U.S. patent application number 14/006252 was filed with the patent office on 2014-10-16 for waste processing.
This patent application is currently assigned to CHINOOK END-STAGE RECYCLING LIMITED. The applicant listed for this patent is Rifat Al Chalabi, Ophneil Henry Perry, John Turner. Invention is credited to Rifat Al Chalabi, Ophneil Henry Perry, John Turner.
Application Number | 20140305354 14/006252 |
Document ID | / |
Family ID | 44012853 |
Filed Date | 2014-10-16 |
United States Patent
Application |
20140305354 |
Kind Code |
A1 |
Chalabi; Rifat Al ; et
al. |
October 16, 2014 |
Waste Processing
Abstract
An apparatus for processing material (29) such as organically
coated waste and organic materials including biomass, industrial
waste, municipal solid waste and sludge is provided. The apparatus
comprises an oven having a rotatable portion comprising a treatment
chamber adapted to receive material for treatment. A plurality of
gas inlets are provided in at least one wall of the treatment
chamber through which hot gasses are introduced to the treatment
chamber to heat the material therein so as to cause the organic
components thereof to pyrolyse or gassify. At least one retarder
means (26) is located in the treatment chamber to retard the
movement of waste material therein as the oven rotates.
Inventors: |
Chalabi; Rifat Al;
(Nottingham, GB) ; Perry; Ophneil Henry;
(Nottingham, GB) ; Turner; John; (Nottingham,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Chalabi; Rifat Al
Perry; Ophneil Henry
Turner; John |
Nottingham
Nottingham
Nottingham |
|
GB
GB
GB |
|
|
Assignee: |
CHINOOK END-STAGE RECYCLING
LIMITED
Nottingham, Nottinghamshire
GB
|
Family ID: |
44012853 |
Appl. No.: |
14/006252 |
Filed: |
March 1, 2012 |
PCT Filed: |
March 1, 2012 |
PCT NO: |
PCT/GB2012/000198 |
371 Date: |
March 27, 2014 |
Current U.S.
Class: |
110/346 ;
110/246 |
Current CPC
Class: |
F23G 5/0273 20130101;
C02F 11/10 20130101; F26B 2200/02 20130101; F23G 2203/204 20130101;
F26B 2200/18 20130101; F26B 25/12 20130101; F26B 25/04 20130101;
F26B 11/02 20130101; Y02W 10/40 20150501; F23G 2203/208 20130101;
F23G 5/20 20130101; F23G 2203/201 20130101 |
Class at
Publication: |
110/346 ;
110/246 |
International
Class: |
F23G 5/20 20060101
F23G005/20 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 19, 2011 |
GB |
1104676.0 |
Claims
1. Apparatus for processing material such as organically coated
waste and organic materials including biomass, industrial waste,
municipal solid waste and sludge; the apparatus comprising: an oven
having a rotatable portion comprising a treatment chamber adapted
to receive material for treatment; a plurality of gas inlets in at
least one wall of the treatment chamber through which hot gasses
are introduced to the treatment chamber to heat the material
therein so as to cause the organic components thereof to pyrolyse
or gassify; and at least one retarder means located in the
treatment chamber to retard the movement of waste material therein
as the oven rotates.
2. An apparatus according to claim 1 wherein the oven has at least
one 15 substantially flat side and the retaining means are provided
on the flat side of the oven.
3. An apparatus according to claim 1 wherein the retarder means can
be moved between an active position in which they protrude into the
treatment chamber by a first distance and an inactive position
wherein protrude into the treatment chamber by a second distance,
the first distance being greater than the second distance.
4. An apparatus according to claim 3 wherein in the inactive
position the retarders are substantially flush with the walls of
the treatment chamber.
5. An apparatus according to claim 3 wherein the retarder means are
made of spring steel and wherein the retarder means resiliently
deforms when the retarder means is moved from its active position
as in inactive position.
6. An apparatus according to claim 3 wherein the retarder means
extend through the walls of the treatment chamber and further
comprise actuator means located outside the treatment chamber for
actuating the retarder means.
7. An apparatus according to claim 1 wherein the treatment chamber
has a double wall, comprising an inner wall and an outer wall,
extending along at least one of its sides and wherein the retarder
means extend through both the inner and the outer wall.
8. An apparatus to claim 1 wherein the retarder means further
comprise a flow path there through and hot gases are introduced
into the treatment chamber through the retarder means.
9. An apparatus according to claim 7 wherein the retarder means
further comprise a flow path there through and hot gases are
introduced into the treatment chamber through the retarder means,
the flow path having at least one flow path inlet in a section
extending thereof between the inner and outer walls, and at least
one outlet in a section thereof extending into the treatment
chamber.
10. An apparatus according to claim 1 wherein the retarder means
each comprise a plurality of inverted hooks arranged in a radial
array about a common central axis with the ends of the hooks spaced
from the common central axis.
11. An apparatus according to claim 1 wherein the retarder means
each comprise at least one hollow tube through which hot gas can
pass into the treatment chamber.
12. An apparatus according to claim 10 wherein the inverted hooks
each comprise a hollow tube through which hot gas can pass into the
treatment chamber.
13. An apparatus according to claim 1 wherein the retarder means
can be rotated.
14. An apparatus according to claim 12 wherein the ends of the
inverted hooks are bent in a direction towards said processing
chamber so that, in use, hot gas emitting from them is directed
away from the surface of the treatment chamber.
15. An apparatus according to claim 1 wherein the retarder means
comprises a shaft and a retarder head, and wherein the shaft is
pivotally connected to the retarder head.
16. A method of processing material such as organically coated
waste and organic materials including: biomass, industrial waste,
municipal solid waste and sludge; the method comprising: placing
material to be treated in an oven having a rotatable portion
comprising a treatment chamber; heating the material in the
treatment chamber by introducing hot gasses thereinto via gas
inlets in at least one wall of the treatment chamber; rotating the
oven so as to cause the material therein to tumble; and retarding
the movement of the material in the processing chamber by placing
retarder means in the movement path of the waste material.
17. The method according to claim 16 further comprising agitating
said material in the processing chamber by moving the retarder
means from an active position in which they protrude into the
treatment chamber from an inactive position wherein they protrude
into the treatment chamber by a lesser amount.
18. The method according to claim 17 comprising repeatedly moving
the retarder means between their active position and their inactive
position.
19. The method according to claim 16 further comprising introducing
hot gasses into the treatment chamber by passing the hot gasses
through a flow path in the retarder means.
20. The method according to claim 16 further comprising agitating
said material in the processing chamber by rotating the retarder
means.
21. The method according to claim 16 further comprising moving to
and retaining in their inactive position at least some of the
retarder means while they are covered material being processed so
as to trap in least some of the material against the wall of
treatment chamber.
22. The method according to claim 21 further comprising continuing
to rotate the oven while retaining said at least some of the
retarder means in their inactive position so as to retain said
trapped material adjacent to the sides of the treatment chamber as
the oven rotates.
23. The method according to claim 16 comprising selectively
retarding the movement of material within the treatment chamber as
the chamber rotates so as to provide a greater contact area between
the chamber walls and the material.
Description
[0001] The present invention relates to improvements in the
processing of materials having an organic component. In particular
the method relates to improvements in the processing of such
materials in rotating ovens.
[0002] The use of large rotating ovens for processing waste is
known in the prior art. Examples of rotating ovens for such use can
be found, for example, in PCT publication WO2004/059229. This
document discloses a rotating oven for processing waste which has a
plurality of nozzles for omitting heated gas into the processing
chamber thereof. Although only a single row of inlets is shown in
this prior art document, in practice an array of inlets covering
the sides of the processing chamber, or at least one side thereof,
can be provided.
[0003] As the oven rotates scrap material therein will fall over
the inlets temporarily blocking them and reducing the gas flow
therethrough. In reality when operating such a system as the
material moves in the processing chamber as the oven is rotated it
tends to move from one side to the other of the oven substantially
as a single bulk movement i.e. once the stiction between the
material to be processed and the surface it is resting on is
overcome by the angle of the up and reaching a particular degree
the entire mass of material will slide down that side of the oven
and then substantially stop until the oven is further rotated so
that the material once again overcomes its stiction. This is
especially the case in processing chambers having at least one flat
side as opposed to circular or tubular ovens. In circular or
tubular ovens a constant tumbling of the material is achieved
whereas in a flat sided oven the bulk movement of the mass of
material as described above occurs. This can be disadvantageous in
the speedy processing of waste material as while the material is
substantially bunched together only the top and bottom surfaces of
the material are exposed to the hot gasses and therefore become
heated to react and release gas.
[0004] A further problem of the mass movement of material in this
way is that, as the material is often quite dense it will tend to
block the flow coming out of the nozzles beneath where it is
resting. This results in more of the flow entering the processing
chamber from nozzles which are not in direct contact with the
material to be processed. This is also disadvantageous as the
quickest way to transfer heat from the hot gasses into the
materials that are being processed is for the hot exhaust gasses to
be injected directly into the materials.
[0005] A further problem with existing rotating ovens, such as that
found in the prior art, is that when an array of gas outlets is
provided around the different sides of the oven and, as described
above, the quickest way to transfer heat into the material is to
directly inject gas into that material, as the material is located
on the lower side of the processing chamber, due to gravity, only a
small proportion of the inlet nozzles are capable of directly
injecting hot gasses into the material being processed. That is, if
as described above, the gas flow from these nozzles has not been
prevented by the mass of material sitting on top of them.
[0006] As described in the prior art, the processing chamber can be
a double-walled chamber that has hot gasses passing between an
inner and outer wall thereof so as to heat the inner wall. As the
materials that are being processed come into contact with this
inner wall, then heat is transferred from the exhaust gasses
circulating between the two walls into the material by its contact
with the hot inner wall. Further, as described above, as the
material within the oven tends to move as a single mass, only a
small part of the inner wall is in contact with the waste material
at any one time, thereby reducing heat transfer efficiency into
displaced material.
[0007] It is the purpose of the present invention to provide an
improved apparatus and method for processing waste that at least
partially mitigates some of the above-mentioned problems.
[0008] According to a first aspect of the invention there is
provided an apparatus for processing material such as organically
coated waste and organic materials including: biomass, industrial
waste, municipal solid waste and sludge; the apparatus comprising:
an oven having a rotatable portion comprising a treatment chamber
adapted to receive material for treatment; a plurality of gas
inlets in at least one wall of the treatment chamber through which
hot gasses are introduced to the treatment chamber to heat the
material therein so as to cause the organic components thereof to
pyrolyse or gassify; and at least one retarder means located in the
treatment chamber to retard the movement of waste material therein
as the oven rotates.
[0009] Preferably the oven has at least one substantially flat side
and the retaining means are provided on the flat side of the
oven.
[0010] The exact reaction causing the breakdown of the organic
material within the processing chamber will depend upon the
processing chamber conditions. If there is zero or substantially
zero oxygen present in the processing chamber, then the reaction
will be predominantly a pyrolysis reaction. Where there is some
oxygen present, there will be a gassification which will include
some oxidation. In either reaction a gas will be produced that can
be used as described in the prior art.
[0011] The retarder means to slow the movement of waste material as
the oven rotates. Without the retarder means of the invention, an
oven having a substantially flat side would rotate until such point
that the gravitational forces on the waste material therein
overcame the stiction forces resisting movement of that material.
Once the stiction forces are overcome then, without the retarder
means, the material would move substantially as one solid mass from
its current position to a new position substantially at the lowest
point of the chamber, sliding across the substantially flat
surface. The retarder means slow the movement of the waste material
as the oven rotates so that it does not have the same sudden
movement as one single mass from one place to another within the
chamber but instead moves more gradually. This more gradual
movement extends the time period for which the waste material is in
contact with the sides of the processing chamber as it passes
thereover and increases the surface area of the material being
processed. By increasing the surface area of the material being
processed, greater heat exchange can take place between the hot
gasses and the material.
[0012] In a preferred embodiment, the retarder means can be moved
between an active position in which they protrude into the
treatment chamber and an inactive position wherein they protrude
into the treatment chamber by a lesser amount. In their inactive
position the retarders may be substantially flush with the walls of
the treatment chamber.
[0013] The apparatus preferably has an array of retarder means
spread about a surface thereof. The retarder means can be moved
between their active position and their inactive position to retard
the movement of the material within the processing chamber by
different amounts as the chamber rotates. By, for example,
activating the retarder means in a rippled effect which may be
slowly released from this current position to slide down the
chamber walls to a new position at the lower-most point of the
chamber. By allowing a gradual movement of the material maximum
heat exchange into that material can be achieved.
[0014] In one preferred embodiment the retarder means are made of
spring steel and the retarder means resiliently deform when the
retarder means move from its active position to its inactive
position. The retarder means may extend through the walls of the
treatment chamber and may further comprise actuator means located
outside the treatment chamber for actuating the retarder means.
This enables the actuators to be maintained in a lower temperature
environment whilst still being able to move the retarder means from
the active position to the inactive position. The actuator means
may, for example, be magnetically driven actuators. In one
preferred embodiment the retarder means may comprise a flow path
therethrough to enable hot gasses to be introduced into the
treatment chamber through the retarder means. In this way, as the
retarder means extend from the walls of the chamber, the gas left
in the retarder means can be deposited directly into the material
being treated as opposed to the prior art systems which only allow
heat to be input into the surfaces of the mass of waste being
processed.
[0015] The treatment chamber may preferably have a double wall,
comprising an inner wall and an outer wall extending along at least
one of its side and its retarder means may extend through both the
inner and the outer walls. In this manner hot gasses can flow
between the inner and outer wall thereby heating the surfaces of
the treatment chamber. In addition hot gasses can pass through
inlets into the interior of the processing chamber and/or
alternatively heated gasses can be passed through the flow paths in
the retarder means so as to be deposited into the material within
the processing chamber. In one preferred embodiment the retarder
means each comprise a plurality of inverted hooks arranged in a
radial way about a common central axis with the ends of the hooks
based from the common central axis. In this way the retarder may
resemble palm trees or the framework of an umbrella. The retarder
means, in particular the inverted hooks, may each comprise a hollow
tube through which hot gas can pass into the treatment chamber
preferably with the ends of the inverted hooks are bent so that hot
gas emitting from them is directed away from the surface of the
treatment chamber. In this way the gas emitting from the ends of
the hook shaped retarder means is directed upwards into the mass of
waste within the processing chamber. In a preferred embodiment the
retarder means can be rotated.
[0016] In one embodiment the retarder means may comprise a shaft
and a retarder head. The shaft can be pivotally connected to the
retarder head. In this manner when the retarder is in its activated
position, the head of the retarder can rotate under the influence
of gravity as the oven as a whole is rotated. According to a second
aspect of the inventions there is provided a method of processed
material such as organically coated waste and organic material
including: biomass, industrial waster, municipal solid waste and
sludge; the method comprising placing a material to be treated in
an oven having a rotatable portion comprising a treatment chamber
heating the material in the treatment chamber by introducing hot
gasses therein to gas inlets in at least one wall of the treatment
chamber; rotating the over so as to cause the material therein to
tumble; and retarding the movement of the waste material in the
processing chamber by placing the retarder means in the movement
path of the waste material.
[0017] As discussed above by retarding the movement of waste
material in the processing chamber in this way a greater surface
area to volume ratio of waste product is exposed to the hot gasses
and the heated sides of the waste processing chamber.
[0018] Preferably the method further comprises agitating the
material in the processing chamber by moving the retarder means
between an active position, in which they protrude into the
treatment chamber, and an inactive position in which they protrude
into the treatment chamber by a lesser amount. Preferably the
retarder means are repeatedly moved between their active position
and their inactive position. This agitation of the material being
processed lifts it from the surface on which it is sitting and, by
agitating it, provides a constant gas path therethrough so that gas
emitted from outlets in the side wall of the processing chamber on
which the waste material is sitting can omit from those outlets and
pass into, and through, the agitated waste material by agitating
the waste material in this way a constant flow of gas is maintained
through the gas outlets, even when a relatively large mass of
material being processed being present in the processing chamber
and located on top of those outlets.
[0019] Preferably hot gases may also be passed through flow paths
in the retarder means, thereby directly delivering hot gas into the
centre of the material being processed.
[0020] The method may further comprise rotating one or more of the
retarder means. The introduction of hot gas directly into the
centre of the waste being processed, together with the retarded
movement of the waste material as the oven is rotated results in a
far quicker heat transfer into the material being processed.
[0021] Method preferably further comprises moving to, and retaining
in, the inactive position at least some of the retarder means while
they are covered with material being processed. This is
particularly advantageous with retainer means such as the inverted
hook type described herein. As the retarder means are moved from
their active position to their inactive position while covered with
the material being processed some of the material being processed
will be trapped underneath the retarder means and retained in place
against the hot surfaces of the oven as the oven rotates. This
again assists in rapid heat transfer into the materials as some of
the material is retained against hot surfaces of the oven whereas
otherwise would fall therefrom by gravity.
[0022] Specific embodiments of the invention will now be described,
by way of example only, with the reference to the accompanying
drawings in which:
[0023] FIG. 1 shows a rotating oven of the invention;
[0024] FIG. 2 shows a partially cut away chamber of the oven of the
invention;
[0025] FIG. 3 shows a isometric view of the details of retarder
means in a processing chamber of the present invention.
[0026] FIGS. 4 and 5 show the movement of the retarder means
between its active and its inactive position,
[0027] FIG. 6 shows a further embodiment of the present invention;
and
[0028] FIGS. 7 and 8 show diagrammatic views of the movement of
material being processed within the oven as it moves both with and
without retarder means being provided.
[0029] Referring to FIG. 1 a rotating oven is shown. The oven 10
comprises a processing chamber 12 and a charging box 14 attached to
the processing chamber that allows the waste to be added to and
removed from the oven. The principle fundamentals of the way in
which this oven works can be found in prior art document WO
2004/059229. Waste material to be processed is loaded into the
charging box which is then attached to the oven. The oven is
rotated as the material therein is heated to cause it to break
down. The material may be heated in a zero or substantially zero %
oxygen environment so that is pyrolyses therein to create gas.
[0030] Although the prior art is described as having an integral
afterburner to combust the gasses being produced it would be
appreciated that this afterburner may be separated from the oven
and connected thereto by a conduit. It will be appreciated by the
skilled person that the afterburner can either act to burn the
gasses produced in the chamber to produce heat that may be usable,
for example, for driving a boiler. Alternatively, the afterburner
could be provided with a source of fuel and a source of oxygen to
burn the fuel so that the gas in the vicinity of the afterburner
that has originated from the processing chamber is heated to a high
temperature so as to destroy any therein but is not in fact
combusted. In this way a clean fuel gas can be produced which can
be, for example, combusted in a gas turbine. Various modifications
to the process parameters to achieve slightly different results
depending upon the exact material being processed will be apparent
to the skilled person.
[0031] Referring to FIG. 2 a partial section through a processing
chamber of the oven is shown. The processing chamber has a double
walled construction having an outer wall 20 and an inner wall 22.
The processing chamber has an open end 24 through which material
may enter the processing chamber from the charging box (see FIG.
1). A plurality of retarder means 26 extends from an actuator 28
located outside the processing chamber, through the space 25
between the outer wall 20 and the inner wall 22, and protrude into
the processing chamber. Although only three such retarder means are
shown for clarity in reality a large number of retainer means may
be used. In particular an XY array of retainer means and the
retainer means may be provided on more than one side of the
processing chamber. As the processing chamber is rotated the
retarder means 26 slow the movement of the material 29 being
processed thereby increasing its exposure to heat.
[0032] Referring to FIG. 3 more detail of the retarder means is
shown. Each retarder means comprises a plurality of inverted hook
elements 30 positioned in a circular array around a common central
axis. The central axis forms a shaft 32 that passes through the
inner wall 22 to a magnetically repelled plate 34 at the end of the
shaft 32 which in turn is activated by an actuator 28 located
outside the processing chamber. The actuator 28 is preferably of
the magnetic type such that when energised the shaft 32 of the
retainer means which is at least in part made from a porous
material, will be pulled down into the actuator thereby moving the
retarder means from its active position 26a to its inactive
position 26b as depicted in FIG. 3. The inner wall 22 has clearance
holds that allow the shaft 32 of the retarder means to pass there
through and guide the shaft loosely as it travels between its
active and inactive positions. The holes in the inner wall do not
have to be gas tight as it is not problematic if a small amount of
gas leaks through these holes. The inner wall 22 has a plurality of
gas inlets 36 that allow hot gasses passing between the outer wall
20 and the inner wall 22 to pass therethrough into the processing
chamber so as to come into direct contact with the material
therein. The passage of the hot gas in the gap between the outer
wall 20 and the inner wall 22 heats the inner wall 22 so that any
material to be processed that is in contact with the inner wall is
heated by means of conduction by the inner wall 22.
[0033] The actuator 28 may also be configured to rotate the
retarder means 26 so as to agitate the material in the oven.
[0034] The inverted hooks of the retarder means 26 may be
manufactured from any suitable material that is resistant to heat
and which has the necessary resilience to allow it to deflect as it
moves between its active position 26a and its inactive position 26b
when the actuator 28 is activated the shaft of the retarder means
is pulled into the actuator and the inverted hooks of the retarder
means are pulled flat against the inner wall of the processing
chamber. The retarder means can move from its inactive position to
its active position by one of two means. Either the actuator 28 can
be a push pull actuator and can directly move the retarder means
from its inactive position 26b to its active position 26a or,
alternatively, the resilience of the inverted hooks of the retarder
means can use their natural spring force to return to their natural
position thereby moving the retarder to its active position.
[0035] FIGS. 4 and 5 show an alternative arrangement of retarder
means wherein the shaft 38 of the retarder means does not extend
through a seal in the outer wall of the processing chamber. In the
example shown in FIGS. 4 and 5 the shaft 38 terminates in a plate
40 within the space between the outer wall 20 and the inner wall
22. In this arrangement the actuator 28 is a strong electromagnet
and the plate 40 and/or shaft 38 are ferrous. Activation of the
electromagnet 28 pulls the plate 40 in the direction of arrow A
thereby moving the retarder means 26 to its inactive position. When
the electromagnet 28 is deactivated the natural resilience of the
retarder means 26 moves it in the direction of arrow b into its
active position. The inverter hooks 30 of the retarder means may
comprise hollow tubes and the retarder means 26 may have a gas
inlet 42 on the shaft 38 that extends between the outer wall 20 and
the inner wall 22. Gas flowing between the two walls can therefore
enter the shaft 38, pass through the inverted hooks of the retarder
means 26 and exit from the ends thereof into the processing
chamber.
[0036] As can be seen from the Figures the ends of the inverted
hooks 30 of the retarder means are bent up so that their end is
facing away from the inner wall 22 of the processing chamber
ensuring that gas can pass into the material sat on top of the
retarder means and not into the inner wall 22.
[0037] Referring now to FIG. 6 an embodiment is shown wherein the
retarders 26 have a hinge joint 44 that is in the processing
chamber when the retarder is in its active position and which is in
the space 25 between the inner wall 22 and the outer wall 20 when
inactive. In this way, as the retarder 26 is raised into its active
position, the tips of the retarder 26 bend at its hinge 44 and the
plurality of hook elements expose themselves to a grater surface
area of the moving material within the chamber thereby increasing
the retarding effect of the movement thereof. Activation of the
electromagnet 28 creates a force on the plate 40 and moves the
actuator to its inactive position. As the hinge 44 passes through
the inner wall 22 it will re-orientate the retarder 26 in its
original position. By hinging the retarders their inverted hooks
act to catch some of the material as it tumbles and this assists in
retaining the material in contact with the largest surface area of
the chamber walls.
[0038] In one mode of operation, when the retarder means are
covered with material that has been processed they may be moved
between there active and inactive positions so as to agitate the
material being processed.
[0039] In use the retarders can be moved between their active and
inactive positions as the oven rotates. It will be appreciated that
the sequencing of the retarders can be varied depending on the
exact material being processed. However, the purpose remains the
same, that is to maximise the exposure of the waste material to the
incoming hot gasses and the sides of the processing chamber that
become heated by the passage of the gasses thereover.
[0040] Referring to FIG. 7, generally, when an oven of the prior
art rotates the material therein tends to move as a single mass as
the oven rotates, that is, as the oven rotates the material does
not initially move due to static friction between the material and
the side of the chamber. Once the rotation reaches a certain level
the static friction is overcome and, as the kinetic friction is
less than the static friction the material moves across the surface
of the chamber (as depicted by the arrow) as a single mass from a
first position depicted by the dashed line to a second position
depicted by the solid line. By moving in this way the lump of
material 29 has a low surface area in contact with the walls of the
chamber and there will be a large area of heated chamber wall 46
that is not in contact with the material in either position. This
increases the time taken to get heat into the material and thereby
increases its processing time.
[0041] Referring to FIG. 8, by using the present invention, when
the gravitational pull on the material is sufficient to overcome
the static friction it starts to move across the surface of the
chamber. However, the retarders 26, which are in their active
extended position on the surface the material is moving across slow
the movement, and separate the material as it moves so that it does
not all move as one mass. This has two effects. Firstly the surface
area/volume ratio of the material is increased and secondly a
larger amount of that area is in contact with the heated walls of
the treatment chamber.
[0042] While the material is spread about the face of the treatment
chamber the retarders can be retracted into their inactive
position. Retracting the retarders in this way will trap a certain
amount of the material being processed between the retarders and
the chamber walls, thereby preventing all the material falling to
the lowest point of the rotating chamber. As the chamber continues
to rotate this material 29a will be held against the wall of the
chamber and, as the walls of the chamber are heated will continue
to have a large surface area available to absorb heat therefrom,
even on the sides of the chamber with which the majority of the
material has contact.
[0043] Some materials being processed may be quite dense and their
mass may be sufficient to block or partially block the flow of hot
gasses into the treatment chamber from the nozzles. The retarders
can, in this case, be moved between their active and their inactive
positions. Moving them in this manner will move the material
covering the jets and enable hot gasses from the jets to better
permeate into the material. As discussed above the retarders
themselves may also have hot gas passages therethrough to disperse
hot gas into the material as they move.
* * * * *