1445 Copper-Molybdenum Concentrator Surveys using ... 10-FC (9HPA3) Background Molybdenite...

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Copper-Molybdenum Concentrator Surveys using Mineralogy and Process Benchmarking Tools to

Improve Overall Plant Performance

David Meadows, Gillian Hall, David Rose, Phil Thompson, Wolfgang Baum,Randy Zahn and Samuel Yu

12th AUSIMM Mill Operators’ Conference1st -3rd September 2014

Townsville, Queensland, Australia


Outline

Introduction

Flow Sheet and Areas of Impact

Process Mineralogy

Process Benchmarking

Concentrator Surveys

Conclusion


Safety Share


INTRODUCTION


Current challenges within the IndustryOver the last ten years there have been clear trends in the copper and molybdenum industry including:

Decline in ore head grades More complex ore mineralogy Harder ores and all that entails in terms of wear and throughput Progressive increase in plant throughputs Increasing operating and capital costs Fluctuating metal prices Increasing cost and availability of power Increasing constraints on water usage and availability Increase in underground operations Tighter environmental controls

This has changed the profit margins of operating mines as well as future planned mines


Copper Concentrators – Lower Grades and Higher Throughputs


How do we respond to these challenges? Typically, mine owners respond by either cost cutting or increasing

tonnage to reduce the unit production cost. These two approaches alone are not sufficient for the future of more complex mineral processing operations and larger plants.

Significant cumulative gains in performance can be made by systematic optimization across an existing flow sheet.

Automated mineral analysers transformed plant surveys into a most effective tool for unlocking process issues and optimising plant performance.

Detailed area by area review to identify process constraints in terms of equipment and operating practice in conjunction with robust diagnostic work based on mineralogical and metallurgical characterisation are required for process evaluation and subsequent optimization.

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FLOW SHEET AND AREAS OF IMPACT


Typical Copper-Molybdenum Block Flow Diagram


Copper-Molybdenum Flow Sheet

Typically includes the following:

Comminution circuit – primary crusher, SAG mill with pebble crusher and a closed ball mill circuit. Typical variations include HPGR replacing SAG or precrush before SAG due to ore hardness or other economic considerations.

Flotation circuit – typically including rougher, regrind, one to three stages of cleaning. Where molybdenum exists as a by-product of copper, the bulk sulphide concentrate will be dewatered and then sent to the molybdenum flotation circuit which includes a rougher circuit and several stages of cleaning. The tailings from the molybdenum roughers are the copper concentrate.


Copper-Molybdenum Flow Sheet continued

Concentrate dewatering circuits, including copper concentrate thickening and filtration and molybdenum concentrate thickening, filtration and drying.

Tailings dewatering, including standard tailings thickeners and in the future a potential combination of thickening and filtration.

Water reticulation systems involving fresh water intake and water recycle systems.

In a typical plant survey and process benchmarking the focus is mainly on the comminution and flotation circuits.


An Underperforming Plant is mainly influenced by the following four factors:

Significant changes in the mineralogy of the ore treated.

Existing process parameters no longer optimum for the new ore characteristics.

Flow sheet and equipment sizing based on samples and test work that no longer represent the current ore treated.

Process equipment, due to mechanical/design issues not running at optimum conditions.


PROCESS MINERALOGY


Process Mineralogy – Back to Basics

Plant feed grade has a direct influence on potential recoverable metal output but ore characteristics and presence and type of copper bearing minerals and especially gangue mineralogy will have a direct impact on the metallurgical performance.

As with any concentrator, ore mineralogy impacts almost every unit operation from comminution and flotation, through to solid liquid separation. Mineralogical information for each unit process provides: Insight to existing operation issues. Guidance to optimise the process.


Process Mineralogy – Grinding Circuit

SAG throughput is the area most often compromised due to insufficient knowledge of the ore hardness and the ore variance.

Over last five years several large concentrators with SAG mills have failed to reach targeted throughput. The root causes are usually associated with insufficient sampling and ore characterisation or inadequate test work or a combination of both.

In addition to the well recognised standard comminution tests, XRD can be used to build quantitative ore hardness profiles by correlating ore hardness to select mineral concentrations.

Certain minerals have an excellent correlation with mill throughput.


Mill Throughput Forecast based on MineralogyOnline NIR (near infrared) or FTNIR (Fourier transform near infrared) predict mill throughput continuously, reliably and at lower cost than occasional Bond work index or JK drop weight tests.

R² = 0.8565

180

200

220

240

260

280

300

320

340

360

380

180 200 220 240 260 280 300 320 340 360

NIR Predicted

Throu

ghpu

t (tph

)

Actual Throughput (tph)

Process Control ‐Mill Throughput

MicaceousMinerals by NIR


Grinding Circuit Operational Parameters influenced by Ore Characteristics

Feed rate Mill load Percent solids of slurry Ball charge level Ball size Mill liner and lifter design and configuration Grate aperture size Mill speed Mill circulating load Cyclone feed density Grinding circuit control philosophy


Process Mineralogy – Flotation Circuit

The complete flotation circuit is very sensitive to and is driven by ore mineralogy. Automated mineral analysis can determine and quantify:

Mineral liberation and locking which govern flotation feed primary grind and regrind sizes and composition of middlings. These can vary considerably within a deposit.

Sulphide and gangue mineralogy which influence choice of reagent scheme, reagent dosages and addition points.

Gangue minerals which can have a detrimental effect on reagent selectivity and copper and molybdenum metallurgical performance.

Mineralogical reasons for losses to tailings


Ore Characterization - Mineralogy

Increasingly complex mineralogy has meant greater use of automated mineralogical analysis techniques – understandingliberation and gangue mineralogy very key

Sample: 10-FC (9HPA3)

BackgroundMolybdeniteChalcopyriteCovelliteBorniteFe SulphidesGalenaCu ArsenidesSphaleriteRutileTi PhasesBariteCu Metal/Ox/CO3Fe-Ox/CO3Ce PhosphateQuartzPlagioclase FeldsparK-FeldsparMuscoviteMicaAl SilicatesSilicatesCarbonatesCa PhosphatesCa SulphatesOthers/Undiff

Mineral Name



21

Optical Microscopy Hand Lens

Petrographic Thin Sections

Manual XRD Analysis

Analog SEM

Past Tools and Equipment Qualitative and Time Consuming


22

1st Automated Mineral AnalyzerIn US Mining – 2001 Phelps Dodge

Courtesy CSIRO

1970-1980s

1st Automated Mineral Analyzer at Cu Mine SiteCerro Verde 2005

From Here….

…To Here!!

Computer DevelopmentThe Initiating Event for Automated Mineralogy

1MineralogyFile = 100’s Megabytes

Up to > 1 Gigabyte


Clay AnalysisXRD Mineralogy

Pol Microscopy

Automated Mineral Analysis

SEM-EDS/WDS

Ore Characterization and Mineralogy Labs / Equipment


Process Mineralogy – Solid Liquid Separation and Water Chemistry Mineralogy can also influence sedimentation and filtration rates as well as govern water chemistry:

Unexpected changes in mineralogy can cause major upsets in the operation of thickeners leading, in extreme cases, to mechanical failure.

Changes in the nature of particles as well as the amount of fine material will affect filtration rates and cake moisture contents.

Water chemistry is strongly influenced by changes in mineralogy and this in turn can severely impact certain parts of the process such as flotation.


PROCESS BENCHMARKING


Process BenchmarkingObjective is to: Establish the efficiency of an existing operation Compare with the past and current test work results Gauge against other similar operations

Determine from this if plant has reached its potential limit in terms of: Throughput tonnage Recovery Product quality Operational cost

Typically requires specifically targeted, well developed plant sampling and laboratory test program. Mineralogy and geological information are key to gain critical insight on plant performance. Interaction with current and future mine planning must also be recognised.


Process Benchmarking – Analyses of Data

Conducted either by unit process or across larger sections of the flowsheet with key process inputs and outputs. Comparative results between plant operation and lab scale tests should be included.

Appreciation of comparative operating data is critical in order to establish potential improvements and also process limitations.

Can use process simulation software programs such as AggFlow and JKSimMet to assist with benchmarking of comminution circuits.

Flotation plant improvements still rely mainly on bench scale test work in parallel to the commercial plant and are driven by the understanding of the ore mineralogy.


Process Benchmarking – Comminution

AggFlow is commonly used in the modelling of crushing and screening circuits. Allows user to run “what if” scenarios. Very user friendly and has a good solid database behind it.

JKSimMet is probably the most advanced simulation program available for modelling comminution circuits in use today. With good quality testwork and a skilled user it can be an extremely useful tool for grinding circuit simulation and optimisation.

Focus should be on the following key parameters: Process throughput – hourly, monthly and annual Process run time Process power usage and overall kWh/t Product liberation and ability to control the process around the

desired product size Maximising individual equipment performance


Process Benchmarking – Flotation

The information that needs to be collected should include the following:

Mineralogical information from around the circuit. Particle size information. Recovery and grade. Recovery, grade and mineralogical information by size for at least the

rougher stage. Reagent schemes, addition points and process water chemistry. Other operational information. Operating control strategy. Level of circuit automation. Level of operator skill. Maintenance quality and procedures.


CONCENTRATOR SURVEYS


Conducting a Plant Survey

The first step is to clearly define the scope including :

A clear objective of the survey.

Defining the concentrator circuit to be surveyed.

Obtaining sufficient background and historical information on the plant and the current flowsheet and key operational parameters.

Building a good team.

Carrying out a preliminary fact finding site visit, if at all possible, as surveys require meticulous planning.


Preparation

Discuss when best to conduct the plant survey Discuss the relevant issues with the plant metallurgists,

mineralogists, geologists etc. Obtain as much background knowledge as possible Discuss whether some portion of sample test work and analysis

can be conducted on site Discuss the on-site laboratory capability Determine the manpower resources available Determine if speciality samplers are available or require purchase Undertake a thorough walk-through of the plant Discuss safety issues Rehearse to establish sampling times and to gauge sample

amounts taken in cuts around the circuit Set up regular communication meetings before, during and after

the survey to minimise delays and disruptions.


Sample and Data Collection, Sample Preparation

Duration – will vary from one day to two weeks.

Sampling – ensure samples taken only when plant at steady state.

Comminution circuit – recommend plant personnel take samples.

Flotation circuit – if possible, samples should be filtered on site.

Collection of plant operating data covering the survey period.

Sample preparation – follow strict procedures according to test work requirements. Samples from same circuit stream may be composited.


Test Work on Samples Collected will depend on Scope and Objective of Plant Survey and can include: Mineralogical analysis, typically size-by-size analyses on ore type

end member samples and flotation circuit samples.

Comminution circuit testing, typically crushing work index, ball mill Bond work index, rod mill Bond work index and abrasion tests, JK drop weight and SMC tests, SAG design test and SPI test.

Flotation testing mainly focused on optimisation, including optimum grind size, flotation kinetics and optimal reagent scheme.

Sedimentation work for thickener optimisation.

Concentrate filtration work focusing on optimising filtration rate and cake moisture content.


Final Reporting

After the test work has been completed and all data extracted the findings must be carefully considered along with all the other information collected. Subsequent benchmarking of the process will provide answers to the following:

How well is the plant operating. What changes need to be made to optimise and improve

throughput, product recovery and quality and operating costs. What are the practical implications of making any adjustments.

Everything relating to the survey is comprehensively documented and discussed in the final report issued to the client.


CONCLUSION


Concluding Comments

In the minerals industry the need to optimise existing mining customer assets and look at ways to reduce operating costs cannot be overstated.

A well conducted concentrator survey including quantitative mineralogical analyses is the most efficient way to ascertain how well the plant is operating and how much potential the operation has for improvement.

The integration of a strong capability in mineralogical analysis, metallurgical testwork and process analysis can provide a tremendous tool to service copper-molybdenum concentrators.

The potential to improve an operation’s profitability is well recognised with these types of surveys. Pay back is very rapid.


Thank You

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1445 Copper-Molybdenum Concentrator Surveys using ... 10-FC (9HPA3) Background Molybdenite...

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