US2398031A - Combustion apparatus - Google Patents

Description

April 9, 1946= D. J. MOSSHART COMBUSTION APPARATUS Filed Nov. 1943 2 Sheets-Sheet 1 mom 3m 0 7. mm mm INVENTOR WITNESSES;

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COMBUSTION APPARATUS Filed Nov. 17, 1945 2 Sheets-Sheet 2 INVENTOR Dona/a J Moss/wt Patented Apr. 9, 1946 2,398,031 COMBUSTION APPARATUS Donald J. Mosshart, Ardmore, Pa, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa, a corporation of Pennsylvania Application November 17, 1943, Serial No. 510,580

Claims. (Cl. 110-414) This invention relates to furnace stokers, more particularly to those involving overfeed sections, and has for an object to provide improved overfeed sections for such stokers.

Another object of the invention is to provide a stoker overfeed section involving novel grate construction.

Yet another object of the invention is to provide novel means for cooling the grate bars of a stoker overfeed section.

A further object of the invention is to providea grate bar with means defining air passages therealong for flow of excess cooling air in contact therewith.

Another object of the invention is to provide means for air cooling the first row of grate bars of a stoker overfeed section which follows an underfeed section, by passing in contact with said bars air to be finally delivered to other bars of Fig. 2 is a side elevational view of the portion of the stoker shown in Fig. l, and,

Fig. 3 is a sectional view, taken along the line III-III of Fig. 2, looking in the direction indicated by the arrows.

Referring now to the drawings more in detail, and particularly to Fig. 1 thereof, the reference character iii indicates, in its entirety, a furnace comprising front and rear walls H and 12, respectively, and side walls It. Positioned in the bottom of the furnace I8 is a stoker, indicated by the referenc character i5, and comprising an underfeed section l6, following in the direction of fuel feed, by a first overfeed section I! and a second overfeed section I8. Fuel is fed from the hopper [9 to the retorts 20 by conventional fuel feeding mechanism 2|. Fuel fed rearwardly along the retorts 2i! discharges over the dead plates 25 onto the first overfeed section ll, thence to the second overfeed section is from which it passes to the dump plates 28, for discharge therefrom to the ash pit 21 therebelow.

Air is supplied from a suitable source, (not shown) to a series of first, second and third plenum chamber 28, 29 and 30, respectively. The air enters the first plenum chamber through the supply conduit 3 I, associated with the inlet opening 32 in the structural member 33, which, with the masonry wall 34, forms the front wall of the first plenum chamber 28. The rear wall of this chamber and the front wall of the second plenum chamber 29 is formed by the masonry wall 35, the structural member 36, and the members 31, 3B and 39. lhe rear wall of the second plenum chamber and the front wall of the third plenum chamber 36 is formed by the structural members 46, ii and 42. The rear wall of the third plenum chamber 3!! is formed by the structural members 53 and M. The bottoms of the second and third plenum chambers are closed by the usual siftings collection hoppers 29a and 30a, respectively.

Referring now to Fig. 2, the first overfeed section I? comprises first and second transverselyextending rows of grate bars and 46, respectively. These grate bars have overlapping adjacent end portions 41 and 48, pivotally connected together by pins 39 which, preferably, are of sufficient length to connect two pairs of first and second row bars 45 and 45. The second row of bars 45 are provided, adjacent their rearward ends, with transversely-extending aligning pins 5% connecting a number of adjacent bars.

The first row grate bars 25 are carried by a plurality of supporting members 5|, pivotally connected by pins 52 to the rearwardly-extending lugs 53 of the bearing brackets 54. Each supporting member 5| has an arm 56 extending upwardly from its forward end, the upper ends of the arms having openings ii! therethrough for passage of supporting pins or rods 58. The rearward ends of the supporting members 5| are provided with openings 59 for the reception of bearing pins 59. As best indicated in Fig. 2, each bearing pin 69 carries a pair of supporting members 5|, the bearing pin being carried by the upper end of a link 6| whose lower end is mounted on a similar pin 62, carried by the bifurcated crank arm 63, pivotally secured to the main transversely-extending shaft 64, which is oscillatable about its axis by suitable means (not shown).

It will be apparent that oscillation of the shaft B l will operate through the crank arms 63 and links Bl to raise and lower the rear ends of the supporting members 5! in pivotal movement about the pivot pins 52. As best shown in Fig. l, the transversely-extending shaft '54 is supported by the structural members 65 through bearings (not shown), the structural members being supported at their ends by the H-beams The forward ends of the first row bars 45 are provided with slots 65 providing upper bearing surfaces 61, the slots receiving the transversely-extending supporting pins or rods 58, carried by the upstanding arms 56 of the supporting members 5|, thereby supporting the forward ends of the first row bars 45.

In operation, oscillation of the transverselyextending shaft 64, operating through the link 6|, raises and lowers the rear ends of the supporting members 5| for pivotal movement about the pivot pins 52. This movement provides for forward and backward movement of the grate bars 45 as well as vertical movement of the rear ends thereof, and, due to the pivotal connection between the first row bars 45 and the second row bars 46, the forward ends of the latter are raised and lowered and the entire bars 46 reciprocated forwardly and rearwardly, with the rear ends thereof sliding upon the supporting plate structure 68 (Fig. 1).

Inasmuch as the means for securing the bars 45 to the supporting members 5|, and the operations of removing and. replacing individual grate bars 45 and 46 of the first overfeed section constitute no part of the present invention, they will not be described further herein, but reference is made to applicants and anothers copending application, Serial No. 504,394, filed September 30, 1943, for a detail description of these features.

The present invention is concerned with means for cooling the bars 45 of the first overfeed section IT, as it has been found that these first row bars are subject to excessive destruction due to direct contact with the burning fuel. This con dition normally prevails at this particular location in the path of fuel travel over the grate surface for several reasons, the two most important reasons being:

First, as the fuel advances rearwardly along the underfeed section 16, it becomes ignited and burns furiously in spaced lanes which overlie the tuyere rows, while the intermediate lanes of fuel overlying the alternating retorts is unignited. As

a result, when the fuel bed reaches the first r0wbars 45 of the first overfeed section I1, that portion which was ignited over the tuyere rows has therebelow a bed of ash between the burning fuel and the grate bars, which layer of ash serves to protect the bars from the burning fuel thereabove. On the other hand, the fuel reaching the bars 45 which are in line with the retorts of the underfeed section, is still in the form of green fuel and, inasmuch as it was not previously ignited, there is no layer of ash between it and the grate bars 45. As soon as this green fuel reaches the overfeed section, and receives air through the grate bars 45, it becomes i nited and burns furiously. Inasmuch as this burning takes place in direct contact with the bars 45, without the benefit of an intervening protective layer of ash, these bars become ignited and are soon burnt out and require replacing. 1.

A second reason for excessive burning of the first row bars of the overfeed sectionis that, whereas the fuel passing over the tuyre rows of the underfeed section becomes ignited while over that section, thus producing a fuel bed structure through which numerous air passages have be- Come formed, he "raw or green fuel discharged onto the overfeed section from the retorts of the underfeed section, having been unignited, is lacking in air passages therethrough with the result that when this fuel passes over the first row bars 45 the air supplied thereto through these bars cannot find flow-paths through the fuel and therefore is diverted laterally or longitudinally along the upper surface of the bars, with the result that intense burning out occurs at the surface of these bars where the excess flow of air takes place.

By the time the fuel bed reaches the second row bars of the first overfeed section, the burning occurring previously has provided sufficient ash to protect the grate bars from the burning fuel thereabove throughout the remainder of the travel of the fuel bed to the ash pit 21 The present invention provides for cooling the first-row bars 45 by passing in contact therewith air in quantities greatly exceeding that normally required for combustion of the fuel thereon. This is accomplished by directing substantially all of the primary air for the overfeed sections longitudinally of the bars 45 through the spaces therebetween. This flow of air is obtained not only by use of a novel arrangement of guiding ribs on the bars 45, but also by a particular relationship of the bars to the openings 10 in the partition between the first and second plenum chambers, which openings 10 pass the primary air for the overfeed sections.

As best shown in Figs. 2 and 3, each bar 45 has, extending laterally from each side, a pair of spaced longitudinally-extending ribs H and 12, preferably, although not necessarily, arranged in parallel relation. The opposed pairs of ribs on adjacent bars, together with the intermediate portions 13 of the bars themselves, define passages 14 for flow of air longitudinally of the grates 45.

From Fig. 3 it will be seen that the main upper portion 11 of each bar 45 has a pair of laterally projecting ribs 18 at the lower edge thereof, which, with the ribs 1|, define passages 19 also for flow of air longitudinally of the bars.

The forward ends of the ribs "H and 12 are spaced a material distance from the forward ends of the bars to permit ready entrance of air to the passages 14 and 19. The rearward ends of the bars are provided with lateral pegs to secure improved heat transfer from the bars to the air leaving the passages 14 and 19. However, these pegs are omitted from the majority of the length of the passages to insure of suitable flow of air therealong.

Another feature of the invention, contributing largely to the cooling operation, is the position of the openings 10, in the supporting brackets 54, with respect to the forward ends of the first-row bars 45. As best shown in Fig. l, the openings 10 are so positioned that the air passing therethrough from the first plenum chamber 28 approaches the spaces or passages 14 and 19 in a direction in longitudinal alignment therewith so that the air flows into these passages with minimum turbulence.

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not So limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and it is desired, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What is claimed is:

1. In combustion apparatus, stoker structure including an underfeed section followed, in the direction of fuel feed, by an overfeed section comprising a plurality of transversely-extending rows of grate bars; means providing first and second plenum chambers beneath the underfeed and the overfeed sections, respectively, and including a partition separating said chambers and having a vertical portion disposed forwardly of the forward ends of the bars of the first transversely-extending row, said vertical portion having an opening therethrough for flow of air from the first to the second plenum chamber; means for supplying air under pressure to the first plenum chamber for flow therefrom to the second plenum chamber, the opening in the partition being disposed in longitudinal alignment with the bars of the first transversely-extending row of bars of the overfeed section, and air guiding means operatively associated with said last-mentioned bars, said air guiding means comprising ribs formed on the sides of the bars of the first row and extending longitudinally thereof, whereby the air admitted to said second plenum chamber is caused to sweep longitudinally of said bars.

2. In combustion apparatus, stoker structure including an underfeed section followed, in the direction of fuel feed, by an overfeed section comprising a plurality of transversely-extending rows of grate bars with the bars of each row pivotally connected to the bars of adjacent rows; means providing first and second plenum chambers beneath the underfeed and overfeed sections, respectively, and including a partition separating said chambers, said partition having one or more openings therethrough near its upper edge and in close proximity to the forward ends of the bars of the first row of overfeed grate bars; means for supplying air under pressure to the first plenum chamber for flow therefrom to the second plenum chamber through said partition opening or openings; and a plurality of parallel, spaced-apart ribs projecting laterally from the sides of the first row grate bars and extending generally longitudinally of the latter, whereby longitudinally-extending passages are provided for directing the air passing through said partition opening or openings in contact with the sides of said grate bars to cool the latter.

3. In combustion apparatus, stoker structure including an underfeed section followed, in the direction of fuel feed, by an overfeed section comprising a plurality of series of articulated grate members disposed in side-byside parallel relation in the direction of fuel feed; means providing first and second plenum chambers beneath the underfeed and overfeed sections, respectively, and including a partition separating said chambers, said partition having openings therethrough for flow of air from the first to the second plenum chamber; and means for supplying air under pressure to the first plenum chamber, the openings in the partition being located in front of and adjacent to the forward ends of the series of grate members and in longitudinal alignment therewith, at least the first grate member of each series of articulated grate members including longitudinally-extending ribs projecting laterally from the sides thereof, whereby air passing through said openings from the first to the second plenum chamber flows longitudinally of the first grate members of the series of members intermediate the same, the ribs on adjacent members having their outer edges spaced apart to permit a portion of the air flowing along the members to pass upwardly therefrom to the fuel bed thereabove on the overfeed section.

4. In combustion apparatus, a grate element having a plurality of ribs projecting laterally therefrom in side-by-side spaced parallel relation and extending longitudinally thereof, the spaces between said ribs being unobstructed throughout, and'said ribs terminating short of both ends of the bar.

5. In combustion apparatus, an elongated grate bar, and a plurality of parallel spaced ribs projecting outwardly from each side of the bar in side-by-side relation and extending longitudinally thereof, the spaces between said ribs being unobstructed throughout their lengths, and providing, when the bar is assembled with an adjacent bar, open-ended passages for flow of air longitudinally of the bars, said ribs and passages terminating short of both ends of the bar.

DONALD J. MOSSHART.

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