Information
-
Patent Grant
-
6397490
-
Patent Number
6,397,490
-
Date Filed
Thursday, July 27, 200024 years ago
-
Date Issued
Tuesday, June 4, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Walberg; Teresa
- Robinson; Daniel
Agents
- Arent Fox Kintner Plotkin & Kahn, PLLC
-
CPC
-
US Classifications
Field of Search
US
- 034 168
- 034 165
- 106 740
- 209 11
- 241 52
- 241 17
- 426 467
-
International Classifications
-
Abstract
A flash drying apparatus has a vertical, cylindrical enclosure. In a lower portion of this enclosure is disposed a rotating disk. Above this disk is provided a crusher that, using blades formed radially thereon, crushes a raw material into a powdery or granular material. The crusher is provided with a material feeder that feeds the raw material to the crusher by letting the raw material fall onto the crusher. A hot wind feeder feeds a hot wind to the powdery or granular material from under the blades. The powdery or granular material blown upward inside the enclosure by the hot wind is exhausted through an exhaust duct provided in an upper portion of the enclosure. This flash drying apparatus prevents degradation in performance resulting from deposition of a raw material.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flash drying apparatus for crushing and drying a raw material containing moisture.
2. Description of the Prior Art
A conventional flash drying apparatus is constructed as shown in FIG.
1
. The flash drying apparatus has an enclosure
5
composed of a plurality of cylindrical or truncated conical members coupled together. In a lower portion of the enclosure
5
is provided an inlet
1
through which a hot wind supplied from a hot wind source (not shown) is fed into the enclosure
5
. Above the inlet
1
is provided a crushing rotor
12
that is driven to rotate by a driving motor
10
through a belt
14
.
The crushing rotor
12
has a plurality of stirrup-shaped hammers
4
that face the inner wall of the enclosure
5
, constituting a crusher
3
in which a raw material is crushed as the hammers rotate. Above the crusher
3
is provided a material feeder
9
through which the raw material is fed in. The material feeder
9
is provided with a screw feeder (not shown) so that the raw material stored in a hopper (not shown) or the like is fed out through an outlet
9
b
so as to fall into the crusher
3
.
In an upper portion of the enclosure
5
is provided a classifier
6
that classifies a powdery or granular material. The classifier
6
has a plurality of classifying blades
13
that are made of thin plates, arranged radially, and driven to rotate by a driving motor
8
. As shown in
FIG. 2
, the classifying blades
13
are each arranged with a predetermined inclination a relative to a center line
6
a.
This arrangement serves to keep the rotation speed of the classifying blades
13
at an appropriate rate and simultaneously limit entry of the powdery or granular material into the classifier
6
. Above the classifier
6
is provided an exhaust duct
7
that is sucked by a blower (not shown) to permit the powdery or granular material to be exhausted together with air and water vapor.
In this flash drying apparatus constructed as described above, a raw material containing moisture is supplied from the material feeder
9
in such a way as to fall onto the crushing rotor
12
that is driven to rotate by the driving motor
10
. The raw material, originally in the form of clusters, collides with the hammers
4
, and is thereby crushed into a powdery or granular material. This powdery or granular material is blown upward from under the hammers
4
by a hot wind introduced through the inlet
1
into the enclosure
5
, and is thereby, while flowing upward inside the enclosure
5
, further dispersed and dried.
On the other hand, the classifying blades
13
that are driven to rotate by the driving motor
8
produces a vortex air stream. The powdery or granular material having flown upward inside the enclosure
5
and come close to the classifier
6
is acted upon simultaneously by the centrifugal force of this vortex air stream and by the centripetal force of the air and water vapor being exhausted. The insufficiently dispersed portion of the powdery or granular material is acted upon more by the centrifugal force, and is therefore thrown out of the classifier so as to fall onto the crusher
3
and be exposed to the hot wind once again.
The powdery or granular material thus dispersed and dried once again is acted upon more by the centripetal force, and is therefore permitted to enter the classifier
6
through the gaps
6
b
between the classifying blades
13
. The powdery or granular material is then exhausted through the exhaust opening
7
a
of the exhaust duct
7
in the form of dry powder or granules of uniform particle size.
When the raw material is slurry or liquid, i.e. a mixture of a powdery or granular material with a large amount of water, the material is usually formed into cakes using a filter press before being supplied. In less usual cases where such a raw material is supplied as it is, i.e. in the form of slurry or liquid, it is fed in through a pipe provided in the material feeder
9
in such a way as to flow down onto the crushing rotor
12
. Then, the raw material, acted upon by centrifugal force, moves outward and makes contact with the hammers
4
. Thus, the raw material is dispersed and formed into liquid droplets, and is then dried by the hot wind.
However, in this conventional flash drying apparatus, the raw material, containing moisture, tends to be deposited on the inner wall of the enclosure
5
. In particular, the portion of the raw material that falls along the inner wall of the enclosure
5
makes contact with the top surfaces of the stirrup-shaped hammers
4
at the same portion thereof. As a result, this portion of the raw material is not dispersed uniformly, but is scattered, before being subjected to heat exchange with the hot wind, in such a way as to be deposited on the inner wall of the enclosure
5
at about the same portion thereof above the hammers
4
.
As this deposit grows, there is a risk of an unduly great pressure loss, or clogging of the passage inside the enclosure
5
, which makes the flash drying apparatus unusable. On the other hand, simply increasing the amount of supplied hot wind causes the powdery or granular material having entered the classifier
6
to collide with the classifying blades
13
and be thereby deposited thereon. This, similarly, may lead to clogging of the gaps
6
b
between the classifying blades
13
, causing an unduly great pressure loss.
In cases where the raw material is slurry or liquid containing a large amount of water and is fed in through a pipe so as to flow onto the crushing rotor
12
, the raw material, acted upon by centrifugal force, flows outward along strip-shaped paths on the top surface of the crushing rotor
12
. Thus, the raw material makes contact with the hammers without being sufficiently dispersed. This causes the raw material to be dispersed in the form of comparatively large drops and thus deposited on the inner wall of the enclosure
5
without being dried. As this deposit grows, clogging of the passage inside the enclosure
5
may result.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a flash drying apparatus that can prevent degradation in performance resulting from deposition of a raw material.
Another object of the present invention is to provide a flash drying apparatus that can satisfactorily dry even a raw material in the form of slurry or liquid containing a large amount of water.
To achieve the above objects, according to the present invention, a flash drying apparatus for drying a material containing moisture is provided with: a vertical, cylindrical enclosure; a crusher, composed of a rotating plate-shaped member and a crushing member provided integrally therewith, and disposed in a lower portion of the enclosure, for crushing the raw material into a powdery or granular material; a material feeder for feeding the raw material to the crusher by letting the raw material fall onto the crusher; a hot wind feeder for feeding a hot wind to the powdery or granular material from under the crushing member; a classifier for classifying the powdery or granular material blown upward inside the enclosure by the hot wind; and an exhauster for exhausting the classified powdery or granular material through an upper portion of the enclosure. Here, the crushing member is composed of a plurality of blades made of thin plates, arranged radially above the plate-shaped member, and supported by being coupled to a ring-shaped member provided substantially parallel to the plate-shaped member.
As described above, according to the present invention, the blades are made of thin plates, and are supported by being coupled to the ring-shaped member. This helps reduce the amount of raw material that falls onto the blades and then remains deposited thereon, and thereby restrain the growth of the deposit on the inner wall of the enclosure. Moreover, an air stream passage is formed that permits the air above the crusher to flow from the inside to the outside through the gaps between the blades. This permits the powdery or granular material to be dried repeatedly and thus more fully.
Moreover, the ring-shaped member prevents the blades from being inclined by centrifugal force, and thus permits the blades to be made higher. This helps increase the length of time for which the raw material is crushed while being exposed to the hot wind. Thus, it is possible to disperse the powdery or granular material more fully than ever immediately after the crushing thereof, and thereby further restrain the deposition of the powdery or granular material on the inner wall of the enclosure in a portion thereof above the blades.
BRIEF DESCRIPTION OF THE DRAWINGS
This and other objects and features of the present invention will become clear from the following description, taken in conjunction with the preferred embodiments with reference to the accompanying drawings in which:
FIG. 1
is a sectional view of a conventional flash drying apparatus;
FIG. 2
is a plan view of the classifying blades of a conventional flash drying apparatus;
FIG. 3
is a diagram showing the configuration of a dryer system employing the flash drying apparatus of a first embodiment of the invention;
FIG. 4
is a sectional view of the flash drying apparatus of the first embodiment of the invention;
FIG. 5
is a plan view of the crushing rotor of the flash drying apparatus of the first embodiment of the invention;
FIG. 6
is a sectional view of the classifier of the flash drying apparatus of the first embodiment of the invention;
FIG. 7
is a plan view of the classifying rotor of the flash drying apparatus of the first embodiment of the invention;
FIG. 8
is a plan view of another design of the crushing rotor of the flash drying apparatus of the first embodiment of the invention;
FIG. 9
is a plan view of another design of the ring-shaped member of the crushing rotor of the flash drying apparatus of the first embodiment of the invention;
FIG. 10
is a developed view illustrating an example of the arrangement of the projections provided on the crushing rotor of the flash drying apparatus of the first embodiment of the invention;
FIG. 11
is a developed view illustrating another example of the arrangement of the projections provided on the crushing rotor of the flash drying apparatus of the first embodiment of the invention;
FIG. 12
is a developed view illustrating still another example of the arrangement of the projections provided on the crushing rotor of the flash drying apparatus of the first embodiment of the invention;
FIG. 13
is a diagram showing the load on the driving motor as observed when projections are provided on the crushing rotor of the flash drying apparatus of the first embodiment of the invention;
FIG. 14
is a diagram showing the load on the driving motor as observed when no projections are provided on the crushing rotor of the flash drying apparatus of the first embodiment of the invention;
FIG. 15
is a sectional view of the flash drying apparatus of a second embodiment of the invention;
FIG. 16
is a plan view of the hammer of the flash drying apparatus of the second embodiment of the invention;
FIG. 17
is a sectional view of the flash drying apparatus of the second embodiment of the invention, with the hammers fitted in a different position;
FIG. 18
is a plan view of the deflector ring of the flash drying apparatus of the second embodiment of the invention;
FIG. 19
is a sectional view of the flash drying apparatus of a third embodiment of the invention;
FIG. 20
is a plan view of the hot wind inlet portion of the flash drying apparatus of the third embodiment of the invention;
FIG. 21
is a schematic perspective view of the protruding pieces of the flash drying apparatus of the third embodiment of the invention;
FIG. 22
is a sectional view of the flash drying apparatus of a fourth embodiment of the invention; and
FIG. 23
is a diagram showing the material heater of the flash drying apparatus of the fourth embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience' sake, elements corresponding to those found in the conventional example shown in
FIG. 1
are identified with the same reference numerals.
FIG. 3
is a diagram schematically showing the configuration of a dryer system employing the flash drying apparatus of a first embodiment of the invention. The flash drying apparatus
25
is, in a substantially central portion thereof, provided with a material feeder
9
that has a hopper
14
and that supplies the flash drying apparatus
25
with a raw material.
Connected to the flash drying apparatus
25
, below the material feeder
9
, is a hot wind generating apparatus
24
that supplies the flash drying apparatus
25
with a hot wind. In an upper portion of the flash drying apparatus
25
is provided an exhaust duct, through which the powdery or granular material crushed and dried inside the flash drying apparatus
25
is exhausted from the flash drying apparatus
25
together with water vapor.
The exhaust duct
7
is connected to a collector
26
, which in turn is connected to a blower
27
. Thus, the powdery or granular material is sucked toward the collector
26
by the blower
27
so as to be collected as indicated by arrow A, and the water vapor is exhausted through the blower
27
to the outside.
FIG. 4
shows a sectional view of the flash drying apparatus
25
. The flash drying apparatus
25
is enclosed in an enclosure
5
composed of an upper casing
5
a
, a liner
5
b
, and a lower casing
5
c
, all cylindrical in shape. The upper and lower casings
5
a
and
5
c
are formed out of sheet steel or the like. The liner
5
b
is formed out of such a material and in such a shape as to have higher strength than the upper and lower casings
5
a
and
5
c
. This helps prevent breakage or wear of the liner
5
b
resulting from collision of the raw material therewith occurring as a crushing rotor
12
, described later, rotates.
The liner
5
b
has brims
5
d
and
5
e
fitted integrally thereto with a plurality of bolts
36
. The upper casing
5
a
is fastened to the brim
5
d
with a plurality of bolts
58
and nuts
59
and with a gasket
57
placed in between. The lower casing
5
c
is fastened to the brim
5
e
with a plurality of bolts
49
and nuts
50
and with a gasket
57
placed in between. The gaskets
57
serve to keep the inside of the enclosure
5
airtight. In addition, between the lower casing
5
c
and the brim
5
e
, a deflector ring
40
is provided.
The lower casing
5
c
has an inlet
1
formed therein, through which a hot wind supplied from the hot wind generating apparatus
24
(see
FIG. 3
) is introduced into the enclosure
5
. The lower casing
5
c
has a bottom plate
51
welded at the bottom end thereof. On the bottom plate
51
, a housing
55
for housing bearings
43
,
44
, and
45
is fitted with bolts
54
. Moreover, on the bottom plate
51
, a dust cover
52
for preventing entry of the powdery or granular material into the housing
55
is fitted with bolts
53
.
Fitted into the bearings
43
,
44
, and
45
is a shaft
42
. The shaft
42
has a pulley
41
fitted thereto at the bottom end thereof, which is coupled to the driving motor
10
(see
FIG. 3
) through a belt (not shown). The bearings
43
,
44
, and
45
are lubricated with lubricating oil that is supplied at their top and drained at their bottom through oil tubes
56
a
and
56
b
connected to an oil feeding apparatus (not shown) that circulates the lubricating oil.
The shaft
42
has a flange
46
fitted thereto at the top end thereof with a bolt
47
. The flange
46
has a disk (plate-shaped member)
32
fitted thereon with bolts
48
. As shown in
FIG. 5
, the disk
32
has a plurality of blades
31
, made of thin plates with a thickness t, arranged radially so as to protrude outward from the outer circumference of the disk
32
and face the liner
5
b.
The blades
31
have projections
31
a
formed at the bottom ends thereof, and these projections
31
a
are press-fitted into slits
32
a
formed in the disk
32
. The blades
31
have their top ends welded to a ring-shaped member
33
. Thus, the disk
32
, blades
31
, and ring-shaped member
33
together constitute a crushing rotor
12
that rotates integrally with the shaft
42
. The blades
31
may be held by fastening together the disk
32
and the ring-shaped member
33
with bolts with the blades
31
sandwiched between them.
In
FIG. 5
, the blades
31
are each arranged with an inclination β relative to a center line
12
a
of the crushing rotor
12
. Thus, as the crushing rotor
12
rotates in the direction indicated by arrow D, it produces an air stream that flows from the inside to the outside of the blades
31
.
Above the crushing rotor
12
, a material feeder
9
is provided so as to protrude into the enclosure
5
. The material feeder
9
has a screw feeder
9
a
provided inside it. As this screw feeder
9
a
rotates, a raw material, in the form of clusters, is fed out through an outlet
9
b
in such a way as to fall onto the crushing rotor
12
.
The raw material thus fed to the crushing rotor
12
is, by the centrifugal force resulting from the rotation of the crushing rotor
12
, transferred to the outer circumference thereof so as to be crushed into a powdery or granular material by the blades
31
. Thus, this portion as a whole constitutes a crusher
3
. Here, to prevent the raw material from reaching the shaft
42
, and to ease the transfer of the raw material to the outer circumference of the crushing rotor
12
, a conical cover
34
is provided on the disk
32
.
At the side of the upper casing
5
a
, a sight glass
39
made of glass is provided that permits inspection of the inside of the enclosure
5
. At the top of the upper casing
5
a
, a classifier
6
is fitted thereto. As shown in
FIG. 6
, the classifier
6
is enclosed in an upper cover
71
and a lower cover
70
that are fastened together with a plurality of bolts and nuts (not shown).
Inside the upper cover
71
, housings
75
a
and
75
b
for housing bearings
68
and
69
are welded thereto. Fitted into the bearings
68
and
69
is a shaft
63
. At the side of the upper cover
71
, an angle
72
is provided, on which the driving motor
8
(
FIG. 3
) is mounted. The shaft
63
is coupled to the driving motor
8
through a belt (not sown) so as to be driven to rotate. In addition, above the upper cover
71
is provided a photoelectric switch
74
for detecting the rotation rate of the shaft
63
.
The lower cover
70
has an opening at the bottom end thereof so as to communicate with the inside of the casing
5
a
. The lower cover
70
is, in an upper portion thereof, sealed by a sealing member
76
. The lower cover
70
has an opening
70
a
formed in the circumferential surface thereof, and has a cylindrical pipe
77
welded thereto so as to cover the opening
70
a.
Thus, the lower cover
70
and the cylindrical pipe
77
together constitute an exhaust duct
7
. As compared with the duct
7
used in the conventional example (see
FIG. 1
) that is formed out of a curved cylindrical pipe, this duct
7
helps increase the cross-sectional area of the exhaust passage around the shaft
63
, and thereby prevent clogging caused by the powdery or granular material deposited on the inner wall of the exhaust duct
7
.
Around the portion of the shaft
63
that penetrates the lower cover
70
is fitted an outer cylinder
64
that rotates together with the shaft
63
by being interlocked therewith by a key
67
. The outer cylinder
64
has a scraper
66
formed integrally therewith. The scraper
66
is made of a thin plate and serves to scrape off the powdery or granular material deposited on the inner wall of the lower cover
70
. To reduce the pressure loss inside the exhaust duct
7
, the scraper
66
has portions
66
a
thereof cut out.
The shaft
63
has, at the bottom end thereof that protrudes into the upper casing
5
a
, a disk
61
fitted thereto with a bolt
62
so as to be rotatable together with the shaft
63
by being interlocked therewith by a key
78
. As shown in
FIG. 7
, the disk
61
has a plurality of classifying blades
13
, made of thin plates, arranged radially.
The classifying blades
13
have their upper ends welded to a ring-shaped member
65
. Thus, the disk
61
, classifying blades
13
, and ring-shaped member
65
together constitute a classifying rotor
79
that rotates integrally with the shaft
63
.
In this flash drying apparatus
25
constructed as described above, as the screw feeder
9
a
rotates, a raw material containing moisture, in the form of clusters, is made to fall onto the crushing rotor
12
that is rotated in the direction D by being driven by the driving motor
10
. The rotation of the crushing rotor
12
produces centrifugal force, by which the raw material is transferred to the outer circumference of the crushing rotor
12
. Then, the raw material collides with the blades
31
and is thereby crushed into a powdery or granular material.
The hot wind generating apparatus
24
(see
FIG. 3
) is driven so that a hot wind is introduced into the flash drying apparatus
25
through the inlet
1
as indicated by arrow B
1
. The hot wind then flows upward outside the dust cover
55
L
1
as indicated by arrows B
2
, and then passes through the gap between the disk
32
and the liner
5
b
as indicated by arrows B
3
. Here, the powdery or granular material crushed by the blades
31
is blown upward by the hot wind while being further dispersed, and thus the powdery or granular material, together with the hot wind, flows upward inside the enclosure
5
as indicated by arrows B
4
.
The classifying blades
13
, by being driven to rotate by the driving motor
8
, produces a vortex air stream. The powdery or granular material having flown upward inside the enclosure
5
and come close to the classifier
6
is subjected to classification by being acted upon simultaneously by the centrifugal force of this vortex air stream and by the centripetal force of the air and water vapor being exhausted. The insufficiently dried powdery or granular material is acted upon more by the centrifugal force, and is therefore thrown out of the classifier
6
so as to be circulated back to the crusher
3
located below.
The sufficiently dried and dispersed powdery or granular material is acted upon more by the centripetal force, and is therefore permitted to enter the classifier
6
through the gaps
6
b
between the classifying blades
13
as indicated by arrows B
5
. Then, the powdery or granular material is exhausted through the exhaust opening
7
a
of the exhaust duct
7
as indicated by arrow B
6
in the form of dry powder or granules of uniform particle size.
In this embodiment, the material feeder
9
protrudes into the enclosure
5
, so that the raw material is fed substantially to the center of the disk
32
. This helps restrain the deposition of the powdery or granular material on the inner wall
5
f
of the enclosure
5
above the blades
31
. It is preferable that the protrusion of the material feeder
9
be such that the end surface
9
c
of the outlet
9
b
thereof, as seen on a plan view, is located on the inside of the blades
31
. However, in cases where the material feeder
9
and the crushing rotor
12
are disposed away from each other, if the material feeder
9
, as seen in a plan view, protrudes at least into the outer circumferential surface of the blades
31
, it is possible to restrain the deposition of the raw material resulting from the raw material in the form of clusters falling along the inner wall of the enclosure
5
below the material feeder
9
.
Using stirrup-shaped hammers
4
(see
FIG. 1
) as in the conventional example permits the raw material to be deposited on the hammers
4
, which prompts the growth of the deposit on the inner wall of the enclosure
5
. However, in this embodiment, the blades
31
have a small thickness t (see FIG.
5
), and thus the amount of raw material that falls onto the blades
31
and is deposited thereon is small. This helps restrain the growth of the deposit on the inner wall
5
f
of the enclosure
5
. As shown in
FIG. 8
, it is also possible to reduce the amount of raw material deposited on the blades
31
by arranging the blades
31
so as to be aligned with center lines
12
a
of the crushing rotor
12
.
Moreover, the upper ends of the blades
31
, which are made of thin plates, are supported by being coupled to the ring-shaped member
33
. This helps prevent the blades
31
from being inclined outward by the centrifugal force produced by the rotation of the crushing rotor
12
. As shown in
FIG. 9
, it is also possible to support the blades
31
by coupling them, at central portions thereof, to the ring-shaped member
33
.
This makes it possible to make the blades
31
higher, and thereby increase the length of time for which the raw material is dispersed and crushed while being exposed to the hot wind. As a result, it is possible to disperse the powdery or granular material more fully than ever immediately after it has passed through the crusher
3
, and thus dry the powdery or granular material more fully. This helps further restrain the deposition of the powdery or granular material on the inner wall of the enclosure
5
above the blades
31
.
Moreover, since the blades
31
are arranged with an inclination (see
FIG. 5
) and are coupled to the ring-shaped member
33
, as the crushing rotor
12
rotates, an air stream passage is formed that leads from the inside to the outside of the blades
31
between the ring-shaped member
33
and the disk
32
as indicated by arrow C
2
. This produces suction force acting toward the inside of the blades
31
as indicated by arrow C
1
, and thereby permits the powdery or granular material to be dried repeatedly. Thus, the powdery or granular material reaches the classifier
6
after being dried fully.
On those surfaces of the blades
31
that face the liner
5
b
, projections
35
are provided, with a predetermined gap secured between each projection
35
and the liner
5
b
. These projections
35
scrape off the powdery or granular material deposited between the blades
31
and the liner
5
b
, and in addition produce a disturbed air stream that helps further disperse the powdery or granular material. As shown in
FIG. 10
, which is a schematic developed view of the crushing rotor
12
, the projections
35
are provided at increasingly lower heights along the direction of rotation (indicated by D) of the crushing rotor
12
.
This makes it possible to scrape off the powdery or granular material over the entire height of the liner
5
b
, and in addition disperse more fully the powdery or granular material thus scraped off. Specifically, for example, the powdery or granular material scraped off by the projection
35
a
is blown upward by the hot wind flowing from below, but then collides with the projection
35
b
that moves as the crushing rotor
12
rotates in the direction D. This limits the upward flow of the powdery or granular material, and thus the powdery or granular material, while being stagnated in this way, is dispersed more fully.
When the raw material being processed does not need to be stagnated, as shown in
FIG. 11
, the projections
35
may be provided at increasingly great heights along the direction of rotation (indicated by D) of the crushing rotor
12
. Alternatively, as shown in
FIG. 12
, it is also possible to provide a plurality of projections
35
on each of the blades
31
so that the projections
35
are arranged at gradually varying heights so as to form a multiple helix, or to provide projections
35
on only part of the blades
31
. It is preferable to design the projections
35
to be fitted in desired positions with bolts or the like, because this permits the projections
35
to be fitted in varying positions according to the type of the raw material actually processed.
FIG. 13
shows the load on the driving motor
10
as observed when the projections
35
are provided as shown in
FIG. 10
, and
FIG. 14
shows the load on the driving motor
10
as observed when the projections
35
are removed.
FIGS. 13 and 14
show the results obtained by using the same raw material, with a gap of
5
mm secured between the liner
5
b
and the blades
31
, a gap of 1.5 mm secured between the liner
5
b
and the projections
35
, the blades
31
and the projections
35
respectively being 100 mm and 15 mm high, and the crushing rotor
12
rotating at a rotation rate of 4,000 rpm.
These diagrams show that, without the projections
35
, the powdery or granular material deposited on the liner
5
b
is scraped off by the blades
31
over the entire height thereof at a time, and thus the load on the driving motor
10
shows large fluctuations. By contrast, with the projections
35
, scraping takes place sequentially in one range of heights after another, and thus the load on the driving motor
10
shows only small fluctuations.
Thus, providing the projections
35
makes it possible to use a driving motor
10
with a lower maximum output and thereby reduce the manufacturing cost of the flash drying apparatus. The size of the projections
35
and the gap between them and the liner
5
b
can best be determined in accordance with the type of the raw material actually processed and other factors, and thus are not limited to any specific dimensions given above.
As shown in
FIG. 7
described earlier, the blades
13
of the classifier
6
are arranged so as to be aligned with center lines
6
a
of the classifier
6
. This helps reduce the probability of the powdery or granular material colliding with the classifying blades
13
when entering the classifier
6
. Moreover, even if the powdery or granular material is deposited on the classifying blades
13
, the deposit readily comes off and does not grow.
In this way, it is possible to prevent clogging of the gaps
6
b
between the classifying blades
13
. It is however to be noted that, in cases where the classifying rotor
79
is driven to rotate at such a rotation rate as is conventionally used, it is easier for the powdery or granular material to enter the classifier
6
. To avoid this, in such cases, it is necessary to provide a greater number of classifying blades
13
than in the conventional example (see FIG.
2
).
Next,
FIG. 15
is a sectional view of the flash drying apparatus
25
of a second embodiment of the invention. Here, such elements as are found also in the first embodiment shown in
FIG. 4
are identified with the same reference numerals. In this embodiment, the classifier
6
is constructed in the same manner as in the conventional example (see FIG.
1
). Accordingly, as shown in
FIG. 2
described earlier, the classifying blades
13
are each arranged with an inclination relative to a center line
6
a
of the classifier
6
.
Moreover, on the disk
32
, a plurality of hammers
82
having a shape as shown in
FIG. 16
, as seen on a plan view, are arranged in a circle, with their tips
82
a
pointing outward. Thus, this portion as a whole constitutes a crushing rotor
12
. Above the crushing rotor
12
, a taper ring
81
having increasingly smaller internal diameters downward is fixed to the inner wall of the liner
5
b
. It is preferable that the internal diameter of the taper ring
81
at the bottom end thereof be smaller than the diameter of the circle described by the inner ends of the hammers
82
. Accordingly, the taper ring
81
is so formed that the inner edge thereof at the bottom end thereof, as seen in a plan view, is located at least inside the outer circumference of the hammers
82
. Moreover, as shown in
FIG. 18
, on the top surface of the deflector ring
40
, a plurality of blades
40
a
are provided, with the blades
40
a
each arranged with an inclination relative to the direction of the circumference of the deflector ring
40
. In other respects, the flash drying apparatus of this embodiment is constructed in the same manner as that of the first embodiment shown in FIG.
4
.
In this flash drying apparatus
25
constructed as described above, the raw material, in the form of clusters, fed in by the screw feeder
9
a
falls off the end surface
9
b
of the material feeder
9
onto the disk
32
. As in the first embodiment, the outlet
9
b
protrudes so that the end surface
9
b
, as seen in a plan view, is located on the inside of the hammers
82
. Thus, the raw material is, while being transferred to the outer circumference of the crushing rotor
12
by centrifugal force, dispersed and partially subjected to heat exchange. This helps restrain the deposition of the powdery or granular material on the inner wall (
5
f
and
5
g
) of the enclosure
5
above the crushing rotor
12
and below the material feeder
9
.
The bottom surface
81
a
of the taper ring
81
is located right above the hammers
82
, and thus there is only a small surface area left on the inner wall of the enclosure
5
for the powdery or granular material to be deposited. This helps further restrain the deposition of the powdery or granular material, and, even if it is deposited, the bottom surface
81
a
restrains the growth of the deposition. Thus, it is possible to prevent an increase in pressure loss and prevent clogging of the enclosure
5
.
The hammers
82
are fixed on the disk
32
with bolts (not shown) so that they can be removed and re-fixed on the bottom surface of the disk
32
as shown in FIG.
17
. In this state, the raw material does not collide with the hammers
82
and thus is not crushed; that is, the raw material is only dispersed by the vortex air stream produced by the rotation of the hammers
82
.
TABLE 1
|
|
Moisture Content
Average Particle
|
Hammer Position
% W.B.
Diameter
|
|
Top Surface
0.09
38
|
Bottom Surface
0.08
63
|
|
Table 1 lists the average particle diameter obtained when calcium carbonate originally having an average particle diameter of 78 μm and containing 20% of moisture was dried until it had a given moisture content with the hammers
82
fitted on the top or bottom surface of the disk
32
. This table shows that, after drying, an average particle diameter of 38 μm was obtained with the hammers
82
fitted on the top surface of the disk
32
as shown in
FIG. 15
, and an average particle diameter of 63 μm was obtained with the hammers
82
fitted on the bottom surface of the disk
32
as shown in FIG.
17
. Thus, with the hammers
82
fitted on the bottom surface, it is possible to obtain a powdery or granular material having a larger particle diameter from the same raw material.
If the powdery or granular material falls off the deflector ring
40
through the gap between the rotor
12
and the liner
5
b
and is deposited on the bottom plate
51
, there is a risk of the powdery or granular material being ignited by the heat of the hot wind. To prevent this, the hot wind supplied from below is made to flow over the deflector ring
40
at a wind velocity of 30 m/s so as to blow the powdery or granular material upward to above the rotor
12
.
Then, as the rotor
12
rotates, it produces a vortex air stream flowing in the direction indicated by arrow E in
FIG. 18
over the deflector ring
40
. This vortex air stream is turned by the blades
40
a
into an air stream flowing toward the outer circumference, and thus the powdery or granular material on the deflector ring
40
is transferred toward the outer circumference and is thereby prevented from falling.
In conventional constructions, a powdery or granular material having a particle diameter as large as 1 mm is prone to fall at a wind velocity of about 30 m/s and, to prevent this, it is necessary to increase the wind velocity, which is inevitably accompanied by an increase in pressure loss. By contrast, in this embodiment, it is possible to keep the powdery or granular material on the deflector ring
40
easily without an increase in pressure loss. The powdery or granular material is then made to collide with the blades
40
a
and is blown upward to above the rotor
12
by the hot wind.
Also in the first embodiment, the reflector ring
40
may be provided with blades
40
a.
Next,
FIG. 19
is a sectional view of the flash drying apparatus
25
of a third embodiment of the invention. Here, such elements as are found also in the first embodiment shown in
FIG. 4
are identified with the same reference numerals. In this embodiment, a hot wind introducer
80
is provided between the liner
5
b
and the lower casing
5
c.
On the inner wall of the upper casing
5
a
, a plurality of protruding pieces
83
having a helical shape are provided so as to face the classifier
6
that is constructed in the same manner as in the first embodiment. On the other hand, the crushing rotor
12
is constructed in the same manner as in the second embodiment, and has hammers
82
. In other respects, the flash drying apparatus of this embodiment is constructed in the same manner as that of the first embodiment.
The hot air introducer
80
is provided with an inlet
1
′ through which it takes in a hot wind supplied from the hot wind generating apparatus
24
(see FIG.
3
). A plan view of the hot air introducer
80
is shown in FIG.
20
. As shown in this figure, the hot air introducer
80
has the inlet
1
′ provided in a decentered position, and has a hot wind passage
80
c
formed around an inner cylinder
80
b
. The bottom surface
80
c
of the hot air passage
80
c
is so formed as to be increasingly high so as to form a helix along the direction F in which the hot wind advances.
In the flash drying apparatus of the first embodiment shown in
FIG. 4
described earlier, the raw material that has fallen down through the gap between the disk
32
and the liner
5
b
is deposited on the bottom plate
51
. The bottom plate
51
becomes hot by being heated by the hot wind introduced through the inlet
1
, and this causes scorching of the raw material deposited on the bottom plate
51
.
By contrast, in this embodiment, where the hot wind passage
80
c
is provided, the raw material that has fallen through the gap between the disk
32
and the liner
5
b
into the hot air introducer
80
can be brought back upward by the hot wind. This helps prevent the deposition of the raw material on the bottom surface
80
a
of the hot wind passage
80
c
and thereby prevent scorching thereof.
A schematic perspective view of the protruding pieces
83
is shown in FIG.
21
. As shown in this figure, the protruding pieces
83
are made of four thin plates that are arranged so as to incline downward relative to the direction of rotation (the direction indicated by D) of the crushing rotor
12
. The raw material, originally in the shape of clusters, that has fallen onto the crushing rotor
12
is crushed and dispersed by the hammers
82
, and is then further dispersed by the vortex air stream produced by the rotation of the crushing rotor
12
.
The force of this vortex air stream is eventually attenuated as a result of the vortex air stream colliding with the bottom surfaces
83
a
of the protruding pieces
83
. This helps reduce the centrifugal force acting upon the powdery or granular material, and thereby reduce the deposition of the powdery or granular material on that portion of the inner wall
5
f
of the enclosure
5
that faces the classifying rotor
79
and simultaneously ease the entry of the powdery or granular material into the classifier
6
disposed substantially at the center of the enclosure
5
.
The force of the vortex air stream can be attenuated even if the protruding. pieces
83
are arranged parallel to center lines of the enclosure
5
. However, arranging the protruding pieces
83
with an inclination and in the form of a helix is preferable, because then the powdery or granular material deposited on those surfaces
83
a
of the protruding pieces
83
with which the vortex air stream collides can more easily be blown off by the hot wind so as to fall downward. There may be provided any number of protruding pieces
83
than specifically given above.
Next,
FIG. 22
is a sectional view of the flash drying apparatus
25
of a fourth embodiment of the invention. Here, such elements as are found also in the first embodiment shown in
FIG. 4
are identified with the same reference numerals. In this embodiment, the material feeder
9
is provided with a pipe
91
, and the crushing rotor
12
has a disk
92
fixed thereto with bolts
95
. This disk
92
has an opening
92
b
into which the pipe
92
is inserted. The disk
92
has a part thereof formed into a flat portion
92
a
, which is held above the disk
32
with washers (not shown) or the like placed in between so as to secure a predetermined gap there.
The material feeder
9
has a heater
9
d
, as shown in
FIG. 23
, for heating the raw material inside the pipe
91
. Inside the heater
9
d
, the pipe
91
is covered with jackets
96
having heating elements (not shown) embedded therein. A raw material in the form of slurry or liquid, i.e. a mixture of a powdery or granular material with water, is stored in a material tank
94
, and is then fed therefrom through the heater
9
d
into the enclosure
5
by a feeding pump
93
.
The classifier
6
provided above the enclosure
5
is constructed in the same manner as in the second embodiment shown in FIG.
15
. The classifier
6
can be removed from the upper casing
5
a
and exchanged with an exhaust duct
7
′. This permits the powdery or granular material to be exhausted without using the classifying rotor
79
. Even in this case, by appropriately setting the internal diameter of the exhaust duct
7
′ and the amount by which it protrudes into the upper casing
5
a
, it is possible to classify the powdery or granular material. In other respects, the flash drying apparatus of this embodiment is constructed in the same manner as in the first embodiment.
In this flash drying apparatus
25
constructed as described above, the raw material, in the form of slurry or liquid, i.e. a mixture of a powdery or granular material with a large amount of water, is fed through the pipe
91
by the feeding pump
93
, and is meanwhile heated by the heating elements so that its water content is evaporated. This increases the flow speed of the raw material inside the pipe
91
and thereby disturbs its flow, which promotes heat transfer and thus promotes evaporation of the water content.
Then, the raw material, now including both water and water vapor, is fed into the enclosure
5
, and flows downward through the pipe
91
so as to be fed through the opening
92
b
onto the disk
32
. The raw material, by its own surface tension, spreads and fills the gap between the disk
92
and the disk
32
, and is thereby dispersed toward the outer circumference of the disk
32
over the entire surface thereof.
Thereafter, the raw material is dispersed by the rotating blades
31
into fine droplets, and is subjected to heat exchange with the hot wind. Moreover, as in the first embodiment, the raw material is dried repeatedly by the suction force acting as indicated by arrow C
1
. This makes it possible to dry fully even a raw material in the form of slurry or liquid. Although with lower drying efficiency, it is also possible to feed the raw material unheated, i.e. without providing the heater
9
d
in the material feeder
9
, into the enclosure by driving the feeding pump
93
.
As described in detail heretofore in connection with some embodiments, according to the present invention, the blades are made of thin plates, and are supported by being coupled to the ring-shaped member. This helps reduce the amount of raw material that falls onto the blades and is deposited thereon, and thereby restrain the growth of the deposit on the inner wall of the enclosure. Moreover, an air stream passage is formed that permits the air above the crusher to flow from the inside to the outside through the gaps between the blades. This permits the powdery or granular material to be dried repeatedly, and thus permits the raw material to be dried more fully.
Moreover, the ring-shaped member prevents the blades from being inclined by centrifugal force, and thus permits the blades to be made higher. This helps increase the length of time for which the raw material is crushed while being exposed to the hot wind. Thus, it is possible to disperse the powdery or granular material more fully than ever immediately after the crushing thereof, and thereby further restrain the deposition of the powdery or granular material on the inner wall of the enclosure above the blades.
Moreover, the projections formed on the outer-circumferential-end surfaces of the blades make it possible to scrape off the powdery or granular material deposited in the gap between the blades and the enclosure. In addition, it is possible to reduce the fluctuation of the load on the driving motor that drives the blades to rotate. This makes it possible to use a driving motor with a comparatively low maximum output and thereby reduce the manufacturing cost of the flash drying apparatus.
Moreover, the projections are provided at heights varying along the circumference, and this makes it possible to scrape off the powdery or granular material over the entire height of the enclosure. In addition, the powdery or granular material thus scraped off by the projections is blown upward by the hot wind supplied from below, and, in accordance with the type of the raw material, can be made to collide with the projections that move as the blades rotate. This helps limit the upward flow of the powdery or granular material and thereby stagnate it so as to achieve fuller dispersion thereof.
Moreover, the material feeder protrudes into the enclosure so as to permit the raw material in the form of clusters to fall onto the area on the inside of the blades. This permits the raw material to be dispersed and crushed while being transferred toward the outer circumference, and thus helps restrain the deposition of the powdery or granular material on the inner surface of the enclosure above the blades.
Moreover, the material feeder protrudes into the enclosure so as to permit the raw material in the form of clusters to fall onto the area inside the outer circumferential surface of the crushing member. This permits the raw material to be dispersed and crushed while being transferred toward the outer circumference, and thus helps restrain the deposition of the raw material that falls along the inner wall of the enclosure above the crushing member.
Moreover, the taper ring provided on the inner wall of the enclosure above the crusher so as to have increasingly smaller internal diameters downward permits the vertex air stream produced by the rotation of the crushing member to collide with the bottom surface of the taper ring and thus serves to attenuate the force of the vortex air stream. This helps reduce the centrifugal force acting upon the powdery or granular material, and thereby reduce the deposition of the powdery or granular material on that portion of the inner wall of the enclosure that faces the classifying rotor and simultaneously ease the entry of the powdery or granular material into the classifier disposed substantially at the center of the enclosure. In addition, the powdery or granular material deposited on those surfaces of the protruding pieces with which the vortex air stream collides can more easily be blown off by the hot wind so as to fall downward.
Moreover, the disk disposed over the plate-shaped member with a gap secured in between permits the raw material in the form of slurry or liquid to flow through a central portion of the disk into the gap. As a result, the raw material, by its own surface tension, spreads and fills the gap between the disk and the plate-shaped member, and is thereby dispersed toward the outer circumference of the plate-shaped member over the entire surface thereof. This makes it possible to dry fully even a raw material in the form of slurry or liquid.
The scraper that rotates integrally with the classifying blades makes it possible to scrape off the powdery or granular material deposited on the inner wall of the exhauster and thereby prevent clogging of the exhauster.
Moreover, the taper ring is so disposed that its bottom surface is located right above the crushing member. Thus, there is only a small surface area left on the inner wall of the enclosure for the powdery or granular material to be deposited. This helps restrain the deposition of the powdery or granular material above the crushing member, and, even if it is deposited, the bottom surface restrains the growth of the deposition. Thus, it is possible to prevent an increase in pressure loss and prevent clogging of the enclosure.
Moreover, the hot wind passage having the shape of a helix permits the raw material that has fallen through the gap between the enclosure and the plate-shaped member into the hot wind passage to be brought back upward by the hot wind. This helps prevent the deposition of the raw material in the hot wind passage and thereby prevent scorching of the raw material.
The air stream generating member disposed on the bottom surface of the plate-shaped member prevents the raw material from colliding with the air stream generating member and thus prevents the raw material from being crushed. Thus, the raw material is only dispersed by the vortex air stream produced by the rotation of the air stream generating member. This makes it possible to obtain, from the raw material supplied, dry powder or granules having a comparatively large particle diameter as desired.
Claims
- 1. A flash drying apparatus for drying a material containing moisture, comprising:a cylindrical enclosure arranged vertically; a crusher disposed in a lower portion of the enclosure for crushing the raw material into a powdery or granular material; a material feeder for feeding the raw material to the crusher by letting the raw material fall onto the crusher; a hot wind feeder for feeding a hot wind to the powdery or granular material from under the crusher; a classifier for classifying the powdery or granular material blown upward inside the enclosure by the hot wind; and an exhauster for exhausting the classified powdery or granular material through an upper portion of the enclosure, wherein the crusher includes a rotating plate-shaped member, a plurality of blades made of thin plates and arranged radially on the plate-shaped member, and a ring-shaped member provided substantially parallel to the plate-shaped member for coupling the blades.
- 2. A flash drying apparatus as claimed in claim 1,wherein the blades have projections formed at end surfaces thereof facing an inner wall of the enclosure.
- 3. A flash drying apparatus as claimed in claim 2,wherein more than one of the blades have projections formed at end surfaces thereof facing an inner wall of the enclosure, the projections being formed at heights gradually varying along a circumference.
- 4. A flash drying apparatus as claimed in claim 1,wherein the material feeder has a screw feeder that moves forward the raw material by being rotated, and the material feeder protrudes inward from an inner wall of the enclosure so that an outlet of the material feeder is located inside the blades.
- 5. A flash drying apparatus as claimed in claim 1,wherein a deflector ring is provided below a gap between the plate-shaped member and the enclosure so as to face the plate-shaped member, and a plurality of anti-falling blades for preventing the powdery or granular material from falling off through the gap are arranged radially on the deflector ring, with each anti-falling blade given a predetermined inclination relative to a direction of a radius.
- 6. A flash drying apparatus for drying a material containing moisture, comprising:a cylindrical enclosure arranged vertically; a crusher, including a rotating plate-shaped member and a crushing member provided integrally therewith, for crushing the raw material into a powdery or granular material, the crusher being disposed in a lower portion of the enclosure; a material feeder for feeding the raw material to the crusher by letting the raw material fall onto the crusher; a hot wind feeder for feeding a hot wind to the powdery or granular material from under the crusher; a classifier for classifying the powdery or granular material blown upward inside the enclosure by the hot wind; a protruding piece arranged on a portion of an inner wall of the cylindrical enclosure facing the classifier so as to incline downward along a rotation direction of the plate-shaped member; and an exhauster for exhausting the classified powdery or granular material through an upper portion of enclosure.
- 7. A flash drying apparatus as claimed in claim 6, wherein the material feeder has a disk disposed parallel to the plate-shaped member with a slight gap secured in between, and the raw material is, in a form of slurry or liquid, introduced through a pipe-shaped member so as to flow onto a central portion of the disk and fed into the gap.
- 8. A flash drying apparatus as claimed in claim 6, wherein a taper ring having increasingly smaller internal diameters downward is provided between the crushing member and the material feeder.
- 9. A flash drying apparatus for drying a material containing moisture, comprising:a cylindrical enclosure arranged vertically; a crusher, including a rotating plate-shaped member and a crushing member provided integrally therewith, for crushing the raw material into a powdery or granular material, the crusher being disposed in a lower portion of the enclosure; a material feeder for feeding the raw material to the crusher by letting the raw material fall onto the crusher; a hot wind feeder for feeding a hot wind to the powdery or granular material from under the crusher; a classifier for classifying the powdery or granular material blown upward inside the enclosure by the hot wind; and an exhauster for exhausting the classified powdery or granular material through an upper portion of the enclosure, wherein, in a portion of an inner wall of the enclosure above the crusher, a taper means is provided having increasingly smaller internal diameters downward.
- 10. A flash drying apparatus as claimed in claimed in claim 9, wherein the material feeder has a disk disposed parallel to the plate-shaped member with a slight gap secured in between, and the raw material is, in a form of slurry or liquid, introduced through a pipe-shaped member so as to flow onto a central portion of the disk and fed into the gap.
- 11. A flash drying apparatus as claimed in claim 9, wherein a taper ring having increasingly smaller internal diameters downward is provided between the crushing member and the material feeder.
- 12. A flash drying apparatus as claimed in claim 9, wherein the hot wind feeder has a helical hot wind passage through which the hot wind introduced through an inlet provided in a decentered position flows upward in a form of a vortex air stream.
- 13. A flash drying apparatus for drying a material containing moisture, comprising:a vertical, cylindrical enclosure; an air stream generator, composed of a rotating plate-shaped member and an air stream generating member provided so as to protrude downward from a bottom surface of the plate-shaped member and not upward above the plate-shaped member, for generating a vortex air stream, the air stream generator being disposed in a lower portion of the enclosure; a material feeder for feeding a raw material onto the plate-shaped member; a hot wind feeder for feeding a hot wind into a gap between the plate-shaped member and an inner wall of the enclosure from below; a classifier for classifying a powdery or granular material blown upward inside the enclosure by the hot wind; and an exhauster for exhausting the classified powdery or granular material through an upper portion of enclosure.
Priority Claims (1)
Number |
Date |
Country |
Kind |
11-215309 |
Jul 1999 |
JP |
|
US Referenced Citations (19)
Foreign Referenced Citations (5)
Number |
Date |
Country |
1931 272 |
Dec 1970 |
DE |
0 410 043 |
Jan 1991 |
EP |
81 449 |
Jul 1979 |
LU |
WO 9719307 |
May 1997 |
WO |
WO 9927316 |
Jun 1999 |
WO |