Note: Descriptions are shown in the official language in which they were submitted.
- 1 - 2898--1249D
BACKGROUND OF THE INV:I~NTION
This is a division of ~pplication Serial No. 433,727
filed August 2, 1983.
This invention relates to apparatus for pulverizing, i.e.,
grinding, material, and more specifically to a vane wheel arrange-
ment that is particularly suited for embodiment in a bowl mill
wherein the vane wheel arrangement is operative to effect a primary
classification of the pulverized material.
It has long been known in the prior art to provide
apparatus that is suitable for employment for purposes of effecting
the grinding, i.e., pulverization, of materials. More specifically,
the prior art is replete with examples of various types of
apparatus that had been used heretofore to effect the grinding
of a multiplicity of different kinds of materials. In this regard,
in many instances discernible differences of a structural nature
can be found to exist between individual ones of the aforesaid
apparatus. The existence of such differences is in turn attribut-
able for the most part of the diverse functional requirements that
are associated with the individual applications in which such
apparatus are designed to be employed. For instance, in the selec-
tion of the particular type of apparatus that is to be utilizied
for a specific application one of the principal factors to which
consideration must be given is that of the nature of the material
that is to be ground in the apparatus.
Coal is one such material wherein there exists a need
to grind the material in order to render it suitable for use
~1`~
i~
in certain applications. Furthermore, fossil fuel fired power
generation systems represent one such application in which it
is desired to employ coal, as the source of fuel therefor, and
wherein a requirement exists to grind, i.e., pulverize, the
coal in order to render it suitable for use for this purpose.
To this end, coal has long been recognized as being one of
this nations most abundant sources of fuel. At one time
earlier in this century, much of the nation's energy needs
were being met through the use of coal. Then, in the degree
to which coal was being employed to generate power a decline
set in. Much of this decline stemmed from the increased usage
of oil and gas as sources of fuel. More recently, the power
being generated from the burning of oil and gas has been
supplemented by the use of nuclear fuel for power producing
purposes. However, with the advent of the oil embargo in the
last decade, which was accompanied by a sharp increase in +he
price of oil and +he existence of restricted oil supplies, and
the increased concern, which has since been expressed over the
rate at which the world's known oil reserves are being
depleted, coal has begun +o regain some of the favor, which it
once had as a source of fuel to meet the nation's energy
needs. To some extent, this has been evidenced Tn a number of
orders, which have been placed in recently passed years, for
power generation systems that are to be coal-fired as well as
the extent to which increased interest has been shown in
effecting the conversion of existing oil and gas fired power
generation systems to coal fired systems.
For purposes of the discussion that follows, the coal
fired systems referred to above are considered to consist of
essentially the following major operating components: a coal
feeder, apparatus for pulverizing the coal, a distribution
system for dis+ributing the coal after the pulverization
thereof, a furnace in which the coal is to be burned, and the
requisite controls for effecting the proper operation of the
coal fired power generation system. Of particular interest
herein is that portion of the coal fired system, which has
been identified above as +he apparatus for pulverizing the
coal. Coal pulverizing apparatus are not new. They have been
known to exist in the prior art for more than half a century.
Furthermore, many improvements in the construction and/or mode
of operation of coal pulverizing apparatus have been made
during this period.
There are a number of features ~hat it ls
advantageous for any coal pulverizing apparatus to possess,
but particularly those which are designed for employment in a
coal fired power generation system. Reference is had here to
features such as reliability, low power consumption, mlnimum
maintenance and wide range of capacity. In addition, such
apparatus advantageously should also be characterized by quiet
operation, integrated lubrication systems, convenient
adjustment and control of coal flow and fineness, and the
ability to handle the high temperature air that is required
for high moisture coal.
One particular type of coal pulverizing apparatus,
which is to be found in the prior art, that is advantageously
- 20 characterized by the embodiment therein of the above recited
features is an apparatus, most commonly referred to in the
industry by the name bowl mill. The latter apparatus 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 in configuration bears a resemblence
to a bowl. Reference may be had by way of exemplification to
U.S. Patent No. 3,465,971, which issued September 9, 1969 to
J. F. Dalenberg et al., and/or U.S. Patent No. 4,002,299,
which issued January 11, 1g77 to C. J. Skalka, both of the
latter patents being assigned to the same assignee as the
instant application, for a teaching of the nature of the
construction and the mode of operation of a prior art form of
bowl mill that is suitable for use in a coal fired power
generation system to effectuate the pulverization of the coal
that is to be burned as fuel therein. As taught by the
aforereferenced patents, a bowl mill essentially consists of a
~;~3Ç6 ~6~
body portion in which a grTnding table is mounted for
rotation, a plurality of grinding rollers that coact with the
grinding table l-o 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, and air
supply means for supplying to the interior of the bowl mill
the air required in the operation of the latter. In
accordance with the mode of operation of such 2 bowl mill, the
coal, which enters the bowl mill, is pulverized by virtue of
the coaction 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 entering the bowl mill. The
stream of air, which now contains pulverized coal particles,
flows through a tortuous path that is es+ablished 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 aforementioned tortuous path, the sharp turns
contained therein effects the separation of the coarse coal
particles from the air stream. These coarse coal particles
are then suitably returned to the grinding table for further
pulverization, while the fine coal particles are carried
through the bowl mill in the air stream, and exit therefrom
along with the air.
In a conventional coal fired power generation system,
a multiplicity of bowl mills of the type shown in the
aforereferenced patents would commonly be employed for
purposes of satisfying the requirements of the system for
pulverized coal. By way of example, the capacity of each of
the individual bowl mills might be on the order of 100 tons
per hour of coal.
- Although bowl mills constructed in accordance with
the teachings of the aforereferenced patents have under actual
operating conditions provided adequate performance to date, a
need has nevertheless been evidenced for improvements to be
made therein. More specifically, prolonaed operation of this
type of bowl mill has revealed the exis+ence of several
conditions of an undeslrable nature that can arise during the
use thereof. One of these 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
therewithin. As employed herein the term primary
classification is intended to refer to the separation of
pulverized material from the air 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 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
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 aforedescribed
primary classification of pu Iverized material therewithin. By
way of exemplification, such a bowl mill comprises the subject
matter of U.S. Patent No. 4,234,132 which issued on November
18, 1980 to one of the two co-inventors of the present
application and which is assigned to the same assignee as the
present application. Although a bowl mill equipped with such
a separator body liner design has proven to be adequate in
terms of accomplishing the subject primary classification of
the pulverized materials in a bowl mill disadvantages
nevertheless are associated with the employment thereof.
Namely, the air deflector means of such a bowl mill is so
located therewlthin for purposes of accomplishing the
aforesaid primary classification of pulverized materials as to
be positioned in overhanging relation to the grinding table of
the bowl mill. As a consequence, access to the internal
workings of a bowl mill equipped with such air deflector means
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- 6 - 289~-1249D
ls limited thereby by the positioning thereof. In addition, damage
can be had thereto when incidents involving tramp iron occur.
Finally, it would be desirable to achieve a better wear distribution
pattern insofar as concerns those members mounted within the bowl
mill which are designed to be used to direct the flow of air through
the bowl mill. A need has thus been evidenced for a new and
improved means suitable for employment in a bowl mill which would
be operative when so positioned therewithin to effect the primary
classification of material being pulverized within the bowl mill.
It is, therefore, an object of the present invention
to provide a new and improved primary classifier means that is
suitably constructed so as to be employable in a bowl mill.
A further object of the present invention is to provide
such a primary classifier means for bowl mills which includes a
converging/diverging orifice means mounted in spacèd relation to
the rotatable grinding surface of the bowl mill and operative to
establish a direction of flow to the air that passes through the
interior of the bowl mill.
A still further object of the present invention is to
~0 provide such a primary classifier means for bowl mills having vane
means and converging/diverging orifice means that function in con-
junction with one another to cause the larger of the particles of
pulverized material which are entrained in the stream of air that
flows through the bowl mill to be separated from the air stream
and to be returned to the rotatable grinding surface for additional
pulverization.
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- 7 - 2898-1249D
Yet another object of the present invention is to provide
such a primary classifier means for bowl mills wherein the wear
surfaces of the vane means and the converging/diverging orifice
means are formed of a highly abrasive resistant material.
Yet still another object of the present invention is to
provide such a primary classifier means for bowl mills which is
suitable for employment in newly constructed bowl mills as well as
being equally suitable for employment in retrofit applications.
SUM~RY OF THE INVENTION
In accordance with the present invention there is pro-
vided a primary classifier means that is particularly suited for
employment in a bowl mill of the type that is operative for pur-
poses of effecting the pulverization therewithin of a material such
as coal. Preferably the subject primary classifier ~eans includes
vane means supported on the periphery of the rotatable grinding
table of the bowl mill. The vane means is operative to cause the
air flowing in surrounding relation to the rotatable grinding
table to change direction and flow counterclockwise to the direc-
tion of rotation of the grinding table thereby causing the pulver-
'~0 ized material that is entrained in the aforesaid air to be carried
in a direction reverse to the direction of rotation of the grinding
table. This in turn has the effect of causing the larger of the
particles of pulverized material to lose their momentum whereby
these larger particles are separated from the air stream and are
returned to the surface of the rotating grinding table.
The subject primary classifier means includes, in
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- 8 - 2~98-1249D
accordance with the invention, a converging/diverging orifice
means that is mounted within the bowl mill in spaced relation to
the surlace of the rotatable grinding table. This converging/
diverging orifice means comprises at least one intermediate liner
support plate mounted within the interior of the bowl mill above
and in spaced relation to the rotatable grinding surface, at least
one intermediate liner mounted on said intermediate liner support
plate in superimposed relation thereto, at least one deflector
liner support plate mounted within the interior of the bowl mill
above and in spaced relation to the rotatable grinding surface, and
a plurality of deflector liners mounted on said deflector liner
support plate in superimposed relation thereto so as to form a
converging/diverging surface. The converging/diverging orifice
means is operative to cause the air stream which has entrained there-
in pulverized material to be directed toward the center of the bowl
mill. This change in direction of the air flow is effective to
cause the larger, i.e., heavier, particles of pulverized material
to lose their momentum whereby they separate out of the air stream
and are returned to the grinding table for additional pulveriza-
~0 tion~
The wear surfaces of both the vane means and theconverging/diverging orifice means are preferably made from a high-
ly abrasive resistant material such as nihard.
BRIEF DESCRIPTION OF THE DRAWING
Figure 1 is a side elevational view partially in section
of a pulverized bowl mill embodying a primary classifier means
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- 8a - 2898-1249D
constructed in accordance with the present invention;
Figure 2 is a side elevational view partially in section
of a primary classifier means for bowl mills constructed in accor-
dance with the present invention;
Figure 3 is a side elevational view partially in section
and on an enlarged scale of a portion of the primary classifier
means for bowl mills of Figure 2 constructed in accordance with
the present invention;
Figure 4 is a side elevational view of a deflector liner
of the converging/diverging orifice means of the primary classifier
means for bowl mills constructed in accordance with the present
invention;
Figure 5 is a side elevational view of a deflector side
liner of the converging/diverging orifice means of the primary
classifier means for bowl mills constructed in accordance with the
present invention;
Figure 6 is a cross-sectional view of an intermediate
liner of the converging/divering orifice means of the primary
classifier means for bowl mills constructed in accordance with the
~0 present invention; and
Figure 7 is a side elevational view of a portion of the
vane means of the primary classifier means constructed in accor-
dance with the present invention.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now to the drawing, and more particularly to
Figure 1 thereof, there is depicted therein a pulverizing
bowl mill, generally designated by reference numeral 10,
constructed in accordance wi+h +he presen+ inven+ion.
Inasmuch as +he na+ure of +he construction and the mode of
operation of pulverizing bowl mills per se are known +o those
skilled in +he art, i+ is no+ deemed necessary, +herefore, to
set for+h herein a de+ailed description of the pulverizing
bowl mill 10 lllustrated in Figure 1 of +he drawing. Ra+her,
it is deemed sufficient for purposes of obtaining an
unders+anding of the pulverizing bowl mill 10 embodying
improved primary classifier means in accordance with the
present invention to merely present herein a description of
the nature of the construction and the mode of operation of
the componen+s of the pulverizing bowl mill 10 with which the
aforesaid primary classifier means 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, e.g., U.S. Patent No. 3,465,971,
which issued September 9, 1969 to J. F. Dalenberg et al.,
and/or U.S. Patent No. 4,002,299, which issued January 11,
1977 to C, J. Skalka.
Referring further to Figure 1 of the drawing, the
pulverizing bowl mill 10 as illustrated therein includes a
substantially closed separator body 120 A grinding table 14
is mounted on a shaft 16, which in turn is operatively
connected to a suitable drive mechanism tnot shown) so as to
be capable of being rotatably driven thereby. With the
aforesaid components arranged within the separator body 12 in
the manner depicted in Figure 1 of the drawing, tha grinding
table 14 is designed to be driven in a clockwise direction.
Continuing with a description of the pulverizing bowl
mill 10, a plurality of grinding rolls 18, preferably three in
number in accord with conventional practice, are suitably
supported within the interior of the separator body 12 so as
to be equidistantly spaced one from another around the
circumference of the separator body 12. In the interest of
-1 O-
maintaining clarity of illustration in the drawing, only one
such grlnding roll 18 has been shown in Figure 1. Wi+h
further regard to the grinding rol!s 18, each of the latter as
best understood with reference to Figure 1 of the drawing is
preferably supported on a shaft (not shown), which in turn is
cooperatively associated with some form of biasing means (not
shown). By way of exemplification, the latter biasing means
(not shown) may take the form of spring means such as that
which is illustrated and described in U.S. Patent ~o.
4,234,132. However, the biasing means (not shown) could
equally well take the form of hydraulic means. In any event
whatever form the biasing means (not shown) takes, it is
intended to be operative to urge the shaft (not shown) and
thereby the grinding roll 18 cooperatively associated
therewith towards the surface of the grinding table 14.
Commonly, the biasing means (not shown) is provided with some
form of adjustment means (not shown) through the operation of
which adjustments can be made in the spacing that exists
between the grinding roll 18 and the surface of the grinding
table 14 on which the pulverization of the material, e.g.,
coal, occurs.
The material, e.g., coal, that is to be pulverized in
the bowl mill 10 is fed thereto by means of any suitable
conventional form of feed means. By way of exemplification in
~hls regard, one such feed means that may be employed for this
purpose is a belt feeder means (not shown). Upon being
discharged from the feed means (not shown) the coal enters the
bowl mill 10 by means of a coal supply means, generally
designated by reference numeral 20, with which the separator
body 12 is suitably provided. In accordance with the
embodiment of the pulverizing bowl mill 10 illustrated in
Figure 1, the coal supply means 20 includes a suitably
dimensioned duct 22 having one end thereof which extends
outwardly of the separator body 12 and preferably terminates
in a funnel-like member (not shown). The lat,er member (not
shown) is suitably shaped so as to facilitate the collection
of the coal particles enterincg the bowl mill 10, and the
guiding thereafter of these coal particles into the duct 22.
The other end 24 of the duct 22 of the coal supply means 20 is
operative to effect the discharge of coal onto the surface of
the grinding table 14. To this end, as shown in Figure 1 of
the drawing, the duct end 24 preferably is suitably supported
within the separator body 12 through the use of any suitable
form of conventional support means (not shown) such that the
duct end 24 is coaxially aligned with the shaft 16 that
supports the grinding table 14 for rotation, and is located in
spaced relation to a suitable outlet 26 provided in the
classifier, generally designated by reference numeral 28,
through which the coal flows in the course of being fed onto
the surface of the grinding table 14.
In accord with the mode of operation of pu1verizing
bowl mills that embody the form of construction depicted in
Figure 1, a gas such as air is u+ilized +o effect the
conveyance of the coal from the grinding table 14 through the
interior of the separator body 12 for discharge from the
` 20 pulverizing bowl mill 10. The air that is used in +his
connection enters the separator body 12 through a suitable
opening (not shown) found +herein for this purpose. From the
aforesaid opening (not shown) in the separator body 12 the air
flows in surrounding relatlon from beneath the grindtng table
14 to above the surface of +he latter. More specifically, -~he
air flows through the space, identified by the reference
numeral 32 in Figure 1, provided for this purpose between +he
inner wall surface of the separator body 12 and the
circumference of the grinding table 14. The path of flow that
the air follows +hereaf+er will be described more fully
hereinafter in connection with the description of the primary
classifier means, generally designated by reference numeral 30
in Figure 1, constructed in accord with the present invention
with which the bowl mill 10 is provided.
Suffice it +o say that as the air is made to flow
through the interior of the bowl mill 10, the coal which is
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-12-
disposqd on the surface of the grinding table 14 is being
pulverized by the action of the grinding rolls 18. As the
coal becomes pulverlzed, the particles that result therefrom
are thrown outwardly by centrifugal force away fro~ the center
of the grinding table 14. Upon reaching the region of the
circumference of the grinding table 14, the coal particles are
picked up by the air flowing upwardly from beneath the
grinding table 14 and are carried away therewith. Thereafter,
and as will be described more fully hereinafter, the stream of
air with the coal particles entrained therein follows a
tortuous path through the interior of the bowl mill 10.
Moreover, in the course of following this tortuous path the
larger of the coal particles are caused to be separated from
the air stream in which they are entrained and are made to
return to the surface of the grinding table 14 whereupon they
undergo further pulvertzation. The lighter of the coal
particles, on the other hand, continue to be carried along in
the air stream. Ultimately, the combined stream of air and
those coal particles that remaln entrained therein flows to
the classifier 28 to whTch reference has previously been had
hereinbefore.
- The classifier 28, in accord with conventional
practice and in a manner which is well-known to those skilled
in this art, operates to effect a further sorting of the coal
particles that remain in the air stream. Namely, those
partlcles of pulverized coal, which are of the desired
particle size, pass through classifier 28 and along with the
air are discharged therefrom and thereby from the bowl mill 10
through the outlets 34 with which the latter is provided for
this purpose. On the other hand, those coal particles which
in size are larger than desired, are returned to the surface
of the grinding table 14 whereupon they undergo additional
pulverization. Thereafter, these coal particles are subject
to a repeat of the process described above. That is, the
particles are thrown outwardly of the grinding table 14, are
picked up by the air exiting from beneath the grinding table
3~
-13-
14, are carried along with the air through the yet to be
described tortuous path that is provided therefor through the
interior of the bowl mill 10, as the air stream follows the
aforesaid tortuous path the heavier particles drop back onto
the grinding table 14, the lighter particles though continue
to be carried along with the air to the classifier 28, those
particles which are of the proper size pass through the
classifier 28 and exit from the bowl mill 10 through the
outlets 34.
Turning now to a consideration of +he nature of the
construction of the primary classifier means 30, reference
will be had for this purpose particularly to Figures 2-7 of
the drawing. As best understood with reference thereto, the
primary classifier means 30 includes vane means, generally
designated by reference numeral 36, and converging/diverging
orifice means, generally designated by reference numeral 38.
In a manner which will be more fully described hereinafter the
vane means 36 is suitably supported on the periphery of the
rotatable grinding table 14 of the bowl mill 10. Moreover,
the vane means 36 is operative to cause the air flowing in
surrounding relation to the grinding table 14 to change
direction and flow counterclockwise to the direction of
rotation of the grinding table 14. This has the effect of
causing the pulverized material, which may be entrained in
this air, to be carried in a direction reverse to the
direction of rotation of the grinding table 14 with the result
that the larger of the particies of pulverized material lose
their momentum, separate from the stream of air and are
returned to the surface of the grinding table 14 for
additional pulverization. The converging/diverging orifice
means 38, on the other hand, as will be mors fully described
hereinafter, is suitably mounted within the interior of the
bowl mill 10 in spaced relation to the surface of the grinding
table i4. As a consequence of being so mounted, the
converging/diverging orifice means 38 is opera-i-ive to cause
the air stream, which has pulverized rnaterial entrained
~:3~
-14-
therein, to be directed toward the center of the interior of
the bowl mill 10. This constitutes a change in the direction
of flow of the air stream and is effective in causing the
larger, i.e., heavier, particles of pulverized material, e.g.,
coal, +o lose their momentum, separate out of the air stream,
and be returned to the surface of the grinding table 14 for
further pulverization.
Reference will be had first to the nature of the
construction of the vane means 36, and in particular for this
purpose to Figures 2, 3 and 7 of the drawing. To this end,
the vane means 36 as best understood with reference to Figure
2 of the drawing includes a vane wheel segment assembly,
generally designated by the reference numeral 40. The latter
vane wheel segment assembly 40 is suitably affixed to the
periphery, i.e., circumference, of the grinding table 14 by
means of any suitable conventional form of fastening means
such as through the use of threaded fasteners 42. In accord
- wtth the best mode embodiment of the invention, slx such vane
wheel segment assemblies 40 are provided suitably spaced one
to another in mounted relation around the circumference of the
grinding table 14.
Further encompassed within the vane means 36 are vane
wheel supports 44 and vane wheel deflector plates 46.
Moreover, insofar as the latter are concerned, preferably the
number of vane wheel supports 44 and vane wheel deflector
plates 46 that are utilized are equal in number to the number
of vane wheel segment assemblies 40 with which the grinding
table 14 is provided. More specifically, since six vane wheel
segment assemblies 40 are, in accord with the best mode
embodimen+ of the invention, employed a like number, i.e., six
vane wheel supports 44 and six vane wheel deflector plates 46,
are also employed.
Referring once again to Figures 2, 3 and 7 of the
drawing, the vane wheel supports 44 are each suitably attached
to a respective one of the vane wheel segment assemblies 40.
Namely, the attachment of the vane wheel suppor-ts 44 to the
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-15-
vane wheel segment assemblies 40 is preferably accomplished
through the use of any suitable conventional form of fastening
means such as threaded fasteners 48. Iikewise, the vane wheel
deflector plates 46 are each suitably mounted through the use
of any conventional form of mounting means tnot shown) in
supported relation to respective ones of the vane wheel
segment assemblies 40. To this end, in accord with the
preferred mode of construction, each vane wheel deflector
plate 46 is suitably mounted so as to be equally spaced across
two adjacent vane wheel segment assemblies 40. Completing the
description of the vane means 36, lastly the latter inc:ludes a
multiplicity of air restriction blocks, identified in Figure 2
by way of exemplifica+ion by the reference numerals 50 and
52. More specifically, as best understood with reference to
15 Figures 2, 3 and 7 of the drawing, a first set of air
restriction blocks 50 are suitably mounted around the
periphery, i.e., circumference of the grinding table 14
through the use of any conventional form of fastening means
such as threaded fasteners 54 . In accord with the best mode
embodiment of the invention, preferably a total of thirty such
air restriction blocks 50 are so mounted around the periphery
of the grinding table 14. For those applications wherein it
is deemed desirable, such as ~or instance because of air flow
considerations, to employ additional air restriction blocks a
second set of air restrtction blocks is suitably ~ounted in
superimposed relation to the air restriction blocks 50 around
the circumference of the grinding table 14. The mounting of
the air restriction blocks 52 in the aforesaid manner is
preferably effected through the use of threaded fasteners 56.
When the U58 of air restriction blocks 52 is deemed desirable,
preferably a total of thirty air restriction blocks 52 are
arranged around the periphery of the grinding table 14.
A description wiil now be had of the mode of
operation of -i-he vane means 36 of the primary classifier means
30 constructed in accordance with the present invention. As a
prelude thereto, however, note is first made of the fact that
.. . . . . . . .
-16-
there exists an open area, i.e~, +he space denoted by the
reference numeral 32, in surrounding relation around the
entire, i.e., 360, circumference of the grinding table 14.
~oreover, in the manner that has been described above, the
grinding table 14 has mounted thereto a plurality of vane
wheel segment assemblies 40. The latter are so attached to
the circumference of the grinding table 14 such as to be
rotatable therewith. Further, the vane portions of the vane
wheel segment assemblies 40 project outwardly of the grinding
table 14 at an angle of approximately 45 counter to the
rotation of the grinding table 14. Consequently, the air
exiting from beneath the grinding table 14 engages the vane
wheel segment assemblies 40 and is made thereby to turn in a
direction away from the direction of rotation of the grinding
table 14. This change in direction of the air flow, in turn,
causes any pulverized material, e.g., coal, which may be
entrained in this air to be carried in a direction opposite to
the direction of rotation of the grinding table 14. The
effect of the latter is that the larger coal particles lose
their momentum whereupon they separate from the air and are
returned to the surface of the grinding table 14 for further
pulverization. Finally, inasmuch as the engagement of the air
having coal particles entrained therein with various surfaces
of the vane means 36 is In the nature of an abrasive action
.~ 25 the wear surfaces of the vane means 36, e.g., the vane wheel
supports 44, the vane wheel deflec+or plates 46, the air
restriction blocks 50 and 52, etc., are each preferably formed
from a material noted for its good abrasive resistant
qualities such as the material known as nihard to those
skilled in this art.
Next a discussion will be had of the other major
component of the primary classifier rneans 30 constructed in
accordance with the present invention; namely, the
converging/diverging orifice means 38. For purposes of this
discussion of the converging/diverging orifice means 38
reference will be had in particular to Figures 2-6 of the
~23~6~
drawing~ Thus, as will be best understood with reference to
Figure 2 and as will be more fully described hereafter the
converging/diverging orifice means 38 encompasses the
following components: intermediate liner support plate 58,
deflector liner support plate 60, intermediate liner 62,
deflector liner 64 and deflector side liner 66.
Continuing with the description of the
converging/diverging orifice means 38, in accord with the best
mode embodiment of the invention three such intermediate liner
support plates 58 are utilized, only one thereof being visible
however in Figure 2 of the drawing. Moreover, for purposes of
effecting the installatton of the intermediate liner support
plate 58 within the interior of the bowl mill 10, each of the
intermediate liner support plates 58 is suitably centered
relative to a respective one of the journal openlngs ~not
shown) with whTch the separator body 12 is suitably provided
for purposes of ac~ommodating therewithin the journal (not
shown) that each of the pulverizer rolls 18 has cooperatively
associated therewith. With the intermediate liner support
plates 58 positioned in the aforesaid manner, they are
preferably secured in place by means of welding, i.e., welded
to the interior of the separator body 12.
Thereafter, the deflector liner support plates 60 are
suitably installed within the interior of the bowl mill 10.
To this end, the deflector liner support plates 60 are
positioned such that they occupy the area that extends between
each pair of adjoining journal openings (not shown). Thus,
inasmuch as the bowl mill 10 in accord with conventional
practice is provided with three such journal openings (not
shown), a like number, i.e., three such deflector liner
support plates 60 are employed in the bowl mill 10. For
purposes of effecting the securing of the deflector liner
support plates 60 in place, the latter are preferably suitably
welded to the interior of the separator body 12.
After the aforesaid has been accomplished, each of
the deflector liner support plates ~0 has affixed thereto in a
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~L~;3&~
-18-
manner ye+ +o be described one of +he deflector side liners
66, i.eO, +ha+ deflec+or side liner which is identified in
Figure 2 by means of +he reference numeral 66a. In this
regard, the detlec+or side liner 66a is sui+ably posi+ioned
such tha+ preferably +he back edge thereof is flush with +he
interior surface of the separator body 12 and such that the
bo+tom edge thereof is arranged so as to be flush with the
previously described intermediate liner support plate 58. In
accord with the best mode embodiment of the invention, the
securing of the deflector side liner 66a in place is effected
+hrough +he use of welding plugs 68. Accordlngly, for this
purpose the deflector side liner 66a is provided with a
plurality of openings, preferably three in number that are
suitably spaced one from another which are utilized to
accommodate therein the aforereferenced welding plugs 68.
Continuing, in accord with the preferred mode of
installation each of the intermediate liner support plates 58
then has a multiplicity of intermediate liners 62 mounted
thereon. The particular number of intermediate liners 62 that
are employed for this purpose is a function of the area that
it is desired to have occupied thereby. To this end, in
accord wlth the best mode embodiment of the invention, each of
the intermediate liner support plates 5~ has a total of three
such Tntermediate liners 62 mounted thereon. Howeverl a
greater or a lesser number thereof could also be employed
without departing from the essence of the invention. Further,
as in the case of the aforedescribed deflector side liner 66a,
the affixation of the intermediate liners 62 to the
intermediate liner support plates 58 preferably is
accomplished through the use of welding plugs 70. As such,
each of the intermediate liners 6Z has a number of openings
formed therein that are each suitably dimensioned so as to be
capable of accommodating a welding plug 70 therein. The use
of welding plugs for this purpose is preferred inasmuch as it
obviates the need to effect the alignment of openings in the
intermediate liners 62 with corresponding openings formed in
~:3%~i~6~3
--1 9~
the intermediate liner support plates 58 if threaded fasteners
were to be empioyed in lieu of welding plugs.
Thereafter, the other deflector side liner, i.e.,
that identified by the reference numeral 66b in Figure 2, is
installed in a fashion similar to that which was set forth
herein previously in connection h' ith -~he description of the
deflector side liner 66a. Namely, the deflector side liner
66b is installed so that the back edge thereof is arranged to
be flush with +he separator body 12 and so that the bottom
edge thereof is arranged to be flush with the intermediate
liner 62. The affixation of the deflector side liner 66b in
the aforedescribed position is preferably accomplished through
the use of welding plugs 72. For this purpose the deflector
side liner 66b is thus provided with a plurality of spaced
openings each suitably dimensioned so as to be capable of
accommodating therewithin a welding plug 72.
To complete the installation of the remaining
components that comprise the converging/diverging orifiçe
means 38, first the bottom row of deflector liners 64 is
`20 installed commencing with the deflector liner that is denoted
Tn Figure 2 by the reference numeral 64a. Thereafter the
remainder of the bottom row of deflector liners 64 is
installed moving from right to left as viewed with reference
to Figure 2 of the drawing. Each of the bottom row of
deflector liners 64 which in accord with the best mode
embodiment of the invention comprise twelve in number, i.e.,
four per each one of the deflector liner support plates 60, is
secured in place preferably through the use of the welding
plugs 74. To this end, each of the bottom row of deflector
liners 64 is provided with a plurality of openings, e.g.,
three in number, the latter each being suitably dimensioned so
as to be capable of accommodating one of the welding plugs 74
therewithin.
Next the middle row of deflector liners 64 is
instailed in mounted relation on the deflector liner support
plates 60. In accord with the preferred method of
~;~3~
-20-
installation the deflector liner identified by means of the
reference numeral 64b in Figure 2 is installed first. Then
the remainder of the middle row of deflector liners 64 is
installed moving from right to left from the deflector liner
64b. In accord with the best mode embodiment of the invention
a total of fifteen deflector liners 64 constitute t~e middle
row thereof with five being employed per each one of the
deflector liner support piates 60. As in the case of the
bottom row of deflector liners 64, each of the middie row of
deflector liners 64 is secured in place by means of welding
plugs 76, the latter being accommodated in corresponding
openings with which each of the deflector liners 64 of the
middle row are provided.
Lastly the top row of deflector liners 64 is
installed beginning with the deflector liner that is
identified in Figure 2 by the reference numeral 64c.
Thereafter, the remainder of the +op row of deflector liners
64 is installed moving from rtght to left as viewed with
reference to Figure 2 in mounted relation on the deflector
liner support plates 60. As with the middle row of defiector
liners 64, preferably the top row of deflector liners 64 is
comprised of a total fifteen such liners, with five thereof
being cooperatively associated with each one of the deflector
liner support plates 60. Each of the top row of deflector
~ 25 Itners 64 is secured in place by means of the welding plugs
78, the latter being suitably received in openings with which
each one of the top row of deflector liners 64 is provlded.
It 7s to be understood that although the bottom row,
middle row and top row of deflector liners 64 have each been
described herewithin as comprising a specific number of
deflector liners 64, a greater or lesser number thereof could
equally well be employed without departing from the essence of
the present invention. One of the primary factors considered
in the determination of the particular number of deflector
liners 64 that is employed is that of the ease with which
individual ones of the deflector liners 64 lend themselves to
-21-
being handled in the course of the effectuation within the
interior of the separator body 12 of their installation
ori~inally followed by their subsequent removai and
replacement when they become worn. Further, as best
understood with reference to Figures 4, 5 and 6 of the drawing
the deflector liner 64, the deflector side liner 66 and the
intermediate liners 62, respectively, are suitably configured
so as to embody surfaces tha+ are complementary in nature to
those members that are designed to be ins+alled in juxtaposed
relation thereto. To this end, and by way of exemplification,
the edge surfaces of the deflector liner 64 of Figure 4 are
suitably configured such as being beveled so as to enable them
+o mate with the complementary edge surfaces of the deflector
liner 64 that adjoin thereto. Thls is not only to facilitate
the intial installation of the deflector liner 64 within the
separator body 12, but also to facilitate their removal and
subsequent replacement when they become worn. Finally,
because of the abrasive action to which they are subjected by
virtue of the air having coal particles entrained therein
striking thereagainst the wear surfaces of the
converging/diverging orifice means 38, i.e., the deflector
liners 64~ the intermediate liners 62 and the deflector side
liners 66 are preferably formed of a material that is noted
for its good abrasive resistant qualities such as nihard.
There will now be set forth a brief description of
the mode of operation of the converging/diverging orifice
means 38 of ~he prlmary classifier means 30 of the bowl mill
lO constructed in accordance with -the present invention. With
the converging/diverging orifice means 38 mounted as has been
described previously hereinabove, i.e., so as to be located
above and in spaced relation to the surface of the grinding
table 14, the converging/diverging orifice means 38 is
operative to cause the stream of air in which the pulverized
coal particles are entrained to be deflected towards the
center of the interior of the bowl mill lO. This change in
direction in turn causes the heavier ones of the coal
~3~68
- 22 - 2~98-1249D
particles to lose their momentum, thereby separating themselves
from the air stream in which they have been entrained, and causing
them to return to the surface of the grinding table 14 for regrind-
ingr i.e., additional puIverization. The converging/diverging
orifice means 38 can thus be seen to be operative to effectuate a
primary classification of the coal particles which have become
entrained in the air stream that flows through the interior of
the bowl mill 10.
Thus, in accordance with the present invention there
has been provided a new and improved primary classifier means that
is suitably constructed so as to be employable in a bowl mill. The
primary classifier means does not inhibit access from being had to
the internal workings of the bowl mill, and preferably includes
vane means suitably supported on the circumference of the rotatable
grinding surface of the bowl mill and operative to establish a
direction of flow to the air that passes through the interior of
the bowl mill. The primary classifier means for bowl mills of the
present invention includes a converging/diverging orifice means
mounted in spaced relation to the rotatable grinding surface of
~0 the bowl mill and is operative to further establish a direction of
flow to the air that passes through the interior of the bowl mill.
The vane means and converging/diverging orifice means function in
conjunction with one another to cause the larger of the particles
of pulverized material which are entrained in the stream of air
that flows through the bowl mill to be separated from the air
stream and to be returned to the rotatable grinding surface for
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~3~
~ 23 - 2898--1249D
additional pulverizationO Preferably the wear surfaces of the
vane means and the converging/diverging orifice means are formed
of a hi~hly abrasive resistant material. Furthermore, in accord
with the present invention the primary classifier means for bowl
mills is suitable for employment in newly constructed bowl mills
as well as being equally suitable for employment in retrofit
applications.
While only one embodiment of our invention has been shown,
it will be appreciated that modifications thereof, some of which
have been alluded to hereinabove, may still be readily made there-
to by those skilled in the art. We, therefore, intend by the
appended claims to cover the modifications alluded ~o herein as
well as all the other modifications which fall within the true
spirit and scope of our invention.
