Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B3/00—Spraying or sprinkling apparatus with moving outlet elements or moving deflecting elements
  • B05B3/02—Spraying or sprinkling apparatus with moving outlet elements or moving deflecting elements with rotating elements
  • B05B3/10—Spraying or sprinkling apparatus with moving outlet elements or moving deflecting elements with rotating elements discharging over substantially the whole periphery of the rotating member, i.e. the spraying being effected by centrifugal forces
  • B05B3/1007—Spraying or sprinkling apparatus with moving outlet elements or moving deflecting elements with rotating elements discharging over substantially the whole periphery of the rotating member, i.e. the spraying being effected by centrifugal forces characterised by the rotating member
  • B05B3/1021—Spraying or sprinkling apparatus with moving outlet elements or moving deflecting elements with rotating elements discharging over substantially the whole periphery of the rotating member, i.e. the spraying being effected by centrifugal forces characterised by the rotating member with individual passages at its periphery
  • B05B3/1028—Spraying or sprinkling apparatus with moving outlet elements or moving deflecting elements with rotating elements discharging over substantially the whole periphery of the rotating member, i.e. the spraying being effected by centrifugal forces characterised by the rotating member with individual passages at its periphery the passages comprising an insert
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B15/00—Details of spraying plant or spraying apparatus not otherwise provided for; Accessories
  • B05B15/14—Arrangements for preventing or controlling structural damage to spraying apparatus or its outlets, e.g. for breaking at desired places; Arrangements for handling or replacing damaged parts
  • B05B15/18—Arrangements for preventing or controlling structural damage to spraying apparatus or its outlets, e.g. for breaking at desired places; Arrangements for handling or replacing damaged parts for improving resistance to wear, e.g. inserts or coatings; for indicating wear; for handling or replacing worn parts
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B3/00—Drying solid materials or objects by processes involving the application of heat
  • F26B3/02—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air
  • F26B3/10—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour carrying the materials or objects to be dried with it
  • F26B3/12—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour carrying the materials or objects to be dried with it in the form of a spray, i.e. sprayed or dispersed emulsions or suspensions

Definitions

• the present invention relates to an insert for an atomizer wheel for a spray dryer, said insert having a longitudinal axis and comprising an inner end face, an outer end face, an external surface and an internal surface defining a channel having a centre axis and extending between an inlet at the inner end face and an outlet at the outer end face.
• the invention furthermore relates to an atomizer for a spray dryer comprising a number of such inserts.
• inwards-protruding inserts which ensure that a layer of liquid will deposit on the internal wall of the wheel dur- ing the rotation and hereby prevent wear. Owing to the centrifugal forces the heavier parts of the layer, i.e. the suspended solid material, is separated from the liquid in the layer and deposited directly on the wall so as to fill the area surrounding the inwardly extending portions of the inserts. In this way the in- ner surface of the wheel rim is protected against abrasion from the feed, since during operation a layer of feed solids will settle on the inside wall to a thickness determined by the length of the protrusion, consequently the abrasion will take place on the sedimented layer itself and not on the inside wall of the wheel.
• each insert is provided with a transition surface in the inwards protruding part of the insert, thereby directing the flow of the feed along the transition surface to the inner side of the external wall thereby avoiding wear on the bushing. It is believed that the wear on the bushings in this way is limited since the whirl formed in front of the insert is controllably led past the front of the insert, during rotation to form a coherent layer of protective material on the inner side of the external wall.
• this object is met by an insert of the kind mentioned in the introduction, which is furthermore characterized in that 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.
• the channel may in principle extend in any suitable manner, provided sufficient material is present in order to secure operation.
• said outlet is offset from the longitudinal axis.
• the centre axis of said channel is substantially parallel with the longitudinal axis of the insert.
• This insert thus has substantially the corresponding flow as a traditional insert having a centrally positioned channel.
• the position and the dimensions of the inlet, and of the outlet and other parts of the channel, may be varied according to for instance the material, the field of application, and dimensions of the insert.
• the inlet lies entirely outside the longitudinal axis, but alternatively, an overlap between the inlet and the longitudinal axis may be provided.
• the cross-section of the inlet is preferably chosen from the group of different shapes comprising circular, elliptical, oval, ovoid, quadratic and rectangular.
• the channel may have a uniform cross-section from said inlet to said outlet.
• the shape may be varied throughout, it is possible also to vary the dimensions of the channel, for instance by providing the channel with a cross-section that decreases or increases from said inlet towards said out- let.
• the channel may have the shape of a funnel in at least one of said inlet or outlet.
• said inlet is symmetrical about at least one axis other than radial.
• the centre axis of the channel may form an angle in the interval 0 to 30° with the longitudinal direction of the insert.
• the centre axis of said channel may form an angle with a plane extending in a radial direction of said insert in the interval 0 to 30°.
• the external surface is of a substantially tapered shape.
• the external surface may be of a cylindrical shape.
• the insert comprises a gripping recess extending from said inner end face to the external surface.
• 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.
• the gripping recess may be formed asymmetrically relative to the longitudinal axis of the insert.
• an atomizer wheel for a spray dryer for atomizing slurries of abrasive material comprises a wheel hub and a substantially cylindrical external wall de- fining an annular chamber of a substantially bowl-like cross-sectional shape coaxially surrounding said hub, a plurality of ejection apertures, each extending in a substantially radial direction, distributed over the circumference of said external wall, and a plurality of inserts arranged in said ejection aper- tures, each insert being formed in accordance with the first aspect of the invention.
• the atomizer wheel may furthermore comprise a bushing mounted externally of the corresponding insert in each ejection aperture.
• Fig. 1 is a partial sectional side view of an atomizer wheel in an embodiment of the invention
• Fig. 2 is a sectional top view of the atomizer wheel shown in Fig. 1 ;
• Fig. 3 is a perspective view of an insert for an atomizer wheel in a first embodiment of the invention;
• Fig. 4 is a top view of the insert of Fig. 3;
• Fig. 5 is a cross-sectional view of the insert of Figs 3 and 4, along the line V-V in Fig. 4;
• Fig. 6a is a schematic top view of an insert in a second embodiment of the invention.
• Fig. 6b is a cross-sectional view of the insert of Fig. 6a, along the line K-K in Fig. 6a;
• Fig. 7a is a schematic bottom view of a third embodiment of an insert according to the invention.
• Fig. 7b is a cross-sectional view of the insert of Fig. 7a, along the line A-A in Fig. 7a;
• 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;
• Figs 9a and 9b are views corresponding to Figs 7a and 7b, respec- tively, of a fifth embodiment of an insert according to the invention, the cross- sectional view taken along the line C-C;
• Fig. 10a is a schematic top view of a sixth embodiment of an insert according to the invention.
• Fig. 10b is a cross-sectional view of the insert of Fig. 10a;
• Figs 1 1 a and 1 1 b are views corresponding to Figs 10a and 10b, respectively, of an insert in a seventh embodiment of the invention.
• Figs 12 to14 are schematic top views of further embodiments of an insert according to the invention. Description of preferred embodiments
• 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.
• 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.
• the atomizer wheel is adapted to rotate in a counter-clockwise direction.
• inserts 20 fitting into the ejection apertures 5 are inserted in the individual ejection apertures 5.
• 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 directlly into the wall of the atomizer wheel.
• a longitudinal direction of the respective inserts 20 coincides with the radial direction of the atomizer wheel.
• 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.
• 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.
• the external surface 23 is of a substantially tapered overall shape.
• the channel 35 has a uniform cross-sectional shape from the inlet 25 to the outlet 26, however with varying dimensions.
• the channel 35 has a centre axis c.
• 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 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.
• 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.
• the offset typically lies in the range 2 to 5 mm.
• the inlet 25 overlaps the longitudinal axis I of the insert 35.
• 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.
• 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.
• the amount of material in this area is increased due to the offset inlet 25, the lifetime of the insert is increased.
• 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.
• 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 .
• 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.
• the gripping recess 30 in the embodiment shown is asymmetrical relative to the longitudinal axis I of the insert 20. This is primarly 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.
• 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.
• 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°.
• the shape of the inlet 25 is substantially elliptical.
• 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.
• a second embodiment of the insert 120 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.
• 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 a with the longitudinal direction / of the insert.
• the angle typically lies in the interval 0 to 30°, here approximately 20°.
• 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°.
• the inlet 125 is substantially circular and so is the oulet 126.
• the cross-sectional shape of the channel 135 is uniformly circular and the dimensions diminish from the inlet 125 to the outlet 126.
• Figs 7a and 7b illustrate a third embodiment of the invention, where
• Fig. 7a the inlet 225 lies entirely outside the longitudinal axis as in the previously described 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.
• 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.
• 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.
• 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.
• 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.
• 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. 1 1 a-b.
• 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.
• an insert 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 insert may be inserted into an atomizer wheel used for the same purpose of spray drying absorption for flue gas cleaning.
• 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.

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• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Microbiology (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
• Nozzles (AREA)

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Citations (9)

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• 2012
  • 2012-12-20 WO PCT/DK2012/050490 patent/WO2014094773A1/en active Application Filing
  • 2012-12-20 CA CA2895397A patent/CA2895397C/en active Active
  • 2012-12-20 CN CN201280077942.9A patent/CN104870070B/zh active Active

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