US2325572A - Kiln structure - Google Patents

Description

n 3 Sheets-Sheet 1 "July 27,1943. y J. T. RoasoN Erm.'

KILR STRUCTURE Filed umn 1o. 1941 d vruns the present description is Patented July 27, 1943 zzasvz' EicE KILN STRUCTURE James T. Robson, Richmond Heights, Emma n.

Watkins, Cleveland, and Avon, Ohio, assignors to I ration. Cleveland, Ohio, l Application March 10, 1941, Serial No. 382,536

'z claims. (C1. zsfuz) l 'Ihis invention relates to air moving means for or the like and more particularly to i-mproved means i'or preheating and directing air to the burners of a tunnel kiln of the type used foi` firing ceramic ware. a

In kilns and other heating structures where air or other gases are caused to circulate and move in predetermined manner through theapparatus it is frequently desirablerto move air or gas under pressure at very high temperatures such as 1500 F. to 2400 4F. So called high temperature fans or blowers have been employed to handle gas not over 1600 F. but -because they must withstand the high temperatures at which they operate they involve diillcult lubrication and upkeep'A problems and are therefore expensive to install and maintain. Such fans cannot successfully handle air as hot as.2400 F. 'I'he present invention provides a simple means for moving highly heated gases which completely avoids the necessity for high temperature -i'an equipment, which will handle much higher temperatures than previously proposed apparatus, is of low rst cost and substantially .completely eliminates maintenance expense.

In this speciilcation our invention is described as applied to supply hot air to kiln burners but other applications where very hot 'gases are to be moved will occur to 'those skilledin the art and to be considered illus--v trative rather than limiting.

Tunnel kilns, in which the ware passes through the kiln on cars or other conveyors, are commonly heated by gas and oil burners suitably located in the ilring section oi' the kiln. 'I'hese burners are suppliedwith fuel through proper valves and the necessary air for combustion may, in some cases, be partially mixed with the fuel and partially discharged around the burner nozzle at the point of-combustion. In such operation the air which is mixed with the fuel and introduced directly through `the burner nozzles is termed primary air whilethe air which is introduced around the burner nozzle is termed secondary air. It will be understood that in other cases the primary air is omitted entirely and all of the air for combustion is introduced around the burner nozzle. v

Various means have been employed for preheating the air supplied to a burner to increase the emciency of combustion, and it is an object of the present invention to provide an improved means i'or supplying pre-heated air to a burner which means will automatically maintain a substantially constant temperature of the supplied Edwin G. Zimmerman, Ferro Enamel- Corpoa corporation of 0hio air during changes in the quantity` ofsuch air supply.`

Other objects of our invention include:y the provision ot a simple and enective means for moving highly heated gases; the provision of a kiln structure in which highly heated atmosphere from within the kiln is withdrawn from the tunnel andmingled with air from outside to .raise the temperature of the mixed air to the desired degree for most eilicient combustion at the burner, and the mixed air supplied to the kiln burners under pressure; the provision of proportional mixing means lfor supplying air for combustion to theburners of of furnace; and the provision of an exceedingly simple and entirely automatic means for supplying air at substantially constant temperature to a burner over a wide range of quantity of air flow; the provisionof simple and economical means for supplying air to a burner at elevated temperature and under pressure, uniform feed of air to the burner at all times and eliminating flashing during changes ofthe burner setting to vary the heat input to the furnace; and the provision of automatic means for maintaining a proper air supply to a' burner during variations oi' the fuel supply.

The above and other objects of our invention will appear from the lfollowing description of one embodiment' thereof, reference being had to the Y accompanying drawings, in which- Figure 1 is a fragmentary somewhat diagrammatic side elevational view of a kiln equipped with our proportional mixing combustion air feeding apparatus.

Figure 2 is a transverse cross sectional view through the kiln shown in Figure 1 taken substantially on line 2 2 of Figure 1.

Figure 3 is a longitudinal vertical sectional view through the refractory proportional inspirating mixers on one side of the kiln structure shown in Figure 1 taken substantially on line 3 3 of Figure 1.

Figure 4 is a transverse taken on line 4 4 of Figure 1.

Figure 5 is a transverse cross sectional view taken on line 5 5 of Figure l.

In Figure 1 a tunnel kiln is indicated generally at I and may be of any suitable and well known form. The ware progresses through the kiln on cars I in the direction oi' the arrow (Fig. 1) and a. pre-heatingsection (not shown) may precede the ilring section F and cooling section C, illustrated in Figure 1.-

' A plurality of burners 'are located in the ilring section, there being four cross sectional view a kiln or other type thus insuring a.

source of supply'of outside 2B to the proportional mixer.

on each side in lthe illustrated embodiment. The burners 2 and 3 may be considered as one set and burners 4, 5 and 6 and similarly located burners on the considered as another set. .The supply of preheated air to burners 2 and 3 is separate from .the supply -for the other burners of the kiln and it will be understood that any suitable. number and arrangement of burners may be employed to achieve the desired heating effect in the kiln.

In the cooling portion C of the kiln there are cooling panels 'I and material. When the ware reaches these panels in its progress through the kiln it is cooled and heat is transmitted through these panels from the ware to the air which flows behind the panels, as will be later described.

The roof of the cooling section of the kiln has spaced refractory Walls 8 and 9. Longitudinal vertical walls I0, II and I2 divide the space betweenthe Walls 8 and 9 into four ducts or passages I3, I4, I5 and I6. A'blower fan I1, driven by any suitable means (not shown), provides a air under pressure and forces air throughthe pipe I8 into each of the passages I3, I4, I5 and I6 and as this air travels over the top of the cooling section of the kiln it is heated to a certain degree. Suitable damper valves I3', I4', I5' and I6 are disposed in ducts I3, I4, Preferably dampers I3 and I6 are connected to operate together and dampers I4' and I5 are also operable as a unit. The two outside ducts I3 and I6 terminate at I9 (Fig. 1) and downwardly extending passages 28 and 2I carry air from the passages I3 and' I6 respectively down past the cooling panels 1 and 8 into longitudinally extending ducts 22 and 23, which extend along the bottom part of the kiln structure on either side thereof.

In Figure 3 our inspirating mixer is illustrated disposed in the duct 22. This hot gas moving device comprises a refractory block 24 having a flared hole 24e extending therethrough to form a nozzle outlet for duct 22. The block 24 is spaced from the refractory Venturi block 25 and a chamber 26 is formed around the spaced gap between the nozzle block 24 and the Venturi block 25. A Ypassage 21 connects the opening The relief port opening 28 leads directly into the interior of the kiln tunnel and when air is discharged through the duct 22 by the fan I'I it passages through the nozzle 24 into the Venturi element 25 ydrawing in with it hot air from the interior of the kiln through passages 26, 21 and 28. As the air from the kiln tunnel is very hot it will raise the temperature of the air which passes on through the duct 22 tothe burner 2 to the desired temperature. When the supply of fuel, or fuel andi air, which is conducted to the burner 2 through pipe 2a and control valve 2b is increased, additional air should also be supplied through the duct 22a and this is accomplished by opening the damper I3' in the duct I`3 which leads to duct 22. The resulting increased flow of air through the duct 22 causes a proportionally increased amount of highly heated air to be drawn into the venturi 25 and mixed with the air from the duct 22.

By properly proportioning and spacing the mixer parts and openings air which is discharged through the duct 22a to the burner 2 will be maintained at a substantially constant temperature over a very considerable range of flow and 8 of relative thin refractory I5 and I6 respectively.v

opposite side of lthe kiln may be grammatically illustrated. Valve 2P- is operated by a, lever 2c connected to and actuated by the operating unit 2d which may be'of either the solenoid or motor type.` Damper I3 is operated 'by a lever I3 actuated by an operating unit I3. The control unit A is connected to the line L and to the operating units 2d and I3' by suitable Wiring W and W and movement ofv the lever A in the proper direction will open or close the valve 2b and damper I3 simultaneously. The details of the control devices are not shown.. as they may be of any suitable and well known type. v

The burner 3 (Fig. v5) is supplied with air through the duct 23which is connected to the duct 23 'having a similar proportional mixing device installed directly opposite the elements 24- and 25. This proportional mixer (which is not seen in the drawings) withdraws air from the kiln tunnel in the manner described above in reference to the proportional mixer 24-25. In like manner the two center ducts I4 and I5 are connected to the ducts 28 and 30 which lead to proportional mixture devices of the same form as previously described and one of which is illustrated at 3I and 32 in Figure 3. A passage 34 connects the inlet to the venturi 32 to the open- (Figure 2) includes a similar proportional mixer.'

(not shown) and supplies air at the proper temperature to the'burners corresponding to, and located on the opposite side of the kiln from, burners 4, 5 and 6. In like manner suitable dampers I4 and' I5 are inserted in the conduits I4 and I5 to control the flow of air therethrough and these conduits are preferably connected to operating means, similar to that describedabove for burner 2, whereby the flow of air is increased when the supply of fuel to the burners is increased. y

, By withdrawing air from the tunnel land mixing it with air which has been pre-heated to a certain degree by passage over the cooling plates I and 8 and through the ducts I3, I4, I5 and I6, a material heat economy is obtained and highly heated air is deliveredV to the burners at the proper temperature at all times regardless' of 'variations in the demand of the burners for air.

' proper temperature uniform and e'iicient burner operation is obtained.

It will be understood that although the drawk mgsmustrate-aangismplyofairwthe f burners, additional air may be introduced with the fuei through the pipes which supply the fuel to the burners. Also, it will be understood that suitable valves and dampers .will be employed to controlthe fuel and air supply to each burner or group of burners. although, for simplicity. the control for burner 2 has been specincally shown and described herein. By lnspirating heatedairfromthetunneLmixingitwithfresh air and forcing this airpositively into the ducts feeding the burners, and by automatically controlling the proportion of outside air to air from thetunnel so that asubstantially constant temperature of the air to the burners is maintained. control of the temperature within the kiln structure is greatly improved and simplied. ,In actual practice of the present invention in ceramic kilns Vthe air from fan I1 is heated to about 800 F. t0 1000 F. in the ducts leading t0 the refractory inspirators and is brought up to about 1400 F. to 1500 Eby uthe vaddition of hot air l spondingly increased.

only

the` supply lof heated air to the-'fburner corre- 3. In a" tunnel lkiln of the type described having a firing section and a coolingsection, a burner positioned to supply heat to said firing section. a pipe for supplying fuel to said burner, valve means for controlling the ilow of fuel to said of air through said from the tunnel. In a typical installation about 70% of the4 air supplied to the burners is drawn from the tunnel and it will be seen that by making possible the withdrawal and handling of the very high temperature furnace atmosphere and by automatically maintaining the proper proportional mixing of air from two sources an adequate supply of air at the desired high temperature is assured. The interconnection of the fuel and air control valves, combined with the proportional mixer for maintaining proper air temperature, results in eflicient and trouble free burner operation at all times.

Although we have described the illustrated embodiment of our invention in considerable detail, it will be understood by those skilled in the art that numerous variations and modifications may be made in the specific form and arrangement of the parts and we do not, therefore, wish to be limited to the particular embodiment herein shown and described but claim for our invention all forms thereof coming within the scope of the appended claims.

We claim:

1. In a kil structure, apparatus for withdrawing highly heated gas from aV part of said kiln structure comprising, a duct disposed within a kiln wall. means for supplying air under pressure to said duct, a refractory nozzle member within said kilnwall and forming an outlet from said duct, a refractory Venturi member within said kiln wall and spaced from but having its inlet end adjacent to the outlet of said nozzle, said kiln wall having a chamber adjacent the space between the outlet from said nozzle and inlet to said venturi, and means for conducting gas from said part of said kiln to said chamber.

2. In a kiln structure having a burner, apparatus for supplying fuel and heated Agas to said burner comprisiill, a Dipe for conducting fuel to said burner, means for controlling the flow of fuel through said pipe, a duct lin a kiln wall, means for moving outside air through said duct, said duct-having a nozzle outlet within said kiln wall, a Venturi inspirating member within said kiln wall adjacent said nozzle outlet, means for f inss.

l said wall, a passage from burner. a duct in heat exchange relation to said cooling section, blower means for moving air into said duct, valve means for controlling the iiow duct, a refractory nozzle forming a discharge outlet for said duct, a refractory Venturi member having inlet and outlet opensaid inlet being positioned to receive air from said nozzle, a e extending from adjacent said Venturi inlet into the kiln tunnel, a passage extending from said Venturi outlet to said burner, and interconnecting means for simultaneously opening and closing said? fuel and air control valves.

4. In a kiln structure having a ware chamber defined by.walls, an air duct in one of said walls,

'a refractory inspirator in said air duct within said wall, a passage from said inspirator through said wall into said ware chamber, and means for moving air through said air duct and refractory inspirator whereby hot air from said ware chamber will be withdrawn -through said inspirator while being maintained within the confines of said kiln walls.

5. In a kiln structure having a ware chamber deiined by walls, an air duct in one of said walls, a refractory inspirator in said air duct within said inspirator through said wall into said ware chamber,v means for moving air through said air duct and refractory inspirator whereby hot air from said ware chamber will be withdrawn through said inspirator while. being maintained within the confines of said kiln walls, a, burner positioned to heat said ware chamber, and a passage within said wall for conducting the air from said air duct and said Ware chamber to said burner.

6. In a kiln structure, a tunnel having a roof and side walls and including a firing section and a cooling section, a passage in said roof over said cooling section, damper means for controlling the iiow of air through said passage, means for forcing air through said passage, a cooling panel in a side wall ofsaid cooling section, duct means in said side wall for conducting air from said roof passage over said cooling panel, said duct means continuing within said side wall toward said firing zone, a refractory nozzle within said wall at the end of said duct means, a refractory Venturi member within said side wall and having its inlet adjacent the outlet of said nozzle, said wall having a chamber around said nozzzle and venturi whereby a refractory inspirator is formed, duct means from said chamber into said tunnel, a burner directed to supply heat to said firing section, and duct means in said wall for conducting mixed fresh air and tunnel atmosphere from said venturi to said burner.

7. In a kiln structure, a tunnel having a roof y and side walls .and including a firing section and side air through said duct win be increased and' duct means from said chamber into said tunnel, a burner directed 'to supply heat to said ring section, duct means in said wall for conducting mixed fresh air and tunnel atmosphere from said venturi to said burner, valve means for .controlling the iiow of fuel to said burner, and interconnected operating means forsaid valve anddamper' whereby opening of said fuel valve means vwill s increase said damper opening.

JAMES T. ROBSON. EDWARD H. WA'I'KINS. EDWIN G. ZIMMERMAN.

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