Separation Techniques in Mineral Processing
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Questions and Answers

What is the primary principle behind froth flotation in mineral separation?

  • Separation based on surface tension (correct)
  • Separation based on magnetic properties
  • Separation based on particle size
  • Separation based on differences in density

    • What key factor influences the settling velocity of a particle in a fluid?

  • Concentration of the ore
  • Shape of the particle (correct)
  • Chemical composition of the fluid
  • Temperature of the fluid

    • In Dense Medium Separation, what property is primarily exploited to separate minerals?

  • Magnetic properties
  • Surface tension differences
  • Density differences (correct)
  • Electrical conductivity

    • What happens to the wear on the grinding medium during wet grinding compared to dry grinding?

    <p>It is 20% greater in wet grinding</p> Signup and view all the answers

    Which of the following is NOT a disadvantage of wet grinding?

    <p>Increased power consumption</p> Signup and view all the answers

    What role does classification play in mineral processing?

    <p>To distinguish minerals based on their settling velocities</p> Signup and view all the answers

    Which method would primarily use electrical conductivity for mineral separation?

    <p>Electrostatic concentration</p> Signup and view all the answers

    What is typically the outcome of increased power consumption in grinding processes?

    <p>Reduced plant efficiency</p> Signup and view all the answers

    Which statement accurately describes the effect of particle size on settling velocities in classification?

    <p>Coarse particles have a higher settling velocity than fine particles of the same density.</p> Signup and view all the answers

    What is the primary characteristic of free settling?

    <p>Particles fall through a fluid with less than approximately 15% solids concentration.</p> Signup and view all the answers

    In hindered settling, what factor primarily causes the falling rate of particles to decrease?

    <p>The increased percentage of solids causing density changes in the pulp.</p> Signup and view all the answers

    How does the viscosity of the carrier fluid affect particle settling rates?

    <p>Increased viscosity reduces the settling rates of particles.</p> Signup and view all the answers

    According to Stokes's Law, which parameter directly affects the terminal settling velocity of small particles?

    <p>Particle size and fluid viscosity.</p> Signup and view all the answers

    What happens to the behavior of particles during hindered settling?

    <p>Particles experience less effective settling due to increased pulp viscosity.</p> Signup and view all the answers

    Which equation represents the settling velocity of larger particles according to Newton's Law?

    <p>$v = \frac{3gd^2 (D_s - D_f)}{D_f}$</p> Signup and view all the answers

    What contributes to the higher settling velocity of high-density particles compared to low-density particles of the same size?

    <p>The gravitational force acting on high-density particles is greater.</p> Signup and view all the answers

    What is the primary mechanism by which particles are classified in a sorting column?

    <p>Particles with settling velocities higher than fluid upward velocity reach the bottom</p> Signup and view all the answers

    Which statement best describes Dense Medium Separation (DMS)?

    <p>It utilizes a liquid with an intermediate density to separate different materials</p> Signup and view all the answers

    In the froth flotation process, what role do flotation reagents play?

    <p>They modify physical-chemical characteristics at various interfaces</p> Signup and view all the answers

    What defines a hydrophobic substance in the context of flotation?

    <p>Substances that can be made to repel water through reagents</p> Signup and view all the answers

    What is the fundamental principle behind hindered settling?

    <p>Settling velocity depends on the difference between particle and fluid densities</p> Signup and view all the answers

    In flotation, which phase is usually represented by liquid?

    <p>Water</p> Signup and view all the answers

    What is the effect of the upward fluid velocity in a sorting column?

    <p>It determines which particles are carried into the overflow product</p> Signup and view all the answers

    Which statement is true regarding hydrophilic substances in flotation?

    <p>They prefer to interact with water rather than air</p> Signup and view all the answers

    Study Notes

    Terminal Velocity

    • A modified Newton's law estimates the terminal velocity of a particle during hindered settling: v = kd(D s − D p 1/ 2

    Separation: Classification

    • Classifiers separate particles based on their settling velocity.
    • Particles with a settling velocity higher than the upward velocity of the fluid reach the bottom of a sorting column as underflow.
    • Particles with a settling velocity lower than the upward velocity of the fluid are carried into the overflow.

    Separation: Dense Medium Separation (DMS)

    • Minerals with different densities are placed in a liquid with an intermediate density.
    • Grains with densities less than the liquid float, while grains with densities greater than the liquid sink.

    Separation: Flotation

    • Flotation involves three phases: solid (ore), liquid (water), and gas (air).
    • The success of flotation depends on the interaction of physical, chemical, and mechanical factors.
    • Flotation reagents modify the physical-chemical characteristics of the system by adsorbing at interfaces.
    • Hydrophilic substances have a greater affinity for water, while hydrophobic substances have a greater affinity for air.
    • Many minerals can be made hydrophobic by the adsorption of collectors or frothers.

    Separation: Classification (cont.)

    • Classification separates minerals based on their size and density.
    • Coarse particles settle faster than fine particles of the same density.
    • High-density particles settle faster than lower-density particles of the same size.
    • Increased density or viscosity of the carrier fluid reduces settling rates of particles.

    Separation: Free Settling

    • Particles fall through a stationary fluid without influencing each other's rate of fall.
    • Occurs when the percentage of solids is less than 15%.
    • Forces acting on particles: gravitational force, buoyancy, and viscous drag.
    • Stokes's Law applies to particles less than 50 µm in diameter: v = gd2 (D s − D f ) / 18
    • Newton's Law applies to particles greater than 0.5 cm in diameter: v =  3gd(D s − D f )  /  D f 1/ 2

    Separation: Hindered Settling

    • Occurs when the percentage of solids exceeds 15%.
    • Crowding causes a decrease in particle falling rate.
    • The system behaves as if the particles are falling through a fluid with the density of the pulp.
    • Pulp density and viscosity are generally higher than those of the carrier fluid, slowing particles down.

    Crushing: Jaw Crusher, Cone Crusher, and Rock Crusher

    • Jaw crushers, cone crushers, and rock crushers are used for crushing rocks and ores.

    Comminution: Grinding

    • Grinding combines impact and abrasion, typically in tumbling mills.
    • Optimal mineral recovery and energy consumption require the correct degree of grinding.
    • Grinding uses the most energy at a mill.
    • Grinding can be done wet or dry.

    Grinding: Ball Mill

    • Ball mills use a grinding medium of steel rods, steel balls, hard rock, or the ore itself.
    • Examples of tumbling mills include rod mills, center peripheral discharge mills, end peripheral discharge mills, overflow mills, ball mills, and autogenous mills.

    Separation: Overall Process

    • The overall process involves:
      • Comminution (crushing and grinding)
      • Separation (classification, flotation, electrostatic concentration, magnetic concentration, dewatering)
      • Reduction and Refining (pyrometallurgy, hydrometallurgy, electrometallurgy)
    • The purpose of separation is to concentrate valuable minerals from gangue.

    Separation: Physical Methods

    • Physical methods utilize differences in physical properties of minerals.
    • Methods include:
      • Dense Medium Separation (based on density)
      • Froth Flotation (based on surface tension)
      • Electrostatic Concentration (based on electrical conductivity)
      • Magnetic Concentration (based on magnetic properties)

    Separation: Classification (cont.)

    • The velocity of a particle falling through a fluid depends upon its shape, size, and density.

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    Related Documents

    Mineral Processing Industry (DDJ) PDF

    Description

    Explore the various methods of particle separation in mineral processing, including terminal velocity, classification, dense medium separation (DMS), and flotation. Understand the principles that govern how particles behave in different fluids and the factors that affect separation efficiency.

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