Considering energy per unit mass of material, which equipment typically requires the highest specific energy input to achieve its target product fineness?

Introduction / Context:
Specific energy in comminution rises dramatically as target size moves into the micron and sub-micron regime. Equipment designed for ultrafine grinding naturally exhibits higher energy per mass than coarse crushers or conventional grinders.

Concept / Approach:
Jaw crushers perform coarse size reduction at relatively low specific energy because crack propagation requires less surface creation per unit mass. Rod and ball mills increase energy usage as they grind finer. Fluid energy (jet) mills use very high-velocity gas to induce interparticle collisions, achieving extremely fine sizes but at high energy cost per kilogram of product.

Step-by-Step Solution:
Compare duty: coarse (jaw) < intermediate (rod/ball) < ultrafine (jet).Recognize that ultrafine targets require much more new surface area → higher energy.Select fluid energy mill as highest specific energy device.

Why Other Options Are Wrong:
Jaw/Rod/Ball mills operate at coarser targets with lower specific energy than jet mills for the same mass.

Final Answer:
Fluid energy (jet) mill