Mineral Processing and Process Metallurgy (MM2102) PDF

Mineral Processing and Process Metallurgy (MM2102) (3 0 3) (4.5 credit) Department of Metallurgical and Materials Engineering IIT Patna Course content 3  Evaluation process: S.no Evaluation pattern Number Weightage 1 Mid Seme...

Mineral Processing and Process Metallurgy (MM2102) (3 0 3) (4.5 credit) Department of Metallurgical and Materials Engineering IIT Patna Course content 3  Evaluation process: S.no Evaluation pattern Number Weightage 1 Mid Semester Evaluation 1 25-30 2 End Semester Evaluation 1 40-45 3 Assignment Submission/Quiz 2 10-15 4 Presentation, viva etc. 1 20 Email: [email protected] Mob: +91-9027186120  Origin Ceramics Precious materials Metals End component Minerals or Rocks? Mineral: ‘Mineral’ means a class of substances occurring in nature, of definite chemical composition and usually, a characteristic crystal structure, Difference between a mineral and a rock…. A mineral is a pure substance with a specific composition and structure, while a rock is typically a mixture of several different minerals Definition of Minerals: Minerals are naturally occurring, inorganic substances that possess a definite chemical composition and a characteristic crystalline structure. They are the building blocks of rocks and are found in the Earth's crust. Minerals are typically solid, although some can exist as liquids or gases under specific conditions. Minerals are vital components of rocks, ores, and soils. Minerals are essential for various industrial processes, including construction, manufacturing, and energy production. Additionally, many minerals are valued for their aesthetic qualities and are used in jewelry and ornamental items. Formation of minerals: How the Minerals forms? Magma: At the high temperatures that exist deep within Earth, some geological materials are liquid. As magma rises up through the crust, either by volcanic eruption or by more gradual processes, it cools and minerals crystallize.  Precipitation from gaseous emanations: The evolution of hydrothermal plume in the air from the volcanic eruption and precipitates in some other regions 9  Precipitation from aqueous solution: (i.e., from hot water flowing underground, from evaporation of a lake or inland sea, or in some cases, directly from seawater) 10  Metamorphism: Formation of new minerals directly from the elements within existing minerals under conditions of elevated temperature and pressure, It involves the change in minerals or geologic texture in preexisting rocks Weathering: During which minerals unstable at Earth’s surface may be altered to other minerals, (ex: Radioactive minerals)  Organic formation: Formation of minerals within shells (primarily calcite) and teeth and bones (primarily apatite) by organisms (these organically formed minerals are still called minerals because they can also be form inorganically). Opal is a mineraloid (i.e., not an actual mineral) because although it has all of the other properties of a mineral, it does not have a specific structure. Pearl is not a mineral because it can only be produced by organic processes. Crystalline: A three dimensional periodic Amorphous: Random arrangement- arrangement of atoms No periodic arrangement of atoms In 3-Dimenion In case of two atoms  Properties of Minerals Minerals are universal: A crystal of hematite on Mars will have the same properties as one on Earth. 1. Color: One of our key ways of identifying objects. Color arises due to varying proportions of trace elements within the mineral: For example, Quartz: Yellow (citrine) due to trace amounts of ferric iron (Fe3+), The mineral Sulphur Not all are by just color: Rose quartz has trace amounts of manganese, is always a distinctive Hematite exits as Red and Black Purple quartz (amethyst) has trace amounts of iron, and unique yellow. and shiny metallic Milky quartz, which is very common, has millions of fluid inclusions (tiny cavities, each filled with water). 2. Streak : Minerals, “colour” is what you see when light reflects off the surface of the sample. Mineral gets ground to a powder and we can get a better impression of its “true” colour  Lustre is the way light reflects off the surface of a mineral, and the degree to which it 3. Lustre: penetrates into the interior. Sulfur reflects less Diamond has an adamantine Quartz is not sparkly and has light than quartz, luster. a vitreous, or glassy, luster. so it has a resinous luster. Two types: Metallic and Non-metallic. Metallic: Light gets reflected from the surface. Even a thin sheet of metal—such as aluminium foil—will not allow light to pass through it/reflective. Non-metallic: Many minerals may look as if light will not pass through them, but if you take a closer look at a thin edge of the mineral you can see that it does. if a non-metallic mineral has a shiny, reflective surface, then it is called “glassy.” If it is dull and non-reflective, it is “earthy.” Other types of non-metallic lustres are “silky,” “pearly,” and “resinous.”  4. Hardness The resistance of a material to local plastic deformation achieved from indentation of a predetermined geometry indenter onto a flat surface of metal under a predetermined load. In 1812 German mineralogist Friedrich Mohs came up with a list of 10 reasonably common minerals that had a wide range of hardnesses. 5. Density Density is a measure of the mass of a mineral per unit volume, Minerals Density (gm/cc) Quartz, feldspar, calcite, amphibole, and 2.6 – 3.0 gm/cc mica Pyrite, hematite, and magnetite >5.0 gm/cc 6. Crystal Habit In a rock, Minerals like to grow in their own shapes Crystallographic habit plane, provided adjacent minerals allows Crystallographic plane is characteristic associated with the crystal structure of materials *Crystal habit is a reflection of how minerals like to grow 7. Cleavage and Fracture : Cleavage and fracture describe how it breaks. Cleavage is the tendency of a mineral to break along certain planes to make smooth surfaces. A mineral that naturally breaks into perfectly flat surfaces is exhibiting cleavage. Cleavage is what we see when a mineral breaks along a specific plane or planes, while fracture is an irregular break. Some minerals tend to cleave along planes at various fixed orientations, some do not cleave at all (they only fracture). Minerals that have cleavage can also fracture along surfaces that are not parallel to their cleavage planes.  Minerals are made up of a cation (a positively charged ion) + an anion (a negatively charged ion (e.g., S2−)) or an anion complex (e.g., SO42−). For example, in the mineral hematite (Fe2O3), the cation is Fe3+ (iron) and the anion is O2− (oxygen). The two Fe3+ ions have an overall charge of +6 and that balances the overall charge of −6 from the three O2− ions. These include oxides, sulphides, carbonates, silicates, and others. Silicates are by far the predominant group in terms of their abundance within the crust and mantle. Exclude those with (CO32-), (SO42-), (SiO44-). If oxygen +Hydrogen -> hydroxide mineral – Limonite & Bauxite Sulphides are mineral with S-2 anion with -2 Sulphates are mineral with SO4-2 anion with -2 Carbonates are mineral with CO3-2 complex. anion with -2 Phosphate are mineral with PO4-2 complex. anion with -2 Silicate minerals include the elements Si and O in varying proportion ranging from Si:O2 to Si-O4 Native elements are single element minerals: Gold, Copper, Sulphur, Graphite Classification of Minerals: To be classified as a mineral, a substance must meet several criteria: Firstly, it must occur naturally, meaning it is not artificially created by human intervention. Secondly, minerals are inorganic, which means they are not derived from living organisms. Thirdly, minerals have a specific chemical composition and structure, composed of various elements in fixed proportions. For example, quartz is composed of silicon and oxygen (SiO2). 22 Minerals can be classified into several categories based on various criteria. Here are some common classifications of minerals: Native Elements: These minerals consist of a single element in their pure form. Examples include gold (Au), silver (Ag), copper (Cu), and diamond (C). Silicates: Silicates are the most abundant group of minerals and are composed primarily of silicon (Si) and oxygen (O). They make up a significant portion of the Earth's crust. Examples of silicate minerals include quartz, feldspar, mica, and clay minerals. Carbonates: Carbonate minerals are composed of carbon (C), oxygen (O), and other elements such as calcium (Ca) or magnesium (Mg). Common carbonate minerals include calcite, dolomite, and siderite. 23 Oxides: Oxide minerals consist of oxygen (O) combined with one or more metallic elements. Examples include hematite (Fe2O3), magnetite (Fe3O4), and rutile (TiO2). Sulfides: Sulfide minerals are composed of sulfur (S) combined with one or more metallic elements. Well-known sulfide minerals include pyrite (FeS2), galena (PbS), and sphalerite (ZnS). Sulfates: Sulfate minerals contain the sulfate ion (SO4) combined with metallic elements. Gypsum (CaSO4·2H2O) and barite (BaSO4) are common sulfate minerals. 24 Halides: Halide minerals are composed of halogen elements such as fluorine (F), chlorine (Cl), bromine (Br), or iodine (I) combined with metallic elements. Examples include halite (NaCl), fluorite (CaF2), and sylvite (KCl). Phosphates: Phosphate minerals contain the phosphate ion (PO4) combined with metallic elements. Apatite, which is an important source of phosphorus, is a well- known phosphate mineral. Sulfosalts: Sulfosalt minerals are complex minerals containing both sulfide and arsenic or antimony combined with metallic elements. Examples include tetrahedrite and enargite. These classifications are based on chemical composition and provide a systematic way to organize and categorize the diverse array of minerals found on Earth. 25 A minimum metal content required for a deposit to qualify as an ore varies from metal to metal. Many non ferrous ore contains only one per metals or some times less then it. Gold can be recovered profitable from an ore containing 1 ppm level of metals Iron containing less then 45 per in an ore is said to be low grade. Every ton of material deposited have Contained value –depend upon metal content and current price of the contained metal. 26 Sampling Sampling is the mean where by a small amount of material is taken from the main bulk in such a manner that it is representative of the large amount. This sampling must be accurate because great responsibility rest on a very small sample. Objective of sampling: is to estimate grades and contents of sampling unit in an unbiased manner and with an acceptable and affordable degree of precision. 27 But the problem is that accurate sampling is difficult due to two main factors one is different size of particles, and inhomogeneity of material. Sampling is the removal from a given lot of material a portion that is representative of the whole yet of convenient size for analysis. How sampling is done It is done either by hand or by machine.  Hand sampling is usually expensive, slow, and inaccurate, so that it is generally applied only where the material is not suitable for machine sampling.  Many different sampling devices are available, including shovels, pipe samplers, and automatic machine samplers. For these sampling machines to provide an accurate representation of the whole lot, the quantity of a single sample, the total number of samples, and the kind of samples taken are of decisive importance.  A number of mathematical sampling models have been developed in order to arrive at the appropriate criteria for sampling. 28 29 Product of comminution Here region A represent valuable mineral Where as AA represents rich in valuable mineral but is highly intergrown with the gangue mineral. During comminution a range of fragments are produced ranging from fully liberated mineral and gangue particles. Here from the figure we can see Type 1- is rich in mineral and are classified as concentrate since as they have an acceptable degree of locking with the gangue, which limits the concentrate grade. Type 4- is tailing since small amount of mineral presents reduces the recovery of mineral into the concentrate. Types 2, 3- are of middle degree where regrinding needed to promote economic liberation of mineral. 30  Minerals Metallic Non-metallic Energy Mineral Ferrous Nonferrous Eg: Clays, Salts, Precious: Eg: Coal, Petroleum Iron based Iron, Mn, Eg: Copper, tin, Al, Sulphur, limestone, Gold, Platinum, Silver and Natural gas Co, Ni Lead.. etc granite Coal : INDIA is 5th largest reserve country of the world: 300 Billion Tonnes (2019) Uses: 1) Power generation, 2) Energy supply to industry and 3) Domestic needs. To meet the gap, India imports Coal Coal occurs in rock series of two main geological ages, namely: 1) Gondowana, a little over 200 million years in age 2) Tertiary deposits which are only about 55 million years old. Coals in India can be subdivided into mainly three locations: 1.Lower Gondowana Coalfields: West Bengal, Bihar, Madhya Pradesh, Maharashtra, Orissa, Andhra Pradesh, Uttar Pradesh, Assam, Sikkim. 2.Upper Gondowana Coalfields: Gujrat, Madhya Pradesh, Maharashtra 3.Tertiary Coalfields: Assam, Jammu and Kashmir, Rajasthan, Madras, Kerala, Gujrat Gondowana Coals are most important in India and account for more than 90% of coal production in country. Tertiary Coals contribute very little of the total coal production in India. They usually have high sulfur content (2-8%).  TYPES OF COAL There are four major types of coal. Type refers to steps in a slow, natural process called “coalification,” during which buried plant matter changes into an ever denser, drier, more carbon rich, and harder material. 1. Anthracite (Age- 350 my): The highest rank of coal. It is a hard, brittle, and black lustrous coal, often referred to as hard coal, containing a high percentage of fixed carbon(90%) with high energy content (34K kJ/Kg above) and a low percentage of volatile matter. 2. Bituminous (Age- 300 my): Bituminous usually has a carbon high %C = 50-70% with energy (25-35 kJ/Kg). Bituminous coal appears shiny and smooth when you first see it, but look closer and you may see it has layers. 3. Subbituminous (Age- 100 my): Subbituminous coal is black in color and dull (not shiny), %C = 40% with energy = 20-25 kJ/Kg. 4. Lignite (Age- 60 my): Lignite coal, aka brown coal, is the lowest grade coal with the least concentration of carbon %C = 30% with energy = 10-20 kJ/Kg Also, there is peat. Peat is not actually coal, but rather the precursor to coal. Peat is a soft organic material consisting of partly decayed plant and, in some cases, deposited mineral matter. When peat is placed under high pressure and heat, it becomes coal. Iron ore: India holds 7th position in iron ore reserve and 4th in production Two important ores: 1) Hematite (Fe2O3) 2) Magnetite(Fe3O4) The total reserves of iron ore in the country were about 20 billion tonnes in the year 2010. About 95 per cent of total reserves of iron ore is located in the States of Odisha, Jharkhand, Chhattisgarh, Karnataka, Goa, Telangana, Andhra Pradesh and Tamil Nadu. In Odisha, iron ore occurs in a series of hill ranges in Sundergarh, Mayurbhanj and Jhar. The important mines are Gurumahisani, Sulaipet, Badampahar (Mayurbhaj), Kiruburu (Kendujhar) and Bonai (Sundergarh). In Jharkhand , most of the important mines such as Noamundi and Gua are located in Poorbi and Pashchimi Singhbhum districts. This belt further extends to Durg, Dantewara and Bailadila. Dalli, and Rajhara in Durg are the important mines of iron ore in the country. In Karnataka, iron ore deposits occur in Sandur-Hospet area of Ballari district, Baba Budan hills and Kudremukh in Chikkamagaluru district and parts of Shivamogga, Chitradurg and Tumakuru districts. In Maharashtra, the districts of Chandrapur, Bhandara and Ratnagiri, In Telangana, Karimnagar and Warangal district. Kurnool, Cuddapah and Anantapur districts of Andhra Pradesh, Salem and Nilgiris districts of Tamil Nadu In Goa, mining is mostly concentrated in four talukas namely, Bicholim in North Goa district and Salcete, Sanguem and Quepem in South Goa district. Types of Iron ore and properties: Mineral potential area:  The total reserves/resources ~ GOLD 501.83 MT (2015) Gold in its purest form, is a bright, slightly reddish yellow, dense, soft malleable and ductile metal. It is one of the least reactive chemical elements and is solid under standard conditions. Gold often occurs in free elemental (native) form, as nuggets or grains, in rocks, in vein, and in alluvial deposits. Gold is a relatively scarce metal in the world and a scarce commodity in India. The domestic demand is mainly met through imports. The consumption of gold produced in the world is about 50% in jewellry, 40% in investment, and 10% in industry. The production of gold ore ~ 582 thousand tonnes during 2016-17 increased by 3% as compared to that in the previous year. Production of primary gold in 2016-17 at 1,594 kg increased by 20% as compared to that in the previous year.  Gold reserves in India 3% 2% 2% 3% Bihar Rajasthan 21% 44% Karnataka West Bengal Andhar Pradesh 25% Jharkand Kerala, MP, Maharashtra Gold usually occurs in Auriferous [(of rocks or minerals) containing gold] rocks. It is also found in sands of several rivers. Karnataka is the largest producer of gold in India. Gold mines are located in Kolar [Kolar Gold Field], Dharwad, Hassan and Raichur [Hutti Gold Field] districts. Kolar Gold Fields (KGF) is one of the deepest mines of the world. [Usually, gold mines are the deepest mines in the world. Bonding and Lattices An Atom always wants to have a full outer shell to be atomically stable (i.e., two electrons for hydrogen and helium or eight electrons for most elements). This is accomplished by: Ionic bonding 1) Transferring electrons with other atoms.... Ionic bond N = 11 N = 17 2) Sharing electrons with other atoms..... Covalent bond Covalent bonding Cl Cl Depiction of a covalent bond between two chlorine atoms Depiction of a Ionic bond between Na and Cl Packing structure of Ionic solids It is necessary to understand the way atoms are Linear packed together or coordinated by larger anions, like oxygen depends on the radius ratio of the cation to the Triangular anion, rAnion/RCation. The number of anions surrounding a central cation Tetrahedral is called Coordination Number (C.N) or ligancy. C.N is a function of the ionic sizes and the space Octahedral Cubic Hexagonal or cubic closed packing  C.N. Coord. Ion (with Ionic Radius, Å Since oxygen is the most abundant element in the Oxygen) Polyhedron crust, oxygen will be the major anion that K+ 8 - 12 cubic to 1.51 (8) - 1.64 closest (12) coordinates the other cations. Na+ 8-6 1.18 (8) - 1.02 (6) cubic to Thus, for the major ions that occur in the crust, we octahedral Ca+2 8-6 1.12 (8) - 1.00 (6) can make the following table showing the Mn+2 6 0.83 coordination and coordination polyhedra that are expected for each of the common cations. Fe+2 6 0.78 Mg+2 6 0.72 Octahedral Fe+3 6 0.65 Ti+4 6 0.61 Al+3 6 0.54 Al+3 4 0.39 Tetrahedral Si+4 4 0.26 C+4 3 Triangular 0.08  Silicate Minerals Silicon and oxygen bond together to create a silica tetrahedron, which is a four-sided pyramid shape with O at each corner and Si in the middle. The bonds in a silica tetrahedron have mixed character of covalent and Ionic bonding. As a result of the ionic character, silicon becomes a cation (with a charge of +4) and oxygen becomes an anion (with a charge of –2). The net charge of a silica tetrahedron (SiO4) is: 4 + 4(−2) = 4 − 8 = −4.  Isolated tetrahedron Olivine Isolated silica tetrahedron (SiO4) is: 4 + 4(−2) = 4 − 8 = −4. Olivine, is composed of isolated tetrahedra bonded to Iron and/or Magnesium ions. In olivine, the −4 charge of each silica tetrahedron is balanced by two divalent (i.e., +2) iron or magnesium cations. Olivine can be either Mg2SiO4 or Fe2SiO4, or some combination of the two (Mg,Fe)2SiO4. The divalent cations of Mg and Fe are quite close in radius (0.73 versus 0.62 angstroms).  Garnet These minerals share a common crystal structure and a generalized chemical composition of X3Y2(SiO4)3. "X" = Ca, Mg, Fe2+ or Mn2+, "Y" = Al, Fe3+, Mn3+, V3+ or Cr3+. These minerals are found throughout the world in Metamorphic, igneous, and sedimentary rock. Garnet Minerals Mineral Composition Specific Gravity Hardness Colors Almandine Fe3Al2(SiO4)3 4.20 7 - 7.5 red, brown Pyrope Mg3Al2(SiO4)3 3.56 7 - 7.5 red to purple orange to red to Spessartine Mn3Al2(SiO4)3 4.18 6.5 - 7.5 brown green, yellow, Andradite Ca3Fe2(SiO4)3 3.90 6.5 - 7 black green, yellow, red, Grossular Ca3Al2(SiO4)3 3.57 6.5 - 7.5 pink, clear Uvarovite Ca3Cr2(SiO4)3 3.85 6.5 - 7 green  Pyroxene: XSiO3 In pyroxene, silica tetrahedra are linked together in a single chain, where one oxygen ion from each tetrahedron is shared with the adjacent tetrahedron, hence there are fewer oxygens in the structure. The result is that the oxygen-to-silicon ratio is lower than in olivine (3:1 instead of 4:1), and the net charge per silicon atom is less (−2 instead of −4). (4 + 3(−2) = 4 − 6 = −2) Therefore, fewer cations are necessary to balance that charge. Pyroxene compositions are of the type MgSiO3, FeSiO3, and CaSiO3, or some combination of these The structure of pyroxene is more “permissive” than that of olivine— meaning that cations with a wider range of ionic radii can fit into it.  Amphibole In amphibole structures, the silica tetrahedra are linked in a double chain that has an oxygen-to-silicon ratio lower than that of pyroxene, and hence still fewer cations are necessary to balance the charge. Amphibole is even more permissive than pyroxene and its compositions can be very complex. Hornblende, for example, can include sodium, potassium, calcium, magnesium, iron, aluminum, silicon, oxygen, fluorine, and the hydroxyl ion (OH−).  Mica In mica structures, the silica tetrahedra are arranged in continuous sheets, where each tetrahedron shares three oxygen anions with adjacent tetrahedra. There is even more sharing of oxygens between adjacent tetrahedra and hence fewer cations are needed to balance the charge of the silica-tetrahedra structure in sheet silicate minerals. Bonding between sheets is relatively weak, and this accounts for the well-developed one-directional cleavage in micas  Quartz Quartz is another 3 dimensional network framework silicate with each tetrahedra corner is attached to neighboring tetrahedras Most common in Igneous and metamorphic rock. Quartz has vast varietis of colors due to impurities: Yellow (citrine) due to trace amounts of ferric iron (Fe3+), Rose quartz has trace amounts of manganese, Purple quartz (amethyst) has trace amounts of iron, Milky quartz, which is very common, has millions of fluid inclusions (tiny cavities, each filled with water). Feldspar: Framework silicates Feldspars are the most common mineral of the earth crust Feldspars are frame work silicates where each tetrahedra share all corner with its four neighboring tetrahedras. A portion of tetradras contain Al3+instead of Si4+. The charge is balance by incorporating Na+, K+ or Ca2+ A three dimensional silica structure with Si:O ratio is 3:8. The three main common feldspars are: 1) Orthoclase: KAlSi3O8 2) Albite: NaAlSi3O8 3) Anorthosite: CaAl2Si2O8  Orthoclase Albite Anorthite Three main common feldspars are: 1) Orthoclase: KAlSi3O8 The Albite and Anorthosite form a solid solution of feldspars called 2) Albite: NaAlSi3O8 Plagioclase 3) Anorthosite: CaAl2Si2O8 Feldspathoids The feldspathoids are a group of tectosilicate minerals which resemble feldspars but have a different structure and much lower silica content. The feldspathoid group minerals are sodium, potassium, and calcium aluminosilicates, many of which resemble the feldspars in appearance. They are relatively rare. The aluminum to silicon ratio is nearly 1:1 in most of the feldspathoids but is closer to 1:3 in most of the feldspars. Theses include Nepheline, Analcime and Leucite Tourmaline is a complex boron silicate mineral with a generalized chemical composition of: XY3Z6(T6O18)(BO3)3V3W Letters in the formula above represent positions in the atomic structure of tourmaline that can be occupied by ions listed below. Important cyclosilicates: „Beryls „Tourmaline „ cordierite CYCLOSILICATES = RING SILICATES 6-fold rings of Si and Al tetrahedra Double island silicates: each tetrahedron shares one corner with another tetrahedron Basic structural unit: (Si2O7) 6- Some sorosilicate: combination of single and double island (ex.: Epidote) COMMINUTION: A process in which the particle size of the ore is progressively reduced until the clean particles of mineral is achieved. An objective of comminution is liberation at the coarsest possible particle size. Liberation of the valuable minerals from the gangue is accomplished by size reduction or comminution, that is, the ore minerals are liberated or free.  Classified according to their interrelations in product size and process environment (dry or wet). 1. Drilling (and blasting) is the technology of achieving primary fragmentation. With natural minerals in the form of sand and gravel. Size reduction: Infinity to 1 m 2. Crushing and screening is the first controlled size reduction stage in the process. Size reduction: Primary Crushing: 1 m to 100 mm Secondary Crushing: 100 mm to 30 mm Tertiary Crushing: 20 mm to 5 mm 3. Grinding is the stage of size reduction (wet or dry) where the liberation size for individual minerals can be reached. Size reduction: Coarse grinding: 5 mm to 1 mm Fine Grinding: 1 mm to 100 µm Very Fine grinding: 100 µm to 10 µm Superfine grinding: 10 µm to 1 µm 4. Slurry processing includes the technologies for wet processing of mineral fractions. 5. Pyro processing includes the technologies for upgrading of the mineral fractions by drying, calcining or sintering. 6. Materials handling includes the technologies for moving the process flow (dry) forward by loading, transportation, storage and feeding. 7. Compaction of minerals includes the technologies for moving and densifying minerals by vibration, impaction and pressure, mainly used in construction applications. The stress forces of rock mechanics Regions A represent Region AA is rich in valuable mineral but valuable mineral is highly intergrown with the gangue mineral. After Comminution: Particles of type 1 are rich in mineral (are high-grade particles) with lesser gangue attached is called Concentrate Particles of type 4 with low mineral and high gangue is called Tailings, Particles of types 2 and 3 represents the small amount of mineral with an acceptable loss of mineral. Called as Middlings  After the valuable mineral particles have been liberated, they must be separated Concentration from the gangue particles. 1. Optical. This is often called sorting, which used to be done by hand but is now mostly accomplished by machine. 2. Density, Gravity concentration, based on the differential movement of mineral particles in water due to their different density and hydraulic properties. i) Belt type Jigging action ii) Chute type 3. Surface properties. Froth flotation (or simply “flotation”), which is the most versatile method of concentration, is effected by the attachment of the mineral particles to air bubbles within an agitated pulp. By adjusting the “chemistry” of the pulp by adding various chemical reagents, it is possible to make the valuable minerals water-repellant (hydrophobic) and the gangue minerals water-avid (hydrophilic). 4. Magnetic susceptibility. Low-intensity magnetic separators can be used to concentrate strongly magnetic minerals such as magnetite (Fe3O4) and pyrrhotite (Fe7S8). 5. Electrical conductivity. Electrostatic separation can be used to separate conducting minerals from nonconducting minerals. Measure of separation: The two most common measures of the separation are grade and recovery. Grade: The grade, or assay, refers to the content of the marketable commodity. In metallic ores, the estimated %metal present. The metal content of the mineral determines the maximum grade of concentrate that can be produced. Thus processing an ore containing Cu in only chalcopyrite (CuFeS2) the maximum attainable grade is 34.6%, while processing an ore containing galena (PbS), the maximum Pb grade is 86.6%. Recovery The recovery is the percentage of the total metal contained in the ore that is recovered to the concentrate. For instance, a recovery of 90% means that 90% of the metal in the ore (feed) is recovered in the concentrate and 10% is lost in (“rejected” to) the tailings. where C is weight of concentrate, F the weight of feed, c the grade (assay) of metal or mineral in the concentrate, and f the grade of metal/mineral in the feed. Provided the metal occurs in only one mineral Numerical:  Crushing: Reduces the particle size of run-of- mine (ROM) ore to such a level that grinding can be carried out until the mineral and gangue are substantially produced as separate particles. Crushing is accomplished by compression of the ore against rigid surfaces, or by impact against surfaces in a rigidly constrained motion path Crushers Three stages of Crushers... Primary, Secondary & Tertiary. Three stages The product size is determined by the size of the opening at the discharge, called the set or setting. The reduction ratio = F80/P80 , is the ratio of feed size to Feed size ~ 1.5 mts product size, often with reference to the 80% passing size. Size reduction ~ 10- Crusher Can be Open circuit or Closed circuit. 20 cm Open Circuit: Feed material is only run through the crusher once. Size reduction ~ 3- 5 cm Closed circuit: Material is continuously return to the crusher until it’s a size pass through the screen Two types of crushers: Size reduction ~ 0.5- 2 cm 1. Jaw Crusher 2. Gyratory Crusher  Jaw Crushers Blake crusher was patented by E. W. Blake in 1858. Patent states that stone breaker “consists of a pair of jaws, one fixed and other movable, between which stones can be broken”. The jaws are set at an acute angle with one jaw pivoting so as to swing relative to the other fixed jaw. The material fed into the jaws is repetitively nipped and released to fall further into crushing chamber until the discharge aperture Jaw classified by the method of pivoting the swing jaw. Blake crusher: The Jaw is pivoted at the top and thus has fixed receiving area and a variable discharge. Dodge crusher: The jaw is pivoted at the bottom, giving it a variable feed area but fixed delivery area. Universal crusher: Pivoted in the middle and thus the variable delivery and receiving area. Blake crusher There are two forms of blake crusher: 1. Double toggle: The oscillating movement of the swinging jaw is effected by vertical movement of the pitman, which moves up and down under the influence of the eccentric. The back toggle plate causes the pitman to move sideways as it is pushed upward. This motion is transferred to the front toggle plate, which in turn causes the swing jaw to close on the fixed jaw, this minimum separation distance being the closed set. Similarly, downward movement of the pitman allows the swing jaw to open, defining the open set (or open side setting). Jaw crushers are rated according to their receiving area, that is, the gape, which is the distance between the jaws at the feed opening, and the width of the plates. For example, a 1,220 X 1,830 mm crusher has a gape of 1,220 mm and a width of 1,830 mm. 2. Single toggle: In single-toggle jaw crushers the swing jaw is suspended on the eccentric shaft, which allows a lighter, more compact design than with the double- toggle machine. The motion of the swing jaw also differs from that of the double-toggle design. Not only does the swing jaw move toward the fixed jaw under the action of the toggle plate, but it also moves vertically as the eccentric rotates. This elliptical jaw motion assists in pushing rock through the crushing chamber. The single-toggle machine therefore has a somewhat higher capacity than the double-toggle machine of the same gape. The eccentric movement, however, increases the rate of wear on the jaw plates. Direct attachment of the swing jaw to the eccentric imposes a high degree of strain on the drive shaft, and as such maintenance costs tend to be higher than with the double-toggle machine. Jaw crusher construction Heavy duty machines and must be robustly constructed. Main frame is made of cast iron or steel connected with tie bolt. Jaws are constructed from cast steel and the liner, made from manganese steel or Ni-hard, Ni-Cr alloyed cast iron. The angle between jaws is lesser than 26 degree. Speed of jaw crushers ~ 100 – 350 rpm  Gyratory crusher The gyratory crusher consists essentially of a long spindle, carrying a hard steel conical grinding element, the head, seated in an eccentric sleeve. The spindle is suspended from a “spider” and, as it rotates, normally between 85 and 150 rpm, it sweeps out a conical path within the fixed crushing chamber, or shell, due to the gyratory action of the eccentric. The spindle is free to turn on its axis in the eccentric sleeve, so that during crushing the lumps are compressed between the rotating head and the top shell segments, In fact, the gyratory crusher can be regarded as an infinitely large number of jaw crushers each of infinitely small width. it has a higher capacity than a jaw crusher of the same gape, roughly by a factor of 2.53, with crushing rates above 900 t h-1  Gyratory crusher Construction The outer shell of the crusher is constructed from heavy steel casting or welded steel plate , with at least one constructional joint, the bottom part taking the drive shaft for the head, the top, and lower shells providing the crushing chamber. The head consists of the steel forgings, which make up the spindle. The head is protected by a mantle (usually of manganese steel) fastened to the head by means of nuts on threads which are pitched so as to be self-tightening during operation. The mantle is typically backed with zinc, plastic cement, or epoxy resin. The vertical profile is often bell-shaped to assist the crushing of material that has a tendency to choke. Some gyratory crushers have a hydraulic mounting and, when overloading occurs, a valve is tripped which releases the fluid, thus dropping the spindle and allowing the “tramp” material to pass out between the head and the bowl. The mounting is also used to adjust the set of the crusher at regular intervals to compensate for wear on the concaves and mantle. Many crushers use simple mechanical means to control the set, the most common method being by the use of a ring nut on the main shaft suspension. Selection of a Jaw or Gyratory Crusher In deciding whether a jaw or a gyratory crusher should be used, the main factor is the maximum size and capacity of ore. Gyratory crushers are, in general, used where high capacity is required. Jaw crushers tend to be used where the crusher gape is more important. A gyratory having the required gape would have a capacity about three times that of a jaw crusher of the same gape. The capital and maintenance costs of a jaw crusher are slightly less than those of the gyratory. However, installation cost is less. Jaw crushers perform better than gyratories on clay or plastic materials due to their greater throw. Gyratories have been found to be particularly suitable for hard, abrasive material.  A guiding relationship was that given by Taggart (1945): if t h-1 < 161.7 X (gape in m2 ), use a jaw crusher; conversely, if the tonnage is greater than this value, use a gyratory crusher. SECONDARY/TERTIARY CRUSHERS: CONE Crusher Secondary crushers are lighter than the heavy-duty, rugged primary machines. Since they take the primary crushed ore as feed, the maximum feed size will normally be less than 15 cm. Secondary/tertiary crushers also operate with dry feeds, and their purpose is to reduce the ore to a size suitable for grinding Ternary crusher are, to all intents and purposes, of the same design as secondary, except that they have a closer set. The essential difference is that the shorter spindle of the cone crusher is not suspended, as in the gyratory, but is supported in a curved, universal bearing below the gyratory head or cone. The bulk of secondary/tertiary crushing is performed by CONE crushers. The throw of cone crushers can be up to five times that of primary crushers, which must withstand heavier working stresses. Cone Crusher Power is transmitted from the source to the countershaft through a V-belt or direct drive. The countershaft has a bevel pinion pressed and keyed to it, and drives the gear on the eccentric assembly. The eccentric has a tapered, offset bore and provides the means whereby the head and main shaft follow an eccentric path during each cycle of rotation. The wide travel of the head creates a large opening between it and the bowl when in the fully open position. The material passing through the crusher is subjected to a series of hammer-like blows rather than being gradually compressed as by the slowly moving head of the gyratory crusher. The high-speed (700- 1000 rpm) action allows particles to flow freely through the crusher. The fast discharge and non-choking characteristics of the cone crusher allow a reduction ratio in the range 3:1 to 7:1. Roll Crusher: Roll crusher operation consists of two horizontal cylinders that revolve toward each other. The gap is determined by shims which cause the spring- loaded roll to be held back from the fixed roll. Unlike jaw and gyratory crushers, where reduction is progressive by repeated nipping(bite) action as the material passes down to the discharge, the crushing process in rolls is one of single pressure. Roll crushers are also manufactured with only one rotating cylinder which revolves toward a fixed plate. Two Roll crusher Single Roll crusher Rolls are driven by V-belts from separate motors Crushing action of roller - The gap to set in for crushing determines the feed particle size Consider a spherical particle of radius r, being crushed by a pair of rolls of radius R, the gap between the rolls being 2a. If μ is the coefficient of friction between the rolls and the particle. θ is the angle formed by the tangents to the roll surfaces at their points of contact with the particle (the angle of nip). C is the compressive force exerted by the rolls on particle. The coefficient of friction between steel and most ore particles is Equating: in the range 0.2-0.3, so that the value of the angle of nip θ should never exceed about 30 degree, or the particle will slip This equation be used to determine the maximum size of rock gripped in relation to roll diameter and the reduction ratio (r/a) required: a = gap btn the rolls Impact Crusher Impact crushers a employ sharp blows applied at high speed to free-falling rocks where comminution is by impact rather than compression. The moving parts are “beaters,” which transfer some of their kinetic energy to the ore particles upon contact. Internal stresses created in the particles are often large enough to cause them to shatter. These forces are increased by causing the particles to impact upon an anvil or breaker plate Two types: Hammer mills impact mills  Hammer Mills The hammers can weigh over 100 kg and can work on feed up to 20 cm. The speed of the rotor varies between 500 and 3,000 rpm. The hammers are pivoted so as to move out of the path of oversize material (or tramp metal) entering the crushing chamber. The hammer mill is designed to give the particles velocities of the order of that of the hammers. Fracture is either due to impact with the hammers or to the subsequent impact with the casing or grid. Since the particles are given high velocities, much of the size reduction is by attrition (i.e., particle on particle breakage). The exit from the mill is perforated, so that material that is not broken to the required size is retained and swept up again by the rotor for further impacting. The hammers are made from manganese steel or nodular cast iron containing chromium carbide, which is extremely abrasion resistant. The breaker plates are made of the same material.  Impact Mills The fractured pieces that can pass between the clearances of the rotor and breaker plate enter a second chamber created by another breaker plate, where the clearance is smaller, and then into a third smaller chamber. The impact plates are reversible to even out wear, and can easily be removed and replaced. The impact mill gives better control of product size than does the hammer mill, since there is less attrition. Large impact crushers will reduce 1.5 m top size ROM ore to 20 cm, at capacities of around 1500 t h-1. Since they depend on high velocities for crushing, wear is greater than for jaw or gyratory crushers. They are a good choice for primary crushing when high reduction ratios are required (the ratio can be as high as 40:1) and the ore is relatively nonabrasive.  The screen is a surface having many apertures, or holes, usually with uniform dimensions. Industrial screening Particles presented to a screen surface either pass through or are retained, according to whether the particles are smaller or larger than the governing dimensions of the apertures. The main purposes in the minerals industry are: a. Sizing or classifying: to separate particles by size, b. Scalping: to remove the coarsest size fractions in the feed material, to crushed or removed from the process. c. Grading: to prepare a number of products within specified size ranges. d. Media recovery: for washing magnetic media from ore in dense medium circuits; or to retain grinding media inside grinding mills. e. Dewatering: to drain free moisture from a wet sand slurry. f. De-sliming or de-dusting: to remove fine material, generally below 0.5 mm, from a wet or dry feed. g. Trash removal: usually to remove coarse wood fibers or tramp material Types of screens Vibrating screens: Most common screening machine in mineral processing application Industrial Screens Laboratory screens Sieve shaker vibrating screen Four deck vibrating screen Vibrating Grizzly screen Horizontal screen Banana screen Gyratory screen High frequency screen Factors effecting screen performance 1. Particle size 2. Feed rate 3. Screen angle 4. Particle shape 5. Open area 6. Vibration frequency, amplitude 7. Moisture  500 micron Particle size analysis The objective of particle size analysis is to obtain quantitative data about the size and 300 size distribution of particles in the material. 200 Size analysis is important to assess the degree of breaking (fine) during the crushing , grinding and other operations Particle size and shape: The exact size of an irregular particle cannot be measured. The term “length”, breadth, or diameter have little meaning because so many different values of these quantities can be determined. For an irregular particle, it is desirable to quote the size of a particle in terms of single quantity called equivalent diameter.  Surface Diameter (Ds)  Volume Diameter (Dv)  Projected Diameter (Dp)  Stokes Diameter (Dst)  Sieve Diameter (Dsieve) Sieve analysis: (50-10,000 µm)Sieve Diameter (Dsieve)  Data representation 400 micron 300 200 Microscopy: (0.2-100 µm)Projected Diameter (Dp) Optical or electron microscopy  Laser diffraction  Sedimentation technique Sub sieve technique: (0.08-300 µm) Stokes Diameter (Dst) For particle size lesser than 38 microns, sieving operation is called Sub-sieve technique. Most widely used methods are: Sedimentation: Material to be sized is dispersed in a fluid and allowed to settle. Elutriation: Samples are sized by allowing the dispersed material to settle against a rising fluid velocity Elutriation technique  Principle of Sedimentation and Elutriation technique: Separate the particles on the basis of resistance to motion in a fluid. When a solid particle falls freely in a vacuum, there is no resistance to the particle’s motion. Therefore, if it is subjected to a constant acceleration. In a viscous medium (such as air or water), there is resistance to this movement and this resistance increases with velocity. When equilibrium is reached between the gravitational force and the resistant force from the fluid, the body reaches its terminal velocity and thereafter falls at a uniform rate. This resistance to motion determines the terminal velocity which particles attains as it is allowed to fall in a fluid under the influence of gravity.  For particles within the sub sieve range, terminal velocity is given by Stokes equation. Where, ν is the terminal velocity of the particle (ms-1), d the particle diameter (m), g the acceleration due to gravity (ms-2), ρs-the particle density (kgm-3), ρf the fluid density (kg m-3), and η the fluid viscosity (Nsm-2); (η = 0.001 Nsm-2 for water at 20C). Stokes’ law is only valid in the region of laminar flow, which sets an upper size limit to the particles that can be tested by sedimentation and elutriation methods in a given liquid. The limit is determined by the particle Reynolds number, a dimensionless quantity defined by: Reynolds number, determines the criteria for fluid flow, steady state (laminar flow) or turbulent state. Reynolds number < 2,000, flow is laminar, whereas, > 2,000, flow is usually turbulent. Classification Classification is a method of separating mixtures of minerals into two or more products on the basis of the velocity with which the particles fall through a fluid medium. In mineral processing, this fluid is usually water, and applied to mineral particles that are too fine ( V2> V3  Department of Metallur \‘\ gical and Materan?isé éng; ‘nizring Indian Institute of Techno : Mid-Semester logy Patna Examination (27" September 202 Programme: B, Tech, 3) Course Name; 4 q Year/Semester: 2023/3™ Sem. Maximum N:a:li:str ggumon to Mineral Processing and Raw Materials ~ Course Code: MM 203 ; Time allowed: 02:00 hours =Notes: * Ma. B e clean useFigures o. anyanddoubt, In ckcase anill /Diagrams to support your answer wherever appropriate. your best judgment and assume accordingly. * Al questions are compulsory. B'VNO' Questions | (a) Describe Concentration, Grade, and Recovery in context of mineral processing. 5 Additionally, present a brief overview of various concentration methods, accompanied by schematic illustrations. (b) Discuss different Laws of crushing and grinding. What is the significance of Bond work index Wi? In grinding a feed material for which 80% passes through a 4-mesh screen, the power requirement was 5.9kW to produce a product 80% of which passes through a 48-mesh 2+143 sereen. What will be required power to produce a finer product 80% of which passes through a 200-mesh screen? What scientific characteristics differentiate pearls from minerals, leading to the classification of pearls as non-mineral substances? Provide a comprehensive scientific discussion on the characteristics and properties of silicate minerals belonging to the Olivine and Garnet groups. 3 What is the primary objective of the sampling process in mineral processing, and provide a detailed analysis J of the figure (in right) to illustrate its relevance to 4. sampling? ‘Q ? Q; C? 3 Ore fragment Products of comminution Cross-sections of ore particles (a) Provide a differentiation of Hematite and Magnetite iron ores, based on their respective iron content percentages, specific gravity values, and color characteristics. Identify the 3 primary Indian states (top 4) with the most substantial gold reserves. 5. —— — (b) Tin concentration in an ore is 2.00%, what is the concentration of cassiterite (SnO2)? Given that Molar mass ofO is 15.99 g/mol and Molar mass of Sn is 118.71 g/mol. 2 (a) A material is crushed in the Jaw crusher in which the feed of average size 60 mm is reduced to 10 mm while consuming 15 kW/(kg/s) energy. Compute the energy consumption 2 to the crush the same material of 80 mm average size to 20 mm. Use Kick’s and Rittenger’s law. 6. | (b) Write a short note on any two of the following: i. Role of the pivot and toggle in blake crusher 2%2 ii. Selection of a Jaw or Gyratory Crusher iii. Center peripheral discharge and Overflow in a rod mill process.