WO2006110117A2

WO2006110117A2 - Method of manufacturing semi-finished product for ferro- and master alloys

Info

Publication number: WO2006110117A2
Application number: PCT/UA2006/000013
Authority: WO
Inventors: Vladyslav Mikhailovich Sokolov
Original assignee: Vladyslav Mikhailovich Sokolov
Priority date: 2005-04-11
Filing date: 2006-03-17
Publication date: 2006-10-19
Also published as: WO2006110117A3; UA76663C2

Abstract

The present invention provides the method of producing a semi-product for manufacturing ferro- and master alloys and relates to metallurgy, specifically to the production of a metal-containing semi-finished product from wastes. Fine and dustlike oxidized metal-containing waste materials are agglomerated and for reducing the agglomerates are blended with metallic iron- or manganese-base melt with a higher content of silicon and carbon. Then the blend is held until complete separation of the metallic melt and the partially reduced semi-finished product. The technical result lies in broadening the types of the range of the wastes types that can be efficiently recycled.

Description

TITLE METHOD OF MANUFACTURING SEMI-FINISHED PRODUCT FOR FERRO-

AND MASTER ALLOYS BACKGROUND OF THE INVENTION This invention relates to the field of technique and technologies that are applied in metallurgy and, more particularly, concerns the method of manufacturing semifinished product from wastes.

The oxidized wastes in the form of fines, dust and sludge are generated in many productions. They may contain the valuable metals - nickel, cobalt, copper, chromium, manganese, molybdenum, tungsten, niobium (columbium) and also iron. Recycling these wastes is complicated basically by their very fine composition and frequently because of poor content of the metals in them. The common pyrometallurgical technologies used for extraction of metals from oxidized ores frequently are not applicable for the wastes. The dumping of the wastes is also a rather expensive operation since they are commonly environmentally hazardous.

Fines and dust in the form of oxides are recycled. The method stipulating the performance of reduction reactions for wastes in a molten metal is disclosed in U. S. Patent No. 5,324,341 Intern'l Class: C21B 015/00, 28.07.1994), wherein the waste is introduced into melt for its partial reduction by the metal. Another reductant is put into the melt for making complete reduction and dissolution of the waste. The final product may be the first metal-base ferroalloy.

Another method comprising the operation of introducing fines into cast iron by blowing is disclosed in a Technical Program, by A.V. Tarasov, P.A. Kovgan, V.M. Paretsky, entitled "Intensification of reduction of oxide nickel ores", p. 18, presented at the TMS 2004 133^rd Annual Meeting & Exhibition. The industrial realization of the both methods requires the installation of a custom-built unit in addition to a traditional smelting furnace. The unit is designed as a place for complete dissolution of the wastes in the melt.

The closest to the invention is the method of ferronickel production from the Ni- containing oxidised fines and dust that is disclosed in Patent EP 0 643 147 Bl Int, Cl.⁷ C22C 33/04, MKI, 19.05.2004. It stipulates a preliminary production of the semifinished product by reduction of the wastes in the medium of the reduction gas at elevated temperatures. Then the semi-finished product in the form of the partially reduced fines is blended with a solid reductant. The produced blend is smelted in a direct current transferred arc plasma furnace. However the application of this type of furnaces is so far limited in the ferroalloy industry. As a matter of fact the semi-finished product is unfit as a charge material for the submerged arc furnaces that are currently prevalent in ferroalloy industry. Since a composition of the semi-finished product is fine its gas permeability is poor. So stability of a smelting operation is disturbed.

SUMMARY OF THE INVANTION

It is therefore the object of the present invention is to develop the production from the wastes of the semi-finished product for ferro- and master alloys based on application of the equipment that is more traditional in metallurgy and foundry. The considered ferro- and master alloys contains sufficient amount of iron or manganese. So₅ they have some similar properties that are utilized in the invention. They are usually associated into a common type of the alloys.

DETAILED DESCRIPTION OF THE INVENTION

To be more specific, the technical object of the present invention is to work out the method of producing the semi-finished product for the ferro- and master-alloy industry with efficient usage of traditional metallurgical and foundry melting equipment. The technical result which can be achieved with the aid of the invention is an essential broadening the range of the wastes types. The mentioned above brings about significant cost savings.

In accordance with this invention the objective of efficient usage of the conventional equipment is gained by providing a method for producing the semifinished product for ferro- and master-alloy industry comprising applying of metal- containing oxidized wastes in the form of something like fines, dust and sludge for their further partial reduction at elevated temperatures, said method being characterized by said wastes being agglomerated with next blending of the produced agglomerates with iron- and manganese-base melt that having a rather high content of carbon and silicon as the efficient reducing agents, and followed by holding the molten blend for complete separation of the metallic melt and the reduced semi-finished product.

Preferred feature of the invention is that the iron-base melt is in the form of molten cast iron containing 1-15% silicon. That is a common content of silicon in the suitable type of cast irons. Further preferred features of the invention provide a ratio between the waste and the molten cast iron to be arranged in such a way that the cast iron after its application has to contain no more than 0.2 % chromium and no more than 0.1 % of tungsten. Otherwise it is a chance for generation of carbides of these elements that are detrimental for properties of the cast irons. Preferably, the iron-base melt is in the form of molten crude ferronickel. This material always contains the higher contents of carbon and silicon than the grades of terminal ferronickel. Preferred feature of the invention is that the manganese-base melt is in the form of molten high carbon ferromanganese or silicomanganese. The melts of cast irons, crude ferronickel, high carbon ferromanganese or silicomanganese (ferrosilicomanganese) are generated in the several types of metallurgical furnaces. They are namely electric furnaces, such as induction and open or submerged arc ones, cupola, blast furnace and some other ones. The melts can be simultaneously used for their basic purpose after application in the wastes recycling operation. The efficiency of this option is provided by preliminary agglomeration of the wastes in order to avoid direct dissolution of the reducing metals from the wastes in the melt. The major part of the valuable metals should go to the composition of the semi-finished product. The optimal size of a produced agglomerated particle is within 4-50 mm. The smaller particle is completely dissolved in the melt. The larger one interacts with the melt not completely. Thus the result of the reduction of the wastes is not sufficient. Therefore the composition of the melt remains stable during its recycling if the size of the particle tolerates the above limits. Preferred feature of the invention is that the wastes contain at least one metal from the group consisting essentially of nickel, cobalt, copper, chromium, manganese, molybdenum, tungsten, niobium (columbium), iron. Preferably, the wastes are dried and heated before their blending with the melt in order to avoid water or moisture and to exclude the blowing risk during contacting the metallic melt and the wastes. Preferably, the semi-finished product is subjected to beneficiation by removing a non-metallic phase. It is a heterogeneous mixture of particles of iron- or manganese-base alloy and slag that consists mainly of oxides of calcium, magnesium, silicon, aluminum. These oxides are mostly non-reducible at the considered conditions. The metallic part of the semi-finished product may be enlarged by its separation from the non-metallic part. The several methods of beneficiation such as mechanical separation floatation and other are applied. Preferably, a carbon-containing reducing agent is put into the wastes just before the agglomeration operation. The preliminary heating of the wastes is accompanied by its partial reduction in this case. Further preferred features of the invention provide for increasing efficiency of further reduction of the wastes. The carbon-containing reducing agent is put as a binding addition for this purpose.

The manufactured semi-finished product is the cost effective burden material for ferro- and master-alloys industry. It can be smelted in the furnaces of different types with high assimilation by a melt due to essential presence of iron in the metallic part of its composition. The efficient reduction process for the valuable elements from the correspondent non-metallic part takes place in the melt. The iron-base master-alloys with the several elements from the group consisting essentially of nickel, cobalt, copper, chromium, molybdenum, tungsten, and niobium(columbium), are produced. The semi- finished product with the proper chemical composition can be used as a cooling agent during refining ferroalloys in converter. Given below are the examples of various applications of the method of the invention to produce a semi-finished product from a fine waste.

EXAMPLES Example I

The experiment was carried out with application of the dried sludge that was generated at the neutralization plant during manufacturing of cutting tools from artificial diamonds. The composition of the solid part of the sludge is 4.00% Al₂O₃; 24.55% Cr₂O₃; 21.30%; Fe₂O₃; 6.62% NiO; 43.53% gangue. It was slightly damped and mixed with 5% carbon dust for further extrusion. None of binding materials was applied. The produced agglomerates were subjected to drying at the air ambient for their induration. The size of the agglomerates particle varied from 10 to 15 mm. Then the agglomerates were heated and blended in portions with the liquid cast iron that took part as the processing agent. Each portion was 5% from the weight of the agent. Any molten blend formed after introduction of a portion of the agglomerates was held until complete separation of the generated phases. The changes in composition of the cast iron after every next blending operation are shown in Table.

TABLE

Order of introduction Content of elements, % ( bv mass. ) of wastes C Si Cr M

0 4.06 1.02 0.035 0.088

1 3.92 0.94 0.086 0.110

2 3.83 0.74 0.160 0.140

3 3.72 0.57 0.190 0.160 The produced semi-finished product contained 62% metallic iron-containing phase in the form of particles - so called "metal beads". The beads contained 0.5-80% Ni and 0.3-30% Cr. The semi-finished product was efficiently applied in producing ferronickel of FN7 grade (TU 48-3-59-84) that contained 3.8 - 5.3% Ni; 3.5 - 6.0% Si; 1.0 - 2.5% C; 2.0 - 3.0% Cr; 5.0 - 6.5% Cu; 0.4% Co; up to 0.1% Mn. The semifinished product should be used as a burden of a ferroalloy submerged arc furnace without pretreating operations. The product should be also subjected to beneficiation in pneumatic separator for getting up to 90% metallic part in it. In this case it should be used in converter as a cooling agent at the last stages of ferronickel refinement. The cast iron after its usage in the recycling operations followed by additional alloying with silicon should be used in a foundry production. Insignificant content of chromium in the cast iron provides absence of the correspondent carbides in the terminal cast iron if also it contains less than 0.1% tungsten.

Example 2

The experiment was carried out with application of the flue dust of laterite ore with the following composition: 3.0% Ni; 0.1% Co; 22% Fe; 35% SiO₂; 16% MgO; 1.5% CaO; 1.0% Cr₂O₃; 2.0% Al₂O₃. The dust was agglomerated with application of molasses as a binder by briquetting in a roll press. The binder reacted as the carbon- containing reducing agent in the recycling process. Each produced briquette was 30-50 mm in size. The briquettes were subjected to drying at the air ambient. Then they were heated at 800 ⁰C and blended in portions with liquid crude ferronickel that contained 5.5% Ni; 0.26% Co; 1.82% Cr; 5.20% Si; 0.25% S; 1.86% C. Each portion was 5% of the weight of the ferronickel bulk. The produced semi-finished product contained 62% iron-base metallic phase in the form of beads. They contained 0.5 - 4.5% Ni and 0.2 - 1.1% Cr. After magnetic separation the beads were used as cooling agents in operations of ferronickel refining in oxygen converter.

Example 3 The fine waste was in the form of the mixture of high carbon ferromanganese close to the grade HC FeMn that contained 75-82%Mn; > 7% C; > 6% Si; 0.2-0.7% P; ; > 0.03% S and silicomanganese of the grade LC that contained < 60%Mn; > 0.3-0.5% C; 25-35% Si; 0.2-0.5% P; ; > 0.03% S. It had been heavily oxidized due to its long term storing at the air ambient. The mixture was agglomerated with addition of bentonite as a binder at the pelletizing plate. Every of the produced pellets measured 4-8 mm. The pellets were dried at the air ambient. Then they were being heated at 800 ⁰C and were blended in portions with liquid HC FeMn. Each portion was 7% of the weight of the ferromanganese bulk. The obtained semi-finished product contained 63% manganese-base phase in a form of metallic fragments. They contained 65 - 75% Mn. The product should be efficiently applied as the ferromanganese burden of submerged arc furnace.

Example 4

The secondary material was in the form of the mixture with mostly the same composition as mentioned in Example 3 was used. The mixture was agglomerated at the roll press with usage of bentonite as a binder. Each produced briquette was 30-40 mm in size. The briquettes were dried at the air ambient. Then they were heated at 800 ⁰C and blended in portions with liquid silicomanganese of the grade LC. Each portion was 7% of the weight of the silicomanganese bulk. The obtained semi-finished product contained 68% manganese-base phase in the form of metallic fragments. They contained 60 - 80% Mn. The rest is Fe, Si and admixtures. So the metal extraction ratio in the current experiment was higher than in the previous one. This result is associated with the higher reduction potential of LC silicomanganese in comparison with that of liquid HC ferromanganese. The produced semi-finished product was efficiently applied as a burden material for production of ferromanganese in submerged arc furnace.

Thus the wastes that contain nickel, chromium, manganese and iron was considered. It is obvious that other wastes that contain cobalt, copper, molybdenum, tungsten, niobium (columbium) are recyclable by the same method with the equal result due to its similar properties.

It is envisaged that the most efficient results of application of the method of this invention is gained at the foundry shops and the ferronickel or manganese master-alloys plants. The sufficient saving of alloying elements is received together with solving the significant environmental problem for getting rid of the hazardous fine wastes.

Claims

1. A method of producing a semi-finished product for manufacturing ferro- and master alloys comprising the utilization of oxidized metal-containing fine and dustlike wastes, their partial reduction at elevated temperatures, said method being characterized by that for partial reduction the wastes are agglomerated and then blended with liquid metallic iron- or manganese-base melt with a higher content of silicon and carbon followed by holding the blend until complete separation of the metallic melt and the reduced semifinished product.

2. The method according to claim 1 wherein said iron-base melt is in the form of molten cast iron containing 1 - 15 % of silicon.

3. The method according to claim 2 wherein the ratio between the wastes and the molten cast iron is arranged in such a way that the cast iron after its utilization contains no more than 0.2 % of chromium and no more than 0.1 % of tungsten.

4. The method according to claim 1 wherein said iron-base melt is in the form of molten crude ferronickel.

5. The method according to claim 1 wherein said manganese-base melt is in the form of molten high carbon ferromanganese.

6. The method according to claim 1 wherein said manganese-base melt is in the form of silicomanganese.

7. The method according to claim 1 wherein said wastes contain at least one metal from the group consisting of nickel, cobalt, copper, chromium, manganese, molybdenum, tungsten, niobium (columbium), iron.

8. The method according to claim 1 wherein said wastes are dried and heated before their blending with the melt.

9. The method according to claim 1 wherein the semi-finished product is subjected to beneficiation by removing of a non-metallic phase.

10. The method according to claim 1 wherein a carbon-containing reducing agent is put into said wastes.

11. The method according to claim 10 wherein the carbon-containing reducing agent is put as a binding addition.