5.U 5 SSS Ore Drs 23-24 Aditya mine.pptx

Ore Dressing

1. Unit – V ORE DRESSING

2. NOTE : The presentation is respect of various topics and units are only indicative and not exhaustive. Students are advised to keep themselves abreast and well informed about the subject by referring to the suggested reference books & latest information available from different available sources. IMP slides/definitions from exam view point are marked . Some lectures are on YouTube: Basic mining by sharad sapkal in Hindi Rest of the material is for general information and subject understanding.

3. Unit Marks as per Curriculum Max Marks [1.5 x Clo.-(2)] Que1 Que-2 Que-3 Que-4 Que-5 Que-6 Total Marks in a paper set Remarks V 10 15 2 4 4 - 6   16  

4. Q asked in 22-23 exams Define “Mineral Processing”. Define “Tabling”. Describe the advantages of ore dressing. 4 Justify the use of various steps such as – 4 Communition , Sizing, Concentration and Dewatering involved in mineral beneficiation Justify the use of magnetic separator and electrostatic separator for mineral beneficiation. 6 Compare Blake and Dodge crushers based on :– 6 Arrangement of Jaws ii) Angle of nip iii) Prime moving machinery. Justify the use of various steps such as communication, sizing, concentration and dewatering involved in mineral benification . Justify the use of magnetic separator and electrostatic separator for mineral beneficiation. 6

5. Unit –V Ore Dressing   Describe the given steps involed in ore beneficiation. Identify ore preparation methods for Ore Dressing. Identify different methods of ore dressing. Describe given agglomeration process. 5.1 Importance of Ore dressing Concept of ore dressing Advantages and importance of mineral beneficiation, Steps involved in mineral beneficiation: liberation and separation. 5.2 Preparation of sample Classification, processes for concentration of valuable minerals, Comminution , sizing, different types of crushing and grinding equipment and their construction. Preparation of Mineral Samples for analysis. 5.3 Methods of ore dressing Gravity Separation: Tabling, Jigging Heavy Media separation. Magnetic separation, Electrostatic Separation froth floatation etc. 5.4 Agglomeration processes Sintering, Briquetting, Palletising, Nodulising their description

6. 5.1 Importance of Ore dressing Concept of ore dressing Advantages and importance of mineral beneficiation, Steps involved in mineral beneficiation: liberation and separation.

7. Abundances of the Elements in the Earth's Crust

8. An  element  is a pure substance consisting only of  atoms  , the fundamental materials of which all matter is composed. Eg . iron, zinc, sulphur and oxygen Atoms consist of protons, neutrons and electrons. The number of protons (the “atomic number”) defines the “ element ". For example oxygen (O) has 8 protons, Uranium (U) has 92 protons. Compounds are chemical substances made up of two or more elements that are chemically bound together in a fixed ratio.H2O,NaCl Total 88 elements found in the Earth's crust -- of these, only 8 make up its 98%: oxygen, silicon, aluminum, iron, calcium, magnesium, potassium and sodium In the whole earth , only 4 elements dominate: iron, oxygen, silicon and magnesium . These general element are reflected in the composition of  original or igneous rocks . Magma or molten rock is parent source of all rocks. The elemental composition of the  human body  and life in general is quite different. These elements go up to make most of the minerals.

9. Mineral: A mineral is a naturally occurring, inorganic solid element or compound substance, with an orderly crystalline structure and a definite, homogeneous chemical composition and specific physical properties. Eg hematite, chalcopyrite, calcite etc. Some minerals occur as single element like gold silver graphite but most in the compound form as oxide, sulphide carbonate etc Rocks A rock is a naturally occurring solid mixture of one or more minerals, or organic matter whereas a mineral is composed of the same substance throughout . There are over a 1,000 different types of rocks on Earth. For example, granite is a mixture of the minerals quartz, feldspar, and biotite . Even though there are more than 2500 minerals ,only nine minerals make up most of the rocks of the Earth's crust -- these are the " rock-forming minerals “ Minerals containing silicon and oxygen are called silicates . These make up more than 95% of the crust . The seven most abundant silicates in the crust are feldspar, quartz, pyroxene, amphibole, mica, clay minerals, and olivine. Olivine and pyroxene are the main constituents of the uppermost mantle . Two other rock-forming minerals are carbonates : calcite (calcium carbonate) and dolomite (calcium-magnesium carbonate).

10. Ore : An ore is naturally occurring solid material which is mixture of valuable minerals and gangue minerals from which at least one of the valuable or economic minerals or metal can be extracted economically. An ore body is a natural concentration of valuable material amenable to economic extraction through mining. Ore bodies ” are rocks containing an enhanced percentage of valuable minerals, high enough to be economic for mining and a lower percentage of gangue minerals. Economic minerals: Are valuable mineral resources which, once extracted and used, are not renewable. Ore minerals are minerals containing metals as their major constituents. Gangue minerals: Usually worthless, non metallic minerals which are introduced/interlocked with the economic mineral or the inclosing rocks within ore body ,they are discarded during beneficiation of the ore. Grade of the ore defines the quality of ore expressed in terms of % age or PPM of useful metal or mineral present in it.

11. Mineral Groups Native Gold Silver Copper diamond Silicates Contain Silicon & Oxygen, Silicates are common rock forming minerals eg . felsphar,mica,pyroxene,olivine etc Carbonates Contain Carbon, Oxygen & One or More Dolomite calcite Oxides Contain Oxygen & One or More Other Elements eg.magnetite , hematite ,Cuprite Cu2O Rutile TiO2, Quartz (SiO2) etc Hydroxide Gibbsite Al2O3 3H2O bauxite minerals Sulfides Contain Sulfur & One or More Other Elements Iron Sulfide – Pyrite, chalcopyrite, ZnS , PbS Sulfates Contain Sulfur & One or More Other Elements CaSO4 2H2O Gypsum,BaSO4 Barites Halides Contain Halogen Ion chlorine, fluorine, bromide and iodine One or More Other Elements Fluorite Phosphate Apatite etc

12. Mineral Commodities Metals Non metals Energy minerals Categories for metals include: •Precious (noble) metals –Resistant to weathering (rust) –Usually mined in their native state –Examples are gold, silver, and the platinum-group metals •Base metals – Metal that oxidizes or corrodes relatively easily –Examples are copper, lead, zinc, and nickel •Ferrous metals –Metals that have a strong chemical affinity with iron –Examples are iron, chromium, cobalt, and manganese

13. Metals are categorized into groups reflecting common usage or properties Non-ferrous metals –Metals that have no affinity with iron (also includes the base metals) –Examples are aluminium, tin, magnesium •Specialty metals –Metals with unusual (exotic) properties making them valuable in specific usages –Examples are cadmium, mercury, titanium, zirconium Some valuable minerals can’t be characterized as metals •Industrial minerals –salt, limestone, marble •Gemstones –diamonds, rubies, emeralds

14. Construction materials –sand and gravel, stone, cement, gypsum, asbestos, lime • Agricultural commodities –phosphate, potash, nitrogen • By-product commodities –gallium, arsenic, germanium, indium, selenium, tellurium 1.Metallic minerals = From which metals can be extracted. 2.Non metallic minerals or industrial minerals used for making cement, glass ceramic, refractories, fertilisers, abrasives etc Metal a solid mineral element that is able to conduct heat and electricity and is pliable under heat or pressure. Common metals include bronze, copper and iron.

15. Exploration is searching for natural resources, it aims at locating the presence of economic deposits and establishing their nature, shape, and grade. It involves testing of a number of places for natural resources, e.g. drilling or boring for collecting samples to examine the possible mineral deposits.   Mining is the science, technique, and business of mineral discovery and exploitation. Smelting : Obtaining a metal from its ore or concentrate. Refining : Reducing impurities from smelter product, to within market specifications. By-product is a secondary or additional product recovered in the extraction process ( mostly refining) (e.g. molybdenum is a common by-product of copper). Run of mine ore:- The ore recovered in natural, unprocessed state from the mine and prior to processing of any sort . It doesn’t include any separately handled waste or Overburden.

16. Defined in sec 3 of MMDR Act 2015, 55 in nos Used for war purpose Ore dressing

17. Def : Concentration, beneficiation or ore dressing It is a physical process done on ROM through which gangue minerals are separated from the economic minerals to a large extent and concentration of useful mineral is upgraded by enhancing its percentage . It includes liberation and separation of gangue minerals the economic minerals . Concentrate: The final product obtained or produced during beneficiation process which is rich in economically valuable mineral and satisfy the specifications of the user industry is called concentrate. Tails: The fraction of feed material which is produced during beneficiation process, and have no economical value are called tailings or rejects. Middling: The fraction of the material produced during beneficiation process, which contain both economic mineral and unwanted minerals are called middling and are generated due to interlocking of the minerals. More middling are generated due to coarser grinding, i.e the size more than liberated size . Coarser grinding is carried out to minimize the operating cost. Once these middling are produced they are further ground to fine size and subjected to concentrations process.

18. Introduction : The economic minerals or ores are rarely found in nature in desired degree of purity & form, which ultimate user industry demands. They are usually associated with gangue , the worthless material, which is required to be separated out from the valuable mineral contents & thus make them usable. This separation is affected by adopting certain physical processes. Separation of economic minerals from gangue is achieved by taking advantages of the difference in their physical properties like shape, colour , specific gravity, hardness , magnetic susceptibility, electrical conductivity, physical behaviour on heating & surface properties ( i.e. affinity of valuable or waste materials to flotation reagents.) The sum total of the treatments to which ore is subjected in order to separate & discard their worthless fraction is known as mineral dressing or ore dressing or ore beneficiation . Beneficiation is a physical process by which an ROM ore is improved in grade so that it can be used by metallurgical or other user industry.

19. Note : The method of mineral dressing are essentially physical where the chemical identity of the mineral is rarely destroyed during the process except when they take recourse of chemical action during leaching process. Note : The mineral dressing processes are not effective in ores where the impurities are present in the chemically combined form with valuable mineral, here improvement however can be brought about by metallurgical treatments like hydrometallurgy, pyro-metallurgy etc. There are several methods involved in mineral dressing. Some of which are required to be adopted for a particular mineral sample, depending upon the nature of association of ore mineral with gangue mineral.

20. Ore dressing process : Ore dressing or beneficiation is physical liberation of valuable and gangue minerals in the ore from each other, followed by concentration of valuable minerals at the cost of gangue minerals without changing their chemical composition. The first stage in beneficiation is to identify clearly under the microscope , the mineral constituents & the nature of intergrowth between the gangue & the valuables to know at what optimum size liberation of gangue from the valuable can take place. 1.Comminution :ROM is subjected to crushing for size reduction which is further subjected to grinding for liberation of valuable minerals from gangue minerals 2.Sizing : This ground ore is subjected to screening through screen or cyclones before concentration or material of different sizes are separated .

21. 3.Concentration is done by taking advantage of difference in physical properties between valuable minerals & gangue minerals. The physical properties could be shape, colour, cleavage, specific gravity, hardness, magnetic susceptibility, electric conductivity, physical behaviour on heating & surface properties etc . In Concentration the percentage of valuable minerals is increased in concentrate at the cost of gangue minerals without changing their chemical composition and the tails containing mostly gangue minerals is discarded. 4.Dewatering Concentration is mostly done in liquid phase the extraction of water from the concentrate pulp through vacuum filters or screen or pressure filters and extraction of water from the tailings from thickener and tailing dam is called Dewatering it reduces make up water of plant.

22. Accordingly the ROM ore is subjected to crushing ,grinding & screening up to liberation size before concentration of valuable minerals. Ore dressing processes classified on the basis of method of exploitation of different physical properties of useful and gangue minerals. They are as follows: On the basis of observation and feel of relative weight or hardness and colour by hand picking & chipping or dressing. Gravity separation of minerals having different specific gravity by washing, scrubbing, air blowing, heavy media separation, jigging, panning, tabling and by using classifiers and cyclones etc 3.Electrostatic separation of minerals having different electrical conductivity . 4.Magnetic separation of minerals having different magnetic susceptibility . 5.Froth flotation of minerals having different surface properties . 6.Combination of one or more of these process suitable for particular mineral.

23. How far are the chances

24. What are the steps involved in mineral processing

25. The major advantages of conducting mineral processing operation are: 1)The ore is upgraded to the desired specification level of different application like, to prepare the feed to smelter with required specification like grade, size composition and moisture etc. 2) physical separation can produce a product with desired specification for user industries like cement, fertilizers, alumina production etc. where the end process is not smelting, as in the case of limestone, rock phosphate , bauxite etc. 3)Total metallurgical cost is reduced due to reduction in tonnage of ore to be treated. 4)Reduce the harmful and objectionable impure minerals to the desired level. 5)Concentrates are only transported , the gangue material is discarded thus transport cost are greatly reduced. 6) due to reduction in tonnage to be transported material handlings problems will be minimized 7) Bulk waste is rejected .

26. 8 ) The usage of fuel, flux, and other ingredients in the feed to smelting operation can be reduced. 9) By employing simple physical beneficiation techniques in ore dressing, value addition can be affected on raw materials. 10) Valuable by products can also be recovered which are present in the ore. 11) The low-grade, sub grade and accumulated mine dumps can be brought into use & their by conservation of minerals is achieved. .

27. Mineral conservation can be achieved through ore dressing Mineral conservation aims at zero wastage of mineral commodity at mining beneficiation & metallurgical stage. Through ore dressing conservation of minerals is achieved as follows: The low-grade, sub grade and mineral rejects accumulated can be brought into use through upgradation . Valuable by products can be recovered and even deleterious material can also be discarded during beneficiation that renders the ore un usable. Reduction in transport and metallurgical cost due to bulk rejection of gangue minerals conservation of fuel ,refractory and flux and other additive minerals can be achieved.

28. 5.2 Preparation of sample Classification, processes for concentration of valuable minerals, Comminution , sizing, different types of crushing and grinding equipment and their construction. Preparation of Mineral Samples for analysis.

29. Preparation of Mineral Samples for Ore Dressing 1.Crushing & grinding After mineralogical study, crushing & sizing precede generally all other beneficiation methods because this operation makes product suitable for beneficiation. Crushing /grinding is done essentially to liberate gangue from valuables which enables the liberated particles to move freely away from each other, when subjected to various treatments. Def : Liberation means Crushing /grinding the rock up such a size that gangue and useful mineral particles are free to move away from each other . There are a number of machines of different make for crushing viz ; Jaw Crusher, Gyratory Crusher, Cone Crusher & hammer mill are used for course grinding / crushing. Ball mill , rod or tube mill are used for fine grinding. Further Jaw , Gyratory & Cone Crusher are used for hard ore and hammer mill are used for soft material. Such crushers are placed in the circuit as primary ( Jaw & Gyratory Crusher ), secondary & tertiary ( Cone Crusher , hammer mill etc ) .

30. Sometimes it may be necessary to put grizzly before the run of mine is fed to primary crushers. Grizzly is a sieve of thick steel rod or bar strong enough to withstand load impact of run off mine when discharged on it. The purpose of grizzly is to allow only sized material perceptible to primary crushers . For crushing sticky material containing clay it is necessary to wash or scrub them before discharging into the crusher to remove fines and clays, which cause stickiness. .

31. 2.Grinding : It refers to final and finer stage of comminution up to the liberation stage. In this process, the crushed material can be further disintegrated in a cylinder mill, which is a cylindrical container built of varying length-to-diameter ratios, mounted with the axis substantially horizontal, and partially filled with grinding bodies ( e.g.,   flint stones, iron or steel balls ) that are caused to tumble, under the influence of gravity, by revolving the container. A special development is the autogenous or semi autogenous mill. Autogenous mills operate without grinding bodies , grinding ore with ore itself by a near fall of mineral on mineral & with abrasive action on each other. The coarser part of the ore simply grinds itself into the smaller fractions. Mineral is ground to powder, which is removed by suction. To semi autogenous mills (which have become widespread), 5 to 10 percent grinding bodies (usually metal spheres) are added. By regulating the air discharge mineral of any size can be obtained. 3.Beneficiation :The ground material is finally subjected to beneficiation process depending on physical properties of mineral constituents. Def : Beneficiation or separation is a physical process of separating gangue and useful mineral particles making use of their different physical properties.

32. Preparing a sample for ore dressing Preparation of sample is also called as reduction of sample. For bench or lab scale study (discontinuous process ) 100 to1000 kg sample is required. For pilot plant study (continuous process ) representative bulk sample 50-500 t of crushed material having boulder size 20-25 cms is needed Geological bulk sample is collected from pits, trenches, exploratory mining or working mines by decimating (every alternate or 5 th or 10 th wagon from ROM). This sample is thoroughly mixed and then after crushing, it is further reduced to required quantity by decimating or other methods of sample reduction. Sample preparation involves alternate crushing for particle size reduction ,blending to make it homogeneous and splitting for reducing sample volume. This is repeated till desired sample size (quantity) is achieved for a particular test. At every reduction stage ratio of lumps , fines and powder should be maintained same in sample and reject and the minimum quantity of material to be collected for sampling depends on size of largest piece in the broken material being reduced.

33. The ratio of minimum weight of sample collected and size of the largest piece present in the material being sampled is governed by formula Q =Kd 2 Q=sample collected in Kg, d= dia in mm of largest piece in the material and K depends on homogeneity of material.

34. Preparing a sample for chemical and mineralogical analysis Preparation of sample is also called as reduction of sample. For easy handling & sending to laboratory for chemical and mineralogical analysis representative small quantity sample 1-2 kg of fine material is preferred . Geological sample of say125 to150 kg of - 50 mm size is further reduced to 1-2 kg of -5mm in sample preparation by coning and quartering. It involves alternate crushing (or grinding as the case may be ) for particle size reduction ,blending to make it homogeneous and splitting for reducing sample volume through coning and quartering . This is repeated till desired sample size (quantity) is achieved . At every reduction stage ratio of lumps , fines and powder should be maintained same in sample and reject and the minimum quantity of material to be collected as sample depends on size of largest piece in the broken material being reduced & governed by formula Q =Kd 2 Q=sample collected in Kg, d= dia in mm of largest piece in the material and K depends on homogeneity of material. After desired reduction in size of sample is sent for mineralogical and chemical analysis.

35. 1 ) Coning & quartering Sampled pieces are first crushed & ground to a reasonable size & mixed thoroughly. The material is poured down from the container so as to make a conical heap. After the cone formation, it is flattened until the height of the disk is 1/10 th of its diameter. The flattened cone is now divided into four equal segments. Alternate quartering as 1 & 3 are again collected & 2 & 4 are rejected & preserved for cross check. The collected material from 1 & 3 is again broken down to smaller size thoroughly mixed & the coning & quartering procedure is repeated until the quantity required for analysis is achieved. Weight Q of sample being reduced should satisfy Q =Kd 2 formula at each reduction stage.

36. Crushers their construction, working limits, size and grading of ore There are a number of machines of different make for crushing viz; Jaw Crusher, Gyratory Crusher, Cone Crusher, hammer mill for course grinding and ball, rod or tube mill for fine grinding

37. Top pivot

38. feed is 1-2 m and product is 10-20cms

39. bottom pivot (pivot)

40. Terms of crushers G: Gape width,= b: maximum feed size, This is generally desired to be between 80% and 90% of the inlet width R: Size reduction ratio The ratio of the gape width to the near side jaw opening. This ratio may vary from 1/3 to 1/9, but is generally 1/3 for and 1/4 for secondary θ: Nip angle The throw is maximum amplitude of swing of the jaw. It is determined by the type of material being crushed and is usually adjusted by changing the eccentric. It varies from 1 to 7 cm depending on the machine size, and is highest for tough, plastic material and lowest for hard, brittle ore.

41. Nip angle : The nip angle is the angle at which the material, pass ing between the jaws can be gripped and crushed without slipping. Or The angle of nip refers to the angle between the jaws when the material being crushed is at its smallest point of contact. . Generally, this value is between 18 and 24 degrees in primary , and between 22 and 28 degrees in in secondary crushers. The nip angle can be 33 degrees maximum. The angle between the jaws is usually less than 26°. The nip angle in primary crushers is lower than in secondary crushers The angle of nip influences the crushing capacity and efficiency of a jaw crusher. A smaller angle of nip provides a more significant grip on the material, resulting in higher capacity, but it may also generate more fines . & larger angle causes particle to slip.

42. Difference In the Blake jaw crusher, the pivot is at the top, It has a fixed receiving area and a variable discharge opening hence less tendency to chock the material. It has higher production capacity and used as primary crusher . It is more commonly used for coarse crushing of hard and abrasive rocks or minerals. Angle of nip is 20 -30 Angle of nip = tan -1 (d2 / d1) Where: d1 is the smallest particle size retained in the crushing zone during the opening phase of the cycle. d2 is the largest particle size that can leave the crushing zone during the opening phase of the cycle.

43. In a Dodge jaw crusher , the swinging jaw is pivoted at the bottom, it gives a variable feed area but a fixed discharge opening, it chocks easily. It is used in secondary/tertiary crushing & mostly in labs . It is generally used for medium or fine crushing of softer rocks or less abrasive materials. Angle of nip = tan -1 (d1 / d2) Where: d1 is the smallest particle size retained in the crushing zone during the closing phase of the cycle. d2 is the largest particle size that can leave the crushing zone during the closing phase of the cycle. The term "prime mover" refers to the power source that drives the crusher. In Blake and Dodge crushers, the prime mover is usually an electric motor or a diesel engine. In Blake Crusher, the eccentric shaft and the pitman moves the movable jaw back and forth. In Dodge Crusher, the action is effected by eccentric movement of the pitman due to the toggle arrangement.

44. Gyratory crusher : A machine that crushes ore between an eccentrically mounted conical spindle and a fixed crushing throat or inverted cone . It has a higher capacity than a jaw crusher. A gyratory crusher is similar in basic concept to a jaw crusher, consisting of a concave surface of crushing throat and suspended conical head ; both surfaces are typically lined with manganese steel surfaces . The inner conical spindle has a slight circular movement, the movement is generated by an  eccentric arrangement. As the material travels downward between the two surfaces it is progressively crushed, until it is small enough to fall out through the gap between the two surfaces. A gyratory crusher is one of the main types of primary crusher s in a mine or ore processing plant. Gyratory crushers are designated in size by the gape ( size of feed opening ) and mantle (Cone) diameter . Gyratory crushers can be used for primary or secondary crushing. The crushing action is caused by the closing of gap between the mantle lines on the central vertical spindle and the concave crushing throat mounted on the main frame of the crusher. The gap is opened and closed by an eccentric on the bottom of the spindle that causes the central vertical spindle to gyrate . The vertical spindle is free to rotate around its own axis. The main shaft is suspended at the top and the eccentric is mounted above the gear.

45. 12 Spider for suspension 1 – Bearing suspension spider for shaft or conical spindle. When pulley 8 rotates it actuates bevel gear 7 & 9 thus shaft 3 rotates, so does the breaking head 5. Crushing chamber 6 is an inverted hollow truncated cone lined with Mn steel plates called mantle. The breaking head 5 is also lined with Mn steel plates .Sleeve 12 lined with bronze imparts small amount of eccentricity to breaking head which gyrates and squeezes the material in the continuous wedge like structure. Material travels downward between the two surfaces being progressively crushed until it is small enough to fall out through the gap between the two surfaces. Feed is 1-2 m and product is 10-20cms It is used where high capacity is required. GYRATORY CRUSHER Spider for suspension 12

46. Cone crusher A  cone crusher  is a specific type of crushing equipment, able to crush any type of medium-hard rock and ores . Cone crusher provides less owning and operating costs and is easier to adjust to a specific application. The cone crusher has a stable structure and is made from heavy-duty materials which increases its efficiency significantly. It is most commonly used as a secondary crushing equipment, because it is almost inefficient to crush hard materials as a primary crushing equipment. It is fed with smaller size products got from primary jaw/gyratory crusher. The cone crusher is composed of a crus hing cone or eccentrically gyrating spindle , which is covered by a wear-resistant mantle, and an enclosing concave hopper , lined with manganese steel bowl liner.  The operators can adjust the discharge opening in order to get materials of the desired size . The easy maintenance, high production and lower costs are boosting its popularity.

47. Cone crusher shaft

48. The working principle of the cone crusher is very similar to the gyratory crusher. The shaft of the cone crusher is driven by a powerful motor which forces the axle of the cone crusher wings to swing, so the crushing walls, known as a mantle and a bowl liner , are face to face . This zone is called the crushing zone . The cone crusher breaks the raw material by squeezing it between its walls of resistant mantle and a bowl liner. The crushing head rotates in the bowl with an eccentric motion. As the head approaches the bowl, the particles are nipped and broken between the mantle and the bowl liner. It offers more area for crushing. Throw =Distance between initial and final position of plates at discharge end. Feed to crusher is 10-20 cm and product 0.5-2cms. When the raw material is pressed and crushed for the first time, it reaches the next crushing process and it is pressed and broken again. This same process continues until the materials are crushed into the desired small pieces.

49. Grinding is a communition process for size reduction of the coarse material to produces fines . The crushed material obtained from initial stages of communition usually becomes the feed to grinding which is the last stage of size reduction. Size reduction takes places due to impact and abrasion tumbling mills are generally used for the grinding operation. Different types of grinding mills Grinding mills are also called as tumbling mills and are classified based on the grinding media used in them as ball mills, rod mills, pebble mills, autogenous mills, and semi autogenous mills etc. In a grinding mill operation the combined load of grinding medium, feed material and water together knows as mill charge and it is usually in the range of 45-55% of the volume of the shell. Material and water occupy very less space, i.e , the interstices between the balls hence the ball load only must be slightly more than half of Inner volume of the mill.

50. The purpose of grinding is to achieve certain objectives like: 1)The primary objective of grinding is to reduce the size of the feed to obtain the desired fineness as demanded by consuming industry . 2)To reduce the size of the feed material up to the liberation size where valuable minerals are unlocked from the gangue materials 3) To reduce the size of the feed material sufficiently to effect differential movement in subsequent concentration process like flotation . 4)Non metallic minerals are ground to get the desired product , and to produce fresh surface of the fine material to be used where chemical reactions is involved.

51. 5.3 Methods of ore dressing Gravity Separation: Tabling, Jigging Heavy Media separation. Magnetic separation, Electrostatic Separation froth floatation etc.

52. The various factor affecting settling of particles in a fluid medium are: Size : if two particles of same specific gravity and shape are allowed to settle in a fluid medium the coarser particles settles faster than finer particles Shape : if two particles of same specific gravity and size are allowed to settle in a fluid material the spherical particles settles faster than angular particles Specific gravity : : if two particles of same size and shape and are allowed to settle in a fluid material the heavier particles settles faster than lighter particles Viscosity of fluid medium : highly viscous fluids offer higher resistance to the movement of particles and decrease their settling velocity Density of the fluid medium: heavy fluids offer more resistance to the movement of particles and decrease their settling velocity

53. Heavy Media separation It is adopted for separation of minerals of course size generally from lumps to +10 mesh. It is of two types: Drum Type Cone Type In this process heavy media is created by suspension of heavy minerals & alloys like Galena, Barites, and Magnetite & Ferro-silicon in water . By mixing any one of the above materials in pulverized form in suitable proportions with water a medium of pre-determined density can be created. This suspension when kept slightly stirred, behaves like a heavy liquid . The density of the medium is normally maintained between the specific gravity of valuable & waste , so that the waste separates as float & the valuable as sink products or vice-versa. In coal washing it is widely used to separate heavier shale from coal. Mesh – It denotes the number of holes per linear inch in a sieve 20 mesh is not equal to 1/20 inch.

54. Jigging :It is the process of concentration based on gravity separation under rising current of water. Simple Jigs consist of a framed sieve . There are several types of jigs from hand operated to mechanical device for giving pulsation in the fluid. The process separates valuables from the gangue when the mixture of the two is allowed to settle in a rising current of water . The heavier minerals, which are usually the valuables , settle at the bottom while the lighter ones rise with the current in a layered or stratified form & are removed from the top. Jigging is usually applicable to size range of particles between -8 to +28 meshes. Hand operated jigs are commonly employed for beneficiation of low-grade manganese ore by the mine owners in India for the removal of associated Quartz & the country rocks where even -15 mm fine are also subjected to jigging.

55. Tabling : The method of tabling is usually applied when the particle size range is -28 to +65 meshes. It works on the principal that larger and lighter particles moves faster with flowing water because the water close to the surface moves slowly due to friction of water adsorbed on the surface . A table consist of a deck kept at a slightly sloping angle . Deck is fitted with riffles , which act as sinking tanks. When the ground mineral and water is allowed to flow down on surface of the table & table is given reciprocating motion at right angles to the flow of the fluid ( generally water) the heavy particles settle down in the riffles because of the force acting upon them & carried along the diagonal line of the table & collected at corner. Gravity and water forces act on the lighter particles. As they don’t settle in the riffles they travel straight & are collected down the slope. Separation is thus effected between heavier & lighter particles. Tabling is conveniently employed usually for beneficiating chromite ore for removing serpentine & talc. Mica can be conveniently separated from quartz although both have nearly same specific gravity . Here the flaky shape of mica helps in being separated from quartz. Mica moves down with the gravity force.

56. Light Large Heavy large Light small heavy small

57. Concentrate zone Slime zone

58. Magnetic Separation

59. Magnetic Separation In this method varying magnetic susceptibility of useful and gangue minerals is used. By varying the magnetic field of separator economic and gangue minerals of different magnetic susceptibilities can be separated from one another. With low intensity the highly magnetic minerals first separate out & then by increasing the intensity of the magnetising current the mineral lower in the series, having feeble magnetic property can be separated. In case where separation is to be affected in finer sizes, wet magnetic separations is used provided the minerals are highly magnetic. Magnetic separation is generally employed for the removal of tramp (as foreign matter) iron, for the concentration of iron minerals pyrotite , siderite, limonite, chromite etc. & manganese minerals.  

60. Electrostatic Separation Principles of Electrostatic Separation Every mineral species has electrostatic properties of momentarily acquiring static electricity when brought under influence of electrostatic field. Conductor minerals will lose the charge to an earthed surface, whilst non-conductors will retain the charge and remain pinned to the earthed surface.  This is the operating principle of the Electrostatic Separator. Basically the separation takes place between conductor & non-conductor minerals. Generally metallic minerals are conductors & non-metallic minerals are non-conductors. As shown in the fig. Conductor (most sulphides ) and non-conductor minerals are fed to a rotating rotor through hopper. Under the influence of a positively charged powerful (20 – 30 KeV).  electrode, the rotor also gets negatively charged because it is earthed. All particles whether they are conducting or non conducting acquire positive induced charge in the influence of positive electrode and get attracted to negatively charged rotor . The conductor particles lose their charge immediately and follow the natural trajectory falling away from rotor .

61. Conductive particles loose charge and follow the trajectory

62. Other non conducting particles take some time to discharge and thus fall right below the rotor or remain pinned up & collected by brush. Mineral is always fed in dry form. Electrostatic separation is used in all plants that process heavy mineral sands bearing  zircon ,  rutile , and  monazite, cleaning of special iron ore and  cassiterite concentrates separating conducting Pyrite from non-conducting Silica Sand.

63. Simplest form : In the simplest form, a mechanical mixture consisting of readily-conducting and poorly-conducting minerals (grains of copper and grains of sand) is dropped on to a electrified roll charged to a high potential. Immediately upon contact with the electrified roll the better-conducting minerals become charged to the same polarity and potential of the plate, and are thrown vigorously away from it due to similar charges .The poorer conductors require a much greater time to reach the electrical potential of the plate, and fall below the roll affecting separation.

64. Some times some reagents called as depressants are added Which attach to undesired Particles which make them stay In pulp

65. I

66. Floatation : It generally implies froth flotation and is mostly used for sulphide minerals. It takes advantage of the difference in physico -chemical surface properties ( greasiness, wettability, adhesion, contact angle, polarity & surface tension) of useful and gangue minerals, in particular, their wettability. Almost all minerals are hydrophilic ie they adhere to water in preference to air however by adding some chemicals one mineral is selectively made hydrophobic ( water-repelling or affinity towards air in preference to water) in pulp solution and removed . Process : Ore is crushed and ground to liberation size to facilitate their separation & increase surface area for better interaction with chemicals . As shown in fig. ground ore is mixed with water and chemical reagents like collectors, frothers etc. in a cell. Collectors like Xanthate for sulphide ores ( copper lead zinc & sulfonate for oxide minerals like hematite, cassiterite) selectively bind to surface of these mineral particles making them hydrophobic . Air is introduced for agitation & formation of air bubbles. Frothers like eucalyptus oil, Pine oil are used to create froth.

67. Frother and collector are added Hydrophobic sulphide mineral Hydrophilic silica mineral

68. Sulphide minerals attach to air bubbles raising to surface with froth which can be scrapped at the lip of cell. The gangue minerals like silica un affected by collectors remain in the pulp and can be drained out as tailings. This process is generally applicable when the size of the particle is finer than 48 mesh. Flotation makes possible the processing of complex inter-grown ores containing copper, lead, zinc, and pyrite in order to separate concentrates and tailings which is an impossible task with gravity, magnetic, or electrostatic separation methods. In the past, these metals were recoverable only with expensive metallurgical processes.

69. Beneficiation investigations : 1. Chemical and mineralogical analysis The quantity of ore sample is 1-2 kgs. Bench scale or laboratory scale beneficiation :Process carried out on any ore by separate batch operation (not continuous) is called bench scale or laboratory scale beneficiation to upgrade its valuable mineral content to maximum possible level keeping economics into consideration. It is a small scale investigation. The quantity of ore sample is few 10-25 kgs. Pilot scale investigation         A bulk Pilot scale processing plant gives company an idea of the mineral beneficiation viability. Pilot plant scale confirms the data collected at bench scale. It is a continuous scale of operating process from grinding to thickening in order to obtain end product . The representative samples for bench scale and pilot plant should be similar to the actual futuristic plant feed to get correct flow sheet. The quantity of ore sample is few tonnes.

70. crushing

71. Metallurgical Recovery – During the milling and concentration ,a proportion of the valuable mineral or metal in the mill feed is inevitably lost and is disposed of with the tailings, i.e. the fine silt of clayey material representing the gangue compositions of the ore. Such losses are partly due to the fine-grained nature of the ore minerals and their intimate intergrowth with the gangue minerals. Excessive grinding would be necessary to release these grains thus increasing costs.

72. (Material means actual wt. of metal in F,C and T) in Recovery from a beneficiation plant

73. Recovery and grade belongs to that of concentrate if higher grade concentrate is required ,recovery will be affected and there will be more losses.

74. 20% grade of conc means in 1 t conc 200 kg cu. hence 4kg cu will be in 20 kg conc which is got from 1 t ore

75. 5.4 Agglomeration processes Sintering, Briquetting, Palletising, Nodulising their description

76. Agglomeration : The process of combining (integrating) the smaller particles into large hard mass retaining the identity of original particles is broadly called “Agglomeration”. The fine particles are brought together into a shape of a ball, cluster or mass in order to increase the size to convert it to a usable product for any particular purpose by the method of pressing, heating etc . Water and a suitable binder like bentonites are added to ore fines to facilitate the adhesion between the fine particles. Usually these agglomerations are heat-treated with for gaining desired strength to withstand from breakage during handling, transportation and feeding into a smelter. Different names have been assigned to agglomeration depending upon the techniques involved in uniting the particles these are as follows: Briquetting Sintering Palletising Nodulising

77. Importance of agglomeration: High grade ore fines which are naturally occurring or generated during mining or beneficiation cannot be utilized directly as feed to metallurgical plant due to size specifications and technical problems . These fines cannot be transported easily to long distance without transport loss or environment pollution . For proper utilization of these fines the only technique available is Agglomeration . In practice, for iron, manganese, chromite ores, and coal, agglomeration techniques is carried out. It is a big step towards mineral conservation .

78. Palletisation process : Def : The process by which “ ore fines are converted into the shape of small balls/pellets using bentonite as binder & later heat hardened is called Palletization. It is an advanced system of sintering where pallets instead of loose mix are fired & heat hardened. In this process high grade iron ore fines -350 mesh (compared to sintering process -100 mesh) of +63% Fe grade are mixed with little limestone & dolomite & water, which is ground in ball mills to desired size. The discharged slurry from ball mills is filtered in pressure filters. The filter cake from filters is then mixed with dry-ground coke fines to which separately ground bentonite is mixed in suitable proportion to form green pellets in pelletizing discs. The green pellets are then dried, heated and fired in indurating machine up to 1250 degree C to produce iron ore pellets . The use of pellets as feed in the blast furnace has several advantages because of their uniform size, known composition high strength and resistance to aberration compared to sinters .

79. Iron ore pellet is a kind of agglomerated fines which can be used as a substitute in blast furnaces in countries where lump ore is not available. The twenty-one palletisation plants in the country, have a total capacity of 66 million tonnes per annum. Steel plants are likely to increase usage of pellets in their production process to reduce pollution and increase productivity . It has emerged as viable charge mix for sponge iron making and also for use in blast furnaces .

80. Sintering In sintering unlike palletisation low grade, Coarser loose mix Iron ore fines are fired & heat hardened . Iron ore fines ( 0.15 mm to 15 mm ), & Low Fe content 55-58%, other iron bearing small lumps and coke dust are blended with fluxing material like limestone and dolomite .Water is added to this & fed to Pugmill which is further conveyed to sinter machine via moving chain. Here the mix is heated at high temperature ( 1200 to 2300 deg C). During heating the ingredients having low melting point melt and bind other particles thus the heat fuses the fines into course lumps/clusters called sinters , that can be charged to a blast furnace. Sinters are brittle compared to pallets. Process is used for iron ore, manganese and chromite. It can be practiced for lead and zinc concentrates in certain cases. The sintering plants in the country, have a total capacity of about 71 million tonnes per annum. Most of the integrated steel plants (ISP) in the country have their own sintering plants. Sinter plants receive raw material mostly from their captive mines .

81. Sq inch the

82. Nodulising involves incipient (gradual) fusion of the particles. This method requires continuous movement between the charge & the equipment & is generally carried in a rotary kiln at a temperature of 1250  C to 1370  C. Nodulising process is used for practically any fixed size but this process is now a days more or less replaced completely by Palletisation & sintering.

83. Thanks

84. L 5 Q & A Ore Dressing

85. Questions asked in 2022 & 23

86. Define “Mineral Processing”. Define “Tabling”. Describe the advantages of ore dressing. 4 Justify the use of various steps such as – 4 Communition Sizing Concentration and Dewatering involved in mineral benification Justify the use of magnetic separator and electrostatic separator for mineral benification . 6 Compare Blake and Dodge crushers based on :– 6 Arrangement of Jaws ii) Angle of nip iii) Prime moving machinery. Justify the use of various steps such as communication, sizing, concentration and dewatering involved in mineral benification . Justify the use of magnetic separator and electrostatic separator for mineral beneficiation. 6

87. How conservation can be achieved through ore dressing? Mineral conservation aims at zero wastage of mineral commodity at mining beneficiation & metallurgical stage. Through ore dressing conservation of minerals is achieved as follows: The low-grade, sub grade and mineral rejects accumulated can be brought into use through upgradation . Valuable by products can be recovered and even deleterious material can also be discarded during beneficiation that renders the ore un usable. Reduction in transport and metallurgical cost due to bulk rejection of gangue minerals conservation of fuel ,refractory and flux and other additive minerals can be achieved.

88. UNIT 5 Q & A Ore Dressing Define “Mineral Processing”. Def : Concentration, beneficiation or ore dressing It is a physical process done on ROM ore through which gangue minerals are separated from the economic minerals to a large extent and concentration of useful mineral is upgraded by enhancing its percentage .It includes liberation and separation of gangue minerals the economic minerals .

89. Explain classification of Ore dressing processes Ore dressing processes classified on the basis of method of exploitation of different physical properties of useful and gangue minerals. They are as follows: On the basis of observation and feel of relative weight or hardness and colour by hand picking & chipping or dressing. Gravity separation of minerals having different specific gravity by washing, scrubbing, air blowing, heavy media separation, jigging, panning, tabling and by using classifiers and cyclones etc 3.Electrostatic separation of minerals having different electrical conductivity . 4.Magnetic separation of minerals having different magnetic susceptibility . 5.Froth flotation of minerals having different surface properties. 6.Combination of one or more of these process suitable for particular mineral

90. Explain advantages of ore dressing 1)The ore is upgraded to the desired specification level of different application like, to prepare the feed to smelter with required specification like grade, size composition and moisture etc. 2) physical separation can produce a product with desired specification for user industries like cement, fertilizers, alumina production etc. where the end process is not smelting, as in the case of limestone, rock phosphate , bauxite etc. 3)Total metallurgical cost is reduced due to reduction in tonnage of ore to be treated. 4)Reduce the harmful and objectionable impure minerals to the desired level. 5)Concentrates are only transported, the gangue material is discarded thus transport cost are greatly reduced.

91. 6 ) due to reduction in tonnage to be transported material handlings problems will be minimized 7) Bulk waste is rejected. 8) The usage of fuel, flux, and other ingredients in the feed to smelting operation can be reduced. 9) By employing simple physical beneficiation techniques in ore dressing, value addition can be affected on raw materials. 10) Valuable by products can also be recovered which are present in the ore. 11) The low-grade, sub grade and accumulated mine dumps can be brought into use & their by conservation of minerals is achieved.

92. Justify the use of various steps such as – 4 Communition Sizing Concentration and Dewatering involved in mineral benification 1.Comminution : ROM is subjected to crushing for size reduction which is further subjected to grinding for liberation of valuable minerals from gangue minerals 2.Sizing : This ground ore is subjected to screening through screen or cyclones before concentration or material of different sizes are separated. .Concentration is done by taking advantage of difference in physical properties between valuable minerals & gangue minerals. In Concentration the percentage of valuable minerals is increased in concentrate at the cost of gangue minerals without changing their chemical composition and the tails containing mostly gangue minerals is discarded.

93. Dewatering Concentration is mostly done in liquid phase the extraction of water from the concentrate pulp through vacuum filters or screen or pressure filters and extraction of water from the tailings from thickener and tailing dam is called Dewatering it reduces make up water of plant. Describe ore dressing . Ore dressing or beneficiation is physical liberation of valuable and gangue minerals in the ore from each other, followed by concentration of valuable minerals at the cost of gangue minerals without changing their chemical composition. Define Liberation ,separation. Def : Liberation means Crushing /grinding the rock up such a size that gangue and useful mineral particles are free to move away from each other. Def: Separation is a physical process of separating gangue and useful mineral particles making use of their different physical properties.

94. Explain samples preparation for Ore-Dressing or chemical and mineralogical analysis Preparing a sample for ore dressing Preparation of sample is also called as reduction of sample. For bench or lab scale study (discontinuous process ) 100 to1000 kg sample is required. For pilot plant study (continuous process ) representative bulk sample 50-500 t of crushed material having boulder size 20-25 cms is needed Geological bulk sample is collected from pits, trenches, exploratory mining or working mines by decimating (every alternate or 5 th or 10 th wagon from ROM). This sample is thoroughly mixed and then after crushing, it is further reduced to required quantity by decimating or other methods of sample reduction. Sample preparation involves alternate crushing for particle size reduction ,blending to make it homogeneous and splitting for reducing sample volume. This is repeated till desired sample size (quantity) is achieved for a particular test.

95. At every reduction stage ratio of lumps, fines and powder should be maintained same in sample and reject and the minimum quantity of material to be collected for sampling depends on size of largest piece in the broken material being reduced. The ratio of minimum weight of sample collected and size of the largest piece present in the material being sampled is governed by formula Q =Kd 2 Q=sample collected in Kg, d= dia in mm of largest piece in the material and K depends on homogeneity of material.

96. Preparing a sample for chemical and mineralogical analysis Preparation of sample is also called as reduction of sample. For easy handling & sending to laboratory for chemical and mineralogical analysis representative small quantity sample 1-2 kg of fine material is preferred. Geological sample of say125 to150 kg of - 50 mm size is further reduced to 1-2 kg of -5mm in sample preparation by coning and quartering. It involves alternate crushing (or grinding as the case may be ) for particle size reduction ,blending to make it homogeneous and splitting for reducing sample volume through coning and quartering . This is repeated till desired sample size (quantity) is achieved . At every reduction stage ratio of lumps, fines and powder should be maintained same in sample and reject and the minimum quantity of material to be collected as sample depends on size of largest piece in the broken material being reduced & governed by formula Q =Kd 2

97. Q=sample collected in Kg, d= dia in mm of largest piece in the material and K depends on homogeneity of material. After desired reduction in size of sample is sent for mineralogical and chemical analysis. 1) Coning & quartering Sampled pieces are first crushed & ground to a reasonable size & mixed thoroughly. The material is poured down from the container so as to make a conical heap. After the cone formation, it is flattened until the height of the disk is 1/10 th of its diameter. The flattened cone is now divided into four equal segments. Alternate quartering as 1 & 3 are again collected & 2 & 4 are rejected & preserved for cross check. The collected material from 1 & 3 is again broken down to smaller size thoroughly mixed & the coning & quartering procedure is repeated until the quantity required for analysis is achieved. Weight Q of sample being reduced should satisfy Q =Kd 2 formula at each reduction stage.

98.   Explain crushing. The economic minerals in ores are usually associated with worthless gangue, which is required to be separated out from the valuable mineral contents. This separation is possible only after liberation of gangue minerals from valuable ones. Crushing is done essentially to reduce the size of material for subjecting it to grinding . After mineralogical study liberation size is determined up to which crushing and subsequent grinding is required. Crushing & sizing (separating the material of different size )precede generally all other beneficiation methods because this operation make product suitable for beneficiation . There are a number of machines of different make for crushing. Jaw Crusher, Gyratory Crusher, Cone Crusher & hammer mill are used for course crushing and ball, rod or tube mill for fine grinding. Further Jaw, Gyratory & Cone Crusher for hard material and hammer mill for soft material. Such crushers are placed in the circuit. Primary crushers are Jaw & Gyratory Crusher where feed is 1-2 m and product is 10-20cms

99. Secondary crushers are Cone Crusher & hammer mill where Feed is 10- 20 cm and product is 0.5-2cms. Sometimes it may be necessary to put grizzly before the run of mine is fed to primary crushers to withstand load impact of run off mine when discharged on it. The purpose of grizzly is to allow only sized material perceptible to primary crushers. For crushing sticky material containing clay it is necessary to wash or scrub them before discharging into the crusher to remove fines or clay, which cause stickiness.

100. Explain Grinding . Grinding: It refers to final and finer stage of comminution up to the liberation stage. In this process, the crushed material can be further disintegrated in a cylindrical mill, mounted on the axis substantially horizontal, and partially filled with grinding bodies (e.g., flint stones, iron or steel balls) which are caused to tumble, under the influence of gravity, by revolving the container. A special development is the autogenous mill. Autogenous mills operate without grinding bodies, grinding ore with ore itself by a near fall of mineral on mineral & with abrasive action on each other. The coarser part of the ore simply grinds itself into the smaller fractions. Mineral is ground to powder, which is removed by suction. In semi autogenous mills 5 to 10 percent grinding bodies (usually metal spheres) are added. By regulating the air discharge mineral of any size can be obtained. Grinding up to liberation stage liberate gangue mineral from the valuable ones so that they are free to move relative to each other, when subjected to various treatments .

101. Q. Describe with sketch the construction & working of Jaw Crusher. ROM is feed is fed from the top of the crusher the material is caught between the to and fro moving jaws and crushed material comes out from the bottom. Feed is 1-2 m and product is 10-20cms.

102. Compare Blake and Dodge crushers based on :– 6 Arrangement of Jaws ii) Angle of nip iii) Prime moving machinery. Nip angle : The nip angle is the angle at which the material, pass ing between the jaws can be gripped and crushed without slipping. Or The angle of nip refers to the angle between the jaws when the material being crushed is at its smallest point of contact. Difference In the Blake jaw crusher, the pivot is at the top, It has a fixed receiving area and a variable discharge opening hence less tendency to chock the material. It has higher production capacity and used as primary crusher . It is more commonly used for coarse crushing of hard and abrasive rocks or minerals. Angle of nip is 20 -30 Angle of nip = tan -1 (d2 / d1)  

103. Where: d1 is the smallest particle size retained in the crushing zone during the opening phase of the cycle. d2 is the largest particle size that can leave the crushing zone during the opening phase of the cycle. In a Dodge jaw crusher , the swinging jaw is pivoted at the bottom, it gives a variable feed area but a fixed discharge opening, it chocks easily. It is used in secondary/tertiary crushing & mostly in labs. It is generally used for medium or fine crushing of softer rocks or less abrasive materials. Angle of nip = tan -1 (d1 / d2) Where: d1 is the smallest particle size retained in the crushing zone during the closing phase of the cycle. d2 is the largest particle size that can leave the crushing zone during the closing phase of the cycle.

104. The term "prime mover" refers to the power source that drives the crusher. In Blake and Dodge crushers, the prime mover is usually an electric motor or a diesel engine. In Blake Crusher, the eccentric shaft and the pitman moves the movable jaw back and forth. In Dodge Crusher, the action is effected by eccentric movement of the pitman due to the toggle arrangement.

105. Describe with well labelled diagram either “Gyratory” crusher.

106. Gyratory crusher has a higher capacity than a jaw crusher. A gyratory crusher is one of the main types of primary crushers. Feed is1-2 m and product is 10-20cms. Ore travels downward between a conical spindle 5,eccentrically mounted on gear 9, and a fixed crushing inverted cone 6. Crushing chamber 6 is an inverted hollow truncated cone lined with Mn steel plates called mantle. Spindle is suspended from a spider 1 through bearing & is free to rotate around its own axis. When pulley 8 rotates it actuates bevel gear 7 & 9 thus shaft 3 and connected breaking head of spindle also rotate. Concave surface of crushing throat and outer surface of conical spindle are typically lined with manganese steel. The inner conical spindle has a slight gyratory movement, by an eccentric arrangement. This gyratory movement squeezes the material in the continuous wedge like structure between spindle and inverted cone & causes gap to open and close on the bottom . As the material travels downward it is progressively crushed between the mantle lines on the central vertical spindle and the concave crushing throat, until it is small enough to fall out through the gap between the two surfaces.

107. Explain construction and working limit of cone crusher with well labelled diagram. –

108. Cone crusher A  cone crusher  is able to crush any type of medium-hard rock and ores & used as a secondary crushing equipment. Feed to crusher is 10-20 cm and product 0.5-2cms.Cone crusher provides less owning and operating costs and is easier to adjust to a specific application. It offers more area for crushing. The easy maintenance, high production and lower costs are boosting its popularity. The cone crusher is composed of a crushing cone covered with wear-resistant manganese steel mantle, and an enclosing concave conical hopper, lined with manganese steel bowl liner. 

109. The shaft of the cone crusher is driven by a powerful motor. The conical crushing head rotates in the bowl with an eccentric motion. As the head approaches the bowl, the particles are nipped and broken between the mantle and the bowl liner. The cone crusher breaks the raw material by squeezing it between its walls of resistant mantle and a bowl liner.   When the raw material is pressed and crushed for the first time, it reaches the next crushing process and it is pressed and broken again. This same process continues until the materials are crushed into the desired small pieces.

110. Explain purpose of grinding 1)The primary objective of grinding is to reduce the size of the feed to obtain the desired fineness as demanded by consuming industry. 2)To reduce the size of the feed material up to the liberation size where valuable minerals are unlocked from the gangue materials 3) To reduce the size of the feed material sufficiently to effect differential movement in subsequent concentration process like flotation. 4)Non metallic minerals are ground to get the desired product, and to produce fresh surface of the fine material to be used where chemical reactions is involved.

111. Explain the factor affecting settling of particles in a fluid medium Size : if two particles of same specific gravity and shape are allowed to settle in a fluid medium the coarser particles settles faster than finer particles Shape : if two particles of same specific gravity and size are allowed to settle in a fluid material the spherical particles settles faster than angular particles Specific gravity : : if two particles of same size and shape and are allowed to settle in a fluid material the heavier particles settles faster than lighter particles Viscosity of fluid medium : highly viscous fluids offer higher resistance to the movement of particles and decrease their settling velocity Density of the fluid medium : heavy fluids offer more resistance to the movement of particles and decrease their settling velocity

112.   Q . Explain Gravity separation & Jigging process of Gravity Separation The process of gravity separation takes into consideration the difference in specific gravity between the valuable & the gangue & their relative movement in different medium. It is effective only when the difference is more than unity. Heavy media separation. It is adopted for separation of minerals of course size generally from lumps to +10 mesh. It is of two types: 1) Drum Type 2)Cone Type. In this process heavy media is created by suspension of heavy minerals & alloys like Galena, Barites, and Magnetite & Ferro-silicon in water. By mixing any one of the above materials in pulverized & keeping the mixture stirred a heavy liquid medium of pre-determined density can be created. The density of the medium is normally maintained between the specific gravity of valuable & waste, so that the lighter waste separates as float & the valuable as sink products or vice-versa.eg In coal washing it is widely used to separate heavier shale from coal.

113. Jigging :It is the process of concentration based on gravity separation under rising current of water. Simple Jigs consist of a framed sieve. There are several types of jigs from hand operated to mechanical device for giving pulsation in the fluid. The process separates valuables from the gangue when the mixture of the two is allowed to settle in a rising current of water . The heavier minerals, which are usually the valuables , settle at the bottom while the lighter ones rise with the current in a layered or stratified form & are removed from the top. Jigging is usually applicable to size range of particles between -8 to +28 meshes. Hand operated jigs are commonly employed for beneficiation of low-grade manganese ore by the mine owners in India for the removal of associated Quartz & the country rocks where even -15 mm fine are also subjected to jigging.

114. Q. Describe Tabling process with well labelled diagram. Tabling : The method of tabling is usually applied when the particle size range is -28 to +65 meshes. It works on the principal that larger and lighter particles moves faster with flowing water because the water close to the surface moves slowly due to friction of water adsorbed on the surface . A table consist of a deck kept at a slightly sloping angle . Deck is fitted with riffles , which act as sinking tanks. When the ground mineral and water is allowed to flow down on surface of the table & table is given reciprocating motion at right angles to the flow of the fluid ( generally water) the heavy particles settle down in the riffles because of the force acting upon them & carried along the diagonal line of the table & collected at corner. Gravity and water forces act on the lighter particles. As they don’t settle in the riffles they travel straight & are collected down the slope. Separation is thus effected between heavier & lighter particles. Tabling is conveniently employed usually for beneficiating chromite ore for removing serpentine & talc.

115. Mica can be conveniently separated from quartz although both have nearly same specific gravity . Here the flaky shape of mica helps in being separated from quartz. Mica moves down with the gravity force.

116. Q . Explain Magnetic separation & Electrostatic separation . Magnetic Separation In this method varying magnetic susceptibility of useful and gangue minerals is used. By varying the magnetic field of separator economic and gangue minerals of different magnetic susceptibilities can be separated from one another. With low intensity the highly magnetic minerals first separate out & then by increasing the intensity of the magnetising current the mineral lower in the series, having feeble magnetic property can be separated. In case where separation is to be affected in finer sizes, wet magnetic separations is used provided the minerals are highly magnetic. Magnetic separation is generally employed for the removal of tramp (as foreign matter) iron, for the concentration of iron minerals pyrotite , siderite, limonite, chromite etc. & manganese minerals.

117. Electrostatic Separation Principles of Electrostatic Separation Every mineral species has electrostatic properties of momentarily acquiring static electricity when brought under influence of electrostatic field. Conductor minerals will lose the charge to an earthed surface, whilst non-conductors will retain the charge and remain pinned to the earthed surface.  This is the operating principle of the Electrostatic Separator. Basically the separation takes place between conductor & non-conductor minerals. Generally metallic minerals are conductors & non-metallic minerals are non-conductors. As shown in the fig. Conductor (most sulphides ) and non-conductor minerals are fed to a rotating rotor through hopper. Under the influence of a positively charged powerful (20 – 30 KeV).  electrode, the rotor also gets negatively charged because it is earthed.

118. All particles whether they are conducting or non conducting acquire positive induced charge in the influence of positive electrode and get attracted to negatively charged rotor . The conductor particles lose their charge immediately and follow the natural trajectory falling away from rotor . Other non conducting particles take some time to discharge and thus fall right below the rotor or remain pinned up & collected by brush. Mineral is always fed in dry form. Electrostatic separation is used in all plants that process heavy mineral sands bearing  zircon ,  rutile , and monazite, cleaning of special iron ore and  cassiterite concentrates separating conducting Pyrite from non-conducting Silica Sand.

119. Simplest form : In the simplest form, a mechanical mixture consisting of readily-conducting and poorly-conducting minerals (grains of copper and grains of sand) is dropped on to a electrified roll charged to a high potential. Immediately upon contact with the electrified roll the better-conducting minerals become charged to the same polarity and potential of the plate, and are thrown vigorously away from it due to similar charges.The poorer conductors require a much greater time to reach the electrical potential of the plate, and fall below the roll affecting separation.

120. Que:-Describe flotation cell with well labelled diagram Floatation : It generally implies froth flotation and is mostly used for sulphide minerals. It takes advantage of the difference in physico -chemical surface properties ( greasiness, wettability, adhesion, contact angle, polarity & surface tension) of useful and gangue minerals, in particular, their wettability. Almost all minerals are hydrophilic ie they adhere to water in preference to air however by adding some chemicals one mineral is selectively made hydrophobic ( water-repelling ) in pulp solution and removed . Process : Ore is crushed and ground to liberation size to facilitate their separation & increase surface area for better interaction with chemicals .

121. As shown in fig. ground ore is mixed with water and chemical reagents like collectors, frothers etc. in a cell. Collectors like Xanthate for sulphide ores selectively bind to surface of sulphide mineral particles making them hydrophobic . Air is introduced for agitation & formation of air bubbles. Frothers like eucalyptus oil, Pine oil are used to create froth. Sulphide minerals attach to air bubbles raising to surface with froth which can be scrapped at the lip of cell. The gangue minerals like silica un affected by collectors remain in the pulp and can be drained out as tailings. This process is generally applicable when the size of the particle is finer than 48 mesh. It is used where other methods cants be applied.

122. Explain Agglomeration & its importance. Agglomeration : The process of combining (integrating) the smaller particles into large hard mass retaining the identity of original particles is broadly called “Agglomeration”. The fine particles are brought together into a shape of a ball, cluster or mass in order to increase the size to convert it to a usable product for any particular purpose by the method of pressing, heating etc . Water and a suitable binder like bentonites are added to ore fines to facilitate the adhesion between the fine particles. Usually these agglomerations are heat-treated with for gaining desired strength to withstand from breakage during handling, transportation and feeding into a smelter. Different names have been assigned to agglomeration depending upon the techniques involved in uniting the particles these are as follows: Briquetting Sintering 3. Palletising 4. Nodulising

123. Importance of agglomeration: High grade ore fines which are naturally occurring or generated during mining or beneficiation cannot be utilized directly as feed to metallurgical plant due to size specifications and technical problems . These fines cannot be transported easily to long distance without transport loss or environment pollution . For proper utilization of these fines the only technique available is Agglomeration . In practice, for iron, manganese, chromite ores, and coal, agglomeration techniques is carried out. It is a big step towards mineral conservation .  

124. Explain Palletisation & Sintering process. Palletisation process : Def : The process by which “ore fines are converted into the shape of small balls/pellets using bentonite as binder & later heat hardened is called Palletization. It is an advanced system of sintering where pallets instead of loose mix are fired & heat hardened. In this process high grade iron ore fines -350 mesh (compared to sintering process -100 mesh) of +63% Fe grade are mixed with little limestone & dolomite & water, which is ground in ball mills to desired size. The discharged slurry from ball mills is filtered in pressure filters. The filter cake from filters is then mixed with dry-ground coke fines to which separately ground bentonite is mixed in suitable proportion to form green pellets in pelletizing discs. The green pellets are then dried, heated and fired in indurating machine up to 1250 degree C to produce iron ore pellets. The use of pellets as feed in the blast furnace has several advantages because of their uniform size, known composition high strength and resistance to aberration compared to sinters. Iron ore pellets are used in blast furnaces where lump ore is not available and in also in sponge iron making .

125.   Sintering In sintering unlike palletisation low grade, Coarser loose mix Iron ore fines are fired & heat hardened . Iron ore fines ( 0.15 mm to 15 mm ), & Low Fe content 55-58%, other iron bearing small lumps and coke dust are blended with fluxing material like limestone and dolomite .Water is added to this & fed to Pugmill which is further conveyed to sinter machine via moving chain. Here the mix is heated at high temperature ( 1200 to 2300 deg C). During heating the ingredients having low melting point melt and bind other particles thus the heat fuses the fines into course lumps/clusters called sinters , that can be charged to a blast furnace. Sinters are brittle compared to pallets. Process is used for iron ore, manganese and chromite. It can be practiced for lead and zinc concentrates in certain cases.

126. thanks