A
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ABC |
Assay Based Controls are changes made to regulatory set-points that are biased on the level or changes in the level of the valuable metal being recovered. |
Activators |
Cause a particular mineral to float with a collector when it otherwise would not. |
Adsorption |
The gathering of a gas, liquid, or dissolved substance on a surface in a condensed layer. |
Aggregate |
A group of unit or parts associated with one another. For example, a particle connected to a bubble. |
Agitator |
A device for shaking or stirring. |
Air Lock |
The blockage of a conduit by an air pocket which prevents flow – the flow resumes when the inlet pressure is high enough to dislodge the air bubble. |
Analog Output |
See manipulated variable. |
Annulus |
A ring. |
Apex |
The bottom opening of a cyclone through which the underflow leaves. |
Assay |
The analysis of the ore to determine its chemical content. |
Attrition Grinding |
Grinding by wearing away through rubbing and chipping. |
Automatic Mode |
Controller operating mode in which the controller changes the manipulated variable to effect control. |
B
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Baffles |
Are used to help the mixing action by breaking up circular flow patterns. |
Ball Mill |
A tumbling mill in which steel balls tumble onto ore particles to break them. |
Bornite |
(Cu5FeS4) A brownish-bronze mineral which contains copper, iron and sulphur. Bornite is a source of copper. |
Bull Gear |
Also called ring gear, the gear that encircles the tumbling mill and transmits the motion of the pinion gear to the mill. The mill rotates as the pinion gear meshes with the bull gear. |
Bypass |
The fraction of fine particles entrained by water in the classifier underflow. |
C
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Calcite |
(CaCO3) A colorless or white mineral which is composed of calcium carbonate. |
Calibrate |
To determine, check, or adjust the scale of a thermometer, gauge, or other measuring instrument. This is usually done by comparison with a standard instrument. |
Carbonate |
A compound which contains a carbonate group (CO3) composed of carbon and oxygen. In a carbonate mineral the carbonate is attached to a metal. |
Cascade Control |
A control methodology where a series of controllers in which the output of one controller is the set point of the next. |
Cascading |
The motion of the charge in a tumbling mill which occurs when the grinding media roll down from the top of the load to the toe of the load. |
Cataracting |
The motion of the charge in a tumbling mill which occurs when the grinding media are ejected from the top of the load onto the toe of the load. |
Cavitation |
The formation and subsequent collapse of bubbles in a liquid. |
Centrifugal Force |
The force that pushes a rotating object outward. |
Chalcocite |
(Cu2S) A black mineral which contains copper and sulphur. Chalcocite is a source of copper. |
Chalcopyrite |
(CuFeS2) A brass-yellow mineral which contains copper, iron and sulphur. Chalcopyrite is an important source of copper. |
Circuit |
A link of all flotation stages. |
Circulating Load |
The quantity of material recycled in a closed circuit. The circulating load is calculated by dividing the flow of material in the recycle by the flow of material in the feed. |
Classification |
The separation of a mixture containing particles of different sizes into a stream containing coarse particles and a stream containing fine particles. |
Cleaners |
A stage in a flotation circuit that treats concentrates from previous stages. |
Closed Circuit |
A grinding circuit in which the underflow from the classifier at the mill discharge returns to the mill while the overflow leaves the circuit. In a normal closed circuit, the feed enters the circuit through the mill. In a reversed closed circuit, the feed |
CMC |
Carboxyl Methyl Cellulose is a depressant that adsorbs in preference to collectors and gives hydrophilic products. |
Coagulate |
The change from a liquid form into a thickened mass. |
Coalescence |
What happens when two or more bubbles join together to form a single large bubble. |
Comminution |
The breaking of large particles into small particles. The most common comminution processes are crushing and grinding. |
Concentrate |
The valuable product from a mineral processing plant. |
Concentrator |
A plant where mineral processing takes place – also called a mill. |
Conditioner |
A tank, usually agitated by an impeller, used to allow mineral particles to react with reagents. |
Controlled Variable |
Variable that the controller tries to maintain at set point |
Coriolis Meter |
A device that uses the bending force generated when a fluid changes direction, through a bend for example, to calculate mass flow. |
Correlation |
A relationship between two things. |
Covalent Bond |
A bond formed by sharing electrons. |
Cut Size |
The particle size at which the classifier feed particles have an equal chance of going to the overflow or the underflow. |
Cyclone |
A classifier which uses centrifugal force to separate a mixture containing particles of different sizes into a coarse stream and a fine stream. |
D
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DCS |
A Distributed Control System distributes the monitor and control duties among several devices. |
Density |
The mass of a material divided by its volume. |
Depressants |
Prevents flotation of a particular mineral which otherwise would not float. |
Digging Shoes |
Pick up the grinding media and ore particles that settle at the bottom of the tower mill. |
Dispersants |
Reagents that dispose the slimes which often agglomerate and cover the surfaces of larger particles, therefore preventing them from being recovered. |
Drag |
Retarding force on a body resulting from the resistance to flow put up by the viscosity of the surrounding fluid. |
E
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Eh |
Pulp Potential. |
Electrochemical |
Electron transfer from one substance to another. |
Electrometallurgy |
The process of using electricity to extract the valuable metal from the concentrate – aluminum is extracted by electrometallurgy. |
Electrons |
Revolve around the nucleus of an atom and have a negative charge. |
Electrowinning |
A refining process which uses electricity – gold is refined by electro-winning. |
Entrainment |
A way in which particles enter the froth by being carried in the water that accompanies each bubble in the film and the wake. |
Extraction |
The removal of the valuable metal from the concentrate – the main extraction methods use heat, chemicals, or electricity. |
F
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Flotation |
A process which uses the fact that different minerals have different affinities for certain chemicals in order to separate the valuable minerals from the gangue. The chemicals loaded with minerals are removed from the slurry by air bubbles. |
Froth |
Bubbles formed on or in a liquid. |
Froth Freezing |
A froth too dry to move. |
Fuzzy Logic Control |
Fuzzy Logic Control determines control action using rules that are based on loose description of the process, for example, “if the level is high then reduce the water flow somewhat”. |
G
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Galena |
(PbS) a bluish gray mineral with which contains lead and sulphur. Galena is a source of lead. |
Gamma Gauge |
A device which uses a weak radioactive source to produce gamma rays to measure density (% solids). |
Gangue |
The unwanted portion of an ore. |
Gland Seal |
A device which consists of packing compressed in a stuffing box for preventing slurry leakage around the rotating shaft joint. |
Grade |
The percentage of a metal in a product. |
Grain |
A small lump of a given mineral. In a typical large ore particle, the grains of valuable minerals are distributed throughout the gangue minerals. |
Graphite |
A soft, black form of carbon with a metallic luster, used for lead in pencils, for lubricating machinery, etc. |
Grind Out |
Procedure in which the mill is run without any solids feed for a short period to time to get rid of slurry in the mill. |
Grinding Media |
Solid bodies which tumble onto ore particles to break them into smaller particles. The most common grinding media are steel balls, steel rods, and large ore particles. |
H
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Hardness |
Term referring to the ability to withstand penetration and deformation. |
Head Pressure |
The energy supplied by the pump to the slurry. The head pressure is the difference between the pump discharge pressure and the pump suction pressure. |
Head Tank |
A tank situated higher than the equipment is feeds. Flow to the equipment is under the force of gravity. |
High Intensity Conditioner |
A conditioner where a vigorous stirring action is used. |
Hydraulic Gradient |
Slope or change of height required for flow. |
Hydrocarbon |
Any of a class of compounds containing only hydrogen and carbon. |
Hydrocyclone |
A cyclone whose feed is a slurry of water and particles. It is also called a wet cyclone. |
Hydrogen Bonds |
Bonds that result from the polar nature of water. |
Hydrometallurgy |
The process of using chemical solutions to extract the valuable metal from the concentrate – gold and silver are extracted by hydrometallurgy. |
Hydrophilic |
Water loving. Hydrophilic surfaces prefer to be in contact with water. |
Hydrophobic |
Water fearing. Hydrophobic surfaces prefer to be in contact with something other than water, air for example. |
Impact Grinding |
Grinding by the violent shattering which results from striking the particles. |
I
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Impede |
To obstruct. |
Impeller |
The rotating blade of a centrifugal pump or blower. |
Inching |
Slowly turning the mill to a new position. This is normally performed when relining the mill. |
Induction Time |
The time it takes a particle to penetrate the water film and reach the air in the bubble. |
Interface |
The boundary between any two phases (solid, liquid or gas). |
Interlocks |
A control methodology where equipment can be permitted to start, started or shutdown based on certain conditions. |
Ion |
A neutral atom that has electrons added or removed from it. |
Ionic Bond |
A bond formed by donating atoms. |
K
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Keying the Charge |
To hold the charge. Lifters key the charge, preventing slippage and allowing the charge to rise. In practice only the bottom layer (height of the lifter) of the charge is actually keyed. |
Kinetics |
The description of the rate of change in a physical or chemical system. |
L
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Launder |
A trough conveying a slurry. |
Leaching |
An extraction method which uses the fact that different minerals have different solubility in chemical solutions to extract the valuable metal from the concentrate – gold and silver are normally extracted by cyanide leaching. |
Liberated Particle |
A particle composed mostly of a single mineral. |
Liberation |
The fundamental step of mineral processing by which the valuable minerals are freed from the gangue mineral. Liberation takes place through size reduction. |
Lifters |
Pieces that “key” the charge to promote the tumbling action. |
Liners |
Pieces that protect the mill shell from wear. |
Locked Particle |
A particle composed of several minerals. |
Logarithm |
In mathematics, an exponent of the power to which a fixed number (usually 10) must be raised in order to produce a given number. |
M
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Manipulated Variable |
The variable that the controller changes. |
Manual Mode |
Controller operating mode in which the manipulated variable is kept constant. The controller suspends control action. |
Marcy Scale |
An apparatus used to measure the density of a slurry. |
Massive Sulphide |
Rock or ore composed mainly of sulphide minerals, both valuable minerals and gangue. |
Measured Variable |
See controlled variable. |
Mesh Size |
The number of openings per linear inch in a screen. |
MIBC |
Methylisobutylcarbinol. A widely used frother. |
Micron |
A measurement unit for length. There are 10,000 microns per centimeter, and 25,400 microns per inch. |
Middlings |
A mixture of partly liberated particles. |
Mill Charge |
See mill load |
Mill Load |
The contents of the mill composed of grinding media and slurry. The total mill load also includes mill shell, liners, etc. that increase the weight at the trunnions. |
Mineral |
Any compound with a fixed chemical composition and fixed physical properties found in the crust of the earth. |
Mineral Processing |
The process of concentrating the valuable minerals in the ore in preparation for the extraction of the valuable metal. |
MSDS |
The material safety data sheet outlines the hazards and first aid measures for each chemical. |
MV |
See measured variable. |
N
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Net Smelter Return |
The economic value of the concentrate after transportation, smelting, refining and penalty charges are applied. |
Neutrons |
Found in the nucleus of an atom and have a neutral charge. |
Niobium |
A rare, steel gray, metallic chemical element that resembles tantalum in chemical properties. |
O
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Open Circuit |
A grinding circuit in which the particles go through the mill once. An open circuit has no classifier at the mill discharge to control particle size. |
Ore |
A mineral deposit that can be mined at a profit. |
Overflow |
The undersize material that leaves a cyclone. |
Overload |
Unstable condition where the amount of material in the mill or in the circulating load increases and is compounded by a reduction in grinding capacity. |
Oxide |
A compound which contains oxygen (O). In an oxide mineral, the oxygen is attached to a metal. |
P
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Particle |
A single physical entity. |
Partition Curve |
A plot which describes how the particles fed to a classifier are divided between the overflow and the underflow. A partition curve gives the percentage of feed particles that report to the underflow for each particle size. |
Percent (%) Solids |
The percentage by weight of solids in a slurry (often called pulp or slurry density). |
pH |
A symbol used to express acid or alkaline content. |
PID Controller |
A common controller which compensates proportionally to the error (P – proportional), compensates for sustained errors (I – integral) and compensates for changes in error (D – derivative). |
Pinion |
The gear connected to the mill motor which causes the mill to rotate as its teeth mesh with the teeth of the bull gear. |
Polar Bond |
A special type of covalent bond produced where there is an uneven sharing of electrons. |
Polarity |
The uneven sharing of electrons. |
Polymetallic |
Containing several valuable metals. |
Porphyry Deposit |
A deposit where the sulphides are distributed through out a non-sulphide gangue. Usually a low grade deposit. |
Power |
Energy per unit of time. |
Precipitate |
To separate (a substance) out from a solution as a solid. |
Process Variable |
See controlled variable. |
Product |
The valuable stream that leaves the circuit. |
Promoter |
A collector normally used in conjunction with another collector. |
Protons |
Found in the nucleus in an atom and have a positive charge. |
Pulp |
See slurry. |
Pump Box |
A vessel which provides the pump with surge capacity. |
PV |
See process variable. |
Pyrite |
(FeS2) a pale brass-yellow mineral which contains sulphur and iron. It is also known as fool’s gold. |
Pyrometallurgy |
The process of using heat to extract the valuable metal from the concentrate – iron is extracted by pyro-metallurgy (smelting). |
Pyrrhotite |
(FeS) A bronze-colored mineral which contains sulphur and iron. |
Q
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Quiescent Zone |
The region between the mixing zone and the froth zone. |
R
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Ratio |
The relationship in quantity, amount or size between two things. Usually calculated by dividing one value by the other. |
Ratio Control |
A control methodology where the controller output is calculated so that a ratio with a measured variable is maintained. |
Reagent |
A substance used for its chemical activity. |
Reagents |
Substances used to produce a desired chemical reaction. |
Recovery |
The percentage of the valuable metal present in the feed that reports to the concentrate. |
Recycle |
The stream that returns to pass again in the equipment. For example, the cyclone underflow in a closed ball mill circuit or the cleaner scavenger concentrate returned to the regrind mill. |
Refining |
The process of removing impurities from the metal after it has been extracted from the concentrate. |
Regulatory Control |
Refers to the low-level control used to stabilize the process. An example of regulatory control is the simple control loop used to maintain tonnage at a fixed value. |
Residence Time |
See retention time. |
Retention Time |
The length of time a slurry spends in a vessel. |