EP0360223B1 - Agent and method for desulfurizing molten ferrous metal and a process for the production of this agent - Google Patents

Agent and method for desulfurizing molten ferrous metal and a process for the production of this agent Download PDF

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Publication number
EP0360223B1
EP0360223B1 EP89117308A EP89117308A EP0360223B1 EP 0360223 B1 EP0360223 B1 EP 0360223B1 EP 89117308 A EP89117308 A EP 89117308A EP 89117308 A EP89117308 A EP 89117308A EP 0360223 B1 EP0360223 B1 EP 0360223B1
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Prior art keywords
agent
magnesium
agent according
calcium carbide
weight
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EP89117308A
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German (de)
French (fr)
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EP0360223A2 (en
EP0360223A3 (en
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Helmut Dr. Lischka
Werner Dr. Gmöhling
Gerd Dr. Hieber
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Evonik Operations GmbH
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SKW Trostberg AG
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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
    • C21C1/00—Refining of pig-iron; Cast iron
    • C21C1/02—Dephosphorising or desulfurising
    • C21C1/025—Agents used for dephosphorising or desulfurising

Definitions

  • the invention relates to an agent for the desulfurization of molten iron, a process for the production thereof and a process for the desulfurization of molten iron.
  • the agent contains calcium carbide and a metallic component.
  • the desulfurization of pig iron outside the blast furnace by means of injection metallurgical processes is a firmly established process in the production of steel.
  • two methods have proven particularly useful for reducing the sulfur content in pig iron, namely desulphurization in the torpedo pan and treatment of the pig iron in the charging pan in the steel mill. Both methods are used to desulfurize by injection metallurgy, i.e. the desulfurization mixture is blown into the pig iron melt by means of an immersion lance using an inert gas stream.
  • a disadvantage of some of these processes is the use of a mixture of substances which is not stable to mixing. Magnesium, which enables rapid and targeted desulphurization of the pig iron, can therefore not be dosed with the necessary accuracy.
  • magnesium is often used in a mixture with slag, with aluminum dross or other oxidic compounds. These agents also separate and therefore do not solve the problem.
  • Patent 4,541,867 teaches the manufacture of a carbon coated granular agent which can be used as an additive to steel baths and for desulfurization thereof.
  • the agent can include consist of magnesium and calcium carbide.
  • the coating is made by mixing the components of the agent with a polymerizable oil, its thermal polymerization and its subsequent partial thermal decomposition. This manufacturing process also requires a relatively large amount of equipment and high energy input.
  • the object was therefore to provide a free-flowing, low-slag and inexpensive agent which contains calcium carbide and a metallic component which is suitable for injection for the desulfurization of pig iron melts and does not have the disadvantages mentioned.
  • an agent for the desulfurization of iron, containing calcium carbide and a metallic component, and a method for its production the agent is characterized in that the calcium carbide and the metallic component are present in such a form that the bulk density of the components used in the range from 0.7 to 1.0 g / cm 3 and the grain size in the range from 0.1 to 3 mm, and in that the particles of the two components are coated with an adhesive and a finely divided dust with a grain size of ⁇ 10 ⁇ m.
  • the inert material (coating agent for magnesium and calcium carbide) has a grain size of ⁇ 10 ⁇ m; it is therefore about a power of ten smaller than the actual desulfurization agent and can therefore be applied to the surface of the components of the desulfurization agent with the aid of an adhesion promoter.
  • an agent for the desulfurization of molten iron which consists of two components which do not separate even when standing for a long time, during transport, during long storage in the silo or during pneumatic conveying and which can therefore be metered very well.
  • This allows the rate of injection of the metallic component to be controlled very well, which is of fundamental importance for a targeted desulfurization with the result of an optimal cost-benefit effect.
  • the agent according to the invention can be used alone for desulfurization. However, it is also suitable for co-injection in conjunction with other desulfurization agents, as described, for example, in EP 0 226 994 A1.
  • the agent according to the invention essentially consists of two components, namely calcium carbide and a metallic component.
  • the metallic component can be calcium, magnesium or alloys thereof. Magnesium metal is preferably used for the desulfurization agent.
  • the respective proportion of the two components in the mixture is not critical per se and can vary within wide limits.
  • the agent according to the invention usually contains 10 to 90% by weight of calcium carbide, preferably 20 to 80% by weight, and 90 to 10% by weight, preferably 80 to 20% by weight of metallic component.
  • the two essential components according to the invention are used in such a way that their bulk density and their grain size are in the same range.
  • the bulk density of the metallic component is adjusted to the bulk weight of calcium carbide, so the bulk density is adjusted to a range from 0.7 to 1.0 g / cm 3 , preferably 0.8 to 0.9 g / cm 3 .
  • the production of the two components with the corresponding bulk density takes place according to methods known per se.
  • the grain size of the two components is also set in the same range by appropriate grinding.
  • the grain size is in the range from 0.1 to 3 mm, preferably 0.3 to 1 mm.
  • the particles of the two components are coated.
  • An adhesive is applied to the particles for coating and then a finely divided dust with a particle size of ⁇ 10 ⁇ m.
  • the coating amounts to 1 to 10% by weight based on the weight of the entire grain.
  • An oily liquid that adheres to the particles is used as the adhesive. Suitable for this are e.g. Vegetable oils, silicone oils and / or mineral oils.
  • a fine-particle dust is applied.
  • Silicate dusts or oxidic dusts such as those produced in the aluminum industry, are suitable for the coating. Examples are finely divided silica, bentonite and / or furnace filter dust from the production of calcium silicon and / or ferro silicon and / or other ferro alloys as well as other oxidic compounds such as e.g. Calcium aluminates.
  • a typical and particularly preferred composition contains 45% by weight of magnesium, 45% by weight of technical calcium carbide, the content of CaC 2 of which is usually 65 to 80% by weight, 0.5% by weight of an oil and 9, 5% by weight of a laminate.
  • the coating of the agent according to the invention is particularly advantageous. This measure produces the surfaces of the same constituents of the two components calcium carbide and metallic component.
  • a surface of the same material, for example in the form of a coating containing silica, not only gives the agent excellent flow properties, but in particular counteracts segregation of the constituents, so that the agent remains fully homogeneous during transport, handling and storage in silos.
  • Highly viscous oils in particular those of vegetable origin, but also silicone oils and / or mineral oils are used as adhesion promoters.
  • Another advantage of this preferred embodiment is that the oil also binds fine fractions of carbide and magnesium and in this way makes the desulfurization agent dust-free. In addition, the sensitivity of the carbide component to moisture is reduced.
  • a layer of fine dust is applied to the adhesive layer. Dusts with a grain size of less than 10 ⁇ m are used for this.
  • the proportion of finely divided dust in the desulfurization agent is 2 to 10% by weight.
  • the agent according to the invention is produced by simply mixing technical calcium carbide and the metallic component in the desired grain size under an inert gas atmosphere.
  • the particle surface is wetted with the oil and the finely divided dust is then applied.
  • the process can be carried out batchwise in drum, trough or truncated cone mixers, as well as continuously, for example in screw mixers.
  • the agent consisting of coated particles is less flammable than fine-particle magnesium
  • the mixing process is also expediently carried out under a dry inert gas atmosphere in order to exclude moisture during production, in which the magnesium and calcium carbide are freely present, and at the same time the risk of a dust explosion from possibly exclude existing fine-particle magnesium.
  • the agent according to the invention can be blown into the molten metal without any additives or diluents using argon or nitrogen as the carrier medium. It can also be used as a co-injection partner with other desulfurization agents. Without fear of iron ejection, the agent as such or together with another desulfurization mixture can be easily blown in at a delivery rate of 10 to 100 kg / min, the preferred delivery rate being 20 to 40 kg / min. The high delivery rate enables a significant reduction in the blowing times and, moreover, the filling level of the pig iron pans can be increased by the quiet blowing behavior of the agent.
  • the productivity of the desulfurization process is considerably improved by using the agent according to the invention.
  • the agent In order to avoid the violent magnesium evaporation reaction in the hot pig iron melt, the agent essentially contains actively desulfurizing calcium carbide and only small amounts of inactive components.
  • the hot metal was desulfurized (RE) in a charging pan containing 230 t of iron at a temperature of 1350 ° C.
  • the mixtures used for desulfurization were blown in pneumatically by means of an immersion lance using argon.
  • Example Nos. 2 and 3 were performed with the agent of the invention CaM 45 of the preferred composition.
  • CaM 45 consists of 45% by weight of technical calcium carbide, 45% by weight of magnesium metal, 9.5% by weight of furnace filter dust from FeSi production and 0.5% by weight of silicone oil.
  • the co-injection experiments No. 4 and No. 5 were carried out with CaM 45 together with CaD C5 (95% by weight technical calcium carbide + 5% by weight flame carbon).
  • Example No. 6 illustrates the co-injection of an agent CaM 25 of the composition: 25% by weight magnesium metal, 65% by weight technical calcium carbide, 9.5% by weight furnace filter dust from the CaSi production and 0.5% by weight Silicone oil, together with CaD 45.
  • a silo with 25-30 t of mixtures 1, 2 and 3 was in each case subjected to a total of 10 m 3 gas / minute for a total of 10 ⁇ 3 minutes via the loosening device. Between the individual loosening steps There was a 5 minute pause for the mixture to settle again. The entire loosening up treatment lasted 80 minutes. The mixture was then unloaded and sampled. The discharge time lasted approx. 60 minutes for 25 t, with a 6 kg sample (10 to 12 samples) being taken every 5 minutes. The removal time for the 6 kg material was approx. 20 seconds. These 6 kg were reduced to a sufficient amount for the analysis of the magnesium content using a standardized sample divider.
  • the coated mixture (CaM 45 coated) practically does not separate, the uncoated mixture (CaM 45 uncoated) undergoes only a slight separation, the size of which has not previously been achieved.
  • a desulfurization agent according to the prior art was examined in which the grain size of the magnesium was between 0.3-1 mm and that of the calcium carbide was ⁇ 0.1 mm. The loosening of this mixture caused a clear visual effect, the magnesium and calcium carbide components separating from one another, which can be seen clearly in FIG. 2.
  • the magnesium content is initially approximately 24% by weight and ends at approximately 17% by weight.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Description

Die Erfindung betrifft ein Mittel zur Entschwefelung von Eisenschmelzen, ein Verfahren zu dessen Herstellung sowie ein Verfahren zur Entschwefelung von Eisenschmelzen. Das Mittel enthält Calciumcarbid und eine metallische Komponente.The invention relates to an agent for the desulfurization of molten iron, a process for the production thereof and a process for the desulfurization of molten iron. The agent contains calcium carbide and a metallic component.

Die Entschwefelung von Roheisen außerhalb des Hochofens durch injektionsmetallurgische Verfahren ist ein fest etablierter Prozeß bei der Herstellung von Stahl. Zur Verminderung des Schwefelgehaltes im Roheisen haben sich in der Praxis zwei Verfahren besonders gut bewährt, nämlich die Entschwefelung in der Torpedopfanne und die Behandlung des Roheisens in der Chargierpfanne im Stahlwerk. Nach beiden Verfahren wird injektionsmetallurgisch entschwefelt, d.h. das Entschwefelungsgemisch wird durch eine Tauchlanze mittels eines Inertgasstromes in die Roheisenschmelze eingeblasen.The desulfurization of pig iron outside the blast furnace by means of injection metallurgical processes is a firmly established process in the production of steel. In practice, two methods have proven particularly useful for reducing the sulfur content in pig iron, namely desulphurization in the torpedo pan and treatment of the pig iron in the charging pan in the steel mill. Both methods are used to desulfurize by injection metallurgy, i.e. the desulfurization mixture is blown into the pig iron melt by means of an immersion lance using an inert gas stream.

Zur Ausübung dieses Verfahrens haben sich in der Praxis Entschwefelungsgemische aus Calciumcarbid und Magnesium mit gegebenenfalls weiteren Zusätzen wie beispielsweise gasabspaltende Kohle, Erdalkalicarbonate, Calciumoxid und Calciumfluorid oder Kalkstickstoff als vorteilhaft herausgestellt. Beispielhaft seien einige Schriften, in denen solche Gemische beschrieben sind, genannt: DE-OS 25 31 047, DE-OS 26 50 113, DE-OS 27 08 424, DE-OS 27 41 588, DE-OS 35 44 562, Stahl und Eisen 105 (1985), Nr. 11, S. 627 bis 630.In practice, desulfurization mixtures of calcium carbide and magnesium with possibly further additives such as gas-releasing coal, alkaline earth carbonates, calcium oxide and calcium fluoride or calcium cyanide have proven to be advantageous for practicing this process. Some documents in which such mixtures are described may be mentioned by way of example: DE-OS 25 31 047, DE-OS 26 50 113, DE-OS 27 08 424, DE-OS 27 41 588, DE-OS 35 44 562, steel and Eisen 105 (1985), No. 11, pp. 627 to 630.

Nachteilig an einigen dieser Verfahren ist der Einsatz eines Stoffgemisches, das nicht mischungsstabil ist. Magnesium, das eine rasche und gezielte Entschwefelung des Roheisens ermöglicht, ist somit in seiner Menge nicht mit der notwendigen Genauigkeit dosierbar.A disadvantage of some of these processes is the use of a mixture of substances which is not stable to mixing. Magnesium, which enables rapid and targeted desulphurization of the pig iron, can therefore not be dosed with the necessary accuracy.

Soweit die vorstehend genannten Verfahren eine getrennte Zugabe des Magnesiums zur Entschwefelungsmischung in Form der Koinjektion vorsehen, ist ein relativ großer apparativer Aufwand erforderlich, um die Komponenten exakt dosieren zu können. Um bei der Koinjektion gezielt dosieren zu können, verwendet man häufig Magnesium im Gemisch mit Schlacke, mit Aluminiumkrätze oder anderen oxidischen Verbindungen. Auch diese Mittel entmischen sich und lösen daher das Problem nicht.If the above-mentioned methods provide for a separate addition of the magnesium to the desulfurization mixture in the form of co-injection, a relatively large amount of equipment is required in order to be able to meter the components precisely. In order to be able to dose precisely during co-injection, magnesium is often used in a mixture with slag, with aluminum dross or other oxidic compounds. These agents also separate and therefore do not solve the problem.

Aus vorgenannten Gründen fehlte es nicht an Versuchen, Magnesium enthaltende Entschwefelungsmittel in Form von Pellets, Fülldrähten oder durch Beschichtung herzustellen, welche diesen Mitteln eine vereinfachte Handhabung und eine erhöhte Verfahrenswirksamkeit verleihen sollten. Ein derartiges Entschwefelungsmittel wird beispielsweise in der DE-AS 12 99 670 offenbart. Es weist einen Mehrschichtenaufbau auf und kann neben Magnesium und Calciumcarbid weitere entschwefelnd wirkende Bestandteile enthalten. Die Dimension und die Zusammensetzung der in dieser Schrift offenbarten Preßlinge ist zum Einsatz beim Koinjektionsverfahren jedoch ungeeignet.For the aforementioned reasons, attempts have not been lacking to produce magnesium-containing desulfurization agents in the form of pellets, cored wires or by coating, which should give these agents simplified handling and increased process efficiency. Such a desulfurization agent is disclosed, for example, in DE-AS 12 99 670. It has a multi-layer structure and, in addition to magnesium and calcium carbide, can contain other components that have a desulfurizing effect. However, the dimensions and the composition of the compacts disclosed in this document are unsuitable for use in the co-injection process.

Des weitern ist aus der DE-OS 24 22 072 ein Entschwefelungsmittel auf der Basis von Calciumcarbid bekannt, das mit Magnesiummetall beschichtet ist. Die Beschichtung erfolgt nach dem Verfahren dieser Schrift durch Bedampfen des Calciumcarbidkorns mit Magnesiumdampf. Das Verfahren ist unter heutigen wirtschaftlichen Gesichtspunkten zu aufwendig und zu kostenintensiv, um dieses Produkt, selbst bei eventueller technischer Eignung, zur Koinjektion einzusetzen. Die Entschwefelung mittels einer Calciumcarbid-Magnesiummetall-Mischung in Form eines Fülldrahtes oder in Form von Stangen, wie sie der DE-OS 27 38 379 entnommen werden kann, scheidet aus verständlichen Gründen beim Koinjektionsverfahren aus. Schließlich lehrt die US-PS 4,541,867 die Herstellung eines mit Kohlenstoff beschichteten, körnigen Mittels, das als Zusatz zu Stahlbädern und zur Entschwefelung derselben verwendet werden kann. Das Mittel kann u.a. aus Magnesium und Calciumcarbid bestehen. Der Überzug wird durch Vermischen der Bestandteile des Mittels mit einem polymerisierbaren Öl, dessen thermischer Polymerisation und seiner anschließenden teilweisen thermischen Zersetzung hergestellt. Auch dieses Herstellungsverfahren erfordert relativ großen apparativen Aufwand und hohen Energieeinsatz.Furthermore, from DE-OS 24 22 072 a desulfurizing agent based on calcium carbide is known, which is coated with magnesium metal. The coating is carried out according to the method of this document by vapor deposition of the calcium carbide grain with magnesium vapor. From today's economic point of view, the process is too complex and too costly to use this product for co-injection, even if it is technically suitable. Desulphurization by means of a calcium carbide-magnesium metal mixture in the form of a cored wire or in the form of rods, as can be found in DE-OS 27 38 379, is out of the question of the co-injection process for understandable reasons. Finally, U.S. Patent 4,541,867 teaches the manufacture of a carbon coated granular agent which can be used as an additive to steel baths and for desulfurization thereof. The agent can include consist of magnesium and calcium carbide. The coating is made by mixing the components of the agent with a polymerizable oil, its thermal polymerization and its subsequent partial thermal decomposition. This manufacturing process also requires a relatively large amount of equipment and high energy input.

Aus der EP-A-0226994 ist es bekannt, einem Mittel, daß aus Calciumcarbid und getrockneter Kohle besteht, Magnesium zuzudosieren, so daß das Mittel als homogenes Gemisch pneumatisch in eine Eisenschmelze gefördert werden kann. Das verwendete Magnesium besitzt eine Korngröße < 1 mm, bevorzugt < 500 um, besonders bevorzugt < 350 um. Die anderen Bestandteile des Mittels, also das Calciumcarbid und die Kohle, werden dort soweit zerkleinert, daß mindestens 90 Gew.-% des Gemisches eine Korngröße < 200 um, bevorzugt aber 90 % eine Korngröße < 100 um, und 40 bis 65 Gew.-% einer Korngröße < 50 um aufweisen. Es wurde jedoch gefunden, daß die Auflockerung bei einem solchen Gemisch einen deutlichen Sichteffekt verursacht, wobei sich die Magnesium- und Calciumcarbidkomponenten voneinander trennen und diese Unterschiede im Gemisch zu Problemen bei der Entschwefelungsbehandlung führen, da sich die Gemischzusammensetzung und damit des in Wirksamkeit im Verlauf der Behandlung ändern, so daß das Gemisch zwar homogen herstellbar ist, beim Transport und Fluidisieren aber einem Trenneffekt unterliegt, bei dem zuerst die größeren (Magnesium) Teilchen ausgetragen werden.From EP-A-0226994 it is known to add magnesium to an agent consisting of calcium carbide and dried coal so that the agent can be pneumatically conveyed as a homogeneous mixture into an iron smelter. The magnesium used has a grain size <1 mm, preferably <500 µm, particularly preferably <350 µm. The other constituents of the agent, that is to say the calcium carbide and the coal, are comminuted there to such an extent that at least 90% by weight of the mixture has a grain size <200 μm, but preferably 90% a grain size <100 μm, and 40 to 65% by weight. % of a grain size <50 microns. However, it has been found that the loosening of such a mixture causes a clear visual effect, the magnesium and calcium carbide components separating from one another and these differences in the mixture leading to problems during the desulfurization treatment, since the mixture composition and therefore the effectiveness of the mixture change over the course of the Change the treatment so that the mixture can be produced homogeneously, but is subject to a separation effect during transport and fluidization, in which the larger (magnesium) particles are discharged first.

Allgemein sei noch angemerkt, daß aufgrund des hohen Magnesiumdampfdruckes bei den Temperaturen des Roheisens der Magnesiumeintrag in die Schmelze Probleme aufwirft. Eine gute Dosierbarkeit der Magnesiumkomponente ist daher verfahrenswesentlich, wird aber von den heute bekannten Entschwefelungsmitteln nicht zufriedenstellend erfüllt. Speziell wenn Magnesium ohne den Koinjektionspartner Calciumcarbid eingeblasen wird, kommt es zum Eisenauswurf und zu Lanzenverstopfern. Ein Nachteil allgemeiner Art bekannter Gemische liegt darin, daß sie einen Füllstoffanteil von 20 bis 34 Gew.-% aufweisen, der nicht an der Entschwefelung beteiligt ist. Ein weiterer Nachteil bekannter Gemische von Magnesium mit Füllstoffen wie Aluminium, Aluminiumoxid oder Kugelmühlenstaub besteht darin, daß diese sich relativ schnell entmischen, so daß der Magnesiumanteil anfangs hoch ist und danach absinkt. Wegen dieser Inhomogenität ist ein höherer Materialeinsatz bei schlechterer Wirkung erforderlich.In general, it should also be noted that, due to the high magnesium vapor pressure at the pig iron temperatures, the magnesium introduction into the melt poses problems. Good meterability of the magnesium component is therefore essential to the process, but is not satisfactorily achieved by the desulfurization agents known today. Especially when magnesium is blown in without the co-injection partner calcium carbide, iron ejection and lance blockages occur. A disadvantage of the general type of known mixtures is that they have a filler content of 20 to 34% by weight, which is not involved in the desulfurization. Another disadvantage of known mixtures of magnesium with fillers such as aluminum, aluminum oxide or ball mill dust is that they separate relatively quickly, so that the magnesium content is initially high and then decreases. Because of this inhomogeneity, a higher use of materials with a poorer effect is required.

Es bestand daher die Aufgabe, ein freifließendes, schlackenarmes und kostengünstiges Mittel bereitzustellen, das Calciumcarbid und eine metallische Komponente enthält, das sich zur Injektion bei der Entschwefelung von Roheisenschmelzen eignet und die genannten Nachteile nicht aufweist.The object was therefore to provide a free-flowing, low-slag and inexpensive agent which contains calcium carbide and a metallic component which is suitable for injection for the desulfurization of pig iron melts and does not have the disadvantages mentioned.

Diese Aufgabe wird gelöst durch ein Mittel zur Entschwefelung von Eisen, enthaltend Calciumcarbid und eine metallische Komponente, sowie ein Verfahren zu dessen Herstellung, das Mittel ist dadurch gekennzeichnet, daß das Calciumcarbid und die metallische Komponente in solcher Form vorliegen, daß das Schüttgewicht der eingesetzten Komponenten im Bereich von 0,7 bis 1,0 g/cm3 und die Korngröße im Bereich von 0,1 bis 3 mm liegt, und daß die Teilchen der beiden Komponenten mit einem Haftmittel und einem feinteiligen Staub einer Korngröße < 10 um beschichtet sind.This object is achieved by an agent for the desulfurization of iron, containing calcium carbide and a metallic component, and a method for its production, the agent is characterized in that the calcium carbide and the metallic component are present in such a form that the bulk density of the components used in the range from 0.7 to 1.0 g / cm 3 and the grain size in the range from 0.1 to 3 mm, and in that the particles of the two components are coated with an adhesive and a finely divided dust with a grain size of <10 μm.

In der Firmenschrift Thyssen Tech. Ber. Heft 1/1987, Seite 21 bis 33 wird angegeben, daß einige Hersteller Dichte- und Korngrößenverteilung des Inertstoffes denen des Magnesiums anpassen, d.h. Magnesium und Inertstoff (zur Erleichterung der pneumatischen Förderung und Hervorrufen des Schatteneffektes beim Übergang des Magnesiusm aus der Lanze in die Schmelze) besitzen eine angepaßte Dichte und Korngröße. Erfindungsgemäß besitzt hingegen das Inertmaterial (Beschichtungsmittel für Magnesium und Calciumcarbid) eine Korngröße von < 10 um; es ist also etwa um eine Zehnerpotenz kleiner als das eigentliche Entschwefelungsmittel, und kann damit mit Hilfe eines Haftvermittlers auf die Oberfläche der Bestandteile des Entschwefelungsmittels aufgebracht werden.In Thyssen Tech. Ber. Booklet 1/1987, pages 21 to 33 states that some manufacturers adapt the density and grain size distribution of the inert substance to that of magnesium, i.e. Magnesium and inert substance (to facilitate the pneumatic conveyance and to cause the shadow effect when the magnesius is transferred from the lance to the melt) have an adapted density and grain size. According to the invention, however, the inert material (coating agent for magnesium and calcium carbide) has a grain size of <10 μm; it is therefore about a power of ten smaller than the actual desulfurization agent and can therefore be applied to the surface of the components of the desulfurization agent with the aid of an adhesion promoter.

Erfindungsgemäß wird ein Mittel zur Entschwefelung von Eisenschmelzen zur Verfügung gestellt, das aus zwei Komponenten besteht, die sich auch bei längerem Stehen, beim Transport, bei längerer Lagerung im Silo oder bei der pneumatischen Förderung nicht entmischen und das daher sehr gut dosierbar ist. Dadurch läßt sich die Einblasrate der metallischen Komponente sehr gut steuern, was von grundlegender Bedeutung für eine gezielte Entschwefelung mit dem Ergebnis eines optimalen Kosten-Nutzen-Effektes ist. Das erfindungsgemäße Mittel kann alleine zur Entschwefelung verwendet werden. Ebenso geeignet ist es jedoch zur Koinjektion in Verbindung mit anderen Entschwefelungsmitteln, wie sie beispielsweise in der EP 0 226 994 A1 beschrieben sind.According to the invention, there is provided an agent for the desulfurization of molten iron, which consists of two components which do not separate even when standing for a long time, during transport, during long storage in the silo or during pneumatic conveying and which can therefore be metered very well. This allows the rate of injection of the metallic component to be controlled very well, which is of fundamental importance for a targeted desulfurization with the result of an optimal cost-benefit effect. The agent according to the invention can be used alone for desulfurization. However, it is also suitable for co-injection in conjunction with other desulfurization agents, as described, for example, in EP 0 226 994 A1.

Das erfindungsgemäße Mittel besteht im wesentlichen aus zwei Komponenten, nämlich Calciumcarbid und einer metallischen Komponente. Die metallische Komponente kann Calcium, Magnesium oder Legierungen hiervon sein. Bevorzugt wird für das Entschwefelungsmittel Magnesiummetall verwendet. Der jeweilige Anteil der beiden Komponenten in dem Gemisch ist an sich nicht kritisch und kann in weiten Bereichen variieren. Üblicherweise enthält das erfindungsgemäße Mittel 10 bis 90 Gew.-% Calciumcarbid, bevorzugt 20 bis 80 Gew.-%, und 90 bis 10 Gew.-%, bevorzugt 80 bis 20 Gew.-% metallische Komponente.The agent according to the invention essentially consists of two components, namely calcium carbide and a metallic component. The metallic component can be calcium, magnesium or alloys thereof. Magnesium metal is preferably used for the desulfurization agent. The respective proportion of the two components in the mixture is not critical per se and can vary within wide limits. The agent according to the invention usually contains 10 to 90% by weight of calcium carbide, preferably 20 to 80% by weight, and 90 to 10% by weight, preferably 80 to 20% by weight of metallic component.

Die beiden erfindungsgemäß wesentlichen Komponenten werden in solcher Form eingesetzt, daß ihr Schüttgewicht und ihre Korngröße im selben Bereich liegen. In der Regel wird dabei das Schüttgewicht der metallischen Komponente an das Schüttgewicht von Calciumcarbid angeglichen, daher wird das Schüttgewicht auf einen Bereich von 0,7 bis 1,0 g/cm3, bevorzugt 0,8 bis 0,9 g/cm3 eingestellt. Die Herstellung der beiden Komponenten mit dem entsprechenden Schüttgewicht geschieht nach an sich bekannten Methoden.The two essential components according to the invention are used in such a way that their bulk density and their grain size are in the same range. As a rule, the bulk density of the metallic component is adjusted to the bulk weight of calcium carbide, so the bulk density is adjusted to a range from 0.7 to 1.0 g / cm 3 , preferably 0.8 to 0.9 g / cm 3 . The production of the two components with the corresponding bulk density takes place according to methods known per se.

Die Korngröße der beiden Komponenten wird ebenfalls im selben Bereich eingestellt durch entsprechende Vermahlung. Die Körngröße liegt im Bereich von 0,1 bis 3 mm, bevorzugt 0,3 bis 1 mm.The grain size of the two components is also set in the same range by appropriate grinding. The grain size is in the range from 0.1 to 3 mm, preferably 0.3 to 1 mm.

Außerdem werden die Teilchen der beiden Komponenten beschichtet. Zur Beschichtung wird ein Haftmittel auf die Teilchen aufgebracht und anschließend ein feinteiliger Staub einer Korngröße von < 10 um. Die Beschichtung betragt 1 bis 10 Gew.-% bezogen auf das Gewicht des gesamten Korns. Als Haftmittel wird dazu eine ölige Flüssigkeit eingesetzt, die auf den Teilchen haftet. Geeignet sind hierzu z.B. Pflanzenöle, Siliconöle und/oder Mineralöle. In einem zweiten Schritt wird dann ein feinteiliger Staub aufgebracht. Geeignet für die Beschichtung sind silicatische Stäube oder oxidische Stäube, wie sie beispielsweise in der Aluminiumindustrie entstehen. Beispiele sind feinteilige Kieselsäure, Bentonit und/oder Ofenfilterstaub aus der Produktion von Calcium-Silicium und/oder Ferro-Silicium und/oder anderen FerroLegierungen sowie andere oxidische Verbindungen wie z.B. Calciumaluminate.In addition, the particles of the two components are coated. An adhesive is applied to the particles for coating and then a finely divided dust with a particle size of <10 μm. The coating amounts to 1 to 10% by weight based on the weight of the entire grain. An oily liquid that adheres to the particles is used as the adhesive. Suitable for this are e.g. Vegetable oils, silicone oils and / or mineral oils. In a second step, a fine-particle dust is applied. Silicate dusts or oxidic dusts, such as those produced in the aluminum industry, are suitable for the coating. Examples are finely divided silica, bentonite and / or furnace filter dust from the production of calcium silicon and / or ferro silicon and / or other ferro alloys as well as other oxidic compounds such as e.g. Calcium aluminates.

Aufgrund der Eigenschaften dieses Mittels ist die Entmischung besonders gering und die Dosierbarkeit damit noch präziser möglich. Eine typische und besonders bevorzugte Zusammensetzung enthält 45 Gew.- % Magnesium, 45 Gew.-% technisches Calciumcarbid, dessen Gehalt an CaC2 üblicherweise bei 65 bis 80 Gew.-% liegt, 0,5 Gew.-% eines Öls und 9,5 Gew.-% eines Schichtstoffes.Due to the properties of this agent, segregation is particularly low, making dosing even more precise. A typical and particularly preferred composition contains 45% by weight of magnesium, 45% by weight of technical calcium carbide, the content of CaC 2 of which is usually 65 to 80% by weight, 0.5% by weight of an oil and 9, 5% by weight of a laminate.

Die Beschichtung des erfindungsgemäßen Mittels ist besonders vorteilhaft. Diese Maßnahme bewirkt die Herstellung stoffgleicher Oberflächen der beiden Bestandteile Calciumcarbid und metallische Komponente. Eine stoffgleiche Oberfläche, beispielsweise in Form eines Kieselsäure enthaltenden Überzuges verleiht dem Mittel nicht nur ausgezeichnete Fließeigenschaften, sondern wirkt insbesondere einer Entmischung der Bestandteile entgegen, so daß beim Transport, bei der Handhabung und Silolagerung die Homogenität des Mittels voll erhalten bleibt.The coating of the agent according to the invention is particularly advantageous. This measure produces the surfaces of the same constituents of the two components calcium carbide and metallic component. A surface of the same material, for example in the form of a coating containing silica, not only gives the agent excellent flow properties, but in particular counteracts segregation of the constituents, so that the agent remains fully homogeneous during transport, handling and storage in silos.

Als Haftvermittler werden hochviskose Öle, insbesondere solche pflanzlicher Herkunft, aber auch Siliconöle und/oder Mineralöle verwendet. Um eine Zersetzung des Carbids zu vermeiden, werden wasserfreie oder wasserarme Öle bevorzugt, deren Gewichtsanteil am Mittel 0,1 bis 1 Gew.-% beträgt. Sie bilden die Grundlage für einen fest haftenden, lückenlosen Überzug, der dem Mittel die gewünschten Eigenschaften verleiht. Ein weiterer Vorteil dieser bevorzugten Ausführungsform liegt darin, daß das Öl auch noch Feinanteile an Carbid und Magnesium bindet und auf diese Weise das Entschwefelungsmittel staubfrei macht. Außerdem wird die Empfindlichkeit der Carbidkomponente gegenüber Feuchtigkeit herabgesetzt.Highly viscous oils, in particular those of vegetable origin, but also silicone oils and / or mineral oils are used as adhesion promoters. In order to avoid decomposition of the carbide, preference is given to anhydrous or low-water oils, the weight fraction of which is 0.1 to 1% by weight. They form the basis for a firmly adhering, gapless coating that gives the agent the desired properties. Another advantage of this preferred embodiment is that the oil also binds fine fractions of carbide and magnesium and in this way makes the desulfurization agent dust-free. In addition, the sensitivity of the carbide component to moisture is reduced.

Auf die Haftschicht wird eine Schicht aus feinteiligem Staub aufgetragen. Dazu werden Stäube mit einer Körnung unter 10 um verwendet. Der Anteil des feinteiligen Staubs am Entschwefelungsmittel beträgt 2 bis 10 Gew.-%.A layer of fine dust is applied to the adhesive layer. Dusts with a grain size of less than 10 µm are used for this. The proportion of finely divided dust in the desulfurization agent is 2 to 10% by weight.

Die Herstellung des erfindungsgemäßen Mittels erfolgt durch einfaches Mischen von technischem Calciumcarbid und der metallischen Komponente in der gewünschten Körnung unter Inertgasatmosphäre.The agent according to the invention is produced by simply mixing technical calcium carbide and the metallic component in the desired grain size under an inert gas atmosphere.

Nach Vermahlung der beiden Komponenten auf die gewünschte Teilchengröße wird die Partikeloberfläche mit dem Öl benetzt und der feinteilige Staub anschließend aufgebracht. Das Verfahren kann sowohl chargenweise in Trommel-, Trog- oder Kegelstumpfmischern, als auch kontinuierlich beispielsweise in Schneckenmischern erfolgen. Obwohl das aus beschichteten Teilchen bestehende Mittel weniger entzündlich ist als feinteiliges Magnesium, erfolgt der Mischvorgang dennoch ebenfalls zweckmäßigerweise unter einer trockenen Inertgasatmosphäre, um bei der Herstellung, bei der das Magnesium und das Calciumcarbid frei vorliegen - Feuchtigkeit auszuschließen und zugleich die Gefahr einer Staubexplosion durch eventuell vorhandenes feinteiliges Magnesium auszuschließen.After the two components have been ground to the desired particle size, the particle surface is wetted with the oil and the finely divided dust is then applied. The process can be carried out batchwise in drum, trough or truncated cone mixers, as well as continuously, for example in screw mixers. Although the agent consisting of coated particles is less flammable than fine-particle magnesium, the mixing process is also expediently carried out under a dry inert gas atmosphere in order to exclude moisture during production, in which the magnesium and calcium carbide are freely present, and at the same time the risk of a dust explosion from possibly exclude existing fine-particle magnesium.

Das erfindungsgemäße Mittel kann ohne irgendwelche Zusätze oder Verdünnungsmittel mit Argon oder Stickstoff als Trägermedium in die Metallschmelze eingeblasen werden. Ebenso kann es als Koinjektionspartner mit anderen Entschwefelungsmitteln verwendet werden. Ohne einen Eisenauswurf befürchten zu müssen, kann das Mittel als solches oder gemeinsam mit einem anderen Entschwefelungsgemisch mit einer Förderrate von 10 bis 100 kg/min problemlos eingeblasen werden, wobei die bevorzugte Förderrate bei 20 bis 40 kg/min liegt. Die hohe Förderrate ermöglicht eine wesentliche Verkürzung der Blaszeiten und darüberhinaus kann der Füllgrad der Roheisenpfannen durch das ruhige Blasverhalten des Mittels erhöht werden.The agent according to the invention can be blown into the molten metal without any additives or diluents using argon or nitrogen as the carrier medium. It can also be used as a co-injection partner with other desulfurization agents. Without fear of iron ejection, the agent as such or together with another desulfurization mixture can be easily blown in at a delivery rate of 10 to 100 kg / min, the preferred delivery rate being 20 to 40 kg / min. The high delivery rate enables a significant reduction in the blowing times and, moreover, the filling level of the pig iron pans can be increased by the quiet blowing behavior of the agent.

Die Produktivität des Entschwefelungsverfahrens wird durch Verwendung des erfindungsgemäßen Mittels beträchtlich verbessert. Zur Vermeidung der heftigen Magnesiumverdampfungsreaktion in der heißen Roheisenschmelze enthält das Mittel im wesentlichen aktiv entschwefelndes Calciumcarbid und nur geringe Mengen inaktiver Komponenten.The productivity of the desulfurization process is considerably improved by using the agent according to the invention. In order to avoid the violent magnesium evaporation reaction in the hot pig iron melt, the agent essentially contains actively desulfurizing calcium carbide and only small amounts of inactive components.

Erfindungsgemäß wird damit ein Mittel zur Verfügung gestellt, das aus technischen, metallurgischen und ökonomischen Gründen eine äußerst flexible Entschwefelungsmethode zuläßt.According to the invention, a means is thus made available which permits an extremely flexible desulfurization method for technical, metallurgical and economic reasons.

Die Erfindung wird durch folgende Figuren und Beispiele erläutert.

  • Figur 1 zeigt ein Diagramm, in dem die Veränderung der Zusammensetzung eines hinsichtlich Korngröße und spez. Gewicht angeglichenen Gemisches aus 55 Gew.-% Calciumcarbid und 45 Gew.-% Magnesium nach der Auflockerung in einem Silo dargestellt wird (+). Bei der Entnahme des Gemisches werden Magnesiumgehalte zwischen 46,4 und 42,3 Gew.-% gefunden, was einen Streubereich von 4,1 Gew.-% Magnesium bedeutet. Ein gleichartiges, jedoch beschichtetes Gemisch aus 45 Gew.-% Calciumcarbid, 45 Gew.-% Magnesium und 10 Gew.-% Beschichtung (D) zeigte nach Auflockerung und Entnahme Magnesiumgehalte zwischen 46,2 und 44,6 Gew.-% Mg, was einem Streubereich von 1,6 Gew.-% entsprach.
  • Figur 2 In diesem Fall bestand das Gemisch aus 20 Gew.-% Magnesium der Körnung 0,3 bis 1 mm und fein aufgemahlenem Calciumcarbid der Körnung < 0,1 mm (vgl. Beispiel 8). Das Diagramm zeigt die Entmischung des Magnesiums bei der Auflockerung und anschließender Entnahme, wobei Magnesium-Gehalte zwischen 24,2 und 17,0 Gew.-% Mg erhalten wurden, was einer Streubreite von 7,2 Gew.-% Mg entsprach.
  • Figur 3 zeigt ein Diagramm, in dem die Veränderungen des Entschwefelungsgrades für ein Gemisch nach dem Stand der Technik (durchgezogene Kurve) dargestellt ist; ferner wird die Streubreite des Endschwefelgehaltes SE - 1/1000 % für ein erfindungsgemäßes Gemisch (schraffierter Bereich) angegeben. In jedem Fall wird die gleiche Gemischzusammensetzung und die gleiche Menge an Gemisch in die Eisenschmelze eingeblasen. Mit dem Gemisch nach dem Stand der Technik war der Entschwefelungseffekt am Beginn der Behandlung größer als am Ende, nachdem das Gemisch dann infolge des Sichteffektes im Silo weniger Magnesium enthielt. Wurde das erfindungsgemäße Gemisch verwendet, blieb der Entschwefelungseffekt innerhalb eines relativ engen Streubereichs konstant.
The invention is illustrated by the following figures and examples.
  • Figure 1 shows a diagram in which the change in the composition of a grain size and spec. Weight adjusted mixture of 55 wt .-% calcium carbide and 45 wt .-% magnesium is shown after loosening in a silo (+). When the mixture is removed, magnesium contents of between 46.4 and 42.3% by weight are found, which means a scattering range of 4.1% by weight of magnesium. A similar but coated mixture of 45% by weight calcium carbide, 45% by weight magnesium and 10% by weight coating ( D ) showed, after loosening and removal, magnesium contents between 46.2 and 44.6% by weight Mg, which corresponded to a range of 1.6% by weight.
  • FIG. 2 In this case, the mixture consisted of 20% by weight of magnesium with a grain size of 0.3 to 1 mm and finely ground calcium carbide with a grain size of <0.1 mm (cf. Example 8). The diagram shows the segregation of the magnesium during loosening and subsequent removal, magnesium contents between 24.2 and 17.0% by weight of Mg being obtained, which corresponded to a spread of 7.2% by weight of Mg.
  • FIG. 3 shows a diagram which shows the changes in the degree of desulfurization for a mixture according to the prior art (solid curve); Furthermore, the spread of the final sulfur content S E - 1/1000% is given for a mixture according to the invention (hatched area). In any case, the same mixture composition and the same amount of mixture are blown into the molten iron. With the mixture according to the prior art, the desulfurization effect was greater at the beginning of the treatment than at the end after the mixture then contained less magnesium due to the visual effect in the silo. If the mixture according to the invention was used, the desulfurization effect remained constant within a relatively narrow scattering range.

BeispieleExamples

Die Entschwefelung des Roheisens (RE) erfolgte in einer Chargierpfanne, die 230 t Eisen mit einer Temperatur von 1350°C enthielt. Die jeweils verwendeten Gemische zur Entschwefelung wurden durch eine Tauchlanze pneumatisch mittels Argon eingeblasen.The hot metal was desulfurized (RE) in a charging pan containing 230 t of iron at a temperature of 1350 ° C. The mixtures used for desulfurization were blown in pneumatically by means of an immersion lance using argon.

Beispiel Nr. 1 stellt ein Vergleichsbeispiel mit einem handelsüblichen Gemisch zur Entschwefelung dar (Mg 50 = 50 Gew.-% Magnesiummetall + 50 Gew.-% Kugelmühlenstaub (AI2O3)).Example No. 1 represents a comparative example with a commercially available mixture for desulfurization (Mg 50 = 50 wt .-% magnesium metal + 50 wt .-% ball mill dust (Al 2 O 3 )).

Beispiel Nr. 2 und 3 wurden mit dem Mittel der Erfindung CaM 45 der bevorzugten Zusammensetzung durchgeführt. CaM 45 besteht aus 45 Gew.-% technischem Calciumcarbid, 45 Gew.-% Magnesiummetall, 9,5 Gew.-% Ofenfilterstaub aus der FeSi-Produktion und 0,5 Gew.-% Siliconöl. Die Koinjektionsversuche Nr. 4 und Nr. 5 erfolgten mit CaM 45 gemeinsam mit CaD C5 (95 Gew.-% techn. Calciumcarbid + 5 Gew.-% Flammkohle).Example Nos. 2 and 3 were performed with the agent of the invention CaM 45 of the preferred composition. CaM 45 consists of 45% by weight of technical calcium carbide, 45% by weight of magnesium metal, 9.5% by weight of furnace filter dust from FeSi production and 0.5% by weight of silicone oil. The co-injection experiments No. 4 and No. 5 were carried out with CaM 45 together with CaD C5 (95% by weight technical calcium carbide + 5% by weight flame carbon).

Beispiel Nr. 6 veranschaulicht die Koinjektion eines Mittels CaM 25 der Zusammensetzung: 25 Gew.-% Magnesiummetall, 65 Gew.-% technisches Calciumcarbid, 9,5 Gew.-% Ofenfilterstaub aus der CaSi-Produktion und 0,5 Gew.-% Silikonöl, gemeinsam mit CaD 45.Example No. 6 illustrates the co-injection of an agent CaM 25 of the composition: 25% by weight magnesium metal, 65% by weight technical calcium carbide, 9.5% by weight furnace filter dust from the CaSi production and 0.5% by weight Silicone oil, together with CaD 45.

Abkürzungen:

  • E = Entschwefelungsgrad des RE
  • SA = Schwefelgehalt (Gew.-% 10-3) im RE vor der Behandlung
  • SE = Schwefelgehalt (Gew.-% ● 10-3) im RE nach der Behandlung
  • AS = SA - SE
    Figure imgb0001
    Figure imgb0002
Abbreviations:
  • E = degree of desulfurization of the RE
  • S A = sulfur content (wt .-% 10-3) in RE before the treatment
  • S E = sulfur content (% by weight ● 10-3) in RE after treatment
  • AS = SA - S E
    Figure imgb0001
    Figure imgb0002

Beispiel 7Example 7

Ein Silo mit 25 - 30 t Gemisch 1, 2 und 3 wurde jeweils insgesamt 10 x 3 Minuten lang über die Auflockerungsvorrichtung mit 10 m3 Gas/Minute beaufschlagt. Zwischen den einzelnen Auflockerungsschritten wurde eine Pause von 5 Minuten eingelegt, damit das Gemisch sich wieder setzen konnte. Die gesamte Auflockerungsbehandlung dauerte 80 Minuten. Danach wurde das Gemisch entladen und beprobt. Die Entladezeit dauerte ca. 60 Minuten für 25 t, wobei alle 5 Minuten eine 6 kg-Probe (10 bis 12 Proben) entnommen wurde. Die Entnahmezeit für die 6 kg Material betrug ca. 20 Sekunden. Diese 6 kg wurden mit einem genormten Probenteiler auf eine für die Analyse des Magnesiumgehalts ausreichenden Menge reduziert.

Figure imgb0003
A silo with 25-30 t of mixtures 1, 2 and 3 was in each case subjected to a total of 10 m 3 gas / minute for a total of 10 × 3 minutes via the loosening device. Between the individual loosening steps There was a 5 minute pause for the mixture to settle again. The entire loosening up treatment lasted 80 minutes. The mixture was then unloaded and sampled. The discharge time lasted approx. 60 minutes for 25 t, with a 6 kg sample (10 to 12 samples) being taken every 5 minutes. The removal time for the 6 kg material was approx. 20 seconds. These 6 kg were reduced to a sufficient amount for the analysis of the magnesium content using a standardized sample divider.
Figure imgb0003

Die Ergebnisse sind in der Figur 1 dargestellt.The results are shown in FIG. 1.

Das beschichtete Gemisch (CaM 45 beschichtet) entmischt sich praktisch nicht, das unbeschichtete Gemisch (CaM 45 unbeschichtet) erfährt lediglich eine leichte Entmischung, die in ihrer Größenordnung bisher nicht erreicht wurde.The coated mixture (CaM 45 coated) practically does not separate, the uncoated mixture (CaM 45 uncoated) undergoes only a slight separation, the size of which has not previously been achieved.

Beispiel 8 (Vergleich)Example 8 (comparison)

Es wurde ein Entschwefelungsmittel gemäß dem Stand der Technik untersucht, bei dem die Körnung des Magnesiums zwischen 0,3 - 1 mm, die des Calciumcarbids < 0,1 mm betrug. Die Auflockerung verursachte bei diesem Gemisch einen deutlichen Sichteffekt, wobei sich die Magnesium- und Calciumcarbidkomponenten voneinander trennen, was deutlich Figur 2 zu entnehmen ist. Der Magnesiumgehalt beträgt anfänglich etwa 24 Gew.-% und endet bei etwa 17 Gew.-%. Diese Unterschiede im Gemisch führen zu Problemen bei der Entschwefelungsbehandlung, da sich die Gemischzusammensetzung und damit dessen Wirksamkeit im Verlaufe der Behandlung ändern.A desulfurization agent according to the prior art was examined in which the grain size of the magnesium was between 0.3-1 mm and that of the calcium carbide was <0.1 mm. The loosening of this mixture caused a clear visual effect, the magnesium and calcium carbide components separating from one another, which can be seen clearly in FIG. 2. The magnesium content is initially approximately 24% by weight and ends at approximately 17% by weight. These differences in the mixture lead to problems in the desulfurization treatment, since the mixture composition and thus its effectiveness change in the course of the treatment.

Entschwefelung mit einem 20 Gew.-% Magnesium enthaltenden Gemisch unterschiedlicher Magnesium- und Calciumcarbidkörnung (Gemisch 3, gemäß Tabelle 1) Dieses Gemisch 3 wurde zur Entschwefelung eingesetzt und Figur 3 stellt die unterschiedlichen Schwefelend-Werte (SE -Werte) dar, die sich bei der Entschwefelungsbehandlung innerhalb einer 25 t-Gemischlieferung einstellen. Man erkennt, daß in Übereinstimmung mit dem aus Figur 3 entnehmbaren Sichteffekt zu Beginn der Entnahme des Gemisches aus dem Silo wesentlich tiefere SE -Werte erreicht werden als mit der Restmenge des im Silo noch vorhandenen Gemisches.Desulfurization with a 20 wt.% Magnesium-containing mixture of different magnesium and calcium carbide grains (mixture 3, according to table 1). This mixture 3 was used for the desulfurization and FIG. 3 shows the different end sulfur values (S E values), which are during desulfurization treatment within a 25 t mixture delivery. It can be seen that, in accordance with the visual effect shown in FIG. 3, at the beginning of the removal of the mixture from the silo, significantly lower S E values are achieved than with the remaining amount of the mixture still present in the silo.

Bei Anwendung des erfindungemäßen, mischungsstabilen Gemisches weichen die SE -Werte nur unwesentlich von dem angestrebten Wert ab, was durch den schraffierten Bereich angezeigt wird.When the mixture according to the invention is used which is stable to mixing, the S E values deviate only insignificantly from the desired value, which is indicated by the hatched area.

Claims (9)

1. Agent for desulphurising iron containing calcium carbide and a metallic component, characterised in that the calcium carbide and the metallic component are present in such a form that the bulk density of the components used lie in the range of 0.7 to 1.0 g/cm3 and the grain size in the range of 0.1 to 3 mm and that the particles of the two components are coated with an adhesive and a finely divided dust of a grain size of < 10 /1.m.
2. Agent according to claim 1, characterised in that the metallic component is magnesium.
3. Agent according to claim 1 or 2, characterised in that it contains 10 to 90 wt.% of magnesium and 90 to 10 wt.% of calcium carbide.
4. Agent according to one of claims 1 to 3, characterised in that the grain size lies in the range of 0.1 to 1 mm.
5. Agent according to one of claims 1 to 4, characterised in that the coating amounts to 1 to 10 wt.%, referred to the coated particles.
6. Agent according to one of claims 1 to 5, characterised in that the adhesive is an oily liquid, preferably a vegetable oil and/or a silicone oil and/or a mineral oil.
7. Agent according to one of claims 1 to 6, characterised in that the coating contains finely divided silicic acid, bentonite and/or furnace filter dust from the production of calcium-silicon and/or ferro-silicon and/or other ferrous alloys and/or other oxidic compounds.
8. Process for the production of an agent according to one of claims 1 to 7, characterised in that one grinds calcium carbide and the metallic component to the necessary size, mixes under inert gas atmosphere and subsequently mixes with an adhesive and coats with the addition of a finely divided material.
9. Process for the desulphurisation of iron, characterised in that one introduces into the iron melt an agent according to one of claims 1 to 7 either alone or in the co-injection process together with further desulphurising agents with a conveying rate of 10 to 100 kg/min.
EP89117308A 1988-09-20 1989-09-19 Agent and method for desulfurizing molten ferrous metal and a process for the production of this agent Expired - Lifetime EP0360223B1 (en)

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DE4002284A1 (en) * 1989-12-04 1991-06-06 Foseco Int Abrasion resistant medium for desulphurising molten iron - consists of fine grain magnesium particles having several coatings
US5149364A (en) * 1990-03-14 1992-09-22 Elkem Metals Company Desulfurization agent
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Also Published As

Publication number Publication date
EP0360223A2 (en) 1990-03-28
FI91169C (en) 1994-05-25
FI91169B (en) 1994-02-15
FI894436A (en) 1990-03-21
EP0360223A3 (en) 1991-05-29
JPH0438808B2 (en) 1992-06-25
FI894436A0 (en) 1989-09-19
JPH02185908A (en) 1990-07-20
PT91761A (en) 1990-03-30
DE3831831C1 (en) 1989-11-02
ES2044001T3 (en) 1994-01-01
IN172425B (en) 1993-07-24
US4943317A (en) 1990-07-24
PT91761B (en) 1995-05-31

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