BRIEF DESCRIPTION OF THE DRAWINGS
In order to facilitate a fuller understanding of the present invention, reference is now made to the appended drawings. These drawings should not be construed as limiting the present invention, but are intended to be illustrative thereof only.
FIG. 1 is a first partial side elevation view of a portion of a prior art primary classifier of a bowl mill type pulverizer.
FIG. 2 is a second side elevation view of the prior art form of primary classifier of the bowl mill type pulverizer of FIG. 1.
FIG. 3 is a side elevation view partially in section of a bowl mill type pulverizer embodying a prior art form of primary classifier.
FIG. 4 is a side elevation view of a primary classifier constructed in accordance with the present invention.
FIG. 5 is a side elevation view partially in section of a portion of the primary classifier constructed in accordance with the present invention of FIG. 4.
FIG. 6 is a side elevational view partially in section and on an enlarged scale of a portion of the primary classifier constructed in accordance with the present invention of FIG. 4.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
FIG. 3 of the drawings depicts a pulverizing bowl mill, generally designated by reference numeral 10, constructed in accordance with the prior art. Inasmuch as the nature of the construction and the mode of operation of pulverizing bowl mills are known to those skilled in the art, it is not deemed necessary to set forth a detailed description of the pulverizing bowl mill 10 illustrated in FIG. 3 of the drawings. Rather, it is deemed sufficient for purposes of obtaining an understanding of the pulverizing bowl mill 10 embodying a prior art form of primary classifier to merely present herein a description of the nature of the construction and the mode of operation of the components of the pulverizing bowl mill 10 with which the aforesaid primary classifier cooperates. For a more detailed description of the nature of the construction and the mode of operation of the components of the pulverizing bowl mill 10 which are not described in depth herein one may have reference to the prior art, including, but not limited to, U.S. Pat. No. 3,465,971, which issued Sep. 9, 1969 to J. F. Dalenberg et al., and/or U.S. Pat. No. 4,002,299, which issued Jan. 11, 1977 to C. J. Skalka.
With further reference to FIG. 3 of the drawings, the pulverizing bowl mill 10 as illustrated therein includes a substantially closed separator body 12. Continuing, as shown therein a grinding table 14 is mounted on a shaft 16, which in turn is operatively connected to a suitable drive mechanism (not shown in the interest of maintaining clarity of illustration in the drawings) so as to be capable of being rotatably driven thereby. With the aforementioned components arranged within the substantially closed separator body 12 in the manner depicted in FIG. 3 of the drawings, the grinding table 14 is operative so as to be driven in a clockwise direction.
Continuing with the description of the pulverizing bowl mill 10, which is illustrated in FIG. 3 of the drawings, a plurality of grinding rolls 18, preferably three in number in accord with conventional practice, are suitably supported within the interior of the substantially closed separator body 12 so as to be equidistantly spaced one from another around the circumference of the substantially closed separator body 12. In the interest of maintaining clarity of illustration in the drawings, only one such grinding roll 18 has been shown in FIG. 3 of the drawings.
The material, e.g., coal, that is to be pulverized in the bowl mill 10, which is constructed in accordance with the illustration thereof in FIG. 3 of the drawings, is fed thereto by means of any conventional form of feed means that is suitable for use for such a purpose. Upon being discharged from such a feed means (not shown in the interest of maintaining clarity of illustration in the drawings) the coal enters the bowl mill 10 by means of a coal supply means, generally designated by reference numeral 20, with which the substantially closed separator body 12 is suitably provided. In accordance with the embodiment of the pulverizing bowl mill 10 illustrated in FIG. 3 of the drawings, the coal supply means 20 includes a suitably dimensioned duct 22 having one end thereof which extends outwardly of the substantially closed separator body 12 and preferably terminates in a funnel-like member (not shown in the interest of maintaining clarity of illustration in the drawings). The latter funnel-like member (which is not shown in the drawings) is suitably shaped so as to facilitate the collection of the coal particles entering the bowl mill 10, and the guiding thereafter of these coal particles into the duct 22.
The other end 24 of the duct 22, as best understood with reference to FIG. 3 of the drawings, is operative to effect the discharge of coal onto the surface of the grinding table 14. To this end, as shown in FIG. 3 of the drawings, the other end 24 of the duct 22 preferably is suitably supported within the substantially closed separator body 12 through the use of any form of conventional support means (not shown), which is suitable for use for such a purpose, such that the other end 24 of the duct 22 is coaxially aligned with the shaft 16 to which reference has previously been had hereinbefore, which is operative to support the grinding table 14 for rotation. Furthermore, the other end 24 of the duct 22 is located in spaced relation to a suitable outlet 26 provided in the classifier, generally designated by reference numeral 28 in FIG. 3 of the drawings, through which the coal is made to flow in the course of being fed onto the surface of the grinding table 14.
In accordance with the mode of operation of the pulverizing bowl mill 10, which is constructed in accordance with the illustration thereof in FIG. 3 of the drawings, a gas, which most commonly is in the form of air, is utilized to effect the conveyance of the coal from the grinding table 14 through the interior of the substantially closed separator body 12 for discharge from said pulverizing bowl mill 10. The air that is employed for this purpose is made to enter the substantially closed separator body 12 through an opening (not shown in the interest of maintaining clarity of illustration in the drawings), which is suitably provided for this purpose I the substantially closed separator body 12. From the aforementioned opening (which is not shown in the drawings) in the substantially closed separator body 12, the air flows from beneath the grinding table 14 in surrounding relation thereto to above the surface of the grinding table 14. More specifically, as will be best understood with reference to FIG. 3 of the drawings, such air flows through the space, identified by the reference numeral 32 in FIG. 3 of the drawings, that for this purpose is provided between the inner wall surface of the substantially closed separator body 12 and the circumference of the grinding table 14. The path of flow that the air follows thereafter will be described more fully hereinafter in connection with the description of a primary classifier constructed in accord with the present invention with which a prior art form of bowl mill, such as the pulverizing bowl mill 10, which has been described hereinbefore and which is illustrated in FIG. 3 of the drawings, is capable of being equipped.
As the air is made to flow through the interior of the bowl mill 10, which is constructed in accordance with the illustration thereof in FIG. 3 of the drawings, the coal that is disposed on the surface of the grinding table 14 is being pulverized by the cooperative action between the grinding rolls 18 and the surface of the grinding table 14. As the coal becomes pulverized in the aforedescribed manner, the particles of coal that are created as a result of such pulverization are thrown as a result of centrifugal force outwardly away from the center of the grinding table 14. Thereupon, these particle of coal, upon reaching the circumferential region of the grinding table 14, are picked up by the air flowing upwardly from beneath the grinding table 14 through the space 32, and these particles of coal become entrained in this flow of air and are carried away therewith. Thereafter, this flow of air, with these particles of coal entrained therein, follows a tortuous path through the interior of the bowl mill 10, which is constructed in accordance with the illustration thereof in FIG. 3 of the drawings. Moreover, in the course of following this tortuous path the larger ones of these particles of coal are caused to be separated from the flow of air in which these larger particles of coal have become entrained, and thus are made to return to the surface of the grinding table 14 whereupon these larger particles of coal undergo further pulverization. On the other hand, the lighter ones of these particles of coal that are entrained in the flow of air continue to be carried along entrained in the flow of air. Ultimately, the combined flow of air and those lighter particles of coal that remain entrained in the flow of air proceed in an upwardly direction, as viewed with reference to FIG. 3 of the drawings, to the classifier 28.
In accord with conventional practice and in a manner which is well-known to those skilled in this art, the classifier 28 is designed to be operative to effect therewith a further sorting of the particles of coal that remain entrained in the flow of air that reaches the classifier. Namely, those particles of pulverized coal, which are of the desired particle size, are permitted to pass through the classifier 28 and along with the flow of air are then discharged therefrom and thus from the bowl mill 10 as well as through the outlets (not shown in the interest of maintaining clarity of illustration in the drawings), with which the bowl mill 10 is suitable provided for this purpose. On the other hand, those particles of coal, which are larger in size than desired, are returned to the surface of the grinding table 14 in order that they may be made to undergo additional pulverization. Thereafter, these particles of coal that have been returned to the surface of the grinding table 14 are subjected to a repeat of the pulverization process, which has been described above previously. That is, these larger particles of coal, which have been returned to the surface of the grinding table 14 for further pulverization, are thrown under the influence of centrifugal force outwardly of the grinding table 14, are then picked up by the flow of air exiting from beneath the grinding table 14 after flowing upwardly through the space 32, are next carried along entrained within the flow of air through the interior of the bowl mill 10, and as this flow of air follows, as previously described hereinbefore, the tortuous path to which reference has been had herein previously, the larger particles of coal drop back onto the grinding table 14, the lighter particles of coal though continue to be carried along entrained within the flow of air to the classifier 28, while those particles of coal, which are of the desired size are permitted to pass through the classifier 28 and are made to exit from the bowl mill 10 through the outlets (not shown in the interest of maintaining clarity of illustration in the drawings), which are suitably provided for this purpose in the bowl mill 10.
Turning now to a consideration of the primary classifier 300 constructed in accordance with the present invention, reference will be had for this purpose particularly to FIG. 4, FIG. 5 and FIG. 6 of the drawings. The principal function of the primary classifier 300 is to manage the direction and velocity of the flow of air at the location within the substantially closed separator body 12 of the bowl mill 10, constructed, by way of exemplification and not limitation, preferably in the manner that has been described herein previously and which can be found illustrated in FIG. 3 of the drawings, whereat the particles of coal, which have been subjected to pulverization as a result of the cooperative action between the grinding rolls 18 of the bowl mill 10 and the surface of the grinding table 14 of the bowl mill 10, become entrained in the flow of air that flows upwardly in the space 32 that is provided for this purpose between the circumference of the grinding table 14 and the interior of the substantially closed separator body 12 of the bowl mill 10. In a manner yet to be described herein, the primary classifier 300 constructed in accordance with the present invention also is operative to create a physical barrier to unwanted spillage of the particles of coal that have been subjected to pulverization as a result of the cooperative action of the grinding rolls 18 of the bowl mill 10 and the surface of the grinding table 14 of the bowl mill 10. This is accomplished by virtue of the fact that the primary classifier 300 constructed in accordance with the present invention is further operative to cause the particles of coal, as these particles of coal leave the surface of the grinding table 14 of the bowl mill 10, to flow upwardly in the direction of flow of the flow of air as the flow of air exits from the space 32, which is provided between the circumference of the grinding table 14 of the bowl mill 10 and the interior of the substantially closed separator body 12 of the bowl mill 10, after the flow of air has passed through the space 32.
As best understood with reference to FIG. 4 of the drawings, the primary classifier 300 constructed in accordance with the present invention includes a vane wheel portion, generally designated in the drawings by the reference numeral 360, and a low profile deflector portion, generally designated in the drawings by the reference numeral 380. The vane wheel portion 360 of the primary classifier 300 constructed in accordance with the present invention, in a manner that will be described more fully hereinafter, is constructed so as to extend circumferentially around the entire interior of the substantially closed separator body 12 of a pulverizer-type bowl mill that embodies a prior art form of construction, such as by way of exemplification and not limitation, the bowl mill 10, which has been described herein previously and which is illustrated in FIG. 3 of the drawings. Continuing, in accordance with the present invention, the vane wheel portion 360 of the primary classifier 300 is designed to be suitably affixed to the periphery, i.e., the circumference, of the grinding table 14 of the bowl mill 10, the bowl mill 10 being constructed as illustrated in FIG. 3 of the drawings, by means of any conventional form of fastening means suitable for use for such a purpose. To this end, there are two standard methods that are most frequently employed for purposes of accomplishing the affixing of the vane wheel portion 360 of the primary classifier 300 to the periphery, i.e., circumference, of the grinding table 14 of the bowl mill 10. The first of these two standard methods is commonly referred to as the “direct bolt on” method. In accordance therewith, as best understood with reference to FIG. 5 of the drawings, the individual segments which collectively comprise the vane wheel portion 360 of the primary classifier 300, are bolted on to the periphery of the grinding table 14 of the bowl mill 10 through the use of conventional threaded fasteners, only one of which, for purposes of maintaining clarity of illustration in the drawings, is depicted in FIG. 5 of the drawings, wherein this threaded fastener is denoted therein by the reference numeral 420. The second of these two standard methods is commonly referred to as the “floating pin” method. In accordance with the second of these two standard methods, i.e., the “floating pin” method (not shown in the interest of maintaining clarity of illustration in the drawings), pins/spacers would be fastened to the periphery, i.e., circumference, of the grinding table 14 of the bowl mill 10 and would be made to project though holes that would be provided for this purpose in the inner ring of the vane wheel portion 360 of the primary classifier 300. The individual segments, which collectively comprise the vane wheel portion 360 of the primary classifier 300, would be welded together so as to create therefrom a solid 360° ring extending around the entire circumference of the grinding table 14 of the bowl mill 10 and this solid 360° ring portion of the vane wheel portion 360 would be allowed to float on the aforementioned pins/spacers. This second of the two standard methods for affixing the vane wheel portion 360 to the periphery of the grinding table 14 of the bowl mill 10 possesses several advantages; namely, it eliminates the need for ensuring that the circumference of the grinding table 14 of the bowl mill 10 embodies a good mating surface and by virtue of the floating action associated therewith it avoids the problem of thermal growth issues.
Continuing with the description of the vane wheel portion 360 of the primary classifier 300 constructed in accordance with the present invention, reference will be had for this purpose in particular to FIG. 6 of the drawings. To this end, as best understood with reference to FIG. 5 of the drawings, the vane wheel 360 of the primary classifier 300 constructed in accordance with the present invention includes a steel inner ring referred to as the inner shroud and denoted in the drawings by the reference numeral 435, and a steel outer ring referred to as the outer shroud and denoted in the drawings by the reference numeral 440. In accordance with the best mode embodiment of the present invention, preferably approximately thirty steel vanes, each such vane being denoted in the drawings by the reference numeral 50, are suitably positioned around the circumference of the grinding table 14 of the bowl mill 10 so as to be equally spaced with approximately six such vanes 50 being associated with each segment of the vane wheel portion 360 of the primary classifier 300. As best understood with reference to FIG. 6 of the drawings, the vanes 50 are operative to effect an interconnection of the inner shroud 435 of the vane wheel portion 360 of the primary classifier 300 with the outer shroud 440 of the vane wheel portion 360 of the primary classifier 300.
Also, the vane wheel portion 360 of the primary classifier 300 constructed in accordance with the present invention is usually provided, as best understood with reference to FIG. 6 of the drawings, with abrasion resistant liners, denoted in the drawings by the reference numeral 52. The abrasion resistant liners 52, which as illustrated in FIG. 6 of the drawings are equipped with horizontal plates, denoted in the drawings by the reference numeral 54, are designed to be operative to protect the vanes 50 from the wear that would otherwise be incurred from the vanes 50 being struck by particles of coal that are entrained in the flow of air as the flow of air flows upwardly through the vane wheel portion 360, which is located in the space 32 of the bowl mill 10. With further reference to the abrasion resistant liners 52 equipped with the horizontal plates 54, the horizontal plate 54 portion of the abrasion resistant liners 52 is most often referred to as the “wing tips”, and it is the length of these wing tips, which function as the means by which control is had over the free area of the vane wheel portion 360 of the primary classifier 300 constructed in accordance with the present invention. The velocity of the flow of air as the flow of air passes through the vane wheel portion 360 of the primary classifier 300 as the flow of air flows upwardly through the space 32 provided for this purpose in the bowl mill 10 is in turn established by the length of the aforedescribed wing tips.
Continuing, the vane wheel portion 360 of the primary classifier 300 may, if so desired, without departing from the essence of the present invention, be provided, as best understood with reference to FIG. 5 of the drawings, with a set of additional liners commonly referred to as being the vane wheel inner shroud liner, denoted in the drawings by the reference numeral 430. In accordance with the present invention, one such vane wheel inner shroud liner 430 is provided, in mounted relation thereto by means of any conventional form of mounting means suitable for use for such a purpose, per each segment of the vane wheel portion 360 of the primary classifier 300 constructed in accordance with the present invention thereby resulting in full 360° protection of the inner shroud 435 and fasteners 420, which are located above the abrasion resistant liners 52 with which the vanes 50 are provided. Normally, however, the vane wheel inner shroud liners 430 are preferably in accordance with the best mode embodiment of the invention mounted by being welded in place after the vane wheel portion 360 of the primary classifier 300 has been affixed to the grinding table 14 around the outer periphery thereof.
A description will now be had herein of the low profile deflector portion 380 of the primary classifier 300 constructed in accordance with the present invention. For this purpose, reference will be had in particular to FIGS. 4 and 5 of the drawings. The low profile deflector portion 380 of the primary classifier 300 is in accordance with the present invention mounted within the interior of the substantially closed separator body 12 of the bowl mill 10 constructed as has been described herein previously and as is illustrated in FIG. 3 of the drawings in closely spaced relation to the surface of the grinding table 14 of the bowl mill 10. This mounting of the low profile deflector portion 380 of the primary classifier 300 constructed in accordance with the present invention is in contrast to the manner in which the prior art type of non-continuous deflector to which reference has been had hereinbefore is mounted. More specifically, the low profile deflector portion 380 of the primary classifier 300 constructed in accordance with the present invention is mounted at an elevation in the substantially closed separator body 12 of the bowl mill 10 below the elevation at which the grinding journal openings/doors 205 are located, as has been illustrated, for example, in FIG. 2 of the drawings. Thus, unlike the prior art type of non-continuous deflector that is illustrated in FIGS. 2 and 3 of the drawings, the low profile deflector portion 380 of the primary classifier constructed in accordance with the present invention is, therefore, continuous about the interior of the substantially closed separator body 12 of the bowl mill 10, as the low profile deflector portion 380 does not have to have sections thereof omitted for purposes of thereby creating open areas to accommodate the grinding journal openings/doors 205.
The low profile deflector portion 380 of the primary classifier 300 constructed in accordance with the present invention encompasses the following components: upper liners, denoted in the drawings by the reference numeral 401, middle liners, denoted in the drawings by the reference numeral 405, and lower liners, denoted in the drawings by the reference numeral 410. In accordance with the best mode embodiment of the invention, each of the liners 401, 405, and 410 is preferably affixed through the use of any conventional form of fastening means suitable for use for this purpose directly to the inner wall of the substantially closed separator body 12 of the bowl mill 10, thereby eliminating the need for employing any type of support plate components. The affixing of the liners 401, 405 and 410 to the inner wall of the substantially closed separator body 12 of the bowl mill 10 could, for example, be accomplished by means of by welding or bolting, although other forms of fastening means could also be utilized, as desired, without departing from the essence of the present invention. Preferably, the liners 401, 405, and 410, in accordance with the best mode embodiment of the invention, are made of an abrasion resistant material that is suitable for use for such a purpose.
The upper liners 401, as best understood with reference to FIG. 5 of the drawings, are in their mounted state affixed to the inner wall of the substantially closed separator body 12 of the bowl mill 10 angled downwardly, preferably at a 45° angle, to thereby be operative to effect the shedding of any particles of coal, which might otherwise settle on the exposed surface of the upper liners 401. Such particles of coal, which are shed from the upper liners 401 again upon being so shed therefrom become entrained in the flow of air that flows in an upwardly direction through the free area of the vane wheel portion 360 of the primary classifier 300 constructed in accordance with the present invention. The middle liners 405, as best understood with reference to FIG. 5 of the drawings, in their mounted state affixed to the inner wall of the substantially closed separator body 12 of the bowl mill 10 are angled inwardly to direct the flow of air that flows through the free area of the vane wheel portion 360 of the primary classifier 300 constructed in accordance with the present invention in an inwardly direction back over the grinding table 14 of the bowl mill 10.
The low profile deflector portion 380 of the primary classifier 300 constructed in accordance with the present invention is operative to direct the flow of air from the free area of the vane wheel portion 360 of the primary classifier 300 in over the grinding table 14 of the bowl mill 10 at approximately the same velocity that flow of air travels through the free area of the vane wheel portion 360 of the primary classifier 300. However, once the flow of air that has traveled through the free area of the vane wheel portion 360 of the primary classifier 300 over the grinding table 14 of the bowl mill 10, this flow of air undergoes a drastic drop in velocity thereby causing the larger particles of coal, which have become entrained in this flow of air to return to the grinding table 14 of the bowl mill 10.
As will be understood by one of ordinary skill in the art, as well as from the discussion above, those particles of coal, which have been pulverized to the desired size are then carried entrained therewith by the flow of air up to the classifier 28 of the bowl mill 10. The flow up to the classifier 28 of the bowl mill 10 of this flow of air within which the particles of coal that have been pulverized to the desired size are entrained takes place in essentially the same manner as such a flow of air with particles of coal entrained therein does in the case when existing prior art types of primary classifiers are being employed. Thus, the primary classifier 300 constructed in accordance with the present invention is capable of being employed with existing prior art types of bowl mills without any difficulty irrespective of whether a dynamic classifier or a static classifier is being employed in such prior art types bowl mills.
Continuing, the low profile deflector portion 380 of the primary classifier 300 constructed in accordance with the present invention is operative to deflect the flow of air from the free area of the vane wheel portion 360 of the primary classifier 300 before the particles of coal are fully entrained in this flow of air, thereby enabling similar flow patterns to be achieved in the bowl mill 10 in which the primary classified 300 constructed in accordance with the present invention has been installed as those that exist in prior art forms of bowl mills that are equipped with prior art forms of primary classifiers, with much less internal wear of the bowl mill 10, which is equipped with the primary classifier 300 constructed in accordance with the present invention. Thus, with the low profile deflector portion 380 of the primary classifier 300 constructed in accordance with the present invention being mounted so as to be affixed directly to the inner wall of the substantially closed separator body 12 of the bowl mill 10 just over the vane wheel portion 360 of the primary classifier 300, particles of coal are kept away from the vane wheel portion 360 of the primary classifier 300, thereby not only reducing the wear to which the vane wheel portion 360 of the primary classifier 300 is subjected, but also minimizing the amount of spillage of particles of coal that is allowed to occur.
The primary classifier 300 constructed in accordance with the present invention as described herein and as illustrated in particular in FIGS. 4, 5 and 6 of the drawings also provides for both ease of installation as well as reduced cost compared to the ease of installation and cost of the prior art forms of primary classifiers that have been employed heretofore in accordance with the prior art in pulverizer-type bowl mills. This is largely attributable to the fact that the low profile deflector portion 380 of the primary classifier 300 constructed in accordance with the present invention is continuous in nature for a full 360°, and thus because no side liners and no support plates need to be utilized with the primary classifier 300 of the present invention.
The present invention is not to be limited in scope by the specific embodiments described herein. Indeed, various modifications of the present invention, in addition to those described herein, will be apparent from the foregoing description and accompanying drawings to those who are skilled in this art. Thus, such modifications are intended to fall within the scope of the appended claims.
Patent Application
20080054112
