Metalliferous Mining - Processing

Terminology

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Table of Contents

TABLE OF CONTENTS............................................................................................................................ 2

INTRODUCTION TO TERMINOLOGY.............................................................................................................. 3 What is this module about?..................................................................................................................... 3 What will you learn in this module? ....................................................................................................... 3 What do you have to do to complete this unit? ....................................................................................... 3 What resources can you use to help?...................................................................................................... 3

INTRODUCTION ........................................................................................................................................... 4

UNITS OF MEASUREMENTS................................................................................................................. 4

Length ..................................................................................................................................................... 4 Area ........................................................................................................................................................ 4 Volume .................................................................................................................................................... 4 Mass/Weight............................................................................................................................................ 4 Flowrate.................................................................................................................................................. 5 Concentration ......................................................................................................................................... 5

MEASUREMENT CONCEPTS ................................................................................................................ 7

Dry .......................................................................................................................................................... 7 Wet .......................................................................................................................................................... 8 The Marcy Density Gauge ...................................................................................................................... 9 Application of Units.............................................................................................................................. 10 Size Distribution ................................................................................................................................... 11 Recovery ............................................................................................................................................... 11

GENERAL MINERAL PROCESSING TERMS................................................................................... 12

Ore ........................................................................................................................................................ 12 Gangue.................................................................................................................................................. 12 Tails or Tailings.................................................................................................................................... 12 Mixtures ................................................................................................................................................ 12 Solution................................................................................................................................................. 13 pH ......................................................................................................................................................... 13

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Introduction to Terminology

What is this module about?

This unit is about the general terminology we use in the processing plant

What will you learn in this module?

• Explain the purpose of a cyclone

• Demonstrate an understanding of how a cyclone operates

• Identify the key components of a cyclone

• Demonstrate an understanding of the factors affecting cyclone performance

What do you have to do to complete this unit?

You will need to complete all the training tasks in your workbook, the review

exercise and the assessment given to you by your supervisor.

Discuss the competency standards for this unit with the Training Coordinator or your

supervisor.

What resources can you use to help?

If you need more information about topics in this unit, then you should approach:

• Your work mates and supervisor

• The training coordinator

• Metallurgists

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Introduction

Units of Measurements Almost all units in use at Sunrise dam are based on the metric system. Units are selected as appropriate to the quantity involved. For example, if someone weighed 80kg, they wouldn’t give their weight as 0.08 Tonnes, or 80 000 grams.

Length

Metre (m) Used for all large dimensions, such as tank height and mill diameter. Millimetre (mm) = 1/1000m Used for most smaller dimensions, such as screen cloth aperture, pipe diameters.

Micron (µµµµm) = 1/1000mm or 1/1000,000m Used for finely ground ore particles.

Area

Square metres (m2)

Volume

The size of a three dimensional space, can refer to air, water, earth etc. Litre (l) Cubic metres (m3) = 1000 Litres, (Often called ‘cubes’)

Mass/Weight

Tonnes (T) = 1000kg, used for quantities of ore Kilograms (kg), used for ore samples, reagents etc. Grams (g) = 1/1000kg, used for gold in ore. Ounces (oz) = 31.1035g, used for Dore, bullion.

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Flowrate

Can refer to liquids, slurries (through pipes), solids (along conveyors) m3/hr - Cubic Metres per hour (most common). l/s - Litres/second l/m - Litres/minute TPH - Tonnes per hour.

Concentration

g/T - Grams per Tonne An ore may have a gold concentration of 2.5 g/T. This means that there are 2.5 grams of gold contained in each tonne of ore. ppm - Parts per Million A sample of air may have a cyanide concentration of 1ppm. This means that there is 1 ‘bit’ of cyanide for every 999,999 ‘bits’ of air. Also used for gold in solution. Note that ppm and g/t are actually the exact same unit, but are used for different things. ie g/t for solids ppm for liquids Density Mass per unit volume An object’s mass divided by its volume. For example 1m3 of water weighs 1000 kg. Density of water = 1000kg/m3 or 1kg/L For example 1m3 of gold weighs 19 300kg Density of gold = 19 300kg/m3 or 19.3 T/m3 Specific gravity (SG) is the density of a substance relative to water. For example SG of water = 1.0 For example SG of gold = 19.3

This means that gold is 19.3 times heavier than water

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Measurement Concepts Ore is treated in two forms: 1. Dry 2. Wet (ie. mixed with water)

Dry

Ore is normally “Dry” when it is mined, but actually contains some moisture (0 - 10%). Dry refers to the solid form as opposed to the liquid form Dry ore does not “flow” and cannot be pumped This property can cause handling difficulties Dry ore can be characterised by two properties: 1. Specific Gravity (SG) The weight of a quantity of ore divided by its volume For example: 1 litre of quartz weights 2.65 kg SG = 2.65kg = 2.65 1 litre 2. Bulk Density Bulk density relates the mass and volume of a pile of ore and takes into account the air spaces in between the rocks For example, quartz has an SG of 2.65 Therefore, 2.65 kg of quartz has a volume of 1 litre

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However, a 265 tonne stockpile of quartz rocks may have a total volume of 200m3 due to airspace between the rock, therefore: bulk density = 265 tonne/ 200m3 = 1.32 Bulk density differs from Specific Gravity because of airspaces between rocks in a stockpile.

Wet

Ore is mixed with water to make it easier to handle When ore is mixed with water it is known as a SLURRY or PULP Slurries will “flow” and can be pumped Slurries are generally characterised by two properties: 1. Specific Gravity The weight of a quantity of slurry divided by its volume For example: If 1 litre of slurry weighs 1.4 kg then its specific gravity is:

1.4kg ÷ 1 litre = 1.4 2. Pulp Density or Percent Solids The weight of dry ore in a slurry divided by the total weight of the slurry and expressed as a percentage

% SOLIDS = mass of dry ore ÷ mass of slurry x 100% For example: If 300g of ore is mixed with 700g of water then the total weight is 1kg

% SOLIDS = 300g ÷ (700g + 300g) x 100%

= 300g ÷ 1000g(“1kg”) x 100% = 0.3 X100%

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= 30% % solids is the most common property used to describe a slurry Measured by Marcy density scales, or in the lab by filtering and weighing (more accurate) % solids plays a major role in the physical behaviour of slurries and the chemical treatment of slurries.

The Marcy Density Gauge

An instrument used to measure slurry density and % SOLIDS. A standard 1 litre container is hung on a spring The spring is attached to a needle gauge/dial and is calibrated to read “0” when the container is filled with water Marcy Density Gauge Faceplates

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Application of Units

Calculating Slurry Flowrate We do not always have the luxury of a magnetic flowmeter on every slurry stream. However if you know the %solids and the tonnes per hour then the slurry flowrate can easily be calculated. Example: There is 150 wet tonnes per hour coming up the mill feed belts with a moisture content of 5%. The combined cyclone overflow %solids is 45% and the assumed solids SG is 2.6, calculate the leach feed flowrate: (1) Calculate Dry tonnes and Moisture Moisture component in (m3/hr) = 150t/h x 0.05

= 7.5t/h ÷ 1 t/m3 (SG of water) = 7.5t/h x 1m3/t = 7.5 m3/h = 7.5tph Dry Tonnes per Hour = 150 tph - 7.5tph = 142.5 tph (2) Calculate Dry solids flowrate in (m3/hr) Dry solids flowrate = dtph / Solids SG = 142.5 / 2.6 = 54.81 m3/hr (3) Calculate Water Component in (m3/hr)

Water Flowrate = [(dtph) ÷ (%solids as decimal)] - (dtph) = (142.5 / 0.45) - 142.5 = 174.17 m3/hr (4) Calculate Slurry flowrate by adding up the components Total Flowrate = 54.81 + 174.17 = 236.48 m3/hr

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Size Distribution

A quantity of solid particles (eg a pile of sand) can be characterised by its size distribution, or size fraction. Not all particles will be the same size, but it is helpful to know the proportion above or below a certain size. Size distribution is measured using sets of sieves.

Supposing a solid sample is screened using a sieve with a 150µm aperture (gap size). 80% of the sample falls through the gaps, but 20% is too big to get through. We can then say the size fraction is:

80% passing 150µm.

Recovery

‘Recovery’ is the proportion of gold successfully processed into bullion, expressed as a percentage of gold in feed. Ideally the plant would extract 100% of the gold from the ore, but this is not always the case. Small amounts of gold can slip through the net and end up going to tailings. This may be because of: - Insufficient grinding. - Insufficient leaching or adsorption time. - Ore types not amenable to leaching.

%R = Au in bullion ÷ Au in feed =Au recovered ÷ (Bullion + Au in tails) (Note: Au is the chemical symbol for gold)

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General Mineral Processing

Terms

Ore

A natural material containing valuable minerals. Examples: Gold ore, Iron ore, Bauxite (Aluminium)

Gangue

The worthless material remaining after the valuable mineral has been extracted from the ore.

Tails or Tailings

The effluent from a mineral processing operation. That is, the waste slurry containing the gangue.

Mixtures

A mixture is formed when substances are mixed and no chemical change takes place, the components all remain in their original form and can be separated physically (eg filtration, settling) Examples: Sand and water, Ore and water (slurry).

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Solution

A solution is formed when substances are mixed (dissolved) and a chemical change takes place and can be formed between:

• A liquid and a solid.

• A liquid and a gas.

• Two (or more) liquids.

• Two (or more) gases. A solution cannot be separated by ordinary filtration or settling. Examples: Salt and water, Sugar and tea, Cyanide and water

pH

The pH scale is a measure of acidity

1 7 14 Acid Neutral Base or Alkaline (Pure Water) Points to remember: Low pH is acidic High pH is non acidic (ie basic) Cyanide reacts to form toxic HCN gas at low pH. For this reason, process streams are maintained with PROTECTIVE ALKALINITY. This means that the pH is kept high (between 9.5-10) by the addition of lime. It is extremely important to maintain the pH of all process streams in the correct range (9.5-10) at all times to minimise the loss of cyanide as HCN gas.