Air disperser for spray-drying, and a method for manufacturing an air disperser comprising metal forming

Abstract

In the air disperser (4) having a number of components including a top, a bottom and an outer circumferential wall forming a space (45) defined within an inner radius and an outer radius and having an air inlet (81), a set of guide vanes (7), and an air outlet (82) at the inner radius adapted to be positioned above a feed outlet from atomizing means, at least some of the components are formed by precision metal forming such as metal spinning.

Claims

1. An air disperser for a spray drying apparatus, comprising a number of components including a top, a bottom, and an outer circumferential wall forming a space defined within an inner radius and an outer radius and having an air inlet, a set of guide vanes, and an air outlet at said inner radius adapted to be positioned above an atomizing feed outlet wherein the bottom and outer wall of said space are provided by a base module formed as a double-walled unit comprising a lower portion and an upper portion, wherein each of the lower portion and the upper portion is formed by metal spinning, and wherein the lower portion is rotationally symmetric about the air outlet, and wherein the upper portion is rotationally symmetric about the air outlet.

2. An air disperser according to claim 1, wherein the lower portion and the upper portion are connected to each other by means of at least one connecting element.

3. An air disperser according to claim 2, wherein the at least one connecting element is formed as a metal plate formed to an appropriate curvature.

4. An air disperser according to claim 1, wherein the top is provided by a top plate.

5. An air disperser according to claim 4, wherein said top plate is formed by metal spinning such that the top plate is rotationally symmetric.

6. An air disperser according to claim 4, wherein the top plate closing off said space is releasably connected to the base module.

7. An air disperser according to claim 6, wherein the top plate has a shape corresponding to an upper edge of the guide vanes of said set of guide vanes in part or in full.

8. An air disperser according to claim 1, wherein the diameter of said base module lies in a range of 0.3 to 3 m.

9. An air disperser according to claim 8, wherein the diameter of said base module lies in a range of 0.5 to 1.5 m.

10. An air disperser according to claim 4, wherein the top plate is rotationally symmetric about the air outlet.

11. An air disperser according to claim 1, wherein the guide vanes of said set of guide vanes are provided with an upper edge having a curved cornute-like shape with a height at the inner radius which is smaller than the height at the outer radius.

12. An air disperser according to claim 1, wherein the lower portion of the base module is adapted to form a ceiling of a drying chamber of a spray drying apparatus.

13. A method for improving the flow of drying air in a spray drying apparatus, the method comprising: providing an air disperser with a number of components including a top, a bottom, and an outer circumferential wall, an air inlet, a set of guide vanes, and an air outlet, and connecting said components to each other, wherein providing at least the bottom and the outer circumferential wall is carried out by forming a base module of a lower portion and an upper portion by metal spinning, and wherein the base module is double-walled, and wherein the lower portion is rotationally symmetric about the air outlet, and wherein the upper portion is rotationally symmetric about the air outlet.

14. The method of claim 13, wherein the upper portion is formed as two sections that are subsequently joined.

15. The method of claim 13, further comprising connecting the lower portion and the upper portion.

16. The method of claim 15, further comprising providing a connecting element and connecting the connecting element to the lower portion and the upper portion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, the invention will be described in further detail by means of the following description of preferred embodiments and with reference to the drawings, in which

(2) FIG. 1 shows a partial perspective and sectional view of a prior art air disperser mounted in the ceiling of a spray drying apparatus;

(3) FIGS. 2 and 3 show partial perspective and sectional views of an air disperser in a first embodiment of the invention;

(4) FIG. 4 is a perspective view of a detail of the air disperser shown in FIGS. 2 and 3;

(5) FIG. 5 is a top view of the air disperser of the first embodiment;

(6) FIG. 6 is a sectional view, on a larger scale, of the air disperser of FIG. 5, along the line A-A;

(7) FIG. 7 is a partial sectional view, on a still larger scale, of section B of FIG. 6; and

(8) FIG. 8 shows a schematic cross-sectional view of a further embodiment of the air disperser according to the invention.

DETAILED DESCRIPTION OF THE INVENTION AND OF PREFERRED EMBODIMENTS

(9) In FIG. 1, relevant parts of the top of a prior art spray drying apparatus generally designated 1 are shown. The spray drying apparatus 1 comprises a drying chamber 2 to which a feed to be spray dried is introduced at the top thereof by means of suitable atomizing means 3 and is set into a, possibly swirling, downward movement in the drying chamber 2 by drying air introduced via an air disperser generally designated 4 mounted at the ceiling of the drying chamber 2 of the spray drying apparatus. The spray drying apparatus may for instance form part of a spray drying plant in which further components are present, in which the drying process and other processes associated with the drying of materials are carried out.

(10) Referring now to FIGS. 2 to 10, a first embodiment of an air disperser designated 4 according to the present invention will be described in some detail. It is noted that parts of a spray drying apparatus, in which the air disperser according to the invention is adapted to be built into, may correspond to those of the prior art apparatus, but may also vary in some details.

(11) The air disperser 4 has a longitudinal axis defining an axial direction and a radial direction extending perpendicularly to the axial direction. The axial direction y is indicated in FIG. 6. The air disperser is connected to a supply of drying air or gas, in the embodiment shown via a separate air inlet part 8, and has an air inlet 81 leading to a space 45 defined within an inner radius and an outer radius. The space 45 is, as shown most clearly in FIG. 2, delimited by a top, a bottom and an outer circumferential wall. In the embodiment shown, the top is provided by top plate 6 and the bottom and the outer wall by a base module 5 constructed as will be described in further detail below. A set of guide vanes 7 is positioned within the space 45. An air outlet 82 is present at the inner radius and, in the mounted condition, surrounds a feed outlet of atomizing means such as a nozzle or a rotary atomizer.

(12) Details regarding the configuration of the guide vanes 7 are described in Applicant's co-pending application on the same date as the present application.

(13) In the embodiment shown in FIGS. 2 to 8, the base module 5 is formed as a double-walled unit comprising a lower portion 51 and an upper portion 52, and wherein the bottom and outer wall of space 45 are formed by the upper portion 52. As shown most clearly in the detailed view of FIG. 6, the air disperser is provided with an insulating material 53 inserted between the lower portion 51 and the upper portion 52.

(14) At the periphery of the base module 5 of the air disperser in the embodiment shown, the lower portion 51 and the upper portion 52 are connected to each other by means of a connecting element 56.

(15) As shown in particular in FIGS. 5 and 6, the air disperser according to the embodiment shown comprises an insulating module 9 for releasable connection with the base module 5. Optionally, the insulating module 9 may be connected with the top plate 6 as well.

(16) At one point along the periphery of the base module, a separate air inlet part 8 is connected to the base module 5. Although not shown in detail, the part 8 includes tubing for supply of drying air and is connected to the air inlet 81 either in the tangential or radial direction to the space 45.

(17) In the embodiment shown in FIGS. 2 to 8, the guide vanes 7 are provided with an upper edge having a curved commute-like shape with a height at the inner radius which is smaller than the height at the outer radius. Other shapes are however conceivable.

(18) In this embodiment, the top of space 45 is closed by a separate top plate 6. The top plate 6, which is optionally a two-part top plate, is connected to the base module by suitable securing means, here bolted to the base module 5, but other releasable connections to the base module 5 are conceivable as well. Also in this embodiment, the top plate 6 has a shape corresponding to the upper edge of the guide vanes 7. Towards the outer edge of the top plate 6 abuts against a stepped portion of the upper portion 52 of the base module 5 via a sealing 57.

(19) Regardless of the shape of the top plate, it may form the positive engagement in the axial direction y, preventing movement of the framework constituted by the set of guide vanes and fixating device.

(20) In FIG. 8, a nozzle lance generally designated 35 of a kind known per se has been inserted to protrude through the air disperser at the air outlet 82. Atomizing means 3 thus provide for atomization of a liquid feed (not shown) during operation of the spray drying apparatus.

(21) As to materials of the parts of the air disperser and the manner of manufacturing, the guide vanes may be made from any suitable material, for instance a metal material, typically steel, and formed by laser cutting. Markings indicating the position in the framework including the set of guide vanes and the fixating device may be provided by laser cutting as well. Other materials that are conceivable are other metal materials or composites, but polymers and ceramic materials may be utilised using manufacturing techniques such as injection moulding, die-casting etc.

(22) Manufacture of components of the air disperser according to the invention will now be described in detail with particular reference to the embodiments of the base module 5 and the top plate 6.

(23) As is described in the above, the air disperser according to the invention comprises a number of components, and at least some of the components are formed by precision metal forming. Precision metal forming requires investment in manufacturing equipment including tools and machinery.

(24) In the embodiment shown, the components include at least the bottom and outer wall of the space 45 in that the bottom and outer wall of the space 45 are provided by the base module 5 formed as a double-walled unit comprising the lower portion 51 and the upper portion 52. The bottom and outer wall of the space 45 are formed by the upper portion 52, and both of the lower portion 51 and the upper portion 52 are formed by precision metal forming.

(25) In the present embodiment, each of the lower portion 51 and the upper portion 52 is formed by metal spinning. It is conceivable to form at least the upper portion 52 of two sections, each formed by metal spinning and subsequently joined to each other, for instance by welding.

(26) As such, metal spinning is a known process for obtaining a symmetric three-dimensional element from a disk-shaped blank.

(27) Virtually any ductile metal may be formed, from aluminum or stainless steel, to high-strength, high-temperature alloys. The diameter and depth of formed parts are limited by the size of the equipment available. The spinning process itself is relatively simple. A formed block is mounted in the drive section of a lathe. A pre-sized metal disk is then clamped against the block by a pressure pad, which is attached to the tailstock. The block and workpiece are then rotated together at high speeds. A localized force is then applied to the workpiece to cause it to flow over the block. The force is usually applied via various levered tools. Simple workpieces are just removed from the block, but more complex shapes may require a multi-piece block. The final diameter of the workpiece is always less than the starting diameter. Spinning tools can be made of hardened steel for using with aluminium or solid brass for spinning stainless steel or mild steel. Some metal spinning tools are allowed to spin on bearings during the forming process. This reduces friction and heating of the tool, extending tool life and improving surface finish. Rotating tools may also be coated with thin film of ceramic to prolong tool life. Rotating tools are commonly used during CNC metal spinning operations. Commercially, rollers mounted on the end of levers are generally used to form the material down to the mandrel in both hand spinning and CNC metal spinning. Rollers vary in diameter and thickness depending on the intended use. The wider the roller the smoother the surface of the spinning; the thinner rollers can be used to form smaller radii. Cutting of the metal is done by hand held cutters, often foot long hollow bars with tool steel shaped/sharpened files attached. In CNC applications, carbide or tool steel cut-off tools are used. The mandrel does not incur excessive forces, as found in other metalworking processes, so it can in principle be made from any material, but for hard materials or high volume use, the mandrel is usually made of metal.

(28) Also in the embodiment shown, the lower portion 51 and the upper portion 52 are connected to each other by means of at least one connecting element 56, which may be formed as a cut metal plate shaped to the appropriate curvature.

(29) Other components provided by precision metal spinning include in the embodiment shown the top, and the top is provided by a top plate 6, which in a not-shown embodiment is a two-part top plate. Also the top plate 6 is here formed by metal spinning.

(30) The diameter of the base module 5 lies in the range 0.3 to 3 m, preferably 0.5 to 1.5 m.

(31) The remaining parts of a spray drying apparatus into which an air disperser according to the invention is adapted to be built into are not shown. These parts could for instance correspond to those shown in FIG. 1 designating the prior art. In one particular field of use of the air disperser according to the present invention, the lower portion 51 of the base module is adapted to form the ceiling of the drying chamber of a spray drying apparatus.

(32) The manner of assembling the air disperser may in principle be chosen freely, as long as they fulfil the demands posed.

(33) The invention should not be regarded as being limited to the embodiment shown and described in the above but various modifications and combinations of features may be carried out without departing from the scope of the following claims.