Note: Descriptions are shown in the official language in which they were submitted.
3~
APPARATUS FOR SEPARATING FLUIDIZING MEDIUM
~ND INCOMBUSTIBLE RESIDUE
Field of Invention:
The present invention relates to a thermal reactor of
the fluidized bed type and more particularly to a separator
for separating non-combustlble residue in such thermal reactor
of the fluidized bed type.
Back~round of Invention:
A thermal reactor of the fluidized bed type has been
utilized for incinerating and/or pyrolyzing municipal refuse
for disposal purposes because such reactox exhibits efficient
incineration and the amount of residue derived from the
incineration of the refuse is kept small.
As an improved type of incinerator of the fluidized
bed type, a thermal reactor has been proposed wherein fluid-
izing medium is subjected to different mass flows at the center
of the reactor and at the sides of the reactor so that side
fluidized beds are formed adjacent the side walls of the
reactor and a central fluidized bed, the fluidizing condition
of which is relatively weak compared with that of the side
fluidizing beds, is formed at the center, whereby the central
bed tends to descend and the side beds tend generally to
move upwardly. Within the body of the reactor, there is
substantially no mechanical obstruction to the movements of
these beds whereby a circulation of the medi~ is such a
manner that at the central bed, it moves downwardly and, at
the sides of the beds, it moves upwardly, while at the bottom
area and the top area, the medium at the cent:ral and side
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beds moves laterally towards the other bedO Such reactor
is disclosed, for example, in U.S. Patent Nos. 4,419~330
and 4,452,155.
The reactor such as disclosed in the U.S. Patents
referred to above is satisfactor~ in its operation and is
appreciated particularly because of the fact that such pre-
treatment as shredding or pulverization, etc. of the object
to be incinerated is substantially unnecessary. Before the
reactor of the type referred to above became available, it
was required to reduce the size of the constituents of the
refuse before charging the same into the fluidizing bed since
variation of the size affects the mode of the fluidizing
condition. Therefore, a major part of the proklems experienced
in the fluidized bed had previously existed in the shredder
or crusher which had to be disposed upstream of the fluidizing
bed. Therefore, the reactor disclosed in said U.S. Patents
disclosed said U.S. Patents dissolved the problems in the
previous fluidizing bed in this regard~
However, the advantage of such reactor leads to another
problem in that the incombustible residue some times involves
large items. The operation of the fluidizing bed is generally
required to discharge incombustible residue together with
some fluidizing medium or sand and the medium discharged
with the incombustible residue is processed such as to be
separated from the residue so that it can b~ re-utilized in
the bed. Thus, if the size of the incombustible residue
becomes large, such residue may cause trouble in the separa-
tion of the medium, for instance, leading to damage of a
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separator such as a sieve and inconvenience in recovering
the fluidi~ing medium. In case of the conventional reactor
of the fluidized bed type which involves pre-shredding or
crushing of the refuse, such trouble was rare since the
residue was small in si~e as the size of the constituents
was reduced by pre-treatment before being charged into the
reactor and thus such drawbacks as damaging the sieve were
not normally caused by such small sized residue.
Accordingly, it has been desired to have an efficient
separating means suitable for the ~luidizing reactor of the
type which does not require pre-shredding or crushing of the
object to be incinerated.
Summary of Invention:
It is, there~ore, an object of the prssent invention
to provide a separating device for separating the incombusti-
ble residue of relatively large size from the mixture of the
fluidizing medium and the incombustible residue discharged
from the fluidizing bed.
The above object is accomplished by the present inven
tion. A novel separator is provided according to the present
invention wherein a screw conveyor is rotatably disposed
within a casing comprising a conveyor housing and a discharge
housing and the mixture of fluidizing medium and the incom-
bustible residue is received within the conveyor housing.
At he portion of the screw conveyor shaft which is within
the discharge housing, a cylindrical sieve is coaxially
connected to the screw conveyor so that the mixture advanced
by the screw conveyor is received into the`cylindrical sieve
` f
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and the fluidizing medium tGgethex with small sized incombus-
tible residue may pass the cylindrical wall of the sieve t the
relatively large sized inco~bustible residue being discharged
at the end of the sieve. Thus the fluidizing medium with
small incomhustible residue and the residue of relatively
large size are separated.
Further details and advantages of the present invention
will be described hereinafter referring to the accompanying
drawings, a brief explanation of which is-summarized below.
Brief Explanation of Draw ngs:
Fig. 1 schematically illustrates a system including a
reactor and a separator according to the present invention;
Fig. 2 is an enlarged sectional view of the separator
shown in Fig. l; and
Fig. 3 is an enlarged view of the portion III shown
in Fig. 2.
Detailed Descripti.on of Preferred Embodiments:
Now the present invention will be explained referring
to the accompanying drawings.
Referring to Fig. 1, there is shown an incineration
plant for incinerating municipal refuse.
A reactor 10 is illustrated as comprising a wall
structure or furnace housing 20 which defines a furnace space
or chamber therein. The furnace housing 20 is generall~
upstandi~g and its horizontal cross section is preferably
: rectangular. At the lower part of the housing, a diffusion
means 30 is disposed which ~omprises a chevron shaped or
roof-}.ike top portion 31 and gas chambers 32, 33 and 34
.,i
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disposed below the top portion 31. Gas chambers 32, 33 and
~4 are arranged to receive pressurized gas from a blower 35,
respectively so as to fluidize the medium or sand on the top
portion 31 by upwardly directing the gas supplied through
the injecking perforations or gaps on the top portion 31.
The side gas chambers 32 and 34 are substantially symmetri-
cally arranged with respect to the vertical center line of
the housing 20. The mass flow of the fluidizing gas or air
(Kg/m2-sec.) blown up through the side gas chambers 32 and
34 is arranged to be sufficient to generate a general movement
of the fluidized bed in the upward direction over the top
portion 31 but the mass flow of the gas blown up through the
center gas chamber 33 is less than that through the side
chambers 32 and 34. For example, the mass flow of the fluid-
izing gas through the side chambers 32 and 34 is 4 - 20 Gmf,
or preferably 6 - 12 Gmf, while the mass flow of the fluidiz-
ing gas blown up through the center gas chamber 33 is 0.5 -
3 Gmf, or preferably 1 - 2.5 Gmf, where 1 Gmf is an indication
of th~ mass flow of the fluidlzing gas or air for minimum
fluidization of a bed, i.e. just past the incipient condition.
The number of gas chambers is optionally selected to
be three or more and the mass flow of the fluîdizing gas
passing through these chambers is arranged to be larger the
nearer chambers to the sides of the housing 20.
In the embodiment shown in Fig~ 1 whe~e the number
of the gas chambers is selected to be three, inclined walls
21 are provided just above the side chambers 32 and 34 as
deflecting means for de~lecting the fluidizing gas towards
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the center of the reactor 10. The upper sides of the respec-
tive inclined walls 21 are also opposi~ely inclined as inclined
walls 22 so that the fluidized medium will not be collected
thereon.
The inclination of the top portion 31 is preferably
5~ - 15~ relative to the horizontal and the inclination of
the walls 21 is preferably 10 - 60 relative to the horizon-
tal. The surface of the walls 21 need not necess~rily be
planar; it may also be concave or convex provided that it
effectively deflects the upwardly directed flow to the center
of the reactor 10.
A material charging port 23 is provided in a ceiling
portion 24 of the reactor 10, and in a position above the
center gas chamber 33 and the port 23 is communicated with
an outlet port 25 of a feeder 26 which is arranged to feed
the refuse to the reactor 10.
As illustrated in Fig. 1, there is no separating means
or chute in the inner space of the reactor 10 between the
ceiling 24 and the diffusion means 30, and only a free board
20 35 is defined by side walls 27 of the housing 20, ceiling 24
and the upper inclined walls 22. Of course, the lower border
of the free board 35 is not clearly defined relative to the
bed portion. The inclined walls may be constructed by
arranging pipes through which the fluidizing gas or air may
be passed so as to be pre-heated before being blown up through
the chambers 32, 33 and 34. The gas passing thxough such
pipes may also serve to cool the walls 21.
Due to the diference with r~spect to the mass flo~
above the diffusion means 30 depending on whether the portion
is adjacent the side walls or the center, the fluidized medium
or sand near the side walls or above the chambers 32 and 3~
r-eceives the strong upwardly injected flow of the gas or air
and is fluidized.
On the other hand, at above the center gas chamber 33,
the upwardly directed gas flow from the chamber is relatively
weak compared to the gas flows blown upwardly through the side
chambers 32 and 34. Thus, while there will also be creating
the fluidization of the medium above the center gas chamber
33, the medium above the center gas chamber tends to descend
relative to the upwardly moving medium near the sides of the
housing 20 and to move laterally at the bottom portion of
the center bed towards the sides near the diffusion means 30.
Also the presence of the inclined walls 21 serves to deflect
the upwardly directed flow of the gas and sand toward the
portion of the bed which has the tendency to descend above
the center gas chamber 33.
Accordingly, there will be produced whirling flows
40 of the fluidizing bed as indicated in Fig. 1~ Thus, the
municipal waste charged through the feeder 26 and the port
23 is trapped in the whirling fluidized beds 40 and is moved
downwardly w~th the descending portion of the fluidizing
beds 40. The combustible constituents of the refuse are
incinerated during the movement with the 1uidiæing medium
: and, eventually, substantially completely incinerated, except
for the incombusti~le residue. The gas generated during the
incineration is discharged thro~gh an ~xhaust opening 29.
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The incombus~ible residue descends on the top portion
31 of the diffusing means 30 and is discharged outwardly
from the reactor 10 through the inclined top portion 31 and
discharge chute passages 28 towards a separator 50. The
discharged residue is naturally accompanied by the fluidizing
medium and such medium is to be recoverecl for re-charging into
the reactor. Heretofore, such separation had been performed
by a mechanical sieve or the like such as a vibrator sieve.
However, the large slze constituents of the residue may be
likely to damage such sieve, as discussed in the foregoing.
Accordingly, the separator 50 is arranged to comprise,
as shown in Fig. 2, a screw conveyor 51 including a screw
shaft 51a and a screw blade 51b which are disposed within
a conveyor housing 55~ The screw conveyor 51 is rotatably
supported by bearings 52a and 52b within the conveyor housing
55 and driven by a motor 53 through a chain 54 or the like.
The walls of the chute passages 28, the housing 55 and the
shaft 51a are preferably formed as a hollow wall in which
cooling medium such as water in circulated. The mixture
of the fluidizing medium and the incombustible residue is
advanced by the rotation of the screw conveyor 51 wi~hin
the housing 55 toward a discharge housing 56 disposed at
the end of ~he conveyor housing 55. The shaft 51a extends
through the discharge housing 56 and, at the extreme end of
~5 the shaft 51a, is supported by the bearing 52b at the outside
o~ the housing 56. Within the housing 56, the screw blade
51b is omitted on the shaft and a cylindrical sieve 57 is
attached to the shaft 51a so as to be rotatable therewith.
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The cylindrical sieve is preferably made of a sheet metal
with punched out perforations so as to be stiff. An intake
opening 57a of the cylindrical siPve 57 is arranged to face
the end of the screw blades 51b so as to introduce the mix
ture advanced by the screw conveyor 51 into the sieve 57.
The axial length of the sieve is arranged to be shorter than
that of the discharge housing 56 and a discharge opening 57b
of the sieve 57 is adapted to discharge the incombustible
residue which does not pass through the perforations or
meshes of the cylindrical sieve 57. The discharge of such
incombustible residue from the discharge opening 57b is
assisted by provision of blades 57c disposed on the inner
surface of the sieve 57. The fluidizing medium or sand is
naturally discharged through the perforations or the meshes
of the sieve 57 during the rotation thereof and falls down
into a shute 58 disposed below the sieve 57.
Also the constituents of that portion of the incom-
bustible residue which is small enough to pass through the
perforations of the sieve 57, passes through the latter into
the chute 58. The constituents of the incombustible residue
which are of relatively large size compared to the perfora-
tions of the sieve 57 are discharged from the discharge
opening 57b into another chute 59. The chutes 58 and S9 are
suitably separated by a dividing wall 56a.
Since the sand discharged through the chute passages
are generally hot and further, particularly at the portion
of the screw conveyor 51 opposite to the discharge housing
56, is subjected to the gas presgure of the fluidizing bed,
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conventional gland packings are easily degraded. Thus, in
the separator 50 of this invention, a special packins means
is provided.
An enlarged view of the portion III circled ln Fig. 2
is shown in Fig. 3. Within a bearing frclme 70, a sleeve 71
is firmly secured to the shaft 51a. On an inner wall 72 of
the bearing frame 70, a stuffing box 73 is provided so as
to receive therein a plurality of annular gland packings 76
around the sleeve 71. A gland 77 is disposed around the
sleeve 71 with a slight gap therebetween and is arranged
to be axially slidable along the sleeve 71. Ad~acent the
gland 77, a flange member 78 is disposed as axially slidable
on the sleeve 71. Another flange member 79 is disposed
around the sleeve 71. Plural studs 80 are mounted on the
flange member 78 in parallel relationship with the shaft 51a
and extend toward the flange member 79 so as to loosely pass
holes provided on the flange member 79. Around the studs 80,
compression springs 81 are disposed so as to urge the flange
member 78 and the gland 77 against the gland packlngs 74,
2Q 75 and 76 whereby gland packings are compressed into the
stuffing hox 73. Further, plural bolts 82 are disposed
between the flange members 78 and 79 and the screw portions
of the bolts are screwed in the flange memher 79 so as to
adjust the compxession of the gland packings 74, 75 and 76.
At the inner cylindrical sur~ace of the flange member 78,
a sealing means such as an "O~-ring 83 is disposed ~etween
the sleeve 71 and ~he flange member 78 so as to provide air
sealing thereat.
.
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~q~
With the arrangement above, when the screw conveyor
51 rotates, the sleeve 71, flange members 78 and 79, and
gland 77 will rotate. The gland 77 rotates while being
compressed against the gland packing 76. Accordingly, the
axial end surface of the yland 77 makes rotation relative
to the stationarily held gland packing 76. Because the
clearance between the sleeve 71 and the gland 77 is small
and there is no relative rotation therebetween, should the
sand in the conveyor housing 55 escape through the gland
lQ packings 74, 75 and 76, there is no tendPncy for such sand
to be caused to escape further and the sand in the gap will
merely rotate together with the sleeve 71. Further, sealing
means such as the "O"-ring 83 prevents the gas from escaping
whereby the sand is satisfactorily sealed.
As illustrated in Fig. 2, the screw blade 51b is
arranged to have a larger pitch near the discharge end and
a smaller pitch at the portion opposite the discharge. It
is noted that this arrangement facilitates the advancement
of the mixture of the sand and incombustible residue within
the conveyor housing 55.
The discharged sand accompanying the incombustible
residue of relatively small size is directed in the direction
of the arr,ow Al in Fig. 1 from the chute 58 towards a recep-
tacle 61 of a lifter 60. Such mixture of the recovered sand
and the small incombustible residue received at the receptacle
is lifted to an upper discharge 62 o~ the lifter 60 where
such mixture is charged to a re~ining sieve 63 in the direc-
tion of the arroW A2.
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The refining sieve 63 separates the sand and the
incombustible residue and forwards such sand to a dist.ributor
64 along the route indicated by the arrow Bl. The distributor
64 is suitably operated to forward, along the route indicated
by the arrow B2, a suitable amount of the sand to a sand
feeder 65 which is adapted to supplement the sand in the
reactor 10. Depending on the operating conditions of the
reactor, a part or whole of the sand forwarded to the dis-
tributor 64 is directed, along the route shown by the arrow
s3, to a sand reservoir 66 in which fresh sand or recovered
sand is stocked until the sand in the reactor 10 is to be
supplemented. When it is determined that sand is to be
supplied, a suitable arnount of the sand is delivered to the
receptacle 61 along the route indicated by the arrow B4 and
it is fed to the sand feeder 65 throuyh the lifter 60, the
upper discharge 62, the sieve 63 and the distributor 64.
The incombustible residue passed through the chute
59 is forwarded along the route shown by the arrow Cl to
a discharge conveyor 67. Also, the incombustible residue
removed at the sieve 63 is fed along the route indicated by
the arrow C~ to the discharge conveyor 67. The discharge
conveyor 67 delivers, via the route shown by the arrow C3,
: the received incombustible residue to an incombustible residue
reservoir 6~ which forwards the residue to a delivery means
such as a truck 69 for further disposal.
As explained in the foregoing, the reactor of the
vertical type, having a generally rectangular shape in its
horizontal cross section and in which the ~luidizing medium
3~
thereof is subjected to different mass flows at the center and
opposite sides within ~ bed chamber which is substantially
free from any mechanical obstruction so that whirling flows
of the medium are generated, is particularly advantageous if
the separating apparatus according to the present invention
is associated with it because the advantage of not needing
to undertake pre shredding or crushing of the object to be
incinerated is greatly enhanced with such separator.
The present invention has been explained in detail
referring to the par-ticular embodiment thereof. However,
the present invention is not limited to what is explained
and it may ~e changed or modified by those skilled in the
art within the sprit and scope of the present invention as
defined by the Claims appended hereto.
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