CA2003155A1 - Method of operating a smelting unit and a smelting unit for that method - Google Patents
Method of operating a smelting unit and a smelting unit for that methodInfo
- Publication number
- CA2003155A1 CA2003155A1 CA002003155A CA2003155A CA2003155A1 CA 2003155 A1 CA2003155 A1 CA 2003155A1 CA 002003155 A CA002003155 A CA 002003155A CA 2003155 A CA2003155 A CA 2003155A CA 2003155 A1 CA2003155 A1 CA 2003155A1
- Authority
- CA
- Canada
- Prior art keywords
- furnace
- charging material
- preheater
- furnace vessel
- charging
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
- F27B3/00—Hearth-type furnaces, e.g. of reverberatory type; Tank furnaces
- F27B3/10—Details, accessories, or equipment peculiar to hearth-type furnaces
- F27B3/18—Arrangements of devices for charging
- F27B3/183—Charging of arc furnaces vertically through the roof, e.g. in three points
- F27B3/186—Charging in a vertical chamber adjacent to the melting chamber
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/52—Manufacture of steel in electric furnaces
- C21C5/527—Charging of the electric furnace
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Vertical, Hearth, Or Arc Furnaces (AREA)
Abstract
ABSTRACT
Method of operating a smelting unit and a smelting unit for that method In a smelting unit comprising a furnace vessel containing a heat source and a furnace hearth, and at least one shaft-like charging material preheater which is arranged laterally on the furnace vessel and the bottom of which is designed to drop away towards the furnace vessel and the interior of which is connected in a region adjoining its bottom to the interior of the furnace vessel through a connecting zone, controlling the supply of energy into the lower region of the column of charging material which is formed in the charging material preheater causes a variation in the spatial extent of a supporting structure (iron block) which is formed by pieces of charging material being welded together, in order to control the flow of material into the furnace hearth.
Method of operating a smelting unit and a smelting unit for that method In a smelting unit comprising a furnace vessel containing a heat source and a furnace hearth, and at least one shaft-like charging material preheater which is arranged laterally on the furnace vessel and the bottom of which is designed to drop away towards the furnace vessel and the interior of which is connected in a region adjoining its bottom to the interior of the furnace vessel through a connecting zone, controlling the supply of energy into the lower region of the column of charging material which is formed in the charging material preheater causes a variation in the spatial extent of a supporting structure (iron block) which is formed by pieces of charging material being welded together, in order to control the flow of material into the furnace hearth.
Description
Z09315~;
Method of operating a smelting unit and a smelting unit for that method Description:
The invention relates to a method and an apparatus as set forth in the classifying portions of claims 1 and 12 respectively.
GbYman utility model No 84 12 739 discloses a method and an apparatus of that kind.
In the known method the charging material, in particular steel scrap, is charged by the shaft-like charging material preheater into a metal sump in the furnace vessel. Particularly when dealing with charging material which varies greatly in weight, when for example it comprises heavy scrap, medium scrap and light scrap, the problem which arises is that of feeding it to the furnace hearth in a controlled fashion. On the one hand, in the smelting process, the charging material must be able to flow away well through the preheater into the molten bath, in spite of the charging material being of greatly fluctuating sizes and bulkiness while on the other hand, after the desired tapping weight in the bath has been reached, it is to be possible to retain the charging material which is st;ll present in the,'preheater, even in the event of a tipping movement of - the furnace vessel and the preheater which is integrated therewith, as is required for the tapping operation. In that cQnnection, mechanical shut-off b OE s which for that purpose are inserted into the ; interior of the preheater have not prcved successful because of the severe thermal and mechanical loadings.
The Iast-mentioned problem does adnittedly become irrelevant when ali the charging material introduced into the preheater is smelted in the smelting phase. In that case however the sensible hP~t of the furnace gases can be utilised for preheating the charging material only over a part of the smelting process and, in relation to - a further smelting process which follows a tapping operation, it is - - , ., ~, :
ZC031.55 necessary to tolerate a comparatively long waiting time for filling of the preheater and melting of the material which has not been preheated.
The object of the invention is to provide a method with which the flow of material into the furnace hearth can be controlled and with which it is readily possible to retain a charging material in the preheater, without the incorporation of mechanical barrier members such as bars or flaps. The invention also seeks to provide a smelting unit for that method. ;
The method of the invention is characterised by the features of claim 1. Advantageous embodiments of the method are set forth in claims 2 to ll. The smelting unit according to the invention for that - ;;
method is characterised by the features of claim 12. Advantageous embcdiments of the smelting unit are set forth in the other claim6. ~;While in the known smelting unit the bottam of the shaft-like charging material preheater drops away towards the bottom of the ;
furnace hearth at a comparatively sm211 angle of inclination so that the bath level is higher over a substantial part of the smelting ~;
pracess than the entire botto~ of the charging material preheater and - ~ -20 the column of charging material at the lower end over the entire ;~
cross-section is in the sump and is thus also exposed to the melting process b,v virtue of the superheated bath, the method according to the invention provides that the bottom is designed to drcp away toward~s the furnace hearth at a l æ ger angle of inclination - an angle of 45 has been found to be advantageous - so that a portion of the bottom is higher than the maximum bath level. That prcvides a 'i ~support region, whichlis~rèmoved from the area ofidirect influence of a superheated bath of molten material, for a supporting structure (iran block) which is formed by pieces of charging material becoming welded together and which can be v æ ied in respect of its spatial extent by contro~ g the melting energy supplied by way of the burners and possibly by temporary cooling. Therefore, the charging .., - ~ ~
ZC!~3155 material itself is used to provide a b æ rier member which can be v æ ied in size and by means of which the feed flow of material can be brought to a halt prior to the tapping operation at the desired time, even when the æ rangement involves a geometrical configuration of the shaft and a size of the connecting zone between the shaft and the furnace vessel, which have an advantageous effect on the flcw of material, so that there is no fear of blockages occurring, even when dealing with bulky charging material.
Temporary cooling of the lower region of the column of charging material may be effected for example by introducing by way of the nozzles gases which undergo an endothermic decomFosition reaction.
For the purposes`of controlling the melting energy supplied to the lower region of the column of charging material, beside the burners, it is also possible to utilise the radiant heat of the arcs and the contact with the superheated bath of molten material, while by producing a stirring action in the molten bath, in p æticular in the region of the connecting zone, it is possible to intensify the melting process in that region. The stirring effect can be produced for example by injecting oxygen into a carbon-bearing molten material or by introducing flushing or scavening gases through bottom scavenging bricks.
The c æbon content of the molten material can be increased in known manner by adding carbon or crude iron in piece or granulate form either by way of the shaft-like charging material preheater or directly into the furnace vessel. As an additional source of energy in that region, it is also possible to use other fossil fuels or organic waste`l materialliwhichiis charged intolthe furnace vessel and burnt adjacent to the connecting zone. Suitable organic waste materials are for example disintegrated motor vehicle tyres, in which case the column of charging material which is always present in the preheater serves as a filter for the dust-laden waste gases.
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Preferably, after the tapping o~eration, a residual molten material remains in the furnace hearth (sump mode of operation); that residual material is still of a volume of about 50 to 100% of the tapping volume, relative to the respective weight. In addition the ;~
5 ratio of the energy introduced by the heating source of the furnace ;
vessel, that is to say the electric arc energy in the case of an electric arc furnace, to the energy introduced by the burners, should be between 1:1 and 5:1. In that manner, after the tapping operation, melting of the supporting structure which was previously necessarily 10 formed is accelerated and thus in the following smelting process, the ;
flow of material into the hearth space can be started exFeditiously.
The smelting unit for the method according to the invention has a charging material preheater bottom which is designed to drop away towards the furnace hearth at a comparatively large angle of inclination - the angle of inclination should be greater than 30 and less than 60 - so that a portion of the bottom is higher than the maxim~m bath level. Preferably the smelting unit is fo~med by a charging material preheater arranged laterally on the furnace vessel of an electric arc furnace, wherein the electrodes of the arc furnace are displaced in kncwn manner out of the centre of the furnace vessel towards the sbaft-like charging material preheater. In order to produce a stirring action, in parti~l~r in the vicinity of the connecting zone, bottom nozzles or bottom scavenging bricks through which gases can be injected are desirably olranged in the bottom region of the furnace vessel, which adjoins the connecting zone. With a view to a sump mode of operation, the capacity of the furnace hearth, which is related ito the weight of the molten metal, should correspond tc 1.5 to 2 times the tapping weight of a bath of molten -metal, at the mEximum bath level.
In order to ensure a good flow of material through the charging material preheater and the connecting zone into the furnace hearth, even when dealing with bulky charging material, not only should the :::
- ::
,.... .................................................................................... :~,.,:, ZC~)3155 flow cross-section in the connecting ~one be as large as possible and extend approximately aver the entire height of the furnace vessel, but also the ratio of the height h to the square root of the mean cross-section q of the shaft-like charging material preheater shauld be in the range of between 1.2 and 3. In conjunction with the comparatively large angle of inclination of the bottom in the region of the charging material preheater, that arrangement ensures a good flow of material in the furnace hearth, even when dealing with bulky charging material, if the spatial extent of the supporting structure (iron block) which acts as a barrier member is sufficiently reduced in the lawer region of the column of charging material by the melting ,, .
energy supplied in that region, or if the supporting structure has been totally elim mated. Preferably, a tap hole which i5 arranged ~ -.~ :
eccentrically in the bottom of the furnace vessel is provided for the tapping operation and the furnace vessel as well as the shaft-like charging material preheater which is integrated therewith can be ~-tilted about an axis which joins th~ middle of the preheater to the middle of the furnace vessel.
With a view to a good flow of material, the cross-section of 20 the interior of the charging material preheater should also be ~
enlarged in a downward direction. A cross-section which is almost ~ -rectangular has been found to be particuLarly advantageaus. A round or aval furnace vessel which is cut off in a segment-like configuratian on the side tcwards the charging material preheater and -25 to which the interior of the rectangular charging material preheater ~ -is joined by the connecting zone ensures that the arrangement has a ; ~;~
comparatively largel~flow opening in the regian of the connecting zone.
The invention will ncw be described in greater detail by means 30 of an embodiment with reference to tWD Figures of drawings in which: ~
Figure 1 is a diagrammatic view in longitudinal section of a -smelting unit for carrying aut the method according to the invention, ~.
- . .. ..
Method of operating a smelting unit and a smelting unit for that method Description:
The invention relates to a method and an apparatus as set forth in the classifying portions of claims 1 and 12 respectively.
GbYman utility model No 84 12 739 discloses a method and an apparatus of that kind.
In the known method the charging material, in particular steel scrap, is charged by the shaft-like charging material preheater into a metal sump in the furnace vessel. Particularly when dealing with charging material which varies greatly in weight, when for example it comprises heavy scrap, medium scrap and light scrap, the problem which arises is that of feeding it to the furnace hearth in a controlled fashion. On the one hand, in the smelting process, the charging material must be able to flow away well through the preheater into the molten bath, in spite of the charging material being of greatly fluctuating sizes and bulkiness while on the other hand, after the desired tapping weight in the bath has been reached, it is to be possible to retain the charging material which is st;ll present in the,'preheater, even in the event of a tipping movement of - the furnace vessel and the preheater which is integrated therewith, as is required for the tapping operation. In that cQnnection, mechanical shut-off b OE s which for that purpose are inserted into the ; interior of the preheater have not prcved successful because of the severe thermal and mechanical loadings.
The Iast-mentioned problem does adnittedly become irrelevant when ali the charging material introduced into the preheater is smelted in the smelting phase. In that case however the sensible hP~t of the furnace gases can be utilised for preheating the charging material only over a part of the smelting process and, in relation to - a further smelting process which follows a tapping operation, it is - - , ., ~, :
ZC031.55 necessary to tolerate a comparatively long waiting time for filling of the preheater and melting of the material which has not been preheated.
The object of the invention is to provide a method with which the flow of material into the furnace hearth can be controlled and with which it is readily possible to retain a charging material in the preheater, without the incorporation of mechanical barrier members such as bars or flaps. The invention also seeks to provide a smelting unit for that method. ;
The method of the invention is characterised by the features of claim 1. Advantageous embodiments of the method are set forth in claims 2 to ll. The smelting unit according to the invention for that - ;;
method is characterised by the features of claim 12. Advantageous embcdiments of the smelting unit are set forth in the other claim6. ~;While in the known smelting unit the bottam of the shaft-like charging material preheater drops away towards the bottom of the ;
furnace hearth at a comparatively sm211 angle of inclination so that the bath level is higher over a substantial part of the smelting ~;
pracess than the entire botto~ of the charging material preheater and - ~ -20 the column of charging material at the lower end over the entire ;~
cross-section is in the sump and is thus also exposed to the melting process b,v virtue of the superheated bath, the method according to the invention provides that the bottom is designed to drcp away toward~s the furnace hearth at a l æ ger angle of inclination - an angle of 45 has been found to be advantageous - so that a portion of the bottom is higher than the maximum bath level. That prcvides a 'i ~support region, whichlis~rèmoved from the area ofidirect influence of a superheated bath of molten material, for a supporting structure (iran block) which is formed by pieces of charging material becoming welded together and which can be v æ ied in respect of its spatial extent by contro~ g the melting energy supplied by way of the burners and possibly by temporary cooling. Therefore, the charging .., - ~ ~
ZC!~3155 material itself is used to provide a b æ rier member which can be v æ ied in size and by means of which the feed flow of material can be brought to a halt prior to the tapping operation at the desired time, even when the æ rangement involves a geometrical configuration of the shaft and a size of the connecting zone between the shaft and the furnace vessel, which have an advantageous effect on the flcw of material, so that there is no fear of blockages occurring, even when dealing with bulky charging material.
Temporary cooling of the lower region of the column of charging material may be effected for example by introducing by way of the nozzles gases which undergo an endothermic decomFosition reaction.
For the purposes`of controlling the melting energy supplied to the lower region of the column of charging material, beside the burners, it is also possible to utilise the radiant heat of the arcs and the contact with the superheated bath of molten material, while by producing a stirring action in the molten bath, in p æticular in the region of the connecting zone, it is possible to intensify the melting process in that region. The stirring effect can be produced for example by injecting oxygen into a carbon-bearing molten material or by introducing flushing or scavening gases through bottom scavenging bricks.
The c æbon content of the molten material can be increased in known manner by adding carbon or crude iron in piece or granulate form either by way of the shaft-like charging material preheater or directly into the furnace vessel. As an additional source of energy in that region, it is also possible to use other fossil fuels or organic waste`l materialliwhichiis charged intolthe furnace vessel and burnt adjacent to the connecting zone. Suitable organic waste materials are for example disintegrated motor vehicle tyres, in which case the column of charging material which is always present in the preheater serves as a filter for the dust-laden waste gases.
~.
:-:
.
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Preferably, after the tapping o~eration, a residual molten material remains in the furnace hearth (sump mode of operation); that residual material is still of a volume of about 50 to 100% of the tapping volume, relative to the respective weight. In addition the ;~
5 ratio of the energy introduced by the heating source of the furnace ;
vessel, that is to say the electric arc energy in the case of an electric arc furnace, to the energy introduced by the burners, should be between 1:1 and 5:1. In that manner, after the tapping operation, melting of the supporting structure which was previously necessarily 10 formed is accelerated and thus in the following smelting process, the ;
flow of material into the hearth space can be started exFeditiously.
The smelting unit for the method according to the invention has a charging material preheater bottom which is designed to drop away towards the furnace hearth at a comparatively large angle of inclination - the angle of inclination should be greater than 30 and less than 60 - so that a portion of the bottom is higher than the maxim~m bath level. Preferably the smelting unit is fo~med by a charging material preheater arranged laterally on the furnace vessel of an electric arc furnace, wherein the electrodes of the arc furnace are displaced in kncwn manner out of the centre of the furnace vessel towards the sbaft-like charging material preheater. In order to produce a stirring action, in parti~l~r in the vicinity of the connecting zone, bottom nozzles or bottom scavenging bricks through which gases can be injected are desirably olranged in the bottom region of the furnace vessel, which adjoins the connecting zone. With a view to a sump mode of operation, the capacity of the furnace hearth, which is related ito the weight of the molten metal, should correspond tc 1.5 to 2 times the tapping weight of a bath of molten -metal, at the mEximum bath level.
In order to ensure a good flow of material through the charging material preheater and the connecting zone into the furnace hearth, even when dealing with bulky charging material, not only should the :::
- ::
,.... .................................................................................... :~,.,:, ZC~)3155 flow cross-section in the connecting ~one be as large as possible and extend approximately aver the entire height of the furnace vessel, but also the ratio of the height h to the square root of the mean cross-section q of the shaft-like charging material preheater shauld be in the range of between 1.2 and 3. In conjunction with the comparatively large angle of inclination of the bottom in the region of the charging material preheater, that arrangement ensures a good flow of material in the furnace hearth, even when dealing with bulky charging material, if the spatial extent of the supporting structure (iron block) which acts as a barrier member is sufficiently reduced in the lawer region of the column of charging material by the melting ,, .
energy supplied in that region, or if the supporting structure has been totally elim mated. Preferably, a tap hole which i5 arranged ~ -.~ :
eccentrically in the bottom of the furnace vessel is provided for the tapping operation and the furnace vessel as well as the shaft-like charging material preheater which is integrated therewith can be ~-tilted about an axis which joins th~ middle of the preheater to the middle of the furnace vessel.
With a view to a good flow of material, the cross-section of 20 the interior of the charging material preheater should also be ~
enlarged in a downward direction. A cross-section which is almost ~ -rectangular has been found to be particuLarly advantageaus. A round or aval furnace vessel which is cut off in a segment-like configuratian on the side tcwards the charging material preheater and -25 to which the interior of the rectangular charging material preheater ~ -is joined by the connecting zone ensures that the arrangement has a ; ~;~
comparatively largel~flow opening in the regian of the connecting zone.
The invention will ncw be described in greater detail by means 30 of an embodiment with reference to tWD Figures of drawings in which: ~
Figure 1 is a diagrammatic view in longitudinal section of a -smelting unit for carrying aut the method according to the invention, ~.
- . .. ..
2(~)3155 and Figure 2 is a diagrammatic plan view of the Figure 1 unit.
The smelting unit shown in the drawings comprises an electric arc furn~ace 1 and a shaft-like charging material prèhèater 2. The æ c ~~~~~ 5 furnace includes a furnace vessel 3 with a cover 4 which can be pivoted away and through which three electrodes which are carried by -~
carrier arms S and which can be pivoted laterally and raised and lowered by means of a lifting and pivoting device can be introduced into the furnace vessel. -The charging material preheater 2 is arranged lAterally on the furnace vessel 3 and is of a virtually rectangular configuration in cross-section (see Figure 2). On the side towards the charging material preheater, the substantially m und furnace vessel is cut off in a segment-like configuration and does not have a side wall at that location, so that the connecting zone 7 between the interior 8 of the charging material preheater and the interior 9 of the furnace vessel extends almost over the entire height of the arc furnace and ~ -approximately over the entire length 10 of the preheater. The lined furnace h3~h which accommodates the molten material is indicated by ~-reference numeral 11 and has an eccentrically arranged tap hole 12.
The furnace vessel 1 and the preheater 2 which is integrated therewith can be tilted in known manner for the tapping operation about the connecting line 28 between the middle of the preheater and the centre point of the circle on which the electrodes are disposed, that is to say in Figure 2 about a horizontal axis. The lined bottom 13 of the preheater 2 drcps away towards the bottom of the furnace hearth ll~at an anglell4 of inclination of about 45. In addition~the cross-section of the interior 8 of the preheater 2 is enlarged in a doon4cLd ~;rection, so that, in conjunction with the comparatively large flow cross-section of the connecting zone 7, that arrangement ensures a good flow of material into the hearth space. Burners or nozzles 15 open in the lower region of the charging material '- ~,"~ ","`"'','`.
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preheater 2, above the lining. In addition, the æ rangement has burners or nozzles 16 which æ e directed tow æ ds the connecting zone 7. In the upper region the ch æ ging material preheater 2 has a closable charging opening 17 and a gas outlet 18. The gas outlet 18 is connected to a chimney by way of a gas pipe 19 and a filter chamber. As can be seen from Figure 2, the electrodes 6 æ e not æ ranged in the middle of the furnace vessel, but æ e displaced tow æ ds the shaft-like ch æ ging material preheater 2. In that way the radiant heat produced by the æ cs can act to an increased extent on the charging material which is supplied by way of the charging material preheater 2 and at the same time the radiant heat loading on the free wall regions of the æ c furnace can be reduc~d. To improve ~uxing of the molten material, nozzles or scavenging bricks 24 through which gases can be introduced æ e æ ranged in the bottom of the furnace vessel in the vicinity of the vertical extension of the shaft wal1 23 adjacent to the furnace vessel. Such scavenging bricks 24 may also be oLlanged at another location in the bottom of the furnace ~essel. Preferably however they æ e disposed in the region between the electrodes and the vertical extension of the shaft wall 23. The desired movement of the molten material could also be produced by electromagnetic eddy fields or a tilting or rocking motion of the furnace vessel.
The method for operating the described smelting unit will now be described.
When the smelting unit is started up cold, the shaft-like charging material preheater 2 is filled with scrap and in ~ tion about 20, to 40% of,the amcunt of scrap required for a bath of molten material is directly charged into the furnace vessel 3 of the electric æ c furnace 1 so that nonmal firing of the electrcdes on to scrap is possible. After closure of the furnace vessel and the opening 17 of the preheater and after the electrodes have been introduced, a combined smelting process with electric æ c energy and Z(~31SS
burner energy is initiated by firing the electrodes and igniting the burners. The hot waste gases which are produced in that procedure are drawn through the preheater by way of the gas outlet into the gas pipe and give up their sensible heat to the scrap.
After a bath of molten material has been formed, the injection of gases through the scavenging brick 24 prcvides for good mixing as between the molten material in the furnace hearth 1, which is more substantially heated under the effect of the arcs, and the relatively cool liquid steel which flows to the furnace hearth over the bottom 13 and which is melted by the burners. If coal, sponge iron or crude iron in piece or granulate form has been added with the scrap which is loaded into the preheater, then the injection of oxygen by way of bottom nozzles which are provided instead of the scavenging bricks can provide for the introduction of additional melting energy into that region.
With an increasing volume of the fluid bath, a supporting structure in the form of a scrap or iron block is formed by a reduction in the melting energy supplied to the lower region of the column 25 of scrap; the supporting structure interrupts the flow of material into the furnace he æth or prevents scrap from falling dcwn into the he æth space. That is achieved by cutting back the burner energy and controlling the electrical energy in such a way that the æcs æe encased in granulated slag and thus the radiant heat effect of the arcs on the lower region of the column of scrap is reduced. An inert scavenging gas is injected through the bottom nozzles instead of oxygen. The formation of the supporting structure can be accelerated if cooling gases 'ar,e injected through the burners or nozzles 15 and 16, suitable gases for that purpose being those which have an endothenmic decomposition reaction such as propane or carbon dioxide.
In good time before reaching the desired overall weight of liquid steel, which corresponds to the tapping weight plus a residual ~", amount of molten material which remains in the furnace vessel in the tapping operation, the burners are completely switched off and the bath is brought to tapping temperature by means of the electric arc energy, in which case a suitable granulated slag provides that the arc is completely covered. The stirring action of the scavenging gases also ensures a good mixing action in this refining phase. The resulting underscouring or undermining of the block of scrap material - the condition is shown in Figure 1 prior to the tapping operation -is not disadvantageous because the substantial inclination of the bottom of the preheater means that there is a sufficient support area -available for the scrap material, above the maximum level of the bath. The underscouring effect even promotes the elimination of the i;ron block structure in the next smelting process which follows the ta~ing operation.
During the smelting process, the column of scrap materi~l is always kept to a minimum height by adding further charging material so that the sensible heat of the waste gases can be utilised for preheating the scrap thrmughout the entire smelting and refining phase. In addition that mode of operation affords the option of utilising the column of scrap material as a filter so that up to a given amcunt, organic waste materials such as disintegrated motor vehicle tyres can be charged into the furnace vessel as energy carriers which require suitable filtering of the waste gases.
; The operation of tapping off the molten material is effected by tilting the æc furnace 1 and the preheater 2 which is integrated therewith, after removal of the electrodes. In that operation, a residual amLunt oflm~lten~material which constitutes about 50% of the .. .. .
tapping weight is left in the furnace vessel. To initiate the next melting process, after the electrcdes have been moved into their operating positions, the arcs and the burners are lit again and gases are injected through the bottom nozzles or scavenging bricks in order also to make use of the thermal content of the superheated molten . ~ ~
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material in the furnace hearth for the melting process in the lower region of the column of charging material. In that way and by virtue of the underscouring of the supporting structure, which has already been produced in the preceding smelting process, the supporting structure can be very rapidly melted away or reduced in respect of its spatial extent, and thus initiate the flow of preheated scrap.
The particular advantage of the method described is that the time of the tapping operation can be determuned by the control effect in respect of the melting energy supplied to the lower region of the - ~-column of charging material, irrespective of whether the scrap is melted at a higher or lower rate in the shaft-like preheater, due to differences in the compoæition thereof. A high sump component, that 1S to say a proportion of the residual molten material of more than 40% of the tapping weight, represents a buffer amount which permits tapping of the arc furnace in a defined manner in respect of time.
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The smelting unit shown in the drawings comprises an electric arc furn~ace 1 and a shaft-like charging material prèhèater 2. The æ c ~~~~~ 5 furnace includes a furnace vessel 3 with a cover 4 which can be pivoted away and through which three electrodes which are carried by -~
carrier arms S and which can be pivoted laterally and raised and lowered by means of a lifting and pivoting device can be introduced into the furnace vessel. -The charging material preheater 2 is arranged lAterally on the furnace vessel 3 and is of a virtually rectangular configuration in cross-section (see Figure 2). On the side towards the charging material preheater, the substantially m und furnace vessel is cut off in a segment-like configuration and does not have a side wall at that location, so that the connecting zone 7 between the interior 8 of the charging material preheater and the interior 9 of the furnace vessel extends almost over the entire height of the arc furnace and ~ -approximately over the entire length 10 of the preheater. The lined furnace h3~h which accommodates the molten material is indicated by ~-reference numeral 11 and has an eccentrically arranged tap hole 12.
The furnace vessel 1 and the preheater 2 which is integrated therewith can be tilted in known manner for the tapping operation about the connecting line 28 between the middle of the preheater and the centre point of the circle on which the electrodes are disposed, that is to say in Figure 2 about a horizontal axis. The lined bottom 13 of the preheater 2 drcps away towards the bottom of the furnace hearth ll~at an anglell4 of inclination of about 45. In addition~the cross-section of the interior 8 of the preheater 2 is enlarged in a doon4cLd ~;rection, so that, in conjunction with the comparatively large flow cross-section of the connecting zone 7, that arrangement ensures a good flow of material into the hearth space. Burners or nozzles 15 open in the lower region of the charging material '- ~,"~ ","`"'','`.
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preheater 2, above the lining. In addition, the æ rangement has burners or nozzles 16 which æ e directed tow æ ds the connecting zone 7. In the upper region the ch æ ging material preheater 2 has a closable charging opening 17 and a gas outlet 18. The gas outlet 18 is connected to a chimney by way of a gas pipe 19 and a filter chamber. As can be seen from Figure 2, the electrodes 6 æ e not æ ranged in the middle of the furnace vessel, but æ e displaced tow æ ds the shaft-like ch æ ging material preheater 2. In that way the radiant heat produced by the æ cs can act to an increased extent on the charging material which is supplied by way of the charging material preheater 2 and at the same time the radiant heat loading on the free wall regions of the æ c furnace can be reduc~d. To improve ~uxing of the molten material, nozzles or scavenging bricks 24 through which gases can be introduced æ e æ ranged in the bottom of the furnace vessel in the vicinity of the vertical extension of the shaft wal1 23 adjacent to the furnace vessel. Such scavenging bricks 24 may also be oLlanged at another location in the bottom of the furnace ~essel. Preferably however they æ e disposed in the region between the electrodes and the vertical extension of the shaft wall 23. The desired movement of the molten material could also be produced by electromagnetic eddy fields or a tilting or rocking motion of the furnace vessel.
The method for operating the described smelting unit will now be described.
When the smelting unit is started up cold, the shaft-like charging material preheater 2 is filled with scrap and in ~ tion about 20, to 40% of,the amcunt of scrap required for a bath of molten material is directly charged into the furnace vessel 3 of the electric æ c furnace 1 so that nonmal firing of the electrcdes on to scrap is possible. After closure of the furnace vessel and the opening 17 of the preheater and after the electrodes have been introduced, a combined smelting process with electric æ c energy and Z(~31SS
burner energy is initiated by firing the electrodes and igniting the burners. The hot waste gases which are produced in that procedure are drawn through the preheater by way of the gas outlet into the gas pipe and give up their sensible heat to the scrap.
After a bath of molten material has been formed, the injection of gases through the scavenging brick 24 prcvides for good mixing as between the molten material in the furnace hearth 1, which is more substantially heated under the effect of the arcs, and the relatively cool liquid steel which flows to the furnace hearth over the bottom 13 and which is melted by the burners. If coal, sponge iron or crude iron in piece or granulate form has been added with the scrap which is loaded into the preheater, then the injection of oxygen by way of bottom nozzles which are provided instead of the scavenging bricks can provide for the introduction of additional melting energy into that region.
With an increasing volume of the fluid bath, a supporting structure in the form of a scrap or iron block is formed by a reduction in the melting energy supplied to the lower region of the column 25 of scrap; the supporting structure interrupts the flow of material into the furnace he æth or prevents scrap from falling dcwn into the he æth space. That is achieved by cutting back the burner energy and controlling the electrical energy in such a way that the æcs æe encased in granulated slag and thus the radiant heat effect of the arcs on the lower region of the column of scrap is reduced. An inert scavenging gas is injected through the bottom nozzles instead of oxygen. The formation of the supporting structure can be accelerated if cooling gases 'ar,e injected through the burners or nozzles 15 and 16, suitable gases for that purpose being those which have an endothenmic decomposition reaction such as propane or carbon dioxide.
In good time before reaching the desired overall weight of liquid steel, which corresponds to the tapping weight plus a residual ~", amount of molten material which remains in the furnace vessel in the tapping operation, the burners are completely switched off and the bath is brought to tapping temperature by means of the electric arc energy, in which case a suitable granulated slag provides that the arc is completely covered. The stirring action of the scavenging gases also ensures a good mixing action in this refining phase. The resulting underscouring or undermining of the block of scrap material - the condition is shown in Figure 1 prior to the tapping operation -is not disadvantageous because the substantial inclination of the bottom of the preheater means that there is a sufficient support area -available for the scrap material, above the maximum level of the bath. The underscouring effect even promotes the elimination of the i;ron block structure in the next smelting process which follows the ta~ing operation.
During the smelting process, the column of scrap materi~l is always kept to a minimum height by adding further charging material so that the sensible heat of the waste gases can be utilised for preheating the scrap thrmughout the entire smelting and refining phase. In addition that mode of operation affords the option of utilising the column of scrap material as a filter so that up to a given amcunt, organic waste materials such as disintegrated motor vehicle tyres can be charged into the furnace vessel as energy carriers which require suitable filtering of the waste gases.
; The operation of tapping off the molten material is effected by tilting the æc furnace 1 and the preheater 2 which is integrated therewith, after removal of the electrodes. In that operation, a residual amLunt oflm~lten~material which constitutes about 50% of the .. .. .
tapping weight is left in the furnace vessel. To initiate the next melting process, after the electrcdes have been moved into their operating positions, the arcs and the burners are lit again and gases are injected through the bottom nozzles or scavenging bricks in order also to make use of the thermal content of the superheated molten . ~ ~
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material in the furnace hearth for the melting process in the lower region of the column of charging material. In that way and by virtue of the underscouring of the supporting structure, which has already been produced in the preceding smelting process, the supporting structure can be very rapidly melted away or reduced in respect of its spatial extent, and thus initiate the flow of preheated scrap.
The particular advantage of the method described is that the time of the tapping operation can be determuned by the control effect in respect of the melting energy supplied to the lower region of the - ~-column of charging material, irrespective of whether the scrap is melted at a higher or lower rate in the shaft-like preheater, due to differences in the compoæition thereof. A high sump component, that 1S to say a proportion of the residual molten material of more than 40% of the tapping weight, represents a buffer amount which permits tapping of the arc furnace in a defined manner in respect of time.
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Claims (22)
1. A method of operating a smelting unit comprising a furnace vessel including a heating source and a furnace hearth, and at least one shaft-shaped charging material preheater arranged laterally on the furnace vessel, the bottom of the charging material preheater being designed to drop away towards the furnace hearth and the interior of the charging material preheater being connected in a region adjoining its bottom to the interior of the furnace vessel through a connecting zone the charging material preheater also being provided in its upper region with a charging opening for charging material and a gas outlet and in its lower region with burners or nozzles, wherein the metallic charging material, in particular steel scrap, which is charged into the charging material preheater through the charging opening, forms a column of charging material which is heated in heat exchange relationship with the hot gases of the furnace vessel and the burners and which is melted in the lower region by the burners and under the effect of the heating source of the furnace vessel and in contact with the liquid sump of the furnace hearth, and the molten material in the furnace hearth is also brought to a tapping temperature and at least partially tapped off, characterised in that the bottom of the shaft-like charging material preheater is designed to drop away to the furnace hearth at such an angle of inclination that a portion of said bottom is higher than the maximum bath level, that during the smelting process the column of charging material is kept at a minimum height by adding charging material, and that the flow of material into the furnace hearth is controlled in that, by controlling the melting energy supplied to the lower region of the column of charging material and possibly by temporary cooling of that region, a supporting structure (iron block) which is formed by pieces of charging material becoming welded together is varied in respect of its spatial extent.
2. A method according to claim 1 characterised in that control of the melting energy supplied to the lower region of the column of charging material or the cooling operation are effected by way of the burners of nozzles.
3. A method according to claim 2 characterised in that control of the melting energy supplied to the lower region of the column of charging material is effected by forced movement of the molten material in the furnace hearth.
4. A method according to one of claims 1 to 3 characterised in that during the smelting phase of a bath of molten material, the supporting structure is melted and substantially removed and during the subsequent refining phase a supporting structure for blocking the flow of material is formed.
5. A method according to one of claims 1 to 4 characterised in that the heating source of the furnace vessel is formed by the arc or arcs of one or more arc electrodes.
6. A method according to one of claims 1 to 5 characterised in that the or an additional heating source of the furnace vessel is formed by the combustion of fossil fuels in the furnace vessel.
7. A method according to one of claims 1 to 6 characterised in that organic waste material is charged into the furnace vessel adjacent to the connecting zone.
8. A method according to one of claims 1 to 7 characterised in that during the smelting process gases for positively moving and improving mixing of the molten material are injected through under-bath nozzles or gas-permeable bottom scavenging bricks.
9. A method according to claim 8 characterised in that the gases are injected in the vicinity of the connecting zone.
10. A method according to one of claims 1 to 9 characterised in that after the tapping operation a residual molten material remains in the furnace hearth (sump mode of operation).
11. A method according to one of claims 1 to 10 characterised in that the relationship of the energy introduced by the heating source of the furnace vessel relative to the energy introduced by the burners is between 1:1 and 5:1.
12. A smelting unit for a method according to one of claims 1 to 11 comprising:
a furnace vessel (3) which includes a heating source and a furnace hearth (11), and at least one shaft-like charging material preheater (12) which is arranged laterally on the furnace vessel (3) and the bottom (13) of which is designed to drop away towards the furnace hearth (11) and the interior (8) of which is connected in a region adjoining its bottom (13) to the interior (9) of the furnace vessel (3) through a connecting zone (7) and which is also provided in its upper region with a closable charging opening (17) for charging material, and a gas outlet (18), and in its lower region above its bottom with burners or nozzles (15, 16), characterised in that the bottom (13) of the charging material preheater is designed to drop away at such an angle of inclination (14) that a portion of said bottom is higher than the maximum bath level and said portion forms a support surface for a supporting structure made up of welded-together pieces of charging material, the spatial extent of which supporting structure is controllable by controlling the melting energy supplied to the lower region of the shaft-like charging material preheater.
a furnace vessel (3) which includes a heating source and a furnace hearth (11), and at least one shaft-like charging material preheater (12) which is arranged laterally on the furnace vessel (3) and the bottom (13) of which is designed to drop away towards the furnace hearth (11) and the interior (8) of which is connected in a region adjoining its bottom (13) to the interior (9) of the furnace vessel (3) through a connecting zone (7) and which is also provided in its upper region with a closable charging opening (17) for charging material, and a gas outlet (18), and in its lower region above its bottom with burners or nozzles (15, 16), characterised in that the bottom (13) of the charging material preheater is designed to drop away at such an angle of inclination (14) that a portion of said bottom is higher than the maximum bath level and said portion forms a support surface for a supporting structure made up of welded-together pieces of charging material, the spatial extent of which supporting structure is controllable by controlling the melting energy supplied to the lower region of the shaft-like charging material preheater.
13. A smelting unit according to claim 12 characterised in that the charging material preheater (2) is arranged laterally on the furnace vessel (3) of an electric arc furnace (1).
14. A smelting unit according to claim 13 characterised in that the electrode or electrodes (6) of the electric arc furnace (1) is or are displaced out of the middle of the furnace vessel (3) towards the shaft-like charging material preheater (2).
15. A smelting unit according to one of claims 12 to 14 characterised in that arranged in the bottom of the furnace vessel (3) between the middle of the vessel and the vertical extension of the adjacent shaft wall (23) is at least one nozzle or gas-pervious bottom scavenging brick (24).
16. A smelting unit according to claim 15 characterised in that the nozzle or the scavenging brick (24) is arranged in the vicinity of the vertical extension of the shaft wall (23) which is adjacent to the furnace vessel.
17. A smelting unit according to one of claims 13 to 16 characterised in that the lowest point of the hearth space in the furnace vessel (3) is in the region under the electrode or electrodes (6).
18. A smelting unit according to one of claims 12 to 17 characterised in that the bottom (13) of the charging material preheater (2) is designed to drop away towards the furnace hearth (11) at an inclined angle (14) of greater than 30° and less than 60°.
19. A smelting unit according to one of claims 12 to 18 characterised in that the capacity of the furnace hearth (11) which is related to the weight of the molten material, at maximum bath level, corresponds to 1.5 to 2 times the tapping weight of a bath of molten material.
20. A smelting unit according to one of claims 12 to 19 characterised in that the ratio of the height (h) to the square root of the mean cross-section (q) of the shaft-like charging material preheater (2) is in the range of between 1.2 and 3.
21. A smelting unit according to one of claims 12 to 20 characterised in that the furnace vessel (3) and the shaft-like charging material preheater (2) which is integrated therewith can be tilted about an axis connecting the middle thereof to the middle of the vessel.
22. A smelting unit according to one of claims 12 to 21 characterised in that the cross-section of the interior (8) of the charging material preheater (2) enlarges downwardly.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3839096A DE3839096A1 (en) | 1988-11-18 | 1988-11-18 | METHOD FOR OPERATING A MELTING UNIT AND MELTING UNIT FOR THIS METHOD |
| DEP3839096.5 | 1988-11-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2003155A1 true CA2003155A1 (en) | 1990-05-18 |
Family
ID=6367463
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002003155A Abandoned CA2003155A1 (en) | 1988-11-18 | 1989-11-16 | Method of operating a smelting unit and a smelting unit for that method |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0372269A1 (en) |
| CA (1) | CA2003155A1 (en) |
| DE (1) | DE3839096A1 (en) |
| ZA (1) | ZA897339B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108642237A (en) * | 2018-07-09 | 2018-10-12 | 中冶京诚工程技术有限公司 | A kind of steelmaking equipment |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT395656B (en) * | 1990-11-19 | 1993-02-25 | Voest Alpine Ind Anlagen | SYSTEM FOR THE PRODUCTION OF LIQUID METALS |
| DE4138118A1 (en) * | 1991-11-19 | 1993-05-27 | Fuchs Systemtechnik Gmbh | Melting-down and refining unit for steel - consists of two adjacent furnaces with lid mechanisms operated simultaneously, for melting down and refining-overheating the melt |
| DE19634348A1 (en) * | 1996-08-23 | 1998-02-26 | Arcmet Tech Gmbh | Melting unit with an electric arc furnace |
| DE19827299C1 (en) * | 1998-06-19 | 2000-03-09 | Schloemann Siemag Ag | Method and device for producing steel in a furnace vessel |
| AU2008299386B2 (en) | 2007-09-14 | 2012-01-12 | Barrick Gold Corporation | Process for recovering platinum group metals using reductants |
Family Cites Families (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB895534A (en) * | 1960-02-06 | 1962-05-02 | Meredith Woodridge Thring | Improvements in electric-arc steel furnaces |
| FR1602675A (en) * | 1968-07-31 | 1971-01-11 | ||
| JPS5141044Y2 (en) * | 1971-08-21 | 1976-10-06 | ||
| AT323778B (en) * | 1972-07-03 | 1975-07-25 | Maerz Ofenbau | METHODS AND FURNACE FOR MELTING STEEL SCRAP |
| DD142491A3 (en) * | 1977-06-29 | 1980-07-02 | Konrad Primke | PLASMA FURNACE |
| DE2735808C2 (en) * | 1977-08-09 | 1984-11-29 | Norddeutsche Affinerie, 2000 Hamburg | Apparatus for smelting and refining contaminated copper |
| US4243209A (en) * | 1979-10-25 | 1981-01-06 | Southwire Company | Multiple level refractory hearth for vertical shaft metal melting furnaces |
| DE3322485A1 (en) * | 1982-06-24 | 1983-12-29 | British Steel Corp., London | Apparatus and process for metal processing or refining |
| DE8412739U1 (en) * | 1984-04-25 | 1986-01-23 | Fuchs Systemtechnik GmbH, 7601 Willstätt | Arc furnace with charge preheater |
| DE3421485A1 (en) * | 1984-06-08 | 1985-12-12 | Fuchs Systemtechnik GmbH, 7601 Willstätt | ARC FURNACE WITH A RECEIVING ROOM FOR CHARGED GOODS ON ONE SIDE OF THE FURNACE |
| ATE37947T1 (en) * | 1984-06-08 | 1988-10-15 | Fuchs Systemtechnik Gmbh | ARC FURNACE WITH A LOADING SPACE PROVIDED ON ONE SIDE OF THE FURNACE BODY. |
| DE3608802C2 (en) * | 1986-03-15 | 1994-10-06 | Mannesmann Ag | Method and device for the continuous melting of scrap |
| AT384669B (en) * | 1986-03-17 | 1987-12-28 | Voest Alpine Ag | PLANT FOR PRODUCING STEEL FROM SCRAP |
-
1988
- 1988-11-18 DE DE3839096A patent/DE3839096A1/en not_active Withdrawn
-
1989
- 1989-09-27 ZA ZA897339A patent/ZA897339B/en unknown
- 1989-11-15 EP EP89121149A patent/EP0372269A1/en not_active Withdrawn
- 1989-11-16 CA CA002003155A patent/CA2003155A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108642237A (en) * | 2018-07-09 | 2018-10-12 | 中冶京诚工程技术有限公司 | A kind of steelmaking equipment |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0372269A1 (en) | 1990-06-13 |
| ZA897339B (en) | 1990-07-25 |
| DE3839096A1 (en) | 1990-05-23 |
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