US1522166A - Kiln and method of operating same - Google Patents

Description

Jan, 6. 1925.

L. WILPUTTE KILN AND METHOD OF OPERATING SAME 4 Sheets-Sheet THU.

Filed Nov. 2.8, 1921 ,f wf R, n# M Nu R, ,Lu/ mWg/N A Jan, 6. 1925.

L. WILPUTTE KILN AND METHOD OF OPERATING SAME Filed Nov. 28, 1921 4 sheets-sheet s E? wwwa M A TT ORNE Y L. WILPUTTE v KI-LN AND METHOD OF OPERATING SAME Filed Nov. 28, 1921 4 Sheets-Sheet 4 a q www. w

1N VEA/TOR L awa WM Parrf BY g /wf/ A NUR/VE Y Jan,V 6. 1925.

.NUFMFWHMF. .uflwww Patented' Jan., 6, 1925i.

, UNITED STATESl PATENT etnica.,

Louis WILPUTTE, or NEW ROCHELLE, NEW YORK, AssiGNoR 'ro AMERicaN iiREssLmt TUNNELI xiLNs, INC., or ,cLEvELnNn cino, A

CORPORATION' or NEW ironic K1LN AND METHOD 0E OPERATING SAME.

i Application filed November 28, 1921. Serial No. 518,207.

To all. whom t may concern.' Y

Be it known that LLoUis WILPTTE, a citizen of the United States, and resident of New Rochelle, in the county of IVestchester yand State of New York, have invented cer# tain new and useful Improvements in Kilns and Methods of Operating'Saine, of which inal conditions in the kiln.

f reverse ,the direction offlow the following is a specification.

My present invention relates to kilns and particularly to continuous tunnel kilns.y

The general object `of my inventionv is to provide an improved methoden and 4apparatus v.for maintaining the desired ther- My yinvention comprises a novel heating system, and a the cooling zone of and also comprises an advantageous kiln heatinv and kiln novel cooling system in the kiln, combination ofnovel cooling provisions. n

My improved heating system is chaiuicter-v ized bythe iow of the heating gases transversely across the kiln chamber in substantially horizontal stream lines. ,This I ac. complish in. practice by introducing the heating gases iiitoztlie kiln chamber through ports in one side wall of vthe kiln chamber and withdrawing the gases through ports in the other side of the kiln chamber, the poits in each side wall being distributed both longitudinally of the kiln `and vertically. vIn order to obtain high temperatures and4 to equalize' the ytemperatures at the opposite sides of the kiln cliaiiiber,'I provideregenerators at each side of the kiln chamber and through the kiln chamber and regenerators at regular intervals. The regenerators wliichreceive heat from the, heating gases leaving thekiln chamber may be employed to prelieat both the fuel gas and the air for combustion. when the .fuelgas is a lean gas,siich as p roducer gas; but when the fuel lgas is aricli gas, such as natural gas `or coke` oven gas.

-I prefer to preheat only t-lie air for combustion. y

In some cases, as in burning brick with fuel gas such as producer gas, I introduce l vthe latter.

' tion of the present invention, I cause a aseouscooling medium, ordinarily air, to ow across the kiln chamber first in one direction and then in the opposite 'direction and employ regenerators at -thetwo sides of the kiln chainber through which the cooling medium flows before entering the kiln, and after leaving By roceeding in this manner the lcooling medium entering the cooling zone of the kiln at any point along the lengtliof the'latter is preheated to a tem'- vperatiire approximately that in rthe kiln chamber at the -poiiit 'at which it enters the latter'thus avoidinginjury to the goods by' exposing them to unduly low temperatures iii cooling; This method of coolingroquires the use of a relatively large volume of cooling medium which is an advantage of 'itself in that it tends to uniformity inv'teni peratureof all portions of the goods at any transverse planevv through the kiln chamber.v

By maintainingy the same direction of cross flowat any instant across the cooling and heating zones of the kiln I desirably niininiize gravity or convection currenty circulation longitudinallyy of the kiln chamber.

' My invention alsofconiprises features of construction and arrangement especially 'del vised to facilitate the niaintenance'of a verv high temperature in a kiln of large capacitiv such as is required for burning silica brick andanalogous purposes. I f 'I The various featuresv of noveltywhich characterize my invention are pointed out with particularity in theclailns annexedto and forming a part of this"specification.

For a better understanding of ymy invention, reference should be had to the draw ings and descriptive matter in which I 'have illustrated and described preferred' enibodiments ofmy invention.

Of the drawings: Fig. 1 Vis the diagrammatic plan view of a twin kiln;

Fig. 2 is 'a transverse `s`ection,`the` left hand portion of the ligure being a section on the line` 1 1 of'Figl and the right hand porfigure being a section on the line 2--2 of Fig-l;l j

Fig.; 8 .is a side elevation of a-portion'ot the kiln shown in Figs. l and 2;

Fig. 4 is a sectional plan, the right hand portion being taken on the line '4i-4l of 2, and the left hand p'ortion being taken on the line QL A ofFig. 2;

iio

Fig. is a transverse section of the entire kiln taken on the same plane as the left hand. portion of Fig. 2; j p. Y

Fig. 6 is a transverse section of the entire ki'ln taken on the same plane as the right hand portion of Fig. 2;

Fig. 7 is an elevation of a portion of the'inner wall of the kiln chamber;

LFi. 8 is a section on the line .8-8 -of Fig; p

l Fig. 9 is apartial transverse section illus trating a modification of the apparatus shown in Figs. 1 to 8;

Fig. 10 is a partial section on' vthe line 10-10 of Fig. 9;

Fig. 11 is a plan View of a single kiln; and

Fig. 12 is a transverse section,` on the broken line 12-12 of Fig. l1. v

The kiln A shown in Figs. l to S or` the drawings is a soTcalled twm tunnel kiln,

having track rails B for two trains of goods carryin cars C which move through the kiln cham er A2 in oppas-ite directions,

as indicated by the two lines of arrows in Fig. 1. The cars C may be of the usual construction employed in tunnel kilns, and the usual provisionsmay be made for sealing the joints between the cars and between the sides of the cars and the adjacent side walls of the kiln chamber, or as shown these joints may be of a labyrinth character tol restrict communication between the portion of the kiln chamber above the refractory bodies of the car and the portion of the kiln chamber below the car bodies and thus avoid overheating the metallic under-portions of the cars and the track rails. Cooling pipes-N may also be provided at. lthe bottom of the kiln chalnber as a .further protection against over-heating this portion of the kiln.

In the construction shown in Figs. l to' 8, the high temperature portion of the kiln is formed of sections a, in each of which there is a regenerator chamber E for prcheating gas and ajregenerator chamber F for'preheating air at each side of the kiln chamber. A plurality-oi` vertical lues or channels D are formed in each section a adjacent each side of the kiln chamber A2 and each of these lues communicates with i the kiln chamber through aI plurality of ports D( located at dierent levels. Each regenerator E is connected at its upper end by channels E tothe tops of the alternate fines Din thcsection at the adjacent side' of the kiln chamber, while the. regenerator chamber F is connected Aby channels F- to the tops of the iues D intermediate of those to which the adjacent regenerator chamber E is connected. TheV regenerator chamber E in each kihi section a at the 'right hand Side of the kiln, as' seen in Fig. 2, is connected by a channel E2 and a valve H to a responding regenerator chambers F.

- site sides of the kiln.

nasales .waste heat conduitK running the full length of the kiln. The regenerator chambers F e at the same side of the kiln are also lconnected to the conduit K each byits individual vchannel F2 and valve HA. The redraft creating device such as an -exhauster L. Valves or dampers M and M form means by which communication between the exhauster L and either of the conduits K and .KA may be closed. The valve membersl close communication between the corre'sponding channels E2 and the conduit K or KA. The valve members H3 proper, of the valves HA connected one to each ofthe channels F2, do not interru t communication at any time between the channels F2'running from the regenerators F to conduits VK and KA, but each ofy these valves when open permits atmospheric air to enter the corresponding channel F2 and pass thence into the cor- The valve members H3 are provided with operating arms H. Combustible gas, which may well be clean producer gas, is supplied at intervals to the bottoms of the regenerator chambers E from gas mains O at the oppo- For this purpose. a branch pi e O', advantageously containing a yregulating cock O2 extends to each regenerator channel E2. .A valve P is provided in each branch Agas pipe O. The valves P are provided with operating arms P. As shown in Figs. l .and 3, the operating arms P, H2 and H4y of the valves P, H, and HA are operated by a. reversing gear including azc'ableJ which passes around the kiln and runs over suitable guide-pulleys. The cable J is provided at suitable intervals with collars J for engaging the valve arms P-, H2 and'H In the contemplated mode of heating the high temperature section of lthe kiln, the valve M will be closed and the valve M will be open during one stage or period of operu ation so that the yconduit KA is then subjected to draft suction while the conduit K is not. 'In this stage of operation at the right hand side of the kiln, as seen in Fig. 2, the valves H will bey closed, and the valves-` Pand HA will be open, while at the oppo site side of the kiln the valves H will be open and the valves P and HA will be closed. In conse uence gas will be supplied to the bottoms o the regenerators E, and air will be supplied to the bottoms ot ibo, regeneratcrs F at the right hand side of the kiln as seen in Fig. 2, andthe air and gas after passing through the regenerators lua) and thence into the conduit KA from which vsuction on the conduit the cooled products ,of combustion pass to the exhauster Lj. In ar succeeding state of operation, thevalve Mv is closed andthe valve M is open thus impressing the draft K and-removing it from the conduit KA. In this. stage of operation the previously open valves H. HA'

and P are closed, and the previously closed valves H, HA and P are-open, `thus .reversing the direction of flow through the various regenei'atorsE andV F and :through ,the kiln chamber.

In practice mechanism-will ordinarily be provided for motor operation of the reversing cable J and'dampers or' valves M and;

M in regular sequence, but I have not illustrated mechanism for this purpose as this mechanism may be like that used in other types of regenerative furnaces and its par-4 ticular construction forms noY part of the present invention.

With the mode of operation described, it is possible with properly designed and operated apparatus to maintain Aa high temperature in the zone of the kiln formed by the kiln section a which does not vary appreciably in any plane transverse to the kiln chamber from one side afA the kiln chamber to the other, or at different levels. Uniformity in temperature atditi'erentlevels. or a graduation in tem levels as vmay bo desired, may readily be secured with properly designed l' apparatus. To provide for the desired regulation of'lieat distribution I advantageously' make provision for adjusting the eiective fiow area of the 'various ports' D if and when this `may become necessary. For this purpose I provide normally closed openings Av in the roof of the kiln chamber adjacent the upper ends-of the lues D through Whichthrottle bricks d may be inserted in or removed from the orifices D to vary the flow area of the latter. (See Figs. 7 and 8.) The inner wall of each flue D is advantageously formed, as shown, of bricks d each notched at its lower edge to form the corresponding port D. The distribution of flow among the different channels E ot' each regeneratorv E, and among the different channels F of each regenerator F, may be regulated by slide bricks or dampers R which may be flues D to the correeraturesy at differenty inserted, adjusted and removed through the outer ends of the channels E and F',

which are provided with doors or valves S for the purpose. The distribution ot flow among the different regenerators F may be regulated by suitable adjustment of the dampers I by which thc draft suction on the different, regenerators is controlled, and by suitable adjustment of the regulating kvalves O2 in the gassupply pipesO.

In the modiication illustrated in Figs. 9l

and 10 the regenerators E are .dispensed with, andv only the air is preheated. In `these figures the fuel gas supply branches `O lead through channels E14 to channels El in the roof of the kiln which communicate at their lower ends through yburner The lnozzles may be replaced and damper brick like the bricks d1"` of Figs. 7 andj8 to provide a kiln portion at each end of. thel kiln in which the temperature varies proessively with the distancefrom the ad jacent endof the kiln from the temperature in the high temperature portionof the kiln, to a temperature at the end of Ithe kiln which does not diil'er from that of the eX- ternal atmosphere suiciently to-cause the entering ware, or the warepassing out ofthe kiln into the external atmosphere to be injured by sudden changes in temperature. In a twinkiln this temperature graduation is automatically obtained in Whole or in part by the transfer ofy heat transversely of the kiln .from the highly heated ware passing away from ,thehigher temperature. central zone ofthe kilnto the ware approaching that zone. y v

In a twin-kiln constructed in accordance with the present invention this transfer of heat from thev hotter goods to the cooler goods in the end portions of the kiln,

facilitated by maintaining a transverse horizontal flow through the end portions of the kiln, of air, and in some cases of air and burning gases For this purpose I provide flues D along the sides of the kiln inthe section a forming the end portions of the kiln, as in the `sections a. and I provide a reeenerator G at leach side of the kiln in eadii section a. Each regenerator G- .is connected to all the adjacent. flues D by channels G', and is connected ,to the adjacent waste heat conduit K oi-,KA b a channel G2 Bmay be identical in construction with the valves HA, and the `operating arms Hf* E and and products. of combustion.-

nozzles El with the tops of the flues D.

and `valve HB. -Thevalves of the valves HB are arranged for engagement and actuation by the reversing cable il so that the valves HB and the'valves HA. l

at the same side of the kiln open and close together.

With this construction, when the flow across the kiln chamber is' from left to right as seen .in Fig. 2, atmospheric air enters.`

is from the kiln chamberinto the regenera-y tor, and gives up heat to the incoming air when the d1rect1on of flow is reversed.

`When the direction of flow through either. end portion of the-kiln is such that the air first passes across the hotter ware and then across the cooler ware, the air serves directly to transfer heat from the hotter ware to the cooler ware. When the iow is reversed this of Icourse is not true and the tendency is then for the air to heat the cooler goods less and to cool the hotter ware more than with the other direction of flow. This tendency may be obviated by supplementing the heat imparted to the incoming air in each corresponding regenerator G, by the combustion of a limited amount of gas. This is accomplished in .the apparatus shown in Figs. l to 5 by supplying a'limited amount of gas to the tops of the regenerators G at the side of each end portion of the kiln adjacent the train of goods carrying cars moving through that endportion of the kiln tov-:ard the central high temperature portion of the kiln. Gas is thus supplied to the regenerators G through extensions of the mains O, and branch pipes O3 leading from said extensions to the outer ends of channels G3 running to the tops of the corresponding regenerators G. Each branch gas pipe O3 preferably contains a throttling valve or cock O2, but ordinarily I prefer not to provide reversing valves in the branches O3 but to permit the gas to iow Icontinuously to the tops of the regenerators. Vhen the flow is downward through the regenerators G supplied with gas, the gas burns in the regenerators and the heat of combustion accumulates in the regenerators and is passed into the kiln chamber when the flow through the regenerators is reversed. By providing for a continuousy discharge of gas into the tops of the appropriate regenerators G as described, I not only increase the rate at which the cooler ware is heated, but. I avoid all danger of failure of the gas to burn which might exist if the gas were supplied to the tops of the regenerators G intermittently, in view of the fact that the temperature at the ends of the kiln may well be below vgraduate the temperature longitudinally of the kiln in the end portions of the kiln as desired, while at the same time vproviding for a rapid absorption of heat by the ware as is necessary to secure a large kiln output. Such relatively high temperatures and rates of heat supply are especially desirable in the case of the kiln employed for burning refractories such as silica bricks for which the invention is Aof especial utility For burning silica bricks and analogous material, the temperature in the central portion of the kiln chamber should ordinarily be not less than 2700 or 2800o F. and'in some cases may advantageously be as high as 30000 F.' The heating system described makes it readily possible to obtain such high temperatures, and the comparatively simple and rugged construction which may bc employed inmy kiln makes possible a kiln structure which will withstand such temperatures. To accommodate the relatively great expansion of the kiln structure resulting from suchfhigh temperatures, espe `cially when the kiln, or at least the high temperature portion of the kiln, is made of silica brick-the most'suitable if not the only practical material for the purpose-, I vform the kiln in scctionsarl and a of comparatively short length,-say 12 to 15 feet each, and provide an open expansion joint am between adjacent sections which are thus free to expand, as the kiln is heated. without a corresponding elongation of the kiln as a whole. The leakage through these expansion joints with the kiln once heated up'is comparatively slight, especially as the regenerators are each formed whollyrin a corresponding kiln section, and the 4pressure differential between the interior of the kiln chamber and the outside atmosphere may be made comparatively small. The expansion of the kiln transversely' to its lengthis controlled and the arch. roof is prevented from sagging by a suitable brick work construction, and by the use of the usual huckstays.

In Figs. l and 12 I have illustrated the use of my invention in a kiln AA which is a single kiln as distinguished from a twin kiln. The central high temperature zone of the kiln AAis formed of sections am and may be constructed exactly as is the central portion of the kiln A first described except that the kiln chamber A20 of the kiln AA is only made wide enough to receive a single line of cars C. In this casev the waste heat a: conduit yK21 running along thev high temperature section of the kiln; The regeneraing up zone tors G in the'sections all forming the 'heatat the entrance end of the kiln are connected to. Waste heat conduits K22 and KA22 at opposite sides of the kiln. The ends of the conduits'K22 and KAzzadjvacent the high temperature zone lof the kiln are connected to theadjacent end ofthe conduit K21 through dampers M4L and M5 respectively. The opposite ends ofthe conduits K22 and KA22 are connected toa draft' creyating device LA through' dampersM2 Vand M3 respectively. ""In this construction the gas'mains O are extended along the heating up zone of the kiln nearly to the entrancev end of the latter,"and these' extensions continuously supply gasto the' tops of the adjacent regenerators G at both sides of the kiln. The valvegconnects to the'under sides Y of the r`regent-Waters: E and F and to the 'regenerators G along the cooling zonesection of the kiln may lbe identical'vvith'the valve connections to the re enerators E, F and G of thefconstruction siliownin Figsgl to 6, but lno valves are, provided :in the connections-HC between the regeneratorsr` and the conduitsK2-2 and KAL22 except the adjustvable dampers orthr'ottling-valves I.

The various valves in lthe regenerator connections, the valves P in the gas supply connections' to theregeneratorE, and the various vdampers M`,1M, M2, M3, M4, M5, M6, and: M7 may all be connected to a common reversing mechanism arranged to operate the various valves and damers so that the direction of {10W-acrossl the en portions of the kiln ,chamber is always in the same directlon "as the flow across thehigh temperature porl tion ofthe kiln chamber. This requires that when the damper yM kis open, the dampers M2, M5 and Mare also open,'an`d the dampers M", M3, M* and Mf'are closed." In this conditionof operation air isdr'avvn outoi the cooling zone section of the kiln' chamber throu h the regenerators G connected-tothe condu1tK2f, andv is" preheated before entering the kiln chamber passing through the regeneratorsGjatthe opposite' side ot the coolin vzone-sectionv of the'fkiln. The air thus rawn intoj the conduit" K passes throu h the conduit 'Knto the conduit K, and passes thence through the regenerators to the tops of tors G.

in'g the Ware at G connected to the conduit K22 intol the heating up zone ofthe kiln'chamber, and thence linto the conduit K22 through 'the regenera-y 1 tors G connected to the latter,"andis'kvvith-v drawn from the conduitl K2 by the draft creating device LA. 5

y When 4,the direction of lovvthrougli the kilnchai'nber is reversed'the dempers 'M,v M3, M4 and M7 are opened and the dampers M, M2, M5 and M6 are closed. Theiiow is then across the cooling zone section of the kiln into the conduit KA, and the air yWithdrawn'into the conduit KAZ" passesthrough thev conduit K21 into the conduit KL2f from Which it-passes through theregenerators G at both sides ofthe heating up section of-'the cooling zoneand thelatter into the conduit KA, and thence to the .draft creating device LA. The heat in the airpassingfrom the conduits K2? and KA20 to the conduits KA22 and Kzzyres'pec'tively, is utilized in the heating up zone of thekiln. 4Adjacent the entrance end of the kiln the heat'contajined in'this air need not be augmented by combustion *with gas, but in the'portion of the heating upzone atwliich higherlt'emperalvtures arerequired the yheat in the'vair is augmented by the combustion of gas suppliedl the vvcorresponding regenerau No explanation is requiredto make 'plain that in the cooling end portion ofthe kiln, the average temperature maintained in each of 'the vcorres'pondin f regenerators G depends y"upon the location" of `the ,regenerator and increases progressively along'the length of the kiln from the extreme end of the kiln to the central'portion'o'f the. kiln. 'The air passing `from the more'highly heated regenf eratorsof the cooling zone section y'into the kiln chamber enters" the kiln` chamber `at la temperature 'not greatly below the `temperature inthe kiln chamberi- The volume of air' which must loel drawnintojthis portion otthekiln4 chamber mustrof course be greati erv than'vvould befrequired-if the cooling air introducedinjto the same portion of the kiln were at atmospheric-ytemperatures. The in# creased; volume voff-'air andy comparatively small temperature dierential betweenthe air andthe goods cooled both' contribute 'to a desirable uniformityin the rateof 4cooldiierent points in atransyverse plane throughaVV corresponding portion'of the'kiln chamber. j l

While in accordance Withthevprovisions of the statutes I have illustrated the best my invention 'now known to me,it will lbe apparent to those 'skilledpin the art that many changes may be madein the forms'of my invention disclosed-Without: departing 'methods of and apparatus forcarrying'out l from the spirit of my 'invent-ion asfsetyforth s in the appended claims and thatcertain-fea-` v tures of my invention may sometimesrbe used to advantage Without a corresponding use of other features,

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is: i

v 1. vThe methodl which consists in causingL a gaseous thermal agent to move through a tunnel kiln chamber Witha direction of flow Which at all. points in the kiln chamber is approximately horizontal and transverse to the length of the kiln.L

2. The method 'of regulating the temperan ture in a continuous tunnel kiln which con-k sists in causing a gaseous medium to flow opposite side of the kiln chamber alternately in opposite directions,and heating the gaseous medium as it passes from the regenerator at one side of the kiln chamber to the regenerator at the other side of the ykiln chamber. f a v -V 4. The method of heating a tunnel kiln Which consists in. passing heating gases along a lplurality of iiovv paths extending transversely across the kiln chamber and distributed ylongitudinally thereof, subject-- ing the medium flowing through each flow path to a regenerative action increasing its h'eat and supplying heat to the medium owing along each of said flow paths in addition to that furnished by regeneration.V

5. The methodof regulating the temperature in a continuous tunnel kiln which consists in causing a gaseousL medium to flow alternately in opposite direct-ions through a regenerative chamber at one side of the kiln chamber thence through the latter and thence through a regenerator at theoppo-y site side'of the kilnchamber, and heating the gaseous medium as it passes into the kiln chamberfrom the corresponding regenerator.

yo. The improved method of abstracting heat from the Ware passing through the cooling zone of a tunnel kiln which consists in passing a gaseous cooling medium along a plurality of flow paths` extending transversely across the kilnchamber and distributed .longitudinally thereof and subjecting the medium flowing through each tlow path to a regenerative action.

' 7. The improved method of abstracting heat from the ware passing through the cooling zone section/cfa tunnel kiln which consists in causing a gaseous cooling medium to flow alternately in opposite directions along'a flow path comprising a regenerator, .the cooling zone section lof the kiln chamber and a second regenerator.

8. In a continuoustunnel kiln, the improvement which consists in means for causing' the heating gases to `l'loW horizontally across the heatingy upk and high temperature zones of the kiln chamber in horizontally and vertically distributed streams. 9. In a continuous tunnel kiln, the improvement which consists in means forcausing the heating gases to ilow horizontally across the heating up :and high temperature zones of the kilnchamber. alternately Ain opposite directions.y v

10. In a continuous tunnel kiln the improvement which consists in. means for maintaining a distributed flow of a temperature regulating gaseous kmedium transversely across the heating up and high temperature `zones ofthe kiln chamber comprisingv ports for the admission ofthe medium distributed ,vertically y andl horizontally along one side Wall of the kiln chamber and exit ports for the medium similarly distribvuted along the-otherside Wall ofthe kiln.

11. lIn a continuous tunnel kiln, .the improvement which consists in ports for lthe admission of the heating gasescdistributed L along oneside l.Wall of theheating up and high temperature zones of the kiln both longitudinally and vertically, and ports for the escape of .the heating gases similarly Iditributedalong `the other-side wall of the n n.

12. In a continuous tunnel kiln, the improvement Whichconsists iu ports for the admission of gas, and air lfor the combustion vof the gas, distributed vertically and horizontally along one side Wall ofl the heating up'and highy temperaturezones of the kiln, and ports for the esca-pe of the heating gases similarly distributed along the opposite side Wall `of the kiln.

13. In a continuous tunnel kiln, the combination `with the kiln chamber of cooperating regenerators at opposite sides of the kiln chamber and cach communicating with the kiln chambenand means for causing a gaseous thermal agent to Howl alternately in opposite directions across the kiln chamber from onev regenerator to the other.

14. In .a continuous twin' tunnel kiln through which goods are passed in two parallel` streams movingY inv the,Av opposite direction, and Which'comprises means for heating` the central portion. .of the` kiln, vthe improvement which consists incausing a gaseous heat transfer mediumto flow across the end portions of the kiln chamber from-the side of each kiln 'end portion adjacent the outgoingstream of goods. l

15. A continuous tunnel kiln formed in gli separate longitudinal sections with expansion joints between adjacent sections, each section being formed Vwith a regenerator chamber at each side of the kiln chamber.

16. A continuous tunnel. kiln formed in separate longitudinal sections with expansion joints between adjacent sections, each section being formed with a regenerator chamber at each side ofthe kiln chamber and with longitudinally and l'horizontally distributed ports in each kiln chamber side wall communicating with thev adjacent regenerator chamber.

17. A continuous tunnel kiln provided with vertical ilues distributed along each side wall of the kiln chamber, and ving ports opening from each otsaid lues to the kiln chamber at different levels, means for supplying gas and air for its' combustion to the llues at one side of the kiln chamber, and for withdrawing products of combustion from the flues at the opposite side of the kiln chamber.

chamber, and for withdrawing products 0f j combustion from the flues at the side of `the kiln chamber opposite to that at which air and gas is then being supplied.

, 19. In a continuous tunnel kiln thefinlv propvement which consists in means j for causing the heating and cooling gases to flow horizontally across the heating up high t temperature and cooling zones of the kiln 4u chamber in horizontally and vertically distributed streams.

Signed at New yYork in the county of New York and State of New York this 26th day of NovemberA. D. 1921.

LoUIs WILPUTTE. i

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