Iron ore preparation and thermal treatment terminology: In metallurgy, “calcination” of iron ores is primarily carried out to achieve which purpose(s)? (Select the most appropriate single best statement.)

Introduction / Context:
Before smelting, ores undergo thermal pretreatments to adjust moisture content, remove volatile components, and alter chemical states. “Calcination” and “roasting” are distinct steps with different atmospheres and objectives. Discriminating between them is vital for correct process selection and exam accuracy.

Given Data / Assumptions:

• We focus on calcination of iron ores after sizing/dressing.
• Calcination takes place in limited or no air (not an oxidising roast).
• Targets include moisture removal and CO2 expulsion from carbonates.

Concept / Approach:
Calcination involves heating the ore below its melting point in a controlled, low-oxygen environment. Its key purposes are to remove hygroscopic and crystallisation water and to decompose carbonates, releasing CO2. Roasting, by contrast, is heating in excess air to oxidise sulfides/arsenides and to drive off volatile impurities; roasting in heaps is a roasting method, not calcination.

Step-by-Step Solution:

Verification / Alternative check:
Metallurgy references explicitly separate calcination (limited air, moisture/CO2 removal) from roasting (excess air, oxidation of sulfides), confirming the chosen description.

Why Other Options Are Wrong:

• Only moisture or only CO2: each is too narrow; calcination accomplishes both where applicable.
• Roasting in heaps: describes a roasting practice, not calcination.

Common Pitfalls:

• Using the terms “calcination” and “roasting” interchangeably.
• Assuming large open heaps always imply calcination; they usually imply roasting.

Final Answer:
To drive off moisture and CO2 from the ore after dressing, typically by heating in limited or no air