SPECIALIST EQUIPMENT
70% of the feed and is a non-fl oating gangue mineral. Regrinding the tailings is the typical solution. In this example the pyroxene is also the main gangue mineral in the concentrate and an oxide gangue depressant is used to improve selectivity. Modifi cation of the frother and gangue depressant was advised as the secondary solution.
Final Tails PGMs
Data for the selected bright phase particles only (This is not the total bulk modal mineral composition)
Gold
PGE Alloys PGE Sulphides PGE Arsenates PGE Sulpharsenates PGE Tellurides
Mass Elemental distribution Total Au Pt Pd Rh
Wt% 12.0 30.1 9.1 24.6 3.0 21.2
%
100 0 0 0 0 0
% 0
11 25 44 3
17
% 0
67 4 3 0
26
% 0 0 0
28 72 0
Too
Summary (wt. %) Well sized
small < 10
micron
0% 43% 8% 0% 0% 15%
10 to 150 micron Liberated
16% 37% 0% 0% 0% 22%
17% 17% 75% 97% 0% 56%
Locked
Too Big
>300 micron
83% 3% 17% 3%
100% 7%
Not the correct process or reagent suite to fl oat a value mineral In a nickel fl otation plant where Betachem/ Nasaco was asked to perform testwork, 35% of the nickel in the fi nal tailing occurred as ultrafi ne particles in pyrrhotite. MLA analysis showed that the pyrrhotite is mainly well sized and liberated and thus available for recovery by fl otation (63% of pyrrhotite reported to the tails). T e plant does not use a reagent collector suite to recover the pyrrhotite and this nickel is thus lost. In discussions the possibility of the
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plant changing to a reagent suite suitable for pyrrhotite recovery was explored. Obviously this would have an eff ect of increasing the mass pull and load on the cleaning circuit, as more than 5% of the tailings mass is pyrrhotite. T e question became: do we increase mass pull by 5.6% and recover the 35% nickel currently lost? T e decision was not to recover the pyrrhotite and use a suitable pyrrhotite depressant. T e mining plan was adjusted and the recoverable nickel grade reduced. T e possibility exists to revisit this when economics are more favourable.
Other reasons, which may include process effi ciency In recent work carried out on a zinc ore, it was found that 53% of the sphalerite losses in the zinc rougher tails were “well sized” (10 to 150 micron) fully liberated particles. T ere is no mineralogical reason for this loss; the experts looked at the reagent suite and it was possible to recommend a more suitable collector and frother. “We have found that off ering meaningful,
process mineralogical data to our clients identifi es process problems. It opens a broad discussion in which we solve the problems together - often, but not always, identifying economical, chemical solutions. A core value for us is working with our clients conducting periodic control testing. which allows us to monitor and handle changes,” says Grobler. ●
Simon Isherwoood is with Nasaco.
www.nasaco.ch
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