US2069196A - Method of and apparatus for making open hearth steel - Google Patents

Description

M. J. CONWAY Feb. 2, 1937.

METHOD OF AND APPARATUS FOR MAKING OPEN HEARTH STEEL Filed Aug. 5, 1955 4.Sheets-Sheet 1 FIG 1 INVENTOR.

'6 Wzag g ATTORNEY.

Feb. 2, 1937. M. J. coNwAY METHOD OF AND APPARATUS FOR MAKING OPEN HEARTH STEEL Filed Aug. 5, 1935 4 Sheets-Sheet 2 FIG 2 INVENTOR. M7

ATTORNEY.

M. J. CONWAY .Feb., 2, 1937.

METHOD OF AND APPARATUS FOR MAKING OPEN HEARTH STEEL Filed Aug. 5, 1955 4 Sheets-Sheet 5 ATTORNEY.

Feb. 2, 1937. M. J. CONWAY 2,069,196

METHOD OF AND APPARATUS FOR MAKING OPEN HEARTI-I STEEL Filed Ag. 5, 19.35 1 4 Sheets-Sheet 4 ooooooooo oooooooo INVENTOR.

ATTORNEY.

Patented Feb. 2; 1937 METHOD OF AND APPARATUS- FOR MAKING OPEN HEARTH STEEL Martin J. Conway, Coatesyille, Pa.

Application August 5, 1935, Serial No. 34,692

7 Claims. .'(01. 263-15) This invention relates to method of and apparatus for making steel by the open hearth process, and the present application is a continuation in part ofv an application serially numbered 731,456 filed June 20, 1934, which has matured as Patent Number 2,027,151 granted January 7, 1936.

. It is among the objects of the invention to provide an open hearth furnace which shall employ 10 unidirectional firing for which purpose preheated air is supplied by recuperators through which the products of combustion of the furnace are drawn in heat exchange relation with the air delivered to the furnace to support combustion.

Another object of the invention is the provision of means for automatically regulating the air supply to the burners and consequently to different portions of the hearth independentlyof and in addition to the volume and regulation of air supplied through the recuperators.

. In the aforementioned copending application, the recuperator structure per se and its coacting function with the furnace is' particularly featured, and the present application is directed pri-' g5 marily to the furnace characteristics beneficial to the metallurgical process by which the melting and refining of the steel is carried out.

While it has been heretofore proposed to melt ores and iron in unidirectional fired reverberatory furnaces, I am unaware of any attempt heretofore made to commercially apply this method of firing in the making of steel by open hearthpro'cess. u I I am familiar with patent to Fitch No. 1,735,608 granted November 12, 1929 which discloses twin furnaces with .a common air preheat device of therecuperator type, thistype of furnace being recommended for melting iron which'is at temperatures approximately 300 less than the tem- 4Q peratures employed for the melting of steel.

I am also familiar with patent granted to Barbanson et al. No. 1,030,152 granted June 18, 1912 which is for a unidirectional fired open hearth furnace especially usefulin the firing of coal-dust.

This patent does not disclose any method of preheating the air and in fact recommends the utilization of air in merely a slightlyheated'condition. v v

My open hearth furnace structure differs from these unidirectional fired prior art devices in the arrangement of hearth and roof structures which, in cooperation with the burners at one, end, spaced to selectively heat the bath of metal, and the gas duct at-the opposite end and through various other regulable control auxiliaries, is conducive to effectively and efficiently refine steel with minimum loss ofheat and a minimum consumption of fuel." I

For metallurgical purposes, the heat application by continuous firing is-desirable as-it permits 5 of better regulation and application of heat to the entire surface of the bath, which obviates the disadvantages inherent in the reversing regenerator type of open hearth furnaces; Thus,

for example the bath is not submitted to alternate 1 oxidizing and reducing atmosphere. In my unidirectional firing type furnace, the air can be definitely measured to suit the fuel volume for producing, within limits, a desired degree of oxidizing or reducing atmosphere. It eliminates air 15 infiltration and lends itself to absolute stack draft control. By unidirectional firing, erosion-- and abrasion of the refractories are confined to one end of the furnace while the burner end maintains its shape and proportions indefinitely. 20

.The heat transferred to the bath for metallurgical reactions is under control at all times because of the steady temperature of the incoming air which, all in all, increases the rate of production of the furnace, lowers the refractory costs 25 perton of the refined metal with a consequent reduction in the cost of the product.

These and other features of the invention will become more apparent frdm a consideration of the accompanying drawings constituting a part 30 hereof in which like reference characters designate like parts and in which:

Fig. -1 is a plan view of a furnace embodying the principles of this invention;

Fig. 2 a vertical section taken on the line 2-2, i 1;

Fig. 3a similar view taken on the line 33, Fig. 1;

Fig. 4 a similar view taken on the line 4-4, m Fig. 1;

Fig. 5 a horizontal section-taken on the lines 5-5, Figs. 3 and 4;

Fig. 6 a vertical section taken on the line 68, Fig. 1. 45 With reference to Fig. 2 of the "drawings, the

reference numeral l designates the permanent hearth upon which'the basic hearth materials are supportechcharging doors 3 and tap hole 4 being provided to respectively charge and discharge the furnace hearth; The hearth-2 is formed with sloping sides 20 which, in cooperation with the roof 5, constricts the-furnace chamber at the respective ends so that the enlarged central heating chamber of the furnace per- 5 I mits of expansion of the fuel gases as their prod- 'ucts of combustion are developed. To this end,

an especially enlarged portion is provided by the sawtooth-shaped portion 6 of theroof above the velocity of the products of combustion which,

-. ing from the recuperator structures as will'be through the gradually reducing area of the furnace, pass out of the duct 1 communicating with a slag pit Ia leading to a series of recuperator structures as will be hereinafter explained.

Burners 8 and 9 project through the burner ports in the end wall and roof of the furnace respectively and are disposed to apply or project a flame streamto blanket first the hearth for sintering before the. hearth is charged with scrap metal, pig iron; etc., and for reducing the charge and blanketing the bath during the melting and refining periods of the process. Burners 8 and 9 are supplied by a common fuel line l0 and have individual regulating valves II and l2 to control the fuel supply to the respective burners. The burners 8 and 9 are disposed in air ducts I3 and I4, respectively, which supply the preheated air from a commonduct |5 leadhereinafter'%scribed. The air ducts 3 and M are provided with dampers |3a and Ma to obtain individual regulation of the air supply to the several burners.

On account of the intense heat developed in the furnace chamber, it is desirable to cool. the refractory constituting the furnace roof, and to this end the structural supports l6, which con stitute hangers for the roof, are covered wit sheet metal I! to constitute a circulating space for a cooling medium such as air which is drawn into the open ends l8 and I9 by a forced draft created by an exhaust duct 20. To provide cooling in the event of failure of the exhaust means, side doors 2| and'a ventilator 22 are provided for setting up a natural draft through the ingress of air which. is circulated by the convection currents produced by hgat radiation through the roof refractory. Other means of forced cooling of the furnace roof will be hereinafter described. i p

The functional character of the furnace of Fig. 2 is briefly; the firing of the furnace chamber atone end and the withdrawal of the products of combustion from the opposite end, the

control of combustion and the velocity of theproducts of combustion through the dimensional variations of the roof and hearth spacing. The regulation of. the preheat to support combustion and produce desirable oxidizing and reducing designate recuperators through which 1thew'aste gases are drawn at gradually reducing temperaconditions will be hereinafter described'in con- 7 nection with the detailed description of the auxiliary apparatus, a plan view of which is shown in Fig. 1 of the drawings. v In Fig. 1, . reference characters 25, 26 and 21 tures, the recuperator structures 25 and 26 consisting of refractory tile and is the primary. re-

and 21 arecommunicative through chamber 36.

Duct 3i communicates with a stack 32 to which f of the recuperator.

the products of combustion may be passed directly from recuperator 26 or after passing through recuperator 21 by duct 33, a suction fan 34 being provided for this purpose.

The air ducts 13 and I4 surrounding theburners 8 and 9 communicate through manifolds 35 and 36 with a common duct 31, one end of which passes to the preheat air chamber of recuperator- 25 to which air is supplied by a blower 38, having .an air duct 39 leading. to the bottom of the recuperator tile structure, as shown in Fig. 3

of .the drawings, and having another air supply. pipe 46 communicating with an injector 4| dis-' fto maintain a balance of pressure on both sides of the recuperator tile for reasonsghereinafter explained.

Air is supplied through the To prevent the development of pressure diiferentials, a regulator 42 is provided, the regulator being of a well-known type that is connected by tubes 43 and 44 to the air and waste gaspa'ssage Ihe regulator is connected by suitable control means 45 in thecircuit of motor 46 that drives the blower 38 to regulate the oper'ation'of the blower to balance the pressures in the recuperator passages.

Duct 26 for circulating the coolingair in the chambr above the: roof by drawing air through the end openings l8 and I9 may be utilized to supply air under pressure by the blower 50, having conduit connection 5| with duct 20, which connection is provided with a gate valve 52. Duct 26 also connects through conduit 53 with a blower 54 that delivers the air drawn from the space 'above the roof of the furnace to the recuperator 21 when gate 55 is open, and gate 52 is closed.

A' regulating damper 56,is provided in conduit 53 and a d'oor5'| which is opened when damper 55 is closed and blower 50 is operated.

Figs. 3 to 6 inclusive show in detail the, air and gas flow passages through recuperators 25, 26 and 21 in which the air duct 31, Fig. 3, is shown communicating with an air collecting chamber 60 at the top of the recup'erator' tile 6| of the.

is shownconnected to the air passage 29.lead-' ing from rccuperator 26 torecuperator 25. In

Fig. 5', the double arrows indicate the movement I of the waste gases orproducts of combustion after leaving the collectingchamber Ia at the bottom of the furnacefiue or duct I, and the single arrows indicate the direction of move- ,ment of air supplied to the heat exchange tile 6| from recuperator 26.

The tile in the recuperator by the numeral 62' and the movement of the waste gases and air are designated by the double and single arrows, respectively. The metal construction of the recuperator 21 is designated by the numeral 63, 64 being the waste'gas passages and the spacing between the members 63 being the air passages as indicated by the single arrow. Bailles .65 are provided in the metallic recuperator to divert the direction of air fiow as shownQthus assuring maximum contact of the air withthe heat exchanging elements. p,

The operation of the above described apparatus is briefly as follows:

With particular reference to Figs. 1 and 2,

26 is designated is charged through the side openings 3, but as the surface 2 of the hearth is renewed-for each charge, the flame from burners 8 are directed to blanket the hearth material with a sheet of flame to sinter the material preliminary to delivering the charge to the chamber. When the tion or waste gases generated in the furnace chamber are withdrawn through flue 1, and by virtue of the divergent path of the gases, the solid particles are precipitated and settled in collecting chamber Ia, thus permitting the free gases to pass into the entire structure of the recuperator 25, from whence it passes through duct 28' to recuperator 26, thence through chamber 3!! to recuperator 21 from which it"is exhausted through conduit 33 by blower 34 and delivered to the stack 32'. I

"The air to support combustion may be preheated initially by being drawn over the roof of the furnace beneath the covering material II where its heat exchange relation with the refractories of the roof portions 5 and 6 produces a preliminary heating of the air which is withdrawn by blower 54 through the duct 20 and de-. livered to the recuperator 21. It is then conducted through the recuperator 26, duct 29 to recuperator 25, and finally passes through duct 31 to the manifold 35 and 36 of the burner ports whence it emerges to envelope the burner tips and mingle with the fuel to form a combustible mixture.

- If it is desired to utilize forced cooling of the furnace roof under conditions of excessive heating of the roof refractories, gate 55 of duct 20 is closed, door 51 opened and the blower 54 draws air from the atmosphere and delivers it to the combustion.

recuperator 2'! from which it is transmitted to the recuperators 26 and .25 as previously explained and as shown by arrows in Figs. 3 to 8 inclusive of the drawings. Gate 52 of conduit 5| is then opened and blower 50 delivers air under pressure to duct 20 which carries it to the chamber constituted between the top of the roof of the furnace and the covering sheet material l1. Under these conditions, the end openings l8 and I9 may be closed to cause the air to leak through the crevices of the roof refractories,

. force cool the refractories and protect the roof against the excessive heat of the".products of If the forced cooling is either by circulating air, by exhaust means or delivering air by pressure means, the generator 22 is opened as are the side doors 2|.

To prevent damage to the recuperator tile by any pressure differential caused by air pressure and gas pressure in the tile structure regulator 42 by controlling. the blower 38 'will maintain a balancedpressure by delivering more of less air to the furnace thereby varying the volume and pressure of the products of combustion passing through the recuperator tile. Such balanced pressure will prevent distortion of the tile structure with consequent leakage resulting in the products of combustion being recirculated through the preheat air duct to the furnace chamber.

' By regulating the burner valves H and I2 and air supply dampers |3a and Ma for the delivery of the volume of the preheated air and the temperature thereof, an oxidizing or reducing atmosphere may be created in the furnace chamber to produce the metallurgical conditions for the bath of metal supported upon the hearth 2. The importance of such regulation is obvious to one skilled in the art, and in addition the location of the burners 8 and 9 will direct the flame to blanket the bath and to furnish an adequate supply of heat to all portions of thebath. By

regulation of the fuel supply to the individual burners and the volume and temperaturebf-the preheat, any temperature condition may be readily obtained in the melting and refining chamber. When the metal has been refined, it is withdrawn from the tap hole 4 into an ingot pouring ladle or other suitable receptacle.

Because of the facilities for definitely measuring the air, the furnace may be fired by a variety of fuels and a definite quantity of air can be supplied for a given quantity of fuel to produce any degree of oxidation or to provide a desirable reducing atmosphere, required and best suited to the condition of the bath. .The stack draft control of this furnace. will cut down oxidation losses and heat transfer losses, both in the bath and recuperator. The destruction of the refractories by erosion and abrasion is confined to the exhaust end of the furnace which can readily be replaced while the burner end is maintained in shape and proportions indefinitely, thus avoiding costly replacement and rebuilding of these complicated parts of the furnace. The heat transferred to the bath for metallurgical reactions is under control at all times by controlling the temperature of the incoming air and the refining of the bath is greatly expedited with a consequent reduction in the tonnage cost of the finished metal.

While in my former application I am claiming the features of pressure balance and temperature control and regulation effected through the recuperators and their controls, I am herein claiming the characteristics of the furnace per se or in combination with certain fuel, air and waste gas regulating devices or parts.

I claim:

1. In an open hearth furnace, a hearth, side walls and roof, forming a heating chamber enlarged intermediate its ends to constitute a plurality of combustion compartments, one of which is elevated with respect to the other, burner openings to said compartments communicating with a source of preheated air, burners projecting into said compartments through said openings inclined to impinge flame streams against the ma terial supported on the hearth, a common exit for the products of combustion remote from said means for opening said cooling chamber and for circulatingair therethrough by withdrawing the air therefrom, said air being thereby heated, burner ports at one end of the furnace chamber, a waste gas passage at the opposite end, means for closing said cooling chamber and for delivering air under pressure therein, and means venting the cooling chamber when the pressure cooling means is inoperative.

3. In an open hearth furnace. a hearth, side walls and roof forming a furnace chamber, said roof being off-set'atone end to form a plurality I end wall of saidfurnace chamber and burner of combustion compartments, burner ports in the ports in the'ofi-set portion of the roof, burners in said ports, a common waste gas passage at the end'of the furnace-chamber opposite'said burners and ports,'said burner ports communicating with a source of preheated air, means for independently regulating the temperature and volume of theair supplied to said burner ports, and means for independently regulating the fuel supply to the burners at the end and'in theofiset portion of the furnace roof whereby indee 'pendently,regulable heat zones are established in selective portions of the furnace chamber.

-4. An open hearth furnace structureias set forth in the next preceding claim characterized by the burners at the end of the chamber being disposed to project a heat fiame parallel with'a portion of the furnace hearth and in the direction of a waste gas passage, and the burners inthe off-set portion of thefurn'ace roof being inclined to. impinge a flame stream substantially centrally of the furnace hearth and in the direction of the waste gas passages.

5. The method of treating steel in an openhearth furnace consisting in the application of a plurality of flame streams spaced longitudinally and transversely of the furnace chamber at. one end thereof to blanket the bath supported by the furnace hearth, supporting combustion in the furnace chamber by a regulable quantity of pre-' 1 heated air, and maintaining the temperature of the preheated'air .constant'during the entire treating period. 5

6. An open hearth furnace comprising a melting hearth having sloping sides and forming the bottom wall ofan enclosed heating chamber, the

roof of said chamber having an inverted vshaped portion to provide an enlarged combustion area, a burnerport inone wall ofvsaid furnace at substantially the level of the hearth and aburner port disposed through the off-set portion of the roof. constituted by one leg of theinverted vgsaid port being spaced a substantial distancehoriz'ontallly of the first named port, the roof and hearth remote from the ports gradually converging to form a common exhaust passage for the products of combustion at the end of the heating chamberopposite the burner ports, and means for independently regulating the fuel -and'preheated air supplyto'said ports.

, 7. In an open hearth furnace, a hearth, side.

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