MCCASTER, Ryan (40 Isles Road, IndooroopillyBrisbane, Queensland 4068, AU)
BRADSHAW, Deirdre Jane (Apartment 7, 8 Twigg StIndooroopill, Brisbane Queensland 4068, AU)
MCCASTER, Ryan (40 Isles Road, IndooroopillyBrisbane, Queensland 4068, AU)
| CLAIMS: 1. Apparatus for flotation of a mineral in a sample including: a vessel for housing a slurry of the sample; a bracket to which the vessel is secured in use, said bracket being mounted for reciprocating rectilinear motion; a drive for facilitating said reciprocating rectilinear motion of said bracket; and a closure for closing an upper end of the vessel; wherein a lower end of said vessel includes an outlet operable between a closed orientation and an open orientation. An apparatus according to claim 1 , wherein said lower end of said vessel has a tapered profile. An apparatus according to claim 1 or 2, wherein said outlet includes a tap. An apparatus according to any one of the preceding claims, wherein said bracket is mounted on a piston associated with a rodless pneumatic cylinder. An apparatus according to claim 4, wherein said drive is a pneumatic drive including a valve operable to pressurise and depressurise opposite sides of the piston, thereby facilitating said reciprocating rectilinear motion of said bracket. An apparatus according to claim 5, wherein the valve is a solenoid valve. An apparatus according to any one of the preceding claims, including at least two sensors that define the extent of said reciprocating rectilinear motion of said bracket. 8. An apparatus according to any one of the preceding claims, including a control module for controlling the frequency of said reciprocating rectilinear motion of said bracket and the number of times said bracket performs each cycle of said reciprocating rectilinear motion. 9. Use of an apparatus according to any one of the preceding claims in the characterisation of a mineral sample. 10. Use of an apparatus according to any one of claims 1 to 8 in the evaluation of efficacy of a reagent during flotation. 1 1. Use according to claim 10, wherein the reagent is a collector. 12. Use of an apparatus according to any one of claims 1 to 8 in the assessment of mineral content of a process stream, feed or tails. |
FIELD OF THE INVENTION
The present invention relates to an apparatus and method for determining mineral separability from an ore. Particularly, the invention relates to an apparatus and method that may be used on a relatively small scale to determine separability of the mineral from the ore.
BACKGROUND TO THE INVENTION
Traditionally, ore deposits are defined by the grades and deportment of the pay metal within them. Increasingly, it is being recognised that in addition to this one must understand the processing characteristics of the deposit to correctly value it and to understand the best processing routes to maximise the recovery of values from it. However, current metallurgical tests use relatively large amounts of material, specialist operators and are generally very expensive. Thus, in general too few tests are conducted to obtain a good representation of the deposit.
It would be advantageous if one could develop a small scale, robust, quick turnaround, domain test for mineral separability with the purpose of evaluating geological variability in ore deposits, as well as identifying any problematic minerals that may be present in any of the domains. This could be used to identify 'red flags' in the early stages of resource evaluation, as well as during mine operation.
An apparatus is disclosed in Australian Patent No. 630365 that is said to be suitable for small scale mineral flotation. A test tube containing a sample to be analysed is mounted on a reciprocating piston assembly. Reciprocation is achieved using a pneumatic system and position sensors that define the frequency and extent of rectilinear motion of the test tube and sample. The apparatus and methodology disclosed in Australian Patent No. 630365 required pipetting of froth from the upper portion of the test tube after agitation to remove the concentrate for further analysis. Generally, this has the potential to cause particles to drop back into the tails in the lower portion of the test tube, thus reducing accuracy of the test.
Advantageously, the apparatus and methodology provided by the invention facilitate testing that is reproducible and which can be performed on many samples for statistical robustness. This may provide the basis for identification of domains or samples requiring more rigorous or precise metallurgical test work, such as through batch or pilot scale tests.
SUMMARY OF THE INVENTION According to the invention there is provided an apparatus for flotation of a mineral in a sample including:
a vessel for housing a slurry of the sample;
a bracket to which the vessel is secured in use, the bracket being mounted for reciprocating rectilinear motion;
a drive for facilitating the reciprocating rectilinear motion of the bracket; and a closure for closing an upper end of the vessel;
wherein a lower end of the vessel includes an outlet operable between a closed orientation and an open orientation. In use, the slurry of the sample is agitated through the reciprocating rectilinear motion of the bracket, to which the vessel containing the slurry of sample is secured. Once stopped, formation of froth in the upper end of the vessel is achieved, while tails sink to the lower end of the vessel. The tails at the lower end of the vessel may be removed by opening the outlet, advantageously without disturbing the froth in the upper end of the vessel. This adds to the precision of the apparatus and associated methodology as it facilitates separation of the tails and froth.
The design of the vessel is not particularly limited, provided that froth and tails can separate when the slurry of sample is agitated. Generally, the vessel is an elongate cell having a generally cylindrical shape. In order to prevent build up of material at the lower end of the vessel, it is preferred that the lower end of the vessel have a tapered profile. This advantageously adds to the precision of the apparatus and associated methodology.
The form of the outlet is not particularly limited. For example, this may include a valve actuable between the open orientation and closed orientation. Preferably, the outlet includes a tap. The bracket is preferably mounted on a piston associated with a rodless pneumatic cylinder. In use the bracket travels along the rodless pneumatic cylinder, as will be described in more detail below. The vessel may be mounted vertically, or at a suitable angle to the vertical. For example, the vessel may be mounted at an angle of up to 15 degrees from the vertical axis on the rodless pneumatic cylinder.
The drive may include any drive the can impart the reciprocating rectilinear motion to the bracket. For example, this may include an electric drive or other form of drive. Preferably, the drive is a pneumatic drive including a valve operable to pressurise and depressurise opposite sides of the piston, thereby facilitating the reciprocating rectilinear motion of the bracket. In this case, it is preferred that the valve be a solenoid valve.
Preferably, the apparatus includes at least two sensors that define the extent of the reciprocating rectilinear motion of the bracket. For example, the sensors may be magnetic sensors that identify the position of the bracket and, therefore, bracket along the length of the rodless pneumatic cylinder. Generally, the apparatus will include three such sensors.
In a preferred embodiment, the apparatus includes a control module for controlling the frequency of the reciprocating rectilinear motion of the bracket and the number of times the bracket performs each cycle of the reciprocating rectilinear motion. The control module may be manual, for example including a pressure regulator for regulating the pressure within the rodless pneumatic cylinder when the apparatus is in operation. The control module may also include a computerised control into which can be entered the desired pressure, correlating to the frequency of the reciprocating rectilinear motion, and the number of cycles to be performed. The invention also provides for the use of an apparatus as described above in the characterisation of a mineral sample.
The invention further provides for the use of an apparatus as described above in the evaluation of efficacy of a reagent during flotation. Generally, the reagent is a collector.
The invention still further provides for the use of an apparatus as described above in the assessment of mineral content of a process stream, feed or tails. It has long been established that flotation performance is a function of particle size, where there is optimum performance obtained for ore particles in the mid size ranges. The breadth of this optimum depends on the ore properties (mineral type / texture etc). The overall recovery is a sum of the performance of the different sizes. The size by size recovery behaviour of minerals in an ore has been shown to remain constant so that by assessing the performance of each size in the ore (as is possible using this apparatus and methodology) it is possible that by knowing the particle size distribution of an ore it is possible to predict overall flotation performance.
This methodology also advantageously provides an added benefit over batch flotation tests in that it is possible to assess the performance of a certain ore type without doing a milling curve first (which is necessary for a batch flotation test) so that much less ore is needed. This means that performance behaviour can be obtained on a diamond drill core sample of less than 1 kg rather than the 6 kgs that is currently the limit. DETAILED DESCRIPTION OF THE INVENTION
The invention will now be described in further detail with reference to the accompanying drawings. The following detailed description is provided for illustration only and should not be construed as limiting on the claims in any way. In the drawings:
Figure 1 illustrates an apparatus for flotation of a mineral within a sample; Figure 2 illustrates a vessel secured to a bracket that is mounted on a rodless pneumatic cylinder;
Figure 3 illustrates the arrangement of Figure 2 without the vessel secured to the bracket;
Figure 4 illustrates the results of Example 1 graphically;
Figure 5 illustrates the results of Example 2 in terms of recovery by size of the copper minerals;
Figure 6 illustrates the results of Example 2 in terms of recovery by size of bornite, chalcocite and chalcopyrite;
Figures 7A and 7B illustrate mineralogical potential of the feed (theoretical grade recovery) for the 75-106mm size fraction;
Figure 8 illustrates copper distribution of the reconstituted feed; and
Figures 9 and 10 illustrate the results of sizing of the ores after 5 minutes milling.
Referring to Figure 1 , an apparatus 10 for flotation of a mineral within a sample is illustrated. The apparatus 10 includes a vessel 1 1 that is generally cylindrical and elongate which is secured to a bracket 12 that is mounted for reciprocating rectilinear motion. Particularly, the bracket 12 is mounted on a piston 13 (see Figures 2 and 3) associated with a rodless pneumatic cylinder 14. The vessel 11 and rodless pneumatic cylinder 14 are both vertically mounted. A closure 15 is also provided to close an upper end of the vessel 11.
In order to achieve precise assessment during operation of the apparatus 10, a tap 16 is provided at a lower end of the vessel 11. The tap 16 advantageously facilitates removal of tails that collect in the lower end of the vessel 11 without disturbing froth that develops in the upper end of the vessel 11. In addition, as best illustrated in Figure 2, the lower end of the vessel 11 is tapered to minimise build up of material in the lower end of the vessel 11 in use.
The bracket 12 includes a recess 17 that receives the lower end of the vessel 1 1 (see Figure 3). A mount 18, also best illustrated in Figure 3, is provided on which the vessel 11 is positioned. Two fasteners 19 (see Figure 2) are provided which secure the vessel 11 to the bracket 12. These are in the form of straps that are secured to and extend from tabs 20 on the mount 18 around the vessel 11.
Magnetic sensors 21 are also provided adjacent the rodless pneumatic cylinder 14. These magnetic sensors 21 identify the position of the bracket 12 relative to the rodless pneumatic cylinder 14. Therefore, they define the extent of movement of the bracket 14 in the reciprocating rectilinear motion. When the magnetic sensors 21 identify that the bracket 14 has reached the end on an upward or downward pass, opposite sides of the piston 13 are pressurised and depressurised causing a change in direction of the bracket 12.
The above components of the apparatus 10 are housed within a housing 22. The housing 22 supports these functional elements of the apparatus 10 and also provides advantages in terms of safety during use. Also illustrated in Figure 1 is a pressure regulator 23 associated with a pressure gauge 24, a bleed valve 25 and so on. As previously noted, adjustment of the pressure within the system via the pressure regulator 23 facilitates adjustment of the frequency of the reciprocating rectilinear motion. As the pressure increases, so too does the frequency of the cycles of the reciprocating rectilinear motion.
In operation, generally, a material to be tested is a selected specified size fraction obtained after milling and screening. Water is added to a sample of the material, for example 10 grams, and this is placed in an ultrasound bath for a period of time, for example 1 minute. The slurry is then placed into the vessel 10 and reagents added. Generally, excess frother is used to ensure more stable product. The slurry is topped up to a desired amount, for example 150ml with distilled water and the closure 15 placed on the upper end of the vessel 11.
A desired number of cycles, for example up to about 90 cycles, and the frequency entered. The frequency may be, for example 5-6 cycles per second. Once the desired number of cycles has been completed, the agitated slurry is left to stabilise, for example for 2 minutes. The closure 15 is then opened to normalise pressure within the vessel 11. The tailings may then be removed by opening the tap 16, and subsequently filtered. Likewise, the concentrate may then be collected and filtered. Each of the tailing and concentrate may then be dried and weighed. Assays may then be conducted.
In order to better understand the methodology of the invention, several examples will now be described.
Example 1 - Cadia Ore (V30)
Samples were selected for MSI from residual samples from batch flotation tests. Each sample was screened and then 10 g of each size fraction selected for testing. Up to 5 repeats of each test were done. Concentrates and tails were weighed and analysed.
Batch Flotation test with V30 gave a 7.2 mass recovery with 86% copper recovery.
Table 1 : MSI Results
Std Dev 2.2% 2.4% 3.64 0.03 1.30
+53 1 13.4% 85.2% 18.69 0.27 91.59
+53 R2 13.4% 85.4% 17.80 0.27 91.19
Mean 13.4% 85.3% 18.25 0.27 91.39
Std Dev 0.0% 0.1% 0.63 0.00 0.28
+38 R1 11.2% 86.0% 33.05 0.53 89.04
+38 R2 11.8% 87.0% 29.22 0.82 82.86
+38 R3 12.0% 83.8% 30.26 0.40 91.55
+38 R4 14.1% 84.1% 24.86 0.26 94.13
+38 R5 12.8% 85.5% 25.99 0.46 89.43
Mean 12.4% 85.3% 28.68 0.49 89.40
Std Dev 1.1% 1.3% 3.31 0.21 4.18
+25 R1 7.0% 91.2% 47.11 1.10 76.67
+25 R2 10.0% 88.7% 33.70 1.15 76.76
Mean 8.5% 90.0% 40.41 1.13 76.72
Std Dev 2.1% 1.8% 9.48 0.04 0.06
The results, in terms of Cu recovery are illustrated graphically in Figure 4.
Example 2 - Evaluation of two ores from Prominent Hill
Context
A campaign of several surveys was undertaken. The results showed differences in behaviour between two ores with Survey 1 (5:2 Red/Green to Red) achieving a higher recovery than that of Survey 2 (100% Red/Green ore). Belt cuts were taken after the two surveys and the samples identified as Ore 1 and Ore 2 respectively.
Objective
To assess whether the apparatus and methodology of the invention can show discrimination between Ore 1 and Ore 2 that was consistent with differences obtained when processed on site. This was not intended to be a comprehensive evaluation but rather a 'proof of concept' to establish whether this technique could be used to measure. mineral recovery in the development of a geometallurgical model.
Experimental Details
The ore samples used in these tests were obtained from the belt cut samples taken after the surveys undertaken at Prominent Hill. A 1 kg feed sample was milled for 5 minutes and samples taken from sieve sizes 150, 106, 75, 53 and 38 microns. It is recognized that these sample size fractions may not be representative of the ore as a whole as 5 minutes does not achieve a particle size distribution typical of that on site. Also, only selected fractions were assayed and tested. Previous work has shown that, within limits, it is reasonable to assume size (by liberation) behaviour is constant.
Problems were encountered in the preliminary test work, particularly with Ore 2 which demonstrated significant drop back at the end of the test, this was addressed by lowering the dosage of collector. In each test 10g of material was used and the reagents added were 0.2 ml of PAX (solution 0.5g/L) and 40 μΙ MIBC.
Results Table 2 and Figures 5 and 6 show the flotation recovery results for both the copper minerals together and separately for chalcocite, bornite and chalcopyrite. The recoveries obtained with Ore 1 for all size fractions were greater than those obtained with Ore 2, which was consistent with the findings of the survey. For both ores the trend between minerals was also consistent, with the recoveries of chalcocite being higher than those of bornite, with the lowest recoveries being obtained with chalcopyrite. The biggest difference was for the 75 - 106 pm size fraction where the recovery from Ore 2 was very low and similar to that obtained for the coarser size fractions, indicating that liberation or grain size may be the reason for the flotation performance.
Table 3 shows the modal mineralogy of the reconstituted feed, both: a) in terms of the major minerals, with the copper minerals grouped together; and b) with the chalcopyrite, chalcocite and bornite. Ore 2 was expected to be higher grade and contain a higher amount of chalcocite, but this was not the case. Ore 2 contained more iron hydroxides, particularly in the finer fractions. Also notable was the increased amount of chalcopyrite in Ore 2 with a less of it liberated, as shown in Table 3. Although there are small differences in the liberation of the ores, the theoretical grade vs recovery of the 75 - 106 mm size fraction shown in Figures 7A and 7B for the two ores shows that the differences between the 'mineralogical potential' of the ores was small and unlikely to be related to the differences in liberation. Table 4 shows the distribution by liberation of the copper minerals and Figure 5 illustrates the distribution of copper minerals in the different size fractions. Although there are differences in the liberation of the two ores the differences are subtle and it is not expected that they are the cause of the difference in behaviour. Table 5 shows the differences in grain size and that in general the grain sizes for all minerals was smaller in Ore 2 than for Ore 1. The grain size of chalcocite was largest and chalcopyrite the lowest with bornite in between. These differences may be significant but further investigation is necessary to confirm this. Figures 9 and 10 shown are the results of sizing of the ores after 5 minutes milling and show that a lower P80 was achieved with Ore 2 indicating that the ore was softer.
Key Findings There were significant differences in the recoveries obtained with the two ores demonstrating the potential of the technique of the invention to identify differences in the ores. Lower recovery was obtained with Ore 2 - consistent with plant results. It was not obvious from the mineralogical investigation what the cause of the different behaviour was but the ores are established as not being equivalent.
Table 2: Recovery of Copper Minerals
Table 3: Modal Mineralogy of Reconstituted Feed
a) Summary
b) Major minerals
Table 4: Distribution by Liberation of Copper Minerals in Reconstituted Feed < 20% liberated 3.71 5.39 7.65 11.47 16.17
20-80% liberated 24.12 25.53 30.22 33.93 38.03
> 80% liberated 72.16 69.08 62.13 54.6 45.79
Ore 2
% Copper Minerals 5.83 5.39 4.89 4.93 4.95
< 20% liberated 3.12 5.74 9.25 11.04 16.16
20-80% liberated 20.98 24.92 32.02 41.96 41.23
> 80% liberated 75.89 69.33 58.73 47 42.61
In the specification the term "comprising" shall be understood to have a broad meaning similar to the term "including" and will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This definition also applies to variations on the term "comprising" such as "comprise" and "comprises".
The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the referenced prior art forms part of the common general knowledge in Australia.
It will of course be realised that the above has been given only by way of illustrative example of the invention and that all such modifications and variations thereto as would be apparent to those of skill in the art are deemed to fall within the broad scope and ambit of the invention as herein set forth.