CA1074567A - Method of continuously melting down scrap, iron sponge or the like - Google Patents
Method of continuously melting down scrap, iron sponge or the likeInfo
- Publication number
- CA1074567A CA1074567A CA245,085A CA245085A CA1074567A CA 1074567 A CA1074567 A CA 1074567A CA 245085 A CA245085 A CA 245085A CA 1074567 A CA1074567 A CA 1074567A
- Authority
- CA
- Canada
- Prior art keywords
- coal
- pieces
- furnace
- zone
- charge material
- 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.)
- Expired
Links
Classifications
-
- 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
- C21C5/56—Manufacture of steel by other methods
- C21C5/562—Manufacture of steel by other methods starting from scrap
-
- 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)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacture And Refinement Of Metals (AREA)
- Vertical, Hearth, Or Arc Furnaces (AREA)
- Processing Of Solid Wastes (AREA)
- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
Abstract
ABSTRACT OF DISCLOSURE
This invention relates to a method of continuously melting down scrap, iron sponge and the like in a vertically arranged shaft furnace in which a flame produced by fuel-oxygen combustion is applied to the bottom of a column of charge material in the furnace to melt such material in an oxidising melting zone, the invention being characterised by the creation of a reducing zone beneath said oxidising melting zone and said reducing zone being provided by admixing slow-reacting large pieces of coal to the charge material so that such pieces of coal will pass through said oxidising melting zone and collect at the bottom of the furnace.
This invention relates to a method of continuously melting down scrap, iron sponge and the like in a vertically arranged shaft furnace in which a flame produced by fuel-oxygen combustion is applied to the bottom of a column of charge material in the furnace to melt such material in an oxidising melting zone, the invention being characterised by the creation of a reducing zone beneath said oxidising melting zone and said reducing zone being provided by admixing slow-reacting large pieces of coal to the charge material so that such pieces of coal will pass through said oxidising melting zone and collect at the bottom of the furnace.
Description
1074S~'7 The present invention relates to a method of continuously rnel-ting down scrap, iron sponge and the like, in a vertically arranged shaft furnace of substantially constant cross section, using a count~r-flow principle in which a flame, produced by fuel-oxygen combustion, is applied to the bottom of a colwnn of charge material in the furnace.
This co~mterflow melting method wi~ll fuel-oxygen burners involves the ris~ of an undesirably high oxidation of the charge. Such oxi~ation may be influenced by various provisi.ons.
10. One possibility resides in ad~ixing coal to the charge, thereby lowering the degree of oxidation and favouring carburisation.
However~ norma].ly this method has the disadvantage that a lar~e proportion of the admixed coal tends to burn up in the combustion gases within the furnace shaft and is correspondingly less effective in the melting-down region of the furnace. The coal which is admixed in this way and burns up in the combustion gases has a-similar action to that involved in melting-down by hypo-stoi.chiometric combustion which is~ howQver, much easier to achieve by appropriate fuel-oxygcn ratios in the burner devices. Moreover~ the pieces of coal which descen~ ~radually with the charge material into the lower region of the shaft furnace are already largely consumed at this point so that in view of their small size they tend to pass out ~ith the continuous molten outflow through the tap hole at the bottom of the furnace.
It has further been suggested to achi.cve recarburisation at the bottolr! of the ~elting~ vessel by blowing in coal, or by inductively heating the bottom of the melting ve3sel~ ei-ther so
This co~mterflow melting method wi~ll fuel-oxygen burners involves the ris~ of an undesirably high oxidation of the charge. Such oxi~ation may be influenced by various provisi.ons.
10. One possibility resides in ad~ixing coal to the charge, thereby lowering the degree of oxidation and favouring carburisation.
However~ norma].ly this method has the disadvantage that a lar~e proportion of the admixed coal tends to burn up in the combustion gases within the furnace shaft and is correspondingly less effective in the melting-down region of the furnace. The coal which is admixed in this way and burns up in the combustion gases has a-similar action to that involved in melting-down by hypo-stoi.chiometric combustion which is~ howQver, much easier to achieve by appropriate fuel-oxygcn ratios in the burner devices. Moreover~ the pieces of coal which descen~ ~radually with the charge material into the lower region of the shaft furnace are already largely consumed at this point so that in view of their small size they tend to pass out ~ith the continuous molten outflow through the tap hole at the bottom of the furnace.
It has further been suggested to achi.cve recarburisation at the bottolr! of the ~elting~ vessel by blowing in coal, or by inductively heating the bottom of the melting ve3sel~ ei-ther so
-2-, I
as to reduce the liquidity point of the molten metal or to raise the temperature of the meltS since generally the temperature of the molten metal is only slightly above the liquidity point.
However, these provisions are complicated and expensive.
It is, therefore, the aim of the present invention to achieve an effective improvement in the recarburisation of the molten metal. ~
According to this invention this aim is achieved by the creation of a reducing zone beneath the oxidising melting zone 10. in the furnace by admixing slow-reacting large pieces of coal to the charge material, said coal pieces being of appropriate dimensions to pass through the said oxidising melting zone and collect at the bottom of the furnace.
For preference the coal pieces used for this purpose weigh between 2kgs. and lO kgs. per plece with a small surface area and a comparatively large diameter, e.g. around 200 mms. A
suitably slow-reacting type of coal is, for example, anthracite.
In addition to this~ the coal pieces may be provided with a reaction-inhibiting coating, for example of milk of lime or a 20. similar substance which protects the coal lumps from combllstion in the oxidising gaseous atmosphere which reigns in the melting down zone of the furnace. The coal lumps are usually added ir the proportion of 2% to 60/o br weight of the charge material.
By using coal lumps of such comparatively small specific surface area and slow combustibility it is possible to cause these ]umps to descend progressively in the shaf~ ~urnacc together ~rith the charg~ materiQl to be l~leltod l~ithout sufferin~ j , ..,.,.... . . j, , 107456'7 any significarlt degrec of combustion. The coal pieces wili then settle at the bottom of the melting vessel in the form of a layer of coal and no individual pieces or lumps will pass out through the outflow in the bottom of the meltlng pot. In this way, a strongly reducing zone is maintained beneath the oxidisin~ melting zone of the furnace wherein the slag which is formed as well as the molten metal triclcling through this zone react optimally with the coal to allow favourable adjustments to be made with regard to the fluxing or slàgging of the iron 10. and its recarburisation. T`he layer of coal is gradually consumed as the carbon is dissolved by the metal trickling therethrough. There is also a corresponding reduction in the FeO content of the slag passing through this layer. Moreover, comparatively small quantities of coal lumps are quite sufficient for this purpose.
One example of a method according to the present invention will now be described with reference to the accompanying drawing which illustrates a shaft furnace 1 with an outflow 3 in the bottom 2 thereof and a column of charge material 4, consisting 20. of scrap metal~ iron sponge or the lllce, within the furnace.
This charge column 4 ls melted down from beneath by means Or burners 5 which extend through the lateral walls of the furnace 1, said walls having a cross sectional configuration which tapers slightly outwardly in the downward directioIl to produce flames in the melting region 7 beneath the charge column 4~ Large, 510w reactin~ lumps of cc,al 8 are added to the charge material and descend contimlous]y with the charge column 4. ~hey pass throllgh the o~idising melting zone in the region of the flames 6 ~074567 and collect at the bottom 2 of the shaft furnace 1. The molten charge material (comprising metal and slag) flows over the coal lumps 8 at the bottom and thereby dissolves the coal. In this way a reducing, recarburising zone is created beneath the oxidis-ing melting zone in the region of the flames 6. Preferably, the aforesaid coal pieces each weigh between 2 kgs. and 10 kgs. per piece, each piece having a small surface area and a comparatively large diameter - e.g. around 200 mms. Conveniently, the coal pieces are added in the proportion of 2% to 6% by weight of the-charge material. Furthermore, the coal pieces may each be pro-vided with a reaction - inhibiting coating (for example milk of lime) which protects the coal from combustion in oxidising melting zone.
The charge column 4 which descends continuously in the course of the melting down process is preferably supported on wall-like accretions which form around the burners 5 as a result of using burners which are each designed in such a way that the oxygen outlet is situated within, or surrounded by, a fuel outlet opening, or, in the case of annular slit burners, within two slit-like fuel outlet openings. Owing to the expansion of the fuel emerging from the burners a comparatively cool region is produced adjacent to the burner outlets with the result that wall-like accretions of molten material will be formed around the burners to provide support for the column of charge material thereabove. Alternatively the charge column may be supported in conventional manner from the bottom 2 of the shaft furnace 1.
1~)74567 Furthermore, if the charge material is compressed into packets or parcels it is possible to add coal, or a carbonaceous material, to these parcels or packets in order to ensure a reducing atmosphere w.ithin such parcels right up to the melting down zone so as to reduce slagging of the charge material duri.ng the melting process.
,
as to reduce the liquidity point of the molten metal or to raise the temperature of the meltS since generally the temperature of the molten metal is only slightly above the liquidity point.
However, these provisions are complicated and expensive.
It is, therefore, the aim of the present invention to achieve an effective improvement in the recarburisation of the molten metal. ~
According to this invention this aim is achieved by the creation of a reducing zone beneath the oxidising melting zone 10. in the furnace by admixing slow-reacting large pieces of coal to the charge material, said coal pieces being of appropriate dimensions to pass through the said oxidising melting zone and collect at the bottom of the furnace.
For preference the coal pieces used for this purpose weigh between 2kgs. and lO kgs. per plece with a small surface area and a comparatively large diameter, e.g. around 200 mms. A
suitably slow-reacting type of coal is, for example, anthracite.
In addition to this~ the coal pieces may be provided with a reaction-inhibiting coating, for example of milk of lime or a 20. similar substance which protects the coal lumps from combllstion in the oxidising gaseous atmosphere which reigns in the melting down zone of the furnace. The coal lumps are usually added ir the proportion of 2% to 60/o br weight of the charge material.
By using coal lumps of such comparatively small specific surface area and slow combustibility it is possible to cause these ]umps to descend progressively in the shaf~ ~urnacc together ~rith the charg~ materiQl to be l~leltod l~ithout sufferin~ j , ..,.,.... . . j, , 107456'7 any significarlt degrec of combustion. The coal pieces wili then settle at the bottom of the melting vessel in the form of a layer of coal and no individual pieces or lumps will pass out through the outflow in the bottom of the meltlng pot. In this way, a strongly reducing zone is maintained beneath the oxidisin~ melting zone of the furnace wherein the slag which is formed as well as the molten metal triclcling through this zone react optimally with the coal to allow favourable adjustments to be made with regard to the fluxing or slàgging of the iron 10. and its recarburisation. T`he layer of coal is gradually consumed as the carbon is dissolved by the metal trickling therethrough. There is also a corresponding reduction in the FeO content of the slag passing through this layer. Moreover, comparatively small quantities of coal lumps are quite sufficient for this purpose.
One example of a method according to the present invention will now be described with reference to the accompanying drawing which illustrates a shaft furnace 1 with an outflow 3 in the bottom 2 thereof and a column of charge material 4, consisting 20. of scrap metal~ iron sponge or the lllce, within the furnace.
This charge column 4 ls melted down from beneath by means Or burners 5 which extend through the lateral walls of the furnace 1, said walls having a cross sectional configuration which tapers slightly outwardly in the downward directioIl to produce flames in the melting region 7 beneath the charge column 4~ Large, 510w reactin~ lumps of cc,al 8 are added to the charge material and descend contimlous]y with the charge column 4. ~hey pass throllgh the o~idising melting zone in the region of the flames 6 ~074567 and collect at the bottom 2 of the shaft furnace 1. The molten charge material (comprising metal and slag) flows over the coal lumps 8 at the bottom and thereby dissolves the coal. In this way a reducing, recarburising zone is created beneath the oxidis-ing melting zone in the region of the flames 6. Preferably, the aforesaid coal pieces each weigh between 2 kgs. and 10 kgs. per piece, each piece having a small surface area and a comparatively large diameter - e.g. around 200 mms. Conveniently, the coal pieces are added in the proportion of 2% to 6% by weight of the-charge material. Furthermore, the coal pieces may each be pro-vided with a reaction - inhibiting coating (for example milk of lime) which protects the coal from combustion in oxidising melting zone.
The charge column 4 which descends continuously in the course of the melting down process is preferably supported on wall-like accretions which form around the burners 5 as a result of using burners which are each designed in such a way that the oxygen outlet is situated within, or surrounded by, a fuel outlet opening, or, in the case of annular slit burners, within two slit-like fuel outlet openings. Owing to the expansion of the fuel emerging from the burners a comparatively cool region is produced adjacent to the burner outlets with the result that wall-like accretions of molten material will be formed around the burners to provide support for the column of charge material thereabove. Alternatively the charge column may be supported in conventional manner from the bottom 2 of the shaft furnace 1.
1~)74567 Furthermore, if the charge material is compressed into packets or parcels it is possible to add coal, or a carbonaceous material, to these parcels or packets in order to ensure a reducing atmosphere w.ithin such parcels right up to the melting down zone so as to reduce slagging of the charge material duri.ng the melting process.
,
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of continuously melting down ferrous scrap or iron sponge in a shaft furnace of substantially constant cross section by use of a counterflow principle in which a flame produced by fuel-oxygen combustion is applied to the bottom of a column of charge material in the furnace to form an oxidizing melting zone beneath said column, characterized in that a reducing zone is created beneath the oxidizing melting zone by admixing slow-reacting pieces of coal to the charge material said coal pieces being of appropriate dimensions to pass through said oxidizing melting zone and collect at the bottom of the shaft furnace.
2. A method according to claim 1, characterized by the use of pieces of coal weighing approximately between 2 kgs and 10 kgs. per piece.
3. A method according to claim 1, characterized by the use of coal pieces which are provided with a reaction inhibiting coating.
4. A method according to claim 3, characterized by the use of coal pieces which are coated with milk of lime.
5. A method according to claim 1, 2 or 3, characterized in that the pieces of coal are added in the proportion of 2% to 6% by weight of the charge material.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19752504889 DE2504889C2 (en) | 1975-02-06 | Process for the continuous melting of scrap, sponge iron or the like |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1074567A true CA1074567A (en) | 1980-04-01 |
Family
ID=5938190
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA245,085A Expired CA1074567A (en) | 1975-02-06 | 1976-02-05 | Method of continuously melting down scrap, iron sponge or the like |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS51105912A (en) |
| BE (1) | BE837840A (en) |
| BR (1) | BR7600732A (en) |
| CA (1) | CA1074567A (en) |
| FR (1) | FR2300133A1 (en) |
| GB (1) | GB1524272A (en) |
| IT (1) | IT1055113B (en) |
| SU (1) | SU683636A3 (en) |
| ZA (1) | ZA76663B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT403586B (en) | 1996-07-24 | 1998-03-25 | Holderbank Financ Glarus | METHOD FOR MELTING OXIDIC SLAGS AND COMBUSTION RESIDES AND DEVICE FOR CARRYING OUT THIS METHOD |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB998213A (en) * | 1963-05-02 | 1965-07-14 | British Oxygen Co Ltd | Improvements in or relating to the operation of cupola furnaces |
| JPS5213490B2 (en) * | 1973-04-25 | 1977-04-14 |
-
1976
- 1976-01-08 GB GB59176A patent/GB1524272A/en not_active Expired
- 1976-01-09 FR FR7600464A patent/FR2300133A1/en active Granted
- 1976-01-23 SU SU762315104A patent/SU683636A3/en active
- 1976-01-23 BE BE163740A patent/BE837840A/en unknown
- 1976-02-05 IT IT1991176A patent/IT1055113B/en active
- 1976-02-05 ZA ZA760663A patent/ZA76663B/en unknown
- 1976-02-05 CA CA245,085A patent/CA1074567A/en not_active Expired
- 1976-02-05 BR BR7600732A patent/BR7600732A/en unknown
- 1976-02-06 JP JP1215976A patent/JPS51105912A/ja active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| AU1084776A (en) | 1977-08-11 |
| GB1524272A (en) | 1978-09-13 |
| DE2504889B1 (en) | 1975-11-20 |
| BE837840A (en) | 1976-05-14 |
| FR2300133A1 (en) | 1976-09-03 |
| FR2300133B1 (en) | 1978-08-18 |
| JPS51105912A (en) | 1976-09-20 |
| IT1055113B (en) | 1981-12-21 |
| SU683636A3 (en) | 1979-08-30 |
| ZA76663B (en) | 1977-02-23 |
| DE2504889A1 (en) | 1975-11-20 |
| BR7600732A (en) | 1976-08-31 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |