US2759722A - Combined bessemer-open hearth furnace - Google Patents

Description

Aug. 21, 1956 L. D. SAVAGE, JR & 3

COMBINED BESSEMER-OPEN HEARTH FURNAE 2 Sheets-Sheet l Filed Jan. 24, 1952 z hflx INVENTOR. 453752? D. SAVA GEJ v Arra/ways 2,759,722 Ptented Aug. 21, 1956 United States Patent Ofihce COMBINED BESSEMER-OPEN FURNACE Lester D. Savage, Jr.,` Minneapolis, Mimi.

Application January 24, 1952, Serial No'. !68,028

6 ClamsL (CI. %G -65) This nvention relatcsgeneral'ly' to op'en hearth furnaces used in the process of reducing undesirable elements froni' iron such as pig iron prior to Conversion of the' iron into steel, and particularly concerns the heat source fo'r' such a fu'nace.

A common type of app'ara'tus u'se'd' to' re'duce the unwanted elements from iron' in' the steel making process is' the open hearth furnace. Thi s type' of furna'ce' has cer& tan advantages over the Bessemer Converter as are welt known in' the art. While' the o' 'en' hearth is s-l'ower operating than' the Besseme'r', it hasa much greate" capacity and' the oxi'dation of elements is' much more' easily controlled It is, however, necessary to provide a' fiel* supply', such' as gas or oit, to the open' hearth' to" keep a flame over the. melt, a need' which is un'doub'ted'ly' more expensive' than in the Bessemer to' which on'l'y oxygen' in some' fojm need be supplied; With this' in mind* 1 have' designed a furna'ce' which is a combination' le'ssemer` and* open h'earth and which retains' the' advantages' of each'.

The prirn'ary object of my irvent oh` is to* provide an open h'earth' furnace with a new and improved heat source* to materially reduce the eXpense of operation.

Another' object of my invention is to provide an improved type of open hat'thfurna'ce having' means for shortern'ng the refinhg period.

Still another' ohject' of' the' ihventbn is to p'rov ide' an open health furna'ce having means* for'heatihg' the lower' portion of' the mel-t to facilitate more rapil otid'ator' of the elements.

With these and other otjects in m'i-nd; my invention broadly conpri ses the comh'ih'in'g of 'a side bTo'wn` Bessemer Converter With a-has'c open* h'ea r'tli fur'ace in' such' a manner as to refi'ne metal in B'cth the Bssemer anti furnace simultaneously' and te utili ze the' 'exother mie Heat* created' in the' Bessemer to providethe flam'eover the'nielt in the firnac'e, and the B'essemer' and furhace s'o` connected that the pure metal s'et fling' or' circul'atin'g' to the hot-'tom' of the melt in the" Bssen-'er will w into the lower portion' of the* melt: i-1=- the` fur ace;

The* above ment'oned and' still additora objec't'- of the ihven'tio'n will Brought to l i'ght dunn the coui'se'of the following specification, reference being mad to the acc'onp'anyin'g: drawing', in

Fi'g: 1 is a: l'ongitdihl vettcal section of the im roved portion` of the fumace with directional'- arrows showing: the direction: of movement of thPYdf of Cbijf' and the melt.

Fi 2: isa transver'se* horizontal: section tkn oh lire 2' -2:of Fig 1 Fi'g 3 is* a transverse vertical'seotientalen online-a s ofi' Fig 1.

Referrng: now more particularly to the di awin'gs; and using: reference; -c'haractep's todesignate"11e struetural fea tures; partsg and'` materials' used' in:: the diffrent figures, the: numenal 1'0: denotes gene-rally a cdnventional open' hearth fumace; only; one side portion-'ot which is shown in ordet that the -important aspectso-f the inventio' rnight` be: clearly displayedindetailt The furnacehas a bed` or liner' 11 of basic refractory material and a roof 12 of acd lin'er connected by a perip'heral side wall 13. This side wall has an acid eXteror section and a basic interor section which run respectively into the roof 12 andbed 11 and which are separated by a zone of neutral refractory I41eading from the interior surface of the wall to the center thereof and' Vertcally downward therein isolating the basic and' acid materials fron one another. The frnace is adapted t'o be filled with molten metal M to a level' at approximately the' pointon the side wall indicated hy number 15, which lies Below the uppemost boundary of the' basic liner.

The Bessemer Converter u'n'it, desgnated generally at 16, is attached' to' the side w of the furnace and may be used in connection with a cn'ventional' fi rhace having slight stru'ctur'al mo'difictions; riad'e' in the wall; The proper ele'vation of the' Converter with respect to the furnce' may be' observed in' Figi 1' and it will be noted that the' Converter' in eife'c't provides an auxiiar chariher t'o' the furnace. The unit 16' ha's a'n acd' liner formiig a' hasin 1`7` at' the Bottom, with the top 18, end' 1j9`, and side' walls 20 continuou'sly curved in a bulhous shape' to denne a corr'husti'on ch'a'mber' 2'1 overthe hasin. The to' rim of the basin 17' is formed b'y* a ridge 2 2 in the ln'e'f extend'n'g on the horizontal around the hasin to thewall 1301? the furha'ce'. It will he noted that the bonem of the Converter' basin sl'opes downwardly toward the' Wall' 1'3 and* that the' ridge 22; particularly at the out'-"efid of the hasin, extends outwardly over the bottom' leaving the end W'all of' the hasin' 23 with' a` concave surface. A slg removal port z 'havng a cl'osufega'te' is provided in one-et the walls 20 (Fig. g

The side wall 13 at th'e' tace of union with the' con- Ve'rt`e`r` 's particularly c'on'stfucfed to allow the' converti* and* frna'ce operation* to be combined. An'` elongat'e'd tuh'ul'ar' passage' or' duet" 2 5 i is' provided through the wall to'lie'ona horizontal planean`d`substantially at'right angle's t'dthe'lohgiti'dinaf aiig ment of the' two units This p'as`- sage' s'eryes as a* header' for a" series' of down'wardly angling tuyere' forming outlets 26 arrange d in'parallef and equally space-d* along' the passgewa'll The tuye're' openingsinto the Converter are' at' substanti'ally theelevation' of the hasin' riin for'hed" b'y'ridg'e 2 2 and the fur'a'nce' melt level' point'1"5. Itis to be' noted that the header passage' is dis po's'ed' substntiallyebove" the melt level line' and" that the tuyere's are disposed at an angle of from preferably five* to" fiftee'n d'egreesto the hofl'zontal An air compreso'r (not shown-'T for fu'nishirig `air` or' other oxygencontaining" gas' uiid'er pressujre' to the passa'geway 2s is'connected to the' p'assa'g'eway bymearsof pip'eZT. immediately aBove the d u'c t or passage 25 wall 13 'is pr'ovidedwth around' port-281 the side wa'lls'29 o'f which diametrically diverge toward theconverte'r to` a-lign' with and jointh'e inwardl'y co'verging interior' s'urf'c'es O'fth'e top 18 and s'id'e'w'alls 20 oftheconvertercoirhtstion chamber 21, `as shbwi'h Fi'gs. l and 2.' Port 2 8 opens into' both the interor of the fur'fa'ce 10 and the con'verter ch'an'ber 21 atelevatons above the normal melt line 15' of' the furnace; Trans-` versely' wide slot like opening-30 and' 31 in the wall 1-3 conh'ect'the hasin 1'7` With thefurnace interior below the melt line (Fig's- 1'-' and 3 opening' so' being disposed 0111 5 slig'htly below t''ye'res 26; and hor''zontally directed while assage -31 eX't e`n'dS b'etwe thebtton of'th'e fWd ui'ts an'd'is diagonally directed as shown' in Fig; 1

In' operation of' the apparatus, the open hearth` furnace is charged in the normal manner with mo1ten= pig i ror'lVL,` an amount of steel scrap beingaadded thereto ifdesired, to' the normal melt level line 15' of the' furnace.- Iron oxide may also beintrodueedinto the melt if necessary' and according to standard practices. As the melt is pouredintothe hearth a small portion thereof Willohviously flow through passages 30` and 3'1 into the hasin of the converter. I find that it is preferable that the basn have a capacity in the range of from one to ten per cent of the furnace melt capacity. When the furnace s filled to the normal melt line the melt level in the basn will come approximately to the mouths of the tuyeres, with the axes of the tuyeres at a slight angle to the surface of melt.

When the furnace has been fully charged, an aeriform oxygen agent, such as air under pressure, is allowed entrance to the passage 25 so as to blast out through the tuyeres 26 to commence the Bessemer process in the converter in a manner well known. The melt M lying in the basm 17 will be rapidly purified, the ovygen combining wth and oxidizing the silicon, manganese, carbon and other elements remaining in the iron, forming acid slag :S on the melt and filling the chamber 21 above the melt n the converter with the intense chemical heat of products of combustion. The blasts of oxygen containing agent issuing from the tuyeres pass across the surface of the melt allowing the oxygen to react therewith, and then tend to follow around the curved walls of the chamber to return toward their source and are guided through the port 28 and into the air space over the main body of melt M in the furnace. The heat thus furnished over the melt causes the carbon and other products in the melt to unte with the oxygen therein allowing the open hearth furnace to function in the normal manner.

Though intense exothermic heat is created by the mixture of carbon monoxide and oxygen in the chamber 21, this heat is even more greatly intensified by passage of the products of combustion into the furnace. This is due to the fact that in the rapid passage of the products through the port 28 the tapered walls 29 cause a further mixture of the carbon monoxide with the free oxygen carried therewith.

It will be obvious that as the upper strata of melt in basin 17 loses its silicon, carbon, etc., and becomes purified thereby it increases in weight per unit of Volume and will settle to the bottom of the basin running downwardly along the slanted bottom thereof and through passage 31 into the bottom of the furnace. This action is accelerated by the oxygen blast from tuyeres 26 which directs the top wave of the melt against the wall 23, resulting in a continuous circulation of the melt in the basin from the upper to the lower strata in the direction indicated by the arrows. As purified melt leaves the converter basin througe passage 31 it is continuously replaced by the more impure melt of the main body fiowing into the basin through the passage 30. Slag accumulating in the converter may be removed through opening 24 after the oxygen supply to tube 27 has been temporarily cut off.

The advantages of my improvement on the open hearth furnace will be readily appreciated. By using the intense exothermic heat generated in the Bessemer as a medium for heating the main body of melt in the furnace in order that oxidation may take place, the expense of an external fuel is eliminated. Additionally the time period for complete refining is appreciably reduced. This is due to several factors: First, the reduction of elements takes place in both units. Secondly, the main mass of melt in the open hearth retains a more even temperature throughout, due to the fact that hot refined melt is continually being supplied through opening 31 to the lower portions of the mass. And, thirdly, as the hot products of combustion are blown through the port 28 they are forced into greater mixture with the excess oxygen traveling therewith causing further combustion of the carbon monoxide and increasing the exothermic heat over the main body of melt.

It is to be noted that the neutral liner 14 crosses the openings 30 and 31 preventing any wearing away of the opening walls by action of the basic and acid materials upon one another.

Of course both the furnace and converter may carry acid or basic lners or the Bessemer a basic and the open hearth an acid if such is desirable. It is realizcd that use of the Bessemer process in combination with an open hearth furnace is not in itself novel. However, it is believed that a workable combination of the Bessemer converter with the furnace is 'heretofore unknown. The present invention makes possible the combined use of an acid Bessemer and a basic open hearth where a high silicon pig iron is the metal to be refined. Or, conversely, where the iron has a low silicon content so as to require an acid open hearth furnace or a basic Bessemer, my Construction may be used for more efiicient refining, as herein set forth.

It is also thought to be of no little importance that the oxygen supply can be controlled in such a manner as to slow the reduction toward the end of the refining period for termination at the proper time. When the oxygen blast is cut ofi there will necessarily be a backwash of the basin melt toward the tuyeres. However, the tuyere angle and the elevation of the header 25 prevent the melt from entering therein.

While herein I have continually referred to the converter as being mounted on the side Wall of the furnace, it is to be understood that the term side" is used relative to the top and bottom of the furnace and is inclusive of the side and end walls thereof. I have found it preferable to associate the converter with the furnace side wall at one end of the furnace and have so shown it in the drawings, although it will be appreciated that the invention can be carried out by mounting the converter on other than the end portion of the wall.

I have accordingly disclosed an improved metal refining furnace which efiiciently and etfectively carries out the aforementioned objectives. It is understood that suitable modifications may be made in the structure as disclosed, provided that such modifications come within the spirit and scope of the appended claims. Having now therefore fully illustrated and described my invention, what I claim to be new and desire to protect by United States Letters Patent is:

1. A furnace for the purfication of metals having a bottom, a top and a continuous side Wall defining a main melting chamber, a second furnace attached to the side wall of said first mentoned furnace and providing an auxiliary melting chamber, said side Wall having a pair of vertically spaced horizontally directed passageways extending therethrough and connecting the two chambers whereby as the main melting chamber s charged to a level intermediate the two passageways the auxiliary chamber will be charged with melt to the same level, oxygen supply means having an outlet in said auxiliary chamber at a level intermediate said passageways for eifecting the Bessemer process on the melt contained in said auxiliary chamber creating hot combustion gases thereover for escape through the upper passageway and into the main chamber, and said side wall having a third passageway below said pair of passageways and connecting the bottom of the auxiliary chamber to the main melting chamber for carrying purified melt from the auxiliary to the main chamber.

2. In an apparatus for refining iron or the like, an open hearth furnace having a continuous side wall enclosing a refining chamber and a heat source for said furnace comprising, a side blown enclosed Bessemer converter mounted on the side wall of the furnace, said converter having a melt receiving basin therein, the side wall having a passageway therethrough providing an open connection between the basin and the refining chamber of the furnace Whereby the basin will receive a portion of a mass of metal melt introduced into the chamber, the side wall having formed therein a plurality of tuyeres disposed adjacent the top of the basin and directed toward the basin, means for supplying an oxygen containing gas to said tuyeres to blast against the top surface of melt in the basin to create hot combustion gases thereover, the side wall having an open port providing a connection between the nteriors of the converter and furnace at an elevation above the converter basin, and the closure walls of the converter above the basin joiutly forming a bulbous shaped interior surface converging to the port to direct the combustion gases through the port and into the chamber.

3. An apparatus for the purification of molten iron or the like comprising an open hearth furnace having a bottom, top and vertical side walls forming a main refining chamber, a second furnace having a bottom, top and side walls forming an auxiliary refining chamber and connected to a portion of the side wall of the open hearth furnace whereby said wall portion serves as a common vertical wall for both chambers, the bottom of said second furnace formed to provide a higher bottom for the second chamber than the bottom of the open hearth furnace provides for the main chamber, said common vertical wal-l having three vertically spaced passageways therethrough providing open connections between the two chambers, whereby when the main chamber is filled with a mass of molten metal to a level intermediate the uppermost and center passageway a portion thereof will flow into the auxiliary chamber filling it to the same level, means in said second furnace for blading oxygen across the top of said melt portion in a direction away from the common wall to efect the Bessemer refining process thereon heating the melt portion and creating hot combustion gases in the second chamber over said melt portion, the lowermost passageway extending diagonally downward from the bottom of the auxiliary chamber to the main chamber for carrying purified melt thereto to heat the bottom portion of the mass, and the side and top walls of the second furnace having their interior surfaces forming a. continuous bulbous shape whereby said gases under influence of the oxygen blast will follow therearound and back toward the common wall for passage through the uppermost passageway and into the main chamber to heat the main mass from above.

4. An apparatus of the character described comprising an open hearth furnace having a peripheral side wall defining a melting chamber within the furnace for holding a mass of metal melt, means for providing sufficient heat in the chamber over the melt mass for purifying the melt, and means for heating the lower strata of the mass which comprises a basin attached outside of and to the side wall of the furnace, said side wall having a pair of vertically spaced passageways providing open connection between the lower half of the chamber and the basin whereby a portion of the mass may flow into the basin, gas injection means for heating the melt portion in the basin, and means for circulating the melt in such a manner as to flow from the chamber to the basin through the upper passageway and from the basin to the chamber through the lower passageway.

5. An apparatus for the refining of pig iron or the like in a molten state comprising a pair of fumace each providing a melt refining chamber, said furnaces integrally connected and arranged in side by side relation with a common vertical wall separaiing the two chambers, means for introducing metal melt into each of the furnace chambers, means associated With one of said furnaces for effecting the Bessemer refining process on melt contained therein, means associated with the other of said furnaces for efiecting the open hearth refining process on melt contained therein, one of said furnaces having a chamber liner of basic refractory material, the other of said furnaces having a chamber liner of acid refractory material, said common wall constructed to have an acid liner facing the acid lined furnace and a basic liner facing the basic liner furnace, said wall liners separated by a zone of neutral refractory material, said common wall having a pair of passageways therethrough for free flow of melt between the two chambers, and means for circulating the melt through the passageways.

6. An apparatus for the purification of molten iron or the like comprising an open hearth furnace having a bottom, top and vertical side walls forming a main refining chamber, a second furnace having a bottom, top and side walls forming an auxiliary refining chamber and connected to a portion of the side wall of the open hearth furnace whereby said wall portion serves as a common vertical wall for both chambers, said wall having at least two vertically spaced passageways therethrough providing open connections between the two chambers, whereby when the main chamber is filled with a mass of molten metal to a level above the extrance of the lowermost passageway to the auxihary chamber a portion of the meta-l will flow into said auxiliary chamber filling it to the same level, means in said second furnace for blasting oxygen across the top of said metal portion in a direction away from the common wall to eifect the Bessemer refining process thereon heating the melt portion and creating hot combustion gases in the second chamber over said metal portion, and the side and top walls of the second furnace having their interior surfaces forming a continuous bulbous shape whereby said gases under influence of the oxygen blast will follow therearound and back toward the common wall for passage through the uppermost passageway and into the main chamber to heat the mass from above.

References Cited in the file of this patent UNITED STATES PATENTS 130,380 Lowe Aug. 13, 1872 465,672 Lindenthal Dec. 22, 1891 596,992 Garretson Jan. 11, 1898 2,526,472 Gilliland Oct. 17, 1950 2,557,651 Gilliland June 19, 1951 FOREIGN PATENTS 93,594 Germany Sept. 13, 1897 326,592 Germany Sept. 30, 1920

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