🔴 Roasting
Definition:
Purpose:
Example:
Key Points:
⚪ Calcination
Definition:
Purpose:
Example:
Key Points:
| Feature | Calcination ⚪ | Roasting 🔴 |
|---|---|---|
| Typical Ore Type | Carbonates, hydroxides, hydrated oxides (e.g., limestone, bauxite) | Sulfides (e.g., zinc blende, galena, pyrite) |
| Atmosphere | Limited or no air (often done in a closed furnace) | Excess air or oxygen (open or fluidized bed furnace) |
| Main Chemical Change | Decomposition: Carbonate → Oxide + CO₂<br>Hydrated oxide → Oxide + H₂O | Oxidation: Sulfide + O₂ → Oxide + SO₂ |
| Key Purpose | Remove CO₂, H₂O, or other volatile impurities | Remove sulfur as SO₂ gas; convert to oxide for further reduction |
| Typical Example | CaCO₃ (limestone) → CaO (lime) + CO₂↑ | 2ZnS (sphalerite) + 3O₂ → 2ZnO + 2SO₂↑ |
| Temperature Range | Usually moderate (500–1000°C), depends on ore | Often higher (500–1200°C+), sometimes below melting point |
| Final Product | Porous, often powdery oxide (or pure metal if combined with reduction) | Oxide or sulfate of the metal |
| Gas Released | CO₂, water vapor | SO₂ (sulfur dioxide, often captured to make sulfuric acid) |
| Reduction/Enrichment | Does not chemically reduce the metal; just purifies | Does not reduce; changes chemical form to oxide for later reduction |
| Feature | Roasting 🔴 | Calcination ⚪ |
|---|---|---|
| Air supply | Excess oxygen | No / limited oxygen |
| Type of ore | Sulphide ores | Carbonate / hydrated ores |
| Gas released | SO₂ | CO₂ / H₂O |
| Main purpose | Oxidation | Thermal decomposition |
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Roasting and Calcination: Differences, Reactions & Comparison is a fundamental concept in inorganic chemistry. Understanding the mechanisms, reaction conditions, and stereo-chemical outcomes is crucial for mastering organic chemistry. Our curated resources provide step-by-step visualizations to help you excel.
SELF TEST
Which type of ore is primarily subjected to the Roasting process?
LEARNING SUPPORT
Sulphide ores are difficult to reduce directly. Roasting (heating strongly in the presence of excess air) converts the metal sulphide into a more easily reducible metal oxide, while simultaneously removing the sulphur impurities as sulphur dioxide gas.
During calcination, a carbonate ore is heated strongly in the absence or limited supply of air. The heat causes thermal decomposition, breaking the carbonate down into a metal oxide and releasing carbon dioxide gas.
No. Both roasting and calcination are solid-state thermal processes. They are strictly carried out at temperatures below the melting point of the ore.