CA1144752A - Blast furnace cooling arrangement - Google Patents

Abstract

BLAST FURNACE COOLING ARRANGEMENT

Abstract of the Disclosure A blast furnace cooling arrangement comprises a cooling screen which is disposed in an annular space between a furnace shell and lining and formed by vertic-ally arranged rows of plates provided with main and ad-ditional internal ducts having common inlets and common outlets. Mounted above the cooling screen are drum sep-arators which communicate through supply pipelines and take-off pipelines with the common inlets and outlets of said main and additional ducts of the plates of each vertical row, the above elements forming closed circuits of natural circulation of a cooling medium. Closed at the common inlets and outlooks of the additional ducts of the vertical rows of the plates are circuits of forced circulation of a cooling medium. Each of the circuits of forced circulation comprises a container communicat-ing with the common outlet of the additional ducts, a heat exchanger connected with the container, and a pump communicating through its inlet with the heat exchanger and through its outlet, with the common inlet of the ad-ditional ducts in the vertical row of the plates.
The common inlets and outlets of the additional ducts are provided with distributing valves intended to select-ively connect the additional ducts to the circuits of natural and forced circulation of a cooling medium.

Description

~4t7s2 .Ti~l~ of ~h~ Inventio~
BLAS~ FURNACE COOLIN~ ~RR~NGEM~
ield of the Invention , . . .
~ he present in~ention relates to ferrous metallurgy and more particularly to furnace cooli~g arrangsment~0 he invention may be employed with particular !

ad~anta~e for cooling hearths, boshe ~ a~d stack3 o~
blast ~urnaces.
The problem of enhancing the efficiency o~ cooling the blast fur~ace portions expo~ed to the most extensive heating i8 comparatively old, and despite numerous at- :
temps directed to the solution thereo~ has not been adeq-uately solved up till now. ~his has been evidenced by grave accidents to blast furnace~ which tooX place in a number of indu~trically developed countrie~ ~or the laat ~ive year3~ Some of these accidents involved lo~a o~ huma~
lives, a~d the total damage to industrial enterpriae~
amounted to se~eral million~ o~ dollar~ All the abo~e accidents were due to inef~icie~cy in cooling of a ~urna-ce ~hell, which in ca~e of a lining burnout resulted in a local melting of ~ur~ace cooler~ and the shell a~d i~
liquid metal breaki~g out ~rom the blast furnace.

2. Description of the Prior Art .

~o~cool the lower portion of a blast furnace stack .:
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and bosh, ther~ i~ still utilized a water cooling ar-rangement co~prising box-like cooling elements dispo~ed in vertical row3 between a furnace shell and lini~g a~d connected through a 9upply pipeline and a take-o~ pipe-line to a proces~ water ~ain and to a cooling medium source as di~closed in US Patent ~o. 3,628,509 and in FRG Patent No. 290419339.
- In intensi~ièd iron making process9 ~or in~tance with oxygen blast, at elevated pressure in a furnaceg and at a large volume thereof the box-like cooler~ fail to provide ef~ective heat remo~al. ~he box-like cooler~ ara built in the lining, and as the latter breaks down they go out o~ action as well~ ~nother disadvantage o~ the ar-ran~ement under consideration consi~t~ in that the boæ;
-like coolers ensure but a local cooling. ~d ~inallyg it i8 impos~ible to provide for reliable tightne~s in those ~ections of a ~urnace ~hell where the box~like cool-ers are built in.
In cooling a hearth a~d a hearth bottom of convent-ional bla~t furnace~, u~e is at pre~ent made o~ the above arrangement in combination with cooling plates disposed in an a~nular s~ace be~ween a ~urnacs shell and a lining~
In some cases, -the hearth and the hearth bottom ma~
be cooled by watering ~he ~urnace ~rom outside~ in addit ion to employing cooling plate~.
Provided tha-t the linirlg is undamaged~ the thermal ~ 4'75Z
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load~ imposed on the cooling plates are not high and the arrangement operates normally~ In the e~ent o~ a damaged li~ing, the arrangemen~ fail~ to provide ~or a suffi-ciently inten~ive removal o~ heat. Uxlder these condition~, there arises a possibility o~ local melting of the cool-ing plate~ hen the liquid iron comes i~to contact with the cooling water, an explosion occurs which results in a destruction of the ~urnace shell~ As calculations ha~e shOEwn, the liquid iron can be preYe~ted ~rom brea~ing out o~ the furnace through the cooling members only i~ the velocity of the cooling water within the arrangement i9 not lower than 8 to 10 m/sec. Such being the case, the . cooling o~ the ~urnace bottom portion only require~ an enormous amount o~ water9 namely ~rom 3000 to 4000 m3/h at a pressure ~rom 10 to 15 atm. It will be understood that pumps o~ the above capaci-ty are to be provided with power~ul drives, and hence the power con~umption o~ th~
: arrangement is extr0mely high~ .
'~ith these consideration~ in view, more promising proved to be an arran~ement o~ evaporative cooling com-prising a cooling screen ~ormed by vertically arranged rows of plate3 provided with series-connected internall ducts co~municating vertically and con~ected through sup-ply pipelines and take-off pipelines with drum separators aa disclosed i~ FRG Patent No. 1~9317957, Cl. 18 a - 7/1iO~
The internal duct~ o~ each plate are di~posed in one ~, 1~4'7SZ

and the ~ame plane and form natural circulation circuits with a respective drum separator. In operation~ the cool-ing water within the internal ducts o~ the plates become~
heated to a boiling point and flows into the drum ~epar-ator wherein liquid phase a~d steam phase are separated from each other and wherein a partial steam condensation occurs. The difference in the specific gravity of a steam--and water mixture in the take-of~ pipeline a~d a cooled water in the supply pipeline ia responsible for a ~atural repeated circulation. An obvious advantage o~ -the evapor-ative cool~ng arrangement co~sists in a comparatively in-tensified circulation o~ a cooling a~ent without an~
pumps and additional power consumption.
It will be understood that the reliability of the svaporative cooling will be the higher -the more circul- :
ation circuits are provided ~ithin the plates o~ the cool-i~g screen a~ disclosed in US Patent No. 3~7049747. Ac~
cording to the specification the internal ducts of each plate are arranged in two planes, ~hich provides for a more efficient removal of heatO
However, in the event of liquid metal reaching the plates o~ the cooling screen throuOh a damaged lining~
the arrangement under consideration does not provide for sufficient heat removal either~ which ia due to the fact that a water velocity withi~ the natural circulation circuit~ should be 8 to 10 m/sec, i.e. the value which ~4~75~

practically cannot be attained~
Kno~n in the art i~ a blast furnace cooling arran~c-ment w~ich combine~ the advantage~ o~ the above arra~e-ments o~ water cooling and evaporative caoling a~ describ-ed in US Patent ~o~ 4,061~317. This arrangement comprises a cooling ~creen arranged in an`annular space between a ~urnace shell and lining. ~he cooling screen is compo~-ed of plate~ ~orming vertical rows and incorporating series-connected main and additional inter~al ducts com-municating vertically with each other. Both the mai~ and the additional ducts have common inlets and outlets. Mount-ed above the cooling 3creen are drum separators communic ating through ~upply pipes and ta~e-off pipes with com~
mon inlets and outlets of the main and the additional ducts in vertical raw~ of the plates and ~orming clo~ed circuite of natural circulstio~. Through distributing valve~ the additional ducts are connected to a proce~
water supply main and ~orm therewith a open circuit of ~orced ciroulation. The distributing val~es ara mounted at the common inlet~ and outlets o~ the additîonaI duct~
and permit a selective connection thereof to the circuits of ~orced circulation.
Provided the lining i~ in good ~orking order~ the additional duct~ of the plate~ in each row are connected to the circuit~ o~ natural circulation9 and the arrange-ment operate~ without any extra consumption o~ powe~

475i2 the event of a damaged lining, the additional ducts are cut Of~ from the circuit o~ natural circulation and conn-ected to the open circuit of forced circulation~ i.e.
to the process water supply mai~. A high velocity o~ the process water within the additional ducts provides for an ef~icient removal of heat from the plates located i~
the hazardous zone, thereby preventing them from breaking down.
However, in emergency condition~ the arrangement be-ing considered su*fers from the formation of scale de-po~it on the interior sur~ace o~ the additional ducts.
In long~time operation, the ~cale deposit grows thicker9 whereby heat exchange between the plates and the furnace lining is materially a~fected even at high velocitie~ of`
the proce~s water. This disadvantage may be overcome by decreasi~g the content of æalts in the watar ~ed into the additional ducts at a rate o~ 3000 to 4000 m3/h, but pu-ri~ication of water in such quantitie~ i~ extremely ex-pen~iYe and will not be co~pensated by a longer service life of the cooling ~creen~

~ummary of the Invention The principal object o~ the present invention is toprovide a blast f~rnace cooling arrangement which enables a relatively small amount o~ chemically pure water to be used for ~eeding the additional ducts of the plates located in a hazardou~ zone and at the ~ame time assur e~ a high velocity of water circulationO
Another important ob~ect o~ the pre~ent invention i3 to pre~ent the ~ormation o~ scale on the interior sur-faces of the additional ducts.
One more object of the invention is to provide a blast ~ur~ace cooling arrangement which ensure~ high e~-ficiency o~ thermal protection during long-time operation of the bla~t furnace.
An additional object of the invention i8 to improve the reliability of the blast furnace cooling arrangement.
Still another object of the inventio~ i~ to provide a bla~t furnace cooling arrangement whic~ e~sures a well--timed tranqition from natural to emergency conditions of operation~
The~e and other ob~e¢t~ of the pre~e~t invention are attained in a blast furnace cooling arrangement comprising a cooli~g ~cree~ which i~ di~po~ed i~ an annular space betwee~ a furnace shell and lining and formed by vertic~
ally arranged row~ of plates provided with serie~-conn-ected main internal ducts and additional ducts communic-ating vertically and having commo~ inleta and common out-lets, drum ~:eparators mounted above the cooling Ecreen w~ich communicate through supply pipeli~e~ and take-o~f pipelines with the common inlet~ and the commo~ outl~ts . - 8 -: :

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of the main duct~ ~nd additional duc-ts in the vertical rows o~ the plate~ and ~orm closed circuits of na-tural circulation of a coolin~ medium~ circuits o~ forced cir-culatio~ o~ the c~oling medium through the additional duct~, and distributing valves mounted at the common in-let~ and the common outlet~ of the sdditional duct~ in the vertical XOW3 0~ the plate~ ~or selecti~ely connect-ing said ducts to the circuitq of natural circulatlon a~d to circuits of ~orced circulation, wherein, according -to the inve~tion, each circuit o~ forced circulation i~
cloed and comprise~ a container communicating with the common outlet o~ the additional ducts in a respective vertical row of the plates, a heat excha~ger connected with sa~d container, and a pump co~municating through its inlet with the heat exchanger and through its outlet, with the common inlet o~ the additional duc~ in the Yert-ical row of the platesO
Thus the constructional arrangement of the circuit of forced circulation as well as the mode o~ it~ connect~
ion with the cooling arrangement provide~ for a consider-able flow rate and velocity o~ chemîcally pure water in the additional dUcts~ though the amount of water in the circuit is comparatively smallO The chemically pure water pre~ent~ the formation o~ ~cale, lengthen~ the service li~e and enhances the el~iciency o~ the arrangement, and practically exclude~ accidents~

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It i~ de~irable that the containe~ of the circuit~
o~ forced circulation be dispo~ed level with the drum separa~or~ and communicate therewith through pipelines under and abov~ the level of the cooli~g liquid, ~hereby *orming pair~ "containar - drum separator'~.
Due to such constructional arrangement, the drum ~eparators and the container3 are connected to a common water level maintenance pipeli~e, have co~mon safety val-ve~ and common level indicator3.
It i8 ~urther degirable that the pipelines connect-ing the container~ with the drum separators be provided with ~hut-o~f valve~ adapted to di~connect the containers from the drum ~eparators in emergency conditions~
It i9 further de~irable that the closed circuit o~
forced circula-tion be provided with a by-pas~ pipeline having distributing valve~ and connected i~ parallel wi~h the ~eat exchanger. This design feature erlable~ the cir-cuit o~ forced circulation to temporarily function in case the heat excha~lger i~ damaged or belng replaced.
It is ~urther de3irable that the common inlet o~
the additional ducts in each vertical row o~ plate~7 con-nected to the closed circuit o~ forced circulation be di~po~ed level wit~ the hearth bottomy whereas the common outlet level with the middle portio~ of the stack. Such~
a modification of the cooling arrangement is the most dependable and provides ~or an efficient protection of .

~ 2 the plate~ and the ~hell in ca~e ~ome irregularitie~
occur in the bla t furnace run.

~rie* Description of the Drawi~gs ~ or a better under3tanding o~ the nature a~d ob~ects of the invention reference i~ made to the following de-tailed description of its speci~ic embodiments t taken in connection with the accompanying drawings, in which:
Fig. 1 shows a section o~ a blast furnace cooling arran~eme~t of the present invention;
Fig. 2 shows the blast furnace cooling arrangement viewed i~ the directio~ of arrow A of ~ig. 1 wherein the container and the drum ~eparator are dispo~ed at one and : the ~ame level;
Fig. 3 shows a part of the circuit of forced cir-culation wit~ the by-pa~a pipeline, according to the in-vention;
Fig. 4 diagrammatically ~how~ a modificatio~ of the cooling ~creen plate provided with ~traight main ducts and with the additional ducts in the ~orm of a coil pipe;:
~ igo 5 diagrammatically show~ a second modi~icatio~
of the cooling ~creen plate provided with the main and additional ducts in the form o~ coil pipe~;
~ ig. 6 diagrammatically show~ a third modi~ication o~ the cooling ~creen plate shaped as a box with parti~-.

ion~ forming a labyrinth;
~ ig. 7 shows a sectional ~ie~ of the cooling screenplate~ taken alo~g line VII-VII of ~ig. 6;
~ igo 8 ~hows a preferred embodiment o~ the cooling arrangement of the pre~ent inv~ntion, Detailed D~scription o~ the Invention Re~erring to ~ig. 1, a blast ~'urnac~ cooling arxange-ment c~mpriees a cooling screen 1 di3po~ed in an a~nuliar space betwesn a furnace shell 2 and lining 3. The cooling screen 1 i8 formed by vertically arranged rows o~ plates 4 and 5. The plate~ 4 are pro~ided with main internal ducts 6 and additional internal duct~ 7, whe~ea~ the plates 5 are provided with the main i~ternal ducts ~ only. The main ducts 6 in a vertical row o~ the plate~ 4 and 5 are connected in series and ~ertically communicate with each other through con~ector3 8~ The additional ducts 7 in a vertical row of the plates 4 are connectQd in aerles and vertically communicate with each other through conn~ctor~
9. Thus~ the main ducts 6 i~ the vertical row o~ the plates 4 and 5 have a commo~ inlet 10 and a common out-let 11O The additional ducts 7 in the ~ertical row o~ the plates 4 have a common inlet 12 and a common outlet 13 a~ well. Mounted above the cooli~g screen 1 are drum se-parators 14 communicating with the common inletB 10 and . .

12 and with common outlet~ 11 a~d 13 of the main ducts 6 and the additional ducts 7 in the vertical row o~ the plates 4 and 5~ ~he common outlet~ 11 a~a 13 are con~-ected with the drum separator~ 14 t~rough take-of~ pipe-lines 15, and the common i~lets 10 and 12 are connected with the drum separator~ 14 through ~upply pipeli~es 16.
In thi~ wa~ the duct~ and the hollow space~ of all the enumerated element~ make up a closed circuit of natural circulation of a cooli~g medium. ~rom the economical point o~ view, chemically pure water i~ the most suitable cooling me~ium.
In addition to the circuits o~ natural circulation;
there are circuits o~ ~orced circulation placed in paral-lel therewith and connected to the common inlets 12 and the common outlet~ 13 of the additional duct~ 7 in the vertical row~ oP the plates 4. According to the invent-io~, eaoh circuit o~ forced circulation i8 clo~ed and com-pri~es a container 17 connected with the ¢ommon outlet 13 of the additional duct~ 7 in a re~pective vertical row (or several rows forming a ~ection) o~ the plates 4~ ~he above container 17 commu~icates through a pipe 18 with a heat exchanger 19 which, in its turn9 communicates through a pipe 20 with the inlet o~ a pump 21~ 2he outlet o~ the pump 21: communicate~ with the common inlet 12 of the ad-ditional duct~ 7 o~ a respectiv~ vertical row (or rows) o~ the plate~ 40 -- . 3 Z
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Distributing valve~ 22 are mounted at the common inlets 12 and distributin~ valve~ 23, at the common out-let8 13 o~ the additional ducts 7. ~he distributing ~alves 22 and 23 may be made in the form of three-way cock~ so as t~ selectively connect the additio~al ducts 7 to the circuit~ of natural circulation a~d to the circuits of forced circulatio~ o~ a cooling mediumQ
The circuit o~ forced circulation i8 filled with chemically pure water.
Reference is ~ow made to ~ig. 2 illustrati~g vertic-al rows of the plates 4 and 5. According to a preferred embodiment of the invention, the co~tainers 17 o~ the cir~
cuits o~ forced circulation are disposed level with the drum separators 14, Said containers 17 communicate with re~pective drum separators 14 throueh plpeline~ 24 and 25, thereby forming pairs "contain~r drum ~eparator"~ ~he pipeline 24 oonnects the inner space o~ the container 17 and that of the drum separator 14 above the level o~ a cooling m0dium contained therein~ wherea~ the pipeline 25, u~der the level o~ the same cooling medium. The pipeli~e~
24 and 25 are fitted with ~hut-o~f valve~ 26 and 27. I~
it~ bottom portion each drum separator 14 is connected with a water le~el maintenanc~ p1peline 28, and in its upper portion it is provided ~ith a steam exhau~t pipe ~9 which incorporates a ~afety valve 30~ The drum separ-a~ors 14 are ~itt~d with level indicators 31.

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Re~er~nce i~ now made to Fig. 3 illu~trating a par~
of the circuit of -forced circulation. According to the invention there i~ provided a by-pass pipeline 34 conn-ected in parallel with the heat exchanger 19 through di~-tributing valves 32 and 33.
It will be understood that the blast *urnace coolîng arrangement described above may be fi-ttcd with Yariou~ly constructed plates. Specifically the plates 4 of the cool-ing ~creen 1 may be con~tructed as ~hown in Fig, 4 o~
the accompanying dra~ing~. ~he main ducts 6 of -this mo-dification may be straight pipe~ contained in the body of the plate 4 and dispo~ed in one plane. ~he additional duct 7 of each plate according to this modification i~
made in the form of a coil pipe.
More preferable ~or the purpose of the present in-vention is a modification of the plate 4 ~hown i~ Figo 5 of the accompanying drawings~ According to thi~ modifi-cation both ~ain duct~ 6 and additional duct~ 7 are coil pipes disposed in di~fere~t plane~
Possible i~ a modi~ication of the plate 4 shown in ~ig~. 6 and 7 o~ the accompanying drawing. According ~o this modification the plate 4 is ~ollow, and it~ inner 8paceY i8 divided into two i~ner ~pace~ by a longitudinal partition 35. On either ~ide o~ the partition 35 the inner ~pace~ of the plate 4 are divided by tran~ver~e partitions 36 and 37 forming a labyrinth between an in-' .

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let 38 and an outlet 39.
Reference i~ now made to ~ig. 8 showing the most reliable modification o~ the blast furnace cooling ar-rangement wherein the comrnon inlet 12 o~ the additional ducts 7 in each vertical row o~ the platea 4 is disposed level with a hearth bottom 40 o* the bla~t furnace~ and the common ou-tlet 13 o~ thc additional ducts 7, level with the middle portion o~ a stack 410 The bla~t ~urnace cooling arran~eme~t operates in the following way. Provided the lining 3 (Fig. 1) of the blast furnace is undamaged9 the cooling arrangement operates on e~aporative cooling with natural circulation.
Specifically, the cooling medlum from the drum ~eparator~
14 flows through the supply pipeline~ 16 to the common inleto 10 and 12 of the main ducts 6 and the additional ducts 7 in each vertical row of the plates 4. As this takes place, the circuit o~ forced circulation i~ di~con-nected. Flowing through the main and additional ductJ 6 and 7 the cooling medium cool~ down the plates 4 and 5 and gets ho~ up to the boiling point~ ~he ~eparation o~
the ~-team phase may occur both in the duct~ of the plates : and in the take-off pipelines 159 ~he re~ulting ~team-and--water mi~ture ~lows through the common vutlet~ 11 and 13 and through the take-of~ pipeline~ 15 to the drum separator~ 14. The di~ference in the speci~ic gravity of the ~team-a~d-water mixture in the take-off pipeline~ 15 and the cooling liquid in the ~upply pipeli~e~ 16 provides !
: ~ 16 - .
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for a stable natural circulation. Normal operating con-ditions of the arrang~ment are maintained with the aid of the water level maintenance pipeline 28 (~ig~ 2) a~d the safety valve 30~
Provided the circuit of ~atural circulation is in good working order, the shut-o~ valve~ 26 and 27 of ~he modification of the cooling arra~gement illustrated in ~ig. 2 o~ the accompanying drawings are opened~ In the event of a burning-out of the lining and liquid metal reachin~ the cooling screen 1 (which may be indicated by an increase in the te~persture difference of the cooling medium, a~ increase in the temperature o~ the furnace shell 2 etc.), the -thermal load~ imposed on the plate~ 4 loca~-ed in the hazardous zone sharply increa~es.
When a signal indicative of the burning out o~ the lining 3 comes, the shut-of~ ~alves 25 and 27 block the pipeline~ 24 and 259 Simultaneously therewith~ -the addit~
ional ducts 7 in respective rows o~ the pla~es 4 are dis-connected ~rom the circuits o.~ natural circulation and connected to the circuits o~,~orced circulation by means o~ distributing valves 22 and 23. A~ this takes place, chemically pure water comes from the container 17 to the pump 21 through the heat exchan~er 19. ~he p~np 21 i~
brought into use and supplies the chemically pure wate~
at a high velocity (of the:order o~ 10 m/sec) into the additional ducts 7 in respecti~e rows o~ the plate~ 4.

: - 17 '7S2 ~he ~ections Of the cooling screen which are located ramotely ~rom the damaged area of the lining 3 con-tinue operating normally ln the conditions o~ na~ural circul-ationp wherea~ the plate~ located in the hazardous zone are cooled due to a~ intensive forçed circulation of the cooling medium.
In case the heat exchanger 19 get~ damaged~ clogged, or ~ails to operate7 it i8 cut of~ from and the pass by pipeli~e 34 i8 connected to the cooling arrangement with the aid of the di~tributing val~e~ 32 (Fig. 3) and 330 The chemically pure water temporarily circulates through the byrpa~8 pipeli~e 34 from the container 17 to the pump 21 so a~ to allow the heat ~xchanger 19 be repaired or replaced. In this way, the arrange~ent of the circuit of Yorced circulatio~ provide~ for an e~icient cooling o~ the plates 4 with a relatively small volume of che~ic-ally pure water in emergency conditions~
~ he modi~ica-tion of the cooling arrangement illust-rated in Fig~ 8 o~ the accompanying drawing~ make~ it po~ible to e~ectively cool, in case o~ necessity, ~ot only the hearth and the hearth bo-ttom but the bo~h and the lower portion of a blast furnace stack as well.
After the campaign is over and the damaged linirlg

3 repaire~, the cooling arrangement i8 brought back to it~ original ~tate for operatio~ i~ the conditions of natural circulation of a cooling medium, _ 18 -1~4~i752 While particular embodiments of the invention have been shown and described, variou~ modi~ications thereo~
will be apparent to those skilled in the art and there-fore it is not intended that the invention be limited to the disclosed embodiments or to the details thereo~ and the departures may be made there~rom within the spirit and ~cope o~ the invention as defined in the claims.

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Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A blast furnace cooling arrangement comprising:
(a) a cooling screen disposed in an annular space between a furnace shell and lining and formed by verti-cally arranged rows of plates provided with series-conn-ected main internal ducts and additional internal ducts communicating vertically and having common inlets and common outlets;
(b) drum separators mounted above said cooling screen and communicating with said common inlets and out-lets of said main and additional ducts of said plates of each vertical row;
(c) take-off pipelines connecting said common out-lets of said main and additional ducts of said plates of each vertical row with said drum separators;
(d) supply pipelines connecting said drum separators with said common inlets of said main and additional ducts of said plates of each vertical row and forming with the above elements a closed circuit of natural circulation of a cooling medium;
(e) circuits of forced circulation, each of which is closed at said common inlet and outlet of said addit-ional ducts in a respective vertical row of said plates and comprises:
1) a container communicating with said common outlet of said additional ducts in the vertical row of said plates;
2) a heat exchanger communicating with said con-tainer;
3) a pump communicating through its inlet with said heat exchanger and through its outlet, with the common inlet of said additional ducts in the vertical row of said plates;
(f) distributing valves mounted at said common in-lets and outlets of said additional ducts in the vertical rows of said plates and intended to selectively connect the additional ducts to the circuits of natural circulat-ion in normal operating conditions and to the circuits of forced circulation in emergency conditions.

2. An arrangement as claimed in claim 1, wherein said containers of the closed circuits of forced circul-ation are disposed level with said drum separators and communicate therewith through pipelines under and above the level of the cooling liquid, thereby forming pairs "container - drum separator".

3. An arrangement as claimed in claim 2, wherein said pipelines connecting said containers with said drum separators are provided with shut-off valves.

4. An arrangement as claimed in claim 1, wherein the closed circuit of forced circulation is provided with a by-pass pipeline disposed in parallel with said heat exchanger and having distributing valves.

5. An arrangement as claimed in claim 1, wherein said common inlet of said additional ducts in each vert-ical row of said plates, connected to the closed circuit of forced circulation is disposed level with a furnace hearth bottom, and the common outlet is disposed level with the middle portion of a stack.