Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to tumbling or grinding mills,
. rotary kilns, dryers, and the like, and more generally to apparatus -
of the kind having a horizontally mounted or slightly inclined
rotary drum along which a charge is caused to flow. The drum is
usually of cylindrical or conical shape, Such apparatus is exten-
sively used in the mineral and metallurgical process industries.
In the majority of cases, the drums are fed and discharged continu-
ously and openings are provided at the axial extremities of the
drums for the ingress and egress of solids and/or fluids such as
water, hot gas, and the like.
In some cases it may sometimes be desired to carry on
two or more stages of the process in sequence within the same drum,
One example of such a requiremant is a two-stage grinding process
in which coarse grinding is performed, using large grinding media,
in the upstream ~nd of a ball mill and fine grinding, using smaller --
grinding media, is performed in the downstream end of the mill. ~;
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A diaphragm partition is usually used to keep the two sizes of
media separate, the diaphragm partition being provided with slots
through which the charge can pass.
.
Furthermore, it ic usually advantageous to ensure that
the charge will flow through the diaphragm in one direction only,
i.e, downstream. This is usually accomplished by constructing a
partition with two diaphragms spaced several inches apart, the up-
stream diaphragm being provided with slots for passage of the
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charge and the downstream diaphragm having a central opening of
comparable size to the main feed and discharge openings of the
drum. The space between the diaphragms is divided into a number
of compartments by means of radial vanes or lifters, whose function
`~ is to elevate material as the drum rotates, the lifted material
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sliding down the lifter radially towards the centre of the mill
shell. A conical deflector is provided at the axial centre of
the diaphragm to deflect the material from the lifters to the outer,
downstreaM side of the partition. In other cases it is sometimes
advantageous to discharge process material or charge from a rota-
ting drum through ports around the periphery of the drum rather
than through an end discharge opening. In such a case, when grind-
ing media have to be retained within the shell, it is usual to
; provide a single slotted grate diaphragm, without lifters, through
which the material can flow and hence through the peripheral ports.
It is an object of the present invention to provide an
apparatus with provision for introducing solids or fluids into the
~ rotary drum, at an intermediate point between the ends of the
drum, without accidental discharge of materials already insidè
. the drum,
:
According to the invention there is provided in an appara-
tus comprising a horizontally mounted rotary drum along which a
charge is caused to flow from an upstream zone of the drum to a
downstream zone which is axially spaced from the upstream zone,
means defining an intermediate zone at which an additional material
may be introduced into the charge, said means comprising a plura-
lity of axially spaced transverse drum partitions defining first,
-. second and third lifting chambers, with deflector means for deflec-
ting the charge and additional material through the chambers to-
: wards the downstream zone, the deflector means providing a trap
. for preventing the passage of material back to the upstream zone~
- The additional material may be a gas or vapor, or a solid or liquid
material or slurry,
In order that the invention may be readily understood,
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two embodiments thereof will now be described, by way of example
; with reference to the accompanying drawings, in which:
Figure 1 is a side elevation of a tumbling mill having
means for introducing a gas or vapour at an intermediate zone of
the mill;
Figure 2 i3 a cross-sectional view of the mill, the
section being taken through the intermediate zone, and certain
parts being broken away to show details of said zone;
Figure 3 is a longitudinal sectional view showing details
of the intermediate zone;
Figure 4 is a longitudinal sectional view corresponding
to Figure 3 of a modified apparatus having means for introducing
. solids or slurries at the intermediate zone, and
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. Figure 5 is a cross-sectional view corresponding to
: Figure 2 of said modified apparatus.
Referring to Figure 1, the tumbling mill comprises a
horizontally mounted rotary drum 10 of cylindrical shape, the drum
. being mounted on bearings 11, 12 and being rotated about its
horizontal axis by a drive motor 13 through a pinion 14 and spur
ri 20 gear 15. The drum has an inlet opening and a discharge opening
~ at its opposite ends. The charge, or material to be processed, is ~:
`~ fed into an upstream zone 16 of the drum by way of a charging chute
` 17, and processed material is discharged from a downstream zone
18 of the drum by way of a discharge chute 19, a conical deflector
- 20 being positioned adjacent to the discharge opening and combined
i with grates and lifters for discharging material into the discharge
`~ chute in the known manner.
Positioned between the upstream and downstream zones 16,
18 is an intermediate zone 22 into which an additional material,
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in this case a gas, may be introduced to be added to the charge.
The details of the intermediate zone are shown in Figures 2 and
3. Essentially, this zone is formed by a plurality of, in this
case four, axially spaced, transverse drum partitions 23,24,25,
26, which define a plurality of chambers, in this case first,
second and third lifting chambers 27,28,29. The first partition
23 is formed by a slotted grid which defines an inlet to the first
chamber 27. Ground material of a suitable size, or slurry or the
like, can pass from the upstream drum zone 16 through the grid
into the first chamber 27. The central portion of the partition
23 is connected to, or formed integrally with, a conical deflector
30 which extends axially for substantially the full axial length
of the first chamber 27. Radial lifters 31 extending from the
conical deflector 30 serve, as the drum 10 rotates, to lift material
in the chamber 27, which material descends by gravity onto the
deflector to be deflected thereby through a central outlet 32 in
the second partition 24. It will be appreciated that the lifters
31, and the lifters 21 and 40 referred to below, need not be
straight as shown, but may be curved to suit the flow characteris-
tics of the material in passage. The second partition 24 i3 formedwith an annular deflector 33 which extends axially for substanti-
ally the entire axial length of the second chamber 28. This deflec-
tor has a frusto-conical outer surface and a frusto-conical inner
surface, the latter defining a central region 28a of the second
chamber 28, which central region is partitioned by the deflector
from the outer annular region of the chamber. Process material
discharged into the central region 28a of the second chamber strikes
the inner frusto-conical surface of the deflector 33 to be deflected
thereby into the third chamber 29. Lifters 21 are provided in the
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second chamber, Their function is to scavenge materials which may
be accidentally deflected from the third chamber and to prevent
them from being discharged via inlet openings 34,
Gas or vapour to be added to the charge is introduced
into ~he drum by way of the peripheral inlet openings 34 which
communicate with the annular region of the second chamber 28,
These openings communicate with a manifold formed by an annular
casing 35 which encircles the drum. Gas or vapour is supplied
to the manifold, at a pressure which is higher than that existing
in the downstream zone 18 of the drum, by way of an inlet duct 36,
and since the casing is stationary, annular seals 37, 38 mounted
on the drum prevent leakage of the gas or vapour as the drum rotates.
~he flow of gas may be induced by means of an exhaust fan on the
outlet side of the drum.
Gas from the annular region of the chamber 28 is dis-
charged through an outlet 39 in the partition 25 into the third
chamber 29. Process material deposited into the third chamber is
lifted by radial lifters 40 extending from a central conical deflec-
tor 41, the deflector 41 extending substantially for the full axial
length of the third chamber and cooperating with a central opening
42 in the fourth partition 26. The process material, having been
lifted is deposited onto the upper surface of the deflector 41,
and is deflected thereby into the downstream zone 18 of the drum.
In this way, gas or vapour is introduced to the drum to be added
to the charge, the intermediate zone being so arranged as to pre- ,
vent the charge from returning from the intermediate zone of the
drum.
The modification illustrated in Figures 4 and 5 differs
from the preceding embodiment in that means are provided for
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adding a heavier-than-air material, such as a granular solid or a
slurry, to the charge at the intermediate zone. In these Figures,
parts which have exact counterparts in Figures 2 and 3 are denoted
by the same reference numerals. In this case, however, instead of
there being gas or vapour admitted to the drum, a granular solid
or a liquid is fed by a chute 43 into an annular chute 44. The
annular chute is formed by an annular casing which encircles the
intermediate zone of the drum 10. The heavier-than-air material
descending into the chute 44 is scooped up by scoops or buckats
45, lifted, and deposited into the second chamber 28 of the inter-
mediate zone via peripheral openings 46. The casing 44, which is
stationary, cooperates with rotary seals 47, 48 to prevent leakage
of the additional material as the drum rotates.
As will be appreciated by those skilled in the art, in
certain applications the axis of the drum may not be truly hori-
zontal, but may be slightly inclined to the horizontal to assist
the flow of material, Such cases are considered to be within the
scope of the invention. Accordingly, the expression "generally
horizontally mounted rotary drum" as used in the specification
and claims is intended to mean a rotary drum which is mounted so
that its axis of rotation is horizontal or slightly inclined to
the horizontal.
Furthermore, it is to be understood that the terms
"conical" and "frusto-conical", as applied to the deflector sur-
faces of the "conical deflectors" and the "annular deflector" are
not restricted to shapes which are conical and frusto-conical in
the strict mathematical sense. In the illustrated embodiments the ~ ~
surfaces described by these terms are essentially flared surfaces ~ -
of revolution which are approximately conical and frusto-conical~
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and the said terms as used in the specification and claims are
deemed to describe such shapes.
