US2273903A - Apparatus for uniformly heating air supplied to a furnace - Google Patents

Description

Feb. 24, 1942. o. SMALLEY EIAL APPARATUS FOR UNIFORMLY HEATING- AIR SUPPLIED TO A FURNACE Filed Nov. 1, 1940 2 Sheets-Sheet l 1/11 min" lolnnwmmmnnu mwfl 7f ulrv a n. 2 d

Feb. 24, 1942. SMALLEY r L 2,273,903

APPARATUS FOR UNIFORMLY HEATI NG AIR SUPPLIED T0 FURNACE Filed Nov. 1,' 1940 2 Sheets-Sheet 2 v 4 4s, 1 2s 43 I 4, L? -1 W N 49 -r1 -w 4+ 4 45 I A\-} I% i V INVENTORS U/Wer Jma/ky Attorneys Patented Feb. 24,1942

UNITED STATE s PATENT OFFICE APPARATUS UNIFORMLY HEATING AIR I SUPPLIED TO A FURNACE Oliver Smalley, Pittsburgh, Pa., and Herbert A. Reece, Cleveland Heights, Ohio, assignors to 'Meehanite Metal Cor Tennessee poration, a corporation of Application November 1, 1940, Serial No. 363,876

I (Cl. 266-30) 9 Claims.

In the following discussion and description the,

operation and structure of a cupola for the remelting of metal will be referred to but it is to be understood that our invention includes the structure and operation of other furnaces and similar devices wherein a blast of air-or. other gases is supplied through a plurality of tuyeres or like openings to the interior of the furnace or similar device. The present invention utilizes the heat generated within the cupola for preeheating the air delivered through the cupolatuyeres to the interior of the cupola. *During operation of the cupola the coke or other similar fuel charged into the cupola burns and generates a large amount of heat within the shaft of the cupola.

The hot gases resulting from the combustion of thecoke penetrate the charge of coke and metal within the cupola and arise up and out through I the top of the cupola, The heat energy borne by these hot. gases is ordinarily lost to atmosphere at the top of the cupola except for the small. amount of heat radiated through the body of the cupola along the circumferential sides thereof.

In pre-heating systems prior to the present inlow to permit the hot gases to flow through the hollow wall and to thus pass the heat through a relatively thin shell of the wall to the air flow,- ing through the air supply system on the outside of the cupola.

- The prior systems, however, were subjected to limitations, defects and disadvantages which did not provide for an efficient and proper pre-heating of the air supply. The air passing through the conduits or wind box of the system was heated only upon one side, that is, only through 55 more uniform the wall next adjacent to the cupola body. There was a lack of uniformity in the heating of the the arrangement of the parts and the inherent disability of the structure. Other limitations preventing the production of the desired results in prel-heating air are apparent upon inspection of the structure of the previous systems and particularly in the light of the disclosure of the re sults obtained from the present invention.

It is an object of the present invention to obviate the limitations, defects and disadvantages of the prior systems.

Another object of the invention is the provisio of an improved system of pre-heating the air supplied to a cupola afl'ording results and presenting advantages not heretofore known or obtainable.

Another object is the provisionifor the obtaining of the maximum amount of heat from the hot gases of the cupola in pre-heating the'air supplied to the cupola.

Another object is the provision for obtaining a cupola. I a

Another object is the provision for a distribution of air flow in a system to obtain a uniform heating of the air supplied to a plurality of cupola tuyres- Another object is the provisionof improved apparatus for the utilization of heat generated by a cupola for the efilcient pre-he'ating ofethe air supplied to the tuyeres of the cupola.

Another object is the provision forestablishing a more eflicient heat exchange relationship between the hot gases of the cupola and the air being supplied to the cupola.

Another object is the provision for passing the hot gases of a furnace in the most advantageous course for the heating to the furnace tuyres.

Another object is the provision for passing the hot gases through conduits in the most advan- I tageous heat exchange relationship with the air to be pre-heated.

Another hot gases of a furnace through conduits disposed in a plane transverse of the furnace and athwart the flow of air of the air supply system delivering air to the tuyres of the furnace.

Another object is the provision for passing the heating of the air supplied to a' of the air to be supplied object is the provision for passing the hot gases of the furnace through courses or passageways which together substantially encircle the furnace and uniformly heat the air in the air supply system of the furnace around the annular extent of the furnace. 1

Another object is the provision for most efficiently by-passing hot gases of a furnace for the pre-heating of the air supplied to the plurality of tuyeres entering the furnace.

A still further object is the provision of an air pre-heating system affording results not heretofore obtainable;

Other objects and a fuller understanding of our invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings; in which:

Figure 1 is a cross-sectional view taken-lengthwise of a cupola and wind box embodying our invention and is a view looking in the direction of the arrows of Figure 2;

Figure 2 is a transverse cross-sectional view taken through the line 2-2 of Figure 1 and is looking in the direction of the arrows 22;

- Figure 3 is a cross-sectional view taken lengthwise -of a cupola and wind box embodying a modified form of our invention and is a view looking in the direction of the arrows 33 of Figure 4; and

and communicate with the lower portion of the wind box.

Figure 4 is a transverse cross-sectional view taken through the line 4-3 of Figure 3 and looking in the direction of the arrows 4-4, the line 44 having an angular junction at the axial center of the cupola.

As shown in the several views of the drawings, the cupola body or shell 2| is in the form of a cylindrical shaft, the inner walls of the cupola body 2| being lined by the fire brick lining 24. The body 2| and the lining 24 are mounted upon the usual bottom plate 21 and thereby form the enclosed shaft or stack of the cupola. Suitable supports may be provided to form a base for the support of the cupola.

With reference to Figures 1 and 2 in which the first form of the invention is illustrated, there is shown a wind box 22 of cylindrical shape mounted upon the cupola body 2| by welding or other suitable means and in the. embodiment shown, the outer wall of the cupola body forms one of the enclosing walls of the wind box 22. It is therefore seen from the views of the drawings that the wind box 22' forms an enclosed jacket surrounding the cupola body 2| in such a way that the air introduced into the wind box may circulate entirely around the cupola body.

An inlet conduit 23 is shown in communication with an air blower or other source of an air blast '(not shown) and the inlet conduit 23 is connected to the upper portion of the wind box 22 so as to aflford comunication between the air blower and the inlet opening 25 of the wind box 22.

In the cupolas illustrated in the drawings there are six tuyeres extending through the wall and lining of the cupola body 2| to establish communication between the interior of the shaft of the cupola and the lower portion of the wind box 22. -All six tuyres 30, 3|, 32, 33,34 and 35 are shown in dotted lines in the transverse cross-sectional views of the drawings and three of the tuyres 30, 3| and 32 as seen from the inside of the shaft of the cupola are illustrated in the cross-sectional views taken lengthwise of the cupola. These six tuyeres are of sub- The description of the first form of the invention is made in conjunction with the showing of Figures 1 and 2. In Figures 1 and 2 there is shown a heating conduit 31 positioned within the wind box 22 intermediateof, and at a dis-,.

tance from, the inlet 25 and the tuyeres 30, 3|, 32, 33, 34 and 35. The conduit 31 is disposed in a plane transverse of the furnace-and in a plane which is substantially parallel to a plane passing through the six tuyeres. The conduit 31 extends circumferentially around the outside of the furnace and is disposed intermediate of; and spaced from. the side walls of the wind box to permit air in the upper portion of the wind box to pass down through the wind box around the conduit 31 to the lower portion of the wind box. The spacing of the conduit 31 is such that it is substantially equi-distant from the confining side walls of the wind box to provide for the passing of'substantially the same amount of air between the conduit 31 and the opposite side walls of the wind box.

A plurality of intake ducts extend through the lining and wall of the cupola to provide communication between the interior of the cupola and the circumferential conduit 31. The intake ducts are distributed at substantially uniform intervals around the circumferential extent of the furnace. In the particular embodiment illustrated there are five intake ducts 38 although in practice a greater or less number of intake ducts may be utilized. Hot gases generated by the combustion within the furnace may pass out through the intake ducts 38 to the conduit 31. By reason of the uniform spacing of the ducts 38 there is provided that substantially equal amouns of hotgases will be drawn off at the several locations around the inner peripheral surface of the furnace. The location of the intake ducts 38 is such that they are above the melting zone within the furnace and are located to receive the hot gases while at a relatively high degree of temperature. The ducts are, however, at a high enough location to prevent gases from entering which are at a sufiiciently'high degree to melt or burn the walls of the ducts and the conduits.

A plurality of discharge ducts 39 are provided for drawing off the hot gases within the conduit 31. The ducts 39 are also spaced at uniform intervals around the peripheral extent of the furnace. The locations where the discharge ducts join the conduit 31 are substantially equidistant from the locations where the intake ducts join the conduit 31. Therefore, the intervals at which the discharge ducts extend from the conduits are alternate with the intervals with which the' intake ducts join the conduit 31. In the embodiment shown there are five discharge ducts 39 although a greater or less number may be utilizing according to requirements. It is seen from the figures of the drawings that the five intake ducts and the five discharge ducts .occur at alternate intervals around the extent stantially equal size and are uniformly spaced aroundthe periphery of the-cupola. The tuyeres enter the cupola body at a low level in the cupola of the conduit 31 encircling the furnace.

A plurality of vertical plates or fins 40 are welded to or otherwise suitably engaged to the conduit 31 in such manner that heat carried by the conduit 31 is carried by conduction out through the fins 40. The plates Mlare substantially rectangular and have an annular inner opening for receiving the round conduit 31. Each plate or fin 40 is disposed radially of the furnace and is also disposedvertically or longitudinally of the wind box. Theplates or fins Mare uniformly spaced apart and provide passageways therebetween for the air flowing from the upper portion of the wind box to the lower portion. By

reason of the vertical disposition of the plates and their uniform spacing tangential flow of air in the wind box is. broken up and the air. is caused to flow vertically down through the wind box, The fiow of air passing down through the restricted passageways provided between the plates 40 and on opposite sides of the conduit 31 is modified; thereby to provide forthe substantially equal distribution of air around the annular extent of the wind box. Theplates or'fins 40 being positioned in intimate relationship with the air passing through thewind box heats the air in its downward flow. Inasmuch as the heating surface provided by the conduit 31 and plates or fins 40 is substantially thesame around the annular extent of the wind box the air flowing through the wind box is substantially uniformly heated at all locations around the annular extent of the wind box.

By the arrangement described the hot gases of the furnace are substantially uniformlydistributed through the conduit 31, the hot gases traveling an equal distance in'the conduit 31 before being drawn off through the discharge ducts 39. The

hot gases flow radially out from the'interior of the furnace through the intake ducts 38 and upon reaching the. junctionof the respective intake ducts and the conduit 31 the flow ofhot gases splits or divides, approximately half of. the hot gases flowing toward one adjacent discharge duct 39 and the remaining portion flowing toward the other adjacent discharge duct 39. In this way the hot gases from each intake duct flow toward the two adjacent discharge ducts and the hot gases received by each discharge duct comes quent intervals around the annular extent of the wind box. The hot gases of course tend to cool because of the heat exchange relationship of the conduit 31 and fins 40 with the pair passing through the wind box. If the hot gases traveled a considerable distance in the horizontal conduit before being drawn oil there would be a tendency to heat the air at somelocation to a higher degree than at other locations because of the gradual coolingof the hot gases. arrangement shown the heat of the hot gases is efiiciently utilized and the heat exchange between the hot gases and the air in-the wind box is substantially uniform around the annular extent of I the wind .box.

It is. to be noted that. the horizontal conduit while made of one continuous conduit for simplicity and economy of construction is in eifect a plurality of passageways for the hot. gases. If there are five intake ducts and five discharge ducts alternately arranged in the manner shown and described then the courses or passageways However, by the for the hot gases constitute segments having a length one-tenth of the entire length of the horizontal conduit. The structure may be modified by installing separate and distinct pipes or conduits foreachof these distinct courses or passageways for the gases. Such a modification is, however, within the spirit and scope of the inventlon as herein'claimed, the embodiment here shown being only an example of structure of the invention.

The hotlgases drawn off through the discharge ducts 39 may be re-introduced into the stackof the cupola. atan upper level thereof, may be joined and introduced into an independent stack or chimney, or may be otherwise discharged into the atmosphere at a distance from the cupola.

Valves 4| may be mounted in the discharge duct 39 for regulating the amount of hot gases fiowing therethrough. By regulating the valves 4| in the ducts 39 the total amount of gases drawn through the ducts 38, the conduit. 31 and up through the ducts 39 may be proportioned as desired.

illustrated in Figures 1 and 2. The longitudinal dimension of the wind box 22 mounted on the cupola of Figures 3 and 4 is somewhat less than that illustrated in connection with the description of the first form of the invention. A bustle pipe or supplementary wind box 43 of circular cross-section is mounted above the main wind box 22. The blast main 23 connects with the bustle pipe 43 to provide for the passing of a blast of air therefrom through the inlet opening 25 into the bustle pipe 43. The inlet conduit may join the bustle pipe at a tangent or it may extend down to join at the top of the bustle pipe as illustrated in Figure 3.

A plurality of uniformly spaced interconnecting pipes 41 extend between the lower part of the bustle pipe and the upper part of the main wind box 22. The spacing and disposition of these interconnecting pipes 41 is such that the air in the bustle pipe. 43 is uniformly supplied to the main wind box 22 around the annular extent of the wind box. In the embodiment shown there are five interconnecting pipes 47, as shown in Figure 4, which provide for an equal fiow of air from the bustle pipe'to the main wind box at substantially all locations around the annular pipe. The radial fins 48 extend radially of the axial center of the heating conduit 44 and also extend circumferentially or the cupoia as shown in Figure 4. The outer radial ends of the fins 48 are spaced from the inner walls of the bustle pipe 43 to permit the air to freely fiow around the heating conduit 44 and around the fins. The air around within the. bustle pipe 43. The air within the bustle pipe 43 is free to flow circumferentially of the furnace and also to flow downwardly around the heating conduit 44 and radial fins 48. The air freely flowing around within the bustle pipe 43 is distributed by the plurality of interconnecting pipes 41 to the upper portion of the main wind box 22.

A plurality of intake ducts 45 are provided for introducing hot gases from the interior of the furnace into the horizontal heating conduit 44. These intake ducts passing through the wall of the furnace are distributed at substantially uniform intervals around the periphery of the fur-v nace'. The openings in the furnace to the intake ducts 45 are somewhat above the melting zone to avoid the burning out of the ducts and are sum- .ciently low in the furnace to receive gases at a relatively high temperature sufllcient to preheat the air supply of the furnace. The intake ducts 45 extend radially and upwardly from the furnace and enter into the horizontal conduit 44 at spaced intervals uniformly around the circumferential extent' of the conduit as illustrated in Figure 4.

A plurality of discharge ducts 46 are also provided for withdrawing the hot gases from the heating conduit 44. The discharge ducts 46 are also spaced at uniform intervals around the circumferential extent of the conduit 44. The intake ducts 45 communicate with the conduit 44 and the discharge ducts 46 communicate-with the conduit 44 at alternate intervals. In the par ticular embodiment illustrated in Figures 3 and 4 there are five intake ducts 45' and there are five discharge ducts 46. The locations where the discharge ducts 4B communicate with the conduit 44 are equi-distant between the locations where the intake ducts communicate with the conduit 44. Therefore, proceeding around the circumferential extent of. the furnace it is seen that there is an alternate occurrence of the intake ducts and the discharge ducts, the discharge ducts being uniformly spaced from the intake ducts at the plane of the conduit 44.

The hot gases flowing through the intake ducts 45 split or divide upon reaching the conduit 44 in a manner that'substantially half goes to one adjacent discharge duct and the remainder goes to the other discharge duct. The gas, therefore,

flowing out through each discharge duct is made 4 up of gases received from the two adjacent intake ducts. Inasmuch as there are five intake ducts and five discharge duct in the particular embodirnent shown the hot gases flow only onetenth of the circumferential distance around the furnace before being drawn 011'. There is thus 1 supplied hot gases to the horizontal conduit 44 at frequent intervals around the extent of the conduit. As the hot gases tend to become cooled by reason of the heat exchange relationship with the surrounding air it is desirable that the temperature of the hot gases in the conduit be substantially the-same at all locations around the the number here being given only by way of example. The flow of hot gases through the intake ducts, the heating conduit, and the discharge ducts may be controlled by suitable valves 4| mounted in the discharge ducts. The balance of the flow of hot gases at different locations any differences in the velocity of the air flow through th wind box.

eflicient' apparatus for pre-heating the air supply to be delivered to the tuyeres of a furnace and, by the use of apparatus embodying our invention, air of uniform temperature may be equally supplied to the tuyres of the furnace and thus promote a proper reaction within th furnace. The heat of the hot gases is efficiently utilized to quickly and uniformly pre-heat the air. The hot gases passing out through the discharge duct may be-either passed back into the shaft of the cupola at an upper level thereof, may be carried off into another stack or may be otherwise discharged into the atmosphere.

For improved control of. the pre-heating of air in accordance with requirements we provide temperature control devices 5| mounted upon the outside of the wind boxe illustrated, the control devices 5| having thermostatic elements 50 extending inwardly of the wind boxes in the path of the flow of air from the location of the heating conduit to the tuyere. A suitable handle 52 permits the manual setting of the degree of responsiveness of the thermostatic element 50 connected to each control device 5|.

V By adjustment of the handles 5| the required temperature of air to be delivered to the tuyeres may be set. Suitable operating connections 53, shown diagrammatically by dot-dash lines 53 connect the control devices with the valves 4| in the discharge ducts. Th control devices 5| and corresponding elements 50 are uniformly distributed around the wind box to sample or test the temperature of the air at different locations around the annular extent of the wind boxes.

In the event that greater heat i required to bring the air up to the desired temperature on one side of the wind box relative to the temperature on another side of the wind box, then the thermostatic control of the valves by suitable operating connections between the control devices and the valves provides for the relative regulation of the valves 4| to admit or restrict the flow of gases through the discharge ducts as required. Air sweeping around through the interior of the wind boxes'er bustle pipes from the air blast inlet is subjected to different degrees of heat exchange through the outer wall of the wind boxes or bustle pipes depending upon the distance covered and the amount of the outer wall encountered. It may be desired, in such a condition, to

provide for a greater or faster flow of hot gases through some portions of the horizontal heating conduits than in other portions in order to bring all of the air in the air supply system up to the same temperature before entering the tuyres. The flexible arrangement here provided of having the gas flow valves controlled by the several thermostatic means facilitates the supplying of air at equal temperature to all of the tuyeres.

Although we have described our invention with a certain degree of particularity, it is to be understood that the present disclosure has been r 2,273,903 made only byway of example and that numerous changes in the details of construction and the combination and arrangement of parts may beresorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

We claim as our invention:

1. Apparatus for pre-heating air delivered to a furnace through a plurality of tuyeres substantially arranged in a plane transverse of the furnace comprising, in combination, disturbing means positioned e'xteriorly of, and around the periphery of, said furnace for distributing said air to the plurality of tuyeres, conduit means for hot gases from the furnace positioned within said distributing means and extending circumferentially of said furnace in a plane substantially parallel to, and above, the plane passing through said tuyres, a plurality of spaced intake ducts providing communication between the interior of the furnace and said conduit means at intervals around the extent of the conduit means, and a plurality of spaced outlet ducts communicating with said conduit means, said outlet ducts being positioned at intervals intermediate of said intake ducts, the arrangement of the conduit means, intake ducts and outlet ducts being such that hot gases from the interior of the furnace flow through the intake ducts, flow through-said conduit means to heat the air in said distributing means prior to delivery to said tuyres and hence flow outwardly through said outlet ducts.

-2. In a furnace having an air distributing chamber positioned around the body of th'efurnace, said chamber having spaced side walls concentric with said, furnace and being in communication with a plurality of furnace tuyres forsupplying air to the tuyres, conduit means positioned within said chamber and intermediate of, and spaced from, said side walls, said conduit means being disposed in a plane substantially transverse of said furnace, a plurality of intake ducts extending radially outward from the interior of said furnace and openinginto said conduit means, and a plurality of discharge ducts,

providing outlets from the conduit means to the exterior of said chamber, said intake ducts and said discharge ducts being arranged at alternate intervals around the circumferential'extent of said chamber, whereby hot gases from the interior of the furnace flowing through the intake 4. In a furnace having an air chamber. positioned adjacent to, and encircling, the furnace for supplying air to a plurality of tuyres entering the furnace, a'plurality-of enclosed courses extending at intervals around the furnace substantially radially outward from the interior of the furnace to the interior of the said chamber, extending in the chamber in a direction substantiallycircumferential of the furnace and athwart' the flow of air, through the chamber to the tuyres, and thence extending outwardly of the chamber, the courses substantially encircling said furnace to heat the air at said intervals around the extent of the chamber by the hot gases flowing through said courses from the furnace, the air being supplied to said tuyeres at temperatures provided by the hot gases in said plurality of courses.

5. In a furnace having a wind box positioned around the exterior of thefurnace for supplying air to a plurality of tuyeres, said wind box having an inlet adapted to communicate with a source of said air and having outlets in communication with said tuyres, a heating conduit positioned'in said wind box intermediate of, and at a distance from, said inlet and said outlets, said heating con'duit beingspaced from the walls of said wind box to permit air to pass around the conduit in flowing from the inlet to the outlets and being disposed in an arcuate line concentric with said furnace, a plurality of spaced heat conducting plates in heat conduction engagement with said conduit and disposed substantially longitudinally of the wind box, said plates being distributed at substantially uniform intervals around the extent of said wind box, the

air passing through the wind box being distribuducts pass through said conduit means and hence out through said discharge ducts and air passing through the chamber intermediate said side walls is pre-heated by the hot gases in said conduit means. v

3. In a furnace having an air chamber encircling the furnace for delivering air to a pmrality of tuyres entering the furnace, conduit means positioned in said chamber in heat exchange relationship with air in the chamber, said conduit means providing courses for' hot ted by said plates in a substantially uniform flow I around the extent of the wind box and being substantially uniformly heated in passing said conduit and plates, and means for passing hot gases from the furnace through said conduit to provide heat thereto.

6. In a, furnace having a wind box for supplying blown air toa plurality of tuyres of the furnace; said wind box having an inlet adapted to communicate with a source of blown air and having outlets in communication with said tuyres, a heater positioned in said wind box intermediate the inlet and the outlets for heating the air passing through the wind box, said heater extending substantially around the wind box and being substantially equi-distant from said outlets to provide for the uniform heating of the air delivered to the plurality of tuyres, said heater comprising conduit means disposed in a plane transverse of said wind box and extended substantially around the extent of the wind box,

- said conduit means providing passageway for hot gases therethrough, the courses being disposed in a plane transverse of said furnace and being disposed around the circumferential extent of the chamber, said courses being supplied at substan-- tially uniform intervals around the extent of the conduit means with hot gases from the interior of the furnace whereby there is provided. a substantially regularly recurring supply of heat in said conduit means around the annular extent.

of the chamber in said plane and the air in said chamber is heated by said conduit means around the annular extent of the chamber prior to being delivered to said tuyres.

gases from the furnace, duct means for introducing 'hot gases from the furnace into said conduit. means and for the discharge of the hot gases from the conduit means, said conduit means being located intermediate the walls of the wind box and athwart the how of air through air and being in communication with said main wind box in substantially the same amount around the circumferential extent of the main wind box, conduit means for hot gases from the furnace positioned within said supplementary wind box and extending in a direction circumferl0 the furnace through said heating conduit, and

ential of, and in a plane transverse to said furnace, said conduit means being positioned intermediate the walls of said supplementary wind box and in the path of the flow of air therethrough, a

plurality of intake ducts providing communication at substantially uniform intervals around the furnace between the interior of the furnace and the said conduit means, and a plurality of discharge ducts providing outlets from the conduit means at substantially uniform intervals around the furnace, the intervals of the intake ductsbeing alternate to'the intervals of the discharge ducts, whereby hot gases from the furnace passing out through the intake ducts flows in said conduit means to heat the same and hence out through the next adjacent discharge ducts, and the air flowing through said supplementary wind box is heated by said conduit means supplied with hot gases at said regular intervals and is supplied in substantially the same amounts to I 8'. In a furnace having a main wind box commumcatmg with a plurality of furnace tuyres and having a supplementary wind box adapted to communicate with a source of air to be supplied to the tuyeres, said main'wind box and said supplementary wind box being interconnected in 40 communication at substantially uniform intervals and in substantially equal amounts around the furnace to provide passage for the flow of asubstantially equal supply of air from th supplementary wind box to the main wind box around the extent of the main wind box, a heating conduit disposed in said supplementary wind box intermediate the walls thereof, said heating conduit being extended in a plane transverse to said furnace, duct meansfor passing hot gases from heat conducting fins radiating from the conduit to heat the 'air adjacent thereto, whereby the air passing through the supplementary wind box is heated by said conduit and fins and is equally" supplied to the main wind box at heated temperature for delivery to said tuyres.

9. In a fumace having a wind box positioned adjacent to, and encircling the furnace for supplying a blast of air to a plurality of tuyeres entering the furnace and having a, bustle pipe adapted to communicate with a source of said air blast and encircling the said furnace, said bustle pipe being disposed above said wind box and being connected in communication therewith by a plurality of uniformly spaced supply pipes 'the air passing through said bustle pipe being heated by the heating conduit and radiating fins ,and being supplied through said spaced supply pipes to the wind box for delivery to said tuyeres.

Y OLIVER SMALLEY.

HERBERT A. REE-CE.

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