US1658331A - Tunnel kiln - Google Patents

Description

Feb. 7, 1928. 1,658,331

' w. HANLEY, JR I TUNNEL KILN 0riginal Filed 0012.14, 1924 2 Sheets-Sheet 1 ATTORNEY Feb; 7, 1928. 1,658,331

w. 1.. HANLEY, JR

TUNNEL KILN Original Filed ovum, 1924 2 Sheets-Sheet 2 INVENTOR 3 BY Q jxxomm c ATTORNEY Patented Feb. 7, 1928.

WILL M LEE HANLE'YQJRL,OFBRADFORD, PENNSYLVANIA.

i TUNNELKIL N. p

' Ap le-amine October 14, 1924, Serial no. 7a.,s'sr.=rysema March 11,1921

My invention consists in the novel features hereinafter described, referencebeing had to the accompanying drawings, which show one form of tunnel kiln embodying-my invention selected by me for purposes of illustration, and the said invention islfully disclosed in the following description and claims. a is p My invention relates to tunnel kilns or 10 ovens designedmore particularly for firing coarse clay products, such as bricks, firebricks, tile, etc., although my. invention is applicable to kilnsfor firing other classesof goods where found desirable and advantageous. In the operation of tunnel kilns, the goods which have been previously dried are moved progressively, either continuously or intermittently and usually are carried upon trucks or cars, themovement of the goods being eiiected in a direction. longitudinally zones of different temperatures so, that the goods being in a green or unfired condition, when they enter the kiln, shall be complete- 1y fired and then cooled to substantially such a temperature that they may behandled at the time they reach the delivery end of the tunnel. Such kilns are divided longitudinally into a plurality of zones which may be described briefly as, first a preheating zone in which the goods are raised to somewhere near the temperature of firing, second the firing zone in which'the goods lv fired during their passage longitudinally thereof, and third the cooling zone inwhich the fired goods are gradually deprived of theirexcess heat and brought to asuflicient- .ly low temperature to enable them :to be handled. It has been customary in the construction and operation of these kilns to effect the conibustionofthe fuel Within combustion flues or'passages extending through the firing zone of the'tunnel, in whichthe greatest amount of heat is radiatedand the products of. combustion through similar flues through the-heating zone to the entrance end of the tunneh'for the purposeof preheating the goods. In the cooling zone at the other end otf the tunnel. the fired goods are cooled by means of air drawn into the tunnel itself or through suitable flues provided in its walls or Within-tho tunnel to abstract the excess are complete-'- are conducted heat irointhe fired goods and this heated airlis in some instances employed in thecombustionfiues, and, in other instances is withdrawn for other purposes. The, construction ofthis, type of kiln is extremely expensive in' its initial cost, and also in its upkeep. and operation. It necessitates practically the use of: gaseous iuel, and Where this is not readily available, it necessitates the erectionand upkeep and continuous operation .ofaproducer gas plant, which is in, itself extremely costly and requires ,1 a high degree of skill for iitsiefiicient operation. The kiln itseli is expensive on accountv of the extensive flue construction, innch of which is. required to boot very high fire S sting. material, andthis flue construction is difficult to keep in repair. Repairs to the fine construction are also exceedingly ex- I pensive inthat they necessitate the removal of the kiln and causing them to pass through Ofthg: goods. and the cooling of the entire kiln structure, to enable the workmen to enter and make the necessary, repairs.

.Furthermoreitis necessaryzto maintain and operate powerfulAair forcing apparatusto secure the circulation otthe products of combustion through the fines inthe firing zoneand preheating,zone, and additional and separate air forcingmeans for passing the cooling air throughthe cooling zone. All otthese considerations have made it almost, if not quite, prohibitive to employ thistype of kiln for the firing of coarse clay products, which on accountof their extreme- 1y low. sale price, must be handled continuouslyat the highest possible volume and. at the lowest possible. costs; bothas toinitial cost and upkeep and daily operating expenses. Efforts have been made toreduce the expense of thesetunnel kilns, but they have usuallybeen in the direction otreducmg the 1. n-1t1al costs 1nconnect1on 'Wlth the other. items above mentioned. 1 For example,

it has been proposed toconstruct :what may be termed twin kilns or double tunnel kilns, in: which two exterior walls are employedywith a centraliwall, thus doubling the capacity atfsomewhat less than double the cost of construction; Butvthe' slight economy involved in disposing of one lateral walL, necessitates the greatly increased initial cost of the'kiln in order to provide two tunnelsi It has also been proposed to oper' decrease in the cost of the plant, and have also been objectionable on account of the lack of efi'iciency due to the difficulty experienced in transferring the heat through a partition wall from one tunnel to the other.

The object of my persent invention is to provide a kiln having provision for the simultaneous treatment of goods carried therethrough on two lines of trucks or cars moving in opposite direct-ions, the cars loaded with goods passing through a single tunnel at each end of the kiln structure, and through separate firing zones adjacent to the portion of the kiln located centrally thereof, longitudinally, the heat for the firing zone beingfurnished preferably by direct firing from a plurality of furnaces arranged on opposite sides of the centrally located firing zones, said furnaces being operated under conditions permitting their accuratecontrol as to the temperature within all parts of the firing zones, the products of combustion being withdrawn, preferably by suction from the firing zones, and conducted away for the purpose of further use in preliminary drying rooms, and otherwise as hereinafter described, the fired goods on leaving the separated firing zones in opposite directions andpassing through the end portions of the kiln on their way to the delivery end, transferring their heat to the green goods moving in the opposite direction within the same tunnel, either by direct radiation, or preferably by continuous circulation of air transversely of the tunnel and upon and through the heated and cooled goods therein, so as to cool the heated goods progressively, while progressively preheating the entering goods. The products of combustion withdrawn from the firing zone, are preferably used first to heat large quantities of air which is distributed to the end portions, or single tunnel sections of the kiln, and introduced thereunto through inlet ports located at a series of different points longitudinally of the respective tunnel sections, by pipes or passages, under the con trol ofsuitable valves or dampers by means of which the temperature of each of said end or single tunnel sections can be controlled with sufficient accuracy for all practical purposes, the said products of combustion being then carried to a separate drier or drying chamber tolbe there used for the preliminary drying of the green brick or other articles or I may introduce unheated air for the same purpose. My present invention also contemplates the provision in each of the of the tunnel from said inlet ports, the said outlet ports being connected by pipes or passages with a suitable means for creating suction, as a suction fan, or a chimney or stack for the purpose of withdrawing from the end tunnel sections, or any desired portions thereof, air, which has collected moisture and gases (water smoke) from the green clay products undergoing preheating therein.

This construction enables me to supply fresh dry unheated or heated air to the end tunnel sections at any desired point or points longitudinally thereof under the control of dampers to both regulate and control the temperature within the kiln at difierent portions longitudinally thereof and also to supply fresh an to compensate for that with drawn through the outlet fines, while the air which becomes charged or admixed with moisture vapors, etc.,geneally characterized by the term water smoke is with drawn at certain points longitudinally of the kiln sections under the control of the dampers, thus greatly facilitating the preheating of the green clay products and bringing them more rapidly and efficiently to the de sired temperature and condition to enter the firing chamber and thus also facilitating the" firing of the clay products in the firing chamber.

In this arrangement or construction, it will be observed that there is a very great decrease in the initial cost of construction, as the greater part of the kiln is composed merely of parallel exterior side walls, and a single crown or roof portion. Moreover direct firing, by which is meant that the products of combustion from the furnaces come directly into contact with the goods to be fired, results in great economy of fuel. The fuel most available at the point where'the kiln is located can be utilized whether gas, oil,-wood or coal, and its combustion can be readily regulated by means of suitable dampers and other controlling mechanism. It will also be seen that the products of combustion in-the firing zonesbeing positively withdrawn therefrom by suction, will not be carried lengthwise of the furnace into the end sections thereof, and this suction may be so regulated in connection with the air forcing means supplying air to the furnaces, as to :withdraw only the products of combustion, or if desired to withdraw some of the air. from the end portions ofthe kiln also, which would result in the admission of cool air at the extremities of the kiln.

It will also be noted that all longitudinal flue constructions through those portions of the kiln at opposite ends of the firing zones are omitted, thus effecting a great'saving in initial cost and upkeep, and in cfiiciency of operation. I I 7 Referring to the accompanying drawings,

Fig. 1 is a diagrannnatic plan view of a tunnel kiln embodying my invention and showing one arrangement for supplying air to the end sections of the kiln under the control of suitable dampers, and for withdrawing moist air, etc-.,"fro1n the end sections of the kiln also under damper control.

Fig. 2 is an enlarged horizontal sectional view of the kiln, parts being broken away.

Fig. 3 is'an enlarged vertical transverse sectional view taken through the firing Zones on line33 of Fig. 2.

Fig. 4 is a similar sect-ion on'line 4 4 of Fig. 2. l I

Fig. 5 IS an enlarged VGltlCZLl transverse section through one or other of the end sec- .tions of the kiln, taken on lines 5-5, or

5'5 of Fig. 2, looking in the direction of the arrows.

Referring to the drawings, A, represents the duplex firing chamber of my improved kiln which is located centrally with respect to the length of the kiln, and is provided at each end with a unitary cooling and preheating chamber, one of which is indicated at A, and the other of which is indicated at A The duplex firing chamber is illustrat ed in section in Figs. 3 and l. It comprises two exteriorwalls, 1, 1, a centralpartition wall,-2, and separate crowns, 3, 3, of any usual or preferred construction, forming two tunnels, 4li, separated by the partition wall, 2, each of whichconstitutes a firing zone. At the outer side of the tunnels of each of the firing Zones are located a plurality of furnaces, 5, for the combustion of any desiredcharacter of fuel, that is to say, 7 gas, or Oll, wood,.coal, etc.

be en lied continuousl I in anv desired or approprlate manner, according to its character, and l have not undertaken to lllLlS-.

trate the particular means for supplying the fuel, which maybe a suitable stoking arrangement in the case of coal, operated either by hand or power, or suitable injector nozzles in the case of liquid or gaseousfuel. The necessary air for combustion will'be supplied in any desired manner.- I have illustrated in Figs. 1 and 2., apair of air forcing devices, 66, for this'purpose, con

'nected by pipe, '7, with thevarious furnaces,

under the control of valves or dampers, {3,

so that the supply to each furnace may be;

regulated and adjusted. I In order to distribute the products of combustion from the furnaces as uniformlyas possible through the goods andsecure' the even firing of the same, each firing Zone is provided with'a vertical jdeflecting wall, 1ndicated at 9., which extends upwardlyfrom the back walls of the furnaces, tapering to The fuel may.

ward thetop, andthe upper portion ispreferably curved Orinclined inwardly towards the chamber occupied by the goods, as indic'ated at 10. The deflecting walls are each provided on their inner faces adjacent to the bottom of the contiguous goods space, with inlet ports, 11, at the inner ends of transverse passages, 12, extending throughthe wall and each communicating at the outer face of the wall with apipe or passage, 13,

soqthatthe products of combustion from.

thegoods space may be withdrawn through the transverse passages-12, and pipes, 13, from the interior of the firing zone. In this instance Thave shown the horizontal fiues arranged between adjacentfurnaces and extending from the firing chamber tothe outside ofthe tunnel kiln where, they arencon nected with a suitable suction device, such as, for example, a common exhaust fiue,11 1,

whichmay be connected with an exhaust fan,

or other exhausting mechanism, by means of which the products of combustion are withdrawn from the interior of the firing zonesand conducted elsewhere for further use. I prefer to provide each of theflues, 13, v

different pipes, 13, the control of the firing zone throughout "its length can be accurately secured, to maintain any desired heat curve. For example, I, find it convenient-to maintain a temperature of approximately 1400 F. at the entering end of each ofthefiring zones, ,and of apprbximately-1900 F. at the opposite end of eacliof the firingzones. These temperatures, however, can be readily varied as circumstances may require, by the means before described. It will be understood that eachof the firing zones is provided with longitudinal rails, indicated at 16-'16, extending thereth'rougli'for support,

ing the wheels of the trucks or cars, indicated diagrammatically at 17 The superstructure .of these trucks is preferably built up of layers of fire resistingmaterial supported upon. the metallic framework of the truck,

'in a well known manner, and the upper layer of the fire resisting materiahpreferablyconsists of hollow slabs, indicatedat '18, provided with horizontal passages, 19, therethrough, which are substantially inalignment with the passages, 12, inthelateralzdefleeting .walls, 9. The supporting slabs, 18-18, are also preferably separated along thelongitudinal central portion of the truck, the object being to facilitate the circulation of the products of combustion downward through the goods and laterally through the passages, 19. In order to protect the metallic portions of the trucks as far as possible, as they pass through the firing zone, the central partition wall, 2, and the vertical deflecting walls, 99, are provided with inwardly extending projections, indicated, at

20, and 21, respectively,which extend over the lateral portions of the true rs and tend to prevent the passage of products of combustion down around the wheels and supporting structure of the trucks.

'Ialso prefer to provide the inner faces of thelateral deflecting walls, 9, with one or more horizontal, inwardly projecting ribs, 22, which-project toward the goods carried bythe trucks These horizontal ribs are below the inwardly extending deflecting portion, 1O, of the lateral deflecting walls, and cooperate therewith in causing the products combustion to distribute themselves through the goods and prevent them from being drawn downwardly adjacent to the deflecting walls, 9. The goods are arranged on the trucks so as to provide a central passage downwardlybetween them indicated at 23, and if the goods are coarse clay products, such as bricks, tile, etc., they will be so arranged as to provide lateral passages, so that the products of combustion may become distributed throughout the stacks or piles of goods on the trucks after leaving the throat formed between the deflecting portion, 10, of the deflecting walls, and the top, 3, of the kiln portion, so that the products of combustion will pass substantially uniformly downwardly through and around the goods and across the bottom of the same through the passages, '19, through the ports, 11, and exit passages, 12, 13, to the outside of the kiln.

It will be noted that I prefer to arrange the firing zones for both lines of cars in alignment with each other, transversely, and located substantially centrally with respect to the entire length of the kiln structure. By this means the heat is concentrated and as the partition wall, 2, is subjected to heat from both sides, there is practically no loss of radiation through this partition wall, as any transfer of heat therethrough would be conserved within one firing zone or the other. At each end of this duplex firing zone. is provided a single tunnel structure preferably having only one crown or arch, and no central partition wall, as indicated in Fig. 5.

These tunnel portions, A, A connect with the central firing zone portions, A, and are provided with two sets of rails which are continuationst of the rails extending through the firing zones. The lateral walls are pro vided with inwardly extending projections, 21, similar to the projections, 21, in the liring zone, and between the sets of rails is located preferably a raised platform, 24. of brick or other fire resisting material, extending slightly above the lateral projections of the truck structure and provided on opposite sides with horizontal inwardly extending ribs or flanges, 25, to prevent the heated air from passing down around the wheels and metallic parts of the truck. The trucks are illustrated diagrammatically in the accompanying drawings, and their spe- -ific structure may be of any usual or preferred character. By reference to 5, which illustrates a section on the line 5-5 of Fig. 2, for example, it will be understood that in the portions, A A of the kiln when in operation, there will be one line. of trucks carrying goods which have been fired and are being moved toward the outer end, and another line of trucks on the other tracks moving in the opposite direction and carrying green or unfiret goods to the firing zone. It will be noted at once that there will be an exchange of heat from the fired goods to the green goods the fired goods are cooled and the green goods are preheated. It will also be seen that this exchange of heat will take place in such a manner that the fired goods will be gradually cooledand the green goods will be gradually heated. I prefer to make the end sections, AA of the tunnel of such length that in handling any particular goods the fired goods will be suliiciently cooled to be handled by the time they are discharged from the kiln, and this will result in a very gradual heating of the green or unfired goods from the time they enter the kiln where they will have opposite them goods which have been very considerably cooled, until they reach he proximity of the firing zone, where they will have opposite them highly heated fired goods which have just left the firing zone, so that by the time the green or untired goods reach the firing zone they have been brought nearly to the firing temperature. Asthese conditions will be somewhat modified by the exterior temperatur of the air and other conditions, variations in the temperature at which the goods are delivered to the firing zone can be accommodated by proper regulation of the furnaces of the firing zone, as her in before described, and by the regula tion of the temperature in the preheating and cooling zones as hereinafter described. For example, if the goods arrive at the firing zone at too low a temperature, the tom perature of the firing zone at the initial end of the same can be increased by regulating the furnaces therefor so that by the time the goods reach the hottest portion of the tiring zone they will be at the desired temperaturec f In like manner, if it is fohndthat the green goods reach the firing zone at a temperature very near the-firing tempera ture, the heat of the furnaces in, the firing zone can be slightly reduced to prevent, excessive temperatures in the firing zone. v,It

will be understood that in the transfer of,

heat from the fired goods to the greengoods,

this will be brought about by direct radiation and by convection air, currenta the circulation of WlilCll 1S;lllI1StI1tGCl in the drawing bythe arrows,in Fig, 5;} The COD:

As above stated, my present invention also contemplates the supplying ofheated or unheated air to each ofthe end sections a of the kiln at different points longitudinally thereof, under the control of suitable independently operabledainpers in order that the temperature of each or any longitudinal portion of said end sections of the kiln may i be directly controlled and regulated. I prefer to heat this air by, means of. the hot products of combustion withdrawn from the heating, zones, by the use of a suitable heat exchanging apparatus, the particular co'n structionof which forms no part of my present invention. Obviously the hot products of combustion from both sets of furnaces maybe conducted to a single heat exchanging device for the purpose of heatin air, which is conducted to both of the rent sections of the kiln and introduced therein under the control of suitable dampers or valves, but I have found it convenient to take the products of combustion from each set of furnaces, on oneside ofthe kiln structure, pass them through a suitable "heat exchanging device,and conduct the heated air therefrom to one of the end sections of the kiln. While this duplicates the heat exchanging apparatus, the apparatus can be kept down to smaller limits 'ofconstruction and the necessary amount piping is reduced so that great efliciency is secured With economy of construction. As shown in Figs.

2 and 5 each of the end sections, ii -A is provided along one side and preferably just above the horizontal rib, 21, with a plurality ofinlet ports, indicated at 40, disposed-fat intervals longitudinally of the kiln, each of said inlet ports being connected by a short section of pipe, 41 with a longitudinal fine 42, which in this instance is connected with a heating coil, 43, of a heat ex changer or air heater, 44, of any usualor preferred construction, atmospheric airfbe ing admitted to the 0011,43, iii/any usual or well known way. Each of theinlet, ports, 40, is independently vcontrolled by aivalve'i. or dampen indicatedat '45., Iha've shown the ordinary butterfly type of valve or damper, but any other preferred form, of

damper may be employed for this purpose. Each of the heat exchanging devices, 44, is connected by a pipe, 45,withthe common exhaustpipe, 14, for theset offurnaces on the adjacent side of the firing zones, and the heat exchange device, 44, is also provided with an exhaust fan or other suction device, indicated at 46, for withdrawing the prod ucts of combustion from the furnaces through the pipe, 14, pipe, 45, andthe heat exchanger, 44. H The products of combustion will give up the greater portion of their heat to the air passing through the coil, or passages, 43, of the heat exchanger and after leavin the heat exchanger the said products, of com bustion, while partlycooled, will still retain a considerable amount of heat and,

each of said heat exchangers furnishing" heated air to the inlet ports, 40, of one end section of thekiln, as shown, and this is my preferred construction, although as before stated, the heated air for the inlet ports, 40, of the said end sections may be supplied in any other desired manner, if preferred.

Asfillustrated in Figs. 1, 2 and 5, I have also shown each of the end sections, A'A of the kiln provided with a plurality of outlet ports, indicated at 50, connected by pipes or passages, 51, witha commoneduction flue, pipe or passage, 52, leadingto any suit able means for creating suction, which may consist of asuction fan or blower, or a yer tical stack or chimney, for example. a In Figs. 1 and 2 I have indicated the suction device,

at 53, andhave shown itconnected to the Eachof'the outlet ports, 50, is controlled by a suitable damper, 54, saiddampers being independently operable and being here shown as of the butterfly type, and located in the connecting pipes, 51, respectively, although they may be ofother forms, located at any" desired point forcontrolling the respective outlet ports, 50, asmay be found most 0011- I venient. By means of these outlet ports'the m'oist air, vapor and gases within the end seotionsof the kiln, and commonly referred to ascrwater smokerfmay be withdrawn" from the end sections throughout their entire length or throughout any longitudinal portions thereof, as may be desired, under the control of the valves or dampers, 54:. This prevents the accumulation within the end sections of moist air and vapors which might otherwise remain therein and delay the preheating of the advancing unfired clay products, on their way to the firing zones. I prefer to locate the outlet ports, 50, on the opposite side of each end section, A, A from theinlet ports to, and to arrange them slightly above the horizontal rib, 21, but I do not limit myself to the exact location of these inlet and outlet ports. By means of the independently controlled inlet ports and outlet ports in the end sections of the kiln, I am able to control very accurately the internal ten'iperatures and the general condition of the air within the end sections of the air delivered by pipe, 42, to approximately 1000 F. By means of the dampers, d5, this heated aircan be admitted to a greater or less extent at all of the inlet ports or certain of them as preferred, and for example, I

,may maintain a certain portion of the end section at a temperature of approximately 500 F, and an intermediate portion at, say, 7 50 F., anda portion adjacent to the firing chamber, at, say, lOOO F the extent of the different portions of the end section to be maintained at a particular ten iperature, be ing readily determined by the operation of the dampers, 45. In like manner, by means of the dampers, 54, the moist air vapor and gases within the end sections, is, for example, what is generally termed water smoke, may be withdrawn froi'n all portions of the end sections or from certain portions thereof, as may be found most desirable in preheating and preparing the unfired clay products on their way to the firing zone. The operation of these dampers will also have an effect in regulating the gradual cooling of the fired clay products on their ,way from the firing zone to the outer end of the end section, thus enabling the operation of the kiln to be very readily and accu rately controlled to obtain the rapid and cilicient and economical firing of the clay products.

It will also be seen that the greater portion of the kiln is of single tunnel construction, and as these portions of the furnaces arenot subjected to as high heat as thefir ing zone, the construction thereof can be coarse clay products, such as bricks, tile, etc., but it may also be employed for firing other classes of goods, if desired.

What we claim and desire to secure by Letters Patent is 1. In a tunnel kiln, the combination of a duplex firing chamber having two separate firing zones provided with heating means located on opposite sides of the duplex firing chamber, and a unitary tunnel section extending longitudinally from each end of the duplex firing chamber, provided with parallel goods conveying means movable in opposite directions, each of which passes through one of the firing zones, each of said end sections: forming a combined cooling and preheating zone, means for introducing a gaseous heat modifying fluid into each of said end sections, at difi'erent points longitudinally thereof, independently operable means for controlling the introduction of said heating fluid at such points, and means for withdrawing the moist air vapor and gases from said end sections of the kiln.

2. In a tunnel kiln, the combination of -a duplex firing chamber having two separate firing zones provided with heating means located on opposite sides of the duplex firing chamber, and a unitary tunnel section extending longitudinally from each end of the duplex firing chamber, provided with parallel goods conveying means movable in opposite directions, each of which passes through one of the firing zones, each of said end sections forming a combined cooling and preheating zone, each of said end sections of the kiln being provided with a plurality of inlet ports located at different points longitudinally thereof, means for supplying heat modifying gaseous fluid to said inlet ports, independently operable dampers for controlling said inlet ports, and means for withdrawing moist air, vapor and gases from said end sections of the kiln.

3. In a tunnel'kiln, the combination of a duplex firing chamber having two separate firing zones provided with heating means located on opposite sides of the duplex firing chamber, and a unitary tunnel section extending longitudinally from each end of the duplex firing chamber, provided with parallel goods conveying means movable in opposite directions, each of which passes through one of the firing zones, each of said end sections forming a combined cooling and preheating zone, means for introducing a gaseous heat modifying fluid into each of said end sections, at different points longitudinally thereof, independently ope able dampers for controlling the introduction of said heat-modifying fluid at such points, means located at different points longitudinally of said end sections for withdrawing moist air, vapor and gases, and independent- 1y operable dampers for controlling the with- ,drawa l of said air, vapor and gases at said points. i. In a tunnel kiln, the combination of a duplex firing chamber having two separate firing zones provided with heating means located on opposite sides of the duplex firing chamber, and a unitary tunnel section extending longitudinally from each end of the duplex firing chamber, provided with parallel goods conveying means movable in opposite directions, each of which passes.

through one of the firing zones, each of said end sections forming a combined cooling and preheating zone, each of said end sections of'the kiln being provided with a plurality of inlet ports located at different points longitudinally thereof, means for supplying heated gaseous fluid to said inlet ports, independently operable dampers for controlling said inlet ports, each of said end sections being also provided with a series of outletports located. at diiferent points longitudina-lly thereof, means connected with said outlet ports for withdrawing the moist an,

vapor and gases, and independently operable damp-ersfOr controlling said outlet ports.

5. In a'tunnel kiln, the combination of a duplex firing chamber having two firing zones separated by a vertical longitudinal partition wall and provided with rows of furnaces located on opposite sides of the duplex firing chamber, the furnaces of each row communicating directly with the adjacent firing zone, means for withdrawing the products of combustion from each firing zone, a unitary tunnel section extending longitudinally from each end of the duplex firing; chamber provided with parallel goods conveying means movable in opposite directions, each of which passes through one of the firing zones, each of said end sections forming a combined cooling and preheating zone, air heating means receiving the products of combustion withdrawn from said fir ing zone, and means for conducting the air heated by said an heating means to and delivering it into said unitary tunnel sections.

6. In a tunnel kiln, the combination of. a duplex firing chamber having two, firing zones separated by a vertical longitudinal partition 'wall and provided with rows of furnaces locatedon opposite sides of the duplex firing chamber, the furnaces of each row communicating directly with the adjacent firing zone, means for withdrawing the products of combustion from each firing zone, a unitary tunnel section extending longitudinally from each end of the duplex firing chamber provided with parallel goods conveying means movable in opposite directions, reach of which passes through one of the firing zones, each of said end sections forming acombined cooling and preheating zone,

air heating means reeeiving'the prodnets of combustion withdrawn from the fircharging it into said unitary tunnel sections at different points longitudinally thereof, [and independently operable dampers for:

controlling theadmissionof heatediair to said unitary tunnel sections at said points;

7. In a tunnel kiln, the combination of a duplex firing chamber having two firing zones separated. by a vertical longitudinal partition wall. andriprovided with rows of furnaces located on opposite sides oft-hep duplex firing chamber, .thefurnacesof each row communicating directly with the ad]a cent firing zone, means for withdrawingthe products er combustion from each firing zone, a unitary tunnel section extending Ion-- gitudinally from each end of the duplex fir" mg zone, means for conductingfthe air heated by said air heating means to and dising chamber provided with parallezzgoods.

conveying means movable in opposite directions, each of which passesthrough one of the firing zones, each of said end sections forming a combined cooling and preheating zone, said unitary tunnel sections being each provided with aplurality ofinlet ports at differentpoints longitudinally thereof, a damper for controlling each of said inlet ports, air heating means provided with p-assages; communicating with the firing chain:

hers for receiving the products of com'bus tion withdrawn therefrom, and with independent air passages communicating with said ports;

8. In a tunnel of thefiring zones, each of said end sections forming a combined cooling and preheating zone, each of said unitary tunnel sections being provided with a plurality of inlet ports at different points longitudinally thereof, an air heating device on eachside of the duplex firing chamber, each provided wits passages communicating with the adjacent firing zone, and with air passages communicati-ng withthe inlet ports of one of said unitary tunnel sections, and independently operable dampers for controlling said inlet ports. i

9. In a tunnelilziln, the combination of aduplex firing chamber having two firing zones separated by a vertical longitudinal partition wall and provided with rowsfof furnaces located on opposite sides of the kiln, the combination of a duplex firing chamber having two firing llt) duplex firing chamber, the furnaces of each the firing zones, each of said end sections forming a combined cooling and preheating zone, each of said unitary tunnel sections being provided with a plurality of inlet ports, and a plurality of outlet ports located at different points longitudinally thereof, independently operable dampers for said inlet and outlet ports, air heating means provided with passages communicating with the firing zones, and independent air passages connected with said inlet ports and air withdrawing means connected with said outlet ports.

10. In a tunnel kiln, the combination of a duplex firing chamber having two firing zones separated by a vertical longitudinal partition wall and provided with rows of furnaces located on opposite sides of the duplex firing chamber, the furnaces of each row communicating directly with the adjacent firing zones, means for withdrawing the products of combustion from each firing zone, a unitary tunnel section extending longitudinally from each end of the duplex firing chamber provided with parallel goods conveying means movable in opposite directions, each of which passes through one of the firing zones, each of said end sections forming a combined cooling and preheating zone, each of said unitary tunnel sections being provided with a plurality of inlet ports, and a plurality of outlet ports located at different points longitudinally thereof, inclependently operable dampers for said ports, an air heating device on each side of the duplex firing chamber having passages communicating with the adjacent firing zone, and independent air passages communicating with the inlet ports of one of said unitary tunnel sections, and an air withdrawing device for each of said unitary tunnel sections connected with the outlet ports thereof.

11. In a tunnel kiln, the combination of a duplex firing chamber havingtwo separate firing zones arranged side by side and pro vided each with a row of furnaces located adjacent to its exterior wall and discharging into the adjacent firing zone, an eduction fiue adjacent to each of said furnaces and communicating with the adjacent firing zone forwithdrawing the products of combustion therefrom, independently operable dampers for said eduction flues, a unitary tunnel section extending longitudinally from each end of the duplex firing chamber, said kiln being provided with twoparallel lines of tracks extending longitudinally there through for two oppositely moving trains of cars, each line of tracks passing through one of the firing zones, and each of said unitary tunnel sections, each of said unitary tunnel sections being provided with a plurality of inlet ports arranged at different points longitudinally thereof, air heating means havpassages communicating with said eduction fines, and independent air passages communicating with said inlet ports, and independently operable dampers for said inlet ports.

l2. In a tunnel kiln, the combination of a duplex firing chamber having two separate firing zones arranged side by side and provided each with a row of furnaces located adjacent to its exterior wall and discharging into the adjacent firing zone, an eduction flue adjacent to each of said furnaces and communicating with the adjacent firing zone for withdrawing the products of combustion therefrom, independently operable dampers for said eduction flues, a unitary tunnel section extending longitudinally from each end of the duplex firing chamber, said kiln being provided with two parallel lines of track extending longitudinally therethrough for two oppositely moving trains of cars, each line of tracks passing through one of the firing zones and each of said unitary tunnel sections, each of said unitary tunnel sections being provided with a plurality of inlet ports arranged at different points lon- 'gitudinally thereof, air heating means having passages communicating with said eduction fines, and independent air passages communicating with said inlet ports, independently operable dampers for said inlet ports, and means for withdrawing moist air, vapors and gases from said unitary tunnel sections.

13. In a tunnel kiln, the combination of a duplex firing chamber having two separate firing zones arran ed side by side and provided each with a row of furnaces located adjacent to its exterior wall and discharging into the adjacent firing zone, an eduction flue adjacent to each of said furnaces and communicating with the adjacent firing zone for withdrawing the products of combustion therefrom, independently operable dampers for said eduction fines, a unitary tunnel sec tion extending longitudinally fromveach end of the duplex firing chamber, said kiln being provided with two parallel lines of tracks extending longitudinally therethrough for two oppositely movingtrains of cars, each line of tracks passing'through one of the-firing zones and each of said unitary tunnel sections, each of said unitary tunnel sections being provided with a plurality of inlet ports arranged at different points longitudinally thereof, air heating means having passages communicating with said educ ll U tionfiues, and independent air passages communicating with said inlet ports, independently operable dampers for said inlet ports,

each of said unitaryrtunnel sections being thereof, independently operable dampers for said outlet ports, and a r withdrawing means operatively connected with said'outlet ports.

14. In a tunnel kiln, the combination of a duplex firing chamber having two separate firing zones, a row. of furnaces located on Opfill posite sides of said chamber, the furnaces of each row communicating with theadjacent firing zone, an eduction flue adjacent to each row of furnaces, connecting flues from each of said eduction fines communicating with the adjacent firing zone at different points longitudinally thereoffor withdrawing the 'products of combustion therefrom, independently operable dainpcrsfor said connecting flues, unitary tunnel section ex' tending longitudinally from each end of the duplex firing chamber, and provided with inlet and outlet ports located at different points longitudinally thereof, independently operable dampers for said inlet and outlet ports-said kiln" being provided with two parallel lines of tracks extending longitudinally therethrough for two oppositely moving trains of cars, each line of tracks passing through one ofthefiring zones, and each of said unitary tunnel sections, air heating means located on opposite sides of the du pleX firing chamber, each provided with passages connected with the adjacent educt-ion flue, and independent air passages connected with the inlet ports of one of said unitary tunnel sections, and air withdrawing means connected withthe outlet ports of each of said unitary tunnel sections. v

15. In a tunnel kiln, the combination with a. centrally located duplex firing chamber, furnaces communicating with the interior of the firing chamber, means for Withdrawing the products of combustion from the firing chamber, a unitary combined preheating and cooling portion located at each end of the firing chamber. and parallel goods conveying means movable in opposite directions through the kiln, of means for introducing a gaseous heat modifying fluid into each of said endsections at different points longitudinally thereof, means for independently controlling the introduction of said fluid at such points to facilitate the water-smoking.

and oxidation of the goods, and means for withdrawing the moist air vapors and gases from said end sections of the kiln.

16. In a tunnel kiln, the combination with a centrally located duplex firing chamber, furnaces discharging their products of combustion directly into said firing chamber, means for withdrawing the products of combustion from said firing chamber, a unitary combined preheating and cooling portion of: mean'sfor iijitro'ducing a gaseous heat modify ing fluid into each of said end secid ation ef the goods,meaiisfor withdrawhe moistair vapors and gasesfrom- Sald.

loiigitudii ally thereof and means for independently controlllng the withdrawal of said "air, vapors and gases at such points.

-' of theikiln at urrmmmpnnm located at eac li end of the firingchamber,

tions, for facilitating the water sinoking and I 15. In a tunnel hilnQthe combination with a centrallylocated duplex firing chamber,fur-

naces therefor discharging their products of a combustion directly intothe firing chamber, means for withdrawing the said products of combustion from saidfiring chamber, a unitary combined preheating andcooling portion located at each end of the firing chamher, and parallel goods conveying means movable in opposite directions throughthe' kiln, of means for introducing a gaseousheat modifying fluid into eachaof sa'idfend sections, means for independently controlling the introduction of saidufiuid atsuch points to facilitate the water-smoking and oxidation of the goods, means for withdrawing the moist air vapors and gases from said end sections of the kiln at d fferent po ntsflongit'udinally thereof, andnneans for independently controllmg the withdrawal of said air, vapors andgases at such points.

18. In a tunnelkiln, the combination of a firing chamber provided with heating means and a unitary tunnel section extending longitudinally from each end of the firing chamber, providedavith parallel goods conveying means movable in opposite directions and extending through the firing chamber, each of said end sections forming a combined cooling and preheating zone, means for introducing a gaseous heat modifying fluid into each of said end sections at different points longitudinally thereof, independently operable means for controlling the introduction of said heating fluid at such points, and means for withdrawing the moist air, vapor and gases from said end sectionof the kiln.

19. In a tunnel kiln, the combination of a firing chamber provided with heating means and a unitary tunnel section extending lon gitudinally from each end of the firing chamber, provided with parallel goods conveying means movable in opposite directions points longitudinally thereof, means for withdrawing the moist air, vapor and gases from said end sections of the kiln at difierent points longitudinally thereof, and indiependently operable means for controlling the withdrawal of said heating fluid at such points. V

20. In a tunnel kiln, the combination oi a tiring chamber provided with heating means and a unitary tunnel section extending 1011- gitudinally ,iirom each end of the firing chamber, provided with parallel goods convey ng means movable in opposite directions and extending through the firing chamber, each of said end sections forming a combined cooling and preheating zone, means for introducing a gaseous heat modifying fluid into each of said end sections at ditterent points longitudinally thereof, independently operable means for controlling the introduction otsaid heating fluid at such points,

means .for withdrawing the moist air, vapor and gases from said end sections of the kiln, and independently operable means for controlling the withdrawal oi said air, vapor L and gases at such points.

21. In a tunnel kiln, the combination of a iiriug chamber provided with heating means i and a unitary tunnel section extending longitudinally from each end of the firing A chamber, provided with parallel goods con- I means for conducting the, air heated by said air heating means to and delivering it into said unitary tunnel sections.

22. In a tunnel kiln, the combination of a firing chamber provided with heating means and a unitary tunnel section extending longitudinally from each end of the firing'chamber, provided with parallel goods conveying means movable in opposite directions and extending through the iiring chamber, each of said end sections torming a combined cool ing and preheating zone, said unitary tunnel sections being each provided with a plurality of inlet ports at different points longitudinally thereof, a damper for controlling each of said inlet ports, air heating means provided with passages comn'i'unieating with the firing chamber for receiving the products of combustion withdrawn therefrom, and being provided with independent air passages communicating with said ports. 7

23. In a tunnel kiln, the combination of a firing chamber provided with heating means and a unitary tunnel section extending longitudinally trom each end of the firing chamber, provided with parallel goods conveying means movable in opposite directions and extending through the firing chamber, each oi said end sections forming a combined cooling and preheating zone, each of said unitarysections being provided with a plurality of inlet ports and a plurality of outlet ports located at different points longitudinally thereof, independently operable dampers for said inlet vports, air heating -means provided with passages communicating with the firing chamber, and provided with independent air passages connected with said inlet ports. and air withdrawing means connected with said outlet ports.

In testimony whereof I aiiiX my signature.

WILLIAM LEE HANLEY, J 1:.

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