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Size reduction equipments by H Luqman (032)


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Size reduction equipments by H Luqman (032)

  1. 1. name 09-12-2013 Name: Hafiz Luqman Khalil (032) Particle Technology Place Photo Here, Otherwise Delete Box Submitted to: Engr. Waqas Qamar 5th Semester, Chemical Engineering Subject: Particle Technology Assignment Topic: Size Reducing Equipment
  2. 2. Size Reduction Equipment Size reduction equipment is divided into crushers, grinders, ultrafine grinders and cutting machines. Crushers do the large work of breaking large pieces of solid material into small lumps. A primary crusher operates on run-of-mine material, accepting anything that comes from the face of mine and breaking it into 150-250 mm lumps. A secondary crusher reduces these lumps to particles perhaps 6 mm in size. Grinders reduce the crushed feed to powder. The product from a intermediate grinder might pass a 40-mesh screen; most of the product from a fine grinder would pass a 200-mesh screen with a 70 μ mm opening. An ultrafine grinder accet feed particles no larger than 6 mm; the product size is typically 1-50 μ mm. Cutters give particles of definite size and shape, 2 to 10 mm in length. A. Crushers Primary crushing reduces this run-of-mine rock to 150-250 mm lumps. The different types of primary crushers are: jaw crushers, gyratory crushers, impact crushers, and autogenous crushers. 1. Jaw Crusher: The jaw crusher squeezes rock between two surfaces, one of which opens and closes like a jaw. Rock enters the jaw crusher from the top. Pieces of rock, that are larger than the opening at the bottom of the jaw, lodge between the two metal plates of the jaw. The
  3. 3. opening and closing action of the movable jaw against the fixed jaw continues to reduce the size of lodged pieces of rock until the pieces are small enough to fall through the opening at the bottom of the jaw. 2. Gyratory Crusher: A gyratory crusher is among the main kinds of primary crushers in a mine or ore processing plant. Gyratory crushers are designated in dimensions either by the gape and mantle diameter or from the size the receiving opening. Gyratory crushers can be utilized for primary or secondary crushing. Because, the gyratory crusher design is broken product quality and production capacity as the primary factor to consider. Gyratory crusher is developed for both dry and wet crushing of brittle, medium-hard materials for the mining, cement, coal, metallurgic material, construction material, road building, and petroleum & chemical industries. A gyratory crusher breaks rock by squeezing the rock between an eccentrically gyrating spindle, which is covered by a wear resistant mantle, and the enclosing concave hopper. As run-of-mine rock enters the top of the gyratory crusher, it becomes wedged and squeezed between the mantle and hopper. Large pieces of ore are broken once, and then fall to a lower position (because they are now smaller) where they are broken again. This process continues until the pieces are small enough to fall through the narrow opening at the bottom of the crusher.
  4. 4. 3. Impact Crusher: Impact crushers, which are also called hammer mills, break rock by impacting the rock with hammers that swing on a rotating shaft. The practical use of impact crushers is limited to soft materials, such as phosphate, gypsum, weathered shales, etc. Impact crushers cannot handle as large a top sized material as jaw, or gyratory, crushers can; however, impact crushers can make a finer sized product. 4. Autogenous Crusher: In recent years, autogenous crushers have been adapted for crushing run-of-mine rock in primary crushing circuits. Consequently, autogenous mills have increased in importance as a means of crushing and grinding. In autogenous crushers, the rock to be crushed also provides the crushing force. Crushing is accomplished by the tumbling action of the rock. Flexible crushing circuits can be constructed so that hard ores, as well as soft ores, can be processed. Wet, sticky ores can be processed in autogenous mills, while the same ore would present difficulties for other types of crushers.
  5. 5. B. Grinders The term grinder refers to a variety of size reduction machines for intermediate duty. Product from a crusher is often fed to a grinder for further reduction. Common commercia l grinder machines are hammer mills, attrition mills, tumbling mills etc. 1. Hammer Mill: A hammer mill is a machine whose purpose is to shred or crush aggregate material into smaller pieces. The material can be put into the machine from the inlet and then under the influence of the guiding plate into the pulverizing cabin. Later on, the materials will be ground with the hammer plates striking and sieve plates friction at fast speed, at last, with the help of centrifugal force and air current, the pulverized materials will be discharged from the foundation through sieve holes. The basic principle is straightforward. A hammer mill is essentially a steel drum containing a vertical or horizontal rotating shaft or drum on which hammers are mounted. The hammers are free to swing on the ends of the cross, or fixed to the central rotor. The rotor is spun at a high speed inside the drum while material is fed into a feed hopper. The material is impacted by the hammer bars and is thereby shredded and expelled through screens in the drum of a selected size. The hammer mill can be used as a primary, secondary, or tertiary crusher.
  6. 6. 2. Roller Mill: Roller mills are mills that use cylindrical rollers, either in opposing pairs or against flat plates, to crush or grind various materials, such as grain, ore, gravel, plastic, and others. Roller grain mills are an alternative to traditional millstone arrangements in gristmil ls. Roller mills for rock complement other types of mills, such as ball mills and hammer mills, in such industries as the mining and processing of ore and construction aggregate; cement milling; and recycling.
  7. 7. 3. Attrition Mill: The Attrition Mill produces particles within a relatively narrow particle size spectrum, from granular (10 to 200 mesh). It is employed primarily for reduction of fibrous materials, but is also suitable for friable products. It is available in three sizes with single- or dual (counter-rotating) powered discs, and an extensive selection of plate designs for optimum performance. In addition to general process applications, Munson Attrition Mills are often utilized for conditioning of materials prior to packaging.
  8. 8. The attrition mill is a device for mechanically reducing solid particle size by intense agitation of a slurry of material being milled and coarse milling media. For example, in 10 hours of milling, specific surfaces of 40 and 25 m2/g were obtained for alumina and barite, corresponding to 38 and 56 nm equivalent spherical diameter, respectively. Size reduction rates for relatively coarse particles were first-order and increased linearly with power input to the mill. Optimum milling medium concentration corresponded to medium particles moving a distance of approximately 0.7 of their diameter before collision with another such particle. Power characteristics of the attrition mill were essentially the same as those of a radial flow turbine mixer. Laminar flow became disrupted at NRe ≈ 200, while turbule nt flow was established at NRe > 8000. Slurries of fine powders exhibited the same linear power-average density dependence as single-phase liquids. However, a differe nt dependence was observed with large particles. 4. Tumbling Mill: Tumbling Mill / Ball Mill consists of a cylindrical shell which slowly turns about a horizontal axis & is filled about half its volume with a solid grinding media. The shell is lined with a replaceable liner which may be of high carbon steel, Manganese steel, Porcelain or rubber. The grinding media is metal or rubber balls in a ball mill, Pebbles or Porcelain in a Pebble Mill & metal rods in a Rod Mill.
  9. 9. In Tumbling Mills the material to be grinded is carried up the side of the shell upto the top from where they fall on the particles underneath. In Ball / Pebble Mill the most of the grinding is achieved by the impact of the Ball / Pebble which drop from nearly the top of the shell whereas in a Rod mill the most of the size reduction is due to rolling attrition & compression. The Tumbling Mills may be batch type or continuous. C. Ultrafine Grinders Ultrafine grinding mill is a high-efficient ultrafine powder grinding mill, comparable to air-blast mill, newly designed on the basis of industrial mill manufacturing experience for many years, which adopts the theory of fluidics and successfully solves the problem of high cost in domestic air-blast mill.
  10. 10. The new type of grinding roll assembly changes the traditional structure, using various means of sealing, getting rid of three defects of old assembly, i.e. oil leak, dust coming in, and disalignment. With a wide range of capabilities in toll powder processing including grinding, flash drying and particle classifying. Fluid Energy is uniquely positioned to process a wide range of coarse, fine and ultrafine materials to your exact specifications, no matter how demanding they may be. We have the capability to meet every powder processing application, no matter how many steps may be involved, in taking your product from raw feed to finished product. Whether the process requires fine grinding, crushing, drying, or classifying out fines, we can handle it. We maintain archives of hundreds of thousands of materials tested and processed which gives us a significant advantage in finding the most cost-effective solution for a particular application. Fluid Energy's Powder Processing Services Divis ion is your single-source supplier because we maintain complete in-house responsibility for the processing and packing of your product. 1. Fluid Energy Mills: Fluid energy mills are used because of their advantages in fine grinding. The materials fed into a jet stream are accelerated to a relatively high velocity from 10 to 200 m/s and although these values are much higher than those encountered in the breeding process of crystals, there are
  11. 11. some similarities between these two operations. In both tiny fragments are produced by the attrition of particles when they collide with each other, with the mixer or the wall of the apparatus. A size-reduction unit depending for its action on collisions between the particles being ground, the energy being supplied by a compressed fluid, (e.g., air or steam) that enters the grinding chamber at high speed. Such mills will give a product of 5 mu m or less; they have been used for the fine grinding of frits, kaolin, zircon, titania, and calcined alumina, but the energy consumed per ton of milled product is high. 2. Colloid Mill: A colloid mill is a machine that is used to reduce the particle size of a solid in suspension in a liquid, or to reduce the droplet size of a liquid suspended in another liquid. This is done by
  12. 12. applying high levels of hydraulic shear to the process liquid. It is frequently used to increase the stability of suspensions and emulsions. In Colloid Mill the product is subjected to high shearing, cutting, and rubbing forces between two toothed surfaces. The product, while passing down the hopper, initially gets seized in the preliminary breaking drum where it is broken and thrown in to the centrifugal effect of the rotor rotating at a speed of 2800 RPM, the material is forced in to second tooth stage. The tooth design of the grinding set causes powerful vibrations, which subject the particles with high degree of forces. Intense whirling multiplies the grinding and mixing effect. The process is continued till the material reaches the lowest grinding stage. The ground material continuously leaves the mill through the outlet pipe, if required, it can be recalculated.