Question

Which method of size reduction is applicable to hammer mill?

• A. Impact
• B. Cutting
• C. Shearing
• D. Crushing

Hint:

To easily match mill types to their size reduction forces:
- Hammer Mill \(\rightarrow\) Impact
- Roller Mill \(\rightarrow\) Compression/Crushing
- Disc Attrition Mill \(\rightarrow\) Shear

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Size reduction equipment operates using distinct mechanical forces: compression (crushing), impact, shear (attrition), or cutting.

Step 2: Detailed Explanation:
1. A hammer mill consists of a high-speed rotating rotor shaft equipped with heavy, free-swinging steel hammers inside a cylindrical chamber.
2. As feed material enters the mill, the rotating hammers strike the particles at high velocity.
3. The primary mechanism of size reduction here is impact (the sudden kinetic energy transfer from the moving hammer to the stationary or slower-moving particles), causing them to fracture.
4. Secondary attrition forces also occur as particles collide with each other and the surrounding screen.

Step 3: Final Answer:
The primary mechanism of size reduction in a hammer mill is Impact.