Download the recovery of fine cassiterite from metasedimentry rock

THE RECOVERY OF FINE CASSITERITE FROM METASEDIMENTRY ROCK
Ismail Ibrahim, Md Muzayin Alimon and Salmah Baharuddin
Mineral Research Centre, Minerals and Geoscience Department Malaysia
Jalan Sultan Azlan Shah, 31400 Ipoh, Perak, Malaysia
Mailing Address: [email protected]
ABSTRACT
It is known that ore containing cassiterite has been our most important source of tin since antiquity and its successful
separation continuously pose problems to mineral processors. The situation is more pronounced since depletion of
the more easily recoverable reserves and forces us to consider the more complex deposits such as hard rock
cassiterite ore, for mining in the near future. In order to understand more about challenges in processing the
complex tin ore deposits, a Malaysian metasedimentary rock ore sample from a mine was used for a study.
Chemical analysis by wet method shows that SnO2 content in the sample was 2.86%, while for mineralogical
analysis, the diffractogram of XRD of the sample had identified that beside cassiterite, the sample also contained
minerals such as quartz (SiO2), clinochlore minerals, ferroan and also glycolated and oriented
(Mg,Fe,Al)6(Si,Al)4O10(OH)8. Furthermore, the field emission scanning electron microscope (FESEM) micrograph
analysis carried out on a polish section of the sample indicated that the fine cassiterite particles (approximately 80
µm) were found to be disseminated in quartz. Prior to separation processes, grinding for 16 minutes on crushed
sample was the most appropriate time period to liberate the cassiterite from other gangue minerals and at the same
time, to avoid from producing higher percentage of fines. For the separation of tin from gangue minerals on the
ground samples, two (2) stages gravity separations by shaking tables were carried out. The first stage was run on
ground samples and for the second stage, the middling product from the first stage was re-tabling. Magnetic
separation process on concentrate 1 (stage 1) and concentrate 2 (stage 2) products from the shaking tables increased
the grade of SnO2 to 46.85% and 61.90% respectively (as non-magnetic product). Further concentration process of
SnO2 on this non-magnetic product by high tension separator has increased the grade of SnO 2 from 85.05% to
98.77%.
Keywords: fine cassiterite, grinding, shaking table, magnetic separation, high tension
1.
INTRODUCTION
It is known that gravity separation processes such as by shaking table, only can be performed effectively for an ore
at certain size ranges (~ between 105 to 600 um). So, at the processing plant, the comminution processes have to be
carried out on the rock containing cassiterite in order to liberate the mineral and also to enable its concentration
process by physical means. However, as the liberation size may well below 105 um and given that the separation
process of the shaking table, magnetic separator or high tension are only suitable for mineral separation in a
relatively coarser size range, using the same method for separation of fine cassiterite is quite challenging.
This paper will discuss the grindability process performance using ball mill grinding on the selected ore sample.
Apart from that, the possibilities of using shaking table, magnetic separator and high tension to recover the fine
cassiterite, will also being studied. For this purposes, the performance of each processes were measured through
grade and recovery of SnO2.
2.
MATERIALS AND METHODS
Sample of metasediment rock used in this experimental works was obtained from Sungai Perlis Bed, Ulu
Paka, Terengganu located in Malaysia. For sample preparation, at first the rock samples were crushed using jaw
and cone crushers and mixed thoroughly. Grindings of crushed materials were performed in 10, 12, 16, 20, 24 and
28 minutes to achieve a particle size in which the particle size corresponds to the liberation size as confirmed by
mineralogical analysis. Then the sieved materials (-600 μm) from batches were mixed together and was gone
through shaking table to pre-concentrate the cassiterite. The middling from tabling was then re-run by shaking table.
Those table concentrates and middling were then passed through double disk magnetic separator to get rid of iron
content. Those non-magnetic materials were then carried out high tension separation test. All products of shaking
1
table (concentrate, middling and tailing) and high tension separator (conductor, middling and non-conductor) were
analyzed by wet assay to determine the percentage of Sn. The Fe content of magnetic and non-magnetic materials
from magnetic separation tests were analyzed by atomic absorption spectrophotometer (AAS). Sample
Characterization such as X-ray Fluorescence (XRF), X-ray diffraction (XRD), field emission scanning electron
microscope (FESEM) and energy dispersive x-ray (EDX) were used to support the studies.
3.
3.1
RESULTS AND DISCUSSIONS
Characterization test
The SnO2 in ROM sample content by wet assay was 2.86%. The chemical composition of the sample in the
experimental works showed the percentage of SiO2 (64.57%), Al2O3 (13.41%), Fe2O3 (9.66%), MgO (1.6%) and
SnO2 (1.25%). The field emission scanning electron microscope (FESEM) micrograph on polish section sample
indicated that the fine cassiterite particles around 100 µm were found to be disseminated in quartz (Figure 1(a) and
1(b)).
Area A
A
A
Figure 1(b): EDAX analysis on polished
ROM sample at Area A from Figure 1(a).
Figure 1(a): FESEM analysis on
polished ROM sample at Area A.
3.2
Grindability tests
Size distribution of particles (Figure 2) was reported as cumulative percentage passing in the size range 8000 µm to
105µm. Grinding for 16 minutes on crushed sample is the most appropriate time period to liberate the cassiterite
from other gangue minerals and to avoid from producing higher fines thus giving 80% passing through the size, d80
= 3400 µm. Sn distribution in various fractions can be shown in Figure 3. For the grinding period of 10 minutes and
12 minutes, there were more than 48% of Sn existed in the size range between 600 µm to 800 µm, whereas for the
grinding period of 20 minutes, 24 minutes and 28 minutes, it was found that more than 30% of Sn in the range
below 105 µm. The ideal grinding time was in 16 minutes where the minimal percentages of Sn for below 105 um
and above 600 µm were identified to be approximately 25%.
90
10 min
60
80
12 min
50
70
60
16 min
50
20 min
% Sn distribution
% Cummulative passing
100
40
30
24 min
20
28 min
16 min
20 min
40
24 min
28 min
30
20
0
0
1000
Size in log (um)
12 min
10
10
100
10 min
10000
100
1000
Size in log (um)
2
Figure 2: Particle size result at different grinding time
3.3
Figure 3: Sn distribution in various size fractions
Tabling, magnetic separation and high tension separation
The separation results of SnO2 for the test sample by shaking table showed that SnO 2 had already increased to
64.21% (in concentrate). Since the grade of SnO2 in middling was 3.75% which is very low, the middling material
was re-tabled and produced 38% SnO2. Magnetic separation processes on concentrate 1 (stage 1) and concentrate 2
(stage 2) products from the shaking tables increased the grade of SnO2 to 46.85% and 61.90% respectively which
identified as non-magnetic product. The concentration process of SnO2 on non-magnetic product by high tension
separator has increased the grade of SnO2 from 85.05% to 98.77% giving 82.08% to 84.35% SnO 2 recovery as
conductor and middling products.
4.
CONCLUSION
Fine cassiterite particles approximately 80 µm were found to be disseminated in quartz. Therefore in order to release
of cassiterite from host minerals or to prevent the formation of a lot of mud, the crushed ROM sample has to be
ground for 16 minutes which can be considered the most appropriate time. Hence, for pre-concentration of
cassiterite, gravity separation by shaking table should be carried out in two (2) stages (i) the first stage of ROM
samples comminuted and (ii) on a sample of middling results from the first stage of tabling process. Subsequently
the grades of SnO2 for non-magnetic products initially from shaking table concentrates 1 and 2 have been increased
to 46.85% and 61.90% respectively. Eventually, the process of high tension separation on non-magnetic product
(non-mag) from the magnetic separation process was a significant to increase of SnO2 grade 85.05% to 98.77%
SnO2 which gave percentage recovery of 82.08% to 84.35% as a conductor and middling products.
ACKNOWLEDGEMENTS
The authors would like to thank and also pleased to acknowledge the support:
The Director of Mineral Research Centre, Minerals and Geoscience Department and fellow staffs of the Centre
especially to the staffs of Section of Mineral Processing Technology Section for their assistance of this research can
be carried-out.
REFERENCES
1.
Abubakre O. K., Sule Y. O. and Muriana R. A., 2009. Exploring the Potentials of Tailings of Bukuru
Cassiterite Production of Iron Ore Pellets, Journal of Minerals & Materials Characterization &
Engineering, Vol. 8, No. 5, pp 359-366.
2.
Fateh Chand (1978), Geological and Mineral Resources of the Ulu Paka Area, Terengganu, Geological
Suvey Malaysia, District Memoir 16.
3.
Ismail Ibrahim, Md Muzayin Alimon dan Salmah Baharuddin (2011), Laporan Kajian Pengasingan Mineral
Sulfida Dari Lombong Rahman Hydraulic Tin Bhd.
4.
Md Muzayin Alimon dan Nazwin Ahmad (2001), “Laporan Kajian Awal Proses Peningkatan Kandungan
Kasiterit Dan Wolframit Dari Hampas Lombong Sungai Ayam, Kemaman Terengganu”. Pusat
Penyelidikan Mineral.
5.
Md Muzayin Alimon, Ismail Ibrahim dan Salmah Baharuddin (2012), laporan Kajian Pencirian, Proses
Pembebasan Mineral dan Pengkonsentratan Kasiterit Untuk Sampel Bijih Kompleks dari Lombong Timah
Induk Timor, Kemaman, Terengganu Darul Iman.
6.
Sandy A.H, 2004. Feed preparation for gravity separation in grinding circuits, Gravity ’04, Perth, Australia.
3