US2511588A - Method and means for accelerating the ignition of pulverized fuel - Google Patents

Description

June 13, 195$ G. P. JACKSON 2,511,538

METHOD AND MEANS FOR ACCELERATING THE IGNITION OF PULVERIZED FUEL Filed May 24, 1946 2 Sheets-Sheet 1 INVENTOR. GEORGE P. J19 CIISON June 13, 1950 G. P. JACKSON 2,511,588

METHOD AND MEANS FOR ACCELERATING THE IGNITION 0F PULVERIZED FUEL Filed May 24, 1946 2 Sheets-Sheet 2 I INVENTOR. GEORGE R Jflc/rso/v Patented June 13, 1950 UNI-TED F I'CE 2,511,5ss- I min-H01) manners im THE IGNITION or PUILYEIFIZWlTFUE'L George 1?. Jackson, Flushing; Nult, [by

mesne assignments, to Gombusti'on iEngineering-Superheater, 1110., a eorpomtionnf Delaware Application May fi; 1946, No; 2,136

This invention relates tb thecombustien of fuels and particularly burning fuels that are dinic'ult to ignite, as low volatile coals:

When burning low volatile fuels carried into a -furnace suspendedrin astream of air-it i'srcus tomary to increase the ratio of fuel to so esto obtain a relatively rich mixture. This has been done because it has been found that the speed of flame propagation: is slower .for low volatile for high fvolatilefuels and that a material reduction in the air marrying the 101w volatile fuels speeds the burning rate 'oithe.

fuel. The reduced amount ofearrying air slowswhen burning certain low 'volatueanthraeites because the primary air needsto he-"reaueedth an amount whieh ap roaches-hr may ev'en m less than that required icr satisi-adtery eperation of the mill for grinding the iuei' wi'th 'ithe' result th-at "the air swept through the mill is ii-rsufilcient to satisfaeterily can? ofithe fuel.

On the other hand the amount of primary alrrequired for directly delivering low 'volaiti-le' fuels from mills-"may be too much for satisfactory ignition of the fuel. One "methet'l -i'inlfile'yed when using an amount of 'air' above the limits coal mixture, between the mill and the learner, into two portions, one portion loihgrelativel? rich in "fuel and. the other relatively peer; Elie rich portion is delivered to the burner anaihto the furnace and the poor portion to a separate nozzle which directs it into the furnace to mix with the rich fuel stream at a location where the fuel portion has attained satisfactory lgm tic-n. To accomplish this separation requires special separating apparatus between the will and burner or separating means within the burner. v

"It is an object of this invention to over 'e the above difficulties by providing means and a 'novel method for burning low- "infla tile fuels. 1

In the drawings:

Figure '1 is a vertical 'cross sebum 3 Glaimsr (Cl. lib--28) g theifairnacehf a steam generator embodying the invention.

Figure 2 is a fragmentary sectional elevation chr-anremarged-scaleshowing the burners of Fig. land zignition eu' ding auxiliary air nozzles therefomrloeated in a wall z-adjacent to that of the n3 is, a diagrammatic View illustrating thel relaticnrzbetween the fuel and auxiliary air streams in FigHr-e a superheater I51: Pnlverized'fuel is delivered to the furnac'e bhrnugh'am offset arch [6 by means burners-ill; There are usually a multiplicity burners in ahnement. The fuel A flows wl'iilelburning within the furnace anclias theafuelegasmix'ture approaches the bott'omit make-ant "tinn at bend i8 and rises up threughjthe furnace to pass thereafter through the screenrtubes I9, thesup'erheater'ilfi, convection 'banlcilaranxi econcmizer I4 to olftake -20.

I11 o'riler to induce a crossfiow of hot gases ast the 'iuel stream-s iA-Iat their points of enwanee into the rurhaee, auseismade of auxiliary nozzles 2| placed in the front wall-2'5 Just below esshownin Figsrl and 2, so-a's to fiiheat :j e'ts o'f :nuidiB at substanti'ally right angles toth'e fclets'ofifrueliA :from burners lLzand between the burners as iihdieated in Fig. 3. whese 21 preferably project their fluid at a higher velocity than that of the entering tuelstreams and for this purpose they may satisfa'o'terily receive air under pressure from any suitable souhce suchas an air "duct 22 through al mpriate cohneetions (not 'show n) therewith. The hur ners 1 1. mayhave' the usual secondary air channels 23 (see Fig. 2) surrounding the primary air and-' iuel *nezzles '22 which secondary air enamels may receive "theirair from duct 22 threugh a uamper-centreueu connection 25.. In the frbhtwall fi "of 'furnac'e I'll there may be auditienm hue-teal (see Fig; 1) for the ur ose of admitting additional air for combustion as the-fuel streams A pass downwardly past them.

Proieeting through the rear wall 28 of furnace Iiiare nozzles- 29 {for-directing further air into the r-urnaee receive their air direct from dill-5t Y i I 7 i hayeifmindithat by arranging the-air nozzles zil"atisubstantially rightangles to and generally ihwbetween' the burner-"nozzles 24 as represented by Figs. 1-2-3, and. that if the air streamsB tween the fuel streams A and the front wall 26.

As shown by the arrows in the Figure 1, thisup ward flow C comprises burningf'fuel' removed, I from the outer layers of the fuel streams A and may include some of the air issuing fromtheupper air ducts 21 adjacent the front wall. Not only a is this burning fuel and gas C taken-'fromithefuel tream extremely hot but the air joining it also becomes extremely hot f rom, heating in the furnace and by participating in combustion;

Thus, as the mixture ofthe two passes between 7 the adjacent fuel jets A below the arch [6 it adds a substantial "amount of heat to the entering. fuel jets A thereby accelerating the rate of.igni-' tion of 'the' fuel. i

- I have found that in burning low'volatilefuels such as anthracite'coal it is difficult to main-. tain ignition at some'distance from the burner, even with a low quantity of primary air, .without the use of the air through air nozzles 2|. When injecting airthrough'the nozzles 2| at a relatively high velocity and creating. said crosscurrents of burning-fuel between the jets Aissuing from the 5 fuel burned nozzles 24, ignition occurs closely adjacent the fuel nozzles 24 and it is ossible to substantially increase the amount of primary 'air." With the use of. the high; velocity jets B throughair nozzles-2| itis possible to increase the amount of primary air entering the furnace with the fuel to the quantitynecessary for successful removal of the pulverized fuel from the mill.- In this manner, the fuel may;-

be delivered directly from mill to burner andzit becomes unnecessary to employ separating means in the 'conduit'betWeen-the mill and the burners or in the burners in order to reduce the quantity of primaryair to enrich the fuel mixture issuing from theburners and'then injecting the separated coal air mixture atother points into the furnace.

Obviously the high velocity air jets B may be produced by means ofsteam jets placed within the air nozzles 2|. to give the air the required velocity. Or, steam jets alone, may be used to induce the flow of gases past the entering jets of fuel. I The nozzles 29 projecting through the rear wall 28 of the furnace deliver jets of air at relatively A preferred form of burner nozzle is one that causes the primary air and fuel stream to issue therefrom with its outer surfaces in a turbulent state. The advantage of this condition is that the turbulent fuel of the outer surfaces of the fuel stream nearest the front wall 26 of the furnace will more easily commingle with the air entering from ducts 21 through the front wall 3-26 and will more quickly burn to furnish heat for igniting the incoming fuel as described above.

In the form illustrated this surface turbulence is accomplished by introducing into the burner 1: nozzle 24-a.restriction 3| (see Fig. 2) forming a .sharp edged orifice 32. Preferably the bottom of the'nozzle 24, beyond orifice 32, with respect to the fuel flow will have its sides 33 flared as 4 shown.

high velocities which act to cause a turbulence in the rising burning fuel-gas stream and thereby increase the rate at which the remaining fuel particles burn. 1 .5

By means of the high velocity air jets B issuing transversely to the fuel streams A as herein disclosed I am able to induce. hot currents C of burning fuel and gas to flow past the fuel jets issuing from the burners ,to cause ignition to occur substantially at the burner nozzle, thereby, more effectively utilizingthe entire furnace volume.. By means of the high velocity air jets D issuing through the rear toward the front wall, I am able to cause greater turbulence and thereby more rapid combustion and to control the flow path of the fuel-gas mixture through the furnace, both of which actions further aiding in more effectively utilizing theentire furnace volume. a j I t- While I have shown and described a preferred embodiment of my invention with a vertical type of burner, it will be understood that the invention' may be adapted to the horizontal and other types of burners without-departing from the spirit 'andscope of the invention as claimed.

' This application is a continuation-in-part of United States application Serial No. 624,899, filed October 26, 1945. u

What'I claim is:

1. In a furnace having a row of spaced burners for'projecting streams of a fuel and air mixture in a" downward direction into the furnace and in spaced relation to a furnace sidewall that runs generally parallel to the burner row; nozzles located in said side-wall of the furnace and mounted in spacedrelationin the intervals berect heating-to those air-fuel streams and thereby duced at a given velocity; burning the fuel so in-i troduced in a flame; delivering into the furnace atone sideof said fuel-laden primary air stream a supplemental stream of further air which has avelocity substantially higher than the primary streams said given velocity;- and directing said supplemental air stream past; said one side of the enteringprimary stream adjacent and generally transversely thereto so as to produce, due to the supplemental streams higher velocity and the relative direction of the two streams, an entrainingqaction which induces from the surface of a burning portion of the primary fuel-air stream a current ofthatstreams burning fuel-air mixtureand which causes said current of the aforesaidhot mixture to flow transversely past a colder portion of. the-.gincoming primary stream of air and fuel .adlaent its point of delivery into the furnace, the aforesaid transverse flow of said not ignition of said fuel and accompanying intensification of said flame. I ,J 3. In a method of burning fuel in a furnaceand 5 accelerating the ignition of that fuel, the steps which comprise delivering said fuel into the furnace in flotation in a stream of primary air introduced downwardly at a given velocity; burning the fuel so introduced in a stream; delivering va supplemental stream of further air substantially horizontally into the furnace at one side of said fuel-laden primary air stream and at a velocity substantially higher than the primary streams said given velocity; and directing said supplemental stream past said one side of the entering primary stream adjacent and generally transversely thereto but in out of contact spacing therefrom so as to produce, due to the supplemental streams higher velocity and the relative direction of the two streams, an entraining ,action which induces from the surface of the burning primary fuel-air stream a current of that streams burning fuel-air mixture and which causes said current of the aforesaid hot mixture to flow transversely past a colder portion of said incoming primary fuel-air stream with resultant acceleration in the ignition of said fuel and accompanying intensification of said flame.

GEORGE P. JACKSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 111,288 Whelpley et al Jan. 24, 1871 812,193 Eldred Feb. 13, 1906 1,149,734 Coutant Aug. 10, 1915 i0 1,258,654 Gram Mar. 12, 1918 1,441,721 Caracriste Jan. 9, 1923 1,670,276 Worthington May 15, 1928 1,738,636 Caracristi Dec. 10, 1929 1,754,277 Lundgren Apr. 15, 1930 15 1,866,404 Frisch et'al. July 5, 1932 2,293,736 Heller Aug. 25, 1942 2,293,737 Hardgrove Aug. 25, 1942 FOREIGN PATENTS Number Country Date 331,555 Great Britain July 4, 1930

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