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Патент USA US3031779

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May 1, 1962
J. WILSON
3,031,769
FLUID BEDS
Filed sept. 25, 1959
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between the pairs of deílectors so as to maintain the par
ticles in a substantially uniform state of turbulence
3,031,769
FLUID BEDS
John Wilson, 208 Bramhall Lane S., Bramhall, England
Filed Sept. 23, 1959, Ser. No. 841,835
Claims priority, application Great Britain Sept. 26, 1958
3,031,769
Patented May 1, 1952
throughout the depth of the bed, at least in the central
part of the bed.
The removal of gas from the central part of the bed
5
»at different levels in the bed tends to prevent the forma
tion of bubbles at each of these levels, while the means
for introducing additional gas at least partly serves to
, This invention relates to fluid beds.
replace the gas so withdrawn from the central part of
The use of fluid beds has become widespread over
recent years particularly in the oil refining and chemical 10 the bed and maintain the ñuidisation. In effect, the
invention is equivalent to the superimposition of several
industries because of their many advantages to such
industries. For example, a Huid bed provides a very
shallow, stable beds.
In one form of the invention the means for admitting
uniform temperature by reason of very rapid heat trans
further gas comprises perforated or porous tubes extend
fer .and the large heat capacity of the solids employed,
-
7 Claims. (Cl. 34-57)
ing horizontally through the bed in the vicinity of the
andthe particles provide very extended surfaces on which
lower edges of the deflectors. With such an arrangement
the deflectors may all be of substantially the same size
When a gas lat very low velocity is admitted through,
and arranged uniformly in pairs one «above the other.
vfor example, a porous plate to the bottom of a con
In another form of the invention the admission of
tainer holding a bed consisting of a large quantity of small
discrete solid particles, the gas percolates upwards through 20 additional gas is achieved by the disposition of the de
rl‘lectors, whereby the additional gas which is admitted to
the bed without Áagitating the individual particles. When
the central part of the bed between the lower edges of
the velocity of the gas is increased suñiciently, the pres
ia pair of deflectors reaches this central part by inward
sure -drop across the bed becomes equal to or slightly in
diffusion from the part of the bed outside the next lower
excess of the weight of the solids present. At this point
the solids are suspended in the 'gas -and the bed is fluid 25 pair of deñectors. With this form of the invention it
has been found that the deflectors should get progressively
ised. A properly ñuidised bed is stable in the sense that
narrower towards the top of the bed in order that the
all the solid particles are in an approximately uniform
desired results can be obtained.
state of turbulence, and the density of the bed remains
In the case of a bed intended for heat exchange pur
approximately uniform throughout. It has been found,
however, that with the conventional fluid bed this condi 30 poses, heating or cooling surfaces may be provided in
tion exists» only when the bed is relatively shallow. As
the part of the bed outside the deñcctors.
The invention may be performed in various ways and
the depth of the bed increases la form of instability oc
two embodiments will now be described by way of ex
curs, in that the fluidising gas tends to form bubble-like
ample with reference to the accompanying drawings, in
cavities which rise upwardly through the bed, expanding
«as they rise. These bubbles occur predominantly in the 35 which:
FIGURE 1 is a transverse vertical section through one
central parts of the bed. In other parts of the bed, on
reactions may occur.
the other hand, the particles «tend to settle into relatively
immobile and closely-packed masses. This phenomenon
embodiment; and
FIGURE 2 is a transverse vertical section through a
is commonly referred to as a “boiling bed” and is recog
second embodiment.
It will be appreciated that the drawings are diagram
nised as giving much less satisfactory performance than 40
matic, the object being to illustrate the principles under
a stable bed, but since deep beds are desirable for many
lying the invention rather than the particular details of
design and construction.
Referring to FIGURE l, the fluid bed comprises a deep
purposes the disadvantages of the “boiling” phenomenon
have had to be tolerated. For example, “boiling" beds
cannot be used for treating materials in the form of
delicate webs, because owing to the excessive and irregu 45 vessel 10 having imperforate side walls 11 and an irn
perforate base 12. Spaced a short distance aboverthe
base 12. is a ñoor 13 which is air-permeable, being corr
the webs to draw them through the bed. Moreover, the
thermal efficiency' of -a “boiling” bed is substantially less
structed, for instance, of porous tiles. To the space
14 between the base 12 and the floor 13, air lis admitted
than that of a stable bed, possibly because of the lower
particle ydensity in the bubbles and the reduced move 50 from a compressor 15 at a pressure of, for instance,
2 lbs. per square inch gauge.
ment of particles in the more static parts of the bed.
lar turbulence considerable tension has to be exerted on
Resting on the floor 13 is a layer of sand which, when
It is an object of the present invention to provide a
’ deep> ñuidised bed which will remain effectively stable
throughout its depth.
A fluidised bed according to the present invention com
prises a vessel containing small discrete solid particles
and having means for admitting gas at or near the bottom
the bed is fluidísed, is maintained in turbulent suspension
55
in the air ñowing upwardly through the vessel. The sand
is carried up to the level 16.
j
Extending for the full length of the vessel are ñve pairs
of inclined dellectors 17. These detlectors are uniformly
spaced one above the other on each side of a longitudinal
of the vessel to ñuidise the particles, and outwardly in
clined deñectors arranged in pairs, one pair above an 60 centre line 18. Adjacent the lower edges of each de
flector 17, except the lowest pair, are horizontal porous
` other, lfor removing upwardly-flowing gas from the cen
tubes 19 through which compressed air is admitted either
tral- part of the bed at different levels and deñecting this
from the air box 14 or from the compressor- 15 through
gas towards outer parts of the bed, these deflectors or
pipes or passages which are not shown.
l y v .
other means being arranged to introduce additional gas
8,031,769
3
As the air rises up through the bed, it carries with it
particles in suspension and in a high state of turbulence,
but as the air continues to rise it would tend to form
bubbles, particularly in the vicinity of the centre line 18.
The `deflectors 17 `and the tubes 19 counteract this
4
llectors of the pair of sufiicient gas to fluidise the par
ticles between the de'ñectofrs of -the pair.
2. A ñuidised bed comprising a vessel, small discrete
solid particles contained in said vessel, gas admission
means adjacent the bottom of said vessel for producing
tendency. By disposing the deflectors as'indicated, some
an upward ñow of gas through said vessel and maintain
of the air rising between each pair of deñectors can
ing said particles in a liuidized state, and a plurality of
escape through the gaps 20 between the upper edges of
pair of boards in said vessel and each completely em
the lower pair of deñectors and the lower edges of the
bedded in said particles beneath the upper level of said
pair immediately above. This removal of air tends to l0 particles in their lluidized state, each said board having
prevent the formation of bubbles. However, if the sup
a longitudinal axis, said longitudinal axes being parallel
ply of `air in the centre of the bed is not to be seriously
«and horizontal, said pairs being arranged one above an
depleted,` ladditional air must be introduced to make up
other and the boards of each' pair being outwardly in
for the air so withdrawn. This air is introduced through
clined to one another to deñect upwardly tlowing gas
the porous tubes 19. IThe resulting elïect is as if the
outwardly, said boards having their lower edges parallel
deep bed illustrated consists of several superimposed
shallow,»stable beds.
In‘view of the turbulence of the particles there isa
considerable «migration of particles towards and away
yand at the same height above the bottom of s-aid vessel
and spaced apart by a `distance to permit the entry be
tween the deilectors of the pair of suñ’icient gas to prop
whatever material isibeing introduced into the bed along
of said particles in their ñuidized state, said pairs being
erly iluidise the particles between the delico-tors ofthe pair.
from the centre line 18, and these particles thus fre 20
3. A fluidised bed comprising «a'vessel, small discrete
quently come into contact with, or into close relation
solid particles contained in said vessel, gas admission
ship with, heat exchanger tubes «21 disposed in the outer
means adjacent thefbottom of said vessel for producing
parts of the bed. At least fa substantial proportion of
ari-‘upward ilow of gas through «s-aid- vessel and maintain
thepar'ticles which receive heat from these tubes or impart
ing said Vparticles in la iluidized state, andv a plurality of
»heat to them will travel to the central part of the bed 25 pairs of parallel defiectors in said vessel and each com
where they will give up heat to or take up heat from
pletely embedded in said particles beneath the upper »level
the centre line 1‘8.
In thefembodiment shown in-FIGURE 2. parts which
-arranged oneabove another, each deliector having a
lower horizontal edge and an-upper horizontal edge, each
are equivalent to the corresponding parts in FIGURE 1 30 pair being arranged with the lower edges ofthe de
are given the same reference numerals with the suilix l.
»In this embodiment there are three sets of deñectors
22, 23 and 2‘4.
Some of the lair which has passed up between the lower
flectors of the air at the same height’ above the bottom ’
of said vessel and closer together than the Vupper edges
of the deñectors of the pair, said lower edges» of the
defleotors of the pair being spaced apart to permit the
pair' of -deñectors`22, having entered through the gap 35 entry between the deñectors of the pair of sufficient gas
25 "between the lower edges of these deñectors, leaves
to properly iluidise the> particles between the deñectors
»the central partr o-f the bed through the gaps 26 between
of the pair.
'the upper edges of the deñcctors 22 and the lower edges
4. A ñuidised bed comprising a vessel, small discrete
of the next higher deflectors 23. A similar outward
solid particles contained inl said vessel, gas admission
movement of air occurs through the gaps 27 between the 40 means adjacent-the bottom of said vessel for producing
deñectors 23 and 24. Replacement of this air is in this
an upward flow of gas through said vessel and maintain
embodiment effected through the same gaps 26 land 27
ing said particles in a> ñuidizedï state,v and la’ plurality
but inthe opposite direction, -by air which was previously
ofpairs of parallel Vdel‘lec'tors- in said vessel and each
rñowing up through the bed outside the defiectors below.
completely embedded in said particles»beneath-the'upper
For'example,‘in thev gaps 26 air will ñow outwardly from 45 level of said-particles in- their ñuidizedfstate," said lpairs
Kbetween the defleotors 22 while air will also flow inward
being arranged one abovel another, each ~deñector having
yly-from outside the del‘lectorsv 22. This inñowing air will
a lower horizontal edge and an-upper horizontal edge,
replace some, but usually not all, of the air ñowing out
each pair being arranged with the lower edges of' the
through the gaps 26, and will enter between the lower
deilec’tors
of the pair closer together than the upper edges
edges of the deñectors 23 to augment the lair which has 50 of the deflectors of the pair and a plurality of horizon
passed up between the deflectors 22 and which has not
tal porous tubes, one arranged adjacent the lower edge
escaped through the gaps 26.
of each'deñector, and means supplying gas through said
Since with this embodiment it is not practicable to
porous tubes and into said particles.
replace from the outer parts of the bed all the air that
5. A ñuidised bed according to claim 4 in which said
escapes thronghthe gaps, the depths of the deñectors have
deilectors are all of the same size and in which »said pairs
to be correspondingly reduced towards the topof the
are arranged at equal distances above> one» another.
bed.
In other words, considering the apparatus as a
6.- A ñuidised bed comprising a vessel, small `discrete
solid particles contained in said vessel, gas admission
shallow'er towards the top.
means I'adjacent the bottom of said vesselV for producing
What I claim as my invention ’and desire to secure by 60 an upward ñovvof «gas through said vessel and maintain
Letters Patent is:
ing said particles in a ñuidized state, 'and a plurality of
1. A ñuidised bed comprising a vessel, smalldiscrete
pairs of parallel deñectors in said vessel and each com
solid particles contained in said vessel, gas admission
pletely embedded in said particles vbeneath the `upper
means adjacentthe bottom of »said vessel for producing
Ilevel of saidr particles in their ñuidized» statepsaid pairs
65
yanupward ñow of >gas through said vessel and maintain
being arranged one above another, eachV deñector having
ing said particles in a cñuidized state, and a plurality of
a lower horizontal edge and an upper horizontal edge,
pairs of horizontally opposed deflectors- in said vesseland
each pair being ‘arranged with the loweredges of the de
each completely embedded in said particles beneath the
flectors of the pair at the same height labove the bottom
upper level of said particles in .their fluidized state, said 70 of said vessel and closer together than theupper edges
pairs being arranged one labove another, the deflectors
of the deñectors of the pair, said lower edges of the de
of each pair being disposed in upwardly divergingv for
d’lectors of the pair being spaced apart by a distance to
mation, and having their lower edges parallel and at the
permit the entry between the deñecto'rs of the pair of
same height above the bottomof said vessel and spaced
suñicient gas to properly ñuidise the particles between
apart by a distance‘to permit thefentry between Athe de 75 the deflectors of >theïpair,~the breadth-ofthe»deñectors
plurality ‘of superimposed shallow beds, these bedsV get
3,031,769
5
getting progressively narrower from the lowermost pair
to the uppermost pair.
7. A tluidised bed comprising a vessel, small discrete
solid particles contained in said vessel, gas admission
means adjacent the bottom of said vessel for producing 5
«an upward flow of gas through said vessel and main
taining said particles in a ñuidized state, «and a plurality of
pairs of parallel deñectors in said vessel and each com
pletely embedded in said particles beneath the upper level
of said particles in their iluidized state, said pairs being 10
'arranged one iabove another, each deñector having a lower
horizontal edge and an upper horizontal edge, each pair
being arranged with the lower edges of the deñectors of
the pair at the same height above the bottom of said vessel
and closer together than the upper edges of the deñeotors 15
6
of the pair, said lower edges of the deflectors of the
pair being spaced apart by a distance to permit the entry
between the deflectors of the pair of suñicient gas to prop
erly fluidise the particles between the deflectors of the
pai-r, and heat exchange surfaces in said vessel.
References Cited in the ñle of this patent
UNITED STATES PATENTS
2,697,881
Kelley ______________ __ Dec. 28, 1945
2,741,546
2,889,269
2,938,276
2,964,852
Sweeney et al. _______ __ Apr. 10,
Micholsen ___________ .__ June 2,
Doleman et al. _______ __ May 31,
ltDolernan et al _________ __ Dec. 20,
1956
1959
1960
1960
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