US1786887A - Method and apparatus for burning pulverized fuel - Google Patents

Description

Den. 30, 1930. v v J. E. BELL; Y 1,785,837

METHOD AND APPARATUS FR BURNING PULVERIZED-FUEL ml'ed April 13, 1922 3 sheets-sheet 1.

I VEN TOR J. E. BELL. 1,786,887

METHODVANDAPPARATUS FOR BURNING PULVERIZED FUEL Dec. 30,1930.

Filed April 15, 1922 3. sheds-sheet 2 1N VENTOR TToRNE YS //f//f Hummm@ I? Y '2%- y mmnmmn gb Y Mmmm@ l METHOD AND APPARATUS FOR URNING PULVERIZED FUEL Filed April 15, 1922 3 Sheetlssheet A3 ,/f I y "Q WITNESS AATTORNE Y Patented* Dec. 30, 1930 UNITED STATES PATENT ori-ICE .JOHN E. BELL, OF

BROOKLYN, NEW YORK, ASSIGNOR TO, COMBUSTION ENGINEERING CORPORATION, A CORPORATION OF YORK METHOD AND APPARATUS FOR `BURN ING PULVERIZED FUEL Application led April 13,

o This invention relates to a method of and apparatus for burning pulverized fueland vit is especially useful in stationary boilers for the generation of'steam. f

One of the primary objects of my invention is ,to secure more efficient andmore perfect combustion. Y Another object is to more effectively utilize the space of the combustion chamber for combustion purposes.

More specifically stated, my invention contemplates the admission of the fuel in such manner that ignition of some'of the fuel takes place very quickly after introduction, thereby holding the iiame near the burner mecha# nism. It also` contemplates ignition taking place over an extended area whereby a maximum portion of the space ofthe combustion chamber is filled with fiame and utilized for combustion purposes; and whereby, among other things, the process vof complete combustion is expedited,vor, stated in another way, whereby a given amount of pulveriz'ed fuel can be burned ina combustion chamber of smaller size.` x

'25 The foregoing, together withosuch other objects or advantages as may hereinafter appear or are incident to my invention, I obtain by means of a process and apparatus illustrated in preferred form in the accomao'panying drawings, wherein:

Fig. 1 is a section through a combustion chamber .of a Water tube boiler of the hori-y zontal type and illustrates one form of my invention; Fig. 2 is a similar section show'- ing another form of my invention; Fig. 3 1s an enlarged end elevation of one form of burner mechanism which may be utilized in lcarrying out my invention; Fig. 4 is an elevation of the burner of Fig. `3; Fig. 5 1s a section through the burner taken on the line 5-5 of Fig. 4; Fig. 6 is a section through the burner taken on the line 6-6 of Fig. 5; Fig.

" 7 is a bottom plan view of the burner of Fig.

6; Fig. 8 is a fragmentary section of another form of burner; and Fig. 9 is a bottom/ plan of the burner of Fig. 8. Y

Heretofore, in the artof burning pulverl ized fuel iii-.stationary boilers, it has been V customary to admitthe fuel either by means 50 of vroundlburners or at burners-sometimes 1922. Serial N0, 552,258.

calledfish-tail burners-and ignition of the fuel, assumino that the furnace has been in operation and is hot, takes place at a well defined point, the distance between the burner and the point ofignition depending upon the velocity at which the fuel, or a mixture of the fuel and air, was admitted. By this arrangement, among other things, it was not possible to hold the flames very closely to the burner, and thus it was not possible to utilize a maximuml portion of the available space of the combustion chamber for combustion purposes.

In accordance with my invention, I propose, inter alia, to admit fuel to different portions of the combustion chamber, at relatively dierent velocities, so that eddying and ignition will take place at relatively earlier or later stages, making it possible to more eifectively utilize the available space fon combustion and to spread or diffuse the ames more nearly throughout the combustion. chamber, and to hold them up vtoward the burner. ing the desired result may be employedbut in the present instance I have shown a single' burner mechanism, constructed yso as t0A de# liver the fuel in the manner herein described.

Referring now to Figs. 1 and 2, the combustion chamber A is roughly rectangular in vertical and horizontal sections; has an outlet 7 in the upper part thereof for the hot products of combustiomthe evaporating Isurfaces, in this instance water tubes 8,-extending over such outlet; 'and is provided with a battery of auxiliary air inlets 9 extending through the front Wall 10 and arranged in horizontal rows, the number of inlets and rows of inlets being dependent upon the size of the particular furnace. These air inlets are damper controlled. In thet bottom of the combustion chamber there is a door 11 for the removal of ash. In the embodiment shown the fuel is preferably delivered into the upper portion of the combustion chamber in a ldownward direction by burners B, the number of which depends upon the horizontal length of the combustion chamber. These burners are adapted to deliver either `the pulverized coal'or a mixture of Various ways of accomplishpulverized coal and air-preferably the latter-and their construction will nowy be described.

Each burner comprises a casing 1Q., open at the bottom and provided with an air inlet 13v on one side near the top. This casing is divided into two compartments 14 and 15 (see Fig. 5) by a division Wall or septum 16, such wall preferably terminating a short distance above the bottom of the casing. The passage 14 is controlled by a damper 17 operated `by the gearing 18, shown in Fig. 3. The burner nozzle 19depends from the upper ends of the casing and extends down into the compartment 15, 'the lower end of the nozzle terminating a short distance (above the lower end of the division wall 16. The nozzle changes from a round section at the top to an elongated narrow section at the bottom, thus being somewhat similar to the fish-tail type. The flow of air induced by the draft-which is preferably created by a stack, not shown-'through the inlet 13 and down through the passage 15, on either side of the nozzle 19, is controlled by means of dampers 2O and 21, out so as to surround the nozzle when closed, as indicated in Fig.l 5. The dampers are operated by gearing 18, as before. A mixture of fuel and air is supplied to the nozzles by means of pipes 22, leading to a suitable source of supply, the amount of velocity of the air being preferably in the neighborhood of that required for carrying purposes from the feeders to the burners. The burner mechanism in all of the forms of my inventionldisclosed is the same, with the exception of the mouth of the nozzle.

These nozzles have been made with the area substantially constant throughout, that is to say, the change in cross section from a circle at the topto a long slot at the bott-om, has been graduated so as to secure a substantially constant area throughout. In a nozzle of this character, the fuel or mixture of fuel,

and air will pass therethrough in a substantially stream line, and as a consequence, since the friction is less, the eddying at the surfaces of the column of fuel delivered is not pronounced, so that the coal does not ignite so readily and neither does the column expand materially in cross section before substantial gasification takes place.

By experimentation I have found that by properly flaring the mouth of the nozzle, with anozzle duct of sufcient length, that a column of fuel will be delivered having the following characteristics: The central portion of such a column will retain its relatively high velocity and its stream line flow characteristic for a longerperiod of time and will, therefore, penetrate more deeply into the combustion chamber before ignition takes place and eddying is set up; While the outer portions of the column will diverge somewhat sharply from the central portion and'wll travel at a portions of relatively lower velocity, with the result that in such portions of the column the stream line flow characteristic is lost much sooner, eddying is quickly set up, and ignition takes place more promptly. As a result, ignition, instead of taking place at a localized point, takes place over an extended area and the flame is held well up toward the burners and is diffused throughout a greater proportion of the combustion chamber. IThis, in addition to reducing the length of travel from the burners necessary to complete combustion, also secures more rapid and more perfect combustion by reason of the fact that there is a greater diffusion and also a greater surface exposure of the fuel particles `and the gases liberated, making 'it more certain that the particles of coaland gases are surrounded and mixed in with oxygen bearing air, 1n-

duced through the burners und through the' inlets 9. The induced air travels at a lower velocity than the incoming fuel, so thatv the particles of the latter are, `in afsense, projected through slower moving bodies of air with the result that as combustion is initiated in the particles, the latter are scoured andthe gases emanating therefrom are removed from the surfaces of the coal particles in the process, thereby ensuring exposure of not only the coal but the gas molecules to fresh air. In this -latter connection, 'attention is directed to the fact that the incoming stream of fuel is surrounded by air induced through `the passage 15, and additional air is supplied through the passage 14 to the space between the descending and the nascending supplied through the inlets 9 carries the additional oxygen ne ded for completion of combustion.

The air induced through the inlets 9, par ticularly the lower inlets, follows, to some extent, the general stream line fiow of the fuel and flame stream providing a bordering stream of air into which the heavier unconsumed or partially consumed particles of fuel may gravitate and there find the oxygen needed for the completion of combustion. At the same time a body of cool air is ensured in the bottom of the combustion chamber, of sufficient depth to cool the precipitating -ash below substantial slag forming temperature lation of the dampers 17, 20 and'21 themo-l mentum of the streams of air drawn through the passages 14 and 15 can be regulated so as not only to provide proper amountsl of 'air immediately around the incoming lfuel, but also to prevent unconsumed fuel and-gases the flame stream, while the air Maase? being drawn immediately around the inner end of thel top wall 23 into the evaporating surfaces. By proper manipulation of the dampers, the momentum of the air passing3 A tions on the inside are more pronounced than they vare onV the outside of the nozzle. These serrated forms are preferred for the following reasons: T he stream, where it issues from the straight portions of the nozzle mouth, retains substantially all of its high velocity and has very little diverging tendency and delivers the fuel to ,the lowest part of the furnace. The center of the stream issuing from the flaring parts of the nozzle mouth retains some of its high velocity and carries the fuel down into the combustion chamber but not as far as the stream issuing from the intermediate straight parts, and there is a more marked tendency to diverge. rlhe outer portions of the stream issuing from the flaring portions, travel at stilllower velocity and diverge rather. sharply. Thus, diierent portions of the column of fuel, considered as a whole, travel at 'dierent relative velocities, retain their stream line Sow characteristics relatively more or relatively less and eddy more or less freely, as the case may be. In consequence, as point-ed out, ignition is more widely spread, the ames more widely diftional area of the delivery orice of the pipe being greater than the cross-sectional area of the pipe at the region Where the flaring begins.

2. The method of 'delivering a mixture of pulverized fuel and air to a combustion chamber which consists in causing the mixture to move in a stream circular in cross section, in gradually changing the stream in cross-section from circular to a thin. wide sheet of approximately the samearea in cross-section, and then in causing the' sheet to 'expand at a multiplicity of spaced points along its Wide dimension and delivering it int/o the chamber.

ln testimony whereof, I have hereunto signed my name.

JOHN E. BELL.

fused and combustion more rapid and perfect.

ln a sense, therefore, the serrated nozzle has the eiectof a group ofsmallnozzles having alternately straight and flaring discharge ends; and in addition to the advantages previously noted, the process of combustion is hastened, because the central portion of the fuel stream is projected a substantial distance through a slower moving body of iame, to the heat of which it is subjected.

l claim: 1

l. powdered fuel burner comprising a nozzle pipe having a fuel inlet end and a fuel delivery end, said pipe being approximately circular-.in cross section at its inlet end and being gradually attened and widened out from the ,inlet end to the fuel delivery end to provide a wide thin delivery slot .at said deliver end, the wall of-the pipe at the tip of t e delivery end being flared outwardly at a multiplicity of spaced pointsv along the longfdimension of the delivery end, so that the delivery orice in face view presents a plurality of s aced narrow 'portiils with Y intermediate ared, portions9 the ciloss-see vse

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