Question

The termil velocity of the material is .................... compared to the air velocity in pneumatic conveying and separation processes.

• A. Lower
• B. Higher
• C. Equal
• D. Zero

Hint:

The conveying air velocity is typically designed to be \(2\) to \(3\) times the termil velocity of the heaviest particle to prevent blockages and line choking.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Termil velocity (\(v_t\)) is the constant velocity reached by a falling particle when the gravitatiol force is balanced by the upward drag force.
In pneumatic conveying and aerodymic separation, air is used as the medium to suspend and transport particles.

Step 2: Detailed Explation:
For a particle to be lifted and transported vertically in an air stream, the upward drag force exerted by the air must exceed the downward force of gravity.
This means the superficial velocity of the air (\(v_a\)) must be greater than the termil settling velocity (\(v_t\)) of the particle: \(v_a > v_t\).
If the air velocity is lower than the termil velocity, the particle will fall or deposit at the bottom of the duct rather than being conveyed.
Thus, the termil velocity of the material must be lower than the air velocity to ensure proper transport and separation.

Step 3: Fil Answer:
The correct option is (A).