Lec16 - Mineral Processing - F2023.pdf

Mining Optimization Laboratory Introduction to Mineral Resources ENGR 2106 - Fall 2023 Lec16 – Mineral Processing Dr. Ahlam Maremi Bharti School of Engineering Laurentian University F215B Email: [email protected] 1 Introduction to Mineral Processing • Ore is composed of the both valuable min...

Mining Optimization Laboratory Introduction to Mineral Resources ENGR 2106 - Fall 2023 Lec16 – Mineral Processing Dr. Ahlam Maremi Bharti School of Engineering Laurentian University F215B Email: [email protected] 1 Introduction to Mineral Processing • Ore is composed of the both valuable minerals as well as uneconomical minerals (gangue). • Mineral processing follows mining and prepares the ore for production of the valuable metal or mineral product. – Mineral processing = ore dressing = ore beneficiation = mineral dressing = milling • Stages of mineral processing: – Comminution – Size separation – Concentration 2 Ahlam Maremi 2 Mining Optimization Laboratory Stages of Mineral Processing 3 • Comminution: – First stage: Crushing (primary, secondary, tertiary) – Second stage: Grinding • Size separation: – Separate feed of ore into undersized and oversized using: • Screens for coarse dry ore. • Centrifugal classifiers for finer ore particles in slurry form. • Concertation: – Ore enrichment, is to remove gangue particles from ore to enhance the percentage of metal in the ore. • • • • • Optical. Density. Surface properties (hydrophobic vs. hydrophilic). Magnetic susceptibility. Electric conductivity. 3 Stages of Mineral Processing • Liberation of the valuable mineral(s) from the gangue is accomplished by comminution (size reduction). • Comminution involves crushing and grinding the ore to such a size that the product is a mixture of relatively pure particles of minerals and gangue. – (1) Acceptably liberated mineral – (2&3) Middlings – (4) Acceptably liberated gangue 4 Ahlam Maremi 4 Mining Optimization Laboratory Stages of Mineral Processing 5 • Once the valuable mineral in the ore has been suitably liberated from the gangue minerals, they are separated from each other using differences in physical and surface properties of the minerals and chemical properties. • There is an important difference between mineral processing and metallurgical processing: – Mineral processing does not change the core chemical composition of the minerals. – Metallurgical processing involves chemical reactions that fundamentally change the minerals. 5 Comminution - Crushing • Crushing is the first stage of comminution to liberate the valuable mineral from the gangue. – Crushing is typically accomplished on relatively dry ore in two or three consecutive stages of size-reduction: • Primary crushing, • Secondary crushing, and • Tertiary crushing. – In crushing, a mineral is placed in compression between two surfaces. • This condition creates a tensile stress normal to the compressive stress. • If the tensile stress is sufficiently large to overcome the interatomic bonds, then the material fractures by crack propagation along the plane of maximum tensile stress. 6 Ahlam Maremi 6 Mining Optimization Laboratory Comminution - Crushing 7 • Comminution circuits are operated in either open-circuit or closed-circuit configurations. – In an open-circuit, there is no recycle of a product to the feed. – In a closed-circuit, the product of stage of comminution undergoes size separation (screening or classification) with the oversize (too coarse) material recycled back to the previous comminution machine while the undersize (sufficiently fine) material stream passes to the next stage. • Primary crushers are heavy duty machines that are designed to crush run-of-mine ore (ROM). • Primary crushers are operated in open circuit. • The two main types of primary crushers are: – Jaw crushers and gyratory crushers. 7 Comminution - Jaw and Gyratory Crushers – Jaw crushers consist of a pair of steel jaws with one fixed and one that swings back and forth on a pivot. – The feed enters at the opening at the top and material is repeatedly nipped and released to fall further down the crusher chamber, until the ore is discharged at the bottom. – https://youtube.com/shorts/2SV4ADicfRM?si=E_BxpGde2Bn1yvVX – Gyratory crushers consist of a stationary outer steel shell with an inverted conical shape. A conically shaped crushing head is suspended from a spider at the top with its central shaft seated in an eccentric sleeve. As the eccentric sleeve rotates, the crusher head gyrates around, resulting in the ore being crushed between the crusher head and sleeve, but also by ore pieces being crushed together. • 8 Ahlam Maremi https://www.youtube.com/watch?v=1sMEl8rmWh0&t=1s 8 Mining Optimization Laboratory 9 Comminution - Crushing • The bulk of secondary/tertiary crushing is performed by cone crushers. – A cone crusher is a modified gyratory crusher with the essential difference being that the crushing head (cone) is supported by a curved universal bearing rather than suspended from a spider. – Cone crushers are generally operated in closed circuit (with ore recycle). – https://www.youtube.com/watch?v=AVRK4aCAjYU 9 Comminution - Grinding • Grinding is the last stage of comminution where the ore particles are reduced in size to a point that achieves mineral liberation. • Grinding is usually performed on ore in slurry form (in a suspension with water) in a cylindrical steel vessel containing a grinding medium (steel rods, steel balls, or rock itself). • The combination of the slurry and the grinding media is called the charge of the mill. • There are three common types of grinding mills used in mining: – Rod mills, ball mills, and semi-autogenous (SAG) mills. 10 Ahlam Maremi 10 Mining Optimization Laboratory Comminution – Grinding - Rod Mills 11 • Rod mills contain several steel rods of assorted diameters that are only a few centimeters shorter than the length of the mill. • As the mill rotates, the rods are lifted to the point where they tumble and roll down the charge which causes them to act like a series of crushing rolls. • Rod mills are used for primary grinding (first stage of grinding) and almost always operated in an open circuit. • https://www.youtube.com/watch?v=1r1ZOmbOczk 11 Comminution – Grinding - Ball Mills • Ball mills use steel balls the grinding media. • They are usually rotated at a speed where gravitational forces are balanced by centrifugal force. • Ball mills usually proceed rod mills or autogenous / semiautogenous (AG/SAG) mills in the second stage of grinding (secondary grinding) and are almost always operated in closed-circuit. • 12 Ahlam Maremi https://www.youtube.com/watch?v=L6sgGXXYdEU 12 Mining Optimization Laboratory Comminution – Grinding - Semi-autogenous 13 • Semi-autogenous (SAG) operate similarly to ball mills but use a combination of the ore and steel balls as the grinding media. • SAG mill and ball mill circuits generally have lower costs and operation benefits over traditional circuits. • https://www.youtube.com/watch?v=l1nD1qC165A 13 Comminution: Crushing and Grinding Crushing Open circuit Open circuit (it could be closed) Grinding Closed circuit Closed circuit Open circuit 14 Ahlam Maremi 14 Mining Optimization Laboratory Size Separation 15 • Size separation is used to separate a stream of material by size. • Two size separation technologies used in mining applications: – Vibrating screens: • Used for coarse dry ore streams – Centrifugal classifiers: • Used for finer ore particles that are in slurry form. • Each technology is used to separate a feed of ore into: – Undersize, U (tonne/h), the particles are smaller than a desired size, – Oversize, O (tonne/h), the particles are too big and require further size reduction. 15 Size Separation - Vibrating Screens • There are several types of screens available for industrial screening, – Vibrating screens: • Vibrating screens are composed of a rectangular surface that has many holes of uniform size with the feed entering on one end and the oversize discharging at opposite end. • The vibrations throw particle up off the screen surface so that as they fall back to the screen surface, they will have another chance of passing through the screen. • https://www.youtube.com/watch?v=PWjzN7h-QzA 16 Ahlam Maremi 16 Mining Optimization Laboratory Size Separation - Centrifugal Classifiers 17 • Centrifugal classifiers (hydro-cyclones) are widely used in closed-circuit grinding. • The feed is introduced under pressure through the tangential entry, which imparts a swirling motion to the pulp. – Larger particles are subject to larger centrifugal forces, so they move quicker, relative to smaller particles, toward the wall of the cyclone, where they slow down and flow down and out the bottom. – Smaller particles, that move slower due to relatively large drag forces, are forced to move opposite the large particles toward the low-pressure vortex and are carried out through the top. • • https://www.youtube.com/shorts/-i8BI_SYoto https://www.youtube.com/watch?v=QfTZUMq-LGI 17 Concentration • The product of comminution/size separation is then subjected to a concentration step. • Concentration is to separate the valuable minerals from the gangue. – Mineral processes uses differences in mineral properties to accomplish this. • The most important properties, and corresponding methods of concentration are as follows: – Optical: sorting of minerals based on their appearance. – 18 Ahlam Maremi https://www.youtube.com/watch?v=pVTpFa-ivWE 18 Mining Optimization Laboratory Concentration 19 – Density: gravity concentration using differences in density and hydraulic properties to cause one mineral to rise while others sink. • Separates heavy minerals from lighter gangue – Large differences in specific gravity (density) needed – All particles settle in the same direction within the device. – Jigs (https://www.youtube.com/watch?v=dauNWfbEBkM) 19 Concentration – Surface properties: flotation of minerals hydrophobic minerals by attachment to rising bubble in a pulp (mixture of ground minerals and water), while hydrophilic minerals remain in the pulp. – Used to physically separate particles based on differences in the water-repellency characteristics of the surfaces of various minerals contained in aqueous slurry. – Air bubbles generated within a separation vessel, collect hydrophobic particles and ascend to the surface. • Particles attached to be removed • Particles that remain wetted stay in the liquid phase • https://www.youtube.com/watch?v=N6_GUs8EJNo 20 Ahlam Maremi 20 Mining Optimization Laboratory Concentration 21 – Magnetic susceptibility: magnetic separation of minerals that are magnetic or paramagnetic (can be made magnetic) from those that are diamagnetic (non-magnetic). – Utilizes the differences in magnetic force between two or more materials • Different levels of magnetic fields depending on the difference in magnetic properties of the particles – Dry vs. wet magnetic separation • Dry: most efficient on closely sized materials • Wet: handle a much wider and finer size range 21 Concentration – Electric conductivity: electrostatic separation of minerals that are electrical conductors from non-conducting minerals. • Almost all minerals show some degree of conductivity, – Use the difference in electrical conductivity or surface charge of the minerals of interest, – Particles under the influence of an electrical field accumulate a charge and can be separated by differential attraction or repulsion. • Device: Plate-type electrostatic separator – 22 Ahlam Maremi https://www.youtube.com/watch?v=vTJb7D7WQpE 22 Mining Optimization Laboratory Learning Outcomes 23 • By the end of the lecture, you should be able to: – Describe mineral processing – Define common terms such as: mineral processing, concentration, comminution, etc.. – Describe the mechanism of crushing and how jaw, gyratory, and cone crushers work. – Describe the mechanism of grinding and how rod, ball, and sag mills crushers work. – Describe two most important methods of size separation (vibratory screening and centrifugal classification) and their applications. – You can list the five mineral/element properties and describe the corresponding methods of concentration. 23 24 Grade Distribution • • • • • • 24 Ahlam Maremi Quiz 1 Quiz 2 Midterm Exam Field Trip Report 1 Field Trip Report 1 Final Exam 5% 5% 35% 7.5% 7.5% 40% Mining Optimization Laboratory Schedule • • • • • • 25 November 16: Lec17 November 21: Lec18 November 23: Field Trip November 28: Lec19 November 30: Last lecture December 05: Final Review 25 Don’t Forget! • • • • 26 Ahlam Maremi Check your LU email and D2L regularly. Review additional resources available on D2L Field Trip – Glencore Smelter – on Nov 23rd Final Exam Dec 7th B-GYM – Lec10 to the End 26 Mining Optimization Laboratory Don’t Forget! 27 • Check your LU email and D2L regularly. • Review additional resources available on D2L. • Nov. 17th Special Guests (Glencore Operations) – Submit a report • Field Trip report due Nov 18th • Nov. 22nd Special Guest • Final Exam: Dec. 12th @ 9:00 AM – B-GYM (Lec10 – Lec19) 27 Ahlam Maremi