US2056904A - Continuous furnace - Google Patents

Description

oct. e, 193s. w. A. Momo@ Er AL 2,056,904*

CONTINUOUS FURNACE Filed July 10, 1934. 2 Sheets-Sheet 1 Oct. 6, 1936. w. A. MoRToN ET AL CONTINUOUS FURNACE Filed July l0, 1934 2 Sheets-Sheet 2 Patented Oct. 6, 1936 UNITED STATS PAE carica 2,056,964 CONTINUOUS FUBNACE Pennsylvania Application .my 16, 1934, sensi No. remco is o im. aai

This invention relates to method of and apparatus for continuous and uniform heating of slabs, billets. blooms or the like, and it is among the obiects thereof to provide a furnace design 5 which embodies an improved firing and heat control system.

In the vart of heating by continuous processes asA heretofore practiced, it has been customary to fire the furnace at numerous points and in most instances at spaced longitudinal intervals, the furnace being divided for that purpose into a so-called heating and soaking chamber, thus ese tablishing multiple heatzones of diierent temperatures. Such division of furnace heating l5 chambers was accomplished by the employment of a roof` structure having a drop or partition member that provided for a relatively long heating chamber and short soaking chamber, each of which was individually red by regulable burners. In accordance with the present invention, a furnace construction embodying a single or unit heating chamber is utilized and the application of the heating medium to the slabs or billets to bring them up to the necessary working or rolling temperature is accomplished in a novel manner to obtain the desirable input of h eat without exposing any. portion of the billets to excessive oxidizing or scaling temperatures, and by means of which maximum heating capacity is obtained.

Another object of the invention is the provision of means for preventing the infiltration of air at the discharge end of the furnace thereby, in euect,

producing a reducing atmosphere at the point of' maximum temperature to prevent scaling.

,Stilla further object .of the invention is .the provision of means for utilizing different fuels in conjunction with recuperator structures which are adapted to develop and maintain a high preheat' of the air' directed to the combustion zone.

49 Still another object 'of the invention is the provision o f means for recirculating a part of the preheated air through the recuperator structure Whereg'ases-of -low B. t. u. value are utilized as fuel thereby lsubstantially reducing the temperature differential between preheated air and waste gases in the walls of the recuperator tile.

Still a' further object of the invention is the l provision of means for heating light billets or the like which controls the temperature at the charg- 50 ing and dischargingends of the furnace chamber by directing the heat name or products of combustion from a single iirlng source whereby great flexibility of heat control is provided.

' These and other objects of the invention will become more apparent from a consideration of the accompanying drawings constituting a part hereof in lwhich like reference characters designate like parts and in which:

Fig. l-is a vertical cross-sectional view longitudinally of a continuous heat furnace embodying u the principles of this invention;

Fig. 2 a horizontal section taken along the line 3 2, Fig. l;

Fig. 3 a vertical section transversely of the furnace taken along the line 3 3, Fig. 1; and 10 Fig. a a horizontal cross-sectional view taken along the line d-, Fig. 1.

With reference to the several figures of the drawings, the structure therein illustrated comprises a heating chamber generally designated by l5 the reference numeral i having a constricted charging end 2 and discharge passage 3; material such asbiiletsor slabs i being supported von skid rails or water cooled pipes 5 and moved through the furnace by means of a pusher mechanism 6, 2o when the gate 'l .is opened. As'the billets advance toward the discharge end of the furnace, they travel from the rails 5 onto a solid uniformly heated hearth portion d. The hearth 8 is provided with aslopingend 9 which, with a tapered 25 roof. portion l0 of the heating chamber, forms the discharge passage 3 that is. controlled by a gate il, the billets being received on a feed-roll table i2 by which they are conveyed to the rolling mill. The door mecha w1 o. are operated in timed relaso tion with the pusher mechanism 6 so that the doors open only as a billet is being charged and discharged intoand out of the furnace.

The tapered roof portion it atthe discharge end of the furnace extends to a roof i3 which 35 is a dat arch asshown'in Fig. 3 and4 gradually slopes downwardly towards the charging end 2 of the chamber. A ber port i4 is provided adjacent theapex of the sloping roof portions andV burnersuldfbeneathvthe billets for the bottom 40 heating 'ci'. heavy stock, there being as manyiburners or ports providedl transversely of the hearth as to supply a heat name of the width of the iurnace. The sloping hearth portion 9 adjacent the discharge end of the fur- 45 nace is provided with an exhaust passage l5, and exhaust pwages la and'i'l are 'provided beneath the billet supporting rails :5, passages l5. I6 and il communicating with recuperator structures i8 and I9 that are separated by a partition wall20. 50 n Dampers iba and ita are provided for passages I5 and it to independently regulate the with drawal of the products of combustion through these passages,- and a damper 2i controls exhausti'on of the gases from the furnace chamber di- 56 rectly to a stack passage 22 to provide additional means to maintain desirable heat condition within the recuperator structure.

The arrangement of the recuperator chambers is more clearly shown in Figs. 2 to 4 inclusive of the drawings in which they are shown divided by the walls 28 and 23, and walls 24 and 25, the latter being provided with openings 28 through which preheated air is conducted to a longitudinal passage 21 and thence to a transverse passage 28. The heat exchange tile 28 is built up in the recuperator chambers, the tile forming vertical waste gas passages and horizontal-air passages, the air passages being connected at the bottom with a manifold 30 having conduits 3| extending to the bottom of the recuperator tile, each conduit being provided with a damper or gate 32 to regulate the quantity of air entering the different portions of the recuperator structures.

Manifold 30 has a transverse main 33 which is connected to a blower 34, the blower being also provided with a conduit 35 leading to the transverse passage 28. The preheated air passes upwardly from wpassage 28 through conduit 3,6 to a burner 31 extending into the ring port I4 on the roof of the furnace. Gas ducts or mains 38 and 39 communicate with the burner 31, the duct 38 being of the lesser diameter as it supplies a natural rich fuel gas while the duct 38 is considerably larger to supply a greater volume of fuel gas such as producer gas that is of a lower B. t. u. value than the natural gas and consequently used in greater volume.

A blower 34 is'provided with a gate valve 48 that regulates the volume of air conducted to the manifolds 30 on the sides of the recuperators and a gate valve 4I for regulating the amount of preheated air drawn from the transverse passage 28 for recirculating with the cold air drawn in through the passage controlled by the gate valve 48 for the purpose to be hereinafter explained.

The waste gases withdrawn from the furnace I through the exhaust passage I5 pass into the recuperator chamber |8 thence downwardly through the vertical .tile passages 42..,to a horizontal passage 43 leading to the exhaust stack passage 44. Passage 43 is controlled by a gate 45. Similarly,'the products of combustion exhausted through the passages I5 and I1 may be drawn directly to the stack passage 22 controlled by the gate 2|, or by closing gate 2| the exhaust gases may be drawn through the vertical recuperator tile passages 42 to an exhaust passage 48 leading to a stack passage 41 that is controlled by a gate 48.

One of the features of the invention is the location of the discharge passage 3 below the horizontal plane of the furnace hearth 8'and also below the opening of the exhaust passage I5. By so locating the discharge passage beneath the hearth and exhaust passage, infiltration of air is prevented. Any' air passing into the discharge passage when, for example, the gate |I is open,

will be drawn through exhaust passage I5 and be prevented from contacting the heated billets supported on the hearth 8. By preventing infiltration of air, scale and oxidization are largely.

eliminated and the withdrawal of air through the exhaust passage I5 produces a. reducing. atmosphere in the portion of the furnace immediately ladjacent the discharge passage 3.

The method of nring the furnace and regulanon ofthe appncauon nf neat to the muets together with the control of the furnace tempera- 7 ture through regulation of the exhaust, and the intensity and volume of the preheated air is as follows: The gaseous fuel is supplied through the hearth 8 at substantially its termination with the billet supporting skid rails 5. When the burner vis first ignited, the exhaust I5 is shut off either through manipulation of the damper I5a or by closing gate 45 so that all of the heat is drawn beneath the long sloping roof portion towards the charging end of the furnace, damper Ilia likewise being shut oif or closed for the initial heating of the furnace. Roof I3 is inclined or sloped as shown in Fig. 1 to reduce the volume of the products of combustion toward the charging end ofthe furnace to obtain uniform heating* by lowering the level of movement of the gases as they pass to the exhaust opening I1. As the furnace chamber is brought up to temperature, billets 4 are charged into the heating chamber by the pusher mechanism 8, eachsuccessive stroke of the pusher advancing the billets along the rail 5 a distance corresponding to the width of the billet, and as they approach the firing ports they will be subjected to maximum heat. On account of the water cooled rails 5 producing cold spots or dark spots on the bottom of the billet, the solid hearth portion 8 is provided to uniformly heat the zol billet before being pushed over the inclined slope 8 of the discharge passage 3.

Dampers I5a and IGa are subsequently opened and gates 48 and 45 are wholly 'or partially opened while gate 2| is wholly or partially closed. Instead of the products of-'combustion passing longitudinally of the furnace to the exhaust I1 and thenceto the stack, they will partially be drawn to the exhaust passage I5 and may be partially withdrawn at the mid-portion of the heat-- ing chamber through the passage I6 and partiallly withdrawn through the end passage I1 thence through the tile structures of recuperator chambers I8, I9 and Isa, and through'their respective stack passages 43 and 45.

Blower 34 is placed in operation and the gate 48 is opened an amount to supply a desired quantityof air to the manifolds 30 from which it is conducted through the gate controlled conduits 3| to the air passages of the recuperators. The air, as it is preheated, rises in the tile structure and passes through 'openings 28 of the recuperator walls 25 into the collecting air passage 21thence to the transverse air passage 28 4upwardly through conduits 36 to the burner 31. It is to be noted that after the preheated air leaves the recuperator tile passages, heat losses by radiation are prevented and it is further heated in the horizontal collecting passage 21 which is adjacent the hottest portion of the waste gas tile passage of the recuperator and beneath the exhaust passages I5 and I6.

Provision is also made for recirculating a part of the preheated air when the leaner fuel gases such as producer gas is employed. That is to say, if air is supplied to vthe recuperators in quantities adequate to support combustion whena rich natural gas is employed, a lesser quantity of air is necessary where gases such as producer gases of lower- B. t. u. are fired in the furnace. At the same time, it isnecessary to maintain sunlciently low temperatures of the recuperator tile to prevent overheating and breakage of the tile and to accomplish this a part of the preheated air is recirculated by exhausting the excess portion used for rich fuel from the transverse passage 28 through the blower conduit '35, this being accom- 2,056,904 plighed by opening the gate M and regulating the gate 40 so a lesser quantity of cold air is drawn into the blower. By thus recirculating the air, the temperature differential between the inner and 5 outer walls of the bottom recuperator tiles is substantially reduced or eliminated and a high preheat of air is maintained at the burner port.

By the arrangement of exhausting the products of combustion at the rear and front portion of l the heating chamber and ring at an intermediate point between the charging end and discharging end, high flame temperatures may be directed to the billets greatly in excess of the nnal rolling temperature of the billets Without 15 heating the billets beyond the desired rolling temperature, thereby accelerating the heating and increasing the capacity of the furnace. By proper regulation of the exhaust through passage l5, loss of heat is prevented once th'e billets have 20 been brought up to suitable rolling temperatures.

By means oi.' the intermediate exhaust passage i6, the .waste gas temperatures may be controlled for any desired heating rate. Cold steel entering the furnace has a higher temperature differ- 25 ential with the waste gases than the steel in the area adjacent the exhaust passage i6 and by manipulation of the dampers, this heat 'differential may be reduced at the charging end and increased above the ordinary in the intermediate 30 area so that more uniform heat absorption prevails along the hearth.

Accordingly, by means of the exhaust passage i6, temperature differential and the heat rate along the hearth is balanced or controlled to 35 maintain a more nearly constant condition. When more heat is drawn down passage I6 as a result of increased tonnage, the temperature in the recuperator is increased, and increased air ,preheat temperatures follow. This automatical- 40 ly increases the flame temperature above the solid hearth portion and assists in maintaining the desired temperature differential by which the heat rate may be accelerated.

By dividing the heat exchangers into groups 4'5 of chambers with separate damper control, more effective regulation of the heat in the furnace is attainable. Also by the employment of the unit heating chamben. the furnace is particularly adapted to thevuse of producer gas fuel which does not efciently lend itself to a large number of burners of small fuel capacity.

From the foregoing description of the invention, itis evident that such a furnace structure is adapted to maintain uniform heat of billets, ifngots, slabs or the like in an economical manner as its regular uniform external wall surface requires a minimum input of heat and is adapte'd to the utilization of the cheaper fuels. By recirculating part of the preheated air, the tile 80 at the exhaust end of the recuperator passages is maintained at suitable temperatures and Ya. high preheat is available for eillcient and economical firing- Although an embodiment of the invention has been herein illustrated and described, it will be evident that various modifications may be made in the details of construction and in the arrangement of parts without departing from'the principles herein set forth. It is also apparent that the method of ming and heat control is applicable to continuous heating of articles other than billets, slabs or the like.

We claim:

1. A continuous heating furnace comprising an elongated heating chamber having Aan inclined roof from the charging end towards the discharge end of the chamber and an inclined roof from the discharge end towards the charging end forming an apex remote from the charging end and near the discharge end of the chamber, a hearth disposed within the chamber below the end of the roof-at the charging end and above the end of the roof at the discharge end, an exhaust passage adjacent the charging and discharge ends of said chamber extending beneath the hearth and means for withdrawing the products of combustion from the chamber in divided paths through the said exhaust passages.

2. A continuous heating furnace comprising an elongated heating chamber having charge and discharge openings at opposite ends, a hearth extending longitudinally of the chamber, exhaust passages in said hearth, recuperator tile structures beneath said hearth communicating with said exhaust passages and separated by partition walls dividing the recuperator structures in separately controllable sections, burner ports in said heating chamber, means for withdrawing therproducts of combustion through the exhaust passages direct to the stack, means for conducting the products of combustion through said re-y cuperator sections, means for4 directing air through the recuperator structures in heat exchange relation with the waste gas passages, means for conducting the preheated air from the recuperator structures to the burner port,

and means between the recuperator and the furnace for regulating the volume of air supplied to the furnace independent of that supplied to the recuperator sections.

3.`A continuous heating furnace comprising an elongated heating chamber having an inclined roof extending from a maximum elevation at a portion of the chamber near the discharge end thereof tothe charge and discharge openings of the chamber, a burnr disposed through the roof adjacent the apex thereof disposed to direct a heat flame toward the hearth in the direction of the'charging end of the furnace chamber, a plurality of recuperator structures beneath the hearth of the heating chamber, an exhaust passage adjacent the discharge end of the furnace with the mouth of the passage above the discharge opening of the chamber, said exhaust passage being vin communication with said recuperator structures, an exhaust passage adjacent the charging end of the chamber in communication with the recuperator structures, means for withdrawing the products of combustion from the heating chamber through the several exhaust passages and their respective recuperator structures, means for supplying air tothe recuperators and for withdrawing the preheated air through a passage leading to the burner ports, and means for independently regulating the quantity of cold and heated air supplied to different portions of the recuperator structures.

4. A continuous heating furnace comprising an elongated chamber having a at arch roof sloping frcm a maximum elevation near the discharge end of the chamber towards a charge and discharge opening at opposite ends of the chamber, a lrecuperator structure beneath the hearth of said chamber, an exhaust passage adjacent the charging and discharge ends of the chamber extending beneath the hearth and communicating with the recuperator structure, lexfhaust means for withdrawing the pr`ducts of combustion from the -heating chamber through the exhaust passages in regulable amounts and .passages extending through the from the exhaust passages through the recuperator structures to a stack, means for supplying air to the bottom of the recuperator structures, and means for collecting the preheated air from the recuperator structures near the top thereofr and conducting it to the burner ports of the heating chamber.

5. A continuous heating furnace comprising an elongated heating chamber having a charging and discharge opening at opposite ends, exhaust hearth adjacent the charge and discharge openings, an exhaust passage extending through the hearth intermediate said flrst named passages, a recuperator structure beneath the hearth of the heating chamber in communication with the exhaust passages of the chamber, partition walls dividing said recuperator structures into independently controllable units for the respective exhaust passages, means for by-passing the products of combustion around said recuperator structures to a stack and means for moving the products of combustion through the exhaust passages and controlling the movement at will in the respective recuperator structures to the stack, means for supplying air to the recuperator structures, means for collectingv the preheated air from all of the recuperator structures and conducting it in heat exchange relation with the exhaust passages of the chamber to the burner ports, and means for regulating the quantity of air supplied to the several recuperator sections.

6. A continuous heating furnace comprising an elongated chamber having charge and discharge openings at opposite ends and having exhaust passages extending through the hearth, the discharge passage of the chamber being below the level of the hearth, burner ports disposed in the roof of the chamber for directing a heating flame towards the hearth and in the direction of the charging end of the furnace chamber, a recuperator structure beneath the hearth. means for withdrawing the products of combustion through the exhaust passages into the recuperator structure, and thence to a stack, means for supplying air to the recuperator structures at the bottom thereof and withdrawing the preheated air` same through the air preheat passages of the recuperator structures.

7. A continuous heating furnace comprising an elongated heating chamber having parallel skids for a portion of its length to support the articles to be heated in spaced relation with the hearth, said skid members terminating in a solid hearth portion near` the discharge end of the furnace whereby' the articles to be heated are initially conveyed along the skid vmembers and subsequently on the solid hearth portion, burners in said chamber below and above said skid mem- .'bers, the burners being located to direct a heating flame on the work at substantially the juncture of the skid members and solid hearthv` portion, and means for withdrawing the products of combustion in desired volumes from the top burners, to eiect a division thereof at substantially the juncture of the skid members and the said solid hearth portion.

8. `A continuous heating furnace'comprising an elongated heating chamber having its roof wall adjacent the discharge the respective ends of "the discharge end being beneath tension with said skid members beneath the apex f of the furnace roof and sloping sharply downward to the discharge opening of the furnace, heating means comprising a gaseous burner extending through the roof of the furnace above the work-supporting hearth that constitutes a continuationv of the skid members, burners beneath said skid members and means beneath the hearth and` skid members for withdrawing the products of combustion from the gaseous burner ln divided paths towards the respective ends of the furnace chamber.

9. A continuous heating furnace having a work-supporting hearth substantially horizontal throughout one end of said hearth declining sharply to constitute. a discharge chute for the articles passing through the furnace, a combustion chamber provided above said hearth and waste gas passages beneath the hearth at the respective ends thereof, the waste gas passage at the inclined portion of the hearth and above the discharge opening of the furnace chamber.

10. A continuous heating furnace having a work-supporting hearth substantially horizontal throughout one end of said hearth declining sharply to constitute a discharge chute for the articles passing through the furnace, a combustion chamber provided above said hearth and waste gas passages beneath the hearth at the respective ends thereof, the waste gas passage at the discharge end being beneath the inclined portion of the hearth and above the discharge opening of the furnace chamber, and regulable means controlling the exhaustion of the products of combustion from the heating chamber through the said Waste gas passages.

1l. A continuous heating furnace comprising a heating chamber and a vhearth with a charging opening at one end and a discharge opening at the opposite end,- a product-supporting hearth extending longitudinally of said chamber andl having-its upper level coextensive with the charging opening and above the discharge opening, burners disposed intermediate the charge and 'discharge ends of said `chambers. and exhaust means for withdrawing products of combustion in desired quantities simultaneously at diiferent points across the hearth of the furnace adjacent the discharge end.

12. A continuous heating furnace comprising a heating chamber and a hearth with a charging opening at one end and a discharge opening at the opposite end, a product supporting hearth extending longitudinally of said chamber and having its upper level coextensive with the charging opening and above the discharge opening, burners disposed intermediate the charge and discharge ends of said chamber, and spaced damper controlled exhaust means adjacent the discharge end of the furnace and connected thereto substantially beneath the hearth for withdrawing products of combustion from the furnace.

13. A continuous heating furnace compris' .g an elongated heating chamber having an inclined roof from the charging end towards the discharge end of -the chamber and an inclined roof from the discharge end towards the charging end forming an apex remate frombthe charging end and near the discharge end of the chamber, a hearth disposed within the chamber below the end o1' the roof at the charging end and above the end of the roof at the discharge end, an exhaust passage adjacent the charging and discharge ends of said chamber and an exhaust passage intermediate said end exhaust passages, said exhaust passages extending beneath the hearth, and means for withdrawing the prcducts of combustion from the \chamber selectively in divided paths through the

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