US1656991A - Apparatus for burning of powdered fuel - Google Patents

Description

Cil

YPatented Jan. 24, 1928.

4vUNITED STATES PATE CARL SCHWARTZ, F NEW ROCHELLE, NEW YORK, ASSIGNOR TO INTERNATIONAL COMBUSTION ENGINEERING CORPORATION, A CORPORATION OF DELAWARE.

`.APPARAUIUS FOR BURNING OF IPOWDERED FUEL.

Application filed January 8, 1924. Serial No. 684,940.

My invention relates to the burning of fuel in suspension, such as pulverized or powdered coal, and even oil, and to furnaces therefor. I aim to provide, in a novel way,

against troublesome slag formation or deposits on the furnace bottom; 'to render means of obviating such deposits that have heretofore been employed more effective and to protect such means from injury by overu heating; and, also, to improve the conditions of combustion and increase the fuel-burning capacity. I have discovered that material improvement in these respects can be achieved by suitable introduction or injec- 5 tion of a cooling medium in the lower region of a furnace of the character above indicated. A

For the sake of greater clearness, I have hereinafter explained my invention in con- 0 nection with an illustrative form of powdered fuel furnace provided with threefold means for obviating slagging difficulties such as above indicated, including one embodiment of my present invention. It Will bey understood, however, that the invention itself is not limited to this particular appli-- cation and embodiment, but can be carried out and applied in various other ways.

In the drawing, Fig. 1 shows a vertical section through a steam'boilcr furnace such as just indicated.

Fig. 2 shows a fragmentary cross section through the furnace combustion chamber, taken as indicated by the line 2 2 in Fic.

As shown in F ig. l, the furnace combustion chamber 5 is a large, deep, unobstructed chamber inclosed by upright Walls that slope outward slightly, so that the chamber as a -whole expands uoward. It has an outlet l0 for products of combustion from its upper region, at the rear. For reasons that will hereinafter appear, .the chamber 5 may preferably be somewhat deeper, proportionately, than in present practice, so as to realize fully the possible advantages of mv invention and to assure complete combustion therein. One or more powdered fuel burners 1l are directed downward into the combustion snare orchamber 5 near its front wall 12, through the roof 13, As shown, such a burner l1 comprises an inner fuel pipe or nozzle with circumjacent damper-controlled air intakes. Powdered fuel with somewhat more than carrying air say or ltijb of the tti-tal yair required for 'proper combustion, mere or less) is fed in or admitted through the burner ll, and is continually igniteifl by the heat of 'the front wall. 19. and of the furnace generally. Air additional to that entering vat the burner 1l is (or may be) supplied tion of refuse from the fuel thereon in trou` blesome forms.

The air thus admitted at the intakes 14 may even be suthcient to form and maintain a cooling zone in the lower region 15 of the chamber 5. i

ln the present instance, there is also a water screen consisting of a series or baul; of water tubes 1G. extending VEfore and aft" across the chamber 5 at a suitable height above the furnace loor l?, and sloping opposilely in alternation. As shown, the front ends of 'the oppositcly sloping tubes 1G are interconnected by a common header 1S, and their rear ends are connected into separate headers 19, 1t). These headers 19, 19 are connected into the general circulation of the boiler 2() by means of piping or lubing Q1, 2Q, so that the water makes a forward pass through the lower screen tubes 16 and returns' rearward thru the upper ones.

(llore and elsewhere, I have used the terms o frontf and rear in reference to the regions where the furnace is fired and whence the products of combustion make their exit from the main combustion chainber 5, respectively.) The water screen 16 is adapted (in conjunction with air admitted at the intakes l-l and as hereinafter described, or even by itself) to maintain a cooling zone in the lower region 15 of the cham ber 5.

Asthus far described, the furnace illus- Vtinted is already known in the art. its op erario-u is, briellv, as follows:

l`he burning stream from the burner 11 (compri-"ng mingled air, powdered fuel. ':oiubustible from the fuel, and prodnets of combustion) descends in the front of Jhe chamber 5 until its momentum is overcome by the upward draft through` the boiler loo llO

- surfaces.

9.0. It then bends upward and ascends through. the rear of the chamber 5, and the products of combustion finally pass upward through the outlet 10 to the boiler` heating (The course of the flames is about as indicated by the dash lines.) The size and depth of the chamber u', the eontiguity of the downward and upward air and fuel streams, their change of direction as described, and the other conditions in the chamber assure rapid and complete Combustion of stream-line character therein. High temperatures are developed, and large amountsl 't 'fuel can be burned rapidljy7 and elliciently.

The relatively heavy incombustible residue from the fuel falling toward the floor 17 in a finely divided, molten state encounters and passes through the cooling zone in the lower region 1 5 of the chamber 5. In this cooling zone 15 (however it be maintained), the falling refuse particles are etteetually cooled below fusion or slagorniing teniperature, so that. they do not run together or eoalesce into a solid mass on the floor 17, out simply collect as dust that can easily be sucked out (or otherwise removed) at cleanout doors E23. lVhen utilized, the Water' a furnace, I make provision 4for introducing a cooling agent or fluid into its lower region 15, Where the cooling, zone is ordinarily maintained as described above. As one means of doing this, I have shown a screenlilre series of perforated pipes or duets S25 extending across the lower region 15 of the chamber 5, in the present instance below and approximately paralleling the Water-screen tubes 16 with which this particular furnace is provided. The ends et the ducts 251 are connected into front and rear headers 2G, 2T that have valve-Controlled supply conneclion.:I 2S. 29 for Cooling fluid. Preferably, the discharge holes lill are in the rounded bottoms of the duets 25, about at a l5@ position. so as to be protected. against clogging up by the 'failing reiuse particles. and to direct the fluid diagonally downvard toward the llooi' 1T. The duets may he el castiron, it preferred. and may he cast with ilat upper surfaces that will accumulate a proi tectivt covering of deposit. or support a ret'i-actory cover of lireh 'ich or the like. Through the ducts Q5 or other suitable means, the coolinfir fluid can he continually introduced in the Aorrn of a substantially (or more or less nearly) horizontal blanket, atanif rate of input desired.

Such introduction of cooling; fluid perfor-nis several functions. In the first place,

'ployeth as hereinafter explained.

it is a means ol n'mint'ainingjr the cooling Zone al: 1:3 to prevent slugging on the lui-nace floor 1T, and ol' suiiplcnientinlgir other means .such as described above in maintaining thc desired low temperature of this zone. l rery clieetual tor preventingr enel-michalent o' the superjacent llanie stri-:nu ou the de sii'ed cooling,r zone, and as a means el regulating and varying the "thune levcVl in the chamber ic---espcifia]lj,v when a cooliner lluid that does not support combustion is ein- In this, u'aterscreen-equipped l'urnaee. in the second place, it is also a means nl.' protecting the screen tulle.` against blistering, hy tempering the heat when the lfurnace is beingr l"forcefh in order to carriv a heavy overload. (Huch blisteringv is due to the friet that under extreme heat the tubesl are partly filled with slcani and thereby thern'io-nsulated troni the cooling4 action of the "vf-.iter in rhein.) It may also tend to lteep the llames from eenling' in contact with the Lubes ol the water screen when the lurnaee operatinpl at very high ratings. In the third place, when the coolingl fluid introduced is el' suit able clau-after, it is a nieans olf supporting the combustion of the iuel and may laire the place ot at least soule ot' the inlets ll.

Frein every point ol' 1rien', thisn continual and definite suppl;v ot' cooling fluid at the critical louer region l5 is of advantage in oliviating` the tendency that would otherwise exist; l'or this region to heeoine a Inere. dead pocket of hot air and `gas. low down, underneath the Water screen 1G here employed, tends to ineke it the more el`- 'lectivo in everlyY wam-besides insurirnbr its contact with the screen as it rises therethrough.

'l'lio character ot the cooling,l lluid to be preferred naturally depends on Ihe elliect particularly desired. It the cooling inediuln is lo pla)r an important part in combustion ot the l'ncl ar: well as hare the other leatui-em el' :olianlaga then a cool supporter ot combustion will he used, suoli :is cold air from out ot' doors' blown through the pipo 2f). Il' maintenance o1' the coeliiug zone, prevention ot flame encroaeluuent, and protection ol the water-screen, are the real need, and it is not desired to atleet the combustion to any gri-eat extent, then an inert niediuni nia)y be prel'erred, such as water, steam ot low pressure and temperature sup-V plied troni any suitable source through the pipe QS. or llue gases similarly supplied.- i. e., products ol combustion that have been sullieiently cooled l'or nu' purpose by contact with boiler tubes, or 4with other heatabsorbing agencies. Such may be taken troni the stack or chimney ol a power plant, 'from uptaltes or lues leading to the stack, or even from sonic, point within a boiler itself Where the gases have become lt is Its iiitroduetioir lill lll)

llo

lill

sudiciently' cool. Under some conditions, where intermediate or combined effects are wanted, air and an inert medium may be supplied together through one of the pipes Q8 or 29: e. g., in such proportionsthat the initial mixture itseltl Will not support combustion, and that its air Will become effective for that purpo-'e only after mingling with the superjaceiit flame stream, Where the inert medium will become too small a proportion ot' the whole to inhibit combustion any longer. i

The quantity ol cooling tluid to be'introduced at l5 will depend both on its character and on the other conditions. If it be wholly inert, the desired flame level and the amount of anti-slagging and protective cooling required will govern. As to air (with or without a' mingled inert medium), the amount will largely depend. on the extent to which it may be admitted at the burner l1 or at the front intakes ll,-siiice any excess over what is necessary to secure proper combustion reduces eiiiciency. Moreover, the admissionot fluid at l5 tends to raise the flame level, and in the ci ot air, to lengthen the llame; so that even though the coiiibustion chamber 5 bc extra deep (as meuf tioned above)4 to allow for such effects to a reasonable extent, admission at 15 ot' an excessive proportion of the total air is liable to bring the llame stream amongst the boiler tubes before combustion is complete, thus lowering eiliciency and producing troublesonie deposits ot refuse onfthe tubes.

lt will' thus be seen that the air (or other cooling medium) may be. employed Fii'narily tor the protection of a Water Srreen, or as an adjunct cooperating with the screen to create a cooling zone, or as a means ior creating the zone.

l claim:

l. The combination oi a pulverizod fuel combustion chamber' with 'a watcrscreen in its lower region tor maii'itenance ol u cooling;- Zone icr falling refuse from fue] burned ihereabove, so :is to prevent slugging of' suc-li rei'use; and n'ieanslor discharging a iluid blanket in said lower region., to aid in maintaining` the cooling,` zone.

2. The combination ot a pulverized fuel combustion chamber with a waterscreen in its lower region for maintenance of a cooliiigr zone for fallingr refuse from fuel burned thereabove' so as to prevent slagginrf of such refuse; and means for discharcgingiA a horizontal air blanket underneath said screen.

3. The combination oi a piilrerized fuel combustion chamber with. a Waterscreen in its lower region for maintenance of a cool ing zone for falling refuse from fuel burned thereabove, so as to prevent slagging of such refuse; and ducts under said screen i'or discharging cooling fluid tlierebencath,. to aid in maintaining the cooling zone and to rise to and protect the screen.

,4. The combination of a pulverized fuel combustion chamber with a screen ot' water tubes across its lower region for maintaining therein a ooolin zone for fallingl refuse from fuel burne thereabove, and a series ot ducts substantially below the screen tubes, :tor discharging cooling luid in sait zone. l

5. The combination of a pulverized fuel combustion chamber with a screen ot watertubes across its lower region for maintaining therein a cooling zone for falling refuse from fuel burned thereabove, and a series of air ducts below and substantially paralleling the screen tubes, and discharging cooling tluid downward toward the bottom of the furnace.

6. A. furnace of the character described comprising a combustion chamber with outlet for products of combustion from its upper region, means for admitting;- a downn xviii-d stream ol fuel and air for combustion :it one side of the chamber, to descendburning therein until its momentum is overcome by the draft and then rise to said outlet, and a water screen in its lower region to maintain a cooling; one for falling refuse ,from fuel burned thereabove, so as to prevent slagging ot such refuse; and means for dischurging` coolingA `fluid in said lower' region, to aid in maintaining the low temperature of the cooiii'ig zone and 'protect the screen from the superjaecnt llame stream. 7. A furnace of the character described comprisingl` a combustion chamber with outlet for products oill combustion from its upper region, means lor admitting a downward stream oij fuel and air for combustion at one side oi" the chamber, to descend burning therein until its momentum is overcome by the draft and then rise to said outlet-7 and a Water screen in its lower region Ito maintain a cooling Zone ior 'fallingr refuse 'from fuel burned thereaboi'c, so as to prevent slagging o' such refuse; and means for discharginu` a horizontal -blanket of vcool air. underneath said screen. v

In testimony whereof, l have hereunto si ned my name.

CARL SCHlVARTZ.

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