The present invention is directed to a bowl mill type pulverizer, and more particularly, to such a primary classifier for use in a bowl mill type pulverizer.
BACKGROUND
Pulverizers for grinding different type materials are well known in the prior art. Coal is one such material wherein there exists a need to grind the material in order to render it suitable for use in certain applications. One particular type of conventional coal pulverizer is that which is commonly referred to in the industry as a bowl mill. Such a coal pulverizer obtains its name by virtue of the fact that the pulverization, i.e., grinding, of the coal, which takes place therein, is effected on a grinding surface that insofar as the configuration thereof is concerned bears a resemblance to a bowl.
A bowl mill essentially includes a body portion in which a grinding table is mounted for rotation, a plurality of grinding rollers that interact with the grinding table to effect the grinding of coal interposed therebetween, coal supply means for feeding to the interior of the bowl mill the coal that is to be pulverized therein, and air supply means for supplying to the interior of the bowl mill the air required for purposes of the operation of the bowl mill. In accordance with the mode of operation of such a bowl mill, the coal, which enters the bowl mill, is pulverized by virtue of the interaction of the grinding rollers with the grinding table. After being pulverized, the coal particles are thrown outwardly by centrifugal force, whereby the particles are fed into a stream of air that is made to enter the bowl mill. This stream of air, which now contains pulverized coal particles, flows through a tortuous path that is established in part by the positioning within the bowl mill of a suitably supported deflector means. As the stream of air and coal particles flows along the afore referenced tortuous path, the sharp turns contained therein function to effect the separation of the coarse coal particles from the air stream. These coarse coal particles, which have been separated from the air stream, are then suitably returned to the grinding table for further pulverization, while the fine coal particles, which

remain entrained in the air stream, are carried through the bowl mill in the air stream, and exit from the bowl mill along with the air stream.
A need has nevertheless been evidenced for improvements to be made thereto. More specifically, prolonged operation of this type of bowl mill has revealed the existence of several undesirable conditions. One of these undesirable conditions is related to the need for and the manner in which a primary classification is had within the bowl mill of the material that is being pulverized. As employed herein the term primary classification is intended to refer to the separation of pulverized material from the air stream in which such material is entrained. In particular, reference is had here to that separation of pulverized material which occurs as a consequence of causing the air stream, within which the pulverized material is entrained, to follow a tortuous path through the bowl mill, whereby in the course of changing directions of flow as necessitated by the nature of this torturous path the larger of the particles of the pulverized material lose their momentum and are made to return to the surface of the grinding table whereat they are subjected to further pulverization.
In accordance with the teachings of the prior art, it has been known to employ a separator body liner design in a bowl mill for purposes of accomplishing the afore described primary classification of pulverized material there within. Although a bowl mill equipped with such a separator body liner design has proven to be adequate in terms of accomplishing the desired primary classification of the pulverized materials, disadvantages associated with the employment thereof have nevertheless been encountered, such as, including but not limited thereto, limited access to the internal workings of such a bowl mill due to the positioning of the deflector therein and the creation of undesirable wear distribution patterns within the interior of such a bowl mill.
In bowl mill (10), particularly in High Performance (HP) bowl mill, as depicted in FIG. 1, a long profile deflector assembly (12) inside mill body is attached with air restriction ring (14) and vane wheel assembly (16). FIG. 1 also depicts a flow path

of air and a flow path of pulverized coal, and a flow path of the air carrying the pulverized coal along the long profile deflector assembly (12). In FIG. 2, unwanted materials like iron particles, rocks and heavy coal are trapped between long profile deflector assembly (12) and the vane wheel assembly (16), which are disposed in the bowl mill (10) having a lower mill housing (10a) and an upper bowl housing (10b) that are coupled via a flange coupling member (10c). An effort, as shown in FIG. 2, was tried in the form of providing a short profile deflector assembly (12a) having a plurality of liner plates (12b) making up a ring that overlaps the top portion (16b) of the vane wheel assembly outer ring (16a) to function as a labyrinth seal to minimize the amount of primary air bypassing the rotating vane wheel (16) from Al to A2. In this particular arrangement, the plurality of liner plates (12b) act as a barrier for unwanted material like iron particles, rocks and heavy coal and this unwanted material gets caught up in a horizontal gap (18) where they are dragged around the overlap ring present in the form of the plurality of liner plates (12b) generating heavy spark showers while rapidly abrading the stationary overlap ring. Compared to the rest of the wheel, the overlap ring present in the form of the plurality of liner plates (12b) and of the vane wheel assembly outer ring (16a) will wear out rapidly, causing the mill to spill coal at unacceptably high rates.
Accordingly, there also exists a need for a primary classifier in which there is no additional wear of the outer ring of the vane wheel assembly and therefore no unwanted spilling of the coal flow.
OBJECTS OF THE INVENTION
It is an object of the present disclosure to provide a primary classifier, without having the erosion from the unwanted material like iron particles, rocks and heavy coal entrained around the outer ring of the vane wheel assembly.
Still another object of the present disclosure is to provide a primary classifier, which does not restrict access to the interior of a bowl mill, particularly when such access is required for maintenance and repair purposes.

The above-stated objects, as well as other objects, features, and advantages, of the present disclosure will become readily apparent from the following detailed description when read in conjunction with the appended drawings.
SUMMARY OF THE INVENTION
In view of the foregoing disadvantages inherent in the prior art, the general purpose of the present disclosure is to provide a new and improved primary classifier for a bowl mill that overcomes the drawbacks inherent in the prior art.
In one aspect of the present disclosure, the primary classifier for a rotatable grinding surface of a bowl mill for grinding material is provided. In one embodiment, the primary classifier includes a vane wheel portion having a plurality of vanes coupled around a circumference of the rotatable grinding surface. The primary classifier includes a stationary deflector portion disposed around the vane wheel portion. The stationary deflector portion includes a plurality of first liners and a plurality of second liners. The plurality of first liners is angled downwardly to shed a pulverized material accumulated on the plurality of first liners. Further, the plurality of second liners is positioned below the plurality of first liners and angled downwardly so as to thereby direct a flow of air that flows through a free area of the vane wheel portion in an inwardly direction back over the grinding surface. Further, due to such an arrangement of the stationary deflector portion, a vertical clearance gap is provided between lower edges of the plurality of second liners and outer ring of the vane wheel portion.
In one embodiment of the present disclosure, a radial clearance is provided between the outer ring of the vane wheel portion and an inner surface of the separator body or a body of the bowl mill, in one example form, along a mill-side top flange inner diameter surface of the bowl mill.

In one embodiment of the present disclosure, each of the plurality of first liners and the plurality of second liners are formed of an abrasion resistant material.
In one embodiment of the present disclosure, the plurality of vanes is disposed between an inner shroud and an outer shroud. The inner shroud may be attached around the circumference of the rotatable grinding surface to form the upper rim of the rotatable grinding surface.
In one another aspect of the present disclosure, a bowl mill for pulverizing a material comprising a primary classifier is provided.
In one another aspect of the present disclosure, a method for assembling a primary classifier in a bowl mill for grinding material is provided. The method includes forming a radial clearance between the outer ring of the vane wheel portion and an inner surface of the separator body or a body of the bowl mill to accommodate the primary classifier.
In one embodiment of the present disclosure, forming of the radial clearance includes angularly grinding the inner surface of the separator body or a body of the bowl mill to obtain an angled mill-side top flange inner diameter surface.
BRIEF DESCRIPTION OF THE DRAWINGS
In order to facilitate a fuller understanding of the present disclosure, reference is now made to the appended drawings. These drawings should not be construed as limiting the present disclosure 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 side elevation view partially in section of a portion of another prior art primary classifier;

FIG. 3 A is a side view of a portion of a vane wheel portion including a plurality of vanes coupled around a circumference of the rotatable grinding surface, in accordance with an exemplary embodiment of the present disclosure;
FIG. 3B illustrates a top view a portion of a vane wheel portion in a bowl mill illustrating primary classifier, in accordance with an exemplary embodiment of the present disclosure;
FIG. 4 is a side elevational view partially in section and on an enlarged scale of a portion of the primary classifier of FIG. 3B, in accordance with an exemplary embodiment of the present disclosure; and
FIG. 5 is an enlarged scaled view of the circled portion of FIG. 4, in accordance with an exemplary embodiment of the present disclosure.
Like reference numerals refer to like parts throughout the description of several views of the drawings.
DETAILED DESCRIPTION
For a thorough understanding of the present disclosure, reference is to be made to the following detailed description, including the appended claims, in connection with the above-described drawings. Although the present disclosure is described in connection with exemplary embodiments, the present disclosure is not intended to be limited to the specific forms set forth herein. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but these are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present disclosure. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having" and variations thereof herein is

meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
The terms, "a" and "an" herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items.
In an embodiment of the present disclosure, the primary classifier for a rotatable grinding surface of a bowl mill for grinding material is provided. The primary classifier may include a vane wheel portion having a plurality of vanes coupled around a circumference of the rotatable grinding surface. The primary classifier may include a stationary deflector portion disposed around the vane wheel portion. The stationary deflector portion may include a plurality of first liners and a plurality of second liners. The plurality of first liners may be angled downwardly to shed a pulverized material accumulated on the plurality of first liners. Further, the plurality of second liners may be positioned below the plurality of first liners and angled downwardly so as to thereby direct a flow of air that flows through a free area of the vane wheel portion in an inwardly direction back over the grinding surface. Further, due to such an arrangement of the stationary deflector portion, a vertical clearance gap is provided between lower edges of the plurality of second liners and outer ring of the vane wheel portion.
In an embodiment of the present disclosure, a bowl mill for pulverizing material comprising a primary classifier is provided.
In a further embodiment of the present disclosure, a method for assembling a primary classifier in a bowl mill for grinding material is provided.
In as much as the construction and arrangement of the bowl mill, various associated elements may be well-known to those skilled in the art, it is not deemed necessary for purposes of acquiring an understanding of the present disclosure that there be recited herein all of the constructional details and explanation thereof. Rather, it is

deemed sufficient to simply note that as shown in FIGS. 1 to 5, in the bowl mill, only those components are shown that are relevant for the description of various embodiments of the present disclosure.
Referring now to FIGS. 3A to 5 to describe various embodiments of the present disclosure. As seen, FIG. 3A is a side view of a portion of a vane wheel portion including a plurality of vanes coupled around a circumference of the rotatable grinding surface, and FIG. 3B illustrates a top view a portion of a vane wheel portion in a bowl mill illustrating primary classifier, in accordance with an exemplary embodiment of the present disclosure. As seen, the present disclosure provides a primary classifier (100) for a rotatable grinding surface of a bowl mill (10) for grinding material. The bowl mill (10) includes a rotating grinding surface provided in a bowl assembly hub where the coal is pulverized through grinding rolls (not shown). The primary classifier (100) may be also supported by shredding plates (600) in the bowl mill (10).
Referring now to FIG. 4, wherein a side elevational view partially in section and on an enlarged scale of a portion of the primary classifier (100) of FIG. 3B is shown; and will be described in conjunction with FIGS. 3A and 3B. As best seen in FIG. 4, the primary classifier (100) constructed in accordance with the present disclosure includes a rotatable vane wheel portion (200). The rotatable vane wheel (200) portion includes a plurality of vanes (210) coupled around the circumference of the rotatable grinding surface. The primary classifier (100) may be a stationary deflector for deflecting pulverized material in presence of air flow. The primary classifier (100) may also be alternatively called a stationary deflector in describing the present disclosure. Such stationary deflector or portion thereof may be disposed around the vane wheel portion (200) and is coupled to the separator body or bowl mill body for example by welding.
Specifically, the primary classifier (100) may include a stationary deflector portion (300) disposed around the vane wheel portion (200). In one embodiment of the

present disclosure, the stationary deflector portion (300) may include a plurality of first liners (310) and a plurality of second liners (320). The plurality of first liners (310) may be angled downwardly to shed the pulverized material accumulated on the plurality of first liners (310) to shed any pulverized material that might otherwise accumulate on the plurality of first liners (310). Further, the plurality of second liners (320) may be positioned below the plurality of first liners (310) and angled downwardly so as to thereby direct a flow of air that flows through a free area (220) of the vane wheel portion (200) in an inwardly direction back over the grinding surface.
Due to such an arrangement of the stationary deflector portion (300), a vertical clearance gap (400) is provided between lower edges (320a) of the plurality of second liners (320) and an outer ring (200a) of the vane wheel portion (200). The vertical clearance gap (400) is provided between the lower edges (320a) of the second liners (320) and the outer ring (200a) of the vane wheel portion (200) enables unwanted material to fall outside of the vane wheel portion (200). Specifically, the advantage of this arrangement is that the unwanted material, for example, iron pyrites, stones and heavy coal particles do not get caught between lower edges (320a) of the second liners (320) and outer ring (200a) of the vane wheel portion (200).
Further, an inner ring of the vane wheel portion (200) may be attached to a bowl assembly hub of the bowl mill (10) through, for example, via fasteners to align the primary classifier (100) with in the bowl mill (10).
In one embodiment of the present disclosure, the vertical clearance gap (400) may for example be provided in a range of about 1 mm to about 20 mm. In one preferable embodiment of the present disclosure, the vertical clearance gap (400) may for example be provided in a range of about 6 mm to about 16 mm.

In one embodiment of the present disclosure, each of the plurality of first liners (310) and the plurality of second liners (320) may be formed of an abrasion resistant material. However, without departing from the scope of the present disclosure, each of the plurality of first liners (310) and the plurality of second liners (320) may be formed may be formed of any other suitable material.
In one embodiment of the present disclosure, the plurality of vanes (210) are disposed between an inner shroud (210a) and an outer shroud (210b). The inner shroud (210a) may be attached around the circumference of the rotatable grinding surface to form the upper rim of the rotatable grinding surface.
Referring now to FIG. 5, an enlarged scaled view of the circled portion of FIG. 4 is depicted and will be described in conjunction with FIGS. 3A to 5. As illustrated in figure 5 (or in FIG. 2), the lower bowl housing (10a) and the upper bowl housing (10b) are coupled via the flange coupling member (10c). A radial clearance (500) is provided between the outer ring (200a) of the vane wheel portion (200) and inner surface of the separator body or a body of the bowl mill (10).. In one embodiment, the radial clearance (500) is provided between the outer ring (200a) of the vane wheel portion (200) and the flange coupling member 10c, i.e. along a mill-side top flange inner diameter surface (lOct) of the bowl mill (10). Such radial clearance (500) may be formed to accommodate the primary classifier (100). In one embodiment of the present disclosure, the radial clearance (500) may be formed by angularly grinding or cutting the mill-side top flange inner diameter surface (lOct). Such grinding or cutting mill-side top flange inner diameter surface (lOct) results the radial clearance (500) and have the primary classifier (100) aligned with the mill-side top flange inner diameter surface (lOct). Such radial clearance (500) is of great importance when the primary classifier (100) of the present disclosure is required to be installed in the bowl mill, such as a conventional bowl mill or new bowl mill.

In one embodiment of the present disclosure, the radial clearance (500) may be provided in the range of about 10 mm to about 40 mm. In one specific embodiment of the present disclosure, the radial clearance (500) may be about 25 mm. In addition to above, such radial clearance (500), upon the accommodation of the primary classifier (100), may also prevent the unwanted material, for example, iron pyrites, stones and heavy coal particles to not be get caught between outer ring of the vane wheel portion and the inner surface of the separator body or bowl mill body.
In one another aspect of the present disclosure, a method for assembling a primary classifier (300) in a bowl mill (10) for grinding material is provided. The method includes forming a radial clearance (500) between the outer ring (200a) of the vane wheel portion (200) and the mill-side top flange inner diameter surface (lOct) of the bowl mill (10) to accommodate the primary classifier (100).
In one embodiment of the present disclosure, forming of the radial clearance (500) includes angularly grinding the mill-side top flange inner diameter surface (lOct) to obtain an angled mill-side top flange inner diameter surface.
The radial clearance (500) may be formed in the conventional bowl mill on the site itself or can be formed in the new bowl mill for installation of the primary classifier (100) in the conventional bowl mill or the new bowl mill.
For installation of the primary classifier (100) on the conventional bowl mill, deflector plates, such as deflector plates (700) as seen in FIG. 1 or 3A, may be removed. Thereafter, all the welds for coupling the deflector plates with the bowl mill are grinded. Further, an air restriction ring, such as the air restriction ring (14), is removed. Furthermore, the mill-side top flange inside diameter of the bowl mill is cut or grinded and radial clearance, such radial clearance (500), is obtained. Once such radial clearance is obtained, the primary classifier (100) may be easily installed or accommodated in the conventional bowl mill.

Moreover, for installation of the primary classifier (100) on the new bowl mill, the mill-side top flange inside diameter of the bowl mill is cut or grinded and radial clearance, such radial clearance (500), is obtained. Once such radial clearance is obtained, the primary classifier (100) may be easily installed or accommodated in the new bowl mill.
The primary classifier constructed in accordance with the present disclosure as described herein and as illustrated in particular in FIGS. 3, 4 and 5 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 lower portion of the deflector of the primary classifier constructed in accordance with the present disclosure is in continuation of the aforesaid changes made in the primary classifier. The primary classifier constructed in accordance with the present disclosure is arrangeable in any type of bowl mill including HP mill and RP Mill.
The foregoing descriptions of specific embodiments of the present disclosure have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present disclosure to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present disclosure and its practical application, to thereby enable others skilled in the art to best utilize the present disclosure and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present disclosure.

1. A primary classifier (100) for a rotatable grinding surface of a bowl mill
(10) for grinding material, the primary classifier (100) comprising:
a vane wheel portion (200) including a plurality of vanes (210) coupled around a circumference of the rotatable grinding surface; and
a stationary deflector (300) portion disposed around the vane wheel portion (200), the stationary deflector portion (300) having:
a plurality of first liners (310) angled downwardly to shed a pulverized material accumulated on the plurality of first liners (310), and
a plurality of second liners (320) positioned below the plurality of first liners (310) and angled downwardly so as to thereby direct a flow of air that flows through a free area (220) of the vane wheel portion (200) in an inwardly direction back over the grinding surface,
wherein a vertical clearance gap (400) is provided between lower edges (320a) of the plurality of second liners (320) and outer ring (200a) of the vane wheel portion (200).
2. The primary classifier (100) as claimed in claim 1, wherein a radial clearance (500) is provided between the outer ring (200a) of the vane wheel portion (200) and an inner surface of the separator body or a body of the bowl mill (10).
3. The primary classifier (100) as claimed in claim 1, wherein the vertical clearance gap (400) is in a range of about 1 mm to about 20 mm.
4. The primary classifier (100) as claimed in claim 1, wherein the vertical clearance gap (400) is in a range of about 6 mm to about 16 mm.
5. The primary classifier (100) as claimed in claim 2, wherein the radial clearance (500) is in a range of about 10 mm to about 40 mm.

6. The primary classifier (100) as claimed in claim 2, wherein the radial clearance (500) is about 25 mm.
7. The primary classifier (100) as claimed in claim 1, wherein the plurality of first liners (310) and the plurality of second liners (320) are each formed of an abrasion resistant material.
8. The primary classifier (100) as claimed in claim 1, wherein the plurality of vanes (210) are disposed between an inner shroud (210a) and an outer shroud (210b), the inner shroud (210a) being attached around the circumference of the rotatable grinding surface to form the upper rim of the rotatable grinding surface.
9. A bowl mill (10) for pulverizing material comprising a primary classifier (100) as claimed in claim 1.
10. A method for assembling a primary classifier as claimed in claim 1 in a bowl mill (10) for grinding material, the method comprising:
forming a radial clearance (500) between the outer ring (200a) of the vane wheel portion (200) and an inner surface of the separator body or a body of the bowl mill (10) to accommodate the primary classifier (100).
11. The method as claimed in claim 10, wherein forming the radial clearance
comprises angularly grinding the inner surface of the separator body or the body of
the bowl mill (10) to obtain an angled mill-side top flange inner diameter surface.