Patent Application
20110114769
This invention relates to updraft pulverizer/classifiers and more particularly to a double course vane structure which is attached to the outer perimeter of the milling bowl.
Pulverizer/classifiers for crushing coal and ore are well known and are described in my previously granted U.S. Pat. Nos. 4,907,751 and 5,090,631. One popular pulverizer/classifier comprises a milling bowl which rotates about a vertical axis and is contacted by several large spring biased pressure wheels. The material to be pulverized drops onto the center of the bowl and moves radially outwardly toward the crusher wheels. Air passes upwardly through a vane structure which is mounted to the outer periphery of the milling bowl to rotate with it. The vane structure includes a plurality of angled vanes mounted between concentric race structures, the inner race structure being affixed to the outer periphery of the milling bowl.
The air passing upwardly through the vane structure entrains the crushed material. The lighter, more thoroughly pulverized material travels upwardly out of the housing for use as fuel for a burner in a steam powered turbine. Heavier, less thoroughly pulverized material falls back down toward the milling bowl where it is again contacted by the crusher wheels until the pulverizing function is thorough enough for that material to be carried up and out by the air stream passing through the vane structure.
The present invention provides an improved vane structure for pulverizer/classifiers of the type described above wherein there are two concentric vane courses mounted to the outer periphery of the milling bowl, the vanes in the first structure being angled in one sense or direction relative to the axis of rotation while the vanes in the other concentric section are angled in the opposite sense. I have found that this structure improves the mixing action in the air entrained updraft and also causes the heavier, less thoroughly crushed coal or ore particles to fall out of the airstream sooner, thus contributing to the efficiency of the pulverizing function.
In the embodiment hereinafter described in detail, the vane structure comprises three concentric annuli or “races”; an inner race, a middle race and an outer race. A first set of vanes is connected such as by welding between the inner and middle races while a second set of vanes is connected between the middle and outer races. As stated above, the first set of vanes is angled, preferably at approximately 45° to the vertical, in one sense while the vanes in the adjacent outermost set are angled in the opposite sense. An arcuate “seal” plate is attached to the upper outer periphery of the outer race such that it lies in close proximity to a deflector structure which is radially outboard of the race structure and attached to the inner sidewall of the pulverizer/classifier housing.
The foregoing and following descriptions of the invention are to be taken with accompanying drawings which describe an illustrative embodiment of the invention in detail.
The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views and wherein:
In operation, the coarse particulate material is dropped through the chute 20 onto the center of the bowl 14 and moves by centrifugal force outwardly onto surface 30 which is contacted by the crusher wheels 16, 18. Crushed material of various sizes and density moves farther outwardly toward the peripheral vane structure 32, the details of which are hereinafter described with reference to
A heavy head structure 42 mounted within the housing by conventional apparatus receives springs 44, 46 to bear against a carrier structure 48 which applies a downward force to the crusher wheels 16, 18 in a known manner. Additional detail with respect to the structure and operation of the pulverizer/classifier 10 can be attained from the aforementioned U.S. Pat. No. 4,907,751. It will be understood that this is representative of a single type of pulverizer/classifier and that other types of classifiers using, for example, different suspension systems for the crusher wheels are known in the art.
Referring now to
In practice, the vane structure can be assembled in a retrofitting operation by removing the original single-course vane wheel and replacing it in segments. Each segment is attached to the bowl 14 and welded to the last-installed segment one segment at a time. to the milling bowl 14 beginning with the attachment of the inner race segments and working outward. The entire race assembly 32 may be replaced as necessary by releasing the bolts which tie it to the milling bowl 14 and separating the segments as necessary. Of course, the double-course vane assembly may be part of an OEM installation as well. Alternatively, the top of the pulverizer housing 12 can be removed at the seam 13 to allow a complete vane wheel structure 32 to be lowered into place and bolted or welded to the pulverizer bowl.
It will be understood that the various surfaces of the vanes 50, 52 which are most consistently impacted by the material being pulverized are treated for wear by welding any of various carbides and/or alloys thereto or, in the case of the top plate 42, constructing the entirety of that plate out of a highly wear resistant material. While the invention has been described with reference to a rotating throat pulverizer/classifier, it can also be used in connection with stationary bowl pulverizers.
