US2039042A - Burner for anthracite coal - Google Patents

Description

Aymfill m, WW0 E. c. WEBB BURNER FOR ANTHRACITE COAL Filed Oct. 31, 1951 3 Sheets-Sheet 1 E. CANEBB 4 TTURNE NW 2%, WW E C WEBB EMWMM BURNER FOR ANTHRACITE COAL Filed D011. 31, 1951 3 SIIQB'tS-ShQQt 3 filldhiil lt hrnest i3. Webb, l artland, @reg assignnr to llran firen nfactng flopany, Portland,

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plication fl'ctober if, ran. aerial l la. whiff i cams.

This invention relates generally to underfeed stolrers, and particularly to a burner for anthracite coal.

lhe main object of this invention is the con struction of a tuyere that will emciently burn the small sizes of anthracite coal such as rice and buckwheat at a high combustion rate (number of pounds per square ft. of projected grate area) with a minimum amount of hy ash, and in so doing to leave the ash in a loose unclinlrered form so that it will drop freely from the sides of the tuyeres with a minimum amount of clearance between the tuyeres and the inner side of the furnace or boiler.

lhe second object is to provide a tuyere which will satisfactorily burn either buckwheat or rice sizes of anthracite coal without making any changes or adjustments for the difierent sizes, and also that it will be capable of efficient intermittent operation.

The third object is to so construct the tuyere elements that fine particles of coal or ash will not enter the air chamber and also that the construction will be relatively simple d inexpensive to manufacture.

Before entering into an explanation of this device it must be understood that it has long been the common practice to construct tuyere elements through which air could enter a retort from a plenum chamber in which the air was allowed to escape into the retort as best it might through all or a few of many openings, which are usually of considerable number, and this number has been increased'to the utmost in an effort to get air up through the center of the fuel bed. However, due to the small horizontal area of the fuel bed below the combustion zone a relatively small amount of air can be forced through the voids in the fine sizes of coal at this point.

also due to the relatively large port area in many of the present styles of tuyeres the velocity of the air leaving the tuyeres is relatively low and the depth of its penetration into the fuel bed is not definite. With large sizes of coal this type of tuyere will penetrate with fair satisfaction, but with fine sizes of coal, to which this present invention relates, or in the presence of clinkers or semi-fused sections, the original direction of the incoming air is easily deflected since the air naturally talres the course of least resistance, which usually means by-passing a major portion of the fuel bed.

a further disadvantage constantly accompanying wt will be referred to as the large port area Ull. lid-d5) tuyere is that if a small section of the fuel bed temporarily opens up, due to a small clinker llli llfil tion, a large volume of air rushes out of this section due to the fact that practically all of the resistance to the flow of air, namely by the fuel bed, has been removed. Once a hole of this liind opens up it tends to stay open, due to the large volume of air, keeping the fuel blown out or burned out at this point, thereby further reducing the quantity of air delivered to the rest of the fuel bed.

Now if the major portion of the resistance to the ,flow of air is in the tuyere openings then a small change in the fuel bed resistance will have a relatively less eflect on the total resistance, that is, of the tuyere and fuel bed combined, and the fuel bed will burn more uniformly with less fly ash, less clinlrering and less excess air.

The problem then is to so admit the air to the retort, first, that it will have a maxim velocity at its point of entrance; second, that the relation of the resistance to the flow of air through the tuyeres and through the fuel bed be properly maintained; third, the relativepositions of the points of admission; fourth, for the direction of flow of injected air; fifth the general distribution of air, namely a few large openings or many small ones; sixth, the feeding of the fuel upwardly and uniformly over the entire area of the retort, and seventh keeping the tuyere ports open and causing the burning fuels to remain in an unclinhered state until the residue passes over the edge of the retort.

These, and other objects, will become more apparent from the specification following as illustrated in the accompanying drawings, in which:

Fig. l is a vertical section through an anthracite burner equipped with an underfeed fuel supply and a clinker grinding mechanism.

Fig. 2 is a horizontal section along the line f-i in Fig. i.

Fig. 3 is a perspective view of one of the tuyere rings.

Fig. i is an enlarged perspective view of the pads positioned in the spaces between the tuyere rings.

Fig. 5 is an enlarged section along the line ii-b in Fi i.

Fig. 6 is an enlarged section through a retort showing somewhat graphically on one side the relative volumes of air delivered at diderent elevations within the retort and also the relative shapes of the green coal zone, the bng coneand the ash acne.

till

lid

hill

ill

Similar numbers of reference refer similar parts throughout the several views.

Referring in detail to the drawings, there is shown a retort l through which fuel is fed by a feed screw H from a magazine (not shown). The retort I0 is connected to this magazine by means of a fuel teed duct it which passes through the setting l3. Surrounding the upper portion of the retort i is an internal gear it which is supported by a crusher ring 55 which is rotatably mounted within the crusher ring guard is at whose upper edge is secured an ash. seal ring H. A clinker arm 18 is secured to the crusher ring ill by means of the screws it.

Resting on the retort i0 is a retort ring 25 which is provided with an upwardly turned cylindrical wall 2| and an upwardly turned outer edge 22, which edge occupies a groove iii in the crusher ring l5. The ring I5 is attached to the gear H by means of the bolts 24..

The parts M to inclusive belong the ash removing portion of the stoker and the operation thereof is well understood in the art.

Referring more particularly to my invention, which resides in the tuyere elements, it will be noted that upon the wall 2i rests a conical tuyre casing 25 and upon the raised rim ill of the retort ring 20 rests the tuyere bottom ring ill, The inner face 28 is inclined approximately the same as the face 29 and is oil-set slightly therefrom. The bottom ring 21 is held 601303811 trio with relation to the raised rim 25 by means of the downturned edge formed around the outside of the bottom of the ring Zl. The upper edge 3! of the face 28 is raised above the top side 32, and the face 33 o! the raised edge at is inclined approximately at the same angle opposite to the face 28. The corner 3% at the upper end of the face 29 is utilized to produce a cascading effect in the fuel passing upwardly from the retort. The top side 52 has formed thereon a series of raised pads 35, and the intorvening spaces 36, in conjunction with the un der side of the next ring above, form the tuyere outlet ports, the areas and positioning oi. which will he discussed later.

The tuyre second ring 31 is also inclined in shape and is provided with a step 38 similar to the corner 54. The lower side 3d of the secand ring 31 rests upon the top faces of the pads Obviously, the pads could be incorporated on the under side of the ring as well as on the top side of the ring.

It will be noted that the face is ofiZ-set from the face 4i, and that the face H is ofi-set from the face 28. It will also be noted that any air which passes from the plenum chamber through the spaces between the pads 35 will be deflected upwardly, as shown graphically in 6, in which the numbers of lines of arrows correspond approximately to the relative volumes of air passing upwardly through the fuel, and while these arrows are indicated to show relatively straight lines it must be understood that this air will naturally be diffused and mingle with the air from other streams being injected into the fuel from other tuyere rings.

The second ring 31 is also provided with a raised edge 3! and pads 35 upon which rest the tuyeres third ring 42. .This ring is provided with a pair of off-sets 43 similar to the ofl-set 38 and its lower edge rests upon the pads 35 of the second ring 31. The third ring 42 is also provided with a raised edge 3i and pads 35 upon which rest the tmere's fourth ring 46. The

fourth ring 44 is also provided with a raised edge 3i and has a single sloping lacs 45 which slopes somewhat less than does the face 45 of the ring 42. The ring 44 is also provided with pads 35 upon which rests a tuyere top ring 41 whose top face 48 slopes less than does the face t5, and whose side i8 slopes downwardly to the horizontal portion 50 which is also provided with pads 55.

Around the top ring M is placed a retaining ring which rests upon the pads 35 oi the ring 51. flange 52 which is sealed within the recess 53 in the tuyere casing 25.

For the sake of clarifying the explanation the various air outlets will be numbered successively commencing with the bottom 54, 55, 56, 51 and 58 respectively, the first being between the. rings ll and 3'! and the last between the members ti and H.

The operation of the device is as follows: The retort if) having been designed to provide a uniformly upward movement of the fuel from the retort into the tuyre sections it will be assumed that static head is maintained in the plenum chamber considerable in excess of that usually maintained in existing devices, and that the area of the spaces '35 is such that the restriction afforded thereby will permit approximately ten per cent or? all of the air delivered to the combustion tln ough the tuyeres to pass through the outlet lit, and that fifteen per cent of all 01 the air delivered will pass through the outlet 55, and that twenty=five per cent oi the air will pass through each of the three outlets 56, W and 58 respectively.

Now it will be noted in Fig. 6 that there is indicated in dotted linesa triangle whose base 59 is approximately the outlet 55 and whose sides 59 are approximately equal to the length of the 5d. The lines 55 and represent the outlines oil what will be referred to as the cone or ignition. In this same figure there is represented by different cross hatched areas the ashes A, the burning coal l3 and the green coal C, which is well below the line 59, and these coals while warm do not begin to burn until they enter the ignition cone.

it is well understood that there is no sharp line of demsrlration between the zones since the transition not instantaneous but gradual, and the illustration is made merely for the sake of facilitating: the explanation of what transpires and the reasons therefor.

Attention h now drawn to the fact that the outlet is well above the outlet 54; also that the outlet 55 well above the outlet 55 and that each succeeding;- outlet 5? and 58 is definitely spaced above its next lower outlet. The reason for this spacing as follows: If, as is commonly practiced,

the openings are uniformly distributed over the burning face of the tuyres the active burning area is limited to the immediate vicinity of the tuyere face. The finer the coal the greater the degree of limitation. Due to the fact that the total heat release occurs over this limited area the temperature of the fuel in this area is necessarily raised to a point above the softening tern stature of the ash in the coal and clinkers are formed. These clinkers are quite porous and allow a large portion of the air supplied through the uniformly distributed tuyre openings to be deflected through them instead of penetrating the fuel bed.

in other words, it may be considered that this The ring 41 has a downwardly extending aoaaeaa region of intense burning forms the clinlrers, and when formed the clinlrers tend to aggravate the condition by deflecting still more of the air through this small area. My object, then, is to admit the air to the fuel bed in a manner that active burning occurs over a larger portion of the retort at high combustion rates and with more complete burning of the fuel before being discharged over the side of the tuyre when operating at these high rates, and also that the stolrer may be operated with a lower excess of air, and that whatever ash is formed and falls from the side of the tuyre is in a soft unclinkered state, thereby simplifying its further removal from the furnace and requiring a minimum clearance between the tuyere and furnace, or permitting a maximum burning area.

Again, when a large number of air openings are distributed over the tuyere there is a tendency to carry the fire down low into the retort. The coal passing along this face close to the tuyeres remains in the heat burning zone a relatively long time before being discharged over the side, and in doing so it is burned completely before reaching the edge of the tuyere, and in this burned or clinkered form is very porous and allows a very large portion of the air to escape without doing much effective burning.

Again returning to the operation of my device, it will be remembered that the flow of air from the plenum chamber into the fuel bed is restricted at the tuyre outlet and that it is directly upward and inward in each instance from the outlets t l to tit inclusive, and also that air at a relatively high velocity is made to penetrate the fuel bed at the place and in the quantities needed, and also that the fuel is not only prevented from stopping the tuyere openings but is actually loosened in cascading past these openings keeping same in a loosened and aerated condition ideally adapted for the complete burning of the fuel at the lowest possible temperature, with the idea in mind of not forming hard clinkers which must otherwise be disposed of, and the reader cannot be too forcibly reminded of the fact that by placing the restriction at the tuyre outlet it is possible to have the air penetrate the fuel and therefore aerate same and hold it in readiness for the subsequent changes which take place from the moment the fuel is first heated until the time its incombustibles are delivered over the rim of the retort into the ash remover.

The result of this relationship may be stated in a few words, namely that the upward moving body of the smaller sizes of anthracite coal will be completely charged with air as it moves upwardly, and the rate of this charging will be directly proportional to the air-consuming requirements of the combustion at the various points of the burning surface.

lit will be noted that this is quite the reverse of the practice commonly accepted in the burning of bituminous coal in which the flow of air is softened toward the rim of the combustion zone.

*' In the present instance the volume increases toward the outermost portion of the burner and that only a relatively small stream is directed into the center of the fuel. This may be readily understood when it is remembered that only a small portion of theburning takes place in the center of the fuel and that the movement of the fuel is directed as nearly as possible normal to the sides til of the cone of ignition, and that in this movement the fuel is further charged by air from the intersecting corners so that by the time each particle of coal or the remains thereof is ready to pass over the side of the ring hi it has been subjected to the lowest possible burning temperature and for the shortest possible space of time consistent with the complete extraction of combustibles therefrom.

I claim:

1. A burner having circular superimposed tuyre elements forming an outwardly flaring fire pot, each adjacent pair of tuyere elements having substantially horizontal air passages formed between same and the lowermost element of each pair having a continuous lip formed around the upper inner edge thereof which lip extends above the top of its respective horizontal air opening, said lip constituting a means for defleeting air streams upwardly and preventing the moving fuel from entering the tuyere openings.

2. An anthracite burner having in combination a plurality of superimposed circular tuyere elements forming a fire pot having an upwardly and outwardly flaring rim, a plenum chamber surrounding said tuyere elements, said tuyere elements having a series of air grooves formed around the upper edge thereof, each of said tuyere elements having an annular flange projecting upwardly above the innermost top side of said air grooves, the total cross-sectional area of the openings formed by said grooves and the next tuyere element above at any one level exceeding the total cross-sectional area of the openings at the next lower level, said openings constituting restricted passages whereby air may be maintained in the plenum chamber at a relatively high static head and delivered to the fuel in upwardly directed penetrating streams of increasing volume toward the uppermost levels.

3. A burner for anthracite coal having in combination a retort provided with means for feeding coal uniformly upward therethrough, a plenum chamber surrounding said retort, a plurality of superimposed tuyere rings mounted over said retort, each of said rings flaring outwardly and each having its uppermost edge projecting into the central opening of the next succeeding ring above forming a deflector, the joint ber tween each pair of rings having air grooves formed therein below the top of the deflector, and communicating between said plenum chamber and the interior of the tuyere rings from which grooves air may be directed upwardly by said deflector, and a fan for delivering air to all of said grooves at a uniform relatively high static head.

4i. A burner for anthracite coal consisting of a plurality of superimposed circular tuyere rings, each of said rings flaring outwardly, the top of each ring forming a support for the next ring above, the upper edge of each ring lfaving an upwardly extending annular flange formed around its innermost side, the top side of each ring outside of said annular flange having air grooves formed therein and a plenum chamber surrounding said tuyere rings from which air may be delivered through the grooves in said rings into the body of the fuel.

ERNEST C. WEBB.

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