CA1086146A - Direct ignition of pulverized coal - Google Patents

Direct ignition of pulverized coal

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Publication number
CA1086146A
CA1086146A CA297,168A CA297168A CA1086146A CA 1086146 A CA1086146 A CA 1086146A CA 297168 A CA297168 A CA 297168A CA 1086146 A CA1086146 A CA 1086146A
Authority
CA
Canada
Prior art keywords
air
coal
fuel stream
combustion zone
ignition
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA297,168A
Other languages
French (fr)
Inventor
Martin E. Smirlock
Donald A. Smith
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Combustion Engineering Inc
Original Assignee
Combustion Engineering Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Combustion Engineering Inc filed Critical Combustion Engineering Inc
Application granted granted Critical
Publication of CA1086146A publication Critical patent/CA1086146A/en
Expired legal-status Critical Current

Links

Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23KFEEDING FUEL TO COMBUSTION APPARATUS
    • F23K1/00Preparation of lump or pulverulent fuel in readiness for delivery to combustion apparatus
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23DBURNERS
    • F23D1/00Burners for combustion of pulverulent fuel
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23KFEEDING FUEL TO COMBUSTION APPARATUS
    • F23K3/00Feeding or distributing of lump or pulverulent fuel to combustion apparatus
    • F23K3/02Pneumatic feeding arrangements, i.e. by air blast
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23DBURNERS
    • F23D2207/00Ignition devices associated with burner

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)

Abstract

Abstract of the Disclosure Pulverized coal is ignited, to furnish energy for warm-up or low load operation of a coal burning furnace, by a technique which does not require the combustion of significant quantities of liquid or gaseous fuels. The direct ignition of pulverized coal in accordance with the present invention contemplates the delivery of a dense phase coal/air stream to an ignition zone where it receives ignition energy and the thus ignited mixture is thereafter contained in a recirculation region until the flame becomes self-sustaining.

Description

Back~xound o~ -the Invention (1) Field o the Invention The present invention relates to burners designed for the combustion of pulverized coal and particularly to such burners as may be utilized in coal-Eired boilers of steam generators. More speci~ically, t~is invention is directed to a method for ~gniting pulverized coal in the absence of a substantial energy input derived from the combustion of a liquid or gaseous fuel. Accordingly, the general objects of the present invention are to provide novel and improved apparatus and method~ of such character.
(2~ Descr~ption of the Prior Art Because of cost and availability, it is becoming increasingly desirable to utilize coal rather than natural gas or oil in electricity generating facilities. However, present day coal-fired steam generator boilers of the types employed by electric utilities nevertheless require substantial quantities of natural gas or oil. Restated, in ordex to insure safe and ef~icient operation, present coal-fired steam generators use premium liquid and gaseous fuels to provide both ignition and low-load ~lame-stabilizing energy. The required amount of these auxiliary premium ~uels is signi~icant. For example, the use of 70,aoo. gallons of oil in a 500 megawatt unit for one start-up is not uncommon. AccordinglY, a need exists for a means of reducing the amount o~ auxiliary fuels needed in pulverized-coal boilers.
_ mmary of the Invention The present invention overcomes the above-discussed and other deficiencies and disadvantages of the prior art by providing for the direct ignition o~ a stream o~ pulverized coal
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and air suppli~d to a buxner.
In accordance with one broad aspect, the invention resides in a method of caus~ng ignition and sustaining combustion of pulverized coal in a comBustion zone comprising the steps of:
introducing into the com~ustion zone a fuel stream consisting essentially o~ a mixture of coal particles and air, the fuel stream h~ving an air-to-coal weight ratio below approximately Q.5; causing a recixculation zone to occur in the combustion zone; operating an ignitor in the recirculation zone in order lQ to ignite the coal; and establish.ing a flow of secondary air coaxial with the fuel stream subsequent to ignition of the coal, the secondary aix supplying oxygen to support combustion.
In the interest of insuring ignition, in addition to exercising control over the air~to-coal weight ratio upstream of the combusti.on cham~er, the velocity of the coal/air mixture will be varied in accordance wi,th the volatiles content and grind of the coal; the. coal~air mixture in~ecti.on velocity being less th,an 150 ft.~sec. and preferably in the range of 60-75 '~, ft./sec. In some cases, the initiation of the secondary air 2~ flow which. causes the recirculation of the hot combustion products- back to the coal~air ïnjecti.~n poïnt will'be delayed; :' this.bei.ng particularly true in the case of hi.gh energy arc ~gnition. Furthe'x in accordance with the invention, the secondar~ ai.r contributes as little as 15~ of the stoichiometric combusti,on air. ~.:
In another broad aspect, the inYention resi.des in apparatus for cauaing ignition and sustaining combustion of pulveri2ed coal in a combustion zone comprising: means for providing a fuel stream consi.sting essentially of a mixture of coal and air having an air-to-coal weight ratio ~elow . :: .

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~6~6 approximately ~.S; means fo~ delivering -the fuel stream into a combustion zone, said delivering means produc.ing in khe combustion zone a fuel stream having an axial re~ion comprised of air and relatively ~ine coal particles; means for inter-mittently providing ignit~on energy in the co~bustion zone, said ignition energy provi~ding means compri~i.ng an electric ignition energy source having a spark gap positioned in said combustion zone in said fuel stream axial region; means for generating a flo~ of secondar~ air in the combustion zone and generally 1~ coaxi,al with the fueI stream; and means for sensing the presence of flame i.n the com~ust~on'zone ~hereby the ~lo~ of secondary air may ~e delayed unti.l aubsequent to the. sensi.ng o~ flame.
~rief Desc:r:iption of the Dra~ing The present invention may ~e better understood and its numerous objects and advantages will become apparent to those skilled in the art by reference to the accompanying drawing wherein like reference numerals refer to like elements in the several figures and in whi.ch:
FIGURE 1 i~ a cross-sectional view of an arc-ignited pulverized coal burner whi`.ch may be employed in th.e practice of the present invention;
FIGURE 2 is a cross-sectional vi.ew of a pulverized coal feed system whi:ch may be associated with the burner of FIGURE l;

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FIGURE 3 is a front elevation view oF the feeder system of FIGURE 2;
FIGURE 4 is a cross-sectional view of a main coal burner which employs the burner of FIGURE 1 as an igniter; and FIGURE 5 is a diagramatic representation of a coal supply system for the igniter and burner of FIGURE 4.
Description of the Preferred Embodiment -The apparatus shown in the accompanying drawing constitutes a representative means for accomplishing the direct igni~ion of a stream of pulverized coal and air in accordance with the invention and without any significant consumption of petroleum or natural gas. The present invention relies on having a dense phase coal/air mixture wherein the transport-air stream-to-coal weight ratio, measured in a delivery conduit upstream of a combustion zone, is 1.0 or less. The ignition energy source is positioned ~;~
so as to be either in or insertable in the flowing air/coal stream in the combustion zone. The energy delivered to the air/coal mixture by the ignition energy source ignites the coal particles. Considering the case where the ignition energy source comprises a high energy electric arc, the ;~
ignitor thus being operated in a pulsed mode, a series of flame pockets are created.
The technique of the present invention also contemplates the establishment of secondary air flow to the combustion zone through burner ~ ~' secondary-air registers. The burner secondary-air registers are designed, in a manner known in the art, so as to establish a region of recirculatin~q~
air and combustion products (hot gases) whereby the pockets of burning coal are recirculated back toward the point of in;tial coal injection and the energy in the recirculation region will increase until th flame becomes self-sustaining.
The technique of the present inven~ion has been successfully practiced employing a high energy electric arc as the ignition energy source.

However, the ignition energy source may also be a resistance heater or heaters or a hydrocarbon fueled pilot torch with minimal energy consump-tion. In a preferred embodiment, the ignitor will be removed fro~ the flame region once the existence of flame has been verified. When a high energy arc supplies the ignition energy, secondary air flow will be delayed until the existence of flame has been verified.
With reference to FIGURE 1, a burner in accordance with a first embodiment of the present invention is shown. A coal pipe 16 is employed to convey coal pneumatically to the ignition zone in the burner. Accord-ingly, as the apparatus is shown in FIGURE 1, the left end o~ coal pipe16 is in communication with the coal feeder of FIGURES 2 and 3 while the right end of coal pipe 16 terminates at a hollow-cone diffuser which is mounted from coa1 pipe 16 by means of supports 21. An ignitor will be positioned immediately downstream o~ the discharge end of coal pipe 16.
In the disclosed embodiment of -the invention the ignitor, which is indicated at 23, enters through the side of the burner and comprises a high-energy arc ignitor similar to the type presently used for igniting oil. It is to be noted that any ignition source which imparts sufficient energy to heat the reactants enough to ignite them may be used. Accordingly, a resistance heater or small pilot torch fueled by natural gas could be employed in place of the high energy arc ignitor. The high energy arc ignitor is, however, preferred because of its rel;ability and controlla-bility. Ignitor 23, as shown in FIGURE 1, w;ll typ;cally be retractably mounted so that it can be removed from the combustion zone into a protective area after the coal has been ignited.
The burner also includes a secondary air supply conduit 20 which is coaxial with coal pipe 16. Conduit 20 communicates with an air chamber 14 which will typically be cylindrical chamber somewhat larger in diameter than that of conduit 20. Air chamber 14 contains a plurality of ~-vanes 12. Vanes 12 are arranged to impart a swirl to air entering conduit 20 from chanlber 14~ An air inlet d~lct 10 leads to air chamber 14 from a pressurized air supply, not shown. Air con~ui-t 20 termirlates in a refractory lined quarrel 24 which de~ines a divergent nozzle. In one reduction to practice of the invention coal pipe 16 had a one inch inner diameter, conduit 20 had a six inch inner diameter and quarrel 24 had a thirteen inch diameter at its open end and an angle of divergence of 35.
FIGURES 2 and 3, which wi11 discussed simultaneously, show a pulverized-coal feed system for supplying a coal-air mixture to the coal pipe or fuel conduit 16. The feed system consists of a pulverized coal hopper 40 that can be supplied by any of a number oF means known in the art. Preferably, hopper 40 should be sized to store sufficient pulverized coal to supply the burner throughout the warm-up period of the furnace in which the burner is to be used. Hopper 40 communicates with gravimeteric feeder 43. Feeder 43 consists of a variable-speed feed device 42, a weight-sensitive conveyor 44 and appropriate control circuitry, not shown.
The speed of rotation of variable-speed feeder 42 determines the amount of coal allowed to drop onto weight-sensitive conveyor 44, and the weight sensed by weight-sensitive conveyor 44 controls the speed of this rotation.
Gravimetric feeder 43 introduces coal into a rotary air-lock feeder 46 at a constant rate.
Rotary air-lock feeder 46 is a cylindrical chamber with blades 47 that approach an air-tight fit with the chamber. At the bottom of the chamber are entrance opening 48 and exit opening 49. The fit of blades 47;
is such that there is almost no free air path between openings 48 or 49 and feeder 43. Accordingly, it is possible for an air stream entering opening 48 to continue out through opening 49 without being deflected into gravimetric feeder 43. The rotation of blades 47 carries pulverized coal dropped onto blades 47 by gravimetric feeder 43 into the air path between ~ ~ ;openings 48 and 49. Compressed air is supplied to feeder 46 by an appro-priate source 50 at a controlled rate whereby a coal-air mixture measured - . , ~ . . .
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in conduit 16 h~s an air-to-coal weiyht ratio of 1~0 or less and preferably 0.5 or less.
In one reduction to practice of the invention, ;n wh;ch subb;-tum;nous C rank coal that had been pulverized to 70 percent minus 200 mesh was employed, the upper limit on air-to coal weight ratio was 1Ø
The optimum air-to-coal weight ra-tio will vary with coal type.
In order to operate the burner of Figure 1, ignitor 23 is moved to its inserted position and turned on. Employing an arc ignitor, sparks produced by the ignitor having an energy contact of approximately 25 joules, lasting about 10 microseconds each, and having a repetition rate of 10 Hertz have been successfully employed. Compressnr 50 is turned on once the ignitor has begun operation, and gravimetr;c feeder 43 is also started. The compressed air flowing through rotary-air-lock feeder 46 entrains measured amounts of pulverized coal and carries it through conduit 16 and hollow-cone diffuser 22. While it is possible to operate the burner of Figure 1 without hollow-cone diffuser 22, it is considered desirable to include diffuser 22 in order to introduce a minor amount of recirculation during the ignition stage of operation. The coal-air mixture brought into the vicinity of ignitor 23 is ignited by the energy imparted by the ignitor and the resultant flame propagates through the coal. As a result, ignition occurs, and a relatively unsteady flame exists at the outlet of the burner.
At this point, an observer 26 or an automatic flame-detection system determines that ignition has occurred and causes a secondary air (ambient or heated) flow through air inlet duct 10. Vanes 12 introduce a rotation into the air flow, and this results in a spiraling, or swirling, stream of air that flows down conduit 20 and through quarrel 24. Quarrel 24 is a divergent nozzle that enhances the recirculating effect that naturally -occurs due to the vortical flow of air. The swirling stream of air envelops the combustion zone, and as a result the hot combustion products are drawn -back into the region of fresh coal injection. The observable effect of .. .

this recirculation is that the flame becomes steady, and the stability of the flame is such that ignitor 23 can be turned off and withdrawn.
Thus retracted, ignitor 23 remains in a protective area, thereby prevent-ing damage to the ignitor due to the in-tense heat of combustion.
It is thought that the direct ignition of pulverized coal provided by the present invention is su~cessful because it provides appropriate conditions for propagation of flame within the flowing coal stream after the ignitor has caused ignition of some of the coal partic1es;
above approximately a 1.0 air-to-coal weight ratio, propagation of the flame is difficult with unheated air, and direct ignition of pulverized coal by an arc ignitor accordingly does not work effectively. On furnace startup~ preheated air is not available and can be produced only through ~;
the expenditure of a significant quant1ty of energy and/or liquid or gaseous fuel. Combined with the provision of proper conditions For propa-gation of the flame is the provision of a recirculation zone that contributes to stability of the resultant coal flame. The recirculation causes hot products to be drawn back into the combustion zone, thereby causing the flame to provide its own ignition energy. Whatever the reasons for its success, however, the present invention does provide a means for satisfactory direct ignition of flowing pulverized coal.
The burner of Figure 1 can be used as a warm-up burner for utility boilers. In utility-boiler operation, it is necessary for the boiler to be brought to an elevated temperature in order for its conven-tional coal burners to work properly. The burners of the present invention can be used to bring the furnace up to a temperature high enough for stable combustion in conventional burners. The present invention can also be used for both ignition and low-load stabilization.
Figure 4 is a side sectional view of a main coal nozzle. The center of the main coal nozzle is occupied by a version of the burner of Figure 1 adapted to use as a center ignitor in a tilting tangential nozzle.

.

Corresponding numbers refer to correspon~ing parts, most of which have already been explained in connection w;th Figure 1. One difference is that quarrel 24 is shown to have a shape in Figure 4 that is somewhat different from its shape in Figure 1. Another difference is that vanes 12 are located within conduit ZO rather than in an air inlet duct.
A main coal pipe 28 is shown coaxial with -the ignitor burner.
Coal and primary air, the air used to dry and convey the pulverized coal, are supplied through main coal pipe 28. Secondary air, the remainder of the air required for combustion, is supplied through a conduit 30 that is concentric with main coal pipe 28. Vanes 38 are positioned at the outlet of conduit 30 and are arranged for tilting so that the air flowing out of conduit 30 may be directed as required. The tilting of vanes 38 would typically be accompanied by the tilting of the ignitor burner, so flexible sections 32, 34, 36 are included in the ignitor burner. In the typical arrangement, vanes 38 and the exit of the ignitor burner would be appro-priately connected so as to tilt together.
In operation, the ignitor burner would be operated as pre-viously explained, and after the ignitor had achieved stable combustion, coal and primary air would be sent to conduit 28, and secondary air would be sent to conduit 30. Ignition would occur due to the presence of the flame from the ignitor burner, and under low-load conditions the stabiliza-tion of the main flame would also be accomplished by the ignitor burner.
Several advantages are inherent in the apparatus of Figure 4 and the method described in using it. In the typical coal nozzle used in a tangentially fired unit, the ignitor is mounted beside the main burner. The apparatus of Figure 4 is an improvement over the typical arrangement because the center position affords greater proximity to the main coal stream, thereby allowing the use of a smaller amount of ignitor energy to produce the sarne effectiveness in igniting the main coal stream.
Another advantage of the Figure 4 arrangement is that the ignitor flame g - .

reaches the coal stream while it is still fuel rich. This is not typically the case when side ignitors are used, and present theory susgests that oxides of nitrogen are less likely -to be produced when a significant amount of combustion occurs in a fuel-rich zone. Test results with the present invention have verified that the center position of the ignitor is environmentally beneficial. A final advantage of the apparatus of Figure 4 is that, since the ignitor uses coal exclusively~ the fuel cost penalty for continuous use no longer exists. Thus, the additional complication of turning the ignitor off after ignition and turning it on again at low loads may be avoided. Furthermore, a single flame-proving device would be adequate, since it is only necessary, if the ignitor is intended to be used continuously, to insure that the ignitor flame is present. No additional flame-proving device need be provided to insure `
that the main flame is present.
Figure 5 schematically depicts a fuel supply system for the ignitor burner and main coal nozzle of Figure 4. Pulverizer 56 is one of the types of coal mills known to the art. Its function is to grind coal for use in pulverized-coal units. It is typical for pulverizers to require hot air for the drying function that is usually carried out in conjunction with the grinding process. The hot air used for this function comes from an air preheater, not shown, that transFers heat from flue gases to air. The resulting hot air is drawn by mill fan 52 through line 51, and it is sent through line 54 to pulverizer 56. The hot air thus blown through the pulverizer dries the coal and entrains pulverized coal in order to convey it out of the pulverizer by way of line 58. ~oal to be pulverized is supplied by means of coal llne 55.
In a cold start-up, the air provided by the air preheater is not at the temperature normally desired for p-lverizer operation. Accord-ingly, a fuel-storage silo is provided. This silo contains enough pulverized coal to supply all the ignitors in the Furnace and one elevation '' ~8~6 of warm-up coal nozzles for aslong as it takes to warm-up the furnace sufficiently to provide hot enough air for the air preheater for proper operation of the pulverizer. Silo 70 accordingly might have a capacity of around 800 tons of pulverized coal. A separator 60 is provided between pulverizer 56 and bin 70. The function of separator 60 is to separate out the air that has entrained the coal in pulverizer 56. The air leaves separator 60 through line 62, and the coal leaves separator 60 through line 6~. Since the air leaving separator 60 is ordinarily not completely free of coal dust, it may not always be desirable to exhaust the separator directly into the boiler. Therefore, appropriate valving may be provided in order to filter the air output of the separator or to add the ou~put of the separator to the main coal feed o~ the boiler. This is illustrated by lines 64 and 66 and valves 63 and 65. Line 64 might be a line to a filter, valve 63 being opened during initial start-up when the main coal feed to -the boiler is not operating, and valve 65 might be open, allowing the air to flow through line 66 to the main coal feed when the main coal feed is operating. ~
Line 72 represents the communication of bin 70 with ignitors ~ -and warnn-up nozzles. Line 72 may, for instance9 be a screw conveyor that supplies coal to a feed system of the type that is illustrated in Figures 2 and 3. Alternately, bin 40 of Figures 2 and 3 could be embodied in bin 70 itself, with feeder 42 being one of several feeders supplied by the same bin. Feed system 76 supplies lines 82, 84, 86, and 88, the feed lines to the ignitors, hy means of line 78 and a riffle distributor 80. Each of the lines 82, 84, 86, and 88 supplies a different level of ignitors.
It may be determined that it is desirable to operate all ignitors whenever the furnace is operating, regardless of whether all elevations of coal nozzles are operating. In such a case, there would be no need to valve any of the lines 82, 84, 86, or 88. Alternately, it could be determined that only those ignitors would be operated that are associated with a coal ::

no~zle that is to be operated. I~ this is the case7 appropriate valving, not shown, would have to be supplied.
In addition to supplying the ignitors, bin 70 would also supply an elevation of warm-up nozzles. Each nozzle would be ignited and ~ -stabili7ed by one of the ignitors fed by line 88. A gravimetric feeder 90 supplied from bin 70 by means of line 72 would supply an exhauster ~, which would force coal and air from the air preheater through line 96 to riffle distributor 98. Riffle distributor 98 supplies each of the warm-up nozzle lines 100, 102, 104, and 106. It would be typical for lines 100, 102, 104, and 106 to be operated together, because they are on khe same elevation. In a typical cold start-up, bin 70 would have been filled with pulverized coal during a previous operation of the boiler. Of course, during the first start up after the unit is built, it would be necessary to ship in enough pulverized coal to fill bin 70 or provide a temporary means of coal drying to allow pulverization. After the first operation of the boiler, however, the silo could always be kept filled by means of the prior operation of the boiler. Feed system 76 would start to operate, sending coal and air mixed accordiny to the present invention to at least the ignitors supplied by line 88, which supplies the ignitors for the warm-up elevation. The ignitors would operate as previously indicated, and an igniting flame would be present at the center of each of the warm-up nozzles. As soon as flame has been proven, feeder 90 and exhauster 94 begin operation, conveying coal and air from bin 70 and the air preheater, respectively, to the warm-up nozzles, where the coal is ignited by the ignitors supplied by line 88. The boiler continues to be operated in this manner, pulverizer 56 and mill fan 52 remaining off, until the boiler has warmed up sufficiently to provide a high enough air temperature at the air-preheater exit. At this point, further elevations in the furnace would typically gegin operation, with the ignitors at each elevation providing ignition and stabilization. Mill fan 52 and pulverizer 56 would also . .

~L~)~3~ 6 begin operation at this time, contro11ed by appropriate sensing devices that monitor the amount of coal stored by silo 70. Thus, the silo is replenished, and enough pu1verized coal is stored to supply the next boiler start-up.
While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it will be understood that the present invention has been described by way of illustration and not limitation.
What is claimed is:
:

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Claims (16)

    THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
    PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
  1. CLAIM 1. A method for causing ignition of pulverized coal in a combustion zone which has not been preheated comprising the steps of:
    providing a source of pulverized coal;
    withdrawing the pulverized coal from the source and entraining the thus withdrawn coal in transport air to form a fuel stream, the air-to-coal weight ratio of the fuel stream being below 0.5;
    delivering the fuel stream to a combustion zone, there being insufficient ignition energy present in the combustion zone to insure ignition of the pulverized coal in the fuel stream;
    discharging the fuel stream into the combustion zone in the form of a diverging stream, the diverging stream having an axial region substantially comprised of air and relatively fine coal particles;
    establishing a series of high energy electric arc discharges in the axial region of the fuel stream in the combustion zone to thereby deliver ignition energy to the coal particles to cause ignition of the pulverized coal;
    verifying the presence of flame in the combustion zone; and establishing a flow of secondary air in the combustion zone and generally coaxial with the fuel stream subsequent to verification of the presence of flame.
  2. CLAIM 2. The method of claim 1 wherein the step of establishing a flow of secondary air comprises:
    directing the secondary air so as to cause recircula-tion of combustion products in the general direction of the point of introduction of the fuel stream into the combustion zone.
  3. CLAIM 3. The method of claim 2 wherein the volume of second-ary air is controlled such that it contributes between 15% and 50% of the stoichiometric combustion air.
  4. CLAIM 4. The method of claim 2 wherein the secondary air is initially at the same temperature as the ambient air.
  5. CLAIM 5. The method of claim 3 wherein the secondary air is initially at the same temperature as the ambient air.
  6. CLAIM 6. The method of claim 1 further comprising the step of:
    terminating the delivery of ignition energy subsequent to establishing the flow of secondary air, the step of terminating the delivery of ignition energy including withdrawal of the means for establishing the arc discharges from the combustion zone.
  7. CLAIM 7. The method of claim 5 further comprising the step of:
    terminating the delivery of ignition energy subsequent to establishing the flow of secondary air, the step of terminating the delivery of ignition energy including withdrawal of the means for establishing the arc discharges from the combustion zone.
  8. CLAIM 8. A method of causing ignition and sustaining combustion of pulverized coal in a combustion zone comprising the steps of:
    introducing into the combustion zone a fuel stream consisting essentially of a mixture of coal particles and air, the fuel stream having an air-to-coal weight ratio below approximately 0.5;
    causing a recirculation zone to occur in the combustion zone;
    operating an ignitor in the recirculation zone in order to ignite the coal; and establishing a flow of secondary air coaxial with the fuel stream subsequent to ignition of the coal, the secondary air supplying oxygen to support combustion.
  9. CLAIM 9. The method of claim 8 wherein the step of operating an ignitor comprises:
    establishing a series of high energy arc discharges.
  10. CLAIM 10. The method of claim 8 wherein the step of introducing the fuel stream into the combustion zone includes:
    causing the fuel stream to become generally divergent with respect to its axis, the recirculation zone in which the ignitor is operated being located at an interior region of the divergent fuel stream.
  11. CLAIM 11. The method of claim 8 wherein the step of establishing a flow of secondary air includes:
    delivering a swirling flow of air initially at the temperature of the ambient air to the combustion zone.
  12. CLAIM 12. The method of claim 11 wherein the step of operating an ignitor comprises:
    establishing a series of high energy arc discharges.
  13. CLAIM 13. The method of claim 12 wherein the step of introducing the fuel stream into the combustion zone includes:
    causing the fuel stream to become generally divergent with respect to its axis, the recirculation zone in which the ignitor is operated being located at an interior region of the divergent fuel stream.
  14. CLAIM 14. Apparatus for causing ignition and sustaining combustion of pulverized coal in a combustion zone comprising:
    means for providing a fuel stream consisting essen-tially of a mixture of coal and air having an air-to-coal weight ratio below approximately 0.5;
    means for delivering the fuel stream into a combustion zone, said delivering means producing in the combustion zone a fuel stream having an axial region comprised of air and relatively fine coal particles;
    means for intermittently providing ignition energy in the combustion zone, said ignition energy providing means comprising an electric ignition energy source having a spark gap positioned in said combustion zone in said fuel stream axial region;
    means for generating a flow of secondary air in the combustion zone and generally coaxial with the fuel stream; and means for sensing the presence of flame in the combustion zone whereby the flow of secondary air may be delayed until subsequent to the sensing of flame.
  15. CLAIM 15. The apparatus of claim 14 wherein said delivering means includes:
    a conduit having a discharge end positioned adjacent the combustion area;
    means for causing the fuel stream to flow through the conduit toward the discharge end thereof; and means for causing the fuel stream discharged from said conduit to diverge whereby a generally conically shaped fuel stream is produced.
  16. CLAIM 16. The apparatus of claim 15 wherein the means for establishing a coaxial flow of secondary air comprises:
    a divergent nozzle positioned so as to encircle the fuel stream in the combustion zone; and means for causing air to flow through said divergent nozzle in order to cause a recirculating flow downstream of the nozzle to thereby direct hot combustion products back into the combustion zone.
CA297,168A 1977-02-18 1978-02-17 Direct ignition of pulverized coal Expired CA1086146A (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US76999577A 1977-02-18 1977-02-18
US769,995 1977-02-18
US86574777A 1977-12-29 1977-12-29
US865,747 1977-12-29

Publications (1)

Publication Number Publication Date
CA1086146A true CA1086146A (en) 1980-09-23

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CA (1) CA1086146A (en)
DE (1) DE2806363C2 (en)
ES (1) ES467075A1 (en)
FI (1) FI62896C (en)
FR (1) FR2381242A1 (en)
GB (1) GB1588078A (en)
IT (1) IT1092756B (en)
NL (1) NL174871C (en)
SE (1) SE433878B (en)

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US4221174A (en) * 1978-05-16 1980-09-09 Combustion Engineering, Inc. Direct ignition of a fluctuating fuel stream
DE2933040C2 (en) * 1979-08-16 1988-12-22 L. & C. Steinmüller GmbH, 5270 Gummersbach Method for igniting a coal dust round burner flame
DE2933060C2 (en) * 1979-08-16 1987-01-22 L. & C. Steinmüller GmbH, 5270 Gummersbach Burners for the combustion of dust-like fuels
DE3031905A1 (en) * 1980-08-23 1982-03-04 L. & C. Steinmüller GmbH, 5270 Gummersbach BURNER SYSTEM
DD153911A1 (en) * 1980-11-12 1982-02-10 Wolfgang Schuster METHOD AND BURNER FOR PRODUCING A ROTATING CARBON FLAME
FR2499681A1 (en) * 1981-02-06 1982-08-13 Stein Industrie DIRECT IGNITION DEVICE FOR POOR PULVERIZED SOLID FUELS IN COLD COMBUSTION CHAMBERS
DE3110284A1 (en) * 1981-03-17 1982-10-07 L. & C. Steinmüller GmbH, 5270 Gummersbach METHOD FOR ENDING A CARBON DUST ROUND BURNER FLAME
DE3238206A1 (en) * 1982-10-15 1984-04-19 Bergwerksverband Gmbh, 4300 Essen IGNITION DEVICE FOR CARBON DUST BURNERS
DE3309905C2 (en) * 1983-01-18 1986-12-04 Stubinen Utveckling AB, Stockholm Method and device for burning solid fuels in powdered form
US4569295A (en) * 1983-01-18 1986-02-11 Stubinen Utveckling Ab Process and a means for burning solid fuels, preferably coal, turf or the like, in pulverized form
DE3325065C2 (en) * 1983-07-12 1986-10-09 L. & C. Steinmüller GmbH, 5270 Gummersbach Process for burning fuel dust
FR2569256B1 (en) * 1984-08-16 1989-04-07 Stein Industrie IGNITION AND COMBUSTION SUPPORT BURNER FOR FULLY SOLID SPRAYED FUEL, AND COMBUSTION CHAMBER COMPRISING SUCH BURNERS
DE3541616A1 (en) * 1985-11-25 1987-05-27 Krupp Polysius Ag Burner for pulverulent fuel
GB2206196A (en) * 1987-06-26 1988-12-29 Air Prod & Chem System for burning pulverised fuel
IT1226691B (en) * 1987-11-27 1991-02-04 Enichem Anic Spa Refuse derived fuel

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US2096945A (en) * 1932-02-15 1937-10-26 Powderco Inc Burner
DE881717C (en) * 1940-03-28 1953-07-02 Steinmueller Gmbh L & C Ignition burner operated with coal dust for coal dust firing

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SE7801871L (en) 1978-08-19
GB1588078A (en) 1981-04-15
FI62896B (en) 1982-11-30
NL174871C (en) 1984-08-16
FR2381242B1 (en) 1983-08-19
IT7820353A0 (en) 1978-02-17
ES467075A1 (en) 1979-08-16
FI780525A (en) 1978-08-19
FR2381242A1 (en) 1978-09-15
DE2806363A1 (en) 1978-08-24
IT1092756B (en) 1985-07-12
AU520507B2 (en) 1982-02-04
AU3362978A (en) 1979-09-06
DE2806363C2 (en) 1985-06-27
FI62896C (en) 1983-03-10
SE433878B (en) 1984-06-18
BR7800999A (en) 1978-12-19
NL7801829A (en) 1978-08-22

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