Elutriation for very fine particles (5–10 μm): in particulate processing, elutriation is fundamentally classified as which type of operation?

Introduction / Context:
Elutriation separates particles in a rising fluid (usually air or water) based on differences in terminal settling velocity. It is widely used for narrow size cuts in the fine range where screens are inefficient or where wet processing is preferred to avoid agglomeration and dust.

Given Data / Assumptions:

• Target size: about 5–10 micrometers.
• Fluidization/elutriation column with controlled upward velocity.
• Particles with different settling velocities are to be separated.

Concept / Approach:
Classification is the generic term for separating particles according to size, shape, or density via differential settling. In elutriation, the upward fluid velocity is set so that lighter/smaller particles are carried out while heavier/larger ones settle. Clarification focuses on removing small solids from a liquid to produce a clear effluent; sedimentation is the gravity settling itself; flocculation is agglomeration to increase effective size.

Step-by-Step Solution:
Recognize mechanism: differential terminal velocity in an upward flow.Map to operation: this is classification by fluid velocity selection.Eliminate: clarification (goal-oriented), sedimentation (settling process), flocculation (pretreatment).

Verification / Alternative check:
Design correlations compare upflow velocity to particle settling velocities to set the cut size, which is the hallmark of classifiers.

Why Other Options Are Wrong:
Clarification: aims at clear liquid, not graded solids split.Sedimentation: general settling term; elutriation specifically creates a size-based split with an imposed upflow.Flocculation: chemical/physical agglomeration step, not a separator.

Common Pitfalls:
Using elutriation data as if it were simple sedimentation; the imposed upflow velocity changes the cut point dramatically.

Final Answer:
classification