Question

For sieving powders with a high moisture content that tend to agglomerate, which type of equipment is preferred?

• A. Vibratory Shaker
• B. Sonic Sifter
• C. Rotary Sifter
• D. Standard Tyler Screen

Hint:

For sticky, cohesive, or damp food powders (such as damp sugar or starch), a rotary sifter is preferred over vibratory shakers because its rotating internal blades actively break up agglomerates to prevent screen clogging.

Answer 1

The Correct Option is C

Step 1: Understanding the Problem:
The question asks to identify the most effective type of industrial sieving equipment for processing powders with high moisture levels that tend to stick together (agglomerate) and clog screens.

Step 2: Detailed Explanation:

• The Challenge of Damp Powders: High-moisture powders exhibit high cohesiveness, causing individual particles to stick together and form large agglomerates. During standard sieving, these agglomerates blind the screen apertures, halting the separation process.

• Limitations of Vibratory Shakers: Standard vibratory shakers (option A) and Tyler screens (option D) rely on vertical or horizontal shaking. This movement can compact damp, sticky powders, worsening screen blinding.

• Rotary Sifter Operation:

• A rotary sifter (centrifugal sifter) utilizes a cylindrical screen with internal, rotating paddle blades.

• The rotating paddles exert centrifugal force, pushing the powder against the screen wall while physically breaking up soft agglomerates.

• This continuous, active shearing action prevents screen blinding and allows high-moisture, cohesive materials to be separated efficiently.

Step 3: Final Answer:
The active mechanical break-up and centrifugal action of a rotary sifter makes it the preferred equipment for sieving sticky, high-moisture powders, corresponding to option (C).