CHE2119 Lecture 4: Extractive Metallurgy PDF

 TABLE OF CONTENTS 2 01 Extractive Metallurgy 02 Mineral Ores UST Chemical Engineering Department 03 Ore Dressing 04 Extraction Processes  TABLE OF CONTENTS 3 05 Extractive Metallurgy of Iron 06 Extractive M...

 TABLE OF CONTENTS 2 01 Extractive Metallurgy 02 Mineral Ores UST Chemical Engineering Department 03 Ore Dressing 04 Extraction Processes  TABLE OF CONTENTS 3 05 Extractive Metallurgy of Iron 06 Extractive Metallurgy of Aluminum UST Chemical Engineering Department 07 Extractive Metallurgy of Copper  TABLE OF CONTENTS 4 01 Extractive Metallurgy 02 Mineral Ores UST Chemical Engineering Department 03 Ore Dressing 04 Extraction Processes  INTRODUCTION 5 UST Chemical Engineering Department Aluminum is made from the aluminum- bearing minerals in bauxite. Source: https://courses.lumenlearning.com/geology/chapter/reading-mining-and-mineral-use/  INTRODUCTION 6 UST Chemical Engineering Department Acid drainage from a surface coal mine in Missouri. Source: https://courses.lumenlearning.com/geology/chapter/reading-mining-and-mineral-use/  EXTRACTIVE METALLURGY 7 deals with the extraction and refining of metals from its naturally existing ore or minerals Source of Minerals Earth’s crust: 8.1% aluminum, 5.1% iron, 3.6% calcium, 2.8% UST Chemical Engineering Department sodium, 2.6% potassium, 2.1% magnesium, 2.1% titanium, 0.10% manganese ocean water: 10,500 g/ton Na, 1270 g/ton Mg, 400 g/ton Ca, 380 g/ton K; ocean nodules: 23.86% Mn, 1.166% Mg, 2.86% Al, 13.80% Fe recycled scrap: at the end of metals’ life EXTRACTIVE METALLURGY 8 UST Chemical Engineering Department manganese nodules in the seabed  EXTRACTIVE METALLURGY 9 Extractive Metallurgy UST Chemical Engineering Department pyrometallurgy hydrometallurgy electrometallurg y  TABLE OF CONTENTS 10 01 Extractive Metallurgy 02 Mineral Ores UST Chemical Engineering Department 03 Ore Dressing 04 Extraction Processes  MINERAL ORES 11 An ore is a mineral deposit which can be profitably exploited. It may contain three groups of minerals namely: o valuable minerals of the metal which is being sought o compounds of associated metals which may be of secondary value UST Chemical Engineering Department o gangue minerals of minimum value Some Types of Ores ❖ oxide ores: Fe2O3, Fe3O4 ❖ sulphide ores: CuFeS2, (Zn,Fe)S, PbS, FeS2 ❖ carbonate ores: CaMg(CO3)2, MgCO3, Cu2CO3(OH)2 ❖ halide ores: rock salts of sodium, magnesium chloride in seawater  MINERAL ORES 12 UST Chemical Engineering Department Chalcocite Garnierite copper sulfide ore nickel silicate ore  TABLE OF CONTENTS 13 01 Extractive Metallurgy 02 Mineral Ores UST Chemical Engineering Department 03 Ore Dressing 04 Extraction Processes  ORE DRESSING 14 physical pre-treatment before ores are subjected to the main chemical treatment meant to affect the concentration of the valuable minerals and to render the enriched material into the most suitable physical condition for UST Chemical Engineering Department subsequent operations Ore dressing may include: ❖ Comminution ❖ Sorting ❖ Agglomeration  ORE DRESSING: COMMINUTION 15 reduction of the size of the ore by crushing, grinding, cutting, and vibrating to such a size that will release or expose all valuable minerals usually followed by screening process UST Chemical Engineering Department  ORE DRESSING: COMMINUTION 16 Examples of crushers/grinders: UST Chemical Engineering Department jaw crusher roll crusher  ORE DRESSING: COMMINUTION 17 Examples of crushers/grinders: UST Chemical Engineering Department industrial-scale jaw crusher inside of a jaw crusher  ORE DRESSING: COMMINUTION 18 Examples of crushers/grinders: UST Chemical Engineering Department gyratory crusher cone crusher  ORE DRESSING: COMMINUTION 19 Examples of crushers/grinders: UST Chemical Engineering Department hammer mill ball mill  ORE DRESSING: SORTING 20 performed to separate particles of ore minerals from gangue (non-valuable) minerals or different ores from one another Classification Process Due to difference in size, shape, and densities, materials are classified in fluids- or water-based processes based on the UST Chemical Engineering Department following factors: 1. Smaller particles fall more slowly in fluids than do larger ones. 2. Centrifugal force have larger influence on larger size particles. 3. Small particles having less inertia tend to behave like the suspending medium or fluid. 4. Larger particles require higher velocity for separation.  ORE DRESSING: SORTING 21 Froth Flotation uses difference in surface properties of the individual minerals to selectively adsorb UST Chemical Engineering Department material on the air bubbles  ORE DRESSING: SORTING 22 Froth Flotation Process UST Chemical Engineering Department  ORE DRESSING: SORTING 23 Froth Flotation Process UST Chemical Engineering Department  ORE DRESSING: SORTING 24 Froth Flotation Process in the Industry UST Chemical Engineering Department copper extraction by froth gold froth flotation tanks  ORE DRESSING: SORTING 25 Magnetic Separation takes advantage of differences in magnetic properties of materials Magnetic Properties Ferromagnetic: magnetic materials Paramagnetic: weakly-attracted into a magnetic field UST Chemical Engineering Department Diamagnetic: weakly-repelled by a magnetic field  ORE DRESSING: SORTING 26 Magnetic Separation takes advantage of differences in magnetic properties of materials UST Chemical Engineering Department  ORE DRESSING: SORTING 27 Electrostatic Separation selective sorting of solid species by means of utilizing forces acting on charged and UST Chemical Engineering Department polarized bodies in an electric field  ORE DRESSING: AGGLOMERATION 28 formation of lumps of appropriate size and strength when ore or concentrate is too small for use in a latter stage of treatment UST Chemical Engineering Department This is done by any of the following methods: iron briquettes ❖ Pelletizing ❖ Briqueting ❖ Sintering  TABLE OF CONTENTS 29 01 Extractive Metallurgy 02 Mineral Ores UST Chemical Engineering Department 03 Ore Dressing 04 Extraction Processes  EXTRACTION PROCESSES: CALCINATION 30 thermal treatment of an ore to affect its decomposition and the elimination of a volatile product, usually carbon dioxide or water CaCO3 🡪 CaO + CO2 T = 1000oC MgCO3 🡪 MgO + CO2 T = 417oC UST Chemical Engineering Department MnCO3 🡪 MnO + CO2 T = 377oC FeCO3 🡪 FeO + CO2 T = 400oC  EXTRACTION PROCESSES: ROASTING 31 process of heating of concentrated ore to a high temperature in excess of air UST Chemical Engineering Department involves chemical changes other than decomposition, usually with furnace atmosphere diagram of a reverberatory furnace  EXTRACTION PROCESSES: ROASTING 32 Roasting vs Calcination Roasting Calcination Ore is heated in the presence of excess Ore is heated in the absence or limited oxygen or air. supply of oxygen or air. This method is employed for sulphide ores. This method is employed for carbonate UST Chemical Engineering Department ores. Sulfur dioxide is produced along with metal Carbon dioxide is produced along with oxide. metal oxide. Sample balanced equation: Sample balanced equations: For the ores ZnS (sphalerite) and Cu2S For the ore, ZnCO3 (calamine): (chalcocite): ZnCO3 🡪 ZnO + CO2 2 ZnS + 3 O2 🡪 2 ZnO + 2 SO2 2 Cu2S + 3 O2 🡪 2 Cu2O + 2 SO3  EXTRACTION PROCESSES: SMELTING 33 Ore (usually mixed with purifying and/or heat generating substances such limestone and coke) is heated at high temperature in an enclosed furnace. It is opposite to roasting (oxidizing reaction) as it involves reducing reactions. UST Chemical Engineering Department The components of the charge in the molten state separate into two or more layers which may be: ❖ matte ❖ slag ❖ speiss EXTRACTION PROCESSES: SMELTING 34 fusible chloride Slag (mixture of metal oxides and SiO2) UST Chemical Engineering Department matte (a solution of metallic sulphides) speiss (a compound of one or more metals with As or Sb) Pb button  TABLE OF CONTENTS 35 05 Extractive Metallurgy of Iron 06 Extractive Metallurgy of Aluminum UST Chemical Engineering Department 07 Extractive Metallurgy of Copper  EXTRACTIVE METALLURGY OF IRON 36 Iron Ores limonite ❖ haematite (Fe2O3) ❖ limonite (FeO(OH).nH2O) ❖ magnetite (FeO.Fe2O3) ❖ Pyrite, (FeS2) UST Chemical Engineering Department Iron Forms pyrite ❖ white cast iron ❖ grey pig iron ❖ steel ❖ alloy grey pig iron EXTRACTIVE METALLURGY OF IRON 37 Raw Materials Iron Ore abundant, makes up 5% of earth’s crust main impurities: silica and alumina Limestone or Dolomite UST Chemical Engineering Department calcium carbonate used to remove impurities Coke produced at the bottom of the blast furnace by carbonization of coal used to heat the furnace and produce CO which acts as the reducing agent  EXTRACTIVE METALLURGY OF IRON 38 Reactions (Complete) UST Chemical Engineering Department  EXTRACTIVE METALLURGY OF IRON 39 Reactions (Complete) UST Chemical Engineering Department  EXTRACTIVE METALLURGY OF IRON 40 Reactions (Simplified) UST Chemical Engineering Department  TABLE OF CONTENTS 41 05 Extractive Metallurgy of Iron 06 Extractive Metallurgy of Aluminum UST Chemical Engineering Department 07 Extractive Metallurgy of Copper  EXTRACTIVE METALLURGY OF ALUMINUM 42 Aluminum is the most abundant metal in earth. Bauxite ore mixture of hydrous aluminum oxides, aluminum hydroxides, clay minerals, and UST Chemical Engineering Department insoluble materials Aluminum Mineral in Bauxite Bauxite Ore  EXTRACTIVE METALLURGY OF ALUMINUM 43 Extraction of aluminum from bauxite is carried out in three stages: 1. Ore Dressing: cleaning ore by means of separation of the metal containing mineral from the waste (gangue) 2. Chemical Treatment of Bauxite: conversion of hydrated UST Chemical Engineering Department aluminum oxide to pure aluminum oxide 3. Reduction of Aluminum from Aluminum Oxide: by the electrolytic process  EXTRACTIVE METALLURGY OF ALUMINUM 44 Bayer Process the process of refining alumina from bauxite by selective extraction of pure aluminum oxide dissolved in sodium hydroxide Bayer process is comprised of four steps: UST Chemical Engineering Department ❖ Digestion ❖ Clarification ❖ Precipitation ❖ Calcination  EXTRACTIVE METALLURGY OF ALUMINUM 45 Bayer Process Digestion: extraction of the alumina through digestion with hot sodium hydroxide solution which dissolves the aluminum hydroxide, forming a solution of sodium aluminate UST Chemical Engineering Department Clarification: removal of undissolved solid impurities (calcium oxide, iron oxide, titanium oxide) that form the “red mud”, which settles down at the bottom of mud thickeners  EXTRACTIVE METALLURGY OF ALUMINUM 46 Bayer Process Precipitation: recovery of crystals of aluminum hydroxide (Al(OH)3) o Precipitation is promoted by seeding the liquor with pure alumina crystals acting as nuclei for the precipitation process. UST Chemical Engineering Department o Crystals of aluminum hydroxide/ alumina trihydrate (Al2O3.3H2O) grow and aggregate.  EXTRACTIVE METALLURGY OF ALUMINUM 47 Bayer Process Calcination: the aluminum hydroxide after separation from the sodium hydroxide is converted to pure aluminum oxide by heating to 1800oF (1000oC) in rotary kilns or fluidized bed calciners. UST Chemical Engineering Department  EXTRACTIVE METALLURGY OF ALUMINUM 48 Hall-Heroult Process production of aluminum by the electrolytic reduction of the aluminum oxide It involves dissolution of UST Chemical Engineering Department aluminum oxide in molten cryolite (mineral containing sodium aluminum fluoride, Na3AlF6) and electrolysis of electrolytic process of manufacturing aluminum the molten salt bath. 12 e-  TABLE OF CONTENTS 49 05 Extractive Metallurgy of Iron 06 Extractive Metallurgy of Aluminum UST Chemical Engineering Department 07 Extractive Metallurgy of Copper  EXTRACTIVE METALLURGY OF COPPER 50 Copper is mostly extracted from ores containing copper sulphides, copper oxides or copper carbonates. Copper ores are generally poor-quality and contain between 1.5 to 5% copper The extraction of copper from its sulphide ore involves: UST Chemical Engineering Department % copper ▪ concentration 15 – 25 ▪ roasting 30 – 45 ▪ smelting - ▪ matte conversion 98 ▪ fire refining 99.5 ▪ electrolytic conversion 99.9  EXTRACTIVE METALLURGY OF COPPER 51 Concentration: separation of the copper mineral from the gangue o In froth flotation cell, the ore particles are lifted by air bubble while the gangue remain in the cell. Roasting: removal of excess sulfur UST Chemical Engineering Department o The dry pulp is fed into the roaster at 600 to 700oC. o The burning of the sulphide ores supplies the heat to maintain the temperature at which roasting takes place.  EXTRACTIVE METALLURGY OF COPPER 52 Matte Smelting: concentrate is smelted in a furnace to produce a mixture of copper UST Chemical Engineering Department Blister Copper Production: conversion of matte into molten blister copper containing 96 to 98% copper and remove the iron-rich slag Slag Formation Stage Blister Copper Formation  EXTRACTIVE METALLURGY OF COPPER 53 Electrolytic Refining: e- flow cathodes produced as a result of the electrolytic refining process contain 99.9% copper UST Chemical Engineering Department  RESOURCES 54 Helen Njeri NJENGA, Industrial Chemistry - African Virtual university Dr. Ajay Kumar Shukla, Department of Metallurgical and Materials Engineering, IIT Madrs, India, (https://mme.iitm.ac.in/shukla/Principles%20of%20Extractive%20Met allurgy.pdf) http://www.majordifferences.com/2013/10/roasting-vs- calcination.html#.WLPTbzt97IU http://www.businessdictionary.com/definition/smelting.html http://www.rocksandminerals.com/aluminum/process.html http://www.idc- online.com/technical_references/pdfs/chemical_engineering/Bayer_p rocess.pdf