Comminution & classification — identify the incorrect statement Which of the following statements about grinding circuits, additives, classifiers, and size enlargement is incorrect?

Introduction / Context:Particle processing spans size reduction, separation, and size enlargement. Many terms sound similar (classifier vs. clarifier), leading to common exam traps. This question checks precise terminology and unit operations knowledge.

Given Data / Assumptions:

• Closed vs. open circuit grinding practices.
• Use of grinding aids in cement milling.
• Definition of classifier vs. clarifier/filter.
• Examples of size enlargement.

Concept / Approach:Classifiers separate particles by size (or settling velocity) in suspensions or pneumatic streams. Removing traces of solids from liquids is the role of clarifiers and filters. Grinding aids reduce agglomeration and energy consumption. Tablet pressing is a classic size enlargement (agglomeration) example.

Step-by-Step Solution:(a) Closed circuit grinding recycles coarse fraction → generally more energy efficient → true.(b) Lubricious additives like animal/vegetable oils and stearates are used as grinding aids → true.(c) Calling a trace-solids remover a “classifier” is wrong; that is a clarifier/filter → incorrect statement.(d) Compressing powders into tablets increases effective particle size → true.

Verification / Alternative check:Unit operations texts list gravity/hydraulic/pneumatic classifiers for sizing; clarifiers and filters for liquid-solid clarification.

Why Other Options Are Wrong:

• (a), (b), (d) align with industrial practice and standard references.

Common Pitfalls:

• Mixing “classifier” and “clarifier” due to similar spelling.

Final Answer:The equipment used for the removal of traces of solids from a liquid is called a classifier.