In a closed-circuit, air-swept ball mill system, which combination is normally used to return coarse material and collect fine product?

Introduction / Context:
Closed-circuit grinding controls product fineness and improves mill efficiency. In an air-swept ball mill, the gas stream transports ground particles to a separator and then to a collector, while the classifier returns coarse particles to the mill inlet.

Given Data / Assumptions:

• An air-swept mill entrains fines with gas.
• A classifier performs size separation.
• A cyclone commonly collects fine product from the gas stream.

Concept / Approach:
The classifier (static or dynamic) splits fines and coarse; the cyclone serves as a dust collector to separate solids from conveying air. Many practical circuits place a cyclone between the mill outlet and classifier plenum to stabilize flow and recover fines, with dust recirculation as designed.

Step-by-Step Solution:
Identify unit for size control: classifier.Identify unit for gas–solid separation: cyclone.Select the combined use of both.

Verification / Alternative check:
Typical cement grinding circuits show air-swept mills connected to cyclones and high-efficiency separators, confirming the configuration.

Why Other Options Are Wrong:
Classifier alone: offers split but needs a collector.Cyclone alone: no cut-size control; only collection.ESP: overkill for this duty and uncommon for mill recycle.

Common Pitfalls:
Assuming a single device can both classify and collect with high precision.

Final Answer:
Both (a) & (b)