US3887133A

US3887133A - Atomizer wheel for the atomization of slurries

Info

Publication number: US3887133A
Application number: US425654A
Authority: US
Inventors: Orla Straarup; Paul Otto Guenther Helmich
Original assignee: Niro Atomizer AS
Current assignee: GEA Process Engineering AS
Priority date: 1972-12-18
Filing date: 1973-12-17
Publication date: 1975-06-03
Anticipated expiration: 1992-06-03
Also published as: AU461264B2; BE808444A; DE2361123C2; DE2361123A1; DK141478C; DD108909A5; JPS4996360A; DK141478B; IT1000518B; ES421772A1; SE394969B; AU6352573A; AR204087A1; CA984875A; FI54072B; JPS5713342B2; SU692545A3; FI54072C; FR2330253A5; ZA739353B

Abstract

An atomizer wheel for the atomization of slurries, particularly slurries of highly abrasive materials like mineral slurries, in the outer cylindrical wall of which a number of ejection orifices are formed which are lined with wear-resistant bushings the inner ends of which project into the interior of the wheel a distance from the side wall and wherein the capacity of the wheel is increased by means of a number of spoke-like projections arranged in the interior of the wheel to have one of their ends situated in the region between the side wall and the inner ends of the spoke-like projections. The spoke-like projections may be secured to the side wall or be fitted in a body surrounding the central hub of the wheel. A further increase in the capacity may be obtained by means of axial projections in addition to the spokelike projections, said axial projections being secured to the covering plate of the wheel.

Description

United States Patent [191 Straarup et al. June 3, 1975 [5 ATOMIZER WHEEL FOR THE 3,419,220 12/1968 Goodwin et al. 239/600 x ATOMIZATION OF SLURRIES 3.454126 7/1969 Nielsen 239/224 [75] Inventors: Orla Straarup, Copenhagen; Paul Primar E M H W d J y xammerenson 0o r. g i Hlllerod Assistant ExamtnerRandolph A. Reese bot o enmar Attorney, Agent, or Firm-Sughrue, Rothwell, Mion, [73] Assignee: Aktieselskabet Nro Atomizer, Zirm & acpeak Soborg, Denmark 22 Filed: Dec. 17, 1973 [57] ABSTRACT An atomizer wheel for the atomization of slurries. par- [21] Appl' 425,654 ticularly slurries of highly abrasive materials like mineral slurries, in the outer cylindrical wall of which a 30 Foreign A fi fi priority Data nurlrliber of ejection (s'ifiges arehformed whigh atr e liti eg wit wear-resistant us mgs e inner en 5 o W [C Umtcd Kingdom 58419/72 project into the interior of the wheel a distance from [52] U S Cl 239/224. 233/32. 233/47 the side wall and wherein the capacity of the wheel is 5 239/59" increased by means of a number of spoke-like projec- [5 I] Int Cl Bosh 3/l0 F23d l 1364b l H00 tions arranged in the interior of the wheel to have one [58] Fieid 'g 239/223 5 228 591 of their ends situated in the region between the side j 66. 47 159/4 wall and the inner ends of the spoke-like projections. H The spoke-like projections may be secured to the side ll or be fitted in a body surrounding the central hub [56] References Cited wa of the wheel. A further Increase in the capacity may UNITED STATES PATENTS be obtained by means of axial projections in addition 1,132,814 3/1915 WBSIOI'I et al 233/32 to the p ke |ike projections aid axial projections i g 3 being secured to the covering plate of the wheel. a ewey t. 3,355,106 11/1967 Graham 239/223 X 11 Claims, 7 Drawing Figures I 6 I A 15' s 22 l is 10 13 l j I a} 11 10k 1 2 10: 13 H 10 l j 21 W036! l 1| Huh. 1 2

ATOMIZER WHEEL FOR THE ATOMIZATION OF SLURRIES The present invention relates to atomizer wheels for the atomization of slurries, in particular of highly abrasive materials such as cement slurry or slurries of clay, ore concentrates or other minerals.

BACKGROUND OF THE INVENTION In atomizer wheels of the above-mentioned kind it is well-known to line the ejection orifices formed in the cylindrical side wall of the wheel and distributed in one or more rows in the axial direction of the wheel with wear-resistant bushings which usually are manufac tured from a sintered material such as aluminium oxide, tungsten carbide or silicon carbide and are arranged in the orifices so as to project into the interior of the wheel with their inner ends situated a short distance from the inner side of the side wall. The object of this measure is to deposit a layer of dispersed material on the side wall and thereby protect the side wall against wear, particularly around the ejection orifices.

The ejection of the slurry through the ejection orifices results from the pressure in the rotating layer of fluid slurry. Therefore, it is to be expected that the capacity of such a wheel will mainly be determined by the thickness of said layer, so that an increased capacity should be obtained by increasing the diameter of the wheel. However, in practice a limit exists for the possibilities of increasing the capacity in this way. Thus, experience has shown that for an atomizer wheel having 24 ejection orifices distributed in two rows of 12 orifices each and rotating at a velocity of 6,000 rpm. a gradual increase of the diameter of the wheel, for example, from I90 to 240 mms will result in a gradually increased capacity up to about 32.4 cubic meters per hour, whereas a further increase of the diameter up to 280 mms will result in a capacity decrease to about 24 cubic meters per hour instead of an increased capacity.

This is due to the fact that the friction between the wheel and the fluid material is insufficient for imparting a rotational velocity to the fluid layer corresponding to that of the wheel and, consequently, a smaller centrifugal force will result therefrom than theoretically expected.

It is known from the atomization of solutions and slurries of materials which are not particularly highly abrasive, such as milk, to attempt to obtain an increased rotational velocity. by providing the bottom of the wheel with ribs or vanes. However, the use of ribs has shown to have little or no effect and the use of ribs as well as of vanes is not suitable for the atomization of highly abrasive material, since the front side of ribs or vanes will be subject to such a high degree of wear that the wheel will be rapidly destroyed.

For the atomization of slurries of highly abrasive materials it has been proposed to provide a wheel having a circular covering plate with a number of cylindrical bodies of a wear-resistant, sintered material, said bodies being clamped between the covering plate and the bottom of the wheel. Even if such cylindrical bodies have shown capable to resist wear and may have a relatively long useful service life, it has been found, however, that a high degree of wear occur at the boundaries between the cylindrical bodies and their contact faces in the covering plate and the bottom of the wheel, re-

spectively, as a result of which the wheel will be rapidly destroyed.

SUMMARY OF THE INVENTION It is the object of the invention to provide an atomizer wheel of the above-mentioned kind useful for the atomization of highly abrasive materials and having a considerably increased capacity relative to known atomizer wheels for this purpose without possessing the disadvantages of a reduced life-time resulting from the proposed known measures for achieving the same object.

According to the invention an atomizer wheel for the atomization of slurries is provided, which comprises a central hub, a substantially cylindrical side wall defining an annular bowl-shaped space concentric with said hub and being formed with a number of ejection orifices, a number of bushings of a wear-resistant material each of which is inserted in an individual one of said orifices so as to project with one end into said bowl shaped space a distance from-the inner side of the side wall and a number of spoke-like projections arranged in said bowl-shaped space with one end of each projection situated in the region between the side wall and the ends of said wear-resistant bushings facing the central hub.

In this connection the term wear-resistant material should be understood as comprising, for example, sintered materials such as aluminium oxide, tungsten carbide or silicon carbide or a non-sintered material such as titanium carbide.

Practical experiments with atomizer wheels constructed in accordance with the invention have shown that for a wheel having a diameter of 280 mms, as mentioned above, and 24 ejection orifices in which every second of the orifices is closed by a plug which is used to secure a radially extending projection, a capacity increase beyond cubic meters per hour is obtained in stead of a capacity decrease to about 24 cubic meters per hour, in spite of the fact that only half the original number of ejection orifices is actually in use.

Owing to the fact that whether the spoke like projections are secured to the hub or the side wall of the wheel the end of each projection remote from the central hub is situated in the region at the side wall, in which a layer of dispersed material is deposited as a result of the projections ends of the wear-resistant bushings, said ends of the spokelike projections and the areas of the side wall surrounding them will be effectively protected so that a considerably longer life-time than possible when employing the known proposals for increasing the rotational velocity of the slurry is obtained beyond the increased capacity.

Simultaneously, an effective reduction of the wear on the inwardly projecting ends of the wear-resistant bushings in the ejection orifices is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS In the following the invention will be explained in greater detail by means of a number of embodiments of an atomizer wheel according to the invention and with reference to the accompanying drawings, in which FIG. 1 is a sectional view along an axial plane through one embodiment of the atomizer wheel according to the invention;

FIG. 2 is a cross-sectional view along the line li-ll in FIG. 1;

FIGS. 3 and 4 show modifications of a fractional part of the atomizer wheel shown in FIG. 1,

FIG. 5 is a cross-sectional view along the line V-V in FIG. 4;

FIG. 6 is a sectional view along an axial plane through a second embodiment of the atomizer wheel;

FIG. 7 is a sectional view along an axial plane through a third embodiment of the atomizer wheel; and

FIG. 8 is a diagrammatical sectional view along a radial plane through a fourth embodiment of the atomizer wheel.

DETAILED DESCRIPTION The atomizer wheel shown in FIGS. I and 2 comprises a bottom I with a central hub 2, a cylindrical side wall 3 and a covering plate 4. The wheel is secured in a known manner on a drive shaft 6.

In covering plate 4 a central bore is formed through which drive shaft 6 extends in a manner so as to form an annular opening 7 between the drive shaft and covering plate 4 for the introduction of the dispersed material to be atomized into the interior of the wheel in a manner not shown per se.

Side wall 3 is formed with a number of ejection orifices which are lined with wear-resistant bushings of a sintered material, only one of said bushings being shown in the figure at 8. As shown, each bushing 8 may be inserted in a sleeve 9.

As far as the remaining ejection orifices are concerned, the total number of orifices being twelve, only the positions of said orifices are indicated, in FIG. 1 by the intersections 10 between the axes of the orifices and the innerside of the cylindrical side wall 3 and in FIG. 2 by radial lines 11 representing the axes of the orifices.

As shown in FIGS. 1 and 2 the inner end of each bushing 8 project into the bowl-shaped space forming the interior of the wheel a short distance from the inner side of the cylindrical side wall 3.

In acco rdance with the invention, a number of spokelike projections 12 are arranged in the interior of the atomizer wheel between the ejection orifices in such a way that the ends of said projections remote from the central hub 2 are situated in the region between the inner side of side wall 3 and the inwardly facing ends of bushings 8 in which a layer of dispersed material is deposited during operation of the wheel. In the embodiment shown in FIGS. 1 and 2, the atomizer wheel is provided with twelve spoke-like projections extending in radial directions of the wheel perpendicular to the axis thereof, only one of said projections being shown in FIG. 1 and only two projections being shown in FIG. 2. The positions of the remaining projections are indicated in FIG. 1 by the intersections 13 between the axes of the projections and the inner side of side wall 3 and in FIG. 2 by radial lines 14 representing the axes of the projections. In the embodiment shown in FIGS. 1 and 2, the spoke-like projections 12 are secured to the side wall 3 by means of pins 15 which are mounted in bores in the side wall and secured to the wall by means of collarshaped flange members 15', said pins fitting in corresponding axial bores in projections 12. It will appear from the following that the projections may be secured in other suitable ways, provisions being taken, however, to account for the fact that projections 12 when made of a sintered material may be subjected substantially to pressure forces only.

While the ejection orifices, on one hand, and the spoke-like projections, on the other hand, in the embodiment shown in FIGS. 1 and 2 are shown as being distributed in two rows it will be appreciated that they may be distributed in a single row or in more than two rows and that the number of projections may differ from the number of orifices. However, it applies in any circumstances that the orifices and the projections have to be distributed in a manner so as to secure that the wheel is balanced statically as well as during operation.

In the embodiment shown, projections I2 have the form of truncated cones and the cross-sectional area of each projection decreases in the direction towards the central hub 2. Thereby, a successful compromise is established between the very purpose of the spoke-like projections, i.e., the object of increasing the rotational velocity of the layer of fluid slurry, to fulfill which each projection should have the greatest possible surface area parallel to the axis of the wheel, and the desire of t the lowest possible degree of wear on the projections which is particularly pronounced, if the projections are made of a sintered material, and the fulfillment of which requires the area of each projection parallel to the axis of the wheel to be as small as possible due to the fact that a sintered material is much more capable to resist frictional wear than impact wear, which makes it desirable that the collisions between the projections and the abrasive particles in the slurry to the extent possible take place in tangential and not in radial directions relative to the projections.

Furthermore, the projections are proportioned so that they extend in the axial direction of the wheel only through part of the bowl-shaped space in the interior of the wheel, whereby clearances are obtained between the projections and the bottom 1 as well as the covering plate 4 with the result that wear on these parts of the wheel is reduced to the lowest degree possible.

In FIG. 3, another way of securing the projections to the side wall are illustrated for a fractional part of the wheel shown in FIGS. 1 and 2, the spoke-like projection being disignated by 18. The solution illustrated in FIG. 3 is particularly suitable in case of providing an existing atomizer wheel with spoke-like projections in accordance with the invention and according to this solution a suitable number of the ejection orifices already present are closed by plug members as shown at 16, into which pins 17 having for this purpose a threaded end are screwed, said pins being formed in their other ends to fit into axial bores in projections 18 which have the form of truncated cones just like the embodiment shown in FIGS. 1 and 2.

However, the spoke-like projections need not necessarily be conical, but may as an alternative be wedgeshaped such as illustrated in FIGS. 4 and 5 which show the same fractional part as shown in FIG. 3 of the wheel shownin FIGS. 1 and 2. In the embodiment shown in FIGS. 4 and 5, the cross-sectional area of each of the wedge-shaped projections which are designated by 19 decreases in the direction towards the central hub of the atomizer wheel just like the embodiments of FIGS. 1-2 and 3. The wedge-shaped form is obtained due to the fact that each projection is defined in the axial direction of the wheel by inclined planes which are symmetrical about a radial symmetry plane through the projection. Because the projections, if made of a sintered material, are much more capable of resisting frictional than impact wear, such as mentioned hereinbefore, the wedge-shaped projections 19 are arranged in the atomizer wheel with their greatest cross-sectional dimension extending perpendicularly to the axial direction of the wheel.

The wedge-shaped projections 19 shown in FIGS. 4 and 5 are secured by pins 20 to the side wall 3 in the same manner as described with reference to FIGS. 1 and 2.

In atomizer wheels in which the ejection orifices are distributed in at least two rows the spoke-like projections which may, for example, have the form of truncated cones, may be secured to side wall 3 between two rows of ejection orifices and have such a dimension in the axial direction of the wheel that both rows are covered, clearances being still provided between the projections and the bottom 1 as well as the covering plate 4.

In order to obtain a further improved protection of the bottom 1 against wear an annular insert 21 of a wear-resistant material may be arranged, in a manner known per se, in contact with bottom 1. Furthermore, a body 22 forming a guide surface for the slurry introduced into the wheel may be arranged around hub 2 in the interior of the wheel.

In FIG 6 another embodiment of the atomizer wheel is illustrated. The structure of the wheel comprising bottom 1, hub 2, side wall 3 and ejection orifices lined with wear-resistant bushings 8 is exactly the same as shown in FIGS. 1 and 2. However, in the embodiment shown in FIG. 6 the spoke-like projections 23 which extend in radial directions are fitted in the abovementioned guide body 22 surrounding hub 2 by means of pins 24 having in one end a collar-shaped flange member 25 forming an abutment face for the outer end of projection 23 and being threaded in the opposite end to be screwed into tapped bores in body 22. In accordance with the invention, projections 23 and pins 24 have such a length that the outer ends of the projections are situated in the region between side wall 3 and the ends of wear-resistant bushings 8 facing hub 2, in which a layer of dispersed material is deposited during operation of the wheel. Preferably, the flange member 25 which together with pin 24 may be made of steel is completely located in said region in which it is subjected to the lowest possible degree of wear.

In FIG. 7, a still further embodiment is illustrated which is particularly suitable for atomizer wheels having very great dimensions. The structure of the wheel comprising a bottom 26, a hub 27, a cylindrical side wall 28, a covering plate 29 and the ejection orifices lined with wear-resistant bushings 30 is essentially the same as shown in FIGS. 1, 2 and 6 apart from the considerably greater wheel diameter.

The radially extending spoke-like projections 31 in FIG. 7 are mounted on pins 33 which are fitted in a body 32 surrounding hub 27 and forming a guide surface for the fluid slurry introduced into the wheel. However, pins 33 extend substantially to side wall 28, their outer ends being separated, for example, by 0.5 to l mm from the inner side thereof, and are not provided with collarshaped abutting flange members, while projections 31 are slideably mounted on pins 33 with a certain longitudinal slip so that they will be pressed during operation of the wheel from a position, in which their inner ends abut against body 32, towards a position in which their outer ends abut against side wall 28.

Furthermore, in the embodiment shown in FIG. 7 an improved effect of the projections is obtained by means of a number of additional, axially extending projections 35 arranged in the bowl-shaped space of the atomizer wheel, said axial projections being secured to covering plate 29 at a shorter distance from hub 27 than from side wall 28 by means of threaded pins 36 which is provided with abutting flange members 37. In spite of the fact that projections 35 are arranged with their greatest dimension parallel to the axial direction of the atomizer wheel, these projections and the areas surrounding their contact faces in covering plate are not particularly subject to wear in this embodiment, because the velocity of the fluid slurry at this place is low relative to that of the wheel.

It will be appreciated that the arrangement of the radially extending projections shown in FIG. 7 is not restricted to an atomizer wheel incorporating axially extending projections, but may also be applied to an embodiment such as shown in FIG. 6.

In the embodiment hitherto'described the spoke-like projections extending transversely to the axis of the atomizer wheel have been radially directed, as a result of which an optimum effect is obtained. However, in order to reduce the wear on the wall of the wheel it might be expedient in certain cases to arrange the spoke-like projections 38 with backward inclinations relative to the rotational direction of the wheel seen from the ends of the projections closest to side wall 3, such as diagrammatically illustrated in FIG. 8, since fluid slurry entering the wheel will then have a lower tendency to disturb the layer of dispersed material deposited during operation of the wheel on the side wall around the ends of the projections.

The capacity increase obtained for an atomizer wheel of the kind mentioned by utilizing the measures according to the present invention will be illustrated best by means of the following examples.

EXAMPLE I A cement slurry having a total solids content of 56 per cent was atomized by means of an atomizer wheel as shown in FIGS. 1 and 2, but having no projections. The outer diameter of the wheel was 225 mms, and the number of ejection orifices was 24, all of which were lined with inwardly projecting, conical bushings of a wear-resistant, sintered material.

At a rotational velocity of 6,000 r.p.m., the maximum capacity was measured to 19 cubic meters per hour.

Thereafter, the bushings in twelve ejection orifices were replaced by plugs as described with reference to FIG. 3, in which conical spoke-like projections were fitted, said projections extending 2S mms into the interior of the wheel from the ends of the wear-resistant bushings facing the hub of the wheel.

At the same rotational velocity as mentioned above the maximum capacity was now measured to 45 cubic meters per hour.

EXAMPLE 2 An atomizer wheel of the type mentioned in example I, but having a diameter of 280 mms, was used. Like example I, the number of ejection orifices was 24, all of which were lined with inwardly facing, wearresistant bushings.

At a rotational speed of 6,300 r.p.m. the maximum capacity when atomizing the same material as mentioned in example 1 was measured to 33 cubic meters per hour.

In the manner as mentioned in example I I2 of the wear-resistant bushings were replaced by plugs carrying conical projections such as described with reference to FIG. 3, said projections extending 25 mms into the interior of the wheel from the ends of the wearresistant bushings facing the hub.

At the same rotational velocity an increase of the maximum capacity to 75 cubic meters per hour was now measured.

What is claimed is:

1. An atomizer wheel for the atomization of slurries, comprising a central hub, a substantially cylindrical side wall defining an annular bowl-shaped space concentric with said hub and being formed with a number of ejection orifices, a number of bushings of a wearresistant material each of which is inserted in an individual one of said orifices so as to project with one end into said bowl-shaped space a distance from the inner side of the side wall and a number of spoke-like projections arranged in said bowl-shaped space with one end of each projection situated in the region between the side wall and the ends of said wear-resistant bushings facing the central hub.

2. An atomizer wheel as claimed in claim 1 further comprising a bottom plate extending between the central hub and the cylindrical side wall and a covering plate connected with the side wall, said bottom and covering plates limiting the bowl-shaped space in the axial direction of the wheel, said spoke-like projection furthermore being proportioned with such a dimension in the axial direction of the wheel that clearances are left between the projections and the bottom plates as well as the covering plate.

3. An atomizer wheel as claimed in claim 2, further comprising a number of projections extending in the axial direction of the wheel and being secured to said covering plate at a shorter distance from the central hub than from the side wall.

4. An atomizer wheel as claimed in claim 1, wherein said spoke-like projections are secured to the cylindrical side wall by means of pins, each of which has one end fitted in one of said projections. while the other end is arranged in a bore in the side wall and secured to the inner side of said wall by means of a collarshaped flange member.

5. An atomizer wheel as claimed in claim 1, wherein said spoke-like projections are screwed into plug members fitted in a number of the ejection orifices by means of pins one end of which is fitted in a projection while the other end is threaded.

6. An atomizer wheel as claimed in claim I, wherein the cross-section area of the spoke-like projections decreases in the direction towards the central hub.

7. An atomizer wheel as claimed in claim 6, wherein the spoke-like projections have the form of truncated cones.

8. An atomizer wheel as claimed in claim 7, wherein the ejection orifices are arranged in at least two rows and the spoke-like projections have a cross-sectional area covering at least two rows of ejection orifices.

9. An atomizer wheel as claimed in claim 6, wherein the spoke-like projections are wedgeshaped with their greatest cross-sectional dimensions perpendicular to the axial direction of the wheel.

10. An atomizer wheel as claimed in claim 1, wherein the spoke-like projections are fitted in a body surrounding the central hub and have their outer ends situated in said region between the side wall and the ends of the wear-resistant bushings facing the central hub.

l 1. An atomizer wheel as claimed in claim 1, wherein the spoke-like projections are slidably mounted with a certain longitudinal slip on pins which are fitted in a body surrounding the central hub and the outer ends of which extend substantially on to the side wall, so that they are pressed against the side wall during operation of the wheel.

* l I l

Claims

1. An atomizer wheel for the atomization of slurries, comprising a central hub, a substantially cylindrical side wall defining an annular bowl-shaped space concentric with said hub and being formed with a number of ejection orifices, a number of bushings of a wear-resistant material each of which is inserted in an individual one of said orifices so as to project with one end into said bowl-shaped space a distance from the inner side of the side wall and a number of spoke-like projections arranged in said bowl-shaped space with one end of each projection situated in the region between the side wall and the ends of said wear-resistant bushings facing the central hub.

4. An atomizer wheel as claimed in claim 1, wherein said spoke-like projections are secured to the cylindrical side wall by means of pins, each of which has one end fitted in one of said projections, while the other end is arranged in a bore in the side wall and secured to the inner side of said wall by means of a collar-shaped flange member.

6. An atomizer wheel as claimed in claim 1, wherein the cross-section area of the spoke-like projections decreases in the direction towards the central hub.

9. An atomizer wheel as claimed in claim 6, wherein the spoke-like projections are wedge-shaped with their greatest cross-sectional dimensions perpendicular to the axial direction of the wheel.