Particle Technology and Screening Equipment

Particle Technology

• Relates to the creation, characterization, management, and use of particles
• Focuses on the relationship of individual particle properties, such as size and shape, to bulk behavior
• Examines particle behavior in various processes, like storage, mixing, fluidization, and agglomeration

Screening

• A method of separating particles based on size alone
• Uses mesh sizes to separate particles based on their passage through mesh openings

Screening Equipment

• Grizzly: A stationary screen for separating very coarse material, consisting of longitudinal bars in a rectangular framework
• Vibrating Screen: Mechanically operated screens that utilize electromagnetic devices to vibrate, often used in multi-deck configurations
• Trommel: A rotating perforated cylinder that gradually separates material based on aperture size, using paddles to move material
• Sieve Shaker: A mechanical device used to agitate sieves, ensuring uniform sample distribution and efficient particle size analysis
• Air Classifiers: Separate particles based on density, using airflow to carry lighter particles while heavier particles settle

Mesh Screens

• Thin textile materials with very small holes, similar to a fishnet
• Used for front and rear projections
• Also referred to as gauze screens
• Mesh number indicates the number of openings per linear inch
• Aperture is the clear space between the individual wire openings

Sieve Scales

• Essential tools for characterizing particle size distribution of granular materials
• Provide a quantitative analysis of the size distribution of particles in a sample

Screening Capacity

• Determined by the ratio of screen open area to total area
• Influenced by factors like feed rate, moisture content, and screen aperture size
• Approximate capacity (tons/ft²/mm/24h) can be estimated for dense materials

Crusher, Mills

• Three stages of size reduction: Coarse, Intermediate, and Fine
• Coarse stage is further classified as soft or hard, involving particles 2.96 inches or more

Kick’s Law

• Describes the energy required to reduce particle size
• Energy is proportional to the ratio of initial particle size to final particle size
• Applies primarily to coarse grinding processes with relatively small increases in surface area per unit mass

Rittinger’s Law

• Defines energy required to reduce particle size as proportional to new surface area created
• Applicable to fine grinding processes with significant surface area increase
• Mathematically expressed as:
  • E = 𝐾𝑟 (𝐴𝑤𝑏 – 𝐴𝑤𝑎)
  • Where:
    • 𝐸 = 𝑒𝑛𝑒𝑟𝑔𝑦 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 𝑝𝑒𝑟 𝑢𝑛𝑖𝑡 𝑚𝑎𝑠𝑠
    • 𝐴𝑤𝑏 = 𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑡ℎ𝑒 𝑝𝑟𝑜𝑑𝑢𝑐𝑡
    • 𝐴𝑤𝑎 = 𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑡ℎ𝑒 𝑓𝑒𝑒𝑑
    • 𝐾𝑟 = 𝑅𝑖𝑡𝑡𝑖𝑛𝑔𝑒𝑟'𝑠 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡

Theoretical Power

• 𝑃 = 𝑁𝑇 (𝐴𝑤𝑏-𝐴𝑤𝑎)
• Where:
  • 𝑃 = 𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑝𝑜𝑤𝑒𝑟
  • 𝑇 = 𝑓𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑓𝑒𝑒𝑑
  • 𝐴𝑤𝑎 =  𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑡ℎ𝑒 𝑝𝑟𝑜𝑑𝑢𝑐𝑡
  • 𝐴𝑤𝑎 =  𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑡ℎ𝑒 𝑓𝑒𝑒𝑑
  • 𝑁 = 𝑅𝑖𝑡𝑡𝑖𝑛𝑔𝑒𝑟'𝑠 𝑁𝑢𝑚𝑏𝑒𝑟

Differential and Cumulative Analysis

• Differential Analysis: Shows the percentage of particles in a sample that falls within each specific size range
• Cumulative Analysis: Obtained from the differential analysis, showing the total percentage of particles smaller than a certain size

Screen Capacity Relationship with Moisture Content

• Increased moisture content reduces screen capacity
• This is because moisture can cause material to stick together, hindering particle passage through the screen openings

Roundness Factor

• A measure of particle shape, indicating the degree to which a particle is similar to a perfect sphere
• Ranges from 0.28 (Mica flakes) to 0.98 (round sand)

Explore the fundamentals of particle technology, including the creation, characterization, and management of particles. This quiz covers key methods of screening particles based on size, as well as the different types of screening equipment used in the industry.