AU2010236082A1

AU2010236082A1 - Flotation Process

Info

Publication number: AU2010236082A1
Application number: AU2010236082A
Authority: AU
Inventors: Robert Andrew Alford; Igor Ametov; Stephen Richard Grano
Original assignee: BHP Billiton Olympic Dam Corp Pty Ltd
Current assignee: BHP Billiton Olympic Dam Corp Pty Ltd
Priority date: 2009-10-29
Filing date: 2010-10-28
Publication date: 2011-05-19

Description

AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Standard Patent Applicant(s): BHP Billiton Olympic Dam Corporation Pty Ltd Invention Title: Flotation Process The following statement is a full description of this invention, including the best method for performing it known to me/us: - 2 FLOTATION PROCESS FIELD OF THE INVENTION 5 The present invention relates to separating at least one sulfide mineral from an ore or ore concentrate that contains two or more than two different sulfide minerals. 10 The present invention particularly relates to separating at least one copper-containing sulfide mineral from an ore or ore concentrate that contains two or more than two copper-containing sulfide minerals. is The present invention also relates to producing copper from an ore or ore concentrate that contains two or more than two different copper-containing sulfide minerals. 20 The term "ore concentrate" is understood herein to include an ore concentrate separated from gangue using a flotation process. The present invention relates particularly, 25 although by no means exclusively, to separating at least one sulfide mineral such as chalcocite, chalcopyrite, pyrite, bornite and optionally other copper-containing sulfides, from a mixed sulfide ore or ore concentrate that contains these minerals to form at least a first product 30 with a relatively higher Cu:S ratio and a second product with a relatively lower Cu:S ratio. The present invention relates particularly, although by no means exclusively, to separating chalcocite 35 from an ore or ore concentrate that contains chalcocite and at least one other sulfide mineral. 2451887_1 (GHMatters) 28/10/10 - 3 The present invention also relates particularly, although by no means exclusively, to producing copper from mixed sulfide ores that contain such minerals as chalcocite, chalcopyrite, pyrite, bornite and optionally 5 other copper-containing sulfide minerals in the ores. BACKGROUND OF THE INVENTION It is an inherent feature of most ore deposits 10 that the distribution of the various types of ore minerals within the deposit are not homogeneous, which can lead to variations in the composition of ore mined over the area of a mine or over the life of the mine. This can present opportunities or challenges when matching a concentrate of is the minerals to a downstream process. It may be necessary or advantageous to separate multiple concentrates or products from an ore. The separation process may include selective mining or other physical or chemical separating methods. 20 One particular example of this situation occurs in an ore reserve of the applicant. The ore contains chalcopyrite, pyrite, chalcocite, bornite and other copper sulfide minerals. The ore is not homogenous. The Cu:S 25 ratio of the concentrate produced from different samples of ore varies widely, from below 1.0 to over 2.0. The opportunity exists to produce multiple concentrates for multiple downstream processes. For example, an individual commercial smelter may put a premium on concentrate with 30 Cu:S ratio in the range 1.0 to 1.3. The present invention is concerned with addressing the above opportunity and providing an alternative to selective mining as a means of separating 35 sulfide minerals on a basis of Cu:S ratio. 2451887_1 (GHMatters) 28/10/10 - 4 SUMMARY OF THE INVENTION s In a first aspect, there is provided a process of separating at least one sulfide mineral from an ore or an ore concentrate that contains two or more than two different sulfide minerals, said process including: conditioning a slurry of the ore or ore 10 concentrate with a conditioning agent to increase or depress the floatability of one or more of the minerals; subjecting the conditioned ore to one or more flotation stages to separate the minerals selectively into a float fraction and a tailings fraction according to is mineral type and produce at least a first product having a relatively high Cu:S ratio and a second product having a relatively low Cu:S ratio. The process may further include a step of 20 producing the ore concentrate by subjecting an ore to flotation to separate the ore concentrate from a gangue phase. The sulfide minerals may be any one or more of 25 chalcocite (Cu 2 S), chalcopyrite (CuFeS 2 ), pyrite (FeS 2 ), and bornite (Cu 5 FeS 4 ). The first product may include chalcocite and/or bornite and the second product may include chalcopyrite and/or pyrite. The second product may contain chalcopyrite as a major component and the first 30 product may contain chalcocite as a major component. The conditioning step may be carried out at an elevated temperature, i.e. a temperature above ambient temperature. 35 The elevated temperature may be from ambient temperature up to the boiling point of the slurry. 2451887_1 (GHMatters) 28/10110 -5 Preferably the temperature is in the range of 40 0 -90 0 C, more preferably from 60*-85 0 C. The conditioning agent may include an oxidant. It 5 may be selected from hydrogen peroxide, an oxygen containing gas such as air, oxygen gas or a oxygen and sulphur dioxide mixture, sodium hypochlorite (NaClO), hydrogen peroxide, potassium permanganate, potassium dichromate and ozone. Preferably, the oxidant comprises an 10 oxygen containing gas, such as an oxygen and sulphur dioxide mixture. The conditioning agent may be oxygen gas and the second product reports to the tailings fraction and the is first product reports to the float fraction. The slurry may be conditioned with oxygen gas in the conditioning step for a period of time from 60-180 minutes. The first product may have a Cu:S ratio above a 20 minimum of 1.6:1 required for example, by a direct to blister smelter such that it can be used as a feedstock for the smelter without difficulty. The second product having the comparatively lower 25 Cu:S ratio may be used as a feedstock for another downstream processing operation for recovering copper from the concentrate. For example, the second product may be used in a known 2-stage smelter that requires a Cu:S ratio of 0.9:1 to 1.3:1 in the feedstock for the furnace. 30 In a second aspect, there is provided a process for producing copper from an ore or an ore concentrate that contains two or more different sulfide minerals, said process including: 35 conditioning a slurry of the ore or ore concentrate with a conditioning agent; subjecting the conditioned ore to one or more 2451887_1 (GHMatters) 28/10/10 - 6 flotation stages to separate the minerals selectively into a float fraction and a tailings fraction according to mineral type and produce at least a first product having a relatively high Cu:S ratio and a second product having a 5 relatively low Cu:S ratio; and processing the first product and the second product and producing copper. In a case of a mixed sulfide mineral ore 10 containing chalcopyrite and chalcocite (and optionally other minerals such as bornite), the method may produce a first product having a comparatively high Cu:S ratio in which chalcocite is a major component and a second product having a lower Cu:S ratio in which chalcopyrite is a major is component. The conditioning step may be carried out an elevated temperature, as described above. 20 The processing step may include concentrate smelting, such as via a direct to blister smelter or a 2 stage smelter. The processing step may include other options 25 such as hydrometallurgical-based processing such as leaching. The processing step may include smelting at least one product and hydrometallurgically processing at least 30 another of the products. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments incorporating all aspects of the 35 invention will now be described by way of example only with reference to the Examples and accompanying drawings in which: 2451887_1 (GHMatters) 28/10/10 - 7 Figure 1 is a schematic diagram of the experimental setup of the flotation tests. 5 Figure 2 is a plot of cumulative Cu:S ratio vs cumulative Cu recovery (%) for flotation of an ore concentrate conditioned with oxygen gas at 60 *C and for times of 60, 120 and 180 minutes. 10 Figure 3 is a plot of the size-by-size mineral recoveries for Test 107S (02 purging for 180 min at 60 0 C). Figure 4 is a plot illustrating the effect of oxygen purging time on copper mineral separation. 15 Figures 5(a) to (d) are plots showing size-by size recoveries for chalcocite, bornite, chalcopyrite and pyrite as a function of flotation time. 20 EXAMPLES The experimented setup 10 for the flotation tests conducted in the Examples is shown schematically in Figure 1. In all Examples, 600 g (wet) samples of ore concentrate 25 12 containing chalcopyrite, pyrite, chalcocite and bornite were homogenised and formed into a slurry 14 having a total slurry volume of 1.5 L. The slurry contained around 25% solids having a particle size of 80% less than approximately 25 pm. The slurry was conditioned by purging 30 with oxygen gas 16 in a 5 L glass beaker 18 continuously stirred with an overhead stirrer 20 for varied periods of time and flowrates of oxygen. Flotation tests were carried out in a 2.5 L flotation cell 22 using sodium ethyl xanthate as the flotation reagent, with the impeller speed 35 maintained at 650 rpm. Air flow rate was 5 L/min. During the tests pH, Eh, DO and temperature were monitored. Measurements of mineral separation were taken at incremental time periods of 1, 4, 5 and 10 minutes (the 2451887_1 (GHMatters) 28/10/10 -8 corresponding cumulative flotation times are 1, 5, 10 and 20 minutes). Example 1 5 The ore concentrate slurry was purged with oxygen gas for varied periods of time ranging from 60 to 180 min at a temperature of 60 0 C. Oxygen purging flow rate was typically 5 L/min. 10 Table 1 presents the results of the differential flotation tests conducted on a number of ore concentrate samples. For each test the Cu:S ratio is presented for the feed concentrate, the float fraction and the tails 15 fraction. In addition the Cu grade and Cu recovery are presented for each of the float and tails fractions. Each shaded row gives the flotation results for a concentrate composition without conditioning and the following rows present results for the same concentrate composition after 20 conditioning at 60 0 C for the indicated period of time. Table 1 indicates that satisfactory results were obtained using oxygen purging times equal to or greater than 60 minutes. The degree of separation of the products 25 having high and low Cu:S ratios generally increased as the oxygen purging time was extended to 180 minutes. Figure 2 shows a plot of the cumulative Cu:S ratio as a function of cumulative recovery of Cu (%) for 30 specific test results presented in Table 1 at 60, 120 and 180 minutes respectively. The four data points on each line correspond to the four cumulative values measured on the float fraction collected after 1, 5, 10 and 20 minutes, respectively. 35 2451887_1 (GHMatters) 28/10/10 -9 Table 1: Typical differential flotation results for ore concentrate purged with oxygen at 60 0 C. Calc. Float Tail Test Conditions Feed C u ad CU Cu/S Cu CU Cu/S C/S Grade RecGrd e Ratio Ratio % % % % 83S Baseline 1.27 1.27 35.0 93.9 1.17 13.7 6.1 93S 02 60', 60*C 1.29 1.90 44.9 45.9 1.01 26.3 54.1 97S Baseline 1.46 1.45 39.5 92.9 1.54 17.1 7.1 OIS 02 90', 60*C 1.42 1.60 42.9 70.5 1.13 25.8 29.5 102S Baseline 1.53 1.53 40.9 89.4 1.56 18.1 10.6 105S 02 60', 60 *C 1.52 1.79 45.0 56.3 1.27 29.7 43.7 107S 02 180', 60 0 C 1.53 2.29 53.7 21.3 1.41 33.6 78.7 114S Baseline 1.60 1.57 43.9 78.8 1.74 30.3 21.2 124S 02 60', 60*C 1.61 2.26 51.7 50.8 1.25 31.5 49.2 116S 02 120', 60* C 1.62 2.33 53.1 50.5 1.24 32.0 49.5 49W Baseline 1.08 1.08 62.2 34.0 1.06 37.8 23.4 55W 02 180', 60"C 1.07 1.55 43.0 37.1 0.90 24.3 62.9 56W 02 120', 60 0 C 1.08 1.40 40.8 27.2 1.00 26.4 72.8 57W 0260', 60*C 1.12 1.44 41.1 41.6 0.97 24.6 58.4 92W Baseline 1.08 1.11 33.8 84.7 0.91 19.9 15.3 79W 02 180', 60 0 C 1.05 1.40 41.8 39.0 0.90 26.4 61.0 85W 02 180', 60 0 C 1.11 1.58 44.1 27.8 0.91 23.1 72.2 95W 02 180', 60*C 1.06 1.33 39.7 43.5 0.92 26.3 56.5 97W 02 60', 60 0 C 1.04 1.16 36.2 69.6 0.84 22.7 30.4 140W 02 180', 60*C 1.03 1.35 39.8 51.2 0.82 21.2 48.8 141W 02 120', 60 0 C 1.05 1.33 34.9 47.0 0.88 22.0 53.0 2451887_1 (GHMatters) 28/10/10 - 10 The results in this example indicate that, in the case of oxygen purging, chalcocite generally reports to the float product, while flotation of chalcopyrite and s pyrite is depressed and those minerals generally report to the tails fraction. The results also indicate that bornite reports largely to the tails fraction. This is illustrated in 10 Figure 3, where size-by-size mineral recoveries to the float fraction for Test 107S (02 purging for 180 min at 60 0 C) are presented. Un-sized mineral recoveries to the high and low Cu:S ratio products for Test 107S are presented in Table 2. 15 Table 2: Mineral recoveries to high and low Cu/S ratio products with oxygen purging at 60 0 C and 180 min (results from QEMSCAN analysis) - Test 107S Mineral Recovery to High Cu/S Recovery to Low Cu/S Product % Product% Chalcocite 56.8 43.2 Bomite 21.5 78.5 Chalcopyrite 6.3 97.3 Pyrite 10.2 89.8 20 In test 107S, recovery of copper bearing minerals to the high Cu:S ratio product was low. This is possibly due to excessive oxidation of chalcocite, resulting from unnecessarily long oxygen purging time, indicating that 25 180 mins is the maximum preferred purging time for this particular sample. This illustrates the advantage of optimising the oxygen conditioning stage to obtain high and low Cu:S ratio products within the specification based on target mineral recoveries, copper grade and Cu:S ratio 30 for varying feed mineralogy. 2451887_1 (GHMatters) 28/10/10 - 11 Example 2 Figure 4 illustrates the effect of oxygen purging 5 time (residence time) on mineral separation in the ore concentrate. Oxygen purging tests were conducted at 60*C. At equivalent purging times, the best separation was achieved 10 at a temperature of at least 60*C and the illustrated results are therefore confined to this temperature. In this example an increase in residence time resulted in better selectivity. However, copper recovery 15 to the concentrate product decreased. Data also suggests that there might be an optimum purging time to achieve effective separation of high and low Cu/S sulphides, while maintaining high recovery of high Cu/S ratio product. It was found that oxygen purging flow rate during feed 20 conditioning at 60 0 C did not affect mineral separation in the particular ore concentrate that was tested, over the range tested. In contrast, oxygen purging time and temperature were key parameters. 25 Example 3 The effect of flotation time and particle size on sulfide mineral recovery were investigated. 30 An ore concentrate having 36.7% Cu, 25.8% S and a Cu:S ratio of 1.42 was conditioned by oxygen purging at 65 C for 60 min. To collect sufficient mass of each fraction (-100 g) several flotation tests were conducted and the corresponding float or tails fractions were then combined. 35 The samples were initially screened using a 38 pm laboratory sieve. The -38 pm fraction was pre-cycloned. The precyclone overflow was separated into Cl to C6 2451887_1 (GHMatters) 28/10/10 - 12 fractions using the cyclosizer. Each size fraction was weighed and assayed individually. For QEMSCAN analysis, the following size fractions were combined: +38pm+Cl, C2+C3 and C4+C5. 5 The float and tails fractions were then analysed using QEMSCAN and size-by-size recoveries for chalcocite, bornite, chalcopyrite and pyrite as a function of flotation time are presented in Figure 5. Chalcocite 10 appears to be the fastest floating mineral. The recovery in the C2+C3 and C4+C5 size fractions reached 90% after 5 min of flotation and then leveled out. Chalcocite recovery in the coarse size fraction (+38 pm+Cl) was approximately 20% lower for all flotation times. 15 The flotation rate of other sulphide minerals was lower than that of chalcocite, and decreased in the following sequence: bornite>chalcopyrite>pyrite. Ultimate mineral recovery followed the same sequence, i.e. highest 20 recovery was observed for chalcocite, while the recovery of pyrite was the lowest. All minerals showed a decrease in recovery with an increase in particle size. It will be understood to persons skilled in the 25 art of the invention that many modifications may be made without departing from the spirit and scope of the invention. 2451887_1 (GHMatters) 28/10/10

Claims

1. A process of separating at least one sulfide mineral from an ore or an ore concentrate that contains 5 two or more than two different sulfide minerals, said process including: conditioning a slurry of the ore or ore concentrate with a conditioning agent to increase or depress the floatability of one or more of the minerals; 10 subjecting the conditioned ore to one or more flotation stages to separate the minerals selectively into a float fraction and a tailings fraction according to mineral type and produce at least a first product having a relatively high Cu:S ratio and a second product having a 15 relatively low Cu:S ratio.

2. The process of claim 1 further including the step of producing the ore concentrate by subjecting an ore to flotation to separate the ore concentrate from a gangue 20 phase.

3. The process of claim 1 or claim 2 wherein the sulfide minerals are any one or more of: chalcocite (Cu 2 S), chalcopyrite (CuFeS 2 ), pyrite (FeS 2 ), and bornite (Cu 5 FeS 4 ). 25

4. The process of any one of the prceding claims wherein the second product includes chalcopyrite and the first product includes chalcocite. 30

5. The process of any one of the preceding claims wherein the conditioning step is carried out at an elevated temperature, i.e. a temperature above ambient temperature. 35

6. The process of claim 5 wherein the elevated temperature is from ambient temperature up to the boiling point of said slurry. 2451887_1 (GHMatters) 28/10/10 - 14

7. The process of any one of the preceding claims, wherein the conditioning agent includes an oxidant.

8. The process of claim 7 wherein the oxidant is 5 selected from an oxygen containing gas such as air, oxygen gas or a oxygen and sulphur dioxide mixture, sodium hypochlorite (NaClO), hydrogen peroxide, potassium permanganate, potassium dichromate and ozone. 10

9. The process of claim 8 in which the conditioning agent is an oxygen containing gas and the second product reports to the tailings fraction and the first product reports to said the float fraction. 15

10. The process of claim 9 wherein said slurry is conditioned with an oxygen containing gas for a period of time from 60-180 minutes.

11. A process for producing copper from an ore or an 20 ore concentrate that contains two or more different sulfide minerals, said process including: conditioning a slurry of the ore or ore concentrate with a conditioning agent; subjecting the conditioned ore to one or more 25 flotation stages to separate the minerals selectively into a float fraction and a tailings fraction according to mineral type and produce at least a first product having a relatively high Cu:S ratio and a second product having a relatively low Cu:S ratio; and 30 processing the first product and the second product and producing copper.

12. A process of separating at least one sulfide mineral from an ore or an ore concentrate that contains 35 two or more than two different sulfide minerals, substantially as herein described with reference to the Examples. 2451887_1 (GHMatters) 28/10/10