Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02364023 2001-11-23
IMPROVED DISTRIBUTION SYSTEM FOR A PASTILLATION MACHINE
FIELD OF THE INVENTION
The present invention relates to an improved distribution system
for use in a pastillation machine, and more particularly, a distribution
system
that provides for an essentially even distribution of a flowable substance at
the outlet thereof.
BACKGROUND OF THE INVENTION
Pastillation machines typically include an inner cylinder that
receives a flowable substance from a source. An outer cylinder rotates about
the inner cylinder and has rows of openings formed therein. The flowable
substance is delivered under pressure from the inner cylinder, through the
rows of openings in the outer cylinder. The flowable substance is then
dropped onto a moving conveyor device and cooled to form hemispherical
pastilles. Pastillation machines are particularly useful for forming elemental
sulphur and sulphur based fertilizer pastilles.
A distribution bar for a machine for extruding flowable
substances is disclosed in U.S. Patent No. 4,623,307 to Froeschke. The
distribution bar is located in a groove that is formed in the outer surface of
the
inner cylinder of the machine: The distribution bar has a series of inlet
holes
that receive the flowable substance from the inner cylinder. The flowable
substance passes through these inlet holes into an elongated slot that is
formed along the length of the distribution bar. The slot is located adjacent
to
the inner wall of the outer cylinder. The holes of the distribution bar are
placed very close together in an attempt to distribute the flowable substance
evenly within the elongated slot of the distribution bar.
Even distribution of the flowable substance is an important
consideration, in order for the flowable substance to be forced out through
the
holes of the outer cylinder evenly and thus, to form pastilles that are
similar in
size. The many holes in the distribution bar of the prior art are subject to
clustering and agglomeration of the flowable substance, which results in
product of inferior quality and inconsistent sizing. The holes also require
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frequent cleaning in order to minimize the clustering and agglomeration of the
flowable substance, which results in increased equipment downtime.
Pasitllation machines typically operate at high temperatures in
order to keep the hot liquid flowable. At such temperatures, the distribution
bar is subjected to heat stress, which may cause the distribution bar to lose
its seal with the flowable substance inlet holes. In addition, warping of the
distribution bar causes uneven wear, particularly on the surface of the
distribution bar that is in constant contact with the rotating outer cylinder.
More importantly, the warped distribution bar may score the outer cylinder.
The outer cylinder is an expensive component to replace and therefore any
unnecessary wear on the outer cylinder is undesirable.
It is therefore an object of an aspect of the present invention to
provide a distribution system that improves the distribution of the flowable
substance at an outlet thereof.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is
provided in a pastillation machine, an improved distribution system for a
flowable substance to be formed into pastilles. The distribution system
comprises: a bar having a bore extending therethrough, a series of holes
located on an inlet surface of the bar, a series of slots located on an outlet
surface of the bar, and a diffuser located in the bore of the bar, the
diffuser
being spaced between the inlet surface and the outlet surface wherein the
series of holes is aligned with flowable substance outlets of the pastillation
machine.
According to another aspect of the present invention there is
provided a diffuser for a distribution system for use in a pastillation
machine.
The diffuser comprises: an elongate body sized to fit into a bore of a
distribution bar, and a centering device coupled to the elongate body for
engaging at least one surface of the bore of the distribution bar wherein the
centering device maintains the elongate body generally spaced from at least
one wall of the bore of a distribution bar of the distribution system.
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According to yet another aspect of the present invention there is
provided a pastillation machine. The machine comprises: a first cylinder
having a first end and a second end and an outer surface, the first cylinder
being supported at the first end and the second end, a cavity formed in the
first cylinder, the cavity being in communication with a source of a flowable
substance, a slot formed in the outer surface of the first cylinder, the slot
being located between the first end and the second end, fluid outlets located
in the slot, the outlets being in communication with the cavity of the first
cylinder, a second cylinder surrounding the first cylinder and being rotatable
thereon, the second cylinder having rows of openings therein, a distribution
bar sized to fit into the slot and being sandwiched between the inner cylinder
and the outer cylinder, the distribution bar having an inlet surface and an
outlet surface and a bore extending therethrough, a series of holes located on
the inlet surface, the holes being aligned with the fluid outlets of the first
cylinder for receiving the flowable substance therefrom, a series of slots
located on the outlet surface, the series of slots of the distribution bar
being in
communication with the rows of openings in succession, and a diffuser
located between the inlet surface and the outlet surface, the diffuser bar
extending axially through the bore of the distribution bar wherein as the
openings of the outer cylinder pass over the series of slots of the
distribution
bar, a predetermined amount of flowable substance passes through the
openings and drops onto a moving conveyor located below the pastillation
machine.
It is an advantage of an aspect of the present invention that the
distribution system distributes essentially evenly the flowable substance to
produce hemispherical pastilles having similar size.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present invention will now be described
more fully with reference to the accompanying drawings in which:
Figure 1 is a perspective view of parts of a pastillation machine
with an outer cylinder partially cut away;
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Figure 2 is a perspective bottom view of a portion of the
machine of Figure 1;
Figure 3 is an exploded view of portions of the machine of
Figure 1 incorporating a distribution system of the present invention;
Figure 4 is an isometric view of a portion of the distribution
system of Figure 3;
Figure 5 is top view of a portion of the distribution system of
Figure 3;
Figure 6 is a side view of a portion of the distribution system of
Figure 3;
Figure 7 is a bottom view of a portion of the distribution bar of
Figure 3;
Figure 8 is an isometric view of an end piece of the distribution
system;
Figure 9 is an isometric view of the diffuser of Figure 3;
Figure 10 is a cross-sectional view of the machine of Figure 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Pastillation machines are used to convert hot liquid mixtures
such as molten elemental sulphur, for example, into tiny essentially
hemispherical, solid pastilles. The hot liquid mixture is deposited as
droplets
onto a moving conveyor and the droplets are subsequently cooled to form
solid pastilles. Pastilles can be formed from virtually any hot liquid mixture
including viscous fluids, semi-solid slurries, molten materials, fertilizers,
chocolates, waxes, resins and other flowable industrial products. Pastillation
machines are also referred to as drop forming or RotoformerT"" machines of
Sandvik Process Systems.
A preferred application of pastillation machines is the production
of elemental sulphur pastilles and fertilizer pastilles such as those
containing
elemental sulphur and swelling clay matrix, and marconutrients (N, P, K) and
micronutrients (Fe, Cu, Zn, Mn etc.).
Referring to Figure 1, a pastillation machine 20 is generally
shown. The machine 20 comprises a double cylinder assembly 22 having an
inner cylinder 24 that is surrounded by a rotatable outer cylinder 26. The
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double cylinder assembly 22 is supported at a first end by a first support
assembly 30 and at a second end by a second support assembly (not
shown).
First support assembly 30 comprises a strut 32 that extends
upwardly from a machine housing 34. A horizontal support 36 joins strut 32
to a bearing housing 38. Bearing housing 38 has a sprocket (not shown)
connected thereto that cooperates with a pulley arrangement (not shown). A
motor 28, typically 5 HP, drives the pulley arrangement. The inner cylinder 24
is supported by the bearing housing 38 and extends horizontally therefrom in
a cantilevered arrangement. The inner cylinder 24 is stationary and does not
rotate.
The outer cylinder 26 is driven by the motor 28 to rotate about
the inner cylinder 24. The outer cylinder 26 is axially slidable onto the
inner
cylinder 24 from the second end. The outer cylinder 26 includes a perforated
shell 40 having enlarged end pieces 42 and 44, that are located at the first
and second ends of the shell 40 respectively. The enlarged end piece 42 is
formed to engage the bearing housing 38 so that the rotation created by
motor 28 is transferred to the outer cylinder 26.
A spring loaded tension plate, supported by a cradle (not
shown) is coupled to the second end of the double cylinder assembly 22.
Tension plate 48 also includes a second bearing housing 58. Second bearing
housing 58 allows the outer cylinder 26 to rotate about the inner cylinder 24.
Tension plate 48 provides a seal at the second end of the double cylinder
assembly 22 to prevent any flowable substance from escaping. Tension plate
48 rests on the cradle when it is installed, which provides support to the
second end of the double cylinder assembly 22.
The pastillation machine further comprises a conveyor device
50. The conveyor device 50 includes a conveyor belt 52, which is located
below the double cylinder assembly 22. The conveyor belt 52 is formed of
stainless steel and moves in the direction indicated by arrow 54. A cooling
device (not shown) is located downstream of the double cylinder assembly
22. The cooling device is typically comprised of a water jet that sprays the
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underside of the conveyor belt 52. The conveyor belt 52 is constructed of
stainless steel in order to conduct the cooling effect of the water spray,
however, the conveyor may be constructed of any material that is highly heat
conductive.
A flowable substance source (not shown) is connected to a
pipeline 56. The flowable substance in a preferred embodiment is a liquid
sulphur based fertilizer. The pipeline 56 is coupled to the inner cylinder 24
and delivers the flowable substance thereto under pressure. The flowable
substance passes from the inner cylinder through momentarily aligned
openings 46 that are formed in rows about the circumference of the
perforated shell 40 of the outer cylinder. Droplets (not shown) of the
flowable
substance fall from the outer cylinder 26 once the momentary opening 46 is
closed and are deposited onto the moving conveyor belt 52. The droplets
subsequently travel past the cooling device to form hemispherical solid
pastilles (not shown).
In the operating condition, the inner cylinder 24 is oriented so
that a channel 100, which is formed in the outer surface thereof, is directed
downwardly towards the conveyor device 50.
Referring to Figure 2, details of the inner cylinder 24 are shown.
The channel 100 of the inner cylinder 24 includes a generally planar base 108
that is surrounded by a ridge 102 having a generally planar surface. A series
of flowable substance outlets 104 project from the base 108 of the channel
100. Each outlet 104 has a spring located therein, which is biased radially
outward. The outlets 104 expel the flowable substance that is fed into the
inner cylinder 24 from the flowable substance source.
Adjacent each outlet 104 is an alternate outlet 106. The
alternate outlets 106 function the same way as the outlets 104, however, in
this embodiment, the alternate outlets 106 have been plugged.
The outer surface of the inner cylinder 24 has a first step 110
and a second step 112 formed therein. The second step 112 is slightly larger
in size and is located adjacent the first end of the inner cylinder 24. The
steps
110 and 112 engage complementing steps formed on the inner surface of the
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outer cylinder 26 and serve to locate the outer cylinder 26 axially on the
inner
cylinder 24.
Referring to Figure 3, a distribution system 60 including a
diffuser bar 90 is shown. The distribution system 60 is sized to fit into the
channel 100 of the inner cylinder 24. In the assembled condition, the diffuser
90 fits inside the distribution system 60 and the outer cylinder 26 sandwiches
the distribution system 60 between itself and the inner cylinder 24. In this
arrangement, the flowable substance flows out of the outlets 104, through the
distribution system 60 and out of openings 46 of the perforated shell 40 of
the
outer cylinder 26.
Distribution system 60 is comprised of a distribution bar 62
having a bore 68, that extends therethrough, and a feeder bar 64. The
distribution bar 62 and feeder bar 64 are coupled together as shown in
Figures 4-7. The feeder bar 64 is secured to the distribution bar 62 by
fasteners 66. Alternatively, the feeder bar 64 is secured to the distribution
bar
62 by welding or any other suitable attachment means.
The construction of the distribution bar 62 and feeder bar 64 of
the distribution system 60 provides a tolerance for heat expansion so that
warping of the distribution system 60 is kept_to a minimum. The distribution
bar 62 is made of stainless steel. This material is preferred because it
provides high corrosion resistance and low thermal expansion. Type 316
stainless steel is preferred, however, any material exhibiting the desired
properties could also be used.
The feeder bar 64 is subject to increased wear due to constant
contact with the outer cylinder 26 as it rotates. In order to ensure that the
feeder bar 64 wears and the outer cylinder 26 does not, the feeder bar 64 is
made of a ductile material. The construction of the distribution system 60
allows for replacement of only the feeder bar 64, once it has been
sufficiently
worn, rather than the entire distribution system 60. The feeder bar 64 could
alternatively be made of carbon steel, cast iron, aluminum or any material
that
wears faster than outer rotating cylinder 26.
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The distribution system 60 has an inlet surface 80 and an
opposing outlet surface 82. The inlet surface 82 is located'on a side of the
distribution bar 62 and comprises a series of holes 84 that are spaced along
the length thereof. The outlet surface 82 is located on an opposing side of
the distribution bar 62 and has a series of slots 86 that are spaced along the
length thereof. The feeder bar 64 has a wear surface 63 that is curved
slightly to complement the curvature of the inner wall of the outer cylinder
26.
A continuous slot 65 extends along the length of the feeder bar 64 and
exposes the series of slots 86 of the distribution bar 62. Continuous slot 65
is
wider than series of slots 86 and provides a reservoir for containing the
flowable substance prior to extrusion of the substance through the rows of
openings 46.
It will be understood by a person skilled in the art that the series
of holes 84 and series of slots 86 do not need to be on opposite surfaces of
the distribution bar 62. A path between the holes 84 to the slots 86 must be
established, however, the actual location of the holes 84 and slots 86 is not
important. In a preferred embodiment, the holes 84 and slots 86 are on
opposite surfaces of the distribution bar 62.
Referring to Figures 5, an end portion of the distribution bar 62
and feeder bar 64 assembly is shown. An end piece 70 of the feeder bar 64
is located at the distal end of the feeder bar 64. Referring also to Figures 5-
7,
end pieces 70 are located at opposite ends of the feeder bar 60 and are
removable to allow for the diffuser 90 to slide into the distribution bar 62
in
order to assemble the distribution system 60. An insert 71 projects from each
end piece 70 to plug into an end of bore 68 of the distribution bar 62. The
insert 71 helps to secure the end piece 70 in place and additionally provides
a
seal so that flowable substance does not escape from the ends of the
distribution bar 62. Fasteners are located through countersunk apertures 72
for securing the end pieces 70 to the feeder bar 64.
In an alternate embodiment of the distribution and feeder bars
62 and 64, the bars may be integrated to form a single part.
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As indicated by arrow 74 in Figure 3, the diffuser 90 is inserted
into the bore 68 of the distribution bar 62. Referring also to Figure 9,
diffuser
90 is comprised of an elongate body 92 having a centering device that
comprises multiple tabs 94. Pairs of tabs 94 extend outwardly from opposing
edges 93 of the body 92 at regular intervals along the length thereof.
Alternating pairs of tabs 94 are bent at approximately 45 degree angles from
the plane of the body 92 in opposing directions so that in an alternating
pattern is produced. The pairs of tabs 94 serve to secure the body 92 in a
generally centered location in the bore 68.
The diffuser 90 effects spreading of the flowable substance so
that the flowable substance fills the bore 68 of the distribution bar 60 and
thus, exits the distribution bar 60 evenly through the series of slots 86. The
spreading effect is achieved by the impact of the flowable substance on the
body 92 of the diffuser 90. The flowable substance is forced to flow along the
length of the body 92 and at the same time, is forced to flow to the edges 93
of the diffuser 90. Thus, the flowable substance is essentially evenly
distributed along the length of the body 92 as it flows around the edges 93 of
the diffuser 90 and out through the series of slots 86.
Referring to Figure 10, the diffuser 90 is shown in section and
the centering effect of the alternating tabs 94 can be seen. The diffuser 90
may be of any construction having an elongate body 92 that is generally
centered in the bore 68 of the distribution bar 62. If the inlet holes 84 and
outlet slots 86 are not located on opposing surfaces of the distribution bar
62,
the diffuser 90 is oriented so as to present a surface, for spreading the
flowable substance, between the holes 84 and slots 86.
In an alternate embodiment, the diffuser 90 is a rod that is
located in the bore 68. The rod may be secured in the bore 68 using tabs 74
in the manner that has been disclosed.
It will be appreciated by a person skilled in the art that the
diffuser 90 may be comprised of any rod or bar having a non-flat surface. A
partially porous surface may also be be used. The degree of porousness of
the diffuser 90 must be controlled to ensure that the flowable substance does
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not simply pass through the diffuser 90 from hole 84 straight into slot 86. A
surface that is too porous will not spread the liquid between the inlet holes
84
and outlet slots 86, and thus will be ineffective.
In another alternate embodiment, the centering device of the
diffuser 90 is a pair of springs that are coupled to the ends of the diffuser
90.
The springs are compressed against the inserts 71, which are plugged into
the ends of the distribution bar 62, in order to maintain the diffuser 90
generally centered within the bore. In a further embodiment, the springs may
be coupled to opposing faces or edges of the diffuser 90 and abut the walls of
the bore 68.
Figure 10 shows the inner cylinder 24, outer cylinder 26 and
distribution system 60, which includes the distribution bar 62, feeder bar 64
and diffuser 90, in the assembled condition. The inner cylinder 24 has an
internal cavity 96 that extends along the length thereof. The internal cavity
96
is in communication with the flowable substance source via the pipeline 56.
The outlets 104 are joined to the internal cavity 96 of the inner cylinder.
The
outlets 104 abut the distribution bar 60 and form a seal therebetween. The
outer cylinder 26 surrounds the inner cylinder 24 and rotates thereabout so
that openings 46 are momentarily aligned with the series of slots 86 of the
distribution bar 60 in succession.
Passages 98 extend along the length of the inner cylinder 24. A
heated medium flows through the passages in order to maintain the flowable
substance in a melted state. Heated mediums that are typically used include
steam and hot oil, however, any suitable material may be used.
Now that the apparatus has been described, operation of the
apparatus to produce sulphur based fertilizer pastilles will now be described.
In operation, the molten fertilizer composition flows under
pressure from the source though pipeline 56 to the internal cavity 96 of the
inner cylinder 24. The molten fertilizer is forced out of the internal cavity
96
through the outlets 104. The molten fertilizer passes from the outlets 104
into
the bore 68 of the distribution bar 62 through holes 84. The molten fertilizer
impacts the diffuser 90 and spreads over the length thereof. At the same
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time, the molten fertilizer flows over the edges 93 of the diffuser 90 so that
the
molten fertilizer is evenly distributed within the bore 68 of the distribution
bar
62. The molten fertilizer then flows out of the slots 86 and fills the feeder
slot
65. The void-free molten fertilizer is contained within the feeder slot 65
prior
to being extruded through the outer cylinder 26. As the openings 46 of the
outer cylinder 26 align with the slots 86, the molten fertilizer is extruded
through the openings 46. The molten fertilizer is formed into droplets as the
openings 46 of the outer cylinder 26 rotate past the distribution bar 62 to
temporarily halt the flow of molten fertilizer through the outer cylinder 26.
The
droplets fall in rows from the outer cylinder 26 onto the moving conveyor belt
52. The conveyor belt 52 moves the droplets past the cooling device, located
underneath moving conveyor belt 52, to form fertilizer pastilles.
The distribution system 60 is effective in receiving the flowable
substance through a series of inlet holes 84 and distributing the flowable
substance along the length and width of a distribution bar 62 so that it flows
essentialy evenly through a series of outlet slots 86. The feeder slot 65
receives the flowable substance from the series of slots 86 and continuously
contains a void-free volume of flowable substance under pressure. This void-
free volume of flowable substance is then essentially evenly extruded from
the openings 46 of the outer cylinder 26 to form pastilles that are generally
equal in size. The inlet holes 84 and outlet slots 86 are of a size that is
sufficient for clustering and agglomeration of the flowable substance to be
unlikely and cleaning of the distribution system 60 can be performed with
relative ease.
For cleaning and maintenance purposes, the distribution system
60 is easily removed from the pastillation machine. First, first tension plate
48
is unscrewed and then the outer cylinder 26 is slid towards the second end of
the inner cylinder 24. This allows the distribution system 60 to be set free.
The outer cylinder 26 does not need to be removed entirely, only withdrawn
far enough to allow the distribution system 60 to be removed from channel
100. The end piece 70 is then removed from the distribution system 60 and
the diffuser 90 is slid out from the bore 68. The distribution system 60 may
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then be cleaned or further disassembled in order to perform further cleaning
or maintenance. The distribution system 60 is designed so that cleaning
without disassembly or removal of the diffuser bar 90 is also highly
effective.
Typically, the distribution system 60 is immersed in a hot oil bath for
cleaning.
Although preferred embodiments of the present invention has
been described, those of skill in the art will appreciate that variations and
modifications may be made without departing from the spirit and scope
thereof as defined by the
appended claims.
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