US1708862A - Apparatus for burning fuel - Google Patents

Description

April 9, 1929. J. E. BELL APPARATUS FOR I BURNING FUEL Filed Sept 16. 1922 3 Sheets-Sheet April 9, 1929.. J. E. BELL APPARATUS FoR BURNING FUEL Filed Sept. s, 1922 3 Sheets-Sheet 2 A in 9, 1929.

J. E. BELL APPARATUS FOR BURNING FUEL 5 Sheets-Sheet Filed Sept. 15, 1922 ,I Iz' Patentec Apr. 9, 1929.

UNITED STATES ,-7os,s6z PATENT OFFICE. i

JOHN E. B-ELL', 'BROOKLYN, NEW YORK, AS SIGNOB TO COMBUSTION ENGINEERING i CORPORATION, A CORI'OBATION OF NEW YORK.

.APPARATUS FOR BURNING FUEL.

Application filed September 16, 1922. Serial No. 588,564.

This application relates to 'an apparatus for burning fuels and it is especially useful in connection with stationary boilers burning pulverized fuel.

One of the primary objects of my invention is to protect the vertical walls of the furiace from erosion.

Another object of the invention has to do with the protection of the walls (and also the bottom) and the prevention of formation of slag withoutuselessly lowering furnace temperatures. V

Still another object-of the invention is the provision of a furnace in which steam is very efliciently generated. y

More specifically stated, my invention has to do with the provision of an improved arrangement of cooling screens for furnace combustion chambers.

The foregoing, together with such other objects as may hereinafter appear, or are incident to my invention, I obtain by means of a Construction which I have illustrated in referred rform in the accompanying draw- 2 ngs, wherein:

Fig. 1 is a section through a stationary boiler and conbustion chamber therefor 'embodying my improvements; Fig. 2 is a front elevation of Fig. 1, Fig. 1 being taken on'th'e line 1-1' of Fig.`2; Fig. 3 is a section taken on the line 3-3 of Fig. 1; and Fig. 4 is a, section taken on the line 4:--4 of Fig. 1.

The boiler is preferably of the type having a drum 7 connected by pipes 8 to a downcomer header 9 from which tubes 10 lead to an upcomer header 11 which in turn is connected withthe drum 7 by means of tubes or pipes 12. The tubes of the boiler eXtend over the outlet opening 13 in the upper' part 40 of the combustion chamber A. fa u The pulverized coal 'or -a mixture of pulverizecl coal and air is admitted into an upper part of the combustion chamber by means of one or more burners B located so as to discharge the fuel ina downward direction adjacent the front wall 14 of the combustion chamber. The fuel and fiame stream, under the action of the draft, take a U-shaped course through the combustion chamber toward the 4 outlet 13, the size of the combustion chamber being such that combustion is completed therein.

` About ten percent of the air needed for combustion is supplied through the burner mechanism and the balance of the -air required for combustion is supplied through the auxiliary air inlets 15, of which there are a battery in the front wall 14, and throu h the inlets 16 located in the side walls of t e combustion chamber adjacent the front wall p and through which air is induced into the chamber from the channel 17 in the side walls. The air induced through the inlets 16 is thus preheated and the side walls are cooled by the absorption of heat, while the air induced through the inlets 15 is of" atmospheric temperature. i

Since the coal is delivered in a downward direction, usually with carrying air, it enters at a velocity greater than the velocity of the ar induc'ed by the draft through the inlets 15 and 16 and the incoming coalis, therefore, projccted through or past slower moving bodies of air. This sets up some measure of eddying very promptly, thus ensuring rela- 75 tively prompt ignition, and in addition the particles of fuel are continually being brought into contact with fresh air' and the gases 'emanating from the, `particles are stripped therefrom exposing fresh surfaces. Furthermore, by virtue of the difference in temperature and also-By' virtue of the force etfect of the downcomig stream or streams of coal,

a portion of the air admitted'through the in lets, particularly the lower inlets, takes a stream-line course bordering the fuel and flame stream on the convex side thereof, pro u viding a body of air into which the heaver gravitating particles of fuel will find their way and there be supplied with oxygen needed go ably damper controlled if desired.

In -the bottom of thecombustion chamber I provide a water screen C composed of a plurality of rearwardly and upwardly inclined tubes 17, the forward ends ofwhich are confor their combustion. The inlets may be suit- 'nected to a header 18 located in advance of the front wall 14, the rear ends of the tubes being connected to a header 19 just back of the bridge wall 20. The header 18 is connected by a plurality of pipes 21 to individual anchored boxes 22 which in turn are connected by a plu- 'rality of pipes 23 to the downcomer header 9 through the medium of the header 24:. The number of pipes 21 and 23 may be variedas the particular installation requires. The manner in which the header 19 is connected into the circulationof the boiler will be later described. i 4 The tubes 17 are spaced suflioiently far 1'10 apart to pel-mit the refuse matter gravitating 'out of the fuel and flame stream to deposit on the floor 25 of the combustion chamber, the function of the screen being to absorb radiant heat from the deposit so as to maintain the temperature thereof below the fusion or slagging point in order that the deposit may remain in the form of an ash which is readily renovable through the cleanout doors. The screen is also utilized for generating steam as it will be' apparent that the water eirculating through the screen will be subject to great eat. e

Immediately in front of the bridge wall 20 is another water screen D, composed of a plurality of substantially vertically disposed pipes 26 connected at their lower ends with the header 19 and at their upper ends with the header 27, just to the rear of the bridge wall. The upper ends of the pipes 26 are bent and extend through the bridge wall for connection with such header. The header 27 is connected by a plurality of pipes 28 to the upcemer header 11, such pipes 28 also extending along the inner face of the upper portion 20' of the bridge wall, so that such pipes are also in the nature of a screen, serving to absorb radiant heat from the bridge wall and from the deposit thereon. V

The side walls 29 of the combustion chamber are also provided with cooling screens E, such screens comprising a plurality of pipes 29 the lower ends of which are bent and passed throu 'h the side'walls for connection with a header 30, the header 30 being in turn connected to the header 18 by means of the pipes 31. The upper ends of the pipes 29 are similarly bent so as to' extend through the side wall for connection witlra header 32. such header being connected to the header 34: by means of pi es 33. The header 34: is connected to drun i by means of pipes 35.

It will be seen from the foregoing that the screen C, the screen E, the screen D and the pipes 28 are all connected in the circulation of the boiler. The function of the screens D and E and pipes 28 is to protect the vertical walls of the combustion chamber .against erosion by absorbing radiant heat from the deposit so that such deposit will not be turned to slag. The deposit is generally in the form of "whiskers' which will break oflz' by reason of their own weight if fusion is prevented Where-slag is formed on th`e side walls, the surface of the brick is washcd away as the slag runs down, which, of course, involves naintenancecharges and other losses incident to shut down, etc'. There may be some deposit on the tubes'of the various screens, but this is relatively slight because of the small area and rounded sui-faces presented. The deposit.

builds up slightly and then runs ofl", the drippings being in the form of nodules which are solidified or cooled by the action of the screens, remaining in nodule form so that their removal presents no difliculty. The screens D and E are located in the zone of highest temperature and are, therefo'e, subject to the greatest heat and they add very naterially to the efiieiency of the boiler in the generation of steam, the contents of the boiler being turned over very rapidly. The chamber A, is, therefore, in eiect, a combined conbustion and boiler space in which provision is made for the abstraction of heat at zones of very high temperature.

In this connection, it will be noted that while the efi'ect of the screens is, of course, to lower temperature, nevertheless, this is brought about by the useful absorption of heat and is, therefore, eflicient. Heretofo'e, in some installations it has been the practice to prevent slag formation by adnitting excess quantities of air, i. e., a material excess over and' above that which is required for the combustion of the coal, but this results ina useless lowering of the furnace temperature and an increase in the Volume of gases to be handled, a method of operation which imposed practical linitations on the eflieiency and CO obtained. According to my invention, I preferably propose to adnit only the 'amount of air that is necessary for securing combu'stion of the coal.

It will be observed that the screens D and E 'present practically no obstruction to the flow of the fuel and flane stream and they pernit of the fuel being fed at a higher rate without danger of forceful impingement of the .flame on the vertical walls because the chilling efi'ect of the tubes in the absorption of hcat prevents or limits flame travel or rather flame spread laterally. The flames nay oecasionally lick the tubes or travel losely adjacent thereto just as in the case with the tubes of the screens C. These latter tubes, while not presenting a Physical barrier to the downward progress of the flame, nevertheless impose a practical limit to the downward travel thereof by virtue of their absorption of heat. The tubes of the screens D and E and pipes 28 may function in less degree in this respect because of their closcr proximity to the walls, but they, nevertheless, serve to limit or define the zone of c'onbustion and measurably prevent contact of the flames on the walls. a

The front wall is protected by virtue of the admission of air therethrough and through the inlets 16 which provide, as previously pointed out, a bordering stream of air on the -convex side of the fuel and flame stream.

At least a portion of the air adnitted through the inlet 16 is drawn along the surface of the side walls by the action of the draft and other forces so thatit is ordinarily unnecessary to carry the screens E further e tion may be said to take place in a zone, the cross sectional dimensions ot which are all less than the corresponding cross sectional dimensions of the combustion chamber, and the vertical dimensions ot' which are less than the distance between the bottom of the conbustion chamher 25 and the tubes 10. The boiler may thus be 'forced to a greater degree without. the liability of torcible impingement upon refraetories and the formation of slag, eombustion being still completed within the eonbustion chanber andno uneonsumed products being earried into the tubes 10 of the boiler.

Other advantages Will occur to those skilled in the art.

"What I claim is:

'1. lu a t'urnace, a conl'ustion ehamber; a hoiler having' a downeoner and an upcomer header; a water screen in the bottom ot the chamber exposed to radiant heat and conprising tubes and-a pair of headers exterior ol" the ehauber with which the tubes are connected; means *for conneeting one of said headers with the downcomer header; a sec-` ond water screen'along the bridge wall exposed to radiant heat and connected with the other of said headers; a header with which the tubes of the second screen are connected; and a' plurality of tubes exposed to radiant heat and extending along the bridge wall for 4 connecting said last header With the upcomer header.

burning boiler furnace, means for admitting the fuel to be burned in suspension therein, a row ot' tubes below and margnal of the zone of combustion and inclined somewhat from` the horizontal, a .header at the upper end of said tubes, a -row comprisinga multiplicity of exposedupright tubes extending over an up'right wall of the'furnace and directly connected to the said header, downcomer means not exposed to high heat leading from the boiler to the lower end of said first mentioned row of tubes, and means connecting the upper end of the row of upright tubes to. 'the boiler.

l. In combination, in a finely divided fuel burning boilerfurnace, a refraetory combustion chamber provided with an outlet, a boiler subject to the outlet flow, burner means at the front wall of the ehamber, a row comtubes into the cireulation of the boiler.

5. In combination, in a finely dividedfuel burning;` furnace, a combustion chaniber, means for admitting fuel to be burned in space therein, a boiler served thereby, a row eomprisin: a 'ultiplicity of relativelj" closely spaced inclined, highly heat absorbing tubes in the bottom of the chamber, a header for the upper end of the tubes of said row, a row compnising a multiplicity of relatzively elosely spaced, highl heat absorbiug tubes in said chamber at a side thereof and rising f mn said header, the upper end ot said last n'eutioned tubes being., connected with a boiler :tor cireulation purposes, and downeoner meansiron the boiler not exposed to high heat. t'or supplying said first mentioned inelined tubes with water.

(l. The coinbinationof a pnlverized fnel frnace with a supcrjacent Watertube boiler, spaced watertubes in the' furnace combustion chamber to obviate slarging, and circulatorv connections from the boiler to the ends of said tubes, including anfupflow pipo, a header at the upper end of said pipo, and horizontal return' tubes ext'ending from said header to the downflow end of the boiler.

7. The combination with a furnace and tubular boiler having a steam and water drum, of means for introducing i'uel to be burned in space in thefurnace, a cooling screen comprising a row of spaced tubes within the furnace, a downcomer for the screen connected to water sp'ace of the boiler, a header for the screen', an upeomer from said header, asecond header,connected to said upcomer, and a plurality of tubes leading from said second header to the drum.

8. In combination with a steam boiler having a steain and water drum, a turnace chamber, a plurality of water tubes arranged in said chan'ber so a to receive hoat therefrom, downtake' and uptake connections between said tubes and boiler, said up'take connection conprising a conduit outside the boiler setting, and a plurality of vertically spaced 4 tubulzr elements lying, in more than one vertical plane connecting said Conduit and 'said drum, at least the topmost one of said elements enter-ing the drum above the. normal water level therein.

In testimony whereot, 1 have hereunto signed my name.

JOHN E. BELL.

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