Patent Application
20120061497
This invention relates to crusher/classifiers for milling coal, mineral ore and similar materials into fine particulates and more particularly to a structure which is effective to enhance the operating effects of a crusher/classifier of the updraft type.
A well-known crusher/classifier used to pulverize coal and mineral ore employs a milling bowl of circular design around which air is caused to flow upwardly through an annular structure comprising angled vanes. The vane structure can be attached to the bowl to rotate with it, or be attached to the crusher/classifier housing just outside of the bowl. After passing through the vanes, the air picks up crushed particles and flows upwardly so as to impact the surface of an inwardly angled deflector which directs the air and particulates back toward the center of the crusher/classifier housing to enhance mixing and to ensure the return of heavier particles to the milling bowl for additional treatment. The air continues to flow upwardly to a classifier section and from there to a combustion chamber via ducts.
The present invention provides an improvement to crusher/classifiers of the updraft type wherein air is caused to flow upwardly around a milling bowl through an annular structure comprising angled vanes. The vanes locally angle the upward flow of air according to the vane angle, before it continues upwardly toward a classifier. In accordance with the invention, an annular structure comprising a series of uniformly spaced-apart, inwardly-extending impactor plates is mounted on the classifier wall above the angled vanes. These impactor plates are essentially vertical and extend radially into the updraft airstream coming off of the vanes. Accordingly, the updraft air and particulates entrained therein impact one or both of the major surfaces of the impactor plates to break the particles down into smaller pieces, thus enhancing the pulverizing effect of the system.
I have found that the present invention is used to its greatest advantage when combined with a double-course vane structure comprising two concentric courses of vanes, the vanes in one course being angled in one direction and the vanes in the other course being angled in the opposite direction. Such a double-course vane structure is disclosed in my previously filed, pending patent application, Ser. No. 12/621,814 entitled “Double Course Vane Wheel” filed on Nov. 19, 2009. Using the double-course vane structure with vanes in one course set opposite to the vanes in the other course brings both major surfaces of the impactor plates into play and further enhances the pulverizing effect.
In the preferred form, the impactor plates of the present invention, as well as a ring structure anchoring the impactor plates, are provided with coin-shaped surface projections to substantially increase impact-pulverizing action. Although the coin shape is illustrated and described herein, it is merely an example of a variety of different surface shapes which can be used. The impactor plate surfaces are hardened or made of a highly wear-resistant material.
In accordance with a preferred embodiment of the invention, an overall structure suitable for use within an updraft crusher/classifier structure comprises an annular support and a plurality of radially inwardly extending impactor plates with opposite surfaces essentially covered with coin-shaped projections, the inner surface of the ring structure between the impactor plates being similarly covered with the projections described above. The structures, including the impactor plates and the ring structure, are preferably made of a high hardness alloy, a carbide or a metal oxide. As stated above, the preferred vane structure has two courses of opposite sense and may be fixed to the crusher housing interior wall or attached to the milling bowl so as to rotate with it.
The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views and wherein:
Referring to the figures, there is shown a crusher/classifier comprising an upright housing 10 within which is rotatably mounted a dish-shaped milling bowl 12 having a vertical axis of rotation 14. Coal or other material falls through a chute 13 onto the bowl 12. The drive mechanism for rotating the milling bowl 12 as well as the crusher wheels 15 which ride thereon and the suspension systems for the crusher wheels are all well known and are described in greater detail in my previously issued U.S. Pat. Nos. 4,907,751, 5,386,619 and 5,819,947, the contents of which are incorporated herein by reference.
Attached to the bowl 12 in the embodiment of
A forced air system causes air to flow upwardly through the vane structure 16 whether or not the vane structure is rotating with the milling bowl 12. The upward movement of the air entrains particulate subject matter from the milling operation to cause upward flow thereof with the housing 10. The angles of the vanes 18, 20 are such as to cause an angled cross-flow of the air which in turn, causes the entrained particulates to impact both surfaces of impactor plates 42 which form part of segments 36 bolted to a ring structure 28 which is integral with the interior of the crusher/classifier housing 10. The ring structure 28 comprises an upper annular support ring 32 and a plurality of tapered radial reinforcing ribs 34 which are welded to the ring 32 as well as to a ledge 33 at the bottom of the structure 28. As such, the segments 36 can be bolted into place with bolts extending through the ring 32 whereupon the plates 42 extend at regular intervals radially inwardly toward the axis of rotation 14 such that they lie within the updraft airstream as described above. After hitting the impactor plates 42, air continues to flow upwardly to a classifier 43. If coal is the material being crushed, air and coal flow out to a combustion chamber via ducts 45.
The surfaces of the impactor plates 42 as well as the surfaces of the inserts 36 between the impactor plates are covered with coin-shaped, spaced-apart protrusions 44 and 40, respectively. The coverage is on the order of 50% to 85%. If a single course is used, only one surface of plates 42 need be coined; i.e., the surface impacted by air coming off of the vanes.
It will be appreciated that the height of the plates 42 is related to the spacing between the plates, those two parameters being selected such that effectively all of the particulate subject matter entrained in the airstream off of the vanes 18, 20 impacts a side of one or more of the plates 42. If the plates 42 are farther apart, they must be vertically longer; if they are vertically shorter, they must be closer together. The designer selects the optimum dimensions for economy of fabrication as well as efficacy of operation. In a workable embodiment, the plates are on the order of 14″ high and the inserts are on the order of 14″ wide.
It will also be appreciated that the invention can be used with single course rotating vane structures. As stated above, a single course of vanes angles the updraft air only one way and uses only one surface of plates 42.
As indicated above, the plates and inserts 36 between them are preferably made of a high hardness, wear resistant material such as a high hardness alloy of steel. Alternatively, they may be hard-faced or made of a carbide or metal oxide for maximum life.
In operation, coal enters the housing by gravity feed through chute 13. It works its way radially outwardly on the bowl 12 until it overflows the edge and gets picked up in the air streams coming off of the vanes 18, 20. The air and entrained coal immediately impacts the surfaces of plates 42, 52 which breaks the particles up into smaller pieces.
It will be appreciated that the embodiments illustrated in the drawing and described above are exemplary and that implementation of the invention can be carried out in various other configurations.
