Method for treating copper concentrates

Abstract

A method for the pyrometallurgical processing of a sulphide material containing copper, the sulphide containing relatively high quantities of silica and relatively low quantities of iron, wherein the process comprises feeding the sulphide material to a TSL furnace operated under oxidising conditions such that the sulphide material forms blister copper containing between 1.2 and 1.5 wt % sulphur and a slag containing between 7 and 13 wt % copper.

Claims

1. A method for the pyrometallurgical processing of a sulphide material containing copper, the sulphide containing between about 10 wt % and 40 wt % silica and less than approximately 20 wt % iron, the method comprising feeding the sulphide material to a top submerged lance furnace operated under such conditions that the sulphide material forms blister copper and a slag having a CaO/SiO.sub.2 ratio of between 0.30 and 0.55 by weight and an SiO.sub.2/Fe ratio of between 1.8 and 2.8 by weight.

2. The method according to claim 1 wherein the sulphide material is a froth flotation concentrate.

3. The method according to claim 1 wherein the sulphide material contains more than about 20 wt % copper.

4. The method according to claim 1 wherein the top submerged lance furnace contains a bath of molten material therein, at least a portion of the molten material comprising the slag.

5. The method according to claim 4 wherein the top submerged lance furnace includes one or more top entry lances, and wherein a lower end of each of the one of more top entry lances is submerged within the bath of molten material during operation.

6. The method according to claim 4 wherein the top submerged lance furnace is operated such that the temperature of the bath of molten material is within a range of from 1100 C. to 1450 C.

7. The method according to claim 6 wherein one or more temperature modifying substances adapted to assist in achieving a desired bath temperature are added to the top submerged lance furnace.

8. The method according to claim 4 wherein the top submerged lance furnace is operated such that the composition of the slag corresponds to a low melting temperature area of a CaOSiO.sub.2FeO.sub.x phase diagram.

9. The method according to claim 8 wherein the composition of the slag is at or close to a trydimite saturation point.

10. The method according to claim 1 wherein the TSL furnace is operated under oxidizing conditions.

11. The method according to claim 1 wherein at least one slag chemistry modifying substances are added to the TSL furnace.

12. The method according to claim 1 wherein the blister copper contains up to 1.6 wt % sulphur.

13. The method according to claim 1 wherein the slag contains between about 7 wt % and 13 wt % copper.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows:

(2) FIG. 1 illustrates a ternary phase diagram of the CaOSiO2FeOx system.

EXAMPLES

(3) Pilot Plant Trials

(4) A suitable sulphide copper concentrate from a local mine was subjected to smelting trial. The pilot plant trials were conducted in a pilot plant size ISASMELT furnace. The furnace consists of a cylindrical furnace with an internal diameter of approximately 305 mm and a height of approximately 1.8 m. The vessel is lined with chrome-magnesite refractory bricks, followed by high alumina bricks and a kaowool lining to the shell. A mass flow control is used to inject natural gas, and air into the bath via a 29 mm inner diameter stainless steel lance. The solid material fed to the furnace is added in known amounts to a calibrated variable speed conveyor belt which drops the feed onto a vibrating feeder and then through a chute at the top of the furnace. Removal of molten products from the furnace can be achieved by opening the single taphole at the base of the furnace and collecting the materials in cast iron ladles. If necessary, the furnace can be tilted around its central axis to completely drain the furnace of its contents. The process off-gases pass through a drop-out box and an evaporative gas cooler, before being directed through a baghouse and a caustic soda scrubber, for removal of any dust and sulphur-containing gases, prior to venting to the stack. Bath temperature is measured continuously via a thermocouple, placed through the refractory lining of the furnace. Independent confirmation of the bath temperature is obtained using an optical pyrometer, a dip-tip measurement during tapping or a dip-tip measurement of the slag through the top of the furnace. The pilot furnace is initially heated and then held at temperature between tests by means of a gas burner located in the taphole.

(5) Tables 1-5 show the feed materials provided for the pilot test work and the chemical composition of the feed materials.

(6) TABLE-US-00001 TABLE 1 Composition of the Copper Concentrate used in the smelting tests (wt %) Sample ID Cu Fe S Si Al As Mg Pb Zn Ca K Na Concentrate 33.6 11.2 17.4 11.0 2.89 0.43 0.51 0.06 0.22 0.56 1.45 0.65

(7) Limestone, sourced from Glencore's Mount Isa Mines operation, was used as the flux for these trials. The composition of the limestone flux is shown in Table 2.

(8) TABLE-US-00002 TABLE 2 Composition Limestone Flux used in the smelting tests (wt %) Sample ID CaCO3 Al2O3 Fe2O3 SiO2 Limestone 93.7 0.80 1.10 4.40

(9) Silica, sourced from a local quarry wholesaler, was used as a trim flux and to create the pseudo concentrate. The composition of the silica is shown in Table 3.

(10) TABLE-US-00003 TABLE 3 Composition of Silica Flux used in the smelting tests (wt %) Sample ID SiO2 Al2O3 Fe2O3 FeSO4 Silica Flux 97.95 1.29 0.56 0.20

(11) Coal, used as a supplementary lump fuel during one of the tests, has an analysis shown in Table 4.

(12) TABLE-US-00004 TABLE 4 Composition of Silica Flux used in the smelting tests (wt %) Fixed Sample ID Moisture Ash Volatiles Carbon Sulfur Lump Coal 1.0 11.9 33.8 51.6 1.7

(13) Additional to the traditional fluxes the feed was also doped with cobalt so that the distribution of cobalt could be determined during this testwork. The doping agent select for use in this testwork was Cobalt Carbonate, sourced from a local ceramics supplier. The composition of the cobalt is shown in Table 5. To be able to make sure that the fine Cobalt Carbonate did not carry-over to the off-gas stream it had to be mixed up with an equal portion of water and 5% of lingo-sulphate binder.

(14) TABLE-US-00005 TABLE 5 Composition of Cobalt Flux (wt %) Sample ID CoCO3 SiO2 Lump Coal 90 10

(15) During the smelting of the feed materials in an ISASMELT furnace, oxygen from the lance air is required to burn the sulphide copper concentrate to produce SO.sub.2 gas, blister copper and slag.

(16) A total of 4 separate tests were completed which ranged from 1 hour to 3 hours in duration. In general 10 kg batches of the mixed feed, previously weighed in buckets, were distributed over 1 metre lengths of the feed conveyor, and the speed of the conveyor was adjusted to give the desired feed rate (typically 45-50 kg/h of wet feed). Additions of limestone flux were weighed out and distributed similarly at a fixed addition rate over each 1 metre length of the conveyor. Silica flux and cobalt flux were also added in the same manner, for the purpose of simulating the high-silica and high-cobalt concentrates that are commercially available and suitable for DtB smelting.

(17) The lance tip was then submerged in the slag bath, the feed to the furnace started and the lance flows changed to those required for the smelting of the feed mix.

(18) The temperature of the slag bath was monitored by means of a thermocouple contained in a sheath in contact with the slag bath. The bath temperature was controlled by means of adjustments to the natural gas flow rate and/or the variation in the oxygen enrichment of the lance air.

(19) Samples of the slag for assay purposes were taken at intervals by means of a dip bar lowered to the base of the furnace. The thickness of the slag frozen on the bar gave a good indication of the degree of fluidity of the molten slag. The temperature of the slag could be measured by raising the lance and inserting a temperature probe into the furnace so that it contacted the slag.

(20) At the completion of a smelting test, the feed and was stopped and the lance raised out of the slag bath. The blister copper and slag were then tapped out of the furnace by opening the tap hole with a combination of drill and oxy-lance. Spoon samples of the blister copper and slag were taken plus a sample of the molten slag was granulated by slowly pouring the molten slag into water.

(21) A description of the individual test conditions, including furnace inputs and outputs, bath temperatures (as shown by furnace thermocouple) etc. is given in Table 6.

(22) TABLE-US-00006 TABLE 6 Summary of Results Starting Feed Silica Cobalt Nat Test Bath Dry Total Limestone flux flux Air Oxygen Gas Coal No. kg Feed type kg/h kg kg kg kg Nm3 Nm3 Nm3 kg 6 50 N Parkes 45 93.6 23.39 11.23 138.9 18.64 16.05 Concentrate 7 50 N Parkes 50 150 37.50 18.00 2.84 188.1 40.07 26.78 Concentrate 8 50 N Parkes 50 130 32.50 15.60 2.46 147.5 40.96 24.59 Concentrate 9 50 N Parkes 50 140 35.00 16.80 2.65 161.8 44.50 20.36 8.40 Concentrate Final Slag Blister Test Temp CaO/SiO.sub.2 SiO.sub.2/Fe Copper No. C. % Co % Cu Ratio Ratio kg % S kg 6 1229 0.02 12.52 0.42 2.29 136.3 1.21 14.2 7 1261 0.65 7.93 0.44 2.41 160.4 1.53 30.0 8 1280 0.66 8.11 0.43 2.43 162.6 1.24 24.1 9 1282 0.83 8.30 0.41 2.57 185.0 1.22 17.0

(23) The pilot plant work set out above demonstrates that by controlled oxidation of the copper concentrate, the furnace can reliably produce blister copper with a sulphur content of 1.2-1.5 wt % S, in equilibrium with a slag containing 7-13 wt % Cu. Cobalt reports to the slag under these conditions.

(24) Surprisingly, the pilot plant experimental work also showed that when the invention was conducted in a top entry lance furnace, uncontrollable foaming of the bath did not occur. The present inventors were of the view that uncontrollable foaming was a likely outcome of the process of the present invention prior to conducting the pilot plant work. It will be understood by those skilled in the art that the oxidation state of iron in equilibrium with blister copper is known to have a strong predisposition to forming magnetite within the slag, saturating the slag and creating ideal conditions for slag foam to occur, when blowing air into a bath of molten slag. However, the pilot plant work demonstrated that either no foaming occurred or that a stable foam was generated. The choice of slag composition is therefore appropriate for the task.

(25) In the present specification and claims (if any), the word comprising and its derivatives including comprises and comprise include each of the stated integers but does not exclude the inclusion of one or more further integers.

(26) Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases in one embodiment or in an embodiment in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

(27) In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.