Stuart Saich

7/27/2019 Stuart Saich

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Typical grade recovery curves for a copper project


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Introduction

Target Audience for presentation/paper

Project managers

Financial managers

Objective

Demystify some of the issues

Provide some real simple rules of thumb


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Cerro Verde

Collahuasi

Escondida

El Salvador

Manto Verde

Frieda River

Golpu Wafi

Ernest Henry

Mount Isa Mines

Lady Loretta

Olympic Dam

Batu Hijau

Bozshakol

OOkiep

Konkola

MMH

El Pachon

El Morro

Antapaccay

Las Bambas

Black Mountain

Project experience listing


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Presentation overview

key issues to discuss

Sample selection philosophy

Prescriptive versus proactive testing The role of mineralogy

Rules of thumb

Test result validation or rejection


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Composite based testing Geologists define perceived ore types based

on lithology, alteration, mineralogy, and

expected metallurgical performance

Individual lengths of drill core aligned with

assay distribution of deposit are selected

Single well blended composite prepared Optimization testing carried out on composites

Basic assumption is that all material selected

for each ore type actually belongs in the ore

type

Ore type selection is not verified based onmetallurgical performance


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Variability Based Testing

Initial assumption of ore types made bygeologists, based on lithology,

alteration, mineralogy

Variability samples (50-60) for each ore

type are selected to provide spatial

distribution Individual variability samples are tested

to evaluate metallurgical performance

Basic assumption is that variability

sample only belongs in the ore type

when metallurgical performance isvalidated

Ore types re-defined upon completion

of this type of testing


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Typical Results from Composite vs Variability

Testing programs


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Metallurgical Testing program

philosophies

Prescriptive

Typically procedural in nature

Scope defined in detail prior to start of testing

Typically completed on composites

Focused on optimization of parameters

Laboratory has little room to move

Proactive

General guidelines given to laboratory

Laboratory needs to understand the clients business

Testing conditions adapted to suit metallurgical response


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Met Testing Rules of thumb!

Commonly heard rules of thumb Grind only as far as required to achieve 40-60% liberation

Target Industry Standard concentrate grade

Typical rougher mass recovery should be 8-12%

Collect no material that is lower in grade then feed

Maximize valuable metal recovery, whilst minimizing mass

recovery

Use proven reagent scheme

Focus on elements because we cannot measure minerals on

line Four of these are valid, the other three lead to poor

results!


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Focus on mineralogy and liberation

Minerals float elements dont

Industry standard concentrate grade concept devalues

project potential when secondary minerals are present

Chalcopyrite - 34.6 % Cu

Bornite - 63.3 % Cu

Chalcocite - 79.8 % Cu

Covelite - 66.5 % Cu

At laboratory scale should target a concentrate grade

equivalent to 80-85% valuable mineral content.

Industry Standard appears to be around 28% Cu


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Difference in results

Prescriptive vs Proactive testingOpen circuit Cleaner

Tests

Red Prescriptive

Green Proactive

Shape of grade

recovery curve is anindication of how close

you are to optimum

conditions

Results are from a

project currently in

development in Peru


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Laboratory met testing execution Flotation is a highly complex, yet surprisingly simple process

The factors affecting flotation are highly inter-dependant

The only time that you can see whether good flotation is occurring is

by being there!

Using a prescribed metallurgical testing program, i.e proven reagent

scheme is a fallacy The laboratory technician needs the freedom (and training) to be

able to make decisions on the fly with regards key flotation

conditions i.e.:

Reagent dosages, Air flow rate, Pulp density

A proper variability based program could never be executed using aprescriptive program as the optimal conditions change for each

sample


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Key flotation testing stages

Primary grind and liberation analysis

Rougher testing

Concentrate liberation evaluation Regrind

Cleaner testing

Locked cycle testing


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Primary Grind and Rougher

flotation testing key objectives Extent of primary Grinding

Grind only as far enough to achieve 40-60% liberation

Rougher flotation is first upgrading stage

Typically target upgrading factor of 8-12 times head grade

Mass/copper recovery Mass recovery to concentrate should be 8-12%

If mass recovery is 20-40% then something is wrong

Kinetics

Rougher float time ~ 8-12 minutes

If using >20 minutes then not applicable for scale-up

Reagents/Conditions

Adjust according to visual flotation response achieved

Monitor results to confirm


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Concentrate liberation

evaluation Use optical mineralogy to see what you have generated

Gn

Gn

Ma

Cp

Rougher concentrate Scavenger concentrate


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Cleaner and LCT Testing objectives

Mineral losses in rougher flotation are typically in coarse

size fraction

Mineral losses in cleaner circuit are typically in ultra fine

fraction

Need to only re-grind those minerals that need it. Use

mineralogy to identify correct target regrind

Avoid generating slow floating fines that compete with

pyrite

Avoid inducing excessive circulating loads


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Cleaner flotation testing


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Locked cycle testing

Initially thought of as method to emulate re-circulating

load in real world plant

Would typically expect LCT result to achieve 1-2 %

increased recovery over open circuit cleaner tests at

same concentrate grade

Seems to be used as a catch all to get perceived

reasonable grade and recovery for financial analysis

LCT results analysis methodology, and subsequent

decision process as to whether to reject test results does

not appear to well understood


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The LCT Test and objectives


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Typical LCT ResultsThe significant shift in

grade and recovery for

the LCT tests is a

major concern and

implies that correct

conditions for design

are not identified.

The question and key

is to find out why!


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Unstable LCTs - Do these exist?

Note the following:

1. The first stage generates

results similar to that of the

open circuit cleaner test

2. From then on recoveryincreases

3. Three stable tests are not

achieved, and the difference

between the first and last

cycles are too big

4. Any LCT that looks like thisshould be rejected and not

used for design or financial

evaluation purposes


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This stream is the

culprit. It represents

middlings particles

that were not fully

liberated in regrind

and now need to

return for a 2nd, 3rd, 4th5th etc time around


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Conclusions Part I

The sample selection philosophy and testing program

may well have an impact on metallurgical results

obtained

The use of either prescriptive or proactive met testing

philosophy and management will probably have a

significant impact on results obtained

A focus on elements only and not mineralogy would

probably result in lower concentrate grades being

accepted

Be very careful of Rules of thumb Some are not good!


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Conclusions Part II If the met testing program does not provide sound data for design,

then the basis for that projects development will always be sub-

optimal

In reality flotation is a very forgiving process and operators tend to

adapt to what they are given to work with ->

However the selection of mechanical equipment and specification of

design criteria that is based on sub-optimal results means that the

project will probably operate at a lower overall efficiency than what it

really could for the life of the mine

Documents

Stuart Saich