Note: Descriptions are shown in the official language in which they were submitted.
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THIS INV~NTION re].ates to an improved method ~nd app~r.~tus
for the combustion of crushed solid fuels and in p~rt;icular
it relates to the combustion of coal in kilns.
Hithertofore the use of coal in the firing oE brick kilns
has been relatively limited with its major use resi.ding
in systems wherein the coal is trickle fed, hand fed,
mechanical or air conveyed by systems such as Gibbons
: ' Octopus and Impactapus or introduced into the kiln in
varîous other ways. For exarnple, the Octopus system
: . ~ 10 resides in a system wherein milled coal is fed to a dis-
tribution point mounted on top of a kiln. The distribution
point has consisted of a fan mounted horizontally on a
s~all p~table chassis. The fan has a circul~r ~asing ~;.th
i~ radial outlets spaced around.its circumference. Flexible
tubes connect these outlets to lances which inject the
~, air/coal mixture into the kiln~ where the coal burns in
~ suspension.- With this particular method and apparatus
¦ ~ several disadvantages become apparent when the system is
1~ i in use. The temperature within a kiln varies from one
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point to another and accordingly there must be some method
. of injecting extra fuel i~to the cooler areas of the kiln
to raise the temperature. Similarly it would be advan-
tageous to be able to completely control the rate of.feed
: .for each indi~idual lance and if necessary to be able to
. shut-off any particular lance.
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It is an object of l;}lis inv~n~ion to provi(le an i~prove~
method and apparatus of supplying coal to a ki].n wherein
t~le above menti.oned disadvantages are eliminated. In
particular the invention will be described for use in
continuous Hoffman type kilns, however~ it will be app-
reciated that it can also be applied to car-~tunnel kilns
and periodic kilns.
In one form the invention resides in a method for the
combustion of crushed solid fuel comprising crushin~ the
~ ` ~ 10 fuel.into a ~owder form, placing the crushed fuel into a
storage bin and fluidising said fuel within said bin,
linking the ~luidised fuel with a mixing chamber, passin~
compressed air through the mixing chamber so as to form a
vena contracta so causing the fuel to flow into the com-
pressed air stream and thence into a kiln.
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Preferably a contr~l device is attached to the compressed
air line to enable the air pressure to be controlled.
In another form the invention resides in an apparatus for
the combustion of crushed solid fuel `comprising a bin
of finely powdered fluidised solid fuel being connected
to a mixing chamber so as to create a vena contracta and
subsequent flow of fuel being mixed with compressed air~
the air/fuel mixture being fed into a kiln~ control of flow
of compressed air being governed by a solenoid valve or
similar unit being operated by a pre-s:et controlling device.
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Preferably every fuel inlet point on a kiln is fitted
with a seperate solenoid valve and pre set control device.
Xn yet another form ~he invention resides in a me-~hod
for the combus~ion of crushed solid fuel comprising
tempora~y s~oring said crushed fuel in a fluidised condition
in a bin, conveying said fuel by air slide means to a
pressure pot, discharging the fuel from the pressure pot
in~o an expanslon bin9 fuel in a flùidised state is then
fed into a trough which is providéd with suitable level
indicators de-airing downpipes and the like, said de-airing
downpipes resulting in a partial compaction of the ~uel
within said trough~ the par~ially compacted fuel is then
fed into one or more burners9 compressed air being passed
through said burner to mix with the fluldised fuel, control
of compressed air being governed by a solenoid valve or
similar unit~
The embodiments of the invention will be bet~er understood
by reference to the following description and accompanying
drawings wherein;
Figure 1 is a schema~ic representation of one
embodiment;
Figure 2 is a:schematic representation of a further
embodime~t;
Fi~ure 3 is a sec~ional side elevation ~ the burner; and
Fi~ure 4 is a sectional side eleva~ion of figure 3 with
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a surrounding C~Sil3g fit;t;ed to incorporate a secondary
air ~low.
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In the embodiment shown in figure 1 of the drawin~ solid
fuel is crushed at 11 by any suitable means and then paased
to bi~ 12 for storage. Generally the bin 12 is provided
with vertical walls with the entire base being covered by
a aerating pad 13. The phl~erised fuel within bin 12 is
',, continuously aerated and maintained in a fluid state. Dry
air of approximately 1 p~s.i. i5 provided to the aeration
pad to maintain the fluidised state of the solid fuel. One
or more hoses 14 link the bin 12 with one or more mixing
chambers or venturi burners 15. The hoses 14 must be a
`, conduc-tor of electricit~ such that no static electrical
charg~ can build up. A carbon impregnated rubber, metallic
tube or similar materials may be used. The diameter of
hose 14 can obviously be varied to suit the specification
~: of the burner 15 and the distance from bin 12 to the burner
15. The size of hose 14 which has been found most suitable
during experimental runs has dimensio~s of 0.375 inch
- 20 internal diameter and allows fuel to be conveyed to the
~t
i burner o~er distances exceeding 30 feèt. Fluidised fuel
is passed from hoses 14 to fuel inlet 16 of burneræ 15.
Compressed air is fed into the burner 15 through inlet 17
and orced throu~h nozzle 18. Generally compressed air in
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the order of 20 p.s.i. to 100 p.s.i. has been f~und most
sa-tiefactory- The result is that fuel is caused to ~low and
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mix with the compressed air as :it passes through venturi
19 into blow pipe 20 and into the kiln. The flow of fuel
may become erratic depending upon the length of hose 14
and the amount of aeration involved, especially if the
compressed air pressure is allowed to fall below 20 p.s.i.
A further method of control of the flow of fuel to the
burner 15 may be achieved by bleeding air into the suction
line/hose 14 so as to increase the air/fuel ratio being
introduced into the burner. The flow of fuel through
burner 15 is varied by means of pulsing the compr~ssed
air flow by use of an automatic electronic timer 21
operating through a solenoid valve 22 or similar such device
or combination of devices. The electronic timer 21 may
be set ~rom 1 ~econd to 3 minu'es ~ON~ with seeond to
3 minutes ~OF~. The ION~OF~7 operation occurring
alternat;vely and automatically. The compressed air press-
ure has little or no effect on the input of the fuel but
rather the ejection path and flow characteristics of the
~uel. Figure 4 of the drawings shows the burner 15 with
an additional surrounding casing 23 incorporating a secondary
air flow. In order to aid combustion~ it may be necessary
, to introduce a secondary air flDw into the kiln. This
can be done by passing air in inlet 24, through chamber 25
which surrounds bIow pipe 20 and then out into the kiln.
The leading end of the burner 15 is provided with a pro-
tecti~e cap 26 and mounting flange 27, flange 27 being
pro~ided to enable the burner to be fitted to a kiln.
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In the second embodiment shown in fi~ure 2 of ~he
drawings an additional flow diagram has been ineluded
showing the pas~ge of moist fuel before fluidisation.
The raw P~el, if too wet to be fluidised, mu~t be suitably
dri~d by using a hollow flight screw conveyor or by under
cover air drying or by rotary kiln or similar commercially
available equipment. The dry solid Euel is then fed into
- a crusher 111 ~nd the resultant crushed fuel passed throug~
!a sieve into storage bin 112- The crushed fuel generally
:. 1 10 used must be capable of passing throu~h a size 14 B.S.S.... ~nesh
and is generally readily achieved by employing a hammer
mill with screen.bars set at 1/16~ gap. Other types of mills
that can be used quite satis*actorily include Eine rolls~
rod and ball ~.ills, gyratory sr~s~ers, pan mjlls and the
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like~ If obtainable~ dry powdered fuel from separation
processes s~ch as wet washing, 5crubbing, electrostatic
~recipitation~ bag filters and cyclones may also be used.
Generally the sto~age bin 112 is provided with vertical
walls and has the entire base covered by a aerating pad
20. 113. The pulverised fuel within the storage bin being
eontin~ously aerated and maintained in a.fluid state. The
. storage ~in 112 is linked by way of air slide 114 a~d pn-
eumatic gate control to a pressure pot 115. On reeeiving a
signal from a le~el sw;tch 116 situated in the Eluidise~ dis-
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`~ ~ tribu~or trough 1179 the pressure pot 115 ~ills and eharges
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a predete~mined measure of f~lel alon~ di6charge line 118
to an expansion hopper 119 located at the appropriate
furnace or kiln, The discharge line 118 may be up to
1,000 feet or more in length and is dependant mainly on
the pressure and volume of air used for propulsion. The
expansion hopper 119 receives the charge of fuel, allows
the air (i.e. conveying medium) to escape via a filter 120
of the con-tinuous reverse air jet type or similar. The
- expansion hopper also allows the received fuel to feed into
a distributor trough system 117. If necessary the expansion
hopper may be fitted w;th gate valves, outlets~ air by-
pass lines and/or such devices as are nece~sary to allow
for multiple trou~h system to operate- Discharge from
the expansion hopper occurs simu'taneously ~-i'h the charge
entry of fuel into the expansion hopper from line 118. The
fuel in the distributor trough 117 is maintained in a fluid
state and at such a level to provide an upper air space
undisrupted throughout the trough system. A plurality
of de-airing down pipes 121 are provided in the base of
trough 117. The de-airin~ pipes allow partiai compaction
of the fuel prior to it entering hose 122 and burner 123.
If the de-a~ring pipes are deleted and the hoses 122
connected directly to trough 117, where the trough is above
the burner 123, then flow of pulverised fuel will occur
down hose 12Z and through the burner 123 rendering the
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system inopcrable. The use and operation o~ the venturi
burner, hose, electronic tiner a~d solenoid valvc are
exactly ~he same as described above with refererlce to
figure 1 of the drawings.
With this method of firing kilns large savings can be
made in the actual cost of fuel consumed.
Whilst the invention has been described with reference
to one specific embodiment it is not limited thereto as
the system may also be fit~ted to tunnel kilns with either
top or side firing~ or to pe~iodic kilns or to types of
~rna~e- o~beF than bri~k ki ns- 1
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