METHOD FOR CONTINUOUSLY CONVERTING NICKEL-CONTAINING COPPER SULPHIDE MATERIALS

Abstract

The present method can be used for converting nickel-containing copper sulphide materials. A method for continuously converting nickel-containing copper sulphide materials into blister copper, waste slag and a copper-nickel alloy includes smelting the materials together with SiO2 and CaO-containing fluxes and coal in a Vanyukov converting furnace to produce blister copper, gases with a high concentration of SO2, and slag with an SiO2/CaO concentration ratio of from 3:1 to 1:1, in which the sum of the iron, nickel and cobalt concentrations is not more than 30 wt %, at a specific oxygen consumption in the range of 150-240 nm3 per ton of dry sulphide material for conversion, and depleting the slag in a separate unit, namely a Vanyukov reduction furnace, using a mixture of an oxygen-containing gas and a hydrocarbon fuel at an oxygen consumption coefficient () in a range of from 0.5 to 0.9, together with coal, to produce waste slag and a copper-nickel alloy. The technical result is the production of blister copper, waste slag and a copper-nickel alloy using a continuous method, while separating the processes of conversion and reduction into separate units, namely two single-zone Vanyukov furnaces.

Claims

1. A method for a continuously converting nickel-containing copper sulphide materials into blister copper, waste slag and copper-nickel alloy comprising oxidizing smelting along with SiO.sub.2 and CaO-containing fluxes and coal to produce blister copper, gases with a high concentration of SO.sub.2, slag with an SiO.sub.2:CaO concentrations ratio of from 3:1 to 1:1 in which a sum of iron, nickel and cobalt concentrations is not more than 30 wt %, at a specific oxygen consumption in a range of 150-240 nm.sup.3 per ton of dry sulphide material for conversion, and depleting this slag using a mixture of oxygen-containing gas and a hydrocarbon fuel at an oxygen consumption coefficient () in a range of from 0.5 to 0.9 along with coal, characterized in that the depletion of the slag is conducted in a separate unit, namely a Vanyukov reduction furnace, thereby producing a waste slag and a copper-nickel alloy.

2. The method of claim 1 characterized in that producing copper-nickel alloy, being a basis for producing commercial products while depleting molten slag.

3. The method of claim 1 characterized in that supplying a CaO-containing flux to oxidizing smelting along with a SiO.sub.2-containing flux to produce slag with SiO.sub.2:CaO concentrations ratio of from 0.4:1 to 3:1.

4. The method of claim 1 characterized in that for reduction supplying coal in an amount of up to 15% of weight of slag produced at the oxidation stage.

5. The method of claim 1 characterized in that supplying by-products to the Vanuykov converting and reduction furnaces.

6. The method of claim 5 characterized in that the by-products contain copper and nickel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The claimed method for continuously converting nickel-containing copper sulphide materials in a complex of two furnaces, namely two Vanuykov furnaces, is presented as shown in FIG. 1. Nickel-containing copper sulphide materials are added along with SiO.sub.2 and CaO-containing fluxes to a Vanuykov converting furnace 1 of continuously converting complex. Oxygen-air mixture and gaseous fuel are added to Vanuykov furnace 1 through furnace tuyeres 2. Blister copper formed during a smelting process in Vanuykov converting furnace 1 is continuously released into a mixer 3, and slag with a high content of copper, nickel and iron passes to a second furnace of continuously converting complex, namely to Vanuykov reduction furnace 4, where it is depleted by reducing gas-air mixture along with coal to produce waste slag and copper-nickel alloy. Reducing gas-air mixture is formed as a result of natural gas combustion in oxygen-air mixture under oxygen shortage conditions. A temperature of oxidation and reduction processes is maintained at a level of 1350 C.

[0018] Smelting products of converting furnace 1 (blister copper) and of reduction furnace 4 (waste slag and copper-nickel alloy) are assumed to be released continuously. To release the smelting products, siphon-type devices (not shown in the drawing), located in the opposite ends of furnaces, are provided. A continuity of the proposed process in a form of complex of two Vanuykov furnaces 1 and 4 paves the way for maintaining constancy of levels of slag and blister copper in the Vanuykov converting furnace 1, and slag and copper-nickel alloy in the Vanuykov reduction furnace 4, that is an important advantage of this process. Blister copper is continuously released through a siphon-type device into the mixer 3 designed for it and then is sent to anodic refining to produce copper anodes. A specific of the slag composition of the new method oxidizing stage is that it contains copper and nickel at a rate of 4:1-5:1, which is favourable for producing valuable copper-nickel alloy, for instance a melchior alloy. Copper-nickel alloy with some content of iron, which is a basis for producing commercial products, is produced as a result of deep reduction of this slag to spoil standards. This copper-nickel alloy can be converted in pyrometallurgical nickel production, or directed to a stage of oxidizing refining in order to remove iron and produce commercial products, which composition is determined for Russia conditions by the State standard (melchior alloy, neusilber etc.).

[0019] An important feature of the developed method is the fact that in case of converting materials containing precious and platinum group metals in the Vanuykov converting furnace 1, these metals are almost completely recovered to blister copper and are not transfered to slag, fed in the Vanuykov reduction furnace 4. It provides a production of copper-nickel alloy being almost free from precious, platinum group metals in the Vanuykov reduction furnace 4.

[0020] It is obvious that the alloy of the Vanuykov reduction furnace 4 is more preferable to be supplied to a customer as a commercial product after refining and casting operations.

[0021] Slag produced in the Vanuykov reduction furnace 4 is the waste one. Its chemical composition allows to use it in the building industry or for the stowing of mines.

[0022] All sulphur contained in nickel-containing copper sulphide materials passes to a gaseous phase of the Vanuykov converting furnace 1.

Embodiment of the Invention

[0023] Since oxidation stage of continuously converting process, conducted in the Vanuykov converting furnace with production of blister copper has passed extensive studies and currently is sufficiently investigated (Tsymbulov L. B., Knyazev M. V., Tsemekhman L, Sh. A method for converting copper sulphide materials to blister copper//The patent of the Russian Federation No 2359046 of Sep. 1, 2008. Pigarev S. P. Structure and features of slag melts of the continuously converting nickel-containing copper sulphide materials. Abstract of PhD dissertation St-Petersburg. 2013. 21 p.), the proposed invention is based on data of experimental studies of the reduction stage of the new method, with searching conditions providing production of waste slag and copper-nickel alloy, which is a basis for producing commercial products, for instance melchior alloy, which is widely used nowadays in industries as the alloy with high anticorrosion properties, and also for producing household products and jewelry.

[0024] A methodology of the experimental studies was as follows. An alundum reactor with an alundum crucible inside, which contains an initial slag, namely oxidative stage slag, with a following composition, wt %: Cu-17.9; Ni-5.6; Fe-23.1; Co-0.135; SiO.sub.2-27.5; CaO-11.9; Al.sub.2O.sub.3-3.1; MgO-0.79. Then the furnace was run with changing an inductor voltage, and heated up to operating temperature of 1350 C.

[0025] After the slag smelting a melt was scavenged via beryllium oxide tube with a reducing gas mixture of the following composition, vol %: CO-44; CO.sub.2-38; H.sub.2-18. Oxygen and the reducing gas mixture partial pressure corresponded that of oxygen in a mixture produced during natural gas combustion at the alpha value ()=0.6.

[0026] In laboratory experiments a duration of the melt scavenging by the gas mixture was varied from 0 to 50 minutes. A gas mixture flow rate was 0.8 l/min. After completion of scavenging, the melt was allowed to settle for 15 minutes and then the furnace was turned off. After that the crucible with the melt was removed out of the furnace and cooled, and slag was separated from metal alloy.

[0027] After appropriate sample preparation, slag and metal alloy have been analyzed by methods of atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry.

[0028] Chemical compositions of metal alloy and slag, produced as a result of conducted experimental studies, are presented in TABLE 1.

[0029] At first, we consider changes in the slag composition according to copper and nickel content when changing a time of the molten slag scavenging by the reducing gas mixture. This dependency is presented in FIG. 2.

[0030] As can be seen at the FIG. 2, with the increase of time of molten slag scavenging by reducing gas mixture, there is a sharp decrease in copper content in slag, and starting from the 17.sup.th minute of scavenging there is also a substantial decrease in nickel content in molten slag on the background of decreasing copper content. After 35.sup.th minute of the molten slag scavenging the decrease in copper and nickel concentrations in slag becomes extremely insignificant.

[0031] As can be seen from the graph presented in FIG. 3, a decrease of copper () and nickel (b) content in the slag is accompanied by an increase a nickel content in metal alloy, reaching a maximum of its content at a level of 21.5% at copper and nickel concentration in slag at a level of 0.8% and 0.4% respectively. Further decrease of copper and nickel content in molten slag to standard values is characterized by a decrease of nickel content in metal alloy, that is associated with a start of active iron recovery and its transfer to metal alloy. This will be discussed subsequently in details.

[0032] As the proposed new method for continuously converting nickel-containing copper sulphide materials assumes simultaneous production of, on the one hand, an alloy with a certain rate of copper and nickel and with a certain standard content of iron in it, and on the other hand, waste slag, it is necessary to choose optimum technological parameters to focus on while implementing thereof.

[0033] So let's consider dynamics of changes in slag and copper-nickel alloy composition during scavenging by reducing gas mixture (FIG. 4).

[0034] FIG. 4 illustrates a line graph, which characterizes changes in nickel and iron content in metal alloy depending on time of molten slag scavenging by reducing gas mixture. Changes in copper and nickel content in slag depending on time of molten slag scavenging by reducing gas mixture are also plotted on the considered graph.

[0035] First of all, an attention on the presented line graphs should be paid to a correlation between copper and nickel content in waste slag and nickel and iron content in metal alloy, produced as a result of reduction. There is a significant decrease in concentrations of both copper and nickel in slag during active nickel reduction from 5.sup.th to 30.sup.th minutes of scavenging, but this residual content is still rather high (Cu-0.8%; Ni-0.4%) and slag cannot be considered as a waste one.

[0036] Only when active iron reduction starts, it becomes possible to decrease copper and nickel concentrations to spoil contents.

[0037] Thereby, on the one hand, in order to obtain a standard iron content in copper-nickel alloy, particularly, in melchior (Fe0.5%), it is necessary to strive for a minimal rate of iron reduction during the depletion process.

[0038] On the other hand, deep reduction of slag according to copper and nickel contents is only possible when producing an alloy with an iron concentration of 5% or more, that will require additional expenditures at a stage of refining when producing trademark copper-nickel alloys. In this regard, it is recommended to conduct the depletion process until the iron concentration in the copper-nickel alloy reaches 6%. In this case, waste slag with a following composition will be obtained, wt %: Cu-0.45; Ni-0.17; Fe-30.3; SiO.sub.2-37.5; CaO-16.2; Al.sub.2O.sub.3-5; MgO-1. A composition of copper-nickel alloy will be as follows, wt %: Cu-73.2; Ni-20.5; Fe-6.1.

[0039] To produce commercial products from this alloy, for instance in a form of melchior alloy, it is necessary to carry out a stage of refining, at which iron content in copper-nickel alloy can be decreased to standard values. Cu:Ni ratio in produced refined metal alloy will be in range of 4:5-5:1, that matches the composition of commercial products. Slag formed during the oxidative refining process, which base are iron oxides, is supplied to a continuous converting complex, namely to an oxidative stage of the process to the Vanuykov converting furnace 1. It is possible to produce other types of products, which composition is determined for Russia conditions by the State standard. A specific feature of the developed method, as was stated above, is fact that precious and platinum group metals, presented in a raw material, are almost completely transferred into blister copper at a converting stage, and production of new types of products will not cause additional losses of these metals.

INDUSTRIAL APPLICABILITY

[0040] The developed method has a significant advantagepossibility to produce new commercial products according to a short flow chart, that in general substantially reduces metallurgical plant's expenses on the commercial products production.

TABLE-US-00001 TABLE 1 No Duration of Content in alloy, wt % Content in slag, wt % exp. scavenging, min Cu Ni Fe Ni Cu Fe.sub.general SiO.sub.2 CaO Al.sub.2O.sub.3 MgO 1 5 98.97 0.89 0.01 5.11 17.26 23.0 27.1 11.7 3.6 0.82 2 10 98.90 1.05 0.01 5.09 12.12 24.8 28.9 12.5 3.9 0.88 3 15 95.62 4.24 0.02 4.40 10.60 25.4 29.6 12.8 4.0 0.90 4 21 92.85 7.00 0.03 3.06 6.85 26.9 31.3 13.5 4.2 0.95 5 25 90.87 8.99 0.04 1.49 5.19 27.5 32.1 13.8 4.3 0.97 6 27 87.70 12.18 0.05 1.32 4.29 28.4 33.1 14.3 4.4 1.01 7 29 80.46 17.79 0.49 0.40 1.54 30.5 38.7 15.4 4.7 1.09 8 30 76.72 21.50 1.72 0.42 0.82 30.9 36.4 15.8 4.9 1.11 9 31 75.68 21.49 2.73 0.29 0.67 30.8 36.9 15.9 4.9 1.12 10 32 74.93 21.37 3.68 0.23 0.58 30.7 37.2 16.0 5.1 1.13 11 35 74.06 21.20 4.72 0.19 0.52 30.5 37.4 16.1 4.9 1.14 12 37 73.30 21.02 5.66 0.16 0.48 30.3 37.6 16.2 5.3 1.14 13 40 72.82 20.26 6.27 0.15 0.25 30.2 37.7 16.3 5.4 1.21 14 45 70.03 20.24 9.61 0.11 0.43 29.4 38.4 16.5 5.3 1.18 15 50 67.95 19.67 12.37 0.09 0.40 28.72 39.1 16.3 5.6 1.23