Rotary kilns are diverse thermal processing machines. This presentation looks at the many options available to customize a rotary kiln to promote improved processing efficiency. This includes, rotary kiln dams, bed disturbers, flights, and more.

1. Customization
Experts in process design and material
processing for over 65 years.
Rotary Kiln

2. Rotary kilns are an advanced thermal
processing tool used to cause a chemical
reaction or physical change in a solid
material through the application of
high temperatures.

3. Rotary kilns are extremely customizable, and
can be configured to fit nearly any process
needs and achieve optimal processing
conditions.

4. Rotary kilns are extremely customizable, and
can be configured to fit nearly any process
needs and achieve optimal processing
conditions.
A variety of available customizations are
explained here…

5. Dams

6. It is often desirable to increase retention time
and/or bed depth in a kiln. This can be done
through the use of a dam.

7. It is often desirable to increase retention time
and/or bed depth in a kiln. This can be done
through the use of a dam.
A rotary kiln dam works by forcing material to
build up behind the dam, causing retention
time and bed depth to increase.

8. End dams are most commonly used, because
they efficiently hold the material where the air
is warmest (at the discharge end in a counter
current kiln).

9. End dams are most commonly used, because
they efficiently hold the material where the air
is warmest (at the discharge end in a counter
current kiln).
If an end dam is not sufficient, internal dams
are also an option.

10. End dam in a rotary kiln

11. Flights

12. While flights are most commonly seen in rotary
dryers, they are on occasion, used in low
temperature kilns.

13. While flights are most commonly seen in rotary
dryers, they are on occasion, used in low
temperature kilns.
Flights work by picking up material and
dropping it through the process gas as the
drum rotates. This maximizes heat transfer
efficiency.

14. Bed Disturbers

15. Some materials may “slip” along the
interior of the drum, causing uneven
distribution of heat throughout the bed.

16. Some materials may “slip” along the
interior of the drum, causing uneven
distribution of heat throughout the bed.
Bed disturbers are used in both direct and
indirect kilns to redistribute the bed of
material in order to promote even heat
distribution.

17. The images above show how a bed disturber can promote even heat
distribution. At left: a slipping bed with large temperature variations.
At right: a bed disturber properly redistributes the bed, promoting even
heat distribution.

18. Bed disturbers work by turning over the
bed of material, redistributing what was
on top, to the bottom, and vice versa.

19. Bed disturbers work by turning over the
bed of material, redistributing what was
on top, to the bottom, and vice versa.
A commonly used bed disturber is a metal
bar affixed to the interior of the kiln,
running the length of the kiln.

20. A bar bed disturber is not always ideal,
however, as the thermal stresses can
cause the bar to bend and break.

21. A bar bed disturber is not always ideal,
however, as the thermal stresses can
cause the bar to bend and break.
In cases where significant gradations in
temperature along the length of the drum
exist, flights can be used as a bed
disturber to avoid this issue.

22. Seals

23. A quality seal is critical to the success of the
processing operation.

24. A quality seal is critical to the success of the
processing operation.
Because rotary kilns run at a negative pressure
(gas doesn’t leak out), air leaks in. And since
the rotary kiln is running at a higher
temperature than the ambient air, any
incoming air will cause the temperature inside
the kiln to drop.

25. Not only will this result in wasted energy, but if
the leak is severe enough, it could potentially
disrupt the reaction occurring inside. Luckily,
many quality seal options are available. Two of
the most commonly used seals include:

26. Not only will this result in wasted energy, but if
the leak is severe enough, it could potentially
disrupt the reaction occurring inside. Luckily,
many quality seal options are available. Two of
the most commonly used seals include:
• Leaf Seals

27. Not only will this result in wasted energy, but if
the leak is severe enough, it could potentially
disrupt the reaction occurring inside. Luckily,
many quality seal options are available. Two of
the most commonly used seals include:
• Leaf Seals
• Purged Double Leaf Seals

28. Leaf Seals
Leaf seals are similar to a deck of cards.
The spring steel ‘cards,’ or leaves, are
fanned out and bolted to the breeching.

29. Leaf Seals
Leaf seals are similar to a deck of cards.
The spring steel ‘cards,’ or leaves, are
fanned out and bolted to the breeching.
They are forced to push against the
seal/wear plate of the rotating kiln,
creating a seal.

30. Purged Double Leaf Seals
The purged double leaf seal is a variation
of the leaf seal. This seal is used in
situations where maintaining the
atmosphere inside the kiln is extremely
critical.

31. The purged double leaf seal consists of
two layers of leaves, set on top of each
other. An inert purge gas (such as
nitrogen) is introduced between the set of
leaves, which pushes outward, preventing
oxygen from flowing inward.

32. Refractory

33. Refractory is also a critical component in
maintaining process efficiency, as well as
prolonging the life of the kiln.

34. Refractory is also a critical component in
maintaining process efficiency, as well as
prolonging the life of the kiln.
Refractory protects the shell of the kiln
from the temperatures within, and also
helps to maintain heat retention inside
the kiln.

35. Refractory is specific to direct-fired kilns. If
an indirect kiln were to be lined with
refractory, efficiency would be
significantly decreased, because it would
be another layer for heat to pass through
before it could reach the material.

36. Two types of refractory are commonly
used: Brick and Castable.

37. Two types of refractory are commonly
used: Brick and Castable.
Each type offers its own advantages and
disadvantages, with the choice
depending on cost, material chemistry,
how abrasive the material to be
processed is, and how hot the kiln will be.

38. Refractory can be customized as well.
When very high temperatures are
involved, it is desirable to use multiple
layers of refractory: a “working” layer, and
an insulating layer.

39. Refractory can be customized as well.
When very high temperatures are
involved, it is desirable to use multiple
layers of refractory: a “working” layer, and
an insulating layer.
The working layer is a durable, thick layer
that can withstand the constant abrasion
of the material and the high temperatures
inside the kiln.

40. However, the more dense the refractory,
the less insulating capability it has.

41. However, the more dense the refractory,
the less insulating capability it has.
For this reason, the insulating layer is
needed beneath the working layer to
protect the shell of the kiln.

42. However, the more dense the refractory,
the less insulating capability it has.
For this reason, the insulating layer is
needed beneath the working layer to
protect the shell of the kiln.
The working layer and insulating layer are
typically made of the same material (brick
or castable).

43. WORKING REFRACTORY
REFRACTORY ANCHORS
INSULATING REFRACTORY
CERAMIC FIBER BACKING
KILN SHELL
MATERIAL BED
CASTABLE
WORKING REFRACTORY
INSULATING REFRACTORY
KILN SHELL
MATERIAL BED
BRICK
The images above show the different types of refractory with working
and insulating layers. In addition, the castable illustration at left shows
optional ceramic fiber backing.

44. Conclusion
Rotary kilns are extremely customizable,
capable of being configured to suit nearly any
processing needs.

45. Conclusion
Rotary kilns are extremely customizable,
capable of being configured to suit nearly any
processing needs.
Components such as seals, bed disturbers,
refractory, and more, can all be customized to
increase the efficiency of the kiln and create
an optimal processing solution.

46. has been a leader in the thermal processing
industry since the 1950s, providing process &
product development, feasibility testing,
maintenance services, and high-quality,
custom rotary kilns.

47. Want to learn more?
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