Note: Descriptions are shown in the official language in which they were submitted.
WO 2022/090216
PCT/EP2021/079664
1
A FLASH DRYER FOR DRYING A PRODUCT AND A METHOD FOR
DRYING A PRODUCT IN A FLASH DRYER
Technical field
The invention relates to a flash dryer for drying a product and a method
for drying a product in a flash dryer or an agitated fluid bed dryer.
Background art
A flash dryer is used for continuous drying of a filter cake, fibrous
materials, paste, sludge or similar materials. The flash dryer uses a rotary
disintegrator, mill or impeller rotor for disintegration of the material and
provides a change of the structure of the material from the paste or fibrous
structure to a more particle shaped structure which is more suitable during
the
drying. Apertures are provided for supply of hot drying gas and for removal of
the spent drying gas and removal of the dried material.
EP 1 719 963 A2 discloses an apparatus for continuous drying of a
product. The apparatus comprises a feeding device, which conveys the
product into a rotating disintegrator. In the lower part of the apparatus the
drying gasses are being introduced and passed upwards through the slot and
into the disintegrator housing. The drying chamber has a conical shape with
the point towards the outlet for the drying gasses. The product, because of
the rotation of the disintegrator, is being pressed by the wall of the cone
away
from the the outlet for the drying air with a resulting accelerating force
which
is greater than the force of gravity. The dried material and the spent drying
air
are discharged through the product outlet in the upper part of the drying
chamber.
A problem with this type of conventional flash dryers is that the rotating
disc in the bottom of the chamber may deform due to the heat from the air
introduced via the air inlets. This will in turn lead to an undesired
engagement
between the disc and the inner wall of the chamber thereby decreasing the
life time of the disc.
Another problem is that the product tends to accumulate between the
rotating disc and the bottom portion of the chamber. In general, accumulation
of material, in particular of waste materials build-up, at the bottom of a
flash
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dryer is cumbersome to handle as removal of this material generally requires
the processing line to be shut down during maintenance, which may entail
disassembling the flash dryer and long waiting times in order for the dryer to
cool to temperatures which permit operator access to the drying chamber.
Summary of the invention
It is an object of the present invention to provide an improvement of the
flash dryers according to prior art. A particular object is to provide an
improved flash dryer which allows for a more secure and effective drying
process of a product.
According to a first aspect, these and other objects, and/or advantages
that will be apparent from the following description of embodiments, are
achieved, in full or at least in part, by a flash dryer for drying a product.
The
flash dryer comprises a chamber having a product inlet and a product outlet,
the product inlet being located in a lower section of the chamber and the
product outlet in a upper section of the chamber, a disc fixedly arranged in
the
lower section of the chamber below the product inlet, such that a gap is
created between an outer edge of the disc and an inner wall of the chamber,
wherein a thickness of the disc is decreasing radially from a mid-section of
the disc towards the outer edge of the disc, a primary air inlet arranged
below
the chamber and arranged to provide air into the chamber via the gap, a drive
unit arranged below the chamber having a drive shaft extending through a
hole in the mid-section of the disc into the lower section of the chamber, a
plurality of rotatable disintegrator elements connected to the drive shaft in
the
lower section of the chamber above the disc, and a rotatable shovel arm
connected to the drive shaft in the lower section of the chamber above the
disc and below the plurality of disintegrator elements. The shovel arm is
adapted to distribute the product in the lower section of the chamber.
This is advantageous in that the new and inventive shape of the disc
eliminates the need to rotate the disc in order to force the product towards
the
gap and the air flowing therefrom. In turn, the risk of the disc engaging with
the inner wall of the chamber due to heat expansion is also eliminated, which
will prolong the life time of the disc and the chamber.
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The specially designed shovel arm will help distributing the product in
the lower portion of the chamber and push the same towards gap and the air
flowing therefrom. The shovel arm is preferably shaped to correspond with
the upper surface of the disc, i.e. it may have an inclined or curved shape
towards the disc.
Another advantage is that the product will no longer be able to
accumulate between the disc and the bottom portion of the chamber as with
the conventional flash dryers due to rotation of the disc.
The flash dryer may further comprise a secondary air inlet arranged in
the lower section of the chamber above the plurality of disintegrator
elements.
The secondary air inlet may comprise a plurality of inner air inlets
providing air into the chamber, the inner air inlets being arranged along a
periphery of the chamber.
The disc may have a domed shape.
The disc may comprise protrusions along its outer periphery adapted to
direct air from the primary air inlet to enter the chamber via the gap in a
substantially vertical direction.
The outer edge of the disc may be at least partly rounded.
The plurality of disintegrator elements may be vertically aligned with
the location of the product inlet.
Each one of the plurality of disintegrator elements may comprise a
grinding edge thereof such that the product is disintegrated and/or grinded
between the grinding edge and the inner wall of the chamber.
The shovel arm may comprise a plurality of recesses in a bottom
section thereof, allowing parts of product located on the disc to escape
therethrough.
The shovel arm may comprise a wing portion attached to an outer
edge thereof, the wing portion being vertically aligned with the product
outlet
such that the product fed into the chamber is cut into pieces when the shovel
arm is rotating therein.
The shovel arm may be arranged in the lower section of the chamber
to vertically correspond with the location of the product inlet.
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The chamber may comprise protrusions arranged at a distance from
each other along a periphery of the inner wall of the cylinder.
Each one of the protrusions may comprise an exchangeable cutting
edge.
5 The flash dryer may further comprise a product conveyer connected to
the product inlet.
According to a second aspect, the objects are achieved in full, or at
least in part, by a method for drying a product in a flash dryer. The method
comprises introducing the product into a chamber of the flash dryer via a
10 product inlet located in a lower section of the chamber onto a disc
fixedly
arranged in the lower section of the chamber below the product inlet, wherein
a thickness of the disc is decreasing radially from a mid-section of the disc
towards the outer edge of the disc, rotating a shovel arm in the lower section
of the chamber above the disc to distribute the product in the lower section
of
15 the chamber, rotating a plurality of rotatable disintegrator elements in
the
lower section of the chamber above the disc and the shovel arm to
disintegrate the product, providing air into the chamber from a primary air
inlet
arranged below the chamber via a gap between an outer edge of the disc and
an inner wall of the chamber to lift and dry the product, providing air into
the
20 chamber from a secondary air inlet arranged in the lower section of the
chamber above the plurality of disintegrator elements to rotate and dry the
product, and exiting the product via a product outlet in a upper section of
the
chamber.
It should be noted that the different embodiments of the flash dryer that
25 is described above are exemplifying only. The embodiments may be
combined with each other in any suitable way depending on the requirements
established for the flash dryer.
It should be further noted that the different steps of the method
described above may be conducted in any suitable order.
30 Effects and features of the second aspect of the present invention are
largely analogous to those described above in connection with the first aspect
the inventive concept. Embodiments mentioned in relation to the first aspect
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of the present invention are largely compatible with the further aspects of
the
invention.
Other objectives, features and advantages of the present invention will
appear from the following detailed disclosure, from the attached claims, as
5 well as from the drawings. It is noted that the invention relates to all
possible
combinations of features.
Generally, all terms used in the claims are to be interpreted according
to their ordinary meaning in the technical field, unless explicitly defined
otherwise herein. All references to "a/an/the [element, device, component,
10 means, step, etc.]" are to be interpreted openly as referring to at
least one
instance of said element, device, component, means, step, etc., unless
explicitly stated otherwise.
As used herein, the term "comprising" and variations of that term are
not intended to exclude other additives, components, integers or steps.
Brief description of the drawings
The above objects, as well as additional objects, features and
advantages of the present invention, will be more fully appreciated by
reference to the following illustrative and non-limiting detailed description
of
20 preferred embodiments of the present invention, when taken in
conjunction
with the accompanying drawings, wherein:
Fig. 1 illustrates a perspective view of an exemplary embodiment of a
flash dryer according to a first aspect of the invention.
Fig. 2 illustrates a cross-section of the flash dryer in Fig. 1.
25 Fig. 3 illustrates a perspective view of an exemplary embodiment of a
disc located in a chamber of the flash dryer.
Detailed description of preferred embodiments of the invention
Fig. 1 and 2 illustrate an exemplary embodiment of a flash dryer 1 for
30 drying a product 2. The flash dryer 1 comprises a chamber 3 having a
product
inlet 4 and a product outlet 5. The product inlet 4 is located in a lower
section
of the chamber 3 and the product outlet 5 is located in a upper section of the
chamber 3.
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A domed shaped disc 6 is fixedly arranged in a bottom 7 of the
chamber 3 below the product inlet 4. The disc 6 has a diameter that is
slightly
smaller than an inner diameter of an inner wall 8 in the lower section of the
chamber 3, such that a gap 9 is created between an outer edge 10 of the disc
5 6 and the inner wall 8 of the chamber 3. As the disc 6 is has a domed
shape,
a thickness of the disc 6 is decreasing radially from a mid-section 11 of the
disc 6 towards the outer edge 10 of the disc 6. The outer edge 10 of the disc
6 is preferably at least partly rounded for manufacturing purposes and
structural strength. The rounded shape of the outer edge 10 of the disc 6
10 makes it possible to avoid welded corner joints which highly contributes
to an
increase structural strength of the disc 6. The radius of the rounded outer
edge is preferably 50 mm or more. Naturally, the exact size and shape of the
disc 6 may be varied. The disc 6 can have a domed shape or for example
straight upper surfaces where the thickness of the disc 6 is decreasing
15 radially from a mid-section 11 of the disc 6 towards the outer edge 10
of the
disc 6. In this specific embodiment, the disc 5 has a domed shape with a
diameter of approximately 3200 mm, maximum height ¨ at the mid-section 11
¨ of approximately 600 mm, and a minimum height ¨ at the outer edge 10 ¨ of
approximately 300 mm.
20 A primary air inlet 12 is arranged below the chamber 3 and arranged to
provide air into the chamber 3 via the gap 9. The disc 6 comprises protrusions
25 along its outer periphery. The protrusions 25 are illustrated in Fig. 3 and
are formed to direct air from the primary air inlet 12 to enter the chamber 3
via
the gap 9 in a substantially vertical direction_
25 The flash dryer 1 further comprises a drive unit 13 arranged below the
chamber 3 which has a drive shaft 14 extending through a hole 15 in the mid-
section 11 of the disc 6 into the lower section of the chamber 3.
A rotatable shovel arm 16 is connected to the drive shaft 14 directly
above the disc 6 in the lower section of the chamber 3. The shovel arm 16
30 rotates above the disc 6 and is used to push the product 2 towards the
gap 9
and the air flowing into the chamber 3 therefrom. In a bottom section 17 of
the
shovel arm 16 is provided a plurality of recesses 18 allowing parts of product
2 located on the disc to escape therethrough. The recesses 18 is used
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minimize the torque of the shovel arm 16 when distributing the product 2
present on the disc 6. More specifically, the shovel arm 16 comprises a first
portion 19 which is flat and extends horizontally from the drive shaft 14
towards the inner wall 8 of the chamber 3, a second portion 20, comprising
5 the recesses 18, which also is flat and extends perpendicular from the
first
portion 19 vertically in a downward direction towards the disc 6, and a wing
portion 21 attached to the first portion 19 at an outer edge 22 thereof. The
second portion is preferably shaped to correspond with the shape of the
domed shaped of the disc 6 thereby nearly engaging with the disc 6. The
10 wing portion 21 is vertically aligned with the product outlet 5 such
that the
product 2 fed into the chamber 3 can be cut into pieces by means of the wing
portion 21.
A plurality of rotatable disintegrator elements 23 is connected to the
drive shaft 14 directly above the shovel arm 16 in the lower section of the
15 chamber 3. The disintegrator elements 23 are vertically aligned with the
location of the product inlet 4. Each one of the disintegrator elements 23
comprises a grinding edge 24 which is used to grind and/or disintegrate the
product 2 towards the inner wall 8 of the chamber 3. The grinding edge 24 is
replaceable and can be turn over in any suitable position. The shape, extent
20 and number of disintegrator elements 23 may naturally be varied in any
suitable way. They can be mounted in different angles in relation to each
other, they can be displaced at a specific distance from each other, and they
can be mounted in a cross or to overlap. By the different mounting
possibilities of the disintegrator elements 23 to the drive shaft 14 any
desired
25 type of disintegration and/or grinding results can be achieved. In this
specific
embodiment, the disintegrator elements 23 extends more or less from the
drive shaft 14 towards the inner wall 8 of the chamber 3 in a tapering manner
with the grinding edge 24 provided on the outermost edge thereof.
A secondary air inlet 26 is arranged in the lower section of the chamber
30 3 above the disintegrator elements 23. The secondary air inlet 26 comprises
an outer air inlet 27 and a plurality of inner air inlets 28 providing air
into the
chamber 3. The inner air inlets 28 are arranged along the entire periphery of
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the chamber 3 in a substantially tangential direction to create circular flow
along the inner wall 8 of the chamber 3.
The lower section of the chamber 3 comprises protrusions 29 arranged
at a distance from each other along the entire periphery of the inner wall 8
of
5 the chamber 3. Each one of the protrusions 29 comprises an exchangeable
cutting edge. The protrusions 29 are vertically aligned with the disintegrator
element 23 such that the product 2 can be grinded and/or disintegrated
between the grinding edges 24 of the disintegrator elements 23 and the
cutting edges of the protrusions 29. The exchangeable cutting edge of the
10 protrusion 29 can be placed in different positions in order to adjust
the
distance between themselves and the grinding edges 24 of the disintegrator
elements 23.
A product conveyer (not shown), preferably a screw product conveyer,
is connected to the product inlet 4 and used to transport the product 2 to the
15 chamber 3 of the flash dryer 1. A pump (not shown) could also be used to
input the product 2 to the chamber 3 of the flash dryer 1 via the product
inlet
4.
An exemplary method for drying the product 2 in the flash dryer 1 will
now be described in greater detail.
20 When the flash dryer 1 is used, the product 2 to be disintegrated and
dried is fed into the chamber 3 via the product inlet 4 by means of the
product
conveyer. The product 2 entering the chamber 3 is cut into pieces by means
of the wing portion 21 of the rotating shovel arm 16 and is thereafter
disintegrated by means of the rotating disintegrator elements 23 when falling
25 towards the disc 6 in the bottom 7 of the chamber 3 by means of gravity.
The
product 2 is further grinded and/or disintegrated between the grinding edges
24 of the disintegrator elements 23 and the cutting edges of the protrusions
29.
When the product 2 reaches the domed shaped disc 6, it will, in
30 cooperation with the second portion 20 of the shovel arm 23, force the
product 2 towards the gap 9 between the outer edge 10 of the disc 6 and the
inner wall 8 of the chamber 3. Air from the primary air inlet 12 flowing into
the
chamber 3 via the gap 9 will thereafter lift the product 2 up from the lower
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section of the chamber 3 towards the upper section thereof. Simultaneously,
air from the secondary air inlet 26 is flowing into the chamber 3 to rotate
the
product 2 therein.
The disintegrated and dried product 2 will finally exit the chamber 3 via
5 the product outlet 5 in the upper section of the chamber 3. Larger pieces
of
the product 2 will fall down towards the disc 6 in the bottom 7 of the chamber
3 by means of gravity, through the disintegrator elements 23 once again, and
reiterate the process described above.
As stated above, it is important to understand that the different method
steps may be conducted in any suitable order and that the detailed
description of the method presented above is of exemplary nature only.
The skilled person realizes that a number of modifications of the
embodiments described herein are possible without departing from the scope
of the invention, which is defined in the appended claims.
15 For instance, the flash dryer 1 can be equipped with a CIP-system
comprising pop-in-pop-out (PIPO) nozzles which are activated by means of
pressure in order to clean the inner surfaces of the flash dryer 1 that are in
contact with the product 2 inside the chamber 3.
The disc 6 can be filled with an insulating material, preferably a non-
20 inflammable, such as vermiculite, in order to increase the isolating
properties
of the disc 6 and limit the heat transfer in a downward direction of the flash
dyer 1.
The disc 6 can be placed in the bottom 7 of the chamber 8 or in fact
constitute the bottom 7 of the chamber 1
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