Note: Descriptions are shown in the official language in which they were submitted.
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W0 97~29617 PCT/EP97/00514
Electro~e and cooling elemQnt for a metallur~ical
ves~Ql
ThQ invention relates to an clectrode for a
metallurgical vessel ana to a cooling element for a wall
of a metallur~ical vessQl, which electroaQ or cooling
Qlemcnt has a cavity an~ a devic~ for cooling by ~ ng
a cooling me~ium (liquia or liquid/gas mixture) in this
cavity.
The invention fur~hs ~ c relate~ to a DC arc
furnace which has at least one electrode according to the
invention.
Tn metallurgical vQssQls for elQctric-furnacQ
~teel -k~ng, for exam~le DC arc furn~ces, electroaes
which arQ incorporatea in the refractory l;n;n~ of thQ
vensel an~ ~enetrate throu~h thiQ linin~ (bottom
electroaes) serve as anodes for producing the electrical
co~nection to the melt. ThosQ ~arts of thQ elQctro~Q
which are in contact with thQ moltQn metal are subject to
high ~ h9 1 wear. For thi~ reason, variou~ cooling
aevice~ for bottom Qlectroaes ha~e alreaay been pro~o~ed.
By way of example, DE-A-38 35 785 ~ro~o~e~ a
cooling sleeve which su vu..~s ana cools that ~art of the
electroae which ~rojQcts out from the vessQl wall. The
cooling power is low, since only a small region of the
electrode is coolea, which region is situatea far ~Lway
from the ~.h9 lly loaaed ContAct surface between the
electroae ana the melt. For this reason, the electrode
melts relatively quickly ana its service life is low.
FYchAnging electrodes is com~licated, sincQ the new
electrodes have to be ;; ~eAAeA in the refractory material
of the furnace wall.
It has therQforQ alrQaay been pro~osQd
(DE-B-40 26 897, DE-A-43 35 065) to proviae cavitie~ in
the elQctroaQ boay ana to cool thesQ cavities by s~raying
water. For safQty rQasons, these cavitiQs are situatQd at
a very consiaerable aistance from that ~art of the
elQctroae which is in contact with the molten metal ana
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are 8itu~ted outside the furnace wall. This considerablQ
~istance is intsn~e~ to QnsUre that in the event of the
coolin~ f~;-; n~ or in the event of an extraor~inary
thermal lo~d on the electrode, the latter does not ~elt
to a ~ufficient extent for molten metal to be able to
break through into this cavity. Contact between the
molten metal and cooling water can lead to explosi~e
roactions, in particular if water is include~ in th~
molten metal, since the ev~~o ~tion an~ ~r~n~ion of the
steam which then takes place tears explosively through
tho melt. Also, it is im~ossible to rule out the chemical
~sr~ _,osition of the water followed by detonatin~ ~as
reaction8. Moreover, molten metal brs~k; n~ throu~h ~nto
the cavities could me~n that the furnace leaks via the
burnt-throu~h electroae and the cavities.
The large distance between cooled cavities an~
molten m~tal which is selQct~a owin~ to thes~ sa oty
consi~er~tions means that the coolin~ action is un atis-
factory and, consequently, also means a hi~h electroae
wear.
Fur~h~ - a, there is a nee~ to cool wall re~ions
of metallur~ical vessels (e.~. electric arc furnaces)
which are subject to particularly hi~h ths -l loa~s~ 80
as to reauce the wear to the vessel wall. For the ~a~e
reasons a8 those cite~ above, a water cooling syste~ is
problematical here, ana in ~articular the ab~ - Lione~
risk of ex~losion ~; n~ ~ If, un~er extraordinary
o~erating conditions, molten metal breaks through the
vessel wall into such a cooling element, under certain
circumstances the vessel can leak via this re~ion which
has been burnt through.
The invention is base~ on the object of ~rovidin~
an electrode and a coolin~ element of the ty~e mentioned
at the outset, which electrode or coolin~ element ha~ a
more efficient cooling ~evice an~ satisfies safety
requiL. - ts.
This object is achieve~ accordin~ to the in~en-
tion by the fact that at least one collecting device for
collecting molten metal which breaks through into the
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cavity is arrange~ in the coolea cavity.
In the context of the invention, the term
"8pr~lyinSJ" i8 to be understood a8 ~q~n; nS~ ~ny ty~?e ~f
dis~ersion of the coolin~ me~ium in the cavity which is
such th~t at least ~art of the internal wall of the
cavity is coolo~ by this me~ium. Finoly disperse~
~praying by mean8 of one or more nozzles is ~referrea.
Water or a water/air mixture is ~referably used as the
cooling me~ium. The use of other cooling -~; n is also
po8sible. A ~rticularly high cooling action can be
~chieved by the use of liqui~ so~ium as the coolantO
~ collecting device ~or molten metal which breaks
through i8 to be understood as me~n; n~ any device which
~v~..ts, or at least aelays, the further ~enetration of
molten metal which has broken throu~h into tho c~vity
towards the outer wall of the metallur~ical vessel. If
soaium is usea as the coolant, the collecting ~evice has
to be designe~ in such a way that it aoes not im~ede the
return flow of the heated medium, or ~oe8 80 only to an
insi~nificant extent.
The term "wall of ~ metallurgical vessel" is to
be interprete~ broaaly and com~rises any wall, for
example the bottom, si~e walls, cover, etc.
In the electrode or cooling element accor~in~ to
the invention, the cavity can ~ro~ect far into the
refractory l~n~n~ of the vessel wall an~ close to the ena
region f~cing towaras the melt without any safety ~isk.
If, in the event of extraor~in~rily un~avourable operat-
ing conaitions, the olectroae shoul~ molt to such an
extent that molten metal breaks throu~h into the ca~ity,
this metal is stop~ed by the collecting ~evice(s) an~ is
..te~ from le~k; ng out of the furnace through the
electrode. The invention has reco~nize~ that owing to the
relatively small quantity of water usea in spray cooling
there is, surprisingly, no risk of ex~losion causQd by
cont~çt beL~J~en molten metal an~ the spray mist The
collecting devices are designed in such a way that they
only ~ ~v~..t the return flow of coolin~ medium to an
insignificant extent. Thus, in the event of molten ~etal
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bre~k;ng through, cooling medium which may still be
present in the corresron~;~ re~ion of the cavity can
quickly flow off or be drawn off. In this way, the molten
metal which has been stopped by the collecting devices is
~ e~e.~te~ from inclu~ing rosidual water to an oxt~nt
which can lea~ to a risk of explosion.
The cooling element accor~ing to the invention
can be incor~orato~ (~rcforably at locations which are
particularly subject to ths 1 lo~ g) in a vessel wall
an~ can ~erform its cooling action at a short distance
from the vessel wall - molten metal ront~ct surface. If,
in the event of an operational fault, molten metal breaks
through the vessQl wall into the cooling element, it is
sto~ped by the collecting ~evices which are provi~e~
accordin~ to the invention.
In the event that water or a water/air mixture is
use~ as the cooling medium, the operatin~ conaition are
advantageously selected in such a way that the water
largely or completely evaporatQs on -k; n~J CQnt~ct with
the inner wall of the cavity which is to be coole~. This
has two a~vanta~es. Firstly, not only the heat-absorption
capacity of tho water, but al80 the si~nificantly greater
heat of ev~lation for the water-steam ~hase transition
is used for cooling, 80 that even relatively small flows
of cooling water produce a high coolin~ action. If, un~er
extraor~inary o~erating conaitions, molten metal breaks
through into the cavity, the tem~erature in the cavity
will rise shortly before this breakthrou~h to such ~n
~tent that virtually all the water evaporates an~ the
molten metal, after bre~k;ng through, comes into contact
not with ~ ~_1 water but only with steam. This further
re~uces the risk of explosion. Thus, setting the
operating conaitions to be such that even in n~ -1
operation the sprayed water, or most of the s~rayea
water, eva2orates on - k;n~ cont~ct with the wall of the
cavity further increases safety.
The heatea water an~/or the steam flowing out of
the cavity is expe~iently sucke~ out using a re~uce~-
pressure source, such as for example a vacuum pum~. It is
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possible to select thQ ~uction ~ 3 of tho ~um~ to be
higher than that whieh is requirea to ~eh.~ve the spray
water. Then, if r~quired, aaditional air can be intro-
ducea throu~h an ad~itional inlet, thus assistin~ with
S ~ -v~l of the eooling medium. It is thus ~ossible to
Qnsur~ that th~re is no buila-up of watQr at the collsct-
ing aevices.
In the electrode according to the invention, the
collectin~r dQvice i8 e ~ sA;ently aQsignQa as a~dQvice Eor
narrowin~ the cross-section of the cavity alon~ the main
axis of the electroae. The main axis of the electroae is
its lon~it~ nAl axis which is air~ctea throu~h the
vessel wall. A narrowin~ of the eross-section of the
cav;ty along this main axis mean~ that the eross-seetion
15 of tho cavity is roduc~a in the ~lan~ ~or~onaicular to
this main axis. Such a n~rrowin~ of the cross-section
stops or aeeeleratos further flow of the molten metal,
which is of hi~her viscosity than the cooling meaium. ~he
narrowing of the eross-seetion is aavanta~eously aesi~ned
in sueh a -nne~ that the clear cross-section is ai~idQd
into a plurality of ~mall cross-sectional arQas. By way
of example, the eolleetin~ aevice may have slotte~ or
~erforatea plates. ~re~;ently, passage o~enin~8 for
cooling meaium to be ~- v~ are present; in the ca e of
a ~erforatea ~late, these are the holes arrAnged therein,
for ex mple $n the form of slots. Where the following
text refers to ~erforatea ~lates, these are to be urlder-
8tOoa ~8 - -n; n~ any plate w ~ch has openinSJs whieh are
suitable for eooling meaium to pass through, such a~ for
exam~le bores, slots, etc.
A perforatea plate aoes not ~ ~ve ~ the coolin~
m~ium whieh has been introaucea into the eavity from
flowing back, but aoes sto~ any molten metal which may
have broken throu~h, on the one hand msch~n;cally by the
narrowing in the cross-sQctional area ana on the other
hana ~hs ~lly owinçrto its heat-absor~tion cal?acity. The
perforatea ~late i heated by the molten material, in the
~ e88 coolin~ the forward front of molten mnterial to
sueh an extent that it either soliaifiQs or at least
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h~e~ -~ 80 viscous that it ean no longer penetrate
throu~rh the o~enings in thel?erforate~ ~late. A ~?lurality
of eolleeting deviees whieh are arranged one behind the
other may be ~rovide~ in oraer to inereasQ the safety. It
S is advanta5Jeous if the collectins;r ~evices (for example
the ~erforate~ ~lates) consist of a material which ha~ a
melting ~oint which lies above the temperature of the
molten metal. In th~ case of a motallurgical v~ss~l for
molten steel, the collecting devices may, for example,
consists of stainless steel ~lates, ana the thickness of
the plates mAy, for exAm~lo, bo 30 mm.
In the easQ of the eleetro~e, the eavity advan-
ta~eously has its largest ~;--n~ion extsnA;ng ~arallel to
the main axis of the eleetrode. It is, for exam~le, of
cylindrieal aesign an~ ~n end side of the cy~ e~, which
may be aesi~ned in the form of a s~herieal eap, faees
towards that en~ of the electrode which is in contact
with the molten metal. The cavity may exten~ far into the
wall of the vessel ana the associatea refraetory l;n;ng,
and the distance from the ena siae of the cavity to that
en~ of the electroae which projects into the vessel
interior neea only be a few eentimetres (e.~. 5 to 10
cm). This allows e~fective coolin~.
Ex~ediently, at least one nozzle for spr~ying
eooling meaium is arran~ea in that ena re~ion of the
eavity w~e~ faees towaras the interior of the metAl-
lurgieal ve~sel. In this way, this ena re~ion of the
eavity, ~r~;eh is subjeeted to high thermal lo~;ng~ is
eoolea ~Artieularly effieiently. In the ease of the
eleetrode, the eoolant ean be su~liea to the nozzle by
--n~ of a tube whieh extenas through the eavity, e~sen-
tially in the aireetion of the main axis of the elee-
trode. In aaaition to its main funetion of supplying the
cool$n~ me~ium, this tube may at the same time narrow the
eross-seetion of the c~vity, thus fo~m;ng ~art of the
colleeting aeviee.
Expeaiently, it is aesigned a8 a thiek-walled
metA1 pi~e. Its external aiameter may, for example, be
a~ o~imately 30 - 70 % of the internal aiameter of the
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(cylinaric~l) cavity. Its thick walls mean that the m~tal
pi~e has a hi~h heat-absorption cApacity An~ thus con-
tributes to the rapid cooling and solidification of any
moltcn mQtal which breaks through.
The collecting devices, or ~arts thereof (~.~.
the ~erforated ~latQs), can hola the tube in the cavity.
If the collecting aevices have perforatea platQs, thesQ
are advantageously arrange~ at an angl~, in such a nm9~
that still-liquia cooling medium which runs onto them and
~oes not arop through thQ opQnin~s is ~uiaQa away towaras
the wall of the cavity, in order to increase the cool~ng
action in that re~ion.
ThQ wall of the cavity expQai~ntly consists o~ a
material with gooa thermal con~uctivity, for exampl 3 of
co~er or a co~per alloy. By way of exam~ie, the cavity
may be surrounaQ~ by a cop~er cylinaer with a closurQ in
the form of a spherical cap. The s~herical-cap-like
clo~ure faces towards the interior of the vess~l.
This ena-sidQ closurQ of the hollow co~per
cyl;n~ may be aajoinea by a metal bo~y which projects
into tho interior Of the metallur~ical vQssQl. This metal
body is a~vantagQously a cAst stQel hooa or a co~er hooa
which is att~chs~ (for example by wel~;n~ snap~ing on or
~rQssin~ on) to the co~er cyl; n~e~ . Co~er hooa ana
co~er cyl~n~s~ may also be inte~rally joine~ to on~
another. ~urin~ o~eration of the electroae, the molten
metal melts the cast steel hooa until th~ -1 e~ ~ium
is est~l; Qh~ . In this way, a so-callQa stQol ~ql~ -n~_
i8 fc ~~ as the elQctrode closurQ ana, aQ~sn~ng on the
3 0 ~h~ ~ 1 loa~; ng ana the tem~erature of the melt, may
b9c ~ lar~er or smaller. By com~arison with a cast ~teQl
hooa, a co~er hooa has an i~_l~ve~ thermal CQ~ CtiVity,
~o that soliaifyin~ stQel al~o forms a 8teQl Q~l r ~n~
on the co~er hooa. When a co~per hooa is usQa, the
h;g!h9~r thermal con~lllctivity of this material --nQ that
it is ~os~ible, as a further safQty measure, to arran~Q
the spray-coolQa cavity at a sli~htly greater aistancQ
from the melt, 80 that there is a still ~reater safety
distancQ L~L~cn melt an~ water-coolea inner surface of
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the ca~rity. A ~r~s~urQ sensor may bo arrangea in thQ
cavity. In the casQ where steel breaks through into the
cavity, the pressure changes ana the water feea c~n be
interru~te~ tely.
The electro~e or the cooling element accordin~ to
the invention may have one or more temperature sensors.
It is particularly aa~anta~eou~ to arran~e in ~ach case
one temperature sensor at the inner en~ wall of the
cavity ana, aajacent thereto, outside the cavity in the
electrode bo~y (the cast steel hoo~). Di~fer~
measurements then allow the tem~erature of the molten
material to be ~ete ; ne~ ~ In the case of the coo~ing
element, temperature sensors may, ~or example, be
arran~ea in or on the wall of the cooling element, w~ich
preferably consists o~ cop~er or steel.
Accor~in~ to the invention, a blowpi~e or a lance
may additionally be provi~e~ for introducing soli~s,
li~uias an~/or gases into the interior of the metallurgi-
cal vessel. As ~ result, it is possible, by way of
example, to introauce oxy~.. for ~;~;~in~ impurities in
tho melt or ~owaere~ coal, for example for the carburiz-
ation of steel. The blowpipe is expeaiently coolea, ana
a~vanta~eously, in the case of the electroae, it runs
concentrically insiae the feeapipe for coolin~ meaium, 80
th~t this cooling meaium flows arouna it.
The ap~?lic~h;l ;ty of an electro~e accorain!J to
the invention is not limited to the su~ply of current to
a molten metal. It may ~180 be used only for the ~urpose
of coolin~ the refractory l;n;n~ of a metallur~ical
v~el ana increasing its ser~ice life. To this en~, in
the same way as when use~ for su~lyin~ current, it is
arranged in the refractory linin~ of this metallur~ical
vessel. There is no neea to change the ae~ign of the
electro~e accorain~ to the inve~t; Qn when it is usea only
for coolin~ purposes, an~ it is possible merely to omit
the aQvices for supplyin~ current. The protection ~ro-
vi~ea by the claims is also intenae~ to extend to a
aevice confi~urea in accoraance with the invention which
is usea exclusively for cooling purposes.
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The in~ention furth~ -re rel_tes to A DC _rc
furn~ce which h~s at leAst one electroae according to the
invention and~or a coolin~ elcment according to tho
in~ention.
Two ox~m~lary ~ ~o~;-~ ts of the in~ention are
describe~ below with reference to the dr~wings, in wh~ch:
Fig. 1 sho~w8 _ lon~it~;nAl 8ection throu~h an elec-
troao accor~in~ to the in~ention;
Fig. 2 shows a lon~it~;~Al section through a secona
electrode accordin~ to the invent;on, which
aaaition~lly h_~ a blow~ipe for introdueing
~ubstances into the interior of the furnace;
Fi~. 3 shows a longit~inAl sQction throu~h _ coolin~
element accoraing to the in~ention for the~wnll
of a met~llurgic~l vessel, which cooling
element is _aait;On~l~y -yro~idea with ~n un~er-
bath nozzlo for the metal bath;
Fig. 4 show8 a cross-8ection through this coolin~
element.
Fi~. 1 shows an eloctroae accorains to the
in~ention which is incvlyo ~te~ in tho bottom of a DC arc
furnace. The furnace wall is of multi-layer aesi~n. It
has ~ metallic outer wall 1, a sAfety course 2 maae of
refr_ctory material and a further refractory l; n; n~ 3
("Ankerhort" refractory ; ng ,~ _ _ ~),
An electrode accordin~ to the in~ention, which is
denotea o~erall by 4, ~enetrates throu~h this furnace
wall. The electroae has a hollow cyl;n~s 5 which is made
of c~a , extenas into the furnace wall ana ends at a
distAnce of ~y v~imately 50 mm from the inner side of
the ~- ;n~ C~ _ ~,.d 3, with a s~hericAl-cap-lik3 or
h~ ; ~herical ena-side closure 6. A steel hood 7, which
~rojects into the interior of the furnace, is welded onto
tho co~er cyl; n~ S in the re~ion of the ena side 6.
ns~sAth the steel hooa 7, the co~er cyl;n~9~ 5 i8
su ~ ed by a conical (or if ay~ o~ iate cylinarical)
casing 8 made of refractory material. The current is
su~pliea to the electrode ~ia a contact cli~ 9 which
surrounds the co~per cylinder 5.
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A thick-wallca stQel pi~ 10 is arrall~e~
concentrically inside the co~per cyl;nAe~ 5, which steel
~i~e is conn~ctea to the inner wall of the co~per cyLin-
aer 5 by means of five ~n~~ ~ ~erforate~ ~lates 11
arran~e~ one beneath the other and i8 held in ~osition by
--n~ of th~sQ ~orforate~l ~lates 11. This ~i~e 10 i8 fea
with cooling medium (preferably wator or air/wat~r
mixture) by means of a fss~l;ne 12. At that en~ which
f~Lces the ena siae 6, the pipe 10 has a nozzle 13r by
-nn of wh;ch, as indicated at 14, the cooling modium is
~ ed in the form of a cone onto the inner surface of
the ena-si~e ena 6. At that ona which is situ~te~ o~o-
site to the end side 6, the copper cyl;nAs~ 5 ha~ an
outlet 15 for removing the heate~ coolin~ me~ium. Thi8
outlet 15 may be connectea to a reaucea-~re~sure source
(vacuum pump or suction action of ~ downpi~e), in o~der
to assist with ~rawin~ off the cooling meaium. Co~nscting
the outlet 15 to a reaucea-~ressure source is useful in
particular if the coolin~ medium, or part ther~of,
~v~~o dtes when it comes into contact with the inner
surface of the ena-side ena 6 an~ then has to be ~ vea
through the outlet 15 not in liquia form but in gas form.
Tem~erature sensors (e~h9 ~coul?les) 16, 17 measure the
tem~erature in the re~ion of the cast steel hooa 7~ on
the one hana, and at the inner wall of the en~ siae 6 of
the co~per cyl~n~s~ 5, on the other han~.
Durin~ operation of the furnace ana the elec-
troae, cooling me~ium is su~liea to the pi~e 10 via the
line 12 ana is s~raye~ in the interior of the co~er
cyl;n~e~ 5 by means of the nozzle 13. The heated cooling
meaium runs ~ownwards essentially along the inner wall of
the co~er cylin~er 5, through the ~erforatea ~lates 11,
an~ is ~ v~ throu~h the outlot 15. Th~ molten metal
(generally a steel melt) situate~ in the furnace melts
the steel hooa until ~he -1 equilibrium is establishea.
The result is a steel ~ 9~ which can extend over
the r~mming compoun~ 3. Owin~ to the high coolin~ action
c~nne~ by ~ ~lng cooling medium, and the short aistance
between the ena siae 6 and the molten material, un~er
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normal operating conaitions thQ stQQl hoo~ or 8t~Ql
fl~lr ~n~ 7 Will not melt completely.
If r~uirea, the vacuum ~ump which is connected
to the outlet 15 may havQ a hi~her discharge ca~acity
than that which is required to remove the volume of water
~la~ea in. In this ease, the water-feeapipe 10 is
oxpe~iQntly concQntric~lly surroun~ by n furthQr ~pi~Q
(not shown in the drawin~), in which ease, in order to
h~l AncQ the ~ressure, external air ean ~ass into the
cavity, whieh is surroundQd by thQ cyl;~Ae~ 5, through
the ~a~ formed between these two pi~es and a ~e9~1; n~
(likewise not shown in the drawin~).
Only in the event of a reduction in or complete
failure of the eoolant 8u~1y ean the steel hood 7 ~melt
to such an ~xtent that molten metal eome3 aireetly into
co~t~ct with the Qnd sidQ 6 of the eopper cyl; ~Ae~ 5. If
the eo~per eylinder 5 then melts and molten metal
penetrates into it~ interior (the eavity 18), the molten
metal eome~ into cont~ct with the thick-walle~ pip~ 10
and the to~ ~erforated plate 11. Owin~ to the reauetion
o~ the cross-seetion of the interior of the eopper
Cyl ;nA~ 5, ~ipe 10 and perforatea plate 11 on the one
hana mech~n;eally ~r ev~t the molten metal from flowing
onwaras ana on the other hana, owin~ to their high heat-
absor~tion eapaeity, they eool the molten materinl to~ueh an extent that the forwara front of molten matQrial
either soliaifies eompletely or at least h9C~ - # 80
viseous that it eannot flow onwards through the u~er
perforntea ~late 11. If, in exeeptional ei ~I Lanees,
the met~l should never~elens break through the fir~t
perforated plate 11, there are four further perforated
plates for eolleetin~ the molten material ~rovidea
beneath the first plate 11. This ensures that the molten
metal eannot unaer any eireumstances penetrate through
the eopper eyl ~n~e~ 5 and into the region situatea
outside the furnaee wall 1, 2, 3, melting the eopper
eylinder, whieh has a eomparatively low meltin~ point, in
the region of the outlet 15, whieh would then eause the
furn~cQ to leak until more or less eompletely empty. The
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perforated ~lates 11 consist, for exam~le, of steel.
Fig. 2 shows an embo~;m~nt of the invention in
which, in addition, a blowpi~e 19 for intro~ucing 801la8,
gases and/or li~uids into the molten metal is ~resent.
The blow~ipe 19 runs concentrically inside the co~per
cyl ~ n~9n 5 and tho ~ipe 10, ~n~ in it# region which runs
inside pipe 10 coolant flows around it, 80 that it is
coolea. In this ~ ~o~; -nt, two or more nozzles 13, wl~ich
are distributed over the circumference of the ~ipe 10,
are provided for the pur~ose of cooling the end-~ide
r~gion 6 o~ tho coppor pi~e 5.
= In the :; bo~; -nts shown, the perforated plates
11 ana the pipe 10 together form the collecting device
accordin~ to the invention.
In a DC arc furnace, a plurality (e.g. six) Of
the electrodes according to the invent~on are ~enerally
arranged as ~o~ in the re~ion of the centre of the
furnace bottom, beneath the cathode on the circumference
of a circle of, for example, ~Lo~imately one metre, at
equal an~ular distances.
If an electrode accordin~ to the invention is to
be used not for su~lying current but only as a cooling
element for ~the refractory l;n;ng of a furnace, the
co~t~ct cli~ 9 is merely omitted and the electrode is not
co~nscted to a current source. Tn this case, only the
cool;~ function of this electrode is utilized, in order
to increase the service life of a refractory l;n~n~, in
particular at locations w~ ;ch are subjected to h~gh
~.hg 1 lo~d8.
3Q Figs. 3 and 4 show another : ho~ ~ ~ent of a
coolin~ element accor~ing to the invention for the wall
of a metallur~ical vessel. Coolin~ elements, which are
denoted by 21, are installed in the wall 20 of a metal-
lurgical vessel (e.~. an electric arc furnace). It is
possible for a ~lurality of these coolin~ el: - ~q 21 to
be arran~ed distributed over the circumference of the
furnace, preferably in a region beneath the liquid level
22 of the steel melt. The housing 23 of the cooling
elements 21 ~referably consists of co~er or steel and is
- CA 02245722 1998-08-07
W0 97/29617 - ~3 - PCT/~P97/00514
incorporatea in the refractory hearth l;n;n~ through the
shell of the bottom ~art of the furnaco. It surrounas thu
eavity 32. Advanta~eously, the eooling elements are
aeeessible from the outsidQ, 80 that maint~n~nce ana~ if
neee88ary, re~lAeement are ~ossible without major outlay.
The ~ hoA; .ent of the eoolin~ element shown has a move-
able unaerbath l~nce for intro~ucing in ~articular soli~
an~/or ~aseous materials into the molten metal. If a
~lurality of these eooling elements aeeor~ing to the
invention are in~tallea aistribute~ over the circumf~r-
enee of the furnaee, a8 a rule only a ~ew o~ the ol;;
will have sueh an underbath lAnee.
Eight spray nozzles 26 ~re arran~ed in a st~in-
le88-steel pl_te 25, which is designe~ as ~ collecting
15 aeViCQ ana is ex~l~; neA in more ~etail below, the s~ray
cones of which nozzles ~arti~lly overl~ one another, ~o
that that re~ion of the eoolin~-element housing or ca~ing
23 whieh faees towar~s the molten metal is essentially
coverea with cooling me~ium (preferably water) over its
entire surfacQ. Between this front si~e of the coolin~
element 21, on whieh eoolant aets, an~ the molten motal,
the wall of the metallurgieal vessel ~ _ ises a refrac-
tory plate 20 with a thickness of 100 mm. This refraetory
plate 20 has a bore allowing the ~assage of the ~ e~th
lanee 24.
The cooling meaium ~ ~y~ in through the nozzles
26 is ~isehar~ed through an outlet 2iPe 27 whieh is
ronnsrtea to a vaeuum pump. The suetion ~ower of the
vacuum ~ump conneete~ to the outlet pi~e 27 is ~reater
than that which i8 recauire~l to suck out the cooling w_ter
which has run back. This is ;ntenAeA to ~ ~e..t a buila-
up of w_ter at the eolleeting ~eviees, whieh _re still to
be eX~l A; neA . In or~er to avoid this inerease~ suction
~ower eAusing signifieant reAl~ce~ ~ressurQ in the
interior of the eooling element 21, an a~ditional pipe
28, throu~h ~ ;ch external air ean be sueke~ in, is
provi~ea. The ~i~e 28 may be provi~ed with a ~re~sure
sensor for monitoring the intern_l pressure in the
cooling element 21. The volume of air flowin~ in through
CA 0224~722 l998-08-07
WO 97/29617 - 14 - PCT/EP97~00514
the ~i~e 28 can bo a~uste~ as roquire~ by menns of a
restrictor (not shown in the drawing).
In order to achieve a hi~h cooling ca~acity, the
cooling element A ccording to the invention is arranged
relatively close to the molten metal, i.e. it is se~ar-
ated from the molten metal only by a relatively thin
refractory ~artition 20. ~f the thickness of the refrac-
tory plAte 20 is reduced further as a result of wear
during operation of the furnace, a soliaified layer of
steel, in the l~nn9 - of a steel ~lr--n~e~ describea
above, can form in front of the cooling elementO If,
under extraordinary o~erating conaitions, molten metal
shoula nevertheless break throu~h into the coolin~
element 21, the collectin~ devices outlined below ~ eveL~t
the furnace from l~k; n~.
A first collectin~ device 25, in the form of a
stainless stQel slotted plate, is arran~ed ess~nt~lly
parallel to the front side, which faces towaras the
molten metal, of the coolin~ element. ~ first barrier
a~ainst lenk; n~ melt is formed. The thickness of the
~tainless steel slottea ~late 25 is 30 mm. Slotted ~late~
29, 30 which run essent;~lly ~er~endicular to the slotted
plate 25 ana the arrangement of which can be seen in
~articular from Fig. 4 are ~rovided as a ~eco~
collecting aevice. A further stainless steel slotted
~late 31 is arran~ed in front of the outlet ~ipe 27 as
third barrier.
~ l~ho~h the stainless steel slotted ~late~, as
collecting devices, allow the cooling water r~nn~ng back
to pAss through them, they form a barrier to the molten
metal which ~enetratQs into the cooling element. The
forward front of the molten metal cools and solidifies
immediately on c~ ~; ng into contact with the stainless
steel plates. The high meltin~ point of the stainless
steel used for the collectin~ devices provides additional
~rotection a~ainst molten metal brs~k; ng throu~h.
The ~ressure in the interior 32 of the cooling
element can be monitored by means of the ~ressure sensor,
which is connected to the pi~e 28. In the event of steel
CA 02245722 l998-08-07
WO 97/29617 ~ 15 - PCT/~P97/00514
br~Ak;n;J through, the int~rnal prQ~3urQ will chans~
nl y. The pressure sensor can then sup~res~ the
~u~ly o~ watQr to the s~ray nozzlQ~ 26 ; ~ tQly, thu~
pre~enting spray water from ~a~sing into the
metallurgic~l ~essQl.
.
