Note: Descriptions are shown in the official language in which they were submitted.
` 1~76~Z'~
This invcntion relates to burning powdered coalO
The advantages of coal as an energy source need no elaboration here~
at this historical juncture. However~ burning coal has also had its dis-
advantages such as initial handlinga handling of waste products of combus-
tion~ equipment corrosion~ and pollution.
In recent years~ fluidized bed combustors have been developed that
solve most of these problems~
Cyclones can be used with fluid beds because of the ash-coarsening
agglomeration that occurs~ as is shown in U.SO Patent 3~431~892 (Godel) and
UOS. Patent 3~171~369 (Stephens et al)O me emission of no~ious trace
elements~ (e.gO3 beryllium~ cadmium and mercury) is minimized in fluidized
beds by their far_lower operating temperatureO
Yet, the low outlet temperatures of conventional fluidized beds
outlet gases cannot be used to provide heat for high-temperature furnaces~
Such low temperatures also create excessive stack-gas losses if conventional
fluidized-bed combustors are retrofitted to existing boilers and space-heat-
ing furnacesc The present invention overcomes these objections by providing
a system with high outlet temperatures that nevertheless permits the char
combustor to be operated at low temperaturesO One prior art system that also
produces outlet temperatures appreciably higher than the char-burner temp- -
erature is found in U.S~ Patent No. 3~358~624 (~ay)O The system uses a
pyrolyzer to separate coal into char and volatiles~ a burner for the char
cooled by excess air~ but only to keep the ash molten so that it will form
as slag on the walls rather than be vaporized~ and a second burner for the
volatiles and combustion products and excess air of the first burner~ giving
a high output temperature.
Numerous pyrolyzers have been developed over the years to remove
volatiles from coalO One requirement is for a pyrolyzer that can handle
caking coals without foulingO The design perfected by the ~OSo Bureau of
Mines ~Bureau of Mines Report of Investigation 7843, 1973), is particularly
~76422
suitable for the nee~s of the present invention. The design has been
modified to withdraw solicl materials in a standpipe, instead of by gas
entrainment from the top, thereby reclucing particle attrition. This
modiEicatioll is suggested in "Spouted Becls," Kishan B. ~lathur, Norman
epstein, Academic Press, New York, 1974.
Tlle invention permits coal to be burnt with great eEEiciency and
witll very greatly reduced corrosion, pollution, and products handling
problems, all with simplicity, capability of automatic operation) and
adaptability to the widest range of installation sizes. Either wet or dry
crushed coal, with or without additives, may be burned. Combustion is quiet
and uniform, and at a closely controllable burning temperature. Furthermore,
near stoichiometric flame temperatures are achieved with little excess oxygen.
Even fine fly ash is removed, along with sulfur, with great efficiency; and
there is minimum formation of trace elements and N0x compounds. Corrosion
of equipment is minimized. Retrofitting existing equipment is practical. -
Altogether, the invention promises to be the lowest cost method of using coal
in an environmentally acceptable manner in high temperature furnaces and in
boilers retrofitted from other fuels.
The present invention provides the method of burning coal which
comprises the steps of: pyrolyzing coal to form char and volatiles, contact-
ing and reacting said volatiles with a sorbent at a zone before or after
separating said char from said volatiles, separating said char from said
volatiles, transferring reacted sorbent from said zone to a burner, burning
said char in heat-transfer relationship with a stoichiometric excess of air
in said burner, forming thereby ash and spent sorbent and a mixture of gases,
said excess of air being~chosen to produce in said ash and spent sorbent a
temperature below the fusion temperature of said ash, separating said mixture
of gases from said ash, and thereafter burning said volatiles in said mixture `~
of gases.
0 In another aspect, the invention provides coal burning apparatus
which comprises, in combination: means for pyrolyzing coal to form char and
volatiles, means for separating sai char from said volatiles, means for
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~764~Z
contacting and reacting said volatiles with a sorbent at a zone before or
aTfter separating saicl char from said volatiles, means for transferring
reactecl sorbent from said zone to a burnerJ a burner for burning said char
in heat-transfer rclationsh:ip with a s-toichiometric exccss of air, form:ing
thereby ash ancl spent sorbent ancl a mixture of gases, means for separating
said mixture of gases from said ash, and means for thereafter burn:ing said
volatiles in said m:ixture of gases.
The invention also provides coal burning apparatus which comprises,
in combination, a spouted fluidized bed pyrolyzer, a fluidized bed combustor,
a first cyclone, a second cyclone, and an afterburner, the pyrolyzer being
connected to accept pulverized coal and to discharge char to the combustor
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1076~ZZ
and gaseous mateFials with entrained particulate material to the first cyc~
lone~ the first cyclone being connected to deliver gases to the afterburner~
the combustor bei.n~ connected to accept al90 a combustion supporting gas and
to del:iver to the second cyclone gaseous materials with entrained particu-
late material~ and the second cyclone being connected to deliver gaseous
material to the afterburner
In preferred embodiments, the invention features also bringing the
stoichiometric excess of air into contact with the char in pyrolyzing,
providing in the pyrolyzer specific characteristics, carrying out the solid~
gas separations in cyclones~ burning char in a solids-recirculating fast
fluidized bed combustor, providing in the combustor specific characteristics~
providing heat in the pyrolyzer by burning therein a portion of the combus-
tibles thereinto, varying fusion temperature by adding a temperature varying
material3 adding a diluent gas to volatiles before burning them~ adding
water at the pyrolyzer~ adding sorbent at the pyrolyzer~ and adding oil at
the afterburner.
Other advantages and features of the present invention will be :
apparent from the following speci:Eic description of preferred embodiments
thereof given by way of example only and with reference to the accompanying
drawings, in which:
Figure 1 is a diagrammatic flow chart illustrating a preferred ~:
embodiment of the invention;
: Figure 2 is a table showing temperatures and throughputs at various
places in said embodiment;
Figure 3 is the preferred embodiment of pyrolyzer used therein,
shown in vertical section;
Figure 4 is a vertical section of the preerred embodiment of
fluidized bed combustor for use therein;
Figure 5 is a partial sectional view taken at 5-5 of Figure 4;
Figure 6 is a vertical sectional view of the afterburner preferred
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64ZZ
for use therein:
Figure 7 is a vertical sectional view of the preheaters preferred
for use therein; and
~ igure 8 is a somewhlt diagrammatic view in perspective of the
preferred embodiment of the inventionO
Turning now to my presently preferred embodiment~ and describing
it in a manner enabling to those skilled in the art, there is shown in
Figure 1 a diagrammatic flow chart illustrating a combination of elements
arranged to burn coal according to my novel inventionO
In this embodiment~ I burn Illinois high volatile bituminous Grade
B coal with 3.0% sulfur content~ ash content of 1005%~ and a heating value
of 11,300 BTU/lb. The coal is dried and crushed to pass 8 mesh at the mineO
Dry limestone crushed to pass 8 mesh is m1xed (not shown) with the
coal just upstream of mixed-coal-and-limestone feed line 10 (Figo 1)~ by
dropping each from its separate screw feeder into a venturi for transport air
(not shown), the two venturis discharging into a common zoneO Downstream
of this~ but just upstream of feed line 10~ bleed air is introduced. (The
compressor for the transport air has a capacity of 40 psi~ and supplies the
transport air for each purpose hereinafter mentioned~ m e blower for the
bleed air has a capacity of 2 psi). Coal~ limestone, transport air~ and
bleed air enter pyrolyzer 12 through line lOo
Gaseous products move through refractory lined line 14 into char
cyclone 16~ which removes entrained particles-O The cleaned gases are then
introduced through refractory lined line 18 into afterburner 200 Most of
the char produced in pyrolyzer 12 pass~s through standpipe 22 into inlet line
24~ me char discharged from cyclone 16 through line 26 also enters line 24
(A venturi in each of l~ne 22 and 26~ each cooperating with transport air
from the transport air compressor, blows the two together in a Y the single
outlet of which is line 24; venturis and compressors are not shownO) Line
24 discharges into fast fluidized-bed combustor 28, which serves as the
: ' ` . ,
3~07~Z2
prcferred char burncrO ~lso di.scharging into the fast fluidized-bed
combustor (transfer l:ine reactor with solids rec:irculat:ion) 28 is combustion
air blown through l:ine 30 by blower 320
Al:L the products of combustion~ nitrogen~ and remaining oxygen
flow through refractory lined line 34 into ash cyclone 36 in which most of
the ash (with spent limestone) is removed through line 420 Most of the
residue (ash ~ spent limestone) leaving the fluid bed combustor 28 does
so through standpipe 400 Residue leaving through standpipe 40 is mixed with
residue leaving ash cyclone 36 through line 42, each of lines 40 and 42
including a venturi (not sho~n) cooperating with transport air~ mixed
residue emerging in line 440 Hot gases leave ash cyclone 36 through
refractory insulated line 46, and mix and burn with gases from line 18 in :
after burner 200 Hot products of combustion leave afterburner 20 and enter
: a furnace (not shown).
This preferred embodiment provides an energy output of 10,000,000
BTU per hour. Input flow rates are 930 pounds per hour of coal transport .:
air, 1380 pounds per hour of bleed air, and 9010 pounds (130% of stoichio- .
metric) of combustion airO ~ines are of piping as follows:
ine No~Standard Pipe Size/I~DO Nonstandard ¦Inches)
2 (standard)
14 10 (I ~Do nonstandard)
18 6 (IoDo nonstandard)
22 2 (IoDo nonstandard)
: 24 12 (IoDo nonstandard)
:~ 26 2 (IoDo nonstandard)
8 (IoDo nonstandard)
34 22 lIoD~ nonstandard)
2 (IoDo nonstandard)
42 2 (IODg nonstandard)
44 3/4 (I~Do nonstandard)
- 5 _
~7f~42Z
ine NoO Standard Pipe Size/IOD, Nonstandard (Inches)
46 12 (I~Do nonstandard)
Only enough air i.s provided in the W rolyzer to b:ring its temp-
erature to 1600 F.~ be].ow the fus:ion point of the ash of the particular coalO
Tcmperature in the upper zone of the fast fluidized-bed combustor
28 is held at 1570Fo (In both the pyrolyzer and the fluidized-bed combus-
tor temperature :i9 maintained by a sensor working with a controller to regu-
late air flow to the respective unitO) If the temperature in the pyrolyzer
falls unduly, less volatiles are produced; this means more combustion in the
fluidized-bed combustor, with consequent increased necessary excess air
there and thus overall lower temperature at the afterburnerO Also~ unduly
lower temperature in the pyrolyzer causes less fuel-nitrogen compound break-
down, compromising what is otherwise one of the advantages of my invention
making possible burning coal with low production of NO compoundsO On the
other hand~ unduly high temperatures in the pyrolyzer and fluidized-bed
combustor result in undesirable slagging and structural problemsO Unduly
high temperature in the fluidized-bed combustor also causes excess lime-
stone useO Unduly low temperatures in the fluidized-bed combustor both cause
excess limestone use and require use of more excess air, and thus lower
afterburner temperature undesirablyO Detailed flow rate data and transport
air quantities are shown in the chart of Figure 20
To start up, when a thermostat moves to call for heat~ the pneumatic
air transport compressor and the air blower turn on. The compressor purges
lines during preheating, while the blower blows air through the preheatersO
Three preheaters (not shown), one for each of the pyrolyzer 12, char cyclone
16, and fluidized-bed combustor 28 are then turned on ~unless a thermo-couple,
carried by each of them, in one or more of them senses that the respective
element is still hot from a recent run)O Each turns off when the component
it is heating reaches the predetermined temperature (minimum operating
temperature), 1200 Fo Gas temperatures out of preheaters are 1300 Fo into
the pyrolyzer and fluidized-bed combustor and 1800Fo into the char cyclone~
- 6 -
'
~0764ZZ
When the elements are tlp to temperature, coal and limestone feed is begunO
Blower air is then redirected from the preheaters to the pyrolyzer and the s
fluidized-bed combustorO Blower air at room temperature is also introduced
tnot shown) into line 18~ just downstream of char cyclone 16~ and with
volatiles (not shown) at the entrance of line 18 to heat ito (This prevents
~mwanted condensation~ as well as unwanted soot build-up, in line 180) When
the downstream end of line 18 reaches its minimum operating tcmperature of
1000F.~ as indicated by a thermocouple~ air to line 18 is shut offO
Lines 24 and 44 are water-cooled.
When the system is shut down the compressor runs for a short
further time, to make sure lines are clear.
Many variations within the spirit and scope of my invention will
be apparent to those skilled in the art. m us, as examples only, the char
burner may be a slow Eluidized-bed combustor or a gas-turbine-type (dilute
phase) combustorO Again~ if low-sulfur coal is used, a single-~one combustor,
for example, can be run at ash agglomerating temperatures Ifrom 1900F. to
2200F~)~ causing agglomeration and permitting efficient flyash removal by
cyclone. A fines separator may be added to the system downstream of the ash
cyclone and upstream of the afterburner (a sand bed filter) or downstream
of the furnace or boiler (various low-temperature filters)O A desulfurizing
chamber may be added, also, as a separate piece of equipment, downstream of
the agglomerating combustor, both upstream of the char cycloneO Pyrolysis
could be achieved by recycling some hot products rather than directly from a
part of the coal, as in the preferred embodimentO Any coal of rank hvAb or
lower may be usedO Or, cooling air or water could be used through a heat
exchanger at the combustor rather than added as combustion air. The sorbent
material for the capture of sulfur compounds may be lime~ half-calcined lime-
stone, or dolomite, rather than limestone. Fluxes may be mixed with the feed
to the pyrolyzer or char burner to lower the ash fusion point; soda ash
~Na20)~ borax (B203), or potash (K20) may be added to reduce the fusion
~L~7t~422
temperature, thereby increasing the tendency to agglomerate and improve
collection efficiencyO Conversely, addition of silica will increase the
fusion point, if desired to prevent slagging. If desired, diluent gases~
such as steam or recirculated products of combustion~ may be added to line
14~ to reduce hydrocarbon concentration in Line 14 and downstream elements~
thereby inhibiting the cracking of saturated hydrocarbons and PoulingO Water
may be added to the pyrolyzer to gasify some of the char~ principally by the
steam-carbon reaction (H20 + C -~ C0 + H2)o This reduces char to the char
burner and increases volatiles to afterburner 200 This reduces needed com-
bustion air (through line 30), and makes possible adding preheated air to
afterburner 200 mis reduces system fuel consumption and increases the flame
temperature and furnace output, permits use of coals with lower volatile-
matter content without reducing outlet flame temperature, and allows the use
of water slurry coal feed--which simplifies coal handling, storage, and trans~
portation--, and eliminates the need for coal drying, and reduces system size
and cost, since the combustion air added at the afterburner bypasses re-
; actors and cyclone)O
If9 as mined~ the coal contains pyrite in amount to give a sulfur
content over three percent, any excess thereover is removed, at the mine
Turning now to a description of each of the elements of Figure 1
in more detail~ there is shown in Figure 3 pyrolyzer 12~ comprising inlet
50~ tank 52, deflector 54, standpipe outlet 56~ and upper outlet 58. Pyro-
lyzer 12 is 12 feet 7 inches high,
Pyrolyzer 12 is refractory lines (TmaX-1800 Fo for tank 52)~ and
has an outer wall of carbon steel.
In operation, the pyrolyzer 12 is first filled with powdered
material. In a new system, the material may be any non-melting substance
such as sand; after run-up~ the char and limestone from the previous run
is used insteadO
m e pyrolyzer contents and walls are heated during start-up by
.
~7~;Z;2
combustion products entering at inlet pipe 10~ as has been previously
describedO When the temperature :in pyroly~er 12 is brought to 1200 Fo by
preheating as previ.ous.Ly described, coal~ limestone~ transport air~ and bleed
air enter inlet 50 from line lOo Conical deflector 54 prevents, on start-up,
jetting of the feed materia.ls through tank 52 and out through outlet 580 The
feed materials accumulate within tank 52 by virtue of the spouted fluidi7ed
bed created by interaction of the incoming stream transport air, coal, lime-
stone~ and bleed air on the char and limestoneO Thus the feed spouts up the ~ .
center of tank 520 Char produced by pyrolysis, along with the limestone, ~
circulates by flowing downward in the annulus~ then being entrained at the ~ -
bottom of tank 52 by the incoming stream, before showering back to the an-
nulusO Pyrolysis of the coal occurs as the incoming particles of coal are
heated by the recirculating char and limestoneO Each particle of incoming
coal is immediately surrounded by several particles of inert, non-sticky~
char and limestone. (This is important if the incoming coal is of the caking
type; without the dilution effect, the incoming coal would agglutinate into
a large lump. The narrowness of the cone, of only 20~ helps promote the
rapid mixing of recirculating solids with incoming coal.) Combustion of
the incoming air with the coal, char~ and volatile matter heats the solid
materials in the pyroly~er by combustion, only enough air is supplied to
create 1600Fo Lime (the reaction products of which are elsewhere herein
referred to as "spent limestone") produced from the thus-calcined limestone
reacts with the emitted sulfur compounds in the volatiles (primarily H2S), -;
thereby scrubbing the gas stream while forming spent sorbent, primarily CaS
(calcium sulfide).
The char and spent limestone pass through standpipe 56 to line 24
and then to combustor 28, as above describedO Gaseous products and entrained
: char and limestone fines pass out through upper outlet 58, through line 14
to char cyclone 16~
Char cyclone 16 is a quite standard cyclone separator designed for
':'' ' : ~ ' .
~07~ Z
highly efficient removal of the entrained particles from the gases leaving
W rolyzer 12. Gases with a velocity oP 50 feet per second enter tangentially
into the side of thc cyclone adjacent its wider top; particles are whirled
to the outsicle~ and spin downwardly until they fall through an outlet in
the bottom connected to line 26. Transport air (from a compressor not shown)
keeps the particles ~oving out of cyclone 16 and through lines 26 and 22 by
ejector actionO Cleaned gases leave through an outlet in the top of the
cyclone connected to line 180 Cyclone 16 is 14 feet high and is lined with
3/4 inch refractory-filled hexagonal steel honeycomb (TmaX-1800F.) anchored
with studs~ surrounded by 3 inch heat insulating refractory and an outer
carbon steel casingO
Char and limestone from line 24 enter fast fluidized-bed combus-
tor 28 (Figo 4)9 where combustion of the char takes placeO Combustor 28
comprises concentric tubes 100 and 102~ which form the main body of the
combustor and define both annular burner zone 104 between the tubes and
inner chamber 106 within tube 1020 Combustor base 108, mounted on struts
105~ has hollow conical portion 109 projecting upward into chamber 1067 a
tapered annulus 106a thereby being defined be~een tube 102 and conical
portion lO9o Annulus 104 is divided into a lower fast fluidized bed ash-
agglomerating combustion zone at 2000F. and an upper fast fluidized beddesulfurizing zone at 1570F. by air entering manifold 113 and through
circumferential slot 115 into annular zone 1040 Deflector rings ll9a and
ll9b prevent solids backflow and assist in defining the two zonesO Tube
102 is spaced above base 108 to define, at the bottom of combustor 28~ zone
107~ which connects ~one 104 with annulus 106a and chamber 106. Circular
char inlet manifold 110 connects l;ne 24 to burner zone 104 by eighteen
tubes 111 fitted through holes in the walls of tube 100 and spaced circum
ferentially thereabout. Air inlet 112 connects line 30 with circular mani-
fold 114~ located within conical portion 109 near its bottom~ and manifold
114 in turn is connècted by twenty-four circumferentially spaced ejector
-- 10 _
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~76~Z
tubes 116 to zone 107, ejcctor tubes 116 being fitted through holes in
conical portion 1090 Also fitted through conical portion lOg is ash outlet
pipe 117, which connects annular zone 106a near the top of conical portion
109 with standpipe 400 Flue 118 connects chamber 106 with line 34. Connect-
ing burner zone 10~ and chamber 106 at the top of combustor 28 is vaned
separator 120, which has twelve equally spaced (75) vanes 121 (Figo 5).
Combustor cover 122 overlies separator 120 and tube 102, connected at its
top to separator 120~
Combustor 28 is 17 feet 8 inches higho Tube 100 has an outer
steel casing (1/4 inch thick)~ which surrounds a 3 inch thick castable
refractory3 which in turn surrounds a 3/4 inch refractory-filled hexagonal
steel honeycombO Tube 102 is composed of an outer wall of 3/4 inch refrac-
tory-filled hexagonal steel honeycomb and an inner wall of the same 3/4
inch refractoryO ~etween the inner and outer honeycombs is 3/16 inch thick
steel tube running the length of tube 102 and welded to the honeycombs on
6 inch centersO Slot 115 is 3/16 inch.
In operation~ preheating of combustor 28 is accomplished~ as above
described9 with preheated air entering through inlet 112 to bring combustor
28 to 1200Fo Combustion air from blower 32 then directly passes to com-
bustor 28 through inlet 1120 Char and limestone from pyrolyzer 12 and char
cyclone 16~ carried by transport air~ enter manifold 110 from line 24~ and
: are distributed through tubes 111 into the bottom portion of burner zone
1040 Air blown from inlet 112 into manifold 114 distributes through ejector
nozzles 116 into zone 107~ and from there sweeps char and limestone upward
through burner zone 104~ Combustion begins in zone 104, ignited by the heat
of recirculating solidsO Combustion continues in an upward directi~n through
zone 104 in the form of a fast fluidized bed composed of char~ limestone~
and combustion air. The products of combustion move upwards with a super-
ficial velocity of 18 feet per secondO Products of combustion7 excess
oxygen~ and unburned char rise up to separator 120~ which~ in conjunction
~ 11 --
.. . . . .
. . : .
~076~Z2
with chamber 106~ acting as a conventional cyclone separator~ causes the
oncoming mass of solids and gases to swirlO Swirling solids comprising ash~
spent ~imestol-e~ and some unburned char enter chamber 106 and fall along the
:inner walls o.f tube 102 into tapered annulus 106aO The swirling action
assures that only ~ery small particles of ash and still-burning coal can
escape from the burnerO
The ejec-tor action caused by air flow from properly dimensioned
ejector tubes 116 draws some of the first to fall solids out through zone
107 and recirculates them back up through zone 104 for burning of any un-
burned char. In spite of the ejector action~ solids so accumulate in annu-
lus 106a in the form of a slow fluidized bedO Nhen the bed reaches the level
of ash outlet pipe 117~ pipe 11? acts as a weir to draw off the excess solids~
made up of ash and spent limestone, and carry them down to standpipe 40;
from there the solids go to line 44~ and finally are flushed out by trans-
port air~ to an ash hopper (not shown).
The maintenance of a stoichiometric excess of air in combustor .
28 holds combustor temperature at 1570F.~ which is the temperature at which
desulfurification by limestone occurs with the least use of the sorbent~
Yet it is desirable to operate a portion of the annulus 104 at a higher
temperature~ 2000Fo~ in order to maximize the agglomeration of fine
flyash particlesO It becomes desirable to operate burner 28 with two
temperature zones~ the lower zone at the higher temperatureO
me two zones are created by placement of a fluid-dynamic check :
valve~ placed in the middle of annulus 10~. The opposing rings forming the
check valve retard slippage of solids by mechanically blocking their flow.
~he check flow action is enhanced by the introduction of the air stream
through slot 115~ which air is also used to cool the gases from the optimum .
ash-agglomerating temperature (2000Fo) to the optimum desulfurification
temperature (1570 F~). me relative amount of air entering through air
inlet 112 and slot 115 is controlled by two temperature sensors~-one in each
'
: - 12 _
,
~.~7~22
annular fast fluidized bed zone; a sensor in the lower zone regulates air
through air inlet 112 to fix lower zone temperature at 2000Fo~ and a sensor
in the upper zone regl~ates air througll slot 115 to maintain the proper
upper zone temperatureO
Similar to char cyclone 16 is ash cyclone 36~ two of which connec~
ted in parallel I use in ny presently preferred embodimentO Ash cyclone
36isa quite standard cyclone separator proportioned for highly efficient
particle removala and is composed of generally the same materials for
refractory and casing as is cyclone 160 Cyclone 36 is 15 feet 10 inches high~
and has a tangential inlet on its side near the top. Upper and lower outlet
configurations are substantially the same as in cyclone 160 In operation~
hot gases from combustor 28 having an inlet velocity of ~5 feet per second
enter through the tangential inletO Ash and spent limestone are centrifu-
gally whirled~ fall downward~ and finally pass through the bottom outlet
. connected to line 42 and then to line 44O Transport air flushes these
solid products out through lines 42 and 44O Clean combustion gases (1570Fo)
leave by the top outlet, and pass through line 46 to afterburner 200
Receiving clean combustible gases from char cyclone 16 through
line 18 and clean combustion gases as well as nitrogen and remaining oxygen
from ash cyclones 36 -through line 46 is afterburner 20 (Figo 6)o Gases from
: line 46 pass axially into cylindrical afterburner 20 through inlet 130n
Gases from line 18 under press~e enter tangentially through inlet 132 into
annular chamber 134~ from which they are uniformly introduced radially into
the flow of gases from inlet 130 for eYen mixing thereof by distributor 136,
a ring having a series of circumferential ports 136a fitted within after-
burner 20 downstream of inlet 130 and concentrically within annular chamber
1340 In operation~ gases from inlets 130 and 132 are hot enough to initiate
combustion in combustion chamber 138 between the combustible gases from
inlet 132 and the unconsumed oxygen from inlet 1300
The afterburner 20 discharges directly into a furnace (not shown)~
- 13 _
1~76422
through a 24 inch ~iameter openingO Afterburner 20 is fitted into a hole
in the furnace wall, by attaching flange 142 to the furnace casing. In this
configuration~ combustion chamber 138 is 4 feet long. Alternatively~ a
flange 142a may be attached to the afterburner as sho~n, and attached to the
Eurnacc~ In the latter case~ the afterburner casing downstream of flange
L42a is removed. In this configuration, combustion chamber 138 is 1015 feet
longO With the collfiguration of flange 142~ combustion is essentially
completed within the afterburnerO ~ith the configuration of flange 142a,
combustion is completed within the furnace. The former configuration may
improve the completeness of combustion, particularly with boilers and other
furnaces where the walls are relatively cold. The latter configuration is
more compact and is cheaper to buildo
~n element used in start-up~ as described above7 is preheater 150
(Figo 7)3 two of one size being used for pyrolyzer 12 and char cyclone 16
and a larger one being used for combustor 28. For each start-up in which
preheating is required, blower 32 blows air (60 Fo) into each preheater 150
through inlet 1520 The air passes into vaned chamber 154~ where it separ-
ates, part flowing axia~Ly through center conduit 156, and part being swirled
outwardly through vanes 155 (approximately 45) into the annuLar spaced
surrounding chamber 154 and then into combustion chamber 158. Natural gas
is admitted through inlet 160 into manifold 162, and issues therefrom into the
annuLar space space surrounding chamber 154, thereby mixing with the swirl-
ing air and burning upon ignition initially by a spark plug (not shown)
located in chamber 1580 Air passing through conduit 156 is swirled by
vortex generator 164, and~ upon leaving conduit 156~ mixes with the gases
passing through chamber 158, which are products of combustionO
~he air passing through vanes 155 is the primary air, and is
approximately the amount required for complete combustion of the gas~ The
air entering through duct 156 is the secondary air~ and is used to cool the
products of combustion to the temperature needed to preheatO ~ithout this
~764;~2
cooling air~ products of combustion leaving the burner 150 would be too hot~
causing structural damage to the piping of lines 109 14~ and 30. ~irflow
through tube 156 a]so cools the tube7 and prevents structural damage that
would otherwLse occur due to the heating by hot gases in combustion zone 1580
Cond~it 156 and chamber 158 are made of stainless steelO The smaller version
of preheater 150 i9 17 inches longO Natural gas flow into inlet 160 iY 200
standard cfh~ and airflow into inlet 152 is 7200 standard cfh for pyrolyzer
12 and 4800 standard cfh for char cyclone 160 The larger version of pre-
heater 150, for combustor 28~ is 42 inches long. Natural gas flow into
inlet 160 is 1000 standard cfh~ and airflow into inlet 152 is 36~000 stand-
ard cfho The heated air passes from outlets 166~ and enters pyrolyzer 12
char cyclone 16, and fluid bed combustor 28 in their usual air entrancesO
~ inally~ there is shown in Figo 8 a burner station such as could
be used in a factory or power plant. Preheaters 150 are not shown in this
figure. ~ compressor 31 is shown adjacent blower 32~ The various elements
are mounted on foundations 6 and 8 ~braces and other supports not shown). A
system of valves (not shown) can be used to coordinate coal~ limestone7 air~
and water feeds for the station, an operator at a central control panel
(not shown~ effectively running the burnerO Hoppers to store powdered coal~
ash~ and limestone are not shownO
_ 15 -
