Metallurgical Testplan

Comminution Tests

Benchscale Tests

Variability Testwork

Pilot Testing

Metallurgical Testplan

The development of a suitable process to treat an orebody appears to be a relatively straightforward matter. However, selecting the optimum process whilst maintaining the overall project development schedule is a complex task. This requires careful balancing of time and budgetary constraints against the benefits of a more closely defined process design.The key to a successful process plant design is the implementation of a well-structured, comprehensive testwork program to ensure that a circuit and reagent scheme is developed that can cater for the variability in the orebody, whilst still providing near optimum economics on the majority of the process plant feed.It is important that Metallurgical Testplan is developed and executed in parallel with the exploration of the deposit and that the results are used to assist in the planning and understanding of the continuing exploration. An understanding of the geology and mineralogy of a deposit, and the consequent sample selection for testwork, has a significant impact on the effectiveness of the plant design. The following factors are important in ensuring that an integrated approach to the design of the processing plant is achieved:

• Understanding the deposit from a process perspective by the geology and mining disciplines;
• Detailed evaluation of geology, mineralogy and mining method of the deposit by the process design team; and
• Assessment of the metallurgical requirements for sample selection.

Frequently, there is insufficient interaction between the major disciplines and this can adversely affect the costs and schedule of the process design phase and, ultimately, the commissioning and operation of the project. The basic mineralogy and geology of a deposit dictate the plant design and testwork requirements and it is important that the whole team has an appreciation of the extractive metallurgy of the ore. For this to occur, process input is required early in the exploration phase to ensure that potential process issues are addressed. For example, exploration drilling and geological analysis can infer a potentially economic gold deposit based solely on gold grades. However, process factors, such as refractoriness leading to low recovery or gangue components leading to high reagent consumption, can complicate the processing of the ore and may render the deposit uneconomic.It is necessary that such issues are identified and understood so that process variables can be assessed throughout the evaluation phase. Metallurgical testwork can be used to evaluate process options that, in turn, can significantly impact on the exploration and geological requirements.It is also important that the exploration and mining teams have an understanding of the potential process implications of the ore. It is not uncommon that a deposit is almost completely explored and a mine plan developed without qualified process input. This can create a disjointed approach to the development of the project. The mine plan can be completely in disagreement with the optimum processing requirements. Either the process design has to be modified to suit the mine plan or a new iteration of the mining plan is required to better suit the processing requirements. Either way, both money and time can be wasted. The optimum mine plan must recognise the balance between low cost, bulk, non-selective mining and the requirements of the process plant in treating the different ore types within the orebody.Before designing a sample collection and testwork program, a thorough understanding of the ore types to be processed is necessary. The process design team must be able to categorise the deposit into areas possibly requiring different processing methods. Therefore, the first stage in the process design must be a complete review of the geology and mineralogy of the deposit. In parallel with this, the mining methods and mine plans should also be assessed. Whilst the results of testwork programs can be used to differentiate between ore types, the cost and time requirements for testwork programs can be reduced significantly through prior use of geological and mineralogical data.

Factors that should be considered in the sampling and testwork program include:

• Head Grade: Head grade of valuable metal is often the only quantitative datum available across the deposit. Therefore, sample collection and testwork should recognise head grade as an important variable. It is important that head grade analysis is not confined to the valuable elements, but also includes those elements which can constrain throughput and recovery, eg. sulfur and arsenic values in a gold deposit. Failure to recognise this has been noticeable in some refractory gold projects. It is a significant omission, since the throughput of the oxidation circuits is dictated by sulfur grade.

Mining Plan: The mining plan dictates a schedule of ore delivery to the process plant. The ore characteristics can significantly change over the life of the mine and may influence the plant design. The requirement for campaign processing or blending of ore types should be considered in Metallurgical Testwork.

Sample Selection for Metallurgical Testwork

The aim of a sampling program is to collect the optimum number and quantity of samples that allows a suitable plant to be designed and metallurgical performance to be predicted.

Unless a significant blending process is allowed for prior to processing, varying ore types can be mined and processed with little or no blending. The design of the plant, therefore, has to cater for the anticipated schedule of ore for treatment and sample collection for a Metallurgical Testplan must recognise this.

Typically, three major sample types are used in the metallurgical evaluation of a deposit:

• Variability Samples: These are individual drill hole intersections or specific composites that represent ore types exhibiting different metallurgical responses, as indicated by the mineralogy/geology and expected process performance. They are used to assess the variability of the orebody, to determine whether the plant design will be suitable for all ore types, and to evaluate metallurgical recovery and/or grade. In this context, it is also important to ensure that testwork is carried out on samples representing the ore to be fed initially to the plant.

• Composite Samples: Composite samples are used for testing reagent or flowsheet variables where comparative testwork must be carried out on the one sample. Typically, several composite samples may be required to assess the major ore types. The number of these composites needs to be rationalised to minimise testwork costs and time.

The composites should represent the ore types that will dictate the plant design, eg. The hardest major ore type, the most difficult ore to float, etc. Factors that should be considered in sample composition and representivity include:

• metallurgical and geological definition of the "ore type"
• variability of the ore (continuity of mineralisation)
• the number of intersections included in the composite
• the drill hole intersection angles through the orebody
• special distribution of intersections
• weighting of intersection samples to make up the composite

There is little value in trying to achieve a representative composite of the entire deposit, as the processing plant will probably never treat such ore at any one time.

• Bulk Samples: Bulk samples are used for pilot plant testing or large scale tests. Pilot plant tests are usually required to demonstrate a high risk process, to increase the confidence level on a marginal project or for the production of concentrate or other downstream products for other testwork (eg. roasting). Pilot plant testwork does not necessarily provide better testwork data than bench scale work and should be evaluated carefully in terms of the high cost of sample collection and the difficulty in achieving adequate sample representation.

Types of Sample for Metallurgical Testwork

There are several types of sample material commonly used for metallurgical testwork:

Reverse Circulation (RC) Drill Chips - Fundamental problems caused by the stratification of heavy particles within RC drill chip samples can result in poor representation. The RC chips also tend to have a bimodal size distribution, with both coarse chips and a large amount of very fine material. The problem is exacerbated with friable ore types, eg. sericites, and can affect testwork results. This leads to another problem arising from the potential oxidation of the sample due to the high fines content. Despite the problems with RC drill chips, the low cost of sample collection compared with other methods makes it a popular choice for simple metallurgical tests such as gold and copper leaching tests. Their use in comminution and flotation tests should, generally, be avoided.

Diamond Drill Core - Fresh diamond drill core provides excellent material for metallurgical testwork. Comminution and flotation testwork generally requires drill core of varying sizes to achieve satisfactory results. NQ (50 mm) and HQ (63 mm) diamond drill core is commonly available from the exploration phase. The core is usually cut into quarters. Typically, only one quarter will be available for metallurgical testwork. There is a number of comminution tests that require at least whole (uncut) HQ core or whole PQ (75 mm) core. Drilling program plans should account for these process sample requirements and may need to include holes drilled specifically for metallurgical sample collection.

Trial Mine Samples - Large samples can be generated from RC chips or drill core, but, as the quantity requirements increase, trial open cut or underground mining may become more economic. Unfortunately, costs usually impose significant limitations with mined bulk samples.

Testwork Required for Engineering Studies

There are different types of the tests which will be carried out based on the type and level of the studies as shown in Table next page. The cost associated with each level of these studies is estimated as follows:

• Conceptual Study- $50,000 +/-20%
• Pre feasibility Study- $200,000 +/- 50% (Simple gold ore, one orebody)
• Bankable Feasibility Study- $500,000 +/- 50% (Simple gold ore)
• Bankable Feasibility Study- $1,000,000 (Base metals + Pilot Plant)

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Comminution Tests

1. Bond Rod Mill Work Index (RWI)
2. Bond Ball Mill Work Index (BWI)
3. Abrasion Index Test (AI)
4. Crushing Work Index (CWI)
5. JK Drop Weight Test
6. Point Load Test (PLT)
7. SAG Mill Comminution (SMC) Test
8. Unconfined Compression Strength (UCS) Test

Bond Rod Mill Work Index (RWI)

• Soft (7-9 kWh/t)
• Medium (9-14 kWh/t)
• Hard (14-20 kWh/t)
• Very hard (>20 kWh/t) 

Bond Ball Mill Work Index (BWI)

The Bond Ball Work Index (BWI) is an indication of how much energy is required to grind a sample in a ball mill, from 3.35mm to about 0.075mm. The BWI can categorise the sample as:

• Soft (7-9 kWh/t)
• Medium (9-14 kWh/t)
• Hard (14-20 kWh/t)
• Very hard (>20 kWh/t)

Abrasion Index Test (AI)

Crushing Work Index (CWI)

JK Drop Weight Test

JK Simulation

Point Load Test (PLT)

SAG Mill Comminution (SMC) Test

Unconfined Compression Strength (UCS) Test

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Mpa

50-100                         soft oxide ores              high crushing rates

101-250                       medium hard              average crushing rates

251-400                       hard ore                       reduced throughput

400>                            very hard ore                crushing difficult, high power

With high power efficiency and grinding to less than 12 microns, the IsaMill technology quickly became very reliable. MIM's development uses relatively cheap materials like rubber and polyurethane compounds that offer long wear lives.  

The grinding chamber consists of a horizontally mounted shell and has a volume of approximately 3000 litres. A shaft is coupled to a motor gearbox driven by a 1500 kW motor where rotating grinding discs are mounted onto the shaft system.  Media and ore particles are continuously fed into the feed ports and mixed in a slurry. A product separator separates the exiting fine product and the media remains inside the mill.       

Some common applications in gold recovery include fine grinding of sulfide concentrates for the conventional cyanide leaching of gold. There is also fine grinding of sulfide concentrates for oxidative leaching processes for production of copper or nickel metal.

·          Low maintenance - simple operation requires few specialists.

·          Compact - the mill system is the smallest of fine grinding equipment.

·          High Energy intensity - high power efficiency with up to 1.1MW operation.

·          Accurate scale-up - good accuracy from pilot to commercial sizes.

Benchscale Tests

Benchscale Tests includes the following :

1. Gold Ore
2. Copper Ore
3. Nickel Ore
4. Other Base Metals (Lead, Zinc, etc.)
5. Uranium Ore
6. Vanadium Ore
7. Iron Ore
8. Mineral Sands
9. Bauxite
10. Miscellaneous Test

Gold Ore

Head Assay:

• Gold: to check the valuable metal level.
• Sulphur: to check the oxidation degree of the mineralisation.
• Other metals: by Inductively Coupled Plasma (ICP) scan to perform a wide spread check for other metals, both beneficial and deleterious.
• Arsenic content.

Gold mineralogy:

• Pyrite
• Pyrrhotite
• Magnetite
• Chalcopyrite
• Bismuth
• Bismuthinite
• Galena

True Specific Gravity

The true specific gravity is determined on ground sample to remove the affect of sample porosity. Determination of true specific gravity of the ore is required for design and is used in any process calculations.

Comminution is the use of crushing and grinding to effect a reduction in particle size of the ore to liberate the valuable minerals from the gangue.

• JK Drop Weight Test (DWT)
• SAG Mill Comminution Test (SMC)
• Point Load Test (PLT)
• Unconfined Compressive Strength (UCS)
• Abrasion Index (AI)
• Crushing Work Index (CWI)
• Bond Rod Mill Work Index (RWI)
• Bond Ball Mill Work Index (BWI) 

The grind establishment test is used to determine the relationship between the laboratory mill, grind time and resulting grind size. The samples will be ground for various times in the laboratory grinding mill and size analyses will be conducted on the grind products.

To check the distributions of gold in the samples. A diagnostic leach is a sequence of leaches using different solvents to differentiate the various gold associations.

A portion of the composite will be subjected to gravity separation prior to conventional leaching. The removal of free gold, in particular, and silver, if present in economical quantities, prior to the traditional leaching processes has a number of advantages. Notably:

• Decrease the circulating load of precious metals in the grinding circuit.
• Potentially significant increase in overall recovery as particles of metallic gold are captured and treated, reducing the possibility of gold escaping as incompletely leached grains through the tails.
• Carbon requirements are lower in the major leaching process.

Determines the recovery and gold production by leaching the concentrate (from Gravity Separation) using an ACACIA type reactor.  This test allows a more accurate assessment of the gravity concentrate as this product contains coarse, free gold which is very hard to assay. The size of the Intensive Leach Reactor is determined from the leach rates and the required throughput. Laboratory tests have proven to be very reliable in predicting full scale performance.

Determines the most economic grind size for leaching.  This will be the size that gives the best compromise between grinding costs and precious metal recovery.

Determines the optimum cyanide concentration at the optimum grind size for best gold recovery.

Indicates the presence of any impurities which will consume oxygen and hence affect the leach kinetics.  It will indicate the possible need for air or oxygen addition during leaching.

Utilises the optimum conditions of grind size, cyanide concentration and oxygen level to determine the overall amenability of the ore to agitated leaching.

Evaluates the type of flocculant and the dosage required for any tails thickener. The results can also be used to provide a preliminary sizing of the thickener.

Evaluates whether lead nitrate enhances the leach test.  The presence of lead in the leach circuit is known to improve leach kinetics in some ores.

Determines the suitability of carbon adsorption in the CIP technique for extraction of the gold.

Detoxification tests are performed on leach tailings to examine the response of the ore to a detox method. There are a number of free cyanide destruction methods, including the INCO process. This process involves adding copper sulphate solution to the slurry (to complex the residual free cyanide) and then oxidising the cyanide with sulphur dioxide and air.  Detoxification of tailings solutions is of vital importance in ensuring that any operation meets environmental controls. It is of particular significance when the water balance within a plant is in surplus and hence water must be discharged.  The results from the detox test will give the conditions required for the INCO process to achieve acceptable cyanide and metal contents.

Cyanide speciation tests determine what form the cyanide is present as in the tailings. The toxicity of cyanide is very dependent on the speciation of the cyanide present. Results from the test include total cyanide, weak acid dissociable cyanide and the whole range of metal cyanide complex speciation. This information is essential in the choice of appropriate cyanide removal or recovery technologies.

Beneficiation in the minerals industry is the process of upgrading the average metal content of the process feed through the selective separation from a low grade component at some point in the comminution train. This can be done by a series of the screening, and scrubbing tests depending on the nature of the ore to determine if it is deemed to improve the gold and silver grade.

This test will provide information on the relationship between the crush size and the recovery possible. From this test the optimum crush size for heap leaching can be determined.

The purpose of percolation tests is to determine the permeability of the ore to the leach solution at the optimum crush size. A percolation test will give a good idea of whether agglomeration will be required or not.

The agglomeration test establishes the optimum agglomerate size, binder amount and strength for optimum heap construct.

The column leach test is a large scale heap leach test conducted over a 30 day period. This test is designed to properly gauge the extraction possible using heap leaching.

The viscosity of the slurry at a typical range of pulp density is determined.  If the viscosity is high then some correction factors need to be applied to the design or special equipment should be used in some sections of the plant.

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Copper Ore

Head Assay :

Head assay is used to identify the more prospective elements and other elements that can be deleterious during extraction process of a copper ore. From the head assay, it is important to identify whether the copper is either sulfide or oxide in nature to determine the best processing route as the next step to extract the copper from the ore. Evaluating the amount of impurities such as Hg, As, Bi is also important as they can be problematic during the processes

Mineralogy :

• Chalcopyrite
• Bornite
• Chalcocite
• Covellite
• Malachite
• Cuprite
• Tenorite
• Tennanite
• Tetrahydrite

Comminution : See gold ore section

True Specific Gravity : See gold ore section

Grind Establishment :See gold ore section

Size Assay :

The size analysis performed provides an idea of the amount of copper distributed at different size fractions.

Floation (Copper Sulphides):

The flotation process separates the different minerals into their respective fractions by using their different physical and chemical surface characteristics. The addition of chemical flotation reagents then causes the valued minerals to attach to air bubbles and rise to the surface of the tank where they overflow as a concentrate. Reagent dosage, kinetics, recovery and grades are studied.

Locked Cycle Floataion Test (Copper Sulphides) :

Usually, a locked cycle flotation test is done to:

• To determine the increase in recovery obtained by recirculation cleaner tailing (or, to know the effect of recycling);
• To determine the variation of reagent requirements to compensate for the circulation load of reagents;
• To determine the effect of build-up of slimes that may interfere with the flotation;
• To determine the froth flotation problems that may arise

The result can give the parameters used to design the flotation circuit, such as the number of roughers, scavengers, and cleaners required to achieve the target recovery and grade.

Column Flotation Test :

Instead of conventional cell used for flotation, column flotation test is sometimes needed. The objectives of the column flotation test are similar to the conventional flotation cell test. Another additional objective, for example, is to perform percolation test. Column flotation can be used for roughing, scavenging, and cleaning.

Thickening and Filtration Testwork :

Following flotation, the concentrate and tails products are thickened and filtered to assess the characteristics of the products at hand.The thickening tests will evaluate the thickening properties. The filtration results will help evaluate the filter performance and cycle time based on the laboratory conditions tested.

Heap Leach Amenability Testwork (Copper Oxides) :

Particularly useful when assessing the suitability of an ore for heap leaching. Leaching kinetics, metal recovery, acid consumption, slumping, percolation rate are variables that can be optimised in this testwork.

Direct Leaching :

Direct leaching is a term used to describe the leaching of all of an ore without prior beneficiation. This test can determine the optimum reagent concentration at the optimum grind size for best copper recovery by varying parameters such as grind size, reagent pH, etc.

Solvent Extraction :

This test provides an indication of the extraction and stripping kinetics as well as the phase separation behaviour for the extraction of copper from leached solution. Factors that are investigated during this test are:

• Operating temperature
• Viscosity of organic phase
• Entrainment level
• Copper in organic loading and extraction efficiency
• Stage efficiencies, etc.

Bacterial Leaching (Copper Sulfides) :

Bacterial leaching is suitable for copper sulfides as they oxidise the sulfur minerals to acquire energy to live, grow and reproduce. The bacteria produce sulfuric acid and copper sulfate. Recovery of the copper from the sulfate solution would be conducted in the later stages of the testwork. The testwork conducted for bacterial leaching would investigate key data such as kinetics, metal recovery and reagent consumption based on certain bacterium.

Pressure Oxidation (POX) Test :

This test is mainly used to determine metal recovery and evaluate and optimise operating conditions, such as pressure, temperature, monitor acid consumption and leach kinetics. Temperature is a critical variable as it influences the kinetic of leaching, and ultimately affects the residence time within the autoclave.

Variability Testwork: See gold ore section

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Nickel Ore

Head Assay :

Head assay is used to identify the more prospective elements and other elements that can be problematic during extraction process of a nickel ore.

Mineralogy :

• Sulphide
• Oxide (Laterite)
• Pentlandite
• Pyrrhotite
• Garnierite
• Gersdorffite
• Millerite
• Niccolite
• Breithauptite

Comminution : See gold ore section

Beneficiation Testwork (Nickel Oxides) :

Beneficiation Test is carried out to determine the nickel content of the ore at various different sizes. A number of size fractions are used to identify the Ni distribution and to determine if there is any barren Ni fraction, especially within the finer size. Such beneficiation result may indicate a certain size range needed for the Ni recovery. A series of wet and/or dry screening are used in beneficiation of an oxide nickel ore.

Bottle Roll Leach Text (Nickel Oxides) :

Bottle leach test is used to determine the maximum nickel recovery profile over time in a concentrated acid solution. Moreover, it is also used to determine maximum acid consumption.

Agglomeration Test :

Agglomeration is done by tumbling the ore with a binder to give the sample strength for supporting the mass of mineralisation. Agglomeration is done prior to the percolation test.

Percolation Test :

Percolation test is carried out to determine if the agglomerated fine grains have better percolation rate and lower slump than material with larger size fractions

Atmospheric and HPAL(High Pressure Acid Leach) Test :

HPAL Test is used for limonitic ores to determine Leach kinetics, nickel recovery, acid consumption of an ore.

POX (Pressure Oxidation) Test:

This test is mainly used to determine mineral recovery and design operating conditions, such as pressure, temperature, monitor acid consumption and leach kinetics. Temperature is a critical variable as it influences the kinetic of leaching, and ultimately affects the residence time within the autoclave

Heap Leach Amenability Testwork (Nickel Oxides):

This test is carried out to find if the ore is suitable for heap leaching. Leaching kinetics, metal recovery, acid consumption, slumping, percolation rate are variables that can be optimised in this testwork.

Oxygen Uptake Test : See gold ore section

Solvent Extration Testwork (Nickel Oxides) :

This test is performed in laboratory scale to determine the reagent dosage, operating pH, extraction, etc.

Batch Flotation Testwork (Nickel Sulphides) :

Batch flotation test is done to determine the most suitable collectors as well as the optimum concentration. The Flotation test results a set of data that is needed for designing the flotation circuit. Grind size, time recovery curve and grade recovery curve are the other data that can be obtained by carrying out this test.

Locked Cycle Floatation Test (Nickel Sulphides) :See Copper ore section

Variability Test:See gold ore section

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Other Base Metals (Lead, Zinc, etc. )

Head Assay

Mineralogy

Comminution

Leach Test

Thickening Test

Filtration Test

Uranium Ore

Head Assay

Mineralogy:

• Uraninite
• Pitchblende
• Brannerite
• Coffinite
• Carnotite
• Autunite
• Davidite
• Gummite
• Torbernite
• Uranophane

Comminution: See gold ore section

True Specific Gravity: See gold ore section

Size Assay: See gold ore section

Floatation:

Thickening and Filtration Testwork

Heap Leach Amenability Testwork

Leaching

Solvent Extraction

Bacterial Leaching

Pressure Oxidation (POX) test

Variability Testwork: See gold ore section

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Vanadium Ore

Head Assay

Mineralogy:

Magnetic Separation :

The vanadium ore may contain the magnetite/hematite mineral which is reduced to an appropriate size and passed over a series of low intensity; medium intensity (rare earth) and then high intensity magnetic separators.

Roast Test:

The purpose of roast testwork is to obtain a flake product with a high vanadium recovery.

Precipitation Test

Variability Testwork: See gold ore section

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Iron Ore

Head Assay

Mineralogy:

• Magnetite
• Hematite
• Goethite
• Siderite
• Pyrite

Comminution : see gold ore section

Beneficiation Tests:

Other Metallurgical tests that can be carried out in the laboratories for iron ore beneficiation are:

• Hydrosizer Simulation
• Ultra Fine Grinding (Regrind)
• Cleaning the Regrind Product
• Davis Tube Test

Hydrosizer Simulation:

This test utilises mild centrifugal as well as gravitational forces to separate the valuable ore from the gangue material. An optional step, only performed should more gangue need to be removed from the magnetic concentrate prior to ultra fine grinding and magnetic separation.

Ultra Fine Grinding:

This technique is used to reduce particle size for increased silica liberation. To perform this test the magnetic separation concentrate will be subject to regrind at 38 µm, 28 µm and 20 µm prior to cleaning.

The regrind test work criteria may be revised based on the mineralogical survey.

Davis Tube Test :

This test determines separation characteristics of the ore under intensely controlled laboratory conditions on:

• Sample of the regrind mill magnetic products
• Reverse flotation magnetite concentrate

The test enables the efficiency of the cleaner separation processes to be compared.

Magnetic Separation Test :

The proposed magnetic separation process is as follows:

Rare Earth Magnetic Separation (REMS)  at 3000, 4000 and 5000 Gauss
Wet High Intensity Magnetic Separation (WHIMS) at 8,000, 10,000 and 12,000 G
This aims to minimise the mass required to be finely milled and maximize the ore recovery. A sample of 100 kg of ore needs to be evaluated at three different sizes 300 µm, 212 µm and 150 µm prior to fine grinding.

Flotation Test :

A 1 kg sample of the ore is ground to the required P80 particle size. The flotation test is conducted using the reagent scheme, conditioning times and froth removal times.

This testwork is aimed at evaluating the characteristics of the final concentrate. These will include:

Concentrate Handling Testwork :

• Thickening : Bench scale cylinder settling tests or vendor thickening tests are used to reduce final moisture content in the concentrate.
• Filterability :Bench scale filter leaf tests or vendor filterability tests are used to measure the adaptability of a liquid-solid system to filtration
• Blaine determination : This test is used to produce surface area measurement.

Tailings Tratment Testwork :

• Thickening : Bench scale cylinder settling tests or vendor thickening tests are used to reduce final moisture content in the tailings.
• Rheology : This tests evaluates the rheological properties (e.g. shear stress) of selected thickening samples, which could be used as a source for pipeline and pump design.

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Mineral Sands

Head Assay

Mineralogy:

• Ilmenite
• Rutile
• Leucoxene
• Chromite
• Tungsten
• Magnetite
• Zircon

Comminution Testwork

Magnetic Separation

Gravity Separation: Spiral

Electrostatic Separation:

This test is used to determine the non-conductors (zircon, monazite, quartz) and conductors (ilmenite, rutile) minerals in an ore.

Beneficiation

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Bauxite

Head Assay

Mineralogy:

• Gibbsite
• Bohemite
• Diaspore

Comminution Testwork

Digestion (Leach) Test

This test is used to determine the optimum temperature, caustic concentration and pressure for alumina extraction from bauxite ores.

Precipitation Test

Tailings Treatment Testwork :

• Thickening
• Filtering
• Beneficiation Test

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Miscellaneous Tests

Digestion (Leach) Test:

The principle of this test is using a liquid or suspension with density between minerals to be separated. All other gravity separations use a fluid less dense than the minerals. This test is used extensively to clean coal and for the concentration ore such as iron, lead-zinc, chrome, manganese, tin, tungsten, fluorspar, magnesite etc.

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Variability Testwork

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Pilot Testing

Pilot testing is conducted:

• to generate bulk concentrate and tailings samples for downstream process testwork (eg. roasting, thickening/settling, filtering);
• to validate and optimise the bench scale flowsheet and provide additional information on operating parameters and potential problems;
• to confirm the effect of flowsheet changes;
• to confirm metallurgical response for continuous operation;
• to increase confidence for capital raising, etc. and
• to allow operator training prior to plant operation.

There are several factors that can complicate this. The high cost involved in generating large quantities of sample for pilot plant testing can result in a compromised sample. Trial pits and shafts are usually mined to the minimum depth required. This can result in the inclusion of supergene or transitional material that may respond differently to the primary ore. Also, the sample is usually only from one specific area in the deposit which may differ significantly from the design ore type.
The cost of the sample generation can also result in short pilot runs. Pilot plants can be difficult to operate, and a lack of sample can result in less than optimum operating conditions due purely to time constraints. It is, therefore, crucial that pilot plant programs are carefully planned and managed.
Approximately 20-30 tonnes of ore sample are required to do pilot testing.

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