In particle-size engineering, a fluid energy mill (also called a jet mill) belongs to which category of comminution equipment used for producing extremely fine powders?

Introduction / Context:
A fluid energy mill, often called a jet mill or micronizer, accelerates particles in high-velocity gas streams where they collide and fracture. It is designed specifically for producing sub-50 microm and even sub-10 microm powders used in pharmaceuticals, pigments, ceramics, and specialty chemicals.

Given Data / Assumptions:

• Equipment: fluid energy (jet) mill.
• Operating principle: gas jets, no mechanical media.
• Target: extremely fine product.

Concept / Approach:
Comminution devices can be grouped into crushers (coarse), grinders (intermediate), and ultrafine grinders. Jet mills create intense interparticle impact and attrition within a gas vortex. The absence of mechanical contact minimizes contamination and enables very fine, narrow cuts—hence the classification as an ultrafine grinder.

Step-by-Step Solution:
Identify function: produce very fine powders.Identify mechanism: high-velocity gas → interparticle collisions.Match category: ultrafine grinder.

Verification / Alternative check:
Commercial jet mills routinely achieve d50 values in the few microm range, far beyond typical ball or hammer mills.

Why Other Options Are Wrong:
Crusher/Cutter: suited for coarse or shape-cutting duties.General grinder: too broad; jet mills are specifically ultrafine.

Common Pitfalls:
Confusing “high energy” with mechanical media mills; jet mills rely on gas energy, not heavy grinding media.

Final Answer:
Ultrafine grinder