; BR112018074331A2; CN109311035B; AU2017272681B2; CA3025587A1; AU2017272681A1; WO2017207606A1; CA3025587C; CN109311035A

Abstract

The invention is directed to a cyclone (1) for the separation of solid particles and/or at least one liquid from a fluid. One ramp (10a) is arranged at the housing cap (5) and/or at an upper wall (9) of the feed channel (7), wherein the slope of the at least one ramp (10a) is in a range of 15° to 60°.

Description

Cyclone for the separation of particles from a fluid

The invention relates to a cyclone for the separation of solid particles and/or at least one liquid from a fluid. The cyclone comprises a housing, an inlet opening for introducing the fluid together with the solid particles and/or the at least one liquid into the housing, a discharge port for the solid particles and/or the at least one liquid, a housing cap which is arranged opposite to the discharge port, a dip tube (immersion tube) being provided in the housing cap (cover) for discharging fluid from the housing and a feed channel which opens out into the inlet opening in the housing for introducing the fluid together with the solid particles and/or the at least one liquid into the housing. Typically, the fluid is a gas stream or, in the case of hydrocyclones, a liquid stream. For most different kinds of applications such as for example a circular fluid bed combustion (CFB combustion), calcining, oil recovery and for other processes it is necessary to remove and/or separate solids or liquids from hot flue gases or product gas mixtures which contain these solids or liquids, before feeding the gas into the next stage of purification, such as for example an electrical precipi- tator (ESP), for fulfilling environmental or in particularly product specifications.

For these processes, typically, gas cyclones are used for filtering out particulate solids from the hot flue gas or from the product gas mixture. But such cyclones are also used in steam power plants for separating water from live steam be- tween the steam generator and the turbine or for condensate separation in gas coolers. With hydrocyclones solid particles which are contained in suspensions can be separated or classified. Therewith also emulsions such as for example oil-water mixtures are resolved. In the different application fields, in principle, the mode of operation of these centrifugal separators is the same. The fluid together with the solids or liquids contained therein is fed from the fluid source via the feed channel into the housing of the cyclone. In the interior of the cyclone the main portion of the volume stream of the fluid (about 90 %) is forced as a main stream onto a helical path, so that due to the centrifugal force the particles to be separated are thrown towards the wall of the housing. This results in the fact that the particles are separated from the stream and fall or flow downwards into the direction of the discharge port. The fluid being purified by removal of the particles exits the cyclone, for example, through a vortex finder in the form of a dip tube.

A secondary stream which amounts to about the residual 10 % of the total volume stream flows through the interface of cap/dip tube directly into the dip tube. In the region of the housing cap opposite to the discharge port a low energy zone is formed in which no efficient separation of the particles takes place. Therefore, the particles are accumulated in this region and, in addition, due to the low pressure in the region of the inner vortex they can be drawn into the direction of the dip tube. Therefore, these particles exit the cyclone through the gas outlet and not, as desired, through the discharge port. Thus, the separation efficiency of the cyclone is considerably compromised.

In the case of older cyclones the feed channel is characterized by a relatively high length. While the fluid flows through such a long feed channel, through the influence of gravitation the particles travel into the direction of the lower wall of the feed channel. So the accumulation of particles in the low energy zone near the housing cap is reduced. But due to their size (length) such feed channels have a very high weight, take up much space and are extremely expensive.

In the case of more modern cyclones the design of the feed channel is shorter and smaller for saving space and costs. But, since the residence time of the fluid in the feed channel is considerably shorter, the particles are not allowed to sufficiently move into the direction of the lower wall of the feed channel. Therefore, the particles are also introduced into the housing of the cyclone directly at the housing cap, and so it is possible that they are accumulated in the low ener- gy zone and compromise the separation efficiency.

A modification of the feed channel is known from US 6,322,601 B1 . An inclined protrusion is provided at the upper wall of the feed channel and extends along the whole length (5 m) and the whole width of the feed channel. The slope of the protrusion is < 20 %, wherein its height from the inner wall to the outer wall of the feed channel decreases. Through this design the particles should be carried off downwards and the separation through gravitation should be supported. The problem of the accumulation of particles in the low energy zone near the housing cap is not addressed. Due to the low slope, with the protrusion it can also not be prevented that the particles are accumulated in the low energy zone near the housing cap and that they compromise the separation efficiency.

Document DE 26 47 486 A1 discloses a hydrocyclones in which the feed channel starts external from the sorting tube and continues in spiral form into the interior of the hydrocyclone. The gas stream introduced through the feed channel is thus guided in the upper annular space tangentially towards the dip tube. This, however, creates the problem that the particles/liquid are guided to the dip tube, accumulate in the boundary layer and may leave the cyclone without separation from the gas stream following the wall of the immersion tube.

Therefore, it is the object of the present invention to provide a cyclone which is characterized by a space-saving design, low production costs and a high separation efficiency. The above object is solved by a cyclone having the features according to claim 1 . The cyclone according to the present invention for the separation of solid particles and/or at least one liquid from a fluid comprises a housing, a discharge port for the solid particles and/or the at least one liquid, a housing cap which is arranged opposite to the discharge port and an inlet opening in the housing. Through the inlet opening in the housing the fluid together with the solid particles and/or the at least one liquid can be introduced into the housing. For that the cyclone is equipped with a feed channel which opens out into the inlet opening in the housing and which may connect the inlet opening with the source of the fluid, such as for example with a blast furnace, fluidized-bed furnace or the like. According to the present invention the cyclone comprises at least one ramp which is arranged at the housing cap and/or at an upper wall of the feed channel, wherein the slope of the at least one ramp is in a range of 15° to 60°, preferably between 25° and 45°, particularly preferably between 20° and 40° and in particularly about 30°.

The relative directions 'upper' and 'lower' are defined by the orientation of the cyclone housing. "Upper" is the side of the cyclone at which the housing cap can be found, while Jower" is defined by the position of the discharge port. In the case of a typical orientation of the cyclone, thus, the downward direction (top down) is identical with the direction of gravitation, because so the particles fall into the direction of the discharge port.

In principle, the shape of the at least one ramp is not restricted, and therefore it may comprise for example steps, rims and/or corrugations. The ramp may be characterized by a continuously rising height, with or without regions of constant height. The slope of the ramp results from the quotient of the maximum height and the length of the ramp. Due to the slope of the ramp according to the present invention the fluid together with the particles is deflected in an efficient manner. The ramp, in particular, directs the particles into a zone of the cyclone in which the distance from the ceiling is higher than the half of the height of the inlet opening. In this zone the particles can efficiently be separated from the fluid. With the ramp according to the present invention at the upper wall of the feed channel the particles are deflected in downward direction, that is into the direction of a lower wall of the feed channel. Therefore, they reach the housing of the cyclone already with a higher distance from the housing cap and with a velocity vector having a component in downward direction. So, in particular, in the sec- ondary stream the contained particles are depleted so that they in great part do not reach the low energy zone near the housing cap.

According to the invention, the ramp ends before reaching the immersion tube. This ensures that the loaded gas stream separates from the wall and is fully exposed to the separation effect of the cyclone.

Due to the ramp according to the present invention at the housing cap particles which are trapped in the low energy zone near the housing cap and circulate in the housing of the cyclone are deflected downwards into a region in which they can be separated from the fluid. The particles gain a velocity component in downward direction and a velocity component in rotation direction. Therefore it is possible to guide all particles onto a helical path in downward direction to the discharge port for the solid particles and/or the at least one liquid. So the separation efficiency is considerably improved. The ramp guides the particles below a certain (imagined) line defined by the thickness of the boundary layer at the housing cap. This prevents that the particles accumulate in the boundary layer and leave the cyclone along the housing cap and the dip tube without separating from the gas stream. The separation efficiency of the cyclone can be improved significantly. As no turbulences are created, the pressure loss in the cyclone is not influenced. According to the present invention it is also possible to provide at the upper wall of the feed channel and/or at the housing cap more than one ramp each. In a preferable embodiment of the invention the feed channel is tangentially arranged at the housing and the ramp at the upper wall of the feed channel rests against the inner wall of the feed channel. By the tangential arrangement of the feed channel an inner wall and an outer wall of the feed channel are defined. The inner wall is that side which has a smaller tangential distance to the center of the cyclone housing. In the case of an arrangement shifted to the left (with respect to the direction of the fluid stream in the feed channel) of the feed channel at the housing of the cyclone which results in a clockwise circulation, thus, the right wall (with respect to the direction of the fluid stream in the feed channel) is the inner wall of the feed channel. In the case of an arrangement shifted to the right of the feed channel which results in an anti-clockwise circulation, the left wall of the feed channel is the inner wall. The wall which is arranged opposite each is the outer wall of the feed channel.

In a preferable embodiment of the invention the length of the at least one ramp at the upper wall of the feed channel is shorter than the length of the feed channel, preferably between 5 and 80 % of the length of the feed channel, particularly preferably between 20 and 50 % of the length of the feed channel, and in particular the ramp extends along about 20 %, 30 %, 40 % or 50 % of the length of the feed channel. The uniform cross-section of the feed channel before the start of the ramp results in synchronizing of the fluid flow in the feed channel and reducing of turbulences so that the flow guidance can be controlled by the ramp and can be achieved with better efficiency and less particles reach the low energy zone. With a short ramp, in addition, in the case of a given length of the feed channel, material and weight can be saved which results in lower costs and in a simpler ability to retrofit already existing plants. In a particularly preferable embodiment of the invention the ramp at the upper wall of the feed channel extends up to the inlet opening of the housing. According to that the ramp starts in the feed channel and ends for example at the posi- tion of the inlet opening. Accordingly, the ramp is not positioned in the center, but at the end of the feed channel. So the particles are deflected downwards directly before the inlet opening of the housing, which results in a particularly effective prevention of an accumulation of particles in the low energy zone. In a preferable embodiment of the invention the at least one ramp may have a design of a wedge. The arrangement of the ramp is chosen such that the ramp in the direction of the inlet opening of the housing becomes higher. A ramp having the shape of a wedge has a particularly simple design and, therefore, can be produced very cost-effective.

In a particular embodiment of the invention the at least one ramp may have a concave design, wherein the slope of the ramp in the direction of the inlet opening of the housing increases. In the case of such a ramp, besides the height, the length and the width, also the radius of curvature of the ramp can be varied. With this additional parameter the flow of the fluid can be optimized in a particularly effective manner.

In a further embodiment of the invention the at least one ramp has a maximum height which corresponds to 10 to 60 %, preferably 25 to 50 % of the height of the feed channel. In particular, it is smaller than 50 %, preferably smaller than 40 %, particularly preferably smaller than 30 % of the height of the feed channel. So the cross-section through which the fluid flows is not narrowed too much, and it is prevented that in the fluid too high velocities are achieved which would result in a higher pressure loss across the cyclone. In a particular embodiment of the invention the at least one ramp at the upper wall of the feed channel does not extend along the whole, but preferably only along 20 to 60 %, particularly preferably 25 to 50 % of the width of the feed channel. In particular, it has a width which is smaller than 50 %, preferably smaller than 40 %, particularly preferably smaller than 30 % of the width of the feed channel. A ramp with this width can already be sufficient for diverting the fluid such that no particles can be accumulated in the low energy zone. At the same time, the cross-section of the feed channel through which the fluid flows is not narrowed too much. In an alternative, the ramp may be allowed to extend across the whole width of the feed channel. Such a ramp arrangement can be manufactured in a particularly simple manner.

In a particular embodiment of the invention the ramp at the housing cap may rest against an outer wall of the housing. The deflection of the circulating fluid in the region near the outer wall of the housing results particularly effectively in the fact that the particles are removed from the low energy zone.

In a further embodiment of the invention the ramp at the housing cap may have a curved design. In such a case, the curvature of the ramp may be adjusted to the curvature of the outer wall of the housing. A ramp which is adjusted such prevents that between a round outer wall and a ramp vortexing takes place, which may have a negative influence onto the flow in the cyclone.

In a further embodiment of the invention the ramp at the housing cap may have a width which corresponds to 20 to 80 %, preferably 40 to 60 % of the distance between the outer wall of the housing and the dip tube. In particular, it is smaller than 60 %, preferably smaller than 50 %, particularly preferably smaller than 40 % of the distance between the outer wall and the dip tube. A ramp having this width is sufficient for removing the particles from the low energy zone without reducing the cross-section through which the fluid flows too strong which would negatively affect the circulation movement.

In a further embodiment of the invention in the feed channel and also at the housing cap a ramp is arranged each, wherein it is possible that these ramps are connected via a, preferably cuboidal, connecting element. By providing both ramps, the above described advantages can be combined. The connecting element prevents a quick expansion of the flowing fluid which would result in the fact that particles again may end up in the low energy zone.

Preferably, the ramp adjoining the inner wall of the feed channel effects the particles traveling at the inner path while the ramp at the housing cap adjoining the outer wall of the housing effects the particles traveling at the outer path. Thereby, the complete boundary layer is separated from the housing cap so that no undesired particle extraction from the cyclone is effected via the boundary layer and the dip tube.

In this case it is possible that the feed channel and the housing cap are characterized by a geometric, in particularly vertical displacement, so that also the respective ramps may be characterized by a geometric, in particularly vertical displacement.

The design according to the present invention provides for improving the separation efficiency of the cyclone by 10 to 20%.

In the following the invention is explained in more detail with the help of embodiment examples with reference to the figures in which the subject matter of the invention is schematically shown. Here, all described and/or depicted features form on its own or in arbitrary combination the subject matter of the invention, independently from their summary in the patent claims or their back references. Fig. 1 a shows a longitudinal section of a cyclone according to a first embodiment;

Fig. 1 b shows the cyclone of Fig. 1 a from above with removed cap;

Fig. 1 c shows a section through the inlet opening of the cyclone of Fig. 1 a;

Fig. 2a shows a view analogous to Fig. 1 a of a cyclone according to a second embodiment;

Fig. 2b shows a view analogous to Fig. 1 b of the cyclone of Fig. 2a;

Fig. 2c shows a view analogous to Fig. 1 c of the cyclone of Fig. 2a;

Fig. 3a shows a view analogous to Fig. 1 a of a cyclone according to a third embodiment;

Fig. 3b shows a view analogous to Fig. 1 b of the cyclone of Fig. 3a;

Fig. 3c shows a view analogous to Fig. 1 c of the cyclone of Fig. 3a;

Fig. 4a shows a view analogous to Fig. 1 a of a cyclone according to a fourth embodiment;

Fig. 4b shows a view analogous to Fig. 1 b of the cyclone of Fig. 4a;

Fig. 4c shows a view analogous to Fig. 1 ac of the cyclone of Fig. 4a; Fig. 5a shows a view analogous to Fig. 1 a of a cyclone according to a fifth embodiment;

Fig. 5b shows a view analogous to Fig. 1 b of the cyclone of Fig. 5a;

Fig. 5c shows a view analogous to Fig. 1 c of the cyclone of Fig. 5a;

Fig. 6a shows a view analogous to Fig. 1 a of a cyclone according to a sixth embodiment;

Fig. 6b shows a view analogous to Fig. 1 b of the cyclone of Fig. 6a;

Fig. 6c shows a view analogous to Fig. 1 c of the cyclone of Fig. 6a;

Fig. 7a shows a view analogous to Fig. 1 a of a cyclone according to a seventh embodiment;

Fig. 7b shows a view analogous to Fig. 1 b of the cyclone of Fig. 7a;

Fig. 7c shows a view analogous to Fig. 1 c of the cyclone of Fig. 7a.

The basic construction of a cyclone 1 as is used for the separation of solids or liquids from a fluid stream is schematically shown in Fig. 1 a. The cyclone 1 according to the present invention of Fig. 1 a comprises a cylindrical upper housing part 2 and a conical lower housing part 3. The cylindrical housing part 2 and the conical housing part 3 together form the housing 2, 3 of the cyclone 1 , i.e. the cyclone housing 2, 3. The upper end of the cyclone housing 2, 3 is closed with a housing cap 5. A dip tube or vortex finder 12 is inserted in a central opening of the housing cap 5 so that the dip tube 12 extends partially outside and partially inside the cyclone housing 2, 3. A feed channel 7 is connected with its first end with an inlet opening 6 in the cylindrical housing part 2 of the cyclone 1 . With the second end the feed channel 7 may, for example, be connected with the discharge opening of a blast furnace/a fluidized bed. The inlet opening 6 and the feed channel 7 which is directly placed thereon are arranged at the upper end of the cylindrical housing part 2. Preferably, in this case the upper wall 9 of the feed channel 7 and the housing cap 5 are arranged in a coplanar manner. Typically, the cyclone 1 is arranged such that the conical housing part 3 is oriented downwards into the direction of the gravitational field. At its lowest point the discharge port 4 is provided through which the particles and/or the liquid which has been extracted from the fluid stream can be discharged.

During operation the fluid stream together with the particles is fed through the feed channel 7 and the inlet opening 6 into the housing part 2. This, typically, is effected in a tangential manner (cf. Fig. 1 b) so that a circular movement of the fluid stream is induced. The fluid stream moves on a helical path from the inlet opening 6 into the direction of the conical region 3. Due to the centrifugal force the particles are transported to the outer wall of the cyclone 1 and there, by the effect of gravitation, they move into the direction of the discharge port 4. The purified gas or, in the case of a hydrocyclone, the purified liquid exits the cy- clone 1 upwards through the dip tube 12.

In the case of the depicted embodiment in the feed channel 7 a first ramp 10a and in the interior of the cyclone housing 2, 3 a second ramp 1 1 a through which the fluid stream is diverted are provided. The first ramp 10 is arranged at the upper wall 9 of the feed channel 7 and has the shape of a wedge. The second ramp 1 1 a is arranged at the housing cap 5 and has the same height as the first ramp 10a. The ramps 10a, 1 1 a are connected via a, for example cuboidal, connecting element 14, wherein between them, in particular, no gap or platform/shoulder is provided. The first ramp 10a in the interior of the feed channel 7 extends along about one third of the length of the feed channel 7 and rests against the inner wall 8 of the feed channel 7. The height of the ramp 10a is about 45 % of the height of the feed channel 7 (based on the free inner cross-section of the feed channel 7). The width of the ramp 10a is about 50 % of the width of the feed channel 7 (cf. Fig. 1 b). The first ramp 10a begins starting from the second end of the feed channel 7 in the second half of the feed channel 7 and extends up to the first end of the feed channel 7 at the inlet opening 6 of the cyclone housing 2, 3. The second ramp 1 1 a is arranged such that it rests against the outer wall 13 of the cylindrical housing part 2 of the cyclone 1 . In addition, the ramp 1 1 a has a curved design so that it is adjusted to the round shape of the outer wall 13 of the cylindrical housing part 2 of the cyclone 1 .

Fig. 1 c shows that both, the second ramp 1 1 a and also the first ramp 10a, have the shape of a wedge with an angle of slope of about 30° each, wherein the height of the ramp 1 1 a increases into the direction of the inlet opening 6.

During operation a gas stream, for example from a blast furnace, together with solid particles contained therein is fed into the feed channel 7. The gas stream flows along the feed channel 7 into the direction of the cyclone housing 2, 3 (in the view of Fig. 1 a from the left side to the right side), and in the upper region of the feed channel 7 it is deflected downwards at the first ramp 10a so that it enters the cylindrical housing part 2 in a distance to the housing cap 5 which at least corresponds to the height of the first ramp 10a. With this redirection at the first ramp 10a a part of the gas and some particles, in addition, are provided with a velocity component in downward direction which supports the transport of the particles into the direction of the discharge port and prevents that the particles enter the low energy zone 15 in the upper region of the cyclone 1 near the housing cap 5. With the tangential arrangement of the feed channel 7 in the cylin- drical housing part 2 a circular movement is initiated which through the centrifu- gal forces results in the separation of the particles from the gas stream. Particles which nevertheless have entered the low energy zone 15 near the housing cap 5 circulate around the dip tube 12. Due to the second ramp 1 1 a at the housing cap 5 these particles are deflected downwards and so they enter a region in which the particles can efficiently be separated from the gas stream. Hence, an accumulation of particles in the low energy zone 15 is prevented. Then the gas stream moves downwards, in large part on a helical path, into the conical housing part 3, wherein during the transport the particles are separated from the gas stream. Then, the purified gas stream exits the cyclone 1 through the dip tube 12.

The Fig. 2a to 2c show a second embodiment of the invention in views which are equivalent to the figures 1 a to 1 c. For the sake of simplicity in the following figures only the differences with respect to the first and/or the preceding embod- iments are described each. For the same elements the same reference signs (optionally with indices a-f for the first to sixth embodiments) are used and reference is made to their preceding description.

The embodiment of the Fig. 2a to 2c is characterized by an alternative arrange- ment of the ramp. As can be seen in Fig. 2a, the first ramp 10b in the feed channel 7 already reaches its maximum height before the inlet opening 6 of the cyclone housing 2, 3. The ramp 10b extends in a, preferably cuboidal, section 16 with constant height up to the inlet opening 6. The length of the first ramp 10b is about 60 % of the length of the feed channel 7. The second ramp 1 1 b does not differ from the second ramp 1 1 a of the first embodiment of the Fig. 1 a to 1 c.

In the case of the third embodiment of the Fig. 3a to 3c the ramp 10c extends along the whole width of the feed channel 7 (cf. Fig. 3b). The characteristic profile of the height of the ramp 10c is identical with that of ramp 10b according to the embodiment of the Fig. 2a to 2c.

In the case of the fourth embodiment of the Fig. 4a to 4c the ramp 10d is char- acterized by a particularly small design so that its width corresponds only to one third of the width of the feed channel 7. Apart from that, the ramp 10d has a similar design as the ramp 10b according to the second embodiment.

In the case of the fifth embodiment of the Fig. 5a to 5c both, the ramp 10e and also the ramp 1 1 e, have a design of a concave ramp. The concave ramps 10e, 1 1 e do not have a constant slope, but a slope which increases into the direction of the inlet opening 6 in the housing 2, 3 each. Here, the lengths and the widths of the ramps 10, 1 1 correspond to those of the embodiment of the Fig. 1 a to 1 c. In the case of the sixth embodiment of the Fig. 6a to 6c the cyclone 1 only comprises one ramp 10f in the feed channel 7, while the second ramp 1 1 at the housing cap 5 was omitted.

In the case of the seventh embodiment of the Fig. 7a to 7c the cyclone 1 is characterized by a geometric displacement between feed channel 7 and housing cap 5. Accordingly, also the ramps 10g, 1 1 g may be characterized by a geometric displacement to each other, which is a vertical displacement here.

It is a matter of course that the shown variants of the first and second ramps 10a-g, 1 1 a-g according to the first to seventh embodiments can arbitrarily be combined with each other. List of reference signs

1 cyclone

2 cylindrical housing part

3 conical housing part

4 discharge port

5 housing cap

6 inlet opening

7 feed channel

8 inner wall of the feed channel

9 upper wall of the feed channel

10a-g ramp in the feed channel

1 1 a-e, g ramp in the housing

12 dip tube

13 outer wall of the housing

14a-e, g connecting element

15 low energy zone

16b-d, f. g cuboidal section

Claims

Patent claims:

1 . A cyclone for the separation of solid particles and/or at least one liquid from a fluid with a housing (2, 3),

an inlet opening (6) for introducing the fluid together with the solid particles and/or the at least one liquid into the housing (2, 3),

a discharge port (4) for the solid particles and/or the at least one liquid, a housing cap (5) being arranged opposite to the discharge port (4), a dip tube (12) being provided in the housing cap (5) for discharging the fluid from the housing (3), and

a feed channel (7) which opens out into the inlet opening (6) in the housing (2, 3) for introducing the fluid together with the solid particles and/or the at least one liquid into the housing (2, 3), characterized in that at least one ramp (10a-g; 1 1 a-e, g) is arranged at the housing cap (5) and/or at an upper wall (9) of the feed channel (7), wherein the slope of the at least one ramp (1 Oa-g; 1 1 a-e, g) is in a range of 15° to 60°, pref- erably between 25° and 45°, particularly preferably about 30°.

2. The cyclone according to claim 1 , characterized in that the feed channel (7) is arranged at the housing (2, 3) in a tangential manner and that the at least one ramp (1 Oa-g) at the upper wall (9) of the feed channel (7) adjoins to an inner wall (8) of the feed channel (7).

3. The cyclone according to claim 1 or 2, characterized in that the ramp (10a-g) at the upper wall (9) of the feed channel (7) extends along 5 to 80 %, preferably between 20 and 50 % of the length of the feed channel (7).

4. The cyclone according to claim 3, characterized in that the at least one ramp (1 Oa-g) at the upper wall (9) of the feed channel (7) extends up to the inlet opening (6) of the housing (2, 3).

5. The cyclone according to one of the preceding claims, characterized in that the at least one ramp (1 Oa-d, f, g; 1 1 a-d, g) has the shape of a wedge in at least certain regions and narrows the cross-section of the feed channel (7) into the direction of the inlet opening (6) of the housing (2, 3).

6. The cyclone according to one of the preceding claims, characterized in that the at least one ramp (10e; 1 1 e) has a concave shape in at least certain regions and that the slope of the ramp (10e; 1 1 e) into the direction of the inlet opening (6) of the housing (2, 3) increases.

7. The cyclone according to one of the preceding claims, characterized in that the at least one ramp (10; 1 1 ) comprises steps or corrugations in at least certain regions or other height displacements in certain sections.

8. The cyclone according to one of the preceding claims, characterized in that the at least one ramp (1 Oa-g; 1 1 a-e, g) has a maximum height which corresponds to 10 to 60 %, preferably between 25 and 50 % of the height of the feed channel (7).

9. The cyclone according to one of the preceding claims, characterized in that the at least one ramp (10a, b, d-g) at the upper wall (9) of the feed channel

(7) has a width which is smaller than the width of the feed channel (7), preferably 20 to 60 %, particularly preferably 25 to 50 % of the width of the feed channel (7), or that the ramp (10c) extends along the whole width of the feed channel (7).

10. The cyclone according to one of the preceding claims, characterized in that the ramp (1 1 a-e, g) at the housing cap (5) rests against an outer wall (13) of the housing (2, 3).

1 1 . The cyclone according to one of the preceding claims, characterized in that the ramp (1 1 a-e, g) at the housing cap (5) has a curved design, wherein the curvature of the ramp (1 1 a-e, g) is adjusted to the curvature of the outer wall of the housing.

12. The cyclone according to one of the preceding claims, characterized in that the ramp (1 1 a-e, g) at the housing cap (5) has a width which corresponds to 20 to 80 %, particularly preferably 40 to 60 % of the distance between the outer wall (13) of the housing (2, 3) and the dip tube (12).

13. The cyclone according to one of the preceding claims, characterized in that one ramp (10a-g) is arranged in the feed channel (7) and one ramp (1 1 a-e, g) is arranged at the housing cap (5).

14. The cyclone according to claim 13, characterized in that the ramps (10a- e, g; 1 1 a-e, g) are connected via a preferably cuboidal connecting element (14).

15. The cyclone according to claim 13, characterized in that the feed channel (7) is characterized by a geometric displacement with respect to the housing cap (5) and/or that the ramps (10g; 1 1 g) are characterized by a geometric dis- placement to each other.