MXPA98003409A - Method for separating tin and if necessary copper from scrap melting, specially tinplate melting or metallic melting - Google Patents

Abstract

The invention concerns a method for separating tin and if necessary copper from scrap melting, specially tinplate melting or metallic melting resulting from processing of garbage or combustion residues which contain metal oxide. The carbon content of the melted mass is set at 3 to 4.2 weight%and hot air, oxygen or oxygen enriched air is blown locally on parts of the surface of the melted mass, whereby the SnO is taken out of the area formed between the carbon enriched bath and the iron oxides resulting from the blowing, with a redox gradient during the gas phase.

Description

PROCEDURE TO SEPARATE TIN. LIKE. IF REQUIRED. COPPER, OF CASTED MASSES OF SCRAP. IN PARTICULAR MASS FLOURS OF TIN PLATE OR METAL FLOW MASSES The present invention relates to a process for separating tin, as well as, if required, copper from melts of scrap melts, in particular melts of tin foil or combustion residues containing metal oxide. In the course of the preparation of waste material or combustion residues containing metallic oxide or slag, certain purification processes have already been proposed in which these slags are purified while forming an iron bath or by the use of an iron bath. Depending on the composition of the starting slags, such melts, which are presented as iron baths, contain a greater or lesser amount of copper. However, the copper contained in crude iron and in particular steel is a metallurgical problem. Copper interferes in the production of flat products such as deep-rolled sheets. Steel plants process more often only those grades of steel that have a copper content of less than 0.1%. With longitudinal products, such as beams and sleepers, structural steels or rails, slightly higher contents of copper can be admitted, but in any case also in these cases the upper limit of the copper content is often less than 0.4% by weight . Copper is introduced through scrap, also in steel production processes, and the amount of copper contained in steel increases as the rate of scrap recycling increases. EP-707083 discloses a method for processing waste material or metal combustion residues containing metal oxide, in which the reduction was carried out after at least partial melt oxidation, slag, under separation of a metal bath. During the course of the reduction, which can be effected, for example, by blowing carbon monoxide and / or carbon dioxide into the material, the copper is introduced into the iron bath, whereby the non-ferrous heavy metals can be separated off. crude bronze shape. After segregation of the crude bronze at a temperature of the order of 1500 ° C, the crude copper having an iron content of the order of 4% by weight was formed, as a general rule, but relatively large amounts were still present anyway. of copper inside the iron bath. The remaining iron alloy typically contains about 8% by weight of copper.

From International Report WO 96/24696 a process for producing crude iron or steel and clinker cement has been known, in which a ferrite slag is formed and this material is similarly reduced in a reduction reactor as that at the same time an iron bath is formed, with the creation of a sintering phase and with the simultaneous combustion of carbon. As in the first mentioned process, the iron bath can then be refined and in this case it is possible that too high copper contents for a certain number of subsequent applications remain in the steel. Even those iron baths used specifically for the refining of slag and in particular the crude iron baths contain more or less high amounts of copper according to the specific cases referring to the histories of the different slags. Another problem with these metallic melts lies in their high tin contents. The tin content within the steel generally ranges from 0.015% to 0.02% by weight, inside the steel. By extrapolation to scrap, on the other hand they will be contained in tin of 0.1% by weight and the presence of tin in quantities So high after creating the scrap melt leads to products that can only be used to a limited extent. This is even more applicable in the case of melts of tin foil and therefore the conclusion can be drawn that it is of great economic importance to have a simple and reliable process for separating tin in order to obtain economically melted products. tools. The processes to melt the scrap and in particular the processes to create melts of tin foil, to date and as a rule have generated products that can only be used to a limited extent and that are no longer suitable for a certain number of applications. A tin content of more than 500 ppm will result in a markedly reduced force and certain deformation properties of the product to the extent that it is evident that a simple and safe process for separating tin can fundamentally improve the melt product. The task of the present invention is to reduce in a particularly simple way the content of tin and at the same time, if so required, the copper content of the metallic melts or melts of scrap in which, in order to solve this problem, it is proposed that the carbon content of the melt be adjusted to a level of 3 to 4.2% by weight and then blow hot wind, oxygen or oxygen enriched air locally over certain partial regions of the surface of the melt, during the which SnO is discharged through the gas phase, from the zone of the "Redox" gradient formed between the carbon rich bath and the iron oxides produced by blowing from above. By adjusting the carbon content of the melt to 3 to 4.2% by weight, a typical reduction potential for raw iron is set. By blowing from above some hot wind or oxygen locally above certain partial regions of the surface of the melt bath a "redox" gradient is formed between a locally developed iron oxide phase and the iron carbon within the bath. This "redox" gradient allows the selective oxidation of tin to bivalent tin and in this way causes the SnO to be continuously separated by evaporation from the equilibrium state within the phase of the redox gradient between the iron oxide phase and the carbon of iron due to the high vapor pressure of SnO. Thus the iron oxide is continuously removed and in those regions above which such separation of tin oxide, which are in the bivalent phase, is possible, there is a limitation with respect to a spherical cap surrounding the iron oxide phase, zone where a very marked redox gradient is exhibited. A high carbon content within the melt is required to maintain this redox gradient. Here it is feasible to remove from this zone formed between the iron oxide phase and the iron carbon, through the gaseous phase, also material such as arsenic in the form of trivalent oxide (As203) in addition to SnO. The complete separation of tin, is feasible, is feasible as a rule with periods of blowing less than 20 minutes. The oxides of As-III can advantageously be removed together with the volatile SnO. When hot wind or air enriched with oxygen is used, it must be protected in the sense that there is no inconvenient increase in the nitrogen content inside the bath. According to another preferred advancement of the invention, such protection is achieved because hot air is blown from above until the carbon content has been burned to a level of less than 0.5% by weight, after which it is further refined with help of oxygen or air enriched with oxygen. In order to guarantee the redox gradient required for the safe production of SnO, the invention advantageously contemplates proceeding in such a way that the carbon content within the bath during local blowing from above oxygen is maintained between 3 and 4.2% by weight, by blown introduction of carbon or carbon carriers. The jet, that is, the air oxygen lance, is directed in this case to a combustion point where the formation of the transition zone that exhibits the redox gradient towards the surrounding iron carbon is ensured. The adjustment and maintenance of the respective carbon content ensures the presence of the corresponding redox gradient throughout the blowing time and thus the safe separation is achieved by the evaporation of SnO from the transition zone, whereby the tin present in metallic form it can be oxidized to SnO in a selective and quantitative manner. The process according to the invention is advantageously carried out in such a way that the oxygen is fed through a lance that blows from above and carbon is introduced through bottom pipes corresponding to a converter, and it is advantageous here to proceed such that the zone exhibiting the redox gradient is maintained until the tin content is less than 500 ppm. By adjusting the melt to a high carbon content, which can approach the degree of carbon saturation within the iron, phase separation can already be achieved previously in the presence of a high copper content and here it is advantageous proceed in such a way that before the evaporation of SnO the copper is separated by phase separation of a molten mass saturated with carbon after which the iron-rich phase is subjected to a tin separation. The high carbon content causes the formation of the two phases that allow the fundamental exhaustion of copper if so required. In addition, the unwanted copper can then be advantageously separated by the system according to which this separation of the copper is carried out after removal of the tin, by introducing sulfur into the metal melt. The temperature of the melt, in particular in the case of melts of tin foil and a carbon content of the order of 4.2% by weight, amounts to an approximate level of 1350 ° C. In the area of the incidence of the oxygen jet coming from the oxygen lance, or from the air enriched with oxygen, iron oxides II and also iron III oxides are formed in the first instance and these materials together with the carbon contained in the iron then gives rise to the formation of the required zone that exhibits a gradient of redox, in the area of the point of combustion of the lance and in turn thus achieves a safe oxidation of metallic tin to SnO and consequently its separation through of the gas phase. Of course, an economical operation of the process is feasible if inexpensive grades of carbon are used, for example, as it contains a high degree of sulfur, a residue containing carbon from the distillation of crude oil with a sulfur content of the order of 7% by weight and other similar materials to achieve the fusion and in particular the fusion of scrap. The resulting introduction of a high degree of sulfur can be used directly to reduce the copper content. In order to effectively decipher the copper-charged melts, it is advantageously proceeded in such a way that the copper layer formed during the fusion with the carbon carriers containing sulfur is removed from the iron bath at temperatures above 1400 ° C and in particular of the order of 1500 ° C. If high quality charcoal is used or when too low a quantity of sulfur is introduced, it is advantageously proceeded in such a way that sulfur is introduced or applied in an at least stoichiometric amount, based on copper, after which the phase is removed of liquid Cu2S (copper layer). When sulfur is introduced or the sulfur is applied to the bath, a copper layer or mat is formed, which can be removed. The amount of sulfur introduced into the raw iron or into the steel melt during feed or application can then be removed again through a conventional desulphurisation, achieving in this case certain additional synergistic effects, in particular in the production of pozzolana slag or clinkers. As already described in EP-707083, in the case of raw, carbon-rich melts, it is possible to carry out phase separation during a first stage. Considering the quantities of copper that remain in the iron-rich and copper-poor phase, in this case it will suffice to supplement the iron-rich phase with sulfur in order to reduce the general introduction of sulfur. Advantageously, the process according to the invention is therefore carried out in such a way that the iron-rich, carbon-rich melts are melted or used as raw iron baths after which in a first step of the process it carries out a phase separation, that is to say, a phase rich in iron is created which contains copper in amounts of 0.5 to 2% by weight and a phase rich in copper containing residual irons in amounts of less than 10% by weight, after which the iron-rich phase is supplemented with sulfur and the supernatant phase of Cu2S is removed. The introduction of sulfur can be effected in a particularly simple manner in the form of sulfur vapor. Advantageously, the process according to the present invention is carried out in such a way that sulfur is introduced in the form of sulfur vapor in a more than stoichiometric amount, based on copper, the sulfur vapor being preferably used in an amount greater than stoichiometric amount, based on copper, with a factor of 1.5 to 2.5. The desulfurization of the iron or steel bath after extracting the copper sulfide phase can be carried out in a simple manner, using CaC2 and / or MgO to desulfurize the metal bath. Advantageously, on the other hand, the clinker, pozzolanic slag or waste incineration slag with a basicity (CaO / SiO2) between 1.3 and 1.7 is used for the desulphurisation, this procedure having the advantage that the clinker or the slag pozzolanic incorporates the sulfur from the crude iron bath practically quantitatively into the interior of the clinker structure. Such a procedure is advantageous from the technological point of view of cement since the addition of gypsum in the production of cement is reduced here. In a particularly simple manner, sulfur can be introduced by means of submerged pipes. The addition of elemental sulfur to steel, which, as mentioned at the beginning will preferably be carried out in at least stoichiometric form, based on the Cu content of the steel, causes the formation of Cu2S droplets. Since they are lighter than the steel melt, such droplets of the copper layer will float on the surface of the steel. Thus, the copper layer in liquid form can be removed without problem, and the remainder of the liquid copper layer remaining in the liquid steel segregates in the solidified steel as a micro-homogeneity. Such shortcomings of micro-inhomogeneity in the deep deep drawing do not represent any adverse effects of any kind nor do they form local electrochemical elements, thus reducing the corrosion of steel. However, in steel desulfurization it is necessary to maintain temperatures of the order of 1650 ° C while a correspondingly lower temperature level can be chosen after carburization or after loading of the crude iron. A temperature level of the order of 1500 ° C at the beginning is sufficient for the desulfurization of the crude iron. The solubility of the liquid copper in the melted raw iron is reduced by the carbon and thus the formation of a two-phase melt with a suitably high content of carbon is generated. With an effectively high carbon content, an iron-rich phase containing about 1% by weight of copper as well as a copper-rich phase and containing approximately 6% by weight of iron can be formed, the two phases, among them, decanting at approximately 1500 ° C. The crude iron fractions as can be used in the embodiment of the present invention typically have copper contents ranging between 0.1% and 8% by weight. The copper-rich fraction withdrawn can be delivered to a first copper plant, with a distribution margin. The iron-rich fraction can then be discovered by sulfurization, whereby the iron-containing copper sulphide will float on the raw iron bath to be removed. Likewise, this copper sulphide can basically be delivered to a primary plant with a low contribution margin. The crude iron left behind has, as a rule, a relatively high content of sulfur in the order of a certain percentage by weight. A typical amount of sulfur is of the order of 2% by weight. Desulfurization is feasible in a conventional manner under basic and reduction conditions, for example, by means of calcium or magnesium carbide, after which refining to steel can be carried out. If clinker or pozzolanic slags are used to desulfurize the raw iron bath, sulfur contents of less than 60 ppm can be obtained, without problem, within the crude iron. Common devices in secondary metallurgy such as purged buckets, as well as processes called RH or DH can be used in the sulfurization process. The introduction of sulfur vapor can be carried out in a simple way through submerged pipes. In particular, when clinker or liquid pozzolan slag phases are used, or a waste incineration slag with a basicity (CaO / Si02) between 1.3 and 1.7, the improvement in the technological properties of the cement is simultaneously achieved. the desulfurization of the raw iron bath, since the agglutination or the setting of sulfur inside the clinker gives rise to a certain number of advantages, as mentioned above. In the following, the invention will be explained in greater detail by way of an exemplary embodiment. Steel slag was melted in a KS type converter (bottom-blown converter, belonging to the "OBM family") under the continuous bottom blowing of low-priced petroleum coke, with a high sulfur content (residue containing carbon from the distillation of crude oil with a sulfur content of 7%). The starting analysis of the steel slag (waste slag, tin foil cans) revealed the following values: A molten mass of iron saturated with carbon was obtained to the maximum extent (3.2% Co) at a temperature of the order of 1350 ° C. A so-called "copper layer or mat" was formed, in which nickel and iron, as well as copper, were dissolved, formed by sulfur introduced by petroleum coke. This copper mat or layer is a highly liquid complex sulfide consisting of Fe, Cu, Ni and traces of other metals ("sulfide formers"). The metals Zn, Pb as well as some phosphorus pass into the gas phase. The copper layer was removed from the iron bath at a level of 1500 ° C. The crude iron left behind still had a copper content of the order of 500 ppm. The desulfurization was then carried out to approximately 1000 ppm of sulfur in the iron bath by means of the slag obtained from the incineration of waste (CaO / Si02 between 1.3 and 1.7). After that, the desulfurized iron bath was "undone" by a hot wind jet (1100 ° C). About 30 to 90 Nm3 of hot air per ton of crude iron were required. This de-annealing procedure was completed within 10 to 20 minutes. The final tin content of the crude iron thus obtained was less than 200 ppm. The raw iron melt had a bath temperature of the order of 1450 to 1550 ° C and the final carbon content reached about 1.5%. Hot air was refined until a carbon content of 0.5% was achieved. The "final refining" was carried out by means of the so-called LD process or OBM with technically pure oxygen in order to obtain final nitrogen contents as low as possible inside the crude steel.

Claims (18)

CLAIMS;

1. A method for separating tin as well as, if so required, copper, from slag melts, in particular tin foil melts or metal melts as they are formed in the processing of waste material or waste. combustion containing metallic oxide, characterized in that the carbon content of the melt is adjusted to 3% up to 4.2% by weight because a hot wind, oxygen or oxygen enriched air is blown locally onto partial regions of the surface of the bath of the melt, by which the SnO is discharged through the gas phase, from the zone exhibiting a gradient of "redox" (reduction / oxidation) formed between the carbon-rich bath and the iron oxides produced by the blowing from above.

2. A method according to claim 1, characterized in that a hot wind is blown from above until the carbon content is burned to a level of + 0.5% by weight after which refining is continued by oxygen or air enriched with oxygen.

3. A process according to claim 1 or 2, characterized in that oxides of As-III are removed together with volatile SnO.

4. A process according to claims 1, 2 or 3, characterized in that the carbon content within the bath during local blowing from above is maintained at a level of 3 to 4.2% by weight by the introduction of carbon or carbon carriers, by blowing .

5. A method according to any of claims 1 to 4, characterized in that oxygen is fed through a lance that blows from above and carbon is introduced through lower pipes of a converter.

6. A process according to any of claims 1 to 5, characterized in that the zone exhibiting the redox gradient is maintained until the tin content at a level below 500 ppm is exhausted.

A process according to any of claims 1 to 6, characterized in that before evaporating the SnO, copper is separated by phase separation of a molten mass saturated with carbon, after which the iron-rich phase is subjected to separation. tin.

A process according to any of claims 1 to 7, characterized in that a separation of copper is carried out before or after the separation of tin, by introducing sulfur into the metal melt.

9. A process according to any of claims 1 to 8, characterized in that the scrap is melted while charging charcoal containing sulfur or coke, such as, for example, petroleum coke.

10. A process according to claim 9, characterized in that the copper layer or mat formed during the fusion with carbon carriers containing sulfur is removed from the iron bath at temperatures of more than 1400 ° C, in particular of the order of 1500 °. C.

A method according to any of claims 8, 9 or 10, characterized in that sulfur is introduced in an at least stoichiometric amount, based on copper, or such sulfur is applied to the material, after which the liquid phase formed is removed of Cu2S (mat or copper layer).

12. A process according to any of claims 1 to 11, characterized in that the iron-rich melts are saturated with carbon or used as raw iron baths after which a separation of the iron is carried out in a first step of the process. phases in a phase rich in iron and containing copper in amounts of 0.5 to 2% by weight and a phase rich in copper and containing residual iron in amounts of less than 10% by weight, after which the phase is supplemented rich in iron with sulfur and the supernatant phase of Cu2S is removed.

13. A process according to claims 8 to 12, characterized in that sulfur is introduced in the form of vapor of sulfur in an amount more than stoichiometric, based on copper.

14. A process according to any of claims 8 to 13, characterized in that the sulfur vapor is used in an amount greater than the stoichiometric amount, based on copper, by a factor of 1.5 to 2.5.

15. A process according to any of claims 8 to 14, characterized in that the crude iron bath remaining behind after removing the Cu2-S phase is desulfurized.

16. A process according to claim 15, characterized in that it is used in CaC2 and / or MgO to desulfurize the metal bath.

17. A process according to claim 15 or 16, characterized in that clinker, pozzolanic slag or a waste incineration slag having a basicity (CaO / Si02) between 1.3 and 1.7 is used to desulfurize the metal bath after removing the Cu2S.

18. A process according to any of claims 8 to 17, characterized in that sulfur is introduced through submerged pipes.