WO2017191242A1

WO2017191242A1 - Cyclone and dip tube for separating a gas

Info

Publication number: WO2017191242A1
Application number: PCT/EP2017/060624
Authority: WO
Inventors: Eugen WEISSENBURGER; Robert MADUTA; Linus PERANDER
Original assignee: Outotec (Finland) Oy
Priority date: 2016-05-04
Filing date: 2017-05-04
Publication date: 2017-11-09
Also published as: AU2017260663A1; UA138563U; DE202016102385U1; CN209663527U; RU191344U1; AU2017101842A4; AU2017260663A2; BR212018072086U2

Abstract

The invention relates to a dip tube (2) for withdrawing a gas stream from a cyclone (1). During operation the gas flows into the dip tube (2) via a gas inlet (8) and flows out again via a gas outlet (9). The dip tube (2) comprises a first region being designed as a nozzle which convergently tapers from an inner nozzle diameter to a smallest inner diameter, and the dip tube (2) comprises a second region through which during operation downstream the first region gas flows and which is designed as a diffusor which convergently tapers from an inner diffusor diameter in the direction of the first region to the smallest inner diameter. The nozzle has the geometry of a lateral surface being rotationally symmetric with respect to an axis in the form of a truncated cone, wherein the included angle between the lateral surface and the axis is between 1° and 88°.

Description

Cyclone and dip tube for separating a gas

The invention relates to a dip tube for withdrawing a gas from a cyclone, wherein the gas during operation flows into the dip tube via a gas inlet and flows out again from the dip tube via a gas outlet. Further, the invention relates to a cyclone for separating solid particles and/or at least one liquid from a gas stream comprising a housing, an opening in the housing for introducing the gas stream 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 liquid and at least one dip tube according to the present invention for withdrawing gas from the housing.

For most different kinds of applications such as for example a circular fluid bed combustion (CFB combustion), the calcining, oil recovery and for other processes it is necessary to remove and/or separate solids from hot flue gases or prod- uct gas mixtures which contain these solids, before feeding the gas into the next and/or the last stage of the purification, such as for example an electrical precipitator (ESP) for fulfilling environmental or in particularly product specifications.

Typically, in the field of application of these processes gas cyclones are used for filtering out solids in the form of particles from the hot flue gas or the product gas mixture. Such cyclones are also used in steam power plants for separating water from live steam between the steam generator and the turbine or for condensate separation in gas coolers. A lot of important parameters which are relevant for the function and the performance of such a cyclone have already been examined in a sufficient extent. These parameters comprise the pressure, the temperature, the velocity and the particle load of the gas as well as also the geometric construction of the cyclone. Here, in particular, the cover plate or the cap, respectively, of the cyclone, the dip tube which is also referred to as vortex finder and the discharge port are of relevance for the discharge of the solid particles.

One disadvantage of a cyclone, compared with other technologies for the sepa- ration of solids and gases, is the relatively low efficiency of this kind of separation, in particularly in the case of very fine particles having a size of smaller than 10 μιτι. The efficiency for particles with this size is mostly limited to 90 to 95 % or even lower. Since the end of the 19th century a lot of investigations have been made for determining the influence of single operating parameters and/or geometric parameters onto the separation efficiency of the gas cyclone.

This efficiency is influenced by a series of parameters such as for example the particle load and the particle size. Also the gas velocities within the cyclone and its subcomponents have a decisive influence onto the performance of the cyclone. The single gas velocities in the subcomponents of the cyclone are directly influenced by the geometry of these parts of the cyclone. In addition, the inner constituents of the cyclone, such as for example the dip tube (vortex finder), the apex (cone-shaped lower tip), the form of the inlet duct, aeration, etc., directly influence the dust entrainment and the separation efficiency.

For fulfilling different industrial requirements, in addition, there are different designs of the cyclones (vertical or horizontal) with respect to the orientation of the inlet (reverse and uniflow). Designs for high throughput are characterized by a shorter body and, in addition, by larger openings which allow a throughput of a large volume. The pressure loss in the case of such a design is most often relatively low, wherein also the deposition rate is lower. In contrast thereto, designs for higher efficiency are characterized by long bodies and small open- ings. On the one hand, such a design results in high deposition rates, but on the other hand, also in high pressure losses.

From EP 0 972 572 A2 a high efficiency countercurrent cyclone comprising a cylindrical vortex finder is known. The document discloses relationships between the sizes and geometries of the single elements of the cyclone which result in a particularly high efficiency of the cyclone.

From the document DE 10 2013 207724 A1 a combustion plant, wherein the main combustion is conducted in a cyclone-like chamber, is known. The dip tube or vortex finder of this cyclone-like chamber has the form of a Venturi flume.

A dip tube or vortex finder which is made of a metallic grid is known from document EP 0 447 802 A2. It consists of several honeycombed parts.

Generally, the efficiency of a well-designed cyclone can be improved by increasing the tangential velocity, but this also results in an increase of the pressure loss across the cyclone. However, such a higher pressure loss across the cyclone inevitably results in a higher pressure loss across the whole system and thus in an increased demand for electric energy. In addition, a higher pressure loss also results in a stronger stressing of the dip tube due to the ensuing high pressure gradient between the inner and outer sides of the dip tube.

Therefore, it is an object of the present invention to provide a novel dip tube enabling a cyclone with a high separation efficiency in combination with moderate pressure losses. This is realized by avoiding the high loss at the inlet of dip tubes having small diameters. Nevertheless, the high tangential velocity is achieved by guiding to a small diameter within the nozzle. Since this small cross-section is only present over a relatively short region and the guiding to it is realized with less pressure loss, the total pressure loss is reduced, wherein at the same time the tangential velocity is nearly the same. With the adjustment of the flow in the same direction and the subsequent diffusor a part of the pressure loss is recovered in addition. The above object is solved by a dip tube being characterized by the features of patent claim 1 and/or a cyclone being characterized by the features of patent claim 10.

Here, for withdrawing a gas stream from the cyclone the dip tube comprises a gas inlet and a gas outlet. During operation the gas flows into the dip tube via the gas inlet and flows out again from the dip tube via the gas outlet. So within the dip tube a gas stream from the gas inlet into the direction of the gas outlet is created. In addition, the dip tube according to the present invention comprises a first region which is designed as a nozzle. This nozzle has on one side an inner nozzle diameter, wherein the diameter of the nozzle in the direction of the flow and from there in the direction of the gas outlet convergently tapers to a smallest inner diameter.

In addition, the dip tube comprises a second region through which after the first region during operation gas flows. This region is designed as a diffusor, wherein the diffusor at its side which is the far side with respect to the first region has an inner diffusor diameter. The inner diameter of the diffusor from there in the direction of the first region convergently tapers to the smallest inner diameter.

The nozzle is characterized by the geometry of a lateral surface of a truncated cone. Such a lateral surface is rotationally symmetrical with respect to an axis which is the symmetry axis of the truncated cone. The included angle of this lateral surface with respect to the axis can have a value of between 1 ° and 88°, in particularly 15° to 65°. This design of the convergent nozzle makes the production thereof particularly simple and thus particularly cost-effective. Moreover, such a design lowers the pressure drop, which is particular important for gas-solid-separation due to the relatively high gas stream.

Thus, the cross-section of the dip tube through which gas flows becomes smaller in a convergent manner starting from a cross-section being defined by the inner nozzle diameter to a smallest cross-section which is defined by the smallest inner diameter. Starting from this bottleneck of the dip tube, the dip tube expands again in the direction of the gas stream up to a larger cross-section being defined by the inner diffusor diameter.

For separating particles from gas, while the particles are the dispersed phase, the gas outlet of a cyclone has to be designed properly concerning its diameter to avoid high pressure losses while maintaining primary function of vortex stabilization and separation efficiency. This is not the case for hydrocyclones, separating gas from a fluid with a higher density, where the gas phase is the dispersed phase and being much less in relative volume flow. Thus the vortex finder can accordingly be designed with a much smaller vortex finder diameter or a rapidly decreasing vortex finder diameter (e.g. exponentially, not linearly) starting from a nozzle inlet shape with a very high angle to the mid axis (trumpet or laval-like shape). This design would still result in moderate pressure losses due to the very small gas volume flow, since being the dispersed phase. On the other hand hydrocyclones sometimes need additional devices at the vortexfinder inlet (e.g. impinging plates) to avoid the denser fluid entering the vortex finder. Such devices are not needed for cyclones separating particles from gas. Actually such devices would be disadvantageous since particles would have the possibility to interact with them which could lead to higher particle breakage (e.g. due to particle impingement). Furthermore the non-linear decrease of the vortex finder diameter would increase the pressure losses for cyclones separating solids from gas, since the gas volume is much higher than the particle volume flow. In a preferable embodiment of the invention the inner nozzle diameter of the nozzle can be 1 .2 to 8 times, in particularly 1 .4 to 2.85 times the smallest inner diameter. In addition, in a preferable embodiment the length of the nozzle which extends from the region with the inner nozzle diameter to the region with the smallest inner diameter can be 0.14 to 4.0 times the smallest inner diameter. Otherwise the length follows from the chosen angle and the inner diameter. With such a geometry the effect according to the present invention can be achieved very strongly so that already in the case of moderate pressure losses across the cyclone a very good separation efficiency is achieved. In a further preferable embodiment of the invention the nozzle can have at the position of the inner nozzle diameter an outer nozzle diameter which is smaller than the sum of the inner nozzle diameter and 4 times the smallest inner diameter (Douter < Dinner + 4^*d). In other words, at the end of the nozzle, thus at the position which is characterized by the inner nozzle diameter, a ring is arranged, wherein the width of this ring is smaller than 4 times the smallest inner diameter (< 4^*d). The arrangement of a ring having these dimensions is in particularly used for a nozzle which has the form of a lateral surface of a truncated cone. With such a ring in a particularly simple way the geometry of the dip tube can be adjusted to the geometry of a Laval nozzle. Such a ring is in particularly suitable for supplementary later adjustments, so that for example the dip tube can be adjusted to amended operational parameters.

In a further preferable embodiment of the invention the outer nozzle diameter can be smaller than the sum of the inner nozzle diameter and 4 times the small- est inner diameter (D_outer < D_inner + 4^*d) and the inner nozzle diameter can be 1 .2 to 8 times the smallest inner diameter. Particularly preferably, the outer nozzle diameter can be smaller than the sum of the inner nozzle diameter and 0.25 times the smallest inner diameter (D_outer < D_inner + 0.25^*d) and the inner nozzle diameter can be 1 .4 to 2.85 times the smallest inner diameter. Also this geome- try is characterized by the form of a ring which is arranged at the end of the nozzle, thus at the position of the inner nozzle diameter. Such a construction is also used for a nozzle which has the design of a sonic nozzle. Also with a ring of this geometry, in particularly afterwards, the gas flow through the dip tube can be influenced in a particularly simple way.

In a preferable embodiment of the invention the diffusor has a design of a lateral surface of a truncated cone or cylinder, respectively. Such a geometry is rota- tionally symmetric with respect to an axis, namely the symmetry axis of the truncated cone or cylinder, respectively. In this case, the included angle be- tween the lateral surface and the axis is between 0° and 45°, preferably 3° to 15°. The symmetry axis of the truncated cone or cylinder, respectively, is also the symmetry axis of the diffusor and can be also the symmetry axis of the nozzle. Since often the diffusor is a particularly large component, with this particularly simple construction of the diffusor a considerable reduction of costs can be achieved.

In a further preferable embodiment of the invention between the nozzle and the diffusor a connecting cylinder can be arranged. So the connecting cylinder connects the nozzle at the site at which the nozzle has the smallest inner diameter with the site of the diffusor at which the diffusor has the smallest inner diameter. The connecting cylinder has therefore and/or at a connecting site an inner connector diameter which is identical with the smallest inner diameter. The length of the connecting cylinder or truncated cone, respectively, which extends from the nozzle to the diffusor, is preferably smaller than 8 times the smallest inner diam- eter (L < 8^*d). A connecting cylinder has an extremely simple geometry so that the passage from the diffusor to the nozzle is a more gentle one. So the flow through the dip tube can be further improved and thus a particularly low pressure loss can be achieved. Further, it is possible that the connecting cylinder from nozzle to diffusor has different thickness providing a better connection between nozzle and diffusor from construction aspects and performance in terms of wear resistance or any deformations e.g. due to different thickness of nozzle and diffusor or cylinder itself, as well, generally i.e. the cylinder profil has a bi-convex, bi-concave, plan-convex or plan-concave curve profil. A further version is characterized by providing in the flow direction before the nozzle and/or after the diffusor at least one further nozzle or one further diffusor, respectively. A design consisting of several convergent nozzles which are adjusted to each other is simple and thus the production costs thereof are low. Several nozzles and/or diffusors which are adjusted to each other provide a high flexibility, when the dip tube should be adjusted best to operational parameters. In the case of such a design the curvature radius can change in the longitudinal direction of the nozzle, wherein the smallest curvature radius is at the site of the highest curvature. In a further preferable embodiment the connecting site between the nozzle and the diffusor and/or the single nozzles and/or diffusors is smoothened. The connecting site can, for example, be polished. Through this smoothing a negative influence onto the flow behavior of the gas is avoided. When between the nozzle and the diffusor a connecting cylinder is arranged, then due to the same reason it is advantages, when the connecting site between the connecting cylinder and the nozzle and/or the connecting site between the connecting cylinder and the diffusor is smoothened, thus for example polished.

In a further preferable embodiment at least one part of the dip tube, such as for example the negative profile of a nozzle, the connecting cylinder and/or the diffusor, consists of one installation part or several installations, respectively. For reducing the weight of the installations, they can be designed as hollow bodies. In other words, the dip tube comprises in its interior facing installations so that a negative profile of the nozzle, the connecting cylinder and/or the diffu- sor is formed. Such a geometry is rotationally symmetric with respect to an axis, namely the symmetry axis of the negative profile. Since the weight of the installations is often lower than that of steel, with the weight reduction and/or the particularly simple construction, e.g. for the fixture of the dip tube, a considerable reduction of costs can be achieved. So this results in the particularly simple possibility to improve the cyclones and/or dip tubes in working plants without extensive building alterations.

In principle it is preferable to manufacture at least parts of the dip tube according to the present invention from heat- and/or erosion-resistant materials such as ceramic fiber materials, carbon fibers, etc. and/or, optionally, to provide them with a surface or coating against erosion.

In addition, the invention comprises a cyclone for separating solid particles and/or at least one liquid from a gas stream comprising an above defined dip tube.

The introduced gas stream may, for example, be also a steam, which only through a later condensation of one of its constituents becomes a gas stream with small liquid particles. This, for example, may only be realized by successive cooling within the cyclone.

A cyclone according to the present invention comprises a housing, an opening in this housing for introducing the gas stream, a discharge port for the separated solid bodies or the liquid and a dip tube for discharging the gas. In this case, typically, the housing may comprise a cylindrical region in which the opening for introducing the gas stream is arranged. In addition, the housing may comprise a region which, starting from the cylindrical region, in the direction of gravitation conically converge. At the end of this conical region, thus at the lowest point with respect to the direction of gravitation, a discharge port is mounted. The cyclone, in addition, comprises a dip tube which can be arranged at the side of the housing opposite to the discharge port at a housing cap. According to the present invention, this dip tube is characterized by the above described features of patent claim 1 or one of the depending patent claims.

The opening in the housing can be designed such that the gas stream together with the solid particles contained therein and/or the at least one liquid is introduced into the housing in tangential orientation. So in the housing a circulatory movement is initiated. The gas stream together with the particles is then moved downwards in a spiral form into the direction of the optionally conical region. Due to the tapering of the housing the circulatory movement strongly increases and thus results in strong centrifugal forces which have an effect onto the particles. So the particles are moved in outward direction and there they hit onto the wall of the housing. The particles separated in such a manner from the gas stream fall downwards in the gravitation field into the direction of the discharge port. The same belongs to a liquid separated from the gas stream which flows along the wall of the housing to the lowest region of the housing, namely the discharge port, and which can be extracted there from the housing. The gas stream from which the particles and/or the liquid have been extracted can sub- sequently leave the cyclone again through the dip tube (vortex finder).

In a preferable embodiment of the invention the at least one dip tube is arranged such that it at least partially projects into the housing. In this case, the dip tube can be arranged such that its gas inlet is placed within the housing and its gas outlet is placed outside the housing. It is also possible that the dip tube is com- pletely arranged inside the housing in such a manner that the gas outlet is positioned directly at the housing at an opening of the housing. In addition, the dip tube can be arranged outside the housing by positioning directly the inlet opening of the dip tube from outside at an opening of the housing. So also with the arrangement of the dip tube within the cyclone the flow behavior can be influenced. Therefore, it is possible, with a given geometry of the dip tube and the cyclone housing, to adjust the cyclone to the exact operational parameters by the arrangement according to the present invention of the dip tube within this housing.

In a further preferable embodiment of the invention several dip tubes of such kind can be provided, wherein a symmetric or asymmetric arrangement of the dip tubes is possible. For example, the dip tubes can be arranged in a mirror- symmetric manner with respect to one plane or several planes. A further possi- bility is an axial symmetry with respect to a mirror axis. In this case, also only the position of the dip tubes may be symmetrical, and the symmetry in total is interrupted, for example, by different sizes, lengths or insertion depths of the dip tubes. With the use of several dip tubes the gas throughput of the cyclone can be increased, without using one single large dip tube. The production and instal- lation of one single large dip tube is much more complicated than the use of several small dip tubes. With the symmetric or asymmetric arrangement, there are a lot of degrees of freedom for adjusting the cyclone to the operational parameters. In a preferable embodiment of the invention the at least one dip tube is at least partially jacketed by a cylinder. In this case, the diameter of the cylinder can be adjusted to the dip tube and correspondingly it can be either the inner nozzle diameter or the outer nozzle diameter. In this case, the cylinder can, in addition, project beyond the inner nozzle diameter into the housing, i.e. beyond the posi- tion at which the nozzle is characterized by the inner nozzle diameter. Such a cylinder can be manufactured and installed very easily and can result in a further improvement of the efficiency of the cyclone.

In a further preferable embodiment of the invention a cylinder can extend from the housing into the interior of the housing, wherein in the cylinder several dip tubes are arranged. Thus it is possible that single dip tubes are enveloped by one cylinder or that a whole group of dip tubes is enveloped by one single cylinder. When several dip tubes are used, then also the arrangement of one single cylinder around the several dip tubes can result in an improvement of the effi- ciency of the cyclone.

In a further preferable embodiment of the invention the area of the housing via which the at least one dip tube enters the housing or on which the at least one dip tube is positioned directly on the housing has a circular form. Then, the dip tube can be arranged centrically or eccentrically with respect to this area. In the case of an arrangement of several dip tubes having a symmetry axis this symmetry axis can be positioned centrically or eccentrically on this area. A centrical arrangement allows a particularly simple installation of the cyclone, since, for example, the orientation of the cap is irrelevant, and an eccentrical and/or asymmetric arrangement takes for example the position of the opening for introducing the gas stream into account.

In the following the invention is explained by means of embodiment examples and with reference to the figures. 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 shows schematically the construction of a cyclone, fig. 2a shows schematically a dip tube, fig. 2b shows schematically a dip tube with a connecting piece,

fig. 3a shows schematically a dip tube with plotted angles, fig. 3b shows schematically a nozzle with a ring, fig. 4 shows schematically a dip tube with the plotted angle of the diffusor, fig. 5a shows an arrangement of the dip tube in the cyclone, fig. 5b shows a further arrangement of the dip tube in the cyclone, fig. 5c shows a further arrangement of the dip tube in the cyclone, fig. 5d shows a further arrangement of the dip tube in the cyclone, fig. 6a shows an arrangement of a dip tube with a cylinder at the housing cap, fig. 6b shows a further arrangement of a dip tube with a cylinder at the housing cap, fig. 6c shows a further arrangement of a dip tube with a cylinder at the housing cap, fig. 6d shows an arrangement of several dip tubes within a cylinder, fig. 7a shows a symmetric arrangement of dip tubes, fig. 7b shows an asymmetric arrangement of dip tubes, fig. 8a shows a cyclone with a symmetrically arranged dip tube, and fig. 8b shows a cyclone with an eccentrically arranged dip tube.

The basic construction of a cyclone 1 as is used for the separation of solid bodies or liquids from a gas stream is shown schematically in fig. 1 . The cyclone 1 consists of a housing 3 comprising a cylindrical region 5 and a coning region or conical region 6. In the cylindrical region 5 the gas feed facility 4 through which the gas stream together with the particles can be injected is positioned. The cyclone 1 is typically arranged such that the coning part 6 is directed downwards into the direction of the gravitation field. At the lowest point thereof the discharge port 7 is positioned through which the particles and/or the liquid which have been extracted from the gas stream can be discharged.

During operation the gas stream together with the particles is introduced into the housing 3 through the gas feed facility 4. This, typically, is realized in tangential orientation so that directly a circular movement of the gas stream is created. The gas stream moves from the feed facility 4 into the direction of the coning region 6 in a spiral form. By the centrifugal forces the particles are transported to the outer wall of the cyclone 1 and there they are moved into the direction of the discharge port 7 by the influence of gravitation. Then, the gas enters the dip tube 2 via the gas inlet 8 in an upwards motion and it exits from it via the gas outlet 9 as purified gas.

Fig. 2a shows the basic construction of a dip tube 2 with a diffusor 12 in a second region 1 1 and a nozzle 13 in a first region 10 which are connected with each other at a connecting site 14. The nozzle 13 comprises a wide opening with the inner nozzle diameter D_inner and a narrow opening with the small inner diameter d. The diffusor, at its connecting site 14 with the nozzle 13, is also characterized by the smallest inner diameter d and in the direction to its other end the diameter thereof becomes larger again up to a wider inner diameter.

Fig. 2b shows the basic construction of a dip tube 2 consisting of a diffusor 12, a nozzle 13 and a connecting piece 15 which at the connecting sites 14 is connected with the diffusor 12 and the nozzle 13. The connecting piece 15 is characterized by a diameter which corresponds to the smallest inner diameter d.

In the figures 2a) and 2b) the gas inlet 8 of the dip tube coincides with an end of the nozzle 13and/or with the position of the inner nozzle diameter. But this must not necessarily be the case. Rather it is also possible that a further component, such as for example a cylinder, is arranged at the nozzle, wherein one end of it, instead of the nozzle, forms the gas inlet.

Fig. 3a shows the dip tube 2 of fig. 2a with plotted dimensions. At the connecting site between the diffusor 12 and the nozzle 13 the dip tube is characterized by the smallest inner diameter d. The nozzle 13 is designed as a lateral surface of a truncated cone and in the case of the variant which is plotted as a dashed line it can have the length or height H. A nozzle 13 with a very flat, i.e. short construction having a smaller height is plotted with a continuous line. The nozzle in the form of a truncated cone is characterized by a symmetry axis 20, wherein the truncated cone is rotationally symmetric with respect to this axis 20. In addi- tion, for the variant which is plotted as a dashed line, the nozzle in the form of a truncated cone has a small included angle a. In the variant which is plotted as a continuous line the included angle is larger. Fig. 3b shows a single nozzle 13 wherein at the end of it an additional ring 18 is arranged. With this ring 18 the nozzle 13 has at its end an inner diameter D_inner and an outer diameter D_outer which is enlarged due to the ring 18. Fig. 4 shows the dip tube 2 of fig. 2a with the plotted included angle β of the diffusor 12. The diffusor 12 of the dip tube 2 is designed as a truncated cone and it has a rotation axis 21 .

The fig. 5a to 5d show different insertion depths of the dip tube 2 in the housing 3 of the cyclone.

In fig. 5a the dip tube 2 is arranged such that it completely projects into the housing 3 so that the gas inlet 8 of the dip tube 2 is arranged below the lower edge of the gas feed facility 4. The gas inlet 8 of the dip tube 2 is placed within the housing 3.

In fig. 5b the dip tube 2 only partially projects into the housing 3 so that the gas inlet 8 of the dip tube 2 is positioned at the same height as the lower edge of the gas feed facility 4.

Fig. 5c shows a variant, wherein only about one half of the dip tube 2 projects into the housing 3 so that the gas inlet 8 of the dip tube 2 is arranged above the lower edge of the gas feed facility 4.

In fig. 5d the whole dip tube 2 is arranged outside the housing 3. From outside the dip tube 2 is arranged with its gas inlet 8 directly at the cap 17 of the housing 3. Fig. 6a shows a dip tube 2 which is completely enveloped by a cylinder 19. The cylinder and the dip tube are arranged at a cap 17 of the housing 3. The figures 6a) to 6d) each show only a section of the housing 3 with the cap 17. In this case the region below the cap 17 is the interior of the housing. Therefore, the cylinder and the dip tube 2 completely project into the housing 3.

Fig. 6b shows an embodiment, wherein the dip tube 2 only partially projects into the housing 3 so that the gas outlet 9 of the dip tube 2 is arranged outside the housing 3 and the gas inlet 8 is arranged within the housing 3. The cylinder 19 is completely positioned within the housing 3 and projects beyond the dip tube 2 into the interior of the housing 3.

Fig. 6c shows an embodiment, wherein the dip tube 2 is mounted from outside the housing 3 directly at the cap 17. The cylinder 19 is present at the same position at the opposite side of the dip tube 2 within the housing 3.

Fig. 6d shows a top view onto a cap 17 with an arrangement of several dip tubes 2 and in the lower field a side view of the same arrangement with the dip tubes 2 which are together completely positioned in a cylinder 19 within the housing 3. Arrangement of the dip tubes may vary as mentioned above see 6b) and 6c)

Fig. 7a shows an arrangement of several dip tubes within a housing 3 of a cyclone 1 which are arranged at the cap 17 of the housing 3 of the cyclone 1 . In this case the arrangement of the dip tubes 12 is symmetrical with respect to a symmetry axis which runs through the dip tube 2 in the center thereof.

Fig. 7b shows the arrangement of fig. 7a with two additional dip tubes 2 which are arranged in an asymmetric manner. In addition, fig. 7b shows a dip tube 2 being arranged in the center which does not completely project into the housing 3 of the cyclone 1 , thus some dip tubes may be positioned at a different height with respect to the gas inlet of the nozzle.

Fig. 8a and 8b illustrate the difference of a centrical arrangement and an eccen- trical arrangement of a dip tube 2. In fig. 8a the dip tube 2 is concentrically arranged with respect to the cap 17 and in fig. 8b the dip tube 2 is arranged outside this center. Therefore, it is an eccentrically arranged dip tube 2. In addition, in fig. 8b the direction and the amount of eccentricity are indicated by arrows.

Embodiment example:

Operating data:

Volumetric flow rate 1 m³/s

Particle load 0.1 kg/kg gas

Median of the particle diameter 10 μιτι

Particle density 2600 kg/m³

Gas density at 30°C 1 .189 kg/m³

Dyn. viscosity of the air at 30°C 1 .84^*10-5 kg/ms

Inlet temperature 30°C

Inlet pressure 1 .033 bar

Geometry of the cyclone:

Inlet width 0.12 m

Inlet height 0.6 m

Radius of the dip tube 0.15 m

Length of the dip tube 0.45 m

Radius of the cyclone 0.45 m

Length of the cyclone 2.25 m

Length of the cylindrical region 0.9 m

Radius of the discharge port 0.15 m

Nozzle Design: RevO RevOA

Inner nozzle diameter 0.075 m 0.105 m

Inner diffusor diameter 0.075 m 0.105 m

Smallest inner diameter 0.04 m 0.059 m

Length of the nozzle 0.04 m 0.04 m

Length of the diffusor 0.4 m 0.7 m

Length of the connecting cylinder 0.01 m 0.01 m

Velocity at the bottleneck 214 m/s 100 m/s Result:

Separation efficiency r \ ~ 96 % (conservative) and > 96 % expected with a preferable embodiment of the invention

Pressure loss ΔΡ: ~ 22 mbar (conservative) and < 25 mbar at 100 m/s expected with a preferable embodiment of the invention

List of reference signs

1 cyclone

2 dip tube

3 housing

4 gas feed facility

5 cylindrical region

6 conical region

7 discharge port

8 gas inlet

9 gas outlet

10 first region

1 1 second region

12 diffusor

13 nozzle

14 connecting site

15 connecting cylinder

17 cap

18 ring

19 cylinder

20 symmetry axis of nozzle

21 symmetry axis of diffusor d smallest inner diameter

Dinner inner nozzle diameter

Douter outer nozzle diameter

H height of the nozzle

Claims

Patent claims

1 . A dip tube (2) for withdrawing a gas from a cyclone (1 ), wherein gas during operation flows into the dip tube (2) via a gas inlet (8) and flows out again via a gas outlet (9), characterized in that the dip tube (2) comprises a first region (10) being designed as a nozzle (13) which convergently tapers from an inner nozzle diameter (D_inner) to a smallest inner diameter (d), that the dip tube (2) comprises a second region (1 1 ) through which during operation downstream the first region (10) gas flows and which is designed as a diffusor (12) which convergently tapers from an inner diffusor diameter in the direction of the first region to the smallest inner diameter (d), and that the nozzle (13,) has the geometry of a lateral surface being rotationally symmetric with respect to an axis (20) in the form of a truncated cone, wherein the included angle (a) between the lateral surface and the axis (20) is between 1 ° and 88°.

2. The dip tube according to claim 1 , characterized in that the included angle (a) between the lateral surface and the axis (20) is between 15° and 65°

3. The dip tube according to claim 1 or 2, characterized in that the inner nozzle diameter (D_inner) of the nozzle (13,) is 1 .2 to 8 times the smallest inner diameter (d) and/or that the length (H) of the nozzle (13,) from the inner nozzle diameter (D_inner) to the smallest inner diameter (d) is 0.2 to 4 times the smallest inner diameter (d).

4. The dip tube according to one of the preceding claims, characterized in that the nozzle (13,) at the position of the inner nozzle diameter (D_inner) has an outer nozzle diameter (D_outer) which is smaller than the sum of the inner nozzle diameter (D_inner) and 4 times the smallest inner diameter (d).

5. The dip tube according to one of the preceding claims, characterized in that the outer nozzle diameter is (D_outer < D_inner + 4^*d) and the inner nozzle diameter (Dinner) is 1 .2 to 8 times the smallest inner diameter (d).

6. The dip tube according to one of the preceding claims, characterized in that the diffusor (1 2) has the geometry of a lateral surface being rotationally symmetric with respect to an axis (21 ) in the form of a truncated cone, wherein the included angle (β) between the lateral surface and the axis (21 ) is between 0° and 45°.

7. The dip tube according to one of the preceding claims, characterized in that between the nozzle (1 3) and the diffusor (1 2) a connecting cylinder (1 5) is arranged, wherein the inner connector diameter thereof is identical with the smallest inner diameter (d).

8. The dip tube according to claim 7, characterized in that the connecting cylinder (1 5) preferably extends from nozzle (1 3,) to diffusor (1 2) over a length which is shorter than 8 times the smallest inner diameter (d).

9. The dip tube according to one of the preceding claims, characterized in that upstream the nozzle ( 1 3, ) at least one further nozzle is provided and/or that downstream the diffusor ( 1 2) a further diffusor is provided.

1 0. A cyclone for separating solid particles and/or at least one liquid from a gas stream comprising a housing (3), an opening (4) in the housing (3) for introducing the gas stream together with the solid particles and/or the at least one liquid into the housing (3), a discharge port (7) for the solid particles and/or the liquid and at least one dip tube (2) for withdrawing gas from the housing (3), characterized in that the dip tube (2) complies with the features of patent claim 1 .

1 1 . The cyclone according to claim 10, characterized in that at least one dip tube (2) is arranged such that it projects at least partially into the housing (3) or that at least one dip tube (2) is arranged outside the housing (3) and the gas inlet (8) of the dip tube (2) is positioned directly on an opening of the housing (3).

12. The cyclone according to claim 10 or 1 1 , characterized in that several dip tubes (2) are provided, wherein the arrangement of the dip tubes (2) is de- signed in a symmetric or asymmetric manner.

13. The cyclone according to one of claims 10 to 12, characterized in that the at least one dip tube (2) is at least partially enveloped by a cylinder (19), wherein the diameter of the cylinder (19) can be higher than the smallest inner diameter (d) and lower than the outer nozzle diameter (D_outer) or the same and/or the cylinder (19) projects beyond the inner nozzle diameter (D_inner) into the housing (3).

14. The cyclone according to one of claims 10 to 12, characterized in that from the housing (3) a cylinder (19) extends into the interior of the housing (3), wherein in the cylinder (19) several dip tubes (2) are arranged.

15. The cyclone according to one of claims 10 to 14, characterized in that those area (17) of the housing (3) via which the at least one dip tube (2) enters the housing (3) or onto which the at least one dip tube (2) is positioned directly on the housing (3) has a circular form and that at least one dip tube (2) is arranged centrically or eccentrically on this area (17).