US2373514A - Blast furnace - Google Patents

Description

Apri] 10, 19.45. Y 1 s, STEWART 2,373,514

BLAST FURNACE Filed March 17, 1943 2 Sheets-Sheet l Y l l H 'f r//////////// April 10 1945- J. s. STEWART 2,373,514

BLAST FURNACE Filed March 17. 1945 2 Sheets-Sheet 2 fr I',

rumn. Atother localities in 'Patented Apr; 1o, 1945 UNITED STATES `PATENT 0F FICE BLAST FURNACE J ohh S. Stewart, New York, N. Y.

Application March 1 7, 1943, Serial No. 479,501 11 Claims. (Cl. 26d-25) This invention relates to blast furnaces of the general type comprising a Vertical stack or shaft adapted to contain the charge of material-ore,

sinter or scrapto be smelted and which latter in conventional to constrict the furnace in the vicinity of the tuyre plane-i. e., the horizontal plane intersecting the discharge nozzles of the tuyres. That is, th'e furnace above the tuyres is usually expanded upwardly and outwardly forming what is known as a "bosh, and aoften this taper is carried all the way up to the ^charging floor at the top of the stack.

Such furnaces, because of' their upwardly expanding diameter, are subject to the disadvantage that the descent of the charge in the stack is slowed down andthe velocity and pressure of the ascending combustion vgases are likewise retarded. Furthermore, the bosh because of such air-permeability with a consequent diminution of the air supply.

Under such conditions, the chargelsubsides very.

slowly and, because of its longer exposure to the hot .ascending combustion gases, the srnelting zone rises higher and higher in the stack, producing what is known as hot tops. Such hot .tops resultA in unsatisfactory furnace performance as evidenced by reduced output, loss of metal by volatilization, and additional metal losses in the` cold slags accompanying such. faulty operation. Y It is an important object of the present invention to provide a blast furnace of the above type which is so constructed and arranged as to overtaper, denes skewbacks upon the baseoi' the stack against which the charge in its semi-fused state can lodge, eventually forming an arch overlying thesmelting zone and blocking the stack passageway.

It is well known that after a furnace has beenin operation for a short time. accretions .begin to collect on the bosh, these secretions forming shelves upon which additional deposits continue to build,.and gradually increase in' thickness and height. Y Finally there remains'only a restricted j openingnear thecenter -of the column of charge l in the nature of afcrack of varying width extending from the tuyreI plane upwardly to the tcp of the charge column. Subsequently, at some place or places in the furnace this crack bridges over so as to form an arch overlying the smelt-` ing zone. Such an arch. besides-preventing the free descent of the charge in the stack, interferes with the uniform and equal distributional the A hot combustion gases therethrough, with the result that eventually a portion of the 4iurnacef'goes "dead" and ceases to smelt.- Under thesedead vspots air pockets fed from several tuyres may form and -develop ruptures,

known as biow holes, extending to thetop of` the charge co1- the furnace the charge choked with nne'ore or other mawith secretions so that it loses its may become terlnl and come the foregoing disadvantages. More particularly, this object is attained by providing t-he furnace at the lower end of the stack with an enlarged smelting chamber, the transverse crosssectional area, of which on the tuyre planer is appreciably greater than the corresponding .area for any horizontal plane intersecting the stackthis being the reverse of usual blast furnace. delsign in which the stack ordinarily increases in width above the tuyre plane to form the bosh.'

Another object of the invention is to provide a blast furnace of the above character so con-1 structed and arranged as to accelerate the downward movement of the furnace charge through the stack, and more especially to prevent'.the charge from bridging over the smelting zone with the consequences previously explained.

Another object of the'invention is to provide a blast furnace of the above character having an enlarged smelting chamber and means for discharging a large volume of air therein for effecting the intense and 'rapid s melting of the furnace charge; and thus increasing'the operat ing capacity of the furnace.

Still anothfer object ofthe invention is to provide a blast furnace of the above character including means for increasing the blast pressure in the stack in order to blow out the ore particles or lines which otherwise would accumulate on the wall o f the stack.

The invention has a further object to provide Va blast furnace of the abovelcharacter in which the tuyres are so .located with respectto the smelting chamber as to insure that the smelting zone is conned entirely within the chamber without extending up into the smallerarea'ot the .stam e e "ce Y Providing s blast fum lenerally er :ne form er mmvemd flmnel. the upwardly sus mmm, an,...

tion of which defines the smelting chamber and the upright tubular portion, the stack. The wall of the smelting chamber preferably is inclined at an angle somewhat greater than the angle of repose of the furnace charge sovas to insure close confinement of the charge within the chamber.

' By reason of the greater value of the smelting chamber relative to the stack per unit of height,

vand because of the larger'smelting zone thereby provided, the subsidence of the charge within the l0 shaft takes place more rapidly than in blast; fur-l naces of conventional boshed design. As a rel sult, there is less opportunity for the combustion zone to rise within the shaft, causing hot topsv and loss ofmetal by volatilization, which further resultsdn cold slags. Also, because the staclr` is smaller in transverse cross-section than that of the sm'elting chamber, a stronger flow of combustion gases will be forced up the stack to carry off the ilnes that tend to collect on the wall of the stack and clog the passageway.

Other objects and advantages will be apparent from the following detailed description of a' preferred embodiment of the invention,v reference being. had to the annexed drawings, in which:

Figure 1 shows in vertical cross-section a schematic view of a blast furnace of a type suitable for the reduction of sintered lead sulphide ores and other lead-bearing materials;

Figure 2 is an enlarged vertical cross-,sectional view through `the smelting chamber ofthey furnace of Fig. l;

' Figure 3 is a plan of the furnace; and

Figure 4 is a transverse cross-sectional View taken on the tuyreplane lthrough a blast furnace of modied shape.

The blast furnace schematically shown in the drawings comprises generally a smelting chamber I, an upright stack 2 rising centrally "from the top of the smelting chamber and having its upper `end communicating through a ring 3 located in the charging floor 4 with a conical hood 5. The

hood 5 leads upwardly into a chimney 6 venting to the atmosphere. A chute I extends downwardly at an angle, passing through the hood, for feeding charges of material to be smelted into the yfurnace from a bin or charge skip, the discharge maintaining combustion to eiect the smelt-ing of the ore, air blasts are directed into the smelt-` ing chamber and into the body of the-charge occupying the chamber from a series of tuyres 9 leading oil' from a bustle pipe I0 encircling thefurnace and connected at IIla with'a source of air under pressure. l f V v The stackand smelting chamber may be of any suitable shape in transverse cross-section, but ordinarily will be circular, as indicated in Fig. 3'. 'I'he walls of the stack and the smelting chamber curedtogether side-byf-side (Fig. 3) and forming to prevent their burning out. The furnace' rests upon a hearth IIv forming ashallow crucible -I2 fromwhlch molten metal ls removed through a.

welll-'|3. For drawing off slag, a tap I4 is provided through the `wall of thesmelting chamber above the hearth level.

.acumenl conduit I s leads oir` nomme chimney 6 and opens into the top of`a, cyclone type of dust-separator I6. A conduit I`I extends from the top of the separator to a bag house (not shown). Within the branchconnection I5, and also within the chimney 6 above the point Aof connection of the branch therewith, are wing dampers I8 and Isa, respectively, which may be so adjusted as to routeA the furnace gases either directly up the chimney to the atmosphere (as will be the case when starting up vthe furnace) or through the separator I6. and flnes carried over from the furnace in the combustion gases and 'the separated material spilling from the lower.end of the separator may be collected in carsV I9 or in any other suitable receptacle. The ilnes may thenbe sintered or agglomerated in any well-known manner and returned to the furnace.

`The smelting chamber'tapers upwardly and inwardly from the hearth at an angle of approximately 65 degrees to the point of itsilunction with the base of the stack. The enlarged smelting chamber thus provided affords space for accommodating a large quantity of coke. Likewise the increasedl diameter 4 of the smelting chamber allows more tuyres 9 to be arranged about its circumference with their discharge nozzles opening into the chamber on the tuyre plane 3-3 for supplying an abundance of 4air to the coke. This results in creating a large, intensely hot smelting zone S within the vor-e lbody filling the smeltng chamber.

The number of tuyres 94 will be determined largely by the size of the furnace which in turn governs the sizeof its smelting zone. lMost of the tuyres are set at right angles to the wall of the smeltingjchamber so as todirect their air blasts of the height of the chamberin order .that thev smelting zone S produced by the -air blasts'is maintained near the bottom of the chamber and sulciently far below the base of the stack to prevent it from creeping up into the stack during the operation of the furnace.

By manning the wan `of the smelunjg chamber at an angle of approximately 65 degrees, -which is slightly more than the angle'of repose'ofthe furnace charge, the entire space of the chamber is kept filled with the charge and this condition is further aided by 4thefweight of the charge .may be composed of hollow metalsections la se- "jackets through which cooling water is circulated column inthe stack. Such an angle also lendsproperproportion to the furnace when the furnace is designed with suitable regardI to the `volumetric relationship-between the smelting chamber and-.the stack. That is, for assuring the descent of the charge through the stack atr the lmost ei'licient rate of travel, `the ratio between the volume o f that part of the smelting chamber included betweenthe tuyre plane," and` the base` 'of the stack 'and the volume of lt'he stack fora corresponding 4rise yin height, should be approximatelyF 231,321.00. Likewise thef'vertical distance between the tuyre plane and the base of the stack, as compared with' the "diameter of the stack, should bear a relationship of about l.00:0.78. Tl'ie'selratios are approximate for blast `Vfurnaces of circular transverse.cross-section and are subjectto variation within reasonable limits.

The. separator removes the dust asvalsiiV reason that it xes the location of the smeltingv zone far enough below the base of the stack to avoid the extension of this zone. during the operation of the furnace, up into the stack.

In the form of blast furnace just described the increased size of the smelting chamber provides for contact of a large volume of coke with a large v'olume of combustion air so as to produce a large, high-temperature zone of combustion. This results in a high CO concentration, rapid smelting and 'relatively low metal losses in the slag. Also the enlarged smelting chamber, because it provides for'a greater amount of furnace charge per unit of jacket surface in comparison with present blast furnaces, results in more economical oper,- ation due to less heat dissipation and hence lower coke consumption. The increased hearth area permits a larger storage-of slag, and hence allows a longer interval between successive slag tappings, which makes for `a better settling of the slag, allows more time for' the reduction of the metal compounds therein, and leads to more uniform temperature conditions within the furnace. Because of the difference in cross-sectional area of the stack and smelting chamber, the

charge will descend rapidly in the stack and spread out in thin layers in the smelting chamber, thus assuring a better and 'more intimate mixture` of the charge. As a' result of the faster descent of the charge throughthe shaft, the shaft may be made shorter in length than in blast furnaces built according to present practice.

An advantage which follows from having the tuyres 9 enter the smelting chamber through its upwardly and inwardly inclined Wall, preferably approximately perpendicular thereto, is that this overcomes to a large lextent the tendency to 'clogging of the tuyeres. Heretofore, inthe usual bosh which inclined upwardly and outwardly,

' considerable diculty was encountered in maintaining the tuyeres open because ofthe flow of the slag on the wall o-f the smelting chamber downwardly into the open ends of the tuyres. By reason of the overhanging wall of the 'smelting chamber in my furnace, the slag cannot drop into or build u'p aroundthe nozzles of the tuyres. The air injected through the tuyres is under suicient pressure to force its way Well into the bottom of the column of charge', thereby causing intensive combustion of the coke and rapid oxidation of the sulphides. This generates a high tem perature within the charge which rapidly melts the ore and creates a large percentage of CQ forthe reduction of the oxides.

Due to the increased number of tuyres, a large volume of air is fed to the smelting chamber, and consequently a large reduction zone is created Within-the-body of the furnace charge. And because this relatively large volume of air must escape through the stack of small cross-sectional area a strong draft will be createdy upwardly through the charge filling the stack so as to carry V off the fines that otherwise would tend to clog the passageway or build up as accretions on the stack wall. These fines, as' has already been explained,

- are recovered in the separator I6.

Other advantagesof vthe blast furnace just described are as follows:

The smaller area of the shaft compared with shafts f present blast furnaces of the same capacity allows a simpler mode of charging, doing away with spreaders, expensive charge cars, etc., and permits the use of a simpler and cheaper .The furnace need'not be circular in shape. In

Fig. 4 isI disclosed a cross-sectional view of a fur I nace of modified form taken on the tuyre plane through its smelting chamber. As indicated in this figure the contour of the smelting chamber is that of a flattened oval as is also. that of the stack 2', indicated in phantom outline. In 'this form of the furnace the same general relationships hold true; that is, the wall of the smelting chamber tapers upwardly and inwardly from the hearth to the base of the stack to provide for an enlarged smelting zone, and the plane of the tuyres 9 is located not substantially more than to 30% of the height of the chamber in order to confine the smelting zone entirely within the chamber. Manifestly the furnace maybe of rectangular or any other shape in cross-section as may be found most satisfactory or desirable.

I am aware that it has heretofore been proposed to provide furnaces with an enlarged hearth area, asexemplied by the heap furnace disclosed in the early patent to C. W. Munson, No. 983,833. Such furnaces, however, are not intended for nor are they capable of carrying out 'blast furnace operations. I am also aware that it has been proposed to design blast furnaces so that their circumferences gradually taper lupwardly and inlwardly throughout the major portion -of their length, but in such furnaces the angle of taper is insufscienf, to matriany affect the rate of suby sidence of the furnace charge or the flow of the .current of combustion gases through the stack, and these furnaces otherwise fail to accomplish the many objects I have above explained.

Manifestly various changes in structure-and design may be made in the form of smelting `furnace described above, which is to be regarded as exemplary and not restrictive of the invention, without departing from the spirit of my invention as defined by the following claims.

rI claim:

1. A blast furnace comprising a smelting chamber, a vertical shaft' extending upwardly from said chamber, said shaft and chamber being adapted to receive and conne a charge of material to be smelted, an opening for charging material into the top of said shaft to substantially ll the shaft and chamber, a series of tuyres discharging through the wall of the chamber in a tuyre plane located sufficiently below the base of the stack as to'avoid extension of the smelting zone from the chamber into the stack, and means for withdrawing slag and molten metal from the,

bottom of said chamber, said chamber having its wall tapered upwardly and inwardly between the tuyre plane and the base of the stack at an `inclination such as to embrace and confine the said chamber, said shaft and chamber being rial to be smelted, an opening for charging material into the top of said shaft to substantially ll the shaft and chamber, a series of tuyresdischarging through the wall of the chamber in a tuyre plane located sufliciently below the base of the stack as to avoid extension of the smelting zone from the chamber into the stack, anda hearth providing a crucible for receiving molten metal at the bottom of said chamber, said chamber having its wall tapered inwardly and up- 4adapted to receive and confine a charge of matewardly at an angle not substantially less than 65 degrees to the horizontal so as to provide space to accommodate an enlarged smelting zone.

3. A blast furnace comprising a smelting chamber, a vertical shaft extending upwardly from said chamber, said shaft and chamber being ,4 adapted to receiv'jand confine a charge of vmaterial. to be smelted,"an opening for charging material into the top ofsaid shaft to substantially fill the shaft and chamber, a series of tuyres discharging through the Wall of the chamber in a tuyre plane located suiiciently below the base of the stack as to avoid extension of the smelting zone from the chamber into the stack, and a *I hearth providing a. crucible for receiving molten metal at the bottom of said chamber, said chamber having its wall tapered upwardly and inwardly from the hearth to the base of the stack,

and said tuyre plane being located not substantially above percent of the vertical height of said, chamber. l

4. A blast furnace comprising a smelting Y chamber, a Vertical shaft extending upwardly from said chamber, said shaft and chamber being adapted to receive and connea charge of material to be smelted, an opening for charging material into the top of said shaft to substan'- tially' fill., the shaft and chamber, a series of tuyres discharging through the wall of the chamber in a tuyre plane located suiciently below the base of the stack as to avoid extension of the smelting zone from 'the chamber into the stack, and a hearth providing a crucible` for said chamber, said shaft and chamber being of circular transverse cross-section and adapted to receive and confine a. charge of material to be smelted, an opening for charging material into the top of the, stack to substantially ll the shaft chambena vertical shaft extending upwardly from said chamber, said shaft and chamber being of circular transverse cross-section and adapted to receive and' confine a charge of material to be smelted, an opening for charging' material into the top 'of the stack to substantially flll the shaft and chamber, a series of tuyres discharging through the wall of the chamber in a tuyre plane located a substantial distance below the bottom of the stack so as to avoid extension of the smelting zone from the chamber into the stack, said tuyres being directed downwardly toward the hearth of the furnace, and a hearth providing a crucible for receiving molten metal at the bottom of said chamber, said chamber `having its wall tapered `,upwardly and inwardly between the hearth and the stack and the ratio of the volume ,of the chamber between the tuyre plane and the stack to the volume of` thestack for an equal rise in height being not substantially less than 2.73:l.00.

'7. A blast furnace comprising asmelting chamber, a vertical shaft extending upwardly from. said chamber, said shaft and chamber being of lcircular transverse cross-section and adapted to 1 receive and conne a charge of material to be smelted, an opening for charging material into the topl of the stack to substantially ll the shaft.

and chamber, a series of tuyres discharging through the Wall of the chamber in a tuyre plane located a substantial distance below the bottom of the stack so as to avoid extension of the smelting zone from the chamber into the stack, said tuyres being directed downwardly toward the hearth of the furnace, and a hearth providinga crucible for receiving molten metal at `the bottom of said member, said chamber having its wall tapered upwardly and inwardly between the hearth and the stack at an angle not substantially less than degrees to the horizontal and the ratio of the volume of the chamber between the tuyre plane and the stack to the `volume of the stack for an equal rise in height being not substantially less than 2.73:1.00, and

the tuyre plane being located not substantially above one-quarter of the vertical height of said chamber.

8. A blast furnace comprising a smelting chamber,a vertical shaft extending `upwardly from said chamber, said shaft and chamber being of circular transverse cross-section and adapted to receive and confine a charge of material to bel smelted, an opening for charging material into the top of the stack to substantially ll the shaft and chamber, a series of tuyres discharging v through the wall of the chamber in a tuyre plane and chamber, a. series of tuyres discharging I through the wall of the 'chamber in a tuyre plane located a substantial distance below the bottom of the stack so as to avoid extension of the smelting zone from the chamber .into the stack, said tuyres being directed downwardly toward the hearth of the furnace, and a. hearth providing a,

crucible for receiving molten metal at the bottom of said chamber, said chamber having its wall tapered," upwardly and inwardly between the tuyre plane and the stack at an angle not less than the angle of repose ofthe material so as to Provide space to accommodate an enlarged smelting zone; f

6. A blast furnace comprising a smelting located 'a substantial distance below the bottom of the stack so as to avoid extension of the smelting zone from the chamber into the stack, said tuyres being directed downwardly toward the hearth of the furnace, and a hearth providing a crucible for receiving molten metal at the bottom of said chamber, said chamber having its wall tapered upwardly and inward-ly between the hearth and the stack and the ratio of the vertical distance between the tuyre plane and the base of the stack and the diameter of the stack being not substantially less than 1.00:0.'78. 1 ,l

9. A blast'furnace comprising a smeltng chamber,` a vertical shaft extending upwardly from said chamber, said shaft and chamber being of circular transverse cross-section and adapted to receive and conne a charge of material to be smelted, an opening for charging material into the top of the stack to substantiany nuv the shaft and chamber, a series of tuyres discharging through the wall of the chamber in a tuyre plane located a substantial distance below the bottom of the stack so as to avoid extension of the smelting zone from the chamber into the stack. said tuyres being directed downwardly toward the hearth of the furnace, and a hearth providing a crucible for receiving molten metal at Ythe bottom of said chamber, said ,chamber having its walltapered upwardly and inwardly between the hearth and the stack at an angle not 'f substantially less than 65 degrees to the horizontal and the ratio of the vertical distance between the tuyre plane and the base ofthe stack and the diameter of the stack being not substantially less than 1.00:0.78.

. 10. A process of smelting which comprises conbase portion and a high gas pressure -area at and below the junction of the column with the base and overlying the smelting zone, whereby to increase the pressure and temperature in the smelting zone so as to give maximum concentration of carbon monoxide in the gases when the charge of carbonaceous material, carbon dioxide and carbon monoxide are in equilibrium` within the smelting zone, and to increase the temperature of the slag.

11. A process of smelting which comprises confining the charge within the walls of a blast flning in a closed chamber the charge to be smelted in the form of an inverted funnel so as to define a base portion in the shape of a truncated cone and a vertical column oi' restricted diameter extending upwardly from the base portion, the walls of the confining chamber completely conning and lying substantially in contact with the body of charge without intervening spaces, said charge comprising a metal-bearing material, a iluxing material and a solid' carbonaceous f fuel, injecting a large volume of air into the base portionadjacent its bottom at -a multiplicity of circumferentially-spaced points so as to produce a smelting zone located wholly within the furnace in the form of a vertical column terminating in an enlarged :base having downwardly and outwardly sloping sides completely confined by and wholly lying in close contact with the celerate the descent of the charge through the column and to increase the pressure of combustion gases within the base.

CERTFICATE 0F CORRECTION`.

rasant Nc,- 2,375,511.

It is hereby certified that error appearsv inthe printed specification of the above numbered patent requiring correction as follows: Page 2, first column, line 7, for the.wrd'va1ue" read -1--vo1u1ne, 'andthat theV said Letters Patent should be read withl this correction thereintha't the same JOHN s. STEWART'.

may conform to( the record ofthe 'case in theI Patent Office.- 'Signed and ysealed this 26th day of June, A. `D. 1914.5.

i (Seal)v Leslie Frazer y Acting commissioner' of Patents.

and chamber, a series of tuyres discharging through the wall of the chamber in a tuyre plane located a substantial distance below the bottom of the stack so as to avoid extension of the smelting zone from the chamber into the stack. said tuyres being directed downwardly toward the hearth of the furnace, and a hearth providing a crucible for receiving molten metal at Ythe bottom of said chamber, said ,chamber having its walltapered upwardly and inwardly between the hearth and the stack at an angle not 'f substantially less than 65 degrees to the horizontal and the ratio of the vertical distance between the tuyre plane and the base ofthe stack and the diameter of the stack being not substantially less than 1.00:0.78.

. 10. A process of smelting which comprises conbase portion and a high gas pressure -area at and below the junction of the column with the base and overlying the smelting zone, whereby to increase the pressure and temperature in the smelting zone so as to give maximum concentration of carbon monoxide in the gases when the charge of carbonaceous material, carbon dioxide and carbon monoxide are in equilibrium` within the smelting zone, and to increase the temperature of the slag.

11. A process of smelting which comprises confining the charge within the walls of a blast flning in a closed chamber the charge to be smelted in the form of an inverted funnel so as to define a base portion in the shape of a truncated cone and a vertical column oi' restricted diameter extending upwardly from the base portion, the walls of the confining chamber completely conning and lying substantially in contact with the body of charge without intervening spaces, said charge comprising a metal-bearing material, a iluxing material and a solid' carbonaceous f fuel, injecting a large volume of air into the base portionadjacent its bottom at -a multiplicity of circumferentially-spaced points so as to produce a smelting zone located wholly within the furnace in the form of a vertical column terminating in an enlarged :base having downwardly and outwardly sloping sides completely confined by and wholly lying in close contact with the celerate the descent of the charge through the column and to increase the pressure of combustion gases within the base.

CERTFICATE 0F CORRECTION`.

rasant Nc,- 2,375,511.

It is hereby certified that error appearsv inthe printed specification of the above numbered patent requiring correction as follows: Page 2, first column, line 7, for the.wrd'va1ue" read -1--vo1u1ne, 'andthat theV said Letters Patent should be read withl this correction thereintha't the same JOHN s. STEWART'.

may conform to( the record ofthe 'case in theI Patent Office.- 'Signed and ysealed this 26th day of June, A. `D. 1914.5.

i (Seal)v Leslie Frazer y Acting commissioner' of Patents.

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