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Questions and Answers
What does size reduction refer to?
What does size reduction refer to?
The process of converting an object from a higher physical dimension to a smaller one.
Which of the following is NOT an objective of size reduction?
Which of the following is NOT an objective of size reduction?
Name four basic methods used for size reduction.
Name four basic methods used for size reduction.
Impact, Compression, Attrition, Cutting
Compression is chosen when the material is sticky.
Compression is chosen when the material is sticky.
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In impact size reduction, particles collide at _____ speed.
In impact size reduction, particles collide at _____ speed.
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Match the following size reduction methods with their characteristics:
Match the following size reduction methods with their characteristics:
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What is the Moh's scale used for?
What is the Moh's scale used for?
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Toughness is the resistance of a material to scratching.
Toughness is the resistance of a material to scratching.
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What properties of solids influence the choice of machine for size reduction?
What properties of solids influence the choice of machine for size reduction?
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Study Notes
Introduction to Size Reduction
- Size reduction involves decreasing the physical dimensions of objects from larger to smaller particles.
- Also known as comminution, diminution, or pulverization.
Objectives of Size Reduction
- Increases surface area, enhancing reaction and transfer rates.
- Produces solid particles of desired shape, size, and surface characteristics.
- Aids in effective separation of unwanted particles.
- Facilitates easier disposal of solid wastes.
- Promotes better intimate mixing of solid particles.
- Improves the handling characteristics for storage and transportation.
Applications of Size Reduction
- Utilized across various industries including:
- Coal washeries and ore processing
- Chemical and paint industries
- Pharmaceutical and cement sectors
- Food processing for sugar, spices, and grains
- Cement industry for lime, aluminum, sand, and clinker
- Fertilizer industry for phosphate rock.
Methods of Size Reduction
- Impact: Involves high-speed collisions of particles; suitable for brittle and hard materials. Examples include hammer mills.
- Compression: Breaks particles between two surfaces; effective for hard, tough, or abrasive materials. Yields coarser sizes.
- Attrition: Achieves size reduction through rubbing action; ideal for fine grinding of non-abrasive materials.
- Cutting: Cuts materials using sharp blades; necessary for fibrous or ductile solids.
Properties of Solids in Size Reduction
- Important factors for selecting size-reduction methods include:
- Size and quantity of the material.
- Properties such as hardness, toughness, stickiness, moisture content, and friability.
- Hardness: Measured on Moh's scale (1-10); influences power consumption and machinery wear.
- Toughness: Indicates impact resistance; tough materials can present challenges during reduction.
- Stickiness: Affects material adherence to grinding surfaces; can complicate operations.
Example Equipment and Processes
- Compression Equipment: Nutcracker for coarse reduction.
- Impact Equipment: Hammer mill for medium particle size.
- Attrition Equipment: Fluid energy mill for fine grinding.
- Cutting Equipment: Rotary knife cutter for producing definite shapes and sizes.
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Description
This quiz introduces the concept of size reduction, focusing on the processes used to decrease the size of larger particles into smaller, desired dimensions. It highlights the importance of external forces in achieving the right particle size and shape. Ideal for students studying material science or engineering.
