US1705477A - Tunnel kiln - Google Patents

Description

March 19, 1929. w..1 HANL-EY, JR 1,705,477

TUNNEL KILN Original Filed Aug. 30, 1926 5 Shets-Sheet 1 ATTORNEY March 19, 1929. w. L. H ANLEY. JR I TUNNEL KILN o i al Filed Aug. 30, 1926 5 Sheets-Sheet 2 Patented Mar. 19, 1929.

. WILLIAM LEE irANLnY, an, or BRADFORD, rnimsrnvaiim.

Application filed August 30, 1926, Serial No. 132,393. Renewed August 8, i928.

vMy invention consistsin the novel features tact with the hot fired products, after they hereinafter described, reference being had to leave the firing zone, thus eifectingthe rethe accompanying drawings, which ilcoveryofa suitablc'amount of heat from thelustrate one embodiment of the same, a nd a fired products, the heating of the air so 60 slight modification thereof, selected by me introduced and facilitating the cooling ;of for purposes of illustration, and the said -inthe fired products, and this highly heated vention is fully disclosed in the following air from the cooling-zone is withdrawn theredescriptionand claims. v v 7 from preferably at the end adjacent to the The object. of my invention is to produce firing zone where the temperature of the fired 5 10 a single tunnel kiln, especially adapted for products is greatest, and isconducted preferthe firing of bricks and other coarse clay ably by means outside of the ki-ln, to the'preproducts. In the construction of such a kiln, heating zone, Where it is introduced and it is desirable to employ a simpleandeconombrought into contact with the unfire'd ware, ical construction inorder to minimizethe for the purpose of raising the temperature 15 very large initial cost of the kiln, and to keep thereof and supplying oxygen thereto,-?, to down the expenses ofupkeep and repair. effect the preheating, water-smoking and In carrying my present invention: into effect, oxidization of the Ware, before it reaches the I employ a single tunnel structure, which is firing zone. I also prefer to providemeans entirely free from longitudinal fines or pasfor withdrawing the air, together with 2 sages, so that it can be very cheaply, convapors, gases, etc., produced in these opera- I structed. The central portion of the tunnel tions, in the preheating zone, so as to prekiln constitutes the firing zone, and is provent the possibility of seumming or staining vided with furnaces preferably arranged in the brick during the preheating thereof.

a row along one side, or along both sides of I also prefer to provide the furnaces, or so 25 the firing zone which discharge their prodburners, with regulating means, and to pronets of combustion directly into the firing Vide the passagesthrough which the products zone, so as to impart the greatest possible heat of combustion are withdrawn from the firing to the goods and economy of fuel, the prodzone, and which are located preferably beucts of combustion being withdrawn from tween adjacent furnaces, with controlling the firing zone preferably adjacent to eachor regulating means, so that the temperature furnace and conducted away from the kiln, of the firing zone may be regulated and; con-' the heat of such products of combustion b'etrolled. I preferably so regulate the teming recovered and utilized for drying the perature of the firing zone that at its enterproducts before firing, for heating air to be ing end it will maintain substantially the supplied to the furnaces, or burners, and for temperature to which the unfired ware has w other purposes. This prevents the products been preheated, in passing through the pre- 1 of combustion from passing into the other heating zone, the temperature of the firing portions of thekiln, which comprise a prezone gradually increasing throughout the heating zone at one end of the firingzon'e, length thereof to the hottest portion, which 40 and a cooling zone at the otherend of the is located'adjacent to the discharge end of heating zone, goods transporting means'bethe firing zone, in accordance with what is ing provided for conveying the goods termeda rising heat curve, which maybe through the entire length of the kiln, s'ucof any desiredcharacteristic, according to cessively through the-preheating zone, firing the regulation of the individual regulating zone, and cooling zone, and comprising prefdevices, before mentioned. invention crably, a plurality of tu'nnel'cars extending provides an extermely' simple tunnel-kiln 1 the entire length of the kiln, and running therefor, the initialccost of which is small, upon suitable tracks. In order to raise the and which is entirely without internal incoming, unfired goods gradually to a temcomplications, contributing both to low ini-' .105 50 ierature approximatelythat ofthe entering tial cost and low cost of upkeep or-repair, and end of the firing zone, to preheat them, and great economy and efficiency of operation, is efi'ectthe water-smoking andoxidization of secured by advantageously utilizing practithe products, and at the same time utilize a ca-lly allofthe heat supplied by the furnaces,

portion of the heat of the furnaces for this portions of which are recovered from the purpose, provide means fordelivering air burned or. fired ware, andused in the pre: to the cooling zone Where 1t comes in conheating zone, and portions. of whlch are re.-

covered from the products of combustion and utilized for air heating and drying purposes. 1

In the accompanying drawings, which illustrate one embodiment of my invention, and a slight modification thereof, I

Fig. l is a diagrammatic, plan view of a single tunnel kiln embodying my invention, and showing a drier for the uniired product-s arranged in connection therewith and. heated from thewasteheat of the kiln furnaces, or

burners;

Fig. 2 is a horizontal, sectional view of a kiln drawn to an enlarged scale, and partly broken away. i

Fig. 3-is avertical section through the preheating zone of the kiln.

Fig. l is a transverse, vertical section through the firing zone of the kiln.

Fig; 5 is a horizontal plan view of a slightly modified form of single tunnel kiln, provided with a rowof furnaces at opposite sides of 7 1-1, extends longitudinally through the entire length of the kiln, and in operation is occupied by a continuous lineof tunnel cars, 2, each carrying a carload of bricks, coarse clay or ceramic products to be fired, indicated at 3, in dotted lines in Fig. 8. It will be understood that the kiln provides a longitudinal goods space, or passage, extending from one end of the kiln" to the other, without either transverse or longitudinal parvt-itions, and without any longitudinal flues.

. The end portions, 13, and C, ofthe tunnel, are

of very simple construction, and comprise the side walls, 4 4, and the crown, 5, which may be of ordinary brick, or any other suitable material. The central portion, A, of the tunnel, which comprises the firing zone, is also a single tunnel structure, which is'preferably made of slightly greater width than the end portions of'the kiln, and comprises the side walls, 4 and crown, 5 -5, the side walls being spaced further apart in order to accommodate a unitary bridge Wall, or walls,'6,between the goods space and the furnaces, 'or'burners, which are preferably arranged in a row on one side of the firing chamber, as shown in Figs. 1 to 4, or on both sides, as shown in Figs.'5 and 6. In the form shown in Figs. 1 to 4, where only one row of furnaces, 0r burners is employed, only one bridge or other wall is employed, arranged on one side only of the goods space, indicated at D', in each of the several zones. The furnaces for firing the goods may be of any usual ordesired ,characterand adapted for the consumption ,of any preferred fuel. In the present in stance I have shown the furnaces, 7, provided with'a burner, 8, for a mixture of and air supplied by pipes, 9 and 10, respectively, under thecontrol of independent valves, 11 and 12, respectively, for each burner, so that each individual furnace may be independently regulated, and a predetermined heat curve may be maintained, increasing from thefentering end of the firing zone to the discharging end thereof. For example, a temperature of 900 to 1400 F., more or less, may be maintained at the entering end of the firing zone, the temperature of the different port-ions of the firing zone increasing, more or less gradually, to a temperature of 1800 to 2100 F., more or less, at the discharge end adjacent to the cooling zone, C. W'here'other forms of furnac es are employed, the means forindepend entlyregulating each furnace will vary with the character of fuel employed. The products of combustion discharged from the furnace, or burners, are conducted upward through passages, indicated at 13, between the side wall of the kiln'and the adjacent bridge wall, 6, and the upper ends. of the bridge walls are pre'ferably'provided. with inwardly extending portions at the top, as indicated at 6*, and if desired, also at one or more points below the top of the bridge wall, as indicated at 6 in order to discharge the hot products of combustion into the upper part of the goods space within the firing zone, and cause them to descend through the goods on the cars instead of between-the goods and the bridge wall, as far aspossible. The bridge wall, 6, is connected with the adjacentwall, 4 of the kiln, on opposite sides of each furnace, or burner, by a-transverse partition, indicated at 20, which does not extend as high as the top of the firing chamber, and preferably has its upper edge considerably below the top oft-he bridge wall, so that the discharge passages, 13, merge into a common discharge passage,'13 above the tops ofthe transverse partitions, 20.

Means are provided, preferably between adjacent furnaces, for withdrawing the products of combustion from the firing zone. To this end, the inner face of the bridge wall is preferably provided adjacent to the level of the lower row, or rows, of goods on the cars, with aplurality of exhaust ports, 14,

preferably, in alignment with the respective transverse partitions, 20, each of said ports being connected by a transverse eduction pipe, or passage, 15, extending outside of the firing chamber, and connected to a header,

16, or COllQOtlHg, flue, extending longitudinally of the firing chamber, eachof the educ- Y kiln construction.

tion ports and the p assage'connected therewith, being provided with regulating means. In this instance I have showneach of the eduction pipes,-'.15,- provided withfi a controlling valve,;17,' for illustrative purposes, but obviously anyxform of. damper or. regulating means, which will withstand the high temperature of the products of combustion will be employed. 'The eduction'pipes, 15, may extend horizontally through the kiln wall, or may be'connected many other manner,witl1 the collecting flue,16, whichmay be located upon or underneath the ground, and below the kiln, if desired. For, greater clearness, have shown the collecting fine in this instance'located outside of the firing zone, in alignment with the. passages, 15,v and ports,14, but these details of construction may be variedto suit the ideas of different constructors and the general character of In order 'to secure the withdrawal of the products of combustion, means are provided to create a suc'tion,for rarifica-tion in: the collecting pipe, and'the eduction ports or passages connected therewith. Any suitable device for this'purPOsecan be employed, In the present instance, I have shown aian or air forcing device, indicated at 18, and provided with an injector nozzle discharging into the collecting flue, v16, as indicated in dotted lines at19, but any other form of means for producing suction may be employed.

I The products of combustion discharged into the collecting fine, 16, are very highly heated, and a considerable portion of this heat can be advantageouslyutilized for heating the drier, or driers, in which the ceramic products are dried, preliminary to firing them in the'kiln. These, products of combustion can also be employed for heating air'to supply thefurnaces, and for other purposes. In the present instance, for example, I have shown the collecting fine, 16, discharging into recuperator, 21, of any desired type, provided-with separate air passages,22, through which air, as from a fan, 23, or other air forcmg device, may be caused to pass, and become highly heated, said air passing out, through a pipe, 24, which maybe connected with the air pipe, 10, which supplies airto the heating burners for'the firing zone,-as' shown in Fig. 1, and this air pipe may-also-be connected directly with the drier and discharge clean, heated air into the same, to assist in the drying of the ceramic products, as indicated in said figure. The products'of combustion themselves are preferably conducted,

after leaving the recuperator, by a pipe, .25, to heating pipes, indicated at 26, Within the drier, out of communication therewith, in

-which they giverup a large percentage of their remaining heat, to the air circulating in the drier, aftenwhichthey are passed, by a pipe, 27,.=t0 a stack, 28, and discharged tinto the atmosphere. -Obviously, the: draft of the stack is suflicient to-provide'the necessary suction inthe-collectingfiue, 16, and

eduction passages connected therewith, the injector fan, 18, or other equivalent means, might be dispensed with.

i The cooling zone, (hot the kiln, is provided with awplurality of induction ports, ,29,

through which fresh air from the outside of the kiln isintroduced into the cooling zone 'at. different points longitudinallythereof, along its entire length, or a portion of its length; The cooling zine is also provided witha plurality of eduction ports, indicatedat 30, for withdrawing this air after ithas been highly heatech'by convection and radiation, as't'rom the cooling fired products on thecars in the cooling zone, the saideduction' ports being located at dilierent points longi-' tudinally of the cooling zone throughout-a portion, or all of its length, and either on the sames'idc as the induction ports, or opposite sides, as preferred. In the present instance, in Fig; 1, I have shown the induction ports located adjacent toithe discharge end of the kiln, remote from the firing zone, and sup plied by a -'pl'urality of pipes, 31, provided .with' regulating. devices, 32, from a header,

33,'connected with ai'an, 34, or other air forcing device. Theeduction ports, 30, are shown 1 located adjacent to the firing zone, where thefired products on the cars are at the highest temperature after leaving the firing zone said educ'tion ports belngconnected wlth eduction pipes, 35, provided with regulating tinuously, I prefer to employ a suitable form of airforcing device, and in the present instance I have shownra fan, indicated at 42, located in the transfer pipe, or passage, 38,

for example. The transfer pipe may be locatedunder ground, or properly protected by insulating materlal, to prevent loss of heat. :In this constructionavery large pro:

portion of the heat of the fired products can be recovered and used for heating large quantities of airdrawn or discharged into the coolingzoneand facilitating the cooling of the.

Ware, the said heated air being transferred to and dlstribnted throughoutthe preheating zone'to effect the preheating, water-smoking andoxidization of the unfired ware. Inintrodilcingthe air into the cooling zone at drznvn at the highest temperature, the-last instruments of heat being impartedito it from -ware which has just issued from the firing zone. The introduction of this heated fresh air into the preheating zone, provides the necessary oxygen for the oxidization and water-smoking of the brick, and in order to withdraw from the preheating zone the' vapors and gases produced in the preheating,

oxidization and water-smoking of the brick, or other products. I preferably provide the preheating zone with a plurality of eduction eduction pipes,

vidcd with regulating means,

ports, indicated at 43, arranged at different points longitudinally of the preheatlng zone and 'connec ted with an eduction pipe, 44, communicating with a header, 45, which isin turn connected by a pipe, 46, with suction producing means, as a stack; 47, or exhaust fan, for positively withdrawing the air, vapors, and gases from the preheating zone, and further insuring a continuous supply of clean, hot air containing the requisite quantity" of oxygen inthe preheating zone. The

i 44, will preferablybe proas valves, 48, and by regulating these valves and the air inlet valves, 41, the desired graduated temperature maybe maintained within the preheating zone, longitudinally thereof, so as to gradually raise the temperature of the ware from the time it enters the preheating zone until it passes into the firing zone, so as to obtain the most effective results without checking or cracking, or otherwise injuring the ware. and so that when the ware passes into the entering end of the firing zone, it will have been broughtto a temperature sub stantially equal to thatwithin the adjacent portion of the firing zone, so that the subsequent step of firing may be. effected by the further and graduated increase in temperature prescribed by the heat curve maintained in the firing zone.

In Figs. 5 and 6 I have shown. a slightly modified form of my invention, in which it is embodied in a kiln, the firing'zone of which is provided with a row of furnaces on each side. In these figures, parts corresponding to its members a centrally located firing zone,

those shown in Figs. to 4, inclusive, are given the same reference numerals wlth 100 added, and where the parts are identical, they will not be again described. As shown m Fig. 6, the firing zone is provided with two bridge walls, 106', and two rows of furnaces, 107-, in'this instance heated by burners, 108, in the same manner as the single row of furnaces shown in the other figures, and the parts are constructed" and operate substantially as hereinbefore described, except that in this instance the products of combustion charged from'both rows offurnaces into the top of the goods space, indicated at D, within,

are disthe firing zone, and pass. down through the goods and thence out through the eduction ports, 114, in the opposite bridge. walls, and through the eduction passages, 115, to the collecting fines, or headers, 116', on opposite sides of the firing zone. Obviously, each of these headers could beconnected to a superheader in the same-manner as the header, 16, in Fig. 1, for example, but I prefer to connect the two headers, 116, together, by a transverse pipe, 116, and pass the products of combustion from both rows of furnaces through a single recuperator, 121, and thence by pipe, 125, to heating passages, 126, in the drier, and

thence to a stack,'128,-by'apipe, 127. The

through a header,133, and regulated in the pipe, 131, provided with valves, 132, and the cooling zone is also provided with-eduction pi is in turn connected with the'transfer pipe, or passage, 138, in which may be located a fan or other suctionmeans, 142, for transferring the heated air from the cooling zone to a header, 139, connected by regulated pipes, 140, with the preheating zone at intervals "throughout its length, under the regulation of suitable regulating valves, 141. The preheating zone is also provided with eduction pipes, 144, provided with regulating valves, 148, and connected with a header, 145, which is inturn connected bya pipe, 146, with a stack or other exhausting means, 147. It will be understood that the operation of this form of kiln is exactly the sameas that previously described, except that the firing zone is provided with two rows of furnaces instead of one.

What I claim and desire to secureby- Letters Patent is 1. A single tunnel kiln, comprising among provided with a series of furnacesdischargis conductedby- 135, connected to a header, 137, which the firing zone is'indicated ing their products of combustion into the fir ing zone, means for'withdrawing the products of combustion directly from the firing zone without permitting appreciable longitudinal flow, a preheating zone extending longitudinally from one end of'the firing zone, a cooling zone extending longitudinally from the other end of the firing zone, a single. hne of goods conveying means extending mount? through all ofsaid zones, means for supplying air from the outside of the kiln to the cooling zone for heating it from the hot fired products therein, and means for Withdrawing said heated air from the cooling zone and discharging it into the preheating zone for preheating, oxidizing and water-sinokingthe unfired products therein.

2. A single'tunnel comprising among its members, a centrally located firing zone, provided with a series of furnaces discharging their products of combustion into the firing zone, independent means for controlling said furnaces, for maintaining a gradually increasing temperature from one end of the firing zone to the other, means for withdrawing the products of combustion directly from the firing zone without permitting appreciable longitudinal flow, a preheating zone located at one end of the firing zone, a cooling zone located at the other end of the firing zone, a

single line of goods conveying means extending through all of said zones, means for introducing air into the cooling zone in contact with the heated, fired products therein, and

means for withdrawing said air heated by the latent heat of said fired products and trans- 'ferring it to and introducing it into the preheating zone for preheating, oxidizing and water-smoking the unfired products during their passage to the firing zone.

3. A single tunnel kiln, comprising among its members, a centrally located firing zone, provided with a series of furnaces discharging their products of combustion into the firing zone, means for withdrawing theprodnets of combustion from the firing zone,'a preheating zone extending longitudinally from one end of the firing zone, a cooling zone extending longitudinally from the other end ofthe firing zone, a single line of goods conveying means extending through all of said zones, means for supplying air from the outside of the kiln to the cooling zone for heating it from the hot fired products therein, the preheating zone being provided with a plurality of air inlets having independent regulating means, located at different points longitudinally of the preheating zone, and means for withdrawing the heated air from the cooling zone and distributing it to the said inlet passages to preheat, oxidize and water-smoke the unfired products, whereby said inlet passages may be regulated to efiect the gradual raising of the temperature of the unfired products as they are moved in a direction toward the firing zone.

4. A single tunnel kiln, comprising among its members, a'centrally located firing zone,

provided with aseries of furnacesdischarging their products of combustion into the firing zone, means for withdrawing the products of combustion from the firing zone, a preheating zone extending longitudinally. from one end of the firing zone, a cooling zone extending longitudinally from the other end of the firing zone, a single line of goods conthe preheating zone being provided with a plurality of air inlets having independent regulating means, located at different points longitudinally of the preheating zone, and means for Withdrawing the heated air from the cooling zone and distributing it to the said inlet passages, to preheat, oxidize and water-smoke the unfired products, whereby said inlet passages may be regulated to eifect the gradual raising of the temperature of the unfired products as they are moved in a direction toward the firing zone.

5. A single tunnel kiln, comprising among its members, a centrally located firing zone, provided with a series of furnaces discharging theirproducts of combustion into the firing zone, means for withdrawing the products of combustion from the firing zone, a preheating zone extending longitudinally from one end of the firing zone, a cooling zone extending longitudinally from the other end of the firingzone, asingle line of goods conveying means extending through all of said zones, means for supp.lyingair from the outside of the kiln to the cooling zone for heating it from the hot fired products therein, means for withdrawing the heated air from the cooling zone and transferring it to and distributing it into the preheating'zone to preheat, oxidize and water-smoke the unfired products therein, said preheating zone being provided with a plurality of eduction passages and means connected therewith for withdrawing air laden with the vapors and gases produced by oxidation and watersmoking from the preheating zone.

6. A single tunnel kiln, comprising among its members, a centrally located firing zone, provided with a series of furnaces discharging their products of combustion into the firing zone, means-for withdrawing the prodnets of combustion from the firing zone, a preheating zone extending longitudinally from one end of the firing zone, a cooling zone extending longitudinally from the other 7 7 end of the firing zone, a single line of goods conveying means extendingthrough all of said zones, means for supplying air from the outside of the kiln to the cooling zone for heating it from the hot fired products therein, said means being located at different point-s longitudinally of the cooling zone, eduction passages communicating with the cooling zone and located at different points longitudinally thereof, means connected with said eduction ports for withdrawing the heated air from the cooling zone and transferring it to the preheating zone, and means for discharging said heated air into the preheating zone at different points longitudinally thereof.

T 7 A single tunnel kiln, comprising among its members, a centrally located firing zone, provided with a series of furnaces discharging their products of combustion into the firing zone, means for withdrawing the products of combustion from the firing zone, a preheating zone extending longitudinally from one end of the firing zone, a cooling zone extending longitudinally from the other end of the firing zone, a single line of goods conveying means extending through all of said zones, means for supplying air from the outside of the kiln to the cooling zone for heating it from the hot fired products therein, said means being located at different points longitudinally of the cooling zone, eduction passages communicating with the cooling zone and located at different points longitudinally thereof, means connected with said eduction ports for Withdrawing the heated air from the" cooling zone and transferring it to the preheating zone, means for discharging said heat ed air into the preheating-zone different points longitudinally thereof, the air inlet passages and eduction passages of the cooling zone being provided with independent regu 'lating means, and independent regulating means for controlling the admission of said heated air at said different points longitudinally of the preheating zone to establish and maintain gradually increasing temperatures therein from the, entering end of the preheating zone, in a direction to ward the firing zone.

8. A single tunnel kiln, comprising among its members, a centrally located firing zone, provided'with a series of furnaces discharging their products of combustion into the firing zone, means for Withdrawing the products of combustion from the firing zone, a preheating zone extending longitudinally from one end of the firing zone, a cooling zone extending longitudinally from the other end of the firing zone, a. single line of goods conveying means extending through all of said zones, means for supplying air from the outside of the kiln to the cooling zone for heating it from the hot fired products therein, said means being located at different points longitudinally of the cooling zone, eduction passages communicating with the cooling zone and located at different points longitudinally thereof, means connected with said eduction ports for withdrawing the heated air from the cooling zone and transferring it to the preheating zone,

.means for, discharging said heated air into the prehet ting zone at different points longitudinally thereof, the air inlets for the cooling zone being located adjacent to the delivery end thereof, and the eduction passages of the cooling zone being located adjacent to the firing zone whereby the air is caused to travel lengthwise of the cooling zone and to become gradually heated, and is withdrawn from the firing zone, means for withdrawing the prodnets of combustion from the firing zone, a preheating zone extending longitudinally from one end of the firing zone, a cooling zone extending longitudinally from the other end of the firing zone, a single line of goods conveying means extending through all of said zones, means for supplying air from the outside of the kiln to the cooling zone for heating it fromthe hot fired products therein, said means being located at different points longitudinally of the cooling zone, eduction passages communicating with the cooling zone and located at different points longitudinally thereof, means connected with said eduction ports for Withdrawing the heat-ed air from the cooling zone and transferring it to the preheating zone, means for discharging said heated air into the preheating zone atdifferent points longitudinally thereof,-independent regulating devices for controlling the inlet of said heated air at. said points, eduction passages connected with said preheating zone and located at different points longitudinally thereof, independent regulating means therefor, and means connected with said eduction passages for withdrawing the heated air admitted thereto laden with vapors and gases produced by the heating, oxidation and water-smoking of the ware.

10. A single tunnel kiln, comprising among its members a centrally located firing zone, provided with a series of furnaces disa charging their products of combustion into the firing zone, means for Withdrawing the products of combustion directly from the firing zone without permitting appreciable longitudinal flow, a preheating zone extend-' ing longitudinally from one end of the firing zone, a cooling zone extending longitudinally from the other end of the firing zone, a single line of goods conveying means extending through all of said zones, means for supplying air from the outside of the kiln to the coolin zone adjacent to the discharge end thereof For heating said air from the hot fired products therein, and means for withdrawing said heated air from the cooling zone adjacent to the end thereof nearest the firing zone, and transferring said air so withdrawn to and discharging it into the preheating zone for preheating, oxidizing and water-smoking the unfired products therein. 11. A single tunnel kiln, comprising among its members a centrally located firing zone, provided with a series of furnaces discharging their products of combustioninto the firing zone, means for withdrawing the products of combustion from the firing zone,

a preheating zone extending longitudinally from one end of the firing zone, a cooling zone extending longitudinally from the other end of the firing zone, a single line of goods conveying means extending through all of said zones, said cooling zone being provided With a plurality of air inlets adjacent to the discharge end of said zone and arranged at different points longitudinally thereof, said cooling zone being also provided With eduction apertures atseparated points longitudinally thereof and located adjacent to the end of the cooling zone nearest the firing zone, and means for Withdrawing the heated air from the cooling zone through said eduction apertures at the points of highest heat in said zone, anddischarging said highly heated air into the preheating zone adjacent to the end thereof nearest the firing zone, and at other separated points longitudinally thereof for preheating, oxidizing and Water-smoking the unfired products therein.

In testimony whereof I aflix my signature.

WILLIAM LEE HANLEY, JR.

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