An improved deflector structure for an updraft classifier mill for coal and ore is described. The improved deflector structure has an impingement surface which is characterized by a pattern of surface irregularities, either raised geometric figures or recesses of varying sizes and shapes to create turbulence in the air emerging from a rotating vane structure and impinging the deflector as it travels upwardly through the mill housing.
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0. 16. A pulverizing mill comprising:
a housing having an interior wall surface;
a milling bowl within the housing;
an annular vane structure adjacent the outer periphery of the bowl for directing air upwardly;
a deflector structure arranged above and around the vane structure such that air directed upwardly impinges upon the deflector structure; wherein the deflector structure presents to the impinging air and annular surface having formed thereon a pattern of raised geometric figures arranged in a fashion that prevents straight-line flow of air therethrough.
1. For use in an updraft pulverizing mill having an annular vane structure arranged about a vertical axis and adjacent a milling surface for the passage of air aiding a particle size separation function:
a deflector structure having an annular impingement surface which, in use, concentrically surrounds said axis and at least part of which angles inwardly toward said axis such that said updraft air impinges on said impingement surface; and
a pattern of discrete, spaced apart geometric figures formed on said surface structure which figures tend to prevent straight-line flow of said air over said surface and between said figures.
9. A pulverizing mill comprising:
a housing having an interior wall surface;
a milling bowl within the housing;
an annular vane structure adjacent the outer periphery of said milling bowl;
an inwardly angled a deflector structure mounted on said interior wall surface proximate and above the vane structure and having an inwardly-angled a deflection surface arranged such that air passing through said vane structure impinges upon said deflection surface and is deflected inwardly toward the center of the housing thereby;
wherein at least part of said surface is characterized by a pattern of raised surface irregularities in the form of discrete geometric figures which are arranged in a vertically staggered pattern to prevent straight-line flow of said air thereover and therethrough.
2. The deflector structure of
3. The deflector structure of
4. The deflector structure of
5. The deflector structure of
6. The deflector structure of
7. The deflector structure as defined in
8. The deflector structure of
10. A pulverizing mill as defined in
11. A pulverizing mill as defined in
12. A milling structure as defined in
14. A pulverizing mill as defined in
15. A pulverizing mill as defined in
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This invention relates to pulverizing mills for coal and ore and more particularly to an improved deflector structure for use in an updraft mill.
Pulverizing mills are commonly used to crush ore and coal for various purposes. One such purpose is to crush coal into fine particles for use as fuel to fire a boiler for a generator turbine. One type of pulverizing mill comprises a milling bowl which can be rotated about a vertical axis, a chute for dropping lump coal or ore onto the milling bowl and an annular vane structure attached to the outer periphery of the milling bowl for rotation therewith. Air is forced to flow upwardly through the vane structure toward the top of the pulverizing mill housing where a classifier structure separates the particles according to size and admits the smaller particles to a system of conduits which extend to a combustion chamber.
Mounted on an interior surface of the mill housing immediately around and above the vane structure is a deflector structure having an inwardly angled surface upon which air passing through the vane structure impinges so as to be deflected back toward the vertical center line of the pulverizing mill as it makes its way upwardly toward the classifier structure. The deflector prevents the abrasive particles from wearing on the walls of the mill housing and speeds up the particle separation process. The rotating vane mill is just one of many mill designs. Other designs use stationary, non-rotating milling bowls and/or stationary, non-rotating vanes. The invention described herein can be used with all such mills.
The present invention provides an improved deflector for pulverizing mills of the updraft type, wherein the deflector is characterized by a pattern of impingement surface irregularities, such as geometric protrusions, geometric recesses or a combination thereof, which tend to prevent laminar, straight-line flow of airborne particulates thereover and thus create turbulence in the upward flow of the impinging air coming from and through a vane structure. This improves the functions of particle separation and the return of larger, heavier particles to the pulverizing area.
As hereinafter disclosed with reference to one or more illustrative embodiments, the surface irregularities comprise rows of geometric figures such as rectangles which are arranged in such a fashion as to eliminate any straight channels directly through the pattern, particularly in the direction in the flow direction of the impinging air from the vane structure. The term “pattern”, as used herein, does not necessarily mean a regular or predictable arrangement of the geometric figures but may include random arrangements so long as they meet the requirement for reducing or eliminating the straight through flow paths or passages between figures to a considerable degree.
In one embodiment, the deflector structures are cast as arcuate segments of an overall annulus which is adapted to be mounted in one or more conventional ways to the interior cylindrical surface of the pulverizing mill outboard of and just above a vane structure. In the illustrated embodiment, the vane structure is mounted on the periphery of the milling bowl but, as stated above, this is not a requirement for the invention. The geometric surface irregularities can be cast into the segments. Alternatively, the deflector structures may be constructed using welded base elements onto which the deflector impingement structures with the aforesaid geometric pattern are attached such as by threaded fasteners and/or welding.
As will be apparent to those of ordinary skill in the pulverizing mill technology, the impingement surface structures are preferably made of a highly wear resistant material because the impingement of solid particles thereon tends to wear the surfaces away over time, requiring replacement thereof. The replacement function necessitates downtime of the pulverizing mill and this is to be minimized for economic reasons.
The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views and wherein:
Air enters a chamber 24 at the lower end of the pulverizer mill 10 through an inlet 22 and flows upwardly through a proprietary double-course vane structure 32 which is attached to the outer periphery of the milling bowl 14 so as to rotate therewith. The double-course vane structure 32 is a proprietary development of SAS Global, Inc. and is the subject of a pending application for U.S. patent application Ser. No. 12/621,814, filed Nov. 19, 2009. As best shown in
Mounted to the cylindrical interior surface 25 of the lower portion of mill housing 12 is a deflector structure 38 having an impingement surface 39 on which air flowing upwardly through the vane structure 32 impinges so as to be deflected back toward the center of the pulverizing mill 12.
As better shown in
Angled vanes 50 are welded between the races 45, 49 and are oriented at a 45° angle relative to the vertical. Reversely angled plates 52 are welded between the race plates 49, 51 and are oriented at 45° from vertical but in the opposite sense to the vane plates 50. An arcuate seal plate 54 is welded to the outside surface of the outer race 51 to narrow the gap between the outer race plate 51 and the deflector structure 38 so that the majority of the upbound air in the updraft pulverizer mill is forced through the vane structure 32.
As shown in
Referring to
The structures 38, 39, 56 and 88 can be cast from alloy steel, with some chromium and molybdenum content. The bolt-on plates can be made of materials such as tungsten carbide, aluminum oxide and hardened steel.
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