Mixers taxonomy — resemblance to ball mills:\nWhich mixer most closely resembles a ball mill without the grinding media (balls)?

Introduction / Context:
Tumbling mixers and ball mills share a cylindrical shell that rotates about its axis. In a ball mill, grinding media fill a fraction of the volume to effect comminution; in a tumbling mixer, the shell is partially filled with solids (or solids plus small liquid additions) and rotated to promote intermixing without intentional grinding media. Recognising these geometric and kinematic similarities helps in understanding mixing limits and scale-up correlations.

Given Data / Assumptions:

• Cylindrical, rotating vessel considered.
• No grinding media present in the mixer.

Concept / Approach:
Tumbling mixers (a.k.a. drum mixers) rely on cascading of particles as the vessel rotates below critical speed. Banbury (internal) mixers are intensive shear kneaders for polymers; pug mills comprise twin mulling paddles; pan mixers use rotating paddles in a stationary pan; sigma-blade kneaders deliver high-viscosity shear. Only the tumbling mixer mirrors the rotating cylinder of a ball mill minus the balls.

Step-by-Step Solution:

Verification / Alternative check:
Photographs and P&IDs show close physical resemblance between laboratory drum mixers and small ball mills sans media.

Why Other Options Are Wrong:

• Banbury/pug/pan/sigma-blade: different geometries and shear-dominated mechanisms.

Common Pitfalls:
Confusing “tumbling” with “planetary” mixers; planetary mixers have rotating tools and revolution motion, not a rotating vessel shell.

Final Answer:
Tumbling mixer