Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to heating matter and is
particularly, but not exclusively, applicable to methods of
heating matter using apparatus as disclosed in Specification EP-B-
68853 published March 11, 1987, British Specifications Nos.
2202618A, 2203670A, 2205049A published September 28, 1988, October
26, 1988 and November 30, 1988, respectively and in Canadian
application Serial No. 580,998 filed October 21, 1988, and in
which matter is moved in a band continuously along an annular path
in an annular zone by directing fluid flow into the zone over the
annular extent thereof with both circumferential and vertical flow
components. It will be understood that by utilising heated fluid
for the fluid flow over at least a portion of the annular extent
of the zone, there will be a heat transfer between the heated
fluid and matter as the heated fluid passes through the band
thereby heating the matter.
A gaseous mixture which is reactable to produce heat may
be used to provide a heated fluid flow, for example the gaseous
mixture may be a combustible gaseous mixture, typically comprising
an air-gaseous fuel mixture.
However, it will be understood that, for the above
process of producing a heated fluid flow to be efficient in a
method of heating matter as described above wherein the heated
fluid flow passes through a band of the matter which is moving
continuously along an annular path in an annular zone, the
reaction which produces the heated fluid flow should occur in the
zone and must be rapid to ensure that the reaction is
substantially completed within the extent of the band, which for
example is typically 50mm deep.
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We have found that the requlred rapld reactlon can be
achleved by supplylng the gaseous mlxture at a temperature above
that at whlch fuel dlssoclation occurs such that spontaneous
ignltlon occurs and no flame front exlsts.
Accordlng to a broad aspect of the lnventlon there ls
provlded a method of heatlng matter comprlslng (1) supplylng sald
matter to a heatlng zone to be heated thereln, such that sald
matter has an extent ln sald heatlng zone and (11) provlding ln
sald heatlng zone a gaseous mlxture whlch ls reactable to produce
heat, sald gaseous mlxture belng provided ln sald heatlng zone, at
a temperature above that at whlch spontaneous lgnltlon thereof
occurs such that sald gaseous mlxture reacts, wlth no flame front
helng preserlt durlng the reactlon, wlthln the extent of sald
rnatter to thereby provlde a heated fluld flow ln sald heatlng
zone.
Accordlng to another broad aspect of the lnventlon there
ls provlded a method of heatlng matter comprlslng (1) supplylng
sald matter to a heatlng zone to be heated thereln such that sald
matter has an extent ln sald heatlng zone and (11) provldlng ln
sald heatlng zone a combustlble gaseous mlxture, sald combustlble
gaseous mlxture belng provlded ln sald heatlng zone at a
temperature above that at whlch spontaneous lgnltlon thereof
occurs such that a combustlon reactlon occurs, wlth no flame front
belng present durlng the reactlon, wlthln the extent of sald
matter to thereby provlde a heated fluld flow ln sald heatlng
zone.
Accordlng to another broad aspect of the lnventlon there
ls provlded a method of heatlng matter comprlslng (1) supplylng
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sald matter to a heatlng zone to be heated thereln such that sald
matter has an extent ln sald heatlng zone and (il) provldlng ln
sald heatlng zone a combustlble alr-gaseous fuel mlxture, sald
alr-gaseous fuel mlxture belng provlded ln sald heatlng zone at a
temperature above that at whlch spontaneous lgnltlon of the
gaseous fuel occurs such that a combustlon reactlon occurs, wlth
no flame front belng present durlng the reactlon, wlthln the
extent of sald matter to thereby provlde a heated fluld flow ln
said heatlng zone.
Although the lnventlon ls appllcable to other methods of
heatlng matter, lt ls especlally appllcable to the above-descrlbed
method, ln whlch case the matter to be heated ls moved ln a band
contlnuously along an annular path ln an annular zone by directlng
fluld flow lnto sald zone over the annular extent thereof wlth
both clrcumferentlal and vertlcal flow components, sald fluld flow
comprlslng sald gaseous mlxture over at least a portlon of the
annular extent of sald zone, and the reactlon thereof belng
suhstantlally completed wlthln the extent of sald band.
The fluld flow may comprlse sald gaseous mlxture over
the annular extent of sald zone.
The matter may comprlse partlculate materlal
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which forms a resident bed moving in said band along
said annular path.
The gaseous mixture may be directed into a first
annular region of said annular zone, which region is
contiguous with and disposed inwardly of a second
annular region of said annular zone such that said
reaction occurs substantially in said first annular
region, and said matter is circulated between said
regions whilst moving in said band.
In embodiments of the invention described
hereinafter the gaseous mixture comprises an air-
gaseous fuel mixture and the fluid flow is directed
into said annular zone through an annular inlet
comprising an annular array of fixed inclined vanes
arranged in overlapping relationship, said gaseous
fuel being mixed with heated air immediately upstream
of respective passages defined between said vanes and
combustion occurring downstream of said vanes.
Preferably the air-gaseous fuel mixture is
confined substantially to the region above the vanes
by directing respective flows through said annular
inlet at the radially inner and outer edges thereof
with radially outwardly and radially inwardly flow
components respectively.
The gaseous fuel may comprise natural gas, and in
an embodiment of the invention an air-natural gas
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mixture is supplied at a temperature greater than 700C. The
temperature of this mixture is obtained by mixing the natural gas
with heated air at a temperature of less than about 1000C, for
example between 850 and 900C.
In order that the invention may be better understood,
some embodiments thereof will now be described, reference being
had to the accompanying drawings, in which:
Figure 1 is a graph showing the effect of the
temperature of an air-gaseous fuel mixture on combustion rate;
Figure 2 is a schematic axial cross-section of an
apparatus for heating matter;
Figure 3 is a cross-section along the line III-III of
Figure 2;
Figure 4 shows the portion indicated by IV in Figure 2
to a larger scale and in more detail than in Figure 2;
Figure 5 is a section taken along the line V-V in Figure
4 showing four blades of the apparatus;
Figure 6 is a top, part section view of three blades of
the apparatus;
Figure 7, on the first sheet of drawings, is a
perspective view of a single blade of the apparatus;
Figure 8 is a schematic top plan view of another
apparatus for heating matter taken along the line VIII-VIII of
Figure 9; and
Figure 9 is an axial cross-section of the same
apparatus.
Referring first to Figure 1, the effect of the
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6 1 336389 67284-8
temperature of a combustible air-gaseous fuel mixture prior to
combustion on the rate of combustion is indicted. It will be
noted that combustion of the mixture at the lowest temperature A
is comparatively slower than combustion of the mixture at higher
temperatures B and C, the temperature /time curves in the later
cases being substantially J-shaped, the temperature generated by
the combustion rising rapidly soon after combustion commences. In
the embodiments of the present invention described hereinafter an
air gaseous fuel mixture is provided for combustion at a
temperature above that at which dissociation of the fuel occurs so
that rapid combustion is achieved.
Referring now to Figures 2 and 3, the illustrated
apparatus comprises a chamber 10 having a circumferential wall 12
which is disposed radially outwardly of an annular inlet 14. The
wall 12 slopes towards the annular inlet, and as shown comprises a
cylindrical portion 16 extending upwardly from a sloping portion
18. In the illustrated apparatus, the sloping portion 18 extends
downwardly to the outer edge of the annular fluid inlet.
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Within the chamber 10 there is a first annular
region disposed above the annular inlet and designated
22 in Figure 2 and a second annular region contiguous
with the first annular region and disposed between
that region and the circumferential wall 12. The
second region is disposed above the sloping portion 18
of the wall in the embodiment.
The apparatus also includes means for directing
fluid through the annular inlet 14 with vertical and
circumferential flow components. The direction of the
fluid flow through the inlet is indicated in Figure 2
by arrows 26 and 28. The flow of fluid through the
inlet is such that it will move matter in the chamber
10 in a band continuously along an annular path in the
regions 22, 24. This matter is moved vertically and
circumferentially whilst in the first region 22 by the
flow of fluid therein, is moved out of this flow of
fluid in the first region into the second region by
circumferential force and is directed back into the
first region by the slope 18. The movement of the
matter into and out of the flow of fluid is indicated
by arrows 30 in Figure 2. It will be understood that
whilst the matter is being circulated as indicated by
arrows 30 it is also moving in the circumferential
direction. Furthermore, it will be understood that
when the matter moves into the outer annular region 24
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1 3363~
it is not subjected therein to the flow of fluid and
falls under gravity towards the annular inlet 14
whereupon it re-enters the fluid flow and is moved
circumferentially and vertically by the fluid flow
therein.
The fluid exits the chamber 10 upwardly as
indicated by arrows 32 after it has passed through the
annular region 22.
In the illustrated apparatus the chamber 10
includes a second circumferential wall 34 extending
upwardly and disposed radially inwardly of the annular
fluid inlet 14. This circumferential wall 34 has a
slope towards the annular fluid inlet such that matter
introduced centrally into the chamber as indicated by
arrows 36 will be directed into the first annular
region 22 above the annular fluid inlet 14. Whilst
the whole of the second circumferential wall is
provided with such a slope in the embodiment and this
slope extends to the radially inner edge 38 of the
annular fluid inlet 14, it is to be understood that
only a portion of the circumferential wall 34 need be
provided with such a slope and that slope need not
extend to the edge 38.
Referring now particularly to Figures 4 to 7, the
means for directing fluid through the annular inlet 14
with vertical and circumferential flow components in
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the illustrated apparatus comprises an annular array
of fixed inclined vanes 40 arranged in overlapping
relationship, and defining therebetween respective
flow passages 42 which extend vertically and
circumferentially. A portion of the annular array of
vanes is schematically illustrated in Figure 3,
however it is to be understood that the array extends
completely around the annular inlet 14.
Each vane 40 is part of a respective blade 44
which is best shown in Figure 7. Adjacent blades 44
nest together as illustrated in Figures 5 and 6 so as
to dispose the vanes in overlapping relationship with
the passages therebetween. Each blade 44 is also
provided with respective side vanes 46 and 48
extending upwardly from radially outer and radially
inner sides of its vane 40. The side vanes 46 and 48
of the blades overlap to define therebetween
respective flow passages 50 and 52. The vanes 46 and
48 are inclined towards each other and the flows
through the passages 50 and 52 at the radially outer
and inner edges of the inlet 14, indicated by arrows
28 in Figure 2, have radially inwardly and radially
outwardly flow components respectively causing the
flow through the passages 42, indicated by arrow 26 in
Figure 2, to be confined substantially to the annular
region 22 above the vanes 40.
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The blades are provided with radially outer and
radially inner mounting portions 54 and 56, by which
they are mounted on annular ledges 58 and 60
respectively radially outwardly and radially inwardly
of the annular inlet 14. Intermediate the mounting
portions the blades are provided with a ribbed portion
62 which extends vertically to the upstream ends of
the vanes 40, 46 and 48. The ribs 64 of the portion
62, extend vertically and are provided on only one
side of the portion 62 in the illustrated blade and
define with the plain opposite side 66 of the portion
62 of an adjacent blade vertically extending flow
passage means 68 communicating with the flow passages
42, 50 and 52 defined between that blade and the
adjacent blade. Each blade is provided with a passage
for receiving a gaseous fuel distributor, or so-called
'sparge', pipe 70. This passage comprises a bore 72
in an enlarged free end portion 74 of the mounting
portion 54 and a slot 76 aligned with the bore 72 and
extending therefrom through the r~m~in;ng portion 78
of the mounting portion 54 into the ribbed portion 62
and ter~in~ting short of the mounting portion 56. In
the ribbed portion 62 the slot is completely open at
the plain side 66 thereof but bridged at spaced apart
locations by the ribs 64 at the other side.
As shown in Figures 5 and 6 a pipe 70 is received
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in the passage therefor in alternate blades 44, each
pipe being provided with radial openings arranged to
supply gaseous fluid to the flow passages defined by
the blade in which the pipe is fitted and the blades
on each side of that blade. The pipes 70 are all
connected via conduit means 80 to an annular gas
header tube, or manifold, 82 disposed externally of
the circumferential wall 12 of the chamber.
In use heated air is caused to swirl about an
annular chamber 84 beneath the annular inlet 14 and to
flow through the passage means 68 defined between
adjacent blades in the passages 42, 50 and 52 defined
between the vanes of those blades. This air mixes
with gaseous fuel from the pipes 70 to form a heated
air-gaseous fuel mixture in the passage means 68 and
this mixture is combusted in the annular region of 22
of the chamber 10 above the inlet 14. The air-gaseous
fuel mixture is heated prior to combustion by the
mixing of the gaseous fuel with the heated air to a
temperature above that at which spontaneous ignition
of the gaseous fuel occurs such that a rapid
combustion reaction occurs as explained hereinbefore
in connection with Figure 1. The rate of combustion is
such that although the velocity of the air mi xi ng with
the fuel is greater than the flame propagation
velocity thereof so that the resulting flow is able to
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12
move matter in a band along an annular path in the
chamber 10, combustion occurs, and is substantially
completed, within the extent of the band, that is
before the mixture passes through the matter in the
band. Additionally because the gaseous fuel is mixed
with the air immediately upstream of the passages 42,
most of the combustion occurs downstream of the blades
44 and accordingly they are not subjected to the full
heat of the combustion reaction.
The above-described embodiment is particularly
applicable for use in heating matter comprising a
particulate material which has to be heated to a
predetermined temperature which is at or below the
temperature at which fast combustion reactions occur,
or which is adversely affected by being continuously
subjected to temperatures above that predetermined
temperature during treatment.
In such an application the combustion reaction
occurs substantially in the first annular region 22 in
the chamber 10. The particulate matter to be heated
is supplied to the chamber centrally thereof and is
fed to the region 22 by the slope of the inner
circumferential wall 34. This particulate material is
then moved in a band continuously along an annular
path in the regions 22 and 24. The particulate
material is moved vertically and circumferentially by
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the fluid flow whilst in the first region, is moved
out of the flow in the first region into the second
region by circumferential force and is thereafter
directed back into the first region by the slope 18 of
the outer circumferential wall 12. Thus, the
particulate material is moved in a band continuously
around the regions 22, 24 whilst being circulated in
this band between the regions such that the material
moves into and out of the heated flow during movement
around the regions.
It will be appreciated that as the combustion
reaction is maintained spaced from the walls 18 and 34
these are not raised to the temperature of the region
22 and therefore contact by the particulate matter of
these walls does not adversely affect the matter.
Although the above-described embodiment is
applicable to heating many types of particulate
matter, particular examples of its application are the
heating of perlite, slate and clay to expand the same.
Referring now to Figures 8 and 9, there is
illustrated an apparatus for heating matter which is
similar to the apparatus illustrated in Figures 2 and
3. Accordingly like reference numerals in these
figures designate like or similar parts. The annular
inlet 14 is spanned by an annular array of inclined
vanes 86 (only a portion of the array being shown in
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Figure 8) which are preferably arranged in overlapping
relationship for directing fluid flow into the annular
zone 88 above the inlet 14 with both circumferential
and vertical flow components for moving a resident bed
of particulate matter in the zone 88 continuously
along an annular path in a compact band 90.
Heated air is caused to swirl about annular
chamber 84 beneath the inlet 14 and to flow between
the vanes 86 into the zone 88. This air mixes with
gaseous fuel from fuel pipes 70 ;m~e~iately upstream
of the vanes to form a heated air-gaseous fuel mixture
which is combined in zone 88. As in the previous
embodiment, the heated mixture prior to combustion is
at a temperature above that at which spontaneous
ignition of the gaseous fuel occurs such that a rapid
combustion occurs. The rate of combustion is such
that combustion is substantially completed within the
extent of the band of particulate matter forming the
resident bed, thus efficiently heating that matter.
Further matter to be heated is either added to the
resident bed or passed therethrough such that heat is
transferred to the further matter from the heated
particulate matter of the bed. This further matter
may comprise gases, liquids or solids.
In the case where the further matter to be heated
is a gas, the heated air-gaseous fuel mixture is
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passed through the bed along a portion of the annular
extent of the zone 88 to heat the bed and the gas is
passed through the bed along another portion of the
annular extent of the zone 88 to be heated by the
matter in the bed.
One example of solid matter which may be heated
by being added to the resident bed is fine powder.
The apparatus and method described above in
connection with Figures 8 and 9 may be used to heat
matter, especially particulate matter directly without
the use of a resident bed. In this case it will be
appreciated that the matter to be heated is introduced
into the zone 88 and is moved continuously along an
annular path in a compact band by the passage of the
heated fluid flow provided by the combustion of the
heated air-gaseous fuel mixture through the matter
whilst heating it.
It is to be understood that an arrangement of
nested blades with fuel sparge pipes fitted to
alternate blades substantially as described in
connection with Figures 4 to 7 may be used in the
apparatus shown in Figures 8 and 9 instead of the more
simple overlapping vane arrangement schematically
illustrated.
Although other gaseous fuels, such as propane,
methane and vapourised oil, may be used, in the
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... . . . . .. .. .
16 1 336389
embodiments described above the gaseous fuel is
natural gas and the air-natural gas mixture prior to
combustion is at a temperature above 700C. To obtain
such a mixture temperature the air is preferably at a
temperature of between 850 and 900C. Other air
temperatures may be used, but it has been found that
at air temperatures above about 1000C carbon deposits
are likely to form in the fuel pipes 70. Thus it is
advantageous to use an air temperature of less than
about 1000C.
Although the embodiments have been described
utilising a heated air-gaseous fuel mixture to provide
a heated flow, other combustible gaseous mixtures or
gaseous mixtures which react to produce heated flow
and whose reaction rate is typified by a substantially
J-shaped temperature/time curve which the mixture
prior to commencement of the reaction is at a
temperature above that at which spontaneous ignition
occurs may be used.
.
