GeoE 498-8

GeoE 498-8

Geological Engineering Civil & Geological Engineering University of Saskatchewan GeoE 498 Introduction to Mining and Mineral Processing Engineering Lecture Notes Fall

2010 University of Saskatchewan Geological Engineering GEOE 498.3 Introduction to Mineral Engineering Lecture 8 Mineral Processing 1 Lorne Schwartz Chief Metallurgist Technical Services

Cameco Corporation Course Structure Part A (7 Lectures) Mine Engineering Part B (6 Lectures) Metallurgical Engineering Grading Assignments 20% Mid term 35% Final 45%

These course notes are a compilation of work conducted by many people. Notes have been taken from the following Edumine courses: The Mill Operating Resource 1&2 Process Mineralogy for Metals Extractive Metallurgy 1 & 2 Hydrometallurgy 1,2,3,4 Economic Evaluation and Optimization of Mineral Projects

Mineral Processing Overview Mineral Processing Terminology, Economics Comminution and Classification Physical processing methods Chemical processing methods Waste products treatment and disposal Process plant

flow sheets: uranium and potash Importance of Mineral Processing No substance has been as important as metal in the story of man's control of his environment. Advances in agriculture, warfare, transport, even cookery are impossible without metal. So is the entire Industrial Revolution, from steam to electricity. Read more: tories.asp?historyid =ab16#ixzz13XSEyvNz Importance of Mineral Processing Bronze Age- Bronze is in use in Sumer, at Ur, in around 2800 BC

Iron Age - from the 11th century BC onwards, steel replaces bronze weapons. It becomes essential, from now on, to have a good steel blade rather than a soft and indifferent one. Lecture 8 Mineral Processing Overview: Geology-Mining-Processing Relationship Mineral Processing Terms

Definitions Mineral Economics review Project Stages Lecture 9 Comminution & classification circuits Comminution Methods Principles Crushing Grinding

Classification Methods Principles Hydrocyclone Screening Assignment Lecture # 10 Physical Processing Methods Gravity

Magnetic Electrostatic Radiometric Froth Flotation Solid/liquid separation Assignment Lecture 11 Chemical Processing Basic Circuits Leaching

Solvent Extraction Precipitation Drying Downstream Purified Product Electrowinning Smelting Assignment Lecture #12 Waste Stream Management: Tailings Disposal

Surface Underground Effluent Treatment Chemical Precipitation Membrane Technology Assignment Lecture # 13 Saskatchewan Mill Process Flowsheets Uranium

Potash Assignment Geology Mining Processing All 3 aspects must be favorable to make a deposit economically viable Geology: Find it. Is it big enough to be economic? Mining: Dig it. Is it economically recoverable from the ground? Processing: Extract it. Is it economically separable

from the host rock? Prevalence of mineral processing In Saskatchewan as of 2009 there were: 3 uranium mills 8 potash mine/mills 1 gold mine/mill coal mines (thermal) Salt mine An identified diamond deposit (Fort a la Corne)

An identified rare earth element deposit (Hoidas Lake) Prevalence of mineral processing Mining is all around us! In Alberta there are: Oil sands process plants (uses mining and mineral processing techniques) Coal plants Industrial minerals (limestone) Nickel/cobalt metallurgical complex

In Manitoba there are: Many copper/zinc mines and mills, feeding the Flin Flon metallurgical complex Nickel mines nearby Thompson smelter In the Northwest Territories there are: 3 operating diamond mines Gold mines Introduction to Mineral Processing Scope of mineral

processing Definitions Economics Project Stages Mining Terminology Review Miners send their products to their customer the mill. Ore : Rock that contains a mineral or minerals in sufficient quantities as to make commercial extraction (mining milling)

profitable. Grade : A measure of concentration of a mineral/metal contained in rock (or ore). Gold and other precious metals g/t or oz/t, base metals - %, uranium kg/tonne, rare earth elements ppm Cut off Grade : The minimum concentration or grade of mineral that is required for rock to be considered ore. Waste : Not Ore. Ore Body: A mineralized deposit (resource) whose

characteristics have been examined and found to be commercially viable. The extents of the ore body are determined by the cut-off grade. Host Rock: The rock containing an ore deposit. Typically composed of 2 or more minerals. Gangue: Minerals in the ore body that are not of economic interest

Mineral Processing Is the recovery of valuable minerals from ore Takes place in a mill, aka concentrator - because it concentrates valuable minerals by removing unwanted material. The two main products are the concentrate streams (valuable minerals) and the tailings streams (rejects). Disciplines related to mineral processing

Fields of Metallurgical Engineering Field Example of topics Beneficiation or Mineral Dressing Theory and practice of liberation of minerals from ores and their

separation by physical methods at ambient conditions Crushing and grinding, magnetic and electrical methods, flotation, etc. Extractive metallurgy Chemical methods

sometimes at high temperature and pressure for treating ores to recover their metal values in a pure form Leaching, precipitation, electrolysis, oxidation, reduction, etc. Physical metallurgy

Study of physical properties of metals and alloys, preparation of alloys Crystal structure, effect of impurities, metallography, heat treatment, etc.

Engineering metallurgy Processing of metals in the molten state Casting, welding, etc. Mechanical metallurgy Processing of metals in the solid state

Forging, rolling, extrusion, piercing Powder metallurgy Processing of metal powders into finished products Preparation of metals in

powder form, hot pressing, etc. Mineral Processing Metal Processing Description Engineering Terminology in Mineral Processing

Circuit: The path that the ore that is being processed takes as it proceeds from one processing point to another. Flow Sheet - Drawing that indicates the path that the mineral takes within a process. Several circuits are often contained within a flow sheet Recovery Rate The percentage of valuable metal/mineral, by mass, in the concentrate from the feed

Mineral Processing The goals of mineral processing are to: separate economic mineral particles from waste or gangue subject minerals to processes in order to concentrate them or to extract metals from them Many forms of mineral processing Depends on feed material and desired product

Mineral Processing Terminology Concentration: Another word for grade Heads: A term that is used to denote the mineral found in the FEED to a circuit. Head Grade: aka feed concentration Concentrate: a purified mineral. May require further downstream processing to convert for end uses. Examples: Copper and nickel sulfides Tailings - Material rejected from a mill after

the recoverable valuable minerals have been extracted. Industrial mineral: is used for end purpose without chemical alteration. Examples: gravel, coal Mineralogy: Description of mineral contents What is mineral processing? Mineral: a)A solid naturally-occurring compound having a definite chemical composition. b) Inorganic substance that are extracted from

the earth for use by man. c) A naturally occurring inorganic element or compound having an orderly internal structure and characteristic chemical composition, crystal form, and physical properties. Mineral classification Nonmetallic processing has some commonalities with metal processing, but lots of differences Examples of minerals

Examples of minerals Mineralogy determines recoverability Impact of mineralogy We mine rocks but we concentrate minerals. Gangue minerals also important

Understanding mineralogy allows design of processes Important for feasibility studies What is mineral processing? Processing Extract values, reject waste Conversion of mined ore into usable product

More expensive/challenging with lower grade ores Numerous processing methods Mineral Processing Methods = beneficiation + extractive metallurgy Beneficiation aka Mineral Dressing Overlap of physical and chemical methods, depending on product Where extractive metallurgy leaves off, metal processing begins

Mineral Processing Terminology Beneficiation: enrichment of ores and separation of unwanted gangue minerals subsequent metals extraction more efficient. Can be divided into two distinct steps: Liberation: the rock is broken down by mechanical means, mineral components become independent of each other, detached Separation: valuable minerals are separated by means of physical and physico-chemical methods making use of differences in specific gravity, magnetic properties, etc.

Extractive metallurgy: Chemical reactions of the processes equipment where reactions take place Flowsheets combinations of processes Typical Beneficiation Steps Beneficiation Terminology Comminution: Reduction of particle size Starts at mine with blasting

Two basic types of equipment used: Crushing breakage by compression Grinding breakage by abrasion and impact Comminution Equipment Shaft

Comminution Equipment Shaft Beneficiation Terminology Classification : Separation based mainly on particle size Behavior affected by size, shape, and density of the particles Two common types of classifiers: Screens dry method, coarser particles

Hydrocyclones wet method, finer particles Classification Equipment Beneficiation Terminology Separation Techniques take advantage of the differences in characteristics between minerals: Flotation: Attachment of minerals to air bubbles - hydrophibicity

Magnetic Separation: Apply magnetic field Gravity Separation: differences in specific gravity of materials Electrostatic Separation: Apply electrostatic polarity

Particle size distribution has large influence on results Separation Equipment Flotation cell Separation Equipment Magnetic separator Separation Equipment

Gravity separation - jig Separation Equipment Electrostatic separator Beneficiation Terminology Dewatering: To remove water from a substance. Also refers to the circuit where this takes place. Dewatering Techniques: Thickener: Allow gravity settling

Filter: Apply air pressure to draw water out Centrifuge: Apply centrifugal force Dryer: Apply heat to evaporate Slurry Density: The amount of solids in a slurry, expressed as a percentage by weight. Dewatering Equipment Thickener Dewatering Equipment

Disc filter Dewatering Equipment Rotary kiln dryer Beneficiation Terminology Waste Disposal - "Mining is waste management ..." The majority of tonnage mined must be disposed of as tailings

Water used must be treated and released Tailings Dam: Built from ground waste rock discharged after processing from the mill Acid Mine Drainage: produced by exposing sulfide minerals to air and water, resulting in oxidation that generates acid.

Waste Rock: Unprocessed non-mineralized / low grade mined material Water Balance: Accounting of water inputs and outputs from a mine/mill site.

Water Treatment: The removal of harmful contaminants from water Waste Disposal Tailings Dam Waste Disposal Waste Rock Pile Waste Disposal

Acid Mine Drainage Waste Disposal Water Balance Mineral Processing Methods = beneficiation + extractive metallurgy Beneficiation aka Mineral Dressing Overlap of physical and chemical methods, depending on product Where extractive metallurgy leaves off, metal processing begins

Extractive Metallurgy Terminology Hydrometallurgy Leaching - the process of extracting a soluble constituent from a solid by means of a (water based) solvent Water changes solubility, by making it acidic or basic, oxidizing or reducing Solvent Extraction transfer between immiscible fluids

Ion Exchange solid resins that adsorb/desorb dissolved chemical species Precipitation convert dissolved into solid Crystallization via evaporation Ionic precipitation - addition of a reagent to a solution creates a metal compound whose solubility is so low that precipitation takes place immediately Hydrometallurgy Equipment Tank leach circuit

Hydrometallurgy Equipment Solvent extraction mixer-settlers Hydrometallurgy Equipment Ion Exchange Hydrometallurgy Equipment Vacuum crystallizer

Extractive Metallurgy Terminology Pyrometallurgy use of heat to induce a chemical transformation Roasting convert to oxide form. Example: 2 CuS2 + 5 O2 2 CuO + 4 SO2 Smelting - uses reducing substances

that will combine with those oxidized elements to free the metal. Example: 2 Fe2O3 + 3 C 4 Fe + 3 CO2 Pyrometallurgy Equipment Smelter Extractive Metallurgy Terminology Electrometallurgy use of electrical energy to induce a chemical

transformation Electrowinning to precipitate a metal from solution using electric potential Electrorefining to purify a metal by dissolving it, then re-precipitating it Electrometallurgy Equipment Alternating anodes and cathodes in a tankhouse for electrowinning

Flowsheet examples Aluminum: from bauxite Copper: from chalcopyrite Iron: from hematite Gold Placer, sulphide and oxide Oil Sands Fort McMurray Aluminum Copper

Iron Gold Oil Sands Mineral Processing Recovery Recovery : Potential for loss every step of the way, in each circuit! Tonnage vs. Recovery: A processing circuit pushed

beyond its capacity will induce recovery loss Feed Grade vs. Recovery : A higher feed grade tends to have higher processing recovery Concentrate Grade vs. Recovery: A higher concentrate grade tends to result in lower processing recovery (= rejection of lower quality minerals to tailings) Concentrate Grade vs. Price: A higher quality

concentrate will fetch a higher price (have lower impurity penalties) Revenue = Production (tonnes) x grade x recovery x price Mining Economics Typical product grade vs. recovery curve for a Cu sulphide flotation mill

Mining Economics Relation between cost and particle size Mineral Economics - Review Discounted Cash Flow (DCF) NPV (net present value) is a means of comparing a dollar today to the value of the same dollar in the future. For mining projects, we apply NPV to determine if a project is worth more than it costs. Free Cash Flow (FCF) is the operating cash flow minus capital includes Taxes, Dividends, Royalties,

Depreciation and Amortization. I.e. the amount of money left after the bills are paid Discount Rate is rate that future cash flows are discounted to determine present value. This is different than interest. IRR (internal rate of return) is the discount rate that results in an NPV of 0. Mineral Economics - Review Net Present Value is common way to evaluate a project Value = Free Cash Flow

Rate = Discount Rate n=Total number of periods i=Period Payback period - the time required for the operating revenue to pay back all the costs, including the initial capital investment used to construct the project. Mineral Economics Typical mining project annual cash flow pattern

R = revenue, C = costs, T = taxes, A = annual loan payment (principal + interest), F = cash flow and K= capital costs. Mining Project Economics What happens when project parameters are changed? Must start with a reasonable base case scenario (technically feasible) before economic optimization (fine tuning) Strong inter-relationships between:

Tonnage Grade Capital costs Operating costs Has effects on: Mine life Cutoff grade Capital and Operating Cost Estimation vs. Tonnage Work by OHara (1980), OHara and Suboleski (1992) and USBM (1987) suggest that the curves for capital and

operating costs can be reasonably approximated by exponential equations, with the general form: Cost = K tx Where: K = a constant specific to the particular cost t = production rate in tonnes per day x = an exponent Capital costs typical range: 0.5 to 0.7 0.6 is a reasonable first estimate

Operating costs in $/t typical range -.3 to -.1 -0.2 is a reasonable first estimate WARNING: These equations should not be used for detailed estimating, although they can give guidance for order of magnitude estimating. Capital and Operating Costs vs. Tonnage If a cost is known accurately, this relationship can be used to factor the cost up or

down for differing production rates, within reasonable limits: Cost at t1 = C1 = K t1x Cost at t2 = C2 = K t2x Then: C1 / C2 = (K t1x) / (K t2x) = t1x / t2x (because K is common it can be eliminated) = (t1 / t2)x Simplified:

C1 / C2 = (t1 / t2)x Then: C2 = C1 (t2 / t1)x For a capital cost or annual operating cost, if C1 and t1 are known, and x can be estimated from experience then C2 can be estimated for a given t2.

Example: For capital cost at 20,000 t/d is $30 million, then at 25,000 t/d can be estimated at: C2 = $30000000 (25000 / 20000)0.6 = $30000000 (1.1433) = $34,298,000 For operating cost of $10.00/tonne, and an exponent of -.2 the unit cost at the higher tonnage will be: C2 = $10.00 (25000 / 20000)-0.2 = $10.00 (0.9564) = $9.56 Capex and Opex vs. Production Rate

NPV Curve An NPV curve is theoretical, always check that the inputs are realistic! Mineral Economics Operating Costs Overall operating costs are broken down into 3 basic areas for economic analysis: Mining determine mine plan input costs, production rate and fully diluted (Run-of-Mine = ROM) grade

Milling determine process flowsheet input costs, recovery rate, product quality General and Administrative (G & A) determine overhead costs : Administration (HR, payroll) Management (site + head office) Safety & Health Environment Quality Management G&A tends to be fixed REGARDLESS of production rate!

Milling Operating Costs Typical relative cost of beneficiating an ore Operation % Crushing 5 - 20

Grinding 25 - 75 Flotation 25 -45 Dewatering and drying

10 -20 Other operations 5 - 10 Project Stages Idea stage Conceptual stage Pre-feasibility stage

Market Studies Feasibility studies Financial analysis Preliminary design Final design and construction Commissioning and start up Closing reports Typical Project Stages

Idea Stage : identify the need for a project to be started or conceptualized philosophic - decide whether this is the type of project that they would like to pursue Discussions of cost and schedule at the idea stage are normally limited to a broad definition Informal - sometimes mentioned to get a reaction Ideas can begin with anyone in the organization

Conceptual Study: establish the shape of the project, and get a better feel for its scope and size Costs can be put to a concept. However, the accuracy of investment costs may be wildly out, probably +/-50%. Rough estimate based on experience and judgment Estimate's usefulness is in establishing an idea of the costs commensurate with the aims of the project Resource and Reserve Categorization Mineral Reserve: This is where things start to get real

Typical Project Stages Pre-feasibility Study : comprehensive study of viability of a mineral project mining method has been established effective method of mineral processing has been determined financial analysis based on reasonable assumptions of technical, engineering, legal, operating, economic, social, and environmental factors

determine if all or part of the mineral resource may be classified as a mineral reserve Feasibility Study: comprehensive study of a mineral deposit all geological, engineering, legal, operating, economic, social, environmental and other relevant factors are considered in sufficient detail could reasonably serve as the basis for a final decision by a financial institution to finance the development of the deposit

for mineral production. Typical Project Stages Detailed design and construction: Engineering design and construction are inseparable, even though two distinct groups normally perform the work. Preliminary design - establish a definite time frame for freezing the process and plant designs so that cost and schedule upsets are minimized effective method of mineral

processing has been determined definitive estimate to an accuracy of 10 to 15% to control the job requires about 20 percent of the total engineering must be done, as measured by completion of drawings. be leery of both steam-rolling a design freeze prematurely, vs. allowing people to continuously change their minds Commissioning: checkout period prior to starting the plant Sometimes the entire plant is run for a period of time without

material Startup usually begins on a reduced output basis, gradually increasing until planned output capacity is reached Typical Project Stages Project emotional stages: Euphoria Wandering off track Catch up and control The Boggs

Project Manager panic Frantic catch up and control Loose ends Sign off

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