Note: Descriptions are shown in the official language in which they were submitted.
2~7~ :
9~ 57 ~ I ''I -' '~7~ 54~'7 COHEN P~IIITRIII ~2
METlIOD ANl~ Al'PAT~A'l US YOR HEATlNC A METALLuR('7lcAL FURNACE
Thc presen~ invenliol~ relates t~) a metl)od of hea~ g a tl~etallurgical furnace, in
particular an electric arc furnace char~ed willl scrap or simila.r solid m~terials. Ivletllods of
this type ale nIlmero~ls ~nd have been kno\vn for a long ~in~e and new olles are bcing
cons~an~ly propose(i. Thus, for instance, in F`ederal Republic of C3ermany P~lellt 14 33 424 a
melting fllrnace is described w hicll can be optionally healed witll burners and electro(les,
oxy~en ;~n~ ow~k.r~.fl fll(~.lc ~ in(rl~ ,c~l vi,~ Ihe l~ .rs. I-iow~vel. Iultllel details
concerllill~ Ille l~urner he~ling are not given in ~llc patcll~. Frcqllcnlly, exclusively ~as or oil
:: burllers arc clllployed in S~lCtl methods, as for installce in ~hc mctllod in accordance with
l~e~Jeral Republic of Gcrlnany 25 41 0P~6.
.~~P-A-O 200 ~0~ ~Ic~-:rlt~s ~ UU ur ~ ur~ rurn~ tn
which ~owdered coal of a particlc sizc Or 4.S ~m and an approxima~ely .stoicl-iollletl-ic
4uanllty of oxy~,en is fe~l tllro~lgll a burner. ln this case, the fuel, th.lt is the coal, is fed by a
.5~ream of vehicle ~as whicll sLIrlollllds tlle inller oxygell cha-lllel allnlllarly. Finally, such a
me~ho~l is i~lso knowll from EP^i~ 4 ~78, carbon of a ~i7.e less thal- 10 /ln- being fed by
mc~lls of an inerl slream of vehicle gas.
The objecl of the preseni in\~entioll is to iml.lroYc thc prior art by a ncw
metllod so that thc heating and melling c~all be carrie~l Oul reliably all(l ecollolllically an~l to
ill(licate ~n apparalus wl~ic~l is l~r~icularly sui~ble rOr IhiS p~lrpoSe. ]`or thiS purpose 4 to 15
I>f po~ ert ll coal of a particle sizc of ~ ''00 ~m per lon of 1i4uid melal produced is red in
an inerl to sli~htly reducillg Yclliclc gas witll a veloci~y Or al leasl 4~5 m/second at lea.s~
124~119.1~C'I'
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d~uing the melting down nf the c~argc and is burned witl~ form~liol) of a ~liffuse ~lame"
stoichiomelrically lo s]ightly al)ove stoichiomelrically l~y oxy en lo~r~ing from Ihc burl)er a~
the spe~d ~f su~lnd and a pre.jsur~ Or a~ si nne ~ar.
With this new loethod all types of steel ~nd ferro-alloys lS we]l as s~lit~ble
noll-ferroos melals can be treat~d. An increase in output of abo~lt ]0"~o as wcll as a redllclion
in the fecd of electric ener~y by abollt 5~ KWh/t can be oblailled alleady wilh av~rage
amollnt.j of chargc.
Advanla~eolls en)bodil~ s Or ~lle invel)tion arc indicated in Ihc other Inetl-odclairns. lt has sllrl~risin~ly been fo~ d th~t as comparcd wi~h the preViO~ls~y known methods
of operalit)ll considerable improve1ncllts in tl~e resull of the operatioll can ~e ob~ained by the
use of the methnd nf thc present invenliOIl~ In this conn~clioll the paramelers of tllc method
were prefer~bly so selected th~t ~I)e pressure of ~he emergillg oxygen is al leas~ 0. ~ bar above
;: ~he intcrllal pressllre prevailillg withill ~he rurnacc that tl-~ p~)~vdered coal is fed in amoullts
of S to 10 I;g/t of liquid mct~l produ~ed ~h.l Il~e velocity of Ihe vehic]e gas is at ~e;~sl ~0 ~ ~ -
M/second and that the pressure in tl~e oxygen line (pre-pressure) is adj~lste-l to 12 In 16 bar ~-
and pr~fera~)ly 13 to 15 bar. l~he fucl ~Ised is preferal)]y a po~v~ler~l co~l con~ail~ 8 ~o
l 5 % vo]~lile colnpollents ~:
If it is intell(led l~l add the SCl;1p b.llch-~Yise fnr insl~nCe in c~lstomary Inanller
in the char~in~ c lge it is advant~olls ln s~art the introd~clioll of coill and oxygen wi~hin
lwo minlltes after thè charging. This inlr( d~lction is ~.dv~n~ageously conlinued for a pèriod
of 9 ~o 17 minutes d~lrin~ a batcb se4ucncc.
.Y:3~J51~9,1~`'1' -2-
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Particularly favor~hle resl~lts ca~ e obtain~d if the raLio of the mass flow of
coal to ~hal Or vehicle gas is 10 to 2t)
l)pon the chargis~ of the furn lce witll scrap or the like l~y means for
inst~llcc of a charging cage, thc l~llrners are preferably ren~o~ed fron~ thc f~rnace, When
introduced l~ll nol in th~ir operatin~ phase or phases lhe burners are chalged with a
.~icavengin~ ~as preferably air al le~st in the fuel cl~anlle~ orcler lO ~eep lhe channels
open 1 h~ qualltity fed amoun~ in this conncction preferah]y IO 170 to 200 lin~'/hr
dependin~ on tllc sizc of lhe ~urner.
A j ~pp~ratus for the carrying out ~)f the ~netl~od tl~ere is yrovid~d a bllrner
which has a shaf~ formed of ~wo concentlic l~ll)CS, lhe annular ch~nllel thereof discl~arging
into a widened annlllar spaCe of ~ distribl~tor holes arranged annularly an~l cohxidlly to the
shaft debourhing into thc annular sp~ce frolll the opposi~e side Ihe l`ee~ side ~ait5 holes
~eing connccted n~ their feed side to a fuel con~ an(J hy ~n oxygen feed line conlleclcd lo
Ihe oxy~en channel formed by Ihe hlller luhe of ~he sllafl Advanl~geollS developmenl~ of Ihe
new burller arc se~ for~h in tl~e 7~lt~ched apparal~ls clail~
rhe method of the invenlion and the app~ratl,s for the calrying out of Ihe
lhod will be explained in fllrlher delail with reference to the drawillgs eacl~ of which
shows onc elnhodin~ent of the metllod and lhe as~par~lus
ln lhe dr.lwing:
I`ig I is ~ diagral7~ of a plan f~)r lhe fee~ing of n~terial to all arc furllace.
Fi~ 2 is a diagrammatic hori~ontal sèc~ion tllrougll the arc f~rnace of l~ig. 1.
Fi~ ~ is an Ou~pllt cllrve of a bllrner.
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02 1 I: 5g ~ 1 2 1 2 972 54~7 CrJHEII P01ITRNI ~5
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~ig. 4 shows the main piece of a burner half in outer view and half in
klngitudinal sectic~n.
~s shown in the diagr~m of l ig 1, in Ihc case of an ele~tric arc furnace I
having three e]ectr/)dcs ~ lwo burllers are inlroduc~ rou~h tl~e walel-cooled ~urnacc wall
c~n ~hc si~e al)o\e the melt Eacll of ~ wo ~)urners ~ and 4 has a pressule conveyor 5 each
provided with a weighing device ass~)ciated wiih it ~he pressurc conYeyors ~ bcing ~upylie~l
fron~ a stora~e bin 6 with powdered coal which i~ possibly c~assified in an interposed
screenin~ d~vice 7 The coal withdrawn Irol~ tlle press~lre conv~yors 5 i5 ïed lo Ihc burners
3 and 4 via cunduits 8 wilh nitr(lgell flol-- ia sn~lrce of ni~ro~cn nol showll The fe~din~ of
oxyg~n to lhe bl~rner~ 3 and 4 is effecled Vi;1 ~wo conduils g. rlle furnace ] is furtllermore
provided with A known device 10 for determinillg the cxllalJs~-~As analysis whicll is used to
regulate the mass flows fe~ lo the burners wilh dlle consideralioll als~- of tl)e efficiency,
reterred to dirfcrellt typeS and Cl)lllpO!;itiOlls of coal The amoull~ of tlue gas is in lhis
conncctio1l nlcasllred by the knowll He-tracer mctho(l usill~ d ~ilreaI11 of helium wl-ich is
introduced illtO the furndce.
Fig. 4 shows the constrl~cli- n of ~he burners: Adjoining a shAt`t l~l which
consists of lwo concentric tutles l l ~nd 12 and can be displa(:ed lo~ udillally into the
furll~ce, ~here is the ~lclual parl of the burncr a ~listribu~or 14 formed of scveral parts of
rotational sylnmetry Thc annular Cll~nlle] 1S de~cloped betweell tl~e two ~u~es 1l al-d l2
debouches in~o a widen~d annular space 16 of lhc di~lribulor 14. J rom the opposile side
namely tlle feed sid~ f~c~llg aw~y from ~hc anl1ular cl~anncl l.~, six ho]es 17 whicll are
arranged annlllarly an(l coaxial lo the shaft 13 ~lèhollch into ~he anlllllar space 16"he holes
N~ Sl I 9.1~ 4-
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' ~2 e~ 2 1 1: 5'3 7 1 2 1 2 972 5487 COHE~I PONTf:llJ I ~G
bcill~ conl)ected on the feed si(ie lo a cylindrical collection space l8 A fllel conduit 8 for
lhe feeding of the coal is flange(l onto ~he cnd ~ f ~l~e collcction s~ace i ~ coaxial lo tl-e
di~triblltor 14 ~he condl)it 9 for the fe~rling of oxy&en is c~nnected (o ~ll anlllllar collection
space 19 which sullounds a po~-sl~aped sLlpport melllber 20 witl-in which the holcs 17 are
arrall~ed Tlle collection space 19 is connecte~l via six radial c)l~nnels I ex(ending in ~ach
case be~ween the holes 17 to the o ~y~en ~llallnel 22 tormed l~y tlle inner l~be 12
-, Tllc ann~llar space 16 is forl~cd by ~ in~,erlioll of a snit~hly sllaped inseltion
member 2~ in s~lch ~l mallller Ihal ~he gr~test part of i~s inller wall wi~lens to\~/ards ~he holes
- ]7 so that the Idr~,cst diam~ter of thc inner wall agrees Willl tlle ~mallest diameter, nalllely
~he corc diarnelcr, of the circle or holes 17 ~n lhc oppusite side, the ann~llar space l ~
rorn~s an end surface 24 All parts of the ~listribu~or 14 are pllshe~J one on Ihe other and
fastened to each other by flange collllectiol~s so Ihat simple assemhljllg and taking aparl of lhe
bllrner is possib~e rhe deve~opmen~ of tl~e (li~lrib~ltor 14 in accordance witll the invenlion
fur~hermore results in ~he a~lvant~ge Or only sli~llt weilr of tlle parts condllclil-g the po~dere~l
coal
~elween the colleclion space 18 all~ lhe fuel condllit 8, a b~ffle plate 27
- havin~ ~hrce openill~,s 28 is provided as ~low distriblltol, it retardill~ ~he str~ Or vellicle
~as laden ~vith coal dust and dividing it into lllree individnal streams The ol~enil)gs 28 are
; ~ so arranged Ihdl cacll Or lhe three indiVid~lal streallls is ~listribll~ecl over ~,vo of Ihc six holes
17, in which it is f~rlhcr decelcrate~l Acceleration lakes pl~ce again only al the transition
into the annl~lar ch,tnnel IS By lhis conslruc~ of tlle nozzle, ~llc wear of the distributor
14 by abrasion is still fllrther reduced
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ILl~usTRA~lyE EJ~ oOlMEl~T
I`he method of the invenîioll was ~l~ed on a 140-t~UHP electric arc fl~rnace, ~he
~rrallg~ment shown in Fig, I being llsed. Tl~e ~wo t)urllt~rs ~ ~nd 4 wcre jo ~rr~ hal the
one burncr 3 ex~ lc~ acl(cct thr~ ugl~ tho 51n6 dool r)S, int~ )r fl)rl~c~ 1 alld the other
t urner 4 was inserted ~hro~gh lhe fllrnace wall 90G away rrol~ )c burncr ~ lhrollglI a
sui~able opening, as cal~ be noted from I~i~,. 2. 1~ c~n r~lrll~ermore bt! noted froll- Fig. 2 lhat - ~
tl)~ burner 4 is directed in the so-calied "cold s~ot" rcgiol~ 26 be~ween l~vO electrodes, while
the burller ~ is arral)ged io nol)-ayllll)letFical In~a-lncl bel~vcell two eleelrodes.
As eoal, a powdered ~I)thracite coal ll~ving tlle rOllowill~ elemcl-t~ry analysis
f tlle raw coal was ~lsed: .
. Carbol) C - 0.~3
~ydrogen H = 0.034
Oxy~en O = 0.01~
Sltlphur S = 0.008 lo 0.01
Ni~rogen N = 0 015
Ash A = 0.093
Lower calorific Yal~le waS hu = 31,800 kJlkg = 8.83 I~Wh/kg
~Jpper caloriJ;c val~le was ho = 32,550 k~/kg = 9.04 kWh/k~,
, ` Frol~ this tllere rcslllted a stoiclliolllelric oxy~cn re41drem~nt Or 0"~ = 1.73
m3 O~/k~ of f~lel and arlel- the stoichiolI~eîric con~b~slion witl~ O., .t fl~le ~,ilS composi~ion of
~CO~ = 79.62~o
l~O = 19.43 %
. ~SOI =~ 0.:32 'Y"
~NI = 0.62%
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I he average charge ~eqllcnce was as toll()ws After a ~`irst cllarge of scrap of
al)olli 76 lOnS h~(l been charged into the arc ~ rnace I in whicl) there was a melt resi~lue
frolll the prece~lin~ batch the l)ulners 3 and 4 were then charged abo~l one n-inllte thereafter
with tl~e ~ine-coal/oxygen mixture The i nilioll of the mixll)re upOI~ emer~el~ce from tl~e
burner took placc in ~11 cases in~media~ely even Whell ll~e ~crap was slili col~l~ As a resull
of ~he cons~rllcti()n of ~he burner a d~ yed n~ixillg ertec[ W`d`j ol~ained in rron~ of ils Inollth
reslllting in a dift;~e ~/idely (~is~ersi~d flallle wl~ich effected excellenl ~ransll1issiol- of the
heat of eoml)~lstion on~o ~e scr~p and tlle ~urface of ~l~e bn~ ]t ~vas noled tha~ after ~he
jgnitk~n of tl~e flame a~ter the cl)arging of lhc scrap a large l-()llow space was meltéd wi~hi
a short tin~e into ~he scrap wilhill wllich spac~ lhe namc developed in stal)le n~anner
Coal charged dosa~ed from the r)ressure conveyors 5 with oxygen was fed
via the conduits 8 to ~he burllers 3 and 4 wi~h sLIch a speed of conveyance th~t a spced ~f
conveyallce of abou~ ~0 me~ers per secollt~ wa~ eslablishe~l ~vitl~in the nozzle Sincc this
speed is elearly above the flame propagation sl)ced of Ib~)ut 35 n~/~econd backward burning
was dependably avoided even in the cvent ur a mixillg Or coal an~l oxy~en wi~hill tlle burner
as a res~llt of distllrb~n es Tlle speed of soulld i~ cstabli~;hed in tlle oxygcn fed via lhe
eonduits 9 to the bllrners so thal upOIl emer~cnce irrom tlle c~rrespolldillg burner a prcssure
of about I bar is presenl Atn~osplleri¢ I)ressllle prcvailed wilhin the .arc f~lrnace ~ The
mass flow of ~he eoal varied l~etweell 2~ and 25 i;~/lllinll~e rOr each burner all(l was regl~la~ed
.~
- in the ~ame way as ~he et)rlespondillg amollnl Or oxyg~n - in acc~)rdance wi~h lhc values
le~ertnincd by ~he fllle-ga~ analysis Tlle an)ollllt o )` oxygel~ wa5 adjlls~ed "n the b~sis of
~toichiometric to slightly over stoichio)nelric combus~ion ~he powdered coal llad an averagc
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'~2 ~11/132 1~ !; 1 21~ ~72 ~i187 COHEII PCIIITRIII 13~ ~
~pecific gravlty of 1,400 k~/cubic melCr al~ n aver~e particlc si%e ~,r abnllt 40 ~n~ The
qual~titative tlow of the nilrogen used as vehicl~ g as was ~(!jusled ~s low as possible,
ob~ining a cl-arging coefficien~ ~u = M~ y of about 18 ~o 2()
Tlle charge of scral~ was mclted do~YIl in about 15 ~ninlltes; ~he burl1ers were
shu~ c t`t` an(~ charged wi~h air~ l`l)ereupoll a second charge of scrap ~Iso ot abo-l~ 7~ tons was
t`ed to tlle are furnace, the strc~ .,r air was sl~ut off and tl~e burllers ignited agai~ or ~he
nleltillg do~v~) of ~he second bd~Ch of scral), which was carricd out in the s~me n~ilnner, only
abou~ 7 minlltes wcre requircd (l~ ) Tbe hurners werc tl~en removed from the furnace
and the mclt was f~nislle~l by lneal~s Or electrode lleatin~ ~nd tapped off l`he ~apping
telllper~lUre was oll tlle average aboll~ IS~U (: The ~apped \Yeigh~ w~s ai O~lt 140 lons and
was distributed over two ladles rhe speeific use of cArboll wa~ abou~ 10 k~ of carboll per
of 1i4uid steel, whic~l corresponds lo a sllpply of el)er~y of abou~ '~0 kWh/~on of s~eel and
a ~legree of subslitution Or elcctri~ energy by coal of morc thall 70% 1`he average tlnalysis
of ~ ferritic special-steel produced had the i`ollowillg values (in weight
,~ C c 008
].~
Mn c 1.0
P C 004
.
S ~ 0 03
Cr = 15 ~ ~ 17 5
Tlle lUbes of ~hc bllrl~er sll~ft 1~ wcre Ina~le of st~inless s~eel and, ~s a result
of tlle diffetent condi~iolls of ~he local arran~elllen~, were o~ different len~h Tlle outside
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diameter ot tl-e sllafl ~vas abvul ~0 nll)l. I he weal on Ille mo~llh ot` the ~Jrners remained
vithin lin~its, even afîe~ numero~ls cll~3r~es~ Both ferritic and aus~enitic stainless sleels ~vere
melted. ~n the case of the melled austeniliC steels the .sl)ecit;c use of coal was nn the aYcrage
set snlaller.
Thc method and the apl)aratlls of ~he i~lventi~n arc llo~ s~ al)le only for newly
erecte~l plallts but, in par~icular, also for the re~rofitting o~ elc~llic arc ~>iants ~hich are
lready ill opera~ion.
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