Insert for an atomizer wheel and atomizer wheel comprising a number of such inserts

Abstract

The insert (20) is adapted to be fitted into an atomizer wheel. Each insert (20) has a longitudinal axis and comprises an inner end face (21), an outer end face (22), an external surface (23) and an internal surface (24) defining a channel (35) having a center axis (c) and extending between an inlet (25) at the inner end face (21) and an outlet (26) at the outer end face (22). At least the inlet (25) is offset from the longitudinal axis such that the center axis of the channel (35) is offset from the longitudinal axis of the insert (20). The insert (20) is adapted to be utilized in an atomizer wheel for a spray dryer for atomizing slurries of abrasive material, for instance for spray drying absorption for flue gas cleaning.

Claims

1. An atomizer wheel for a spray dryer for atomizing slurries of abrasive material, comprising: a substantially cylindrical external wall defining an annular chamber and a radial direction of the atomizer wheel, a plurality of ejection apertures distributed over the circumference of said external wall, and a plurality of inserts arranged in said ejection apertures, each insert spanning at least the entire width of the external wall of the atomizer wheel and having a longitudinal axis and comprising: an inner end face configured to be exposed to an annular chamber of the atomizer wheel, the insert being configured for the inner end face to extend into the annular chamber; an outer end face configured to be exposed to an outside of the atomizer wheel; an external surface; and an internal surface defining only a single substantially straight channel having a centre axis and extending between an inlet at the inner end face and an outlet at the outer end face, the insert being configured for said inlet to be positioned in the annular chamber, and an outlet at the outer end face, wherein at least said inlet is offset from the longitudinal axis such that the centre axis of the channel is substantially parallel to and offset from the longitudinal axis of the insert, whereby the insert is provided with an enlarged portion at the inner end face and the inlet containing a larger amount of material between the external surface and the internal surface in one segment of the insert than in an opposite segment relative to the centre axis.

2. The atomizer wheel according to claim 1, said outlet is offset from the longitudinal axis.

3. The atomizer wheel according to claim 2, wherein the centre axis of said channel is substantially parallel with said longitudinal axis.

4. The atomizer wheel according to claim 1, wherein the inlet lies entirely outside the longitudinal axis.

5. The atomizer wheel according to claim 1, wherein there is an overlap between the inlet and the longitudinal axis.

6. The atomizer wheel according to claim 1, wherein the cross-section of the inlet is chosen from the group of different shapes comprising circular, elliptical, oval, ovoid, quadratic and rectangular.

7. The atomizer wheel according to claim 6, wherein said channel has a uniform cross-section from said inlet to said outlet.

8. The atomizer wheel according to claim 6, wherein said channel has a cross-section that decreases or increases from said inlet towards said outlet.

9. The atomizer wheel according to claim 1, wherein said channel has the shape of a funnel in at least one of said inlet or outlet.

10. The atomizer wheel according to claim 1, wherein said inlet is symmetrical about at least one axis other than radial.

11. The atomizer wheel according to claim 1, wherein the centre axis of said channel forms an angle in the interval 0 to 30 with the longitudinal direction of the insert.

12. The atomizer wheel according to claim 11, wherein the centre axis of said channel forms an angle with a plane extending in a radial direction of said insert in the interval 0 to 30.

13. The atomizer wheel according to claim 1, wherein said external surface is of a substantially tapered shape or of a cylindrical shape.

14. The atomizer wheel according to claim 1 comprising a gripping recess extending from said inner end face to the external surface.

15. The atomizer wheel according to claim 14, wherein the gripping recess comprises a first transition surface extending at angle from the inner end face to a second transition surface extending at an angle from said first transition surface towards said external surface face.

16. The atomizer wheel according to claim 14, wherein the gripping recess is asymmetrical relative to the longitudinal axis of the insert.

17. An atomizer wheel for a spray dryer for atomizing slurries of abrasive material, comprising: a substantially cylindrical external wall defining an annular chamber and a radial direction of the atomizer wheel, a plurality of ejection apertures distributed over the circumference of said external wall, each ejection aperture extending substantially in said radial direction, and a plurality of inserts arranged in said ejection apertures, each insert spanning at least the entire width of the external wall of the atomizer wheel and having a longitudinal axis and comprising: an inner end face configured to be exposed to the annular chamber of the atomizer wheel the insert being configured for the inner end fact to extend into the annular chamber; an outer end face configured to be exposed to an outside of the atomizer wheel; an external surface; and an internal surface, said internal surface defining only a single substantially straight channel having a centre axis and extending between an inlet at the inner end face, the insert being configured for said inlet to be positioned in the annular chamber, and an outlet at the outer end face, wherein at least said inlet is offset from the longitudinal axis such that the centre axis of the channel is substantially parallel to and offset from the longitudinal axis of the insert, whereby the insert is provided with an enlarged portion at the inner end face and the inlet containing a larger amount of material between the external surface and the internal surface in one segment of the insert than in an opposite segment relative to the centre axis.

18. The atomizer wheel as claimed in claim 17, wherein each insert comprises an insert lining and an insert jacket, each having an internal side and an external side, the external side of the insert jacket constituting the external surface of the insert facing the ejection aperture, and the internal side of the insert lining constituting the internal surface defining the channel of the insert.

19. The atomizer wheel as claimed in claim 18, wherein the insert jacket is substantially asymmetrical.

20. The atomizer wheel as claimed in claim 19, wherein the internal side of the insert jacket has the shape of an oblique cone.

21. The atomizer wheel as claimed in claim 18, wherein the insert lining is symmetrical.

22. The atomizer wheel as claimed in claim 21, wherein the external side of the insert lining has the shape of a straight cone.

23. The atomizer wheel according to claim 22, wherein the internal side of the insert jacket has the shape of an oblique cone.

24. An atomizer wheel for a spray dryer for atomizing slurries of abrasive material, comprising: a substantially cylindrical external wall defining an annular chamber and a radial direction of the atomizer wheel, a plurality of ejection apertures distributed over the circumference of said external wall, and a plurality of inserts arranged in said ejection apertures, each insert spanning at least the entire width of the external wall of the atomizer wheel and having a longitudinal axis and comprising: an inner end face configured to be exposed to an annular chamber of the atomizer wheel, the insert being configured for the inner end face to extend into the annular chamber; an outer end face configured to be exposed to an outside of the atomizer wheel; an external surface; and an internal surface defining a substantially straight channel having a centre axis and extending between an inlet at the inner end face and an outlet at the outer end face, the insert being configured for said inlet to be positioned in the annular chamber, and an outlet at the outer end face, wherein at least the inlet is offset from the longitudinal axis such that the centre axis of the channel is offset from the longitudinal axis of the insert, whereby the insert is provided with an enlarged portion at the inner end face and the inlet containing a larger amount of material between the external surface and the internal surface in one segment of the insert than in an opposite segment relative to the centre axis, and wherein a centre of the longitudinal axis of the insert passes through at least a portion of the channel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a partial sectional side view of an atomizer wheel in an embodiment of the invention;

(2) FIG. 2 is a sectional top view of the atomizer wheel shown in FIG. 1;

(3) FIG. 3 is a perspective view of an insert for an atomizer wheel in a first embodiment of the invention;

(4) FIG. 4 is a top view of the insert of FIG. 3;

(5) FIG. 5 is a cross-sectional view of the insert of FIGS. 3 and 4, along the line V-V in FIG. 4;

(6) FIG. 6a is a schematic top view of an insert in a second embodiment of the invention;

(7) FIG. 6b is a cross-sectional view of the insert of FIG. 6a, along the line K-K in FIG. 6a;

(8) FIG. 7a is a schematic bottom view of a third embodiment of an insert according to the invention,

(9) FIG. 7b is a cross-sectional view of the insert of FIG. 7a, along the line A-A in FIG. 7a;

(10) FIGS. 8a and 8b are views corresponding to FIGS. 7a and 7b, respectively, of a fourth embodiment of an insert according to the invention, the cross-sectional view taken along the line F-F;

(11) FIGS. 9a and 9b are views corresponding to FIGS. 7a and 7b, respectively, of a fifth embodiment of an insert according to the invention, the cross-sectional view taken along the line C-C;

(12) FIG. 10a is a schematic top view of a sixth embodiment of an insert according to the invention,

(13) FIG. 10b is a cross-sectional view of the insert of FIG. 10a;

(14) FIGS. 11a and 11b are views corresponding to FIGS. 10a and 10b, respectively, of an insert in a seventh embodiment of the invention;

(15) FIGS. 12 to 14 are schematic top views of further embodiments of an insert according to the invention;

(16) FIG. 15 is a part sectional top view of an atomizer wheel in a still further embodiment;

(17) FIG. 16 is a partial view of detail XVI in FIG. 15, on a larger scale; and

(18) FIG. 17 is a sectional view of a two-part insert of the atomizer wheel shown in FIGS. 15 and 16.

DESCRIPTION OF PREFERRED EMBODIMENTS

(19) In FIGS. 1 and 2, an embodiment of an atomizer wheel 1 for atomizing slurries of abrasive material is illustrated, where the atomizer wheel 1 comprises a wheel hub 2 defining an axial direction of the atomizer wheel, and a substantially cylindrical external wall 3 defining an annular chamber 4 of a substantially bowl-like cross-sectional shape coaxially surrounding the hub 2, which is delimited by a cover 8 and a bottom portion 10. The slurries to be atomized are provided concentrically around the hub 1 through an aperture 9 in the cover 8. The circumference of the external wall 3 of the atomizer wheel 1 is provided with a number of ejection apertures 5, through which a supplied slurry is ejected outwards in atomized form during operation into a surrounding drying chamber in which the fine particles formed by the atomization are dried so that their content of solids drops down to the bottom of the drying chamber, possibly in the form of a fine powder.

(20) As shown most clearly in FIG. 2, the ejection apertures 5 each extends in a substantially radial direction of the atomizer wheel and are distributed over the circumference of said external wall. In the embodiment shown, the atomizer wheel is adapted to rotate in a counter-clockwise direction.

(21) In order to prevent wear on the atomizer wheel 1 itself, inserts 20 fitting into the ejection apertures 5 are inserted in the individual ejection apertures 5. In the embodiment shown, each insert 20 is in turn fitted into a steel bushing 6; however, in some fields of application, it is also conceivable to fit the inserts 20 directly into the wall of the atomizer wheel. As indicated and as will be described in further detail below, a longitudinal direction of the respective inserts 20 coincides with the radial direction of the atomizer wheel.

(22) FIGS. 3 to 5 illustrate a first embodiment of the insert 20 adapted to fit into a corresponding ejection aperture 5 in an atomizer wheel, for instance an atomizer wheel having the overall properties shown in FIGS. 1 and 2.

(23) The insert 20 has a longitudinal axis I and comprises an inner end face 21, an outer end face 22, an external surface 23 and an internal surface 24 defining a channel 35 extending between an inlet 25 at the inner end face 21 and an outlet 26 at the outer end face 22. As the inner end face 21 has a larger extension than the outer end face 22 in the first embodiment, the external surface 23 is of a substantially tapered overall shape. Furthermore, is is noted that In the embodiment shown in FIGS. 3 to 5, the channel 35 has a uniform cross-sectional shape from the inlet 25 to the outlet 26, however with varying dimensions.

(24) Referring in particular to FIG. 5, the channel 35 has a centre axis c. As indicated in the above, the longitudinal axis I of the insert 20 substantially coincides with the radial direction of the atomizer wheel 1 in the mounted position of the insert in the atomizer wheel. The centre axis c of the channel 35, however, is eccentric to or offset from the longitudinal axis I of the insert 20 and hence relative to the radial direction of the atomizer wheel 1 in the mounted position.

(25) In the first embodiment shown in FIGS. 3 to 5, the offsetting is provided in that the inlet 25 and the outlet 26 are both offset from the longitudinal axis I of the insert, such that the centre axis c of the channel 35 is offset from the longitudinal axis I of the insert 20 in parallel therewith. The offset marked by ecc in FIGS. 4 and 5 is thus the same throughout the channel 35, from the inlet 25 (cf. the distance between lines 27 and 28 denoting the longitudinal axis I and the centre axis c, respectively, in FIG. 4) to the outlet 26. The range of the offset may vary according to other parameters of the insert, such as the overall dimensions of the insert, shape of the channel 35, thickness of the wall between the external surface 23 and the internal surface 24, etc. Typically, however, for an insert having an overall diameter at the inner end face 21 of 30 to 40 mm, and a diameter of 20 to 30 mm at the outer end face 22, the offset typically lies in the range 2 to 5 mm. In the first embodiment, the inlet 25 overlaps the longitudinal axis I of the insert 35. However, it is also conceivable to offset the inlet opening to such an extent that no overlap is provided and the inlet lies entirely outside the longitudinal axis.

(26) As a consequence of the offset inlet 25, the insert 20 is provided with an enlarged portion at the inner end face 21 containing a larger amount of material between the external surface 23 and the internal surface 24 in one segment of the insert 20 than in the opposite. Referring back to FIG. 2, when in use, an insert 20 of this kind thus meets the slurry at the uppermost portion of the internal surface 24 positioned at the trailing edge of the inlet 25, when seen in the tangential direction of the atomizer wheel, which is thus the edge that is worn more heavily due to abrasion. As the amount of material in this area is increased due to the offset inlet 25, the lifetime of the insert is increased.

(27) In the first embodiment, a further feature is present which is particularly efficient in ensuring minimal wear on the bushings of the atomizer wheel, namely that the insert 20 has at the inner end face 21 a gripping recess, generally designated 30, which extends from the inner end face 21 to the external surface 23, best illustrated in FIG. 5. In the embodiment shown, the gripping recess 30 comprises a first transition surface 31 extending at angle from the inner end face 21 to a second transition surface 32 extending at an angle from the first transition surface 31 towards the external surface 23. The gripping recess and transition surface(s) may take other forms as well, as described in further detail in the above-mentioned European patent No. EP 1 184 081 B1. Thus, it is also conceivable that the gripping recess 30 may comprise more than two portions, or only one portion thus forming a bevelled gripping recess. The gripping recess 30 may also be designed as any suitable surface or combination of surface portions having an all in all concave shape. As indicated, the gripping recess 30 in the embodiment shown is asymmetrical relative to the longitudinal axis I of the insert 20. This is primarily due to the fact that there is no need for a gripping recess, or transition surface(s), at the trailing side of the insert. It has turned out that a shape of the enlarged portion extending substantially in parallel with the tangential direction of the atomizer wheel provides for an advantageous flow pattern such that flow of slurry meeting the following insert in the circumferential direction is not adversely affected.

(28) When inserted into the atomizer wheel in FIGS. 1 and 2, the gripping recess 30 of the insert 20 faces the slurry in the counter-clockwise rotation of the atomizer wheel 1, which entails that the direction of the flow of the slurry to be atomized is changed by virtually 90 degrees and is thus led past the bushing 6 and further onto the internal surface 24, thereby minimizing the wear on the bushing. However, in other embodiments of the insert according to the invention, there is not necessarily a gripping recess, or the gripping recess may have other configurations.

(29) Independently of the provision of a gripping recess, the transition between the inner end face 21 and the internal surface 24 may as shown be provided as a bevelled or chamfered edge, which is believed to postpone the point in time when the abrasion leads to noticeable wear on the trailing edge of the inlet 25 and hence the enlarged portion, as a sharp edge will be more prone to wear and tear. The chamfered edge needs not extend throughout the circumference but may be formed only in a sector covering for instance 20-50.

(30) In the first embodiment shown in FIGS. 3 to 5, the shape of the inlet 25 is substantially elliptical. By forming the inlet other than for instance circular, a larger surface subjected to the load of the slurries is provided. This, in turn, is believed to have an advantageous effect on the lifetime of the insert. The elliptical shape of the inlet 25 is present throughout the channel 35; however as is most apparent from the cross-sectional view of FIG. 5, the first portion of the channel 35 is substantially straight, whereas the remaining portion towards the outlet 26 is narrowed. The shape may in principle be varied in any suitable manner as will be described in further detail below; however, it is preferred that inlet is symmetrical about at least one axis other than radial.

(31) Other features, and variations thereof, will now be described.

(32) Referring to FIGS. 6a and 6b, a second embodiment of the insert 120 according to the invention is shown. Elements having the same or analogous function as in the embodiment of FIGS. 3 to 5, carry the same reference numerals to which 100 is added. In the second embodiment the inlet 125 of the insert 120 lies substantially entirely outside the longitudinal axis I and extends towards the outlet 126 with decreasing cross-section of the channel. The shape of the channel 135 through the inlet 25 towards the outlet 26 forms an angle with the longitudinal direction I of the insert. The angle typically lies in the interval 0 to 30, here approximately 20. In this embodiment, the channel 135 also forms an angle with a plane extending in a radial direction of the insert, which is indicated in FIG. 6b. This angle also typically lies in the interval 0 to 30, here approximately 30.

(33) Notice is taken regarding the embodiment illustrated in FIGS. 6a and 6b that a gripping recess corresponding to gripping recess 30 is absent, which does not exclude the option of incorporating a gripping recess in this embodiment as well.

(34) The inlet 125 is substantially circular and so is the outlet 126. The cross-sectional shape of the channel 135 is uniformly circular and the dimensions diminish from the inlet 125 to the outlet 126.

(35) FIGS. 7a and 7b illustrate a third embodiment of the invention, where 200 is added to reference numerals of elements having the same or analogous function as in the embodiment of FIGS. 3 to 5. In FIG. 7a the inlet 225 lies entirely outside the longitudinal axis as in the previously described embodiment. However, contrary to the previous embodiment the channel has a uniform cross-sectional dimension from the inlet 225 to the outlet 226, extending in parallel with the longitudinal axis, best illustrated in FIG. 7b.

(36) FIGS. 8a and 8b illustrate a fourth embodiment of the invention, where 300 is added to reference numerals of elements having the same or analogous function as in the embodiment of FIGS. 3 to 5. The insert is in this embodiment provided with a gripping recess 330 at the inlet 325, while having an uniform cross-section of the channel, best illustrated in FIG. 8b. As shown in FIG. 8b, the insert 320 has a substantially cylindrical external shape, as the external surface 323 takes the form of a cylindrical surface. This shape is not as such preferred, as the insert 320 is dependent on shoulders on the bushing or on the atomizer wheel itself. Even more important, the cylindrical shape does not entail the positive engagement provided by the tapered external shape of the other embodiments, which in turn does not entail the security against unintentional release of the inserts from the atomizer wheel in the case of failure of the bushing or other retaining elements.

(37) In a fifth embodiment illustrated in FIGS. 9a and 9b, with 400 added to reference numerals of elements having the same or analogous function as in the embodiment of FIGS. 3 to 5, the centre axis of the channel forms an angle in the interval 0 to 30 with the longitudinal direction of the insert, while having an increasing cross-section from the inlet 425 to the outlet 426.

(38) In a sixth embodiment of the invention, illustrated in FIGS. 10a and 10b, the channel has the shape of a funnel extending with the narrow end from the inlet 525 to the outlet 526, best illustrated in FIG. 10b, while still maintaining a larger surface area of the external wall 523.

(39) Alternatively, in a seventh embodiment the funnel shape of the channel extends with the widest end from the inlet 625 to the outlet 626, while still maintaining the larger surface area of the external wall 623, best illustrated in FIG. 11a-b.

(40) Furthermore, the shape of the inlet and the outlet and other parts of the channel of the insert may differ in different embodiments, as illustrated in FIG. 12 trough FIG. 14, by the cross-section of the channel, seen from the inlet 725, 825, 925, being chosen from the group of different shapes comprising circular, elliptical, oval, ovoid, quadratic and rectangular.

(41) Referring now to FIGS. 15 to 17, a still further embodiment of the atomizer wheel is shown. The atomizer wheel generally designated 801 has a a substantially cylindrical external wall 803 defining an annular chamber and a radial direction of the atomizer wheel. Ejection apertures 805 are distributed over the circumference of the external wall 803 in such a way that the individual ejection aperture 805 extends substantially in the radial direction. In each ejection aperture 805, an insert generally designated 820 is accommodated.

(42) Each insert 820 has a longitudinal axis I and comprises an insert lining 811 and an insert jacket 812. The insert lining 811 has an inner end face 821 facing the interior of the atomizer wheel 801, an outer end face 822, an external side 823 and an internal side 824. The internal side 824 of the insert lining 811 forms the internal surface of the insert 820 and defines a channel 835 having a centre axis c and extending between an inlet 825 at the inner end face 821 and an outlet 826 at the outer end face 822.

(43) In the embodiment shown, the centre axis c of the channel 835 in the insert lining 811 coincides with a rotational symmetry axis of the insert lining 811. Furthermore, the external side 823 is of a substantially tapered overall shape to provide the insert lining 811 with the shape of a straight cone.

(44) The insert jacket 812 has an external side 843 which is substantially cylindrical and with stepped portions known per se and not described in detail, including recesses for one or more sealings and for cooperation with corresponding portions of the external wall 803 of the atomizer wheel 801. The insert jacket 812 has an internal side 844 which in the embodiment shown is asymmetric and formed as an oblique cone.

(45) Positioning the symmetrical insert lining 811 in the asymmetrical insert jacket 812 thus entails that the centre axis c of the channel 835 is offset from the longitudinal axis I of the insert 820 and hence relative to the radial direction of the atomizer wheel 801 in the mounted position. When the atomizer wheel turns, in the counter-clockwise direction in the embodiment shown, liquid to be atomized forced radially outwards from the hub forming the center (not shown) in the annular chamber. The inner portions of the insert 820 thus collide with the liquid which is guided into the inlet 825, through the channel 835 and out through the outlet 826. Due to the configuration of the insert 820, the trailing or back edge of the inlet 825 is positioned closer to the center of the atomizer wheel than the front edge. In turn, this has shown to contribute to an increase in the liquid flow through the channel of the insert. Hence, the overall production efficiency is increased. Depending on the dimensions of the insert 820, the distance measured in the radial direction between the trailing edge and the front edge typically lies in the range 2-3 mm in an insert having typically overall outer dimensions of 30-45 mm wide, i.e. here diameter, and 30-45 mm long, i.e. length between inner end and outer end.

(46) The atomizer wheel may be used for spray drying absorption for flue gas cleaning or industrial off gasses, from for example power plants and metal industries, respectively. The flue gas may emanate from for instance power plants, industrial off gases, e.g. from metal industries. The invention is also useful for drying of abrasive feeds in general, e.g. in the chemical industry or in the mining industry.

(47) The invention should not be regarded as been delimited to the embodiments shown and described in the above, but various modifications and combinations may be carried out without departing from the scope of the appended claims.