CA2525559C - Method for recovering metallic elements, especially metallic chromium, from slag containing metal oxides in an electric-arc furnace - Google Patents
Method for recovering metallic elements, especially metallic chromium, from slag containing metal oxides in an electric-arc furnace Download PDFInfo
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- CA2525559C CA2525559C CA 2525559 CA2525559A CA2525559C CA 2525559 C CA2525559 C CA 2525559C CA 2525559 CA2525559 CA 2525559 CA 2525559 A CA2525559 A CA 2525559A CA 2525559 C CA2525559 C CA 2525559C
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B34/00—Obtaining refractory metals
- C22B34/30—Obtaining chromium, molybdenum or tungsten
- C22B34/32—Obtaining chromium
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- 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
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- 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
- C21C5/5264—Manufacture of alloyed steels including ferro-alloys
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- 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
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- 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
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0087—Treatment of slags covering the steel bath, e.g. for separating slag from the molten metal
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B5/00—General methods of reducing to metals
- C22B5/02—Dry methods smelting of sulfides or formation of mattes
- C22B5/10—Dry methods smelting of sulfides or formation of mattes by solid carbonaceous reducing agents
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
- C22B7/04—Working-up slag
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- 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
- C21C2005/5276—Charging of the electric furnace with liquid or solid rest, e.g. pool, "sumpf"
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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Abstract
The invention relates to a method for recovering metallic elements, especially metallic chromium, from slag containing oxides, especially chromium oxides, in an electric-arc furnace. According to said method, the slag is not reduced in a separate step after melting, but the following steps are carried out: a charge is introduced into the electric-arc furnace, and melted, forming a molten metal and slag; said molten metal is tapped off, leaving the unreduced slag in the furnace vessel; a further charge of scrap metal including reducing agents for the slag is added; the slag is reduced during the melting of said charge; and the slag and the molten metal are then tapped off. The inventive method can also be used in ladle metallurgy or converter metallurgy.
Description
METHOD FOR RECOVERING METALLIC ELEMENTS, ESPECIALLY
METALLIC CHROMIUM, FROM SLAG CONTAINING METAL
OXIDES IN AN ELECTRIC-ARC FURNACE
The invention concerns a method for recovering metallic elements, especially metallic chromium, from slags that contain oxides, especially chromium oxides, in an electric arc furnace, a converter, and in ladle metallurgy.
During the melting down of metal scrap in arc furnaces, oxidation processes occur in which the metallic elements of the melt react to oxides. In the case of high-grade steels, such as chromium steels and chromium-nickel steels, it is mainly the expensive chromium which is oxidized. Parallel to this process, the oxides are also reduced again. In the case of high-chromium steels, especially chromium oxide reduction with carbon constitutes a fundamental mechanism. In this regard, the primary oxidation of the chromium is compensated by a parallel reduction with the carbon dissolved in the melt. This reaction takes place at the bubble surface and at the metal/slag phase boundary. The product of the reactions, metallic chromium, is returned to the melt. The carbon monoxide that forms is carried off into the furnace atmosphere after diffusion in bubbles at the surface.
The following reactions occur:
METALLIC CHROMIUM, FROM SLAG CONTAINING METAL
OXIDES IN AN ELECTRIC-ARC FURNACE
The invention concerns a method for recovering metallic elements, especially metallic chromium, from slags that contain oxides, especially chromium oxides, in an electric arc furnace, a converter, and in ladle metallurgy.
During the melting down of metal scrap in arc furnaces, oxidation processes occur in which the metallic elements of the melt react to oxides. In the case of high-grade steels, such as chromium steels and chromium-nickel steels, it is mainly the expensive chromium which is oxidized. Parallel to this process, the oxides are also reduced again. In the case of high-chromium steels, especially chromium oxide reduction with carbon constitutes a fundamental mechanism. In this regard, the primary oxidation of the chromium is compensated by a parallel reduction with the carbon dissolved in the melt. This reaction takes place at the bubble surface and at the metal/slag phase boundary. The product of the reactions, metallic chromium, is returned to the melt. The carbon monoxide that forms is carried off into the furnace atmosphere after diffusion in bubbles at the surface.
The following reactions occur:
{02} = 2 [0] dissociation (1) [C] + [0] = {CO} direct decarbonization (2) 2 [Cr] + 3 [0] = (Cr70;3) chromium oxidation (3) These reactions occur under the following thermodynamic equilibrium:
K(T)= Q'CrP(;,,() (4) aca('r203 where togK(T)_- 40536 T + 25.63 +p (5) in which p is a parameter.
Due to the incompleteness of the chromium reduction with the carbon, portions of the chromium oxide in the form of various spinels enter the slag. Depending on the type of process management, the chromium oxide content of the slag varies and is more or less above 5%. The economy of the process is based on reducing the chromium oxides and recovering the metallic chromium.
This is usually accomplished by carrying out a separate reduction of the slag with high-affinity silicon in the form of FeSi at the end of the meltdown process.
K(T)= Q'CrP(;,,() (4) aca('r203 where togK(T)_- 40536 T + 25.63 +p (5) in which p is a parameter.
Due to the incompleteness of the chromium reduction with the carbon, portions of the chromium oxide in the form of various spinels enter the slag. Depending on the type of process management, the chromium oxide content of the slag varies and is more or less above 5%. The economy of the process is based on reducing the chromium oxides and recovering the metallic chromium.
This is usually accomplished by carrying out a separate reduction of the slag with high-affinity silicon in the form of FeSi at the end of the meltdown process.
4 Al describes a solution to the problem of making the process of recovering metallic chromium from slags that contain chromium oxide more economical in converter processes or vacuum processes. It is proposed that the conventional treatment step of slag reduction be omitted. Slag that is present, for example, after an oxygen-blowing operation in a converter or in a ladle is removed unreduced from the metal melt and charged to an upstream arc furnace. With the addition of carbon and with silicon from the scrap charged to the arc furnace, possibly with residual dusts, the chromium oxide in the slag is then directly reduced to metallic chromium during the meltdown process.
WO 02/33130 Al describes a process in which metallic chromium is recovered in a metallurgical vessel in which both a melting process and a blowing process are carried out, especially by the conarc process. In this process, slag that forms after the first blowing process remains unreduced in the vessel. The slag, together with the next charge, is heated in the same vessel, reduced, and then tapped. The next blowing process then takes place, and the slag which now forms is again left in the vessel.
Proceeding from this prior art, the objective of the invention is to make available an economical process for the reduction of oxides, especially chromium oxides, in the slag that forms in electric arc furnaces after the meltdown process.
This objective is achieved by the methods in accordance with the present invention.
In a first aspect, the present invention resides in a method for recovering metallic elements from a slag that contains oxides in an electric arc furnace by an electric arc furnace process comprising the sequence of the following steps: (a) introduction of a first charge into the arc furnace; (b) meltdown of the first charge by the electric arc furnace process to produce a metal melt and an unreduced slag, no reduction taking place after the meltdown of the first charge; (c) a partial tapping of the melt received during the electric arc furnace process while leaving metal bottoms and the unreduced slag in the furnace vessel of the electric arc furnace; (d) introduction of a second charge into the electric arc furnace and onto the metal bottoms and the unreduced slag, which charge contains scrap and reducing agents for the slag; (e) meltdown of the second charge by the electric arc furnace process and direct reduction of the slag during the electric arc furnace process by the reducing agents in the second charge during the melting process; and (g) tapping of the received melt and the reduced slag.
In a further aspect, the recovering metallic elements comprise metallic chromium and wherein the slag contain chromium oxides and wherein the reducing agents for the slag contain at least one of carbon, silicon and aluminum.
In yet a further aspect, the method in accordance with the present invention provides method melting down of a buildup melt at the beginning of a melting campaign in steps (a) and (b);
partial tapping of the buildup melt in step (c) while leaving metal bottoms in the furnace vessel of the electric arc furnace;
charging of the second charge onto the remaining metal bottoms and the slag in step (d); after the meltdown of the charge and the reduction of the slag in step (e), in step (g) tapping of the slag and tapping of less than all of the metal melt; and repetition of the steps of charging, melting and slag reduction for each melt of the campaign or termination of the campaign by total tapping of a separation melt together with the metal bottoms.
In a second aspect, the present invention resides in a method for recovering metallic elements from a slag that contain oxides in a ladle or a converter comprising the sequence of the following steps: (a) introduction of a first metal melt with slag into a ladle or a converter; (b) after the treatment of the melt by a ladle metallurgy process or a converter metallurgy process, tapping of the first melt while leaving metal bottoms and the unreduced slag in the ladle or converter, whereby no reduction takes place in the first metal melt; (c) introduction of a second melt together with reducing agents for the unreduced slag into the ladle or converter and onto the metal bottoms and the slag; (d) thorough mixing of the melt with the unreduced slag, resulting in an initial direct reduction of the slag by the reducing agents; and (g) after reduction of the slag tapping the melt and the reduced slag.
4a In accordance with the second aspect, the present invention provides partial tapping of less then all of the metal melt in step (b) while leaving metal bottoms in the ladle; charging of a second melt onto the remaining-metal bottoms and the slag according to step (c); partial tapping of the metal melt in step (g) after reduction of the slag;
repetition of the steps of charging and of slag reduction for each melt of a campaign or termination of a campaign by total tapping of a separation melt together with the metal bottoms.
The basic idea of the invention is to dispense with the --previously customary -- slag reduction after the melting operation to obtain the first melt. The treatment step of slag reduction is not carried out until after the second melting of a second charge or additional charges.
In detail, the following process steps are carried out: A
scrap charge is introduced into the arc furnace and melted down to produce a metal melt and slag. The conventional slag reduction step is then omitted. The melt is tapped, and the slag, which has a high chromium oxide content and is saturated with manganese-iron oxide, remains unreduced in the furnace vessel.
The next charge is then charged onto this slag. This charge consists of scrap and reducing agents for the slag, especially carbon and/or silicon. It is advisable to add the 4b carbon and/or silicon in the form of carbon-rich and silicon-rich alloying materials. Carbon and silicon are contained, for example, in charge chromium, ferrochromium, or ferronickel.
They are sufficient for most of the reduction. In certain cases, aluminum or additional carbon and/or silicon additives, such as FeSi, may be added. Reducing agents can also be contained in residual dusts that are charged to the furnace.
During the melting process produced by electric power, the slag is directly reduced with the aid of these reducing agents.
Direct reduction of the chromium oxide with carbon and/or silicon takes place in the arc furnace under atmospheric pressure. The metal oxidation that occurs during the melting process is (over)compensated by reduction reactions, and the metallic chromium is recovered. The slag is then removed. An analogous process takes place in ladle metallurgy, in which the metal is already present as a melt.
The process in the electric arc furnace is considerably improved by carrying out the method with the use of residual metal bottoms. The reduction quality of the slag is considerably improved by metal bottoms. In this case, the first melt is not completely tapped but rather is only partially tapped to leave metal bottoms in the melting vessel. This has the advantage that the slag floating on these metal bottoms remains in the furnace and thus cannot become stuck to or caked on the bottom of the furnace. In this advantageous modification of the method of the invention, a melting campaign comprises a buildup melt phase, a separation melt phase, and a repeating phase of meltdown and reduction that occurs between the buildup and separation phases. In contrast to the previously known method in the conarc process, which comprises melting down and blowing with oxygen to produce steel, the present method pertains to the recovery of chromium during meltdown in an arc furnace, and in this method, the process is comparatively simpler and shorter. The chromium concentrations are also not comparable; the chromium concentrations of the slag during meltdown are lower, e.g., on the order of 14-150.
The proposed method is used especially with high-grade steels that contain chromium or chromium-nickel. Depending on the overall technology, i.e., a high-grade steel technology without a separate reduction treatment of the slag in an electric arc furnace, this process can be optimized with respect to costs and power consumption. It is unimportant for the method whether the slag is in a solid, liquid, or intermediate state. This has an effect only on the meltdown time and the power consumption in the arc furnace.
The thorough mixing necessary for the reduction during the melting process is preferably produced by inert gases, which are introduced through bottom nozzles and/or side nozzles in the arc furnace and/or through a top lance. The reaction surface between the slag and the metal is increased in this way.
All together, the proposed method has the following advantages:
= shortening of the total treatment time of the melt by up to 15 minutes, depending on the type of technology by elimination of the conventional separate reduction step;
= reduction of FeSi consumption;
= reduction of the consumption of fluxes;
= high metal melt output;
= increased service life of the refractory material of the furnace;
= increased service life of the porous plugs/nozzles;
= improved energy balance of the electric arc furnace; and = improved degree of purity of the metal The individual steps of the method are described in detail below with reference to the sole figure in the form of a process flowchart, which shows the working of the metal in the EAF or electric arc furnace process.
In a first step, a buildup melt without bottom product is produced by melting a scrap charge to form a metal melt and a slag. The melt is tapped, but only partially, so that metal bottoms with slag floating on top remains in the furnace vessel.
The slag is unreduced.
In the melting and reduction phase that follows, scrap is charged onto these metal bottoms with slag. In addition, reducing agents for the slag, such as carbon and silicon, are added. During the meltdown process, the slag is reduced. The following reduction reactions with carbon and silicon take place:
(CR>O.3) + 3[C1 = 2[Cr] + 3 {CO}
2 (Cr2O3) + 3 [Si] = 4[Cr] + 3 (SiO2) These reactions lower the chromium oxide concentration of the slag to values below the initial value.
The now reduced slag is tapped. In the further course of the process, the melt is tapped, but again only partially, to leave metal bottoms at the bottom of the furnace vessel.
Further material is then charged onto these metal bottoms. The slag that forms during the meltdown process is directly reduced again. These steps are repeated for each melt of a campaign.
When the campaign has been completed, instead of a partial tapping of the melt, the melt is totally tapped, together with the metal bottoms.
The method can be carried out in an electric arc furnace or other types of melting furnaces as well as in ladle metallurgy or converter metallurgy or other metallurgical vessels.
WO 02/33130 Al describes a process in which metallic chromium is recovered in a metallurgical vessel in which both a melting process and a blowing process are carried out, especially by the conarc process. In this process, slag that forms after the first blowing process remains unreduced in the vessel. The slag, together with the next charge, is heated in the same vessel, reduced, and then tapped. The next blowing process then takes place, and the slag which now forms is again left in the vessel.
Proceeding from this prior art, the objective of the invention is to make available an economical process for the reduction of oxides, especially chromium oxides, in the slag that forms in electric arc furnaces after the meltdown process.
This objective is achieved by the methods in accordance with the present invention.
In a first aspect, the present invention resides in a method for recovering metallic elements from a slag that contains oxides in an electric arc furnace by an electric arc furnace process comprising the sequence of the following steps: (a) introduction of a first charge into the arc furnace; (b) meltdown of the first charge by the electric arc furnace process to produce a metal melt and an unreduced slag, no reduction taking place after the meltdown of the first charge; (c) a partial tapping of the melt received during the electric arc furnace process while leaving metal bottoms and the unreduced slag in the furnace vessel of the electric arc furnace; (d) introduction of a second charge into the electric arc furnace and onto the metal bottoms and the unreduced slag, which charge contains scrap and reducing agents for the slag; (e) meltdown of the second charge by the electric arc furnace process and direct reduction of the slag during the electric arc furnace process by the reducing agents in the second charge during the melting process; and (g) tapping of the received melt and the reduced slag.
In a further aspect, the recovering metallic elements comprise metallic chromium and wherein the slag contain chromium oxides and wherein the reducing agents for the slag contain at least one of carbon, silicon and aluminum.
In yet a further aspect, the method in accordance with the present invention provides method melting down of a buildup melt at the beginning of a melting campaign in steps (a) and (b);
partial tapping of the buildup melt in step (c) while leaving metal bottoms in the furnace vessel of the electric arc furnace;
charging of the second charge onto the remaining metal bottoms and the slag in step (d); after the meltdown of the charge and the reduction of the slag in step (e), in step (g) tapping of the slag and tapping of less than all of the metal melt; and repetition of the steps of charging, melting and slag reduction for each melt of the campaign or termination of the campaign by total tapping of a separation melt together with the metal bottoms.
In a second aspect, the present invention resides in a method for recovering metallic elements from a slag that contain oxides in a ladle or a converter comprising the sequence of the following steps: (a) introduction of a first metal melt with slag into a ladle or a converter; (b) after the treatment of the melt by a ladle metallurgy process or a converter metallurgy process, tapping of the first melt while leaving metal bottoms and the unreduced slag in the ladle or converter, whereby no reduction takes place in the first metal melt; (c) introduction of a second melt together with reducing agents for the unreduced slag into the ladle or converter and onto the metal bottoms and the slag; (d) thorough mixing of the melt with the unreduced slag, resulting in an initial direct reduction of the slag by the reducing agents; and (g) after reduction of the slag tapping the melt and the reduced slag.
4a In accordance with the second aspect, the present invention provides partial tapping of less then all of the metal melt in step (b) while leaving metal bottoms in the ladle; charging of a second melt onto the remaining-metal bottoms and the slag according to step (c); partial tapping of the metal melt in step (g) after reduction of the slag;
repetition of the steps of charging and of slag reduction for each melt of a campaign or termination of a campaign by total tapping of a separation melt together with the metal bottoms.
The basic idea of the invention is to dispense with the --previously customary -- slag reduction after the melting operation to obtain the first melt. The treatment step of slag reduction is not carried out until after the second melting of a second charge or additional charges.
In detail, the following process steps are carried out: A
scrap charge is introduced into the arc furnace and melted down to produce a metal melt and slag. The conventional slag reduction step is then omitted. The melt is tapped, and the slag, which has a high chromium oxide content and is saturated with manganese-iron oxide, remains unreduced in the furnace vessel.
The next charge is then charged onto this slag. This charge consists of scrap and reducing agents for the slag, especially carbon and/or silicon. It is advisable to add the 4b carbon and/or silicon in the form of carbon-rich and silicon-rich alloying materials. Carbon and silicon are contained, for example, in charge chromium, ferrochromium, or ferronickel.
They are sufficient for most of the reduction. In certain cases, aluminum or additional carbon and/or silicon additives, such as FeSi, may be added. Reducing agents can also be contained in residual dusts that are charged to the furnace.
During the melting process produced by electric power, the slag is directly reduced with the aid of these reducing agents.
Direct reduction of the chromium oxide with carbon and/or silicon takes place in the arc furnace under atmospheric pressure. The metal oxidation that occurs during the melting process is (over)compensated by reduction reactions, and the metallic chromium is recovered. The slag is then removed. An analogous process takes place in ladle metallurgy, in which the metal is already present as a melt.
The process in the electric arc furnace is considerably improved by carrying out the method with the use of residual metal bottoms. The reduction quality of the slag is considerably improved by metal bottoms. In this case, the first melt is not completely tapped but rather is only partially tapped to leave metal bottoms in the melting vessel. This has the advantage that the slag floating on these metal bottoms remains in the furnace and thus cannot become stuck to or caked on the bottom of the furnace. In this advantageous modification of the method of the invention, a melting campaign comprises a buildup melt phase, a separation melt phase, and a repeating phase of meltdown and reduction that occurs between the buildup and separation phases. In contrast to the previously known method in the conarc process, which comprises melting down and blowing with oxygen to produce steel, the present method pertains to the recovery of chromium during meltdown in an arc furnace, and in this method, the process is comparatively simpler and shorter. The chromium concentrations are also not comparable; the chromium concentrations of the slag during meltdown are lower, e.g., on the order of 14-150.
The proposed method is used especially with high-grade steels that contain chromium or chromium-nickel. Depending on the overall technology, i.e., a high-grade steel technology without a separate reduction treatment of the slag in an electric arc furnace, this process can be optimized with respect to costs and power consumption. It is unimportant for the method whether the slag is in a solid, liquid, or intermediate state. This has an effect only on the meltdown time and the power consumption in the arc furnace.
The thorough mixing necessary for the reduction during the melting process is preferably produced by inert gases, which are introduced through bottom nozzles and/or side nozzles in the arc furnace and/or through a top lance. The reaction surface between the slag and the metal is increased in this way.
All together, the proposed method has the following advantages:
= shortening of the total treatment time of the melt by up to 15 minutes, depending on the type of technology by elimination of the conventional separate reduction step;
= reduction of FeSi consumption;
= reduction of the consumption of fluxes;
= high metal melt output;
= increased service life of the refractory material of the furnace;
= increased service life of the porous plugs/nozzles;
= improved energy balance of the electric arc furnace; and = improved degree of purity of the metal The individual steps of the method are described in detail below with reference to the sole figure in the form of a process flowchart, which shows the working of the metal in the EAF or electric arc furnace process.
In a first step, a buildup melt without bottom product is produced by melting a scrap charge to form a metal melt and a slag. The melt is tapped, but only partially, so that metal bottoms with slag floating on top remains in the furnace vessel.
The slag is unreduced.
In the melting and reduction phase that follows, scrap is charged onto these metal bottoms with slag. In addition, reducing agents for the slag, such as carbon and silicon, are added. During the meltdown process, the slag is reduced. The following reduction reactions with carbon and silicon take place:
(CR>O.3) + 3[C1 = 2[Cr] + 3 {CO}
2 (Cr2O3) + 3 [Si] = 4[Cr] + 3 (SiO2) These reactions lower the chromium oxide concentration of the slag to values below the initial value.
The now reduced slag is tapped. In the further course of the process, the melt is tapped, but again only partially, to leave metal bottoms at the bottom of the furnace vessel.
Further material is then charged onto these metal bottoms. The slag that forms during the meltdown process is directly reduced again. These steps are repeated for each melt of a campaign.
When the campaign has been completed, instead of a partial tapping of the melt, the melt is totally tapped, together with the metal bottoms.
The method can be carried out in an electric arc furnace or other types of melting furnaces as well as in ladle metallurgy or converter metallurgy or other metallurgical vessels.
Claims (8)
1. Method for recovering metallic elements from a slag that contains oxides in an electric arc furnace by an electric arc furnace process comprising the sequence of the following steps:
(a) introduction of a first charge into the electric arc furnace;
(b) meltdown of the first charge by the electric arc furnace process to produce a metal melt and an unreduced slag, no reduction taking place after the meltdown of the first charge;
(c) a partial tapping of the melt received during the electric arc furnace process while leaving metal bottoms and the unreduced slag in the furnace vessel of the electric arc furnace;
(d) introduction of a second charge into the electric arc furnace and onto the metal bottoms and the unreduced slag, which charge contains scrap and reducing agents for the slag;
(e) meltdown of the second charge by the electric arc furnace process and direct reduction of the slag during the electric arc furnace process by the reducing agents in the second charge during the melting process; and (g) tapping of the received melt and the reduced slag.
(a) introduction of a first charge into the electric arc furnace;
(b) meltdown of the first charge by the electric arc furnace process to produce a metal melt and an unreduced slag, no reduction taking place after the meltdown of the first charge;
(c) a partial tapping of the melt received during the electric arc furnace process while leaving metal bottoms and the unreduced slag in the furnace vessel of the electric arc furnace;
(d) introduction of a second charge into the electric arc furnace and onto the metal bottoms and the unreduced slag, which charge contains scrap and reducing agents for the slag;
(e) meltdown of the second charge by the electric arc furnace process and direct reduction of the slag during the electric arc furnace process by the reducing agents in the second charge during the melting process; and (g) tapping of the received melt and the reduced slag.
2. The method in accordance with Claim 1, wherein the reducing agents are charged in the form of alloying materials with a high carbon and silicon content.
3. The method in accordance with Claim 1, wherein residual dusts are charged as reducing agents for the slag.
4. The method in accordance with Claim 1, wherein thorough mixing is carried out by means of inert gases, which are introduced through at least one of bottom nozzles in the arc furnace, side nozzles in the arc furnace and through a top lance.
5. Method for recovering metallic elements from a slag that contain oxides in a ladle or a converter comprising the sequence of the following steps:
(a) introduction of a first metal melt with slag into the ladle or the converter;
(b) after the treatment of the melt by a ladle metallurgy process or a converter metallurgy process, tapping of the first melt while leaving metal bottoms and the unreduced slag in the ladle or converter, whereby no reduction takes place in the first metal melt;
(c) introduction of a second melt together with reducing agents for the unreduced slag into the ladle or converter and onto the metal bottoms and the slag;
(d) thorough mixing of the melt with the unreduced slag, resulting in an initial direct reduction of the slag by the reducing agents; and (g) after reduction of the slag tapping the melt and the reduced slag.
(a) introduction of a first metal melt with slag into the ladle or the converter;
(b) after the treatment of the melt by a ladle metallurgy process or a converter metallurgy process, tapping of the first melt while leaving metal bottoms and the unreduced slag in the ladle or converter, whereby no reduction takes place in the first metal melt;
(c) introduction of a second melt together with reducing agents for the unreduced slag into the ladle or converter and onto the metal bottoms and the slag;
(d) thorough mixing of the melt with the unreduced slag, resulting in an initial direct reduction of the slag by the reducing agents; and (g) after reduction of the slag tapping the melt and the reduced slag.
6. The method in accordance with claim 1, wherein the recovering metallic elements comprise metallic chromium and wherein the slag contain chromium oxides and wherein the reducing agents for the slag contain at least one of carbon, silicon and aluminum.
7. The method in accordance with claim 1, comprising melting down of a buildup melt at the beginning of a melting campaign in steps (a) and (b); partial tapping of the buildup melt in step (c) while leaving metal bottoms in the furnace vessel of the electric arc furnace; charging of the second charge onto the remaining metal bottoms and the slag in step (d); after the meltdown of the charge and the reduction of the slag in step (e), in step (g) tapping of the slag and tapping of less than all of the metal melt; and repetition of the steps of charging, melting and slag reduction for each melt of the campaign or termination of the campaign by total tapping of a separation melt together with the metal bottoms.
8. The method in accordance with claim 5, comprising partial tapping of less then all of the metal melt in step (b) while leaving metal bottoms in the ladle; charging of a second melt onto the remaining metal bottoms and the slag according to step (c); partial tapping of the metal melt in step (g) after reduction of the slag; repetition of the steps of charging and of slag reduction for each melt of a campaign or termination of a campaign by total tapping of a separation melt together with the metal bottoms.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2003123507 DE10323507A1 (en) | 2003-05-24 | 2003-05-24 | Process for the recovery of metallic elements, in particular metallic chromium, from slags containing metal oxide in an electric arc furnace |
| DE10323507.8 | 2003-05-24 | ||
| PCT/EP2004/004313 WO2004104233A1 (en) | 2003-05-24 | 2004-04-23 | Method for recovering metallic elements, especially metallic chromium, from slag containing metal oxides in an electric-arc furnace |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2525559A1 CA2525559A1 (en) | 2004-12-02 |
| CA2525559C true CA2525559C (en) | 2011-07-26 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2525559 Expired - Fee Related CA2525559C (en) | 2003-05-24 | 2004-04-23 | Method for recovering metallic elements, especially metallic chromium, from slag containing metal oxides in an electric-arc furnace |
Country Status (13)
| Country | Link |
|---|---|
| US (1) | US20060196308A1 (en) |
| EP (1) | EP1627085B1 (en) |
| JP (1) | JP4912880B2 (en) |
| KR (1) | KR20060012288A (en) |
| CN (1) | CN100350057C (en) |
| CA (1) | CA2525559C (en) |
| DE (2) | DE10323507A1 (en) |
| ES (1) | ES2277253T3 (en) |
| RU (1) | RU2352672C2 (en) |
| TW (1) | TW200502404A (en) |
| UA (1) | UA82239C2 (en) |
| WO (1) | WO2004104233A1 (en) |
| ZA (1) | ZA200508277B (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102006052181A1 (en) * | 2006-11-02 | 2008-05-08 | Sms Demag Ag | A process for the continuous or discontinuous recovery of a metal or metals from a slag containing the metal or compound of the metal |
| EP2053137A1 (en) * | 2007-10-19 | 2009-04-29 | Paul Wurth S.A. | Recovery of waste containing copper and other valuable metals |
| JP5326475B2 (en) * | 2008-10-07 | 2013-10-30 | 新日鐵住金株式会社 | Method for recovering chromium from chromium-containing slag |
| JP5455193B2 (en) * | 2009-04-30 | 2014-03-26 | 日新製鋼株式会社 | Stainless steel manufacturing method |
| WO2011045755A1 (en) * | 2009-10-13 | 2011-04-21 | Petrus Hendrik Ferreira Bouwer | Ferrochrome alloy production |
| JP2013124417A (en) * | 2011-12-16 | 2013-06-24 | Nippon Steel & Sumitomo Metal Corp | METHOD FOR TREATING Cr-CONTAINING SLAG |
| CN102864311B (en) * | 2012-09-21 | 2014-11-26 | 承德建龙特殊钢有限公司 | Recovery method of chromium in high chromium-content slag in steel making-LF (ladle furnace) working procedure |
| CN104087709B (en) * | 2014-07-18 | 2016-08-24 | 承德建龙特殊钢有限公司 | A kind of method of melting and reducing height chromium slag in induction furnace |
| CN104087704B (en) * | 2014-07-18 | 2016-08-24 | 承德建龙特殊钢有限公司 | A kind of method that melting and reducing vanadium extraction waste carries out pneumatic steelmaking |
| CN104789736B (en) * | 2015-05-18 | 2017-01-11 | 安徽富凯特材有限公司 | Method for reducing chromium element in electric arc furnace slag |
| CN105670667B (en) * | 2016-01-19 | 2019-05-07 | 青岛理工大学 | Method for synchronously treating chromium slag and chlorine-free plastic |
| WO2024127339A1 (en) | 2022-12-16 | 2024-06-20 | Danieli & C. Officine Meccaniche S.P.A. | Process and plant for slag treatment |
Family Cites Families (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT381583B (en) * | 1984-06-01 | 1986-11-10 | Voest Alpine Ag | TILTABLE METALLURGICAL TUBE |
| DE3444962A1 (en) * | 1984-12-10 | 1986-06-12 | Klöckner-Humboldt-Deutz AG, 5000 Köln | METHOD AND DEVICE FOR THE REDUCING TREATMENT OF MELT-LIQUID METALS AND / OR THEIR SLAGS |
| JPH0196322A (en) * | 1987-10-08 | 1989-04-14 | Nkk Corp | Ladle refining method |
| DE4108687A1 (en) * | 1991-03-16 | 1992-11-05 | Metallgesellschaft Ag | METHOD FOR REDUCING NE-METAL OXIDES IN SLAGS |
| JPH06200311A (en) * | 1993-01-05 | 1994-07-19 | Nkk Corp | Method for dephosphorizing molten iron |
| ZA963234B (en) * | 1995-05-02 | 1996-07-29 | Holderbank Financ Glarus | Process for the production of hydraulic binders and/or alloys such as e g ferrochromium of ferrovanadium |
| JPH09157724A (en) * | 1995-12-01 | 1997-06-17 | Nippon Steel Corp | Production of stainless steel using scrap |
| DE19643459A1 (en) * | 1996-10-10 | 1998-04-16 | Mannesmann Ag | Process for depleting high-melting materials |
| DE19728102C2 (en) * | 1997-07-02 | 1999-08-05 | Schloemann Siemag Ag | Method and device for the production of steels with high Cr content and / or ferro alloys |
| NO308418B1 (en) * | 1998-12-09 | 2000-09-11 | Elkem Materials | Process for the production of stainless steel |
| AT407644B (en) * | 1999-06-08 | 2001-05-25 | Voest Alpine Ind Anlagen | METHOD FOR SLAG CONDITIONING AND APPARATUS THEREFOR |
| US6679931B1 (en) * | 1999-06-23 | 2004-01-20 | Sms Demag Ag | Method for recovering metallic chromium from slag containing chromium oxide |
| JP4189112B2 (en) * | 2000-02-24 | 2008-12-03 | 新日本製鐵株式会社 | Processing method for slag refining stainless steel |
| KR100819126B1 (en) * | 2000-10-18 | 2008-04-02 | 에스엠에스 데마그 악티엔게젤샤프트 | Method for producing stainless steels, in particular high-grade steels containing chromium and chromium-nickel |
| JP2002256323A (en) * | 2001-02-27 | 2002-09-11 | Nippon Steel Corp | Method for reforming roughly decarburized slag in molten stainless steel |
-
2003
- 2003-05-24 DE DE2003123507 patent/DE10323507A1/en not_active Withdrawn
-
2004
- 2004-04-23 ES ES04729097T patent/ES2277253T3/en not_active Expired - Lifetime
- 2004-04-23 UA UAA200512438A patent/UA82239C2/en unknown
- 2004-04-23 RU RU2005140569A patent/RU2352672C2/en not_active IP Right Cessation
- 2004-04-23 CN CNB2004800142153A patent/CN100350057C/en not_active Expired - Fee Related
- 2004-04-23 US US10/556,496 patent/US20060196308A1/en not_active Abandoned
- 2004-04-23 DE DE200450002628 patent/DE502004002628D1/en not_active Expired - Lifetime
- 2004-04-23 JP JP2006529705A patent/JP4912880B2/en not_active Expired - Fee Related
- 2004-04-23 EP EP20040729097 patent/EP1627085B1/en not_active Expired - Lifetime
- 2004-04-23 KR KR1020057021614A patent/KR20060012288A/en not_active Application Discontinuation
- 2004-04-23 CA CA 2525559 patent/CA2525559C/en not_active Expired - Fee Related
- 2004-04-23 WO PCT/EP2004/004313 patent/WO2004104233A1/en active IP Right Grant
- 2004-04-26 TW TW093111577A patent/TW200502404A/en unknown
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2005
- 2005-10-13 ZA ZA2005/08277A patent/ZA200508277B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| UA82239C2 (en) | 2008-03-25 |
| KR20060012288A (en) | 2006-02-07 |
| ZA200508277B (en) | 2006-12-27 |
| CN1795276A (en) | 2006-06-28 |
| JP4912880B2 (en) | 2012-04-11 |
| DE10323507A1 (en) | 2004-12-09 |
| JP2007502369A (en) | 2007-02-08 |
| CN100350057C (en) | 2007-11-21 |
| ES2277253T3 (en) | 2007-07-01 |
| CA2525559A1 (en) | 2004-12-02 |
| RU2352672C2 (en) | 2009-04-20 |
| RU2005140569A (en) | 2006-05-10 |
| TW200502404A (en) | 2005-01-16 |
| DE502004002628D1 (en) | 2007-02-22 |
| US20060196308A1 (en) | 2006-09-07 |
| WO2004104233A1 (en) | 2004-12-02 |
| EP1627085A1 (en) | 2006-02-22 |
| EP1627085B1 (en) | 2007-01-10 |
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