US2491625A - Kiln and method of firing the same - Google Patents

Description

, Dec. 20, 1949 E. E. sLlcK KILN AND METHOD OF FIRING THE SAME 3 Sheets-Sheet l Filed Deo. 14, 1946 Irllllll l nventor Edwin .Slick Gttomeg 5* Dec. 20, 1949 E E, SUCK 2,491,625

KILN AND METHOD oF FIRING THE SAME Filed Dec. 14, 194e 3 Sheets-5heet 2 M' J5 I nventor Gttornegs Dec. 20, 1949 E. E. sLlcK KILN AND METHOD OF FIRING THE SAME 5 Sheets-Sheet 3 Filed Deo. 14, 1946 '1, Inn,

l l l Cttorneg 5I Patented Dec. 20, 1949 UNITED STATESEPATENT oFFice KILN AND METHOD OF FIRING THE SAME Edwin E. siick',"rittsburgh, Pa..

Application December 14, 1946, Serial No. 716,366

7 Claims.. (Cl. 25-151) part of the kiln and the labor and skill required it has been proposed to use mechanical stokers of conventional type in which the coal is forced up through a central passage or retort and as it burns, the ash is clinkered and the clinkers removed from time to time.

Many types of ceramic or refractory articles are extremely sensitive to temperature changes during burning. Silica brick, for example, is red at a temperature of around 2700 F. and the temperature must be gradually and uniformly increased to avoid damage.

With hand firing of coal burners the attendant is very likely to let the fires burn down, then throw in a quantity of fuel, resulting in uneven firing and the opening of the doors for throwing in coal and removing ash admits cold air that is detrimental. Not infrequently as much as 10% of the w-are in the kiln is damaged by uneven firing, and a high percentage of loss is always expected.

While conventional stokers tend to keep a more uniform rate of combustion the ash is accumulated in the fire pot and is converted into a clinker. The operator must frequently open the fire door and remove these `clinkers. During this operation, air enters through the fire door, tending to reduce thetemperature, thus detrimentally affecting the burning of the ware.

According to the present invention there is pro-` vided a stoker arrangement wherein the ash is continuously forced from the fire pot or combustion zone as it is produced, where it falls into a pit in which it may accumulate during the entire period of the operation of the firing of the kiln, or at least during that period of the firing which is critical, so that it is unnecessary to open the firing door at any time after the fires have been Thereby it becomes possible to uniformly increase the temperature within the kiln and avoid damage to the ware.. due to any sudden variation or dropping of the" temperature in any particular 'of the attendant is greatly reduced.

In the arrangement contemplated by the present invention the kiln is provided with a number of similar stokers more or less equally spaced around the side of the kiln. The coal feeds uniformly and continuously into each Stroker moving radially toward the center of the furnace, and as it moves combustion takes place. At the inner end of the stoker unit the coal will have been converted to ash and the ash drops out of the stoker into the ash pit where it may accumulate for a considerable period of time.

While the stoker has been especially designed for use in a brick burning kiln, it is also applicable to other operations where it is desired to autoz matically stoke and effect removal of the ashes of such furnace;

, 50` started, nor is it necessary to open the ash door.

, Fig. 2 is a side elevation of a portion of the furnace shown in Fig.` 1;

Fig. 3 is a fragmentary section through the wall of the kiln showing one of the stokers partly in side elevation and partly in section, the view being on a larger scale than Figs. 1 and 2;

Fig. 4 is a horizontal section in the plane of line IV-IV of Fig. 3;

Fig. 5 shows the apparatus disclosed in Fig. 3 in an end elevation; and

Fig. 6 is a fragmentary transverse section through the fire-pot, the view being substantially in the plane of line VI--VI of Fig. 3.

Referring to the drawings there is shown a more or less conventional form of kiln, which kiln is completely circular as is well understood by those skilled in the art, and has a side wall 2 and a dome-shaped to-p 3. One or more entrance doors are provided in the side at 4. The Stoker units are designated generally as 5 and they are disposed at regular intervals around the periphery of the kiln with their longitudinal axes radial to the kiln.

As more clearly shown in Figs. 3, 4, 5 and 6, the stokers are provided with a feed hopper 6 which delivers coal into a screw conveyor 1 that extends horizontally beneath the hopper. A motor 8 drives a shaft 9, which in turn has a worm thereon for engaging a worm wheel l0 for turning alternas 3 the conveyor screw I I. The shaft 9 also drives a blower fan (not shown) but which is of conventional form, and which is contained within a fan housing I2 alongside the gear box for the screw conveyor drive.

The fan housing has an intake opening I3 and delivers air into a duct I4 that extends along one side of the screw conveyor tube 1 as most clearly shown in Fig. 4. Both the screw conveyor and the duct pass through the wall 2 of the kiln.

The inner end of the screw conveyor tube opens into a trough-shaped retort or a nre-pot designated generally as I5 and which, as shown in Fig. 5, extends radially inwardly. This retort or nre-box is shown in Fig. 6 as having a rounded bottom I6 with upwardly diverging sides l1, these sides merging into outwardly-turned rim portions !8. A sheet metal casing I9 extends downwardly from the edges of the rim I8 and under the bottom of the trough forming a wind box 20 into which the vair duct I4 opens.

As best shown in Fig. v3, the top edge of the retort or nre-pot slopes downwardly l.and inwardly while the linn'ern'rcst part `of the bottom of the ltrough I6 extends inwardly and upwardly, therebei'ig ja sornewhai'. rounded end wall portion EI at Athe inner `end of the trough. The sheet metal casing I9 also joins the downwardlyturned flange ZI' at the outer edge of this rim for closing the wind box. The Yupwardly sloping portion of the bottom 1:6 is designated Iii (see Fig. s). l 4

The side rims :I8 yat each lside of the trough and the end rim vportion 2-I are provided with numerous openings Ythat v direct currents of air inwardly and "upwardly toward the mid plane of the trough, these vopenings providing the combustion air for lburning the fuel. The rim of the fire-pot thus constitutesa tuyr'e.

In 'operation the screw *delivers coal into the trough. The coal moves radially inwardly and upwardly filling the troughiand combustion takes place lcontinuously 'along the rim which forms the tuyre for supplying vthe Vcombustion air. There is progressive movement of -the whole body of coal inwardly and the rate of fee'd is so adjusted to the rate of con'ilcustion and the length of the trough that by the time lthe coal reaches the inner end ZI of the retort or combustion chamber it will have been 'substantially entirely reduced to ash. This Vash falls downwardly in the space between the skirt 2l forming the end of the stoker lunit and the r,bag `wall 22 of the kiln. The stoker is supported o'n bars 23 which are commonly vprovided `atrthe present time in kilns, and below the bars h2i! there is a large ash pit 24 or other ash receiver which extends from the outer vertical wall inwardly toward the bag wall 22.

, l,As best seen in Fig. 5, there are two ash doors 26 opening into the 'ash pit, V'one at each side of the mid plane ofthe, stoker which seal it against vfree inflow of outside air. `Likewise there are two nring doors 21, fone being at each side of the fuel hopper and :affording access to the combustion unit. All these doors are normally closed during operation.

`As best shown in Figs. 4 'and 6, there is brick work 28 slo-ping upwardly and outwardly from the tops of the tuyres forprev'ent'ing [fuel from overflowing at the sides of Athe retort and allowing the burning fuel to spread yout toa limited extent.

VAll of the Stoker units are the same and while I have "shown one particular form lof drive for 4 the screw feeds of the stokers, it will be understood that this is merely lby way of illustration, and that various other drives for the screw feeds may be provided. Ordinarily in an operation of this kind the stoker operates more or less continuously and the rate of feed and the rate at which the fuel bed is moved is coordinated to the length of the trough (and also the rate of combustion) to assure substantial consumption of the fuel before it reachesthe discharge end. This is simply obtained Yby a proper adjustment of the feed of the screw or of the speed of the y motor which drives it. Each of the stokers provides an elevated trough-shaped retort or fire pot that iextends radially inwardly so that in the operation of the kiln there is at each station an inwardlyprogressing burning bed of fuel which,

by the time it reaches the innermost end of the retort, has been substantially reduced to ash, and which before any substantial clinkering takesplace, discharges freely into the large ash pit "or ashreceiver provided under the Stoker. This a'rrangeno'ent enables substantially uniform conditions of combustion to be maintained at each nr'ing station and uniform rates of combustion to be maintained, and the operation of firing can take place after the kiln is started without there 'normally'being 4any need for opening the fire doors or the lash removal doors. Hence ceramic articles, and particularly articles such as silica brick which are very sensitive during firing to any heat'changes, can be burned with-inet only Aa lc'msiderable economy of fuel, but Awith considerably less loss due to temper- Y alture changes. The ash "discharges beyond the Azone of combustion so that any dust that may be formed by the falling ash is in a quiescent atmosphere and is not carried into the furnace. Y

-As hereinbefore indicated, wh'ile the Stoker has special'adaptation to 'akiln ofthe class described, it is also applicable to other arrangements where coal is to be burned and the `ash is to be auto- Iatoally discharged.

While -I have illustrated `and described one specic embodiment of my invention, it will be understood that this is 'by way of illustration and that various changes and finodications may be made therein.

1. A kiln for the burning of products to be red comprising a kiln structure having side walls and "a roof, and a plurality of stokers around the sidewalls of ythe kiln, each stoker beingconstructe'd to fnove a burning body of fuel at "a controlledra'te "inwardly toward the center o'f the kiln and ldischarge 'the ash at the end remote from fthe side wall.

2. A kiln for the burning of products to be fired comprising la/kiln structure having side wallsan'd aroofjanda plurality of stokers around the side walls'of the kiln, each stoker being coi.- structed to `move "a burning Ibody of fuel at a controlled rate `inwardly toward vthe center of thekiln and discharge the ash at the end remote from th-e side wall, the kiln having an ash pit therein under the stoker for holding an accumulation of ashes so discharged, said ash pit being closed against free circulation of air therethrough, each Stoker having means for delivering air to the fuel bed under positive pressure. n 3. A kiln for the burning of products to be nred comprising` 'a kiln structure having side walls and a "roof, and stokermeans at a pluality Ioffst'atiori's around `the wall of the kiln,

said stokers operating to move the fuel as it burns inwardly at a controlled rate toward the center of the kiln and discharge the resulting ash at the inner end of the stoker, there being an ash compartment under each stoker into which the ash is discharged and which is normally closed against free ingress o-f outside air.

4. A kiln for burning ceramic and like articles comprising a circular structure having a plurality of stokers around its periphery, each stoker being provided with an inwardly elongated re pot whereby the burning coal moves progressively as it burns radially of the structure and discharges at the inner end thereof, each stoker having means for advancing the burning fuel along the elongated ilre pot at a controlled rate, and means for supplying air to the lire-pot.

5. A kiln for burning ceramic and like articles comprising a circular structure having a plurality of stokers around its periphery, each stoker being provided with an inwardly elongated fire pot whereby the burning coal moves progressively as it burns radially of the structure and discharges at the inner end thereof, the nre-pot having an end wall to retard the free movement of fuel along the fire-pot and maintain the fuel bed at a controlled depth, the ash being discharged over the end wall, each stoker having means for effecting the movement of the fuel bed at a controlled rate along the hre-pot, and an ash receiver normally closed against ingress of outside air into which the ashes fall from the inner end of the stoker, the stoker having means for supplying air along the fire-pot to the fuel.

6. A kiln for burning ceramic and like articles comprising a circular structure having a plurality of stokers around its periphery, an ash pit under each stoker, each ash pit having an ash door for removal of ashes therefrom, each stoker being designed to progressively move coal as it burns at a controlled rate radially of the structure and discharge the ash into the ash pit, there being a passageway at the inner end of each stoker opening vertically into the iirepit, said passageway being inwardly of the combustion zone and the ash pit being air-tight whereby a counter flow of air to float fine ash upwardly through the passageway is avoided.

7. The method of ring a coal-red kiln which comprises progressively advancing the coal while it is burning from several stations around the periphery of the kiln toward the center at a controlled rate, dropping the resulting ash at the end of its travel into an ash receiver which is normally closed against the free inflow of out side air whereby firing temperature in the kiln may be uniformly reached and opening of the kiln during ring avoided.

EDWIN E. SLICK.

REFERENCES CITED The following references are of record iin the ile of this patent:

UNITED STATES PATENTS Number Name Date 316,397 Plumb Apr. 21, 1885 1,407,288 Marris i Feb. 21, 1922 1,599,103 Schlotterer Sept. 7, 1926 1,797,608 Goodwin Mar. 24, 1931 2,262,078 Yarick Nov. 11, 1941 2,362,127 Gehl Nov. '7, 1944 FOREIGN PATENTS Number Country Date 453,304 Great Britain Sept. 9, 19.36

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