Proposed Grinding System based on Small-scale Data

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Proposed Grinding System

based on Small-scale Data

prepared for

I I vvaannhhooee M M iinnee s s L Lt t d d ..

at SGS Lakefield Research Limited

Progress Report 1 ARM-0566

LR -10044-070

July 14, 2003

A.R. MacPherson Consultants Ltd.

Table of Contents

Introduction....................................................................................................................................... 4

Discussion ......................................................................................................................................... 5

1 Ore Characterisation........................................................................................................... 5

1.1 JKTech Drop-weight Test Results..................................................................................... 5

1.2 MacPherson Autogenous Grindability Test....................................................................... 5

1.2.1 Autogenous Work Index............................................................................................ 6

1.2.2 Density Measurements............................................................................................... 8

1.3 Bond Ball Mill Grindability Test....................................................................................... 9

1.4 Bond Rod Mill Grindability Test..................................................................................... 10

1.5 Bond Abrasion Test ......................................................................................................... 11

1.6 Conclusion on Ore Characterisation ................................................................................ 12

APPENDIX A: MacPherson Autogenous Grindability Test Details

APPENDIX B: Bond Ball Mill Grindability Test Details

APPENDIX C: Bond Rod Mill Grindability Test Details

APPENDIX D: Bond Abrasion Test Details

ENCLOSURE: JKTech Report

List of Tables

Table 1: JKTech Drop-weight Test Summary................................................................................... 5

Table 2: MacPherson Grindability Test Summary ............................................................................ 6

Table 3: Density Measurement .......................................................................................................... 8

Table 4: Bond Ball Mill Work Index Test Summary ........................................................................ 9

Table 5: Bond Rod Mill Work Index Test Summary ...................................................................... 10

Table 6: Bond Abrasion Test Summary........................................................................................... 11

Table 7: Grindability Testing Summary .......................................................................................... 12

List of Figures

Figure 1: MacPherson Autogenous Grindability Test Database ....................................................... 7

Figure 2: 18” Mill Product Database ................................................................................................. 7Figure 3: Bond Ball Mill Grindability Test Database ....................................................................... 9

Figure 4: Bond Rod Mill Grindability Test Database...................................................................... 10

Figure 5: Bond Abrasion Test Database .......................................................................................... 11

Figure 6: Work Index Correlations.................................................................................................. 12

Figure 7: Correlation between Autogenous Work Index and Drop-weight Test Data .................... 13

Figure 8: Correlation between Rod Mill Work Index and Drop-weight Test Data......................... 14

Figure 9: Correlation between Ball Mill Work Index and Drop-weight Test Data......................... 14

Introduction

A.R. MacPherson Consultants Ltd. (ARMC) was requested by Ivanhoe Mines Ltd. (Ivanhoe) to

conduct a grindability study for the pre-feasibility design of the Oyu Tolgoi deposit.

The test program was directed by Monsieur Maurice Tagami Consultant to Ivanhoe.

Prepared by: Reviewed by:

________________________________ ______________________________

André McKen Mike Ounpuu

Technical Associate Senior Metallurgist

Discussion

Ore Characterisation

The ore characterisation was performed on seven ore composites, and each composite was

submitted to the following grindability tests:

JKTech Drop-weight Test

MacPherson Autogenous Grindability Test

Bond Rod Mill Grindability Test

Bond Ball Mill Grindability Test

Bond Abrasion Test

1.1 JKTech Drop-weight Test Results

The drop-weight test was performed at Lakefield under the supervision of ARMC. The test results

were interpreted by Contract Support Services (JKTech’s North American agent), who issued a

separate report (Enclosure). The data are summarised in Table 1.

Table 1: JKTech Drop-weight Test Summary

Sample

Composite

Ore Zone A b A x b Percentile of

Hardness

ta Percentile of

Hardness

Ore Density

(g/cm3)

Sample #1 SW Oyu 49.9 0.98 48.9 58 0.42 22 2.82

Sample #2 SW Oyu 49.9 0.88 43.9 48 0.79 58 2.81

Sample #3 SW Oyu 52.1 0.69 36.0 77 0.46 51 2.82

Sample #4 Central Oyu 57.9 1.95 112.9 12 1.18 13 2.74

1.2 MacPherson Autogenous Grindability Test

The MacPherson autogenous grindability test is a continuous test, which is performed in an 18”

mill (~46-cm). The test is run until steady state is reached, for a minimum of 6 hours. The test

details are appended (Appendix A), along with a description of the test procedure, and

methodology.

1.2.1 Autogenous Work Index

The test results are summarised in Table 2, and the work index results are compared to our

database in Figure 1.

Table 2: MacPherson Grindability Test Summary

Sample

Composite

Ore Zone Feed

(kg/h)

Gross Work

Index (kWh/t)

Correlated Work

Index (kWh/t)

Percentile of

Hardness

Sample #1 SW Oyu 6.6 22121 310 24.2 17.9 77

Sample #2 SW Oyu 7.6 22206 319 21.6 16.8 69Sample #3 SW Oyu 6.2 22205 299 26.1 18.6 83

Sample #4 Central Oyu 18.0 22200 273 8.9 8.9 8

When the gross autogenous index is greater than 10.0 kWh/t (metric), a correlation factor is

applied to arrive at the index used in the grinding circuit design, as the 18” mill becomes less

efficient as the ore becomes harder. The correlation factor has been determined by grinding a

large number of samples in the 18” Aerofall mill and comparing the results obtained with data

from grinding the same type of material in a pilot and large commercial mill.

The ores showed a wide spread of hardness. The Southwest Oyu samples were generally hard,

ranking 69th

to 83rd

in our database. On the other hand, the Central Oyu samples were softer, all

below the 30th

percentile of hardness. The Composite sample number 4 was particularly soft.

Frequency Curve of Autogenous Mill Work Indices

1 3 5 7 9 11 13 15 17 19 21 23 25 27 >28Autogenous Work Index - Metric

F r e q u e n c y

Dat abase Oyu Tolgoi

Figure 1: MacPherson Autogenous Grindability Test Database

2 5 7 5 1 2 5

> 7 0 0

MacPherson Mill Product K 80

F r e q u e n c y

Dat abase Oyu Tolgoi

Figure 2: 18” Mill Product Database

The 18” product P80 is compared to our database in Figure 2. The P80’s for all the Oyu Tolgoi

samples were consistent, and ranged between 250 and 310 microns, which is lower than the

database median. Note that the 18” mill P80 is ore dependent, and is indicative of the actual P80

that can be obtained in industrial scale mills.

1.2.2 Density Measurements

Several density measurements are performed as part of the MacPherson grindability test

procedure. The results are presented in Table 3, and the drop-weight test densities are presented as

comparison.

Table 3: Density Measurement

Sample

Composite

Ore Zone Feed -1/4"

Specific

Gravity*

Charge -1/4"

Specific

Gravity*

Charge +1/2"

Density**

Drop-weight Test

Rocks (+1")

Density**

Sample #1 SW Oyu 2.81 2.82 2.81 2.82

Sample #2 SW Oyu 2.89 2.81 2.79 2.81

Sample #3 SW Oyu 2.92 2.82 2.82 2.82

Sample #4 Central Oyu 2.84 2.79 2.80 2.74

* Gas Pycnometer in g/cm3; ** Water Displacement in g/cm3

The ore charge specific determinations were performed by 1) gas pycnometer on minus ¼

“sample, and 2) water displacement on 18 individual coarse rocks in the range ½” to 1-¼”. The

feed specific gravity was performed with a gas pycnometer on a minus ¼” sample. The ore

densities from the drop-weight test procedure are obtained by water displacement on 30 rocks in

the range 1” to 1 ¼”.

The results were consistent. The S.G.’s at fine size measured with the gas pycnometer were

slightly higher than those obtained with water displacement, which could be caused by the

presence of internal cracks in the coarser rocks. There was no significant build-up of heavier

material in the mill steady-state charge at the test completion.

1.3 Bond Ball Mill Grindability Test

Bond ball mill grindability test was performed at 100 mesh of grind. The results are summarised

in Table 4, and compared to our database in Figure 3. Test details are Appended (Appendix C).

The Central Oyu and SW Oyu samples were soft and hard, respectively, with respect to Bond ball

mill work index.

Table 4: Bond Ball Mill Work Index Test Summary

Sample

Composite

Ore Zone Mesh of

Gram per

Revolution

Work Index

(kWh/t)

Percentile of

Hardness

Sample #1 SW Oyu 100 2221 111 1.12 19.1 91

Sample #2 SW Oyu 100 1579 118 1.35 18.2 85

Sample #3SW Oyu

100 1924 114 1.15 19.4 92Sample #4 Central Oyu 100 1539 112 2.54 10.4 12

Sample #5 Central Oyu 100 1913 116 2.14 11.9 21

1 3 5 7 9 11 13 15 17 19 21 23 25 27 >28

Bond Ball Mill Work Index - Metric

F r e q u e n c y

Database

Oyu Tolgoi

Figure 3: Bond Ball Mill Grindability Test Database

1.4 Bond Rod Mill Grindability Test

Each composite was also tested for the Bond rod mill grindability test at 14 mesh of grind, and the

results are summarised in Table 5. The results are compared to our database in Figure 4. Test

details are Appended (Appendix D). The results of the rod mill work index were similar to those

of the ball mill. Again, the Central Oyu and Southwest Oyu samples can be grouped in two

different categories, i.e. soft and hard.

Table 5: Bond Rod Mill Work Index Test Summary

Sample

Composite

Ore Zone Mesh of

Gram per

Revolution

Work Index

(kWh/t)

Percentile of

Hardness

Sample #1 SW Oyu 14 9239 891 6.21 18.6 82

Sample #2 SW Oyu 14 10336 954 7.31 17.2 72Sample #3 SW Oyu 14 10247 908 5.57 19.7 90

1 3 5 7 9 11 13 15 17 19 21 23 25 27 >28

Bond Rod Mill Work Index - Metric

F r e q u e n c y

Database

Oyu Tolgoi

Figure 4: Bond Rod Mill Grindability Test Database

1.5 Bond Abrasion Test

Each composite was tested for ‘abrasiveness’, with the Bond abrasion test. The test details are

appended (Appendix D) and the results are summarised in Table 6. Comparison to our database is

depicted in Figure 5. All the abrasion indices are softer than the database median, which is 0.3.

The samples can be considered as mildly abrasive.

Table 6: Bond Abrasion Test Summary

Sample

Composite

Ore Zone Abrasion

Percentile of

Hardness

Sample #1 SW Oyu 0.1116 17

Sample #2 SW Oyu 0.1904 31

Sample #3SW Oyu

0.1621 28Sample #4 Central Oyu 0.0803 10

Sample #5 Central Oyu 0.1986 32

0. 0 5

0. 1 5

0. 2 5

0. 3 5

0. 4 5

0. 5 5

0. 6 5

0. 7 5

0. 8 5

0. 9 5

1. 0 5

1. 1 5

1. 2 5

1. 3 5

1. 4 5

Abrasion Index

F r e q u e n c y

Database Oyu Tolgoi

Figure 5: Bond Abrasion Test Database

1.6 Conclusion on Ore Characterisation

The grindability results are summarised in Table 7. The work index data for each sample were

consistent, and the correlation between the different Bond indices was good as depicted in Figure

6. This shows that the Oyu Tolgoi ore hardness is relatively invariable with size on the range

tested. The autogenous work index was generally slightly lower than both the Bond ball mill and

Bond rod mill work index.

Table 7: Grindability Testing Summary

Sample

Composite

Ore Zone AWi RWi BWi A x b ta Ai

Sample #1 SW Oyu 17.9 18.6 19.1 48.9 0.42 0.112

Sample #2 SW Oyu 16.8 17.2 18.2 43.9 0.79 0.190

Sample #3 SW Oyu 18.6 19.7 19.4 36.0 0.46 0.162

Sample #4 Central Oyu 8.9 11.3 10.4 112.9 1.18 0.080

0 5 10 15 20

Autogenous Work Index (kWh/t)

B W i , R W i ( k W h / t )

Ball Mill Work Index

Rod Mill Work Index

Figure 6: Work Index Correlations

Figure 7 shows that both the drop-weight test impact (A x b) and abrasion (t a) portions, correlate

well with the autogenous work index, which is expected as the autogenous work index test

measures both simultaneously. The values that diverge slightly from the trend are the “A x b”

from Sample #5, and the “ta” from Sample #2.

0 5 10 15 20

Autogenous Work Index (kWh/t)

Figure 7: Correlation between Autogenous Work Index and Drop-weight Test Data

The same correlation curves were presented, with the Bond rod mill and ball mill work. The

results are presented in Figure 8 and Figure 9. It shows that there is also a correlation between the

drop-weight test parameters and the Bond rod and ball mill work indices, but it is more scattered.

0 5 10 15 20 25

Rod Mill Work Index (kWh/t)

Figure 8: Correlation between Rod Mill Work Index and Drop-weight Test Data

0 5 10 15 20 25

Ball Mill Work Index (kWh/t)

Figure 9: Correlation between Ball Mill Work Index and Drop-weight Test Data

Proposed Grinding System based on Small-scale Data

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