CA2245722C - Electrode and cooling element for a metallurgical vessel - Google Patents

Abstract

An electrode and a cooling element for a metallurgical vessel are disclosed with at least one cavity (18) and at least one cooling device (10, 12, 13) for spraying a cooling medium in this cavity. The invention is characterised in that at least one collecting means (11) for collecting molten metal breaking through the cavity (18) is provided in the cavity (18). The cavity (18) can thus be recessed in the furnace wall and be placed relatively close to the molten metal. The collecting means prevent furnace leaks in the event of molten metal breaking through into the electrode or cooling element and reduces risks of explosions caused by water enclosed by the molten metal.

Description

CA 0224~722 1998-08-07 .~ .
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 CA 0224~722 1998-08-07 W0 97/29617 - 2 - PC~/EP97/00514 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 CA 0224~722 1998-08-07 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 CA 0224~722 1998-08-07 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 . CA 0224~722 1998-08-07 .

W0 97/29617 - 5 - PCT/~P97/00514 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 . CA 0224~722 1998-08-07 .

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 CA 0224~722 1998-08-07 .
W0 97/29617 - 7 - PCT/EP97~00514 (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 CA 0224~722 l998-08-07 WO 97~29617 - 8 - PCT/EP97/00514 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.

CA 02245722 l998-08-07 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.

CA 02245722 l998-08-07 WO 97/29617 ~ lO ~ PCT/EP97/00514 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 CA 0224~722 1998-08-07 W0 97/29617 - 11 - PCT/~P97/00514 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 CA 0224~722 1998-08-07 W0 97~29617 - 12 - PCT/EP97/00514 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 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.

.

Claims (31)

claims

1. Electrode for a metallurgical vessel, having at least one cavity (18) and at least one device (10, 12, 13) for cooling by spraying a cooling medium in this cavity (18), characterized in that at least one collecting device (11) for collecting molten metal which breaks through into the cavity (18) is arranged in the cavity (18).

2. Electrode according to Claim 1, characterized in that the collecting device (11) is designed as a device for narrowing the cross-section of the cavity (18) along the main axis of the electrode.

3. Electrode according to Claim 2, characterized in that the collecting device (11) has passage openings for cooling medium which is to be removed.

4. Electrode according to Claim 3, characterized in that the collecting device has at least one perforated plate (11).

5. Electrode according to one of Claims 1 to 4, characterized in that the cavity (18) has its largest dimension extending parallel to the main axis of the electrode.

6. Electrode according to Claim 5, characterized in that at least one nozzle (13) for spraying the cooling medium is arranged in that end region of the cavity (18) which faces towards the interior.

7. Electrode according to Claim 6, characterized in that the coolant is fed to the nozzle (13) by means of a tube (10) which extends through the cavity (18) essentially in the direction of the main axis of the electrode.

8. Electrode according to Claim 7, characterized in that this tube is designed as a thick-walled metal pipe (10).

9. Electrode according to one of Claims 7 and 8, characterized in that collecting devices (11) hold the tube in the cavity.

10. Electrode according to one of Claims 1 to 9, characterized in that the wall of the cavity (18) consists of a material with good thermal conductivity.

11. Electrode according to Claim 10, characterized in that this material is copper or a copper alloy.

12. Electrode according to one of Claims 1 to 11, characterized in that it has a metal body (7) which is arranged at that end region (6) of the cavity (18) which faces towards the interior of the electrode, and which metal body projects into the interior of the metallurgical vessel.

13. Electrode according to Claim 12, characterized in that this metal body is a cast steel hood (7).

14. Electrode according to one of Claims 1 to 13, characterized in that it has at least one temperature sensor (16, 17).

15. Electrode according to one of Claims 1 to 14, characterized in that it additionally has a blowpipe (19) (lance) for introducing solids and/or liquids and/or gases into the interior of the metallurgical vessel.

16. Electrode according to Claim 15, characterized in that the blowpipe (19) has a cooling device.

17. Electrode according to one of Claims 1 to 16, characterized in that water or a water/gas mixture is used as the cooling medium.

18. Electrode according to one of Claims 1 to 16, characterized in that sodium is used as the cooling medium.

19. DC arc furnace, characterized in that it has at least one bottom electrode according to one of Claims 1 to 18.

20. Cooling element for a wall of a metallurgical vessel, having at least one cavity (32) and at least one device (26) for cooling by spraying a cooling medium in this cavity (32), characterized in that at least one collecting device (25, 30, 31) for collecting molten metal which breaks through into the cavity (32) is arranged in the cavity (32).

21. Cooling element according to Claim 20, characterized in that the collecting device (25, 30, 31) has passage openings f or cooling medium which is to be removed.

22. Cooling element according to Claim 21, characterized in that the collecting device has at least one perforated plate or slotted plate (25, 30, 31).

23. Cooling element according to one of Claims 20 to 22, characterized in that at least one nozzle (26) for spraying the cooling medium is arranged in that region of the cavity (32) which faces towards the interior of the metallurgical vessel.

24. Cooling element according to one of Claims 20 to 23, characterized in that the wall of the cavity (32) consists of a material with good thermal conductivity.

25. Cooling element according to Claim 24, characterized in that this material is copper or a copper alloy.

26. Cooling element according to one of Claims 20 to 25, characterized in that it has a metal body which is arranged at that end region of the cavity which faces towards the interior of the metallurgical vessel, and which metal body projects into the interior of the metallurgical vessel.

27. Cooling element according to Claim 26, characterized in that this metal body is a cast steel or copper hood.

28. Cooling element according to one of Claims 20 to 26, characterized in that it has at least one temperature sensor.

29. Cooling element according to one of Claims 20 to 28, characterized in that it additionally has a blowpipe (24) (lance) for introducing solids and/or liquids and/or gases into the interior of the metallurgical vessel.

30. Cooling element according to one of Claims 20 to 29, characterized in that water or a water/gas mixture is used as the cooling medium.

31. Cooling element according to one of Claims 20 to 29, characterized in that sodium is used as the cooling medium.