Kupfermelt_Final Report Upgrading Nickel Ores from Dikoloti BCL and BML 30 October 2014 - rev 3
1. 1
Kupfermelt Metal Processing C.C.
Reg No CK 972333823
37 Sentraal Street
Industrial Area
Modimolle 0510
P.O. Box 1571
Kokanje 0515
South Africa
Tel: 014 715 2696
Fax: 014 715 2696
Mobile: 082 8866275
E-mail: johann.steynberg@telkomsa.net
Report:
Metallurgical test series performed to identify a beneficiation process to
upgrade the Nickel ore from Dikoloti, BCL and BML deposits in Botswana
Prepared for:
Ms Patience Showa
(Plant Metallurgist)
BCL
Botswana
Prepared by:
Johann Steynberg GK Mosanga
Metallurgical Consultant Metallurgist
Kupfermelt Metal Processing BCL
30 October 2014
3. 3
Executive Summary
The results confirmed the writer’s previous findings that a 2% Ni concentrate grade
could be produced with a 20% Dikoloti blend with 80% BCL ore achieving nickel
recoveries in excess of 90%.
The results conclusively demonstrated that to achieve a 2% plus nickel concentrate
grade the Dikoloti ore has to be mixed with BCL material prior to flotation.
The leaching results showed that excellent nickel and copper recoveries could be
achieved with a 1:2 ore: acid mix namely a 95.5 % Cu and 96.5% Ni recovery at ambient
temperature. An iron recovery of 95% was recorded.
A number of processes exist to recover the Cu and Ni from the solution i.e.
precipitation of the salts, IX, SX followed by EW of the base metals.
Precipitation offers the cheapest process by precipitating the copper as a sulphide, the
iron as a hydroxide and the nickel as a carbonate. This work was not covered in this test
programme but requires involving a study on its own.
Flotation tests on the BML disseminated ore produced good concentrate grades and
recoveries, 2.4% Ni and 93.7% respectively.
The nickel recovery on the BML massive ore at 71.4%b was much lower than the
disseminated ore, but produced a higher concentrate grade of 3.62% Ni compared to
2.4% Ni.
Blending the BML with 70% BCL ore produced good concentrate grades and recoveries
and proves to be an option to BCL to supplement their feed stock.
Leaching the Dikoloti ore offers a great potential for improving both the nickel and
copper recoveries and should certainly be further explored.
Particularly to avoid the high iron dissolution and to recover the nickel and copper as
good saleable products.
4. 4
1. Introduction
A large number of flotation tests were carried out by Kupfermelt, BCL and Mintek in an
attempt to identify and establish an efficient and feasible process to upgrade nickel and
copper ores from the Dikoloti and BCL deposits in Botswana.
The results demonstrated that the pentlandite was very finely disseminated in the
pyrrhotite matrix of the Dikoloti ore and that good Ni concentrate grades similar to
BCL’s ore cannot be produced.
Ultra-fine re-grinding of the rougher concentrate prior to cleaning further confirmed
the difficulty selectively separating the pentlandite from the pyrrhotite.
Blending the Dikoloti with BCL ore in a ratio of 20% DK + 80% BCL showed some
promise since a nickel grade of 2.1% Ni and a nickel recovery of 95.0% was achieved.
To confirm these findings, additional tests were carried out on this blend.
To establish whether higher nickel and copper recoveries could be obtained by leaching
the ore, a series of tests were carried with sulphuric acid.
A series of flotation tests were also performed on massive and disseminated ores from
the BML/BCL deposit.
The results of this study are summarised in this report.
2. Sample Preparation
2.1 Flotation
Ore samples from Dikoloti and BCL were crushed to minus 1mm in size.
Representative samples were extracted by means of a rotary splitter for the
subsequent flotation tests.
2.2 Test Procedure
1. Head samples of Dikoloti, BCL and BML ores were analysed for Cu and Ni.
2. A series of flotation tests were carried out using 1000g of the minus 1 mm
material from the Dikoloti, BCL and BML ores milled to different float feed
particle sizes.
3. A flotation test was also performed on a reground rougher concentrate.
4. A two litre Wemco laboratory flotation machine was used for this test
programme.
5. Different reagent combinations were used.
6. All the samples were dried, weighed and assayed for Ni and Cu.
5. 5
3. Results
3.1. Head Assays
The head assays of Dikoloti, BCL BML massive and disseminated are shown in Table 1
below.
Head assays Dikoloti, BCL BML
Table 1
Name Ni Cu
Dikoloti 0.5 0.411
BCL 0.722 0.611
BML Massive 2.703 0.796
BML Disseminated 0.658 0.319
3.2 Blend BCL and Dikoloti Ore
The flotation feed was milled to a P80 of 139 micron.
Four 5 minute concentrates were produced.
During each concentrate float 20g/t and 30g/t of SIBX (xanthate) and 3477
Dithiophospate) was added respectively.
The results are shown in Tables 2 and 3 below
Flotation Results
Dikoloti /BCL 20: 80 Collectors SIBX & Cytec 3477
Table 2
Test DK 822
Mass % % Ni % Cu % Ni % Cu
Concentrate 1 9.2 2.56 4.09 30.04 51.09
Concentrate 2 9.0 2.28 2.13 26.12 25.97
Concentrate 3 13.3 1.8 0.87 30.59 15.71
Concentrate 4 5.4 1.38 0.4 9.5 2.92
Total concentrate 36.8 2.05 1.91 96.25 95.69
Tailings 63.2 0.05 0.05 3.75 4.31
Total 100.0 100 100
Feed Calculated 100.0 0.78 0.74
Feed assay 1.19 0.85
Assays Recovery
6. 6
Flotation Results
Dikoloti /BCL 20: 80 Collectors SIBX & Cytec 3477 Plus CMC
Table 3
Test DK 823
Mass % % Ni % Cu % Ni % Cu
Concentrate 1 10.4 3.25 5.235 41.9 78.23
Concentrate 2 14.6 1.87 0.776 33.85 16.27
Concentrate 3 9.0 1.46 0.215 16.29 2.78
Concentrate 4 3.7 0.94 0.17 4.31 0.91
Total concentrate 37.8 2.06 2.08 96.35 98.18
Tailings 62.2 0.05 0.02 3.65 1.82
Total 100.0 100 100
Feed Calculated 100.0 0.81 0.7
Feed assay 1.15 0.76
Assays Recovery
Comments
1. The results confirmed the previous findings that a 2% Ni concentrate grade could
be produced with a 20% Dikoloti blend with 80% BCL ore achieving nickel
recoveries in excess of 90%.
2. No grade or recovery improvement was achieved with the addition of CMC.
3. The results conclusively demonstrated that to achieve a 2% plus nickel
concentrate grade the Dikoloti ore has to be mixed with BCL material prior to
flotation.
4. Leaching Tests
A series of leaching tests were carried out on the Dikoloti ore to establish whether
higher nickel and copper recoveries could be achieved.
The Dikoloti ore was milled to a P80 of 120 micron prior to leaching.
4.1 Direct Acid Leaching
Six direct leaching tests were carried out with sulphuric acid at three different acid
additions and two temperatures for a period of three hours.
The results are shown in Table 4 below
7. 7
Direct Leaching Tests with Sulphuric Acid
Table 4
Acid Concentration
Temperature (o
C) % Ni %Cu % Ni %Cu % Ni %Cu
25 6.9 2.3 5.4 2.1 5.1 2.1
80 8.8 2.6 8.2 4.8 9 4.8
200 kg H2SO4/ton of ore 400 kg H2SO4 /ton of ore 600 kg H2SO4/ton of ore
Comments
1. The results clearly showed that a direct sulphuric acid leach was totally
ineffective.
2. Very poor nickel and copper recoveries were achieved even at 80 degrees C.
3. This was not unexpected since it is known that sulphides do not readily leach with
sulphuric acid even at high concentrations and elevated temperatures.
4.2 Sulphating Leaching
It is known that sulphides can be successfully leached when converted to sulphates.
The process consists of dry mixing the ore with concentrated sulphuric acid at different
ratios, curing the product at ambient or higher temperatures for a specified period.
The sulphates are then leached with water to produce a nickel, copper and iron
sulphate solution.
The valuable metals are thereafter separately been recovered by means of selective
precipitation, IX or SX followed by electro-winning.
A series of tests were carried out mixing the ore with different ratios of sulphuric acid.
Three, ore: acid ratios namely: 1:1, 1.5:1 and 2:1 were tested
The effect on an oxidising agent namely hydrogen peroxide was also evaluated.
The ore mix was cured at 200 degrees for three hours before it was used for the
leaching tests.
50 g samples of the cured material were leached with water at ambient temperature
and 80 degrees C for 60 minutes.
The results are shown in Tables 5 to 12 below.
8. 8
Leaching Results 1: 1 Ore: Acid Mix at Ambient Temperature
Table 5
Product Mass (g) / Vol (cc) Cu Ni Fe Cu Ni Fe
Leach Residue 21.2 0.464 0.452 12.530 79.2 55.4 6.5
Filtrate1 697.0 0.037 0.111 54.667 20.8 44.6 93.5
Total 100.0 100.0 100.0
Feed Calc'd 50.0 0.248 0.346 81.516
Feed Assayed 0.249 0.359 15.716
Test DK 1 D (ambient temp) Assay (%) (g/l) Recovery %
Leaching Results 1: 1 Ore: Acid Mix at 80 Degrees C
Table 6
Product Mass (g) / Vol (cc) Cu Ni Fe Cu Ni Fe
Leach Residue 19.5 0.525 0.478 10.078 73.6 48.3 19.6
Filtrate1 590.0 0.062 0.169 13.700 26.4 51.7 80.4
Total 100.0 100.0 100.0
Feed Calc'd 50.0 0.278 0.386 20.096
Feed Assayed 0.249 0.359 15.716
Test DK 1 C (HOT) Assay (%) (g/l) Recovery %
Leaching Results 1: 1 Ore: Acid Mix plus H2O2 at Ambient Temperature
Table 7
Product Mass (g) / Vol (cc) Cu Ni Fe Cu Ni Fe
Leach Residue 20.4 0.484 0.425 12.042 77.4 47.4 29.9
Filtrate1 930.0 0.031 0.103 6.200 22.6 52.6 70.1
Total 100.0 100.0 100.0
Feed Calc'd 50.0 0.255 0.366 16.445
Feed Assayed 0.249 0.359 15.716
Test DK 1 E (ambient Temp with H2O2) Assay (%) (g/l) Recovery %
Leaching Results 1: 1 Ore: Acid Mix plus H2O2 at 80 Degrees C
Table 8
Product Mass (g) / Vol (cc) Cu Ni Fe Cu Ni Fe
Leach Residue 21.6 0.519 0.411 15.213 78.7 50.3 39.3
Filtrate1 940.0 0.032 0.093 5.400 21.3 49.7 60.7
Total 100.0 100.0 100.0
Feed Calc'd 50.0 0.285 0.353 16.724
Feed Assayed 0.249 0.359 15.716
Recovery %Assay (%) (g/l)Test DK 2 E (HOT with H2O2)
9. 9
Leaching Results 1: 1.5 Ore: Acid Mix at Ambient Temperature
Table 9
Product Mass (g) / Vol (cc) Cu Ni Fe Cu Ni Fe
Leach Residue 15.1 0.156 0.091 6.191 19.8 9.6 11.8
Filtrate1 690.0 0.138 0.187 10.167 80.2 90.4 88.2
Total 0.119 0.142 7.950 100.0 100.0 100.0
Feed Calc'd 50.0 0.237 0.285 15.900
Feed Assayed 0.239 0.306 16.376
Test DK 8 (with H2O at Ambient Temp) Assay (%) (g/l) Recovery %
Leaching Results 1: 2 Ore: Acid Mix at Ambient Temperature
Table 10
Product Mass (g) / Vol (cc) Cu Ni Fe Cu Ni Fe
Leach Residue 8.6 0.143 0.102 6.367 4.2 3.5 5.0
Filtrate1 740.0 0.378 0.325 14.000 95.8 96.5 95.0
Total 100.0 100.0 100.0
Feed Calc'd 50.0 0.239 0.308 17.118
Feed Assayed 0.239 0.306 16.376
Test DK 9 (with H20 at Ambient Temp) Assay (%) (g/l) Recovery %
Leaching Results 1: 2 Ore: Acid Mix at 80 Degrees C
Table 11
Product Mass (g) / Vol (cc) Cu Ni Fe Cu Ni Fe
Leach Residue 15.1 0.156 0.091 6.191 19.8 9.6 11.8
Filtrate1 690.0 0.138 0.187 10.167 80.2 90.4 88.2
Total 0.119 0.142 7.950 100.0 100.0 100.0
Feed Calc'd 50.0 0.237 0.285 15.900
Feed Assayed 0.239 0.306 16.376
Test DK 8 (with H2O at Ambient Temp) Assay (%) (g/l) Recovery %
Leaching Results 1: 2 Ore: Acid Mix at 80 Degrees C
Cured product was roasted at 450C for 3 hours
Table 12
Product Mass (g) / Vol (cc) Cu Ni Fe Cu Ni Fe
Leach Residue 13.7 0.083 0.009 1.373 9.3 0.8 2.3
Filtrate1 790.0 0.140 0.192 9.967 90.7 99.2 97.7
Total 100.0 100.0 100.0
Feed Calc'd 50.0 0.244 0.306 16.124
Feed Assayed 0.239 0.306 16.376
Test DK 10 (with H20 at Ambient Temp) Assay (%) (g/l) Recovery %
10. 10
Comments
1. The results showed that a 1: 1 ore: acid mix only achieved 26% and 52% Cu and
Ni recovery respectively leaching at 80 degrees C. About 80% of the Fe was
leached at the same time. See Table 6
2. By adding an oxidising agent namely H2O2 showed no benefits. See Tables 7 & 8.
3. At a 1: 1.5 ore: acid mix and leaching at ambient temperature the recoveries
improved to 80% and 90% for the Cu and Ni respectively, with an Fe recovery of
88.2%.
4. The best results were achieved with a 1:2 ore: acid mix with a 95.5 % Cu and
96.5% Ni recovery at ambient temperature. An iron recovery of 95% was
recorded. See Table 10.
5. The large sulphuric acid addition can be attributed to the high iron content
(pyrrhotite) to convert it to iron sulphate.
6. In an attempt to reduce the iron dissolution by decomposing the iron sulphate to
hematite, the 1: 2 cured product was roasted at 480 degrees C for 3 hours prior
to leaching.
7. The Ni recovery increased marginally but the iron dissolution remained
unchanged. A change in colour, typically reflecting the red hematite was also not
apparent.
8. The poor oxidation and conversion of the pyrrhotite (iron sulphate) to hematite,
which has a low iron solubility in sulphuric acid, can perhaps be attributed to a
lack of oxygen, roasting time, etc. but this has to be further investigated.
9. A number of processes exist to recover the Cu and Ni from the solution i.e.
precipitation of the salts, IX, SX followed by EW of the base metals.
10. Precipitation offers the cheapest process by precipitating the copper as a
sulphide, the iron as a hydroxide and the nickel as a carbonate.
11. This work was not covered in this test programme but rather requires a study on
its own.
12. Another processing option would be to produce a pyrrhotite flotation
concentrate mix it with sulphuric, cure it for certain period, roast to convert the
iron sulphate to hematite, and leach to recover the Cu and Ni.
13. The residue predominantly hematite could be sold as source of iron ore.
14. This work was only briefly examined during this study but justifies a further
investigation.
5. Flotation BML Ore
A series of flotation tests were carried out on massive and disseminated BML ore
and certain ore blends.
The flotation feed was milled to a size with a P80 of 139 micron.
Four 5 minute concentrates were generated, only SIBX was added as a collector
at 20g/t ahead of each float.
The results are summarised in Tables 12 to 16 below
11. 11
Flotation Test Results Disseminated Ore
Table 12
Product Mass
% % Ni % Cu % Ni % Cu
Conc 1 5.9 3.67 3.823 32.74 70.40
Conc 2 8.1 2.36 0.480 28.91 12.12
Conc 3 8.0 1.91 0.160 23.23 4.02
Conc 4 3.4 1.73 0.145 8.84 1.53
Total conc 25.3 2.44 1.11 93.72 88.07
Tails 78.1 0.05 0.049 6.28 11.93
Total 100.0 100.00 100.00
Feed Cal'd 100.0 0.66 0.32
Feed assay 0.99 0.42
Assays Recovery
-
Flotation Test Results Massive Ore
Table 13
Product Mass
% % Ni % Cu % Ni % Cu
Conc 1 9.9 5.12 4.488 19.43 55.87
Conc 2 11.5 3.98 1.058 17.55 15.28
Conc 3 11.2 3.45 0.745 14.86 10.52
Conc 4 18.9 2.70 0.395 19.56 9.39
Total conc 51.5 3.62 1.41 71.40 91.06
Tails 48.5 1.54 0.147 28.60 8.94
Total 100.0 100.00 100.00
Feed Cal'd 100.0 2.61 0.80
Feed assay 2.70 0.81
Assays Recovery
Flotation Test Results Massive Ore, Flotation Feed Size with a P80 of 100 micron
Table 14
Product Mass
% % Ni % Cu % Ni % Cu
Conc 1 20.7 6.03 3.763 21.04 47.79
Conc 2 25.1 4.61 1.490 19.47 22.92
Conc 3 23.7 3.87 0.739 15.48 10.78
Conc 4 40.1 2.66 0.337 17.96 8.29
Total conc 52.3 4.00 1.33 73.95 89.78
Tails 47.7 1.55 0.166 26.05 10.22
Total 100.0 100.00 100.00
Feed Cal'd 2.83 0.78
Feed assay 2.73 0.77
Assays Recovery
12. 12
Flotation Test Results 70% Massive Ore 30% Disseminated
Table 15
Product Mass
% % Ni % Cu % Ni % Cu
Conc 1 9.9 5.42 4.859 24.82 73.72
Conc 2 7.7 4.23 0.858 15.05 10.11
Conc 3 9.3 3.38 0.353 14.56 5.04
Conc 4 17.8 2.47 0.125 20.36 3.40
Total conc 44.6 3.61 1.35 74.79 92.27
Tails 55.4 0.98 0.091 25.21 7.73
Total 100.0 100.00 100.00
Feed Cal'd 100.0 2.15 0.65
Feed assay 2.41 0.54
Assays Recovery
Flotation Test Results
BCL 70% and 30% BML (70% Massive & 30% disseminated)
Table 16
Product Mass
% % Ni % Cu % Ni % Cu
Conc 1 17.9 3.78 3.281 50.93 74.70
Conc 2 10.6 2.80 0.588 22.25 7.91
Conc 3 10.2 2.21 0.209 17.04 2.72
Conc 4 4.8 1.76 1.992 6.41 12.27
Total conc 43.5 2.95 1.76 96.63 97.60
Tails 56.5 0.08 0.033 3.37 2.40
Total 100.0 100.00 100.00
Feed Cal'd 100.0 1.33 0.79
Feed assay 1.86 0.75
Assays Recovery
Comments
1. The BML disseminated ore produced a good concentrate grade of 2.4% Ni at
93.7% Ni recovery.
2. The corresponding copper concentrate grade and recovery was 1.1% Cu and
88.1%.
3. The flotation kinetics was fast since about 85% of the nickel floated within 15
minutes.
4. The BML disseminated head grade assayed 0.99% Ni and 0.42% Cu.
5. The BML massive head grade was much higher and assayed 2.7% Ni and 0.81%
Cu.
6. A 3.62% Ni concentrate grade was produced with a nickel recovery of 71.4%, with
slow flotation kinetics.
7. In contrast a very good copper recovery of 91.1% was achieved.
13. 13
8. Grinding the flotation feed to a finer size (from P80 139 to a P80 of 100 micron)
only marginally improved the nickel recovery from 71% to 74% but increase the
nickel grade from 3.6% Ni to 4.0% Ni.
9. Blending the massive and disseminated ores in a 70: 30 ratio showed very little
benefit in terms of improving the concentrate grades or recoveries.
10. Blending the same ratio with 70% BCL ore produced good concentrate grades and
recoveries.
11. This proves to be an option to BCL to supplement their feed stock.
6. Conclusions
1. The results confirmed the previous findings that a 2% Ni concentrate grade could
be produced with a 20% Dikoloti blend with 80% BCL ore achieving nickel
recoveries in excess of 90%.
2. The results conclusively demonstrated that to achieve a 2% plus nickel
concentrate grade the Dikoloti ore has to be mixed with BCL material prior to
flotation.
3. The leaching results showed that excellent nickel and copper recoveries could be
achieved with a 1:2 ore: acid mix namely a 95.5 % Cu and 96.5% Ni recovery at
ambient temperature. An iron recovery of 95% was recorded.
4. The large sulphuric acid addition can be attributed to the high iron content
(pyrrhotite) to convert it to iron sulphate.
5. A number of processes exist to recover the Cu and Ni from the solution i.e.
precipitation of the salts, IX, SX followed by EW of the base metals.
6. Precipitation offers the cheapest process by precipitating the copper as a
sulphide, the iron as a hydroxide and the nickel as a carbonate.
7. This work was not covered in this test programme but merits a study on its own.
8. Another processing option which could be investigated is to produce a pyrrhotite
flotation concentrate, mix it with sulphuric cure it for certain period, roast to
convert the iron sulphate to hematite, and leach to recover the Cu and Ni.
9. The residue, predominantly hematite could be sold as source of iron ore.
10. This work was only briefly touched on during this study but justifies a further
investigation.
11. Flotation tests on the BML disseminated ore produced good concentrate grades
and recoveries, 2.4% Ni and 93.7% respectively.
14. 14
12. The flotation kinetics was fast since about 85% of the nickel floated within 15
minutes.
13. The nickel recovery on the BML massive ore at 71.4%b was much lower than the
disseminated ore, but produced a higher concentrate grade of 3.62% Ni
compared to 2.4% Ni. The flotation kinetics was slower.
14. Blending the massive and disseminated ores in a 70: 30 ratio showed very little
benefit in terms of improving the concentrate grades or recoveries.
15. Blending the same ratio with 70% BCL ore produced good concentrate grades and
recoveries.
16. This proves to be an option to BCL to supplement their feed stock.
7. Recommendations
1. A pilot plant flotation test be undertaken blending the Dikoloti and BCL ore in a
20:80 ratio
2. Leaching the Dikoloti ore offers a great potential for improving both the nickel
and copper recoveries and should certainly be further explored.
3. Further assessment would be recommended, particularly to avoid the high iron
dissolution and to recover the nickel and copper as good saleable products.
8. Acknowledgement
The writer wishes to thank Mr Moroka, Mothusi, Ms Patience Showa and Mr Godwin
Kangambeu from BCL for the opportunity given to perform this very interesting and
challenging study.
In addition, especially acknowledging Mr Kabo Mosanga, metallurgist from BCL, who
carried out all the physical test-work in the laboratory and performed an excellent task.
Johann Steynberg
Metallurgical Consultant
Kupfermelt Metal Processing
October 2014
